Secondary battery

Abstract

The present invention relates to a secondary battery, and more particularly to a secondary battery having a porous member capable of venting gas.

Description

[Technical field]

[0001] The present invention relates to a secondary battery, and more particularly to a secondary battery having a porous member capable of venting gas.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0007919 dated January 19, 2022, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference. [Background technology]

[0003] Secondary batteries are classified into cylindrical batteries and prismatic batteries in which an electrode assembly is housed in a cylindrical or prismatic metal case, and pouch batteries in which an electrode assembly is housed in a pouch case made of an aluminum laminate sheet, according to the shape of the battery case. Among them, cylindrical batteries have the advantages of being relatively large in capacity and structurally stable.

[0004] The electrode assembly built into the battery case is a chargeable / dischargeable power generating element having a laminated structure of a positive electrode / separator / negative electrode, and is classified into a jelly roll type in which a separator is interposed between a long sheet-like positive electrode and a negative electrode coated with an active material and then wound up, and a stack type in which a number of positive electrodes and negative electrodes of a predetermined size are sequentially stacked with a separator interposed therebetween. Among them, the jelly roll type electrode assembly has the advantages of being easy to manufacture and having a high energy density per weight.

[0005] A cylindrical secondary battery is fabricated by housing a jelly-roll type electrode assembly in a cylindrical case, injecting an electrolyte into the cylindrical case, and then attaching a cap having an electrode terminal to the open top of the case.

[0006] Meanwhile, a large amount of gas may be generated during the activation of the secondary battery, which may deteriorate the performance of the secondary battery and cause safety problems.

[0007] Generally, in the case of pouch-type secondary batteries and square-type secondary batteries, the gases are removed in advance by adding an activation gas exhaust process during the manufacturing process, but in contrast, in the case of cylindrical secondary batteries, the activation gas exhaust process cannot be used due to the structural feature that the battery must be kept sealed after the electrolyte is injected.

[0008] In a cylindrical secondary battery in which the activation gas cannot be discharged separately during the manufacturing process through an activation gas discharge process, the internal pressure is likely to increase during actual use, which may cause a serious accident such as a battery explosion.

[0009] Therefore, there is a need to develop a cylindrical secondary battery with a new structure that can solve the problem of the increase in internal pressure of the cylindrical battery. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Korean Patent Publication No. 10-2012-0052586 Summary of the Invention [Problem to be solved by the invention]

[0011] Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide a secondary battery that can easily remove activation gases and the like generated inside a battery can housing an electrode assembly during activation or use of the secondary battery.

[0012] Other objects and advantages of the present invention can be understood from the following description and will become more clearly apparent from the embodiments of the present invention. Also, it will be easily understood that the objects and advantages of the present invention can be realized by the means and combinations thereof as set forth in the claims. [Means for solving the problem]

[0013] According to the present invention, there is provided a secondary battery comprising: an electrode assembly; a battery can in which the electrode assembly is housed; a cap assembly including an upper cap plate forming a positive terminal and disposed on an upper portion of the battery can; and a gasket enclosing an edge of the cap assembly and interposed between the battery can and the cap assembly, the secondary battery further comprising a porous member disposed between the cap assembly and the gasket for discharging gas generated within the battery can to the outside.

[0014] In addition, the cap assembly may further include a safety vent coupled to a lower portion of the upper cap plate and having a downwardly protruding shape, and the safety vent may protrude upward and burst when pressure inside the battery can rises above a set pressure.

[0015] In addition, the cap assembly may further include a current interruption element having at least a portion of an upper portion electrically connected to the upper cap plate and a lower portion electrically connected to the electrode assembly, and the current interruption element may interrupt electrical connection to at least one of the upper cap plate and the electrode assembly when the pressure inside the battery can rises above a set pressure.

[0016] Specifically, the porous member may be coupled to at least one of an inner circumferential surface of a gasket facing the cap assembly and an outer circumferential surface of the cap assembly facing the gasket.

[0017] More specifically, the porous member may be additionally interposed on an outer circumferential surface of the gasket facing the battery can.

[0018] According to one embodiment, the porous member may be a porous film that wraps around the edge of the gasket or cap assembly.

[0019] According to another embodiment, the porous member may be a porous coating layer applied to the edge of the gasket or cap assembly.

[0020] According to another embodiment, the porous member may be a porous ring extending around the circumference of the gasket and cap assembly.

