Pouch film and pouch-type secondary battery case comprising same

Abstract

The present invention relates to a pouch film and a pouch-type secondary battery case comprising same. The pouch film comprises an outer layer, a barrier layer and a sealant layer, which are sequentially stacked, wherein: the barrier layer comprises an aluminum alloy; particles of the aluminum alloy comprise a plurality of crystal grains; and the standard deviation is 21.0 or less in proportions (%) of crystal grains having <001> crystal orientation, crystal grains having <101> crystal orientation, and crystal grains having <111> crystal orientation, as measured by electron backscatter diffraction analysis under conditions of an accelerating voltage of 20.0 Kv, a WD 19.0 mm, a measurement magnification of 1500x (width 150 μm x height 50 μm), and a step size of 0.2 μm.

Description

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

[0001] Cross-citation with related applications

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0188046 filed December 17, 2024 and Korean Patent Application No. 10-2025-0111503 filed August 12, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of the specification.

[0003] Technology field

[0004] The present invention relates to a pouch film and a pouch-type secondary battery case including the same.

[0005] 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.

[0006] Therefore, when forming the pouch film, it is essential to secure sufficient space so that the pouch film can accommodate the electrode assembly. To this end, methods such as press forming or deep drawing forming are used, and the shape of the cup portion is determined through this process. At this time, stress may be concentrated at the corners of the cup portion, so if it is not formed properly, there is a possibility that the film may tear or deform. In particular, if a crack occurs in the barrier layer of the pouch film at a stress-bearing area, the electrolyte may leak out or the insulation resistance may be destroyed. Since this can lead to a significant decrease in cell stability or severe performance degradation, the characteristics of the barrier layer play a very important role.

[0007] Therefore, in order to solve these problems when manufacturing pouch-type battery cases, there is a need to develop technology that improves the characteristics of the barrier layer to enhance deep drawing formability, handling during molding, and shape stability after molding.

[0008] The problem to be solved by the present invention is to provide a pouch film with improved mechanical properties while securing molding depth by controlling the ratio of crystal orientation of a plurality of crystal grains included in an aluminum alloy within a barrier layer, and a pouch-type secondary battery case including the same.

[0009] 1. The present invention comprises an outer layer, a barrier layer, and a sealant layer sequentially stacked, wherein the barrier layer comprises an aluminum alloy, and the particles of the aluminum alloy comprise a plurality of crystal grains, and the invention is measured by electron backscatter diffraction analysis under conditions of an acceleration voltage of 20.0 kV, WD 19.0 mm, a measurement magnification of 1500x (width 150 μm * height 50 μm), and a step size of 0.2 μm <001> Proportion of grains with crystal orientation (%), <101> Proportion (%) of grains having a crystal orientation and <111> A pouch film is provided having a standard deviation of the ratio (%) of crystal grains having a crystal orientation of 21.0 or less.

[0010] 2. The present invention provides a pouch film according to 1. above, wherein the plurality of crystal grains have a value calculated according to Formula 1 below of 3.6 or higher and 7.0 or lower.

[0011] [Equation 1]

[0012] High-angle grain boundary ratio (%) / Low-angle grain boundary ratio (%)

[0013] In the above Equation 1, high-angle grain boundaries (%) are the proportion of grain boundaries with an angle greater than 15° measured by electron backscatter diffraction analysis under conditions of acceleration voltage 20.0 kV, WD 19.0 mm, measurement magnification 1500x (width 150 μm * height 50 μm), and step size 0.2 μm among all grain boundaries, and low-angle grain boundaries (%) are the proportion of grain boundaries with an angle of 2° or more and 15° or less measured by electron backscatter diffraction analysis under conditions of acceleration voltage 20.0 kV, WD 19.0 mm, measurement magnification 1500x (width 150 μm * height 50 μm), and step size 0.2 μm among all grain boundaries.

[0014] 3. The present invention provides a pouch film according to 2. above, wherein the ratio of the high-angle grain boundary of the plurality of grains is 78.0% or more and 88.0% or less.

[0015] 4. The present invention provides a pouch film according to 2. or 3. above, wherein the ratio of the low-angle grain boundary of the plurality of grains is 12.5% ​​or more and 22.0% or less.

[0016] 5. The present invention provides a pouch film in which, in any one of 1 to 4 above, the average crystal grain size of the plurality of crystal grains is 5.0 μm or more and 8.0 μm or less.

[0017] 6. The present invention provides a pouch film in which, in any one of 1 to 5 above, the area-weighted average crystal grain size of the plurality of crystal grains is 10.0 μm or more and 16.0 μm or less.

[0018] 7. The present invention provides a pouch film in which, in any one of 1 to 6 above, the standard deviation of the crystal grain size of the plurality of crystal grains is 3.7 or more and 6.0 or less.

[0019] 8. The present invention provides a pouch film in which, in any one of 1 to 7 above, the minimum crystal grain size of the plurality of crystal grains is 0.5 μm or more and 1.7 μm or less.

[0020] 9. The present invention provides a pouch film in which, in any one of 1 to 8 above, the maximum crystal grain size of the plurality of crystal grains is 20.0 μm or more and 38.0 μm or less.

[0021] 10. The present invention, in any one of 1 to 9 above, wherein the above <001> The present invention provides a pouch film having a crystal orientation with a crystal grain ratio of 15.0% or more and 50.0% or less.

