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

Abstract 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 LiNi0.6Co0.2Mn0.2O2 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 LiNi0.6Co0.2Mn0.2O2 material. In addition, the results of charge-discharge test showed that 1 wt%WO3 coating LiNi0.6Co0.2Mn0.2O2 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 LiNi0.6Co0.2Mn0.2O2 cathode materials.