Skip to Main Content U.S. Department of Energy
Energy Storage

Energy Storage Publications

NOTE: Each Program Area has it's own Publications page. Visit the Program Area pages for an abridged list of publications.

2017

  • Shuhong Jiao, Jianming Zheng, Qiuyan Li, Xing Li, Mark H. Engelhard, Ruiguo Cao, Ji-Guang Zhang, and Wu Xu. "Behavior of Lithium Metal Anodes under Various Capacity Utilization and High Current Density in Lithium Metal Batteries " Joule 2018, 2,1-15 (Nov. 2017 online).

    Abstract:Lithium (Li) metal batteries (LMBs) have recently attracted extensive interest in the energy-storage field after silence from the public view for several decades. However, many challenges still need to be overcome before their practical application, especially those that are related to the interfacial instability of Li metal anodes. Here, we reveal for the first time that the thickness of the degradation layer on the metallic Li anode surface shows a linear relationship with Li areal capacity utilization up to 4.0 mAh cm−2 in a practical LMB system. The increase in Li capacity utilization in each cycle causes variations in the morphology and composition of the degradation layer on the Li anode. Under high Li capacity utilization, the current density for charge (i.e., Li deposition) is identified to be a key factor controlling the corrosion of the Li metal anode. These fundamental findings provide new perspectives for the development of rechargeable LMBs.

  • B. D. Adams, J. Zheng, X. Ren, W. Xu, and J.-G. Zhang. " Accurate Determination of Coulombic Efficiency for Lithium Metal Anodes and Lithium Metal Batteries " Adv. Energy Mater.. 2017, 1702097 (Oct. 2017).

    Abstract:Lithium (Li) metal is an ideal anode material for high energy density batteries. However, the low Coulombic efficiency (CE) and the formation of dendrites during repeated plating and stripping processes have hindered its applications in rechargeable Li metal batteries. The accurate measurement of Li CE is a critical factor to predict the cycle life of Li metal batteries, but the measurement of Li CE is affected by various factors that often lead to conflicting values reported in the literature. Here, several parameters that affect the measurement of Li CE are investigated and a more accurate method of determining Li CE is proposed. It is also found that the capacity used for cycling greatly affects the stabilization cycles and the average CE. A higher cycling capacity leads to faster stabilization of Li anode and a higher average CE. With a proper operating protocol, the average Li CE can be increased from 99.0% to 99.5% at a high capacity of 6 mA h cm−2 (which is suitable for practical applications) when a high-concentration ether-based electrolyte is used.
  • Bin Liu, Wu Xu, Jianming Zheng, Pengfei Yan, Eric D. Walter, Nancy Isern, Mark E. Bowden, Mark H. Engelhard, Sun Tai Kim, Jeffrey Read, Brian D. Adams, Xiaolin Li, Jaephil Cho, Chongmin Wang, and Ji-Guang Zhang. "Temperature Dependence of the Oxygen Reduction Mechanism in Nonaqueous Li–O2 Batteries " ACS Energy Letters 2017, 2(11) 2525-2530 (Oct. 2017).

    Abstract:The temperature dependence of the oxygen reduction mechanism in nonaqueous Li–O2 batteries is investigated within the temperature range of −20 to 40 °C. The discharge capacity of the Li–O2 battery first decreases from 7492 mAh g–1 at 40 °C to 2930 mAh g–1 at 0 °C and then increases sharply with a further decrease in temperature and reaches a very high capacity of 17 716 mAh g–1 at −20 °C at 0.1 mA cm–2. The lifetime of superoxide intermediates and the solution pathway were found to play a dominant role in the discharge of the Li–O2 battery in the temperature range of −20 to 0 °C, but the electrochemical kinetics of oxygen reduction and the surface pathway dominate the discharge behavior of the Li–O2 batteries between 0 and 40 °C. This work will broaden the fundamental understanding of the oxygen reduction process in the Li–O2 battery, especially at different temperatures.

  • Brian D. Adams, Emily V. Carino, Justin G. Connell, Kee Sung Han, Ruiguo Cao, Junzheng Chen, Jianming Zheng, Qiuyan Li, Karl T. Mueller, Wesley A. Henderson, Ji-Guang Zhang. " Long Term Stability of Li-S Batteries Using High Concentration Lithium Nitrate Electrolytes" Nano Energy. 2017, 607-617.(Oct. 2017).
    Abstract: The lithium-sulfur (Li-S) battery is a very promising candidate for the next generation of energy storage systems required for electrical vehicles and grid energy storage applications due to its very high theoretical specific energy (2500 W h kg−1). However, low Coulombic efficiency (CE) during repeated Li metal plating/stripping has severely limited the practical application of rechargeable Li-S batteries. In this work, a new electrolyte system based on a high concentration of LiNO3 in diglyme (G2) solvent is developed which enables an exceptionally high CE for Li metal plating/stripping and thus high stability of the Li anode in the sulfur-containing electrolyte. The tailoring of electrolyte properties for the Li anode has proven to be a highly successful strategy for improving the capacity retention and cycle life of Li-S batteries. This electrolyte provides a CE of greater than 99% for over 200 cycles of Li plating/stripping. In contrast, the Li anode cycles for less than 35 cycles (with a high CE) in the state-of-the-art 1 M LiTFSI + 0.3 M LiNO3 in 1,3-dioxolane:1,2-dimethoxyethane (DOL:DME) electrolyte under the same conditions. The stable Li anode enabled by the new electrolyte may accelerate the applications of high energy density Li-S batteries in both electrical vehicles and large-scale grid energy storage markets.
  • Lu, X, HJ Chang, JF Bonnett, NL Canfield, K Jung, VL Sprenkle, G Li. "Effect of cathode thickness on the performance of planar Na-NiCl2 battery." Journal of Power Sources 365: 456-462 (Oct. 2017).
    Abstract:Na-beta alumina batteries (NBBs) are one of the most promising technologies for renewable energy storage and grid applications. Commercial NBBs are typically constructed in tubular designs, primarily because of their ease of sealing. However, planar designs are considered superior to tubular counterparts in terms of power output, cell packing, ease of assembly, and thermal management. In this paper, the performance of planar NBBs has been evaluated at an intermediate temperature. In particular, planar Na-NiCl2 cells with different cathode loadings and thicknesses have been studied at 190°C. The effects of the cathode thickness, charging current, and discharging power output on the cell capacity and resistance have been investigated. More than 60% of theoretical cell capacity was retained with constant discharging power levels of 200, 175, and 100 mW/cm2 for 1x, 2x, and 3x cathode loadings, respectively. The cell resistance with 1x and 2x cathode loadings was dominated by ohmic resistance with discharging currents up to 105 mA/cm2, while for 3x cathode loading, it was primarily dominated by ohmic resistance with currents less than 66.67 mA/cm2 and by polarization resistance above 66.67 mA/cm2.
  • Pan, H., Chen, J., Cao, R., Vijay, M., Rajput, N.N., Han, K.S., Persson, K., Estevez, L., Engelhard, M.H., Zhang, J.G., Mueller, K.T., Cui, Y., Shao, Y., Liu, J. " Non-encapsulation Approach for High Performance Li-S Batteries through Controlled Nucleation and Growth" Natrue Energy. 2017, 2,813-820 (Sept. 2017)

    Abstract:High-surface-area, nanostructured carbon is widely used for encapsulating sulfur and improving the cyclic stability of Li–S batteries, but the high carbon content and low packing density limit the specific energy that can be achieved. Here we report an approach that does not rely on sulfur encapsulation. We used a low-surface-area, open carbon fibre architecture to control the nucleation and growth of the sulfur species by manipulating the carbon surface chemistry and the solvent properties, such as donor number and Li+ diffusivity. Our approach facilitates the formation of large open spheres and prevents the production of an undesired insulating sulfur-containing film on the carbon surface. This mechanism leads to ~100% sulfur utilization, almost no capacity fading, over 99% coulombic efficiency and high energy density (1,835 Wh kg−1 and 2,317 Wh l−1). This finding offers an alternative approach for designing high-energy and low-cost Li–S batteries through controlling sulfur reaction on low-surface-area carbon. 

  • H. Wang, D. Lin, Y. Liu, Y. Li, Y. Cui. " Ultrahigh-current density anodes with interconnected Li metal reservoir through overlithiation of mesoporous AlF3 framework" Sci. Adv. e170130 (Sept. 2017).

    Abstract:Lithium (Li) metal is the ultimate solution for next-generation high–energy density batteries but is plagued from commercialization by infinite relative volume change, low Coulombic efficiency due to side reactions, and safety issues caused by dendrite growth. These hazardous issues are further aggravated under high current densities needed by the increasing demand for fast charging/discharging. We report a one-step fabricated Li/Al4Li9-LiF nanocomposite (LAFN) through an “overlithiation” process of a mesoporous AlF3 framework, which can simultaneously mitigate the abovementioned problems. Reaction-produced Al4Li9-LiF nanoparticles serve as the ideal skeleton for Li metal infusion, helping to achieve a near-zero volume change during stripping/plating and suppressed dendrite growth. As a result, the LAFN electrode is capable of working properly under an ultrahigh current density of 20 mA cm−2 in symmetric cells and manifests highly improved rate capability with increased Coulombic efficiency in full cells. The simple fabrication process and its remarkable electrochemical performances enable LAFN to be a promising anode candidate for next-generation lithium metal batteries.
  • H. Lee, X. Ren, C. Niu, L. Yu, M. H. Engelhard, I. Cho, M.-H. Ryou, H. S. Jin, H.-T. Kim, J. Liu, W. Xu, and J.-G. Zhang. " Suppressing Lithium Dendrite Growth by Metallic Coating on Separator " Appl.Mater. Interfaces. 2017, 9 (36), 30635–30642(Aug. 2017).

    Abstract: A single-component coating was formed on lithium (Li) metal in a lithium iodide/organic carbonate [dimethyl carbonate (DMC) and ethylene carbonate (EC)] electrolyte. LiI chemically reacts with DMC to form lithium methyl carbonate (LMC), which precipitates and forms the chemically homogeneous coating layer on the Li surface. This coating layer is shown to enable dendrite-free Li cycling in a symmetric Li∥Li cell even at a current density of 3 mA cm–2. Adding EC to DMC modulates the formation of LMC, resulting in a stable coating layer that is essential for long-term Li cycling stability. Furthermore, the coating can enable dendrite-free cycling after being transferred to common LiPF6/carbonate electrolytes, which are compatible with metal oxide cathodes. 

  • X. Wei, W. Pan, W. Duan, A. Hollas, Z. Yang, B. Li, Z. Nie, J. Liu, D. Reed, W. Wang, V. Sprenkle. "Materials and Systems for Organic Redox Flow Batteries: Status and Challenges " ACS Energy Letters 2017, 2,(9),2187-2204. (Aug. 2017).
    Abstract:Redox flow batteries (RFBs) are propitious stationary energy storage technologies with exceptional scalability and flexibility to improve the stability, efficiency, and sustainability of our power grid. The redox-active materials are the key component for RFBs with which to achieve high energy density and good cyclability. Traditional inorganic-based materials encounter critical technical and economic limitations such as low solubility, inferior electrochemical activity, and high cost. Redox-active organic materials (ROMs) are promising alternative “green” candidates to push the boundaries of energy storage because of the significant advantages of molecular diversity, structural tailorability, and natural abundance. Here, the recent development of a variety of ROMs and associated battery designs in both aqueous and nonaqueous electrolytes are reviewed. The critical challenges and potential research opportunities for developing practically relevant organic flow batteries are discussed.
  • X. Wei, W. Pan, W. Duan, A. Hollas, Z. Yang, B. Li, Z. Nie, J. Liu, D. Reed, W. Wang, V. Sprenkle. "Materials and Systems for Organic Redox Flow Batteries: Status and Challenges " ACS Energy Letters 2017, 2,(9),2187-2204. (Aug. 2017).
    Abstract:Redox flow batteries (RFBs) are propitious stationary energy storage technologies with exceptional scalability and flexibility to improve the stability, efficiency, and sustainability of our power grid. The redox-active materials are the key component for RFBs with which to achieve high energy density and good cyclability. Traditional inorganic-based materials encounter critical technical and economic limitations such as low solubility, inferior electrochemical activity, and high cost. Redox-active organic materials (ROMs) are promising alternative “green” candidates to push the boundaries of energy storage because of the significant advantages of molecular diversity, structural tailorability, and natural abundance. Here, the recent development of a variety of ROMs and associated battery designs in both aqueous and nonaqueous electrolytes are reviewed. The critical challenges and potential research opportunities for developing practically relevant organic flow batteries are discussed.
  • Wu D, M Kintner-Meyer, T Yang, P Balducci. "Analytical sizing methods for behind-the-meter battery storage." Journal of Energy Storage 12: 297-304 (Aug. 2017).
    Abstract:In behind-the-meter application, battery storage system (BSS) is used to reduce a commercial or industrial customer's payment for electricity use, including energy and demand charges. The potential value of BSS in payment reduction and the optimal size can be determined by formulating and solving standard mathematical programming problems. In such mathematical programming methods, users input system information such as load profiles, energy/demand charge rates, and battery characteristics to construct a standard programming problem, which typically involves a large number of constraints and decision variables. The problems are then solved by optimization solvers to obtain numerical solutions. Such kind of methods cannot directly link the obtained optimal battery sizes to input parameters and requires case-by-case analysis. In this paper, we present an objective quantitative analysis of costs and benefits for customer-side BSS, and thereby identify key factors that affect optimal sizing. We then develop simple but effective guidelines for determining the most cost-effective battery size. The proposed analytical sizing methods are innovative, and provide engineering insights on how the optimal battery size varies with system characteristics. We illustrate the proposed methods using practical building load profile and utility rate. The obtained results are compared with the ones using mathematical programming based methods for validation.
  • J. Zhang, Z. Yang, I. A. Shkrob, R. S. Assary, S. Tung, B. Silcox, W. Duan, J. Zhang, C. Liao, Z. Zhang, W. Wang, L. A. Curtiss, L. Thompson, X. Wei, L. Zhang. " Annulated dialkoxybenzenes as catholyte materials for nonaqueous redox flow batteries: achieving high chemical stability through bicyclic substitution " Advanced Energy Materials. 2017, 7, 1701272. (July. 2017).

    Abstract: 1,4-Dimethoxybenzene derivatives are materials of choice for use as catholytes in non-aqueous redox flow batteries, as they exhibit high open-circuit potentials and excellent electrochemical reversibility. However, chemical stability of these materials in their oxidized form needs to be improved. Disubstitution in the arene ring is used to suppress parasitic reactions of their radical cations, but this does not fully prevent ring-addition reactions. By incorporating bicyclic substitutions and ether chains into the dialkoxybenzenes, a novel catholyte molecule, 9,10-bis(2-methoxyethoxy)-1,2,3,4,5,6,7,8-octahydro-1, 4:5,8- dimethanenoanthracene (BODMA), is obtained and exhibits greater solubility and superior chemical stability in the charged state. A hybrid flow cell containing BODMA is operated for 150 charge–discharge cycles with a minimal loss of capacity.

  • Michael S. Ding, Qiuyan Li, Xing Li, Wu Xu, Kang Xu."Effects of Solvent Composition on Liquid Range, Glass Transition, and Conductivity of Electrolytes of a (Li, Cs)PF6 Salt in EC-PC-EMC Solvents."Journal of Physical Chemistry C 121 (21): 11178-11183 (May 2017).
    Abstract: Electrolytes of 1 M LiPF6 (lithium hexafluorophosphate) and 0.05 M CsPF6 (cesium hexafluorophosphate) in EC-PC-EMC (ethylene carbonate-propylene carbonate-ethyl methyl carbonate) solvents of varying solvent compositions were studied for the effects of solvent composition on the lower limit of liquid range, glass transition temperature (as a reflection of viscosity), and electrolytic conductivity. In addition, a ternary phase diagram of EC-PC-EMC was constructed, and crystallization temperatures of EC and EMC were calculated to assist the interpretation and understanding of the change of liquid range with solvent composition. A function based on the Vogel–Fulcher–Tammann equation was fitted to the conductivity data in their entirety and was plotted as conductivity surfaces in solvent composition space for more direct and clear comparisons and discussions. Changes of viscosity and dielectric constant of the solvents with their composition, in relation to those of the solvent components, were found to be underlying many of the processes studied.
  • Cho SJ, MJ Uddin, PK Alaboina, SS Han, MI Nandasiri, YS Choi, E Hu, KW Nam, AM Schwarz, SK Nune, JS Cho, KH Oh, D Choi. "Exploring Lithium Deficiency in Layered Oxide Cathode for Li-Ion Battery." Advanced Sustainable Systems 1 (7) (June 2017).
    Abstract:The ever-growing demand for high capacity cathode materials is on the rise since the futuristic applications are knocking on the door. Conventional approach to developing such cathode relies on the lithium-excess materials to operate the cathode at high voltage and extract more lithium-ion. Yet, they fail to satiate the needs because of their unresolved issues upon cycling such as, for lithium manganese-rich layered oxides-their voltage fading, and for as nickel-based layered oxides-the structural transition. Here, in contrast, lithium-deficient ratio is demonstrated as a new approach to attain high capacity at high voltage for layered oxide cathodes. Rapid and cost effective lithiation of a porous hydroxide precursor with lithium deficient ratio is acted as a driving force to partially convert the layered material to spinel phase yielding in a multiphase structure (MPS) cathode material. Upon cycling, MPS reveals structural stability at high voltage and high temperature and results in fast lithium-ion diffusion by providing a distinctive solid electrolyte interface (SEI) chemistry-MPS displays minimum lithium loss in SEI and forms a thinner SEI. MPS thus offers high energy and high power applications and provides a new perspective compared to the conventional layered cathode materials denying the focus for lithium excess material.
  • K. Shah, N. Balsara, S. Banerjee, M. Chintapalli, A. P. Cocco, W. K. S. Chiu, I. Lahiri, S. Martha, A. Mistry, P. P. Mukherjee, V. Ramadesigan, C. S. Sharma, V. R. Subramanian, S. Mitra, and A. Jain. "State of the Art and Future Research Needs for Multiscale Analysis of Li-Ion Cells " J. Electrochem. En. Conv. Stor. 2017, 14 (2) 020801-17 (May. 2017).

    Abstract: The performance, safety, and reliability of Li-ion batteries are determined by a complex set of multiphysics, multiscale phenomena that must be holistically studied and optimized. This paper provides a summary of the state of the art in a variety of research fields related to Li-ion battery materials, processes, and systems. The material presented here is based on a series of discussions at a recently concluded bilateral workshop in which researchers and students from India and the U.S. participated. It is expected that this summary will help understand the complex nature of Li-ion batteries and help highlight the critical directions for future research.
  • Chen, J., Henderson, W.A., Pan, H., Perdue, B.R., Cao, R., Hu, J. Z., Wan, C., Han, K.S., Mueller, K.T., Zhang, J.G., Shao, Y., Liu, J. " Improving Lithium–Sulfur Battery Performance Under Lean Electrolyte Through Nanoscale Confinement in Soft Swellable Gels" Nano Letters. 2017, 17, (5) 3061-3067 (April. 2017).

    Abstract: Li–S batteries have been extensively studied using rigid carbon as the host for sulfur encapsulation, but improving the properties with a reduced electrolyte amount remains a significant challenge. This is critical for achieving high energy density. Here, we developed a soft PEO10LiTFSI polymer swellable gel as a nanoscale reservoir to trap the polysulfides under lean electrolyte conditions. The PEO10LiTFSI gel immobilizes the electrolyte and confines polysulfides within the ion conducting phase. The Li–S cell with a much lower electrolyte to sulfur ratio (E/S) of 4 gE/gS (3.3 mLE/gS) could deliver a capacity of 1200 mA h/g, 4.6 mA h/cm2, and good cycle life. The accumulation of polysulfide reduction products, such as Li2S, on the cathode, is identified as the potential mechanism for capacity fading under lean electrolyte conditions. 

  • Duan, W, J Huang, JA Kowalski, IA Shkrob, M Vijayakumar, E Walter, B Pan, Z Yang, JD Milshtein, B Li, C Liao, Z Zhang, W Wang, J Liu, JS Moore, FR Brushett, L Zhang, X Wei. "“Wine-Dark Sea” in an Organic Flow Battery: Storing Negative Charge in 2,1,3-Benzothiadiazole Radicals Leads to Improved Cyclability."ACS Energy Letters 2 (5): 1156-1161 (April. 2017).
    Abstract:Redox-active organic materials (ROMs) have shown great promise for redox flow battery applications but generally encounter limited cycling efficiency and stability at relevant redox material concentrations in nonaqueous systems. Here we report a new heterocyclic organic anolyte molecule, 2,1,3-benzothiadiazole, that has high solubility, a low redox potential, and fast electrochemical kinetics. Coupling it with a benchmark catholyte ROM, the nonaqueous organic flow battery demonstrated significant improvement in cyclable redox material concentrations and cell efficiencies compared to the state-of-the-art nonaqueous systems. Especially, this system produced exceeding cyclability with relatively stable efficiencies and capacities at high ROM concentrations (>0.5 M), which is ascribed to the highly delocalized charge densities in the radical anions of 2,1,3-benzothiadiazole, leading to good chemical stability. This material development represents significant progress toward promising next-generation energy storage.
  • Wan C ,Xu S ,Hu M Y,Cao R ,Qian J ,Qin Z ,Liu J ,Mueller K T,Zhang J ,Hu J Z. "Multinuclear NMR Study of the Solid Electrolyte Interface Formed in Lithium Metal Batteries" Applied Materials & Interfaces 9 (17): 14741-14748 (April 2017).
    Abstract: The composition of the solid electrolyte interphase (SEI) layers formed in Cu|Li cells using lithium bis(fluorosulfonyi)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1,2-dimethoxyethane (DME) electrolytes is determined by a multinuclear solid-state MAS NMR study at high magnetic field. It is found that the “dead” metallic Li is largely reduced in the SEI layers formed in a 4 M LiFSI–DME electrolyte system compared with those formed in a 1 M LiFSI–DME electrolyte system. This finding relates directly to the safety of Li metal batteries, as one of the main safety concerns for these batteries is associated with the “dead” metallic Li formed after long-term cycling. It is also found that a large amount of LiF, which exhibits superior mechanical strength and good Li+ ionic conductivity, is observed in the SEI layer formed in the concentrated 4 M LiFSI–DME and 3 M LiTFSI–DME systems but not in the diluted 1 M LiFSI–DME system. Quantitative 6Li MAS NMR results indicate that the SEI associated with the 4 M LiFSI–DME electrolyte is denser than those formed in the 1 M LiFSI–DME and 3 M LiTFSI–DME systems. These studies reveal the fundamental mechanisms behind the excellent electrochemical performance associated with higher concentration LiFSI–DME electrolyte systems.
  • Chang HJ ,Lu X ,Bonnett J F,Canfield N L,Son S ,Park YC ,Jung K ,Sprenkle V L,Li G. "Development of intermediate temperature sodium nickel chloride rechargeable batteries using conventional polymer sealing technologies." Journal of Power Sources 348: 150-157 (April 2017).
    Abstract:Developing advanced and reliable electrical energy storage systems is critical to fulfill global energy demands and stimulate the growth of renewable energy resources. Sodium metal halide batteries have been under serious consideration as a low cost alternative energy storage device for stationary energy storage systems. Yet, there are number of challenges to overcome for the successful market penetration, such as high operating temperature and hermetic sealing of batteries that trigger an expensive manufacturing process. Here we demonstrate simple, economical and practical sealing technologies for Na-NiCl2 batteries operated at an intermediate temperature of 190°C. Conventional polymers are implemented in planar Na-NiCl2 batteries after a prescreening test, and their excellent compatibilities and durability are demonstrated by a stable performance of Na-NiCl2 battery for more than 300 cycles. The sealing methods developed in this work will be highly beneficial and feasible for prolonging battery cycle life and reducing manufacturing cost for Na-based batteries at elevated temperatures (<200°C).
  • Li Y ,An Q ,Cheng Y ,Liang Y ,Ren Y ,Sun CJ ,Dong H ,Tang Z ,Li G ,Yao Y. "A high-voltage rechargeable magnesium-sodium hybrid battery." Nano Energy 34: 188-194 (April 2017).
    Abstract:Growing global demand of safe and low-cost energy storage technology triggers strong interests in novel battery concepts beyond state-of-art Li-ion batteries. Here we report a high-voltage rechargeable Mg-Na hybrid battery featuring dendrite-free deposition of Mg anode and Na-intercalation cathode as a low-cost and safe alternative to Li-ion batteries for large-scale energy storage. A prototype device using a Na3V2(PO4)3 cathode, a Mg anode, and a Mg-Na dual salt electrolyte exhibits the highest voltage (2.60 V vs. Mg) and best rate performance (86% capacity retention at 10C rate) among reported hybrid batteries. Synchrotron radiation-based X-ray absorption near edge structure (XANES), atomic-pair distribution function (PDF), and high-resolution X-ray diffraction (HRXRD) studies reveal the chemical environment and structural change of Na3V2(PO4)3 cathode during the Na ion insertion/deinsertion process. XANES study shows a clear reversible shift of vanadium K-edge and HRXRD and PDF studies reveal a reversible two-phase transformation and V-O bond length change during cycling. The energy density of the hybrid cell could be further improved by developing electrolytes with a higher salt concentration and wider electrochemical window. This work represents a significant step forward for practical safe and low-cost hybrid batteries.
  • Jianming Zheng, Joshua Lochala, Alexander Kwok, Zhiqun Daniel Deng, Jie Xiao."Research Progress towards Understanding the Unique Interfaces between Concentrated Electrolytes and Electrodes for Energy Storage Applications."Advanced Science 4 (8) (March 2017).
    Abstract: The electrolyte is an indispensable component in all electrochemical energy storage and conversion devices with batteries being a prime example. While most research efforts have been pursued on the materials side, the progress for the electrolyte is slow due to the decomposition of salts and solvents at low potentials, not to mention their complicated interactions with the electrode materials. The general properties of bulk electrolytes such as ionic conductivity, viscosity, and stability all affect the cell performance. However, for a specific electrochemical cell in which the cathode, anode, and electrolyte are optimized, it is the interface between the solid electrode and the liquid electrolyte, generally referred to as the solid electrolyte interphase (SEI), that dictates the rate of ion flow in the system. The commonly used electrolyte is within the range of 1-1.2 M based on the prior optimization experience, leaving the high concentration region insufficiently recognized. Recently, electrolytes with increased concentration (>1.0 M) have received intensive attention due to quite a few interesting discoveries in cells containing concentrated electrolytes. The formation mechanism and the nature of the SEI layers derived from concentrated electrolytes could be fundamentally distinct from those of the traditional SEI and thus enable unusual functions that cannot be realized using regular electrolytes. In this article, we provide an overview on the recent progress of high concentration electrolytes in different battery chemistries. The experimentally observed phenomena and their underlying fundamental mechanisms are discussed. New insights and perspectives are proposed to inspire more revolutionary solutions to address the interfacial challenges.
  • Rajput NN ,Murugesan V ,Shin Y ,Han KS ,Lau KC ,Chen J ,Liu J ,Curtiss L A,Mueller K T,Persson K A. "Elucidating the Solvation Structure and Dynamics of Lithium Polysulfides Resulting from Competitive Salt and Solvent Interactions" Chemistry of Materials 29 (8): 3375-3379 (March 2017).
    Abstract: Designing optimal electrolytes is key to enhancing the performance of energy storage devices,especially relating to cycle life, efficiency, and stability.1 Specifically, for future beyond-Li ion energy storage, there is still ample room for electrolyte improvements. Among the candidates for higher gravimetric energy storage, the Li−S battery is considered quite promising, owing to its theoretical specific energy density (2600 Wh/kg) and specific capacity (1675 mAh/g) and significantly lower cost as compared to state-of-art lithium-ion batteries.2−4 However, despite these attractive attributes, successful commercialization of Li−S batteries is currently hindered by poor cycling performance and capacity retention that is primarily caused by the parasitic reactions between the Li metal anode and dissolved polysulfide (PS) species from the cathode during the cycling process.3,5
  • Vijayakumar, M., Han, K.S., Hu, J., Mueller, K.T. " Molecular Level Structure and Dynamics of Electrolytes Using 17O Nuclear Magnetic Resonance Spectroscopy " eMagRes. 2017, 3, 71-82 (March. 2017).
    Abstract: Electrolytes help harness the energy from electrochemical processes by serving as solvents and transport media for redox-active ions. Molecular-level interactions between ionic solutes and solvent molecules – commonly referred to as solvation phenomena – give rise to many functional properties of electrolytes such as ionic conductivity, viscosity, and stability. It is critical to understand the evolution of solvation phenomena as a function of competing counterions and solvent mixtures to predict and design the optimal electrolyte for a target application. Probing oxygen environments is of great interest as oxygens are located at strategic molecular sites in battery solvents and are directly involved in inter- and intramolecular solvation interactions. NMR signals from 17O nuclei in battery electrolytes offer nondestructive bulk measurements of isotropic shielding, electric field gradient tensors, and transverse and longitudinal relaxation rates, which are excellent means for probing structure, bonding, and dynamics of both solute and solvent molecules. This article describes the use of 17O NMR spectroscopy in probing the solvation structures of various electrolyte systems ranging from transition metal ions in aqueous solution to lithium cations in organic solvent mixtures.
  • Bin Liu, Wu Xu, Pengfei Yan, Sun Tai Kim, Mark H. Engelhard, Xiuliang Sun, Donghai Mei, Jaephil Cho, Chongmin Wang, Ji-Guang Zhang."Stabilization of Li Metal Anode in DMSO-Based Electrolytes via Optimization of Salt–Solvent Coordination for Li–O2 Batteries."Advanced Energy Materials 7 (14) (March 2017).
    Abstract: The conventional electrolyte of 1 m lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in dimethyl sulfoxide (DMSO) is unstable against the Li metal anode and therefore cannot be used directly in practical Li–O2 batteries. Here, we demonstrate that a highly concentrated electrolyte based on LiTFSI in DMSO (with a molar ratio of 1:3) can greatly improve the stability of the Li metal anode against DMSO and significantly improve the cycling stability of Li–O2 batteries. This highly concentrated electrolyte contains no free DMSO solvent molecules, but only complexes of (TFSI−)a-Li+-(DMSO)b (where a + b = 4), and thus enhances their stability with Li metal anodes. In addition, such salt–solvent complexes have higher Gibbs activation energy barriers than the free DMSO solvent molecules, indicating improved stability of the electrolyte against the attack of superoxide radical anions. Therefore, the stability of this highly concentrated electrolyte at both Li metal anodes and carbon-based air electrodes has been greatly enhanced, resulting in improved cycling performance of Li–O2 batteries. The fundamental stability of the electrolyte in the absence of free-solvent against the chemical and electrochemical reactions can also be used to enhance the stability of other electrochemical systems.
  • D. Lin, J. Zhao, J. Sun, H. Yao, Y. Liu, K. Yan, Y. Cui. "Three-dimensional stable lithium metal anode with nanoscale lithium islands embedded in ionically conductive solid matrix" Proc. Natl. Acad.Sci. 114: 4613-4618(Mar.2017).

    Abstract:Rechargeable batteries based on lithium (Li) metal chemistry are attractive for next-generation electrochemical energy storage. Nevertheless, excessive dendrite growth, infinite relative dimension change, severe side reactions, and limited power output severely impede their practical applications. Although exciting progress has been made to solve parts of the above issues, a versatile solution is still absent. Here, a Li-ion conductive framework was developed as a stable “host” and efficient surface protection to address the multifaceted problems, which is a significant step forward compared with previous host concepts. This was fulfilled by reacting overstoichiometry of Li with SiO. The as-formed LixSi–Li2O matrix would not only enable constant electrode-level volume, but also protect the embedded Li from direct exposure to electrolyte. Because uniform Li nucleation and deposition can be fulfilled owing to the high-density active Li domains, the as-obtained nanocomposite electrode exhibits low polarization, stable cycling, and high-power output (up to 10 mA/cm2) even in carbonate electrolytes. The Li–S prototype cells further exhibited highly improved capacity retention under high-power operation (∼600 mAh/g at 6.69 mA/cm2). The all-around improvement on electrochemical performance sheds light on the effectiveness of the design principle for developing safe and stable Li metal anodes.

