Cylindrical secondary battery

Abstract

Embodiments of this disclosure relate to a cylindrical secondary battery, comprising: a cylindrical can having a circular bottom, a side extending from the bottom, a rolled edge recessed at one end of the side, and a crimped portion formed by bending this end of the side; an electrode assembly housed within the can; and a cap assembly sealing the can and having a gasket for insulating the can, wherein the upper portion of the gasket in the direction away from the electrode assembly has a thinner thickness than the lower portion in the direction of the electrode assembly. According to embodiments of this disclosure, by improving the shape of the gasket, components such as the top cover and safety vent are not deformed by the pressure applied when the crimped portion and rolled edge are formed on the can during assembly of the cap assembly. Therefore, the stability of the secondary battery can be improved.

Description

[0001] This application claims priority and benefit to Korean Patent Application No. 10-2022-0004074, filed on January 11, 2022, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0002] Embodiments of this disclosure relate to a cylindrical secondary battery with an improved cover assembly structure. Background Technology

[0003] Typically, a cylindrical secondary battery includes a cylindrical electrode assembly, a cylindrical can for containing the electrode assembly and electrolyte, and a cover assembly attached to the upper opening of the can to seal the can and allow current generated in the electrode assembly to flow to an external device.

[0004] The lid assembly is secured to the can by forming a crimp portion on the top of the can, placing the lid assembly on the crimp portion, and forming a rolled edge to secure the lid assembly. Therefore, the lid assembly includes a gasket for insulation from the can. However, when the rolled edge is formed, the lid assembly may deform under pressure applied to it, thus the top cover and safety vent may deform.

[0005] The information disclosed above in this background section is only intended to enhance the understanding of the background of the invention, and therefore may contain information that does not constitute prior art. Summary of the Invention

[0006] This disclosure provides a cylindrical secondary battery with an improved structure for the cover assembly, thereby preventing deformation of the components during the assembly of the cover assembly.

[0007] A cylindrical secondary battery according to an embodiment of the present disclosure may include: a cylindrical can having a circular bottom, a side extending from the bottom, a rolled edge recessed at one end of the side, and a crimped portion formed by bending said one end of the side; an electrode assembly housed in the can; and a cap assembly sealing the can and having a gasket for insulating the can, wherein the upper portion of the gasket in the direction away from the electrode assembly has a thickness less than the lower portion in the direction of the electrode assembly.

[0008] The washer may have a shape in which the thickness of the upper part decreases toward the said end.

[0009] The washer may have an annular body, a connecting portion extending from the body, and an extension portion extending downward from the connecting portion, and the thickness of the body decreases toward said end.

[0010] The cover assembly may include an upper cover disposed between the crimping portion and the rolled edge portion, a safety vent disposed below the upper cover, and a lower cover disposed below the safety vent and electrically connected to the electrode assembly, and a gasket may insulate the safety vent and the upper cover from the can.

[0011] The lower surface of the edge of the safety vent can be in close contact with the upper surface of the cover, and the gasket can be bent to surround the edge of the safety vent.

[0012] The washer may have a beveled surface with a chamfer on the inner circumferential surface of the body.

[0013] The inclined surface can make close contact with the upper surface of the edge of the safety vent.

[0014] The bending position (F) of the curved upper surface of the safety vent (where the straight segment begins at the bending position) can correspond to the starting position of the inclined surface. Attached Figure Description

[0015] Figure 1 This is a longitudinal cross-sectional view showing a typical cylindrical secondary battery.

[0016] Figure 2A It shows when assembly according to Figure 1 A partial cross-sectional view showing the direction of the pressure applied when the cover assembly is in use.

[0017] Figure 2B It shows in detail the basis Figure 2A A local cross-sectional view of the pressure distribution.

[0018] Figure 3 It is shown in the assembly according to Figure 1 CT images of the deformed state after the cover assembly.

[0019] Figure 4 It shows the basis Figure 1 A partial cross-sectional view of the compression area of ​​the cover assembly based on the gasket position.

[0020] Figure 5 It is used to determine the basis Figures 1 to 4 A partial perspective view comparing the gasket with a gasket according to an embodiment of the present disclosure.

[0021] Figure 6 This is a partial perspective view showing the detailed structure of a gasket according to an embodiment of the present disclosure.

