Composite copper foil current collector and manufacturing method therefor, negative electrode, lithium-ion battery, and electric device

Abstract

The present application discloses a composite copper foil current collector and a manufacturing method therefor, a negative electrode, a lithium-ion battery, and an electric device. 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, the conductive material layer is attached to at least one surface of the polymer layer, and the polymer composite layer has a first surface and a second surface opposite to each other; and a copper layer attached to the first surface and the second surface of the polymer composite layer.

Description

Composite copper foil current collector and its preparation method, negative electrode, lithium-ion battery and electrical equipment

[0001] This application claims priority to Chinese Patent Application No. 202510352524.5, filed with the Chinese Patent Office on March 24, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, specifically to a composite copper foil current collector and its preparation method, a negative electrode, a lithium-ion battery, and electrical equipment. Background Technology

[0003] Lithium-ion batteries have been widely used in portable electronic products, electric vehicles, and energy storage due to their advantages such as small size, high energy density, good rate performance, and flexible design. In particular, with the increasing development and popularization of electric vehicles and lithium battery electrochemical energy storage, the requirements for driving range / single cell energy storage capacity and safety are placing increasingly stringent demands on the energy density and electrical performance of lithium-ion batteries.

[0004] In related technologies, reducing the thickness of copper foil is often an effective way to improve battery energy density, thereby increasing battery energy density. Using novel composite copper foil as the negative electrode current collector for lithium-ion batteries is an important research direction proposed in recent years for improving battery energy density, enhancing battery performance, and reducing battery costs. Invention Overview

[0005] The improvement effect of existing composite copper foil structures is limited. For example, directly depositing a copper layer on the surface of a polymer material matrix results in the copper layer's bonding strength, easy shedding of active materials, and the need to improve the overall performance of the battery, such as energy density, cycle stability, and thermal safety.

[0006] This application provides a composite copper foil current collector and its preparation method, a negative electrode, a lithium-ion battery, and an electrical device, which can solve the problems of poor adhesion between the polymer substrate and the copper coating layer, and the need to improve the conductivity of the current collector and the cycle stability of the battery in related technologies.

[0007] In a first aspect, embodiments of this application provide a composite copper foil current collector, the composite copper foil current collector comprising:

[0008] A polymer composite layer includes a polymer layer and a conductive material layer, wherein the polymer layer has two opposing 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 opposite to each other.

[0009] A copper layer is attached to the first and second surfaces of the polymer composite layer.

[0010] In some possible implementations, the material of the polymer layer is selected from at least one of polyimide, polyethylene, polypropylene, and polyethylene terephthalate.

[0011] In some possible implementations, the thickness of the polymer layer is 1 μm to 3 μm.

[0012] In some possible implementations, the overall thickness of the composite copper foil current collector is between 3 μm and 11 μm.

[0013] In some possible implementations, a conductive material layer is attached to two opposing surfaces of the polymer layer.

[0014] In some possible implementations, the thickness of the conductive material layer ranges from 20 μm to 100 nm.

[0015] In some possible implementations, the thickness of the conductive material layer ranges from 20 μm to 50 nm.

[0016] In some possible implementations, the conductive material layer is made of conductive carbon material.

[0017] In some possible implementations, the conductive carbon material is selected from at least one of conductive carbon black, carbon nanotubes, and graphene.

[0018] In some possible implementations, 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 a 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 vapor deposition; and the second copper layer is a copper layer deposited by electrochemical deposition.

[0019] In some possible implementations, the thickness of the first copper layer is from 20 μm to 500 nm.

[0020] In some possible implementations, the thickness of the first copper layer is 20 μm to 50 nm.

[0021] In some possible implementations, the thickness of the second copper layer is 1 μm to 3 μm.

[0022] In some possible implementations, the composite copper foil current collector has through holes along its thickness direction; the through holes are filled with a first lithiophilic polymer material.

[0023] In some possible implementations, the aperture of the through-hole is between 1 μm and 5 μm.

[0024] In some possible implementations, the aperture of the through-hole is 2μm to 3μm.

[0025] In some possible implementations, the number of through holes is 20 to 40 per square millimeter of the composite copper foil current collector surface.

[0026] In some possible implementations, the horizontal direction is defined as the thickness direction perpendicular to the composite copper foil current collector, and the horizontal distance between the centerlines of two adjacent through holes is 200μm~1000μm.

[0027] In some possible implementations, the horizontal distance between the centerlines of two adjacent vias is 300~500μm.

[0028] In some possible implementations, the first lithiophilic polymer material is selected from at least one of polyacrylamide, polydopamine, polyethylene oxide, and polyvinyl alcohol.

[0029] Secondly, embodiments of this application also provide a method for preparing the above-mentioned composite copper foil current collector, comprising:

[0030] Step S1: Coat at least one surface of the polymer substrate with a conductive material slurry 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;

[0031] Step S2: Copper material is plated onto the first and second surfaces 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.

[0032] In some possible implementations, in step S1, the polymer substrate and the conductive material layer are thermally extruded to form a polymer composite layer.

[0033] In some possible implementations, the temperature of hot extrusion is 250°C to 270°C.

[0034] In some possible implementations, the equipment for hot extrusion is a hot roller.

[0035] In some possible implementations, in step S1, the conductive material slurry includes a conductive material, a solvent, and a surfactant.

[0036] In some possible implementations, the solvent is N-methylpyrrolidone and / or dimethylformamide.

[0037] In some possible implementations, the surfactant is polyacrylic acid and / or polyvinyl alcohol.

