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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.

2019

  • Jeonghun Oh, Hearin Jo, Hongkyung Lee, Hee-Tak Kim, Yong Min Lee, Myung-Hyun Ryou."Polydopamine-treated three-dimensional carbon fiber-coated separator for achieving high-performance lithium metal batteries."Journal of Power Sources 430: 130-136 (August 2019).
    Abstract: The development of safe and high-performance lithium (Li) metal anodes has been a challenging issue that has not been addressed for decades. In this study, we have developed a thermally stable polydopamine-treated three-dimensional (3D) carbon fiber-coated separator (P3D-CFS) using an economical and environment-friendly process. P3D-CFS has a conductive coating layer that is used as a 3D hosting structure, which does not cause morphological changes in the Li metal anode. As a result, the unit cells (LiMn2O4/Li metal) employing P3D-CFS improve the cycle performance and rate capability compared to commercial polyethylene (PE) separators. P3D-CFS maintained 83.1% of the initial discharge capacity at the 400th cycle, whereas bare PE maintains only 74.3% of the initial discharge capacity after the 250th cycle (C/2 = 0.5 mA cm−2). P3D-CFS maintains 42.8% of the initial discharge capacity at a 7C rate (7 mA cm−2), whereas only 0.19% is maintained by bare PE under the same condition. Owing to the thermally stable properties of P3D-CFS, the open-circuit voltage of the unit cells (LiMn2O4/graphite) that employed P3D-CFS is maintained for over 60 min at 140 °C, whereas the unit cells that employed bare PE show a sudden voltage drop after only 3 min.
  • Xiaodi Ren, Lianfeng Zou, Xia Cao, Mark H. Engelhard, Wen Liu, Sarah D. Burton, Hongkyung Lee, Chaojiang Niu, Bethany E. Matthews, Zihua Zhu, Chongmin Wang, Bruce W. Arey, Jie Xiao, Jun Liu, Ji-Guang Zhang."Enabling High-Voltage Lithium-Metal Batteries under Practical Conditions."Joule 3 (7): 1662-1676 (July 2019).
    Abstract: High-energy-density Li-metal batteries are promising next-generation energy-storage systems. However, their development is greatly restricted because of the lack of functional electrolytes that can work efficiently on both the reactive Li anode and the aggressive cathodes under practical conditions, where high-voltage, high-loading cathode, thin Li anode and lean electrolyte are all indispensable. Here, we chose ether as the base solvent, which has intrinsic good cathodic but poor anodic stabilities and redesigned the electrolyte in a localized high-concentration electrolyte (LHCE) formulation to build the protective interphases onto both the anode and the cathode, simultaneously. Ether-based LHCE can effectively suppress side reactions, resulting in stable cycling of Li||NMC811 cells under voltages up to 4.5 V and under practical conditions. This electrolyte design provides critical insights for future electrolyte development for practical high-energy-density Li-metal batteries.
  • Chaojiang Niu, Huilin Pan, Wu Xu, Jie Xiao, Ji-Guang Zhang, Langli Luo, Chongmin Wang, Donghai Mei, Jiashen Meng, Xuanpeng Wang, Ziang Liu, Liqiang Mai, Jun Liu."Self-smoothing anode for achieving high-energy lithium metal batteries under realistic conditions."Nature Nanotechnology 14: 594-601 (June 2019).
    Abstract: Despite considerable efforts to stabilize lithium metal anode structures and prevent dendrite formation, achieving long cycling life in high-energy batteries under realistic conditions remains extremely difficult due to a combination of complex failure modes that involve accelerated anode degradation and the depletion of electrolyte and lithium metal. Here we report a self-smoothing lithium–carbon anode structure based on mesoporous carbon nanofibres, which, coupled with a lithium nickel–manganese–cobalt oxide cathode with a high nickel content, can lead to a cell-level energy density of 350–380 Wh kg−1 (counting all the active and inactive components) and a stable cycling life up to 200 cycles. These performances are achieved under the realistic conditions required for practical high-energy rechargeable lithium metal batteries: cathode loading ≥4.0 mAh cm−2, negative to positive electrode capacity ratio ≤2 and electrolyte weight to cathode capacity ratio ≤3 g Ah−1. The high stability of our anode is due to the amine functionalization and the mesoporous carbon structures that favour smooth lithium deposition.
