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

Abstract 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 Li 6 PS 5 Cl and a polar poly(vinylidene fluoride‐ co ‐trifluoroethylene) (P(VDF‐TrFE)) framework is prepared via an electrospinning‐infiltration‐hot‐pressing method. The interaction between Li 6 PS 5 Cl 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 LiNbO 3 ‐coated LiNi 0.8 Co 0.1 Mn 0.1 O 2 and Li 6 PS 5 Cl, 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.