secondary batteries

Abstract

The present invention relates to a secondary battery comprising: an electrode assembly; a can that accommodates the electrode assembly; a cap assembly that includes a vent, a current interrupter (CID) filter located at a lower portion of the vent, and a CID gasket located at one end of the current interrupter filter and that finishes the open upper portion of the can; and a gasket that is crimped while being interposed between the cap assembly and the upper portion of the can to maintain insulation and sealing between the cap assembly and the can; wherein the vent of the cap assembly has an outer surface, an upper surface, and a lower surface that are in close contact with an inner surface and an upper surface of the gasket, respectively, and a curvature radius of a portion where the outer surface and the upper surface of the vent end meet is 0.3 mm or less.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0067812 dated June 2, 2022, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a secondary battery, and more particularly to a secondary battery in which deflection of a vent portion of a cylindrical battery is improved. [Background technology]

[0003] As technological development and demand for mobile devices increases, rechargeable secondary batteries are widely used as energy sources for various mobile devices. Secondary batteries are also attracting attention as energy sources for electric vehicles and hybrid vehicles, which have been proposed as a solution to address air pollution caused by conventional gasoline and diesel vehicles.

[0004] Secondary batteries are classified into coin-type batteries, cylindrical batteries, prismatic batteries, and pouch-type batteries depending on the shape of the battery case in which the electrode assembly is housed.

[0005] Among these, the cylindrical battery is composed of an electrode assembly, a cylindrical can that houses the electrode assembly, a cap assembly, and a gasket.

[0006] The electrode assembly is a cylindrically wound structure of a positive electrode, a negative electrode, and a separator interposed between the two electrodes, and a positive electrode tab and a negative electrode tab can be pulled out from the positive electrode and the negative electrode, respectively. Typically, the positive electrode tab is pulled out upward, and the negative electrode tab is pulled out downward.

[0007] The can is a roughly cylindrical metallic container for a cylindrical secondary battery, and can be formed by a processing method such as deep drawing, etc. Therefore, the can itself can serve as a terminal.

[0008] The cap assembly completes the open top of the can and may include a vent, a current interrupter, etc. The positive electrode of the electrode assembly may be electrically connected to the cap assembly through a positive electrode tab extending upward, and the negative electrode may be connected to the bottom of the can through a negative electrode tab extending downward. Of course, the polarity may be reversed.

[0009] A gasket is located between the cap assembly and the can to insulate and seal the two.

[0010] During the CCR / CSZ (cylindrical crimping / cylindrical sizing) process of such cylindrical batteries, the dispersion of H0 dimensions increases, and this increase in H0 dimensions increases the amount of deflection of the vent, which may cause a drop in short-circuit voltage.

[0011] Therefore, research into methods for improving vent deflection is needed. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Korean Patent Publication No. 2019-0131794 Summary of the Invention [Problem to be solved by the invention]

[0013] An object of the present invention is to provide a secondary battery having an optimally shaped vent portion that can solve the problem of sagging of the vent portion that occurs during the CCR / CSZ process of cylindrical batteries. [Means for solving the problem]

[0014] In order to achieve the above purpose, The present invention provides a secondary battery comprising: an electrode assembly; a can that houses the electrode assembly; a cap assembly that finishes the open top of the can, the cap assembly including a vent, a current interrupter (CID) filter located below the vent, and a CID gasket located at one end of the CID filter; and a gasket that is crimped between the cap assembly and the top of the can while being interposed between the cap assembly and the top of the can to maintain insulation and sealing between the cap assembly and the can; wherein the outer surface, upper surface, and lower surface of the end of the vent of the cap assembly are in close contact with the inner surface and upper surface of the gasket, respectively, and the radius of curvature of the portion where the outer surface of the end of the vent and the upper surface meet is 0.3 mm or less.

[0015] In one embodiment of the present invention, the radius of curvature of the portion where the outer surface and the upper surface of the end of the vent meet may be 0.1 to 0.3 mm.

[0016] In one embodiment of the present invention, an adhesive layer may be formed on at least a portion of the outer surface and upper surface of the end of the vent, or a double-sided adhesive tape may be attached thereto.

[0017] In one embodiment of the present invention, the current interrupter (CID) filter may be joined to an electrode tab extending upward from one electrode of the electrode assembly.

[0018] In one embodiment of the present invention, the end of the vent may be formed by bending the metal plate upward by 180 degrees to overlap in two stages.

[0019] In one embodiment of the present invention, the outer shape of the can is cylindrical and the vent may be a flat disc shape. [Effects of the Invention]

[0020] The secondary battery of the present invention is provided with a vent portion of an optimal shape, thereby making it possible to prevent bending of the vent portion that occurs during the CCR / CSZ process of a cylindrical battery. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a partially enlarged cross-sectional view of a cylindrical secondary battery according to an embodiment of the present invention. [Figure 2] 3 is another partially enlarged cross-sectional view of a cylindrical secondary battery according to an embodiment of the present invention. FIG. [Figure 3] FIG. 1 is a schematic diagram showing an analytical model according to an embodiment of the present invention. [Figure 4] 1 is a graph of measurements from an analytical model according to one embodiment of the present invention. [Figure 5] FIG. 10 is a diagram showing measured contour lines of the vent deformation rate in an analytical model according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily understand and practice the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments set forth herein.

