Metallic copper composite current collector, method for preparing the same, electrode sheet, and battery

Abstract

The application discloses a metal copper composite current collector and a preparation method thereof, an electrode sheet and a battery, wherein the metal copper composite current collector comprises a polymer film, a conductive MXene layer arranged on at least one side surface of the polymer film, and an electroplated copper layer arranged on a surface of the conductive MXene layer. Compared with the preparation method of the composite copper current collector in the prior art, the preparation method of the application does not need to adopt a physical vapor deposition step, avoids high-energy-consumption and high-cost magnetron sputtering or evaporation processes, greatly simplifies the production process of the ultrathin copper, reduces the production energy consumption of the ultrathin copper, and can significantly reduce the cost of the ultrathin copper, thereby promoting the large-scale application of the ultrathin copper.

Description

Technical Field

[0001] This invention belongs to the field of batteries, and in particular relates to a copper composite current collector, its preparation method, electrode sheet, and battery. Background Technology

[0002] Copper foil is one of the fundamental materials in the electronics industry, widely used in industrial lithium-ion batteries, communication equipment, consumer electronics, automotive electronics, electronic shielding, and other fields, with a growing trend towards thinner and lighter designs. Taking copper foil for lithium-ion batteries as an example, as people pursue higher energy density, lighter weight, and greater flexibility in batteries, the thickness of the negative electrode current collector copper foil has gradually decreased from 12μm to 4.5μm. The thinner the copper foil, the better its ability to carry the negative electrode active material, resulting in a larger battery capacity and lighter weight, thus providing higher energy density. However, further thinning of the copper foil reduces its mechanical strength, leading to decreased processing performance. Traditional electrolytic and rolling copper foil technologies struggle to obtain ultra-thin copper foil (thickness < 4.5μm).

[0003] To obtain ultrathin copper foil, composite copper foil current collectors based on polymer films have attracted attention and application. Conventional composite copper foil current collectors typically include a polymer film layer and a metallic copper layer formed on the polymer film layer by methods such as physical vapor deposition (PVD). The corresponding preparation process usually includes: (1) depositing a layer of copper on the polymer film using physical vapor deposition (magnetron sputtering or evaporation) to prepare a composite copper current collector semi-finished product with certain conductivity; (2) further processing the composite copper current collector semi-finished product using electroplating to prepare the composite copper current collector. Compared with traditional current collectors (electrolytic copper foil), composite copper current collectors based on polymer films have the characteristics of low cost, light weight, and good internal insulation. These characteristics enable the composite copper current collector to reduce the cost of secondary batteries and improve the energy density and safety of batteries when used in secondary batteries. However, the physical vapor deposition process involved in the preparation of conventional composite copper current collectors has the problem of high energy consumption, which will lead to an increase in the cost of composite copper current collectors. Summary of the Invention

[0004] The purpose of this invention is to address the technical problems of high energy consumption and high cost in existing polymer membrane composite copper current collector processes, and to provide a method for preparing a metallic copper composite current collector containing ultrathin copper.

[0005] The first aspect of the present invention provides a copper composite current collector, which includes: a polymer film; a conductive MXene layer disposed on at least one surface of the polymer film; and an electroplated copper layer disposed on the surface of the conductive MXene layer.

[0006] In some embodiments, the thickness of the conductive MXene layer is between 1 nm and 50 μm; preferably, between 10 nm and 10 μm; more preferably, between 100 nm and 5 μm; and even more preferably, between 200 nm and 2 μm.

[0007] In some embodiments, the thickness of the electroplated copper layer is between 10 nm and 100 μm; preferably, the thickness is between 100 nm and 10 μm; more preferably, it is between 200 nm and 5 μm; and even more preferably, it is between 500 nm and 1.5 μm.

[0008] In some embodiments, the thickness of the polymer film is between 1 μm and 50 μm; preferably, it is between 1 μm and 10 μm.

[0009] In some embodiments, the chemical formula of the above-mentioned MXene material is represented as M. n+1 X n T x Where M represents one or more transition metal elements; X represents one or more carbon, nitrogen, or boron; T represents surface functional groups; 1≤n≤4, 0<x≤2.

[0010] In some embodiments, the M in the chemical formula of the above-mentioned MXene material is selected from one or more of Ti, Nb, Ta, V, Mo, and Zr.

[0011] In some embodiments, the mass content of MXene material in the conductive MXene layer is between 30% and 100%; preferably, it is between 50% and 100%, and more preferably, it is between 90% and 100%.

[0012] In some embodiments, the polymer film described above is a non-conductive polymer.

