Stable and Flexible Sulfide Composite Electrolyte for High-Performance Solid-State Lithium Batteries

Sulfide-based lithium (Li)-ion conductors represent one of the most popular solid electrolytes (SEs) for solid-state Li metal batteries (SSLMBs) with high safety. However, the commercial application of sulfide SEs is significantly limited by their chemical instability in air and electrochemical instability with electrode materials (metallic Li anode and oxide cathodes). To address these difficulties, here, we design and successfully demonstrate a novel sulfide-incorporated composite electrolyte (SCE) through the combination of inorganic sulfide Li argyrodite (Li₇PS₆) with poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) polymer. In this composite structure, Li₇PS₆ is embedded in PVDF-HFP polymer matrix, making the SCE flexible and air-stable and achieve great chemical and electrochemical stability. Meanwhile, the presence of sulfide facilitates Li-ion transport in SCE, leading to a superior room-temperature ionic conductivity of 1.1 × 10^-4 S cm^-1. Using the SCE with enhanced stability while maintaining high conductivity, Li||Li symmetric cells achieved stable cycling up to 1000 h at 0.2 mA cm^-2. In addition, LiFePO₄ (LFP)||SCE||Li cells can deliver an impressive specific capacity of 160 mAh g^-1 over 150 cycles. These features indicate that Li₇PS₆/PVDF-HFP SCE is a promising candidate to contribute to the practical development of SSLMBs.