0.3Li(2)MnO(3)center dot 0.7LiNi(0.5)Mn(0.5)O(2) composite cathode powders with a mixed-layer crystal structure comprising Li2MnO3 and LiNi0.5Mn0.5O2 phases are prepared by spray pyrolysis. The composition of the cathode powders is found to be Li1.19Ni0.39Mn0.61O2 by ICP analysis. At a constant current density of 30 mA g(-1), the initial discharge capacities of the composite cathode powders post-treated at 700, 750, 800, and 850 degrees C are 177, 202, 215, and 212 mAh g(-1), respectively. The discharge capacity of the composite cathode powders post-treated at 800 degrees C decreases from 215 mAh g(-1) to 205 mAh g(-1) by the 40th cycle, in which the capacity retention is 95%. The first cycle has a low Coulombic efficiency of 75%. However, in the subsequent cycles, the Coulombic efficiency is retained at nearly 100%. The dQ/dV curves show that Mn exists as Mn4+ in the sample. The Mn4+ ions in the cathode powders become increasingly active as the cycle number increases and participate in the electrochemical reaction. (c) 2012 Elsevier Ltd. All rights reserved.