Layered cathode materials with the nominal compositions of (1−2x)LiNi1/2Mn1/2O2·xLi[Li1/3Mn2/3]O2·xLiCoO2 (0≤ x ≤0.5) were synthesized by a simple solid-state reaction on the basis of good structural compatibility between the three layered compounds, LiNi1/2Mn1/2O2, Li[Li1/3Mn2/3]O2, and LiCoO2. Increasing contents of Li[Li1/3Mn2/3]O2 and LiCoO2 in the materials decreased the occupancy of transitional metal ions in Li layers and thus remarkably improved electrochemical performances; but it also brought about an irreversible initial charge plateau when x reached 0.3. The comparative studies on cooling rates showed that different cooling rates in the material preparation hardly gave different electrode performances.