Copper-aluminum composite connecting piece and production process thereof

Abstract

The invention relates to the technical field of lithium batteries, in particular to a copper-aluminum composite connecting piece and a production process thereof. The connecting piece comprises an aluminum plate and a copper layer; the aluminum plate is fixedly connected with the copper layer; the thickness d1 of the copper layer ranges from 0.1 mm to 40 mm. The thickness d2 of the aluminum plate is less than or equal to 50mm; and the thickness ratio d1 / d2 of the copper layer to the aluminum plate is more than 0.05 and less than 2. Comprising the following steps that an aluminum plate serves as a base material, magnetron sputtering, water electroplating, copper layer forming and rolling are sequentially conducted on the surface of the aluminum plate, and the copper-aluminum composite connecting piece is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, in particular to a copper-aluminum composite connector and a production process thereof. Background Art

[0002] New energy power batteries and energy storage batteries have experienced rapid development. Battery packs used in conventional electric vehicles or energy storage power stations are assembled from individual cells. The patent describes a product application scenario in which the negative electrode of a battery cell is typically connected to an external terminal tab via friction welding. Another application scenario involves assembling a battery pack with external connections via a guide plate, typically made of pure copper.

[0003] The conventional method of bonding aluminum and copper sheets together is to add a layer of adhesive in the middle. The two metal sheets are bonded together by the bonding force of the chemical bond and the metal bond of the adhesive.

[0004] In the existing technology, there is a problem with friction welding of the negative electrode, that is, the welding strength is insufficient, which easily leads to cold welding and causes the battery structure to break and fail; the guide plate on the outside of the battery pack is made of pure copper, which is expensive, and the copper layer has excess conductivity, and the price of copper is higher than that of aluminum; adding adhesive between the copper and aluminum plates will affect the conductivity of the connector, and the adhesive, as an organic polymer material, is a non-conductive material. Summary of the Invention

[0005] The object of the present invention is to provide a copper-aluminum composite connector and a production process thereof to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A copper-aluminum composite connector comprises an aluminum plate and a copper layer; the aluminum plate and the copper layer are fixedly connected; the thickness d1 of the copper layer is 0.1 mm to 40 mm; and the thickness d2 of the aluminum plate is ≤50 mm.

[0008] The copper layer has high conductivity. While the aluminum sheet's conductivity isn't as good as the copper layer, it's still quite good. Furthermore, the aluminum sheet is lighter and less expensive than the copper layer. Composite panels made of aluminum and copper can be reduced in weight due to their conductivity. Copper is a strategic resource with limited availability. Connecting the copper layer to the aluminum sheet reduces dependence on copper resources, achieving the rational allocation and utilization of both, in line with the concept of sustainable development.

[0009] Furthermore, the thickness ratio of the copper layer to the aluminum plate is 0.05<d1 / d2<2, which can ensure that the alloy plate has a certain proportion of aluminum, effectively control the overall thickness and weight, and is conducive to improving the battery energy density; the composite plate has both the toughness of copper and the strength of aluminum, improving the deformation resistance and impact resistance; the aluminum plate can protect the surface of the alloy plate to a certain extent, reduce the risk of corrosion, and extend the service life, especially in some humid or corrosive media environments.

[0010] Furthermore, the thickness d1 of the copper layer is 1 mm to 10 mm, and the thickness d2 of the aluminum plate is 2 mm to 20 mm. When the thickness is within this range, the performance can be guaranteed to meet the requirements while reducing the cost.

[0011] Furthermore, the ratio of the density of the copper layer to the density of the aluminum plate is 0.65 to 0.75, which is conducive to reducing stress concentration, improving deformation coordination, and reducing crack initiation and expansion at the interface, thereby improving the toughness and fatigue resistance of the composite plate.

[0012] Furthermore, the formula for the ratio of the copper layer density to the aluminum plate density is: ratio of the copper layer density to the aluminum plate density = (copper layer density / copper standard density) / (aluminum plate density / aluminum standard density).

