Preparation Of Lithium Ion Battery Cathode Material Of Doped And Carbon-coated LiFePO₄ Electode Material

With the development of the new energy vehicle industry and the national policy support,as the cathode material lithium iron phosphate?LiFePO₄?was considered to be the most valuable for its high safety,stable structure,excellent cyclability,non-toxicity and low-cost.However,there is a main obstacles that is the bulk electronic conductivity of LiFePO₄?LFP?is quite low,which leads to poor rate capability and initial capacity loss preventing LiFePO₄ to be put into commercially used.In this work,LiFePO₄ was synthesized by hydrothermal rection,and systematically studied the vanadium-doped,ratio of the doped ingredients,reaction temperature,reaction time,different kinds of surfactants and other factors on the material composition,phase structure,morphology and electrochemical properties.A robust synthesis method based on solid state reaction is proposed to prepare LiFePO₄,and systematically studied the ball-milling in view of heat treating factors on the material composition,phase structure,morphology and electrochemical properties.The study found that LiV_xFe_1-xPO₄ were synthesized via hydrotheoretical only a certain doped ingredient ratio,reaction temperature,reaction time to obtain pure phase the vanadium-doped cathode materials.The study also found that the effects of different kinds of surfactants can reduce the particle size?400-800nm?and electrochemical performance.the sample obtained at the present of CTAB displayed the best electrochemical performance.At last,the vanadium-doped LiFePO₄ materials were carbon coated,the sample showed excellent electrochemical performance.At 0.1C,the discharge specific capacity was about 104.8 mAh/g.The results of the study show that using FeC2O2 as the materials,Li2CO3 as lithium source,glucose as carbon source?source content is 20mass%?,mix up the glucose with NH3H2PO₄,700'C sinter for 10 h to prepare LiFePO₄/C.The XRD pattern indicated that all the samples identified to be ordered olivine structure?All peaks can be indexed as pure and well-crystallized LiFePO₄ phase?.The ball milling can reduce the particle size and create close contact of the reactants.The mechanical activation process also allows the in situ formation of a carbon coat on the LiFePO₄ particles when a suitable organic/polymeric compound is incorporated as the carbon source during the synthesis.The carbon generated from sucrose is amorphous carbon,which have the positive influence to control the particle size and improve the microcosmic figure of the LiFePO₄,the samples has a discharge specific capacity of about 112.1mAh/g?0.1C?.