Laser welding device for electrode tabs and electrode leads and welding method using the same

Abstract

The present invention relates to a laser welding apparatus and a welding method using the same, comprising: an upper jig located on an overlapping portion of a first member and a second member; a laser irradiator that irradiates a laser beam toward a part or all of the overlapping portion; a photographing member for obtaining an internal image of the upper jig; a calculation unit that obtains welding level information of spatter generated inside the upper jig during welding from the internal image of the upper jig and determines a welding order from the welding level information; and a control unit that receives a signal from the calculation unit and controls the operation of the laser irradiator, thereby minimizing spatter adhesion during welding and improving welding quality.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0030979 filed on March 9, 2023 and Korean Patent Application No. 10-2024-0023841 filed on February 19, 2024, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a laser welding apparatus for an electrode tab and an electrode lead and a welding method using the same, and more particularly, to a laser welding apparatus for an electrode tab and an electrode lead, which can minimize welding defects caused by spatters deposited on a welding jig during a laser welding process for connecting the electrode tab and the electrode lead, and can extend the period for replacing the spatters or for cleaning the electrode tab and the electrode lead, and a welding method using the same. [Background technology]

[0003] As the development speed of lithium secondary batteries, which have high energy density and are classified as environmentally friendly energy, increases, the use of lithium secondary batteries as energy sources for various devices requiring high capacity and high output, such as electric vehicles, hybrid electric vehicles, and plug-in hybrid electric vehicles, is increasing.

[0004] Depending on the shape of the exterior material, lithium secondary batteries can be classified into prismatic secondary batteries and cylindrical secondary batteries in which an electrode assembly is housed in a metal can, and pouch-type secondary batteries in which an electrode assembly is housed in a battery case made of an aluminum laminate sheet.

[0005] Pouch-type secondary batteries have the advantages of being easily deformable and having a high energy density. An electrode assembly is housed inside an exterior material, an electrolyte is injected into the interior of the exterior material, and the exterior material is sealed by thermal welding to assemble the battery.

[0006] In general, electrode assemblies housed inside a pouch-type secondary battery include a stack-type electrode assembly in which a plurality of unit cells are stacked, each of which is formed by stacking a rectangular positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes; a stack / folding-type electrode assembly manufactured by arranging each unit cell on a separator film and then rolling up the separator film; and a jelly-roll-type electrode assembly manufactured by rolling up a long sheet-shaped positive electrode sheet or a long sheet-shaped negative electrode sheet with a separator sheet disposed on each of both sides of the sheet.

[0007] The electrode assembly housed inside the pouch-type secondary battery includes a positive electrode tab and a negative electrode tab attached to or extending from an electrode plate, the positive electrode tab being connected to a positive electrode lead and the negative electrode tab being connected to a negative electrode lead, and the positive electrode lead and the negative electrode lead are disposed to protrude outward from the outer periphery of a pouch-type battery case of the pouch-type secondary battery.

[0008] On the other hand, laser welding is used to join the positive electrode tab and the positive electrode lead, and the negative electrode tab and the negative electrode lead. Specifically, the electrode tab and the electrode lead are arranged so as to overlap each other, an upper jig is placed on the upper part of the overlapping part, and then, with the upper jig pressing the overlapping part, a laser is irradiated to weld the electrode tab and the electrode lead.

[0009] At this time, the upper jig may be hollow, and spatters generated during laser welding may adhere to the inner surface of the upper jig.

[0010] In addition, since the welding order is fixed in laser welding, the later the welding order is, the more excessive spatter is generated due to preheating of the base material.

[0011] Therefore, the closer to the welded portion formed last on the inner surface of the upper jig, the faster the spatters grow on the upper jig. If the spatters grow quickly in some areas, the laser beam for those areas may be blocked by the spatters, causing poor welding. In addition, the replacement and cleaning cycles for the spatters may become shorter, reducing process efficiency.

[0012] Patent Document 1 discloses a contact jig and a welding method for laser welding of secondary battery tabs, which includes an upper contact jig including a ring-shaped injection part capable of surface injection in order to suppress deterioration of welding quality due to reaction with hydrogen or oxygen in the air and occurrence of short circuits due to sputter deposition occurring during welding during the laser welding process for forming electrode terminals.

[0013] Although the technique disclosed in Patent Document 1 can prevent short circuits caused by sputter deposition, it has a problem in that a new welding device must be installed since an upper contact jig including a ring-shaped injection part capable of surface injection must be used. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Korean Patent Publication No. 10-2021-0046096 Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention has been made to solve the above problems, and an object of the present invention is to provide a laser welding device for electrode tabs and electrode leads, which can prevent welding defects while using a conventional upper jig, and a welding method using the same.

