Cylindrical secondary battery

Abstract

The present invention relates to a secondary battery, and the problem to be solved is to provide a secondary battery that enables high capacity by increasing the internal space of the case through the integration of a current collector and a vent plate, and enables low cost by reducing material and processing costs. To this end, the present invention provides a secondary battery comprising: an electrode assembly including a first electrode plate, a separator, and a second electrode plate; a case accommodating the electrode assembly; a rivet terminal penetrating the case and electrically connected to the first electrode plate of the electrode assembly; and a vent plate that seals the case and is directly electrically connected to the second electrode plate of the electrode assembly.

Description

Technology Field

[0001] The present invention relates to a cylindrical secondary battery. Background Technology

[0002] Rechargeable batteries are power storage systems that provide excellent energy density by converting electrical energy into the form of chemical energy for storage. Unlike primary batteries, which are non-rechargeable, rechargeable batteries are widely used in IT devices such as smartphones, cellular phones, laptops, and tablet PCs. Recently, interest in electric vehicles has increased due to the need to prevent environmental pollution, leading to the adoption of high-capacity rechargeable batteries in these vehicles. These rechargeable batteries require characteristics such as high density, high output, and stability.

[0003] The information described above disclosed in the background technology of this invention is intended only to enhance understanding of the background of the present invention and may therefore include information that does not constitute prior art. The problem to be solved

[0004] The present invention provides a secondary battery that integrates a current collector (or current collector plate) and a vent plate, enabling high capacity by increasing the internal space of the case and low cost by reducing material and processing costs.

[0005] The present invention provides a secondary battery with improved weldability between an electrode assembly and a vent plate by welding the electrode assembly and a vent plate together with a laser beam to electrically and mechanically combine them, wherein the vent plate is provided with a welding line extending from the winding leading edge of the electrode assembly to the winding end and a welding line extending from the winding end of the electrode assembly to the winding leading edge.

[0006] The present invention provides a secondary battery with improved sealing power of the case by mutually joining a vent plate and a case using a mechanical joining structure, adopting a crimping method, a curling method, and / or a welding method for the mechanical joining structure. means of solving the problem

[0007] A cylindrical secondary battery according to the present invention may include an electrode assembly comprising a first electrode plate, a separator, and a second electrode plate; a case accommodating the electrode assembly; a rivet terminal penetrating the case and electrically connected to the first electrode plate of the electrode assembly; and a vent plate sealing the case and directly electrically connected to the second electrode plate of the electrode assembly.

[0008] In some examples, the vent plate may further include a plurality of welding lines that allow the vent plate to be directly electrically connected to the second electrode plate.

[0009] In some examples, the plurality of welding lines may include at least one first welding line provided by welding from the center of the vent plate toward the perimeter, and at least one second welding line provided by welding from the perimeter of the vent plate toward the center.

[0010] In some examples, the plurality of welding lines may include a shape that spreads radially from the center of the vent plate toward the circumference.

[0011] In some examples, the plurality of welding lines may be provided by a laser beam.

[0012] In some examples, the vent plate may further include a plurality of vent grooves.

[0013] In some examples, the plurality of vent grooves may include a plurality of straight first vent grooves that spread radially from the center of the vent plate toward the circumference.

[0014] In some examples, the plurality of vent grooves may include an inner circular second vent groove that is concentric with the center of the vent plate and is closer to the center than to the circumference, and an outer circular second vent groove that is concentric with the center of the vent plate and is closer to the circumference than to the center.

[0015] In some examples, the plurality of welding lines may be provided between the inner circular second vent groove and the outer circular second vent groove.

[0016] In some examples, the plurality of vent grooves include a plurality of straight first vent grooves spreading radially from the center of the vent plate toward the perimeter, an inner circular second vent groove concentric with the center of the vent plate and closer to the center than to the perimeter, and an outer circular second vent groove concentric with the center of the vent plate and closer to the perimeter than to the center, and the plurality of welding lines may be provided between the inner circular second vent groove and the outer circular second vent groove.

[0017] In some examples, the plurality of linear first vent grooves may intersect the inner circular second vent groove and the outer circular second vent groove.

[0018] In some examples, the vent plate may include a first flat portion coupled to the case, an inclined portion provided inclinedly toward the electrode assembly from the first flat portion, and a second flat portion extending flatly toward the center from the inclined portion.

[0019] In some examples, the second flat portion of the vent plate may further include a plurality of welding lines that allow the vent plate to be directly electrically connected to the second electrode plate.

[0020] In some examples, the vent plate may further include a concave portion facing the electrode assembly at the center of the second flat portion.

[0021] In some examples, the case and the vent plate may be joined to each other by a crimping portion provided in the case.

[0022] In some examples, the case and the vent plate may be joined to each other by a crimping portion and a beading portion provided in the case.

[0023] In some examples, the case and the vent plate may be joined to each other by a curling portion provided in the case.

[0024] In some examples, the case and the vent plate may be joined to each other by a seaming portion provided on the case and the vent plate.

[0025] In some examples, the case and the vent plate may be joined to each other by a welding line provided on the case and the vent plate.

[0026] In some examples, the current collector may further include a terminal connection portion located between the electrode assembly and the case, to which the rivet terminal is connected, a electrode plate connection portion to which the first electrode plate is connected, and a fuse portion located between the terminal connection portion and the electrode plate connection portion.

