Secondary batteries and methods for manufacturing secondary batteries

Abstract

This application relates to secondary batteries and methods for manufacturing secondary batteries. A secondary battery according to an embodiment of the present invention includes: an electrode assembly; a battery case housing the electrode assembly and having an open upper portion; and a cover assembly coupled to the open upper portion of the battery case, wherein the cover assembly includes a safety vent with a notch, and wherein the gap formed by the notch is closed.

Description

Technical Field

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2020-0183516, filed with the Korean Intellectual Property Office on December 24, 2020, the disclosure of which is incorporated herein by reference.

[0003] This disclosure relates to a secondary battery and a method for manufacturing the secondary battery, and more specifically, to a secondary battery having improved vibration resistance and a method for manufacturing the secondary battery. Background Technology

[0004] Recently, with rising energy prices due to the depletion of fossil fuels and increasing concerns about environmental pollution, the demand for environmentally friendly alternative energy sources will inevitably play a vital role in future life. Therefore, research is underway on various technologies for generating electricity, such as nuclear, solar, wind, and tidal power, and energy storage devices for more efficient use of the generated energy are also attracting widespread attention.

[0005] In particular, with the development of technology and the increasing demand for mobile devices, the demand for batteries as an energy source has also increased rapidly, and as a result, a great deal of research has been conducted on batteries that can meet various needs.

[0006] Typically, there is a high demand for lithium secondary batteries, such as lithium-ion batteries or lithium-ion polymer batteries, which have advantages such as high energy density, discharge voltage, and output stability.

[0007] Furthermore, secondary batteries can be classified based on the structure of the electrode assembly, which has the following structure: in this structure, the cathode and anode are stacked together, and a separator is inserted between the cathode and anode. Examples of such structures include jelly roll type electrode assemblies and stacked electrode assemblies. The jelly roll type electrode assembly has the following structure: in this structure, long cathode and anode sheets are rolled up with separators inserted between them. The stacked electrode assembly has the following structure: in this structure, multiple cathodes and multiple anodes cut to a certain size are sequentially stacked with separators inserted between them. In recent years, to address the problems caused by jelly roll type and stacked electrode assemblies, stacked / folded electrode assemblies have been developed. These stacked / folded electrode assemblies are a combination of jelly roll type and stacked electrode assemblies, and have the following structure: in this structure, cell units stacked in predetermined units of cathodes and anodes are sequentially wound up, with separators inserted between the anode and cathode while already placed on a separator membrane.

[0008] Furthermore, based on the shape of the battery box, secondary batteries are classified into cylindrical batteries with electrode assemblies installed in cylindrical boxes, prismatic batteries with electrode assemblies installed in prismatic cans, and pouch batteries with electrode assemblies installed in pouch boxes formed of aluminum laminates.

[0009] Meanwhile, secondary batteries can be appropriately used in the market, provided they meet the performance requirements for their intended use and are also safe. When designing secondary batteries, these performance and safety aspects are considered simultaneously to determine design factors. The designed and manufactured batteries undergo performance evaluations, such as lifespan, high-rate characteristics, and high / low temperature characteristics, as well as safety evaluations, such as overcharge, over-discharge, impact, nail tests, and thermal chamber tests.

[0010] Among various types of secondary batteries, cylindrical secondary batteries may include a current interruption device (CID) that interrupts the current between the electrode terminals and electrode tabs to prevent further reactions when gas is suddenly generated inside the secondary battery in an abnormal state such as overcharging and the internal pressure exceeds a certain level.

[0011] Figure 1 This is a partial cross-sectional view showing the upper portion of a conventional cylindrical secondary battery.

[0012] Reference Figure 1 The cylindrical secondary battery 10 can be manufactured by housing the electrode assembly 20 in the cylindrical box 30 and attaching the cover assembly 40 to the open upper part of the cylindrical box 30.

[0013] The electrode assembly 20 can be a jelly roll type electrode assembly with a first electrode 21, a second electrode 22 and a separator 23 wound around it.

[0014] The cover assembly 40 may include an upper cover 41, an internal pressure drop safety vent 42, and a current interruption device (CID) 43. The upper cover 41 and the safety vent 42 may form a structure in close contact with each other, and the safety vent 42 may be connected to the central portion of the current interruption device 43. A first electrode tab 21t protruding from the first electrode 21 may be connected to the lower end portion of the current interruption device 43. Here, the first electrode 21 may be a cathode, and the first electrode tab 21t may be a cathode tab.

[0015] As described above, the upper cover 41 can be directly or indirectly connected to the safety vent 42, the current interruption device 43 and the first electrode contact 21t, thereby electrically connecting to the electrode assembly 20, and the upper cover 41 can be used as an electrode terminal.

[0016] Meanwhile, a gasket 70 for sealing between the cover assembly 40 and the cylindrical box 30 and a CID gasket 80 for wrapping the edge of the current interruption device 43 can be arranged.

[0017] Figure 2 It shows when Figure 1 A partial cross-sectional view of the state of a cylindrical secondary battery when the internal pressure increases.

[0018] Reference Figure 2 When the cylindrical secondary battery 10 is exposed to high temperatures or operates under abnormal conditions, increasing internal pressure, the shape of the safety vent 42 is reversed, and the current interruption device 43 is disengaged to interrupt the current. Specifically, the current interruption device 43 is divided into a portion 43a connected to the safety vent 42 and a portion 43b connected to the first electrode contact 21t, thereby interrupting the flow of current between the upper end cap 41, which serves as the electrode terminal, and the first electrode contact 21t. Furthermore, if the internal pressure increases significantly, the notch portion of the safety vent 42 is cut, the safety vent 42 is opened, and the internal gas is discharged.

[0019] When the top cover 41 is provided as in a conventional cylindrical secondary battery 10, the structure has excellent rigidity. However, when the internal gas is discharged at the same time as the safety vent 42 is opened, the following disadvantages exist: the space is degraded by the top cover 41, and therefore, the safety vent 42 cannot be fully opened and the gas discharge is restricted. Summary of the Invention

[0020] Technical issues

[0021] The purpose of this disclosure is to provide a secondary battery and a method for manufacturing the secondary battery, which has vibration resistance and structural rigidity while effectively providing an internal gas exhaust path.

[0022] However, the problems to be solved by the embodiments of this disclosure are not limited to the problems described above, and various extensions can be made within the scope of the technical ideas included in this disclosure.

[0023] Technical solution

[0024] According to one embodiment of the present disclosure, a secondary battery is provided, the secondary battery comprising: an electrode assembly; a battery case that houses the electrode assembly and has an open upper portion; and a cover assembly coupled to the open upper portion of the battery case, wherein the cover assembly includes a safety vent with a notch, and wherein the gap formed by the notch is closed.

[0025] The safety vent can be exposed to the outside from the open upper part of the battery box.

[0026] The safety vent can be a disc-shaped plate, and the recessed portion can have a shape in which the groove extends along the circle.

[0027] One end of the upper portion of the battery box can be bent to wrap around the cover assembly and form a rolled edge.

[0028] The rolled edge of the battery box can cover the safety vent.

[0029] The safety vent may include a rolled portion bent at the outer periphery of the safety vent, and the rolled portion may wrap around the rolled portion to form a rolled joint.

[0030] Safety vents can have a bent portion that bends in an upward direction.

[0031] According to another embodiment of the present disclosure, a method for manufacturing a secondary battery is provided, the method comprising the steps of: manufacturing a safety vent; manufacturing a cover assembly including the safety vent; accommodating an electrode assembly in a battery case having an open upper portion; and engaging the cover assembly to the open upper portion of the battery case, wherein the step of manufacturing the safety vent comprises: forming a notch on a surface of a metal sheet; and closing the gap formed by the notch.

