Secondary battery comprising cell lead having hole for gap measurement, and method for welding cell lead

Abstract

This disclosed secondary battery assembly has cell leads respectively provided for a plurality of secondary batteries, wherein: the cell leads vertically overlap; and a through hole is formed in a cell lead among the plurality of cell leads, which is positioned at an upper level in the overlapping direction, thereby allowing a gap between the vertically overlapping cell leads to be measured through the through hole.

Description

Secondary battery including a cell lead having a hole for gap measurement and a welding method for the cell lead

[0001] The present invention relates to a secondary battery comprising a cell lead having a gap measuring hole that allows for the prior identification of whether there is an excessive gap between the cell leads that causes welding defects when welding multiple cell leads by overlapping them, and a method for welding the cell leads.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0131807 filed on September 27, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0003] Unlike primary batteries, secondary batteries are rechargeable and are currently the subject of extensive research and development due to their potential for miniaturization and high capacity. The demand for secondary batteries as an energy source is increasing rapidly due to the growing technological development and demand for mobile devices, as well as the rise of electric vehicles and energy storage systems driven by the contemporary need for environmental protection.

[0004] Rechargeable batteries are classified into coin batteries, cylindrical batteries, prismatic batteries, and pouch batteries according to the shape of the battery case. In rechargeable batteries, the electrode assembly mounted inside the battery case is a power generation device capable of charging and discharging, consisting of a laminated structure of electrodes and separators.

[0005] Electrode assemblies can be roughly classified into a jelly roll type, which is wound with a separator interposed between sheet-type positive and negative electrodes coated with active material; a stack type, which is sequentially stacked with multiple positive and negative electrodes interposed with a separator; and a stack and folding type, which is wound with stack-type unit cells into a long separator film.

[0006] Rechargeable batteries are applied in various technological fields as a form in which multiple batteries are electrically connected and structurally bundled. By electrically connecting multiple batteries, various performance characteristics such as target output and capacity can be achieved, while structural connection and management enable the effective design of long-term safety and durability. Such groups of multiple batteries can be referred to by various terms such as modules, blocks, or packs; for example, dozens or hundreds of batteries can be mounted in the form of modules, blocks, or packs on electric vehicles.

[0007] To electrically connect multiple secondary batteries, the exposed electrodes or terminals of each secondary battery are interconnected in series and / or parallel. Welding is primarily used for connecting the electrodes, and thin conductors called cell leads are used to ensure good welding. The cell leads to be welded can be provided in various forms depending on the structure or case type of the secondary battery. For example, in pouch batteries, the electrodes protruding from the case themselves may constitute the cell leads, whereas in the case of prismatic batteries, terminals are usually provided in the case, so a separate cell lead assembly may be used.

[0008] Since cell leads are made of a flexible material, multiple cell leads have traditionally been welded using a relatively rigid conductor called an inter-busbar or busbar. Recently, however, there has been a trend toward reducing weight and cost by directly welding cell leads together without an inter-busbar, known as inter-busbar free welding.

[0009] When welding cell leads directly to each other, the gap between the overlapping cell leads must be kept to a minimum to achieve good welding quality. If the gap between the cell leads is excessive, welding defects such as burn marks like soot and weak welding occur, and post-correction work is required to correct this.

[0010] Therefore, in the welding of cell leads of an inter-busbar free structure, it is important to minimize the gap between the vertically overlapping cell leads, but since the gap between the overlapping cell leads cannot be measured in the welding direction (overlapping direction), it is difficult to prevent welding defects in advance.

[0011] The present invention aims to prevent welding defects caused by excessive gaps by identifying the gap between vertically overlapping cell leads in advance of the welding operation.

[0012] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description of the invention below.

[0013] In one embodiment, the secondary battery assembly provided by the present invention has cell leads provided for each of the plurality of secondary batteries stacked vertically, and a through hole is formed in the cell lead located on the upper side of the stacked direction among the plurality of cell leads, so that the gap between the vertically stacked cell leads can be measured through the through hole.

