Composite copper foil current collector and preparation method thereof, negative electrode, lithium ion battery and electric equipment

Abstract

The invention discloses a composite copper foil current collector and a preparation method thereof, a negative electrode, a lithium ion battery and electric equipment, and belongs to the technical field of batteries. The composite copper foil current collector comprises a polymer composite layer which comprises a polymer layer and a conductive material layer, the polymer layer has two opposite surfaces, and the conductive material layer is attached to at least one surface of the polymer layer; the polymer composite layer is provided with a first surface and a second surface which are opposite; and the copper layer is attached to the first surface and the second surface of the polymer composite layer. The conductive material is introduced to the surface of the polymer base material and then copper plating is performed, so that the binding force is stronger compared with the binding force between the polymer and copper; meanwhile, the conductive material is compounded on the polymer base material and replaces part of the polymer insulating material to form a coherent conductive network, so that the composite copper foil current collector has higher conductivity; volume expansion hardly occurs in the charging and discharging process, active substances are prevented from falling off from the current collector, and the cycling stability of the battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and in particular, to a composite copper foil current collector, a preparation method thereof, a negative electrode, a lithium-ion battery, and an electrical device. Background Art

[0002] Lithium-ion batteries have been widely used in various fields such as portable electronic products, electric vehicles, and energy storage due to their advantages of small size, high energy density, good rate performance, and flexible design. Especially with the increasing development and popularization of electric vehicles and lithium battery electrochemical energy storage, their cruising range / monomer energy storage capacity and safety requirements have put forward increasingly stringent requirements for the energy density and electrical performance of lithium-ion batteries.

[0003] In the prior art, effectively improving the battery energy density is often achieved by reducing the thickness of the copper foil, and thus improving the battery energy density. Using a new type of composite copper foil as the negative electrode current collector of a lithium-ion battery is an important research direction proposed in recent years for improving the battery energy density, improving the battery performance, and reducing the battery cost.

[0004] However, the improvement effect of the existing composite copper foil structure is limited. For example, directly plating a copper layer on the surface of a polymer material matrix makes the comprehensive performance such as the bonding force of the copper layer, the easy shedding of active substances, the battery energy density, the cycle stability, and the thermal safety performance still need to be improved. Summary of the Invention

[0005] The main purpose of the present application is to provide a composite copper foil current collector, a preparation method thereof, a negative electrode, a lithium-ion battery, and an electrical device to solve the problems of poor bonding force between the polymer substrate and the copper-coated layer, and the need to improve the conductivity of the current collector and the cycle stability of the battery in the prior art.

[0006] To achieve the above object, according to one aspect of the present application, a composite copper foil current collector is provided, which includes:

[0007] A polymer composite layer, including a polymer layer and a conductive material layer. The polymer layer has two opposite surfaces, and the conductive material layer is attached to at least one surface of the polymer layer; the polymer composite layer has a first surface and a second surface that are opposite to each other;

[0008] A copper layer, which is attached to the first surface and the second surface of the polymer composite layer.

[0009] Further, the material of the polymer layer is selected from at least one of polyimide, polyethylene, polypropylene, and polyethylene terephthalate.

[0010] Further, the thickness of the polymer layer is 1-3 μm.

[0011] Further, the overall thickness of the composite copper foil current collector is 3 to 11 μm.

[0012] Further, the conductive material layer is attached to two opposite surfaces of the polymer layer.

[0013] Further, the thickness of the conductive material layer is 20 to 100 nm; for example, 20 to 50 nm.

[0014] Further, the material of the conductive material layer is a conductive carbon material.

[0015] Further, the conductive carbon material is selected from at least one of conductive carbon black, carbon nanotubes, and graphene.

[0016] Further, the copper layer attached to the first surface includes a first copper layer and a second copper layer in sequence in the direction away from the polymer composite layer; the copper layer attached to the second surface is the second copper layer, or includes a first copper layer and a second copper layer in sequence in the direction away from the polymer composite layer; wherein, the first copper layer is a copper layer deposited by chemical vapor deposition; the second copper layer is a copper layer deposited by electrochemistry.

[0017] Further, the thickness of the first copper layer is 20 to 500 nm; for example, 20 to 50 nm.

[0018] Further, the thickness of the second copper layer is 1 to 3 μm.

[0019] Further, through holes penetrating in the thickness direction are formed in the composite copper foil current collector; the first lithiumophilic polymer material is filled in the through holes.

[0020] Further, the aperture of the through hole is 1 to 5 μm; for example, 2 to 3 μm.

[0021] Further, the number of through holes is 20 to 40 through holes formed on the surface of each square millimeter of the composite copper foil current collector.

[0022] Further, taking the direction perpendicular to the thickness direction of the composite copper foil current collector as the horizontal direction, the distance between the center lines of two adjacent through holes in the horizontal direction is 200 to 1000 μm; for example, 300 to 500 μm.

[0023] Further, the first lithiumophilic polymer material is selected from at least one of polyacrylamide, polydopamine, polyethylene oxide, and polyvinyl alcohol.

[0024] According to the second aspect of the present application, there is provided a method for preparing the above composite copper foil current collector, including:

[0025] Step S1: Coating a conductive material slurry on at least one surface of a polymer substrate to form a conductive material layer on the surface of the polymer substrate; the polymer substrate and the conductive material layer form a polymer composite layer;

[0026] Step S2: Deposit copper material on the first surface and the second surface of the polymer composite layer to form a copper layer on the surface of the polymer composite layer, thereby forming a composite copper foil current collector.

[0027] Further, in step S1, the polymer substrate and the conductive material layer are formed into a polymer composite layer through hot extrusion.

[0028] Further, the temperature of the hot extrusion is 250°C to 270°C.

[0029] Further, the equipment for hot extrusion is a hot pair roll.

[0030] Further, in step S1, the conductive material slurry includes a conductive material, a solvent, and a surfactant.

[0031] Further, the solvent is N-methylpyrrolidone and / or dimethylformamide.

[0032] Further, the surfactant is polyacrylic acid and / or polyvinyl alcohol.

