Pouch film, pouch-type battery case and secondary battery comprising same, and method for manufacturing same

Abstract

The present invention relates to a pouch film comprising a sealant layer, a barrier layer, a second outer layer, and a first outer layer which are sequentially laminated, wherein the second outer layer comprises a nylon-based resin, the thickness of the second outer layer is 35-60 μm inclusive, and the tensile strength ratio of the barrier layer and the second outer layer measured according to the measuring condition below is 0.9-1.2 inclusive. [Measuring condition] The barrier layer and the second outer layer of the pouch film are peeled so as to make respective test pieces having a width of 15 mm, and then, at room temperature, the test pieces are fixed between two jigs of a tensile tester (UTM) (initial jig gap 50 mm), and then the stroke (mm) and strength (N) of the test pieces are measured while pulling each test piece in the MD direction at a measuring speed of 50 mm / min. The x-axis in a graph derived from the measured values is stroke (mm), and the y-axis is tensile strength (N), and the tensile strength of the barrier layer and the second outer layer when the stroke is 5 mm is measured.

Description

Pouch film, pouch-type battery case and secondary battery including the same, and method for manufacturing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0143316, filed October 24, 2023, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

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

[0006]

[0007] Secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. These batteries are used in small products such as digital cameras, DVD players, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, as well as larger products requiring high output, such as electric and hybrid vehicles, as well as power storage devices that store surplus power or renewable energy, and as backup power storage devices.

[0008] To manufacture these secondary batteries, first, an electrode active material slurry is applied to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and these are laminated on both sides of a separator to form an electrode assembly of a predetermined shape. Then, the electrode assembly is housed in a battery case, filled with electrolyte, and sealed.

[0009] Secondary batteries can be classified into pouch, cylindrical, and square types depending on the type of outer material of the case that accommodates the electrode assembly.

[0010] Among these secondary batteries, pouch-type batteries are in the form where the electrode assembly (cell) is built into a pouch made of a metal laminate sheet. They are easy to manufacture, have low manufacturing costs, and are particularly advantageous in that it is easy to manufacture a large-capacity battery pack by connecting multiple unit cells in series or parallel. Therefore, they are mainly used in fields that require large-capacity secondary batteries, such as electric vehicles. The pouch, which is the case of the pouch-type secondary battery, is manufactured by performing press processing on a flexible pouch film to form a cup portion. Then, when the cup portion is formed, the electrode assembly is accommodated in the accommodating space of the cup portion, and the sealing portion is sealed to manufacture the secondary battery. Here, the cup portion refers to a portion that accommodates the electrode assembly, and the sealing portion refers to an edge portion of the cup portion where the pouch film is sealed.

[0011] Meanwhile, in the case of secondary batteries with high energy density using pouch films, the most ideal method is to increase the formability and insert the maximum amount of active material into a single packaging. In order to increase the energy density of secondary batteries using the pouch film, it is necessary to improve the formability of the pouch film to insert the maximum amount of battery active material into the pouch, and for this purpose, the pouch film needs to ensure higher formability. However, the current pouch film has a problem in that the residual thickness of the barrier layer is stretched and reduced during forming, which can cause problems such as moisture infiltration and electrolyte leakage, and thus stability is not guaranteed.

[0012] Currently commercialized pouch films are 183 ㎛ products composed of PP80 / Al60 / Nylon25 / PET12. However, the high-molding pouches only have a formability of about 12 to 15 mm, and the residual thickness of the Al after molding is only about 30 ㎛, making it difficult to completely protect battery materials that are sensitive to air and moisture. Therefore, research is being conducted to secure high formability and a residual thickness of the barrier layer (Al) after molding.

[0013]

[0014] The problem to be solved by the present invention is to provide a pouch film laminate having high formability, a pouch-type battery case including the same, a secondary battery, and a method for manufacturing the same.

[0015]

[0016] The present invention provides a pouch film laminate, a pouch-type battery case including the same, a secondary battery, and a method for manufacturing the same.

[0017] (1) The present invention provides a pouch film comprising a sealant layer, a barrier layer, a second outer layer, and a first outer layer sequentially laminated, wherein the second outer layer comprises a nylon-based resin, the thickness of the second outer layer is 35 ㎛ or more and 60 ㎛ or less, and the tensile strength ratio of the barrier layer and the second outer layer measured under the following measurement conditions satisfies the following equation 1.

[0018] [Formula 1]

[0019] 0.9≤Tensile strength of barrier layer / Tensile strength of second outer layer≤1.2

[0020]

[0021] [Measurement conditions]

[0022] After peeling off the barrier layer and the second outer layer of the above pouch film to manufacture a specimen with a width of 15 mm, the specimen is fixed between two jigs of a tensile tester (UTM) at room temperature (initial jig gap 50 mm), and the stroke (mm) and strength (N) of the specimen are measured while pulling at a measurement speed of 50 mm / min in the MD direction. The X-axis of the graph derived from the measured values ​​represents the stroke (mm), the Y-axis represents the tensile strength (N), and the tensile strength of the barrier layer and the second outer layer is measured when the stroke is 5 mm.

[0023] (2) The present invention provides a pouch film in (1) above, wherein the thickness ratio of the barrier layer and the second outer layer is 1:0.5 or more and 0.7 or less.

[0024] (3) The present invention provides a pouch film in which the thickness of the barrier layer in (1) or (2) is 40 ㎛ or more and 100 ㎛ or less.

[0025] (4) The present invention provides a pouch film in which the sum of the thicknesses of the first outer layer and the second outer layer is 40 µm or more and 100 µm or less in any one of the above (1) to (3).

[0026] (5) The present invention provides a pouch film in which the ratio of the thickness of the barrier layer to the sum of the thicknesses of the first outer layer and the second outer layer is 1:0.65 or more and 0.9 or less in any one of the above (1) to (4).

[0027] (6) The present invention provides a pouch film in which, in any one of the above (1) to (5), the MD and TD elongations of the second outer layer are each independently 50% or more and 300% or less.

[0028] (7) The present invention provides a pouch film in which the tensile strength of the second outer layer in the MD direction is 200 N / 15 mm or more and 300 N / 15 mm or less in any one of the above (1) to (6).

[0029] (8) The present invention provides a pouch film in which the thickness remaining ratio of the barrier layer according to the following formula 2 is 55% or more in any one of the above (1) to (7).