     

  • Chang HJ ,Canfield N L,Jung K ,Sprenkle V L,Li G. "Advanced Na-NiCl2 Battery Using Nickel-Coated Graphite with Core-Shell Microarchitecture." ACS Applied Materials & Interfaces 9 (13): 11609-11614 (March 2017).
    Abstract:Stationary electric energy storage devices (rechargeable batteries) have gained increasing prominence due to great market needs, such as smoothing the fluctuation of renewable energy resources and supporting the reliability of the electric grid. With regard to raw materials availability, sodium-based batteries are better positioned than lithium batteries due to the abundant resource of sodium in Earth's crust. However, the sodium-nickel chloride (Na-NiCl2) battery, one of the most attractive stationary battery technologies, is hindered from further market penetration by its high material cost (Ni cost) and fast material degradation at its high operating temperature. Here, we demonstrate the design of a core�shell microarchitecture, nickel-coated graphite, with a graphite core to maintain electrochemically active surface area and structural integrity of the electron percolation pathway while using 40% less Ni than conventional Na-NiCl2 batteries. An initial energy density of 133 Wh/kg (at ~C/4) and energy efficiency of 94% are achieved at an intermediate temperature of 190°C.
  • Jianming Zheng, Mark H. Engelhard, Donghai Mei, Shuhong Jiao, Bryant J. Polzin, Ji-Guang Zhang, Wu Xu."Electrolyte additive enabled fast charging and stable cycling lithium metal batteries."Nature Energy 2, Article number: 17012 (March 2017).
    Abstract: Batteries using lithium (Li) metal as anodes are considered promising energy storage systems because of their high energy densities. However, safety concerns associated with dendrite growth along with limited cycle life, especially at high charge current densities, hinder their practical uses. Here we report that an optimal amount (0.05 M) of LiPF6 as an additive in LiTFSI–LiBOB dual-salt/carbonate-solvent-based electrolytes significantly enhances the charging capability and cycling stability of Li metal batteries. In a Li metal battery using a 4-V Li-ion cathode at a moderately high loading of 1.75 mAh cm−2, a cyclability of 97.1% capacity retention after 500 cycles along with very limited increase in electrode overpotential is accomplished at a charge/discharge current density up to 1.75 mA cm−2. The fast charging and stable cycling performances are ascribed to the generation of a robust and conductive solid electrolyte interphase at the Li metal surface and stabilization of the Al cathode current collector.
  • Shidong Song, Wu Xu, Ruiguo Cao, Langli Luo, Mark H. Engelhard, Mark E. Bowden, Bin Liu, Luis Estevez, Chongmin Wang, Ji-Guang Zhang."B4C as a stable non-carbon-based oxygen electrode material for lithium-oxygen batteries."Nano Energy 33: 195-204 (March 2017).
    Abstract: Lithium-oxygen (Li-O2) batteries have extremely high theoretical specific capacities and energy densities when compared with Li-ion batteries. However, the instability of both electrolyte and carbon-based oxygen electrode related to the nucleophilic attack of reduced oxygen species during oxygen reduction reaction and the electrochemical oxidation during oxygen evolution reaction are recognized as the major challenges in this field. Here we report the application of boron carbide (B4C) as the non-carbon based oxygen electrode material for aprotic Li-O2 batteries. B4C has high resistance to chemical attack, good conductivity, excellent catalytic activity and low density that are suitable for battery applications. The electrochemical activity and chemical stability of B4C are systematically investigated in an aprotic electrolyte. Li-O2 cells using B4C-based air electrodes exhibit better cycling stability than those using carbon nanotube- and titanium carbide-based air electrodes in the electrolyte of 1 M lithium trifluoromethanesulfonate in tetraglyme. The performance degradation of B4C-based electrode is mainly due to the loss of active sites on B4C electrode during cycles as identified by the structure and composition characterizations. These results clearly demonstrate that B4C is a very promising alternative oxygen electrode material for aprotic Li-O2 batteries. It can also be used as a standard electrode to investigate the stability of electrolytes.
  • Soto F A,Yan P ,Engelhard M H,Marzouk A ,Wang C ,Liu J ,Sprenkle V L,El-Mellouhi F ,Balbuena P B,Li X. "Tuning the Solid Electrolyte Interphase for Selective Li- and Na-Ion Storage in Hard Carbon." Advanced Materials 29 (18): 1606860 (March 2017).
    Abstract:Solid-electrolyte interphase (SEI) films with controllable properties are highly desirable for improving battery performance. In this paper, a combined experimental and theoretical approach is used to study SEI films formed on hard carbon in Li- and Na-ion batteries. It is shown that a stable SEI layer can be designed by precycling an electrode in a desired Li- or Na-based electrolyte, and that ionic transport can be kinetically controlled. Selective Li- and Na-based SEI membranes are produced using Li- or Na-based electrolytes, respectively. The Na-based SEI allows easy transport of Li ions, while the Li-based SEI shuts off Na-ion transport. Na-ion storage can be manipulated by tuning the SEI layer with film-forming electrolyte additives, or by preforming an SEI layer on the electrode surface. The Na specific capacity can be controlled to < 25 mAh g-1;= 1/10 of the normal capacity (250 mAh g-1). Unusual selective/preferential transport of Li ions is demonstrated by preforming an SEI layer on the electrode surface and corroborated with a mixed electrolyte. This work may provide new guidance for preparing good ion-selective conductors using electrochemical approaches.
  • Tianyuan Ma, Gui-Liang Xu, Yan Li, Li Wang, Xiangming He, Jianming Zheng, Jun Liu, Mark H. Engelhard, Peter Zapol, Larry A. Curtiss, Jacob Jorne, Khalil Amine, Zonghai Chen."Revisiting the Corrosion of the Aluminum Current Collector in Lithium-Ion Batteries."Journal of Physical Chemistry Letters 8 (5): 1072-1077 (February 2017).
    Abstract: The corrosion of aluminum current collectors and the oxidation of solvents at a relatively high potential have been widely investigated with an aim to stabilize the electrochemical performance of lithium-ion batteries using such components. The corrosion behavior of aluminum current collectors was revisited using a home-build high-precision electrochemical measurement system, and the impact of electrolyte components and the surface protection layer on aluminum foil was systematically studied. The electrochemical results showed that the corrosion of aluminum foil was triggered by the electrochemical oxidation of solvent molecules, like ethylene carbonate, at a relative high potential. The organic radical cations generated from the electrochemical oxidation are energetically unstable and readily undergo a deprotonation reaction that generates protons and promotes the dissolution of Al3+ from the aluminum foil. This new reaction mechanism can also shed light on the dissolution of transitional metal at high potentials.
  • Duan, W, RS Vemuri, D Hu, Z Yang, X Wei. "A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery." Journal of Visualized Experiments 120 (Feb. 2017).
    Abstract:Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid and deployment of renewable energy technologies. Among the many flow battery chemistries, non-aqueous flow batteries have the potential to achieve high energy density because of the broad voltage windows of non-aqueous electrolytes. However, significant technical hurdles exist currently limiting non-aqueous flow batteries to demonstrate their full potential, such as low redox concentrations, low operating currents, under-explored battery status monitoring, etc. In an attempt to address these limitations, we recently reported a non-aqueous flow battery based on a highly soluble, redox-active organic nitronyl nitroxide radical compound, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO). This redox material exhibits an ambipolar electrochemical property, and therefore can serve as both anolyte and catholyte redox materials to form a symmetric flow battery chemistry. Moreover, we demonstrated that Fourier transform infrared (FTIR) spectroscopy could measure the PTIO concentrations during the PTIO flow battery cycling and offer reasonably accurate detection of the battery state of charge (SOC), as cross-validated by electron spin resonance (ESR) measurements. Herein we present a video protocol for the electrochemical evaluation and SOC diagnosis of the PTIO symmetric flow battery. With a detailed description, we experimentally demonstrated the route to achieve such purposes. This protocol aims to spark more interests and insights on the safety and reliability in the field of non-aqueous redox flow batteries.
  • Shidong Song, Wu Xu, Jianming Zheng, Langli Luo, Mark H. Engelhard, Mark E. Bowden, Bin Liu, Chongmin Wang, Ji-Guang Zhang."Complete Decomposition of Li2CO3 in Li–O2 Batteries Using Ir/B4C as Noncarbon-Based Oxygen Electrode."Nano Letters 17 (3): 1417-1424 (February 2017).
    Abstract: Instability of carbon-based oxygen electrodes and incomplete decomposition of Li2CO3 during charge process are critical barriers for rechargeable Li–O2 batteries. Here we report the complete decomposition of Li2CO3 in Li–O2 batteries using the ultrafine iridium-decorated boron carbide (Ir/B4C) nanocomposite as a noncarbon based oxygen electrode. The systematic investigation on charging the Li2CO3 preloaded Ir/B4C electrode in an ether-based electrolyte demonstrates that the Ir/B4C electrode can decompose Li2CO3 with an efficiency close to 100% at a voltage below 4.37 V. In contrast, the bare B4C without Ir electrocatalyst can only decompose 4.7% of the preloaded Li2CO3. Theoretical analysis indicates that the high efficiency decomposition of Li2CO3 can be attributed to the synergistic effects of Ir and B4C. Ir has a high affinity for oxygen species, which could lower the energy barrier for electrochemical oxidation of Li2CO3. B4C exhibits much higher chemical and electrochemical stability than carbon-based electrodes and high catalytic activity for Li–O2 reactions. A Li–O2 battery using Ir/B4C as the oxygen electrode material shows highly enhanced cycling stability than those using the bare B4C oxygen electrode. Further development of these stable oxygen-electrodes could accelerate practical applications of Li–O2 batteries.
  • Dongping Lu, Jinhui Tao, Pengfei Yan, Wesley A. Henderson, Qiuyan Li, Yuyan Shao, Monte L. Helm, Oleg Borodin, Gordon L. Graff, Bryant Polzin, Chongmin Wang, Mark Engelhard, Ji-Guang Zhang, James J. De Yoreo, Jun Liu, Jie Xiao."Formation of Reversible Solid Electrolyte Interface on Graphite Surface from Concentrated Electrolytes."Nano Letters 17 (3):1602-1609 (February 2017).
    Abstract: Li-ion batteries (LIB) have been successfully commercialized after the identification of ethylene-carbonate (EC)-containing electrolyte that can form a stable solid electrolyte interphase (SEI) on carbon anode surface to passivate further side reactions but still enable the transportation of the Li+ cation. These electrolytes are still utilized, with only minor changes, after three decades. However, the long-term cycling of LIB leads to continuous consumption of electrolyte and growth of SEI layer on the electrode surface, which limits the battery’s life and performance. Herein, a new anode protection mechanism is reported in which, upon changing of the cell potential, the electrolyte components at the electrode-electrolyte interface reorganize reversibly to form a transient protective surface layers on the anode. This layer will disappear after the applied potential is removed so that no permanent SEI layer is required to protect the carbon anode. This phenomenon minimizes the need for a permanent SEI layer and prevents its continuous growth and therefore may lead to largely improved performance for LIBs.
  • Li B, Liu, J. "Progress and directions in low-cost redox-flow batteries for large-scale energy storage." National Science Review 4 (1): 91-105 (Jan. 2017).
    Abstract:Compared to lithium-ion batteries, redox-flow batteries have attracted widespread attention for long-duration, large-scale energy-storage applications. This review focuses on current and future directions to address one of the most significant challenges in energy storage: reducing the cost of redox-flow battery systems. A high priority is developing aqueous systems with low-cost materials and high-solubility redox chemistries. Highly water-soluble inorganic redox couples are important for developing technologies that can provide high energy densities and low-cost storage. There is also great potential to rationally design organic redox molecules and fine-tune their properties for both aqueous and non-aqueous systems. While many new concepts begin to blur the boundary between traditional batteries and redox-flow batteries, breakthroughs in identifying/developing membranes and separators and in controlling side reactions on electrode surfaces also are needed.

