Various xLi2MnO3·(1 − x)LiCo1/3Ni1/3Mn1/3O2 (x = 0.1, 0.2, 0.3, 0.4, and 0.5) cathode materials were prepared by the one-step sol–gel route. The structure of xLi2MnO3·(1 − x)LiCo1/3Ni1/3Mn1/3O2 composites was determined by X-ray diffraction analysis. The surface morphology and microstructure of xLi2MnO3·(1 − x)LiCo1/3Ni1/3Mn1/3O2 composites were characterized using scanning electron microscopy and transmission electron microscopy. Electrochemical performance of xLi2MnO3·(1 − x)LiCo1/3Ni1/3Mn1/3O2 composites was evaluated in terms of capacity, cycling performance and rate capability. Although the morphology and structure were found to be affected by the Li2MnO3 content, all composites showed an α-NaFeO2 structure with R3m space group. Electrochemical results showed that cells using 0.3Li2MnO3·0.7LiCo1/3Ni1/3Mn1/3O2 composites had good performance, in terms of large reversible capacity, prolonged cycling stability, and excellent rate capability.