Cylindrical secondary battery

Abstract

A cylindrical secondary battery includes: an electrode assembly; a case, the lower end of which is open to accommodate the electrode assembly; and a cover plate coupled to the lower end of the housing, in which the cover plate includes a central region, an edge region, and a connection region connecting the central region and the edge region, an exhaust port being located in at least one of the central region and the connection region, and a region of the cover plate in which the exhaust port is formed has a thickness smaller than that of other regions of the cover plate.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0115069 filed in the Korean Intellectual Property Office on August 31, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] Aspects of some embodiments of the present disclosure relate to cylindrical secondary batteries. Background Art

[0004] Unlike primary batteries that cannot be recharged, secondary batteries are batteries that can be charged and discharged. Low-capacity secondary batteries are used in small portable electronic devices such as smartphones, feature phones, tablet computers, notebook computers, digital cameras, and camcorders, while high-capacity secondary batteries are widely used as batteries for driving motors and storing electricity in hybrid vehicles, electric vehicles, etc.

[0005] Such secondary batteries can be classified into cylindrical, prismatic, pouch-type, etc. depending on their appearance. Among them, a cylindrical secondary battery generally includes an electrode assembly, a can, a cap assembly, etc., and has a structure in which the electrode assembly is inserted into the can to form a crimping portion, the cap assembly is mounted thereon, and a crimping portion is formed and fixed.

[0006] In addition, the cap assembly is formed with a current interrupt device (CID) capable of blocking the current when an abnormality occurs in the secondary battery. For example, during a forced discharge evaluation, the CID of the cap assembly operates to block the current, thereby preventing or reducing the secondary battery from catching fire or exploding. However, in the case of a cylindrical secondary battery without a CID, there is no current blocking function to suppress heat generation. Therefore, there is a need to develop a new secondary battery structure that can meet the forced discharge conditions corresponding to a specific standard.

[0007] The above information disclosed in this Background section is only for enhancement of understanding of the background technology, and therefore the information discussed in this Background section does not necessarily constitute prior art. Summary of the invention

[0008] Aspects of some embodiments of the present disclosure include a cylindrical secondary battery having a relatively improved structure for forced discharge characteristics.

[0009] According to some embodiments of the present disclosure, a cylindrical secondary battery includes: an electrode assembly; a shell, the lower end of which is open to accommodate the electrode assembly; and a cover plate connected to the lower end of the shell, wherein the cover plate includes a central area, an edge area, and a connecting area connecting the central area and the edge area, an exhaust port is located in at least one of the central area and the connecting area, and the area of ​​the cover plate where the exhaust port is formed has a thickness smaller than the thickness of other areas of the cover plate.

[0010] According to some embodiments, the cap plate may be formed in a shape in which the central region is bent toward the electrode assembly compared with the edge region.

[0011] According to some embodiments, the central region and the connection region of the cover plate may be formed concavely toward the interior of the housing compared to the edge region.

[0012] According to some embodiments, the exhaust port may have a recess formed in an inner surface of the cover plate.

[0013] According to some embodiments, the thickness of the cover plate in the region where the exhaust port is formed may be approximately 0.1 to 0.3 times the thickness of a material of the cover plate.

[0014] According to some embodiments, the exhaust port is provided in the central region of the cover plate, and may have a circular ring shape continuously formed along a circumference of the central region of the cover plate.

[0015] According to some embodiments, an inner diameter of the exhaust port may be approximately 0.5 to 1 times a core diameter of the electrode assembly.

[0016] According to some embodiments, the exhaust port may be provided in the central region and the connection region of the cover plate, and may have a cross shape extending from the center of the cover plate toward the connection region.

[0017] According to some embodiments, a length of each of a horizontal line and a vertical line of the exhaust port may be approximately 0.5 to 5.5 times the core diameter of the electrode assembly.

[0018] According to some embodiments, the exhaust port may be provided in the connection region, and may have at least one liner-shaped exhaust port extending from the central region.

[0019] According to some embodiments, the exhaust port is composed of a plurality of linear-shaped exhaust ports, and the linear-shaped exhaust ports may be formed to be spaced apart from each other based on the central area.

[0020] According to some embodiments, the exhaust port is composed of a plurality of exhaust ports in a linear shape, and lengths of the plurality of exhaust ports in a linear shape may be formed to be different from each other.

[0021] According to some embodiments, the length of a relatively long linear shaped exhaust port among the multiple linear shaped exhaust ports may be approximately 1 to 10 times the length of a relatively short linear shaped exhaust port among the multiple linear shaped exhaust ports, and the length of the relatively short linear shaped exhaust port among the multiple linear shaped exhaust ports may be approximately 0.1 to 1 times the length of the relatively long linear shaped exhaust port among the multiple linear shaped exhaust ports.

[0022] According to some embodiments, the exhaust port is composed of a plurality of linear-shaped exhaust ports, and thicknesses of the cover plate in regions where the plurality of linear-shaped exhaust ports are formed are formed to be different from each other.

[0023] According to some embodiments, the exhaust port may be formed so that a thickness of the cover plate in an area where relatively short linear-shaped exhaust ports among the plurality of linear-shaped exhaust ports are formed is greater than a thickness of the cover plate in an area where relatively long linear-shaped exhaust ports among the plurality of linear-shaped exhaust ports are formed.

[0024] According to some embodiments, the exhaust port may consist of 1 to 4 exhaust ports in a linear shape.

[0025] According to some embodiments, the exhaust port may be provided in the central region and the connection region of the cover plate, and may have a spiral shape or a pinwheel shape extending from the central region.

