Composite current collector and preparation method thereof, electrode plate and battery

Abstract

The invention relates to the technical field of batteries, in particular to a composite current collector, a preparation method thereof, an electrode plate and a battery. The invention provides a composite current collector. The composite current collector comprises a polymer base material, a first modified layer and a second modified layer, wherein the first modified layer and the second modified layer are respectively arranged on two opposite surfaces of the polymer base material; the first metal layer is arranged on the surface of one side, deviating from the polymer base material, of the first modified layer, and the second metal layer is arranged on the surface of one side, deviating from the polymer base material, of the second modified layer; wherein the first modified layer comprises acrylic resin; the second modified layer comprises polyurethane modified epoxy resin. The prepared composite current collector provided by the invention can adapt to the stress difference requirement during deformation or bending of the composite current collector, so that the mechanical property of the composite current collector is improved, and stable work of a battery is guaranteed.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to composite current collectors and their preparation methods, electrode sheets, and batteries. Background Technology

[0002] Batteries, as the driving force of electric vehicles, play a crucial role in their development. Battery performance directly affects the range, lifespan, and safety of electric vehicles. With the increasing popularity and development of electric vehicles, battery development has also received significant attention. Composite current collectors based on polymer substrates offer advantages such as lightweight design, high safety (less prone to short-circuit fires), and controllable cost, leading to their widespread application in energy storage batteries, power batteries, and other fields.

[0003] Existing wound batteries generally consist of a casing and a core and electrolyte placed inside the casing. The core is typically formed by spiral winding a positive electrode sheet, a separator, and a negative electrode sheet. In the manufacturing process of existing wound batteries, especially cylindrical wound batteries, to achieve higher energy density, the positive and negative electrode sheets and the separator often undergo significant bending during the winding process. This bending amplifies the structural stress on the current collector, and during battery charging and discharging, the positive and negative electrodes repeatedly expand and contract, causing the current collector to be subjected to repeated stress changes. At this time, the composite current collector will experience significant stress differences between its inner and outer sides due to tension and compression during deformation and bending. If this difference exceeds its tolerance limit, it can easily lead to microcracks or even fracture, resulting in battery conductivity failure or cycle performance degradation. Therefore, it is necessary to specifically optimize the composite current collector to adapt to the above-mentioned stress differences, ultimately improving the mechanical properties of the composite current collector and ensuring stable battery operation. Summary of the Invention

[0004] Based on this, this application provides a composite current collector and its preparation method, an electrode sheet, and a battery. The composite current collector provided in this application can adapt to the stress difference requirements when the composite current collector is deformed or bent, thereby improving the mechanical properties of the composite current collector and ensuring stable battery operation.

[0005] A first aspect of this application provides a composite current collector, comprising: a polymer substrate and a first modified layer and a second modified layer disposed on two surfaces of the polymer substrate opposite to each other; and a first metal layer disposed on the surface of the first modified layer opposite to the polymer substrate, and a second metal layer disposed on the surface of the second modified layer opposite to the polymer substrate.

[0006] The first modified layer comprises acrylic resin; the second modified layer comprises polyurethane-modified epoxy resin.

[0007] In some embodiments, the first modified layer further includes nanomaterials and a first polysiloxane.

[0008] In some embodiments, the second modified layer further includes a second polysiloxane.

[0009] In some embodiments, the thickness of the first modified layer is greater than the thickness of the second modified layer.

[0010] In some embodiments, the thickness of the first metal layer is greater than the thickness of the second metal layer.

[0011] In some embodiments, the mass fraction of magnesium in the first metal layer is higher than the mass fraction of magnesium in the second metal layer.

[0012] In some embodiments, the acrylic resin is formed by polymerization of one or more monomers selected from methyl acrylate, ethyl acrylate, methyl methacrylate, and butyl methacrylate.

[0013] In some embodiments, the glass transition temperature of the acrylic resin is 20°C to 35°C.

[0014] In some embodiments, the polyurethane-modified epoxy resin has an elongation at break of 60% to 150%.

[0015] In some embodiments, the polymer substrate is polyethylene terephthalate doped with silicon dioxide.

[0016] In some embodiments, the thickness of the polymer substrate is 2 μm to 6 μm.

[0017] In some embodiments, the thickness of the first modified layer is 0.5 μm to 2 μm.

[0018] In some embodiments, the mass ratio of the acrylic resin to the nanomaterial in the first modified layer is (5~7):(1~2).

[0019] In some embodiments, the nanomaterials include one or more of nano-silica and carbon nanotubes.

[0020] In some embodiments, the mass ratio of the acrylic resin to the first polysiloxane in the first modified layer is (50~70):(0.5~2).

[0021] In some embodiments, the thickness of the second modified layer is 0.1 μm to 1 μm.

[0022] In some embodiments, the mass ratio of the polyurethane-modified epoxy resin to the second polysiloxane in the second modified layer is (65~80):(0.5~2).

[0023] In some embodiments, the first metal layer comprises aluminum and magnesium in a mass ratio of (9~19):1.

[0024] In some embodiments, the thickness of the first metal layer is 1.5 μm to 3 μm.

[0025] In some embodiments, the second metal layer comprises aluminum and magnesium in a mass ratio of (9~19):1.

[0026] In some embodiments, the thickness of the second metal layer is 0.5 μm to 1 μm.

[0027] In some embodiments, a first alumina layer is further provided between the polymer substrate and the first modified layer.

[0028] In some embodiments, a second alumina layer is further provided between the polymer substrate and the second modified layer.

[0029] A second aspect of this application provides a method for preparing a composite current collector, comprising the following steps:

[0030] A first modified liquid and a second modified liquid are provided respectively; wherein, the first modified liquid comprises an acrylic resin and a first solvent; and the second modified liquid comprises a polyurethane-modified epoxy resin and a second solvent;

[0031] The first modified liquid and the second modified liquid are respectively coated on two opposing surfaces of the polymer substrate, and after drying and curing, a first modified layer and a second modified layer are formed respectively.

[0032] A first metal layer is formed on the surface of the first modified layer opposite to the polymer substrate, and a second metal layer is formed on the surface of the second modified layer opposite to the polymer substrate, thereby preparing the composite current collector.

[0033] In some embodiments, the first modified liquid further includes: nanomaterials and a first polysiloxane.

[0034] In some embodiments, the second modified liquid further includes a second polysiloxane.

[0035] In some embodiments, the thickness of the first modified layer is greater than the thickness of the second modified layer.

[0036] In some embodiments, the thickness of the first metal layer is greater than the thickness of the second metal layer.

[0037] In some embodiments, the mass fraction of magnesium in the first metal layer is higher than the mass fraction of magnesium in the second metal layer.

[0038] In some embodiments, the first modified liquid comprises, by mass fraction: 50% to 70% acrylic resin, 10% to 20% nanomaterials, 0.5% to 2% first polysiloxane, and 10% to 35% first solvent.