[0038] In some possible implementations, step S2, which involves plating copper material onto two opposing surfaces of the polymer composite layer, includes methods I and II; wherein,

[0039] Method I includes:

[0040] Step S2-1: Copper material is deposited on the first surface of the polymer composite layer using a vapor deposition method to form the first copper layer;

[0041] Step S2-2: Copper material is deposited onto the surface of the first copper layer away from the polymer composite layer using electrochemical deposition to form the first second copper layer; and copper material is deposited onto the second surface of the polymer composite layer using electrochemical deposition to form the first second copper layer.

[0042] Method II includes:

[0043] Step S2-1: Copper material is deposited on the first and second surfaces of the polymer composite layer using a vapor deposition method to form a second type of first copper layer;

[0044] Step S2-2: Copper material is deposited onto two opposite surfaces of the second type of first copper layer away from the polymer composite layer using an electrochemical deposition method to form the second type of second copper layer;

[0045] Among some possible implementations, the vapor deposition method is magnetron sputtering.

[0046] Among some possible implementations, electrochemical deposition is electroplating.

[0047] In some possible implementations, step S2 is followed by step S3: opening a through hole along the thickness direction of the composite copper foil current collector.

[0048] In some possible implementations, a laser drilling machine is used to drill through holes along the thickness direction of the composite copper foil current collector.

[0049] In some possible implementations, 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; under first illumination, the first monomer material undergoes in-situ self-polymerization on the surface of the copper layer and inside the through holes to attach a first lithiophilic polymer material layer to the surface of the copper layer and fill the through holes with the first lithiophilic polymer material; removing the first lithiophilic polymer layer attached to the surface of the copper layer, while retaining the first lithiophilic polymer material filling the through holes.

[0050] In some possible implementations, the first lithiophilic polymer material is selected from at least one of polyacrylamide, polydopamine, polyethylene oxide, and polyvinyl alcohol.

[0051] In some possible implementations, the first illumination condition includes ultraviolet lamp irradiation and / or xenon lamp irradiation.

[0052] Thirdly, embodiments of this application also provide a negative electrode, 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.

[0053] Fourthly, embodiments of this application also provide a lithium-ion battery, including a positive electrode, a negative electrode, and an electrolyte; the negative electrode is the aforementioned negative electrode.

[0054] Fifthly, embodiments of this application also provide an electrical device, including a power supply; the power supply includes the aforementioned lithium-ion battery.

[0055] The beneficial effects of this application are as follows: By introducing conductive materials onto the surface of a polymer substrate and then plating copper, the bonding force between the polymer and copper is stronger than that between the polymer and copper directly. At the same time, the conductive materials on the polymer substrate replace part of the polymer insulating materials, effectively forming a continuous conductive network, which makes the composite copper foil current collector have stronger overall conductivity. With the polymer as the substrate of the current collector, the current collector hardly expands in volume during charging and discharging, avoiding the active material from falling off the current collector and improving the cycle stability of the battery. Attached Figure Description

[0056] Figure 1 is a side view schematic diagram of the composite current collector structure of some implementations of this application;

[0057] Figure 2 is a side view schematic diagram of the composite current collector structure of some implementations of this application;

[0058] Figure 3 is a side view schematic diagram of the composite current collector structure of some implementations of this application;

[0059] Figure 4 is a side view schematic diagram of the composite current collector structure of some implementations of this application;

[0060] Figure 5 is a side view schematic diagram of the composite current collector structure of some implementations of this application;

[0061] Figure 6 is a side view schematic diagram of the composite current collector structure of some implementations of this application;

[0062] Figure 7 is a scanning electron microscope image of the surface through-hole of the composite current collector in some implementations of this application.

[0063] Explanation of reference numerals in the attached figures:

[0064] 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 lithium-loving polymer material. Embodiments of the present invention

[0065] In the description of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0066] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, where the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, where the first feature is at a lower horizontal level than the second feature.

[0067] In the description of this embodiment, the terms "upper," "lower," "left," "right," "front," and "rear," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for distinction in description and have no special meaning.

[0068] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0069] As mentioned earlier, in related technologies, composite copper foil current collectors often use copper layers directly plated on the surface of a polymer material substrate. In this type of current collector, the bonding force between the copper layer and the polymer material substrate is relatively weak, which makes it easy for the active material to fall off, affecting the battery's cycle stability and thermal safety performance. The conductivity of this type of current collector still needs to be improved.

[0070] According to one aspect of this application, a composite copper foil current collector is provided, as shown in FIG1. ​​The composite copper foil current collector includes a polymer composite layer and a copper layer. The polymer composite layer includes a polymer layer 1 and a conductive material layer 2. The polymer layer 1 has two opposing 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 opposing each other. The copper layer is attached to the first surface and the second surface of the polymer composite layer.

[0071] The composite copper foil current collector of this application uses a polymer as the substrate. This polymer exhibits almost no volume expansion during charging and discharging, preventing active material from detaching from the current collector and thus improving battery cycle stability. In particular, by introducing a conductive material onto the polymer substrate surface before copper plating, the bonding strength is stronger than that between the polymer and copper directly. This is because the conductive carbon layer activates the substrate surface, enhancing the physical adsorption between the metal material and the polymer, thereby improving battery cycle stability and thermal safety. Simultaneously, the conductive material attached to the polymer substrate replaces part of the polymer insulating material in the current collector, effectively forming a continuous conductive network, giving the composite copper foil current collector overall stronger conductivity. Therefore, this application, by improving the composite structure of the current collector, enables the aforementioned novel composite copper foil current collector to possess better cycle stability, thermal safety, and superior conductivity.

[0072] In some embodiments, the polymer layer is selected from at least one of polyimide, polyethylene, polypropylene, and polyethylene terephthalate. These polymers possess excellent electrical insulation, chemical stability, and mechanical strength, making them suitable as base materials for battery current collectors; they also exhibit good plasticity, which is beneficial for better composite molding effects between the polymer layer and the conductive material layer attached to its surface; simultaneously, the polymer and the copper layer also exhibit good composite molding effects; especially when polypropylene is selected as the polymer, it is more suitable as a current collector substrate and exhibits better composite molding effects with conductive materials.

