Secondary battery

Abstract

A secondary battery includes: a cylindrical can; an electrode assembly accommodated in the cylindrical can together with an electrolyte; and a cap assembly coupled to a top of the cylindrical can, the cap assembly including an upper cap, a safety plate coupled to a lower surface of the upper cap, and an insulating liner wrapping the upper cap and the safety plate, the insulating liner having a gap filling portion between the upper cap and the safety plate.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0106091 filed in the Korean Intellectual Property Office on August 14, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] Embodiments of the present disclosure relate to a secondary battery. Background Art

[0004] A secondary battery may be a power storage system that converts electrical energy into chemical energy, stores the chemical energy, and provides a relatively high energy density.

[0005] Compared to non-rechargeable primary batteries, secondary batteries should be rechargeable and are widely used in information technology (IT) devices such as smart phones, cellular phones, laptop computers, and / or tablet personal computers (PCs).

[0006] Recently, in order to prevent or reduce environmental pollution, people's interest in electric vehicles has increased, and high-capacity secondary batteries are adopted in electric vehicles. For such secondary batteries, characteristics such as high capacity and / or high energy density are desired and / or required.

[0007] In the past, secondary batteries having an ultra-thin cap assembly of a coverless type or kind (eg, secondary batteries having a cap that does not substantially protrude in an upward direction) were developed to increase the battery cell capacity and energy density of the secondary batteries.

[0008] However, as a component such as a cap assembly becomes thinner, the component may be more easily deformed due to a force applied thereto during formation of a battery cell, and a cap assembly of a non-cap-type or kind may be more easily deformed.

[0009] Therefore, it is desirable to develop a technology capable of ensuring the battery cell capacity and energy density of a cylindrical secondary battery and supplementing airtightness while ensuring durability by providing an upper cover against a force applied during formation of a battery cell.

[0010] The information disclosed in this section is provided only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art. Summary of the invention

[0011] Aspects of one or more embodiments of the present disclosure relate to a secondary battery cell, which is configured so that a peripheral portion of an upper cover is half-curled in a downward direction toward a safety plate, whereby the total thickness of the cover assembly is less than the total thickness of a comparable cover assembly in the related art, thereby improving the airtightness of the cover assembly while ensuring a relatively large capacity.

[0012] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the embodiments presented in the disclosure.

[0013] A secondary battery according to one or more embodiments of the present disclosure includes: a cylindrical can; an electrode assembly contained in (e.g., received in) the cylindrical can together with an electrolyte; and a cover assembly connected to the top of the cylindrical can, the cover assembly including an upper cover, a safety plate connected to a lower surface of the upper cover, and an insulating gasket configured to wrap (e.g., wrap or surround) the upper cover and the safety plate, the insulating gasket having a gap-filling portion between the upper cover and the safety plate.

[0014] In one or more embodiments, the width of the gap-filling portion gradually decreases in an upward direction.

[0015] In one or more embodiments, the gap-filling portion may have a triangular cross-section.

[0016] In one or more embodiments, the gap-filling portion may have a ring shape in a plan view of the gap-filling portion.

[0017] In one or more embodiments, the gap-filling portion may be formed by melting a portion of the insulating liner.

[0018] In one or more embodiments, the gap-filling portion may be formed by melting a portion of the insulating liner at a temperature of 250° C. to 280° C.

[0019] In one or more embodiments, the insulating gasket may be made of a thermoplastic material.

[0020] In one or more embodiments, the insulating gasket may be made of a polymer selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, perfluoroalkoxyalkanes, cross-linked polyethylene, cross-linked polypropylene, cross-linked polyethylene terephthalate, cross-linked polybutylene terephthalate, and cross-linked perfluoroalkoxyalkanes.

[0021] In one or more embodiments, the insulating gasket may include: a gasket bottom flat portion, at the lower surface of the peripheral portion of the safety plate; a gasket bending portion, bent in an upward direction from the gasket bottom flat portion, the gasket bending portion being configured to surround (for example, the gasket bending portion surrounds) the side surface of the upper cover; and a gasket top flat portion, bent from the gasket bending portion in a direction toward the upper surface of the upper cover, the gasket top flat portion being configured to surround (for example, the gasket top flat portion surrounds) the upper surface of the peripheral portion of the upper cover, and the gap filling portion may be on the gasket bottom flat portion.

[0022] In one or more embodiments, the cover assembly may further include a lower cover connected to the safety plate, a lower surface of a central portion of the safety plate and an upper surface of a central portion of the lower cover may contact each other, and the insulating gasket may include a gasket extension portion extending between the safety plate and the lower cover.

[0023] In one or more embodiments, the cover assembly may further include a lower cover connected to the safety plate and a connecting ring between the safety plate and the lower cover, and the lower surface of the central portion of the safety plate and the upper surface of the central portion of the lower cover may contact each other.

[0024] In one or more embodiments, the upper cover may include an upper cover peripheral flat portion and an upper cover peripheral bent portion bent in a downward direction from the upper cover peripheral flat portion.

[0025] In one or more embodiments, the safety plate may include a safety plate peripheral flat portion, and a portion of an outer surface of the safety plate peripheral flat portion may contact a portion of an inner surface of the upper cover peripheral bent portion.

[0026] In one or more embodiments, the gap filling portion may be between a remaining portion of the inner surface of the upper cover peripheral bent portion and another (e.g., other) portion of the outer surface of the peripheral flat portion of the safety plate, and the remaining portion does not include the portion of the inner surface of the upper cover peripheral bent portion that contacts the portion of the outer surface of the peripheral flat portion of the safety plate.