[0039] In some embodiments, the acrylic resin is formed by polymerization of one or more monomers selected from methyl acrylate, ethyl acrylate, methyl methacrylate, and butyl methacrylate.

[0040] In some embodiments, the glass transition temperature of the acrylic resin is 20°C to 35°C.

[0041] In some embodiments, the nanomaterials include one or more of nano-silica and carbon nanotubes.

[0042] In some embodiments, the viscosity of the first polysiloxane at 25°C is 100 mPa•s to 500 mPa•s.

[0043] In some embodiments, the surface tension of the first polysiloxane at 25°C is 20 mN / m to 45 mN / m.

[0044] In some embodiments, the first solvent includes one or more of butyl acetate, ethyl acetate, isobutyl acetate, and butyl propionate.

[0045] In some embodiments, the second modified liquid comprises, by mass fraction: 65% to 80% polyurethane-modified epoxy resin, 0.5% to 2% second polysiloxane, and 18% to 34.5% second solvent.

[0046] In some embodiments, the polyurethane-modified epoxy resin has an elongation at break of 60% to 150%.

[0047] In some embodiments, the viscosity of the second polysiloxane at 25°C is 100 mPa•s to 500 mPa•s.

[0048] In some embodiments, the surface tension of the second polysiloxane at 25°C is 20 mN / m to 45 mN / m.

[0049] In some embodiments, the second solvent includes one or more of butyl acetate, ethyl acetate, isobutyl acetate, and butyl propionate.

[0050] In some embodiments, the polymer substrate is polyethylene terephthalate doped with silicon dioxide.

[0051] In some embodiments, the thickness of the polymer substrate is 2 μm to 6 μm.

[0052] In some embodiments, the thickness of the first modified layer is 0.5 μm to 2 μm.

[0053] In some embodiments, the thickness of the second modified layer is 0.1 μm to 1 μm.

[0054] In some of these embodiments, the drying temperature is 80°C to 120°C.

[0055] In some embodiments, the curing method includes one or more of UV curing and thermal curing.

[0056] In some embodiments, the step of forming the first metal layer on the surface of the first modified layer opposite to the polymer substrate includes:

[0057] The first metal layer is prepared on the surface of the first modified layer away from the polymer substrate using a vapor deposition method. Optionally, the vapor deposition rate is 0.5 μm / min to 2 μm / min. Optionally, the first metal layer comprises aluminum and magnesium in a mass ratio of (9 to 19):1. Optionally, the thickness of the first metal layer is 1.5 μm to 3 μm.

[0058] In some embodiments, the step of forming the second metal layer on the surface of the second modified layer opposite to the polymer substrate includes:

[0059] The second metal layer is prepared on the surface of the second modified layer away from the polymer substrate using a vapor deposition method. Optionally, the vapor deposition rate is 0.5 μm / min to 2 μm / min. Optionally, the second metal layer comprises aluminum and magnesium in a mass ratio of (9 to 19):1. Optionally, the thickness of the second metal layer is 0.5 μm to 1 μm.

[0060] In some embodiments, prior to the step of coating the first modified liquid onto the surface of the polymer substrate, the method further includes:

[0061] A first alumina layer is formed on the surface of the polymer substrate; wherein the first alumina layer is disposed between the polymer substrate and the first modified layer.

[0062] In some embodiments, prior to the step of coating the second modified liquid onto the surface of the polymer substrate, the method further includes:

[0063] A second alumina layer is formed on the surface of the polymer substrate. The second alumina layer is disposed between the polymer substrate and the second modified layer.

[0064] In some embodiments, the thickness of the first alumina layer is 1.5 to 3 times the thickness of the second alumina layer.

[0065] In some embodiments, the thickness of the second alumina layer is 5 nm to 20 nm.

[0066] A third aspect of this application provides an electrode sheet comprising the composite current collector described in the first aspect of this application, or a composite current collector prepared by any of the preparation methods in the second aspect of this application.

[0067] A fourth aspect of this application provides a battery including the electrode sheet described in the second aspect of this application.

[0068] Optionally, the battery is a cylindrical wound battery.

[0069] The composite current collector provided in this application has at least the following advantages:

[0070] The composite current collector provided in this application has a first modified layer and a second modified layer of specific components disposed on two opposing surfaces of a polymer substrate. These layers, together with the first and second metal layers, can adapt to the stress differences required by the composite current collector during deformation or bending, thereby improving the mechanical properties of the composite current collector and ensuring stable battery operation. Specifically, the high elasticity of the acrylic resin in the first modified layer absorbs and disperses the compressive stress generated by bending or deformation of the polymer substrate and the first metal layer, and its excellent adhesion properties strengthen the bond between the first modified layer and the polymer substrate and the first metal layer.

[0071] The polyurethane elastic segments of the polyurethane-modified epoxy resin in the second modified layer can disperse and buffer the tensile stress generated on the outer side during bending through flexible deformation, improving the cracking phenomenon caused by stress concentration. Furthermore, the adhesion of the epoxy resin segments in the polyurethane-modified epoxy resin can enhance the bonding stability between the epoxy resin and the polymer substrate and the second metal layer, improving interlayer delamination during deformation or bending. Therefore, the first modified layer in the composite current collector provided in this application can adapt to the compressive stress during bending, and the second modified layer can adapt to the tensile stress during bending. Combined with the first and second metal layers, this improves the mechanical properties of the composite current collector. It allows the composite current collector to withstand compressive and tensile stresses on the inner and outer sides respectively during bending or deformation without easily cracking or delamination, while also ensuring the conductivity stability of the bimetallic layer. Ultimately, the composite current collector simultaneously possesses excellent bending fatigue resistance, interlayer bonding strength, and current conduction efficiency, making it particularly suitable for the stringent application requirements of current collectors in scenarios such as cylindrical wound battery cells. Attached Figure Description

[0072] Figure 1This is an SEM image of the uncracked surface of the composite current collector in Example 1 of this application after SEM characterization testing;

[0073] Figure 2 The image shows the microcracked surface of the composite current collector in Example 10 of this application after SEM characterization testing.

[0074] Figure 3 This is a SEM image of the severely cracked surface of the composite current collector in Comparative Example 1 of this application after SEM characterization testing. Detailed Implementation

[0075] The composite current collector, its preparation method, electrode sheet, and battery of this application are further described in detail below with reference to specific embodiments. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0076] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0077] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0078] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise stated or in case of conflict, the terms or phrases used herein have the following meanings:

[0079] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more or more.

[0080] In this application, the terms "first aspect," "second aspect," "third aspect," and "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," and "fourth," etc., serve only a non-exhaustive enumeration purpose and should be understood not to constitute a closed limitation on quantity.

[0081] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0082] In this application, the terms "combinations thereof", "any combination thereof", and "any combination thereof" include all suitable combinations of any two or more of the listed items.

