Search

CN-122010073-A - Preparation method of ferric phosphate, lithium iron phosphate, preparation method and application thereof

CN122010073ACN 122010073 ACN122010073 ACN 122010073ACN-122010073-A

Abstract

The application provides a preparation method of ferric phosphate, lithium iron phosphate and a preparation method and application thereof, and belongs to the technical field of lithium batteries. The preparation method of the iron phosphate comprises the steps of S1, carrying out primary crystallization reaction on a mixed solution of an iron source and a phosphorus source in a protective atmosphere to form crystal nuclei, S2, heating to 70-85 ℃, adjusting and maintaining the pH to 2.8-3.2, carrying out secondary crystallization reaction, S3, adjusting the pH to 3.5-4.0, carrying out tertiary crystallization and curing reaction at 80-90 ℃, wherein the particle size D50 of the iron phosphate is 1-1.5 mu m, the iron-phosphorus molar ratio Fe/P is 0.98-1.02, and the tap density is more than or equal to 1.1 g/cm 3 . According to the application, through optimizing the preparation process of the ferric phosphate and combining the steps of specific carbon source combination, sectional calcination and the like, the electrochemical performance of the lithium iron phosphate is effectively improved, so that the lithium iron phosphate has excellent comprehensive performance in terms of specific capacity and cycle stability.

Inventors

  • WANG LONG
  • LI QIFENG
  • CHEN ZHIXIN
  • CHEN LIPENG
  • HOU JUNKE
  • Ruan Dongjie
  • LONG BIAO
  • CHEN PENGJIE

Assignees

  • 福安国隆纳米材料有限公司

Dates

Publication Date
20260512
Application Date
20260410

Claims (9)

  1. 1. The preparation method of the ferric phosphate is characterized by comprising the following steps of: s1, under a protective atmosphere, adding a mixed solution of an iron source and a phosphorus source and an oxidant into a reactor containing a base solution in parallel flow, and carrying out primary crystallization reaction under the condition of 40-55℃, pH to 1.5-2.0 to form crystal nuclei; S2, heating the system in the step S1 to 70-85 ℃, regulating and maintaining the pH value to 2.8-3.2, and carrying out secondary crystallization reaction to enable crystals to grow; S3, regulating the pH value of the system in the step S2 to 3.5-4.0, performing tertiary crystallization and curing reaction at 80-90 ℃, and performing solid-liquid separation, washing and drying after the reaction to obtain ferric phosphate; Wherein, a crystal face modifier is added in the primary crystallization reaction and/or the secondary crystallization reaction, and the crystal face modifier is at least one selected from citric acid, tartaric acid, malic acid, ascorbic acid and salts thereof; The particle diameter D50 of the ferric phosphate is 1-1.5 mu m, the iron-phosphorus molar ratio Fe/P is 0.98-1.02, and the tap density is more than or equal to 1.1 g/cm 3 .
  2. 2. The method for producing iron phosphate according to claim 1, wherein the crystal face modifier is added in an amount of 0.2 to 2.0% by mass of the iron element in the iron source.
  3. 3. The preparation method of the lithium iron phosphate is characterized by comprising the following steps of: (1) Mixing the ferric phosphate according to any one of claims 1-2 with a lithium source, a carbon precursor and a dispersing agent, and grinding to obtain a first slurry; (2) Adding a nano conductive carbon material into the first slurry, uniformly dispersing to obtain composite slurry, homogenizing, and then performing spray drying to obtain composite powder; (3) And (3) carrying out sectional calcination on the composite powder in a protective reducing atmosphere, and carrying out calcination post-treatment to obtain the lithium iron phosphate.
  4. 4. The method for producing lithium iron phosphate according to claim 3, wherein in the step (1), the lithium source is lithium hydroxide, and the molar ratio of the lithium element to the iron element in the iron phosphate is 1.03 to 1.08:1; And/or the carbon precursor is at least one of polyethylene glycol, polyvinyl alcohol and sucrose, and the addition amount of the carbon precursor is 3-8% of the mass of the ferric phosphate; and/or the dispersing agent is ammonium polyacrylate, and the adding amount of the dispersing agent is 0.1-0.5% of the mass of the ferric phosphate.
  5. 5. The method for preparing lithium iron phosphate according to claim 3, wherein in the step (2), the nano conductive carbon material is a mixture of mercapto-modified carbon fiber and conductive carbon black, and the mass ratio of the mercapto-modified carbon fiber to the conductive carbon black is 1-3:1.
  6. 6. A method of producing lithium iron phosphate according to claim 3, wherein in step (2), the spray-dried inlet air temperature is 180-220 ℃ and the spray-dried outlet air temperature is 80-100 ℃ and is conducted under inert atmosphere protection.
  7. 7. The method for producing lithium iron phosphate according to claim 3, wherein in the step (3), the step of calcining comprises: The first stage, heating to 400-500 ℃ at the speed of 2-5 ℃ per minute, and preserving heat for 1-3 hours; the second stage, continuously heating to 650-750 ℃ at the speed of 1-3 ℃ per minute, and preserving heat for 3-6 hours; The protective reducing atmosphere is a mixed gas of nitrogen and hydrogen, wherein the hydrogen accounts for 2-10% of the total volume.
  8. 8. A lithium iron phosphate prepared by the method of any one of claims 3-7.
  9. 9. The use of the lithium iron phosphate according to claim 8, wherein the lithium iron phosphate is used in a positive electrode sheet of a lithium ion battery.

