A method for laser welding of tabs of high-capacity lithium batteries

Abstract

The application provides a large-capacity lithium battery tab laser welding method, comprising the following steps: S1: ultrasonic pre-welding of the tab of the battery cell; S2: aligning and pressing the pre-welded tab of the battery cell and the connecting piece; S3: first cross laser welding of the tab of the battery cell; S4: dust removal of the surface of the tab of the battery cell; and S5: second cross laser welding of the tab of the battery cell. The large-capacity lithium battery tab laser welding method can ensure the welding area required by the large-size and large-capacity battery cell by forming multiple welding marks through cross laser welding, and effectively reduces the internal resistance of the battery cell. The application avoids the influence of laser interference and mutual splashing of metal dust when two welding heads are simultaneously used for same-direction welding through twice cross welding, and reduces the influence of metal residue left and uneven temperature distribution when two welding marks are sequentially welded by a single welding head, thereby greatly improving the welding efficiency and product qualification rate.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, and in particular relates to a laser welding method for the tabs of a large-capacity lithium battery. Background Technology

[0002] Lithium-ion batteries have become the energy source for electronic products, electric vehicles, and energy storage due to their high energy density and rechargeability. The production process of lithium-ion batteries is complex and rigorous, with laser welding of the tabs being an essential step in most lithium battery manufacturing processes.

[0003] Current electrode laser welding processes primarily involve pre-welding the electrodes and then joining the connecting piece to the pre-welded electrodes using laser welding. Generally, a single weld line of suitable size is sufficient to meet the process requirements, depending on the design and process specifications. However, for large-size, high-capacity battery cells, a larger weld area is often needed to ensure the overall current-carrying area of ​​the cell, thereby reducing internal resistance. Increasing the area of ​​a single weld line is technically challenging.

[0004] Currently, most high-capacity lithium batteries use two welding marks to solve the above problems. However, when two laser welding heads are used to weld two marks simultaneously, interference will occur between the two laser beams, leading to issues such as explosions and over-welding. When using a single laser welding head to weld two marks sequentially, not only is the efficiency low, but the metal slag left on the tab surface by the first weld mark will seriously affect the welding of the second weld mark. Summary of the Invention

[0005] The technical problem to be solved by this invention is how to improve the welding efficiency and product qualification rate of large-capacity lithium batteries.

[0006] The present invention solves the above-mentioned technical problems through the following technical means: This invention provides a method for laser welding of electrode tabs in high-capacity lithium batteries, comprising the following steps: S1: Perform ultrasonic pre-welding on the battery cell tabs; S2: Align and press the pre-welded battery cell tabs with the connecting piece; S3: Perform the first cross-laser welding on the battery cell tabs; S4: Remove dust from the surface of the battery cell tabs; S5: Perform a second cross-laser welding on the battery cell tabs.

[0007] Beneficial Effects: The laser welding method for large-capacity lithium battery tabs of this invention, through cross-laser welding to form multiple weld marks, ensures the required weld mark area for large-size, high-capacity cells, effectively reducing the internal resistance of the cells. This application also avoids the effects of laser interference and metal dust splashing that occur when two welding heads are used simultaneously in the same direction; it also reduces the impact of metal residue and uneven temperature distribution caused by sequentially welding two weld marks with a single welding head, greatly improving welding efficiency and product qualification rate.

[0008] Preferably, in step S1, the battery cell tabs include a positive tab and a negative tab; the surface of the battery cell tabs pre-welded by the ultrasonic welding process must be clean and free of contamination.

[0009] Preferably, the number of positive electrode tabs is ≤60 layers; the number of negative electrode tabs is ≤61 layers.

[0010] Preferably, the ultrasonic pre-welding parameters for the positive electrode foil are: energy of 600±100J, pressure of 4±1bar, and power of 500±50W; and the ultrasonic pre-welding parameters for the negative electrode foil are: energy of 950±50J, pressure of 4±1bar, and power of 650±50W.