[0026] According to some embodiments, the exhaust port may extend from a start point in the central region to an end point in the connection region, and may have a spiral shape with an increasing radius of the spiral line.

[0027] According to some embodiments, the thickness of the cover plate in the region where the exhaust port is formed may increase in a tapered shape from the start point to the end point.

[0028] According to some embodiments, the exhaust port may have the pinwheel shape in which a plurality of arcs having a constant radius are arranged at equal intervals based on the center of the cover plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a perspective view illustrating a cylindrical secondary battery according to some embodiments of the present disclosure.

[0030] Figure 2is an example in the vertical direction according to some embodiments of the present disclosure Figure 1 Cross-sectional view of a cylindrical secondary battery in FIG.

[0031] Figure 3 is an example of some embodiments according to the present disclosure Figure 2 A longitudinal cross-sectional view of the cover portion in FIG.

[0032] Figure 4 is an example of some embodiments according to the present disclosure Figure 1 A plan view of an example of a cover plate of a cylindrical secondary battery.

[0033] Figure 5 is an example of some embodiments according to the present disclosure Figure 1 A plan view of another example of a cover plate of a cylindrical secondary battery.

[0034] Figure 6 is a cross-sectional view illustrating an example of a cover plate according to some embodiments of the present disclosure, for comparison Figure 5 The thickness of the cap plate in the cylindrical secondary battery in FIG. 1 in a region where the notch is formed, the notch having a cross section taken along line AA′.

[0035] Figures 7 to 9 is an example of some embodiments according to the present disclosure Figure 1 1 is a plan view of another example of a cover plate in a cylindrical secondary battery. DETAILED DESCRIPTION

[0036] The aspects of some embodiments of the present disclosure are illustrated and described to more completely illustrate the aspects of some embodiments of the present disclosure to those skilled in the art, and the following embodiments may be modified into various other forms, and the scope of the present invention is not limited to the following embodiments. On the contrary, these embodiments are provided so that the present disclosure will be comprehensive and complete, and the spirit of the present disclosure will be conveyed to those skilled in the art.

[0037] In addition, in the accompanying drawings, the size (e.g., thickness) of each component is exaggerated for brevity and clarity. The same reference numerals always refer to the same elements. As used herein, the term "and / or" includes any and all combinations of one or more related listed items. In addition, it will be understood that when element A is referred to as being "connected to" element B, element A may be directly connected to element B or an intervening element C may be present therebetween so that element A and element B are indirectly connected to each other.

[0038] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, the singular form is intended to also include the plural form, unless the context clearly states otherwise. It will be further understood that when used in this specification, the terms "include" and / or "comprise" specify the presence of the features, numbers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, elements, parts and / or combinations thereof.

[0039] Although the terms "first", "second", etc. are used herein to describe various components, elements, regions, layers and / or sections, it is clear that these components, elements, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one component, element, region, layer and / or section from another component, element, region, layer and / or section. Thus, for example, the first component, first element, first region, first layer and / or first section discussed below can be referred to as the second component, second element, second region, second layer and / or second section without departing from the teachings of the present disclosure.

[0040] Spatially relative terms such as "under", "below", "below", "above", and "on" are used herein to facilitate understanding of the relationship between one element or feature and another element or feature shown in the drawings. These spatially relative terms are provided to facilitate understanding of the present disclosure according to various process states or use states of the present disclosure, and are not intended to limit the present disclosure. For example, when a first element or feature in a drawing is turned over, the first element described as "below" or "below" a second element or feature will then be "on" or "above" the second element or feature. Therefore, the term "under" may cover both "above" and "below".

[0041] Hereinafter, aspects of the cylindrical secondary battery 100 will be described in more detail with reference to the accompanying drawings.

[0042] Figure 1 is a perspective view illustrating a cylindrical secondary battery 100 according to some embodiments of the present disclosure. Figure 2 is illustrated in the vertical direction Figure 1 sectional view of a cylindrical secondary battery 100 in FIG.

[0043] like Figure 1 and Figure 2 As shown in , a cylindrical secondary battery 100 according to some embodiments of the present disclosure may include a shell 110, an electrode assembly 120 accommodated in the shell 110, a terminal 150 connected to a terminal hole provided in one end of the shell 110, and a cap plate 160 for sealing or closing an opening in the other end of the shell 110.

[0044] The housing 110 includes a circular upper surface portion 111 and a side surface portion 112 extending downwardly from the edge of the upper surface portion 111. The upper surface portion 111 and the side surface portion 112 of the housing 110 may be formed integrally. In addition, a bent portion 111a bent into an arc shape may be further included between the upper surface portion 111 and the side surface portion 112.

[0045] The circular upper surface portion 111 has a flat circular plate shape, and the central portion 113 may protrude away from the electrode assembly 120 in an outward direction. The central portion 113 may be located at the center of the upper surface portion 111, and may be located at the outer side of the housing 110 compared to the upper surface portion 111, so that a step may be formed between the central portion 113 and the upper surface portion 111. A connecting portion 113a connecting the outer edge of the central portion 113 and the inner edge of the upper surface portion 111 may be further included. Due to the step formed between the central portion 113 and the upper surface portion 111, the connecting portion 113a may be provided to be inclined. Here, when the planar shape of the central portion 113 is circular, the connecting portion 113a may connect the central portion 113 and the upper surface portion 111 in a circular ring shape.

[0046] The central portion 113 may have a terminal hole 113b substantially passing through the center thereof. The terminal 150 may be inserted into the terminal hole 113b coupled to the central portion 113. The terminal hole 113b may have a circular shape, but is not limited thereto.

