A copper-aluminum composite plate and a preparation method thereof

Abstract

The application discloses a copper-aluminum composite plate and a preparation method thereof. The preparation method comprises the following steps: pretreatment, rolling, and friction stir welding. The copper-aluminum composite plate is prepared by the combined use of rolling and friction stir welding, so that the energy consumption in the production process can be effectively reduced, the defects and the number of intermetallic compounds in the composite interface can be reduced, the influence of the copper-aluminum composite interface on the overall electrical conductivity can be effectively reduced, the quality of the copper-aluminum composite pole can be improved, and the prepared copper-aluminum composite plate has excellent comprehensive performance and is helpful to improve the service life of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and in particular to a copper-aluminum composite plate and its preparation method. Background Technology

[0002] Battery terminals are a crucial component of new energy power batteries, serving as essential parts connecting the battery's internal and external components. One end connects to the internal cell of the lithium battery, while the other end connects to the external circuitry, enabling the battery to charge and discharge. Therefore, the quality of the terminal assembly and its manufacturing process directly affects the performance of the battery cell and even the entire battery.

[0003] Currently, because the negative electrode current collector inside the battery cell is made of copper foil, the terminals are often designed to be made of copper. However, copper terminals have drawbacks such as high material cost and heavy weight. In order to reduce weight and cost, many external circuits connected to lithium batteries often use aluminum for connection. Therefore, copper-aluminum composite terminals have emerged.

[0004] Hot pressing is a commonly used method for preparing copper-aluminum composite electrodes. It involves stacking copper and aluminum together at high temperatures and performing continuous hot pressing. Hot pressing requires a high-temperature environment (e.g., CN115911779A), consumes a lot of energy, and easily forms a thick intermetallic compound layer (typically >10μm) at the interface. These intermetallic compounds are characterized by hardness, brittleness, low strength, and high electrical resistance; excessive presence may affect conductivity and accelerate battery degradation. Summary of the Invention

[0005] This invention provides a copper-aluminum composite plate and its preparation method, which can solve the above-mentioned problems existing in the preparation process of existing copper-aluminum composite plates.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for preparing a copper-aluminum composite plate, comprising the following steps: (1) Pretreatment: Prepare copper plates and aluminum plates, and pretreat the surfaces of the copper plates and aluminum plates to be laminated until the surfaces are clean; (2) Rolling: After the copper plate and aluminum plate to be laminated are tightly bonded together, a pre-bonded layer is formed at the interface after rolling. The total rolling reduction is 10-30% of the initial total thickness of the copper plate and aluminum plate. (3) Friction stir welding: The rolled copper-aluminum plate is subjected to multiple passes of friction stir welding to obtain the copper-aluminum composite plate.

[0007] In a preferred embodiment of the present invention, in step (1), the pretreatment includes grinding the surfaces of the copper plate and aluminum plate to be composited to a surface roughness of 0.8-1.0 μm, acid washing, and alkali washing.

[0008] In a preferred embodiment of the present invention, in step (1), the thickness of the copper plate is less than the thickness of the aluminum plate.

[0009] In a preferred embodiment of the present invention, the thickness ratio of the copper plate to the aluminum plate is 1:2 to 5.

[0010] In a preferred embodiment of the present invention, in step (3), the process conditions for friction stir welding are: room temperature, the distance between the stirring head and the interface between the copper plate and the aluminum plate is 0.1 to 0.5 mm, the stirring head rotation speed is 900 to 1200 rpm, and the welding speed is 50 to 100 mm / min.

[0011] In a preferred embodiment of the present invention, in step (3), the number of welding passes is ≥3 and the overlap rate of adjacent passes is 40-60%.

[0012] To solve the above-mentioned technical problems, the present invention also provides a copper-aluminum composite plate prepared by the above method, comprising a copper layer and an aluminum layer, which are composited by a rolled pre-bonding layer and a friction stir welding metallurgical bonding layer, wherein the thickness of the intermetallic compound layer is ≤5μm, the interface peel strength is ≥18 N / mm, and the electrical conductivity is ≥70% IACS.

