Rechargeable battery and method for manufacturing rechargeable battery

Abstract

The present invention relates to a rechargeable battery which can be repeatedly charged and discharged, and a method for manufacturing a rechargeable battery. The method for manufacturing a rechargeable battery according to an embodiment of the present invention may comprise: a connection step of connecting an electrode lead extending through a cap and an electrode tab of an electrode assembly; a packaging step of wrapping, with a laminate sheet, the electrode assembly and the cap through which the electrode lead extends; and a sealing step of sealing the laminate sheet and the cap, wherein the sealing step comprises: a pre-sealing step of sealing at least parts of a widthwise edge and a longitudinal edge of a side overlapping part, which is overlapped with each other, of the laminate sheet; a cap sealing step of sealing the cap and a portion, which faces the cap, of the laminate sheet; and a main sealing step of sealing the longitudinal edge of the side overlapping part.

Description

Secondary battery and method for manufacturing a secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0193984 filed on December 23, 2024, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0003] Technology field

[0004] The present invention relates to a secondary battery capable of repeated charging and discharging and a method for manufacturing a secondary battery.

[0005] Unlike primary batteries, which cannot be recharged, rechargeable batteries are batteries that can be charged and discharged. Low-capacity rechargeable batteries are used in small portable electronic devices such as mobile phones, laptop computers, and camcorders, while high-capacity batteries are widely used as power sources for motors in hybrid vehicles and the like.

[0006] These secondary batteries can have various structures. For example, the secondary battery may have a pouch cell structure in which an electrode assembly and an electrolyte are housed in an internal space formed by a laminate sheet and a cap.

[0007] Pouch cells having such a structure must be sealed to prevent leakage of the electrolyte. Specifically, the side folding portion of the laminate sheet of the secondary battery that does not form an internal space accommodating the electrode assembly and the electrolyte must be sealed, and the portion of the laminate sheet facing the cap must be sealed.

[0008] When the side folding portion of the laminate sheet and the portion of the laminate sheet facing the cap are sealed, the internal space formed by the laminate sheet and the cap is sealed from the outside, thereby preventing leakage of the electrolyte.

[0009] Conventionally, the part of the side folding portion of the laminate sheet adjacent to the internal space containing the electrode assembly and electrolyte was sealed first, and the part of the laminate sheet facing the cap was sealed second. Subsequently, the edges on both sides of the side folding portion were sealed third, and then the main sealing process of the laminate sheet was carried out.

[0010] In other words, conventional secondary battery sealing processes include a step of pre-sealing the laminate sheet before and after the step of sealing the laminate sheet and the cap, respectively, which resulted in a problem of excessive time and cost being required for the pre-sealing of the laminate sheet.

[0011] The present invention was devised in recognition of the above-mentioned problems, and the objective of the present invention is to provide a secondary battery and a method for manufacturing a secondary battery that can reduce the time and cost required for sealing a pouch-type secondary battery.

[0012] A method for manufacturing a secondary battery according to a first embodiment of the present invention comprises: a connecting step of connecting an electrode lead passing through a cap and an electrode tab of an electrode assembly; a packaging step of wrapping the electrode assembly and the cap through which the electrode lead passes with a laminate sheet; and a sealing step of sealing the laminate sheet and the cap, wherein the sealing step may include a pre-sealing step of sealing a portion of the width-direction edge and the length-direction edge of a side overlap portion that overlaps with each other among the laminate sheets; a cap sealing step of sealing a portion of the cap and the laminate sheet facing the cap; and a main sealing step of sealing the length-direction edge of the side overlap portion.

[0013] The above pre-sealing step may include the step of applying heat and pressure to each of the two ends of the side overlap portion to form a first sealing portion extending in the width direction of the side overlap portion and a second sealing portion extending in the length direction of the side overlap portion.

[0014] In the above pre-sealing step, the first sealing part and the second sealing part can be formed simultaneously.

[0015] The first sealing part and the second sealing part can be connected to each other.

[0016] The length ratio of the second sealing part and the first sealing part may be 1:1 to 1:10.

[0017] The length ratio of the second sealing part and the first sealing part may be 1:1.5 to 1:5.

[0018] The above cap sealing step may include a step of heat-fusing the cap and the laminate sheet by applying heat and pressure to the portion of the cap and the laminate sheet facing the cap.

[0019] The main sealing step described above may include the step of forming a third sealing portion extended in the longitudinal direction of the side overlap portion by applying heat and pressure to one edge in the longitudinal direction of the side overlap portion.

[0020] At least a portion of the third sealing portion may overlap with the second sealing portion.

