Terminal structure for secondary batteries and secondary batteries equipped therewith

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 the contents disclosed in the document of the Korean patent application are included as part of this specification.

Background Art

[0003] Unlike primary batteries, secondary batteries can be recharged and miniaturized compared to large capacities, 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 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 sheet-shaped positive and negative electrodes coated with an active material and wound, a stack type in which a large number of positive and negative electrodes are sequentially laminated with a separator interposed therebetween, and a stack and folding type in which unit cells of the stack type are 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 exposed outside the battery case. For example, leads on the electrode assembly and the negative and positive terminals of the battery case may be connected to each other by busbars.

[0007] In this process, laser welding is used to join the busbars to the negative and positive terminals, but many problems occurred, including terminal corrosion due to over-welding, thermal damage and corrosion caused by spatter generated by over-welding, melting of the lead tape, melting of the separation membrane of the electrode assembly, and low voltage due to welding defects. [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to provide a terminal structure for secondary batteries that can solve the problems caused by over-welding that occurs when welding the busbar and the electrode terminals of the battery case.

[0009] However, the technical problems that the present invention aims to solve are not limited to those described above, and other problems not mentioned can be clearly understood by an ordinary person of the art from the description of the invention below. [Means for solving the problem]

[0010] The present invention relates to a terminal structure for a secondary battery, and in one example includes a conductive first member having a protrusion with a circular cross-section, and a conductive second member having a through hole into which the protrusion of the first member is inserted, wherein a welded portion is formed along the circular edges of the second member into which the protrusion of the first member is inserted and which come into contact with each other.

[0011] The above-mentioned protrusion can be inserted only partially relative to the overall depth of the through-hole.

[0012] In one embodiment of the present invention, the through hole may include an annular step that limits or indicates the insertion depth of the protrusion.

[0013] For example, the above-mentioned step may be a reducing step that limits the insertion depth of the above-mentioned protrusion.

[0014] Alternatively, the above-mentioned step may be an expanding step that indicates the insertion depth of the above-mentioned protrusion.

[0015] The first component is a terminal component provided on a cap plate that covers one side of the battery, and the second component may be a busbar that is electrically connected to the leads of the electrode assembly.

[0016] On the other hand, the present invention provides a secondary battery comprising the above-described secondary battery terminal structure, wherein, in one example, an electrode assembly comprising a plurality of battery cells and protruding leads that electrically connect the plurality of battery cells; a battery case having at least one open side to house the electrode assembly; a cap plate that closes the open side of the battery case and has a positive electrode terminal and / or a negative electrode terminal; the first member which is a conductive terminal component provided on the cap plate and electrically connected to the positive electrode terminal and / or the negative electrode terminal; and the second member which is a busbar electrically connected to the leads of the electrode assembly.

[0017] In one embodiment of the present invention, the battery case has an open top surface, and the cap plate may be a top cap equipped with the positive terminal and the negative terminal.

[0018] In one example, the step in the through-hole is a reducing step that limits the insertion depth of the protrusion, and the welded portion may be formed along the corner of the protrusion that is exposed relative to the reducing step.

[0019] In other examples, the step in the through-hole is an expanding step indicating the insertion depth of the projection, and the weld can be formed along the interface between the expanding step and the projection.

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 portions 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 portion, 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, by performing welding inside the through-hole, the possibility that spatter generated during welding scatters toward 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] It is a drawing showing an example of a square battery to which the terminal structure for a secondary battery according to the present invention can be applied. [Figure 2] It is a drawing showing a structure in which the first member and the second member are welded to each other. [Figure 3] It is a drawing showing another structure in which the first member and the second member are welded to each other. [Figure 4] This is a drawing showing an embodiment in which the second member is provided with a reduced-sized step. [Figure 5] This is a drawing showing an embodiment in which the second member is provided with an extended-type step. [Figure 6] This is a drawing showing an example in which the terminal structure for a secondary battery of the present invention is applied to the rectangular battery of FIG. 1. [Figure 7] This is a drawing showing an embodiment of a cap plate provided in the rectangular battery of FIG. 6. [Figure 8] This is a drawing showing a structure in which a welding portion is formed on the reduced-sized step of FIG. 4. [Figure 9] This is a drawing showing a structure in which a welding portion is formed on the extended-type step of FIG. 5.

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] Furthermore, in this invention, when a part such as a layer, film, region, or plate is described as being "on top" of another part, this includes not only the case where it is "directly on top" of the other part, but also the case where another part is located in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "directly below" the other part, but also the case where another part is located in between. Also, in this application, being "on top" may include being located not only at the top but also at the bottom.

[0029] The present invention relates to a terminal structure for a secondary battery, and in one example includes a conductive first member having a protrusion with a circular cross-section, and a conductive second member having a through hole into which the protrusion of the first member is inserted, wherein a welded portion is formed along the circular edges that come into contact with each other when the protrusion of the first member is inserted into the through hole of the second member.

[0030] Preferably, the above-mentioned protrusion can be inserted only partially with respect to the overall depth of the through-hole.