[0013] In some embodiments, the material of the polymer film is selected from one or more of the following: polypropylene, polyethylene, polyethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyimide, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, polyamide, and derivatives of the above polymers.

[0014] In some embodiments, a protective layer is provided on the surface of the electroplated copper layer.

[0015] A second aspect of the present invention also provides a method for preparing the above-mentioned copper composite current collector, comprising the following steps:

[0016] Coating step: Coating at least one side of the surface of the polymer film with MXene material to form a conductive MXene layer;

[0017] Electroplating step: The surface of the conductive MXene layer is electroplated to form an electroplated copper layer.

[0018] In some embodiments, the above coating step may include, more specifically, coating and / or spraying the MXene dispersion onto the polymer film and drying it to form the conductive MXene layer.

[0019] In some embodiments, during the coating step described above, the polymer film is immersed and pulled from the MXene dispersion, and then dried to form the conductive MXene layer.

[0020] In some embodiments, the MXene dispersion comprises MXene material and a solvent; preferably, the solvent is selected from water and / or alcohols.

[0021] In some embodiments, the above-mentioned MXene dispersion is composed of MXene material and solvent.

[0022] In some embodiments, the concentration of MXene material in the above-mentioned MXene dispersion is between 0.01 mg / ml and 80 mg / ml.

[0023] In some embodiments, the MXene dispersion contains a binder; preferably, the binder is selected from one or more of LA133 waterborne adhesive, methylcellulose (CMC), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), and waterborne polyurethane.

[0024] In some embodiments, the above preparation method further includes a passivation step: passivating the surface of the electroplated copper to form a protective layer.

[0025] A third aspect of the present invention provides an electrode sheet comprising the above-described copper composite current collector; or, a copper composite current collector obtained by the preparation method described above.

[0026] A fourth aspect of the present invention provides a battery comprising the electrode sheets described above.

[0027] The fifth aspect of the present invention provides an electrical device including the battery described above, which can be an electric vehicle, an electric bicycle, an energy storage system, an electronic appliance, etc.

[0028] The sixth aspect of this invention provides an application of MXene material in polymer film interface electroplating.

[0029] The technical concept of this invention lies in forming a conductive MXene layer on the surface of a polymer film, and then electroplating an ultrathin copper layer on the surface of the conductive MXene layer. The technical solution of this invention forms a conductive MXene layer on the surface of a polymer film using simple film-forming methods such as spraying, coating, or immersion, and then electroplats copper on the surface of the conductive MXene layer to obtain an ultrathin copper layer (10nm~100μm).

[0030] Compared with existing methods for preparing composite copper current collectors, the method of the present invention does not require physical vapor deposition, avoids high-energy-consuming and high-cost magnetron sputtering or evaporation processes, greatly simplifies the production process of ultrathin copper, reduces the energy consumption of ultrathin copper production, and thus significantly reduces the cost of ultrathin copper, promoting the large-scale application of ultrathin copper.

[0031] The difference between the ultrathin copper layer obtained by the electroplating process in the metal composite current collector of the present invention and the ultrathin copper layer obtained by the physical vapor deposition process in the prior art is as follows:

[0032] Existing technologies employ physical vapor deposition (PVD) to magnetron sputter or vapor-deposit copper atoms onto a polymer substrate. These copper atoms then serve as nucleation sites for subsequent copper electroplating, resulting in the growth of an ultrathin copper layer. However, these dot-shaped copper atoms are difficult to completely cover the polymer film, meaning that non-conductive gaps (or pore defects) in the polymer substrate remain exposed. This prevents the deposition of copper during subsequent electroplating, resulting in gap / pore defects on the surface of the ultrathin copper layer, which affects its performance and applications.

[0033] The ultrathin copper layer prepared by the electroplating method of this invention uses MXene material with a two-dimensional structure as a nucleating agent. The stacked MXene material with a two-dimensional structure can completely cover the polymer matrix, avoiding the exposure of non-conductive polymer gaps or pore defects. The metallic copper grows based on the nucleation of MXene two-dimensional sheets, and the surface of the obtained ultrathin copper layer has the characteristics of being dense and smooth, which significantly improves the surface quality of the ultrathin copper. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a copper composite current collector according to Embodiment 1 of the present invention;

[0035] Figure 2 This is a schematic diagram of another metal-copper composite current collector in Embodiment 1 of the present invention;

[0036] Figure 3 (a) Photograph of the PET / MXene / Cu composite current collector in Example 2 of the present invention; (b) SEM image of the cross section; (c) SEM image of the surface of the electroplated copper layer.

[0037] Figure 4 The images shown are (a) and (b) cross-sectional SEM images of the copper composite current collector in Embodiment 3 of the present invention.

