Preparation and electrochemical studies of Fe-doped Li3V2(PO4)3 cathode materials for lithium-ion batteries

The Fe-doped Li3V2(PO4)3 cathode materials for Li-ion batteries were synthesized by a conventional solid-state reaction, and the Fe-doping effects on the Li electrochemical extraction/insertion performance of Li3V2(PO4)3 were investigated by galvanostatic charge/discharge and cyclic voltammetry measurements. The optimal Fe-doping content x is 0.02-0.04 in Li3FexV2-x(PO4)3 system. The Fe-doped Li3V2(PO4)3 samples showed a better cyclic ability between 3.0 and 4.9V, for example, the discharge capacity of Li3Fe0.02V1.98(PO4)3 was 177mAhg-1 in the 1st cycle and 126mAhg-1 in the 80th cycle. The retention rate of discharge capacity is about 71%, much higher than 58% of the undoped system. The improved electrochemical performances of the Li3V2(PO4)3 could be attributed to the increased electrical conductivity and structural stability deriving from the incorporation of the Fe3+ ions.