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CN-121172081-B - Battery cell, battery device and electricity utilization device

CN121172081BCN 121172081 BCN121172081 BCN 121172081BCN-121172081-B

Abstract

The application provides a battery monomer, a battery device and an electricity utilization device. The specific surface area relative proportion of carbon structures with different microcosmic forms in the surface layer of the carbon-coated lithium iron phosphate material is regulated, and specifically, when the carbon-coated lithium iron phosphate material has a carbon coating factor eta and the eta is more than or equal to 0.81 and less than or equal to 0.95, the lithium iron phosphate material has high-quality carbon coating, the capacity of the lithium iron phosphate material is favorably exerted, the pole piece dehydration efficiency is obviously improved, and the prepared battery monomer has excellent energy density, cycle performance and processing performance.

Inventors

  • LIU HONGYU
  • BIE CHANGFENG
  • LENG XUE
  • LIU NA

Assignees

  • 宁德时代新能源科技股份有限公司

Dates

Publication Date
20260512
Application Date
20210823

Claims (20)

  1. 1. A battery cell, comprising: the positive pole piece and the negative pole piece are arranged in a laminated manner; The positive electrode plate comprises a positive electrode current collector and a positive electrode film layer positioned on at least one side surface of the positive electrode current collector, wherein the positive electrode film layer comprises olivine-structure lithium-containing phosphate, the olivine-structure lithium-containing phosphate comprises carbon-coated lithium iron phosphate materials, the carbon-coated lithium iron phosphate materials comprise lithium iron phosphate base materials and carbon coating layers positioned on the surfaces of the base materials, Carbon coating factor of the carbon coated lithium iron phosphate material Wherein BET1 is the specific surface area of the mesoporous and macroporous structures of the carbon-coated lithium iron phosphate, BET2 is the total specific surface area of the carbon-coated lithium iron phosphate material, and eta is more than or equal to 0.81 and less than or equal to 0.95; The battery cell includes an electrolyte including a solvent including ethylene carbonate and dimethyl carbonate.
  2. 2. The battery cell of claim 1, wherein η is 0.85 +.η≤0.93.
  3. 3. The battery cell of claim 2, wherein η is 0.88 +.η≤0.92.
  4. 4. The battery cell according to any one of claims 1-2, wherein, The BET1 has a value ranging from 5.5 to 9.5m 2 /g and the BET2 has a value ranging from 6.0 to 11.5m 2 /g.
  5. 5. The battery cell according to any one of claim 1 to 3, wherein, The carbon component accounts for 0.7-1.3% of the total mass of the carbon-coated lithium iron phosphate.
  6. 6. The battery cell of claim 5, wherein the carbon component comprises 0.9% -1.3% of the total mass of the carbon-coated lithium iron phosphate.
  7. 7. The battery cell of claim 6, wherein the carbon component comprises 0.9% -1.1% of the total mass of the carbon-coated lithium iron phosphate.
  8. 8. The battery cell according to any one of claim 1 to 3, wherein, The ratio H/D of the thickness H of the carbon coating layer to the average particle diameter D of the carbon-coated lithium iron phosphate is 0.01-0.04.
  9. 9. The battery cell according to any one of claim 1 to 3, wherein, The volume average particle diameter Dv50 of the carbon-coated lithium iron phosphate is 840 nm-3570 nm.
  10. 10. The battery cell of claim 9, wherein the volume average particle size Dv50 of the carbon-coated lithium iron phosphate satisfies 1170 nm ∈dv50 ∈1820-nm.
  11. 11. The battery cell of any one of claims 1-3, wherein the carbon-coated lithium iron phosphate has a powder compaction density of no less than 2.4g/cm 3 .
  12. 12. The battery cell of claim 11, wherein the carbon-coated lithium iron phosphate has a powder compaction density of no less than 2.5g/cm 3 .
  13. 13. The battery cell of claim 12, wherein the carbon-coated lithium iron phosphate has a powder compaction density of no less than 2.6g/cm 3 .
  14. 14. The battery cell of any one of claims 1-3, wherein the graphitization degree of the carbon-coated lithium iron phosphate is 0.15-0.32.
  15. 15. The battery cell of claim 14, wherein the graphitization degree of the carbon-coated lithium iron phosphate is 0.19-0.26.
  16. 16. The battery cell of any one of claims 1-3, wherein the carbon-coated lithium iron phosphate has a powder resistivity of no more than 60 Ω -m.
  17. 17. The battery cell of claim 16, wherein the carbon-coated lithium iron phosphate has a powder resistivity of no more than 30 Ω -m.
  18. 18. The battery cell of claim 17, wherein the carbon-coated lithium iron phosphate has a powder resistivity of no more than 20 Ω -m.
  19. 19. The battery cell of any one of claims 1-3, wherein the lithium iron phosphate substrate is doped with elemental carbon.
  20. 20. The battery cell of claim 19, wherein the lithium iron phosphate substrate is doped with 0.1% to 0.5% elemental carbon, based on the mass of the lithium iron phosphate substrate.

Description

Battery cell, battery device and electricity utilization device The application is a divisional application of patent application 202180083427.0 based on a carbon-coated lithium iron phosphate positive electrode active material, a preparation method thereof, a positive electrode plate containing the same and a lithium ion battery which are filed on the basis of day 08 and 23 of 2021. Technical Field The application relates to the field of electrochemistry, in particular to a battery cell, a battery device and an electricity utilization device. Background Along with the rapid development of the new energy field, the lithium ion battery is widely applied to various large-scale power devices, energy storage systems and various consumer products by virtue of the advantages of excellent electrochemical performance, no memory effect, small environmental pollution and the like, and is particularly widely applied to the fields of new energy automobiles such as pure electric automobiles, hybrid electric automobiles and the like. Among positive electrode active materials commonly used in lithium ion batteries, lithium iron phosphate is one of the most widely used positive electrode active materials in lithium ion batteries currently being industrialized. However, since the gram capacity of lithium iron phosphate is lower than that of ternary materials, in recent years, the improvement of the lithium iron phosphate capacity has been mainly developed as a research and development hot spot. However, only the improvement of the capacity performance of lithium iron phosphate is emphasized, and other performances of the battery, such as cycle performance, processability, etc., are inevitably lost. Therefore, it is desirable to design a lithium ion battery having a high energy density, a high cycle performance, and excellent processability. Disclosure of Invention In view of the problems existing in the background art, the application aims to provide a carbon-coated lithium iron phosphate positive electrode active material which has high capacity exertion, high compaction density and easy dehydration of a pole piece, so that a lithium ion battery has excellent energy density, cycle performance and processing performance, the production efficiency of the battery can be obviously improved, and the production cost of the battery is reduced. The first aspect of the application provides a carbon-coated lithium iron phosphate positive electrode active material, which comprises a lithium iron phosphate substrate and a carbon coating layer positioned on the surface of the substrate, wherein the lithium iron phosphate substrate has a structural general formula LiFe 1-aMaPO4, M is more than one kind selected from Cu, mn, cr, zn, pb, ca, co, ni, sr, nb, ti, a is more than or equal to 0 and less than or equal to 0.01, and the carbon coating factor of the carbon-coated lithium iron phosphate materialWherein BET1 is the specific surface area of the mesoporous and macroporous structures of the carbon-coated lithium iron phosphate, BET2 is the total specific surface area of the carbon-coated lithium iron phosphate, and eta is more than or equal to 0.81 and less than or equal to 0.95. In any embodiment, the eta is selected to be 0.85≤eta≤0.93, and further is selected to be 0.88≤eta≤0.92. In any embodiment, the BET1 has a value ranging from 5.5 to 9.5m 2/g and the BET2 has a value ranging from 6.0 to 11.5m 2/g. In any embodiment, the ratio H/D of the thickness H of the carbon coating layer to the average particle diameter D of the carbon-coated lithium iron phosphate is 0.01 to 0.04. In any embodiment, the carbon component in the carbon coating layer accounts for 0.7% -1.3%, optionally 0.9% -1.3%, and more optionally 0.9% -1.1% of the total mass of the lithium iron phosphate positive electrode active material. In any embodiment, the volume average particle diameter Dv50 of the carbon-coated lithium iron phosphate satisfies 840 nm≤Dv50≤3570 nm, optionally 1170 nm≤Dv50≤1820 nm. In any embodiment, the powder compaction density of the carbon-coated lithium iron phosphate is not less than 2.4g/cm 3, alternatively 2.5g/cm 3, and more alternatively 2.6g/cm 3. In any embodiment, the graphitization degree of the carbon-coated lithium iron phosphate is 0.15-0.32, and optionally 0.19-0.26. In any embodiment, the carbon-coated lithium iron phosphate has a powder resistivity of no more than 60 Ω -m, alternatively no more than 30 Ω -m, and more alternatively no more than 20 Ω -m. A second aspect of the present application provides a method of preparing the positive electrode active material according to the first aspect of the present application, the method comprising the steps of: Providing a lithium iron phosphate substrate; The lithium iron phosphate substrate is subjected to carbon coating to obtain the positive electrode active material, wherein the positive electrode active material comprises a lithium iron phosphate substrate and a carbon coating