[0027] In one or more embodiments, another (e.g., other) portion of the outer surface of the peripheral flat portion of the safety plate can be spaced apart and / or separated (e.g., spaced apart or separated) from the remaining portion of the inner surface of the peripheral bent portion of the upper cover, and the remaining portion does not include (e.g., excludes) the portion of the inner surface of the peripheral bent portion of the upper cover that is in contact with the portion of the outer surface of the peripheral flat portion of the safety plate.

[0028] In one or more embodiments, the distance between the other portion of the outer surface of the peripheral flat portion of the safety plate and the remaining portion of the inner surface of the peripheral bent portion of the upper cover may gradually increase in the downward direction.

[0029] In one or more embodiments, the inner surface of the upper cover peripheral bent portion may contact the portion of the outer surface of the safety plate peripheral flat portion in a downwardly inclined state.

[0030] In one or more embodiments, the safety plate may further include: an upper bending portion, which is bent from the inner part of the peripheral flat portion of the safety plate in the upward direction; a lower bending portion, which is connected to the upper bending portion and is bent in the downward direction; an inner flat portion, which is connected to the lower bending portion and is lower than the peripheral flat portion of the safety plate; and a recess in the lower surface of the upper bending portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings incorporated in this specification illustrate example embodiments and are used to further illustrate the technical concept of the present disclosure in conjunction with the detailed description of the following exemplary embodiments, and the present disclosure should not be construed as being limited to the contents shown in these drawings. In the drawings:

[0032] Figure 1 is a perspective view of a secondary battery according to one or more embodiments of the present disclosure;

[0033] Figure 2 is a cross-sectional view of a secondary battery according to one or more embodiments of the present disclosure;

[0034] Figure 3 is an exploded perspective view of a secondary battery according to one or more embodiments of the present disclosure;

[0035] Figure 4 is a cross-sectional view showing an upper cover and a cover assembly in a secondary battery according to one or more embodiments of the present disclosure with a gap-filling portion interposed therebetween;

[0036] Figure 5 FIG. 1 is a diagram showing a security panel and a Figure 4 A cross-sectional view of the gap between the upper covers;

[0037] Figure 6 is a cross-sectional view illustrating an upper cover and a gasket extension portion with a gap-filling portion interposed therebetween according to one or more embodiments of the present disclosure;

[0038] Figure 7are cross-sectional views showing a comparable secondary battery (a) of the related art and a secondary battery (b) according to one or more embodiments of the present disclosure for thickness comparison therebetween; and

[0039] Figure 8 are cross-sectional views showing a related art comparable secondary battery (a) and a secondary battery (b) according to one or more embodiments of the present disclosure for thickness comparison therebetween. DETAILED DESCRIPTION

[0040] The present disclosure can be modified in many alternative forms, and therefore specific embodiments will be illustrated in the drawings and described in more detail. However, it should be understood that this is not intended to limit the present disclosure to the specific forms disclosed, but is intended to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure.

[0041] Hereinafter, example embodiments will be described in more detail with reference to the accompanying drawings. However, the present disclosure may be implemented in a variety of different forms and should not be construed as being limited to the embodiments illustrated herein. On the contrary, these embodiments are provided as examples so that the present disclosure will be detailed and complete, and will fully convey the aspects and features of the present disclosure to those skilled in the art. Accordingly, processes, elements, and techniques that are not necessary for the aspects and features of the present disclosure that are fully understood by those of ordinary skill in the art may not be described.

[0042] In the following drawings, the thickness or size of each layer may be exaggerated for convenience and / or clarity of description. In the drawings, the relative sizes of elements, layers, and regions may be exaggerated for clarity. Unless otherwise specified, the same reference numerals denote the same elements throughout the drawings and written descriptions, and therefore, repeated descriptions thereof may not be provided.

[0043] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. It will be understood that when an element such as a region, layer, film, area, or portion is referred to as being "on," "connected to," or "coupled to" another element, it can be directly on, connected to, or coupled to the other element, or there can be one or more intervening elements. Additionally, it will be understood that when an element is referred to as being "between" two elements, it can be the only element between the two elements, or there can also be one or more intervening elements.

[0044] The terms used in this article are only used for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to also include plural forms, unless the context clearly states otherwise. It will be further understood that the terms "comprise", "include" and "have" when used in this specification clearly indicate the presence of stated features, integers, steps, operations, elements, parts and / or their groups, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or their groups.

[0045] As used herein, the terms "use" and "used" may be considered synonymous with the terms "utilize" and "utilized," respectively.

[0046] It will be understood that although the terms "first", "second", "third", etc. may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Therefore, the first element, component, region, layer or section described below may be referred to as a second element, component, region, layer or section without departing from the spirit and scope of the present disclosure.

[0047] For ease of explanation, spatially relative terms such as "on ... ", "below," "down," "below," "above," and "on" may be used herein to describe the relationship between an element or feature and another element or feature as illustrated in the figure. It will be understood that, in addition to the orientation depicted in the accompanying drawings, spatially relative terms are intended to cover different orientations of the device in use or operation. For example, if the device in the figure is flipped, the element described as "below" or "under" or "below" other elements or features will then be oriented "above" the element or feature. Therefore, the example terms "below" and "below" can cover the orientation of both above and below. The device can be oriented in other ways (e.g., rotated 90 degrees or in other orientations), and the spatially relative descriptors used in this article should be interpreted accordingly.

[0048] It will be understood that the description of features or aspects in each embodiment should generally be considered applicable to other similar features or aspects in other embodiments, unless otherwise described. Therefore, as will be apparent to those of ordinary skill in the art, unless otherwise specifically stated, features, characteristics and / or elements described in conjunction with a particular embodiment may be used alone or in combination with features, characteristics and / or elements described in conjunction with other embodiments.

