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High-entropy electrolytes for practical lithium metal batteries

Nature Energy volume 8, pages 814–826 (2023)Cite this article

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Abstract

Electrolyte engineering is crucial for improving battery performance, particularly for lithium metal batteries. Recent advances in electrolytes have greatly improved cyclability by enhancing electrochemical stability at the electrode interfaces, but concurrently achieving high ionic conductivity has remained challenging. Here we report an electrolyte design strategy for enhanced lithium metal batteries by increasing the molecular diversity in electrolytes, which essentially leads to high-entropy electrolytes. We find that, in weakly solvating electrolytes, the entropy effect reduces ion clustering while preserving the characteristic anion-rich solvation structures, which is characterized by synchrotron-based X-ray scattering and molecular dynamics simulations. Electrolytes with smaller-sized clusters exhibit a twofold improvement in ionic conductivity compared with conventional weakly solvating electrolytes, enabling stable cycling at high current densities up to 2C (6.2 mA cm−2) in anode-free LiNi0.6Mn0.2Co0.2 (NMC622)||Cu pouch cells. The efficacy of the design strategy is verified by performance improvements in three disparate weakly solvating electrolyte systems.

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Fig. 1: Design framework for HEEs.
Fig. 2: Electrochemical performance of HEEs.
Fig. 3: Microscopic and mesoscopic solvation structures.
Fig. 4: Electroplating morphology and the interphase.
Fig. 5: Electrochemical performance of broader HEE systems.

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All data are available in the main text or the Supplementary Information.

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Acknowledgements

S.T.O. acknowledges support from the TomKat Center Fellowship for Translational Research at Stanford University. D.T.B. acknowledges the National Science Foundation Graduate Research Fellowship Program for funding. Z.H. acknowledges support from an American Association of University Women International Fellowship. The battery and electrolyte measurement parts were supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, of the U.S. Department of Energy under the Battery Materials Research Program and the Battery500 Consortium programme. Part of this work was performed at the Stanford Nano Shared Facilities. We acknowledge J. Nelson Weker for fruitful discussions on X-ray scattering experiments.

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  1. These authors contributed equally: Sang Cheol Kim, Jingyang Wang.

Authors and Affiliations

  1. Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA

    Sang Cheol Kim, Jingyang Wang, Rong Xu, Pu Zhang, Zhuojun Huang, Yufei Yang, Wenbo Zhang, Louisa C. Greenburg, Yusheng Ye & Yi Cui

  2. Department of Chemistry, Stanford University, Stanford, CA, USA

    Yuelang Chen, Zhiao Yu, David T. Boyle & Philaphon Sayavong

  3. Department of Chemical Engineering, Stanford University, Stanford, CA, USA

    Solomon T. Oyakhire, Mun Sek Kim, Jian Qin & Zhenan Bao

  4. Department of Energy Science and Engineering, Stanford University, Stanford, CA, USA

    Yi Cui

  5. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA

    Yi Cui

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Contributions

S.C.K. and J.W. contributed equally. S.C.K. and Y. Cui conceived and designed the investigation. S.C.K. conducted materials synthesis and electrochemical performance testing. J.W. conducted MD simulations. R.X. conducted multiphysics simulations. P.Z. and Z.H. conducted X-ray scattering experiments. Y. Chen conducted DOSY-NMR experiments. Y. Yang conducted SEM characterizations. Z.Y. conducted electrolyte solvent synthesis. Z.H. conducted viscosity characterization. S.T.O. and L.C.G. conducted XPS characterization. S.C.K. conducted solvation measurements. W.Z., P.S., M.S.K., D.T.B. and Y. Ye assisted with interpretation of results. J.Q., Z.B. and Y. Cui supervised the project. S.C.K., J.W. and Y. Cui co-wrote the paper. All authors discussed the results and commented on the paper.

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Correspondence to Yi Cui.

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Kim, S.C., Wang, J., Xu, R. et al. High-entropy electrolytes for practical lithium metal batteries. Nat Energy 8, 814–826 (2023). https://doi.org/10.1038/s41560-023-01280-1

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