High bonding strength composite aluminum foil and method for manufacturing the same

Abstract

The application relates to the technical field of composite aluminum foil, and particularly discloses a high-bonding-strength composite aluminum foil and a preparation method thereof, the preparation method comprises the following steps: S1. loading a film onto a winding type coating machine, one side surface of the film is formed with an aluminum pre-plating layer; S2. performing nitrogen plasma pretreatment on the film to obtain a film base material; and S3. depositing an aluminum layer on both side surfaces of the film base material through one-time vacuum evaporation plating to obtain the high-bonding-strength composite aluminum foil. The nitrogen plasma pretreatment is used to replace the traditional argon plasma pretreatment, the activation of the film surface can be better realized, the bonding strength of the aluminum layer and the film base material can be effectively improved, and the corrosion resistance and service life of the composite aluminum foil are improved.

Description

Technical Field

[0001] This invention relates to the field of composite aluminum foil technology, and in particular to a high-bonding-strength composite aluminum foil and its preparation method. Background Technology

[0002] Composite aluminum foil uses a polymer film material as the substrate, and a conductive aluminum layer is prepared on both sides of the substrate by roll-to-roll vacuum evaporation deposition. It is used as a novel current collector material to replace traditional aluminum foil in the positive electrode of lithium batteries. Due to its significant weight and thinning effect, and the fact that the supporting layer is a polymer insulating material, it can effectively improve the energy density and safety of lithium batteries.

[0003] Vacuum-wound evaporation deposition technology is simple in principle, has high deposition efficiency, moderate cost, and produces high-purity coating materials, making it one of the more ideal technologies for mass production of composite aluminum foil materials. The preparation process uses plasma bombardment of the substrate surface to improve the bonding strength between the metal layer and the substrate, and achieves heat exchange through a relatively low main roller temperature, thereby avoiding thermal damage to the substrate during aluminum atom evaporation deposition. This allows the composite aluminum foil to meet the application requirements of lithium batteries. However, existing technologies generally use argon gas for plasma pretreatment, which cannot effectively improve the bonding strength between the metal layer and the substrate. Furthermore, to avoid thermal damage to the substrate, a relatively low main roller temperature is used for heat exchange, and the lack of differentiated cooling temperatures for the A and B sides of the composite aluminum foil can easily lead to a decrease in aluminum coating quality and insufficient density, resulting in insufficient bonding strength between the metal layer and the substrate, making it prone to peeling in electrolyte immersion environments. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a high-bonding-strength composite aluminum foil and its preparation method. Using nitrogen plasma pretreatment instead of traditional argon plasma pretreatment can better activate the film surface, effectively improve the bonding strength between the aluminum layer and the film substrate, and enhance the corrosion resistance and service life of the composite aluminum foil.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention first provides a method for preparing high-bonding-strength composite aluminum foil, which includes the following steps: S1. The film is fed into a roll-to-roll coating machine, and an aluminum pre-coating layer is formed on one side surface of the film; S2. Perform nitrogen plasma pretreatment on the thin film to obtain a thin film substrate; S3. A high-bonding-strength composite aluminum foil is obtained by depositing an aluminum layer on both sides of the thin film substrate through a single vacuum evaporation process.

[0006] This invention uses nitrogen plasma pretreatment instead of traditional argon plasma pretreatment, which can better activate the thin film surface and effectively improve the bonding strength between the aluminum layer and the thin film substrate.

[0007] As a further improvement to the above-mentioned scheme of the present invention, in step S2, the power of the plasma for nitrogen plasma pretreatment is 1500-2500W, and the nitrogen flow rate is 50-150 sccm.

[0008] As a further improvement to the above-mentioned solution of the present invention, the vacuum chamber of the roll-to-roll coating machine has a first main roller and a second main roller arranged in sequence, and the aluminum pre-coating layer is arranged facing the first main roller.

[0009] As a further improvement to the above-described solution of the present invention, the temperature of the first main roller is lower than that of the second main roller.