[0030] [Formula 2]

[0031] Thickness Residual Rate (%) = (Thickness of barrier layer after molding / Thickness of barrier layer before molding) × 100

[0032] In the above equation 2,

[0033] The thickness of the barrier layer after molding was measured by cutting a pouch film excluding the sealing portion to create a specimen measuring 266 mm (TD) x 240 mm (MD) x 15 mm (width), then applying LDPE (low-density polyethylene) to both sides of the sample, and then molding it at a molding depth of 17 mm by applying pressure of 0.3 Mpa using a test molding machine measuring 30 mm x 75 mm. At this time, the measurement was performed 6 times at each of the 4 corners of the rectangular molding shape, and the average value of the barrier layer thickness was calculated.

[0034] (9) The present invention provides a pouch film according to any one of the above (1) to (8), wherein the second outer layer comprises a single layer or two or more laminated layers.

[0035] (10) The present invention provides a pouch film according to any one of the above (1) to (9), wherein the thickness of the pouch film is 205 ㎛ or more and 250 ㎛ or less.

[0036] (11) The present invention provides a pouch film in any one of the above (1) to (10), wherein the first outer layer comprises at least one material selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber.

[0037] (12) The present invention provides a pouch film according to any one of (1) to (11), wherein the thickness of the first outer layer is 5 ㎛ or more and 40 ㎛ or less.

[0038] (13) The present invention provides a pouch film in any one of the above (1) to (12), wherein the barrier layer includes at least one material selected from the group consisting of aluminum, stainless steel, copper, titanium, and alloys thereof.

[0039] (14) The present invention provides a pouch-type battery case including a pouch film according to any one of (1) to (13).

[0040] (15) The present invention provides a secondary battery including an electrode assembly formed by stacking a positive electrode, a separator, and a negative electrode, and a pouch-shaped battery case according to (14) for storing the electrode assembly.

[0041] (16) The present invention provides a method for manufacturing a pouch film, comprising the steps of laminating a sealant film on one side of a barrier film, and sequentially laminating a second outer layer and a first outer layer on the other side of the barrier film, wherein the second outer layer includes a nylon-based resin, and the second outer layer is manufactured by a blown method.

[0042]

[0043] The pouch film of the present invention has excellent tensile strength and elongation, and thus can have high molding properties.

[0044] In addition, the pouch film of the present invention has an excellent thickness retention rate after forming the barrier layer, thereby preventing moisture penetration and electrolyte leakage.

[0045] In addition, the pouch film of the present invention has high formability and can accommodate a large amount of electrode assemblies, so it can have high electric capacity and efficiency.

[0046]

[0047] Figure 1 is a schematic diagram showing the configuration of the pouch film of the present invention.

[0048] Figure 2 is a graph showing the tensile strength (N) values ​​versus the stroke (mm) of the barrier layer and the second outer layer.

[0049] Figure 3 is an SEM photograph showing the remaining thickness of the barrier layer after molding in Example 1.

[0050] Figure 4 is an SEM photograph showing the remaining thickness of the barrier layer after molding in Comparative Example 2.

[0051]

[0052] Hereinafter, the present invention will be described in more detail to facilitate understanding. The terms and words used in this specification and claims should not be interpreted based on their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that aligns with the technical spirit of the present invention.

[0053] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0054] In this specification, it should be understood that the terms “include,” “comprising,” or “having” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0055] In the present specification, when each layer of the secondary battery pouch is included, it is not necessarily composed of only that layer, but additional layers may be included.

[0056] In this specification, being formed 'on' a specific layer includes not only being formed directly on that layer, but also being formed after interposing an additional layer.

[0057] In this specification, the extrusion coating (EC) layer refers to an extrusion layer of a resin, such as a polyolefin-based resin, preferably a polypropylene-based resin, that is extruded for lamination with a barrier layer as part or the entirety of a sealant layer. When a non-stretched polypropylene (CPP) layer and an extrusion coating (EC) layer exist simultaneously in the sealant layer, the extrusion coating (EC) layer is located on the barrier layer side.

[0058] In this specification, the polypropylene (PP) layer of the sealant layer is a core resin layer forming the sealant layer and performs a sealing function, and may be formed of one or more layers made of polypropylene resin. It is in contrast to 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., the side opposite the barrier layer) based on the aforementioned extrusion bonding coating (EC) layer.

[0059]

[0060] pouch film

[0061] The present invention provides a pouch film comprising a sealant layer, a barrier layer, a second outer layer, and a first outer layer sequentially laminated, wherein the second outer layer comprises a nylon-based resin, the thickness of the second outer layer is 35 ㎛ or more and 60 ㎛ or less, and the tensile strength ratio of the barrier layer and the second outer layer measured under the following measurement conditions satisfies the following equation 1.

[0062] [Formula 1]

[0063] 0.9≤Tensile strength of barrier layer / Tensile strength of second outer layer≤1.2

[0064] [Measurement conditions]

[0065] After peeling off the barrier layer and the second outer layer of the above pouch film to manufacture a specimen with a width of 15 mm, the specimen is fixed between two jigs of a tensile tester (UTM) at room temperature (initial jig gap 50 mm), and the stroke (mm) and strength (N) of the specimen are measured while pulling at a measurement speed of 50 mm / min in the MD direction. The X-axis of the graph derived from the measured values ​​represents the stroke (mm), the Y-axis represents the tensile strength (N), and the tensile strength of the barrier layer and the second outer layer is measured when the stroke is 5 mm.

[0066] The outer layer included in the pouch film is required to have excellent processability and moldability because it serves to prevent contact with the outside and seal the electrode assembly accommodated inside, and the processability and moldability are affected by the mechanical properties, and in particular, are greatly affected by the mechanical properties of the outer layer. The inventor of the present invention has discovered a problem that in the case of a conventional pouch film, a molding process is performed according to the size of the electrode assembly in order to accommodate an electrode assembly having a desired size, but the remaining thickness of the barrier layer (metal layer) is stretched and reduced during molding, which may cause problems such as moisture penetration and electrolyte leakage.

[0067] In order to solve these problems, the inventor of the present invention provides a pouch film having high formability by controlling the thickness of a second outer layer including a nylon-based resin to a specific range and the tensile strength ratio between a barrier layer and the second outer layer to maintain excellent levels of tensile strength and elongation at the same time, and increasing the thickness retention rate after forming, thereby preventing moisture penetration and electrolyte leakage.

