Fluorinated Li GeP S Enables Stable All-Solid-State Lithium Batteries.

The instability of Li GeP S toward moisture and that toward lithium metal are two challenges for the application in all-solid-state lithium batteries. In this work, Li GeP S is fluorinated to form a LiF-coated core-shell solid electrolyte LiF@Li GeP S . Density-functional theory calculations confirm the hydrolysis mechanism of Li GeP S solid electrolyte, including H O adsorption on Li atoms of Li GeP S and the subsequent PS 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, Li GeP S shows one order lower electronic conductivity, which can significantly suppress lithium dendrite growth and reduce the side reaction between Li GeP S and lithium, realizing three times higher critical current density to 3 mA cm . The assembled LiNbO @LiCoO /LiF@Li GeP S /Li battery exhibits an initial discharge capacity of 101.0 mAh g with a capacity retention of 94.8% after 1000 cycles at 1 C.