Secondary battery and manufacturing method thereof

Abstract

A secondary battery according to an embodiment of the present invention includes an electrode assembly, a battery case that houses the electrode assembly and has an open top, and a cap assembly that is coupled to the open top of the battery case. The cap assembly includes a safety vent that has a notch formed therein, and the gap formed by the notch is closed.

Description

[Technical field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0183516 filed on December 24, 2020, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a secondary battery and a manufacturing method thereof, and more particularly to a secondary battery having improved vibration resistance and a manufacturing method thereof. [Background technology]

[0003] Recently, as the price of energy sources rises due to the depletion of fossil fuels and concerns about environmental pollution grow, the demand for environmentally friendly alternative energy sources has become an essential factor for future life. As a result, research into various power generation technologies such as atomic, solar, wind, and tidal power is ongoing, and there is also great interest in power storage devices to use the energy produced in this way more efficiently.

[0004] In particular, the demand for batteries as an energy source is rapidly increasing due to technological development and increased demand for mobile devices, and accordingly, much research is being conducted into batteries that can meet various demands.

[0005] 2. Description of the Related Art There is a high demand for lithium secondary batteries, such as lithium ion batteries and lithium ion polymer batteries, which have advantages such as high energy density, discharge voltage, and output stability.

[0006] Secondary batteries can also be classified according to the structure of the electrode assembly, which is a stack of positive electrodes, negative electrodes, and a separator interposed between the positive and negative electrodes. Representative examples include a jelly-roll type electrode assembly in which long sheet-like positive and negative electrodes are wound with a separator interposed therebetween, and a stack type electrode assembly in which a number of positive and negative electrodes cut into a predetermined size are stacked in sequence with a separator interposed therebetween. Recently, in order to solve the problems of the jelly-roll type electrode assembly and the stack type electrode assembly, a stack / fold type electrode assembly has been developed as a combination of the jelly-roll type and the stack type, in which unit cells in which a predetermined number of positive and negative electrodes are stacked with a separator interposed therebetween are positioned on a separator film and wound in sequence.

[0007] In addition, secondary batteries can be classified according to the shape of the case into cylindrical batteries in which the electrode assembly is built into a cylindrical case, prismatic batteries in which the electrode assembly is built into a prismatic case, and pouch batteries in which the electrode assembly is built into a pouch-type case made of an aluminum laminate sheet.

[0008] Meanwhile, in order for secondary batteries to be effectively used in the market, they must meet the performance required for their intended use while also being safe. When designing secondary batteries, design factors are determined by considering both performance and safety aspects at the same time. Once the design and manufacture of batteries is complete, they undergo performance evaluations such as lifespan, high rate characteristics, and high / low temperature characteristics, as well as safety evaluations such as overcharging, overdischarging, impact, nail tests, and hot boxes.

[0009] Among various types of secondary batteries, cylindrical secondary batteries may include a current interrupt device (CID) that cuts off the current between the electrode terminals and the electrode tabs to prevent additional reactions from occurring when gas is suddenly generated inside the secondary battery in an abnormal state such as overcharging and the internal pressure exceeds a certain level.

[0010] FIG. 1 is a partial cross-sectional view showing a cross section of the upper part of a conventional cylindrical secondary battery.

[0011] Referring to FIG. 1, an electrode assembly 20 is housed in a cylindrical case 30, and a cap assembly 40 is attached to the open top of the cylindrical case 30, thereby manufacturing a cylindrical secondary battery 10.

[0012] The electrode assembly 20 may be a jelly-roll type electrode assembly in which a first electrode 21, a second electrode 22, and a separator 23 are wound up.

[0013] The cap assembly 40 may include an upper cap 41, a safety vent 42 for reducing internal pressure, and a current interruption member (43, Current Interrupt Device, CID). The upper cap 41 and the safety vent 42 may form an adhesive structure, and the safety vent 42 may be connected to a center of the current interruption member 43. A first electrode tab 21t protruding from the first electrode 21 may be connected to a lower end of the current interruption member 43. Here, the first electrode 21 may be a positive electrode, and the first electrode tab 21t may be a positive electrode tab.

