Structural analysis and ionic conduction mechanism of sulfide-based solid electrolytes doped with Br.

Sulfide glasses can exhibit notable ionic conductivity because of annealing-associated crystallization. One well-known example is LiPS. Our research showed that adding bromine (Br) to LiPS sulfide glass results in a similar crystal structure and high ionic conductivity comparable to that of another compound LiGePS. This structure differs from the PS anion framework of LiPS. In addition, the ionic conductivity decreases owing to a structural transition to the β-phase. Herein, we present our findings on the local structure of LiPS sulfide glass and its crystallized glass ceramic with the addition of Br. This analysis relies on the pair distribution function analysis obtained from high-energy X-ray diffraction. Moreover, using the bond valence sum method, we verified that incorporating Br promotes the formation of Li ionic conduction pathways. Our results indicate that precise control over the anion molecular structure by introducing halogens holds promise for achieving high Li-ion conductivity.