[0047] In addition, the planar shape of the fastening portion 152 of the terminal 150 may correspond to the shape of the terminal hole 113b. That is, when the terminal hole 113b is circular, the fastening portion 152 of the terminal 150 may have a cylindrical shape. Therefore, when the terminal hole 113b is circular, no separate corner is provided, and therefore the terminal hole 113b can be fastened and coupled to the terminal 150 regardless of the angle.

[0048] The first gasket 116 for sealing and electrical insulation may be further interposed between the terminal hole 113b and the terminal 150. Therefore, according to some embodiments, the flat outer diameter of the fastening portion 152 of the terminal 150 may be smaller than the flat outer diameter of the terminal hole 113b. The first gasket 116 prevents the terminal 150 from contacting the housing 110, so that the housing 110 and the terminal 150 are electrically separated. The first gasket 116 may seal the terminal hole 113b of the central portion 113 of the housing 110. The first gasket 116 may be made of a resin material such as polyethylene (PE), polypropylene (PP) or polyethylene terephthalate (PET).

[0049] In addition, the case 110 may further include an inner insulating member 117 provided to cover the inner surface of the central portion 113. Here, the inner insulating member 117 may be attached to the inner surface of the central portion 113 by a coating or an adhesive. Here, the inner surface of the central portion 113 is a surface facing the upper surface of the first current collector 130 between the case 110 and the electrode assembly 120, and may be the lower surface of the central portion 113. The inner insulating member 117 may prevent or reduce contact between the central portion 113 of the case 110 and the first electrode plate 121 of the electrode assembly 120. For example, the inner insulating member 117 may prevent or reduce contact between the case 110 and the first current collector 130.

[0050] In the case 110, the central portion 113 protrudes in the outward direction, thereby reducing the separation distance between the upper surface portion 111 and the first current collector 130, which reduces the loss of the internal space of the case 110. That is, because the case 110 can reduce the separation distance between the upper surface portion 111 and the first current collector 130, it may be desirable that the inner insulating member 117 covers the inner surface of the upper surface portion 111 or covers the inner surface of the upper surface portion 111 and the bent portion 111b, rather than the inner insulating member 117 being located only inside the central portion 113.

[0051] Meanwhile, the lower portion of the housing 110 of the cylindrical secondary battery 100 is open during the manufacturing process. Accordingly, during the manufacturing process of the cylindrical secondary battery 100, the electrode assembly 120 may be placed into the housing 110 through the open lower portion of the housing 110 together with the electrolyte. In this case, the electrolyte and the electrode assembly 120 may be placed into the housing 110 when the open lower portion faces upward. In the housing 110, after the electrolyte and the electrode assembly 120 are placed, the cap plate 160 is coupled to the open lower portion to seal the interior of the housing 110. Here, the electrolyte is used to allow lithium ions to move between the first electrode plate 121 and the second electrode plate 122 constituting the electrode assembly 120. Such an electrolyte may be a non-aqueous organic electrolyte that is a mixture of a lithium salt and a high-purity organic solvent. In addition, the electrolyte may be a polymer electrolyte or a solid electrolyte using a polymer, and the type of the electrolyte is not limited thereto.

[0052] The housing 110 may be made of steel, steel alloy, aluminum, aluminum alloy or equivalent thereof, but the material is not limited thereto. In addition, in the housing 110, an inwardly concave crimping portion 114 is formed in an upper portion centered on the cap plate 160 to prevent or reduce the electrode assembly 120 from being separated to the outside, and an inwardly bent crimping portion 115 may be formed below the crimping portion 114.

[0053] After the electrode assembly 120 is inserted into the case 110 through the opened lower portion, the crimping portion 114 is formed to prevent or reduce separation between the electrode assembly 120 and the case 110 .

[0054] The electrode assembly 120 includes a first electrode plate 121, a second electrode plate 122, and a separator 123. The first electrode plate 121 may be a positive electrode plate, and the second electrode plate 122 may be a negative electrode plate. Of course, the opposite is also possible. Hereinafter, for ease of explanation, the case where the first electrode plate 121 is a positive electrode plate and the second electrode plate 122 is a negative electrode plate will be described.

[0055] The first electrode plate 121 is a plate-shaped metal foil made of aluminum (Al), at least one side of which is coated with a positive electrode active material made of a transition metal oxide. In addition, the first electrode plate 121 may be provided with a positive electrode uncoated portion at its upper end portion that is not coated with a positive electrode active material. The positive electrode uncoated portion may protrude upward from the electrode assembly 120. That is, the positive electrode uncoated portion of the first electrode plate 121 may protrude further upward than the second electrode plate 122 and the separator 123.

[0056] The second electrode plate 122 is a plate-shaped metal foil made of copper (Cu) or nickel (Ni), at least one side of which is coated with a negative electrode active material (such as graphite or carbon). In addition, the second electrode plate 122 may have a negative electrode uncoated portion at its lower end portion that is not coated with a negative electrode active material. The negative electrode uncoated portion may protrude downward from the electrode assembly 120. That is, compared with the first electrode plate 121 and the separator 123, the negative electrode uncoated portion of the second electrode plate 122 may protrude further downward.

[0057] The separator 123 may be polyethylene (PE) or polypropylene (PP), but is not limited thereto according to the embodiment of the present disclosure. The separator prevents or reduces an electrical short circuit between the first electrode plate 121 and the second electrode plate 122 and may allow only movement of lithium ions.