2016

  • Fu S ,Zhu C ,Song J ,Engelhard M H,Li X ,Zhang P ,Xia H ,Du D ,Lin Y. "Template-directed synthesis of nitrogen- and sulfur-codoped carbon nanowire aerogels with enhanced electrocatalytic performance for oxygen reduction." Nano Research 10 (6): 1888-1895 (Dec. 2016).
    Abstract:Heteroatom doping, precise composition control, and rational morphology design are efficient strategies for producing novel nanocatalysts for the oxygen reduction reaction (ORR) in fuel cells. Herein, a cost-effective approach to synthesize nitrogen- and sulfur-codoped carbon nanowire aerogels using a hard templating method is proposed. The aerogels prepared using a combination of hydrothermal treatment and carbonization exhibit good catalytic activity for the ORR in alkaline solution. At the optimal annealing temperature and mass ratio between the nitrogen and sulfur precursors, the resultant aerogels show comparable electrocatalytic activity to that of a commercial Pt/C catalyst for the ORR. Importantly, the optimized catalyst shows much better long-term stability and satisfactory tolerance for the methanol crossover effect. These codoped aerogels are expected to have potential applications in fuel cells.
  • Shamie J S,Liu C H,Shaw L L,Sprenkle V L. "New Mechanism for the Reduction of Vanadyl Acetylacetonate to Vanadium Acetylacetonate for Room Temperature Flow Batteries." ChemSusChem 10 (3): 533-540 (Dec. 2016).
    Abstract:In this study, a new mechanism for the reduction of vanadyl acetylacetonate, VO(acac)2, to vanadium acetylacetonate, V(acac)3, is introduced. V(acac)3 has been studied for use in redox flow batteries (RFBs) for some time; however, contamination by moisture leads to the formation of VO(acac)2. In previous work, once this transformation occurs, it is no longer reversible because there is a requirement for extreme low potentials for the reduction to occur. Here, we propose that, in the presence of excess acetylacetone (Hacac) and free protons (H+), the reduction can take place between 2.25 and 1.5 V versus Na/Na+ via a one-electron-transfer reduction. This reduction can take place in situ during discharge in a novel hybrid Na-based flow battery (HNFB) with a molten Na-Cs alloy as the anode. The in situ recovery of V(acac)3 during discharge is shown to allow the Coulombic efficiency of the HNFB to be =100% with little or no capacity decay over cycles. In addition, utilizing two-electron-transfer redox reactions (i.e., V3+/V4+ and V2+/V3+ redox couples) per V ion to increase the energy density of RFBs becomes possible owing to the in situ recovery of V(acac)3 during discharge. The concept of in situ recovery of material can lead to more advances in maintaining the cycle life of RFBs in the future.
  • Han KS ,Rajput NN ,Vijayakumar M ,Wei X ,Wang W ,Hu J Z,Persson K A,Mueller K T. "Preferential Solvation of an Asymmetric Redox Molecule" Journal of Physical Chemistry C 120 (49): 27834-27839 (Nov. 2016)
    Abstract: The fundamental correlations between solubility and solvation structure for the electrolyte system comprising N-(ferrocenylmethyl)-N,N-dimethyl-N-ethylammonium bistrifluoromethylsulfonimide (Fc1N112-TFSI) dissolved in a ternary carbonate solvent mixture is analyzed using combined NMR relaxation and computational methods. Probing the evolution of the solvent–solvent, ion–solvent and ion–ion interactions with an increase in solute concentration provides a molecular level understanding of the solubility limit of the Fc1N112-TFSI system. An increase in solute concentration leads to pronounced Fc1N112-TFSI contact-ion pair formation by diminishing solvent–solvent and ion–solvent type interactions. At the solubility limit, the precipitation of solute is initiated through agglomeration of contact-ion pairs due to overlapping solvation shells.
  • Murugesan, V, Q Luo, R Lloyd, Z Nie, X Wei, B Li, VL Sprenkle, JD Londono, M Unlu, W Wang. "Tuning the Perfluorosulfonic Acid Membrane Morphology for Vanadium Redox-Flow Batteries."ACS Applied Materials and Interfaces 8 (50): 34327-34334 (Nov. 2016).
    Abstract: The microstructure of perfluorinated sulfonic acid proton-exchange membranes such as Nafion significantly affects their transport properties and performance in a vanadium redox-flow battery (VRB). In this work, Nafion membranes with various equivalent weights ranging from 1000 to 1500 are prepared and the morphology-property-performance relationship is investigated. NMR and small-angle X-ray scattering studies revealed their composition and morphology variances, which lead to major differences in key transport properties related to proton conduction and vanadium-ion permeation. Their performances are further characterized as VRB membranes. On the basis of this understanding, a new perfluorosulfonic acid membrane is designed with optimal pore geometry and thickness, leading to higher ion selectivity and lower cost compared with the widely used Nafion 115. Excellent VRB single-cell performance (89.3% energy efficiency at 50 mA·cm-2) was achieved along with a stable cyclical capacity over prolonged cycling.
  • Park, M, J Ryu, W Wang, J Cho. "Material design and engineering of next-generation flow-battery technologies." Nature Review Materials 2 (Nov. 2016).
    Abstract: Spatial separation of the electrolyte and electrode is the main characteristic of flow-battery technologies, which liberates them from the constraints of overall energy content and the energy/power ratio. The concept of a flowing electrolyte not only presents a cost-effective approach for large-scale energy storage, but has also recently been used to develop a wide range of new hybrid energy storage and conversion systems. The advent of flow-based lithium-ion, organic redox-active materials, metal-air cells and photoelectrochemical batteries promises new opportunities for advanced electrical energy-storage technologies. In this Review, we present a critical overview of recent progress in conventional aqueous redox-flow batteries and next-generation flow batteries, highlighting the latest innovative alternative materials. We outline their technical feasibility for use in long-term and large-scale electrical energy-storage devices, as well as the limitations that need to be overcome, providing our view of promising future research directions in the field of redox-flow batteries.
  • Sookyung Jeong, Xiaolin Li, Jianming Zheng, Pengfei Yan, Ruiguo Cao, Hee Joon Jung, Chongmin Wang, Jun Liu, Ji-Guang Zhang."Hard carbon coated nano-Si/graphite composite as a high performance anode for Li-ion batteries."Journal of Power Sources 329: 323-329 (October 2016).
    Abstract: With the ever-increasing demands for higher energy densities in Li-ion batteries, alternative anodes with higher reversible capacity are required to replace the conventional graphite anode. Here, we demonstrate a cost-effective hydrothermal carbonization approach to prepare a hard carbon coated nano-Si/graphite (HC-nSi/G) composite as a high performance anode for Li-ion batteries. In this hierarchical structured composite, the hard carbon coating not only provides an efficient pathway for electron transfer, but also alleviates the volume variation of Si during charge/discharge processes. The HC-nSi/G composite electrode shows excellent performance, including a high specific capacity of 878.6 mAh g−1 based on the total weight of composite, good rate performance, and a decent cycling stability, which is promising for practical applications.
  • Mehdi, BL, A Stevens, J Qian, C Park, W Xu, WA Henderson, J Zhang, KT Mueller, ND Browning. "The Impact of Li Grain Size on Coulombic Efficiency in Li Batteries."Scientific Reports 6: Article number 34267 (Oct. 2016).
    Abstract:One of the most promising means to increase the energy density of state-of-the-art lithium Li-ion batteries is to replace the graphite anode with a Li metal anode. While the direct use of Li metal may be highly advantageous, at present its practical application is limited by issues related to dendrite growth and low Coulombic efficiency, CE. Here operando electrochemical scanning transmission electron microscopy (STEM) is used to directly image the deposition/stripping of Li at the anode-electrolyte interface in a Li-based battery. A non-aqueous electrolyte containing small amounts of H2O as an additive results in remarkably different deposition/stripping properties as compared to the “dry” electrolyte when operated under identical electrochemical conditions. The electrolyte with the additive deposits more Li during the first cycle, with the grain sizes of the Li deposits being significantly larger and more variable. The stripping of the Li upon discharge is also more complete, i.e., there is a higher cycling CE. This suggests that larger grain sizes are indicative of better performance by leading to more uniform Li deposition and an overall decrease in the formation of Li dendrites and side reactions with electrolyte components, thus potentially paving the way for the direct use of Li metal in battery technologies.
  • Cheng, Y, HJ Chang, H Dong, D Choi, VL Sprenkle, J Liu, Y Yao, G Li. "Rechargeable Mg-Li hybrid batteries: status and challenges."Journal of Materials Research 31 (20) :3125-3141 (Oct. 2016).
    Abstract: A magnesium-lithium (Mg-Li) hybrid battery consists of an Mg metal anode, a Li+ intercalation cathode, and a dual-salt electrolyte with both Mg2+ and Li+ ions. The demonstration of this technology has appeared in literature for few years and great advances have been achieved in terms of electrolytes, various Li cathodes, and cell architectures. Despite excellent battery performances including long cycle life, fast charge/discharge rate, and high Coulombic efficiency, the overall research of Mg-Li hybrid battery technology is still in its early stage, and also raised some debates on its practical applications. In this regard, we focus on a comprehensive overview of Mg-Li hybrid battery technologies developed in recent years. Detailed discussion of Mg-Li hybrid operating mechanism based on experimental results from literature helps to identify the current status and technical challenges for further improving the performance of Mg-Li hybrid batteries. Finally, a perspective for Mg-Li hybrid battery technologies is presented to address strategic approaches for existing technical barriers that need to be overcome in future research direction.
  • Wang Y, P Yan, J Xiao, X Lu, J Zhang, VL Sprenkle. "Effect of Al2O3 on the sintering of garnet-type Li6.5La3Zr1.5Ta0.5O12."Solid State Ionics 294: 108-115 (Oct. 2016).
    Abstract:It is widely recognized that Al plays a dual role in the fabrication of garnet-type solid electrolytes, i.e., as a dopant that stabilizes the cubic structure and a sintering aid that facilitates the densification. However, the sintering effect of Al2O3 has not been well understood so far because Al is typically "unintentionally" introduced into the sample from the crucible during the fabrication process. In this study, we have investigated the sintering effect of Al on the phase composition, microstructure, and ionic conductivity of Li6.5La3Zr1.5Ta0.5O12 by using an Al-free crucible and intentionally adding various amounts of y-Al2O3. It was found that the densification of Li6.5La3Zr1.5Ta0.5O12 occurred via liquid-phase sintering, with evidence of morphology change among different compositions. Among all of the compositions, samples with 0.05mol Al per unit formula of garnet oxide (i.e., 0.3wt% Al2O3) exhibited the optimal microstructure and the highest total ionic conductivity of 5x10-4Scm-1 at room temperature.
  • Choi D, C Zhu, S Fu, D Du, MH Engelhard, Y Lin. "Electrochemically Controlled Ion-exchange Property of Carbon Nanotubes/Polypyrrole Nanocomposite in Various Electrolyte Solutions." Electroanalysis 29 (3): 929-936 (Sept. 2016).
    Abstract: The electrochemically controlled ion-exchange properties of multi-wall carbon nanotube (MWNT)/electronically conductive polypyrrole (PPy) polymer composite in the various electrolyte solutions have been investigated. The ion-exchange behavior, rate and capacity of the electrochemically deposited polypyrrole with and without carbon nanotube (CNT) were compared and characterized using cyclic voltammetry (CV), chronoamperometry (CA), electrochemical quartz crystal microbalance (EQCM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It has been found that the presence of carbon nanotube backbone resulted in improvement in ion-exchange rate, stability of polypyrrole, and higher anion loading capacity per PPy due to higher surface area, electronic conductivity, porous structure of thin film, and thinner film thickness providing shorter diffusion path. Chronoamperometric studies show that electrically switched anion exchange could be completed more than 10 times faster than pure PPy thin film. The anion selectivity of CNT/PPy film is demonstrated using X-ray photoelectron spectroscopy (XPS).
  • Fu, S, C Zhu, J Song, MH Engelhard, X Li, D Du, Y Lin. "Highly Ordered Mesoporous Bimetallic Phosphides as Efficient Oxygen Evolution Electrocatalysts."ACS Energy Letters 1 (4) :792-796 (Sept. 2016).
    Abstract: Oxygen evolution from water using earth-abundant transition-metal-based catalysts is of importance for the commercialization of water electrolyzers. Herein, we report a hard templating method to synthesize transition metal phosphides with uniform shape and size. By virtue of the structural feature, synergistic effects among metals, and the in situ formed active species, the as-prepared phosphides with optimized composition present enhanced electrocatalytic performance toward the oxygen evolution reaction in alkaline solution. In detail, the catalyst with optimized composition reaches a current density of 10 mA/cm2 at a potential of 1.511 V vs a reversible hydrogen electrode, which is much lower than that of a commercial RuO2 catalyst. Our work offers a new strategy to optimize the catalysts for water splitting by controlling the morphology and composition.
  • Li X, P Yan, MH Engelhard, AJ Crawford, V Viswanathan, C Wang, J Liu, VL Sprenkle. "The importance of solid electrolyte interphase formation for long cycle stability full-cell Na-ion batteries."Nano Energy 27: 664-672 (Sept. 2016).
    Abstract: Na-ion battery, as an alternative high-efficiency and low-cost energy storage device to Li-ion battery, has attracted wide interest for electrical grid and vehicle applications. However, demonstration of a full-cell battery with high energy and long cycle life remains a significant challenge. Here, we investigated the role of solid electrolyte interphase (SEI) formation on both cathodes and anodes and revealed a potential way to achieve long-term stability for Na-ion battery full-cells. Pre-cycling of cathodes and anodes leads to preformation of SEI, and hence mitigates the consumption of Na ions in full-cells. The example full-cell of Na0.44MnO2-hard carbon with pre-cycled and capacity-matched electrodes can deliver a specific capacity of ~116 mAh/g based on Na0.44MnO2 at 1 C rate (1 C=120 mA/g). The corresponding specific energy is ~313 Wh/kg based on the cathode. Excellent cycling stability with ~77% capacity retention over 2000 cycles was demonstrated at 2 C rate. Our work represents a leap forward in Na-ion battery development.
  • Wei X, W Duan, J Huang, L Zhang, B Li, DM Reed, W Xu, VL Sprenkle. "A High-Current, Stable Nonaqueous Organic Redox Flow Battery."ACS Energy Letters 1: 705-711 (Sept. 2016).
    Abstract:Nonaqueous redox flow batteries are promising in pursuit of high energy density storage systems owing to the broad voltage windows (>2 V) but currently are facing key challenges such as limited cyclability and rate performance. To address these technical hurdles, here we report the nonaqueous organic flow battery chemistry based on N-methylphthalimide anolyte and 2,5-di-tert-butyl-1-methoxy-4-[2'-methoxyethoxy]benzene catholyte, which harvests a theoretical cell voltage of 2.30 V. The redox flow chemistry exhibits excellent cycling stability under both cyclic voltammetry and flow cell tests upon repeated cycling. A series of Daramic and Celgard porous separators are evaluated in this organic flow battery, which enable the cells to be operated at greatly improved current densities as high as 50 mA·cm-2 compared to those of other nonaqueous flow systems. The stable cyclability and high-current operations of the organic flow battery system represent significant progress in the development of promising nonaqueous flow batteries.
  • Huang, J, B Pan, W Duan, X Wei, RS Assary, L Su, FR Brushett, L Cheng, C Liao, MS Ferrandon, W Wang, Z Zhang, AK Burrell, LA Curtiss, IA Shkrob, JS Moore, L Zhang. "The lightest organic radical cation for charge storage in redox flow batteries." Scientific Reports 6: Article number 32102 (Aug. 2016).
    Abstract:In advanced electrical grids of the future, electrochemically rechargeable fluids of high energy density will capture the power generated from intermittent sources like solar and wind. To meet this outstanding technological demand there is a need to understand the fundamental limits and interplay of electrochemical potential, stability, and solubility in low-weight redox-active molecules. By generating a combinatorial set of 1,4-dimethoxybenzene derivatives with different arrangements of substituents, we discovered a minimalistic structure that combines exceptional long-term stability in its oxidized form and a record-breaking intrinsic capacity of 161 mAh/g. The nonaqueous redox flow battery has been demonstrated that uses this molecule as a catholyte material and operated stably for 100 charge/discharge cycles. The observed stability trends are rationalized by mechanistic considerations of the reaction pathways.
  • Qian, J, BD Adams, J Zheng, W Xu, WA Henderson, J Wang, ME Bowden, S Xu, JZ Hu, J Zhang. "Anode-Free Rechargeable Lithium Metal Batteries." Advanced Functional Materials 26 (39): 7094-7102 (Aug. 2016).
    Abstract:Anode-free rechargeable lithium (Li) batteries (AFLBs) are phenomenal energy storage systems due to their significantly increased energy density and reduced cost relative to Li-ion batteries, as well as ease of assembly because of the absence of an active (reactive) anode material. However, significant challenges, including Li dendrite growth and low cycling Coulombic efficiency (CE), have prevented their practical implementation. Here, an anode-free rechargeable lithium battery based on a Cu||LiFePO4 cell structure with an extremely high CE (>99.8%) is reported for the first time. This results from the utilization of both an exceptionally stable electrolyte and optimized charge/discharge protocols, which minimize the corrosion of the in situly formed Li metal anode.
  • Cheng, L, LA Curtiss, KR Zavadil, AA Gewirth, Y Shao, KG Gallagher. "Sparingly Solvating Electrolytes for High Energy Density Lithium–Sulfur Batteries." ACS Energy Letters 1 (3): 503-509 (July 2016).
    Abstract:Moving to lighter and less expensive battery chemistries compared to contemporary lithium-ion requires the control of energy storage mechanisms based on chemical transformations rather than intercalation. Lithium–sulfur (Li/S) has tremendous theoretical specific energy, but contemporary approaches to control this solution-mediated, precipitation–dissolution chemistry require large excesses of electrolyte to fully solubilize the polysulfide intermediates. Achieving reversible electrochemistry under lean electrolyte operation is the most promising path for Li/S to move beyond niche applications to potentially transformational performance. An emerging Li/S research area is the use of sparingly solvating electrolytes and the creation of design rules for discovering new electrolyte systems that fundamentally decouple electrolyte volume from sulfur and polysulfide reaction mechanism. This Perspective presents an outlook for sparingly solvating electrolytes as a key path forward for long-lived, high energy density Li/S batteries including an overview of this promising new concept and some strategies for accomplishing it.
  • Bin Liu, Pengfei Yan, Wu Xu, Jianming Zheng, Yang He, Langli Luo, Mark E. Bowden, Chongmin Wang, Ji-Guang Zhang."Electrochemically Formed Ultrafine Metal Oxide Nanocatalysts for High-Performance Lithium–Oxygen Batteries."Nano Letters 16 (8): 4932-4939 (July 2016).
    Abstract: Lithium–oxygen (Li–O2) batteries have an extremely high theoretical specific energy density when compared with conventional energy-storage systems. However, practical application of the Li–O2 battery system still faces significant challenges. In this work, we report a new approach for synthesis of ultrafine metal oxide nanocatalysts through an electrochemical prelithiation process. This process reduces the size of NiCo2O4 (NCO) particles from 20–30 nm to a uniformly distributed domain of ∼2 nm and significantly improves their catalytic activity. Structurally, the prelithiated NCO nanowires feature ultrafine NiO/CoO nanoparticles that are highly stable during prolonged cycles in terms of morphology and particle size, thus maintaining an excellent catalytic effect to oxygen reduction and evolution reactions. A Li–O2 battery using this catalyst demonstrated an initial capacity of 29 280 mAh g–1 and retained a capacity of >1000 mAh g–1 after 100 cycles based on the weight of the NCO active material. Direct in situ transmission electron microscopy observations conclusively revealed the lithiation/delithiation process of as-prepared NCO nanowires and provided in-depth understanding for both catalyst and battery chemistries of transition-metal oxides. This unique electrochemical approach could also be used to form ultrafine nanoparticles of a broad range of materials for catalyst and other applications.
  • Pan, H, KS Han, M Vijayakumar, J Xiao, R Cao, J Chen, J Zhang, KT Mueller, Y Shao, J Liu. "Ammonium Additives to Dissolve Lithium Sulfide through Hydrogen Binding for High-Energy Lithium–Sulfur Batteries."Applied Materials & Interfaces 9 (5): 4290-4295 (July 2016).
    Abstract:In rechargeable Li–S batteries, the uncontrollable passivation of electrodes by highly insulating Li2S limits sulfur utilization, increases polarization, and decreases cycling stability. Dissolving Li2S in organic electrolyte is a facile solution to maintain the active reaction interface between electrolyte and sulfur cathode, and thus address the above issues. Herein, ammonium salts are demonstrated as effective additives to promote the dissolution of Li2S to 1.25 M in DMSO solvent at room temperature. NMR measurements show that the strong hydrogen binding effect of N–H groups plays a critical role in dissolving Li2S by forming complex ligands with S2– anions coupled with the solvent’s solvating surrounding. Ammonium additives in electrolyte can also significantly improve the oxidation kinetics of Li2S, and therefore enable the direct use of Li2S as cathode material in Li–S battery system in the future. This provides a new approach to manage the solubility of lithium sulfides through cation coordination with sulfide anion.
  • Hongfa Xiang, Pengcheng Shi, Priyanka Bhattacharya, Xilin Chen, Donghai Mei, Mark E. Bowden, Jianming Zheng, Ji-Guang Zhang, Wu Xu."Enhanced charging capability of lithium metal batteries based on lithium bis(trifluoromethanesulfonyl)imide-lithium bis(oxalato)borate dual-salt electrolytes."Journal of Power Sources 318: 170-177 (June 2016).
    Abstract: Rechargeable lithium (Li) metal batteries with conventional LiPF6-carbonate electrolytes have been reported to fail quickly at charging current densities of about 1.0 mA cm−2 and above. In this work, we demonstrate the rapid charging capability of Li||LiNi0.8Co0.15Al0.05O2 (NCA) cells can be enabled by a dual-salt electrolyte of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(oxalato)borate (LiBOB) in a carbonate solvent mixture. The cells using the LiTFSI-LiBOB dual-salt electrolyte significantly outperform those using the LiPF6 electrolyte at high charging current densities. At the charging current density of 1.50 mA cm−2, the Li||NCA cells with the dual-salt electrolyte can still deliver a discharge capacity of 131 mAh g−1 and a capacity retention of 80% after 100 cycles. The Li||NCA cells with the LiPF6 electrolyte start to show fast capacity fading after the 30th cycle and only exhibit a low capacity of 25 mAh g−1 and a low retention of 15% after 100 cycles. The reasons for the good chargeability and cycling stability of the cells using the LiTFSI-LiBOB dual-salt electrolyte can be attributed to the good film-formation ability of the electrolyte on the Li metal anode and the highly conductive nature of the sulfur-rich interphase layer.
  • Xuyong Feng, Hailin Zou, Hongfa Xiang, Xin Guo, Tianpei Zhou, Yucheng Wu, Wu Xu, Pengfei Yan, Chongmin Wang, Ji-Guang Zhang, Yan Yu."Ultrathin Li4Ti5O12 Nanosheets as Anode Materials for Lithium and Sodium Storage."ACS Applied Materials & Interfaces 8 (26): 16718-16726 (June 2016).
    Abstract: Ultrathin Li4Ti5O12 (LTO) nanosheets with ordered microstructures were prepared via a polyether-assisted hydrothermal process. Pluronic P123, a polyether, can impede the growth of Li2TiO3 in the precursor and also act as a structure-directing agent to facilitate the (Li1.81H0.19)Ti2O5·2H2O precursor to form the LTO nanosheets with the ordered microstructure. Moreover, the addition of P123 can suppress the stacking of LTO nanosheets during calcining of the precursor, and the thickness of the nanosheets can be controlled to be about 4 nm. The microstructure of the as-prepared ultrathin and ordered nanosheets is helpful for Li+ or Na+ diffusion and charge transfer through the particles. Therefore, the ultrathin P123-assisted LTO (P-LTO) nanosheets show a rate capability much higher than that of the LTO sample without P123 in a Li battery with over 130 mAh g–1 of capacity remaining at the 64C rate. For intercalation of larger size Na+ ions, the P-LTO still exhibits a capacity of 115 mAh g–1 at a current rate of 10 C and a capacity retention of 96% after 400 cycles.
  • Cheng Y, L Luo, L Zhong, J Chen, B Li, W Wang, SX Mao, C Wang, VL Sprenkle, G Li, J Liu. "Highly Reversible Zinc-Ion Intercalation into Chevrel Phase Mo6S8 Nanocubes and Applications for Advanced Zinc-Ion Batteries."ACS Applied Materials and Interfaces 8 (22):13673-13677 (June 2016).
    Abstract: This work describes the synthesis of Chevrel phase Mo6S8 nanocubes and its application as the anode material for rechargeable Zn-ion batteries. Mo6S8 can host Zn(2+) ions reversibly in both aqueous and nonaqueous electrolytes with specific capacities around 90 mAh/g, and exhibited remarkable intercalation kinetics and cyclic stability. In addition, we assembled full cells by integrating Mo6S8 anodes with zinc-polyiodide (I(-)/I3(-))-based catholytes, and demonstrated that such full cells were also able to deliver outstanding rate performance and cyclic stability. This first demonstration of a zinc-intercalating anode could inspire the design of advanced Zn-ion batteries.
  • Li B, J Liu, Z Nie, W Wang, DM Reed, J Liu, P McGrail, VL Sprenkle. "Metal-Organic Frameworks as Highly Active Electrocatalysts for High-Energy Density, Aqueous Zinc-Polyiodide Redox Flow Batteries." Nano Letters 16 (7): 4335-4340 (June 2016).
    Abstract: The new aqueous zinc-polyiodide redox flow battery (RFB) system with highly soluble active materials as well as ambipolar and bifunctional designs demonstrated significantly enhanced energy density, which shows great potential to reduce RFB cost. However, the poor kinetic reversibility and electrochemical activity of the redox reaction of I3-/I- couples on graphite felts (GFs) electrode can result in low energy efficiency. Two nanoporous metal-organic frameworks (MOFs), MIL-125-NH2 and UiO-66-CH3, that have high surface areas when introduced to GF surfaces accelerated the I3-/I- redox reaction. The flow cell with MOF-modified GFs serving as a positive electrode showed higher energy efficiency than the pristine GFs; increases of about 6.4% and 2.7% occurred at the current density of 30 mA/cm2 for MIL-125-NH2 and UiO-66-CH3, respectively. Moreover, UiO-66-CH3 is more promising due to its excellent chemical stability in the weakly acidic electrolyte. This letter highlights a way for MOFs to be used in the field of RFBs.
  • Estevez L, DM Reed, Z Nie, AM Schwarz, MI Nandasiri, JP Kizewski, W Wang, EC Thomsen, J Liu, J Zhang, VL Sprenkle, B Li. "Tunable oxygen functional groups as electrocatalysts on graphite felt surfaces for all-vanadium flow batteries."ChemSusChem 9 (12): 1455-1461 (May 2016).
    Abstract: A dual oxidative approach using O2 plasma followed by treatment with H2O2 to impart oxygen functional groups onto the surface of a graphite felt electrode. When used as electrodes for an all-vanadium redox flow battery (VRB) system, the energy efficiency of the cell is enhanced by 8.2 % at a current density of 150 mA cm-2 compared with one oxidized by thermal treatment in air. More importantly, by varying the oxidative techniques, the amount and type of oxygen groups was tailored and their effects were elucidated. It was found that O-C=O groups improve the cells performance whereas the C-O and C=O groups degrade it. The reason for the increased performance was found to be a reduction in the cell overpotential after functionalization of the graphite felt electrode. This work reveals a route for functionalizing carbon electrodes to improve the performance of VRB cells. This approach can lower the cost of VRB cells and pave the way for more commercially viable stationary energy storage systems that can be used for intermittent renewable energy storage.
  • Shen F, W Luo, J Dai, Y Yao, M Zhu, E Hitz, Y Tang, Y Chen, VL Sprenkle, X Li, L Hu. "Ultra-Thick, Low-Tortuosity, and Mesoporous Wood Carbon Anode for High-Performance Sodium-Ion Batteries."Advanced Energy Materials 6 (14) (May 2016).
    Abstract: Pyrolysis of earth-abundant wood yields to ultra-thick, low-tortuosity, and mesoporous carbon anodes for sodium-ion batteries. Such a low-tortuosity and porous structure promotes electrolyte diffusion and provides fast transport channels for Na ions, which enables a high areal capacity.
  • Prabhakaran V ,Mehdi B L,Ditto J J,Engelhard M H,Wang B ,Gunaratne KD D,Johnson D C,Browning N D,Johnson G E,Laskin J. "Rational design of efficient electrode–electrolyte interfaces for solid-state energy storage using ion soft landing" Nature Communications 7 (April 2016).
    Abstract: The rational design of improved electrode–electrolyte interfaces (EEI) for energy storage is critically dependent on a molecular-level understanding of ionic interactions and nanoscale phenomena. The presence of non-redox active species at EEI has been shown to strongly influence Faradaic efficiency and long-term operational stability during energy storage processes. Herein, we achieve substantially higher performance and long-term stability of EEI prepared with highly dispersed discrete redox-active cluster anions (50 ng of pure ∼0.75 nm size molybdenum polyoxometalate (POM) anions on 25 μg (∼0.2 wt%) carbon nanotube (CNT) electrodes) by complete elimination of strongly coordinating non-redox species through ion soft landing (SL). Electron microscopy provides atomically resolved images of a uniform distribution of individual POM species soft landed directly on complex technologically relevant CNT electrodes. In this context, SL is established as a versatile approach for the controlled design of novel surfaces for both fundamental and applied research in energy storage.
  • Crawford, A, E Thomsen, D Reed, D Stephenson, V Sprenkle, J Liu, V Viswanathan. "Development and validation of chemistry agnostic flow battery cost performance model and application to nonaqueous electrolyte systems." International Journal of Energy Research 40 (12): 1611-1623 (Apr. 2016).
    Abstract:A chemistry agnostic cost performance model is described for a nonaqueous flow battery. The model predicts flow battery performance by estimating the active reaction zone thickness at each electrode as a function of current density, state of charge, and flow rate using measured data for electrode kinetics, electrolyte conductivity, and electrode-specific surface area. Validation of the model is conducted using a 4 kW stack data at various current densities and flow rates. This model is used to estimate the performance of a nonaqueous flow battery with electrode and electrolyte properties used from the literature. The optimized cost for this system is estimated for various power and energy levels using component costs provided by vendors. The model allows optimization of design parameters such as electrode thickness, area, flow path design, and operating parameters such as power density, flow rate, and operating SOC range for various application duty cycles. A parametric analysis is done to identify components and electrode/electrolyte properties with the highest impact on system cost for various application durations. A pathway to 100$ kW h−1 for the storage system is identified. Copyright © 2016 John Wiley & Sons, Ltd.
  • Dong H, Y Li, Y Liang, G Li, CJ Sun, Y Ren, Y Lu, Y Yao. "A magnesium-sodium hybrid battery with high operating voltage."Chemical Communications 52: 8263-8266 (April 2016).
    Abstract: We report a high performance magnesium-sodium hybrid battery utilizing a magnesium-sodium dual-salt electrolyte, a magnesium anode, and a Berlin green cathode. The cell delivers an average discharge voltage of 2.2 V and a reversible capacity of 143 mA h g-1. We also demonstrate the cell with an energy density of 135 W h kg-1 and a high power density of up to 1.67 kW kg-1.
  • Cao, R, J Chen, KS Han, W Xu, D Mai, P Bhattacharya, MH Engelhard, KT Mueller, J Liu, J Zhang. "Effect of the Anion Activity on the Stability of Li Metal Anodes in Lithium-Sulfur Batteries." Advanced Functional Materials 26 (18): 3059-3066 (March 2016).
    Abstract:With the significant progress made in the development of cathodes in lithium-sulfur (Li-S) batteries, the stability of Li metal anodes becomes a more urgent challenge in these batteries. Here the systematic investigation of the stability of the anode/electrolyte interface in Li-S batteries with concentrated electrolytes containing various lithium salts is reported. It is found that Li-S batteries using LiTFSI-based electrolytes are more stable than those using LiFSI-based electrolytes. The decreased stability is because the N–S bond in the FSI− anion is fairly weak and the scission of this bond leads to the formation of lithium sulfate (LiSOx) in the presence of polysulfide species. In contrast, in the LiTFSI-based electrolyte, the lithium metal anode tends to react with polysulfide to form lithium sulfide (LiSx), which is more reversible than LiSOx formed in the LiFSI-based electrolyte. This fundamental difference in the bond strength of the salt anions in the presence of polysulfide species leads to a large difference in the stability of the anode-electrolyte interface and performance of the Li-S batteries with electrolytes composed of these salts. Therefore, anion selection is one of the key parameters in the search for new electrolytes for stable operation of Li-S batteries.
  • Chen, J, KS Han, WA Henderson, KC Lau, M Vijayakumar, T Dzwiniel, H Pan, LA Curtiss, J Xiao, KT Mueller, Y Shao, J Liu. "Restricting the Solubility of Polysulfides in Li-S Batteries Via Electrolyte Salt Selection."Advanced Energy Materials 6 (11) (March 2016).
    Abstract:Lithium 2-trifluoromethyl-4,5-dicyanoimidazole as a supporting salt in electrolytes achieves a reduced Li2S8 solubility by tuning the chemical production to Li4S8 dimer. Ab initio molecular dynamics and nuclear magnetic resonance calculation confirms the solvation structure radius increase by 20%. Combined with Li2S8 and LiNO3, the electrolyte can demonstrate a stable 300 cycling battery of practical sulfur loading.
  • Deng, X, M Hu, X Wei, W Wei, KT Mueller, Z chen, JZ Hu. "Nuclear magnetic resonance studies of the solvation structures of a high-performance nonaqueous redox flow electrolyte." Journal of Power Sources 308: 172-179 (March 2016).
    Abstract:Understanding the solvation structures of electrolytes is important for developing nonaqueous redox flow batteries that hold considerable potential for future large scale energy storage systems. The utilization of an emerging ionic-derivatived ferrocene compound, ferrocenylmethyl dimethyl ethyl ammonium bis(trifluoromethanesulfonyl)imide (Fc1N112-TFSI), has recently overcome the issue of solubility in the supporting electrolyte. In this work, 13C, 1H and 17O NMR investigations were carried out using electrolyte solutions consisting of Fc1N112-TFSI as the solute and the mixed alkyl carbonate as the solvent. It was observed that the spectra of 13C experience changes of chemical shifts while those of 17O undergo linewidth broadening, indicating interactions between solute and solvent molecules. Quantum chemistry calculations of both molecular structures and chemical shifts (13C, 1H and 17O) are performed for interpreting experimental results and for understanding the detailed solvation structures. The results indicate that Fc1N112-TFSI is dissociated at varying degrees in mixed solvent depending on concentrations. At dilute solute concentrations, most Fc1N112+ and TFSI− are fully disassociated with their own solvation shells formed by solvent molecules. At saturated concentration, Fc1N112+-TFSI- contact ion pairs are formed and the solvent molecules are preferentially interacting with the Fc rings rather than interacting with the ionic pendant arm of Fc1N112-TFSI.
  • Duan, W, RS Vemuri, JD Milshtein, S Laramie, RD Dmello, J Huang, L Zhang, D Hu, M Vijayakumar, W Wang, J Liu, RM Darling, L Thompson, K Smith, JS Moore, FR Brushett, X Wei. "A symmetric organic-based nonaqueous redox flow battery and its state of charge diagnostics by FTIR." Journal of Materials Chemistry A 4: 5448-5456 (March 2016).
    Abstract:Redox flow batteries have shown outstanding promise for grid-scale energy storage to promote utilization of renewable energy and improve grid stability. Nonaqueous battery systems can potentially achieve high energy density because of their broad voltage window. In this paper, we report a new organic redox-active material for use in a nonaqueous redox flow battery, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) that has high solubility (>2.6 M) in organic solvents. PTIO exhibits electrochemically reversible disproportionation reactions and thus can serve as both anolyte and catholyte redox materials in a symmetric flow cell. The PTIO flow battery has a moderate cell voltage of ∼1.7 V and shows good cyclability under both cyclic voltammetry and flow cell conditions. Moreover, we demonstrate that FTIR can offer accurate estimation of the PTIO concentration in electrolytes and determine the state of charge of the PTIO flow cell, suggesting FTIR as a powerful online battery status sensor. This study is expected to inspire more insights in this under-addressed area of state of charge analysis aiming at operational safety and reliability of flow batteries.
  • Wan, C, MY Hu, O Borodin, J Qian, Z Qin, J Zhang, JZ Hu. "Natural abundance 17O, 6Li NMR and molecular modeling studies of the solvation structures of lithium bis(fluorosulfonyl)imide/1,2-dimethoxyethane liquid electrolytes."Journal of Power Sources 307: 231-243 (March 2016).
    Abstract:Natural abundance 17O and6Li NMR experiments, quantum chemistry and molecular dynamics studies were employed to investigate the solvation structures of Li+ at various concentrations of LiFSI in DME electrolytes. It was found that the chemical shifts of both 17O and 6Li changed with the concentration of LiFSI, indicating the changes of solvation structures with concentration. For the quantum chemistry calculations, the coordinated cluster LiFSI(DME)2 forms at first, and its relative ratio increases with increasing LiFSI concentration to 1 M. Then the solvation structure LiFSI(DME) become the dominant component. As a result, the coordination of forming contact ion pairs between Li+ and FSI− ion increases, but the association between Li+ and DME molecule decreases. Furthermore, at LiFSI concentration of 4 M the solvation structures associated with Li+(FSI−)2(DME), Li+2(FSI−)(DME)4 and (LiFSI)2(DME)3 become the dominant components. For the molecular dynamics simulation, with increasing concentration, the association between DME and Li+ decreases, and the coordinated number of FSI− increases, which is in perfect accord with the DFT results.
  • Jianming zheng, Pengfei Yan, Ruiguo Cao, Hongfa Xiang, Mark H. Engelhard, Bryant J. Polzin, Chongmin Wang, Ji-Guang Zhang, Wu Xu."Effects of Propylene Carbonate Content in CsPF6-Containing Electrolytes on the Enhanced Performances of Graphite Electrode for Lithium-Ion Batteries."ACS Applied Materials & Interfaces 8 (8):5715-5722 (February 2016).
    Abstract: The effects of propylene carbonate (PC) content in CsPF6-containing electrolytes on the performances of graphite electrode in lithium half cells and in graphite∥LiNi0.80Co0.15Al0.05O2 (NCA) full cells are investigated. It is found that the performance of graphite electrode is significantly affected by PC content in the CsPF6-containing electrolytes. An optimal PC content of 20% by weight in the solvent mixtures is identified. The enhanced electrochemical performance of graphite electrode can be attributed to the synergistic effects of the PC solvent and the Cs+ additive. The synergistic effects of Cs+ additive and appropriate amount of PC enable the formation of a robust, ultrathin, and compact solid electrolyte interphase (SEI) layer on the surface of graphite electrode, which is only permeable for desolvated Li+ ions and allows fast Li+ ion transport through it. Therefore, this SEI layer effectively suppresses the PC cointercalation and largely alleviates the Li dendrite formation on graphite electrode during lithiation even at relatively high current densities. The presence of low-melting-point PC solvent improves the sustainable operation of graphite∥NCA full cells under a wide temperature range. The fundamental findings also shed light on the importance of manipulating/maintaining the electrode/electrolyte interphasial stability in various energy-storage devices.
  • Jianming Zheng, Pengfei Yan, Donghai Mei, Mark H. Engelhard, Samuel S. Cartmell, Bryant J. Polzin, Chongmin Wang, Ji-Guang Zhang, Wu Xu."Highly Stable Operation of Lithium Metal Batteries Enabled by the Formation of a Transient High-Concentration Electrolyte Layer."Advanced Energy Materials 6 (8) (February 2016).
    Abstract: Lithium (Li) metal has been extensively investigated as an anode for rechargeable battery applications due to its ultrahigh theoretical specific capacity and the lowest redox potential. However, significant challenges including dendrite growth and low Coulombic efficiency are still hindering the practical applications of rechargeable Li metal batteries. It is demonstrated that long-term cycling of Li metal batteries can be realized by the formation of a transient high-concentration electrolyte layer near the surface of Li metal anode during high rate discharge process. The highly concentrated Li+ ions in this transient layer will immediately be solvated by the available solvent molecules and facilitate the formation of a stable and flexible solid electrolyte interphase (SEI) layer composed of a poly(ethylene carbonate) framework integrated with other organic/inorganic lithium salts. This SEI layer largely suppresses the corrosion of Li metal anode attacked by free organic solvents and enables the long-term operation of Li metal batteries. The fundamental findings in this work provide a new direction for the development of Li metal batteries that could be operated at high current densities for a wide range of applications.
  • Kumar G R,Savariraj D A,Karthick S N,Selvam S ,Balamuralitharan B ,Kim HJ ,Viswanathan K K,Vijayakumar M ,Prabakar K. "Phase transition kinetics and surface binding states of methylammonium lead iodide perovskite" Phys. Chem. Chem. Phys. 18: 7284-7297 (Feb. 2016).
    Abstract: AbstractWe have presented a detailed analysis of the phase transition kinetics and binding energy states of solution processed methylammonium lead iodide (MAPbI3) thin films prepared at ambient conditions and annealed at different elevated temperatures. It is the processing temperature and environmental conditions that predominantly control the crystal structure and surface morphology of MAPbI3 thin films. The structural transformation from tetragonal to cubic occurs at 60 °C with a 30 minute annealing time while the 10 minute annealed films posses a tetragonal crystal structure. The transformed phase is greatly intact even at the higher annealing temperature of 150 °C and after a time of 2 hours. The charge transfer interaction between the Pb 4f and I 3d oxidation states is quantified using XPS.
  • Bin Liu, Ji-Guang Zhang, Guozhen Shen."Pursuing two-dimensional nanomaterials for flexible lithium-ion batteries."Nano Today 11 (1):82-97 (February 2016).
    Abstract: Stretchable/flexible electronics provide a foundation for various emerging applications that beyond the scope of conventional wafer/circuit board technologies due to their unique features that can satisfy a broad range of applications such as wearable devices. Stretchable electronic and optoelectronics devices require the bendable/wearable rechargeable Li-ion batteries, thus these devices can operate without limitation of external powers. Various two-dimensional (2D) nanomaterials are of great interest in flexible energy storage devices, especially Li-ion batteries. This is because 2D materials exhibit much more exposed surface area supplying abundant Li-insertion channels and shortened paths for fast lithium ion diffusion. Here, we will review the recent developments on the flexible Li-ion batteries based on two dimensional nanomaterials. These researches demonstrated advancements in flexible electronics by incorporating various 2D nanomaterials into bendable batteries to achieve high electrochemical performance, excellent mechanical flexibility as well as electrical stability under stretching/bending conditions.
  • Cheng Y, D Choi, KS Han, KT Mueller, J Zhang, VL Sprenkle, J Liu, G Li. "Toward the design of high voltage magnesium-lithium hybrid batteries using dual-salt electrolytes." Chemical Communications 52: 5379-5382 (Feb. 2016).
    Abstract: We report a design of high voltage magnesium-lithium (Mg-Li) hybrid batteries through rational control of the electrolyte chemistry, electrode materials and cell architecture. Prototype devices with a structure of Mg-Li/LiFePO4 (LFP) and Mg-Li/LiMn2O4 (LMO) have been investigated. A Mg-Li/LFP cell using a dual-salt electrolyte 0.2 M [Mg2Cl2(DME)4][AlCl4]2 and 1.0 M LiTFSI exhibits voltages higher than 2.5 V (vs. Mg) and a high specific energy density of 246 W h kg-1 under conditions that are amenable for practical applications. The successful demonstrations reported here could be a significant step forward for practical hybrid batteries.
  • Choi D, X Li, WA Henderson, Q Huang, SK Nune, JP Lemmon, VL Sprenkle. "LiCoPO4 cathode from a CoHPO4xH2O nanoplate precursor for high voltage Li-ion batteries." Heliyon 2 (2) (Feb. 2016).
    Abstract: A highly crystalline LiCoPO4/C cathode material has been synthesized without noticeable impurities via a single step solid-state reaction using CoHPO4xH2O nanoplate as a precursor obtained by a simple precipitation route. The LiCoPO4/C cathode delivered a specific capacity of 125 mAhg-1 at a charge/discharge rate of C/10. The nanoplate precursor and final LiCoPO4/C cathode have been characterized using X-ray diffraction, thermogravimetric analysis - differential scanning calorimetry (TGA-DSC), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) and the electrochemical cycling stability has been investigated using different electrolytes, additives and separators.
  • Hu, JZ, Z Zhao, MY Hu, J Feng, X Deng, X Chen, W Xu, J Liu, J Zhang. "In situ7Li and 133Cs nuclear magnetic resonance investigations on the role of Cs+ additive in lithium-metal deposition process." Journal of Power Sources 304: 51-59 (Feb. 2016).
    Abstract:Cesium ion (Cs+) has been reported to be an effective electrolyte additive to suppress Li dendrite growth which prevents the application of lithium (Li) metal as an anode for rechargeable Li batteries. In this work, we investigated the effect of Cs+ additive on Li depositions using quantitative in situ7Li and 133Cs nuclear magnetic resonance (NMR) with planar symmetric Li cells. It's found that the addition of Cs+ can significantly enhance both the formation of well aligned Li nanorods and reversibility of the Li electrode. In situ133Cs NMR directly confirms that Cs+ migrates to Li electrode to form a positively charged electrostatic shield during the charging process. Much more electrochemical “active” Li was found in Li films deposited with Cs+ additive, while more electrochemical “dead” and thicker Li rods were identified in Li films deposited without Cs+. Combining the in situ and the previous ex-situ results, a Li deposition model has been proposed to explain these observations.
  • Li G, X Lu, JY Kim, KD Meinhardt, HJ Chang, NL Canfield, VL Sprenkle. "Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density." Nature Communications 7:10683 (Feb. 2016).
    Abstract: Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well known redox system. One of the roadblocks hindering market penetration is the high operating temperature. Here we demonstrate that planar sodium-nickel chloride batteries can be operated at an intermediate temperature of 190°C with ultra-high energy density. A specific energy density of 350 Wh kg -1, higher than that of conventional tubular sodium-nickel chloride batteries (280°C), is obtained for planar sodium-nickel chloride batteries operated at 190°C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium-nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.
  • Reed DM, EC Thomsen, B Li, W Wang, Z Nie, BJ Koeppel, VL Sprenkle. "Performance of a low cost interdigitated flow design on a 1 kW class all vanadium mixed acid redox flow battery." Journal of Power Sources 306: 24-31 (Feb. 2016).
    Abstract: Three flow designs were operated in a 3-cell 1 kW class all vanadium mixed acid redox flow battery. The influence of electrode surface area and flow rate on the coulombic, voltage, and energy efficiency and the pressure drop in the flow circuit will be discussed and correlated to the flow design. Material cost associated with each flow design will also be discussed.
  • Wang W, VL Sprenkle. "Energy storage: Redox flow batteries go organic."Nature Chemistry 8 (3): 204-206 (Feb. 2016).
    Abstract: Access to sustainable and affordable energy is the foundation for the economic growth and future prosperity of our society. Given the drive to also reduce the carbon footprint associated with traditional fossil-based electricity generation, renewable resources could provide a clean and sustainable energy future. However, while the amount of energy produced from renewable resources such as solar and wind is steadily increasing, and the generation costs continuously falling, it still only represents a small fraction of current energy production. One big issue is the intermittent and fluctuating nature of energy produced from renewables and this will threaten the stability of the grid when the energy share from these resources surpasses 20% of the overall energy capacity1. Electrical energy storage is a potentially cost-effective approach to solving this problem and would be beneficial for renewable energy integration, balancing the mismatch between supply and demand, as well as improving the overall reliability and efficiency of the grid.
  • Jianming Zheng, Pengfei Yan, Wang Hay Kan, Chongmin Wang, Arumugam Manthiram."A Spinel-Integrated P2-Type Layered Composite: High-Rate Cathode for Sodium-Ion Batteries."Journal of the Electrochemical Society 163 (3):A584-A591 (January 2016).
    Abstract: Sodium-ion batteries (SIB) are being intensively investigated, owing to the natural abundance and low cost of Na resources. However, the SIBs still suffer from poor rate capability due to the large ionic radius of Na+ ion and the significant kinetic barrier to Na+-ion transport. Here, we present an Fd-3m spinel-integrated P2-type layered composite (P2 + Fd-3m) material as a high-rate cathode for SIBs. The P2 + Fd-3m composite material Na0.50Ni1/6Co1/6Mn2/3O2 shows significantly enhanced discharge capacity, energy density, and rate capability as compared to the pure P2-type counterpart. The composite delivers a high capacity of 85 mA h g−1 when discharging at a very high current density of 1500 mA g−1 (10 C rate) between 2.0 and 4.5 V, validating it as a promising cathode candidate for high-power SIBs. The superior performance is ascribed to the improved kinetics in the presence of the integrated-spinel phase, which facilitates fast electron transport to coordinate with the timely Na+-ion insertion/extraction. The findings of this work also shed light on the importance of developing lattice doping, surface coating, and electrolyte additives to further improve the structural and interfacial stability of P2-type cathode materials and fully realize their practical applications in sodium-ion batteries.

