Pouch film and pouch-type secondary battery case comprising same

Abstract

The present invention relates to a pouch film comprising an inner sealant layer, a barrier layer comprising aluminum, and an outer layer, which are sequentially stacked, wherein the outer layer comprises a first outer layer and a second outer layer disposed between the first outer layer and the barrier layer, and RTD / RMD is in the range of 1.5 to 3.0.

Description

Pouch film and pouch-type secondary battery case including the same

[0001] Cross-citation with related applications

[0002] The present invention claims the benefit of priority based on Korean Patent Application No. 10-2024-0191754 filed on December 19, 2024, and includes all contents disclosed in the document of said Korean patent application as part of this specification.

[0003]

[0004] Technology field

[0005] The present invention relates to a pouch film and a pouch-type secondary battery case including the same.

[0006]

[0007] Secondary batteries are capable of repeated charging and discharging and can be classified into cylindrical, prismatic, and pouch-type secondary batteries depending on their structure and manufacturing method. Among these, pouch-type secondary batteries are in which an electrode assembly (cell) is embedded in a pouch made of a metal laminate sheet; they are widely used in energy storage devices such as automotive batteries due to their relatively simple structure and relatively high capacity per unit volume. The pouch, which serves as the case for the pouch-type secondary battery, is manufactured by forming a cup portion through molding, such as press processing, on a flexible pouch film. Once the cup portion is formed, the electrode assembly is housed in the receiving space of the cup portion, and the sealing portion is sealed to manufacture the secondary battery. In this way, the electrode assembly sealed by the pouch film can be substantially protected from external exposure.

[0008] When the above pouch film forms a cup portion through molding, such as press processing, to secure a space for the electrode assembly, the cup portion must be formed to match the shape of the electrode assembly. In particular, stress may be concentrated at the edges and corners of the cup portion, so if it is not properly molded, the film may tear or deform. Therefore, a process to check whether the molding is done well is required, and at this time, the R value after molding can be used as a measure to check the molding quality of the cup portion.

[0009] The R-value after forming is an important indicator for evaluating the forming quality of a pouch film, representing the radius of curvature that indicates how well the corner portions, including the edges and vertices of the cup portion of the pouch film, have been formed. If the R-value after forming is too small (the curvature is too steep), the pouch film may become too thin or tear at the corner portions. Conversely, if the R-value after forming is too large (the curvature is too gentle), the cup portion of the pouch film may not fit well with the electrode assembly, resulting in inefficient use of internal space. However, if the R-value after forming is appropriate, the pouch film has sufficient curvature even at the corner portions, including the edges and vertices, to distribute stress. Therefore, by maintaining the R-value after forming appropriately, the pouch film can be accurately fitted to the electrode assembly, and the durability and performance of the film can be guaranteed.

[0010] Meanwhile, when forming a pouch film to seal long cells in which the long side of the electrode assembly is significantly longer than the short side, there was a problem in which an undesirable post-forming R-value appeared at the long side of the cup portion. Since pouch-type secondary batteries manufactured using pouch films with such inappropriate post-forming R-values ​​may cause issues in terms of battery performance, safety, lifespan, or space efficiency, it is important to secure an appropriate post-forming R-value during the formation of the pouch film.

[0011]

[0012] The problem to be solved by the present invention is to provide a pouch film with improved moldability for a long cell in which the length of the long side is significantly longer than the length of the short side, and a pouch-type secondary battery case including the same.

[0013]

[0014] 1. The present invention provides a pouch film comprising an inner sealant layer sequentially stacked; a barrier layer including aluminum; and an outer layer, wherein the outer layer comprises a first outer layer and a second outer layer disposed between the first outer layer and the barrier layer, and wherein the slope derived from a graph derived according to the following measurement method satisfies the following Equation 1.

[0015] [Equation 1]

[0016] 1.5≤ R TD / R MD ≤3.0

[0017] The above R TD is the slope of the increasing section between the upper yield point of the outer layer measured when pulling the outer layer film in the TD direction and the strength at a stroke of 25 mm, and

[0018] The above R MD is the slope of the increasing section between the upper yield point of the outer layer measured when the outer layer film is pulled in the MD direction and the strength at a stroke of 25 mm.

[0019] [measurement method]

[0020] After preparing a specimen that does not include an inner sealant layer and a barrier layer with a width of 15 mm by peeling off the outer layer of the above pouch film, the specimen is fixed between two jigs of a tensile testing machine (UTM) with an initial jig gap of 30 mm at room temperature, and the stroke (mm) and strength (N) of the specimen are measured while pulling the specimen in the TD and MD directions, respectively, at a measurement speed of 50 mm / min until fracture. The X-axis of the graph derived from the measured values ​​is the stroke (mm), and the Y-axis is the strength (N). At this time, the R TD and R MD This is the measured slope of the straight line connecting the upper yield point and the strength at a stroke of 25 mm.

[0021] 2. The present invention provides a pouch film according to 1. above, wherein the strokes in the TD and MD directions corresponding to the breaking strength of the outer layer are each independently 20 mm or more and 100 mm or less.

[0022] 3. The present invention provides a pouch film according to 1. or 2. above, wherein the first outer layer comprises one or more compounds selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyethylene naphthalate.

[0023] 4. The present invention provides a pouch film in which, in any one of 1 to 3 above, the second outer layer comprises one or more compounds selected from the group consisting of polyamide compounds, polyester compounds, polyolefin compounds and polyacrylic compounds.

[0024] 5. The present invention provides a pouch film in which, in any one of 1 to 4 above, the inner sealant layer comprises one or more compounds selected from the group consisting of polypropylene, polyethylene, polyvinyl chloride, polyurethane, polybutylene, and copolymers derived from monomers derived from ethylene or propylene and monomers derived from alpha-olefins.

[0025] 6. In any one of 1 to 5 above, the present invention is such that Formula 1 is 1.6 < R TD / R MD Provides a pouch film that is ≤2.7.

[0026] 7. The present invention provides a pouch film in which, in any one of 1 to 6 above, the angle between the RTD and the RMD is 10 degrees or more and 70 degrees or less.

[0027] 8. The present invention provides a pouch film having an average R value after molding, measured by a 3D shape analyzer, of 1 or more and 4 or less, in any one of 1 to 7 above.

[0028] 9. The present invention provides a pouch film in any one of 1 to 8 above, wherein the pouch film comprises a cup portion, and the length ratio of the long side portion to the short side portion of the cup portion is 2.0 or more and 8.0 or less:1.

[0029] 10. The present invention provides a pouch-type secondary battery case comprising a pouch film according to any one of 1 to 9 above.

[0030]

[0031] The pouch film of the present invention can have the effect of improving moldability so that, when housing an electrode assembly within the pouch film, the error in the R value after molding of the pouch film is reduced, thereby allowing an electrode assembly of a desired size to be accommodated without error in the accommodating space.

[0032]

[0033] FIG. 1 is a schematic diagram showing the composition of the pouch film of the present invention.

[0034] Figure 2 is a graph showing the results of the tensile elongation test in the MD direction of the outer layer of Example 1.

[0035] Figure 3 is a graph showing the tensile elongation test results in the TD direction of the outer layer of Example 1.

[0036] Figure 4 is a graph showing the results of the tensile elongation test in the MD direction of the outer layer of Example 3.

[0037] Figure 5 is a graph showing the tensile elongation test results in the TD direction of the outer layer of Example 3.

[0038] Figure 6 is a graph showing the results of the tensile elongation test in the MD direction of the outer layer of Comparative Example 1.

[0039] Figure 7 is a graph showing the tensile elongation test results in the TD direction of the outer layer of Comparative Example 1.

[0040] Figure 8 is a graph showing the results of the tensile elongation test in the MD direction of the outer layer of Comparative Example 3.

[0041] Figure 9 is a graph showing the tensile elongation test results in the TD direction of the outer layer of Comparative Example 3.

[0042] Figure 10 shows the position where the R value is measured after molding the long side of the pouch film of the present invention.

[0043]

[0044] Hereinafter, the present invention will be described in more detail to aid in understanding the invention.

[0045] Terms and words used in this specification and claims shall not be interpreted as being limited to their ordinary or dictionary meanings, but shall be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0046] The terms used in this specification are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0047] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0048] In the present specification, when each layer of a secondary battery pouch is included, it is not necessarily composed only of that layer, but may include additional layers.

[0049] In this specification, being formed on a specific layer includes not only being formed directly on the layer but also being formed after interposing an additional layer.

[0050] In this specification, the extrusion lamination coating (EC) layer refers to an extruded layer of a resin, such as a polyolefin resin, preferably a polypropylene resin, extruded for bonding with a barrier layer as a part layer of the sealant layer. The extrusion lamination (EC) layer of the sealant layer is located on the barrier layer side with respect to the following polypropylene resin layer.

[0051] In this specification, the polypropylene (PP) layer of the sealant layer serves as a core resin layer forming the sealant layer and performs a sealing function, and may consist of one or more layers made of polypropylene-based resin. It is contrasted with the aforementioned extrusion coating (EC) layer for bonding with the barrier layer and is located on the inner side of the pouch film (i.e., opposite side of the barrier layer) relative to the aforementioned extrusion coating (EC) layer.

[0052]

[0053] Pouch film

[0054] The present invention provides a pouch film comprising an inner sealant layer sequentially stacked; a barrier layer containing aluminum; and an outer layer, wherein the outer layer comprises a first outer layer and a second outer layer disposed between the first outer layer and the barrier layer, and wherein the slope derived from a graph derived according to the following measurement method satisfies the following Equation 1.

[0055] [Equation 1]

[0056] 1.5≤ R TD / R MD ≤3.0

[0057] The above R TD is the slope of the increasing section between the upper yield point of the outer layer measured when pulling the outer layer film in the TD direction and the strength at a stroke of 25 mm, and

[0058] The above R MD is the slope of the increasing section between the upper yield point of the outer layer measured when the outer layer film is pulled in the MD direction and the strength at a stroke of 25 mm.

[0059] [measurement method]

[0060] After preparing a specimen that does not include an inner sealant layer and a barrier layer with a width of 15 mm by peeling off the outer layer of the above pouch film, the specimen is fixed between two jigs of a tensile testing machine (UTM) with an initial jig gap of 30 mm at room temperature, and the stroke (mm) and strength (N) of the specimen are measured while pulling the specimen in the TD and MD directions, respectively, at a measurement speed of 50 mm / min until fracture. The X-axis of the graph derived from the measured values ​​is the stroke (mm), and the Y-axis is the strength (N). At this time, the R TD and R MD This is the measured slope of the straight line connecting the upper yield point and the strength at a stroke of 25 mm.

[0061]

[0062] The outer layer of the pouch film serves to prevent contact with the outside and to seal the electrode assembly contained within, and thus requires excellent processability and moldability. These processability and moldability are influenced by mechanical properties, particularly the mechanical properties of the outer layer. The inventors of the present invention discovered that in the case of conventional pouch films, the molding process was performed to accommodate an electrode assembly corresponding to a long cell, where the length of the long side is significantly longer than the length of the short side, in order to accommodate said electrode assembly. However, they found that the R value after molding of the long side did not reach the desired level, resulting in difficulties in the process, such as the occurrence of an uneven gap between the cup portion of the pouch film and the electrode assembly. To solve the above problems, the inventors derived the relationship between the mechanical strength of the outer layer in the TD and MD directions and the R value after molding, and controlled it within a specific range, thereby developing a pouch film capable of improving moldability while possessing excellent mechanical properties.

[0063] FIG. 1 shows the composition of a pouch film of the present invention. The pouch film of the present invention includes an inner sealant layer, an outer layer, and a barrier layer containing aluminum between the inner sealant layer and the outer layer. Additionally, the outer layer includes a first outer layer and a second outer layer.

[0064] The outer layer may be the outermost layer of the pouch film for the exterior of the lithium secondary battery, and the outer layer may have an appropriate thickness within a range that ensures sufficient mechanical strength and sufficient moldability as an exterior material. For example, the thickness of the outer layer may be 12㎛ or more, 15㎛ or more, 17㎛ or more, 20㎛ or more, 22㎛ or more, 25㎛ or more, 27㎛ or more, 30㎛ or more, 32㎛ or more, 35㎛ or more, 37㎛ or more, 70㎛ or less, 50㎛ or less, or 40㎛ or less. When the above range is satisfied, the dielectric breakdown voltage may be maintained at a high level.

