Cylindrical secondary battery

Abstract

The present invention relates to a cylindrical secondary battery and, more specifically, to a cylindrical secondary battery in which an electrode assembly inside a battery can can be prevented from moving upward even when the battery can is heated. A cylindrical secondary battery according to the present invention comprises: a battery can having the upper end open; an electrode assembly accommodated in the battery can; a top cap assembly coupled to the upper end of the battery can and having formed therein a gas outlet for discharging gas generated inside the battery can; and a thermal expansion tape that is attached to the upper region of the inner wall of the battery can and expands when the battery can is heated, thereby preventing the gas outlet formed in the upper portion of the battery can from being blocked, by suppressing the electrode assembly accommodated in the battery can from moving upward even when heat is applied to the battery can.

Description

Cylindrical secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0102377, filed August 4, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a cylindrical secondary battery, and more particularly, to a cylindrical secondary battery capable of suppressing an electrode assembly inside a battery can from moving upward even when the battery can is heated.

[0005] Secondary batteries (rechargeable batteries) are batteries that can be charged and discharged, unlike primary batteries that cannot be recharged. Secondary batteries can take various shapes, such as cylindrical, pouch-shaped, and prismatic. A cylindrical battery cell can be formed by interposing a separator between the positive and negative electrodes, winding the separator to form a jelly-roll-shaped electrode assembly, inserting the assembly into a battery can, and injecting an electrolyte. Here, since the electrode assembly must be inserted into the cylindrical battery can, it is formed to be smaller than the battery can, and a gap may be formed between the inner wall of the battery can and the electrode assembly.

[0006] Meanwhile, various stability tests can be performed during the manufacturing of cylindrical secondary batteries. In particular, since cylindrical secondary batteries are frequently exposed to high-temperature heat sources, such as in automobile interiors, a burning test can be performed during the manufacturing process to examine the risk of explosion and self-extinguishing ability of the cylindrical secondary batteries after heating them.

[0007] Figure 1 is a drawing showing a conventional cylindrical secondary battery being heated. At this time, the electrode assembly (10) of the cylindrical secondary battery can receive heat and move inside the battery can (100), and in particular, the electrode assembly (10) can move to the upper part of the battery can (100) to which the top cap assembly (200) is coupled.

[0008] Here, a gas discharge port (210) is formed in the top cap assembly (200) to discharge gas generated inside the battery can (100) to the outside, and the electrode assembly (10) that has received heat can move to the upper part of the battery can (100) and block the gas discharge port (210). In this case, the gas inside the battery can (100) cannot be discharged to the outside but accumulates, and there is a problem that the battery can (100) exposed to a high temperature environment explodes.

[0009]

[0010] The present invention has been conceived in recognition of the above problems, and provides a cylindrical secondary battery capable of preventing an electrode assembly housed in a battery can from moving upward even when heat is applied to the battery can, thereby preventing a gas exhaust port formed at the top of the battery can from being blocked.

[0011] A cylindrical secondary battery according to the present invention comprises: a battery can having an open upper end; an electrode assembly accommodated in the battery can; a top cap assembly coupled to the upper end of the battery can and having a gas exhaust port formed therein for exhausting gas generated inside the battery can; and a thermal expansion tape attached to an upper area of ​​an inner wall of the battery can and expanding when the battery can is heated.

[0012] The above electrode assembly may be a jelly-roll that is rolled into a cylindrical shape after laminating a negative electrode plate, a positive electrode plate, and a separator.

[0013] The above thermal expansion tape may be attached to a first region of the upper region of the inner wall of the battery can, which faces the upper edge of the jelly roll.

[0014] The above thermal expansion tape may be a ring-shaped tape extending along the longitudinal direction of the first region.

[0015] The above thermal expansion tape may be a plurality of pad-shaped tapes spaced apart and attached along the longitudinal direction of the first region.

[0016] The above pad-shaped tapes can be attached facing each other with the jelly roll in between.

[0017] The above pad-shaped tapes can be attached at equal intervals along the longitudinal direction of the first region.

[0018] A beaded portion may be formed below the upper portion of the battery can, with a portion of the battery can being recessed inward.

[0019] The above thermal expansion tape can be attached to an area lower than the second area where the beading portion is formed.

[0020] The above thermal expansion tape may be attached to an upper region of the inner wall of the battery can, higher than a first region facing the upper edge of the jelly roll.

[0021] The above thermal expansion tape may include a plurality of swelling layers that expand when electrolyte is penetrated or heat is applied.

