Secondary battery pouch film with sealant layer yield strength, sealant layer thickness ratio and sealant layer glass transition temperature that are controlled such that excellent room-temperature and high-temperature sealing strength characteristics are provided, and manufacturing method therefor

Abstract

Disclosed are a secondary battery pouch film and a manufacturing method therefor, the pouch film being composed of a stack in which at least an outer layer, a barrier layer and a sealant layer are sequentially stacked, wherein the sealant layer comprises a polypropylene (PP) layer, the thickness ratio of the PP layer in the sealant layer being greater than 0.5, the upper yield strength (N / mm2) in the MD direction of the sealant layer being 17.50-19.99, the upper yield strength (N / mm2) in the TD thereof being 17.00-19.99, and the glass transition temperature (Tg) of the sealant layer being -20°C to -10°C. The pouch film not only has excellent sealing strength at room temperature and a high temperature, but also has excellent room-temperature sealing strength maintenance characteristics and, particularly, excellent high-temperature sealing strength maintenance characteristics.

Description

A pouch film for secondary batteries having excellent room-temperature and high-temperature sealing strength characteristics by controlling the yield strength of the sealant layer, the thickness ratio of the sealant layer, and the glass transition temperature of the sealant layer, and a method for manufacturing the same

[0001] The present specification relates to a pouch film for a secondary battery having excellent room-temperature and high-temperature sealing strength characteristics and a method for manufacturing the same, and more particularly, to a pouch film for a secondary battery having excellent heat bonding strength, i.e., sealing strength, at room temperature and high temperature and excellent sealing strength maintenance characteristics at room temperature and particularly at high temperatures by controlling the yield strength of the sealant layer of the pouch film for a secondary battery, the thickness ratio of the polypropylene (PP) layer among the sealant layers, and the glass transition temperature (Tg) of the sealant layer, and a method for manufacturing the pouch film for a secondary battery.

[0002] <National Research and Development Project Supporting This Invention>

[0003] [Project ID] 2410004468

[0004] [Assignment Number] 20022450

[0005] Ministry of Trade, Industry and Energy

[0006] [Name of Project Management (Specialist) Agency] Korea Industrial Technology Evaluation and Planning Institute

[0007] [Research Project Name] Material and Components Technology Development

[0008] [Research Project Name] Development of a Next-Generation Secondary Battery Pouch Capable of Delivering More Than Double the Highest Adhesive Strength (60°C)

[0009] [Name of Project Performing Organization] Yulchon Chemical Co., Ltd.

[0010] Research Period: September 1, 2022 - December 31, 2024

[0011] Lithium secondary batteries (LiBs) are being used in many applications due to their various advantages, including high energy density and excellent output.

[0012] Secondary battery pouch film is a multilayer packaging laminated film that wraps the electrode group and electrolyte of such secondary batteries. It is a key component material that determines the safety, life characteristics, and operational durability of the battery, and requires mechanical flexibility and strength, high oxygen / water vapor barrier properties, high thermal bonding strength, chemical resistance to electrolyte, electrical insulation, and high-temperature safety.

[0013] Secondary battery pouch films are typically composed of an outer layer / barrier layer / inner sealant layer.

[0014] The outer layer, or outermost layer, is composed of nylon, a blend of nylon and PET (polyethylene terephthalate), OPP (oriented polypropylene), polyethylene, etc. The required properties of this outer layer, or outermost layer, include heat resistance, pinhole resistance, chemical resistance, formability, and insulation.

[0015] Barrier layers require formability along with barrier properties against water vapor and other gases. In this regard, formable metals such as aluminum (Al), iron (Fe), copper (Cu), and nickel (Ni) are used for barrier layers, with aluminum currently being the most commonly used.

[0016] The inner sealant layer is required to have thermal adhesiveness, formability, electrolyte resistance, and insulation resistance as it is a layer that comes into contact with the electrolyte.

[0017] Meanwhile, as the application areas of lithium secondary batteries expand from small-sized batteries to medium-sized and large-sized batteries for automobiles and ESS, secondary battery pouch films also need characteristics suitable for medium-sized and large-sized batteries that require high safety.

[0018] Accordingly, it is necessary to have excellent sealing strength at room temperature as well as sealing strength at high temperature (60℃), and furthermore, to maintain the sealing strength at room temperature and especially at high temperature without deterioration. However, it is not easy to secure and maintain high sealing strength at room temperature and especially at high temperature in the actual manufacturing process of pouch films used in medium and large secondary batteries.

[0019] In exemplary embodiments of the present invention, in one aspect, the present invention provides a pouch film for a secondary battery having excellent sealing strength at room temperature and sealing strength at high temperature, as well as excellent sealing strength retention characteristics at high temperature along with excellent sealing strength retention characteristics at room temperature, and a method for manufacturing the same.

[0020] In exemplary embodiments of the present invention, a secondary battery pouch film is configured as a laminate in which at least an outer layer, a barrier layer, and a sealant layer are sequentially laminated, wherein the sealant layer includes at least a polypropylene layer, preferably a non-stretched polypropylene (CPP) layer, and the thickness ratio of the polypropylene (PP) layer among the sealant layers is greater than 0.5, and the yield strength in the MD direction of the sealant layer is (N / mm) 2 ) is 17.50~19.99, preferably 17.50~19.80, and the yield strength in the TD direction (N / mm 2 ) is 17.00 to 19.99, preferably 17.00 to 19.50, and the glass transition temperature (Tg) of the sealant layer is -20°C to -10°C.

[0021] In addition, in exemplary embodiments of the present invention, as a method for manufacturing the secondary battery pouch film described above, the method includes manufacturing a sealant layer such that the thickness ratio of the polypropylene (PP) layer among the sealant layers is greater than 0.5, and the yield strength (N / mm) in the MD direction of the sealant layer 2 ) is 17.50~19.99, preferably 17.50~19.80, and the yield strength in the TD direction (N / mm 2 ) is 17.00 to 19.99, preferably 17.00 to 19.50, and the glass transition temperature (Tg) of the sealant layer is -20°C to -10°C.

[0022] In addition, in exemplary embodiments of the present invention, a secondary battery is provided that is exteriorized with the aforementioned secondary battery pouch film.

[0023] In addition, exemplary embodiments of the present invention provide a method for manufacturing a secondary battery, including a step of covering a secondary battery with the secondary battery pouch film described above.

[0024] The pouch films of exemplary embodiments of the present invention have excellent sealing strength at room temperature and high temperature, as well as excellent room temperature sealing strength retention characteristics and particularly excellent high temperature sealing strength retention characteristics by controlling the yield strength of the sealant layer and the thickness of the polypropylene (PP) layer of the sealant layer, and also controlling the glass transition temperature of the sealant layer.

[0025] These secondary battery pouch films are useful as medium- to large-sized secondary battery pouches for electric vehicles and energy storage devices that require safety, especially high-temperature safety.

[0026] Figure 1 is a schematic diagram showing the configuration of a secondary battery pouch film.

[0027] Figure 2 is a schematic diagram of the jig used in this experimental example, and Figure 3 is a photograph showing a battery pack sample attached to the jig in this experimental example.

[0028] Definition of terms

[0029] In the present specification, when each layer of the secondary battery pouch is included, it is not necessarily composed of only that layer, but additional layers may be included.

[0030] In this specification, being formed 'on' a specific layer includes not only being formed directly on that layer, but also being formed after interposing an additional layer.

