Secondary battery

Abstract

The present invention relates to a secondary battery capable of charging and discharging. A secondary battery according to one embodiment of the present invention comprises: an electrode assembly; a sheet-type exterior material having an inner space accommodating the electrode assembly and an exterior material opening allowing the inner space to communicate with the outside; and a cap inserted into the exterior material opening and coupled to the sheet-type exterior material to seal the inner space, wherein a folding line is formed in a portion of the sheet-type exterior material covering a corner of the cap, the sheet-type exterior material includes a coupling unit coupled to the cap, and a space forming unit connected to the coupling unit and forming the inner space accommodating the electrode assembly, and the thickness of the coupling unit may be less than or equal to the thickness of the space forming unit.

Description

secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0191593 filed December 19, 2024 and Korean Patent Application No. 10-2025-0190725 filed December 4, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of this specification.

[0003] Technology field

[0004] The present invention relates to a rechargeable secondary battery.

[0005] A secondary battery refers to a battery that can be charged and discharged, unlike a primary battery which cannot be recharged. Such secondary batteries are widely used in electronic devices such as mobile phones, laptops, and camcorders.

[0006] Such secondary batteries may be pouch-type batteries having an electrode assembly in which electrodes and separators are alternately stacked, a sheet-type outer material that accommodates the electrode assembly, and an electrode lead that is electrically connected to the electrode tab of the electrode assembly and has a portion formed protruding from the pouch.

[0007] When manufacturing a pouch-type battery, a process must be performed in which a cap is inserted into an opening of a sheet-type outer material that forms an internal space for accommodating an electrode assembly, and then the cap and the sheet-type outer material are heat-fused. At this time, the operator may apply heat and pressure to the sheet-type outer material and the cap while holding the sheet-type outer material in one direction.

[0008] Among the sheet-type exterior materials, the part in contact with the cap is subjected to heat and pressure while tension is applied, which causes a problem where the thickness becomes thinner compared to the surrounding area. In this case, the thinned part can become a leak point. Additionally, as the durability of the thinned part decreases, that part may rupture upon external impact, thereby degrading the sealing performance of the sheet-type exterior material.

[0009] The present invention was devised in recognition of the above problems, and the objective of the present invention is to provide a secondary battery that can prevent the thickness of the part coupled to the cap among the sheet-type exterior materials from becoming thin.

[0010] A secondary battery according to the present invention comprises: an electrode assembly; a sheet-type outer material having an internal space accommodating the electrode assembly and an outer material opening communicating the internal space with the outside; and a cap inserted into the outer material opening and coupled to the sheet-type outer material to seal the internal space, wherein a folding line is formed in a portion of the sheet-type outer material that covers a corner of the cap, and the sheet-type outer material comprises: a coupling portion coupled to the cap; and a space-forming portion connected to the coupling portion and forming an internal space accommodating the electrode assembly, wherein the thickness of the coupling portion may be less than or equal to the thickness of the space-forming portion.

[0011] The above sheet-type exterior material may be formed by rolling or folding a laminate sheet containing a metal layer so that one end and the other end of the laminate sheet meet each other.

[0012] The above cap may include a body having a lead insertion opening through which an electrode lead passes; and a gasket that surrounds at least a portion of the body and is coupled to a joint portion of the sheet-type outer material.

[0013] The above body may include a square plate having the lead insertion opening formed therein; and a leg formed protruding along the edge of the square plate.

[0014] The above gasket is provided with a fastening groove into which the above leg is fastened, and a plurality of angled corners may be formed on the outer surface of the above gasket.

[0015] The above folding line can be formed in the portion covering each corner of the outer surface of the gasket among the above sheet-type exterior material.

[0016] The thickness of the portion of the above-mentioned joint where the folding line is formed may be less than or equal to the thickness of the space-forming portion.

[0017] Each of the above-mentioned connecting portion and space forming portion may include a metal substrate layer composed of a metal material.

[0018] Each of the above-mentioned coupling portion and space-forming portion may include: an outermost layer composed of a resin material; a shock-absorbing layer formed below the outermost layer and above the metal substrate layer, composed of a stretchable material to absorb external shocks; and an innermost layer formed below the metal substrate layer, composed of a resin material.

[0019] The thickness of the metal substrate layer of the above-mentioned coupling portion may be less than or equal to the thickness of the metal substrate layer of the above-mentioned space-forming portion.

[0020] The thickness of the metal substrate layer in the portion where the folding line is formed among the above-mentioned joint portions may be less than or equal to the thickness of the metal substrate layer in the space-forming portion.

[0021] The ratio of the thickness of the metal substrate layer of the above-mentioned joint portion to the thickness of the metal substrate layer of the above-mentioned space-forming portion may be 0.81:1 to 1:1.

[0022] The ratio of the thickness of the metal substrate layer of the above-mentioned joint portion to the thickness of the metal substrate layer of the above-mentioned space-forming portion may be 0.9:1 to 1:1.

[0023] Meanwhile, a secondary battery according to another embodiment of the present invention comprises: an electrode assembly; a sheet-type outer material having an internal space accommodating the electrode assembly and an outer material opening communicating the internal space with the outside; and a cap inserted into the outer material opening and coupled to the sheet-type outer material to seal the internal space, wherein a folding line is formed in a portion of the sheet-type outer material that covers a corner of the cap, and the folding line may be formed only in the portion of the sheet-type outer material that covers a corner of the cap.

[0024] The above cap may include a first cap inserted into one side of the sheet-type exterior material; and a second cap inserted into the other side of the sheet-type exterior material.

[0025] The above folding line may include a first folding line formed in a portion covering the corner of the first cap among the sheet-type exterior material; and a second folding line formed in a portion covering the corner of the second cap among the sheet-type exterior material.

[0026] According to a secondary battery according to one embodiment of the present invention, a portion of the sheet-type exterior material having a folding line formed therein is coupled to a cap, so that the sheet-type exterior material can be coupled to the cap without pulling the sheet-type exterior material. In this case, it is possible to prevent the thickness of the portion of the sheet-type exterior material coupled to the cap from becoming thin.

[0027] FIG. 1 is an exploded perspective view of a secondary battery according to a first embodiment of the present invention.

[0028] FIG. 2 is a cross-sectional view showing the internal structure of a secondary battery according to a first embodiment of the present invention.

[0029] FIG. 3 is a drawing showing a plurality of folding lines formed on a sheet-type outer material of a secondary battery according to the first embodiment of the present invention.

[0030] Figure 4 is a drawing showing the joint and space-forming portions of a sheet-type exterior material.

[0031] FIG. 5 is a drawing for explaining how a cap and a sheet-type outer material are sealed in a secondary battery according to the first embodiment of the present invention.

[0032] FIG. 6 is a drawing illustrating the sealing of a cap and a sheet-type outer material in a conventional pouch-type secondary battery.

[0033] FIG. 7 is a diagram illustrating the difference in thickness of the metal substrate layer between a secondary battery according to the first embodiment of the present invention and a conventional pouch-type secondary battery.

[0034] FIG. 8 is a cross-sectional view showing the internal structure of a secondary battery according to a second embodiment of the present invention.

[0035] FIG. 9 is a drawing showing the first and second folding lines formed on the sheet-type outer material of a secondary battery according to the second embodiment of the present invention.

[0036] Hereinafter, preferred embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited or restricted by the following embodiments.

[0037] In order to clearly explain the present invention, detailed descriptions of related prior art that are irrelevant to the explanation or that may unnecessarily obscure the essence of the invention have been omitted. Furthermore, when assigning reference numerals to the components of each drawing in this specification, identical or similar reference numerals are assigned to identical or similar components throughout the entire specification.

[0038] Furthermore, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0039] First embodiment

[0040] FIG. 1 is an exploded perspective view of a secondary battery according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the internal structure of a secondary battery according to a first embodiment of the present invention. FIG. 3 is a drawing showing a plurality of folding lines formed on a sheet-type outer material of a secondary battery according to a first embodiment of the present invention.

[0041] Referring to FIGS. 1 to 3, a secondary battery (10) according to a first embodiment of the present invention may include an electrode assembly (100), an internal space (S) accommodating the electrode assembly (100), a sheet-type exterior material (200) having an exterior material opening (h) communicating the internal space (S) with the outside, and a cap (300) inserted into the exterior material opening (h) and coupled to the sheet-type exterior material (200) to seal the internal space (S). At this time, a folding line (L) may be formed in the portion of the sheet-type exterior material (200) that covers the corner of the cap (300).