[0013] Furthermore, the surface roughness of the aluminum plate in contact with the copper layer is less than 20 μm, preferably 10 to 20 μm. This further enhances the bending resistance of the copper-aluminum composite connector. The surface roughness of the aluminum plate in contact with the copper layer can be controlled by controlling the surface roughness of the pressing roller and the roller pressure.

[0014] Furthermore, the copper-aluminum composite connector also includes an intermetallic compound layer composed of copper and aluminum, and a thickness d3 of the intermetallic compound layer ranging from 0 to 50 nm, preferably from 5 to 50 nm. Controlling the thickness of the intermetallic compound within 5 to 50 nm not only effectively improves the bonding strength between the copper layer and the aluminum plate, but also enhances corrosion resistance, further improving fatigue resistance, and extending its service life in the battery.

[0015] A production process for a copper-aluminum composite connector comprises the following steps: using an aluminum plate as a substrate, sequentially performing magnetron sputtering and water electroplating on the surface of the aluminum plate to form a copper layer, and then winding the plate to obtain the copper-aluminum composite connector. The aluminum plate cannot be directly electroplated with water, as aluminum is relatively active in air and easily forms an oxide film on its surface. This oxide film is an insulating material, and direct electroplating would result in a slow copper layer deposition rate and uneven thickness. Magnetron sputtering sputters copper atoms onto the aluminum plate to form a copper film, ensuring a secure connection between the aluminum plate and the copper layer.

[0016] Furthermore, the roughness of the aluminum plate is controlled by controlling the roughness of the pressing rollers used for rolling the aluminum plate.

[0017] Furthermore, the longer the hot pressing time, the thicker the intermetallic compound.

[0018] Furthermore, the magnetron sputtering process parameters are: vacuum ≤ 0.01 Pa; magnetron sputtering speed 20 m / min; target power 6-10 kW, target voltage 200 V; and argon flow rate 20-50 sccm in an argon atmosphere. The sputtering rate of copper atoms on the aluminum plate surface increases with increasing magnetron sputtering power, increasing the number of sputtered copper atoms and improving the deposition rate of copper atoms on the aluminum plate. Appropriate increases in power result in better crystallinity and a denser structure for the copper film.

[0019] Furthermore, the process parameters for water electroplating are: a water electroplating speed of 10 m / min; a sulfuric acid concentration of 100-130 g / L, a copper sulfate concentration of 70-150 g / L, and a chloride ion concentration of 50-60 ppm in the electroplating solution; a current gradient of 5-35 A; and an initial current of 0.5-3 A. The copper film attached to the aluminum plate after magnetron sputtering is relatively thin, and continuing to use magnetron sputtering would increase production costs. Water electroplating can also achieve the effect of increasing the copper layer thickness.

[0020] Furthermore, when a circular copper target is selected for magnetron sputtering, the magnetic field distribution is relatively more uniform under an argon atmosphere, so that the bombardment of the target surface by argon ions is more uniform, which is conducive to obtaining a uniform copper film on the surface of the aluminum plate. When the circular structure is installed on the sputtering equipment, it has good adaptability to the equipment, and it is relatively easy to fix and adjust the position, which can ensure the stability of the target during the sputtering process. Argon is an inert gas and is easily ionized under the polarization action of the arc voltage to form a plasma containing argon ions, electrons, etc., which provides the necessary ion source for sputtering. The argon ions are accelerated and bombarded by the magnetic field under the action of the copper target, transferring their own kinetic energy to the copper atoms of the copper target, so that the copper atoms obtain sufficient energy to be sputtered from the surface of the target.