  • Chaojiang Niu, Hongkyung Lee, Shuru Chen, Qiuyan Li, Jason Du, Wu Xu, Ji-Guang Zhang, M. Stanley Whittingham, Jie Xiao, Jun Liu."High-energy lithium metal pouch cells with limited anode swelling and long stable cycles."Nature Energy 4: 551-559 (May 2019).
    Abstract: Lithium metal anodes have attracted much attention as candidates for high-energy batteries, but there have been few reports of long cycling behaviour, and the degradation mechanism of realistic high-energy Li metal cells remains unclear. Here, we develop a prototypical 300 Wh kg−1 (1.0 Ah) pouch cell by integrating a Li metal anode, a LiNi0.6Mn0.2Co0.2O2 cathode and a compatible electrolyte. Under small uniform external pressure, the cell undergoes 200 cycles with 86% capacity retention and 83% energy retention. In the initial 50 cycles, flat Li foil converts into large Li particles that are entangled in the solid-electrolyte interphase, which leads to rapid volume expansion of the anode (cell thickening of 48%). As cycling continues, the external pressure helps the Li anode maintain good contact between the Li particles, which ensures a conducting percolation pathway for both ions and electrons, and thus the electrochemical reactions continue to occur. Accordingly, the solid Li particles evolve into a porous structure, which manifests in substantially reduced cell swelling by 19% in the subsequent 150 cycles.
  • Shuru Chen, Chaojing Niu, Hongkyung Lee, Qiuyan Li, Lu Yu, Wu Xu, Ji-Guang Zhang, Eric J. Dufek, M. Stanley Whittingham, Shirley Meng, Jie Xiao, Jun Liu."Critical Parameters for Evaluating Coin Cells and Pouch Cells of Rechargeable Li-Metal Batteries."Joule 3 (4): 1094-1105 (April 2019).
    Abstract: Lithium-metal anode has regained broad interest because of the steadily increasing demand for high-energy batteries. In this paper, we first investigate and demonstrate how the cycle performance of Li-metal batteries varied depending on the critical experimental parameters of coin cells, such as the electrolyte amount, Li-metal thickness, and the cathode loading. We then design and build a representative Li-metal pouch cell with specific energy of 300 Wh/kg to provide an effective validation of electrode materials and accurate cell performance evaluations. Finally, we propose a set of coin-cell parameters and testing conditions for the battery research community to bridge the gap between fundamental research and practical adoption of new ideas or materials and to expedite their full integration into realistic battery systems.
  • Xiaodi Ren, Lianfeng Zou, Shuhong Jiao, Donghai Mei, Mark H. Engelhard, Qiuyan Li, Hongkyung Lee, Chaojiang Niu, Brian D. Adams, Chongmin Wang, Jun Liu, Ji-Guang Zhang, Wu Xu."High-Concentration Ether Electrolytes for Stable High-Voltage Lithium Metal Batteries."ACS Energy Letters 4 (4), 896-902 (April 2019).
    Abstract: High-voltage (>4.3 V) rechargeable lithium (Li) metal batteries (LMBs) face huge obstacles due to the high reactivity of Li metal with traditional electrolytes. Despite their good stability with Li metal, conventional ether-based electrolytes are typically used only in <4.0 V LMBs because of their limited oxidation stability. Here we report high-concentration ether electrolytes that can induce the formation of a unique cathode electrolyte interphase via the synergy between the salt and the ether solvent, which effectively stabilizes the catalytically active cathodes and preserves their structural integrity under high voltages. Eventually, LMBs can retain 92% capacity after 500 cycles at 4.3 V with very limited Li consumption. More importantly, such ether electrolytes enable stable battery cycling not only under voltages as high as 4.5 V but also on highly demanding Ni-rich layered cathodes. These findings significantly expand knowledge of ether electrolytes and provide new perspectives of electrolyte design for high-energy-density LMBs.
  • Jun Liu, Zhenan Bao, Yi Cui, Eric J. Dufek, John B. Goodenough, Peter Khalifah, Qiuyan Li, Bor Yann Liaw, Ping Liu, Arumugam Manthiram, Y. Shirley Meng, Venkat R. Subramanian, Michael F. Toney, Vilayanur V. Viswanathan, M. Stanley Whittingham, Jie Xiao, Wu Xu, Jihui Yang, Xiao-Qing Yang, Ji-Guang Zhang."Pathways for practical high-energy long-cycling lithium metal batteries."Nature Energy 4, 180-186 (March 2019).