2015

  • Bin Liu, Wu Xu, Pengfei Yan, Xiuliang Sun, Mark E. Bowden, Jeffrey Read, Jiangfeng Qian, Donghai Mei, Chongmin Wang, Ji-Guang Zhang."Enhanced Cycling Stability of Rechargeable Li–O2 Batteries Using High-Concentration Electrolytes."Advanced Functional Materials 26 (4):605-613 (December 2015).
    Abstract: The stability of electrolytes against highly reactive, reduced oxygen species is crucial for the development of rechargeable Li–O2 batteries. In this work, the effect of lithium salt concentration in 1,2-dimethoxyethane (DME)-based electrolytes on the cycling stability of Li–O2 batteries is investigated systematically. Cells with highly concentrated electrolyte demonstrate greatly enhanced cycling stability under both full discharge/charge (2.0–4.5 V vs Li/Li+) and the capacity-limited (at 1000 mAh g−1) conditions. These cells also exhibit much less reaction residue on the charged air-electrode surface and much less corrosion of the Li-metal anode. Density functional theory calculations are used to calculate molecular orbital energies of the electrolyte components and Gibbs activation energy barriers for the superoxide radical anion in the DME solvent and Li+–(DME) n solvates. In a highly concentrated electrolyte, all DME molecules are coordinated with salt cations, and the C–H bond scission of the DME molecule becomes more difficult. Therefore, the decomposition of the highly concentrated electrolyte can be mitigated, and both air cathodes and Li-metal anodes exhibit much better reversibility, resulting in improved cyclability of Li–O2 batteries.
  • Liu L, X Wei, Z Nie, VL Sprenkle, W Wang. "A Total Organic Aqueous Redox Flow Battery Employing a Low Cost and Sustainable Methyl Viologen Anolyte and 4-HO-TEMPO Catholyte." Advanced Energy Materials 6(3):1-8 (Dec. 2015).
    Abstract: Increasing worldwide energy demands and rising CO2 emissions have motivated a search for new technologies to take advantage of renewables such as solar and wind energies. Redox flow batteries (RFBs) with their high power density, high energy efficiency, scalability (up to MW and MWh), and safety features are one suitable option for integrating such energy sources and overcoming their intermittency. However, resource limitation and high system costs of current RFB technologies impede wide implementation. Here, a total organic aqueous redox flow battery (OARFB) is reported, using low-cost and sustainable methyl viologen (MV, anolyte) and 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-HO-TEMPO, catholyte), and benign NaCl supporting electrolyte. The electrochemical properties of the organic redox active materials are studied using cyclic voltammetry and rotating disk electrode voltammetry. The MV/4-HO-TEMPO ARFB has an exceptionally high cell voltage, 1.25 V. Prototypes of the organic ARFB can be operated at high current densities ranging from 20 to 100 mA cm2, and deliver stable capacity for 100 cycles with nearly 100% Coulombic efficiency. The MV/4-HO-TEMPO ARFB displays attractive technical merits and thus represents a major advance in ARFBs.
  • Oleg Borodin, Marco Olguin, P. Ganesh, Paul R.C. Kent, Joshua L. Allen, Wesley A. Henderson."Competitive lithium solvation of linear and cyclic carbonates from quantum chemistry."Physical Chemistry Chemical Physics 18: 164-175 (November 2015).
    Abstract: AbstractThe composition of the lithium cation (Li+) solvation shell in mixed linear and cyclic carbonate-based electrolytes has been re-examined using Born–Oppenheimer molecular dynamics (BOMD) as a function of salt concentration and cluster calculations with ethylene carbonate:dimethyl carbonate (EC:DMC)–LiPF6 as a model system. A coordination preference for EC over DMC to a Li+ was found at low salt concentrations, while a slightly higher preference for DMC over EC was found at high salt concentrations. Analysis of the relative binding energies of the (EC)n(DMC)m–Li+ and (EC)n(DMC)m–LiPF6 solvates in the gas-phase and for an implicit solvent (as a function of the solvent dielectric constant) indicated that the DMC-containing Li+ solvates were stabilized relative to (EC4)–Li+ and (EC)3–LiPF6 by immersing them in the implicit solvent. Such stabilization was more pronounced in the implicit solvents with a high dielectric constant. Results from previous Raman and IR experiments were reanalyzed and reconciled by correcting them for changes of the Raman activities, IR intensities and band shifts for the solvents which occur upon Li+ coordination. After these correction factors were applied to the results of BOMD simulations, the composition of the Li+ solvation shell from the BOMD simulations was found to agree well with the solvation numbers extracted from Raman experiments. Finally, the mechanism of the Li+ diffusion in the dilute (EC:DMC)LiPF6 mixed solvent electrolyte was studied using the BOMD simulations.
  • Savariraj D A,Rajendrakumar G ,Selvam S ,Karthick S N,Balamuralitharan B ,Kim HJ ,Viswanathan K K,Vijayakumar M ,Prabakar K. "Stacked Cu1.8S nanoplatelets as counter electrode for quantum dot-sensitized solar cell" RCS Advances 5: 100560-100567 (Nov. 2015).
    Abstract: It is found that the electrocatalytic activity of Cu2−xS thin films used in quantum dot-sensitized solar cells (QDSSCs) as counter electrode (CE) for the reduction of polysulfide electrolyte depends on the surface active sulfide and disulfide species and the deficiency of Cu. The preferential bonding between Cu2+ and S2−, leading to the selective formation of a Cu1.8S stacked platelet-like morphology, is determined by the cetyl trimethyl ammonium bromide surfactant and deposition temperature; the crab-like Cu–S coordination bond formed dictates the surface area to volume ratio of the Cu1.8S thin films and their electrocatalytic activity. The Cu deficiency enhances the conductivity of the Cu1.8S thin films, which exhibit near-infrared localized surface plasmon resonance due to free carriers, and UV-vis absorption spectra show an excitonic effect due to the quantum size effect. When these Cu1.8S thin films were employed as CEs in QDSSCs, a robust photoconversion efficiency of 5.2% was obtained for the film deposited at 60 °C by a single-step chemical bath deposition method.
  • Liu B, Xu W, Yan P, Bhattacharya P, Cao R, Bowden ME, Engelhard MH, Wang CM, Zhang JG."In-Situ-Grown ZnCo2O4 on Single-Walled Carbon Nanotubes as Air Electrode Materials for Rechargeable Lithium-Oxygen Batteries."ChemSusChem 8 (21): 3697-703 (November 2015).
    Abstract: The development of highly efficient catalysts is critical for the practical application of lithium-oxygen (Li-O2) batteries. Nanosheet-assembled ZnCo2O4 (ZCO) microspheres and thin films grown in-situ on single-walled carbon nanotube (ZCO/SWCNT) composites as high-performance air electrode materials for Li-O2 batteries are reported. The in-situ grown ZCO/SWCNT electrodes delivered high discharge capacities, decreased the onset of the oxygen evolution reaction by 0.9 V during the charging process, and led to longer cycling stability. These results indicate that in-situ grown ZCO/SWCNT composites can be used as highly efficient air electrode materials for oxygen reduction and evolution reactions. The enhanced catalytic activity displayed by the uniformly dispersed ZCO catalyst on nanostructured electrodes is expected to inspire further development of other catalyzed electrodes for Li-O2 batteries and other applications.
  • Lu X, G Li, JY Kim, KD Meinhardt, VL Sprenkle. "Enhanced sintering of ß"-Al2/O3/YSZ with the sintering aids of TiO2 and MnO2." Journal of Power Sources 295:167-174 (Nov. 2015).
    Abstract: ß"-Al2O3 has been the dominated choice for the electrolyte materials of sodium batteries because of its high ionic conductivity, excellent stability with the electrode materials, satisfactory mechanical strength, and low material cost. To achieve adequate electrical and mechanical performance, sintering of ß"-Al2O3 is typically carried out at temperatures above 1600°C with deliberate efforts on controlling the phase, composition, and microstructure. Here, we reported a simple method to fabricate ß"-Al2O3/YSZ electrolyte at relatively lower temperatures. With the starting material of boehmite, single phase of ß"-Al2O3 can be achieved at as low as 1200°C. It was found that TiO2 was extremely effective as a sintering aid for the densification of ß"-Al2O3 and similar behavior was observed with MnO2 for YSZ. With the addition of 2 mol% TiO2 and 5 mol% MnO2, the ß"-Al2O3/YSZ composite was able to be densified at as low as 1400°C with a fine microstructure and good electrical/mechanical performance. This study demonstrated a new approach of synthesis and sintering of ß"-Al2O3/YSZ composite, which represented a simple and low-cost method for fabrication of high-performance ß"-Al2O3/YSZ electrolyte.
  • Reed DM, EC Thomsen, B Li, W Wang, Z Nie, BJ Koeppel, JP Kizewski, VL Sprenkle. "Stack Developments in a kW Class All Vanadium Mixed Acid Redox Flow Battery at the Pacific Northwest National Laboratory." Journal of the Electrochemical Society 163 (1):A5211-A5219 (Nov. 2015).
    Abstract: Over the past several years, efforts have been focused on improving the performance of kW class all vanadium mixed acid redox flow battery stacks with increasing current density. The influence of the Nafion membrane resistance, an interdigitated design to reduce the pressure drop in the electrolyte circuit, the temperature of the electrolyte, and the electrode structure will be discussed and correlated to the electrical performance. Improvements to the stack energy efficiency and how those improvements translate to the overall system efficiency will also be discussed.
  • Wei X, G Xia, BW Kirby, EC Thomsen, B Li, Z Nie, GG Graff, J Liu, VL Sprenkle, W Wang. "An Aqueous Redox Flow Battery Based on Neutral Alkali Metal Ferri/ferrocyanide and Polysulfide Electrolytes." Journal of The Electrochemical Society 163(1):A5150-A5153 (Nov. 2015).
    Abstract: We have demonstrated a new ferri/ferrocyanide - polysulfide (Fe/S) flow battery, which employs less corrosive, relatively environmentally benign neutral alkali metal ferri/ferrocyanide and alkali metal polysulfides as the active redox couples. A cobalt nanoparticle - decorated graphite felt was used at the polysulfide side as the catalyst. Excellent electrochemical performance was successfully acquired in the Fe/S flow cells with high cell efficiencies (99% coulombic efficiency and ~74% energy efficiency) and good cycling stability over extended charge/discharge operations. The positive half-cell appears to be the performance - limiting side in the Fe/S flow battery determined by using a carbon cloth probe. The inexpensive redox materials and possibly cell part materials can lead to reduced capital cost, making the Fe/S flow battery a promising cost-effective energy storage technology.
  • Liang Xiao, Xilin Chen, Ruiguo Cao, Jiangfeng Qian, Hongfa Xiang, Jianming Zheng, Ji-Guang Zhang, Wu Xu."Enhanced performance of Li|LiFePO4 cells using CsPF6 as an electrolyte additive."Journal of Power Sources 293: 1062-1067 (October 2015).
    Abstract: The practical application of lithium (Li) metal anode in rechargeable Li batteries is hindered by both the growth of Li dendrites and the low Coulombic efficiency (CE) during repeated charge/discharge cycles. Recently, we have discovered that CsPF6 as an electrolyte additive can significantly suppress Li dendrite growth and lead to highly compacted and well aligned Li nanorod structures during Li deposition on copper substrates. In this paper, the effect of CsPF6 additive on the performance of rechargeable Li metal batteries with lithium iron phosphate (LFP) cathode is further studied. Li|LFP coin cells with CsPF6 additive in electrolytes show well protected Li anode surface, decreased resistance, enhanced rate capability and extended cycling stability. In Li|LFP cells, the electrolyte with CsPF6 additive shows excellent long-term cycling stability (at least 500 cycles) at a charge current density of 0.5 mA cm−2 without internal short circuit. At high charge current densities, the effect of CsPF6 additive becomes less significant. Future work needs to be done to protect Li metal anode, especially at high charge current densities and for long cycle life.
  • Crawford A, V Viswanathan, D Stephenson, W Wang, EC Thomsen, DM Reed, B Li, PJ Balducci, M Kinter-Meyer, VL Sprenkle. "Comparative analysis for various redox flow batteries chemistries using a cost performance model." Journal of Power Sources 293: 388-399 (Oct. 2015).
    Abstract: The total energy storage system cost is determined by means of a robust performance-based cost model for multiple flow battery chemistries. Systems aspects such as shunt current losses, pumping losses and various flow patterns through electrodes are accounted for. The system cost minimizing objective function determines stack design by optimizing the state of charge operating range, along with current density and current-normalized flow. The model cost estimates are validated using 2-kW stack performance data for the same size electrodes and operating conditions. Using our validated tool, it has been demonstrated that an optimized all-vanadium system has an estimated system cost of < $350 kWh-1 for 4-h application. With an anticipated decrease in component costs facilitated by economies of scale from larger production volumes, coupled with performance improvements enabled by technology development, the system cost is expected to decrease to 160 kWh-1 for a 4-h application, and to $100 kWh-1 for a 10-h application. This tool has been shared with the redox flow battery community to enable cost estimation using their stack data and guide future direction.
  • Cheng, Y, Y Shao, LR Parent, ML Sushko, G Li, PV Sushko, ND Browning, C Wang, J Liu. "Interface Promoted Reversible Mg Insertion in Nanostructured Tin–Antimony Alloys."Advanced Materials 27 (42): 6598-6605 (Sept. 2015).
    Abstract:An interface promoted approach is developed for guiding the design of stable and high capacity materials for Mg batteries using SnSb alloys as model materials. Experimental and theoretical studies reveal that the SnSb alloy has exceptionally high reversible capacity (420 mA h g−1), excellent rate capability, and good cyclic stability for hosting Mg ions due to the stabilization/promotion effects of the interfaces between the multicomponent phases generated during repeated magnesiation–demagnesiation.
  • Hongfa Xiang, Donghai Mei, Pengfei Yan, Priyanka Bhattacharya, Sarah D. Burton, Arthur von Wald Cresce, Ruiguo Cao, Mark H. Engelhard, Mark E. Bowden, Zihua Zhu, Bryant J. Polzin, Chongmin Wang, Kang Xu, Ji-Guang Zhang, Wu Xu."The Role of Cesium Cation in Controlling Interphasial Chemistry on Graphite Anode in Propylene Carbonate-Rich Electrolytes."ACS Applied Materials & Interfaces 7 (37): 20687-20695 (September 2015).
    Abstract: Despite the potential advantages it brings, such as wider liquid range and lower cost, propylene carbonate (PC) is seldom used in lithium-ion batteries because of its sustained cointercalation into the graphene structure and the eventual graphite exfoliation. Here, we report that cesium cation (Cs+) directs the formation of solid electrolyte interphase on graphite anode in PC-rich electrolytes through its preferential solvation by ethylene carbonate (EC) and the subsequent higher reduction potential of the complex cation. Effective suppression of PC-decomposition and graphite-exfoliation is achieved by adjusting the EC/PC ratio in electrolytes to allow a reductive decomposition of Cs+-(EC)m (1 ≤ m ≤ 2) complex preceding that of Li+-(PC)n (3 ≤ n ≤ 5). Such Cs+-directed interphase is stable, ultrathin, and compact, leading to significant improvement in battery performances. In a broader context, the accurate tailoring of interphasial chemistry by introducing a new solvation center represents a fundamental breakthrough in manipulating interfacial reactions that once were elusive to control.
  • Cosimbescu L, X Wei, M Vijayakumar, W Xu, ML Helm, SD Burton, CM Sorensen, J Liu, VL Sprenkle, W Wang. "Anion-Tunable Properties and Electrochemical Performance of Functionalized Ferrocene Compounds." Scientific Reports 5:14117 (Sept. 2015).
    Abstract:We report a series of ionically modified ferrocene compounds for hybrid lithium-organic non-aqueous redox flow batteries, based on the ferrocene/ferrocenium redox couple as the active catholyte material. Tetraalkylammonium ionic moieties were incorporated into the ferrocene structure, in order to enhance the solubility of the otherwise relatively insoluble ferrocene. The effect of various counter anions of the tetraalkylammonium ionized species appended to the ferrocene, such as bis(trifluoromethanesulfonyl)imide, hexafluorophosphate, perchlorate, tetrafluoroborate, and dicyanamide on the solubility of the ferrocene was investigated. The solution chemistry of the ferrocene species was studied, in order to understand the mechanism of solubility enhancement. Finally, the electrochemical performance of these ionized ferrocene species was evaluated and shown to have excellent cell efficiency and superior cycling stability.
  • Liang Xiao, Jie Xiao, Xiqian Yu, Pengfei Yan, Jianming Zheng, Mark Engelhard, Priyanka Bhattacharya, Chongmin Wang, Xiao-Qing Yang, Ji-Guang Zhang. "Effects of structural defects on the electrochemical activation of Li2MnO3."Nano Energy 16: 143-151 (September 2015).
    Abstract: Structural defects, e.g. Mn3+/oxygen non-stoichiometry, largely affect the electrochemical performance of both Li2MnO3 and lithium-rich manganese-rich (LMR) layered oxides with Li2MnO3 as one of the key components. Herein, Li2MnO3 samples with different amount of structural defects of Mn3+/oxygen non-stoichiometry are prepared. The results clearly demonstrate that the annealed Li2MnO3 (ALMO), quenched Li2MnO3 (QLMO), and quenched Li2MnO3 milled with Super P (MLMO) all show pure C2/m monoclinic phase with stacking faults. MLMO shows the largest amount of Mn3+, followed by the QLMO and then the ALMO. The increased amount of Mn3+ in Li2MnO3 (such as sample MLMO) facilitates the activation of Li2MnO3 and leads to the highest initial discharge specific capacity of 167.7 mA h g−1 among the samples investigated in this work. However, accelerated activation of Li2MnO3 also results in faster structural transformation to spinel-like phase, leading to rapid capacity degradation. Therefore, the amount of Mn3+ needs to be well controlled during synthesis of LMR cathode in order to reach a reasonable compromise between the initial activity and long-term cycling stability. The findings of this work could be widely applied to explain the effects of Mn3+ on different kinds of LMR cathodes.
  • Zhu, Z, Y Zhou, P Yan, RS Vemuri, W Xu, R Zhao, X Wang, S Thevuthasan, DR Baer, CM Wang. "In Situ Mass Spectrometric Determination of Molecular Structural Evolution at the Solid Electrolyte Interphase in Lithium-Ion Batteries." Nano Letters 15 (9): 6170-6176 (Aug. 2015).
    Abstract:Dynamic structural and chemical evolution at solid–liquid electrolyte interface is always a mystery for a rechargeable battery due to the challenge to directly probe a solid–liquid interface under reaction conditions. We describe the creation and usage of in situ liquid secondary ion mass spectroscopy (SIMS) for the first time to directly observe the molecular structural evolution at the solid–liquid electrolyte interface for a lithium (Li)-ion battery under dynamic operating conditions. We have discovered that the deposition of Li metal on copper electrode leads to the condensation of solvent molecules around the electrode. Chemically, this layer of solvent condensate tends to be depleted of the salt anions and with reduced concentration of Li+ ions, essentially leading to the formation of a lean electrolyte layer adjacent to the electrode and therefore contributing to the overpotential of the cell. This observation provides unprecedented molecular level dynamic information on the initial formation of the solid electrolyte interphase (SEI) layer. The present work also ultimately opens new avenues for implanting the in situ liquid SIMS concept to probe the chemical reaction process that intimately involves solid–liquid interface, such as electrocatalysis, electrodeposition, biofuel conversion, biofilm, and biomineralization.
  • Lu X, ME Bowden, VL Sprenkle, J Liu. "A Low Cost, High Energy Density, and Long Cycle Life Potassium-Sulfur Battery for Grid-Scale Energy Storage." Advanced Materials 27(39):5915-5922 (Aug. 2015).
    Abstract:A potassium-sulfur battery using K+-conducting beta-alumina as the electrolyte to separate a molten potassium metal anode and a sulfur cathode is presented. The results indicate that the battery can operate at as low as 150°C with excellent performance. This study demonstrates a new type of high-performance metal-sulfur battery that is ideal for grid-scale energy-storage applications.
  • Dongping Lu, Pengfei Yan, Yuyan Shao, Qiuyan Li, Seth Ferrara, Huilin Pan, Gordon L. Graff, Bryant Polzin, Chongmin Wang, Ji-Guang Zhang, Jun Liu, Jie Xiao."High performance Li-ion sulfur batteries enabled by intercalation chemistry."Chemical Communications 51: 13454-13457 (July 2015).
    Abstract: AbstractThe unstable interface of lithium metal in high energy density Li sulfur (Li–S) batteries raises concerns of poor cycling, low efficiency and safety issues, which may be addressed by using intercalation types of anode. Herein, a new prototype of Li-ion sulfur battery with high performance has been demonstrated by coupling a graphite anode with a sulfur cathode (2 mA h cm−2) after successfully addressing the interface issue of graphite in an ether based electrolyte.
  • Canfield NL, JY Kim, JF Bonnett, RL Pearson III, VL Sprenkle, J Kung. "Effects of fabrication conditions on mechanical properties and microstructure of duplex ß"-Al2O3 solid electrolyte." Materials Science and Engineering: B 197: 43-50 (July 2015).
    Abstract:Na-beta batteries are an attractive technology as a large-scale electrical energy storage for grid applications. However, additional improvements in performance and cost are needed for wide market penetration. To improve cell performance by minimizing polarizations, reduction of electrolyte thickness was attempted using a duplex structure consisting of a thin dense electrolyte layer and a porous support layer. In this paper, the effects of sintering conditions, dense electrolyte thickness, and cell orientation on the flexural strength of duplex BASEs fabricated using a vapor phase approach were investigated. It is shown that sintering at temperatures between 1500 and 1550°C results in fine grained microstructures and the highest flexural strength after conversion. Increasing thickness of the dense electrolyte has a small impact on flexural strength, while the orientation of load such that the dense electrolyte is in tension instead of compression has major effects on strength for samples with a well-sintered dense electrolyte.
  • Deng X, MY Hu, X Wei, W Wang, Z Chen, J Liu, JZ Hu. "Natural abundance 17O nuclear magnetic resonance and computational modeling studies of lithium based liquid electrolytes." Journal of Power Sources 285: 146-155 (July 2015).
    Abstract:Natural abundance 17O NMR measurements were conducted on electrolyte solutions consisting of Li[CF3SO2NSO2CF3] (LiTFSI) dissolved in the solvents of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and their mixtures at various concentrations. It was observed that 17O chemical shifts of solvent molecules change with the concentration of LiTFSI. The chemical shift displacements of carbonyl oxygen are evidently greater than those of ethereal oxygen, strongly indicating that Li+ ion is coordinated with carbonyl oxygen rather than ethereal oxygen. To understand the detailed molecular interaction, computational modeling of 17O chemical shifts was carried out on proposed solvation structures. By comparing the predicted chemical shifts with the experimental values, it is found that a Li+ ion is coordinated with four double bond oxygen atoms from EC, PC, EMC and TFSI anion. In the case of excessive amount of solvents of EC, PC and EMC the Li+ coordinated solvent molecules are undergoing quick exchange with bulk solvent molecules, resulting in average 17O chemical shifts. Several kinds of solvation structures are identified, where the proportion of each structure in the liquid electrolytes investigated depends on the concentration of LiTFSI.
  • Qian, J, W Xu, P Bhattacharya, M Engelhard, WA Henderson, Y Zhang, J Zhang. "Dendrite-free Li deposition using trace-amounts of water as an electrolyte additive." Nano Energy 15: 135-144 (July 2015).
    Abstract:Residual water (H2O) presents in nonaqueous electrolytes has been widely regarded as a detrimental factor for lithium (Li) batteries. This is because H2O is highly reactive with the commonly used LiPF6 salt leading to the formation of HF which subsequently corrodes battery materials. In this work, we demonstrate that a controlled trace-amount of H2O (25–50 ppm) can be an effective electrolyte additive for achieving dendrite-free Li metal deposition in LiPF6-based electrolytes, while avoid detrimental effects. Detailed analyses revealed that the trace amount of HF derived from the decomposition reaction of LiPF6 with H2O is electrochemically reduced during the initial Li deposition process to form a uniform and dense LiF-rich solid electrolyte interphase (SEI) layer on the surface of the substrate. This LiF-rich SEI layer leads to a uniform distribution of the electric field on the substrate surface thereby enabling uniform and dendrite-free Li deposition. Meanwhile, the detrimental effect of HF on the other cell components is diminished due to the consumption of the HF in the LiF formation process. Microscopic analysis reveals that the as-deposited, dendrite-free Li films exhibit a self-aligned and highly-compact Li nanorod structure which is consistent with a vivid blue color due to structural coloration. These findings clearly demonstrate a novel approach to control the nucleation and grow processes of Li metal films using a well-controlled, trace-amount of H2O, as well as illuminate the effect of H2O on other electrodeposition processes.
  • Reed DM, ED Thomsen, W Wang, Z Nie, B Li, X Wei, BJ Koeppel, VL Sprenkle. "Performance of Nafion® N115, Nafion® NR-212, and Nafion® NR-211 in a 1 kW class all vanadium mixed acid redox flow battery."Journal of Power Sources 285:425-430 (July 2015).
    Abstract:Three Nafion® membranes of similar composition but different thicknesses were operated in a 3-cell 1 kW class all vanadium mixed acid redox flow battery. The influence of current density on the charge/discharge characteristics, coulombic and energy efficiency, capacity fade, operating temperature and pressure drop in the flow circuit will be discussed and correlated to the Nafion® membrane thickness. Material costs associated with the Nafion® membranes, ease of handling the membranes, and performance impacts will also be discussed.
  • Wei X, W Xu, J Huang, L Zhang, ED Walter, CW Lawrence, M Vijayakumar, WA Henderson, TL Liu, L Cosimbescu, B Li, VL Sprenkle, W Wang. "Radical Compatibility with Nonaqueous Electrolytes and Its Impact on an All-Organic Redox Flow Battery." Angewandte Chemie 54 (30):8684-8687 (July 2015).
    Abstract:Nonaqueous redox flow batteries hold the promise of achieving higher energy density because of the broader voltage window than aqueous systems, but their current performance is limited by low redox material concentration, cell efficiency, cycling stability, and current density. We report a new nonaqueous all-organic flow battery based on high concentrations of redox materials, which shows significant, comprehensive improvement in flow battery performance. A mechanistic electron spin resonance study reveals that the choice of supporting electrolytes greatly affects the chemical stability of the charged radical species especially the negative side radical anion, which dominates the cycling stability of these flow cells. This finding not only increases our fundamental understanding of performance degradation in flow batteries using radical-based redox species, but also offers insights toward rational electrolyte optimization for improving the cycling stability of these flow batteries.
  • Pengfei Yan, Jianming Zheng, Jie Xiao, Chongmin Wang, Ji-Guang Zhang."Recent advances on the understanding of structural and composition evolution of LMR cathodes for Li-ion batteries."Frontiers in Energy Research (June 2015).
    Abstract: Lithium-and-manganese-rich (LMR) cathode materials have been regarded as very promising for lithium (Li)-ion battery applications. However, their practical application is still limited by several barriers such as their limited electrochemical stability and rate capability. In this work, we present recent progress on the understanding of structural and compositional evolution of LMR cathode materials, with an emphasis being placed on the correlation between structural/chemical evolution and electrochemical properties. In particular, using Li[Li0.2Ni0.2Mn0.6]O2 as a typical example, we clearly illustrate the structural characteristics of pristine materials and their dependence on the material-processing history, cycling-induced structural degradation/chemical partition, and their correlation with electrochemical performance degradation. The fundamental understanding that resulted from this work may also guide the design and preparation of new cathode materials based on the ternary system of transitional metal oxides.
  • Kerisit, S, M Vijayakumar, KS Han, KT Mueller. "Solvation structure and transport properties of alkali cations in dimethyl sulfoxide under exogenous static electric fields." Journal of Chemical Physics 142 (22) 224502 (June 2015).