[0021] Specifically, the thickness of each of the porous members (porous film, porous coating layer, and porous ring) may be 0.1 mm to 1.0 mm.

[0022] The porous member has a pore size of 0.05 μm to 5.0 μm and an air permeability of 0.05 cm at 1 kPa. 3 / cm 2 *s~10cm 3 / cm 2 *s may be used.

[0023] Meanwhile, the gasket includes a side support portion facing the side of the cap assembly, and a horizontal bent portion extending from the upper and lower ends of the side support portion, bent toward the cap assembly, and contacting the upper and lower surfaces of the cap assembly, and at least one of the porous rings may be disposed between the horizontal bent portion of the gasket and the upper surface of the cap assembly, and between the horizontal bent portion and the lower surface of the cap assembly.

[0024] Meanwhile, a gas discharge passage communicating with the porous ring may be formed between an inner circumferential surface of the gasket and an opposing outer circumferential surface of the cap assembly.

[0025] Specifically, a vent groove may be formed extending along the entire or a portion of the inner peripheral surface of the gasket, and the gas exhaust passage may be formed between the vent groove and the outer peripheral surface of the cap assembly.

[0026] More specifically, the venting grooves extending partially may be formed at regular intervals along an inner circumferential surface of the gasket.

[0027] In addition, recesses may be formed along an outer circumferential surface of the cap assembly at regular intervals, and the gas discharge passage may be formed between the recesses and an inner circumferential surface of the gasket. Effect of the Invention

[0028] According to the present invention, it is possible to prevent a phenomenon in which the outer shape of a battery can is deformed due to an increase in pressure inside the secondary battery caused by gas generated inside the secondary battery.

[0029] Furthermore, according to the present invention, accidents such as explosion of the secondary battery due to an increase in pressure inside the secondary battery can be effectively prevented. [Brief description of the drawings]

[0030] [Figure 1] 1 is an exploded perspective view and a partial cross-sectional view of a secondary battery of the present invention; [Diagram 2] 1 shows a battery can included in a secondary battery of the present invention and its modified examples. [Diagram 3] 1 is a perspective view and a partial cross-sectional view of a cap assembly included in a secondary battery according to a first embodiment of the present invention and a gasket coupled thereto; [Figure 4] 5 is a perspective view and a partial cross-sectional view of a cap assembly and a gasket coupled thereto included in a secondary battery according to a second embodiment of the present invention; FIG. [Diagram 5] 11 is a perspective view and a partial cross-sectional view of a cap assembly included in a secondary battery according to a third embodiment of the present invention and a gasket coupled thereto; FIG. [Figure 6] 1 is a perspective view and a partial cross-sectional view of a porous ring included in a secondary battery according to a fourth embodiment of the present invention; [Figure 7] 11 is a perspective view and a partial cross-sectional view of a cap assembly and a gasket coupled thereto included in a secondary battery according to a fourth embodiment of the present invention; FIG. [Figure 8] 13A and 13B are a perspective view and a cross-sectional view of a gasket included in a secondary battery according to a fifth embodiment of the present invention. [Figure 9]1A and 1B are a cross-sectional view and a partially enlarged view of a secondary battery according to a fifth embodiment of the present invention. [Figure 10] 13A and 13B are a perspective view and a cross-sectional view of a gasket included in a secondary battery according to a sixth embodiment of the present invention. [Figure 11] 11A and 11B are a cross-sectional view and a partially enlarged view of a secondary battery according to a sixth embodiment of the present invention. [Figure 12] FIG. 13 is an exploded perspective view of a cap assembly of a secondary battery according to a seventh embodiment of the present invention. [Figure 13] 13A and 13B are a cross-sectional view and a partially enlarged view of a secondary battery according to a seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Hereinafter, detailed configurations of the present invention will be described in detail with reference to the accompanying drawings and various embodiments. The embodiments described below are illustratively shown to facilitate understanding of the present invention, and the accompanying drawings are not drawn to actual scale to facilitate understanding of the present invention, and the dimensions of some components may be exaggerated.

[0032] Since the present invention can be modified in various ways and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the text, but it is not intended to limit the present invention to the specific disclosed forms, and it should be understood that the present invention includes all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0033] FIG. 1 is an exploded perspective view and a partial cross-sectional view of a secondary battery of the present invention.