[0022] The above swelling layer may be composed of an aqueous self-healing binder having a glass transition temperature of -50°C to -30°C.

[0023] A cylindrical secondary battery according to the present invention includes a battery can having an open upper end, an electrode assembly accommodated in the battery can, a top cap assembly coupled to the upper end of the battery can and having a gas exhaust port formed therein for exhausting gas generated inside the battery can, and a heat-expanding tape attached to an upper region of an inner wall of the battery can and expanding when the battery can is heated, thereby having the advantageous effect of suppressing upward movement of the electrode assembly accommodated in the battery can even when heat is applied to the battery can, thereby preventing the gas exhaust port formed in the upper end of the battery can from being blocked.

[0024] Figure 1 is a cross-sectional view showing a conventional cylindrical secondary battery being heated.

[0025] Fig. 2 is a cross-sectional view showing a state of heating a cylindrical secondary battery according to Example 1 of the present invention.

[0026] Figure 3 is a perspective view showing the internal structure of a cylindrical secondary battery according to Example 1 of the present invention.

[0027] FIG. 4a is a cross-sectional view showing a state in which one swelling layer is formed on a thermal expansion tape attached to a cylindrical secondary battery according to Example 1 of the present invention.

[0028] FIG. 4b is a cross-sectional view showing a plurality of swelling layers formed on a thermal expansion tape attached to a cylindrical secondary battery according to Example 1 of the present invention.

[0029] FIG. 5 is a drawing showing a ring-shaped thermal expansion tape attached to a cylindrical secondary battery according to Example 1 of the present invention.

[0030] FIG. 6 is a drawing showing a pad-type thermal expansion tape attached to a cylindrical secondary battery according to Example 1 of the present invention.

[0031] FIG. 7a is a drawing showing a cylindrical secondary battery according to Example 1 of the present invention in which pad-type thermal expansion tapes are attached at equal intervals.

[0032] Figure 7b is a plan view of Figure 7a.

[0033] Figure 8 is a cross-sectional view showing a cylindrical secondary battery according to Example 2 of the present invention.

[0034] Figure 9 is an enlarged view of part P of Figure 8.

[0035] Fig. 10 is a cross-sectional view showing a cylindrical secondary battery according to Example 3 of the present invention.

[0036] Fig. 11 is a cross-sectional view showing a beading portion formed in a cylindrical secondary battery according to Example 3 of the present invention.

[0037] Hereinafter, with reference to the attached drawings, preferred embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited or restricted by the following examples.

[0038] In order to clearly explain the present invention, a detailed description of a part that is irrelevant to the description or a related known technology that may unnecessarily obscure the gist of the present invention has been omitted, and when adding reference signs to components of each drawing in this specification, the same or similar reference signs are attached to the same or similar components throughout the specification.

[0039] In addition, terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0040] Hereinafter, a cylindrical secondary battery according to the present invention will be described with reference to the drawings.

[0041]

[0042] Example 1

[0043] Fig. 2 is a cross-sectional view showing a state in which a cylindrical secondary battery according to Example 1 of the present invention is heated, and Fig. 3 is a perspective view showing the internal structure of a cylindrical secondary battery according to Example 1 of the present invention. Fig. 4a is a cross-sectional view showing a state in which one swelling layer is formed on a thermal expansion tape attached to a cylindrical secondary battery according to Example 1 of the present invention, and Fig. 4b is a cross-sectional view showing a state in which multiple swelling layers are formed on a thermal expansion tape attached to a cylindrical secondary battery according to Example 1 of the present invention.

[0044] Fig. 5 is a drawing showing a state in which a ring-shaped thermal expansion tape is attached to a cylindrical secondary battery according to Example 1 of the present invention, and Fig. 6 is a drawing showing a state in which a pad-shaped thermal expansion tape is attached to a cylindrical secondary battery according to Example 1 of the present invention. Fig. 7a is a drawing showing a state in which pad-shaped thermal expansion tapes are attached at equal intervals to a cylindrical secondary battery according to Example 1 of the present invention, and Fig. 7b is a plan view of Fig. 7a.

[0045] Referring to FIG. 2, a cylindrical secondary battery according to Embodiment 1 of the present invention may include a battery can (100) having an open upper end, an electrode assembly (10) accommodated in the battery can (100), a top cap assembly (200) coupled to the upper end of the battery can (100) and having a gas exhaust port (210) formed therein for exhausting gas generated inside the battery can (100), and a heat-expanding tape (300) attached to an upper region of the inner wall of the battery can (100) and expanding when the battery can (100) is heated. The heat-expanding tape (300) attached to the upper region of the inner wall of the battery can (100) is made of a material that expands when heated, and thus its thickness may increase when the battery can (100) is heated.