[0038] Figure 5 This is a cross-sectional SEM image of the conductive MXene layer and the electroplated copper layer in the copper-metal composite current collector of Embodiment 4 of the present invention.

[0039] Figure 6 This is a schematic diagram of the polymer / MXene composite membrane in this invention.

[0040] Figure 7 SEM images of (a) the cross-section and (b) the surface of the graphene electroplated with copper in Comparative Example 1 of this invention.

[0041] Figure 8 This is a schematic diagram of the electrode sheet in Embodiment 5 of the present invention.

[0042] Explanation of key figure labels:

[0043] 100, 200 Copper composite current collector; 300 Electrode sheet; 10 Polymer film; 20 Conductive MXene layer; 30 Electroplated copper layer; 40 Lithium base layer; 110 Polymer / MXene composite film; 21 MXene two-dimensional sheet. Detailed Implementation

[0044] The technical solution of the present invention is illustrated below through specific embodiments. It should be understood that the one or more steps mentioned in the present invention do not preclude the existence of other methods and steps before or after the combined steps, or that other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Unless otherwise stated, the numbering of each method step is only for the purpose of identifying each method step, and not for limiting the order of each method or limiting the scope of the present invention. Changes or adjustments to their relative relationships, without substantial changes to the technical content, can also be considered as within the scope of the present invention.

[0045] The MXene material and graphene used in this embodiment of the invention were purchased from Jinan Sanchuan New Material Technology Co., Ltd., wherein Ti3C2T x The slurry product model is SC02003LW, with concentrations of 5 mg / ml and 50 mg / ml. This Ti3C2T... x The slurry contains two-dimensional MXeneTi3C2T x MXene was obtained by etching the Al layer of the MAX phase material Ti3AlC2 followed by ultrasonic exfoliation. The MXene powder was made from Ti3C2T. x The graphene in the comparative example was prepared by redox method at a concentration of 0.5 wt.%.

[0046] The raw materials and instruments used in the examples are not subject to any specific restrictions on their source; they can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0047] In preparing composite copper current collectors using conductive MXene layers, the following properties and characteristics were discovered: 1) The MXene layer exhibits excellent affinity with the electroplating solution, primarily due to the abundance of hydrophilic functional groups such as -OH and -O on the MXene surface; 2) The use of MXene significantly reduces the deposition overpotential of metallic copper, as the abundant surface functional groups of MXene serve as nucleation sites for copper; 3) MXene materials enable uniform deposition and growth of metallic copper ions on their surface, thanks to MXene's high conductivity and high specific surface area, which greatly homogenizes the electric field and ion flow distribution during electroplating; 4) A dense, ultrathin copper layer and an ultrathin composite current collector were obtained on the MXene material, due to the atomically thin two-dimensional structure of MXene, which greatly reduces the thickness of the composite current collector. The technical features of this invention are further illustrated below through specific embodiments.

[0048] Example 1

[0049] This embodiment provides a copper composite current collector 100 and 200 and its preparation method, the steps of which include:

[0050] S01: MXene material is coated onto the polymer film 10 to form a conductive MXene layer 20;

[0051] S02: Electroplating the surface of the conductive MXene layer 20 to obtain an ultrathin electroplated copper layer 30.

[0052] In step S01, the coating method for forming a conductive MXene layer by coating the surface of the polymer film with MXene material can be either a dry process or a wet process. The dry process involves forming a film layer on the surface of a substrate using MXene powder and binders under solvent-free conditions. The wet process involves coating the substrate surface with an MXene dispersion through spraying, dipping, or coating methods, and then drying to remove the solvent to form a conductive MXene layer. The dry process avoids the solvent removal step, simplifying the process flow. However, forming a stable and continuous conductive layer requires the addition of a binder; non-conductive binders reduce the continuous conductivity of the conductive MXene layer surface. Therefore, the wet process is preferred. The wet process also allows for a more uniform dispersion of the MXene material on the surface of the polymer film. Although it includes a solvent removal step, due to the good hydrophilicity of MXene, aqueous solvents (including water and / or alcohol solvents) are typically used, which are low-cost and easy to remove. In one specific embodiment, the method includes: coating the surface of a polymer film with an MXene dispersion through one or more spraying and / or coating processes to form an MXene film, and drying it to form a conductive MXene layer; in another specific embodiment, the method includes: repeatedly lifting and / or immersing the polymer film from the MXene dispersion to allow the two-dimensional MXene sheets in the dispersion to be directionally and continuously coated onto the surface of the polymer film under the action of surface tension, and drying it to form a conductive MXene layer.