[0013] The beneficial effects of this invention are: the method for preparing a copper-aluminum composite plate of this invention, by combining rolling and friction stir welding, can effectively reduce energy consumption in the production process, and can reduce defects and the number of intermetallic compounds at the composite interface, effectively reduce the impact of the copper-aluminum composite interface on the overall conductivity, improve the quality of the copper-aluminum composite electrode, and the prepared copper-aluminum composite plate has excellent comprehensive performance, which helps to improve the service life of the battery. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the friction stir welding process in the preparation method of a copper-aluminum composite plate according to the present invention. Figure 2 This is a schematic diagram of the cross-sectional structure of the copper-aluminum composite plate prepared in a preferred embodiment 1 of the present invention; The components in the attached diagram are labeled as follows: 10. Copper plate, 20. Aluminum plate. Detailed Implementation

[0015] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0016] Example 1 This invention discloses a method for preparing a copper-aluminum composite plate, comprising the following steps: (1) Pretreatment: Prepare a 2mm thick T2 copper plate 10 and a 4mm thick 1060 aluminum plate 20; perform grinding, pickling and alkaline washing pretreatment on the surfaces to be laminated on the copper plate 10 and the aluminum plate 20 respectively.

[0017] Specifically, first wipe the copper and aluminum plates to be laminated with anhydrous ethanol to remove oil stains and loose particles, and then use a grinder to grind the roughness of the laminated surfaces to 0.8-0.9μm.

[0018] After polishing, copper plate 10 and aluminum plate 20 are immersed in 10% HNO3 solution for 3 minutes to completely dissolve the oxide layer. After removal, they are washed with water and the surface shows a uniform metallic luster.

[0019] Finally, the sample is immersed in a 5% NaOH solution for 3 minutes, then rinsed with water to complete the pretreatment. Alkaline washing removes surface grease and acidic substances, and slightly etches the metal surface to create a uniform micro-roughness, enhancing rolling adhesion.

[0020] (2) Rolling: The pre-treated copper plate and aluminum plate are tightly bonded together and then rolled. The single reduction is controlled at 5%, and the rolling is performed 3 times. The total thickness of the composite plate after rolling is 4.5 mm. After rolling, a pre-bonded layer (mechanical interlocking interface) is formed at the interface.

[0021] Rolling induces plastic deformation on the surfaces of copper and aluminum plates, forming a preliminary physical bond, i.e., mechanical interlocking. This reduces interfacial gaps, results in lower residual stress within the rolled plate, and ensures a tighter interfacial bond. This improves the uniformity of heat distribution during subsequent friction stir welding, reduces the amount of intermetallic compounds, and decreases the thickness of the metallurgical bonding layer. Furthermore, room-temperature rolling results in low energy consumption.

[0022] (3) Friction stir welding: The rolled copper-aluminum composite plate is fixed on the worktable with the aluminum plate facing upward, ensuring that the plate is flat and without warping. At room temperature, the tungsten carbide stirring head is vertically aligned with the copper-aluminum interface. The mechanical sensor is used to accurately position it to a distance of 0.1 mm from the interface. The stirring head speed is controlled at 900 rpm and the welding speed is 50 mm / min. The first pass is along the center line of the interface, and the subsequent two passes are offset to both sides by 1.5 mm (covering 50% of the previous pass). A total of three passes are used to ensure that the interface is completely bonded and a metallurgical bonding layer is formed.

[0023] After welding, the surface of the composite plate is cleaned and polished to obtain a copper-aluminum composite plate for use as an electrode post.

