Role of Li2MnO3 Modification in Improving the Electrochemical Performance of Lithium-Rich Manganese-Based Oxide Electrodes

Li-rich cathode materials have high specific capacities which exceed 250 mA h/g, but the arrangement of lithium inside them will cause the cations of transition metals to be mixed, resulting in the phase change and capacity loss in the charge and discharge cycle process. We propose surface modification by Li2MnO3, and its crystal structure is in consistence with the structure of lithium-rich manganese-based oxides, so that nickel ions can be orderly arranged between the transition metal layers during the cycle. We prepare Li1.2Mn0.54Ni0.13Co0.13O2 by the co-precipitation method and coat Li2MnO3 on its surface. This surface-modified structure will reduce the phase transition, inhibit the irreversible capacity loss, and improve the structural stability and cycle stability. The specific capacity of the pristine modified by 5 wt % Li2MnO3 is 224 mA h/g at 300 mA/g, and the capacity retention ratio is 96.2% after 100 cycles, while the unmodified pristine under the same conditions is only 197 mA h/g with its capacity retention ratio being 75.9%. In addition, the modified electrode showed better initial Coulombic efficiency, rate capacity, and impedance parameters.