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CN-122010081-A - Phosphate positive electrode material and carbon coating method thereof

CN122010081ACN 122010081 ACN122010081 ACN 122010081ACN-122010081-A

Abstract

The invention discloses a phosphate positive electrode material and a carbon coating method of the phosphate positive electrode material, and belongs to the technical field of battery materials. The invention solves the problem of poor carbon coating effect of phosphate anode materials in the prior art. The preparation method comprises the following steps of S1, synthesizing cationic emulsion containing cationic emulsion particles, S2, preparing anionic precursor slurry of a phosphate positive electrode material, S3, mixing the cationic emulsion and the anionic precursor slurry according to a proportion to obtain a mixed material, S4, spray-drying the mixed material, removing a solvent, and demulsifying to obtain a demulsified solid material, and S5, sintering the demulsified solid material in an inert atmosphere to obtain the carbon-coated phosphate positive electrode material. The invention can form uniform carbon-coated lithium iron phosphate/lithium manganese iron phosphate anode material by carbonizing the organic coating film.

Inventors

  • ZHANG XIAOGUO
  • FU QUANJUN
  • Xiong Songmei
  • LUO XIANMING
  • DENG BOSONG

Assignees

  • 德阳川发龙蟒新材料有限公司

Dates

Publication Date
20260512
Application Date
20260318

Claims (10)

  1. 1. A carbon coating method of a phosphate positive electrode material is characterized by comprising the following steps: S1, synthesizing cationic emulsion containing cationic emulsion particles; S2, preparing anionic precursor slurry of a phosphate positive electrode material; s3, mixing the cationic emulsion and the anionic precursor slurry according to a proportion to obtain a mixed material; S4, spray drying the mixed material, removing the solvent and demulsifying to obtain a demulsified solid material; S5, sintering the demulsified solid material in an inert atmosphere to obtain a carbon-coated phosphate positive electrode material; s1 and S2 have no sequence.
  2. 2. The method for carbon coating of phosphate positive electrode material according to claim 1, wherein S2, the raw material for preparing the phosphate positive electrode material is ground to a set particle size to obtain an anionic precursor slurry, and the alcohol-water ratio of the solvent added during grinding is 1:3-6.
  3. 3. The method for carbon coating a phosphate-based positive electrode material according to claim 2, wherein the solid content of the anionic precursor slurry is 20-50%.
  4. 4. The method for carbon coating a phosphate-based positive electrode material according to claim 2, wherein the particle size after polishing is 0.35 to 0.40. Mu.m.
  5. 5. The method for carbon coating of phosphate positive electrode material according to any one of claims 1 to 4, wherein in S3, the anionic precursor slurry is stirred, then the cationic emulsion is added into the anionic precursor slurry according to the solid content of the anionic precursor slurry and the solid content mass ratio of the cationic emulsion is 100:5-20, and then the precursor coated with the emulsion particle film is obtained by spray drying after the reaction for 0.1-2 hours under the water bath condition of 25-50 ℃.
  6. 6. The method for carbon coating a phosphate-based positive electrode material according to any one of claims 1 to 4, wherein the raw materials for preparing the phosphate-based positive electrode material in S2 comprise a lithium source, an iron source, a manganese source, a phosphorus source, and a carbon source; wherein the lithium source is one or a combination of more of lithium dihydrogen phosphate, lithium hydrogen phosphate, lithium carbonate, lithium hydroxide, lithium oxalate and lithium acetate; the iron source is one or more of ferrous oxalate, ferrous acetate, ferric oxide, ferric phosphate, ferric hydroxide, ferric carbonate, ferric citrate and ferric acetate; The manganese source is one or a combination of a plurality of manganese tetraoxide, manganese dioxide, manganese monoxide, manganese carbonate, manganese oxalate and manganese acetate; The phosphorus source is one or a combination of more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate and ammonium phosphate; The carbon source is one or a combination of more of glucose, PEG, PVP, citric acid, sodium dodecyl benzene sulfonate, ethylenediamine tetraacetic acid, isooctyl alcohol ether phosphate and sodium secondary alkyl sulfonate.
  7. 7. The method for carbon coating a phosphate positive electrode material according to any one of claims 1 to4, wherein the carbon-coated phosphate positive electrode material is obtained after sintering at 350 to 500 ℃ for 2 to4 hours and 600 to 750 ℃ for 6 to 10 hours in S5.
  8. 8. The method for carbon coating a phosphate-based positive electrode material according to any one of claims 1 to 4, wherein the method for preparing the cationic emulsion in S1 comprises the steps of: S101, preparing a solution A, namely mixing styrene, butyl methacrylate, allyl caproate, ethylene glycol dimethacrylate, cetyltrimethylammonium chloride and deionized water according to a mass ratio of 10-30:5-20:1-15:1-10:0.5-5:100 for pre-emulsification; S102, preparing a solution B, namely mixing 2, 2-azo (2-methylpropyl-mi) dihydrochloride with deionized water according to a mass ratio of 1-10:100; S103, preparing a solution C, namely mixing butyl acrylate, ethylene glycol dimethacrylate, cetyltrimethylammonium chloride, 2-azo (2-methylpropyl) dihydrochloride and deionized water according to a mass ratio of 10-50:2-20:0.5-10:0.05-2:100 for pre-emulsification; s104, discharging oxygen in the solution A, heating the solution A and the solution B to 20-50 ℃, and slowly adding the solution B into the solution A, wherein the mass ratio of the solution A to the solution B is 100:1-20; And S105, heating the mixed solution obtained in the step S104 to 40-70 ℃, and slowly adding the solution C into the mixed solution to prepare the cationic emulsion, wherein the mass ratio of the solution A to the solution C is 100:25-100.
  9. 9. The carbon coating method of a phosphate positive electrode material according to claim 8, wherein the diameter of the cationic latex particles in S1 is less than 100nm, the core-shell structure is adopted, and the solid content is 5% -40%.
  10. 10. A phosphate-based positive electrode material obtained by the carbon coating method of the phosphate-based positive electrode material according to any one of claims 1 to 9.

