Modulating Lithium-Ion Transport in LiAlBr

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 Li1.2AlBr3.8S0.2. Ab initio molecular dynamics simulations reveal restricted diffusion in LiAlBr4, whereas Li1.2AlBr3.8S0.2 features a delocalized network indicative of improved macroscopic Li+ transport. Li1.2AlBr3.8S0.2 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(Li1.2AlBr3.8S0.2): 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.