A composite current collector and its preparation method and application

Abstract

The present invention provides a composite current collector and its preparation method and application. The composite current collector includes a polymer support layer and a reinforced modification layer located on at least one side of the polymer support layer, and a metal layer is further provided on the surface of the reinforced modification layer; the reinforced modification layer and the polymer support layer are crosslinked and connected through functional groups; the reinforced modification layer includes a conductive metal modification layer. In the present invention, the reinforced modification layer and the polymer support layer are crosslinked and connected through functional groups, which improves the bonding strength, and at the same time also enhances the strength and bonding strength of the support layer; and the conductive metal in the reinforced modification layer provides a large number of deposition sites for the deposition of the metal layer, thereby obtaining a composite current collector with high support strength, high bonding strength and low sheet resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and relates to a composite current collector and a preparation method and application thereof. Background Art

[0002] Compared with mainstream chemical batteries, lithium-ion batteries have advantages such as high energy density, wide voltage window, and long service life, and are widely used in high-value-added consumer electronics fields and power battery fields. Some institutions predict that the global electric vehicle sales volume will reach 18 million in 2025, and the compound growth rate from 2021 to 2025 will be 36%; in such a rapidly developing industry, people's requirements for the lightweight and high energy density of battery cells are gradually increasing, and at the same time, the cost reduction of battery cells in the consumer market is also extremely challenging. The energy density of traditional lithium-ion battery cathode materials has approached the theoretical value, and how to further improve the energy density of lithium-ion batteries is an urgent problem for lithium battery enterprises. Metal foil is the carrier and current collector of the positive and negative electrode materials of lithium batteries. Starting from the requirement of improving the mass energy density / volume energy density of lithium batteries, the mass ratio / volume ratio of the current collector in lithium batteries should be as low as possible. Therefore, the current collector is developing towards thinner, microporous, high tensile strength, high elongation rate, and composite directions, and the application of polymer-coated metal composite current collectors to replace traditional pure metal current collectors is gradually mature. The composite current collector with low cost and high quality has positive significance for the development of power batteries.

[0003] Currently, the common preparation methods of composite current collectors are mainly obtained by plating corresponding metal layers on the surface of polymer support layers through methods such as vacuum evaporation, vacuum magnetron sputtering, and electroplating with water. For example, CN111987320A relates to a current collector with a three-dimensional network three-dimensional structure and a preparation method and application thereof. The current collector with the three-dimensional network three-dimensional structure includes: a polymer current collector matrix and a metal conductive layer; the polymer current collector matrix has a three-dimensional network pore structure; the metal conductance layer is composed of a metal material deposited on the polymer current collector matrix by a physical deposition method. When directly plating metal on the polymer support layer, the physical and chemical properties of the polymer and the metal are quite different, and there is no corresponding chemical structure to chelate the two, which often results in weak bonding force between the metal layer and the polymer layer. The stress caused by the rolling of the electrode sheet and the cyclic expansion of the battery cell will cause peeling and falling off of the metal layer and the polymer layer.

[0004] To solve the above problems, a transition layer is constructed between the polymer support layer and the metal layer to enhance the bonding force between the metal and the polymer. It mainly includes the following aspects: (1) First, magnetron sputtering / alkaline electroplating / electroless plating a transition layer such as Cu, Ni, Cr, NiCu alloy, NiCr alloy, etc. on the polymer support layer, and then depositing the target metal layer by evaporation sputtering / hydroelectroplating. This method is beneficial to the subsequent coating deposition, but there is no corresponding bonding when the metal is in direct contact with the polymer, and the improvement of the two-phase bonding effect is limited. (2) First, coat a layer of ceramic slurry on the surface of the polymer support layer. The slurry contains an organic binder, which can effectively bond the polymer and the ceramic. At the same time, the ceramic enhances the strength of the polymer support layer; however, the ceramic is insulating, which hinders the subsequent electron transmission and increases the internal resistance of the battery cell. (3) Coat a layer of conductive carbon slurry on the polymer support layer. Carbon can effectively promote electron transmission, but the binder itself is an oligomer, and the strength of the polymer support layer after coating depends on the support layer itself, and the improvement effect is relatively single.

