Composite current collector and preparation method thereof

Abstract

The invention relates to the technical field of batteries, in particular to a composite current collector and a preparation method thereof. The composite current collector comprises a base material layer, and the base material layer is made of a flexible composite material and is a thin film; the conductive layers are arranged on the base material layer, each conductive layer comprises one or more of a metal material, a carbon-based conductive material and a conductive polymer material, and the number of the conductive layers is multiple; the metal layers are arranged between the adjacent conductive layers, the material of the metal layers is any one of Ni, Cr, NiCr alloy, Ti and Ti alloy, and the thickness of the metal layers is 0.5-3 nm; and sequentially plating the base layer, the conductive layer, the metal layer, the conductive layer, the metal layer and the like on the base material layer in a manner of double rotating cathodes and direct current magnetron sputtering. By arranging the metal layer between the film layers, interlayer defects and stress can be reduced, and the adhesive force of the film layers can be improved, so that the resistance of the current collector to a corrosive environment is improved, the cycle life of the battery is prolonged, and the overall quality of the lithium battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a composite current collector and a preparation method thereof. Background Art

[0002] Aluminum foil and copper foil are widely used as current collectors for positive and negative electrodes in batteries. However, because they are composed of pure metal and are brittle and have low toughness, they are prone to breakage and edge damage during the coating, rolling, drying, slicing, and other processes in the production of lithium-ion battery electrode materials that are exposed to heat and tension. This results in material waste, poor product consistency, and reduced production efficiency. Increasing the thickness of the metal current collector reduces its thermal conductivity, leading to heat accumulation and uneven temperature distribution, increasing costs. This also increases manufacturing costs and the cost of materials used, and reduces energy density.

[0003] Therefore, many studies have begun to focus on replacing traditional metal current collectors with lightweight, flexible metal / plastic composite film materials to achieve higher safety, higher volumetric energy density, and higher mass energy density in lithium batteries. However, compared with traditional metal foil, the conductive metal Al layer of this composite current collector is thinner, resulting in more severe corrosion in electrolyte environments than traditional metal aluminum foil.

[0004] The composite current collector obtained by providing a conductive layer on the surface of a low-density polymer film can effectively reduce the density of the current collector in lithium-ion batteries and increase the weight energy density of lithium-ion batteries. However, when depositing the polymer film on the conductive layer, internal stress will be generated in the film due to bombardment by sputtered ions, interface mismatch, film growth phase transition stress, thermal stress, and other reasons. After the film is deposited, the internal stress of the film will be partially released over time through plastic deformation of the substrate and the disappearance of film defects. As the internal stress is partially released, the internal stress gradually decreases, which in turn leads to a decrease in the shear stress acting on the base film-coating interface, resulting in partial film bonding failure and reduced film bonding performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing composite current collector plated with a polymer film has low film adhesion, poor weather resistance and a short battery cycle life.

[0006] To this end, the present invention provides a composite current collector coating structure and a preparation method thereof.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] A composite current collector comprising:

[0009] A substrate layer, wherein the substrate layer is made of a flexible composite material and is a film;

[0010] A conductive layer, the conductive layer being disposed on the substrate layer, the conductive layer comprising one or more of a metal material, a carbon-based conductive material, and a conductive polymer material, and the conductive layer being provided with multiple layers;

[0011] The metal layer is provided between adjacent conductive layers, and the material of the metal layer is any one of Ni, Cr, NiCr alloy, Ti, and Ti alloy.

[0012] Furthermore, the thickness of the metal layer is 0.5-3 nm.

[0013] Furthermore, when the conductive layer includes a metal material, the conductive layer includes one or more of Al, Cu, Ni, Ti, Ag, NiCu alloy and AlZr alloy.

[0014] Furthermore, when the conductive layer includes a carbon-based conductive material, the conductive layer includes one or more of graphite, superconducting carbon, carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0015] Furthermore, when the conductive layer comprises a conductive polymer material, the conductive layer comprises one or more of polysulfur nitride, aliphatic conjugated polymer, aromatic ring conjugated polymer and aromatic heterocyclic conjugated polymer.

[0016] Furthermore, the thickness of the conductive layer is 5-500 nm.