[0021] Meanwhile, the method for manufacturing a secondary battery according to the second embodiment of the present invention may further include a folding step performed after the sealing step, in which the side overlap portion is folded toward the portion of the laminate sheet that forms an internal space in which the electrode assembly is accommodated.

[0022] In the above folding step, a folding line may be formed in the portion of the side overlap where the third sealing portion is formed.

[0023] Meanwhile, 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 to cover the internal space, wherein the sheet-type outer material comprises a space-forming portion forming the internal space; and a side-overlapping portion overlapping each other on one side of the space-forming portion, wherein a sealing portion is formed in the side-overlapping portion, wherein the sheet-type outer material overlapping each other is sealed, and the sealing portion may include a first portion having a relatively thick average thickness; and a second portion having a relatively thin average thickness.

[0024] The first portion extends along one side of the longitudinal edge of the side overlap portion, and the second portion is formed at each end of one side of the longitudinal edge of the side overlap portion, and the entirety of the second portion may overlap with the first portion.

[0025] The sealing portion may further include a third portion in which sheet-type exterior materials are sealed and overlapped with each other at the widthwise edge of the side overlap portion. The average thickness of the third portion may be thinner than the average thickness of the first portion.

[0026] The length ratio of the second part and the third part may be 1:1 to 1:10.

[0027] The length ratio of the second part and the third part may be 1:1.5 to 1:5.

[0028] Meanwhile, the first portion extends along the longitudinal direction of the side overlap portion, and the second portion is formed at each end of one side of the longitudinal edge of the side overlap portion, and a part of the second portion may overlap with the first portion.

[0029] Here, the sealing portion may further include a third portion in which sheet-type exterior materials are sealed and overlapped with each other at the width-direction edges of the side overlap portions.

[0030] One end of the third part overlaps with the first part, and the average thickness of the third part may be thinner than the average thickness of the first part.

[0031] A method for manufacturing a secondary battery according to one embodiment of the present invention may include a step of simultaneously pre-sealing the width-direction edges and length-direction edges at both ends of the excess portion of a sheet-type outer material. In this case, there is an advantageous effect of reducing the time and cost required for pre-sealing the secondary battery.

[0032] Figure 1 is an exploded perspective view illustrating the structure of a pouch-type secondary battery.

[0033] FIG. 2 is a drawing for explaining a plurality of sealing portions formed in a pouch-type secondary battery.

[0034] FIG. 3 is a flowchart for sequentially explaining each step of a secondary battery manufacturing method according to a first embodiment of the present invention.

[0035] FIG. 4 is a flowchart for explaining in detail the sealing step of a secondary battery manufacturing method according to the first embodiment of the present invention.

[0036] FIG. 5 is a drawing for explaining the process of forming a first sealing portion at both ends of a side overlap portion in a secondary battery manufacturing method according to a first embodiment of the present invention.

[0037] FIG. 6 is a flowchart for sequentially explaining each step of a secondary battery manufacturing method according to a second embodiment of the present invention.

[0038] FIG. 7 is a perspective view illustrating the difference in thickness of the sealing portion of a secondary battery according to the present invention.

[0039] FIG. 8 is a drawing illustrating a secondary battery according to the present invention in which the first and second parts of the sealing portion overlap only partially.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] Method for manufacturing secondary batteries

[0044] FIG. 1 is an exploded perspective view to explain the structure of a pouch-type secondary battery. FIG. 2 is a drawing to explain a plurality of sealing portions formed in a pouch-type secondary battery.

[0045] FIG. 3 is a flowchart for sequentially explaining each step of a secondary battery manufacturing method according to a first embodiment of the present invention. FIG. 4 is a flowchart for explaining in detail the sealing step of a secondary battery manufacturing method according to a first embodiment of the present invention. FIG. 5 is a diagram for explaining the process of forming a first sealing portion at both ends of a side overlap portion of a secondary battery manufacturing method according to a first embodiment of the present invention.

[0046] Referring to FIGS. 1 to 5, a secondary battery manufacturing method according to a first embodiment of the present invention may include: a connecting step (S100) of connecting an electrode lead (120) passing through a cap (400) and an electrode tab (110) of an electrode assembly (100); a packaging step of wrapping the electrode assembly (100) and the cap (400) through which the electrode lead (120) passes with the laminate sheet (200); a cap insertion step of inserting the cap (400) through an opening (300); and a sealing step (S300) of sealing the laminate sheet (200) and the cap (400).