[0014] As described above, the upper end cap 41 can be directly or indirectly connected to the safety vent 42, the current interrupting member 43, and the first electrode tab 21t to be electrically connected to the electrode assembly 20 and can function as an electrode terminal.

[0015] Meanwhile, a gasket 70 for sealing between the cap assembly 40 and the cylindrical case 30 and a CID gasket 80 surrounding the edge of the current interrupting member 43 may be disposed.

[0016] FIG. 2 is a partial cross-sectional view showing a state when the internal pressure of the cylindrical secondary battery of FIG. 1 increases.

[0017] 2, when the cylindrical secondary battery 10 is exposed to high temperatures or placed in an abnormal operating state and the internal pressure rises, the shape of the safety vent 42 is reversed and the current interrupting member 43 is separated to interrupt the current. Specifically, the current interrupting member 43 is separated into a portion 43a connected to the safety vent 42 and a portion 43b connected to the first electrode tab 21t, interrupting the flow of current between the upper end cap 41, which functions as an electrode terminal, and the first electrode tab 21t. In addition, when the internal pressure rises significantly, the notch portion of the safety vent 42 breaks, opening the safety vent 42 and discharging the internal gas.

[0018] When the top cap 41 is provided as in the conventional cylindrical secondary battery 10, the structural rigidity is excellent, but there is a disadvantage that when the safety vent 42 is opened to release the internal gas, the safety vent 42 is not fully opened due to the inferior spatial portion caused by the top cap 41, and the gas release is restricted. Summary of the Invention [Problem to be solved by the invention]

[0019] An object of the present invention is to provide a secondary battery that has an effective discharge path for internal gas while having vibration resistance and structural rigidity, and a battery module including the same.

[0020] However, the problem to be solved by the embodiments of the present invention is not limited to the above problem, and can be variously expanded within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0021] According to an embodiment of the present invention, a secondary battery includes an electrode assembly, a battery case in which the electrode assembly is housed and has an open top, and a cap assembly coupled to the open top of the battery case, the cap assembly including a safety vent having a notch formed therein, and a gap formed by the notch is closed.

[0022] The safety vent may be exposed to the outside at the top.

[0023] The safety vent may be a disc-shaped plate and the notch may be in the form of an indented groove running along a circle.

[0024] An upper end of the battery case may be bent to surround the cap assembly and form a crimping portion.

[0025] The crimping portion of the battery case may surround the safety vent.

[0026] The safety vent may include a curling portion bent about a periphery of the safety vent, and the crimping portion may surround the curling portion to form a crimped joint.

[0027] The safety vent may be formed with an upwardly deflected bend.

[0028] A method for manufacturing a secondary battery according to an embodiment of the present invention includes the steps of: forming a safety vent; forming a cap assembly including the safety vent; housing an electrode assembly in a battery case having an open top; and coupling the cap assembly to the open top of the battery case. The step of forming the safety vent includes the steps of forming a notch on one side of the metal plate; and closing a gap formed by the notch.

[0029] The safety vent may be exposed to the outside at the top.

[0030] The safety vent may be a disc-shaped plate and the notch may be in the form of an indented groove running along a circle.

[0031] The joining of the cap assembly may include bending an upper end of the battery case to form a crimping portion surrounding the cap assembly, and the manufacturing of the safety vent may include bending a flange portion formed on the metal plate to form a curling portion. In the forming of the crimping portion, the crimping portion may surround the curling portion.

[0032] In the step of closing the gap formed by the notch, a forging process may be performed on both parts with the gap therebetween. Effect of the Invention

[0033] According to an embodiment of the present invention, by removing the top cap and exposing the safety vent to the outside, and eliminating spatial constraints on the safety vent, the safety vent can be fully opened when internal pressure increases, and can be effective in discharging gas.

[0034] Furthermore, by providing the notch portion of the safety vent with a closed structure, it is possible to increase the vibration resistance and structural rigidity of the notch portion when a lead is attached to the safety vent.

