Composite current collector and preparation method thereof

Abstract

The invention provides a composite current collector and a preparation method thereof, and belongs to the technical field of composite current collector manufacturing. The composite current collector comprises a polymer base material layer, a polymer transition layer and a conductive metal layer. The surface of the polymer base material layer has polar groups; the polymer transition layer is located on one side or two sides of the high-molecular base material layer, the polymer transition layer is made of a polar material, and the polymer transition layer is connected with polar groups on the surface of the high-molecular base material layer through chemical bonds; the conductive metal layer is located on the side, away from the polymer base material layer, of the polymer transition layer. The polymer base material layer and the conductive metal layer in the composite current collector have excellent bonding strength. Meanwhile, the thickness of the polymer transition layer prepared by the preparation method can be flexibly adjusted, and the polymer transition layer can be easily nanoscale, so that the corresponding composite current collector has relatively excellent energy density; in addition, the whole preparation process of the polymer transition layer does not need to use any solvent, and the method has the advantages of being environmentally friendly and free of pollution.

Description

Technical Field

[0001] This application relates to the field of composite current collector manufacturing technology, and more specifically, to a composite current collector and its preparation method. Background Technology

[0002] In existing technologies, composite current collectors often use polymer materials such as PP, PET, or PI as the intermediate layer. Due to their low surface energy, polymer materials are difficult to bond stably with the conductive metal layer, especially non-polar materials like PP, where the bonding force is even weaker. This causes the conductive metal layer to easily detach from the polymer substrate layer, resulting in a significant reduction in the battery's lifespan. Therefore, there is an urgent need to optimize the structure of composite current collectors to improve the bonding strength between the polymer substrate layer and the conductive metal layer.

[0003] Based on this, technicians have considered adding a polymer transition layer between the polymer substrate layer and the conductive metal layer. However, existing preparation processes usually employ wet coating or solution immersion methods. For example, patent CN 119340400B discloses coating the surface of the polymer substrate layer with a solution containing polymethyl methacrylate, then drying it to form a polymer-containing gel transition layer, and then forming a conductive metal layer on the surface of the transition layer. Another example is patent CN 118156512A, which discloses immersing a polyolefin porous membrane in a solution containing polyimide, then drying it to form a polymer transition layer, and then forming a conductive metal layer on the surface of the transition layer.

[0004] However, the transition layers prepared by these processes usually have some common problems: (1) the thickness of the transition layer is relatively large, making it difficult to prepare a thickness of less than 1 μm, which leads to a decrease in the energy density of the corresponding battery; (2) there is no chemical bond between the transition layer and the substrate layer, resulting in a low bonding strength; (3) the transition layer has poor thickness uniformity. In addition, these preparation processes themselves usually have some common problems: (1) various solvents are used, requiring frequent cleaning and maintenance of equipment, which is cumbersome and causes environmental pollution; for oily slurries, an additional explosion-proof device is usually required; (2) a drying step is usually required afterward, otherwise adhesion between the film layers is likely to occur, resulting in reduced production efficiency and increased energy consumption.

[0005] Therefore, there is an urgent need to optimize the preparation process of composite current collectors containing transition layers in order to improve the aforementioned problems in the existing preparation process. Summary of the Invention

[0006] The purpose of this application is to provide a composite current collector and its preparation method. The polymer substrate layer and the conductive metal layer in the composite current collector have excellent bonding strength. At the same time, the thickness of the polymer transition layer prepared by this method can be flexibly adjusted and can be easily achieved at the nanometer level, so that the corresponding composite current collector has excellent energy density. Furthermore, the entire preparation process of the polymer transition layer does not require the use of any solvents and has the advantages of being environmentally friendly and pollution-free.

[0007] The embodiments of this application are implemented as follows: In a first aspect, embodiments of this application provide a composite current collector, comprising a polymer substrate layer, a polymer transition layer, and a conductive metal layer; the surface of the polymer substrate layer has polar groups; the polymer transition layer is located on one or both sides of the polymer substrate layer, the polymer transition layer is made of a polar material, and the polymer transition layer is connected to the polar groups on the surface of the polymer substrate layer by chemical bonds; the conductive metal layer is located on the side of the polymer transition layer away from the polymer substrate layer.

[0008] In the above technical solution, a polar polymer transition layer is added between the polymer substrate layer and the conductive metal layer of the composite current collector. Specifically, the surface of the polymer substrate layer has polar groups, and the polymer transition layer is connected to the polar groups on the surface of the polymer substrate layer through chemical bonds. This connection method has the advantage of being relatively strong. At the same time, the polar polymer substrate layer has high surface energy and can also be stably bonded to the conductive metal layer. Thus, the added polymer transition layer can improve the bonding strength between the polymer substrate layer and the conductive metal layer, so as to achieve a stable bond between the two.

