Doping effects of conductivity improvement in anti-perovskite Na₃OBr solid electrolytes

Abstract Improving the ionic conductivity of solid-state sodium (Na) ion electrolytes is an urgent issue, given their widespread application in all solid-state commercial batteries, and the problems facing this industry, including source shortage, high cost, and safety issues. Substituting halogen and oxygen ions (O2-) with larger atoms is expected to enlarge this bottleneck, as the introduction of distortions in the material can result in an improvement in its ionic conductivity. In this paper, two approaches to introduce distortions into Na3OBr solid electrolytes are provided. Adding either I- or S2- to replace the smaller ions, Br- or O2-, can achieve this result. The lattice distortion increases with increasing concentration of I- or S2- in Na3OBr electrolytes, improving their ionic conductivity. We also discuss the crystallinity of electrolytes, which is an important factor for the diffusion of mobile ions.