[0058] After stacking the first electrode plate 121, the second electrode plate 122 and the separator 123, the electrode assembly 120 is wound from the winding start end and is wound into a substantially cylindrical shape. In addition, in the electrode assembly 120, the uncoated portion of the positive electrode not coated with the positive electrode active material may protrude upward from the first electrode plate 121, and the uncoated portion of the negative electrode not coated with the negative electrode active material may protrude downward from the second electrode plate 122. In addition, in the electrode assembly 120, the outermost portion of the uncoated portion of the positive electrode may not protrude upward, and the outermost portion of the uncoated portion of the negative electrode may not protrude downward. That is, the electrode assembly 120 may be provided with a concave step at the outermost portion of the upper and lower portions compared to other regions. In the electrode assembly 120, when the inner insulating member 117 is not formed in the bent portion 111b of the shell 110, the contact between the electrode assembly 120 and the shell 110 can be prevented or reduced.

[0059] The first current collector 130 may be a circular metal plate having a shape corresponding to the upper surface of the electrode assembly 120. The planar size of the first current collector 130 may be less than or equal to the size of the upper surface of the electrode assembly 120. The first current collector 130 may be made of aluminum (Al). The first current collector 130 may be fixed and electrically connected to the first electrode plate 121 exposed upward at the electrode assembly 120 by welding while its lower surface is in contact with the upper surface of the electrode assembly 120. The first current collector 130 may be fixed and electrically connected to the terminal 150 by welding while its upper surface is in contact with the lower surface of the terminal 150. The first current collector 130 may be a path for current flow between the first electrode plate 121 of the electrode assembly 120 and the terminal 150. The first current collector 130 may be welded to the electrode assembly 120, housed in the housing 110, and then welded to the terminal 150.

[0060] The second current collector 140 may have a circular shape corresponding to the lower surface of the electrode assembly 120. The upper surface of the second current collector 140 may be in contact with the lower surface of the electrode assembly 120. The second current collector 140 is fixed and electrically connected to the second electrode plate 122 exposed downward at the electrode assembly 120 by welding while its upper surface is in contact with the lower surface of the electrode assembly 120. In addition, the second current collector 140 may be in contact with the inner surface of the crimping portion 114 and coupled to the inner surface of the crimping portion 114. Here, the inner surface may be the inner surface of the housing 110. The second current collector 140b may be a path for current flow between the second electrode plate 122 of the electrode assembly 120 and the housing 110. That is, the housing 110 may be a negative terminal. In addition, the second current collector 140 may be provided at its center with a through hole 141 passing between the upper surface and the lower surface, and the electrolyte may be easily injected into the electrode assembly 120 through the through hole 141. According to some embodiments, a size (diameter) of the through hole 141 may correspond to a core diameter of the electrode assembly 120 .

[0061] The terminal 150 may be inserted into the terminal hole 113b of the housing 110 and electrically connected to the first current collector 130. The terminal 150 may be electrically connected to the first electrode plate 121 of the electrode assembly through the first current collector 130. That is, the terminal 150 may be a positive terminal. The terminal 150 and the housing 110 may have different polarities. The terminal 150 may be formed of a material that is the same as or similar to that of each of the first current collector 130 and the first electrode plate 121.

[0062] The terminal 150 may include a head 151 exposed upward at the housing 110 and a fastening portion 152 extending from the center of the head 151 to the inside of the housing 110. The planar size of the head 151 may be larger than the planar size of the fastening portion 152. That is, the diameter of the head 151 may be larger than the diameter of the fastening portion 152. The upper end of the fastening portion 152 of the terminal 150 may be connected to the lower surface of the head 151, and the head 151 and the fastening portion 152 may be formed integrally. The terminal 150 may be coupled to the terminal hole 113b of the housing 110 in a direction from the outside to the inside. In this case, the first pad 116 may be between the terminal 150 and the housing 110.

[0063] The terminal 150 may be inserted into the terminal hole 113b of the housing 110 in the direction from the outside to the inside and then fixed. In this case, the terminal 150 may be fixed by a coupling portion made of an insulating material, but is not limited thereto. In addition, the lower surface of the fastening portion 152 may be in contact with the upper surface of the first current collector 130 and coupled to the upper surface of the first current collector 130 by welding. The fastening portion 152 may further protrude downward compared to the lower surface of the central portion 113 of the housing 110. In addition, since the upper surface of the first current collector 130 is coupled to the lower surface of the terminal 150 (which is the lower surface of the fastening portion 152), the fastening portion 152 may be interposed between the central portion 113 and the first current collector 130.

[0064] The first gasket 116 is interposed between the fastening portion 152 and the terminal hole 113b of the housing 110, and its upper end portion may extend between the head 151 and the central portion 113 of the housing 110. In this case, the upper end portion of the first gasket 116 may extend beyond the head 151. That is, the first gasket 116 is interposed between the lower surface of the head of the terminal 150 and the upper surface of the central portion 113 of the housing 110 and between the fastening portion 152 of the terminal 150 and the terminal hole 113b of the housing 110, thereby electrically insulating and sealing between the terminal 150 and the housing 110. The first gasket 116 is shown as an integral structure, but the component between the lower surface of the head of the terminal 150 and the upper surface of the central portion 113 of the housing 110 and the component between the fastening portion 152 of the terminal 150 and the terminal hole 113b of the housing 110 may be a separate component. The first gasket 116 may contact the upper and lower surfaces of the central portion 113 of the housing 110. The first gasket 116 may be in contact with the inner insulation member 117 .

[0065] The cap plate 160 may be a circular metal plate and is coupled to the lower end portion of the housing 110. The lower surface of the cap plate 160 may be exposed to the outside. The cap plate 160 is coupled to the lower end portion of the housing 110 with the second gasket 118 interposed therebetween, thereby preventing or reducing the situation where the cap plate 160 is electrically connected to the housing 110. Since the cap plate 160 is not electrically connected to the positive electrode or the negative electrode of the electrode assembly 120, it may not have a separate electrical polarity.

