Preparation and electrochemical properties of high-capacity LiFePO 4-Li3V2(PO4)3/C composite for lithium-ion batteries

LiFePO4-Li3V2(PO4) 3/C (LFP-LVP/C) composite is prepared by a modified solid-state method, along with LFP/C composite as a reference. The structure and morphology of the as-prepared materials are analyzed by X-ray diffraction (XRD) and electron microscopy. LFP-LVP/C composite is well-crystallized and a matrix is formed by conductive carbon surrounding the LFP-LVP particles. LFP-LVP/C exhibits V-doped LFP in the bulk phase as determined by Rietveld analysis of XRD data, and mixed phase regions of V-doped LFP and LVP when analyzed at the particle-scale using high-resolution transmission electron microscopy. Electrochemical tests show that the initial discharge capacity of the LFP-LVP/C composite is 165.2 mAh g-1 at 0.1 C. Furthermore, the composite exhibits excellent performance with an initial discharge capacity of 135.4 mAh g-1 at a constant current density of 1 C, with no noticeable capacity fading after 100 cycles (141.6 mAh g-1), which is higher than that of LFP/C prepared by the same method for comparison. Thus, the introduction of LVP acts to improve electronic conductivity and Li+ diffusion of LFP/C