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.
Keywords: Li 10GeP 2S 12; all-solid-state lithium batteries; core-shell structure; gas-phase treatment; moisture and lithium stability.
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