A method of manufacturing a composite metal foil

Abstract

The application discloses a preparation method of a composite metal foil and application thereof, and relates to the technical field of metal foils, in particular to a preparation method of a composite metal foil and application thereof. The method comprises the following steps: preparing a polymer material into a continuous film; performing surface pretreatment on the continuous film; performing chemical plating on the pretreated film to form a metal conductive layer; and performing electrochemical deposition of a metal layer after the formation of the metal conductive layer to obtain the composite metal foil. The composite metal foil prepared according to the technical scheme of the application has strong plating layer bonding force, is more uniform, and has strong conductivity. The preparation method has the advantages of simple operation, short process flow, low production cost, and high production efficiency.

Description

A method for preparing composite metal foil Technical Field

[0001] This invention belongs to the field of composite metal materials, and specifically relates to a method for preparing composite metal foil. Background Technology

[0002] Composite metal foil is a composite material with a "metal-polymer material-metal" sandwich structure. The most common composite metal foils are composite copper foil and composite aluminum foil, which are currently widely used as current collectors in new energy batteries.

[0003] As organic components, polymer films exhibit very weak adhesion to metal surfaces, making direct metal electroplating impossible. Therefore, traditional fabrication processes typically employ two or three-step methods. The two-step method involves first depositing a metal layer onto the film surface using magnetron sputtering to increase adhesion, followed by electroplating to deposit the metal layer. The three-step method, based on the two-step method, adds a vacuum evaporation process between magnetron sputtering and electroplating to accelerate metal deposition. However, when depositing copper onto a base film using magnetron sputtering, the high speed and temperature conditions can cause particles to sputter and melt through the base film, creating perforations. Furthermore, magnetron sputtering and vacuum evaporation technologies are complex, requiring additional steps such as bonding, increasing equipment investment and production costs, and reducing production efficiency.

[0004] Currently, two- or three-step processes for manufacturing composite copper foil suffer from low yield and insufficient adhesion between layers. Furthermore, these processes are complex, requiring multiple steps and reducing production efficiency. In contrast, one-step processes offer shorter flow rates, higher efficiency, and improved product yield and coating uniformity, making them a popular choice. Based on whether the process involves water, one-step processes can be categorized into fully wet methods (such as chemical plating) and fully dry methods (such as magnetron sputtering and vacuum evaporation).

[0005] For all-dry methods, magnetron sputtering may reduce the physical properties of composite copper foil during continuous sputtering, and it is also costly. Furthermore, achieving a thickness of 1 μm through vacuum evaporation is difficult, inefficient, results in poor copper foil surface smoothness, and leads to high energy consumption and production costs. In addition, due to the strong corrosion resistance of polymer materials such as PET, PP, and PI, it is impossible to directly electroplate copper layers using traditional ABS electroplating methods. By chemically depositing a conductive metal layer before electroplating, the non-conductive nature of polymer materials can be overcome.

[0006] Plastic electroplating, also known as wet electroplating or aqueous solution electroplating, is a technique that deposits a metal layer onto the surface of non-metallic substrates such as plastics using electrochemical methods. It typically requires pretreatment of the plastic surface (such as roughening, sensitization, activation, and electroless nickel plating) to enhance the adhesion between the metal coating and the plastic substrate. Plastic electroplating coats the plastic surface with metal, imparting metallic properties and fully utilizing the characteristics of both plastic and metal. Plastic electroplated products are used in industries such as electronics, automobiles, and household goods. Currently, the most widely used electroplatable plastics are ABS (acrylonitrile (A)-butadiene (B)-styrene (S) terpolymer) or PC / ABS alloy materials. However, there is a lack of a one-step continuous method for preparing composite metal foils that offers high production efficiency, strong coating adhesion, a smooth metal layer surface, low cost, and low energy consumption. Summary of the Invention

[0007] To address the shortcomings of existing technologies and solve at least one problem in them, this invention provides a method for preparing composite metal foil. This method uses polymer materials as substrates and combines continuous chemical plating under dynamic conditions with continuous electroplating to prepare composite metal foil in a one-step electroplating process. The method is simple to operate, has low production costs, high coating adhesion, short process flow, and high production efficiency.