[0065] The above outer layer comprises a first outer layer and a second outer layer, and the first outer layer may comprise one or more compounds selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyethylene naphthalate.

[0066] In addition, the second outer layer, which is a heat-resistant resin layer having a melting point greater than the heat sealing temperature of the sealant layer, may comprise one or more compounds selected from the group consisting of polyamide compounds, polyester compounds, polyolefin compounds, and polyacrylic compounds.

[0067] According to one embodiment of the present invention, the outer layer may be composed of a laminated film of a first outer layer (polyethylene terephthalate) and a second outer layer (nylon). In this case, the thinner the thickness of the first outer layer and the thicker the thickness of the second outer layer, the more advantageous it is for moldability. However, the thinner the thickness of the first outer layer, the more disadvantageous it may be in terms of dielectric breakdown voltage. In this regard, exemplarily, the thickness of the second outer layer may be 10 μm or more, 12 μm or more, 15 μm or more, 20 μm or more, 40 μm or less, 35 μm or less, 30 μm or less, 27 μm or less, or 25 μm or less, and the thickness of the first outer layer may be 5 μm or more, 8 μm or more, 10 μm or more, 12 μm or more, 30 μm or less, 25 μm or less, 20 μm or less, 17 μm or less, or 15 μm or less.

[0068] In addition, the outer layer of the pouch film of the present invention satisfies the slope of the increasing section between the upper yield point and the strength when the stroke is 25 mm, as shown in Equation 1 below.

[0069] [Equation 1]

[0070] 1.5≤ R TD / R MD ≤3.0

[0071] In the above Equation 1, R TDis the slope of the increasing section between the upper yield point of the outer layer measured when pulling the outer layer film in the TD direction and the strength at a stroke of 25 mm, and

[0072] The above R MD is the slope of the increasing section between the upper yield point of the outer layer measured when the outer layer film is pulled in the MD direction and the strength at a stroke of 25 mm.

[0073] Conventionally, when manufacturing long cells where the length of the long side is significantly longer than the length of the short side, if the slopes in the TD and MD directions between the upper yield point and the fracture strength of the outer layer of the pouch film are similar, the R-value of the long side of the cup portion of the molded pouch film tended to increase after molding. In other words, when using an outer layer film containing an isotropic material with identical characteristics in both the TD and MD directions during the manufacturing of long cells, a problem arose in which the molding quality was so low that the cup portion of the pouch film could not accommodate the battery body.

[0074] The pouch film of the present invention includes an anisotropic material in the outer layer that is controlled such that the deviation in the slopes of the TD and MD directions, respectively, between the upper yield point and the fracture strength widens to a level greater than a certain threshold. By including such an outer layer in the pouch film, even if a cup portion is formed where the long side is significantly longer than the short side through processing and molding, the R value after molding of both the short and long sides is identical to the designed value, thereby providing an effect of overall improved formability. Here, the upper yield point refers to the strength (N) at which the outer layer subjected to force can no longer maintain elasticity and begins to deform permanently, and the section prior to the upper yield point can recover to an elastic section. Additionally, the fracture strength refers to the strength at which the outer layer fractures when force is applied. Furthermore, the stroke refers to the length of the specimen that increases due to deformation of the specimen when pressure is applied.

[0075] Referring to Figures 2 and 3, even when pressure is continuously applied, a section where the stroke changes rapidly occurs in a section where the stroke changes little, and the point where the stroke changes rapidly corresponds to the upper yield point. In addition, when pressure is continuously applied, the point where the measured specimen fractures as the stroke changes corresponds to the fracture strength.

[0076] Meanwhile, when the slope between the upper yield point and the fracture strength was measured multiple times, a problem occurred in which a deviation in the slope occurred as the number of measurements and the stroke increased. In order to measure accurate parameter values, the slope from the upper yield point to the strength was measured based on the strength measured at a stroke of 25 mm, which is the section before the deviation in slope occurred.

[0077] According to one embodiment of the present invention, the R TD / R MD It can be 1.5 or more and 3.0 or less. For example, it may be 1.50 or higher, 1.51 or higher, 1.53 or higher, 1.55 or higher, 1.57 or higher, 1.59 or higher, 1.60 or higher, 1.61 or higher, 1.63 or higher, 1.64 or higher, 1.65 or higher, 1.67 or higher, 1.69 or higher, 1.70 or higher, 1.71 or higher, 1.73 or higher, 1.75 or higher, 1.77 or higher, 1.79 or higher, 1.80 or higher, 1.81 or higher, 1.83 or higher, 1.86 or higher, 1.87 or higher, or 1.89 or higher, and also 3.0 or lower, 2.9 or lower, 2.8 or lower, 2.7 or lower, 2.6 or lower, 2.5 or lower, 2.4 or lower, 2.3 or lower, 2.2 or lower, 2.1 or lower, It may be 2.0 or less, or 1.9 or less. More specifically, the above R TD / R MD It may be greater than 1.6 and less than or equal to 2.7.

[0078] The ratio (R) of the slope of the strength zone at a stroke of 25 mm and the upper yield point of the outer layer measured when pulling in the TD direction, and the slope of the strength zone at a stroke of 25 mm measured when pulling in the MD direction. TD / R MD If the above numerical range is not satisfied, the R value of the long side of the cup portion of the pouch film after molding appears high, so the battery body portion cannot be properly accommodated, and the stress generated during the molding process cannot be uniformly distributed in the TD direction, so excessive stress may be concentrated in a specific area.

[0079] Referring to Figures 2 and 3, it can be seen that in the case of Figure 2, the difference in slope between the MD direction and the TD direction is large, and in the case of Figure 3, the difference in slope between the MD direction and the TD direction is small.

[0080] Meanwhile, the above R of the present invention TD / R MD The ratio of may be influenced by the draw ratio of the first outer layer (polyethylene terephthalate) and the second outer layer (nylon), temperature conditions during the manufacturing process of the pouch film, pressure conditions, tensile speed, extrusion speed, type of resin, and orientation. By controlling the above conditions, the present invention [increases] R TD / R MDThe ratio can be controlled, thereby providing a pouch film that has optimal moldability and a maximum molding length capable of accommodating an electrode assembly of a desired size without error in the accommodation space. For example, the above temperature conditions can be adjusted to 10 ℃ or higher, 11 ℃ or higher, 13 ℃ or higher, 15 ℃ or higher, 17 ℃ or higher, 19 ℃ or higher, 20 ℃ or higher, 21 ℃ or higher, 23 ℃ or higher, 25 ℃ or higher, 40 ℃ or lower, 39 ℃ or lower, 37 ℃ or lower, 35 ℃ or lower, 33 ℃ or lower, 31 ℃ or lower, and 30 ℃ or lower, and the tensile speed can be adjusted to 30 mm / min or higher, 35 mm / min or higher, 40 mm / min or higher, 45 mm / min or higher, 50 mm / min or higher, 70 mm / min or lower, 65 mm / min or lower, 60 mm / min or lower, and 55 mm / min or lower.

