Search

CN-122000365-A - Composite current collector, preparation method thereof and lithium battery

CN122000365ACN 122000365 ACN122000365 ACN 122000365ACN-122000365-A

Abstract

The invention relates to a composite current collector, a preparation method thereof and a lithium battery, wherein the composite current collector comprises: the metal layer is at least two layers and is respectively provided with two opposite side surfaces of the substrate layer. The overall elastic modulus of the composite current collector at 25 ℃ is less than or equal to 600MPa, and the thickness ratio of the substrate layer to the metal layer is 3-10. The composite current collector has proper flexibility by limiting the overall elastic modulus of the composite current collector to be less than or equal to 600MPa at 25 ℃, and the thickness ratio of the substrate layer to the metal layer to be 3-10, so that the flexibility of the substrate layer and the structural support of the metal layer are balanced, and the performance imbalance caused by the excessive thickness or the excessive thinness of a single layer body is avoided. The design is favorable for inhibiting the growth of lithium dendrites and preventing the lithium dendrites from penetrating through the diaphragm, can improve the safety performance of the battery, and is favorable for balancing the flexibility and the structural stability of the composite current collector, so that the structural integrity of the battery in the assembly and circulation processes is ensured.

Inventors

  • ZHOU JIANGANG
  • QIU GUOCHAO
  • TANG CHUNMING

Assignees

  • 哲创(中山)新材料有限公司

Dates

Publication Date
20260508
Application Date
20260226

Claims (10)

  1. 1. A composite current collector, the composite current collector comprising: the composite current collector comprises a substrate layer and a metal layer, wherein the metal layer is at least two layers and is respectively provided with two opposite side surfaces of the substrate layer, the overall elastic modulus of the composite current collector at 25 ℃ is less than or equal to 600 MPa, and the thickness ratio of the substrate layer to the metal layer is 3-10.
  2. 2. The composite current collector of claim 1, wherein the composite current collector has an overall elastic modulus of 300 to 500mpa.
  3. 3. A composite current collector according to claim 1, wherein the flexural rigidity of the composite current collector is 1 to 50 N.mm 2 , and/or, The elastic modulus of the substrate layer is 100MPa to 400MPa.
  4. 4. The composite current collector of claim 1, wherein the thickness of the substrate layer is 1 μm to 10 μm, and/or, The thickness of the metal layer is 0.5-2 mu m.
  5. 5. The composite current collector of claim 1 wherein said metal layer comprises copper and said metal layer has a copper purity greater than or equal to 99.5% and a conductivity greater than or equal to 58MS/m.
  6. 6. The composite current collector of claim 5, wherein the metal layer further comprises trace elements, the trace elements are at least one of Ag, sn and Zn, and the mass fraction of the trace elements is 0.01-0.5wt%.
  7. 7. The composite current collector according to claim 1, wherein the substrate layer is modified PET, the components of the modified PET comprise a PET matrix and a modifier, the modifier is at least one of polyethylene glycol, adipic acid or isophthalic acid, and the mass fraction of the modifier is 1-5wt%.
  8. 8. The composite current collector of claim 7, wherein an antioxidant and an ultraviolet absorber are further added in the substrate layer, the antioxidant is a hindered phenol antioxidant, the addition amount of the antioxidant is 0.1-0.3% of the mass of the PET substrate, the ultraviolet absorber is a benzotriazole ultraviolet absorber, and the addition amount of the ultraviolet absorber is 0.05-0.2% of the mass of the PET substrate.
  9. 9. A method of preparing a composite current collector according to any one of claims 1 to 8, comprising the steps of: the pretreatment of a substrate layer, namely performing plasma cleaning or corona treatment on the PET film to remove oil stains and impurities on the surface; Preparing a transition layer, namely sequentially depositing the transition layer on two sides of the pretreated PET substrate, wherein the sputtering power is 50-200W, the vacuum degree is 1X 10 -3 ~5×10 -3 Pa, and the deposition speed is 0.01-0.05 mu m/min by adopting a magnetron sputtering process; Depositing a metal layer on the surface of the transition layer by adopting a magnetron sputtering or electroplating process, wherein the magnetron sputtering process parameter is that the sputtering power is 100-300W, the vacuum degree is 1 multiplied by 10 -3 ~5×10 -3 Pa, the deposition speed is 0.05-0.2 mu m/min, the electroplating process parameter is that the electroplating liquid is copper sulfate plating liquid or copper alloy plating liquid, the current density is 1-5A/dm < 2 >, and the electroplating temperature is 20-40 ℃; and (3) post-treatment, namely annealing the deposited composite film, wherein the annealing temperature is 80-150 ℃, the heat preservation time is 1-3 hours, if the copper alloy layer is prepared, the passivation treatment is required to be carried out after the annealing, the passivation solution is chromate solution or phosphate solution, the passivation temperature is 25-40 ℃, and the passivation time is 1-5 minutes.
  10. 10. A lithium battery comprising a positive electrode, a negative electrode, a separator, an electrolyte, and the composite current collector of any one of claims 1 to 8, wherein the composite current collector supports a negative electrode active material as a negative electrode current collector.