[0032] The safety vent can be exposed to the outside from the open upper part of the battery box.

[0033] The safety vent can be a disc-shaped plate, and the recessed portion can have a shape in which the groove extends along the circle.

[0034] The steps of joining the cover assembly may include bending one end of the upper portion of the battery box to form a rolled edge portion that wraps around the cover assembly; the steps of manufacturing the safety vent may include bending a flange portion formed on a sheet metal to form a rolled-up portion; and in the step of forming the rolled edge portion, the rolled edge portion may wrap around the rolled-up portion.

[0035] In the step of closing the gap formed by the notch, the forging step can be performed on the two parts that have a gap between them.

[0036] Beneficial effects

[0037] According to an embodiment of this disclosure, the upper cover is removed and the safety vent is exposed to the outside, thereby eliminating the space restriction on the safety vent, whereby the safety vent can be fully opened when the internal pressure increases, which can effectively release gas.

[0038] In addition, the notch of the safety vent is designed as a closed structure, which increases the vibration resistance and structural rigidity of the notch when the lead wire is attached to the safety vent.

[0039] The effects of this disclosure are not limited to those mentioned above, and those skilled in the art will clearly understand from the description of the appended claims any additional effects not described above. Attached Figure Description

[0040] Figure 1 This is a partial cross-sectional view showing the upper portion of a conventional cylindrical secondary battery.

[0041] Figure 2 It shows when Figure 1 A partial cross-sectional view of the state of a cylindrical secondary battery when the internal pressure increases.

[0042] Figure 3 This is an exploded perspective view of a secondary battery according to an embodiment of the present disclosure.

[0043] Figure 4 Is included Figure 3 A three-dimensional cross-sectional view of the safety venting component in a secondary battery.

[0044] Figure 5 This is a cross-sectional view of the upper portion of a secondary battery according to an embodiment of the present disclosure.

[0045] Figure 6 This is a cross-sectional view of the upper portion of a secondary battery according to a comparative example of this disclosure.

[0046] Figures 7a to 7c This is a schematic diagram used to explain a method for manufacturing a secondary battery according to an embodiment of the present disclosure.

[0047] Figures 8a to 8c This is a schematic diagram used to explain a method for manufacturing a secondary battery according to a comparative example of this disclosure.

[0048] Figure 9 This is a cross-sectional view showing the appearance of the rolled edge portion according to an embodiment of the present disclosure. Detailed Implementation

[0049] In the following, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, enabling those skilled in the art to readily implement these embodiments. The present disclosure can be modified in various different ways and is not limited to the embodiments set forth herein.

[0050] Parts irrelevant to the description will be omitted in order to clearly describe this disclosure, and throughout the description, the same reference numerals denote the same elements.

[0051] Furthermore, the dimensions and thicknesses of each element in the accompanying drawings are arbitrarily illustrated for ease of description, and this disclosure is not limited to those dimensions and thicknesses shown in the drawings. The thicknesses of layers, regions, etc., are exaggerated in the drawings for clarity. The thicknesses of some layers and regions are exaggerated in the drawings for ease of description.

[0052] Additionally, it should be understood that when an element, such as a layer, film, region, or plate, is described as being "on" or "above" another element, the element may be directly on the other element, or there may be intermediate elements present. Conversely, when an element is described as being "directly on" another element, it means that there are no other intermediate elements present. Furthermore, the terms "on" or "above" mean that it is positioned on or below a reference portion, and do not necessarily mean that it is positioned on the upper end of the reference portion facing the opposite direction of gravity.

[0053] Furthermore, throughout the description, when a part is referred to as “including” or “containing” a component, unless otherwise stated, it means that the part may include other components without excluding other components.

[0054] Furthermore, throughout the description, when referred to as a "plane," it means viewing the target portion from above, while when referred to as a "cross section," it means viewing the target portion from the side of a vertically cut cross section.

