In-situ XRD patterns of LiCuO2 were obtained during charge and discharge at a range of 1.5 to 4.6 V. Li1-xCuO2 phase was not observed. The electrochemical oxidation of LiCuO2 leads to form small sized-CuO with an evolution of O-2 gas. The ab-initio electronic calculation was used for the estimation of cell potentials using Li in the Li2CuO2-LiCuO2 system. Based on the results of the observation and calculation, we propose the possibility of the reversible reaction of CuO with Li in the LiCuO2 system. We found that the CuO can work as a cathode material in Li-secondary battery. (C) 2012 Elsevier B.V. All rights reserved.