Perovskite-type compounds in anion-substituted LiSr1−0.5xTiTaO6−xFx electrolyte for improving lithium-ion conduction

All-solid-state lithium (Li) ion batteries are regarded as optimal solutions to secure energy problems because of their characteristics, such as no leakage and nonflammability. However, low Li-ion conductivity in these batteries limits their applications. Perovskite-type Li-ion conductors have been considered promising solid electrolytes by replacing A- and B-site ions to improve ion conductivity. In this study, the strategy of replacing O2- anions with F- in perovskite-type structure LiSr1−0.5xTiTaO6−xFx was carried out. Solid electrolytes were successfully prepared by conventional solid-state reactions. The influence of fluorine ion (F-) content in these compounds was systematically investigated regarding ion conductivity. Total conductivity attained was as high as 3.67 × 10−4 S·cm−1 at room temperature in samples with x = 0.1. However, excessive F- doping causes octahedral distortions and produced narrow bottlenecks surrounded by [TiO6] octahedra, which led to decreased conductivity and increased migration activation energy.