Electrochemical properties of F-doped LiFePO4/C prepared by solid-state synthesis

F-doped lithium iron phosphates were synthesized and in situ carbon coated by two-step solid-state reaction using Fe(III) compound as the iron source and polypropylene as the reductive agent and carbon source. The results show that the synthesized powders are near-spherical particles of 50-200mn with the olivine type LiFePO4 structure. Two-step solid-state reaction inhibits the growth of LiFePO4 particles more efficient compared with one-step solid-state reaction. The results of electrochemical measurement show that fluorin doping improves the rate capability of LiFePO4 and decreases the polarization of LiFePO4 electrode effectively. The discharge capacities of LiFePO3.98F0.02/C cathode material are 146mAh/g, 137mAh/g, 122mAh/g at charge and discharge rates of 1C, 2C, 3C, respectively. Cycling efficiency of 99.3% can be obtained after 55 cycles at 1C rate.