Cylindrical secondary battery, battery pack including the same, and automobile

Abstract

The present invention relates to a cylindrical secondary battery including an insulating gasket interposed between a housing and a terminal. The insulating gasket included in the cylindrical secondary battery according to an embodiment of the present invention includes a predetermined polymer resin and a predetermined flame-retardant additive, thereby improving the safety of the cylindrical secondary battery. In particular, the present invention can prevent a short circuit between the positive and negative electrodes even after a fire or explosion has already occurred, thereby preventing a chain reaction of fires or explosions.

Description

[Technical Field]

[0001] The present invention relates to a cylindrical secondary battery, a battery pack including the same, and an automobile, and more particularly to a cylindrical secondary battery with improved safety, a battery pack including the same, and an automobile.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0126545, filed on October 4, 2022, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings thereof. [Background technology]

[0003] Secondary batteries, which are easily applicable to various products and have electrical properties such as high energy density, are widely used not only in portable devices but also in electric vehicles (EVs) and hybrid electric vehicles (HEVs) that are driven by electrical sources.

[0004] These secondary batteries are attracting attention as a new energy source that not only has the primary advantage of dramatically reducing the use of fossil fuels, but also is environmentally friendly because they do not produce any by-products associated with energy use and can improve energy efficiency.

[0005] Known types of secondary batteries include cylindrical, prismatic, and pouch-type secondary batteries. In cylindrical secondary batteries, an insulating separator is placed between the positive and negative electrodes, which is then wound up to form a jelly-roll-shaped electrode assembly. This assembly is then inserted into a housing along with an electrolyte to complete the battery. Strip-shaped electrode tabs are connected to the uncoated portions of the positive and negative electrodes, and the electrode tabs connect the electrode assembly to the exposed electrode terminals. However, conventional cylindrical secondary batteries with this structure have problems with high resistance, excessive heat generation, and poor current collection efficiency because current concentrates in the strip-shaped electrode tabs connected to the uncoated portions of the positive and / or negative electrodes.

[0006] Resistance and heat generation are not major issues for small cylindrical secondary batteries with form factors such as 1865 and 2170. However, when the form factor of cylindrical secondary batteries is increased to be used in electric vehicles, a lot of heat is generated around the electrode tabs during the fast charging process, which can cause fire problems in the cylindrical secondary battery.

[0007] To solve these problems, a cylindrical secondary battery (so-called tab-less cylindrical secondary battery) has been proposed, which has a structure in which positive and negative non-coated areas are located at the top and bottom of a jelly roll type electrode assembly, respectively, and current collecting plates are welded to these non-coated areas to improve current collection efficiency.

[0008] Figures 1 to 3 are diagrams showing the manufacturing process of a conventional tabless cylindrical secondary battery. Figure 1 shows the structure of the electrode plate, Figure 2 shows the winding process of the electrode plate, and Figure 3 shows the process of welding a current collecting plate to the bent surface of the non-coated portion. Figure 4 is a cross-sectional view of a conventional tabless cylindrical secondary battery cut in the longitudinal direction (Y direction).

[0009] 1 to 4, the positive electrode plate 210 and the negative electrode plate 211 have a structure in which an active material 221 is coated on a sheet-shaped current collector 220, and include a non-coated portion 222 on one long side along the winding direction (X direction).

[0010] The electrode assembly A is fabricated by sequentially stacking a positive electrode plate 210 and a negative electrode plate 211 together with two separators 212 as shown in Fig. 2, and then winding them in one direction (X direction). At this time, the non-coated portion of the positive electrode plate 210 and the non-coated portion of the negative electrode plate 211 are arranged in opposite directions.

[0011] After the winding process, the non-coated portion 210a of the positive electrode plate 210 and the non-coated portion 211a of the negative electrode plate 211 are bent toward the core side, and then the current collecting plates 230 and 231 are welded and joined to the non-coated portions 210a and 211a, respectively.

[0012] The positive electrode non-coated portion 210a and the negative electrode non-coated portion 211a do not have separate electrode tabs attached, and the current collecting plates 230 and 231 are connected to external electrode terminals, forming a current path with a large cross-sectional area along the winding axis direction of the electrode assembly A (see arrow), which has the advantage of lowering the resistance of the secondary battery. This is because resistance is inversely proportional to the cross-sectional area of the path through which current flows.

[0013] However, as the form factor of cylindrical secondary batteries increases and the magnitude of charging current increases during fast charging, heat generation problems also occur in tableless cylindrical secondary batteries.

[0014] Specifically, as shown in Figure 4, a conventional tabless cylindrical secondary battery 240 includes a housing 241 and a sealing body 242. The sealing body 242 includes a cap 242a, a sealing gasket 242b, and a connection plate 242c. The sealing gasket 242b surrounds the periphery of the cap 242a and is fixed by a crimping portion 243. In addition, the electrode assembly A is fixed in the housing 241 by a beading portion 244 to prevent vertical movement.