[0055] Figure 3 This is an exploded perspective view of a secondary battery according to an embodiment of the present disclosure. Figure 4 Is included Figure 3 A three-dimensional cross-sectional view of the safety venting component in a secondary battery. Figure 5This is a cross-sectional view of the upper portion of a secondary battery according to an embodiment of the present disclosure. Specifically, Figure 5 It is a cross-sectional view, which shows the cross-section of the diagram. Figure 3 The upper part of the cross-section taken along the xz plane after the various components of the secondary battery are assembled.

[0056] Reference Figures 3 to 5 The secondary battery 100 according to an embodiment of the present disclosure includes: an electrode assembly 200; a battery case 300, the battery case 300 housing the electrode assembly 200 and having an open upper portion; and a cover assembly 400 connected to the open upper portion of the battery case 300.

[0057] First, the electrode assembly 200 according to this embodiment may include a first electrode 210, a second electrode 220, and a separator 230. The first electrode 210, the second electrode 220, and the separator 230 may be wound together to form a jelly roll-shaped electrode assembly 200. The separator 230 may be inserted between the first electrode 210 and the second electrode 220.

[0058] Although not specifically illustrated, the first electrode 210 can be formed by applying an electrode active material to the first electrode current collector. Meanwhile, the portion of the first electrode current collector where no electrode active material is applied and thus exposed can be attached with a first electrode tab 213 by a method such as welding.

[0059] The second electrode 220 can be formed by applying an electrode active material to the second electrode current collector. Meanwhile, the portion of the second electrode current collector that is exposed without the application of electrode active material can be attached with a second electrode tab 223 by a method such as welding.

[0060] At this time, the first electrode 210 can be a cathode, and the second electrode 220 can be an anode. Therefore, the first electrode tab 213 can be a cathode tab, and the second electrode tab 223 can be an anode tab. Simultaneously, the first electrode tab 213 and the second electrode tab 223 can protrude in opposite directions relative to the wound electrode assembly 200. Figure 3 As shown, the first electrode tab 213 can protrude along the direction (z-axis direction) where the cover assembly 400 is located, and the second electrode tab 223 can protrude along the direction (-z-axis direction) where the bottom portion of the battery case 300 is located.

[0061] Meanwhile, the battery box 300 is a structure that houses the electrode assembly 200 impregnated with electrolyte solution. The battery box 300 may include metal material and may be a cylindrical box.

[0062] The cover assembly 400 according to this embodiment includes a safety vent 410, in which a recess 410N is formed. More specifically, the cover assembly 400 may include the safety vent 410 and a current interruption device (CID) located below the safety vent 410.

[0063] Compared with conventional cylindrical secondary batteries 10 (see Figure 1 Unlike other embodiments, the cover assembly 400 according to this embodiment has a structure in which the upper cover is removed, wherein the safety vent 410 can be exposed to the outside from the upper end.

[0064] Safety vent 410 is located on and electrically connected to current interruption device 420. Specifically, the central portion of safety vent 410 and the first portion 421 of current interruption device 420, described later, can be physically and electrically connected. First electrode tab 213 protruding from first electrode 210 can be connected to the lower end portion of current interruption device 420.

[0065] The safety vent 410 is a thin structure through which current flows and can be a disc-shaped plate. The recessed portion 410N formed in the safety vent 410 can have a groove extending along a circle. The safety vent 410, the current interruption device 420, and the first electrode contact 213 are connected in sequence such that the safety vent 410 can be used as an electrode terminal for the electrical connection of the guiding electrode assembly 200.

[0066] The current interruption device 420 according to this embodiment is a plate member in which current flows, and the current interruption device 420 may have a through hole 420H for venting gas. Furthermore, the current interruption device 420 may include a first portion 421 connected to the safety vent 410 and a second portion 422 connected to the first electrode contact 213, wherein the first portion 421 may be located in the central portion of the current interruption device 420, and the second portion 422 may be located in the outer peripheral portion of the current interruption device 420.