[0031] In this specification, the yield strength refers to the point where the specimen stretches in proportion to the increase in load, but when the elastic limit is exceeded, it begins to stretch disproportionately to the load. This point is called the yield point, and the force applied up to the yield point is called the yield strength.

[0032] In this specification, the upper yield strength refers to the maximum value (peak value) of the yield strength. That is, there is an upper yield point (a point at which the yield strength is maximum among the yield points) and a lower yield point (a point at which the yield strength is minimum among the yield points), and the upper yield strength refers to the maximum value (peak value) of the yield strength at the yield point [i.e., the yield strength at the upper yield point], and the lower yield strength refers to the minimum value of the yield strength at the yield point [i.e., the yield strength at the lower yield point]. Depending on the yield strength measurement target, the upper yield point and the lower yield point may be the same.

[0033] In this specification, the extrusion coating (EC) layer refers to an extrusion coating layer of a resin, such as a polyolefin-based resin, that is extruded for lamination with a barrier layer among sealant layers [hereinafter abbreviated as an extrusion layer or an extrusion (EC) layer]. The extrusion (EC) layer of the sealant layer is located on the barrier layer side with respect to the polypropylene-based resin layer.

[0034] In this specification, the polypropylene resin layer of the sealant layer is a core resin layer forming the sealant layer, which performs a sealing function, and is composed of one or more layers. It is in contrast to the aforementioned extruded (EC) layer for bonding with the barrier layer, and is located on the inner side of the pouch film (i.e., the side opposite the barrier layer) based on the aforementioned extruded (EC) layer.

[0035] In this specification, energy is an item for evaluating the sealing strength maintenance characteristics, and when measuring the change in the sealing strength (Y-axis) value according to the stroke (distance) [X-axis] that pulls the sealing portion, it is the area in the stroke section (0 to 20 mm) of the graph representing the sealing strength change, that is, the integral value for the sealing strength change graph in the stroke section (0 to 20 mm) and the stroke (distance) axis [X-axis], and since it is the product of force and distance, it can be expressed as energy.

[0036] In this specification, the maximum stroke is also an item that can evaluate the sealing strength maintenance characteristics. As the stroke (distance) that pulls the sealing portion increases, the sealing strength increases, and the stroke (distance) at which the sealing strength value reaches its maximum is called the maximum stroke.

[0037]

[0038] Description of exemplary implementations

[0039] Hereinafter, exemplary implementation examples of the present invention are described in detail.

[0040] As a method for manufacturing a sealant layer in the manufacture of a secondary battery pouch, there are, for example, the extrusion lamination method and the solvent-dry lamination (abbreviated as SDL) method.

[0041] The solvent dry lamination method uses a solvent-based adhesive to bond a barrier layer (metal layer) onto a polypropylene (PP) layer and then dries the solvent-based adhesive. The resulting sealant layer is then made of a polypropylene (PP) layer. While the solvent-based adhesive may remain on the polypropylene (PP) layer after drying, the remaining amount is minimal, approximately 4㎛ or less, and thus can be ignored.

[0042] Meanwhile, the extrusion lamination method is a method of extruding a polyolefin resin, preferably a polypropylene resin, which is mainly used in the sealant layer, when adhering the polypropylene-based resin layer, particularly the non-stretched polypropylene (CPP) resin layer, to the barrier layer (metal layer). As a result, the sealant layer is composed of an extrusion coating (EC) layer (mainly an extruded polypropylene layer) and a polypropylene (PP) layer resin, preferably a non-stretched polypropylene (CPP) layer, underneath it (on the inside based on the pouch film). Fig. 1 is a schematic diagram showing a case including an extrusion layer. In Fig. 1, for example, when there is no extrusion layer, it is manufactured by a solvent dry lamination manufacturing method.

[0043] The present inventors have surprisingly confirmed that when bonding a sealant layer to a barrier layer as described above, by controlling the yield strength of the sealant layer while controlling the relative thickness of the polypropylene (PP) layer of the sealant layer [or controlling the relative thickness occupied by the polypropylene (PP) layer among the sealant layers], and also controlling the glass transition temperature (Tg) of the sealant layer, not only the room temperature sealing strength characteristics of the secondary battery pouch film are excellent, but also the sealing strength characteristics at high temperatures are excellent, and in particular, the sealing strength maintenance characteristics at high temperatures are also excellent, and have conducted repeated studies to arrive at the present invention.

[0044] Sealing strength characteristics, especially high-temperature sealing strength characteristics, are essential for the safety of medium- to large-sized batteries such as automotive batteries. In particular, it is necessary to maintain high-temperature sealing strength as much as possible to ensure the safety of medium- to large-sized batteries in high-temperature environments. However, when manufacturing a pouch film, multiple layers are laminated, and various manufacturing conditions are involved in the manufacturing of the sealant layer, making it difficult to control the sealing strength characteristics, especially the maintenance of high-temperature sealing strength characteristics. This difficulty becomes even greater when manufacturing a thick secondary battery pouch film, such as one with a total thickness of 153㎛ or more, and especially 180㎛ or more.

[0045] As described above, it has been discovered by the present invention that when the sealant layer of the pouch film is manufactured so that it has a predetermined yield strength while controlling the thickness ratio of the polypropylene resin (PP) layer of the sealant layer and also so that the sealant layer has a predetermined glass transition temperature (Tg), not only is the room temperature sealing strength characteristic and the high temperature sealing strength characteristic excellent, but also the high temperature sealing strength maintenance characteristic is excellent.

[0046] In the manufacture of a secondary battery pouch film, especially a secondary battery pouch film having a thick overall thickness as described above, when bonding a sealant layer to a barrier layer, it is understood that the yield strength of the sealant layer of the pouch film, the thickness ratio of the polypropylene resin (PP) layer of the sealant layer, and the glass transition temperature (Tg) of the sealant layer are related to the room temperature and high temperature sealing strength characteristics, especially the maintenance characteristics of the high temperature sealing strength.

[0047] Specifically, in exemplary embodiments of the present invention, a secondary battery pouch film is configured as a laminate in which at least an outer layer, a barrier layer, and a sealant layer are sequentially laminated, and the sealant layer is configured as at least a polypropylene (PP) layer which is a sealing resin layer, and the thickness ratio of the polypropylene (PP) layer among the sealant layers is greater than 0.5, and the yield strength in the MD direction of the sealant layer is (N / mm2 ) is 17.50~19.99, preferably 17.50~19.80, and the yield strength in the TD direction (N / mm 2 ) is 17.00 to 19.99, preferably 17.00 to 19.50, and the glass transition temperature (Tg) of the sealant layer is in the range of -20°C to -10°C.

[0048] In an exemplary embodiment, the thickness ratio of the polypropylene (PP) layer among the sealant layers may be 0.500 or more, 0.525 or more, 0.550 or more, 0.575 or more, 0.600 or more, 0.625 or more, 0.650 or more, 0.675 or more, 0.700 or more, 0.725 or more, 0.750 or more, or 0.775 or more in the extrusion lamination manufacturing method. In an exemplary embodiment, the thickness ratio of the polypropylene (PP) layer among the sealant layers may be less than 1 in the extrusion lamination manufacturing method. In an exemplary embodiment, the thickness ratio of the polypropylene (PP) layer among the sealant layers may be 1 in the solvent dry lamination manufacturing method (i.e., the ratio of the extrusion layer is 0).