[0042] In the case of a secondary battery (10) having such a structure, a folding line (L) is formed in the part of the sheet-type exterior material (200) that covers the corner of the cap (300), so that the sheet-type exterior material (200) can be attached to the cap (300) without pulling it even before the sealing process is performed. That is, when sealing the sheet-type exterior material (200) and the cap (300), the process of pulling the sheet-type exterior material (200) can be omitted, so that the thickness of the part of the sheet-type exterior material (200) that is sealed to the cap (300) can be prevented from becoming thin.

[0043] The secondary battery (10) is a battery capable of repeated charging and discharging and can be configured in various ways. For example, the secondary battery (10) may have a pouch-type cell structure in which an electrode assembly (100) and an electrolyte are housed inside a sheet-type outer material (200) composed of a laminate sheet and a cap (300).

[0044] The electrode assembly (100) is a laminate comprising an anode, a cathode, and a separator, and may have various structures. For example, the electrode assembly may be a stack-type electrode assembly in which the anode, cathode, and separator are stacked in one direction, or a stack-folding type electrode assembly in which the anode, cathode, and separator are stacked in one direction and then folded.

[0045] Here, the positive electrode comprises a positive current collector and a positive active material coated on the positive current collector, and the negative electrode may comprise a negative current collector and a negative active material coated on the negative current collector. The separator is a membrane of insulating material interposed between the positive electrode and the negative electrode to block contact between the positive electrode and the negative electrode, and a plurality of pores through which cations pass may be formed in the separator.

[0046] The unpaired portions of a plurality of electrodes constituting the electrode assembly (100) can be welded together to form an electrode tab (110) having the same polarity, and the electrode tab (110) can be connected to an electrode lead (120). At this time, a portion of the electrode lead (120) can be exposed to the outside of the secondary battery (10). Specifically, a portion of the electrode lead (120) can pass through a through hole formed in the cap (300) and be exposed to the outside of the secondary battery (10).

[0047] The sheet-type exterior material (200) may have an internal space (S) that accommodates an electrode assembly (100) and an exterior material opening (h) that communicates the internal space (S) with the outside. The sheet-type exterior material (200) may be formed by folding the laminate sheet (200a) so that one end (201a) and the other end (202a) of the laminate sheet (200a) including a metal layer meet each other.

[0048] Specifically, a plurality of pre-formed folding lines (L) may be formed in the laminate sheet (200a), and the laminate sheet (200a) may be folded along the plurality of folding lines (L) to form a sheet-type exterior material (200). At this time, when the sheet-type exterior material (200) is combined with the cap (300) described later, the plurality of folding lines (L) may cover each corner of the cap (300).

[0049] The cap (300) can be coupled to the sheet-type outer material (200) to seal the internal space (S) in which the electrode assembly (100) is accommodated. Specifically, the cap (300) can be inserted into the outer material openings (h) formed on both sides of the sheet-type outer material (200) to block both sides of the internal space (S).

[0050] Electrolyte may be injected into this internal space (S), and the cap (300) can seal the internal space (S) to prevent leakage of the electrolyte from the internal space (S). Specifically, the cap (300), inserted through an exterior material opening (h) that communicates the internal space (S) with the outside, can be combined with the inner surface of the sheet-type exterior material (200) to seal the internal space (S).

[0051] Meanwhile, the cap (300) may include a body (310) having a lead insertion opening (311a) through which an electrode lead (120) passes, and a gasket (320) that wraps around at least a part of the body (310) and is coupled to a sheet-type outer material (200).

[0052] The gasket (320) is an insulator that surrounds the body (310) and may be composed of a resin-based material. For example, the gasket (320) may be composed of the same material as the innermost layer of the sheet-type exterior material (200). Additionally, the gasket (320) may surround only a part of the body (310). In particular, the gasket (320) may surround only the part of the body (310) that comes into contact with the sheet-type exterior material (200).

[0053] This gasket (320) is a member that surrounds the body (310) and can prevent the electrolyte from leaking between the sheet-type exterior material (200) and the body (310). At this time, the gasket (320) may also serve as a medium for a strong connection between the exterior material (200) and the body (310).