[0011] Preferably, in step S1, the electrode tabs of the battery cell after ultrasonic pre-welding form a pre-welded area.

[0012] Preferably, in step S2, the alignment and clamping are accomplished by a fixing device.

[0013] Preferably, the cross laser welding involves parallel welding paths and opposite welding directions.

[0014] Preferably, the solder marks of the battery cell tabs after cross-laser welding are cross-distributed.

[0015] Preferably, the parameters for the two cross-laser welding of the battery cell tabs are the same.

[0016] Preferably, the battery cell tabs are formed by two cross laser welding processes, with the horizontal spacing of the welding marks being 1-2 mm and the vertical spacing of the welding marks being 1-2 mm.

[0017] The advantages of this invention are: The laser welding method for high-capacity lithium battery tabs of this invention, through cross-laser welding to form multiple weld marks, ensures the weld mark area required for large-size, high-capacity cells, effectively reducing the internal resistance of the cells. This application also avoids the effects of laser interference and metal dust splashing that occur when two welding heads are used simultaneously in the same direction; it further reduces the impact of metal residue and uneven temperature distribution caused by sequentially welding two weld marks with a single welding head, greatly improving welding efficiency and product yield. Attached Figure Description

[0018] Figure 1 This is a flowchart of the laser welding process for the tabs of a large-capacity lithium battery provided by the present invention; Figure 2 This is a schematic diagram of the first cross-laser welding provided by the present invention; Figure 3 This is a schematic diagram of the second cross laser welding provided by the present invention; In the diagram, the markings are: 210 - foil, 220 - connecting piece, 230 - pre-welding area, 231 - first solder mark, 232 - second solder mark, 310 - third solder mark, and 320 - second solder mark. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please refer to the attached document. Figure 1-3 This invention provides a laser welding method for the tabs of a large-capacity lithium battery, comprising the following steps: S1: Perform ultrasonic pre-welding on the battery cell tabs 210 to remove the air between the battery cell tabs 210 and make the battery cell tabs 210 tightly connected together, forming a pre-welding area 230. S2: Align and press the pre-welded battery cell tabs 210 and connecting pieces 220 together; S3: Perform the first cross laser welding on the battery cell tabs to form the first weld mark 231 and the second weld mark 232; S4: Remove dust from the surface of the battery cell tabs; S5: Perform a second cross-laser welding on the battery cell tabs to form the third weld mark 310 and the fourth weld mark 320.

[0021] Before ultrasonic welding, this method requires ensuring that the surface of the battery cell tab 210 is clean and free of contaminants. The battery cell tab includes a positive tab and a negative tab; the number of layers of the positive tab is ≤60, and the number of layers of the negative tab is ≤61; the ultrasonic pre-welding parameters for the positive tab are: energy of 600±100J, pressure of 4±1bar, and power of 500±50W; the ultrasonic pre-welding parameters for the negative tab are: energy of 950±50J, pressure of 4±1bar, and power of 650±50W.

[0022] After pre-welding, the battery cell tab 210 and the connecting piece 220 are pressed and aligned by a fixing device, and then the first cross laser welding is performed. The welding paths of the first cross laser welding are parallel and the welding directions are opposite. The first weld mark 231 formed by the first cross laser welding is away from the battery cell tab 210, and the second weld mark 232 formed is close to the battery cell tab 210. The first weld mark 231 and the second weld mark 232 are distributed crosswise.

[0023] The welding paths of the second cross-laser welding are parallel, but the welding directions are opposite. The third weld mark 310 formed by the second cross-laser welding is away from the cell tab 210, while the fourth weld mark 320 is close to the cell tab 210. The position of the third weld mark 310 is parallel to the second weld mark 232, and the position of the fourth weld mark 320 is parallel to the first weld mark 231. The distance between the first weld mark 231 and the third weld mark 310 is d1, and 1mm ≤ d1 ≤ 2mm. The distance between the first weld mark 231 and the fourth weld mark 320 is d2, and 1mm ≤ d2 ≤ 2mm.

