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 the top of the cylindrical can, the cap assembly including an upper cap including a peripheral flat portion and an upper cap peripheral bent portion bent upward in a downward direction from the upper cap peripheral flat portion, and a safety plate, and the safety plate is connected to the upper cover peripheral flat part and the upper cover peripheral bent part.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0106092 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 battery cell capacity and energy density of a cylindrical secondary battery 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 configured such that a peripheral portion of an upper cover is half-curled in a downward direction toward a safety plate, whereby a total thickness of the cover assembly is still less than that of a comparable cover assembly in the related art, thereby 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] According to one or more embodiments, a secondary battery includes: a cylindrical can; an electrode assembly, which is contained in (e.g., received in) the cylindrical can together with an electrolyte; and a cover assembly, which is connected to the top of the cylindrical can, the cover assembly including an upper cover and a safety plate, the upper cover including 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, and the safety plate is connected to the upper cover peripheral flat portion and the upper cover peripheral bent portion.

[0014] In one or more embodiments, the upper cover may further include a terminal flat portion at a central portion of the upper cover protruding in an upward direction and a bridging portion bent from a peripheral flat portion of the upper cover to the terminal flat portion in the upward direction, the bridging portion connecting the peripheral flat portion of the upper cover and the terminal flat portion to each other (for example, being configured to connect the peripheral flat portion of the upper cover and the terminal flat portion to each other), and the bridging portion has at least one opening.

[0015] In one or more embodiments, the safety plate may include a safety plate peripheral flat portion, and an outer surface of the safety plate peripheral flat portion may at least partially contact an inner surface of the upper cover peripheral bent portion.

[0016] In one or more embodiments, the safety plate may include a safety plate peripheral flat portion, and an outer surface of the safety plate peripheral flat portion may be in contact with the entire inner surface of the upper cover peripheral bent portion.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] In one or more embodiments, the upper cover peripheral bent portion may be bent from the upper cover peripheral flat portion toward the outer surface of the safety plate at an angle of 60 degrees (°) to 90 degrees (°).

[0022] In one or more embodiments, the safety plate may further include: an upper bending portion, bent in an upward direction from an inner portion of a 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 bending portion, the inner flat portion being lower than the peripheral flat portion of the safety plate; and a recess in the lower surface of the upper bending portion.

[0023] In one or more embodiments, the welding area may be between the upper cover peripheral flat portion and the safety plate peripheral flat portion.

[0024] In one or more embodiments, the welding area may pass through the lower surface of the peripheral flat portion of the safety plate.

[0025] In one or more embodiments, the welding region may be a line (eg, formed in or as a line) (eg, may have a shape of a line).

[0026] In one or more embodiments, the cover assembly may further include an insulating gasket between the peripheral portions of the upper cover and the safety plate and the cylindrical can, the insulating gasket surrounding (e.g., configured to surround) the peripheral flat portion of the upper cover, the peripheral bent portion of the upper cover, and the peripheral flat portion of the safety plate.

[0027] In one or more embodiments, the cover assembly may further include a connecting ring coupled to the bottom of the peripheral flat portion of the safety plate and a lower cover coupled to the bottom of the connecting ring, the lower cover electrically connecting the electrode plate of the electrode assembly and the safety plate to each other.

[0028] In one or more embodiments, the cylindrical can may include a bottom portion, a side portion extending in an upward direction from the bottom portion, a rolled portion at an upper portion of the side portion and recessed inwardly at the cover assembly, and a crimped portion at an upper portion of the rolled portion and bent toward the interior of the cylindrical can.

[0029] In one or more embodiments, the thickness of the crimping portion may be 3.1% to 3.5% of the total height from the bottom portion of the cylindrical can to the cap assembly.