[0047] At this time, the sealing step (S300) may include a pre-sealing step (S310) for sealing a portion of the width-direction edge and length-direction edge of the side overlap portions (210, 220) that overlap each other among the laminate sheet (200), a cap sealing step (S320) for sealing a portion of the cap (400) and the laminate sheet (200) that faces the cap (400), and a main sealing step (S330) for sealing the length-direction edge of the side overlap portions (210, 220).

[0048] In this case, the pre-sealing process of pre-sealing the side overlap portions (210, 220) of the laminate sheet (200) is performed at once, which has the advantageous effect of reducing the time and cost required for the sealing process of the secondary battery.

[0049] In the connection step (S100) of connecting a cap (400) to an electrode assembly (100), an electrode tab (110), which is an electrode bundle of the electrode assembly (100), can be connected to an electrode lead (120) that passes through a through hole formed in the cap (400). The electrode tab (110) and the electrode lead (120) can be connected in various ways. For example, the electrode tab (110) and the electrode lead (120) can be connected by welding. At this time, since the electrode lead (120) passes through a through hole formed in the cap (400) and is connected to the cap (400), the cap (400) can be connected to the electrode assembly (100) in the connection step (S100) to form a single structure.

[0050] 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.

[0051] 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.

[0052] The sheet-type outer material (200) is formed by folding or winding a pouch, which is a laminate sheet (200), in one direction, and an internal space for accommodating an electrode assembly (100) can be formed inside the wound laminate sheet (2). Additionally, both sides of the internal space can be in communication with the outside.

[0053] Specifically, the sheet-type outer material (200) is a pouch having a first end (210) and a second end (220) spaced apart from the first end (210) in a predetermined direction, and the sheet-type outer material (200) can be formed by rolling or folding a laminate sheet (200) so that the first end (210) and the second end (220) meet. The first end (210) and the second end (220) of the laminate sheet (200) can be joined to each other in various ways. For example, the first end (210) and the second end (220) can be bonded with an adhesive, or the first end (210) and the second end (220) can be heat-fused to each other by receiving heat and pressure.

[0054] One end (210) of the laminate sheet (200) may be joined to the inner or outer surface of the other end (220). As shown in FIG. 2, the outer surface of one end (210) of the laminate sheet (200) may be joined to the inner surface of the other end (220). Additionally, the inner surface of one end (210) of the laminate sheet (200) may be joined to the inner surface of the other end (220).

[0055] These first end (210) and second end (220) correspond to parts of the laminate sheet (200) other than the parts forming the internal space, and may be referred to as the excess parts of the laminate sheet (200). Additionally, the first end (210) and second end (220) overlap each other on one side of the laminate sheet (200), and may be referred to as the side overlap parts (210, 220) of the laminate sheet (200).

[0056] Meanwhile, the laminate sheet (200) may be a laminate sheet comprising a metal layer such as aluminum or stainless steel. In this case, a resin layer may be formed on the outer surface and the inner surface of the metal layer, respectively.

[0057] The metal layer can serve as a substrate that maintains mechanical strength and as a barrier layer that prevents the penetration of moisture and oxygen. In addition to preventing the ingress or leakage of foreign substances such as gas and moisture, the metal layer may be composed of aluminum or an aluminum alloy to improve the strength of the battery case. Aluminum alloys such as alloy numbers 8079, 1N30, 8021, 3003, 3004, 3005, 3104, and 3105 may be used, and these may be used individually or in combination of two or more.

[0058] The first resin layer coated on the outer surface of the metal layer must have excellent resistance to the external environment to protect the electrode assembly from the outside; therefore, the first resin layer requires excellent tensile strength and corrosion resistance relative to its thickness. For such a first resin layer, polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), and polyolefin-based resins such as polyethylene and polypropylene may be used.

[0059] A second resin layer coated on the inner surface of a metal layer can be combined with a cap (400) described later to seal an internal space (220), and the second resin layer may be composed of a polyolefin-based resin. For example, the second resin layer may use CPP (Casted Polypropylene), chlorinated polypropylene, polyethylene, ethylene-propylene copolymer, polyethylene-acrylic acid copolymer, and polypropylene-acrylic acid copolymer.

[0060] Meanwhile, in the packaging step (S200), the electrode assembly (100) and the cap (400) may be wrapped or rolled up with a laminate sheet (200). At this time, the internal space in which the electrode assembly (100) is accommodated and the opening (300) communicating the internal space with the outside may be covered by the cap (400).

