Pouch film laminate and secondary battery

Abstract

The pouch film laminate according to the present invention comprises a base layer, a gas barrier layer, and a sealant layer laminated in this order, wherein the gas barrier layer comprises stainless steel and has a thickness of 50 μm or more, and the thickness of the base layer is 10% to 30% of the thickness of the gas barrier layer.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0182365, filed December 22, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a pouch film laminate and a secondary battery produced by molding the same. [Background technology]

[0003] Generally, types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, lithium-ion polymer batteries, etc. These secondary batteries are used not only in small products such as digital cameras, P-DVDs, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, but also in large products requiring high output such as electric vehicles and hybrid vehicles, as well as in power storage devices and backup power storage devices that store surplus generated power and new renewable energy.

[0004] To manufacture such a secondary battery, first, an electrode active material slurry is applied to a positive electrode current collector and a negative electrode current collector to form a positive electrode and a negative electrode, which are then stacked on both sides of a separator to form an electrode assembly of a predetermined shape.The electrode assembly is then placed in a battery case, an electrolyte is injected, and the battery case is sealed.

[0005] Secondary batteries are divided into pouch types and can types depending on the material of the case that houses the electrode assembly. Pouch types house the electrode assembly in a pouch made of flexible polymer material, while can types house the electrode assembly in a case made of metal or plastic.

[0006] The pouch, which is the case of a pouch-type secondary battery, is manufactured by pressing a flexible pouch film laminate to form a cup portion. Once the cup portion is formed, an electrode assembly is placed in the receiving space of the cup portion, and the seal portion is sealed to manufacture a secondary battery.

[0007] Generally, a pouch film laminate is formed of multiple layers, with a substrate layer laminated on one side of a metal gas barrier layer and a sealant layer laminated on the other side. Aluminum pouches, which use aluminum for the gas barrier layer, have the advantages of ensuring a certain level of mechanical strength, light weight, and heat dissipation, as well as complementing the electrochemical properties of the electrode assembly and electrolyte. However, aluminum pouches can melt or deform when the internal pressure and temperature of the cell increase due to a fire or other cause. Therefore, technologies have been developed to prevent deformation due to high temperatures and pressures by using stainless steel instead of aluminum for the gas barrier layer. However, using stainless steel for the metal barrier layer can reduce pouch formability. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a pouch film laminate and a pouch-type secondary battery that can ensure the insulation properties of a pouch containing stainless steel and improve formability. [Means for solving the problem]

[0009] According to one embodiment of the present invention, there is provided a pouch film laminate comprising a base layer, a gas barrier layer, and a sealant layer laminated in this order, wherein the gas barrier layer comprises stainless steel, the thickness of the gas barrier layer is 50 μm or more, and the thickness of the base layer is 10% to 30% of the thickness of the gas barrier layer.

[0010] The thickness of the pouch film laminate according to the present invention can be 200 μm or less.

[0011] According to the present invention, the thickness of the base layer can be 2.5% to 6.5% of the thickness of the pouch film laminate. Specifically, the thickness of the base layer can be 5 μm to 20 μm. The base layer can also contain polyethylene terephthalate (PET).

[0012] According to the present invention, the thickness of the gas barrier layer can be 50 μm to 100 μm, and the melting point of the gas barrier layer can be 1000° C. or higher.

[0013] The stainless steel contained in the gas barrier layer may contain 10% to 20% by weight of chromium and 5% to 20% by weight of nickel.

[0014] According to another embodiment of the present invention, there is provided a pouch-type secondary battery comprising a pouch-type battery case in which an electrode assembly is housed, the pouch-type battery case comprising a pouch film laminate, the pouch film laminate comprising a substrate layer, a gas barrier layer, and a sealant layer laminated in that order, the gas barrier layer comprising stainless steel, the thickness of the gas barrier layer being 50 μm or more, and the thickness of the substrate layer being 10% to 30% of the thickness of the gas barrier layer. [Effects of the Invention]

[0015] The pouch film laminate according to the present invention is characterized in that the thickness of the stainless steel-containing gas barrier layer is 50 μm or more, and the thickness of the substrate layer is 10% to 30% of the thickness of the gas barrier layer. When these conditions are met, the pouch film laminate ensures insulation and chemical resistance, and the formability of the pouch film laminate is significantly improved, thereby ensuring the forming depth of the pouch. As a result, it is easy to realize large-area pouch batteries for use in electric vehicles using the pouch film laminate according to the present invention. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view of a pouch film laminate according to the present invention. [Figure 2] 1 is an exploded view of a pouch-type secondary battery according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0017] The advantages and features of the present invention, as well as methods for achieving them, will become clearer with reference to the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and can be embodied in various different forms. However, the present embodiments are provided to fully disclose the present invention and fully convey the scope of the invention to those skilled in the art. The present invention is defined only by the claims. The same reference symbols refer to the same elements throughout the specification.

[0018] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in the sense that can be commonly understood by a person having ordinary skill in the art to which the present invention belongs. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless they are clearly and specifically defined.

[0019] The terms used in this specification are for the purpose of describing embodiments and are not intended to limit the present invention. In this specification, the singular includes the plural unless otherwise stated in the text. The words "comprises" and / or "comprising" used in this specification do not exclude the presence or addition of one or more other elements in addition to the elements mentioned.

[0020] In this specification, when a part is said to include a certain component, this does not mean that it excludes other components, but that it may further include other components, unless otherwise specified to the contrary.

[0021] In this specification, the phrase "A and / or B" means A, or B, or A and B.

[0022] In this specification, "%" means % by weight unless expressly indicated otherwise.

[0023] Pouch film laminate The pouch film laminate according to the present invention comprises a base layer, a gas barrier layer, and a sealant layer laminated in this order, the gas barrier layer comprising stainless steel and having a thickness of 50 μm or more, and the thickness of the base layer being 10% to 30% of the thickness of the gas barrier layer.

[0024] Fig. 1 is a cross-sectional view of a pouch film laminate 100 according to the present invention. As shown in Fig. 1, the pouch film laminate 100 may include a substrate layer 110, a gas barrier layer 120, and a sealant layer 130 laminated in this order.

[0025] According to the present invention, the thickness of the base material layer 110 is 10% to 30% of the thickness of the gas barrier layer 120, specifically 10% to 20%, and more specifically 10% to 15%. If the thickness of the base material layer 110 is less than 10% of the thickness of the gas barrier layer 120, there is a problem that the chemical resistance and insulating properties of the pouch are reduced. If the thickness of the base material layer 110 is more than 30% of the thickness of the gas barrier layer 120, the overall thickness of the pouch becomes thick, which may reduce the energy density per volume of the secondary battery.

[0026] When the thickness of the base layer 110 is 10% to 30% of the thickness of the gas barrier layer 120, the formability of the pouch film laminate 100 can be more affected by the thickness of the gas barrier layer 120 than by the thickness of the base layer 110. Therefore, in the present invention, by setting the thickness of the gas barrier layer 120 to 50 μm or more, the formability of the pouch film laminate 100 including the thin base layer 110 can be ensured.

[0027] The thickness of the pouch film laminate 100 can be 200 μm or less, specifically 100 μm to 200 μm, more specifically 100 μm to 180 μm. When the thickness of the pouch film laminate satisfies the above range, the pouch cup portion can be easily formed, and sufficient mechanical strength to withstand the internal pressure of the pouch can be ensured.

[0028] Hereinafter, each component of the pouch film laminate of the present invention will be described in more detail.

[0029] (1) Base material layer The substrate layer 110 is formed as the outermost layer of the pouch film laminate 100 to protect the secondary battery from external friction and impact. The substrate layer 110 is made of a polymer and can electrically insulate the electrode assembly from the outside.

[0030] The substrate layer 110 may have a single layer structure made of any one material, or alternatively, the substrate layer 110 may have a composite layer structure made of two or more materials.

[0031] Specifically, the substrate layer 110 according to the present invention may include a first layer, a second layer, and / or an adhesive layer. Here, the thickness of the substrate layer 110 refers to the total thickness of the first layer, the second layer, and / or the adhesive layer. The first layer may be disposed as the outermost layer of the pouch film laminate, and the second layer may be disposed between the first layer and the gas barrier layer. The adhesive layer may be disposed between the first layer and the second layer, or between the second layer and the gas barrier layer. The first layer, the second layer, and the adhesive layer may be made of materials with different materials and / or physical properties. An interface may exist between the first layer, the second layer, and the adhesive layer. This means that the first layer, the second layer, and the adhesive layer are different layers and may be formed separately. Alternatively, the substrate layer 110 may include only the adhesive layer without the first layer and the second layer. In this case, the adhesive layer may be disposed as the outermost layer of the pouch film laminate.

[0032] The first layer may be the outermost layer of the pouch film laminate. In this case, the first layer may serve to prevent moisture penetration from the outside of the pouch. The first 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 first layer may include at least one polyester film, such as polyethylene terephthalate or polybutylene terephthalate, which has abrasion resistance and heat resistance. More preferably, the first layer includes polyethylene terephthalate (PET), which has excellent external insulation properties, flexibility, and is easy to manufacture at a thin thickness.

[0033] As described above, the second layer may be a layer disposed between the first layer and the gas barrier layer 120. In this case, the second layer may serve to improve the formability of the pouch. The second layer may include at least one polyamide film such as, but not limited to, nylon 6, nylon 6,6, nylon MXD6, and nylon 4,10. Preferably, the second layer may include nylon 6, which has the advantage of improving the formability of the pouch due to the excellent stretchability of nylon 6.

[0034] The thickness of the base layer 110 may be 2.5% to 6.5%, specifically 3.0% to 6.5%, and more specifically 3.0% to 6.0% of the thickness of the pouch film laminate 100. When the ratio of the thickness of the base layer 110 to the thickness of the pouch film laminate 100 satisfies the above numerical range, the external insulation and chemical resistance of the pouch are ensured, and the overall thickness of the pouch is not large, resulting in excellent energy density per volume of the secondary battery.

[0035] The thickness of the base layer 110 can be 5 μm to 30 μm, specifically 5 μm to 25 μm, and more specifically 5 μm to 20 μm. When the thickness of the base layer 110 satisfies this range, the overall thickness of the pouch is not large, the secondary battery has excellent energy density relative to its volume, and the pouch's external insulation properties and chemical resistance can be ensured.

[0036] (2) Gas barrier layer The gas barrier layer 120 is laminated between the base layer 110 and the sealant layer 130 to ensure the mechanical strength of the pouch, block the entry and exit of gases or moisture outside the secondary battery, and prevent electrolyte leakage from inside the pouch-type battery case.

[0037] The gas barrier layer 120 according to the present invention includes stainless steel. Specifically, the gas barrier layer 120 may be manufactured by molding and / or processing a stainless steel thin film. The gas barrier layer 120 including stainless steel has relatively low thermal conductivity, which is effective in preventing or delaying heat diffusion to other cells during thermal runaway. It also has relatively high toughness, which can prevent cracks from occurring in the pouch during use of the pouch battery.

[0038] The stainless steel may contain at least one selected from the group consisting of copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), zinc (Zn), molybdenum (Mo), carbon (C), phosphorus (P), sulfur (S), and nitrogen (N) other than iron (Fe).

[0039] Specifically, the stainless steel may contain 10 to 20% by weight of chromium, more specifically 16 to 20% by weight, and more specifically 18 to 20% by weight. When the above numerical range is satisfied, the stainless steel has the effect of having excellent corrosion resistance.

[0040] Furthermore, the stainless steel may contain 5 to 20% by weight of nickel, specifically 6 to 15% by weight, and more specifically 8 to 14% by weight. When the content of nickel is within this range, the corrosion resistance of the stainless steel in neutral and weakly acidic environments is further improved.

[0041] The thickness of the gas barrier layer 120 according to the present invention is 50 μm or more, specifically, 50 μm to 100 μm, and more specifically, 60 μm to 85 μm. If the thickness of the gas barrier layer 120 is less than 50 μm, the gas barrier layer 120 will not be uniformly stretched, resulting in a low elongation rate of the pouch film laminate, poor pouch formability, and an insufficient processing depth for the pouch cup portion. As a result, it is difficult to realize a large-area pouch-type battery suitable for electric vehicles. Furthermore, if the thickness of the gas barrier layer 120 is less than 50 μm, the gas barrier properties of the gas barrier layer 120 will be reduced.

[0042] The melting point of the gas barrier layer 120 can be 1000° C. or higher, specifically 1200° C. to 1500° C., and more specifically 1300° C. to 1450° C. When the melting point of the gas barrier layer 120 is within the above range, structural collapse of the pouch can be prevented even when the temperature of the pouch cell rises suddenly due to thermal runaway.

[0043] (3) Sealant layer The sealant layer 130 is intended to completely seal the interior of the pouch-type battery case by being thermally bonded to each other at the seal portion when the pouch-type battery case accommodating the electrode assembly inside is sealed. To this end, the sealant layer 130 may be made of a material having excellent thermal adhesive strength.

[0044] The sealant layer 130 may be formed of a material having insulating properties, corrosion resistance, and sealing properties. Specifically, since the sealant layer 130 is in direct contact with the electrode assembly and / or electrolyte inside the pouch-type battery case, it may be formed of a material having insulating properties and corrosion resistance. Furthermore, since the sealant layer 130 must completely seal the interior of the pouch-type battery case and prevent the transfer of materials between the inside and outside, it may be formed of a material having high sealing properties (e.g., excellent thermal adhesive strength). To ensure such insulating properties, corrosion resistance, and sealing properties, the sealant layer 130 may be formed of a polymer material.

[0045] The sealant layer 130 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, and is preferably made of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be cast polypropylene (CPP), acid-modified polypropylene (PPa), polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer.

[0046] The thickness of the sealant layer 130 can be 30 μm to 130 μm, specifically 50 μm to 120 μm, and more specifically 70 μm to 100 μm. When the thickness of the sealant layer satisfies the above range, it is possible to ensure the seal strength of the sealed portion and the formability of the pouch film laminate.

[0047] Meanwhile, the sealant layer 130 according to the present invention may have a single film structure made of any one material. Alternatively, the sealant layer 130 may have a composite film structure formed by layers of two or more materials. Specifically, the sealant layer 130 may include a first sealant layer and a second sealant layer. In this case, the first sealant layer may be a layer disposed adjacent to the gas barrier layer, and the second sealant layer may be a layer disposed on the first sealant layer. The first sealant layer and the second sealant layer may be made of materials having different materials and / or physical properties. An interface may exist between the first sealant layer and the second sealant layer. This means that the first sealant layer and the second sealant layer are different layers and may be formed separately.

[0048] In order to ensure long-term adhesion between the gas barrier layer and the first sealant layer, it is particularly preferable that the first sealant layer is made of acid-modified polypropylene (PPa), which may be maleic anhydride polypropylene (MAH PP).

[0049] The second sealant layer may be formed of a material having insulating, corrosion-resistant, and sealing properties. Specifically, since the second sealant layer is in direct contact with the electrode assembly (260 in FIG. 2) and / or the electrolyte inside the accommodating space (224 in FIG. 2), it may be formed of a material having insulating and corrosion-resistant properties. Furthermore, since the second sealant layer must completely seal the interior of the battery case and prevent the transfer of materials between the interior and exterior, it may be formed of a material having high sealing properties. To ensure such insulating, corrosion-resistant, and sealing properties, the second sealant layer may be formed 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 second sealant layer may be formed of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be composed of unstretched polypropylene, acid-modified polypropylene, polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer. Here, the acid-modified polypropylene may be maleic anhydride polypropylene (MAH PP). More preferably, the second sealant layer may include cast polypropylene (CPP), which has heat sealability and high tensile strength.

[0050] Pouch-type secondary battery Next, the pouch-type secondary battery according to the present invention will be described.

[0051] The pouch-type secondary battery according to the present invention includes a pouch-type battery case in which an electrode assembly is housed, the pouch-type battery case including a pouch film laminate, the pouch film laminate including a substrate layer, a gas barrier layer, and a sealant layer laminated in this order, the gas barrier layer including stainless steel and having a thickness of 50 μm or more, and the thickness of the substrate layer being 10% to 30% of the thickness of the gas barrier layer.

[0052] Hereinafter, each component of the pouch-type secondary battery of the present invention will be described in more detail with reference to Fig. 2. Fig. 2 is an exploded view of a pouch-type secondary battery 200 according to the present invention. As shown in Fig. 2, the pouch-type secondary battery 200 of the present invention may include a pouch-type battery case 210, an electrode assembly 260, an electrode lead 280, an insulating part 290, and an electrolyte (not shown).

[0053] (1) Pouch-type battery case The pouch-type battery case 210 can house the electrode assembly 260 inside. The pouch-type battery case 210 can be manufactured by molding the pouch film laminate of the present invention described above. The detailed structure and physical properties of the pouch film laminate are as described above, and a detailed description thereof will be omitted.

[0054] The pouch film laminate may be drawn and stretched using a punch or the like to manufacture the pouch-type battery case 210. As a result, the pouch-type battery case 210 may include a cup portion 222 and a receiving portion 224. The receiving portion 224 is a portion that receives the electrode assembly, and may refer to a bag-shaped receiving space formed inside the cup portion 222 when the cup portion 222 is formed.

[0055] According to one embodiment of the present invention, the pouch-type battery case 210 may include a first case 220 and a second case 230, as shown in Fig. 2. The first case 220 includes a receiving portion 224 that can receive the electrode assembly 260, and the second case 230 may cover the receiving portion 224 from above to prevent the electrode assembly 260 from falling out of the battery case 210. The first case 220 and the second case 230 may be manufactured with one side connected to each other as shown in Fig. 2, but are not limited to this and may be manufactured in various ways, such as being separately manufactured.

[0056] According to another embodiment of the present invention, when forming cup portions in a pouch film laminate, two symmetrical cup portions 222, 232 may be formed adjacent to each other by drawing one pouch film laminate. In this case, as shown in FIG. 2, the first case 220 and the second case 230 may have the cup portions 222, 232, respectively. After the electrode assembly 260 is accommodated in the accommodating portion 224 of the cup portion 222 of the first case 220, the bridge portion 240 formed between the two cup portions 222, 232 may be folded so that the two cup portions 222, 232 face each other. In this case, the cup portion 232 of the second case 230 may accommodate the electrode assembly 260 from above. Therefore, since two cup portions 222, 232 accommodate one electrode assembly 260, an electrode assembly 260 that is thicker than when there is only one cup portion 222 can be accommodated. In addition, folding the pouch-type battery case 210 forms one corner of the secondary battery 200, which reduces the number of corners to be sealed during the subsequent sealing process, thereby improving the processing speed of the pouch-type secondary battery 200 and reducing the number of sealing processes.

[0057] The pouch-type battery case 210 may be sealed with the electrode assembly 260 housed therein so that a portion of the electrode lead 280, i.e., a terminal portion, described below, is exposed. Specifically, after the electrode lead 280 is connected to the electrode tab 270 of the electrode assembly 260 and an insulating portion 290 is formed on a portion of the electrode lead 280, the electrode assembly 260 may be housed in the housing portion 224 provided in the cup portion 222 of the first case 220, and the second case 230 may cover the housing portion 224 from above. Next, an electrolyte may be injected into the housing portion 224, and the sealing portion 250 formed on the periphery of the first case 220 and the second case 230 may be sealed.

[0058] The sealing portion 250 may serve to seal the receiving portion 224. Specifically, the sealing portion 250 may be formed along the periphery of the receiving portion 224 to seal the receiving portion 224. The temperature at which the sealing portion 250 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 is within this range, the pouch-type battery case 210 can ensure sufficient seal strength through thermal bonding.

[0059] According to the present invention, when the sealant layers of the first case 220 and the second case 230 are laminated and abutted against each other and then sealed for 1.6 seconds under conditions of 210°C and 1.2 MPa, the thickness of the sealant layer of the seal portion 250 formed in the pouch-type battery case 210 can be 54% to 86%, specifically 55% to 85%, and more specifically 60% to 85%, of the thickness of the sealant layer of the pouch film laminate. When the thickness of the sealant layer of the seal portion 250 satisfies this numerical range relative to the thickness of the sealant layer of the pouch film laminate, sufficient sealing strength can be ensured and insulating properties can be maintained.

[0060] (2) Electrode assembly The electrode assembly 260 can be inserted into the pouch-type battery case 210 and sealed by the pouch-type battery case 210 after the electrolyte is injected.

[0061] The electrode assembly 260 may be formed by sequentially stacking a positive electrode, a separator, and a negative electrode. Specifically, the electrode assembly 260 may include two electrodes, a positive electrode and a negative electrode, and a separator interposed between the electrodes to insulate the electrodes from each other.

[0062] 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. The slurry may be formed by stirring a granular active material, auxiliary conductor, binder, conductive material, etc., in a solvent. The solvent may be removed in a subsequent process.

[0063] A slurry containing a mixture of 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, which are then stacked on both sides of a separator to manufacture a predetermined shape of the electrode assembly 260. The electrode assembly 260 may be categorized into a stack type, a jelly roll type, a stack and folding type, etc., but is not limited thereto.

[0064] The electrode assembly 260 may include an electrode tab 270 .

[0065] The electrode tabs 270 are connected to the positive and negative electrodes of the electrode assembly 260, respectively, and protrude from the electrode assembly 260 to serve as paths for electrons to move between the inside and outside of the electrode assembly 260. The electrode current collector included in the electrode assembly 260 may be composed of a portion coated with an electrode active material and an end portion, i.e., a plain portion, where the electrode active material is not coated. The electrode tabs 270 may be formed by cutting the plain portion or by connecting a separate conductive member to the plain portion by ultrasonic welding, for example. As shown in FIG. 2, the electrode tabs 270 may protrude in different directions from the electrode assembly 260, but are not limited thereto. They may protrude in various directions, such as protruding in parallel from one side in the same direction.

[0066] (3) Electrode lead The electrode lead 280 may supply electricity to the outside of the secondary battery 200. The electrode lead 280 may be connected to the electrode tab 270 of the electrode assembly 260 by spot welding or the like.

[0067] The electrode lead 280 may be connected to the electrode assembly 260 and may protrude to the outside of the pouch-type battery case 210 through the sealing portion 250. Specifically, one end of the electrode lead 280 may be connected to the electrode assembly 260, particularly the electrode tab 270, and the other end of the electrode lead 280 may protrude to the outside of the pouch-type battery case 210.

[0068] The electrode lead 280 may include a positive electrode lead 282 having one end connected to the positive electrode tab 272 and extending in the direction in which the positive electrode tab 272 protrudes, and a negative electrode lead 284 having one end connected to the negative electrode tab 274 and extending in the direction in which the negative electrode tab 274 protrudes. The other ends of the positive electrode lead 282 and the negative electrode lead 284 may protrude to the outside of the battery case 210. This allows electricity generated inside the electrode assembly 260 to be supplied to the outside. In addition, since the positive electrode tab 272 and the negative electrode tab 274 protrude in different directions, the positive electrode lead 282 and the negative electrode lead 284 may also extend in different directions. The positive electrode lead 282 and the negative electrode lead 284 may be made of different materials. That is, the positive electrode lead 282 may be made of the same aluminum (Al) material as the positive electrode current collector, and the negative electrode lead 284 may be made of the same copper (Cu) material as the negative electrode current collector or a copper material coated with nickel (Ni). A portion of the electrode lead 280 protruding outside the battery case 210 serves as a terminal portion and may be electrically connected to an external terminal.

[0069] (4) Insulation section The insulating portion 290 prevents electricity generated from the electrode assembly 260 from flowing to the battery case 210 via the electrode lead 280, thereby maintaining the seal of the battery case 210. To this end, the insulating portion 290 may be formed of an insulator having low electrical conductivity. Generally, the insulating portion 290 is formed of a relatively thin insulating tape or film that is easily attached to the electrode lead 280, but is not limited thereto, and any material that can insulate the electrode lead 280 may be used.

[0070] The insulating part 290 may be disposed to surround the outer circumferential surface of the electrode lead 280. Specifically, at least a portion of the electrode lead 280 may be surrounded by the insulating part 290. In this case, the insulating part 290 may be disposed between the electrode lead 280 and the pouch-type battery case 210. The insulating part 290 may be located only in the seal part 250 where the first case 220 and the second case 230 of the pouch-type battery case 210 are heat-sealed, and may bond the electrode lead 280 to the battery case 210.

[0071] (5) Electrolyte The pouch-type secondary battery 200 according to the present invention may further include an electrolyte (not shown) injected into the pouch-type battery case 210. The electrolyte is used to move lithium ions generated by an electrochemical reaction of the electrodes during charging / discharging of the secondary battery 200, and may include a non-aqueous organic electrolyte solution 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 sulfide-based, oxide-based, or polymer-based solid electrolyte, and such a solid electrolyte may have flexibility that makes it easily deformable under external force.

[0072] The present invention will be described in more detail below with reference to specific examples. However, the following examples are merely illustrative and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope and technical concept of the present description, and it goes without saying that such changes and modifications are within the scope of the appended claims.

[0073] Examples and Comparative Examples Example 1: Manufacturing of a pouch film laminate A first adhesive film measuring 266 mm wide, 50 mm long, and 3 μm thick, and a polyethylene terephthalate (PET) film measuring 266 mm wide, 50 mm long, and 6 μm thick were laminated in this order on one side of a stainless steel thin film measuring 266 mm wide, 50 mm long, and 80 μm thick. A polypropylene (PP) film measuring 266 mm wide, 50 mm long, and 80 μm thick was laminated on the other side of the stainless steel thin film. As a result, a pouch film laminate was produced with a structure in which polypropylene film / stainless steel thin film / first adhesive film / polyethylene terephthalate film were laminated in this order.

[0074] Here, the polypropylene film is a sealant layer, the stainless steel thin film is a gas barrier layer, and the first adhesive film and the polyethylene terephthalate film are base layers.

[0075] Example 2: Manufacturing of a pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that a stainless steel thin film having a thickness of 60 μm was used.

[0076] Example 3: Preparation of a pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that a stainless steel thin film having a thickness of 50 μm was used.

[0077] Comparative Example 1: Production of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that a first adhesive film measuring 266 mm wide, 50 m long, and 3 μm thick, a nylon film measuring 266 mm wide, 50 m long, and 25 μm thick, a second adhesive film measuring 266 mm wide, 50 m long, and 3 μm thick, and a polyethylene terephthalate (PET) film measuring 266 mm wide, 50 m long, and 25 μm thick were laminated in this order on one side of a stainless steel thin film measuring 266 mm wide, 50 m long, and 80 μm thick.

[0078] Here, the polypropylene film is a sealant layer, the stainless steel thin film is a gas barrier layer, and the first adhesive film, nylon film, second adhesive film and polyethylene terephthalate film are base layers.

[0079] Comparative Example 2: Production of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that only a first adhesive film having a thickness of 3 μm and a thin stainless steel film having a thickness of 60 μm were used as the base layer.

[0080] Comparative Example 3: Production of pouch film laminate A pouch film laminate was produced in the same manner as in Example 1, except that a stainless steel thin film having a thickness of 45 μm was used.

[0081] Experimental Example 1: Evaluation of processing depth and formability of pouch film laminate The forming depth was measured for each of the pouch film laminates produced in Examples 1 to 3 and Comparative Examples 1 to 3. Specifically, the pouch film laminate was cut to a size of 266 mm wide and 200 mm long, and then the cut pouch film laminate was processed and stretched using a pouch forming device manufactured by Gwangshin Hi-Tech Co., Ltd., to form a cup portion measuring 90 cm wide and 160 cm long until the pouch film laminate broke. The forming depth (unit: mm) of the cup portion was measured and is shown in Table 1 below.

[0082] Furthermore, the formation of a cup portion on the pouch film laminate was carried out a total of 10 times, and it was visually confirmed whether or not the pouch film laminate broke during the formation of the cup portion. The results are shown in Table 1 below.

[0083] -Good: No breakage of the pouch film laminate occurred after 10 measurements - Poor: Breakage of the pouch film laminate occurs at least once during 10 measurements.

[0084] Experimental Example 2: Evaluation of the insulation properties of pouch film laminates The pouch film laminates produced in Examples 1-3 and Comparative Examples 1-3 were each cut to a size of 90 mm x 150 mm and stored in a vacuum oven at 60°C for 24 hours. The breakdown voltage was then measured in a dry room using a breakdown voltage measurement device manufactured by HIOKI Corporation. Specifically, 5µm-thick aluminum thin films were placed on the top and bottom of the pouch film laminate, and the positive electrode of the measurement device was connected to the gas barrier layer of the pouch film laminate, and the negative electrode of the measurement device was connected to the aluminum thin film in contact with the base layer. A voltage was then applied at a rate of 100 V / s. The applied voltage at which the measured leakage current was 0.5 mA or greater was measured as the breakdown voltage, and the insulation properties were evaluated according to the following criteria.

[0085] -Good: Breakdown voltage is 1000V or more -Fail: Breakdown voltage is less than 1000V

[0086] [Table 1]

[0087] According to Table 1, in Examples 1 to 3 in which the thickness of the gas barrier layer containing stainless steel is 50 μm or more and the thickness of the base layer is 10% to 30% of the thickness of the gas barrier layer, it can be confirmed that the processing depth of the cup portion is even greater than in Comparative Examples 2 and 3, the pouch formability is excellent, and the insulation property is better than in Comparative Example 2.

[0088] On the other hand, Comparative Example 1 has similar moldability to the Examples, but the thickness of the pouch film laminate exceeds 200 μm, resulting in a decrease in cell energy density, and the base layer has a four-layer structure, which increases the manufacturing process cost. Comparative Example 2 has inferior moldability compared to Examples 1 to 3, and the base layer is thin, meaning that the insulation properties of the pouch are not ensured. Comparative Example 3 has inferior moldability compared to Examples 1 to 3. [Explanation of symbols]

[0089] 100 Pouch film laminate 110 Base material layer 120 Gas barrier layer 130 Sealant Layer 200 Pouch-type secondary battery 210 Pouch-type case 220 Case 1 222 Cup section 224 Storage Unit 230 Case 2 232 Cup section 240 Bridge section 250 Seal part 260 Electrode assembly 270 Electrode Tab 272 Positive electrode tab 274 Negative electrode tab 280 Electrode Lead 282 Positive lead 284 Negative lead 290 Insulation

Claims

1. A pouch film laminate comprising a base layer, a gas barrier layer, and a sealant layer laminated in this order, The gas barrier layer includes stainless steel and has a thickness of 50 μm or more; A pouch film laminate, wherein the thickness of the base layer is 10% to 30% of the thickness of the gas barrier layer.

2. The pouch film laminate according to claim 1 , wherein the thickness of the pouch film laminate is 200 μm or less.

3. The pouch film laminate according to claim 1, wherein the thickness of the base layer is 2.5% to 6.5% of the thickness of the pouch film laminate.

4. The pouch film laminate according to claim 1, wherein the thickness of the base layer is 5 μm to 20 μm.

5. The pouch film laminate of claim 1 , wherein the substrate layer comprises polyethylene terephthalate (PET).

6. 2. The pouch film laminate according to claim 1, wherein the gas barrier layer has a thickness of 50 μm to 100 μm.

7. The pouch film laminate according to claim 1 , wherein the gas barrier layer has a melting point of 1000° C. or higher.

8. 2. The pouch film laminate according to claim 1, wherein the stainless steel contains 10% to 20% by weight of chromium.

9. 2. The pouch film laminate according to claim 1, wherein the stainless steel contains 5% to 20% by weight of nickel.

10. A pouch-type secondary battery including a pouch-type battery case in which an electrode assembly is housed, the pouch-type battery case includes a pouch film laminate; The pouch film laminate includes a base layer, a gas barrier layer, and a sealant layer laminated in this order, The gas barrier layer includes stainless steel and has a thickness of 50 μm or more; The pouch-type secondary battery, wherein the thickness of the substrate layer is 10% to 30% of the thickness of the gas barrier layer.

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