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 LiAlBr₄ lowers the migration energy barrier, facilitating lithium redistribution, and enhanced ionic conductivity in Li_1.2AlBr_3.8S_0.2. Ab initio molecular dynamics simulations reveal restricted diffusion in LiAlBr₄, whereas Li_1.2AlBr_3.8S_0.2 features a delocalized network indicative of improved macroscopic Li⁺ transport. Li_1.2AlBr_3.8S_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|Li₆PS₅Cl|2(Li_1.2AlBr_3.8S_0.2): TiS₂ cell, outperforming the LiAlBr₄-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.