Preparation method of composite metal foil

Abstract

The invention discloses a preparation method of a composite metal foil. The method comprises the following steps: paving a layer of metal foil on each of the upper surface and the lower surface of a layer of PET (Polyethylene Terephthalate) film, preheating through a tunnel furnace heating device, rolling and compounding through heated upper and lower working rollers, and finally rolling into the composite metal foil with a metal foil-macromolecule-metal foil sandwich structure. Compared with common magnetron sputtering and electroplating processes in the prior art, the preparation process has the beneficial effects that pollution can be reduced, the cost can be reduced, and meanwhile, the composite surface of the prepared composite metal foil is high in bonding strength and good in surface quality.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium battery materials and relates to a method for preparing a composite metal foil. Background Art

[0002] Aluminum foil and copper foil are usually used as carriers and current collectors for positive and negative electrode materials of lithium batteries, respectively. With the rapid development of the lithium battery industry, the demand for copper foil and aluminum foil is increasing, and lithium battery copper foil and aluminum foil are developing towards thinner, microporous, high tensile strength and high elongation. The common production processes of lithium battery copper foil and aluminum foil are electrolytic copper foil and rolled copper foil. Compared with these copper foil and aluminum foil, PET composite copper foil and PET composite aluminum foil have the advantages of high safety, high specific volume, long life and high compatibility. Chinese patent applications CN115700295A and CN109554738A prepare PET composite copper foil by combining magnetron sputtering and electroplating processes, and CN114914453A prepares composite copper foil by combining coating or spraying processes with electroplating processes. Magnetron sputtering and electroplating processes have problems such as high cost and difficulty in process control. Chinese patent CN114161787A discloses a negative electrode copper foil for soft-pack lithium batteries and a preparation method thereof, wherein a hot-melt insulating resin is extruded through a die head, and a layer of copper foil is sent on each side of the molten resin, and then compounded by extrusion molding to form a composite copper foil semi-finished product, and then the semi-finished copper foil is subjected to copper reduction on both sides and anti-oxidation treatment according to the thickness requirements of the battery material. However, after the hot-melt insulating resin is extruded through the die head, it is difficult to control the thickness and shape of the film due to the influence of gravity, which affects the quality of the final composite copper foil. Chinese patent CN111933952A first applies adhesive on both sides of the PET film; then, aluminum foil is attached to both sides of the PET film to form a composite aluminum foil; finally, the composite aluminum foil is corroded by strong alkali and strong acid, and then cleaned and dried to obtain a composite lithium battery aluminum foil. The use of strong alkali and strong acid in its preparation process will cause pollution problems.

[0003] Titanium foil has the characteristics of strong antioxidant ability, high melting point and high strength. In recent years, people have tried to use titanium foil as the positive electrode current collector of lithium batteries to make ultra-thin lithium batteries. Chinese patent CN202503073U discloses an ultra-thin lithium-ion battery that uses titanium foil or titanium alloy foil or chromium foil as the positive electrode current collector to make thinner batteries. The ultra-thin lithium-ion battery has low self-discharge at high voltage, stable and reliable storage and use, and long service life. However, the high price of titanium foil leads to high production costs, which limits its large-scale application. In addition, ultra-thin lithium batteries are often used in wearable devices, which will be bent repeatedly during use, requiring the battery material to have good toughness, but the plastic toughness of titanium foil is poor. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing a composite metal foil. The method of the present invention can reduce pollution and cost, and at the same time, the composite metal foil prepared has high composite surface bonding strength and good surface quality.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical scheme.

[0006] The present invention provides a method for preparing a composite metal foil, which comprises the following steps: (1) Unwind the metal foil roll, the PET film roll and another metal foil roll at the same time, and lay them flat through upper and lower guide rollers in the order of metal foil, PET film and metal foil; (2) Preheating by tunnel furnace heating device; (3) Using heated upper and lower working rollers to roll and laminate the preheated metal foil and PET film; (4) The rolled composite metal foil is rolled up by a winding device.

[0007] In the present invention, in step (1), the metal foil is any one of copper foil, aluminum foil and titanium foil; the thickness of the metal foil is between 0.5-100 μm, and the thickness of the PET film is between 3-200 μm.

[0008] In the present invention, the preheating temperature of the tunnel furnace heating device in step (2) is 40-160°C.

[0009] In the present invention, in step (3), the roller heating temperature is 40-160°C.

