Comparative investigation of phosphate-based composite cathode materials for lithium-ion batteries.

Li3V2(PO4)3-LiVPO4F, LiFePO4-Li3V2(PO4)3, and LiFePO4-Li3V2(PO4)3-LiVPO4F composite cathode materials are synthesized through mechanically activated chemical reduction followed by annealing. X-ray diffraction (XRD) results reveal that the obtained products are pure phase, and the molar ratio of each phase in the composites is consistent with that in raw material. Transmission electron microscopy (TEM) images show that each phase coexists in the composites. The LiFePO4-Li3V2(PO4)3-LiVPO4F composites exhibit the best electrochemical performance. These composites can deliver a capacity of 164 mAh g(-1) at 0.1 C and possess favorable capacities at rates of 0.5, 1, and 5 C. The excellent electrochemical performance is attributed to the mutual modification and the synergistic effects.