Cylindrical secondary battery

Abstract

A cylindrical secondary battery includes: an electrode assembly including a first electrode plate, a separator, and a second electrode plate; a case accommodating the electrode assembly and having a lower end that is open and electrically connected to the second electrode plate; a first current collector plate between a top surface of the electrode assembly and the case and electrically connected to the first electrode plate; a terminal passing through a terminal hole in a top surface portion of the housing and including a lower end electrically and mechanically coupled to a top surface of the first current collector plate; and a cover plate configured to seal the lower end of the housing. The terminal includes: a lower terminal including a welding groove having a depth from a top surface of the lower terminal in a downward direction; and an upper terminal in the welding groove of the lower terminal.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority and benefit of Korean Patent Application No. 10 - 2024 - 0013086, filed with the Korean Intellectual Property Office on January 29, 2024, the entire disclosure of which is incorporated herein by reference. Technical field

[0003] Embodiments relate to a cylindrical secondary battery. Background art

[0004] Generally, a cylindrical secondary battery includes a cylindrical electrode assembly, a cylindrical can that houses the electrode assembly and an electrolyte, and a cap assembly that is coupled to an opening on one side of the can to seal the can and is electrically connected to the electrode assembly to electrically connect an external device or component to the electrode assembly.

[0005] A battery module may include a plurality of cylindrical secondary batteries connected to each other through bus bars. However, since the bus bars must be connected to the upper and lower parts of the secondary battery respectively, there are limitations in that the structure is complex and the manufacturing process time increases.

[0006] To solve this limitation, the can may be provided with terminal holes at the upper end or the lower end, and the positive electrode rivet terminal and the can are insulated from each other within the terminal holes. Accordingly, bus bars are provided on the same surface of the secondary battery to facilitate the connection of the bus bars in the battery module.

[0007] To prevent foreign substances from being generated inside the electrode assembly, welding may be performed between the rivet terminal and the current collector plate of the electrode assembly through a groove provided outside the rivet terminal. However, if an alignment error occurs during welding with the bus bar due to the groove outside the rivet terminal, insufficient welding area or welding defects may occur.

[0008] The above information disclosed in the art used as the background of the present disclosure is only for improving the understanding of the background of the present disclosure, and thus may include information that does not constitute related art. Summary of the invention

[0009] Aspects of some embodiments of the present disclosure provide a cylindrical secondary battery in which a terminal and a current collector plate are welded outside a case through a welding groove provided in a lower terminal to prevent welding impurities from being generated inside the case and / or prevent the electrode assembly from being thermally damaged by welding.

[0010] Other aspects of some embodiments of the present invention provide a cylindrical secondary battery, in which a welding groove provided in a lower terminal is filled with an upper terminal, such that the terminal has a substantially flat top surface. Thus, if a plurality of secondary batteries are welded by a bus bar, welding defects due to misalignment (which may occur due to the welding groove) or an increase in resistance due to insufficient welding area can be prevented.

[0011] According to some embodiments, a cylindrical secondary battery includes: an electrode assembly including a first electrode plate, a separator, and a second electrode plate; a case accommodating the electrode assembly and having an open lower end for electrical connection to the second electrode plate; a first current collector plate between a top surface of the electrode assembly and the case and electrically connected to the first electrode plate; a terminal passing through a terminal hole in a top surface portion of the case and having a lower end electrically and mechanically coupled to a top surface of the first current collector plate; and a cover configured to seal the lower end of the case. The terminal includes: a lower terminal provided with a welding groove having a depth starting from a top surface of the lower terminal in a downward direction; and an upper terminal extending into the welding groove of the lower terminal.

[0012] The lower terminal may include: a head provided on an upper side of the top surface portion of the case; and a coupling portion extending from a central portion of the head into the case and integral with the head.

[0013] The first current collector plate may be welded outside the terminal through the welding groove such that a top surface of the first current collector plate contacts a bottom surface of the lower terminal, so that a weld bead is in the welding groove.

[0014] The welding groove may pass through the central portion of the head and be provided downward from an upper portion of the coupling portion.

[0015] A planar dimension of the head may be larger than a planar dimension of the coupling portion.

[0016] A planar dimension of a lower portion of the coupling portion may be larger than a planar dimension of the coupling portion in the terminal hole of the case.

[0017] The lower terminal may include: a head on a lower side of the top surface portion of the case; and a coupling portion extending from a central portion of the head to the outside of the case and integral with the head.

[0018] The welding groove may be defined downward from a central portion of a top surface of the coupling portion.

[0019] The cylindrical secondary battery may further include: a coupling member, on an upper side of the top surface portion of the housing, and coupled to the coupling portion.

[0020] The coupling member may include a coupling hole passing through a center thereof, and the coupling portion of the lower terminal may include a deformable portion, an upper side of the deformable portion passing through the coupling hole and being coupled to the coupling member by riveting.

[0021] The coupling member may further include a protrusion protruding from a lower region of the coupling hole, and a stepped portion may be provided in the coupling hole.

[0022] The deformable portion of the lower terminal may be above the protrusion of the coupling member.

[0023] The upper terminal may include: a main body extending into the welding groove; and a flange extending from an upper portion of the main body to cover a top surface of the lower terminal.

[0024] A bottom surface of the main body may be spaced apart from a bottom surface of the welding groove.

[0025] A thickness of an edge region of the flange may be smaller than a thickness of each of other regions of the upper terminal.

[0026] The edge region of the flange may have a stepped portion or an inclined surface.

[0027] The main body may have an outer diameter smaller than an inner diameter of the welding groove.

[0028] The cylindrical secondary battery may further include an anisotropic conductive material between a bottom surface of the flange and the top surface of the lower terminal.

[0029] A top surface of the upper terminal may protrude further upward than the top surface of the lower terminal.

[0030] A lower region of the upper terminal in the welding groove may have an outer diameter larger than an outer diameter of an upper region of the upper terminal outside the welding groove.

[0031] The upper terminal may include a flange extending along the top surface of the lower terminal.

[0032] The flange may have a stepped portion or an inclined surface.

[0033] A top surface of the upper terminal may be lower than the top surface of the lower terminal.

[0034] The upper terminal may include a release groove extending upward from its bottom surface.

[0035] The upper terminal can be welded to the lower terminal.

[0036] The top surface of the terminal can have a diameter of about (substantially) 11 mm or greater, and the diameter can be less than the diameter of the top surface portion of the housing.

[0037] The welding groove can have an upper inner diameter larger than its lower inner diameter.

[0038] The cylindrical secondary battery can further include a first gasket between the terminal and the housing.

[0039] The housing can include: a crimping portion recessed into the housing above the cover plate; and a crimping portion at a lower portion of the housing, the crimping portion being bent inward to fix the cover plate.