[0010] In the present invention, step (2) is omitted, and rolling and compounding are performed twice in step (3).

[0011] In the present invention, in step (3), the reduction amount of each rolling composite pass is 0.1-5 μm.

[0012] In the present invention, step (3) further includes a rolling thinning step; during the rolling thinning, the roller heating temperature is 40-160° C., and the pass reduction is 0.5-5 μm.

[0013] In the present invention, the difference between the winding and unwinding speeds and the rolling speed is 1%-10%, so that the metal foil and the PET film are subjected to tension and maintain a good plate shape.

[0014] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. The copper foil and PET film are softened by combining preheating and heating the roller, which reduces the deformation resistance of the material and makes the metal foil and PET film more firmly bonded; 2. Compared with magnetron sputtering and electroplating processes, it can reduce pollution and reduce costs; 3. The rolled composite has high bonding strength and good surface quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the composite metal foil prepared by the present invention.

[0016] In the figure: 1-metal foil layer, 2-PET layer, 3-metal foil layer. DETAILED DESCRIPTION

[0017] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this application should be included in the scope of protection of this application.

[0018] Figure 1 The structure of the composite metal foil prepared in the present invention is schematically shown, and it has a "sandwich" structure of a metal foil layer 1, a PET layer 2, and a metal foil layer 3. In a specific embodiment, according to the national standard GB / T 29847-2013, a uniaxial tensile testing machine is used to measure the peel strength and tensile strength.

[0019] Example 1

[0020] The upper copper foil roll, the lower copper foil roll and the PET film roll are unwound at the same time (where the copper foil thickness is 1 μm and the PET film thickness is 5 μm), flattened and pressed under the action of the upper guide roller and the lower guide roller, and then preheated by the tunnel furnace heating device, the preheating temperature is 50-150°C; then rolled and compounded under the action of the upper working roller and the lower working roller, the pass reduction is 0.5 μm, the heating temperature of the working roller is 50-150°C, and the PET composite copper foil roll is formed after the winding process. The PET composite copper foil prepared in this embodiment has a thickness of 6.5 μm, and is composed of a copper foil layer of about 1 μm, a PET film layer of about 4.5 μm and a copper foil layer of about 1 μm, with an average peel strength of not less than 0.8 N / mm and a tensile strength of 305 MPa.

[0021] Example 2

[0022] The upper copper foil roll, the lower copper foil roll and the PET film roll are unwound at the same time (where the copper foil thickness is 3.5μm and the PET film thickness is 6μm), flattened and pressed under the action of the upper guide roller and the lower guide roller, and then preheated by the tunnel furnace heating device, the preheating temperature is 50-150℃; then rolled and compounded under the action of the upper working roller and the lower working roller, the pass reduction is 3μm, the heating temperature of the working roller is 50-150℃, and the PET composite copper foil roll is formed after the winding process, and finally rolled and thinned, the reduction is 3μm, and the heating temperature of the working roller is 50-150℃. The PET composite copper foil prepared in this embodiment has a thickness of 7μm, and is composed of a copper foil layer of about 2μm, a PET film layer of about 3μm and a copper foil layer of about 2μm, and the average peel strength is not less than 0.83N / mm, and the tensile strength is 331MPa.

[0023] Example 3

[0024] The upper aluminum foil roll, the lower aluminum foil roll and the PET film roll are unwound at the same time (wherein the thickness of the aluminum foil is 1.25 μm and the thickness of the PET film is 5 μm), flattened and pressed under the action of the upper guide roller and the lower guide roller, and then preheated by the tunnel furnace heating device, the preheating temperature is 45-155°C; then rolled and compounded under the action of the upper working roller and the lower working roller, the pass reduction is 1 μm, the heating temperature of the working roller is 45-155°C, and the PET composite aluminum foil roll is formed after the winding process. The PET composite aluminum foil prepared in this embodiment has a thickness of 6.5 μm, and is composed of an aluminum foil layer of about 1 μm, a PET film layer of about 4.5 μm and an aluminum foil layer of about 1 μm, with an average peel strength of not less than 0.75 N / mm and a tensile strength of 255 MPa.