[0023] In order to clearly explain the present invention, parts that are not relevant to the description will be omitted, and the same reference numerals will be used to refer to the same or similar components throughout the specification.

[0024] Furthermore, the terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that an inventor can appropriately define the concept of a term in order to explain his or her invention in the best possible way.

[0025] FIG. 1 is a partially enlarged cross-sectional view of a secondary battery according to an embodiment of the present invention.

[0026] Referring to FIG. 1, a secondary battery according to one embodiment of the present invention includes an electrode assembly (not shown); a can (100) that houses the electrode assembly; a cap assembly that includes a vent (210), a current interrupter (CID) filter (220) located below the vent (210), and a CID gasket (230) located at one end of the current interrupter filter (220) and that completes the open top of the can (100); and a gasket (300) that is crimped between the cap assembly and the top of the can (100) and maintains insulation and sealing between the cap assembly and the can (100).

[0027] In a secondary battery according to an embodiment of the present invention, the electrode assembly may be fabricated in a "jelly roll" shape by forming the positive and negative electrodes into wide plates to increase electrical capacity, stacking them with a separator between them to insulate them from each other, and rolling them into a circular shape. The positive and negative electrodes may be formed by coating active material slurry on current collectors made of aluminum and copper metal foil or metal mesh, respectively. Uncoated areas where no slurry is applied may exist at the beginning and end of the current collector in the direction in which the electrode plate is wound. One electrode tab may be attached to each electrode plate in the uncoated areas, with one electrode tab extending upward toward the opening of the cylindrical can and the other extending downward from the electrode. However, the present invention is not limited thereto.

[0028] In a secondary battery according to an embodiment of the present invention, the can 100 is a cylindrical container made of a lightweight, conductive metal material such as aluminum or an aluminum alloy, and can be formed by a processing method such as deep drawing. An electrode assembly (not shown) can be installed inside the cylindrical can. A center pin (not shown) can be inserted into the empty space in the center of the jelly roll to prevent the jelly roll from loosening and to function as a passageway for internal gas.

[0029] In a secondary battery according to one embodiment of the present invention, the cap assembly 200 includes a vent 210, a current interrupter filter 220, and a CID gasket 230, and as shown in FIG. 1, the current interrupter, the CID gasket 230, and the vent 210 are arranged in this order from bottom to top.

[0030] In a secondary battery according to one embodiment of the present invention, the vent 210 is located at the top of the cap assembly 200. A current interrupt device (CID) 120 is installed below the vent 210. The CID 120 is configured to break when the protrusion 112 of the vent 210 is deformed upwardly by internal pressure.

[0031] In the secondary battery according to an embodiment of the present invention, the vent 210 may be in the shape of a flat disk.

[0032] In the secondary battery according to an embodiment of the present invention, the end of the vent 210 may be folded in two stages by bending the metal plate upward by 180 degrees.

[0033] In the secondary battery according to one embodiment of the present invention, the current breaker filter 220 is located below the vent 210 and is designed to break when the vent 210 is deformed.

[0034] In the secondary battery according to one embodiment of the present invention, when gas accumulates inside the battery, the CID gasket 230 falls due to pressure, and the current interrupt filter can function to interrupt the current.

[0035] In a secondary battery according to one embodiment of the present invention, the gasket 300 is positioned between the top of the can 100 and the cap assembly 200. The gasket 300 is crimped while interposed between the cap assembly 200 and the top of the can 100, thereby maintaining insulation and sealing between the cap assembly 200 and the can 100. To complete the opening of the can 100, the gasket 300 is inserted into the can 100, and the cap assembly 200 is placed on the gasket 300, followed by a crimping process. The clipping process is a bending process in which a cap up (not shown) or the like placed inside the gasket (300) is used to apply pressure to the inside and bottom of the upper opening of the cylindrical can with a plug, thereby sewing the can (100), thereby sealing the can (100), gasket (300), and cap assembly (200).

[0036] In the secondary battery according to an embodiment of the present invention, the outer surface, upper surface, and lower surface of the end of the vent 210 of the cap assembly 200 are in close contact with the inner surface and upper surface of the gasket 300. The radius of curvature of the contact area between the outer surface and upper surface of the end of the vent 210 is set to 0.3 mm or less.

[0037] In the secondary battery according to one embodiment of the present invention, the radius of curvature of the portion where the outer surface of the end of the vent 210 meets the upper surface may be 0.1 mm or more, 0.2 mm or more, or 0.3 mm or less, 0.2 mm or less. When the radius of curvature of the portion where the outer surface of the end of the vent 210 meets the upper surface is limited within this range, the sealing force between the cap assembly 200 and the gasket 300 of the secondary battery according to the present invention can be improved.

