Constructing a Li<sub>2</sub>O/LiZn Mixed Ionic Electron\nConductive Layer by Ultrasonic Spraying to Enhance Li/Garnet Solid\nElectrolyte Interface Stability for Solid-State Batteries

Garnet-type Li<sub>6.25</sub>Ga<sub>0.25</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub>(LGLZO) is believed to be a promising\nsolid\nelectrolyte for solid-state batteries due to its high ionic conductivity,\nsafety, and good stability toward Li. However, one of the most challenges\nin practical application of LGLZO is the poor contact between Li and\nLGLZO. Herein, a ZnO layer is prepared on the surface of LGLZO pellet\nby ultrasonic spraying. Then, a Li<sub>2</sub>O/LiZn mixed ionic and\nelectron conductive (MIEC) layer is formed at the Li/LGLZO interface\nvia the conversion reaction between ZnO and molten Li. Experiments\nand theoretical calculations reveal that this MIEC layer can simultaneously\nimprove interface contact, optimize interfacial kinetics, and guide\nhomogeneous Li deposition. As a result, the interface impedance decreases\nsignificantly to 36 Ω cm<sup>2</sup>, the critical current density\n(CCD) can reach as high as 2.15 mA cm<sup>–2</sup>, and the\nLi/ZnO@LGLZO/LiFePO<sub>4</sub> all-solid-state cells stably cycle\n100 times at 0.5 C. This simple and effective approach may provide\na viable strategy for improving the cycle performance of solid lithium\nmetal batteries.