Self-diffusion in garnet-type Li₇La₃Zr₂O₁₂ solid electrolytes

Tetragonal garnet-type Li₇La₃Zr₂O₁₂ is an important candidate solid electrolyte for all-solid-state lithium ion batteries because of its high ionic conductivity and large electrochemical potential window. Here we employ atomistic simulation methods to show that the most favourable disorder process in Li₇La₃Zr₂O₁₂ involves loss of Li₂O resulting in lithium and oxygen vacancies, which promote vacancy mediated self-diffusion. The activation energy for lithium migration (0.45 eV) is much lower than that for oxygen (1.65 eV). Furthermore, the oxygen migration activation energy reveals that the oxygen diffusion in this material can be facilitated at higher temperatures once oxygen vacancies form.