[0049] Figure 1 , Figure 2 and Figure 3are respectively a perspective view, a cross-sectional view, and an exploded perspective view, each showing a secondary battery according to one or more embodiments of the present disclosure, Figure 4 is a cross-sectional view showing an upper cover and a cover assembly in a secondary battery according to one or more embodiments of the present disclosure with a gap-filling portion interposed therebetween, Figure 5 FIG. 1 is a diagram showing a security panel and a Figure 4 A cross-sectional view of the gap between the upper cover and Figure 6 is a cross-sectional view illustrating an upper cover and a gasket extending portion with a gap-filling portion interposed therebetween according to one or more embodiments of the present disclosure.

[0050] refer to Figure 1 , Figure 2 and Figure 3 , the secondary battery 10 according to one or more embodiments may include a cylindrical can 100 , an electrode assembly 200 , and a cap assembly 400 . The secondary battery 10 according to one or more embodiments may further include a center pin 300 .

[0051] The cylindrical can 100 may include a circular bottom portion 110 and a side portion 120 extending in an upward direction from the bottom portion 110 by a set or predetermined length. During the process of manufacturing the secondary battery 10, the top of the cylindrical can 100 may be open. Therefore, during the process of manufacturing the secondary battery 10, the electrode assembly 200 may be inserted into the cylindrical can 100 together with the electrolyte. The cylindrical can 100 may be formed of iron, iron alloy, aluminum, aluminum alloy, or an equivalent thereof, but the material is not limited thereto.

[0052] In order to prevent or substantially prevent the cap assembly 400 from separating outward from the cylindrical can 100, the cylindrical can 100 may have an inwardly concave curling portion 130 formed at a portion of the cylindrical can 100 located below the cap assembly 400 and an inwardly bent crimping portion 140 formed at a portion of the cylindrical can 100 located above the cap assembly 400.

[0053] The cylindrical can 100 may be filled with an electrolyte that allows lithium ions generated by electrochemical reactions on the negative electrode plate 210 and the positive electrode plate 220 in the battery during charging and discharging to move through the electrolyte. The electrolyte may be a non-aqueous organic electrolyte that is a mixture of a lithium salt and a high-purity organic solvent. The electrolyte may be, but is not limited to, a polymer using a polymer electrolyte or a solid electrolyte.

[0054] The first insulating plate 160 may be interposed between the electrode assembly 200 and the bottom portion 110, the first insulating plate 160 being coupled to the cylindrical can 100 and having a first hole 161 formed in the center and a second hole 162 formed in the outer side thereof. The first insulating plate 160 may be used to prevent or substantially prevent the electrode assembly 200 from electrically contacting the bottom portion 110 of the cylindrical can 100. The first insulating plate 160 may be used to prevent or substantially prevent the positive electrode plate 220 of the electrode assembly 200 from electrically contacting the bottom portion 110. The first hole 161 of the first insulating plate 160 may be used to allow the gas to quickly move upward through the center pin 300 in the event that a large amount of gas is generated due to an abnormality of the secondary battery 10, and the second hole 162 of the first insulating plate 160 may be used to allow the negative electrode tab 240 to extend therethrough and be welded to the bottom portion 110.

[0055] The second insulating plate 170 may be interposed between the electrode assembly 200 and the cap assembly 400, the second insulating plate 170 being coupled to the cylindrical can 100 and having a first hole 171 formed in the center and a plurality of second holes 172 formed on the outside thereof. The second insulating plate 170 may be used to prevent or substantially prevent the electrode assembly 200 from electrically contacting the cap assembly 400. The second insulating plate 170 may be used to prevent or substantially prevent the negative electrode plate 220 of the electrode assembly 200 from electrically contacting the cap assembly 400. The first hole 171 of the second insulating plate 170 may be used to allow the gas to quickly move to the cap assembly 400 in the event that a large amount of gas is generated due to an abnormality of the secondary battery 10, and one of the second holes 172 of the second insulating plate 170 may be used to allow the positive electrode tab 250 to extend therethrough and be welded to the cap assembly 400. The other second holes 172 of the second insulating plate 170 may be used to allow the electrolyte to quickly flow into the electrode assembly 200 during the process of injecting the electrolyte.

[0056] The diameters of the first holes 161 , 171 of the first and second insulating plates 160 , 170 , respectively, may be smaller than the diameter of the center pin 300 to prevent or substantially prevent the center pin 300 from electrically contacting the bottom portion 110 or the cap assembly 400 of the cylindrical can 100 by external impact.

[0057] The electrode assembly 200 may be received in the cylindrical can 100. The electrode assembly 200 may include a negative electrode plate 210 coated with a negative electrode active material (e.g., graphite or carbon), a positive electrode plate 220 coated with a positive electrode active material (e.g., a transition metal oxide (LiCoO2, LiNiO2, or LiMn2O4)), and a separator 230 located between the negative electrode plate 210 and the positive electrode plate 220 to prevent or reduce the possibility of a short circuit therebetween and allow only lithium ions to move. The negative electrode plate 210, the positive electrode plate 220, and the separator 230 may be wound in a generally cylindrical shape. The negative electrode plate 210 may be made of copper (Cu) foil or nickel (Ni) foil, the positive electrode plate 220 may be made of aluminum (Al) foil, and the separator 230 may be made of polyethylene (PE) or polypropylene (PP); however, the present disclosure is not limited thereto. At least one negative electrode tab 240 may protrude downward from the negative electrode plate 210 and extend a set or predetermined length, and at least one positive electrode tab 250 may protrude upward from the positive electrode plate 220 and extend a set or predetermined length. The negative electrode tab 240 and the positive electrode tab 250 may be made of separate metal plates and may be welded to the negative electrode plate 210 and the positive electrode plate 220, respectively. In one or more embodiments, the negative electrode tab 240 may protrude upward from the electrode assembly 200 and extend, and the positive electrode tab 250 may protrude downward from the electrode assembly 200 and extend. The negative electrode tab 240 may be made of copper or nickel, and the positive electrode tab 250 may be made of aluminum; however, the present disclosure is not limited thereto.