[0016] Another object of the present invention is to provide a laser welding apparatus for electrode tabs and electrode leads, which can extend the replacement cycle and cleaning cycle of spatters, and a welding method using the same. [Means for solving the problem]

[0017] In order to achieve the above-mentioned object, the laser welding apparatus according to the present invention is characterized by including: an upper jig located on an overlapping portion of a first member and a second member; a laser irradiator that irradiates a laser beam toward a part or all of the overlapping portion; a photographing member for obtaining an internal image of the upper jig; a calculation unit that obtains welding level information of spatter generated inside the upper jig during welding from the internal image of the upper jig and determines a welding order from the welding level information; and a control unit that receives a signal from the calculation unit and controls the operation of the laser irradiator.

[0018] In the laser welding apparatus according to the present invention, the upper jig is in the form of a frame having a hollow space therein, and the frame is polygonal, elliptical or circular.

[0019] In the laser welding apparatus according to the present invention, the photographing member is a scanner or a vision camera.

[0020] In the laser welding device according to the present invention, the first member is an electrode tab, and the second member is an electrode lead.

[0021] In addition, a laser welding method according to the present invention is a method for welding a first member and a second member using an upper jig and a laser irradiator, the method including a first step of photographing the upper jig, a second step of acquiring information on a deposition level of spatter inside the upper jig generated during welding from the image photographed in the first step, a third step of determining a welding sequence based on the information on the deposition level of the spatter, and a fourth step of irradiating a laser beam according to the welding sequence and performing welding so as to form a plurality of welds.

[0022] In addition, the laser welding method according to the present invention may further include, before the fourth step, a step of overlapping a portion of the first member and a portion of the second member, and then positioning the upper jig on an upper portion of the overlapping portion.

[0023] In the laser welding method according to the present invention, the upper jig is in the form of a frame having a hollow space therein.

[0024] In the laser welding method according to the present invention, the frame is preferably polygonal, elliptical or circular.

[0025] In the laser welding method according to the present invention, the first step may include photographing an internal image of the upper jig using a scanner or a camera disposed above the upper jig.

[0026] In the laser welding method according to the present invention, the camera is a vision camera.

[0027] In the laser welding method according to the present invention, the information on the welding level of the spatter in the second step is at least one of an area, a shape, and a position of the spatter.

[0028] In addition, in the laser welding method according to the present invention, the third stage welding sequence is characterized in that a weld is formed by irradiating a laser beam from a point where the distance between the intended irradiation point of the laser beam and the welded spatter is close.

[0029] In addition, in the laser welding method according to the present invention, the third stage welding sequence is characterized in that when spatters are overlapping and located within a certain radius from the planned point of irradiation with the laser beam, a weld is formed by irradiating the laser beam from a point where the overlapping area of ​​the spatters is large.

[0030] In addition, the laser welding method according to the present invention may further include, before the fourth step, a step of positioning the first member and the second member above a lower jig.

[0031] In the laser welding method according to the present invention, the first member is an electrode tab, and the second member is an electrode lead. Effect of the Invention

[0032] As described above, according to the laser welding apparatus for electrode tabs and electrode leads and the welding method using the same of the present invention, the replacement cycle of the upper jig can be extended by minimizing unevenness in the growth rate of spatters deposited on the upper jig during the laser welding process.

[0033] In addition, the laser welding apparatus for electrode tabs and electrode leads and the welding method using the same according to the present invention can prevent spatters from growing excessively at a specific portion, thereby minimizing the problem of the path of the laser beam being blocked during the welding process, which can contribute to improving the welding quality. [Brief description of the drawings]

[0034] [Figure 1] 1 is a conceptual diagram showing a laser welding device for an electrode tab and an electrode lead according to the present invention. [Diagram 2] 11 is a plan view showing a state in which an upper jig is disposed above an overlapping portion of an electrode tab and an electrode lead according to the present invention; FIG. [Diagram 3] 3 is a plan view showing a state in which sputters have grown on the upper jig in FIG. 2. FIG. [Figure 4] 4 is a flowchart showing a welding method using the laser welding device according to the present invention. [Diagram 5] FIG. 2 is a first schematic diagram for explaining the entire position to which the laser beam must be irradiated and the position to which the laser beam is preferentially irradiated. [Figure 6]FIG. 2 is a second schematic diagram for explaining the entire position to which the laser beam must be irradiated and the position to which the laser beam is preferentially irradiated. [Figure 7] FIG. 4 is a diagram for explaining the order in which a laser beam moves in the first embodiment. [Figure 8] FIG. 11 is a diagram for explaining the order in which a laser beam moves in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Hereinafter, with reference to the accompanying drawings, a detailed description will be given of an embodiment of the present invention that can be easily implemented by a person having ordinary skill in the art to which the present invention pertains. In describing the operation principle of the embodiment of the present invention in detail, if it is determined that a detailed description of related well-known functions or configurations may obscure the gist of the present invention, the detailed description thereof will be omitted.

