Composite current collector and preparation method thereof, pole piece and battery

Abstract

The invention relates to a composite current collector and a preparation method thereof, a pole piece and a battery, and belongs to the technical field of batteries. According to the preparation method, a first base film and a second base film which are different in corrosion resistance are spliced to form a composite base film, metal seed layers are formed on the surfaces of the two opposite sides of the composite base film through a magnetron sputtering or vacuum evaporation technology, and then at least part of the first base film is removed through selective corrosion; after rolling, the part, corresponding to the removed part of the first base film, of the metal seed layer can be in contact and conducted, and finally, the surface of the metal seed layer is thickened and deposited to form a metal layer, so that a tab area and a coating area can be integrally formed on the composite current collector in situ, and the problem that the tab of the composite current collector needs to be switched over during welding is effectively solved; the preparation method has the advantages of simple process, low cost, firm interface bonding, good product flexibility and high reliability, and can be effectively suitable for preparing high-safety and high-energy-density lithium ion batteries.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a composite current collector and its preparation method, an electrode, and a battery. Background Technology

[0002] Composite current collectors have a sandwich structure of metal layer-polymer layer-metal layer. Due to their advantages such as light weight, low cost, high energy density, and ability to effectively suppress thermal runaway and improve battery safety, they have become a research hotspot for key materials in lithium-ion batteries.

[0003] However, because the polymer layer (such as PET or PP) in the middle of the composite current collector is an insulator, the two metal layers cannot conduct electricity during tab welding. The current industry-standard solution is to use processes such as ultrasonic welding to first weld a section of pure metal foil (such as pure copper or pure aluminum foil) as an adapter piece to at least one edge of the composite current collector, and then weld the tab to this adapter piece. However, this adapter welding process increases process complexity, production costs, and material costs, while also introducing additional connection resistance and potential failure points, resulting in lower reliability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a composite current collector and its preparation method, an electrode, and a battery, effectively improving the problems of complex preparation processes, high costs, and insufficient connection reliability between the tab region and the coating region in existing composite current collectors.

[0005] In a first aspect, embodiments of this application provide a method for preparing a composite current collector, comprising the following steps: S1: Provide a composite base film, the composite base film including at least one first base film and at least one second base film arranged side by side along a first direction, the first base film and the second base film being made of different materials; S2: A first metal seed layer and a second metal seed layer are formed on opposite sides of the composite base film by magnetron sputtering or vacuum evaporation to obtain a first intermediate. S3: The first intermediate is subjected to selective etching in a chemical etchant to remove at least part of the first base film while retaining the second base film, thereby obtaining the second intermediate; S4: Roll the second intermediate so that the portion of the first metal seed layer and the second metal seed layer corresponding to the area where the first base film is removed comes into contact and becomes conductive; S5: A first metal layer and a second metal layer are deposited on the surfaces of the first metal seed layer and the second metal seed layer respectively to form a composite current collector; along the thickness direction, the part of the first metal layer and the second metal layer that are conductive is defined as the tab region, and the other part of the corresponding part of the second base film is defined as the coating region.

[0006] In the above-mentioned technical solution, this application achieves in-situ formation of the tab region and coating region within the composite current collector through a combination of chemical etching and rolling, eliminating the need for a transfer welding process. Furthermore, the chemical etching and rolling units can be easily integrated into existing battery manufacturing production lines, enabling continuous production, which simplifies the manufacturing process and reduces production costs. Moreover, the integrated formation of the tab region and coating region helps reduce stress concentration at the interface between them, improving structural stability, effectively reducing connection resistance, and enhancing reliability.

[0007] By defining the first and second base films as having different materials (i.e., different corrosion resistance), corresponding chemical etchants can be selected for selective etching to effectively remove at least a portion of the first base film while completely preserving the second base film. Furthermore, by defining the formation of the first and second metal seed layers using magnetron sputtering or vacuum evaporation processes, the metal layers formed by these processes exhibit island-like or columnar crystal growth structures. These layers naturally contain point defects, dislocations, nanopores, and numerous grain boundary interstices, allowing the chemical etchant to easily penetrate and diffuse into the first base film for etching, thereby selectively removing at least a portion of the first base film. Moreover, since the metal seed layer is typically thin, the deposition and thickening of the first and second metal layers can fill in the defects, thus ensuring the structural stability and performance reliability of the composite current collector. In some embodiments, in step S3, selective etching is used to remove part of the first base film, forming multiple through-holes in the first base film, with the pore size being 0.1 μm to 100 μm.

[0008] In the above technical solution, by partially removing the first base film, the first and second metal seed layers can be partially embedded in the through-holes after roll forming, creating mechanical and electrical contacts, thereby achieving effective conductivity. The remaining porous polymer skeleton, embedded between the first and second metal seed layers, can act as a "rivet" or "reinforcing rib," significantly improving the lateral tear resistance and overall flexibility of the tab area. Furthermore, compared to mechanical or physical drilling followed by electroplating to fill metal, the through-holes generated by chemical etching have a larger diameter range and wider distribution. Combined with roll forming, the metal filling effect within the through-holes is better, thus effectively improving conductivity reliability.

[0009] In some implementations, in step S3, selective etching is used to completely remove the first base film.

[0010] In the above technical solution, the first base film is completely removed by chemical etching, and the first metal seed layer and the second metal seed layer are completely contacted and bonded together after rolling to form a conductive connection, resulting in excellent conductivity and strong interfacial bonding, which can further reduce sheet resistance and enhance reliability.

[0011] In some embodiments, the material of the first base film includes at least one of an ester-based polymer, an amide-based polymer, or a nitrile-based polymer; the second base film includes a polyolefin polymer; and in step S3, the chemical etchant is an alkaline etchant.

[0012] In the above technical solution, the ester, amide, and nitrile groups in the first base film are all alkali-sensitive functional groups, which are prone to hydrolysis, molecular chain breakage, or cross-linking structure destruction under alkaline etching system; while the polyolefin polymer in the second base film is an alkali-resistant polymer, which can maintain structural stability in alkaline etching system. Therefore, the use of alkaline etching agent can effectively perform selective etching to remove at least part of the first base film.