[0040] The cylindrical secondary battery can further include: a second gasket between the cover plate and the crimping portion and between the cover plate and the crimping portion, and the cover plate can be non-polar. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings are included to provide a further understanding of the present disclosure, and the drawings are incorporated into and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the specification, are used to explain the principles of the present disclosure. In the drawings:

[0042] Figure 1 A perspective view illustrating a cylindrical secondary battery according to an embodiment of the present disclosure;

[0043] Figure 2 Illustrating Figure 1 a cross-sectional view of the cylindrical secondary battery;

[0044] Figure 3 Illustrating Figure 2 an enlarged cross-sectional view of part A;

[0045] Figure 4A and Figure 4B Illustrating Figure 2 an enlarged cross-sectional view of another embodiment of part A;

[0046] Figure 5 A cross-sectional view illustrating a cylindrical secondary battery according to an embodiment of the present disclosure;

[0047] Figure 6 Illustrating Figure 5 an enlarged cross-sectional view of part B;

[0048] Figure 7 A cross-sectional view illustrating a cylindrical secondary battery according to an embodiment of the present disclosure;

[0049] Figure 8 Illustration Figure 7 An enlarged cross-sectional view of part C;

[0050] Figure 9 An illustration of a cross-sectional view of a cylindrical secondary battery according to an embodiment of the present disclosure;

[0051] Figure 10 is Figure 9 An enlarged cross-sectional view of the terminal portion of; and

[0052] Figure 11A and Figure 11B is Figure 9 An enlarged cross-sectional view of another embodiment of the terminal portion of. Detailed Description of Specific Embodiments

[0053] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

[0054] However, the embodiments of the present disclosure may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that those skilled in the art will thoroughly understand the present disclosure. These embodiments are provided so that the present disclosure will be thorough and complete and will fully convey the scope of the present disclosure to those skilled in the art.

[0055] In addition, in the following drawings, for convenience and clarity of description, the dimensions (e.g., thickness) of each layer are exaggerated, and the same reference numerals in the drawings refer to the same elements. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. In this specification, it will also be understood that if component A is referred to as being connected to component B, component A may be directly connected to component B or indirectly connected to component B through component C therebetween.

[0056] The terms used in this specification are for illustrative purposes only of the present disclosure and should not be construed as limiting the meaning or scope of the present disclosure. As used in this specification, the singular form may include the plural form unless specifically indicated otherwise from the context. In addition, the expressions "comprising" and / or "including" used in this specification only specify the presence of the recited shapes, numbers, processes, operations, components, elements, and / or groups thereof, but do not exclude the presence or addition of one or more other different shapes, numbers, processes, operations, components, elements, and / or groups thereof.

[0057] As used herein, terms such as "first", "second", etc. are used to describe various components, parts, regions, layers, and / or sections. However, it is obvious that the components, parts, regions, layers, and / or sections should not be limited by these terms. These terms do not imply a specific order, top or bottom, or superiority, and are only used to distinguish one component, part, region, layer, or section from another component, part, region, layer, or section. Therefore, the first component, part, region, layer, or section described may also be referred to as the second component, part, region, layer, or section without departing from the teachings of the present disclosure.

[0058] For ease of description, spatial relative terms such as "below", "beneath", "under", "above", "on", etc. are used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures. These spatial relative terms are intended to facilitate understanding of the present invention according to various process states or usage states of the present invention, and thus are not limited thereto according to embodiments of the present disclosure. For example, if the element or feature shown in the drawings is turned upside down, the element or feature described as "beneath" or "below" may become "above" or "on". Therefore, the term "below" may encompass the terms "above" or "below".

[0059] Preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present disclosure.

[0060] Here, throughout the specification, parts having similar configurations and operations are denoted by the same reference numerals. In addition, in the following description, if any part is referred to as being "electrically connected" to another part, it should be understood that the former can be "directly connected" to the latter, or "connected" to the latter via an intermediate member.

[0061] Figure 1 A perspective view illustrating a cylindrical secondary battery 100 according to an embodiment, Figure 2 Illustrate Figure 1 a cross-sectional view of the cylindrical secondary battery 100. Figure 3 Illustrate Figure 2 an enlarged cross-sectional view of part A. Hereinafter, the cylindrical secondary battery 100 will be described with reference to Figures 1 to 3 the description.

[0062] As Figure 1 and Figure 2 shown in, the secondary battery 100 according to an embodiment may include a case 110, an electrode assembly accommodated in the case 110, a terminal 150 coupled to a terminal hole provided in one end (e.g., the upper end) of the case 110, and a cover plate 160 sealing an opening of the other end (e.g., the lower end) of the case 110.

[0063] The housing 110 may include a circular top surface portion 111 and a side surface portion 112 that extends downward from an edge (e.g., a perimeter) of the top surface portion 111 by a predetermined length. The top surface portion 111 and the side surface portion 112 of the housing 110 may be integral with each other. In one or more embodiments, a bent portion 111b that is bent into an arc shape (e.g., a rounded corner) may be provided between the top surface portion 111 and the side surface portion 112.

[0064] The circular top surface portion 111 may have a flat circular plate shape and may include a terminal hole 111a that passes through a center (or substantially center) portion thereof. The terminal 150 may be inserted into the terminal hole 111a. A first gasket 115 for sealing and electrical insulation may be provided between the terminal hole 111a and the terminal 150. The first gasket 115 may prevent contact between the terminal 150 and the housing 110 to electrically separate or isolate the terminal 150 and the housing 110 from each other. The first gasket 115 may seal the terminal hole 111a of the top surface portion 111 of the housing 110. The first gasket 115 may be made of a resin material (such as polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET), etc.).

[0065] In one or more embodiments, the housing 110 may further include an inner insulating member 117 that is provided to cover an inner surface of the top surface portion 111. In one or more embodiments, the inner insulating member 117 may be attached to the inner surface of the top surface portion 111 by coating or adhesion. In one or more embodiments, the inner surface of the top surface portion 111 may be a surface that faces the top surface of the electrode assembly 120 and may be the bottom surface of the top surface portion 111. The inner insulating member 117 may prevent the top surface portion 111 of the housing 110 and the first electrode plate 121 of the electrode assembly 120 from contacting each other. In one or more embodiments, the inner insulating member 117 may extend to an inner surface of the bent portion 111b. The inner insulating member 117 may be provided to cover the inner surface of the top surface portion 111 and the inner surface of the bent portion 111b, or may be provided to cover only the inner surface of the top surface portion 111.

[0066] In the cylindrical secondary battery 100, the lower portion (e.g., the lower end) of the housing 110 may be open during the manufacturing process. In some embodiments, during the process of manufacturing the cylindrical secondary battery 100, the electrode assembly 120 may be inserted together with the electrolyte through the open lower portion (e.g., the lower end) of the housing 110. In one or more embodiments, the electrolyte and the electrode assembly 120 may be inserted into the housing 110 in a state or configuration where the open lower portion (e.g., the lower end) is oriented upward. After the electrolyte and the electrode assembly 120 are inserted into the housing 110, the cover plate 160 may be coupled to the open lower end to seal the interior of the housing 110. The electrolyte is used to enable lithium ions to move between the positive electrode plate 121 and the negative electrode plate 122 of the electrode assembly 120. The electrolyte may be a non-aqueous organic electrolyte that is a mixture of a lithium salt and a high-purity organic solvent. In one or more embodiments, the electrolyte may be a polymer electrolyte or a solid electrolyte including a polymer, but the present disclosure is not limited to a specific type of electrolyte.