[0036] The same reference numerals are used throughout the drawings for parts with similar functions and operations. Throughout the specification, when one part is said to be connected to another part, this includes not only a direct connection but also an indirect connection through another element therebetween. In addition, the inclusion of one component does not mean the exclusion of other components, but may further include other components, unless otherwise specified.

[0037] Descriptions that specify elements by limiting or adding elements are applicable to all inventions unless otherwise specified, and are not limited to descriptions of a particular invention.

[0038] Throughout the description and claims of this application, the singular includes the plural unless specifically stated otherwise.

[0039] Throughout the description and claims of this application, "or" includes "and" unless otherwise stated. Thus, "including A or B" means all three cases: including A, including B, or including both A and B.

[0040] In the following, an electrode tab and an electrode lead are taken as examples of objects to be welded, but the objects to be welded are not necessarily limited to this as long as laser welding is possible.

[0041] The invention will now be described with reference to the drawings, together with detailed embodiments.

[0042] FIG. 1 is a conceptual diagram showing a laser welding apparatus for an electrode tab and an electrode lead according to the present invention, FIG. 2 is a plan view showing a state in which an upper jig is placed on the upper part of an overlapping portion of an electrode tab and an electrode lead according to the present invention, and FIG. 3 is a plan view showing a state in which sputters have grown on the upper jig of FIG. 2.

[0043] Referring to Figures 1 to 3, the laser welding apparatus according to the present invention may include a jig 100 for placing or supporting each workpiece, a laser irradiator 200, a photographing member 300, a calculation unit 400, and a control unit 500.

[0044] First, the jig 100 may be composed of an upper jig 110 and a lower jig 120. The upper jig 110 is located above the welded portion of each workpiece, i.e., the overlapping portion 30 where the workpieces overlap, and presses each workpiece, while the lower jig 120 is located below the overlapping portion. Here, the lower jig 120 may be omitted if necessary.

[0045] Specifically, the upper jig 110 has a frame shape with a hollow space 111. Specifically, when the upper jig 110 is viewed from above, the frame may be a polygon including a rectangle, a hexagon, an octagon, etc., with a full width formed by a curve and a full length formed by a straight line, an ellipse, or a circle.

[0046] When the top jig 110 is polygonal, the corner where two sides meet can be in the form of a square corner or a rounded corner.

[0047] Since the laser welding apparatus according to the present invention can be used to manufacture an electrode assembly included in a pouch-type battery cell, each workpiece can be an electrode tab corresponding to the first member 10 and an electrode lead corresponding to the second member 20.

[0048] Of course, it is self-evident that when the first member is an electrode lead, the second member must be an electrode tab.

[0049] The first member 10 and the second member 20 are connected to each other by a spot welding method such that a portion of the end of each of the first member 10 and the second member 20 overlap each other to form an overlapping portion 30, and a laser beam is irradiated onto an upper portion of the overlapping portion 30 to form a welded portion 31.

[0050] FIG. 2 shows a configuration in which ten welds 31 are arranged in two rows, however this is merely an example, and the number of welds can be selectively adjusted depending on the width and length of the first member 10 and the second member 20 and the area of ​​the overlapping portion 30 thereof.

[0051] Also, the welded portion 31 may have various shapes such as a dot, a linear shape such as a solid line or a dotted line, a circle, an ellipse, a polygon, and the like.

[0052] The laser irradiator 200, which is linked to a laser generator (not shown), is located above the overlapping portion 30 and irradiates a laser beam toward the overlapping portion 30. More specifically, the laser irradiator 200 irradiates a laser beam toward a part or all of the area of ​​the overlapping portion 30 through a space 111 formed inside the upper jig 110, thereby connecting and fixing the overlapping portion 30 of the first member 10 and the second member 20.

