Optimizing Li‐Ion Transport in <scp>LaCl_3−<i>x</i>Br_<i>x</i></scp> Solid Electrolytes Through Anion Mixing

ABSTRACT Solid‐state batteries based on versatile halide solid electrolytes with outstanding ionic conductivity, electrode compatibility, and stability are attracting significant research attention. Recent experimental studies have illustrated the outstanding performance of LaCl 3 as a solid electrolyte capable of conducting Li ions through its one‐dimensional channels that can be interconnected into a three‐dimensional network through the creation of La vacancies. In this work, we present a composition optimization strategy for maximizing the Li‐ion conductivity in LaCl 3− x Br x solid electrolytes based on density functional theory and ab initio molecular dynamics simulations. Our simulations show LaCl 2.5 Br 0.5 to have a remarkable Li‐ion conductivity of 66 mS cm −1 at 300 K and the lowest activation energy of 0.10 eV, followed by LaCl 0.5 Br 2.5 with values of 14 mS cm −1 and 0.13 eV, respectively. Both these compositions are predicted to be easily synthesizable, have large band gaps, and are likely to be of experimental interest given their outstanding Li‐ion transport properties. Our results highlight the potential for enhanced Li‐ion conductivity in LaCl 3− x Br x solid electrolytes that can be achieved through anion mixing. image