[0068] Figure 1 illustrates the configuration of a pouch film of the present invention. The pouch film of the present invention includes a sealant layer on the inner side, an outer layer, and a barrier layer containing aluminum between the inner sealant layer and the outer layer. In addition, the outer layer includes a first outer layer and a second outer layer. Specifically, the outer layer may be formed of a laminated film of the first outer layer and the second outer layer. The second outer layer may include a heat-resistant resin having a melting point higher than the heat bonding temperature of the sealant layer, and the second outer layer may include a nylon-based resin.

[0069] In addition, the outer layer may be the outermost layer of the lithium secondary battery outer pouch film, and the thickness of the outer layer may be specified within a range that can secure sufficient mechanical strength and sufficient formability as an outer material, and in particular, in the case of the second outer layer of the outer layer of the present invention, it may have a thickness thicker than that of a conventional second outer layer by further considering the thickness residual ratio of the barrier layer.

[0070] The thickness of the second outer layer of the present invention is 35 ㎛ or more and 60 ㎛ or less. For example, it may be 35 ㎛ or more, 37 ㎛ or more, 39 ㎛ or more, 40 ㎛ or more, 43 ㎛ or more, 45 ㎛ or more, 47 ㎛ or more, 50 ㎛ or more, 60 ㎛ or less, 59 ㎛ or less, 57 ㎛ or less, 55 ㎛ or less, 53 ㎛ or less, or 51 ㎛ or less, and specifically, the thickness of the second outer layer may be 40 ㎛ or more and 55 ㎛ or less. If the thickness of the second outer layer is out of the range, the tensile strength may be lowered, and the formability of the pouch film may be deteriorated.

[0071] Additionally, the second outer layer may comprise a single layer or two or more laminated layers. To increase the thickness of the second outer layer and achieve a balance of properties with the barrier layer, the second outer layer may be formed as a single layer or may be formed by laminating two or more separate layers.

[0072] In addition, the pouch film of the present invention has a tensile strength ratio value of the barrier layer and the second outer layer according to Equation 1 of 0.9 or more and 1.2 or less. For example, the tensile strength of the barrier layer / tensile strength of the second outer layer according to Equation 1 is 0.90 or more, 0.91 or more, 0.93 or more, 0.95 or more, 0.97 or more, 1.00 or more, 1.01 or more, 1.03 or more, 1.05 or more, 1.07 or more, 1.09 or more, 1.20 or less, 1.19 or less, 1.17 or less, 1.15 or less, 1.13 or less, 1.11 or less, 1.10 or less, and specifically, the values ​​are 0.95 or more and 1.17 or less. The tensile strength and elongation of the barrier layer and the outer layer are one of the main characteristics that can be linked to the formability of the pouch film. For example, as tensile strength increases, toughness may increase, and as elongation increases, the formability limit may increase.

[0073] Fig. 2 is a graph showing the tensile strength of the barrier layer and the outer layer. In Fig. 2, the dotted lines represent the tensile strength curves of the barrier layer (Al) with thicknesses of 60 ㎛ and 80 ㎛, respectively, and the solid lines represent the tensile strength curves of the second outer layer (Ny) for each thickness. If the tensile strength of the second outer layer is too low compared to the tensile strength of the barrier layer, the formability is significantly reduced. Therefore, by increasing the thickness of the second outer layer, the tensile strength ratio of the barrier layer and the second outer layer was controlled to approach 1.

[0074] That is, the pouch film of the present invention is controlled to simultaneously satisfy the thickness range of the second outer layer and the tensile strength ratio between the barrier layer and the second outer layer, thereby simultaneously having optimal tensile strength and elongation characteristics. Through this, the present invention can increase the thickness remaining ratio of the barrier layer and provide a pouch film having excellent molding that can be precisely and accurately molded into a desired size.

[0075]

[0076] According to one embodiment of the present invention, the thickness of the first outer layer may be 5 ㎛ or more and 40 ㎛ or less. The thinner the first outer layer and the thicker the second outer layer, the more advantageous the formability. However, the thinner the first outer layer may be in terms of insulation breakdown voltage. From this point of view, the thickness of the first outer layer may be 5 ㎛ or more, 8 ㎛ or more, 10 ㎛ or more, 12 ㎛ or more, 40 ㎛ or less, 39 ㎛ or less, 37 ㎛ or less, 35 ㎛ or less, 33 ㎛ or less, 31 ㎛ or less, 30 ㎛ or less, 29 ㎛ or less, 27 ㎛ or less, 25 ㎛ or less, 23 ㎛ or less, 21 ㎛ or less, 20 ㎛ or less, 19 ㎛ or less, 17 ㎛ or less, 15 ㎛ or less, or 13 ㎛ or less.

[0077]

[0078] According to one embodiment of the present invention, the thickness of the barrier layer may be 40 μm or more and 100 μm or less. The barrier layer may be an intermediate layer of the lithium secondary battery external pouch film (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.

[0079] The above barrier layer is not particularly limited in type, but may include one or more materials selected from the group consisting of aluminum, stainless steel, copper, titanium, and alloys thereof, and specifically may include aluminum.

[0080] In addition, by way of example, the thickness of the barrier layer is 40 ㎛ or more, 42 ㎛ or more, 44 ㎛ or more, 46 ㎛ or more, 48 ㎛ or more, 50 ㎛ or more, 52 ㎛ or more, 54 ㎛ or more, 56 ㎛ or more, 58 ㎛ or more, 60 ㎛ or more, 62 ㎛ or more, 64 ㎛ or more, 66 ㎛ or more, 68 ㎛ or more, 70 ㎛ or more, 72 ㎛ or more, 74 ㎛ or more, 75 ㎛ or more, 100 ㎛ or less, 99 ㎛ or less, 98 ㎛ or less, 96 ㎛ or less, 94 ㎛ or less, 92 ㎛ or less, 90 ㎛ or less, 88 ㎛ or less, 86 ㎛ or less, 84 ㎛ or less, 82 ㎛ or less, 80 ㎛ or less, 78 ㎛ or less, 76 ㎛ or less. and, specifically, may be 70 ㎛ or more and 90 ㎛ or less. When the thickness range of the barrier layer is satisfied, the intrusion of gas and / or moisture can be effectively prevented, and at the same time, the tensile strength ratio with respect to the second outer layer can be maintained within a specific range, thereby ensuring excellent formability.