[0053] In this invention, the MXene dispersion refers to a liquid or semi-liquid (gel or slurry) mixture containing MXene material. Optionally, the MXene dispersion also includes a certain amount of binder (0.01% to 50% of the dry material by mass). The binder content is determined by a combination of bonding performance and electroplating performance. Under the premise of ensuring good electroplating effect and bonding performance, the lower the binder content, the better. Preferably, the binder is a water-based binder. Optionally, the binder is selected from one or more of LA133 water-based adhesive, methylcellulose (CMC), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), water-based polyurethane, etc.

[0054] In some implementations, the adhesion between the conductive MXene layer and the polymer film can be enhanced by roughening the surface of the polymer film (e.g., corona treatment or etching), i.e., etching "pits" on the surface of the polymer matrix, thereby reducing the amount of adhesive used or eliminating the need for adhesive.

[0055] In a specific embodiment, the thickness of the polymer film is between 1 μm and 50 μm; optionally, the polymer film material includes one or more of the following polymers: polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyimide (PI), polypropylene, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polystyrene (PS), polyamide (PA), and derivatives of the above polymers.

[0056] A schematic diagram of the obtained copper composite current collector is shown below. Figure 1 and 2 As shown, the copper composite current collector of the present invention can form a conductive MXene layer on both sides or one side of a polymer film, and then electroplate and grow a composite material with an electroplated copper layer on both sides or one side on the surface of the conductive MXene layer.

[0057] Optionally, the thickness of the polymer film is between 1 μm and 50 μm, preferably between 2 μm and 20 μm; optionally, the thickness of the conductive MXene layer is between 1 nm and 10 μm, preferably between 3 nm and 1 μm. The thickness of the electroplated copper layer is between 10 nm and 50 μm; when used as a current collector in a battery, it is preferably between 100 nm and 5 μm; more preferably between 1 and 3 μm; even more preferably, it is 1 μm. It should be noted that when the metal copper composite current collector has double-sided electroplated copper layers, the thickness of the electroplated copper layers can be the same or different. The electroplating conditions of the electroplated copper layer of the present invention are optimized through experiments based on different metal ion conditions; preferably, the electroplating DC voltage is 1V to 5V, and the electroplating current is 0.5 to 100 A / dm. 2 The electroplating time is between 10 seconds and 60 minutes; more preferably, the electroplating current is 2 to 65 A / dm. 2 The electroplating time is between 10 seconds and 5 minutes.

[0058] In a preferred embodiment of the present invention, the polymer film has a thickness of 1 to 3 μm, the conductive MXene layer has a thickness of 10 nm to 100 nm, and both sides have electroplated copper layers with a thickness of 1 μm, resulting in an ultrathin composite copper current collector with a total thickness of approximately 3 μm to 5 μm.

[0059] In another preferred embodiment of the present invention, the polymer film has a thickness of 5 to 6 μm, the conductive MXene layer has a thickness of 200 nm to 500 nm, and both sides have electroplated copper layers with a thickness of 1 μm, resulting in an ultrathin composite copper current collector with a total thickness of about 7 μm to 9 μm.

[0060] The chemical formula of the MXene material in this invention can be represented as M n+1 X n T x In this context, M represents one or more transition metal elements; X represents one or more of carbon, nitrogen, or boron; and T represents a surface functional group; 1 ≤ n ≤ 4, 0 < x ≤ 2; in some embodiments, M is selected from one or more of Ti, Nb, Ta, Nb, V, Mo, Zr, and Cr. MXene materials are typically prepared by etching the A component of the precursor MAX phase. Common MXene materials include Ti3C2T. x Ti2CT x V2CT x Nb2CT x Mo2CT x Ti4C3T x Ta2CT x Ta4C3T x TiNbCT x wait.

[0061] In some embodiments, a binder is added to the conductive MXene layer as needed to increase the adhesion between the conductive MXene layer and the substrate; that is, the mass content of MXene material in the conductive MXene layer is between 30% and 100%. Higher MXene material content in the conductive MXene layer results in better conductivity and hydrophilicity, but reduces adhesion to the polymer film. In some embodiments, the adhesion between the conductive MXene layer and the polymer film can be enhanced by roughening the polymer film surface (e.g., corona treatment or etching), i.e., etching "pits" on the surface of the polymer substrate, thereby reducing the amount of binder used or eliminating the need for binder. Therefore, preferably, the mass content of MXene material in the conductive MXene layer is between 50% and 100%, more preferably between 80% and 100%, and even more preferably between 90% and 100%.

