Failure mechanism of solid-state electrolyte Li10GeP2S12 in a moist atmosphere: a first-principles study

All-solid-state lithium-ion batteries (ASSLIBs) have commercial potential for industrial applications in long-range electric vehicles. The chemical properties of solid-sate electrolytes (SSEs) play a key role in the performance of ASSLIBs. Among all kinds of SSEs, sulfide solid-sate electrolytes are advantageous to ASSLIBs due to their high ionic conductivity and excellent electrochemical stability. However, sulfide electrolytes have poor stability in air due to their propensity to react with H2O to generate toxic H2S gas. Herein to understand the specific failure mechanism, we use first-principles calculations to study the kinetic and thermodynamic mechanism of the reaction between Li10GeP2S12, which is a typical sulfide electrolyte, and H2O in the atmosphere. We find that the H2O molecules preferentially react with the sulfur atoms of the PS4 tetrahedra to produce H2S. As the sulfur atoms of the PS4 tetrahedra in the bulk continuously emerge towards the surface, this reaction occurs repeatedly. Meanwhile, the oxygen atoms from H2O molecules can also diffuse into the bulk. These reactions continue until the sulfur atoms of the PS4 tetrahedra in Li10GeP2S12 are completely replaced by oxygen atoms. Furthermore, we study the influence of Sb doping on Li10GeP2S12, and kinetically explain the mechanism of hydrolysis inhibition when doping Sb in Li10GeP2S12.