[0009] In some alternative embodiments, the polar group is selected from at least one of -COOH, -OH and -NH2; and / or the monomer material of the polymer transition layer is selected from at least one of acrylic acid, acrylamide, vinylimidazole, glycidyl methacrylate, methyl methacrylate, allyl glucoside and N-vinylpyrrolidone; and / or the thickness of the polymer transition layer is less than 1 μm; and / or the thickness of the polymer substrate layer is 2 to 50 μm; and / or the thickness of the conductive metal layer is 5 to 5000 nm.

[0010] In the above technical solutions, there are many types of monomer materials applicable to both the polar groups and the polymer transition layer, which can provide a variety of feasible implementation schemes, thereby facilitating the promotion and application of the technical solutions provided in the embodiments of this application; the thickness of the polymer transition layer is less than 1 μm, so that adding the polymer transition layer between the polymer substrate layer and the conductive metal layer will not cause a significant increase in the thickness of the composite current collector, so that it still has a high energy density; in addition, the thickness of both the polymer substrate layer and the conductive metal layer has a large range of selectable thicknesses, which can be compatible with various specifications of composite current collector products at present.

[0011] In some alternative embodiments, the peel strength between the polymer substrate layer and the conductive metal layer is 0.93 to 1.23 N / cm.

[0012] In the above technical solution, the peel strength between the polymer substrate layer and the conductive metal layer is as high as 0.93~1.23 N / cm, so that the corresponding composite current collector has excellent structural stability and can be compatible with various application environments.

[0013] Secondly, embodiments of this application provide a method for preparing a composite current collector, comprising the following steps: S1 provides a polymer substrate layer, which is placed in a pretreatment chamber for plasma treatment; S2 places the plasma-treated polymer substrate layer in a polymerization chamber, and introduces gaseous polar monomers into the polymerization chamber, causing the polar monomers to polymerize in situ on the surface of the polymer substrate layer to form a polymer transition layer; S3 forms a conductive metal layer on the side of the polymer transition layer away from the polymer substrate layer to obtain a composite current collector.

[0014] In the above technical solution, plasma treatment of the polymer substrate layer can clean and activate the surface of the polymer substrate layer, thereby forming numerous polar groups on its surface. Then, gaseous polar monomers are provided into the polymerization chamber containing the plasma-treated polymer substrate layer. The numerous polar groups can then serve as reaction sites, allowing the polar monomers to be grafted onto the polar groups and form a corresponding polar polymer transition layer through chain polymerization. A conductive metal layer is then formed on the side of the polymer transition layer away from the polymer substrate layer. Since the polar polymer transition layer can stably bond with both sides of the polymer substrate layer and the conductive metal layer (specifically, the polar groups on the surface of the polymer transition layer are connected by chemical bonds, which has the advantage of being relatively strong; at the same time, the polar polymer substrate layer has high surface energy and can also stably bond with the conductive metal layer), a high-quality composite current collector with a reliable bond between the polymer substrate layer and the conductive metal layer can be prepared through this process. Furthermore, the polymer transition layer is formed directly by in-situ polymerization of gaseous polar monomers on the surface of the polymer substrate layer. The thickness of the polymer transition layer can be flexibly adjusted and can be easily achieved at the nanoscale, with minimal impact on the product thickness, so that the corresponding composite current collector still has excellent energy density. Moreover, the entire preparation process does not require the use of any solvents (i.e., it is prepared using a completely dry process), which also has the advantages of being environmentally friendly and pollution-free.

[0015] In some optional embodiments, in the plasma treatment step, the treatment power is 0.5~2 KW, the gas flow rate is 50~1000 sccm, and the vacuum degree in the pretreatment chamber is 0.1~50 Pa; or / and, in the plasma treatment step, the gas type is selected from a mixture of inert gas and active gas; or / and, the inert gas is selected from at least one of argon, helium and nitrogen, and the active gas is selected from at least one of oxygen, ammonia and carbon dioxide.

[0016] In the above technical solution, limiting the processing power, gas flow rate, and vacuum degree in the plasma treatment step to the aforementioned ranges provides suitable processing conditions, thereby improving the cleaning effect on the polymer substrate layer and forming a greater number of polar groups on the surface. The gas used in the plasma treatment step can be a single inert gas or an active gas, or a mixed gas containing both inert and active gases, offering numerous implementation options and facilitating adaptive adjustments based on actual needs. Using a mixed gas containing both inert and active gases in the plasma treatment step allows the inert gas to focus more on surface cleaning and increasing surface roughness, while the active gas focuses more on forming polar groups on the surface. The mixed gas integrates the advantages of both gases, resulting in better cleaning and activation effects. A wide variety of inert and active gases are applicable, providing numerous implementation options and facilitating adaptive adjustments based on actual needs.

