Secondary battery and method of manufacturing the same

Abstract

The present invention relates to a secondary battery and a method for manufacturing the secondary battery, and to a secondary battery that can improve battery quality by enabling an airtight connection between a safety vent and a current interrupt device (CID) to prevent a leak path of an internal electrolyte or the like from occurring at the connection between the safety vent and the CID, and that can easily detect a weak connection defect by X-ray inspection or the like even if a weak connection between the safety vent and the CID occurs, thereby preventing the occurrence of the defect.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0151921 filed November 14, 2022 and Korean Patent Application No. 10-2023-0127168 filed September 22, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a secondary battery and a method for manufacturing the secondary battery, and to a secondary battery that can improve battery quality by enabling an airtight connection between a safety vent and a current interrupt device (CID) to prevent a leak path of an internal electrolyte or the like from occurring at the connection between the safety vent and the CID, and that can easily detect a weak connection defect by X-ray inspection or the like even if a weak connection between the safety vent and the CID occurs, thereby preventing the occurrence of the defect. [Background technology]

[0003] Depending on the shape of the battery case, secondary batteries are classified into cylindrical batteries and prismatic batteries, in which the electrode assembly is housed in a cylindrical or prismatic metal can, and pouch batteries, in which the electrode assembly is housed in a pouch-shaped case made of an aluminum laminate sheet.

[0004] The electrode assembly housed in the battery case is a chargeable and dischargeable power generating element having a laminated structure of a positive electrode / separator / negative electrode, and is classified into a jelly roll structure in which a separator is interposed between a long sheet-like positive electrode and a negative electrode coated with an active material and wound up; a stack structure in which a plurality of positive electrodes and a negative electrodes of a predetermined size are sequentially stacked with a separator interposed between them; and a stack / folding type electrode assembly having a structure in which a bicell or full cell in which a predetermined unit of positive electrodes and a negative electrodes are stacked with a separator interposed between them is wound up.

[0005] Among these, jelly-roll electrode assemblies have the advantages of being easy to manufacture and having a high energy density per weight, and are therefore widely produced. A jelly-roll electrode assembly can be fabricated by assembling a laminate consisting of long sheet-shaped positive and negative electrodes with a separator interposed therebetween, and winding the sheet in the longitudinal direction while contacting one end of the electrode laminate with a winding core. Furthermore, such a jelly-roll electrode assembly can be inserted into a battery case consisting of a cylindrical metal can to form a cylindrical secondary battery.

[0006] Such cylindrical secondary batteries are designed to have high energy density, and such increased energy density requires lithium secondary batteries to have a high level of stability, which tends to increase the demand for cylindrical batteries.

[0007] Fig. 1 is a diagram showing a state in which a safety vent and a current interruption device in a conventional secondary battery are welded together by full penetration welding, and Fig. 2 is a diagram showing a state in which a safety vent and a current interruption device in a conventional secondary battery are welded together by non-penetration welding.

[0008] Referring to FIG. 1, a conventional secondary battery 1 includes an electrode assembly, a can housing the electrode assembly, and a cap assembly 2 covering the upper opening of the can. FIG. 1 specifically illustrates the cap assembly 2. For ease of explanation, the electrode assembly and the can are not shown. In FIG. 1, the cap assembly 2 may include a top cap 11, a safety vent 12, and a current interrupt device 13. The top cap 11 may be configured to form the outermost terminal for electrical connection to the outside. The safety vent 12 may be located below the top cap 11 and connected to the top cap 11 at its outer edge. The safety vent 12 may be attached to a main gasket 14 at its outer edge. The safety vent 12 may be configured such that a central region 15, which is an inner region of the outer edge, deforms when the internal pressure of the can increases.

[0009] Alternatively, the current interrupting device 13 may be located below the safety vent 12, have an electrode tab connected to the electrode assembly on its underside, and be connected to the safety vent 12 in the central region 15 of the safety vent 12. A subgasket may be located on the outer edge of the current interrupting device to prevent the safety vent 12 and the current interrupting device 13 from coming into contact with each other except in the central region.

[0010] Conventionally, central region 15 of safety vent 12 and central region of current interruption device 13 have been welded together. In FIG. 1 , the portion indicated by an inverted triangle is the portion where central region 15 of safety vent 12 and central region of current interruption device 13 are welded together. Furthermore, notch 13-a may be formed around central region 15, which is the welded portion. Notch 13-a may be a portion that breaks when the internal pressure of the can rises above a threshold. When notch 13-a breaks, the inner central region portion of notch 13-a and the outer portion of notch 13-a break and separate from each other, thereby interrupting the current.

[0011] Specifically, before notch 13-a breaks, a current path is formed from the electrode of the electrode assembly to the electrode tab connected to the electrode, from the electrode tab to current interruption device 13 connected to the electrode tab, from current interruption device 13 to safety vent 12 which is welded to the safety vent 12, and further to top cap 11 which is connected to the safety vent 12 at the outer edge of the safety vent 12. However, when notch 13-a breaks due to an increase in the internal pressure of the can, no further current flows from current interruption device 13 to safety vent 12, and the current is interrupted.

[0012] When the internal pressure of the can rises, the central portion 15 of the safety vent 12 moves upward. At that time, the inner central portion of the notch 13-a of the current interrupting device 13, which is welded to the central portion of the safety vent 12, moves upward together with the safety vent 12, while the outer portion of the notch 13-a of the current interrupting device 13 does not rise but remains in its original position. Therefore, the notch 13-a portion breaks, interrupting the current. For this current interruption operation, the central portion of the safety vent 12 and the central portion of the current interrupting device 13 are connected to each other. Conventionally, this connection has been made by welding.

[0013] However, problems have arisen when manufacturing a secondary battery 1 using such welding. For example, as shown in Fig. 1, if a full penetration weld occurs when welding the center portion of the safety vent 12 to the center portion of the current interrupter 13, a leak path for the internal electrolyte or the like may occur at the joint between the safety vent 12 and the current interrupter 13. In this case, there is a risk of leakage, which can lead to problems such as a deterioration in the quality and safety of the secondary battery.

[0014] Furthermore, as shown in Figure 2, if non-penetration welding occurs when welding the center part of the safety vent 12 to the center part of the current interruption device 13, there is a possibility that a weak weld may occur, which poses a risk of the current in the cell being interrupted. Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention has been made to solve the above problems, and an object of the present invention is to provide a secondary battery and a method for manufacturing the secondary battery that can improve battery quality by enabling an airtight connection between a safety vent and a current interrupt device (CID) and preventing a leak path of an internal electrolyte or the like from occurring at the connection between the safety vent and the CID. Also, an object of the present invention is to provide a secondary battery and a method for manufacturing the secondary battery that can easily detect a weak connection defect by X-ray inspection or the like even if a weak connection between the safety vent and the CID occurs, thereby preventing the occurrence of the defect. [Means for solving the problem]

[0016] The secondary battery according to the present invention includes an electrode assembly, a can in which the electrode assembly is housed, and a cap assembly that covers the opening of the can. The cap assembly includes a top cap that forms an outermost terminal for electrical connection to the outside, a safety vent located below the top cap and connected to the top cap at an outer edge, the safety vent changing shape or position at a predetermined region inside the outer edge when the internal pressure of the can rises above a threshold, and a current interrupt device (CID) located below the safety vent, having an electrode tab connected to the electrode assembly at its underside and connected to the safety vent at a predetermined region of the safety vent. One of the safety vent and the current interrupt device (CID) has a recessed portion with a recessed shape, and the other of the safety vent and the current interrupt device (CID) has a protruding portion that protrudes in a shape corresponding to the recessed portion. The recessed portion and the protruding portion are press-fitted together, thereby connecting the safety vent and the current interrupt device (CID) at a predetermined region.

[0017] The predetermined area may be a central portion of the safety vent.

[0018] The indentation may be formed as a groove on the top surface of the current interrupt device (CID), and the protrusion may be formed on the safety vent.

[0019] The stiffness of the current interrupt device (CID) may be greater than the stiffness of the safety vent.

[0020] The grooves formed in the top surface of the current interrupt device (CID) may have a diameter or width that increases with depth.

[0021] The protrusion formed on the safety vent may include a first safety vent portion extending downward, a second safety vent portion extending from an end of the first safety vent portion in a direction parallel to the bottom surface of the groove, and a third safety vent portion extending upward from an end of the second safety vent portion.

[0022] The indentation may be formed in the shape of a groove on the underside of the safety vent, and the protrusion may be formed on the current interrupt device (CID).

[0023] The stiffness of the safety vent may be greater than the stiffness of the current interrupt device (CID).

[0024] The grooves formed in the lower surface of the safety vent may increase in diameter or width with depth.

[0025] The protrusion formed on the current interrupter (CID) may include a first current interrupter portion extending upward, a second current interrupter portion extending from an end of the first current interrupter portion in a direction parallel to the bottom surface of the groove, and a third current interrupter portion extending downward from an end of the second current interrupter portion.

[0026] The recess may be formed by bending a portion of a current interruption device (CID) downward, and the protrusion may be formed by bending a portion of a safety vent downward.

[0027] The stiffness of the safety vent may be greater than the stiffness of the current interrupt device (CID).

[0028] The indentation formed in the current interrupting device (CID) may include a first current interrupting device bent portion extending downward, a second current interrupting device bent portion extending in an angled direction from an end of the first current interrupting device bent portion, and a third current interrupting device bent portion extending upward from the end of the second current interrupting device bent portion, and the protrusion formed in the safety vent may include a first safety vent bent portion extending downward, a second safety vent bent portion extending from an end of the first safety vent bent portion in a direction parallel to the extension direction of the second current interrupting device bent portion, and a third safety vent bent portion extending upward from the end of the second safety vent bent portion.

[0029] The indentation may increase in diameter or width with depth.

[0030] The recessed portion may be formed by bending a portion of the safety vent upward, and the protrusion may be formed by bending a portion of the current interrupter device (CID) upward.

[0031] The stiffness of the current interrupt device (CID) may be greater than the stiffness of the safety vent.

[0032] The indentation formed in the safety vent may include a first safety vent bent portion extending upward, a second safety vent bent portion extending in a direction bent at an angle from an end of the first safety vent bent portion, and a third safety vent bent portion extending downward from the end of the second safety vent bent portion, and the protrusion formed in the current interrupting device may include a first current interrupting device bent portion extending upward, a second current interrupting device bent portion extending from the end of the first current interrupting device bent portion in a direction parallel to the extension direction of the second safety vent bent portion, and a third current interrupting device bent portion extending downward from the end of the second current interrupting device bent portion.

[0033] The indentation may increase in diameter or width with depth.

[0034] The manufacturing method of a secondary battery according to the present invention relates to a manufacturing method of a secondary battery for manufacturing the above-mentioned secondary battery, and includes the steps of providing an electrode assembly, providing a can in which the electrode assembly is housed, and providing a cap assembly to cover the opening of the can, wherein the providing the cap assembly step includes a connecting process of connecting the safety vent and a current interrupting device at a predetermined region of the safety vent, and the connecting process includes a first step of placing the safety vent on top of the current interrupting device, and a second step of using a pressure unit located above the safety vent or below the current interrupting device to pressurize the upper surface of the safety vent or the lower surface of the current interrupting device to press-fit and couple the safety vent and the current interrupting device together.

