Secondary battery comprising vent plate and method for manufacturing secondary battery

Abstract

An objective of the present disclosure is to provide a secondary battery comprising a vent plate and a method for manufacturing the secondary battery. The secondary battery according to the present disclosure comprises: an electrode assembly formed by winding a first electrode, a separator, and a second electrode; a case having the electrode assembly embedded therein; and a vent plate sealing one side opening of the case, wherein the vent plate may comprise a welding portion where the outer boundary of the vent plate extends in a direction in which the case extends and is coupled to the opening; a first planarization portion connected to the welding portion and formed perpendicularly to the direction in which the case extends; and a second planarization portion which is located at the center of the vent plate and has a step with respect to the first planarization portion.

Description

Secondary battery including a vent plate and method for manufacturing a secondary battery

[0001] The present disclosure relates to a secondary battery comprising a vent plate and a method for manufacturing the secondary battery.

[0002] Unlike primary batteries, which cannot be recharged, secondary batteries are batteries capable of both charging and discharging. Low-capacity secondary batteries are used in small portable electronic devices such as smartphones, feature phones, laptop computers, digital cameras, and camcorders, while high-capacity secondary batteries are widely used as power sources for motor drive systems and power storage batteries in hybrid and electric vehicles. Such secondary batteries include an electrode assembly consisting of a positive electrode and a negative electrode, a case housing the assembly, and electrode terminals connected to the electrode assembly.

[0003] Although rechargeable batteries are used in various environments due to their excellent electrical characteristics, conventional small batteries have had limitations in terms of designable energy density. Since the amount of electrical energy that can be stored is limited relative to the size and weight of the battery, there is a gradually increasing demand for large batteries with higher energy density in applications such as electric vehicles.

[0004] During prolonged repeated charging and discharging of a secondary battery, gas is generated inside the battery, causing internal pressure to rise, and heat may be generated through electrochemical reactions within the battery. As a result, the battery cells, particularly the vent plates, may gradually deform or warp, potentially causing changes in the overall cell specifications.

[0005] 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.

[0006] The problem that the present invention aims to solve is to provide a secondary battery and a method for manufacturing a secondary battery to solve the above technical problem.

[0007] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems can be clearly understood by those skilled in the art from the description of the invention below.

[0008] A secondary battery according to an embodiment of the present invention for solving the above technical problem comprises an electrode assembly formed by winding a first electrode, a separator, and a second electrode, a case housing the electrode assembly, and a vent plate sealing an opening on one side of the case, wherein the vent plate may include a welded portion formed by extending the outer circumference of the vent plate in the extension direction of the case and joining with the opening, a first flat portion connected to the welded portion and formed perpendicular to the extension direction of the case, and a second flat portion located at the center of the vent plate and having a step difference relative to the first flat portion.

[0009] According to one embodiment of the present disclosure, the height of the first flat portion relative to the plane formed by the end of the opening in the extension direction of the case may be equal to or greater than the height of the second flat portion.

[0010] According to one embodiment of the present disclosure, the welded portion includes an inclined surface formed to facilitate the insertion of a vent plate into an opening, and the inclined surface may form an acute angle with the extension direction of the case.

[0011] According to one embodiment of the present disclosure, a groove corresponding to a welded portion may be formed on the inner surface of the end of the opening.

[0012] According to one embodiment of the present disclosure, the vent plate includes a circumferential notch, and the notch may be formed on one side of a first flat portion.

[0013] According to one embodiment of the present disclosure, the vent plate may further include an injection port penetrating the vent plate and a sealing member for sealing the injection port.

[0014] A secondary battery according to one embodiment of the present disclosure further includes a current collector that electrically connects a first electrode and a vent plate, and the current collector may be connected to a second flat portion.

[0015] According to one embodiment of the present disclosure, the vent plate comprises a material having ferromagnetism, and the welded portion, the first flat portion, and the second flat portion may be integrally formed of the same material.

[0016] According to one embodiment of the present disclosure, the vent plate may include ferrite-based stainless steel or martensite-based stainless steel.

[0017] According to one embodiment of the present disclosure, the vent plate may include austenitic SUS.

[0018] According to one embodiment of the present disclosure, the diameter of the case may be 40 mm to 50 mm.

[0019] A method for manufacturing a secondary battery according to an embodiment of the present invention for solving a technical problem comprises the steps of: winding a first electrode, a separator, and a second electrode to form an electrode assembly; inserting the electrode assembly through an opening on one side of a case; and sealing the opening of the case with a vent plate. The vent plate may include a welded portion formed by extending the outer circumference of the vent plate in the direction of extension of the case and joining with the opening; a first flat portion connected to the welded portion and formed perpendicular to the direction of extension of the case; and a second flat portion located at the center of the vent plate and having a step difference relative to the first flat portion.

[0020] According to some embodiments of the present disclosure, when a vent plate including multiple folds is inserted into the case opening of a cylindrical secondary battery, the insertability of the component can be improved by the elasticity derived from the multiple fold structure. In addition, this can resolve the issue of the accuracy of the alignment between the outer diameter of the vent plate and the case opening, thereby increasing the process productivity of the entire secondary battery.

[0021] According to some embodiments of the present disclosure, the material of the vent plate can be modified to improve durability and new properties can be imparted to enable the movement and assembly of secondary battery cells using magnets.

[0022] According to some embodiments of the present disclosure, the structure of the new vent plate prevents deformation of the overall cell dimensions or specifications even when the central part of the vent plate protrudes outward due to an increase in internal pressure caused by long-term use, thereby extending the lifespan of the secondary battery and simultaneously providing a more standardized secondary battery cell.

