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

xLi(3)V(2)(PO4)(3)center dot 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 mu m 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 3.0-4.4V, 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. (C) 2012 Elsevier Ltd. All rights reserved.