Studies of V doping for the LiFePO4-based Li Ion batteries

Alien atom doping has been adopted to modify the electrochemical performance of olivine type LiFePO4 for cathode material. Here, we report that vanadium-doping can improve the performance of LiFePO4/C immensely. LiFePO4/C and V-doped LiFePO4/C cathode materials were first synthesized by carbothermal reduction method. Physico-chemical characterizations were done by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Electrochemical behavior of the cathode materials was analyzed using cyclic voltammetry (CV) and galvanostatic measurements. ICP and XRD analyses indicated that V ions were sufficiently doped in LiFePO4 and did not alter its crystal structure and exhibited the variation of lattice parameters with the doped degree. From the CV, the V ion doping affected the Li+ ionic diffusion coefficient during both the delithiation and lithiation processes and it became larger with an appropriate amount doping. From the results, it is noted that vanadium ions doping can improve performance of LiFePO4, especially on the aspect of stable cycle-life at higher C rate.