High ionic conductivity materials Li 3 YBr 6 and Li 3 LaBr 6 for solid-state batteries: first-principles calculations.

High ionic conductivity solid-state electrolytes are essential for powerful solid-state lithium-ion batteries. With density functional theory and ab initio molecular dynamics simulations, we investigated the crystal structures of Li 3 YBr 6 and Li 3 LaBr 6 . The lowest energy configurations with uniform distribution of lithium ions were identified. Both materials have wide electrochemical stability windows (ESW): 2.64 V and 2.57 V, respectively. The experimental ESW for Li 3 YBr 6 is 2.50 V. Through extrapolating various temperature diffusion results, the conductivity of Li 3 YBr 6 was obtained at room temperature, approximately 3.9 mS cm -1 , which is comparable to the experimental value 3.3 mS cm -1 . Li 3 LaBr 6 has a higher conductivity, a 100% increase compared with Li 3 YBr 6 . The activation energies of Li 3 YBr 6 and Li 3 LaBr 6 through the Arrhenius plot are 0.26 eV and 0.24 eV, respectively, which is also close to the experimental value of 0.30 eV for Li 3 YBr 6 . This research explored high ionic conductivity halide materials and will contribute to developing solid-state lithium-ion batteries.