[0046] Accordingly, when heat is applied to the battery can (100), the heat expansion tape (300) increases in thickness in the direction from the inner wall of the battery can (100) toward the electrode assembly (10), thereby applying frictional force to the electrode assembly (10) to block upward movement of the electrode assembly (10). Here, the electrode assembly (10) exists in a state spaced apart from the top cap assembly (200) at the upper end of the battery can (100), so that even when the battery can (100) is heated, there is an advantageous effect of being able to prevent the electrode assembly (10) from blocking the gas exhaust port (210) formed in the top cap assembly (200).

[0047] The battery can (100) is a metal case that forms a receiving space (S1) for receiving the electrode assembly (10), and a certain gap may exist between the electrode assembly (10) received inside the receiving space (S1) and the inner wall of the battery can (100). The receiving space (S1) is a space for receiving the electrode assembly (10), and the electrode assembly (10) may be impregnated with an electrolyte solution in the receiving space (S1). There is no particular limitation on the structure or shape of the battery can (100), and as illustrated in FIG. 3, the battery can (100) may have a hollow cylindrical can structure for receiving the electrode assembly (10).

[0048] The electrode assembly (10) is a rechargeable power generation element composed of a laminated structure of electrodes and a separator, and may have a jelly-roll shape in which a negative electrode plate (11), a positive electrode plate (12), and a separator (13) are laminated and then rolled into a cylindrical shape. The negative electrode plate (11) may include a negative electrode current collector and an active material coated on the negative electrode current collector. The negative electrode current collector may be a metal foil composed of copper (Cu) or nickel (Ni), and the active material coated on the negative electrode current collector may be composed of artificial graphite, lithium, a lithium alloy, carbon, activated carbon, graphite, a silicon compound, a tin compound, a titanium compound, or an alloy thereof.

[0049] The positive electrode plate (12) may include a positive electrode collector and an active material coated on the positive electrode collector. The positive electrode collector may be formed of an aluminum foil, and the active material coated on the positive electrode collector may be formed of lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate, or a compound containing one or more of these.

[0050] The separator (13) is made of an insulating material and can be alternately laminated with the negative electrode plate (11) and the positive electrode plate (12). For example, the separator (13) can be positioned between the negative electrode plate (11) and the positive electrode plate (12). In addition, the separator (13) can be made of a multilayer film made of polyethylene, polypropylene, or a combination thereof, or a solid polymer film such as polyvinylidene fluoride (PVDF), polyethylene oxide, or polyacrylonitrile (PAN).

[0051] Meanwhile, a cylindrical center pin (14) may be inserted into the core of the jelly roll-shaped electrode assembly (10). The center pin (14) may have a rod structure in the form of a rounded, hollow shape made of a rigid metal plate. The center pin (14) may fix and support the electrode assembly, and may act as a passage for discharging gas generated by an internal reaction of the electrode assembly (10) during operations such as charging and discharging. Specifically, the gas generated by the internal reaction may be discharged to the outside through an opening formed at the upper end of the housing (15) of the electrode assembly (10) and a gas discharge port (210) of a top cap assembly (200) coupled to the upper end of the battery can (100).

[0052] The top cap assembly (200) is coupled to the open upper portion of the battery can (100), and the top cap assembly (200) and the upper portion of the battery can (100) can be coupled in various ways. For example, the top cap assembly (200) and the upper portion of the battery can (100) can be coupled by screwing or welding. Meanwhile, the top cap assembly (200) can be formed with one or more gas exhaust ports (210) for discharging high-pressure gas generated inside the electrode assembly (10).

[0053] Meanwhile, as illustrated in FIGS. 4a and 4b, the thermal expansion tape (300) may be formed into a multilayer structure including at least one swelling layer (310), a substrate layer (320), and an adhesive layer (330). At this time, the swelling layer (310) is a layer that can fill the gap between the inner wall of the battery can (100) and the electrode assembly (10) by swelling when in contact with electrolyte or when heat is applied, and can realize a volume increase rate of 100% or more. This swelling layer (310) may be composed of an aqueous self-healing binder having a glass transition temperature of -50°C to -30°C.

[0054] The aqueous self-healing binder is a polymer having a property of swelling upon contact with an organic solvent contained in an electrolyte or upon heat, and may include at least one compound selected from the group consisting of arginate, chitosan, and CMC (Ceramic Matrix Composite). In particular, the aqueous self-healing binder may include at least one compound selected from the group consisting of arginate and chitosan.

