As-grown, amorphous LiCoO2 cathodes grown using a sputtering system were annealed in the temperature range of 650-900 degreesC under an Ar and O-2 ambients, respectively, in order to obtain crystalline LiCoO2 cathodes. The resulting cathodes were then systematically compared with respect to their charge-discharge proper-ties. The post-annealing process under an O-2 ambient resulted in superior cycling performance and thermal stability at high temperature than the Ar ambient. This effect is discussed in terms of grain boundary, surface roughness, and the outdiffusion of oxygen. (C) 2004 Elsevier B.V. All rights reserved.