[0073] In some embodiments, the thickness of the polymer layer is from 1 μm to 3 μm; for example, the thickness is any value among 1 μm, 1.5 μm, 2.0 μm, 2.5 μm, and 3.0 μm, or any value between two of these; for example, 1.5 to 3 μm; and another example, 2 μm. Controlling the thickness of the polymer layer, the main substrate of the current collector, within the above-mentioned thickness range is beneficial for balancing the overall performance of the battery, such as energy density, electrochemical performance, mechanical strength, thermal management, and cost. If the polymer layer is too thick or too thin, it will affect its overall performance as the main substrate of the current collector. For example, if it is too thick, it will affect the battery's energy density and weight; if it is too thin, it may affect properties such as insulation and support strength.

[0074] 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 a conductive material layer is attached to one surface of the polymer layer, its effect is already better than that of a current collector without a conductive material layer attached to the surface of the polymer layer. When conductive material layers are attached to both opposite surfaces of the polymer layer, the bonding force between the polymer and the copper layer can be further improved, thereby optimizing and improving the cycle stability of the battery and the overall conductivity of the current collector.

[0075] In some embodiments, the thickness of the conductive material layer is from 20 nm to 100 nm. For example, the single-sided thickness is any value or a range between 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, and 100 nm; for example, 20 nm to 60 nm; and for another example, 20 nm to 50 nm. The aforementioned thickness refers to a conductive material layer attached to one surface of the polymer layer, with a thickness of 20nm to 100nm. Another conductive material layer, also with a thickness of 20nm to 100nm, is attached to the opposite surface of the polymer layer. Each of the two opposite surfaces of the polymer layer has a conductive material layer of equal thickness. Controlling the thickness of the conductive material layer on one side to 20nm to 100nm provides a good conductive network without increasing the weight of the current collector, thereby improving the battery's energy density. This thickness also helps improve the bonding force between the conductive material layer and the polymer layer, as well as 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 thickness of the conductive material layer on one side is too thin, it is detrimental to the bonding force with the polymer and copper layers and also hinders the formation of a good conductive network. In summary, controlling the thickness of the conductive material layer within the aforementioned range ensures the comprehensive performance of the current collector, including conductivity, inter-material bonding, and lithium-ion transport, and is particularly helpful in improving battery energy density, cycle stability, and thermal safety.

[0076] In some embodiments, the conductive material layer is made of conductive carbon material or a modified version of 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 carbon materials, carbon nanotubes and carbon fibers have strong toughness and tensile strength, which can further improve the overall tensile and compressive strength of the composite copper foil current collector, avoid short circuits in the battery, and reduce the probability of thermal runaway; at the same time, carbon materials have better conductivity, which can further improve the conductivity of the current collector.

[0077] In some embodiments, as shown in FIG3, the copper layer attached to the first surface includes a first copper layer 3 and a second copper layer 4 in sequence in the direction away from the polymer composite layer; the copper layer attached to the second surface is the second copper layer 4, or includes a first copper layer 3 and a second copper layer 4 in sequence in the direction away from the polymer composite layer; wherein, the first copper layer 3 is a copper layer deposited by vapor deposition; and the second copper layer 4 is a copper layer deposited by electrochemical deposition.

[0078] In the composite copper foil current collector structure described in this application, the first copper layer or the second copper layer, as the material layer directly in contact with the electrolyte, must be disposed on both opposite surfaces of the polymer composite layer; for example, the first copper layer can be disposed on both opposite surfaces of the polymer composite layer, or the second copper layer can be disposed on both; or, for example, the first copper layer can be sandwiched between the polymer composite layer and the second copper layer, and can be attached to one side of the polymer composite layer or to both opposite surfaces of the polymer composite layer; the first copper layer is a copper layer plated by a vapor deposition method, such as a copper layer plated by magnetron sputtering, which is dense and thin, resulting in stronger adhesion between the first copper layer and the polymer composite layer, and significantly enhancing the adhesion between the subsequent electroplated second copper layer and the substrate. To prevent copper layer detachment during battery use, the first copper layer deposited by magnetron sputtering serves as a seed copper layer. Its smaller grains, with their higher surface energy and activity, improve the grain quality of subsequent electroplated copper layers, thus enhancing the overall performance of the copper layer. Simultaneously, the magnetron sputtered seed copper layer possesses a continuous conductive network, improving the substrate's conductivity and ensuring uniform plating of the second copper layer (the thickened electroplated copper layer), resulting in a high-quality electroplated copper layer. Electroplating the second copper layer offers advantages: it easily yields a thicker copper layer, and the relatively rough surface of the electroplated copper layer increases the contact area with the electrode active layer, providing more electron transport channels to reduce contact resistance and improve the overall conductivity of the current collector. By combining magnetron sputtering deposition of a dense copper layer with electroplating for thickening, a composite copper foil current collector with high bonding strength, controllable thickness, good crystal quality, and excellent conductivity can be prepared, thereby improving the battery's cycle performance and safety.