[0014] The plurality of cell leads have folded surfaces that overlap each other vertically, and the through hole may be formed on the folded surface.

[0015] The above through hole may be formed in the longitudinal central region of the cell lead.

[0016] Alternatively, at least two through holes may be spaced apart along the longitudinal direction of the cell lead.

[0017] In one embodiment, the plurality of secondary batteries may each be a pouch battery.

[0018] Meanwhile, the present invention provides a method for welding cell leads, comprising the steps of: cutting and / or bending each cell lead of a secondary battery to a predetermined length and / or angle, and forming a through hole on a cell lead exposed to the outside among a plurality of secondary battery cell leads; preparing for welding by making the cell lead of a plurality of secondary batteries with the through hole formed therein an upper cell lead and a cell lead of another secondary battery a lower cell lead that overlaps the bottom surface of the upper cell lead; measuring the gap between the upper cell lead and the lower cell lead through the through hole; and performing welding if the measured gap between the upper cell lead and the lower cell lead is within a predetermined specification.

[0019] The gap between the upper cell lead and the lower cell lead, measured through the above-mentioned through hole, can be measured by a contact-type and / or non-contact-type distance measuring device.

[0020] Welding of the upper cell lead and lower cell lead can be performed by laser welding.

[0021] In addition, the measurement of the gap between the upper cell lead and the lower cell lead through the through hole and the welding of the upper cell lead and the lower cell lead can be performed by a single laser welding device.

[0022] The welding method for cell leads provided by the present invention can be applied to a plurality of pouch batteries.

[0023] According to the configuration of the present invention as described above, a through hole is formed in the upper cell lead among a plurality of cell leads that overlap each other, and it is possible to measure the gap between the cell leads that overlap vertically through the through hole.

[0024] Before performing welding of the cell leads, it is possible to verify in advance whether the gap between the upper and lower cell leads satisfies the specified level, and if an excessive gap that could cause welding defects is discovered, appropriate measures can be taken in advance, thereby preventing various losses due to welding defects.

[0025] However, the technical effects obtainable through the present invention are not limited to those described above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description of the invention below.

[0026] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0027] FIG. 1 is a drawing illustrating an example of a conventional secondary battery assembly in which a plurality of secondary batteries are grouped into a single group.

[0028] FIG. 2 is a drawing illustrating the cross-sectional structure of part "A" of FIG. 1.

[0029] FIG. 3 is a drawing illustrating an example of a secondary battery assembly according to an embodiment of the present invention.

[0030] FIG. 4 is a drawing illustrating an example of a secondary battery assembly according to another embodiment of the present invention.

[0031] FIG. 5 is a flowchart illustrating a welding method for a cell lead according to the present invention.

[0032] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are to be described in detail below.

[0033] However, this is not intended to limit the invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0034] In the present invention, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0035] Furthermore, in the present invention, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only cases where it is "immediately above" the other part, but also cases where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "under" another part, this includes not only cases where it is "immediately below" the other part, but also cases where there is another part in between. Additionally, in the present application, being "placed on" may include cases where it is placed on the lower part as well as on the upper part.

[0036]

[0037] In one embodiment, the secondary battery assembly provided by the present invention has cell leads provided for each of the plurality of secondary batteries stacked vertically, and a through hole is formed in the cell lead located on the upper side of the stacked direction among the plurality of cell leads, so that the gap between the vertically stacked cell leads can be measured through the through hole.

[0038] According to the configuration of the present invention as described above, a through hole is formed in the upper cell lead among a plurality of cell leads that overlap each other, and it is possible to measure the gap between the cell leads that overlap vertically through the through hole.

[0039] Before performing welding of the cell leads, it is possible to verify in advance whether the gap between the upper and lower cell leads satisfies the specified level, and if an excessive gap that could cause welding defects is discovered, appropriate measures can be taken in advance, thereby preventing various losses due to welding defects.

