Chemical Bond Covalency in Superionic Halide Solid‐State Electrolytes

作者：Jiamin Fu, Han Su, Jing Luo, Xiaona Li, Jianwen Liang, Changhong Wang, Jung Tae Kim, Yang Hu, Feipeng Zhao, Shumin Zhang, Hui Duan, Xiaoge Hao, Weihan Li, Jian Peng, Jue Liu, Shuo Wang, Tsun‐Kong Sham, Xueliang Sun · 发表于：Angewandte Chemie International Edition · 年份：2025 · DOI：10.1002/anie.202508835 · 被引用次数：12 · 研究领域：Advanced Battery Materials and Technologies、Thermal Expansion and Ionic Conductivity、Solid-state spectroscopy and crystallography

Abstract Halide solid‐state electrolytes (SSEs) are promising superionic conductors with high oxidative stability and ionic conductivity, making them attractive for all‐solid‐state lithium‐ion batteries. However, most studies have focused on ion‐stacking structures, overlooking the role of bond characteristics in ionic transport. Here, we investigate bond dynamics and the superionic transition (SIT) in bromide electrolyte, Li 3 InBr 6 , using synchrotron X‐ray techniques and ab initio molecular dynamics (AIMD) simulations. We demonstrate that the SIT in halide SSEs is driven by a thermally induced transition in bonding character (ionic to covalent) rather than a change in crystal phase. AIMD simulations further reveal enhanced Li⁺ diffusion and collective anion motion at elevated temperatures. Expanding our study to Li 3 LnBr 6 (Ln = Gd, Tb, Ho, Tm, and Lu), we confirm the widespread occurrence of SIT in this material class, with Li 3 GdBr 6 exhibiting the highest ionic conductivity (5.2 mS cm −1 at 298 K). More importantly, the ionic‐covalent transition is highly tunable through electrolyte modifications, such as cation/anion substitution and synthesis methods. Our findings provide a new perspective on ionic transport, highlighting the critical role of chemical bond characteristics in halide SSEs.