Mechanical Properties of Li2S–P2S5 Glasses with Lithium Halides and Application in All-Solid-State Batteries

Mechanical properties of solid electrolytes are important as well as ionic conductivity to achieve all-solid-state batteries with large capacities and long cycle life. In this study, it is shown that Li2S–P2S5 glasses with lithium halides, especially LiI, exhibit both high ionic conductivity and favorable mechanical properties. Mechanical properties, such as Young's modulus and formability at powder compaction, are evaluated for the solid electrolytes. The addition of lithium halides decreases the Young's modulus of the electrolytes. In addition, fewer pores and grain boundaries were observed in the powder-pressed pellets of Li2S–P2S5 glasses with lithium halides. All-solid-state batteries using Si electrodes and glass electrolytes with lithium halides exhibited a larger capacity of 20 cycles compared to those without lithium halides. These results provide guidelines for the construction of all-solid-state batteries from the viewpoint of the mechanical properties of solid electrolytes.