[0067] The housing 110 may be made of steel, a steel alloy, aluminum, an aluminum alloy, or the like, but the material thereof is not limited thereto. In one or more embodiments, in the housing 110, an inwardly recessed caulking portion 113 may be provided above the cover plate 160 in the housing 110 to prevent the cover assembly 120 from separating from the housing 110, and an inwardly bent crimping portion 114 may be provided at the lower portion of the housing 110 below the cover assembly 120.

[0068] In the housing 110, after the electrode assembly 120 is inserted through the open lower end, the caulking portion 113 may be provided to prevent the electrode assembly 120 from separating from the housing 110.

[0069] The electrode assembly 120 may include 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, and vice versa. Hereinafter, for convenience of description, the first electrode plate 121 will be referred to as the positive electrode plate, and the second electrode plate 122 will be referred to as the negative electrode plate.

[0070] In the first electrode plate 121, at least one surface of a plate-shaped metal foil made of aluminum (Al) is coated with a positive electrode active material made of a transition metal oxide. In one or more embodiments, the first electrode plate 121 may have a positive electrode uncoated portion at its upper end where the positive electrode active material is not coated. The positive electrode uncoated portion may protrude toward the upper side of the electrode assembly 120. In one or more embodiments, 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.

[0071] The second electrode plate 122 may be coated with a negative electrode active material (such as graphite or carbon) on at least one surface of a plate-shaped metal foil made of copper (Cu) or nickel (Ni). In one or more embodiments, the second electrode plate 122 may have a negative electrode uncoated portion at its lower end where the negative electrode active material is not coated. The negative electrode uncoated portion may protrude toward the lower side of the electrode assembly 120. In one or more embodiments, the negative electrode uncoated portion of the second electrode plate 122 may protrude further downward than the first electrode plate 121 and the separator 123.

[0072] The separator 123 may be made of polyethylene (PE) or polypropylene (PP), but embodiments of the present disclosure are not limited thereto. The separator 123 may be between the first electrode plate 121 and the second electrode plate 122 to prevent short circuits and allow the movement of lithium ions.

[0073] After the first electrode plate 121, the second electrode plate 122, and the separator 123 are stacked on one another, the electrode assembly 120 may be wound from the winding front end into a substantially cylindrical shape. In one or more embodiments, in the electrode assembly 120, a positive electrode uncoated portion where the positive electrode active material is not coated may protrude upward from the first electrode plate 121, and a negative electrode uncoated portion where the negative electrode active material is not coated may protrude downward from the second electrode plate 122. In one or more embodiments, the electrode assembly 120 may be configured such that the outermost positive electrode uncoated portion may not protrude upward, and the outermost negative electrode uncoated portion may not protrude downward. In one or more embodiments, the electrode assembly 120 may have a stepped portion where the outermost sides of each of its upper portion and lower portion are recessed further than other regions. In the electrode assembly 120, if the inner insulating member 117 is not provided on the bent portion 111b of the housing 110, contact between the electrode assembly 120 and the housing 110 can be prevented.

[0074] The first current collector plate 130 may be a circular metal plate having a shape corresponding to the top surface of the electrode assembly 120. The planar dimension of the first current collector plate 130 may be equal to or smaller than the dimension of the top surface of the electrode assembly 120. The first current collector plate 130 may be made of aluminum (Al). The first current collector plate 130 may be fixed (e.g., welded) and electrically connected to the first electrode plate 121 exposed on the upper side of the electrode assembly 120 such that the bottom surface of the first current collector plate 130 contacts the top surface of the electrode assembly 120. The first current collector plate 130 may be fixed (e.g., welded) and electrically connected to the terminal 150 such that the top surface of the first current collector plate 130 contacts the bottom surface of the terminal 150. The first current collector plate 130 may serve as a path for current flow between the first electrode plate 121 of the electrode assembly 120 and the terminal 150. The first current collector plate 130 may be welded to the electrode assembly 120 and housed in the housing 110, and then welded to the terminal 150. As described in more detail below, the first current collector plate 130 may have a thickness smaller than the lower thickness 151h of the lower terminal 151 of the terminal 150 to improve weldability.

[0075] The second current collector plate 140 may include a circular planar portion 141 corresponding to the bottom surface of the electrode assembly 120 and an extension portion 142 extending downward from the edge of the planar portion 141. The top surface of the planar portion 141 may contact the bottom surface of the electrode assembly 120. The top surface of the planar portion 141 may be fixed (e.g., welded) and electrically connected to the second electrode plate 122 exposed on the lower side of the electrode assembly 120 such that the top surface of the planar portion 141 contacts the bottom surface of the electrode assembly 120.

[0076] The extension portion 142 may extend downward from the edge of the planar portion 141. In one or more embodiments, the second current collector plate 140 may include a plurality of extension portions 142 spaced apart from each other along the edge of the planar portion 141. In one or more embodiments, four extension portions 142 may be provided to be symmetric with each other with respect to the planar portion 141, but the embodiments of the present disclosure are not limited thereto. The extension portion 142 may be bent to extend downward from the edge of the planar portion 141. In one or more embodiments, the extension portion 142 may contact the inner surface of the pressing portion 113. In one or more embodiments, the extension portion 142 may be rounded or bent (e.g., curved) along the pressing portion 113. In one or more embodiments, the inner surface may be the inner surface of the housing 110. The end of the extension portion 142 may be between the pressing portion 113 and the second gasket 118. The extension portion 142 may contact and be coupled to the pressing portion 113 of the housing 110. In one or more embodiments, the extension portion 142 may be coupled to and contact the inner surface of the pressing portion 113 of the housing 110 by welding. The second current collector plate 140 may serve as a path for current flow between the second electrode plate 122 of the electrode assembly 120 and the housing 110. In one or more embodiments, the housing 110 may be a negative electrode terminal. In one or more embodiments, the second current collector plate 140 may include a hole passing through between the top surface and the bottom surface at the center (or substantially the center) of the planar portion 141, and the electrolyte may be injected into the electrode assembly 120 through the hole.

[0077] The terminal 150 may be inserted into the terminal hole 111a in the top surface portion 111 of the housing 110, and contact and be electrically connected to the first electrode current collector plate 130. The terminal 150 may be electrically connected to the first electrode plate 121 of the electrode assembly 120 through the first current collector plate 130. In one or more embodiments, the terminal 150 may be a positive electrode terminal. The terminal 150 and the housing 110 may have different polarities. In one or more embodiments, the terminal 150 may be made of the same or similar material as that of each of the first current collector plate 130 and the first electrode plate 121.

[0078] The terminal 150 may include a lower terminal 151 and an upper terminal 152. The lower terminal 151 may include a head 151a exposed to the upper side of the housing 110 and a coupling portion 151b extending (e.g., downward) from a central portion of the head 151a into the interior of the housing 110. The planar size of the head 151a may be larger than the planar size of the coupling portion 151b. In the lower terminal 151, the upper end of the coupling portion 151b may be connected to the bottom surface of the head 151a, and the head 151a and the coupling portion 151b may be integral or monolithic with each other. The outer side of the lower terminal 151 may be coupled inside the terminal hole 111a of the housing 110. In one or more embodiments, a first gasket 115 may be between the lower terminal 151 and the housing 110. The lower portion of the coupling portion 151b may be compressed and deformed (compression molded) by riveting, which seals the terminal hole 111a. In one or more embodiments, the planar size of the lower portion of the coupling portion 151b may be larger than the planar size of the terminal hole 111a of the housing 110. In one or more embodiments, the coupling portion 151b may have a diameter that gradually increases from the terminal hole 111a toward the interior of the housing 110. The coupling portion 151b may have a larger diameter in the region inside the housing 110 than in the region inside the terminal hole 111a of the housing 110. In one or more embodiments, the diameter of the bottom surface of the coupling portion 151b may be larger than the diameter of each of the other regions of the coupling portion 151b. In one or more embodiments, the lower side of the coupling portion 151b may overlap the housing 110 along a plane.

