WO3 membrane-encapsulated layered LiNi0.6Co0.2Mn0.2O2 cathode material for advanced Li-ion batteries

Despite Nickel-rich materials have all the advantages of high capacity, long cycle life and low cost, there is still a disadvantage that the capacity decreases rapidly as the number of cycles increases. In order to solve this problem, WO₃ was uniformly coated on the surface of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials by wet coating, and its cycling performance was greatly improved with the higher capacity. The coated materials were analyzed by X-ray diffraction(XRD), Scanning electron microscope (SEM), high resolution Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy(XPS). The results showed that the coating thickness was around 3.15?nm, and some tungsten ions were doped into the lattice of the near surface area of the LiNi_0.6Co_0.2Mn_0.2O₂ material. In addition, the results of charge-discharge test showed that 1?wt%WO₃ coating LiNi_0.6Co_0.2Mn_0.2O₂ had the best performance, and delivered a discharge capacity of 140 mAh g^?1 (the capacity retention rate is 84.8%) in the potential interval of 2.8–4.3?V at 1?C (1?C?=?165?mA?g^?1) after 200 cycles, while the bare cathode material only delivered a discharge capacity of 120 mAhg^?1 (the capacity retention rate is 75%). The phenomenon indicates that the WO₃ coating plays a role in inhibiting the harmful side reactions between the cathode material and the electrolyte, improving the electrochemical and structure stability of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials.