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CN-119208594-B - Lithium iron phosphate cathode material, preparation method thereof, cathode plate and secondary battery

CN119208594BCN 119208594 BCN119208594 BCN 119208594BCN-119208594-B

Abstract

The application provides a lithium iron phosphate cathode material, a preparation method thereof, a cathode plate and a secondary battery, and belongs to the technical field of cathode materials of batteries, wherein the chemical general formula of the lithium iron phosphate cathode material is Li x FeTi y P z B w O (4z+3w+2y) /C, wherein x, y, z and w are all non-0 positive numbers, x is more than or equal to 1.02 and less than or equal to 1.05,0.01 and y is more than or equal to 0.05,0.92 and z is less than or equal to 0.95, w is more than or equal to 0.05 and less than or equal to 0.15, and the mass content of C is 1.00% -1.35% based on the mass of the cathode material of the phosphoric acid. The lithium iron phosphate borate positive electrode material provided by the application is low in price, excellent in ion conductivity, high in capacity and excellent in rate capability, and meanwhile, the cycling stability is further improved, so that the lithium iron phosphate positive electrode material has a wider application prospect.

Inventors

  • WANG QIN
  • JIANG XUELIN
  • XU SEN
  • GAO KAI

Assignees

  • 湖北万润新能源科技股份有限公司

Dates

Publication Date
20260512
Application Date
20240911

Claims (11)

  1. 1. The lithium iron phosphate borate positive electrode material is characterized in that the general formula of the lithium iron phosphate borate positive electrode material is Li x FeTi y P z B w O (4z+3w+2y) /C, wherein x, y, z and w are all non-0 positive numbers, x is more than or equal to 1.02 and less than or equal to 1.05,0.01 and less than or equal to 0.05,0.92, z is more than or equal to 0.95 and w is more than or equal to 0.05 and less than or equal to 0.15, the mass fraction of carbon element in the lithium iron phosphate borate positive electrode material is 1.00-1.35%, and the valence of Ti element is +3.
  2. 2. The lithium iron phosphate borate positive electrode material of claim 1, wherein the lithium iron phosphate borate material has a D10 particle size of 0.50 μm or less, a D50 particle size of 1.60 μm or less, and a D90 particle size of 19.00 μm or less.
  3. 3. The lithium iron phosphate borate positive electrode material of claim 1, wherein the compaction density of the lithium iron phosphate borate positive electrode material is 2.35 g/mL to 2.50 g/mL, the specific surface area is 10.1m 2 /g~14.3 m 2 /g, and the powder resistivity is 4.0 Ω -cm to 13.0 Ω -cm.
  4. 4. The lithium iron phosphate borate positive electrode material according to any one of claims 1 to 3, wherein the lithium iron phosphate borate positive electrode material has an iron elution of 3.0ppm to 10.0ppm, an elemental iron of 0.01ppm to 0.05ppm, a chloride ion of 40.0ppm to 80.0ppm, a water content of 280ppm to 350ppm, free lithium of 140ppm to 200ppm, and a magnetic impurity content of 1ppm or less.
  5. 5. The preparation method of the lithium iron phosphate cathode material is characterized by comprising the following steps of: Mixing a lithium source, a ferrous source, a trivalent titanium source, a carbon source, phosphoric acid, boric acid and a solvent to obtain mixed slurry; preheating and drying the mixed slurry to obtain a pre-dried material; And calcining the pre-dried material to obtain the lithium iron phosphate cathode material.
  6. 6. The method according to claim 5, wherein the molar ratio of the iron element in the ferrous source, the titanium element in the trivalent titanium source, the lithium element in the lithium source, the carbon element in the carbon source, the phosphorus element in the phosphoric acid and the boron element in the boric acid is 1 (0.01-0.05): 1.02-1.05): 0.36-1.32): 0.92-0.95): 0.05-0.15.
  7. 7. The method of preparing a lithium iron phosphate cathode material according to claim 6, wherein the ferrous source comprises at least one of ferrous acetate and/or ferrous chloride; the lithium source comprises at least one of lithium chloride and/or lithium acetate; The trivalent titanium source comprises titanium trihalides; mixing a lithium source, a ferrous source, a trivalent titanium source, a carbon source, phosphoric acid, boric acid and a solvent, wherein the phosphoric acid is mixed with the solvent to form a phosphoric acid solution, and then the phosphoric acid solution is mixed with the lithium source, the ferrous source, the trivalent titanium source and the boric acid; the carbon source comprises at least one of ascorbic acid and/or citric acid.
  8. 8. The method for preparing a lithium iron phosphate cathode material according to claim 7, wherein the trivalent titanium source is titanium trichloride; The mass fraction of phosphoric acid in the phosphoric acid solution is 70% -80%; The carbon source is a mixture of ascorbic acid and citric acid, and the mass ratio of the ascorbic acid to the citric acid is (0.05-0.2) (0.92-0.95).
  9. 9. The method for preparing a lithium iron phosphate cathode material according to claim 5, wherein, Preheating and drying the mixed slurry at 100-150 ℃ to obtain a pre-dried material with the mass fraction of H 2 O being less than or equal to 0.5%; and/or, the step of calcining the pre-dried material to obtain the lithium iron phosphate cathode material comprises the following steps: in a protective atmosphere, after the pre-dried material is subjected to first heat preservation at a first calcination temperature for a first heat preservation time, obtaining the lithium iron phosphate borate anode material at a second calcination temperature for a second heat preservation time; Wherein the first calcining temperature is 120-150 ℃, and the first heat preservation time is 2-4 h; the second calcining temperature is 600-700 ℃, and the second heat preservation time is 4-6 h.
  10. 10. A positive electrode sheet, characterized in that the positive electrode sheet comprises the lithium iron phosphate borate positive electrode material according to any one of claims 1 to 4 or a lithium iron phosphate borate positive electrode material obtained by the preparation method of the lithium iron phosphate borate positive electrode material according to any one of claims 5 to 9.
  11. 11. A secondary battery, characterized in that the secondary battery comprises the lithium iron phosphate borate positive electrode material according to any one of claims 1 to 4 or the positive electrode sheet according to claim 10.

