The xLi2MnO3·(1−x)Li(Mn0.33Co0.33Ni0.33)O2 (x = 0.3, 0.5, 0.7) cathode material with uniform spherical morphology has been successfully prepared by a facile carbonate co-precipitation method. These cathode materials are characterized by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), and inductively coupled plasma emission spectrometry (ICP-AES). The electrochemical properties of these cathode materials have been studied by charge/discharge cycling at various current rates. The results of these studies suggest that among these materials, the composite cathode with x = 0.5 (Li1.2Mn0.54Co0.13Ni0.13O2) exhibiting the better electrochemistry performances than those with x = 0.3 and 0.7. Correspondingly, 2 wt% CuO-coated Li1.2Mn0.54Co0.13Ni0.13O2 possess better cycling stability (173.9 mAh g−1 after 50 cycles at 1C rate and 50 cycles at 2C rate) and rate capability than the pristine one. Meanwhile, the CuO-coating layer of the material has a contribution to improve its thermal stability. We believe it is a promising cathode for the high energy lithium batteries.