[0015] Typically, the cap 242a of the sealed body 242 serves as the positive terminal, and the housing 241 serves as the negative terminal. Thus, the current collecting plate 230 attached to the uncoated portion 210a of the positive electrode plate 210 is electrically connected to the connection plate 242c attached to the cap 242a via a strip-shaped lead 245. The current collecting plate 231 attached to the uncoated portion 211a of the negative electrode plate 211 is electrically connected to the bottom of the housing 241. The insulator 246 covers the current collecting plate 230 to prevent the uncoated portion 210a of the positive electrode plate 210 from coming into contact with the other housing 241, which has a different polarity, and causing a short circuit.

[0016] A strip-shaped lead 245 is used to connect the current collecting plate 230 to the connection plate 242c. The lead 245 is either attached separately to the current collecting plate 230 or integrally formed with the current collecting plate 230. However, since the lead 245 is a thin strip, its cross-sectional area is small, and therefore a large amount of heat is generated when a fast charging current flows. Furthermore, excessive heat generated in the lead 245 is transferred to the electrode assembly A side, causing the separator 212 to contract, which can lead to an internal short circuit, a major cause of thermal runaway.

[0017] That is, secondary batteries can overheat and explode if exposed to high temperatures, or if they are overcharged (exceeding the allowed current and voltage), or if they are subjected to an internal short circuit or abnormal battery operation due to external physical force. Therefore, safety measures must be taken to prevent secondary battery fires and explosions. In particular, electric vehicles containing cylindrical secondary batteries often contain hundreds of cylindrical secondary batteries, so an enhanced safety design is required to prevent chain reactions of fires and explosions in the event of a fire or explosion in one cylindrical secondary battery. Summary of the Invention [Problem to be solved by the invention]

[0018] An object of the present invention is to provide a cylindrical secondary battery with improved safety, and a battery and an automobile including the same.

[0019] Other objects and advantages of the present invention can be realized by the instrumentalities or methods, and combinations thereof, as claimed in the appended claims. [Means for solving the problem]

[0020] In order to achieve the above object, according to one aspect of the present invention, an electrode assembly in which a core and an outer circumferential surface are defined by winding a first electrode, a second electrode, and a separator interposed therebetween around a winding shaft, the first electrode and the second electrode each including a first non-coated portion and a second non-coated portion that are not coated with an active material layer along the winding direction; a housing that accommodates the electrode assembly through an opening formed at a lower end thereof and is electrically connected to the second non-application portion; a terminal electrically connected to the first non-coating portion and exposed to the outside of the housing through a closing portion of the housing located on the opposite side of the opening; An insulating gasket is provided on the closed portion side of the housing and is interposed between the housing and the terminal, The insulating gasket may include a polymer resin and a flame-retardant additive.

[0021] A sealing gasket may be provided on the opening side of the housing and interposed between the housing and the cap so that the cap seals the opening, and the sealing gasket may include a polymer resin and a flame retardant additive.

[0022] The polymer resin may include polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), or two or more thereof.

[0023] The flame retardant additive may include a phosphorus-based flame retardant, an inorganic flame retardant, a halogen flame retardant, or two or more thereof.

[0024] The flame retardant additive may be a phosphorus-based flame retardant.

[0025] The flame retardant additive may be halogen-free.

[0026] The insulating gasket may contain 5% to 30% of the flame retardant additive based on the total weight of the insulating gasket.

[0027] The flame retardant additive contained in the sealing gasket may be contained in an amount of 5% to 30% based on the total weight of the sealing gasket.

[0028] According to another aspect of the present invention, there is provided a battery pack including the cylindrical secondary battery described above.

[0029] According to yet another aspect of the present invention, there is provided a vehicle including the battery pack. [Effects of the Invention]

[0030] The present invention improves the safety of cylindrical secondary batteries by incorporating an insulating gasket between a housing and a terminal, which contains a predetermined polymer resin and a predetermined flame-retardant additive. In particular, the present invention can prevent short-circuiting between the positive and negative electrodes, even after a fire or explosion has already occurred, thereby preventing further fires or explosions.

[0031] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention, so the present invention should not be interpreted as being limited to the details shown in the drawings. Note that the shape, size, scale, or ratio of elements in the drawings attached to this specification may be exaggerated to emphasize a clearer description. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a plan view showing the structure of an electrode plate used in a conventional tabless cylindrical secondary battery. [Figure 2] 1A and 1B are diagrams illustrating a winding process of an electrode assembly included in a conventional tabless cylindrical secondary battery. [Figure 3] 3 is a diagram showing a process of welding a current collecting plate to a bent surface of a non-coated portion in the electrode assembly of FIG. 2. FIG. [Figure 4]FIG. 1 is a cross-sectional view of a conventional tablets cylindrical secondary battery cut in the longitudinal direction (Y direction). [Figure 5] 1 is a diagram showing the appearance of a cylindrical secondary battery according to an embodiment of the present invention; [Figure 6] 1 is a cross-sectional view showing the internal structure of a cylindrical secondary battery according to an embodiment of the present invention. [Figure 7] 1 is a partial cross-sectional view showing an upper structure of a cylindrical secondary battery according to an embodiment of the present invention; [Figure 8] 1 shows the results (image) of evaluating a flame test of a cylindrical secondary battery according to Comparative Example 1. [Figure 9] 1 shows the results (image) of evaluating a flame test of the cylindrical secondary battery according to Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed as meanings and concepts corresponding to the technical concept of the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of terms in order to best explain the invention. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical concept of the present invention, and therefore, various equivalents and modifications that can be substituted therefor may exist at the time of filing this application.

