Improvement of chemical stability of Li3PS4 glass electrolytes by adding MxOy (M = Fe, Zn, and Bi) nanoparticles

Abstract

Sulfide glasses in the system Li₂S–P₂S₅ are attractive as solid electrolytes for all-solid-state lithium batteries because of their high conductivity and high electrochemical stability. In the present study, we have focused on chemical stability in air of the sulfide glass electrolytes and succeeded in suppressing H₂S generation by preparing composite electrolytes of the Li₃PS₄ glass and one of the metal oxides with the formula M_xO_y (M_xO_y: Fe₂O₃, ZnO and Bi₂O₃). The H₂S amounts generated decreased in the order of the composite with Fe₂O₃, ZnO, and Bi₂O₃. It is noteworthy that the use of a favorable M_xO_y with a larger negative Gibbs energy change (ΔG) for the reaction with H₂S is effective in improving the chemical stability of sulfide electrolytes. The composite electrolyte of 90Li₃PS₄·10ZnO (mol%) exhibited a relatively high ionic conductivity of over 10⁻⁴ S cm⁻¹, negligible electronic conductivity and a wide electrochemical window over 5 V. The all-solid-state In/LiCoO₂ cell using the 90Li₃PS₄·10ZnO composite electrolyte operated as a lithium secondary battery with excellent cycleability at room temperature.