Description

Preparation method of ferric phosphate, lithium iron phosphate, preparation method and application thereof Technical Field The application relates to the technical field of lithium batteries, in particular to a preparation method of ferric phosphate, lithium iron phosphate and a preparation method and application thereof. Background At present, the synthesis methods of lithium iron phosphate materials are mainly divided into a solid-phase method and a liquid-phase method. The solid phase method mainly utilizes ferric salt, lithium salt and phosphate to realize the synthesis of lithium iron phosphate by high-temperature sintering. The liquid phase method is to dissolve soluble ferric salt, lithium salt and phosphate in a solvent, prepare lithium iron phosphate or a precursor thereof by utilizing ion reaction, and prepare a finished product by high-temperature sintering. The solid phase method has simple reaction, easy processing of raw materials and high yield, but the morphology of the raw materials is not easy to control, and the tap density and the compaction density of the product are low. Some new synthetic methods, such as microwave synthesis, ultrasonic co-precipitation, can be generalized to solid phase synthesis. The liquid phase method needs to use a reaction kettle for pre-treatment, and meanwhile, the liquid phase method also needs to use processes such as drying, filtering and the like, so that the process is complex. But the sphericity of the product is generally better, the tap density is higher, and the capacity and high-rate performance are excellent. CN103715452a discloses a low-temperature lithium iron phosphate lithium ion power battery, which adopts a nano-sized lithium iron phosphate coated by a discontinuous graphene structure as an anode active material, wherein the median particle diameter of the nano-sized lithium iron phosphate is 5-10nm, the graphene is 3-8 layers of multi-layer graphene, the coating area accounts for 40% -70% of the total surface area of the lithium iron phosphate material, and the compaction density of the prepared anode sheet is lower, so that the energy density is lower. The solution has the problem of low electrochemical performance, so it is necessary to develop a lithium iron phosphate positive electrode material capable of achieving high electrochemical performance. Disclosure of Invention The present application has been made in view of the above problems, and an object thereof is to provide a method for producing iron phosphate, lithium iron phosphate, and a method for producing and using the same. Specifically, the first aspect of the present application provides a method for preparing iron phosphate, comprising the following steps: s1, under a protective atmosphere, adding a mixed solution of an iron source and a phosphorus source and an oxidant into a reactor containing a base solution in parallel flow, and carrying out primary crystallization reaction under the condition of 40-55℃, pH to 1.5-2.0 to form crystal nuclei; S2, heating the system in the step S1 to 70-85 ℃, regulating and maintaining the pH value to 2.8-3.2, and carrying out secondary crystallization reaction to enable crystals to grow; s3, regulating the pH value of the system in the step S2 to 3.5-4.0, performing tertiary crystallization and curing reaction at 80-90 ℃, and performing solid-liquid separation, washing and drying after the reaction to obtain ferric phosphate; Wherein, a crystal face modifier is added in the primary crystallization reaction and/or the secondary crystallization reaction, and the crystal face modifier is at least one selected from citric acid, tartaric acid, malic acid, ascorbic acid and salts thereof. The particle diameter D50 of the ferric phosphate is 1-1.5 mu m, the iron-phosphorus molar ratio Fe/P is 0.98-1.02, and the tap density is more than or equal to 1.1 g/cm 3. Further, the adding amount of the crystal face modifier is 0.2% -2.0% of the mass of the iron element in the iron source. The second aspect of the application provides a method for preparing lithium iron phosphate, comprising the following steps: (1) Mixing the ferric phosphate with a lithium source, a carbon precursor, a dispersing agent and a solvent, and grinding to obtain first slurry; (2) Adding a nano conductive carbon material into the first slurry, uniformly dispersing to obtain composite slurry, homogenizing, and then performing spray drying to obtain composite powder; (3) And (3) carrying out sectional calcination on the composite powder in a protective reducing atmosphere, and carrying out calcination post-treatment to obtain the lithium iron phosphate. Further, in the step (1), the lithium source is lithium hydroxide, and the molar ratio of the lithium element to the iron element in the ferric phosphate is 1.03-1.08:1; And/or the carbon precursor is at least one of polyethylene glycol, polyvinyl alcohol and sucrose, and the addition amount of the carbon precursor is 3-8% of the ma