[0033] Further, in step S2, depositing the copper material on the two opposite surfaces of the polymer composite layer includes Method I and Method II; wherein,

[0034] Method I includes:

[0035] Step S2-1: Deposit the copper material on the first surface of the polymer composite layer by physical vapor deposition to form a first type of first copper layer;

[0036] Step S2-2: Deposit the copper material on the surface of the first type of first copper layer away from the polymer composite layer by electrochemcial deposition to form a first type of second copper layer; and deposit the copper material on the second surface of the polymer composite layer by electrochemcial deposition to form a first type of second copper layer;

[0037] Method II includes:

[0038] Step S2-1: Deposit the copper material on the first surface and the second surface of the polymer composite layer by physical vapor deposition to form a second type of first copper layer;

[0039] Step S2-2: Deposit the copper material on the two opposite surfaces of the second type of first copper layer away from the polymer composite layer by electrochemcial deposition to form a second type of second copper layer;

[0040] Further, the physical vapor deposition is magnetron sputtering.

[0041] Further, the electrochemcial deposition is electroplating.

[0042] Further, after step S2, step S3 is further included: a through hole is opened through the composite copper foil current collector along the thickness direction thereof.

[0043] Further, a laser drilling machine is used to drill a through hole through the thickness of the composite copper foil current collector along the thickness direction thereof.

[0044] Further, after step S3, step S4 is further included: the composite copper foil current collector with the through hole is placed in a first solution containing a first monomer material and a first photoinitiator. Under the first light irradiation condition, the first monomer material undergoes in-situ self-polymerization on the surface of the copper layer and in the through hole to attach a first lithiumophilic polymer material layer on the surface of the copper layer and fill the first lithiumophilic polymer material in the through hole; the first lithiumophilic polymer layer attached to the surface of the copper layer is removed, and the first lithiumophilic polymer material filled in the through hole is retained.

[0045] Further, the first lithiumophilic polymer material is selected from at least one of polyacrylamide, polydopamine, polyethylene oxide, and polyvinyl alcohol.

[0046] Further, the first light irradiation condition includes ultraviolet lamp irradiation and / or xenon lamp irradiation.

[0047] According to the third aspect of the present application, a negative electrode is provided, including a negative electrode current collector and a negative electrode active material layer; the negative electrode current collector is the above-mentioned composite copper foil current collector or the composite copper foil current collector prepared by the above-mentioned preparation method.

[0048] According to the fourth aspect of the present application, a lithium-ion battery is provided, including a positive electrode, a negative electrode, and an electrolyte; the negative electrode is the above-mentioned negative electrode.

[0049] According to the fifth aspect of the present application, an electrical device is provided, including a power supply; the power supply includes the above-mentioned lithium-ion battery.

[0050] Applying the technical solution of the present application, a composite copper foil current collector, a preparation method thereof, a lithium-ion battery, and an electrical device are provided; by introducing a conductive material on the surface of a polymer substrate and then plating copper, compared with the bonding force between the polymer and copper directly, the bonding force is stronger; at the same time, a conductive material is compounded on the polymer substrate, and the conductive material replaces part of the polymer insulating material, effectively forming a coherent conductive network, so that the composite copper foil current collector as a whole has stronger conductive ability; using the polymer as the current collector substrate, there is almost no volume expansion during the charge and discharge process, avoiding the shedding of active substances from the current collector and improving the battery cycle stability. Description of the Drawings

[0051] The specification drawings constituting a part of the present application are used to provide a further understanding of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0052] Figure 1 Shows a schematic side view structure of the composite current collector according to Embodiment 1 of the present application;

[0053] Figure 2 Shows a schematic side view structure of the composite current collector according to Embodiment 2 of the present application;

[0054] Figure 3 Shows a schematic side view structure of the composite current collector according to Embodiment 3 of the present application;

[0055] Figure 4 Shows a schematic side view structure of the composite current collector according to Embodiment 5 of the present application;

[0056] Figure 5 Shows a schematic side view structure of the composite current collector according to Embodiment 6 of the present application;

[0057] Figure 6 Shows a schematic side view structure of the composite current collector according to Embodiment 7 of the present application;

[0058] Figure 7 Shows a scanning electron microscope image of the surface through-holes of the composite current collector according to Embodiment 5 of the present application.

[0059] Reference numerals:

[0060] 1, polymer layer; 2, conductive material layer; 3, first copper layer (magnetron sputtered copper layer); 4, second copper layer (electroplated copper layer); 5, through-hole; 6, first lithiophilic polymer material. Detailed implementation manners

[0061] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0062] As described in the background art, the composite copper foil current collector often directly deposits a copper layer on the surface of the polymer material matrix. In the current collector with this structure, the bonding force between the copper layer and the polymer material substrate is weak, which easily causes the active substances to fall off, affecting the battery cycle stability and thermal safety performance. The conductivity of the current collector with this structure still needs to be improved.

[0063] According to one aspect of the present application, a composite copper foil current collector is provided, as Figure 1 shown, the composite copper foil current collector includes: a polymer composite layer, including a polymer layer 1 and a conductive material layer 2, the polymer layer 1 has two opposite surfaces, and the conductive material layer 2 is attached to at least one surface of the polymer layer 1; the polymer composite layer has a first surface and a second surface that are opposite to each other;

[0064] A copper layer, the copper layer is attached to the first surface and the second surface of the polymer composite layer.

[0065] The novel composite copper foil current collector of the present application uses a polymer as the current collector substrate. This polymer has almost no volume expansion during charge and discharge, avoiding the shedding of active substances from the current collector, thereby improving the cycle stability of the battery. In particular, by first introducing a conductive material on the surface of the polymer substrate and then plating copper, compared with the bonding force between the polymer and copper directly, its bonding force is stronger. This is because the conductive carbon layer can activate the surface of the substrate and enhance the physical adsorption between the metal material and the polymer material, thereby improving the cycle stability and thermal safety of the battery. At the same time, a conductive material is attached to the polymer substrate, and this conductive material replaces part of the polymer insulating material of the current collector, effectively forming a coherent conductive network, making the overall composite copper foil current collector have stronger conductive ability. Therefore, by improving the composite structure of the current collector, the above novel composite copper foil current collector has good cycle stability, thermal safety and better conductive ability.

[0066] In some embodiments, the material of the polymer layer is selected from at least one of polyimide, polyethylene, polypropylene and polyethylene terephthalate. The above polymers have excellent electrical insulation, chemical stability and mechanical strength, and are suitable for the basic materials of battery current collectors. They also have good plasticity, which is more conducive to better composite molding effects between the polymer layer and the conductive material layer attached to its surface. At the same time, the polymer and the copper layer also have good composite moldability. In particular, when the polymer is polypropylene, it is more suitable as the current collector substrate and has better composite properties with the conductive material.