[0021] Further, by adjusting the concentration of the electroplating solution and the size of the current, the thickness of the copper layer deposited is controlled; the electroplating copper ion concentration is unchanged, the current is reduced, and the copper layer density is improved. The higher the copper ion concentration in the electroplating solution, the more copper ions are available on the cathode surface, the faster the reduction reaction rate, and the copper layer deposition rate is also increased. A thicker copper layer can be deposited in the same time. If the electroplating solution concentration is too high, it may cause the cathode surface copper ion reduction rate to be too fast, and problems such as coarse crystallization and rough coating surface may occur, affecting the quality of the copper layer. When the concentration is too low, the copper ion supply is insufficient, the deposition rate slows down, and it is difficult to reach the required copper layer thickness within the specified time. The coating may also be uneven. When electroplating copper, the greater the current, the more electricity is passed per unit time, the more copper ions are involved in the reduction reaction, and the deposition thickness of the copper layer is also greater.

[0022] Furthermore, the copper-aluminum composite connector also includes an aluminum-silicon metal alloy layer, and the preparation method includes: using an aluminum plate (1) as a substrate; using an aluminum-silicon alloy as a target material, setting a vacuum degree of ≤1.5×10 -4 Pa, introduce argon gas with an argon pressure of 0.5 Pa and a deposition rate of 0.14 to 0.16 nm / s, anneal at 200 to 400° C., and plasma clean to obtain an aluminum-silicon metal alloy layer; magnetron sputtering and water electroplating are sequentially performed on the surface to form a copper layer (2), and the copper-aluminum composite connector is wound up.

[0023] Furthermore, the silicon content in the aluminum-silicon alloy is 1 to 5 wt%.

[0024] Furthermore, the thickness d4 of the aluminum-silicon metal alloy layer is 50-200 nm.

[0025] A further solution involves adding an aluminum-silicon alloy layer, which offers the following advantages: First, aluminum-silicon alloys are less expensive than pure copper; second, the silicon introduced into the aluminum-silicon alloy layer refines the grain size and reduces brittle intermetallic compounds at the Al / Cu interface, thereby improving bond strength and flexibility, and increasing the number of bending cycles. It's important to note that the thickness of this layer and the silicon content in the aluminum-silicon alloy should not be too high, as this can affect interfacial properties.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The copper-aluminum composite connector produced by this method can be used for battery cell terminals and external copper-aluminum composite connectors between packs and cells. Using an aluminum plate as the substrate, the surface is first magnetron sputtered, followed by a copper primer treatment and then a thickened copper layer via electroplating. The magnetron sputtering treatment at the copper-aluminum interface achieves a bonding strength exceeding 1000 N / m, ensuring structural stability. This product can also be used as external copper-aluminum composite connectors between battery cells and packs, replacing existing pure copper copper-aluminum composite connectors and significantly reducing cost and weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the present invention.

[0029] In the figure: 1. Aluminum plate; 2. Copper layer. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] It should be noted that the following parts are parts by mass, and all raw materials involved in the present invention are purchased from manufacturers without any special restrictions. Examples include: In the following embodiments, the chloride ions in the electroplating solution come from HCl.

[0032] The following examples are particularly described:

[0033] (1) The aluminum plate 1 is fixedly connected to the copper layer 2;

[0034] (2) The formula for the ratio of the density of the copper layer 2 to the density of the aluminum plate 1 is: the ratio of the density of the copper layer 2 to the density of the aluminum plate 1 = (density of the copper layer 2 / standard density of copper) / (density of the aluminum plate 1 / standard density of aluminum);

[0035] (3) The metal compound layer consists of copper and aluminum;

[0036] (4) The thickness d3 of the metal compound layer can be obtained by first spraying copper powder on the surface of the aluminum plate and then using laser melting technology to obtain the alloy layer, or by further hot pressing the connector after magnetron sputtering, or by using copper-aluminum alloy targets at the same time and directly magnetron sputtering to obtain the alloy layer.

[0037] (5) The surface roughness of the surface of the aluminum plate 1 in contact with the copper layer 2 can be achieved by rolling the aluminum plate 1.

