biostudies-literatureFu JNatural Science Foundation of Beijing Municipality"Innovation Yongjiang 2035" Key R&D ProgramNational Key R&D Program of ChinaNational Natural Science Foundation of ChinaNational Key Research and Development Program of ChinaBeijing Natural Science Foundatione202508835https://www.ebi.ac.uk/biostudies/studies/S-EPMC12322641biostudies-literatureUnknown64(32)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, Li₃InBr₆, 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 Angewandte Chemie (International ed. in English)Chemical Bond Covalency in Superionic Halide Solid-State Electrolytes.PMC12322641JQ220282025Z06322409103223791272022YFB35063002024Z040W2441017Liu JHu YWang CHao XZhang SSun XSu HKim JTDuan HLi WSham TKLi XLuo JWang SLiang JFu JZhao FPeng JfalseChemical Bond Covalency in Superionic Halide Solid-State Electrolytes.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, Li₃InBr₆, 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 2025-01-01T00:00:00Z2025 Aug2026-03-27T17:14:18.974Z2025-08-30T03:09:44.709ZS-EPMC123226414043781110.1002/anie.202508835