[0013] In some embodiments, the material of the first base film includes at least one of polyethylene terephthalate, polycarbonate, polyamide, or polyacrylonitrile, and the material of the second base film includes at least one of polypropylene or polyethylene; in step S3, the chemical etchant includes at least one of a methanol solution of lithium methoxide, an ethanol solution of lithium ethoxide, an ethanol solution of sodium hydroxide, or an ethylenediamine solution of sodium hydroxide.

[0014] In the above technical solution, the alkaline etchant contains strong bases such as lithium methoxide, lithium ethoxide, or sodium hydroxide. Polyethylene terephthalate, polycarbonate, polyamide, or polyacrylonitrile contains ester, amide, or nitrile groups, which are easily hydrolyzed in the alkaline etchant. Polypropylene or polyethylene, however, can maintain structural stability in the alkaline etchant system. Therefore, using an alkaline etchant can effectively perform selective etching to remove at least a portion of the first base film forming the tab region, while ensuring the insulation and structural integrity of the coated area.

[0015] In some embodiments, the concentration of the alkaline etchant is 0.1 mol / L to 2.5 mol / L, the temperature of the selective etching treatment is 25°C to 60°C, and the time is 5 min to 60 min; optionally, the thickness of the first base film and the second base film are each independently 3 μm to 10 μm. In the above technical solution, by controlling the concentration of alkaline corrosive agent, the temperature and time of selective corrosion treatment, and the thickness of the base film, it is possible to control whether the first base film is partially or completely removed, as well as the size and distribution of pores formed in the first base film. This is beneficial for flexibly adjusting the structure of the tab region and further improving conductivity and reliability.

[0016] Furthermore, when selectively etching to remove part of the first base film, the concentration of the alkaline etchant is 0.1 mol / L to 1 mol / L, the temperature of the selective etching treatment is 25℃ to 45℃, and the time is 5 min to 30 min; when selectively etching to completely remove the first base film, the concentration of the alkaline etchant is 1 mol / L to 2.5 mol / L, the temperature of the selective etching treatment is 25℃ to 60℃, and the time is 20 min to 60 min.

[0017] In some embodiments, in step S4, the pressure of the roller is 1 MPa to 100 MPa. In the above technical solution, by controlling the pressure of the roller press within a suitable range, it is beneficial to tightly bond the first metal seed layer and the second metal seed layer, or to enable the first metal seed layer and the second metal seed layer to be effectively embedded in the through hole to achieve conductivity, thereby further improving the conductivity reliability of the first metal seed layer and the second metal seed layer in the tab area and the structural stability of the composite current collector.

[0018] In some embodiments, step S2 employs magnetron sputtering, with a vacuum level of 0.1 Pa to 1 Pa in the coating chamber, a sputtering power of 0.1 kW to 10 kW, a film feed speed of 0.1 m / min to 5 m / min, and a cooling roller temperature of -25°C to 0°C; or, step S2 employs vacuum evaporation, with a vacuum level greater than 10 kPa in the coating chamber. -3 Pa, the distance from the evaporation source is 10cm~25cm, and the deposition time is 5m / min~100m / min.

[0019] In the above technical solution, by controlling the process parameter range of magnetron sputtering and vacuum evaporation, the defect range, size and uniformity of the metal seed layer can be controlled and adjusted, while taking into account the conductivity continuity of the seed layer.

[0020] In some embodiments, the thickness of the first metal seed layer and the second metal seed layer are each independently 10 nm to 100 nm.

[0021] In the above technical solution, due to the thinner seed layer, the chemical etchant penetrates faster and the corrosion efficiency is higher. Furthermore, the thinner first and second metal seed layers have better flexibility, allowing for uniform plastic deformation during rolling, resulting in a stronger bond and further improving conductivity and structural stability.

[0022] In some embodiments, the first metal seed layer and the second metal seed layer are each made of at least one of copper or aluminum.

[0023] In some embodiments, before step S2, the composite base film is further subjected to plasma treatment.

[0024] In the above technical solution, plasma treatment can improve the interfacial adhesion and film formation continuity of the metal seed layer on the surface of the composite base film, thereby improving the structural reliability and stability of the composite current collector.

[0025] In some embodiments, the first base film has a first surface and a second surface along the thickness direction, and the second base film has a third surface and a fourth surface along the thickness direction, with the first surface and the third surface being flush and the second surface and the fourth surface being flush.

[0026] In the above technical solution, the first base film and the second base film have equal thickness and are spliced ​​flat, so that the overall thickness of the composite base film is uniform and there are no steps (thickness difference) on the surface, which is beneficial to improving the deposition uniformity, continuity and adhesion of the metal seed layer.

[0027] In some embodiments, in step S5, the first metal layer and the second metal layer are formed by electroplating, electroless plating, or magnetron sputtering to thicken the deposition. In the above technical solution, the above process is used to thicken and deposit metal seed layer on the surface. During the deposition process, the metal will preferentially nucleate and grow at defects such as nanopores and grain boundaries in the seed layer, which can fill the microscale defects of the seed layer and form a uniform, dense and highly adhesive metal layer. Moreover, these process steps are compatible with roll-to-roll continuous production processes for batteries, which is conducive to achieving industrial mass production.

[0028] In some embodiments, the thicknesses of the third metal layer, the first metal layer, the fourth metal layer, and the second metal layer are each independently 1 μm to 6 μm.

[0029] In the above technical solution, forming a thicker metal layer on the surface of the metal seed layer can effectively compensate for the structural defects of the metal seed layer and improve the conductivity continuity and structural reliability.

[0030] In some embodiments, the first metal layer and the second metal layer are each made of at least one of copper or aluminum. In the above technical solution, the materials of the first metal layer and the second metal layer can be selected as needed, which is highly flexible and adaptable to the needs of positive or negative electrode sheets. Secondly, embodiments of this application also provide a composite current collector, which is prepared using the preparation method provided in the first aspect of this application.

