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CN-122000364-A - Composite current collector and preparation method thereof

CN122000364ACN 122000364 ACN122000364 ACN 122000364ACN-122000364-A

Abstract

The invention relates to a composite current collector and a preparation method thereof. The conductive layer at least comprises a first grain layer and a second grain layer, the first grain layer is arranged between the second grain layer and the substrate layer and is connected with the substrate layer, the average grain size of the first grain layer is 150-1300 nm, and the ratio of the average grain size of the second grain layer to the average grain size of the first grain layer is (1.5-10): 1. Under the stress and thermal action of battery circulation, the structure can obviously inhibit the growth trend of crystal grains, especially the transmission of coarsening phenomena to interfaces, so that the micro roughness and mechanical interlocking capability of the surface of the conductive layer are maintained for a long time, further the decline of peeling strength is facilitated to be delayed, and the structural integrity and reliability of the current collector in long-term circulation are improved.

Inventors

  • QIU GUOCHAO
  • ZHOU JIANGANG
  • 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: a substrate layer; The conductive layer at least comprises a first grain layer and a second grain layer, the first grain layer is arranged between the second grain layer and the substrate layer and is connected with the substrate layer, the average grain size of the first grain layer is 150-1300 nm, and the ratio of the average grain size of the second grain layer to the average grain size of the first grain layer is (1.5-10): 1.
  2. 2. The composite current collector of claim 1 wherein the first seed layer has a thickness of 20% to 50% of the total thickness of the conductive layer and the second seed layer has a thickness of 50% to 80% of the total thickness of the conductive layer.
  3. 3. The composite current collector of claim 1, wherein the conductive layer comprises copper, and the conductive layer is further doped with a doping element having a total content of 0.01 to 2.0 at%, and the doping element comprises one or more of Ag, zn, sn, cr, zr, ti, mg, al.
  4. 4. A composite current collector according to claim 3, wherein the local concentration of the doping element at the grain boundaries is higher than its average concentration inside the grains, and at least part of the grain boundaries are present as reinforcing phase grain boundaries of intermetallic compounds containing the doping element, and/or, The doping elements comprise Cr and Ag, wherein the content of Cr is 0.05-0.5 at% and the content of Ag is 0.1-1.0 at%.
  5. 5. A composite current collector according to claim 3, wherein the concentration of the doping element decreases from the side closer to the base material layer to the side farther from the base material layer, and the concentration gradient thereof is 0.5 to 5 at%/μm.
  6. 6. A composite current collector according to claim 1 wherein the area of grains having {111} orientation in the first grain layer is 40% -70%, and/or, In the second crystal grain layer, the area ratio of the crystal grains with {200} orientation is 50% -80%.
  7. 7. The composite current collector of claim 1, further comprising a transition layer disposed between the first seed layer and the substrate layer, the transition layer comprising an organic-inorganic hybrid material comprising carboxyl or hydroxyl functional groups, and the transition layer having a thickness of 10-100 nm.
  8. 8. The composite current collector of claim 1, wherein a side of the conductive layer remote from the substrate layer is provided with a pore structure, the pore diameter of the pore structure is 50-200 nm, and the pore density is 10 8 ~10 10 pores/cm 2 .
  9. 9. A method for preparing a composite current collector according to any one of claims 1-8, comprising the steps of: Carrying out surface activation treatment on the surface of the substrate layer; metallizing the surface of the substrate layer, and forming a metal seed layer by vacuum sputtering; A conductive layer is deposited on the metallized PET substrate layer by adopting a segmented electrodeposition process, electrolyte used in electrodeposition contains copper ions and doping elements, trace elements comprise one or more of Ag, zn, sn, cr, zr, ti, mg, al, A first stage, depositing and forming a first crystal grain layer under the conditions of the current density of 0.5-2A/dm 2 and the temperature of 20-35 ℃; A second stage, depositing a second crystal grain layer on the first crystal grain layer under the conditions that the current density is 2-8A/dm 2 and the temperature is 30-45 ℃; and carrying out sectional annealing heat treatment on the deposited conductive layer, namely firstly preserving heat for 5-15 min at 120-160 ℃, and then raising the temperature to 180-230 ℃ and preserving heat for 3-10 min.
  10. 10. The method for preparing a composite current collector according to claim 9, wherein the step of performing the sectional annealing heat treatment on the deposited conductive layer comprises the steps of firstly preserving heat at 120-160 ℃ for 5-15 min, then raising the temperature to 180-230 ℃ and preserving heat for 3-10 min, and then further comprises the steps of: Performing micro-hole etching treatment on the surface of the conductive layer, and/or, The electrolyte also comprises an organic carboxylate complexing agent, wherein the organic carboxylate is citrate, tartrate or ethylenediamine tetraacetate.