[0079] In one or more embodiments, an outer insulating member 116 may be between the head 151a and the top surface portion 111 of the housing 110. The head 151a may be on the top surface portion 111, and the outer insulating member 116 that prevents electrical contact may be in a region where the head 151a and the top surface portion 111 overlap each other in a plane. In one or more embodiments, the outer insulating member 116 may be between the head 151a and the top surface portion 111 of the housing 110 such that the outer insulating member 116 does not overlap the first gasket 115 in a plane.

[0080] The first gasket 115 can be between the coupling part 151b and the terminal hole 111a of the housing 110, and the upper end of the first gasket 115 can extend between the head part 151a and the top surface part 111 of the housing 110. In one or more embodiments, the end of the upper end of the first gasket 115 can contact the outer insulating member 116. In one or more embodiments, the first gasket 115 and the outer insulating member 116 can be between the lower terminal 151 and the housing 110 to electrically insulate and seal the lower terminal 151 and the housing 110. In one or more embodiments, the first gasket 115 and the outer insulating member 116 can be integral. The first gasket 115 can contact the top surface and the bottom surface of the top surface part 111 of the housing 110. The lower end of the first gasket 115 can contact the inner insulating member 117.

[0081] The lower terminal 151 can include a welding groove 151c having a depth in the direction from the top surface of the head part 151a to the coupling part 151b. The welding groove 151c can pass through the central part of the head part 151a and extend downward from the upper side (e.g., the upper part) of the coupling part 151b. The inner diameter of the lower side of the welding groove 151c can be less than or equal to the inner diameter of the upper side of the welding groove 151c.

[0082] In one or more embodiments, the lower inner diameter of the welding groove 151c can be less than the diameter of the terminal hole 111a. The lower inner diameter of the welding groove 151c can be approximately (roughly) 0.5 mm to approximately (roughly) 2 mm. In one or more embodiments, if the lower inner diameter of the welding groove 151c is less than approximately (roughly) 0.5 mm, welding with the first current collector plate 130 may not be easy due to insufficient welding area. In one or more embodiments, if the lower inner diameter of the welding groove 151c is greater than approximately (roughly) 2 mm, riveting may not be easy due to an increase in the size of the lower terminal 151 and a decrease in stiffness. In one or more embodiments, the upper inner diameter of the welding groove 151c can be approximately (roughly) 2 mm to approximately (roughly) 5 mm. If the upper inner diameter of the welding groove 151c is less than approximately (roughly) 2 mm, it may not be easy to ensure the welding area, and if welding is performed in an area outside the welding groove 151c, damage to the head part 151a may occur. In one or more embodiments, if the upper inner diameter of the welding groove 151c is greater than approximately (roughly) 5 mm, riveting may not be easy due to an increase in the size of the terminal 150 and a decrease in stiffness.

[0083] The height of the welding groove 151c can be less than the total height of the lower terminal 151. Since the lower terminal 151 is provided with the welding groove 151c, the lower thickness 151h of the connecting portion 151b of the lower terminal 151 can be reduced. The lower thickness 151h of the connecting portion 151b can be the thickness from the bottom surface of the welding groove 151c to the bottom surface of the connecting portion 151b. The lower thickness 151h of the connecting portion 151b can be reduced by the welding groove 151c, so that the lower terminal 151 and the first current collector plate 130 can be welded to each other outside the housing 110.

[0084] The lower thickness 151h of the connecting portion 151b can be approximately (roughly) 0.5 mm to approximately (roughly) 1.5 mm. In one or more embodiments, if the lower thickness 151h of the connecting portion 151b is less than approximately (roughly) 0.5 mm, it may be difficult to maintain the rigidity of the housing 110. In one or more embodiments, if the lower thickness 151h of the connecting portion 151b is greater than approximately (roughly) 1.5 mm, the welding between the lower terminal 151 and the first current collector plate 130 performed outside the housing 110 may not be easy.

[0085] In one or more embodiments, the upper inner diameter of the welding groove 151c can be greater than the lower inner diameter of the welding groove 151c. Additionally, since the lower terminal 151 includes the welding groove 151c, even if the outside of the lower terminal 151 is welded to the first current collector plate 130, a weld bead can be provided inside the welding groove 151c to prevent the weld bead from protruding from the lower terminal 151. In one or more embodiments, in a configuration where the flat bottom surface of the lower terminal 151 contacts the top surface of the first current collector plate 13o, the lower terminal 151 can be welded to the first current collector plate 130.

[0086] In one or more embodiments, the lower terminal 151 can be provided with the welding groove 151c to allow welding with the first current collector plate 130 outside the housing 110, thereby preventing welding foreign matters from being generated inside the housing 110 and preventing the electrode assembly 120 from being damaged by welding heat.

[0087] The upper terminal 152 can include a main body 152a inserted into the welding groove 151c provided in the head 151a of the lower terminal 151 and a flange 152b extending from the upper portion of the main body 152a along the top surface of the lower terminal 151. The upper terminal 152 can have a plate shape with a flat top surface. The upper terminal 152 can have a diameter of approximately (roughly) 11 mm or more and less than the top surface portion 111 of the housing 110. In the upper terminal 152, a plurality of cylindrical secondary batteries can be connected to each other through a bus bar, and welding can be performed even if there is a deviation in the alignment of the terminals of each cylindrical secondary battery.

[0088] The top surface of the upper terminal 152 can be equal to or less than the head 151a of the lower terminal 151. The top surface of the upper terminal 152 can be the top surface of the terminal 150.

[0089] The flange 152b can have a substantially flat plate shape. The upper terminal 152 can include a flange 152b having a flat plate shape and a body 152a protruding downward from the approximate center of the flange 152b. The bottom surface of the flange 152b can contact the top surface of the head 151a of the lower terminal 151. In one or more embodiments, the body 152a can extend into a welding groove 151c in the head 151a. When the upper terminal 152 is coupled to the lower terminal 151, the body 152a can facilitate position adjustment or alignment. In one or more embodiments, the outer diameter of the body 152a can be smaller than the inner diameter of the welding groove 151c. In one or more embodiments, the body 152a can have a lower outer diameter that is smaller than the upper outer diameter of the body 152a, so that insertion into the welding groove 151c can be easier.

