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WO-2026091348-A1 - LITHIUM-ION SECONDARY BATTERY, POSITIVE ELECTRODE ACTIVE MATERIAL AND ELECTRIC DEVICE

WO2026091348A1WO 2026091348 A1WO2026091348 A1WO 2026091348A1WO-2026091348-A1

Abstract

The present application relates to a lithium-ion secondary battery, a positive electrode active material and an electric device. The lithium-ion secondary battery comprises a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode film layer; the positive electrode film layer comprises a positive electrode active material; the positive electrode active material comprises a mixture of a granular first lithium-containing phosphate material and a rod-shaped second lithium-containing phosphate material; the X-ray diffraction patterns of the first and second lithium-containing phosphate materials have a diffraction peak A of between 29° and 30° and a diffraction peak B of between 25° and 26°, and the intensity ratio of the diffraction peak A to the diffraction peak B is I A /I B ; the second lithium-containing phosphate material satisfies: 1.1≥I A /I B ≥0.95; the ratio I A /I B of the second lithium-containing phosphate material is greater than the ratio I A /I B of the first lithium-containing phosphate material; and the first lithium-containing phosphate material and the second lithium-containing phosphate material both contain carbon coating layers, and the coating amount of carbon in the first lithium-containing phosphate material is less than the coating amount of carbon in the second lithium-containing phosphate material.

Inventors

  • CHEN, XUDONG
  • BIE, Changfeng
  • LIU, HONGYU
  • HE, SIYUAN
  • Li, Xiaojing
  • Lin, Yingxi
  • JIA, Xiaoyang
  • NI, Huan
  • LIU, Na

Assignees

  • 宁德时代新能源科技股份有限公司

Dates

Publication Date
20260507
Application Date
20250227
Priority Date
20241104

Claims (20)

  1. A lithium-ion secondary battery includes a positive electrode sheet comprising a positive electrode film layer; the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprising a mixture of a first lithium-containing phosphate material containing granules and a second lithium-containing phosphate material containing rods, wherein the first lithium-containing phosphate material and the second lithium-containing phosphate material have diffraction peak A between 29° and 30° and diffraction peak B between 25° and 26° in an X-ray diffraction pattern, and the intensity ratio of diffraction peak A to diffraction peak B is IA / IB ; the second lithium-containing phosphate material satisfies: 1.1 ≥ IA / IB ≥ 0.95; the IA / IB ratio of the second lithium-containing phosphate material is greater than that of the first lithium-containing phosphate material; both the first and second lithium-containing phosphate materials contain a carbon coating layer, the carbon coating amount in the first lithium-containing phosphate material is less than that in the second lithium-containing phosphate material, and the carbon coating amount refers to the mass content of carbon.
  2. The lithium-ion secondary battery as described in claim 1, wherein, in the positive electrode active material, the mass content of the first lithium phosphate material is greater than or equal to the mass content of the second lithium phosphate material.
  3. The lithium-ion secondary battery according to any one of claims 1 to 2, wherein, in the total mass of the first lithium-containing phosphate material and the second lithium-containing phosphate material, the mass content of the second lithium-containing phosphate material is 5% to 50%.
  4. The lithium-ion secondary battery as described in claim 3, wherein, in the total mass of the first lithium-containing phosphate material and the second lithium-containing phosphate material, the mass content of the second lithium-containing phosphate material is 10% to 30%.
  5. The lithium-ion secondary battery according to any one of claims 1 to 4, wherein at least one of the following conditions is satisfied: (1) The carbon coating content in the first lithium phosphate material is 1% to 1.3%; (2) The carbon coating content in the second lithium phosphate material is 1.3% to 1.8%; (3) The difference between the carbon coating amount in the second lithium phosphate material and the carbon coating amount in the first lithium phosphate material is 0.1% to 0.8%.
  6. The lithium-ion secondary battery according to any one of claims 1 to 5, wherein at least one of the following conditions is satisfied: (1) The first lithium phosphate material satisfies: 0.92 ≥ I<sub> A</sub> / I<sub> B </sub> ≥ 0.8; (2) The second lithium phosphate material satisfies: 1.05≥IA / IB≥0.95 .
  7. The lithium-ion secondary battery according to any one of claims 1 to 6, wherein the average primary particle size of the first lithium phosphate material is greater than the average primary particle size of the second lithium phosphate material.
  8. The lithium-ion secondary battery as described in claim 7, wherein the ratio of the average primary particle size of the first lithium phosphate material to the average primary particle size of the second lithium phosphate material is 3 to 40.
  9. The lithium-ion secondary battery according to any one of claims 1 to 8, wherein the average particle size of the primary particles of the first lithium phosphate material is 700 nm to 1500 nm.
  10. The lithium-ion secondary battery as described in claim 8, wherein the average particle size of the primary particles of the first lithium phosphate material is 700 nm to 1200 nm.
  11. The lithium-ion secondary battery according to any one of claims 1 to 10, wherein the average particle size of the primary particles of the second lithium phosphate material is 20 nm to 260 nm.
  12. The lithium-ion secondary battery as described in claim 11, wherein the average particle size of the primary particles of the second lithium phosphate material is 80 nm to 160 nm.
  13. The lithium-ion secondary battery according to any one of claims 1 to 12, wherein the aspect ratio of the second lithium phosphate material is (1.1 to 3.9):1.
  14. The lithium-ion secondary battery according to any one of claims 1 to 13, wherein at least one of the following conditions is satisfied: (1) The compaction density of the first lithium phosphate material under a pressure of 3t is 2.38 g/ cm³ to 2.68 g/ cm³ . (2) The compacted density of the second lithium phosphate material under a pressure of 3t is 1.85 g/ cm³ to 2.35 g/ cm³ . (3) The compaction density of the positive electrode film layer on one side of the positive electrode sheet is 2.45 g/ cm3 to 2.8 g/ cm3 .
  15. The lithium-ion secondary battery according to any one of claims 1 to 14, wherein the lithium-containing phosphate in the first lithium-containing phosphate material and the second lithium-containing phosphate material has the chemical formula Li β Fe α M (1-α) PO 4 , wherein 0.2≤α≤1, 1≤β≤1.1, and M includes at least one of Ti, V, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, and Sr.
  16. The lithium-ion secondary battery according to any one of claims 1 to 5, wherein the total mass content of the positive electrode active material in the positive electrode film layer is 92% to 98%.
  17. The lithium-ion secondary battery according to any one of claims 1 to 16, wherein the positive electrode film layer further comprises a binder, and the positive electrode film layer satisfies at least one of the following characteristics: (1) In the positive electrode film layer, the mass content of the binder is 1% to 4%; (2) The adhesive includes at least one of polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, sodium carboxymethyl cellulose, polyurethane, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorinated acrylate resin.
  18. The lithium-ion secondary battery according to any one of claims 1 to 17, wherein the positive electrode film further comprises a conductive agent, and the positive electrode film satisfies at least one of the following characteristics: (1) In the positive electrode film layer, the mass content of the conductive agent is 1% to 4%; (2) The conductive agent includes at least one of conductive carbon, metal fiber and organic conductive polymer.
  19. The lithium-ion secondary battery as described in claim 18 is characterized in that the conductive carbon includes at least one of carbon nanotubes, graphite, graphene, carbon black, Ketjen black, carbon dots, and carbon nanofibers, and the carbon black includes acetylene black.
  20. The lithium-ion secondary battery according to any one of claims 1 to 19, wherein the lithium-ion secondary battery further comprises an electrolyte, the electrolyte comprising an additive, the additive comprising at least one selected from 1-methyl-3-[(3-trimethoxysilyl)-propyl]imidazolium bis(trifluoromethanesulfonamide), alumina-grafted 1-methyl-3-propylpyrrolidine bis(trifluoromethanesulfonic acid)imide, lithium difluorodioxolane borate, fluoroethylene carbonate, and 1,3-dioxane.

