Protection Effect of ZrO₂ Coating Layer on LiCoO₂ Thin Film

摘要

The protection effect of a ZrO2 coating layer on a LiCoO2 thin film was characterized. A wide and smooth LiCoO2 thin film offers sufficient opportunity for careful observation of the reaction at the interface between cathode (coated and uncoated) and electrolyte. The formation of a ZrO2 coating on a LiCoO2 thin film was confirmed by secondary ion mass spectrometry. Scanning electron and atomic force microscopy were used to characterize the surface morphologies of coated and uncoated films before and after cycling. A ZrO2-coated LiCoO2 film showed a higher discharge capacity and rate capability than an uncoated film. This may be associated with a surface protection effect of the coating. The surface of a pristine film was damaged during cycling, whereas the coated film maintained a relatively clear surface under the same measurement conditions. This result clearly demonstrates the protection effect of a ZrO2 coating on a LiCoO2 thin film.