CN115106653A - Welding method of battery multilayer tab - Google Patents

Abstract

The invention provides a welding method of a battery multilayer tab, which comprises the following steps: step S1: pre-welding the multilayer tabs; step S2: pressing a plurality of layers of tabs on a piece to be welded, and scanning and heating the surfaces of the tabs through laser; step S3: and performing laser final welding on the multilayer tab and the to-be-welded piece through laser. And adding a scanning heating step before the laser final welding of the multilayer tab and the piece to be welded. In the scanning heating step, the surface of the multilayer tab is subjected to scanning filling by a laser, so that the surface of the prewelding area is forced to be heated, micro-melted or roughened, the laser absorption rate of the tab is improved, and the welding quality of subsequent laser final welding is higher.

Description

Welding method of battery multilayer tab

Technical Field

The invention relates to the technical field of battery production processes, in particular to a welding method of a battery multilayer tab.

Background

With the rapid development of power battery technology, the application of laser technology in the production process of power batteries is more and more extensive. In the welding process of the multilayer tab and the connecting sheet or the multilayer tab and the cover plate, the trend that laser final welding gradually replaces ultrasonic final welding is more and more obvious. However, the multilayer tab is made of aluminum or copper, and due to the high inverse optical characteristics of copper and aluminum, the laser absorption rate at room temperature is low (about 10% of aluminum at room temperature and about 5% of red copper), and the laser welding quality is difficult to effectively guarantee.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is to overcome the defect of poor laser welding quality of the battery multilayer tab in the prior art, thereby providing a welding method of the battery multilayer tab.

In order to solve the problems, the invention provides a welding method of a battery multilayer tab, which comprises the following steps: step S1: pre-welding the multilayer tabs; step S2: pressing a plurality of layers of tabs on a to-be-welded part, and scanning and heating the surfaces of the tabs through laser; step S3: and performing laser final welding on the multilayer tab and the to-be-welded piece through laser.

Alternatively, in step S2: if the multilayer tab is made of copper, the power of a laser is within the range of 3000W to 4000W, and the scanning speed of a galvanometer welding head is within the range of 400mm/s to 800 mm/s; if the material of the multilayer tab 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 800 mm/s.

Alternatively, in step S2, the galvanometer welding head performs defocusing.

Optionally, the galvanometer welded joint has a defocus value in the range of +10mm to +20 mm.

Optionally, the scanned area is less than or equal to the pre-weld area and greater than the laser final weld area.

Alternatively, in step S2, the laser is scanned in a linear track or a Z-track.

Optionally, after the step S1 is performed, and before the step S2 is performed, the surfaces of the multi-layer tab and the surfaces of the pieces to be welded are cleaned.

Optionally, in step S3, the laser final welding trajectory includes a starting segment, a middle segment and an ending segment, wherein the galvanometer welding head welds the starting segment with negative defocus; and the galvanometer welding head welds the end section by positive defocusing.

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

Optionally, the defocusing value of the galvanometer welding head is in the range of-1 mm to +1mm when the middle section is laser welded.

Optionally, the ratio of the lengths of the starting section, the intermediate section and the ending section is 1:2: 1.

The invention has the following advantages:

by utilizing the technical scheme of the invention, a scanning and heating step is added before the laser final welding of the multilayer tab and the part to be welded. In the scanning heating step, the surfaces of the multilayer tabs are filled in a scanning mode through laser, so that the surfaces of the prewelding areas are forced to be heated, micro-melted or roughened, the laser absorption rate of the tabs is improved, and the welding quality of subsequent laser final welding is higher. Therefore, the technical scheme of the invention overcomes the defect of poor laser welding quality of the battery multilayer tab in the prior art.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a schematic flow chart illustrating a method for welding a multi-layer tab of a battery according to the present invention;

fig. 2 shows a schematic representation of a pre-weld area of the pre-welded multi-layer tab surface of the welding method of fig. 1;

FIG. 3 shows a schematic view of a straight-line trace scan in the pre-weld area of FIG. 2;

FIG. 4 shows a schematic view of a Z-track scan in the pre-weld area of FIG. 2;

FIG. 5 shows a schematic view of the pre-weld area of FIG. 2 after final welding; and

fig. 6 is a schematic diagram showing a change in position of a galvanometer welding head on a welding track in laser final welding of the welding method in fig. 1.

Description of the reference numerals:

10. a tab; 20. a part to be welded; 30. and (5) welding a vibrating mirror.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

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

As shown in fig. 1, the method for welding the multi-layer tab of the battery of the present embodiment includes:

step S1: pre-welding the multilayer tab 10;

step S2: compressing the multilayer tab 10 on a to-be-welded piece 20, and scanning and heating the surface of the multilayer tab 10 by laser;

step S3: and performing laser final welding on the multilayer tab 10 and the piece to be welded by laser.

