ALD-Induced Changes in Lithium Dynamics throughout Garnet-Type Solid-State Electrolytes: Insights from ⁷ Li NMR T ₁ Relaxation

Al₂O₃ atomic layer deposition (ALD) on garnet-type Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) powder has been shown to induce extensive lithium diffusion during layer formation, likely driven by proton-lithium exchange reactions. Here, we use ⁷Li MAS NMR and T₁ relaxation data to study the influence on bulk lithium dynamics in LLZTO with respect to ALD coating thickness before high-temperature sintering. Considerable variation in relaxation characteristics was observed for the samples investigated, which could be traced back to diffusion phenomena occurring throughout the ALD process. These results suggest that surface modifications via ALD can significantly alter the lithium mobility of its host structure, underlining the necessity of material monitoring at different stages of cell production for a mechanistic understanding of various properties at device level. This work establishes spectrally resolved ⁷Li NMR T₁ relaxation as sensitive tool for tracking ALD-induced changes in Li environments and ion dynamics relevant for systematic optimization of solid-state battery materials.