[0008] Specifically, the present invention is achieved through the following method:

[0009] On one hand, the present invention provides a method for preparing a composite metal foil, comprising:

[0010] Fabricating continuous thin films from polymer materials;

[0011] Surface pretreatment of continuous thin films;

[0012] The pretreated film is then chemically plated to form a conductive metal layer.

[0013] Then, an electrochemical metal layer is deposited to obtain a composite metal foil.

[0014] In this invention, the thin film contains two or more components, at least one of which can be etched.

[0015] Further, the content of the etched thin film component is less than 30 wt%; preferably, the content of the etched thin film component is less than 20 wt%; more preferably, the content is 5-30 wt%. In some embodiments, too high a content of the etched thin film component can lead to perforation problems during the roughening process, while too low a content can lead to reduced adhesion between the thin film and the metal. Perforation problems during the roughening process mainly affect the strength of the composite metal foil and the smoothness of the composite copper foil surface, making the composite metal foil prone to perforation and other defects, thus affecting the yield of the composite metal foil.

[0016] Furthermore, the polymeric materials used to prepare continuous films include, but are not limited to, two or more of the following: polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyamide (PA), polyphenylene sulfide (PPS), polysulfone (PPSU), polyimide (PI), polyvinylidene fluoride (PVDF), polylactic acid (PLA), polycaprolactone (PCL), polystyrene (PS), polymethyl methacrylate (PMMA), terpolymers of acrylonitrile (A)-butadiene (B)-styrene (S) (ABS), thermoplastic elastomers (TPU, TPE, etc.), and their derivatives, crosslinks, and copolymers.

[0017] Furthermore, in the method of fabricating thin films from polymer materials, the etchable component is first blended with the target polymer material. The blending process can be achieved using a Banbury mixer, single-screw extruder, twin-screw extruder, or multi-screw extruder, or by melt blending in a polymerization reactor. Preferably, the blending process is melt blending in a polymerization reactor.

[0018] Furthermore, the process conditions such as the melting temperature, stirring speed, blending and stirring time of the polymer material can be selected according to the type of polymer material actually used.

[0019] Furthermore, by selecting appropriate blending processing methods and raw material ratios, the etchable components can be uniformly dispersed within the main polymer, which is beneficial for subsequent etching to form uniform pits. However, this invention is not limited to the case of uniform distribution of the etchable components; other suitable dispersion conditions, such as island structures and interpenetrating networks, are also within the scope of this invention.

[0020] Furthermore, the composite material obtained after blending is processed into sheets through melting, screw extrusion, casting and casting processes; then the resulting sheets are processed into composite films through biaxial stretching.

[0021] Furthermore, the thickness of the continuous film made of polymer material is 1-15 μm; preferably, the thickness of the film is 2-14 μm, 3-13 μm, 4-12 μm, 5-11 μm, 6-10 μm, or 7-9 μm; more preferably, the thickness of the film is 2-6 μm.

[0022] Because these polymer materials and the films prepared from them are organic, their adhesion to metals is very weak, making it impossible to directly electroplate a metal layer onto their surfaces. Existing technologies typically employ vapor deposition (VCD) to deposit a metal layer on the polymer surface before subsequent electroplating. However, VCD results in weak adhesion between the coating and the polymer layer, and the high-temperature vaporization of the metal during deposition can easily damage the polymer and generate internal stress during production. This application, however, pre-treats the film surface. The pre-treatment process is performed at room temperature, using an etchant solution to etch the polymer surface, creating micro-pits. Metal atoms are then deposited into these micro-pits using electroless plating, avoiding high-temperature damage to the polymer and eliminating the need for expensive VCD equipment. The pre-treatment process includes roughening, sensitization, activation, and electroless nickel plating. Roughening refers to treating the substrate with solutions of strong acids (such as chromic acid and sulfuric acid), strong alkalis, and strong oxidizing agents to create a microscopically rough surface, increasing the contact area between the coating and the substrate. This process forms numerous hydrophilic groups on the substrate surface, transforming it from a hydrophobic to a hydrophilic material. The roughened substrate surface carries a negative charge, making it highly susceptible to Sn adsorption. 2+ Ag + These processes ensure that sensitization, activation, and electroless plating can proceed smoothly.