[0031] In the above technical solution, the composite current collector prepared by the above preparation method has the tab region and the coating region integrally formed in situ. The tab region has low contact resistance and good stability, high conductivity, and can also effectively improve the mechanical strength of the composite current collector and reduce the thickness and weight of the composite current collector.

[0032] Thirdly, embodiments of this application also provide an electrode sheet, including a composite current collector according to the second aspect of this application and an active material layer disposed on at least one side surface of the composite current collector.

[0033] In the above technical solution, the electrode prepared by the above composite current collector can be greatly simplified in the preparation process. It does not require the electrode tab welding, electrode tab shaping, and insulation treatment of the welding area in the conventional electrode preparation process, which is conducive to improving the production yield and stability of the electrode.

[0034] Fourthly, embodiments of this application also provide a battery, including the electrode provided in the third aspect of this application.

[0035] In the above technical solution, the battery prepared by using the above composite current collector can effectively improve the energy density and safety performance of the battery due to the thinning, lightweighting, and improved conductivity and safety of the composite current collector. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A process flow diagram of the preparation method of the composite current collector provided in one embodiment of this application.

[0038] Figure 2 This is a cross-sectional schematic diagram of a composite base film provided in an embodiment of this application.

[0039] Figure 3 In order to be in Figure 2 The diagram shows a cross-sectional view of the first intermediate obtained after forming a first metal seed layer and a second metal seed layer on the surface of the composite base film.

[0040] Figure 4 To be Figure 3 A schematic cross-sectional view of the second intermediate obtained after the first base film portion is removed, as shown in the figure.

[0041] Figure 5 To Figure 4 The diagram shows a cross-section of the second intermediate after it has been rolled.

[0042] Figure 6 This is a cross-sectional schematic diagram of a composite current collector provided in an embodiment of this application.

[0043] Figure 7 To be Figure 3The diagram shows a cross-sectional view of the second intermediate obtained after the first base film has been completely removed.

[0044] Figure 8 To Figure 7 The diagram shows a cross-section of the second intermediate after it has been rolled.

[0045] Figure 9 A cross-sectional schematic diagram of a composite current collector provided for another embodiment of this application.

[0046] Figure 10 This is an EBSD diagram of the cross-section of the copper seed layer in Example 1.

[0047] Figure 11 This is an optical microscope image of the porous polymer skeleton formed after the PET film in Example 1 was partially etched.

[0048] Figure 12 This is an optical microscope image of the cross-section of the composite current collector in Example 2, showing the PET film completely corroded.

[0049] Explanation of reference numerals in the attached figures: 100, 200 - Composite current collector; 10 - Composite base film; 11 - First base film; 12 - Second base film; 20 - First intermediate; 13 - First metal seed layer; 14 - Second metal seed layer; 30a, 30b - Second intermediate; 31 - Porous polymer skeleton; 32 - Through hole; 40 - First metal layer; 42 - Second metal layer; Y - Region to be connected; A - Tab region; B - Coating region; X - First direction; Z - Thickness direction. Detailed Implementation The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the composite current collector, the method for preparing the composite current collector, the electrode, and the battery. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0050] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0052] Composite current collectors, with their metal-polymer-metal sandwich structure, have become a research hotspot due to their advantages such as high safety, lightweight, and high energy density. A major problem with composite current collectors is that the intermediate polymer layer (such as PET or PP) is insulating, preventing electrical conductivity between the upper and lower metal layers.

[0053] The solutions commonly used in the industry include: (1) First, a section of pure metal foil (such as pure copper foil or pure aluminum foil) is welded on at least one side of the composite current collector by ultrasonic roll welding as an adapter piece, and then the tab is welded to this adapter piece. This adapter welding process requires the introduction of a welding machine, the use of more metal foil, and consideration of the connection reliability between the metal foil and the composite current collector body, as well as between the metal foil and the tab. This increases the process complexity, production cost and material cost, and also introduces additional connection resistance and potential failure points. (2) First, the tab area and coating area are divided on the polymer film. Mechanical or laser drilling is performed in the tab area, and then an electroplating or chemical plating process is used to form a metal layer on the surface of the polymer film. At the same time, conductive metal is filled in the through holes in the tab area to achieve the conduction between the upper and lower layers. However, due to the insulation of the polymer layer, the metal plating layer cannot effectively fill the through holes. Furthermore, due to the limitation of the hole size and distribution of mechanical or laser drilling, as well as the mechanical damage to the polymer film, the conductivity reliability of the tab area is low, and the mechanical properties are affected.

[0054] Based on this, this application provides a method for preparing a composite current collector; please refer to [link to method]. Figure 1 The preparation method includes the following steps: S1: Provide a composite base film, the composite base film including at least one first base film and at least one second base film arranged side by side along a first direction, the first base film and the second base film being made of different materials; S2: A first metal seed layer and a second metal seed layer are formed on opposite sides of the composite base film by magnetron sputtering or vacuum evaporation to obtain a first intermediate. S3: The first intermediate is subjected to selective etching in a chemical etchant to remove at least part of the first base film while retaining the second base film, thereby obtaining the second intermediate; S4: Roll the second intermediate so that the portion of the first metal seed layer and the second metal seed layer corresponding to the area where the first base film is removed comes into contact and becomes conductive; S5: A first metal layer and a second metal layer are deposited on the surfaces of the first metal seed layer and the second metal seed layer respectively to form a composite current collector; along the thickness direction, the part of the first metal layer and the second metal layer that are conductive is defined as the tab region, and the other part of the corresponding part of the second base film is defined as the coating region.

[0055] In this application, the tab region and coating region can be formed in situ within the composite current collector using a combination of chemical etching and rolling, eliminating the need for a transfer welding process. Furthermore, the chemical etching and rolling units can be easily integrated into existing battery manufacturing production lines, enabling continuous production, simplifying the manufacturing process, and reducing production costs. Moreover, the integrated formation of the tab region and coating region helps reduce stress concentration at their interface, improving structural stability, effectively reducing connection resistance, and enhancing reliability.

