Constructing a Li₂O/LiZn Mixed Ionic Electron Conductive Layer by Ultrasonic Spraying to Enhance Li/Garnet Solid Electrolyte Interface Stability for Solid-State Batteries

Garnet-type Li_6.25Ga_0.25La₃Zr₂O₁₂(LGLZO) is believed to be a promising solid electrolyte for solid-state batteries due to its high ionic conductivity, safety, and good stability toward Li. However, one of the most challenges in practical application of LGLZO is the poor contact between Li and LGLZO. Herein, a ZnO layer is prepared on the surface of LGLZO pellet by ultrasonic spraying. Then, a Li₂O/LiZn mixed ionic and electron conductive (MIEC) layer is formed at the Li/LGLZO interface via the conversion reaction between ZnO and molten Li. Experiments and theoretical calculations reveal that this MIEC layer can simultaneously improve interface contact, optimize interfacial kinetics, and guide homogeneous Li deposition. As a result, the interface impedance decreases significantly to 36 Ω cm², the critical current density (CCD) can reach as high as 2.15 mA cm^-2, and the Li/ZnO@LGLZO/LiFePO₄ all-solid-state cells stably cycle 100 times at 0.5 C. This simple and effective approach may provide a viable strategy for improving the cycle performance of solid lithium metal batteries.