[0023] However, the effects obtainable through the present invention are not limited to those described above, and other unmentioned technical effects will be clearly understood by those skilled in the art from the description of the invention below.

[0024] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0025] FIG. 1 is a cross-sectional view showing an example of a secondary battery according to one embodiment of the present disclosure.

[0026] FIG. 2 is a plan view showing the appearance of a vent plate before and after use according to one embodiment of the present disclosure.

[0027] FIG. 3 is a perspective view showing a vent plate according to one embodiment of the present disclosure.

[0028] FIG. 4 is a longitudinal cross-sectional view of a vent plate according to one embodiment of the present disclosure, cut along line AA of FIG. 3.

[0029] FIG. 5 is a drawing showing the appearance of a vent plate before insertion according to one embodiment of the present disclosure.

[0030] FIG. 6 is a drawing showing the appearance after insertion of a vent plate according to one embodiment of the present disclosure.

[0031] FIG. 7 is a plan view showing a cross-section of a case with a vent plate attached according to one embodiment of the present disclosure.

[0032] FIG. 8 is a cross-sectional view showing an example of a secondary battery according to one embodiment of the present disclosure.

[0033] FIG. 9 is a flowchart illustrating an example of a method for manufacturing a secondary battery according to the present disclosure.

[0034] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor can appropriately define the concepts of terms to best describe their invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. It should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0035] Additionally, as used herein, “comprise, include” and / or “comprising, including” 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.

[0036] Additionally, to aid in understanding the invention, the attached drawings are not drawn to actual scale, and the dimensions of some components may be exaggerated. Furthermore, the same reference numerals may be assigned to identical components in different embodiments.

[0037] The statement that two subjects of comparison are 'identical' means that they are 'substantially identical'. Therefore, substantial identity may include deviations considered low in the industry, for example, deviations within 5%. Additionally, the statement that a parameter is uniform in a given area may mean that it is uniform from an average perspective.

[0038] Although terms such as "first," "second," etc., are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless specifically stated otherwise, the first component may also be the second component.

[0039] Throughout the specification, unless specifically stated otherwise, each component may be singular or plural.

[0040] The statement that any component is positioned on the "upper (or lower) side" or the "upper (or lower) side" of a component implies not only that any component is positioned in contact with the upper (or lower) surface of said component, but also that another component may be interposed between said component and any component positioned on (or below) said component. Additionally, the area between the upper and lower parts of a component depicted in the drawings, or the remaining part excluding the upper and lower parts, may be referred to as a "side" or "lateral side." Furthermore, the direction facing the internal space of the component may be referred to as the "inner side," and the direction protruding into the open external space may be referred to as the "outer side." Such relative terms, such as "upper" and "upper side," may be used to describe the relationship between components depicted in the drawings, and the present disclosure is not limited by such terms.

[0041] Spatial relative terms such as "beneath," "below," "lower," "above," and "upper" may be used herein for ease of explanation to describe the relationship between one element or feature and another element(s) or feature(s) as illustrated in the drawings. Spatially relative positions are to be understood as encompassing different orientations of the device in use or operation, in addition to the orientations depicted in the figures. For example, if the device in the drawing is inverted, an element described as "below" or "below" is understood as "above" or "upper" of another element. Thus, the term "below" may encompass both the up and down directions.

[0042] Furthermore, where one component is described as being "on," "connected to," or "coupled to" another component, it should be understood that while the components may be directly connected or coupled to each other, another component may be "interposed" between each component, or that each component may be "connected," "coupled," or "coupled" through another component.

[0043] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. Additionally, the use of “may” when describing embodiments of the present disclosure relates to “one or more embodiments of the present disclosure.” Expressions such as “one or more” preceding a list of elements modify the entire list of elements and do not modify individual elements of the list.

[0044] Throughout the specification, "A and / or B" means A, B, or A and B unless specifically stated otherwise, and "C to D" means C or more and D or less, unless specifically stated otherwise.

[0045] In this specification, terms such as first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or sections, but these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Accordingly, the first element, component, region, layer, or section discussed below may be named the second element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0046] The terms used in this specification are intended to describe embodiments of the present disclosure and are not intended to limit the present disclosure.

[0047] FIG. 1 is a cross-sectional view showing an example of a secondary battery according to one embodiment of the present disclosure.

[0048] Referring to FIG. 1, a secondary battery (100) according to one embodiment of the present invention may include an electrode assembly (110) formed by winding a first electrode, a separator, and a second electrode, a case (120) housing the electrode assembly (110), and a vent plate (130) sealing an opening (122) on one side of the case (120).

[0049] The first electrode of the electrode assembly (110) may be an electrode corresponding to a positive or negative electrode in a secondary battery. The second electrode may be an electrode corresponding to a pole opposite to the first electrode. For example, if the first electrode is a positive electrode, the second electrode may be a negative electrode. Conversely, if the first electrode is a negative electrode, the second electrode may be a positive electrode.

[0050] In one embodiment, the electrode assembly (110) is formed in a jelly roll state by sequentially winding the first electrode, the separator, and the second electrode. The first electrode and the second electrode each include a coated portion in which an active material is applied to both sides of a substrate formed by a thin metal plate, and an uncoated portion in which the substrate is exposed because no active material is applied. As an example, the first electrode may form a positive electrode by coating a positive active material on an aluminum (Al) substrate, and the second electrode may form a negative electrode by coating a negative active material on a copper (Cu) substrate. The first electrode, the second electrode, and the separator may be impregnated with an electrolyte (not shown).