[0083] In this application, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0084] In this application, terms such as "preferred," "better," "more suitable," and "ideal" are used only to describe implementation methods or embodiments with better effects, and should be understood not to constitute a limitation on the scope of protection of this application.

[0085] In this application, terms such as "further," "even further," and "particularly" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0086] In this application, the terms "optionally," "optionally," and "optional" refer to options that are optional, meaning they can be selected from either "with" or "without." If multiple "optional" options appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" option is independent.

[0087] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0088] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0089] In this application, percentage content refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures, unless otherwise specified.

[0090] In this application, unless otherwise specified, percentage concentrations refer to final concentrations. The final concentration refers to the percentage of the added component in the system after its addition.

[0091] During the bending process, the inner side refers to the compressive side of the composite current collector when it is bent, which is mainly subjected to compressive stress. The outer side refers to the tensile side of the composite current collector when it is bent, which is mainly subjected to tensile stress.

[0092] During bending or deformation, the stress mechanisms on the inner and outer sides of the current collector differ significantly: the outer side experiences tensile stress, while the inner side experiences compressive stress. This uneven stress can easily lead to metal layer fracture or detachment, resulting in light transmission observed in the bending area. This severely affects the capacity and cycle performance of flexible batteries or batteries with wound cells. To disperse the tensile or compressive stress during bending, traditional techniques often use adhesive bonding. However, this method not only increases the overall thickness and weight of the composite current collector but also easily leads to delamination after repeated bending due to insufficient adhesion between the adhesive and the polymer substrate and metal layer, thus exacerbating stress concentration. Furthermore, the insulating properties of the adhesive also affect the conductivity of the current collector.

[0093] Based on this, in a first aspect, a composite current collector is provided, comprising: a polymer substrate and a first modified layer and a second modified layer disposed on two surfaces of the polymer substrate opposite to each other; and a first metal layer disposed on the surface of the first modified layer opposite to the polymer substrate, and a second metal layer disposed on the surface of the second modified layer opposite to the polymer substrate.

[0094] The first modified layer comprises acrylic resin; the second modified layer comprises polyurethane-modified epoxy resin.

[0095] In some of these examples, the acrylic resin is formed by polymerization of one or more monomers selected from methyl acrylate, ethyl acrylate, methyl methacrylate, and butyl methacrylate. Further examples include, but are not limited to, German Mantes AC143, Guangdong Keding Functional Materials J7105, and Guangdong Keding Functional Materials MR1763C.

[0096] In some of these examples, the glass transition temperature of the acrylic resin is 20°C to 35°C.

[0097] In some examples, the types of polyurethane-modified epoxy resins include, but are not limited to, EPU-300A. The elongation at break of the polyurethane-modified epoxy resin is 60% to 150%.

[0098] In some examples, the polymer substrate is polyethylene terephthalate doped with silica. The types of polymer substrates include, but are not limited to, Kanghui New Materials Technology KH2678H and Toray Industries XR40H.

[0099] In some of these examples, the thickness of the polymer substrate is 2 μm to 6 μm.

[0100] In some of these examples, the thickness of the first modified layer is 0.5 μm to 2 μm.

[0101] In some of these examples, the thickness of the second modified layer is 0.1 μm to 1 μm.

[0102] In some of these examples, the first metal layer comprises aluminum and magnesium in a mass ratio of (9 to 19):1.

[0103] In some of these examples, the thickness of the first metal layer is 1.5 μm to 3 μm.

[0104] In some of these examples, the second metal layer comprises aluminum and magnesium in a mass ratio of (9 to 19):1.

[0105] In some of these examples, the thickness of the second metal layer is 0.5 μm to 1 μm.

[0106] In some examples, the first modified layer further includes nanomaterials and a first polysiloxane. For example, in the first modified layer, the mass ratio of acrylic resin to nanomaterials is (5~7):(1~2). For example, the mass ratio of acrylic resin to the first polysiloxane is (50~70):(0.5~2).

[0107] In some examples, the nanomaterials include one or more of nano-silica and carbon nanotubes. These nanomaterials can further "reinforce" the bending interface, making the first modified layer less prone to wrinkling under compressive stress, and can also inhibit crack propagation. In some examples, the types of nano-silica include, but are not limited to, Shanghai Huijing Asia Nanomaterials SP10, Zhongjingneng Nanomaterials Technology N80T, and Zhongjingneng Nanomaterials Technology N100.

[0108] In some of these examples, the viscosity of the first polysiloxane at 25°C is 100 mPa•s to 500 mPa•s.

[0109] In some of these examples, the surface tension of the first polysiloxane at 25°C is 20 mN / m to 45 mN / m.

[0110] In some examples, the first polysiloxanes include, but are not limited to, BYK-333, BD-3345, and BD-3134.

[0111] In some examples, the second modified layer further includes a second polysiloxane. Further, in the second modified layer, the mass ratio of the polyurethane-modified epoxy resin to the second polysiloxane is (65~80):(0.5~2).

[0112] In some of these examples, the viscosity of the second polysiloxane at 25°C is 100 mPa•s to 500 mPa•s.

[0113] In some of these examples, the surface tension of the second polysiloxane at 25°C is 20 mN / m to 45 mN / m.

[0114] In some of these examples, the types of second polysiloxanes include, but are not limited to, BYK-333, BD-3345, and BD-3134.

[0115] In some of these examples, the thickness of the first modified layer is greater than the thickness of the second modified layer.

[0116] In some of these examples, the thickness of the first metal layer is greater than the thickness of the second metal layer.

[0117] In some of these examples, the mass fraction of magnesium in the first metal layer is higher than that in the second metal layer.

[0118] In some of these examples, a first alumina layer is also provided between the polymer substrate and the first modified layer.

[0119] In some of these examples, a second alumina layer is also provided between the polymer substrate and the second modified layer.

[0120] In some of these examples, the thickness of the first alumina layer is 1.5 to 3 times the thickness of the second alumina layer.

[0121] In some of these examples, the thickness of the second alumina layer is 5 nm to 20 nm.

[0122] Understandably, the composition of the first modified layer, the composition of the second modified layer, the properties of the first metal layer, the properties of the second metal layer, the properties of the first alumina, and the properties of the second alumina layer in the composite current collector provided in the first aspect of this application are the same as those in the second aspect of this application, so they will not be repeated here.

[0123] A second aspect of this application provides a method for preparing a composite current collector, comprising the following steps:

[0124] S10: Provide a first modified liquid and a second modified liquid. The first modified liquid includes an acrylic resin and a first solvent; the second modified liquid includes a polyurethane-modified epoxy resin and a second solvent.

[0125] S20: The first modifying liquid and the second modifying liquid are respectively coated on two opposing surfaces of the polymer substrate, and after drying and curing, the first modified layer and the second modified layer are formed respectively.