[0034] In order to facilitate understanding of the invention, the accompanying drawings may be drawn not to scale but with some components exaggerated. The same reference numerals may be used to refer to the same components in different embodiments.

[0035] When two comparison objects are "identical," it means that they are "substantially identical." Therefore, "substantially identical" may include deviations that are considered low in the art, for example, deviations within 5%. Furthermore, uniformity of any parameter in a given region may mean uniformity on average.

[0036] Terms such as "first" and "second" are used to describe various components, but these terms do not limit the components. These terms are used to distinguish only one component from another, and unless otherwise specified, the first component may be the second component.

[0037] Throughout the specification, unless otherwise specified, each element may be singular or plural.

[0038] When any structure is placed "on top (or bottom)" of a component or "above (or below)" a component, it can mean that the structure is placed directly on the top (or bottom) surface of the component, but also that other structures may be interposed between the component and any structure placed above (or below) the component.

[0039] Furthermore, when a component is described as being "coupled," "coupled," or "connected" to another component, it should be understood that the components may be directly coupled or connected to each other, but that other components may be "intervening" between the components, or that each component may be "coupled," "coupled," or "connected" by other components.

[0040] Throughout the specification, unless otherwise specified, a reference to "A and / or B" means "A," "B," or "A and B," and a reference to "C through D" means at least C and at most D, unless otherwise specified.

[0041] For ease of explanation, the direction along the longitudinal direction of the winding shaft of the electrode assembly wound into a jelly roll shape will be referred to as the axial direction (Y direction). The direction surrounding the winding shaft will be referred to as the circumferential direction (X direction). The direction toward or away from the winding shaft will be referred to as the radial direction. Of these, the direction toward the winding shaft will be referred to as the centripetal direction, and the direction away from the winding shaft will be referred to as the centrifugal direction.

[0042] 5 to 7, the cylindrical secondary battery 1 according to the embodiment of the present invention includes an electrode assembly 10, a housing 20, a terminal 40, and an insulating gasket 50. In addition to the above-mentioned components, the cylindrical secondary battery 1 may further include a cap 30 and / or a first current collector 60 and / or an insulator 70 and / or a second current collector 80 and / or a sealing gasket 90.

[0043] <Electrode assembly> The electrode assembly 10 includes a first electrode having a first polarity, a second electrode having a second polarity, and a separator interposed between the first and second electrodes. The first electrode is a positive or negative electrode, and the second electrode has the opposite polarity to the first electrode.

[0044] The electrode assembly 10 may have, for example, a jelly-roll structure. That is, the electrode assembly 10 may be manufactured by stacking sheet-like first and second electrodes at least once with a separator interposed therebetween, and winding the stack around the winding center C. In this case, a separator may be further provided on the outer periphery of the electrode assembly 10 for insulation from the housing 20. Any jelly-roll structure known in the art may be applied to the present invention without limitation.

[0045] The first electrode includes a first electrode current collector and a first electrode active material coated on one or both sides of the first electrode current collector. An uncoated portion where the first electrode active material is not coated is present at one end of the first electrode current collector in the width direction (direction parallel to the Z axis). The uncoated portion functioning as the first uncoated portion 11 is hereinafter referred to as the first uncoated portion 11. The first uncoated portion 11 is provided at the upper portion in the height direction (direction parallel to the Z axis) of the electrode assembly 10 housed in the housing 20. That is, the first electrode current collector includes the first uncoated portion 11 at the long side end where the active material layer is not coated and is exposed to the outside of the separator, and a portion of the first uncoated portion 11 is used as an electrode tab. The first uncoated portion 11 may be, for example, a positive electrode tab.

[0046] Meanwhile, at least a portion of the first non-coated portion 11 may include a plurality of segments separated along the winding direction of the electrode assembly 10. In this case, the plurality of segments may be folded along the radial direction of the electrode assembly 10. The folded plurality of segments may be overlapped in multiple layers. In this case, a first non-coated portion joining portion 62 of the first current collector 60 (described below) may be joined to a region where the plurality of segments are overlapped in multiple layers. Meanwhile, the electrode assembly 10 may include a welding target region, which is a region where the number of overlapping layers of the segments of the first non-coated portion 11 is maintained constant along the radial direction of the electrode assembly 10. Because the number of overlapping layers is maintained at a substantially maximum in this region, it is advantageous to perform welding between the first current collector 60 and the first non-coated portion 11 (described below) within this region. For example, this is to prevent the laser beam from penetrating the first non-coated portion 11 and damaging the electrode assembly 10 when increasing the laser output to improve welding quality during laser welding. This is also to effectively prevent foreign matter such as welding spatter from entering the inside of the electrode assembly 10.

