Improvement of electrochemical performance of layered manganese enriched electrode material with the coating of Ni0.25Mn0.75Ox composite oxides

Abstract

Layered solid solution cathode Li1.2Ni0.2Mn0.6O2 has been synthesized and coated by composite oxides Ni0.25Mn0.75Ox with varying amounts (2, 5 and 8wt%) in this paper. The effect of coated Ni0.25Mn0.75Ox on the physical and electrochemical properties of the materials has been discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), electrochemical impedance spectroscopy (EIS), discharge, cyclic performance and rate capability. The discharge capacities and coulombic efficiencies of Li1.2Ni0.2Mn0.6O2 in the first cycle have been improved and increase with the increasing content of coated Ni0.25Mn0.75Ox. The 8wt% Ni0.25Mn0.75Ox coated Li1.2Ni0.2Mn0.6O2 delivers 298mAhg−1 for the first discharge capacity and 91.9% for the first coulombic efficiency, compared with 228mAhg−1 and 66.1% for pristine Li1.2Ni0.2Mn0.6O2. However, the 5wt% Ni0.25Mn0.75Ox coated Li1.2Ni0.2Mn0.6O2 shows the best capacity retention (94.2% for 80 cycles) and rate capability (106mAhg−1 at 10°C). Electrochemical impedance spectroscopy (EIS) results show that the Rct of Li1.2Ni0.2Mn0.6O2 electrode decreases after coating, which is responsible for superior rate capability.