[0049] When the thickness ratio is less than 0.5, that is, when the thickness of the polypropylene (PP) layer is thinned to less than half the thickness of the sealant layer, the yield strength may decrease, and thus the sealing strength may decrease. Here, the thickness ratio of the polypropylene (PP) layer among the sealant layers being 0.500 or more means that the thickness of the extrusion (EC) layer must be thinner than the thickness of the polypropylene (PP) layer.

[0050] In an exemplary embodiment, the yield strength (N / mm) in the MD direction of the sealant layer 2 ) is within the range of 17.50 to 19.99, and may also have a numerical range between the following values ​​existing within that range. The yield strength (N / mm) in the MD direction of the sealant layer 2) is outside the above range, the room temperature and high temperature sealing strength characteristics, especially the high temperature sealing strength retention characteristics, may be poor as can be confirmed from the data described below.

[0051] In a non-limiting example, the yield strength (N / mm) in the MD direction of the sealant layer 2) is 17.50 or more, 17.51 ​​or more or less, 17.52 or more or less, 17.53 or more or less, 17.54 or more or less, 17.55 or more or less, 17.56 or more or less, 17.57 or more or less, 17.58 or more or less, 17.59 or more or less, 17.60 or more or less, 17.61 or more or less, 17.62 or more or less, 17.63 or more or less, 17.64 or more or less, 17.65 or more or less, 17.66 or more or less, 17.67 or more or less, 17.68 or more or less, 17.69 or more or less, 17.70 or more or less, 17.71 or more or less, 17.72 or more or less, 17.73 or more or less, 17.74 or more, 17.75 or more, 17.76 or more, 17.77 or more, 17.78 or more, 17.79 or more, 17.80 or more, 17.81 or more, 17.82 or more, 17.83 or more, 17.84 or more, 17.85 or more, 17.86 or more, 17.87 or more, 17.88 or more, 17.89 or more, 17.90 or more, 17.91 or more, 17.92 or more, 17.93 or more, 17.94 or more, 17.95 or more, 17.96 or more, 17.97 or more, 17.98 Over or under, 17.99 over or under, 18.00 over or under, 18.01 over or under, 18.02 over or under, 18.03 over or under, 18.04 over or under, 18.05 over or under, 18.06 over or under, 18.07 over or under, 18.08 over or under, 18.09 over or under, 18.10 over or under, 18.11 over or under, 18.12 or more or less, 18.13 or more or less, 18.14 or more or less, 18.15 or more or less, 18.16 or more or less, 18.17 or more or less, 18.18 or more or less, 18.19 or more or less, 18.20 or more or less, 18.21 or more or less, 18.22 or more or less, 18.23 or more or less, 18.24 or more or less, 18.25 or more or less, 18.26 or more or less, 18.27 or more or less, 18.28 or more or less, 18.29 or more or less, 18.30 or more or less, 18.31 or more or less, 18.32 or more or less, 18.33 or more or less, 18.34 or more or less, 18.35 or more or less, 18.36 Over or under, 18.37 over or under, 18.38 over or under, 18.39 over or under, 18.40 over or under, 18.41 over or under, 18.42 over or under, 18.43 over or under, 18.44 over or under, 18.45 over or under, 18.46 over or under, 18.47 over or under, 18.48 over or under, 18.49 over or under, 18.50 over or under, 18.51 over or under, 18.52 over or under, 18.53 over or under, 18.54 over or under, 18.55 over or under, 18.56 over or under, 18.57 over or under, 18.58 over or under, 18.59 over or under, 18.60 over or under, 18.61 or more or less, 18.62 or more or less, 18.63 or more or less, 18.64 or more or less, 18.65 or more or less, 18.66 or more or less, 18.67 or more or less, 18.68 or more or less, 18.69 or more or less, 18.70 or more or less, 18.71 or more or less, 18.72 or more or less, 18.73 or more or less, 18.74 or more or less, 18.75 or more or less, 18.76 or more or less, 18.77 or more or less, 18.78 or more or less, 18.79 or more or less, 18.80 or more or less, 18.81 or more or less, 18.82 or more or less, 18.83 or more or less, 18.84 or more or less, 18.85 or more or less, 18.86 or more or less, 18.87 or more or less, 18.88 or more or less, 18.89 or more or less, 18.90 or more or less, 18.91 or more or less, 18.92 or more or less, 18.93 or more or less, 18.94 or more or less, 18.95 or more or less, 18.96 or more, 18.97 or more or less, 18.98 Over or under, 18.99 over or under, 19.00 over or under, 19.01 over or under, 19.02 over or under, 19.03 over or under, 19.04 over or under, 19.05 over or under, 19.06 over or under, 19.07 over or under, 19.08 over or under, 19.09 over or under, 19.10 over or under, 19.11 over or under, 19.12 over or under, 19.13 over or under, 19.14 over or under, 19.15 over or under, 19.16 over or under, 19.17 over or under, 19.18 over or under, 19.19 over or under, 19.20 over or under, 19.21 over or under, 19.22 over or under, 19.23 or more or less, 19.24 or more or less, 19.25 or more or less, 19.26 or more or less, 19.27 or more or less, 19.28 or more or less, 19.29 or more or less, 19.30 or more or less, 19.31 or more or less, 19.32 or more or less, 19.33 or more or less, 19.34 or more or less, 19.35 or more or less, 19.36 or more or less, 19.37 or more or less, 19.38 or more or less, 19.39 or more or less, 19.40 or more or less, 19.41 or more or less, 19.42 or more or less, 19.43 or more or less, 19.44 or more or less, 19.45 or more or less, 19.46 or more or less, 19.47 or more or less, 19.48 or more or less, 19.49 or more or less, 19.50 or more or less, 19.51 or more or less, 19.52 or more or less, 19.53 or more or less, 19.54 or more or less, 19.55 or more or less, 19.56 or more or less, 19.57 or more or less, 19.58 or more or less, 19.59 or more or less, 19.60 Over or under, 19.61 over or under, 19.62 over or under, 19.63 over or under, 19.64 over or under, 19.65 over or under, 19.66 over or under, 19.67 over or under, 19.68 over or under, 19.69 over or under, 19.70 over or under, 19.71 over or under, 19.72 over or under, 19.73 over or under, 19.74 over or under, 19.75 over or under, 19.76 over or under, 19.77 over or under, 19.78 over or under, 19.79 over or under, 19.80 over or under, 19.81 over or under, 19.82 over or under, 19.83 over or under, 19.84 over or under, 19.85 or more or less, 19.86 or more or less, 19.87 or more or less, 19.88 or more or less, 19.89 or more or less, 19.90 or more or less, 19.91 or more or less, 19.92 or more or less, 19.93 or more or less, 19.94 or more or less, 19.95 or more or less, 19.96 or more or less, 19.97 or more or less, 19.It can be 98 or more, or 19.99 or less.

[0052] In an exemplary embodiment, the yield strength (N / mm) in the TD direction of the sealant layer 2 ) is within the range of 17.00 to 19.99, and may have a numerical range between the following values ​​existing within the range. The yield strength (N / mm) in the TD direction of the sealant layer 2 ) is outside the above range, the room temperature and high temperature sealing strength characteristics, especially the high temperature sealing strength retention characteristics, may be poor as can be confirmed from the data described below.

