Terminal structure for secondary battery and secondary battery including the same

Abstract

The disclosed invention relates to a terminal structure for a secondary battery. In one example, it includes a conductive first member having a protruding portion with a circular cross-section, and a conductive second member having a through-hole into which the protruding portion of the first member is inserted. A welding portion is formed along a circular edge where the protruding portion of the first member is inserted into the through-hole of the second member and they come into contact with each other.

Description

Technical Field

[0001] The present invention relates to a structure for electrically connecting an electrode assembly and an external terminal in a secondary battery.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0032901 filed on March 14, 2023, and all contents disclosed in the literature of the Korean patent application are included as part of this specification.

Background Art

[0003] Unlike a primary battery, a secondary battery is rechargeable and can be miniaturized compared to a large capacity, so many studies on secondary batteries have been conducted in recent years. With the development of battery technology, the demand for mobile devices, and the emergence of electric vehicles and energy storage systems (ESS) due to the increasing awareness of environmental protection, the demand for using secondary batteries as a power source is increasing.

[0004] Secondary batteries can be classified into coin-type batteries, cylindrical batteries, prismatic batteries, and pouch-type batteries according to the shape of the battery case. The electrode assembly mounted inside the battery case in a secondary battery is a rechargeable power generation element having a laminated structure of electrodes and a separator.

[0005] The electrode assembly can be roughly classified into a jellyroll type in which a separator is interposed between a sheet-shaped positive electrode and a negative electrode coated with an active material and wound, a stack type in which a plurality of positive electrodes and negative electrodes are sequentially laminated with a separator interposed therebetween, and a stack and folding type in which a unit cell of the stack type is wound with a long separation film.

[0006] The electrode assembly housed within the battery case is electrically connected internally to the negative and positive terminals that are exposed outside the battery case. For example, the leads provided on the electrode assembly and the negative and positive terminals of the battery case can be connected to each other by a bus bar.

[0007] Here, when joining the bus bar to the negative and positive terminals, laser welding is used. However, in this process, many problems have occurred, such as terminal corrosion due to overwelding, thermal damage and corrosion caused by spatter generated by overwelding, melting of the lead tape, melting of the separator membrane of the electrode assembly, and low voltage due to poor welding.

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide a terminal structure for a secondary battery that can solve the problems caused by overwelding that occur when welding a bus bar to the electrode terminals of a battery case.

[0009] However, the technical problems to be solved by the present invention are not limited to the above problems, and other problems not mentioned can be clearly understood by those of ordinary skill in the art from the description of the invention described below.

Means for Solving the Problems

[0010] The present invention relates to a terminal structure for a secondary battery. In one example, it includes a conductive first member having a protruding portion with a circular cross-section, and a conductive second member having a through-hole into which the protruding portion of the first member is inserted. A welding portion is formed along the circular edge where the protruding portion of the first member is inserted into the through-hole of the second member and they come into contact with each other.

[0011] The protruding portion may be inserted only partially with respect to the entire depth of the through-hole.

[0012] In one embodiment of the present invention, the through hole may have an annular step that restricts or indicates the insertion depth of the protruding portion.

[0013] For example, the step may be a reduced step that restricts the insertion depth of the protruding portion.

[0014] Or, the step may be an extended step that indicates the insertion depth of the protruding portion.

[0015] And, the first member is a terminal component provided on a cap plate that covers one surface of the battery, and the second member may be a bus bar that is electrically connected to a lead of the electrode assembly.

[0016] On the other hand, the present invention provides a secondary battery including the above-described terminal structure for a secondary battery. In one example, a plurality of battery cells are assembled, an electrode assembly in which leads for electrically connecting the plurality of battery cells protrude, a battery case having at least one surface opened so as to accommodate the electrode assembly, a cap plate that closes the opened surface of the battery case and includes a positive terminal and / or a negative terminal, the first member which is a conductive terminal component provided on the cap plate and electrically connected to the positive terminal and / or the negative terminal, and the second member which is a bus bar electrically connected to a lead of the electrode assembly.

[0017] In one embodiment of the present invention, the battery case may have an upper surface that forms an opened surface, and the cap plate may be a top cap including the positive terminal and the negative terminal.

[0018] In one example, the step of the through hole is a reduced step that restricts the insertion depth of the protruding portion, and the welded portion may be formed along a corner portion of the protruding portion exposed to the reduced step.

[0019] In another example, the step of the through hole is an extended step that indicates the insertion depth of the protruding portion, and the welded portion may be formed along an interface between the extended step and the protruding portion.