Description

Composite current collector and preparation method thereof Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a composite current collector and a preparation method thereof. Background With the rapid development of new energy automobiles and energy storage industries, the performance requirements of lithium batteries on current collectors are increasingly improved. The traditional copper foil current collector has the problems of heavy weight, high cost, easy occurrence of reduced binding force in the repeated charge and discharge process and the like. In recent years, PET (polyethylene terephthalate) composite copper foil has been receiving attention because of its light weight, low cost, good flexibility and other advantages. However, in practical application, it is found that in the cyclic charge and discharge process of the lithium battery adopting the PET composite copper foil, due to the stress change generated by lithium ion intercalation/deintercalation and the change of the working temperature of the battery, the size of copper foil grains can be increased, so that the surface of the copper foil tends to be flattened, and the peel strength between the copper foil and the PET substrate is obviously reduced. When serious, the copper foil is partially or largely fallen off, which affects the cycle life and the safety performance of the battery. The conventional solutions at present mainly focus on improving the adhesive performance or surface roughening treatment, but the methods are difficult to fundamentally inhibit the growth trend of copper foil grains under the action of thermal stress, and have limited long-term effect. Disclosure of Invention Based on the above, it is necessary to provide a composite current collector of a lithium battery and a preparation method thereof, which effectively inhibit the growth of crystal grains caused by stress and temperature effect in the cyclic charge and discharge process of the battery by designing a special copper foil microstructure, thereby maintaining the bonding strength between the copper foil and the PET substrate and improving the cycle life and safety of the battery. The composite current collector comprises a substrate layer and a conductive layer, wherein the conductive layer at least comprises a first grain layer and a second grain layer, the first grain layer is arranged between the second grain layer and the substrate layer and is connected with the substrate layer, the average grain size of the first grain layer is 150-1300 nm, and the ratio of the average grain size of the second grain layer to the average grain size of the first grain layer is (1.5-10): 1. In one embodiment, the thickness of the first grain layer is 20% -50% of the total thickness of the conductive layer, and the thickness of the second grain layer is 50% -80% of the total thickness of the conductive layer. In one embodiment, the material of the conductive layer includes copper, and the conductive layer is further doped with a doping element with a total content of 0.01-2.0 at%, where the doping element includes one or more of Ag, zn, sn, cr, zr, ti, mg, al. In one embodiment, the local concentration of the doping element at the grain boundaries is higher than its average concentration inside the grains, and at least part of the grain boundaries are present as strengthening phase grain boundaries of the intermetallic compound comprising the doping element. In one embodiment, the doping elements include Cr and Ag, wherein the Cr content is 0.05-0.5 at% and the Ag content is 0.1-1.0 at%. In one embodiment, the concentration of the doping element decreases from the side close to the substrate layer to the side far from the substrate layer, and the concentration gradient is 0.5-5 at%/μm. In one embodiment, the first die layer has a {111} oriented die area ratio of 40% -70%. In one embodiment, the second die layer has a {200} oriented die area ratio of 50% -80%. In one embodiment, the composite current collector further comprises a transition layer, the transition layer is disposed between the first grain layer and the substrate layer, the transition layer comprises an organic-inorganic hybrid material containing carboxyl or hydroxyl functional groups, and the thickness of the transition layer is 10-100 nm. In one embodiment, a hole structure is arranged on one side surface, far away from the substrate layer, of the conductive layer, the hole diameter of the hole structure is 50-200 nm, and the hole density is 10 8~1010 holes/cm 2. A method for preparing a composite current collector for preparing any one of the above composite current collectors, comprising the steps of: Carrying out surface activation treatment on the surface of the substrate layer; metallizing the surface of the substrate layer, and forming a metal seed layer by vacuum sputtering; Depositing a conductive layer on the metallized PET substrate layer by adoptin