Description

Lithium-ion secondary batteries, positive electrode active materials and electrical devices Related applications This application claims priority to Chinese Patent Application No. 2024115563633, filed on November 4, 2024, entitled "Lithium-ion Secondary Battery, Positive Electrode Active Material and Electrical Device", the entire contents of which are incorporated herein by reference. Technical Field This application relates to the field of battery technology, and in particular to a lithium-ion secondary battery, a positive electrode active material, and an electrical device. Background Technology In recent years, with the increasingly wide application of lithium-ion rechargeable batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Among them, lithium iron phosphate batteries and other lithium-containing phosphate batteries have achieved tremendous development. With the increasing demand for batteries, higher requirements are being placed on their energy density and low-temperature performance. However, lithium iron phosphate materials and other lithium phosphate materials have inherently low electronic conductivity, which leads to a significant decrease in ion diffusion rate at low temperatures. This, in turn, affects their performance under low-temperature conditions, particularly their energy density, capacity retention, and power performance. Summary of the Invention To achieve the above objectives, the first aspect of this application provides a lithium-ion secondary battery, a positive electrode active material, and an electrical device that exhibit good energy density, capacity retention, and power performance under low-temperature conditions. In a first aspect, this application provides a lithium-ion secondary battery, including a positive electrode sheet, the positive electrode sheet including a positive electrode film layer; the positive electrode film layer including a positive electrode active material, the positive electrode active material including a mixture of a first lithium-containing phosphate material containing granules and a second lithium-containing phosphate material containing rods, wherein the first lithium-containing phosphate material and the second lithium-containing phosphate material have a diffraction peak A between 29° and 30° and a diffraction peak B between 25° and 26° in an X-ray diffraction pattern, the intensity ratio of the diffraction peak A to the diffraction peak B is IA / IB ; the second lithium-containing phosphate material satisfies: 1.1 ≥ IA / IB ≥ 0.95; the IA / IB of the second lithium-containing phosphate material is greater than the IA / IB of the first lithium-containing phosphate material; both the first and second lithium-containing phosphate materials contain a carbon coating layer, the carbon coating amount in the first lithium-containing phosphate material is less than the carbon coating amount in the second lithium-containing phosphate material, the carbon coating amount referring to the mass content of carbon. Thus, the lithium-ion secondary battery of this application mainly improves the positive electrode sheet. Specifically, it achieves a better compact packing effect by grading lithium phosphate materials with different morphologies, such as granular and rod-shaped materials, thereby increasing the compaction density of the positive electrode sheet and thus improving the energy density of the lithium-ion secondary battery. In addition, the second lithium phosphate material has diffraction peaks at specific positions, and the intensity ratio IA / IB of diffraction peak A to diffraction peak B is limited. Furthermore, the differences in carbon coating amount and IA / IB between the first and second lithium phosphate materials are controlled, thereby improving the low-temperature performance of the lithium-ion secondary battery and achieving good energy density, capacity retention, and power performance under low-temperature conditions. In some embodiments, the mass content of the first lithium phosphate material in the positive electrode active material is greater than or equal to the mass content of the second lithium phosphate material. In some embodiments, the mass content of the second lithium phosphate material is 5% to 50% of the total mass of the first lithium phosphate material and the second lithium phosphate material. In some embodiments, the mass content of the second lithium phosphate material is 10% to 30% of the total mass of the first lithium phosphate material and the second lithium phosphate material. As the amount of the second lithium phosphate material increases, the power performance of the battery is improved; however, a large amount of the second lithium phosphate material will affect the energy dens