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, wherein the gas barrier layer comprises stainless steel and is disposed between the base layer and the sealant layer, and wherein the difference between the breaking energy of the gas barrier layer in the machine direction (MD) and the breaking energy of the gas barrier layer in the transverse direction (TD) is 2000 J or less.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0182363, 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, DVD players, MP3 players, mobile phones, PDAs, portable game devices, power tools, and electric bicycles, 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 from a laminate of polymer and metal thin film. Can types house the electrode assembly in a case made from materials such as 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 sealing 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 gas barrier layer made of a metal material 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, being lightweight, and providing support for the electrochemical properties of the electrode assembly and electrolyte, as well as heat dissipation. However, aluminum pouches can suffer from problems such as melting or deformation when the internal pressure and temperature of the cell increase due to a fire or other reasons.

[0008] To address these issues, a technology has been developed that uses high-strength materials, such as stainless steel, instead of aluminum for the gas barrier layer to prevent deformation due to high temperatures and pressures. However, pouch film laminates using high-strength materials as gas barrier layers have poor formability, which can lead to problems such as insufficient forming depth during cup formation, resulting in breakage of the pouch film laminate. If the pouch film laminate does not have sufficient forming depth, the number of electrode assemblies that can be housed inside is limited, making it difficult to improve cell energy density.

[0009] Therefore, there is a need to develop a pouch film that can be durable under high temperature and pressure conditions and has sufficient processing depth. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention provides a pouch film laminate and a pouch-type secondary battery that can improve the formability of high-strength pouches. [Means for solving the problem]

[0011] According to one embodiment of the present invention, a pouch film laminate may be provided, including a substrate layer, a gas barrier layer, and a sealant layer, which are laminated in this order. The gas barrier layer may include stainless steel. The difference in breaking energy according to the following formula 1 may be 2000 J or less. [Formula 1] Difference in breaking energy (J) = |Breaking energy of the gas barrier layer in the MD direction (J) - Breaking energy of the gas barrier layer in the TD direction (J)|

[0012] Next, according to one embodiment of the present invention, the breaking energy of the gas barrier layer in the MD direction may be 5000 J or more, and the breaking energy of the gas barrier layer in the TD direction may be 5000 J or more.

[0013] Next, according to one embodiment of the present invention, the difference in tensile elongation at break according to the following formula 2 may be 10% or less.

[0014] [Formula 2] Difference in tensile elongation at break (%) = |tensile elongation at break in the MD direction of the gas barrier layer (%) - tensile elongation at break in the TD direction of the gas barrier layer (%) |

[0015] Next, according to one embodiment of the present invention, the tensile elongation at break in the MD direction of the gas barrier layer may be 15% or more, and the tensile elongation at break in the TD direction of the gas barrier layer may be 15% or more.

[0016] Next, according to one embodiment of the present invention, the difference in tensile strength at break according to the following formula 3 may be 150 MPa or less.

[0017] [Formula 3] Difference in tensile breaking strength (MPa) = |tensile breaking strength in the MD direction of the gas barrier layer (MPa) - tensile breaking strength in the TD direction of the gas barrier layer (MPa)|

[0018] Next, according to one embodiment of the present invention, the gas barrier layer may have a tensile break strength of 400 MPa or more in the MD direction, and may have a tensile break strength of 400 MPa or more in the TD direction.

[0019] Next, according to one embodiment of the present invention, the thickness of the gas barrier layer may be 30 μm to 100 μm.

[0020] Next, according to one embodiment of the present invention, the percentage R of the thickness of the gas barrier layer relative to the thickness of the pouch film laminate calculated by the following formula 4: t can be between 10% and 50%.

[0021] [Formula 4] R t (%) = (gas barrier layer thickness / pouch film laminate thickness) x 100

[0022] Next, according to one embodiment of the present invention, the thickness of the pouch film laminate may be 80 μm to 300 μm.

[0023] According to another embodiment of the present invention, a pouch-type secondary battery may be provided, which includes a pouch-type battery case housing an electrode assembly, the pouch-type battery case including a pouch film laminate. The pouch film laminate may include a substrate layer, a gas barrier layer, and a sealant layer laminated in order. The gas barrier layer may include stainless steel. The difference in breaking energy according to Equation 1 may be 2000 J or less.

