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CN-122025649-A - Composite current collector, negative electrode plate, positive electrode plate, secondary battery, power utilization device and preparation method

CN122025649ACN 122025649 ACN122025649 ACN 122025649ACN-122025649-A

Abstract

The application provides a composite current collector, a negative electrode plate, a positive electrode plate, a secondary battery, an electric device and a preparation method, wherein the composite current collector comprises a supporting layer and a conductive layer arranged on at least one side of the supporting layer, and the supporting layer is an organic supporting layer; the expansion coefficient of the composite current collector is more than or equal to 150 Pa.m.

Inventors

  • LIU XIN
  • LIU XIANGHUI
  • HUANG QISEN
  • LI MINGLING
  • LI CHENG

Assignees

  • 宁德时代新能源科技股份有限公司

Dates

Publication Date
20260512
Application Date
20230529

Claims (20)

  1. 1. The composite current collector is characterized by comprising a supporting layer and a conductive layer arranged on at least one side of the supporting layer, wherein the supporting layer is an organic supporting layer; the expansion coefficient of the composite current collector is more than or equal to 150 Pa.m.
  2. 2. The composite current collector according to claim 1, wherein the coefficient of expansion of the composite current collector= (d1×t1- (d2×t2) × (1- α) -d1×q1×α), wherein α=g1/(g1+g2); The thickness of the supporting layer is d1, the tensile breaking strength is T1, the yield strength is Q1, and the elastic modulus is G1; The total thickness of the conductive layer is d2, the tensile breaking strength is T2, and the elastic modulus is G2.
  3. 3. The composite current collector of claim 2, wherein the thickness d1 of the support layer is 2-13 μιη; optionally, the thickness d1 of the support layer is 2.4 μm-8 μm; further alternatively, the thickness d1 of the support layer is 2.8 μm to 6 μm.
  4. 4. A composite current collector according to claim 2 or 3, wherein the tensile breaking strength T1 of the support layer is not less than 200MPa; optionally, the tensile breaking strength T1 of the supporting layer is more than or equal to 300MPa.
  5. 5. The composite current collector according to any one of claims 2 to 4, wherein the yield strength Q1 of the supporting layer is not less than 80MPa; optionally, the yield strength Q1 of the supporting layer is more than or equal to 100MPa.
  6. 6. The composite current collector according to any one of claims 2 to 5, wherein the composite current collector satisfies any one or more of the following characteristics: The total thickness d2 of the conductive layer is 0.6-2.4 mu m, alternatively, the total thickness d2 of the conductive layer is 1-2.4 mu m, further alternatively, the total thickness d2 of the conductive layer is 1.4-2.0 mu m; The single-side thickness d2 s of the conductive layer is 0.3-1.2 mu m, alternatively, the single-side thickness d2 s of the conductive layer is 0.5-1.2 mu m, and further alternatively, the single-side thickness d2 s of the conductive layer is 0.7-1.0 mu m; The thickness D a of the composite current collector is 3-15 mu m, alternatively, the thickness D a of the composite current collector is 3-10 mu m, and further alternatively, the thickness D a of the composite current collector is 4.4-6 mu m.
  7. 7. The composite current collector according to any one of claims 2 to 6, wherein the tensile breaking strength T2 of the conductive layer is not less than 250MPa; Optionally, the tensile breaking strength T2 of the conductive layer is more than or equal to 300MPa.
  8. 8. The composite current collector according to any one of claims 2 to 7, wherein the composite current collector satisfies any one or more of the following characteristics: the elastic modulus G1 of the supporting layer is more than or equal to 2GPa, alternatively, the elastic modulus G1 of the supporting layer is more than or equal to 3GPa; the elastic modulus G2 of the conductive layer is 40 GPa-70GPa, alternatively, the elastic modulus G2 of the conductive layer is 45 GPa-55GPa; The alpha is 0.045-0.30, optionally 0.05-0.15, and further optionally 0.055-0.12.
  9. 9. The composite current collector according to any one of claims 2 to 8, wherein an expansion coefficient of the composite current collector is not less than 200 Pa m; Optionally, the expansion coefficient of the composite current collector is more than or equal to 250 Pa m.
  10. 10. The composite current collector according to any one of claims 1 to 9, wherein the material of the support layer is a polymer-based material.
  11. 11. The composite current collector according to any one of claims 1 to 9, wherein the material of the support layer is a polymer matrix composite.
  12. 12. The composite current collector of claim 10 wherein the polymer component in the support layer comprises one or more of polyimide, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene oxide, polyphenylene sulfide, polyethylene glycol, a sulfur-nitride-based polymer material, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy, phenolic resin, and derivatives of the foregoing materials, crosslinks of the foregoing materials, and copolymers of the foregoing materials.
  13. 13. The composite current collector of claim 10 wherein the polymer component in said support layer comprises an acrylonitrile-butadiene-styrene copolymer.
  14. 14. The composite current collector according to any one of claims 1 to 13, wherein the polymer component in the support layer comprises polyimide, the polyimide comprising one or both of a benzene-type polyimide and a biphenyl-type polyimide; Optionally, the polymer component in the support layer comprises biphenyl polyimide; further optionally, the supporting layer comprises biphenyl polyimide with a mass ratio of more than or equal to 50%; Still further optionally, the support layer comprises biphenyl polyimide with a mass ratio of 80% or more; still further alternatively, the material of the supporting layer is biphenyl polyimide.
  15. 15. The composite current collector of any of claims 1-14 wherein said conductive layer comprises a metallic material comprising one or more of copper and copper alloy.
  16. 16. The composite current collector of any of claims 1-15 wherein said conductive layer comprises a metallic material comprising one or more of aluminum and an aluminum alloy.
  17. 17. A negative electrode sheet comprising the composite current collector of any one of claims 1-15.
  18. 18. The negative electrode tab of claim 17, comprising the composite current collector and a negative electrode film layer disposed on at least one side of the composite current collector, at least one of the negative electrode film layers comprising a negative electrode active material layer, any of the negative electrode active material layers independently containing a negative electrode active material comprising one or more of graphite and a silicon-based material.
  19. 19. A positive electrode sheet comprising the composite current collector of any one of claims 1 to 14 and 16.
  20. 20. The positive electrode tab of claim 19 comprising the composite current collector and a positive electrode film layer disposed on at least one side of the composite current collector, at least one of the positive electrode film layers comprising a positive electrode active material layer, any one of the positive electrode active material layers independently containing a positive electrode active material comprising a lithium ion material; optionally, the positive electrode active material includes a lithium transition metal oxide; Further alternatively, the positive electrode active material includes lithium nickel cobalt manganese oxide.

