Secondary battery

Abstract

The present invention relates to a cylindrical secondary battery having a folded portion provided in an opening of a case to prevent a welding portion from breaking due to swelling of the case during welding to a cap plate. As an example, disclosed in the present invention is a secondary battery comprising: an electrode assembly; a case that accommodates the electrode assembly through a space of which a portion is open; and a cap plate that seals the space of the case, wherein a folded portion is formed in the case by being folded along at least one area, and the cap plate may be coupled to the folded portion.

Description

secondary battery

[0001] Various embodiments of the present invention relate to secondary batteries.

[0002] Secondary batteries, unlike primary batteries that cannot be recharged, are batteries that can be charged and discharged. Low-capacity batteries in which one battery cell is packaged in a pack form are used in small portable electronic devices such as mobile phones and camcorders, and large-capacity batteries in which dozens of battery packs are connected are widely used as power sources for driving motors in hybrid and electric vehicles.

[0003] A secondary battery can be constructed by housing an electrode assembly formed by interposing a separator between a positive and negative electrode plate and an electrolyte in a case, and installing a cap plate in the case. Here, the case and the cap plate are physically sealed from the inside and outside through a process such as crimping or welding.

[0004] Meanwhile, when charging and discharging a secondary battery, the chemical reaction of the positive / negative active materials causes reversible or irreversible expansion in the thickness direction of the electrode plates, and as the charge / discharge reaction cycle of the secondary battery progresses, the amount of expansion increases, causing the thickness of the electrode assembly to increase in the stacking direction of the electrode plates. At this time, the gap between the electrode assembly and the case may decrease, and when the gap disappears, a swelling phenomenon may occur in which the case is pushed out and swells. When this swelling phenomenon occurs, there is a problem in that the joint between the case and the cap plate, which have weak structural strength, is broken.

[0005] The above-described information disclosed in the background technology of this invention is only intended to improve understanding of the background of the present invention, and therefore may include information that does not constitute prior art.

[0006] The present invention provides a secondary battery having a bending portion provided in an opening of a case to prevent breakage of a welded portion due to swelling of the case when welding to a cap plate.

[0007] In addition, the present invention provides a secondary battery capable of increasing the strength of the opening of the case in proportion to the thickness and length of the welded portion by folding a bend formed in the opening of the case and then welding it with a cap plate.

[0008] In addition, the present invention provides a secondary battery capable of securing a sufficient welding area between the opening of the case and the cap plate compared to the conventional one.

[0009] A secondary battery according to an embodiment of the present invention comprises: an electrode assembly; a case that accommodates the electrode assembly through a space that is partially open; and a cap plate that seals the space of the case, wherein the case has a folded portion formed by folding along at least one area, and the cap plate can be joined to the folded portion.

[0010] The above-mentioned bending portion can be bent toward the inside or outside of the case.

[0011] The above-mentioned bending portion can be formed by bending along at least one side of the case.

[0012] The above-mentioned folded portion may be formed by folding to cover a portion of an open space of the case.

[0013] The above-mentioned bending portion can be welded to the cap plate.

[0014] The above cap plate can be formed to extend to cover the area of ​​the folded portion bent toward the outside of the case.

[0015] The above-mentioned bending portion can be bent at least once toward the inside of the case.

[0016] The above-mentioned bending portion may include a first bending portion bent in a downward direction inside the case and a second bending portion extending from the first bending portion in a horizontal direction inside the case.

[0017] Both sides of the cap plate can be formed to correspond to the shapes of the first bend portion and the second bend portion.

[0018] The thickness of the cap plate may be formed to be equal to or greater than the bending height bent in the inner lower direction of the case at the first bending portion.

[0019] The above case is formed in a pipe shape with one end open, and the bending portion can be formed by folding along the circumference of the open end of the pipe shape.

[0020] The above-mentioned folded portion may be formed by cutting at least in one area and overlapping in a folded structure.

[0021] Additionally, the bending portion may be formed on at least one of a pair of long or short sides facing each other of the case.

[0022] Additionally, the width of the bending portion may be set smaller than the width of the long side or short side of the case in which the bending portion is formed.

[0023] A secondary battery according to one embodiment of the present invention has a bending portion provided in the opening of the case to prevent breakage of the welded portion due to swelling of the case when welding to the cap plate.