[0126] S30: A first metal layer is formed on the surface of the first modified layer away from the polymer substrate, and a second metal layer is formed on the surface of the second modified layer away from the polymer substrate, to prepare a composite current collector.

[0127] Furthermore, the thickness of the first modified layer is greater than the thickness of the second modified layer. The thickness of the first metal layer is greater than the thickness of the second metal layer. The mass fraction of magnesium in the first metal layer is greater than the mass fraction of magnesium in the second metal layer.

[0128] Understandably, this application does not limit the order in which the first modified layer and the second modified layer are prepared, as long as the first modified layer is obtained before the preparation step of the first metal layer and the second modified layer is obtained before the preparation step of the second metal layer. For example, the first modified layer can be prepared first, the second modified layer can be prepared first, or the first and second modified layers can be prepared simultaneously. Similarly, this application does not limit the order in which the first metal layer and the second metal layer are prepared; the first metal layer can be prepared first, the second metal layer can be prepared first, or the first and second metal layers can be prepared simultaneously.

[0129] In some of these examples, the first modified liquid also includes: nanomaterials and a first polysiloxane.

[0130] In some of these examples, the second modified liquid also includes a second polysiloxane.

[0131] The preparation method provided in this application uses a first modified liquid and a second modified liquid of specific components to prepare a first modified layer and a second modified layer on two opposing surfaces of a polymer substrate. These, along with the first and second metal layers, can adapt to the stress differences required during deformation or bending of the composite current collector, thereby improving the mechanical properties of the composite current collector and ensuring stable battery operation. Specifically, the high elasticity of the acrylic resin in the first modified liquid absorbs and disperses the compressive stress generated by bending or deformation of the polymer substrate and the first metal layer. Its excellent adhesion properties strengthen the bond between the first modified layer and the polymer substrate and the first metal layer. Furthermore, with the support of the crack propagation inhibition properties of nanomaterials, the first modified layer can effectively suppress cracking or interfacial delamination caused by stress concentration in the composite current collector. In addition, the first polysiloxane in the first modified liquid, along with the first solvent, adjusts the viscosity and film-forming properties of the system, further improving the bending fatigue resistance of the modified layer.

[0132] The second modified layer is prepared using a first modified liquid with specific components. The polyurethane elastic segments of the polyurethane-modified epoxy resin can disperse and buffer the tensile stress generated on the outer side during bending through flexible deformation, preventing cracking caused by stress concentration. Furthermore, the adhesion of the epoxy resin segments in the polyurethane-modified epoxy resin enhances the bonding stability between the epoxy resin and the polymer substrate and the first metal layer, preventing interlayer delamination during deformation or bending. In addition, the second polysiloxane in the second modified liquid, in conjunction with the second solvent, adjusts the viscosity and film-forming properties of the system, further improving the bending fatigue resistance of the second modified layer.

[0133] Therefore, the preparation method provided in this application can obtain a first modified layer adapted to compressive stress during bending and a second modified layer adapted to tensile stress during bending. With the addition of a first metal layer and a second metal layer of different thicknesses and magnesium contents, the mechanical properties of the composite current collector can be improved. This allows the composite current collector to withstand compressive and tensile stresses on the inner and outer sides respectively during bending or deformation without cracking or peeling. It also ensures the conductivity stability of the bimetallic layer. Ultimately, the composite current collector possesses excellent bending fatigue resistance, interlayer bonding force, and current conduction efficiency, fully meeting the stringent requirements for current collectors in scenarios such as flexible batteries and wound cells.

[0134] Furthermore, the preparation method provided in this application only requires changing the components of the first and second modified liquids in the traditional preparation steps, and it is suitable for industrial application.

[0135] In some of these examples, the first modifying liquid comprises, by mass fraction: 50% to 70% acrylic resin, 10% to 20% nanomaterials, 0.5% to 2% first polysiloxane, and 10% to 35% first solvent.

[0136] Understandably, the mass fraction of the acrylic resin can be selected from any value between 50% and 70%. For example, the mass fraction of the acrylic resin includes, but is not limited to, 50%, 55%, 60%, 61%, 63%, 65%, 68%, or 70%, or any two of the above values ​​as endpoints. The mass fraction of the nanomaterial includes, but is not limited to, 10%, 13%, 15%, 16%, 17%, 18%, or 20%, or any two of the above values ​​as endpoints. The mass fraction of the first polysiloxane includes, but is not limited to, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, or 2%, or any two of the above values ​​as endpoints. The mass fraction of the first solvent includes, but is not limited to, 10%, 15%, 18%, 19%, 20%, 25%, 30%, or 35%, or any two of the above values ​​as endpoints.

[0137] The mass fraction of each component in the first modified liquid is further limited. It can ensure elasticity to disperse compressive stress through a relatively high mass proportion of acrylic resin, and suppress cracking through a specific mass fraction of nanomaterials. Furthermore, with the synergy of the film-forming properties of the first polysiloxane and the suitable viscosity of the first solution, the first modified liquid can be uniformly coated on the surface of the polymer substrate to form a first modified layer with controllable thickness, smooth surface and tight bonding. At the same time, it can ensure that the first modified layer has both excellent compressive stress resistance and structural stability, laying the foundation for the subsequent formation of the first metal layer and the improvement of the overall mechanical properties of the composite current collector.

[0138] In some of these examples, the acrylic resin is formed by polymerization of one or more monomers selected from methyl acrylate, ethyl acrylate, methyl methacrylate, and butyl methacrylate. Further examples include, but are not limited to, German Mantes AC143, Guangdong Keding Functional Materials J7105, and Guangdong Keding Functional Materials MR1763C.

[0139] In some examples, the glass transition temperature of the acrylic resin is 20°C to 35°C. The glass transition temperature of the acrylic resin includes, but is not limited to, 25%, 27%, 30%, or 35%. This application has discovered that acrylic resins with glass transition temperatures within the above range exhibit high elasticity at room temperature. When stress is generated in the polymer substrate and metal layer due to bending, deformation, or thermal expansion and contraction, they can absorb and disperse the stress through their own deformation, thereby avoiding metal layer cracking or interface delamination caused by stress concentration.

[0140] In some examples, the nanomaterials include one or more of nano-silica and carbon nanotubes. These nanomaterials can further "reinforce" the bending interface, making the first modified layer less prone to wrinkling under compressive stress, and can also inhibit crack propagation. In some examples, the types of nano-silica include, but are not limited to, Shanghai Huijing Asia Nanomaterials SP10, Zhongjingneng Nanomaterials Technology N80T, and Zhongjingneng Nanomaterials Technology N100.

[0141] In some of these examples, the viscosity of the first polysiloxane at 25°C is 100 mPa•s to 500 mPa•s.

[0142] In some of these examples, the surface tension of the first polysiloxane at 25°C is 20 mN / m to 45 mN / m.