[0017] Furthermore, the thickness of the conductive layer is 10-50 nm.

[0018] Furthermore, it also includes a base layer, which is arranged on the substrate layer. The material of the base layer is any one of Ni, Cr, NiCr alloy, Ti, and Ti alloy. The base layer is arranged between the conductive layer arranged close to the substrate layer and the substrate layer.

[0019] A method for preparing a composite current collector comprises the following steps:

[0020] The substrate layer material is placed on the unwinding roller of the magnetron sputtering coating machine. The target materials for the base layer, conductive layer, and metal layer are placed in different chambers of the magnetron sputtering coating machine. The distance between the target material and the substrate surface is adjusted to 10 cm. Each chamber is evacuated and filled with process gas.

[0021] Cleaning the surface of the substrate layer;

[0022] By means of double rotating cathode and DC magnetron sputtering, a base layer, a conductive layer, a metal layer and a conductive layer are plated on the substrate layer in sequence.

[0023] Furthermore, when the conductive layer is plated, 300 sccm of argon gas is introduced into the chamber, the chamber pressure is stabilized at 0.3 Pa, the dual rotating cathode and DC magnetron sputtering power are 0.5Kw to 5Kw, and when the metal layer is plated, 300 sccm of argon gas is introduced into the chamber, the chamber pressure is stabilized at 0.3Pa, and the dual rotating cathode and DC magnetron sputtering power are 5Kw to 15Kw.

[0024] The beneficial effect of the present invention is that, firstly, a flexible substrate layer is used to alleviate stress cracking of the film layer caused by temperature changes.

[0025] Adding a metal layer to the flexible substrate layer can help regulate stress distribution within the film. By interrupting grain growth and promoting grain refinement in the conductive layer, the grain boundary size is increased, thereby dispersing internal stress and reducing defects caused by stress concentration. Furthermore, because the lattice constants of the extremely thin metal layer and the conductive layer material differ, optimizing the material can effectively adjust the residual stress of the film, thereby reducing performance degradation caused by stress. Furthermore, the metal layer can improve the interface quality between the film layers, reduce defects and stress, and enhance the adhesion of the film layers.

[0026] By adding an extremely thin metal layer, the surface energy of the conductive layer can be optimized, and the surface roughness of the film can be reduced, resulting in a smoother film surface, which is beneficial for improving the film's electrical properties. The metal layer can optimize crystal orientation and reduce interface defects, increasing the film's carrier mobility and improving the overall conductivity of the film.

[0027] The ultra-thin metal layer can reduce defects such as holes and cracks during film growth, resulting in better thermal stability of the current collector at high battery temperatures and improving the overall quality of the lithium battery. The addition of an ultra-thin metal layer also results in smaller grains and more grain boundaries in the conductive layer, improving the current collector's resistance to corrosive environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below with reference to the accompanying drawings and examples.

[0029] Figure 1 It is a schematic structural diagram of the composite current collector in the present invention.

[0030] In the figure: 1. Base material layer; 2. Base layer; 3. Conductive layer; 4. Metal layer. DETAILED DESCRIPTION

[0031] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0033] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0034] Example 1

[0035] A composite current collector comprises a substrate layer 1, a primer layer 2, a conductive layer 3 and a metal layer 4.

[0036] Among them, the substrate layer 1 is a flexible material, and the substrate layer 1 can be a biaxially oriented polypropylene film (OPP), a cast polypropylene film (CPP), a polyethylene terephthalate film (PET), a polyimide film (PI) or a polyethylene naphthalate film (PEN), and the thickness of the substrate layer 1 is 3 to 20 μm.

[0037] It should be noted that in the field of battery current collectors, since hard substrates are usually unable to achieve large-area rapid coating, and during coating, due to the different thermal expansion coefficients of the substrate and the coating material, when the temperature changes, the substrate and the coating shrink or expand inconsistently, which will generate stress in the coating. The rigidity of the hard substrate is relatively high and it is not easy to deform, so it is impossible to release these stresses by deformation, which easily leads to cracking of the coating, and the thicker the coating, the greater the stress. Therefore, the use of a flexible substrate can alleviate the stress cracking caused by temperature changes, and the flexible substrate is suitable for large-area coating preparation products, with excellent uniformity and low cost. The base layer 2 is arranged on one or both sides of the substrate layer 1. The material of the base layer 2 is preferably Ni, Cr, NiCr alloy, Ti, Ti alloy, etc., and the thickness is preferably 1 to 20 nm. In other embodiments, the base layer 2 may not be provided on the substrate layer 1.

