Compared to Li-ion batteries, rechargeable sodium (Na) batteries hold much promise for medium and large-scale energy storage systems due to the decreased price, natural abundance and suitable electrochemical window of Na metal. In addition to Na-S and ZEBRA batteries, solid-state Na batteries that operate at room temperature are highly desirable. To realize this target, solid electrolytes with highly ionic conductivities are necessitated. Na₃SbS₄ is a newly discovered Na-ion conductor ^[1] and exhibits an excellent ionic conductivity of 1 mS cm^-1. To further improve its performance in solid-state Na batteries, faster Na-ion transportation through Na₃SbS₄ is expected. In this report, we introduced halide ions into Na₃SbS₄ solid electrolyte and studied doping effect on the crystal structure and conductive properties of Na₃SbS₄. It was found that the iodide (I^-) doping expanded the lattice structure of Na₃SbS₄ without generating a new phase. Tuning the dopant concentration led to an overall higher ionic conductivity in doped Na₃SbS₄. The enhancement of ionic conductivity is explained by the creation of vacancies due to alivolent anion substitution.

Reference

[1] Wang, H., Chen, Y., Hood, Z.D., Sahu, G., Pandian, A.S., Keum, J.K., An, K. and Liang, C., An Air‐Stable Na3SbS4 Superionic Conductor Prepared by a Rapid and Economic Synthetic Procedure. Angewandte Chemie International Edition, 2016, 55(30), pp.8551-8555.