Fu Jiamin, Su Han, Luo Jing, Li Xiaona, Liang Jianwen, Wang Changhong, Kim Jung Tae, Hu Yang, Zhao Feipeng, Zhang Shumin, Duan Hui, Hao Xiaoge, Li Weihan, Peng Jian, Liu Jue, Wang Shuo, Sham Tsun-Kong, Sun Xueliang
Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, N6A 5B9, Canada.
Department of Chemistry, University of Western Ontario, London, Ontario, N6A 5B7, Canada.
Angew Chem Int Ed Engl. 2025 Aug 4;64(32):e202508835. doi: 10.1002/anie.202508835. Epub 2025 Jun 16.
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, LiInBr, 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 LiLnBr (Ln = Gd, Tb, Ho, Tm, and Lu), we confirm the widespread occurrence of SIT in this material class, with LiGdBr exhibiting the highest ionic conductivity (5.2 mS cm 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.
卤化物固态电解质（SSEs）是一类很有前景的超离子导体，具有高氧化稳定性和离子导电性，这使得它们在全固态锂离子电池领域颇具吸引力。然而，大多数研究都集中在离子堆积结构上，而忽略了键特性在离子传输中的作用。在此，我们使用同步加速器X射线技术和从头算分子动力学（AIMD）模拟，研究了溴化物电解质LiInBr中的键动力学和超离子转变（SIT）。我们证明，卤化物SSEs中的SIT是由键特性（从离子键到共价键）的热诱导转变驱动的，而不是由晶相变化驱动的。AIMD模拟进一步揭示了在高温下Li⁺扩散增强和阴离子集体运动。将我们的研究扩展到LiLnBr（Ln = Gd、Tb、Ho、Tm和Lu），我们证实了这种材料类别中广泛存在SIT，LiGdBr在298 K时具有最高的离子电导率（5.2 mS cm）。更重要的是，通过电解质改性，如阳离子/阴离子取代和合成方法，离子-共价转变是高度可调的。我们的研究结果为离子传输提供了一个新的视角，突出了化学键特性在卤化物SSEs中的关键作用。