[0017] In some optional embodiments, the polar monomer is selected from at least one of acrylic acid, acrylamide, vinylimidazole, glycidyl methacrylate, methyl methacrylate, allyl glucoside, and N-vinylpyrrolidone; and / or, the vacuum degree in the polymerization chamber is 50~1000 Pa, the flow rate of the polar monomer is 10~1000 sccm, and the polymerization temperature is 40~100℃; and / or, the polymerization process is carried out under the assistance of plasma treatment; and / or, in step S3, a conductive metal layer is formed on the side of the polymer transition layer away from the polymer substrate layer by magnetron sputtering; and / or, during the magnetron sputtering process, the vacuum degree in the coating chamber is 0.1~10 Pa, and the coating power is 0.1~10 KW.

[0018] In the above technical solution, the polar monomers are selected from the aforementioned types. These polar monomers have low boiling points, enabling them to polymerize at lower temperatures to form a polymer transition layer. This offers advantages such as energy saving and minimal damage to the polymer substrate layer. Furthermore, these polar monomers are commonly used gaseous monomers, resulting in lower operating costs. By limiting the vacuum level, polar monomer flow rate, and polymerization temperature within the aforementioned ranges, suitable polymerization conditions are provided, leading to efficient formation of the polymer transition layer. The polymerization process is conducted under plasma-assisted conditions, which allows for better control of the polymer substrate layer during polymerization. Simultaneous cleaning and activation help improve the formation efficiency of the polymer transition layer and enhance the bonding strength between the polymer substrate layer and the conductive metal layer in the final composite current collector. Magnetron sputtering is used to prepare the conductive metal layer, resulting in advantages such as good thickness uniformity, high density, and strong bonding with the polymer transition layer. This process is also environmentally friendly and has broad material applicability. Limiting the vacuum level and deposition power in the deposition chamber to the aforementioned ranges provides suitable deposition conditions, thereby forming a high-quality conductive metal layer.

[0019] In some alternative implementations, steps S1 to S3 are performed sequentially and continuously in the three chambers of the same reaction apparatus.

[0020] In the above technical solution, steps S1 to S3 are completed sequentially and continuously in the three chambers of the same reaction equipment, which can improve the production efficiency of composite current collectors and reduce the risk of product contamination by impurities. Attached Figure Description

[0021] 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.

[0022] Figure 1 A process flow diagram of a method for preparing a composite current collector provided in an embodiment of this application; Figure 2 A schematic diagram of the structure of the first composite current collector preparation apparatus provided in the embodiments of this application; Figure 3 A schematic diagram of the preparation apparatus for the second composite current collector provided in the embodiments of this application; Figure 4 This is a photograph of the actual product showing the peel strength test results of Embodiment 3 of this application; Figure 5 This is a photograph of the actual product showing the peel strength test results of Embodiment 4 of this application; Figure 6 This is a photograph of the actual product showing the peel strength test results of Comparative Example 1 of this application; Figure 7 This is a photograph of the actual peel strength test results of Comparative Example 2 of this application.

[0023] Icons: 10-Composite current collector preparation device; 100-Unwinding chamber; 110-Unwinding roller; 200-Pretreatment chamber; 210-First electrode plate; 300-Polymerization chamber; 310-Second electrode plate; 400-Coating chamber; 410-Coating cold roller; 420-Metal target; 500-Rewinding chamber; 510-Rewinding roller. Detailed Implementation

[0024] 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.

[0025] It should be noted that the terms "and / or" in this application, such as "feature 1 and / or feature 2", all refer to the three cases of "feature 1" alone, "feature 2" alone, and "feature 1" plus "feature 2".

[0026] In addition, in the description of this application, unless otherwise stated, "one or more" means two or more; the range of "numerical value a to numerical value b" includes the two endpoints "a" and "b"; and "unit of measurement" in "numerical value a to numerical value b + unit of measurement" represents the "unit of measurement" of both "numerical value a" and "numerical value b".

[0027] The following is a detailed description of a composite current collector and its preparation method according to an embodiment of this application.

[0028] In a first aspect, embodiments of this application provide a composite current collector, comprising a polymer substrate layer, a polymer transition layer, and a conductive metal layer; the surface of the polymer substrate layer has polar groups; the polymer transition layer is located on one or both sides of the polymer substrate layer, the polymer transition layer is made of a polar material, and the polymer transition layer is connected to the polar groups on the surface of the polymer substrate layer by chemical bonds; the conductive metal layer is located on the side of the polymer transition layer away from the polymer substrate layer.

[0029] In this application, a polar polymer transition layer is added between the polymer substrate layer and the conductive metal layer of the composite current collector. Specifically, the surface of the polymer substrate layer has polar groups, and the polymer transition layer is connected to the polar groups on the surface of the polymer substrate layer through chemical bonds. This connection method has the advantage of being relatively strong. At the same time, the polar polymer substrate layer has high surface energy and can also be stably bonded to the conductive metal layer. Thus, the added polymer transition layer can improve the bonding strength between the polymer substrate layer and the conductive metal layer, so as to achieve a stable bond between the two.