[0024] Meanwhile, according to yet another embodiment of the present invention, there is provided a pouch film laminate. The pouch film laminate includes a substrate layer, a gas barrier layer, and a sealant layer. The gas barrier layer may include stainless steel, and may be disposed between the substrate layer and the sealant layer. The difference between the breaking energy of the gas barrier layer in the machine direction (MD) and the breaking energy of the gas barrier layer in the transverse direction (TD) may be 2000 J or less. The MD direction may be parallel to the rolling direction during production of the gas barrier layer, and the TD direction may be perpendicular to the rolling direction during production of the gas barrier layer.

[0025] Next, according to yet another embodiment of the present invention, the gas barrier layer may have a breaking energy of 5000 J or more in the MD direction, and may have a breaking energy of 5000 J or more in the TD direction.

[0026] Next, according to yet another embodiment of the present invention, the difference between the tensile elongation at break in the MD direction of the gas barrier layer and the tensile elongation at break in the TD direction of the gas barrier layer may be 10% or less.

[0027] Next, according to yet another embodiment of the present invention, the tensile elongation at break in the MD of the gas barrier layer may be 15% or more of the original length of the gas barrier layer in the MD, and the tensile elongation at break in the TD of the gas barrier layer may be 15% or more of the original length of the gas barrier layer in the TD.

[0028] Next, according to yet another embodiment of the present invention, the difference between the tensile breaking strength in the MD direction of the gas barrier layer and the tensile breaking strength in the TD direction of the gas barrier layer may be 150 MPa or less.

[0029] Next, according to yet another embodiment of the present invention, the tensile break strength of the gas barrier layer in the MD direction may be 400 MPa or more, and the tensile break strength of the gas barrier layer in the TD direction may be 400 MPa or more.

[0030] Next, according to yet another embodiment of the present invention, the thickness of the gas barrier layer may be 10% to 50% of the thickness of the pouch film laminate.

[0031] Next, according to yet another embodiment of the present invention, the thickness of the gas barrier layer may be 30 μm to 100 μm.

[0032] Next, according to yet another embodiment of the present invention, the thickness of the pouch film laminate may be 80 μm to 300 μm.

[0033] Meanwhile, according to yet another embodiment of the present invention, there is provided a pouch-type secondary battery. The pouch-type secondary battery may include a pouch-type battery case in which an electrode assembly is housed. The pouch-type battery case may include a pouch film laminate. The pouch film laminate may include a substrate layer, a gas barrier layer, and a sealant layer. The gas barrier layer may include stainless steel. The gas barrier layer may be disposed between the substrate layer and the sealant layer. The difference between the breaking energy of the gas barrier layer in the machine direction (MD) and the transverse direction (TD) may be 2000 J or less. The MD direction may be parallel to the rolling direction during manufacturing of the gas barrier layer, and the transverse direction (TD) may be perpendicular to the rolling direction during manufacturing of the gas barrier layer.

[0034] Next, according to yet another embodiment of the present invention, the gas barrier layer may have a breaking energy of 5000 J or more in the MD direction, and may have a breaking energy of 5000 J or more in the TD direction.

[0035] Next, according to yet another embodiment of the present invention, the difference between the tensile elongation at break in the MD direction of the gas barrier layer and the tensile elongation at break in the TD direction of the gas barrier layer may be 10% or less.

[0036] Next, according to yet another embodiment of the present invention, the tensile elongation at break in the MD of the gas barrier layer may be 15% or more of the original length of the gas barrier layer in the MD, and the tensile elongation at break in the TD of the gas barrier layer may be 15% or more of the original length of the gas barrier layer in the TD.

[0037] Next, according to yet another embodiment of the present invention, the difference between the tensile breaking strength in the MD direction of the gas barrier layer and the tensile breaking strength in the TD direction of the gas barrier layer may be 150 MPa or less.

[0038] Next, according to yet another embodiment of the present invention, the tensile break strength of the gas barrier layer in the MD direction may be 400 MPa or more, and the tensile break strength of the gas barrier layer in the TD direction may be 400 MPa or more.

[0039] Next, according to yet another embodiment of the present invention, the thickness of the gas barrier layer may be 10% to 50% of the thickness of the pouch film laminate.

[0040] Next, according to yet another embodiment of the present invention, the thickness of the gas barrier layer may be 30 μm to 100 μm.

[0041] According to another embodiment of the present invention, there is provided a method for manufacturing a pouch-type secondary battery, the method including the steps of: providing a pouch film laminate including a substrate layer, a gas barrier layer, and a sealant layer, the gas barrier layer being disposed between the substrate layer and the sealant layer; measuring a first fracture energy of the gas barrier layer along a first direction of the gas barrier layer; measuring a second fracture energy of the gas barrier layer along a second direction perpendicular to the first direction of the gas barrier layer; determining a difference between the first fracture energy and the second fracture energy to be equal to or less than a predetermined critical value; and forming the pouch film laminate and housing an electrode assembly therein to manufacture a pouch-type secondary battery.

