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CN-121974318-A - Lithium iron phosphate material, preparation method thereof, positive electrode plate and lithium ion battery

CN121974318ACN 121974318 ACN121974318 ACN 121974318ACN-121974318-A

Abstract

The invention provides a lithium iron phosphate material and a preparation method thereof, an anode plate and a lithium ion battery, wherein the preparation method comprises the steps of dissolving soluble ferric salt and a ligand in water to form an iron-based complex, so as to obtain a first solution; placing carboxylated cellulose material in a first solution to form an iron-cellulose complex, obtaining a first mixed material, carrying out first separation and drying on the first mixed material to obtain the iron-cellulose complex, mixing and heating a lithium source, an iron source, a phosphorus source, a carbon source and the iron-cellulose complex in a solvent, carrying out second separation on the obtained reaction mixed material, and sintering the obtained solid to obtain the lithium iron phosphate material. According to the method, the iron-cellulose complex is used as a one-dimensional structure template, so that the lithium iron phosphate material with a one-to-many electron transmission mechanism is successfully constructed, the conductivity, the multiplying power performance and the working voltage of the material are improved, and the capacity attenuation problem of the lithium iron phosphate material under high current density is further solved.

Inventors

  • QIN BING
  • WANG YI
  • JIA XUEYING

Assignees

  • 合肥国轩高科动力能源有限公司

Dates

Publication Date
20260505
Application Date
20260104

Claims (11)

  1. 1. A method for preparing a lithium iron phosphate material, which is characterized by comprising the following steps: dissolving soluble ferric salt and a ligand in water to form an iron-based complex to obtain a first solution, and placing carboxylated cellulose material in the first solution to form an iron-cellulose complex to obtain a first mixed material; Step (2), the first mixed material is subjected to first separation and drying to obtain an iron-cellulose complex; And (3) mixing and heating a lithium source, an iron source, a phosphorus source, a carbon source and the iron-cellulose complex in a solvent to obtain a reaction mixture, and performing secondary separation on the reaction mixture to obtain a solid, and sintering the solid to obtain the lithium iron phosphate material.
  2. 2. The method for producing a lithium iron phosphate material according to claim 1, wherein the degree of substitution of carboxyl groups in the carboxylated cellulose material is 0.5 to 4.0mmol/g; and/or the ratio of the sum of the molar amount of the Li element in the lithium source, the molar amount of the Fe element in the iron source, and the molar amount of the Fe element in the iron-cellulose complex to the molar amount of the P element in the phosphorus source is (0.95-1.05): (0.95-1.00): (0.98-1.02); And/or, in the step (1), after the carboxylated cellulose material is placed in the first solution, the ratio of the mass concentration of the carboxylated cellulose material in the obtained system to the molar concentration of the ligand added is (0.3-3.0) mg/L (0.01-0.5) mol/L; And/or the sum of the weight of the carbon source and the weight of the iron-cellulose complex is 5-20% of the weight of the dry basis in the reaction mixture.
  3. 3. The method for preparing a lithium iron phosphate material according to claim 1, wherein the molar ratio of Fe ions in the soluble iron salt to the ligand is 1 (0.5 to 3.0); and/or the mole ratio of Fe ions in the soluble ferric salt and the ligand is 1 (1.0-2.0); And/or the concentration of the ligand after being dissolved in the water is 0.01-0.5 mol/L.
  4. 4. A method of preparing a lithium iron phosphate material according to any one of claims 1 to 3, wherein the ligand is selected from one or more of gluconic acid, sodium gluconate, potassium gluconate, glucoheptonic acid, sodium glucoheptonate and potassium glucoheptonate.
  5. 5. A method of producing a lithium iron phosphate material according to any one of claims 1 to 3, wherein in the step (1), a buffer solution is added to adjust the pH of the system to be alkaline at the time of producing the iron-based complex; and/or adjusting the pH to 8-13; and/or, the buffer solution is glycine-sodium hydroxide buffer solution; and/or forming the iron-cellulose complex at a temperature of 40-100 ℃ for a time of 1-7 days.
  6. 6. The method for producing a lithium iron phosphate material according to any one of claims 1 to 3, wherein the heating temperature in the step (3) is 40 to 200 ℃ for 1 to 72 hours; and/or the sintering process comprises the steps of firstly heating to the sintering temperature at the heating rate of 1-5 ℃ per minute, and then preserving heat to perform the sintering operation; And/or, the sintering process is performed under a protective gas atmosphere; and/or the drying temperature is 80-200 ℃ and the drying time is 18-36 h; And/or, the first separation comprises a first washing and filtering; And/or mixing the cellulose nanofiber material with an oxidant to convert hydroxyl groups on the surface of the cellulose nanofiber material into carboxyl groups to obtain a second mixed material, and sequentially washing, suction filtering and drying the second mixed material to obtain the carboxylated cellulose material.
  7. 7. The method for preparing a lithium iron phosphate material according to claim 6, wherein the sintering temperature is 500-800 ℃ and the time is 2-12 hours; And/or the protective atmosphere is at least one selected from nitrogen, argon, nitrogen/hydrogen mixed gas or argon/hydrogen mixed gas; And/or performing the first washing operation using an aprotic solvent selected from one or more of dimethyl sulfoxide, N-N dimethylformamide, acetone, and diethyl ether; and/or the mass ratio of the cellulose nanofiber material to the oxidant is 1 (0.1-0.2); And/or the cellulose nanofiber material is selected from one or more of a plant cellulose nanofiber material, a bacterial cellulose nanofiber material, and a seaweed cellulose nanofiber material.
  8. 8. A method of preparing a lithium iron phosphate material according to any one of claims 1 to 3, wherein the soluble iron salt is selected from one or more of ferric chloride, ferric nitrate and ferric sulphate; and/or the lithium source is selected from one or more of lithium carbonate, lithium oxide and lithium hydroxide; And/or the phosphorus source is selected from one or more of ammonium dihydrogen phosphate, lithium phosphate and phosphoric acid; And/or the carbon source is selected from one or more of glucose, sucrose, citric acid, polyvinyl alcohol and polyethylene glycol; And/or the solvent is selected from one or more of ethanol, glycol, glycerol and tert-butanol.
  9. 9. A lithium iron phosphate material, characterized in that the lithium iron phosphate material is prepared by the preparation method of the lithium iron phosphate material according to any one of claims 1 to 8.
  10. 10. A positive electrode sheet comprising a positive electrode active material layer, wherein a material of the positive electrode active material layer comprises the lithium iron phosphate material of claim 9.
  11. 11. A lithium ion battery characterized in that the positive electrode sheet of the lithium ion battery is the positive electrode sheet of claim 10.

