Amorphous Li2O–LiI–MoO3 solid electrolytes: mechanochemical synthesis and application to all-solid-state batteries

Abstract

All-solid-state batteries are attractive because of their high safety and energy densities. The use of oxide solid electrolytes in all-solid-state batteries can enhance safety. Crystalline oxide solid electrolytes have attracted attention owing to their high ionic conductivity. However, they require high-temperature sintering for densification, which leads to unfavorable side reactions; hence, an oxide solid electrolyte with high ionic conductivity, ductility, and stability to Li metal prepared by low-temperature synthesis is required. In this study, amorphous-type Li₂O–LiI–MoO₃ solid electrolytes are prepared using a mechanochemical method. The materials are synthesized, characterized, and fabricated, and measurements were subsequently obtained under specific conditions of temperature and pressure. The Li₂O–LiI–MoO₃ solid electrolytes exhibit a high ionic conductivity of 10⁻⁵ S cm⁻¹ at 25 °C, sufficient ductility to densify by pressing at room temperature, and stability to Li metals. In addition, full cells with Li₂S and Si as active materials and the Li₂O–LiI–MoO₃ solid electrolytes work reversibly at 25 °C. This study demonstrates the potential of amorphous solid electrolytes to enhance the performance of all-solid-state batteries, thereby prompting further research and development of oxide-based solid electrolytes.