[0056] By defining the first and second base films as having different materials (i.e., different corrosion resistance), corresponding chemical etchants can be selected for selective etching to effectively remove at least a portion of the first base film while completely preserving the second base film. Furthermore, by defining the formation of the first and second metal seed layers using magnetron sputtering or vacuum evaporation processes, the metal layers formed by these processes exhibit island-like or columnar crystal growth structures. These layers naturally contain point defects, dislocations, nanopores, and numerous grain boundary interstices, allowing the chemical etchant to easily penetrate and diffuse into the first base film for etching, thereby selectively removing at least a portion of the first base film. Moreover, since the metal seed layer is typically thin, the deposition and thickening of the first and second metal layers can fill in the defects, thus ensuring the structural stability and performance reliability of the composite current collector.

[0057] In addition, compared with the method of coating and heating to peel off the first base film, this application uses chemical etching combined with subsequent rolling, which eliminates adhesive residue pollution, strengthens the bond between the first and second metal seed layers in the tab region, improves conductivity, and reduces stress at the junction of the tab region and the coating region, resulting in a more stable overall structure of the composite current collector.

[0058] This preparation method solves the problem of needing to transfer the welding of composite current collector tabs. It has the advantages of simple process, low cost, strong interface bonding, good product flexibility and high reliability, and is particularly suitable for high safety and high energy density lithium-ion batteries.

[0059] The composite current collector and its preparation method according to embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0060] Please see Figures 2 to 6 This application provides a method for preparing a composite current collector 100, comprising the following steps: S11: Please see Figure 2 A composite base film 10 is provided, which includes at least one first base film 11 and at least one second base film 12 arranged in parallel along a first direction X, wherein the first base film 11 and the second base film 12 are made of different materials.

[0061] Understandably, this application does not impose specific restrictions on the materials of the first base film 11 and the second base film 12, or on the chemical etchant used in the subsequent selective etching treatment. Any conventional materials and reagents in the art can be selected, as long as the chemical etchant can be used to etch the first base film 11 without affecting the structure of the second base film 12.

[0062] It should be noted that this application does not specifically limit the shape and size of the composite base film 10, the first base film 11, and the second base film 12. They can be rectangular, circular, or any other shape. The first direction X is a direction parallel to the plane of the composite base film 10. When the first base film 11 and the second base film 12 are rectangular, the first direction X can be the width direction or the length direction of the composite base film 10.

[0063] In this embodiment, the first base film 11 and the second base film 12 are arranged along their own length direction X, and the widths of the first base film 11 and the second base film 12 can be the same or different.

[0064] It should be noted that the composite base film 10 may include a plurality of first base films 11 and a plurality of second base films 12 to form a plurality of tab regions, wherein the first base films 11 and the second base films 12 are arranged alternately along the first direction X.

[0065] In this application, the first base film 11 and the second base film 12 can be spliced ​​using conventional methods in the art, such as hot pressing, ultrasonic welding, or adhesive bonding. It should be noted that when adhesive splicing is used, the adhesive must be chemically resistant, meaning it will not decompose during subsequent selective corrosion treatment. For example, alkali-resistant polyurethane adhesive or epoxy-modified resin adhesive can be used. Preferably, the first base film 11 and the second base film 12 are spliced ​​by hot pressing their edges.

[0066] In some embodiments, the material of the first base film 11 includes at least one of an ester-based polymer, an amide-based polymer, or a nitrile-based polymer; the second base film 12 includes a polyolefin polymer.

[0067] Furthermore, the first base film 11 is made of at least one of polyethylene terephthalate (PET), polycarbonate (PC), polyamide (PA), or polyacrylonitrile (PAN), and the second base film 12 is made of at least one of polypropylene (PP) or polyethylene (PE). Preferably, the first base film 11 is made of PET.

[0068] In some embodiments, the first direction X is the length direction of the composite base film 10, the length of the first base film 11 is 5mm to 50mm, and the length of the second base film 12 is 200mm to 1000mm. As an example, the length of the first base film 11 is any one value or any two values ​​between 5mm, 10mm, 20mm, 30mm, 40mm, and 50mm; the length of the second base film 12 is any one value or any two values ​​between 200mm, 300mm, 500mm, 600mm, 800mm, and 1000mm.

[0069] Understandably, the widths of the first base film 11 and the second base film 12 can be the same or different.

[0070] In some embodiments, the thickness of the first base film 11 and the second base film 12 is independently 3 μm to 10 μm. As an example, the thickness of the first base film 11 and the second base film 12 is independently any one value or a range between any two values ​​of 3 μm, 5 μm, 6 μm, 8 μm, and 10 μm.

[0071] The thicknesses of the first base film 11 and the second base film 12 can be the same or different. Preferably, the thicknesses of the first base film 11 and the second base film 12 are the same.

[0072] In some embodiments, the first base film 11 has a first surface and a second surface along the thickness direction Z, and the second base film 12 has a third surface and a fourth surface along the thickness direction. The first surface and the third surface are flush, and the second surface and the fourth surface are flush. In other embodiments, the first surface and the third surface may not be flush, and / or the second surface and the fourth surface may not be flush.

[0073] S21: Please see Figure 3 A first metal seed layer 13 and a second metal seed layer 14 are formed on opposite sides of the composite base film 10 by magnetron sputtering or vacuum evaporation to obtain a first intermediate 20.

[0074] Understandably, the first metal seed layer 13 and the second metal seed layer 14 are formed along the thickness direction Z on opposite sides of the composite base film 10.

[0075] In some embodiments, magnetron sputtering is used in step S2, with a vacuum degree of 0.1 Pa to 1 Pa in the coating chamber, a sputtering power of 0.1 kW to 10 kW, a film feeding speed of 0.1 m / min to 5 m / min, and a cooling roller temperature of -25°C to 0°C.

[0076] In other embodiments, step S2 employs a vacuum evaporation process, with the vacuum level of the coating chamber exceeding 10. -3Pa, the distance from the evaporation source is 10cm~25cm, and the deposition time is 5m / min~100m / min.

