xLi3V2(PO4)3·LiVPO4F/C composite cathode materials for lithium ion batteries

xLi3V2(PO4)3·LiVPO4F/C composite is synthesized by mechanically activated chemical reduction. The value of x is designed to be 2.0 but in fact is 2.7 in the prepared sample because of volatilization of HF or VF3. The as-prepared powders with the average primary size of 0.5–1 μm are coated with amorphous carbon layer. Structural analysis of the composite indicates that two phases of monoclinic Li3V2(PO4)3 and triclinic LiVPO4F coexist. The composite as cathode for LIB shows excellent electrochemical performances. In the potential range of 3.0–4.4 V, it delivers initial discharge capacity of 139, 137, 131, and 123 mAh g−1 at 0.1, 1, 5 and 10 C, respectively. And 97.4% of initial capacity is retained even after 300 cycles at 10 C. The cyclic voltammetry (CV) and AC impedance analysis indicate that the prepared composite separately shows good ionic diffusivity and low resistance.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Novel xLi3V2(PO4)3·LiVPO4F/C composite cathode material for Li-ion battery has been prepared. ► The synthetic method of mechanical activated chemical reduction is simple, energy-saving and susceptible to control. ► The prepared material exhibits good electrochemical performance, including excellent rate capability and good cycle performance. ► Synergistic effect of Li3V2(PO4)3–LiVPO4F composite has been emphasized in this manuscript. ► The diffusion coefficient of lithium ion in the composite is a little larger than that in LVP reported by others.