We report the preparation and characterization of Li1.2Ni0.2Mn0.6O2 (=0.5Li2MnO3·0.5LiNi0.5Mn0.5O2) microspheres as cathode materials for lithium ion batteries. These microspheres were synthesized by carbonate co-precipitation and calcination with lithium salt. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma-atomic emission spectrometer, and nitrogen adsorption. It is found that the synthesized samples, of spherical morphology with primary nanoparticles assembled in secondary microparticles, have a diameter of ∼5μm. When used as the cathode materials for lithium ion batteries, the sample prepared at aging time of 9h with ammonia concentration of 0.6molL−1 shows excellent electrochemical performance. Their charge capacities are 274mAhg−1 at the current density of 20mAg−1, much higher than those of the commercial LiCoO2 and LiFePO4. More importantly, they exhibit excellent rate performances with a capacity of 165 and 144mAhg−1 at the current densities of 600 and 1000mAg−1, respectively, superior to those of other reported Li-rich cathode materials. This work illustrates the relation among synthesis condition, inner structure and electrochemical performance, which has a positive effect on industry production.