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CN-122025519-A - Preparation method of lithium ferrous fluoride sulfate material, positive electrode plate and secondary battery

CN122025519ACN 122025519 ACN122025519 ACN 122025519ACN-122025519-A

Abstract

The application provides a preparation method of a lithium ferrous fluoride sulfate material, a positive electrode plate and a secondary battery, belonging to the field of lithium batteries, wherein the preparation method comprises the following steps of mixing ferrous sulfate heptahydrate, a lithium source, a fluorine source and a carbon source to obtain first powder; the method comprises the steps of crushing the first powder, sieving to obtain second powder, and carrying out sectional sintering on the second powder to obtain a lithium ferrous fluoride sulfate material, wherein the sectional sintering comprises a first section sintering, a second section sintering, a third section sintering and a fourth section sintering, the temperature of the first section sintering is 118-122 ℃, the temperature of the second section sintering is 145-155 ℃, the temperature of the third section sintering is 215-225 ℃, and the temperature of the fourth section sintering is 350-400 ℃. The application is helpful for reducing the impurity phase in the lithium ferrous fluoride sulfate material by optimizing the temperature curve in the sintering process.

Inventors

  • SHI ZHIXIANG
  • LV FEI
  • CAI RONGHUI
  • CHEN YIXIN

Assignees

  • 湖北万润新能源科技股份有限公司

Dates

Publication Date
20260512
Application Date
20260205

Claims (10)

  1. 1. The preparation method of the lithium ferrous fluoride sulfate material is characterized by comprising the following steps of: mixing ferrous sulfate heptahydrate, a lithium source, a fluorine source and a carbon source to obtain first powder; Crushing the first powder, and sieving to obtain second powder; The second powder is subjected to sectional sintering to obtain a lithium ferrous fluoride sulfate material; the sectional sintering comprises a first section sintering, a second section sintering, a third section sintering and a fourth section sintering, wherein the temperature of the first section sintering is 118-122 ℃, the temperature of the second section sintering is 145-155 ℃, the temperature of the third section sintering is 215-225 ℃, and the temperature of the fourth section sintering is 350-400 ℃.
  2. 2. The method according to claim 1, wherein the first stage sintering time is1 to 3 hours, and/or, The second stage sintering time is 1-3 h, and/or, The third sintering time is 0.8-1.2 h, and/or, And the fourth sintering time is 1-10 h.
  3. 3. The method according to claim 1, wherein the step of sintering further comprises sintering a first transition section before the step of sintering, the temperature of the first transition section is 88-92 ℃, and/or, The sectional sintering further comprises a second transition section sintering positioned between the second section sintering and the third section sintering, wherein the temperature of the second transition section sintering is 175-185 ℃, and/or, The sectional sintering further comprises a third transition section sintering located between the third section sintering and the fourth section sintering, and the temperature of the third transition section sintering is 295-305 ℃.
  4. 4. The method according to claim 3, wherein the first transition section is sintered for 0.5 to 2 hours and/or, The sintering time of the second transition section is 1-3 h, and/or, And the sintering time of the third transition section is 1-3 hours.
  5. 5. The method of claim 4, wherein the lithium source comprises at least one water-soluble lithium salt comprising one or more of lithium acetate, lithium oxalate, lithium carbonate, lithium fluoride, lithium hydroxide, lithium sulfate, lithium phosphate, and/or, The carbon source comprises one or more of nano graphite, carbon nano tube, graphene and graphene oxide, and/or, The fluorine source comprises a first fluorine-containing compound and a second fluorine-containing compound, wherein the first fluorine-containing compound comprises one or more of lithium fluoride, ammonium fluoride and polyvinylidene fluoride, and the second fluorine-containing compound comprises one or more of ammonium fluoride and polyvinylidene fluoride.
  6. 6. The preparation method of the iron (II) sulfate heptahydrate, the lithium source, the fluorine source and the carbon source according to the preparation method of the iron (II) sulfate heptahydrate, the lithium source, the fluorine source and the carbon source are in a molar ratio of 1:1 (1.05-1.10) to 0.02-0.04.
  7. 7. The method according to claim 1, wherein in the step of pulverizing the first powder and sieving to obtain the second powder, the second powder has a D50 particle size of 1 to 3 μm and a D100 particle size of 8 to 15 μm.
  8. 8. The method according to claim 1, wherein the step of pulverizing the first powder and sieving to obtain the second powder is performed by jet milling, and/or, The screen used in the sieving is 400 mesh screen.
  9. 9. A positive electrode sheet comprising the lithium ferrous fluoride sulfate material produced by the production method of any one of claims 1 to 8.
  10. 10. A secondary battery comprising the positive electrode tab of claim 9.