[0067] In some embodiments, the thickness of the polymer layer is 1-3 μm; for example, the thickness is any value among 1 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm or the range value between any two of them; for example, 1.5-3 μm; or 2 μm for another example. Controlling the thickness of the polymer layer, which is the main substrate of the current collector, within the above thickness range is beneficial to balancing comprehensive properties such as battery energy density, electrochemical performance, mechanical strength, thermal management, and cost. If the thickness of the polymer layer is too thick or too thin, it will affect its comprehensive performance as the main substrate of the current collector. For example, being too thick will affect the battery energy density and weight, and being too thin may affect properties such as insulation and support strength.

[0068] In some embodiments, the conductive material layer 2 is attached to two opposite surfaces of the polymer layer 1. By attaching the conductive material layer to the surface of the polymer layer, the bonding force between the polymer layer and the copper layer can be improved, thereby ensuring good cycle stability of the battery. When the conductive material layer is attached to one surface of the polymer layer, its effect is already better than that of the current collector without attaching the conductive material layer to the surface of the polymer layer. When the conductive material layer is attached to each of the two opposite surfaces of the polymer layer, the bonding force between the polymer and the copper layer can be further improved, thereby optimizing and enhancing the cycle stability of the battery and the overall conductive performance of the current collector.

[0069] In some embodiments, the thickness of the conductive material layer is 20 to 100 nm. For example, the single-sided thickness is any value among 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or a range value between any two of them; for example, 20 to 60 nm; or for example, 20 to 50 nm. The above thickness refers to a layer of conductive material attached to one surface of the polymer layer, and the thickness of this layer is 20 to 100 nm. Another layer of conductive material is attached to the other opposite surface of the polymer layer, and the thickness of this layer is 20 to 100 nm. A layer of conductive material is attached to each of the two opposite surfaces of the polymer, and the thickness of the conductive material layer is the same. Controlling the thickness of the single side of the conductive material layer within 20 to 100 nm can provide a good conductive network without increasing the weight of the current collector, thereby improving the energy density of the battery. This thickness is more conducive to improving the bonding force between the conductive material layer and the polymer layer and the bonding force between the conductive material layer and the copper layer, indirectly improving the bonding force between the polymer and the copper layer, and increasing the stability of the current collector structure. If the single-sided thickness of the conductive material layer is too thin, it is not conducive to the bonding force with the polymer and the copper layer, nor is it conducive to forming a good conductive network. In summary, controlling the thickness of the conductive material layer within the above range can ensure the comprehensive performance such as the conductivity of the current collector, the bonding force between materials, and the lithium-ion transmission effect, especially helping to improve the battery energy density, cycle stability, and thermal safety performance.

[0070] In some embodiments, the material of the conductive material layer is a conductive carbon material or a modified material of the conductive carbon material. For example, the conductive carbon material is selected from at least one of conductive carbon black, carbon nanotubes, and graphene. When the conductive material is selected from carbonaceous materials, due to the strong toughness and tensile strength of carbon nanotubes and carbon fibers, etc., the overall tensile strength and compressive strength of the composite copper foil current collector can be further improved, avoiding the occurrence of short circuits in the battery and reducing the probability of thermal runaway. At the same time, the carbonaceous material has better conductivity, which can further improve the conductive performance of the current collector.

[0071] In some embodiments, as Figure 3 shown, the copper layer attached to the first surface sequentially includes a first copper layer 3 and a second copper layer 4 in the direction away from the polymer composite layer; the copper layer attached to the second surface is the second copper layer 4, or sequentially includes a first copper layer 3 and a second copper layer 4 in the direction away from the polymer composite layer. Among them, the first copper layer 3 is a copper layer deposited by chemical vapor deposition; the second copper layer 4 is a copper layer deposited by electrochemistry.

[0072] In the above-mentioned composite copper foil current collector structure of the present application, the first copper layer or the second copper layer is used as the material layer in direct contact with the electrolyte, and it must be provided on both opposite surfaces of the polymer composite layer; for example, the first copper layer is provided on both opposite surfaces of the polymer composite layer, or the second copper layer is provided on both opposite surfaces; for another example, the first copper layer is sandwiched between the polymer composite layer and the second copper layer, and it can be attached to one surface of the polymer composite layer or on both opposite surfaces of the polymer composite layer; the first copper layer is a copper layer deposited by a physical vapor deposition method. For example, the copper layer deposited by magnetron sputtering is dense and thin, and the bonding strength between the first copper layer and the polymer composite layer is stronger, which can significantly enhance the bonding strength between the subsequently electroplated second copper layer and the substrate, and prevent the copper layer from peeling off during the use of the battery; the first copper layer deposited by magnetron sputtering is used as the metal seed copper layer, and its crystal grains are smaller. The fine crystal grain structure has greater surface energy and higher activity, which can improve the crystal grain quality of the subsequently electroplated copper layer, thereby improving the overall performance of the copper layer; at the same time, the metal seed copper layer deposited by magnetron sputtering has a continuous conductive network, which can improve the conductivity of the substrate, ensure the uniform plating of the second copper layer, that is, the electroplated thickened copper layer, and then obtain a high-quality electroplated copper layer; the second copper layer is electroplated. First, it is easy to obtain a thicker copper layer. Second, the electroplated copper layer has a relatively rough surface, which can increase the contact area with the electrode active layer and provide more electron transport channels to reduce the contact resistance and improve the overall conductivity of the current collector. By first depositing a dense copper layer by magnetron sputtering and then electroplating to thicken the copper layer, the two methods are combined to prepare a composite copper foil current collector with high bonding strength, controllable thickness, good crystallization quality and excellent electrical conductivity, thereby improving the cycle performance and safety of the battery.