[0079] In some embodiments, the thickness of one side of the first copper layer 3 is 20 nm to 500 nm; the thickness of one side of the second copper layer 4 is 1 μm to 3 μm; and the overall thickness of the composite copper foil current collector is 3 μm to 11 μm. For example, the thickness of one side of the first copper layer is any value or a range between any two of 20 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, and 500 nm; for example, 20 nm to 60 nm; or even more specifically, 20 nm to 50 nm. The thickness of one side of the second copper layer is any value or a range between any two of 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.5 μm, 2.8 μm, and 3.0 μm; for example, 1.5 μm to 2.5 μm; or even more specifically, 2.0 μm. The overall thickness of the composite copper foil current collector is any value or a range between any two of the following: 3μm, 3.5μm, 4μm, 4.5μm, 5.0μm, 5.5μm, 6.0μm, 6.5μm, 7μm, 7.5μm, 8.0μm, 8.5μm, 9.0μm, 9.5μm, 10μm, 10.5μm, and 11.0μm; for example, 3μm to 6μm. Controlling the thickness of the metal seed copper layer to between 20 nm and 500 nm is beneficial for improving the adhesion between the polymer composite layer and the copper layer, and also contributes to the quality of the subsequent thickened copper layer. Controlling the thickness of the thickened copper layer to between 1 μm and 3 μm helps improve the overall conductivity of the current collector. A metal seed layer that is too thin or too thick is detrimental to the formation of a dense seed layer, providing better adhesion and grain quality. Conversely, a thickened copper layer that is too thick or too thin is detrimental to its adhesion to the polymer substrate, negatively impacting the overall conductivity of the current collector, its weight, and the battery's energy density. In particular, controlling the thicknesses of the first copper layer, the second copper layer, the conductive layer, and the polymer substrate to between 3 μm and 6 μm is even more beneficial for improving the adhesion between the polymer and the copper layer, the conductivity of the current collector, and the battery's cycle performance.

[0080] In some embodiments, as shown in FIG4, a through-hole 5 is formed in the composite copper foil current collector along its thickness direction; the through-hole is filled with a first lithiophilic polymer material 6. By forming the through-hole 5 in the current collector and filling the through-hole 5 with the lithiophilic polymer, the overall weight of the current collector can be reduced. The lithiophilic polymer material in the through-hole attracts lithium ions in the electrode active material, which can promote the uniform deposition of lithium ions on the surface of the current collector, thereby improving the battery cycle performance and battery energy density.

[0081] In some embodiments, the aperture of the via is 1 μm to 5 μm; for example, any value or a range between 1 μm, 2 μm, 3 μm, 4 μm, and 5 μm; for example, 2 to 3 μm; and again, 3 μm. The number of vias is 20 to 40 per square millimeter of the composite copper foil current collector surface; for example, 25 to 35; and again, 30. With the thickness direction of the composite copper foil current collector as the horizontal direction, the horizontal distance between the centerlines of two adjacent vias is 200 μm to 1000 μm; for example, any value or a range between 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, and 1000 μm; for example, 300 μm to 900 μm; and again, 300 to 500 μm. By setting the aperture size of the through-hole and the number density on the current collector, it is beneficial for lithium ions to be deposited uniformly on the current collector, which promotes the battery to have a stable and uniform energy density and cycle performance, and reduces the occurrence of thermal runaway.

[0082] In some embodiments, the first lithiophilic polymer material may be at least one selected from polyacrylamide, polydopamine, polyethylene oxide, and polyvinyl alcohol. These polymers and lithium ions in the active material exhibit strong interactions, such as adsorption and chemical bonding, which facilitate lithium ion deposition. In particular, the use of polydopamine further promotes lithium ion storage, transport, and uniform deposition on the current collector, thereby improving battery energy density, cycle performance, and thermal stability.

[0083] According to a second aspect of this application, a method for preparing the aforementioned composite copper foil current collector is provided, comprising:

[0084] Step S1: Coat at least one surface of the polymer substrate with a conductive material slurry 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;

[0085] Step S2: Copper material is plated onto the first and second surfaces 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.

[0086] The preparation method of the above-mentioned composite copper foil current collector is simple and easy to implement; by improving the composite structure of the current collector, the above-mentioned composite copper foil current collector has better cycle stability, thermal safety and better conductivity.

[0087] In some embodiments, in step S1, the polymer substrate and the conductive material layer are hot-extruded to form a polymer composite layer; the hot extrusion temperature is 250°C to 270°C; the hot extrusion equipment is a hot roller. At the above extrusion temperature, the conductive material is pressed into the surface of the polymer substrate by the hot extrusion roller, partially incorporating it into the polymer substrate, so that the polymer substrate and the conductive material become a better whole, which is beneficial to the formation of a stable conductive network.

[0088] In some embodiments, in step S1, the conductive material slurry includes a conductive material, a solvent, and a surfactant; the solvent includes N-methylpyrrolidone and dimethylformamide. The surfactant includes polyacrylic acid and polyvinyl alcohol. This method is simple to operate because it involves preparing the conductive material into a conductive slurry and then attaching it to a polymer substrate through coating or other methods.

[0089] In some embodiments, step S2, depositing copper material onto two opposing surfaces of the polymer composite layer, includes methods I and II; wherein,

[0090] Method I includes:

[0091] Step S2-1: Copper material is deposited on the first surface of the polymer composite layer using a vapor deposition method to form the first copper layer;

[0092] Step S2-2: Copper material is deposited onto the surface of the first copper layer away from the polymer composite layer using electrochemical deposition to form the first second copper layer; and copper material is deposited onto the second surface of the polymer composite layer using electrochemical deposition to form the first second copper layer.

[0093] The current collector structure formed by this method consists of, from one side surface of the current collector to the opposite side surface, a second copper layer, a first copper layer, a polymer composite layer, and a second copper layer; or a second copper layer, a polymer composite layer, a first copper layer, and a second copper layer.

[0094] Method II includes:

[0095] Step S2-1: Copper material is deposited on the first and second surfaces of the polymer composite layer using a vapor deposition method to form a second type of first copper layer;

[0096] Step S2-2: Copper material is deposited onto two opposite surfaces of the second type of first copper layer away from the polymer composite layer using an electrochemical deposition method to form the second type of second copper layer.