[0081] According to one embodiment of the present invention, the strokes in the TD and MD directions corresponding to the fracture strength of the outer layer may each be independently 20 mm or more and 100 mm or less. When the breaking strength of the outer layer included in the pouch film of the invention is measured based on the measurement method described above, the strokes in the TD and MD directions may each independently be 20 mm or more and 100 mm or less, and exemplarily, 20 mm or more, 21 mm or more, 23 mm or more, 25 mm or more, 27 mm or more, 30 mm or more, 31 mm or more, 33 mm or more, 35 mm or more, 37 mm or more, 39 mm or more, 40 mm or more, 41 mm or more, 43 mm or more, 45 mm or more, 47 mm or more, 49 mm or more, 50 mm or more, 51 mm or more, 53 mm or more, 55 mm or more, 57 mm or more, 59 mm or more, 60 mm or more, 100 mm or less, 97 mm or less, 95 mm or less, 93 mm or less, 91 mm or less, 90 mm or less, 89 mm or less, 87 mm or less, The stroke may be 85 mm or less, 83 mm or less, 81 mm or less, or 80 mm or less. Each of the strokes refers to the length of deformation until fracture occurs when force is applied independently in the MD direction and the TD direction, and a longer stroke implies a higher elongation. Accordingly, when the stroke satisfies the above numerical range, excellent formability can be secured.

[0082] The sealant layer may be the innermost layer of the pouch film for the exterior of the lithium secondary battery. That is, the sealant layer may come into direct contact with the battery body (e.g., electrode, separator, and / or electrolyte). Therefore, the sealant layer must have excellent electrolyte resistance and excellent insulation properties. To this end, the sealant layer may include at least a polyolefin resin. The polyolefin resin has excellent electrolyte resistance and excellent insulation properties, and accordingly, the sealant layer containing the polyolefin resin may also have excellent electrolyte resistance and excellent insulation properties derived from the polyolefin resin.

[0083] The above polyolefin resin may include, for example, a polyolefin derived from an olefin or its derivative, a copolymer thereof, or a blend comprising at least one of these. For example, the above polyolefin resin may include one or more selected from the group consisting of polyethylene, polypropylene, polybutylene, copolymers derived from monomers derived from ethylene and / or propylene and monomers derived from alpha-olefins, or blends thereof.

[0084] The thickness of the sealant layer may, for example, be 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, or 60 μm or less, and if the above numerical range is satisfied, it may have excellent electrolyte resistance and insulation properties.

[0085] According to one embodiment of the present invention, the sealant layer may be composed of two or more layers to diversify its functions. As a specific example, the sealant layer may include a first sealant layer disposed on the barrier layer and a second sealant layer disposed on the first sealant layer. Here, the first sealant layer may be a layer that assists in the adhesion between the barrier layer and the second sealant layer while simultaneously enhancing the function as a sealant layer, and the second sealant layer may be a layer that constitutes the innermost sealant layer of the pouch film and performs the function of sealing while simultaneously preventing leakage of a secondary battery, particularly a non-aqueous electrolyte. The first sealant layer may be an extrusion lamination coating (EC) layer (mainly an extruded polypropylene layer), and the second sealant layer may be a polypropylene (PP) layer resin, preferably an unoriented polypropylene (CPP) layer, located below the first sealant layer (inner side relative to the pouch film). In this case, for example, the thickness of the unoriented polypropylene (CPP) layer of the sealant layer may be, for example, 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, 80 μm or less, 70 μm or less, or 60 μm or less, and the thickness of the polypropylene (PP) layer of the sealant layer may be, for example, 0 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, 60 μm or less, 50 μm or less, or 40 μm or less.

[0086] In addition, according to one embodiment of the present invention, the polypropylene (PP) layer of the sealant layer may contain various additives (rubber, elastomer, slip agent, etc.) depending on the required physical properties.

[0087] The barrier layer may be an intermediate layer of the pouch film for the exterior of the lithium secondary battery (e.g., a layer disposed between the outer layer and the sealant layer) and may serve to prevent the intrusion of gas and / or moisture. Although the type of the barrier layer is not particularly limited, it may include at least one selected from the group consisting of aluminum, stainless steel, copper, titanium, and alloys thereof, and specifically, may include aluminum.

[0088] The barrier layer may have an appropriate thickness within a range that effectively prevents the intrusion of the aforementioned gas and / or moisture while ensuring sufficient moldability. For example, the thickness of the barrier layer may be 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, 55 μm or more, 60 μm or more, 150 μm or less, 140 μm or less, 130 μm or less, 125 μm or less, 120 μm or less, 115 μm or less, 110 μm or less, 105 μm or less, 100 μm or less, 95 μm or less, 90 μm or less, 85 μm or less, or 80 μm or less.

[0089] According to one embodiment of the present invention, the R TD and R MD The angle between them may be 20 degrees or more and 70 degrees or less. More specifically, the above R TD and R MD The angle between may be 20 degrees or more, 25 degrees or more, 30 degrees or more, 35 degrees or more, 40 degrees or more, or 45 degrees or more, and may also be 70 degrees or less, 65 degrees or less, 60 degrees or less, 55 degrees or less, or 50 degrees or less. The above R TD and R MD represents the slope in the TD and MD directions explained earlier, indicating the relationship between the pressure applied to the outer layer and the stroke, and signifies a factor that allows verification of the extent of deformation in length relative to the applied pressure. Here, the above R TD and R MDWhen the angle between satisfies the above numerical range, the tensile elongation in the TD direction is significantly greater than the tensile elongation in the MD direction, allowing the pouch film to stretch more in the TD direction. This enables the thickness of the pouch film to stretch evenly in the TD direction during the molding process, thereby ensuring that the thickness of the pouch film remains uniform after molding. Furthermore, by uniformly distributing the stress generated during the molding process in the TD direction, it is possible to prevent excessive stress from concentrating in specific areas. Thus, the above R TD and R MD The numerical range of the angle between them allows for obtaining a desired level of post-molding R value on the long side of the cup portion of the pouch film formed through processing and molding.