[0027] In some examples, the fuse portion may include a fuse hole provided along a portion of the outer circumference of the terminal connection portion; and a connection portion electrically connecting the terminal connection portion and the electrode plate connection portion.

[0028] In some examples, the rivet terminal may include a head located on the outside of the case and a fastening portion extending from the center of the head to the inside of the case and welded to the terminal connection portion. Effects of the invention

[0029] The present invention provides a secondary battery that integrates a current collector (or current collector plate) and a vent plate, enabling high capacity by increasing the internal space of the case and low cost by reducing material and processing costs.

[0030] The present invention provides a secondary battery with improved weldability between an electrode assembly and a vent plate by welding the electrode assembly and a vent plate together with a laser beam to electrically and mechanically combine them, wherein the vent plate is provided with a welding line extending from the winding leading edge of the electrode assembly to the winding end and a welding line extending from the winding end of the electrode assembly to the winding leading edge.

[0031] The present invention provides a secondary battery with improved sealing power of the case by mutually joining a vent plate and a case using a mechanical joining structure, adopting a crimping method, a curling method, and / or a welding method for the mechanical joining structure. Brief explanation of the drawing

[0032] FIG. 1 is a perspective view illustrating an exemplary cylindrical secondary battery according to the present invention. FIG. 2 is a cross-sectional view of an exemplary cylindrical secondary battery shown in FIG. 1. FIG. 3a is a perspective view showing an exemplary vent plate in an exemplary cylindrical secondary battery shown in FIG. 1, and FIG. 3b and FIG. 3c are enlarged plan views showing an exemplary welding line along the welding direction. FIG. 4a is a partial cross-sectional view illustrating an exemplary coupling structure between a vent plate and a case by crimping in an exemplary cylindrical secondary battery according to the present invention, and FIG. 4b is a cross-sectional view showing an enlarged portion of FIG. 4a. FIG. 5 is a partial cross-sectional view illustrating an exemplary coupling structure between a vent plate and a case by curling in an exemplary cylindrical secondary battery according to the present invention. FIG. 6 is a partial cross-sectional view illustrating an exemplary coupling structure between a vent plate and a case by welding in an exemplary cylindrical secondary battery according to the present invention. FIG. 7 is a partial cross-sectional view illustrating an exemplary coupling structure between a vent plate and a case by curling in an exemplary cylindrical secondary battery according to the present invention. FIG. 8 is a plan view illustrating an exemplary positive current collector plate in an exemplary cylindrical secondary battery according to the present invention. Specific details for implementing the invention

[0033] Hereinafter, preferred embodiments 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 invention to those skilled in the art, and the following embodiments may be modified in various different forms, and the scope of the invention is not limited to the following embodiments. Rather, these embodiments are provided to make the disclosure more faithful and complete and to fully convey the spirit of the invention to those skilled in the art.

[0035] Additionally, in the drawings below, the thickness or size of each layer is exaggerated for convenience and clarity of explanation, and like reference numerals in the drawings refer to like elements. As used herein, the term "and / or" may include any one of the listed items and all combinations of one or more thereof. Furthermore, in this specification, the meaning of "connected" refers not only to cases where Member A and Member B are directly connected, but also to cases where Member C is interposed between Member A and Member B, thereby indirectly connecting Member A and Member B.

[0036] The terms used herein are for describing specific embodiments and are not intended to limit the invention. As used herein, the singular form may include the plural form unless the context clearly indicates otherwise. Additionally, as used herein, "comprise" and / or "comprising" specify the presence of the mentioned features, numbers, steps, actions, parts, elements, and / or groups thereof, and do not exclude the presence or addition of one or more other features, numbers, actions, parts, elements, and / or groups.

[0037] Although terms such as "first," "second," etc. are used in this specification to describe various components, parts, regions, layers, and / or parts, it is obvious that these components, parts, regions, layers, and / or parts should not be limited by these terms. These terms are used solely to distinguish one component, part, region, layer, or part from another region, layer, or part. Accordingly, the first component, part, region, layer, or part described below may refer to the second component, part, region, layer, or part 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 and another element or feature. These spatial terms are intended to facilitate understanding of the invention according to various process or usage states of the invention and are not intended to limit the invention. For example, if an element or feature in the drawings is inverted, an element described as "beneath" or "below" becomes "upper" or "on top." Therefore, "below" is a concept that encompasses "upper" or "below."

[0039] Preferred embodiments of the present invention are described in detail with reference to the attached drawings so that a person skilled in the art can easily practice the present invention.

[0040] Herein, parts having similar configurations and operations throughout the specification are given the same reference numerals. Additionally, when a part is described as being electrically coupled with another part, this may include not only cases where they are directly connected but also cases where they are connected with other components in between.

[0042] FIG. 1 is a perspective view illustrating an exemplary cylindrical secondary battery (100) according to the present invention, and FIG. 2 is a cross-sectional view of the exemplary cylindrical secondary battery (100) illustrated in FIG. 1.

[0043] Referring to FIGS. 1 and 2, an exemplary cylindrical secondary battery (100) according to the present invention may include a case (110), an electrode assembly (120), a positive current collector plate (130), a rivet terminal (150), and a vent plate (160).

