Abstract:The Li₃V₂(PO₄)₃/C composite cathode material was synthesized via sol-gel method using three different chelating agents (citric acid, salicylic acid and polyacrylic acid) at pH value of 3 or 7. The crystal structure, morphology, specific surface area and electrochemical performance of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge test. The results show that the effects of pH value on the performance of the prepared materials are greatly related to the chelating agents. With salicylic acid or polyacrylic acid as the chelating reagent, the structure, morphology and electrochemical performance of the samples are greatly influenced by the pH values. However, the structure of the materials with citric acid as the chelating agent does not change as pH value changes, and the materials own uniform particle size distribution and good electrochemical performance. It delivers an initial discharge capacity of 113.58 mA·h/g at 10C, remaining as high as 108.48 mA·h/g after 900 cycles, with a capacity retention of 95.51%.

Key words: Li₃V₂(PO₄)₃; cathode material; sol-gel method; chelating agents; pH value