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.@en

Sulfide solid electrolytes possess high ionic conductivity and moderate dendrite suppression capability, but rather poor compatibility against oxide cathodes and metallic Li. Here, we report O-doped Li6PS5Br as solid electrolyte synthesized by a facile solid-state sintering. Different from other O-incorporated sulfides, the O atoms in Li6PS5-xOxBr prefer to substitute the S atoms at free S2− sites rather than those at the PS4 tetrahedra. Remarkably, without deteriorating the ionic conductivity, this inorganic solid electrolyte with O doping exhibits comprehensively enhanced properties including excellent dendrite suppression capability, superior electrochemical and chemical stability against Li metal as well as high voltage oxide cathodes, and good air stability. Li(Ni0.8Co0.1Mn0.1)O2 and LiCoO2-based all-solid-state batteries with Li6PS4.7O0.3Br electrolyte deliver high specific capacity, superior rate capability, and outstanding cycling stability accompanied with low interfacial resistivity. This type of inorganic solid electrolytes is promising for all-solid-state batteries with high energy density.@en