[0044] The case (110) may include a circular bottom portion (111) and a side portion (112) extending upward from the edge of the bottom portion (111). The bottom portion (111) and the side portion (112) of the case (110) may be integral with each other. In some examples, the case (110) may include or be referred to as a can, housing, or casing. In some examples, the case (110) may be provided by press forming of a sheet metal. For example, a case (110) having a seamless bottom portion and side portion may be manufactured by placing a sheet metal on a deep drawing die and then pressing the sheet metal with a punch. In some examples, a non-ferrous metal billet may be fed into an extruder and extruded to provide a pipe having only a seamless side portion, and then the bottom portion may be welded to one side of the pipe to manufacture the case (110).

[0045] In some examples, the bottom portion (111) may have a flat circular plate shape and may include a terminal hole (111a) penetrating the center. A rivet terminal (150) may be inserted into the terminal hole (111a) of the bottom portion (111). A first gasket (115) for sealing and electrical insulation may be further interposed between the terminal hole (111a) and the rivet terminal (150). The first gasket (115) is inserted into the terminal hole (111a) and may extend to the lower part of the bottom portion (111). The first gasket (115) can electrically isolate the rivet terminal (150) and the case (110) by blocking contact between the rivet terminal (150) and the case (110). The terminal hole (111a) of the bottom portion (111) of the case (110) may be sealed by the first gasket (115). The first gasket (115) can be provided with a resin material such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), etc.

[0046] The upper part of the case (110) of the cylindrical secondary battery (100) may be opened during the manufacturing process. Thus, the electrode assembly (120) may be inserted through the open upper part of the case (110) during the manufacturing process of the cylindrical secondary battery (100). After the electrode assembly (120) and the electrolyte (optional) are inserted, the case (110) may be sealed by attaching a vent plate (160) to the open upper part. In some examples, the electrolyte serves to enable the movement of lithium ions between the first electrode plate (121) and the second electrode plate (122) constituting the electrode assembly (120). This electrolyte may be a non-aqueous organic electrolyte, which is a mixture of a lithium salt and a high-purity organic solvent. Additionally, the electrolyte may be a polymer using a polymer electrolyte or a solid electrolyte.

[0047] In some examples, the case (110) may comprise steel, steel alloy, aluminum, aluminum alloy, nickel, or nickel alloy. Additionally, the case (110) may further include a beading part (113) (optional) that is inwardly recessed below the vent plate (160) and a crimping part (114) that is inwardly bent above the vent plate (160) to prevent the electrode assembly (120) from being ejected outward. The beading part (113) and the crimping part (114) can prevent the vent plate (160) from being separated from the case (110).

[0048] The electrode assembly (120) may include a first electrode plate (121), a second electrode plate (122), and a separator (123). The electrode assembly (120) may include or be referred to as an electrode group or a jelly roll. The first electrode plate (121) may be a positive electrode plate (or cathode plate), and the second electrode plate (122) may be a negative electrode plate (or anode plate). Of course, the opposite is also possible. Generally, the anode and cathode are interpreted as positive (+) and negative (-), respectively, but in the field of batteries, this is reversed, and the anode and cathode are referred to as negative (-) and positive (+), respectively.

[0049] For convenience of explanation, the first electrode plate (121) will be referred to as the positive electrode plate and the second electrode plate (122) as the negative electrode plate.

[0050] The positive plate (121) is provided by applying a positive active material, such as a transition metal oxide, to a positive current collector provided as a metal foil such as aluminum (Al), and may include a positive non-positive portion (or positive substrate tab) (1211), which is an area where the positive active material is not applied. In some examples, the positive non-positive portion (1211) may protrude downward from the electrode assembly (120). In some examples, the positive plate (121) may have the positive non-positive portion (1211) protrude further downward relative to the negative plate (122) and the separator (123).

[0051] The negative plate (122) is provided by applying a negative active material, such as graphite or carbon, to a negative current collector provided as a metal foil such as copper (Cu) or nickel (Ni), and may include a negative non-negative portion (or negative substrate tab) (1221), which is an area where the negative active material is not applied. In some examples, the negative non-negative portion (1221) may protrude upward from the electrode assembly (120). In some examples, the negative plate (122) may have the negative non-negative portion (1221) protrude further upward relative to the positive plate (121) and the separator (123).

[0052] The separator (123) may be polyethylene (PE) or polypropylene (PP), but is not limited thereto in the present invention. The separator can prevent an electrical short circuit between the positive plate (121) and the negative plate (122) and allow only the movement of lithium ions.

[0053] The electrode assembly (120) can be wound from the winding end and approximately cylindrical in shape after the positive plate (121), negative plate (122), and separator (123) are laminated. In some examples, the part of the electrode assembly where the winding begins is referred to as the winding end, and the part where the winding is completed is referred to as the winding end.

[0054] In some examples, the electrode assembly (120) may have an anode-free portion (1211) that is not coated with an anode active material protruding downward from the anode plate (121), and a cathode-free portion (1221) that is not coated with a cathode active material protruding upward from the cathode plate (122).