[0073] In some embodiments, the single-sided layer thickness of the first copper layer 3 is 20 - 500 nm; the single-sided layer thickness of the second copper layer 4 is 1 - 3 μm; and the overall thickness of the composite copper foil current collector is 3 - 11 μm. For example, the single-sided thickness of the first copper layer is any value among 20 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm or the range value between any two of them; for example, 20 - 60 nm; or for another example, 20 - 50 nm. The single-sided thickness of the second copper layer is any value among 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3.0 μm or the range value between any two of them; for example, 1.5 - 2.5 μm; or for another example, 2.0 μm. The overall thickness of the composite copper foil current collector is any value among 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5.0 μm, 5.5 μm, 6.0 μm, 6.5 μm, 7 μm, 7.5 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm, 10 μm, 10.5 μm, 11.0 μm or the range value between any two of them; for example, 3 - 6 μm. Controlling the thickness of the metal seed copper layer within 20 - 500 nm is beneficial to improving the bonding force between the polymer composite layer and the copper layer, and helps the quality of the subsequent thickened copper layer during plating. Controlling the thickness of the thickened copper layer within 1 - 3 μm helps to improve the overall conductivity of the current collector. If the thickness of the metal seed layer is too thin or too thick, it is not conducive to forming a dense seed layer, providing better bonding force and grain quality. If the thickness of the thickened copper layer is too thick or too thin, it is not conducive to the bonding force with the polymer substrate, and is not conducive to the performance of the overall conductivity of the current collector, the weight of the current collector, the battery energy density, etc. In particular, controlling the thicknesses of the first copper layer, the second copper layer, the conductive layer, and the polymer substrate within 3 - 6 μm is more beneficial to improving the bonding force between the polymer and the copper layer, the conductive performance of the current collector, and the battery cycling performance.

[0074] In some embodiments, as Figure 4 shown, the composite copper foil current collector is provided with a through hole 5 penetrating along its thickness direction; the through hole is filled with a first lithiumophilic polymer material 6. By providing the through hole 5 in the current collector and filling the lithiumophilic polymer in the through hole 5, the overall weight of the current collector can be reduced. The lithiumophilic polymer material in the through hole attracts lithium ions in the electrode active material more, which can promote the uniform deposition of lithium ions on the surface of the current collector, thereby improving the battery cycling performance and the battery energy density.

[0075] In some embodiments, the aperture diameter of the through-holes is 1 - 5 μm; for example, any value among 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or a range value between any two of them; for example, 2 - 3 μm; and for another example, 3 μm. The number of through-holes is 20 - 40 through-holes formed on the surface of the composite copper foil current collector per square millimeter; for example, 25 - 35; and for another example, 30. Taking the thickness direction perpendicular to the composite copper foil current collector as the horizontal direction, the distance between the centerlines of two adjacent through-holes in the horizontal direction is 200 - 1000 μm; for example, any value among 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm or a range value between any two of them; for example, 300 - 900 μm; and for another example, 300 - 500 μm. By setting the aperture size of the through-holes, the number density on the current collector, etc., it is beneficial for lithium ions to be uniformly deposited on the current collector, promoting the battery to have a stable and uniform energy density and cycling performance, and reducing the occurrence of thermal runaway.

[0076] In some embodiments, the first lithium-philic polymer material can be selected from at least one of polyacrylamide, polydopamine, polyethylene oxide, and polyvinyl alcohol. The above polymers have a strong interaction with lithium ions in the active material, such as adsorption, chemical bonding, etc.; which helps to deposit lithium ions; especially when polydopamine is selected, it is more helpful for lithium ion storage, transmission, and uniform deposition on the current collector, and can improve the battery energy density, cycling performance, and thermal stability.

[0077] According to the second aspect of the present application, a method for preparing the above composite copper foil current collector is provided, including:

[0078] Step S1: Coating a conductive material slurry on at least one surface of a polymer substrate to form a conductive material layer on the surface of the polymer substrate; the polymer substrate and the conductive material layer form a polymer composite layer;

[0079] Step S2: Plating a copper material on the first surface and the second surface of the polymer composite layer to form a copper layer on the surface of the polymer composite layer, thereby forming a composite copper foil current collector.

[0080] The method for preparing the above composite copper foil current collector is simple and easy to implement; by improving the composite structure of the current collector, the above composite copper foil current collector has better cycling stability, thermal safety, and better conductive ability.

[0081] In some embodiments, in step S1, the polymer substrate and the conductive material layer are formed into a polymer composite layer after hot extrusion; the temperature of the hot extrusion is 250°C to 270°C; the hot extrusion equipment is a hot pair roll. At the above extrusion temperature, the conductive material is pressed into the surface of the polymer substrate through the hot extrusion roll and partially incorporated into the polymer substrate, so that the polymer substrate and the conductive material better form a whole, which is beneficial to the formation of a stable conductive network.

[0082] In some embodiments, in step S1, the conductive material paste includes a conductive material, a solvent, and a surfactant; the solvent includes N-methylpyrrolidone and dimethylformamide. The surfactant includes polyacrylic acid and polyvinyl alcohol. By making the conductive material into a conductive paste and then attaching the conductive material to the polymer substrate by means of coating or the like, this method is simple to operate.

[0083] In some embodiments, in step S2, plating the copper material on two opposite surfaces of the polymer composite layer includes Method I and Method II; wherein,

[0084] Method I includes:

[0085] Step S2-1: Using chemical vapor deposition to plate the copper material on the first surface of the polymer composite layer to form a first type of first copper layer;

[0086] Step S2-2: Using electroplating to plate the copper material on the surface of the first type of first copper layer away from the polymer composite layer to form a first type of second copper layer; and using electroplating to plate the copper material on the second surface of the polymer composite layer to form a first type of second copper layer.

[0087] For the current collector structure formed by this method, from one surface of the current collector to the opposite surface, it is in turn: the second copper layer, the first copper layer, the polymer composite layer, the second copper layer; or the second copper layer, the polymer composite layer, the first copper layer, the second copper layer.

[0088] Method II includes:

[0089] Step S2-1: Using chemical vapor deposition to plate the copper material on the first surface and the second surface of the polymer composite layer to form a second type of first copper layer;

[0090] Step S2-2: Using electroplating to plate the copper material on two opposite surfaces of the second type of first copper layer away from the polymer composite layer to form a second type of second copper layer.

[0091] For the current collector structure formed by this method, from one surface of the current collector to the opposite surface, it is in turn: the second copper layer, the first copper layer, the polymer composite layer, the first copper layer, the second copper layer.