[0090] In one or more embodiments, the bottom surface of the body 152a can be spaced apart from the bottom surface of the welding groove 151c. Accordingly, since the body 152a is spaced apart from the bottom surface of the welding groove 153, contact defects between the bottom surface of the flange 152b of the upper terminal 152 and the top surface of the head 151a of the lower terminal 151 due to weld beads generated in the welding groove 151c of the lower terminal 151 can be prevented (or at least mitigated). The bottom surface of the flange 152b of the upper terminal 152 and the top surface of the head 151a of the lower terminal 151 can be joined and electrically connected by a weld bead while being in contact with each other.

[0091] In one or more embodiments, the upper terminal 152 may include an edge region 152c that is the outermost side (e.g., the peripheral or circumferential edge) of the flange 152b in a plane. In one or more embodiments, the edge region 152c may be thinner than each of the other regions of the flange 152b. In one or more embodiments, the top surface of the edge region 152c may be lower when compared to the top surfaces of the other regions of the flange 152b. In one or more embodiments, the top surface of the edge region 152c may have a height difference relative to each of the top surfaces of the other regions of the flange 152b. The edge region 152c of the upper terminal 152 may be joined and electrically connected to the head 151a of the lower terminal 151 by welding at its upper portion and side portions. In one or more embodiments, the edge region 152c may include a welded portion over all or a part of this region. In one or more embodiments, the edge region 152c may include a welded portion having a circular shape or at least one arcuate shape in a plane. In one or more embodiments, the thickness of the edge region 152c may be from about (substantially) 0.5 mm to about (substantially) 1.5 mm. In one or more embodiments, the outermost side of the edge region 152c may be in the same plane as the outermost side of the head 151a of the lower terminal 151, or the edge region 152c may be inside the head 151a.

[0092] In one or more embodiments, as Figure 4A shown, the edge region 152c may be inclined. In one or more embodiments, the edge region 152c may have an inclined surface and a bottom surface. In one or more embodiments, the edge region 152c may have an inclined surface where the angle in cross-section that contacts the top surface of the flange 152b is an obtuse angle, and the angle that contacts the bottom surface of the flange 152b is an acute angle.

[0093] In one or more embodiments, as Figure 4B shown, the edge region 152c may have both a stepped portion and an inclined surface. In one or more embodiments, the edge region 152c may be thinner than each of the other regions of the flange 152b. The edge region 152c may have an inclined surface and a bottom surface. The uppermost end of the inclined surface of the edge region 152c may be lower than the top surface of each of the other regions of the flange 152b.

[0094] In one or more embodiments, the edge region 152c may be lower than the top surface of the upper terminal 152 or may have an inclined surface to prevent the weld bead generated due to the welding between the lower terminal 151 and the upper terminal 152 from protruding upward higher than the top surface of the upper terminal 152. The upper terminal 152 may have a flat top surface. In one or more embodiments, a plurality of cylindrical secondary batteries 100 may be electrically connected to each other through a bus bar, and a welding defect in which the bus bar above the welding groove 151c is not welded to the terminal 150 due to the positional deviation between the terminals 150 of the plurality of cylindrical secondary batteries 100 may be prevented.

[0095] In addition, an anisotropic conductive material (e.g., anisotropic conductive paste (ACP) or anisotropic conductive film (ACF)) may be between the bottom surface of the flange 152b of the upper terminal 152 and the top surface of the head 151a of the lower terminal 151. The upper terminal 152 and the lower terminal 151 may be in contact with and coupled to each other through the anisotropic conductive material instead of through welding.

[0096] The cover plate 160 may be a circular metal plate and may be coupled to the lower end of the housing 110. The bottom surface of the cover plate 160 may be exposed to the outside. The cover plate 160 may be coupled to the lower end of the housing 110 in a state where the second gasket 118 is between the cover plate 160 and the housing 110 to prevent the cover plate 160 from being electrically connected to the housing 110. Since the cover plate 160 is not electrically connected to the positive electrode or the negative electrode of the electrode assembly 120, there may be no separate electrode polarity.

[0097] The cover plate 160 may be fixed in a state where the edge region of the cover plate 160 is between the crimping portion 113 and the caulking portion 114 of the housing 110. In one or more embodiments, the cover plate 160 may be disposed on the lower portion of the second gasket 118 in a configuration where the second gasket 118 is in the lower portion of the crimping portion 113 of the housing 110. The caulking portion 114 of the housing 110 may be bent to the inside of the edge of the cover plate 160 to press the second gasket 118, thereby coupling the cover plate 160 to the housing 110. The second gasket 118 may be made of a resin material (such as polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET), etc.). The second gasket 118 may press the housing 110 and the cover plate 160 to seal the gap between the housing 110 and the cover plate 160, thereby preventing the cover plate 160 from separating from the housing 110. The second gasket 118 may have an upper portion between the crimping portion 113 and the cover plate 160 and a lower portion between the caulking portion 114 and the cover plate 160. The lower end of the second gasket 118 may protrude further toward the center of the cover plate 160 than the caulking portion 114.

[0098] The cover plate 160 may include a central region 161 below the second current collector plate 140 and an edge region 162 between the caulking portion 113 and the crimping portion 114 of the housing 110 and coupled to the housing 110. In one or more embodiments, the central region 161 of the cover plate 160 may be recessed toward the interior of the housing 110 compared to the edge region 162. In one or more embodiments, the edge region 162 of the cover plate 160 may protrude further outward toward the bottom of the housing 110 than the central region 161. In one or more embodiments, the cover plate 160 may further include a connection region 163 connecting the central region 161 to the edge region 162. The connection region 163 may be an inclined stepped portion between the central region 161 and the edge region 162. In one or more embodiments, bending portions may be further provided between the connection region 163 and the central region 161 and between the connection region 163 and the edge region 162.

[0099] The cover plate 160 may include an exhaust port 165 in the central region 161, and the exhaust port 165 is configured to be opened at a threshold pressure. The cover plate 160 may have a thickness thinner than the thickness of each of the other regions of the cover plate 160 at the exhaust port 165. The exhaust port 165 may be a notch extending upward from the bottom surface of the cover plate 160.

[0100] If excessive internal pressure occurs inside the housing 110 of the cylindrical secondary battery 100, the exhaust port 165 may rupture to release the excessive internal pressure. The exhaust port 165 of the cover plate 160 may be spaced apart from the center of the cover plate 160 and may have an annular shape on the plane of the cover plate 160. In one or more embodiments, the exhaust port 165 may have at least one pattern having a straight or curved shape on the plane. The thickness of the cover plate 160 at the exhaust port 165 may be less than the thickness of each of the other regions of the cover plate 160.

[0101] In the cylindrical secondary battery 100, the terminal 150 and the first current collector plate 130 may be welded outside the housing 110 through a welding groove 151c provided in the lower terminal 151. In one or more embodiments, the cylindrical secondary battery 100 may prevent welding impurities from appearing inside the housing 110 and / or prevent the electrode assembly 120 from being damaged by welding heat.

[0102] In one or more embodiments, the cylindrical secondary battery 100 may be electrically connected to another adjacent cylindrical secondary battery 100 via a bus bar. In the cylindrical secondary battery 100, the bus bar may contact and be coupled to the terminal 150 or the case 110. Due to the upper terminal 152 coupled to the upper side of the lower terminal 151 having a welding groove 151c, the top surface of the cylindrical secondary battery 100 may have a flat (planar) shape, and thus welding to the bus bar may be easy, simple, and / or straightforward.

