Composite metal foil, preparation method therefor and use thereof
By using a porous polymer base film and chemically plating metal in the composite metal foil, the problem of insufficient adhesion between the polymer base film layer and the metal layer was solved, the peel strength and mechanical strength of the composite metal foil were improved, and the battery performance was enhanced.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SHANGHAI ENERGY NEW MATERIALS TECHNOLOGY CO LTD
- Filing Date
- 2025-01-22
- Publication Date
- 2026-07-09
Smart Images
Figure CN2025073854_09072026_PF_FP_ABST
Abstract
Description
A composite metal foil, its preparation method and application Technical Field
[0001] This invention belongs to the field of composite metal foil, specifically relating to a composite metal foil, its preparation method, and its application. Background Technology
[0002] Traditional lithium-ion batteries (LIBs) are constantly evolving to improve their electrochemical performance and safety. Over the past decade, research on electrode and electrolyte materials has significantly advanced traditional batteries. However, current collectors in traditional LIBs have not received sufficient attention. As a crucial unit for collecting and dispersing electrons from the electrodes and conducting current, the performance of the current collector significantly impacts the performance of the LIB. Current collectors possess essential properties such as electrochemical stability, conductivity, mechanical strength, density, sustainability, and cost.
[0003] The wettability and surface properties of the current collector affect the electrochemical performance of lithium battery cells (LIBs), while surface cleanliness and cutting quality affect their safety. Thickness, however, significantly impacts their energy density. Reducing the current collector thickness helps increase the battery's mass-to-weight ratio and volumetric energy density. Therefore, with the development of LIBs, the thickness of the copper foil has decreased to 4-8 μm, and its mass percentage in the battery has decreased from 19.3% to approximately 6%. Although the current collector thickness can be further reduced, ultra-thin current collectors with weaker mechanical properties are prone to wrinkling and breakage during the coating process. Furthermore, manufacturing costs continue to increase.
[0004] To meet the growing demand for high energy density and safety in batteries, particularly for the commercialization of electric vehicles, further advancements are needed. Metallized plastic current collectors (MPCCs) with metal-polymer-metal multilayer composite structures offer an innovative solution. This approach has several advantages. First, it effectively reduces the weight and thickness of lithium-ion batteries, thereby increasing their energy density. Second, the polymer in the MPCC, with its electrical insulation and high elongation properties, significantly improves the safety performance of lithium-ion batteries by preventing thermal runaway.
[0005] Novel current collector structures have been reported that support a metal layer on a polymer-based film, with the metal layer serving as a support for the electrode active material layer, and the metal layer located on at least one surface. The main drawbacks of existing composite current collector technologies are: easy peeling and detachment of the copper foil, and poor adhesion. These drawbacks are mainly due to differences in chemical structure and physical properties between the polymer-based film and the metal layer, as well as improper surface treatment.
[0006] Existing technologies typically compensate for this deficiency by adding adhesives or multiple conductive layers, but this increases the number of processes involved. How to more effectively and conveniently improve the adhesion between the polymer-based composite current collector film and the metal layer is a problem worthy of research in this field. Summary of the Invention
[0007] The purpose of this invention is to address the insufficient bonding strength between the polymer-based film layer and the metal layer in the prior art, and to provide a composite metal foil with higher peel strength.
[0008] Another object of the present invention is to provide a method for preparing the composite metal foil.
[0009] Another object of the present invention is to provide applications of the composite metal foil.
[0010] The above-mentioned objectives of the present invention are achieved through the following technical solutions:
[0011] A composite metal foil includes a substrate layer and a metal layer located on the surface of the substrate layer. The substrate layer includes a porous polymer base film and a metal embedded in the pores of the porous polymer base film. The metal content in the substrate layer is 8-25 wt%.
[0012] The metal in the substrate layer and the metal layer covering the surface of the substrate layer are formed in the same process.