[0066] The edge area 162 of the cover plate 160 can be fixedly located between the crimping portion 114 and the crimping portion 115 of the shell 110. In more detail, the cover plate 160 can be installed below the crimping portion 114 in a state where the second gasket 118 is located below the crimping portion 114 of the shell 110. Thereafter, the crimping portion 115 of the shell 110 is bent in the inward direction of the cover plate 160 and presses the second gasket 118 to connect the cover plate 160 and the shell 110. The second gasket 118 can be made of a resin material such as polyethylene (PE), polypropylene (PP) or polyethylene terephthalate (PET). The second gasket 118 can squeeze and seal the space between the shell 110 and the cover plate 160, and can prevent or reduce the situation where the cover plate 160 is separated from the shell 110. The upper portion of the second gasket 118 may be interposed between the crimping portion 114 and the cover plate 160, and the lower portion may be interposed between the crimping portion 115 and the cover plate 160. The lower end portion of the second gasket 118 may protrude more toward the center of the cover plate 160 than the crimping portion 115.

[0067] The cap plate 160 may include a central region 161 located below the through hole 141 of the second current collector 140 and an edge region 162 interposed between the crimping portion 114 and the crimping portion 115 of the case 110 and coupled to the case 110. In addition, the central region 161 of the cap plate 160 may be in contact with the second current collector 140, or connected to the second current collector 140. That is, the upper surface of the cap plate 160 may be in contact with the lower surface of the second current collector 140. Accordingly, the cap plate 160 may be formed such that the central region 161 is bent toward the electrode assembly 120 compared to the edge region 162. In addition, the cap plate 160 may further include a connection region 163 connecting the central region 161 and the edge region 162. According to some embodiments, the central region 161 and the connection region 163 may be recessed toward the inside of the case 110 compared to the edge region 162. That is, the edge region 162 of the cap plate 160 may protrude more outward from the case 110 than the central region 161 and the connection region 163. In addition, the connection region 163 and the edge region 162 may be connected to be inclined due to a step.

[0068] The cover plate 160 is provided with an exhaust port 165 that opens at a set pressure. The exhaust port 165 may be provided in the central area 161 or the connection area 163 of the cover plate 160. In addition, the exhaust port 165 may be provided in both the central area 161 and the connection area 163. The area of ​​the cover plate 160 where the exhaust port 165 is formed may be thinner than other areas of the cover plate 160. The exhaust port 165 may be (or have) a notch formed in a direction from the top to the bottom of the cover plate 160. That is, the exhaust port 165 is formed in the inner surface of the cover plate 160, and the notch is not visible from the outside.

[0069] That is, when excessive internal pressure occurs inside the housing 110 of the cylindrical secondary battery 100, the vent 165 ruptures, thereby enabling the excessive internal pressure to be released. The vent 165 of the cap plate 160 may be spaced apart from the center of the cap plate 160 and formed to have an annular shape in a plan view. As another example, the vent 165 may have at least one pattern having a linear or curved shape in a plan view. In the region where the vent 165 is formed, the thickness of the cap plate 160 may be less than the thickness of other regions of the cap plate 160.

[0070] In the region where the vent 165 is formed, the thickness of the cap plate 160 may be about 0.1 to 0.3 times the thickness of the material of the cap plate 160. In this case, the battery cell rupture pressure may range from about 17 to 35 kgf / cm 2 . When the thickness of the cap plate 160 in the area where the vent 165 is formed is about 0.1 times or more of the material thickness of the cap plate 160, the cap plate 160 can be easily subjected to a cutting process or a pressing process. In addition, when the thickness of the cap plate 160 in the area where the vent 165 is formed is less than about 0.1 times of the material thickness of the cap plate 160, deformation or cracks may occur even when the internal pressure of the cylindrical secondary battery 100 does not increase. In addition, when the thickness of the cap plate 160 in the area where the vent 165 is formed exceeds about 0.3 times of the material thickness of the cap plate 160, even when the internal pressure of the cylindrical secondary battery 100 increases, the vent 165 may not rupture and may not be used as a vent. In addition, when the thickness of the cap plate 160 in the area where the vent 165 is formed is about 0.3 times or less of the material thickness of the cap plate 160, the cap plate 160 may rupture at a desired rupture pressure.

[0071] At the same time, the cylindrical secondary battery 100 should be tested according to standard specifications to minimize or reduce the risks that may occur during air transport, land transport or ship transport. The test may include tests for altitude, thermal shock, vibration, impact, external short circuit, compression / collision, forced discharge and overcharge. Among these, in the forced discharge test, an external power supply can be connected to a fully discharged battery to cause overdischarge and induce polarity reversal of the battery. In this case, the voltage drops below 0V and becomes negative. That is, the battery is damaged, no longer provides voltage, and acts as a resistor, resulting in a voltage drop. This may cause the battery to heat up and cause a fire or spark. The forced discharge test verifies the safety of the battery design under the limitation of the appropriate discharge current specification. When the current limit is too high, the increase in heat generated may cause the battery to overheat and ultimately cause thermal runaway (fire and / or explosion).

[0072] However, the cylindrical secondary battery 100 without a CID does not have a heat reduction function using a cutoff device, and when the battery cell size (total area or diameter) is large, the heat cannot be dissipated. In addition, when the cylindrical secondary battery 100 has a large core size (diameter), a failure (NG) may occur due to core deformation during exhaust.

