High pressure molding Li10SnP2S12 ceramic electrolyte with low-grain-boundary-resistance for all-solid-state batteries

Abstract

Pressure can rebuild the structure-function relationship of materials by adjusting their electronic/crystal structure and microstructure. Particularly, ionic transport properties of solid ion conductors with high-symmetry structure are prone to being influenced by pressure. Herein, the effect of pressure on lithium migration and diffusion in sulfide solid electrolyte, tetragonal-phase Li10SnP2S12 (LSPS), throughout grain body/grain boundary and the interface with cathode is studies carefully. Optimal pressure (1.8 GPa) is found to minimize grain boundary resistance and improve interfacial Li+ ion diffusion, which is attributed to more short-circuit of ion migration, greater electrode/electrolyte contact area, and higher interior deviatoric stress, compensating the negative consideration of channel size reduction. Furthermore, we report for first time that powder sulfide LSPS is pressed as ceramic pellet without breakage under 1.8 GPa by two-anvil hydraulic press, and assembled as solid electrolyte within LiFePO4//Li solid-state battery, demonstrating higher initial discharge capacity of 139.62 mAh·g−1 (coulombic efficiency of 99.48%) and favourable cycling stability at room temperature and 0.1C rate. Microstructural modification by controlling the contact and porosity of the LSPS particles is shown effective in decreasing the interfacial and charge transfer resistances and improving the reaction kinetics. The current research provides a more extensive comprehension of solid electrolytes based on LSPS, thus presenting a new and promising approach for practical application distinguished by cost-effective production and improved ionic conductivity.