[0034] Referring to FIG. 1, a secondary battery according to the present invention includes an electrode assembly 200 , a battery can 300 , a cap assembly 100 , and a gasket 120 .

[0035] The electrode assembly 200 is housed in a battery can 300 with a positive electrode plate and a negative electrode plate disposed with a separator therebetween. The electrode assembly 200 is also called a jelly roll because it is wound up in the form of a jelly roll. The electrode plate of the electrode assembly 200 is formed as a structure in which an active material slurry is applied to a current collector, and the slurry may be typically formed by mixing an active material, a conductive material, a binder, a plasticizer, and the like in a solvent. It is preferable that there are uncoated areas where no slurry is applied at the beginning and end of the current collector in the direction in which the electrode plate is wound, and electrode leads 210 corresponding to each electrode plate may be attached to the uncoated areas. In general, the positive electrode lead is attached to the upper end of the electrode assembly 200 and electrically connected to the upper cap plate 110, and the negative electrode lead is attached to the lower end of the electrode assembly 200 and electrically connected to the bottom of the battery can 300.

[0036] Meanwhile, an insulating plate 400 may be disposed on the upper end of the electrode assembly 200 , and the insulating plate 400 serves to insulate the electrode assembly 200 from the upper cap plate 110 .

[0037] The battery can 300 may be made of a lightweight conductive metal material such as aluminum, stainless steel, or an alloy thereof, and may have a cylindrical structure having an open top and a closed bottom opposite the open top. The electrode assembly 200 and an electrolyte are accommodated in the internal space of the battery can 300.

[0038] A beading portion 310 for mounting the cap assembly 100 may be formed at an upper portion of the battery can 300. The beading portion 310 is recessed between the cap assembly 100 and the electrode assembly 200, and more specifically, a lower end portion of the cap assembly 100 may be seated and fixed at an upper portion of the recessed inner surface of the beading portion 310, and an upper end portion of the electrode assembly 200 may be located at a lower portion of the recessed inner surface of the beading portion 310.

[0039] FIG. 2 shows a battery can 300 included in the secondary battery of the present invention and its modified examples.

[0040] 2(a), a beading portion 310 recessed inwardly from the upper portion of the battery can 300 is formed extending along the circumference of the battery can 300. However, the battery can 300 of the present invention is not limited thereto, and the battery can 300 of the present invention may not be formed with the beading portion 310 as shown in FIG 2(b). In this case, a protrusion (not shown) protruding to a certain length may be formed on the inner surface of the battery can 300 so that the cap assembly 100 can be seated thereon.

[0041] For ease of understanding, the present invention will be described based on the battery can 300 on which the beading portion 310 is formed.

[0042] After the cap assembly 100 is inserted and seated inside the battery can 300 , the upper end of the battery can 300 is bent toward the cap assembly 100 to form a crimping portion 320 .

[0043] The crimping part 320 presses and fixes the upper surface of the cap assembly 100 so that the cap assembly 100 does not slip out to the outside, and at the same time, completely seals the secondary battery from the outside. Specifically, the crimping part 320 is formed by pressing the uppermost end of the battery can 300 against the upper surface of the gasket 120 that encloses the edge of the upper cap plate 110.

[0044] The cap assembly 100 of the present invention is inserted into the inside of the battery can 300 and placed on the upper part of the battery can 300 .

[0045] The cap assembly 100 includes an upper cap plate 110 disposed at an upper portion thereof to form a positive electrode terminal. More specifically, the upper cap plate 110 is disposed at the top of the cap assembly 100 in a protruding upward direction to form a positive electrode terminal. Thus, the upper cap plate 110 electrically connects the secondary battery to the outside.

[0046] The upper cap plate 110 may be made of a metal material such as stainless steel or aluminum, taking into consideration strength and conductivity.

[0047] As shown in the drawings, the upper cap plate 110 has a shape in which the center is protruded, and the side of the protruding portion is formed with an inclined surface along the edge of the protruding portion.

[0048] The edge of the upper cap plate 110 can be designed to remain level with the bottom of the battery can 300, but is not limited to this.

[0049] The diameter of the upper cap plate 110 is preferably the same as the inner diameter of the battery can 300 so that it can be inserted into the battery can 300, or may be slightly smaller.