[0067] When the internal pressure of the secondary battery 100 increases, the shape of the safety vent 410 can be flipped. As the safety vent 410 flips, the first portion 421 of the current interruption device 420 rises together, allowing the first portion 421 and the second portion 422 of the current interruption device 420 to separate from each other. To ensure this separation is caused by the increase in internal pressure, the space between the first portion 421 and the second portion 422 can be designed to have slightly weaker strength. Due to the separation of the first portion 421 and the second portion 422, the current between the safety vent 410, which serves as an electrode terminal, and the first electrode contact 213 is interrupted.

[0068] Furthermore, when the internal pressure increases, the notch 410N of the safety vent 410 is cut or torn open, the safety vent 410 is opened, and the internal gas is released. In a conventional cylindrical secondary battery 10 (see...), Figure 1 In the case of a conventional cylindrical secondary battery 100, the upper cover 41 is located on the safety vent 42, causing partial deterioration of the space and preventing the safety vent 42 from being fully opened. Therefore, gas cannot be effectively released. Furthermore, the upper cover 41 itself may obstruct gas release. In contrast, in the secondary battery 100 according to this embodiment, since the safety vent 410 is exposed to the outside from the upper end without the upper cover, its shape can be freely flipped or separated when the internal pressure increases. Therefore, gas release is more efficient compared to a conventional cylindrical secondary battery 10.

[0069] Next, we will refer to Figure 5 and Figure 6 The advantages of the safety vent 410 according to this embodiment over the safety vent 41' of the comparative example according to this disclosure are described.

[0070] Figure 6 This is a cross-sectional view of the upper portion of a secondary battery according to a comparative example of this disclosure. (Refer to...) Figure 6 According to this comparative example, the secondary battery 10' includes a cover assembly 40', wherein the cover assembly 40' includes a safety vent 41' and a current interruption device 42'. In this case, a notch 41N for gas discharge can be formed in the safety vent 41', wherein the notch 41N can be formed as an open structure, and the gap is widened.

[0071] When the top cover is removed and the safety vent 41' is exposed from the top and used as an electrode terminal, electrode leads, etc., can be attached to the safety vent 41'. At this time, vibration can be used to attach the electrode leads to the safety vent 41'; however, when using vibration, the vibration resistance may be reduced due to the open notch portion 41N, which may limit the electrode lead attachment process. In other words, the notch portion 41N cannot withstand the applied vibration, which may lead to problems such as being cut or torn. If the depth of the notch portion 41N is set shallower to improve this, the notch portion 41N will not break when the internal pressure increases, which may cause the safety vent 410 to malfunction.

[0072] Unlike the open notch 41N in the comparative example, refer to Figure 4 and Figure 5 The gap formed by the notch portion 410N according to this embodiment is closed. Figure 4 and Figure 5In this embodiment, to explain the groove structure, the gap of the notch portion 410N is shown as slightly widened; however, this is for ease of explanation. Furthermore, the notch portion 410N according to this embodiment can have a closed structure, allowing the two portions with the gap to contact each other. Because the notch portion 410N forms a closed structure in this way, vibration resistance and structural rigidity are improved. Therefore, even when vibration is applied to the safety vent 410 for attaching electrode leads, the electrode leads can be attached without damaging the safety vent 410. Simultaneously, since the depth of the groove structure in the notch portion 410N remains unchanged, when the internal pressure increases, the notch portion 410N is cut, allowing the separation of the safety vent 410 to proceed normally. That is, when the internal pressure increases, gas discharge can proceed smoothly.

[0073] At the same time, refer to again Figure 5 The battery case 300 according to this embodiment may include a rolled edge portion 300C and a curled portion 300B. The curled portion 300B refers to a portion of the cylindrical battery case 300 that is recessed along the central direction of the electrode assembly 200; this portion is used to stably connect the cover assembly 400 and prevent the electrode assembly 200 from flowing. The rolled edge portion 300C is located above the curled portion 300B and refers to the portion that wraps around the cover assembly 400. One end of the upper portion of the battery case 300 may be bent to wrap around the cover assembly 400 and form the rolled edge portion 300C.

