Improved electrochemical performance of Li1.2Ni0.2Mn0.6O2 cathode material with fast ionic conductor Li3VO4 coating

摘要

Layered lithium-enriched nickel manganese oxides Li1.2Ni0.2Mn0.6O2 have been synthesized and coated by fast ionic conductor Li3VO4 with varying amounts (1, 3, and 5 wt%) in this paper. The effect of Li3VO4 on the physical and electrochemical properties of Li1.2Ni0.2Mn0.6O2 has been discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), discharge, cyclic performance, rate capability, and electrochemical impedance spectroscopy (EIS). The discharge capacity and coulomb efficiency of Li1.2Ni0.2Mn0.6O2 in the first cycle have been improved after Li3VO4 coating. And, the 3 wt% Li3VO4-coated Li1.2Ni0.2Mn0.6O2 shows the best discharge capacity (246.8 mAh g(-1)), capacity retention (97.3 % for 50 cycles), and rate capability (90.4 mAh g(-1) at 10 C). Electrochemical impedance spectroscopy (EIS) results show that the R (ct) of Li1.2Ni0.2Mn0.6O2 electrode decreases after Li3VO4 coating, which is due to high lithium ion diffusion coefficient of Li3VO4, is responsible for superior rate capability.