Synthesis and electrochemical performance of Li3V2(PO4)3−xClx/C cathode materials for lithium-ion batteries

The Cl-doping Li3V2(PO4)3/C (LVP/C) cathode materials were synthesized by a sol–gel method. The effects of Cl-doping amount on electrochemical properties, structure and morphology of Li3V2(PO4)3/C were studied by electrochemical impedance spectroscopy, cyclic voltammetry, X-ray diffraction, FTIR spectrum and scanning electron microscopy. The results indicate that the Li3V2(PO4)2.88Cl0.12/C composite presents an excellent discharge capacity as high as 106.95 mAh g−1 after 80 cycles at 8 C. The same monoclinic structure of Li3V2(PO4)2.88Cl0.12/C sample can be obtained from XRD analysis while the particle size is smaller than that of pristine sample (x = 0). The FTIR results further confirm the substitution of Cl− for PO43−. The reasons for the relatively enhanced capability are attributed to the decreased polarization and the reduced charge transfer resistance of electrode, with the suitable Cl-doping amount of x = 0.12.

► Cl-doping Li3V2(PO4)3/C composite was firstly reported via a sol–gel method.
► The reduced particle size is responsible for the improved high-rate performance.
► Partial substitution of Cl− strengthens the structure stability of PO43−.
► Cl-doping reduces the charge-transfer resistance of Li+.