[0030] It should be noted that there are no restrictions on the types of polar groups, and they can be selected and set in accordance with the conventional methods in this field.

[0031] As an example, the polar group is selected from at least one of -COOH, -OH and -NH2.

[0032] In this embodiment, a wide variety of polar groups are applicable, providing more feasible implementation schemes, thereby facilitating the promotion and application of the technical solutions provided in the embodiments of this application.

[0033] It should be noted that the material of the polymer transition layer is not limited and can be selected and set in accordance with the conventional methods in this field.

[0034] As an example, the monomer material of the polymer transition layer is selected from at least one of acrylic acid, acrylamide, vinylimidazole, glycidyl methacrylate, methyl methacrylate, allyl glucoside, and N-vinylpyrrolidone.

[0035] In this embodiment, a wide variety of monomer materials are applicable to both the polar groups and the polymer transition layer, providing numerous feasible implementation schemes and facilitating the promotion and application of the technical solutions provided in this application.

[0036] As an example, the polymer substrate layer is made of at least one of polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polydiphenylene dimethyl phthalate, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalate), polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, polycarbonate, cellulose, cellulose derivatives, starch, starch derivatives, protein, protein derivatives, polyvinyl alcohol, polyvinyl alcohol crosslinks, polyethylene glycol, and polyethylene glycol crosslinks.

[0037] As an example, the material of the conductive metal layer is selected from at least one of gold, silver, copper, aluminum, iron, chromium, nickel, titanium and their alloys.

[0038] As an example, the thickness of the polymer transition layer is less than 1 μm, for example, but not limited to, a point value or a range between any two of the following thicknesses: 1 nm, 5 nm, 7 nm, 10 nm, 12 nm, 20 nm, 30 nm, 40 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, and 800 nm.

[0039] In this embodiment, the thickness of the polymer transition layer is less than 1 μm, so that adding the polymer transition layer between the polymer substrate layer and the conductive metal layer will not cause a significant increase in the thickness of the composite current collector, thus ensuring that it still has a high energy density.

[0040] It should be noted that the thickness of the polymer substrate layer and the conductive metal layer is not limited and can be set according to conventional choices in the field.

[0041] As an example, the thickness of the polymer substrate layer is 2 to 50 μm, for example, but not limited to any one of the following thicknesses: 2 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm and 50 μm, or any range between two of them.

[0042] As an example, the thickness of the conductive metal layer is 5 to 5000 nm, for example, but not limited to any one of the following values ​​or any range between two: 5 nm, 10 nm, 50 nm, 100 nm, 200 nm, 500 nm, 1000 nm, 2000 nm, 3000 nm, 4000 nm and 5000 nm.

[0043] In this embodiment, the thickness of both the polymer substrate layer and the conductive metal layer has a wide range of selectable thicknesses, which can be compatible with various specifications of composite current collector products at present.

[0044] As an example, the peel strength between the polymer substrate layer and the conductive metal layer is 0.93~1.23 N / cm.

[0045] In this embodiment, the peel strength between the polymer substrate layer and the conductive metal layer is as high as 0.93~1.23 N / cm, so that the corresponding composite current collector has excellent structural stability and can be compatible with various application environments.

[0046] It should be noted that, for composite current collectors, any structural or functional units not specifically described or limited can be selected and configured in accordance with conventional practices in the field.

[0047] Secondly, embodiments of this application provide a method for preparing a composite current collector, comprising the following steps: S1 provides a polymer substrate layer, which is placed in a pretreatment chamber for plasma treatment; S2 places the plasma-treated polymer substrate layer in a polymerization chamber, and introduces gaseous polar monomers into the polymerization chamber, causing the polar monomers to polymerize in situ on the surface of the polymer substrate layer to form a polymer transition layer; S3 forms a conductive metal layer on the side of the polymer transition layer away from the polymer substrate layer to obtain a composite current collector.

[0048] In this application, plasma treatment of the polymer substrate layer can clean and activate the surface of the polymer substrate layer, thereby forming numerous polar groups on its surface. Then, gaseous polar monomers are provided into the polymerization chamber containing the plasma-treated polymer substrate layer, and the numerous polar groups can be used as reaction sites to graft the polar monomers onto the polar groups and form a corresponding polar polymer transition layer through chain polymerization. Then, a conductive metal layer is formed on the side of the polymer transition layer away from the polymer substrate layer. Since the polar polymer transition layer can be stably bonded to both sides of the polymer substrate layer and the conductive metal layer (specifically, the polar groups on the surface of the polymer transition layer are connected to the polymer substrate layer through chemical bonds, which has the advantage of being relatively strong; at the same time, the polar polymer substrate layer has high surface energy and can also be stably bonded to the conductive metal layer), a high-quality composite current collector with a strong bond between the polymer substrate layer and the conductive metal layer can be prepared by this process.