[0143] In some of these examples, the first solvent includes one or more of butyl acetate, ethyl acetate, isobutyl acetate, and butyl propionate.

[0144] The first polysiloxane and the first solvent work synergistically to optimize the film uniformity of the first modified layer, improve the bending resistance and interfacial adhesion of the first modified layer after curing, and ensure that the first modified liquid forms a stable film and plays a role in resisting compressive stress.

[0145] In some examples, the second modifying liquid, by mass fraction, comprises: 65%–80% polyurethane-modified epoxy resin, 0.5%–2% second polysiloxane, and 18%–34.5% second solvent. In the above-mentioned formulation of the second modifying liquid, the high proportion of polyurethane-modified epoxy resin, with its excellent elongation at break and toughness, adapts to the external stress of bending. The second polysiloxane optimizes film formation and interfacial adhesion, while the second solvent adjusts viscosity for easy coating and reduces defects caused by uneven surface tension, thus efficiently preparing a bend-resistant second modified layer.

[0146] For example, the mass fraction of the polyurethane-modified epoxy resin includes, but is not limited to, 65%, 70%, 75%, 76%, 78%, or 80%, or any two of the above values ​​as endpoints. The mass fraction of the second polysiloxane includes, but is not limited to, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.7%, or 2%, or any two of the above values ​​as endpoints. The mass fraction of the second solvent includes, but is not limited to, 20%, 23%, 25%, 28%, 29.5%, or 34.5%, or any two of the above values ​​as endpoints.

[0147] In some examples, the elongation at break of the polyurethane-modified epoxy resin is 60% to 150%. Examples of polyurethane-modified epoxy resins include, but are not limited to, EPU-300A. The high elongation at break of the polyurethane-modified epoxy resin, coupled with its viscosity and toughness, allows it to absorb and dissipate tensile strain through its own deformation, thereby mitigating the stress mismatch between the second metal layer and the polymer substrate.

[0148] In some of these examples, the viscosity of the second polysiloxane at 25°C is 100 mPa•s to 500 mPa•s.

[0149] In some of these examples, the surface tension of the second polysiloxane at 25°C is 20 mN / m to 45 mN / m.

[0150] In some examples, the types of the first or second polysiloxane include, but are not limited to, BYK-333, BD-3345, and BD-3134.

[0151] In some of these examples, the second solvent includes one or more of butyl acetate, ethyl acetate, isobutyl acetate, and butyl propionate.

[0152] In some examples, the coating method in step S20, in which the first modified liquid and the second modified liquid are respectively coated onto two opposing surfaces of the polymer substrate, includes, but is not limited to, coating. As a further example, the coating is a microgravure coating method.

[0153] In some examples, in step S20, the thickness of the first modified layer formed after the first modified liquid has solidified is 0.5 μm to 2 μm.

[0154] In some examples, in step S20, the thickness of the second modified layer formed after the second modified liquid has cured is 0.1 μm to 1 μm.

[0155] This application discovers that different coating thicknesses of the first and second modified liquids can be adapted to first and second metal layers of different thicknesses to meet the performance requirements of the inner and outer sides of the bend. Furthermore, the aforementioned coating thicknesses can effectively cover surface defects in the polymer substrate, providing sufficient stress buffering, and do not impede the conductivity of the subsequent first and second metal layers.

[0156] In some examples, the drying temperature in step S20 is 80°C to 120°C. This drying temperature allows the first and second solvents to fully evaporate, which is beneficial for forming a dense first and second modified layer.

[0157] In some examples, step S20 involves curing via one or more of UV curing and thermosetting. After further curing, the polymers in the first modified liquid / first modified layer and the second modified liquid / second modified layer, such as acrylic resin and polyurethane-modified epoxy resin, can further crosslink and cure, enhancing the flexural strength of the first and second modified layers. In some examples, the thermosetting conditions are heat curing at 100°C to 160°C for 1 to 5 minutes.

[0158] In some of these examples, the polymer substrate is polyethylene terephthalate doped with silica. In this example, the types of polymer substrates selected include, but are not limited to, Kanghui New Materials Technology KH2678H and Toray Industries XR40H.

[0159] In other examples, the polymer substrate is polyethylene terephthalate.

[0160] In some of these examples, the thickness of the polymer substrate is 2 μm to 6 μm.

[0161] In some examples, step S30, forming a first metal layer on the surface of the first modified layer facing away from the polymer substrate, includes:

[0162] A first metal layer is prepared on the surface of the first modified layer away from the polymer substrate using a vapor deposition method. Optionally, the vapor deposition is performed under vacuum conditions. For example, the vacuum degree of the vapor deposition is 0.5 × 10⁻⁶. -2 Pa~2×10 -2 Pa. As a further example, the vacuum degree of the vapor deposition is 1 × 10⁻⁶. -2 Pa. Optionally, the apparatus for performing vapor deposition includes, but is not limited to, a vacuum vapor deposition machine. Optionally, the vapor deposition rate is 0.5 μm / min to 2 μm / min. The above-mentioned vapor deposition rate is beneficial for forming a dense, uniform, and strongly adherent first metal layer. Optionally, the first metal layer comprises aluminum and magnesium in a mass ratio of (9 to 19):1. It is understood that, in order to keep the mass ratio of aluminum to magnesium in the first metal layer within the above range, aluminum and magnesium in a mass ratio of (9 to 19):1 can be selected as the vapor deposition material. Optionally, the thickness of the first metal layer is 1.5 μm to 3 μm.

[0163] This application discovers that introducing magnesium into the metal layer can improve the flexibility of the metal layer and refine the grains, thereby optimizing the bending resistance of the first metal layer. Furthermore, when the magnesium content is within the aforementioned range, it avoids the drawbacks of increased alloy layer resistance due to excessive magnesium and insignificant modification due to insufficient magnesium content. Further, this application discovers that the aforementioned magnesium content can also avoid the difficulty in controlling the vapor deposition process caused by the high vapor pressure of magnesium. For example, the mass ratio of aluminum to magnesium in the first metal layer includes, but is not limited to, 9:1, 11:1, 13:1, 15:1, 18:1, or 19:1.

[0164] In some examples, step S30, forming a second metal layer on the surface of the second modified layer facing away from the polymer substrate, includes:

[0165] A second metal layer is prepared on the surface of the second modified layer away from the polymer substrate using a vapor deposition method. Optionally, the vapor deposition rate is 0.5 μm / min to 2 μm / min. Optionally, the second metal layer comprises aluminum and magnesium in a mass ratio of (9 to 19):1. It is understood that, in order to keep the mass ratio of aluminum to magnesium in the second metal layer within the above range, aluminum and magnesium in a mass ratio of (9 to 19):1 can be selected as the vapor deposition materials. Optionally, the thickness of the second metal layer is 0.5 μm to 1 μm.