[0038] Conductive layer 3 is disposed on the side of primer layer 2 away from substrate layer 1. Multiple conductive layers 3 may be provided, with at least two conductive layers 3 provided on each side of substrate layer 1. The number N of conductive layers 3 is 2 to 1000, and the thickness of each conductive layer 3 is 5 nm to 500 nm, preferably 10 to 50 nm. In this embodiment, two conductive layers 3 are provided on each side of the substrate. When primer layer 2 is not provided on substrate layer 1, conductive layer 3 is provided directly on substrate layer 1.

[0039] The conductive layer 3 comprises one or more of a metal material, a carbon-based conductive material, and a conductive polymer material. It should be noted that when the conductive layer 3 comprises a metal material, the conductive layer 3 comprises one or more of Al, Cu, Ni, Ti, Ag, NiCu alloy, and AlZr alloy; when the conductive layer 3 comprises a carbon-based conductive material, the conductive layer 3 comprises one or more of graphite, superconducting carbon, carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; and when the conductive layer 3 comprises a conductive polymer material, the conductive layer 3 comprises one or more of polysulfur nitride, aliphatic conjugated polymers, aromatic ring conjugated polymers, and aromatic heterocyclic conjugated polymers.

[0040] The metal layer 4 is arranged between adjacent conductive layers 3. The material of the metal layer 4 is preferably Ni, Cr, NiCr alloy, Ti, Ti alloy, etc., the thickness is preferably 0.5 to 3 nm, and the number of metal layers 4 is N layers; it should be noted that the materials of multiple conductive layers 3 can be different materials, and the materials of multiple metal layers 4 can also be different materials.

[0041] A metal layer 4 is placed between the conductive layers 3. The addition of this extremely thin metal layer 4 provides a suitable surface for thin film growth, facilitating the nucleation and growth of the conductive layer 3. This promotes uniform growth of the conductive layer 3 and improves its crystalline quality. Selecting a specific material for the metal layer 4 can guide the crystal orientation of the thin film, resulting in a specific crystal structure for the deposited conductive layer 3. For example, an extremely thin Ti layer can enhance the {111} fiber texture of the Cu thin film in the conductive layer 3. This specific crystal orientation can improve the physical properties of the film.

[0042] When coating a substrate surface, as the film thickness increases, the stress within the film increases, causing cracks, warping, or delamination. These stresses may originate from thermal stress, residual stress, or lattice mismatch during film growth. Adding an extremely thin metal layer 4 can help regulate the stress distribution in the film by interrupting grain growth, promoting grain refinement of the conductive layer 3, and increasing the grain boundary size, thereby dispersing internal stress and reducing defects caused by stress concentration. At the same time, since the lattice constants of the extremely thin metal layer 4 and the conductive layer 3 materials are different, the residual stress of the film can be effectively adjusted by optimizing the material, thereby reducing performance degradation caused by stress.

[0043] To improve the weather resistance of batteries, increasing film thickness is a common practice. However, thicker conductive films can form a weak adhesion interface between the substrate and the film layer, which can lead to shedding or flaking of the conductive film, especially under thermal cycling or mechanical stress. The extremely thin metal layer 4 can improve the interface quality between the conductive layer and the substrate, reducing defects and stress, and improving the adhesion of the film layer.

[0044] The addition of an extremely thin metal layer 4 optimizes the surface energy of the conductive layer 3 and reduces the surface roughness of the film, resulting in a smoother surface. This improves the film's electrical properties. The metal layer 4 also optimizes crystal orientation and reduces interface defects, increasing the film's carrier mobility and overall conductivity.

[0045] The addition of an ultra-thin metal layer 4 reduces defects during film growth, such as holes and cracks. This improves the thermal stability of the current collector at high battery temperatures and the overall quality of the lithium battery. The addition of this ultra-thin metal layer 4 also results in smaller grains and more grain boundaries in the conductive layer 3, enhancing the current collector's resistance to corrosive environments.