[0097] The current collector structure formed by this method consists of, from one side surface of the current collector to the opposite side surface, a second copper layer, a first copper layer, a polymer composite layer, a first copper layer, and a second copper layer, in sequence.

[0098] In some embodiments, step S2 is followed by step S3: creating through holes along the thickness direction of the composite copper foil current collector; for example, a laser drill is used to drill through holes along the thickness direction of the composite copper foil current collector. The through holes penetrate the entire current collector, and both ends of the through holes are connected to the outside; the number, diameter, and spacing of the through holes are as described above. Creating through holes can reduce the weight of the current collector, and filling the through holes with a lithium-philic polymer can make lithium ions deposit uniformly, promoting the conductivity of the current collector.

[0099] 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; under first illumination, the first monomer material undergoes in-situ self-polymerization on the surface of the copper layer and inside the through holes to attach a first lithium-philic polymer material layer to the surface of the copper layer and fill the through holes with the first lithium-philic polymer material; removing the first lithium-philic polymer layer attached to the surface of the copper layer, while retaining the first lithium-philic polymer material filling the through holes. The in-situ polymerization method allows for the appropriate formation of a filling material based on the characteristics of the through hole structure.

[0100] According to a third aspect of this 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 composite copper foil current collector described above or the composite copper foil current collector prepared by the above preparation method.

[0101] According to a fourth aspect of this application, a lithium-ion battery is provided, comprising a positive electrode, a negative electrode, and an electrolyte; the negative electrode is the aforementioned negative electrode.

[0102] According to a fifth aspect of this application, an electrical device is provided, including a power source; the power source includes the aforementioned lithium-ion battery.

[0103] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0104] The raw materials used in the embodiments of this application are all existing technologies and are commercially available.

[0105] Example 1

[0106] Using N-methylpyrrolidone as a solvent, conductive graphene and a surfactant were added and stirred thoroughly to form a stable conductive graphene slurry. The conductive graphene was uniformly coated on both surfaces of a 2μm thick PP film, dried at 100℃, and then subjected to hot roller extrusion at an ambient temperature of 260℃. After cooling to room temperature, the conductive graphene was extruded into the surface of the PP substrate. The thickness of the conductive graphene layer was 20nm, resulting in a conductive graphene-modified PP substrate.

[0107] The obtained conductive graphene-modified PP substrate was cleaned sequentially with acetone and ethanol, then rinsed with a large amount of deionized water. After removal, it was dried in a 100℃ constant temperature drying oven, and then electroplated in an acidic plating solution to obtain a 2μm thickened copper layer on one side. The resulting composite copper foil was passivated in a passivation solution to prevent oxidation of the electroplated copper layer. After passivation, the composite copper foil was dried in a 60℃ vacuum drying oven to obtain a high-adhesion composite copper foil. Its structure, from one surface to the other, is as follows: electroplated copper layer 4, conductive layer 2, polymer layer 1, conductive layer 2, and electroplated copper layer 4, as shown in Figure 1.

[0108] Example 2

[0109] Using N-methylpyrrolidone as a solvent, a certain weight of conductive graphene and surfactant were added and stirred thoroughly to form a stable conductive graphene slurry. The conductive graphene was uniformly coated onto a 2µm thick PP film, dried at 100℃, and then subjected to hot roller extrusion at an ambient temperature of 260℃. After cooling to room temperature, the conductive graphene was extruded into the surface of the PP substrate, with a thickness of 20nm, resulting in a conductive graphene-modified PP substrate.

[0110] The obtained conductive graphene-modified PP substrate was cleaned sequentially with acetone and ethanol, then rinsed with a large amount of deionized water, and then dried in a 100℃ constant temperature drying oven. The dried substrate was placed in a double-sided magnetron sputtering device for magnetron sputtering copper plating, resulting in a first sputtered metal seed copper layer with a thickness of 20nm, thus obtaining a high-adhesion composite copper foil. Its structure from one side surface to the other side surface is as follows: magnetron sputtered copper layer 3, conductive layer 2, polymer layer 1, conductive layer 2, and magnetron sputtered copper layer 3; as shown in Figure 2.

[0111] Example 3

[0112] Using N-methylpyrrolidone as a solvent, a certain weight of conductive graphene and surfactant were added and stirred thoroughly to form a stable conductive graphene slurry. The conductive graphene was uniformly coated onto a 2µm thick PP film, dried at 100℃, and then subjected to hot roller extrusion at an ambient temperature of 260℃. After cooling to room temperature, the conductive graphene was extruded into the surface of the PP substrate, with a thickness of 20nm, resulting in a conductive graphene-modified PP substrate.

[0113] The obtained conductive graphene-modified PP substrate was cleaned sequentially with acetone and ethanol, then rinsed with a large amount of deionized water, and dried in a 100℃ constant temperature drying oven. The dried substrate was placed in a double-sided magnetron sputtering device for magnetron sputtering copper plating, resulting in a first sputtered metal seed copper layer with a single-sided thickness of 20nm. The resulting initial composite copper foil was then electroplated in an acidic plating solution to obtain an electroplated thickened copper layer with a single-sided thickness of 2μm. The obtained composite copper foil was then passivated in a passivation solution to prevent oxidation of the electroplated copper layer. After passivation, the composite copper foil was dried in a 60℃ vacuum drying oven to obtain a high-adhesion composite copper foil. Its structure, from one surface to the other, is as follows: electroplated copper layer 4, magnetron sputtered copper layer 3, conductive layer 2, polymer layer 1, conductive layer 2, magnetron sputtered copper layer 3, and electroplated copper layer 4; as shown in Figure 3.

[0114] Example 4

[0115] Using N-methylpyrrolidone as a solvent, conductive graphene and a surfactant were added and stirred thoroughly to form a stable conductive graphene slurry. The conductive graphene was uniformly coated onto a 2µm thick PP film, dried at 100°C, and then subjected to hot roller extrusion at an ambient temperature of 260°C. After cooling to room temperature, the conductive graphene was extruded into the surface of the PP substrate, with a thickness of 20nm, resulting in a conductive graphene-modified PP substrate.

