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

Li 6 PS 5 X (X = Cl, Br, I) argyrodites possess high ionic conductivity but with rather scattered values due to various processing conditions. In this work, Li 6 PS 5 X solid electrolytes were prepared by solid-state sintering or mechanical alloying and optimized with or without excess Li 2 S. Solid-state sintering prefers excess Li 2 S, whereas mechanical alloying prefers stoichiometric Li 2 S to synthesize high-purity samples with high ionic conductivity. Solid-state sintering is also more suitable than mechanical milling for high ionic conductivity. Li 6 PS 5 Cl with the highest ionic conductivity among Li 6 PS 5 X was comprehensively characterized for electrochemical performance and air stability. MoS 2 /Li 6 PS 5 Cl all-solid-state batteries assembled with Li 6 PS 5 Cl-coated MoS 2 as cathode and with Li 6 PS 5 Cl as solid electrolyte demonstrate high capacity and good cycling stability.