Improved cycling performance of Li2MoO4-inlaid LiNi0.5Co0.2Mn0.3O2 cathode materials for lithium-ion battery under high cutoff voltage

Abstract

Uniform spherical xLi2MoO4-inlaid LiNi0.5Co0.2Mn0.3O2 materials were successfully prepared through a solid state synthesis. To investigate the material characterization and electrochemical performance after Li2MoO4 modification, X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) mapping, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical tests were applied. The results of the XRD, Rietveld refinement, SEM and EDS analyses showed that a Mo atom may be incorporated into the crystal lattice of the layer structure. Moreover, the presence of Li2MoO4 on the LiNi0.5Co0.2Mn0.3O2 surface was observed. The thickness of the Li2MoO4 coating layer on the xLi2MoO4-inlaid LiNi0.5Co0.2Mn0.3O2 material (x = 0.02) was approximately 25 nm. Similarly, XPS was performed to determine the effect of Li2MoO4 modification, confirming the presence of Li2MoO4. The xLi2MoO4-inlaid (x = 0.02) LiNi0.5Co0.2Mn0.3O2 materials exhibited a retention capacity 83.5% higher than that of the bare material (40.9%) after 200 cycles at 0.5 C between 3.0 and 4.4 V, and it also exhibited the best electrochemical properties at a cutoff voltage of 4.5 V. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) confirmed that the modification of Li2MoO4 plays an important role in improving the electrochemical performance of pristine LiNi0.5Co0.2Mn0.3O2.