Modulating Lithium‐Ion Transport in LiAlBr4 via S‐Modified Anion Sublattice

Tailoring the structures or chemical compositions of the host lattice modulates cation–anion interactions, enhancing active cation transport. Herein, a Br‐S mixed‐anion sublattice in LiAlBr 4 lowers the migration energy barrier, facilitating lithium redistribution, and enhanced ionic conductivity in Li 1.2 AlBr 3.8 S 0.2 . Ab initio molecular dynamics simulations reveal restricted diffusion in LiAlBr 4 , whereas Li 1.2 AlBr 3.8 S 0.2 features a delocalized network indicative of improved macroscopic Li + transport. Li 1.2 AlBr 3.8 S 0.2 exhibits excellent cycling stability and rate capability in all‐solid‐state batteries, delivering a high specific capacity of 150.2 mAh g −1 at 2C in a Li‐In|Li 6 PS 5 Cl|2(Li 1.2 AlBr 3.8 S 0.2 ): TiS 2 cell, outperforming the LiAlBr 4 ‐based system (45.2 mAh g −1 ) under the same conditions. These findings offer key insights into structure‐ion transport relationships, enabling the design of high‐performance solid electrolytes.