Blended cathode materials LiCoO₂/LiNi_0.8Co_0.15Al_0.05O₂(LCO/NCA) with different mass ratios of LiCoO₂ to LiNi_0.8Co_0.15Al_0.05O₂ were prepared by ball milling method. The phase structure and morphology of the blended cathode materials were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrochemical properties of the prepared cathodes were examined in half cells. It follows that after the ball milling, the crystal structure of the blended cathode materials did not change, however, the initial secondary NCA microspheres were broken into nano-sized fragments, which were then uniformly filled into the gaps between LCO microspheres, resulting in enhancement of the contact between the two cathode materials, and therewith, the density of the film prepared on cathode. For LCO:NCA = 6:4, the blended cathode material displayed the best grain-gradation effect and good electrochemical performances: namely the initial columbic efficiency of 92.4%, the capacity retention of 78% at 10 C (1 C=140 mA·g^-1) referencing to that at 0.2 C, and capacity retention of 89.8% after 100 cycles at 1 C. A synergistic effect on the rate performance between the two cathode materials was obviously demonstrated.