[0024] Example 2 This invention discloses a method for preparing a copper-aluminum composite plate, comprising the following steps: (1) Pretreatment: Prepare a 3mm thick T2 copper plate 10 and a 9mm thick 1060 aluminum plate 20; perform grinding, pickling and alkaline washing pretreatment on the surfaces to be laminated on the copper plate 10 and the aluminum plate 20 respectively.

[0025] Specifically, first wipe the copper and aluminum plates to be laminated with anhydrous ethanol to remove oil stains and loose particles, and then use a grinder to grind the roughness of the laminated surfaces to 0.9-1.0μm.

[0026] After polishing, copper plate 10 and aluminum plate 20 are immersed in a 10% HNO3 solution for 3 minutes to completely dissolve the oxide layer. After removal, they are washed with water and the surface shows a uniform metallic luster.

[0027] Finally, the sample is immersed in a 5% NaOH solution for 3 minutes, then rinsed with water to complete the pretreatment. Alkaline washing removes surface grease and acidic substances, and slightly etches the metal surface to create a uniform micro-roughness, enhancing rolling adhesion.

[0028] (2) Rolling: The pre-treated copper plate and aluminum plate are tightly bonded together and then rolled. The single reduction is controlled at 10%, and the rolling is performed twice. The total thickness of the composite plate after rolling is 9mm.

[0029] Rolling induces plastic deformation on the surfaces of copper and aluminum plates, forming a preliminary physical bond, i.e., mechanical interlocking. This reduces the interfacial gap, results in lower residual stress inside the rolled plate, and ensures a tighter interfacial bond. This is beneficial for improving the uniformity of heat distribution during subsequent friction stir welding, reducing the amount of intermetallic compounds, and decreasing the thickness of the metallurgical bonding layer.

[0030] (3) Friction stir welding: The rolled copper-aluminum composite plate is fixed on the worktable with the aluminum plate facing upward, ensuring that the plate is flat and without warping. At room temperature, the tungsten carbide stirring head is vertically aligned with the copper-aluminum interface. The mechanical sensor is used to accurately position it to a distance of 0.1 mm from the interface. The stirring head speed is controlled at 1200 rpm and the welding speed is 100 mm / min. The first pass is along the center line of the interface, and the subsequent two passes are offset to the sides by 1.5 mm respectively (the subsequent passes cover 50% of the previous pass). A total of three passes are used for welding to ensure that the interface is completely bonded and a metallurgical bonding layer is formed.

[0031] After welding, the surface of the composite plate is cleaned and polished to obtain a copper-aluminum composite plate for use as an electrode post.

[0032] Comparative Example 1 Compared with Example 1, the pretreated copper plate and aluminum plate to be laminated are tightly bonded together and then directly subjected to friction stir welding, and the processing conditions are the same as in Example 1.

[0033] Comparative Example 2 Compared with Example 1, the pretreated copper plate and aluminum plate are tightly bonded together and then rolled in a single pass to achieve a total thickness of about 5 mm for the composite plate.

[0034] Comparative Example 3 Compared with Example 1, the pretreated copper and aluminum plates to be composited are tightly bonded together and placed in a hot pressing mold in a hot pressing sintering furnace; the hot pressing sintering furnace is heated to 500°C and held for 70 minutes to allow the aluminum to plastically flow (without melting) and diffusely combine with the copper plate; during the heating process, the hot pressing mold is pressurized to 5.0 MPa; the hot pressing sintering furnace is then stopped and cooled to obtain the copper-aluminum composite pole.

[0035] The copper-aluminum composite plates prepared in Examples 1, 2, 1, 2, and 3 were subjected to performance testing. The interfacial peel strength was tested according to ISO 6892; the electrical conductivity was tested according to ASTM B193; and the thickness of the intermetallic compound layer was measured according to GB / T 6394-2017. The results are shown in Table 1 below.