[0035] In a first step, the safety vent may be placed on top of a current interruption device (CID) having a groove-shaped recess formed on its upper surface, and in a second step, a pressure unit may pressurize the upper surface of the safety vent at a position corresponding to the recess, thereby pressurizing the safety vent into the current interruption device.

[0036] In a first step, a current interrupting device is placed on the underside of a safety vent having a groove-shaped indentation formed on its underside, and in a second step, a pressure unit applies pressure to the underside of the current interrupting device at a position corresponding to the indentation to press-fit the current interrupting device into the safety vent.

[0037] In the second step, the pressure unit may pressurize the safety vent and the current interrupting device together from the upper surface of the safety vent to form a protrusion in the safety vent and simultaneously form a recess in the current interrupting device, thereby press-fitting the safety vent and the current interrupting device together.

[0038] In the second step, a support unit having a shape corresponding to the pressurizing unit may be further provided, and the support unit may support the current interrupting device and the safety vent from below the current interrupting device.

[0039] In the second step, the pressure unit may pressurize both the current interrupting device and the safety vent from the underside of the current interrupting device to form a protrusion in the current interrupting device and at the same time a recess in the safety vent, thereby press-fitting the current interrupting device and the safety vent together.

[0040] In the second step, a support unit having a shape corresponding to the pressurizing unit may be further provided, and the support unit may support the safety vent and the current interrupting device from above the safety vent. [Effects of the Invention]

[0041] The present invention relates to a secondary battery and a method for manufacturing the secondary battery, which enables airtight connection between a safety vent and a current interrupt device (CID), preventing leakage paths of internal electrolytes and the like from occurring at the connection between the safety vent and the CID, thereby improving battery quality. Even if a weak connection between the safety vent and the CID occurs, the occurrence of a weak connection defect can be easily detected by X-ray inspection or the like, thereby preventing the occurrence of defects. [Brief explanation of the drawings]

[0042] [Figure 1] FIG. 10 is a diagram showing a state where a safety vent and a current interruption device are welded together in a conventional secondary battery. [Figure 2] FIG. 10 is a diagram showing a non-penetration welded state between a safety vent and a current interruption device in a conventional secondary battery. [Figure 3] 1A to 1C are diagrams relating to a secondary battery and a method for manufacturing the secondary battery according to a first embodiment of the present invention. [Figure 4] 5A to 5C are diagrams relating to a secondary battery and a method for manufacturing the secondary battery according to a second embodiment of the present invention. [Figure 5] 10A to 10C are diagrams relating to a secondary battery and a method for manufacturing the secondary battery according to a third embodiment of the present invention. [Figure 6] 10A to 10C are diagrams relating to a secondary battery and a method for manufacturing the secondary battery according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0043] The present invention will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily understand the preferred embodiments of the present invention. However, the present invention can be realized in various different forms and is not limited to the following embodiments.

[0044] In order to clearly explain the present invention, detailed descriptions of parts that are not relevant to the explanation or related known technologies that may obscure the gist of the present invention will be omitted, and when referring to components in each drawing in this specification, the same or similar reference symbols will be used for the same or similar components throughout the specification.

[0045] Furthermore, the terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that an inventor can appropriately define the concept of a term in order to best explain his or her invention.

[0046] <Embodiment 1> 3A and 3B are diagrams relating to a secondary battery and a method for manufacturing the secondary battery according to embodiment 1 of the present invention. Specifically, (a) of Fig. 3 is a diagram relating to a method for manufacturing a secondary battery by combining a safety vent and a current interruption device of the secondary battery, and (b) of Fig. 3 is a diagram illustrating a secondary battery in a completed state in which the safety vent and the current interruption device are press-fitted together.

[0047] Hereinafter, the secondary battery and the method for manufacturing the secondary battery according to the first embodiment of the present invention will be described with reference to FIG.

[0048] The secondary battery 10 according to the first embodiment of the present invention includes an electrode assembly (not shown), a can (not shown), and a cap assembly 100 .

[0049] The electrode assembly may be formed by alternately arranging a positive electrode, a separator, and a negative electrode. The electrode assembly may be a jelly-roll type electrode assembly in which electrodes and separators are alternately arranged and wound up. Such an electrode assembly may be an electrode roll in which one or more positive electrodes, one or more negative electrodes, and one or more separators are wound around one another.

[0050] The can may be configured to receive the electrode assembly. The can may have an internal space, and the electrode assembly may be inserted vertically into the internal space. "Vertical insertion" may mean that the electrode assembly is inserted such that the winding axis of the electrode assembly is perpendicular to the bottom of the can. The can may have an opening on the top. That is, the can may be configured to be open at the top and include a bottom and sidewalls. The electrode assembly and the can may be the same as those used in conventional cylindrical secondary batteries.

[0051] 3(b), the cap assembly 100 may be configured to cover the upper opening of a can. Specifically, the cap assembly 100 may include a top cap 110, a safety vent 120, and a current interrupt device (CID) 130.

[0052] The top cap 110 may be configured to form an outermost terminal for electrical connection to the outside, and may include a central portion that bulges upward so as to be spaced a predetermined distance from the safety vent 120 described below, and an outer edge portion that is connected to the safety vent 120.

[0053] The safety vent 120 may be located below the top cap 110 and connected to the top cap 110 at its outer periphery. The safety vent 120 may also be configured such that the shape or position of a predetermined area inside the periphery changes when the internal pressure of the can rises above a threshold. The predetermined area inside the periphery may be in the shape of a portion of a disk with the lowest height in the center. The safety vent may be interconnected with the current interruption device 130, described below, at its center portion 136.

[0054] The current interruption device 130 may be located below the safety vent 120. An electrode tab to be connected to the electrode assembly may be connected to the lower surface of the current interruption device 130. The current interruption device 130 may also be configured to be connected to the safety vent 120 in the predetermined region of the safety vent 120.