[0050] A gas hole 111 through which gas can be discharged may be formed in the upper cap plate 110. The gas hole 111 may be formed, for example, in a side surface, i.e., an inclined surface, of a protruding portion of the upper cap plate 110. Specifically, a safety vent 140 for isolating an internal space communicated with the gas hole 111 from the electrode assembly 200 may be further provided inside the cap assembly 100.

[0051] The safety vent 140 is coupled to the lower part of the upper cap plate 110 and has a downwardly protruding shape.

[0052] The safety vent 140 protrudes upward and bursts when the pressure inside the secondary battery exceeds a preset pressure, thereby discharging gas to the outside.

[0053] Under normal conditions, gas generated inside the secondary battery cannot be discharged from the gas hole 111 due to the safety vent 140. However, if an abnormality occurs in the electrode assembly 200 and an excessive amount of gas is generated, causing the gas pressure to exceed a certain value, the safety vent 140 may burst to discharge the gas filled inside to the outside, thereby preventing an explosion of the secondary battery.

[0054] The safety vent 140 is configured to burst when the gas pressure inside the secondary battery increases to a certain level, for example, 12 kgf / cm. 2 ~25kgf / cm 2 It may burst when

[0055] The cap assembly 100 of the present invention may further include a current interruption element 150 .

[0056] The current interrupting element 150 is a component of the cap assembly 100, at least a portion of an upper portion of which is connected to a lower end of the safety vent 140. More specifically, the current interrupting element 150 is disposed between the safety vent 140 and the electrode assembly 200.

[0057] The current interrupting element 150 may cut off an electrical connection with at least one of the upper cap plate 110 and the electrode assembly 200 when the pressure inside the battery can 300 rises above a set pressure. Specifically, in a normal state, a lower protruding portion of the safety vent 140 contacts the current interrupting element 150, but when the internal pressure (gas pressure) increases due to gas generation and the shape of the safety vent 140 is reversed, the electrical connection between the current interrupting element 150 and the safety vent 140 may be cut off. In addition, a lower portion of the current interrupting element 150 may be connected to the electrode assembly 200 by an electrode lead 210. Therefore, in a normal state, the current interrupting element 150 allows electricity to flow between the electrode assembly 200 and the safety vent 140. The current interrupting element 150 may be deformed or broken together with the safety vent 140 due to an increase in pressure inside the secondary battery, and thus the electrical connection with the electrode assembly 200 may be cut off.

[0058] The cap assembly 100 of the present invention may further include a safety element (not shown) provided under the upper cap plate 110. Preferably, the safety element is interposed between the upper cap plate 110 and the safety vent 140, and electrically connects the upper cap plate 110 and the safety vent 140. The safety element is for blocking the flow of current inside the battery due to overheating of the battery, and may be formed of, for example, a PTC (Positive Temperature Coefficient) element.

[0059] As shown in FIG. 1( a ), the gasket 120 wraps the edge of the cap assembly 100 and is interposed between the battery can 300 and the cap assembly 100 .

[0060] The gasket 120 may be made of an electrically insulating, impact resistant, resilient and durable material, such as polyolefin or polypropylene.

[0061] The gasket 120 insulates the cap assembly 100 from being electrically connected to the battery can 300. In addition, the gasket 120 prevents the electrolyte solution stored inside the battery can 300 from leaking through a minute gap between the cap assembly 100 and the battery can 300.

[0062] The gasket 120 may be roughly divided into a side support portion 120a and a horizontal bent portion 120b. Specifically, the gasket 120 includes a side support portion 120a facing the side of the cap assembly 100, and a horizontal bent portion 120b extending from the upper and lower ends of the side support portion 120a, bent toward the cap assembly 100, and contacting the upper and lower surfaces of the cap assembly 100. The side support portion 120a of the gasket 120 supports and encloses the side of the cap assembly 100, and the horizontal bent portions 120b extending from the upper and lower ends of the side support portion 120a press the upper and lower surfaces of the edge of the cap assembly 100, respectively, to be completely in contact with the cap assembly 100.

[0063] The porous member 130 is disposed between the gasket 120 and the upper cap plate 110 and discharges gas generated within the battery can 300 to the outside.

[0064] The porous member 130 includes a porous material so as to selectively discharge gas generated inside the secondary battery to the outside.