[0053] In a non-limiting example, the yield strength (N / mm) in the TD direction of the sealant layer 2) is 17.00 or more, 17.01 or more or less, 17.02 or more or less, 17.03 or more or less, 17.04 or more or less, 17.05 or more or less, 17.06 or more or less, 17.07 or more or less, 17.08 or more or less, 17.09 or more or less, 17.10 or more or less, 17.11 or more or less, 17.12 or more or less, 17.13 or more or less, 17.14 or more or less, 17.15 or more or less, 17.16 or more or less, 17.17 or more or less, 17.18 or more or less, 17.19 or more or less, 17.20 or more or less, 17.21 or more or less, 17.22 or more or less, 17.23 or more or less, 17.24 or more or less, 17.25 or more or less, 17.26 or more or less, 17.27 or more or less, 17.28 or more or less, 17.29 or more or less, 17.30 or more or less, 17.31 or more or less, 17.32 or more or less, 17.33 or more or less, 17.34 or more or less, 17.35 or more or less, 17.36 or more or less, 17.37 or more or less, 17.38 or more or less, 17.39 or more or less, 17.40 or more or less, 17.41 or more or less, 17.42 or more or less, 17.43 or more or less, 17.44 or more or less, 17.45 or more or less, 17.46 or more or less, 17.47 or more or less, 17.48 Over or under, 17.49 over or under, 17.50 over or under, 17.51 ​​over or under, 17.52 over or under, 17.53 over or under, 17.54 over or under, 17.55 over or under, 17.56 over or under, 17.57 over or under, 17.58 over or under, 17.59 over or under, 17.60 over or under, 17.61 over or under, 17.62 or more or less, 17.63 or more or less, 17.64 or more or less, 17.65 or more or less, 17.66 or more or less, 17.67 or more or less, 17.68 or more or less, 17.69 or more or less, 17.70 or more or less, 17.71 or more or less, 17.72 or more or less, 17.73 or more or less, 17.74 or more or less, 17.75 or more or less, 17.76 or more or less, 17.77 or more or less, 17.78 or more or less, 17.79 or more or less, 17.80 or more or less, 17.81 or more or less, 17.82 or more or less, 17.83 or more or less, 17.84 or more or less, 17.85 or more or less, 17.86 Over or under, 17.87 over or under, 17.88 over or under, 17.89 over or under, 17.90 over or under, 17.91 over or under, 17.92 over or under, 17.93 over or under, 17.94 over or under, 17.95 over or under, 17.96 over or under, 17.97 over or under, 17.98 over or under, 17.99 over or under, 18.00 over or under, 18.01 over or under, 18.02 over or under, 18.03 over or under, 18.04 over or under, 18.05 over or under, 18.06 over or under, 18.07 over or under, 18.08 over or under, 18.09 over or under, 18.10 over or under, 18.11 or more or less, 18.12 or more or less, 18.13 or more or less, 18.14 or more or less, 18.15 or more or less, 18.16 or more or less, 18.17 or more or less, 18.18 or more or less, 18.19 or more or less, 18.20 or more or less, 18.21 or more or less, 18.22 or more or less, 18.23 or more or less, 18.24 or more or less, 18.25 or more or less, 18.26 or more or less, 18.27 or more or less, 18.28 or more or less, 18.29 or more or less, 18.30 or more or less, 18.31 or more or less, 18.32 or more or less, 18.33 or more or less, 18.34 or more or less, 18.35 or more or less, 18.36 or more or less, 18.37 or more or less, 18.38 or more or less, 18.39 or more or less, 18.40 or more or less, 18.41 or more or less, 18.42 or more or less, 18.43 or more or less, 18.44 or more or less, 18.45 or more or less, 18.46 or more or less, 18.47 or more or less, 18.48 Over or under, 18.49 over or under, 18.50 over or under, 18.51 over or under, 18.52 over or under, 18.53 over or under, 18.54 over or under, 18.55 over or under, 18.56 over or under, 18.57 over or under, 18.58 over or under, 18.59 over or under, 18.60 over or under, 18.61 over or under, 18.62 over or under, 18.63 over or under, 18.64 over or under, 18.65 over or under, 18.66 over or under, 18.67 over or under, 18.68 over or under, 18.69 over or under, 18.70 over or under, 18.71 over or under, 18.72 over or under, 18.73 or more or less, 18.74 or more or less, 18.75 or more or less, 18.76 or more or less, 18.77 or more or less, 18.78 or more or less, 18.79 or more or less, 18.80 or more or less, 18.81 or more or less, 18.82 or more or less, 18.83 or more or less, 18.84 or more or less, 18.85 or more or less, 18.86 or more or less, 18.87 or more or less, 18.88 or more or less, 18.89 or more or less, 18.90 or more or less, 18.91 or more or less, 18.92 or more or less, 18.93 or more or less, 18.94 or more or less, 18.95 or more or less, 18.96 or more or less, 18.97 or more or less, 18.98 or more or less, 18.99 or more or less, 19.00 or more or less, 19.01 or more or less, 19.02 or more or less, 19.03 or more or less, 19.04 or more or less, 19.05 or more or less, 19.06 or more or less, 19.07 or more or less, 19.08 or more or less, 19.09 or more or less, 19.10 More than or equal to 19.11, More than or equal to 19.12, More than or equal to 19.13, More than or equal to 19.14, More than or equal to 19.15, More than or equal to 19.16, More than or equal to 19.17, More than or equal to 19.18, More than or equal to 19.19, More than or equal to 19.20, More than or equal to 19.21, More than or equal to 19.22, More than or equal to 19.23, More than or equal to 19.24, More than or equal to 19.25, More than or equal to 19.26, More than or equal to 19.27, More than or equal to 19.28, More than or equal to 19.29, More than or equal to 19.30, More than or equal to 19.31, More than or equal to 19.32, More than or equal to 19.33, More than or equal to 19.34, 19.35 or more or less, 19.36 or more or less, 19.37 or more or less, 19.38 or more or less, 19.39 or more or less, 19.40 or more or less, 19.41 or more or less, 19.42 or more or less, 19.43 or more or less, 19.44 or more or less, 19.45 or more or less, 19.46 or more or less, 19.47 or more or less, 19.48 or more or less, 19.49 or more or less, 19.50 or more or less, 19.51 or more or less, 19.52 or more or less, 19.53 or more or less, 19.54 or more or less, 19.55 or more or less, 19.56 or more or less, 19.57 or more or less, 19.58 or more or less, 19.59 or more or less, 19.60 or more or less, 19.61 or more or less, 19.62 or more or less, 19.63 or more or less, 19.64 or more or less, 19.65 or more or less, 19.66 or more or less, 19.67 or more or less, 19.68 or more or less, 19.69 or more or less, 19.70 or more or less, 19.71 or more or less, 19.72 More than or equal to 19.73, More than or equal to 19.74, More than or equal to 19.75, More than or equal to 19.76, More than or equal to 19.77, More than or equal to 19.78, More than or equal to 19.79, More than or equal to 19.80, More than or equal to 19.81, More than or equal to 19.82, More than or equal to 19.83, More than or equal to 19.84, More than or equal to 19.85, More than or equal to 19.86, More than or equal to 19.87, More than or equal to 19.88, More than or equal to 19.89, More than or equal to 19.90, More than or equal to 19.91, More than or equal to 19.92, More than or equal to 19.93, More than or equal to 19.94, More than or equal to 19.95, More than or equal to 19.96, It can be 19.97 or more or less, 19.98 or more or less, or 19.99 or less.

[0054] In an exemplary embodiment, the yield strength (N / mm) in the MD direction of the sealant layer 2 ) and yield strength in TD direction (N / mm 2) is 34.5 or more and 39.9 or less, preferably 34.5 or more and 39 or less, more preferably 34.61 to 38.85.