[0062] Example 2

[0063] This embodiment provides a specific copper composite current collector and its preparation method. In this embodiment, a 10 μm thick PET film is used as the polymer film, and the specific preparation method includes:

[0064] (1) Prepare Ti3C2T with a mass concentration of 2 mg / ml x Aqueous dispersion;

[0065] (2) Impregnate a 10 μm thick PET film with Ti3C2T x After dispersing the PET film in an aqueous solution, slowly and uniformly lift the film out of the water to allow the Ti3C2T to disperse. xTwo-dimensional Ti3C2T in aqueous dispersion x The surface tension of the aqueous solution is applied to the surface of the PET film. After the PET film is pulled out and air-dried naturally, it is repeatedly pulled up and dried several times (5 times). Then it is placed in a vacuum oven and vacuum dried at 50°C for 4 hours to obtain the PET / MXene composite layer.

[0066] (3) The dried PET / MXene composite layer is placed in an electroplating apparatus for electroplating treatment. Specifically, the electroplating process includes:

[0067] a. Electroplating solution formulation for electrodeposition of copper: copper sulfate pentahydrate with a copper ion concentration of 80 g / L, concentrated sulfuric acid of 100 g / L, concentrated hydrochloric acid of 15 mg / L, polyethylene glycol (PEG) of 5 mg / L, hydroxyethyl cellulose (HEC) of 8 mg / L, sodium polydithiopropane sulfonate (SP) of 3 mg / L, and collagen of 10 mg / L.

[0068] b. At an operating temperature of 50℃ and a current density of 9A / dm 2 Under the conditions of 2V DC electrodeposition for 45s, an electroplated copper layer is formed on the surface of the PET / MXene composite layer. After cleaning and drying, the metal copper composite current collector PET / MXene / Cu of the present invention is obtained.

[0069] For ease of demonstration, a portion of the PET / MXene composite layer was placed in an electroplating apparatus for electroplating, resulting in a photograph of the PET / MXene / Cu metallic copper composite current collector. Figure 3 a) You can see that the lower part is a metallic-looking electroplated copper layer, and the upper part is a black conductive MXene layer. Figure 3 b presents cross-sectional SEM images of the conductive MXene layer and the electroplated copper layer in this copper-metal composite current collector. It can be seen that the thickness of both the conductive MXene layer and the electroplated copper layer is approximately 1 μm. Figure 3 c shows an SEM image of the surface of the copper composite current collector. It can be seen that the surface of the electroplated copper layer is smooth and flat. The surface of the electroplated copper layer has the characteristics of being smooth and dense, which shows that high-quality electroplating of copper can be achieved on the surface of the conductive MXene layer.

[0070] By controlling the electroplating process conditions, including temperature, current density, and electroplating time, the thickness range of the electroplated copper layer can be easily controlled. In some embodiments, the thickness of the electroplated copper layer is between 10 nm and 500 μm. However, when used in a metal composite current collector, the thickness of the electroplated copper layer is preferably between 1 μm and 4 μm (1 μm ≤ thickness ≤ 4 μm); in a specific embodiment, the thickness of the electroplated copper layer is 3.5 μm, 2.5 μm, or 1.5 μm.

[0071] Example 3

[0072] This embodiment provides another specific method for preparing a copper composite current collector. Similar to Example 2, the difference lies in that a high concentration of MXene dispersion (50 mg / ml) is coated onto a polymer film using a doctor blade in this embodiment. More specific steps include:

[0073] (1) Prepare Ti3C2T with a mass concentration of 50 mg / ml x Aqueous dispersion (viscous slurry);

[0074] (2) The Ti3C2T x An aqueous dispersion was coated onto one side of a PET film using a doctor blade to form a Ti3C2T layer. x The Ti3C2T membrane can be easily controlled by the gap between the doctor blade and the PET film. x The thickness of the film was determined by vacuum drying at 50°C for 4 hours to form a conductive MXene layer, resulting in a PET / MXene composite layer.

[0075] (3) The dried PET / MXene composite layer was placed in an electroplating apparatus for electroplating. The specific electroplating process was similar to that in Example 2, except that the electroplating current was 65 A / dm. 2 The electroplating time is 30s to obtain the metal copper composite current collector of the present invention. Figure 4 a). Through cross-sectional SEM images ( Figure 4 b) It can be seen that the thickness of the electroplated copper layer is about 10 μm, and the thickness of the conductive MXene layer is about 3 μm.

[0076] Example 4

[0077] This embodiment provides another specific copper composite current collector and its preparation method, similar to Embodiment 2, except that the polymer film used is a PP film with a thickness between [thickness range missing], and MXene Ti3C2T [material missing]. x The aqueous dispersion is coated onto the surface of the PP film using a spraying method. More specific steps include:

[0078] (1) Prepare Ti3C2T with a mass concentration of 1 mg / ml x Aqueous dispersion;

[0079] (2) The Ti3C2T x The aqueous dispersion was sprayed onto one or both sides of a PP film with a thickness of 10μm using a sprayer. After air drying, it was placed in a vacuum oven and vacuum dried at 50℃ for 4 hours to obtain a PP / MXene composite layer.