[0030] In one or more embodiments, the length from the lower end of the rolled portion to the bottom portion of the cylindrical can may be 96% to 97% of the total height from the bottom portion of the cylindrical can to the cap assembly. 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 a relationship between a cylindrical can and a cap assembly of a secondary battery according to one or more embodiments of the present disclosure;

[0036] Figure 5 and Figure 6 Each is a cross-sectional view showing a contact structure between a peripheral bent portion of an upper cover and a peripheral flat portion of a safety plate;

[0037] Figure 7 are 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

[0038] Figure 8 Schematic diagrams of a comparable secondary battery in the related art (a) and a secondary battery according to one or more embodiments of the present disclosure (b) for thickness comparison therebetween. DETAILED DESCRIPTION

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] As used herein, the terms "use" and "used" may be considered synonymous with the terms "utilize" and "utilized," respectively.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] Figure 1 , Figure 2 and Figure 3 are 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 a relationship between a cylindrical can and a cap assembly of a secondary battery according to one or more embodiments of the present disclosure, and Figure 5 and Figure 6 2 is a cross-sectional view showing a contact structure between a peripheral bent portion of an upper cover and a peripheral flat portion of a safety plate.

[0049] 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 .

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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. The negative electrode plate 210 may include at least one negative electrode tab 240 that protrudes downward and extends a set or predetermined length, and the positive electrode plate 220 may include at least one positive electrode tab 250 that protrudes upward and extends 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 and extend upward from the electrode assembly 200, and the positive electrode tab 250 may protrude and extend downward from the electrode assembly 200. 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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 .

[0062] The upper cover peripheral flat portion 411 corresponds to a peripheral portion of the upper cover 410 and may have a flat structure.

[0063] The upper cover peripheral bent portion 412 may be bent downward from the upper cover peripheral flat portion 411 (eg, at the outer periphery of the upper cover 410) to wrap the outer surface of the safety plate 420 coupled to the bottom thereof. Figure 5As shown in FIG. 4 , the inner surface 412a of the upper cover peripheral bent portion 412 may contact (eg, be press-fitted to) 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.

[0064] The upper cover peripheral bent portion 412 may be bent from the upper cover peripheral flat portion 411 toward the outer surface 421 a of the safety plate peripheral flat portion 421 at an angle of about 60 degrees (°) to 90 degrees (°).

[0065] If the upper cover peripheral bending portion 412 is bent at an angle of 90 degrees (°), as shown in FIG. Figure 5 As shown in FIG. 4 , 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 be in contact with each other (eg, in close contact).

[0066] If the upper cover peripheral bending portion 412 is bent at an angle less than 90 degrees (°) (60°≤θ<90°), as Figure 6 As shown in part A of the upper cover peripheral bent portion 412, a portion of the inner surface 412a of the upper cover peripheral bent portion 412 and a portion of the outer surface 421a of the safety plate peripheral flat portion 421 may contact each other. The inner surface 412a of the upper cover peripheral bent 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 apart and / or separated (e.g., spaced apart 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 contact at the top but be separated in the middle, and the distance therebetween gradually increases toward the bottom, thereby producing a cross-section in the shape of a roughly right triangle.

[0068] The upper cover 410 may be formed in a dome shape, and a central portion of the upper cover 410 protrudes upward. The terminal flat portion 413 may be at a central portion of the upper cover 410 protruding in an upward direction. 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 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.

[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 pass through the lower surface of 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 the shape of a line). 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 connection ring 430 may be interposed between the security plate 420 and the lower cover 450. The connection ring 430 may be interposed between the lower surface of the security plate peripheral flat portion 421 and the upper surface of the peripheral portion of the lower cover 450. The connection ring 430 may be made of a resin such as polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET).

[0079] 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, so as 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 periphery of the upper cap 410 and the safety plate 420 and the upper end opening of the cylindrical can 100 in a tightly fitting manner. 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. The crimping portion 140 may be bent at an upper portion of the crimping portion 130 toward the inside of the cylindrical can 100 .

[0080] The insulating gasket 440 may be made of a resin such as 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.

[0081] The lower cover 450 may be coupled to the safety plate 420. The lower cover 450 may be formed as a circular plate. An exhaust hole 451 may be formed at one side of the lower cover 450, and the exhaust hole 451 may be used to exhaust internal gas in the event of excessive pressure generated in the cylindrical can 100. The inner flat portion 425 of the safety plate 420 may be raised by the gas exhausted through the exhaust 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. The lower cover 450 may electrically connect the positive electrode plate 220 of the electrode assembly 200 and the safety plate 420 to each other.