[0055] In an exemplary embodiment, in the case of extrusion lamination, the yield strength (N / mm) in the MD direction of the sealant layer 2 ) is the yield strength in the TD direction (N / mm 2 ) may be large. Due to the characteristics of the extrusion coating (EC) process or the lamination process using a PP layer on the sealant layer, slight elongation may occur in the MD (Machine Direction, longitudinal direction). Accordingly, the yield strength in the MD direction is thought to be greater than that in the TD (Transverse Direction, transverse direction) direction where no elongation occurs.

[0056] In an exemplary embodiment, the glass transition temperature (Tg) of the sealant layer has a value within the range of -20°C to -10°C, preferably -19°C to -11°C, and may have a numerical range between the following values ​​within the range. When the glass transition temperature (Tg) of the sealant layer is outside the range of -20°C to -10°C, as can be seen from the data described below, the sealing strength properties, particularly the high-temperature sealing strength properties, particularly the high-temperature sealing strength retention properties, may be deteriorated.

[0057] In a non-limiting example, the glass transition temperature (Tg) of the sealant layer may be -20°C or higher, -19.5°C or higher, -19°C or higher, -18.5°C or higher, -18°C or higher, -17.5°C or higher, -17°C or higher, -16.5°C or higher, -16°C or higher, -15.5°C or higher, -15°C or higher, -14.5°C or higher, -14°C or higher, -13.5°C or higher, -13°C or higher, -12.5°C or higher, -12°C or higher, -11.5°C or higher, -11°C or higher, or -10.5°C or higher. Or it may be -10℃ or lower, -10.5℃ or lower, -11℃ or lower, -11.5℃ or lower, -12℃ or lower, -12.5℃ or lower, -13℃ or lower, -13.5℃ or lower, -14℃ or lower, -14.5℃ or lower, -15℃ or lower, -15.5℃ or lower, -16℃ or lower, -16.5℃ or lower, -17℃ or lower, -17.5℃ or lower, -18℃ or lower, -18.5℃ or lower.

[0058] In an exemplary embodiment, the secondary battery pouch film may have a maximum sealing strength (unit: N / 15mm) measured at room temperature when sealed under sealing conditions at 220°C as measured by the following method, which may be 150 N / 15mm or more and 205 N / 15mm or less in both the MD direction and the TD direction.

[0059] In a non-limiting example, the room temperature measurement value of the maximum sealing strength when sealed under the above 220°C sealing condition may be 150 N / 15mm or more, 155 N / 15mm or more, 160 N / 15mm or more, 165 N / 15mm or more, 170 N / 15mm or more, 175 N / 15mm or more, 180 N / 15mm or more, 185 N / 15mm or more, 190 N / 15mm or more, 195 N / 15mm or more, or 200 N / 15mm or more in at least one of the MD direction and the TD direction.

[0060] In an exemplary embodiment, the high temperature measurement value (measured after leaving at 60°C for 3 minutes) of the maximum sealing strength (unit: N / 15 mm) when the secondary battery pouch film is sealed under sealing conditions at 220°C as measured by the method below is 115 N / 15 mm or more and 170 N / 15 mm or less in at least one of the MD direction and the TD direction.

[0061] In a non-limiting example, the high temperature measurement value (measured after leaving at 60°C for 3 minutes) of the maximum sealing strength when sealed under the above 220°C sealing condition may be 115 N / 15mm or more, 120 N / 15mm or more, 125 N / 15mm or more, 130 N / 15mm or more, 135 N / 15mm or more, 140 N / 15mm or more, 145 N / 15mm or more, 150 N / 15mm or more, 155 N / 15mm or more, 160 N / 15mm or more, or 165 N / 15mm or more in at least one of the MD direction and the TD direction.

[0062] [Method for measuring maximum sealing strength when sealing at 220℃ sealing conditions]

[0063] After manufacturing the secondary battery pouch film to 100 mm X 200 mm, fold it in half, seal it, and then cut it into pieces with a width of 15 mm perpendicular to the sealing direction to manufacture a specimen.

[0064] The sealing conditions are seal bar width 200mm x seal thickness 10mm, sealing time 2.0 seconds, 0.2Mpa, and temperature 220℃.

[0065] Each sealing strength (load) is measured by pulling the specimen in the MD and TD directions using a sealing strength measuring device (e.g., AGS-X model UTM equipment from SHIMADZU). The measurement conditions are a test speed of 10 mpm and a grip gap of 30 mm.

[0066] For room temperature measurements, measurements were taken at room temperature, and for high temperature measurements, the values ​​were measured after leaving the sample at 60℃ for 3 minutes. When measuring the sealing strength by pulling the sealing area, the maximum strength is indicated as the maximum sealing strength.

[0067] In an exemplary embodiment, the secondary battery pouch film preferably has a maximum sealing strength parameter of 1.1 or more and 1.8 or less when sealed under sealing conditions at 220°C.

[0068] [Maximum sealing strength parameter]

[0069] (Maximum sealing strength in MD direction at room temperature X Maximum sealing strength in TD direction at room temperature) / (Maximum sealing strength in MD direction at high temperature X Maximum sealing strength in TD direction at high temperature)

[0070] In a non-limiting example, the maximum sealing strength parameter may be within a range of values ​​between any two of the following values: 1.1, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80.

[0071] In an exemplary embodiment, the room temperature energy of the secondary battery pouch film measured by the following method is 2.0 to 3.0 KN x mm.

[0072] In an exemplary embodiment, the high temperature energy of the secondary battery pouch film measured by the following method is 1.5 to 2.5 KN x mm.

[0073] In an exemplary embodiment, the difference between the room temperature energy and the high temperature energy of the secondary battery pouch film measured by the following method is 0.4 to 0.6 KN x mm.

[0074] [Room Temperature Energy and High Temperature Energy Measurement]

[0075] Measured in the same manner as the sealing strength measurement method described above, but the room temperature energy or high temperature energy is the area between the sealing strength graph according to the stroke and the stroke X-axis when the X-axis is the stroke (distance) for pulling the sealing portion at room temperature or high temperature (the high temperature is measured after leaving it at 60℃ for 3 minutes) and the Y-axis is the sealing strength (i.e., the integral value between the sealing strength graph and the X-axis), and the stroke at the time of integration is integrated from 0 mm to 20 mm.

[0076] In an exemplary embodiment, the maximum stroke at room temperature of the secondary battery pouch film measured by the following method is 15 to 25 mm.

[0077] In an exemplary embodiment, the high temperature maximum stroke of the secondary battery pouch film measured by the following method is 18 to 24 mm.

[0078] [Measurement of maximum stroke at room temperature and maximum stroke at high temperature]

[0079] Measure as in the sealing strength measurement method described above, but at room temperature or high temperature (high temperature is measured after leaving at 60℃ for 3 minutes), the X-axis is the stroke (distance) for pulling the sealing part, and the Y-axis is the sealing strength. As the stroke increases, the sealing strength curve increases, and the stroke (distance) at which the sealing strength value reaches the maximum is evaluated as the maximum stroke. If evaluated at room temperature, it is the room temperature maximum stroke, and if evaluated at high temperature, it is the high temperature maximum stroke.

[0080] In an exemplary embodiment, the outer layer may be composed of nylon, PET (polyethylene terephthalate), PBT (polybutylene terephthalate), a blended layer of nylon and PET (a laminated film of nylon and PET), etc.