[0022] Figure 7 It will be based on Figures 1 to 4 A diagram comparing the bending state of the gasket with that of the gasket according to an embodiment of the present disclosure.

[0023] Figure 8The image shows the state after the cover assembly according to an embodiment of the present disclosure has been assembled. Detailed Implementation

[0024] Examples of this disclosure are provided to explain it more fully to those skilled in the art, and the following examples may be modified in various other forms. However, this disclosure may be implemented in many different forms and should not be construed as limited to the exemplary (or exemplary) embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will convey to those skilled in the art aspects and features of this disclosure.

[0025] Furthermore, for the sake of brevity and clarity, the dimensions or thicknesses of various components are exaggerated in the accompanying drawings. The same reference numerals always refer to the same elements. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Furthermore, it will be understood that when element A is referred to as being "connected to" element B, element A may be directly connected to element B, or an intermediary element C may exist between element A and element B such that element A and element B are indirectly connected to each other.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit disclosure. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising or including” and / or variations thereof are used in this specification, it indicates the presence of the stated features, quantities, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, quantities, steps, operations, elements, components, and / or groups thereof.

[0027] It will be understood that although the terms first, second, etc., may be used herein to describe various components, elements, regions, layers, and / or parts, these components, elements, regions, layers, and / or parts should not be limited by these terms. These terms are used only to distinguish one component, element, region, layer, and / or part from another component, element, region, layer, and / or part. Thus, for example, without departing from the teachings of this disclosure, the first component, first element, first region, first layer, and / or first part discussed below may be referred to as a second component, second element, second region, second layer, and / or second part.

[0028] For ease of description, spatial relative terms such as “below,” “under,” “lower,” “above,” and “upper” may be used herein to describe the relationship between one element or feature as shown in the accompanying drawings and another element or feature (or other elements or features). It will be understood that, in addition to covering the orientation depicted in the drawings, the spatial relative terms are intended to also cover different orientations of the device in use or operation. For example, if an element or feature in the drawings is flipped, an element described as “below” or “under” other elements or features would subsequently be oriented as “above” or “on” other elements or features. Thus, the exemplary term “below” can cover both above and below orientations.

[0029] In the following text, a typical cylindrical secondary battery will be briefly described with reference to the accompanying drawings.

[0030] Figure 1 This is a longitudinal cross-sectional view showing a typical cylindrical secondary battery.

[0031] like Figure 1 As shown, a typical cylindrical secondary battery 1 includes a cylindrical can 10 having one end open in the longitudinal direction, an electrode assembly 30 housed in the can 10, and a lid assembly 50 that seals the can 10.

[0032] The can 10 includes a circular bottom 12 and a side 14 extending upward from the bottom 12, with the top of the side 14 being open. In the manufacturing process of the secondary battery 1, the electrode assembly 30, together with the electrolyte, is contained through the opening of the can 10. The can 10 may be made of steel, steel alloy, nickel-plated steel, nickel-plated steel alloy, aluminum, aluminum alloy, or equivalents thereof.

[0033] A rolled edge 16 and a crimping portion 18 are formed on the side portion 14 to secure the cap assembly 50. The rolled edge 16 is formed by bending the side portion 14 concavely toward the interior of the can 10. The rolled edge 16 is the portion on which the cap assembly 50 is positioned during assembly. The crimping portion 18 is formed by bending the end of the side portion 14 toward the interior of the can 10 after the cap assembly 50 is positioned on the can 10. The crimping portion 18 prevents the cap assembly 50 from separating. The rolled edges 16 are spaced apart to avoid contact with the electrode assembly 30.

[0034] The electrode assembly 30 includes a negative electrode plate 31 coated with a negative electrode active material (e.g., graphite, carbon, etc.), a positive electrode plate 32 coated with a positive electrode active material (e.g., transition metal oxides (LiCoO2, LiNiO2, LiMn2O4, etc.)), and a diaphragm 33 disposed between the negative electrode plate 31 and the positive electrode plate 32 to prevent short circuits between them. The negative electrode plate 31 may be copper (Cu) foil or nickel (Ni) foil, the positive electrode plate 32 may be aluminum (Al) foil, and the diaphragm 33 may be polyethylene (PE) or polypropylene (PP). A negative electrode connector 34 protruding downwards is welded to the negative electrode plate 31, and a positive electrode connector 35 protruding upwards is welded to the positive electrode plate 32. The negative electrode connector 34 is welded to the bottom 12 of the can 10, and the positive electrode connector 35 is welded to the cover assembly 50. Therefore, the can 10 operates as a negative electrode, and the cover assembly 50 operates as a positive electrode. The negative electrode plate 31, the positive electrode plate 32, and the diaphragm 33 are wound in a cylindrical shape and housed inside the can 10.