[0080] (3) The dried PP / MXene composite layer is placed in an electroplating device for electroplating treatment. The specific electroplating process is similar to that in Example 2, except that the electroplating time is 1 min, and the metal copper composite current collector PP / MXene / Cu of the present invention is obtained.

[0081] Figure 5 Cross-sectional SEM images of the conductive MXene layer and the electroplated copper layer in the copper-metal composite current collector are presented. It can be seen that the thickness of the conductive MXene layer is about 1 μm and the thickness of the electroplated copper layer is about 2 μm.

[0082] To prevent oxidation of the electroplated copper layer surface, preferably, the preparation method of the present invention further includes a passivation step: passivating the surface of the electroplated copper layer to form a protective layer.

[0083] In Examples 2 to 4, the passivation treatment step specifically includes: after electroplating, the electroplated composite film is placed in a pure water cleaning tank for cleaning, and then passivated in a passivation tank to prepare a surface protective layer. The passivation solution is an aqueous solution of 5 g / L potassium dichromate at a temperature of 25°C. Finally, the cleaned composite film is dried in an oven at a temperature of 70°C.

[0084] It should be noted that in embodiments 2 to 4, Ti3C2T x The main component of the aqueous dispersion is Ti3C2T x And water, that is, Ti3C2T x Aqueous dispersion composed of Ti3C2T x It is composed of water, but trace amounts of impurities cannot be ruled out. Due to Ti3C2T x It exhibits good hydrophilicity and can be stably dispersed in aqueous solutions, thus eliminating the need for dispersants. Ti3C2T x The MXene layer, formed by the overlapping of micron-sized two-dimensional sheets, leverages the high specific surface area and van der Waals forces of two-dimensional materials to create strong adhesion between the MXene sheets, thus eliminating the need for binders. Conventional dispersants and binders are non-conductive components; their addition to the dispersion would inevitably affect the conductivity of the coated MXene layer, thereby impacting the electroplating effect on the MXene layer surface. Of course, this invention does not preclude the addition of small amounts of binders and / or other functional additives to the MXene dispersion as needed; in some embodiments, the MXene dispersion also includes a binder.

[0085] Compared to the coating method in Example 3 and the spraying method in Example 4, the dip-coating method in Example 2 is preferred because during the dipping process, the surface tension of the liquid causes the MXene two-dimensional sheets in the MXene dispersion to be oriented and spread evenly onto the surface of the polymer film, resulting in a thinner MXene layer that completely covers the surface of the polymer matrix. Figure 6 As shown in the schematic diagram, MXene two-dimensional sheets 21 are laid flat and stacked on the surface of the polymer film to form an ultrathin MXene layer. The thickness of the MXene layer can be as low as the thickness of several MXene two-dimensional sheets (1nm to 3nm). Since the MXene two-dimensional sheets are also flexible, the ultrathin MXene layer can adhere to the surface of the polymer film, so that the MXene material covers the surface of the polymer film while having an ultrathin conductive MXene layer (1nm to 100nm).

[0086] Comparative Example 1

[0087] Using a method similar to that in Example 2, the MXene dispersion was replaced with a graphene dispersion to prepare a composite with a conductive graphene layer on the surface of a PET film. Copper electroplating was then performed under the same conditions. The cross-sectional and surface SEM images of the resulting product are shown below. Figure 7 As shown, it is difficult to achieve dense electroplating of metallic copper on the surface of graphene layer. The bonding force between metallic copper and graphene layer is poor, the plating layer is easy to peel off, the surface of electroplated copper layer is uneven and has a porous structure, resulting in poor electroplating effect.

[0088] Since the preparation method of the copper composite current collector of this invention involves a copper electroplating process, which requires immersion in an aqueous electroplating solution for deposition, the conductive nucleation layer on the polymer film must possess both good hydrophilicity and conductivity. While existing graphene technologies share a similar two-dimensional sheet structure with MXene, conductive graphene (such as mechanically exfoliated, electrochemically processed, or reduced graphene) typically lacks hydrophilicity; and while hydrophilic graphene oxide exhibits poor conductivity, it is difficult to achieve good electroplating results when applied to copper deposition processes.

