Preparation And Characterization Of Nano-iron Phosphate Lithium

LiFePO4is considered as a promising cathode material for lithium-ion batteries dueto its advantages such as abundant raw materials, environmentally friendliness, highcapacity, good cycle performance and preferable safety. Well, solid-state method which isstill adopted to prepare LiFePO4in industrial production has some defects such as highcost, low purity and poor efficiency and the electrochemical properties of the electrodematerials is not satisfactory. Liquid-state co-precipitation method to prepare LiFePO4becomes the new pop research among the cathode materials of lithium ion battery for itsadvantaged superiority because of low energy consumption, excellent thermal stability,low cost and being prone to modification.In this thesis, pure LiFePO4was successfully prepared by liquid phaseco-precipitation method based on the continuous the ordered dynamic micro layer groupmixing method technology which is primarily used two-step synthesis of nano-lithiumiron phosphate of step generates process. Firstly, I obtained the precursor of lithium ironphosphate precipitate by co-precipitation mixing, then coated on the precursor andcalcined under the protection of inert gas, at last, the final product nanometer lithium ironphosphate would be got.The effects of the structural properties of the material in the different reactionparameters and reaction conditions by thermal gravimetric analysis, electron microscopy,XRD analysis, tap density measurement and initial characterization of the electrochemicalproperties and a preliminary discussion on the impact of aging temperature, nitrogen flow,the presence of water vapor, the thickness of the material layer on the system size andmorphology of the nano-lithium iron phosphate. The precursor of lithium iron phosphateas an intermediate product prepared by precipitation based on the continuous the ordereddynamic micro layer group mixing method technology was mainly studied calcinationstemperature and reaction time, total raw material particle size and reaction pressurecontrol of the preparation of nanometer-scale lithium iron phosphate powder. Through aseries of comparative tests, I want to explore a more appropriate nano-lithium ironphosphate preparation route.The experimental results showed that the best molar proportion of lithium and iron is1.1. The material sintered for12h at700℃under nitrogen gas had a complete olivinestructure, uniform surface morphology, high tapped density and excellent electrochemicalperformances. However, the attenuation problem still exists, has not been completelyresolved with the increasing of the discharge rate.In order to improve the electrical properties of the material, we also study the impactof carbon-coated on the nano-lithium iron phosphate cathode material. Homogeneously mixed with glucose, respectively, and n-amyl alcohol azeotropic distillation synthesizednano-lithium iron phosphate of Carbon composite materials and systematic study of theinfluence of different calcination temperature and reaction time on the conductiveproperties of the material. The results showed that carbon coating can effectively enhancethe electrochemical performance for nano-lithium iron phosphate because of a more-looseparticle spatial structure. This is mainly because of the carbon dispersed in the particleseffectively enhance the conductivity of the material and a good effect on nano-particles, sothat the lithium iron phosphate material even under high rate discharge, still reflect abetter electrochemical performance.