Synthesis Of Lithium Iron Phosphate By New Liquid Precipitation And Modi6Cation With Polycarbonate And Glucose

Due to its good cycling property, safety, and low cost of raw materials, lithium iron phosphate has been widely considered to be one of the most promising candidates of cathode material for lithium-ion battery. But its low conductivity and poor high-rate discharge ability obstructs its commercial usage. To improve its electrochemical property, this paper focuses on the following aspects:reaction conditions of liquid-phase precipitation and the improvement of carbon coating procedure.(1)LiFePO4was synthesized by new liquid-precipitation method. Precursor was used in liquid sub-step and the sintering system calcined precursor preparation materials. Different process conditions effect on the electrochemical properties. Finally,The optimum synthesis condition we got from our experiments are to set the water bath temperature at85℃, phosphoric acid concentration at2mol/1, lithium-iron ratio at1.02:1, the sintering temperature at700℃, the sintering time for4h. The instruments we used to measure the properties such as morphology, crystal structure, and electrochemical properties were X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), tap density measurements. The.LiFePO4we got from above mentioned synthesis condition showed the following results:at0.5C discharge between2.5-4.2V, after30cycles of charge/discharge, compared to its maximum discharge capacity, it retained141.9mAh/g mAh/g, as98.30%of its original capacity.(2) We tested the structure and properties of LiFePO4that coated by polycarbonate or glucose separately. Coated LiFePO4was tested at0.5C discharge between2.5-4.2V, compared to the maximum discharge capacity, it retained151.4mAh/g and156.4mAh/g,99.49%and100%as polycarbonate and glucose coating content were15%and5%respectively. These indicated the coated material has higher discharge capacity and better cycling property. We found5%of glucose carbon-coating has better property.(3) Explored ultrasonic agitation instead of mechanical agitation, glucose liquid carbon coated synthetic process optimization on the structure and properties of LiFePO4material. The LiFePO4produced by using liquid coating procedure has discharge capacity of166.4mAh/g between2.5-4.2V under0.5C discharge, compared to the maximum discharge capacity167.9mAh/g, retaining99.11%after30cycles charge/discharge, and compared with the maximum discharge capacity154.2mAh/g at1C discharge, it retained136.5mAh/g,88.52%after200cycles at1C. The improved liquid precipitation method can effectively control the size growth of precursor particle, and enhancing the lithium ion transfer rate by reduce the particle size, while the carbon-coated materials are also improved the conductivity greatly, thereby enhancing the electrochemical performance.