[0089] In addition, the MXene material of this application differs from graphene in that: (1) the surface of the MXene material has abundant functional groups, especially halogen-containing functional groups (such as -F). This can reduce the nucleation overpotential of copper deposition, promote the uniform growth of metallic copper, and obtain a dense and uniform metallic copper coating; (2) the MXene material is a transition metal carbon and / or nitride, and its constituent elements include transition metal elements. When MXene is used as a nucleating agent, the transition metal elements in it have similar metallic properties to metallic copper, which is conducive to the formation of a tightly bonded metallic copper coating.

[0090] In a specific embodiment of the present invention, MXene Ti3C2T was used. x Since MXene materials are a class of two-dimensional materials, they possess similar physicochemical properties, such as hydrophilicity, abundant surface functional groups, and conductivity. In other embodiments, other types of MXene materials, such as Ti2CT, can be substituted. x V2CT x Mo2CT x Nb2CT x Ta2CT x Ta3C2T x Ta4C3T x Ti4C3T x It is reasonable to expect that it will also be able to produce something similar to MXene Ti3C2T. x The same technical effect. The application of these different types of MXene materials to metal composite current collectors, or the application of these MXene materials to electroplating metal onto polymer film surfaces, are both within the scope of this invention.

[0091] Example 5

[0092] This embodiment provides an electrode sheet and a battery utilizing the copper composite current collector of the present invention. Specifically, the electrode sheet is a negative electrode sheet for a lithium metal battery. Molten lithium metal or lithium alloy slurry is coated onto the surface of the electroplated copper layer of the copper composite current collector of the present invention. After cooling, a lithium base layer 40 is formed, resulting in the electrode sheet of the present invention. Figure 8 As shown, the thickness of the lithium substrate is between 1 μm and 100 μm, preferably between 1 μm and 10 μm. More specific steps include:

[0093] (1) Place 400mg of lithium metal in a stainless steel crucible and heat it to 350°C in an argon atmosphere in a glove box to melt the lithium metal into a liquid state.

[0094] (2) Add 40 mg of magnesium metal flakes to the liquid lithium metal, followed by 50 mg of MXene Ti3C2T. x The powder is stirred and mixed, and the magnesium sheet is melted to form a liquid lithium-magnesium alloy. Stirring is continued for about 30 minutes to achieve the desired Ti3C2T alloy composition. x Uniform dispersion yields a gel-like mixed lithium slurry;

[0095] (3) The mixed lithium slurry is coated onto the surface of the electroplated copper layer of the copper composite current collector by a scraper. After cooling, a lithium base layer is formed, resulting in an electrode sheet with a lithium base layer on the surface of the electroplated copper layer.

[0096] In other embodiments, MXene material may be added to liquid lithium metal to form a lithium metal layer.

[0097] The electrode sheet is assembled into a battery, specifically, a lithium metal battery is obtained.

[0098] The role of adding MXene material to liquid lithium metal or lithium alloy is to reduce the surface tension of liquid lithium metal, making it form a semi-solid (gel-like) composite that can be easily coated onto the metal composite current collector, and the thickness can be controlled to obtain an ultra-thin lithium base layer (1μm~5μm). In addition, during the charging and discharging process of lithium metal batteries, as lithium metal on the negative electrode sheet is repeatedly peeled off and deposited, the MXene material in the lithium base layer also has a nucleation effect on lithium metal, reducing the nucleation overpotential of lithium metal, controlling the nucleation sites of lithium metal with MXene, and controlling the controllable growth of lithium metal based on two-dimensional sheets, avoiding the formation of sharp lithium branches, thereby improving the safety of lithium metal batteries. Embodiments of the preparation method and technical effects of the above-mentioned ultra-thin lithium base layer are described in the applicant's patent applications with application numbers 201911241973.3 and 201911242747.7. However, using other methods, such as physical rolling, to composite lithium metal or lithium alloy onto the copper current collector of the present invention, the resulting electrode sheet is also within the technical concept of the present invention.

[0099] The lithium metal electrode sheet of the present invention can also be used in solid-state lithium metal batteries. Specifically, the electrode sheet is assembled with a solid electrolyte separator and a positive electrode sheet to obtain a solid-state lithium metal battery. In a preferred embodiment, the positive electrode material in this solid-state battery is a high-nickel ternary positive electrode material (LiNi). 0.8 Co 0.1 Mn 0.1 O2, NCM811).

[0100] The copper composite current collector of the present invention can also replace the current copper foil current collector for use as the negative electrode current collector of lithium-ion batteries (the negative electrode material is graphite and / or silicon material). By reducing the amount of copper used, not only is the cost of the battery reduced, but the weight of the battery is also reduced, thereby improving the energy density of the lithium-ion battery.