[0051] The outer surface of the electrode assembly (110) may include a separator or a substrate layer constituting the electrode. Specifically, the outer surface of the electrode assembly (110) may be one end of a separator that extends from the separator to prevent the active material constituting the first electrode or the second electrode from being exposed to the outside. In another example, the outer surface of the electrode assembly (110) may be one end of a substrate layer formed by extending a blank portion of the substrate layer on which the active material constituting the first electrode or the second electrode is not coated.

[0052] For the purpose of explaining the invention, the secondary battery (100) in FIGS. 1 to 8 below is shown in the form of a cylindrical secondary battery, but the scope of the present disclosure is not limited thereto. The secondary battery (100) of the present invention is not limited to a cylindrical secondary battery and includes secondary batteries of any shape, such as a prismatic secondary battery, a pouch secondary battery, or a coin secondary battery.

[0053] The case (120) forms the overall exterior of the secondary battery (100) and may be formed of a conductive metal such as aluminum, aluminum alloy, stainless steel (e.g., SUS), or nickel-plated steel. Additionally, the case (120) may provide a space for accommodating the electrode assembly (110). For example, if the secondary battery (100) is a cylindrical secondary battery, the case (120) may have the shape of a cylinder.

[0054] The case (120) has a fully open opening (122) to allow the electrode assembly (110) to be inserted on one side. A vent plate (130) can be coupled to seal the opening (122) after the electrode assembly (110) is inserted into the case (120). The vent plate (130) may include a weld (132) that is welded to at least a portion of the opening (122) of the case (120) to seal the case (120). The configuration and welding method of the weld (132) will be described later in FIG. 4.

[0055] The vent plate (130) is configured to cover the opening (122) of the case (120) and seals the interior of the secondary battery (100) from the external environment to prevent leakage of electrolyte, etc., protects the internal components of the secondary battery (100) from external moisture or dust, and provides a welding area or contact area to an external component (e.g., an external terminal) to electrically connect the secondary battery cell.

[0056] According to one embodiment of the present disclosure, the vent plate (130) may include a material exhibiting ferromagnetism. Specifically, the vent plate (130) may include at least a portion of a ferromagnetic material so that the secondary battery (100) can be moved and assembled by an external device or means that generates a magnetic field without mechanical assembly or chemical attachment processes.

[0057] For example, the vent plate (130) may comprise an alloy such as Alnico, Permalloy, Silicon Steel, Neodymium (NdFeB), composed of iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), zinc (Zn), chromium (Cr), titanium (Ti), or a combination including these.

[0058] According to one embodiment, the vent plate (130) may comprise a ferrite stainless steel (SUS) made of an alloy of iron and chromium. Specifically, at least a portion of the vent plate (130) may comprise SUS 430, SUS 409, SUS 446, or a combination including these.

[0059] According to one embodiment, the vent plate (130) may comprise a martensitic SUS made of an alloy of iron and chromium containing high carbon. Specifically, at least a portion of the vent plate (130) may comprise SUS 410, SUS 420, SUS 440, or a combination including these.

[0060] According to one embodiment of the present disclosure, the vent plate (130) may include a paramagnetistic SUS alloy. For example, the vent plate (130) may include an austenitic SUS alloy composed of iron, nickel, and chromium. Specifically, at least a portion of the vent plate (130) may include SUS 304, SUS 316, SUS 310, SUS 321, or a combination thereof. The austenitic SUS is an alloy comprising 16 to 26% chromium, 6 to 12% nickel, and 62% to 78% iron, and may have excellent corrosion resistance, machinability, and mechanical properties against external stress compared to aluminum (Al).

[0061] According to some embodiments of the present disclosure, by providing a vent plate (130) made of a SUS alloy material having high durability and stress resistance, the vent plate (130) is prevented from protruding outward even during long-term use of the secondary battery (100), thereby extending the lifespan of the secondary battery (100) and providing a standardized secondary battery (100).

[0062] In one embodiment, the vent plate (130) may include a welded portion (132) formed by extending the outer circumference of the vent plate (130) in the extension direction (a) of the case (120) and joining with the opening (122), a first flat portion (134) connected to the welded portion (132) and formed perpendicularly to the extension direction (a) of the case (120), and a second flat portion (136) located at the center of the vent plate (130) and connected to the first flat portion (134) with a step. Here, the extension direction (a) of the case (120) may refer to the direction extending vertically in FIG. 1.

[0063] Specifically, the second flat portion (136) may protrude in a direction opposite to the direction in which the electrode assembly (110) housed within the case (120) is located relative to the first flat portion (134). The degree of protrusion of the second flat portion (136) may be varied according to selection within a range in which the second flat portion (136) does not exceed the upper surface or height of the weld portion (132). The shape and structure of the vent plate (130) will be described later in FIGS. 2 to 6.

[0064] The vent plate (130) may further include an injection port (138) penetrating the vent plate (130) and a sealing member (150) that seals the injection port (138).

[0065] In one embodiment, the sealing member (150) may be in the shape of a rivet, such as a solid rivet, fender rivet, punch rivet, or blind rivet, corresponding to the size of the injection port (138). For example, when the sealing member (150) is implemented in the shape of a rivet, it may include a body portion that contacts the outer surface of the area where the injection port (138) is formed on the case (120), and a leg portion that penetrates the injection port (138) on the case (120) and contacts the inner surface of the area where the injection port (138) is formed. The body portion and the leg portion of the sealing member (150) may be integral with each other.

