Electrochemical properties of 0.3Li2MnO3·0.7LiNi0.5Mn0.5O2 composite cathode powders prepared by large-scale spray pyrolysis

Abstract 0.3Li 2 MnO 3 ·0.7LiNi 0.5 Mn 0.5 O 2 composite cathode powders with a mixed-layer crystal structure comprising Li 2 MnO 3 and LiNi 0.5 Mn 0.5 O 2 phases are prepared by spray pyrolysis. The composition of the cathode powders is found to be Li 1.19 Ni 0.39 Mn 0.61 O 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.