Abstract
Liquid electrolytes in batteries are typically treated as macroscopically homogeneous ionic transport media despite having a complex chemical composition and atomistic solvation structures, leaving a knowledge gap of the microstructural characteristics. Here, we reveal a unique micelle-like structure in a localized high-concentration electrolyte, in which the solvent acts as a surfactant between an insoluble salt in a diluent. The miscibility of the solvent with the diluent and simultaneous solubility of the salt results in a micelle-like structure with a smeared interface and an increased salt concentration at the centre of the salt–solvent clusters that extends the salt solubility. These intermingling miscibility effects have temperature dependencies, wherein a typical localized high-concentration electrolyte peaks in localized cluster salt concentration near room temperature and is used to form a stable solid–electrolyte interphase on a Li metal anode. These findings serve as a guide to predicting a stable ternary phase diagram and connecting the electrolyte microstructure with electrolyte formulation and formation protocols of solid–electrolyte interphases for enhanced battery cyclability.
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Data availability
The authors declare that all data supporting the findings of this study are included within the paper and its Supplementary Information. Source data are available from the corresponding authors (B.L. and Y.Q.) upon reasonable request.
Code availability
The Python scripts that have been used for MD analyses are available from the corresponding author (Y.Q.) upon request.
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Acknowledgements
B.L. on behalf of the authors from National Laboratories and Y.Q. on behalf of the authors from Brown University thank the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the US Department of Energy through the Advanced Battery Materials Research Program (Battery500 Consortium) and NASA (grant no. 80NSSC21M0107), respectively, for the financial support. Idaho National Laboratory (INL) is operated by Battelle Energy Alliance under contract no. DE-AC07-05ID14517 for the US Department of Energy. Pacific Northwest National Laboratory (PNNL) is operated by Battelle under contract no. DE-AC05-76RLO1830 for the US Department of Energy. The authors from Boise State University thank the Micron School of Materials Science and Engineering of this university for the additional financial support. We acknowledge the Atomic Films Laboratory at Boise State University for the use of the PHI-5600 XPS system. This research also used resources of the Center for Functional Nanomaterials and the SMI beamline (12-ID) of the National Synchrotron Light Source II, both supported by the US Department of Energy, Office of Science facilities at Brookhaven National Laboratory (BNL) under contract no. DE-SC0012704. We thank E. Graugnard, J. D. Hues and J. Soares for support with XPS, N. Bulloss for support with FESEM and P. H. Davis for support with Raman, as well as S. Tan from BNL for electrolyte sample preparation.
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B.L. and Y.Q. conceived the original idea and designed the experiments. Q.W. and Y.Q. conducted all MD simulations and DFT calculations, as well as computational analyses. C.M.E. and B.L. collected and processed the Raman and FESEM data. C.M.E. and N.G. prepared and cycled the coin cells. X.C. prepared electrolytes and cycled the Coulombic efficiency cells. H.Z. and C.M.E. collected and processed the XPS results. Y.Z., B.L., Y.Q., E.H., X.-Q.Y. and J.L. collected and processed the SAXS-WAXS results. C.M.E., Q.W., Y.Q. and B.L. wrote the manuscript. All authors contributed to the discussions and revisions of the manuscript.
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Efaw, C.M., Wu, Q., Gao, N. et al. Localized high-concentration electrolytes get more localized through micelle-like structures. Nat. Mater. 22, 1531–1539 (2023). https://doi.org/10.1038/s41563-023-01700-3
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DOI: https://doi.org/10.1038/s41563-023-01700-3