[0055] The positive current collector plate (130) may be a circular metal plate having a shape corresponding to the lower surface of the electrode assembly (120). The area (or size) of the positive current collector plate (130) may be equal to or smaller than the area (or size) of the upper surface of the electrode assembly (120). The positive current collector plate (130) may be provided with aluminum (Al). The positive current collector plate (130) may be fixed and electrically connected to the positive plate (121) exposed to the lower part of the electrode assembly (120) by welding, with its upper surface in contact with the lower surface of the electrode assembly (120). The positive current collector plate (130) may be fixed and electrically connected to the rivet terminal (150) by welding, with its lower surface in contact with the upper surface of the rivet terminal (150). The positive current collector plate (130) serves as a passage for current flow between the positive plate (121) of the electrode assembly (120) and the rivet terminal (150).

[0056] The rivet terminal (150) can be inserted into a terminal hole (111a) provided in the bottom portion (111) of the case (110) and electrically connected to the positive current collector plate (130). That is, the rivet terminal (150) can be a positive terminal. The rivet terminal (150) and the case (110) may have different polarities. The rivet terminal (150) may be made of the same or similar material as the positive current collector plate (130) and the positive plate (121). The diameter of the rivet terminal (150) at the portion exposed to the bottom of the case (110) and the diameter located inside the case (110) may be larger than the diameter located in the terminal hole (111a).

[0057] The rivet terminal (150) may include a head (151) exposed to the bottom of the case (110) and a fastening part (152) located inside the case (110) and coupled with the positive current collector plate (130). The rivet terminal (150) may be coupled to the terminal hole (111a) of the case (110) from the outside inward. At this time, the head (151) may be located outside the case (110). Additionally, the fastening part (152) may be compressed by riveting (compressive molding) and compressed with the first gasket (115) interposed on the upper part of the bottom portion (111). Here, the fastening part (152) may have a larger diameter as it extends from the terminal hole (111a) toward the inside of the case (110). In other words, the diameter of the upper part of the fastening part (152) may be larger than the diameter of the lower part. Here, the lower portion of the fastening portion (152) may refer to the part connected to the head (151). The diameter of the upper portion of the fastening portion (152) may be larger than the diameter of the terminal hole (111a), and the diameter of the terminal hole (111a) may be larger than the diameter of the lower portion of the fastening portion (152). Additionally, the head (151) may be in close contact with the lower part of the bottom portion (111) with the first gasket (115) interposed therein. At this time, the first gasket (115) may be interposed between the rivet terminal (150) and the terminal hole (111a). The rivet terminal (150) may be electrically connected to the positive plate (121) of the electrode assembly (120) through the positive current collector plate (130).

[0058] Additionally, an insulating member (117) may be further interposed between the head (151) and the bottom portion (111) of the case (110). That is, the head (151) is located at the bottom portion (111), and an insulating member (117) that blocks electrical contact between the rivet terminal (150) and the case (110) may be interposed in the area where the head (151) and the bottom portion (111) overlap in a plane. The diameter of the insulating member (117) may be larger than the diameter of the head (151). Accordingly, the outer periphery (or end) of the insulating member (117) may be extended and exposed to the outside of the head (151).

[0059] The first gasket (115) is interposed between the fastening portion (152) and the terminal hole (111a) of the case (110), and its lower portion may extend between the head (151) and the bottom portion (111) of the case (110). At this time, the end of the lower portion of the first gasket (115) may come into contact with the insulating member (117). That is, the first gasket (115) and the insulating member (117) are interposed between the rivet terminal (150) and the bottom portion (111) of the case (110), thereby electrically insulating and sealing the rivet terminal (150) and the case (110). Of course, the first gasket (115) and the insulating member (117) may be formed as a single unit.

[0060] The rivet terminal (150) may further include a welding groove (153) having a certain depth from the bottom portion of the head (151) toward the fastening portion (152). That is, the welding groove (153) may penetrate the center of the head (151) and be provided from the bottom toward the top of the fastening portion (152). By this welding groove (153), the thickness of the fastening portion (152) is reduced, making it easy to weld the fastening terminal (150) and the positive current collector plate (130) from the outside of the case (110).

[0061] In some examples, the rivet terminal (150) may not include a weld groove (153). In this case, the thickness of the fastening portion (152) may be provided to be thicker than the thickness of the head (151).

[0062] The vent plate (160) is a circular metal plate and, as described above, can be attached to the case (110) by a beading portion (114) and a crimping portion (115). In some examples, the upper surface of the vent plate (160) may be directly exposed to the outside. In some examples, the vent plate (160) may include or be referred to as a terminal (e.g., a negative terminal), a cap, or a sealing plate. The vent plate (160) may be made of the same or similar material as the case (110). In some examples, the vent plate (160) may include steel, steel alloy, aluminum, aluminum alloy, nickel, or nickel alloy. In some examples, the vent plate (160) may be attached to the top of the case (110) with a second gasket (116) (optional) interposed therein, so as to be electrically isolated from the case (110).

[0063] The vent plate (160) may have a negative polarity because it is directly electrically connected to the negative plate (122) of the electrode assembly (120), for example, the negative non-negative portion (1221). In some examples, the vent plate (160) may include a number of welding lines (166) so that it can be directly electrically connected to the negative non-negative portion (1221). In some examples, the welding lines (166) may be provided by a laser beam. In some examples, a laser beam is provided to the upper surface of the vent plate (160), and accordingly, a portion of the vent plate (160) may be mechanically / electrically connected to the negative non-negative portion (1221) as a portion of the vent plate (160) melts and cools.