[0046] Example 2

[0047] A method for preparing a composite current collector comprises the following steps:

[0048] The coating structure is preferably prepared under vacuum conditions using processes such as evaporation, sputtering, and CVD. Since the uniformity of the film formed by sputtering is better than that of the film formed by evaporation, etc., sputtering is preferred when forming a film on a large substrate; the sputtering method can use alternating current (AC) magnetron sputtering, direct current (DC) magnetron sputtering, and radio frequency (RF) magnetron sputtering. Since the silver target is a conductor, direct current (DC) magnetron sputtering is preferred.

[0049] Step 1: In multiple chambers of a winding magnetron sputtering coating machine, the processed flexible substrate is placed on the unwinding roller of the unwinding chamber and wound onto the winding roller; at the same time, the required target materials: base layer 2A, conductive layer 3A1, metal layer 4B1, conductive layer 3A2, and extremely thin metal layer 4B2 are placed in sequence on the corresponding cathode target positions of chambers C1, C2, C3, C4, and C5. The coating chambers for placing the base layer 2, conductive layer 3, and metal layer 4 are adjacent to each other, and the adjacent coating chambers are separated by air-isolating baffles; and the distance from the target material to the substrate surface is adjusted to 10 cm; all chamber doors are closed, and the front pump and molecular pump are opened in sequence. When the vacuum degree of the chamber reaches 5×10-4Pa, the process gas is filled in to the process vacuum, the cathode and drive roller are opened to start coating, and the winding speed is controlled at 5-12m / min. During the magnetron sputtering deposition coating, the temperature in all chambers is kept constant at -15°C to 15°C.

[0050] Step 2: Pre-treatment of flexible substrate

[0051] Argon gas is introduced into the vacuum chamber and ionized by supplying 800W of power to the ion source to clean the surface of the substrate;

[0052] Step 3: Formation of the bottom layer 2A compound

[0053] Argon gas with a purity of not less than 99.99% is introduced into chamber C1 at a rate of 400 sccm. The chamber pressure is stabilized at 0.3 Pa. A base layer 2 compound layer of a certain thickness is formed on the base film using target material A by means of a dual-rotating cathode and DC magnetron sputtering. The composition of the base layer 2 compound layer is the same as that of the sputtering target material A. The power of the dual-rotating cathode and DC magnetron sputtering is 5 kW to 15 kW.

[0054] Step 4: Formation of the conductive layer 3A1

[0055] After the base layer 2 compound layer A is formed, sputtering gas argon with a purity of not less than 99.99% is introduced into chamber C2, the argon gas volume is 300 sccm, and the chamber pressure is stabilized at 0.3 Pa. By using a dual-rotating cathode and DC magnetron sputtering method, an A1 target material is used to form a dielectric layer A1 of a certain thickness on the film layer base layer 2 compound layer A. The composition of the film layer is the same as that of the sputtering target material A1; the dual-rotating cathode and DC magnetron sputtering power is 0.5Kw~5Kw.

[0056] Step 5: Formation of an extremely thin metal layer 4B1

[0057] After the film layer A1 is formed, sputtering gas argon with a purity of not less than 99.99% is introduced into chamber C3 at a rate of 300 sccm. The chamber pressure is stabilized at 0.3 Pa. By means of dual-rotating cathode and DC magnetron sputtering, a B1 layer of a certain thickness is formed on the film layer A1 using the B2 target material. The composition of B1 is the same as that of the sputtering target material B1. The dual-rotating cathode and DC magnetron sputtering power is 5 kW to 15 kW.

[0058] Repeat steps 4 to 5, sequentially plating the conductive layer 3A2, the ultra-thin metal layer 4B2, the conductive layer 3A3, the ultra-thin metal layer 4B3, etc.

