Improved Lithium Diffusion in Anion-Substituted Li7TaO6

One approach to enhance the conductivity of a lithium-containing material is to widen the diffusion channel, such as the case of the superionic material Li10GeP2S6. This work unravels the enhanced diffusivity of Li+ in Li7TaS6 and Li7TaSe6, which are based on the known Li7TaO6 superionic conductor. Using density functional theory, we calculate the electronic and structural properties of the three materials and utilize ab initio molecular dynamics simulations to model the diffusion dynamics. Both Li7TaS6 and Li7TaSe6 are shown to exhibit an order of magnitude improvement in the diffusion coefficient relative to the parent material and a slight drop in their corresponding activation barriers. These materials are potential candidates for application in lithium solid-state electrolytes, with performance that is competitive with Li10GeP2S6.