[0065] The material of the porous member 130 includes pores, and is made of a material that selectively allows only gas to pass through while preventing the flow of liquid through the pores. For example, the porous member 130 can be made of a porous polytetrafluoroethylene (PTFE) material. However, it is preferable that the size of the pores of the porous member 130 is designed to be sufficiently small so as to allow only gas such as gas to pass through and not allow the electrolyte inside the secondary battery to pass to the outside. For example, the size of the pores is 0.05 to 5.0 μm, and the air permeability at 1 kPa is 0.05 to 10 cm. 3 / cm 2 *s.

[0066] The porous member 130 may be independently manufactured in the form of a film or a circular ring. Alternatively, it may be manufactured by coating the surface of another member. More specifically, the porous member 130 of the present invention may be in the form of at least one of a porous film, a porous coating layer, and a porous ring 130a. In this case, the thickness of each of the porous film, the porous coating layer, and the porous ring 130a is preferably 0.1 mm to 1.0 mm, and more preferably 0.3 mm to 0.8 mm. If the thickness of the porous member 130 having various shapes is less than 0.1 mm, a large amount of gas cannot move smoothly, and if it exceeds 1.0 mm, the sealing force of the electrolyte in a liquid state inside the secondary battery may be reduced, and the structural stability of the secondary battery may be reduced.

[0067] The secondary battery of the present invention may have various embodiments depending on the shapes, structures and attachment positions of the porous member 130, the gasket 120 and the cap assembly 100.

[0068] FIG. 3 relates to the secondary battery-related configuration according to the first embodiment, FIG. 4 relates to the secondary battery-related configuration according to the second embodiment, FIG. 5 relates to the secondary battery-related configuration according to the third embodiment, FIGS. 6 to 7 relate to the secondary battery-related configuration according to the fourth embodiment, FIGS. 8 to 9 relate to the secondary battery-related configuration according to the fifth embodiment, FIGS. 10 to 11 relate to the secondary battery-related configuration according to the sixth embodiment, and FIGS. 12 to 13 relate to the secondary battery-related configuration according to the seventh embodiment.

[0069] (First embodiment) The porous member 130 included in the secondary battery according to the first embodiment may be a film-like porous film that can be attached to the surface of the cap assembly 100 and the surface of the gasket 120 so as to be interposed between the cap assembly 100 and the gasket 120.

[0070] The porous member 130 is interposed between the gasket 120 and the cap assembly 100. More specifically, the porous member 130 may be coupled to at least one of an inner circumferential surface of the gasket 120 facing the cap assembly 100 and an outer circumferential surface of the cap assembly 100 facing the gasket 120.

[0071] The porous member 130 may be attached and coupled to an inner circumferential surface of the gasket 120 and extended along a circumferential direction of the gasket 120. In this case, the gasket 120 is coupled to an edge of the cap assembly 100 with the porous member 130 attached to its inner circumferential surface.

[0072] FIG. 3 is a perspective view and a partial cross-sectional view of a cap assembly 100 included in a secondary battery according to a first embodiment of the present invention and a gasket 120 coupled thereto.

[0073] As shown in the figure, the porous member 130 is interposed between the cap assembly 100 and the gasket 120. At this time, the cap assembly 100 and the gasket 120 are spaced apart from each other by the porous member 130 at a predetermined distance.

[0074] The porous member 130 is disposed in contact with the entire inner circumferential surface of the side support portion 120a and the horizontal bent portion 120b of the gasket 120. In this case, the porous member 130 may be formed to protrude by a predetermined length from an end of the horizontal bent portion 120b of the gasket 120 as shown in the drawings.

[0075] The porous member 130 serves as a path for gas to move between the cap assembly 100 and the gasket 120. That is, gas frequently generated in the battery can 300 moves through the porous member 130 interposed between the cap assembly 100 and the gasket 120, and escapes between the upper cap plate 110 of the cap assembly 100 and the gasket 120 to be discharged to the outside.

[0076] Second embodiment The porous member 130 included in the secondary battery according to the second embodiment is additionally formed on the outer circumferential surface of the gasket 120. In this case, the porous member 130 may be a film-like porous film that can be attached to the surface of the cap assembly 100 and the surface of the gasket 120 so as to be interposed between the cap assembly 100 and the gasket 120 and between the battery can 300 and the gasket 120, similar to the first embodiment.

[0077] In detail, the porous member 130 is formed on the outer circumferential surface of the gasket 120 facing the battery can 300 and is extended in the circumferential direction of the gasket 120 .