[0042] Next, according to yet another embodiment of the present invention, the preset critical value may be 2000 J or less.

[0043] Next, according to yet another embodiment of the present invention, the first direction may be the MD direction of the gas barrier layer, and the MD direction of the gas barrier layer may be parallel to the rolling direction during production of the gas barrier layer. [Effects of the Invention]

[0044] The pouch film laminate according to the present invention includes a gas barrier layer containing stainless steel, and is characterized in that the difference between the MD and TD breaking energies of the gas barrier layer is 2000 J or less. A pouch film laminate using a gas barrier layer that satisfies the above conditions has excellent durability at high temperatures and high pressures, and the formability of the pouch film laminate is significantly improved, ensuring sufficient forming depth. [Brief explanation of the drawings]

[0045] [Figure 1] 1 is a photographic image of a gas barrier layer for explaining the MD direction and TD direction of the gas barrier layer. [Figure 2] 1 is a cross-sectional view of a pouch film laminate according to the present invention. [Figure 3] 1 is an exploded view of a pouch-type secondary battery according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0046] 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 to fully convey the scope of the invention to those skilled in the art to which the present invention pertains. The present invention is defined only by the claims. The same reference symbols refer to the same elements throughout the specification.

[0047] 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 knowledge in the technical field 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.

[0048] 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 specifically 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.

[0049] In this specification, the phrase "A and / or B" means A, or B, or A and B.

[0050] In this specification, "%" means % by weight unless expressly indicated otherwise.

[0051] In this specification, the MD (Machine Direction) direction refers to the direction parallel to the rolling direction of the thin film for forming a gas barrier layer during production, and the TD (Transverse Direction) direction refers to the direction perpendicular to the rolling direction of the thin film for forming a gas barrier layer during production. For example, as shown in Figure 1, the MD and TD directions of the gas barrier layer can be visually confirmed by a pattern formed on the surface of the gas barrier layer. Figure 1 shows a veining pattern extending along the MD direction and perpendicular to the TD direction.

[0052] As used herein, the term "breaking energy" refers to the total energy required to break a test specimen when pulled in one direction (e.g., when the test specimen breaks and has two or more separated parts), and can correspond to the area of ​​a stress-strain curve. The breaking energy can be measured by cutting a test specimen to a width of 15 mm and a length of 100 mm, fastening both longitudinal ends of the test specimen to the upper and lower fixtures of a UTM (here, the distance between the end of the part fastened to the upper fixture and the end of the part fastened to the lower fixture can be 50 mm), and conducting a tensile test at room temperature (25°C) at a rate of 5 mm / min in a 180° direction.

[0053] In this specification, the tensile elongation at break refers to the percentage (%) of the length of a test specimen stretched in one direction to break relative to its initial length. The tensile elongation at break can be measured by cutting a test specimen to a width of 15 mm and a length of 100 mm, fastening both longitudinal ends of the test specimen to the upper and lower fixtures of a UTM (here, the distance between the end of the portion fastened to the upper fixture and the end of the portion fastened to the lower fixture can be 50 mm), and conducting a tensile test at room temperature (25°C) by pulling the specimen in a 180° direction at a rate of 5 mm / min.

[0054] In this specification, the tensile breaking strength refers to the value obtained by dividing the maximum load applied until a test specimen breaks when pulled in one direction by the cross-sectional area of ​​the test specimen before pulling. More specifically, the tensile breaking strength may be defined as the value obtained by dividing the maximum load applied until the test specimen breaks when a test specimen having a width of 15 mm and a length of 100 mm is prepared, both longitudinal ends of the test specimen are fastened to the upper and lower fixtures of a UTM (here, the distance between the end of the portion fastened to the upper fixture and the end of the portion fastened to the lower fixture may be 50 mm), and then pulled in a 180° direction at room temperature (25°C) at a rate of 5 mm / min, by the cross-sectional area of ​​the test specimen before pulling.

[0055] 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, wherein the gas barrier layer comprises stainless steel, and the difference in breaking energy according to the following formula 1 is 2000 J or less.