[0058] The negative electrode tab 240 of the electrode assembly 200 may be welded to the bottom portion 110 of the cylindrical can 100. Therefore, the cylindrical can 100 may be used as a negative electrode. In one or more embodiments, the positive electrode tab 250 may be welded to the bottom portion 110 of the cylindrical can 100, in which case the cylindrical can 100 may be used as a positive electrode.

[0059] The center pin 300 may be in the form of a hollow cylindrical tube that may be coupled to the approximate center of the electrode assembly 200. The center pin 300 may be formed of steel, a steel alloy, aluminum, an aluminum alloy, or polybutylene terephthalate; however, the present disclosure is not limited thereto. The center pin 300 may be used to suppress or reduce deformation of the electrode assembly 200 during charging and discharging of the secondary battery 10, and may be used as a conduit for gas generated in the secondary battery 10. In one or more embodiments, the center pin 300 may not be provided.

[0060] The cap assembly 400 may be coupled to the top of the cylindrical can 100. The cap assembly 400 may include an upper cap 410 located at the uppermost portion of the secondary battery 10 and a safety plate 420 installed below the upper cap 410. The cap assembly 400 may further include a connection ring 430 installed below the safety plate 420, an insulating gasket 440 configured to couple the peripheral portion of the upper cap 410 and the peripheral portion of the safety plate 420 to each other, and a lower cap 450 coupled to the lower surface of the connection ring 430. The positive electrode tab 250 may be fixed to the lower surface of the lower cap 450.

[0061] The upper cover 410 may be formed with a convex central top so as to be electrically connected to an external circuit. The upper cover 410 may also have an opening (hereinafter referred to as a vent hole) 414a that provides a path for the gas generated in the cylindrical can 100 to be discharged. The upper cover 410 may be electrically connected to the electrode assembly 200, and may transmit the current generated by the electrode assembly 200 to the external circuit.

[0062] refer to Figure 4 The upper cover 410 may include an upper cover peripheral flat portion 411 , an upper cover peripheral bent portion 412 , a terminal flat portion 413 and a bridging portion 414 .

[0063] The upper cover peripheral flat portion 411 corresponds to a peripheral portion of the upper cover 410 and may have a flat structure.

[0064] The upper cover peripheral bent portion 412 may be bent downward from the upper cover peripheral flat portion 411 to wrap the outer surface of the safety plate 420 connected to the bottom thereof. Figure 5 As shown in FIG. 4 , the inner surface 412a of the upper cover peripheral bent portion 412 may contact the outer surface 421a of the safety plate 420. The outer surface 421a of the safety plate 420 may refer to the outer surface 421a of the safety plate peripheral flat portion 421, which will be described below.

[0065] refer to Figure 5 , the upper cover peripheral bent portion 412 may be bent at an angle of about 60 degrees (°) to 90 degrees (°) from the upper cover peripheral flat portion 411 toward the outer surface 421a of the safety plate peripheral flat portion 421 (for example, at the outer periphery of the upper cover 410). If the upper cover peripheral bent portion 412 is bent at an angle of 90 degrees (°), the entire inner surface 412a of the upper cover peripheral bent portion 412 and the entire outer surface 421a of the safety plate peripheral flat portion 421 may contact each other (for example, in close contact or press fit).

[0066] In one or more embodiments, reference Figure 5In the enlarged view of part A of the upper cover peripheral bending portion 412, if the upper cover peripheral bending portion 412 is bent at an angle less than 90 degrees (°) (60°≤θ<90°), a portion of the inner surface 412a of the upper cover peripheral bending portion 412 and a portion of the outer surface 421a of the safety plate peripheral flat portion 421 may contact each other. In one or more embodiments, the inner surface 412a of the upper cover peripheral bending portion 412 may be inclined downward and may contact the outer surface 421a of the safety plate peripheral flat portion 421.

[0067] The outer surface 421a of the security plate peripheral flat portion 421 may be spaced and / or separated (e.g., spaced or separated) from the remaining portion of the inner surface 412a of the upper cover peripheral bent portion 412 except for the above-mentioned portion thereof at the gap B, the remaining portion not including the portion of the inner surface 412a of the upper cover peripheral bent portion 412 that contacts the portion of the outer surface 421a of the security plate peripheral flat portion 421. The distance between another portion of the outer surface 421a of the security plate peripheral flat portion 421 and the remaining portion of the inner surface 412a of the upper cover peripheral bent portion 412 may gradually increase in the downward direction. The contact structure between the outer surface 421a of the security plate peripheral flat portion 421 and the inner surface 412a of the upper cover peripheral bent portion 412 may be configured so that the distance between the outer surface 421a of the security plate peripheral flat portion 421 and the inner surface 412a of the upper cover peripheral bent portion 412 gradually increases in the downward direction. Therefore, the inner surface 412a of the upper cover peripheral bent portion 412 and the outer surface 421a of the safety plate peripheral flat portion 421 may be in contact at the top, but separated in the middle, and the distance therebetween gradually increases toward the bottom, thereby generating a gap B having a cross-section in a substantially right triangle shape. The gap B may be filled with a gap filling portion 444, which is a component of the insulating gasket 440, which will be described in more detail below.

[0068] The terminal flat portion 413 may be formed in a dome shape with the central portion of the upper cover 410 protruding upward. The terminal flat portion 413 may serve as a positive electrode terminal.

[0069] The bridge portion 414 may be bent in an upward direction from the upper cover peripheral flat portion 411 toward the terminal flat portion 413 to connect the upper cover peripheral flat portion 411 and the terminal flat portion 413 to each other. At least one exhaust hole 414a may be formed in the bridge portion 414 to allow internal gas to be discharged to the outside in the event that abnormal pressure is generated in the cylindrical can 100.

