Synthesis And Pilot Scale Production Of LiFePO₄Cathode Material In Lithium-ion Battery

LiFePO₄,which is olivine-type structure, is rich in its sources of raw materials,inexpensive, and environmentally safe; when used as a cathode material, it has nomemory, high theory discharge specific capacity, high voltage’s platforms（vs.Li/Li+=3.4V）, good stability, excellent cycling performance and many otheradvantages, is to become the most promising cathode materials for lithium-ion. But itsinherent disadvantages which are the low electronic conductivity and low lithium iondiffusion rate limit its further development.The subject combined with the advantages of solid-phase method and the liquidphase method using liquid composite crystal method, and studied precursorpreparation process, spray drying process and post-process research. At the same time,the material’s properties and stability conditions were optimized in small scale,moreover, carried out pilot preliminary studies to optimize the pilot rotary kilnsintering parameters, material morphology and electrical characterization.Different dispersant, the amount of dispersant, different carbon sources, and theamount of carbon source in pre-preparation process of the materials, were studied toimproved materials’ properties. The experiment determined the best preparationconditions: CTAB was as a dispersing agent, and the amount of it is5g/mol; added inglucose as coated carbon source, and the amount of coating is4g/mol. The materialsprepared were uniform in the particle size distribution, and had high electricalconductivity.It discussed the correlation of the spray drying process and material properties,which included the spray concentration, the spray air inlet temperature, the feed rate ofmother liquor. It determined experimentally the optimum value of these parameters:spray concentration was0.67mol/L, the inlet temperature was250°C, and the feed ratewas35ml/min. The material prepared had high tap density, low moisture and goodelectrical properties.Explored the post-processing process, such as tablet press before burnedtreatment, the ball milling before high temperature burning, particle size sieved afterburned, which determined the conditions of preparation:10Mpa hydraulic pressure hadbetter effect when tablet treatment, and ball milling frequency was30Hz, and the timewas10min, and materials sieved400mesh for particle size classification after burning.Based on small test experimental conditions optimized, we conducted preliminarypilot study, and tried to carry out10Kg grade materials production. It mainly discussedthe operating parameters of the pilot rotary sintering furnace, such as high-temperature sintering time, sintering temperature, sintering atmosphere, and characterized pilotmaterial physical and electrical properties. At the same time, it compared theperformance with the small test materials, in order to evaluate the pros and cons of thepilot materials. Materials whose high-temperature in sintering stage was660°C,sintered in argon atmosphere for8h, had the best performance. XRD analysis showedthat the material had a single LiFePO₄olivine structure; particle size analysis showedthat basically the particle size distribution was normal distribution, and the particlesize distribution mainly was in the0to10μm, and5to20μm; spectroscopy analysisshowed that the material was pure phase; electrical performance analysis showed thatthe small charge-discharge rate performance of materials were very good, such as0.1C and0.2C, the discharge capacity almost were157.6mAh/g and155.7mAh/g.Although, the large magnification performance was to be improved, and the firstdischarge capacity was99.9mAh/g when the charge-discharge rate was10C. In general,the performance of material had been basically stable.