[0024] In addition, one embodiment of the present invention can increase the strength of the opening of the case in proportion to the thickness and length of the welded portion by folding the bend formed in the opening of the case and then welding it with the cap plate.

[0025] In addition, one embodiment of the present invention can secure a sufficient welding area between the opening of the case and the cap plate compared to the conventional one.

[0026] FIG. 1A is a perspective view illustrating a secondary battery according to one embodiment of the present invention.

[0027] Fig. 1b is a cross-sectional view taken along line A-A' of Fig. 1a.

[0028] Figure 2 is a perspective view showing the case of the secondary battery illustrated in Figure 1a.

[0029] Figure 3 is a perspective view showing the state before the case and cap plate of the secondary battery shown in Figure 1a are combined.

[0030] FIGS. 4A to 4D are perspective views illustrating various embodiments of the case of the secondary battery illustrated in FIG. 1A.

[0031] FIG. 5 is a perspective view illustrating a cylindrical secondary battery according to various embodiments of the present invention.

[0032] Figure 6 is a cross-sectional view taken along line BB' of Figure 5.

[0033] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0034] The embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. The following embodiments may be modified in various ways, and the scope of the present invention is not limited to the embodiments described below. Rather, these embodiments are provided to more faithfully and completely explain the present disclosure and fully convey the spirit of the present invention to those skilled in the art.

[0035] In addition, in the drawings below, the thickness and size of each layer are exaggerated for convenience and clarity of explanation, and the same reference numerals in the drawings indicate the same elements. As used herein, the term "and / or" includes any one and all combinations of one or more of the listed items. In addition, the meaning of "connected" in this specification means not only when member A and member B are directly connected, but also when member C is interposed between member A and member B, so that member A and member B are indirectly connected.

[0036] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the present invention. As used herein, the singular forms "a," "an," and "the" include plural forms unless the context clearly dictates otherwise. Furthermore, when used herein, the words "comprise" and / or "comprising" specify the presence of stated features, numbers, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, elements, components, and / or groups thereof.

[0037] Although the terms first, second, etc. are used herein to describe various elements, components, regions, layers, and / or portions, it is to be understood that these elements, components, regions, layers, and / or portions are not limited by these terms. These terms are only used to distinguish one element, component, region, layer, or portion from another. Accordingly, a first element, component, region, layer, or portion described below may refer to a second element, component, region, layer, or portion without departing from the teachings of the present invention.

[0038] Spatial terms such as "beneath," "below," "lower," "above," and "upper" are used to facilitate understanding of one element or feature depicted in the drawings relative to another element or feature. These spatial terms are intended to facilitate understanding of the present invention in various process states or usage states and are not intended to limit the present invention. For example, if an element or feature in a drawing is flipped, an element described as "beneath" or "below" becomes "above" or "above." Therefore, "beneath" is a concept encompassing "top" or "below."

[0039] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings so that a person having ordinary skill in the art to which the present invention pertains can easily carry out the present invention.

[0040] Here, parts with similar configurations and operations are designated by the same drawing reference numerals throughout the specification. Furthermore, when a part is said to be electrically coupled to another part, this includes not only direct connection but also connection with another element intervening between them.

[0041] Referring to Fig. 1a, a perspective view of a secondary battery according to one embodiment of the present invention is illustrated. Referring to Fig. 1b, a cross-sectional view taken along line A-A' of Fig. 1a is illustrated.

[0042] As illustrated in FIGS. 1A and 1B, a secondary battery (100) according to one embodiment of the present invention includes an electrode assembly (110), a first current collector (120) electrically connected to one side of the electrode assembly (e.g., a first electrode tab), a first terminal portion (130) electrically connected to the first current collector (120), a second current collector (121) electrically connected to the other side of the electrode assembly (e.g., a second electrode tab), a second terminal portion (150) electrically connected to the second current collector (121), a case (160) that accommodates the electrode assembly, and a cap assembly (170) coupled to an opening of the case (160).

[0043] The secondary battery (100) according to an embodiment of the present invention is described as a square lithium ion secondary battery as an example. However, the present invention is not limited thereto, and the present invention can be applied to various types of batteries, such as lithium polymer batteries.