[0013] In existing technologies, especially in the battery field, non-porous polymer base films are generally used as the base film for preparing composite metal foils. However, the inventors have discovered that by using porous polymers as the base film, some metal can enter the pores of the porous polymer during the metal plating process, thereby forming a porous polymer base film embedded with metal. This base film bonds more firmly to the metal layer, enabling the composite metal foil to have higher peel strength.
[0014] Preferably, the porosity of the porous polymer-based membrane is 15-40%. Suitable porosity allows the composite metal foil to possess good mechanical strength and thermal shrinkage properties. More preferably, the porosity of the porous polymer-based membrane is 20-35%.
[0015] The method for preparing the porous polymer-based membrane described in this invention can be carried out with reference to known techniques for preparing porous polymer-based membranes. For example, when the polymer is a polyolefin, it can be prepared with reference to the method described in CN118772479A.
[0016] Preferably, the polymer of the porous polymer-based membrane is selected from polyethylene, polytetrafluoroethylene, polyvinylidene fluoride, polyimide, polyethylene terephthalate, polypropylene, polysulfone, polydimethylsiloxane, polyamide, polystyrene, polyvinyl chloride, aramid, polydiphenylene dimethylformamide, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalate), polypropylene, polyamide urea, polyoxymethylene, epoxy resin, phenolic resin, silicone rubber, polycarbonate, polyvinyl alcohol, polyethylene glycol, or any combination thereof.
[0017] Preferably, in the substrate layer, the metal accounts for 0.04–0.12 g / cm³ of the substrate layer by mass volume. 3 .
[0018] More preferably, in the substrate layer, the metal accounts for 0.055–0.09 g / cm³ of the substrate layer by mass volume. 3 In this invention, the mass of the metal in the substrate layer can be obtained by subtracting the mass of the metal layer from the mass of the composite metal foil, and then subtracting the mass of the porous polymer base film. The mass of the metal layer can be obtained by physical methods or by calculation using scanning electron microscopy. The physical method involves peeling off the metal layer with adhesive tape and then weighing it.
[0019] The calculation method involves determining the metal layer thickness using a scanning electron microscope and then calculating it based on the metal layer thickness × metal layer area × metal density.
[0020] Preferably, the peel strength of the composite metal foil is greater than 400 N / m.
[0021] More preferably, the peel strength of the composite metal foil is greater than 500 N / m.
[0022] In this invention, the test method for the peel strength of the composite metal foil is as follows:
[0023] Cut a 24mm wide and 300mm long sample from the prepared flat metal foil sample. Fold one end of the cut sample together with adhesive to form a folded layer about 12mm long. Attach the other end of the sample to one end of the steel plate and roll it twice with an adhesive tape roller at a speed of 600mm / min. Then place it in an electronic peel tester and set the test speed to 250mm / min. The equipment automatically records the force value during the peeling process and reports the peel strength of the sample accordingly.
[0024] Preferably, the thickness of the substrate layer is 2–8 μm.
[0025] Preferably, the thickness of the metal layer is 0.1 to 1.0 μm.
[0026] Preferably, the metal layer is formed by chemical plating.
[0027] The method for preparing the composite metal foil includes the following steps:
[0028] S1 is used to roughen the porous polymer-based membrane;
[0029] S2 is used to sensitize the roughened base film;
[0030] S3 is used to wash the sensitized base film with water.
[0031] S4 is used to activate the base film after water washing;
[0032] S5 performs chemical plating on the activated base film to cover the surface of the substrate layer with a metal layer.
[0033] More preferably, the roughening process described in S1 is achieved by plasma treatment.
[0034] The plasma treatment can be performed once or multiple times.
[0035] More preferably, the power of each plasma treatment is 50-150W. The duration of each plasma treatment is 30-180 seconds.
[0036] More preferably, the sensitization treatment in S2 involves immersing the roughened base film in a stannous salt solution for a soaking time of 1 to 2 minutes.
