Lead-tab coupling structures and Secondary battery having the same

Abstract

The present invention relates to a lead-tab coupling structure formed in a ring shape, into which a tab portion and an electrode lead are inserted, and provided with a clip made of an elastic material at the top so that the center can be bent upward and downward, thereby facilitating coupling between an electrode lead and an electrode tab and simultaneously performing a protection circuit function, and to a secondary battery including the same.

Description

Technology Field

[0001] The present invention relates to a lead-tab coupling structure that facilitates coupling between an electrode lead and an electrode tab and simultaneously performs a protection circuit function in a secondary battery, and to a secondary battery including the same. Background Technology

[0002] Generally, among lithium secondary batteries, pouch-type batteries feature a pouch casing composed of a multilayer film consisting of a metal foil layer and a synthetic resin layer covering it. Since the use of this design allows for a significant reduction in battery weight compared to cylindrical or prismatic lithium secondary batteries that utilize metal cans, the lightweighting of lithium secondary batteries has evolved in the direction of pouch-type batteries.

[0003] As shown in FIG. 1, this pouch-type lithium secondary battery has a structure in which a positive electrode plate (4) and a separator interposed between them, in the form of an electrode assembly (3) wound multiple times, are accommodated in a pouch outer material (not shown), and an electrode lead (8) connected to electrode tabs (5) protruding from one side of the electrode assembly protrudes into the pouch outer material.

[0004] At this time, methods such as ultrasonic welding, resistance welding, and laser welding are generally used to connect electrode tabs and electrode leads; however, laser welding involves high equipment costs and difficult maintenance, such as the replacement of expensive parts. Resistance welding has a limited range of application, is difficult to apply to aluminum materials, and suffers from reduced reliability of the welded joint after welding. Additionally, ultrasonic welding exhibits significant quality variation and poses a risk of damage to the protection circuit module due to vibration.

[0005] Meanwhile, lithium secondary batteries pose a risk of explosion as they heat up due to IR heat generation when exposed to high temperatures or when a large current flows within a short period of time due to overcharging, external short circuits, needle penetration, or localized damage. Accordingly, lithium secondary batteries are used in combination with protection circuits to protect them from abnormal situations such as the occurrence of overcurrent. However, unlike cylindrical or prismatic secondary batteries, pouch-type secondary batteries use a pouch as the outer casing instead of a can, and thus do not contain a protection circuit within the battery. To apply a protection circuit, a method of connecting a separate protection circuit in series with the electrode leads must be used; however, due to structural difficulties caused by space constraints within the pouch outer casing, protection circuits are not currently being applied. Prior art literature

[0006] Korean Published Patent Application No. 2017-0042134 (October 11, 2018) The problem to be solved

[0007] The present invention has been devised to solve the problems described above, and aims to provide a lead-tab coupling structure that facilitates coupling between an electrode lead and an electrode tab and simultaneously performs a protection circuit function, and a secondary battery including the same. means of solving the problem

[0008] A lead-tab coupling structure according to one example of the present invention comprises: a tab portion having electrode tabs stacked therein and a body on which an electrode lead electrically connected to the tab portion is seated; and a clip provided on the upper part of the body and connected to the body, wherein the center of the clip may be bent upward and downward.

[0009] The above clip may be composed of a first clip and a second clip that form a stacked structure in the vertical direction, and may have a structure in which the second clip is closely coupled to the upper part of the first clip.

[0010] The second clip may be made of a material having a higher coefficient of thermal expansion than the first clip.

[0011] A secondary battery according to one example of the present invention comprises: an electrode assembly; a tab portion having stacked electrode tabs protruding from one side of the electrode assembly; an electrode lead electrically connected to the tab portion; and a lead-tab coupling structure comprising a body in which the tab portion and the electrode lead are seated, and a clip provided on the upper part of the body and connected to the body, wherein the center of the clip of the lead-tab coupling structure may be bent upward and downward.

[0012] The clip of the above lead-tab coupling structure may be made of an elastic material.

[0013] The clip of the above lead-tab coupling structure is composed of a first clip and a second clip that form a stacked structure in the vertical direction, and may have a structure in which the second clip is closely coupled to the upper part of the first clip.

[0014] The second clip may be made of a material having a higher coefficient of thermal expansion than the first clip.

[0015] The clip of the above lead-tab coupling structure can have its center rise upward as the temperature increases when a specific temperature is exceeded.

