Hydrothermal Preparation Of Lithium Ion Battery Cathode Material Of Lithium Iron Phosphate And Its Performance

As a new type of lithium ion battery cathode material, Olivine LiFePO4 has received wide attention and research due to its excellent safety performance, cycle performance, economic characteristics, green environmental protection, and so on. LiFePO4 has been hailed as "the most potential of a new generation of lithium battery cathode material".In this article,LiFePO4 was synthesized by a one-step hydrothermal method, we systematically studied the ratio of ingredients, order of addition, reactant concentration, reaction temperature, reaction time, pH and other factors on the material composition, phase structure and electrochemical properties. The study found that only up to a certain ingredient ratio to obtain pure phase materials, and we can not obtain pure lithium iron phosphate in the small amount of lithium. The materials also existence of impurity phase under the first order of addition. Different reactant concentrations will not affect the phase structure of the material, but the particle size and agglomeration of the material will be different with different concentrations. The morphology and electrochemical properties of the materials will be affected by the different reaction temperature and time and pH.In order to improve the electrochemical performance of lithium iron phosphate, this paper of lithium iron phosphate materials were carbon coated. We mainly studies the impact of packaging factors of carbon, carbon source, carbon content and electrochemical properties of materials. The results showed that the phase structure of the carbon addition and will not affect the lithium iron phosphate, but the way carbon package, carbon source and carbon content will effcet the material particle size, morphology and electrochemical performance.The results showed that LiOH, FeSO4, H3PO4 as raw materials, and we choose ratio of reactants for Li:Fe:P=3:1:1. Under the secondary order of addition, the concentration of reactants is 0.3 mol/L while keeping the pH=6～7, and hydro-thermal reaction in 10 h under 220℃. Finally, we get the good performance of LiFePO4 material of pure phase. Carbon coating selection of the lithium iron phosphate doped with 20% of sucrose by situ carbon coating. LiFePO4/C composites electrochemical performance is superior,the initial discharge capacity of 110.5 mAh/g in the 0.1 C ratio,and the capacity to maintain was higher after 20 times cycle.