Microstructural and Electrochemical Properties of Ti-doped Al_2O_3 Coated LiCoO_2 Films

摘要

We studied the microstructural and electrochemical properties of Ti-doped Al_2O_3 (Ti-Al_2O_3) coated LiCoO_2 thin films depending on the Ti composition. The 1.27 at.% Ti-Al_2O_3 coated films had an amorphous structure with better conductivity than that of pure Al_2O_3 films. The Ti-Al_2O_3 coating layer effectively suppressed the dissolution of Co and the formation of lower Li conductivity SL1 films at the interface between the LiCoO_2 film and electrolyte. The Ti-Al_2O_3 coating improved the cycling performance and capacity retention at high voltage (4.5 V) of the LiCoO_2 films. The Ti-Al_2O_3 coated LiCoO_2 films showed better eiectrochemical properties than did the pure Al_2O_3 coated LiCoO_2 films. These results were closely related to the enhanced Li-conductivity and interfacial quality of the Ti-Al_2O_3 film.