[0035] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is a partial cross-sectional view showing a cross section of an upper portion of a conventional cylindrical secondary battery. [Diagram 2] 2 is a partial cross-sectional view showing a state when the internal pressure of the cylindrical secondary battery of FIG. 1 increases. FIG. [Diagram 3] 1 is an exploded perspective view of a secondary battery according to an embodiment of the present invention; [Figure 4] 4 is a cross-sectional perspective view of a safety vent included in the secondary battery of FIG. 3. [Diagram 5] 2 is a cross-sectional view of an upper portion of a secondary battery according to an embodiment of the present invention; [Figure 6] 4 is a cross-sectional view of an upper portion of a secondary battery according to a comparative example of the present invention; [Figure 7a] 1 is a schematic diagram illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention; [Figure 7b] 1 is a schematic diagram illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention; [Figure 7c] 1 is a schematic diagram illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention; [Figure 8a] 5A to 5C are schematic diagrams for explaining a method for manufacturing a secondary battery according to a comparative example of the present invention. [Figure 8b] 5A to 5C are schematic diagrams for explaining a method for manufacturing a secondary battery according to a comparative example of the present invention. [Figure 8c] 5A to 5C are schematic diagrams for explaining a method for manufacturing a secondary battery according to a comparative example of the present invention. [Figure 9] 5A to 5C are cross-sectional views illustrating a process of forming a crimping portion according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention may, however, be embodied in various different forms and should not be construed as being limited to the embodiments set forth herein.

[0038] In order to clearly describe the present invention, parts that are not relevant to the description will be omitted, and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0039] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, and the present invention is not necessarily limited to those shown. In the drawings, thicknesses are exaggerated to clearly express multiple layers and regions. In the drawings, thicknesses of some layers and regions are exaggerated for convenience of explanation.

[0040] In addition, when a part such as a layer, film, region, or plate is said to be "on" or "above" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part in between. Conversely, when a part is said to be "directly on" another part, it means that there is no other part in between. In addition, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" or "above" the opposite direction of gravity.

[0041] Also, throughout the specification, when a part "comprises" a certain element, this means that it may further include other elements, but not excluding other elements, unless specifically stated to the contrary.

[0042] Also, throughout the specification, "in a plane" means when the subject part is viewed from above, and "in cross section" means when the subject part is cut vertically and viewed from the side.

[0043] Fig. 3 is an exploded perspective view of a secondary battery according to an embodiment of the present invention. Fig. 4 is a cross-sectional perspective view of a safety vent included in the secondary battery of Fig. 3. Fig. 5 is a cross-sectional view of an upper part of a secondary battery according to an embodiment of the present invention. In particular, Fig. 5 is a cross-sectional view showing an upper part of a cross section cut along an xz plane after assembling each component of the secondary battery of Fig. 3.

[0044] 3 to 5, a secondary battery 100 according to an embodiment of the present invention includes an electrode assembly 200; a battery case 300 in which the electrode assembly 200 is housed and which has an open top; and a cap assembly 400 which is coupled to the open top of the battery case 300.

[0045] First, the electrode assembly 200 according to the present 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 are wound together to form a jelly roll type electrode assembly 200. The separator 230 may be interposed between the first electrode 210 and the second electrode 220.

[0046] Although not specifically shown, the first electrode 210 is formed by coating an electrode active material on a first electrode collector. Meanwhile, a first electrode tab 213 may be attached by a method such as welding to a portion of the first electrode collector where the electrode active material is not coated and the first electrode collector is exposed.

[0047] The second electrode 220 is formed by coating an electrode active material on a second electrode collector. Meanwhile, a second electrode tab 223 may be attached by a method such as welding to a portion of the second electrode collector where the electrode active material is not coated and the second electrode collector is exposed.

[0048] In this case, the first electrode 210 may be a positive electrode, and the second electrode 220 may be a negative electrode. Therefore, the first electrode tab 213 may be a positive electrode tab, and the second electrode tab 223 may be a negative electrode tab. Meanwhile, the first electrode tab 213 and the second electrode tab 223 may protrude in opposite directions with respect to the wound electrode assembly 200. As shown in FIG. 3, the first electrode tab 213 may protrude in a direction in which the cap assembly 400 is located (z-axis direction), and the second electrode tab 223 may protrude in a direction in which the bottom of the battery case 300 is located (-z-axis direction).