[0077] In some embodiments, the thickness of the first metal seed layer 13 and the second metal seed layer 14 is independently 10 nm to 100 nm. As an example, the thickness of the first metal seed layer 13 and the second metal seed layer 14 is independently any one value or a range between any two values ​​of 10 nm, 30 nm, 50 nm, 60 nm, 80 nm, and 100 nm.

[0078] The thicknesses of the first metal seed layer 13 and the second metal seed layer 14 can be the same or different. Preferably, the thicknesses of the first metal seed layer 13 and the second metal seed layer 14 are the same.

[0079] In some embodiments, the first metal seed layer 13 and the second metal seed layer 14 are each made of at least one of copper or aluminum.

[0080] In some embodiments, before step S21, the composite base film 10 is further subjected to plasma treatment.

[0081] Furthermore, plasma treatment may include using Ar, O2 or N2 plasma, which can increase the surface energy of the composite base film 10, introduce active functional groups, or achieve surface micro-roughening, enhance the adhesion of the seed layer, and improve film uniformity.

[0082] S31: Please refer to Figure 4 The first intermediate 20 is subjected to selective etching in a chemical etchant to remove part of the first base film 11 to form the conductive region Y, thereby obtaining the second intermediate 30a. The conductive region Y includes a porous polymer framework 31 and a first metal seed layer 13 and a second metal seed layer 14 formed on opposite sides of the porous polymer framework 31. Multiple through holes 32 are formed in the porous polymer framework 31 along the thickness direction Z.

[0083] Understandably, since the through-holes 32 are formed through a corrosion treatment, their shape, size, and distribution are not specifically limited. The through-holes 32 can be any shape, such as hourglass, cone, or cylinder. Furthermore, compared to the spacing limitations of physical drilling, the spacing between adjacent through-holes 32 formed by chemical corrosion can be zero, and the diameter deviation is large. This increases the number of through-holes 32, further improving conductivity.

[0084] In some embodiments, the aperture of the through hole 32 can be 0.1 μm to 100 μm.

[0085] In some embodiments, selective corrosion treatment employs an alkaline corrosive agent.

[0086] Furthermore, the alkaline corrosive agent includes at least one of the following: a methanol solution of lithium methoxide, an ethanol solution of lithium ethoxide, an ethanol solution of sodium hydroxide, and an ethylenediamine solution of sodium hydroxide.

[0087] Furthermore, the concentration of the alkaline corrosive agent is 0.1 mol / L to 1.0 mol / L, the temperature of the selective corrosion treatment is 25℃ to 45℃, and the time is 5 min to 30 min.

[0088] As an example, the concentration of the alkaline corrosive agent is any one value or any two values ​​between 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, and 1.0 mol / L; the temperature of the selective corrosion treatment is any one value or any two values ​​between 25°C, 30°C, 35°C, 40°C, and 45°C; and the time is any one value or any two values ​​between 5 min, 10 min, 20 min, and 30 min.

[0089] It should be noted that when the first metal seed layer 13 and the second metal seed layer 14 are seed layers, due to their thin thickness and the fact that the metal layer deposited by magnetron sputtering or vacuum evaporation has a lot of defect structures, alkaline etchants can quickly penetrate and diffuse through the first metal seed layer 13 and the second metal seed layer 14 to react with the first base film 11.

[0090] It should be noted that in practical applications, the concentration of alkaline corrosive agent, the treatment temperature and time can be controlled as needed to control the degree of corrosion of the first base film 11.

[0091] Understandably, after selective etching, the process also includes cleaning and drying the second intermediate 30a.

[0092] S41: Please see Figure 4 , Figure 5 The second intermediate 30a is rolled so that the portions of the first metal seed layer 13 and the second metal seed layer 14 corresponding to the porous polymer skeleton 31 can make contact and conduct through the through hole 32.

[0093] In some embodiments, the pressure of the roller pressing is 1 MPa to 100 MPa. As an example, the pressure of the roller pressing is any one value or a range between any two values ​​of 1 MPa, 10 MPa, 30 MPa, 50 MPa, 60 MPa, 80 MPa, and 100 MPa.

[0094] S51: Please refer to Figure 6A first metal layer 40 and a second metal layer 42 are formed on the surfaces of the first metal seed layer 13 and the second metal seed layer 14, respectively, to obtain a composite current collector 100; along the thickness direction Z, the part of the first metal layer 40 and the second metal layer 42 that are conductive is defined as the tab region A, and the other part of the corresponding part of the second base film 12 is defined as the coating region B.

[0095] In some embodiments, the first metal layer 40 and the second metal layer 42 are formed by electroplating, chemical plating or magnetron sputtering to thicken the deposition.

[0096] Furthermore, the preparation process parameters for electroplating include: electroplating solution concentration of 80g / L~160g / L, temperature of 25℃~30℃, and current density of 1.0A / dm²~4.0A / dm².

[0097] The preparation process parameters for electroless plating include: copper sulfate solution concentration range of 5 g / L to 15 g / L, reducing agent range of 20 g / L to 40 g / L, temperature range of 25℃ to 75℃, and pH value of 9 to 13.

[0098] The fabrication process parameters for magnetron sputtering include: a vacuum degree of 0.1 Pa to 1 Pa in the coating chamber, a sputtering power of 0.1 kW to 10 kW, a film feed speed of 0.1 m / min to 5 m / min, and a cooling roller temperature of -25℃ to 0℃.

[0099] In some embodiments, the first metal layer 40 and the second metal layer 42 are each made of at least one of copper or aluminum.

[0100] In some embodiments, the thickness of the first metal layer 40 and the second metal layer 42 is independently 1 μm to 6 μm. As an example, the thickness of the first metal layer 40 and the second metal layer 42 is independently any one value or a range between any two values ​​from 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, to 6 μm. Further, the thicknesses of the first metal layer 40 and the second metal layer 42 are equal.