[0031] The terminal structure for secondary batteries of the present invention, having the configuration described above, prevents the problem of over-welding that occurred when the first and second members were stacked and spot-welded at their center, by forming a weld along the circular edge where the protrusion of the first member is inserted into the through-hole of the second member and they come into contact. In other words, welding quality is improved by welding along the contact surface between the protrusion and the through-hole, and over-welding can be avoided by dispersing the welding heat along the circular edge.

[0032] Furthermore, in embodiments in which the protruding portion is inserted only a portion of the overall depth of the through-hole, welding is performed inside the through-hole, which reduces the possibility of spatter generated during welding scattering towards the electrode assembly. This effectively protects the electrode assembly, which is susceptible to damage from overheating, thereby improving the quality of the secondary battery.

[0033] Hereinafter, specific embodiments of the terminal structure for secondary batteries according to the present invention will be described in detail with reference to the attached drawings. For reference, the directions front and back, up and down and left and right used to specify relative positions in the following description are for the purpose of aiding the understanding of the invention, and unless otherwise defined, the directions shown in the drawings shall be used as the reference.

[0034] (First Embodiment) Figure 1 is a drawing showing an example of a prismatic battery to which the terminal structure for secondary batteries according to the present invention (hereinafter simply referred to as "terminal structure") can be applied. The prismatic battery shown in Figure 1 is a unidirectional battery, that is, one exemplary embodiment in which the positive terminal 132 and the negative terminal 134 are located on the same plane, in Figure 1, on the upper surface of the battery case 120. The terminal structure for secondary batteries according to the present invention relates to the welding structure of the busbar 150 to the positive terminal 132 and / or negative terminal 134, and before describing the overall configuration of the exemplary prismatic battery, the terminal structure of the present invention, which can be uniformly applied to various forms of secondary batteries 100, will be described in detail.

[0035] Figure 2 is a diagram showing a structure in which a conductive first member 10 and a 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 that covers one side of a battery, and the second member 20 may be a busbar 150 that is electrically connected to the lead 114 of an electrode assembly 110. Alternatively, the first member 10 may be the busbar 150. For electrical connection, both the first member 10 and the second member 20 are made of a conductive material.

[0036] The first member 10 has a circular cross-section projection 12, and the second member 20 has a through hole 22 into which the projection 12 is inserted. Of course, other shapes besides a circular cross-section are possible, such as an elliptical or polygonal cross-section, but considering the ease of processing and welding, it is common to make the projection 12 and the through hole 22 circular.

[0037] As shown in Figure 2, a circular contact edge is created when the protrusion 12 of the first member 10 is fitted into the through hole 22 of the second member 20. The welded portion 30 formed by laser welding follows the circular edge, thereby joining the first member 10 and the second member 20 along their contacting circumferential surfaces. Since the welding action occurs across the entire circumferential surface, uniform welding quality is ensured, and excessive welding heat is not generated, thus preventing the problem of over-welding.

[0038] Figure 3 is a diagram showing another structure in which a conductive first member 10 and a second member 20 are welded to each other. In the joining of the first member 10 and the second member 20, the protrusion 12 is inserted only partially into the overall depth of the through hole 22, and the welded portion 30 is formed in an annular shape inside the through hole 22 along the contact edge between the first member 10 and the second member 20. By performing laser welding inside the through hole 22, the scattering of high-temperature spatter generated during the welding process is reduced, which significantly reduces the problem of the heat-sensitive lead tape or separation film of the electrode assembly 110 melting.

[0039] Furthermore, in some embodiments of the present invention, a step 24 may be provided in the through-hole 22 to limit the insertion depth of the protrusion 12. Depending on the shape of the step 24, it will either physically limit the insertion depth of the protrusion 12 or indicate how far it should be inserted. The configuration of the step 24 ensures that only a portion of the protrusion 12 is inserted into the overall depth of the through-hole 22.

[0040] Figure 4 shows the configuration of the reducing step 24-1 that physically limits the insertion depth of the protrusion 12. The reducing step 24-1 is formed in the middle of the direction in which the protrusion 12 is inserted into the through hole 22, with a shape in which the diameter abruptly decreases, and the insertion depth of the protrusion 12 that is blocked by the reducing step 24-1 is limited.

[0041] Figure 5 shows the configuration of the expanding step 24-2 that indicates the insertion depth of the protrusion 12. In contrast to the contracting step 24-1 in Figure 4, the expanding step 24-2 in Figure 5 is formed in a form in which the diameter rapidly increases in the middle of the direction in which the protrusion 12 is inserted into the through hole 22. The expanding step 24-2 cannot physically limit the insertion depth of the protrusion 12, but it indirectly defines the insertion depth by visually indicating that the protrusion 12 should be inserted to the point where the surface of the expanding step 24-2 and the surface of the protrusion 12 coincide. In terms of limiting the insertion depth, the expanding step 24-2 is less effective than the contracting step 24-1, but it has advantages in terms of welding quality and productivity because it can secure sufficient welding space.