[0066] A secondary battery (100) according to one embodiment of the present disclosure further comprises a current collector (140) that electrically connects a first electrode and a vent plate (130), and the current collector (140) may be connected to a second flat portion (136). Specifically, the current collector (140) may be interposed between the first electrode and the vent plate (130) and may be electrically connected to the inner surface of the second flat portion (136) in the direction of the electrode assembly (110) through welding. Additionally, the electrode assembly (110) may be electrically connected to the current collector (140) by welding the uncoated portion (112) of the electrode assembly (110) to the current collector (140). The current collector (140) may include a bottom portion and a folded wing portion so as to be welded to the uncoated portion of the electrode assembly (110) or the inner surface of the second flat portion (136). The shape of the entire house (140) will be described later in FIG. 7.

[0067] Specifically, the unbonded portion of the current collector (140) and the electrode assembly (110), or the inner surface of the current collector (140) and the second flat portion (136), may be welded using any one of the following methods: ultrasonic welding, laser welding, resistance welding, TIG welding (Tungsten Inert Gas Welding), or a combination thereof. The welding method is not limited to the types of welding listed above, and various methods generally used for welding two materials may be used at the choice of a person skilled in the art.

[0068] According to some embodiments of the present disclosure, when a vent plate (130) including multiple bends such as a welded portion (132) and a first flat portion is inserted into a case opening (122) of a cylindrical secondary battery, the insertability of the part can be improved by the elasticity derived from the multiple bend structure. In addition, this can solve the problem of the accuracy of the outer diameter of the vent plate (130) and the case opening (122), thereby increasing the process productivity of the entire secondary battery.

[0069] In addition, according to some embodiments of the present disclosure, the material of the vent plate (130) can be modified to improve durability, and new properties can be imparted to the vent plate (130) to enable the movement and assembly of the secondary battery (100) cell using a magnet.

[0070] FIG. 2 is a plan view showing the appearance of a vent plate before and after use according to one embodiment of the present disclosure.

[0071] Referring to FIG. 2, the vent plate (230) according to one embodiment of the present disclosure may protrude outwardly from the electrode assembly (210) due to gas generated as the secondary battery is used. However, the secondary battery having the configuration of the illustrated vent plate (230) can maintain its total height regardless of the protrusion or deformation of the vent plate (230).

[0072] Specifically, according to the results of a practical test for a secondary battery having a case (220) diameter of 40 mm to 50 mm, when the height difference between the center of the vent plate (240) after swelling due to use of the secondary battery and the center of the vent plate (230) before swelling is denoted as d, the d of the secondary battery according to one embodiment of the present disclosure that has reached the end of its lifespan is 0.25 mm to 0.5 mm, and the height difference between the second flat portion (236) and the welded portion (232) of the vent plate (230) is maintained at or greater than that. As a result, the total height of the secondary battery does not change regardless of the deformation of the vent plate (240) caused by the increase in internal pressure of the secondary battery. The description of the configuration other than that is the same as the description given above with reference to FIG. 1.

[0073] According to some embodiments of the present disclosure, the structure of the new vent plate (230) prevents deformation of the overall cell dimensions or specifications even when the central part of the vent plate (230) protrudes outward due to an increase in internal pressure caused by long-term use, thereby extending the lifespan of the secondary battery and simultaneously providing a more standardized secondary battery cell.

[0074] Compared to the illustrated embodiment of the present invention, the secondary battery of another embodiment corresponding to the control group includes the same electrode assembly (210) and case (220) as the secondary battery of the present invention, but the shape and material of the vent plate (230) may differ from the secondary battery of the present invention described above in FIG. 1. Specifically, the secondary battery vent plate of another embodiment may include an aluminum alloy, and the secondary battery vent plate (230) of the embodiment of the present invention may include ferritic SUS, martensitic SUS, or austenitic SUS.

[0075] In a secondary battery according to one embodiment of the present disclosure, the height difference (d) between the center of the vent plate (240) after the secondary battery has reached the end of its lifespan and the center of the vent plate (230) before use can be reduced to 25% compared to the height difference between the center of the vent plate of another embodiment including an aluminum alloy.

[0076] FIG. 3 is a perspective view showing a vent plate according to one embodiment of the present disclosure. FIG. 4 is a longitudinal section view of a vent plate according to one embodiment of the present disclosure taken along line AA of FIG. 3.

[0077] Referring to FIGS. 3 and 4, in one embodiment, the vent plate (300) may include a welded portion (310) formed by extending the outer circumference of the vent plate (300) and joining with the opening of the case, a first flat portion (320) connected to the welded portion (310) and formed perpendicular to the extension direction of the welded portion (310), a second flat portion (330) located at the center of the vent plate (300) and having a step difference relative to the first flat portion (320), and a liquid injection port (350) penetrating the vent plate (300).

[0078] The heights of the first flat section (320) and the second flat section (330) are different from each other, so there may be a step difference between them. For example, the first flat section (320) and the second flat section (330) of the vent plate (300) are parallel planes to each other, and subsequently, when the vent plate (300) seals the case (420) of the secondary battery, the second flat section (330) may protrude in a direction opposite to the direction in which the electrode assembly accommodated in the case (420) is located relative to the first flat section (320).