[0023] Furthermore, before surface pretreatment of the continuous film, steps such as degreasing, cleaning, and drying are included. Degreasing can be performed using solutions such as alkalis, acids, and organic solvents, and methods include immersion brushing, ultrasonic cleaning, or spraying; heating degreasing can also be used.

[0024] Furthermore, the surface pretreatment of the continuous thin film described in this invention is an etching process, wherein the etching process can be carried out by chemical etching using acid, alkali or reactive gas, or by etching using plasma.

[0025] Furthermore, surface pretreatment of continuous thin films involves immersing the film in an etching solution to create micropits on the film surface.

[0026] Furthermore, the etching solution includes acids (chromic acid, hydrochloric acid, sulfuric acid, or nitric acid, etc.), alkalis (sodium hydroxide or potassium hydroxide, etc.), salt solutions (potassium permanganate, etc.), and organic solvents (chloroform, tetrachloromethane, dichloromethane, trichloroethane, acetone, etc.). In this invention, the etching solution is not limited to a single component; it can also be a mixture containing two or more components, such as a mixture of chromic acid and hydrochloric acid. In this application, when the etching solution is an acid or alkali, the acid or alkali's destructive effect on the polymer chains partially etches the etchable components. Simultaneously, the acid or alkali's oxidizing effect generates hydrophilic polar groups on the polymer surface, thereby enhancing the adhesion to the coating. When an organic solvent is used as the etching solution, the principle of "like dissolves like" is utilized, allowing the etchable components to dissolve in the solution, thus leaving micropits on the film surface.

[0027] Furthermore, the etching process forms micropits with a diameter of less than 0.5 μm on the surface of the thin film; preferably, the diameter of the micropits is less than 0.3 μm.

[0028] In this invention, the diameter of the micropit is related to the residence time of the thin film in the etching solution and the concentration of the etching solution. This application preferably uses the aforementioned micropit diameter, as diameters within this range facilitate the deposition of metal atoms on and inside the micropit, thereby enhancing the adhesion of the metal thin film. However, the invention is not limited to the aforementioned diameter range.

[0029] This invention involves blending an etchable component with a target polymer material to form a thin film. The etchable component is removed from the continuous film by etching, while the target polymer is retained. This creates pits on the surface of the polymer film, increasing its specific surface area. During subsequent electroless plating, metal atoms are deposited in these pits, effectively enhancing the adhesion between the film and the plating metal. Because the etchable component is uniformly distributed throughout the film, it is present on both sides. During surface pretreatment, the entire film is immersed in a solution, creating micropits on both surfaces. Therefore, metal atoms can be deposited simultaneously on both sides of the film during subsequent electroless and electroplating processes.

[0030] Furthermore, before electroless plating, the pretreated film also includes conventional steps of existing technologies such as reduction, activation, and desizing.

[0031] Furthermore, the pretreated film is subjected to electroless plating to form a conductive metal layer. Electroless plating refers to the process of adding a catalyst to the electroless plating solution during the plating stage, which reduces metal ions to atoms and allows them to deposit on the film surface. In this way, the bonding force between the metal atoms and the film is enhanced without damaging the polymer film.

[0032] Preferably, the material of the metal conductive layer is selected from one or more of copper, gold, silver, aluminum, nickel, titanium, aluminum, chromium, zinc, cadmium, lead, platinum, iron, cobalt, manganese, antimony, bismuth, gallium, indium, thallium, palladium, rhenium, rhodium, osmium, iridium, niobium, and tungsten; more preferably, it is selected from one or more of nickel, copper, gold, silver, and aluminum.

[0033] Furthermore, the thickness of the conductive metal layer formed by electroless plating is 10-500 nm. Preferably, the thickness is 20-100 nm (i.e., 0.02-0.1 μm).