[0081]

[0082] According to one embodiment of the present invention, the thickness ratio of the barrier layer and the second outer layer may be 1: 0.5 or more and 0.7 or less. For example, the thickness ratio of the barrier layer and the second outer layer may be 1: 0.50 or more, 0.51 or more, 0.53 or more, 0.55 or more, 0.57 or more, 0.59 or more, 0.60 or more, 0.61 or more, 0.63 or more, 0.70 or less, 0.69 or less, 0.67 or less, 0.65 or less, and specifically, the thickness ratio of the barrier layer and the second outer layer may be 1: 0.5 or more and 0.69 or less.

[0083] In addition, according to one embodiment of the present invention, the sum of the thicknesses of the first outer layer and the second outer layer may be 50 ㎛ or more and 80 ㎛ or less. For example, it may be 50 ㎛ or more, 52 ㎛ or more, 55 ㎛ or more, 57 ㎛ or more, 60 ㎛ or more, 62 ㎛ or more, 80 ㎛ or less, 78 ㎛ or less, 76 ㎛ or less, 74 ㎛ or less, 72 ㎛ or less, 70 ㎛ or less, 69 ㎛ or less, 67 ㎛ or less, 65 ㎛ or less, and specifically, the sum of the thicknesses of the first outer layer and the second outer layer may be 52 ㎛ or more and 67 ㎛ or less.

[0084] In addition, according to one embodiment of the present invention, the ratio of the thickness of the barrier layer to the sum of the thicknesses of the first outer layer and the second outer layer may be 1: 0.65 or more and 0.9 or less. For example, the ratio of the thickness of the barrier layer to the sum of the thicknesses of the first outer layer and the second outer layer may be 1: 0.65 or more, 0.67 or more, 0.69 or more, 0.70 or more, 0.71 or more, 0.73 or more, 0.75 or more, 0.77 or more, 0.78 or more, 0.90 or less, 0.89 or less, 0.87 or less, 0.85 or less, 0.84 or less, 0.83 or less, 0.81 or less, 0.80 or less, and specifically, the ratio of the thickness of the barrier layer to the sum of the thicknesses of the first outer layer and the second outer layer may be 1: 0.65 or more and 0.84 or less.

[0085] The thickness ratio of the barrier layer and the second outer layer, the sum of the thicknesses of the first outer layer and the second outer layer, and the ratio of the thickness of the barrier layer to the sum of the thicknesses of the first outer layer and the second outer layer are intended to simultaneously maintain high tensile strength and elongation, and to lower the thickness residual ratio of the barrier layer after molding to secure excellent formability, thereby controlling the balance between the properties of the outer layer and the barrier layer. That is, when the thickness ranges among the barrier layer, the first outer layer, and the second outer layer are satisfied, the thickness residual ratio of the barrier layer can be increased, and excellent formability can be maintained.

[0086] According to one embodiment of the present invention, the MD and TD elongations of the second outer layer may each independently be 50% or more and 300% or less. For example, the MD and TD elongation of the first outer layer may be 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 300% or less, 290% or less, 280% or less, 270% or less, 260% or less, 250% or less, 240% or less, 230% or less, 220% or less, 210% or less, 200% or less, 190% or less, 180% or less, 170% or less, 160% or less, 150% or less, 140% or less, 130% or less, 120% or less, 110% or less, 100% or less, 95% or less, 90% or less, 85% or less, 80% or less.

[0087] Additionally, according to one embodiment of the present invention, the tensile strength of the second outer layer in the MD direction may be 200 N / 15 mm or more and 300 N / 15 mm or less. For example, the tensile strength in the MD direction of the second outer layer is 200 N / 15mm or more, 205 N / 15mm or more, 210 N / 15mm or more, 213 N / 15mm or more, 215 N / 15mm or more, 220 N / 15mm or more, 225 N / 15mm or more, 230 N / 15mm or more, 235 N / 15mm or more, 240 N / 15mm or more, 245 N / 15mm or more, 250 N / 15mm or more, 255 N / 15mm or more, 300 N / 15mm or less, 295 N / 15mm or less, 290 N / 15mm or less, 285 N / 15mm or less, 280 N / 15mm or less, 276 N / 15mm or less, 275 N / 15mm or less, 270 It can be N / 15mm or less, 269 N / 15mm or less, 265 N / 15mm or less, or 260 N / 15mm or less.

[0088] When the range of elongation and tensile strength of the second outer layer is satisfied, the balance of physical properties with the barrier layer can be optimally maintained, and the thickness remaining ratio of the barrier layer after molding can be increased.

[0089] According to one embodiment of the present invention, the thickness retention ratio of the barrier layer according to the following equation 2 may be 55% or more.

[0090] [Formula 2]

[0091] Thickness Residual Rate (%) = (Thickness of barrier layer after molding / Thickness of barrier layer before molding) × 100

[0092] In the above equation 2,

[0093] The thickness of the barrier layer after molding was measured by cutting a pouch film excluding the sealing portion to create a specimen measuring 266 mm (TD) x 240 mm (MD) x 15 mm (width), then applying LDPE (low-density polyethylene) to both sides of the sample, and then molding it at a molding depth of 17 mm by applying pressure of 0.3 Mpa using a test molding machine measuring 30 mm x 75 mm. At this time, the measurement was performed 6 times at each of the 4 corners of the rectangular molding shape, and the average value of the barrier layer thickness was calculated.

[0094] The thickness retention ratio of the above barrier layer is a very important criterion for determining the formability of the pouch film. Even after the forming process to a desired depth, the barrier layer may shrink due to stretching, which may cause problems such as moisture penetration and electrolyte leakage. Therefore, it is important that the thickness of the barrier layer be maintained at a high level after forming. For example, the thickness retention ratio may be 55% or more, 57% or more, 59% or more, 60% or more, 61% or more, 63% or more, or 65% or more. When the thickness retention ratio of the barrier layer is satisfied, a formability of 17 mm or more per 1 cup can be secured, and a formability of 30 mm or more per 2 cups can be secured. Here, the LDPE (low-density polyethylene) may also include PE (polyethylene) as a film to be laminated instead of the CPP (non-stretched polypropylene) film laminated to one side of the barrier layer in order to conduct a formability test, and the thickness of the LDPE (low-density polyethylene) may be 40 ㎛ or more and 60 ㎛ or less, and preferably 50 ㎛. In addition, the friction coefficient of the LDPE may be 0.05 or more and 0.5 or less, and preferably 0.1.