[0038] Basic implementation process: A production process for copper-aluminum composite connectors, including the following steps:

[0039] Step 1: Using an aluminum plate 1 as a substrate, magnetron sputtering and water electroplating are sequentially performed on the surface of the aluminum plate 1 to form a copper layer 2, which is then rolled up to obtain a copper-aluminum composite connector;

[0040] The specific parameters of magnetron sputtering are: vacuum degree ≤ 0.01Pa; magnetron sputtering speed is 20m / min; target power is 6-10KW, target voltage is 200V; in argon atmosphere, argon flow rate is 20-50sccm;

[0041] The specific parameters of water electroplating are: water electroplating speed is 10m / min; in the electroplating solution, the sulfuric acid concentration is 100-130g / L, the copper sulfate concentration is 70-150g / L, and the chloride ion concentration is 50-60ppm; the current gradient is 5-35A; the initial density is 0.5-3A;

[0042] The thickness d1 of the above-mentioned copper layer 2 is 1 mm to 10 mm; the thickness d2 of the aluminum plate 1 is 2 to 20 mm; the thickness ratio of the copper layer 2 to the aluminum plate 1 is 0.05 < d1 / d2 < 2; the density ratio of the copper layer 2 to the density of the aluminum plate 1 is 0.65 to 0.75; the surface roughness of the surface of the aluminum plate 1 in contact with the copper layer 2 is < 20 μm; the copper-aluminum composite connector includes an intermetallic compound layer, the intermetallic compound layer components are copper and aluminum, and the thickness d3 of the intermetallic compound layer is 0 to 50 nm.

[0043] Example 1: Based on the basic example process, the process parameters of magnetron sputtering are as follows: vacuum degree of 0.01 Pa; magnetron sputtering speed of 20 m / min; target power of 6 kW, target voltage of 200 V; argon atmosphere, argon flow rate of 20 sccm;

[0044] The specific process parameters of water electroplating are as follows: water electroplating speed is 10m / min; in the electroplating solution, the sulfuric acid concentration is 100g / L, the copper sulfate concentration is 70g / L, and the chloride ion concentration is 50ppm; the current gradient is 35A; the initial density is 3A;

[0045] The thickness d1 of the above-mentioned copper layer 2 is 1 mm; the thickness d2 of the aluminum plate 1 is 20 mm; the thickness ratio of the copper layer 2 to the aluminum plate 1 is 0.05; the density ratio of the copper layer 2 to the density of the aluminum plate 1 is 0.6; the surface roughness of the contact surface of the aluminum plate 1 and the copper layer 2 is 4.0 μm; the copper-aluminum composite connector includes an intermetallic compound layer, the intermetallic compound layer components are copper and aluminum, and the thickness d3 of the intermetallic compound layer is 0 nm.

[0046] Example 2: Based on Example 1, the thickness d2 of the aluminum plate 1 is adjusted to 2 mm; the thickness ratio of the copper layer 2 to the aluminum plate 1 is 0.5.

[0047] Example 3: Based on Example 1, the thicknesses of the copper layer 2 and the aluminum plate 1 are adjusted to 10 mm and 20 mm respectively, with a thickness ratio of 0.5.

[0048] Example 4: Based on Example 1, the thickness of the copper layer 2 is adjusted to 10 mm, the thickness d2 of the aluminum plate 1 is adjusted to 5 mm; and the thickness ratio of the copper layer 2 to the aluminum plate 1 is 2.

[0049] Example 5: Based on Example 3, the density ratio of the copper layer 2 to the aluminum plate 1 is adjusted to 0.75; the current gradient is 10A; and the initial density is 0.5A.

[0050] Example 6: Based on Example 3, the density ratio of the copper layer 2 to the aluminum plate 1 is adjusted to 0.8; the current gradient is 5A; and the initial density is 0.5A.

[0051] Example 7: Based on Example 5, the surface roughness of the surface of the aluminum plate 1 in contact with the copper layer 2 was adjusted to 6 μm.

[0052] Example 8: Based on Example 5, the surface roughness of the surface of the aluminum plate 1 in contact with the copper layer 2 was adjusted to 10 μm.

