Stable Li₇P₃S₁₁ Sulfide/PVDF-HFP composited solid-state electrolyte for solid-state Lithium metal batteries

Solid-state lithium metal batteries (SSLMBs) are regarded as promising next-generation energy storage systems due to their high energy density and improved safety. Compared with liquid electrolytes, solid-state electrolytes effectively suppress lithium dendrite growth and offer superior thermal and electrochemical stability. However, polymer solid electrolytes suffer from low ionic conductivity, while sulfide electrolytes are limited by poor air stability and interfacial incompatibility. Herein, a novel sulfide composite electrolyte (CSE) is developed by incorporating a glass–ceramic sulfide electrolyte, Li₇P₃S₁₁ (LPS), into a poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix with LiTFSI, forming a flexible LPS/PVDF-HFP/LiTFSI composite film. This composite structure simultaneously enhances air stability, mechanical flexibility, and electrochemical stability. The introduction of LPS promotes lithium salt dissociation and increases the amorphous phase content of the polymer, resulting in improved lithium-ion transport. An optimal ionic conductivity of 3.01 × 10−4 S cm−1 is achieved at an LPS content of 3 wt%. The optimized CSE enables stable cycling of a Li|Li symmetric cell for over 1200 h at 0.1 mA cm−2 and delivers a reversible capacity of 160 mAh g−1 after 150 cycles in a LiFePO₄|Li full cell.