[0090] According to one embodiment of the present invention, the ratio of the length of the long side and the short side of the cup portion of the pouch film may be 2.0 or more and 8.0 or less:1. More specifically, the length ratio of the long side to the short side of the cup portion of the pouch film is 2.0 or more:1, 2.1 or more:1, 2.2 or more:1, 2.3 or more:1, 2.4 or more:1, 2.5 or more:1, 2.6 or more:1, 2.7 or more:1, 2.8 or more:1, 2.9 or more:1, 3.0 or more:1, 3.1 or more:1, 3.2 or more:1, 3.3 or more:1, 3.4 or more:1, 3.5 or more:1, 3.6 or more:1, 3.7 or more:1, 3.8 or more:1, 3.9 or more:1, 4.0 or more:1, 4.1 or more:1, 4.2 or more:1, 4.3 or more:1, 4.4 or more:1, 4.5 or more:1, 4.6 or more:1, 4.7 or more:1, 4.8 It may be 8.0 or higher:1, 4.9 or higher:1, 5.0 or higher:1, or 5.1 or higher:1, and also 8.0 or lower:1, 7.9 or lower:1, 7.8 or lower:1, 7.7 or lower:1, 7.6 or lower:1, 7.5 or lower:1, 7.4 or lower:1, 7.3 or lower:1, 7.2 or lower:1, 7.1 or lower:1, 7.0 or lower:1, 6.9 or lower:1, 6.8 or lower:1, 6.7 or lower:1, 6.6 or lower:1, 6.5 or lower:1, 6.4 or lower:1, 6.3 or lower:1, 6.2 or lower:1, 6.1 or lower:1, 6.0 or lower:1, 5.9 or lower:1, 5.8 or lower:1, 5.7 or lower:1, 5.6 or lower:1, 5.5 or lower:1, 5.4 It may be 1, 5.3 or less:1, or 5.2 or less:1. The present invention is particularly suitable for a long cell in which the length of the long side is significantly longer than the length of the short side, and R TD / R MD By adjusting the numerical range, the moldability of the cup portion corresponding to the battery body portion of the above length ratio can be improved. Specifically, the R value after molding for the long side portion of the cup portion of the pouch film satisfying the above length ratio can be reduced.

[0091] According to one embodiment of the present invention, the pouch film may include a cup portion. The cup portion may be formed on the pouch film through a molding process and may include one or more cup portions on the pouch film.

[0092] For example, through the forming process of the above pouch film, two cup portions can be manufactured on the pouch film with a minimum gap of 1 mm. The forming process is performed by placing the pouch film in a thermoforming device and forming the film into a desired cup shape under conditions that prevent wrinkling by using a pneumatic pressure of 0.2 MPa to 0.7 MPa at room temperature. At this time, the thickness of the cup portions can be formed to be 3 mm to 8 mm.

[0093] The R value after molding is an important indicator for evaluating the molding quality and durability of the pouch film, representing the radius of curvature indicating how well the corner portion of the pouch film's cup is molded. If the R value after molding is too small (if the curvature is too steep), the pouch film may become too thin or tear at the corner portion. Conversely, if the R value after molding is too large (if the curvature is too gentle), the cup portion of the pouch film may not fit well with the electrode assembly, resulting in inefficient use of internal space. However, if the R value after molding is appropriate, the pouch film has sufficient curvature even at the corner portion, allowing for stress distribution. In other words, the R value after molding can be used as basic data to determine whether wrinkles or deformation may occur during the molding process of the pouch film. By maintaining the R value after molding appropriately, the pouch film can be accurately fitted to the electrode assembly, thereby guaranteeing the film's durability and performance.

[0094] Meanwhile, the R value of the pouch film after molding can be measured using a 3D shape analyzer. More specifically, a measurement location is selected so that the molded part is not deformed, and the part is cut with scissors. Then, the shape is analyzed three-dimensionally in 3D using a 3D shape analyzer, and a virtual circle is drawn on the corner to measure the R value after molding.

[0095] The smaller the R value after molding, the more precisely the pouch film is molded at the corners of the cup portion, allowing it to stably wrap and protect the battery body. This enables the pouch film to adhere closely to the battery body, allowing for efficient use of internal space and enabling the realization of higher energy density in a battery of the same size. Furthermore, a small R value after molding ensures that the pouch film is evenly distributed at the corners, preventing stress concentration in specific areas and thereby enhancing the long-term mechanical stability of the pouch film. In addition, by ensuring a tight seal without gaps between the battery body and the pouch film as described above, the possibility of electrolyte leakage is minimized, which can significantly improve the safety of the battery. For these reasons, maintaining a small R value after molding is crucial for manufacturing high-quality pouch-type secondary batteries. Through this, the pouch film according to the present invention can guarantee durability and quality while maintaining excellent moldability.

[0096] According to one embodiment of the present invention, the R value after molding may be 1 or more and 4 or less. For example, the R value after molding measured according to the [measurement method] may be 1.0 or more, 1.2 or more, 1.5 or more, 1.8 or more, 4.0 or less, 3.8 or less, 3.5 or less, 3.2 or less, 3.0 or less, 2.8 or less, 2.5 or less, 2.2 or less, and 2.0 or less.

[0097]

[0098] Pouch-type secondary battery case

[0099] The secondary battery of the present invention comprises a pouch-type secondary battery case including the battery body portion and the pouch film, wherein the battery body portion is sealed by the pouch-type secondary battery case. For example, the secondary battery may be a lithium secondary battery, and in this case, the battery body portion may include a negative electrode for a lithium secondary battery, a positive electrode for a lithium secondary battery, and an electrolyte.

[0100] The above-mentioned cathode for a lithium secondary battery may be used without limitation as long as it is commonly used as a cathode for a lithium secondary battery. For example, the above-mentioned cathode for a lithium secondary battery may be LiCoO2, LiMnO2, LiFePO4, Li(Ni 0.6 Mn 0.2 Co 0.2 It may include positive active materials such as O2.