[0059] Furthermore, in order to verify the adhesion of the film layer having the above-mentioned composite current collector, a 180° adhesive peeling method was used. The adhesive method is suitable for films with relatively low adhesion, that is, the adhesion between the film and the substrate must be less than the adhesion between the film and the adhesive. The selected adhesive should have a very small volume shrinkage rate after curing. The peeling method is to adhere an adhesive tape of a certain width to the surface of the film, and then apply tension to the adhesive tape at a certain angle. After pulling the adhesive tape off, the adhesion strength can be judged based on the peeling condition of the film. The specific steps are as follows: prepare a composite current collector sample with a width of 25 mm and a length of 150 mm. For different positive electrode current collectors, set up multiple experimental groups as shown in Table 1, and set up a control group. Among them, the composite current collector samples in the experimental groups are composite current collectors as described in Example 1, prepared using the preparation method of Example 2. The current collector of the control group only includes a base layer 2, and pure copper is plated on the base layer 2.

[0060] Adhere the tape to the current collector samples of experimental groups 1-9 and control group 1, and use a 4.5lb roller to fully compact the tape to ensure good adhesion. Leave the bonded tape and sample for a period of time to allow it to rest to ensure that the adhesion between the tape and the coating on the sample is sufficiently stable. Use an electronic tensile testing machine to perform a peeling test at a peeling speed of 100mm / min±5mm / min; test each group of samples three times and take the average value, which is recorded as the initial value; after testing the initial value, test the sample with double 85 cycles for 7 days, and then re-sample and test its peel strength, and record this value as the 7-day value.

[0061] Table 1 Current collector film adhesion test results

[0062]

[0063]

[0064] In summary, the initial adhesion of the film layer on the composite current collector (experimental groups 1-9) as described in Example 1 prepared by the method of Example 2 is stronger than the adhesion of the coating on the control group 1, and its initial adhesion is mostly above 3N / cm. After 7 days of double 85 cycle test, the adhesion of the control group 1 decreased by 42.9%, while the adhesion rate of the experimental group did not exceed 30%, and the adhesion rate of most experimental groups was about 10%, that is, the composite current collector film layer as described in Example 1 prepared by the method of Example 2 has strong adhesion.

[0065] Furthermore, in order to verify the performance of the battery having the composite current collector, a charge and discharge performance test at a 1C rate was performed using an 18650 battery to test the cycle life of the battery after coating.

[0066] About the preparation of battery materials:

[0067] Lithium iron phosphate (LiFePO4) is selected as the positive electrode material of the battery, graphite is used as the negative electrode active material of the battery, and polypropylene (PP) or polyethylene (PE) is selected as the battery separator. The electrolyte in the battery is composed of lithium salt (such as LiPF6), solvent (such as EC / DMC / DEC) and additives.

[0068] It should be noted that for different negative electrode current collectors, multiple experimental groups as shown in Table 2 were set up, and a control group was set up, wherein the current collector in the experimental group was a composite current collector as described in Example 1 prepared by the preparation method of Example 2, and the current collector in the control group only included a base layer 2, and pure copper was plated on the base layer 2.

[0069] The production of the battery includes the following steps:

[0070] S1 slurry preparation: Mix the positive or negative electrode active material with the binder and conductive agent, add an appropriate amount of solvent, and stir evenly to form a slurry.

[0071] S2 coating: Use a coating machine to evenly coat the slurry on the aluminum foil (positive electrode) or copper foil (negative electrode) to form a pole piece.

[0072] S3 Drying: Dry the coated electrode in an oven to remove the solvent and excess water.

[0073] S4 compaction: Compact the dried electrode to improve the density and conductivity of the electrode.

[0074] S5 Slitting and Lamination: Slitting the pole pieces according to the size requirements of 18650 batteries. The pole pieces are processed, including welding the pole tabs.

[0075] S6 Winding: The positive electrode sheets, negative electrode sheets and separators are stacked alternately and rolled into a cylindrical core using a winding machine.

[0076] S7: Insert the rolled core into the 18650 battery case. Weld the corresponding contact points between the tabs and the battery case.

[0077] S8 injection: Under the protection of inert gas, inject the electrolyte into the battery shell.

[0078] S9 Sealing: Seal the battery case to prevent electrolyte leakage.

[0079] S10 formation: The battery is charged for the first time after injection to form a solid electrolyte interface (SEI).

[0080] S11 cycle life test.