[0103] Figure 5 A cross-sectional view of a cylindrical secondary battery according to an embodiment of the present disclosure is illustrated. Figure 6 Illustrated Figure 5 An enlarged cross-sectional view of part B of.

[0104] As Figure 5 and Figure 6 As shown in, the secondary battery 200 according to an embodiment of the present disclosure may include a case 110, an electrode assembly 120 accommodated in the case 110, a terminal 250 coupled to a terminal hole 111a provided at one end (e.g., the upper end) of the case 110, and a cover plate 160 sealing an opening at the other end (e.g., the lower end) of the case 110. In one or more embodiments, the cylindrical secondary battery 200 may include a first current collector plate 130 electrically connecting the first electrode plate 121 of the electrode assembly 120 to the terminal 250 and a second current collector plate 140 connecting the case 110 to the second electrode plate 122 of the electrode assembly 120.

[0105] The case 110, the electrode assembly 120, the first current collector plate 130, the second current collector plate 140, and the cover plate 160 of the cylindrical secondary battery 200 may be the same as those of the cylindrical secondary battery 100 illustrated in Figures 1 to 3 . In one or more embodiments, the terminal 250 of the cylindrical secondary battery 200 may have an upper terminal 252 having the same structure as the upper terminal 152 of the terminal 150 of the cylindrical secondary battery 100 illustrated in Figures 1 to 3 , but may have a lower terminal 251 and a coupling member 253 different from those of the cylindrical secondary battery 100.

[0106] Accordingly, the description of the cylindrical secondary battery 200 will focus on the structures of the lower terminal 251 and the coupling member 253 different from those of the cylindrical secondary battery 100.

[0107] The lower terminal 251 may include a head portion 251a inside the housing 110 and a coupling portion 251b extending from the center (or substantially the center) of the head portion 251a toward the outside of the housing 110. The planar dimension of the head portion 251a may be larger than the planar dimension of the coupling portion 251b. In the lower terminal 251, the lower end of the coupling portion 251b may be connected to the top surface of the head portion 251a, and the head portion 251a and the coupling portion 251b may be integral or monolithic with each other. The lower terminal 251 may be coupled to the terminal hole 111a of the housing 110 from the inside to the outside. In one or more embodiments, a first gasket 115 may be provided between the lower terminal 251 and the housing 110. The upper end of the coupling portion 251b of the lower terminal 251 may be inserted into the coupling hole 253a of the coupling member 253 and then compression deformed (compression molded) by riveting to seal the terminal hole 110a of the housing 110. The compression deformation (molding) portion that is the end of the coupling portion 251b of the lower terminal 251 may be referred to as a deformable portion 251d.

[0108] In one or more embodiments, the coupling member 253 may be outside the housing 110. The coupling member 253 may have a flat plate shape and may be provided with a coupling hole 253a at substantially the center of the flat plate shape. The planar dimension of the coupling hole 253a of the coupling member 253 at the upper side of the coupling member 253 may be larger than the planar dimension at the lower side of the coupling member 253. The coupling member 253 may include a protrusion 253b protruding from the lower region of the coupling member 253 into the coupling hole 253a. In other words, the protrusion 253b may protrude from the lower region of the coupling hole 253a. In one or more embodiments, the coupling member 253 may be provided with a stepped portion within the coupling hole 253a. The deformable portion 251d of the lower terminal 251 may be pressed to contact the top surface of the protrusion 253b.

[0109] A welding groove 251c having a depth may be provided from substantially the center of the top surface of the coupling portion 251b of the lower terminal 251 toward the head portion 251a. The lower terminal 251 may be provided with the welding groove 251c to reduce the lower thickness 251h of the lower terminal 251. The lower thickness 251h of the lower terminal 251 may be the thickness from the bottom surface of the welding groove 251c to the bottom surface of the head portion 251a. The lower thickness 251h of the lower terminal 251 may be reduced by the welding groove 251c, and thus welding of the lower terminal 251 to the first current collector plate 130 may be performed outside the housing 110. The welding groove 251c may have an inner diameter similar to the inner diameter of the welding groove 151c at the upper side. The welding groove 251c may have an inner diameter equal to or smaller than the inner diameter at the lower side at the upper side.

[0110] The lower thickness 251h of the lower terminal 251 may be similar to the lower thickness 151h of the lower terminal 151.

[0111] The outer diameter of the connection part 251b at the area outside the housing 110 may be larger than the outer diameter of the connection part 251b at the area inside the terminal hole 111a of the housing 110. In one or more embodiments, the outer diameter of the deformable part 251d may be larger than the outer diameter of the connection part 251b.

[0112] Figure 7 An exemplary cross-sectional view of a cylindrical secondary battery according to an embodiment of the present disclosure. Figure 8 Exemplary Figure 7 magnified cross-sectional view of part C.

[0113] As Figure 7 and Figure 8 shown, the secondary battery 300 according to an embodiment may include a housing 110, an electrode assembly 120 accommodated in the housing 110, a terminal 350 connected to a terminal hole 111a provided at one end (e.g., the upper end) of the housing 110, and a cover plate 160 sealing an opening at the other end (e.g., the lower end) of the housing 110. In one or more embodiments, the cylindrical secondary battery 300 may include a first current collector plate 130 that electrically connects the first electrode plate 121 of the electrode assembly 120 to the terminal 350 and a second current collector plate 140 that connects the housing 110 to the second electrode plate 122 of the electrode assembly 120.

[0114] The housing 110, the electrode assembly 120, the first current collector plate 130, the second current collector plate 140, and the cover plate 160 of the cylindrical secondary battery 300 may be the same as those of the cylindrical secondary battery 100 exemplified in Figures 1 to 3 . In one or more embodiments, the terminal 350 of the cylindrical secondary battery 300 may have a lower terminal 351 having the same structure as the lower terminal 151 of the terminal 150 of the cylindrical secondary battery 100 exemplified in Figures 1 to 3 , but may have an upper terminal 352 different from the upper terminal of the cylindrical secondary battery 100.

[0115] Accordingly, the description of the cylindrical secondary battery 300 will focus on the structure of the upper terminal 352 different from the upper terminal of the cylindrical secondary battery 100.

[0116] The upper terminal 352 can be inserted into the welding groove 151c provided in the head 151a of the lower terminal 151. The upper terminal 352 can be filled (or substantially filled) into the welding groove 151c of the lower terminal 151. The upper terminal 352 can be inserted into the welding groove 151c of the lower terminal 151 and then fixed to the lower terminal 151 by welding on the upper side. The upper terminal 352 can have a flat top surface 352a. The outer diameter of the upper terminal 352 can correspond to the inner diameter of the welding groove 151c. The top surface 352a of the upper terminal 352 can be lower than the top surface of the head 151a of the lower terminal 151. A stepped portion can be provided between the top surface 352a of the upper terminal 352 and the top surface of the head 151 (for example, the top surface 352a of the upper terminal 352 can be recessed lower than the top surface of the head 151). The height difference between the top surface 352a of the upper terminal 352 and the top surface of the head 151 can be about (substantially) 0.05 mm to about (substantially) 0.1 mm. The height difference between the top surface 352a of the upper terminal 352 and the top surface of the head 151 can be provided such that after the upper terminal 352 and the head 151 are joined to each other by welding, the weld bead does not protrude higher than the head 151.

