Study On Industrial Synthesis And Properties Of LiFePO₄ As Cathode Material

Cathode material is the key material for the lithium-ion batteries.Olivine-structured LiFePO4 is considered as a promising cathode material for lithium-ion batteries,due to its advantages such as environmentally friendliness,abundant raw materials,inexpensive price and high safety,especially its high thermal stability,high safety and high cycle life is unmatched by other anode materials.The paper for the actual industrial production,solid phase synthesis method,using different performance of the synthesized LiFePO4/C cathode material,and material synthesis and material properties were studied.Several industrial LiFePO4/C materials were developed for practical large-scale production.LiFePO4/C cathode material was prepared by by high-temperature solid-state method using low cost Fe2O3.Effects of different experimental conditions on the properties of thematerials were studied.Carbon doped effectively restrain the particles in the.process of synthesis of LiFePO4/C grew up,and effectively improve the electrochemical properties of the materials.The best synthesis process is.doped carbon 6%,sintering temperature of 720?,12 h insulation.LiFePO4/C was synthesized using Fe2O3 and LiH2PO4 by orthogonal experiment.Among various kinds of influence factors of LiFePO4/C given is the biggest impact of the lithium iron ratio,followed by mixing carbon,and then the sintering temperature and time.The influence of various factors on the properties of ceramic materials was studied.The optimum synthesis process for synthesis of LiFePO4/C material using Fe2O3 and LiH2PO4 was:lithium iron ratio of 1.005,with 10%carbon,700? heat preservation 8 h.LiFePO4/C was synthesized using FePO4·2H2O as iron source,Li2CO3 and LiOH·H2O as lithium source with wet ball mill and spray drying granulation technology spherical.The ball mill process and sintering temperature were studied,LiFePO4/C has good spherical shape,excellent electrochemical performance.The capacities of LiFePO4/C are 155 and 157mAh/g respectively.The diffusion coefficient of Li+,D=9.98×10-14cm2·s-1.The influences of different organic carbon source on the properties of ceramic materials were studied.Carbon source play an important role on the tap density and specific surface area of material.LiFePO4/C synthesized with glucose as carbon source has the large density,small specific surface area and particle size.The capacities of LiFePO4/C are 160.6 and 148.5mAh/g at 0.1 and 1C respectively.The electrical performance of LiFePO4/C is good at low temperature.The effects of FePO4·2H2O on the properties of LiFePO4/C were studied.The particle size of LiFeP04/C,tap density and particle size and tap density is proportional to the FePO4·2H2O.FePO4·2H2O iron phosphorus ratio less than 1 material specific capacity decrease and the ratio of performance was significantly poorer.The Nb5+ doping in LiFeP04/C were studied.Nb doping caused first capacity decreased,but increased high rate performance of material.The structure refinement showed that Nb can effectively doped in LiFePO4,and Nb mass in Li,while Fe also exist in the Li position.A new idea of controlling on the morphology,particles and nanometer material to improve the performance of LiFeP0O4/C was put forward in the paper.The particle size of the LiFeP04/C was controlled by mechanical mill or air slide disintegrating mill,and the morphology,structure and electrochemical properties of the material were characterized.The smaller particle size distribution and better particle size could be got using the above two kinds of granularity control methods.The analysis shows that:the special capacity of the material is reduced and the rate discharge performance deteriorates,due to the stripping of carbon.The electrochemical performance of the nanometer LiFeP04/C material is excellent.The LiFeP04/C has an initial discharge specific capacity of 161.8mAh/g at a rate of o.1C and specific capacity of 148.7.120.9mAh/g at rates of 1 and 5C rate,respectively.The recycling performance of LiFePO4/C is good,the discharge capacity remained at 95.8%,81.7%after 500,1000 cycles respectively at 5C.5Ah and 10Ah soft package batteries were made and tested.The performance of batteries is good.All the indexes of the LiFeP04/C can better meet the requirements of production materials.The synthesis of LiFePO4/C by FeP04·2H2O was expanded to ton,for the industrial production.Industrialization of LiFePO4/C was studied.Four types of commercial production LiFePO4 cathode material were developed.The main performance of the LiFeP0O4/C is excellent.The discharge capacity of WM02 LiFePO4/C is 163.3mAh/g.The discharge capacities are 147.7,135.0 and 121.8mAh/g at 1C,3C and 5C respectively.The tap density of the material ups to 1.45g/cm3.