Preparation method of composite aluminum current collector and composite aluminum current collector

Abstract

The invention provides a preparation method of a composite aluminum current collector. The preparation method comprises the following steps: S1, respectively forming a first seed layer and a second seed layer on two surfaces in the thickness direction of a thin film at a thin film walking speed of V1; s2, forming functional layers on the surfaces of the first seed layer and the second seed layer at the film walking speed of V2; wherein V1 is greater than V2. According to the method, the film running speed in the step S1 is greater than the film running speed in the step S2, so that an amorphous structure can be formed in the seed layer in the step S1, the amorphous structure has the characteristics of compactness and no grain boundary, and the risk that the film is curled or burnt through in the subsequent process of forming the functional layer can be prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a preparation method of an aluminum composite current collector and a composite aluminum current collector. Background Art

[0002] In the existing process of preparing composite current collectors, the seed layer formed on the surface of the film is not dense enough, resulting in the high temperature of evaporation damaging the film when the functional layer is subsequently formed on the seed layer, such as causing the risk of film curling or even burn-through. Summary of the Invention

[0003] In view of the above-mentioned deficiencies in the prior art, on the one hand, the purpose of the present invention is to provide a wire feeding device for a metal wire to solve the problem in the background art that the current collector may cause the film to curl or even burn through during the process of forming the functional layer.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing a composite aluminum current collector, comprising: step S1, forming a first seed layer and a second seed layer on two surfaces in a thickness direction of the film at a film running speed of V1; step S2, forming a functional layer on the surfaces of the first seed layer and the second seed layer at a film running speed of V2; wherein V1 is greater than V2.

[0005] Furthermore, the speed V1 of the film in step S1 is greater than or equal to 10 times the speed V2 of the film in step S2, and the speed V1 of the film in step S1 is less than or equal to 60 times the speed V2 of the film in step S2.

[0006] Furthermore, the step S2 includes step S2-1 and step S2-2, wherein step S2-1 is: forming a first functional layer on the surface of the first seed layer; and step S2-2 is: forming a second functional layer on the surface of the second seed layer.

[0007] Furthermore, the step S2-1 and the step S2-2 are completed in the same vacuum evaporation equipment.

[0008] Furthermore, the running speed V1 of the film in step S1 is greater than or equal to 200 m / min and less than or equal to 600 m / min.

[0009] Furthermore, the running speed V2 of the film in step S2 is greater than or equal to 10 m / min and less than or equal to 30 m / min.

[0010] Furthermore, the first functional layer is formed by double-drum single-time evaporation, and the second functional layer is also formed by double-drum single-time evaporation.

[0011] Furthermore, the seed layer is formed twice on two surfaces of the film in a vacuum evaporation device.

[0012] Furthermore, the vacuum evaporation equipment includes a first cooling main drum and a second cooling main drum. During the vacuum coating process, the temperature of the first cooling main drum is greater than or equal to -15° and less than or equal to 15°, and the temperature of the second cooling main drum is maintained at greater than or equal to -15° and less than or equal to 15°.

[0013] On the other hand, the present invention also provides a composite aluminum current collector, which is prepared by the preparation method of the composite aluminum current collector described above, and the composite aluminum current collector has no wrinkles under the conditions of a temperature of 120° C. and a tension of 70N.

[0014] Compared to the prior art, the present invention's method for preparing a composite aluminum current collector includes the following steps: Step S1, forming a first seed layer and a second seed layer on both surfaces of the film in the thickness direction at a film speed of V1; Step S2, forming a functional layer on the surfaces of the first seed layer and the second seed layer at a film speed of V2; wherein V1 is greater than V2. Because the film speed in Step S1 is greater than the film speed in Step S2, the seed layer in Step S1 forms an amorphous structure. The amorphous structure is dense and has no grain boundaries, which helps prevent the risk of film curling or burn-through during the subsequent formation of the functional layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flow chart of the method for preparing the composite aluminum current collector provided by the present invention; Figure 2 A structural diagram of the vacuum evaporation equipment provided by the present invention; Figure 3 This is a structural diagram of the composite aluminum current collector provided by the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0017] It should be noted that when a component is referred to as being “mounted on,” “fixed on,” or “disposed on” another component, it may be directly on the other component or there may be an intermediate component. When a component is referred to as being “connected to” another component, it may be directly connected to the other component or there may be an intermediate component.

