Pouch laminate film for secondary battery, pouch exterior material, and secondary battery

Abstract

The present invention relates to a pouch laminate film, and to a pouch laminate film, a pouch exterior material, and a secondary battery comprising same, wherein, when the pouch exterior material and a lead tab film are sealed, a polymer material that is pushed out from a sealed portion at a tab portion is uniformly formed even at an unsealed portion, so that the thickness of a sealant layer is prevented from becoming thinner, and thus insulation defects are prevented and long-term reliability such as chemical resistance can be improved.

Description

Pouch laminate film for secondary batteries, pouch outer material and secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0021092, filed February 14, 2024, and Korean Patent Application No. 10-2024-0182943, filed December 10, 2024, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present invention relates to a pouch laminate film for a secondary battery, a pouch outer material, and a secondary battery including the same.

[0006]

[0007] Recently, as the application areas of secondary batteries have rapidly expanded to include not only power supply for electronic devices such as electric, electronic, communication, and computer devices, but also power storage for large-area devices such as automobiles and power storage devices, the demand for high-capacity, high-output, and high-stability lithium secondary batteries is increasing.

[0008] Lithium secondary batteries are generally manufactured by applying a positive electrode active material capable of inserting and de-inserting lithium ions or a negative electrode active material capable of absorbing and releasing lithium ions, and optionally a material mixed with a binder and a conductive material, to a positive electrode current collector and a negative electrode current collector, respectively, to manufacture the negative electrode and the positive electrode, laminating these on both sides of a separator to form an electrode assembly of a predetermined shape, and then inserting this electrode assembly and a non-aqueous electrolyte into a battery case.

[0009] Lithium secondary batteries can be divided into cylindrical secondary batteries, square secondary batteries, and pouch-type secondary batteries depending on their structure. Among these, pouch-type secondary batteries are manufactured by accommodating the electrode assembly within a pouch-type sheet and then sealing the sheet. Compared to other types of secondary batteries, they have a simple structure and a large capacity per unit volume, so they are widely used in automobile batteries and energy storage devices.

[0010] The case of these pouch-type secondary batteries is a pouch-shaped sheet that protects the electrodes and electrolyte from the outside, and is composed of a metal film and a polymer material for sealing. The polymer material used for the sealant layer is a thermoplastic, heat-sealing material composed of an olefin-based material such as polypropylene or polyethylene.

[0011] When using the case of the above pouch-type secondary battery, in order to maintain electrical connection from the electrode assembly housed inside the case to the outside of the case, the tab needs to be extended outside the case. Accordingly, when sealing the case of the above pouch-type secondary battery, the lead tab film and the pouch-type sheet are directly sealed at the tab area.

[0012] However, unlike other sealed areas, in areas directly sealed to the lead tab film, there is a problem in that the polymer material of the sealant layer is pushed between the sealed area (sealing area) formed on the lead tab film after sealing and the unsealed area (unsealed area) in the direction of the storage area of ​​the electrode assembly of the case of the pouch-type secondary battery (occurrence area).

[0013] Specifically, when directly sealing a pouch-shaped sheet on a lead tab film at a tab portion, the phenomenon of the polymer material of the sealant layer being pushed from the sealed portion (sealed portion) to the unsealed portion (unsealed portion) can be confirmed from a cross-sectional image of the sealed portion for the tab portion, as shown in Fig. 1. When sealing the lead tab film and the pouch-shaped sheet at the tab portion, the sealed portion (sealed portion) is pressurized and heated by the sealing block, and at this time, the polymer material of the sealant layer is pushed from the sealed portion (sealed portion) formed on the lead tab film to the unsealed portion (unsealed portion). Accordingly, the thickness of the unsealed area (unsealed area) will inevitably increase due to the pushed out polymer material, and unlike the sealed area (sealed area), the pressurization and heating by the sealing block in the unsealed area (unsealed area) are not evenly transferred to the ambient pressure and ambient heat, so the sealant layer cannot be evenly fused onto the lead tab film. Therefore, as shown in Fig. 1, the polymer material pushed out from the sealed area (sealed area) at the tab area flows unevenly in the unsealed area (unsealed area), cools, clumps, and lifts, and as a result, an area where the sealant layer is thinner than the original thickness occurs. If an area where the sealant layer is thinner occurs, long-term reliability issues such as poor insulation and reduced chemical resistance may occur in that area.

[0014]

[0015] The problem to be solved by the present invention is that, when accommodating a secondary battery using a pouch outer material including a pouch laminate film, when the pouch laminate film and the lead tab film are sealed, a polymer material pushed out from the sealed area at the tab area is uniformly formed even in an unsealed area, thereby preventing the thickness of the sealant layer from becoming thinner, thereby preventing insulation failure and improving long-term reliability such as chemical resistance.