[0056] [Formula 1] Difference in breaking energy (J) = |Breaking energy of the gas barrier layer in the MD direction (J) - Breaking energy of the gas barrier layer in the TD direction (J)|

[0057] The present invention is characterized by solving the problem of reduced formability that has traditionally been a problem when using stainless steel, a high-strength material, as a component of a gas barrier layer by adjusting the difference in fracture energy between the MD and TD of the gas barrier layer to within a specific range. According to the present invention, even when stainless steel is used as a component of the gas barrier layer, the difference in fracture energy between the MD and TD is adjusted to a specific level or less, thereby preventing the problems of the pouch film breaking or pinholes occurring in the direction with a relatively low fracture energy. As a result, the pouch film laminate of the present invention has excellent durability and high formability, which allows for the storage of a large number of electrode assemblies, improves cell energy density, and enables the realization of a pouch-type secondary battery that is highly durable against high heat and high pressure.

[0058] Fig. 2 is a cross-sectional view of a pouch film laminate 100 according to the present invention. As shown in Fig. 2, the pouch film laminate 100 may have a substrate layer 110, a gas barrier layer 120, and a sealant layer 130 laminated in this order. Each component of the pouch film laminate of the present invention will be described in more detail below.

[0059] (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.

[0060] The thickness of the base material layer 110 can be 5 μm to 100 μm, specifically 7 μm to 70 μm, and more specifically 25 μm to 60 μm. When the thickness of the base material layer 110 satisfies this range, the external insulation is excellent, the overall thickness of the pouch is not large, and the energy density relative to the volume of the secondary battery can be excellent.

[0061] The substrate layer 110 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 is made of abrasion-resistant and heat-resistant polyethylene terephthalate (PET), nylon, or a combination thereof. More preferably, the substrate layer may include polyethylene terephthalate; or polyethylene terephthalate and nylon.

[0062] The substrate layer 110 may have a single film structure.

[0063] The substrate layer 110 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. The substrate layer may preferably include at least one polyester film, such as polyethylene terephthalate or polybutylene terephthalate, which has abrasion resistance and heat resistance, specifically, but is not limited to, polyethylene terephthalate.

[0064] In the present invention, the pouch film laminate may further include an adhesive layer interposed between the substrate layer 110 and a gas barrier layer 120 described below. The adhesive layer may be introduced for bonding or adhering the substrate layer and the gas barrier layer, and any adhesive layer known in the art may be used without limitation.

[0065] Meanwhile, the substrate layer 110 may have a composite film structure in which two or more materials are formed into layers.

[0066] Specifically, the substrate layer 110 according to the present invention may include a first substrate layer, a second substrate layer, and / or an adhesive layer. Here, the thickness of the substrate layer 110 refers to the total thickness of the first substrate layer, the second substrate layer, and / or the adhesive layer. The first substrate layer may be disposed as the outermost layer of the pouch film laminate, and the second substrate layer may be disposed between the first substrate layer and the gas barrier layer. The adhesive layer may be disposed between the first substrate layer and the second substrate layer, or between the second substrate layer and the gas barrier layer. The first substrate layer, the second substrate layer, and the adhesive layer may be made of materials with different materials and / or physical properties. An interface may exist between the first substrate layer, the second substrate layer, and the adhesive layer. This means that the first substrate layer, the second substrate layer, and the adhesive layer are different layers and may be formed separately.

[0067] The first substrate layer may be the outermost layer of the pouch film laminate. In this case, the first substrate layer may serve to prevent moisture from penetrating from outside the pouch. The first 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 first substrate layer may include at least one polyester film, such as polyethylene terephthalate or polybutylene terephthalate, which has abrasion resistance and heat resistance, but is not limited thereto.

[0068] As described above, the second substrate layer may be a layer disposed between the first substrate layer and the gas barrier layer 120. In this case, the second substrate layer may improve the formability of the pouch. The second substrate layer may include at least one of polyamide films such as, but not limited to, nylon 6, nylon 6,6, nylon MXD6, and nylon 4,10. Preferably, the second substrate layer may include nylon 6, which has the advantage of improving the formability of the pouch due to the excellent stretchability of nylon 6.

[0069] (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.

[0070] 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. A 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. While the inclusion of stainless steel in the gas barrier layer can reduce the formability of the pouch film laminate, as described below, the present invention can improve durability at high temperatures and pressures by adjusting the relationship between the MD and TD fracture energies of the gas barrier layer to a specific level, thereby enabling the realization of a pouch film with improved formability.

[0071] The stainless steel may contain one or more metal elements other than iron (Fe), such as copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0072] Meanwhile, the grade and type of stainless steel are not limited as long as the difference in fracture energy in Equation 1 is adjusted to 2000 J or less. For example, the SUS grade of the stainless steel may be at least one of SUS304, SUS304I, SUS304L, and SUS316L, and more specifically, at least one of SUS304I and SUS316L.