[0078] FIG. 4 is a perspective view and a partial cross-sectional view of a cap assembly 100 and a gasket 120 coupled thereto, which are included in a secondary battery according to a second embodiment of the present invention.

[0079] As shown in the figure, the porous member 130 is attached to the inner and outer circumferential surfaces of the gasket 120. In this case, the gas generated inside the secondary battery can move through two paths, so that the gas discharge efficiency can be improved. That is, the gas frequently generated in the battery can 300 moves through the porous member 130 interposed between the cap assembly 100 and the gasket 120 and the porous member 130 interposed between the battery can 300 and the gasket 120, and is discharged to the outside through the gap between the cap assembly 100 and the gasket 120 and the gap between the battery can 300 and the gasket 120, respectively.

[0080] Third embodiment The porous member 130 included in the secondary battery according to the third embodiment is coated on the edge of the gasket 120 or the cap assembly 100. For example, the porous member 130 may be manufactured as a film in a separate process and provided by coating the entire surface of the gasket 120, rather than being attached to the cap assembly 100 and the gasket 120.

[0081] FIG. 5 is a perspective view and a partial cross-sectional view of a cap assembly 100 and a gasket 120 coupled thereto, which are included in a secondary battery according to a third embodiment of the present invention.

[0082] As shown, the porous member 130 covers the entire surface of the gasket 120. In this case, a process of separately manufacturing the porous member 130 and attaching it to the cap assembly 100 and the gasket 120 can be omitted, which may improve manufacturing efficiency. In addition, gas generated inside the secondary battery can move through two paths as in the second embodiment, and the porous member 130 is formed in a wider area than in the second embodiment, which may improve gas discharge efficiency.

[0083] (Fourth embodiment) The porous member 130 of the present invention may be a ring-shaped porous ring 130 a that extends around the gasket 120 and the cap assembly 100 .

[0084] FIG. 6 is a perspective view and partial cross-sectional view of a porous ring 130a of the present invention.

[0085] The porous ring 130a may be circular in cross-sectional shape as shown, but may also be polygonal, such as triangular and rectangular.

[0086] The ring-shaped porous member 130 does not need to be manufactured with the shape and structure of the cap assembly 100 or the gasket 120 in mind, as in the first and second embodiments, and the process of coating the porous member 130 on the surface of the gasket 120 as in the third embodiment can be omitted. This can improve the manufacturing efficiency of the secondary battery. In addition, since a plurality of porous rings 130a having various diameters can be installed on the cap assembly 100, it is easy to adjust the gas discharge performance.

[0087] At least one of the porous rings 130a may be disposed between the horizontal bent portion 120b of the gasket 120 and the upper surface of the cap assembly 100, and at least one of the porous rings 130a may be disposed between the horizontal bent portion 120b and the lower surface of the cap assembly 100. For example, two or more of the porous rings 130a may be disposed on each of the upper surface and the lower surface of the cap assembly 100.

[0088] FIG. 7 is a perspective view and a partial cross-sectional view of a cap assembly 100 and a gasket 120 coupled thereto, which are included in a secondary battery according to a fourth embodiment of the present invention.

[0089] As shown, the porous ring 130a may be provided at the upper and lower parts of the cap assembly 100, being interposed between the cap assembly 100 and the gasket 120. Although not shown, the porous ring 130a may be located between a side surface of the cap assembly 100 and a side support portion 120a of the gasket 120.

[0090] A gas exhaust passage communicating with the porous ring 130a is formed between an inner circumferential surface of the gasket 120 and an opposing outer circumferential surface of the cap assembly 100. Specifically, the gasket 120 and the cap assembly 100 are spaced apart from each other by the porous ring 130a interposed therebetween, and the space forms a gas exhaust passage through which gas can move. The gas exhaust passage selectively moves gas by the porous ring 130a, so that electrolyte inside the secondary battery is not exhausted to the outside through the gas exhaust passage.

[0091] Meanwhile, if the porous ring 130a is not interposed between the side of the cap assembly 100 and the side support portion 120a of the gasket 120, the side of the cap assembly 100 and the side support portion 120a of the gasket 120 may come into close contact with each other, causing a problem that the gas exhaust passage may be blocked. Therefore, in this case, the cap assembly 100 may be designed to be spaced apart laterally from the gasket 120 by a predetermined distance. For example, the diameter of the cap assembly 100 may be smaller than the diameter of the inner circumferential surface of the gasket 120.

