Electrochemical performance of Co-doped LiVPO4F/C composite cathode material for lithium ion batteries prepared by modified solid state method

The LiV1-xCoxPO4F/C (x = 0, 0.01, 0.03 and 0.05) composite cathode material for lithium ion batteries has been successfully prepared through the modified solid state method assisted by sonication and mechanical activation. Here, the influence of cobalt doping on the physical and electrochemical performances are investigated. In this paper, we adopted the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM)/energy dispersive spectrometer (EDS), cycle voltammetry (CV), electrochemical impedance spectrum (EIS) and charge-discharge test to investigate the influence of cobalt doping on the different aspects of the materials, including the physical and electrochemical properties. Compared with the original simple, the cycle and rate performance of cobalt doped samples has increased to some extent. We found that the LiV0.97Co0.03PO4F/C sample showed the best electrochemical performance. The lithium ions diffusion constant (DLi+) of the LiV0.97Co0.03PO4F/C (1.86321 × 10−13 cm2 s−1) is much higher than that of LiVPO4F/C (2.06453 × 10−14 cm2 s−1).