[0025] Example 4

[0026] The upper aluminum foil roll, the lower aluminum foil roll and the PET film roll are unwound at the same time (wherein the thickness of the aluminum foil is 3 μm and the thickness of the PET film is 7.5 μm), flattened and pressed under the action of the upper guide roller and the lower guide roller, and then preheated by the tunnel furnace heating device, the preheating temperature is 45-155°C; then rolled and compounded under the action of the upper working roller and the lower working roller, the pass reduction is 3 μm, the heating temperature of the working roller is 45-155°C, and the PET composite aluminum foil roll is formed after the winding process, and finally rolled and thinned, the reduction is 3 μm, and the heating temperature of the working roller is 45-155°C. The PET composite aluminum foil prepared in this embodiment has a thickness of 7.5 μm, and is composed of an aluminum foil layer of about 2 μm, a PET film layer of about 3.5 μm and an aluminum foil layer of about 2 μm, and the average peel strength is not less than 0.77 N / mm, and the tensile strength is 276 MPa.

[0027] Example 5

[0028] The upper titanium foil roll, the lower titanium foil roll and the PET film roll are unwound at the same time (where the thickness of the titanium foil is 2μm and the thickness of the PET film is 4μm), flattened and pressed under the action of the upper guide roller and the lower guide roller, and then rolled and compounded under the action of the upper working roller and the lower working roller, with a pass reduction of 0.5μm and a heating temperature of the working roller of 40-160℃; then rolled again under the action of the upper working roller and the lower working roller to strengthen the bonding surface, with a pass reduction of 0.5μm and a heating temperature of the working roller of 40-160℃, and finally rolled through the guide roller to form a composite titanium foil roll. The composite titanium foil prepared in this embodiment has a thickness of 7μm, and is composed of a titanium foil layer of about 1.8μm, a PET film layer of about 3.4μm and a titanium foil layer of about 1.8μm, with an average peel strength of not less than 0.78N / mm and a tensile strength of 365MPa.

[0029] Example 6

[0030] The upper titanium foil roll, the lower titanium foil roll and the PET film roll are unwound at the same time (wherein the thickness of the titanium foil is 5μm and the thickness of the PET film is 10μm), flattened and pressed under the action of the upper guide roller and the lower guide roller, and then rolled and compounded under the action of the upper working roller and the lower working roller, with a pass reduction of 3μm and a heating temperature of the working roller of 40-160℃; then rolled again under the action of the upper working roller and the lower working roller to strengthen the bonding surface, with a pass reduction of 3μm and a heating temperature of the rolling roller of 40-160℃, and finally rolled through the guide roller to form a composite titanium foil roll. The composite titanium foil prepared in this embodiment has a thickness of 14μm, and is composed of a titanium foil layer of about 4μm, a PET film layer of about 6μm and a titanium foil layer of about 4μm, with an average peel strength of not less than 0.8N / mm and a tensile strength of 382MPa.

Claims

1. A method for preparing a composite metal foil, characterized in that: The following steps are included: (1) Unwind the metal foil roll, the PET film roll and another metal foil roll at the same time, and lay them flat through upper and lower guide rollers in the order of metal foil, PET film and metal foil; (2) Preheating by tunnel furnace heating device; (3) Using heated upper and lower working rollers to roll and laminate the preheated metal foil and PET film; (4) The rolled composite metal foil is rolled up by a winding device.

2. The method for preparing the composite metal foil according to claim 1, characterized in that: In step (1), the metal foil is any one of copper foil, aluminum foil and titanium foil; the thickness of the metal foil is between 0.5-100 μm, and the thickness of the PET film is between 3-200 μm.

3. The method for preparing the composite metal foil according to claim 1, characterized in that: The preheating temperature of the tunnel furnace heating device in step (2) is 40-160°C.

4. The method for preparing the composite metal foil according to claim 1, characterized in that: In step (3), the roller heating temperature is 40-160°C.

5. The method for preparing the composite metal foil according to claim 1, characterized in that: Step (2) is omitted, and rolling and bonding are performed twice in step (3).

6. The method for preparing the composite metal foil according to claim 1, characterized in that: In step (3), the reduction amount of each rolling composite pass is 0.1-5 μm.

7. The method for preparing the composite metal foil according to claim 1, characterized in that: After step (3), the method further includes a rolling thinning step; during the rolling thinning step, the roller heating temperature is 40-160° C., and the pass reduction is 0.5-5 μm.

8. The method for preparing the composite metal foil according to claim 1, characterized in that: The difference between the winding and unwinding speeds and the rolling speed is 1%-10%, so that the metal foil and PET film are under tension and maintain a good plate shape.

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