Synthesis and characterization of argyrodite solid electrolytes for all-solid-state Li-ion batteries

Li₆PS₅X (X = Cl, Br, I) argyrodites possess high ionic conductivity but with rather scattered values due to various processing conditions. In this work, Li₆PS₅X solid electrolytes were prepared by solid-state sintering or mechanical alloying and optimized with or without excess Li₂S. Solid-state sintering prefers excess Li₂S, whereas mechanical alloying prefers stoichiometric Li₂S to synthesize high-purity samples with high ionic conductivity. Solid-state sintering is also more suitable than mechanical milling for high ionic conductivity. Li₆PS₅Cl with the highest ionic conductivity among Li₆PS₅X was comprehensively characterized for electrochemical performance and air stability. MoS₂/Li₆PS₅Cl all-solid-state batteries assembled with Li₆PS₅Cl-coated MoS₂ as cathode and with Li₆PS₅Cl as solid electrolyte demonstrate high capacity and good cycling stability.