[0005] Therefore, how to improve the support strength of the current collector in the polymer layer, enhance the bonding force between the polymer layer and the metal layer, and reduce the sheet resistance of the current collector is a technical problem that needs to be solved urgently. Summary of the Invention

[0006] The purpose of the present invention is to provide a composite current collector, its preparation method and application. In the present invention, the enhanced modification layer and the polymer support layer are cross-linked through functional groups, which improves the bonding strength and also enhances the strength of the support layer; and the conductive metal in the enhanced modification layer provides a large number of deposition sites for the deposition of the metal layer, thereby obtaining a composite current collector with high support strength, high bonding strength and low sheet resistance.

[0007] To achieve the purpose of this invention, the following technical solutions are adopted:

[0008] In the first aspect, the present invention provides a composite current collector, which includes a polymer support layer and an enhanced modification layer located on at least one side of the polymer support layer, and a metal layer is further provided on the surface of the enhanced modification layer; the enhanced modification layer and the polymer support layer are cross-linked through functional groups; the enhanced modification layer includes a conductive metal modification layer.

[0009] The polymer support layer in the present invention has been pretreated, and certain functional groups are formed on its surface, which are cross-linked with the enhanced modification layer through functional groups, improving the bonding strength and mechanical properties of the support layer; and the conductive metal in the enhanced modification layer provides a large number of deposition sites for the deposition of the metal layer, and the conductive metal is also beneficial to current transmission, thereby obtaining a composite current collector with high support strength, high bonding strength and low sheet resistance.

[0010] In the enhanced modification layer of the present invention, there is not only conductive metal, but also other substances that can crosslink and connect with the functional groups after pretreatment of the polymer support layer. If there is no crosslinking connection of functional groups between the polymer support layer and the enhanced modification layer, the characteristic of high bonding strength cannot be achieved; if the enhanced modification layer is not included, it will result in poor bonding between the metal layer and the support layer and easy peeling off.

[0011] Preferably, the thickness of the polymer support layer is 2.5 - 6 μm, such as 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm or 6 μm, etc.

[0012] Preferably, the polymer in the polymer support layer includes any one or a combination of at least two of polyurethane, polyamide, polyimide, polybenzimidazole, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylenediamine terephthalate), polyterephthalate, polyvinyl formal, polyvinyl butyral or polyvinyl acetate.

[0013] In the present invention, a film obtained from the above polymer or its derivative is used as the polymer support layer, and then it is pretreated.

[0014] Preferably, the thickness of the enhanced modification layer is ≤ 1 μm, such as 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1 μm, etc.

[0015] Preferably, the conductive metal modification layer includes metal powder, thermosetting resin, coupling agent and curing agent.

[0016] In the conductive metal modification layer provided by the present invention, the thermosetting resin, coupling agent and curing agent can carry out crosslinking reaction with the functional groups generated on the surface of the polymer support layer, enhancing the bonding effect, and can also enhance the strength of the support layer and improve its mechanical properties.

[0017] Preferably, the metal powder includes any one or a combination of at least two of gold powder, silver powder, aluminum powder, nickel powder, copper powder or cadmium powder, and preferably silver powder.

[0018] In the present invention, the silver powder enhances the conductivity of the surface of the polymer support layer, can reduce the surface resistance of the new composite current collector, and when plating the metal layer subsequently, the metal silver powder provides a large number of metal sites for the deposition of the plating metal, effectively promoting the combination of the metal layer and the support layer; since the conductivity of silver is better than that of other metals, if other metal powders are selected, the increase in surface resistance will be weaker.

[0019] Preferably, the D50 of the silver powder is 10 - 500 nm, such as 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, or 500 nm, etc.

[0020] Preferably, the curing temperature of the thermosetting resin ≤ 200 °C, such as 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, or 200 °C, etc.

[0021] Preferably, the thermosetting resin includes any one or a combination of at least two of unsaturated polyester resin, phenolic resin, melamine - formaldehyde resin, furan resin, epoxy resin, polybutadiene resin, thermosetting acrylic resin, or urea - formaldehyde resin.

[0022] Preferably, the coupling agent includes any one or a combination of at least two of vinyl silane coupling agent, amino silane coupling agent, epoxy - based silane coupling agent, mercapto silane coupling agent, or methacryloxy silane coupling agent.

[0023] Preferably, the curing agent includes acid anhydride - type curing agents, and more preferably includes any one or a combination of at least two of phthalic anhydride, tetrahydrophthalic anhydride, glycerol phthalate anhydride, polyazelic anhydride, polysebacic anhydride, tung oil anhydride, 647 anhydride (endo - or exo - adduct of cyclopentadiene and maleic anhydride), chlorendic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, diphenyl ether tetracarboxylic dianhydride, or cyclopentanetetracarboxylic dianhydride.