[0034] Furthermore, an electrochemical metal layer is deposited on the electroless plated film to obtain a composite metal foil. Electrochemical metal deposition refers to depositing a dense metal layer on the surface of the film using an electrochemical process, with the film as the cathode and an electrolytic metal foil or metal plate as the anode.

[0035] Preferably, the metal layer is selected from one or more of copper, gold, silver, aluminum, nickel, titanium, aluminum, chromium, zinc, cadmium, lead, platinum, iron, cobalt, manganese, antimony, bismuth, gallium, indium, thallium, palladium, rhenium, rhodium, osmium, iridium, niobium, and tungsten; more preferably, it is selected from one or more of nickel, copper, gold, silver, and aluminum.

[0036] Furthermore, during the electrochemical deposition process, electroplating continues until the metal layer thickness is greater than 0.5 μm.

[0037] In this invention, the electrochemically deposited metal layer can be plated with one or more metals according to actual needs, forming one or more metal layers. Therefore, depending on the metal to be electroplated and the number of metal layers, the electrochemical deposition process can continue electroplating until the metal layer reaches the required thickness. Therefore, this invention is not limited to the above-mentioned range of electroplated metal layer thickness.

[0038] Preferably, the electroplating process uses a conductive thin film as the cathode and a metal (titanium, gold, silver, copper, etc.) as the anode, and the electroplating is carried out in an electrolyte. More preferably, the electroplating process uses a thin film as the cathode and a solid copper plate as the anode, and the electroplating is carried out in a copper sulfate electrolyte.

[0039] By controlling the concentration of metal ions, current density, and additive concentration in the electrolyte, the metal layer can be thickened to a specified thickness.

[0040] Furthermore, the electroplated film is passivated and dried to give the final product excellent antioxidant properties.

[0041] Furthermore, the composite metal foil of the present invention is a continuous body, which can be subsequently cut into different specifications according to actual needs.

[0042] On the one hand, the present invention also provides a composite metal foil prepared by the above preparation method.

[0043] On the other hand, the present invention also provides the application of the composite metal foil prepared by the above preparation method in the preparation of new energy batteries.

[0044] The beneficial effects of this invention are:

[0045] Existing technologies require two-step (magnetron sputtering + electroplating) or three-step (magnetron sputtering + vacuum evaporation + electroplating) processes to produce the final product, which has problems such as cumbersome process, low production efficiency, high cost, poor interlayer bonding strength of metals, and poor uniformity of copper metal.

[0046] The present invention provides a method for preparing composite metal foil, which involves surface pretreatment of the thin film, chemical plating, and electrochemical deposition of a metal layer without interruption or replacement of the fixture, thus achieving one-step continuous production from thin film to composite metal foil.

[0047] The method of the present invention first prepares a continuous thin film containing two or more polymer materials, and forms micropits on the surface of the film by etching at least one of the components. The formed micropits enhance the adhesion between the film and the coating metal, and then the conductive metal is deposited by subsequent chemical plating and electroplating.

[0048] The method for preparing composite metal foil provided by this invention is simple to operate, has low production cost, short process flow, and high production efficiency; the obtained composite metal foil has strong coating adhesion, good uniformity, and strong conductivity. Attached Figure Description

[0049] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0050] Figure 1 is a schematic diagram of the composite metal foil structure prepared in Example 6 of the present invention.

[0051] Figure 2 shows the composite metal foil prepared in Example 6 of the present invention.

[0052] Figure 3 is a scanning electron microscope image of the surface pretreatment film in Embodiment 8 of the present invention.

[0053] Figure 4 is a scanning electron microscope image of the surface pretreated thin film in Comparative Example 3 of the present invention.

[0054] Figure 5 is a flowchart of the continuous electroplating process of the composite metal foil of the present invention. Detailed Implementation

[0055] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0056] Unless otherwise specified, all materials mentioned herein are commercially available, and all methods mentioned herein are conventional methods.

[0057] Example 1

[0058] Polymer material 1 is PP M09, manufactured by China Petroleum & Chemical Corporation Maoming Branch.