[0035] The cover assembly 50 includes a safety vent 51, an upper cover 52 disposed above the safety vent 51, and a lower cover 53 disposed below the safety vent 51. The cover assembly 50 also includes an insulating member 54 and an insulating gasket 55. The insulating member 54 is inserted between the safety vent 51 and the lower cover 53 for insulation, preventing any portion other than the central portion of the safety vent 51 from contacting the lower cover 53. The insulating gasket 55 insulates the cover assembly 50 and the can 10 from each other. In the safety vent 51, the central portion of the can 10 contacts the lower cover 53, and the portion supported by the insulating member 54 is spaced apart from the lower cover 53. The safety vent 51 has a notch 51a, which is formed to rupture and release gas when the internal pressure rises above a certain level.

[0036] Figure 2A It shows when assembly according to Figure 1 A partial cross-sectional view showing the direction of the pressure applied when the cover assembly is in use. Figure 2B It shows in detail the basis Figure 2A A local cross-sectional view of the pressure distribution. Figure 3 It is shown in the assembly according to Figure 1 CT images of the deformed state after the cover assembly. Figure 4 It shows the basis Figure 1 A partial cross-sectional view of the compression area of ​​the cover assembly based on the gasket position.

[0037] like Figure 2AAs shown, in order to form the crimped portion 16, when the side portion 14 of the can 10 is pressed with a side clamp (crimping tool), pressure is applied from the crimped portion 16 to the washer 55 in the order of arrows ①, ②, and ③. Furthermore, in order to form the crimped portion 18, when the top end of the side portion 14 is pressed with an upper clamp, pressure is applied from the crimped portion 18 to the washer 55 in the order of ①, ②, and ③.

[0038] Here, Figure 2B Region A is the region where a load is generated by pressure applied from the top, and region B is the region where stress is generated by pressure applied from the bottom. Therefore, washer 55 is compressed due to the pressure received in the vertical direction. Furthermore, the pressure transmitted to washer 55 causes it to compress, and along... Figure 2B The direction of the arrow is transmitted to the lower cover 53 via the upper cover 52, the safety vent 51, and the insulating member 54. The force transmitted thereby causes the safety vent 51 and the upper cover 52 to deform in the downward direction.

[0039] Reference Figure 3 In fact, on the CT image of the cover assembly 50, it can be seen that the upper surface 52a and the lower surface 52b of the cover 52 are not parallel to the guide lines L1-1 and L1-2, which are parallel to the horizontal center line L1, but sag downwards. That is, the cover 52 is deformed in the downward direction. Due to the deformation of the cover 52, the safety vent 51 also receives the load and deforms in the downward direction (in Figure 3 In the diagram, vertical guide lines L2 and L2-1 are guide lines used to indicate that L1, L1-1, and L1-2 are perpendicular to the vertical guide lines.

[0040] Reference Figure 4 If region D, the upper region of washer 55, is compressed by 7% compared to before deformation, then region E, the lower region of washer 55, exhibits a 54% compression compared to before deformation. That is, the lower region (region E) can withstand a relatively large amount of pressure. This is because washer 55 and safety vent 51 ( Figure 4 The contact areas differ between the parts indicated by the thick lines (the contact portions), and the lower part, with its smaller contact area compared to the other parts, can receive a larger load. Therefore, localized deformation (recessing) occurs in the direction of the smaller contact area, and localized sagging may occur.

[0041] As described above, the stability and reliability of the secondary battery 1 deteriorate when the cover assembly 50 deforms. Therefore, to solve this problem, in this embodiment, a gasket 500 with a novel shape is proposed (the details of which will be omitted). Figures 1 to 4 The structure is the same as the detailed description of the structure. ), wherein, in the upper region of the washer 55, which is a region with a relatively large contact area, the shape of the region C that contacts the safety vent 51 is changed.