[0073] That is, since fire may occur during the forced discharge evaluation, the cylindrical secondary battery 100 should be formed into a structure capable of suppressing heat generation and preventing or reducing fire. Therefore, the cylindrical secondary battery 100 may be formed into a structure capable of reducing internal short circuits by exhaust delay and peaceful exhaust under evaluation conditions capable of minimizing or reducing applied current. Peaceful exhaust may mean a gradual decrease in pressure.

[0074] In the following, reference will be made to Figure 3 and Figure 4 Structures for minimizing or reducing internal deformation during exhaust are described in greater detail, as well as exhaust port shapes formed to reduce the size of the exhaust ports compared to alternative exhaust ports to delay exhaust and make exhaust smoother.

[0075] Figure 3 is an example Figure 2 A longitudinal cross-sectional view of the cover plate portion in FIG. Figure 4 is an example Figure 1 A plan view of an example of a cover plate in a cylindrical secondary battery.

[0076] like Figure 3 As shown in , the cylindrical secondary battery 100 is designed to have a core diameter a of the electrode assembly 120 that is smaller than the core diameter of an alternative system, so that internal deformation during exhaust can be minimized or reduced. For example, the core diameter a of the electrode assembly 120 can be within a range of about 5% to 15% of the inner diameter b of the housing 110.

[0077] refer to Figure 4, the exhaust port 165a may be provided in the central area 161 of the cap plate 160. In this case, the central area 161 may be a circular (in a plan view) area starting from the center of the cap plate 160 and having a size corresponding to the core diameter of the electrode assembly 120. In addition, the exhaust port 165a may correspond to the circular central area 161 and have a circular ring shape formed along the periphery of the central area 161 in a plan view. The area of ​​the annular exhaust port 165a may be determined based on the core diameter a of the electrode assembly 120. That is, the inner diameter c of the ring shape of the exhaust port 165a may vary in proportion to the core diameter a of the electrode assembly 120. For example, the inner diameter c of the ring shape of the exhaust port 165a may be approximately 0.5 to 1 times the core diameter a of the electrode assembly 120. In addition, according to some embodiments, the exhaust port 165a may be located in the connection area 163 of the cap plate 160, or in both the connection area 163 and the central area 161. In this case, the inner diameter c of the ring shape of the exhaust port 165 a may be, for example, about 0.5 to 5.5 times the core diameter a of the electrode assembly 120 .

[0078] As another example, the exhaust port 165 may have at least one pattern having a linear or curved shape in a plan view. Figures 5 to 9 Describes various shapes of exhaust ports for delayed and peaceful exhaust.

[0079] Figure 5 is an example Figure 1 A plan view of another example of a cover plate in a cylindrical secondary battery, Figure 6 is a cross-sectional view illustrating an example of a cover plate for comparison Figure 5 The thickness of the cap plate in the cylindrical secondary battery in the region where the notch is formed, the notch having a cross section taken along line AA', and Figures 7 to 9 is an example Figure 1 1 is a plan view of another example of a cover plate in a cylindrical secondary battery.

[0080] refer to Figure 5 In a plan view, the vent 165b may have a cross shape extending from the center of the cap plate 160 toward the connection area 163. In this case, the thickness of the cap plate 160 may be the same in the area where the vent 165b is formed. In the area where the vent 165b is formed, the thickness of the cap plate 160 is about 0.1 to 0.3 times the thickness of the material of the cap plate 160. In this case, the battery cell rupture pressure range may be about 17 to 35 kgf / cm 2 .

[0081] According to some embodiments, Figure 6As shown in , the thickness of the cover plate 160 in the area where the notch is formed can increase from its center along the extension direction of the exhaust port 165b. That is, the thickness of the cover plate 160 in the area where the notch is formed can be small so that the portion corresponding to the central area 161 can be easily exhausted, and the thickness of the cover plate 160 in the area where the notch can be formed can increase as the distance from the central area 161 increases. For example, the maximum thickness of the cover plate 160 in the area where the exhaust port 165b is formed can be approximately 0.25 to 0.3 times the thickness of the material of the cover plate 160. In this case, the battery cell rupture pressure can be approximately 35kgf / cm 2 In addition, the minimum thickness of the cap plate 160 in the region where the vent 165b is formed may be about 0.1 to 0.15 times the thickness of the material of the cap plate 160. In this case, the battery cell rupture pressure may be about 17 kgf / cm 2 Meanwhile, although the description has been made based on the cross-shaped exhaust port 165b, in the case of the above-mentioned circular-shaped exhaust port 165a, the following linear-shaped exhaust port 165c, the spiral-shaped exhaust port 165d, and the pinwheel-shaped exhaust port 165e, as Figure 6 As shown in FIG. 1 , the thickness of the cover plate 160 in the region where the recess is formed may increase from one side to the other side.

[0082] like Figure 5 As shown in , the exhaust port 165b may be provided in the central region 161 and the connection region 163 of the cap plate 160. In this case, the length of each of the horizontal and vertical lines of the cross-shaped exhaust port 165b may be about 0.5 to 5.5 times the core diameter a of the electrode assembly 120. The exhaust port 165b may be provided only in the central region 161. In this case, the length of the horizontal and vertical lines of the cross-shaped exhaust port 165b may be about 0.5 to 1 times the core diameter a of the electrode assembly 120.