[0024] Preferably, the thickness of the metal layer is 0.8 - 1.2 μm, such as 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, or 1.2 μm, etc.

[0025] Preferably, the metal in the metal layer includes any one or a combination of at least two of aluminum, copper, nickel, or copper - nickel alloy.

[0026] In a second aspect, the present invention provides a method for preparing a composite current collector as described in the first aspect. The preparation method includes the following steps:

[0027] Pre - treat the polymer film to obtain a polymer support layer, coat the conductive metal paste on at least one side of the polymer support layer, cure it to obtain a reinforced and modified layer, and composite a metal layer on the surface of the reinforced and modified layer to obtain the composite current collector.

[0028] In the preparation method provided by the present invention, after the polymer membrane is pretreated, the surface roughness of the polymer support layer is increased, and corresponding functional groups are generated on the surface of the polymer support layer. These functional groups can undergo cross-linking reactions with the resin, coupling agent, curing agent, etc. in the conductive metal paste coating during curing, improving the bonding effect between the polymer support layer and the enhanced modification layer; and after the cross-linking reaction occurs, the strength of the support layer is enhanced, its mechanical properties are improved, and the conductive metal provides a large number of sites for metal deposition in the subsequent metal layer, promoting the combination of the metal layer and the support layer, thereby obtaining a composite current collector with high support strength, high bonding strength and low sheet resistance, and being adapted to the existing cell preparation process.

[0029] In the present invention, if the polymer membrane is not pretreated, the purpose of cross-linking modification to enhance the binding force cannot be achieved; and if the metal layer is directly plated after pretreatment, it is also not conducive to the combination between the metal layer and the polymer support layer.

[0030] Preferably, the pretreatment includes chemical etching.

[0031] In the present invention, through the method of chemical etching, some polyester bonds on the polymer surface layer can be broken, forming polar functional groups such as carboxyl groups and hydroxyl groups. At the same time, the micro-defects at the broken positions make the surface roughness of the polymer support layer larger, which is more conducive to the attachment of organic / inorganic substances.

[0032] Preferably, the time of the pretreatment is 30-70 min, such as 30 min, 40 min, 50 min, 60 min or 70 min, etc.

[0033] In the present invention, if the pretreatment time is too long, the degree of etching of the polymer membrane will be relatively high, and the surface defects will increase, resulting in a decrease in the mechanical properties of the polymer support layer itself, which is not conducive to the subsequent processing of the composite current collector.

[0034] Preferably, the chemical etching includes acid etching and / or alkali etching.

[0035] Preferably, the conductive metal paste includes metal powder, thermosetting resin, coupling agent and curing agent, and the above substances are mixed to obtain the paste.

[0036] Preferably, in terms of mass parts, the conductive metal paste includes:

[0037]

[0038] Among them, the mass parts of the metal powder can be 75 parts, 78 parts, 80 parts, 83 parts, 85 parts, 88 parts, 90 parts, 93 parts or 95 parts, etc., the mass parts of the thermosetting resin can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts, etc., the mass parts of the coupling agent can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts, etc., and the mass parts of the curing agent can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts, etc.

[0039] The mass parts range provided by the present invention minimizes the usage amount of the metal powder, especially the silver powder, under the condition of meeting the sheet resistance requirement.

[0040] Preferably, drying is carried out before curing.

[0041] Preferably, the curing temperature is 120 - 180 °C, such as 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C or 180 °C, etc.

[0042] For the curing temperature provided by the present invention, if the temperature is too low, it is not conducive to the curing reaction of the thermosetting resin and the coupling agent, while if the temperature is too high, the polymer support layer will shrink and curl, affecting the cross-linking reaction between the support layer and the conductive metal paste.

[0043] Preferably, the method for forming the composite metal layer includes any one or a combination of at least two of evaporation coating, magnetron sputtering or electroplating.

[0044] In a third aspect, the present invention provides an electrode pole piece, which includes the composite current collector as described in the first aspect and an electrode layer located on the surface of the composite current collector.