[0022] 11. The present invention, in any one of 1 to 10 above, wherein the above <101> The present invention provides a pouch film having a crystal orientation with a crystal grain ratio of 7.0% or more and 50.0% or less.

[0023] 12. The present invention, in any one of 1 to 11 above, wherein the above <111> The present invention provides a pouch film having a crystal orientation with a crystal grain ratio of 20.0% or more and 50.0% or less.

[0024] 13. The present invention provides a pouch film in which, in any one of 1 to 12 above, the outer layer comprises one or more compounds selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, and nylon-based resin.

[0025] 14. The present invention provides a pouch film in which, in any one of 1 to 13 above, the thickness of the barrier layer is 40.0 μm or more and 60.0 μm or less.

[0026] 15. The present invention provides a pouch film in any one of 1 to 14 above, wherein the barrier layer further comprises one or more elements selected from the group consisting of stainless steel, copper, iron, silicon, nickel, titanium, and manganese.

[0027] 16. The present invention provides a pouch-type secondary battery case comprising a pouch film according to any one of 1 to 15 above.

[0028] The pouch film of the present invention can have the effect of improving mechanical properties and formability by controlling the ratio of crystal orientation of a plurality of crystal grains included in the aluminum alloy within the barrier layer.

[0029] Figure 1 shows the electron backscatter diffraction (EBSD) pattern of a plurality of crystal grains included in an aluminum alloy particle included in a barrier layer within a pouch film of Example 1.

[0030] Hereinafter, the present invention will be described in more detail to aid in understanding the invention.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038]

[0039] Pouch film

[0040] The present invention comprises an outer layer, a barrier layer, and a sealant layer sequentially stacked, wherein the barrier layer comprises an aluminum alloy, and the particles of the aluminum alloy comprise a plurality of crystal grains, and measured by electron backscatter diffraction analysis <001> Proportion of grains with crystal orientation (%), <101> Proportion (%) of grains having a crystal orientation and <111> A pouch film is provided having a standard deviation of the ratio (%) of crystal grains having a crystal orientation of 21.0 or less.

[0041] The inventor of the present invention confirmed that in the case of conventional pouch films, a problem arises in which stress is concentrated in the barrier layer during drawing molding in the battery manufacturing process, causing cracks. Such cracks can lead to major defects in cell stability, such as electrolyte leakage or insulation resistance breakdown. Accordingly, to solve the above problem, the inventor developed a pouch film that improves deep drawing formability, handling during molding, and shape stability after molding by controlling the size, direction, and boundaries of multiple crystals within the barrier layer of the pouch film.

[0042] Figure 1 shows the electron backscatter diffraction (EBSD) pattern of an SEM image of a cross-section of a barrier layer of a pouch film of the present invention (measured by electron backscatter diffraction analysis under conditions of acceleration voltage 20.0 kV, WD 19.0 mm, measurement magnification 1500x (width 150 μm * height 50 μm), step size 0.2 μm).

[0043] The crystal orientation of the crystal grains contained in the aluminum alloy particles included in the barrier layer can be confirmed through the aforementioned electron backscattering diffraction analysis method. The crystal orientation of the crystal grains indicates how the lattices of individual crystal grains are arranged in space; it can be used as an indicator to identify the orientation in which a lattice in a specific direction is preferred, and this orientation can have a significant impact on the mechanical and physical properties of the pouch film.

[0044] According to one embodiment of the present invention, among a plurality of crystal grains included in the aluminum alloy particles, <001> The proportion of grains having a crystal orientation may be 15.0% or more and 50.0% or less. More specifically, among the total grains, the above <001> The proportion of grains having a crystal orientation may be 15.0% or more, 15.5% or more, 16.0% or more, 16.5% or more, 17.0% or more, 17.5% or more, 18.0% or more, 18.5% or more, 19.0% or more, 19.5% or more, 20.0% or more, 20.5% or more, 21.0% or more, 21.5% or more, 22.0% or more, 22.5% or more, 23.0% or more, 23.5% or more, 24.0% or more, 24.5% or more, or 25.0% or more, and may also be 50.0% or less, 49.0% or less, 48.0% or less, 47.0% or less, 46.0% or less, 45.0% or less, 44.0% or less, 43.0% It may be 42.0% or less, 41.0% or less, 40.0% or less, 39.0% or less, 38.0% or less, 37.0% or less, 36.0% or less, 35.0% or less, 34.0% or less, 33.0% or less, 32.0% or less, 31.0% or less, or 30.0% or less. The above <001> The crystal orientation is generally along the axial direction of the unit cell of the crystal structure, which can facilitate plastic deformation and provide uniform deformation characteristics, and among the plurality of crystal grains included in the aluminum alloy particles, <001> When the ratio of crystal grains having a crystal orientation satisfies the above range, the ductility and strength of the aluminum alloy are balanced, so formability and durability can be improved, and deformation or cracking caused by thermal stress can be suppressed even in high-temperature environments.