    Abstract: State-of-the-art lithium (Li)-ion batteries are approaching their specific energy limits yet are challenged by the ever-increasing demand of today’s energy storage and power applications, especially for electric vehicles. Li metal is considered an ultimate anode material for future high-energy rechargeable batteries when combined with existing or emerging high-capacity cathode materials. However, much current research focuses on the battery materials level, and there have been very few accounts of cell design principles. Here we discuss crucial conditions needed to achieve a specific energy higher than 350 Wh kg−1, up to 500 Wh kg−1, for rechargeable Li metal batteries using high-nickel-content lithium nickel manganese cobalt oxides as cathode materials. We also provide an analysis of key factors such as cathode loading, electrolyte amount and Li foil thickness that impact the cell-level cycle life. Furthermore, we identify several important strategies to reduce electrolyte-Li reaction, protect Li surfaces and stabilize anode architectures for long-cycling high-specific-energy cells.
  • Yuliang Cao, Matthew Li, Jun Lu, Jun Liu, Khalil Amine."Bridging the academic and industrial metrics for next-generation practical batteries."Nature Nanotechnology 14, 200-207 (March 2019).
    Abstract: Batteries have shaped much of our modern world. This success is the result of intense collaboration between academia and industry over the past several decades, culminating with the advent of and improvements in rechargeable lithium-ion batteries. As applications become more demanding, there is the risk that stunted growth in the performance of commercial batteries will slow the adoption of important technologies such as electric vehicles. Yet the scientific literature includes many reports describing material designs with allegedly superior performance. A considerable gap needs to be filled if we wish these laboratory-based achievements to reach commercialization. In this Perspective, we discuss some of the most relevant testing parameters that are often overlooked in academic literature but are critical for practical applicability outside the laboratory. We explain metrics such as anode energy density, voltage hysteresis, mass of non-active cell components and anode/cathode mass ratio, and we make recommendations for future reporting. We hope that this Perspective, together with other similar guiding principles that have recently started to emerge, will aid the transition from lab-scale research to next-generation practical batteries.
  • Jinhong Lee, Yun-Jung Kim, Hyun Soo Jin, Hyungjun Hoh, Hobeom Kwack, Hyunwon Chu, Fangmin Ye, Hongkyung Lee, Hee-Tak Kim."Tuning Two Interfaces with Fluoroethylene Carbonate Electrolytes for High-Performance Li/LCO Batteries."ACS Omega 4 (2), 3220-3227 (February 2019).
    Abstract: Various electrolytes have been reported to enhance the reversibility of Li-metal electrodes. However, for these electrolytes, concurrent and balanced control of Li-metal and positive electrode interfaces is a critical step toward fabrication of high-performance Li-metal batteries. Here, we report the tuning of Li-metal and lithium cobalt oxide (LCO) interfaces with fluoroethylene carbonate (FEC)-containing electrolytes to achieve high cycling stability of Li/LCO batteries. Reversibility of the Li-metal electrode is considerably enhanced for electrolytes with high FEC contents, confirming the positive effect of FEC on the stabilization of the Li-metal electrode. However, for FEC contents of 50 wt % and above, the discharge capacity is significantly reduced because of the formation of a passivation layer on the LCO cathodes. Using balanced tuning of the two interfaces, stable cycling over 350 cycles at 1.5 mA cm–2 is achieved for a Li/LCO cell with the 1 M LiPF6 FEC/DEC = 30/70 electrolyte. The enhanced reversibility of the Li-metal electrode is associated with the formation of LiF and polycarbonate in the FEC-derived solid electrolyte interface (SEI) layer. In addition, electrolytes with high FEC contents lead to lateral Li deposition on the sides of Li deposits and larger dimensions of rodlike Li deposits, suggesting the elastic and ion-conductive nature of the FEC-derived SEI layer.

2018

  • Hongkyung Lee, Hyung-Seok Lim, Xiaodi Ren, Lu Yu, Mark H. Engelhard, Kee Sung Han, Jinhong Lee, Hee-Tak Kim, Jie Xiao, Jun Liu, Wu Xu, Ji-Guang Zhang."Detrimental Effects of Chemical Crossover from the Lithium Anode to Cathode in Rechargeable Lithium Metal Batteries."ACS Energy Letters 3 (12), 2921-2930 (December 2018).