[0101] Please see Figure 6An embodiment of this application also provides a composite current collector 100 prepared by the above-described preparation method, comprising at least one porous polymer skeleton 31 and at least one second base membrane 12 arranged side by side along a first direction X. The porous polymer skeleton 31 has a plurality of through holes 32. A first metal seed layer 13 and a second metal seed layer 14 are integrally formed on opposite sides of the porous polymer skeleton 31 and the second base membrane 12, respectively. A portion of the first metal seed layer 13 and the second metal seed layer 14 fills the through holes 32 to form a mechanical bond and electrical conductivity. A first metal layer 40 is provided on the surface of the first metal seed layer 13 facing away from the porous polymer skeleton 31 and the second base membrane 12, and a second metal layer 42 is provided on the surface of the second metal seed layer 14 facing away from the porous polymer skeleton 31 and the second base membrane 12.

[0102] Along the thickness direction Z of the composite current collector 100, a portion of the area corresponding to the porous polymer framework 31 can be defined as tab region A, and another portion of the area corresponding to the second base film 12 can be defined as coating region B. Understandably, the number of tab regions A can be one or more. As an example, the composite current collector 100 includes one tab region A and one coating region B; or the composite current collector 100 includes one coating region B and two tab regions A, with the two tab regions A located on opposite sides of the coating region B; or the composite current collector 100 includes multiple tab regions A and multiple coating regions B, with tab regions A and coating regions B arranged alternately.

[0103] Please see Figure 2 , Figure 3 as well as Figures 7 to 9 An embodiment of this application also provides a method for preparing a composite current collector 200, which is substantially the same as the method for preparing a composite current collector 100, and may include the following steps: S12: Please refer to Figure 2 A composite base film 10 is provided, which includes at least one first base film 11 and at least one second base film 12 arranged in parallel along a first direction X, wherein the first base film 11 and the second base film 12 are made of different materials.

[0104] S22: Please see Figure 3 A first metal seed layer 13 and a second metal seed layer 14 are formed on opposite sides of the composite base film 10 by magnetron sputtering or vacuum evaporation to obtain a first intermediate 20.

[0105] Steps S12 and S22 are largely the same as steps S11 and S21 described above, and will not be repeated here.

[0106] S32: Please refer to Figure 7 The first intermediate 20 is placed in a chemical etchant for selective etching treatment to completely remove the first base film 11 to form the conductive region Y, thereby obtaining the second intermediate 30b.

[0107] In the same step S31, the concentration of alkaline corrosive agent, the processing temperature and time can be controlled to ensure that the first base film 11 is completely corroded and removed.

[0108] In some embodiments, the concentration of the alkaline corrosive agent is 1.0 mol / L to 2.5 mol / L, the temperature of the selective corrosion treatment is 25°C to 60°C, and the time is 20 min to 60 min.

[0109] As an example, the concentration of the alkaline corrosive agent is any one value or a range between any two values ​​from 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2.0 mol / L, and 2.5 mol / L; the temperature of the selective corrosion treatment is any one value or a range between any two values ​​from 25°C, 35°C, 45°C, 55°C, and 60°C; and the time is any one value or a range between any two values ​​from 20 min, 30 min, 40 min, 50 min, and 60 min.

[0110] S42: Please see Figure 7 , Figure 8 The second intermediate 30b is rolled so that the portion of the first metal seed layer 13 and the second metal seed layer 14 corresponding to the region Y to be conducted adheres and conducts.

[0111] In the same step S41, the pressure of the roller can be controlled to make the first metal seed layer 13 and the second metal seed layer 14 tightly bonded together.

[0112] S52: Please refer to Figure 9 A first metal layer 40 and a second metal layer 42 are formed on the surfaces of the first metal seed layer 13 and the second metal seed layer 14, respectively, to obtain a composite current collector 200; along the thickness direction Z, the part of the first metal layer 40 and the second metal layer 42 that are conductive is defined as the tab region A, and the other part of the corresponding part of the second base film 12 is defined as the coating region B.

[0113] Please see Figure 9This application also provides a composite current collector 200 prepared by the above-described preparation method. The composite current collector 200 includes at least one tab region A and at least one coating region B along the thickness direction Z. The coating region B includes a second base film 12, a first metal seed layer 13 and a first metal layer 40 stacked on one side of the second base film 12, and a second metal seed layer 14 and a second metal layer 42 stacked on the other side of the second base film 12. The first metal seed layer 13, the first metal layer 40, the second metal seed layer 14, and the second metal layer 42 extend and converge on at least one side of the coating region B to form the tab region A. That is, the tab region A includes the second metal layer 42, the second metal seed layer 14, the first metal seed layer 13, and the first metal layer 40 stacked along the thickness direction Z.

[0114] In addition, this application embodiment also provides an electrode sheet, including the above-mentioned composite current collector and an active material layer disposed on at least one side surface of the composite current collector.

[0115] Understandably, the active material layer is disposed on the surface of the coating area of ​​the composite current collector.

[0116] Depending on the materials of the first and second metal seed layers in the composite current collector, it can be applied to both positive and negative electrode sheets.

[0117] In addition, this application embodiment also provides a battery including the above-mentioned electrode sheet.

[0118] This application does not specify the type of battery; for example, it can be a lithium-ion battery.

[0119] Furthermore, the battery may include a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.

[0120] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0121] Example 1 This embodiment provides a composite current collector, the preparation method of which includes the following steps: (1) Take a PET film with a thickness of 4.5μm and a length of 50mm (i.e., the first base film) and a PP film with a thickness of 4.5μm and a length of 450mm (i.e., the second base film), and splice them along the length direction by hot pressing the edges to obtain a composite base film.

[0122] (2) Ar plasma treatment was performed on the composite base film; then magnetron sputtering was performed on the opposite two sides of the composite base film, with the vacuum degree controlled at 0.5 Pa, the sputtering power at 1 kW, the tape speed at 0.5 m / min, and the cooling roller temperature controlled at -20 °C, to deposit copper seed layers (i.e., the first metal seed layer and the second metal seed layer) with a thickness of 100 nm respectively, to obtain the first intermediate.

[0123] The copper seed layer was characterized by electron backscatter diffraction (EBSD). Figure 10 The image shown is an EBSD plot of the copper seed layer cross-section in Example 1. Figure 10 As can be seen, the copper seed layer formed by magnetron sputtering deposition has many defects on its surface and inside, which allows the subsequent chemical etchant to penetrate and diffuse smoothly into the first base film for etching, thereby selectively etching away part of the PET film.