[0049] Meanwhile, the battery case 300 is a structure for housing the electrode assembly 200 impregnated with an electrolyte, and may be made of a metal material and may be a cylindrical case.

[0050] The cap assembly 400 according to the present embodiment includes a safety vent 410 having a notch part 410N formed therein. More specifically, the cap assembly 400 may include the safety vent 410 and a current interrupt device (420) located under the safety vent 410.

[0051] The cap assembly 400 according to the present embodiment is different from the conventional cylindrical secondary battery (10, see FIG. 1) in that the upper end cap is removed, and the safety vent 410 can be exposed to the outside at the upper end.

[0052] The safety vent 410 may be located on the current interrupting member 420 and may be electrically connected to the current interrupting member 420. In particular, a center portion of the safety vent 410 may be physically and electrically connected to a first portion 421 of the current interrupting member 420, which will be described later. A first electrode tab 213 protruding from the first electrode 210 may be connected to a lower end portion of the current interrupting member 420.

[0053] The safety vent 410 is a thin film structure through which current can pass, and may be a disk-shaped plate, and the notch portion 410N formed in the safety vent 410 may have a shape in which an indented groove continues along a circle. The safety vent 410, the current interrupting member 420, and the first electrode tab 213 are sequentially connected, and the safety vent 410 may function as an electrode terminal that guides the electrical connection of the electrode assembly 200.

[0054] The current interrupting member 420 according to the present embodiment is a plate member through which current passes, and may have a through hole 420H for discharging gas. The current interrupting member 420 may include a first portion 421 connected to the safety vent 410 and a second portion 422 connected to the first electrode tab 213, the first portion 421 being located at a central portion of the current interrupting member 420, and the second portion 422 being located at an outer periphery of the current interrupting member 420.

[0055] When the internal pressure of the secondary battery 100 increases, the shape of the safety vent 410 may be reversed. As the shape of the safety vent 410 is reversed, the first portion 421 of the current interrupting member 420 rises together, and the first portion 421 and the second portion 422 of the current interrupting member 420 are separated from each other. In order to induce such separation due to an increase in internal pressure, the first portion 421 and the second portion 422 may be designed to have a somewhat weak strength between them. As the first portion 421 and the second portion 422 are separated, the current between the safety vent 410 and the first electrode tab 213, which functions as an electrode terminal, is interrupted.

[0056] Also, when the internal pressure rises, the notch portion 410N of the safety vent 410 is torn or torn, opening the safety vent 410 and discharging the internal gas. In the case of a conventional cylindrical secondary battery (10, see FIG. 1), the upper end cap 41 is located on the safety vent 42, and therefore the safety vent 42 is not fully opened due to the inferior spatial portion. As a result, gas cannot be effectively discharged. Also, the upper end cap 41 itself may be an obstacle to gas discharge. In contrast, the secondary battery 100 according to the present embodiment does not have an upper end cap and the safety vent 410 is exposed to the outside at the upper end, so that the safety vent 410 can freely reverse its shape or separate when the internal pressure rises. Therefore, it is more effective at discharging gas than the conventional cylindrical secondary battery 10.

[0057] Hereinafter, with reference to FIGS. 5 and 6, advantages of the safety vent 410 according to this embodiment will be described in comparison with the safety vent 41' according to the comparative example of the present invention.

[0058] 6 is a cross-sectional view of the upper part of a secondary battery according to a comparative example of the present invention. Referring to FIG 6, a secondary battery 10' according to the comparative example includes a cap assembly 40', which includes a safety vent 41' and a current interrupting member 42'. In this case, a notch portion 41N for discharging gas may be formed in the safety vent 41', and the notch portion 41N may have an open structure with its gap widened.