[0037] The stannous salt solution is preferably a stannous chloride solution. Its concentration is preferably 30–40 g / L.
[0038] The purpose of the water washing process described in S3 is to form a gel film on the sensitized base film, which facilitates the activation process in S4. Specifically, the water washing process may involve washing the sensitized base film in deionized water at a temperature of 20–50°C.
[0039] Preferably, the washing time can be 10 to 20 seconds.
[0040] The purpose of the S4 activation treatment is to prepare for electroless copper plating.
[0041] More specifically, the activation is achieved by immersing the water-washed base film in an activation liquid.
[0042] The soaking time is 1 to 2 minutes. The activating liquid can be a palladium chloride solution with a concentration of 0.5-1.0 g / L.
[0043] The electroless metal plating described in S5 can be performed by referring to existing methods for plating metal on the surface of a base film.
[0044] More specifically, taking copper plating as an example, the main components of the copper plating solution for electroless metal plating include a mixed solution of 10.0 g / L copper sulfate, 15.0 g / L sodium hydroxide, 36.0 g / L potassium sodium tartrate tetrahydrate, 10.0 g / L disodium ethylenediaminetetraacetate, 10.0 mL / L formaldehyde, 5.0 mL / L 2'2 bipyridine, and 5.0 g / L nickel sulfate.
[0045] The electroless copper plating time is 3 to 5 minutes.
[0046] Preferably, before S1, a step of cleaning the base film is included. The purpose of cleaning is to remove oil or impurities from the base film.
[0047] Preferably, after step S5, an antioxidant treatment step is also included.
[0048] More preferably, in this invention, the metal layer is a metal layer formed of copper, nickel, and / or aluminum, or a carbide layer of copper, nickel, and / or aluminum. More preferably, the metal layer is a metal layer formed of copper.
[0049] The composite metal foil is used as a negative electrode current collector.
[0050] Compared with the prior art, the present invention has the following beneficial effects:
[0051] This invention provides a composite metal foil in which a suitable amount of metal is embedded in a substrate layer, resulting in a tighter bond between the metal and a metal layer located on the surface of the substrate layer. The metal also supplements the strength of the substrate film and improves its bending resistance, giving the composite metal foil better peel strength. This composite metal foil, especially a copper foil, can serve as a negative electrode current collector, enabling lightweight battery products. It not only improves the peel strength of the copper foil but also enhances its conductivity in localized areas. Simultaneously, the copper metal embedding structure provides a fast thermal response interface, improving battery safety. Attached Figure Description
[0052] Figure 1 is a SEM image of the composite metal foil prepared in Example 4.
[0053] Figure 2 is a magnified SEM image of the composite metal foil embedded layer structure prepared in Example 5.
[0054] Figure 3 is a schematic SEM image of the composite metal foil prepared in Comparative Example 3.
[0055] Wherein, 1 is the metal layer, 2 is the substrate layer, 3 is the metal embedded in the pores of the substrate layer, and 4 is the pores of the substrate layer. Detailed Implementation
[0056] The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.
[0057] Examples 1-5 and Comparative Examples 1 and 2
[0058] Referring to Table 1, PE base films with different porosities were selected, and composite copper foils were prepared according to the following process.
[0059] The PE base film was prepared in-house, specifically by adjusting the parameters according to the method described in the example of CN118772479A.
[0060] Base membrane porosity P = [1 - (base membrane mass / skeleton density) / base membrane apparent volume] × 100%
[0061] Base film quality: The actual quality of the PE base film can be measured using a balance.
[0062] Skeleton density: The density of the raw materials used in PE base film, that is, the density of the raw materials when a porous structure is not created.
[0063] Apparent volume of the base film: The volume of the PE base film in its natural state (with a porous structure already created) can be obtained through physical measurement.