[0054] Meanwhile, the body (310) and the gasket (320) may have various shapes. Typically, the body (310) may be composed of a square plate (311) having a lead insertion opening (311a) formed therein and a leg (312) formed protruding along the edge of the square plate (311).

[0055] Additionally, a fastening groove (321) is formed in the gasket (320) to which the leg (312) of the body (310) is fastened, and a plurality of angled corners (322) may be formed on the outer surface of the gasket (320). At this time, each of the corners (322) formed on the outer surface of the gasket (320) may be in contact with the folding line (L) of the aforementioned sheet-type exterior material (200). That is, the folding line (L) may be formed in the part of the sheet-type exterior material (200) that covers each of the corners (322) on the outer surface of the gasket (320).

[0056] Meanwhile, Fig. 4 is a drawing showing the joint and space-forming portions of the sheet-type exterior material.

[0057] Referring to FIG. 4, the sheet-type exterior material (200) may be composed of a coupling portion (210) that is coupled to a cap (300) and a space-forming portion (220) that is connected to the coupling portion (210) and forms an internal space (S) that accommodates an electrode assembly (100). At this time, the thickness of the portion of the sheet-type exterior material (200) corresponding to the coupling portion (210) may be less than or equal to the thickness of the portion of the sheet-type exterior material (200) corresponding to the space-forming portion (220). In particular, the thickness of the portion of the coupling portion (210) of the sheet-type exterior material (200) where a folding line (L) is formed may be less than or equal to the average thickness of the space-forming portion (220).

[0058] Specifically, the sheet-type exterior material (200) may have a multilayer sheet structure composed of four different layers. The sheet-type exterior material (200) may be composed of an outermost layer, a shock-absorbing layer formed below the outermost layer, a metal substrate layer formed below the shock-absorbing layer, and an innermost layer formed below the metal substrate layer.

[0059] That is, each of the bonding part (210) and the space forming part (220) constituting the sheet-type exterior material (200) may be composed of an outermost layer (210a, 220a) made of a resin material, an impact absorption layer (210b, 220b) formed below the outermost layer (210a, 220a) and composed of a stretchable material to absorb external impact, a metal substrate layer (210c, 220c) formed below the impact absorption layer (210b, 220b) and composed of a metal material, and an innermost layer (210d, 220d) formed below the metal substrate layer (210c, 220c) and composed of a resin material.

[0060] At this time, the outermost layer (210a, 220a) must have excellent resistance to the external environment in order to protect the electrode assembly from the outside, so the outermost layer (210a, 220a) requires excellent tensile strength and corrosion resistance relative to its thickness. For such outermost layer (210a, 220a), polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), and polyolefin-based resins such as polyethylene and polypropylene may be used.

[0061] The shock-absorbing layer (210b, 220b) may be a layer that absorbs external shocks and is composed of a stretchable material. This shock-absorbing layer (210b, 220b) may be composed of various materials. For example, nylon may be used for the shock-absorbing layer (210b, 220b).

[0062] The metal substrate layer (210c, 220c) can serve as a substrate that maintains mechanical strength and as a barrier layer that prevents the penetration of moisture and oxygen. The metal substrate layer (210c, 220c) may be composed of aluminum or an aluminum alloy so as to perform the function of improving the strength of the battery case in addition to the function of preventing the inflow or leakage of foreign substances such as gas and moisture. Aluminum alloys such as alloy numbers 8079, 1N30, 8021, 3003, 3004, 3005, 3104, 3105, etc. may be used, and these may be used alone or in combination of two or more.

[0063] The innermost layer (210d, 220d) is a layer that seals the internal space (S) by being combined with the aforementioned cap (300), and the innermost layer (210d, 220d) may be composed of a polyolefin-based resin. For example, the innermost layer (210d, 220d) may use CPP (Casted Polypropylene), chlorinated polypropylene, polyethylene, ethylene-propylene copolymer, polyethylene-acrylic acid copolymer, and polypropylene-acrylic acid copolymer.

[0064] Meanwhile, the thickness of each layer of the sheet-type exterior material (200) can be varied. For example, the thickness of each layer constituting the sheet-type exterior material (200) can become progressively thicker from the outermost layer (210a, 220a) to the innermost layer (210d, 220d).

