Influence of multistep sintering method on electrochemical performances of 7LiFePO4·Li3V2(PO4)3/C composite cathode material for lithium ion batteries

Abstract

In this work, influence of multistep sintering method on electrochemical performances of 7LiFePO4·Li3V2(PO4)3/C composite cathode material for lithium ion batteries has been researched in detail, and a 7LiFePO4·Li3V2(PO4)3/C cathode composite material with excellent cycling stability and rate capability is successfully synthesized. X-ray diffraction and scanning electron microscope analysis results demonstrate that the multistep sintering method has significant effect on the crystal structure and surface morphology of the synthesized materials. Cycle voltammetry, electrochemical impedance spectroscopy, and charge/discharge test are further carried out to investigate the influence of the sintering time on the electrochemical performances of the cathode materials. The electrochemical analysis results indicate that, when sintered at 650 °C for 12 h and then 750 °C for 4 h, the cathode material 7LiFePO4·Li3V2(PO4)3/C shows the most excellent electrochemical performances. It exhibits a good rate capability with the initial discharge specific capacities of 162.8, 149.8, and 122.2 mAh g−1 at 1, 2, and 5 C, respectively. Moreover, after a total of 150 cycles at different rates, this cathode material still maintains an excellent cycling stability without significant capacity fading, in which it can deliver the discharge specific capacities of 160.8, 146.9, and 120.6 mAh g−1 after 50 cycles at 1, 2, and 5 C, while the capacity retentions can reach to 98.8, 98.1, and 98.7 %, respectively.