[0059] When the upper end cap is removed and the safety vent 41' is exposed at the upper end to the outside and functions as an electrode terminal, an electrode lead or the like can be connected to the safety vent 41'. At this time, the electrode lead can be attached to the safety vent 41' using vibration, but in the case of a method using vibration, the open notch portion 41N reduces vibration resistance and the electrode lead attachment process may be limited. That is, the notch portion 41N may not be able to withstand the applied vibration and may break or tear. If the depth of the notch portion 41N is set shallow to improve this, the notch portion 41N may not break when the internal pressure increases, and a problem may occur in which the safety vent 410 does not operate properly.

[0060] Unlike the notch portion 41N in the comparative example, which is open, the gap formed by the notch portion 410N according to the present embodiment is closed as shown in FIGS. 4 and 5. In FIGS. 4 and 5, the gap of the notch portion 410N is shown to be somewhat wide in order to explain that it is a groove structure, but this is for convenience of explanation, and the notch portion 410N according to the present embodiment can form a closed structure in which both parts with a gap between them abut each other. Since the notch portion 410N forms a closed structure in this way, vibration resistance and structural rigidity are improved. Therefore, even if vibration is applied to the safety vent 410 to attach the electrode lead, the electrode lead can be attached without damaging the safety vent 410. At the same time, the depth of the groove structure in the notch portion 410N is maintained as it is, so that the notch portion 410N breaks when the internal pressure increases, and the safety vent 410 can be normally separated. That is, gas can be smoothly discharged when the internal pressure increases.

[0061] Meanwhile, referring again to Fig. 5, the battery case 300 according to the present embodiment may include a crimping portion 300C and a beading portion 300B. The beading portion 300B refers to a portion of the cylindrical battery case 300 that is indented toward the center of the electrode assembly 200, and is intended to stably couple the cap assembly 400 and prevent movement of the electrode assembly 200. The crimping portion 300C refers to a portion located on the upper portion of the beading portion 300B and surrounding the cap assembly 400, and is intended to stably couple the cap assembly 400. One end of the upper portion of the battery case 300 may be bent to surround the cap assembly 400, forming the crimping portion 300C.

[0062] The sealing gasket 700 is attached to the inner surfaces of the crimping portion 300C and the beading portion 300B to increase the sealing force between the cap assembly 400 and the battery case 300. That is, the gasket 700 is positioned between the battery case 300 and the cap assembly 400, and the upper end of the battery case 300 is bent to form a crimping connection to form the crimping portion 300C. This allows the cap assembly 400 to be attached and the secondary battery 100 to be sealed. The gasket 700 may be positioned between the crimping portion 300C and the safety vent 410.

[0063] Meanwhile, the safety vent 410 according to the present embodiment may have a bent portion 410B. Specifically, as shown in FIG. 5, a bent portion 410B is formed by bending a portion of the safety vent 410 in an upward direction. The formation of such a bent portion 410B can reduce deformation transferred to the safety vent 410 during crimping. In addition, as described above, the shape of the safety vent 410 is reversed in an abnormal operating state, so that the first portion 421 of the current interrupting member 420 rises together and the first portion 421 and the second portion 422 of the current interrupting member 420 are separated from each other. This blocks the flow of current, and it is preferable that a certain amount of space is formed between the safety vent 410 and the current interrupting member 420 for effective current interruption. Therefore, the height of the cap assembly 400 itself can be minimized, and the bent portion 410B bent in an upward direction can be formed to increase the space between the safety vent 410 and the current interrupting member 420.

[0064] Meanwhile, in the case of crimping, a strong physical pressure may be applied to the cap assembly 400, which may cause a problem of damaging the cap assembly 400. In particular, in a structure in which the safety vent 410 is exposed without an upper end cap, as in the present embodiment, there is a risk of damaging the safety vent 410. However, if the safety vent 410 is made thicker than before in order to supplement the rigidity of the safety vent 410, there is a high possibility that the safety vent 410 may not be properly embodied in a reversible shape or separated when the internal pressure increases.