[0042] Figure 5 It is used to determine the basis Figures 1 to 4 A partial perspective view comparing the gasket with a gasket according to an embodiment of the present disclosure. Figure 6 This is a partial perspective view showing the detailed structure of a gasket according to an embodiment of the present disclosure.

[0043] like Figure 1 and Figure 5 As shown, the washer 55 has a generally annular shape to surround and support the edge of the safety vent 51 and the edge of the cover 52. The washer 55 has an outer circumferential surface 55a and an inner circumferential surface 55b, and the upper surface of the inner circumferential surface 55b is partially chamfered (beveled) to have a short inclined surface 55c. However, compared to the short inclined surface 55c formed on the inner circumferential surface 55b of the washer 55, the washer 500 according to an embodiment of the present disclosure has a shape with a chamfered shape having a long inclined surface 516.

[0044] like Figure 6 As shown, the washer 500 of this embodiment has a substantially ring shape and includes a body 510 having a predetermined length in the vertical direction, a connecting portion 530 that bends substantially vertically from the body 510 (bending substantially perpendicular to the body 510), and an extension portion 550 that extends approximately downward vertically from the connecting portion 530 (extending approximately downward perpendicular to the connecting portion 530). Here, expressing "substantially vertical" means that the angles between the body 510 and the connecting portion 530, and between the connecting portion 530 and the extension portion 550, are vertical or nearly vertical, but are not limited to these angles.

[0045] The main body 510 may include a flat outer circumferential surface 512 in the vertical direction, an inner circumferential surface 514 and an inclined surface 516 inside the outer circumferential surface 512, and an upper surface 518 connecting the outer circumferential surface 512 and the inclined surface 516. Figure 1 Like gasket 55, the outer circumferential surface 512 is the surface that contacts the side 14 of tank 10. The inner circumferential surface 514 is the surface that contacts the safety vent (51', see...) Figure 8 The edge and top cover (52', see) Figure 8The edge of the gasket 500 is in close contact with the outer circumferential surface 512, which is roughly bisected vertically. When the gasket 500 bends, only a portion of the upper side of the inner circumferential surface 514 bends to contact the upper part of the safety vent 51'. The inclined surface 516 refers to the upper part of the outer circumferential surface 512, which is roughly bisected vertically. The inclined surface 516 is formed into an inclined shape by chamfering the portion that was previously an inner circumferential surface. The inclined surface 516 has a shape in which the distance (thickness of the body) from the outer circumferential surface 512 decreases upward. That is, the gasket 500 is characterized in that the thickness of the upper part in the direction away from the electrode assembly 30 is less than the thickness of the lower part (the part where the connecting part and the extension are located). In addition, the gasket 500 is characterized in that it has an upper thickness that decreases towards its tip.

[0046] The connecting portion 530 is a portion that is bent substantially perpendicular to the main body 510 to have a predetermined length again in the horizontal direction. The connecting portion 530 has an outer surface 532 and an inner surface 534, and the distance between the outer surface 532 and the inner surface 534 (the thickness of the connecting portion) can be equal to or close to the distance between the outer circumferential surface 512 and the inner circumferential surface 514 of the main body 510.

[0047] The extension 550 is a portion that is bent substantially vertically at the end of the connecting portion 530 and extends downward to have a predetermined length. The extension 550 has an outer circumferential surface 552 and an inner circumferential surface 554, an inclined connecting surface 556 connected to the inner surface 534 of the connecting portion 530, and a lower surface 558 connecting the outer circumferential surface 552 and the inner circumferential surface 554.

[0048] The main body 510, the connecting portion 530, and the extension portion 550 have been described separately above, but this is only for the purpose of clearly showing the structure. The main body 510, the connecting portion 530, and the extension portion 550 are integrally formed, and the washer 500 is formed as a ring that is integrally connected.

[0049] Figure 7 It will be based on Figures 1 to 4 A diagram comparing the bending state of the gasket with that of the gasket according to an embodiment of the present disclosure.