[0024] Example 1 This embodiment provides a laser welding method for the tabs of a large-capacity lithium battery, including the following steps: Taking the positive electrode tab as an example, 60 layers of positive electrode tabs are arranged neatly and ultrasonically pre-welded. The parameters used are set to 600J*4ar*500W. After 2 seconds, the ultrasonic pre-welding is completed, leaving the welding area.

[0025] The pre-welded positive electrode tab and positive electrode connecting piece are aligned and pressed together using a clamping device. In this embodiment, the laser welding adopts a fiber-to-semiconductor welding method. The parameters of each laser welding head are kept consistent: the fiber power is set to 2000W, the semiconductor power is set to 1500W, and the welding speed is set to 450mm / s. Then, the first cross laser welding is performed, forming two 2×25mm weld marks at both ends of the pre-welded area, with the two weld marks intersecting. After the first welding is completed, the positive electrode tab-connecting piece is cleaned of dust.

[0026] After dust removal and repositioning, the laser welding head parameters were kept consistent with the parameters of the first cross-laser welding, and a second laser welding was performed, forming two 2×25mm weld marks at both ends of the pre-welded area. Figure 3 As shown, after welding is completed, the distance between the two weld marks is d1=1mm in the horizontal direction and d2=1mm in the vertical direction, thus completing the welding.

[0027] In this example, the formation of multiple weld marks through cross-laser welding ensures the required weld mark area for large-size, high-capacity cells, effectively reducing the internal resistance of the cells. This embodiment employs a two-stage laser cross-welding method, where two lasers weld simultaneously in opposite directions during the welding process. This reduces interference between the two lasers and also minimizes the impact of metal spatter during laser welding on subsequent welding, thereby improving welding efficiency and ensuring the product qualification rate.

[0028] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for laser welding tabs of a high-capacity lithium battery, characterized in that, Includes the following steps: S1: Perform ultrasonic pre-welding on the battery cell tabs; S2: Align and press the pre-welded battery cell tabs with the connecting piece; S3: Perform the first cross-laser welding on the battery cell tabs; S4: Remove dust from the surface of the battery cell tabs; S5: Perform a second cross-laser welding on the battery cell tabs; Cross laser welding involves parallel welding paths and opposite welding directions; the weld marks of the battery cell tabs after cross laser welding are distributed in a cross pattern; the battery cell tabs form weld marks after two cross laser welding processes, with the horizontal weld mark spacing being 1-2mm and the vertical weld mark spacing being 1-2mm.

2. The laser welding method for high-capacity lithium battery tabs according to claim 1, characterized in that, In step S1, the battery cell tabs include positive and negative tabs; the surface of the battery cell tabs must be clean and free of contamination before ultrasonic pre-welding.

3. The laser welding method for high-capacity lithium battery tabs according to claim 2, characterized in that, The number of positive electrode tabs is ≤60; the number of negative electrode tabs is ≤61.

4. The laser welding method for high-capacity lithium battery tabs according to claim 2, characterized in that, Ultrasonic pre-welding parameters for the positive electrode tab: energy 600±100J, pressure 4±1bar, power 500±50W; ultrasonic pre-welding parameters for the negative electrode tab: energy 950±50J, pressure 4±1bar, power 650±50W.

5. The laser welding method for high-capacity lithium battery tabs according to claim 1, characterized in that, In step S1, the electrode tabs of the battery cell after ultrasonic pre-welding form a pre-welded area.

6. The laser welding method for high-capacity lithium battery tabs according to claim 1, characterized in that, In step S2, alignment and clamping are accomplished using a fixing device.

7. The laser welding method for high-capacity lithium battery tabs according to claim 1, characterized in that, The parameters for the two cross-laser welding of the battery cell tabs are the same.

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