Glassy oxide electrolytes in the system Li<sub>4</sub>SiO<sub>4</sub>–Li<sub>2</sub>SO<sub>4</sub> with excellent formability
Yohei Yoneda, Chie Hotehama, Atsushi Sakuda, Masahiro Tatsumisago, Akitoshi Hayashi
Abstract
All-solid-state batteries using oxide electrolytes are regarded as safe batteries. However, most crystalline oxide solid electrolytes require high-temperature sintering for densification. Oxide electrolytes with high formability, which enable the construction of high-performance batteries, are thus required. In this study, Li4SiO4–Li2SO4 glasses and glass-ceramics were prepared by mechanochemical treatment and subsequent heat treatment at 270 °C to achieve electrolytes with high formability. As the Li2SO4 content was increased, the formability of the electrolyte increased. The 90Li4SiO4·10Li2SO4 glass-ceramic electrolyte with a hexagonal structure (a P63/mmc space group) showed the highest ionic conductivity of 2.2 × 10−6 S cm−1 at 25 °C. In this crystal structure, oxygen anions form a hexagonal close-packed structure, and silicon and sulfur cations randomly occupy the tetrahedral sites formed by oxygen anions. An all-solid-state Li–In/LiNi1/3Mn1/3Co1/3O2 cell using a 90Li4SiO4·10Li2SO4 glass-ceramic electrolyte operated at 100 °C as a secondary battery without high-temperature sintering. These oxide materials are promising solid electrolytes for oxide-type all-solid-state batteries.