[0055] Arginate is a high molecular weight polymer with excellent self-healing properties, which allows it to fill internal gaps upon impact, effectively suppressing upward movement of the electrode assembly (10) when used as a swelling layer (310). Chitosan is an environmentally friendly material, is inexpensive, and contains a large amount of hydroxyl groups, which provides the advantage of excellent bonding performance. Therefore, when chitosan is used as a swelling layer (310), it has the advantageous effect of improving the adhesiveness of the swelling layer (310).

[0056] Meanwhile, the substrate layer (320) is a film or sheet-shaped layer that has the property of expanding when in contact with a fluid such as an electrolyte, and may have a shape such as a circle, a triangle, or an amorphous shape in addition to a square shape. There is no particular limitation on the composition of the substrate layer (310), and the substrate layer (310) may be composed of at least one polymer material selected from the group consisting of polypropylene, polyamide, polycarbonate, polyacrylate, thermoplastic polyurethane (TPU), polyvinyl chloride, polyethylene terephthalate, and polystyrene.

[0057] The adhesive layer (330) is a layer added to easily attach and detach the thermal expansion tape (300) to the electrode assembly (100), and can be designed to implement appropriate adhesive strength and peeling strength for the electrode assembly (100). Specifically, the peeling strength of the adhesive layer (330) can be changed depending on the size of the three-dimensional shape to be implemented or the gap to be filled, and the lower limit can be 100 gf / 25mm or more, 200 gf / 25mm or more, 400 gf / 25mm or more, 600 gf / 25mm or more, 800 gf / 25mm or more, 1,000 gf / 25mm or more, 1,200 gf / 25mm or more, 1,400 gf / 25mm or more, 1,600 gf / 25mm or more, or 1,800 gf / 25mm or more. Meanwhile, the upper limit of the peel strength of this adhesive layer (330) is not particularly limited as long as it has a general range, but may be approximately 5,000 gf / 25 mm or less.

[0058] This adhesive layer (330) may include an acrylic polymer having a weight average molecular weight (Mw) of 400,000 or more. Specifically, the acrylic polymer may include a polymer in the form of a polymerization of a (meth)acrylic acid ester monomer and a copolymerizable monomer having a crosslinking functional group. At this time, the weight ratio of each monomer is not particularly limited and may be appropriately designed in consideration of the desired peeling strength.

[0059] Meanwhile, the thermal expansion tape (300) may be attached to a first region (A1) facing the upper edge of the jelly roll among the upper regions of the inner wall of the battery can (100). In this case, the thermal expansion tape (300) receives heat and swells in the first region (A1), thereby pressurizing the jelly roll in a horizontal direction, thereby suppressing the jelly roll from moving upward.

[0060] The thermal expansion tape (300) can be attached to the upper area of ​​the inner wall of the battery can (100) in various ways. For example, as illustrated in FIG. 5, the thermal expansion tape (300) can be a ring-shaped tape extending along the longitudinal direction of the first region (A1). In this case, the thermal expansion tape (300) wraps around the upper edge of the jelly roll in the first region (A1), so that when the thermal expansion tape (300) swells, it can strongly press the upper end of the jelly roll, thereby having the advantageous effect of suppressing the jelly roll from moving upward.

[0061] In addition, a portion of the ring-shaped thermal expansion tape (300) attached at a position higher than the upper end of the jelly roll can swell toward the central axis of the jelly roll past the upper edge of the jelly roll. In this case, the portion is located at the upper end of the upper surface of the jelly roll and functions as a blocking member that blocks the jelly roll from moving upward, thereby having the advantageous effect of effectively preventing the jelly roll from moving upward.

[0062] Meanwhile, as illustrated in FIG. 6, the thermal expansion tape (300) may be a plurality of pad-shaped tapes spaced apart and attached along the longitudinal direction of the first region (A1). Here, the plurality of pad-shaped tapes may be attached to face each other with the jelly roll interposed therebetween. In addition, as illustrated in FIGS. 7a and 7b, the plurality of pad-shaped tapes may be attached spaced apart at equal intervals along the longitudinal direction of the first region (A1). In each case, a portion of the plurality of pad-shaped tapes that is attached at a position higher than the upper end of the jelly roll may swell toward the central axis of the jelly roll past the upper edge of the jelly roll. The portion is positioned at the upper end of the jelly roll and functions as a blocking member that blocks the jelly roll from moving upward, thereby having the advantageous effect of effectively preventing the jelly roll from moving upward.