    Abstract: Interfacial stability is one of the crucial factors for long-term cyclability of lithium (Li) metal batteries (LMBs). While cross-contamination phenomena have been well-studied in Li-ion batteries (LIBs), similar phenomena have rarely been reported in LMBs. Here, we investigated cathode failure triggered by chemical crossover from the anode in LMBs. In contrast to LIBs, the cathode in LMBs suffers more significant capacity fading, and its capacity cannot be fully recovered by replacing the Li anode. In-depth surface characterization reveals severe deterioration related to the accumulation of highly resistive polymeric components in the cathode–electrolyte interphase. The soluble byproducts generated by extensive electrolyte decomposition at the Li metal surface can diffuse toward the cathode side, resulting in severe deterioration of the cathode and separator surfaces. A selective Li-ion permeable separator with a polydopamine coating has been developed to mitigate the detrimental chemical crossover and enhance the cathode stability.
  • Hongkyung Lee, Shuru Chen, Xiaodi Ren, Abraham Martinez, Vaithiyalingam Shutthanandan, Vijayakumar Murugesan, Kee Sung Han, Qiuyan Li, Jun Liu, Wu Xu, Ji-Guang Zhang."Electrode Edge Effects and the Failure Mechanism of Lithium‐Metal Batteries."ChemSusChem 11 (21) 3821-3828 (November 2018).
    Abstract: The very high specific capacity of Li metal makes it an ideal anode for high‐energy batteries. However, Li dendrite growth and the formation of isolated (or “dead”) Li during repeated Li plating/stripping processes leads to a low coulombic efficiency (CE). In this work, we discovered, for the first time, that electrode edge effects play an important role in the failure of Li‐metal batteries. The dead Li formed on the edge of Cu substrate was systematically investigated through SEM, energy‐dispersive X‐ray (EDX) spectroscopy, and 2D X‐ray photoelectron spectroscopy (XPS). To minimize the Li loss at the edge of the Cu exposed to pressure‐free space, a modified Li∥Cu cell configuration with a Cu electrode smaller than Li metal is preferred. It was clearly demonstrated that using an electrode configuration with a minimal open space or pressure‐free space across electrodes can reduce accumulation of dead Li during cycling and increase Li CE. This phenomenon was also verified in Li‐metal batteries (Li∥LiNi1/3Mn1/3Co1/3O2) and should be considered in the design of practical Li‐metal batteries.
  • Yun-Jung Kim, Hyun S. Jin, Dong-Hyun Lee, Jaeho Choi, Wonhee Jo, Hyungjun Noh, Jinhong Lee, Hyunwon Chu, Hobeom Kwack, Fangmin Ye, Hongkyung Lee, Myung-Hyun Ryou, Hee-Tak Kim."Guided Lithium Deposition by Surface Micro‐Patterning of Lithium‐Metal Electrodes."ChemElectroChem 5 (21), 3169-3175 (November 2018).
    Abstract: Uncontrolled lithium (Li) deposition has hampered the evolution of Li‐metal electrode‐based Li‐batteries. In this work, we report the differences of a guided Li deposition with a size change of the square hole micro‐patterns carved on the Li‐metal surface with two different dimensions using a simple stamping method. Li deposition is preferentially initiated on the top edge for the smaller pattern and on the bottom for the larger pattern. Although the two patterns lead to a more uniform utilization of the Li, the larger pattern shows a higher cycling stability within a LiFePO4/Li cell than that of the smaller one indicating that initiating the Li deposition from the bottom of the hole is more efficient in confining the deposited Li. Based on the impedance analysis of the compressed Li electrodes, we suggest that the guided Li deposition on the bottom of the hole is attributed to a large contrast in the resistance of native surface passivation layer between the top and hole surfaces. This improved understanding can further advance guided Li deposition induced by surface patterns for high performance Li‐metal batteries.
  • Liang Yin, Gerard S. Mattei, Zhou Li, Jianming Zheng, Wengao Zhao, Fredrick Omenya, Chengcheng Fang, Wangda Li, Jianyu Li, Qiang Xie, Ji-Guang Zhang, M. Stanley Whittingham, Ying Shirley Meng, Arumugam Manthiram, Peter G. Khalifah."Extending the limits of powder diffraction analysis: Diffraction parameter space, occupancy defects, and atomic form factors."Review of Scientific Instruments 89 (9), article number 093002 (September 2018).