[0047] The second electrode includes a second electrode current collector and a second electrode active material coated on one or both sides of the second electrode current collector. The second electrode current collector has a non-coated portion at the other end in the width direction (direction parallel to the Z axis) where the second electrode active material is not coated. The non-coated portion functioning as the second non-coated portion 12 is hereinafter referred to as the second non-coated portion 12. The second non-coated portion 12 is provided at the lower portion in the height direction (direction parallel to the Z axis) of the electrode assembly 10 housed in the housing 20. That is, the second electrode current collector includes the second non-coated portion 12 at the long side end where the active material layer is not coated and is exposed to the outside of the separator, and at least a portion of the second non-coated portion 12 functions as an electrode tab. The second non-coated portion 12 may be, for example, a negative electrode tab. Meanwhile, at least a portion of the second non-coated portion 12 may include a plurality of segments separated along the winding direction of the electrode assembly 10. In this case, the plurality of segments may be folded along the radial direction of the electrode assembly 10. The folded plurality of segments may be overlapped in multiple layers. In this case, the second non-coated portion coupling portion 82 of the second current collector 80 (described later) may be coupled to the region where the plurality of segments are overlapped in multiple layers. Meanwhile, the electrode assembly 10 may include a welding target region, which is a region where the number of overlapping layers of the segments of the second non-coated portion 12 is maintained constant along the radial direction of the electrode assembly 10. Because the number of overlapping layers is maximized in this region, it is advantageous to perform welding between the second current collector 80 and the second non-coated portion 12 (described later) within this region. For example, this is to prevent the laser beam from penetrating the second non-coated portion 12 and damaging the electrode assembly 10 when increasing the laser output to improve welding quality during laser welding. This is also to effectively prevent foreign matter, such as welding spatter, from entering the interior of the electrode assembly 10.

[0048] The first non-coated portion 11 and the second non-coated portion 12 extend in opposite directions along the height direction (direction parallel to the Z axis) of the cylindrical secondary battery 1. The first non-coated portion 11 extends toward a closed portion located on the opposite side of the opening formed at the bottom end of the housing 20, and the second non-coated portion 12 extends toward the open portion of the housing 20.

[0049] In the embodiment of the present invention, the positive electrode active material coated on the positive electrode plate and the negative electrode active material coated on the negative electrode plate may be any active material known in the art without any limitation.

[0050] The separation membrane may be any separation membrane known in the art, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, either alone or in combination, or a separation membrane having a coating layer of inorganic particles on at least one surface thereof.

[0051] <Housing> The housing 20 is a generally cylindrical container having an opening at the bottom and may be made of a conductive material such as metal. Examples of materials for the housing 20 include steel, stainless steel, and nickel-plated steel. The bottom of the housing 20 having the opening is defined as an open end. The top opposite the opening (or open end) is defined as a closed portion or closed end. The side (outer periphery) and the closed portion of the housing 20 may be integrally formed. Alternatively, the side wall and the closed portion of the housing 20 may be formed separately and joined together by welding or the like. The top surface (surface parallel to the XY plane) of the housing 20, i.e., the outer surface 20a of the closed portion, has a generally flat shape. The housing 20 may accommodate the electrode assembly 10 through the opening at the bottom, along with the electrolyte.

[0052] The housing 20 is electrically connected to the electrode assembly 10. The housing 20 is electrically connected to the second non-application portion 12 of the electrode assembly 10. In this case, the housing 20 has the same polarity as the second non-application portion 12.

[0053] The housing 20 may have a beading portion 21 and a crimping portion 22 formed at its lower end. The beading portion 21 is located below the electrode assembly 10. The beading portion 21 is formed by press-fitting around the outer periphery of the housing 20. More specifically, the beading portion 21 may be press-fit inward in a region between an opening formed on one side of the battery housing 20 and a receiving portion that receives the electrode assembly 10. The crimping portion 22 is formed below the beading portion 21. The crimping portion 22 extends from the lower beading portion 21. The crimping portion 22 is bent to surround the outer periphery of the cap 30 located below the beading portion 21 and a portion of the lower surface of the cap 30. The crimping portion 22 may fix a sealing gasket 90 in addition to the cap 30. However, the present invention does not exclude a case in which the housing 20 does not include the beading portion 21 and / or the crimping portion 22. In an embodiment of the present invention, when the housing 20 does not have a beading portion 21 and / or a crimping portion 22, the fixing of the electrode assembly 10 and / or the fixing of the cap 30 and / or the sealing of the housing 20 may be achieved, for example, by additionally applying a part that can function as a stopper for the electrode assembly 10 and / or additionally applying a structure to which the cap 30 can be attached and / or welding the housing 20 and the cap 30 together.