[0055] In a secondary battery according to an embodiment of the present invention, one of the safety vent 120 and the current interruption device 130 (CID) may have a recessed portion formed therein, and the other of the safety vent 120 and the current interruption device 130 (CID) may have a protrusion formed therein that protrudes in a shape corresponding to the recessed portion.

[0056] In addition, the indentation and the protrusion are press-fitted together, connecting the safety vent 120 and the current interruption device 130 (CID) at a predetermined region, and current is interrupted when the internal pressure of the can rises above a threshold. The current may be interrupted by changing the shape or position of the predetermined region. Specifically, the shape or position of the predetermined region may change, causing the predetermined region and the outer shell of the current interruption device 130 (CID) to separate from each other, or the predetermined region and the outer shell of the safety vent 120 to separate from each other, thereby interrupting current. The predetermined region may be the center portion 136 of the safety vent 120, for example.

[0057] In particular, referring to (b) of FIG. 3, the secondary battery according to the first embodiment of the present invention may have the following specific configuration.

[0058] That is, a recessed portion 131 having a recessed shape may be formed on the top surface of the current interruption device 130 (CID), and a protrusion 121 may be formed on the safety vent 120 so as to protrude in a shape corresponding to the recessed portion 131. The recessed portion 131 and the protrusion 121 may be press-fitted together, thereby connecting the safety vent 120 and the current interruption device 130 (CID) at a predetermined region. Here, the predetermined region may be a central portion 136.

[0059] Also, the recess 131 may be formed in a groove shape on the upper surface of the current interruption device 130 (CID), and the protrusion 121 may be formed on the safety vent 120. Here, the rigidity of the current interruption device 130 (CID) may be greater than the rigidity of the safety vent 120. Therefore, it is advantageous for the safety vent 120 to be deformed and press-fitted into the current interruption device 130.

[0060] In addition, in the secondary battery according to the first embodiment of the present invention, the groove formed on the upper surface of the current interrupt device 130 (CID) may have a diameter or width that increases as it goes deeper. When the groove is formed in such a shape, a stronger bond can be achieved. Also, a weak bond can be more quickly identified by means of X-rays or the like.

[0061] In the secondary battery according to the first embodiment of the present invention, the protrusion 121 formed on the safety vent 120 may specifically include a first safety vent portion 121-1 extending downward, a second safety vent portion 121-2 extending from an end of the first safety vent portion 121-1 in a direction parallel to the bottom surface of the groove, and a third safety vent portion 121-3 extending upward from an end of the second safety vent portion 121-2. The first safety vent portion 121-1, the second safety vent portion 121-2, and the third safety vent portion 121-3 may be press-fitted into the grooves in a tight contact manner. For example, they may be interference-fitted.

[0062] The secondary battery according to the first embodiment of the present invention enables airtight connection between the safety vent 120 and the current interruption device 130 through press-fit connection, and can prevent a leak path of the internal electrolyte or the like from occurring at the connection portion between the safety vent 120 and the current interruption device 130. This improves the quality of the battery. While a leak path may occur in the case of full penetration welding, the present invention can completely block the leak path through press-fit connection.

[0063] Furthermore, with such a press-fit connection, even if a weak connection occurs between the safety vent 120 and the current interruption device 130, the occurrence of such a defect can be easily detected by X-ray inspection or the like, thereby preventing the occurrence of such a defect.

[0064] The secondary battery according to the first embodiment of the present invention can be operated in the following manner.

[0065] Specifically, referring to (b) of FIG. 3, before notch 135 breaks, a current path may be formed from the electrode of the electrode assembly to the electrode tab connected to the electrode, from the electrode tab to current interruption device 130 connected to the electrode tab, from current interruption device 130 to safety vent 120 connected by a press-fit coupling, and further to top cap 110 connected to safety vent 120 at the outer edge of safety vent 120.

[0066] Furthermore, when the internal pressure of the can increases during use and the notch 135 breaks, no more current flows from the current interrupter 130 to the safety vent 120, and the current is interrupted.

[0067] Specifically, when the internal pressure of the can rises, central portion 136 of safety vent 120 moves upward, but at that time, the inner central portion of notch 135 of current interrupting device 130, which is firmly joined to central portion 136 of safety vent 120 by a press-fit connection, moves upward together with safety vent 120, and in this case, the outer portion of notch 135 of current interrupting device 130 does not rise and remains in its original position. Therefore, notch 135 is broken, and the inner region and outer region move away from each other based on the broken notch, thereby interrupting the current.

[0068] Meanwhile, a method for manufacturing the secondary battery according to the first embodiment of the present invention is as follows.

[0069] The method for manufacturing a secondary battery according to the first embodiment of the present invention includes the steps of providing an electrode assembly, providing a can in which the electrode assembly is housed, and providing a cap assembly 100 that covers the opening of the can.

[0070] Here, the step of providing the cap assembly 100 also includes a process of connecting the safety vent 120 and the current interruption device 130 at a predetermined region of the safety vent 120 .

[0071] Furthermore, the connection process may include a first step and a second step.

[0072] The first step may be a step of arranging the safety vent 120 on top of the current interruption device 130. In the method for manufacturing a secondary battery according to the first embodiment of the present invention, specifically, the safety vent 120 may be arranged on top of the current interruption device 130 (CID) having a groove-shaped recess 131 formed on the top surface (see (a) of FIG. 3).