[0064] Preparation of composite copper foil:
[0065] S1 base film roughening treatment is plasma treatment:
[0066] Place the cleaned base film into the vacuum plasma chamber, close the valve, turn on the power, and evacuate to 5×10⁻⁶. -2 Pa, introduce working gas, which is one or a mixture of nitrogen, argon, and oxygen, with working pressure controlled at 1 Pa, working power set between 150 W, temperature at 25 °C, and time at 90 seconds, to obtain a roughened base film after plasma treatment.
[0067] Sensitization of the S2 base film:
[0068] The roughened base film is completely immersed in the sensitization liquid for 1-2 minutes at a temperature of 30°C.
[0069] The sensitizing solvent is a self-made stannous chloride solution with a concentration of 30 g / L.
[0070] Water washing treatment of S3 base film:
[0071] The sensitized base film is removed from the sensitization liquid and washed in deionized water at 45°C to form a gel film on the surface of the base film. The washing time is 10-15 seconds.
[0072] Activation of S4 base film:
[0073] Immerse the cleaned base film completely in the activation liquid for 1-2 minutes at a temperature of 25°C.
[0074] The activation solvent is a self-made palladium chloride solution with a concentration of 1.0 g / L.
[0075] S5 chemical copper plating:
[0076] Chemical copper plating is performed on the surface of the base film after S4 treatment.
[0077] The electroless copper plating solution comprises a mixture of 10.0 g / L copper sulfate, 15.0 g / L sodium hydroxide, 36.0 g / L potassium sodium tartrate tetrahydrate, 10.0 g / L disodium ethylenediaminetetraacetate, 10.0 mL / L formaldehyde, 5.0 mL / L 2',2-bipyridine, and 5.0 g / L nickel sulfate. After preparing the above solution, mix thoroughly. The treated substrate film is then horizontally immersed in the electroless copper plating solution. The plating time is 3–5 minutes at 40°C, and ultrasonic vibration is used to further homogenize the solution. After copper plating, the film is removed, washed with deionized water, and subjected to anti-oxidation treatment. Finally, it is dried in a drying oven.
[0078] Comparative Examples 3 and 4
[0079] PE-based films with porosities of 0% and 30% were processed using magnetron sputtering, and then electroless copper plating was performed under the same conditions as in S5 above. The resulting composite copper films served as Comparative Examples 3 and 4. The specific operation of the magnetron sputtering method is as follows:
[0080] Close the front door of the vacuum chamber, and then evacuate the chamber to a vacuum level of 8.0 × 10⁻⁶. -4 Pa. Introduce argon gas at different flow rates and adjust the gate valve position to adjust the working gas pressure to the required range. After the working gas pressure stabilizes, set the coating roller speed to 10 m / min, set the required RF sputtering power to 350 W, set the working gas pressure within the range of 0.02 Pa, and start the deposition of the thin film. The deposition time is 5 mins.
[0081] The method for testing peel strength is as follows:
[0082] Cut a 24mm wide and 300mm long sample from the prepared flat metal foil sample. Fold one end of the cut sample together with adhesive to form a folded layer about 12mm long. Attach the other end of the sample to one end of the steel plate and roll it twice with an adhesive tape roller at a speed of 600mm / min. Then place it in an electronic peel tester and set the test speed to 250mm / min. The equipment automatically records the force value during the peeling process and reports the peel strength of the sample accordingly.
[0083] Copper content in the substrate layer = Mass of copper in the substrate layer (g) / Mass of the substrate film (g)
[0084] The mass of copper in the substrate layer = the mass of the composite copper foil (g) - the mass of the base film (g) - the mass of the copper layer (g);
[0085] In addition, scanning electron microscopy and EDS of the cross-section were used to observe whether copper was embedded in the substrate layer.
[0086] The quality of the copper layer can be obtained through physical methods or by combining scanning electron microscopy (SEM) calculations. The physical method involves peeling off the copper layer with adhesive tape and then weighing it.