[0061] This packaging step (S200) may be a step of placing the electrode assembly (100) and the cap (400) on the upper surface of the laminate sheet (200) in an unfolded state, and then rolling or folding the laminate sheet (200) to package them. Alternatively, the packaging step (S200) may be a step of first forming an internal space and an opening (300) by rolling or folding the laminate sheet (200), and then inserting the electrode assembly (100) and the cap (400) into the opening (300). In both of the above cases, the electrode assembly (4) can be accommodated inside the outer material without separate cup molding.

[0062] The cap (400) may be a member that is coupled to the sheet-type outer material (200) and blocks the internal space. The internal space of the sheet-type outer material (200) in which the electrode assembly (100) is housed may be filled with an electrolyte, and the cap (400) can seal this internal space to prevent leakage of the electrolyte. Specifically, the cap (400), inserted into the opening (300) of the sheet-type outer material (200) that communicates the internal space with the outside, may be coupled to the inner surface of the sheet-type outer material (200) to seal the internal space. Here, the inner surface of the sheet-type outer material (200) may be the aforementioned second resin layer.

[0063] The length of the portion of the cap (400) that is inserted into the interior of the sheet-type exterior material (200) can be formed in various ways. For example, only a portion of the cap (400) may be inserted into the interior of the sheet-type exterior material (200), and the remaining portion of the cap (400) may be exposed to the outside of the sheet-type exterior material (200). Additionally, the entire cap (400) may be inserted into the interior of the sheet-type exterior material (200).

[0064] The cap (400) may be made of a material that is not easily permeable to moisture in order to be combined with the inner surface of the sheet-type exterior material (200) and to seal the inner space of the sheet-type exterior material (200). For example, the cap (400) may be obtained from metal or resin, or from a laminate sheet in which a resin layer is formed on both sides of a metal layer.

[0065] Meanwhile, the cap (400) may have various shapes. For example, the cap (400) may be composed of a body (410) and a gasket (420) to block the internal space of the sheet-type exterior material (200). Specifically, a through hole through which an electrode lead (120) passes may be formed in the body (410). At this time, the electrode tab (110) of the electrode assembly (100) may be electrically connected to the electrode lead (120) passing through the body (410).

[0066] The gasket (420) is a member that surrounds the body (410) and can prevent the electrolyte from leaking between the sheet-type exterior material (200) and the body (410). In this case, the gasket (420) may also serve as a medium for a strong connection between the sheet-type exterior material (200) and the body (410).

[0067] These gaskets (420) may have various shapes. For example, the gasket (420) may have a picture frame shape that wraps around the side of the outer surface of the body (410). Additionally, the gasket (420) may be formed to wrap around both the inner and outer surfaces of the body (410).

[0068] Additionally, the cap (400) may have a rectangular box shape. In this case, the four sides of the cap (400) inserted into the aforementioned opening (300) face the inner surface of the sheet-type exterior material (200). Since all four sides of the cap (400) are composed of flat planes, the four sides of the cap (400) are firmly joined to the inner surface of the sheet-type exterior material (200) to effectively seal the inner space of the sheet-type exterior material (200).

[0069] Meanwhile, in the sealing step (S300) for sealing the laminate sheet (200) and the cap (400), heat and pressure are applied to the laminate sheet (200) and the cap (400) to form a plurality of sealing portions.

[0070] Specifically, the sealing step (S300) may include a pre-sealing step (S310) for sealing a portion of the width-direction edge and length-direction edge of the side overlap portions (210, 220) that overlap each other among the laminate sheet (200), a cap sealing step (S320) for sealing a portion of the cap (400) and the laminate sheet (200) that faces the cap (400), and a main sealing step (S330) for sealing the portion between the side overlap portions (210, 220) that were sealed in the pre-sealing step (S300).

[0071] The pre-sealing step (S310) may include the step of applying heat and pressure to each end of the side overlap portions (210, 220) to form a first sealing portion (S1) extending in the width direction of the side overlap portions (210, 220) and a second sealing portion (S2) extending in the length direction of the side overlap portions (210, 220). At this time, the second sealing portion (S2) may be formed as part of the length direction edge of the side overlap portions (210, 220) at a location adjacent to the inner region in which the electrode assembly (100) is accommodated.

[0072] In this pre-sealing step (S310), a portion (S2) of the longitudinal edge of the side overlap (210, 220) is sealed, and if degassing is performed before the main sealing process (S320), internal gas can be effectively discharged through the unsealed portion of the longitudinal edge of the side overlap (210, 220).