[0073] The second process may be a process in which a pressure unit located above the safety vent 120 or below the current interrupting device 130 applies pressure to the upper surface of the safety vent 120 or the lower surface of the current interrupting device 130 to press-fit the safety vent 120 and the current interrupting device 130 together. In the method for manufacturing a secondary battery according to the first embodiment of the present invention, specifically, the pressure unit may be located above the safety vent 120 and apply downward pressure (F1) to the upper surface of the safety vent 120. The pressure unit may apply pressure to the upper surface of the safety vent 120 at a position corresponding to the recess 131 of the current interrupting device 130 to press-fit the safety vent 120 into the current interrupting device 130. Here, the rigidity of the current interrupting device 130 (CID) may be greater than the rigidity of the safety vent 120. In this case, it is more advantageous for the safety vent 120 to be deformed and press-fit into the current interrupting device 130.

[0074] <Embodiment 2> 4A and 4B are diagrams relating to a secondary battery and a method for manufacturing the secondary battery according to embodiment 1 of the present invention. Specifically, (a) of Fig. 4 is a diagram relating to a method for manufacturing a secondary battery by combining a safety vent and a current interruption device of the secondary battery, and (b) of Fig. 4 is a diagram illustrating a secondary battery in a completed state in which the safety vent and the current interruption device are press-fitted together.

[0075] The second embodiment of the present invention is different from the first embodiment in that the groove, which is the indentation in the secondary battery according to the first embodiment of the present invention, is formed in a safety vent rather than in a current interruption device.

[0076] The following describes embodiment 2, omitting as much as possible the content common to embodiment 1. In other words, it goes without saying that content not described in embodiment 2 can be considered as content of embodiment 1, if necessary.

[0077] Referring to FIG. 4(b), the secondary battery 20 according to the second embodiment of the present invention may have the following specific configuration.

[0078] That is, the lower surface of the safety vent 220 may have a recessed portion 221 formed thereon, and the current interrupting device 230 may have a protruding portion 231 formed thereon that protrudes in a shape corresponding to the recessed portion 221. The recessed portion 221 and the protruding portion 231 may be press-fitted together, thereby connecting the safety vent 220 and the current interrupting device 230 (CID) at a predetermined region. Here, the predetermined region may be a central portion 236. When the internal pressure of the can rises above a threshold, a notch 235 formed in the current interrupting device 230 breaks, thereby interrupting the current.

[0079] Also, the recessed portion 221 may be formed in a groove shape on the lower surface of the safety vent 220, and the protrusion 231 may be formed on the current interrupting device 230. Here, the rigidity of the safety vent 220 may be greater than the rigidity of the current interrupting device 230. Therefore, it is advantageous for the current interrupting device 230 to be deformed and press-fitted into the safety vent 220.

[0080] In addition, in the secondary battery according to the first embodiment of the present invention, the groove formed on the lower surface of the safety vent 220 may have a diameter or width that increases as it goes deeper (in FIG. 4(b), the diameter or width increases as it goes upward). When the groove is formed in such a shape, a stronger bond can be achieved. Also, a weak bond can be more quickly identified.

[0081] In the secondary battery according to the first embodiment of the present invention, the protrusion 231 formed on the current interrupting device 230 may specifically include a first current interrupting device portion 231-1 extending upward, a second current interrupting device portion 231-2 extending from an end of the first current interrupting device portion 231-1 in a direction parallel to the bottom surface of the groove, and a third current interrupting device portion 231-3 extending downward from an end of the second current interrupting device portion 231-2. In addition, the first safety vent 220 portion, the second safety vent 220 portion, and the third safety vent 220 portion may be press-fitted into the groove in a tight contact manner.

[0082] The secondary battery according to the second embodiment of the present invention enables airtight connection between the safety vent 220 and the current interruption device 230 through press-fit connection, and can prevent a leak path of the internal electrolyte from occurring at the connection between the safety vent 220 and the current interruption device 230. This can improve the quality of the battery.

[0083] Furthermore, with this type of press-fit connection, even if a weak connection occurs between the safety vent 220 and the current interruption device 230, the occurrence of such a defect can be easily detected by X-ray inspection or the like, thereby preventing the occurrence of such a defect.

[0084] Meanwhile, a method for manufacturing a secondary battery according to embodiment 2 of the present invention is as follows.

[0085] The first and second steps are different from those of the first embodiment.

[0086] The first step may be a step of arranging the safety vent 220 on top of the current interruption device 230. Specifically, in the method for manufacturing a secondary battery according to the second embodiment of the present invention, the current interruption device 230 may be arranged on top of the safety vent 220 having the groove-shaped recessed portion 221 formed on the lower surface thereof.

[0087] Specifically, in the second step in the method for manufacturing a secondary battery according to the second embodiment of the present invention, a pressure unit may be positioned below the current interrupting device 230 and apply upward pressure (F2) to the lower surface of the current interrupting device 230. The pressure unit may apply pressure to the lower surface of the current interrupting device 230 at a position corresponding to the recessed portion 221 of the safety vent 220, thereby press-fitting the current interrupting device 230 into the safety vent 220. Here, the rigidity of the safety vent 220 may be greater than the rigidity of the current interrupting device 230. In this case, it is more advantageous for the current interrupting device 230 to be deformed and press-fit into the safety vent 220.

[0088] <Embodiment 3> Fig. 5 is a diagram relating to a secondary battery and a method for manufacturing the secondary battery according to embodiment 3 of the present invention. Specifically, Fig. 5(a) to (d) are diagrams relating to a method for manufacturing a secondary battery by combining a safety vent and a current interruption device of the secondary battery, and Fig. 5(e) is a diagram showing a secondary battery in a state where the manufacturing is completed with the safety vent and the current interruption device press-fitted together.

[0089] The third embodiment of the present invention differs from the first and second embodiments in that the safety vent and the current interrupting device are pressurized together to form a recess and a protrusion, unlike the secondary batteries according to the first and second embodiments of the present invention in which a press-fit connection is performed with a separate groove formed in the safety vent or the current interrupting device.

