Improved electrochemical performances of 9LiFePO_4·Li_3V_2(PO_4)/C composite prepared by a simple solid-state method

摘要

9LiFePO_4·Li_3V_2(PO_4)_3/C is synthesized via a carbon thermal reaction using petroleum coke as both reduction agent and carbon source. The as-prepared material is not a simple mixture of LiFePO_4 (LFP) and Li_3V_2(PO_4)_3 (LVP), but a composite possessing two phases: one is V-doped LFP and the other is Fe-doped LVP. The typical structure enhances the electrical conductivity of the composite and improves the electrochemical performances. The first discharge capacity of 9LFP·LVP/C in 18650 type cells is 168 mAh g~(-1) at 1 C (1 C_(9LEP·LVP/C)=166mAg~(-1)), and exhibits high reversible discharge capacity of 125 mAhg~(-1) at 10C even after 150 cycles. At the temperature of -20℃, the reversible capacity of 9LFP·LVP/C can maintain 75% of that at room temperature.