[0064] In other words, the negative electrode collector plate may be omitted in the present invention. Generally, the negative electrode non-coupling portion (1221) of the electrode assembly (120) is electrically connected to the negative electrode collector plate, and the negative electrode collector plate may be electrically connected to the vent plate (160) and / or case (110). However, in the present invention, such a negative electrode collector plate may be omitted, and the negative electrode non-coupling portion (1221) may be directly electrically connected to the lower surface of the vent plate (160). In some examples, at least part or all of the negative electrode non-coupling portion (1221) may be bent toward the center of the electrode assembly (120), and the area thus bent may be in direct contact with the lower surface of the vent plate (160). Alternatively, after the vent plate (160) presses the negative electrode non-existent portion (1221), a laser beam is irradiated onto the vent plate (160) so that welding lines (166) can be provided on the vent plate (160). By these welding lines (166), the negative electrode non-existent portion (1221) of the electrode assembly (120) can be electrically / mechanically coupled to the vent plate (160).

[0065] The vent plate (160) may include a first flat portion (161) coupled to the case (110), an inclined portion (163) provided inclined toward the electrode assembly (120) from the first flat portion (161), and a second flat portion (162) extending flatly toward the center from the inclined portion (163). In some examples, the vent plate (160) may further include a concave portion (164) concave toward the electrode assembly (120) at the center of the second flat portion (162).

[0066] The first flat section (161) can be interposed between the beading section (113) and the crimping section (114) of the case (110) and combined with the case (110). The first flat section (161) can be fixed in a position between the beading section (113) and the crimping section (114) of the case (110). In some examples, the first flat section (161) can be seated on the upper part of the second gasket (116) with the second gasket (116) interposed on the upper part of the beading section (113) of the case (110). After that, the crimping section (114) of the case (110) can be bent inward toward the vent plate (160) to press the second gasket (116), thereby combining the vent plate (160) and the case (110). The second gasket (116) can be in close contact between the case (110) and the vent plate (160). Additionally, the second gasket (116) can be in close contact with the inner side of the beading portion (113) and the crimping portion (114). The end of the second gasket (116) located between the vent plate (160) and the crimping portion (114) is provided to extend inward toward the case (110) beyond the end of the crimping portion (114) so ​​as to be exposed to the outside. The end of the second gasket (116) located between the vent plate (160) and the beading portion (113) can be provided to protrude inward toward the case (110) beyond the beading portion (113). The second gasket (116) can be provided in a resin material such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), etc.

[0067] The sloped portion (163) may be provided to slope downward from the first flat portion (161) toward the second flat portion (162). Thus, the sloped portion (163) causes the second flat portion (162) to be located lower than the first flat portion (161). The location and height of the sloped portion (163) may vary depending on the characteristics required for the battery. In some examples, the location of the sloped portion (163) may be provided closer to the first flat portion (161) than to the concave portion (164). In some examples, the location of the sloped portion (163) may be provided closer to the concave portion (164) than to the first flat portion (161). In some examples, the bottom of the sloped portion (163) may be located higher than the beading portion (113). In some examples, the bottom of the slope (163) may overlap the beading portion (113) or be below the beading portion (113).

[0068] The second flat section (162) may extend flatly from the inclined section (163) to the concave section (164). The second flat section (162) is subjected to a set pressure (e.g., approximately 10 ± 3 kgf / cm²). 2 It may include a plurality of vent grooves (165) that can be opened in the vent plate (160). The vent grooves (165) may be thinner than other areas of the vent plate (160). The vent grooves (165) may be notches provided from the upper surface of the vent plate (160) downward. In some examples, the vent grooves (165) may be provided radially and / or circularly.

[0069] The second flat section (162) may include a plurality of welding lines (166) that electrically / mechanically connect the vent plate (160) and the negative non-existent section (1221) of the electrode assembly (120). In some examples, the plurality of welding lines (166) may be provided by a laser beam. In some examples, the welding lines (166) may be provided radially.

[0070] The recess (164) may be provided concavely from the second flat portion (162) toward the electrode assembly (120). The depth of the recess (164) may be varied according to the battery characteristics. In some examples, the depth of the recess (164) may be appropriately designed according to the breaking pressure required for the vent plate (160) and / or the internal volume required for the battery. In some examples, the bottom of the recess (164) may be higher or lower than the bottom of the beading portion (113).

[0072] FIG. 3a is a perspective view showing an exemplary vent plate (160) in an exemplary cylindrical secondary battery (100) shown in FIG. 1, and FIG. 3b and FIG. 3c are enlarged plan views showing exemplary welding lines (166) along the welding direction. In FIG. 3a, FIG. 3b and FIG. 3c, straight arrows indicate the welding direction by the laser beam.

[0073] Referring to FIG. 3a, a plurality of welding lines (166) allow the vent plate (160) and the electrode assembly (120) (e.g., the negative electrode-free portion) to be electrically and mechanically connected to each other. In some examples, the plurality of welding lines (166) may be provided in a roughly radial straight line from the center of the vent plate (160) toward the circumference. Specifically, the plurality of welding lines (166) may be provided in a roughly radial straight line from the concave portion (164) of the vent plate (160) toward the inclined portion (163).