[0090] The following describes embodiment 3, omitting as much as possible the content common to embodiments 1 and 2. In other words, it goes without saying that content not described in embodiment 3 can be considered to be the content of embodiments 1 and 2, if necessary.

[0091] Referring to (e) of FIG. 5, the secondary battery according to the third embodiment of the present invention may have the following specific configuration.

[0092] That is, the current interrupting device 330 may have a recessed portion 331 formed therein, and the safety vent 320 may have a protruding portion 321 formed therein that protrudes in a shape corresponding to the recessed portion 331 of the current interrupting device 330. The recessed portion 331 and the protruding portion 321 may be press-fitted together, thereby connecting the safety vent 320 and the current interrupting device 330 (CID) at a predetermined region. Here, the predetermined region may be a central portion 336. When the internal pressure of the can rises above a threshold, a notch 335 formed in the current interrupting device 330 is ruptured, thereby interrupting the current.

[0093] Also, the recess 331 may be formed by bending a portion of the current interruption device 330 (CID) downward. The protrusion 321 may be formed by bending a portion of the safety vent 320 downward. Here, the rigidity of the safety vent 320 may be greater than the rigidity of the current interruption device 330 (CID). That is, the rigidity of the current interruption device 330 (CID) may be less than the rigidity of the safety vent 320.

[0094] To manufacture the secondary battery according to the third embodiment of the present invention, the second step in the above-described method for manufacturing a secondary battery is performed differently.

[0095] 5(a) to 5(d), in the second step, the pressurizing unit 360 may pressurize the safety vent 320 and the current interrupting device 330 together from the upper surface of the safety vent 320 (F3). This forms a protrusion 321 on the safety vent 320 and a recess 331 on the current interrupting device 330 at the same time. This allows the safety vent 320 and the current interrupting device 330 to be press-fitted together. The process of the pressurizing unit 360 sequentially applying pressure is shown in order from 5(a) to 5(d). 5(d) shows the state in which the pressurizing unit 360 has completed pressurization and been removed.

[0096] In addition, in the second step of the method for manufacturing a secondary battery according to the third embodiment of the present invention, a support unit 370 having a shape corresponding to the pressing unit 360 may be further provided. The support unit 370 may support the current interruption device 330 and the safety vent 320 from below the current interruption device 330.

[0097] When press-fitted using this manufacturing method, the deformation of the current interrupting device 330 is greater than that of the safety vent 320. Therefore, in this case, it is more advantageous if the rigidity of the safety vent 320 is greater than that of the current interrupting device 330 (CID), i.e., if the rigidity of the current interrupting device 330 is relatively smaller.

[0098] In the secondary battery according to the third embodiment of the present invention manufactured by such a manufacturing method, the recessed portion 331 and the protruding portion 321 may be specifically formed as follows.

[0099] Referring to (e) of Figure 5, the recess 331 formed in the current interrupting device 330 (CID) may include a first current interrupting device bent portion 331-1 extending downward, a second current interrupting device bent portion 331-2 extending in an angled direction from the end of the first current interrupting device bent portion 331-1 (in Figure 5, a horizontal direction is shown as an example), and a third current interrupting device bent portion 331-3 extending upward from the end of the second current interrupting device bent portion 331-2.

[0100] Correspondingly, the protrusion 321 formed on the safety vent 320 may include a first safety vent bent portion 321-1 extending downward, a second safety vent bent portion 321-2 extending from the end of the first safety vent bent portion 321-1 in a direction parallel to the direction in which the second current interrupter bent portion 331-2 extends, and a third safety vent bent portion 321-3 extending upward from the end of the second safety vent bent portion 321-2.

[0101] In the secondary battery according to the third embodiment of the present invention, the diameter or width of the indentation 331 may also increase as it goes deeper, thereby achieving stronger bonding.

[0102] The secondary battery according to the third embodiment of the present invention enables airtight connection between the safety vent 320 and the current interruption device 330 through press-fit connection, and can prevent a leak path of the internal electrolyte from occurring at the connection between the safety vent 320 and the current interruption device 330. This can improve the quality of the battery.

[0103] In addition, with this type of press-fit connection, even if a weak connection occurs between the safety vent 320 and the current interruption device 330, the occurrence of the defect can be prevented because the weak connection defect can be easily detected by X-ray inspection or the like.

[0104] <Embodiment 4> Fig. 6 is a diagram relating to a secondary battery and a method for manufacturing the secondary battery according to embodiment 4 of the present invention. Specifically, Fig. 6(a) to (d) are diagrams relating to a method for manufacturing a secondary battery by combining a safety vent and a current interruption device of the secondary battery, and Fig. 6(e) is a diagram showing a secondary battery in a state where the manufacturing is completed with the safety vent and the current interruption device press-fitted together.

[0105] Unlike the secondary batteries according to the first and second embodiments of the present invention, in which press-fit coupling is performed with a separate groove formed in the safety vent or current interrupting device, the fourth embodiment of the present invention differs from the first and second embodiments in that the safety vent and the current interrupting device are pressurized together to form a recess and a protrusion. Also, the fourth embodiment of the present invention differs from the third embodiment in that the deformation direction is upward, opposite to that in the third embodiment.

[0106] The content common to embodiments 1 to 3 will be omitted as much as possible and embodiment 4 will be described. In other words, it goes without saying that content not described in embodiment 4 can be considered as content of embodiments 1 to 3, if necessary.

[0107] Referring to (e) of FIG. 6, the secondary battery according to the fourth embodiment of the present invention may have the following specific configuration.

[0108] That is, the safety vent 420 may have a recessed portion 421 formed therein, and the current interrupting device 430 may have a protruding portion 431 formed therein that protrudes in a shape corresponding to the recessed portion 421 of the safety vent 420. The recessed portion 421 and the protruding portion 431 may be press-fitted together, thereby connecting the safety vent 420 and the current interrupting device 430 (CID) at a predetermined region. Here, the predetermined region may be a central portion 436. When the internal pressure of the can rises above a threshold, a notch 435 formed in the current interrupting device 430 is broken, thereby interrupting the current.