[0095]

[0096] According to one embodiment of the present invention, the thickness of the pouch film may be 205 μm or more and 250 μm or less. For example, the total thickness of the pouch film may be 205 μm or more, 210 μm or more, 212 μm or more, 215 μm or more, 220 μm or more, 222 μm or more, 225 μm or more, 227 μm or more, 250 μm or less, 245 μm or less, 240 μm or less, 235 μm or less, or 230 μm or less. If the total thickness of the pouch film becomes excessively thick, the physical property balance between tensile strength and elongation may be biased to one side, so it is preferable to maintain the thickness of the pouch film within the above range.

[0097]

[0098] According to one embodiment of the present invention, the first outer layer may include one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber. For example, the first outer layer may include polyethylene terephthalate.

[0099]

[0100] The sealant layer may be the innermost layer of the pouch film for the external lithium secondary battery. That is, the sealant layer may be in direct contact with the battery main body (e.g., electrode, separator, and / or electrolyte). Therefore, the sealant layer must have excellent electrolyte resistance and excellent insulation. To this end, the sealant layer may include at least a polyolefin-based resin. The polyolefin-based resin has excellent electrolyte resistance and excellent insulation, and accordingly, the sealant layer including the polyolefin-based resin may also have excellent electrolyte resistance and excellent insulation derived from the polyolefin-based resin.

[0101] The polyolefin-based resin may include, for example, a polyolefin derived from an olefin or a derivative thereof, a copolymer thereof, or a blend comprising at least one of the foregoing. For example, the polyolefin-based resin may include at least one selected from the group consisting of polyethylene, polypropylene, polybutylene, a copolymer derived from a monomer derived from ethylene and / or propylene and a monomer derived from an alpha-olefin, or a blend thereof.

[0102] The thickness of the above sealant layer may be, for example, 20 ㎛ or more, 30 ㎛ or more, 40 ㎛ or more, 50 ㎛ or more, 100 ㎛ or less, 90 ㎛ or less, 80 ㎛ or less, 70 ㎛ or less, or 60 ㎛ or less, and when the above numerical range is satisfied, excellent electrolyte resistance and insulation may be achieved.

[0103] According to one embodiment of the present invention, the sealant layer may be composed of a laminate of two or more layers in order to diversify 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 adhesion between the barrier layer and the second sealant layer, while further 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 may be a layer that simultaneously seals and prevents leakage of the secondary battery, particularly, the non-aqueous electrolyte. The first sealant layer may be an extrusion coating (EC) layer (mainly an extruded polypropylene layer), and the second sealant layer may be a polypropylene (PP) layer resin, preferably a non-stretched polypropylene (CPP) layer, disposed under the first sealant layer (inner side based on the pouch film). In this case, for example, the thickness of the non-stretched polypropylene (CPP) layer of the sealant layer may be, for example, 20 ㎛ or more, 30 ㎛ or more, 40 ㎛ or more, 50 ㎛ or more, 80 ㎛ or less, 70 ㎛ or less, or 60 ㎛ or less, and the thickness of the polypropylene (PP) layer of the sealant layer may be, for example, 0 ㎛ or more, 10 ㎛ or more, 20 ㎛ or more, 30 ㎛ or more, 60 ㎛ or less, 50 ㎛ or less, or 40 ㎛ or less.

[0104] Additionally, 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 properties.

[0105]

[0106] Pouch-type secondary battery case and secondary battery

[0107] The secondary battery of the present invention includes a pouch-type secondary battery case including the battery body part and the pouch film, and the secondary battery case may include the pouch film of the present invention. The battery body part 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 part may include a lithium secondary battery negative electrode, a lithium secondary battery positive electrode, and an electrolyte.

[0108] The above lithium secondary battery positive electrode can be used without limitation as long as it is a positive electrode commonly used for lithium secondary batteries. For example, the above lithium secondary battery positive electrode can be LiCoO2, LiMnO2, LiFePO4, LiFeO2, Li(Ni 0.6 Mn 0.2 Co 0.2 ) may contain a positive electrode active material such as O2.

[0109] 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 commonly used as electrolytes and organic solvents for lithium secondary batteries, respectively.

[0110] The above-mentioned negative electrode for a lithium secondary battery may be used without limitation as long as it is one that is commonly used as a negative electrode for a lithium secondary battery. For example, the above-mentioned negative electrode for a lithium secondary battery may include a negative electrode active material such as a carbon-based active material or a silicon-based active material.

[0111] The above pouch-type secondary battery case may have excellent sealing strength characteristics. Accordingly, the problem of the battery body sealed by the pouch-type secondary battery case being exposed to the external environment may not occur.

[0112]

[0113] Pouch film manufacturing method

[0114] Hereinafter, a method for manufacturing a pouch film of the present invention will be described. The method for manufacturing the pouch film is not limited to the manufacturing method described below, and the manufacturing method described below may be one of several methods for manufacturing pouch films.

[0115]

[0116] The present invention provides a method for manufacturing a pouch film, comprising the steps of laminating a sealant film on one side of a barrier film, and sequentially laminating a second outer layer and a first outer layer on the other side of the barrier film, wherein the second outer layer comprises a nylon-based resin, and the second outer layer is manufactured by a blown method.

[0117] The blown method is a method of melting and extruding a polymer, then injecting air to inflate the film like a balloon, and can be mainly used when producing high-strength films such as nylon. Specifically, the blown method can be composed of extrusion, tube forming, blowing, cooling, platen, and winding steps. The extrusion step refers to a step of heating polymer pellets and then melting them through an extruder, and the tube forming step refers to a step of extruding the melted polymer into a cylindrical tube shape through a die. The blowing step refers to a step of injecting air into the center of the tube to expand the tube, and the thickness of the film can be controlled in the blowing step. Thereafter, the second outer layer can be manufactured through a cooling step of cooling the expanded tube, a platen step of passing the cooled tube between compression rollers to form a film, and a winding step of winding the film into a roll shape.