    Abstract:A combination of molecular dynamics simulations and pulsed field gradient nuclear magnetic resonance spectroscopy is used to investigate the role of exogenous electric fields on the solvation structure and dynamics of alkali ions in dimethyl sulfoxide (DMSO) and as a function of temperature. Good agreement was obtained, for select alkali ions in the absence of an electric field, between calculated and experimentally determined diffusion coefficients normalized to that of pure DMSO. Our results indicate that temperatures of up to 400 K and external electric fields of up to 1 V nm−1 have minimal effects on the solvation structure of the smaller alkali cations (Li+ and Na+) due to their relatively strong ion-solvent interactions, whereas the solvation structures of the larger alkali cations (K+, Rb+, and Cs+) are significantly affected. In addition, although the DMSO exchange dynamics in the first solvation shell differ markedly for the two groups, the drift velocities and mobilities are not significantly affected by the nature of the alkali ion. Overall, although exogenous electric fields induce a drift displacement, their presence does not significantly affect the random diffusive displacement of the alkali ions in DMSO. System temperature is found to have generally a stronger influence on dynamical properties, such as the DMSO exchange dynamics and the ion mobilities, than the presence of electric fields.
  • Kim JY, NL Canfield, JF Bonnett, VL Sprenkle, K Jung, I Hong. "A Duplex ß"-Al2O3 Solid Electrolyte Consisting of A Thin Dense Layer and A Porous Substrate."Solid State Ionics 278: 192-197 (June 2015).
    Abstract:To improve the performance of Na-beta batteries at intermediate temperatures (≤200°C) where much improved cyclability and reduced degradation can be achieved, there is a need to lower the resistance/polarization coming from BASEs while maintaining good strength. In this paper, the concept of a duplex BASE consisting of a thin dense electrolyte and a porous support was proposed as a solution to achieve low area-specific resistance while maintaining good mechanical strength. The effects of various factors including porosity, composition, and the homogeneity of ingredients on the flexural strength of duplex BASEs were examined. In summary, lower porosity, higher YSZ content in the structure, and the attrition milling of powders resulted in improved strength. The area-specific resistance measurement exhibited that the resistance of duplex BASEs was mainly originated from a dense layer. Overall, the maximum strength of 260 MPa and the ASR value of 0.31 cm2 (at 350°C) was achieved from a duplex BASE consisting of a 50 µm thick dense layer (Al2O3: YSZ = 7:3 in volume) and a 500 µm thick porous support (Al2O3: YSZ = 4:6 in volume with 19% open porosity). The effects of various factors on the properties of duplex BASEs will be explained in details.
  • Li G, X Lu, JY Kim, V Viswanathan, KD Meinhardt, MH Engelhard, VL Sprenkle. "An Advanced Na-FeCl2 ZEBRA Battery for Stationary Energy Storage Application." Advanced Energy Materials 5(12) (June 2015).
    Abstract:In article number 1500357, Guosheng Li, Jin Y. Kim, and co-workers report a remarkably reliable Na-FeCl2 ZEBRA battery for stationary energy storage applications. The removal of surface oxide passivation layers on iron particles is critical and it is attributed to polysulfide species generated from sulfur-based additives through polysulfide reactions. The Na-FeCl2 cells presented can be assembled at the discharge state (NaCl + Fe powder) without handling highly hazardous materials such as anhydrous FeCl2 and metallic sodium.
  • Shamie JS, C Liu, LL Shaw, VL Sprenkle. "Room Temperature, Hybrid Sodium-Based Flow Batteries with Multi-Electron Transfer Redox Reactions." Scientific Reports 5, article number 11215 (June 2015).
    Abstract:We introduce a new concept of hybrid Na-based flow batteries (HNFBs) with a molten Na alloy anode in conjunction with a flowing catholyte separated by a solid Na-ion exchange membrane for grid-scale energy storage. Such HNFBs can operate at ambient temperature, allow catholytes to have multiple electron transfer redox reactions per active ion, offer wide selection of catholyte chemistries with multiple active ions to couple with the highly negative Na alloy anode, and enable the use of both aqueous and non-aqueous catholytes. Further, the molten Na alloy anode permits the decoupled design of power and energy since a large volume of the molten Na alloy can be used with a limited ion-exchange membrane size. In this proof-of-concept study, the feasibility of multi-electron transfer redox reactions per active ion and multiple active ions for catholytes has been demonstrated. The critical barriers to mature this new HNFBs have also been explored.
  • Jianming Zheng, Pengfei Yan, Meng Gu, Michael J. Wagner, Kevin A. Hays, Junzheng Chen, Xiaohong Li, Chongmin Wang, Ji-Guang Zhang, Jun Liu, Jie Xiao."Interfacial reaction dependent performance of hollow carbon nanosphere – sulfur composite as a cathode for Li-S battery."Frontiers in Energy Research (May 2015).
    Abstract: Lithium-sulfur (Li-S) battery is a promising energy storage system due to its high energy density, cost effectiveness, and environmental friendliness of sulfur. However, there are still a number of technical challenges, such as low Coulombic efficiency and poor long-term cycle life, impeding the commercialization of Li-S battery. The electrochemical performance of Li-S battery is closely related with the interfacial reactions occurring between hosting substrate and active sulfur species, which are poorly conducting at fully oxidized and reduced states. Here, we correlate the relationship between the performance and interfacial reactions in the Li-S battery system, using a hollow carbon nanosphere (HCNS) with highly graphitic character as hosting substrate for sulfur. With an appropriate amount of sulfur loading, HCNS/S composite exhibits excellent electrochemical performance because of the fast interfacial reactions between HCNS and the polysulfides. However, further increase of sulfur loading leads to increased formation of highly resistive insoluble reaction products (Li2S2/Li2S), which limits the reversibility of the interfacial reactions and results in poor electrochemical performances. These findings demonstrate the importance of the interfacial reaction reversibility in the whole electrode system on achieving high capacity and long cycle life of sulfur cathode for Li-S batteries.
  • Wei X, B Li, W Wang. "Porous Polymeric Composite Separators for Redox Flow Batteries." Polymer Reviews 55(2):247-272 (May 2015).
    Abstract:Currently, the most commonly used membranes in redox flow batteries (RFB) are ion-exchange membranes. In particular, in all vanadium flow battery systems (VRB), perfluorinated polymers such as Nafion® are widely used, owing to their high proton conductivity and chemical stability; however, the extremely high cost of currently available membranes has limited the commercialization of VRB technology. Recently, low-cost porous polymeric composite separators (e.g., polytetrafluoroethylene [PTFE]/silica), as an alternative to traditional ion-exchange membranes, have attracted a great deal of interest because of their significantly lower cost. Porous separators prepared from various polymer materials and inorganic fillers have demonstrated comparable electrochemical performances to that of Nafion® in flow battery tests with different redox chemistries. This paper provides a review of porous separators for flow battery applications. In addition to discussions of separator material selection and preparation methods, we also emphasize the electrochemical performance of various flow battery systems, especially the capacity fade mechanism that is closely related to ion-transport across porous separator.
  • Pan, H, X Wei, WA Henderson, Y Shao, J Chen, P Bhattacharya, J Xiao, J Liu. "On the Way Toward Understanding Solution Chemistry of Lithium Polysulfides for High Energy Li–S Redox Flow Batteries." Advanced Energy Materials 5 (16)(Apr. 2015).
    Abstract:Lithium–sulfur (Li–S) redox flow battery (RFB) is a promising candidate for high energy large-scale energy storage application due to good solubility of long-chain polysulfide species and low cost of sulfur. Here, the fundamental understanding and control of lithium polysulfide chemistry are studied to enable the development of liquid phase Li–S redox flow prototype cells. These differ significantly from conventional static Li–S batteries targeting for vehicle electrification. A high solubility of the different lithium polysulfides generated at different depths of discharge and states of charge is required for a flow battery in order to take full advantage of the multiple electron transitions. A new dimethyl sulfoxide based electrolyte is proposed for Li–S RFBs, which not only enables the high solubility of lithium polysulfide species, especially for the short-chain species, but also results in excellent cycling with a high Coulombic efficiency. The challenges and opportunities for the Li–S redox flow concept have also been discussed in depth.
  • Wei X, W Xu, J Huang, L Zhang, E Walter, C Lawrence, M Vijaykumar, WA Henderson, T Liu, L Cosimbescu, B Li, V Sprenkle, W Wang. "Radical Compatibility with Nonaqueous Electrolytes and Its Impact on an All-Organic Redox Flow Battery."Angewandte Chemie 54 (30): 8684-8687 (Apr. 2015).
    Abstract:Nonaqueous redox flow batteries hold the promise of achieving higher energy density because of the broader voltage window than aqueous systems, but their current performance is limited by low redox material concentration, cell efficiency, cycling stability, and current density. We report a new nonaqueous all-organic flow battery based on high concentrations of redox materials, which shows significant, comprehensive improvement in flow battery performance. A mechanistic electron spin resonance study reveals that the choice of supporting electrolytes greatly affects the chemical stability of the charged radical species especially the negative side radical anion, which dominates the cycling stability of these flow cells. This finding not only increases our fundamental understanding of performance degradation in flow batteries using radical-based redox species, but also offers insights toward rational electrolyte optimization for improving the cycling stability of these flow batteries.
  • Cao, R, W Xu, D Lu, J Xiao, J Zhang. "Anodes for Rechargeable Lithium-Sulfur Batteries." Advanced Energy Materials 5 (16)(Apr. 2015).
    Abstract:With the significant progress that has been made toward the development of cathode materials and electrolytes in lithium-sulfur (Li-S) batteries in recent years, the stability of the anode in Li-S batteries has become one of the more urgent challenges in order to reach long-term stability of Li-S batteries. In Li-S batteries, a passivation layer is easily formed on the metallic Li anode surface because of the presence of polysulfides and electrolyte additives. Although the passivation layer on the Li metal anode can significantly suppress Li dendrite growth and improve the safety of Li-S batteries, continuous corrosion of the Li metal anode eventually leads to battery failure due to the increased cell impedance and the depletion of electrolyte. Here, the recent developments on the protection of the Li metal anode in Li-S batteries are reviewed. Various strategies used to minimize the corrosion of Li anodes and to reduce its impedance increase are analyzed. Other alternative anodes used in sulfur-based rechargeable batteries are also discussed.
  • Chen J, D Wu, E Walter, M Engelhard, P Bhattacharya, H Pan, Y Shao, F Gao, J Xiao, J Liu. "Molecular-confinement of polysulfides within mesoscale electrodes for the practical application of lithium sulfur batteries."Nano Energy 13: 267-274 (Apr. 2015).
    Abstract:Nitrogen-doped porous carbon (NPC) and multi-wall carbon nanotubes (MWCNT) have been frequently studied to immobilize sulfur in lithium–sulfur (Li–S) batteries. However, neither NPC nor MWCNT itself can effectively confine the soluble polysufides if cathode thickness e.g. sulfur loading is increased. In this work, NPC was combined with MWCNTs to construct an integrated host structure to immobilize sulfur at a relevant scale. The function of doped nitrogen atoms was revisited and found to effectively attract sulfur radicals generated during the electrochemical process. The addition of MWCNT facilitated the uniform coating of sulfur nanocomposites to a practically thickness and homogenized the distribution of sulfur particles in the pristine electrodes, while NPC provided sufficient pore volume to trap the dissolved polysulfides species. More importantly, the difficulty of electrode wetting, a critical challenge for thick sulfur cathodes, is also mitigated after the adoption of MWCNT, leading to a high areal capacity of ca. 2.5 mA h/cm2 with a capacity retention of 81.6% over 100 cycles.
  • Cheng Y, RM Stolley, KS Han, Y Shao, BW Arey, NM Washton, KT Mueller, ML Helm, VL Sprenkle, J Liu, G Li. "Highly Active Electrolytes for Rechargeable Mg Batteries Based on [Mg2(μ-Cl)2]2+ Cation Complex in Dimethoxyethane. "Physical Chemistry Chemical Physics 17: 13307-13314 (Apr. 2015).
    Abstract:A novel [Mg2(μ-Cl)2]2+ cation complex, which is highly active for reversible Mg electrodeposition, was identified for the first time in this work. This complex was found to be present in electrolytes formulated in dimethoxyethane (DME) through dehalodimerization of non-nucleophilic MgCl2 by reacting with either Mg salts (such as Mg(TFSI)2, TFSI = bis(trifluoromethane)sulfonylimide) or Lewis acid salts (such as AlEtCl2 or AlCl3). The molecular structure of the cation complex was characterized by single crystal X-ray diffraction, Raman spectroscopy and NMR. The electrolyte synthesis process was studied and rational approaches for formulating highly active electrolytes were proposed. Through control of the anions, electrolytes with an efficiency close to 100%, a wide electrochemical window (up to 3.5 V) and a high ionic conductivity (>6 mS cm-1) were obtained. The understanding of electrolyte synthesis in DME developed in this work could bring significant opportunities for the rational formulation of electrolytes of the general formula [Mg2(μ-Cl)2][anion]x for practical Mg batteries.
  • Yu, X, H Pan, Y Zhou, P Northrup, J Xiao, S Bak, M Liu, KW Nam, D Qu, J Liu, T Wu, XQ Yang. "Direct Observation of the Redistribution of Sulfur and Polysufides in Li–S Batteries During the First Cycle by In Situ X-Ray Fluorescence Microscopy." Advanced Energy Materials 5 (16) (March 2015).
    Abstract:A novel in situ X-ray fluorescence microscopy combined with X-ray absorption spectroscopy technique is reported to investigate the Li–S batteries during electrochemical cycling. The evolution of morphology changes of the electrode is monitored in real time using the X-ray fluorescence images, while the changes of the sulfur chemical state are characterized simultaneously using the X-ray absorption spectroscopy spectra.
  • Welch D A,Mehdi B L,Hatchell H J,Faller R ,Evans J E,Browning N D. "Using molecular dynamics to quantify the electrical double layer and examine the potential for its direct observation in the in-situ TEM." Advanced Structural and Chemical Imagining 1 (1) (March 2015).
    Abstract: Understanding the fundamental processes taking place at the electrode-electrolyte interface in batteries will play a key role in the development of next generation energy storage technologies. One of the most fundamental aspects of the electrode-electrolyte interface is the electrical double layer (EDL). Given the recent development of high spatial resolution in-situ electrochemical fluid cells for scanning transmission electron microscopy (STEM), there now exists the possibility that we can directly observe the formation and dynamics of the EDL. In this paper we predict electrolyte structure within the EDL using classical models and atomistic Molecular Dynamics (MD) simulations. Classical models are found to greatly differ from MD in predicted concentration profiles. It is thus suggested that MD must be used in order to accurately predict STEM images of the electrode-electrolyte interface. Using MD and image simulation together for a high contrast electrolyte (the high atomic number CsCl electrolyte), it is determined that, for a smooth interface, concentration profiles within the EDL should be visible experimentally. When normal experimental parameters such as rough interfaces and low-Z electrolytes (like those used in Li-ion batteries) are considered, observation of the EDL appears to be more difficult.
  • Xiao J ,Hu J Z,Chen H ,Vijayakumar M ,Zheng J ,Pan H ,Walter E D,Hu M Y,Deng X ,Feng J ,Liaw BY ,Gu M ,Deng Z ,Lu D ,Xu S ,Wang C M,Liu J. "Following the Transient Reactions in Lithium–Sulfur Batteries Using an In Situ Nuclear Magnetic Resonance Technique." Nano Letters 15 (5): 3309-3316 (March 2015).
    Abstract:A fundamental understanding of electrochemical reaction pathways is critical to improving the performance of Li–S batteries, but few techniques can be used to directly identify and quantify the reaction species during disharge/charge cycling processes in real time. Here, an in situ 7Li NMR technique employing a specially designed cylindrical microbattery was used to probe the transient electrochemical and chemical reactions occurring during the cycling of a Li–S system. In situ NMR provides real time, semiquantitative information related to the temporal evolution of lithium polysulfide allotropes during both discharge/charge processes. This technique uniquely reveals that the polysulfide redox reactions involve charged free radicals as intermediate species that are difficult to detect in ex situ NMR studies. Additionally, it also uncovers vital information about the 7Li chemical environments during the electrochemical and parasitic reactions on the Li metal anode. These new molecular-level insights about transient species and the associated anode failure mechanism are crucial to delineating effective strategies to accelerate the development of Li–S battery technologies.
  • Dongping Lu, Jianming Zheng, Qiuyan Li, Xi Xie, Seth Ferrara, Zimin Nie, Layla B. Mehdi, Nigel D. Browning, Ji-Guang Zhang, Gordon L. Graff, Jun Liu, Jie Xiao."High Energy Density Lithium–Sulfur Batteries: Challenges of Thick Sulfur Cathodes."Advanced Energy Materials 5 (16)(March 2015).
    Abstract: High energy and cost-effective lithium sulfur (Li–S) battery technology has been vigorously revisited in recent years due to the urgent need of advanced energy storage technologies for green transportation and large-scale energy storage applications. However, the market penetration of Li–S batteries has been plagued due to the gap in scientific knowledge between the fundamental research and the real application need. Here, a facile and effective approach to integrate commercial carbon nanoparticles into microsized secondary ones for application in high loading sulfur electrodes is proposed The slurry with the integrated particles is easily cast into electrode laminates with practically usable mass loadings. Uniform and crack-free coating with high loading of 2–8 mg cm−2 sulfur are successfully achieved. Based on the obtained thick electrodes, the dependence of areal specific capacity on mass loading, factors influencing electrode performance, and measures used to address the existing issues are studied and discussed.
  • Shao Y ,Rajput NN ,Hu J Z,Hu M Y,Liu T L.,Wei Z ,Gu M ,Deng X ,Xu S ,Han KS ,Wang J ,Nie Z ,Li G ,Zavadil K ,Xiao J ,Wang C M,Henderson W A,Zhang J ,Wang Y ,Mueller K T,Persson K A,Liu J. "Nanocomposite polymer electrolyte for rechargeable magnesium batteries." Nano Energy 12: 750-579 (March 2015).
    Abstract:Nanocomposite polymer electrolytes present new opportunities for rechargeable magnesium batteries. However, few polymer electrolytes have demonstrated reversible Mg deposition/dissolution and those that have still contain volatile liquids such as tetrahydrofuran (THF). In this work, we report a nanocomposite polymer electrolyte based on poly(ethylene oxide) (PEO), Mg(BH4)2 and MgO nanoparticles for rechargeable Mg batteries. Cells with this electrolyte have a high coulombic efficiency of 98% for Mg plating/stripping and a high cycling stability. Through combined experiment-modeling investigations, a correlation between improved solvation of the salt and solvent chain length, chelation and oxygen denticity is established. Following the same trend, the nanocomposite polymer electrolyte is inferred to enhance the dissociation of the salt Mg(BH4)2 and thus improve the electrochemical performance. The insights and design metrics thus obtained may be used in nanocomposite electrolytes for other multivalent systems.
  • Vijayakumar M, N Govind, B Li, X Wei, Z Nie, S Thevuthasan, VL Sprenkle, W Wang. "Aqua-vanadyl ion interaction with Nafion® membranes."Frontiers in Energy Research 3, article number 10 (March 2015).
    Abstract:Lack of comprehensive understanding about the interactions between Nafion membrane and battery electrolytes prevents the straightforward tailoring of optimal materials for redox flow battery applications. In this work, we analyzed the interaction between aqua-vanadyl cation and sulfonic sites within the pores of Nafion membranes using combined theoretical and experimental X-ray spectroscopic methods. Molecular level interactions, namely, solvent share and contact pair mechanisms are discussed based on vanadium and sulfur K-edge spectroscopic analysis.
  • Mehdi, BL, J Qian, E Nasybulin, C Park, DA Welch, R Faller, H Mehta, WA Henderson, W Xu, CM Wang, JE Evans, J Liu, J Zhang, KT Mueller, ND Browning. "Observation and Quantification of Nanoscale Processes in Lithium Batteries by Operando Electrochemical (S)TEM." <Nano Letters 15 (3): 2168-2173 (Feb. 2015).
    Abstract:An operando electrochemical stage for the transmission electron microscope has been configured to form a “Li battery” that is used to quantify the electrochemical processes that occur at the anode during charge/discharge cycling. Of particular importance for these observations is the identification of an image contrast reversal that originates from solid Li being less dense than the surrounding liquid electrolyte and electrode surface. This contrast allows Li to be identified from Li-containing compounds that make up the solid-electrolyte interphase (SEI) layer. By correlating images showing the sequence of Li electrodeposition and the evolution of the SEI layer with simultaneously acquired and calibrated cyclic voltammograms, electrodeposition, and electrolyte breakdown processes can be quantified directly on the nanoscale. This approach opens up intriguing new possibilities to rapidly visualize and test the electrochemical performance of a wide range of electrode/electrolyte combinations for next generation battery systems.
  • Qian J, WA Henderson, W Xu, P Bhattacharya, M Engelhard, O Borodin, J Zhang. "High rate and stable cycling of lithium metal anode."Nature Communications 6: Article number 6362 (Feb. 2015).
    Abstract:Lithium metal is an ideal battery anode. However, dendrite growth and limited Coulombic efficiency during cycling have prevented its practical application in rechargeable batteries. Herein, we report that the use of highly concentrated electrolytes composed of ether solvents and the lithium bis(fluorosulfonyl)imide salt enables the high-rate cycling of a lithium metal anode at high Coulombic efficiency (up to 99.1%) without dendrite growth. With 4 M lithium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane as the electrolyte, a lithium|lithium cell can be cycled at 10 mA cm−2 for more than 6,000 cycles, and a copper|lithium cell can be cycled at 4 mA cm−2 for more than 1,000 cycles with an average Coulombic efficiency of 98.4%. These excellent performances can be attributed to the increased solvent coordination and increased availability of lithium ion concentration in the electrolyte. Further development of this electrolyte may enable practical applications for lithium metal anode in rechargeable batteries.
  • Li B, Z Nie, M Vijayakumar, G Li, J Liu, VL Sprenkle, W Wang. "Ambipolar zinc-polyiodide electrolyte for a high-energy density aqueous redox flow battery." Nature Communications 6 article number 6303 (Feb. 2015).
    Abstract:Redox flow batteries are receiving wide attention for electrochemical energy storage due to their unique architecture and advantages, but progress has so far been limited by their low energy density (~25Whl-1). Here we report a high-energy density aqueous zinc-polyiodide flow battery. Using the highly soluble iodide/triiodide redox couple, a discharge energy density of 167Whl-1 is demonstrated with a near-neutral 5.0 M Znl2 electrolyte. Nuclear magnetic resonance study and density functional theory-based simulation along with flow test data indicate that the addition of an alcohol (ethanol) induces ligand formation between oxygen on the hydroxyl group and the zinc ions, which expands the stable electrolyte temperature window to from -20 to 50°C, while ameliorating the zinc dendrite. With the high-energy density and its benign nature free from strong acids and corrosive components, zinc-polyiodide flow battery is a promising candidate for various energy storage applications.
  • Jianming zheng, Pinghong Xu, Meng Gu, Jie Xiao, Nigel D. Browning, Pengfei Yan, Chongmin Wang, Ji-Guang Zhang."Structural and Chemical Evolution of Li- and Mn-Rich Layered Cathode Material."Chemistry of Materials 27 (4):1381-1390 (January 2015).
    Abstract: Lithium (Li)- and manganese-rich (LMR) layered-structure materials are very promising cathodes for high energy density lithium-ion batteries. However, the voltage fading mechanism in these materials as well as its relationships to fundamental structural changes is far from being sufficiently understood. Here we report the detailed phase transformation pathway in the LMR cathode (Li[Li0.2Ni0.2Mn0.6]O2) during cycling for samples prepared by the hydrothermal assisted (HA) method. It is found that the transformation pathway of the LMR cathode is closely correlated to its initial structure and preparation conditions. The results reveal that the LMR cathode prepared by the HA approach experiences a phase transformation from the layered structure (initial C2/m phase transforms to R3‾m phase after activation) to a LT-LiCoO2 type defect spinel-like structure (with the Fd3‾m space group) and then to a disordered rock-salt structure (with the Fm3‾m space group). The voltage fade can be well correlated with Li ion insertion into octahedral sites, rather than tetrahedral sites, in both defect spinel-like and disordered rock-salt structures. The reversible Li insertion/removal into/from the disordered rock-salt structure is ascribed to the Li excess environment that permits Li percolation in the disordered rock-salt structure despite the increased kinetic barrier. Meanwhile, because of the presence of a large quantity of oxygen vacancies, a significant decrease in the Mn valence is detected in the cycled particle, which is below that anticipated for a potentially damaging Jahn-Teller distortion (+3.5). Clarification of the phase transformation pathway, cation redistribution, oxygen vacancy and Mn valence change provides unique understanding of the voltage fade and capacity degradation mechanisms in the LMR cathode. The results also inspire us to further enhance the reversibility of the LMR cathode via improved surface structural stability.
  • Qiang Wang, Jianming Zhang, Eric Walter, Huilin Pan, Dongping Lu, Pengjian Zuo, Honghao Chen, Z. Daniel Deng, Bor Yann Liaw, Xiqian Yu, Xiaoqing Yang, Ji-Guang Zhang, Jun Liu, Jie Xiao."Direct Observation of Sulfur Radicals as Reaction Media in Lithium Sulfur Batteries."Journal of the Electrochemical Society 162 (3): A474-A478 (January 2015).
    Abstract: Lithium sulfur (Li-S) battery has been regaining tremendous interest in recent years because of its attractive attributes such as high gravimetric energy, low cost and environmental benignity. However, it is still not conclusively known how polysulfide ring/chain participates in the whole cycling and whether the discharge and charge processes follow the same pathway. Herein, we demonstrate the direct observation of sulfur radicals by using in situ electron paramagnetic resonance (EPR) technique. Based on the concentration changes of sulfur radicals at different potentials and the electrochemical characteristics of the cell, it is revealed that the chemical and electrochemical reactions in Li-S cell are driving each other to proceed through sulfur radicals, leading to two completely different reaction pathways during discharge and charge. The proposed radical mechanism may provide new perspectives to investigate the interactions between sulfur species and the electrolyte, inspiring novel strategies to develop Li-S battery technology.
  • Wei X ,Cosimbescu L ,Xu W ,Hu J Z,Vijayakumar M ,Feng J ,Hu M Y,Deng X ,Xiao J ,Liu J ,Sprenkle V L,Wang W. "Towards High-Performance Nonaqueous Redox Flow Electrolyte Via Ionic Modification of Active Species." Advanced Energy Materials 5 (1): 1400678 (Jan. 2015).
    Abstract:Nonaqueous redox flow batteries are emerging flow-based energy storage technologies that have the potential for higher energy densities than their aqueous counterparts because of their wider voltage windows. However, their performance has lagged far behind their inherent capability due to one major limitation of low solubility of the redox species. Here, a molecular structure engineering strategy towards high performance nonaqueous electrolyte is reported with significantly increased solubility. Its performance outweighs that of the state-of-the-art nonaqueous redox flow batteries. In particular, an ionic-derivatized ferrocene compound is designed and synthesized that has more than 20 times increased solubility in the supporting electrolyte. The solvation chemistry of the modified ferrocene compound. Electrochemical cycling testing in a hybrid lithium–organic redox flow battery using the as-synthesized ionic-derivatized ferrocene as the catholyte active material demonstrates that the incorporation of the ionic-charged pendant significantly improves the system energy density. When coupled with a lithium-graphite hybrid anode, the hybrid flow battery exhibits a cell voltage of 3.49 V, energy density about 50 Wh L−1, and energy efficiency over 75%. These results reveal a generic design route towards high performance nonaqueous electrolyte by rational functionalization of the organic redox species with selective ligand.
  • Liu, T, JT Cox, D Hu, X Deng, J Hu, MY Hu, J Xiao, Y Shao, K Tang, J Liu. "A fundamental study on the [(μ-Cl)3Mg2(THF)6]+ dimer electrolytes for rechargeable Mg batteries." Chemical Communications 51: 2312-2315 (Jan. 2015).
    Abstract:The long sought solvated [MgCl]+ species in the Mg-dimer electrolytes was characterized by soft mass spectrometry. The presented study provides an insightful understanding on the electrolyte chemistry of rechargeable Mg batteries.