[0082] For example, Figure 7 As 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.

[0083] 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-layer 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 D of about 0.8 mm.

[0084] 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.

[0085] 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.

[0086] Figure 7 and Figure 8 is a diagram showing a comparable secondary battery in the related art (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 respectively 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 of the present disclosure.

[0087] 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), it can be seen that the joining 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 joining 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.

[0088] 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.

[0089] For example, in a secondary battery (b) according to one or more embodiments, the thickness of the crimped 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.

[0090] 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.

[0091] 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 (e.g., substantially not), 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.

[0092] As is apparent from the above description, in a secondary battery according to one or more embodiments of the present disclosure, 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 smaller than the total thickness of a comparable cover assembly in the related art, thereby ensuring a relatively large capacity.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] Furthermore, the use of “may” when describing embodiments of the present disclosure refers to “one or more embodiments of the present disclosure”.

[0097] 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: The upper cover comprises a flat portion at the periphery of the upper cover and a bent portion at the periphery of the upper cover bent in a downward direction from the flat portion at the periphery of the upper cover; and The safety plate is connected to the flat portion of the upper cover periphery and the bent portion of the upper cover periphery.

2. The secondary battery according to claim 1, wherein the upper cover further comprises: a terminal flat portion at a central portion of the upper cover that protrudes in an upward direction; and A bridge portion is bent in the upward direction from the upper cover peripheral flat portion toward the terminal flat portion, the bridge portion connects the upper cover peripheral flat portion and the terminal flat portion to each other, and the bridge portion has at least one opening.

3. The secondary battery according to claim 1, wherein The security panel includes a security panel perimeter flat portion, and The outer surface of the flat portion of the periphery of the safety plate is in at least partial contact with the inner surface of the bent portion of the periphery of the upper cover.

4. The secondary battery according to claim 1, wherein The security panel includes a security panel perimeter flat portion, and The outer surface of the flat portion of the periphery of the safety plate contacts the entire inner surface of the bent portion of the periphery of the upper cover.

5. The secondary battery according to claim 1, wherein The security panel includes a security panel perimeter 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.

6. A secondary battery according to claim 5, 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. 7 . The secondary battery according to claim 6 , 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. 8 . The secondary battery according to claim 5 , 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. 9 . The secondary battery according to claim 1 , wherein the upper cover peripheral bent portion is bent from the upper cover peripheral flat portion toward the outer surface of the safety plate at an angle of 60 to 90 degrees.

10. The secondary battery according to claim 3, 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. 11 . The secondary battery according to claim 3 , wherein a welding area is between the upper cover peripheral flat portion and the safety plate peripheral flat portion. 12 . The secondary battery according to claim 11 , wherein the welding area passes through a lower surface of a peripheral flat portion of the safety plate. 13 . The secondary battery according to claim 12 , wherein the weld region has a line shape.

14. The secondary battery according to claim 3, wherein the cap assembly further comprises an insulating gasket between the upper cap and the peripheral portions of the safety plate and the cylindrical can, the insulating gasket surrounding the upper cap peripheral flat portion, the upper cap peripheral bent portion and the safety plate peripheral flat portion.

15. The secondary battery according to claim 3, wherein the cap assembly further comprises: A connecting ring connected to the bottom of the flat portion of the periphery of the safety plate; and A lower cover is coupled to a bottom of the connection ring, and the lower cover electrically connects the electrode plate of the electrode assembly and the safety plate to each other.

16. The secondary battery according to claim 1, wherein the cylindrical can comprises: bottom part; a side portion extending in an upward direction from the bottom portion; a rolled portion, recessed inwardly at an upper portion of the side portion and at the cover assembly; as well as A crimping portion is located at an upper portion of the crimping portion and is bent toward the inside of the cylindrical can. 17 . The secondary battery according to claim 16 , wherein a thickness of the crimping portion is 3.1% to 3.5% of a total height from the bottom portion of the cylindrical can to the cap assembly. 18 . The secondary battery according to claim 16 , wherein a length from a lower end of the rolled portion to the bottom portion of the cylindrical can is 96% to 97% of a total height from the bottom portion of the cylindrical can to the cap assembly.

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