[0116] The obtained conductive graphene-modified PP substrate was cleaned sequentially with acetone and ethanol, then rinsed with a large amount of deionized water. After removal, it was dried in a 100℃ constant temperature drying oven. The dried substrate was then placed in a double-sided magnetron sputtering apparatus for magnetron sputtering copper plating, resulting in a first sputtered metal seed copper layer with a single-sided thickness of 20 nm. The resulting initial composite copper foil was then electroplated in an acidic plating solution to obtain an electroplated thickened copper layer with a single-sided thickness of 2 μm. The obtained composite copper foil was then passivated in a passivation solution to prevent oxidation of the electroplated copper layer. After passivation, the composite copper foil was dried in a 60℃ vacuum drying oven to obtain a high-adhesion composite copper foil.

[0117] A through-hole structure with a pore diameter of 2 μm and a center-to-center distance of 200 μm between adjacent holes was prepared on the composite current collector using an ultraviolet picosecond laser drilling machine. The distribution density of the through-holes on the current collector was 30 through-holes per square millimeter of composite copper foil. The composite copper foil with the through-hole structure was repeatedly cleaned with deionized water. The structure, from one side surface to the other side surface, is as follows: 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, and the current collector has through-holes 5 with a through-thickness.

[0118] Example 5

[0119] Using N-methylpyrrolidone as a solvent, a certain weight of conductive graphene and surfactant were added and stirred thoroughly to form a stable conductive graphene slurry. The conductive graphene was uniformly coated onto a 2µm thick PP film, dried at 100℃, and then subjected to hot roller extrusion at an ambient temperature of 260℃. After cooling to room temperature, the conductive graphene was extruded into the surface of the PP substrate, with a thickness of 20nm, resulting in a conductive graphene-modified PP substrate.

[0120] The obtained conductive graphene-modified PP substrate was cleaned sequentially with acetone and ethanol, then rinsed with a large amount of deionized water. After removal, it was dried in a 100℃ constant temperature drying oven. The dried substrate was then placed in a double-sided magnetron sputtering apparatus for magnetron sputtering copper plating, resulting in a first sputtered metal seed copper layer with a single-sided thickness of 20 nm. The resulting initial composite copper foil was then electroplated in an acidic plating solution to obtain an electroplated thickened copper layer with a single-sided thickness of 2 μm. The obtained composite copper foil was then passivated in a passivation solution to prevent oxidation of the electroplated copper layer. After passivation, the composite copper foil was dried in a 60℃ vacuum drying oven to obtain a high-adhesion composite copper foil.

[0121] A through-hole structure with a pore size of 2 μm and a center-to-center distance of 200 μm between adjacent pores was prepared on the composite current collector using a UV picosecond laser drilling machine. The distribution density of the through-holes on the current collector was 30 pores per square millimeter of composite copper foil surface. The composite copper foil with the through-hole structure was repeatedly washed with deionized water and fixed to the bottom of an open container. An appropriate amount of buffer solution was introduced into the container, and then appropriate amounts of dopamine and photoinitiator benzophenone were added to the mixture. The dopamine was irradiated with a 36W UV lamp. The solution is used to polymerize the polydopamine, and then excess polydopamine on the copper surface is scraped off with a scraper to ensure that the first lithiophilic polymer, polydopamine, is completely filled in the through-holes. The surface is then rinsed with ultrapure water and dried with N2. The structure, from one side to the other, is as follows: 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, and the current collector has through-holes 5 with a through-thickness, and the through-holes are filled with polymer material 6; as shown in Figure 4. The through-hole structure of the composite current collector surface is shown in Figure 7.

[0122] Example 6

[0123] 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; no magnetron sputtering is performed before electroplating; the resulting composite copper foil current collector structure, from one side surface to the other side surface, is as follows: electroplated copper layer 4, conductive layer 2, polymer layer 1, conductive layer 2, and electroplated copper layer 4; the current collector has a through hole 5 with a through thickness, and the through hole has a first lithium-philic polymer filler 6; as shown in Figure 5.

[0124] Example 7

[0125] The difference between Example 7 and Example 5 is that the PP composite material is directly 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 20 nm; no second copper layer is electroplated after magnetron sputtering; the resulting composite copper foil current collector structure consists of the following layers from one side to the other: magnetron sputtered copper layer 3, conductive layer 2, polymer layer 1, conductive layer 2, and magnetron sputtered copper layer 3; the current collector has a through hole 5 with a through thickness, and the through hole is filled with a first lithium-affinity polymer 6; as shown in Figure 6.

[0126] Example 8

[0127] The difference between Example 8 and Example 5 is that the polymer substrate PP is replaced with polyimide.

[0128] Example 9

[0129] The difference between Example 9 and Example 5 is that conductive graphene is replaced with carbon nanotubes.

[0130] Example 10

[0131] The difference between Example 10 and Example 5 is that conductive graphene is replaced with conductive carbon black.

[0132] Example 11

[0133] The difference between Example 11 and Example 5 is that the conductive graphene thickness is 50 nm.

[0134] Example 12

[0135] The difference between Example 12 and Example 5 is that the thickness of the conductive graphene is 100 nm.

[0136] Example 13

[0137] The difference between Example 13 and Example 5 is that the conductive graphene thickness is 200 nm.

[0138] Example 14

[0139] The difference between Example 14 and Example 5 is that the conductive graphene thickness is 350 nm.

[0140] Example 15

[0141] The difference between Example 15 and Example 5 is that the conductive graphene thickness is 500 nm.