Description

Lithium iron phosphate material, preparation method thereof, positive electrode plate and lithium ion battery Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a lithium iron phosphate material and a preparation method thereof, a positive electrode plate and a lithium ion battery. Background In the context of a continuous increase in global energy demand, green low-carbon conversion of energy production and consumption is urgent. The secondary battery is used as a key technology for storing and converting renewable energy sources, and has an irreplaceable effect on promoting energy structure optimization and promoting green low-carbon development. Particularly, the technology of the secondary battery is widely applied in the fields of electric automobiles, large-scale energy storage and the like, and the progress of the technology of the secondary battery is directly related to the success or failure of energy transformation. In this process, the improvement of the performance of the secondary battery, in particular, the optimization of the energy density, safety and cycle life thereof, has become a core target of the technical innovation. The positive electrode material is one of the key factors determining the performance of the secondary battery, and it is directly related to the energy storage capacity and the cycle stability of the battery. Among the numerous positive electrode materials, lithium iron phosphate (LiFePO 4, abbreviated as LFP) has become a star material in the field of positive electrode materials due to its excellent cycle life, high thermal stability, environmental friendliness and cost advantages, and is widely used in energy storage and power lithium batteries. However, the conductivity of LFP materials is generally low, mainly due to the presence of anionic groups (especially PO 43-) in their crystal structure, which prevent rapid conduction of electrons. The slow electron transport kinetics results in a significant degradation of battery performance at high rates, limiting the potential of LFP materials in high power applications. To address this problem, researchers have tried various methods to increase the conductivity of materials, with carbon coating being one of the most common strategies. The carbon coating can provide an additional conductive network for the LFP particles, but the conductive network formed around the LFP material by the traditional carbon coating method often forms random point-to-point contact, and the contact mode has low electron transmission efficiency, and is easy to cause the breakage of a carbon layer in the high-rate charge-discharge process, so that the conductivity of the material is not obviously improved, and the conductivity of the material is even further reduced. In summary, how to overcome the defects of the prior art, solve the inherent defects of the LFP material in terms of conductivity, and the limitation of the carbon cladding technology in terms of improving the electron transmission efficiency, improve the multiplying power performance and working voltage performance of the LFP positive electrode material, so that the LFP material can better adapt to the requirements of high-power application, thereby providing a more stable and higher-performance battery solution for new energy automobiles, large-scale energy storage systems and the like, and becoming the problem to be solved urgently. Disclosure of Invention The invention mainly aims to provide a lithium iron phosphate material, a preparation method thereof, a positive electrode plate and a lithium ion battery, so as to solve the inherent defect of the lithium iron phosphate material in the aspect of conductivity in the prior art and the limitation of the traditional carbon coating technology in improving the electron transmission efficiency of the lithium iron phosphate material, and aims to further improve the conductivity, multiplying power performance, working voltage and other performances of the lithium iron phosphate material, so that the lithium iron phosphate material can better adapt to the application requirements of high-power batteries. The application provides a preparation method of a lithium iron phosphate material, which comprises the following steps of (1) dissolving soluble ferric salt and a ligand in water to form an iron-based complex to obtain a first solution, placing a carboxylated cellulose material in the first solution to form an iron-cellulose complex to obtain a first mixed material, (2) separating and drying the first mixed material to obtain an iron-cellulose complex, and (3) mixing and heating a lithium source, an iron source, a phosphorus source, a carbon source and the iron-cellulose complex in a solvent to obtain a reaction mixed material, and sintering the obtained solid after the reaction mixed material is subjected to second separation to obtain the lithium iron phosphate material. Further, i