[0092] In some embodiments, step S2 is followed by step S3: opening through holes along the thickness direction of the composite copper foil current collector; for example, using a laser drill to drill through holes along the thickness direction of the composite copper foil current collector. The opened through holes penetrate the entire current collector, and both ends of the through holes are connected to the outside world; the number, aperture, and spacing of the through holes are as described above. The weight of the current collector can be reduced by opening through holes, and lithium-philic polymers can be filled into the through holes to allow lithium ions to be uniformly deposited, thereby promoting the conductivity of the current collector.

[0093] In some embodiments, step S3 is followed by step S4: placing the composite copper foil current collector with through holes in a first solution containing a first monomer material and a first photoinitiator, and in a first light condition, the first monomer material is self-polymerized in situ on the surface of the copper layer and in the through hole, so that a first lithium-philic polymer material layer is attached to the surface of the copper layer and the first lithium-philic polymer material is filled in the through hole; the first lithium-philic polymer layer attached to the surface of the copper layer is removed, and the first lithium-philic polymer material filled in the through hole is retained. The in-situ polymerization method can form a filling material appropriately according to the characteristics of the through hole structure.

[0094] According to a third aspect of the present application, a negative electrode is provided, comprising a negative electrode current collector and a negative electrode active material layer; the negative electrode current collector is the above-mentioned composite copper foil current collector or the composite copper foil current collector prepared by the above-mentioned preparation method.

[0095] According to a fourth aspect of the present application, a lithium-ion battery is provided, comprising a positive electrode, a negative electrode and an electrolyte; the negative electrode is the negative electrode described above.

[0096] According to a fifth aspect of the present application, there is provided an electrical device, comprising a power supply; the power supply comprises the above-mentioned lithium-ion battery.

[0097] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0098] The raw materials used in the examples of this application are all prior art and can be purchased commercially.

[0099] Example 1

[0100] N-methylpyrrolidone is used as a solvent, conductive graphene and a surfactant are added, and the mixture is stirred thoroughly to form a stable conductive graphene slurry; the conductive graphene is evenly coated on both surfaces of a 2 μm thick PP film, dried at 100°C, and then subjected to hot roller extrusion in an ambient temperature of 260°C and then cooled to room temperature, so that the conductive graphene is extruded into the surface of the PP body, the thickness of the conductive graphene layer is 20 nm, and a conductive graphene-modified PP substrate is obtained.

[0101] The obtained conductive graphene-modified PP substrate was successively cleaned with acetone and ethanol, then washed with a large amount of deionized water, taken out and dried in an oven at a constant temperature of 100 °C, and then placed in an acidic plating solution for electroplating to obtain an electroplated thickened copper layer with a single-sided thickness of 2 μm. The obtained composite copper foil was placed in a passivation solution for passivation to prevent oxidation of the electroplated copper layer. After passivation, the composite copper foil was dried in a vacuum drying oven at 60 °C to obtain a composite copper foil with high adhesion; its structure from one surface to the other surface was successively: electroplated copper layer 4, conductive layer 2, polymer layer 1, conductive layer 2, electroplated copper layer 4. As Figure 1 shown.

[0102] Example 2

[0103] Using N-methylpyrrolidone as a solvent, a certain weight of conductive graphene and a surfactant were added, and they were fully stirred to form a stable conductive graphene slurry. The conductive graphene was evenly coated on a 2-μm-thick PP film, dried at 100 °C, and then subjected to hot roll extrusion in an environment with a temperature of 260 °C and cooled to room temperature, so that the conductive graphene was extruded into the surface of the PP body, and the thickness of the conductive graphene was 20 nm, obtaining a conductive graphene-modified PP substrate.

[0104] The obtained conductive graphene-modified PP substrate was successively cleaned with acetone and ethanol, then washed with a large amount of deionized water, taken out and dried in an oven at a constant temperature of 100 °C. The dried substrate was placed in a dual-magnetron sputtering device for magnetron sputtering copper plating to obtain a first sputtered metal seed copper layer with a thickness of 20 nm, and then a composite copper foil with high adhesion was obtained; its structure from one surface to the other surface was successively: magnetron sputtered copper layer 3, conductive layer 2, polymer layer 1, conductive layer 2, magnetron sputtered copper layer 3; as Figure 2 shown.

[0105] Example 3

[0106] Using N-methylpyrrolidone as a solvent, a certain weight of conductive graphene and a surfactant were added, and they were fully stirred to form a stable conductive graphene slurry. The conductive graphene was evenly coated on a 2-μm-thick PP film, dried at 100 °C, and then subjected to hot roll extrusion in an environment with a temperature of 260 °C and cooled to room temperature, so that the conductive graphene was extruded into the surface of the PP body, and the thickness of the conductive graphene was 20 nm, obtaining a conductive graphene-modified PP substrate.

[0107] The conductive graphene-modified PP substrate obtained is cleaned with acetone and ethanol in turn, and then cleaned with a large amount of deionized water. After being taken out, it is placed in a constant temperature drying oven at 100°C for drying. The dried substrate is placed in a double-sided magnetron sputtering device for magnetron sputtering copper plating to obtain a first sputtered metal seed copper layer with a single-sided thickness of 20nm. The initial composite copper foil obtained is placed in an acidic plating solution for electroplating to obtain an electroplated thickened copper layer with a single-sided thickness of 2μm. The obtained composite copper foil is placed in a passivation solution for passivation to prevent oxidation of the electroplated copper layer. After passivation, the composite copper foil is placed in a 60°C vacuum drying oven for drying to obtain a composite copper foil with high adhesion; its structure is as follows from one side surface to the other side surface: electroplated copper layer 4, magnetron sputtered copper layer 3, conductive layer 2, polymer layer 1, conductive layer 2, magnetron sputtered copper layer 3, electroplated copper layer 4; such as Figure 3 shown.

[0108] Example 4

[0109] N-methylpyrrolidone is used as a solvent, conductive graphene and a surfactant are added, and the mixture is fully stirred to form a stable conductive graphene slurry. The conductive graphene is evenly coated on a 2um thick PP film, dried at 100°C, and then hot-rolled in an ambient temperature of 260°C and cooled to room temperature to achieve the conductive graphene being extruded into the surface of the PP body. The thickness of the conductive graphene is 20nm, and a conductive graphene-modified PP substrate is obtained.