Description

Composite current collector, negative electrode plate, positive electrode plate, secondary battery, power utilization device and preparation method RELATED APPLICATIONS The application is a divisional application of a Chinese patent application with the application number 202310617611X, named as 'composite current collector, negative electrode plate, secondary battery, electricity utilization device and preparation method' applied on 29 months of 2023, and is incorporated herein by reference in its entirety. Technical Field The application relates to the technical field of secondary batteries, in particular to a composite current collector, a negative electrode plate, a positive electrode plate, a secondary battery, an electricity utilization device and a preparation method. Background Along with the gradual popularization of secondary battery technologies such as lithium ion batteries in the fields of consumer electronics, electric automobiles, energy storage power stations and the like, the requirements on the energy density of the secondary batteries are also higher and higher. The composite current collector formed by introducing the polymer-based support layer on the basis of the metal current collector has lighter density under the condition of the same thickness, and has special advantages in terms of safety and cost. However, the processability of the composite current collector is poor, and further popularization and application of the composite current collector are seriously affected. Therefore, further development of new products of the composite current collector is necessary. Disclosure of Invention In view of the above, the present application provides a composite current collector, a negative electrode tab, a positive electrode tab, a secondary battery, an electric device, and a method of manufacturing the same. The composite current collector can have significantly improved processability while maintaining good energy density. In a first aspect, the present application provides a composite current collector, including a support layer and a conductive layer disposed on at least one side of the support layer, where the support layer is an organic support layer; the thickness of the supporting layer is denoted as d1, the tensile breaking strength is denoted as T1, the yield strength is denoted as Q1, and the elastic modulus is denoted as G1; The total thickness of the conductive layer is denoted as d2, the tensile breaking strength is denoted as T2, and the elastic modulus is denoted as G2; the composite current collector satisfies the following conditions (d1×T1- (d2×T2) × (1- α) -d1×Q1×α) > Pa ·m, wherein α=G1/(G1+G2). For a composite current collector comprising an organic support layer and a conductive layer, by reasonably matching the thickness d1 of the support layer, the tensile breaking strength T1, the yield strength Q1 and the elastic modulus G1, and the thickness d2 of the conductive layer, the tensile breaking strength T2 and the elastic modulus G2, while also finely adjusting the distribution of the elastic modulus between the support layer and the conductive layer by using the distribution coefficient α=g1/(g1+g2), it is possible to define (d1×t1- (d2×t2) × (1- α) -d1×q1×α) as the coefficient of expansion of the composite current collector, which may represent the residual force that can be tolerated per unit width of the support layer when the composite current collector is subjected to elastic deformation into the yield deformation stage under stress, which may substantially correspond to the residual force after deducting the elastic limit when the composite current collector is broken, the greater the residual force, the greater the elongation of the composite current collector at the time of plastic deformation at the later stage will be made based on the stress-strain relationship. When the expansion coefficient of the composite current collector is more than or equal to 150, the composite current collector has higher fracture elongation and better mass production processability, is favorable for reducing the fracture of the composite current collector in the pole piece processing process, improves the processing quality, can reduce or avoid the increase of local interface side reaction caused by wrinkling of the pole piece in the charging and discharging process, further improves the battery cycle performance, is favorable for reducing the cracking problem possibly caused by gradually increasing the expansion force of the pole piece in the later stage of the battery cell cycle, and is favorable for improving the cycle performance and the safety and reliability of the battery cell. In some embodiments, the support layer has a thickness d1 of 2 μm to 13 μm; optionally, the thickness d1 of the support layer is 2.4 μm-8 μm; further alternatively, the thickness d1 of the support layer is 2.8 μm to 6 μm. The thicker the composite current collector, the lower the energy density o