[0063]

[0064] Example 2

[0065] Fig. 8 is a cross-sectional view showing a cylindrical secondary battery according to Example 2 of the present invention, and Fig. 9 is an enlarged view of part P of Fig. 8.

[0066] Embodiment 2 of the present invention differs from Embodiment 1 in that a beading portion (110) is formed in the battery can (100) in which a portion of the battery can (100) is recessed inward. Common contents with Embodiment 1 will be omitted as much as possible, and Embodiment 2 will be described focusing on the differences. In other words, it is self-evident that contents not described in Embodiment 2, if necessary, may be considered as contents of Embodiment 1.

[0067] Referring to FIGS. 8 and 9, a cylindrical secondary battery according to Embodiment 2 of the present invention may have a beading portion (110). Specifically, the beading portion (110) is formed below the upper end of the battery can (100) and may have a shape in which a portion of the battery can (100) is recessed inward.

[0068] The beading portion (110) is a separation prevention structure for preventing the top cap assembly (200) from being separated from the battery can (100). This beading portion (110) can be formed by pressing the outer surface of the battery can (100) after the top cap assembly (200) is mounted on the battery can (100). The beading portion (110) can have a shape that protrudes from the inner surface of the battery can (100) toward the central axis of the battery can (100).

[0069] Meanwhile, the thermal expansion tape (300) may be attached to a region lower than the second region (A2) where the beading portion (110) is formed among the upper regions of the battery can (100). In particular, the thermal expansion tape (300) may be attached to a region facing the upper edge of the jelly roll among the regions lower than the second region (A2). The thermal expansion tape (300) wraps around the upper edge of the jelly roll, and can horizontally press the upper end of the jelly roll when the thermal expansion tape (300) swells. In this case, the upward movement of the jelly roll is suppressed, which has the advantageous effect of preventing the beading portion located at the upper end of the jelly roll from being damaged due to the rise of the jelly roll.

[0070] In addition, a portion of the thermal expansion tape (300) attached at a position higher than the upper end of the jelly roll can swell toward the central axis of the jelly roll past the upper edge of the jelly roll. This portion is located at the upper end of the jelly roll's upper surface and functions as a blocking member that blocks the jelly roll from moving upward, thereby effectively preventing the jelly roll from moving upward. In this case, since the jelly roll is blocked from moving upward, it has the advantageous effect of preventing the beading portion located at the upper end of the jelly roll from being damaged due to the rise of the jelly roll.

[0071]

[0072] Example 3

[0073] Fig. 10 is a cross-sectional view showing a cylindrical secondary battery according to Example 3 of the present invention, and Fig. 11 is a cross-sectional view showing a beading portion formed in a cylindrical secondary battery according to Example 3 of the present invention.

[0074] Embodiment 3 of the present invention differs from Embodiments 1 and 2 in that the thermal expansion tape (300) is attached to an area higher than the first area (A1) facing the upper edge of the jelly roll among the upper areas of the inner wall of the battery can (100). Common contents with Embodiments 1 and 2 will be omitted as much as possible, and Embodiment 3 will be described focusing on the differences. In other words, it is obvious that contents not described in Embodiment 3, if necessary, can be regarded as contents of Embodiments 1 and 2.

[0075] Referring to FIG. 10, a cylindrical secondary battery according to Embodiment 3 of the present invention may include a thermal expansion tape (300) attached above a first region (A1) facing an upper edge of a jelly-roll among the upper regions of the inner wall of a battery can (100). Here, all parts of the thermal expansion tape (300) are attached at a position higher than the upper end of the jelly-roll, so that when heat is transferred to the thermal expansion tape (300), the thermal expansion tape (300) can swell toward the central axis of the jelly-roll past the upper end edge of the jelly-roll. In this case, the thermal expansion tape (300) is positioned above the upper surface of the jelly-roll and functions as a blocking member that blocks the jelly-roll from moving upward, thereby having the advantageous effect of effectively preventing the jelly-roll from moving upward.

[0076] Referring to Fig. 11, a cylindrical secondary battery according to Embodiment 3 of the present invention may have a beading portion (110). The beading portion (110) is formed below the upper end of the battery can (100) and may have a shape in which a portion of the battery can (100) is recessed inward. Here, the thermal expansion tape (300) may be attached above a first area (A1) facing the upper edge of the jelly roll among areas below the area where the beading portion is formed. The thermal expansion tape (300) is positioned above the upper surface of the jelly roll and functions as a blocking member that blocks the jelly roll from moving upward, thereby having the advantageous effect of preventing the beading portion located at the upper end of the jelly roll from being damaged due to the rise of the jelly roll.