[0053] Example 9: Based on Example 5, the surface roughness of the surface of the aluminum plate 1 in contact with the copper layer 2 was adjusted to 20 μm.

[0054] Example 10: Based on Example 5, the surface roughness of the surface of the aluminum plate 1 in contact with the copper layer 2 was adjusted to 25 μm.

[0055] Example 11: Based on Example 8, the thickness d3 of the intermetallic compound layer is adjusted to 5 nm, and the intermetallic compound layer is obtained by magnetron sputtering of a copper-aluminum alloy target with a copper-aluminum mass ratio of 1:4.

[0056] Example 12: Based on Example 11, the thickness d3 of the intermetallic compound layer is adjusted to 30 nm.

[0057] Example 13: Based on Example 11, the thickness d3 of the intermetallic compound layer is adjusted to 50 nm.

[0058] Example 14: Based on Example 11, the thickness d3 of the intermetallic compound layer is adjusted to 60 nm.

[0059] Example 15: Based on Example 8, the copper-aluminum composite connector further includes an aluminum-silicon metal alloy layer; the specific process is as follows: using aluminum plate 1 as the substrate; using aluminum-silicon alloy as the target, the distance from the substrate is 8 cm, and the vacuum degree is set to 1.5×10 -4Pa, introduce argon gas with an argon pressure of 0.5 Pa and a deposition rate of 0.15 nm / s, anneal at 300°C, and plasma clean to obtain an aluminum-silicon metal alloy layer; then magnetron sputter an intermetallic compound layer with a thickness d3 of 50 nm of a copper-aluminum alloy layer, and sequentially perform magnetron sputtering and water electroplating on the surface to form a copper layer 2, and roll it up to obtain a copper-aluminum composite connector;

[0060] The silicon content in the aluminum-silicon alloy is 5 wt %; the thickness d4 of the aluminum-silicon metal alloy layer is 100 nm; and the other parameters not mentioned are the same as those in Example 8.

[0061] Example 16: Based on Example 8, the copper-aluminum composite connector further includes an aluminum-silicon metal alloy layer; the specific process is as follows: using aluminum plate 1 as the substrate; using aluminum-silicon alloy as the target, the distance from the substrate is 8 cm, and the vacuum degree is set to 1.5×10 -4 Pa, introduce argon gas with an argon pressure of 0.5 Pa and a deposition rate of 0.15 nm / s, anneal at 300°C, and plasma clean to obtain an aluminum-silicon metal alloy layer; magnetron sputtering and water electroplating are sequentially performed on the surface to form a copper layer 2, and the copper-aluminum composite connector is obtained by winding;

[0062] The silicon content in the aluminum-silicon alloy is 5 wt %; the thickness d4 of the aluminum-silicon metal alloy layer is 100 nm; and the other parameters not mentioned are the same as those in Example 8.

[0063] Comparative Example 1: Based on Example 1, the thickness d2 of the aluminum plate 1 is adjusted to 4 mm; the thickness ratio of the copper layer 2 to the aluminum plate 1 is 2.5.

[0064] Test experiment 1: The copper-aluminum composite connectors prepared in Examples 1 to 16 and Comparative Example 1 were tested for their performance: (1) Peeling force test: The copper-aluminum composite connectors prepared in Examples 1 to 16 and Comparative Example 1 were tested for their peeling force performance. A sample with a width of 24 mm and a length of 300 mm was cut from the sample, and one end of the cut sample was folded with the adhesive surface to form a folded layer of about 12 mm long; the other end of the sample was pasted on one end of the steel plate and rolled twice with an adhesive tape roller at a speed of 600 mm / min; the sample was placed in an electronic peeling tester, and the test speed was set to 300 mm / min and the sample width was 24 mm; the equipment automatically recorded the force value during the peeling process and reported the peeling strength of the sample accordingly; (2) Bending resistance test: The copper-aluminum composite connectors prepared in Examples 1 to 16 and Comparative Example 1 were taken, and the above samples were cut into samples with a longitudinal width of 200 mm and a length of 250 mm, and cut into 5 15×150 mm long longitudinal strips using a sampler. The folding endurance tester was used to measure five times and take the average value. The measuring angle was set to 180° and the bending speed was set to 50 times / minute. The number of bends when the copper and aluminum were separated was recorded. The results are shown in Table 1.