[0059] Example 2

[0060] Polymer material 2: 75 wt% PP M09 and 25 wt% TPU material are blended and modified to prepare polymer material 2. The blending modification can be achieved by internal mixer, single screw, twin screw or multi-screw blending, or by melt blending in a polymerization reactor. It is preferred to use melt blending in a polymerization reactor to achieve uniform dispersion. The blending temperature does not exceed 280 ℃, the blending time does not exceed 24 h, and the stirring speed is not less than 100 rpm.

[0061] Example 3

[0062] Polymer material 3: Polymer material 3 is prepared by blending and modifying 95 wt% PET and 5 wt% TPE materials. The blending and modification can be achieved by internal mixer, single screw, twin screw or multi-screw blending, or by melt blending in a polymerization reactor. It is preferred to use melt blending in a polymerization reactor to achieve uniform dispersion. The blending temperature does not exceed 300℃, the blending time does not exceed 24 h, and the stirring speed is not less than 100 rpm.

[0063] Example 4

[0064] Polymer material 4: Polymer material 4 is prepared by blending and modifying 75 wt% PET, 5 wt% TPU and 20 wt% TPE. The blending and modification can be achieved by internal mixer, single screw, twin screw or multi-screw blending, or by melt blending in a polymerization reactor. It is preferred to use melt blending in a polymerization reactor to achieve uniform dispersion. The blending temperature does not exceed 300 ℃, the blending time does not exceed 24 h, and the stirring speed is not less than 100 rpm.

[0065] Example 5

[0066] Polymer material 5: Polymer material 5 is prepared by blending and modifying 65% PET and 35% TPE materials. The blending and modification can be achieved by internal mixer, single screw, twin screw or multi-screw blending, or by melt blending in a polymerization reactor. It is preferred to use melt blending in a polymerization reactor to achieve uniform dispersion. The blending temperature does not exceed 300 ℃, the blending time does not exceed 24 h, and the stirring speed is not less than 100 rpm.

[0067] Example 6

[0068] Polymer material 2 is fabricated into a continuous film with a thickness of 6 μm. Specifically, the uniformly mixed composite material is processed through melting, screw extrusion, casting, and casting to form a sheet with a certain thickness and width. The sheet is then subjected to a biaxial stretching process to ultimately form a continuous composite film.

[0069] The above-mentioned thin film was continuously electroplated using a continuous electroplating apparatus.

[0070] First, a polymer film is hung on the surface so that it can be connected to the power source to form a closed circuit, allowing electroplating to proceed smoothly.

[0071] The film was then placed in a roughening tank and continuously immersed in an etching solution to form micropits on the film surface, with an average micropit diameter of 0.12 μm. The roughening solution in the tank was a high-chromic acid type roughening solution containing 400 g / L chromic anhydride and 400 g / L sulfuric acid, and the treatment was carried out at 70 °C for 12 min.

[0072] The roughened film was fed into a reduction tank for reduction treatment, and then rinsed with clean water in a cleaning tank. The reduction solution was a 1 g / L sodium borohydride aqueous solution, and the process was carried out at room temperature for 10 min. After reduction treatment, the film was rinsed with clean water in a cleaning tank.

[0073] After reduction treatment, the film is placed in an activation tank for activation treatment, and then rinsed with clean water in a cleaning tank. The activation solution in the activation tank is a Pd-Sn activation solution, specifically containing 250 mL / L hydrochloric acid, 2-8 g / L stannous chloride and 15 ppm palladium, at a temperature of 35 ℃ for 4 min.

[0074] After activation, the film is placed in a desizing tank for desizing, and then rinsed with clean water in a cleaning tank. The desizing solution in the desizing tank is 80 g / L hydrochloric acid, the temperature is 35 ℃, and the time is 8 min.

[0075] Next, the treated film was subjected to electroless copper plating to form metallic copper with a thickness of 0.06 μm. The electroless copper plating solution included: copper sulfate 16 g / L, potassium sodium tartrate 14 g / L, sodium hydroxide 14.5 g / L, formaldehyde 15 mL / L, and 2,2′ The concentrations were: bipyridine 2 mg / L, EDTA 19.5 g / L, potassium ferrocyanide 2 mg / L, methanol 2 mg / L, pH 12.5, temperature 35 ℃, and time 7 min.

