Conductivity of Li-ion with a corundum-related structure in a LiNbO₃–Al₂O₃ system

Abstract

An oxide solid electrolyte with high Li-ion conductivity is in strong demand to improve the safety of all-solid-state Li-ion batteries. However, only a limited number of crystal structures have been reported as solid electrolytes due to the difficulty of exploring superior solid electrolytes. In this study, we focused on a corundum-related structure of a LiNbO₃-type one in LiNbO₃ because a corundum-type structure was previously reported as an anode material. A LiNbO₃–Al₂O₃ system was synthesized via a conventional solid-state reaction, and its crystal structure and ionic conductivities were evaluated. The substitution of Al₂O₃ into LiNbO₃ was revealed by X-ray diffraction results, and the substitution limit of Al₂O₃ was 40 mol % to LiNbO₃. AC impedance measurements showed an enhancement of ionic conductivity of LiNbO₃, with 1.5 × 10⁻⁵ S/cm as the highest value.