[0142] Example 16

[0143] The difference between Example 16 and Example 5 is that the thickness of the PP substrate is 1 μm.

[0144] Example 17

[0145] The difference between Example 17 and Example 5 is that the thickness of the PP substrate is 3 μm.

[0146] Example 18

[0147] The difference between Example 18 and Example 5 is that the thickness of the first sputtered metal seed copper layer on one side is 100 nm.

[0148] Example 19

[0149] The difference between Example 19 and Example 5 is that the thickness of the first sputtered metal seed copper layer on one side is 300 nm.

[0150] Example 20

[0151] The difference between Example 20 and Example 5 is that the thickness of the first sputtered metal seed copper layer on one side is 500 nm.

[0152] Example 21

[0153] The difference between Example 21 and Example 5 is that the thickness of the second electroplated copper layer on one side is 1 μm.

[0154] Example 22

[0155] The difference between Example 22 and Example 5 is that the thickness of the second electroplated copper layer on one side is 3 μm.

[0156] Example 23

[0157] The difference between Example 23 and Example 5 is that the diameter of the through hole is 2μm.

[0158] Example 24

[0159] The difference between Example 24 and Example 5 is that the diameter of the through hole is 5 μm.

[0160] Example 25

[0161] The difference between Example 25 and Example 5 is that the distribution density of through holes on the current collector is 20 through holes per square millimeter on the surface of the composite copper foil current collector.

[0162] Example 26

[0163] The difference between Example 26 and Example 5 is that the distribution density of through holes on the current collector is 40 through holes per square millimeter on the surface of the composite copper foil current collector.

[0164] Example 27

[0165] The difference between Example 27 and Example 5 is that the first lithiophilic polymer filled in the through-hole is polyvinyl alcohol, and the monomer is ethylene alcohol.

[0166] Comparative Example 1

[0167] A PP substrate was placed in a double-sided magnetron sputtering apparatus for magnetron sputtering copper plating, resulting in a first sputtered metal seed copper layer with a single-sided thickness of 20 nm. The resulting initial composite copper foil was then electroplated in an acidic plating solution to obtain an electroplated thickened copper layer with a single-sided thickness of 2 μm. The obtained composite copper foil was then passivated in a passivation solution to prevent oxidation of the electroplated copper layer. After passivation, the composite copper foil was dried in a 60°C vacuum drying oven to obtain a high-adhesion composite copper foil.

[0168] A through-hole structure with a pore size of 2 μm and a center-to-center distance of 200 μm between adjacent pores was prepared on the composite current collector using a UV picosecond laser drilling machine. The distribution density of the through-holes on the current collector was 30 pores per square millimeter of composite copper foil surface. The composite copper foil with the through-hole structure was repeatedly washed with deionized water and fixed at the bottom of an open container. An appropriate amount of buffer solution was introduced into the container, and then an appropriate amount of dopamine was added to the mixture. The dopamine solution was irradiated with a 36W UV lamp to induce polymerization. Excess polydopamine on the surface was then scraped off with a scraper to ensure that the first lithium-philic polymer, polydopamine, was contained within the pores. The surface was then rinsed with ultrapure water and dried with N2.

[0169] Comparative Example 2

[0170] A PP substrate was placed in a double-sided magnetron sputtering apparatus for magnetron sputtering copper plating, resulting in a first sputtered metal seed copper layer with a single-sided thickness of 20 nm. The resulting initial composite copper foil was then electroplated in an acidic plating solution to obtain an electroplated thickened copper layer with a single-sided thickness of 2 μm. The obtained composite copper foil was then passivated in a passivation solution to prevent oxidation of the electroplated copper layer. After passivation, the composite copper foil was dried in a 60°C vacuum drying oven to obtain a high-adhesion composite copper foil.

[0171] Comparative Example 3

[0172] The current collector is made of pure copper foil with a thickness of 6µm.

[0173] Test case

[0174] (1) Electrode peeling force test

[0175] The composite copper foils of Examples 1-27 and Comparative Examples 1-3 were used to make negative electrode sheets, and the cold-pressed electrode sheets were subjected to peel force testing using a universal tensile testing machine.

[0176] (2) 25℃ 1C charge-discharge cycle test

[0177] 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, with lithium iron phosphate as the positive electrode; PE separator as the separator; and EC / PC / EMC / VC / LiPF6 as the electrolyte. The batteries were charged and discharged at 1C for 2000 cycles at 25°C, with a voltage range of 2.5-3.65V. The capacity retention rate was calculated as: capacity retention rate = (2000-cycle discharge capacity / initial discharge capacity) × 100%.

[0178] (3) Energy density

[0179] 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 batteries were then charged at a constant current of 0.1C to 3.65V at 25°C, and then charged at a constant voltage of 3.65V to a current ≤0.05C. After standing for 5 minutes, the batteries were discharged at a constant current of 0.1C to 2.5V to obtain the discharge energy Q. The battery energy density was calculated as Q / m.

[0180] (4) Test method for peak thermal runaway temperature: The peak thermal runaway temperature was tested in accordance with the safety requirements for power batteries for electric vehicles in GB 38031-2020. The test results are shown in Table 1.

[0181] Table 1

[0182]

[0183] As shown in Table 1, compared with Comparative Examples 1 to 3, Examples 1 to 27 of this application show that attaching a carbon layer to the surface of the polymer substrate can significantly improve the overall performance of the battery. For example, the bonding force between the polymer layer and the copper layer, the conductivity, the cycle performance and thermal safety performance of the battery are all improved; in particular, the electrode peeling force is improved by more than 2 times.