Advantages of the Invention

[0020] In the terminal structure for a secondary battery of the present invention having the above-described configuration, by forming a welded portion along the circular edge where the protruding portion of the first member is inserted into the through hole of the second member and they come into contact with each other, the problem of excessive welding generated by overlapping the conventional first member and second member and performing spot welding at their centers is prevented. That is, by performing welding along the contact surface between the protruding portion and the through hole, the welding quality is improved, and by dispersing the welding heat along the circular edge, excessive welding can be avoided.

[0021] And in an embodiment where the protruding portion is inserted only partially with respect to the entire depth of the through hole, since welding is performed inside the through hole, the possibility of spatter generated during welding scattering to the electrode assembly side is reduced, effectively protecting the electrode assembly that is easily damaged by overheating, and thereby improving the quality of the secondary battery.

[0022] However, the technical effects that can be obtained by the present invention are not limited to the above-described effects, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0023] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further understand the technical idea of the present invention together with the detailed description of the invention to be described later. Therefore, the present invention should not be construed as being limited only to the matters described in such drawings.

Brief Description of the Drawings

[0024]

Figure 1

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Figure 9

Embodiments for Carrying Out the Invention

[0025] Since the present invention can be subjected to various modifications and can have various embodiments, specific embodiments will be described in detail below.

[0026] However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0027] In the present invention, terms such as "including" and "having" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and do not preclude the presence or addition possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0028] 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 the case where it is directly "above" the other part but also the case 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 the case where it is directly "below" the other part but also the case where there is another part in between. Also, in the present application, being "disposed on" can include not only the upper part but also the case of being disposed in the lower part.

[0029] The present invention relates to a terminal structure for a secondary battery. In one example, it includes a conductive first member having a protruding portion with a circular cross-section and a conductive second member having a through-hole into which the protruding portion of the first member is inserted. A welding portion is formed along the circular edge where the protruding portion of the first member is inserted into the through-hole of the second member and they come into contact with each other.

[0030] Preferably, only a part of the protruding portion can be inserted with respect to the entire depth of the through-hole.

[0031] In the terminal structure for a secondary battery of the present invention having the above-described configuration, by forming a welding portion along the circular edge where the protruding portion of the first member is inserted into the through-hole of the second member and they come into contact with each other, the problem of over-welding generated by overlapping the conventional first member and second member and performing spot welding at their center is prevented. That is, welding is performed along the contact surface between the protruding portion and the through-hole, thereby improving the welding quality, and by dispersing the welding heat along the circular edge, over-welding can be avoided.

[0032] And in an embodiment where only a part of the protruding portion is inserted with respect to the entire depth of the through-hole, since welding is performed inside the through-hole, the possibility of spatter generated during welding scattering to the electrode assembly side is reduced, effectively protecting the electrode assembly that is easily damaged by overheating, and thereby improving the quality of the secondary battery.

[0033] Hereinafter, specific embodiments of the terminal structure for a secondary battery according to the present invention will be described in detail with reference to the accompanying drawings. For reference, the front-back, up-down, left-right directions specifying relative positions used in the following description are for assisting in understanding the invention, and are based on the directions shown in the drawings unless otherwise defined specifically.

[0034] (First Embodiment) FIG. 1 is a drawing showing an example of a rectangular battery to which the terminal structure for a secondary battery according to the present invention (hereinafter, may be simply referred to as "terminal structure") can be applied. The rectangular battery shown in FIG. 1 is a one-way battery, that is, an exemplary embodiment in which the positive electrode terminal 132 and the negative electrode terminal 134 are on the same surface, and in FIG. 1, are arranged on the upper surface of the battery case 120. The terminal structure for a secondary battery according to the present invention relates to the welding structure of the bus bar 150 to the positive electrode terminal 132 and / or the negative electrode terminal 134. Before explaining the overall configuration of the exemplified rectangular battery, the terminal structure of the present invention that can be uniformly applied to various forms of secondary batteries 100 will be described in detail.

[0035] FIG. 2 is a drawing showing a structure in which the conductive first member 10 and the second member 20 are welded to each other. For example, the first member 10 may be a terminal component 140 provided on a cap plate 130 covering one surface of the battery, and the second member 20 may be a bus bar 150 electrically connected to the lead 114 of the electrode assembly 110. Or, conversely, the first member 10 may be the bus bar 150. And, for electrical connection, both the first member 10 and the second member 20 are made of a conductive material.

