Super Long‐Cycling All‐Solid‐State Battery with Thin Li ₆ PS ₅ Cl‐Based Electrolyte

All-solid-state batteries (ASSBs) using sulfide electrolytes have attracted ever-increasing interest due to high ionic conductivity of the sulfides. Nevertheless, a thin, strong solid-state sulfide electrolyte membrane maintaining high ionic conductivity is highly desired for ASSBs. Here, a thin, flexible composite solid electrolyte membrane composed of argyrodite sulfide Li6PS5Cl and a polar poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) framework is prepared via an electrospinning-infiltration-hot-pressing method. The interaction between Li6PS5Cl and polar P(VDF-TrFE) ensures a high lithium-ion conductivity (≈1.2 mS cm–1) at room temperature and good mechanical ductility of the composite electrolyte membrane. The coin-type ASSB cells with the thin composite electrolyte membrane, a composite cathode of LiNbO3-coated LiNi0.8Co0.1Mn0.1O2 and Li6PS5Cl, and a lithium-indium anode, show super cycling performance, and the capacity retention is 92% after 1000 cycles and 71% even after 20 000 cycles at 1.0 mA cm–2 (i.e., 1.61 C) at room temperature. Moreover, pouch-type ASSB cells with a high mass loading of active materials are made to demonstrate the potential and feasibility in future commercial applications.