[0109] In addition, the recessed portion 421 may be formed by bending a portion of the safety vent 420 upward. The protrusion 431 may be formed by bending a portion of the current interruption device 430 upward. Here, the rigidity of the current interruption device 430 may be greater than the rigidity of the safety vent 420. That is, the rigidity of the safety vent 420 may be less than the rigidity of the current interruption device 430.

[0110] To manufacture the secondary battery according to the fourth embodiment of the present invention, the second step in the above-described method for manufacturing a secondary battery is performed differently.

[0111] 6(a) to 6(d), in the second step, the current interrupting device 430 and the safety vent 420 may be pressurized together from the underside of the current interrupting device 430 (F4). This allows a protrusion 431 to be formed on the current interrupting device 430 and an indentation 421 to be formed on the safety vent 420 at the same time. This allows the current interrupting device 430 and the safety vent 420 to be press-fitted together. The process of the pressurizing unit 460 sequentially applying pressure is shown in order from FIG. 6(a) to FIG. 6(d). FIG. 6(d) shows the state in which the pressurizing unit 460 has completed pressurization and been removed.

[0112] In addition, in the second step of the method for manufacturing a secondary battery according to the fourth embodiment of the present invention, a support unit 470 having a shape corresponding to the pressurizing unit 460 may be further provided. The support unit 470 may support the safety vent 420 and the current interruption device 430 from above the safety vent 420.

[0113] When press-fitted using this manufacturing method, the deformation of the safety vent 420 is greater than that of the current interrupting device 430. Therefore, in this case, it is more advantageous if the rigidity of the current interrupting device 430 is greater than that of the safety vent 420, i.e., if the rigidity of the safety vent 420 is relatively smaller.

[0114] In the secondary battery according to the fourth embodiment of the present invention manufactured by such a manufacturing method, the recessed portion 421 and the protruding portion 431 may be specifically formed as follows.

[0115] Referring to (e) of Figure 6, the recess 421 formed in the safety vent 420 may include a first safety vent bent portion 421-1 extending upward, a second safety vent bent portion 421-2 extending in an angled direction from the end of the first safety vent bent portion 421-1 (in Figure 6, a horizontal direction is shown as an example), and a third safety vent bent portion 421-3 extending downward from the end of the second safety vent bent portion 421-2.

[0116] Correspondingly, the protrusion 431 formed on the current interrupting device 430 may include a first current interrupting device bent portion 431-1 extending upward, a second current interrupting device bent portion 431-2 extending from the end of the first current interrupting device bent portion 431-1 in a direction parallel to the direction in which the second safety vent bent portion 421-2 extends, and a third current interrupting device bent portion 431-3 extending downward from the end of the second current interrupting device bent portion 431-2.

[0117] In the secondary battery according to the fourth embodiment of the present invention, the diameter or width of the indentation 421 may also increase as it goes deeper, thereby achieving stronger bonding.

[0118] The secondary battery according to the fourth embodiment of the present invention enables airtight connection between the safety vent and the current interrupting device through press-fit connection, and can prevent a leak path of the internal electrolyte or the like from occurring at the connection between the safety vent and the current interrupting device, thereby improving the quality of the battery.

[0119] Furthermore, with this type of press-fit connection, even if a weak connection occurs between the safety vent and the current interrupter, the occurrence of such a defect can be easily detected by X-ray inspection or the like, thereby preventing the occurrence of such a defect.

[0120] Although the present invention has been described above using limited embodiments and drawings, the present invention is not limited thereto, and various implementations within the technical spirit of the present invention and the scope of equivalents of the appended claims can be made by a person having ordinary skill in the art to which the present invention pertains. [Explanation of symbols]

[0121] 10, 20 Secondary battery 100, 200, 300, 400 Cap Assembly 110, 210, 310, 410 top cap 120, 220, 320, 420 Safety Vent 121 Protrusion 121-1 First safety vent section 121-2 Second safety vent section 121-3 Third safety vent section 131 Bay 135, 235, 335, 435 notches 136, 236, 336, 436 central part 130, 230, 330, 430 Current Interrupting Device (CID) 140, 240, 340, 440 Main gasket 150, 250, 350, 450 subgasket 221, 331, 421 Bay 231, 321, 431 protrusion 231-1 First current breaker part 231-2 Second current breaker part 231-3 Third current breaker part 321-1, 421-1 First safety vent bend 321-2, 421-2 Second safety vent bend 321-3, 421-3 Third safety vent bend 331-1, 431-1 First current breaker bent part 331-2, 431-2 Second current breaker bent part 331-3, 431-3 Third current breaker bent part 360, 460 pressure unit 370, 470 support unit

Claims

1. an electrode assembly; a can in which the electrode assembly is housed; a cap assembly for covering an opening of the can; The cap assembly includes: a top cap forming an outermost terminal for electrical connection to the outside; a safety vent located below the top cap, connected to the top cap at an outer periphery, the safety vent changing shape or position of a predetermined area inside the periphery when the internal pressure of the can rises above a threshold; a current interrupt device (CID) located below the safety vent, having an electrode tab connected to the electrode assembly at its lower surface, and connected to the safety vent at the predetermined region of the safety vent; a recessed portion having a recessed shape is formed in one of the safety vent and the current interrupting device (CID), and a protrusion having a shape corresponding to the recessed portion is formed in the other of the safety vent and the current interrupting device (CID); The secondary battery, wherein the recess and the protrusion are press-fitted together, thereby connecting the safety vent and the current interrupt device (CID) at the predetermined region.

