Effect of Manganese Vanadate Formed on the Surface of Spinel Lithium Manganese Oxide Cathode on High Temperature Cycle Life Performance

摘要

Rate capability and cyclability of LiMn2O4 should be improved in order to use it as a cathode material of lithium-ion batteries for hybrid-electric-vehicles (HEV). To enhance the rate capability and cyclability of LiMn2O4, it was coated with MhV2O6 by a sol-gel method. A V2O5 sol was prepared by a melt-quenching method and the LiMn2O4 coated with the sol was heat-treated to obtain the MnV2O6 coating layer. Crystal structure and morphology of the samples were examined by X-ray diffraction, SEM and TEM. The electrochemical performances, including cyclability at 60 °C, and rate capability of the bare and the coated LiMn2O4 were measured and compared. Overall, MnV2O6 coating on LiMn2O4 improves the cyclability at high temperature and rate capability at room temperature at the cost of discharge capacity. The improvement in cyclability at high temperature and the enhanced rate capability is believed to come from the reduced contact between the electrode, and electrolyte and higher electric conductivity of the coating layer. However, a dramatic decrease in discharge capacity would make it impractical to increase the coating amount above 3 wt %.