[0044] The electrode assembly may be formed of a first electrode plate, a second electrode plate, and a separator interposed between the first and second electrode plates. The electrode assembly may be formed by winding or overlapping a laminate of the first electrode plate, the separator, and the second electrode plate, which are formed in a thin plate shape or a film shape. Here, the first electrode plate may operate as an anode and the second electrode plate may operate as a cathode, or conversely, the first electrode plate may operate as a cathode and the second electrode plate may operate as an anode. However, for the convenience of explanation, the present invention will be described by way of example in which the first electrode plate operates as an anode and the second electrode plate operates as a cathode.

[0045] The first electrode plate is formed by applying a first electrode active material such as a transition metal oxide to a first electrode current collector formed of a metal foil such as aluminum or an aluminum alloy, and may include a first electrode tab (or first uncoated portion) which is a region where the first electrode active material is not applied. The first electrode tab serves as a path for current flow between the first electrode plate and the first current collector (120).

[0046] The second electrode plate is formed by applying a second electrode active material such as a transition metal oxide to a second electrode current collector formed of a metal foil such as copper or nickel, and may include a second electrode tab (or second uncoated region) which is an area where the second electrode active material is not applied. The second electrode tab serves as a passage for current flow between the second electrode plate and the second current collector (121).

[0047] The separator is located between the first electrode plate and the second electrode plate to prevent short circuits and enable the movement of lithium ions, and is made of polyethylene or a composite film of polyethylene and polypropylene.

[0048] Such electrode assemblies are housed in a case (160) together with, for example but not limited to, an electrolyte. The electrolyte may be composed of a lithium salt such as LiPF6 or LiBF4 in an organic solvent such as EC, PC, DEC, EMC, or DMC. In addition, the electrolyte may be liquid, solid, or gel-like.

[0049] The first terminal portion (130) is electrically connected to the first electrode tab of the electrode assembly through the first collector portion (120). Here, the first terminal portion (130) may include a first terminal pillar (131) penetrating the cap plate (171) of the cap assembly (170), and the first collector portion (120) is electrically connected to the first terminal pillar (131) inside the case (160). Furthermore, the first electrode tab of the electrode assembly is electrically connected to the first collector portion (120). In addition, the first terminal portion (130) includes a first terminal plate (132) (for example, made of aluminum) positioned on the cap plate (171) and coupled to the first terminal pillar (131). Here, the first terminal pillar (131), the first terminal plate (132), and the first collector portion (120) are electrically insulated from the cap plate (171). Additionally, the cap plate (171) and the case (160) may have the same polarity as the first terminal portion (130). That is, the secondary battery (100) may be positively charged at the case (160) and the cap plate (171).

[0050] In addition, this first terminal portion (130) is only an example for understanding the embodiment of the present invention, and those skilled in the art will understand that the first terminal portion (130) can be modified into various shapes / structures.

[0051] The second terminal portion (150) is electrically connected to the second electrode tab of the electrode assembly through the second current collector portion (121). Here, the second terminal portion (150) may include a second terminal pillar (151) penetrating the cap plate (171) of the cap assembly (170), and the second current collector portion (121) is electrically connected to the second terminal pillar (151) on the inside of the case (160). Furthermore, the second electrode tab of the electrode assembly is electrically connected to the second current collector portion (121). In addition, the second terminal portion (150) includes a second terminal plate (152) (for example, made of aluminum) positioned on the cap plate (171) and coupled to the second terminal pillar (151). Here, the second terminal pillar (151), the second terminal plate (152), and the second current collector portion (121) are electrically insulated from the cap plate (171).

[0052] In addition, this second terminal portion (150) is only an example for understanding the embodiment of the present invention, and those skilled in the art will understand that the second terminal portion (150) can be modified into various shapes / structures.

[0053] The case (160) may be in the shape of a roughly rectangular parallelepiped with an opening formed at the top. An electrode assembly may be inserted into the interior of the case (160) through this opening. In addition, a first current collector (120) and a second current collector (121) may also be positioned inside the case (160). Referring to FIG. 2, the case (160) may include a rectangular bottom portion (161) having long sides and short sides, long side portions (162, 163) that are bent and extended from each long side of the bottom portion (161) toward the cap assembly (170), and short side portions (164, 165) that extend from each short side and long side portion (162, 163) of the bottom portion (161).

