Welding Method for Multi-Layer Tab of Battery

Abstract

The present invention provides a welding method for a multi-layer tab of a battery, which includes: Step S1: pre-welding the multi-layer tab; Step S2: pressing the multi-layer tab onto the workpiece to be welded, and scanning and heating the surface of the multi-layer tab by laser; Step S3: performing laser final welding on the multi-layer tab and the workpiece to be welded. A scanning heating step is added before the laser final welding of the multi-layer tab and the workpiece to be welded. In the scanning heating step, the surface of the multi-layer tab is scanned and filled by a laser, forcing the surface of the pre-welded area to be heated, slightly melted or textured, thereby improving the laser absorption rate of the tab and making the welding quality of the subsequent laser final welding higher.

Description

Technical Field

[0001] The present invention relates to the technical field of battery production processes, and particularly relates to a welding method for multi-layer tabs of a battery. Background Art

[0002] With the rapid development of power battery technology, laser technology has been increasingly widely used in the production process of power batteries. In the welding process of multi-layer tabs and connecting pieces or multi-layer tabs and covers, the trend of laser final welding gradually replacing ultrasonic final welding is becoming more and more obvious. However, since the multi-layer tabs are made of aluminum or copper, due to the high-reflectivity optical properties of copper and aluminum themselves, the laser absorption rate at room temperature is relatively low (about 10% for aluminum at room temperature and about 5% for pure copper), and it is difficult to effectively guarantee the laser welding quality. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defect of poor laser welding quality of multi-layer tabs of a battery in the prior art, so as to provide a welding method for multi-layer tabs of a battery.

[0004] To solve the above problems, the present invention provides a welding method for multi-layer tabs of a battery, including: Step S1: pre-welding the multi-layer tabs; Step S2: pressing the multi-layer tabs on the workpiece to be welded, and scanning and heating the surface of the multi-layer tabs by laser; Step S3: performing laser final welding on the multi-layer tabs and the workpiece to be welded by laser.

[0005] Optionally, in Step S2: if the material of the multi-layer tabs is copper, the power of the laser is in the range of 3000W to 4000W, and the scanning speed of the galvanometer welding head is in the range of 400mm / s to 800mm / s; if the material of the multi-layer tabs is aluminum, the power of the laser is in the range of 1500W to 2500W, and the scanning speed of the galvanometer welding head is in the range of 400mm / s to 800mm / s.

[0006] Optionally, in Step S2, the galvanometer welding head is defocused.

[0007] Optionally, the defocus value of the galvanometer welding head is in the range of +10mm to +20mm.

[0008] Optionally, the scanned area is less than or equal to the pre-welding area and greater than the laser final welding area.

[0009] Optionally, in Step S2, the laser scans in a linear trajectory or a Z-shaped trajectory.

[0010] Optionally, after performing Step S1 and before performing Step S2, the surfaces of the multi-layer tabs and the workpiece to be welded are cleaned.

[0011] Optionally, in step S3, the trajectory of the final laser welding includes a starting segment, an intermediate segment, and an ending segment. Among them, the galvanometer welding head welds the starting segment with negative defocus; the galvanometer welding head welds the ending segment with positive defocus.

[0012] Optionally, the value of the negative defocus is in the range of -1 mm to -5 mm, and the value of the positive defocus is in the range of +1 mm to +5 mm.

[0013] Optionally, when laser welding the intermediate segment, the defocus value of the galvanometer welding head is in the range of -1 mm to +1 mm.

[0014] Optionally, the length ratio of the starting segment, the intermediate segment, and the ending segment is 1:2:1.

[0015] The present invention has the following advantages:

[0016] By using the technical solution of the present invention, a scanning heating step is added before the final laser welding of the multi-layer tabs and the workpiece to be welded. In the scanning heating step, the surface of the multi-layer tabs is scanned and filled with laser, forcing the surface of the pre-welding area to be heated, micro-melted or textured, thereby improving the laser absorption rate of the tabs and making the welding quality of the subsequent final laser welding higher. Therefore, the technical solution of the present invention solves the defect of poor laser welding quality of the multi-layer tabs of the battery in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 shows a schematic flow chart of the welding method for the multi-layer tabs of the battery of the present invention;

[0019] Figure 2 shows Figure 1 a schematic diagram of the pre-welding area on the surface of the multi-layer tabs after pre-welding in the welding method in;

[0020] Figure 3 shows Figure 2 a schematic diagram of a linear trajectory scan in the pre-welding area in;

[0021] Figure 4 shows Figure 2 a schematic diagram of a Z-shaped trajectory scan in the pre-welding area in;

[0022] Figure 5 shows Figure 2Schematic diagram after final welding of the pre-welding area; and

[0023] Figure 6 Shows Figure 1 Schematic diagram of the position change of the galvanometer welding head on the welding track during the laser final welding of the welding method in the middle.