[0083] refer to Figure 7 In a plan view, the exhaust port 165c may have a linear shape extending from the central region 161. The linear exhaust port 165c may be located in the connection region 163. Figure 7As shown in , the exhaust port 165c of a linear shape may have four exhaust ports spaced apart from each other based on the central area 161. However, the exhaust port is not limited thereto and may be formed by a plurality of exhaust ports, but according to some embodiments, it is described as having 1 to 4 exhaust ports. For example, when there is one exhaust port 165c of a linear shape, the exhaust port 165c may be formed as a linear line without any separated parts. In addition, when there are two exhaust ports 165c of a linear shape, the two exhaust ports 165c may be formed as linear lines spaced apart from each other based on the central area 161. In addition, when there are three exhaust ports 165c of a linear shape, the three exhaust ports 165c may be formed as linear exhaust ports spaced apart from each other. Alternatively, when there are three exhaust ports 165c of a linear shape, the three exhaust ports 165c may be formed as three linear lines spaced apart from each other based on the central area 161, and the spacing between the linear lines is consistent.

[0084] At the same time, in the linear-shaped exhaust port 165c, rupture may occur in at least one of the multiple exhaust ports. In this case, in order to minimize or reduce the internal deformation of the battery cell due to exhaust, it may be advantageous to have fewer exhaust positions. In addition, when there are two or more linear-shaped exhaust ports 165c, the spacing between the exhaust ports may be the same. In addition, according to some embodiments, it may be advantageous when the notch shapes are different to minimize or reduce the exhaust area when the exhaust port 165c is broken. Therefore, when there are two or more linear-shaped exhaust ports 165c, the lengths of the linear-shaped exhaust ports 165c may be different. For example, the length of the long portion (ie, the relatively long linear-shaped exhaust port) may be about 1 to 10 times the length of the relatively short portion (ie, the relatively short linear-shaped exhaust port). In addition, the length of the short portion (ie, the relatively short linear-shaped exhaust port) may be about 0.1 to 1 times the length of the relatively long portion (ie, the relatively long linear-shaped exhaust port). When the length difference is less than about 0.1 times or greater than about 10 times, implementation of the cover plate 160 may be difficult.

[0085] In addition, when the linear-shaped vent 165c has two or more linear lines, the thickness of the cap plate 160 in the region where the vent 165c is formed may be different. In this case, the thickness of the cap plate 160 in the region where the vent 165c is formed may be about 0.1 to 0.3 times the material thickness of the cap plate 160. In this case, the battery cell rupture pressure range may be about 17 to 35 kgf / cm 2. For example, the thickness of the cover plate 160 in the area where the relatively long linear portion of the exhaust port 165c (i.e., the exhaust port of a long linear shape) is formed can be relatively small (e.g., can be about 0.1 times the thickness of the cover plate material). In addition, the thickness of the cover plate 160 in the area where the relatively short linear portion of the exhaust port 165c (i.e., the exhaust port of a short linear shape) is formed can be relatively large (e.g., can be about 0.3 times the thickness of the cover plate material). That is, for the relatively long linear portion, the notch depth can be increased to facilitate exhaust, and for the relatively short linear portion, the notch depth can be reduced.

[0086] refer to Figure 8 and Fig. 9 , in a plan view, the exhaust ports 165d and 165e may have a spiral shape and a pinwheel shape extending from the central region 161, respectively. The exhaust ports 165d and 165e may be located in both the connection region 163 and the central region 161 of the cap plate 160. In this case, a distance from a start point to an end point of each of the spiral-shaped exhaust port 165d and the pinwheel-shaped exhaust port 165e may be about 0.5 to 5.5 times the core diameter a of the electrode assembly 120.

[0087] like Figure 8 As shown in , the spiral-shaped exhaust port 165d may have a spiral shape extending from a starting point in the central area 161 to an end point in the connecting area 163. That is, the spiral-shaped exhaust port 165d may have a shape in a plan view in which the radius of the spiral line increases. In this case, the thickness of the cover plate 160 may be consistent in the area where the spiral-shaped exhaust port 165d is formed. As described above, the thickness of the cover plate 160 in the area where the exhaust port 165d is formed may be approximately 0.1 to 0.3 times the thickness of the material of the cover plate 160. In this case, the battery cell rupture pressure range may be approximately 17 to 35 kgf / cm 2 .

[0088] According to some embodiments, the thickness of the cover plate 160 in the area where the spiral-shaped exhaust port 165d is formed may increase from its center along the extension direction. Therefore, by changing the thickness of the cover plate 160 in the area where the exhaust port 165d is formed for each position, the exhaust area can be adjusted when a problem occurs inside the battery cell. In the area where the spiral-shaped exhaust port 165d is formed, the thickest thickness of the cover plate 160 may be about 0.3 times the material thickness of the cover plate 160. In this case, the battery cell rupture pressure may be about 35kgf / cm 2In addition, the thinnest thickness of the cap plate 160 in the region where the spiral-shaped exhaust port 165d is formed may be about 0.1 times the material thickness of the cap plate 160. In this case, the battery cell rupture pressure may be about 17 kgf / cm 2 .

[0089] According to some embodiments, Fig. 9 As shown in , the exhaust port 165e may have a pinwheel shape in which a plurality of circular arcs having the same radius are arranged at equal intervals based on the center or central axis (rotation axis) within the circular exhaust port. In the region where the pinwheel-shaped exhaust port 165e is formed, the thickness of the cover plate 160 may increase in the direction of extension from the center. That is, when the internal pressure increases after exhaust along the initial arc of the pinwheel-shaped exhaust port 165e, the entire exhaust port 165e including the extended portion of the circular exhaust port 165e formed along the planar perimeter of the cover plate 160 may be exhausted. In the region where the pinwheel-shaped exhaust port 165e is formed, the thickest thickness of the cover plate 160 may be approximately 0.25 to 0.3 times the material thickness of the cover plate 160. In this case, the battery cell rupture pressure may be approximately 35 kgf / cm 2 In addition, the minimum thickness of the cap plate 160 in the region where the pinwheel-shaped exhaust port 165e is formed may be about 0.1 to 0.15 times the material thickness of the cap plate 160. In this case, the battery cell rupture pressure may be about 17 kgf / cm 2 .