[0045] According to one embodiment of the present invention, among a plurality of crystal grains included in the aluminum alloy particles, <101> The proportion of grains having a crystal orientation may be 7.0% or more and 50.0% or less. More specifically, among the total grains, the above <101> The proportion of grains having a crystal orientation is 7.0% or more, 7.5% or more, 8.0% or more, 8.5% or more, 9.0% or more, 9.5% or more, 10.0% or more, 10.5% or more, 11.0% or more, 11.5% or more, 12.0% or more, 12.5% ​​or more, 13.0% or more, 13.5% or more, 14.0% or more, 14.5% or more, 15.0% or more, 15.5% or more, 16.0% or more, 16.5% or more, 17.0% or more, 17.5% or more, 18.0% or more, 18.5% or more, 19.0% or more, 19.5% or more, 20.0% or more, 20.5% or more, 21.0% or more, 21.5% or more, 22.0% or more, 22.5% or more, 23.0% or more, 23.5%. It may be % or more, 24.0% or more, 24.5% or more, 25.0% or more, 25.5% or more, 26.0% or more, 26.5% or more, 27.0% or more, 27.5% or more, or 28.0% or more, and also 50.0% or less, 49.0% or less, 48.0% or less, 47.0% or less, 46.0% or less, 45.0% or less, 44.0% or less, 43.0% or less, 42.0% or less, 41.0% or less, 40.0% or less, 39.0% or less, 38.0% or less, 37.0% or less, 36.0% or less, 35.0% or less, 34.0% or less, 33.0% or less, 32.0% or less, 31.0% or less, or It may be 30.0% or less.The above <101> Crystal orientation is generally the direction in which the two axes of the unit cell intersect in the crystal structure, and can play an important role in the deformation resistance and shear strength of the crystal structure, and among the plurality of crystal grains included in the aluminum alloy particles, <101> When the ratio of crystal grains having a crystal orientation satisfies the above range, the shear strength and thermal stability of the aluminum alloy can be further enhanced.

[0046] According to one embodiment of the present invention, among a plurality of crystal grains included in the aluminum alloy particles, <111> The proportion of grains having a crystal orientation may be 20.0% or more and 50.0% or less. More specifically, among the total grains, the above <111> The proportion of grains having a crystal orientation is 20.0% or more, 20.5% or more, 21.0% or more, 21.5% or more, 22.0% or more, 22.5% or more, 23.0% or more, 23.5%. It may be % or more, 24.0% or more, 24.5% or more, 25.0% or more, 25.5% or more, 26.0% or more, 26.5% or more, 27.0% or more, 27.5% or more, or 28.0% or more, and also 50.0% or less, 49.0% or less, 48.0% or less, 47.0% or less, 46.0% or less, 45.0% or less, 44.0% or less, 43.0% or less, 42.0% or less, 41.0% or less, 40.0% or less, 39.0% or less, 38.0% or less, 37.0% or less, 36.0% or less, 35.0% or less, 34.0% or less, 33.0% or less, 32.0% or less, 31.0% or less, or It may be 30.0% or less. The above <111> Crystal orientation is generally the most stable direction, characterized by the minimum lattice spacing and high density within the crystal structure, and plays an important role in the strength, tensile strength, conductivity, corrosion resistance, and durability of the crystal structure. Among the multiple crystal grains contained in the aluminum alloy particles mentioned above, <111> When the ratio of crystal grains having a crystal orientation satisfies the above range, improved performance can be obtained in terms of mechanical strength, durability, electrical properties, etc. of the aluminum alloy.

[0047] According to one embodiment of the present invention, among a plurality of crystal grains included in the aluminum alloy particles, <001> Proportion of grains with crystal orientation (%), <101> Proportion (%) of grains having a crystal orientation and <111> The standard deviation of the ratio (%) of crystal grains having the crystal orientation is 21.0 or less. More specifically, the standard deviation of the ratio (%) of crystal grains having each of the above crystal orientations may be 21.0 or less, 20.0 or less, 19.0 or less, 18.0 or less, 17.0 or less, 16.0 or less, 15.0 or less, 14.0 or less, 13.0 or less, 12.0 or less, 11.0 or less, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, or 5.0 or less, and additionally, the lower limit is not particularly restricted but may be 1.0 or more, 2.0 or more, 3.0 or more, or 4.0 or more. Among the plurality of crystal grains included in the above aluminum alloy particles, <001> Proportion of grains with crystal orientation (%), <101> Proportion (%) of grains having a crystal orientation and <111> If the standard deviation of the ratio (%) of crystal grains having the crystal orientation satisfies the above range, the mechanical properties and formability of the pouch film are improved, and cell stability can be expected. However, among the plurality of crystal grains included in the aluminum alloy particles, <001> Proportion of grains with crystal orientation (%), <101> Proportion (%) of grains having a crystal orientation and <111> When the standard deviation of the ratio (%) of crystal grains having a crystal orientation exceeds 21.0, the elongation of the barrier layer decreases rapidly, and the formability of the pouch film decreases, resulting in a problem where sufficient forming depth is not secured.

[0048] The grain boundary ratio of the aluminum alloy particles included in the barrier layer can be confirmed through the aforementioned electron backscattering diffraction analysis method. In this case, the grain boundary refers to the interface between different grains, and the grain boundary ratio refers to the proportion of a specific type of boundary within the total grain boundaries.