[0024] Description of reference numerals:

[0025] 10. Tab; 20. Component to be welded; 30. Galvanometer welding head. Detailed implementation manners

[0026] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0028] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0029] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] As Figure 1 shown, the welding method of the battery multi-layer tabs in this embodiment includes:

[0031] Step S1: Pre-weld the multi-layer tabs 10;

[0032] Step S2: Press the multi-layer tabs 10 onto the workpiece to be welded 20, and scan and heat the surface of the multi-layer tabs 10 with a laser;

[0033] Step S3: Perform final laser welding on the multi-layer tabs 10 and the workpiece to be welded with a laser.

[0034] Using the technical solution of this embodiment, a scanning heating step is added before the final laser welding of the multi-layer tabs 10 and the workpiece to be welded 20. In the scanning heating step, the surface of the multi-layer tabs 10 is scanned and filled with a laser, forcing the surface of the pre-welding area to be heated, micro-melted or textured, thereby improving the laser absorption rate of the tabs 10 and making the welding quality of the subsequent final laser welding higher. Therefore, the technical solution of this embodiment solves the defect of poor laser welding quality of the multi-layer battery tabs in the prior art.

[0035] It should be noted that the pre-welding in the above step S1 is ultrasonic pre-welding. After the multi-layer tabs 10 are subjected to the above ultrasonic pre-welding treatment, a pre-welding area as shown in Figure 2 is formed and meets certain density requirements.

[0036] It should be noted that the above step S2 is also a laser pre-treatment step. The pre-welding area is scanned with a laser, and the purpose is to heat the surface of the multi-layer tabs 10 to make it micro-melted or textured. After performing step S2, the laser absorption rate of the surface of the multi-layer tabs 10 is increased.

[0037] When performing step S3, final laser welding is performed on the surface of the multi-layer tabs 10. Since the laser absorption rate of the surface of the multi-layer tabs 10 is increased in step S2, the quality of the final laser welding in step S3 is higher.

[0038] It should be noted that the above workpiece to be welded 20 is a transition piece or a battery cover plate.

[0039] Furthermore, in the above step S2, according to the different materials of the multi-layer tabs 10, the scanning parameters of the laser are also different. Specifically:

[0040] If the material of the multi-layer tabs 10 is copper, the power of the laser is in the range of 3000W to 4000W, and the scanning speed of the galvanometer welding head 30 is in the range of 400mm / s to 800mm / s;

[0041] If the material of the multi-layer tabs is aluminum, the power of the laser is in the range of 1500W to 2500W, and the scanning speed of the galvanometer welding head 30 is in the range of 400mm / s to 800mm / s.

[0042] As Figure 1As shown, in the technical solution of this embodiment, in step S2, the galvanometer welding head 30 is defocused. After the galvanometer welding head 30 is defocused, the spot area acting on the surface of the multi-layer tab 10 increases, which is beneficial to increasing the scanning area of the laser.

[0043] Preferably, the defocus value of the galvanometer welding head 30 is in the range of +10 mm to +20 mm. Specifically, the focus after defocus is located above the surface of the multi-layer tab 10, that is, the defocus value is positive.

[0044] As Figure 3 shown, in the technical solution of this embodiment, the scanned area is less than or equal to the pre-welding area and greater than the laser final welding area.

[0045] In addition, when performing the above step S2, a fixture is used to clamp the multi-layer tab 10 and the workpiece to be welded 20, and no air is left between the two.

[0046] As Figure 3 and Figure 4 shown, in the above step S2, the laser can be scanned in a linear trajectory or a Z-shaped trajectory. Figure 3 shows a schematic diagram of the laser scanned in a linear trajectory, Figure 4 shows a schematic diagram of the laser scanned in a Z-shaped trajectory.