[0117] In one or more embodiments, the bottom surface of the upper terminal 352 can be spaced apart from the bottom surface of the welding groove 151c. In one or more embodiments, the upper terminal 352 can include a release groove 352b extending upward at a substantially central portion of the bottom surface. The release groove 352b of the upper terminal 352 can prevent contact between the upper terminal 352 and the weld bead generated in the welding groove 151c of the lower terminal 151. In one or more embodiments, the release groove 352b can prevent the upper terminal 352 from protruding upward due to the weld bead in the welding groove 151c. The top surface of the head 151a of the lower terminal 151 can be the top surface of the terminal 350. The diameter of the head 151 of the lower terminal 151 can be about (substantially) 11 mm or more and can be less than the diameter of the top surface portion 111 of the housing 110. Each of the top surface of the head 151 of the lower terminal 151 and the top surface of the upper terminal 352 can be the top surface of the terminal 350.

[0118] In one or more embodiments, the lower terminal 151 can be replaced by Figure 5 and Figure 6 the lower terminal 251 and the coupling member 253 illustrated in

[0119] The upper terminal 352 can be inserted into the welding groove 151c of the lower terminal 151 to prevent the sealing force from deteriorating due to damage that may occur during welding between the lower terminal 151 and the first current collector plate 130 and to maintain the flatness of the top surface of the terminal 150.

[0120] Figure 9Illustrate a cross-sectional view of a cylindrical secondary battery according to an embodiment. Figure 10 is Figure 9 an enlarged cross-sectional view of the terminal portion of

[0121] As Figure 9 and Figure 10 shown in

[0122] a secondary battery 400 may include a case 110, an electrode assembly 120 accommodated in the case 110, a terminal 450 coupled to a terminal hole provided in one end (e.g., the upper end) of the case 110, and a cover plate 160 sealing an opening of the other end (e.g., the lower end) of the case 110. In one or more embodiments, the cylindrical secondary battery 400 may include a first current collector plate 130 electrically connecting a first electrode plate 121 of the electrode assembly 120 to the terminal 450 and a second current collector plate 140 connecting the case 110 to a second electrode plate 122 of the electrode assembly 120.

[0122] The case 110, the electrode assembly 120, the first current collector plate 130, the second current collector plate 140, and the cover plate 160 of the cylindrical secondary battery 400 may be the same as those of the cylindrical secondary battery 100 illustrated in Figures 1 to 3 In one or more embodiments, the terminal 450 of the cylindrical secondary battery 400 may be different from the terminal of the cylindrical secondary battery 100.

[0123] Accordingly, the description of the cylindrical secondary battery 400 will focus on the structure of the terminal 450 different from the terminal of the cylindrical secondary battery 100.

[0124] The lower terminal 451 may include a head 451a inside the case 110 and a coupling portion 451b extending from the center (or substantially the center) of the head 451a toward the outside of the case 110. The planar size of the head 451a may be larger than the planar size of the coupling portion 451b. In the lower terminal 451, the lower end of the coupling portion 451b may be connected to the top surface of the head 451a, and the head 451a and the coupling portion 451b may be integral or monolithic with each other. The lower terminal 451 may be coupled to the terminal hole 111a of the case 110 in an outward direction from the inside of the case 110. In one or more embodiments, a first gasket 115 may be provided between the lower terminal 451 and the case 110. The coupling portion 451b of the lower terminal 451 may be compression deformed (compression molded) by riveting to seal the terminal hole 110a of the case 110. The compression deformed (molded) portion as the end of the coupling portion 451b of the lower terminal 451 may be referred to as a deformable portion 451d. The first gasket 115 may be provided between the deformable portion 451d and the case 110.

[0125] A welding groove 451c with a depth can be provided that extends downward from the approximate center of the top surface of the connection portion 451b of the lower terminal 451 toward the head 451a. The lower terminal 451 can be provided with the welding groove 451c to reduce the lower thickness of the lower terminal 451. The lower thickness of the lower terminal 451 can be the thickness from the bottom surface of the welding groove 451c to the bottom surface of the head 451a. The lower thickness of the lower terminal 451 can be reduced by the welding groove 451c, so that the welding of the lower terminal 451 and the first current collector plate 130 can be performed outside the housing 110. The welding groove 451c can have an inner diameter similar to that of the welding groove 151c at the upper side. The lower thickness of the lower terminal 451 can be similar to the lower thickness 151h of the lower terminal 151.

[0126] The welding groove 451c of the lower terminal 451 can have an inner diameter of approximately (roughly) 11 mm to approximately (roughly) 18 mm at the upper side. The welding groove 451c can have an inner diameter at the upper side that is equal to or greater than the inner diameter of the welding groove 451c at the lower side.

[0127] The upper terminal 452 can extend into the welding groove 451c provided in the lower terminal 451. The upper terminal 452 can fill (or substantially fill) the welding groove 451c of the lower terminal 451. The upper terminal 452 can be inserted into the welding groove 451c of the lower terminal 451 and then fixed to the lower terminal 451 by welding. The upper terminal 452 can have a flat top surface 452a.

[0128] The outer diameter of the upper terminal 452 can correspond to the inner diameter of the welding groove 451c. The top surface 452a of the upper terminal 452 can protrude higher than the deformable portion 451d of the lower terminal 451. The lower region of the upper terminal 452 inserted into the welding groove 451c can have an outer diameter larger than the outer diameter of the upper region of the upper terminal 452 protruding outside the welding groove 451c. The upper terminal 452 can have a stepped portion on the side wall. The top surface of the lower region of the upper terminal 452 can have the same surface as the top surface of the deformable portion 451d (for example, the top surface of the lower region of the upper terminal 452 and the top surface of the deformable portion 451d can be coplanar or substantially coplanar). The upper terminal 452 and the lower terminal 451 can be joined to each other by welding between the top surface of the lower region of the upper terminal 452 and the top surface of the deformable portion 451d.

[0129] A stepped portion can be provided between the top surface 452a of the upper terminal 452 and the top surface of the deformable portion 451d. The diameter of the top surface of the upper terminal 452 can be approximately (roughly) 11 mm or greater, and this diameter can be smaller than the diameter of the top surface portion 111 of the housing 110. The top surface of the upper terminal 452 can be the top surface of the terminal 450.

[0130] In one or more embodiments, the bottom surface of the upper terminal 452 may be spaced apart from the bottom surface of the welding groove 451c. In one or more embodiments, the upper terminal 452 may include a release groove 452b extending upward at a substantially center of the bottom surface. The release groove 452b of the upper terminal 452 may prevent contact between the upper terminal 452 and the weld bead formed in the welding groove 451c of the lower terminal 451. In one or more embodiments, the release groove 452b may prevent the upper terminal 452 from protruding upward due to the weld bead in the welding groove 451c.