[0045] In a fourth aspect, the present invention further provides a lithium-ion battery, which includes the electrode pole piece as described in the third aspect.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] After the pretreatment of the polymer film in the present invention, the surface roughness of the polymer support layer is increased, and corresponding functional groups are generated on the surface of the polymer support layer. These functional groups can generate cross-linking reactions with the resin, coupling agent, curing agent, etc. in the conductive metal paste coating during the curing process, improving the bonding effect between the polymer support layer and the enhanced modification layer; and after the cross-linking reaction occurs, the strength of the support layer is enhanced, its mechanical properties are improved, and the conductive metal provides a large number of sites for the metal deposition in the subsequent metal layer, promoting the combination of the metal layer and the support layer, thereby obtaining a composite current collector with high support strength, high bonding strength and low sheet resistance, and being compatible with the existing cell preparation process. Brief Description of the Drawings

[0048] Figure 1 Schematic structural diagram of the composite current collector provided for Example 1.

[0049] Among them, 1 - polymer support layer, 2 - enhanced modification layer, 3 - metal layer. Detailed Description of the Invention

[0050] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0051] Example 1

[0052] This example provides a composite current collector, as Figure 1 shown. The composite current collector includes a polymer support layer 1 and enhanced modification layers 2 on both sides of the polymer support layer 1. A metal layer 3 is further provided on the surface of the enhanced modification layer 2; the enhanced modification layer 2 and the polymer support layer 1 are crosslinked and connected through functional groups.

[0053] The preparation method of the composite current collector is as follows:

[0054] (1) Pretreatment of the polymer support layer: Prepare an 8% NaOH and 8% Na2CO3 pretreatment solution, immerse the polymer support layer (polyethylene terephthalate (PET) film, with a thickness of 4.5 μm) in the pretreatment solution, soak it at 60°C for 60 min, and then wash it multiple times to remove excess alkali salts to obtain the pretreated polymer support layer;

[0055] (2) Coating of conductive silver paste: Mix silver powder, 4,5-epoxy tetrahydrophthalic acid diglycidyl ester, KH-971 coupling agent, KH560 coupling agent, and polyazelaic anhydride curing agent according to the weight ratio of 90:6:1:1:2, disperse them at high speed using a high-speed disperser to obtain a uniform slurry, grind the slurry using a three-roll mill, and finally remove air bubbles after vacuum pumping to obtain a uniformly dispersed conductive silver paste. Coat the conductive silver paste uniformly on the pretreated polymer support layer, with a coating thickness of 0.5 μm. After drying, perform double-sided coating, and then cure it at 160°C to obtain the enhanced modification layers on both sides of the polymer;

[0056] (3) Place the polymer support layer after double-sided coating in a hydroplating device, adjust the current, copper ion concentration, brightener concentration, auxiliary agent concentration, pH value, and electrolyte temperature, and form a layer of copper metal coating with a thickness of 1 μm on the surface of the enhanced modification layer.

[0057] Example 2

[0058] The difference between this example and Example 1 is that in step (2) of this example, the mass ratio of silver powder, diglycidyl 4,5-epoxytetrahydrophthalate, KH-971 coupling agent, KH560 coupling agent and polyazelanic anhydride curing agent is 92:5:0.8:0.8:1.2.

[0059] The remaining preparation methods and parameters are the same as those in Example 1.

[0060] Example 3

[0061] The difference between this example and Example 1 is that in step (2) of this example, the mass ratio of silver powder, diglycidyl 4,5-epoxytetrahydrophthalate, KH-971 coupling agent, KH560 coupling agent and polyazelanic anhydride curing agent is 88:7:1.2:1.2:2.6.

[0062] The remaining preparation methods and parameters are the same as those in Example 1.

[0063] Example 4

[0064] The difference between this example and Example 1 is that the curing temperature in step (2) of this example is 140 °C.

[0065] The remaining preparation methods and parameters are the same as those in Example 1.

[0066] Example 5

[0067] The difference between this example and Example 1 is that the curing temperature in step (2) of this example is 180 °C.

[0068] The remaining preparation methods and parameters are the same as those in Example 1.

[0069] Example 6

[0070] The difference between this example and Example 1 is that the curing temperature in step (2) of this example is 200 °C.

[0071] The remaining preparation methods and parameters are the same as those in Example 1.

[0072] Example 7

[0073] The difference between this example and Example 1 is that the soaking time in step (1) of this example is 30 min.

[0074] The remaining preparation methods and parameters are the same as those in Example 1.

[0075] Example 8

[0076] The difference between this example and Example 1 is that the soaking time in step (1) of this example is 70 min.

[0077] The remaining preparation methods and parameters are the same as those in Example 1.