[0049] In this specification, 'high-angle grain boundary (%)' refers to the proportion of grain boundaries with an angle greater than 15° measured by electron backscatter diffraction analysis among all grain boundaries, and said high-angle grain boundary (%) may affect the recrystallization and grain growth of a material composed of multiple grains. In addition, in this specification, 'low-angle grain boundary (%)' refers to the proportion of grain boundaries with an angle between 2° and 15° measured by electron backscatter diffraction analysis among all grain boundaries, and said low-angle grain boundary (%) is related to the deformation or recovery characteristics of a material composed of multiple grains. The value calculated according to the following Equation 1 is related to the strength, ductility, thermal stability, etc. of a material composed of multiple grains.

[0050] [Equation 1]

[0051] High-angle grain boundary ratio (%) / Low-angle grain boundary ratio (%)

[0052] According to one embodiment of the present invention, the plurality of crystal grains may have a value calculated according to Equation 1 of 3.6 or higher and 7.0 or lower. More specifically, the plurality of crystal grains may have a value calculated according to Formula 1 of 3.6 or more, 3.7 or more, 3.8 or more, 3.9 or more, 4.0 or more, 4.1 or more, 4.2 or more, 4.3 or more, 4.4 or more, 4.5 or more, 4.6 or more, 4.7 or more, 4.8 or more, 4.9 or more, 5.0 or more, 5.1 or more, 5.2 or more, 5.3 or more, or 5.4 or more, and may also have a value of 7.0 or less, 6.9 or less, 6.8 or less, 6.7 or less, 6.6 or less, 6.5 or less, 6.4 or less, 6.3 or less, 6.2 or less, 6.1 or less, 6.0 or less, 5.9 or less, 5.8 or less, 5.7 or less, 5.6 or less, or 5.5 or less. If the value calculated according to the above Equation 1 satisfies the above range, the mechanical, thermal, and processing properties of the material can be improved in a balanced manner.

[0053] According to one embodiment of the present invention, the ratio (%) of the high-angle grain boundaries of the plurality of grains may be 78.0% or more and 88.0% or less. More specifically, the ratio (%) of the high-angle grain boundaries of the plurality of grains may be 78.0% or more, 78.5% or more, 79.0% or more, 79.5% or more, 80.0% or more, 80.5% or more, 81.0% or more, 81.5% or more, 82.0% or more, 82.5% or more, 83.0% or more, 83.5% or more, or 84.0% or more, and may be 88.0% or less, 87.5% or less, 87.0% or less, 86.5% or less, 86.0% or less, 85.5% or less, 85.0% or less, 84.9% or less, 84.8% or less, 84.7% or less, 84.6% or less, 84.5% or less, 84.4% or less, or 84.3% or less. When the ratio (%) of high-angle grain boundaries of the aforementioned plurality of grains satisfies the above range, thermal stability and processability can be improved while maintaining a balance of strength, ductility, and durability of the aluminum alloy. In addition, performance at high temperatures can be improved as microstructural stability is enhanced.

[0054] According to one embodiment of the present invention, the ratio (%) of the low-angle grain boundaries of the plurality of grains may be 12.5% ​​or more and 22.0% or less. More specifically, the ratio (%) of the low-angle grain boundaries of the plurality of grains may be 12.5% ​​or more, 13.0% or more, 13.5% or more, 14.0% or more, 14.5% or more, 15.0% or more, 15.1% or more, 15.2% or more, 15.3% or more, 15.4% or more, 15.5% or more, 15.6% or more, or 15.7% or more, and may also be 22.0% or less, 21.5% or less, 21.0% or less, 20.5% or less, 20% or less, 19.5% or less, 19.0% or less, 18.5% or less, 18.0% or less, 17.5% or less, 17.0% or less, 16.5% or less, or 16.0% or less. When the ratio (%) of the low-angle grain boundaries of the above plurality of grains satisfies the above range, the strength, durability, fatigue resistance, and thermal stability of the aluminum alloy can be improved, and deformation resistance can be increased to further improve processability.

[0055] The size of the crystal grains contained in the aluminum alloy particles within the barrier layer can be confirmed through the aforementioned electron backscattering diffraction analysis method. In this context, the crystal grain diameter refers to the diameter of individual crystal grains, while the average value of multiple crystal grains measured using an analysis program is referred to as the average crystal grain diameter. This is related to the mechanical properties of the material, such as strength, ductility, impact resistance, and creep resistance.

[0056] According to one embodiment of the present invention, the average crystal grain size of the plurality of crystal grains may be 5.0 μm or more and 8.0 μm or less. More specifically, the average crystal grain size of the plurality of crystal grains may be 5.0 μm or more, 5.1 μm or more, 5.2 μm or more, 5.3 μm or more, 5.4 μm or more, 5.5 μm or more, 5.6 μm or more, 5.7 μm or more, 5.8 μm or more, 5.9 μm or more, 6.0 μm or more, 6.1 μm or more, 6.2 μm or more, 6.3 μm or more, 6.4 μm or more, or 6.5 μm or more, and may also be 8.0 μm or less, 7.9 μm or less, 7.8 μm or less, 7.7 μm or less, 7.6 μm or less, 7.5 μm or less, 7.4 μm or less, or 7.3 μm or less. When the average crystal grain size of the above plurality of crystal grains satisfies the above range, the stability of the microstructure can be increased to suppress deformation or cracking, long-term performance stability can be secured, and moldability is improved to maintain uniform characteristics during the pouch film forming process.