[0054] <Terminal> The terminals 40 may be made of a conductive metal material, such as aluminum (Al).

[0055] The terminal 40 is electrically connected to, for example, the first non-coated portion 11 of the electrode assembly 10. In this case, the terminal 40 has a first polarity. As a result, the terminal 40 can function as a first electrode terminal in the cylindrical secondary battery 1 according to an embodiment of the present invention. When the terminal 40 has the first polarity, the terminal 40 is electrically insulated from the housing 20, which has a second polarity. In an embodiment of the present invention, insulation can be achieved by interposing an insulating gasket 50, as described below, between the terminal 40 and the housing 20.

[0056] The terminal 40 is exposed to the outside of the housing from the closed portion located on the opposite side of the housing opening, and may include a terminal exposing portion 41 and a terminal inserting portion 42. The terminal inserting portion 42 may include an electrical connection portion 42a and a flange portion 42b. The terminal exposing portion 41 is exposed to the outside of the housing 20. The terminal exposing portion 41 may be located approximately at the center of the closed portion of the housing 20. The maximum width of the terminal exposing portion 41 may be larger than the maximum width of a central hole formed in the housing 20 for inserting the terminal 40. That is, the outer diameter of the terminal 40 exposed to the outside of the closed portion may be larger than the inner diameter of a through hole formed in the closed portion of the housing 20 for exposing the terminal 40. As a result, the cross section of the through hole formed in the closed portion for exposing the terminal 40 may be included within the cross section of the terminal 40 exposed to the outside of the closed portion. In addition, the portion of the terminal 40 exposed to the outside of the closed portion may axially cover at least a portion of the closed portion of the housing 20. The terminal insertion portion 42 passes through approximately the center of the closed portion of the housing 20, and the electrical connection portion 42a of the terminal insertion portion 42 may be electrically connected to the first non-coating portion 11. The flange portion 42b of the terminal insertion portion 42 may be formed around the electrical connection portion 42a and rivet-connected to the inner surface of the closed portion of the housing 20. That is, the flange portion 42b of the terminal insertion portion 42 may have a shape that is bent toward the inner surface of the closed portion of the housing 20. As a result, the maximum width of the terminal insertion portion 42 after a riveting process for fixing the terminal 40 is performed may be larger than the maximum width of the center hole formed in the housing 20 so that the terminal insertion portion 42 can pass through.

[0057] Meanwhile, when the cylindrical secondary battery 1 according to the present invention includes a first current collector 60, the electrical connection portion 42a of the terminal insertion portion 42 may be coupled to the first current collector 60. The electrical connection portion 42a of the terminal insertion portion 42 may be, for example, substantially cylindrical. Of course, the shape of the electrical connection portion 42a of the terminal insertion portion 42 is not limited thereto. The electrical connection portion 42a of the terminal insertion portion 42 may have various shapes, such as a cylindrical shape with an oval cross section, a rectangular prism, a hexagonal prism, or an octagonal prism. The bottom surface of the electrical connection portion 42a of the terminal insertion portion 42 may be at least partially substantially flat. The bottom surface of the central region of the terminal insertion portion 42 may be coupled to the first current collector 60 by, for example, laser welding, spot welding, or ultrasonic welding.

[0058] In an embodiment of the present invention, the upper surface of the housing 20, i.e., the outer surface 20a of the closed portion of the housing 20 and the upper surface of the terminal exposed portion 41 of the terminal 40 exposed to the outside of the housing 20, may have opposite polarities and face the same direction.

[0059] <Insulating gasket> The insulating gasket 50 is interposed between the housing 20 and the terminal 40 to prevent contact between the housing 20 and the terminal 40, which have opposite polarities. As a result, the substantially flat upper surface of the housing 20 can function as the second electrode terminal of the cylindrical secondary battery 1. For example, the entire area of the upper surface of the housing 20 as viewed from above the cylindrical secondary battery 1, excluding the area occupied by the terminal 40 and the insulating gasket 50, can serve as the second electrode terminal of the polarity opposite to that of the terminal 40.

[0060] 7, the insulating gasket 50 may include a gasket exposing portion 51 and a gasket inserting portion 52. The gasket exposing portion 51 is interposed between the terminal exposing portion 41 of the terminal 40 and the housing 20. The gasket exposing portion 51 extends longer than the terminal exposing portion 41, and thus may be exposed outside the terminal exposing portion 41 when the cylindrical secondary battery 1 is viewed from above. The gasket inserting portion 52 is interposed between the terminal inserting portion 42 of the terminal 40 and the housing 20. The gasket inserting portion 52 may be deformed during riveting of the flange portion 42b of the terminal inserting portion 42, and thus may be in close contact with the inner surface of the closure portion of the housing 20.