[0040] Hereinafter, specific embodiments of a secondary battery including a cell lead having a gap measuring hole according to the present invention and a welding method for the cell lead will be described in detail with reference to the attached drawings. For reference, the directions of front, back, up, down, left, and right used to specify relative positions in the following description are intended to aid in understanding the invention, and unless otherwise specifically defined, the directions shown in the drawings are used as the reference.

[0041]

[0042] [First embodiment]

[0043] FIG. 1 illustrates an example of a secondary battery assembly (10) in which a plurality of secondary batteries (100) are grouped together. The secondary battery assembly (10) illustrated as an example includes a plurality of pouch batteries. However, this is merely an example, and the present invention may also be applied to cell leads applied to secondary batteries of a different structure other than pouch batteries, such as prismatic secondary batteries.

[0044] The secondary battery assembly (10) of FIG. 1 is a conventional secondary battery assembly (10) in which a plurality of secondary batteries (100) are arranged in a row. An exemplary secondary battery (100) is a bidirectional pouch battery in which cell leads (110) are separated and arranged in both the front and rear directions (based on FIG. 1). Furthermore, the illustrated secondary battery assembly (10) corresponds to a secondary battery assembly (10) of a so-called cell-to-pack structure in which a plurality of secondary batteries (100) are exposed on the top and bottom surfaces. However, since the welding of the cell leads (110) itself can be applied to other secondary battery assemblies other than the cell-to-pack structure, for example, a secondary battery assembly of a module structure in which all six sides are closed, the technical scope of the present invention is not limited to the illustrated secondary battery assembly (10) illustrated in the drawing.

[0045] A plurality of secondary batteries (100) are connected by welding adjacent cell leads (110) on a busbar frame (20) positioned on the front and rear of a secondary battery assembly (10), thereby electrically connecting the plurality of secondary batteries (100). The cell leads (110) of each secondary battery (100) are distinguished as a negative electrode and a positive electrode, and the polarity of adjacent cell leads (110) is appropriately arranged so that a series and / or parallel connection designed to match the specified output is formed when aligning the secondary batteries (100). A cover (not shown) may be mounted on the busbar frame (20) to protect the cell leads (110), and side beams (30) capable of applying appropriate pressure along the thickness direction of the plurality of secondary batteries (100) in consideration of swelling, etc. may be attached to both sides of the secondary battery assembly (10).

[0046] FIG. 2 illustrates a cross-sectional structure of section "A" in FIG. 1. FIG. 2 shows a structure in which the cell leads (110) of adjacent secondary batteries (100) are stacked vertically, and in this state, the cell leads (110) are welded to each other. In particular, the welding structure illustrated in FIG. 2 is a so-called inter-busbar free method, which allows for a reduction in weight and cost by directly welding the cell leads (110) to each other without inter-busbars.

[0047] FIG. 2 illustrates a problem that often occurs in such an inter-busbar-free welding structure. Based on FIG. 2, cell leads (110) provided for each of the multiple secondary batteries (100) are stacked vertically, and in this state, the cell leads (110) are welded directly to each other. The welding operation is performed on the upper cell lead (112), but as shown in FIG. 2, even if the lower cell lead (114) is bent downward, this problem cannot be detected due to the upper cell lead (112). If welding is performed in this state, welding defects occur, such as burn marks like soot and weak welding, due to an excessive gap (g). Furthermore, if welding defects are discovered later, a separate post-correction operation must be performed to correct them. Therefore, it is necessary to devise a new solution suitable for a welding environment without an inter-busbar supporting the welding surface of the vertically stacked cell leads (110).

[0048] FIG. 3 illustrates a secondary battery assembly (10) according to one embodiment of the present invention. FIG. 3 is illustrated with two adjacent secondary batteries (100) for the sake of understanding the invention, and the busbar frame (20) is omitted. The welding structure of FIG. 3 can be applied to all parts where the cell leads (110) of adjacent secondary batteries (100) are directly welded together throughout the secondary battery assembly (10) of FIG. 1.