    Abstract: Although the determination of site occupancies is often a major goal in Rietveld refinement studies, the accurate refinement of site occupancies is exceptionally challenging due to many correlations and systematic errors that have a hidden impact on the final refined occupancy parameters. Through the comparison of results independently obtained from neutron and synchrotron powder diffraction, improved approaches capable of detecting occupancy defects with an exceptional sensitivity of 0.1% (absolute) in the class of layered NMC (Li[NixMnyCoz]O2) Li-ion battery cathode materials have been developed. A new method of visualizing the diffraction parameter space associated with crystallographic site scattering power through the use of f* diagrams is described, and this method is broadly applicable to ternary compounds. The f* diagrams allow the global minimum fit to be easily identified and also permit a robust determination of the number and types of occupancy defects within a structure. Through a comparison of neutron and X-ray diffraction results, a systematic error in the synchrotron results was identified using f* diagrams for a series of NMC compounds. Using neutron diffraction data as a reference, this error was shown to specifically result from problems associated with the neutral oxygen X-ray atomic form factor and could be eliminated by using the ionic O2− form factor for this anion while retaining the neutral form factors for cationic species. The f* diagram method offers a new opportunity to experimentally assess the quality of atomic form factors through powder diffraction studies on chemically related multi-component compounds.
  • Enyue Zhao, Kaihui Nie, Xiqian Yu, Yong-Sheng Hu, Fangwei Wang, Jie Xiao, Hong Li, Xuejie Huang."Advanced Characterization Techniques in Promoting Mechanism Understanding for Lithium–Sulfur Batteries."Advanced Functional Materials 23 (38): 1707543 (September 2018).
    Abstract: Due to their numerous advantages, such as high specific capacity, lithium–sulfur batteries (Li–S batteries) have attracted much attention as next‐generation energy storage systems. To meet future needs for commercial application, Li–S batteries will require both improved cycle life and high energy density. It is of critical importance to understand the fundamental mechanisms in Li–S systems to further improve the overall battery performance. Various advanced characterization techniques, over the past few years, have proven their important role in promoting the mechanism understanding for Li–S batteries. Here, the recent progress of mechanism understanding, including redox reactions, Li polysulfides dissolution, etc., in Li–S systems based on the advanced characterization techniques is reviewed. Special focus is placed on how these advanced characterization techniques are being employed and what characteristic or capability they possess. The importance of the combination of multiple characterization techniques, differences between ex situ and in situ experimental methods, as well as effects of characterization conditions in Li–S batteries are also discussed.
  • Lu Yu, Shuru Chen, Hongkyung Lee, Linchao Zhang, Mark H. Engelhard, Qiuyan Li, Shuhong Jiao, Jun Liu, Wu Xu, Ji-Guang Zhang."A Localized High-Concentration Electrolyte with Optimized Solvents and Lithium Difluoro(oxalate)borate Additive for Stable Lithium Metal Batteries."ACS Energy Letters 3 (9) 2059-2067 (September 2018).
    Abstract: We report a carbonate-based localized high-concentration electrolyte (LHCE) with a fluorinated ether as a diluent for 4-V class lithium metal batteries (LMBs), which enables dendrite-free Li deposition with a high Li Coulombic efficiency (∼98.5%) and much better cycling stability for Li metal anodes than previously reported dimethyl carbonate-based LHCEs at lean electrolyte conditions. This electrolyte consists of 1.2 M lithium bis(fluorosulfonyl)imide (LiFSI) in a cosolvent mixture of ethylene carbonate (EC)/ethyl methyl carbonate (EMC) with bis(2,2,2-trifluoroethyl) ether (BTFE) as the diluent and 0.15 M lithium difluoro(oxalate)borate (LiDFOB) as an additive. A Li||LiNi1/3Mn1/3Co1/3O2 battery with a high areal loading of 3.8 mAh cm–2 maintains 84% of its initial capacity after 100 cycles. The enhanced stability can be attributed to the robust solid–electrolyte interface (SEI) layer formed on the Li metal anode, arising from the preferential decomposition of LiDFOB salt and EC solvent molecules.
  • Shuhong Jiao, Xiaodi Ren, Ruiguo Cao, Mark H. Engelhard, Yuzi Liu, Dehong Hu, Donghai Mei, Jianming Zheng, Wengao Zhao, Qiuyan Li, Ning Liu, Brian D. Adams, Cheng Ma, Jun Liu, Ji-Guang Zhang, Wu Xu."Stable cycling of high-voltage lithium metal batteries in ether electrolytes."Nature Energy 3: 739-746 (September 2018).