2014

  • Parent LR, Y Cheng, PV Sushko, Y Shao, J Liu, CM Wang, ND Browning. "Realizing the Full Potential of Insertion Anodes for Mg-Ion Batteries Through the Nanostructuring of Sn." Nano Letters 15 (2): 1177-1182 (Dec. 2014).
    Abstract:Magnesium is of great interest as a replacement for lithium in next-generation ion-transfer batteries but Mg-metal anodes currently face critical challenges related to the formation of passivating layers during Mg-plating/stripping and anode–electrolyte–cathode incompatibilities.1−6 Alternative anode materials have the potential to greatly extend the spectrum of suitable electrolyte chemistries2,7 but must be systematically tailored for effective Mg2+ storage. Using analytical (scanning) transmission electron microscopy ((S)TEM) and ab initio modeling, we have investigated Mg2+ insertion and extraction mechanisms and transformation processes in β-SnSb nanoparticles (NPs), a promising Mg-alloying anode material. During the first several charge–discharge cycles (conditioning), the β-SnSb particles irreversibly transform into a porous network of pure-Sn and Sb-rich subparticles, as Mg ions replace Sn atoms in the SnSb lattice. After electrochemical conditioning, small Sn particles/grains (<33 ± 20 nm) exhibit highly reversible Mg-storage, while the Sb-rich domains suffer substantial Mg trapping and contribute little to the system performance. This result strongly indicates that pure Sn can act as a high-capacity Mg-insertion anode as theoretically predicted,8 but that its performance is strongly size-dependent, and stable nanoscale Sn morphologies (<40 nm) are needed for superior, reversible Mg-storage and fast system kinetics.
  • Li G, X Lu, JY Kim, MH Engelhard, JP Lemmon, and VL Sprenkle. "The Role of FeS in Initial Activation and Performance Degradation of Na-NiCl2 Batteries." Journal of Power Sources 272:398-403 (Dec 2014).
    Abstract: The role of iron sulfide (FeS) in initial cell activation and degradation in the Na-NiCl2 battery was investigated in this work. The research focused on identifying the effects of the FeS level on the electrochemical performance and morphological changes in the cathode. The x-ray photoelectron spectroscopy study along with battery tests revealed that FeS plays a critical role in initial battery activation by removing passivation layers on Ni particles. It was also found that the optimum level of FeS in the cathode resulted in minimum Ni particle growth and improved battery cycling performance. The results of electrochemical characterization indicated that sulfur species generated in situ during initial charging, such as polysulfide and sulfur, are responsible for removing the passivation layer. Consequently, the cells containing elemental sulfur in the cathode exhibited similar electrochemical behavior during initial charging compared to that of the cells containing FeS.
  • Wei X, W Xu, M Vijayakumar, L Cosimbescu, TL Liu, VL Sprenkle, and W Wang. "TEMPO-based Catholyte for High Energy Density Nonaqueous Redox Flow Batteries." Advanced Materials 26(45):7649-7653 (Dec 2014).
    Abstract:A TEMPO-based non-aqueous electrolyte with the TEMPO concentration as high as 2.0 M is demonstrated as a high-energy-density catholyte for redox flow battery applications. With a hybrid anode, Li|TEMPO flow cells using this electrolyte deliver an energy efficiency of ca. 70% and an impressively high energy density of 126 W h L-1.
  • Zhang Y ,Qian J ,Xu W ,Russell S M,Chen X ,Nasybulin E ,Bhattacharya P ,Engelhard M H,Mei D ,Cao R ,Ding F ,Cresce A V,Xu K ,Zhang J. "Dendrite-Free Lithium Deposition with Self-Aligned Nanorod Structure." Nano Letters 14 (12): 6889-6896 (Nov. 2014).
    Abstract:Suppressing lithium (Li) dendrite growth is one of the most critical challenges for the development of Li metal batteries. Here, we report for the first time the growth of dendrite-free lithium films with a self-aligned and highly compacted nanorod structure when the film was deposited in the electrolyte consisting of 1.0 M LiPF6 in propylene carbonate with 0.05 M CsPF6 as an additive. Evolution of both the surface and the cross-sectional morphologies of the Li films during repeated Li deposition/stripping processes were systematically investigated. It is found that the formation of the compact Li nanorod structure is preceded by a solid electrolyte interphase (SEI) layer formed on the surface of the substrate. Electrochemical analysis indicates that an initial reduction process occurred at ∼2.05 V vs Li/Li+ before Li deposition is responsible for the formation of the initial SEI, while the X-ray photoelectron spectroscopy indicates that the presence of CsPF6 additive can largely enhance the formation of LiF in this initial SEI. Hence, the smooth Li deposition in Cs+- containing electrolyte is the result of a synergistic effect of Cs+ additive and preformed SEI layer. A fundamental understanding on the composition, internal structure, and evolution of Li metal films may lead to new approaches to stabilize the long-term cycling stability of Li metal and other metal anodes for energy storage applications.
  • Adams B D,Black R ,Radtke C ,Williams Z ,Mehdi B L,Browning N D,Nazar L F. "The Importance of Nanometric Passivating Films on Cathodes for Li–Air Batteries" ACS Nano 8 (12): 12483-12493 (Nov. 2014).
    Abstract: Recently, there has been a transition from fully carbonaceous positive electrodes for the aprotic lithium oxygen battery to alternative materials and the use of redox mediator additives, in an attempt to lower the large electrochemical overpotentials associated with the charge reaction. However, the stabilizing or catalytic effect of these materials can become complicated due to the presence of major side-reactions observed during dis(charge). Here, we isolate the charge reaction from the discharge by utilizing electrodes prefilled with commercial lithium peroxide with a crystallite size of about 200–800 nm. Using a combination of S/TEM, online mass spectrometry, XPS, and electrochemical methods to probe the nature of surface films on carbon and conductive Ti-based nanoparticles, we show that oxygen evolution from lithium peroxide is strongly dependent on their surface properties. Insulating TiO2 surface layers on TiC and TiN - even as thin as 3 nm–can completely inhibit the charge reaction under these conditions. On the other hand, TiC, which lacks this oxide film, readily facilitates oxidation of the bulk Li2O2 crystallites, at a much lower overpotential relative to carbon. Since oxidation of lithium oxygen battery cathodes is inevitable in these systems, precise control of the surface chemistry at the nanoscale becomes of upmost importance.
  • Jianming Zhang, Meng Gu, Jie Xiao, Bryant J. Polzin, Pengfei Yan, Xilin Chen, Chongmin Wang, Ji-Guang Zhang."Functioning Mechanism of AlF3 Coating on the Li- and Mn-Rich Cathode Materials."Chemistry of Materials 26 (22): 6320-6327 (October 2014).
    Abstract: We report systematic studies of the microstructural changes of uncoated and AlF3-coated Li-rich Mn-rich (LMR) cathode materials (Li1.2Ni0.15Co0.10Mn0.55O2) before and after cycling using a combination of aberration-corrected scanning/transmission electron microscopy (S/TEM) and electron energy loss spectroscopy (EELS). TEM coupled with EELS provides detailed information about the crystallographic and electronic structure changes that occur after cycling, thus revealing the fundamental improvement mechanism of surface coating. The results demonstrate that the surface coating reduces oxidation of the electrolyte at high voltage, suppressing the accumulation of a thick solid electrolyte interface (SEI) layer on electrode particle surface. Surface coating significantly enhances the stability of the surface structure and protects the electrode from severe etching/corrosion by the acidic species in the electrolyte, reducing the formation of etched surfaces and corrosion pits. Moreover, surface coating alleviates the undesirable voltage fade by mitigating layered to spinel-like phase transformation in the bulk region of the material. These fundamental findings may also be widely applied to explain the functioning mechanisms of other surface coatings used in a broad range of electrode materials.
  • Han, KS, NN Rajput, X wei, W Wang, JZ Hu, KA Persson, KT Mueller. "Diffusional motion of redox centers in carbonate electrolytes" Journal of Physical Chemistry 141(10): 104509 (Sept. 2014).
    Abstract: Ferrocene (Fc) and N-(ferrocenylmethyl)-N,N-dimethyl-N-ethylammonium bistrifluoromethyl-sulfonimide (Fc1N112-TFSI) were dissolved in carbonate solvents and self-diffusion coefficients (D) of solutes and solvents were measured by (1)H and (19)F pulsed field gradient nuclear magnetic resonance (NMR) spectroscopy. The organic solvents were propylene carbonate (PC), ethyl methyl carbonate (EMC), and a ternary mixture that also includes ethylene carbonate (EC). Results from NMR studies over the temperature range of 0-50 °C and for various concentrations (0.25-1.7 M) of Fc1N112-TFSI are compared to values of D simulated with classical molecular dynamics (MD). The measured self-diffusion coefficients gradually decreased as the Fc1N112-TFSI concentration increased in all solvents. Since TFSI(-) has fluoromethyl groups (CF3), D(TFSI) could be measured separately and the values found are larger than those for D(Fc1N112) in all samples measured. The EC, PC, and EMC have the same D in the neat solvent mixture and when Fc is dissolved in EC/PC/EMC at a concentration of 0.2 M, probably due to the interactions between common carbonyl structures within EC, PC, and EMC. A difference in D (D(PC) < D(EC) < D(EMC)), and both a higher E(a) for translational motion and higher effective viscosity for PC in the mixture containing Fc1N112-TFSI reflect the interaction between PC and Fc1N112(+), which is a relatively stronger interaction than that between Fc1N112(+) and other solvent species. In the EC/PC/EMC solution that is saturated with Fc1N112-TFSI, we find that D(PC) = D(EC) = D(EMC) and Fc1N112(+) and all components of the EC/PC/EMC solution have the same E(a) for translational motion, while the ratio D(EC/PC/EMC)/D(Fc1N112) is approximately 3. These results reflect the lack of available free volume for independent diffusion in the saturated solution. The Fc1N112(+) transference numbers lie around 0.4 and increase slightly as the temperature is increased in the PC and EMC solvents. The trends observed for D from simulations are in good agreement with experimental results and provide molecular level understanding of the solvation structure of Fc1N112-TFSI dissolved in EC/PC/EMC.
  • Vijayakumar, M., Nie, Z., Walter, E., Hu, J., Liu, J., Sprenkle, V. and Wang, W. "Understanding Aqueous Electrolyte Stability through Combined Computational and Magnetic Resonance Spectroscopy: A Case Study on Vanadium Redox Flow Battery Electrolytes." ChemPlusChem doi: 10.1002/cplu.201402139 (Sept 2014).
    Abstract: Commercial sodium-sulphur or sodium-metal halide batteries typically need an operating temperature of 300-350°C, and one of the reasons is poor wettability of liquid sodium on the surface of beta alumina. Here we report an alloying strategy that can markedly improve the wetting, which allows the batteries to be operated at much lower temperatures. Our combined experimental and computational studies suggest that addition of caesium to sodium can markedly enhance the wettability. Single cells with Na-Cs alloy anodes exhibit great improvement in cycling life over those with pure sodium anodes at 175 and 150°C. The cells show good performance even at as low as 95°C. These results demonstrate that sodium-beta alumina batteries can be operated at much lower temperatures with successfully solving the wetting issue. This work also suggests a strategy to use liquid metals in advanced batteries that can avoid the intrinsic safety issues associated with dendrite formation.
  • Cheng Y, LR Parent, Y Shao, CM Wang, VL Sprenkle, G Li, and J Liu. "Facile Synthesis of Chevrel Phase Nanocubes and their Applications for Multivalent Energy Storage." Chemistry of Materials 26(17):4904-4907. doi:10.1021/cm502306c (Aug 2014).
    Abstract: The Chevrel phases (CPs, MxMo6T8, M=metal, T=S or Se) are capable of rapid and reversible intercalation of multivalent ions and are the most practical cathode materials for rechargeable magnesium batteries. For the first time, we report a facile method for synthesizing Mo6S8 nanoparticles and demonstrate that these nanoparticles have significantly better Mg2+ intercalation kinetics compared with microparticles. The results described in this work could inspire the synthesis of nanoscale CPs, which could substantially impact their application.
  • Wei X, L Cosimbescu, W Xu, JZ Hu, M Vijayakumar, J Feng, MY Hu, X Deng, J Xiao, J Liu, VL Sprenkle, and W Wang. "Towards High Performance Nonaqueous Redox Flow Electrolyte Via Ionic Modification of Active Species." Advanced Energy Materials (1400678), doi:DOI: 10.1002/aenm.201400678 (Aug 2014).
    Abstract: Nonaqueous redox flow batteries are emerging flow-based energy storage technologies that have the potential for higher energy densities than their aqueous counterparts because of their wider voltage windows. However, their performance has lagged far behind their inherent capability due to one major limitation of low solubility of the redox species. Here, a molecular structure engineering strategy towards high performance nonaqueous electrolyte is reported with significantly increased solubility. Its performance outweighs that of the state-of-the-art nonaqueous redox flow batteries. In particular, an ionic-derivatized ferrocene compound is designed and synthesized that has more than 20 times increased solubility in the supporting electrolyte. The solvation chemistry of the modified ferrocene compound. Electrochemical cycling testing in a hybrid lithium-organic redox flow battery using the as-synthesized ionic-derivatized ferrocene as the catholyte active material demonstrates that the incorporation of the ionic-charged pendant significantly improves the system energy density. When coupled with a lithium-graphite hybrid anode, the hybrid flow battery exhibits a cell voltage of 3.49 V, energy density about 50 Wh L-1, and energy efficiency over 75%. These results reveal a generic design route towards high performance nonaqueous electrolyte by rational functionalization of the organic redox species with selective ligand.
  • X. Lu, G. Li, J.Y. Kim, D. Mei, J.P. Lemmon, and V.L. Sprenkle, "Liquid-metal electrode to enable ultra-low temperature sodium–beta alumina batteries for renewable energy storage." Nat. Commun. 5:4578 (Aug 2014).
    Abstract: Commercial sodium–sulphur or sodium-metal halide batteries typically need an operating temperature of 300–350°C, and one of the reasons is poor wettability of liquid sodium on the surface of beta alumina. Here we report an alloying strategy that can markedly improve the wetting, which allows the batteries to be operated at much lower temperatures. Our combined experimental and computational studies suggest that addition of caesium to sodium can markedly enhance the wettability. Single cells with Na-Cs alloy anodes exhibit great improvement in cycling life over those with pure sodium anodes at 175 and 15°C. The cells show good performance even at as low as 95°C. These results demonstrate that sodium–beta alumina batteries can be operated at much lower temperatures with successfully solving the wetting issue. This work also suggests a strategy to use liquid metals in advanced batteries that can avoid the intrinsic safety issues associated with dendrite formation.
  • Eduard Nasybulin, Wu Xu, B. Layla Mehdi, Edwin Thomsen, Mark H. Engelhard, Robert C. Masse, Priyanka Bhattacharya, Meng Gu, Wendy Bennett, Zimin Nie, Chongmin Wang, Nigel D. Browning, Ji-Guang Zhang. "Formation of Interfacial Layer and Long-Term Cyclability of Li–O2 Batteries."ACS Applied Materials & Interfaces 6 (16):14141-14151 (July 2014).
    Abstract: The long-term operation of Li–O2 batteries under full discharge/charge conditions is investigated in a glyme-based electrolyte. The formation of stable interfacial layer on the electrode surface during the initial cycling stabilizes reaction products at subsequent cycling stages as demonstrated by quantitative analyses of the discharge products and the gases released during charging. There is a quick switch from the predominant formation of Li2O2 to the predominant formation of side products during the first few cycles. However, after the formation of the stable interfacial layer, the yield of Li2O2 in the reaction products is stabilized at about 33–40%. Extended cycling under full discharge/charge conditions is achievable upon selection of appropriate electrode materials (carbon source and catalyst) and cycling protocol. Further investigation on the interfacial layer, which in situ forms on air electrode, may increase the long-term yield of Li2O2 during the cycling and enable highly reversible Li–O2 batteries required for practical applications.
  • Nasybulin E N,Xu W ,Mehdi B L,Thomsen E C,Engelhard M H,Masse R C,Bhattacharya P ,Gu M ,Bennett W D,Nie Z ,Wang C M,Browning N D,Zhang J. "Formation of Interfacial Layer and Long-Term Cyclability of Li-O2 Batteries." ACS Applied Materials & Interfaces 6 (16): 14141-14151 (July 2014).
    Abstract:The long-term operation of Li–O2 batteries under full discharge/charge conditions is investigated in a glyme-based electrolyte. The formation of stable interfacial layer on the electrode surface during the initial cycling stabilizes reaction products at subsequent cycling stages as demonstrated by quantitative analyses of the discharge products and the gases released during charging. There is a quick switch from the predominant formation of Li2O2 to the predominant formation of side products during the first few cycles. However, after the formation of the stable interfacial layer, the yield of Li2O2 in the reaction products is stabilized at about 33–40%. Extended cycling under full discharge/charge conditions is achievable upon selection of appropriate electrode materials (carbon source and catalyst) and cycling protocol. Further investigation on the interfacial layer, which in situ forms on air electrode, may increase the long-term yield of Li2O2 during the cycling and enable highly reversible Li–O2 batteries required for practical applications.
  • Du Y ,Gu M ,Varga T ,Wang C M,Bowden M E,Chambers S A .  "Strain Accommodation by Facile WO6 Octahedral Distortion and Tilting during WO3 Heteroepitaxy on SrTiO3(001)" Applied Materials & Interfaces 6 (16):14253-14258 (July 2014)
    Abstract: In this work, we demonstrate that WO6 octahedra in tungsten trioxide (WO3) undergo an unusually large degree of distortion and tilting to accommodate interfacial strain. This motion strongly impacts nucleation, structure, and defect formation during the epitaxial growth of WO3 on SrTiO3(001). A metastable tetragonal phase can be stabilized by heteroepitaxy and a thickness-dependent phase transition (tetragonal to monoclinic) is observed. In contrast to misfit dislocation formation, facile WO6 octahedral deformation gives rise to three types of planar defects. The thicknesses of affected regions can range from several to tens of nanometers with graded lattice parameters, allowing the strain from interfacial lattice mismatch to be relieved gradually. These atomically resolved, unique interfacial defects may significantly alter the electronic, electrochromic, and mechanical properties of WO3 epitaxial films.
  • Cao R ,Walter E D,Xu W ,Nasybulin E N,Bhattacharya P ,Bowden M E,Engelhard M H,Zhang J. "The Mechanisms of Oxygen Reduction and Evolution Reactions in Nonaqueous Lithium–Oxygen Batteries." ChemSusChem 7 (9):2436-2440 (July 2014).
    Abstract:A fundamental understanding of the mechanisms of both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in nonaqueous lithium–oxygen (Li–O2) batteries is essential for the further development of these batteries. In this work, we systematically investigate the mechanisms of the ORR/OER reactions in nonaqueous Li–O2 batteries by using electron paramagnetic resonance (EPR) spectroscopy, using 5,5-dimethyl-pyrroline N-oxide as a spin trap. The study provides direct verification of the formation of the superoxide radical anion (O2.−) as an intermediate in the ORR during the discharge process, while no O2.− was detected in the OER during the charge process. These findings provide insight into, and an understanding of, the fundamental reaction mechanisms involving oxygen and guide the further development of this field.
  • Xiaolin Li, Meng Gu, Shenyang Hu, Rhiannon Kennard, Pengfei Yan, Xilin Chen, Chongmin Wang, Michael J. Sailor, Ji-Guang Zhang, Jun Liu. "Mesoporous silicon sponge as an anti-pulverization structure for high-performance lithium-ion battery anodes."Nature Communications 5: Article number 4105 (July 2014).
    Abstract: Nanostructured silicon is a promising anode material for high-performance lithium-ion batteries, yet scalable synthesis of such materials, and retaining good cycling stability in high loading electrode remain significant challenges. Here we combine in-situ transmission electron microscopy and continuum media mechanical calculations to demonstrate that large (>20 μm) mesoporous silicon sponge prepared by the anodization method can limit the particle volume expansion at full lithiation to ~30% and prevent pulverization in bulk silicon particles. The mesoporous silicon sponge can deliver a capacity of up to ~750 mAh g-1 based on the total electrode weight with >80% capacity retention over 1,000 cycles. The first cycle irreversible capacity loss of pre-lithiated electrode is >5%. Bulk electrodes with an area-specific-capacity of ~1.5 mAh cm-2 and ~92% capacity retention over 300 cycles are also demonstrated. The insight obtained from this work also provides guidance for the design of other materials that may experience large volume variation during operations.
  • Anqiang Pan, Yaping Wang, Wu Xu, Zhiwei Nie, Shuquan Liang, Zimin Nie, Chongmin Wang, Guozhong Cao, Ji-Guang Zhang. "High-performance anode based on porous Co3O4 nanodiscs."Journal of Power Sources 255: 125-129 (June 2014).
    Abstract: In this article, two-dimensional, Co3O4 hexagonal nanodiscs are prepared using a hydrothermal method without surfactants. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been employed to characterize the structural properties. As revealed by the SEM and TEM experiments, the thickness of our as-fabricated Co3O4 hexagonal nanodiscs is about 20 nm, and the pore diameters range from several nanometers to 30 nm. As an anode for lithium-ion batteries, porous Co3O4 nanodiscs exhibit an average discharge voltage of ∼1 V (vs. Li/Li+) and a high specific charge capacity of 1161 mAh g−1 after 100 cycles. They also demonstrate excellent rate performance and high Columbic efficiency at various rates. These results indicate that porous Co3O4 nanodiscs are good candidates as anode materials for lithium-ion batteries.
  • BR Chalamala, T Soundappan, GR Fisher, MA Anstey, VV Viswanathan, ML Perry. "Redox Flow Batteries: An Engineering Perspective." Proceedings of the IEEE 102 (6): 976 - 999 (June 2014).
    Abstract:Redox flow batteries are well suited to provide modular and scalable energy storage systems for a wide range of energy storage applications. In this paper, we review the development of redox-flow-battery technology including recent advances in new redox active materials, cell designs, and systems, all from the perspective of engineers interested in applying this technology. We discuss cost, performance, and reliability metrics that are critical for deployment of large flow-battery systems. The technology, while relatively young, has the potential for significant improvement through reduced materials costs, improved energy efficiency, and significant reduction in the overall system costs.
  • Yingwen Cheng, Yuyan Shao, Ji-Guang Zhang, Vincent L. Sprenkle, Jun Liu and Guosheng Li, "High performance batteries based on hybrid magnesium and lithium chemistry" Chem. Commun., 2014, 50, 9644-9646 (June 2014).
    Abstract: This work studied hybrid batteries assembled with a Mg metal anode, a Li+ ion intercalation cathode and a dual-salt electrolyte containing Mg2+ and Li+ ions. We show that such hybrid batteries were able to combine the advantages of Li and Mg electrochemistry. They delivered outstanding rate performance (83% capacity retention at 15 C) with superior safety and stability (B5% fade for 3000 cycles).
  • J.T. Vaughey, Gao Liu, Ji-Guang Zhang."Stabilizing the surface of lithium metal."MRS Bulletin 39 (5): 429-435 (May 2014).
    Abstract: The success of high capacity energy storage systems based on lithium (Li) batteries relies on the realization of the promise of Li-metal anodes. Li metal has many advantageous properties, including an extremely high theoretical specific capacity (3860 mAh g–1), the lowest electrochemical potential (–3.040 V versus standard hydrogen electrode), and low density (0.59 g cm–3), which, all together, make it a very desirable electrode for energy storage devices. However, while primary Li batteries are used for numerous commercial applications, rechargeable Li-metal batteries that utilize Li-metal anodes have not been as successful. This article discusses the properties of Li metal in the absence of surface stabilization, as well as three different approaches currently under investigation for stabilizing the surface of Li metal to control its reactivity within the electrochemical environment of a Li-based battery.
  • Mehdi B L,Gu M ,Parent L R,Xu W ,Nasybulin E N,Chen X ,Unocic R R,Xu P ,Welch D A,Abellan P ,Zhang J ,Liu J ,Wang C M,Arslan I ,Evans J E,Browning N D. "In-situ electrochemical transmission electron microscopy for battery research." Microscopy & Microanalysis 20 (2): 484-492 (April 2014).
    Abstract:The recent development of in-situ liquid stages for (scanning) transmission electron microscopes now makes it possible for us to study the details of electrochemical processes under operando conditions. As electrochemical processes are complex, care must be taken to calibrate the system before any in-situ/operando observations. In addition, as the electron beam can cause effects that look similar to electrochemical processes at the electrolyte/electrode interface, an understanding of the role of the electron beam in modifying the operando observations must also be understood. In this paper we describe the design, assembly, and operation of an in-situ electrochemical cell, paying particular attention to the method for controlling and quantifying the experimental parameters. The use of this system is then demonstrated for the lithiation/delithiation of silicon nanowires.
  • Jianming Zheng, Meng Gu, Arda Genc, Jie Xiao, Pinghong Xu, Xilin Chen, Zihua Zhu, Wenbo Zhao, Lee Pullan, Chongmin Wang, Ji-Guang Zhang. "Mitigating Voltage Fade in Cathode Materials by Improving the Atomic Level Uniformity of Elemental Distribution."Nano Letters 14 (5): 2628-2635 (April 2014).
    Abstract: Lithium- and manganese-rich (LMR) layered-structure materials are very promising cathodes for high energy density lithium-ion batteries. However, their voltage fading mechanism and its relationships with fundamental structural changes are far from being well understood. Here we report for the first time the mitigation of voltage and energy fade of LMR cathodes by improving the atomic level spatial uniformity of the chemical species. The results reveal that LMR cathodes (Li[Li0.2Ni0.2M0.6]O2) prepared by coprecipitation and sol–gel methods, which are dominated by a LiMO2 type R3‾m structure, show significant nonuniform Ni distribution at particle surfaces. In contrast, the LMR cathode prepared by a hydrothermal assisted method is dominated by a Li2MO3 type C2/m structure with minimal Ni-rich surfaces. The samples with uniform atomic level spatial distribution demonstrate much better capacity retention and much smaller voltage fade as compared to those with significant nonuniform Ni distribution. The fundamental findings on the direct correlation between the atomic level spatial distribution of the chemical species and the functional stability of the materials may also guide the design of other energy storage materials with enhanced stabilities.
  • Vijayakumar M ,Govind N ,Walter E D,Burton S D,Shukla A K,Devaraj A ,Xiao J ,Liu J ,Wang C M,Karim A M,Thevuthasan S. "Molecular structure and stability of dissolved lithium polysulfide species." Phys. Chem. Chem. Phys. 16: 10923-10932 (March 2014).
    Abstract:The ability to predict the solubility and stability of lithium polysulfide is vital in realizing longer lasting lithium–sulfur batteries. Herein we report combined experimental and computational analyses to understand the dissolution mechanism of lithium polysulfide species in an aprotic solvent medium. Multinuclear NMR, variable temperature ESR and sulfur K-edge XAS analyses reveal that the lithium exchange between polysulfide species and solvent molecules constitutes the first step in the dissolution process. Lithium exchange leads to de-lithiated polysulfide ions (Sn2−) which subsequently form highly reactive free radicals through dissociation reaction (Sn2− → 2Sn2˙−). The energy required for the dissociation and possible dimer formation reactions of the polysulfide species is analyzed using density functional theory (DFT) based calculations. Based on these findings, we discuss approaches to optimize the electrolyte in order to control the polysulfide solubility.
  • Jianming Zheng, Jie Xiao, Meng Gu, Pengjian Zuo, Chongmin Wang, Ji-Guang Zhang. "Interface modifications by anion receptors for high energy lithium ion batteries." Journal of Power Sources 250: 313-318 (March 2014).
    Abstract: Li-rich, Mn-rich (LMR) layered composite has attracted extensive interests because of its highest energy density among all cathode candidates for lithium ion batteries (LIB). However, capacity degradation and voltage fading remain the major challenges for LMR cathodes prior to their practical applications. Here, we demonstrate that anion receptor, tris(pentafluorophenyl)borane ((C6F5)3B, TPFPB), substantially enhances the stability of electrode/electrolyte interface and thus improves the cycling stability of LMR cathode Li[Li0.2Ni0.2Mn0.6]O2. In the presence of 0.2 M TPFPB, Li[Li0.2Ni0.2Mn0.6]O2 shows an improved capacity retention of 76.8% after 500 cycles. It is proposed that TPFPB effectively confines the highly active oxygen species released from structural lattice through its strong coordination ability and high oxygen solubility. The electrolyte decomposition caused by the oxygen species attack is therefore largely mitigated, forming reduced amount of byproducts on the cathode surface. Additionally, other salts such as insulating LiF derived from electrolyte decomposition are also soluble in the presence of TPFPB. The collective effects of TPFPB mitigate the accumulation of parasitic reaction products and stabilize the interfacial resistances between cathode and electrolyte during extended cycling, thus significantly improving the cycling performance of Li[Li0.2Ni0.2Mn0.6]O2.
  • Abellan Baeza P ,Mehdi B L,Parent L R,Gu M ,Park C ,Xu W ,Zhang Y ,Arslan I ,Zhang J ,Wang C M,Evans J E,Browning N D. "Probing the Degradation Mechanisms in Electrolyte Solutions for Li-Ion Batteries by in Situ Transmission Electron Microscopy" Nano Letters 14 (3): 1293-1299 (Feb. 2014).
    Abstract:Development of novel electrolytes with increased electrochemical stability is critical for the next generation battery technologies. In situ electrochemical fluid cells provide the ability to rapidly and directly characterize electrode/electrolyte interfacial reactions under conditions directly relevant to the operation of practical batteries. In this paper, we have studied the breakdown of a range of inorganic/salt complexes relevant to state-of-the-art Li-ion battery systems by in situ (scanning) transmission electron microscopy ((S)TEM). In these experiments, the electron beam itself caused the localized electrochemical reaction that allowed us to observe electrolyte breakdown in real-time. The results of the in situ (S)TEM experiments matches with previous stability tests performed during battery operation and the breakdown products and mechanisms are also consistent with known mechanisms. This analysis indicates that in situ liquid stage (S)TEM observations could be used to directly test new electrolyte designs and identify a smaller library of candidate solutions deserving of more detailed characterization. A systematic study of electrolyte degradation is also a necessary first step for any future controlled in operando liquid (S)TEM experiments intent on visualizing working batteries at the nanoscale.
  • Ran Yi, Jinkui Feng, Dongping Lu, Mikhail Gordin, Shuru Chen, Daiwon Choi, Donghai Wang, "GeOx/Reduced Graphene Oxide Composite as an Anode for Li-ion Batteries: Enhanced Capacity via Reversible Utilization of Li2O along with Improved Rate Performance" Advanced Functional Materials, 24, p.1059-1066 (Feb 2014).
    Abstract: A self-assembled GeOx/reduced graphene oxide (GeOx/RGO) composite, where GeOx nanoparticles are grown directly on reduced graphene oxide sheets, is synthesized via a facile one-step reduction approach and studied by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, electron energy loss spectroscopy elemental mapping, and other techniques. Electrochemical evaluation indicates that incorporation of reduced graphene oxide enhances both the rate capability and reversible capacity of GeOx, with the latter being due to the RGO enabling reversible utilization of Li2O. The composite delivers a high reversible capacity of 1600 mAh g-1 at a current density of 100 mA g-1, and still maintains a capacity of 410 mAh g-1 at a high current density of 20 A g-1. Owing to the flexible reduced graphene oxide sheets enwrapping the GeOx particles, the cycling stability of the composite is also improved significantly. To further demonstrate its feasibility in practical applications, the synthesized GeOx/RGO composite anode is successfully paired with a high voltage LiNi0.5Mn1.5O4 cathode to form a full cell, which shows good cycling and rate performance.
  • Viswanathan VV, AJ Crawford, DE Stephenson, S Kim, W Wang, B Li, GW Coffey, EC Thomsen, GL Graff, PJ Balducci, MCW Kintner-Meyer, and VL Sprenkle. 2014. "Cost and Performance Model for Redox Flow Batteries." Journal of Power Sources, 247:1040-1051. doi:10.1016/j.jpowsour.2012.12.023 (Feb 2014).
    Abstract: A cost model is developed for all vanadium and iron-vanadium redox flow batteries. Electrochemical performance modeling is done to estimate stack performance at various power densities as a function of state of charge and operating conditions. This is supplemented with a shunt current model and a pumping loss model to estimate actual system efficiency. The operating parameters such as power density, flow rates and design parameters such as electrode aspect ratio and flow frame channel dimensions are adjusted to maximize efficiency and minimize capital costs. Detailed cost estimates are obtained from various vendors to calculate cost estimates for present, near-term and optimistic scenarios. The most cost-effective chemistries with optimum operating conditions for power or energy intensive applications are determined, providing a roadmap for battery management systems development for redox flow batteries. The main drivers for cost reduction for various chemistries are identified as a function of the energy to power ratio of the storage system.
  • Xilin Chen, Xiaolin Li, Donghai Mei, Ju Feng, Mary Y Hu, Jianzhi Hu, Mark Engelhard, Jianming Zheng, Wu Xu, Jie Xiao, Jun Liu, Ji-Guang Zhang. "Reduction Mechanism of Fluoroethylene Carbonate for Stable Solid–Electrolyte Interphase Film on Silicon Anode." ChemSusChem 7 (2): 549-554 (Feb. 2014).
    Abstract: Fluoroethylene carbonate (FEC) is an effective electrolyte additive that can significantly improve the cycling ability of silicon and other anode materials. However, the fundamental mechanism of this improvement is still not well understood. Based on the results obtained from 6Li NMR and X-ray photoelectron spectroscopy studies, we propose a molecular-level mechanism for how FEC affects the formation of solid electrolyte interphase (SEI) film: 1)FEC is reduced through the opening of the five-membered ring leading to the formation of lithium poly(vinyl carbonate), LiF, and some dimers; 2)the FEC-derived lithium poly(vinyl carbonate) enhances the stability of the SEI film. The proposed reduction mechanism opens a new path to explore new electrolyte additives that can improve the cycling stability of silicon-based electrodes.
  • G, Li, X. Lu, J.Y. Kim, J.P. Lemmon, and V.L. Sprenkle, "Improved cycling behavior of ZEBRA battery operated at intermediate temperature of 175°C," Journal of Power Sources, 249 (2014) 414-417 (Jan. 2014).
    Abstract: Operation of the sodium-nickel chloride battery at temperatures below 200°C reduces cell degradation and improves cyclability. One of the main technical issues with operating this battery at intermediate temperatures such as 175°C is the poor wettability of molten sodium on β"”-alumina solid electrolyte (BASE), which causes reduced active area and limits charging. In order to overcome the poor wettability of molten sodium on BASE at 175°C, a Pt grid was applied on the anode side of the BASE using a screen printing technique. Cells with their active area increased by metallized BASEs exhibited deeper charging and stable cycling behavior.