[0061] Although not shown, the gasket exposed portion 51 of the insulating gasket 50 may have a shape that extends so as to cover the outer peripheral surface of the terminal exposed portion 41 of the terminal 40. Furthermore, the gasket exposed portion 51 may have a shape that extends so as to cover not only the outer peripheral surface of the terminal exposed portion 41 but also part of the upper surface.

[0062] The insulating gasket 50 includes a polymer resin and a flame retardant additive. In this case, the insulating gasket 50 is bonded to the housing 20 and the terminal 40 by thermal welding, which can enhance the airtightness at the bonding interface between the insulating gasket 50 and the terminal 40 and at the bonding interface between the insulating gasket 50 and the housing 20. Meanwhile, when the gasket exposure portion 51 of the insulating gasket 50 extends to the upper surface of the terminal exposure portion 41, the terminal 40 can be bonded to the insulating gasket 50 by insert injection.

[0063] The polymer resin may include polyolefin, polyester, polyarylene sulfide, thermoplastic polyester elastomer (TPEE), perfluoroalkoxy resin, polyimide, or two or more thereof. Specifically, the polymer resin may include polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), or two or more thereof.

[0064] The inclusion of the above-mentioned polymer resins ensures the moldability and flexibility of insulating gaskets, and they can exhibit excellent heat resistance and mechanical properties. In particular, polybutylene terephthalate (PBT) is an elastomer with good elasticity, improving injection properties and making gaskets easy to mold. Its high melting point ensures high stability at high temperatures. Furthermore, while the addition of flame retardant additives to polymer resins typically reduces physical properties such as strength and elongation, the addition of flame retardant additives to polybutylene terephthalate minimizes this reduction in physical properties.

[0065] In addition, the polymer resin may have a melting point of 250° C. or higher and a heat distortion temperature of 200° C. or higher. When a polymer resin satisfying these properties is included, even in the event of an electrical short circuit inside the secondary battery or abnormal overheating due to the external environment, the polymer resin does not exhibit fluidity below its melting point, thereby suppressing structural deformation at the site where the gasket comes into contact and preventing further current flow, thereby ensuring the safety of the battery.

[0066] However, if the insulating gasket contains only the polymer resin, the secondary battery may still be heated and ignite or explode if exposed to high temperatures or in an environment where the battery is operating abnormally, so a safety-enhanced design is required. Therefore, in an embodiment of the present invention, a flame-retardant additive is included together with the polymer resin to prevent short circuits between terminals and prevent chain reactions of fire and explosion, thereby enhancing safety.

[0067] In an embodiment of the present invention, the insulating gasket contains a flame-retardant additive, thereby enhancing the safety of cylindrical secondary batteries. In particular, while cylindrical secondary batteries are prone to cascading fires and explosions, an embodiment of the present invention has the advantage of preventing a short circuit between the first and second electrodes, i.e., the positive and negative electrodes, thereby preventing cascading fires and explosions even after an ignition or explosion has occurred.

[0068] In particular, in the present invention, when manufacturing an insulating gasket, a polymer resin and a flame-retardant additive are mixed and then injection-molded, so that the entire gasket can function as a flame retardant, thereby significantly preventing short circuits.If a flame retardant is not mixed into the gasket when manufacturing the gasket and a separate flame retardant is filled into the internal space of the secondary battery, unlike the present invention, the gasket will not function to prevent short circuits between the positive and negative electrodes, making it difficult to prevent chain fires and explosions.

[0069] The flame-retardant additive may include a phosphorus-based flame retardant, an inorganic flame retardant, a halogen-based flame retardant, or two or more of these. Preferably, the flame-retardant additive does not contain a halogen element in consideration of environmental conservation, and more preferably, the flame-retardant additive may be a phosphorus-based flame retardant. In particular, when a flame-retardant additive is added to a polymer resin, physical properties such as strength and elongation are typically reduced. However, when polybutylene terephthalate is used as the polymer resin and a phosphorus-based flame retardant is used as the flame-retardant additive, the reduction in the excellent physical properties of polybutylene terephthalate is significantly reduced. Therefore, when polybutylene terephthalate and a phosphorus-based flame retardant are mixed to form an insulating gasket, the excellent effect of ensuring the injectability and high-temperature stability of polybutylene terephthalate while simultaneously maintaining the flame-retardant properties of the phosphorus-based flame retardant is achieved.

[0070] The flame retardant additive may be included in an amount of 5% to 30%, 5% to 15%, or 10% to 15% of the total weight of the insulating gasket. When the flame retardant additive is included within this range, the insulating gasket maintains its moldability and flexibility while preventing short circuits between the positive and negative electrodes, thereby preventing chain reactions of fire or explosion even after a fire or explosion has occurred. In particular, if the content does not meet this range, the effect of the flame retardant additive is minimal, making it difficult to prevent short circuits. However, if the content exceeds this range, the physical properties of the polymer resin may be degraded.

[0071] Meanwhile, the insulator 70 and the sealing gasket 90 may be made of the same material as the insulating gasket 50, but this is not essential.

