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

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.