Defect-Mediated Lithium-Ion Migration and Activation Energies in Cubic Li₇La₃Zr₂O₁₂ Solid Electrolyte

The cubic phase of Li₇La₃Zr₂O₁₂ (LLZO), a garnet-type solid electrolyte for solid-state lithium-ion batteries, has attracted great interest for its high ionic conductivity. We investigate how specific defect configurations influence lithium-ion (Li⁺) migration pathways and activation energies by using ab initio density functional theory. Our results show that defects strongly affect Li⁺ transport. Specifically, V_Li, V_La, and Zr_Li + V_La exhibit low activation energies of 0.058, 0.073, and 0.089 eV, respectively. The Schottky-type, 2V_Li + La_Li and La_Li + V_O + V_Zr configurations also show reduced barriers (0.114–0.197 eV). In contrast, defect-free LLZO requires higher activation energies of 0.207 eV and 0.595 eV for two distinct migration routes. Interstitial and Frenkel-type migrations display much higher barriers, 3.10 eV and 2.05 eV, respectively. These findings highlight the critical role of specific defect configurations in enhancing Li⁺ mobility and provide insights for optimizing ionic conductivity in cubic LLZO.