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

[0043] The rectangular battery in Figure 6 includes an electrode assembly 110 with multiple battery cells 112 and leads 114 protruding from it that electrically connect them, a battery case 120 with at least one side open to house the electrode assembly 110, and a cap plate 130 that closes the open side of the battery case 120. The cap plate 130 may have a positive terminal 132 and / or a negative terminal 134, but the rectangular battery shown is a unidirectional battery, the battery case 120 has an open top surface, and the cap plate 130 that closes the open surface consists of a top cap 130' having a positive terminal 132 and a negative terminal 134. If it is a bidirectional battery, although not shown, with a positive terminal 132 and a negative terminal 134 on each side of the rectangular battery, each cap plate would have either a positive terminal 132 or a 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 busbar 150, electrically connects the leads 114 of the electrode assembly 110 to the first member 10. For example, as shown in Figure 7, if a rectangular battery is constructed with a structure in which one electrode assembly 110 is arranged and connected on each side of a single cap plate 130 (also called a butterfly structure due to its symmetrical form), the leads 114 of the electrode assemblies 110 on both sides are arranged to have the same polarity, and the paired leads 114 are joined to the busbar 150, which is the second member 20, by ultrasonic welding or the like, and as the terminal structure of the first embodiment, each busbar 150 is joined to the first member 10 by laser welding or the like.

[0045] For example, Figure 8 is a diagram showing a structure in which a welded portion 30 is formed on the reduced step 24-1 of Figure 4. As shown in Figure 8, the welded portion 30 can be formed along the corner of the protruding portion 12 that is exposed relative to the reduced step 24-1. Alternatively, in the expanding step 24-2 which indicates the insertion depth of the protruding portion 12, as shown in Figure 9, the welded portion 30 can be formed along the interface between the expanding step 24-2 and the protruding portion 12. With the terminal structures of Figures 8 and 9, the welded portion 30 is formed in an annular shape inside the through-hole 22 along the contact edge between the first member 10 and the second member 20. By performing laser welding inside the through-hole 22 in this way, the scattering of high-temperature spatter generated during the welding process is reduced, thereby eliminating the problem of the lead tape or separation film of the heat-sensitive electrode assembly 110 melting.

[0046] The present invention has been described in more detail above through the drawings and embodiments. However, the configurations described in the drawings or embodiments described herein are merely one embodiment of the present invention and do not represent the entire technical concept of the present invention. Therefore, there may be various equivalents and modifications that can substitute for them at the time of filing. [Explanation of symbols]

[0047] 10: First component 12:Protrusion 20: Second component 22: Through Hole 24: Step 24-1: Reducing step 24-2: Expandable step 30: Welded section 100: Secondary battery 110: Electrode assembly 112: Battery cell 114: Lead 120: Battery case 130: Cap plate 130': Top cap 132: Positive terminal 134: Negative terminal 140: Terminal components 150: Bus bar

Claims

1. A conductive first member having a protruding portion with a circular cross-section, A conductive second member having a through hole into which the protruding portion of the first member is inserted, Includes, The protruding portion of the first member is inserted into the through-hole of the second member, and a welded portion is formed along the circular edge where they come into contact with each other. The aforementioned protrusion is a terminal structure for a secondary battery, which is inserted only partially into the overall depth of the through-hole.

2. The terminal structure for a secondary battery according to claim 1, wherein the through-hole has an annular step.

3. The terminal structure for a secondary battery according to claim 2, wherein the diameter of the through hole at the location where the step is located is smaller than the diameter of the protrusion.

4. The terminal structure for a secondary battery according to claim 2, wherein the diameter of the through hole at the position where the step is located is larger than the diameter of the protrusion.

5. The first component is a terminal component provided on a cap plate that covers one side of the battery. The terminal structure for a secondary battery according to claim 1, wherein the second member is a busbar electrically connected to the lead of the electrode assembly.

6. In a secondary battery comprising the terminal structure for a secondary battery described in claim 1 or 5, An electrode assembly comprising multiple battery cells, with leads protruding from it that electrically connect the multiple battery cells, A battery case having at least one side open to accommodate the electrode assembly, A cap plate that closes the open surface of the battery case and is provided with a positive terminal and / or a negative terminal, The first member 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 busbar electrically connected to the lead of the electrode assembly, Rechargeable batteries, including those mentioned above.

7. A secondary battery comprising a terminal structure for a secondary battery as described in any one of Claims 2 to 4, An electrode assembly comprising multiple battery cells, with leads protruding from it that electrically connect the multiple battery cells, A battery case having at least one side open to accommodate the electrode assembly, A cap plate that closes the open surface of the battery case and is provided with a positive terminal and / or a negative terminal, The first member 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 busbar electrically connected to the lead of the electrode assembly, Rechargeable batteries, including those mentioned above.

8. The aforementioned battery case has an open top surface. The secondary battery according to claim 6, wherein the cap plate is a top cap having the positive electrode terminal and the negative electrode terminal.

9. The diameter of the through hole at the position where the step is located is smaller than the diameter of the protrusion, The secondary battery according to claim 7, wherein the welded portion is formed along the corner of the protruding portion that is exposed relative to the step.

10. The diameter of the through hole at the position where the step is located is greater than the diameter of the protrusion. The secondary battery according to claim 7, wherein the welded portion is formed along the interface between the step and the protruding portion.

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