[0036] The first member 10 includes a protruding portion 12 having a circular cross-section, and the second member 20 includes a through hole 22 into which the protruding portion 12 is inserted. Of course, other forms other than a circular cross-section, for example, an elliptical or polygonal cross-section can also be formed, but considering the ease of processing and welding, it will be common to make the protruding portion 12 and the through hole 22 circular.

[0037] Referring to FIG. 2, when the protruding portion 12 of the first member 10 is fitted into the through hole 22 of the second member 20, a circular contact edge is formed. The welded portion 30 formed by laser welding is along the circular edge, whereby the first member 10 and the second member 20 are joined along the circumferential surfaces in contact with each other. Since the welding action occurs over the entire circumferential surface, uniform welding quality is ensured and excessive welding heat is not generated, thus preventing the problem of over-welding.

[0038] FIG. 3 is a drawing showing another structure in which the conductive first member 10 and the second member 20 are welded to each other. In the connection of the first member 10 and the second member 20, the protruding portion 12 is inserted only partially with respect to the entire depth of the through hole 22, and the welded portion 30 is formed annularly along the contact edge between the first member 10 and the second member 20 inside the through hole 22. Since the laser welding is performed inside the through hole 22, the scattering of the high-temperature spatter generated in the welding process to the periphery is reduced, and thus the problem that the lead tape and the separator film of the heat-sensitive electrode assembly 110 melt is significantly reduced.

[0039] And according to an embodiment of the present invention, a step 24 for limiting the insertion depth of the protruding portion 12 may be provided in the through hole 22, but depending on the form of the step 24, it will physically limit the insertion depth of the protruding portion 12 or perform a function of indicating how far to insert. With the configuration of the step 24, it is ensured that the protruding portion 12 is inserted only partially with respect to the entire depth of the through hole 22.

[0040] FIG. 4 shows the configuration of a reduced step 24-1 that physically limits the insertion depth of the protruding portion 12. The reduced step 24-1 is formed in a form in which the diameter rapidly decreases in the middle of the direction in which the protruding portion 12 is inserted into the through hole 22, and the insertion depth of the protruding portion 12 blocked by the reduced step 24-1 is limited.

[0041] FIG. 5 shows the configuration of the extended step 24-2 that indicates the insertion depth of the protrusion 12. Contrary to the reduced step 24-1 in FIG. 4, the extended step 24-2 in FIG. 5 is formed in such a form that the diameter rapidly increases in the middle of the direction in which the protrusion 12 is inserted into the through-hole 22. Although the extended step 24-2 cannot physically limit the insertion depth of the protrusion 12, it indirectly defines the insertion depth by instructing to insert up to the point where the surface of the extended step 24-2 coincides with the surface of the protrusion 12 visually. In terms of restricting the insertion depth, the extended step 24-2 is inferior in effect compared to the reduced step 24-1, but since a sufficient welding space can be ensured, it has advantages in terms of welding quality and productivity.

[0042] (Second Embodiment) In the second embodiment of the present invention, an exemplary embodiment in which the terminal structure described in the first embodiment is applied to the secondary battery 100 will be described. FIG. 6 is a drawing showing an example in which the terminal structure for a secondary battery of the present invention is applied to a rectangular battery which is one form of the secondary battery 100 in FIG. 1. In the embodiment of FIG. 6, the first member 10 is a conductive terminal component 140 provided on a cap plate 130 that covers one surface of the battery, and the second member 20 corresponds to a bus bar 150 that is electrically connected to the lead 114 of the electrode assembly 110.

[0043] The rectangular battery shown in Fig. 6 includes an electrode assembly 110 with a plurality of battery cells 112 and leads 114 protruding therefrom for electrically connecting them, a battery case 120 with at least one open side for housing the electrode assembly 110, and a cap plate 130 for closing the open side of the battery case 120. The cap plate 130 may be provided with a positive terminal 132 and / or a negative terminal 134. The illustrated rectangular battery is a unidirectional battery, with the upper surface of the battery case 120 forming the open side, and the cap plate 130 closing the open side is constituted by a top cap 130' provided with a positive terminal 132 and a negative terminal 134. Although not shown, in the case of a bidirectional battery where the positive terminal 132 and the negative terminal 134 are respectively arranged on both side surfaces of the rectangular battery, each cap plate will be provided with either the positive terminal 132 or the negative terminal 134 as a side cap.