[0016] The electrode lead is positioned on the upper part of the tab portion, and when the center of the clip is bent upward, the electrode lead can move upward along the clip and be separated from the tab portion.

[0017] It may further include a connecting member connecting the clip and the electrode lead.

[0018] The length of one direction of the first clip may be longer than the length of one direction of the second clip. Effects of the invention

[0019] According to the present invention, the electrode lead and the electrode tab can be electrically connected using a lead-tab coupling structure, thereby increasing the ease of manufacturing. Furthermore, since the electrode tabs and the tab portion and the electrode lead are separated from each other by the lead-tab coupling structure in the event of a rapid temperature rise, the electrical flow is blocked, thereby significantly reducing the possibility of events such as ignition or explosion of the secondary battery and ensuring safety in the use of the secondary battery. Brief explanation of the drawing

[0020] Figure 1 is a schematic diagram showing the general structure of a conventional electrode assembly. FIGS. 2 and 3 are perspective views of a lead-tab coupling structure according to an example of the present invention, where FIG. 2 shows the center of the clip bent downward, and FIG. 3 shows the center of the clip bent upward. FIGS. 4 and 5 are schematic diagrams showing a lead-tab coupling structure coupled to an electrode lead and an electrode tab, where FIG. 4 shows the center of the clip bent downwards and FIG. 5 shows the center of the clip bent upwards. Figures 6 and 7 show the front view of AA' of Figures 4 and 5, respectively. FIG. 8 is a perspective view of a lead-tab coupling structure according to another example of the present invention, showing that the front-rear lengths of the first clip and the second clip are different. FIG. 9 is a drawing for showing a connecting member that connects an electrode lead and a clip. Specific details for implementing the invention

[0021] Hereinafter, the present invention will be described with reference to the attached drawings.

[0022] FIGS. 2 and 3 are perspective views of a lead-tab coupling structure according to an example of the present invention, where FIG. 2 shows the center of the clip bent downward, and FIG. 3 shows the center of the clip bent upward. FIGS. 4 and 5 are schematic diagrams showing the lead-tab coupling structure coupled to an electrode lead and an electrode tab, where FIG. 4 shows the center of the clip bent downward, and FIG. 5 shows the center of the clip bent upward. FIG. 5 shows the lead-tab coupling structure of FIG. 3 coupled to an electrode lead and an electrode tab, and FIG. 6 and 7 show the AA' front views of FIG. 4 and FIG. 5, respectively.

[0023] As described above, the lead-tab coupling structure (10) of the present invention is such that the center of the clip (200), which is an upper structure, can be bent upward and downward. The lead-tab coupling structure (10) can accommodate a tab portion (30) in which electrode tabs (31) are stacked and an electrode lead (40) disposed on the upper part of the tab portion (30) inside, thereby performing the function of closely coupling the tab portion (30) and the electrode lead (40) to each other.

[0024] First, referring to FIG. 4, the tab portion (30) and the electrode lead (40) are described as follows: the tab portion (30) is formed by stacking multiple electrode tabs (31) that extend in one direction from each electrode plate (21) of the electrode assembly (20) and protrude from one side of the electrode assembly (20). The tab portion (30) corresponds to electrode tabs (31) having the same polarity that protrude from the electrode plate (21) having the same polarity among the electrode plates (21) composed of a positive plate or a negative plate. In FIG. 4 and 5, the positive plate and the negative plate are not shown separately, and when the positive plate and the negative plate are stacked alternately one by one, the positive tab stacking portion protruding from the positive plate is formed by stacking positive tabs extending in one direction of each positive plate, and the negative tab stacking portion protruding from the negative plate can be formed by stacking negative tabs extending in the other direction of the negative plate, which is different from the one direction of the positive plate. However, since the positive plate and the negative plate are alternately stacked while being mutually insulated through a separator, the positive tab and the negative tab may be formed in one direction. In the following description of the present invention, the positive tab and the negative tab, or the positive plate and the negative plate, will not be distinguished and will be referred to as the electrode tab and the electrode plate, respectively.

[0025] The electrode lead (40) is a plate-shaped plate or metal bar made of a conductive material and can be electrically connected to the electrode tabs (31) by contacting the upper surface of the electrode tab (31) located at the top of the tab portion (30). This electrode lead (40) performs a function corresponding to a predetermined electrode interface that electrically connects the electrode assembly (20) and an external application device.

[0026] The lead-tab coupling structure (10) of the present invention is a structure for electrically connecting electrode tabs (31) of the tab portion (30) and electrode leads (40) by bringing them into close contact with each other, and may comprise a widely open ring-shaped body (100) and a clip (200) provided on the upper part of the body (100).

[0027] The body (100) may provide a space within which a tab portion (30) and an electrode lead (40) are seated. Specifically, the body (100) may be formed in a shape that is open to the front and back, consisting of a bottom surface (110) and side portions (120) that extend vertically from the bottom surface (110) at each of the two ends of the bottom surface (110), and the tab portion (30) and the electrode lead (40) may be seated in the internal space defined by the bottom surface (110) and the side portions (120). The body (100) may be made of a metal or non-metal material, may be made of an insulating material, and it may be preferable to be made of a material with high thermal conductivity. The width of the internal space formed by the bottom surface (110) and the two sides (120) of the body (100) can be formed to correspond to the width of the electrode tabs (31) and the electrode lead (40). More specifically, the width between the two sides (120) can be formed slightly wider than the width of the electrode tabs (31) and the electrode lead (40) so that there is a predetermined gap between the left and right ends of the electrode tabs (31) and the electrode lead (40) and the two sides (120) of the body (100). This not only facilitates the seating of the electrode tabs and the electrode lead inside the body, but also allows the electrode lead to move easily by reducing the frictional force between the electrode lead and the two sides of the body when the electrode lead moves upward along the clip and separates from the electrode tab, as described later.

[0028] The clip (200) is provided at the upper part of the internal space and may be configured to be provided at the upper part of the body (100) to connect the two sides (120) of the body (100). By means of the body (100) and the clip (200), the lead-tap coupling structure (10) of the present invention may have a hollow ring shape, and the tab portion (30) and the electrode lead (40) may be inserted into the hollow in a fitted structure.

[0029] At this time, the clip (200) may be made of an elastic material, and accordingly, the center may be bent upward or downward. That is, FIG. 2 shows the center of the clip (200) bent downward, and FIG. 3 shows the center of the clip (200) bent upward. The clip (200) is made of an elastic material, and at the same time, the width of the clip (200) is formed to be larger than the width of the bottom surface (110). Furthermore, as both ends of the clip (200) in the width direction are fixed by the two sides (120) of the body (100), the center of the clip (200) may be bent downward or upward.

[0030] According to the lead-tab coupling structure (10) having such a structure, when the center of the clip (200) is bent upward, the internal space of the structure (10) is expanded, and in this state, the electrode lead (40) and the tab portion (30) are inserted into the interior of the structure (10), and after the electrode lead (40) and the tab portion (30) are inserted, the center of the clip (200) is bent downward, thereby pressing the electrode lead (40) from the top to the bottom by the elastic force of the clip (200), and accordingly, the electrode tabs (31) of the electrode lead (40) and the tab portion (30) can be closely joined to each other. That is, the lead-tab coupling structure of the present invention has a structure in which the clip is made of an elastic material and the center can be bent upward and downward, so that the structure can be easily inserted into the electrode lead / tab part while the center of the clip (200) is bent upward, and furthermore, after inserting the structure into the electrode lead / tab part, the center of the clip is bent downward, thereby creating a compressive force in the internal space by the clip and the bottom surface of the body, so that the electrode leads and electrode tabs located in the internal space are strongly pressed against each other, thereby ensuring stable electrical connectivity between the electrode leads and electrode tabs.

[0031] At this time, the present invention may form the clip (200) into a structure of a first clip (210) and a second clip (220) so that the structure (10) can further perform a protection circuit function. Specifically, as shown in FIGS. 2 and 3, the clip (200) may be composed of a first clip (210) and a second clip (220) that form a stacked structure of different materials in the vertical direction, and at the same time, may have a structure in which the second clip (220) is closely coupled to the upper part of the first clip (210). That is, the first clip (210) may be placed at the bottom and the second clip (220) may be placed at the top of the first clip (210), and the lower surface of the second clip (220) and the upper surface of the first clip (210) may be in close contact. At this time, the structure may have a structure in which the two sides of the first clip (210) are connected to the two sides (120) of the body (100) and the second clip (220) is stacked on top of the first clip (210), or the two sides of the second clip (220) are connected to the two sides (120) of the body (100) and the first clip (210) is stacked on bottom of the second clip (220). Additionally, FIGS. 2 and 3 show that the front-rear length of the first clip (210) and the front-rear length of the second clip (220) are the same, but as in FIG. 8, the front-rear length (L_210) of the first clip (210) and the front-rear length (L_220) of the second clip (220) may be different from each other.

[0032] Furthermore, in the clip (200) having the structure described above, the coefficient of thermal expansion of the first clip (210) may be formed to be smaller than the coefficient of thermal expansion of the second clip (220). That is, the coefficient of thermal expansion of the material forming the first clip (210) may be smaller than the coefficient of thermal expansion of the material forming the second clip (220), and this may cause the degree of volume expansion of the first clip (210) and the degree of volume expansion of the second clip (220) to be different when heat is generated. More specifically, when a certain temperature is exceeded, as the temperature increases, the second clip expands more than the first clip, so the center of the clip (200) may gradually rise upward according to the bimetal principle. The material forming the first clip (210) may be tungsten, molybdenum, iron, nickel, or an alloy thereof, and the material forming the second clip (220) may be copper, silver, manganese, aluminum, zinc, or an alloy thereof.

[0033] As described above, there is a risk that a lithium secondary battery may explode if it is exposed to high temperatures or if a large current flows within a short period of time due to overcharging, external short circuits, needle penetration, or local damage, as the battery heats up due to IR heating. In particular, if an overcurrent exceeding a limit flows through a lithium secondary battery, the battery generates heat due to Joule heating, causing the internal temperature of the battery to rise rapidly. Furthermore, this rapid rise in temperature can cause a decomposition reaction of the electrolyte, which can eventually lead to the explosion of the battery, and can even lead to a so-called thermal runaway phenomenon where the explosion of one battery leads to the explosion of neighboring batteries.

[0034] When the internal temperature rises rapidly, the temperature of the lead-tab coupling structure (10) provided adjacent to the electrode assembly (20) also rises. In this case, since the first clip (210) is made of a material with a smaller coefficient of thermal expansion than the second clip (220), the degree of volume expansion of the second clip (220) becomes greater than the degree of volume expansion of the first clip (210), and due to the difference in volume expansion rates between the first clip (210) and the second clip (220), the center of the first clip (210) and the second clip (220) rises upward. Accordingly, the internal space of the structure (10) expands, and the force of the clip (200) pressing the electrode lead (40) and the tab portion (30) weakens, so that each electrode tab (310) of the tab portion can be spaced apart from each other at a predetermined distance as shown in FIG. 9.

[0035] In the present invention, a specific temperature can be appropriately set by considering the internal temperature of the secondary battery at the time of thermal runaway, the material of the first and second clips, the size of the structure, and the distance between the structure and the electrode assembly. Additionally, by comprehensively considering the shape, material, coefficient of thermal expansion, width, and length of the first and second clips, the clips can be appropriately designed so that the center of the clip remains bent downwards below a specific temperature, and the center of the clip bends upwards above a specific temperature.

[0036] Furthermore, in the present invention, when an abnormal situation occurs in the battery and the internal temperature of the battery rises rapidly, the electrode lead (40) may be connected to the clip (200) to separate the electrode lead (40) from the tab portion (30). That is, when the center of the clip (200) is bent upward, the electrode lead (40) may move upward along the clip (200) and be separated from the tab portion (30), so that the electrode lead (40) and the clip (200) may be connected. The method of connecting the electrode lead (40) and the clip (200) can be varied; for example, the lower surface of the first clip and the upper surface of the electrode lead may be connected using an adhesive member, or the electrode lead and the clip may be connected by further providing a connecting member (C) that connects the lower surface of the first clip and the upper surface of the electrode lead as shown in FIG. 8.

[0037] Thus, the lead-tab coupling structure of the present invention can facilitate the coupling of the structure with the electrode lead / electrode tab by bending the clip upward when coupling the electrode lead and the electrode tab together, and furthermore, after coupling the lead-tab coupling structure to the electrode lead / electrode tab, the clip can be bent downward to firmly secure the electrode lead and the electrode tab together. Moreover, by configuring the clip with first and second clips having different coefficients of thermal expansion, it can perform a protection circuit function by interrupting the electrical flow between the electrode tabs or between the tab portion and the electrode lead in the event of an abnormal situation in the battery.

[0038] In the present invention, the lead-tab coupling structure is composed of a body and a clip formed on the upper part of the body. The clip may be constructed by laminating materials with different thermal conductivity, but as another embodiment, the material constituting the body may also be constructed by laminating materials with different thermal conductivity, just like the clip. Through this, when the temperature rises due to overcurrent, the electrode lead and the tab can be electrically separated by utilizing the characteristic of different thermal conductivity (bimetal principle).

[0039] Hereinafter, a secondary battery including the lead-tab coupling structure described above will be explained. Content that overlaps with what has been explained previously will be omitted.

[0040] FIGS. 4 and 5 are partial perspective views of a secondary battery of the present invention, FIG. 4 shows the center of the clip of the lead-tab coupling structure bent downward, and FIG. 5 shows the center of the clip of the lead-tab coupling structure bent upward.

[0041] The secondary battery of the present invention may largely comprise an electrode assembly (20), a tab portion (30) in which electrode tabs (31) protruding from one side of the electrode assembly (20) are stacked, an electrode lead (40) disposed on the upper part of the tab portion (30), and a lead-tab coupling structure (30) surrounding the tab portion (30) and the electrode lead (40). Although not illustrated, it may further comprise a pouch outer material that accommodates the electrode assembly and the tab portion inside and causes one side of the electrode lead to protrude to the outside.

[0042] As such, unlike conventional pouch batteries, the secondary battery of the present invention allows for the electrical connection of electrode leads and electrode tabs using a lead-tab coupling structure without the use of welding, thereby increasing the ease of manufacturing. Furthermore, compared to conventional pouch batteries, which lack a protection circuit and thus make it difficult to respond to abnormal situations, the secondary battery of the present invention has a structure in which the electrode tabs and the tab portion and electrode leads are separated from each other by the lead-tab coupling structure upon a rapid temperature rise, thereby blocking the electrical flow and significantly reducing the possibility of events such as ignition or explosion of the secondary battery, thereby ensuring safety in the use of the secondary battery.

[0043] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. Explanation of the symbols

[0044] 1: Secondary battery 10: Lead-tab joint structure 100: Body 110, 120: Bottom surface, both sides 200: Clip 210, 220: Clip 1, Clip 2 20: Electrode assembly 21: Electrode plate 30: Tab section 31: Each electrode tab 40: Electrode lead

Claims

Claim 1 A lead-tab coupling structure comprising: a tab portion having electrode tabs stacked therein and a body on which an electrode lead electrically connected to the tab portion is seated; and a clip provided on the upper part of the body and connected to the body; wherein the center of the clip is bent upward and downward, and the clip is made of an elastic material, so that when the center is bent upward, the internal space of the body expands, and when the center is bent downward, the tab portion and the electrode lead are pressed downward to tightly connect. Claim 2 In claim 1, the clip is composed of a first clip and a second clip that form a stacked structure in the vertical direction, and has a structure in which the second clip is closely coupled to the upper part of the first clip, forming a lead-tab coupling structure. Claim 3 A lead-tab coupling structure according to paragraph 2, wherein the second clip is made of a material having a higher coefficient of thermal expansion than the first clip. Claim 4 A secondary battery comprising: an electrode assembly; a tab portion having stacked electrode tabs protruding from one side of the electrode assembly; an electrode lead electrically connected to the tab portion; and a lead-tab coupling structure comprising a body in which the tab portion and the electrode lead are seated, and a clip provided on the upper part of the body and connected to the body; wherein the tab portion and the electrode lead are arranged in an overlapping manner in the vertical direction when seated on the body, and the clip is made of an elastic material and has its center bent downward to press the tab portion and the electrode lead downward to tightly bond them. Claim 5 In paragraph 4, the clip of the lead-tab coupling structure is made of an elastic material, a secondary battery. Claim 6 A secondary battery according to claim 5, wherein the clip of the lead-tab coupling structure is composed of a first clip and a second clip that form a stacked structure in the vertical direction, and the second clip is closely coupled to the upper part of the first clip. Claim 7 A secondary battery according to claim 6, wherein the second clip is made of a material having a higher coefficient of thermal expansion than the first clip. Claim 8 In claim 7, the clip of the lead-tab coupling structure is a secondary battery in which the center rises upward as the temperature increases when a specific temperature is exceeded. Claim 9 A secondary battery according to claim 8, wherein the electrode lead is positioned on the upper part of the tab portion, and when the center of the clip is bent upward, the electrode lead moves upward along the clip and is separated from the tab portion. Claim 10 A secondary battery according to claim 9, further comprising a connecting member connecting the clip and the electrode lead. Claim 11 A secondary battery according to claim 6, wherein the length of one direction of the first clip is longer than the length of one direction of the second clip.

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