Increased Vacancy Concentrations Improve Li⁺ Diffusion in Solid State Battery Electrolyte Li₃OCl

All solid-state batteries are a promising new technology that can replace the current Li-ion batteries. The solid inorganic electrolyte offers advances in safety, durability, and volumetric and gravimetric energy density. The anti-perovskites lithium oxychloride (Li3OCl) and the hydroxychloride (Li3−xHxOCl) are promising solid electrolytes, though more optimization is required. Performance of these lithium rich anti-perovskites can be improved through understanding the diffusion mechanism through simulation. Here, we report the first comprehensive study varying Li+ concentrations in Li3OCl using ab-initio molecular dynamics simulations. The simulations accurately capture the complex interactions between Li+ vacancies (V’), with concentrations between 0.5-2%. Analysis of discretized local diffusion events in both space and time lend insight into the effect of vacancy concentration on the diffusion mechanism and the lowering of the activation energy barrier. The results reveal the critical interplay between lattice polarization, disorder, and correlated dynamics in promoting ionic conductivity in Li3OCl.