[0131] As Figure 11A and Figure 11B shown, the upper terminal 452 may further include a flange 452c that covers at least a portion of the top surface of the deformable portion 451c of the lower terminal 451. In one or more embodiments, the upper terminal 452 may extend such that the flange 452c covers the deformable portion 451c of the lower terminal 451. As Figure 11A shown, the flange 452c may extend obliquely from the top surface of the upper terminal 452. In one or more embodiments, the flange 452c may have an inclined top surface and a bottom surface. In one or more embodiments, in cross-section, the flange 452c may have an inclined surface where the angle in contact with the top surface of the upper terminal 452 is an obtuse angle and the angle in contact with the bottom surface of the flange 452c is an acute angle. The upper terminal 452 may be coupled to the lower terminal 451 by welding at the upper side of the flange 452c.

[0132] In one or more embodiments, as Figure 11B shown, the flange 452c may extend to be inclined below the top surface of the upper terminal 452. In one or more embodiments, as Figure 3 shown, the flange 452c may be stepped in the edge region. In one or more embodiments, the thickness of the flange 452c may be about (substantially) 0.5 mm to about (substantially) 1.5 mm.

[0133] In a cylindrical secondary battery according to various embodiments, the terminal and the current collector plate may be welded outside the case through a welding groove provided in the lower terminal to prevent any welding impurities from being generated inside the case and / or to prevent the electrode assembly from being damaged by welding heat.

[0134] In a cylindrical secondary battery according to various embodiments, since the current collector plate and the terminal are welded inside the welding groove of the terminal, the weld bead may be inside the terminal groove to prevent the terminal from protruding due to the weld bead.

[0135] In a cylindrical secondary battery according to various embodiments, a welding groove provided in a lower terminal may be filled (or substantially filled) by an upper terminal such that a top surface of the terminal may have a substantially flat top surface. Thus, if a plurality of secondary batteries are connected together by a bus bar, it is possible to prevent welding defects due to misalignment (which may occur due to the welding groove) or an increase in resistance due to insufficient welding area.

[0136] The above embodiments are merely embodiments of the cylindrical secondary battery, and thus the present invention is not limited to the foregoing embodiments, and those of ordinary skill in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention defined by the claims.

Claims

1. A cylindrical secondary battery, comprising: An electrode assembly, including a first electrode plate, a separator, and a second electrode plate; A housing that houses the electrode assembly, the housing including an open lower end that is electrically connected to the second electrode plate; A first current collector plate, between the top surface of the electrode assembly and the housing, the first current collector plate being electrically connected to the first electrode plate; A terminal that passes through a terminal hole in the top surface portion of the housing, the terminal including a lower end that is electrically and mechanically coupled to the top surface of the first current collector plate; And A cover plate configured to seal the lower end of the housing, Wherein the terminal includes: A lower terminal including a welding groove having a depth starting from the top surface of the lower terminal in a downward direction; And An upper terminal within the welding groove of the lower terminal.

2. The cylindrical secondary battery according to claim 1, wherein the lower terminal includes: A head on the upper side of the top surface portion of the housing; And A coupling portion extending from the central portion of the head toward the interior of the housing, the coupling portion and the head being integral.

3. The cylindrical secondary battery according to claim 1, wherein the top surface of the first current collector plate is coupled to the bottom surface of the lower terminal through a weld bead in the welding groove.

4. The cylindrical secondary battery according to claim 2, wherein the welding groove extends through the central portion of the head and extends downward from the upper portion of the coupling portion.

5. The cylindrical secondary battery according to claim 2, wherein the planar dimension of the head is larger than the planar dimension of the coupling portion.

6. The cylindrical secondary battery according to claim 2, wherein the planar dimension of the lower portion of the coupling portion is larger than the planar dimension of the terminal hole of the housing.

7. The cylindrical secondary battery according to claim 1, wherein the lower terminal includes: A head on the lower side of the top surface portion of the housing; And A coupling portion extending from the central portion of the head toward the exterior of the housing, the coupling portion being integral with the head.

8. The cylindrical secondary battery according to claim 7, wherein the welding groove extends downward from the central portion of the top surface of the coupling portion.

9. The cylindrical secondary battery according to claim 7, further comprising: A coupling member on the upper side of the top surface portion of the housing and coupled to the coupling portion.

10. The cylindrical secondary battery according to claim 9, wherein the coupling member includes a coupling hole passing through the center of the coupling member, and Wherein the coupling portion of the lower terminal includes a deformable portion that passes through the coupling hole and is riveted to the coupling member.

11. The cylindrical secondary battery according to claim 10, wherein the coupling member further includes a protrusion protruding from the lower region of the coupling hole, and wherein a stepped portion is in the coupling hole.

12. The cylindrical secondary battery according to claim 11, wherein the deformable portion of the lower terminal is above the protrusion of the coupling member.

13. The cylindrical secondary battery according to claim 1, wherein the upper terminal includes: A body within the welding groove; And A flange that extends from an upper portion of the main body and covers the top surface of the lower terminal.

14. The cylindrical secondary battery according to claim 13, wherein a bottom surface of the main body is spaced apart from a bottom surface of the welding groove.

15. The cylindrical secondary battery according to claim 13, wherein a thickness of an edge region of the flange is less than a thickness of other regions of the flange.

16. The cylindrical secondary battery according to claim 15, wherein the edge region of the flange includes a stepped portion or an inclined surface.

17. The cylindrical secondary battery according to claim 13, wherein the main body has an outer diameter smaller than an inner diameter of the welding groove.

18. The cylindrical secondary battery according to claim 13, further comprising an anisotropic conductive material between a bottom surface of the flange and the top surface of the lower terminal.

19. The cylindrical secondary battery according to claim 1, wherein a top surface of the upper terminal protrudes further upward than the top surface of the lower terminal.

20. The cylindrical secondary battery according to claim 19, wherein an outer diameter of a lower region of the upper terminal in the welding groove is greater than an outer diameter of an upper region of the upper terminal outside the welding groove.

21. The cylindrical secondary battery according to claim 19, wherein the upper terminal includes a flange extending along the top surface of the lower terminal.

22. The cylindrical secondary battery according to claim 21, wherein the flange includes a stepped portion or an inclined surface.

23. The cylindrical secondary battery according to claim 1, wherein a top surface of the upper terminal is lower than the top surface of the lower terminal.

24. The cylindrical secondary battery according to claim 1, wherein the upper terminal includes a release groove extending upward from a bottom surface of the upper terminal.

25. The cylindrical secondary battery according to claim 1, wherein the upper terminal and the lower terminal are welded to each other.

26. The cylindrical secondary battery according to claim 1, wherein a top surface of the terminal has a diameter of 11 mm or more, and wherein the diameter of the top surface of the terminal is less than a diameter of a top surface portion of the housing.

27. The cylindrical secondary battery according to claim 1, wherein an upper inner diameter of the welding groove is greater than a lower inner diameter of the welding groove.

28. The cylindrical secondary battery according to claim 1, further comprising a first gasket between the terminal and the housing.

29. The cylindrical secondary battery according to claim 1, wherein the housing includes: A crimping portion that is recessed into the housing above the cover plate; And A crimping portion at a lower portion of the housing, wherein the crimping portion is bent inward and fixes the cover plate.

30. The cylindrical secondary battery according to claim 29, further comprising: A second gasket between the cover plate and the crimping portion and between the cover plate and the crimping portion, wherein the cover plate is non-polar.

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