[0070] The safety plate 420 may be formed as a circular plate corresponding to the upper cover 410, and may be coupled to the upper cover peripheral flat portion 411 and the upper cover peripheral bent portion 412. The lower surface of the central portion of the safety plate 420 and the upper surface of the central portion of the lower cover 450 may contact each other. The safety plate 420 may include a safety plate peripheral flat portion 421, a notch 422, an upper bent portion 423, a lower bent portion 424, an inner flat portion 425, and a welding area 426. In one or more embodiments, the distance d between the safety plate 420 and the upper cover 410 may be at least 1.6 mm to allow the notch 422 to break.

[0071] The safety plate peripheral flat portion 421 may be a peripheral portion of the safety plate 420 and may be flat.

[0072] The upper bent portion 423 may be formed in a state of being bent in an upward direction at an inner portion of the safety plate peripheral flat portion 421. For example, the upper bent portion 423 may be convex in an upward direction.

[0073] The lower bending portion 424 may be connected to the upper bending portion 423 and may be bent in a downward direction. For example, the lower bending portion 424 may be inclined from the upper bending portion 423 in a downward direction (ie, inclined toward the inner flat portion 425).

[0074] The inner flat portion 425 may be connected to the lower bent portion 424 , may be formed lower than the safety plate peripheral flat portion 421 , and may contact an upper surface of the lower cover 450 .

[0075] A notch 422 may be provided in the bottom (e.g., lower surface) of the upper bent portion 423, the notch 422 being configured to guide rupture of the safety plate 420. If a short circuit occurs in the secondary battery 10, internal pressure may increase, causing internal gas to be discharged through the vent hole 451 of the lower cover 450. The discharged gas may cause the inner flat portion 425 of the safety plate 420 to rise, causing the safety plate 420 and the lower cover 450 to be electrically separated from each other, thereby interrupting the current.

[0076] If abnormal pressure is generated in the cylindrical can 100, the safety plate 420 may discharge internal gas while interrupting the current. If the internal pressure of the cylindrical can 100 exceeds the operating pressure of the safety plate 420, the inner flat portion 425 may rise upward due to the gas discharged through the exhaust hole 451 of the lower cover 450, whereby the inner flat portion 425 may be electrically separated from the safety plate 420. If the internal pressure of the cylindrical can 100 exceeds a rupture pressure higher than the operating pressure of the safety plate 420, the notch 422 of the safety plate 420 may rupture to prevent or reduce the possibility of explosion of the secondary battery 10 (e.g., protect the secondary battery 10 from explosion).

[0077] The welding area 426 may be formed between the upper cover peripheral flat portion 411 and the safety plate peripheral flat portion 421. The welding area 426 may be an area provided for welding through the lower surface of the safety plate peripheral flat portion 421, and may be a line (e.g., formed in a line or formed as a line) (e.g., may have a line shape). The lower surface of the upper cover peripheral flat portion 411 and the upper surface of the safety plate peripheral flat portion 421 may be connected to each other by welding. The upper cover peripheral flat portion 411 and the safety plate peripheral flat portion 421 may be welded to each other by laser welding, ultrasonic welding, resistance welding, or their equivalents.

[0078] The connecting ring 430 may be interposed between the safety plate 420 and the lower cover 450. The connecting ring 430 may be interposed between the lower surface of the safety plate peripheral flat portion 421 and the upper surface of the peripheral portion of the lower cover 450. The connecting ring 430 may be made of a resin such as polyethylene (PE), polypropylene (PP) or polyethylene terephthalate (PET). The connecting ring 430 may be replaced by a portion of the insulating gasket 440, so the connecting ring 430 may not be provided. This will be described in more detail below.

[0079] The insulating gasket 440 may be coupled to the top of the cylindrical can 100 , and may have a structure configured to wrap the upper cover 410 , the safety plate 420 coupled to the lower surface of the upper cover 410 , and a coupling portion between the upper cover 410 and the safety plate 420 .

[0080] like Figure 4 As shown in FIG. 4 , the insulating gasket 440 may include a gasket bottom flat portion 441 , a gasket bending portion 442 , a gasket top flat portion 443 , and a gap-filling portion 444 .

[0081] The pad bottom flat portion 441 may be located at a lower surface of a peripheral portion of the safety plate 420 .

[0082] The gasket bent portion 442 may be bent in an upward direction from the gasket bottom flat portion 441 to surround a side surface of the upper cover 410 .

[0083] The gasket top flat portion 443 may be bent from the gasket bent portion 442 in a direction toward the upper surface of the upper cover 410 to surround the upper surface of the peripheral portion of the upper cover 410 .

[0084] The gap filling portion 444 may fill the gap B between the upper cover 410 and the safety plate 420, and may be formed on the gasket bottom flat portion 441. The gap filling portion 444 may be between the inner surface 412a of the upper cover peripheral bending portion 412 and the outer surface 421a of the safety plate peripheral flat portion 421. A portion of the inner surface 412a of the upper cover peripheral bending portion 412 and a portion of the outer surface 421a of the safety plate peripheral flat portion 421 may contact each other, and the gap filling portion 444 is between the remaining portion of the inner surface 412a of the upper cover peripheral bending portion 412 and another portion of the outer surface 421a of the safety plate peripheral flat portion 421. The gap filling portion 444 may be formed in a shape in which the width of the gap filling portion 444 gradually decreases in an upward direction, whereby the gap filling portion 444 may have a substantially triangular cross-section. However, since the insulating gasket 440 is shaped to surround the upper cover 410 , the gap-filling portion 444 may be ring-shaped when viewed in a plan view of the gap-filling portion 444 (eg, when viewed in a plan view of the gap-filling portion 444 ).