[0074] In some examples, the plurality of welding lines (166) may include at least one first welding line (1661) welded from the center of the vent plate (160) toward the circumference and at least one second welding line (1662) welded from the circumference of the vent plate (160) toward the center. Specifically, the plurality of welding lines (166) may include at least one first welding line (1661) welded from the concave portion (164) of the vent plate (160) toward the inclined portion (163) and at least one second welding line (1662) welded from the inclined portion (163) of the vent plate (160) toward the concave portion (164).

[0075] In some examples, a pair of first welding lines (1661) may be provided facing each other with respect to the center or recess (164) of the vent plate (160), and a pair of second welding lines (1662) may also be provided facing each other with respect to the center or recess (164) of the vent plate (160). In some examples, the first welding lines (1661) and the second welding lines (1662) may be provided in a generally cross (+) shape. In some examples, the first welding lines (1661) and the second welding lines (1662) may be provided intersecting in a circumferential direction.

[0076] Additionally, as described above, the vent plate (160) may include a first flat portion (161), an inclined portion (163), a second flat portion (162), and a concave portion (164), and a plurality of vent grooves (165) may be provided in the second flat portion (162).

[0077] In some examples, the plurality of vent grooves (165) may include a plurality of straight first vent grooves (1651) that spread radially from the center of the vent plate (160) toward the circumference. Specifically, the plurality of vent grooves (165) may include a plurality of straight first vent grooves (1651) that spread radially from the concave portion (164) of the vent plate (160) toward the inclined portion (163).

[0078] In some examples, a plurality of vent grooves (165) may include an inner circular second vent groove (1652) that is concentric with the center of the vent plate (160) and is closer to the center than to the periphery, and / or an outer circular second vent groove (1653) that is concentric with the center of the vent plate (160) and is closer to the periphery than to the center. Specifically, a plurality of vent grooves (165) may include an inner circular second vent groove (1652) that is concentric with the concave portion (164) of the vent plate (160) and is closer to the concave portion (164) than to the inclined portion (163), and / or an outer circular second vent groove (1653) that is concentric with the concave portion (164) of the vent plate (160) and is closer to the inclined portion (163) than to the concave portion (164).

[0079] In some examples, a plurality of welding lines (166) may be provided between the inner circular second vent groove (1652) and the outer circular second vent groove (1653). In some examples, both ends of the welding lines (166) may be spaced apart from the inner circular second vent groove (1652) and the outer circular second vent groove (1653).

[0080] In some examples, a plurality of straight first vent grooves (1651) may intersect an inner circular second vent groove (1652) and / or an outer circular second vent groove (1653). In some examples, a plurality of straight first vent grooves (1651) may extend past the outer circular second vent groove (1653) to the perimeter of the second flat section (162) (i.e., to the inclined section (163)).

[0081] Meanwhile, as shown in FIGS. 3b and 3c, the welding lines (166) may have different shapes depending on the welding direction.

[0082] First, as illustrated in FIG. 3b, when welding by a laser beam starts at the center of the vent plate (160) (e.g., the inner circular second vent groove (1652)) and ends at the periphery (outer circular second vent groove (1653)), the "circular melt mark" provided by the laser beam (i.e., the end of the first welding line (1661)) remains near the periphery of the vent plate (160) (outer circular second vent groove (1653)).

[0083] On the other hand, as illustrated in FIG. 3c, if welding by a laser beam starts at the perimeter of the vent plate (160) (outer circular second vent groove (1653)) and ends at the center (inner circular second vent groove (1652)), the "circular melt mark" provided by the laser beam (i.e., the end of the second welding line (1662)) remains near the center of the vent plate (160) (inner circular second vent groove (1652)).

[0084] In this way, by providing the first welding line (1661) and the second welding line (1662) in opposite directions, the welding quality between the vent plate (160) and the electrode assembly (i.e., the negative electrode non-reinforced portion (1221)) can be further improved.

[0086] FIG. 4a is a partial cross-sectional view illustrating an exemplary coupling structure between a vent plate (160) and a case (110) by crimping in an exemplary cylindrical secondary battery (100) according to the present invention, and FIG. 4b is a cross-sectional view showing an enlarged portion of FIG. 4a.

[0087] As illustrated in FIGS. 4a and 4b, an exemplary cylindrical secondary battery (100) according to the present invention may have a vent plate (160) and a case (110) joined to each other by a crimping portion (114). In some examples, the vent plate (160) and the case (110) may be joined to each other by the crimping portion (114) alone, without a beading portion.

[0088] In some examples, after the vent plate (160) is electrically / mechanically connected to the electrode assembly (120), the electrode assembly (120) can be inserted into the case (110). In some examples, a gasket (116) may or may not be interposed around the vent plate (160). In some examples, the upper portion of the case (110) is bent with a curvature toward the inner direction of the vent plate (160), so that the upper region of the case (110) (i.e., the crimping portion (114)) can cover the perimeter of the vent plate (160) with a curvature. In some examples, the crimping portion (114) can be manufactured by compression using a mold.

