High total Li-ion conductivity of LiTa2PO8 ceramics sintered using Bi2O3 as an additive

Abstract

Lithium tantalum phosphate LiTa2PO8 ceramics have attracted significant attention as solid electrolytes in oxide-based all-solid-state batteries owing to their superior bulk conductivity of more than 1 mS cm−1 at room temperature. However, high-temperature sintering at 1050 °C, which is required to achieve a dense morphology, results in a high interfacial resistance at the grain boundaries. In this study, dense LiTa2PO8 ceramics were successfully synthesized via a conventional solid-state method at a low sintering temperature of 900 °C using Bi2O3 as the additive. A total lithium-ion conductivity of 1.41 × 10−3 S cm−1 at 25 °C was achieved. The microstructures of the sintered LiTa2PO8 ceramics were analyzed by X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Large LiTa2PO8 grains grew in the dense solid-electrolyte body together with the interfacial BiPO4 phase, which acted as a sintering flux material, at a low sintering temperature of 900 °C. Thus, these LiTa2PO8 ceramics can serve as oxide solid electrolytes for all-solid-state lithium batteries owing to their high total Li-ion conductivity.