[0166] Preferably, the magnesium content in the first metal layer is higher than that in the second metal layer, the mass ratio of aluminum to magnesium in the first metal layer is (9~12):1, and the mass ratio of aluminum to magnesium in the second metal layer is (13~19):1. This application finds that the higher magnesium content of the first metal layer, located on the inner side of the bend, combined with the first modified layer, reduces wrinkling of the first metal layer during bending; the lower magnesium content of the second metal layer, located on the outer side of the bend, combined with the second modified layer, reduces the probability of cracks in the metal layer, thereby improving the light transmission of the composite current collector during bending.

[0167] Preferably, the thickness of the first metal layer is greater than the thickness of the second metal layer. This application finds that the greater thickness of the first metal layer compared to the second metal layer allows the first metal layer, when located on the inner side of the bend, to have enhanced compressive strength due to its thicker structure, reducing deformation or wrinkling caused by inner compressive stress, while also providing a more stable path for current conduction. The lower thickness of the second metal layer reduces its tensile stiffness on the outer side of the bend, making it easier to flexibly expand and contract with the second modified layer, reducing the risk of cracking under tensile stress, and simultaneously ensuring the basic conductivity requirements while also considering the overall lightweight and bending fatigue resistance of the composite current collector.

[0168] In some examples, prior to the step of coating the first modifying liquid onto the surface of the polymer substrate, the method further includes:

[0169] S11: A first alumina layer is formed on the surface of a polymer substrate, wherein the first alumina layer is disposed between the polymer substrate and the first modified layer.

[0170] In some examples, prior to the step of coating the second modified liquid onto the surface of the polymer substrate, the method further includes:

[0171] S12: A second alumina layer is formed on the surface of the second modified layer on the side opposite to the polymer substrate.

[0172] Understandably, the preparation of a first alumina layer may optionally be included before the preparation of the first modified layer. The preparation of a second alumina layer may optionally be included before the preparation of the second modified layer. Furthermore, this application does not limit the relative order of steps S11 and S12. The alumina layer disposed between the modified layer and the polymer substrate can further improve the corrosion resistance of the composite current collector.

[0173] This application reveals that if the first metal layer, the first alumina layer, the polymer substrate, the second alumina layer, and the second metal layer are directly stacked, the light transmittance of the inner first metal layer is improved after bending. However, the light transmittance is more severe on the outer side due to the fracture of the second metal layer. Specifically, alumina is highly brittle, and the inner alumina layer reduces the ductility of the first metal layer, thus reducing wrinkling. However, the outer second metal layer and the second alumina layer are more susceptible to deformation damage during bending than pure metal layers, making them more prone to cracking and light transmission.

[0174] Therefore, preferably, in some examples, the thickness of the first alumina layer is 1.5 to 3 times the thickness of the second alumina layer. The thickness of the second alumina layer is 5 nm to 20 nm. By setting the thicknesses of the first and second alumina layers, the thinner outer second alumina layer can reduce the probability of cracks during bending; the thicker inner first alumina layer can reduce wrinkling during extrusion, and together with the first metal layer, they can improve the light transmission phenomenon caused by cracks in the composite current collector during bending.

[0175] A third aspect of this application provides an electrode sheet. This electrode sheet comprises the composite current collector provided in the first aspect of this application. Alternatively, the electrode sheet comprises the composite current collector prepared by the preparation method provided in the second aspect of this application.

[0176] In a fourth aspect, this application provides a battery including the electrode sheet provided in the third aspect of this application.

[0177] Optionally, the battery is a cylindrical wound battery.

[0178] The following detailed embodiments illustrate this application in more detail. It should also be understood that the following embodiments are for further explanation only and should not be construed as limiting the scope of protection of this application. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of this application fall within the scope of protection of this application. The specific process parameters, etc., in the following embodiments are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not necessarily limited to the specific values ​​in the embodiments below.

[0179] Example 1

[0180] Example 1 provides a composite current collector and its preparation method, including the following steps:

[0181] (1) Preparation of the first modified liquid: Mix 60% acrylic resin (Germany Mantes AC143), 15% nano SiO2 (Zhongjingneng Nanomaterials Technology N100), 1% polydimethylsiloxane (Dow Corning DC184) and 24% butyl acetate to prepare the first modified liquid.

[0182] (2) Preparation of the second modified liquid: 72% polyurethane modified epoxy resin (purchased from Complex High-Tech Materials Shanghai Co., Ltd., model: EPU-300A), 1% polydimethylsiloxane (Dow Corning DC184) and 27% butyl acetate were used to prepare the second modified liquid.

[0183] (3) Preparation of the first and second modified layers: The first and second modified liquids were coated onto two opposing surfaces of a polymer substrate (polyethylene terephthalate doped with silica, purchased from Kanghui New Materials Technology Co., Ltd., model: KH2678H, thickness 4μm) using a microgravure coating method. The coated first modified liquid was dried at 100℃ and then heat-cured at 130℃ for 3 minutes to form a first modified layer with a thickness of 1μm. The coated second modified liquid was dried at 80℃ and then heat-cured at 110℃ for 2 minutes to form a second modified layer with a thickness of 0.5μm.

[0184] (4) Preparation of the first and second metal layers: A first metal layer with a thickness of 1.5 μm was prepared on the side of the first modified layer away from the polymer substrate using an aluminum-magnesium alloy with a mass ratio of 9:1 and a vapor deposition rate of 1 μm / min. A second metal layer with a thickness of 0.5 μm was prepared on the side of the second modified layer away from the polymer substrate using an aluminum-magnesium alloy with a mass ratio of 19:1 and a vapor deposition rate of 0.5 μm / min.

[0185] Example 2

[0186] Example 2 is basically the same as Example 1. The main difference is that in step (4) of Example 2, an aluminum-magnesium alloy with a mass ratio of 10:1 is used as the vapor deposition material and a vapor deposition rate of 1.5 μm / min is used to prepare a first metal layer with a thickness of 2 μm on the side of the first modified layer away from the polymer substrate. A second metal layer with a thickness of 0.8 μm is prepared on the side of the first modified layer away from the polymer substrate using an aluminum-magnesium alloy with a mass ratio of 13:1 and a vapor deposition rate of 0.5 μm / min.

[0187] Example 3

[0188] Example 3 is basically the same as Example 1. The main difference is that in Example 3, in step (4), an aluminum-magnesium alloy with a mass ratio of 12:1 is used as the vapor deposition material and a vapor deposition rate of 2.5 μm / min is used to prepare a first metal layer with a thickness of 3 μm on the side of the first modified layer away from the polymer substrate. A second metal layer with a thickness of 1 μm is prepared on the side of the first modified layer away from the polymer substrate using an aluminum-magnesium alloy with a mass ratio of 15:1 and a vapor deposition rate of 0.8 μm / min.