[0054] The cap assembly (170) may first include a cap plate (171) in the form of a flat plate. That is, the cap plate (171) is made of a thin plate material and is coupled to an opening of the case (160) to seal the opening. In addition, the cap plate (171) includes an electrolyte injection portion for injecting electrolyte into the interior of the sealed case (160), and the electrolyte injection portion is sealed by a sealing plug after the electrolyte is injected. In addition, the cap plate (171) includes a vent hole, and a vent plate (173) is installed in the vent hole to be ruptured when the internal pressure of the sealed case (160) exceeds a set pressure.

[0055] The cap plate (171) is welded to the opening of the case (160) to seal the opening.

[0056] Since such a secondary battery (100) has both a cathode and anode on the upper surface, when a plurality of cylindrical secondary batteries (100) are electrically connected via a bus bar, the connection only needs to be made on the upper surface, so the bus bar connection structure can be simplified.

[0057] FIG. 2 is a perspective view showing the case of the secondary battery shown in FIG. 1a, and FIG. 3 is a perspective view showing the state before the case and cap plate of the secondary battery shown in FIG. 1a are combined.

[0058] In the present invention, in order to secure a welding area when welding the cap plate (171) and the case (160), a folded portion is formed by folding along at least one area of ​​the case (160). First, the folded portion may be folded toward the inside or outside of the case (160). This folded portion may be formed by folding along at least one side of the case (160). For example, the folded portion may be fixed to a bending machine or a press mold and then folded into a predetermined shape.

[0059] For example, as illustrated in FIGS. 2 and 3, the bent portions (162a, 163a) may be formed to extend upwardly from the long sides (162, 163) of the case (160) and be bent inwardly of the case (160), and the upper surfaces of the bent portions (162a, 163a) may be welded to the cap plate (171). In addition, the bent portions (162a, 163a) may be formed to extend from the long sides (162, 163) of the case (160), and the extended area may be formed by folding toward the outside of the case (160). Here, the cap plate (171) may be formed to extend so as to cover the area of ​​the bent portions (162a, 163a) bent toward the outside of the case (160) for welding with the bent portions (162a, 163a). Through this, it is possible to prevent breakage of the welding area due to swelling of the case (160). At this time, the bent portions (162a, 163a) are shown as being formed on the long side (162) of the case (160), and the width of the bent portions (162a, 163a) may be formed to be somewhat smaller than the width of the long side (162). Therefore, the bending operation of the bent portions (162a, 163a) may not be hindered by the long side (162).

[0060] FIGS. 4A to 4D are perspective views illustrating various embodiments of the case of the secondary battery illustrated in FIG. 1A.

[0061] As illustrated in FIG. 4a, the folded portions (164a, 165a) may be formed by being folded toward the inside of the case (160) so as to cover a portion of an open space of the case (160). That is, the folded portions (164a, 165a) are formed by extending from the short sides (164, 165) of the case (160), and the extended area is formed by being folded toward the inside of the case (160).

[0062] As illustrated in FIGS. 4b to 4c, the folded portions (164b, 165b) (164c, 165c) may be formed by being folded toward the outside of the case (160). That is, the folded portions (164b, 165b) (164c, 165c) are formed by extending from the short sides (164, 165) of the case (160), and the extended area is formed by being folded toward the outside of the case (160). Here, the cap plate (171) may be formed to extend so as to cover the area of ​​the folded portions (164b, 165b) (164c, 165c) that are folded toward the outside of the case (160) for welding with the folded portions (164b, 165b) (164c, 165c). In addition, the bent portions (164b, 165b) (164c, 165c) may be formed by extending from the short side portions (164, 165) of the case (160), and the extended area may be formed by folding toward the inside of the case (160).

[0063] As illustrated in FIG. 4d, the bent portions (164d, 165d) are formed to extend from the short sides (164, 165) of the case, and the extended areas may be bent at least once toward the inside of the case (160). These bent portions (164d, 165d) may include a first bent portion (164d1) bent toward the inner lower side of the case (160) and a second bent portion (164d2) extending from the first bent portion (164d1) toward the inner horizontal direction of the case (160). Here, both sides of the cap plate (171) may be formed to correspond to the shapes of the first bent portion (164d1) and the second bent portion (164d2) for welding with the bent portions (164d, 165d). Additionally, the thickness of the cap plate (171) can be formed to be equal to or greater than the bending height (H) bent in the inner lower direction of the case (160) at the first bending portion (164d1).