[0085] The gap filling portion 444 may be formed by melting a portion of the insulating gasket 440. The insulating gasket 440 having a melting point of 600° C. to 700° C. may be melted at an operating temperature of 250° C. to 280° C., so that the gap between the upper cover 410 and the safety plate 420 is filled with a portion of the insulating gasket 440. The insulating gasket 440, which may be made of a thermoplastic material, may be melted at an operating temperature of 250° C. to 280° C., so that the gap between the upper cover 410 and the safety plate 420 is filled with a portion of the insulating gasket 440. In one or more embodiments, the insulating gasket 440 may be made of a thermoplastic material (e.g., polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or perfluoroalkoxyalkane (PFA)). In one or more embodiments, the insulating pad 440 may be made of a cross-linked thermoplastic material (e.g., cross-linked polyethylene (PEX), cross-linked polypropylene (PPX), cross-linked polyethylene terephthalate (PETX), cross-linked polybutylene terephthalate (PBTX), or cross-linked perfluoroalkoxyalkane (PFAX)). The thermoplastic material may be a polymer selected from the following or a copolymer containing at least one of the following polymers as a structural unit: polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), perfluoroalkoxyalkane (PFA), cross-linked polyethylene (PEX), cross-linked polypropylene (PPX), cross-linked polyethylene terephthalate (PETX), cross-linked polybutylene terephthalate (PBTX), and cross-linked perfluoroalkoxyalkane (PFAX). Preferably, the insulating pad 440 may be made of a resin such as cross-linked polyethylene (PEX). In one or more embodiments, the insulating gasket 440, which may be made of cross-linked polyethylene (PEX), may have a melting point of 600° C. to 700° C. For example, cross-linked polyethylene (PEX) may exhibit a melting point comparable to that of conventional polyethylene; however, it is able to maintain its cross-linked structure within a temperature range of 600° C. to 700° C. The cross-linked material effectively prevents transition to a liquid phase at temperatures exceeding its melting point, thereby delaying the onset of liquefaction.

[0086] The structure of the gap between the upper cover 410 and the safety plate 420 will be described in more detail below. In one or more embodiments, the melting point of the insulating gasket 440 may be a temperature at which it begins to change from a solid state to a liquid state. Moreover, the operating temperature of the insulating gasket 440 may be a temperature of a fixture in a device, which allows some areas of the insulating gasket 440 to melt and form a gap filling portion 444. For example, at the operating temperature, the insulating gasket 440 may only partially change, while mostly maintaining its normal mechanical and chemical properties.

[0087] The insulating gasket 440 may be interposed between the rest of the cap assembly 400 and the cylindrical can 100 while wrapping the upper cap periphery flat portion 411, the upper cap periphery bent portion 412, and the safety plate periphery flat portion 421 to insulate the cap assembly 400 from the side portion 120 of the cylindrical can 100. The insulating gasket 440 may be substantially pressed between the crimping portion 130 and the crimping portion 140 formed at the side portion 120 of the cylindrical can 100. The insulating gasket 440 may be assembled between the outer periphery of the upper cap 410 and the safety plate 420 and the upper end opening of the cylindrical can 100 in a close fit. The upper cap 410 coupled to the safety plate 420 may be fixed to the upper end of the cylindrical can 100 by the crimping portion 140 formed at the upper end of the cylindrical can 100, with the insulating gasket 440 interposed between the upper cap 410 and the upper end of the cylindrical can 100.

[0088] The insulating gasket 440 may be made of a resin such as cross-linked polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET). The insulating gasket 440 may prevent or reduce the possibility of the cap assembly 400 being separated from the cylindrical can 100.

[0089] The lower cover 450 may be coupled to the safety plate 420. The lower cover 450 may be formed as a circular plate. A vent hole 451 may be formed at one side of the lower cover 450, and the vent hole 451 may be used to discharge internal gas in the event that excessive pressure is generated in the cylindrical can 100. The inner flat portion 425 of the safety plate 420 may be raised by the gas discharged through the vent hole 451, whereby the inner flat portion 425 of the safety plate 420 and the lower cover 450 may be separated from each other. If the internal pressure of the cylindrical can 100 is normal, the inner flat portion 425 of the safety plate 420 may be electrically connected to the positive electrode tab 250 via the lower cover 450.

[0090] In one or more embodiments, Figure 6 , the insulating gasket 440 may further include a gasket extension portion 445 extending between the safety plate 420 and the lower cover 450. The gasket extension portion 445 may be formed integrally with the insulating gasket 440 instead of the connecting ring 430. The insulating gasket 440 integrally formed with (e.g., integrally provided with) the gasket extension portion 445 may extend from the bottom of the safety plate peripheral flat portion 421 to the top of the upper cover peripheral flat portion 411 to connect the safety plate peripheral flat portion 421 and the upper cover peripheral flat portion 411 to each other and allow the connecting ring 430 to be omitted.

[0091] For example, Figure 7As shown in the figure, a comparable cylindrical secondary battery (a) in the related art is provided with a bent portion that is curled so that the peripheral portion of the safety plate located below the upper cover wraps the peripheral portion of the upper cover. Therefore, the wing portion of the cover assembly can be a three-layer wing portion having an upper region (first layer), a middle region (second layer), and a lower region (third layer) of the safety plate connected to the bent portion of the safety plate, in which the peripheral portion of the safety plate is curled upward and raised above the peripheral portion of the upper cover, the middle region (second layer) is the peripheral portion of the upper cover wrapped by the peripheral portion of the safety plate, and the wing portion can have a thickness of about 1.2 mm.

