Preparation method of battery-grade spherical iron phosphate for lithium-ion battery and its effect on the performance of lithium-ion battery

The hydrothermal method is to fully react the raw materials under high temperature and high pressure to prepare the required samples. Its production process is relatively simple, but due to the limitation of the reactor, its output is small, and industrial scale processing is inhibited. Using Fe(NO3)•H2O and (NH4)2HPO4 as raw materials, Zhang Haojie first prepared spherical hydrated basic iron phosphate by hydrothermal method, and then calcined at 500°C to produce basic iron phosphate with a diameter of 5μm. Then it is calcined with Li2CO3 to prepare spherical lithium iron phosphate ions. In this experiment, by controlling the morphology and size of iron phosphate, using the in-situ reaction of glucose on the surface of hydrated basic iron phosphate, LiFePO4 particles of uniform size were prepared, and the LiFePO4 particles prepared had high specific capacity and good cycle stability. The high-temperature solid-phase method is a relatively simple method in the preparation of lithium-ion battery materials, and it is also the most commonly used preparation method in the current industrial processing. Using (NH4)2HPO4, Fe(NO3)•H2O and aniline as raw materials, Wang et al. first prepared a polyaniline-coated iron phosphate precursor, which was then uniformly mixed with a lithium ion source and a carbon source to prepare a spherical LiFePO4 material. During the reaction, polyaniline was directly coated on the surface of FePO4, which promoted the formation of spherical particles. The homogeneous precipitation method uses a chemical reaction to release the crystalline ions in the solution slowly and uniformly from the solution. By controlling the concentration of the precipitant in the solution, the precipitation is ensured to be in a balanced state, thereby controlling the growth rate of the particles to obtain Nano materials with uniform particle size and high purity. This method overcomes the local inhomogeneity of the precipitation agent caused by directly adding the precipitation agent to the solution from the outside. Zheng Dianmo et al. used iron sulfate as the iron source and phosphoric acid as the phosphorus source, adjusted the pH with ammonia water, and introduced an ethanol-water system to prepare FePO4 particles with an average particle size of 60-300 nm. The sol-gel method, namely sol-gel, is to disperse the raw materials in a solvent, and make it through hydrolysis and condensation to obtain a sol. During the aging process, the colloidal particles gradually polymerize to form a gel. At this time, the gel has a certain degree of After drying, the space structure is calcined at high temperature to obtain the required material. Compared with the traditional solid-phase method, the sample obtained by this method has a uniform particle size, and it is easy to obtain materials with no impurities and excellent performance. Due to the structural characteristics of the lithium iron phosphate material, its electronic conductivity and ion diffusion coefficient are low, resulting in a higher internal resistance of the lithium iron phosphate battery. Internal resistance is an important parameter to measure battery performance, and is closely related to battery life, capacity, rate, safety and other performance. The problem of high internal resistance has always been a major problem hindering the widespread application of lithium iron phosphate batteries. The uniformity of the morphology, particle size and particle size of lithium iron phosphate particles will have a great impact on their electrical properties. Through experiments, the conclusions are as follows: (1) The morphology has a significant influence on the internal resistance of lithium iron phosphate batteries. Compared with the non-spherical lithium iron phosphate ion, the internal resistance of the spherical shape lithium iron phosphate battery is reduced by 17.4m; (2) The shape of the lithium iron phosphate ion can affect the AC impedance of the battery. The charge transfer resistance and lithium diffusion resistance of the spherical lithium iron phosphate battery are low; (3) The reduction of internal resistance has a significant effect on improving the rate performance of the lithium iron phosphate battery. The spherical lithium iron phosphate battery with low internal resistance exhibits excellent rate performance. In addition, powders composed of spherical particles have a higher bulk density than powders with flake, granular and irregular morphology. Moreover, the spherical particles have excellent fluidity, dispersibility, and process performance, which are very beneficial for the preparation of positive electrode material slurry and electrode coating, and improve the quality of the electrode sheet. Recent studies have shown that compared with powders with irregular morphology, powders with spherical particles have the characteristics of lower interfacial energy and higher specific energy. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete.