Pouch-type secondary battery

Abstract

A pouch-type secondary battery according to the present invention comprises: an electrode assembly; an exterior comprising an accommodation unit for accommodating the electrode assembly, and a terrace unit formed along the circumference of the accommodation unit and having a sealing unit in which a portion of the width is sealed; an electrode lead which is electrically connected to the electrode assembly and protrudes to the outside of the exterior; a lead film disposed between the electrode lead and the exterior; a gas induction unit disposed between the electrode lead and the lead film and including a transmission unit provided outside the sealing unit and at least one gas flow path extending from the transmission unit toward the electrode assembly via the sealing unit; and a reinforcing film disposed on the lead film so as to cover at least a portion of the transmission unit, wherein the reinforcing film has a single-layer structure.

Description

pouch-type secondary battery This specification relates to a pouch-type secondary battery, and more specifically, to a pouch-type secondary battery including a gas induction unit for discharging gas inside. Secondary batteries are used in a wide range of applications, from small products like digital cameras, DVDs, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, to larger, high-power products like electric and hybrid vehicles, as well as power storage devices that store surplus power or renewable energy, and as backup power storage devices. Types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. Secondary batteries can be manufactured by housing an electrode assembly, in which a positive electrode, a negative electrode, and a separator interposed therebetween are alternately laminated, in a battery case, injecting an electrolyte, and then sealing the battery case. Secondary batteries are classified into pouch types and can types depending on the material of the case housing the electrode assembly. Among them, pouch type batteries can be manufactured by performing press processing on a flexible pouch film laminate to form a cup portion, housing the electrode assembly in the inner space of the cup portion, and sealing the seal portion. Pouch-type secondary batteries can generate gas within the pouch during high-temperature operation, overcharging, or short-circuiting. If gas pressure within the pouch increases, the pouch can vent, potentially leading to an explosion or fire. Accordingly, research is being conducted on various types of gas exhaust components to solve the above problems, and the need for gas exhaust components that simultaneously consider gas exhaust, moisture infiltration from the outside, and electrolyte leakage, gas exhaust components that can withstand high internal pressure but have low operating pressure, and gas exhaust components with excellent durability is continuously increasing. The present invention is intended to solve the above problems, and to provide a pouch-type secondary battery and a battery pack including the same, which solve the problem of moisture infiltration or electrolyte leakage due to stretching of the film in a gas-permeable portion of a secondary battery equipped with a gas induction portion by applying a reinforcing film to prevent deformation of the gas induction portion, while maintaining the gas discharge rate at an appropriate level. In addition, the present invention provides a pouch-type secondary battery including a gas induction unit that can improve durability while maintaining gas discharge performance by applying a reinforcing film to prevent deformation of the gas induction unit in the secondary battery, and employing a single-layer structure as the reinforcing film, thereby minimizing the interface between films and preventing delamination between layers, and a battery pack including the same. [1] In one aspect of the present specification, a pouch-type secondary battery is provided, comprising: an electrode assembly; an outer shell including a receiving portion for receiving the electrode assembly, and a terrace portion formed along a periphery of the receiving portion, the terrace portion having a sealing portion with a portion of the width sealed; an electrode lead electrically connected to the electrode assembly and protruding to the outside of the outer shell; a lead film disposed between the electrode lead and the outer shell; a gas induction portion disposed between the electrode lead and the lead film, the gas induction portion including a permeation portion provided on an outside of the sealing portion and one or more gas channels extending from the permeation portion toward the electrode assembly via the sealing portion; and a reinforcing film disposed on the lead film so as to cover at least a portion of the permeation portion, wherein the reinforcing film has a single-layer structure. is provided. [2] In the above [1], the secondary battery may be configured such that the interface between the lead film and the gas induction film is opened along the gas path due to an increase in the internal pressure of the outer material, thereby providing a gas discharge path. [3] In the above [1] and / or [2], the reinforcing film may be placed on the lead film so that the entirety of the transmission portion is covered. [4] In at least one of the above [1] to [3], an insertion portion that occupies a portion of the width of the sealing portion may be included, and the insertion portion may be a region in which one end of the reinforcing film extends in the direction of the inner side of the outer material and is inserted between the outer material of the sealing portion and the lead film. [5] In at least one of the above [1] to [4], the reinforcing film includes an insertion portion occupying a portion of the width of the sealing portion, and the insertion portion is a region in which one end of the reinforcing film extends inwardly toward the outer material and is inserted between the outer material of the sealing portion and the lead film, and the length ratio of the insertion portion to the width of the sealing portion is characterized in that it is 0.05 to 0.90. [6] In at least one of the above [1] to [5], the reinforcing film may have a thickness of 60 ㎛ to 150 ㎛. [7] In at least one of the above [1] to [6], the reinforcing film may have a melting temperature (Tm) of 110°C to 170°C. [8] In at least one of the above [1] to [7], the reinforcing film may have a tensile strength of 3.5 MPa to 5.5 MPa at 60°C. [9] In at least one of the above [1] to [8], the reinforcing film may include a modified polyolefin resin.

[0010] In at least one of the above [1] to [9], the reinforcing film may include a modified polyolefin resin, and the modified polyolefin resin may include at least one selected from acid-modified polypropylene and acid-modified polyethylene.

[0011] In at least one of the above [1] to

[0010] , the gas induction unit may include an adhesive resin layer in contact with the electrode lead and a permeable resin layer in contact with the lead film.

[0012] In the above

[0011] , the adhesive resin layer may have one end protruding toward the outside of the outer material more than one end of the permeable resin layer protruding toward the outside of the outer material.

[0013] In the above

[0011] and / or

[0012] , the lead film may have one end protruding toward the outside of the outer material more than one end of the permeable resin layer protruding toward the outside of the outer material.

[0014] In another aspect of the present specification, a battery pack is provided, comprising: a plurality of pouch-type secondary batteries; and a packaging for accommodating the secondary batteries, wherein the pouch-type secondary batteries include: an electrode assembly; an outer case including a receiving portion for accommodating the electrode assembly, and a terrace portion formed along a periphery of the receiving portion, the terrace portion having a sealing portion having a portion of the width sealed; an electrode lead electrically connected to the electrode assembly and protruding to the outside of the outer case; a lead film disposed between the electrode lead and the outer case; a gas induction portion disposed between the electrode lead and the lead film, the gas induction portion including a permeation portion provided on an outside of the sealing portion and one or more gas channels extending from the permeation portion toward the electrode assembly via the sealing portion; and a reinforcing film disposed on the lead film so as to cover at least a portion of the permeation portion, wherein the reinforcing film has a single-layer structure. In one aspect of the present specification, a pouch-type secondary battery and battery pack can prevent whitening caused by continuous tension of a lead film as gas is discharged by introducing a reinforcing film covering a permeable portion of a gas induction portion, solve the problem of electrolyte leakage, and have the advantage of reducing the possibility of moisture infiltration in the long term. In another aspect of the present specification, a pouch-type secondary battery and battery pack introduce a reinforcing film that covers a permeable portion of a gas induction portion, and a part of the reinforcing film is inserted into a sealing area so that they are sealed together, so that even if the process of opening the interface between the gas induction portion and the lead film when discharging gas is repeated, the sealing strength is excellent, and the phenomenon of film slipping, etc. can be prevented. Furthermore, by adopting a single-layer structure, the inter-film interface is minimized, thereby preventing the problem of sealing structure disintegration caused by interlayer delamination in multilayer films. Furthermore, operating pressure and discharge speed can be maintained at levels not significantly different from conventional levels, thereby preventing deterioration in gas emission performance. Accordingly, the pouch-type secondary battery offers the advantage of improved durability while maintaining acceptable gas emission performance. Figure 1 is an exploded assembly diagram of a pouch-type secondary battery. Figure 2 is a cross-sectional view of a sealed pouch-type secondary battery. Figure 3 is an example of an enlarged cross-sectional view of part A of box 2, showing the state before the interface between the lead film and the gas induction part is opened. Fig. 4 is an example of an enlarged cross-sectional view of part A of box 2, showing a state in which the interface between the lead film and the gas induction section is open. Figure 5 is another example of an enlarged cross-sectional view of part A of box 2, showing the state before the interface between the lead film and the gas induction film is opened. Figure 6 is another example of an enlarged cross-sectional view of part A of box 2, showing the state before the interface between the lead film and the gas induction film is opened. Figure 7 is an example of a top perspective view in the B direction for part A of box in Figure 2. The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification. Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise. The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned. In this specification, when it is said that a part includes a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless specifically stated otherwise. In this specification, the description of “A and / or B” means A, or B, or A and B. In this specification, “%” means weight percent unless explicitly indicated otherwise. The pouch-type secondary battery described in this specification includes at least one of the technical configurations described below, and may include any combination between technically possible configurations among the technical configurations below. In one aspect, a pouch-type secondary battery includes an electrode assembly; an outer case including a receiving portion for receiving the electrode assembly and a terrace portion formed along a periphery of the receiving portion; an electrode lead connected to the electrode assembly and protruding to the outside of the outer case via the terrace portion; a lead film disposed between the electrode lead and the outer case; a gas induction portion disposed between the electrode lead and the lead film; and a reinforcing film disposed on the lead film. In addition, in the pouch-type secondary battery, the terrace portion is provided with a sealing portion whose width is partly sealed along the periphery of the receiving portion, the gas induction portion includes a permeation portion provided on the outside of the sealing portion, and at least one gas path provided through the sealing portion so that the permeation portion and the inside of the outer material are connected to each other, and the reinforcing film covers the entire permeation portion of the gas induction portion, and the reinforcing film is characterized in that it has a single-layer structure with a thickness of 60 ㎛ to 150 ㎛ and includes a modified polyolefin resin. First, each component of the pouch-type secondary battery is briefly explained with reference to the drawing. Fig. 1 is an exploded assembly diagram of a pouch-type secondary battery (100), and Fig. 2 is a cross-sectional view of a sealed pouch-type secondary battery (100). In Fig. 2, some of the components of the pouch-type secondary battery (100) are omitted for ease of understanding. As illustrated in Figs. 1 and 2, the pouch-type secondary battery (100) includes an outer material (110), an electrode assembly (160), an electrode lead (180), a lead film (190), a gas induction part (200), and a reinforcing film (300). (1) Exterior material In one aspect, the outer casing (110) can accommodate an electrode assembly (160) inside. The outer casing (110) can be manufactured by molding a pouch film laminate. In this case, the pouch film laminate can include a substrate layer, a gas barrier layer, and a sealant layer. In the pouch film laminate, the substrate layer, the gas barrier layer, and the sealant layer can be sequentially laminated. The substrate layer is formed on the outermost layer of the pouch film laminate to protect the secondary battery from friction and collision with the outside world. The substrate layer is made of polymer and can electrically insulate the electrode assembly from the outside world. The substrate layer may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. Preferably, the substrate layer may be made of polyethylene terephthalate (PET), nylon, or a combination thereof, which have wear resistance and heat resistance. The substrate layer may have a single-layer structure composed of a single material. Alternatively, the substrate layer may have a composite-layer structure composed of two or more materials, each formed as a layer. The thickness of the substrate layer may be 5 ㎛ to 50 ㎛, specifically 7 ㎛ to 40 ㎛, and more specifically 25 ㎛ to 38 ㎛. When the thickness of the substrate layer satisfies the above range, the external insulation is excellent, and the thickness of the entire pouch is not thick, so the energy density per volume of the secondary battery can be excellent. The gas barrier layer is laminated between the substrate layer and the sealant layer to secure the mechanical strength of the pouch, block the ingress of gas or moisture from outside the secondary battery, and prevent electrolyte leakage from inside the outer material. The gas barrier layer may be formed of a metal, and specifically, may be formed of an aluminum alloy thin film. When the gas barrier layer is formed using an aluminum alloy thin film, a mechanical strength higher than a predetermined level can be secured, while being light in weight and ensuring complementary electrochemical properties and heat dissipation properties due to the electrode assembly and electrolyte. The aluminum alloy thin film may include at least one selected from the group consisting of metal elements other than aluminum (Al), for example, iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn). The thickness of the gas barrier layer may be 40 ㎛ to 100 ㎛, specifically 50 ㎛ to 90 ㎛, and more specifically 55 ㎛ to 85 ㎛. When the thickness of the gas barrier layer satisfies the above range, the formability and gas barrier performance are excellent when forming the cup portion. The sealant layer is intended to completely seal the interior of the outer material by thermally bonding the outer material with the electrode assembly when the outer material is sealed. To this end, the sealant layer may be formed of a material having excellent thermal bonding strength. The sealant layer may be formed of a material having insulating, corrosion-resistant, and sealing properties. Specifically, since the sealant layer is in direct contact with the electrode assembly and / or electrolyte inside the outer case, it may be formed of a material having insulating and corrosion-resistant properties. In addition, since the sealant layer must completely seal the inside of the outer case to prevent material movement between the inside and the outside, it may be formed of a material having high sealing properties (e.g., excellent thermal bonding strength). To secure such insulating, corrosion-resistant, and sealing properties, the sealant layer may be formed of a polymer material. The sealant layer may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber, and preferably may be made of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be composed of cast polypropylene (CPP), acid modified polypropylene (Acid Modified Polypropylene, PPa), polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer. The thickness of the sealant layer may be 30 ㎛ to 130 ㎛, specifically 50 ㎛ to 120 ㎛, and more specifically 70 ㎛ to 100 ㎛. When the thickness of the sealant layer satisfies the above range, there is an effect of securing the sealing strength of the sealing portion while also securing the formability of the pouch film laminate. The pouch film laminate can be drawn and stretched by a punch or the like to manufacture the outer material (110). As a result, the outer material (110) can include a cup portion (122) and a receiving portion (124). The receiving portion (124) is a place for receiving the electrode assembly, and can mean a receiving space formed in the shape of a pocket on the inside of the cup portion (122) as the cup portion (122) is formed. In one aspect, the outer case (110) may include a first case (120) and a second case (130) as illustrated in FIG. 1. The first case (120) includes a receiving portion (124) capable of receiving an electrode assembly (160), and the second case (130) may cover the receiving portion (124) from above to prevent the electrode assembly (160) from being separated from the outside of the battery case (110). The first case (120) and the second case (130) may be manufactured with one side connected to each other as illustrated in FIG. 1, but are not limited thereto and may be manufactured in various ways, such as being manufactured separately and separated from each other. In another aspect, when forming a cup portion on a pouch film laminate, two symmetrical cup portions (122, 132) can be drawn and formed adjacent to each other on one pouch film laminate. In this case, cup portions (122, 132) can be formed in the first case (120) and the second case (130) respectively as illustrated in FIG. 1. After the electrode assembly (160) is accommodated in the receiving portion (124) provided in the cup portion (122) of the first case (120), the bridge portion (140) formed between the two cup portions (122, 132) can be folded so that the two cup portions (122, 132) face each other. In this case, the cup portion (132) of the second case (130) can accommodate the electrode assembly (160) from above. Accordingly, since two cup portions (122, 132) accommodate one electrode assembly (160), an electrode assembly (160) having a thicker thickness can be accommodated than when there is only one cup portion (122). In addition, since one corner of the secondary battery (100) is formed by folding the outer casing (110), the number of corners to be sealed can be reduced when performing a sealing process later. Accordingly, the process speed of the pouch-type secondary battery (100) can be improved, and the number of sealing processes can be reduced. The outer material (110) may be sealed while housing the electrode assembly (160) so that a portion of the electrode lead (180) described later, i.e., a terminal portion, is exposed. Specifically, when the electrode lead (180) is connected to the electrode tab (170) of the electrode assembly (160) and a lead film (190) is formed on a portion of the electrode lead (180), the electrode assembly (160) may be housed in a receiving portion (124) provided in a cup portion (122) of the first case (120), and the second case (130) may cover the receiving portion (124) from above. Subsequently, an electrolyte may be injected into the receiving portion (124), and a portion of the terrace portion (150) formed along the perimeter of the first case (120) and the second case (130) may be sealed to form a sealing portion (not shown). The sealing portion can serve to seal the receiving portion (124). Specifically, the sealing portion can seal the receiving portion (124) by being formed on the terrace portion (150) formed along the perimeter of the receiving portion (124). The temperature at which the sealing portion is sealed may be 180°C to 250°C, specifically 200°C to 250°C, and more specifically 210°C to 240°C. When the sealing temperature satisfies the above numerical range, the exterior material (110) can secure sufficient sealing strength through thermal bonding. (2) Electrode assembly In one aspect, the electrode assembly (160) can be inserted into the outer material (110) and sealed by the outer material (110) after electrolyte injection. The electrode assembly (160) may be formed by sequentially stacking an anode, a separator, and a cathode. Specifically, the electrode assembly (160) may include two types of electrodes, an anode and a cathode, and a separator interposed between the electrodes to mutually insulate the electrodes. The positive and negative electrodes may each have a structure in which an active material slurry is applied to an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper, respectively. The slurry is typically formed by stirring granular active materials, auxiliary conductors, binders, and conductive agents with the addition of a solvent. The solvent can be removed in a subsequent process. A slurry containing an electrode active material, a binder, and / or a conductive material is applied to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and these are laminated on both sides of a separator, thereby manufacturing an electrode assembly (160) in a predetermined shape. The types of electrode assembly (160) may include, but are not limited to, a stack type, a jelly roll type, a stack and folding type, etc. The electrode assembly (160) may include an electrode tab (170). The electrode tabs (170) are respectively connected to the positive and negative electrodes of the electrode assembly (160), and may protrude outward from the electrode assembly (160) to serve as a path for electrons to move between the inside and the outside of the electrode assembly (160). The electrode current collector included in the electrode assembly (160) may be composed of a portion where an electrode active material is applied and a terminal portion where the electrode active material is not applied, i.e., a non-coated portion. The electrode tabs (170) may be formed by cutting the non-coated portion or by connecting a separate conductive member to the non-coated portion by ultrasonic welding, etc. As illustrated in FIG. 1, the electrode tabs (170) may protrude in different directions of the electrode assembly (160), but are not limited thereto, and may be formed to protrude in various directions, such as protruding in parallel in the same direction from one side. (3) Electrode lead In one aspect, the electrode lead (180) can supply electricity to the outside of the secondary battery (100). The electrode lead (180) can be connected to the electrode tab (170) of the electrode assembly (160) by spot welding or the like. The electrode lead (180) is connected to the electrode assembly (160) and may protrude to the outside of the outer material (110) via the sealing portion (150). Specifically, one end of the electrode lead (180) is connected to the electrode assembly (160), particularly to the electrode tab (170), and the other end of the electrode lead (180) may protrude to the outside of the outer material (110) via the terrace portion (150). The electrode lead (180) may include a positive lead (182) having one end connected to the positive tab (172) and extending in the direction in which the positive tab (172) protrudes, and a negative lead (184) having one end connected to the negative tab (174) and extending in the direction in which the negative tab (174) protrudes. Both the positive lead (182) and the negative lead (184) may have other ends protruding outward from the battery case (110). Accordingly, electricity generated inside the electrode assembly (160) may be supplied to the outside. In addition, since the positive tab (172) and the negative tab (174) are formed to protrude in various directions, the positive lead (182) and the negative lead (184) may also extend in various directions, respectively. The positive lead (182) and the negative lead (184) may be made of different materials. That is, the positive electrode lead (182) may be made of the same aluminum (Al) material as the positive electrode collector, and the negative electrode lead (184) may be made of the same copper (Cu) material as the negative electrode collector or a nickel (Ni)-coated copper material. A portion of the electrode lead (180) protruding outside the battery case (110) may serve as a terminal portion and be electrically connected to an external terminal. One surface of the electrode lead (180) that is in direct contact with the lead film (190) and / or the gas induction unit (200) may be coated with at least one selected from the group consisting of chromium (Cr), nickel (Ni), aluminum oxide (Al2O3), zirconium (Zr)-based anhydride salts, and titanium (Ti)-based anhydride salts. In this case, corrosion resistance against the electrolyte and adhesion to the lead film (190) and / or the gas induction unit (200) can be secured. (4) Lead film In one aspect, the lead film (190) prevents electricity generated from the electrode assembly (160) from flowing to the battery case (110) through the electrode lead (180) and can maintain the sealing of the battery case (110). To this end, the lead film (190) may be formed of a non-conductive material that does not conduct electricity well. In general, the lead film (190) is often made of an insulating tape that is easy to attach to the electrode lead (180) and / or the gas induction unit (200) and has a relatively thin thickness, but is not limited thereto, and any material capable of insulating the electrode lead (180) may be used. The lead film (190) may be arranged to surround the outer circumference of the electrode lead (180) and the gas induction unit (200). Specifically, the electrode lead (180) and the gas induction unit (200) may be in contact with each other at one side, and at least a portion of the electrode lead (180) and the gas induction unit (200) may be surrounded by the lead film (190). The lead film (190) may be positioned limited to the sealing portion (150) where the first case (120) and the second case (130) of the outer material (110) are thermally fused, and may adhere the electrode lead (180) and the gas induction unit (200) to the battery case (110). The lead film (190) may be placed between the electrode lead (180) and / or the gas induction unit (200) and the outer material (110). For example, as illustrated in FIG. 2, the lower case (110), the lead film (190), the electrode lead (180), the gas induction unit (200), the lead film (190), and the upper case (110) may be sequentially stacked in the terrace unit (150) area. Meanwhile, the lead film (190) may include one or more layers. Specifically, the lead film (190) may include a sequentially laminated metal adhesive layer, a core layer, and a pouch adhesive layer. The metal adhesive layer may be in direct contact with the electrode lead (180) and may be used to adhere the lead film (190) to the electrode lead (180). The metal adhesive layer may include any material that is easily adhered to the electrode lead (180). Specifically, the metal adhesive layer may include a modified polyolefin-based resin, for example, an acid-modified polyolefin. For example, the metal adhesive layer may include at least one of acid-modified polypropylene (PPa), acid-modified polyethylene (PEa), and plasma-treated polypropylene, but is not limited thereto. The thickness may be 50 ㎛ to 80 ㎛, specifically 50 ㎛ to 75 ㎛, and more specifically 60 ㎛ to 75 ㎛. When the thickness of the metal adhesive layer satisfies the above numerical range, there is an effect of preventing pinholes and leaks at the edge when fusion occurs between the electrode lead and the lead film. The above acid-modified polyolefin refers to a polyolefin resin that has been graft-modified with an acid. For example, the acid-modified polyolefin may be a polyolefin resin in which a carboxyl group is introduced (graft-modified) by reacting an unsaturated carboxylic acid. In this case, the unsaturated carboxylic acid may include the concept of a carboxylic anhydride, and the carboxyl group may include the concept of a carboxylic anhydride group. The unsaturated carboxylic acid to be reacted with the polyolefin resin may include at least one selected from the group consisting of maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, tetrahydrophthalic acid, aconitic acid, maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, aconitic anhydride, norbornene dicarboxylic anhydride, and tetrahydrophthalic anhydride, but is not limited thereto. The core layer may be a layer located at the center of the lead film (190). The core layer may include an unmodified polyolefin resin, and may include, for example, polypropylene resin, polyolefin elastomer (POE), and / or additives such as a colorant, but is not limited thereto. Among these, the core layer may include, for example, a polypropylene homopolymer. When the core layer includes a polypropylene homopolymer, the melting point of the core layer can be controlled within the above numerical range, and deformation due to heat can be minimized, which is advantageous in terms of securing insulation. The thickness of the core layer may be 40 ㎛ to 70 ㎛, specifically, 50 ㎛ to 70 ㎛, and more specifically, 60 ㎛ to 70 ㎛. When the thickness of the core layer satisfies the above numerical range, deformation due to heat applied during fusion and sealing is prevented, thereby providing a robust design effect in terms of securing insulation. The pouch adhesive layer may be a layer that directly contacts the battery case (110), specifically, the sealant layer of the pouch film laminate. The pouch adhesive layer may include an unmodified polyolefin resin, and for example, may include a polypropylene resin or a polyolefin elastomer (POE, Polyolefin Elastomer), but is not limited thereto. Among these, the pouch adhesive layer may include a polypropylene copolymer such as a polypropylene random copolymer or a polypropylene block copolymer. The melting point of the pouch adhesive layer including the copolymer as described above can be controlled within the above numerical range, and has a melting point similar to that of the polymer in the sealant layer of the pouch film laminate, which is advantageous in securing sealing processability. The thickness of the pouch adhesive layer may be 40 ㎛ to 100 ㎛, specifically, 40 ㎛ to 80 ㎛, and more specifically, 40 ㎛ to 60 ㎛. When the thickness of the pouch adhesive layer satisfies the above numerical range, there is an effect of securing a polymer (e.g., polypropylene) residual ratio sufficient to secure strength when sealing between the electrode lead and the pouch film laminate. (5) Gas induction unit In one aspect, the gas induction unit (200) is provided to discharge gas from the inside of the outer material (110) to the outside, and may include a permeation unit (230) provided on the outside of the outer material (110) and one or more gas passages (240) extending from the permeation unit (230) toward the electrode assembly (160) via the sealing unit. As illustrated in FIG. 2, the gas induction unit (200) of the present invention may be disposed between the electrode lead (180) and the lead film (190). In this case, in the area between the electrode lead (180) and the lead film (190), where the gas induction unit (200) is disposed, the electrode lead (180) and the lead film (190) do not come into direct contact, and in the area where the gas induction unit (200) is not disposed, the electrode lead (180) and the lead film (190) may come into direct contact. Hereinafter, the gas induction unit (200) of the present invention will be described in more detail with reference to FIGS. 3 and 4. FIG. 3 is a cross-sectional view of a pouch-type secondary battery before the interface between the gas induction unit (200) and the lead film (190) is opened, and FIG. 4 is a cross-sectional view of a pouch-type secondary battery after the interface between the gas induction unit (200) and the lead film (190) is opened. As illustrated in FIGS. 3 and 4, the interface between the gas induction unit (200) and the lead film (190) may be normally not open, and when the pressure inside the outer casing (110) increases, the interface between the gas induction unit (200) and the lead film (190) may be opened along the gas path (240), thereby forming a gas discharge path (250). The gas inside the outer casing (110) may move to the permeation unit (230) along the gas discharge path (250) on the gas path (240), and at this time, when a gas pocket is formed on the permeation unit (230), the gas may permeate the lead film (190) and be discharged to the outside of the outer casing (110). As a result, the internal pressure of the outer casing (110) may be lowered, thereby preventing explosion or ignition of the secondary battery. As illustrated in FIGS. 3 and 4, the gas induction unit (200) includes an adhesive resin layer (210) that is in contact with the electrode lead (180) and a permeable resin layer (220) that is disposed on the adhesive resin layer (210). The adhesive resin layer (210) is in contact with the electrode lead (180) and may be used to adhere the gas induction unit (200) to the electrode lead (180). In one aspect, as shown in FIG. 3, the adhesive resin layer (210) of the gas induction unit (200) may be formed so that the end in the outer direction (E) of the outer material is longer than the end in the outer direction (E) of the permeable resin layer (220). Accordingly, a structure may be formed in which the adhesive resin layer (210) is in direct contact with the lead film (190) at the end in the outer direction (E) of the gas induction unit (200). Independently of this, the end of the lead film (190) protruding in the outer direction (E) of the outer material may be positioned to protrude further outward (E) than the end of the adhesive resin layer (210) in the same direction and come into direct contact with the electrode lead (180). In addition, independently of this, the end of the lead film (190) protruding in the outer direction (E) of the outer material may be arranged to protrude further outward (E) than the end of the permeable resin layer (220) in the same direction. When the adhesive resin layer (210) is formed to protrude further outward (E) of the outer casing than the permeable resin layer (220), or when the lead film (190) is formed to protrude further outward than one end of the permeable resin layer (220) and / or the adhesive resin layer (210) in the outer casing, the adhesive strength between the electrode lead (180) and the gas induction portion (200), and between the electrode lead (180) and the lead film (190) can be excellent, and thus, a decrease in durability due to an increase in internal pressure can be prevented, and since it is easy to secure the area of ​​the permeable portion (230) on the permeable resin layer (220), stable gas discharge can be possible. In another aspect, as shown in FIG. 5, the lead film (190) may be arranged so that one end protruding in the case outer direction (E) protrudes further than the case outer direction (E) end of the gas induction unit (200) and comes into direct contact with the electrode lead (180). Independently, the outer direction (E) ends of the two layers on the gas induction unit (200) may be formed to coincide. In another aspect, as shown in FIG. 6, the adhesive resin layer (210) may be formed such that one end protruding in the case outer direction (E) protrudes further than the case outer direction (E) end of the permeable resin layer (220), but the outer direction (E) end of the adhesive resin layer (210) matches the outer direction (E) end of the lead film (190). In this case, the lead film (190) may have a structure in which it does not directly contact the electrode lead (180) but rather contacts the adhesive resin layer (210). In the case where the arrangement structure of the lead film (190), electrode lead (180) and gas induction unit (200) is formed as in FIG. 3, FIG. 5 or FIG. 6, it may be advantageous in terms of securing durability and securing the area of ​​the permeable unit (230) compared to the case where the lead film (190) is not arranged so that one end protrudes further outward from the outer material (110) than the gas induction unit (200) but is arranged on the permeable resin layer (220) of the gas induction unit (200). However, it may be arranged as in FIG. 3 most preferably, but the structure of FIG. 5 or FIG. 6 may also be applied depending on the case, and either structure may be selectively applied. The adhesive resin layer (210) may include any material that is easily bonded to the electrode lead (180). For example, the adhesive resin layer (210) may include a modified polyolefin-based resin, and may include at least one of an acid-modified polyolefin and a silane-modified polyolefin. When the adhesive resin layer (210) includes a modified polyolefin-based resin, the adhesive strength between the gas guide portion (200) and the electrode lead (180) is improved, so that even when the pouch-type secondary battery is stored in a high-temperature environment, the problem of the gas guide portion (200) being detached from the electrode lead (180) and pushed out of the pouch or the electrolyte inside the pouch leaking can be prevented. The above acid-modified polyolefin refers to a polyolefin resin that has been graft-modified with an acid. For example, the acid-modified polyolefin may be a polyolefin resin in which a carboxyl group is introduced (graft-modified) by reacting an unsaturated carboxylic acid. In this case, the unsaturated carboxylic acid may include the concept of a carboxylic anhydride, and the carboxyl group may include the concept of a carboxylic anhydride group. The unsaturated carboxylic acid to be reacted with the polyolefin resin may include at least one selected from the group consisting of maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, tetrahydrophthalic acid, aconitic acid, maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, aconitic anhydride, norbornene dicarboxylic anhydride, and tetrahydrophthalic anhydride, but is not limited thereto. Among these, it is preferable to apply maleic anhydride to improve the adhesive strength between the gas induction unit (200) and the electrode lead (180). The acid-modified polyolefin may include at least one selected from the group consisting of acid-modified polypropylene (PPa) and acid-modified polyethylene (PEa), but is not limited thereto. The above silane-modified polyolefin refers to a polyolefin resin that has been graft-modified with an unsaturated silane compound. The silane-modified polyolefin may have a structure in which an unsaturated silane compound is graft-copolymerized onto a polyolefin resin, which is the main chain. The silane-modified polyolefin resin may include, but is not limited to, one or more selected from the group consisting of a silane-modified polypropylene resin and a silane-modified ethylene-vinyl acetate copolymer. The adhesive resin layer (210) may be modified, and the modification treatment may include ion implantation treatment, plasma treatment, radiation treatment, heat treatment, etc., and a treatment that changes the bonding structure of the polymer layer is preferable. These modification treatments may be performed singly by one type, or may be performed in combination of two or more types. The modified adhesive resin layer (210) may include, but is not limited to, plasma-treated polypropylene (PP). The thickness of the adhesive resin layer (210) may be 5 µm to 130 µm, specifically 30 µm to 120 µm, and more specifically 30 µm to 80 µm. When the thickness of the adhesive resin layer (210) satisfies the above numerical range, the adhesive resin layer (210) is melted within a set production time (tact time), so that the gas induction unit (200) and the electrode lead (180) can be easily fused together. The permeable resin layer (220) may be a layer in contact with the lead film (190). The permeable resin layer (220) may include at least one of polytetrafluoroethylene (PTFE) and polyimide (PI). The permeable resin layer (220) is preferable in that it does not have high adhesive strength with the lead film (190), so that even if the relevant portion is sealed, the interface with the lead film (190) may be opened when the pressure inside the case (110) increases, thereby forming a gas discharge path (250). The thickness of the permeable resin layer (220) may be 40 ㎛ to 100 ㎛, specifically 40 ㎛ to 90 ㎛, and more specifically 45 ㎛ to 75 ㎛. When the thickness of the permeable resin layer (220) satisfies the above numerical range, the permeable resin layer (220) may not melt during the sealing process, and when the internal pressure of the case (110) increases, the interface between the permeable resin layer (220) and the lead film (190) may be opened to form a gas discharge path (250). Meanwhile, the ratio (D1 / D2) of the thickness (D1) of the adhesive resin layer to the thickness (D2) of the permeable resin layer (220) may be 0.4 to 2.0, specifically 0.4 to 1.5, and more specifically 0.4 to 1.0. When the ratio (D1 / D2) satisfies the above numerical range, when the internal pressure of the case (110) increases, the interface between the permeable resin layer (220) and the lead film (190) is lifted to form a gas discharge path, while improving the adhesive strength between the gas induction unit (200) and the electrode lead (180). The above-described transparent resin layer (220) and adhesive resin layer (210) can be laminated through thermocompression, and can be combined after forming an adhesive layer therebetween, or can be in the form of a tape in which an adhesive is applied to one surface of the transparent resin layer (220) or the adhesive resin layer (210) and a release film is attached, and can be combined after the release film is removed. There is no particular limitation on the method for laminating the above-described transparent resin layer (220) and adhesive resin layer (210), and in addition to the above-described method, any method can be applied as long as the two layers can adhere well to each other. (6) Reinforcing film In one aspect, the reinforcing film (300) is characterized in that it is placed on the lead film (190) so as to cover at least a portion of the permeable portion (230) of the gas induction portion (200), thereby preventing whitening and electrolyte seepage. The above pouch-type secondary battery (100) has a series of mechanisms in which, when the internal pressure increases, the interface between the gas induction unit (200) and the lead film (190) is opened, and the laminates including the lead film (190) and the outer covering (110) thereon are lifted upward only in the portion where the gas induction unit (200) is arranged, thereby forming a gas discharge path (250), and the gas inside is discharged to the outside by passing through the lead film (190) in the permeation portion (230) through the gas discharge path (250) thus formed. When this gas discharge mechanism is repeated, the lead film (190) located on the gas-permeable portion, i.e., the permeable portion (230) of the gas induction portion (200), is continuously subjected to tension, and as the internal pressure increases, the tension applied to the lead film (190) increases, and a whitening phenomenon may occur in the relevant portion. The whitening phenomenon may occur when the molecular structure inside the film is deformed due to the continuous stretching of the lead film (190), the internal stress increases due to the deformation, and the bonding force between molecules is weakened accordingly, and in the portion where the bonding force between molecules is weakened. Meanwhile, when the gas is discharged and the internal pressure is lowered again, that is, when a series of charge / discharge reactions are completed and the battery is placed in a storage state and all the gas inside is discharged, the lifted lead film (190) returns to its original state and the gas discharge path (250) is closed again. The closure of the gas discharge path (250) can minimize the possibility of the electrolyte leaking to the outside. However, as described above, a part where the bonding force between molecules is weakened occurs inside the lead film (190), and the electrolyte can infiltrate through this part. This can be observed as a phenomenon of electrolyte seepage in the permeable part (230) of the gas induction part (200) on the lead film (190), or in severe cases, a problem of leakage can occur. Once the phenomenon of electrolyte seepage or leakage occurs, the possibility of moisture infiltration from the outside also increases. In addition, if the above phenomenon is repeated, the electrode lead (180) may be corroded, and if the internal pressure increases, a problem may occur in which a vent occurs centered on the part where the bonding strength of the lead film (190) is weakened. Accordingly, the inventors of the present invention have attempted to solve the above problem by introducing a reinforcing film (300) on the permeable portion (230) of the gas induction portion (200), which is an area where gas is permeated on the lead film (190) of the pouch-type secondary battery (100), thereby ensuring durability by suppressing deterioration of the gas induction portion (200) and the lead film (190) due to continuous gas discharge. In one aspect, the reinforcing film (300) is characterized by having a single-layer structure, and due to this structure, even if sealing is performed under optimal conditions after sealing, the problem of interlayer delamination within the film itself that may occur in a multi-layered film can be fundamentally eliminated, and the gas discharge performance can also be expected to have the advantage of being able to be maintained as the reduction in operating pressure and gas discharge speed is not significant. In one aspect, the reinforcing film (300) may have a thickness of 60 ㎛ to 150 ㎛, preferably 70 ㎛ or more, 75 ㎛ or more, 80 ㎛ or more, 85 ㎛ or more, 90 ㎛ or more, or 95 ㎛ or more, and may also have