With the technical solution of this embodiment, a scanning heating step is added before the laser final welding of the multilayer tab 10 and the piece to be welded 20. In the scanning heating step, the surface of the multilayer tab 10 is filled in a scanning manner by laser, so that the surface of the prewelding area is forced to be heated, micro-melted or roughened, and the laser absorption rate of the tab 10 is improved, and the welding quality of subsequent laser final welding is higher. Therefore, the technical scheme of the embodiment overcomes the defect of poor laser welding quality of the multi-layer battery tab in the prior art.

Note that the pre-welding in step S1 is ultrasonic pre-welding. After the ultrasonic pre-welding treatment is performed on the multilayer tab 10, a pre-welded region as shown in fig. 2 is formed, and a certain density requirement is met.

In step S2, that is, the laser preprocessing step, the prewelding area is scanned by laser, and the purpose of the laser preprocessing step is to heat the surface of the multilayer tab 10 so as to slightly melt or roughen the surface. After step S2 is performed, the laser absorption rate of the surface of the multilayer tab 10 is improved.

In step S3, the surface of the multilayer tab 10 is subjected to laser final welding. Since the surface laser absorption rate of the multilayer tab 10 is increased in step S2, the laser final welding quality in step S3 is higher.

The to-be-welded member 20 is an interposer or a battery cover plate.

Further, in step S2, the scanning parameters of the laser are different according to the material of the multilayer tab 10, specifically:

if the material of the multilayer tab 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 800 mm/s;

if the multi-layer tab is made of 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 800 mm/s.

As shown in fig. 1, according to the present embodiment, in step S2, the galvanometer welded joint 30 is defocused. After the galvanometer welding head 30 is defocused, the area of light spots acting on the surface of the multilayer tab 10 is increased, which is beneficial to increasing the scanning area of a laser.

Preferably, the galvanometer welded joint 30 has a defocus value in the range of +10mm to +20 mm. Specifically, the focus after defocusing is located above the surface of the multilayer tab 10, that is, the defocusing value is a positive value.

As shown in fig. 3, in the technical solution of this embodiment, the scanned area is smaller than or equal to the pre-welding area and larger than the laser final welding area.

Further, in performing the above-described step S2, the multilayer tab 10 and the to-be-welded piece 20 are clamped using a jig so that air does not remain therebetween.

As shown in fig. 3 and 4, in the above step S2, the laser may be scanned in a linear track or a Z track. Fig. 3 shows a schematic view of the laser scanning in a linear track and fig. 4 shows a schematic view of the scanning in a Z-track.

Preferably, the filling distance and the filling angle of the linear tracks and the Z-shaped tracks can be determined by those skilled in the art according to actual needs.

Preferably, after the step S1 is performed and before the step S2 is performed, the surfaces of the multi-layered tab 10 and the surfaces of the pieces to be welded 20 are cleaned. Specifically, before the laser pretreatment (i.e., before the step S2), the surfaces of the multi-layered tab 10 and the piece to be welded 20 are cleaned with alcohol.

As shown in fig. 1, 5 and 6, in the technical solution of the present embodiment, in step S3, the trajectory of the laser final welding includes a start segment, an intermediate segment and an end segment, wherein the galvanometer welding head 30 welds the start segment with a negative defocus and the galvanometer welding head 30 welds the end segment with a positive defocus.

The laser final welding method can improve the consistency of weld penetration, and specifically comprises the following steps:

in the prior art, the laser final welding mode after ultrasonic pre-welding includes single-pass spiral laser welding, double-pass spiral laser welding, laser pre-welding plus laser final welding, laser final welding plus laser edge remelting and the like. However, the above laser welding method has the following problems:

in single-channel spiral laser welding, the weld penetration consistency is difficult to control, the initial position section of the weld is shallow, the middle position of the weld is moderate, the end position of the weld is deep, a part to be welded is easy to weld through, the edge of the weld has air hole defects, and the mechanical property of the weld is poor.

In the double-channel spiral welding, except that the weld penetration consistency is difficult to control, the first laser welding process generates heat accumulation on the surface, the second laser welding process has different parameters from the first process, and the process adjustment difficulty is high.

The problem that the weld penetration consistency is difficult to control also exists in laser prewelding and laser final welding.

In laser final welding and laser edge remelting, the remelting on two sides of a main welding seam eliminates the defects of welding seam air holes and cracks, and besides the welding seam fusion depth consistency is difficult to control, the welding process is longer and the efficiency is lower.

In this embodiment, the trajectory of the laser final weld is divided into a start section, an intermediate section, and an end section. In the initial welding, the galvanometer welding head 30 welds the multilayer tab 10 and the to-be-welded piece 20 in a negative defocusing mode, the welding heat is high, and the multilayer tab 10 and the to-be-welded piece 20 are ensured to be welded through. In the welding of the final segment, the galvanometer welding head 30 welds the multilayer tab 10 and the piece to be welded 20 in a positive defocusing mode, the welding heat is low, and the multilayer tab 10 and the piece to be welded 20 are prevented from being welded through.