[0078] Example 9

[0079] The difference between this example and Example 1 is that the soaking time in step (1) of this example is 90 min.

[0080] The remaining preparation methods and parameters are the same as those in Example 1.

[0081] Example 10

[0082] The difference between this example and Example 1 is that the metal powder in step (2) of this example is copper powder.

[0083] The remaining preparation methods and parameters are the same as those in Example 1.

[0084] Comparative Example 1

[0085] The difference between this comparative example and Example 1 is that in this comparative example, the pretreatment in step (1) is not carried out, and the conductive silver paste is directly coated.

[0086] The remaining preparation methods and parameters are the same as those in Example 1.

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 1 is that step (2) is not carried out, and step (3) is directly carried out after step (1).

[0089] The remaining preparation methods and parameters are the same as those in Example 1.

[0090] Comparative Example 3

[0091] The difference between this comparative example and Example 1 is that the pretreatment in step (1) is not carried out, and step (2) is not carried out either. Step (3) is directly carried out, that is, copper is directly plated on both sides of the polymer support layer.

[0092] The remaining preparation methods and parameters are the same as those in Example 1.

[0093] The composite current collectors provided in Examples 1-10 and Comparative Examples 1-3 were subjected to tensile, peel, and sheet resistance performance tests. The test conditions were: 25 °C, humidity of 20-60%, tensile sample width of 15 mm, speed of 10 mm / min. The peel strength was tested by 180° peeling with 3M tape on a tensile testing machine, and the sheet resistance was tested with a four-probe sheet resistance meter. The test results are shown in Table 1.

[0094] Table 1

[0095] Tensile strength (MPa) Peel strength (N / m) Sheet resistance (Ω / □) Example 1 210.5±5 163.5±3 14±3 Example 2 209.8±5 161.6±3 10±3 Example 3 212.0±5 164.3±3 15±3 Example 4 211.2±5 162.8±3 14±3 Example 5 216.3±5 156.6±3 14±3 Example 6 176.4±5 144.1±3 15±3 Example 7 209.7±5 157.3±3 15±3 Example 8 209.9±5 162.5±3 14±3 Example 9 182.8±5 162.9±3 15±3 Example 10 208.5±5 164.0±3 18±3 Comparative Example 1 199.1±5 150.8±3 15±3 Comparative Example 2 158.2±5 110.6±3 25±3 Comparative Example 3 161.7±5 106.8±3 29±3

[0096] From the data results of Example 1 and Examples 4-6, it can be seen that too high curing temperature has a certain impact on the peel strength and tensile strength of the composite current collector. When it exceeds 180 °C, it will cause the polymer support layer to shrink and curl at a higher temperature, affecting the crosslinking reaction between the support layer and the conductive silver paste and its mechanical properties.

[0097] From the data results of Example 1 and Examples 7-9, it can be seen that too long pretreatment time leads to a higher degree of etching of the polymer support layer, increasing the surface defects, and thus the mechanical properties of the support layer itself will decline.

[0098] From the data results of Example 1 and Comparative Example 1, it can be seen that for the polymer support layer without pretreatment, there are no corresponding functional groups to crosslink with the organic components in the conductive metal paste during curing, so the adhesion force will be relatively weak and the peel strength will be relatively low.

[0099] From the data results of Example 1 and Comparative Example 2, it can be seen that the introduction of the conductive metal paste and its curing process not only enhances the tensile strength of the new composite current collector, the bonding force between the metal coating and the polymer support layer, but also effectively reduces the sheet resistance. Due to the presence of silver particles, it plays a promoting role in the subsequent electron transport of the electrode sheet.

[0100] From the data results of Example 1 and Comparative Examples 2 and 3, it can be seen that directly plating metal on the pretreated polymer support layer makes the bonding strength of the current collector low, resulting in poor mechanical properties of the current collector and a significant increase in sheet resistance.

[0101] In summary, after pretreating the polymer film, the surface roughness of the polymer support layer is increased, and at the same time, corresponding functional groups are generated on the surface of the polymer support layer. These functional groups can crosslink with resins, coupling agents, curing agents, etc. during the curing of the conductive metal paste coating, improving the bonding effect between the polymer support layer and the reinforced modification layer; and after the crosslinking reaction occurs, the strength of the support layer is enhanced, its mechanical properties are improved, and the conductive metal provides a large number of sites for metal deposition in the subsequent metal layer, promoting the combination of the metal layer and the support layer, thus obtaining a composite current collector with high support strength, high bonding strength and low sheet resistance, and being compatible with the existing battery cell preparation process.