[0081] The battery is tested for capacity, internal resistance, cycle life, etc. During the entire process, the cleanliness and humidity of the production environment, as well as the battery charging and discharging conditions, need to be strictly controlled to ensure the safety and performance of the battery.

[0082] Table 2 Battery cycle life test results

[0083]

[0084]

[0085] The cycle life test results of the experimental and control group batteries are shown in Table 2. Referring to Table 2, the batteries with the current collector described in Example 2 (experimental groups 1-9) have a cell capacity retention rate of more than 90% after 800 charge and discharge cycles, which is significantly better than the batteries in the control group.

[0086] In summary, the addition of an extremely thin metal layer 4 during the current collector preparation process not only affects the film's microstructure but also directly impacts its macroscopic properties. The metal layer 4 improves the interface quality between the base layer 2 and the substrate, reduces defects and stress, enhances film adhesion, and reduces the film's surface roughness, resulting in a smoother film surface. This improves the film's electrical properties and the current collector's resistance to corrosive environments, thereby increasing the battery's cycle life and overall quality.

[0087] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical spirit of this invention. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A composite current collector, characterized in that: include, A substrate layer (1), wherein the substrate layer (1) is made of a flexible composite material and is a film; A conductive layer (3), the conductive layer (3) being arranged on the substrate layer (1), the conductive layer (3) comprising one or more of a metal material, a carbon-based conductive material and a conductive polymer material, and the conductive layer (3) being provided with multiple layers; A metal layer (4) is provided between adjacent conductive layers (3), and the material of the metal layer (4) is any one of Ni, Cr, NiCr alloy, Ti, and Ti alloy.

2. The composite current collector according to claim 1, characterized in that The thickness of the metal layer (4) is 0.5-3 nm.

3. The composite current collector according to claim 1, wherein: When the conductive layer (3) comprises a metal material, the conductive layer (3) comprises one or more of Al, Cu, Ni, Ti, Ag, NiCu alloy and AlZr alloy.

4. The composite current collector according to claim 1, characterized in that When the conductive layer (3) comprises a carbon-based conductive material, the conductive layer (3) comprises one or more of graphite, superconducting carbon, carbon black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

5. The composite current collector according to claim 1, characterized in that: When the conductive layer (3) comprises a conductive polymer material, the conductive layer (3) comprises one or more of polysulfur nitrides, aliphatic conjugated polymers, aromatic ring conjugated polymers and aromatic heterocyclic conjugated polymers.

6. The composite current collector according to claim 1, characterized in that The thickness of the conductive layer (3) is 5-500 nm.

7. The composite current collector according to claim 5, characterized in that: The thickness of the conductive layer (3) is 10-50 nm.

8. The composite current collector according to claim 1, characterized in that: The invention also includes a primer layer (2), which is arranged on the substrate layer (1). The material of the primer layer (2) is any one of Ni, Cr, NiCr alloy, Ti, and Ti alloy. The primer layer (2) is arranged between the conductive layer (3) arranged close to the substrate layer (1) and the substrate layer (1).

9. A method for preparing a composite current collector, characterized in that: The following steps are included: The substrate layer (1) material is placed on the unwinding roller of the magnetron sputtering coating machine, and the target materials of the base layer (2), the conductive layer (3), and the metal layer (4) are placed in different chambers of the magnetron sputtering coating machine, and the distance between the target material and the substrate surface is adjusted to 10 cm. Each chamber is evacuated and filled with process gas; Cleaning the surface of the substrate layer (1); By means of double rotating cathodes and direct current magnetron sputtering, a base layer (2), a conductive layer (3), a metal layer (4), and a conductive layer (3) are plated on the substrate layer (1) in sequence.

10. The method for preparing a composite current collector according to claim 9, wherein: When the conductive layer (3) is plated, 300 sccm of argon gas is introduced into the chamber, the chamber pressure is stabilized at 0.3 Pa, the dual-rotating cathode and DC magnetron sputtering power are 0.5Kw to 5Kw, and when the metal layer (4) is plated, 300 sccm of argon gas is introduced into the chamber, the chamber pressure is stabilized at 0.3 Pa, and the dual-rotating cathode and DC magnetron sputtering power are 5Kw to 15Kw.

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