[0018] It should also be noted that the directional terms such as left, right, up, and down in the embodiments of the present invention are merely relative concepts or are based on the normal use status of the product and should not be considered as restrictive.

[0019] In the existing process of preparing composite aluminum current collectors, the seed layer formed on the surface of the film is not dense enough, resulting in the subsequent formation of the functional layer on the seed layer. The high temperature of evaporation will damage the film, such as causing the film to curl or even burn through. Therefore, the inventors proposed a method for preparing aluminum composite current collectors, such as Figure 1 As shown, step S1 forms a first seed layer and a second seed layer on both surfaces of the film in the thickness direction at a film speed of V1; step S2 forms a functional layer on the surfaces of the first seed layer and the second seed layer at a film speed of V2; wherein V1 is greater than V2. In this way, since the film speed in step S1 is greater than the film speed in step S2, the seed layer in step S1 can form an amorphous structure. The amorphous structure has the characteristics of being dense and without grain boundaries, which helps to prevent the risk of the film curling or burning through in the subsequent process of forming the functional layer. Preferably, the film speed V1 in step S1 is greater than or equal to 10 times the film speed V2 in step S2, and the film speed V1 in step S1 is less than or equal to 60 times the film speed V2 in step S2. Not only can the seed layer in step S1 form an amorphous structure, preventing the risk of the film curling or burning through in the subsequent process of forming the functional layer, but it can also improve the production efficiency of the seed layer and the functional layer, and reduce the occurrence of pinholes in the film during the seed layer formation process. Preferably, the speed V1 of the film in step S1 is greater than or equal to 200m / min and less than or equal to 600m / min. For example, 200m / min, 300m / min, 400m / min, 450m / min, 500m / min, 550m / min or 600m / min. In this way, the seed layer on the film can be made denser, and the heating time of the film can be reduced to prevent damage to the film. Preferably, the speed V2 of the film in step S2 is greater than or equal to 10m / min and less than or equal to 30m / min. For example, 10m / min, 15m / min, 20m / min, 25m / min or 30m / min. On the one hand, this is conducive to quickly forming a functional layer on the seed layer, and on the other hand, it is conducive to making the functional layer formed on the seed layer more uniform, so that the square resistance is more uniform. In the present invention, the seed layer can be aluminum oxide, aluminum nitride or an alloy of aluminum, etc. The functional layer can be metallic aluminum or an aluminum alloy, etc.

[0020] Furthermore, in the present invention, the first functional layer is formed by double-drum single-pass evaporation, and the second functional layer is also formed by double-drum single-pass evaporation. This can also increase the evaporation rate and reduce the formation of pinholes, because the probability of pinhole formation increases with the number of evaporation times.

[0021] Furthermore, in the present invention, step S2 includes steps S2-1 and S2-2, wherein step S2-1 comprises forming a first functional layer on the surface of the first seed layer; and step S2-2 comprises forming a second functional layer on the surface of the second seed layer. This allows for a current collector with uniform sheet resistance and thickness on both sides. Preferably, steps S2-1 and S2-2 are performed within the same vacuum evaporation apparatus. This reduces equipment usage and improves production efficiency. Preferably, the sum of the thickness of the first seed layer and the second seed layer, and the sum of the thickness of the first and second functional layers, is less than or equal to 2 μm. For example, the sum of the thickness of the first seed layer and the second seed layer, and the thickness of the first and second functional layers, can be 500 nm, 1 μm, 1.5 μm, or 2 μm. This can reduce the weight of the composite current collector while maximizing its tensile strength, for example. Specifically, the thickness of the first seed layer and the second seed layer is 10 nm, respectively, while the thickness of the first functional layer can be 490 nm, and the thickness of the second functional layer can also be 490 nm. Alternatively, the thickness of the first seed layer and the thickness of the second seed layer are 60 nm respectively, while the thickness of the first functional layer can be 940 nm, and the thickness of the second functional layer can also be 940 nm. Of course, other combinations are also possible and will not be listed here.