[0049] Furthermore, it should be emphasized that in the step of preparing the polymer transition layer, the polymer transition layer is directly formed by in-situ polymerization of gaseous polar monomers on the surface of the polymer substrate layer. The thickness of the polymer transition layer can be flexibly adjusted and can be easily achieved at the nanoscale, with little impact on the product thickness, so that the corresponding composite current collector still has a relatively excellent energy density. Moreover, the entire preparation process does not require the use of any solvents (i.e., it adopts a completely dry process), which also has the advantages of being environmentally friendly and pollution-free.

[0050] It should be noted that the specific configuration of the polymer substrate layer can be referred to the composite current collector provided in the first aspect embodiment.

[0051] It should be noted that the polymer transition layer can be disposed on only one side of the polymer substrate layer or on both sides of the polymer substrate layer. Similarly, the conductive metal layer can be disposed on only one side of the polymer substrate layer or on both sides of the polymer substrate layer.

[0052] As an example, in the plasma treatment step, the treatment power is 0.5~2 KW, for example, but not limited to any one of 0.5 KW, 0.8 KW, 1.0 KW, 1.2 KW, 1.4 KW, 1.6 KW, 1.8 KW and 2.0 KW or any range between two; the gas flow rate is 50~1000 sccm, for example, but not limited to any one of 50 sccm, 100 sccm, 200 sccm, 400 sccm, 600 sccm, 800 sccm and 1000 sccm or any range between two; the vacuum degree in the pretreatment chamber is 0.1~50 Pa, for example, but not limited to any one of 0.1 Pa, 0.5 Pa, 1 Pa, 2 Pa, 5 Pa, 8 Pa, 10 Pa, 20 Pa, 30 Pa, 40 Pa and 50 Pa or any range between two.

[0053] In this embodiment, limiting the processing power, gas flow rate, and vacuum level in the plasma treatment step to the above-mentioned ranges can provide more suitable processing conditions, thereby improving the cleaning effect on the polymer substrate layer and forming more polar groups on the surface.

[0054] As an example, in the plasma treatment step, the gas type is selected from inert gas and / or reactive gas.

[0055] In this embodiment, the gas used in the plasma treatment step can be a single inert gas or an active gas, or a mixture containing both inert and active gases. This provides a variety of implementation options and allows for adaptive adjustments based on actual needs.

[0056] As an example, in the plasma treatment step, the gas type is selected from a mixture of inert and active gases.

[0057] In this embodiment, the gas selected in the plasma treatment step is a mixture of inert and active gases. The effect of the inert gas is more focused on surface cleaning and increasing surface roughness, while the effect of the active gas is more focused on forming polar groups on the surface. Using a mixed gas can integrate the advantages of the two gases, thereby achieving better cleaning and activation effects.

[0058] As an example, the inert gas is selected from at least one of argon, helium and nitrogen, and the active gas is selected from at least one of oxygen, ammonia and carbon dioxide.

[0059] In this embodiment, a wide variety of inert and active gases are applicable, providing numerous feasible solutions that can be adapted to meet specific needs.

[0060] As an example, the polar monomer is selected from at least one of acrylic acid, acrylamide, vinylimidazole, glycidyl methacrylate, methyl methacrylate, allyl glucoside, and N-vinylpyrrolidone.

[0061] In this embodiment, the polar monomers are selected from the above-mentioned types. These polar monomers have the characteristic of low boiling point, which can polymerize at a lower temperature to form a polymer transition layer. They have the advantages of energy saving and are not easy to damage the polymer substrate layer. At the same time, these polar monomers are commonly used gaseous monomers, which also have the advantage of low cost.

[0062] As an example, the vacuum level in the polymerization chamber is 50 to 1000 Pa, for example, but not limited to any one of 50 Pa, 100 Pa, 200 Pa, 300 Pa, 400 Pa, 500 Pa, 600 Pa, 700 Pa, 800 Pa, 900 Pa, and 1000 Pa, or any range between two; the flow rate of the polar monomer is 10 to 1000 sccm, for example, but not limited to any one of 10 sccm, 50 sccm, 100 sccm, 200 sccm, 400 sccm, 600 sccm, 800 sccm, and 1000 sccm, or any range between two; and the polymerization temperature is 40 to 100°C, for example, but not limited to any one of 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C, or any range between two.

[0063] In this embodiment, limiting the vacuum level, the flow rate of polar monomers, and the polymerization temperature in the polymerization chamber to the aforementioned ranges provides suitable polymerization conditions, thereby efficiently forming the polymer transition layer.

[0064] As an example, the polymerization process is carried out under conditions assisted by plasma treatment.

[0065] In this embodiment, the polymerization process is carried out under the auxiliary conditions of plasma treatment, which enables simultaneous cleaning and activation of the polymer substrate layer during the polymerization process. This helps to improve the formation efficiency of the polymer transition layer and better enhance the bonding strength between the polymer substrate layer and the conductive metal layer in the final composite current collector.

