Antimony substitution stabilizes the cubic CsSnCl 3 structure and promotes chloride-ion conduction

Solid chloride electrolytes with simultaneously high structural stability and rapid chloride-ion conduction are highly desirable for next-generation energy storage systems, yet their development remains a critical challenge. Herein, we report a Sb-doped CsSnCl 3 solid electrolyte through a Sn-site substitution strategy to overcome the intrinsic instability of Sn-based chloride perovskites while maintaining efficient Cl - transport. Sb incorporation suppresses structural distortion and stabilizes the cubic phase, while the accompanying chloride-rich composition provides abundant mobile Cl - carriers. The optimized CsSn 0.925 Sb 0.075 Cl 3.075 electrolyte exhibits excellent low-temperature phase stability, a wide electrochemical stability window of 5.91 V, a low activation energy of 0.23 eV, and a high room-temperature ionic conductivity of 2.39 × 10 -4 S cm -1 , outperforming previously reported Bi-doped (1.3 × 10 -4 S cm -1 ) and Na-doped (2.1 × 10 -4 S cm -1 ) counterparts. This work demonstrates an effective strategy to overcome the trade-off between structural stability and ionic conductivity through dopant engineering and defect regulation, providing new insights into the design of high-performance halide solid electrolytes.