Visualization and quantification of Li distribution in garnet solid electrolytes Li6.25La3Zr2Al0.25O12.

Garnet-type Li₇La₃Zr₂O₁₂ (LLZO) is a promising solid electrolyte for all-solid-state batteries due to its structural stability and high Li⁺ ionic conductivity, but high-purity LLZO crystallizes in a low-conductivity tetragonal phase at room temperature (RT). Al doping stabilizes the cubic structure, yet its impact on Li⁺ migration is not fully understood. Using Li_6.25La₃Zr₂Al_0.25O₁₂ (LLZAO) as a model, we conducted temperature-dependent neutron powder diffraction (NPD), neutron pair distribution function (nPDF), and density-functional theory (DFT) computations. NPD results, supported by nPDF, show Li⁺ ions at 24d and 96h sites, excluding 48g. Al at 24d adjusts the distribution of Li, improving ionic conductivity near RT. Maximum Entropy Method analyses indicate a temperature-driven 3D Li diffusion pathway of 24d-96h-96h-24d channels, confirmed by DFT. This work will enhance the understanding of Li diffusion and the optimization of ionic conductivity in garnet-type solid electrolytes. [ABSTRACT FROM AUTHOR]