[0066] It should be noted that the plasma treatment during the polymerization process can be carried out in accordance with the plasma treatment in step S1, and no specific limitation is made here.

[0067] It should be noted that during the polymerization process under the auxiliary conditions of plasma treatment, the flow ratio between polymerizable polar monomers and non-polymerizable gases is not limited and can be adjusted adaptively according to actual needs.

[0068] As an example, the flow ratio between the polymerizable polar monomer and the non-polymerizable gas (i.e., the gas used for plasma treatment) is 1:(0.1 to 10), for example, but not limited to any one of the flow ratios of 1:0.1, 1:0.5, 1:1, 1:2, 1:4, 1:6, 1:8 and 1:10 or any range between the two.

[0069] It should be noted that there are no restrictions on the preparation method of the conductive metal layer, and it can be prepared according to conventional processes in this field.

[0070] As an example, in step S3, a conductive metal layer is formed on the side of the polymer transition layer away from the polymer substrate layer by magnetron sputtering.

[0071] In this embodiment, a conductive metal layer is prepared by magnetron sputtering deposition, which gives the prepared conductive metal layer advantages such as good thickness uniformity, high density and strong bonding force with the polymer transition layer. In addition, this process is also more environmentally friendly and has strong material versatility.

[0072] As an example, during magnetron sputtering coating, the vacuum level in the coating chamber is 0.1~10 Pa, for example, but not limited to any one of 0.1 Pa, 0.5 Pa, 1 Pa, 2 Pa, 4 Pa, 6 Pa, 8 Pa and 10 Pa or any range between any two; the coating power is 0.1~10 KW, for example, but not limited to any one of 0.1 KW, 0.5 KW, 1 KW, 2 KW, 4 KW, 6 KW, 8 KW and 10 KW or any range between any two.

[0073] In this embodiment, by limiting the vacuum level and coating power in the coating chamber to the above-mentioned ranges, more suitable coating conditions can be provided, thereby forming a high-quality conductive metal layer.

[0074] As an example, steps S1 to S3 are performed sequentially and continuously in the three chambers of the same reaction apparatus.

[0075] In this embodiment, steps S1 to S3 are completed sequentially and continuously in the three chambers of the same reaction device, which can improve the production efficiency of the composite current collector and reduce the risk of product contamination by impurities.

[0076] It should be noted that when using a continuous production process to prepare composite current collectors, the conveying speed of the membrane material can be uniformly controlled. Specifically, the conveying speed of the membrane material can be controlled to be 0.5~10 m / min, for example, but not limited to any one of the following values ​​or any range between two: 0.5 m / min, 1 m / min, 2 m / min, 3 m / min, 4 m / min, 5 m / min, 6 m / min, 7 m / min, 8 m / min, 9 m / min, and 10 m / min.

[0077] It should be noted that for any processes or steps in the preparation of composite current collectors that are not specifically described or limited, they can be carried out in accordance with conventional processes in this field.

[0078] As an example, a process flow diagram of the preparation method of the composite current collector is exemplarily shown below. Figure 1 .

[0079] To better understand the technical solutions for continuous production processes, structural diagrams of two composite current collector preparation devices are provided here for further explanation.

[0080] See Figure 2 , Figure 2 This represents a schematic diagram of a composite current collector fabrication device 10 that prepares a conductive metal layer on only one side of a polymer substrate layer. Specifically, it includes: an unwinding chamber 100, a pretreatment chamber 200, a polymerization chamber 300, a coating chamber 400, and a winding chamber 500, which are sequentially connected and allow film material to pass through. The unwinding chamber 100 contains an unwinding roller 110; the pretreatment chamber 200 contains opposing first electrode plates 210, through which the film material passes; the polymerization chamber 300 contains opposing second electrode plates 310, through which the film material passes; the coating chamber 400 contains a coating cooling roller 410 and a plurality of metal targets 420 for forming the conductive metal layer, spaced circumferentially along the coating cooling roller 410; and the winding chamber 500 contains a winding roller 510.

[0081] It is understood that each chamber is also equipped with guide rollers for conveying the film material. This application embodiment does not make specific limitations, and the configuration can be selected according to the conventional choices in the art.

[0082] See Figure 3 , Figure 3This represents a schematic diagram of the composite current collector fabrication device 10, which fabricates conductive metal layers on both sides of a polymer substrate layer. Figure 2 The only difference is that: the coating chamber 400 is provided with two coating cold rollers 410 that are spaced apart along the film material conveying direction, and each coating cold roller 410 is provided with multiple spaced metal targets 420 for forming a conductive metal layer in the circumferential direction.

[0083] It should be noted that, for any structural or functional units in the composite current collector preparation device that are not specifically described or limited, they can be set according to conventional choices in the field, and the embodiments of this application do not impose specific limitations.