[0064] In this way, one embodiment of the present invention can secure a sufficient welding area between the opening of the case (160) and the cap plate (171) compared to the past by folding the bend formed in the opening of the case (160) and then welding it with the cap plate (171), and can increase the strength of the opening of the case (160) in proportion to the thickness and length of the welding portion.

[0065] FIG. 5 is a perspective view illustrating a cylindrical secondary battery according to various embodiments of the present invention, and FIG. 6 is a cross-sectional view illustrating a cross-section taken along line A-A' of the cylindrical secondary battery illustrated in FIG. 5.

[0066] As illustrated in FIGS. 5 and 6, a cylindrical secondary battery (200) according to various embodiments of the present invention may include a cylindrical case (210), an electrode assembly (220) housed inside the cylindrical case (210), a rivet terminal (250) coupled to a terminal hole provided at one end of the cylindrical case (210), and a cap plate (260) sealing an opening at the other end of the cylindrical case (210).

[0067] A cylindrical case (210) includes a circular upper surface (211), a side surface (212) extending downward from an edge of the upper surface (211) by a predetermined length, and a folded portion (213) extending inward from an end of the side surface (212) by a predetermined length and being folded. The upper surface (211), the side surface (212), and the folded portion (213) of the cylindrical case (210) may be formed as an integral body.

[0068] The circular upper surface (211) may have a flat circular plate shape and may have a terminal hole (211a) penetrating through the center. The upper surface (211) may be coupled by inserting a rivet terminal (250) into the terminal hole (211a). A first gasket (211b) for sealing and electrical insulation may be further interposed between the terminal hole (211a) and the rivet terminal (250). The first gasket (211b) may block contact between the rivet terminal (250) and the cylindrical case (210), thereby electrically isolating them. The terminal hole (211a) of the upper surface (211) of the cylindrical case (210) may be sealed by the first gasket (211b). The first gasket (211b) can be formed of a resin material such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), etc.

[0069] In addition, the bending portion (213) is formed by bending a certain length inwardly of the cylindrical case (210). At this time, the bending portion (213) can be formed by bending only a certain length to form a space into which the electrode assembly (220) can be inserted. The end of the bending portion (213) is welded to a cap plate (260). In addition, a cut portion can be formed in a certain area of ​​the bending portion of the bending portion in order to facilitate bending and prevent wrinkles from forming during subsequent sealing.

[0070] The cylindrical secondary battery (200) has an open bottom of a cylindrical case (210) during the manufacturing process. Therefore, the cylindrical secondary battery (200) can be inserted with an electrolyte through the open bottom of the cylindrical case (210) during the manufacturing process. At this time, the electrolyte and the electrode assembly (220) can be inserted into the cylindrical case (210) with the open bottom facing upward. After the electrolyte and the electrode assembly (220) are inserted into the cylindrical case (210), a cap plate (260) can be coupled to the open bottom to seal the inside of the cylindrical case (210). Here, the electrolyte serves to enable lithium ions to move between the positive electrode plate (221) and the negative electrode plate (222) constituting the electrode assembly (220). Such electrolytes may be non-aqueous organic electrolytes, which are mixtures of lithium salts and high-purity organic solvents. Furthermore, the electrolytes may be polymers using high-molecular-weight electrolytes or solid electrolytes, and the type of electrolyte is not limited herein.

[0071] The cylindrical case (210) may be formed of steel, steel alloy, aluminum, aluminum alloy or an equivalent thereof, but the material is not limited thereto.

[0072] The electrode assembly (220) includes a positive electrode plate (221) coated with a positive electrode active material, a negative electrode plate (222) coated with a negative electrode active material, and a separator (223) interposed between the positive electrode plate (221) and the negative electrode plate (222) to prevent a short circuit between the positive electrode plate (221) and the negative electrode plate (222) and to allow only the movement of lithium ions. The electrode assembly (220) is formed by stacking the positive electrode plate (221), the negative electrode plate (222), and the separator (223), and then being wound from the winding end to form a roughly cylindrical shape. In addition, the electrode assembly (220) may have a positive electrode non-coated portion protruding upward from the positive electrode plate (221), and a negative electrode non-coated portion protruding downward from the negative electrode plate (222).