[0189] Example 4

[0190] Example 4 is basically the same as Example 1. The main difference is that in steps (1) and (3) of Example 4, 50% acrylic resin, 15% nano SiO2, 0.5% polydimethylsiloxane and 34.5% butyl acetate are mixed to prepare the first modified liquid by mass percentage, and the thickness of the first modified layer is 0.5 μm.

[0191] In steps (2) and (3) of Example 4, 65% polyurethane modified epoxy resin, 1% polydimethylsiloxane and 34% butyl acetate were mixed to prepare a second modified liquid by mass percentage, and the thickness of the second modified layer was 0.1 μm.

[0192] Example 5

[0193] Example 5 is basically the same as Example 1. The main difference is that in steps (1) and (3) of Example 5, 70% acrylic resin, 10% nano SiO2, 2% polydimethylsiloxane and 18% butyl acetate are mixed to prepare the first modified liquid by mass percentage, and the thickness of the first modified layer is 2μm.

[0194] In steps (2) and (3) of Example 5, 80% polyurethane modified epoxy resin, 0.5% polydimethylsiloxane and 19.5% butyl acetate were mixed by mass percentage to prepare a second modified liquid, and the thickness of the second modified layer was 1 μm.

[0195] Example 6

[0196] Example 6 is basically the same as Example 1, except that Example 6 further includes step (a): a first alumina layer with a thickness of 7.5 nm is prepared on one side surface of the polymer substrate, and a second alumina layer with a thickness of 5 nm is prepared on the other side surface of the polymer substrate. A first modified layer is disposed on the surface of the first alumina layer, and a second modified layer is disposed on the surface of the second alumina layer.

[0197] Example 7

[0198] Example 7 is basically the same as Example 6, the main difference being that in step (a), a first alumina layer with a thickness of 20 nm is prepared on one side of the polymer substrate, and a second alumina layer with a thickness of 10 nm is prepared on the other side of the polymer substrate.

[0199] Example 8

[0200] Example 8 is basically the same as Example 6, the main difference being that in step (a), a first alumina layer with a thickness of 45 nm is prepared on one side of the polymer substrate, and a second alumina layer with a thickness of 15 nm is prepared on the other side of the polymer substrate.

[0201] Example 9

[0202] Example 9 is basically the same as Example 6, the main difference being that in step (a), a first alumina layer with a thickness of 50 nm is prepared on one side of the polymer substrate, and a second alumina layer with a thickness of 20 nm is prepared on the other side of the polymer substrate.

[0203] Example 10

[0204] Compared with Example 1, the thickness of both the first metal layer and the second metal layer is 1.5 μm.

[0205] Example 11

[0206] Compared with Example 1, the thickness of both the first metal layer and the second metal layer is 0.5 μm.

[0207] Example 12

[0208] Compared with Example 1, both the first metal layer and the second metal layer are aluminum-magnesium alloys with a mass ratio of 9:1.

[0209] Example 13

[0210] Compared with Example 1, both the first metal layer and the second metal layer are aluminum-magnesium alloys with a mass ratio of 19:1.

[0211] Comparative Example 1

[0212] Compared with Example 1, the composite current collector provided in Comparative Example 1 does not have a first modified layer and a second modified layer.

[0213] Test case

[0214] Winding test: The current collector was wound using a winding machine. The winding radius was set to 1mm~8mm, and the side containing the first modified layer was considered the inner side of the winding during the winding process.

[0215] SEM characterization test: The cracking of the first and second metal layers near the roll area was tested. The degree of cracking was quantified by crack width. When the crack width was 0 μm, the degree of cracking was represented as "no cracking". When 0 μm < crack width < 5 μm, the degree of cracking was represented as "micro-cracking". When 5 μm ≤ crack width ≤ 20 μm, the degree of cracking was represented as "severe cracking". The corresponding test results are shown in Table 1. As can be seen from Table 1, no cracking was found on the inner and outer sides of the composite current collectors of Examples 1 to 9. For example, after SEM characterization testing, the SEM image of the uncracked surface of the composite current collector in Example 1 is shown below. Figure 1 As shown. The composite current collectors of Examples 10 to 13 exhibit microcracks on their inner or outer sides. For example, the SEM image corresponding to the microcracks on the outer side of the composite current collector of Example 10 is shown below. Figure 2 As shown, the composite current collector in Comparative Example 1 exhibits obvious cracking on both its inner and outer surfaces. For example, after SEM characterization testing, the SEM image of the cracked surface of the composite current collector in Comparative Example 1 is shown below. Figure 3 As shown.

[0216] Peel strength test: The composite current collectors prepared in the above examples and comparative examples were tested for peel strength using a BLD-200H electronic peel tester. 50*125mm test pieces were cut and attached to the peeling steel plate, and 20*125mm A4 white paper / Nitto double-sided tape was cut. The test results are shown in Table 2.

[0217] Table 1

[0218]

[0219] Table 2

[0220]

[0221] As can be seen from Tables 1 and 2, the composite current collectors of Examples 1 to 13 of this application exhibit better bending resistance and interlayer peel strength than Comparative Example 1. This demonstrates that by incorporating the first and second modified layers, this application can significantly improve the performance of the composite current collector.

[0222] Further examining Examples 1-13, the composite current collectors of Examples 1-6 exhibit slightly better bending resistance and interlayer peel strength than those of Examples 10-13. In Examples 10 and 11, the thicknesses of the first and second metal layers were not differentiated; similarly, in Examples 12 and 13, the magnesium content in the first and second metal layers was not differentiated. This resulted in slightly poorer bending resistance on the inner or outer side of the composite current collector.

[0223] Furthermore, Examples 1 to 3 are essentially the same, with the main differences being the thickness and magnesium content of the first metal layer, and the thickness and magnesium content of the second metal layer. Examples 1, 4, and 5 are essentially the same, with the main differences being the thickness and component content of the first modified layer, and the thickness and component content of the second modified layer. Examples 1 and 6 to 9 are essentially the same, with the main differences being the thickness of the first alumina layer and the second alumina layer. As can be seen from Tables 1 and 2, Examples 1 to 9, by regulating the functional layers of the composite current collector, exhibit superior bending resistance and peel strength compared to Comparative Example 1 and Examples 10 to 13.

[0224] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0225] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A composite current collector, characterized in that, include: A polymer substrate and a first modified layer and a second modified layer respectively disposed on two surfaces opposite to each other on the polymer substrate; And, a first metal layer disposed on the surface of the first modified layer opposite to the polymer substrate, and a second metal layer disposed on the surface of the second modified layer opposite to the polymer substrate; The first modified layer comprises acrylic resin; the second modified layer comprises polyurethane-modified epoxy resin.

2. The composite current collector according to claim 1, characterized in that, The first modified layer further includes nanomaterials and a first polysiloxane; and / or, The second modified layer further includes: a second polysiloxane; and / or, The thickness of the first modified layer is greater than the thickness of the second modified layer; and / or, The thickness of the first metal layer is greater than the thickness of the second metal layer; and / or, The mass fraction of magnesium in the first metal layer is higher than that in the second metal layer.