a thickness of 140 ㎛ or less, 130 ㎛ or less, 120 ㎛ or less, or 115 ㎛ or less. When the thickness is designed in the range of 60 ㎛ to 150 ㎛, it is expected to have an effect of preventing whitening and an effect of increasing supply and demand stability or unit price competitiveness by improving the film forming process. Referring to FIGS. 3 and 4, a gas induction unit (200) is disposed on an electrode lead (180), a lead film (190) is disposed on the gas induction unit (200), and the reinforcing film (300) is disposed on the lead film (190) and can cover at least a portion of the permeation unit (230) of the gas induction unit (200), and preferably, can cover the entire surface of the permeation unit (230). When the reinforcing film (300) covers the entire surface of the permeation unit (230), it is possible that the gas discharge speed may be relatively slow compared to when a portion of the permeation unit is covered. However, considering that the excellent effects of preventing whitening and increasing durability may outweigh the deterioration of gas discharge performance, the secondary battery can be appropriately modified and applied depending on the application to which it is applied. The reinforcing film (300) may have an area based on the outer circumference of the reinforcing film (300) that is 100% to 500% of the area of ​​the permeable portion (230) of the gas induction portion (200). That is, the reinforcing film (300) may be arranged to cover at least the entire area of ​​the permeable portion (230), and the area (S) of the permeable portion (230) A) can be arranged to cover up to 500% of the area of ​​the transmission portion (230). As long as the area of ​​the reinforcing film (300) covering the transmission portion (230) is designed to cover the entire area, there is no particular problem, but it may be disadvantageous in terms of design, such as the sealing process and the thickness of the terrace portion after sealing, so it may be desirable to design it to satisfy the above-mentioned range. In addition, in order to effectively suppress the electrolyte seepage phenomenon and prevent the whitening phenomenon due to stretching, it is desirable to design the area of ​​the reinforcing film (300) to be 110% or more, 130% or more, or 150% or more of the area of ​​the transmission portion (230). When designing the area covering the transmission section (230), the above-mentioned reinforcing film (300) can be arranged so that a portion of the reinforcing film exceeding the area of ​​the transmission section (230) can also cover a portion of the gas path (240). That is, in order to effectively prevent electrolyte seepage and whitening due to stretching, in the case where the area of ​​the permeation portion (230) of the gas induction portion (200) is designed to exceed the area of ​​the permeation portion (230) of the gas induction portion (200), it may be desirable to design the reinforcement film (300) to be wide in the width direction of the electrode lead (180) and long in the length direction of the electrode lead (180), and preferably, it may be arranged to cover not only the permeation portion (230) but also the gas inlet (240). In one aspect, the reinforcing film (300) is characterized by including an insertion portion (301) that occupies a portion of the width of the sealing portion (151). The insertion portion (301) may refer to a region where one end of the reinforcing film (300) extends in the inner direction (I) of the outer material and is inserted between the outer material of the sealing portion (151) and the lead film. In this case, the sealing strength can be improved, and thereby the durability can be improved by maintaining the sealing strength even when the interface between the lead film (190) and the gas induction portion (200) is repeatedly opened, thereby preventing an unintended venting phenomenon. The insertion part (301) of the above reinforcing film (300) has a sealing width (W) of the sealing part (151). S ) may be 0.05 to 0.90. When the insertion portion (301) is formed so that the length ratio satisfies the range, it is expected that the sealing strength can be secured at a level that does not lower the fairness of the sealing process. That is, when the reinforcing film (300) is inserted deep within the sealing width so that the insertion portion (301) covers the entire sealing portion (151), peeling may occur at the interface between the reinforcing films (300) having a multi-layer structure. Therefore, by making the end of the reinforcing film (300) in the inner direction (I) of the outer material cover only a part of the sealing width, it is possible to prevent the problem of interface peeling as described above by covering the sealing portion (151). To further enhance this effect, preferably, the length ratio may be 0.07 or more, 0.09 or more, 0.10 or more, or 0.11 or more, and may also be 0.85 or less, 0.83 or less, 0.80 or less, 0.79 or less, or 0.78 or less. In one aspect, the reinforcing film (300) may include a modified polyolefin resin. It is preferable that the reinforcing film (300) have similarities with the material of the film that comes into contact with the upper and lower portions, such that the lower portion comes into contact with the lead film (190) and the upper portion comes into contact with the outer material (110) at some points. In addition, it may be preferable that the thermal characteristics, which act as a major factor in the sealing process, be also taken into consideration when applying the reinforcing film (300). Therefore, a modified polyolefin resin may be applied. When the modified polyolefin resin is included, it is expected that a strong adhesive force with the lead film and the exterior material can be realized. The modified polyolefin resin may be an acid-modified polyolefin or a plasma-treated polyolefin, and may include, for example, at least one of acid-modified polypropylene (PPa), acid-modified polyethylene (PEa), and plasma-treated polypropylene. The acid-modified polyolefin refers to a polyolefin resin that has been graft-modified with an acid. For example, the acid-modified polyolefin may be a polyolefin resin in which a carboxyl group is introduced (graft-modified) by reacting an unsaturated carboxylic acid. The unsaturated carboxylic acid to be reacted with the polyolefin resin may include at least one selected from the group consisting of maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, tetrahydrophthalic acid, aconitic acid, maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, aconitic anhydride, norbornene dicarboxylic anhydride, and tetrahydrophthalic anhydride, but is not limited thereto. Among these, it is preferable to apply maleic anhydride to improve the adhesive strength between the gas discharge portion (200) and the electrode lead (180). The above reinforcing film (300) includes a modified polyolefin-based resin, and in some cases, may further include an unmodified polyolefin-based resin. The unmodified polyolefin-based resin may further include, for example, a polypropylene copolymer such as a polypropylene random copolymer or a polypropylene block copolymer. In addition, the unmodified polyolefin-based resin may be an unstretched polyolefin, and the unstretched polyolefin-based resin is manufactured through casting without being stretched in a specific direction during the manufacturing or processing process, and is flexible compared to stretched polyolefin-based resins, does not have a problem of tearing in a specific direction, and may be relatively easy to process. When the unmodified polyolefin-based resin is included in the reinforcing film, it may be advantageous in implementing a stronger sealing strength during sealing, and it is expected to have the advantage of desirably implementing an effect of reducing gas discharge performance by minimizing resistance at the interface with the lead film (190) when gas is transmitted. In one aspect, the reinforcing film (300) may have a tensile strength of 3.5 MPa to 5.5 MPa at 60°C. Here, the tensile strength is the maximum value of the force applied when the reinforcing film is cut to a width of 15 mm and a length of 90 mm, inserted into a grip at each end of 20 mm using a UTM, and then stretched by 20 mm at 1 mm / min at 60°C. The tensile strength of the reinforcing film may vary depending on the layer structure, the material of each layer, the thickness of each layer, etc., and manufacturing or obtaining a reinforcing film (300) having a specific tensile strength may be easy for a person having common technical knowledge in this industry. The tensile strength of the above reinforcing film (300) may be preferably applied at a level that can prevent deformation of the lead film (190) due to tension, thereby suppressing the whitening phenomenon, and prevent the opening of the interface between the lead film (190) and the gas induction unit (200) when gas is discharged, thereby preventing the operating pressure from increasing. If the above range is satisfied, it is advantageous for achieving such an effect, and may be preferably 3.7 MPa or more, 3.9 MPa or more, 4.0 MPa or more, or 4.5 MPa or more, and may also be 5.4 MPa or less, 5.3 MPa or less, 5.2 MPa or less, or 5.0 MPa or less. The above reinforcing film (300) may have a melting temperature (Tm) of 110°C to 170°C. It may be desirable to control the melting temperature range in consideration of the possibility of a situation in which a high temperature is temporarily applied to the electrode lead portion, such as during rapid charging, and the ease of the sealing process considering the amount of heat applied during the sealing process. From this perspective, the melting temperature of the resin included in the reinforcing film may preferably be 120°C or higher, 130°C or higher, or 140°C or higher, and 165°C or lower, 160°C or lower, or 158°C or lower. (7) Electrolyte The pouch-type secondary battery (100) according to the present invention may further include an electrolyte (not shown) injected into the exterior material (110). The electrolyte is for moving lithium ions generated by an electrochemical reaction of an electrode during charging / discharging of the secondary battery (100), and may include a non-aqueous organic electrolyte that is a mixture of a lithium salt and an organic solvent, or a polymer using a polymer electrolyte. Furthermore, the electrolyte may include a solid electrolyte of a sulfide type, an oxide type, or a polymer type, and such a solid electrolyte may have flexibility that allows it to be easily deformed by an external force. battery pack In one aspect, the battery pack may include a pouch-type secondary battery. In this case, the secondary battery (3) may be configured in multiple units. The battery pack may include packaging that accommodates multiple pouch-type secondary batteries therein. The packaging may be configured to protect the pouch-type secondary batteries from external impact or contamination. A description of the pouch-type secondary batteries is omitted here as they have been described above. The above packaging may be provided as a box-shaped structure. The packaging may be made of metal or plastic with a predetermined rigidity. The packaging may have a structure in which multiple plates are joined together. The shape or structure of the above packaging may be modified as needed. For example, at least a portion of the packaging may have a curved shape. Furthermore, the packaging may additionally include other components. For example, the packaging may include a bus bar electrically connected to a plurality of secondary batteries and / or a venting component that connects the interior and exterior of the packaging. Hereinafter, the present invention will be described in more detail through specific examples. However, the following examples are merely illustrative and serve to aid understanding of the present invention and do not limit its scope. It will be apparent to those skilled in the art that various modifications and variations are possible within the scope and technical spirit of this disclosure, and such modifications and variations are naturally within the scope of the appended claims. Examples and Comparative Examples Example 1 (1) Manufacturing of exterior materials A polyethylene terephthalate (PET) film measuring 266 mm wide, 50 m long, and 12 ㎛ thick and a nylon film measuring 266 mm wide, 50 m long, and 25 ㎛ thick were laminated on one side of an aluminum alloy film measuring 266 mm wide, 50 m long, and 60 ㎛ thick, and a polypropylene film measuring 266 mm wide, 50 m long, and 80 ㎛ thick was laminated on the other side, thereby manufacturing a pouch film laminate having a polyethylene terephthalate / nylon / aluminum alloy film / polypropylene film structure. Here, the polyethylene terephthalate film and nylon film are the substrate layer, the aluminum alloy thin film is the gas barrier layer, and the polypropylene film is the sealant layer. The above pouch film laminate was molded to manufacture an outer material including a receiving portion and a sealing portion. (2) Manufacturing of pouch-type secondary batteries An electrode assembly was manufactured by stacking and laminating the cathode, anode, and porous polyethylene separator. Thereafter, an electrode lead was attached to the electrode assembly. An electrolyte was prepared by dissolving LiPF6 in a solvent (EC:EMC:DMC = 3:3:4 volume ratio) to a concentration of 1.0 M. The electrode assembly was housed in the outer case with the tip of the electrode lead extended outward, and the electrolyte was poured. A 50 ㎛ thick polytetrafluoroethylene tape (permeable resin layer) was attached to a 43 ㎛ thick acid-modified polypropylene film (adhesive resin layer) on the upper surface of the electrode lead to form a gas induction section. Next, a 200 μm thick lead film was laminated on the lower surface of the electrode lead and the upper surface of the gas induction unit, respectively. The lead film includes a 75 μm thick metal adhesive layer containing a polypropylene random copolymer and an acid-modified polypropylene, a 65 μm thick core layer containing a homopolymer polypropylene, and a 60 μm thick pouch adhesive layer containing a copolymer polypropylene. Finally, a reinforcing film was placed on the upper surface of the lead film on which the gas induction section was formed, such that the reinforcing film was inserted inwardly of the case by about 80% of the sealing width, and was placed outwardly so as to cover the entire surface of the transmission section. The above reinforcing film was made of 93 ㎛ thick acid-modified polypropylene applied to the upper surface of the lead film, had a melting temperature of 143°C, and a tensile strength of 5.0 MPa at 60°C. Here, the tensile strength is the maximum value of the force applied when the reinforcing film was cut to a width of 15 mm and a length of 90 mm, inserted into a grip at each end of 20 mm using a UTM, and then stretched by 20 mm at 1 mm / min at 60°C. Afterwards, the sealing part of the outer material was sealed for 2 seconds under the conditions of a seal bar area of ​​200 mm x 10 mm, 220°C, and 0.27 MPa, and then left at 60°C for 4 hours to manufacture a pouch-type secondary battery. Example 2 A pouch-type secondary battery was manufactured in the same manner as in Example 1, except that a reinforcing film having a melting temperature of 157°C and a tensile strength of 4.5 MPa at 60°C was used. Comparative Example 1 A pouch-type secondary battery was manufactured in the same manner as in Example 1, except that a reinforcing film was not formed. Comparative Example 2 A pouch-type secondary battery was manufactured in the same manner as in Example 1, except that a 200 ㎛ lead film (a three-layer structure of a 75 ㎛ thick film containing a polypropylene random copolymer and acid-modified polypropylene, a 65 ㎛ thick film containing a homopolymer polypropylene, and a 60 ㎛ thick film containing a copolymer polypropylene, Tm of 160°C and a tensile strength at 60°C of 6.0 MPa) was used as a reinforcing film. Experimental Example 1: Measurement of gas emission rate The gas emission rate was measured for each pouch-type secondary battery manufactured in the examples and comparative examples. Specifically, CO2 was injected into the pouch-type secondary battery using pressure equipment from ITS Corporation to increase the pressure inside the pouch to 1.5 atm, and the amount of gas emitted for 24 hours was measured, and the results are shown in Table 1 below. Experimental Example 2: Measuring the operating pressure of the gas induction unit The internal pressure at which gas emission begins was measured for each pouch-type secondary battery manufactured in the examples and comparative examples. Specifically, while injecting CO2 into the pouch-type secondary battery using pressure equipment from ITS Corporation and increasing the pressure inside the pouch by 0.1 atm units, the battery was left for 24 hours at each pressure, and the pressure at the point where the permeation part of the gas induction part was completely deformed (when the interface between the lead film of the permeation part and the gas induction part was both opened) was measured, and the results are shown in Table 1 below. Experimental Example 3: Film Deformation and Electrolyte Seepage For each pouch-type secondary battery manufactured in Examples and Comparative Examples, a penetrant (mega check, MAGNAFLUX) was included in the electrolyte at 0.1 wt%, CO2 (dry ice) was injected into the pouch-type secondary battery to increase the pressure inside the pouch to 2.0 atm, and then it was checked at 60°C for 5 days whether deformation of the lead film occurred at the edge of the gas induction part and whether the electrolyte was seeped through. Experimental Example 4: Measurement of Sealing Strength For each pouch-type secondary battery manufactured in Examples and Comparative Examples, the sealing portion was cut at 15 mm intervals, the electrode lead was attached to the lower jig of the UTM, and the outer material was attached to the upper jig. Then, the low-speed sealing strength was calculated by calculating the average value in the 8 mm section from the point exceeding 4.5 kgf / 15 mm among the sealing strength graphs measured by pulling in a 180° direction at a speed of 5 mm / min at room temperature. Gas discharge rate (cc / day)Operating pressure (atm)Film deformation and electrolyte penetrationSealing strength (kgf / 15mm)Example 12.31.5X14.67Example 22.01.5X15.27Comparative example 13.41.5O15.38Comparative example 21.22.0X- According to Table 1 above, in the case of Examples 1 and 2, when a film with an appropriate thickness and an appropriate high-temperature tensile strength was applied as a reinforcing film, it was confirmed that gas discharge started at an early point in time while the discharge speed was at a satisfactory level, and there was no problem with the sealing strength. On the other hand, in the case of Comparative Example 1 where the reinforcing film was not applied, the discharge speed was fast, but the film was deformed and the electrolyte seepage phenomenon was observed, confirming that commercialization was difficult. In addition, when a thick film was applied as in Comparative Example 2, the start of gas discharge was late and the speed was slow, indicating a problem with the discharge performance. Through this, it was confirmed that when applying a reinforcing film, applying a single-layer structure can exhibit excellent performance in terms of gas discharge performance and film deformation. [Explanation of symbols] 100: Pouch-type secondary battery 110: Exterior material 120: Case 1 122: Cup 124: Reception area 130: Case 2 132: Cup 140: Bridge section 150: Terrace 151: Sealing part 160: Electrode assembly 170: Electrode tab 172: Positive tab 174: Negative tab 180: Electrode lead 182: Positive lead 184: Negative lead 190: Lead Film 200: Gas induction unit 210: Adhesive resin layer 220: Permeable resin layer 230: Transmission section 240: Gas Euro 250: Gas discharge path 300: Reinforcement film 301: Insert