[0101] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a metallic copper composite current collector, characterized in that, The copper composite current collector comprises: a polymer film; a conductive MXene layer disposed on at least one surface of the polymer film; and, An electroplated copper layer is disposed on the surface of the conductive MXene layer; The preparation method includes the following steps: Coating step: The MXene dispersion is coated onto the surface of at least one side of the polymer film by coating, spraying or dip-coating, and a conductive MXene layer is formed after drying; Electroplating step: The surface of the conductive MXene layer is electroplated to form a dense electroplated copper layer.

2. The method for preparing the metallic copper composite current collector as described in claim 1, characterized in that, The thickness of the conductive MXene layer is between 1 nm and 50 μm; And / or, the thickness of the electroplated copper layer is between 10 nm and 100 μm; And / or, the thickness of the polymer film is between 1 μm and 50 μm.

3. The method for preparing the metallic copper composite current collector as described in claim 1, characterized in that, The thickness of the conductive MXene layer is between 10 nm and 10 μm; And / or, the thickness of the electroplated copper layer is between 100 nm and 10 μm; And / or, the thickness of the polymer film is between 1 μm and 10 μm.

4. The method for preparing the metallic copper composite current collector as described in claim 1, characterized in that, The thickness of the conductive MXene layer is between 100 nm and 5 μm; And / or, the thickness of the electroplated copper layer is between 200 nm and 5 μm.

5. The method for preparing the metallic copper composite current collector as described in claim 1, characterized in that, The thickness of the conductive MXene layer is between 200 nm and 2 μm; And / or, the thickness of the electroplated copper layer is between 500 nm and 1.5 μm.

6. The method for preparing the metallic copper composite current collector as described in claim 1, characterized in that, The chemical formula of the MXene material is represented by M. n+1 X n T x Where M represents one or more transition metal elements; X represents one or more of carbon, nitrogen, or boron; and T represents a surface functional group; 1 ≤ n ≤4, 0< x ≤2.

7. The method for preparing the metallic copper composite current collector as described in claim 6, characterized in that, M is selected from one or more of Ti, Nb, Ta, V, Mo, and Zr.

8. The method for preparing the metallic copper composite current collector as described in claim 1, characterized in that, The mass content of MXene material in the conductive MXene layer is between 30% and 100%.

9. The method for preparing the metallic copper composite current collector as described in claim 1, characterized in that, The mass content of MXene material in the conductive MXene layer is between 50% and 100%.

10. The method for preparing the metallic copper composite current collector as described in claim 1, characterized in that, The mass content of MXene material in the conductive MXene layer is between 90% and 100%.

11. The method for preparing the metallic copper composite current collector as described in claim 1, characterized in that, The polymer film is a non-conductive polymer; And / or, a protective layer is provided on the surface of the electroplated copper layer.

12. The method for preparing the metallic copper composite current collector as described in claim 1, characterized in that, The polymer film is made of one or more of the following materials: polypropylene, polyethylene, polyethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyimide, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, polyamide, and derivatives of the above polymers.

13. The method for preparing the metallic copper composite current collector as described in claim 1, characterized in that, The MXene dispersion includes MXene material and solvent; Alternatively, the MXene dispersion may consist of MXene material and a solvent.

14. The method for preparing the metallic copper composite current collector as described in claim 13, characterized in that, The solvent is selected from water and / or alcohols; And / or, the concentration of MXene material in the MXene dispersion is between 0.01 mg / ml and 80 mg / ml.

15. The method for preparing the metallic copper composite current collector as described in claim 13, characterized in that, The MXene dispersion contains a binder.

16. The method for preparing the metallic copper composite current collector as described in claim 15, characterized in that, The adhesive is selected from one or more of LA133 waterborne adhesive, methylcellulose, polytetrafluoroethylene, polyvinyl alcohol, styrene-butadiene rubber, and waterborne polyurethane.

17. The method for preparing the metallic copper composite current collector according to any one of claims 1 to 16, characterized in that, The preparation method further includes a passivation step: passivating the surface of the electroplated copper to form a protective layer.

18. A metallic copper composite current collector prepared by any one of claims 1 to 17.

19. An electrode sheet, characterized in that, Including the metal copper composite current collector as described in claim 18.

20. A battery, characterized in that, Includes the electrode sheet as described in claim 19.

21. An electrical appliance, characterized in that, Includes the battery as described in claim 20.

22. The use of an MXene material as a conductive layer in polymer film interface electroplating, characterized in that, The application is used to prepare a copper composite current collector, wherein the MXene material serves as a conductive layer on the surface of the polymer film to achieve copper electroplating without a physical vapor deposition step, thereby forming a continuous and dense copper electroplating layer on the polymer film.

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