[0079] Specifically, as illustrated in FIG. 4, the height (h1) of the first flat section (320) relative to the plane (B) formed by the end of the opening (422) in the extension direction of the case (420) may be equal to or greater than the height (h2) of the second flat section (330). Here, the degree of protrusion of the second flat section (330) may be varied according to selection within a range where the second flat section (330) does not exceed the height of the welded section (310). For example, the difference between the height (h1) of the first flat section (320) and the height (h2) of the second flat section (330) may be 0.25 mm to 0.5 mm.

[0080] In one embodiment, the weld (310) of the vent plate (300) may be welded (424) to at least a portion of the opening (422) of the case (420) to seal the case (420).

[0081] Specifically, at least a portion of the weld (310) of the vent plate (300) and the opening (422) of the case (420) may be welded using any one of ultrasonic welding, laser welding, resistance welding, TIG welding (Tungsten Inert Gas Welding), or a combination thereof. The welding method is not limited to the types of welding listed above, and various methods generally used for welding two materials may be used at the choice of a person skilled in the art.

[0082] According to one embodiment, the vent plate (300) may include a notch (340) configured to break when pressure exceeding a set value is applied. Specifically, the notch (340) may function as a vent that deforms or ruptures when the internal pressure of the secondary battery exceeds a certain pressure (operating pressure) to release gas generated inside the secondary battery to the outside of the secondary battery.

[0083] The location or shape of the notch (340) may vary. For example, the vent plate (300) may include a circumferential notch (340) as shown in FIGS. 3 and 4. The notch (340) may be formed continuously over the entire area along the circumferential direction of the vent plate (300), or it may be formed in multiple numbers spaced apart at predetermined intervals. The cross-section of the notch (340) may be semicircular or gradually narrowing wedge-shaped, but is not limited thereto.

[0084] As illustrated in FIG. 4, in one embodiment, a notch (340) may be formed on one side facing the electrode assembly in the first flat portion (320) of the vent plate (300). According to another embodiment, the notch (340) may be formed on one side facing the electrode assembly in the second flat portion (330) of the vent plate (300). Specifically, if the location of the notch (340) is the second flat portion (330) formed towards the center of the vent plate (300), the fracture pressure of the notch (340) may be high, and if the location of the notch (340) is the first flat portion (320) formed towards the outer side of the vent plate (300), the fracture pressure of the notch (340) may be low. Therefore, the location of the notch (340) may be varied depending on the design of the fracture pressure of the notch (340).

[0085] According to some embodiments of the present disclosure, when an abnormal event such as a short circuit within an electrode assembly occurs in a secondary battery, a notch (340) located on one side of the vent plate (300) facing the electrode assembly is directly exposed to gas generated in the secondary battery and then receives concentrated internal pressure, easily cut, thereby releasing the internal pressure of the secondary battery to the outside and preventing a secondary explosion.

[0086] FIG. 5 is a drawing showing the appearance of a vent plate before insertion according to one embodiment of the present disclosure. FIG. 6 is also a drawing showing the appearance of a vent plate after insertion according to one embodiment of the present disclosure.

[0087] Referring to FIGS. 5 and 6, the welded portion (510) of the vent plate (500) according to one embodiment of the present disclosure includes an inclined surface (512) formed to facilitate the insertion of the vent plate (500) into the opening (562), and the inclined surface (512) may form an acute angle with the extension direction (a) of the case (560).

[0088] Specifically, the outer diameter of the vent plate (500) formed along the weld (510) may correspond to the inner diameter of the opening (562) of the case (560). Even if the outer diameter of the vent plate (500) is slightly larger than the inner diameter of the opening (562) of the case (560), the vent plate (500), with improved insertability due to the bevel (512), can be fitted and easily inserted.

[0089] In one embodiment, the first flat section (520), the second flat section (530), and the welded section (510) can be integrally formed from an elastic material. Through this, even if the welded section (510) is bent along the inclined surface (512) as the vent plate (500) is inserted, the first flat section (520), the second flat section (530), and the injection port (550) can maintain the same shape as shown in FIGS. 5 and 6.

[0090] According to some embodiments of the present disclosure, when a vent plate (500) including multiple bends is inserted into an opening (562) of a case (560) of a cylindrical secondary battery, the insertability of the part may be improved by the elasticity derived from the multiple bend structure. In addition, this may solve the problem of the alignment accuracy between the dimensions of the vent plate (500) and the opening (562) of the case (560), thereby increasing the process productivity of the entire secondary battery.

[0091] FIG. 7 is a plan view showing a cross-section of a case with a vent plate attached according to one embodiment of the present disclosure.

[0092] According to one embodiment of the present disclosure, a groove (790) corresponding to a weld (710) may be formed on the inner surface of the end of the opening (762) of the case (760). Specifically, the length of the groove (790) may correspond to the length of the weld (710), and the thickness of the groove (790) may be less than or equal to the thickness of the weld (710). The groove (790) may be formed in a circumferential shape carved along the opening (762) of the case (760) corresponding to the shape of the weld (710) of the vent plate (700).

[0093] According to some embodiments of the present disclosure, the groove (790) guides the vent plate (700) to be fixed in close contact with the case (760) at a predetermined position so that the first flat portion (720), the second flat portion (730), and the notch (740) are positioned at the designed positions.

[0094] In one embodiment, the groove (790) of the case (760) may include a coating layer (792). The coating layer (792) may prevent leakage of the electrolyte, inhibit corrosion that may occur when the groove (790) is exposed to the electrolyte, and provide electrical insulation.

