Garnet-Type Li₇La₃Zr₂O₁₂Solid Electrolyte Thin Films Grown by CO₂-Laser Assisted CVD for All-Solid-State Batteries

The detailed characterization of garnet-type Li-ion conducting Li7La3Zr2O12 (LLZO) solid electrolyte thin films grown by novel CO2-laser assisted chemical vapor deposition (LA-CVD) is reported. A deposition process parameter study reveals that an optimal combination of deposition temperature and oxygen partial pressure is essential to obtain high quality tetragonal LLZO thin films. The polycrystalline tetragonal LLZO films grown on platinum have a dense and homogeneous microstructure and are free of cracks. A total lithium ion conductivity of 4.2·10−6 S·cm−1 at room temperature, with an activation energy of 0.50 eV, is achieved. This is the highest total lithium ion conductivity value reported for tetragonal LLZO thin films so far, being about one order of magnitude higher than previously reported values for tetragonal LLZO thin films prepared by sputtering and pulsed laser deposition. The results of this study suggest that the tetragonal LLZO thin films grown by LA-CVD are applicable for the use in all-solid-state thin film lithium ion batteries.