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 Li 6 PS 5 Br as solid electrolyte synthesized by a facile solid-state sintering. Different from other O-incorporated sulfides, the O atoms in Li 6 PS 5-x O x Br prefer to substitute the S atoms at free S 2− sites rather than those at the PS 4 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(Ni 0.8 Co 0.1 Mn 0.1)O 2 and LiCoO 2-based all-solid-state batteries with Li 6 PS 4.7 O 0.3 Br 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.

The relation between the argyrodite solid-electrolyte morphology and solid-state Li-ion battery performance is investigated, suggesting different morphologies for the electrode in combination electrolyte regions.

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.

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