[0016] That is, the present invention is a film laminate of a pouch outer case for accommodating a secondary battery, and the purpose of the present invention is to provide a pouch laminate film in which, when the pouch outer case and the lead tab film are sealed, a polymer material pushed out from the sealed area at the tab area is uniformly formed even in an unsealed area.

[0017] In addition, the present invention aims to provide a pouch outer material including the above pouch laminate film.

[0018] In addition, the present invention aims to provide a secondary battery including the pouch outer material.

[0019]

[0020] To solve the above problem, the present invention provides a pouch outer material for a secondary battery and a secondary battery including the same.

[0021] (1) The present invention comprises an outer layer, a barrier layer, a first sealant layer, and a second sealant layer, wherein the crystallization temperature of the second sealant layer is 100° C. or less, the melting point of the first sealant layer is higher than the melting point of the second sealant layer, the difference (MFR1-MFR2) between the melting index (MFR1) of the first sealant layer and the melting index (MFR2) of the second sealant layer is 10 g / 10 min or more and 20 g / 10 min or less, and the difference (UTS1-UTS2) between the upper yield strength (UTS1) of the first sealant layer and the upper yield strength (UTS2) of the second sealant layer is -1 N / mm 2 More than 10 N / mm 2A pouch laminate film having the following properties is provided.

[0022] (2) The present invention provides a pouch laminate film in the above (1), wherein the first sealant layer is at least one selected from the group consisting of random polypropylene, homo polypropylene, and block polypropylene.

[0023] (3) The present invention provides a pouch laminate film in (1) or (2), wherein the second sealant layer is at least one selected from the group consisting of random polypropylene and terpolymer polypropylene.

[0024] (4) The present invention provides a pouch laminate film in any one of the above (1) to (3), wherein the melting point of the first sealant layer is 10°C or higher than the melting point of the second sealant layer.

[0025] (5) The present invention provides a pouch laminate film according to any one of the above (1) to (4), wherein the first sealant layer has a crystallization temperature of 92°C or higher.

[0026] (6) The present invention provides a pouch laminate film according to any one of (1) to (5) above, wherein the first sealant layer has a melting point of 145°C or higher.

[0027] (7) The present invention provides a pouch laminate film in any one of the above (1) to (6), wherein the first sealant layer has a melting index of 15 g / 10 min or more and 24 g / 10 min or less.

[0028] (8) In any one of the above (1) to (7), the first sealant layer has an upper yield strength of 12 N / mm. 2 Above, 20 N / mm 2 A pouch laminate film having the following properties is provided.

[0029] (9) The present invention provides a pouch laminate film according to any one of (1) to (8), wherein the second sealant layer has a melting point of 150°C or lower.

[0030] (10) The present invention provides a pouch laminate film in any one of the above (1) to (9), wherein the second sealant layer has a melting index of 3 g / 10 min or more and 15 g / 10 min or less.

[0031] (11) In any one of the above (1) to (10), the second sealant layer has an upper yield strength of 12 N / mm. 2 Above, 20 N / mm 2 A pouch laminate film having the following properties is provided.

[0032] (12) The present invention provides a pouch outer material including a pouch laminate film according to any one of (1) to (11).

[0033] (13) The present invention provides a secondary battery including a pouch outer case according to (12).

[0034]

[0035] The pouch outer material of the present invention can uniformly form a polymer material that is pushed out from the sealed portion at the tab portion when the pouch laminate film and the lead tab film are sealed, even in the unsealed portion, thereby preventing the thickness of the sealant layer of the pouch laminate film from becoming thin, thereby preventing insulation failure and improving long-term reliability such as chemical resistance.

[0036]

[0037] Figure 1 is an optical image showing a sealed portion (sealed portion) and an unsealed portion (unsealed portion) of a tab portion of a pouch outer material manufactured according to a comparative example of the present invention.

[0038] FIG. 2 is an optical image showing a sealed portion (sealed portion) and an unsealed portion (unsealed portion) of a tab portion of a pouch outer material manufactured according to an embodiment of the present invention.

[0039] Figure 3 is a schematic diagram showing the configuration of a pouch laminate film according to the present invention.