[0095] For example, the coating layer (792) may be made of a polymer coating including Teflon (PTFE, Polytetrafluoroethylene), polypropylene (PP, Polypropylene), polyethylene terephthalate (PET, Polyethylene terephthalate), polycarbonate (PC, Polycarbonate), or a combination thereof.

[0096] Alternatively, the coating layer (792) may be made of a metal coating including nickel (Ni) plating or chrome (Cr) plating to minimize reaction with the electrolyte and protect the surface of the groove (790).

[0097] In one embodiment, the coating layer (792) may be made of a ceramic coating comprising alumina (Al2O3), zirconia (ZrO2), paralylene, epoxy resin, or a combination thereof. The coating layer (792) is not limited to the materials listed above and may include various materials with excellent durability according to the choice of a person skilled in the art.

[0098] Other details regarding the configuration are as described above with reference to Fig. 1.

[0099] FIG. 8 is a cross-sectional view showing an example of a secondary battery according to one embodiment of the present disclosure.

[0100] Referring to FIG. 8, a secondary battery according to one embodiment of the present disclosure includes an electrode assembly (810) that performs charging and discharging, a case (820) that houses the electrode assembly (810), a first current collector plate (830) and a second current collector plate (850) connected to the electrode assembly (810), an electrode terminal (841), a vent plate (842), and a gasket (860). Here, the vent plate (842) may be the same as the vent plate described above in FIG. 1 to FIG. 7.

[0101] In FIG. 8, the vent plate (842) is shown positioned on the upper part of the secondary battery and the electrode terminal (841) is shown positioned on the lower part of the secondary battery, but this is not limited thereto. Depending on the usage environment or requirements of the secondary battery, the vent plate (842) and the electrode terminal (841) may be changed to be positioned on the lower part and the upper part of the secondary battery, respectively.

[0102] The electrode assembly (810) is formed into a cylindrical jelly roll state with an empty core by winding the first electrode (811a, 811b), separator (813), and second electrode (812a, 812b). The first electrode (811a, 811b) and the second electrode (812a, 812b) each include a coated portion (811a, 812a) in which an active material is applied to both sides of a substrate formed by a thin metal plate, and an uncoated portion (811b, 812b) in which the substrate is exposed and the active material is not applied.

[0103] The first electrode (811a, 811b) may be an electrode corresponding to a positive or negative electrode in a secondary battery. The second electrode (812a, 812b) may be an electrode corresponding to a pole opposite to the first electrode (811a, 811b). For example, if the first electrode (811a, 811b) is a positive electrode, the second electrode (812a, 812b) may be a negative electrode. Conversely, if the first electrode (811a, 811b) is a negative electrode, the second electrode (812a, 812b) may be a positive electrode.

[0104] For example, the first electrode (811a, 811b) may be formed as a positive electrode by coating a positive active material on an aluminum (Al) substrate, and the second electrode (812a, 812b) may be formed as a negative electrode by coating a negative active material on a copper (Cu) substrate. The uncoated portion (811b) of the first electrode and the uncoated portion (812b) of the second electrode are respectively provided at both ends in the winding axis direction of the electrode assembly (810), but electrode terminals (841) and cases (820) having different polarities are provided together in the same direction. A vent plate (842) is located on the opposite side of the electrode terminal (841).

[0105] The case (820) is formed as a cylinder to house the electrode assembly (810), and the electrode terminal (841) and the vent plate (842) are respectively provided at both ends of the case (820) in the axial direction so as to face each other.

[0106] According to one embodiment of the present disclosure, the diameter of the case (820) may be 40 mm to 50 mm.

[0107] The electrode terminal (841) is connected to the first electrode (811a, 811b) via the first current collector plate (830) through a rivet (843), and the case (820) is connected to the second electrode (812a, 812b) via the second current collector plate (850). At this time, the vent plate (842) is electrically separated from the second current collector plate (850) and the case (820) and does not have polarity.

[0108] An electrode terminal (841) connected to the first electrode (811a, 811b) of the electrode assembly (810) inserted into the case (820) from the outside is installed on one side of the case. The case (820) has a through hole (821) that is partially open on one side.

[0109] For example, the electrode terminal (841) may be installed in a through hole (821) of the case (820) in a rivet structure. To this end, the electrode terminal (841) may be connected to a rivet (843). One end of the rivet (843) is welded to the first current collector plate (830) and positioned to pass through the through hole (821). The electrode terminal (841) is connected to the rivet (843) and positioned on the outside of the case (820). The electrode terminal (841) may be formed to protrude above the outer surface of the case (820) around the through hole (821) and used as an anode terminal. At this time, the first current collector plate (830) becomes an anode current collector plate.

[0110] At this time, the first current collector plate (830) is electrically connected to the unoccupied portion (811b) of the first electrode through a rivet (843) and is electrically and mechanically connected to the electrode terminal (841). The first current collector plate (830) is electrically connected to the electrode terminal (841) in a structure that reduces resistance by contacting most of the unoccupied portion (811b) of the first electrode. The rivet (843) included in the electrode terminal (841) is installed in a state of electrical insulation from the case (820) while forming a hermetic structure against the electrolyte by interposing an insulator (823) in the through hole (821).

[0111] Here, the insulator (823) may be made of a polymer comprising ethylene propylene rubber (EPDM), polypropylene (PP), polyimide (PI), polyethylene terephthalate (PET), polycarbonate (PC), or a combination thereof.