[0110] The conductive graphene-modified PP substrate was cleaned with acetone and ethanol in turn, and then cleaned with a large amount of deionized water, taken out and placed in a 100°C constant temperature drying oven for drying, and the dried substrate was placed in a double-sided magnetron sputtering device for magnetron sputtering copper plating to obtain a first sputtered metal seed copper layer with a single-sided thickness of 20nm, and the obtained initial composite copper foil was placed in an acidic plating solution for electroplating to obtain an electroplated thickened copper layer with a single-sided thickness of 2μm. The obtained composite copper foil was placed in a passivation solution for passivation to prevent oxidation of the electroplated copper layer, and after passivation, the composite copper foil was placed in a 60°C vacuum drying oven for drying to obtain a composite copper foil with high adhesion.

[0111] A through-hole structure with a pore size of 2 μm and a center distance of 200 μm between adjacent holes is prepared for the composite current collector using an ultraviolet picosecond laser drilling machine. The distribution density of the through-holes on the current collector is 30 through-holes per square millimeter of the composite copper foil current collector surface. The composite copper foil with the through-hole structure is repeatedly cleaned with deionized water. The structure is as follows from one surface to the other: an electroplated copper layer 4, a magnetron sputtered copper layer 3, a conductive layer 2, a polymer layer 1, a conductive layer 2, a magnetron sputtered copper layer 3, and an electroplated copper layer 4. The current collector has a through-hole 5 that penetrates the thickness.

[0112] Example 5

[0113] Using N-methylpyrrolidone as a solvent, a certain weight of conductive graphene and a surfactant are added, and they are fully stirred to form a stable conductive graphene slurry. The conductive graphene is evenly coated on a 2-μm-thick PP film, dried at 100 °C, and then subjected to hot roll extrusion in an environment with a temperature of 260 °C and cooled to room temperature, so that the conductive graphene is extruded into the surface of the PP body. The thickness of the conductive graphene is 20 nm, and a conductive graphene-modified PP substrate is obtained.

[0114] The obtained conductive graphene-modified PP substrate is successively cleaned with acetone and ethanol, then washed with a large amount of deionized water, taken out and dried in a 100 °C constant-temperature drying oven. The dried substrate is placed in a dual-sided magnetron sputtering device for magnetron sputtering to deposit copper, and a first sputtered metal seed copper layer with a single-sided thickness of 20 nm is obtained. The obtained initial composite copper foil is placed in an acidic plating solution for electroplating to obtain an electroplated thickened copper layer with a single-sided thickness of 2 μm. The obtained composite copper foil is placed in a passivation solution for passivation to prevent the oxidation of the electroplated copper layer. After passivation is completed, the composite copper foil is dried in a 60 °C vacuum drying oven to obtain a composite copper foil with high adhesion.

[0115] A through-hole structure with a hole diameter of 2 μm and a center distance between adjacent holes of 200 μm is prepared on the composite current collector using an ultraviolet picosecond laser drilling machine. The distribution density of the through-holes on the surface of the composite copper foil current collector is 30 through-holes per square millimeter of the composite copper foil current collector surface. The composite copper foil with a through-hole structure is repeatedly washed with deionized water and fixed at the bottom of an open container. An appropriate amount of buffer solution is introduced into the container, and then an appropriate amount of dopamine, photoinitiator benzophenone, etc. are added to the mixed solution. The dopamine solution is irradiated with a 36-w ultraviolet lamp to polymerize it, and then the excess polydopamine on the copper surface is scraped off with a spatula to ensure that the first lithium-philic polymer, polydopamine, is all in the through-holes (filling the entire through-hole). Then, the surface is rinsed with ultrapure water and dried with N2. Its structure from one surface to the other surface is successively: electroplated copper layer 4, magnetron sputtered copper layer 3, conductive layer 2, polymer layer 1, conductive layer 2, magnetron sputtered copper layer 3, electroplated copper layer 4. The current collector has a through-hole 5 penetrating the thickness, and the through-hole has a polymer filler 6; as Figure 4 shown. The through-hole structure on the surface of the composite current collector is as Figure 7 shown.

[0116] Example 6

[0117] The difference between Example 6 and Example 5 is that the PP composite material is directly placed in an acidic plating solution for electroplating to obtain an electroplated thickened copper layer with a single-sided thickness of 2 μm; magnetron sputtering is not carried out before electroplating; the structure of the obtained composite copper foil current collector from one surface to the other surface is successively: electroplated copper layer 4, conductive layer 2, polymer layer 1, conductive layer 2, electroplated copper layer 4; the current collector has a through-hole 5 penetrating the thickness, and the through-hole has a first lithium-philic polymer filler 6; asFigure 5 as shown

[0118] Example 7

[0119] The difference between Example 7 and Example 5 is that the PP composite material is directly placed in a dual - magnetron sputtering device for magnetron sputtering copper plating to obtain a single - side thickness of 20 nm for the first sputtered metal seed copper layer; after magnetron sputtering, electroplating the second copper layer is not carried out; the obtained composite copper foil current collector structure from one side surface to the other side surface is successively: magnetron sputtered copper layer 3, conductive layer 2, polymer layer 1, conductive layer 2, magnetron sputtered copper layer 3; the current collector has a through - hole 5 with a first lithium - philic polymer filler 6; as Figure 6 shown

[0120] Example 8

[0121] The difference between Example 8 and Example 5 is that the polymer substrate PP is replaced by polyimide.

[0122] Example 9

[0123] The difference between Example 9 and Example 5 is that the conductive graphene is replaced by carbon nanotubes.

[0124] Example 10

[0125] The difference between Example 10 and Example 5 is that the conductive graphene is replaced by conductive carbon black.

[0126] Example 11

[0127] The difference between Example 11 and Example 5 is that the thickness of the conductive graphene is 50 nm.

[0128] Example 12

[0129] The difference between Example 12 and Example 5 is that the thickness of the conductive graphene is 100 nm.

[0130] Example 13

[0131] The difference between Example 13 and Example 5 is that the thickness of the conductive graphene is 200 nm.

[0132] Example 14

[0133] The difference between Example 14 and Example 5 is that the thickness of the conductive graphene is 350 nm.

[0134] Example 15

[0135] The difference between Example 15 and Example 5 is that the thickness of the conductive graphene is 500 nm.

[0136] Example 16

[0137] Example 16 is different from Example 5 in that the thickness of the PP substrate is 1 μm.

[0138] Example 17

[0139] Example 17 is different from Example 5 in that the thickness of the PP substrate is 3 μm.