[0057] According to one embodiment of the present invention, the area-weighted average crystal grain size of the plurality of crystal grains may be 10.0 μm or more and 16.0 μm or less. More specifically, the area-weighted average crystal grain diameter of the plurality of crystal grains may be 10.0 μm or more, 10.1 μm or more, 10.2 μm or more, 10.3 μm or more, 10.4 μm or more, 10.5 μm or more, 10.6 μm or more, 10.7 μm or more, 10.8 μm or more, 10.9 μm or more, 11.0 μm or more, 11.1 μm or more, 11.2 μm or more, 11.3 μm or more, 11.4 μm or more, 11.5 μm or more, 11.6 μm or more, 11.7 μm or more, 11.8 μm or more, 11.9 μm or more, or 12.0 μm or more, and may also be 16.0 μm or less, 15.9 μm or less, 15.8 μm or less, or 15.7 μm It may be 15.6 μm or less, 15.5 μm or less, 15.4 μm or less, 15.3 μm or less, 15.2 μm or less, 15.1 μm or less, 15.0 μm or less, 14.9 μm or less, 14.8 μm or less, 14.7 μm or less, 14.6 μm or less, 14.5 μm or less, 14.4 μm or less, 14.3 μm or less, 14.2 μm or less, 14.1 μm or less, or 14.0 μm or less. While the average crystal grain size of the plurality of crystal grains is significantly affected by small crystal grains when the crystal grain sizes are not evenly distributed, the area-weighted average crystal grain size of the plurality of crystal grains reflects the proportion occupied by large crystal grains, thereby further emphasizing the influence of large crystal grains on the properties of the material. When the area-weighted average crystal grain size of the plurality of crystal grains satisfies the above range, the formability of the pouch film can be further improved and the long-term performance stability of the cell can be secured, just as when the range of the average crystal grain size is satisfied.

[0058] According to one embodiment of the present invention, the standard deviation of the crystal grain size of the plurality of crystal grains may be 3.7 or more and 6.0 or less. More specifically, the standard deviation of the crystal grain size of the plurality of crystal grains may be 3.7 or more, 3.8 or more, 3.9 or more, 4.0 or more, 4.1 or more, 4.2 or more, 4.3 or more, 4.4 or more, 4.5 or more, 4.6 or more, 4.7 or more, or 4.8 or more, and may be 6.0 or less, 5.9 or less, 5.8 or less, 5.7 or less, 5.6 or less, 5.5 or less, 5.4 or less, 5.3 or less, 5.2 or less, 5.1 or less, 5.0 or less, or 4.9 or less. When the standard deviation of the aforementioned multiple crystal grain sizes satisfies the above range, the mechanical strength, ductility, and fatigue durability of the aluminum alloy are balanced, allowing the barrier layer to provide stable performance, and the plasticity and processability are improved, which has the advantage of enabling stable forming during the manufacturing process.

[0059] According to one embodiment of the present invention, the minimum crystal grain size of the plurality of crystal grains may be 0.5 μm or more and 1.7 μm or less. More specifically, the minimum crystal grain size of the plurality of crystal grains may be 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, or 1.0 μm or more, and may also be 1.7 μm or less, 1.6 μm or less, 1.5 μm or less, 1.4 μm or less, 1.3 μm or less, 1.2 μm or less, or 1.1 μm or less. When the minimum crystal grain size of the plurality of crystal grains satisfies the above range, the stability of the microstructure is enhanced, allowing it to better respond to external impacts or stresses and prevent cracking of the pouch film.

[0060] According to one embodiment of the present invention, the maximum crystal grain size of the plurality of crystal grains may be 20.0 μm or more and 38.0 μm or less. More specifically, the maximum crystal grain size of the plurality of crystal grains may be 20.0 μm or more, 20.5 μm or more, 21.0 μm or more, 21.5 μm or more, 22.0 μm or more, 22.5 μm or more, 23.0 μm or more, 23.5 μm or more, 24.0 μm or more, 24.5 μm or more, 25.0 μm or more, 25.5 μm or more, 26.0 μm or more, 26.5 μm or more, 27.0 μm or more, 27.5 μm or more, 28.0 μm or more, 28.5 μm or more, 29.0 μm or more, 29.5 μm or more, or 30.0 μm or more, and may also be 38.0 μm or less, 37.5 μm or less, 37.0 μm or less, 36.5 μm or less, It may be 36.0 μm or less, 35.5 μm or less, 35.0 μm or less, 34.5 μm or less, 34.0 μm or less, 33.5 μm or less, 33.0 μm or less, 32.5 μm or less, 32.0 μm or less, 31.5 μm or less, 31.0 μm or less, or 30.5 μm or less. When the maximum crystal grain size of the plurality of crystal grain sizes satisfies the above range, the plastic properties of the aluminum alloy can be improved, thereby providing advantageous properties in processability and manufacturing processes.

[0061] According to one embodiment of the present invention, 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. The type of the barrier layer is not particularly limited, but may further include at least one selected from the group consisting of iron, silicon, nickel, titanium, manganese, stainless steel, copper, and alloys thereof, and specifically may include one or more metals selected from the group consisting of nickel and titanium.

[0062] According to one embodiment of the present invention, 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 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, or 50 μm or more, and may also be 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, 80 μm or less, 75 μm or less, 70 μm or less, 65 μm or less, 60 μm or less, or 55 μm or less.