3. The composite current collector according to claim 2, characterized in that, The composite current collector has one or more of the following characteristics: (1) The acrylic resin is formed by polymerization of one or more monomers selected from methyl acrylate, ethyl acrylate, methyl methacrylate and butyl methacrylate; (2) The glass transition temperature of the acrylic resin is 20℃~35℃; (3) The elongation at break of the polyurethane-modified epoxy resin is 60%~150%; (4) The polymer substrate is polyethylene terephthalate doped with silicon dioxide; (5) The thickness of the polymer substrate is 2μm~6μm; (6) The thickness of the first modified layer is 0.5 μm to 2 μm; (7) In the first modified layer, the mass ratio of the acrylic resin to the nanomaterial is (5~7):(1~2); (8) The nanomaterials include one or more of nano-silica and carbon nanotubes; (9) In the first modified layer, the mass ratio of the acrylic resin to the first polysiloxane is (50~70):(0.5~2); (10) The thickness of the second modified layer is 0.1 μm to 1 μm; (11) In the second modified layer, the mass ratio of the polyurethane modified epoxy resin to the second polysiloxane is (65~80):(0.5~2); (12) The first metal layer comprises aluminum and magnesium in a mass ratio of (9~19):1; (13) The thickness of the first metal layer is 1.5 μm to 3 μm; (14) The second metal layer comprises aluminum and magnesium in a mass ratio of (9~19):1; (15) The thickness of the second metal layer is 0.5μm~1μm.

4. The composite current collector according to any one of claims 1 to 3, characterized in that, A first alumina layer is further provided between the polymer substrate and the first modified layer; and / or, A second alumina layer is further provided between the polymer substrate and the second modified layer.

5. A method for preparing a composite current collector, characterized in that, Includes the following steps: A first modified liquid and a second modified liquid are provided respectively; wherein, the first modified liquid comprises an acrylic resin and a first solvent; and the second modified liquid comprises a polyurethane-modified epoxy resin and a second solvent; The first modified liquid and the second modified liquid are respectively coated on two opposing surfaces of the polymer substrate, and after drying and curing, a first modified layer and a second modified layer are formed respectively. A first metal layer is formed on the surface of the first modified layer opposite to the polymer substrate, and a second metal layer is formed on the surface of the second modified layer opposite to the polymer substrate, thereby preparing the composite current collector.

6. The method for preparing the composite current collector according to claim 5, characterized in that, The first modified liquid further includes: nanomaterials and a first polysiloxane; and / or, The second modified liquid further includes: a second polysiloxane; and / or, The thickness of the first modified layer is greater than the thickness of the second modified layer; and / or, The thickness of the first metal layer is greater than the thickness of the second metal layer; and / or, The mass fraction of magnesium in the first metal layer is higher than that in the second metal layer.

7. The method for preparing the composite current collector according to claim 6, characterized in that, The first modified liquid has one or more of the following characteristics: (1) By mass fraction, the first modified liquid comprises: 50% to 70% acrylic resin, 10% to 20% nanomaterials, 0.5% to 2% first polysiloxane and 10% to 35% first solvent; (2) The acrylic resin is formed by polymerization of one or more monomers selected from methyl acrylate, ethyl acrylate, methyl methacrylate and butyl methacrylate; (3) The glass transition temperature of the acrylic resin is 20℃~35℃; (4) The nanomaterials include one or more of nano-silica and carbon nanotubes; (5) The viscosity of the first polysiloxane at 25°C is 100 mPa•s to 500 mPa•s; (6) The surface tension of the first polysiloxane at 25°C is 20mN / m~45mN / m; (7) The first solvent includes one or more of butyl acetate, ethyl acetate, isobutyl acetate and butyl propionate.

8. The method for preparing the composite current collector according to claim 6, characterized in that, The second modified liquid has one or more of the following characteristics: (1) By mass fraction, the second modified liquid comprises: 65% to 80% polyurethane modified epoxy resin, 0.5% to 2% second polysiloxane and 18% to 34.5% second solvent; (2) The elongation at break of the polyurethane-modified epoxy resin is 60%~150%; (3) The viscosity of the second polysiloxane at 25°C is 100 mPa•s to 500 mPa•s; (4) The surface tension of the second polysiloxane at 25°C is 20mN / m~45mN / m; (5) The second solvent includes one or more of butyl acetate, ethyl acetate, isobutyl acetate and butyl propionate.

9. The method for preparing the composite current collector according to any one of claims 5 to 8, characterized in that, The polymer substrate is silicon dioxide-doped polyethylene terephthalate; and / or, The thickness of the polymer substrate is 2μm~6μm; and / or, The thickness of the first modified layer is 0.5 μm to 2 μm; and / or, The thickness of the second modified layer is 0.1 μm to 1 μm; and / or, The drying temperature is 80℃~120℃; and / or, The curing methods include one or more of UV curing and heat curing.

10. The method for preparing the composite current collector according to any one of claims 5 to 8, characterized in that, The step of forming the first metal layer on the surface of the first modified layer opposite to the polymer substrate includes: The first metal layer is prepared on the surface of the first modified layer away from the polymer substrate using a vapor deposition method; optionally, the vapor deposition rate is 0.5 μm / min to 2 μm / min; optionally, the first metal layer comprises aluminum and magnesium in a mass ratio of (9~19):1; optionally, the thickness of the first metal layer is 1.5 μm to 3 μm; and / or, The step of forming the second metal layer on the surface of the second modified layer opposite to the polymer substrate includes: The second metal layer is prepared on the side of the second modified layer away from the polymer substrate by vapor deposition; optionally, the vapor deposition rate is 0.5 μm / min to 2 μm / min; optionally, the second metal layer comprises aluminum and magnesium in a mass ratio of (9 to 19):1; optionally, the thickness of the second metal layer is 0.5 μm to 1 μm.

11. The method for preparing the composite current collector according to any one of claims 5 to 8, characterized in that, Before the step of coating the first modified liquid onto the surface of the polymer substrate, the method further includes: A first alumina layer is formed on the surface of the polymer substrate; wherein the first alumina layer is disposed between the polymer substrate and the first modified layer; And / or, prior to the step of coating the second modified liquid onto the surface of the polymer substrate, the method further includes: A second alumina layer is formed on the surface of the polymer substrate; wherein the second alumina layer is disposed between the polymer substrate and the second modified layer; and / or, The thickness of the first alumina layer is 1.5 to 3 times the thickness of the second alumina layer; and / or, The thickness of the second alumina layer is 5nm~20nm.

12. An electrode sheet, characterized in that, It includes the composite current collector as described in any one of claims 1 to 4, or the composite current collector prepared by any one of claims 5 to 11.

13. A battery, characterized in that, Including the electrode sheet as described in claim 12, Optionally, the battery is a cylindrical wound battery.

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