Li-Ion Cooperative Migration and Oxy-Sulfide Synergistic Effect in Li14P2Ge2S16-6xOx Solid-State-Electrolyte Enables Extraordinary Conductivity and High Stability

Critical to the development of all-solid-state lithium-ion batteries technology are novel solid-state electrolytes with high ionic conductivity and robust stability under inorganic solid-electrolyte operating conditions. Herein, by using density functional theory and molecular dynamics, a mixed oxygen-sulfur-based Li-superionic conductor is screened out from the local chemical structure of beta-Li3PS4 to discover novel Li14P2Ge2S8O8 (LPGSO) with high ionic conductivity and high stability under thermal, moist, and electrochemical conditions, which causes oxygenation at specific sites to improve the stability and selective sulfuration to provide an O-S mixed path by Li-S/O structure units with coordination number between 3 and 4 for fast Li-cooperative conduction. Furthermore, LPGSO exhibits a quasi-isotropic 3D Li-ion cooperative diffusion with a lesser migration barrier (approximate to 0.19 eV) compared to its sulfide-analog Li14P2Ge2S16. The theoretical ionic conductivity of this conductor at room temperature is as high as approximate to 30.0 mS cm(-1), which is among the best in current solid-state electrolytes. Such an oxy-sulfide synergistic effect and Li-ion cooperative migration mechanism would enable the engineering of next-generation electrolyte materials with desirable safety and high ionic conductivity, for possible application in the near future.