[0049] Referring to FIG. 3, among the plurality of cell leads (110), a through hole (120) is formed in the cell lead (110) located on the upper side in the overlapping direction. As a result, the lower cell lead (114) overlapping below it is exposed through the through hole (120) of the upper cell lead (112). Accordingly, the gap between the upper and lower overlapping cell leads (110) can be measured through the through hole (120). In this respect, the through hole (120) formed through the upper cell lead (112) can be called a through hole for measuring the gap.

[0050] The gap between the vertically overlapping cell leads (110) can be measured using various types of displacement sensors or distance measuring devices currently known. For example, a dial gauge or a contact displacement sensor can be used as a contact distance measuring device. Alternatively, a laser measuring device, an optical measuring device, an ultrasonic measuring device, a magnetic measuring device, etc., can be used as a non-contact distance measuring device. For example, if an optical measuring device using a vision camera is used, the distance to the upper cell lead (112) and the lower cell lead (114) can be calculated through information regarding the focal length when acquiring an image. Regardless of which measuring device is used, the basic principle for measuring the gap (g) between the upper cell lead (112) and the lower cell lead (114) is that the gap (g) corresponds to the difference between the distance to the upper cell lead (112), measured at a certain fixed position, and the distance to the lower cell lead (114) exposed through the through hole (120), minus the thickness of the upper cell lead (112).

[0051] In the embodiment of FIG. 3, the welding direction follows the front and rear sides of the secondary battery assembly (10), and the cell leads (110) of the secondary battery (100) are parallel to this welding direction. Accordingly, in order to secure an accessible welding surface, the cell leads (110) of each secondary battery (100) are bent in a direction that overlaps each other vertically. In this case, a plurality of cell leads (110) have a bent surface (116) that overlaps each other vertically, and a through hole (120) can be formed on the bent surface (116) of the upper cell lead (112). Of course, FIG. 3 is one embodiment, and the configuration of the through hole (120) can be applied even when the bent surface (116) is not formed on the cell lead (110).

[0052] In one embodiment, as shown in FIG. 3, the through hole (120) may be formed in the longitudinal central region of the cell lead (110). The position or shape of the lower cell lead (114), such as folding or bending, may vary, but the through hole (120) formed in the central region of the upper cell lead (112) can be considered a suitable location for identifying excessive gaps that would adversely affect welding quality.

[0053] Alternatively, as in the embodiment illustrated in FIG. 4, at least two through holes (120) may be formed spaced apart along the longitudinal direction of the cell lead (110). By measuring the gap between the cell leads (110) at multiple locations through the multiple through holes (120), a more reliable preliminary evaluation may be possible. However, since too many through holes (120) may be a factor in reducing the strength of the cell lead (110), it may be necessary to select an appropriate number considering the welding strength. Also, according to FIG. 3 and FIG. 4, the through holes (120) are circular, but the configuration of the through holes (120) is not limited to the illustrated shape. For example, the through holes (120) can be formed in various shapes, such as circular, elliptical, and various polygons.

[0054]

[0055] [Second embodiment]

[0056] FIG. 5 is a flowchart illustrating a welding method for a cell lead according to the present invention. With reference to FIG. 5, the welding method for a cell lead provided by the present invention will be described in detail. Here, as explained in the first embodiment, the welding method for a cell lead provided by the present invention can be applied to welding the cell leads (110) of a plurality of pouch batteries.

[0057] First, the cell lead welding method of the present invention performs the step of cutting and / or bending the cell lead (110) of each secondary battery (100) to a predetermined length and / or angle, and forming a through hole (120) on the cell lead (110) that is exposed to the outside among the cell leads (110) of the plurality of secondary batteries (100). The cell lead (110) that is exposed to the outside among the cell leads (110) of the plurality of secondary batteries (100) corresponds to the upper cell lead (112) among the cell leads (110) that are stacked vertically, as described above. The through hole (120) may be formed on the upper cell lead (112) after aligning the plurality of secondary batteries (100), or may be formed during the cutting and / or bending of the cell lead (110). In other words, the formation of the through hole (120) may be performed at an appropriate time.