[0118] In addition, the blown method can be divided into a bottom-up method and a top-down method depending on the direction of air injection in the blowing step. The bottom-up method is advantageous in manufacturing a film with a thickness of 25 ㎛ or less, but it is difficult to increase the thickness to more than 25 ㎛, and quality control may be difficult due to cooling uniformity issues. As the thickness increases, there is a high possibility of cooling unevenness, which affects the mechanical properties or quality of the film, so there is a limit to applying thick nylon for secondary batteries with the current technology. In addition, the top-down method is easy to manufacture a film with a thickness of 40 ㎛ or less with the help of gravity, and can relatively stably maintain a thickness between 25 and 40 ㎛. However, as the thickness increases excessively, the cooling efficiency decreases, which may cause quality problems.

[0119] Since the second outer layer manufactured by the above blown method can be elongated together with the barrier layer during molding, the moldability of the pouch film can be excellent.

[0120] In addition to the above blown method, when using a biaxial stretching method, tensile strength and durability can be improved, but flexibility and elongation are very low, which has the problem of resulting in an inferior level of formability.

[0121]

[0122] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0123]

[0124] <Examples and Comparative Examples>

[0125] Example 1

[0126] The outer layer, barrier layer, and sealant layer were laminated, and the outer layer was a laminated film of a polyethylene terephthalate (PET) film (thickness 12 ㎛) as the outermost layer, a first nylon (Ny) film (thickness 25 ㎛) and a second nylon (Ny) film (thickness 25 ㎛) on the inner side thereof. The barrier layer was made of aluminum (thickness 80 ㎛), and the sealant layer (thickness 80 ㎛) was manufactured by using an extrusion lamination method to include a polypropylene extrusion coating (EC) layer (thickness 30 ㎛) and a non-stretched polypropylene film (CPP) (thickness 50 ㎛). The above first and second nylon composite films were manufactured by a blown upward method, and were manufactured by controlling the draw ratio of the barrier layer and the first nylon film, the extrusion speed, the temperature, the pressure conditions, etc., and at this time, the ratio of the thickness of the second outer layer (Ny1+Ny2) / the thickness of the barrier layer (Al) is 0.63, the ratio of the thickness of the entire outer layer (PET+Ny1+Ny2) / the thickness of the barrier layer (Al) is 0.78, and the ratio of the tensile strength of the barrier layer (Al) / the tensile strength of the second outer layer (Ny1+Ny2) is 1.00.

[0127]

[0128] Example 2

[0129] The outer layer, barrier layer, and sealant layer were laminated, and the outer layer was a laminated film of a polyethylene terephthalate (PET) film (thickness 12 ㎛) as the outermost layer, a first nylon (Ny) film (thickness 15 ㎛) and a second nylon (Ny) film (thickness 25 ㎛) on the inner side thereof. The barrier layer was made of aluminum (thickness 80 ㎛), and the sealant layer (thickness 80 ㎛) was manufactured by extrusion lamination to include a polypropylene extrusion coating (EC) layer (thickness 30 ㎛) and a non-stretched polypropylene film (CPP) (thickness 50 ㎛). The above first and second nylon composite films were manufactured by a blown bottom-up method, and were manufactured by controlling the draw ratio of the barrier layer and the first nylon film, the extrusion speed, the temperature, the pressure conditions, etc., and at this time, the ratio of the thickness of the second outer layer (Ny1+Ny2) / the thickness of the barrier layer (Al) is 0.50, the ratio of the thickness of the entire outer layer (PET+Ny1+Ny2) / the thickness of the barrier layer (Al) is 0.65, and the ratio of the tensile strength of the barrier layer (Al) / the tensile strength of the second outer layer (Ny1+Ny2) is 1.17.

[0130]

[0131] Example 3

[0132] The outer layer, barrier layer, and sealant layer were laminated, and the outer layer was a laminated film of a polyethylene terephthalate (PET) film (thickness 12 ㎛) as the outermost layer, a first nylon (Ny) film (thickness 25 ㎛) and a second nylon (Ny) film (thickness 30 ㎛) as the inner layer. The barrier layer was made of aluminum (thickness 80 ㎛), and the sealant layer (thickness 80 ㎛) was manufactured by using an extrusion lamination method to include a polypropylene extrusion coating (EC) layer (thickness 30 ㎛) and a non-stretched polypropylene film (CPP) (thickness 50 ㎛). The above first and second nylon composite films were manufactured by a blown bottom-up method, and were manufactured by controlling the draw ratio of the barrier layer and the first nylon film, the extrusion speed, the temperature, the pressure conditions, etc., and at this time, the ratio of the thickness of the second outer layer (Ny1+Ny2) / the thickness of the barrier layer (Al) was 0.69, the ratio of the thickness of the entire outer layer (PET+Ny1+Ny2) / the thickness of the barrier layer (Al) was 0.84, and the ratio of the tensile strength of the barrier layer (Al) / the tensile strength of the second outer layer (Ny1+Ny2) was 0.95.

[0133]

[0134] Example 4

[0135] The outer layer, barrier layer, and sealant layer were laminated, and the outer layer used a polyethylene terephthalate (PET) film (thickness 12 ㎛) as the outermost layer and a nylon (Ny) film (thickness 40 ㎛) as the inner layer. The barrier layer used aluminum (thickness 80 ㎛), and the sealant layer (thickness 80 ㎛) was manufactured by using an extrusion lamination method to include a polypropylene extrusion coating (EC) layer (thickness 30 ㎛) and a non-stretched polypropylene film (CPP) (thickness 50 ㎛). The above nylon layer was manufactured by a blown top-down method, and was manufactured by controlling the draw ratio of the barrier layer and the nylon film, the extrusion speed, the temperature, the pressure conditions, etc., and at this time, the ratio of the thickness of the second outer layer (Ny) / the thickness of the barrier layer (Al) was 0.50, the ratio of the thickness of the entire outer layer (PET+Ny) / the thickness of the barrier layer (Al) was 0.65, and the ratio of the tensile strength of the barrier layer (Al) / the tensile strength of the second outer layer (Ny) was 0.99.

[0136]

[0137] Comparative Example 1

[0138] A pouch film was manufactured in the same manner as in Example 1, except that a laminated film of a first nylon (Ny) film (thickness 25 ㎛) and a second nylon (Ny) film (thickness 25 ㎛) was used, and instead of aluminum, a nylon (Ny) film (thickness 25 ㎛) was used for the barrier layer (thickness 80 ㎛) and aluminum was used for the barrier layer (thickness 60 ㎛).