[0081] In an exemplary embodiment, the nylon film among the outer layers preferably has a thickness of 20 μm or more, and more preferably 25 μm or more, from the standpoint of formability. However, if the nylon film thickness exceeds 30 μm, the insulation breakdown voltage may decrease. Therefore, the preferred nylon film thickness may be 20 μm to 30 μm, and preferably 25 μm to 30 μm.

[0082] In an exemplary embodiment, the thinner the PET film and the thicker the nylon film among the outer layers, the more advantageous the formability. However, since a thinner PET film may be disadvantageous in terms of insulation breakdown voltage, from this perspective, the PET film is preferably 7 µm to 12 µm.

[0083] In an exemplary embodiment, the metal layer may be composed of a metal such as aluminum, SUS, or copper, and has moisture permeability and impact resistance.

[0084] In an exemplary embodiment, the non-stretched polypropylene (CPP) layer or non-stretched polypropylene (CPP) film of the sealant layer may contain various additives (rubber, elastomer, slip agent, etc.) depending on the required properties.

[0085] In an exemplary embodiment, the total thickness of the secondary battery pouch film may be 153 μm or more, and in particular, may be a thick thickness of 180 μm or more. For example, it may be 183 μm or more, and may be 183 μm to 203 μm. In one embodiment, the secondary battery pouch film may be 180 μm or more, 183 μm or more, 186 μm or more, 189 μm or more, 192 μm or more, 195 μm or more, or 198 μm or more.

[0086] In an exemplary embodiment, the metal layer thickness may be, for example, 20 to 80 μm, preferably 40 to 60 μm.

[0087] In an exemplary embodiment, the sealant layer thickness may be, for example, 20 to 80 μm.

[0088] In an exemplary embodiment, the thickness of the non-stretched polypropylene (CPP) layer of the sealant layer may be, for example, 20 to 80 μm.

[0089] In an exemplary embodiment, the thickness of the extruded polypropylene (PP) layer, which is the extruded (EC) layer of the sealant layer, may be, for example, 0 to 60 μm.

[0090] Meanwhile, a method for manufacturing a secondary battery pouch film of exemplary embodiments of the present invention is a method for manufacturing a secondary battery pouch film in which at least an outer layer, a barrier layer, and a sealant layer are sequentially laminated, and the sealant layer includes a polypropylene (PP) layer, and includes a step of manufacturing the polypropylene (PP) layer among the sealant layers so that the thickness ratio is greater than 0.5, and the upper yield strength (N / mm) of the sealant layer in the MD direction 2 ) is 17.50~19.99, preferably 17.50~19.80, and the yield strength in the TD direction (N / mm 2 ) is 17.00 to 19.99, preferably 17.00 to 19.50, and the glass transition temperature (Tg) of the sealant layer is within the range of -20°C to -10°C.

[0091] The thickness ratio of the polypropylene (PP) layer among the sealant layers can be obtained by selecting a manufacturing method such as an extrusion lamination manufacturing method or a solvent dry lamination manufacturing method, selecting the thickness of the polypropylene (PP) layer itself, and in the case of an extrusion lamination manufacturing method, controlling the thickness of the extruded layer (EC) layer during extrusion of the extruded resin.

[0092] The upper yield strength and glass transition temperature can also be easily controlled by a skilled artisan. As is well known, the upper yield strength and glass transition temperature can be determined by the type and softness of the polypropylene (PP) resin in the sealant layer, as well as the content of the elastomer additive used in the sealant layer. Therefore, the upper yield strength and glass transition temperature can be controlled by selecting the appropriate type and properties of polypropylene and elastomer additives known to have the desired upper yield strength and glass transition temperature.

[0093] Meanwhile, exemplary embodiments of the present invention provide a secondary battery sheathed with the aforementioned secondary battery pouch film. Such a secondary battery may be, for example, a lithium secondary battery, and in particular, a medium- to large-sized secondary battery for use in electric vehicles (EVs) or energy storage systems (ESSs).

[0094] In addition, exemplary embodiments of the present invention provide a method for manufacturing a secondary battery, including a step of covering a secondary battery with the aforementioned secondary battery pouch film.

[0095] The following examples further illustrate exemplary embodiments of the present invention. The embodiments disclosed herein are for illustrative purposes only, and the present invention may be implemented in various forms and should not be construed as limited to the embodiments described herein.

[0096] [Experimental Method]

[0097] In the examples and comparative examples, the outer layer was composed of a composite layer of nylon (25 μm) and PET (12 μm), and the metal layer used aluminum foil (60 μm). However, as shown in Table 1 below, the thickness of the extruded layer (in the case of extrusion lamination) and the polypropylene (CPP, non-stretched polypropylene) layer of the sealant layer were controlled, and those having the yield strength and Tg values ​​shown in the table below were used. In the case where the extruded layer was not formed, the sealant layer was made into a polypropylene (CPP, non-stretched polypropylene) layer by the solvent dry lamination method (Example 5). In addition, the yield strength, Tg, and sealing strength were evaluated by the method described below. The total thickness was 183 μm including the adhesive layer.

[0098] [Table 1]

[0099]

[0100] Surrender Robbery

[0101] The sample is made by peeling off the sealant layer of the pouch film and then making it 15 mm wide x 100 mm long.

[0102] The yield strength was measured using SHIMADZU's AGS-X model UTM equipment, and the conditions were a test speed of 50 mpm and a grip gap of 30 mm.

[0103] As the load increases, the specimen stretches in proportion to the load. When the elastic limit is exceeded, the specimen begins to stretch disproportionately to the load. This is called the yield point. In the case of CPP, there is no lower yield point, so the yield point is also the upper yield point.

[0104] <Tg 측정 방법>

[0105] TA's DSC250 equipment was used. Measurement conditions were a temperature range of -50℃ to 200℃, a heating rate of 10℃ / min, and a cooling rate of -20℃ / min. The Tg value was calculated using an analysis program (TRIOS) at -50℃, which is the approximate Tg value range of PP.

[0106] <Maximum sealing strength when sealed under 220℃ sealing conditions>

[0107] The production of the sample was done by making a pouch film of 100 mm X 200 mm, folding it in half, sealing it, and then cutting it into pieces with a width of 15 mm perpendicular to the sealing direction.

[0108] The sealing conditions were a seal bar width of 200 mm x seal thickness of 10 mm, 2.0 seconds, 0.2 Mpa, and a temperature of 220°C.

[0109] The sealing strength measurement method is to measure each sealing strength (load) by pulling the specimen in the MD and TD directions with a sealing strength measuring device (e.g., AGS-X model UTM equipment from SHIMADZU). The measurement conditions are a test speed of 10 mpm and a grip gap of 30 mm.

[0110] For room temperature measurements, measurements were taken at room temperature, and for high temperature measurements, measurements were taken after leaving the sample at 60℃ for 3 minutes, and the results are shown in Table 2 below.

[0111] The maximum value among the sealing strength measurements is considered the maximum sealing strength. In other words, when measuring the sealing strength while pulling the sealing area, the maximum strength is indicated as the maximum sealing strength.