[0087] The calculation method involves determining the copper layer thickness using a scanning electron microscope and then calculating it as copper layer thickness × copper layer area × copper density. In this embodiment, the calculation method is used to obtain the copper layer mass.
[0088] The mass-volume content of copper particles in the substrate layer = mass of copper in the substrate film (g) / apparent volume of copper in the substrate film (cm³) 3 )
[0089] Bending resistance test: Using cutting equipment, different samples of the same size (15mm×100mm) were prepared. They were bent dozens of times using a bending resistance tester or manually. The peeling of copper foil and the falling of copper powder were observed. The surface wrinkles and cracks at the bending points were observed with an optical microscope for comprehensive judgment.
[0090] The criteria of "no copper foil peeling, no copper powder shedding, and minor surface cracks" are considered excellent; "no copper foil peeling, minor copper powder shedding, and minor surface cracks" are considered relatively excellent; and "less than copper foil peeling, minor copper powder shedding, and surface cracks" are considered average.
[0091] Safety performance test: The composite copper foils of Examples 1 to 5 were used to prepare batteries. In the small-capacity soft-pack battery nail penetration test, no fire or smoke occurred.
[0092] Table 1. Test data of composite copper foils prepared in Examples 1-5 and Comparative Examples 1-4.
[0093] As can be seen from Examples 1-5, Comparative Examples 1 and 3, and Figures 1-3, the present invention utilizes a porous polymer base film to prepare a composite metal foil with effective metal embedding in the base film layer, resulting in a composite metal foil exhibiting higher metal peel strength. Comparative Example 2 shows that if the porosity of the polymer base film is low, it is difficult to allow a sufficient amount of copper to enter the polymer base film, thus making it difficult to achieve the desired improvement in peel strength. Comparative Example 4 shows that other processing methods do not allow copper to enter the polymer base film more effectively, resulting in minimal improvement in peel strength.
[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A composite metal foil, comprising a substrate layer and a metal layer located on the surface of the substrate layer, characterized in that, The substrate layer comprises a porous polymer base membrane and a metal embedded in the pores of the porous polymer base membrane; the metal content in the substrate layer is 8-25 wt%.
2. The composite metal foil according to claim 1, characterized in that, The porosity of the porous polymer-based membrane is 15-40%.
3. The composite metal foil according to claim 1 or 2, characterized in that, The porosity of the porous polymer-based membrane is 20-35%.
4. The composite metal foil according to claim 1, characterized in that, The polymer of the porous polymer-based membrane is selected from polyethylene, polytetrafluoroethylene, polyvinylidene fluoride, polyimide, polyethylene terephthalate, polypropylene, polysulfone, polydimethylsiloxane, polyamide, polystyrene, polyvinyl chloride, aramid, polydiphenylene dicarboxylate, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalate), polypropylene, polyamide urea, polyoxymethylene, epoxy resin, phenolic resin, silicone rubber, polycarbonate, polyvinyl alcohol, polyethylene glycol, or any combination thereof.
5. The composite metal foil according to claim 1, characterized in that, In the substrate layer, the metal content by mass volume is 0.04–0.12 g / cm³. 3 .
6. The composite metal foil according to claim 1, characterized in that, The peel strength of the composite metal foil is greater than 400 N / m.
7. The composite metal foil according to claim 1, characterized in that, The thickness of the substrate layer is 2–8 μm.
8. The composite metal foil according to claim 1, characterized in that, The metal layer is a metal layer formed of copper, nickel and / or aluminum, or a carbide layer of copper, nickel and / or aluminum.
9. A method for preparing the composite metal foil according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Roughening treatment is applied to the porous polymer-based membrane; S2. Sensitize the roughened base film; S3. The sensitized base film is washed with water. S4. Activate the base film after water washing; S5. Perform chemical plating on the activated base film to cover the surface of the substrate layer with a metal layer.
10. The application of the composite metal foil according to any one of claims 1 to 7 as a negative electrode current collector.