2. The secondary battery according to claim 1 , wherein the predetermined area is a central portion of the safety vent.

3. The recessed portion is formed in a groove shape on an upper surface of the current interruption device (CID), The secondary battery according to claim 1 or 2, wherein the protrusion is formed on the safety vent.

4. The secondary battery according to claim 3 , wherein the current interruption device (CID) has a stiffness greater than that of the safety vent.

5. The secondary battery of claim 3 , wherein the groove formed on the top surface of the current interrupt device (CID) has a diameter or width that increases in a depth direction.

6. 4. The secondary battery of claim 3, wherein the protrusion formed on the safety vent includes a first safety vent portion extending downward, a second safety vent portion extending from an end of the first safety vent portion in a direction parallel to a bottom surface of the groove, and a third safety vent portion extending upward from an end of the second safety vent portion.

7. The recessed portion is formed in a groove shape on the lower surface of the safety vent, The secondary battery according to claim 1 or 2, wherein the protrusion is formed on the current interrupting device (CID).

8. The secondary battery according to claim 7 , wherein the rigidity of the safety vent is greater than the rigidity of the current interruption device (CID).

9. The secondary battery of claim 7 , wherein the groove formed on the lower surface of the safety vent has a diameter or width that increases in a depth direction.

10. 10. The secondary battery of claim 7, wherein the protrusion formed on the current interrupting device (CID) includes a first current interrupting device portion extending upward, a second current interrupting device portion extending from an end of the first current interrupting device portion in a direction parallel to a bottom surface of the groove, and a third current interrupting device portion extending downward from an end of the second current interrupting device portion.

11. The recessed portion is formed by bending a part of a current interruption device (CID) downward, The secondary battery according to claim 1 or 2, wherein the protrusion is formed by bending a portion of the safety vent downward.

12. The secondary battery according to claim 11, wherein the safety vent has a stiffness greater than that of the current interruption device (CID).

13. the recessed portion formed in the current interrupting device (CID) includes a first current interrupting device bent portion extending downward, a second current interrupting device bent portion extending in a direction bent at an angle from an end of the first current interrupting device bent portion, and a third current interrupting device bent portion extending upward from an end of the second current interrupting device bent portion, 12. The secondary battery of claim 11, wherein the protrusion formed on the safety vent includes a first safety vent bent portion extending downward, a second safety vent bent portion extending from an end of the first safety vent bent portion in a direction parallel to an extension direction of the second current interrupting device bent portion, and a third safety vent bent portion extending upward from an end of the second safety vent bent portion.

14. The secondary battery of claim 11, wherein the diameter or width of the indentation increases as it goes deeper.

15. The recessed portion is formed by bending a part of the safety vent upward, The secondary battery according to claim 1 or 2, wherein the protrusion is formed by bending a part of the current interruption device (CID) upward.

16. The secondary battery according to claim 15, wherein the current interruption device (CID) has a stiffness greater than that of the safety vent.

17. the recessed portion formed in the safety vent includes a first safety vent bent portion extending upward, a second safety vent bent portion extending in a direction bent at an angle from an end of the first safety vent bent portion, and a third safety vent bent portion extending downward from an end of the second safety vent bent portion, 16. The secondary battery of claim 15, wherein the protrusion formed on the current interrupting device includes a first current interrupting device bent portion extending upward, a second current interrupting device bent portion extending from an end of the first current interrupting device bent portion in a direction parallel to the direction in which the second safety vent bent portion extends, and a third current interrupting device bent portion extending downward from an end of the second current interrupting device bent portion.

18. The secondary battery of claim 15, wherein the diameter or width of the indentation increases as it goes deeper.

19. 3. A method for manufacturing the secondary battery according to claim 1 or 2, providing an electrode assembly; providing a can in which the electrode assembly is housed; and providing a cap assembly to cover the opening of the can; The step of providing a cap assembly includes: a connecting step of connecting the safety vent and the current interruption device at the predetermined region of the safety vent; The connection process includes: a first step of placing the safety vent on top of the current interruption device; a second step in which a pressure unit located above the safety vent or below the current interruption device presses the upper surface of the safety vent or the lower surface of the current interruption device to press-fit the safety vent and the current interruption device together.

20. In the first step, The safety vent is placed on top of a current interruption device (CID) having a groove-shaped recess on its upper surface, In the second step, 20. The method of manufacturing a secondary battery according to claim 19, wherein the pressure unit presses an upper surface of the safety vent at a position corresponding to the recess to press-fit the safety vent into the current interruption device.

21. In the first step, The current interrupting device is placed under a safety vent having a groove-shaped recess formed on the underside thereof, In the second step, 20. The method of claim 19, wherein the pressure unit presses a lower surface of the current interrupting device at a position corresponding to the recess to press-fit the current interrupting device into the safety vent.

22. In the second step, 20. The method of manufacturing a secondary battery according to claim 19, wherein the pressure unit presses the safety vent and the current interrupting device together from an upper surface of the safety vent to form a protrusion in the safety vent and simultaneously form a recess in the current interrupting device, thereby press-fitting and coupling the safety vent and the current interrupting device.

23. In the second step, a support unit having a shape corresponding to the pressure unit is further provided; The method of manufacturing a secondary battery according to claim 22, wherein the support unit supports the current interruption device and the safety vent from below the current interruption device.

24. In the second step, 20. The method of manufacturing a secondary battery according to claim 19, wherein the pressurizing unit presses the current interrupting device and the safety vent together from a lower surface of the current interrupting device to form a protrusion in the current interrupting device and a recess in the safety vent, thereby pressurizing the current interrupting device and the safety vent together.

25. In the second step, a support unit having a shape corresponding to the pressure unit is further provided; The method of manufacturing a secondary battery according to claim 24, wherein the support unit supports the safety vent and the current interruption device from above the safety vent.

Images