[0112] <Measurement of room temperature energy, high temperature energy, and maximum stroke at room temperature and high temperature in the TD direction when sealed under 220℃ sealing conditions>

[0113] In order to see the maintenance characteristics of the sealing strength in the TD direction, room temperature energy and high temperature energy were evaluated. For this, the sealing strength was measured in the same way as the sealing strength measurement method in the case of sealing under the sealing condition of 220℃ mentioned above, but when the X-axis is the stroke (distance) for pulling the sealing part in the TD direction at room temperature or high temperature (the high temperature is measured after leaving it at 60℃ for 3 minutes), and the Y-axis is the sealing strength, the area between the graph of the change in sealing strength according to the stroke and the X-axis representing the stroke (i.e., the integral value of the graph of the change in sealing strength according to the stroke) is defined as room temperature energy (energy when measured at room temperature) or high temperature energy (energy when measured after leaving it at 60℃ for 3 minutes), and the stroke is integrated from 0 mm to 20 mm during integration.

[0114] Meanwhile, to examine the maintenance characteristics of the sealing strength in the TD direction, the maximum stroke at room temperature and high temperature was measured.

[0115] That is, when measuring in the same manner as the sealing strength measurement method described above in the case of sealing under the aforementioned 220℃ sealing conditions, but at room temperature or high temperature (high temperature is measured after leaving at 60℃ for 3 minutes), the X-axis is the stroke (distance) for pulling the sealing portion in the TD direction, and the Y-axis is the sealing strength. As the stroke increases, the sealing strength curve increases, and the stroke (distance) at which the sealing strength value reaches the maximum is evaluated as the maximum stroke. If evaluated at room temperature, it is the room temperature maximum stroke, and if evaluated at high temperature, it is the high temperature maximum stroke.

[0116] As mentioned above, the maximum stroke and energy (integral value between the stroke axis and the sealing strength graph) are important items for evaluating the maintenance characteristics (reliability) of the sealing strength. That is, even if the peak value of the maximum sealing strength is large, the sealing strength maintenance characteristics cannot be determined with the maximum sealing strength alone. However, depending on the maximum stroke, it is possible to know how quickly the maximum sealing strength reaches the maximum value and then drops. In addition, it is possible to evaluate whether the sealing strength is well maintained, i.e., reliable, through the area (integral value) formed by the stroke and sealing strength curves.

[0117] For medium- to large-sized batteries such as electric vehicles, there are many molding models in the MD direction, and since the MD direction sealing characteristics are generally superior to the TD direction sealing characteristics, the maintenance of sealing strength in the TD direction sealing (Pouch to Pouch sealing), which has relatively weaker sealing characteristics than the MD direction sealing (Tap to Pouch sealing), becomes a more important measurement interest. Accordingly, the change in sealing strength according to the stroke change in the TD direction was measured and shown in Table 3 below.

[0118] Leakage Test

[0119] Examples and Comparative Examples After forming the secondary battery pouch film with a molding machine (6 mm forming), a total of 20 simple battery pack samples were produced (200 mm X 110 mm). A tab (Sumitomo Corporation product) was inserted into the battery pack sample. After inserting the simple battery pack sample into the jig, the upper and lower gaps (6 mm) of the jig were fixed and combined. Fig. 2 is a schematic diagram of the jig used in this experimental example, and Fig. 3 is a photograph showing the battery pack sample combined with the jig in this experimental example.

[0120] After 90 days under 80℃ conditions, the presence of leakage was evaluated (long-term reliability evaluation), and the number of cases where leakage occurred (Fail) out of a total of 20 was measured and shown in Table 4 below.

[0121] <Evaluation Results>

[0122] Table 2 below shows the results of the maximum sealing strength test when sealing at 220°C sealing conditions for the examples and comparative examples.

[0123] [Table 2]

[0124]

[0125] In addition, the energy values ​​and maximum strokes of the sealed pouch at room temperature and high temperature are listed in Table 3 below.

[0126] [Table 3]

[0127]

[0128] As shown in Table 3, the room temperature energy, high temperature energy, room temperature maximum stroke, and high temperature maximum stroke of the examples are all significantly superior to those of the comparative examples, indicating that the sealing strength maintenance characteristics at high temperatures are superior as well as the sealing strength maintenance characteristics at room temperature.

[0129] Table 4 shows the results of the leakage test measurements of the examples and comparative examples.

[0130] [Table 4]

[0131]

[0132] As shown in Table 4, the leakage test results show that the number of leakages in the examples is significantly less than in the comparative examples, indicating that the battery pack has excellent long-term reliability at high temperatures and thus excellent battery safety.

[0133] While non-limiting and exemplary embodiments of the present invention have been described above, the technical spirit of the present invention is not limited to the accompanying drawings or the above description. Those skilled in the art will readily appreciate that various modifications are possible without departing from the spirit and scope of the present invention, and such modifications are within the scope of the claims of the present invention.

[0134] The secondary battery pouch film of the present invention is useful as a medium- to large-sized secondary battery pouch for electric vehicles or energy storage devices that require safety, particularly high-temperature safety.

Claims

1. As a secondary battery pouch film, It is composed of a laminate in which at least an outer layer, a barrier layer, and a sealant layer are sequentially laminated, wherein the sealant layer includes a polypropylene (PP) layer, and the thickness ratio of the polypropylene (PP) layer among the sealant layers is greater than 0.

5. The yield strength of the sealant layer in the MD direction (N / mm) 2 ) is 17.50~19.99, and the yield strength in the TD direction (N / mm 2 ) is 17.00~19.99, A secondary battery pouch film characterized in that the glass transition temperature (Tg) of the sealant layer is -20°C to -10°C.

2. In paragraph 1, The yield strength of the sealant layer in the MD direction (N / mm) 2 ) and yield strength in TD direction (N / mm 2 ) is 34.5 or more and 39.9 or less.

3. In paragraph 2, The yield strength of the sealant layer in the MD direction (N / mm) 2 ) is the yield strength in the TD direction (N / mm 2 ) is characterized by a large secondary battery pouch film.

4. In paragraph 1, The secondary battery pouch film is characterized in that the maximum room temperature sealing strength measured when sealed under 220°C sealing conditions as measured by the following method is 150 N or more and 205 N or less in both the MD direction and the TD direction. [Method for measuring maximum room temperature sealing strength when sealing under 220℃ sealing conditions] After manufacturing the secondary battery pouch film to 100mm X 200mm, fold it in half, seal it, and then cut it to a width of 15mm perpendicular to the sealing direction to manufacture a specimen. The sealing conditions are seal bar width 200mm x seal thickness 10mm, sealing time 2.0 seconds, 0.2Mpa, and temperature 220℃. The sealing strength of the specimen in the MD and TD directions was measured at room temperature using a sealing strength measuring device. The sealing conditions were a test speed of 10 mpm and a grip gap of 30 mm. The maximum value among the sealing strength measurements is the maximum sealing strength.

5. In paragraph 1, The secondary battery pouch film is characterized in that the maximum high-temperature sealing strength measured value (the sealing strength measured after leaving it at 60°C for 3 minutes) when sealed under sealing conditions at 220°C measured by the following method is 115 N or more and 170 N or less in at least one direction among the MD direction and the TD direction. [Method for measuring maximum high-temperature sealing strength when sealing under 220℃ sealing conditions] After manufacturing the secondary battery pouch film to 100mm X 200mm, fold it in half, seal it, and then cut it to a width of 15mm perpendicular to the sealing direction to manufacture a specimen. The sealing conditions are seal bar width 200mm x seal thickness 10mm, sealing time 2.0 seconds, 0.2Mpa, and temperature 220℃. The sealing strength of at least one of the MD and TD directions of the specimen is measured using a sealing strength measuring device under conditions of 60℃ after leaving it for 3 minutes. The sealing conditions are a test speed of 10 mpm and a grip gap of 30 mm. The maximum value among the sealing strength measurements is the maximum sealing strength.