[0077] Meanwhile, the thermal expansion tape (300) may include a multi-layer swelling layer (310) that expands when an electrolyte penetrates or heat is applied. A plurality of swelling layers (310) may be formed in the thermal expansion tape (300), and a substrate layer (320) may be interposed between the swelling layers (310). According to the above structure in which the thermal expansion tape (300) has multiple layers, the thermal expansion tape (300) may be attached thickly in an area above the first area (A1), so that the thermal expansion tape (300) may be positioned above the upper surface of the jelly roll when swelling, thereby blocking upward movement of the jelly roll.

[0078] Meanwhile, as described above in Example 1 of the present invention, the swelling layer (310) may be composed of an aqueous self-healing binder having a glass transition temperature of -50°C to -30°C. In this case, the aqueous self-healing binder has high adhesiveness, which has the advantageous effect of allowing the use of an additional adhesive such as an acrylic pressure-sensitive adhesive ('PSA') to be omitted.

[0079] In addition, the aqueous self-healing binder can completely fill the gap between the electrode assembly (10) and the battery can (100) due to its property of expanding due to heat or impact. Therefore, when the battery can (100) is heated, the aqueous self-healing binder swells and presses the electrode assembly (10) in the horizontal direction, thereby preventing upward movement of the electrode assembly (10). In this case, there is an advantageous effect of being able to prevent the electrode assembly (10) from blocking the gas exhaust port (210) formed in the top cap assembly (200).

[0080]

[0081] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and various embodiments are possible within the scope equivalent to the technical idea of ​​the present invention and the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

[0082]

[0083] [Explanation of symbols]

[0084] 10: Electrode assembly 11: Negative plate

[0085] 12: Bipolar plate 13: Separator

[0086] 14: Center pin 15: Housing

[0087] 100: Battery can 110: Beading part

[0088] 200: Top cap assembly 210: Gas outlet

[0089] 300: Thermal expansion tape 310: Swelling layer

[0090] 320: Base layer 330: Adhesive layer

[0091] S1: Reception space A1: Area 1

[0092] A2: Area 2

Claims

1. Battery can with open top; An electrode assembly accommodated in the above battery can; A top cap assembly coupled to the upper end of the battery can and having a gas exhaust port formed therein for exhausting gas generated inside the battery can; and A cylindrical secondary battery comprising a thermal expansion tape attached to an upper area of ​​the inner wall of the battery can and expanding when the battery can is heated.

2. In claim 1, A cylindrical secondary battery characterized in that the electrode assembly is a jelly roll that is rolled into a cylindrical shape after laminating a negative electrode plate, a positive electrode plate, and a separator.

3. In claim 2, A cylindrical secondary battery, characterized in that the thermal expansion tape is attached to a first region facing the upper edge of the jelly roll among the upper regions of the inner wall of the battery can.

4. In claim 3, A cylindrical secondary battery, characterized in that the above thermal expansion tape is a ring-shaped tape extending along the longitudinal direction of the first region.

5. In claim 3, A cylindrical secondary battery, characterized in that the above thermal expansion tape is a plurality of pad-shaped tapes spaced apart and attached along the longitudinal direction of the first region.

6. In claim 5, A cylindrical secondary battery characterized in that the above pad-shaped tapes are attached facing each other with the jelly roll interposed therebetween.

7. In claim 5, A cylindrical secondary battery characterized in that the above pad-shaped tapes are attached at equal intervals along the longitudinal direction of the first region.

8. In claim 1, A cylindrical secondary battery characterized in that a beaded portion is formed below the upper portion of the battery can, with a portion of the battery can being recessed inward.

9. In claim 8, A cylindrical secondary battery characterized in that the thermal expansion tape is attached to an area lower than the second area where the beading portion is formed.

10. In claim 2, A cylindrical secondary battery characterized in that the thermal expansion tape is attached to an upper region of the inner wall of the battery can, higher than a first region facing the upper edge of the jelly roll.

11. In claim 10, A cylindrical secondary battery characterized in that the above thermal expansion tape includes a plurality of swelling layers that expand when an electrolyte penetrates or heat is applied.

12. In claim 11, A cylindrical secondary battery characterized in that the swelling layer is composed of an aqueous self-healing binder having a glass transition temperature of -50°C to -30°C.

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