[0073] In addition, since the entire width-direction edge (S1) of the side overlap portions (210, 220) is sealed during the pre-sealing step (S310), sufficient bonding force can be secured between the side overlap portions (210, 220). Therefore, even if a degassing process to remove the internal pressure of the secondary battery (10) is performed before the main sealing process (S320), the alignment of the side overlap portions (210, 220) can be prevented from becoming misaligned.

[0074] Meanwhile, in the pre-sealing step (S310), the first sealing part (S1) and the second sealing part (S2) may be formed simultaneously. At this time, the first sealing part (S1) and the second sealing part (S2) may be connected to each other. Specifically, the pre-sealing step (S310) may be a step of applying pressure to both ends of the side overlapping parts (210, 200) using an L-shaped sealing block.

[0075] Such L-shaped sealing blocks can be configured in various ways. For example, the L-shaped sealing block may be provided with a flat pressure surface, and a heating wire that generates heat when an external power source is applied may be provided inside the L-shaped sealing block.

[0076] Additionally, in the pre-sealing step (S310), the side overlap portions (210, 220) can be pressed in both directions. Specifically, in the pre-sealing step (S310), the upper and lower surfaces of both ends of the side overlap portions (210, 220) can be pressed simultaneously to form sealing portions (S1, S2).

[0077] Meanwhile, the length ratio of the second sealing part (S2) and the first sealing part (S1) may be 1:1 to 1:10. If the length of the second sealing part (S2) is excessively long, the internal gas of the secondary battery (10) may not be smoothly discharged through the gap between the second sealing part (S2) during the degassing process. Additionally, if the length of the second sealing part (S2) is excessively short, sufficient sealing force may not be secured, and electrolyte leakage may occur.

[0078] These problems can be solved by adjusting the length ratio of the second sealing part (S2) and the first sealing part (S1) to 1:1 to 1:10. In particular, if the length ratio of the second sealing part (S2) and the first sealing part (S1) is adjusted to 1:1.5 to 1:5, the above problems can be fully solved.

[0079] Meanwhile, the cap sealing step (S320) may be a step of heat-fusing the cap (400) and the laminate sheet (200) by applying heat and pressure to the portion of the cap (400) and the laminate sheet (200) facing the cap (400).

[0080] In the cap sealing step (S320), the four sides of the laminate sheet (200) facing the cap (400) may be pressed simultaneously or sequentially. Each of these four sides of the laminate sheet (200) may be heat-fused with the four sides of the cap (400) to seal the opening (300) of the laminate sheet (200). That is, a fourth sealing portion (S4) may be formed on the four parts of the laminate sheet (200) facing the cap (400).

[0081] Meanwhile, the main sealing step (S330) may be a step of forming a third sealing part (S3) extended in the longitudinal direction of the side overlapping part (210, 220) by applying heat and pressure to one longitudinal edge of the side overlapping part (210, 220). At this time, the third sealing part (S3) may cover one longitudinal edge of the side overlapping part (210, 220).

[0082] Specifically, the third sealing portion (S3) may be formed as part of the longitudinal edge of the side overlap portions (210, 220) at a location adjacent to the inner region in which the electrode assembly (100) is accommodated. At this time, a part of the third sealing portion (S3) may be attached to the second sealing portion (S2). Specifically, the entirety of the second sealing portion (S2) may be included in the third sealing portion (S3), or a part of the second sealing portion (S2) may be included in the third sealing portion (S3).

[0083] Meanwhile, FIG. 6 is a flowchart for sequentially explaining each step of a secondary battery manufacturing method according to a second embodiment of the present invention.

[0084] Referring to FIG. 6, the method for manufacturing a secondary battery according to the second embodiment of the present invention is performed after the aforementioned sealing step (S300) and may further include a folding step (S400) in which the side overlapping portions (210, 220) are folded toward the portion forming an internal space in the laminate sheet (200). In this case, the side overlapping portions (210, 220) of the sheet-type exterior material (200) are folded toward the portion forming an internal space in which the electrode assembly (100) is accommodated in the sheet-type exterior material (200), thereby having the advantageous effect of reducing the volume of the secondary battery (10) and improving energy density.

[0085] Meanwhile, this folding step (S400) is a step of folding along a folding line formed in the side overlapping portions (210, 220), and the folding line of the side overlapping portions (210, 220) can be formed in various ways. In particular, this folding line may be identical to the part of the side overlapping portions (210, 220) where the aforementioned third sealing portion (S3) is formed.

[0086] The third sealing portion (S3) may be formed as part of the longitudinal edge of the side overlap portion (210, 220) at a location adjacent to the inner region in which the electrode assembly (100) is accommodated. If the folding line of the side overlap portion (210, 220) is the same as the part where the third sealing portion (S3) is formed, the entire side overlap portion (210, 220) is folded, thereby minimizing the volume of the secondary battery (10).