[0010] As a further improvement to the above-mentioned solution of the present invention, the temperature of the first main roller and the second main roller is 25-70°C, and the temperature difference between the first main roller and the second main roller is 15-40°C.

[0011] As a further improvement to the above-mentioned solution of the present invention, the winding speed of the roll coating machine is 5-20m / min.

[0012] The present invention also provides a high bonding strength composite aluminum foil, which is prepared by the preparation method described above.

[0013] As a further improvement to the above-described solution of the present invention, the high-bonding-intensity composite aluminum foil includes a thin film substrate, an aluminum pre-plating layer disposed on one surface of the thin film substrate, and an aluminum layer disposed on the other surface of the thin film substrate and the surface of the aluminum pre-plating layer. The surface aluminum layer is obtained by vacuum evaporation deposition, therefore there is no interface parallel to the surface of the thin film substrate inside the aluminum layer.

[0014] As a further improvement to the above-mentioned solution of the present invention, the thickness of the thin film substrate is 2-15 μm, and the thickness of the aluminum pre-coating layer is 2-5 nm.

[0015] As a further improvement to the above-mentioned solution of the present invention, the thickness of the aluminum layer is 800-2000 nm.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention uses nitrogen plasma pretreatment instead of traditional argon plasma pretreatment, which can better activate the film surface, effectively improve the bonding strength between the aluminum layer and the film substrate, and enhance the electrolyte corrosion resistance and service life of the composite aluminum foil. In the roll-to-roll evaporation process, the actual plasma treatment time on the film substrate is very short, only a few seconds. Under these conditions, argon can only remove surface contaminants (higher power treatment would damage the substrate surface structure). Nitrogen treatment, while removing surface contaminants, can implant a small number of nitrogen-containing groups (basic groups) onto the substrate surface. These small number of basic groups do not affect the overall alkalinity of the substrate surface, but they increase the relative alkalinity of individual groups, resulting in stronger interaction with Al and more space for Al atoms to grow better. If more basic groups are introduced, the total basicity of the thin film substrate increases, but the increase is less than the increase in the number of groups. There will also be the introduction of weakly basic groups, which is not conducive to the bonding with Al. Moreover, too many groups affect the nucleation space of Al, which is not conducive to grain growth, thus affecting the bonding strength. Therefore, this invention controls the winding speed of the roll-to-roll coating machine at 5-20 m / min and controls the nitrogen plasma treatment time to avoid the problem of insufficient or excessive introduction of basic groups.

[0017] This invention first forms an aluminum pre-coating layer on one side of the film surface. During vacuum evaporation deposition, this pre-coating layer is positioned facing the first main roller. This reduces the need for preparing adhesive layers on both sides of the film, improving production efficiency and yield. Furthermore, during vacuum evaporation deposition, the applied bias voltage allows for a tighter adhesion between the aluminum pre-coating layer and the film substrate, preventing thermal damage to the film and protecting the main roller, reducing the risk of roller puncture and significantly saving on coating roller maintenance costs. The thinner aluminum pre-coating layer used in this invention does not significantly affect the consistency of the composite aluminum foil on both sides.

[0018] This invention achieves better effective activation of the film surface by controlling the film winding speed and nitrogen plasma treatment time, combined with high-power nitrogen plasma bombardment. Furthermore, by employing differentiated main roller temperatures to address the different states of the two sides of the film, it ensures no thermal damage to the film material while increasing atomic mobility, enhancing the integrity of the double-sided aluminum layer nucleation, improving the density of the aluminum layer, reducing microscopic defects, further improving the corrosion resistance of the coating in the electrolyte environment, and extending the service life of the composite aluminum foil. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a high-bonding-strength composite aluminum foil proposed in this invention.

[0020] Reference numerals: 1. Thin film substrate; 2. Aluminum pre-coating layer; 3. Aluminum layer. Detailed Implementation

[0021] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0023] Example 1 Reference Figure 1 This embodiment proposes a high-bonding-strength composite aluminum foil, which includes a thin film substrate 1, an aluminum pre-plating layer 2 disposed on one side of the thin film substrate 1, and an aluminum layer 3 disposed on the other side of the thin film substrate 1 and the surface of the aluminum pre-plating layer 2. In this embodiment, the thin film substrate 1 is a 6μm thick PET film; the aluminum pre-plating layer 2 has a thickness of 2nm; and the aluminum layer 3 has a thickness of 1000nm, and there is no interface layer parallel to the surface of the thin film substrate inside it.