[0072] The thickness of the insulating gasket 50 may gradually decrease downward from the middle region where the gasket exposing portion 51 and the gasket inserting portion 52 are connected, and may increase slightly at the end of the gasket inserting portion 52. Such a compression structure of the insulating gasket 50 may further improve the sealing performance for the space between the terminal 40 and the housing 20.

[0073] Preferably, the riveting structure of the terminal 40 according to the above-described embodiment of the present invention can be applied to cylindrical secondary batteries having a form factor larger than 21700.

[0074] In recent years, as cylindrical secondary batteries are being applied to electric vehicles, the form factor of cylindrical secondary batteries is increasing beyond the conventional 1865, 2170, etc. The increase in form factor brings about an increase in energy density, increased safety against thermal runaway, and improved cooling efficiency.

[0075] Furthermore, in the cylindrical secondary battery 1 to which the riveting structure of the terminal 40 is applied, all electrical wiring of the positive electrode / negative electrode can be performed on one side. Furthermore, the terminal 40 having the riveting structure described above has a large cross-sectional area and therefore low electrical resistance, which is very advantageous for rapid charging.

[0076] <Other components> According to an embodiment of the present invention, the cylindrical secondary battery 1 may further include a cap 30 and / or a first current collector 60 and / or an insulator 70 and / or a second current collector 80 and / or a sealing gasket 90 in addition to the above-mentioned components.

[0077] Referring to FIG. 6 , the cap 30 may be made of, for example, a metal material to ensure rigidity. The cap 30 seals an opening (or an open end) formed at the bottom of the housing 20. That is, the cap 30 may form the bottom surface of the cylindrical secondary battery 1. In the cylindrical secondary battery 1 according to the present embodiment, the cap 30 may not have polarity even if it is made of a conductive metal material. Not having polarity means that the cap 30 is not electrically connected to the electrode assembly 10. When the cap 30 is not electrically connected to the electrode assembly 10, the cap 30 does not function as a positive or negative terminal. That is, in the present embodiment, the cap 30 does not need to be electrically connected to the electrode assembly 10 and the housing 20, and the material thereof does not necessarily have to be a conductive metal.

[0078] 6 and 7, the first current collector 60 is disposed on the upper portion of the electrode assembly 10, and the first current collector 60 may be coupled to the terminal 40. That is, the first current collector 60 may be configured to electrically connect the first non-coated portion 11 of the electrode assembly 10 to the terminal 40. The first current collector 60 may be made of a conductive metal material and may be connected to the first non-coated portion 11.

[0079] The first current collector 60 may be bonded to an end of the first non-coated portion 11. The first non-coated portion 11 and the first current collector 60 may be bonded together by, for example, laser welding. The laser welding may be performed by partially melting the base material of the first current collector 60, or may be performed with solder interposed between the first current collector 60 and the first non-coated portion 11. In this case, it is preferable that the solder has a lower melting point than the first current collector 60 and the first non-coated portion 11.

[0080] 6, the second current collector 80 is disposed at the bottom of the electrode assembly 10, and may be configured to electrically connect the second non-coated portion 12 of the electrode assembly 10 to the housing 20. The second current collector 80 may be made of a conductive metal material and may be connected to the second non-coated portion 12.

[0081] The second current collector 80 may be bonded to an end of the second uncoated portion 12. The second uncoated portion 12 and the second current collector 80 may be bonded together by, for example, laser welding. The laser welding may be performed by partially melting the base material of the second current collector 80, or may be performed with solder interposed between the second current collector 80 and the second uncoated portion 12. In this case, it is preferable that the solder has a lower melting point than the second current collector 80 and the second uncoated portion 12.

[0082] The insulator 70 may be provided between the upper end of the electrode assembly 10 and the inner surface of the housing 20, or between the first current collector 60 coupled to the upper part of the electrode assembly 10 and the inner surface of the closed portion of the housing 20. The insulator 70 prevents contact between the first non-coated portion 11 and the housing 20 and / or the first current collector 60 and the housing 20. Alternatively, the insulator 70 may be interposed between the upper end of the outer periphery of the electrode assembly 10 and the sidewall of the housing 20. That is, the insulator 70 may be interposed between the first non-coated portion 11 and the sidewall of the housing 20. The first current collector 60 may be a plate extending completely across the upper end of the outer periphery of the electrode assembly 10. However, the present invention is not limited thereto, and the first current collector 60 may be formed to extend partially across the upper end of the outer periphery of the electrode assembly 10.

[0083] When the cylindrical secondary battery 1 according to an embodiment of the present invention includes the insulator 70, the terminal insertion portion 42 of the terminal 40 is coupled to the first current collector 60 or the first non-coated portion 11 through a hole formed in the insulator 70.

[0084] Referring to FIG. 6, the sealing gasket 90 may be interposed between the cap 30 and a fixing structure provided on the open side of the housing 20 to ensure airtightness of the housing 20 .