[0065] In the cap assembly according to this embodiment, instead of simply increasing the thickness of the safety vent 410, a curling part (410C) can be provided at a portion of the safety vent 410 corresponding to the crimping part 300C. Specifically, the safety vent 410 can include a curling part 410C that is curved at the outer periphery of the safety vent 410. For convenience of explanation, Figs. 3 and 4 show the flange part (410F) before the curling part 410C is formed, and Fig. 5 shows the flange part 410F curved to form the curling part 410C.

[0066] The crimping part 300C of the battery case 300 may surround the safety vent 410 with the gasket 700 therebetween, and among them, the crimping joint may be formed by surrounding the curling part 410C of the safety vent 410. Therefore, the central part of the safety vent 410 provided with the notch part 410N is made of a single layer, while the outer peripheral part of the safety vent 410 surrounded by the crimping part 300C is made of a double layer. That is, by providing the curling part 410C, damage to the safety vent 410 that may occur during the crimping joint is prevented, and at the same time, the safety vent 410 is prevented from being reversed in shape or separated when the internal pressure increases.

[0067] Hereinafter, a method for manufacturing a secondary battery according to an embodiment of the present invention will be described in detail with reference to Figures 7a to 7c and Figures 8a to 8c, etc. However, parts that overlap with the contents previously described will be omitted to avoid repetition.

[0068] 7a to 7c are schematic diagrams illustrating a method for manufacturing a secondary battery according to one embodiment of the present invention.

[0069] 3, 5, and 7a to 7c, a method for manufacturing a secondary battery according to an embodiment of the present invention includes the steps of: manufacturing a safety vent 410; manufacturing a cap assembly 400 including the safety vent 410; housing an electrode assembly 200 in a battery case 300 with an open top; and coupling the cap assembly 400 to the open top of the battery case 300. The step of manufacturing the safety vent 410 includes the steps of forming a notch portion 410N in a metal plate; and closing a gap formed by the notch portion 410N.

[0070] Specifically, the metal plate is a member for forming the safety vent 410 and may be a disk-shaped plate. As shown in FIG. 7a, the outer periphery of the metal plate may be bent upward to form a flange portion 410F. Then, as shown in FIG. 7b, a notch portion 410N may be formed on one side of the metal plate. The notch portion 410N formed in the safety vent 410 may have a shape in which an indented groove continues along a circle. Meanwhile, FIG. 7b shows a case in which the notch portion 410N is formed on the lower surface of the metal plate, but the notch portion 410N may also be formed with the flange portion 410F facing upward, i.e., on the upper surface of the metal plate.

[0071] 7c, the metal plate is bent upward to form bent portion 410B, followed by closing the gap formed by notch portion 410N. That is, a structure can be formed in which the bent portion 410B is formed and the gap formed by notch portion 410N is abutted against each other to close the gap.

[0072] To explain the step of closing the gap of the notch portion 410N in more detail, a forging process is performed. That is, in the step of closing the gap of the notch portion 410N, a forging process can be performed on both parts P1 and P2 with the gap therebetween. The forging process is to reduce the thickness of the area adjacent to the notch portion 410N, and by reducing the thickness of both parts P1 and P2 with the gap therebetween, the corresponding parts are naturally pushed out to both sides, and the gap formed by the notch portion 410N can be closed.

[0073] Meanwhile, FIGS. 8a to 8c are schematic views for explaining a method for manufacturing a secondary battery according to a comparative example of the present invention.

[0074] Referring to FIG. 8a, the outer periphery of the metal plate material may be bent upward to form a flange portion 41F. Next, as shown in FIG. 8b, the metal plate material is bent to form a bent portion 41B. Next, as shown in FIG. 8c, a notch portion 41N may be formed on one side of the metal plate material. In this comparative example, the bent portion 41B and the notch portion 41N are formed in the metal plate material, but a forging process for closing the gap of the notch portion 41N is not performed. On the other hand, in this embodiment, a forging process may be additionally performed when forming the bent portion 410B in the metal plate material after forming the notch portion 410N. By adding a forging process to the process for forming the bent portion 410B, the bent portion 410B may be formed and the gap formed by the notch portion 410N may be closed. That is, the notch portion 41N having an open structure as shown in FIG. 6 may be manufactured by the method for manufacturing a secondary battery according to this comparative example, and the notch portion 410N having a closed structure as shown in FIG. 5 may be manufactured by the method for manufacturing a secondary battery according to this embodiment.