Description

Lithium iron phosphate cathode material, preparation method thereof, cathode plate and secondary battery Technical Field The invention relates to the technical field of battery anode materials, in particular to a lithium iron phosphate anode material, a preparation method thereof, an anode plate and a secondary battery. Background With the development of new energy automobiles, the competition is more and more vigorous, the requirements on the cost performance are higher, the requirements on the continuous voyage mileage of the new energy automobiles are higher, the new energy automobiles are low in price, the cost ratio of the battery in the new energy automobiles is generally over 40%, the cost performance of the new energy automobiles is directly determined, and the cost ratio of the positive electrode material in the battery is over 30%, so that the cost of the positive electrode material is reduced, the performance of the positive electrode material is improved, and the competitiveness of the new energy automobiles can be effectively improved. The lithium iron phosphate has the advantages of low cost, high safety and the like, but the ratio of the lithium iron phosphate as a positive electrode material of a battery in a new energy automobile is higher and higher, and how to continuously improve the performance of the lithium iron phosphate and continuously reduce the production cost of the lithium iron phosphate is the key of the stable development of the lithium iron phosphate. In view of this, the present invention has been made. Disclosure of Invention In view of the technical problems in the background art, the application provides a lithium iron phosphate cathode material, a preparation method thereof, a cathode plate and a secondary battery, and aims to solve the problems that the existing lithium iron phosphate cathode material still has lower performance and higher production cost. In a first aspect, the embodiment of the application provides a lithium iron phosphate borate positive electrode material, which has a chemical general formula of Li xFeTiyPzBwO(4z+3w+2y)/C, wherein x, y, z and w are all non-0 positive numbers, x is more than or equal to 1.02 and less than or equal to 1.05,0.01 and less than or equal to y and less than or equal to 0.05,0.92 and less than or equal to z and less than or equal to 0.95, w is more than or equal to 0.05 and less than or equal to 0.15, and the mass fraction of carbon element is 1.00% -1.35% based on 100% of the mass of the lithium iron phosphate positive electrode material. The lithium iron phosphate borate positive electrode material provided by the embodiment of the application adopts trivalent titanium for cation doping, adopts boron element for anion doping, and is coated with carbon, so that the trivalent titanium has larger ionic radius and more defects, thereby ensuring that the lithium iron phosphate borate positive electrode material has better ionic conductivity and higher capacity, the boron element is doped in the form of borate ions, the molar mass of borate is smaller than that of phosphate, the capacity of the lithium iron phosphate borate positive electrode material is improved, and the carbon serving as a coating layer is beneficial to improving the conductivity of the lithium iron phosphate borate positive electrode material and the cycle stability. In some embodiments, the lithium iron phosphate borate material has a D10 particle size of 0.5 μm or less, a D50 particle size of 1.60 μm or less, and a D90 particle size of 19.00 μm or less. In the embodiment, the particle size of the lithium iron phosphate cathode material is more uniform, so that the capacity and the cycle stability of the battery prepared by taking the lithium iron phosphate cathode material as the cathode material are improved. In some embodiments, the pH value of the lithium iron phosphate borate positive electrode material is 8.50-9.00, so that the subsequent process of preparing the positive electrode slurry is more beneficial to homogenate, and the preparation of the positive electrode plate with uniform dispersion and stable performance of the positive electrode material is also more beneficial. In some embodiments, the lithium iron phosphate borate positive electrode material has a compacted density of 2.35 g/mL-2.50 g/mL, a specific surface area of 10.1m 2/g～14.3m2/g, and a powder resistivity of 4.0 Ω cm-13.0 Ω cm. In the embodiment, the compaction density of the lithium iron phosphate borate cathode material is higher, the specific surface area is larger, the powder resistivity is lower, and further the capacity of a battery formed by adopting the lithium iron phosphate borate cathode material is improved. In some embodiments, the lithium iron phosphate cathode material has an iron dissolution of 3.0ppm to 10.0ppm, an elemental iron of 0.01ppm to 0.05ppm, a chloride ion of 40.0ppm to 80.0ppm, a water content of 280ppm to 350ppm, a free lithium of 140ppm to 200ppm,