[0065] Heat and pressure are applied to the portion of the sheet-type exterior material (200) that is sealed to the cap (300), so the thickness of the portion of the sheet-type exterior material (200) that is sealed to the cap (300) may be thinner than the thickness of the portion of the sheet-type exterior material (200) that is not sealed to the cap (300). In particular, the thickness of the metal substrate layer (210c) of the portion of the sheet-type exterior material (200) that is sealed to the cap (300) may be thinner than the thickness of the metal substrate layer (220c) of the portion of the sheet-type exterior material (200) that is not sealed to the cap (300). Additionally, among the sheet-type exterior material (200), a folding line (L) is formed, and the thickness of the metal substrate layer (210c) of the portion sealed to the corner of the cap (300) may be less than or equal to the average thickness of the metal substrate layer (220c) of the space-forming portion (220).

[0066] That is, the thickness of the metal substrate layer (210c) of the bonding portion (210) of the sheet-type exterior material (200) may be less than or equal to the thickness of the metal substrate layer (220c) of the space-forming portion (220) of the sheet-type exterior material (200). Specifically, the ratio of the thickness of the metal substrate layer (210c) of the bonding portion (210) to the thickness of the metal substrate layer (220c) of the space-forming portion (220) may be 0.81:1 to 1:1. In particular, the ratio of the thickness of the metal substrate layer (210c) of the bonding portion (210) to the thickness of the metal substrate layer (220c) of the space-forming portion (220) may be 0.9:1 to 1:1.

[0067] FIG. 5 is a drawing for explaining how a cap and a sheet-type outer material are sealed in a secondary battery according to the first embodiment of the present invention.

[0068] FIG. 5 illustrates a sheet-type exterior material (200) with a folding line (L) formed thereon and a cap (300) being sealed by receiving heat and pressure. The connecting part (210) of the sheet-type exterior material (200) that is joined to the cap (300) can be heated and pressurized toward the cap (300) using a high-temperature jig. At this time, since the sheet-type exterior material (200) is folded to fit the specifications of the cap (300), the multiple folding lines (L) can be heated and pressurized while in contact with each corner of the cap (300).

[0069] That is, when sealing the cap (300) and the sheet-type exterior material (200), the worker can apply heat and pressure directly to the sheet-type exterior material (200) and the cap (300) without the process of pulling the sheet-type exterior material (200) to fit the specifications of the cap (300).

[0070] FIG. 6 is a drawing illustrating the sealing of a cap and a sheet-type outer material in a conventional pouch-type secondary battery.

[0071] In the conventional secondary battery (10), the sheet-type exterior material (200) does not have a folding line formed therein, so the operator must pull the sheet-type exterior material (200) to press the sheet-type exterior material (200) against the cap (300) before applying heat and pressure to the sheet-type exterior material (200) and the cap (300) using a jig or the like. In this case, the part of the sheet-type exterior material (200) that is joined to the cap (300) is subjected to heat and pressure while stretched by the application of tension, and thus there was a problem in that the thickness of that part became excessively thin.

[0072] FIG. 7 is a diagram illustrating the difference in thickness of the metal substrate layer between a secondary battery according to the first embodiment of the present invention and a conventional pouch-type secondary battery.

[0073] FIG. 7 shows a table comparing the thickness of the portion of the sheet-type outer material (200) that is heat-fused to the cap (300) in two different ways after the sheet-type outer material (200), having an initial thickness of 60 μm of the metal substrate layer, is heat-fused to the cap (300).

[0074] In the case of a secondary battery (10) according to the first embodiment of the present invention in which a folding line (L) is formed on a sheet-type exterior material (200), the thickness of the metal substrate layer (210c) of the bonding portion (210) heat-fused to the cap (300) of the sheet-type exterior material (200) was measured to be 58.4 μm to 59.2 μm. At this time, the average thickness measurement value of the metal substrate layer (210c) was 58.8 μm, which corresponds to 97.9% of the initial thickness of 60 μm.