In the laser final welding method, the focal position changes in real time relative to the surface of the workpiece, so that the zooming welding is realized, and the consistency of weld penetration can be ensured to a certain degree.

Preferably, 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 +1mm to +5 mm.

Further, when the middle section of the laser welding is performed, the galvanometer welding head 30 performs welding in a zero-defocus manner. Specifically, the defocus value of the galvanometer welded joint 30 is in the range of-1 mm to +1 mm.

In the laser final welding, the laser beam is scanned spirally.

Further, in the above laser final welding process, there is a difference according to the number of layers, materials, and thicknesses of the pieces to be welded 20 of the tab 10. Specifically, the copper multilayer tab 10 has a laser power of 3500W to 4500W and a welding speed of 300mm/s to 500mm/s during welding. The aluminum multi-layer tab 10 has the laser power of 2000W to 3500W during welding and the welding speed of 300mm/s to 500 mm/s.

Of course, the above parameters can be adjusted by those skilled in the art according to the actual working conditions.

Preferably, the ratio of the lengths of the starting section, the intermediate section and the ending section is 1:2: 1. Namely, the initial section accounts for 25% of the whole final welding track, the middle section accounts for 50% of the whole final welding track, and the final section accounts for 25% of the whole final welding track.

Of course, the ratio of the initial section, the middle section and the final section to the whole final welding track can be adjusted by those skilled in the art according to the actual working condition.

As shown in fig. 6, in the present embodiment, the zoom welding is performed by adjusting the vertical position of the galvanometer welding head 30 during the welding process. Specifically, when the welding is performed in the initial stage, the galvanometer welding head 30 is positioned low, and the focus position is positioned below the surface of the multilayer tab 10, so that negative defocusing is realized. During the middle period of welding, the galvanometer welding head 30 is raised (returned to the initial position) to raise the position of the focal point, thereby achieving zero defocus. When the welding is completed, the position of the galvanometer welding head 30 is continuously raised, and the position of the focus is again raised, thereby realizing zero defocus.

Of course, the zoom welding can be achieved in other ways, for example, the position of the collimating lens in the laser welding device is adjusted during the welding process, so as to achieve the adjustment of the focal position. Compared with the method for adjusting the position of the galvanometer welding head 30, the method does not need to adjust the relative position of the laser welding device and the lower workpiece, and the process is simpler.

According to the above description, the welding method of the battery multilayer tab in the present embodiment has the following advantages:

1. the laser final welding money adopts a large defocusing mode of a vibrating mirror welding head to preheat the surfaces of the multilayer tabs, and large light spots act on the surfaces to be welded in advance, so that the surfaces of the multilayer tabs are slightly dissolved, heated or roughened, and the laser absorption rate of final welding is increased;

2. in laser final welding, the focal position changes in real time relative to the surface of a workpiece, zooming welding is realized, and the consistency of weld penetration can be ensured to a certain degree.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (11)

1. A method for welding a multi-layer tab of a battery is characterized by comprising the following steps:

step S1: pre-welding the multilayer tab (10);

step S2: the multilayer tab (10) is pressed on a part to be welded (20), and the surface of the multilayer tab (10) is scanned and heated through laser;

step S3: and carrying out laser final welding on the multilayer tab (10) and the piece to be welded by laser.

2. The welding method according to claim 1, characterized in that in said step S2:

if the material of the multilayer tab (10) is copper, the power of a laser is within the range of 3000W to 4000W, and the scanning speed of a galvanometer welding head (30) is within the range of 400mm/s to 800 mm/s;

if the material of the multilayer tab (10) is aluminum, the power of a 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 800 mm/s.

3. The welding method according to claim 1, characterized in that in the step S2, the galvanometer welding head (30) is defocused.

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 +20 mm.

5. The welding method of claim 1, wherein the scanned area is less than or equal to a pre-weld area and greater than a laser final weld area.

6. The welding method according to claim 1, wherein in the step S2, the laser is scanned in a linear trajectory or a Z-shaped trajectory.

7. The welding method according to claim 1, characterized in that after the step S1 is performed and before the step S2 is performed, the surfaces of the multilayer tab (10) and the surface of the member to be welded (20) are cleaned.

8. The welding method according to any one of claims 1 to 7, characterized in that in the step S3, the trajectory of the laser final welding includes a start section, an intermediate section, and an end section, wherein,

the galvanometer welding head (30) welds the initial section with negative defocusing;

the galvanometer welding head (30) welds the end section by positive defocusing.

9. The welding method according to claim 8, wherein the negative defocus value is in a range of-1 mm to-5 mm, and the positive defocus value is in a range of +1mm to +5 mm.

10. The welding method according to claim 8, wherein a defocus value of the galvanometer-welded joint (30) when the intermediate section is laser-welded is in a range of-1 mm to +1 mm.

11. The welding method of claim 8, wherein the starting section, the middle section, and the ending section have a length ratio of 1:2: 1.

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