Prediction of Novel Trigonal Chloride Superionic Conductors as Promising Solid Electrolytes for All‐Solid‐State Lithium Batteries

Abstract Recently emerging lithium ternary chlorides have attracted increasing attention for solid‐state electrolytes (SSEs) due to their favorable combination between ionic conductivity and electrochemical stability. However, a noticeable discrepancy in Li‐ion conductivity persists between chloride SSEs and organic liquid electrolytes, underscoring the need for designing novel chloride SSEs with enhanced Li‐ion conductivity. Herein, an intriguing trigonal structure (i.e., Li₃SmCl₆ with space group P3₁12) is identified using the global structure searching method in conjunction with first‐principles calculations, and its potential for SSEs is systematically evaluated. Importantly, the structure of Li₃SmCl₆ exhibits a high ionic conductivity of 15.46 mS cm⁻¹ at room temperature due to the 3D lithium percolation framework distinct from previous proposals, associated with the unique in‐plane cation ordering and stacking sequences. Furthermore, it is unveiled that Li₃SmCl₆ possesses a wide electrochemical window of 0.73−4.30 V vs Li⁺/Li and excellent chemical interface stability with high‐voltage cathodes. Several other Li₃MCl₆ (M = Er, and In) materials with isomorphic structures to Li₃SmCl₆ are also found to be potential chloride SSEs, suggesting the broader applicability of this structure. This work reveals a new class of ternary chloride SSEs and sheds light on strategy for structure searching in the design of high‐performance SSEs.