[0053] A laser welding device using a laser beam, i.e., a laser generator and a laser irradiator, etc., correspond to known techniques, and therefore a detailed description thereof will be omitted.

[0054] Meanwhile, spatter (S in FIG. 3) is inevitably generated during the laser welding process, and the spatter S may be deposited on the inner surface of the upper jig 110.

[0055] The deposited spatter S becomes an obstacle that blocks the path of the laser beam, which may cause a bonding failure between the first member 10 and the second member 20.

[0056] That is, as shown in FIG. 3, the sputters S deposited on the inner surface of the upper jig 110 grow to fill the space 111, so that the sputters S can block the laser beam.

[0057] The photographing member 300 is configured to photograph an internal image of the upper jig 110. The photographing member 300 is for acquiring information on spatter S generated during the laser welding process described above that is welded to the frame of the upper jig 110 as an image, and the type of the photographing member 300 is not particularly limited as long as it can acquire an image and obtain information, but it may be a scanner or a camera, more specifically, a vision camera.

[0058] Here, the internal image of the upper jig 110 can be captured in real time during the welding process, or after the welding process of the pair of workpieces is completed.

[0059] Next, the calculation unit 400 analyzes the welding level information of the spatters S acquired by the photographing member 300 and determines the welding sequence, i.e., the moving path of the laser beam, which will be described in detail later.

[0060] Meanwhile, the control unit 500 receives the signal determined by the calculation unit 400 and controls the operation of the laser irradiator. That is, the control unit 500 controls whether or not the laser beam is irradiated and the laser irradiator moves along a predetermined moving path, and it is obvious that the control unit 500 can also control whether or not the photographing member 300 is operated.

[0061] A welding method using the above-mentioned laser welding device will now be described.

[0062] FIG. 4 is a flowchart showing a welding method using the laser welding apparatus of the present invention, FIG. 5 is a first schematic diagram for explaining the overall position to which the laser beam must be irradiated and the position to which the laser beam is preferentially irradiated, and FIG. 6 is a second schematic diagram for explaining the overall position to which the laser beam must be irradiated and the position to which the laser beam is preferentially irradiated.

[0063] Moreover, FIG. 7 is a diagram for explaining the order in which the laser beam moves in the first embodiment, and FIG. 8 is a diagram for explaining the order in which the laser beam moves in the second embodiment.

[0064] First, referring to FIG. 4, the welding method according to the present invention includes a first step of photographing a space in an upper jig, a second step of acquiring information on a deposition level of spatter S generated in the space inside the upper jig during welding from the image photographed in the first step, a third step of determining a welding sequence based on the deposition level information of the spatter S, and a fourth step of irradiating a laser beam according to the welding sequence to perform welding so as to form a plurality of welds.

[0065] The first step is to take an image of the space inside the upper jig using a scanner or a camera.

[0066] Here, after overlapping a portion of the first and second components, which are the objects to be welded, an image is taken with the upper jig positioned above the overlapping portion of the first and second components, or the upper jig is photographed before being positioned above the overlapping portion to obtain an image of the welded spatter S.

[0067] Of course, it is preferable to obtain in advance an image of the upper jig in an unused state with absolutely no spatter S deposited thereon.

[0068] The second step of acquiring information on the deposition level of the spatters S from the captured image and the third step of determining the welding sequence are performed by the calculation unit. Here, the deposition level information of the spatters S is at least one of the area, shape, and position of the spatters S when the upper jig is viewed from above or below.

[0069] 5, when a laser beam is irradiated to form 10 welds, it is preferable that the closer the shortest linear distance between each weld and the spatter S, the higher the priority of the laser beam irradiation. For example, since a first linear distance L1, which is the shortest linear distance between point "A" and the spatter S, is smaller than a second linear distance L2, which is the shortest linear distance between point "B" and the spatter S, this means that point "A" is welded before point "B".

[0070] Here, the straight-line distance may refer to the shortest distance between the center of the weld point irradiated with the laser beam and the outermost edge of the spatter S when the shape and area of ​​each weld are the same.

[0071] Of course, if the shape and area of ​​each weld are different, the straight-line distance can be defined as the shortest distance between the edge of the weld where the laser beam is irradiated and the outermost periphery of the spatter S.

[0072] Furthermore, as shown in FIG. 6, when a laser beam is irradiated to form 10 welds, and the spatter S is overlapping and positioned within a certain radius at each weld, it is preferable that the larger the overlapping area of ​​the spatter is, the higher the priority of irradiating the laser beam.