    Abstract: The key to enabling long-term cycling stability of high-voltage lithium (Li) metal batteries is the development of functional electrolytes that are stable against both Li anodes and high-voltage (above 4 V versus Li/Li+) cathodes. Due to their limited oxidative stability ( <4 V), ethers have so far been excluded from being used in high-voltage batteries, in spite of their superior reductive stability against Li metal compared to conventional carbonate electrolytes. Here, we design a concentrated dual-salt/ether electrolyte that induces the formation of stable interfacial layers on both a high-voltage LiNi1/3Mn1/3Co1/3O2 cathode and the Li metal anode, thus realizing a capacity retention of >90% over 300 cycles and ~80% over 500 cycles with a charge cut-off voltage of 4.3 V. This study offers a promising approach to enable ether-based electrolytes for high-voltage Li metal battery applications.
  • Shuru Chen, Jianming Zheng, Lu Yu, Xiaodi Ren, Mark H. Engelhard, Chaojiang Niu, Hongkyung Lee, Wu Xu, Jie Xiao, Jun Liu, Ji-Guang Zhang."High-Efficiency Lithium Metal Batteries with Fire-Retardant Electrolytes."Joule 2 (8), 1548-1558 (August 2018).
    Abstract: A safe electrolyte for 4-V class lithium metal batteries (LMBs) was reported by diluting a fire-retardant high-concentration electrolyte (HCE) with an electrochemically “inert” and poorly solvating fluorinated ether. Named localized high-concentration electrolyte (LHCE), it inherits the merits from the HCE but dramatically overcomes its disadvantages. The fire-retardant LHCE enables dendrite-free and stable cycling of a Li metal anode with high Coulombic efficiency of up to 99.2% and greatly enhances the cycling stability of Li||NMC622 batteries for more than 600 cycles. The excellent electrochemical performances of the LHCE is ascribed to the well-reserved, locally concentrated solvation structures and its improved interfacial reaction kinetics and stability. These findings open up a new avenue for developing highly stable and safe electrolyte systems for high-energy-density LMBs for practical applications.
  • Xiaodi Ren, Shuru Chen, Hongkyung Lee, Donghai Mei, Mark H. Engelhard, Sarah D. Burton, Wengao Zhao, Jianming Zheng, Qiuyan Li, Michael S. Ding, Marshall Schroeder, Judith Alvarado, Kan Xu, Y. Shirley Meng, Jun Liu, Ji-Guang Zhang, Wu Xu."Localized High-Concentration Sulfone Electrolytes for High-Efficiency Lithium-Metal Batteries."Chem 4 (8), 1877-1892 (August 2018).
    Abstract: For high-voltage rechargeable lithium (Li)-metal batteries (LMBs), electrolytes with good stabilities on both the highly oxidative cathodes and the highly reductive Li-metal anodes are urgently desired. Sulfones have excellent oxidative stability, yet their high viscosity, poor wettability, and, in particular, incompatibility with Li anodes greatly hinder their applications in LMBs. Here, we demonstrate that a high Li Coulombic efficiency (CE) of 98.2% during repeated Li plating and stripping cycles can be realized in concentrated lithium bis(fluorosulfonyl)imide (LiFSI)-tetramethylene sulfone electrolyte. More importantly, the localized high-concentration electrolyte, formed by the dilution of the high-concentration electrolyte with a non-solvating fluorinated ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, solves the viscosity and wettability issues, further improves Li CE (98.8%), and improves the high-voltage (4.9 V) performance of LMBs with effective Al protection.
  • Ye F, H Noh, JH Lee, H Lee, and HT Kim.Ye F, H Noh, JH Lee, H Lee, and HT Kim."Li2S/Carbon Nanocomposite Strips from a Low-Temperature Conversion of Li2SO4 as High-Performance Lithium-Sulfur Cathodes." Journal of Materials Chemistry A 6(15): 6617-6624 (March 2018).
    Abstract:Carbothermal conversion of Li2SO4 provides a cost-effective strategy to fabricate high-capacity Li2S cathodes, however, Li2S cathodes derived from Li2SO4 at high temperatures (> 800 oC), having high crystallinity and large crystal size, result in a low utilization of Li2S. Here, we report a Li2SO4/poly(vinyl alcohol)-derived Li2S/Carbon nanocomposite (Li2S@C) strips at a record low temperature of 635 oC. These Li2S@C nanocomposite strips as a cathode shows a low initial activation potential (2.63 V), a high initial discharge capacity (805 mAh g-1 Li2S) and a high cycling stability (0.2 C and 1 C). These improvedresults could be ascribed to the nano-sized Li2S particles as well as their low crystallinity due to the PVA-induced carbon network and the low conversion temperature, respectively. An XPS analysis reveals that the C=C and C=O bonds derived from the carbonization of PVA can promote the conversion of Li2SO4 at the low temperature.
