Dependence of Al(2)O(3) Coating Thickness and Annealing Conditions on Microstructural and Electrochemical Properties of LiCoO(2) Film

• Published in: Metals and materials international Vol. 16; no. 1; pp. 93 - 98
• Main Authors: Park, Sun-Gyu, Lee, Seong-Rae, Cho Ii, Won, Cho, Byung Won
• Format: Journal Article
• Language: English
• Published: 01.02.2010
• Subjects: Annealing; Cathodes; Cathodic coating (process); Coating; Cobalt; Grain size; Microstructure; Morphology; Optimization; Phases; Photoelectron spectroscopy; X-ray photoelectron spectroscopy; X-rays
• ISSN: 1598-9623
• DOI: 10.1007/s12540-010-0093-9

We studied the dependence of Al(2)O(3) coating thickness and annealing conditions on the surface morphology and electrochemical properties of Al(2)O(3) coated LiCoO(2) films. The optimum coating thickness allowing for the highest capacity retention was about 24 nm. A sample consisting of Al(2)O(3) coated on unnealed LiCoO(2) film with additional annealing at 400 degree C had a uniform coating layer between the coating materials and cathode films. This sample showed the best capacity retention of~91 % with a charge-cut off of 4.5 V after 30 cycles, while the bare cathode film showed a capacity retention of~32 % under the same conditions. The formation of second phases such as Co-Al-O was observed in the coating films by X-ray photoelectron spectroscopy (XPS). The Co-Al-O containing samples showed a higher initial capacity because of their smaller grain size, but less capacity retention than the Al(2)O(3) containing samples.