Description

Preparation method of lithium ferrous fluoride sulfate material, positive electrode plate and secondary battery Technical Field The invention relates to the technical field of lithium batteries, in particular to a preparation method of a lithium ferrous fluoride sulfate material, a positive electrode plate and a secondary battery. Background The lithium iron fluoride sulfate (LiFeSO 4 F) is used as a novel lithium ion battery anode material, has the advantages of low raw material cost, simple preparation process, sufficient resources and the like, has energy density equivalent to that of the traditional lithium iron phosphate material (LiFePO 4, LFP), and has good application prospect. At present, the lithium ferrous fluoride sulfate material is generally prepared by adopting a high-temperature solid-phase synthesis method, namely, after ferrous sulfate and lithium fluoride are mixed, high-temperature calcination is directly carried out. The product prepared by the method often has more impurity phases, the crystal purity is lower, and the charge and discharge capacity of the battery prepared based on the product is poorer. Disclosure of Invention In view of the technical problems in the background art, the application provides a preparation method of a lithium ferrous fluoride sulfate material, a positive electrode plate and a secondary battery, and aims to reduce the impurity phase in the lithium ferrous fluoride sulfate material. In a first aspect, an embodiment of the present application provides a method for preparing a lithium ferrous fluoride sulfate material, the method for preparing a lithium ferrous fluoride sulfate material including the steps of: mixing ferrous sulfate heptahydrate, a lithium source, a fluorine source and a carbon source to obtain first powder; Crushing the first powder, and sieving to obtain second powder; The second powder is subjected to sectional sintering to obtain a lithium ferrous fluoride sulfate material; the sectional sintering comprises a first section sintering, a second section sintering, a third section sintering and a fourth section sintering, wherein the temperature of the first section sintering is 118-122 ℃, the temperature of the second section sintering is 145-155 ℃, the temperature of the third section sintering is 215-225 ℃, and the temperature of the fourth section sintering is 350-400 ℃. In the technical scheme of the embodiment of the application, by constructing a reasonable temperature curve, the crystallization water in the reaction system can be gradually and fully discharged before high-temperature sintering, thereby being beneficial to reducing the impurity phase in the lithium ferrous fluoride sulfate material, forming a material with higher phase purity and better performance, and simultaneously, the release speed of the crystallization water is regulated, so that the pore distribution in the lithium ferrous fluoride sulfate material is more uniform, thereby being beneficial to improving the compaction density of the material. Therefore, when the lithium ferrous fluoride sulfate material is used for preparing the positive electrode plate of the lithium ion battery, the charge and discharge capacity of the battery can be improved. In addition, the method has simple process flow and can realize mass production. In some embodiments, the first sintering time is 1-3 hours, and/or the second sintering time is 1-3 hours, and/or the third sintering time is 0.8-1.2 hours, and/or the fourth sintering time is 1-10 hours. In the embodiment, the time of the first stage sintering is controlled within the range, ferrous sulfate heptahydrate in the reaction system can be fully converted into ferrous sulfate tetrahydrate, the time of the second stage sintering is controlled within the range, ferrous sulfate tetrahydrate can be fully removed of crystal water to form ferrous sulfate monohydrate, the time of the third stage sintering is controlled within the range, crystal water in the reaction system can be fully removed, the impurity phase formed by residual crystal water is reduced, the time of the fourth stage sintering is controlled within the range, crystal form can be fully grown and reconstituted, and the lithium ferrous fluoride sulfate material with an excellent crystal form structure is formed. In some embodiments, the staged sintering further comprises a first transition sintering prior to the first stage sintering, the first transition sintering having a temperature of 88-92 ℃. In the embodiment, the first transition temperature zone is arranged before the first section sintering, so that the second powder in the room temperature state (10-40 ℃) can be preheated in the first transition temperature zone before entering the first section sintering, on one hand, the temperature curve can be more stable, the problem that the material is not heated uniformly due to rapid heating, and therefore the problem that the material is difficult to discharge in time d