[0073] In the pouch film laminate of the present invention, the difference in breaking energy according to the following formula 1 may be 2000 J or less, specifically 2000 J or less, more specifically 1950 J or less, and even more specifically 800 J or less. Meanwhile, the lower limit of the difference in breaking energy according to the following formula 1 is not particularly limited, and for example, the difference in breaking energy according to the following formula 1 may be 150 J or more, specifically 200 J or more. Here, the breaking energy refers to the total energy that can be absorbed until a test specimen breaks when pulled in one direction. If the difference between the breaking energy in the MD direction and the breaking energy in the TD direction exceeds 2000 J, the difference between the breaking energy in the MD direction and the breaking energy in the TD direction increases, resulting in problems such as the pouch film laminate breaking in the direction with the relatively low breaking energy or the formation of pinholes.

[0074] [Formula 1] Difference in fracture energy (J) = |Fracture energy of gas barrier layer in MD (J) - Fracture energy of gas barrier layer in TD (J)|

[0075] The breaking energy in the MD direction of the gas barrier layer 120 can be 5000 J or more, specifically 8000 J or more, more specifically 10000 J or more, and even more specifically 14300 J or more. The upper limit of the breaking energy in the MD direction of the gas barrier layer 120 is not particularly limited and can be, for example, 20000 J or less. When the above numerical range is satisfied, the breaking energy in the TD direction of the gas barrier layer 120 can be 5000 J or more, specifically 8000 J or more, more specifically 10000 J or more, and even more specifically 13000 J or more. On the other hand, the upper limit of the breaking energy in the TD direction of the gas barrier layer 120 is not particularly limited and can be, for example, 20000 J or less. When the breaking energy in the MD or TD direction satisfies the above-mentioned numerical range, even if energy above a predetermined level is applied to the pouch film laminate during pouch formation, the pouch film laminate will not immediately break but will stretch, thereby ensuring pouch formability.

[0076] In the present invention, the fracture energy in the MD and TD of the gas barrier layer can be changed as needed by adjusting the physical properties of the stainless steel contained in the gas barrier layer. For example, the fracture energy in the MD and TD of the gas barrier layer can be achieved by adjusting the rolling temperature, cooling temperature, cooling time, etc. of the stainless steel contained in the gas barrier layer.

[0077] In the pouch film laminate of the present invention, the difference in tensile elongation at break according to the following formula 2 can be 10% or less, specifically 0.2% to 10%, more specifically 0.4% to 9.2%, and even more specifically 0.4% to 3.0%. Here, the tensile elongation at break refers to the percentage (%) of the length that a test piece extends to break relative to its initial length when pulled in one direction. When the difference between the tensile elongation at break in the MD direction and the tensile elongation at break in the TD direction satisfies the above numerical range, the deviation between the elongation rates in the MD and TD directions is reduced during pouch formation, which has the effect of improving pouch formability.

[0078] [Formula 2] Difference in tensile elongation at break (%) = |tensile elongation at break in the MD direction of the gas barrier layer (%) - tensile elongation at break in the TD direction of the gas barrier layer (%) |

[0079] The tensile elongation at break in the MD of the gas barrier layer 120 can be 15% or more, specifically 16% to 60%, more specifically 17% to 55%. The tensile elongation at break in the TD of the gas barrier layer 120 can be 15% or more, specifically 16% to 60%, more specifically 17% to 55%. When the tensile elongation at break in the MD or TD satisfies the above numerical range, the pouch film laminate increases sufficiently during pouch formation, ensuring the processing depth of the cup portion.

[0080] In the pouch film laminate of the present invention, the difference in tensile breaking strength according to the following formula 3 can be 150 MPa or less, specifically 140 MPa or less, more specifically 120 MPa or less, and even more specifically 40 MPa or less. Meanwhile, the lower limit of the difference in tensile breaking strength according to formula 3 is not particularly limited, and for example, the tensile breaking strength according to formula 3 can be 10 MPa or more, specifically 20 MPa or more. Here, the tensile breaking strength refers to the value obtained by dividing the maximum load applied until a test specimen breaks when pulled in one direction by the cross-sectional area of ​​the test specimen before pulling. When the difference between the tensile breaking strength in the MD direction and the tensile breaking strength in the TD direction satisfies the above-mentioned numerical range, the deviation between the tensile strengths in the MD direction and the TD direction during pouch formation is reduced, thereby improving the formability of the pouch.

