Preparation Of LiFePO₄/C Cathode Materials By Sol-Gel And Its Performance Research

In this paper, the sol-gel method combined with spray drying means to obtain LiFePO₄/Ccathode material.The effects of reaction temperature calcining temperature,sintering temperature, the ratio of raw materials, the sol concentration, p H and other factors for the sol-gel liquid; using laboratory oligomers polyacrylonitrile LPAN and different carbon sources to change the material covered resistance, finally, spray drying equipment feed rate、air inlet temperature parameters were optimized;to study the structure and properties of materials by XRD、SEM、TG、CV、TEM characterization methods and so on.The temperature of the reaction system through research, has for the system reaction temperature 60℃、70℃、80℃、90℃ and found that the reaction at 90℃shaped material Maung terms with increasing temperature more uniform particle distribution crystal high peak intensity, the highest electrochemical properties, the discharge capacity of up to 131.2m Ah/g.LiFePO₄/Ccathode material by TG found organic matter the material, crystal water and other substances in weightlessness more serious between 200℃ to 600℃ by physical and chemical changes; To study its calcining temperature 350℃、450℃、550℃ three temperatures and found that the best crystal structure and properties at 450℃. select six temperature from 600℃ to 850℃ to studies the Sintering temperature found that at 700℃has a significant impact on the material: the maximum discharge capacity electrochemical performance and the most complete for crystalline material.The ratio of reactants great Affect material, the study found lithium source: phosphorus source: iron source is less than 1.2: 1.2: 1.0 appears Fe impurities, and the ratio of 1.6: 1.6: 1 ratio is the best; the raw materials citric acid iron（FeC₆H₅O₇ ? 5H₂O） after optimize and the discovery of lithium source: phosphorus source: source of iron is 1.1: 1.1: 1.0 is the best electrochemical performance.When using ammonia and citric acid to study the sol p H found that both raise or lower the p H, the materials electrochemical properties and crystallinity of crystalline are declining trend, in which the best performance is the original sol p H 2.97,While exploring the sol reaction concentration found that the concentration is 0.10mol/L,the crystal diffraction peak intensityis better,the best discharge capacity of stable is132.51 m Ah/g.To study the effects of different carbon content for the material using homemade polyacrylonitrile LPAN and different carbon sources on coated modified the materials. Whether added LPAN or citric acid、dextrose、sucrose, the electrochemical properties are declining, and dropped to 25 m Ah/g or less, and when not add any carbon source the material is up to the best electrochemical energy 145.48 m Ah/g, so the citric acid can provide improved performance by decomposition itself carbon.Spray drying equipment is to provide important support in the synthesis of LiFePO₄/Ccathode material, its parameters must impact on the structure and morphology of the material, the paper is to optimize the feed rate and its inlet temperature,the feed rate found is not impact obvious, 30r/min and 45r/min the discharge capacity is slightly higher than 60r/min; the inlet temperature is the main factor, set the inlet temperature of is 160℃、200℃、240℃ and found 200℃ discharge capacity s highest, 105.58 m Ah/g.