Electrochemical properties of 0.3Li ₂MnO ₃·0. 7LiNi _0.5Mn _0.5O ₂ composite cathode powders prepared by large-scale spray pyrolysis

0.3Li ₂MnO ₃·0.7LiNi _0.5Mn _0.5O ₂ composite cathode powders with a mixed-layer crystal structure comprising Li ₂MnO ₃ and LiNi _0.5Mn _0.5O ₂ phases are prepared by spray pyrolysis. The composition of the cathode powders is found to be Li _1.19Ni _0.39Mn _0.61O ₂ 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°C are 177, 202, 215, and 212 mAh g ^-1, respectively. The discharge capacity of the composite cathode powders post-treated at 800°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 Mn ⁴⁺ in the sample. The Mn ⁴⁺ ions in the cathode powders become increasingly active as the cycle number increases and participate in the electrochemical reaction.