[0112] As another example, the insulator (823) may be made of a ceramic material including epoxy resin, alumina (Al2O3), zirconia (ZrO2), aramid fiber, Nomex, or a combination thereof. However, the material of the insulator (823) is not limited to the materials listed above and may include various materials with excellent plasticity and insulation properties depending on the choice.

[0113] In one embodiment, the first current collector plate (830) may include a metal plate (831) comprising at least one bridge (832). For example, the first current collector plate (830) may be composed of a conductive metal, specifically a conductive metal such as nickel, aluminum, copper, silver, zinc, tin, stainless steel (e.g., SUS), or nickel-plated steel or a combination thereof (alloy). Additionally, the metal plate (831) and the bridge (832) constituting the first current collector plate (830) may all be made of the same material to form a single unit.

[0114] Here, the bridge (832) of the first collector plate (830) can be configured to break if a current exceeding a set value flows. For example, the bridge (832) normally operates as part of a circuit through which current flows, but if a current exceeding what is needed flows, it can act as a fuse that melts due to the heat generated to cut off the circuit.

[0115] An insulating tape (845) may be attached to one side of the first current collector plate (830). The insulating tape (845) may be interposed between the first current collector plate (830) and the case (820) or between the uninsulated portion (811b) of the first electrode and the case (820) to electrically insulate each component. In one embodiment, the central portion of the insulating tape (845) may include a perforation (846) corresponding to the shape of a rivet (843) so that the rivet (843) can come into contact with the first current collector plate (830). Additionally, the insulating tape (845) may include a side wall (847) to wrap around a part of the electrode assembly (810).

[0116] Additionally, the case (820) is provided with a fully open opening (822) to allow the electrode assembly (810) to be inserted on the other side. The vent plate (842) seals the opening (822) after the electrode assembly (810) is inserted into the case (820) and is electrically separated from the case (820).

[0117] At this time, the second current collector plate (850) is electrically connected to the non-transferable portion (812b) of the second electrode and is electrically connected to the case (820) or the vent plate (842). The second current collector plate (850) is connected to the case (820) or the vent plate (842) in a structure that reduces resistance by contacting most of the non-transferable portion (812b) of the second electrode.

[0118] The second current collector plate (850) includes a bottom portion (851) welded to the non-removable portion (812b) of the second electrode and a wing portion (852) formed adjacent to the bottom portion (851) and welded to the vent plate (842). The second current collector plate (850) is formed by cutting and bending a circular plate, and may have a plurality of bottom portions (851) and wing portions (852), respectively, and may be arranged alternately along the circumferential direction. In one embodiment, the wing portion (852) may repeatedly form axial (upward) bending and radial (outer) bending of the electrode assembly (810).

[0119] In one embodiment, when the uncoated portion (812b) of the second electrode and the bottom portion (851) of the second current collector plate (850) are welded, the bottom portion (851) can form a weld line in the diameter direction of the second current collector plate (850). Thus, the bottom portion (851) can be evenly connected along the circumferential direction in the area of ​​the uncoated portion (812b) of the second electrode, and the wing portion (852) can be evenly connected along the circumferential direction in the area of ​​the beading portion (829). This enables a uniform current flow along the circumferential direction from the uncoated portion (812b) of the second electrode to the entire area of ​​the beading portion (829) of the case (820).

[0120] Additionally, the second collector plate (850) is provided with a hole (853) in the center, so it can absorb and mitigate deformation caused by welding between the bottom part (851) and the non-welded part (812b) of the second electrode, as well as vibrations and shocks that may be transmitted between the wing part (852) and the bottom part (851). The hole (853) may have a size within a range that can absorb vibrations and shocks without increasing current resistance between the wing part (852) and the bottom part (851).

[0121] The vent plate (842) is electrically connected to the second current collector plate (850) and installed in the opening (822) of the case (820) through a welding process. Due to the connection of the second current collector plate (850), the case (820) and the vent plate (842) can be used as negative terminals. At this time, the second current collector plate (850) becomes a negative current collector plate. The vent plate (842) may have the same or similar configuration as the vent plates (130, 230, 300, 500, 700) described with reference to FIGS. 1 to 7.

[0122] The sealing tape (890) can be attached to wrap the outer surface of the jelly roll of the electrode assembly (810) at least once. Additionally, the electrode assembly (810) is inserted into the case (820) with the sealing tape (890) attached, and the sealing tape (890) can be positioned between the electrode assembly (810) and the case (820). Thus, the secondary battery assembled is prevented from moving the electrode assembly (810) up and down or forward and backward within the case (820), thereby preventing the separation of terminals or damage to the components, and even when the electrode assembly (810) expands due to charging and discharging, cracks in the case (820) or the electrode assembly (810) caused by excessive expansion of the electrode assembly (810) can be suppressed.

[0123] A secondary battery according to one embodiment of the present invention may be applied to automobiles, mobile phones, and / or various types of electric devices, etc., but the present invention is not limited thereto.

[0124] FIG. 9 is a flowchart illustrating an example of a method for manufacturing a secondary battery according to the present disclosure.

[0125] A method for manufacturing a secondary battery (900) according to one embodiment of the present invention may be disclosed by winding a first electrode, a separator, and a second electrode to form an electrode assembly (S910). Here, the diameter of the electrode assembly may be 40 mm to 50 mm.

[0126] Afterwards, the electrode assembly can be inserted into the case (S920).

