Glassy oxide electrolytes in the system Li₄SiO₄–Li₂SO₄ with excellent formability

抄録

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/LiNi_1/3Mn_1/3Co_1/3O₂ 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.