[0073] The positive electrode plate (221) is a plate-shaped metal foil made of aluminum (Al), and at least one surface of the positive electrode current collector plate is coated with a positive electrode active material made of a transition metal oxide. In addition, the positive electrode plate (221) may have a positive electrode non-coated portion on the upper portion where the positive electrode active material is not coated. Such a positive electrode non-coated portion may protrude upward from the electrode assembly (220). That is, the positive electrode non-coated portion of the positive electrode plate (221) may protrude further upward than the negative electrode plate (222) and the separator (223).

[0074] The negative electrode plate (222) is a plate-shaped metal foil made of copper (Cu) or nickel (Ni), and at least one surface of the negative electrode current collector plate is coated with a negative electrode active material such as graphite or carbon. In addition, the negative electrode plate (222) may have a negative electrode non-coated portion on the lower portion where the negative electrode active material is not coated. Such a negative electrode non-coated portion may protrude downward from the electrode assembly (220). That is, the negative electrode non-coated portion of the negative electrode plate (222) may protrude further downward than the positive electrode plate (221) and the separator (223).

[0075] The separator (223) may be polyethylene (PE) or polypropylene (PP), but is not limited thereto in the present invention. The separator can prevent electrical shorts between the positive electrode plate (221) and the negative electrode plate (222) and only allow the movement of lithium ions.

[0076] The positive electrode collector plate (230) may be a circular metal plate having a shape corresponding to the upper surface of the electrode assembly (220). The planar size of the positive electrode collector plate (230) may be equal to or smaller than the size of the upper surface of the electrode assembly (220). The positive electrode collector plate (230) may be made of aluminum (Al). The positive electrode collector plate (230) may be fixed and electrically connected to the positive electrode plate (221) exposed to the upper portion of the electrode assembly (220) by welding while the lower surface thereof is in contact with the upper surface of the electrode assembly (220). The positive electrode collector plate (230) may be fixed and electrically connected to the rivet terminal (250) by welding while the upper surface thereof is in contact with the lower surface of the rivet terminal (250). The positive electrode collector plate (230) serves as a passage for current flow between the positive electrode plate (221) of the electrode assembly (220) and the rivet terminal (250).

[0077] The negative electrode collector plate (240) has a circular flat plate shape to correspond to the lower surface of the electrode assembly (220). The upper surface of the negative electrode collector plate (240) can be in contact with the lower surface of the electrode assembly (220). The upper surface of the negative electrode collector plate (240) can be fixed and electrically connected to the negative electrode plate (222) exposed to the lower portion of the electrode assembly (220) by welding while in contact with the lower surface of the electrode assembly (220). The negative electrode collector plate (240) can be fixed and electrically connected to the cylindrical case (210) by welding while the edge is in contact with the inner surface of the can (212). Here, the inner surface can be the inner surface of the cylindrical case (210). Therefore, the negative electrode collector plate (240) becomes a current flow path between the negative electrode plate (222) of the electrode assembly (220) and the cylindrical case (210).

[0078] The rivet terminal (250) can be inserted into a terminal hole (211a) provided on the upper surface (211) of the cylindrical case (210) and be electrically connected to the positive electrode collector plate (230). The rivet terminal (250) can be made of the same or similar material as the positive electrode collector plate (230) and the positive electrode plate (221). The diameter of the portion of the rivet terminal (250) exposed to the upper portion of the cylindrical case (210) and the diameter located inside the cylindrical case (210) can be larger than the diameter located in the terminal hole (211a). For convenience, the portion of the rivet terminal (250) exposed to the upper portion of the cylindrical case (210) is referred to as the upper portion, and the portion located inside the cylindrical case (210) and facing the electrode assembly (220) is referred to as the lower portion of the rivet terminal (250). The rivet terminal (250) can be joined from the bottom to the top in the terminal hole (211a) of the upper surface (211) of the cylindrical case (210), and then the upper end can be compressed (compressively molded) by a processing method such as pressing or spinning to be tightly attached to the upper surface (211). At this time, a first gasket (211b) is interposed between the rivet terminal (250) and the terminal hole (211a), so as to electrically insulate and seal the rivet terminal (250) and the cylindrical case (210). The rivet terminal (250) can be electrically connected to the positive electrode plate (221) of the electrode assembly (220) through the positive electrode collector plate (230).