[0084] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0085] Example 1 This application provides a method for preparing a composite current collector, using methods such as... Figure 3 The composite current collector preparation apparatus shown includes the following steps: S1 uses a 4.5 μm thick and 100 m long polypropylene film (obtained by biaxial stretching) as the polymer substrate layer, and then installs it on the unwinding roller in the unwinding chamber by winding. The polymer substrate layer is then unwound and conveyed to the pretreatment chamber for plasma treatment. The film conveying speed is 1 m / min, the gas introduced is oxygen with a flow rate of 1000 sccm, the processing power is 1000 W, and the vacuum degree in the pretreatment chamber is 0.5 Pa.

[0086] S2 transports the plasma-treated polymer substrate layer to the polymerization chamber, and then introduces gaseous acrylic monomers at a flow rate of 200 sccm into the polymerization chamber with a vacuum of 60 Pa, so that the acrylic monomers are polymerized in situ on both sides of the polymer substrate layer to form a polymer transition layer of polyacrylic acid material with a single layer thickness of 5 nm.

[0087] S3 The film material from S2 is further transported to a coating chamber with a vacuum of 5 Pa. Metal Cu is used as the cathode target and the magnetron sputtering power is set to 6 KW to form a conductive metal layer on the surface of the polymer transition layer on both sides of the polymer substrate layer, thus obtaining a composite current collector. Then the prepared composite current collector is transported to a winding chamber and wound up by a winding roller to obtain a composite current collector roll.

[0088] Example 2 This application provides a method for preparing a composite current collector, which differs from Example 1 only in that: S2 transports the plasma-treated polymer substrate layer to the polymerization chamber, and then introduces gaseous acrylic monomers at a flow rate of 200 sccm into the polymerization chamber with a vacuum degree of 60 Pa and a temperature of 55°C, so that the acrylic monomers are polymerized in situ on both sides of the polymer substrate layer to form a polymer transition layer of polyacrylic acid material with a single layer thickness of 7 nm.

[0089] Example 3 This application provides a method for preparing a composite current collector, which differs from Example 1 only in that: S2 transports the plasma-treated polymer substrate layer to the polymerization chamber, and then introduces gaseous acrylic monomers at a flow rate of 400 sccm into the polymerization chamber with a vacuum degree of 60 Pa and a temperature of 55°C, so that the acrylic monomers are polymerized in situ on both sides of the polymer substrate layer to form a polymer transition layer of polyacrylic acid material with a single layer thickness of 10 nm.

[0090] Example 4 This application provides a method for preparing a composite current collector, which differs from Example 1 only in that: S2 transports the plasma-treated polymer substrate layer to the polymerization chamber, and then introduces gaseous acrylic monomers at a flow rate of 400 sccm and oxygen at a flow rate of 200 sccm into the polymerization chamber with a vacuum degree of 60 Pa and a temperature of 55°C. At the same time, the processing power of the electrode plate is set to 1000 W, so that the acrylic monomers are polymerized in situ on both sides of the polymer substrate layer to form a polymer transition layer of polyacrylic acid material with a single layer thickness of 12 nm.

[0091] Comparative Example 1 This application provides a comparative example of a method for preparing a composite current collector, using methods such as... Figure 2 The composite current collector preparation apparatus shown includes the following steps: A 4.5 μm thick and 100 m long polypropylene film (prepared by biaxial stretching) was used as the polymer substrate layer and then mounted on the unwinding roller in the unwinding chamber by winding. The polymer substrate layer was then unwound and transported to a coating chamber with a vacuum of 5 Pa. Using Cu metal as the cathode target and setting the magnetron sputtering power to 6 kW, a conductive metal layer was directly formed on one side of the polymer substrate layer to obtain a composite current collector. The prepared composite current collector was then transported to the winding chamber and wound up by the winding roller to obtain a composite current collector roll.

[0092] Comparative Example 2 This application provides a comparative example of a method for preparing a composite current collector, using methods such as... Figure 3 The composite current collector preparation apparatus shown includes the following steps: S1 uses a 4.5 μm thick and 100 m long polypropylene film (obtained by biaxial stretching) as the polymer substrate layer, and then installs it on the unwinding roller in the unwinding chamber by winding. The polymer substrate layer is then unwound and conveyed to the pretreatment chamber for plasma treatment. The film conveying speed is 1 m / min, the gas introduced is oxygen with a flow rate of 1000 sccm, the processing power is 1000 W, and the vacuum degree in the pretreatment chamber is 0.5 Pa.

[0093] S2 The plasma-treated film material is further transported to a coating chamber with a vacuum of 5 Pa. Metal Cu is used as the cathode target and the magnetron sputtering power is set to 6 KW to form a conductive metal layer on the surface of the polymer transition layer on both sides of the polymer substrate layer, thus obtaining a composite current collector. Then the prepared composite current collector is transported to a winding chamber and wound up by a winding roller to obtain a composite current collector roll.