[0063] According to one embodiment of the present invention, 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㎛, 15㎛ or more, 20㎛ or more, 25㎛ or more, 27㎛ 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.

[0064] According to one embodiment of the present invention, the outer layer may include a first outer layer and a second outer layer, and the first outer layer may include one or more compounds selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyethylene naphthalate.

[0065] 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.

[0066] 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.

[0067] According to one embodiment of the present invention, 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). Accordingly, 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.

[0068] According to one embodiment of the present invention, the polyolefin resin may comprise, for example, a polyolefin derived from an olefin or a derivative thereof, a copolymer thereof, or a blend comprising at least one of these. For example, the polyolefin resin may comprise 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.

[0069] According to one embodiment of the present invention, the thickness of the sealant layer may be, for example, 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 when satisfying the above numerical range, it may have excellent electrolyte resistance and insulation properties.

[0070] 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.

[0071] 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.

[0072]

[0073] Pouch-type secondary battery case

[0074] 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.

[0075] 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, LiFeO2, Li(Ni 0.6 Mn 0.2 Co 0.2 It may include positive active materials such as O2.

[0076] 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.

[0077] 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.

[0078] 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.

[0079]

[0080] 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.

[0081]

[0082] Preparation Example

[0083] Aluminum ingots were prepared and melted in a high-temperature furnace to a liquid state, and then the ingots were manufactured and melted in a melting furnace to remove impurities and bubbles. During this process, decarburization or deoxidation processes may be performed, and metal elements other than aluminum may be added. Subsequently, the aluminum from which impurities and bubbles have been removed was heated to approximately 600 to 800°C, and the heated aluminum was formed into a thin film through a hot rolling process. The rolled product was further thinned into a coil form through a cold rolling process, and the thickness was homogenized through rough rolling and double rolling processes. Next, the mechanical properties and ductility of the aluminum were improved through a post-processing process to produce a thin aluminum alloy in a thin film state.

[0084] At this time, several aluminum alloys with different degrees of metal crystallinity were manufactured by adjusting the above rolling and cooling conditions.

[0085]

[0086] Examples and Comparative Examples

[0087] A pouch film was manufactured by laminating an outer layer, a barrier layer, and a sealant layer. The outer layer used 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 used an aluminum alloy prepared in the above manufacturing example. The sealant layer (thickness 80 μm) was 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). Additionally, an adhesive layer located between the polyethylene terephthalate film and the nylon film was bonded to have a thickness of 3 to 5 μm, and an adhesive layer located between the nylon film and the barrier layer was also bonded to have a thickness of 3 to 5 μm. At this time, the thickness of the barrier layer is as shown in Table 1 below.

[0088]

[0089] Experimental Example 1: Electron Backscatter Diffraction Analysis

[0090] 1) Grain boundary ratio

[0091] A specimen was prepared by cutting the thin-film aluminum alloy prepared in the above manufacturing example into a 2 mm x 2 mm piece. For the prepared specimen, the ratio of high-angle grain boundaries (%) and the ratio of low-angle grain boundaries (%) of multiple grains included in the measurement point (150 µm x 70 µm) were observed using OIM Analysis software, which is a connected program for an electron backscatter diffraction instrument (OXFORD, acceleration voltage 20.0 kV, WD 19.0 mm, measurement magnification 1500x (width 150 µm * height 50 µm), step size 0.2 µm, specimen tile 70°, hit rate 83.85%), and are shown in Table 1 below. In addition, the value obtained by dividing the ratio of high-angle grain boundaries (%) by the ratio of low-angle grain boundaries (%) was calculated as the grain boundary ratio and is shown in Table 1 below.

[0092]

[0093] 2) Grain orientation

[0094] A specimen was prepared by cutting the thin-film aluminum alloy prepared in the above manufacturing example into a 2 mm x 2 mm piece. For the prepared specimen, using OIM Analysis software, which is a connected program for an electron backscattering diffraction instrument (OXFORD, acceleration voltage 20.0 kV, WD 19.0 mm, measurement magnification 1500x (width 150 µm * height 50 µm), step size 0.2 µm, specimen tile 70°, hit rate 83.85%), among multiple crystal grains included at the measurement point (150 µm x 70 µm) <001> , <101> and <111> The percentage (%) of grains having a crystal orientation was measured and is shown in Table 1 below. In addition, the above-measured <001> , <101> and <111> The standard deviation of the ratio (%) of crystal grains having a crystal orientation was calculated and is shown in Table 1 below.

[0095]

[0096] 3) Grain size

[0097] A specimen was prepared by cutting the aluminum alloy in a thin film state prepared in the above manufacturing example into a 2 mm x 2 mm piece. For the prepared specimen, the number of multiple crystal grains and the average crystal grain size contained in the measurement point (150 µm x 70 µm) were measured using OIM Analysis software, which is a connected program for an electron backscatter diffraction instrument (OXFORD, acceleration voltage 20.0 kV, WD 19.0 mm, measurement magnification 1500x (width 150 µm * height 50 µm), step size 0.2 µm, specimen tile 70°, hit rate 83.85%), and the results are shown in Table 1 below.

