Enhanced electrochemical performance of Li-rich cathode Li1.2Ni0.2Mn0.6O2 by surface modification with WO3 for lithium ion batteries

WO3-coated Li1.2Ni0.2Mn0.6O2 cathode materials have been synthesized by using co-precipitation method along with a liquid-evaporation coating process. Investigations via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) reveal that a WO3 layer is uniformly distributed on the surface of bulk Li1.2Ni0.2Mn0.6O2. After coating appropriate amount of WO3, the Li-rich cathode materials exhibit improved electrochemical performance. In particular, the 2 wt% WO3 coated sample (WO3-0.02 LLNMO) can deliver an initial discharge capacity of 252.2 mA h g-1 with a low irreversible capacity loss of 44.6 mA h g-1 and remarkable cycling stability of 97% capacity retention after 100 cycles at a current density of 52 mA g−1. This is mainly due to the effects of the WO3 coating layer which can suppress the initial activation of Li2MnO3 and improve the stability of surface structure of Li-rich materials by protecting it from corrosion by HF and other side reactions.