[0101] The above electrolyte may include a lithium salt and a non-aqueous organic solvent. Here, the lithium salt and the non-aqueous organic solvent may be used without limitation as long as they are those commonly used as electrolytes and organic solvents for lithium secondary batteries, respectively.

[0102] The negative electrode for the lithium secondary battery described above may be used without limitation as long as it is one that is conventionally used as a negative electrode for a lithium secondary battery. For example, the negative electrode for the lithium secondary battery may include a negative electrode active material such as a carbon-based active material or a silicon-based active material.

[0103] The above pouch-type secondary battery case can have excellent sealing strength characteristics. Therefore, the problem of the battery body sealed by the above pouch-type secondary battery case being exposed to the external environment may not occur.

[0104]

[0105] The present invention will be explained in more detail below through examples. However, the following examples are intended to illustrate the present invention and do not limit the scope of the present invention.

[0106]

[0107] Examples

[0108] Example 1

[0109] A pouch film was manufactured by laminating an outer layer, a barrier layer, and a sealant layer, wherein the outer layer is a laminated film of an outermost polyethylene terephthalate (PET) film (thickness 12 μm) and an inner nylon (Ny) film (thickness 15 μm), the barrier layer is aluminum (thickness 40 μm), and the sealant layer (thickness 80 μm) is manufactured by using an extrusion lamination method to include a polypropylene extrusion coating (EC) layer (thickness 30 μm) and an unoriented polypropylene film (CPP) layer (thickness 50 μm). The stretching ratio of the nylon film (MD stretching ratio: 2.7, TD stretching ratio: 3.8) was controlled, and conditions such as the die temperature (260°C to 266°C) and extrusion pressure (0.3 MPa) were also controlled. In addition, a biaxial stretching process was performed using a double-bubble method. At this time, the slope (R) in the TD and MD directions between the upper yield point of the outer layer measured by Experimental Example 1 below and the strength at a stroke of 25 mm TD / R MD ) was 1.74.

[0110]

[0111] Example 2

[0112] A pouch film was manufactured by laminating an outer layer, a barrier layer, and a sealant layer, wherein the outer layer is a laminated film of an outermost polyethylene terephthalate (PET) film (thickness 12 μm) and an inner nylon (Ny) film (thickness 15 μm), the barrier layer is aluminum (thickness 40 μm), and the sealant layer (thickness 80 μm) is manufactured by using an extrusion lamination method to include a polypropylene extrusion coating (EC) layer (thickness 30 μm) and an unoriented polypropylene film (CPP) layer (thickness 50 μm). The stretching ratio of the nylon film (MD stretching ratio: 2.8, TD stretching ratio: 3.7) was controlled, and conditions such as the die temperature (260°C to 266°C) and extrusion pressure (0.3 MPa) were also controlled. In addition, a biaxial stretching process was performed using a double-bubble method. At this time, the slope (R) in the TD and MD directions between the upper yield point of the outer layer measured by Experimental Example 1 below and the strength at a stroke of 25 mm TD / R MD ) was 1.51.

[0113]

[0114] Example 3

[0115] A pouch film was manufactured by laminating an outer layer, a barrier layer, and a sealant layer, wherein the outer layer is a laminated film of an outermost polyethylene terephthalate (PET) film (thickness 12 μm) and an inner nylon (Ny) film (thickness 25 μm), the barrier layer is aluminum (thickness 60 μm), and the sealant layer (thickness 80 μm) is manufactured by using an extrusion lamination method to include a polypropylene extrusion coating (EC) layer (thickness 30 μm) and an unoriented polypropylene film (CPP) layer (thickness 50 μm). The stretching ratio of the nylon film (MD stretching ratio: 2.4, TD stretching ratio: 4.2) was controlled, and conditions such as the die temperature (260°C to 266°C) and extrusion pressure (0.3 MPa) were also controlled. In addition, a biaxial stretching process was performed using a double-bubble method. At this time, the slope (R) in the TD and MD directions between the upper yield point of the outer layer measured by Experimental Example 1 below and the strength at a stroke of 25 mm TD / R MD ) was 2.70.

[0116]

[0117] Example 4

[0118] A pouch film was manufactured by laminating an outer layer, a barrier layer, and a sealant layer, wherein the outer layer is a laminated film of an outermost polyethylene terephthalate (PET) film (thickness 12 μm) and an inner nylon (Ny) film (thickness 25 μm), the barrier layer is aluminum (thickness 60 μm), and the sealant layer (thickness 80 μm) is manufactured by using an extrusion lamination method to include a polypropylene extrusion coating (EC) layer (thickness 30 μm) and an unoriented polypropylene film (CPP) layer (thickness 50 μm). The stretching ratio of the nylon film (MD stretching ratio: 2.6, TD stretching ratio: 4.0) was controlled, and conditions such as the die temperature (260°C to 266°C) and extrusion pressure (0.3 MPa) were also controlled. In addition, a biaxial stretching process was performed using a double-bubble method. At this time, the slope (R) in the TD and MD directions between the upper yield point of the outer layer measured by Experimental Example 1 below and the strength at a stroke of 25 mm TD / R MD ) was 2.08.

[0119]

[0120] Example 5

[0121] A pouch film was manufactured by laminating an outer layer, a barrier layer, and a sealant layer, wherein the outer layer is a laminated film of an outermost polyethylene terephthalate (PET) film (thickness 12 μm) and an inner nylon (Ny) film (thickness 25 μm), the barrier layer is aluminum (thickness 60 μm), and the sealant layer (thickness 80 μm) is manufactured by using an extrusion lamination method to include a polypropylene extrusion coating (EC) layer (thickness 30 μm) and an unoriented polypropylene film (CPP) layer (thickness 50 μm). The stretching ratio of the nylon film (MD stretching ratio: 2.3, TD stretching ratio: 4.4) was controlled, and conditions such as the die temperature (260°C to 266°C) and extrusion pressure (0.3 MPa) were also controlled. In addition, a biaxial stretching process was performed using a double-bubble method. At this time, the slope (R) in the TD and MD directions between the upper yield point of the outer layer measured by Experimental Example 1 below and the strength at a stroke of 25 mm TD / R MD ) was 2.95.