[0065] Table 1

[0066]

[0067] In summary, this solution uses aluminum as the substrate and sequentially performs magnetron sputtering and water electroplating on the surface of the aluminum plate to form a copper layer; it effectively improves the peeling force and bending resistance of the copper-aluminum composite connector, achieving structural stability and reducing costs.

[0068] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A copper-aluminum composite connector, characterized in that: The connecting piece comprises an aluminum plate (1) and a copper layer (2); the aluminum plate (1) and the copper layer (2) are fixedly connected; the thickness d1 of the copper layer (2) is 0.1 mm to 40 mm; the thickness d2 of the aluminum plate (1) is ≤ 50 mm; and the thickness ratio of the copper layer (2) to the aluminum plate (1) is 0.05 < d1 / d2 < 2.

2. The copper-aluminum composite connector according to claim 1, characterized in that: The ratio of the density of the copper layer (2) to the density of the aluminum plate (1) is 0.65 to 0.

75.

3. The copper-aluminum composite connector according to claim 2, characterized in that: The surface roughness of the surface of the aluminum plate (1) in contact with the copper layer (2) is less than 20 μm, preferably 10 to 20 μm.

4. The copper-aluminum composite connector according to claim 2, characterized in that: The copper-aluminum composite connector further includes an intermetallic compound layer. The intermetallic compound layer comprises copper and aluminum. The thickness d3 of the intermetallic compound layer is 0 to 50 nm, preferably 5 to 50 nm.

5. The production process of a copper-aluminum composite connector according to any one of claims 1 to 4, characterized in that: The following steps are involved: An aluminum plate (1) is used as a substrate, magnetron sputtering and water electroplating are sequentially performed on the surface of the aluminum plate (1) to form a copper layer (2), and the copper layer (2) is rolled up to obtain a copper-aluminum composite connector.

6. The production process of a copper-aluminum composite connector according to claim 5, characterized in that: Before magnetron sputtering is used to form a copper layer on the aluminum plate, a rolling process is also included. The process parameters of the magnetron sputtering are: vacuum degree ≤ 0.01 Pa; magnetron sputtering speed is 20 m / min; target power is 6 to 10 kW, target voltage is 200 V; in an argon atmosphere, the argon flow rate is 20 to 50 sccm.

7. The production process of a copper-aluminum composite connector according to claim 5, characterized in that: The process parameters of the water electroplating are: a water electroplating speed of 10 m / min; a sulfuric acid concentration of 100-130 g / L, a copper sulfate concentration of 70-150 g / L, and a chloride ion concentration of 50-60 ppm in the electroplating solution; a current gradient of 5-35 A, and an initial current of 0.5-3 A.

8. The production process of a copper-aluminum composite connector according to claim 7, characterized in that: The copper-aluminum composite connector also includes an aluminum-silicon metal alloy layer, and the preparation method includes: using an aluminum plate (1) as a substrate; using an aluminum-silicon alloy as a target material, setting a vacuum degree of ≤1.5×10 -4 Pa, introduce argon gas with an argon pressure of 0.5 Pa and a deposition rate of 0.14 to 0.16 nm / s, anneal at 200 to 400° C., and plasma clean to obtain an aluminum-silicon metal alloy layer; magnetron sputtering and water electroplating are sequentially performed on the surface to form a copper layer (2), and the copper-aluminum composite connector is wound up.

9. The production process of a copper-aluminum composite connector according to claim 8, characterized in that: The silicon content in the aluminum-silicon alloy is 1-5 wt%.

10. The production process of a copper-aluminum composite connector according to claim 8, characterized in that: The thickness d4 of the aluminum-silicon metal alloy layer is 50-200 nm.

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