[0073] For example, within a certain radius of point "A", a certain portion of the spatter S overlaps with the point "A", while within the same radius of point "B", there is no spatter S, which means that point "A" will be welded before point "B".

[0074] As described above, the deposited spatter S causes poor bonding by blocking the path of the laser beam, and since the deposition of the spatter S grows unevenly, it is necessary to prevent excessive deposition of the spatter S at specific locations.

[0075] 7, the laser beam is preferentially irradiated to welds that have the shortest linear distance between each weld and the spatter S. Specifically, based on the information on the spatter S deposited in the space 111 inside the frame of the upper jig 110, the laser beam is irradiated to the ten welds in the order of the third, fifth, second, first, fourth, sixth, eighth, seventh, tenth, and ninth in the clockwise direction from the top left.

[0076] Referring to FIG. 8 for yet another example, it is preferable that the ten welds are irradiated with the laser beam in the following order starting from the top left and moving clockwise: fourth, sixth, third, second, fifth, first, eighth, seventh, tenth, and ninth.

[0077] Of course, the laser beam is applied in the specified order, and once the welding is completed, steps 1 to 4 are repeated to photograph the inside of the upper jig.

[0078] On the other hand, when the deposition level information of the spatter S is photographed in real time during welding, the welding sequence can be determined in real time before welding is performed.

[0079] This is because, for example, even if the welding sequence of each weld is determined before the start of welding, the deposition level of the spatter S near the weld may change due to non-uniform deposition of the spatter S.

[0080] Those skilled in the art will appreciate that the present invention can be applied and modified in various ways within the scope of the present invention based on the above content. [Explanation of symbols]

[0081] 10 First member 20 Second member 30 Superimposed section 31 Welding 100 Jig 110 Upper jig 111 Space section 120 Lower Jig 200 Laser Illuminator 300 Photography materials 400 Arithmetic section 500 Control section S Spatter L1 1st straight line distance L2 Second straight line distance

Claims

1. an upper jig located above an overlapping portion of the first member and the second member; a laser irradiator that irradiates a laser beam toward a part or all of the overlapping area; a photographing member for obtaining an internal image of the upper jig; a calculation unit that acquires deposition level information of spatters generated inside the upper jig during welding from an internal image of the upper jig and determines a welding sequence based on the deposition level information; a control unit that receives a signal from the calculation unit and controls operation of the laser irradiator.

2. The laser welding apparatus according to claim 1 , wherein the upper jig is in the form of a frame having a hollow space therein, and the frame is in the form of a polygon, an ellipse or a circle.

3. The laser welding apparatus according to claim 1 , wherein the photographing member is a scanner or a vision camera.

4. The laser welding apparatus according to claim 1 , wherein the first member is an electrode tab and the second member is an electrode lead.

5. A method for welding a first member and a second member using an upper jig and a laser irradiator, comprising the steps of: A first step of photographing the upper jig; a second step of acquiring information on a deposition level of spatters inside the upper jig generated during welding from the image captured in the first step; A third step of determining a welding order based on the spatter deposition level information; and a fourth step of irradiating the laser beam according to the welding sequence to form a plurality of welds.

6. 6. The laser welding method of claim 5, further comprising the step of overlapping a portion of the first member and a portion of the second member and then positioning the upper jig on an upper portion of the overlapping portion before the fourth step.

7. The laser welding method according to claim 6 , wherein the upper jig is in the form of a frame having a hollow space therein.

8. The laser welding method according to claim 7 , wherein the frame is polygonal, elliptical or circular.

9. The laser welding method according to claim 7 , wherein the first step comprises taking an image of the inside of the upper jig using a scanner or a camera disposed above the upper jig.

10. The laser welding method of claim 9 , wherein the camera is a vision camera.

11. The laser welding method of claim 9, wherein the information on the deposition level of the spatter in the second step is at least one of an area, a shape, and a position of the spatter.

12. 12. The laser welding method according to claim 11, wherein in the third stage of the welding sequence, the weld is formed by irradiating the laser beam from a point where a distance between a planned irradiation point of the laser beam and the deposited spatter is short.

13. 12. The laser welding method according to claim 11, wherein in the third stage welding sequence, when the spatters are overlapping and located within a certain radius from a planned point of irradiation of the laser beam, the weld is formed by irradiating the laser beam from a point where the overlapping area of ​​the spatters is large.

14. The laser welding method of claim 6, further comprising the step of positioning the first member and the second member above a lower jig before the fourth step.

15. The laser welding method according to claim 5 , wherein the first member is an electrode tab and the second member is an electrode lead.

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