[0047] Preferably, for the filling distance and angle of the above linear trajectory and Z-shaped trajectory, those skilled in the art can determine according to actual needs.

[0048] Preferably, after performing step S1 and before performing step S2, the surfaces of the multi-layer tab 10 and the workpiece to be welded 20 are cleaned. Specifically, before the laser pretreatment (that is, before performing step S2), the surfaces of the multi-layer tab 10 and the workpiece to be welded 20 are cleaned with alcohol.

[0049] As Figure 1 、 Figure 5 and Figure 6 shown, in the technical solution of this embodiment, in step S3, the laser final welding trajectory includes a starting segment, an intermediate segment, and an ending segment. Among them, the galvanometer welding head 30 welds the starting segment with negative defocus, and the galvanometer welding head 30 welds the ending segment with positive defocus.

[0050] The above laser final welding method can improve the consistency of the weld penetration depth. Specifically:

[0051] In the prior art, the laser final welding methods after ultrasonic pre-welding include single-pass spiral laser welding, double-pass spiral laser welding, laser pre-welding plus laser final welding, laser final welding plus laser edge remelting, etc. However, the above laser welding methods have the following problems:

[0052] In single-pass spiral laser welding, it is difficult to control the consistency of the weld penetration depth. The starting section of the weld is relatively shallow, the middle section of the weld is at an appropriate position, the ending section of the weld is relatively deep, the workpiece to be welded is prone to being welded through, and there are porosity-like defects at the weld edge, resulting in poor mechanical properties of the weld.

[0053] In double-pass spiral welding, in addition to the difficulty in controlling the consistency of the weld penetration depth, the first-pass laser welding generates heat accumulation on the surface, and the parameters of the second-pass laser welding are different from those of the first process, making the process adjustment difficult.

[0054] In laser pre-welding plus laser final welding, there is also the problem of difficulty in controlling the consistency of the weld penetration depth.

[0055] In laser final welding plus laser edge remelting, the remelting on both sides of the main weld eliminates the porosity and crack defects of the weld. In addition to the difficulty in controlling the consistency of the weld penetration depth, the welding process is long and the efficiency is low.

[0056] In this embodiment, the trajectory of the laser final welding is divided into a starting section, a middle section, and an ending section. In the welding of the starting section, the galvanometer welding head 30 welds the multi-layer tabs 10 and the workpiece to be welded 20 in a negative defocus manner, with relatively high welding heat to ensure that the multi-layer tabs 10 and the workpiece to be welded 20 are welded through. In the welding of the ending section, the galvanometer welding head 30 welds the multi-layer tabs 10 and the workpiece to be welded 20 in a positive defocus manner, with relatively low welding heat to prevent the multi-layer tabs 10 and the workpiece to be welded 20 from being welded through.

[0057] In the above laser final welding method, the focal position changes in real time relative to the workpiece surface, thereby realizing zoom welding, which can ensure the consistency of the weld penetration depth to a certain extent.

[0058] Preferably, the value of the above negative defocus is in the range of -1 mm to -5 mm, and the value of the above positive defocus is in the range of +1 mm to +5 mm.

[0059] Furthermore, when welding the middle section of the laser, the galvanometer welding head 30 welds in a zero defocus manner. Specifically, the defocus value of the galvanometer welding head 30 is in the range of -1 mm to +1 mm.

[0060] In addition, in the above laser final welding, the laser is scanned in a spiral manner.

[0061] Furthermore, in the above laser final welding process, it varies according to the number of layers, material of the tabs 10, and the thickness of the workpiece to be welded 20. Specifically, when welding the copper multi-layer tabs 10, the laser power is 3500 W to 4500 W, and the welding speed is 300 mm / s to 500 mm / s. When welding the aluminum multi-layer tabs 10, the laser power is 2000 W to 3500 W, and the welding speed is 300 to 500 mm / s.

[0062] Of course, those skilled in the art can adjust each of the above parameters according to the actual working conditions.

[0063] Preferably, the length ratio of the starting segment, the middle segment, and the ending segment is 1:2:1. That is, the starting segment accounts for 25% of the entire final welding trajectory, the middle segment accounts for 50% of the entire final welding trajectory, and the ending segment accounts for 25% of the entire final welding trajectory.