  • Yu L, NL Canfield, S Chen, H Lee, X Ren, MH Engelhard, Q Li, J Liu, W Xu, and J Zhang."Enhanced Stability of Li Metal Anode by using a 3D Porous Nickel Substrate." ChemElectroChem 5 (5): 761-769 (March 2018).
    Abstract:Lithium (Li) metal is considered the “holy grail” anode for high energy density batteries, but its applications in rechargeable Li metal batteries are still hindered by the formation of Li dendrites and low Coulombic efficiency for Li plating/stripping. An effective strategy to stabilize Li metal is by embedding Li metal anode in a three-dimensional (3D) current collector. Here, a highly porous 3D Ni substrate is reported to effectively stabilize Li metal anode. Using galvanostatic intermittent titration technique combined with scanning electron microscopy, the underlying mechanism on the improved stability of Li metal anode is revealed. It is clearly demonstrated that the use of porous 3D Ni substrate can effectively suppress the formation of “dead” Li and forms a dense surface layer, whereas a porous “dead” Li layer is accumulated on the 2D Li metal which eventually leads to mass transport limitations. X-ray photoelectron spectroscopy results further revealed the compositional differences in the solid-electrolyte interphase layer formed on the Li metal embedded in porous 3D Ni substrate and the 2D copper substrate.

2017

  • Hongkyung Lee, Xiaodi Ren, Chaojiang Niu, Lu Yu, Mark H. Engelhard, Inseong Cho, Myung-Hyun Ryou, Hyun Soo Jin, Hee-Tak Kim, Jun Liu, Wu Xu, Ji-Guang Zhang."Suppressing Lithium Dendrite Growth by Metallic Coating on a Separator."Advanced Functional Materials 27 (45) 1704391 (December 2017).
    Abstract: Lithium (Li) metal is one of the most promising candidates for the anode in high‐energy‐density batteries. However, Li dendrite growth induces a significant safety concerns in these batteries. Here, a multifunctional separator through coating a thin electronic conductive film on one side of the conventional polymer separator facing the Li anode is proposed for the purpose of Li dendrite suppression and cycling stability improvement. The ultrathin Cu film on one side of the polyethylene support serves as an additional conducting agent to facilitate electrochemical stripping/deposition of Li metal with less accumulation of electrically isolated or “dead” Li. Furthermore, its electrically conductive nature guides the backside plating of Li metal and modulates the Li deposition morphology via dendrite merging. In addition, metallic Cu film coating can also improve thermal stability of the separator and enhance the safety of the batteries. Due to its unique beneficial features, this separator enables stable cycling of Li metal anode with enhanced Coulombic efficiency during extended cycles in Li metal batteries and increases the lifetime of Li metal anode by preventing short‐circuit failures even under extensive Li metal deposition.
  • Xuefeng Wang, Minghao Zhang, Judith Alvarado, Shen Wang, Mahsa Sina, Bingyu Lu, James Bouwer, Wu Xu, Jie Xiao, Ji-Guang Zhang, Jun Liu, Ying Shirley Meng."New Insights on the Structure of Electrochemically Deposited Lithium Metal and Its Solid Electrolyte Interphases via Cryogenic TEM." Nano Letters17 (12): 7606-7612 (November 2017).
    Abstract:Lithium metal has been considered the “holy grail” anode material for rechargeable batteries despite the fact that its dendritic growth and low Coulombic efficiency (CE) have crippled its practical use for decades. Its high chemical reactivity and low stability make it difficult to explore the intrinsic chemical and physical properties of the electrochemically deposited lithium (EDLi) and its accompanying solid electrolyte interphase (SEI). To prevent the dendritic growth and enhance the electrochemical reversibility, it is crucial to understand the nano- and mesostructures of EDLi. However, Li metal is very sensitive to beam damage and has low contrast for commonly used characterization techniques such as electron microscopy. Inspired by biological imaging techniques, this work demonstrates the power of cryogenic (cryo)-electron microscopy to reveal the detailed structure of EDLi and the SEI composition at the nanoscale while minimizing beam damage during imaging. Surprisingly, the results show that the nucleation-dominated EDLi (5 min at 0.5 mA cm–2) is amorphous, while there is some crystalline LiF present in the SEI. The EDLi grown from various electrolytes with different additives exhibits distinctive surface properties. Consequently, these results highlight the importance of the SEI and its relationship with the CE. Our findings not only illustrate the capabilities of cryogenic microscopy for beam (thermal)-sensitive materials but also yield crucial structural information on the EDLi evolution with and without electrolyte additives.