Claims

1. Electrode assembly; An outer material including a receiving portion for receiving the electrode assembly and a terrace portion formed along the periphery of the receiving portion, the terrace portion having a sealing portion with a portion of the width thereof sealed; An electrode lead electrically connected to the electrode assembly and protruding outward from the outer surface of the outer material; A lead film disposed between the electrode lead and the outer material; A gas induction unit disposed between the electrode lead and the lead film, including a permeable portion provided on the outside of the sealing portion, and at least one gas path extending from the permeable portion toward the electrode assembly through the sealing portion; and A reinforcing film disposed on the lead film so as to cover at least a portion of the above-mentioned transmission portion; The above reinforcing film is a pouch-type secondary battery having a single-layer structure.

2. In paragraph 1, The above secondary battery, A pouch-type secondary battery, wherein the interface between the lead film and the gas induction film is opened along the gas path by an increase in internal pressure of the outer material, thereby providing a gas discharge path.

3. In paragraph 1, The above reinforcing film, A pouch-type secondary battery arranged on a lead film so that the entire above-mentioned transmission portion is covered.

4. In paragraph 1, The above reinforcing film Including an insertion portion occupying a portion of the width of the above sealing portion, A pouch-type secondary battery, wherein the above insertion portion is a region in which one end of the reinforcing film extends inwardly toward the outer material and is inserted between the outer material of the sealing portion and the lead film.

5. In paragraph 1, Including an insertion portion occupying a portion of the width of the above sealing portion, The above insertion portion is an area where one end of the reinforcing film extends inwardly toward the outer material and is inserted between the outer material of the sealing portion and the lead film. A pouch-type secondary battery, wherein the ratio of the length of the insertion portion to the width of the sealing portion is 0.05 to 0.

90.

6. In paragraph 1, The above reinforcing film, A pouch-type secondary battery having a thickness of 60 ㎛ to 150 ㎛.

7. In paragraph 1, The above reinforcing film A pouch-type secondary battery comprising a resin having a melting temperature (Tm) of 110°C to 170°C.

8. In paragraph 1, The above reinforcing film A pouch-type secondary battery having a tensile strength of 3.5 MPa to 5.5 MPa at 60°C.

9. In paragraph 1, The above reinforcing film A pouch-type secondary battery comprising a modified polyolefin resin.

10. In paragraph 1, The above reinforcing film, Contains modified polyolefin resin, A pouch-type secondary battery, wherein the modified polyolefin resin comprises at least one selected from acid-modified polypropylene and acid-modified polyethylene.

11. In paragraph 1, The above gas induction unit, A pouch-type secondary battery comprising an adhesive resin layer in contact with an electrode lead and a permeable resin layer in contact with a lead film.

12. In paragraph 11, The above adhesive resin layer, A pouch-type secondary battery, wherein one end protruding outwardly from the outer surface of the outer material protrudes further than one end of the permeable resin layer protruding outwardly from the outer surface of the outer material.

13. In paragraph 11, The above lead film, A pouch-type secondary battery, wherein one end protruding outwardly from the outer surface of the outer material protrudes further than one end of the permeable resin layer protruding outwardly from the outer surface of the outer material.

14. A plurality of pouch-type secondary batteries; and a packaging for accommodating the secondary batteries, The above pouch-type secondary battery, electrode assembly; An outer material including a receiving portion for receiving the electrode assembly and a terrace portion formed along the periphery of the receiving portion, the terrace portion having a sealing portion with a portion of the width thereof sealed; An electrode lead electrically connected to the electrode assembly and protruding outward from the outer surface of the outer material; A lead film disposed between the electrode lead and the outer material; A gas induction unit disposed between the electrode lead and the lead film, including a permeable portion provided on the outside of the sealing portion, and at least one gas path extending from the permeable portion toward the electrode assembly through the sealing portion; and A reinforcing film disposed on the lead film so as to cover at least a portion of the above-mentioned transmission portion; The above reinforcing film is a battery pack having a single-layer structure.

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