[0074] A sealing gasket 700 can be installed on the inner surfaces of the rolled edge portion 300C and the curled portion 300B to increase the sealing force between the cover assembly 400 and the battery box 300. Specifically, the gasket 700 is located between the battery box 300 and the cover assembly 400, and one end of the upper portion of the battery box 300 can be bent to form a rolled edge joint, thereby forming the rolled edge portion 300C. This allows for the installation of the cover assembly 400 and the sealing of the secondary battery 100. The gasket 700 can be located between the rolled edge portion 300C and the safety vent 410. A CID gasket 800 can be arranged to cover the edge of the current interruption device 420.

[0075] Meanwhile, a bent portion 410B may be formed in the safety vent 410 according to this embodiment. Specifically, as shown in... Figure 5As shown, a portion of the safety vent 410 can be bent in an upward direction to form a bent portion 410B. Forming such a bent portion 410B reduces the deformation transferred to the safety vent 410 during the crimping process. Furthermore, as described above, when the shape of the safety vent 410 is flipped in an abnormal operating state, the first portion 421 of the current interruption device 420 rises together, and the first portion 421 and the second portion 422 of the current interruption device 420 separate from each other. Therefore, the flow of current is interrupted, and preferably, a certain amount of gap is formed between the safety vent 410 and the current interruption device 420 for effective current interruption. Therefore, the bent portion 410B, bent in an upward direction, can be formed to increase the distance between the safety vent 410 and the current interruption device 420 while minimizing the height of the cover assembly 400 itself.

[0076] Meanwhile, in the case of crimped joints, strong physical compression can be applied to the cover assembly 400, which may lead to damage to the cover assembly 400. In particular, as in this embodiment, in a structure where the safety vent 410 is exposed without an upper cover, there is a risk that the safety vent 410 may be damaged. Even so, if the safety vent 410 is formed thicker than before to compensate for its rigidity, the shape of the safety vent 410 may not be able to flip or separate properly when the internal pressure increases.

[0077] In the cover assembly according to this embodiment, a folded portion 410C may be provided in the portion of the safety vent 410 corresponding to the rolled edge portion 300C, instead of simply increasing the thickness of the safety vent 410. Specifically, the safety vent 410 may include a folded portion 410C bent at the outer peripheral edge of the safety vent 410. For ease of explanation, Figure 3 and Figure 4 The state of the flange portion 410F before the formation of the folded portion 410C is shown, and Figure 5 The state in which the flange portion 410F is bent to form the rolled portion 410C is shown.

[0078] The rolled edge portion 300C of the battery box 300 can wrap around the safety vent 410, wherein a gasket 700 is inserted between the rolled edge portion 300C and the safety vent 410. The rolled edge joint can be formed around the rolled portion 410C of the safety vent 410. Therefore, the central portion of the safety vent 410 with the notch 410N is made of one layer, but the outer peripheral portion of the safety vent 410 wrapped around the rolled edge portion 300C can be formed of two layers. That is, by providing the rolled portion 410C, damage to the safety vent 410 that may occur during rolling is prevented, and at the same time, when the internal pressure increases, it will not prevent the shape of the safety vent 410 from flipping or separating.

[0079] Next, we will refer to Figures 7a to 7c as well as Figures 8a to 8c A method for manufacturing a secondary battery according to embodiments of the present disclosure will be described in detail. However, portions overlapping with the above description will be omitted to avoid repetition.

[0080] Figures 7a to 7c This is a schematic diagram used to explain a method for manufacturing a secondary battery according to an embodiment of the present disclosure.