[0090] In a cylindrical secondary battery according to some embodiments of the present disclosure, a vent and a core structure are designed to meet forced discharge items of standard specifications to suppress heat generation and prevent or reduce fire during forced discharge evaluation.

[0091] In addition, in the cylindrical secondary battery according to some embodiments of the present disclosure, heat generation may be suppressed by forming a vent structure that gradually releases pressure so that exhaust gradually proceeds.

[0092] Additionally, in a cylindrical secondary battery according to some embodiments of the present disclosure, a vent structure is formed to increase the vent rupture pressure and reduce the diameter of the pole core to minimize or reduce internal deformation of the battery cell during venting.

[0093] In addition, since the cylindrical secondary batteries according to some embodiments of the present disclosure are provided with both negative and positive electrodes on one side, when a plurality of cylindrical secondary batteries are electrically connected by a bus bar, the bus bar connection structure can be simplified by allowing connection only on one side.

[0094] Although the aforementioned embodiments are merely embodiments for implementing the present disclosure and are not limited to the disclosed embodiments, those skilled in the art will understand that various changes in form and details may be made therein without departing from the spirit and scope of the embodiments according to the present disclosure as defined by the claims and their equivalents.

Claims

1. A cylindrical secondary battery, comprising: Electrode assembly; a shell, the lower end of which is open to accommodate the electrode assembly; as well as a cover plate coupled to the lower end of the housing, The cover plate includes a central area, an edge area, and a connecting area connecting the central area and the edge area, the exhaust port is located in at least one of the central area and the connecting area, and the area of ​​the cover plate where the exhaust port is formed has a thickness smaller than that of other areas of the cover plate. 2 . The cylindrical secondary battery according to claim 1 , wherein the cap plate is formed in a shape in which the central region is bent toward the electrode assembly compared with the edge region. 3 . The cylindrical secondary battery according to claim 2 , wherein the central region and the connection region of the cap plate are formed concavely toward the inside of the case compared to the edge region. 4 . The cylindrical secondary battery according to claim 1 , wherein the vent has a notch formed in an inner surface of the cap plate. 5 . The cylindrical secondary battery according to claim 1 , wherein a thickness of the cap plate in the region where the vent is formed is in the range of 0.1 to 0.3 times a thickness of a material of the cap plate. 6 . The cylindrical secondary battery according to claim 1 , wherein the exhaust port is provided in the central region of the cap plate and has a circular ring shape continuously formed along a periphery of the central region of the cap plate. 7 . The cylindrical secondary battery according to claim 6 , wherein an inner diameter of the exhaust port is in the range of 0.5 to 1 times a core diameter of the electrode assembly. 8 . The cylindrical secondary battery according to claim 1 , wherein the exhaust port is provided in the central region and the connection region of the cap plate and has a cross shape extending from the center of the cap plate toward the connection region. 9 . The cylindrical secondary battery according to claim 8 , wherein a length of each of a horizontal line and a vertical line of the exhaust port is within a range of 0.5 to 5.5 times a core diameter of the electrode assembly. 10 . The cylindrical secondary battery according to claim 1 , wherein the vent is provided in the connection region and has at least one linear shape extending from the central region. 11 . The cylindrical secondary battery according to claim 10 , wherein the exhaust port comprises a plurality of linear-shaped exhaust ports spaced apart from each other based on the central area. 12 . The cylindrical secondary battery according to claim 10 , wherein the vent comprises a plurality of linear-shaped vents, and lengths of the plurality of linear-shaped vents are different from each other.

13. The cylindrical secondary battery according to claim 12, wherein the length of a relatively long linear shaped vent among the plurality of linear shaped vents is in the range of 1 to 10 times the length of a relatively short linear shaped vent among the plurality of linear shaped vents, The length of the relatively short exhaust port among the plurality of exhaust ports having a linear shape is in a range of 0.1 to 1 times the length of the relatively long exhaust port among the plurality of exhaust ports having a linear shape. 14 . The cylindrical secondary battery according to claim 10 , wherein the vent includes a plurality of linear-shaped vents, and thicknesses of the cap plate in regions where the plurality of linear-shaped vents are formed are different from each other.

15. The cylindrical secondary battery according to claim 14, wherein the exhaust port is formed so that a thickness of the cap plate in a region where short linear-shaped exhaust ports among the plurality of linear-shaped exhaust ports are formed is greater than a thickness of the cap plate in a region where long linear-shaped exhaust ports among the plurality of linear-shaped exhaust ports are formed. 16 . The cylindrical secondary battery according to claim 10 , wherein the vent comprises 1 to 4 vents in a linear shape. 17 . The cylindrical secondary battery according to claim 1 , wherein the vent is in the central region and the connection region of the cap plate and has a spiral shape or a pinwheel shape extending from the central region. 18 . The cylindrical secondary battery according to claim 17 , wherein the exhaust port extends from a start point in the central region to an end point in the connection region and has a spiral shape in which a radius of the spiral line increases. 19 . The cylindrical secondary battery according to claim 18 , wherein the thickness of the cap plate in the region where the vent is formed increases from the start point to the end point. 20 . The cylindrical secondary battery according to claim 17 , wherein the exhaust port has the pinwheel shape in which a plurality of arcs having a constant radius are arranged at equal intervals based on the center of the cap plate.

Images