Fluorinated Li 10 GeP 2 S 12 Enables Stable All‐Solid‐State Lithium Batteries

Abstract The instability of Li 10 GeP 2 S 12 toward moisture and that toward lithium metal are two challenges for the application in all‐solid‐state lithium batteries. In this work, Li 10 GeP 2 S 12 is fluorinated to form a LiF‐coated core–shell solid electrolyte LiF@Li 10 GeP 2 S 12 . Density‐functional theory calculations confirm the hydrolysis mechanism of Li 10 GeP 2 S 12 solid electrolyte, including H 2 O adsorption on Li atoms of Li 10 GeP 2 S 12 and the subsequent PS 4 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, Li 10 GeP 2 S 12 shows one order lower electronic conductivity, which can significantly suppress lithium dendrite growth and reduce the side reaction between Li 10 GeP 2 S 12 and lithium, realizing three times higher critical current density to 3 mA cm −2 . The assembled LiNbO 3 @LiCoO 2 /LiF@Li 10 GeP 2 S 12 /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.