[0085] The sealing gasket 90 may include a polymer resin and a flame retardant additive. In this case, the sealing gasket 90 is bonded to the housing 20 and the cap 30 by thermal welding, thereby enhancing the airtightness at the bonding interface between the sealing gasket 90 and the cap 30 and the bonding interface between the sealing gasket 90 and the housing 20.

[0086] For the polymer resin and flame retardant additive contained in the sealing gasket, please refer to the description of the insulating gasket above. For example, the sealing gasket 90 may contain the same polymer resin and flame retardant additive as those contained in the insulating gasket 50.

[0087] Hereinafter, the present invention will be described in detail with reference to examples. However, the examples according to the present invention can be modified in various ways, and the scope of the present invention is not limited to the following examples. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art. [Example]

[0088] [Comparative Example 1] An insulating gasket was manufactured using polybutylene terephthalate (PBT, melting point 223°C, LGCHEM).

[0089] [Example 1] An insulating gasket was manufactured by mixing a flame retardant additive with polybutylene terephthalate (PBT, melting point 223°C, LGCHEM). The flame retardant additive was a halogen-free phosphorus-based flame retardant (LGCHEM) added at 12% of the total weight of the insulating gasket.

[0090] [Performance evaluation] The insulating gaskets manufactured according to Comparative Example 1 and Example 1 were applied to cylindrical secondary batteries, and a flame test was carried out.

[0091] The flame test involved applying a flame to the terminals and insulating gasket of each cylindrical secondary battery for 15 seconds to evaluate whether a short circuit had occurred. The occurrence of a short circuit was confirmed by measuring the resistance. When measuring the resistance, a PASS was given if it was 5 Ω or more, and a NG was given if it was less than 5 Ω.

[0092] The occurrence of short circuits and the results of resistance measurements are shown in Table 1.

[0093] [Table 1]

[0094] In the case of Comparative Example 1, the insulating gasket melted and a short circuit occurred. Figure 8 shows an image of Comparative Example 1 after the flame test.

[0095] In the case of Example 1, the insulating gasket remained and no short circuit occurred. Figure 9 shows an image of Example 1 after the flame test. [Explanation of symbols]

[0096] 1: Cylindrical secondary battery 10: Electrode assembly C: Winding center 11: First non-coated area 12: Second non-coated area 20: Housing 30: Cap 40: Terminal 50: Insulation gasket 60: First current collector 70: Insulator 80: Second current collector 90: Sealing gasket

Claims

1. an electrode assembly in which a core and an outer circumferential surface are defined by winding a first electrode, a second electrode, and a separator interposed therebetween around a winding shaft, the first electrode and the second electrode each including a first non-coated portion and a second non-coated portion that are not coated with an active material layer along the winding direction; a housing that receives the electrode assembly through an opening formed at a lower end thereof and is electrically connected to the second non-application portion; a terminal electrically connected to the first non-application portion and exposed to the outside of the housing through a closed portion of the housing located on the opposite side of the opening; An insulating gasket is provided on the closed portion side of the housing and is interposed between the housing and the terminal, The insulating gasket comprises a polymer resin and a flame-retardant additive.

2. a sealing gasket is provided on the opening side of the housing and is interposed between the housing and the cap so that the cap seals the opening; The cylindrical secondary battery according to claim 1 , wherein the sealing gasket comprises a polymer resin and a flame-retardant additive.

3. 2. The cylindrical secondary battery according to claim 1, wherein the polymer resin comprises polyolefin, polyester, polyarylene sulfide, thermoplastic polyester elastomer (TPEE), perfluoroalkoxy resin, or polyimide, or two or more thereof.

4. 2. The cylindrical secondary battery according to claim 1, wherein the polymer resin has a melting point of 250°C or higher and a heat distortion temperature of 200°C or higher.

5. The cylindrical secondary battery according to any one of claims 1 to 4, characterized in that the polymer resin contains polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or polyphenylene sulfide (PPS), or two or more of these.

6. 5. The cylindrical secondary battery according to claim 1, wherein the flame retardant additive comprises a phosphorus-based flame retardant, an inorganic flame retardant, or a halogen flame retardant, or two or more of these.

7. 5. The cylindrical secondary battery according to claim 1, wherein the flame retardant additive is a phosphorus-based flame retardant.

8. 5. The cylindrical secondary battery according to claim 1, wherein the flame retardant additive does not contain a halogen element.

9. 10. The cylindrical secondary battery according to claim 1, wherein the insulating gasket contains a flame-retardant additive in an amount of 5% to 30% based on the total weight of the insulating gasket.

10. The cylindrical secondary battery according to claim 2, wherein the flame retardant additive contained in the sealing gasket is contained in an amount of 5% to 30% based on the total weight of the sealing gasket.

11. A battery pack comprising the cylindrical secondary battery according to any one of claims 1 to 4.

12. A motor vehicle comprising the battery pack of claim 11.

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