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Olivine - type LiFePO4 has the advantages of high capacity , abundant raw material resources , security and environmental friendly , which is considered to be the most potential applications of new lithium ion battery cathode material . LiFePO4 electronic conductivity and lithium ion conductivity were low , making it in the high rate charge and discharge capacity is low . Therefore , in order to promote the broad application of this material must be modified research , improve its electronic conductivity and lithium ion diffusion capacity . Doped metal ions using solid-phase sintering were prepared LiFePO4 / C composite cathode materials for lithium carbonate, ferrous oxalate , diammonium phosphate , sucrose , and metal salts as the main raw material . Using SEM (Scanning electron microscope, scanning electron microscope ) , charge-discharge test , AC impedance (Electrochemical Impedance Spectroscopy, EIS) and other experimental means , surface morphology and electrochemical properties of the materials studied . Carbon surface modified with glucose as the carbon source of LiFePO4 synthesized LiFePO4 / C composite cathode material . Different amount of carbon-doped material properties . The results show that : the introduction of the carbon element , the material remains the standard olivine-type crystal structure of LiFePO4 ; its charging and discharging performance has been significantly improved , the initial discharge capacity of 140mAh / g ; as the carbon content increases , the material's electrical chemical the impedance significantly reduced , the lithium ion diffusion coefficient increased . LiFePO4 / C composite metal ion doping modification . The results show that : the materials are maintained within the scope of the doping , the olivine-type LiFePO4 structure . Increase its specific capacity than undoped . Solution resistance and the charge transfer resistance of the material is significantly reduced , little change of the electric double layer capacitor value , the Warburg impedance value decreases , the lithium ion diffusion coefficient increased by three orders of magnitude , to achieve a 5.8 × 10 - 14cm2 / s , the material having a more excellent electrochemical performance .
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