Fluorine and carbonate regulated nonflammable polymer electrolyte for ultrastable high-voltage Li metal batteries

Abstract

Polymer electrolytes are promising electrolytes for solid-state Li metal batteries owing to their low flammability, non-leakage, easy processing and good flexibility. However, low ionic conductivity and inferior oxidation stability of conventional polymer electrolytes hinder their application in high-voltage Li metal batteries. Herein, we develop a fluorine and carbonate regulated nonflammable polymer electrolyte (F-HV) for high-voltage Li metal batteries. Fluorinated main chains endow F-HV with high oxidative stability (4.9 V vs. Li⁺/Li) and promote the formation of robust LiF-rich interfaces, effectively enhancing the interfacial stability of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathodes and Li metal anodes. Carbonate side chains facilitate dissociation and conduction of Li⁺, effectively enhancing the ionic conductivity to 1.97 mS cm⁻¹. F-HV possesses excellent flame resistance and favorable dimension stability up to 200 °C. F-HV markedly boosts the performance of Li||NCM811 and Li||LiFePO₄ (LFP) cells, which exhibit an ultralong cycle life of 3000 cycles with an impressive capacity retention of 86.3%. F-HV also enables Li||NCM811 cells with enhanced cycle stability at high temperature (60 °C) and high voltage (4.5 V). This work provides an effective strategy for achieving high-performance solid-state Li metal batteries.