[0044] Here, the first member 10, which is a conductive terminal component 140, is provided on the cap plate 130 so as to be electrically connected to the positive terminal 132 and / or the negative terminal 134, and the second member 20, which is a bus bar 150, electrically connects the lead 114 of the electrode assembly 110 and the first member 10. For example, as shown in Fig. 7, if a rectangular battery is configured in a structure where one electrode assembly 110 is arranged and connected on each side of one cap plate 130 (also referred to as a butterfly structure due to its symmetric form), the leads 114 of the electrode assemblies 110 on both sides are arranged to have the same polarity with each other, and the paired leads 114 are joined to the bus bar 150, which is the second member 20, by ultrasonic welding or the like. As the terminal structure of the first embodiment, each bus bar 150 is joined to the first member 10 by laser welding or the like.

[0045] For example, FIG. 8 is a drawing showing a structure in which a welded portion 30 is formed on the reduced-height step 24-1 of FIG. 4. As shown in FIG. 8, the welded portion 30 can be formed along the corner of the protruding portion 12 exposed with respect to the reduced-height step 24-1. Alternatively, in the extended-height step 24-2 indicating the insertion depth of the protruding portion 12, as shown in FIG. 9, the welded portion 30 can be formed along the boundary surface between the extended-height step 24-2 and the protruding portion 12. With the terminal structures of FIGS. 8 and 9, the welded portion 30 is formed annularly along the contact edge between the first member 10 and the second member 20 inside the through hole 22. By performing laser welding inside the through hole 22 in this way, the scattering of high-temperature spatter generated during the welding process to the surroundings is reduced, thereby solving the problem that the lead tape and the separator film of the heat-sensitive electrode assembly 110 melt.

[0046] As described above, the present invention has been described in more detail through the 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 of the technical ideas of the present invention. Therefore, there can be various equivalents and modifications that can replace them at the time of this application.

Description of Reference Numerals

[0047] 10: First member 12: Protruding portion 20: Second member 22: Through hole 24: Step 24-1: Reduced-height step 24-2: Extended-height step 30: Welded portion 100: Secondary battery 110: Electrode assembly 112: Battery cell 114: Lead 120: Battery case 130: Cap plate 130’: Top cap 132: Positive electrode terminal 134: Negative electrode terminal 140: Terminal component 150: Bus bar

Claims

1. a conductive first member having a protrusion with a circular cross section; a conductive second member having a through hole into which the protruding portion of the first member is inserted; Including, The terminal structure for a secondary battery, wherein the protrusion of the first member is inserted into the through hole of the second member and a weld is formed along a circular edge where they contact each other.

2. The protrusion is The terminal structure for a secondary battery according to claim 1 , wherein the through hole is only partially inserted with respect to its entire depth.

3. The terminal structure for a secondary battery according to claim 2 , wherein the through hole has an annular step that limits or indicates an insertion depth of the protrusion.

4. The step is The terminal structure for a secondary battery according to claim 3 , wherein the protrusion has a reduced step for limiting an insertion depth thereof.

5. The step is The terminal structure for a secondary battery according to claim 3 , wherein the protrusion has an extended step that indicates an insertion depth of the protrusion.

6. the first member is a terminal part provided on a cap plate that covers one surface of the battery, The terminal structure for a secondary battery according to claim 1 , wherein the second member is a bus bar electrically connected to a lead of an electrode assembly.

7. A secondary battery including the terminal structure for a secondary battery according to any one of claims 1 to 6, an electrode assembly in which a plurality of battery cells are assembled and from which leads protrude for electrically connecting the plurality of battery cells; a battery case having at least one side open to accommodate the electrode assembly; a cap plate that closes an open surface of the battery case and is provided with a positive electrode terminal and / or a negative electrode terminal; The first member is a conductive terminal part provided on the cap plate and electrically connected to the positive electrode terminal and / or the negative electrode terminal; and The second member is a bus bar electrically connected to a lead of the electrode assembly. A secondary battery comprising:

8. The battery case has an open top surface, The secondary battery according to claim 7 , wherein the cap plate is a top cap including the positive terminal and the negative terminal.

9. the step of the through hole is a reduced step that limits the insertion depth of the protrusion, The secondary battery according to claim 7 , wherein the welded portion is formed along a corner of the protrusion exposed to the reduced step.

10. The step of the through hole is an expansion step that indicates the insertion depth of the protrusion, The secondary battery according to claim 7 , wherein the welded portion is formed along a boundary surface between the expanded step and the protrusion.

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