[0098]

[0099] Experimental Example 2: Evaluation of Pouch Film Physical Properties

[0100] 1) Evaluation of tensile strength and elongation

[0101] The above tensile strength was determined by peeling off the barrier layer and the second outer layer of the pouch film prepared in the above examples and comparative examples to produce specimens of 150 mm (MD) x 1.5 mm (TD) and 150 mm (TD) x 1.5 mm (MD), respectively. Then, the specimens were fixed between two jigs of a tensile testing machine (UTM) at room temperature (initial jig gap 30 mm), and the stroke (mm) and strength (N) of the specimens were measured while pulling them in the MD direction at a measurement speed of 50 mm / min. The measured tensile strength values ​​are shown in Table 1 below.

[0102] In addition, the elongation in the present invention was measured by the following method. Two parallel lines were drawn in the center of the specimen, and the initial distance between these lines was set to 30 mm. Then, the specimen was mounted on a tensile testing machine to perform a tensile strength test, and the actual length between the lines stretched by the tension was measured.

[0103] The elongation is calculated according to the following mathematical formula 1, and the above elongation is shown in Table 1 below.

[0104] [Mathematical Formula 1]

[0105] Elongation = ((Increased length - 30mm) / 30mm) x 100,

[0106] In the above mathematical formula 1,

[0107] The above increased length is the final distance between the two lines after the tensile test.

[0108]

[0109] 2) Penetration strength

[0110] The pouch films prepared in the above examples and comparative examples were cut to produce specimens of 400 mm (MD) x 50 mm (TD), and the specimens prepared were attached in the MD direction to the jig of a UTM TESTER (Dynamic Mode, Shimadzu Scientific, AGS-X), and then the puncture strength was measured at a speed of 50 mm / min and is shown in Table 1 below.

[0111]

[0112] 3) Formation depth

[0113] The pouch films prepared in the above examples and comparative examples were cut to produce specimens measuring 240 mm (MD) X 266 mm (TD), and the formability was evaluated using a forming machine (a Cr-coated 1-cup forming machine). The results of the forming were measured 10 times, and the maximum forming depth of the pouch that was formed without cracking in all 10 attempts was evaluated and is shown in Table 1 below. The pressure during forming was fixed at 0.3 MPa, and the R value (corner radius of curvature) of the forming machine was 4R (4 mm). The forming size during forming was 90 mm X 120 mm, and the process was performed as a single forming machine.

[0114] In addition, the pouch films prepared in the above examples and comparative examples were cut to produce specimens measuring 300 mm (MD) X 400 mm (TD), and the formability was evaluated using a forming machine (a 2-cup forming machine coated with Cr). The results of the forming were measured 10 times, and the maximum forming depth of the pouch that was formed without cracking in all 10 attempts was evaluated and is shown in Table 1 below. The pressure during forming was fixed at 0.7 MPa, and the R value (corner radius of curvature) of the forming machine was 1R (1 mm). The forming size during forming was 90 mm X 120 mm, and the process was performed as a single forming machine.

[0115]

[0116] Analysis Item Unit Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Barrier Layer Thickness ㎛ 40 40 60 60 40 40 60 EBSD Cross-sectional Shape Analysis Grain Boundary Ratio High-angle Grain Boundary Ratio (HAB, >15°) % 84.8 80.0 84.4 84.6 77.1 77.8 88.2 Low-angle Grain Boundary Ratio (LAB, 2~15°) 15.2 20.0 15.6 15.4 22.9 22.2 12.2 HAB / LAB 5.6 4.0 5.4 5.5 3.4 3.5 7.2 Grain Orientation 00 1 (Red) % 24.3 16.8 22.9 32.0 17.3 17.1 12.3 10 1 (Green) 10.3 4.1 23.8 22.7 3.3 3.5 6.2 111 (Blue) 44.0 27.4 33.0 25.0 45.5 58.0 53.2 Standard deviation -16.9 13.8 5.6 4.8 21.5 28.4 25.6 Grain size ea 16 4 15 8 21 4 2 12 33 4 3 14 121 Average grain size ㎛ 6.1 6.5 6.3 7.3 4.1 4.9 8.1 Area-weighted average crystal Particle size 11.5 15.1 11.7 14.3 8.8 9.8 16.2 Minimum 0.8 0.7 1.5 0.8 0.7 0.7 1.8 Maximum 23.8 34.8 20.8 29.7 17.5 21.7 38.1 Standard deviation -4.1 4.8 4.4 5.2 3.0 3.6 6.1 Al Raw Material Physical Properties Tensile Strength MDN / mm 2 94.8 101.4 94.3 97.5 94.2 93.0 90.1 TD 90.6 98.0 93.0 95.9 90.1 92.0 87.6 Elongation MD% 19.2 22.9 24.9 17.0 20.2 18.4 19.4 TD 18.4 26.0 26.0 20.8 23.2 21.0 18.1 Puncture Strength N 6.4 6.5 10.9 10.8 6.9 7.2 10.4 Pouch Properties Forming Depth 1-cup_MD mm 8.0 8.5 16.5 17.0 7.0 7.5 15.5 1-cup_TD 8.0 8.5 16.0 16.5 6.0 6.0 16.0 MD / TD Deviation 000 0.5 0.5 11.5 0.5 2-cup_MD781112 5.5 6.5 10 2-cup_TD7810.5 11.5 5.5 5.5 9.5 MD / TD Deviation - 0.5 0.5 0.5 0 10.5

[0117] Referring to Table 1 above, it can be confirmed that Examples 1 to 4, in which the standard deviation of the crystal orientation of a plurality of crystal grains included in the aluminum alloy particles included in the barrier layer satisfies 21.0 or less, have superior mechanical strength and formability compared to Comparative Examples 1 to 3, which fall outside the above range.