[0094] Test case Peel strength test of polymer substrate layer and conductive metal layer in composite current collector Test method: The composite current collectors prepared in Examples 1-4 and Comparative Examples 1-2 were used as samples. The peel strength of the polymer substrate layer and the conductive metal layer in each sample was then tested. The specific test steps were as follows: 3M 681 tape was used to adhere to the sample surface, and a rubber roller was used to roll it back and forth twice under its own weight only. Then, the tape was cut along the edge with a blade, and a 180° peel test was performed using a universal tensile testing machine. The tape width was 20 mm, the gauge length was 100 mm, the roller weight was 2 kg, and the tensile speed was 50 mm / min. The test results were then summarized in Table 1.

[0095] Table 1

[0096] Refer to Table 1 and combine it with Figures 4-7 ( Figure 4 and Figure 5 The 3M 681 tape in the middle did not have a conductive metal layer bonded to it, while Figure 6 and Figure 7 Each layer contains a large number of conductive metal layers, and Figure 6 The ratio of the amount of conductive metal layer bonded in the middle Figure 7 As can be seen from the test results of Examples 1-4 and Comparative Examples 1-2, the preparation of the composite current collector according to the preparation process provided in the embodiments of this application, that is, adding a polymer transition layer with a thickness of less than 1 μm between the polymer substrate layer and the conductive metal layer, can effectively improve the bonding strength between the polymer substrate layer and the conductive metal layer.

[0097] The test results of Examples 1-4 show that the in-situ polymerization carried out under plasma-assisted and heated conditions resulted in the best bonding strength between the polymer substrate layer and the conductive metal layer in the prepared composite current collector.

[0098] 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 composite current collector, characterized by, The composite current collector comprises: a polymer substrate layer, a surface of the polymer substrate layer having polar groups; a polymer transition layer, the polymer transition layer being located on one side or both sides of the polymer substrate layer, the polymer transition layer being of a polar material, and the polymer transition layer being connected to the polar groups on the surface of the polymer substrate layer through chemical bonds; a conductive metal layer, the conductive metal layer being located on a side of the polymer transition layer away from the polymer substrate layer.

2. The composite current collector of claim 1, wherein The polar groups are selected from at least one of -COOH, -OH and -NH2; or / and, the monomer material of the polymer transition layer is selected from at least one of acrylic acid, acrylamide, ethylene imidazole, glycidyl methacrylate, methyl methacrylate, allyl glucoside and N-vinyl pyrrolidone; or / and, the thickness of the polymer transition layer is less than 1 μm; or / and, the thickness of the polymer substrate layer is 2-50 μm; or / and, the thickness of the conductive metal layer is 5-5000 nm.

3. The composite current collector according to claim 1 or 2, characterized in that, The peeling strength between the polymer substrate layer and the conductive metal layer is 0.93-1.23 N / cm.

4. A method of making a composite current collector, characterized by, The method comprises the following steps: S1 providing a polymer substrate layer, and placing the polymer substrate layer in a pretreatment chamber for plasma treatment; S2 placing the polymer substrate layer after the plasma treatment in a polymerization chamber, introducing a gaseous polar monomer into the polymerization chamber, and allowing the polar monomer to polymerize in situ on the surface of the polymer substrate layer to form a polymer transition layer; S3 forming a conductive metal layer on a side of the polymer transition layer away from the polymer substrate layer to obtain the composite current collector.

5. The method of making a composite current collector of claim 4, wherein, In the step of plasma treatment, the treatment power is 0.5-2 KW, the gas flow rate is 50-1000 sccm, and the vacuum degree in the pretreatment chamber is 0.1-50 Pa; or / and, in the step of plasma treatment, the gas type is selected from a mixed gas containing an inert gas and an active gas; or / and, the inert gas is selected from at least one of argon, helium and nitrogen, and the active gas is selected from at least one of oxygen, ammonia and carbon dioxide.

6. The method of making a composite current collector of claim 4, wherein, In step S2, the material of the polar monomer is selected from at least one of acrylic acid, acrylamide, ethylene imidazole, glycidyl methacrylate, methyl methacrylate, allyl glucoside and N-vinyl pyrrolidone; or / and, the vacuum degree in the polymerization chamber is 50-1000 Pa, the flow rate of the polar monomer is 10-1000 sccm, and the polymerization temperature is 40-100℃; or / and, the polymerization process is carried out under the condition of plasma treatment assistance; or / and, in step S3, the conductive metal layer is formed on a side of the polymer transition layer away from the polymer substrate layer by using a magnetron sputtering film plating method; or / and, in the process of magnetron sputtering film plating, the vacuum degree in the film plating chamber is 0.1-10 Pa, and the film plating power is 0.1-10 KW.

7. The method of making a composite current collector of any one of claims 4-6, wherein, Steps S1-S3 are sequentially and continuously completed in three chambers of the same reaction equipment.

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