[0092] In order to increase the capacity of the cylindrical secondary battery, it is necessary to increase the length of the portion of the cylindrical secondary battery below the rolled portion. To this end, in the secondary battery (b) of one or more embodiments of the present disclosure, for example, Figure 7 4, the wing portion of the upper cover 410 may be only half-rolled in the downward direction until the wing portion of the upper cover 410 contacts the outer surface of the safety plate 420, instead of rolling the wing portion of the safety plate 420 as in the related art. In this case, the wing portion of the cover assembly 400 may be a double-layered wing portion having a peripheral portion (first layer) of the upper cover 410 and a peripheral portion (second layer) of the safety plate 420. The wing portion may have a thickness of about 0.8 mm.

[0093] As described above, a gap B can be formed between the inner surface 412a of the peripheral bent portion 412 of the upper cover and the outer surface 421a of the peripheral flat portion 421 of the safety plate, and the gap B can be filled with a gap filling portion 444, which can be formed by melting a portion of the insulating gasket 440, so that the leakage path formed by the gap B is blocked, thereby improving the airtightness of the secondary battery 10.

[0094] Thinning of the components is essential for high capacity and high energy density of cylindrical battery cells. However, if the upper cover is removed, the components may be bent due to the force applied thereto during the formation of the battery cell. Therefore, it may be desirable or appropriate to be able to achieve a high capacity and high energy density structure of a cylindrical battery cell with the upper cover present.

[0095] Therefore, in one or more embodiments, the cap assembly can be formed to be ultra-thin in the presence of the upper cover to ensure the capacity and energy density of the cylindrical battery cell. Hereinafter, a comparable secondary battery (a) with an upper cover of the related art and a secondary battery (b) according to one or more embodiments will be described by comparison between them.

[0096] Figure 7 and Figure 8 is a comparison of the secondary batteries (in Figure 7 and Figure 8 The left side shows (a)) and a secondary battery according to one or more embodiments (in Figure 7 and Figure 8 The right side of FIG. 1 is a view (b) for thickness comparison therebetween. Figure 7 are cross-sectional views showing a cap assembly of a comparable secondary battery (a) of the related art and a cap assembly of a secondary battery (b) according to one or more embodiments.

[0097] refer to Figure 7 and Figure 8 , the comparable secondary battery (a) of the related art and the secondary battery (b) according to one or more embodiments have the same total height of about 70.00 mm. The total height can be defined as the length from the bottom portion of the cylindrical can to the cover assembly. In the comparable secondary battery (a) of the related art, it can be seen that the bonding thickness t1 between the upper cover and the safety plate is about 2.72 mm, the thickness of the rolled portion is about 0.08 mm, and the height of the internal space of the battery cell is about 67.20 mm. In the secondary battery (b) according to one or more embodiments, it can be seen that the bonding thickness t2 between the upper cover and the safety plate is about 2.20 mm, the thickness of the rolled portion is about 0.10 mm, and the height of the internal space of the battery cell is about 67.70 mm. Therefore, compared with the comparable secondary battery (a) of the related art, the secondary battery (b) according to one or more embodiments can further ensure that the height of the internal space of the battery cell is about 0.52 mm higher.

[0098] In a comparable secondary battery (a) in the related art, the thickness t1 of the crimped portion in the longitudinal direction of the cylindrical can may account for approximately 3.9% of the total height, and the length from the lower end of the crimped portion to the bottom portion of the cylindrical can (the height of the J / R space in the battery cell) may account for approximately 96% of the total height. In a secondary battery (b) according to one or more embodiments, the thickness t2 of the crimped portion in the longitudinal direction of the cylindrical can may account for approximately 3.1% of the total height, and the length from the lower end of the crimped portion to the bottom portion of the cylindrical can may account for approximately 97% of the total height. Therefore, in the secondary battery (b) according to one or more embodiments, it can be seen that, compared with a comparable secondary battery in the related art, the thickness of the crimped portion is reduced by approximately 20%, and the length from the lower end of the crimped portion to the bottom portion of the cylindrical can is increased by approximately 0.7%. However, these figures are based on Figure 7 and Figure 8 One or more embodiments of the present invention, and the percentage may vary according to the size of the secondary battery.

[0099] For example, in a secondary battery (b) according to one or more embodiments, the thickness of the crimping portion may be about 3.1% to about 3.5% of the total height, and the length from the lower end of the crimped portion to the bottom portion of the cylindrical can may be about 96% to about 97% of the total height.

[0100] Therefore, it can be seen that in a secondary battery according to one or more embodiments, compared with another battery having the same total height, as the thickness of the crimping portion decreases, the length from the lower end of the rolled portion to the bottom portion of the cylindrical can (i.e., the internal space of the battery cell) increases.

[0101] As described above, in the secondary battery according to one or more embodiments, as the joint thickness of the cap assembly decreases, the thickness of the rolled portion increases slightly, but the height of the internal space of the battery cell increases to ensure the internal space of the battery cell. Therefore, the reduction in the thickness of the wing portion of the cap assembly can increase the internal space of the battery cell, which in turn can increase the overall size of the electrode assembly, thereby increasing the capacity and increasing the energy density compared to another secondary battery of the same size.

[0102] As is apparent from the above description, in a secondary battery according to one or more embodiments, the peripheral portion of the upper cover can be half-curled in a downward direction toward the safety plate, whereby the total thickness of the cover assembly can be less than the total thickness of a comparable cover assembly in the related art, thereby improving the airtightness of the cover assembly while ensuring a relatively large capacity.

[0103] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those commonly understood by those of ordinary skill in the art to which the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and / or this specification, and should not be interpreted in an idealized or overly formal sense unless explicitly defined as such in this article.