[0087] In addition, the method for manufacturing a secondary battery according to the second embodiment of the present invention is performed after the folding step (S400) and may further include a fixing step (not shown) in which the folded side overlapping portions (210, 220) are fixed with an adhesive or fixing tape. In this case, the position of the folded side overlapping portions (210, 220) is fixed, so that the position of the side overlapping portions (210, 220) is prevented from shifting even when the internal pressure of the secondary battery (10) increases or an external force is applied to the secondary battery (10).

[0088] secondary battery

[0089] A secondary battery (10) according to the present invention may include an electrode assembly (100), an internal space accommodating the electrode assembly (100), a sheet-type exterior material (200) having an exterior material opening (300) communicating the internal space with the outside, and a cap (400) inserted into the exterior material opening (300) to cover the internal space. At this time, the sheet-type exterior material (200) includes a space-forming part (230) forming the internal space and side overlapping parts (210, 220) that overlap each other on one side of the space-forming part (230), and a sealing part formed on the side overlapping parts (210, 220) in which the sheet-type exterior material (200) overlapped each other is sealed may be formed.

[0090] At this time, an electrode tab (110) is formed in the electrode assembly (100), and the electrode tab (110) can be welded to the electrode lead (120). The electrode tab (110) may be a bundle in which the electrode uncoated portion of one of the plurality of electrodes constituting the electrode assembly (100) is welded, or a metal bundle separately connected to the plurality of electrodes constituting the electrode assembly (100).

[0091] The electrode lead (120) is welded to the electrode tab (110) to electrically connect the electrode assembly (100) to an external device, and the electrode lead (120) can pass through a through hole formed in the cap (400).

[0092] Meanwhile, FIG. 7 is a perspective view illustrating the thickness difference of a sealing portion of a secondary battery according to the present invention. Referring to FIG. 7, the sealing portion may include a first portion (A1) having a relatively thick thickness and a second portion (A2) having a relatively thin thickness. That is, the average thickness of the first portion (A1) may be thicker than the average thickness of the second portion (A2). At this time, the second portion (A2) is formed at each end of one side of the longitudinal edge of the side overlapping portions (210, 220), and the first portion (A1) may be formed between the second portions (A2).

[0093] Additionally, a third part (A3) may be formed at the widthwise edge of the side overlapping portions (210, 220) in which sheet-type exterior materials (200) that overlap each other are sealed. That is, the sealing portion may include the third part (A3). At this time, the average thickness of the third part (A3) may be thinner than the average thickness of the first part (A1).

[0094] The first part (A1) and the second part (A2) are formed on the edge portion adjacent to the space-forming portion (230) among the longitudinal edges of the side overlap portions (210, 220), and the portions forming the first part (A1) and the second part (A2) among the side overlap portions (210, 220) can be heat-fused to each other to seal the internal space of the space-forming portion (230). The third part (A3) is formed on each side of the widthwise edge of the side overlap portions (210, 220), and can strengthen the adhesive force between the side overlap portions (210, 220).

[0095] The first part (A1) may be a portion of the side overlap portions (210, 220) that is sealed during the main sealing step (S330). That is, during the main sealing step (S330), one side of the longitudinal edge of the side overlap portions (210, 220) may be heated and pressed with a high-temperature sealing tool to form the first part (A1). At this time, the side overlap portions (210, 220) constituting the first part (A1) may have a thickness of 8 to 12 mm.

[0096] The second part (A2) may be a portion of the side overlap portions (210, 220) that is sealed during the pre-sealing step (S310). That is, during the pre-sealing step (S310), the two ends of one longitudinal edge of the side overlap portions (210, 220) may be heated and pressed with a high-temperature sealing tool to form the second part (A2). At this time, the side overlap portions (210, 220) constituting the second part (A2) may have a thickness of approximately 8 mm. That is, the thickness of the second part (A2) may be thinner than the thickness of the first part (A1).

[0097] Meanwhile, the entirety of the second part (A2) may overlap with the first part (A1). That is, the area corresponding to the second part (A2) may be completely contained within the first part (A1). In this case, the area corresponding to the second part (A2) is heated and pressurized during both the pre-sealing step (S310) and the main sealing step (S330), and the thickness of the part may be 8 mm or less.

