Electrochemical characterizations and structure of Li 0.99Na 0.01FePO 4/C as cathode material for Li-ion battery

In order to improve the rate performance of lithium iron phosphate, Na+ doped LiFePO4/C cathode materials were prepared by carbothermal reduction technology. Samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transfer infrared spectroscopy (FT-IR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Their electrochemical performances were investigated by galvanostatic charge/discharge in terms of cycling performance and rate capability. The results show that the samples have well regulated olivine type structures without any impurity peaks. Na-doping improves the conductivity and the Li+ diffusion rate of composite materials and decreases the polarization of electrode, and enhances the cycling performance and rate capability effectively. Compared with LiFePO4/C, Li0.99Na0.01FePO4/C exhibits good electrode properties with discharge capacities of 147.6, 126.4 and 105.1 mAh/g at 0.5C, 2.0C and 5C rates, respectively. In addition, it has excellent cycle stability at different rates and good performance.