[0081] Reference Figure 3 , Figure 5 as well as Figures 7a to 7c A method for manufacturing a secondary battery includes the steps of: manufacturing a safety vent 410; manufacturing a cover assembly 400 including the safety vent 410; accommodating an electrode assembly 200 in a battery case 300 having an open upper portion; and engaging the cover assembly 400 to the open upper portion of the battery case 300. The step of manufacturing the safety vent 410 includes: forming a notch 410N on a surface of a metal sheet; and closing the gap formed by the notch 410N.

[0082] Specifically, the metal sheet is a component used to form the safety vent 410, and can be a disc-shaped plate. For example... Figure 7a As shown, the outer periphery of the metal sheet can be bent upwards to form a flange portion 410F. Next, as... Figure 7b As shown, a recess 410N can be formed on one surface of the metal sheet. The recess 410N formed in the safety vent 410 can have a shape where the groove extends along a circle. Meanwhile, in Figure 7b The diagram shows a notch 410N formed on the lower surface of a metal sheet, but the notch 410N can also be formed in the upward direction of the flange 410F, i.e., on the upper surface of the metal sheet.

[0083] Next, as Figure 7cAs shown, the steps of bending the metal sheet in an upward direction to form the bent portion 410B and closing the gap formed by the notch portion 410N can be performed. That is, a closed structure can be formed such that the gaps formed by the notch portion 410N come into contact with each other as the bent portion 410B is formed.

[0084] More specifically, in the step of closing the gap in the notch portion 410N, a forging step can be performed. That is, in the step of closing the gap in the notch portion 410N, a forging step can be performed on the two portions P1 and P2 that have a gap between them. The forging step is to reduce the thickness of the area near the notch 410N. When the thickness of the two portions P1 and P2 that have a gap between them becomes thinner, the corresponding portions are naturally pushed to one side, and the gap formed by the notch portion 410N can be closed.

[0085] at the same time, Figures 8a to 8c This is a schematic diagram used to explain a method for manufacturing a secondary battery according to a comparative example of this disclosure.

[0086] First, refer to Figure 8a The outer periphery of the metal sheet can be bent upwards to form a flange portion 41F. Next, as... Figure 8b As shown, the step of bending the metal sheet to create the bent portion 41B can be performed. Next, as... Figure 8c As shown, a notch 41N can be formed on one surface of a metal sheet. In this comparative example, the bent portion 41B and the notch 41N are formed in the metal sheet, but a forging step to close the gap of the notch 41N is not performed. However, in this embodiment, when the bent portion 410B is formed on the metal sheet after the notch 410N is formed, a forging step can be performed additionally. By adding a forging step to the step of forming the bent portion 410B, the bent portion 410B can be formed, and the gap formed by the notch 410N can be closed. That is, a secondary battery can be manufactured using the method for manufacturing a secondary battery according to this comparative example. Figure 6 The recessed portion 41N shown has an open structure and can be manufactured using the method for manufacturing a secondary battery according to this embodiment. Figure 5 The notch portion 410N shown has a closed structure.

[0087] Subsequently, in the step of manufacturing the safety vent 410, the flange portion 410F (see...) Figure 4 and Figure 7a It can be bent to form a rolled portion 410C (see...) Figure 5 ).

[0088] at the same time, Figure 9This is a cross-sectional view showing the state in which the rolled edge portion is formed according to an embodiment of the present disclosure.

[0089] Reference Figure 3 and Figure 9 The safety vent 410 and current interruption device 420, manufactured through the above process, can be joined together to manufacture the cover assembly 400. The electrode assembly 200 and electrolyte solution are contained in the battery case 300, and then the cover assembly 400 can be attached to the open upper portion of the battery case 300. As described above, the cover assembly 400 according to this embodiment has a structure in which the upper cover is removed, and the safety vent 410 can be exposed to the outside from the upper end.

[0090] Specifically, the upper end portion 300U of the battery case 300 can be bent to form a rolled edge joint and to form a rolled edge portion 300C for the cover assembly 400 (see...). Figure 5 A gasket 700 for sealing can be positioned between the cover assembly 400 and the battery compartment 300.

