A Study of Electrochemical Performance of LiFePO4/C Composites Doped with Na and V

作者：Chen Ya Wen^*; Chen Jenn Shing

来源：International Journal of Electrochemical Science, 2012, 7(9): 8128-8139.

• LiFePO4
• Lithium-ion batteries
• Cathode material
• Na-Doping
• V-Doping

Metal-doping was applied to modify the electrochemical performance of olivine type LiFePO4, for use as a cathode material. In this work, LiFePO4/C, Na-doped LiFePO4/C, V-doped LiFePO4/C and Na, V-doped LiFePO4/C composites were synthesized using the sol-gel method. All samples were characterized using inductively coupled plasma (ICP), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET surface area, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge-discharge tests. ICP and XRD analyses indicated that the sufficient doping of Na and V ions in LiFePO4 was not to alter its crystal structure, but to slightly change the lattice parameters, which facilitates the diffusion of Li+ ions and decreases the resistance to Li ions and electron transfer on the electrode. The doped samples exhibit better high-rate and cycle performances than the un-doped LiFePO4/C. The electrochemical performance depends on the different ionic dopants used to prepare the electrode. The V-doped sample outperformed all other samples, because doping with a V cation, which has a greater intrinsic conductivity, confers the sample with smaller charge-transfer resistance and better kinetic behavior.

• 出版日期2012-9