6. In paragraph 1, The secondary battery pouch film is characterized in that the maximum sealing strength parameter below is 1.1 or more and 1.8 or less when sealed under sealing conditions at 220°C. [Maximum sealing strength parameter] (Maximum sealing strength in MD direction at room temperature X Maximum sealing strength in TD direction at room temperature) / (Maximum sealing strength in MD direction at high temperature X Maximum sealing strength in TD direction at high temperature) 7. In paragraph 1, The secondary battery pouch film is characterized in that the room temperature energy in the TD direction is 2.0 to 3.0 KN x mm when sealed under sealing conditions of 220°C as measured by the following method. [Measurement of room temperature energy in the TD direction when sealed under 220℃ sealing conditions] After manufacturing the secondary battery pouch film to 100mm X 200mm, fold it in half, seal it, and then cut it to a width of 15mm perpendicular to the sealing direction to manufacture a specimen. The sealing conditions are seal bar width 200mm x seal thickness 10mm, sealing time 2.0 seconds, 0.2Mpa, and temperature 220℃. The change in sealing strength was measured by pulling the specimen in the TD direction with a sealing strength measuring device at room temperature. The measurement conditions were a test speed of 10 mpm and a grip gap of 30 mm. When the X-axis is the stroke (distance) that pulls the sealing part in the TD direction and the Y-axis is the sealing strength, the area between the graph of the change in sealing strength according to the stroke and the X-axis that represents the stroke - the integral value of the graph of the change in sealing strength according to the stroke - is defined as the room temperature energy, and the integration is from the stroke range of 0 mm to 20 mm.

8. In paragraph 1, The secondary battery pouch film is characterized in that the high temperature energy in the TD direction is 1.5 to 2.5 KN x mm when sealed under sealing conditions of 220°C as measured by the following method. [Measurement of high temperature energy in the TD direction when sealing under 220℃ sealing conditions] After manufacturing the secondary battery pouch film to 100mm X 200mm, fold it in half, seal it, and then cut it to a width of 15mm perpendicular to the sealing direction to manufacture a specimen. The sealing conditions are seal bar width 200mm x seal thickness 10mm, sealing time 2.0 seconds, 0.2Mpa, and temperature 220℃. The change in sealing strength is measured by pulling the specimen in the TD direction with a sealing strength measuring instrument under high temperature conditions after leaving it at 60℃ for 3 minutes. The measurement conditions are a test speed of 10 mpm and a grip gap of 30 mm. When the X-axis is the stroke (distance) that pulls the sealing part in the TD direction and the Y-axis is the sealing strength, the area between the graph of the change in sealing strength according to the stroke and the X-axis that represents the stroke - the integral value of the graph of the change in sealing strength according to the stroke - is defined as the high temperature energy, and the integration is from the stroke range of 0 mm to 20 mm.

9. In paragraph 1, The secondary battery pouch film is characterized in that the difference between the room temperature energy and the high temperature energy in the TD direction is 0.4 to 0.6 KN x mm when the secondary battery pouch film is sealed under sealing conditions of 220°C as measured by the following method. [Measurement of room temperature energy and high temperature energy in the TD direction when sealed under 220℃ sealing conditions] After manufacturing the secondary battery pouch film to 100mm X 200mm, fold it in half, seal it, and then cut it to a width of 15mm perpendicular to the sealing direction to manufacture a specimen. The sealing conditions are seal bar width 200mm x seal thickness 10mm, sealing time 2.0 seconds, 0.2Mpa, and temperature 220℃. The change in sealing strength is measured by pulling the specimen in the TD direction with a sealing strength measuring instrument under room temperature conditions or high temperature conditions after leaving it at 60℃ for 3 minutes. The measurement conditions are a test speed of 10 mpm and a grip gap of 30 mm. When the X-axis is the stroke (distance) that pulls the sealing part in the TD direction and the Y-axis is the sealing strength, the area between the graph of the change in sealing strength according to the stroke and the X-axis that represents the stroke - the integral value of the graph of the change in sealing strength according to the stroke - is defined as room temperature energy or high temperature energy, and the integration is from the stroke range of 0 mm to 20 mm. Energy measured under room temperature conditions is room temperature energy, and energy measured under high temperature conditions is high temperature energy.

10. In paragraph 1, The secondary battery pouch film is characterized in that the maximum stroke at room temperature in the TD direction is 15 to 25 mm when sealed under sealing conditions at 220°C as measured by the following method. [Measurement of maximum stroke at room temperature in the TD direction when sealed under 220℃ sealing conditions] After manufacturing the secondary battery pouch film to 100mm X 200mm, fold it in half, seal it, and then cut it to a width of 15mm perpendicular to the sealing direction to manufacture a specimen. The sealing conditions are seal bar width 200mm x seal thickness 10mm, sealing time 2.0 seconds, 0.2Mpa, and temperature 220℃. The change in sealing strength was measured by pulling the specimen in the TD direction with a sealing strength measuring device at room temperature. The measurement conditions were a test speed of 10 mpm and a grip gap of 30 mm. When the X-axis is the stroke (distance) for pulling the sealing part in the TD direction and the Y-axis is the sealing strength, the sealing strength curve increases as the stroke increases, and the stroke (distance) at which the sealing strength value reaches the maximum is evaluated as the maximum stroke.

11. In paragraph 1, The secondary battery pouch film is characterized in that the high temperature maximum stroke in the TD direction is 18 to 24 mm when sealed under sealing conditions at 220°C as measured by the following method. [Measurement of high temperature maximum stroke in TD direction when sealed under 220℃ sealing conditions] After manufacturing the secondary battery pouch film to 100mm X 200mm, fold it in half, seal it, and then cut it to a width of 15mm perpendicular to the sealing direction to manufacture a specimen. The sealing conditions are seal bar width 200mm x seal thickness 10mm, sealing time 2.0 seconds, 0.2Mpa, and temperature 220℃. The change in sealing strength is measured by pulling the specimen in the TD direction with a sealing strength measuring instrument under high temperature conditions after leaving it at 60℃ for 3 minutes. The measurement conditions are a test speed of 10 mpm and a grip gap of 30 mm. When the X-axis is the stroke (distance) for pulling the sealing part in the TD direction and the Y-axis is the sealing strength, the sealing strength curve increases gradually as the stroke increases, and the stroke (distance) at which the sealing strength value reaches the maximum is evaluated as the maximum stroke.

12. A method for manufacturing a secondary battery pouch film, wherein at least an outer layer, a barrier layer, and a sealant layer are sequentially laminated, and the sealant layer includes a polypropylene (PP) layer. Including a step of manufacturing the polypropylene (PP) layer among the sealant layers so that the thickness ratio is greater than 0.5, The yield strength of the sealant layer in the MD direction (N / mm) 2 ) is 17.50~19.99, and the yield strength in the TD direction (N / mm 2 ) is 17.00~19.99, A method for manufacturing a secondary battery pouch film, characterized in that the glass transition temperature (Tg) of the sealant layer is -20°C to -10°C.

13. A secondary battery characterized by being exteriorized with a secondary battery pouch film according to any one of claims 1 to 11.

14. In paragraph 13, A secondary battery characterized in that the secondary battery is for an electric vehicle or an energy storage device.

15. A method for manufacturing a secondary battery, A method for manufacturing a secondary battery, characterized by comprising a step of enclosing a secondary battery with a secondary battery pouch film according to any one of claims 1 to 11.

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