High ionic conductivity materials Li₃YBr₆ and Li₃LaBr₆ 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 Li₃YBr₆ and Li₃LaBr₆. 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 Li₃YBr₆ is 2.50 V. Through extrapolating various temperature diffusion results, the conductivity of Li₃YBr₆ was obtained at room temperature, approximately 3.9 mS cm⁻¹, which is comparable to the experimental value 3.3 mS cm⁻¹. Li₃LaBr₆ has a higher conductivity, a 100% increase compared with Li₃YBr₆. The activation energies of Li₃YBr₆ and Li₃LaBr₆ 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 Li₃YBr₆. This research explored high ionic conductivity halide materials and will contribute to developing solid-state lithium-ion batteries.