[0184] Comparing Examples 1 to 27, it can be seen that, in addition to attaching a conductive carbon material layer to the surface of the polymer substrate to improve the bonding force, the copper layer can be further deposited by first magnetron sputtering a first metal seed copper layer and then electroplating a second thickened copper layer. This increases the surface roughness of the copper layer, improves the specific surface area, and increases the amount of lithium ions deposited in the copper layer, thereby improving the conductivity of the current collector, the energy density of the battery, and the cycle performance of the battery. Furthermore, through-holes with a thickness that penetrate the surface of the current collector can be opened and filled with a first lithium-loving polymer material to improve the bonding force, reduce the weight of the current collector, and adsorb lithium ions for uniform deposition, thereby improving the energy density of the battery and the cycle performance of the battery.

[0185] Comparative Example 3 uses pure copper foil as the negative electrode current collector; its weight is significantly greater than that of the polymer substrate current collector, which reduces the battery energy density.

Claims

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

2. The composite copper foil current collector according to claim 1, wherein, The polymer layer is made of at least one of polyimide, polyethylene, polypropylene, and polyethylene terephthalate. And / or, the thickness of the polymer layer is 1 μm to 3 μm; And / or, the overall thickness of the composite copper foil current collector is 3 μm 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 nm to 100 nm; And / or, the material of the conductive material layer is a conductive carbon material; 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, wherein, The thickness of the conductive material layer is 20 nm to 50 nm.

4. The composite copper foil current collector according to any one of claims 1 to 3, wherein, The copper layer attached to the first surface comprises, in order away from the polymer composite layer, a first copper layer and a second copper layer; the copper layer attached to the second surface is the second copper layer, or comprises, in order away from the polymer composite layer, a first copper layer and a second copper layer. Wherein, the first copper layer is a copper layer deposited by vapor phase deposition; the second copper layer is a copper layer deposited by electrochemical deposition; And / or, the thickness of the first copper layer is 20 nm to 500 nm; And / or, the thickness of the second copper layer is 1 μm to 3 μm.

5. The composite copper foil current collector according to claim 4, wherein, The thickness of the first copper layer is 20 nm to 50 nm.

6. The composite copper foil current collector according to any one of claims 1 to 5, wherein, The composite copper foil current collector has through holes along its thickness direction; the through holes are filled with a first lithium-philic polymer material. The diameter of the through hole is 1 μm to 5 μm; The number of through holes is 20 to 40 per square millimeter on the surface of the composite copper foil current collector; 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 200μm to 1000μm.

7. The composite copper foil current collector according to claim 6, wherein, The diameter of the through hole is 2~3μm; And / or, the distance between the centerlines of two adjacent through holes in the horizontal direction is 300~500μm.

8. The composite copper foil current collector according to claim 6 or 7, wherein, The first lithium-loving polymer material is selected from at least one of polyacrylamide, polydopamine, polyethylene oxide, and polyvinyl alcohol.

9. A method for preparing a composite copper foil current collector according to any one of claims 1 to 8, comprising: Step S1: Coat at least one surface of the polymer substrate with a conductive material slurry 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 onto the first and second surfaces 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.

10. The method for preparing the composite copper foil current collector according to claim 9, wherein, In step S1, the polymer substrate and the conductive material layer are thermally extruded to form the polymer composite layer; The temperature of the hot extrusion is 250℃~270℃; The hot extrusion equipment is a hot roller; And / or, in step S1, the conductive material slurry includes a conductive material, a solvent, and a surfactant; The solvent is N-methylpyrrolidone and / or dimethylformamide; The surfactant is polyacrylic acid and / or polyvinyl alcohol; And / or, in step S2, the method of plating the copper material onto the first surface and the second surface of the polymer composite layer includes method I and method II; wherein, Method I includes: Step S2-1: The copper material is deposited onto the first surface of the polymer composite layer using a vapor deposition method to form a first copper layer; Step S2-2: The copper material is deposited on the surface of the first copper layer away from the polymer composite layer using an electrochemical deposition method to form a first second copper layer; and the copper material is deposited on the second surface of the polymer composite layer using an electrochemical deposition method to form the first second copper layer. Method II includes: Step S2-1: The copper material is deposited onto the first and second surfaces of the polymer composite layer using a vapor deposition method to form a second type of first copper layer; Step S2-2: The copper material is deposited on two opposite surfaces of the second type of first copper layer away from the polymer composite layer using an electrochemical deposition method to form a second type of second copper layer; The vapor deposition method is magnetron sputtering; The electrochemical deposition method is electroplating; And / or, step S2 is followed by step S3: opening a through hole along the thickness direction of the composite copper foil current collector; A laser drilling machine is used to drill through holes along the thickness direction of the composite copper foil current collector, penetrating the thickness. And / or, step S3 is followed by step S4: placing the composite copper foil current collector with the through hole in a first solution containing a first monomer material and a first photoinitiator; under first illumination, the first monomer material undergoes in-situ self-polymerization on the surface of the copper layer and inside the through hole to attach a first lithium-loving polymer material layer to the surface of the copper layer and fill the through hole with the first lithium-loving polymer material; removing the first lithium-loving polymer layer attached to the surface of the copper layer, while retaining the first lithium-loving polymer material filling the through hole; The first lithium-loving polymer material is selected from at least one of polyacrylamide, polydopamine, polyethylene oxide, and polyvinyl alcohol; The first illumination conditions include ultraviolet lamp irradiation and / or xenon lamp irradiation.

11. A negative electrode, comprising a negative electrode current collector and a negative electrode active material layer; wherein the negative electrode current collector is the composite copper foil current collector according to any one of claims 1 to 8 or the composite copper foil current collector prepared by the preparation method according to claim 9 or 10.

12. A lithium-ion battery, comprising a positive electrode, a negative electrode, and an electrolyte; wherein the negative electrode is the negative electrode as described in claim 11.

13. An electrical device, comprising a power source; said power source comprising the lithium-ion battery of claim 12.

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