  • Xinxin Cao, Anqiang Pan, Sainan Liu, Jiang Zhou, Site Li, Guozhong Cao, Jun Liu, Shuquan Liang."Chemical Synthesis of 3D Graphene‐Like Cages for Sodium‐Ion Batteries Applications."Advanced Energy Materials7 (20) 1700797 (October 2017).
    Abstract: Sodium (Na) super ion conductor structured Na3V2(PO4)3 (NVP) is extensively explored as cathode material for sodium‐ion batteries (SIBs) due to its large interstitial channels for Na+ migration. The synthesis of 3D graphene‐like structure coated on NVP nanoflakes arrays via a one‐pot, solid‐state reaction in molten hydrocarbon is reported. The NVP nanoflakes are uniformly coated by the in situ generated 3D graphene‐like layers with the thickness of 3 nm. As a cathode material, graphene covered NVP nanoflakes exhibit excellent electrochemical performances, including close to theoretical reversible capacity (115.2 mA h g−1 at 1 C), superior rate capability (75.9 mA h g−1 at 200 C), and excellent cyclic stability (62.5% of capacity retention over 30000 cycles at 50 C). Furthermore, the 3D graphene‐like cages after removing NVP also serve as a good anode material and deliver a specific capacity of 242.5 mA h g−1 at 0.1 A g−1. The full SIB using these two cathode and anode materials delivers a high specific capacity (109.2 mA h g−1 at 0.1 A g−1) and good cycling stability (77.1% capacity retention over 200 cycles at 0.1 A g−1).
  • 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.
  • 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.
  • Jinhong Lee, Jongchan Song, Hongkyung Lee, Hyungjun Noh, Yun-Jung Kim, Sung Hyun Kwon, Seung Geol Lee, Hee-Tak Kim."A Nanophase-Separated, Quasi-Solid-State Polymeric Single-Ion Conductor: Polysulfide Exclusion for Lithium–Sulfur Batteries."ACS Energy Letters 2 (5): 1232-1239 (April 2017).
    Abstract: Formation of soluble polysulfide (PS), which is a key feature of lithium sulfur (Li–S) batteries, provides a fast redox kinetic based on a liquid–solid mechanism; however, it imposes the critical problem of PS shuttle. Here, we address the dilemma by exploiting a solvent-swollen polymeric single-ion conductor (SPSIC) as the electrolyte medium of the Li–S battery. The SPSIC consisting of a polymeric single-ion conductor and lithium salt-free organic solvents provides Li ion hopping by forming a nanoscale conducting channel and suppresses PS shuttle according to the Donnan exclusion principle when being employed for Li–S batteries. The organic solvents at the interface of the sulfur/carbon composite and SPSIC eliminate the poor interfacial contact and function as a soluble PS reservoir for maintaining the liquid–solid mechanism. Furthermore, the quasi-solid-state SPSIC allows the fabrication of a bipolar-type stack, which promises the realization of a high-voltage and energy-dense Li–S battery.
  • Wonhee Jo, Hong Suk Kang, Jaeho Choi, Hongkyung Lee, Hee-Tak Kim."Plasticized Polymer Interlayer for Low-Temperature Fabrication of a High-Quality Silver Nanowire-Based Flexible Transparent and Conductive Film."Applied Materials & Interfaces 9 (17): 15114-15121 (April 2017).
    Abstract: Silver nanowires (AgNWs) are one of the most promising materials to replace commercially available indium tin oxide in flexible transparent conductive films (TCFs); however, there are still numerous problems originating from poor AgNW junction formation and improper AgNW embedment into transparent substrates. To mitigate these problems, high-temperature processes have been adopted; however, unwanted substrate deformation prevents the use of these processes for the formation of flexible TCFs. In this work, we present a novel poly(methyl methacrylate) interlayer plasticized by dibutyl phthalate for low-temperature fabrication of AgNW-based TCFs, which does not cause any substrate deformation. By exploiting the viscoelastic properties of the plasticized interlayer near the lowered glass-transition temperature, a monolithic junction of AgNWs on the interlayer and embedment of the interconnected AgNWs into the interlayer are achieved in a single-step pressing. The resulting AgNW-TCFs are highly transparent (∼92% at a wavelength of 550 nm), highly conductive (<90 Ω/sq), and environmentally and mechanically robust. Therefore, the plasticized interlayer provides a simple and effective route to fabricate high-quality AgNW-based TCFs.
  • 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.

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