Description

Phosphate positive electrode material and carbon coating method thereof Technical Field The invention belongs to the technical field of battery materials, and particularly relates to a phosphate positive electrode material and a carbon coating method of the phosphate positive electrode material. Background Lithium iron phosphate and lithium manganese iron phosphate are common phosphate cathode materials, wherein lithium iron phosphate (LiFePO 4, LFP) has become a mainstream choice of lithium ion battery cathode materials by virtue of excellent heat stability, low cost and environment-friendly characteristics, and is widely applied to the fields of power batteries and energy storage. As an important evolution direction of LFP, lithium manganese iron phosphate (LiMn xFe1-xPO4, LMFP) significantly improves the working voltage and energy density by introducing manganese element, and is considered as a powerful competitor for next-generation high-cost-performance cathode materials. However, both LFP and LMFP face inherent technical bottlenecks in that their olivine crystal structures cause FeO 6 octahedra to be isolated by PO 4 tetrahedra, and a continuous conductive network cannot be formed, so that the electronic conductivity is extremely low (about 10 -9 S/cm), and the high-rate charge and discharge performance is severely restricted. In order to break through the bottleneck, a carbon coating technology is widely adopted, and the electron conduction efficiency can be effectively improved by constructing a conductive network on the surface of the particles. However, in the prior art, the carbon coating of the lithium iron phosphate/lithium manganese iron phosphate is mainly carried out by simply mixing the carbon coating with a carbon source, drying the mixture, adhering the dried mixture to the surface of particles, sintering the dried mixture to carbon at a high temperature, and forming a carbon layer, so that the carbon coating effect is limited by the uniformity, the continuity and the thickness regulation difficulty of the carbon layer, the conventional single carbon layer is difficult to consider the conductivity and the compaction density, and the problems of falling of the carbon layer, increase of contact resistance and the like are easy to occur under the high-rate and long-cycle working condition, and the electrochemical performance is attenuated. Aiming at lithium iron manganese phosphate, carbon coating is also required to simultaneously cope with the structural instability challenge caused by manganese dissolution, so that the urgency and the necessity of optimizing the coating technology are further highlighted. Disclosure of Invention Aiming at the problem of poor carbon coating effect of phosphate positive electrode materials in the prior art, the invention provides a phosphate positive electrode material and a carbon coating method of the phosphate positive electrode material. The technical scheme adopted by the invention is as follows: A carbon coating method of a phosphate positive electrode material comprises the following steps: S1, synthesizing cationic emulsion containing cationic emulsion particles; S2, preparing anionic precursor slurry of a phosphate positive electrode material; s3, mixing the cationic emulsion and the anionic precursor slurry according to a proportion to obtain a mixed material; S4, spray drying the mixed material, removing the solvent and demulsifying to obtain a demulsified solid material; S5, sintering the demulsified solid material in an inert atmosphere to obtain a carbon-coated phosphate positive electrode material; s1 and S2 have no sequence. Preferably, in S2, the raw material for preparing the phosphate-based cathode material is ground to a set particle size to obtain an anionic precursor slurry, and the alcohol-water ratio of the solvent added during grinding is 1:3-6. After the technical scheme is adopted, the alcohol-water ratio of the anionic precursor slurry is too low, the particle dispersibility is poor, and the latex particles are connected together after sintering. The alcohol-water ratio of the anionic precursor slurry is too high, the potential difference between the latex particles and the surfaces of the particles is small, the electrostatic adsorption acting force is reduced, and the surface coating is easy to fall off. Preferably, the alcohol in the added solvent is ethanol. Preferably, the solid content of the anionic precursor slurry is 20-50%. Preferably, the particle size after grinding is 0.35 to 0.40um. Preferably, in the step S3, the anionic precursor slurry is stirred, then the cationic emulsion is added into the anionic precursor slurry according to the ratio of the solid content of the anionic precursor slurry to the solid content mass ratio of the cationic emulsion of 100:5-20, and then the precursor coated by the emulsion particle film is obtained after the reaction for 0.1-2 hours under the water bath condition of 25-50 ℃ and the