[0081] [Formula 3] Difference in tensile breaking strength (MPa) = |tensile breaking strength in the MD direction of the gas barrier layer (MPa) - tensile breaking strength in the TD direction of the gas barrier layer (MPa)|

[0082] The tensile breaking strength in the MD of the gas barrier layer 120 may be 400 MPa or more, specifically 400 MPa to 1000 MPa, more specifically 400 MPa to 900 MPa. The tensile breaking strength in the TD of the gas barrier layer 120 may be 400 MPa or more, specifically 400 MPa to 1000 MPa, more specifically 400 MPa to 900 MPa. When the tensile breaking strength in the MD or TD satisfies the above range, problems such as breakage of the pouch film laminate or the formation of pinholes can be prevented even when a tensile load of a predetermined level or more is applied to the pouch during pouch formation.

[0083] The thickness of the gas barrier layer 120 can be 30 μm to 100 μm, specifically 40 μm to 90 μm, and more specifically 50 μm to 80 μm. When the thickness of the gas barrier layer 120 satisfies this range, excellent moldability and gas barrier performance can be achieved when the cup portion is formed, and sufficient mechanical strength to withstand the internal pressure of the pouch can be ensured.

[0084] Since the gas barrier layer according to the present invention contains stainless steel, there may be no or only a small change in the thickness of the gas barrier layer due to the process of forming or stretching the cup portion of the pouch film laminate.

[0085] In the present invention, the percentage R of the thickness of the gas barrier layer relative to the thickness of the pouch film laminate calculated by the following formula 4 is t can be 10% to 50%, specifically 25% to 40%, and more specifically 30% to 37%. When the content is within this range, it is possible to realize a pouch film laminate that has sufficient gas barrier performance, excellent durability against high temperatures and high pressures, and excellent formability.

[0086] [Formula 4] R t (%) = (gas barrier layer thickness / pouch film laminate thickness) x 100

[0087] (3) Sealant layer The sealant layer 130 is intended to completely seal the inside 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. For this purpose, the sealant layer 130 may be made of a material having excellent thermal adhesive strength.

[0088] The sealant layer 130 may be formed of a material having insulating, corrosion-resistant, 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 and corrosion-resistant properties. Furthermore, since the sealant layer 130 must completely seal the interior of the pouch-type battery case and prevent the transfer of substances 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.

[0089] 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.

[0090] 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.

[0091] 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 different from each other in material 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 from each other and may be formed separately.

[0092] 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).

[0093] 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 and / or electrolyte inside the accommodating space 224, 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.

[0094] Meanwhile, the thickness of the pouch film laminate according to the present invention can be 80 μm to 300 μm, specifically 80 μm to 250 μm, more specifically 100 μm to 250 μm, even more specifically 120 μm to 230 μm, and even more specifically 120 μm to 190 μm. When the thickness of the pouch film laminate satisfies the above range, the pouch cup can be easily formed, and sufficient mechanical strength to withstand the internal pressure of the pouch can be ensured.

[0095] Pouch-type secondary battery Next, the pouch-type secondary battery according to the present invention will be described.

[0096] 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 base layer, a gas barrier layer, and a sealant layer laminated in that order, the gas barrier layer including stainless steel, and a difference in breaking energy according to the following formula 1 being 2000 J or less:

[0097] [Formula 1] Difference in breaking energy (J) = |Breaking energy of the gas barrier layer in the MD direction (J) - Breaking energy of the gas barrier layer in the TD direction (J)|

[0098] Hereinafter, each component of the pouch-type secondary battery of the present invention will be described in more detail with reference to FIG.

[0099] 3 is an exploded view of a pouch-type secondary battery 200 according to the present invention. As shown in FIG. 3, the pouch-type secondary battery 200 according to the present invention may include a pouch-type battery case 210, an electrode assembly 260, an electrode lead 280, an insulating portion 290, and an electrolyte (not shown).

[0100] (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.

[0101] 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 as the cup portion 222 is formed.

[0102] 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. 3. 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. 3, but are not limited to this and may be manufactured in various ways, such as being separated from each other and manufactured separately.

[0103] 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. 3, the first case 220 and the second case 230 may be formed with 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] (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.

[0108] 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.

[0109] 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.

[0110] 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 of a stack type, a jelly roll type, a stack and folding type, or the like, but is not limited thereto.

[0111] The electrode assembly 260 may include an electrode tab 270 .

[0112] 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. 3, 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.

[0113] (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.

[0114] The electrode lead 280 is connected to the electrode assembly 260 and may protrude to the outside of the pouch-type battery case 210 via the sealing portion 250. Specifically, one end of the electrode lead 280 is 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.

[0115] 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. Furthermore, 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.