2013

  • Jiuchun Jiang, Wei Shi, Jianming Zheng, Pengjian Zuo, Jie Xiao, Xilin Chen, Wu Xu, Ji-Guang Zhang. "Optimized Operating Range for Large-Format LiFePO4/Graphite Batteries." Journal of the Electrochemical Society 161 (3): A336-A341 (Dec. 2013).
    Abstract: Long-term cycling performances of LiFePO4/graphite batteries have been investigated in different state-of-charge (SOC) ranges. It is found that batteries cycled in the medium SOC range exhibit superior cycling stability over those cycled at both ends of the SOC ranges. A variety of characterization techniques, including galvanostatic intermittent titration technique (GITT) analysis, model-based parameter identification, electrochemical impedance spectroscopy analysis, and entropy change test, were used to investigate the performance difference of the batteries cycled in different SOC ranges. The results reveal that batteries at the end of SOC exhibit much higher polarization impedance than those within the medium-SOC range. This result can be attributed to the significant structural change of the cathode and anode materials as revealed by the large entropy change within these SOC regions. Identification of the best operating conditions for LiFePO4/graphite batteries will significantly extend their cycle life. The general control principle obtained in this work, such as modulating the charge/discharge current to minimize the impedance extremes can also be used in the operation control of other battery systems.
  • Sacci R L,Dudney N J,More K L,Parent L R,Arslan I ,Browning N D. "Direct visualization of initial SEI morphology and growth kinetics during lithium deposition by in situ electrochemical transmission electron microscopy."Chemical Communications 17: 2104-2107 (Dec. 2013).
    Abstract: Deposition of Li is a major safety concern existing in Li-ion secondary batteries. Here we perform the first in situ high spatial resolution measurement coupled with real-time quantitative electrochemistry to characterize SEI formation on gold using a standard battery electrolyte. We demonstrate that a dendritic SEI forms prior to Li deposition and that it remains on the surface after Li electrodissolution.
  • B Li, M Gu, Z Nie, X Wei, C Wang, V Sprenkle, and W Wang, "Nanorod Niobium Oxide as Powerful Catalysts for an All Vanadium Redox Flow Battery", Nano Letters, 2014, 14, 158-165 (Dec 2013).
    Abstract: A powerful low-cost electrocatalyst, nanorod Nb2O5, is synthesized using hydrothermal method with monoclinic phases and simultaneously deposited on the surface of graphite felt (GF) electrode in an all vanadium flow battery (VRB). Cyclic voltammetry (CV) study confirmed that Nb2O5 has catalytic effects towards redox couples of V(II)/V(III) at the negative side and V(IV)/V(V) at the positive side to facilitate the electrochemical kinetics of the vanadium redox reactions. Because of poor conductivity of Nb2O5, the performance of the Nb2O5 loaded electrodes is strongly dependent on the nanosize and uniform distribution of catalysts on GFs surfaces. Accordingly, optimal amounts of W-doped Nb2O5 nanorods with minimum agglomeration and improved distribution on GFs surfaces are established by adding water-soluble compounds containing tungsten (W) into the precursor solutions. The corresponding energy efficiency is enhanced by ~10.7% at high current density (150 mA.cm-2) as compared with one without catalysts. Flow battery cyclic performance also demonstrates the excellent stability of the as prepared Nb2O5 catalyst enhanced electrode. These results suggest that Nb2O5-based nanorods, replacing expensive noble metals, uniformly decorating GFs holds great promise as high-performance electrodes for VRB applications.
  • Eduard Nasybulin, Wu Xu, Mark H. Engelhard, Zimin Nie, Xiaohong S. Li, Ji-Guang Zhang. "Stability of polymer binders in Li–O2 batteries."Journal of Power Sources 243: 899-907 (Dec. 2013).
    Abstract: The stability of various polymer binders was systematically investigated in the oxygen-rich environment required for the operation of Li–O2 batteries. Due to the coverage on air electrode surface by the discharge products and decomposition products of the electrolyte during the discharge process of Li–O2 batteries, the binder in the air electrode is hard to be detected making the evaluation of its stability problematic. Therefore, stability of the binder polymers against the reduced oxygen species generated during the discharge process was investigated by ball milling the polymers with KO2 and Li2O2, respectively. Most of the studied polymers are unstable under these conditions and their decomposition mechanisms are proposed according to the analyzed products. Polyethylene was found to exhibit excellent stability when exposed to superoxide and peroxide species and is suggested as a robust binder for air electrodes. In addition, the binding strength of the polymer significantly affects the discharge performance of Li–O2 batteries.
  • Jie Xiao, Xiqian Yu, Jianming zheng, Yungang Zhou, Fei Gao, Xilin Chen, Jianming Bai, Xiao-Qing Yang, Ji-Guang Zhang. "Interplay between two-phase and solid solution reactions in high voltage spinel cathode material for lithium ion batteries."Journal of Power Sources 242: 736-741 (Nov. 2013).
    Abstract: Lithium ion batteries (LIBs) are attracting intensive interests worldwide because of their potential applications in transportation electrification and utility grid. The intercalation compounds used in LIBs electrochemically react with Li+ ions via single or multiple phase transitions depending on the nature of the material structure as well as the synthesis and operating conditions. For LiNi0.5Mn1.5O4 high voltage spinel, a promising candidate positive electrode material for LIBs, there are three spinel-structured phases sequentially appeared through two successive two-phase reactions during the delithiation/lithiation processes. Here we demonstrate, experimentally and theoretically, that through elemental substitution, the solid solution ranges for both the first and second phases are significantly extended during the electrochemical charge–discharge process. This type of structural changes with more solid solution regions facilitate fast Li+ diffusion by reducing the number of phase boundaries that Li+ ions have to overcome and resulted in less shrinkage of the unit cells at the end of charge process. This work unravels the fundamental interactions between structural and electrochemical properties by using spinel as the platform, which may be widely adopted to explain or tailor the properties of materials for energy storage and conversion.
  • G. Li, X. Lu, J.Y. Kim, J.P. Lemmon, and V.L. Sprenkle, "Cell Degradation of a Na-NiCl2 (ZEBRA) Battery," Journal of Materials Chemistry A, 47 (2013) 14935 - 14942 (Nov 2013).
    Abstract: In this work, the parameters influencing the degradation of a Na-NiCl2 (ZEBRA) battery were investigated. Planar Na-NiCl2 cells using β"”-alumina solid electrolyte (BASE) were tested with different C-rates, Ni/NaCl ratios, and capacity windows, in order to identify the key parameters for the degradation of Na-NiCl2 battery. The morphology of NaCl and Ni particles were extensively investigated after 60 cycles under various test conditions using a scanning electron microscope. A strong correlation between the particle size (NaCl and Ni) and battery degradation was observed in this work. Even though the growth of both Ni and NaCl can influence the cell degradation, our results indicate that the growth of NaCl is a dominant factor in cell degradation. The use of excess Ni seems to play a role in tolerating the negative effects of particle growth on degradation since the available active surface area of Ni particles can be still sufficient even after particle growth. For NaCl, a large cycling window was the most significant factor, of which effects were amplified with decrease in Ni/NaCl ratio.
  • Gu M ,Parent L R,Mehdi B L,Unocic R R,Mcdowell M T,Sacci R L,Xu W ,Connell J G,Xu P ,Abellan Baeza P ,Chen X ,Zhang Y ,Perea D E,Evans J E,Lauhon L ,Zhang J ,Liu J ,Browning N D,Cui Y ,Arslan I ,Wang C M. "Demonstration of an Electrochemical Liquid Cell for Operando Transmission Electron Microscopy Observation of the Lithiation/Delithiation Behavior of Si Nanowire Battery Anodes." Nano Letters 13 (12): 6106-6112 (Nov. 2013).
    Abstract:Over the past few years, in situ transmission electron microscopy (TEM) studies of lithium ion batteries using an open-cell configuration have helped us to gain fundamental insights into the structural and chemical evolution of the electrode materials in real time. In the standard open-cell configuration, the electrolyte is either solid lithium oxide or an ionic liquid, which is point-contacted with the electrode. This cell design is inherently different from a real battery, where liquid electrolyte forms conformal contact with electrode materials. The knowledge learnt from open cells can deviate significantly from the real battery, calling for operando TEM technique with conformal liquid electrolyte contact. In this paper, we developed an operando TEM electrochemical liquid cell to meet this need, providing the configuration of a real battery and in a relevant liquid electrolyte. To demonstrate this novel technique, we studied the lithiation/delithiation behavior of single Si nanowires. Some of lithiation/delithation behaviors of Si obtained using the liquid cell are consistent with the results from the open-cell studies. However, we also discovered new insights different from the open cell configuration—the dynamics of the electrolyte and, potentially, a future quantitative characterization of the solid electrolyte interphase layer formation and structural and chemical evolution.
  • Shao Y ,Liu T L.,Li G ,Gu M ,Nie Z ,Engelhard M H,Xiao J ,Lu D ,Wang C M,Zhang J ,Liu J. "Coordination Chemistry in magnesium battery electrolytes: how ligands affect their performance." Scientific Reports 3 (Nov. 2013).
    Abstract:Magnesium battery is potentially a safe, cost-effective, and high energy density technology for large scale energy storage. However, the development of magnesium battery has been hindered by the limited performance and the lack of fundamental understandings of electrolytes. Here, we present a study in understanding coordination chemistry of Mg(BH4)2 in ethereal solvents. The O donor denticity, i.e. ligand strength of the ethereal solvents which act as ligands to form solvated Mg complexes, plays a significant role in enhancing coulombic efficiency of the corresponding solvated Mg complex electrolytes. A new electrolyte is developed based on Mg(BH4)2, diglyme and LiBH4. The preliminary electrochemical test results show that the new electrolyte demonstrates a close to 100% coulombic efficiency, no dendrite formation, and stable cycling performance for Mg plating/stripping and Mg insertion/de-insertion in a model cathode material Mo6S8 Chevrel phase.
  • Vijayakumar M, W Wang, Z Nie, VL Sprenkle, and JZ Hu. "Elucidating the Higher Stability of Vanadium (V) Cations in Mixed Acid Based Redox Flow Battery Electrolytes." Journal of Power Sources 241:173-177. doi:10.1016/j.jpowsour.2013.04.072 (Nov 2013).
    Abstract:The Vanadium (V) cation structures in mixed acid based electrolyte solution were analysed by density functional theory (DFT) based computational modelling and 51V and 35Cl Nuclear Magnetic Resonance (NMR) spectroscopy. The Vanadium (V) cation exists as di-nuclear [V2O3Cl2.6H2O]2+ compound at higher vanadium concentrations (=1.75M). In particular, at high temperatures (>295K) this di-nuclear compound undergoes ligand exchange process with nearby solvent chlorine molecule and forms chlorine bonded [V2O3Cl2.6H2O]2+ compound. This chlorine bonded [V2O3Cl2.6H2O]2+ compound might be resistant to the de-protonation reaction which is the initial step in the precipitation reaction in Vanadium based electrolyte solutions. The combined theoretical and experimental approach reveals that formation of chlorine bonded [V2O3Cl2.6H2O]2+ compound might be central to the observed higher thermal stability of mixed acid based Vanadium (V) electrolyte solutions.
  • Xu W ,Wang J ,Ding F ,Chen X ,Nasybulin E N,Zhang Y ,Zhang J. "Lithium metal anodes for rechargeable batteries" Energy & Environmental Science 7: 513-537 (Oct. 2013).
    Abstract:Lithium (Li) metal is an ideal anode material for rechargeable batteries due to its extremely high theoretical specific capacity (3860 mA hg-1), low density (0.59 g cm-3) and the lowest negative electrochemical potential (−3.040 V vs. the standard hydrogen electrode). Unfortunately, uncontrollable dendritic Li growth and limited Coulombic efficiency during Li deposition/stripping inherent in these batteries have prevented their practical applications over the past 40 years. With the emergence of post-Li-ion batteries, safe and efficient operation of Li metal anodes has become an enabling technology which may determine the fate of several promising candidates for the next generation energy storage systems, including rechargeable Li–air batteries, Li–S batteries, and Li metal batteries which utilize intercalation compounds as cathodes. In this paper, various factors that affect the morphology and Coulombic efficiency of Li metal anodes have been analyzed. Technologies utilized to characterize the morphology of Li deposition and the results obtained by modelling of Li dendrite growth have also been reviewed. Finally, recent development and urgent need in this field are discussed.
  • Jianming Zheng, Wei Shi, Meng Gu, Jie Xiao, Pengjian Zuo, Chongmin Wang, Ji-Guang Zhang. "Electrochemical Kinetics and Performance of Layered Composite Cathode Material Li[Li0.2Ni0.2Mn0.6]O2." Journal of the Electrochemical Society 160 (11): A2212-A2219 (Oct. 2013).
    Abstract: Lithium-rich, manganese-rich (LMR) layered composite cathode material Li[Li0.2Ni0.2Mn0.6]O2synthesized by a co-precipitation method delivers a high discharge capacity of 281 mAh g−1 at a low current density of C/25. However, significant increase of cell polarization and decrease of discharge capacity are observed at voltage below 3.5 V with increasing current densities. Galvanostatic intermittent titration technique (GITT) analysis and electrochemical impedance spectroscopy (EIS) measurements demonstrate that lithium ion intercalation/de-intercalation reactions into/out of this material are kinetically controlled by Li2MnO3 component and its activated MnO2 component. The relationship between the electrochemical kinetics and rate performance as well as cycling stability has been systematically investigated. High discharge capacity of 149 mAh g−1 can be achieved at 10 C charge rate and C/10 discharge rate, indicating that the LMR cathode could withstand high charge rate (except initial activation process), which is very promising for practical applications. The results also reveal that the continuous formation of poorly conducting spinel phase is responsible for the capacity fading of LMR cathodes.
  • B Li, Q Luo, X Wei, Z Nie, E Thomsen, B Chen, V Sprenkle, and W Wang, "Capacity Decay Mechanism of Microporous Separator-Based All-Vanadium Redox Flow Batteries and its Recovery", ChemSusChem, 2014, 7, 577-584 (Oct 2013).
    Abstract: The results of the investigation of the capacity decay mechanism of vanadium redox flow batteries with microporous separators as membranes are reported. The investigation focuses on the relationship between the electrochemical performance and electrolyte compositions at both the positive and negative half-cells. Although the concentration of total vanadium ions remains nearly constant at both sides over cycling, the net transfer of solution from one side to the other and thus the asymmetrical valance of vanadium ions caused by the subsequent disproportionate self-discharge reactions at both sides lead to capacity fading. Through in situ monitoring of the hydraulic pressure of the electrolyte during cycling at both sides, the convection was found to arise from differential hydraulic pressures at both sides of the separators and plays a dominant role in capacity decay. A capacity-stabilizing method is developed and was successfully demonstrated through the regulation of gas pressures in both electrolyte tanks.
  • Gu M ,Kushima A ,Shao Y ,Zhang J ,Liu J ,Browning N D,Li J ,Wang C M. "Probing the Failure Mechanism of SnO2 Nanowires for Sodium-Ion Batteries." Nano Letters 13 (11): 5203-5211 (Sept. 2013).
    Abstract:Nonlithium metals such as sodium have attracted wide attention as a potential charge carrying ion for rechargeable batteries. Using in situ transmission electron microscopy in combination with density functional theory calculations, we probed the structural and chemical evolution of SnO2 nanowire anodes in Na-ion batteries and compared them quantitatively with results from Li-ion batteries (Huang, J. Y.; et al. Science 2010, 330, 1515−1520). Upon Na insertion into SnO2, a displacement reaction occurs, leading to the formation of amorphous NaxSn nanoparticles dispersed in Na2O matrix. With further Na insertion, the NaxSn crystallized into Na15Sn4 (x = 3.75). Upon extraction of Na (desodiation), the NaxSn transforms to Sn nanoparticles. Associated with the dealloying, pores are found to form, leading to a structure of Sn particles confined in a hollow matrix of Na2O. These pores greatly increase electrical impedance, therefore accounting for the poor cyclability of SnO2. DFT calculations indicate that Na+ diffuses 30 times slower than Li+ in SnO2, in agreement with in situ TEM measurement. Insertion of Na can chemomechanically soften the reaction product to a greater extent than in lithiation. Therefore, in contrast to the lithiation of SnO2 significantly less dislocation plasticity was seen ahead of the sodiation front. This direct comparison of the results from Na and Li highlights the critical role of ionic size and electronic structure of different ionic species on the charge/discharge rate and failure mechanisms in these batteries.
  • Jie Xiao, Jianming Zheng, Xiaolin Li, Yuyan Shao, Ji-Guang Zhang. "Hierarchically structured materials for lithium batteries."Nanotechnology 24 (42) (Sept. 2013).
    Abstract: The lithium-ion battery (LIB) is one of the most promising power sources to be deployed in electric vehicles, including solely battery powered vehicles, plug-in hybrid electric vehicles, and hybrid electric vehicles. With the increasing demand for devices of high-energy densities (>500 Wh kg−1), new energy storage systems, such as lithium–oxygen (Li–O2) batteries and other emerging systems beyond the conventional LIB, have attracted worldwide interest for both transportation and grid energy storage applications in recent years. It is well known that the electrochemical performance of these energy storage systems depends not only on the composition of the materials, but also on the structure of the electrode materials used in the batteries. Although the desired performance characteristics of batteries often have conflicting requirements with the micro/nano-structure of electrodes, hierarchically designed electrodes can be tailored to satisfy these conflicting requirements. This work will review hierarchically structured materials that have been successfully used in LIB and Li–O2 batteries. Our goal is to elucidate (1) how to realize the full potential of energy materials through the manipulation of morphologies, and (2) how the hierarchical structure benefits the charge transport, promotes the interfacial properties and prolongs the electrode stability and battery lifetime.
  • Soowhan Kim, Edwin Thomsen, Guanguang Xia, Zimin Nie, Jie Bao, Kurtis Recknagle, Wei Wang, Vilayanur Viswanathan, Qingtao Luo, Xiaoliang Wei, Alasdair Crawford, Greg Coffey, Gary Maupin, Vincent Sprenkle. "1 kW/1 kWh advanced vanadium redox flow battery utilizing mixed acid electrolytes". Journal of Power Sources 237 (2013) 300-309 (Sept 2013).
    Abstract: This paper reports on the recent demonstration of an advanced vanadium redox flow battery (VRFB) using a newly developed mixed acid (sulfuric and hydrochloric acid) supporting electrolyte at a kW scale. The developed prototype VRFB system is capable of delivering more than 1.1 kW in the operation range of 15~85% state of charge (SOC) at 80 mA cm-2 with an energy efficiency of 82% and energy content of 1.4 kWh. The system operated stably without any precipitation at electrolyte temperatures >45°C. At similar electrolyte temperatures, tests with a conventional sulfuric acid electrolyte suffered from precipitation after 80 cycles. By operating stably at elevated temperatures (>40°C), the mixed acid system enables significant advantages over the conventional sulfate system, namely; 1) high stack energy efficiency due to better kinetics and lower electrolyte resistance, 2) lower viscosity resulting in reduced pumping losses, 3) lower capital cost by elimination of heat exchanger, 4) higher system efficiency and 5) simplified system design and operation. Demonstration of the prototype stack with the mixed acid electrolyte has been shown to lower the cost of conventional VRFB systems for large-scale energy storage applications.
  • X. Wei, Q. Luo, B. Li, Z. Nie, E. Miller, J. Chambers, V. Sprenkle, and W. Wang. "Performance Evaluation of Microporous Separator in Fe/V Redox Flow Battery." ECS Transactions 45(26):17-24. (Sept 2013).
    Abstract: The newly developed Fe/V redox flow battery has demonstrated attractive cell performance. However, the deliverable energy density is relatively low due to the reduced cell voltage. To compensate this disadvantage and compete with other redox flow battery systems, cost reduction of the Fe/V system is necessary. This paper describes evaluation of hydrocarbon-based Daramic® microporous separators for use in the Fe/V system. These separators are very inexpensive and have exceptional mechanical properties. Separator B having ion exchange capacity demonstrated excellent capacity retention capability, and exhibited energy efficiency above 65% over a broad temperature range of 5-50°C and at current densities up to 80mA/cm2. Therefore, this separator shows great potential to replace the expensive Nafion® membrane. This will drive down the capital cost and make the Fe/V system a promising low-cost energy storage technology.
  • W Xu, X Chen, W Wang, D Choi, F Ding, J Zheng, Z Nie, YJ Choi, J Zhang, and Z Yang. "Simply AlF3-treated Li4Ti5O12 composite anode materials for stable and ultrahigh power lithium-ion batteries."Journal of Power Sources 236 (2013), 169 -174. (Aug 2013).
    Abstract: The commercial Li4Ti5O12 (LTO) is successfully modified by AlF3 via a low temperature process. After being calcined at 400°C for 5 h, AlF3 reacts with LTO to form a composite material, which mainly consists of Al3+ and F- co-doped LTO with small amounts of anatase TiO2. Al3+ and F- co-doped LTO demon- strates ultrahigh rate capability comparing to the pristine LTO. Since the amount of the byproduct TiO2 is relatively small, the modified LTO electrodes retain the main voltage characteristics of LTO with a minor feature similar to those of anatase TiO2. The doped LTO anodes deliver slightly higher discharge capacity and maintain the excellent long-term cycling stability when compared to the pristine LTO anode. Therefore, Al3+ and F- co-doped LTO composite material synthesized at low temperature is an excellent stable and ultra-high power lithium-ion batteries.
  • Jianming Zheng, Meng Gu, Jie Xiao, Pengjian Zuo, Chongmin Wang, Ji-Guang Zhang. "Corrosion/Fragmentation of Layered Composite Cathode and Related Capacity/Voltage Fading during Cycling Process."Nano Letters 13 (8): 3824-3830 (June 2013).
    Abstract: The Li-rich, Mn-rich (LMR) layered structure materials exhibit very high discharge capacities exceeding 250 mAh g–1 and are very promising cathodes to be used in lithium ion batteries. However, significant barriers, such as voltage fade and low rate capability, still need to be overcome before the practical applications of these materials. A detailed study of the voltage/capacity fading mechanism will be beneficial for further tailoring the electrode structure and thus improving the electrochemical performances of these layered cathodes. Here, we report detailed studies of structural changes of LMR layered cathode Li[Li0.2Ni0.2Mn0.6]O2 after long-term cycling by aberration-corrected scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). The fundamental findings provide new insights into capacity/voltage fading mechanism of Li[Li0.2Ni0.2Mn0.6]O2. Sponge-like structure and fragmented pieces were found on the surface of cathode after extended cycling. Formation of Mn2+ species and reduced Li content in the fragments leads to the significant capacity loss during cycling. These results also imply the functional mechanism of surface coatings, for example, AlF3, which can protect the electrode from etching by acidic species in the electrolyte, suppress cathode corrosion/fragmentation, and thus improve long-term cycling stability.
  • Dongyang Chen, Soowhan Kim, Vincent Sprenkle, Michael A. Hickner. "Composite blend polymer membranes with increased proton selectivity and lifetime for vanadium redox flow batteries". Journal of Power Sources 231 (2013) 301-306. (Jun 2013).
    Abstract: Composite membranes based on blends of sulfonated fluorinated poly(arylene ether) (SFPAE) and poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-co-HFP)) were prepared with varying P(VDF-co-HFP) content for vanadium redox flow battery (VRFB) applications. The properties of the SFPAE-P(VDF-co-HFP) blends were characterized by atomic force microscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy. The water uptake, mechanical properties, thermal properties, proton conductivity, VO2+] permeability and VRFB cell performance of the composite membranes were investigated in detail and compared to the pristine SFPAE membrane. It was found that SFPAE had good compatibility with P(VDF-co-HFP) and the incorporation of P(VDF-co-HFP) increased the mechanical properties, thermal properties, and proton selectivity of the materials effectively. An SFPAE composite membrane with 10 wt.% P(VDF-co-HFP) exhibited a 44% increase in VRFB cell lifetime as compared to a cell with a pure SFPAE membrane. Therefore, the P(VDF-co-HFP) blending approach is a facile method for producing low-cost, high-performance VRFB membranes.
  • Xiaochuan Lu, Guosheng Li, Jin Y Kim, John P. Lemmon, Vincent L Sprenkle, Zhenguo Yang, "A novel low-cost sodium-zinc chloride battery." Energy & Environmental Science 6(6): 1837-1843 (Jun 2013).
    Abstract: The sodium-metal halide (ZEBRA) battery has been considered as one of the most attractive energy storage systems for stationary and transportation applications. Even though Na-NiCl2 battery has been widely investigated, there is still a need to develop a more economical system to make this technology more attractive for commercialization. In the present work, a novel low-cost Na-ZnCl2 battery with a planar β"-Al2O3 solid electrolyte (BASE) was proposed, and its electrochemical reactions and battery performance were investigated. Compared to the Na-NiCl2 chemistry, the ZnCl2-based chemistry was more complicated, in which multiple electrochemical reactions including liquid-phase formation occurred at temperatures above 253°C. During the first stage of charge, NaCl reacted with Zn to form Na in the anode and Na2ZnCl4 in the cathode. Once all the residual NaCl was consumed, further charging led to the formation of a NaCl-ZnCl2 liquid phase. At the end of charge, the liquid phase reacted with Zn to produce solid ZnCl2. To identify the effects of liquid-phase formation on electrochemical performance, button cells were assembled and tested at 280°C and 240°C. At 280°C where the liquid phase formed during cycling, cells revealed quite stable cyclability. On the other hand, more rapid increase in polarization was observed at 240°C where only solid-state electrochemical reactions occurred. SEM analysis indicated that the stable performance at 280°C was due to the suppressed growth of Zn and NaCl particles, which were generated from the liquid phase during discharge of each cycle.
  • Jianming Zheng, Jie Xiao, Zimin Nie, Ji-Guang Zhang. "Lattice Mn3+ Behaviors in Li4Ti5O12/LiNi0.5Mn1.5O4 Full Cells."Journal of Electrochemical Society 160 (8): A1264-A1268 (May 2013).
    Abstract: High voltage spinels LiNi0.5Mn1.5O4 (LNMO) with different contents of residual lattice Mn3+ have been evaluated in full cells using Li4Ti5O12 (LTO) as anode. Greatly improved cycling stability has been observed for all spinels in LTO-limited full cell, compared with those in LNMO-limited ones, while the underlying mechanisms are quite different. “Shallow cycling” of LNMO in LTO-limited cells does not require complete transition to the third cubic phase, reducing the phase boundaries that Li+ has to overcome and thus improving the cell performances. However, in LNMO-limited cells, influences of lattice Mn3+ are more easily exemplified in the Li+ deficient environment and superior electrochemical performance are observed for spinel with higher content of lattice Mn3+.
  • Bin Li, Liyu Li, Wei Wang, Zimin Nie, Baowei Chen, Xiaoliang Wei, Qingtao Luo, Zhenguo Yang, and Vincent Sprenkle. "Fe/V Redox Flow Battery Electrolyte Investigation and Optimization". Journal of Power Sources 229 (2013) 1-5. (May 2013).
    Abstract: The recently invented iron (Fe)/vanadium (V) redox flow battery (IVB) system has attracted increasing attention because of its long-term cycling stability and low-cost membrane/separator. In this paper, we describe our extensive matrix study of factors such as electrolyte composition; state of charge (SOC), and temperature that influence the stability of electrolytes in both positive and negative half-cells. During the study, an optimized electrolyte that can be operated in a temperature range from -5°C to 50°C without precipitation is identified. Fe/V flow cells using the optimized electrolyte and low-cost separator exhibit satisfactory cycling performance at different temperatures. Efficiencies, capacities, and energy densities of flow batteries at various temperatures are studied.
  • X. Wei, Z Nie, Q Luo, B Li, V. Sprenkle, and W. Wang, "Polyvinyl Chloride/Silica Nanoporous Composite Separator for All-Vanadium Redox Flow Battery Applications." Journal of the Electrochemical Society, 160(8):A1215 - A1218, 2013. (May 2013).
    Abstract: We demonstrate application of a commercial nanoporous polyvinyl chloride (PVC)/silica separator in an all-vanadium redox flow battery (VRB) as a low-cost alternative to expensive Nafion® membranes. This hydrophilic separator is composed of silica particles enmeshed in a PVC matrix that creates unique porous structures. These nano-scale pores with an average pore size of 45nm and a porosity of 65% serve as ion transport channels that are critically important for flow battery operation. The VRB flow cell using the PVC/silica separator produces excellent electrochemical performance in a mixed-acid VRB system with average energy efficiency (EE) of 79% at the current density of 50mAcm-2. This separator affords the VRB flow cell with excellent rate capability with its EE higher than that of Nafion® membrane at current densities above 100mAcm-2. With this separator, the EE of the VRB flow cell exhibits great tolerance to temperature fluctuations in the typical operational temperature range of the mixed-acid VRB system. More importantly, the flow cell using the separator demonstrates an excellent capacity retention over cycling, which enables the VRB system to operate in the long term with minimal electrolyte maintenance.
  • D Reed, G Coffey, E Mast, N Canfield, J Mansurov, X Lu, VL Sprenkle. "Wetting of sodium on ß-Al2O3/YSZ composites for low temperature planar sodium-metal halide batteries". Journal of Power Sources 227: 94-100 (Apr 2013).
    Abstract:Wetting of Na on ß-Al2O3/YSZ composites was investigated using the sessile drop technique. The effects of moisture and surface preparation were studied at low temperatures. Electrical conductivity of Na/ß-Al2O3/YSZ/Na cells was also investigated at low temperatures and correlated to the wetting behavior. The use of planar ß-Al2O3 substrates at low temperature with low cost polymeric seals is realized due to improved wetting at low temperature and conductivity values consistent with the literature.
  • Eduard Nasybulin, Wu Xu, Mark H. Engelhard, Xiaohong S. Li, Meng Gu, Dehong Hu, Ji-Guang Zhang. "Electrocatalytic properties of poly(3,4-ethylenedioxythiophene) (PEDOT) in Li-O2 battery."Electrochemistry Communications 29: 63-66 (April 2013).
    Abstract: The catalytic activity of poly(3,4-ethylenedioxythiophene) (PEDOT) was investigated during oxygen reduction/evolution reactions in Li–O2 batteries. PEDOT was prepared by in situ chemical polymerization of 3,4-ethylenedioxythiophene monomer in carbon matrix. PEDOT significantly reduces the overvoltage of the charging process in a Li–O2 battery. The electrocatalytic effect of PEDOT can be attributed to its redox activity. Apparently, PEDOT acts as a mediator in electron transfer during discharge and charge processes.
  • Jianming Zheng, Jie Xiao, Wu Xu, Xilin Chen, Meng Gu, Xiaohong Li, Ji-Guang Zhang. "Surface and structural stabilities of carbon additives in high voltage lithium ion batteries."Journal of Power Sources 227: 211-217 (April 2013).
    Abstract: The stabilities of different conductive carbon additives have been systematically investigated in high voltage lithium ion batteries. It is found that the higher surface area of conductive additives leads to more parasitic reactions initiating from different onset voltages. A closer inspection reveals that for the low surface area carbon such as Super P, PF6 anions reversibly intercalate into carbon structure at around 4.7 V. For high surface area carbons, in addition to the electrolyte decomposition, the oxidation of functional groups at high voltage further increases the irreversible capacity and Li+ ion consumption. Coulombic efficiency, irreversible capacity and cycling stability observed by using different carbon additives are correlated with their structure and surface chemistry, thus providing information for predictive selection of carbon additives in different energy storage systems.
  • X. Wei, Z. Nie, Q. Luo, B. Li, B. Chen, K. Simmons, V. Sprenkle, W. Wang, "Nanoporous Polytetrafluoroethylene/Silica Composite Separator as a High-Performance All-Vanadium Redox Flow Battery Membrane". Advanced Energy Materials, 3, 1215-1220, 2013. (Apr 2013).
    Abstract:A novel low-cost nanoporous polytetrafluoroethylene (PTFE)/silica composite separator has been prepared and evaluated for its use in an all-vanadium redox flow battery (VRB). The separator consists of silica particles enmeshed in a PTFE fibril matrix. It possesses unique nanoporous structures with an average pore size of 38 nm and a porosity of 48%. These pores function as the ion transport channels during redox flow battery operation. This separator provides excellent electrochemical performance in the mixed-acid VRB system. The VRB using this separator delivers impressive energy efficiency, rate capability, and temperature tolerance. In addition, the flow cell using the novel separator also demonstrates an exceptional capacity retention capability over extended cycling, thus offering excellent stability for long-term operation. The characteristics of low cost, excellent electrochemical performance and proven chemical stability afford the PTFE/silica nanoporous separator great potential as a substitute for the Nafion membrane used in VRB applications.
  • B. Li, M. Gu, Z. Nie, Y. Shao, Q. Luo, X. Wei, X. Li, J. Xiao, C. Wang, V. Sprenkle, and W. Wang, "Bismuth Nanoparticle Decorating Graphite Felt as a High-Performance Electrode for an All-Vanadium Redox Flow Battery". Nano Letters, 13, 1330-1335, 2013. (Feb 2013).
    Abstract: Employing electrolytes containing Bi3+, bismuth nanoparticles are synchronously electrodeposited onto the surface of a graphite-felt electrode during operation of an all-vanadium redox flow battery (VRFB). The influence of the Bi nanoparticles on the electrochemical performance of the VRFB is thoroughly investigated. It is confirmed that Bi is only present at the negative electrode and facilitates the redox reaction between V(II) and V(III). However, the Bi nanoparticles significantly improve the electrochemical performance of VRFB cells by enhancing the kinetics of the sluggish V(II)/V(III) redox reaction, especially under high power operation. The energy efficiency is increased by 11% at high current density (150 mA.cm-2) owing to faster charge transfer as compared with one without Bi. The results suggest that using Bi nanoparticles in place of noble metals offers great promise as high-performance electrodes for VRFB application.
  • Q Luo, L Li, W Wang, Z Nie, X Wei, B Li, B Chen, Z Yang, and VL Sprenkle. "Capacity Decay and Remediation of Nafion-based All-Vanadium Redox Flow Batteries". ChemSusChem 6(2) 268-274. (Feb 2013).
    Abstract: The relationship between the electrochemical performance of vanadium redox flow batteries (VRB) and electrolyte compositions has been investigated, and the reasons for capacity decay over charge-discharge cycling have been analyzed and are discussed in this paper. The results show that the reasons for capacity fading over real charge-discharge cycling include not only the imbalanced vanadium active species, but also the asymmetrical valence of vanadium ions in positive and negative electrolytes. The asymmetrical valence of vanadium ions leads to the SOC range to decrease in positive electrolyte and increase in negative electrolyte, respectively. As a result, the higher SOC range in negative half-cells further aggravate the capacity fading by creating a higher over-potential and possible hydrogen evolution. Based on this finding, we developed two methods for restoring the lost capacity; thereby enabling long-term operation of VRBs to be achieved without the substantial loss of energy resulting from periodic remixing of electrolytes.
  • W Wang, Q Luo, B Li, X Wei, L Li, and Z Yang. "Recent Progress in Redox Flow Battery Research and Development".Advanced Functional Materials 23 (8), 970-986.(Feb 2013).
    Abstract: With the increasing need to seamlessly integrate renewable energy with the current electricity grid, which itself is evolving into a more intelligent, efficient, and capable electrical power system, it is envisioned that energy-storage systems will play a more prominent role in bridging the gap between current technology and a clean sustainable future in grid reliability and utilization. Redox flow battery technology is a leading approach in providing a well-balanced approach for current challenges. In this paper, we review recent progress in the research and development of redox flow battery technology, including cell-level components of electrolytes, electrodes, and membranes. Our review focuses on new redox chemistries for both aqueous and non-aqueous systems.
  • X. Lu, JP Lemmon, JY Kim, VL Sprenkle, and ZG Yang. "High Energy Density Na-S/NiCl2 Hybrid Battery." Journal of Power Sources 224 (2013) 312- 316. (Feb 2013).
    Abstract: High temperature (250-350°C) sodium-beta alumina batteries (NBBs) are attractive energy storage devices for renewable energy integration and other grid related applications. Currently, two technologies are commercially available in NBBs, e.g., sodium-sulfur (Na-S) battery and sodium-metal halide (ZEBRA) batteries. In this study, we investigated the combination of these two chemistries with a mixed cathode. In particular, the cathode of the cell consisted of molten NaAlCl4 as a catholyte and a mixture of Ni, NaCl and Na2S as active materials. During cycling, two reversible plateaus were observed in cell voltage profiles, which matched electrochemical reactions for Na-S and Na-NiCl2 redox couples. An irreversible reaction between sulfur species and Ni was identified during initial charge at 280°C, which caused a decrease in cell capacity. The final products on discharge included Na2Sn with 1< n < 3, which differed from Na2S3 found in traditional Na-S battery. Reduction of sulfur in the mixed cathode led to an increase in overall energy density over ZEBRA batteries. Despite of the initial drop in cell capacity, the mixed cathode demonstrated relatively stable cycling with more than 95% of capacity retained over 60 cycles under 10mA/cm2. Optimization of the cathode may lead to further improvements in battery performance.
  • Eduard Nasybulin, Wu Xu, Mark H. Engelhard, Zimin Nie, Sarah D. Burton, Lelia Cosimbescu, Mark E. Gross, Ji-Guang Zhang. "Effects of Electrolyte Salts on the Performance of Li–O2 Batteries."Journal of Physical Chemistry C 117 (6): 2635-2645 (Jan. 2013).
    Abstract: The effects of lithium salts on the performance of Li–O2 batteries and the stability of salt anions in the O2 atmosphere during discharge/charge processes were systematically investigated by studying seven common lithium salts in tetraglyme as electrolytes for Li–O2 batteries. The discharge products of Li–O2 reactions were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, and nuclear magnetic resonance spectroscopy. The performance of Li–O2 batteries was strongly affected by the salt used in the electrolyte. Lithium tetrafluoroborate (LiBF4) and lithium bis(oxalato)borate (LiBOB) decomposed and formed LiF and lithium oxalate, respectively, as well as lithium borates during discharge of Li–O2 batteries. In the case of other salts, including lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTf), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), and lithium bromide (LiBr), the discharge products mainly consisted of Li2O2 and carbonates with minor signs of decomposition of LiTFSI, LiTf, and LiPF6. LiBr and LiClO4 showed the best stability during the discharge process. For the cycling performance, LiTf and LiTFSI were the best among the studied salts. In addition to the instability of lithium salts, decomposition of tetraglyme solvent was a more significant factor contributing to the limited cycling stability. Thus, a more stable nonaqueous electrolyte including organic solvent and lithium salt still needs to be further developed to reach a fully reversible Li–O2 battery.
  • Wang W, D Choi, and Z Yang."Li-Ion Battery with LiFePO4 Cathode and Li4Ti5O12 Anode for Stationary Energy Storage". Metallurgical and Materials Transactions A, Physical Metallurgy and Materials Science 44A(1 Supplement): 21-25. (Jan 2013).
    Abstract: Li-ion batteries based on commercially available LiFePO4 cathode and Li4Ti5O12 anode were investigated for potential stationary energy storage applications. The full cell that operated at flat 1.85 V demonstrated stable cycling up to 200 cycles followed by a rapid fade. A Li-ion full cell with Ketjen black modified LiFePO4 cathode and an unmodified Li4Ti5O12 anode exhibited negligible fade after more than 1200 cycles with a capacity of ~130 mAh/g at C/2. The improved stability, along with its cost-effectiveness, environmental benignity, and safety, make the LiFePO4/Li4Ti5O12 combination Li-ion battery a promising option for storing renewable energy.
  • X Lu, BW Kirby, W Xu, G Li, JY Kim, JP Lemmon, VL Sprenkle, and ZG Yang. "Advanced Intermediate-Temperature Na-S Battery." Energy & Environmental Science 6(1) (2013) 299 - 306. (Jan 2013).
    Abstract: In this study, we reported an intermediate-temperature (~150°C) sodium-sulfur (Na-S) battery. With a reduced operating temperature, this novel battery can potentially reduce the cost and safety issues associated with the conventional high-temperatures (300~350°C) Na-S battery. A dense β"-Al2O3 solid membrane and tetraglyme were utilized as the electrolyte separator and catholyte solvent in this battery. Solubility tests indicated that cathode mixture of Na2S4 and S exhibited extremely high solubility in tetraglyme (e.g., > 4.1 M for Na2S4 + 4 S). CV scans of Na2S4 in tetraglyme revealed two pairs of redox couples with peaks at around 2.22 and 1.75 V, corresponding to the redox reactions of polysulfide species. The discharge/charge profiles of the Na-S battery showed a slope region and a plateau, indicating multiple steps and cell reactions. In-situ Raman spectra during battery operation suggested that polysulfide species were formed in the sequence of Na2S5 + S → Na2S5 + Na2S4 → Na2S4 + Na2S2 during discharge and in a reverse order during charge. This battery showed dramatic improvement in rate capacity and cycling stability over room-temperature Na-S batteries, which makes it extremely attractive for renewable energy integration and other grid related applications.