[0122]

[0123] Comparative Example 1

[0124] The outer layer is a laminated film consisting of an outermost polyethylene terephthalate (PET) film (thickness 12 μm) and an inner nylon (Ny) film (thickness 15 μm), the barrier layer contains aluminum (thickness 40 μm), and the sealant layer (thickness 80 μm) is a polypropylene extrusion coating (EC) layer; a commercially available pouch film in which the outer layer, barrier layer, and sealant layer are laminated was purchased and used. At this time, R of the outer layer TD / R MD It was 1.30.

[0125]

[0126] Comparative Example 2

[0127] The outer layer is a laminated film consisting of an outermost polyethylene terephthalate (PET) film (thickness 12 μm) and an inner nylon (Ny) film (thickness 15 μm), the barrier layer contains aluminum (thickness 40 μm), and the sealant layer (thickness 80 μm) is a polypropylene extrusion coating (EC) layer; a commercially available pouch film in which the outer layer, barrier layer, and sealant layer are laminated was purchased and used. At this time, R of the outer layer TD / R MD It was 1.11.

[0128]

[0129] Comparative Example 3

[0130] The outer layer is a laminated film consisting of an outermost polyethylene terephthalate (PET) film (thickness 12 μm) and an inner nylon (Ny) film (thickness 25 μm), the barrier layer contains aluminum (thickness 60 μm), and the sealant layer (thickness 80 μm) is a polypropylene extrusion coating (EC) layer; a commercially available pouch film in which the outer layer, barrier layer, and sealant layer are laminated was purchased and used. At this time, R of the outer layer TD / R MD It was 1.39.

[0131]

[0132] Comparative Example 4

[0133] The outer layer is a laminated film consisting of an outermost polyethylene terephthalate (PET) film (thickness 12 μm) and an inner nylon (Ny) film (thickness 15 μm), the barrier layer contains aluminum (thickness 40 μm), and the sealant layer (thickness 80 μm) is a polypropylene extrusion coating (EC) layer; a commercially available pouch film in which the outer layer, barrier layer, and sealant layer are laminated was purchased and used. At this time, R of the outer layer TD / R MD It was 3.30.

[0134]

[0135] Comparative Example 5

[0136] The outer layer is a laminated film consisting of an outermost polyethylene terephthalate (PET) film (thickness 12 μm) and an inner nylon (Ny) film (thickness 15 μm), the barrier layer contains aluminum (thickness 40 μm), and the sealant layer (thickness 80 μm) is a polypropylene extrusion coating (EC) layer; a commercially available pouch film in which the outer layer, barrier layer, and sealant layer are laminated was purchased and used. At this time, R of the outer layer TD / R MD It was 3.60.

[0137]

[0138] Experimental Example

[0139] Experimental Example 1: Measurement of the slope between the upper yield point and the strength at a stroke of 25 mm

[0140] After preparing a specimen that does not include an inner sealant layer and a barrier layer with a width of 15 mm by peeling off the outer layer film of the pouch film of the above examples and comparative examples, the specimen was fixed between two jigs of a tensile testing machine (UTM) with an initial jig gap of 30 mm at room temperature, and the stroke (mm) and strength (N) of the specimen were measured while pulling in the TD and MD directions at a measurement speed of 50 mm / min. The measured values ​​are shown in Table 1 below. Furthermore, for the pouch films of Example 1, Example 3, Comparative Example 1, and Comparative Example 3, the stroke (mm) and strength (N) were measured 3 or 5 times each, and the average value was calculated. A graph was derived with the X-axis representing the stroke (mm) and the Y-axis representing the strength (N), and is shown in FIGS. 2 to 9. At this time, the slope between the upper yield point in the TD direction and MD direction and the strength at a stroke of 25 mm is the slope of the straight line connecting the upper yield point and the strength value at a stroke of 25 mm.

[0141] Classification Direction Upward Yield Point Stroke 25 Inclination R TD / R MDExample 1 MD Stroke: 1.5 Strength: 37 Stroke: 25 Strength: 731.531.74 TD Stroke: 1.3 Strength: 31 Stroke: 25 Strength: 942.66 Example 2 MD Stroke: 1.7 Strength: 37 Stroke: 25 Strength: 711.461.51 TD Stroke: 1.9 Strength: 33 Stroke: 25 Strength: 842.21 Example 3 MD Stroke: 1.4 Strength: 53 Stroke: 25 Strength: 911.612.70 TD Stroke: 1.4 Strength: 36 Stroke: 25 Strength: 1394.34 Example 4 MD Stroke: 1.8 Strength: 52 Stroke: 25 Strength: 961.892.08 TD Stroke: 1.9 Strength: 37 Stroke: 25 Strength: 1283.94 Example 5 MD Stroke: 1.6 Strength: 52 Stroke: 25 Strength: 890.1652.95 TD Stroke: 1.6 Strength: 37 Stroke: 25 Strength: 1470.056 Comparative Example 1 MD Stroke: 1.4 Strength: 40 Stroke: 25 Strength: 771.571.30 TD Stroke: 1.1 Strength: 33 Stroke: 25 Strength: 822.05 Comparative Example 2 MD Stroke: 1.4 Strength: 38 Stroke: 25 Strength: 781.691.11 TD Stroke: 1.6 Strength: 36 Stroke: 25 Strength: 801.88 Comparative Example 3MD Stroke: 2.3 Strength: 51 Stroke: 25 Strength: 1002.161.39 TD Stroke: 2.0 Strength: 44 Stroke: 25 Strength: 1133.00 Comparative Example 4MD Stroke: 1.6 Strength: 50 Stroke: 25 Strength: 540.1653.30 TD Stroke: 1.6 Strength: 33 Stroke: 25 Strength: 460.050 Comparative Example 5MD Stroke: 1.6 Strength: 49 Stroke: 25 Strength: 530.1803.60 TD Stroke: 1.6 Strength: 33 Stroke: 25 Strength: 480.050

[0142] Experimental Example 2: Measurement of average R-value after molding

[0143] The pouch films of the above examples and comparative examples were formed to produce two cup portions spaced 1 mm apart. At this time, the length of one cup portion in the MD direction was 100 mm, the length in the TD direction was 510 mm, and the thickness was 4 mm. The forming process of the pouch film was carried out using a thermoforming device at room temperature and by forming the film into a desired cup shape under conditions that prevent wrinkles using a pneumatic pressure of 0.2 MPa to 0.7 MPa.