[0022] Furthermore, after the first functional layer is formed on the film through step S2-1, a second functional layer is formed on the second surface of the seed layer after a time T, wherein the value of time T is less than or equal to 3 hours and greater than or equal to 10 minutes. Since stress may be generated due to thermal expansion on one side of the film after the first aluminum plating. After time T, the second functional layer is formed on the second surface of the seed layer to allow the film to fully cool to room temperature, release the internal thermal stress, and avoid curling, wrinkling or deformation of the film due to uneven heating on both sides during double-sided vapor deposition. Moreover, after the first aluminum plating, a very thin aluminum oxide layer will be formed in the process of breaking the vacuum of the coating equipment after the first aluminum plating. As a "base" during the second-side vapor deposition, it may change the deposition behavior of aluminum atoms. For example, the surface energy of the oxide layer is low, which may promote a more orderly arrangement of aluminum atoms, forming a denser and more uniform grain structure, and improving the conductive properties of the composite current collector.

[0023] Furthermore, if Figure 2As shown, the vacuum evaporation equipment includes a unwinding roller 1, which is used to unwind the film. After passing the unwinding roller, the film passes through the first guide roller 2, the second guide roller 3 and the third guide roller 4. The guide rollers are used to guide the movement of the film while giving the film tension. After passing the third guide roller 4, the film arrives at the first cooling main drum 5. While the film is cooled at the first cooling main drum 5, a functional layer is coated on the surface. After passing the first cooling main drum 5, the film passes through the fourth guide roller 6. After passing the fourth guide roller 6, the film passes through the fifth guide roller 7 and the first bending roller 8. The first bending roller 8 can ensure that the film fits better with the second cooling main drum 9 and can give the film better tension. The film then arrives at the second cooling main drum 9. After being cooled at the second cooling main drum 9 and forming another functional layer on the functional layer of the film, the film passes through the sixth guide roller 10 and the seventh guide roller 11, and then passes through the second bending roller 12 and the eighth guide roller 13, and is wound behind the winding roller 14. Preferably, during the vacuum coating process, the temperature of the first cooling drum 5 is maintained between -15°C and 15°C, while the temperature of the second cooling drum 9 is maintained between -15°C and 15°C. This unified temperature setting reduces the complexity of process adjustments, reduces the risk of operational errors, and improves the continuity and stability of the production line. Preferably, the temperature of the first cooling drum 5 is maintained between 10°C and 15°C, while the temperature of the second cooling drum 9 is maintained between -5°C and 0°C. Maintaining a higher temperature on the first cooling drum 5 slows the cooling rate, allowing the film to initially set, while the lower temperature on the second cooling drum further stabilizes the structure. This progressive cooling effectively distributes thermal stress, ensuring film flatness and dimensional stability. Excessive temperature differences prevent the film from experiencing rapid localized shrinkage, which could lead to internal stress and curling, wrinkling, or deformation. Furthermore, the higher temperature of the first cooling drum 5 than the second cooling drum 9 reduces energy use and costs. In particular, the higher first cooling drum temperature (5) prolongs the migration time of metal atoms, such as aluminum atoms, within the coating, promoting orderly grain arrangement and proper growth, resulting in a larger, more uniform crystal structure. This improves the conductivity, reflectivity, and mechanical strength of the aluminum layer. The subsequent rapid cooling in the second stage "freezes" this structure, preventing over-crystallization and grain boundary defects, ensuring stable performance.