[0116] (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 that is electrically non-conductive and does not easily pass electricity. Generally, the insulating portion 290 is formed of an insulating tape or film that is easily attached to the electrode lead 280 and has a relatively thin thickness, but is not limited thereto, and any material that can insulate the electrode lead 280 may be used.

[0117] 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 thermally sealed, and may bond the electrode lead 280 to the battery case 210.

[0118] (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.

[0119] Meanwhile, when pressure is applied due to external force or gas generation, peeling can occur at interfaces with relatively weak adhesive strength in the sealed battery case 210. For example, peeling can occur along the interface between heat-bonded sealant layers. However, in the case of a battery case manufactured using the pouch film laminate of the present invention, the sealant layers have improved flow properties when melted, allowing for smooth heat bonding between the sealant layers, thereby maintaining high adhesive strength at the interface and providing excellent seal strength.

[0120] 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.

[0121] Examples and Comparative Examples Example 1: Manufacturing of a pouch film laminate A 3 μm thick first adhesive film, a 25 μm thick nylon film, a 3 μm thick second adhesive film, and a 12 μm thick polyethylene terephthalate (PET) film were laminated in this order on one side of a 60 μm thick stainless steel thin film. An 80 μm thick polypropylene (PP) film 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 / nylon film / second adhesive film / polyethylene terephthalate film were laminated in this order.

[0122] Here, the SUS grade of the stainless steel contained in the stainless steel thin film was SUS304I.

[0123] 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.

[0124] 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 with different tensile and breaking properties was used.

[0125] The SUS grade of the stainless steel contained in the stainless steel thin film of Example 2 was SUS304I.

[0126] 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 with different tensile and breaking properties was used.

[0127] The SUS grade of the stainless steel contained in the stainless steel thin film of Example 3 was SUS304I.

[0128] Example 4: 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 with different tensile and breaking properties was used.

[0129] The SUS grade of the stainless steel contained in the stainless steel thin film of Example 4 was SUS304I.

[0130] Example 5: 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 with different tensile and breaking properties was used.

[0131] The SUS grade of the stainless steel contained in the stainless steel thin film of Example 5 was SUS316L.

[0132] 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 stainless steel thin film with different tensile and breaking properties was used.

[0133] The SUS grade of the stainless steel contained in the stainless steel thin film of Comparative Example 1 was SUS304I.

[0134] Comparative Example 2: 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 with different tensile and breaking properties was used.

[0135] The SUS grade of the stainless steel contained in the stainless steel thin film of Comparative Example 2 was SUS304I.

[0136] 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 with different tensile and breaking properties was used.

[0137] The SUS grade of the stainless steel contained in the stainless steel thin film of Comparative Example 3 was SUS304I.

[0138] Experimental Example 1: Measurement of mechanical properties of stainless steel thin film The mechanical properties of each of the stainless steel thin films of Examples 1 to 5 and Comparative Examples 1 to 3 were measured and are shown in Table 1 below.

[0139] Specifically, the tensile strength, tensile elongation, and breaking energy of the stainless steel thin film were measured by cutting the stainless steel thin film into test pieces 15 mm wide and 100 mm long, fastening both longitudinal ends of the test piece to the upper and lower fixtures of the UTM (here, the distance between the end fastened to the upper fixture and the end fastened to the lower fixture was 50 mm), and then conducting a tensile test at room temperature (25°C) by pulling in a 180° direction at a rate of 5 mm / min. The measurement results are shown in Table 1 below.

[0140] Experimental Example 2: Maximum Forming Depth Evaluation The maximum forming depth was measured for each of the pouch film laminates produced in Examples 1 to 5 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 cold-formed to form a cup portion measuring 90 mm wide and 160 mm long. The maximum forming depth (unit: mm) was defined as the forming depth immediately before the pouch film laminate broke. Ten pouch film laminates in Examples 1 to 5 and Comparative Examples 1 to 3 were prepared, and the above-mentioned maximum forming depth measurement experiment was performed 10 times. The average values ​​are shown in Table 1 below.

[0141] [Table 1]

[0142] According to Table 1, in Examples 1 to 5, in which the difference between the MD and TD breaking energies of the gas barrier layer was 2000 J or less, the processing depth of the cup portion was even greater than in Comparative Examples 1 and 2. This confirms that the formability of the pouch film laminates produced in Examples 1 to 5 was superior to that of Comparative Examples 1 and 2.