[0144] Afterward, the shape of the molded pouch film was analyzed in 3D using a 3D shape analyzer (Micor-vu, EXCEL 501UC), and the long side of the cup portion was divided into five equal intervals to set positions (positions (1) to (5) in Fig. 10 below). Imaginary circles were drawn at each position to measure the R value after molding, and the average value of these was used as the average R value after molding and is shown in Table 2 below.

[0145]

[0146] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Average R value after molding (1) 0.9 2 1.7 2 2.2 3 2.6 5 1.2 0 4.3 9 3.4 8 3.6 4 3.1 0 3.40 (2) 1.5 9 1.7 2 2.3 1 2.5 6 1.9 0 6.9 2 5.0 6 3.9 9 3.1 5 3.50 (3) 2.2 0 1.6 6 1.5 8 2.6 3 2.40 10.3 8 3.8 4.1 2 3.2 5 3.60 (4)1.691.722.422.062.1012.063.556.343.303.70(5)1.262.512.561.902. 608.939.964.423.203.60Avg.1.531.872.222.362.048.545.174.503.203.56

[0147]

[0148] Referring to Tables 1 and 2 above, the pouch films of Examples 1 to 5 have an outer layer R TD / R MDBy falling within the numerical range of the present invention, it is possible to have a smaller R value after molding overall than the comparative example, thereby maintaining an excellent level of processability and moldability. Specifically, when comparing Example 1 and Comparative Example 1, in which the thicknesses of the barrier layer and the nylon layer are the same, Example 1 shows a much smaller R value after molding compared to Comparative Example 1, confirming that it has an excellent level of moldability.

[0149] In addition, referring to Table 2 above, while Comparative Examples 1 to 5 showed that the R value after molding varied depending on the position of the long side, Examples 1 to 5 did not show a large deviation throughout the long side. In particular, in the case of Comparative Example 1, the R value after molding was very small at position (1) at 4.39, but the R value after molding was very large at position (4) at 12.06. Through this, it can be confirmed that the Examples were molded with a uniform thickness compared to the Comparative Examples.

[0150]

[0151] Acknowledgement 1

[0152] [Project ID] 2410004468

[0153] [Assignment No.] 20022450

[0154] [Ministry Name] Ministry of Trade, Industry and Energy

[0155] [Project Management (Specialized) Agency Name] Korea Institute of Industrial Technology Planning and Evaluation

[0156] [Research Project Name] Development of Materials and Components Technology (Leading Company)

[0157] [Project Title] Development of Next-Generation Secondary Battery Pouch Capable of Achieving More Than Twice the High Adhesion Strength (60℃)

[0158] [Contribution Rate] 1 / 1

[0159] [Name of Project Performing Organization] Yulchon Chemical Co., Ltd.

[0160] [Research Period] 2024-01-01 ~ 2024-12-31

[0161]

[0162] Acknowledgement 2

[0163] [Project ID] 2410013070

[0164] [Assignment No.] 20022450

[0165] [Ministry Name] Ministry of Trade, Industry and Energy

[0166] [Project Management (Specialized) Agency Name] Korea Institute of Industrial Technology Planning and Evaluation

[0167] [Research Project Name] Development of Materials and Components Technology (Leading Company)

[0168] [Project Title] Development of Next-Generation Secondary Battery Pouch Capable of Achieving More Than Twice the High Adhesion Strength (60℃)

[0169] [Contribution Rate] 1 / 1

[0170] [Name of Project Performing Organization] Yulchon Chemical Co., Ltd.

[0171] [Research Period] 2025-01-01 ~ 2025-12-31

Claims

1. Inner sealant layers stacked sequentially; a barrier layer containing aluminum; and an outer layer, comprising, The above outer layer includes a first outer layer; and a second outer layer disposed between the first outer layer and the barrier layer, and A pouch film in which the slope derived from the graph obtained according to the measurement method below satisfies Equation 1 below: [Equation 1] 1.5≤ R TD / R MD ≤3.0 The above R TD is the slope of the increasing section between the upper yield point of the outer layer measured when pulling the outer layer film in the TD direction and the strength at a stroke of 25 mm, and The above R MD is the slope of the increasing section between the upper yield point of the outer layer measured when the outer layer film is pulled in the MD direction and the strength at a stroke of 25 mm. [measurement method] After preparing a specimen that does not include an inner sealant layer and a barrier layer with a width of 15 mm by peeling off the outer layer of the above pouch film, the specimen is fixed between two jigs of a tensile testing machine (UTM) with an initial jig gap of 30 mm at room temperature, and the stroke (mm) and strength (N) of the specimen are measured while pulling the specimen in the TD and MD directions, respectively, at a measurement speed of 50 mm / min until fracture. The X-axis of the graph derived from the measured values ​​is the stroke (mm), and the Y-axis is the strength (N). At this time, the R TD and R MD This is the measured slope of the straight line connecting the upper yield point and the strength at a stroke of 25 mm.

2. In Paragraph 1, A pouch film in which the strokes in the TD and MD directions corresponding to the breaking strength of the outer layer are each independently 20 mm or more and 100 mm or less.

3. In Paragraph 1, A pouch film in which the first outer layer comprises one or more compounds selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyethylene naphthalate.

4. In Paragraph 1, A pouch film wherein the second outer layer comprises one or more compounds selected from the group consisting of polyamide compounds, polyester compounds, polyolefin compounds and polyacrylic compounds.

5. In Paragraph 1, A pouch film wherein the inner sealant layer comprises one or more compounds selected from the group consisting of polypropylene, polyethylene, polyvinyl chloride, polyurethane, polybutylene, and copolymers derived from monomers derived from ethylene or propylene and monomers derived from alpha-olefins.

6. In Paragraph 1, Equation 1 above is 1.6 < R TD / R MD Pouch film that is ≤2.

7.

7. In Paragraph 1, A pouch film in which the angle between the RTD and RMD is 10 degrees or more and 70 degrees or less.

8. In Paragraph 1, A pouch film having an average R value after molding, measured by a 3D shape analyzer, of 1 or more and 4 or less.

9. In Paragraph 1, The above pouch film includes a cup portion, and A pouch film having a length ratio of the long side to the short side of the cup portion of the above-mentioned cup portion of 2.0 or more and 8.0 or less:

1.

10. A pouch-type secondary battery case comprising a pouch film according to any one of claims 1 to 9.

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