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    1. Guangdong Liandong New Energy Co., Ltd. focuses on R&D and production of new energy batteries


      Lithium iron phosphate production process route

      Times:07/29/2014    Hits:1415
       High-temperature solid-phase method 
      High-temperature solid-phase method is the main method of production of lithium iron phosphate, is also the most mature way, usually iron (such as ferrous oxalate FeC2O4 · 2H O), phosphates (such as diammonium phosphate (NH4) 2HPO4) and lithium salts (such as lithium carbonate Li2CO3) as raw materials, stoichiometric mix well, in an inert atmosphere to go through a low temperature pre-decomposition, and then the high-temperature roasting, grinding and pulverizing. 
      Advantages: High-temperature solid-phase synthesis route design and process operation is simple, easy to control the process parameters, material properties of the preparation of stable, easy to implement industrial mass production. 
      Disadvantages: ① powder materials require a long time to ask for grinding and mixing, and mixing limited extent, poor doping modification effect; ② require a higher heat treatment temperatures and longer treatment time, energy consumption; ③ in the composition of the product exists, the structure, particle size distribution and other large difference, prone Fe impurity phase; ④ electrochemical properties of the material is difficult to control; ⑤ using ferrous oxalate more expensive, higher material costs; requires a lot of inert shielding gas reaction high cost of inert gas; ⑥ while sintering process will produce ammonia, water, carbon dioxide, bicarbonate crystal particles generated when they go through the process of cooling in the furnace caused by contamination of the product. In addition, ammonia produced is not conducive to environmental protection, should further increase the exhaust gas treatment equipment. 
      Carbothermal reduction 
      High-temperature carbon thermal reduction method is also a solid-phase method is relatively easy synthesis method of industrialization, most lithium dihydrogen phosphate, ferric oxide or iron oxide, sucrose as raw material, even after mixing, temperature and under argon or nitrogen roasting, carbon reduction of the ferric iron (II), which is synthesized by carbothermal reduction of lithium iron phosphate. 
      Advantages: Solving the raw material mixture in the oxidation reaction process may be triggered during the synthetic process more reasonable while improving the conductivity of the material. 
      Disadvantages: relatively long reaction time, temperature, difficult to control, product consistency requirements of the control conditions more demanding, difficult to adapt to industrial production. 
      Hydrothermal synthesis method 
      Hydrothermal synthesis method belongs to wet areas, it is soluble ferrous salts, lithium salts and phosphoric acid as raw materials in the direct synthesis under hydrothermal conditions LiFePO4, because the oxygen solubility in the hydrothermal system is small, the hydrothermal system as LiFePO4 Synthesis provide excellent inert environment. 
      Advantages: can be prepared by hydrothermal method of ultrafine particles in the liquid phase, the feedstock may be mixed at the molecular level. Phase with uniform, small particle size powders and easy operation, and are easy to mass production, bulk products and good stability, the advantages of cheap and easily obtained materials. While the production process does not require an inert atmosphere. 
      Cons: The product structure prepared by hydrothermal synthesis in the presence of iron is often misplaced, generated metastable FePO4, affecting the chemical and electrochemical properties of the product. There is also a non-uniform particle size, phase is not pure, large investment in equipment (high pressure high temperature reactor design and manufacturing difficulties, the cost is high) or process more complex defects. 
      Sol-gel synthesis 
      Sol-gel synthesis is iron alkoxide, lithium salt and phosphate as raw materials for the organic chelate, an alcohol as a solvent to prepare a homogeneous sol gel, after drying, calcining at 300 ~ 800 ℃ you can get a few hours of lithium iron phosphate. 
      Pros: chemical precursor solution good uniformity (up to molecular level), low temperature heat treatment gel, powder particle size is small and narrow distribution, good powder sintering properties, the reaction process is easy to control, simple equipment. 
      Disadvantages: drying shrinkage, long synthetic cycle, while during the preparation of the complex, harsh conditions, high cost, so the industrial production difficult. Further metal alkoxides are expensive, and the alkoxide is generally toxic solvents commonly used. 
      Liquid coprecipitation 
      Liquid is the first co-precipitation method (Ⅱ) Preparation of a compound with an oxidizing agent FePO4 Fe, and then restore the preparation of LiI LiFePO4, LiFePO4 crystals obtained after heat treatment. In the production phase, especially co-precipitation stage to pay attention to prevent Fe. The oxidation problems, in addition to control pH of the solution is to get a pure phase olivine key technologies. 
      Advantages: great activity, small particle size and particle size distribution characteristics, in addition also reduces the heat treatment temperature and shorten heat treatment time, reduced energy consumption. 
      Disadvantages: This method is also due to the requirements of different materials having similar hydrolysis or precipitation conditions limited the choice of materials, the impact of its practical application. General use of H2O2, LiI and ascorbic acid and other raw materials, not only to select a narrow range of raw materials, and increased complexity of the cost of the product and production process. 
      Microwave synthesis 
      Lithium salt, phosphates, iron as raw material, the use of hydrogen protection, quick and easy to prepare good electrochemical performance of lithium iron phosphate. 
      Advantages: a short reaction time (3 ~ 10 min), low energy consumption, high synthetic efficiency, uniform particles and so on. Produced using the same production process of activated carbon to absorb microwave heating rapidly reducing atmosphere precursor, eliminating the process of Walter inert gas. 
      Disadvantages: the reaction raw material selection phosphate, ammonium dihydrogen phosphate, inevitably produced during the reaction of ammonia will not environmentally friendly, only through the exhaust gas treatment, while increasing the complexity of the process; Furthermore, the production process is difficult to control, equipment investment large, it is difficult for the industrialized production. In addition, redox technology, spark plasma sintering technique, spray pyrolysis technique and pulsed laser deposition technique is also used in the synthesis of LiFePO4. However, the device is limited, it is difficult to achieve the industrialized production ton batch. Even if it can small batch production, the cost is relatively high. 
      The above comparison, the liquid phase synthesis is uniformly mixed at the molecular level the reaction batch with a stable product, it is easy to control, easy to adjust the synthetic route, to select a wide range of reactants, etc.. However, preparation of complex or higher equipment requirements and other reasons, it is difficult for large-scale production. 
      Lithium iron phosphate production is now basically uses two solid-phase method and carbothermal reduction method, such as the U.S. and Canada A123 Phostech company uses solid-phase method, the United States Valence company carbothermal reduction method.
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