[0076] The treated film was then electrochemically deposited with metallic copper until a thickness of 1.2 μm was achieved, resulting in a composite copper foil. The electroplating process used the film as the cathode and the copper foil as the anode. The electroplating solution consisted of 200 g / L copper sulfate, 35 g / L sulfuric acid, and 100 mL / L hydrochloric acid. The plating time was 45 min, and the temperature was 25 ℃.

[0077] The aforementioned thin film is formed into a composite metal foil with a certain metal layer thickness through an electroplating process, resulting in a dense, smooth, and flat electroplated copper layer.

[0078] After electroplating, the film is rinsed in a water-filled washing tank, then passivated in a passivation tank, followed by another water-filled washing tank. Finally, the film is dried in a dryer at 60 °C for 30 min. The passivation temperature is room temperature, the passivation solution is an aqueous solution containing 3 g / L benzotriazole, the film running speed is 30 m / h, and the passivation time is 20 min.

[0079] After completing all the steps, hang the film.

[0080] Example 7

[0081] The preparation method of the composite metal foil is the same as in Example 6, except that:

[0082] The treated film was then chemically plated to form metallic silver with a thickness of 0.06 μm.

[0083] The composition and process conditions for electroless silver plating are as follows: silver nitrate 5 g / L, EDTA 5 g / L, ethanol 50 mL / L, OP-10 2 mL / L, and formaldehyde 5 mL / L. The process is carried out at room temperature for 30 min.

[0084] Example 8

[0085] The preparation method of the composite metal foil is the same as in Example 6, except that:

[0086] Polymer material 3 was fabricated into a continuous film with a thickness of 6 μm;

[0087] Example 9

[0088] The preparation method of the composite metal foil is the same as in Example 6, except that:

[0089] Polymer material 4 was fabricated into a continuous film with a thickness of 6 μm;

[0090] Example 10

[0091] The preparation method of the composite metal foil is the same as in Example 6, except that:

[0092] Polymer material 4 is fabricated into a continuous film with a thickness of 4 μm;

[0093] The polymer film was continuously immersed in the etching solution to form micropits on the surface of the polymer base film, with an average micropit diameter of 0.19 μm.

[0094] The treated film was then chemically plated to form 0.10 μm thick metallic copper.

[0095] Electrochemically deposit metallic copper onto the treated film until the thickness reaches 1.5 μm to obtain a composite copper foil.

[0096] Example 11

[0097] The preparation method of the composite metal foil is the same as in Example 6, except that:

[0098] Acetone was used as the etching solution during the roughening stage.

[0099] Comparative Example 1

[0100] The preparation method of the composite metal foil is the same as in Example 6, except that:

[0101] Polymer material 1 is fabricated into a continuous film with a thickness of 6 μm;

[0102] Comparative Example 2

[0103] The composite copper foil was prepared using a two-step method purchased from the market, with a PET thickness of 6 μm and a copper layer thickness of 1 μm.

[0104] Comparative Example 3

[0105] The preparation method of the composite metal foil is the same as in Example 8, except that:

[0106] Polymer material 5 was fabricated into a continuous film with a thickness of 6 μm.

[0107] Test Example 1

[0108] Method for testing the peel strength of composite metal foil:

[0109] (1) Cut the composite copper foil material into 100mm×50mm pieces; (2) Lay the composite copper sample flat on the stainless steel substrate and gently press it with a leather mallet to ensure that the sample is in close contact with the stainless steel substrate; (3) Place it in a peel force tester, set the test speed to 2mm / min, and perform a peel force test. The peel force tester will automatically record the maximum peel force N between the sample and the metal substrate. Repeat the test 5 times and take the average value; (4) Calculate the adhesion: Calculate the adhesion of the sample according to the following formula based on the recorded maximum peel force and the sample size.

[0110] Adhesion (N / cm) = Maximum peel force (N) / Sample contact area (cm²)

[0111] Test Example 2

[0112] Tensile strength and elongation at break of the film: The roughened film was tested according to the method for determining tensile strength and elongation at break in section 7.1 of standard GB / T 29847—2013 "Test Methods for Copper Foil for Printed Circuit Boards", with a test speed of 5 mm / min.