[0139]

[0140] Comparative Example 2

[0141] A pouch film was manufactured in the same manner as in Example 1, except that a nylon (Ny) film (thickness 25 μm) was used instead of a laminated film of a first nylon (Ny) film (thickness 25 μm) and a second nylon (Ny) film (thickness 25 μm).

[0142]

[0143] Comparative Example 3

[0144] A pouch film was manufactured in the same manner as in Example 1, except that a nylon (Ny) film (thickness 30 μm) was used instead of a laminated film of a first nylon (Ny) film (thickness 25 μm) and a second nylon (Ny) film (thickness 25 μm).

[0145]

[0146] Experimental example

[0147] (1) Tensile strength and elongation evaluation

[0148] The tensile strength was measured by peeling off the barrier layer and the second outer layer of the pouch film of the examples and comparative examples to prepare a specimen with a width of 15 mm, fixing the specimen between two jigs of a tensile tester (UTM) at room temperature (initial jig gap 50 mm), and then pulling the specimen in the MD direction at a measurement speed of 50 mm / min, thereby measuring the stroke (mm) and strength (N). The measured tensile strength values ​​are shown in Table 1 below.

[0149] In addition, the elongation in the present invention is measured by the following method. Two parallel lines are drawn in the center of the specimen, and the initial distance between these lines is set to 30 mm. Then, the specimen is mounted on a tensile testing machine, a tensile strength test is performed, and the actual length between the lines elongated by tension is measured.

[0150] The elongation is calculated according to the following mathematical formula 1, and the elongation is shown in Table 1 below.

[0151] [Mathematical Formula 1]

[0152] Elongation = ((increased length - 30mm) / 30mm) x 100,

[0153] In the above mathematical formula 1,

[0154] The above increased length is the final distance between the two lines after the tensile test.

[0155] Thereafter, the X-axis of the graph derived from the above measured values ​​represents the stroke (mm), the Y-axis represents the tensile strength (N), and the tensile strength of the barrier layer and the second outer layer when the stroke is 5 mm is measured, and the ratio of the barrier layer (Al) tensile strength / second outer layer (Ny1+Ny2) tensile strength is shown in Table 1 below.

[0156]

[0157] (2) Evaluation of residual thickness after molding

[0158] The thickness of the barrier layer after molding was measured by cutting the pouch film of the above examples and comparative examples so as not to include the sealing part to make a specimen of 266 mm (TD) × 240 mm (MD) × 15 mm (width), and then applying LDPE (low-density polyethylene) to both sides of the sample, and then using a test molding machine with a specification of 30 mm × 75 mm to pressurize at 0.3 Mpa and mold to a molding depth of 17 mm. At this time, the average value of the thickness of the barrier layer was calculated by measuring 6 times at each of the 4 corners of the rectangular molding shape. Thereafter, the measured residual thickness and thickness residual ratio of the barrier layer after molding are shown in Table 1 below.

[0159]

[0160] (3) Max plasticity measurement evaluation

[0161] In addition, for the pouch films manufactured in the above examples and comparative examples, 1 cup molding was evaluated and the average value of the maximum molding length was measured using a vernier caliper.

[0162]

[0163] Classification Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 First outer layer thickness (㎛) PET 1 2 1 2 1 2 1 2 1 2 1 2 1 2 Second outer layer thickness (㎛) Ny 2 2 5 2 5 3 0 4 0 2 5 2 5 3 0 4 0 2 5 3 0 Ny 1 2 5 1 5 2 5 Barrier layer thickness (㎛) Al 8 0 8 0 8 0 8 0 6 0 8 0 8 Sealant layer thickness (㎛) PP 3 0 3 0 3 0 3 0 3 0 3 0 CPP 5 0 5 0 5 0 5 0 5 0 Total thickness of pouch film (㎛) 2 2 2 2 1 2 2 7 2 1 2 1 7 7 1 9 7 2 0 Total thickness of second outer layer (Ny 1 + Ny 2) (㎛) 5 0 4 0 5 5 4 0 2 5 2 5 3 0 Total outer layer (PET + Ny 1 + Ny 2) Thickness (㎛) 625 26 75 23 7 3 7 4 2 Second outer layer (Ny1 + Ny2) thickness / barrier layer (Al) thickness 0.63 0.50 0.69 0.50 0.42 0.31 0.38 Total outer layer (PET + Ny1 + Ny2) thickness / barrier layer (Al) thickness 0.78 0.65 0.84 0.65 0.62 0.46 0.53 Second outer layer elongation (MD) 78 7 3 6 9 7 2 6 3 6 3 5 9 Second outer layer elongation (TD) 69 6 4 6 2 6 3 5 9 5 5 Second outer layer Tensile strength (N / 15mm) MD (top) / TD (bottom) 269 270 213 229 276 290 210 225 148 150 152 154 173 173 Barrier layer (Al) tensile strength / 2nd outer layer (Ny1+Ny2) tensile strength 1.00 1.17 0.95 0.99 1.25 1.67 1.54 1 Thickness at cup forming (㎛) 18.0 17.5 19.0 17.5 13.0 15.0 15.5 Residual thickness of barrier layer after forming (㎛) 48 445 0 443 0 363 5 Residual thickness of barrier layer after forming (%) 60.0 55.0 62.5 55.0 50.0 45.0 43.8

[0164] Referring to Table 1 and Figures 3 and 4 above, in the case of Examples 1 to 4 that satisfy the second outer layer thickness and the tensile strength ratio of the second outer layer and the barrier layer according to the present invention, the thickness at the time of 1 cup molding is thicker than that of the comparative example, and the thickness residual ratio of the barrier layer after molding is high, so it can be confirmed that it has excellent moldability.

[0165] In addition, in the case of Example 4, it can be confirmed that the second outer layer is a single-layer film rather than a laminated film, and has an equivalent level of formability compared to Examples 1 to 3.

[0166] On the other hand, in the case of Comparative Examples 1 to 3, which do not satisfy the second outer layer thickness and tensile strength ratio, the thickness at the time of 1 cup molding is thinner than that of the Example, and the residual thickness ratio after molding is also low, so it can be confirmed that they have inferior moldability compared to the Example.

