Mechanisms of Li ⁺ transport in garnet-type cubic Li _3+xLa ₃M ₂O ₁₂ (M = Te, Nb, Zr)

We have studied a promising lithium-ion conductor, garnet-type cubic Li oxides, at various Li concentrations. The ab initio calculations performed on these materials revealed two distinct mechanisms of Li-ion transport, with very different energy barriers and a strong dependence on Li distribution. Our findings explain the origin of the vastly varying ionic conductivities at different Li concentrations and suggest possible principles to improve such materials for solid-state electrolyte applications.