[0113] Test Example 3

[0114] Resistance: The electroplated composite copper foil was measured according to the relevant methods for mass resistivity in GB / T 2036.

[0115] The test results are shown in Table 1. As can be seen from Table 1, compared with the composite metal foils of Comparative Examples 1-3, the composite metal foils prepared by the method provided by the present invention (Examples 6-10) significantly improved the adhesion between the film and the coated metal. This is because when only one substrate component is used (Comparative Example 1), it is difficult to control the size of the micropores formed by etching, and thus difficult to control the adhesion between the metal layer and the film. Therefore, the adhesion between the metal and the film is low. In the prior art, since the metal layer is directly deposited on the surface of the film (Comparative Example 2), the adhesion between the metal and the film is low, and the film is prone to internal stress. Therefore, the adhesion between the metal and the film obtained in the test is also weak. When the etchable component is greater than 30 wt% (Comparative Example 3), the increase in the etchable component leads to perforation in the film, affecting the deposition smoothness of the metal layer and the strength of the substrate, resulting in poor adhesion between the film and the metal layer.

[0116] The mechanical test results also show that this application ensures the continuity of the substrate film by controlling the content of the etchable components, resulting in a composite metal foil with higher mechanical strength, especially compared to Comparative Example 3 which has perforations. This indicates that surface treatment of the film alone, ensuring the continuity of the substrate, is beneficial for enhancing the mechanical properties of the composite metal foil.

[0117] Resistance test results show that the conductivity of the composite metal foil prepared in this application is comparable to that of the composite foil prepared by the two-step method in the prior art, indicating that the composite metal foil of this application can be used as a current collector for new energy batteries.

[0118] Table 1: Test Results of Examples and Comparative Examples

[0119]

[0120] 4. Scanning electron microscopy (SEM) testing

[0121] The microstructure of the pretreated films in Example 8 and Comparative Example 3 was characterized using scanning electron microscopy (SEM). The test results are shown in Figures 3 and 4. It can be clearly seen from Figure 3 that the surface of the pretreated film in Example 8 was uniformly etched with micropits, which is beneficial for the deposition of metal atoms in the electroless plating stage. However, in Comparative Example 3 (Figure 4), the etched component was greater than 30%, resulting in excessive etching of the film surface and even the formation of perforations. Due to the excessive etching, it was difficult to deposit a complete and continuous metal layer under the same electroless plating conditions, which affected the deposition of metal onto the film surface in the electroless plating stage, making it difficult to prepare a composite metal foil with good adhesion between the metal and the film.

[0122] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for preparing a composite metal foil, characterized in that, The process includes the following steps: blending an etchable component with a target polymer material to form a continuous film, wherein the etchable component is a thermoplastic elastomer (TPU) and / or TPE, and the target polymer material is polypropylene or polyethylene terephthalate; the content of the etchable component is 5-30 wt%; and performing surface pretreatment on the continuous film, wherein the surface pretreatment refers to immersing the film in a solution to form micropits on the film, wherein the diameter of the micropits is less than 0.5 μm. The pretreated film is chemically plated to form a conductive metal layer; the chemically plated film is then electrochemically deposited to obtain a composite metal foil.

2. The method according to claim 1, characterized in that, The thickness of the film is 1-15 μm.

3. The method according to claim 1, characterized in that, The electroless plating refers to the process in which a catalyst is added to a solution during the electroless plating stage to reduce metal ions to atoms and then deposit them on the surface of a thin film; the metal is selected from one or more of nickel, copper, gold, silver, and aluminum.

4. The method according to claim 1, characterized in that, The electrochemically deposited metal layer refers to the deposition of a dense metal layer on the surface of a thin film using an electrochemical action, with the thin film as the cathode and a metal plate as the anode. The metal is selected from one or more of nickel, copper, gold, silver, and aluminum.

5. The composite metal foil prepared by any one of the preparation methods described in claims 1-4.

6. The application of the composite metal foil according to claim 5 in the preparation of new energy batteries.

Images