[0064] Of course, those skilled in the art can adjust the ratio of the above starting segment, middle segment, and ending segment in the entire final welding trajectory according to the actual working conditions.

[0065] Combined with Figure 6 As shown, in this embodiment, the way to achieve the above-mentioned zoom welding is to adjust the vertical position of the galvanometer welding head 30 during the welding process. Specifically, during the welding of the initial segment, the position of the galvanometer welding head 30 is relatively low, so that the focal point position is below the surface of the multi-layer tab 10, thereby achieving negative defocus. During the welding of the middle segment, the position of the galvanometer welding head 30 rises (returns to the initial position), thereby raising the focal point position and achieving zero defocus. During the welding of the ending segment, the position of the galvanometer welding head 30 continues to rise, thereby raising the focal point position again and achieving positive zero defocus.

[0066] Of course, other methods can also be used to achieve the above-mentioned zoom welding. For example, during the welding process, the position of the collimating mirror in the laser welding device is adjusted to achieve the adjustment of the focal point position. Compared with the above method of adjusting the position of the galvanometer welding head 30, this method does not need to adjust the relative position of the laser welding device and the workpiece below, and the process is simpler.

[0067] According to the above description, the welding method of the battery multi-layer tab in this embodiment has the following advantages:

[0068] 1. Before the final laser welding, the galvanometer welding head is used to preheat the surface of the multi-layer tab in a large defocus mode. The large spot acts on the surface to be welded in advance, making the surface of the multi-layer tab slightly melted, heated or textured, and increasing the laser absorption rate of the final welding;

[0069] 2. During the final laser welding, the focal point position changes in real time relative to the surface of the workpiece and zoom welding is achieved, which can ensure the consistency of the weld penetration to a certain extent.

[0070] Obviously, the above embodiments are only examples given for clear illustration, and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A welding method for multi-layer tabs of a battery, characterized in that, Including: Step S1: Pre-weld the multi-layer tabs (10). Step S2: Press the multi-layer tabs (10) onto the workpiece to be welded (20), and scan and heat the surface of the multi-layer tabs (10) with a laser. Through the laser scanning and heating, perform a scanning fill on the surface of the multi-layer tabs (10), forcing the surface of the pre-weld area to be heated, micro-melted or textured to improve the laser absorption rate of the multi-layer tabs (10). Step S3: Perform a final laser weld on the multi-layer tabs (10) and the workpiece to be welded. The trajectory of the final laser weld formed by the galvanometer welding head (30) of the laser includes a starting segment, an intermediate segment, and an ending segment. Among them, The galvanometer welding head (30) welds the starting segment with negative defocus. The galvanometer welding head (30) welds the ending segment with positive defocus. Among them, the area of the laser scanning and heating is less than or equal to the pre-weld area and greater than the final laser weld area. Before performing Step S2, clean the surfaces of the multi-layer tabs and the workpiece to be welded.

2. The welding method according to claim 1, characterized in that, In Step S2: If the material of the multi-layer tabs (10) is copper, the power of the laser is in the range of 3000W to 4000W, and the scanning speed of the galvanometer welding head (30) is in the range of 400 mm / s to 800 mm / s. If the material of the multi-layer tabs (10) is aluminum, the power of the laser is in the range of 1500W to 2500W, and the scanning speed of the galvanometer welding head (30) is in the range of 400 mm / s to 800 mm / s.

3. The welding method according to claim 1, characterized in that, In Step S2, the galvanometer welding head (30) performs defocusing.

4. The welding method according to claim 3, characterized in that, The defocus value of the galvanometer welding head (30) is in the range of +10mm to +20mm.

5. The welding method according to claim 1, characterized in that, In Step S2, the laser scans in a linear trajectory or a Z-shaped trajectory.

6. The welding method according to claim 1, characterized in that, The value of the negative defocus is in the range of -1mm to -5mm, and the value of the positive defocus is in the range of +1mm to +5mm.

7. The welding method according to claim 1, characterized in that, When laser-welding the intermediate segment, the defocus value of the galvanometer welding head (30) is in the range of -1mm to +1mm.

8. The welding method according to claim 1, characterized in that, The length ratio of the starting segment, the intermediate segment, and the ending segment is 1:2:1.

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