[0143] In particular, in the case of Comparative Examples 1 to 3, the maximum processing depth is significantly lower than that of the Examples, and in this case, there is a limit to increasing the number of electrode assemblies that can be accommodated in the pouch film, which makes it difficult to improve the cell energy density of the secondary battery. [Explanation of symbols]

[0144] 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 substrate layer, a gas barrier layer, and a sealant layer; the gas barrier layer comprises stainless steel; the gas barrier layer is disposed between the base layer and the sealant layer; a difference between the breaking energy of the gas barrier layer in a machine direction (MD) and the breaking energy of the gas barrier layer in a transverse direction (TD) of 2000 J or less;

2. the gas barrier layer has a breaking energy in the MD direction of 5000 J or more, The pouch film laminate according to claim 1 , wherein the gas barrier layer has a breaking energy in the TD direction of 5000 J or more.

3. The pouch film laminate according to claim 1 , wherein a difference between the tensile elongation at break in the MD direction of the gas barrier layer and the tensile elongation at break in the TD direction of the gas barrier layer is 10% or less.

4. the tensile elongation at break in the MD direction of the gas barrier layer is 15% or more of the original length in the MD direction of the gas barrier layer, The pouch film laminate according to claim 1 , wherein the tensile elongation at break in the TD direction of the gas barrier layer is 15% or more of the original length in the TD direction of the gas barrier layer.

5. The pouch film laminate according to claim 1 , wherein a difference between the tensile breaking strength of the gas barrier layer in the MD direction and the tensile breaking strength of the gas barrier layer in the TD direction is 150 MPa or less.

6. the gas barrier layer has a tensile break strength in the MD direction of 400 MPa or more; The pouch film laminate according to claim 1 , wherein the gas barrier layer has a tensile breaking strength in the TD direction of 400 MPa or more.

7. 2. The pouch film laminate according to claim 1, wherein the thickness of the gas barrier layer is 10% to 50% of the thickness of the pouch film laminate.

8. 2. The pouch film laminate according to claim 1, wherein the gas barrier layer has a thickness of 30 μm to 100 μm.

9. The pouch film laminate according to claim 1, wherein the thickness of the pouch film laminate is 80 μm to 300 μm.

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, the gas barrier layer comprises stainless steel; the gas barrier layer is disposed between the base layer and the sealant layer; a difference between a breaking energy of the gas barrier layer in a machine direction (MD) and a breaking energy of the gas barrier layer in a transverse direction (TD) of 2000 J or less;

11. the gas barrier layer has a breaking energy in the MD direction of 5000 J or more, The pouch-type secondary battery according to claim 10 , wherein the gas barrier layer has a breaking energy in the TD direction of 5000 J or more.

12. The pouch-type secondary battery according to claim 10 , wherein a difference between a tensile elongation at break in the MD direction of the gas barrier layer and a tensile elongation at break in the TD direction of the gas barrier layer is 10% or less.

13. the tensile elongation at break in the MD direction of the gas barrier layer is 15% or more of the original length in the MD direction of the gas barrier layer, 11. The pouch-type secondary battery according to claim 10, wherein the tensile elongation at break in the TD direction of the gas barrier layer is 15% or more of the original length in the TD direction of the gas barrier layer.

14. The pouch-type secondary battery according to claim 10 , wherein a difference between the tensile breaking strength of the gas barrier layer in the MD direction and the tensile breaking strength of the gas barrier layer in the TD direction is 150 MPa or less.

15. the gas barrier layer has a tensile break strength in the MD direction of 400 MPa or more; The pouch-type secondary battery according to claim 10 , wherein the gas barrier layer has a tensile break strength in the TD direction of 400 MPa or more.

16. The pouch-type secondary battery according to claim 10, wherein the thickness of the gas barrier layer is 10% to 50% of the thickness of the pouch film laminate.

17. 11. The pouch-type secondary battery according to claim 10, wherein the gas barrier layer has a thickness of 30 μm to 100 μm.

18. providing a pouch film laminate comprising a substrate layer, a gas barrier layer, and a sealant layer, the gas barrier layer being disposed between the substrate layer and the sealant layer; measuring a first fracture energy of the gas barrier layer along a first direction of the gas barrier layer; measuring a second fracture energy of the gas barrier layer along a second direction perpendicular to the first direction of the gas barrier layer; determining a difference between the first break energy and the second break energy to be equal to or less than a predetermined critical value; forming the pouch film laminate and housing an electrode assembly therein to manufacture a pouch secondary battery.

19. The method of claim 18, wherein the predetermined critical value is 2000 J or less.

20. the first direction is the MD direction of the gas barrier layer, The method for producing a pouch-type secondary battery according to claim 18 , wherein the MD direction of the gas barrier layer is parallel to a rolling direction during production of the gas barrier layer.

Images