| The influence of synthesized temperature, time, Li sources, carbon coating and metal ion doping on the structure and performance of LiFePO4 was studied. The microstructure of LiFePO4 was characterized by X-ray diffraction (XRD) and field emission-scanning electron microscopy (SEM). The galvanostatic charge/discharge, cycle performance, cyclic voltammetry(CV) and electrochemical impendance spectroscopy (EIS) were used to study the electrochemical properties of LiFePO4.LiFePO4 cathode material was synthesized by use of carbothermal reduction method which was constitutive of high temperature solid reaction in two different temperature ranges. Sucrose, CH3COOLi·2H2O, Fe2O3, V2O5 and pure nitrogen gas were used as carbon source, Li source, iron source, dopping and protective gas, respectively. Two different kinds of cathode materials for lithium ion battery were synthesized in the temperature of 300℃for 5 hours and 700℃for 24 hours, which included, LiFePO4/C pure phase of olivine structure only with carbon coating, Li1-5xVxFePO4/C pure phase of olivine structure with carbon coating and V additive.The results showed that all the samples had olivine structure by XRD analysis, and they belonged to the space group of Pmnb. At the charge and discharge current rate of C/10, the first discharge capacity of carbon-coated LiFePO4/C was about 137.9 mAh/g. CV test showed that the material had good reversibility and smaller polarization. Carbon-coated and vanadium-doped Li1-5xVxFePO4/C had the best electrochemical properties when X reached to 0.008. At the charge and discharge current rate of C/10, the first discharge capacity was about 163.0 mAh/g, and it reached to 165.8 mAh/g at the 7th cycle. The conductivities of these materials were measured by AC impedance method. It was found that Li0.96V0.008FePO4/C exhibited the best electrochemical behavior and the conductivity was higher than that of pure LiFePO4/C.
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