Synthesis and characterization of vanadium-doped LiFePO4@C electrode with excellent rate capability for lithium-ion batteries

Herein, the vanadium-doped LiFePO4@C composites (abbreviated as LiFe1-xVxPO4@C, x = 0.01, 0.03 and 0.05) were successfully fabricated through a facile sol-gel method followed by a thermal treatment. The effects of vanadium-doping on the crystal structure, morphology and electrochemical performance of LiFePO4@C were systematically studied in this work. XRD and XPS results reveal that the low content of vanadium-ion has been doped into the lattice structure of LiFePO4 without destroying the phase of LiFePO4@C material. SEM and TEM images show that all the LiFe1-xVxPO4@C samples have regular and uniform crystals with a particle size of 100 nm. Compared to the undoped LiFePO4@C, the LiFe1-xVxPO4@C electrodes exhibit superior rate performances and cycling stabilities for lithium-ion batteries. Particularly, the LiFe0.97V0.03PO4@C shows the best lithium storage performance among the vanadium-doped samples with a high reversible capacity of 112.7 mAh g(-1) after 200 cycles at 10C. The reasons for the enhanced rate performances of LiFe1-xVxPO4@C electrodes are studied in detail in this work.