[0058] Next, a step of preparing for welding is performed by making the cell lead (110) having a through hole (120) formed among a plurality of secondary batteries (100) into an upper cell lead (112), and making the cell lead (110) of another secondary battery (100) into a lower cell lead (114) that overlaps the bottom surface of the upper cell lead (112).

[0059] Then, a step is performed to measure the gap between the upper cell lead (112) and the lower cell lead (114) through the through hole (120). For example, the gap between the upper cell lead (112) and the lower cell lead (114) measured through the through hole (120) can be measured by various distance measuring devices as described in the first embodiment, namely various contact-type distance measuring devices and / or non-contact-type distance measuring devices.

[0060] Then, welding is performed if the gap between the measured upper cell lead (112) and the lower cell lead (114) is within the preset specifications. If an excessive gap outside the specifications is found, the lower cell lead (114) is adjusted to satisfy the gap within the specifications. Here, if an excessive gap outside the specifications is found, an alarm or the like may be output to notify the operator.

[0061] In one embodiment, welding of the upper cell lead (112) and the lower cell lead (114) can be performed by laser welding. Additionally, measuring the gap between the upper cell lead (112) and the lower cell lead (114) through the through hole (120) and welding of the upper cell lead (112) and the lower cell lead (114) can be performed by a single laser welding device. That is, a distance measuring device may be integrally provided with the laser welding device.

[0062]

[0063] The present invention has been described in more detail above through drawings and embodiments. However, the configurations described in the drawings or embodiments described in this specification are merely one embodiment of the present invention and do not represent all technical concepts of the present invention; therefore, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0064]

[0065] [Explanation of the symbol]

[0066] 10: Secondary battery assembly

[0067] 20: Busbar frame

[0068] 30: Side beam

[0069] 100: Secondary battery

[0070] 110: Cell Lead

[0071] 112: Upper cell lead

[0072] 114: Lower cell lead

[0073] 116: Folded surface

[0074] 120: Through hole

[0075] g: gap

Claims

1. Cell leads provided for each of the multiple secondary batteries are overlapped vertically, and Among the plurality of cell leads mentioned above, a through hole is formed in the cell lead located on the upper side of the overlapping direction, and Accordingly, a secondary battery assembly capable of measuring the gap between vertically overlapping cell leads through the above-mentioned through-hole.

2. In Paragraph 1, The above plurality of cell leads have folded surfaces that overlap each other vertically, and The above through hole is formed on the above-mentioned bent surface, in a secondary battery assembly.

3. In Paragraph 1 or 2, The above through hole is formed in the longitudinal central region of the cell lead, in a secondary battery assembly.

4. In Paragraph 1 or 2, A secondary battery assembly in which at least two through holes are spaced apart along the longitudinal direction of the cell lead.

5. In Paragraph 1, The above plurality of secondary batteries are each pouch batteries, forming a secondary battery assembly.

6. A step of cutting and / or bending the cell leads of each secondary battery to a predetermined length and / or angle, and forming a through hole on the cell lead exposed to the outside among the cell leads of the plurality of secondary batteries; A step of preparing for welding by using a cell lead having the through hole formed therein among a plurality of secondary batteries as the upper cell lead, and using a cell lead of another secondary battery as the lower cell lead that overlaps the bottom surface of the upper cell lead; A step of measuring the gap between the upper cell lead and the lower cell lead through the through hole; and A step of performing welding if the measured gap between the upper cell lead and the lower cell lead is within a preset specification; A welding method for cell leads including 7. In Paragraph 6, The gap between the upper cell lead and the lower cell lead measured through the above-mentioned through-hole is, A welding method for cell leads, measured by a contact and / or non-contact distance measuring device.

8. In Paragraph 7, A welding method for cell leads, wherein the welding of the upper cell lead and the lower cell lead is performed by laser welding.

9. In Paragraph 8, A method for welding cell leads, wherein the gap between the upper cell lead and the lower cell lead is measured through the above-mentioned through-hole, and the welding of the upper cell lead and the lower cell lead is performed by a single laser welding device.

10. In Paragraph 6, A welding method for cell leads, wherein the above plurality of secondary batteries are each pouch batteries.

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