[0167]

[0168] (4) Evaluation of residual thickness after molding according to nylon manufacturing method

[0169] As shown below, a nylon composite film (layer) was formed using a biaxial stretching method rather than a blown method, and then a pouch film including the same was manufactured. For Example 1 and Comparative Examples a and b below, measurements were performed as in the evaluation of the remaining thickness after molding in (2). The remaining thickness and thickness retention rate of the barrier layer after molding are shown in Table 2 below.

[0170] <Comparative Example a>

[0171] A pouch film was manufactured in the same manner as in Example 1, except that the nylon laminated film was manufactured using a biaxial stretching method instead of a blown method.

[0172] <Comparative Example b>

[0173] A pouch film was manufactured in the same manner as in Example 1, except that a nylon laminated film was manufactured using a biaxial stretching method instead of a blown method, and a nylon (Ny) film (thickness 45 ㎛) was used instead of a laminated film of a first nylon (Ny) film (thickness 25 ㎛) and a second nylon (Ny) film (thickness 25 ㎛).

[0174]

[0175] ClassificationExample 1Example 4Comparative Example aComparative Example bFirst outer layer thickness (㎛)PET12121212Second outer layer thickness (㎛)Ny225402545Ny12525Barrier layer thickness (㎛)Al80808080Sealant layer thickness (㎛)PP30303030CPP50505050Second outer layer manufacturing methodBlown upwardBlown downwardAxial stretching methodAxial stretching methodResidual thickness of barrier layer after molding (㎛)48443837Residual thickness of barrier layer after molding (%)60.055.047.546.25

[0176] Referring to Table 2 above, it can be confirmed that Examples 1 and 4 manufactured by the blown upward and downward methods according to the present invention have significantly superior formability compared to Comparative Examples a and b manufactured by the conventional biaxial stretching method.

[0177]

[0178] Acknowledgement

[0179] The present invention is a result of the following task support.

[0180] Assignment Number: 20022450

[0181] Ministry Name: Ministry of Trade, Industry and Energy

[0182] Project Management (Professional) Agency Name: Korea Institute of Industrial Technology Planning and Evaluation

[0183] Research Project Name: Material and Components Technology Development (Leeumsung Corporation)

[0184] Research Project Title: Development of Next-Generation Secondary Battery Pouches Capable of Delivering More Than Double the Bonding Strength (60°C)

[0185] Contribution rate: 1 / 1

[0186] Project implementation organization name: Yulchon Chemical Co., Ltd.

[0187] Research period: January 1, 2024 - December 31, 2024

Claims

1. Contains a sealant layer, a barrier layer, a second outer layer, and a first outer layer sequentially laminated, The second outer layer comprises a nylon resin, The thickness of the second outer layer is 35 ㎛ or more and 60 ㎛ or less, A pouch film in which the tensile strength ratio of the second outer layer and the barrier layer measured under the following measurement conditions satisfies the following equation 1. [Formula 1] 0.9≤Tensile strength of barrier layer / Tensile strength of second outer layer≤1.2 [Measurement conditions] After peeling off the barrier layer and the second outer layer of the above pouch film to manufacture a specimen with a width of 15 mm, the specimen is fixed between two jigs of a tensile tester (UTM) at room temperature (initial jig gap 50 mm), and the stroke (mm) and strength (N) of the specimen are measured while pulling at a measurement speed of 50 mm / min in the MD direction. The X-axis of the graph derived from the measured values ​​represents the stroke (mm), the Y-axis represents the tensile strength (N), and the tensile strength of the barrier layer and the second outer layer is measured when the stroke is 5 mm.

2. In claim 1, A pouch film wherein the thickness ratio of the barrier layer and the second outer layer is 1:0.5 or more and 0.7 or less.

3. In claim 1, A pouch film wherein the thickness of the barrier layer is 40 ㎛ or more and 100 ㎛ or less.

4. In claim 1, A pouch film wherein the sum of the thicknesses of the first outer layer and the second outer layer is 40 ㎛ or more and 100 ㎛ or less.

5. In claim 1, A pouch film wherein the ratio of the thickness of the barrier layer to the sum of the thicknesses of the first outer layer and the second outer layer is 1:0.65 or more and 0.9 or less.

6. In claim 1, A pouch film wherein the MD and TD elongation of the second outer layer are each independently 50% or more and 300% or less.

7. In claim 1, A pouch film having a tensile strength in the MD direction of the second outer layer of 200 N / 15 mm or more and 300 N / 15 mm or less.

8. In claim 1, A pouch film having a thickness residual ratio of 55% or more according to the following formula 2 of the above barrier layer. [Formula 2] Thickness Residual Rate (%) = (Thickness of barrier layer after molding / Thickness of barrier layer before molding) × 100 In the above equation 2, The thickness of the barrier layer after molding was measured by cutting a pouch film excluding the sealing portion to create a specimen measuring 266 mm (TD) × 240 mm (MD) × 15 mm (width), then applying LDPE (low-density polyethylene) to both sides of the sample, and then molding it at a molding depth of 17 mm by applying pressure of 0.3 MPa using a test molding machine measuring 30 mm × 75 mm. At this time, the thickness of the barrier layer was measured six times at each of the four corners of the rectangular molding shape, and the average value of the thickness of the barrier layer was calculated.

9. In claim 1, A pouch film wherein the second outer layer comprises a single layer or two or more laminated layers.

10. In claim 1, A pouch film having a thickness of 205 ㎛ or more and 250 ㎛ or less.

11. In claim 1, A pouch film wherein the first outer layer comprises at least one material selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber.

12. In claim 1, A pouch film having a thickness of the first outer layer of 5 ㎛ or more and 40 ㎛ or less.

13. In claim 1, A pouch film wherein the barrier layer comprises at least one material selected from the group consisting of aluminum, stainless steel, copper, titanium, and alloys thereof.

14. A pouch-type battery case comprising a pouch film according to claim 1.

15. An electrode assembly formed by stacking a positive electrode, a separator, and a negative electrode; and A secondary battery comprising a pouch-shaped battery case according to claim 14 for storing the electrode assembly.

16. A step of laminating a sealant film to one side of the barrier film; A step of sequentially laminating a second outer layer and a first outer layer on the other surface of the barrier film is included, The second outer layer comprises a nylon resin, A method for manufacturing a pouch film, wherein the second outer layer is manufactured using a blown method.

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