[0124] (3) Prepare a 0.5 mol / L lithium methoxide (CH3OLi)-methanol solution as an alkaline etchant; pass the first intermediate strip obtained above through a tank containing the alkaline etchant at a speed of 2 m / min, control the liquid temperature at 40°C, and soak for 5 min. The PET film (i.e., the first base film) undergoes partial depolymerization to form a porous polymer skeleton with multiple through-holes, while the PP film (i.e., the second base film) is completely retained, thus obtaining the second intermediate.

[0125] Figure 11 This is an optical microscope image of the porous polymer framework formed after the PET film in Example 1 was etched. From... Figure 11 As can be seen, after etching, multiple through-holes of varying sizes are formed on the PET film, ranging from 1μm to 100μm.

[0126] (4) The above-mentioned second intermediate strip is washed and dried in sequence through a deionized water spray tank and a hot air drying oven (80°C). Then, at room temperature (25°C), the dried strip is rolled with a roller with a pressure of 50MPa, so that the upper and lower copper seed layers (i.e., the first metal seed layer and the second metal seed layer) corresponding to the porous polymer skeleton are embedded in the through holes and form a connection.

[0127] (5) Copper sulfate electroplating is used with a concentration of 100 g / L and a current density of 1.5 A / dm³. 2 The time is controlled at about 5 minutes to increase the total thickness of the copper seed layer (i.e. the first metal seed layer and the second metal seed layer) to 1.0 μm, forming the first metal layer and the second metal layer, and obtaining the composite current collector.

[0128] The composite current collector is divided into a tab region and a coating region along the thickness direction. The tab region is 50 mm long and includes a second metal layer (1.0 μm thick), a copper seed layer (i.e., the second metal seed layer, 100 nm thick), a porous polymer skeleton (4.5 μm thick), a copper seed layer (i.e., the first metal seed layer, 100 nm thick), and a first metal layer (1.0 μm thick) stacked sequentially along the thickness direction. The porous polymer skeleton has multiple through holes, and the upper and lower copper seed layers are embedded in the through holes to form a connection. That is, the tab region is copper layer-porous PET skeleton-copper. The coating area is 450 mm long and includes a first metal layer (1.0 μm thick), a copper seed layer (i.e., the second metal seed layer, 100 nm thick), a PP film (i.e., the second base film, 4.5 μm thick), a copper seed layer (i.e., the first metal seed layer, 100 nm thick), and a second metal layer (1.0 μm thick) stacked sequentially along the thickness direction. That is, the coating area retains a complete copper-PP-copper structure.

[0129] Example 2 This embodiment provides a composite current collector, the preparation method of which includes the following steps: (1) Take a PET film with a thickness of 4.5μm and a length of 50mm (i.e., the first base film) and a PP film with a thickness of 4.5μm and a length of 450mm (i.e., the second base film), and splice them along the length direction by hot pressing the edges to obtain a composite base film.

[0130] (2) Ar plasma treatment was performed on the composite base film; then magnetron sputtering was performed on the opposite two sides of the composite base film, with the vacuum degree controlled at 0.5 Pa, the sputtering power at 1 kW, the tape speed at 0.5 m / min, and the cooling roller temperature controlled at -20 °C, to deposit copper seed layers (i.e., the first metal seed layer and the second metal seed layer) with a thickness of 100 nm respectively, to obtain the first intermediate.

[0131] (3) Prepare a 2.2 mol / L lithium methoxide (CH3OLi)-methanol solution as an alkaline etchant; pass the first intermediate strip obtained above through a tank containing the alkaline etchant at a speed of 0.5 m / min, control the liquid temperature at 50°C, and soak for 30 min until the PET film (i.e. the first base film) is completely etched away, while the PP film (i.e. the second base film) is completely retained, to obtain the second intermediate.

[0132] (4) The above-mentioned second intermediate strip is washed and dried in sequence through a deionized water spray tank and a hot air drying oven (80°C). Then, at room temperature (25°C), the dried strip is rolled with a roller with a pressure of 10MPa so that the upper and lower parts of the copper seed layer (i.e. the first metal seed layer and the second metal seed layer) of the original PET film (i.e. the first base film) come into contact and become conductive.

[0133] (5) Copper sulfate electroplating is used with a concentration of 100 g / L and a current density of 1.5 A / dm³. 2 The time is controlled at about 5 minutes to increase the total thickness of the copper seed layer (i.e. the first metal seed layer and the second metal seed layer) to 1.0 μm, forming the first metal layer and the second metal layer, and obtaining the composite current collector.

[0134] Figure 12 This is an optical microscope image of the cross-section of the composite current collector in Example 2, showing the PET film completely etched. Figure 12 As can be seen, the PET film in the tab area is completely etched, the upper and lower copper layers are completely bonded after rolling, the thickened copper layer is not significantly different from the seed copper layer, and the edge is the coating area where the polymer is completely retained.

[0135] The composite current collector is divided into a tab region and a coating region along its thickness direction. The tab region is 50 mm long and includes a second metal layer (1.0 μm thick), a copper seed layer (i.e., the second metal seed layer, 100 nm thick), a copper seed layer (i.e., the first metal seed layer, 100 nm thick), and a first metal layer (1.0 μm thick) stacked sequentially along the thickness direction. In other words, the tab region is a pure metal foil formed by directly laminating copper layers. The coating region is 450 mm long and includes a second metal layer (1.0 μm thick), a copper seed layer (i.e., the second metal seed layer, 100 nm thick), a PP film (i.e., the second base film, 4.5 μm thick), a copper seed layer (i.e., the first metal seed layer, 100 nm thick), and a first metal layer (1.0 μm thick) stacked sequentially along the thickness direction. In other words, the coating region retains a complete copper-PP-copper layer structure.

[0136] Comparative Example 1 This comparative example provides a composite current collector, the preparation method of which includes the following steps: (1) Take a PP film with a thickness of 4.5μm and a length of 450mm.