[0024] On the other hand, the present invention also provides a composite aluminum current collector, which is prepared according to the preparation method of the composite aluminum current collector, such as Figure 3As shown, the composite aluminum current collector includes a support layer 15, a seed layer 16 is provided on the upper surface and or lower surface of the support layer in the thickness direction, and a functional layer 17 is provided on the side of the seed layer away from the support layer. The composite current collector has no wrinkles under the conditions of a temperature of 120°C and a tension of 70N. The advantage of this is that the composite aluminum current collector needs to be operated under the conditions of 120°C and a tension of 70N in subsequent processing stages, such as coating or rolling. If the composite aluminum current collector has wrinkles under the conditions of a temperature of 120°C and a tension of 70N, it will inevitably lead to uneven coating during thickness coating, thereby affecting the performance of the final battery. The present invention controls the composite aluminum current collector by first controlling the film's travel speed V1 in step S1 to be greater than or equal to the film's travel speed V2 in step S2, thereby preventing the composite aluminum current collector from being damaged, deformed, or wrinkled by high temperatures. This prevents the composite aluminum current collector from wrinkling under conditions of a temperature of 120°C and a tension of 70N. Furthermore, after forming a first functional layer on the film through step S2-1, a second functional layer is formed on the second surface of the seed layer after a time T, wherein the time T is less than or equal to 3 hours and greater than or equal to 10 minutes. This further prevents the composite aluminum current collector from wrinkling under conditions of a temperature of 120°C and a tension of 70N. This ensures that the composite aluminum current collector produced by the composite aluminum current collector preparation method will not wrinkle under conditions of a temperature of 120°C and a tension of 70N, thereby improving the performance of batteries using the composite aluminum current collector. Among them, the seed layer 16 on the upper surface of the supporting layer can be called a first seed layer, the seed layer 16 on the small surface in the thickness direction of the supporting layer can be called a second seed layer, the functional layer 17 arranged on the side of the first seed layer away from the supporting layer is called a first functional layer, and the functional layer 17 arranged on the side of the second seed layer away from the supporting layer is called a second functional layer. Specifically, the material of the support layer can be one or more of polyoxymethylene, polyethylene, polyvinyl methyl ether, polyvinyl ethyl ether, ethylene-propylene copolymer, polyvinyl alcohol, polyvinyl acetate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polyvinylidene chloride, polypropylene, polyacrylic acid, polymethyl methacrylate, polyethyl acrylate, poly(α-cyanobutyl acrylate), polyacrylonitrile, polyisobutylene rubber, chloroprene rubber, natural rubber, gutta-percha rubber, styrene-butadiene rubber, polydecylene formamide, polyhexamethylene adipamide, polyhexamethylene sebacamide, polyethylene terephthalate, polyethylene oxide, polyphenylene sulfide, poly[bis(trifluoroethoxy)phosphazene], polydimethylsiloxane, and biaxially oriented polypropylene film. The thickness of the support layer is 3 μm-10 μm, and can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm.

[0025] In summary, the present invention provides a method for preparing a composite aluminum current collector of the present invention, comprising the following steps: Step S1, forming a first seed layer and a second seed layer on both surfaces of the film in the thickness direction at a film speed of V1; Step S2, forming a functional layer on the surfaces of the first seed layer and the second seed layer at a film speed of V2; wherein V1 is greater than V2. Because the film speed in Step S1 is greater than the film speed in Step S2, the seed layer in Step S1 forms an amorphous structure. The amorphous structure has the characteristics of being dense and free of grain boundaries, which helps to prevent the risk of curling or burn-through of the film during the subsequent formation of the functional layer.

[0026] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a composite aluminum current collector, characterized in that: The following steps are involved: Step S1, forming a first seed layer and a second seed layer respectively on the two surfaces in the thickness direction of the film at a film moving speed of V1; Step S2, forming a functional layer on the surface of the first seed layer and the second seed layer at a film moving speed of V2; wherein V1 is greater than V2.

2. The method for preparing a composite aluminum current collector according to claim 1, wherein: The speed V1 of the film in step S1 is greater than or equal to 10 times the speed V2 of the film in step S2, and the speed V1 of the film in step S1 is less than or equal to 60 times the speed V2 of the film in step S2.

3. The method for preparing a composite aluminum current collector according to claim 1, wherein: The step S2 includes step S2-1 and step S2-2. The step S2-1 is: forming a first functional layer on the surface of the first seed layer; the step S2-2 is: forming a second functional layer on the surface of the second seed layer.

4. The method for preparing a composite aluminum current collector according to claim 3, wherein: The step S2-1 and the step S2-2 are completed in the same vacuum evaporation equipment.

5. The method for preparing a composite aluminum current collector according to claim 2, wherein: The film moving speed V1 in step S1 is greater than or equal to 200 m / min and less than or equal to 600 m / min.

6. The method for preparing a composite aluminum current collector according to claim 5, characterized in that: The film moving speed V2 in step S2 is greater than or equal to 10 m / min and less than or equal to 30 m / min.

7. The method for preparing a composite aluminum current collector according to claim 4, wherein: The first functional layer is formed by double-drum single-time evaporation, and the second functional layer is also formed by double-drum single-time evaporation.

8. The method for preparing a composite aluminum current collector according to claim 7, wherein: The vacuum evaporation equipment includes a first cooling main drum and a second cooling main drum. During the vacuum coating process, the temperature of the first cooling main drum is greater than or equal to -15° and less than or equal to 15°, and the temperature of the second cooling main drum is maintained at greater than or equal to -15° and less than or equal to 15°.

9. A composite aluminum current collector, characterized in that: The current collector is prepared according to the method for preparing the current collector according to any one of claims 1 to 8, and the composite current collector has no wrinkles under the conditions of a temperature of 120° C. and a tension of 70N.

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