[0024] The method for preparing high-bonding-strength composite aluminum foil in this embodiment includes the following steps: S1. A film with an aluminum pre-coating layer on one side is fed into a roll-to-roll coating machine. The roll-to-roll coating machine can perform simultaneous coating on both sides. The vacuum chamber of the roll-to-roll coating machine is equipped with a first main roller and a second main roller. After entering the vacuum chamber, the film first passes around the first main roller and then around the second main roller to be wound up, and the side of the film with the aluminum pre-coating layer is facing the first main roller.

[0025] This embodiment does not limit the preparation method of the aluminum pre-plating layer; it can be prepared by vacuum evaporation plating.

[0026] S2. Evacuate to 5.0×10 -3 Pa, turn on the winding system, the winding speed is 10m / min, the film is pretreated with nitrogen plasma before entering the vacuum chamber: the plasma power is 1500W, the nitrogen flow rate is 50 sccm, and the film substrate is obtained.

[0027] S3. The thin film substrate then enters the vacuum chamber, where an aluminum layer is deposited on the other side surface of the thin film substrate and the surface of the aluminum pre-plating layer by vacuum evaporation, wherein the temperature of the first main roller is 40°C and the temperature of the second main roller is 60°C.

[0028] Example 2 The difference between this embodiment and embodiment 1 is that: the thickness of the aluminum pre-plating layer in this embodiment is 10nm; in the preparation of the high bonding strength composite aluminum foil in this embodiment, the power of the nitrogen plasma pretreatment plasma in step S2 is 2500W and the nitrogen flow rate is 150 sccm; in step S3, the temperature of the first main roller is 30℃ and the temperature of the second main roller is 70℃.

[0029] Comparative Example 1 The difference between this comparative example and Example 1 is that, in the preparation of this comparative example, argon plasma pretreatment was used instead of nitrogen plasma pretreatment in step S2, with a plasma power of 1500W and an argon flow rate of 50 sccm.

[0030] Comparative Example 2 The difference between this comparative example and Example 1 is that the temperature of the first main roller and the second main roller in this comparative example is 10°C during preparation.

[0031] Comparative Example 3 The difference between this comparative example and Example 1 is that the winding speed in step S2 of this comparative example is 25 m / min.

[0032] It should be noted that when preparing composite aluminum foil using a thin film substrate without an aluminum pre-coating layer on its surface according to the method of Example 1, phenomena such as arcing and discharge may occur, causing damage to the surfaces of the first and second main rollers and breakage of the composite aluminum foil sample surface. Using plasma power higher than 2500W and nitrogen flow rate higher than 150sccm may damage the thin film substrate, resulting in a significant reduction in the mechanical strength of the composite aluminum foil. Using a main roller temperature higher than 70°C may cause severe thermal damage to the surface of the composite aluminum foil sample. Therefore, no additional comparative examples are provided for the above situations.

[0033] Test case The composite aluminum foils prepared in Examples 1-2 and Comparative Examples 1-3 were subjected to performance tests: The composite aluminum foils were completely immersed in 1 mol / L LiPF6 electrolyte, sealed and stored at 60°C, and removed at different time intervals. After removing the residual electrolyte on the surface, they were dried and subjected to a 180° peel test using 3M 681 tape. The test results are shown in Table 1.

[0034] Table 1. Peel Test Results

[0035] Table Explanation: This indicates that the aluminum layer has not peeled off; This indicates that the aluminum layer has peeled off sporadically (less than 10% of the tape area). × indicates that a large area of ​​the aluminum layer has peeled off (more than 50% of the tape area); × indicates that the aluminum layer has completely separated from the support layer.