[0036] Table 1 As shown in Table 1, the test results of Example 1 and Comparative Example 1 indicate that the combined rolling and friction stir welding process can significantly improve the interfacial bonding strength and electrical conductivity of the copper-aluminum composite plate, and effectively reduce the amount of intermetallic compounds and the thickness of the intermetallic compound layer. As shown in the test results of Example 1, Comparative Example 1 and Comparative Example 2, multiple rolling processes are more beneficial to improving the performance of the copper-aluminum composite plate. As shown in the data of Comparative Example 3, the intermetallic compound layer thickness of the method of the present invention is only 1 / 4 of that of the hot pressing method, which effectively reduces the interfacial layer thickness and thus reduces the amount of intermetallic compounds.

[0037] The preparation method of the present invention has the following advantages: (1) The preparation process is carried out at room temperature, the production power consumption is low, and the size of the composite board does not need to be limited by the size of the high-temperature equipment, making it suitable for large-scale production.

[0038] (2) The rolling process can pre-composite (physical bonding) copper and aluminum plates, and eliminate the gap between the two plates. This helps to reduce or avoid interface defects during the stir friction welding process. Furthermore, by controlling the single reduction amount and the number of rolling cycles, the plate can be processed to the specified thickness.

[0039] (3) The friction stir welding process generates local high temperature, which can effectively eliminate the internal stress generated during rolling. Therefore, no heat treatment is required after rolling, which can save energy.

[0040] (4) Placing the aluminum surface on the top side helps to control the heat input of the welding zone and form appropriate material flowability; controlling the distance between the stirring head and the interface can make the copper-aluminum interface form a thinner metallurgical bonding layer (i.e., generate less intermetallic compounds), reducing the impact on the electrical conductivity of the composite plate; friction stir welding does not change the workpiece size, so there is no need for secondary machining, effectively simplifying the preparation steps.

[0041] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a copper-aluminum composite plate, characterized in that, Includes the following steps: (1) Pretreatment: Prepare copper plate and aluminum plate, and pretreatment the surfaces of copper plate and aluminum plate to be laminated until the surfaces are clean; the thickness of the copper plate is less than the thickness of the aluminum plate, and the thickness ratio of the copper plate to the aluminum plate is 1:2 to 5. (2) Rolling: After the copper plate and aluminum plate to be laminated are tightly bonded together, a pre-bonded layer is formed at the interface after rolling. The total rolling reduction is 10-30% of the initial total thickness of the copper plate and aluminum plate. (3) Friction stir welding: The rolled copper-aluminum plate is subjected to friction stir welding in 3 or more passes, with an overlap rate of 40-60% between adjacent passes, to obtain the copper-aluminum composite plate; the process conditions for friction stir welding are: room temperature, distance between the stirring head and the interface between the copper plate and the aluminum plate is 0.1-0.5 mm, stirring head rotation speed is 900-1200 rpm, and welding speed is 50-100 mm / min; The friction stir welding process generates local high temperatures, which effectively eliminates the internal stress generated during rolling. No heat treatment is required after step (3). The prepared copper-aluminum composite plate includes a copper layer and an aluminum layer, which are combined by rolling a pre-bonded layer and friction stir welding metallurgical bonding layer. The thickness of the intermetallic compound layer is ≤5μm, the interface peel strength is ≥18 N / mm, and the electrical conductivity is ≥70% IACS.

2. The method for preparing a copper-aluminum composite plate according to claim 1, characterized in that, In step (1), the pretreatment includes: first grinding the surfaces of the copper plate and aluminum plate to be laminated to a surface roughness of 0.8-1.0 μm, then acid washing, and finally alkali washing.

3. A copper-aluminum composite plate prepared by the method according to any one of claims 1-2, characterized in that, It includes a copper layer and an aluminum layer, which are combined with a metallurgical bonding layer by a rolled pre-bonding layer and a friction stir welding layer. The thickness of the intermetallic compound layer is ≤5μm, the interface peel strength is ≥18 N / mm, and the electrical conductivity is ≥70% IACS.

Images