Atomistic analysis of Li migration in $\text{Li}_{1+x} \text{Al}_x \text{Ti}_{2-x} {(\text{P} \text{O}_4)}_3$ (LATP) solid electrolytes

We examine the ionic migration of Li in LATP [$\text{Li}_{1+x} \text{Al}_x \text{Ti}_{2-x} {(\text{P} \text{O}_4)}_3$] solid electrolytes from an atomistic viewpoint by means of density functional theory calculations. We vary the Al content and investigate its effects on the crystal structure of LATP and on the migration energy landscape of interstitial Li ions. The energy profiles governing the Li diffusion are found to be systematically influenced by the position of Al ions in direct vicinity of the migration path, and we derive a simplified classification scheme of three universal energy profile shapes. The overall influence of the Al/Ti-ratio on the Li migration is analyzed by a separation into chemical and geometrical aspects. This work provides a solid basis for a resource-efficient computational examination of the ionic conductivity of Li in LATP with varying Al/Ti concentrations.