[0038] In a secondary battery according to an embodiment of the present invention, as the R value of the upper portion of the vent (210) increases, the contact area between the can (100) and the gasket (300) decreases during secondary clipping, resulting in an increase in contact pressure (increased gasket pressure) and a shortened contact end position between the vent (210) and the gasket (300). As a result, the gasket (300) presses the front end of the vent (210), increasing the moment of the vent (210). This increases the deformation rate of the vent (210), which increases the angle of the vent (210), and can result in an increase in the H0 dimension.

[0039] In a secondary battery according to one embodiment of the present invention, an increase in contact pressure between the can (100) and the gasket (300) may cause the gasket (300) to be further pressed due to the increased pressure applied to the gasket (300), resulting in an increase in the deformation rate of the vent (210) and an increase in the angle of the vent (210).

[0040] In a secondary battery according to one embodiment of the present invention, an adhesive layer may be formed on at least a portion of the outer surface and upper surface of the end of the vent (210) or a double-sided adhesive tape may be attached to further improve the adhesion between the vent (210) and the gasket (300).

[0041] In the secondary battery according to an embodiment of the present invention, the current interrupter (CID) filter 220 may be joined to an electrode tab extending upward from one electrode of the electrode assembly.

[0042] Preferred examples will be described below to aid in understanding the present invention. However, the following examples are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical idea of ​​the present invention. Naturally, such changes and modifications also fall within the scope of the appended claims.

[0043] Example 1. Analysis model information The analysis model was constructed as shown in Figure 3. The load and constraint conditions were as follows. First, 2D Cylindrical Axis Symmetric conditions were applied. Specifically, reflecting the CCR process conditions, the height of the primary CCR was set to 3.0 mm and the height of the secondary CCR was set to 2.2 mm, and the CSZ fixed condition was also reflected. Displacement movement conditions were given for the 3-jaw, primary / secondary molds, and sizing mold.

[0044] The physical properties of the materials used are shown in Table 1 below.

[0045] [Table 1]

[0046] 2. Analysis results Cylindrical secondary battery models equipped with a can, vent, current breaker, and CID gasket were manufactured while changing the curvature radius of the area where the outer surface of the vent end meets the top surface as shown in Table 2.

[0047] [Table 2]

[0048] For the model, 1) H0 dimension, 2) vent angle, 3) vent deformation rate (Vent Von Mises deformation rate), 4) contact pressure between the can and gasket, and 5) position of the contact end between the vent and gasket were measured and are shown in Table 3 below.

[0049] [Table 3]

[0050] From the results in Table 3, it can be seen that an increase in the contact pressure between the can and the gasket causes the gasket to be pushed further due to the increased pressure applied to the gasket, which increases the deformation rate of the vent and increases the vent angle. If the contact end position between the vent and the gasket is short, the gasket will push the front end of the vent, which will increase the vent moment.

[0051] Figure 4 shows the H0 value and angle (degrees) as the R value of the top of the vent changes. As the R value of the top of the vent increases, the H0 dimension tends to increase due to the increase in the vent angle. Specifically, in Comparative Example 1, where the R value of the top of the vent is 0.4 mm, it can be seen that the H0 dimension increases by about 9.5% compared to Example 1, where the R value of the top of the vent is 0.1 mm. Therefore, since the H0 dimension increases as the R value of the top of the vent increases, it is determined that R value management of the vent parts is necessary to reduce H0 dispersion.

[0052] Figure 5 shows the contour of the vent deformation rate after secondary crimping. As the R-value of the top of the vent increases, the contact area between the can and gasket decreases during secondary crimping, increasing the contact pressure (increasing the amount of gasket pressure), and the contact end position between the vent and gasket becomes shorter. As a result, the gasket presses the front end of the vent, increasing the vent moment. This is thought to be due to an increase in the vent angle caused by an increase in the deformation rate of the vent, which in turn increases the H0 dimension.

[0053] [Explanation of symbols] 100:Can 200: Cap assembly 210: Vent 220: Current breaker filter 230: CID gasket 300: Gasket

Claims

1. electrode assembly; a can containing the electrode assembly; a cap assembly that completes the open top of the can, the cap assembly including a vent, a current interrupter (CID) filter located below the vent, and a CID gasket located at one end of the current interrupter filter; and a gasket that is crimped between the cap assembly and the top of the can while being interposed therebetween to maintain insulation and sealing between the cap assembly and the can; The outer surface, upper surface, and lower surface of the end of the vent of the cap assembly are in close contact with the inner surface and upper surface of the gasket, respectively; The secondary battery has a curvature radius of 0.1 to 0.3 mm at the portion where the outer surface of the end of the vent meets the upper surface.

2. The secondary battery according to claim 1 , wherein an adhesive layer is formed on at least a part of the outer surface and the upper surface of the end of the vent, or a double-sided adhesive tape is attached to the outer surface and the upper surface of the end of the vent.

3. The secondary battery according to claim 1 , wherein the current interrupter (CID) filter is joined to an electrode tab extending upward from one electrode of the electrode assembly.

4. The secondary battery according to claim 1 , wherein the end of the vent is formed by folding the metal plate upward by 180° to form two overlapping layers.

5. The secondary battery according to claim 1 , wherein the outer shape of the can is cylindrical, and the vent is a flat, disc-shaped one.

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