[0098] The third part (A3) may be a portion of the side overlap portions (210, 220) that is sealed during the pre-sealing step (S310). That is, during the pre-sealing step (S310), the portions on both sides of the width-direction edge of the side overlap portions (210, 220) may be heated and pressed with a high-temperature sealing tool to form the third part (A3). At this time, the side overlap portions (210, 220) constituting the third part (A3) may have a thickness of approximately 8 mm. That is, the thickness of the third part (A3) is substantially the same as the thickness of the second part (A2), and the thickness of the third part (A3) may be thinner than the thickness of the first part (A1).

[0099] Meanwhile, the length ratio of the second part (A2) and the third part (A3) may be 1:1 to 1:10. If the length of the second part (A2) is excessively long, the internal gas of the secondary battery (10) may not be smoothly discharged into the area between the second part (A2) during the degassing process performed before the main sealing process. In addition, if the length of the second part (A2) is excessively short, sufficient sealing force may not be secured, and electrolyte leakage may occur.

[0100] These problems can be solved by adjusting the length ratio of the second part (A2) and the third part (A3) to 1:1 to 1:10. In particular, the above problems can be fully solved by adjusting the length ratio of the second part (A2) and the third part (A3) to 1:1.5 to 1:5.

[0101] Meanwhile, a fourth part (A4) in which the sheet-type exterior material (200) and the cap (400) are heat-fused may be formed in the part of the sheet-type exterior material (200) that faces the cap (400). Specifically, a part of the space-forming part (230) that forms an internal space in the sheet-type exterior material (200) faces the cap (400), and the said part and the cap may be sealed by heat and pressure. Since the space-forming part (230) faces the cap (400) on four sides, four fourth parts (A4) may be formed in the secondary battery (10).

[0102] Additionally, the side overlap portions (210, 220) can be folded toward the space forming portion (230). There is no limit to the number of times the side overlap portions (210, 220) can be folded. When the side overlap portions (210, 220) are folded toward the space forming portion (230), the secondary battery (10) may further include a fixing member (not shown) for fixing the folded side overlap portions (210, 220) to the space forming portion (230).

[0103] These fixing members can be configured in various ways. For example, the fixing member may be a fixing tape that fixes the end of the folded side overlap (210, 220) to one side of the space forming member (230). Additionally, the fixing member may be an adhesive layer that adheres one side of the folded side overlap (210, 220) to one side of the space forming member (230).

[0104] When the side overlapping portions (210, 220) are folded and then fixed to the space forming portion (230), the total volume of the secondary battery (10) can be reduced, which has the advantageous effect of increasing the total energy density of the secondary battery (10).

[0105] Meanwhile, FIG. 8 is a drawing illustrating that in a secondary battery according to the present invention, the first part and the second part of the sealing portion overlap only partially.

[0106] In the case of the secondary battery (10) illustrated in FIG. 8, only a portion of the second part (A2) constituting the sealing portion may overlap with the first part (A1). Specifically, the first part (A1) extends along the longitudinal direction of the side overlap portions (210, 220), and the second part (A2) may be formed at each end of one side of the longitudinal edge of the side overlap portions (210, 220). At this time, a portion of the second part (A2) overlaps with the first part (A1), and the remainder of the second part (A2) may not overlap with the first part (A1).

[0107] The first part (A1) is formed on the inner side of the longitudinal edge of the side overlap portion (210, 220), and the right end of the second part (A2) may overlap with the left end of the first part (A1). The first part (A1) is a part that is heated and pressurized in the main sealing step (S330), and the second part (A2) is a part that is heated and pressurized in the pre-sealing step (S310). The part where the first part (A1) and the second part (A2) overlap may be heated and pressurized in both the pre-sealing step (S310) and the main sealing step (S330). Accordingly, the average thickness of the part where the first part (A1) and the second part (A2) overlap may be thinner than the average thickness of the first and second parts (A1, A2).

[0108] Meanwhile, the sealing portion includes a third portion (A3) in which sheet-type exterior materials are sealed and overlapped at the widthwise edges of the side overlapping portions (210, 220), and one end of the third portion (A3) may overlap with the first portion (A1). At this time, the area where the third portion (A3) and the first portion (A1) overlap may be heated and pressurized during both the pre-sealing step (S310) and the main sealing step (S330). Accordingly, the average thickness of the corresponding overlapping portion may be thinner than the average thickness of the first and third portions (A1, A3).

[0109] 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.