[0075] On the other hand, in the case of a comparative example where a folding line (L) is not formed in the sheet-type exterior material (200) and heat-fused to the cap (300) while tension is applied to the sheet-type exterior material (200), the thickness of the metal substrate layer in the portion of the sheet-type exterior material (200) heat-fused to the cap (300) was measured to be 46.0 μm to 48.5 μm. At this time, the average thickness of the metal substrate layer heat-fused to the cap was 47.3 μm, which corresponds to 78.8% of the initial thickness of 60 μm.

[0076] Accordingly, in the case of the secondary battery (10) according to the first embodiment of the present invention, the sheet-type outer material (200) having a folding line (L) formed therein is heat-fused to the cap (300), and in this process, there is an advantageous effect of minimizing the loss of the metal substrate layer (210c) of the sheet-type outer material (200).

[0077] 2nd embodiment

[0078] The secondary battery according to the second embodiment of the present invention differs from the first embodiment in that the folding line is formed only in the portion covering the corner of the cap among the sheet-type exterior materials. Content common to the first embodiment will be omitted as much as possible, and the second embodiment will be described focusing on the differences. That is, it is obvious that if content not explained in the second embodiment is necessary, it can be considered as content of the first embodiment.

[0079] FIG. 8 is a cross-sectional view showing the internal structure of a secondary battery according to a second embodiment of the present invention. FIG. 9 is a drawing showing the first and second folding lines formed on the sheet-type outer material of a secondary battery according to a second embodiment of the present invention.

[0080] Referring to FIGS. 8 and 9, a secondary battery (10) according to a second embodiment of the present invention may include an electrode assembly (100), an internal space (S) accommodating the electrode assembly (100), a sheet-type exterior material (200) having an exterior material opening (h) communicating the internal space (S) with the outside, and a cap (300) inserted into the exterior material opening (h) and coupled to the sheet-type exterior material (200) to seal the internal space (S). At this time, a folding line (L) may be formed in the portion of the sheet-type exterior material (200) that covers the corner of the cap (300). At this time, a plurality of folding lines (L) are formed in the sheet-type exterior material (200) of the secondary battery (10), and these plurality of folding lines (L) may be formed only in the portion of the sheet-type exterior material (200) that covers the corner of the cap (300).

[0081] Specifically, the cap (300) blocking the internal space (S) may be composed of a first cap (300a) inserted into one side of the sheet-type exterior material (200) and a second cap (300b) inserted into the other side of the sheet-type exterior material (200). At this time, the folding line (L) may include a first folding line (L1) formed in the part covering the corner of the first cap (300a) of the sheet-type exterior material (200) and a second folding line (L2) formed in the part covering the corner of the second cap (300b) of the sheet-type exterior material (200). That is, in the sheet-type exterior material (200), the folding lines (L1, L2) are formed only in the parts fused to each corner of the pair of caps (300a, 300b), and the part between the folding lines (L1, L2) of the sheet-type exterior material (200) may be maintained in an unfolded state.

[0082] After pre-forming first and second folding lines (L1, L2) on the sheet-type exterior material (200) to correspond to the specifications of each of the pair of caps (300a, 300b), the worker can fold the sheet-type exterior material (200) along the first and second folding lines (L1, L2). At this time, the portion between the first and second folding lines (L1, L2) of the sheet-type exterior material (200) may not be folded and may remain rolled in one direction.

[0083] Afterwards, to block the internal space (S), a cap (300) is inserted into the opening (h) of the exterior material, and heat and pressure can be applied to the cap (300a, 300b) and the sheet-type exterior material (200) to seal them. At this time, since folding lines (L1, L2) are formed in the sheet-type exterior material (200) to match the specifications of the cap (300a, 300b), the sheet-type exterior material (200) and the cap (300a, 300b) can be maintained in a close contact state without applying tension to the sheet-type exterior material (200), and heat and pressure can be applied while the sheet-type exterior material (200) and the cap (300a, 300b) are in close contact.

[0084] In this case, the sheet-type exterior material (200) is subjected to heat and pressure while not being pulled, so the loss of the metal substrate layer of the sheet-type exterior material (200) can be minimized during sealing of the sheet-type exterior material (200) and the cap (300a, 300b).

[0085] Although the present invention has been described above by limited embodiments and drawings, the present invention is not limited thereto, and various implementations 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.