[0104] As used herein, the terms "substantially", "about" and similar terms are used as approximate terms rather than terms of degree, and are intended to illustrate the inherent deviations in measured or calculated values ​​that will be recognized by those of ordinary skill in the art. As used herein, "substantially" includes the stated values ​​and means within the acceptable deviation range of the specific value determined by those of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "substantially" can mean within one or more standard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

[0105] Moreover, any numerical range recorded in this article is intended to include all sub-ranges of the same numerical precision contained in the recorded range. For example, the range of "1.0-10.0" is intended to include all sub-ranges between the recorded minimum value 1.0 and the recorded maximum value 10.0 (and including the recorded minimum value 1.0 and the recorded maximum value 10.0), that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as 2.4-7.6. Any maximum numerical limit recorded in this article is intended to include all lower numerical limits contained therein, and any minimum numerical limit recorded in this specification is intended to include all higher numerical limits contained therein. Accordingly, the applicant reserves the right to modify this specification (including claims) to explicitly record any sub-ranges contained in the range explicitly recorded in this article.

[0106] Furthermore, the use of “may” when describing embodiments of the present disclosure refers to “one or more embodiments of the present disclosure”.

[0107] Although the embodiments of the present disclosure have been described, it should be understood that the present disclosure should not be limited to these embodiments, but one or more appropriate changes and modifications may be made by one of ordinary skill in the art within the spirit and scope of the present disclosure defined by the claims and their equivalents.

Claims

1. A secondary battery comprising: Cylindrical tank; an electrode assembly, contained in the cylindrical can together with an electrolyte; as well as A cover assembly is coupled to the top of the cylindrical tank, the cover assembly comprising: Upper cover, a safety plate coupled to the lower surface of the upper cover, and An insulating gasket wraps the upper cover and the safety plate, the insulating gasket having a gap-filling portion between the upper cover and the safety plate. 2 . The secondary battery according to claim 1 , wherein a width of the gap-filling portion gradually decreases in an upward direction. The secondary battery according to claim 1 , wherein the gap-filling portion has a triangular cross-section. 4 . The secondary battery according to claim 1 , wherein the gap-filling portion has a ring shape in a plan view of the gap-filling portion. 5 . The secondary battery according to claim 1 , wherein the gap-filling portion is formed by melting a portion of the insulating gasket. 6 . The secondary battery according to claim 1 , wherein the gap-filling portion is formed by melting a portion of the insulating gasket at a temperature of 250° C. to 280° C. 7 . The secondary battery according to claim 1 , wherein the insulating gasket is made of a thermoplastic material.

8. The secondary battery according to claim 1, wherein the insulating gasket is made of a polymer selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, perfluoroalkoxyalkane, cross-linked polyethylene, cross-linked polypropylene, cross-linked polyethylene terephthalate, cross-linked polybutylene terephthalate, and cross-linked perfluoroalkoxyalkane.

9. The secondary battery according to claim 1, wherein The insulating pad comprises: a pad bottom flat portion at a lower surface of the peripheral portion of the safety plate; a gasket bent portion, bent upward from the gasket bottom flat portion, the gasket bent portion surrounding the side surface of the upper cover; as well as a gasket top flat portion, bent from the gasket bent portion in a direction toward the upper surface of the upper cover, the gasket top flat portion surrounding the upper surface of the peripheral portion of the upper cover, and The gap-filling portion is on the pad bottom flat portion.

10. The secondary battery according to claim 1, wherein the cap assembly further comprises: a lower cover coupled to the safety plate, A lower surface of a central portion of the safety plate and an upper surface of a central portion of the lower cover are in contact with each other, and The insulating gasket includes a gasket extension portion extending between the safety plate and the lower cover.

11. The secondary battery according to claim 1, wherein the cap assembly further comprises: a lower cover coupled to the safety plate, and a connecting ring between the safety plate and the lower cover, and A lower surface of a central portion of the safety plate and an upper surface of a central portion of the lower cover contact each other.

12. The secondary battery according to claim 1, wherein the upper cover comprises: A flat portion around the upper cover; and The upper cover peripheral bent portion is bent downward from the upper cover peripheral flat portion.

13. The secondary battery according to claim 12, wherein The safety plate includes a safety plate peripheral flat portion, and A portion of the outer surface of the flat peripheral portion of the safety plate contacts a portion of the inner surface of the bent peripheral portion of the upper cover.

14. A secondary battery according to claim 13, wherein the gap filling portion is between the remaining portion of the inner surface of the peripheral bent portion of the upper cover and another portion of the outer surface of the peripheral flat portion of the safety plate, and the remaining portion does not include the portion of the inner surface of the peripheral bent portion of the upper cover that is in contact with the portion of the outer surface of the peripheral flat portion of the safety plate.

15. A secondary battery according to claim 13, wherein another portion of the outer surface of the flat portion around the safety plate is separated from the remaining portion of the inner surface of the bent portion around the upper cover, and the remaining portion does not include the portion of the inner surface of the bent portion around the upper cover that is in contact with the portion of the outer surface of the flat portion around the safety plate. 16 . The secondary battery according to claim 15 , wherein a distance between the other portion of the outer surface of the safety plate peripheral flat portion and the remaining portion of the inner surface of the upper cover peripheral bent portion gradually increases in the downward direction. 17 . The secondary battery according to claim 13 , wherein the inner surface of the upper cover peripheral bent portion contacts the portion of the outer surface of the safety plate peripheral flat portion in a state of being inclined downward.

18. The secondary battery according to claim 13, wherein the safety plate further comprises: An upper bent portion, bent in an upward direction from an inner portion of the peripheral flat portion of the safety plate; a lower bending portion connected to the upper bending portion, the lower bending portion being bent in the downward direction; An inner flat portion connected to the lower bent portion, the inner flat portion being lower than the peripheral flat portion of the safety plate; as well as A notch is in the lower surface of the upper bent portion.

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