Li⁺ transportation mechanisms in the halide solid-state electrolytes Li₃YCl₆ and Li₃InCl₆

Developing outstanding halide solid-state electrolytes (SSEs) has attracted a lot of attention in the area of all-solid-state batteries, owing to their excellent compatibility with high-voltage active materials. In halide compounds, lithium (Li⁺) ions are usually confined in the center of octahedral units, which seriously impedes the fast transportation of lithium ions. However, the representative SSEs, Li₃YCl₆ and Li₃InCl₆, present ultrafast ionic conductivities below 0.1 mS/cm at room temperature, which may be closely connected with their particular configurations. Through assessments of the transportation mechanisms in Li₃YCl₆ and Li₃InCl₆ by careful density functional theory simulations, two kinds of lithium-ion diffusion channels can be identified. Furthermore, the overall performances of Li₃YCl₆ and Li₃InCl₆, including energetic stability, electronic chemical window and electronic structures, are systematically studied. This will bring deep insights into and reliable criteria for exploring next-generation halide SSEs.