[0091] This manufacturing method allows for the production of a secondary battery 100 with a safety vent 410, which includes a recessed portion 410N with a closed structure and a rolled portion 410C located on the outer periphery.

[0092] Although this document uses terms indicating direction such as front, back, left, right, up, and down, it will be apparent to those skilled in the art that these are merely for ease of interpretation and that these terms may vary depending on the position of the object, the position of the observer, etc.

[0093] The aforementioned multiple secondary batteries can be combined to form a battery module. The battery module can be installed with various control and protection systems such as BDU (Battery Disconnect Unit), BMS (Battery Management System), and cooling systems to form a battery pack.

[0094] The secondary batteries, battery modules, and battery packs mentioned above can be applied to various devices. Such devices can be applied to vehicle devices such as electric bicycles, electric vehicles, or hybrid vehicles, but this disclosure is not limited thereto, and this disclosure applies to various devices that can use secondary batteries.

[0095] Although the preferred embodiments of the present disclosure have been described in detail above, the scope of the present disclosure is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts of the present disclosure as defined in the appended claims are also within the scope of the present disclosure.

[0096] [Explanation of reference numerals in the attached figures]

[0097] 100: Secondary battery

[0098] 400: Electrode assembly

[0099] 410: Safety Vent

[0100] 410N: Notch portion

[0101] 410C: Folded part.

Claims

1. A secondary battery, the secondary battery comprising: Electrode assembly; A battery case that houses the electrode assembly and has an open upper portion; as well as A cover assembly, the cover assembly being connected to the open upper portion of the battery compartment. The cover assembly includes a safety vent with a notch, and The gap formed by the notch is closed, such that the two portions of the safety vent with the gap are at least partially in contact with each other, and the notch is cut when the internal pressure of the secondary battery increases. The safety vent is exposed to the outside from the open upper portion of the battery box.

2. The secondary battery according to claim 1, wherein: The safety vent is a disc-shaped plate, and The notch portion has a shape in which the groove extends along the circle.

3. The secondary battery according to claim 1, wherein: One end of the upper portion of the battery box is bent to wrap around the cover assembly and form a rolled edge.

4. The secondary battery according to claim 3, wherein: The rolled edge portion of the battery box wraps around the safety vent.

5. The secondary battery according to claim 4, wherein: The safety vent includes a rolled portion bent at the outer periphery of the safety vent, and The rolled edge portion wraps around the folded portion to form a rolled edge joint.

6. The secondary battery according to claim 1, wherein: The safety vent has a bent portion that bends in an upward direction.

7. A method for manufacturing a secondary battery, the method comprising the following steps: Manufacturing safety ventilation components; Manufacturing a cover assembly including the aforementioned safety vent; The electrode assembly is housed in a battery compartment with an open upper section; as well as The cover assembly is attached to the open upper portion of the battery compartment. The steps for manufacturing the safety ventilator include: A notch is formed on one surface of a metal sheet; and The gap formed by the notch is closed, such that the two portions of the safety vent with the gap are at least partially in contact with each other, and the notch is cut off when the internal pressure of the secondary battery increases. The safety vent is exposed to the outside from the open upper portion of the battery box.

8. The method for manufacturing a secondary battery according to claim 7, wherein: The safety vent is a disc-shaped plate, and The notch portion has a shape in which the groove extends along the circle.

9. The method for manufacturing a secondary battery according to claim 7, wherein: The step of engaging the cover assembly includes bending one end of the upper portion of the battery compartment to form a rolled edge portion that wraps around the cover assembly. The steps of manufacturing the safety vent include bending a flange portion formed on the metal sheet to form a rolled portion, and In the step of forming the rolled edge portion, the rolled edge portion wraps around the folded portion.

10. The method for manufacturing a secondary battery according to claim 7, wherein: In the step of closing the gap formed by the notch portion, a forging step is performed on the two portions having the gap therebetween.

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