[0137] (2) Ar plasma treatment was performed on the PP film; then magnetron sputtering was performed on the opposite two sides of the PP film, with the vacuum degree controlled at 0.5 Pa, the sputtering power at 1 kW, the tape speed at 0.5 m / min, and the cooling roller temperature controlled at -20 °C, to deposit copper seed layers (i.e., the first metal seed layer and the second metal seed layer) with a thickness of 100 nm respectively.

[0138] (3) Copper sulfate electroplating was used with a concentration of 100 g / L and a current density of 1.5 A / dm³. 2 The time is controlled at about 5 minutes to increase the total thickness of the copper seed layer (i.e. the first metal seed layer and the second metal seed layer) to 1.0 μm, forming the first metal layer and the second metal layer, and obtaining the composite current collector.

[0139] Performance testing and results analysis Sheet resistance and welding tests were performed on the composite current collectors obtained in Example 1, Example 2, and Comparative Example 1. The test results are shown in Table 1. The specific test methods are as follows: (1) Sheet resistance: Sheet resistance is tested using a four-probe sheet resistance tester.

[0140] (2) Welding pull force: In Examples 1 and 2, an ultrasonic spot welding machine was used to directly weld the tab area of ​​a single-layer or multi-layer composite current collector to a nickel adapter piece, with a weld mark size of 5mm×5mm. Cut the welded sample into a length of 90mm and a width of 15mm, and clamp it vertically on the tensile testing machine. The copper foil for the transfer welding is clamped above, and the composite current collector is clamped below. Select the tensile test mode, set the tensile gauge length to 50mm, and the tensile speed to 50mm / min. Record the maximum force at tensile fracture.

[0141] Table 1 Performance test results of composite current collectors

[0142] As can be seen from Table 1, the sheet resistance of Examples 1 and 2 is significantly lower than that of Comparative Example 1, indicating that the upper and lower metal layers of the foil in Examples 1 and 2 have achieved conductivity. Furthermore, judging from the welding effect, a firm weld with the adapter piece can be achieved, and multi-layer direct welding can also be achieved.

[0143] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for preparing a composite current collector, characterized in that, Includes the following steps: S1: Provide a composite base film, the composite base film including at least one first base film and at least one second base film arranged side by side along a first direction, the first base film and the second base film being made of different materials; S2: A first metal seed layer and a second metal seed layer are formed on opposite sides of the composite base film by magnetron sputtering or vacuum evaporation to obtain a first intermediate. S3: The first intermediate is subjected to selective etching treatment in a chemical etchant to remove at least part of the first base film while retaining the second base film, thereby obtaining the second intermediate; S4: Roll the second intermediate so that the first metal seed layer and the second metal seed layer come into contact and become connected at the part corresponding to where the first base film is removed; S5: A first metal layer and a second metal layer are deposited on the surfaces of the first metal seed layer and the second metal seed layer respectively to obtain a composite current collector; along the thickness direction, the conductive part is defined as the tab region, and the other part corresponding to the second base film is defined as the coating region.

2. The preparation method according to claim 1, characterized in that, In step S3, selective etching is used to remove part of the first base film, forming a plurality of through holes in the first base film; optionally, the pore size of the through holes is 0.1μm~100μm; Alternatively, in step S3, selective etching is used to completely remove the first base film.

3. The preparation method according to claim 1, characterized in that, The material of the first base film includes at least one of ester-containing polymers, amide-containing polymers, or nitrile-containing polymers; the second base film includes a polyolefin polymer; in step S3, the chemical etchant is an alkaline etchant. Optionally, the material of the first base film includes at least one of polyethylene terephthalate, polycarbonate, polyamide, or polyacrylonitrile; the material of the second base film includes at least one of polypropylene or polyethylene; and the chemical etchant includes at least one of a methanol solution of lithium methoxide, an ethanol solution of lithium ethoxide, an ethanol solution of sodium hydroxide, or an ethylenediamine solution of sodium hydroxide.

4. The preparation method according to claim 3, characterized in that, The concentration of the alkaline corrosive agent is 0.1 mol / L to 2.5 mol / L, and the temperature of the selective corrosion treatment is 25℃ to 60℃, and the time is 5 min to 60 min. Optionally, the thickness of the first base film and the second base film are each independently 3μm to 10μm.

5. The preparation method according to claim 1, characterized in that, In step S4, the pressure of the roller is 1MPa~100MPa.

6. The preparation method according to claim 1, characterized in that, In step S2, magnetron sputtering is used, with a vacuum level of 0.1 Pa to 1 Pa in the coating chamber, a sputtering power of 0.1 kW to 10 kW, a film feed speed of 0.1 m / min to 5 m / min, and a cooling roller temperature of -25℃ to 0℃; or, in step S2, vacuum evaporation is used, with a vacuum level greater than 10 kPa in the coating chamber. -3 Pa, evaporation source distance is 10cm~25cm, deposition time is 5m / min~100m / min; Optionally, the thickness of the first metal seed layer and the second metal seed layer are each independently 10 nm to 100 nm; Optionally, the materials of the first metal seed layer and the second metal seed layer are each independently at least one of copper or aluminum; Optionally, before step S2, the composite base film is further subjected to plasma treatment; Optionally, the first base film has a first surface and a second surface along the thickness direction, and the second base film has a third surface and a fourth surface along the thickness direction, wherein the first surface and the third surface are flush, and the second surface and the fourth surface are flush.

7. The preparation method according to claim 1, characterized in that, In step S5, the first metal layer and the second metal layer are respectively thickened and deposited on the surfaces of the first metal seed layer and the second metal seed layer by electroplating, chemical plating or magnetron sputtering processes. Optionally, the thickness of the first metal layer and the second metal layer are each independently 1 μm to 6 μm; Optionally, the first metal layer and the second metal layer are each made of at least one of copper or aluminum.

8. A composite current collector, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. An electrode sheet, characterized in that, It includes the composite current collector as described in claim 8 and an active material layer disposed on at least one side surface of the composite current collector.

10. A battery, characterized in that, Including the electrode as described in claim 9.

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