[0036] As can be seen from Table 1: The composite aluminum foils prepared in Examples 1 and 2 showed no aluminum layer peeling after immersion in an electrolyte environment for more than 360 hours, and only sporadic peeling after immersion for 720 hours, exhibiting excellent resistance to electrolytic corrosion. The sporadic peeling after immersion for 720 hours may be related to the wrinkles in the sample.

[0037] Compared to Examples 1 and 2, the composite aluminum foil in Comparative Example 1 showed sporadic peeling of the aluminum layer after immersion for 168 hours. After immersion exceeding 360 hours, severe peeling and even separation of the aluminum layer from the support layer occurred. Further immersion resulted in complete separation of the aluminum layer from the support layer, rendering it unusable. This demonstrates that the nitrogen plasma treatment described in this application can effectively improve the bonding strength between the aluminum layer and the support layer compared to traditional argon plasma treatment, thereby improving the durability of the composite aluminum foil in an electrolyte environment.

[0038] Compared to Examples 1 and 2, the aluminum layer of the composite aluminum foil in Comparative Example 2 began to peel off after immersion for 72 hours. The peeling became more severe with increasing immersion time, and after immersion for 360 hours, the aluminum layer completely separated from the support layer, rendering it unusable. This indicates that a lower roller temperature and a lack of differentiation are detrimental to obtaining a dense aluminum layer, reducing its durability in the electrolyte environment and adversely affecting the service life of the composite aluminum foil.

[0039] In Comparative Example 3, the excessively fast winding speed led to a shortened nitrogen plasma treatment time. As a result, the aluminum layer of the composite aluminum foil began to peel off after immersion for 360 hours, and a large area of ​​peeling occurred after immersion for 720 hours. Compared to Comparative Examples 1 and 2, the composite aluminum foil of Comparative Example 3 exhibited better resistance to electrolyte corrosion, but was slightly inferior to Examples 1 and 2. This indicates that using an appropriate nitrogen plasma treatment time can further improve the bonding strength of the composite aluminum foil.

[0040] It should be noted that the 180° peel test results of the composite aluminum foil in the examples and comparative examples presented in Table 1 do not clearly distinguish between sides A and B of the sample, because sides A and B showed the same test results during the test.

[0041] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0042] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a high-bonding-strength composite aluminum foil, characterized in that, It includes the following steps: S1. A film is fed into a roll-to-roll coating machine, and an aluminum pre-coating layer is formed on one side surface of the film; the vacuum chamber of the roll-to-roll coating machine has a first main roller and a second main roller arranged in sequence, and the aluminum pre-coating layer is positioned towards the first main roller; the temperature of the first main roller is lower than the temperature of the second main roller, the temperature of the first main roller and the second main roller is 25-70℃, and the temperature difference between the first main roller and the second main roller is 15-40℃; S2. The thin film is subjected to nitrogen plasma pretreatment to obtain a thin film substrate; the power of the nitrogen plasma pretreatment is 1500-2500W, and the nitrogen flow rate is 50-150 sccm. S3. A high-bonding-strength composite aluminum foil is obtained by depositing an aluminum layer on both sides of the thin film substrate through a single vacuum evaporation process.

2. The method for preparing high-bonding-strength composite aluminum foil according to claim 1, characterized in that, The winding speed of the roll-to-roll coating machine is 5-20 m / min.

3. A high-bonding-strength composite aluminum foil, characterized in that, It is prepared by the preparation method as described in any one of claims 1-2.

4. The high bonding strength composite aluminum foil according to claim 3, characterized in that, The high bonding strength composite aluminum foil includes a thin film substrate, an aluminum pre-plating layer disposed on one side of the thin film substrate, and an aluminum layer disposed on the other side of the thin film substrate and on the surface of the aluminum pre-plating layer.

5. The high bonding strength composite aluminum foil according to claim 4, characterized in that, The thickness of the thin film substrate is 2-15 μm, and the thickness of the aluminum pre-coating layer is 2-5 nm.

6. The high bonding strength composite aluminum foil according to claim 4, characterized in that, The thickness of the aluminum layer is 800-2000 nm.

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