Synthesis of Nano FePO4 and Electrochemical Characterization of Composite Cathode Material LiFePO4/C

Nano FePO4·xH2O powders were synthesized by controlled crystallization method, using Fe(3) compound as the iron source. The nano FePO4·xH2O powders were pretreated at 500 or 4 h in air to obtain nano FePO4 precursor. Then the olivine nano LiFePO4/C composites were obtained through carbonthermal reduction process at different temperatures. The structure, morphology, physicochemical properties and electrochemical properties of the nano FePO4·xH2O powder, FePO4 precursor and LiFePO4/C composites synthesized at different temperatures were characterized in detail by thermogravimetric/differential scanning calorimeter (TG/DSC), X―ray diffraction (XRD), scanning?electron?microscope (SEM), Brunauer―Emmett―Teller (BET) surface area measurement and electrochemical measurement. The results show that the nano LiFePO4/C composite calcined at 700 or 10 h has fine particle sizes of about 40―100 nm .The BET test shows that the as―prepared nano LiFePO4/C composite has great specific surface area of 79.8 m2/g. The nano LiFePO4/C composite cathode material can deliver an initial discharge capacity of 156.5, 134.9, 105.8, 90.3 and 80.9 mAh/g in the voltage range of 2.5―4.2 V, at rate of 0.1C, 1C, 5C, 10C and 15C respectively, which exhibits good rate performance. The nano LiFePO4/C composite also demonstrates excellent cyclic performance.