[0110] [Explanation of the symbol]

[0111] 10: Secondary battery 100: Electrode assembly

[0112] 110: Electrode tab 120: Electrode lead

[0113] 200: Laminate sheet 210, 220: Side overlap

[0114] 300: Opening 400: Cap

[0115] 410: Body 420: Gasket

[0116] S1: 1st sealing part S2: 2nd sealing part

[0117] S3: 3rd sealing part S4: 4th sealing part

[0118] A1: Part 1 A2: Part 2

[0119] A3: Part 3 A4: Part 4

Claims

1. A connection step of connecting an electrode lead passing through a cap and an electrode tab of an electrode assembly; A packaging step of wrapping the cap through which the electrode assembly and the electrode lead pass with a laminate sheet; and It includes a sealing step for sealing the above laminate sheet and the above cap, The above sealing step is, A pre-sealing step of sealing parts of the width-direction edges and length-direction edges of the mutually overlapping side overlap portions of the laminate sheets; A cap sealing step for sealing the portion of the cap and the laminate sheet facing the cap; and A method for manufacturing a secondary battery comprising a main sealing step for sealing the longitudinal edge of the above-mentioned side overlap portion.

2. In Claim 1, The above pre-sealing step is, A method for manufacturing a secondary battery comprising the step of applying heat and pressure to each of the two ends of the side overlap portion to form a first sealing portion extending in the width direction of the side overlap portion and a second sealing portion extending in the length direction of the side overlap portion.

3. In Claim 2, A method for manufacturing a secondary battery in which, in the above-mentioned pre-sealing step, the first sealing portion and the second sealing portion are formed simultaneously.

4. In Claim 2, A method for manufacturing a secondary battery in which the first sealing part and the second sealing part are connected to each other.

5. In Claim 2, A method for manufacturing a secondary battery in which the length ratio of the second sealing portion and the first sealing portion is 1:1 to 1:

10.

6. In Claim 5, A method for manufacturing a secondary battery in which the length ratio of the second sealing portion and the first sealing portion is 1:1.5 to 1:

5.

7. In Claim 1, The above cap sealing step is, A method for manufacturing a secondary battery comprising the step of heat-fusing the cap and the laminate sheet by applying heat and pressure to the portion facing the cap among the cap and the laminate sheet.

8. In Claim 2, The above main sealing step is, A method for manufacturing a secondary battery comprising the step of applying heat and pressure to one longitudinal edge of the side overlap portion to form a third sealing portion extended in the longitudinal direction of the side overlap portion.

9. In Claim 8, A method for manufacturing a secondary battery in which at least a portion of the third sealing portion overlaps with the second sealing portion.

10. In Claim 8, A method for manufacturing a secondary battery, further comprising a folding step performed after the sealing step, wherein the side overlap portion is folded toward a portion of the laminate sheet that forms an internal space in which the electrode assembly is accommodated.

11. In Claim 10, A method for manufacturing a secondary battery in which, in the folding step above, a folding line is formed in the portion of the side overlap portion where the third sealing portion is formed.

12. 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 covers the interior space, The above sheet-type exterior material comprises: a space-forming portion forming the internal space; and a side-overlapping portion that overlaps each other on one side of the space-forming portion. In the above side overlapping portion, a sealing portion is formed in which sheet-type exterior materials that overlap each other are sealed. The above sealing portion comprises a first portion having a relatively thick average thickness; and a second portion having a relatively thin average thickness, in a secondary battery.

13. In Claim 12, The above first portion extends along one side of the longitudinal edge of the side overlap portion, and The above second part is formed at each of both ends of one side of the longitudinal edge of the side overlap portion, and The entirety of the second part above is a secondary battery that overlaps with the first part above.

14. In Claim 12, The above sealing part is, A secondary battery further comprising a third portion in which sheet-type exterior materials are sealed and overlapped with each other at the width-direction edges of the above-mentioned side overlap portions.

15. In Claim 14, A secondary battery in which the average thickness of the third part is thinner than the average thickness of the first part.

16. In Claim 15, A secondary battery in which the length ratio of the second part and the third part is 1:1 to 1:

10.

17. In Claim 16, A secondary battery in which the length ratio of the second part and the third part is 1:1.5 to 1:

5.

18. In Claim 12, The above first portion extends along the longitudinal direction of the side overlap portion, and The second portion is formed at each end of one side of the longitudinal edge of the side overlap portion, and a portion of the second portion overlaps with the first portion, forming a secondary battery.

19. In Claim 18, The above sealing part is, A secondary battery further comprising a third portion in which sheet-type exterior materials are sealed and overlapped with each other at the width-direction edges of the above-mentioned side overlap portions.

20. In Claim 19, A secondary battery in which one end of the third part overlaps with the first part, and the average thickness of the third part is thinner than the average thickness of the first part.

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