[0092] Fifth embodiment When the secondary battery of the present invention includes the porous ring 130a, the gasket 120 may have a venting groove a extending along the inner circumferential surface thereof or the venting groove a extending over a portion of the inner circumferential surface thereof.

[0093] FIG. 8 is a perspective view and a cross-sectional view of a gasket 120 included in a secondary battery according to a fifth embodiment of the present invention.

[0094] As shown in the figure, the venting groove a is formed on the inner circumferential surface of the gasket 120 and extends in the circumferential direction of the gasket 120 .

[0095] The venting groove a is formed for the purpose of making the gap between the side surface of the cap assembly 100 and the side support portion 120a of the gasket 120 wider, thereby facilitating the movement of gas.

[0096] The venting groove a is preferably formed on the side support portion 120 a of the gasket 120 .

[0097] FIG. 9 is a cross-sectional view and a partially enlarged view of a secondary battery according to a fifth embodiment of the present invention.

[0098] Even if the side of the cap assembly 100 and the side support portion 120a of the gasket 120 are in close contact to some extent, a certain gap for gas movement is created by the vent groove a as shown in the figure. That is, a gas exhaust passage is formed between the vent groove 10a and the outer circumferential surface of the cap assembly 100.

[0099] However, in order to allow gas movement, the size of the venting groove a is preferably larger than the thickness of the cap assembly 100 .

[0100] Sixth embodiment When the secondary battery of the present invention includes the porous ring 130a, the gasket 120 may have venting grooves a formed at regular intervals along the inner circumferential surface.

[0101] FIG. 10 is a perspective view and a cross-sectional view of a gasket 120 included in a secondary battery according to a sixth embodiment of the present invention.

[0102] As shown in the figure, the venting grooves a are formed at regular intervals along the inner circumferential surface of the gasket 120. In this case, the spaces between the venting grooves a on the inner circumferential surface of the gasket 120 are supported by being in close contact with the side surface of the cap assembly 100 inserted therein, and the spaces in which the venting grooves a are formed may be spaced apart from the side surface of the cap assembly 100 at a predetermined interval to form a gas exhaust passage.

[0103] FIG. 11 is a cross-sectional view and a partially enlarged view of a secondary battery according to a sixth embodiment of the present invention.

[0104] As shown in the figure, the secondary battery according to the sixth embodiment, like the fifth embodiment, transfers gas through the venting groove a. The space of the venting groove a of the gasket 120 included in the secondary battery according to the sixth embodiment is relatively smaller than that of the venting groove a included in the gasket 120 of the secondary battery according to the fifth embodiment, so that the gas exhaust efficiency may be somewhat reduced, but the side fixing effect of the cap assembly 100 by the gasket 120 is superior.

[0105] However, it is preferable that the size of the venting groove a is larger than the thickness of the cap assembly 100 so that gas movement is possible as in the fifth embodiment.

[0106] Seventh embodiment When the secondary battery of the present invention includes the porous ring 130a, the cap assembly 100 may include recesses b formed at regular intervals along the outer circumferential surface. This feature is the same even when the cap assembly 100 includes multiple components. For example, when the cap assembly 100 includes an upper cap plate 110 and a safety vent 140, the recesses b are formed in both the upper cap plate 110 and the safety vent 140. In this case, the positions of the recesses b formed in the upper cap plate 110 and the safety vent 140 coincide with each other.

[0107] FIG. 12 is an exploded perspective view of a cap assembly 100 for a secondary battery according to the seventh embodiment of the present invention.

[0108] As shown, the upper cap plate 110 and the edge of the safety vent 140 joined to the lower part of the upper cap plate 110 are formed with recesses b spaced apart at regular intervals.

[0109] The safety vent 140 is coupled to the lower part of the upper cap plate 110 by adjusting the position of the recess b of the safety vent 140 to coincide with the position of the recess b of the upper cap plate 110 .

[0110] FIG. 13 is a cross-sectional view and a partially enlarged view of a secondary battery according to a seventh embodiment of the present invention.

[0111] As shown in the figure, the space between the recesses b on the side of the cap assembly 100 is tightly attached to the side support portion 120a of the gasket 120, and the space in which the recesses b are formed becomes a gas exhaust passage through which gas moves.