[0089] In some examples, the vent plate (160) may press against the electrode assembly (120) by a crimping portion (114) having curvature. In some examples, after the vent plate (160) is electrically / mechanically coupled to the electrode assembly (120) (i.e., after laser welding), the electrode assembly (120) may be inserted into the case (110). In some examples, after the electrode assembly (120) is inserted into the case (110), the vent plate (160) may be laser welded to the electrode assembly (120). In some examples, after the vent plate (160) and the case (110) are mutually coupled by the crimping portion (114), the vent plate (160) may be laser welded to the electrode assembly (120). These processes may be performed identically or similarly in all embodiments of the present invention and may be varied depending on the characteristics required for the battery.

[0091] FIG. 5 is a partial cross-sectional view illustrating an exemplary coupling structure between a vent plate (160) and a case (110) by curling in an exemplary cylindrical secondary battery (100) according to the present invention.

[0092] As illustrated in FIG. 5, an exemplary cylindrical secondary battery (100) according to the present invention may have a vent plate (160) and a case (110) joined to each other by a curling portion (1141). In some examples, a gasket may or may not be interposed between the vent plate (160) and the case (110). In some examples, the upper region of the case (110) may be bent inward horizontally, and the bent region (i.e., the curling portion (1141)) may press against the perimeter region of the vent plate (160). In some examples, the curling portion (1141) may be bent inward by the rotation of a roller. In some examples, the curling portion (1141) may have a smaller or almost no curvature compared to the crimping portion (114) described above.

[0094] FIG. 6 is a partial cross-sectional view illustrating an exemplary coupling structure between a vent plate (160) and a case (110) by curling in an exemplary cylindrical secondary battery (100) according to the present invention.

[0095] As illustrated in FIG. 6, an exemplary cylindrical secondary battery (100) according to the present invention may have a vent plate (160) and a case (110) joined to each other by a seaming portion (1142). In some examples, a gasket may or may not be interposed between the vent plate (160) and the case (110). In some examples, the upper region of the case (110) may be extended in an outward horizontal direction, and after the perimeter region of the vent plate (160) is seated on the extended region, a seaming process may be performed.

[0096] In some examples, the abutting area of ​​the vent plate (160) and the case (110) may be folded at least once by a seaming process to provide a seaming portion (1142), and the vent plate (160) and the case (110) may be joined to each other by this seaming portion (1142). In some examples, the perimeter end of the vent plate (160) may be inserted between the folded areas of the case (110), or the perimeter end of the vent plate (160) may finish the perimeter end of the case (110).

[0098] FIG. 7 is a partial cross-sectional view illustrating an exemplary coupling structure between a vent plate (160) and a case (110) by welding in an exemplary cylindrical secondary battery (100) according to the present invention.

[0099] As illustrated in FIG. 7, an exemplary cylindrical secondary battery (100) according to the present invention may have a vent plate (160) and a case (110) joined to each other by a weld (1143).

[0100] In some examples, the weld (1143) may be provided on the side of the boundary area between the vent plate (160) and the case (110) or on the upper side of the boundary area between the vent plate (160) and the case (110).

[0101] In some examples, the weld (1143) may be provided by arc welding, atomic hydrogen welding, carbon arc welding, plasma arc welding, shielded arc welding, submerged arc welding, MIG (Metal inert gas welding) welding, electro-slag welding, laser welding, electron beam welding, cold welding, friction welding, explosive welding, ultrasonic welding, electric resistance welding, butt welding, upset welding, flash welding, etc. In some examples, the various welding methods described above may be used for the electrical / mechanical connection between the electrode assembly (120) and the vent plate (160).

[0103] FIG. 8 is a plan view illustrating an exemplary positive current collector plate (130) in an exemplary cylindrical secondary battery (100) according to the present invention.

[0104] As illustrated in FIG. 8, the positive current collector (130) may include a terminal connection portion (131) and an electrode plate connection portion (132). In some examples, the positive current collector (130) may further include a fuse portion (135). The terminal connection portion (131) is located at the center of the positive current collector (130) and may be provided in a roughly circular shape. A fastening portion (152) of a rivet terminal (150) may be welded to the lower surface of the terminal connection portion (131). In some examples, the area (or size) of the terminal connection portion (131) may be larger than the area (or size) of the fastening portion (152). In some examples, the thickness of the terminal connection portion (131) may be provided to be thicker than the thickness of the electrode plate connection portion (132). Thus, when the rivet terminal (150) is welded to the terminal connection portion (131), the terminal connection portion (131) may be prevented from being deformed. The electrode plate connection portion (132) is located on the outside of the terminal connection portion (131) and can be electrically connected to the positive plate (121) of the electrode assembly (120). For example, the positive non-positive portion of the positive plate (121) protruding to the bottom of the electrode assembly (120) can be welded to the upper surface of the electrode plate connection portion (132). In some examples, a fuse portion (135) may be provided between the terminal connection portion (131) and the electrode plate connection portion (132). The fuse portion (135) may include a fuse hole (136) and a connection portion (137). The fuse portion (135) can cut off the current flowing to the secondary battery (100) by causing the connection portion (137) to melt and cut due to the heat generated when a short circuit or overcurrent occurs in the secondary battery (100). The fuse hole (136) is formed in a roughly 'C' shape along a part of the outer periphery of the terminal connection part (131), so that the two ends of the fuse hole (136) can face each other. The fuse hole (136) can separate the terminal connection part (131) and the electrode connection part (132). That is, the terminal connection part (131) and the electrode connection part (132) can be separated from each other by the fuse hole (136). The connection part (137) can connect the terminal connection part (131) and the electrode connection part (132).The connecting portion (137) can improve the safety of the secondary battery (100) by melting and cutting due to the heat generated when a short circuit or overcurrent occurs in the secondary battery (100), thereby cutting off the current. The width (W1) of the connecting portion (137) may refer to the length between one end and the other end of the fuse hole (136).