[0079] The cap plate (260) is a circular metal plate and can be welded to the lower surface of the folded portion (213) of the cylindrical case (210). In this way, by welding the folded portion (213) of the cylindrical case (210) and the cap plate (260), a welding area between the opening of the cylindrical case (210) and the cap plate (260) can be secured sufficiently compared to the past, and the strength of the opening of the cylindrical case (210) can be increased in proportion to the thickness and length of the welding area.

[0080] Of course, the cap plate (260) may be prevented from being electrically connected to the cylindrical case (210) by being coupled with the second gasket in the folded portion (213) of the cylindrical case (210). Accordingly, the cap plate (260) is not electrically connected to the positive or negative electrode of the electrode assembly (220), and thus may not have a separate electrical polarity. The second gasket may be formed of a resin material such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), or the like. This second gasket may pressurize and seal the space between the cap plate (260) and the cylindrical case (210), and may prevent the cap plate (260) from being separated from the cylindrical case (210).

[0081] The cap plate (260) can be welded to the bending portion (213) of the cylindrical case (210) to seal the inside of the cylindrical case (210). The cap plate (260) can have a notch formed so that it can be opened at a set pressure. When the internal pressure of the cylindrical case (210) becomes higher than the rupture pressure, the notch can be ruptured to prevent the cylindrical secondary battery (200) from exploding. That is, when excessive internal pressure occurs inside the cylindrical case (210), the notch can be ruptured to discharge the excessive internal pressure. The notch of the cap plate (260) can be formed to be spaced apart from the center and to have a ring shape on a plane. As another example, the notch can be formed to have a plurality of patterns, and the shape of the notch is not limited in the present invention.

[0082] The above description is only one embodiment for implementing the secondary battery according to the present invention, and the present invention is not limited to the above-described embodiment, and as claimed in the following claims, it will be understood that the technical spirit of the present invention exists to the extent that various modifications can be implemented by anyone having ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention.

Claims

1. Electrode assembly; a case accommodating the electrode assembly through a partially open space; and Includes a cap plate that seals the space of the above case, A secondary battery in which a folded portion is formed by folding along at least one area of ​​the case, and the cap plate is joined to the folded portion.

2. In paragraph 1, A secondary battery in which the above-mentioned bending portion is bent toward the inside or outside of the case.

3. In paragraph 1, A secondary battery in which the above-mentioned bending portion is formed by bending along at least one side of the case.

4. In paragraph 2, A secondary battery formed by folding the above-mentioned folded portion to cover a portion of an open space of the above-mentioned case.

5. In paragraph 1, A secondary battery in which the above-mentioned bending portion is welded to the above-mentioned cap plate.

6. In paragraph 2, The above cap plate is a secondary battery formed to extend to cover the area of ​​the folded portion bent toward the outside of the case.

7. In paragraph 2, A cylindrical secondary battery in which the above-mentioned bending portion is bent at least once toward the inside of the case.

8. In paragraph 2, A secondary battery, wherein the above-mentioned bending portion includes a first bending portion bent in the inner downward direction of the case and a second bending portion extending from the first bending portion in the inner horizontal direction of the case.

9. In paragraph 8, A secondary battery in which both sides of the cap plate are formed to correspond to the shapes of the first bending portion and the second bending portion.

10. In paragraph 8, A secondary battery in which the thickness of the cap plate is formed to be equal to or greater than the bending height bent in the inner lower direction of the case at the first bending portion.

11. In paragraph 1, The above case is formed in the shape of a pipe with one end open, A secondary battery formed by folding the above-mentioned folded portion along the circumference of the open end of the above-mentioned pipe shape.

12. In paragraph 11, A secondary battery in which the above-mentioned folded portion is cut in at least one area and is formed by overlapping in a folded structure.

13. In paragraph 1, A secondary battery in which the above-mentioned bending portion is formed on at least one of a pair of long sides or short sides facing each other of the case.

14. In paragraph 13, A secondary battery in which the width of the above-mentioned bending portion is set smaller than the width of the long side or short side of the case in which the above-mentioned bending portion is formed.

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