[0075] Thereafter, in the step of manufacturing the safety vent 410, the flange portion (410F, see FIGS. 4 and 7a) may be bent to form the curled portion (410C, see FIG. 5).

[0076] Meanwhile, FIG. 9 is a cross-sectional view showing a state in which a crimping portion is formed according to an embodiment of the present invention.

[0077] 3 and 9, the safety vent 410 and the current interrupting member 420 manufactured by the above processes may be joined together to manufacture the cap assembly 400. After the electrode assembly 200 and the electrolyte are accommodated in the battery case 300, the cap assembly 400 may be coupled to the open upper portion of the battery case 300. As described above, the cap assembly 400 according to the present embodiment has a structure in which the upper cap is removed, and the safety vent 410 may be exposed to the outside at the upper end.

[0078] Specifically, a crimped portion (300C, see FIG. 5 ) surrounding the cap assembly 400 may be formed by bending an upper end 300U of the battery case 300 to form a crimped connection. A gasket 700 for sealing may be positioned between the cap assembly 400 and the battery case 300.

[0079] By using such a manufacturing method, it is possible to manufacture a secondary battery 100 having a safety vent 410 including a notch portion 410N having a closed structure and a curling portion 410C located on the outer periphery.

[0080] In this embodiment, terms indicating directions such as front, back, left, right, up, and down are used, but these terms are used for convenience of explanation and may change depending on the position of the target object or the position of the observer, etc.

[0081] A plurality of secondary batteries according to the present embodiment may be assembled to form a battery module, and the battery module may be attached to various control and protection systems, such as a Battery Management System (BMS) and a cooling system, to form a battery pack.

[0082] The secondary battery, the battery module, or the battery pack may be applied to various devices, specifically, to transportation means such as electric bicycles, electric cars, and hybrid vehicles, but is not limited thereto, and may be applied to various devices in which a secondary battery can be used.

[0083] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention. [Explanation of symbols]

[0084] 100 Secondary battery 400 Cap Assembly 410 Safety Vent 410N Notch 410C Curling Club

Claims

1. electrode assembly; a battery case in which the electrode assembly is housed and which has an open top; and a cap assembly coupled to the open top of the battery case, the cap assembly includes a safety vent made of sheet metal having a notch formed therein; The safety vent is exposed to the outside at an upper end; The notch portion is formed on one side of the safety vent and has a shape of a continuous recessed groove, the gap formed by the notch portion is closed so that the two portions with the gap formed by the notch portion therebetween abut against each other.

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

3. The secondary battery according to claim 1 or 2, wherein an upper end of the battery case is bent to surround the cap assembly and form a crimping portion.

4. The secondary battery of claim 3 , wherein the crimped portion of the battery case surrounds the safety vent.

5. the safety vent includes a curled portion curved at a periphery of the safety vent; The secondary battery according to claim 4 , wherein the crimping portion surrounds the curling portion to form a crimped connection.

6. The secondary battery according to claim 1 , wherein the safety vent is formed with a bent portion that is bent upward.

7. manufacturing a safety vent; manufacturing a cap assembly including said safety vent; placing the electrode assembly in an open-top battery case; and coupling the cap assembly to an open top of the battery case; The step of manufacturing the safety vent comprises: forming a notch portion having a shape of a groove on one side of the metal plate; and closing the gap formed by the notch portion so that both portions abut against each other with the gap formed by the notch portion therebetween; The safety vent is exposed to the outside at an upper end; In the step of closing the gap formed by the notch portion, a forging process is performed on both parts with the gap therebetween. A method for manufacturing a secondary battery.

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

9. The coupling of the cap assembly includes bending an upper end of the battery case to form a crimping portion surrounding the cap assembly, The manufacturing step of the safety vent includes bending a flange portion formed on the metal plate to form a curling portion, The method for manufacturing a secondary battery according to claim 7 or 8, wherein in the forming of the crimped portion, the crimped portion surrounds the curled portion.

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