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Although high-voltage lithium (Li) metal batteries are promising next-generation energy storage devices, their practical use is hindered by their poor cycling stability owing to low electrolyte compatibility with both Li metal anodes and 5 Vclass cathodes. In this study, we report that the gelation of saltconcentrated electrolytes with weakly coordinating poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) effectively improves the cycling stability of high-voltage Li metal batteries. The PVDF-HFP-based gel polymer electrolyte with a saltconcentrated electrolyte comprising lithium bis(fluorosulfonyl)-amide (LiFSA) and sulfolane (SL) achieves a high Coulombic efficiency and dense deposition morphology of Li metal anodes, along with sufficient oxidation stability against 5 V-class cathodes. Experimental and computational analyses show that the solvation structures of SL−Li+−FSA−, similar to those in the original concentrated electrolyte, are maintained in the PVDF-HFP matrix, which leads to the formation of a low-resistance solid electrolyte interphase (SEI) rich in lithium fluoride and sulfur compounds. These findings indicate that the low-resistance SEI in the gel polymer electrolyte promotes dense Li deposits, which suppresses electrolyte decomposition and inactive Li formation, improving the Coulombic efficiency of Li metal anodes. We demonstrate that the stable cycling of a Li metal battery with a 5 V-class LiNi0.5Mn1.5O4 cathode is enabled by the gel electrolyte, which inhibits the deposition of transition metals dissolved from the cathode onto the anode. This electrolyte and interface design is an effective strategy for developing 5 V-class Li metal batteries and can be applied to other high-energy-density metal batteries with high-voltage cathodes.

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  This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Applied Polymer Materials, copyright © 2025 American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acsapm.4c03396.

Keyword: Gel Polymer Electrolytes, Salt-Concentrated Electrolytes, Lithium Metal Batteries

Date published: 2025-02-14

Publisher: American Chemical Society (ACS)

Journal:

• ACS Applied Polymer Materials (ISSN: 26376105) vol. 7 issue. 3 p. 1629-1638

Funding:

• Japan Society for the Promotion of Science JP21K14731
• Japan Society for the Promotion of Science JP22H04626
• Japan Society for the Promotion of Science JP23K13833
• Iketani Science and Technology Foundation 0331058-A
• GteX Program Japan JPMJGX23S3

Manuscript type: Author's version (Submitted manuscript)

MDR DOI: https://doi.org/10.48505/nims.5989

First published URL: https://doi.org/10.1021/acsapm.4c03396

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Updated at: 2025-12-11 08:30:10 +0900

Published on MDR: 2025-12-11 08:24:20 +0900