[0140] Example 18

[0141] Example 18 is different from Example 5 in that the single-sided thickness of the first sputtered metal seed copper layer is 100 nm.

[0142] Example 19

[0143] Example 19 is different from Example 5 in that the single-sided thickness of the first sputtered metal seed copper layer is 300 nm.

[0144] Example 20

[0145] Example 20 is different from Example 5 in that the single-sided thickness of the first sputtered metal seed copper layer is 500 nm.

[0146] Example 21

[0147] Example 21 is different from Example 5 in that the single-sided thickness of the second electroplated copper layer is 1 μm.

[0148] Example 22

[0149] Example 22 is different from Example 5 in that the single-sided thickness of the second electroplated copper layer is 3 μm.

[0150] Example 23

[0151] Example 23 is different from Example 5 in that the aperture of the through hole is 2 μm.

[0152] Example 24

[0153] Example 24 is different from Example 5 in that the aperture of the through hole is 5 μm.

[0154] Example 25

[0155] Example 25 is different from Example 5 in that the distribution density of the through holes on the current collector is 20 through holes are opened on the surface of the composite copper foil current collector per square millimeter.

[0156] Example 26

[0157] Example 26 is different from Example 5 in that the distribution density of the through holes on the current collector is 40 through holes are opened on the surface of the composite copper foil current collector per square millimeter.

[0158] Example 27

[0159] The difference between Example 27 and Example 5 is that the first lithiumophilic polymer filled in the through holes is polyvinyl alcohol, and the monomer is vinyl alcohol.

[0160] Comparative Example 1

[0161] Place the PP substrate in a dual - magnetron sputtering device for magnetron sputtering to deposit copper, obtaining a first sputtered metal seed copper layer with a single - side thickness of 20 nm. Place the obtained initial composite copper foil in an acidic plating solution for electroplating to obtain an electroplated thickened copper layer with a single - side thickness of 2 μm. Place the obtained composite copper foil in a passivation solution for passivation to prevent the oxidation of the electroplated copper layer. After passivation, place the composite copper foil in a 60 °C vacuum drying oven for drying to obtain a composite copper foil with high adhesion.

[0162] Use an ultraviolet picosecond laser drilling machine to prepare through - hole structures with a hole diameter of 2 μm and a center - to - center distance of 200 μm on the composite current collector. The distribution density of the through - holes on the current collector is 30 through - holes per square millimeter of the surface of the composite copper foil current collector. Repeatedly wash the composite copper foil with through - hole structures with deionized water, fix it at the bottom of an open container, pour an appropriate amount of buffer solution into the container, then add an appropriate amount of dopamine to the mixture, irradiate the dopamine solution with a 36 w ultraviolet lamp to cause polymerization, and then scrape off the excess polydopamine on the surface to ensure that the first lithiumophilic polymer, polydopamine, is all in the holes. Then rinse the surface with ultrapure water and dry it with N2.

[0163] Comparative Example 2

[0164] Place the PP substrate in a dual - magnetron sputtering device for magnetron sputtering to deposit copper, obtaining a first sputtered metal seed copper layer with a single - side thickness of 20 nm. Place the obtained initial composite copper foil in an acidic plating solution for electroplating to obtain an electroplated thickened copper layer with a single - side thickness of 2 μm. Place the obtained composite copper foil in a passivation solution for passivation to prevent the oxidation of the electroplated copper layer. After passivation, place the composite copper foil in a 60 °C vacuum drying oven for drying to obtain a composite copper foil with high adhesion.

[0165] Comparative Example 3

[0166] The current collector is a pure copper foil with a thickness of 6 μm.

[0167] Test Example

[0168] (1) Pole piece peel strength test

[0169] Make the composite copper foils of Examples 1 - 27 and Comparative Examples 1 - 3 into negative pole pieces, and use a universal tensile testing machine to conduct peel strength tests on the cold - pressed pole pieces.

[0170] (2) 25 °C 1C charge - discharge cycle test

[0171] The composite copper foils of Examples 1 to 27 and Comparative Examples 1 to 3 were applied to lithium iron phosphate-graphite system lithium-ion batteries. The positive electrode was lithium iron phosphate; the separator was a PE separator, and the electrolyte was EC / PC / EMC / VC / LiPF6. At 25°C, it was charged and discharged at 1C for 2000 cycles, and the voltage range was 2.5 - 3.65V. The capacity retention rate was calculated, and the capacity retention rate = discharge capacity after 2000 cycles / initial discharge capacity × 100%.

[0172] (3) Energy density

[0173] The composite copper foils of Examples 1 to 27 and Comparative Examples 1 to 3 were applied to lithium iron phosphate-graphite system lithium-ion batteries. Then, at 25°C, the battery was charged at a constant current of 0.1C to 3.65V, and then charged at a constant voltage of 3.65V until the current ≤ 0.05C. After standing for 5 minutes, it was discharged at a constant current of 0.1C to 2.5V to obtain the discharge energy Q. The calculation method of the battery energy density was Q / m.

[0174] (4) Thermal runaway peak temperature test method: The thermal runaway peak temperature was tested in accordance with GB 38031-2020 Safety Requirements for Power Batteries for Electric Vehicles. The above test results are shown in Table 1.

[0175] Table 1

[0176]

[0177]

[0178]

[0179] As shown in Table 1, compared with Examples 1 to 27 and Comparative Examples 1 to 3 of the present application, by attaching a carbon layer on the surface of the polymer substrate, the comprehensive performance of the battery can be significantly improved. For example, the bonding strength between the polymer layer and the copper layer, the electrical conductivity, the cycle performance and the thermal safety performance of the battery are all improved; especially, the pole piece peel strength is increased by more than 2 times.

[0180] Comparing Examples 1 to 27, it can be seen that in addition to attaching a conductive carbon material layer on the surface of the polymer substrate to improve the bonding strength, the copper layer can also be plated by first magnetron sputtering a first metal seed copper layer and then electroplating a second thickened copper layer, so as to increase the surface roughness of the copper layer, increase the specific surface area, increase the deposition amount of lithium ions on the copper layer, and thus improve the conductivity of the current collector, the energy density of the battery and the cycle performance of the battery; it can also be further through opening through-holes penetrating the thickness on the surface of the current collector and filling with a first lithium-philic polymer material to improve the bonding strength, reduce the weight of the current collector, adsorb the uniform deposition of lithium ions, and thus improve the energy density of the battery and the cycle performance of the battery.

