PVDF-HFP-Based Composite Electrolyte Membranes having High Conductivity and Lithium-Ion Transference Number for Lithium Metal Batteries

Lithium metal batteries (LMBs) with liquid-based electrolytes usually suffer from safety problems such as the growth of Li dendrites and the leakage and volatilization of organic solvents. Replacing liquid-based electrolytes using solid polymer electrolytes may resolve these problems. In this study, sulfonated polyvinylidene fluoride lithium-hexafluoropropylene (SPVDFLi-HFP), a single-ion conductive polymer, is synthesized from polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and chlorosulfonic acid, and a series of LMBs are fabricated using SPVDFLi-HFPx/PVDF-HFP composite electrolyte membranes and characterized. The as-prepared SPVDFLi-HFPx/PVDF-HFP composite electrolyte membranes possess high conductivity (2.84 × 10–4 S cm–1), a wide electrochemical window (5.4 V, vs Li/Li+), and high interface compatibility with lithium metal anodes. Benefiting from the single-ion conductive nature of SPVDFLi-HFP, SPVDFLi-HFP50/PVDF-HFP exhibits a high lithium-ion transference number of 0.81. A solid-state LiFePO4|SPVDFLi-HFP50/PVDF-HFP|Li battery exhibits an initial capacity of 147.9 mA h g–1, a capacity retention of 89.1% at the end of 200 cycles, and an average Coulombic efficiency exceeding 99% at 0.2 C, demonstrating strong application potential in LMBs.