2012

  • GS Li, XC Lu, CA Coyle, JY Kim, JP Lemmon, VL Sprenkle, and ZG Yang. "Novel ternary molten salt electrolytes for intermediate-temperature sodium/nickel chloride batteries."Journal of Power Sources 220, 193 -198. (Dec 2012).
    Abstract: The sodium-nickel chloride (ZEBRA) battery is typically operated at relatively high temperature (250~350°C) to achieve adequate electrochemical performance. Reducing the operating temperature in the range of 150 to 200°C can lead to enhanced cycle life by suppressing temperature related degradation mechanisms. The operation at these intermediate temperatures also allows for lower cost materials of construction such as elastomeric sealants and gaskets. To achieve adequate electrochemical performance at lower operating temperatures requires an overall reduction in ohmic losses associated with temperature. This includes reduction in the ohmic resistance of β"-alumina solid electrolyte (BASE) and the incorporation of low melting point molten salt as the secondary electrolyte. In present work, planar-type Na/NiCl2 cells with a thin flat BASE (600 μm) and low melting point secondary electrolyte were evaluated at reduced temperatures. Molten salts used as secondary electrolytes were fabricated by the partial replacement of NaCl in the standard secondary electrolyte (NaAlCl4) with other lower melting point alkali metal salts such as NaBr, LiCl, and LiBr. Electrochemical characterization of these ternary molten salts demonstrated improved ionic conductivity and sufficient electrochemical window at reduced temperatures. Furthermore, Na/NiCl2 cells with 50 mol% NaBr-containing secondary electrolyte exhibited reduced polarizations at 175°C compared to the cell with the standard NaAlCl4 catholyte. The cells also exhibited stable cycling performance even at 150°C.
  • Q Luo, L Li, Z Nie, W Wang, X Wei, B Li, B Chen, Z Yang. "In-situ investigation of vanadium ion transport in redox flow battery." Journal of Power Sources 218 (2012) 15-30 (Nov 2012).
    Abstract: Flow batteries with vanadium and iron redox couples as the electroactive species were employed to investigate the transport behavior of vanadium ions in the presence of an electric field. It was shown that the electric field accelerated the positive-to-negative and reduced the negative-to-positive transport of vanadium ions in the charging process and affected the vanadium ion transport in the opposite way during discharge. In addition, a method was designed to differentiate the concentration-gradient-driven vanadium ion diffusion and electric-field-driven vanadium ion migration. A simplified mathematical model was established to simulate the vanadium ion transport in real charge-discharge operation of the flow battery. The concentration gradient diffusion coefficients and electric-migration coefficients of V2+, V3+, VO2+, and VO2+ across a NAFION® membrane were obtained by fitting the experimental data.
  • X Wei, L Li, Q Luo, Z Nie, W Wang, B Li, GG Xia, E Millar, J Chambers, Z Yang. "Microporous separators for Fe/V redox flow batteries." (2013) Journal of Power Sources 218 (2012) 39-45 (Nov 2012).
    Abstract: The Fe/V redox flow battery has demonstrated promising performance with distinct advantages over other redox flow battery systems. Due to the less oxidative nature of the Fe(III) species, hydrocarbon-based ion exchange membranes or separators can be used. Daramic® microporous polyethylene separators were tested on Fe/V flow cells using sulfuric/chloric mixed acid-supporting electrolytes. Among them, separator C exhibited good flow cell cycling performance with satisfactory repeatability over a broad temperature range of 5-50°C. Energy efficiency (EE) of C remains around 70% at current densities of 50-80 mA.cm-2 in temperatures ranging from room temperature to 50°C. The capacity decay problem could be circumvented through hydraulic pressure balancing by means of applying different pump rates to the positive and negative electrolytes. Stable capacity and energy were obtained over 20 cycles at room temperature and 40°C. These results show that extremely low-cost separators ($1-20/m2) are applicable in the Fe/V flow battery system with acceptable energy efficiency. This represents a remarkable breakthrough: a significant reduction of the capital cost of the Fe/V flow battery system, which could further its market penetration in grid stabilization and renewable integration.
  • D Stephenson, S Kim, F Chen, E Thomsen, V Viswanathan, W Wang, VL Sprenkle. "Electrochemical Model of the Fe/V Redox Flow Battery."Journal of the Electrochemical Society 159 (12): A1993-A2000 (Oct 2012).
    Abstract: A zero-dimensional electrochemical model of the Fe/V redox flow battery (RFB) is presented that can model RFB performance at low flow rates (<0.5 mL min-1 cm-2) and varied temperatures. The electrochemical model is appropriate for practical RFBs and provides good agreement with experimental data. In addition, a proposed non-ideal electrode model is introduced that accounts for higher voltage losses at low flow rates. Semi-quantitative operation strategies and electrode design guidelines can be obtained from the model. We found that ohmic losses associated with the electrolyte were dominating our electrode losses, which means operating the cell at higher temperature will reduce electrolyte ohmic losses and viscosity, thus leading to higher system efficiency. Thinner electrodes than the 4.5-mm-thick felt used in this study should reduce ohmic losses as well as pumping losses if the same space velocity is maintained. This electrochemical model can be easily incorporated into system-level and cost models, which will help in system optimization, system control, and pump selection and help avoid potential risks of large scale RFB system development.
  • W Wang, L Li, Z Nie, B Chen, Q Luo, Y Shao, X Wei, F Chen, G Xia, Z Yang. "A new hybrid redox flow battery with multiple redox couples." Journal of Power Sources 216 (2012), 99-103. (Oct 2012).
    Abstract: A redox flow battery using V4+/V5+ vs. V2+/V3+ and Fe2+/Fe3+ vs. V2+/V3+ redox couples in chloric/sulfuric mixed acid supporting electrolyte was investigated for potential stationary energy storage applications. The Fe/V hybrid redox flow cell using mixed reactant solutions and operated within a voltage window of 0.5~1.7 V demonstrated stable cycling over 100 cycles with energy efficiency ~80% and negligible capacity fading at room temperature. A 66% improvement in the energy density of the Fe/V hybrid cell was achieved compared with the previously reported Fe/V cell using only Fe2+/Fe3+ vs. V2+/V3+ redox couples.
  • X Lu, GS Li, JY Kim, JP Lemmon, VL Sprenkle, and ZG Yang. "The effects of temperature on the electrochemical performance of sodium-nickel chloride batteries." Journal of Power Sources 215 (2012), 288-295. (Oct 2012).
    Abstract: The sodium-nickel chloride (ZEBRA) battery is typically operated at relatively high temperatures (≥ 300°C) to achieve adequate electrochemical performance. In the present study, the effects of operating temperature on the electrochemical performance of planar-type sodium-nickel chloride batteries were investigated in order to evaluate the feasibility of the battery operation at low temperatures (≥ 200°C). Electrochemical test results revealed that the battery was able to be cycled at C/3 rate at as low as 175°C despite the higher cell polarization at the reduced temperature. Overall, low operating temperature resulted in a considerable improvement in the stability of cell performance. Cell degradation was negligible at 175°C, while 55% increase in end-of-charge polarization was observed at 280°C after 60 cycles. SEM analysis indicated that the performance degradation at higher temperatures was related to the particle growth of both nickel and sodium chloride in the cathode. The cells tested at lower temperatures (e.g., 175 and 200°C), however, exhibited a sharp drop in cell voltage at the end of discharge due to the diffusion limitation, possibly caused by the limited ionic conductivity of NaAlCl4 melt or the poor wettability of sodium on the β"-Al2O3 solid electrolyte (BASE). Therefore, improvements in the ionic conductivity of a secondary electrolyte and sodium wetting as well as reduction in the ohmic resistance of BASE are required to further enhance the battery performance at low temperatures.
  • Jianming Zheng, Jie Xiao, Xiqian Yu, Libor Kovarik, Meng Gu, Fredrick Omenya, Xilin Chen, Xiao-Qing Yang, Jun Liu, Gordon L. Graff, M. Stanley Whittingham, Ji-Guang Zhang. "Enhanced Li+ ion transport in LiNi0.5Mn1.5O4 through control of site disorder." Physical Chemistry Chemical Physics 14: 13515-13521 (Sept. 2012).
    Abstract: High voltage spinel LiNi0.5Mn1.5O4 is a very promising cathode material for lithium ion batteries that can be used to power hybrid electrical vehicles (HEVs). Through careful control of the cooling rate after high temperature calcination, LiNi0.5Mn1.5O4 spinels with different disordered phase and/or Mn3+ contents have been synthesized. It is revealed that during the slow cooling process (<3 °C min−1), oxygen deficiency is reduced by the oxygen intake, thus the residual Mn3+ amount is also decreased in the spinel due to charge neutrality. In situ X-ray diffraction (XRD) demonstrates that the existence of a disordered phase fundamentally changes the spinel phase transition pathways during the electrochemical charge–discharge process. The presence of an appropriate amount of oxygen deficiency and/or Mn3+ is critical to accelerate the Li+ ion transport within the crystalline structure, which is beneficial to enhance the electrochemical performance of LiNi0.5Mn1.5O4. LiNi0.5Mn1.5O4 with an appropriate amount of disordered phase offers high rate capability (96 mAh g−1 at 10 °C) and excellent cycling performance with 94.8% capacity retention after 300 cycles. The fundamental findings in this work can be widely applied to guide the synthesis of other mixed oxides or spinels as high performance electrode materials for lithium ion batteries.
  • Xilin Chen, Wu Xu, Jie Xiao, Mark H. Engelhard, Fei Deng, Donghai Mei, Dehong Hu, Jian Zhang, Ji-Guang Zhang."Effects of cell positive cans and separators on the performance of high-voltage Li-ion batteries."Journal of Power Sources 213: 160-168 (Sept. 2012).
    Abstract:The effects of different cell positive cans and separators on first-cycle Coulombic efficiency and long-term cycling stability of a high-voltage spinel cathode are investigated systematically. Compared to stainless steel (SS) positive cans, aluminum (Al)-clad SS-316 positive cans are much more resistant to oxidation at high voltages; therefore, the initial Coulombic efficiency of the batteries with Al-clad can is improved by more than 13%. Among the five separators studied in this work, the polyethylene (PE) separator exhibits the best electrochemical stability. The cells using LiCr0.05Ni0.45Mn1.5O4 as the cathode, an Al-clad positive can, and a PE separator exhibits a first-cycle Coulombic efficiency of about 90% and a capacity fading of only 0.01% per cycle.
  • Xilen Chen, Xiaolin Li, Fei Ding, Wu Xu, Jie Xiao, Yuliang Cao, Praveen Meduri, Jun Liu, Gordon L. Graff, Ji-Guang Zhang. "Conductive Rigid Skeleton Supported Silicon as High-Performance Li-Ion Battery AnodesConductive Rigid Skeleton Supported Silicon as High-Performance Li-Ion Battery Anodes."Nano Letters 12 (8): 4124-4130 (July 2012).
    Abstract: A cost-effective and scalable method is developed to prepare a core–shell structured Si/B4C composite with graphite coating with high efficiency, exceptional rate performance, and long-term stability. In this material, conductive B4C with a high Mohs hardness serves not only as micro/nano-millers in the ball-milling process to break down micron-sized Si but also as the conductive rigid skeleton to support the in situ formed sub-10 nm Si particles to alleviate the volume expansion during charge/discharge. The Si/B4C composite is coated with a few graphitic layers to further improve the conductivity and stability of the composite. The Si/B4C/graphite (SBG) composite anode shows excellent cyclability with a specific capacity of ∼822 mAh·g–1 (based on the weight of the entire electrode, including binder and conductive carbon) and ∼94% capacity retention over 100 cycles at 0.3 C rate. This new structure has the potential to provide adequate storage capacity and stability for practical applications and a good opportunity for large-scale manufacturing using commercially available materials and technologies.
  • Cao Y, L Xiao, ML Sushko, W Wang, b Schwenzer, J Xiao, Z Nie, LV Saraf, Z Yang, J Liu. "Sodium Ion Insertion in Hollow Carbon Nanowires for Battery Applications." Nano Letters 12 (7): 3783-3787 (June 2012).
    Abstract: Hollow carbon nanowires (HCNWs) were prepared through pyrolyzation of a hollow polyaniline nanowire precursor. The HCNWs used as anode material for Na-ion batteries deliver a high reversible capacity of 251 mAh g-1 and 82.2% capacity retention over 400 charge-discharge cycles between 1.2 and 0.01 V (vs Na+/Na) at a constant current of 50 mA g-1 (0.2 C). Excellent cycling stability is also observed at an even higher charge-discharge rate. A high reversible capacity of 149 mAh g-1 also can be obtained at a current rate of 500 mA g-1 (2C). The good Na-ion insertion property is attributed to the short diffusion distance in the HCNWs and the large interlayer distance (0.37 nm) between the graphitic sheets, which agrees with the interlayered distance predicted by theoretical calculations to enable Na-ion insertion in carbon materials.
  • Wang W, W Xu, L Cosimbescu, D Choi, L Li, and Z Yang. "Anthraquinone with Tailored Structure for Nonaqueous Metal-Organic Redox Flow Battery." Chemical Communications 48(53):6669-6671. (May 2012).
    Abstract: A nonaqueous, hybrid metal-organic redox flow battery based on tailored anthraquinone structure is demonstrated to have an energy efficiency of ~82% and a specific discharge energy density similar to these of aqueous redox flow batteries, which is due to the significantly improved solubility of anthraquinone in supporting electrolytes.
  • Jie Xiao, Xilin Chen, Peter V. Sushko, Maria L. Sushko, Libor Kovarik, Jijun Feng, Zhiqun Deng, Jianming Zheng, Gordon L. Graff, Zimin Nie, Daiwon Choi, Jun Liu, Ji-Guang Zhang, M.Stanley Whittingham."High-Performance LiNi0.5Mn1.5O4 Spinel Controlled by Mn3+ Concentration and Site Disorder."Advanced Materials 24 (16): 2109-2116 (April 2012).
    Abstract:The complex correlation between Mn3+ ions and the disordered phase in the lattice structure of high voltage spinel, and its effect on the charge transport properties, are revealed through a combination of experimental study and computer simulations. Superior cycling stability is achieved in LiNi0.45Cr0.05Mn1.5O4 with carefully controlled Mn3+ concentration. At 250th cycle, capacity retention is 99.6% along with excellent rate capabilities.
  • Xiaolin Li, Praveen Meduri, Xilin Chen, Wen Qi, Mark H. Engelhard, Wu Xu, Fei Ding, Jie Xiao, Wei Wang, Chongmin Wang, Ji-Guang Zhang, Jun Liu."Hollow core–shell structured porous Si–C nanocomposites for Li-ion battery anodes."Journal of Materials Chemistry 22: 11014-11017 (April 2012).
    Abstract:Hollow core–shell structured porous Si–C nanocomposites with void space up to tens of nanometres are designed to accommodate the volume expansion during lithiation for high-performance Li-ion battery anodes. An initial capacity of ∼760 mA h g−1 after formation cycles (based on the entire electrode weight) with ∼86% capacity retention over 100 cycles is achieved at a current density of 1 A g−1. Good rate performance is also demonstrated.
  • Wang W, Z Nie, B Chen, F Chen, Q Luo, X Wei, G Xia, M Skyllas-Kazacos, L Li, and Z Yang. "A New Fe/V Redox Flow Battery Using Sulfuric/Chloric Mixed Acid Supporting Electrolyte." Advanced Energy Materials 2(4): 487-493. (Feb. 2012).
    Abstract: A redox flow battery using Fe2+/Fe3+ and V2+/V3+ redox couples in chloric/sulfuric mixed-acid supporting electrolyte was investigated for potential stationary energy storage applications. The Fe/V redox flow cell using mixed reactant solutions operated within a voltage window of 0.5~1.35 V with a nearly 100% utilization ratio and demonstrated stable cycling over 100 cycles with energy efficiency > 80% and no capacity fading at room temperature. A 25% improvement in the discharge energy density of the Fe/V cell was achieved compared with the previous reported Fe/V cell using pure chloride-acid supporting electrolyte. Stable performance was achieved in the temperature range between 0°C and 50°C as well as using a microporous separator as the membrane. The improved electrochemical performance makes the Fe/V redox flow battery a promising option as a stationary energy storage device to enable renewable integration and stabilization of the electric grid.
  • Wu Xu, Adam Read, Phillip K. Koech, Dehong Hu, Chongmin Wang, Jie Xiao, Asanga B. Padmaperuma, Gordon L. Graff, Jun Liu, Ji-Guang Zhang."Factors affecting the battery performance of anthraquinone-based organic cathode materials."Journal of Materials Chemistry 22: 4032-4039 (Jan. 2012).
    Abstract:Two organic cathode materials based on the poly(anthraquinonyl sulfide) structure with different substitution positions were synthesized and their electrochemical behavior and battery performance were investigated. The substitution positions on the anthraquinone structure, the type of binders for electrode preparation, and electrolyte formulations have been found to have significant effects on the performance of batteries containing these organic cathode materials. The polymer with less steric hindrance at the substitution positions has higher capacity, longer cycle life and better high-rate capability. Polyvinylidene fluoride binder and ether-based electrolytes are favorable for the high capacity and long cycle life of the anthraquinonyl organic cathodes.

2011

  • Zhang J, L Li, Z Nie, B Chen, M Vijayakumar, S Kim, W Wang, B Schwenzer, J Liu, and Z Yang. "Effects of additives on the stability of electrolytes for all-vanadium redox flow batteries." Journal of Applied Electrochemistry 41(10 - Special Issue S1):1215-1221. (Oct 2011).
    Abstract: The stability of the electrolytes for all-vanadium redox flow battery was investigated with ex-situ heating/cooling treatment and in situ flow-battery testing methods. The effects of inorganic and organic additives have been studied. The additives containing the ions of potassium, phosphate, and polyphosphate are not suitable stabilizing agents because of their reactions with V(V) ions, forming precipitates of KVSO6 or VOPO4. Of the chemicals studied, polyacrylic acid and its mixture with CH3SO3H are the most promising stabilizing candidates, which can stabilize all the four vanadium ions (V2+, V3+, VO2+, and VO2+) in electrolyte solutions up to 1.8 M. However, further effort is needed to obtain a stable electrolyte solution with >1.8 M V5+ at temperatures higher than 40°C.
  • J Xiao, NA Chernova, S Upreti, X Chen, Z Li, Z Deng, D Choi, W Xu, Z Nie, GL Graff, J Liu, MS Whittingham, J Zhang."Electrochemical performances of LiMnPO4 synthesized from non-stoichiometric Li/Mn ratio."Journal of Physical Chemistry Chemical Physics 13: 18099-18106 (Sept. 2011).
    Abstract:In this paper, the influences of the lithium content in the starting materials on the final performances of as-prepared LixMnPO4 (x hereafter represents the starting Li content in the synthesis step which does not necessarily mean that LixMnPO4 is a single phase solid solution in this work) are systematically investigated. It has been revealed that Mn2P2O7 is the main impurity when Li < 1.0 while Li3PO4 begins to form once x > 1.0. The interactions between Mn2P2O7 or Li3PO4 impurities and LiMnPO4 are studied in terms of the structural, electrochemical, and magnetic properties. At a slow rate of C/50, the reversible capacity of both Li0.5MnPO4 and Li0.8MnPO4 increases with cycling. This indicates a gradual activation of more sites to accommodate a reversible diffusion of Li+ ions that may be related to the interaction between Mn2P2O7 and LiMnPO4 nanoparticles. Among all of the different compositions, Li1.1MnPO4 exhibits the most stable cycling ability probably because of the existence of a trace amount of Li3PO4 impurity that functions as a solid-state electrolyte on the surface. The magnetic properties and X-ray absorption spectroscopy (XAS) of the MnPO4·H2O precursor, pure and carbon-coated LixMnPO4 are also investigated to identify the key steps involved in preparing a high-performance LiMnPO4.
  • Wang W, S Kim, B Chen, Z Nie, J Zhang, G Xia, L Li, and Z Yang. "A New Redox Flow Battery Using Fe/V Redox Couples in Chloride Supporting Electrolyte." Energy & Environmental Science 4(10):4068-4073. (June 2011).
    Abstract: A new redox flow battery using Fe2+/Fe3+ and V2+/V3+ redox couples in chloride-supporting electrolyte was proposed and investigated for potential stationary energy storage applications. The Fe/V redox flow cell using mixed reactant solutions operated within a voltage window of 0.5~1.35 V with a nearly 100% utilization ratio and demonstrated stable cycling with energy efficiency around 80% at room temperature. Stable performance was also achieved in the temperature range between 0°C and 50°C. The improved stability and electrochemical activity over a broader temperature range over the current technologies (such as Fe/Cr redox chemistry) potentially eliminate the necessity of external heat management and use of catalysts, making the Fe/V redox flow battery a promising option as a stationary energy storage device to enable renewable integration and stabilization of the electrical grid.
  • Anqiang Pan, Ji-Guang Zhang, Guozhong Cao, Shuquan Liang, Chongmin Wang, Zimin Nie, Bruce W. Arey, Wu Xu, Dawei Liu, Jie Xiao, Guosheng Li, Jun Liu."Nanosheet-structured LiV3O8 with high capacity and excellent stability for high energy lithium batteries."Journal of Materials Chemistry 21: 10077-10084 (May 2011).
    Abstract:Highly stable LiV3O8 with a nanosheet-structure was successfully prepared using polyethylene glycol (PEG) polymer in the precursor solution as the structure modifying agent, followed by calcination in air at 400 °C, 450 °C, 500 °C, and 550 °C. These materials provide the best electrochemical performance ever reported for LiV3O8 crystalline electrodes, with a specific discharge capacity of 260 mAh g-1 and no capacity fading over 100 cycles at 100 mA g-1. The excellent cyclic stability and high specific discharge capacity of the material are attributed to the novel nanosheets structure formed in LiV3O8. These LiV3O8 nanosheets are good candidates for cathode materials for high-energy lithium battery applications.
  • Anqiang Pan, Daiwon Choi, Ji-Guang Zhang, Shuquan Liang, Guozhong Cao, Zimin Nie, Bruce W. Arey, Jun Liu."High-rate cathodes based on Li3V2(PO4)3 nanobelts prepared via surfactant-assisted fabrication."Journal of Power Sources 196 (7):3646-3649 (April 2011).
    Abstract:In this work, we have synthesized monoclinic Li3V2(PO4)3 nanobelts via a single-step, solid-state reaction process in a molten hydrocarbon. The as-prepared Li3V2(PO4)3 nanoparticles have a unique nanobelt shape and are ∼50-nm thick. When cycled in a voltage range between 3.0 V and 4.3 V at a 1C rate, these unique Li3V2(PO4)3 nanobelts demonstrate a specific discharge capacity of 131 mAh g−1 (which is close to the theoretical capacity of 132 mAh g−1) and stable cycling characteristics.
  • Schwenzer B, S Kim, M Vijayakumar, Z Yang, J Liu. "Correlation of structural differences between Nafion/polyaniline and Nafion/polypyrrole composite membranes and observed transport properties."Journal of Membrane Science 327 (1-2): 11-19 (Apr. 2011).
    Abstract:Polyaniline/Nafion and polypyrrole/Nafion composite membranes, prepared by chemical polymerization, are studied by scanning electron microscopy, infrared and nuclear magnetic resonance spectroscopy. Differences in vanadium ion diffusion through the membranes and in the membranes' area specific resistance are linked to analytical observations that polyaniline and polypyrrole interact differently with Nafion. Polypyrrole, a weakly basic polymer, binds less strongly to the sulfonic acid groups of the Nafion membrane. Infrared spectroscopy results suggest that the hydrophobic polymer aggregates in the center of the Nafion channel rather than attaching to the hydrophilic walls containing sulfonic acid groups. This results in a drastically elevated membrane resistance and only slightly decreased vanadium ion diffusion compared to a Nafion membrane. Polyaniline, on the other hand, polymerizes along the sides of the Nafion pores and on the membrane surface, binding tightly to the sulfonic acid groups of Nafion, polyaniline's greater basicity possibly causing the difference in polymerization behavior. This leads to a more effective reduction in vanadium ion transport across the polyaniline/Nafion membranes and the increase in membrane resistance is less severe. The performance of selected polypyrrole/Nafion composite membranes is tested in a static vanadium redox cell. Increased coulombic efficiency, compared to a cell employing a pure Nafion membrane, further confirms the reduced vanadium ion transport through the composite membranes.
  • Li L, S Kim, W Wang, M Vijayakumar, Z Nie, B Chen, J Zhang, G Xia, JZ Hu, GL Graff, J Liu, and Z Yang. "A Stable Vanadium Redox-Flow Battery with High Energy Density for Large-scale Energy Storage." Advanced Energy Materials 1(3):394-400. (March 2011).
    Abstract: The all-vanadium redox flow battery is a promising technology for large-scale renewable and grid energy storage, but is limited by the low energy density and poor stability of the vanadium electrolyte solutions. A new vanadium redox flow battery with a significant improvement over the current technology is reported in this paper. This battery uses sulfate-chloride mixed electrolytes, which are capable of dissolving 2.5 M vanadium, representing about a 70% increase in energy capacity over the current sulfate system. More importantly, the new electrolyte remains stable over a wide temperature range of -5 to 50°C, potentially eliminating the need for electrolyte temperature control in practical applications. This development would lead to a significant reduction in the cost of energy storage, thus accelerating its market penetration.
  • Yang Z, J Zhang, MCW Kintner-Meyer, X Lu, D Choi, JP Lemmon, and J Liu. "Electrochemical Energy Storage for Green Grid." Chemical Reviews 111(5):3577 -3613. (March 2011).
    Abstract: Electrochemical Energy Storage (EES) is an established, valuable approach for improving the reliability and overall use of the entire power system (generation, transmission, and distribution [T&D]). Sited at various T&D stages, EES can be employed for providing many grid services, including a set of ancillary services such as (1) frequency regulation and load following (aggregated term often used is balancing services), (2) cold start services, (3) contingency reserves, and (4) energy services that shift generation from peak to off -peak periods. In addition, it can provide services to solve more localized power quality issues and reactive power support.
  • Deyu Wang, Jie Xiao, Wu Xu, Zimin Nie, Chongmin Wang, Gordon L. Graff, Ji-Guang Zhang."Preparation and electrochemical investigation of Li2CoPO4F cathode material for lithium-ion batteries."Journal of Power Sources 196 (4): 2241-2245 (Feb. 2011).
    Abstract:In this paper, we report the electrochemical characteristics of a novel cathode material, Li2CoPO4F, prepared by solid-state reactions. The solid-state reaction mechanism involved in synthesizing the Li2CoPO4F also is analyzed in this paper. When cycled between 2.0 V and 5.0 V during cyclic voltammetry measurements, the Li2CoPO4F samples present one, fully reversible anodic reaction at 4.81 V. When cycled between 2.0 V and 5.5 V, peaks occurring at 4.81 V and 5.12 V in the first anodic scan evolved to one broad oxidative, mound-like pattern in subsequent cycles. Correspondingly, the X-ray diffraction (XRD) pattern of the Li2CoPO4F electrode discharged from 5.5 V to 2.0 V is slightly different from the patterns exhibited by a fresh sample and the sample discharged from 5.0 V to 2.0 V. This difference may correspond to a structural relaxation that appears above 5 V. In the constant current cycling measurements, the Li2CoPO4F samples exhibited a capacity as high as 109 mAh g-1 and maintained a good cyclability between 2.0 V and 5.5 V vs. Li/Li+. XRD measurements confirmed that the discharged state is Li2CoPO4F. Combining these XRD results and electrochemical data proved that up to 1 mol Li+ is extractable when charged to 5.5 V.

2010

  • Wu Xu, Nathan L. Canfield, Deyu Wang, Jie Xiao, Zimin Nie, Ji-Guang Zhang."A three-dimensional macroporous Cu/SnO2 composite anode sheet prepared via a novel method."Journal of Power Sources 195 (21): 7403-7408 (Nov. 2010).
    Abstract:A three-dimensional macroporous Cu/SnO2 composite anode sheet for lithium ion batteries was prepared via a novel method that is based on selective reduction of metal oxides at appropriate temperatures. SnO2 particles were imbedded on the Cu particles within the three-dimensionally interconnected Cu substrate, and the whole composite sheet was used directly as an electrode without adding extra conductive carbons and binders. Compared with the SnO2-based electrode prepared via the conventional tape-casting method on Cu foil, the porous Cu/SnO2 composite electrode shows significantly improved battery performance. This methodology produces limited wastes and is also adaptable to many other materials. It is a promising approach to make macroporous electrode for Li-ion batteries.
  • Jie Xiao, Wu Xu, Deyu Wang, Daiwon Choi, Wei Wang, Xiaolin Li, Gordon L. Graff, Jun Liu, Ji-guang Zhang."Stabilization of Silicon Anode for Li-Ion Batteries."Journal of the Electrochemical Society 157 (10): A1047-A1051 (Aug. 2010).
    Abstract:Micrometer-sized Si particles with nanopore structures were investigated as anode material for Li-ion batteries. The porous structure of Si helps accommodate the large volume variations that occur during the Li insertion/extraction processes. To improve the electronic integrity of the Si-based anode, a two-step process was utilized. First, chemical vapor deposition (CVD) was used to enhance the electronic conductivity of individual Si particles by depositing a uniform carbon coating on both the exterior surfaces and the pores. Next, the electronic contact among silicon particles was improved by adding Ketjenblack (KB) carbon, which exhibits an elastic, chainlike structure that maintains a stable electronic contact among silicon particles during cycling. Using this approach, an anode with a reversible capacity of more than 1600 mAh/g after 30 cycles was obtained. The combination of the nanopore structure, CVD-coated carbon on the Si surface, and the elastic carbon (KB) among the silicon particles provides a cost-effective approach to utilize the large micrometer-sized Si particles in Li-ion batteries.
  • Wu Xu, NL Canfield, D Wang, J Xiao, Z Nie, XS Li, WD Bennett, CC Bonham, J Zhang. "An Approach to Make Macroporous Metal Sheets as Current Collectors for Lithium-Ion Batteries."Journal of the Electrochemical Society 157 (7): A765-A769 (May 2010).
    Abstract:A simple method and approach is described to produce macroporous metal sheets as current collectors for lithium-ion batteries. This method is based on slurry blending, tape casting, sintering, and reducing of metal oxides and produces a uniform macroporous metal sheet. As an example, a macroporous copper sheet was prepared and used as the current collector for a silicon thin-film anode material. Such a porous copper substrate allows Si to have a much better adhesion, lower electrical contact resistance, higher capacity, capacity retention, and longer cycle life than on surface-roughened Cu foil and smooth Cu foil. This methodology produces very limited wastes and is also adaptable to many other materials such as Ni porous sheets at an industrial-scale production that is easy to be achieved.

2009

  • Jie Xiao, Wu Xu, Daiwon Choi, Ji-Guang Zhang."Synthesis and Characterization of Lithium Manganese Phosphate by a Precipitation Method."Journal of the Electrochemical Society 157 (2): A142-A147 (Dec. 2010).
    Abstract:LiMnPO4 is synthesized from MnPO4•H2O precursor precipitated via a spontaneous reaction. These MnPO4•H2O nanoplates react quickly with the lithium source and form a pure phase of LiMnPO4 that has good electrochemical properties. Thermogravimetric analysis was used to determine the optimum synthesis temperature. The crystallization of LiMnPO4 occurs before 438°C. After full nucleation at 550°C, the samples exhibit a discharge capacity of 115 mAh/g-1 (C/20 rate, 2.5-4.4 V) in the first cycle. The Coulombic efficiency is maintained at near 100% after the first few cycles. When the synthesis temperature decreases to 350°C, the particle size of the LiMnPO4 is further reduced to 10-50 nm with a reversible capacity of more than 90 mAh g-1. For 550°C synthesized LiMnPO4, 73% of the initial capacity was retained at the 60th cycle. After high rate (5C) discharge, the reversible capacity of the LiMnPO4 can be recovered to nearly the original value of 110 mAh g-1 at the C/20 rate. This precipitation method is a cost effective approach for manufacturing high performance LiMnPO4 cathode materials.

Energy Storage

Program Areas

Resources