[0112] The cap assembly 100 included in the secondary battery of the seventh embodiment has a gas exhaust passage between the recess b and the inner surface of the gasket 120, and similar to the sixth embodiment, exhausts gas to the outside through the gas exhaust passages formed at predetermined intervals along the circumferential direction of the cap assembly 100 or the gasket 120.

[0113] Unlike the fifth and sixth embodiments in which a vent groove a is formed on the inner circumferential surface of the gasket 120 to form a gas exhaust passage, the seventh embodiment has the advantage of being highly convenient for manufacturing the secondary battery in that there is no need to place any restrictions on the size or shape of the recess b.

[0114] The present invention has been described in more detail above with reference to the drawings and embodiments, etc. However, the configurations described in the drawings or embodiments, etc. in this specification are merely one embodiment of the present invention and do not represent all of the technical ideas of the present invention, so it should be understood that there may be various equivalents and modifications that can replace them at the time of filing this application. [Explanation of symbols]

[0115] 100: Cap assembly 110: Upper cap plate 111: Gas hole 120: Gasket 120a: Side support part 120b: Horizontal bending part 130: Porous member 130a: Porous ring 140: Safety vent 150: Current interruption element 200: Electrode assembly 210: Electrode lead 300: Battery can 310: Beading section 320: Crimping section 400: Insulating plate a: Venting groove b: Recess G: Gas transfer path

Claims

1. electrode assembly, a battery can in which the electrode assembly is housed; a cap assembly disposed on an upper portion of the battery can, the cap assembly including an upper cap plate forming a positive terminal; and a gasket that encloses an edge of the cap assembly and is interposed between the battery can and the cap assembly; The secondary battery further includes a porous member disposed between the cap assembly and the gasket, the porous member discharging gas generated within the battery can to the outside.

2. the cap assembly further includes a safety vent coupled to a lower portion of the upper cap plate and having a downwardly protruding shape, The secondary battery according to claim 1 , wherein the safety vent is displaced upward and bursts when pressure inside the battery can rises to or exceeds a set pressure.

3. the cap assembly further includes a current interruption device, at least a portion of an upper portion of which is electrically connected to the upper cap plate and a lower portion of which is electrically connected to the electrode assembly; 2. The secondary battery of claim 1, wherein the current interrupting device interrupts electrical connection between at least one of the upper cap plate and the electrode assembly when pressure inside the battery can rises above a predetermined pressure.

4. The secondary battery of claim 1 , wherein the porous member is coupled to at least one of an inner circumferential surface of the gasket facing the cap assembly and an outer circumferential surface of the cap assembly facing the gasket.

5. The secondary battery according to claim 4 , wherein the porous member is additionally interposed on an outer circumferential surface of the gasket facing the battery can.

6. The secondary battery according to claim 1 , wherein the porous member is a porous film that wraps around an edge of the gasket or the cap assembly.

7. The secondary battery according to claim 1 , wherein the porous member is a porous coating layer coated on an edge of the gasket or the cap assembly.

8. The secondary battery according to claim 1 , wherein the porous member is a porous ring extending around the gasket and the cap assembly.

9. The secondary battery according to any one of claims 6 to 8, wherein the thickness of each of the porous members is 0.1 mm to 1.0 mm.

10. the gasket includes side support portions facing sides of the cap assembly, and horizontal bent portions extending from upper and lower ends of the side support portions and bent toward the cap assembly to contact upper and lower surfaces of the cap assembly, 9. The secondary battery of claim 8, wherein at least one of the porous rings is disposed between the horizontal bent portion of the gasket and an upper surface of the cap assembly and between the horizontal bent portion of the gasket and a lower surface of the cap assembly.

11. The secondary battery according to claim 8 , wherein a gas exhaust passage communicating with the porous ring is formed between an inner circumferential surface of the gasket and an outer circumferential surface of the cap assembly facing the inner circumferential surface of the gasket.

12. A vent groove is formed extending along the entire or a part of the inner circumferential surface of the gasket, The secondary battery according to claim 11 , wherein the gas exhaust passage is formed between the vent groove and an outer circumferential surface of the cap assembly.

13. The secondary battery of claim 12 , wherein the venting grooves are spaced apart at regular intervals along an inner circumferential surface of the gasket.

14. The cap assembly has recesses spaced apart at regular intervals along its outer periphery; The secondary battery according to claim 11 , wherein the gas discharge passage is formed between the recess and an inner circumferential surface of the gasket.

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