Synthesis and properties of Li3V2−xCex(PO4)3/C cathode materials for Li-ion batteries

Ce-doped compounds Li3V2−xCex(PO4)3/C (x = 0, 0.03, 0.05, 0.07, 0.10) were successfully prepared by a sol–gel process with CH3COOLi·2H2O, NH4VO3, NH4H2PO4, citric acid and Ce(CH3COO)3·5H2O as raw materials. X-ray diffraction analysis suggests that single-phase Li3V2−xCex(PO4)3/C with monoclinic structure can be obtained for x ≤ 0.10. The result of Rietveld refinement analysis indicates that cell volume increases with the increasing of the Ce content. As compared with the pure Li3V2(PO4)3, although there is a small decrease in the initial specific capacity at low rate (0.2 C), a proper amount of Ce3+ doping, e.g. x = 0.05, could improve its cycle and rate performances. When discharge at 0.2 C and 10 C, the initial specific discharge capacities of Li3V1.95Ce0.05(PO4)3 were 120 and 88.6 mAh g−1 respectively. Furthermore, the capacity retention at the 100th cycle was 96.8% and 94.3% for the respective discharge capacities, which displayed excellent cycling properties.

► A new doping strategy using rare earth metal as the dopant was used to modify Li3V2(PO4)3.
► Ce doping caused lattice expansion of Li3V2(PO4)3.
► Appropriate Ce doping can significantly enhance the electrochemical properties of Li3V2(PO4)3.