Description

Composite current collector, preparation method thereof and lithium battery Technical Field The invention relates to the technical field of lithium ion battery materials, in particular to a composite current collector, a preparation method thereof and a lithium battery. Background Lithium ion batteries have been widely used in the fields of new energy automobiles, portable electronic devices, energy storage systems, and the like due to their advantages of high energy density, long cycle life, and the like. The current collector is used as one of the core components of the lithium battery, and has the main functions of bearing active substances and conducting current, and the performance of the current collector directly influences the energy density, the cycling stability and the safety performance of the battery. The traditional lithium battery current collector mostly adopts pure copper foil as a negative electrode material and pure aluminum foil as a positive electrode material, but the pure metal current collector has the defects of high density, high cost, poor flexibility and the like, and limits the development of the lithium battery in the directions of light weight and high energy density. In order to solve the above problems, a composite current collector has been developed, and among them, a PET (polyethylene terephthalate) composite copper foil has been a research hot spot and an industrialization direction in recent years because of its advantages of light weight, high flexibility, low cost, and the like. However, after the conventional PET composite copper foil is practically applied to a lithium battery, the technical problems that lithium dendrites are easy to grow and puncture a diaphragm are easy to occur, namely, in the process of charging and discharging cycles of the lithium battery, uneven deposition of lithium ions on the surface of a negative electrode is easy to occur, needle-shaped lithium dendrites are formed, and along with the increase of the cycle times, the lithium dendrites are continuously grown, but the conventional PET composite copper foil cannot effectively inhibit the growth of the lithium dendrites, so that the lithium dendrites puncture the diaphragm, internal short circuit of the battery is caused, and serious safety problems such as thermal runaway, fire and explosion are caused, so that the large-scale application of the PET composite copper foil in the field of lithium batteries is greatly limited. Disclosure of Invention Based on the above, it is necessary to provide a composite current collector, a preparation method thereof and a lithium battery, which can adapt to and relieve stress generated by growth of lithium dendrites through specific mechanical property regulation, thereby improving intrinsic safety of the lithium battery. The composite current collector comprises a substrate layer and a metal layer, wherein the metal layer is at least two layers and is respectively provided with two opposite side surfaces of the substrate layer, the overall elastic modulus of the composite current collector at 25 ℃ is less than or equal to 600 MPa, and the thickness ratio of the substrate layer to the metal layer is 3-10. In one embodiment, the overall elastic modulus of the composite current collector is 300-500 MPa. In one embodiment, the bending rigidity of the composite current collector is 1-50 N.mm 2. In one embodiment, the elastic modulus of the substrate layer is 100MPa to 400MPa. In one embodiment, the thickness of the substrate layer is 1 μm to 10 μm. In one embodiment, the thickness of the metal layer is 0.5 μm to 2 μm. In one embodiment, the metal layer comprises copper, and the metal layer has a copper purity greater than or equal to 99.5% and a conductivity greater than or equal to 58MS/m. In one embodiment, the metal layer further comprises a trace element, wherein the trace element is at least one of Ag, sn and Zn, and the mass fraction of the trace element is 0.01-0.5wt%. In one embodiment, the substrate layer is modified PET, the components of the modified PET comprise a PET matrix and a modifier, the modifier is at least one of polyethylene glycol, adipic acid or isophthalic acid, and the mass fraction of the modifier is 1-5wt%. In one embodiment, an antioxidant and an ultraviolet absorber are further added into the substrate layer, the antioxidant is a hindered phenol antioxidant, the addition amount of the antioxidant is 0.1-0.3% of the mass of the PET substrate, the ultraviolet absorber is a benzotriazole ultraviolet absorber, and the addition amount of the ultraviolet absorber is 0.05-0.2% of the mass of the PET substrate. The preparation method of the composite current collector comprises the following steps: the pretreatment of a substrate layer, namely performing plasma cleaning or corona treatment on the PET film to remove oil stains and impurities on the surface; Preparing a transition layer, namely sequentially depositing the transition laye