[0102] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a composite current collector, characterized in that The composite current collector includes a polymer support layer and a reinforced modification layer located on at least one side of the polymer support layer, and a metal layer is further provided on the surface of the reinforced modification layer; the reinforced modification layer and the polymer support layer are crosslinked and connected through functional groups; the reinforced modification layer includes a conductive metal modification layer; The conductive metal modification layer includes metal powder, thermosetting resin, coupling agent and curing agent; In the conductive metal modification layer, the thermosetting resin, coupling agent and curing agent carry out crosslinking reaction with the functional groups generated on the surface of the polymer support layer; the metal powder is silver powder; the thickness of the polymer support layer is 2.5 - 6μm; The preparation method includes the following steps: Pre-treat the polymer film to obtain a polymer support layer, coat the conductive metal paste on at least one side of the polymer support layer, and cure to obtain a reinforced modification layer, and composite a metal layer on the surface of the reinforced modification layer to obtain the composite current collector; The conductive metal paste includes metal powder, thermosetting resin, coupling agent and curing agent; The curing temperature is 120 - 180°C; By mass, the conductive metal paste includes: Metal powder 75 - 95 parts Thermosetting resin 1 - 10 parts Coupling agent 1 - 10 parts Curing agent 1 - 10 parts.

2. The preparation method of the composite current collector according to claim 1, wherein The polymer in the polymer support layer includes any one or a combination of at least two of polyurethane, polyamide, polyimide, polybenzimidazole, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), poly(terephthalate), poly(vinyl formal), poly(vinyl butyral) or poly(vinyl acetate).

3. The preparation method of the composite current collector according to claim 1, wherein, The thickness of the reinforced modification layer ≤ 1μm.

4. The preparation method of the composite current collector according to claim 1, wherein, The D50 of the silver powder is 10 - 500nm.

5. The preparation method of the composite current collector according to claim 1, wherein, The curing temperature of the thermosetting resin ≤ 200°C.

6. The preparation method of the composite current collector according to claim 1, characterized in that, The thermosetting resin includes any one or a combination of at least two of unsaturated polyester resin, phenolic resin, melamine formaldehyde resin, furan resin, epoxy resin, polybutadiene resin, thermosetting acrylic resin or urea formaldehyde resin.

7. The preparation method of the composite current collector according to claim 1, wherein The coupling agent includes any one or a combination of at least two of vinyl silane coupling agent, amino silane coupling agent, epoxy silane coupling agent, mercapto silane coupling agent or methacryloxy silane coupling agent.

8. The preparation method of the composite current collector according to claim 1, wherein, The curing agent includes acid anhydride curing agents.

9. The preparation method of the composite current collector according to claim 1, wherein, The curing agent includes any one or a combination of at least two of phthalic anhydride, tetrahydrophthalic anhydride, glycerol phthalate anhydride, polyazelaic anhydride, polysebacic anhydride, tung oil anhydride, 647 anhydride, chlorendic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, diphenyl ether tetracarboxylic dianhydride or cyclopentanetetracarboxylic dianhydride.

10. The preparation method of the composite current collector according to claim 1, characterized in that, The thickness of the metal layer is 0.8 - 1.2μm.

11. The preparation method of the composite current collector according to claim 1, characterized in that, The metal in the metal layer includes any one or a combination of at least two of aluminum, copper, nickel or copper-nickel alloy.

12. The preparation method of the composite current collector according to claim 1, wherein, The pre-treatment includes chemical etching.

13. The preparation method of the composite current collector according to claim 1, characterized in that, The time of the pre-treatment is 30 - 70min.

14. The method for preparing a composite current collector according to claim 12, wherein The chemical etching includes acid etching and / or alkali etching.

15. The preparation method of the composite current collector according to claim 1, wherein, Before curing, drying is carried out.

16. The preparation method of the composite current collector according to claim 1, characterized in that, The composite method of the metal layer includes any one or a combination of at least two of evaporation plating, magnetron sputtering or electroplating.

17. An electrode sheet, characterized in that, The electrode sheet includes a composite current collector prepared by the preparation method according to any one of claims 1-14, and an electrode layer located on the surface of the composite current collector.

18. A lithium-ion battery, characterized in that, The lithium-ion battery includes the electrode sheet according to claim 17.

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