Fluorinated Li10 GeP2 S12 Enables Stable All-Solid-State Lithium Batteries

The instability of Li₁₀ GeP₂ S₁₂ toward moisture and that toward lithium metal are two challenges for the application in all-solid-state lithium batteries. In this work, Li₁₀ GeP₂ S₁₂ is fluorinated to form a LiF-coated core-shell solid electrolyte LiF@Li₁₀ GeP₂ S₁₂ . Density-functional theory calculations confirm the hydrolysis mechanism of Li₁₀ GeP₂ S₁₂ solid electrolyte, including H₂ O adsorption on Li atoms of Li₁₀ GeP₂ S₁₂ and the subsequent PS₄ ^3- dissociation affected by hydrogen bond. The hydrophobic LiF shell can reduce the adsorption site, thus resulting in superior moisture stability when exposing in 30% relative humidity air. Moreover, with LiF shell, Li₁₀ GeP₂ S₁₂ shows one order lower electronic conductivity, which can significantly suppress lithium dendrite growth and reduce the side reaction between Li₁₀ GeP₂ S₁₂ and lithium, realizing three times higher critical current density to 3 mA cm^-2 . The assembled LiNbO₃ @LiCoO₂ /LiF@Li₁₀ GeP₂ S₁₂ /Li battery exhibits an initial discharge capacity of 101.0 mAh g^-1 with a capacity retention of 94.8% after 1000 cycles at 1 C.