[0086] [Explanation of the symbol]

[0087] 10: Secondary battery 100: Electrode assembly

[0088] 110: Electrode tab 120: Electrode lead

[0089] 200: Sheet-type exterior material 210: Joint part

[0090] 220: Space forming part 300: Cap

[0091] 310: Body 311: Square plate

[0092] 312: Leg 320: Gasket

[0093] 321: Join Home 322: Corner

Claims

1. Electrode assembly; A sheet-type exterior material having an internal space accommodating the electrode assembly and an exterior material opening communicating the internal space with the outside; and It includes a cap that is inserted into the opening of the exterior material and is coupled to the sheet-type exterior material to seal the interior space, and A folding line is formed in the portion of the above sheet-type exterior material that covers the corner of the above cap, and The above sheet-type exterior material is, A coupling part coupled to the above cap; and It includes a space forming part that is connected to the above-mentioned coupling part and forms an internal space for accommodating an electrode assembly, and A secondary battery in which the thickness of the above-mentioned coupling portion is less than or equal to the thickness of the above-mentioned space-forming portion.

2. In Claim 1, The above sheet-type exterior material is a secondary battery formed by rolling or folding a laminate sheet containing a metal layer so that one end and the other end of the laminate sheet meet each other.

3. In Claim 1, The above cap is, A body having a lead insertion opening through which an electrode lead passes; and A secondary battery comprising a gasket that wraps at least a portion of the body and is coupled to the joint portion of the sheet-type exterior material.

4. In Claim 3, The above body is, A square plate having the above-mentioned lead insertion hole formed therein; and A secondary battery comprising a leg formed protruding along the edge of the square plate.

5. In Claim 4, The above gasket is provided with a fastening groove into which the above leg is fastened, and A secondary battery having multiple angled corners formed on the outer surface of the above gasket.

6. In Claim 5, The above folding line is a secondary battery formed in the portion covering each corner of the outer surface of the gasket among the above sheet-type exterior material.

7. In Claim 1, A secondary battery in which the thickness of the portion where the folding line is formed among the above-mentioned joint portions is less than or equal to the thickness of the space-forming portion.

8. In Claim 1, Each of the above-mentioned connecting part and space-forming part is, A secondary battery comprising a metal substrate layer composed of a metal material.

9. In Claim 8, Each of the above-mentioned connecting part and space-forming part is, The outermost layer composed of resin material; A shock-absorbing layer formed below the outermost layer and above the metal substrate layer, composed of a stretchable material to absorb external shocks; and A secondary battery comprising an innermost layer formed below the above-mentioned metal substrate layer and composed of a resin material.

10. In claim 8, A secondary battery in which the thickness of the metal substrate layer of the above-mentioned coupling portion is less than or equal to the thickness of the metal substrate layer of the above-mentioned space-forming portion.

11. In Claim 9, A secondary battery in which the thickness of the metal substrate layer in the portion where the folding line is formed among the above-mentioned joint portions is less than or equal to the thickness of the metal substrate layer in the space-forming portion.

12. In claim 8, A secondary battery in which the ratio of the thickness of the metal substrate layer of the coupling portion to the thickness of the metal substrate layer of the space-forming portion is 0.81:1 to 1:

1.

13. In Claim 12, A secondary battery in which the ratio of the thickness of the metal substrate layer of the coupling portion to the thickness of the metal substrate layer of the space-forming portion is 0.9:1 to 1:

1.

14. Electrode assembly; A sheet-type exterior material having an internal space accommodating the electrode assembly and an exterior material opening communicating the internal space with the outside; and It includes a cap that is inserted into the opening of the exterior material and is coupled to the sheet-type exterior material to seal the interior space, and A folding line is formed in the portion of the above sheet-type exterior material that covers the corner of the above cap, and The above folding line is formed only in the part of the sheet-type exterior material that covers the corner of the cap, in a secondary battery.

15. In Claim 14, The above cap comprises a first cap inserted into one side of the sheet-type outer material; and a second cap inserted into the other side of the sheet-type outer material, in a secondary battery.

16. In Claim 15, The above folding line comprises: a first folding line formed in a portion covering the corner of the first cap among the sheet-type exterior material; and a second folding line formed in a portion covering the corner of the second cap among the sheet-type exterior material.

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