[0181] Comparative Example 3 uses pure copper foil as the negative current collector; its weight is significantly greater than that of the current collector made of polymer substrate, reducing the energy density of the battery.

[0182] It should be noted that the terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those described herein.

[0183] The above are only the embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A composite copper foil current collector, characterized in that: The composite copper foil current collector comprises: A polymer composite layer, comprising a polymer layer and a conductive material layer, wherein the polymer layer has two opposite surfaces, and the conductive material layer is attached to at least one surface of the polymer layer; the polymer composite layer has a first surface and a second surface that are opposite to each other; A copper layer is attached to the first surface and the second surface of the polymer composite layer.

2. The composite copper foil current collector according to claim 1, characterized in that: The material of the polymer layer is selected from at least one of polyimide, polyethylene, polypropylene and polyethylene terephthalate; and / or, the thickness of the polymer layer is 1 to 3 μm; And / or, the overall thickness of the composite copper foil current collector is 3 to 11 μm; and / or, the conductive material layer is attached to two opposite surfaces of the polymer layer; and / or, the thickness of the conductive material layer is 20 to 100 nm, preferably 20 to 50 nm; And / or, the conductive material layer is made of conductive carbon material; Preferably, the conductive carbon material is selected from at least one of conductive carbon black, carbon nanotubes and graphene.

3. The composite copper foil current collector according to claim 1 or 2, characterized in that: The copper layer attached to the first surface includes a first copper layer and a second copper layer in a direction away from the polymer composite layer; the copper layer attached to the second surface is the second copper layer, or includes the first copper layer and the second copper layer in a direction away from the polymer composite layer; wherein the first copper layer is a copper layer deposited by vapor phase deposition; and the second copper layer is a copper layer deposited by electrochemical deposition; And / or, the thickness of the first copper layer is 20 to 500 nm; preferably 20 to 50 nm; And / or, the second copper layer has a thickness of 1-3 μm.

4. The composite copper foil current collector according to any one of claims 1 to 3, characterized in that: The composite copper foil current collector has a through hole extending through the composite copper foil current collector along its thickness direction; the through hole is filled with a first lithium-philic polymer material; Preferably, the aperture of the through hole is 1 to 5 μm; more preferably, it is 2 to 3 μm; Preferably, the number of the through holes is 20 to 40 per square millimeter of the composite copper foil current collector surface; Preferably, with the thickness direction perpendicular to the composite copper foil current collector as the horizontal direction, the distance between the center lines of two adjacent through holes in the horizontal direction is 200 to 1000 μm, preferably 300 to 500 μm.

5. The composite copper foil current collector according to claim 4, characterized in that: The first lithium-philic polymer material is selected from at least one of polyacrylamide, polydopamine, polyethylene oxide and polyvinyl alcohol.

6. A method for preparing the composite copper foil current collector according to any one of claims 1 to 5, characterized in that: The preparation method comprises: Step S1: coating a conductive material slurry on at least one surface of a polymer substrate to form a conductive material layer on the surface of the polymer substrate; the polymer substrate and the conductive material layer form a polymer composite layer; Step S2: Copper material is plated on the first surface and the second surface of the polymer composite layer to form a copper layer on the surface of the polymer composite layer, thereby forming the composite copper foil current collector.

7. The method for preparing a composite copper foil current collector according to claim 6, characterized in that: In the step S1, the polymer substrate and the conductive material layer are subjected to hot extrusion to form the polymer composite layer; Preferably, the temperature of the hot extrusion is 250°C to 270°C; Preferably, the hot extrusion device is a hot roller; And / or, in step S1, the conductive material slurry includes a conductive material, a solvent and a surfactant; Preferably, the solvent is N-methylpyrrolidone and / or dimethylformamide; Preferably, the surfactant is polyacrylic acid and / or polyvinyl alcohol; And / or, in the step S2, the method of plating the copper material on the first surface and the second surface of the polymer composite layer includes method I and method II; wherein, The method I comprises: Step S2-1: using a vapor deposition method to plate the copper material on the first surface of the polymer composite layer to form a first copper layer; Step S2-2: using an electrochemical deposition method to plate the copper material on the surface of the first copper layer away from the polymer composite layer to form a first second copper layer; and using an electrochemical deposition method to plate the copper material on the second surface of the polymer composite layer to form the first second copper layer; The method II includes: Step S2-1: using a vapor deposition method to plate the copper material on the first surface and the second surface of the polymer composite layer to form a second first copper layer; Step S2-2: using an electrochemical deposition method to plate the copper material on two opposite surfaces of the second first copper layer away from the polymer composite layer to form a second second copper layer; Preferably, the vapor deposition method is magnetron sputtering; Preferably, the electrochemical deposition method is electroplating; And / or, the step S2 further includes a step S3: opening a through hole along the thickness direction of the composite copper foil current collector; Preferably, a laser drill is used to drill the through hole penetrating the thickness of the composite copper foil current collector along the thickness direction of the composite copper foil current collector; And / or, the step S3 further includes a step S4: placing the composite copper foil current collector having the through-hole in a first solution containing a first monomer material and a first photoinitiator, and the first monomer material undergoes in-situ self-polymerization on the surface of the copper layer and in the through-hole under a first illumination condition, so as to attach a first lithium-philic polymer material layer to the surface of the copper layer and fill the through-hole with the first lithium-philic polymer material; removing the first lithium-philic polymer layer attached to the surface of the copper layer, and retaining the first lithium-philic polymer material filled in the through-hole; Preferably, the first lithium-philic polymer material is selected from at least one of polyacrylamide, polydopamine, polyethylene oxide and polyvinyl alcohol; Preferably, the first lighting condition includes ultraviolet lamp irradiation and / or xenon lamp irradiation.

8. A negative electrode, comprising a negative electrode current collector and a negative electrode active material layer; characterized in that: The negative electrode current collector is the composite copper foil current collector according to any one of claims 1 to 5 or the composite copper foil current collector prepared by the preparation method according to claim 6 or 7.

9. A lithium ion battery comprising a positive electrode, a negative electrode and an electrolyte; characterized in that: The negative electrode is the negative electrode according to claim 8.

10. An electrical device, comprising a power supply; characterized in that: The power source comprises the lithium-ion battery of claim 9.

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