[0127] Then, one side opening of the case can be sealed with a vent plate (S930). Here, the vent plate may include a welded portion formed by extending the outer circumference of the vent plate in the direction of extension of the case and joining with the opening, a first flat portion connected to the welded portion and formed perpendicular to the direction of extension of the case, and a second flat portion located at the center of the vent plate and having a step difference relative to the first flat portion. Additionally, a groove corresponding to the welded portion may be formed on the inner surface of the end of the opening. According to one embodiment, the welded portion includes an inclined surface formed to facilitate the insertion of the vent plate into the opening, and the inclined surface may form an acute angle with the direction of extension of the case.

[0128] According to one embodiment, the height of the first flat portion relative to the plane formed by the end of the opening in the extension direction of the case may be equal to or greater than the height of the second flat portion.

[0129] According to one embodiment, the vent plate may further include an injection port penetrating the vent plate and a sealing member sealing the injection port. A secondary battery according to one embodiment may further include a current collector electrically connecting the first electrode and the vent plate, and the current collector may be connected to a second flat portion.

[0130] According to one embodiment, the vent plate may include a material exhibiting ferromagnetism. For example, the vent plate may include ferrite or martensitic stainless steel. According to another embodiment, the vent plate may include austenitic stainless steel.

[0131] In addition, a vent plate according to one embodiment includes a circumferential notch, and the notch may be formed on one side of a first flat portion.

[0132] Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs. Since various substitutions, modifications, and changes are possible within the scope of the technical spirit of the present invention without departing from it, by those skilled in the art to which the present invention belongs, the present invention is not limited by the aforementioned embodiments and attached drawings.

Claims

1. An electrode assembly formed by winding a first electrode, a separator, and a second electrode; A case housing the above electrode assembly; and A vent plate that seals an opening on one side of the above case Includes, The above vent plate is A welded portion formed by extending the outer circumference of the vent plate in the extension direction of the above case and joining with the opening; A first flat portion connected to the welded portion and formed perpendicular to the extension direction of the case; and A second flat portion located at the center of the above-mentioned vent plate and having a step difference relative to the first flat portion A secondary battery including 2. In Paragraph 1, A secondary battery in which the height of the first flat portion relative to the plane formed by the end of the opening in the extension direction of the above case is equal to or greater than the height of the second flat portion.

3. In Paragraph 1, The above welded portion includes an inclined surface formed to facilitate the insertion of the vent plate into the opening, and A secondary battery in which the above-mentioned inclined plane forms an acute angle with the extension direction of the above-mentioned case.

4. In Paragraph 1, A secondary battery having a groove corresponding to the welded portion formed on the inner surface of the end of the above opening.

5. In Paragraph 1, The above-mentioned vent plate includes a circumferential notch, and The above notch is formed on one side of the first flat portion, a secondary battery.

6. In Paragraph 1, The above vent plate has an injection port penetrating the above vent plate and A secondary battery further comprising a sealing member for sealing the above-mentioned injection port.

7. In Paragraph 1, It further includes a current collector that electrically connects the first electrode and the vent plate, and The above current collector is a secondary battery connected to a second flat section.

8. In Paragraph 1, The above vent plate includes a ferromagnetic material, and A secondary battery in which the welded portion, the first flat portion, and the second flat portion are integrally formed of the same material.

9. In Paragraph 8, The above vent plate comprises a ferritic SUS or a martensitic SUS, and is a secondary battery.

10. In Paragraph 1, The above vent plate comprises austenitic SUS, a secondary battery.

11. In Paragraph 1, A secondary battery having a case diameter of 40 mm to 50 mm.

12. A step of forming an electrode assembly by winding the first electrode, the separator, and the second electrode; A step of inserting the electrode assembly through an opening on one side of the case; and The method includes the step of sealing the opening of the above case with a vent plate, The above vent plate is A welded portion formed by extending the outer circumference of the vent plate in the extension direction of the above case and joining with the opening; A first flat portion connected to the welded portion and formed perpendicular to the extension direction of the case; and A second flat portion located at the center of the above-mentioned vent plate and having a step difference relative to the first flat portion A method for manufacturing a secondary battery comprising 13. In Paragraph 12, A method for manufacturing a secondary battery, wherein the height of the first flat portion relative to the plane formed by the end of the opening in the extension direction of the case is greater than or equal to the height of the second flat portion.

14. In Paragraph 12, The above welded portion includes an inclined surface formed to facilitate the insertion of the vent plate into the opening, and A method for manufacturing a secondary battery, wherein the above-mentioned inclined plane forms an acute angle with the extension direction of the above-mentioned case.

15. In Paragraph 12, A method for manufacturing a secondary battery, wherein a groove corresponding to the weld is formed on the inner surface of the end of the opening.

16. In Paragraph 12, The above-mentioned vent plate includes a circumferential notch, and A method for manufacturing a secondary battery, wherein the above notch is formed on one side of the above first flat portion.

17. In Paragraph 12, The above vent plate has an injection port penetrating the above vent plate and A method for manufacturing a secondary battery, further comprising a sealing member for sealing the above-mentioned injection port.

18. In Paragraph 12, A method for manufacturing a secondary battery, further comprising the step of connecting the second flat portion and the current collector so that the first electrode and the vent plate are electrically connected.

19. In Paragraph 12, The above vent plate includes a material exhibiting ferromagnetism, and A method for manufacturing a secondary battery in which the welded portion, the first flat portion, and the second flat portion are integrally formed of the same material.

20. In Paragraph 19, A method for manufacturing a secondary battery, wherein the above-mentioned vent plate comprises ferrite or martensite-based SUS (stainless steel).

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