[0118] Specifically, when comparing Example 1, Example 2, Comparative Example 1, and Comparative Example 2, in which the thickness of the barrier layer is 40 μm, it can be seen that Example 1 and 2 secured excellent tensile strength while maintaining similar levels of elongation and puncture strength compared to Comparative Examples 1 and 2, and that the forming depth was improved.

[0119] In addition, when comparing Example 3, Example 4, and Comparative Example 3, which have the same barrier layer thickness of 60 μm, it can be seen that Example 3 and Example 4 have much higher tensile strength and elongation than Comparative Example 3, and secure a deep forming depth.

[0120]

[0121] Acknowledgement

[0122] [Project ID] 2410004468

[0123] [Assignment No.] 20022450

[0124] [Ministry Name] Ministry of Trade, Industry and Energy

[0125] [Project Management (Specialized) Agency Name] Korea Institute of Industrial Technology Planning and Evaluation

[0126] [Research Project Name] Development of Materials and Components Technology (Leading Company)

[0127] [Project Title] Development of Next-Generation Secondary Battery Pouch Capable of Achieving More Than Twice the High Adhesion Strength (60℃)

[0128] [Contribution Rate] 1 / 1

[0129] [Name of Project Performing Organization] Yulchon Chemical Co., Ltd.

[0130] [Research Period] 2024-01-01 ~ 2024-12-31

Claims

1. Includes an outer layer, a barrier layer, and a sealant layer stacked sequentially, and The above barrier layer comprises an aluminum alloy, and The particles of the above aluminum alloy contain a plurality of crystal grains, and Measured by electron backscatter diffraction analysis under conditions of acceleration voltage 20.0 kV, WD 19.0 mm, measurement magnification 1500x (width 150 µm * height 50 µm), and step size 0.2 µm <001> Proportion of grains with crystal orientation (%), <101> Proportion (%) of grains having a crystal orientation and <111> A pouch film having a standard deviation of the ratio (%) of crystal grains having a crystal orientation of 21.0 or less.

2. In Paragraph 1, A pouch film wherein the plurality of crystal grains have a value calculated according to Formula 1 below of 3.6 or more and 7.0 or less: [Equation 1] High-angle grain boundary ratio (%) / Low-angle grain boundary ratio (%) In the above Equation 1, High-angle grain boundaries (%) is the ratio of grain boundaries with an angle greater than 15° measured by electron backscatter diffraction analysis under conditions of an acceleration voltage of 20.0 kV, WD of 19.0 mm, a magnification of 1500x (width 150 μm * height 50 μm), and a step size of 0.2 μm out of the total grain boundaries, and The low-angle grain boundary (%) is the proportion of grain boundaries with an angle of 2° or more and 15° or less, measured by electron backscatter diffraction analysis under conditions of acceleration voltage 20.0 kV, WD 19.0 mm, measurement magnification 1500x (width 150 μm * height 50 μm), and step size 0.2 μm among all grain boundaries.

3. In Paragraph 2, A pouch film having a high-angle grain boundary ratio (%) of the plurality of grains above of 78.0% or more and 88.0% or less.

4. In Paragraph 2, A pouch film having a low-angle grain boundary ratio (%) of the plurality of grains above of 12.5% ​​or more and 22.0% or less.

5. In Paragraph 1, A pouch film having an average crystal grain size of the plurality of crystal grains of the above, which is 5.0 μm or more and 8.0 μm or less.

6. In Paragraph 1, A pouch film having an area-weighted average crystal grain diameter of the plurality of crystal grains of the above, which is 10.0 μm or more and 16.0 μm or less.

7. In Paragraph 1, A pouch film having a standard deviation of the crystal grain size of the plurality of crystal grains above of 3.7 or more and 6.0 or less.

8. In Paragraph 1, A pouch film having a minimum crystal grain size of the plurality of crystal grains of the above, which is 0.5 μm or more and 1.7 μm or less.

9. In Paragraph 1, A pouch film having a maximum crystal grain size of the plurality of crystal grains of the above, which is 20.0 μm or more and 38.0 μm or less.

10. In Paragraph 1, The above <001> A pouch film having a ratio of crystal grains having a crystal orientation of 15.0% or more and 50.0% or less.

11. In Paragraph 1, The above <101> A pouch film having a ratio of crystal grains having a crystal orientation of 7.0% or more and 50.0% or less.

12. In Paragraph 1, The above <111> A pouch film having a ratio of crystal grains having a crystal orientation of 20.0% or more and 50.0% or less.

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

14. In Paragraph 1, A pouch film having a barrier layer thickness of 40.0 μm or more and 60.0 μm or less.

15. In Paragraph 1, A pouch film in which the barrier layer further comprises one or more elements selected from the group consisting of stainless steel, copper, iron, silicon, nickel, titanium, and manganese.

16. A pouch-type secondary battery case comprising a pouch film according to any one of claims 1 to 15.

Images