[0106] The above description is merely one embodiment for implementing a cylindrical secondary battery according to the present invention, and the present invention is not limited to the above-described embodiment. The technical spirit of the present invention extends to the scope in which various modifications can be made by anyone with ordinary knowledge in the field to which the invention belongs, without departing from the gist of the invention as claimed in the following patent claims. Explanation of the symbols

[0107] 100: Secondary battery 110: Case 120: Electrode assembly 130: Positive current collector 150: Rivet terminal 160: Vent plate

Claims

Claim 1 A secondary battery comprising: an electrode assembly including a first electrode plate, a separator, and a second electrode plate; a case housing the electrode assembly; a rivet terminal penetrating the case and electrically connected to the first electrode plate of the electrode assembly; and a vent plate sealing the case and directly electrically connected to the second electrode plate of the electrode assembly. Claim 2 A secondary battery according to claim 1, wherein the vent plate further comprises a plurality of welding lines that allow the vent plate to be directly electrically connected to the second electrode plate. Claim 3 A secondary battery according to paragraph 2, wherein the plurality of welding lines comprises at least one first welding line provided by welding from the center of the vent plate toward the perimeter, and at least one second welding line provided by welding from the perimeter of the vent plate toward the center. Claim 4 A secondary battery according to paragraph 2, wherein the plurality of welding lines include a shape that spreads radially from the center of the vent plate toward the circumference. Claim 5 In paragraph 2, the plurality of welding lines are provided by a laser beam, a secondary battery. Claim 6 A secondary battery according to claim 1, wherein the vent plate further comprises a plurality of vent grooves. Claim 7 A secondary battery according to claim 6, wherein the plurality of vent grooves include a plurality of straight first vent grooves that spread radially from the center of the vent plate toward the circumference. Claim 8 A secondary battery according to claim 6, wherein the plurality of vent grooves include an inner circular second vent groove that is concentric with the center of the vent plate and is closer to the center than to the circumference, and an outer circular second vent groove that is concentric with the center of the vent plate and is closer to the circumference than to the center. Claim 9 A secondary battery according to claim 8, wherein a plurality of welding lines are provided between the inner circular second vent groove and the outer circular second vent groove. Claim 10 In claim 6, the plurality of vent grooves include a plurality of straight first vent grooves spreading radially from the center of the vent plate toward the periphery, an inner circular second vent groove concentric with the center of the vent plate and closer to the center than to the periphery, and an outer circular second vent groove concentric with the center of the vent plate and closer to the periphery than to the center, and a plurality of welding lines provided between the inner circular second vent groove and the outer circular second vent groove, a secondary battery. Claim 11 In item 10, the plurality of linear first vent grooves intersect the inner circular second vent groove and the outer circular second vent groove, a secondary battery. Claim 12 A secondary battery according to claim 1, wherein the vent plate comprises a first flat portion coupled to the case, an inclined portion provided inclinedly toward the electrode assembly from the first flat portion, and a second flat portion extending flatly toward the center from the inclined portion. Claim 13 A secondary battery according to claim 12, wherein the second flat portion of the vent plate further comprises a plurality of welding lines that allow the vent plate to be directly electrically connected to the second electrode plate. Claim 14 A secondary battery according to claim 12, wherein the vent plate further comprises a concave portion facing the electrode assembly at the center of the second flat portion. Claim 15 A secondary battery according to claim 1, wherein the case and the vent plate are mutually coupled by a crimping portion provided in the case. Claim 16 A secondary battery according to claim 1, wherein the case and the vent plate are mutually coupled by a crimping portion and a beading portion provided in the case. Claim 17 A secondary battery according to claim 1, wherein the case and the vent plate are mutually coupled by a curling portion provided to the case. Claim 18 A secondary battery according to claim 1, wherein the case and the vent plate are mutually coupled by a seaming portion provided on the case and the vent plate. Claim 19 A secondary battery according to claim 1, wherein the case and the vent plate are joined to each other by a welding line provided on the case and the vent plate. Claim 20 A secondary battery according to claim 1, further comprising a current collector plate having a terminal connection portion located between the electrode assembly and the case, to which the rivet terminal is connected, a electrode plate connection portion to which the first electrode plate is connected, and a fuse portion located between the terminal connection portion and the electrode plate connection portion. Claim 21 A secondary battery according to claim 20, wherein the fuse portion comprises: a fuse hole provided along a part of the outer circumference of the terminal connection portion; and a connection portion electrically connecting the terminal connection portion and the electrode plate connection portion. Claim 22 A secondary battery according to claim 21, wherein the rivet terminal comprises a head located on the outside of the case and a fastening portion extending from the center of the head to the inside of the case and welded to the terminal connection portion.

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