[0050] like Figure 7 As shown, unlike a conventional washer 55, the washer 500 according to this embodiment can be formed with a chamfered shape from the bend position F to the top, creating an inclined surface. Here, the bend position F is where the washer 500 forms a rolled edge (see...). Figure 2AWhen the gasket 500 bends around the edge of the safety vent 51 and the edge of the cover 52, it begins to contact the upper surface of the safety vent 51'. That is, the bending position F signifies the point where the flat, straight portion (straight segment) begins at the bent portion of the safety vent 51'. The reason for forming the inclined surface 516 by chamfering from this portion to the upper surface is to reduce the... Figure 4 The contact area between the upper part of the gasket 55 and the safety vent 51' described herein is used to minimize the transmission of pressure applied downward to the gasket 500 to other parts.

[0051] As described above, by forming an inclined surface 516 that is relatively longer than that of the existing gasket 55, the compression and deformation of the gasket 500 caused by can processing can be minimized by reducing the upper thickness of the gasket 500 (the thickness of the body 510). Therefore, deformation of the cap assembly can be prevented.

[0052] Figure 8 The image shows the state after the cover assembly according to an embodiment of the present disclosure has been assembled.

[0053] Reference Figure 8 In fact, on the CT image of the cover assembly 50', it can be seen that the upper surface 52a' and lower surface 52b' of the upper cover 52' ​​are parallel to the guide lines L3-1 and L3-2, which are parallel to the horizontal center line L3. That is, even when the pressing part 18' is formed, the upper cover 52' ​​does not deform in the downward direction. Since the upper cover 52' ​​is not deformed, the safety vent 51' is not deformed, indicating that part of the cover assembly 50' is not deformed (in Figure 8 In the diagram, vertical guide line L4 is used to indicate that L3, L3-1, and L3-2 are perpendicular to the vertical guide line.

[0054] As described above, according to embodiments of this disclosure, by improving the shape of the gasket, components such as the top cover and safety vent are not deformed by the pressure applied when forming the crimped portion and rolled edge in the can during assembly of the cover assembly. Therefore, the stability of the secondary battery can be improved.

[0055] In embodiments of this disclosure, by improving the shape of the gasket, components such as the top cover and safety vent will not deform due to the pressure when the cover assembly is assembled in the can to form a crimped portion and a rolled edge, thereby improving the stability of the secondary battery.

[0056] Although the foregoing embodiments are merely one example of implementing this disclosure, and this disclosure is not limited to these embodiments, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope of this disclosure as defined by the claims.

Claims

1. A cylindrical secondary battery comprising: a cylindrical can having a circular bottom, a side portion extending from the bottom, a crimped portion formed recessively at one end of the side portion, a press-contact portion formed by bending the one end of the side portion; an electrode assembly accommodated in the can; and a cap assembly sealing the can and including an upper cap between the press-contact portion and the crimped portion, a safety vent hole disposed below the upper cap, and a gasket for insulating the safety vent hole and the upper cap from the can, wherein an upper portion of the gasket in a direction away from the electrode assembly has a thickness smaller than that of a lower portion in a direction of the electrode assembly, wherein the safety vent hole has an edge curved to be in close contact with an upper surface of the upper cap, wherein the gasket has a ring-shaped main body including an inner circumferential surface curved to surround and be in contact with the edge of the safety vent hole and an inclined surface inclined from the inner circumferential surface, and wherein a curved position of an upper surface of the edge of the safety vent hole corresponds to a start position of the inclined surface. The gasket has a shape in which the thickness of the upper portion decreases toward the one end.

2. The cylindrical secondary battery according to claim 1, wherein The gasket further has a connecting portion extending from the main body and an extension portion extending downward from the connecting portion, and the thickness of the main body decreases toward the one end.

3. The cylindrical secondary battery according to claim 2, wherein The cap assembly further includes a lower cap disposed below the safety vent hole and electrically connected to the electrode assembly.

4. The cylindrical secondary battery according to claim 3, wherein A lower surface of the edge of the safety vent hole is in close contact with the upper surface of the upper cap.

5. The cylindrical secondary battery according to claim 4, wherein The main body further includes a flat outer circumferential surface and a surface connecting the outer circumferential surface and the inclined surface.

6. The cylindrical secondary battery according to claim 1, wherein The inclined surface is in close contact with the upper surface of the edge of the safety vent hole.

7. The cylindrical secondary battery according to claim 1, wherein The main body, the connecting portion, and the extension portion are integrally formed.

8. The cylindrical secondary battery according to claim 3, wherein ​

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