[0040]

[0041] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0042] The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0043]

[0044] The present invention provides a pouch laminate film. Fig. 3 is a schematic diagram showing the configuration of a pouch laminate film according to the present invention. According to one embodiment of the present invention, the pouch laminate film includes an outer layer, a barrier layer, a first sealant layer, and a second sealant layer, wherein the crystallization temperature of the second sealant layer is 100° C. or lower, and the melting point of the first sealant layer is higher than the melting point of the second sealant layer. In this way, when the melting points of the first sealant layer and the second sealant layer are controlled, the difference in the melting points of the first sealant layer and the second sealant layer can be controlled during sealing, and thus, the occurrence of an unmelted region in both a sealed area and an unsealed area can be prevented.

[0045] In addition, the difference (MFR1-MFR2) between the melting index (MFR1) of the first sealant layer and the melting index (MFR2) of the second sealant layer is 10 g / 10 min or more and 20 g / 10 min or less, and the difference (UTS1-UTS2) between the upper yield strength (UTS1) of the first sealant layer and the upper yield strength (UTS2) of the second sealant layer is -1 N / mm 2 More than 10 N / mm 2 Hereinafter. As a specific example, the difference between the melting index of the first sealant layer and the melting index of the second sealant layer may be 10 g / 10 min or more, 10 g / 10 min or more, 11 g / 10 min or more, 12 g / 10 min or more, 13 g / 10 min or more, 14 g / 10 min or more, 15 g / 10 min or more, 20 g / 10 min or less, 19 g / 10 min or less, 18 g / 10 min or less, 17 g / 10 min or less, or 16 g / 10 min or less. If the difference in melting index of the first sealant layer and the second sealant layer does not satisfy the above range and goes beyond the lower limit, the sealing strength is lowered, thereby reducing long-term reliability, and if it goes beyond the upper limit, it may not melt during the sealing process, causing a pushing phenomenon.

[0046] In addition, the difference between the upper yield strength of the first sealant layer and the upper yield strength of the second sealant layer is -1 N / mm 2 Above, 0 N / mm 2 Above, 1 N / mm 2 Above, 2 N / mm 2 Above, 3 N / mm 2 Above, 4 N / mm 2 Above, 5 N / mm 2 Above, 10 N / mm 2 Below, 9 N / mm 2 Below, 8 N / mm 2 Below, 7 N / mm 2 Below, 6 N / mm 2It may be as follows. Here, the upper yield strength refers to the strength when the sealant layer receiving the force can no longer maintain elasticity and begins to deform permanently, and the section before the upper yield strength is an elastic section and can be recovered. In addition, if the difference in the upper yield strength of the first sealant layer and the second sealant layer does not satisfy the above range, the sealing strength may be reduced, or the sealing area may not be melted during the sealing process, causing a pushing phenomenon, which may cause a problem of reduced long-term reliability.

[0047] The pouch laminate film of the present invention can maintain a uniform sealing shape without a phenomenon of shrinkage in the sealing area, prevent insulation failure, and improve long-term reliability such as chemical resistance by controlling the crystallization temperature of the second sealant layer, the melting point between the first sealant layer and the second sealant layer, the melting index, and the difference in upper yield strength.

[0048] According to one embodiment of the present invention, the first sealant layer may be at least one selected from the group consisting of random polypropylene, homo polypropylene, and block polypropylene.

[0049] According to one embodiment of the present invention, the second sealant layer may be at least one selected from the group consisting of random polypropylene and terpolymer polypropylene. In this case, the second sealant layer may be non-stretched polypropylene.

[0050] According to one embodiment of the present invention, each of the polypropylene-based resins of the first sealant layer and the second sealant layer may be a matrix resin forming the first sealant layer and the second sealant layer, and rubber particles may be dispersed as domains on the matrix resin.

[0051] According to one embodiment of the present invention, the first sealant layer and the second sealant layer may include a polyolefin-based resin, and the polyolefin-based resin may include various types of polypropylene-based resins described above.

[0052] The physical properties of the first sealant layer and the second sealant layer mentioned in the present invention, such as crystallization temperature, melting point, melting index, and yield strength, may be related to polypropylene corresponding to the matrix resin.

[0053] According to one embodiment of the present invention, the melting point of the first sealant layer may be 10°C or higher than the melting point of the second sealant layer. As a specific example, the melting point of the first sealant layer may be 10°C or higher, 11°C or higher, 12°C or higher, 13°C or higher, 14°C or higher, 15°C or higher, 16°C or higher, 17°C or higher, 18°C ​​or higher, 19°C or higher, 20°C or higher, 21°C or higher, or 22°C or higher than the melting point of the second sealant layer. The upper limit may be 30°C or lower, 29°C or lower, 28°C or lower, 27°C or lower, 26°C or lower, 25°C or lower, 24°C or lower, 23°C or lower, or 22°C or lower.

[0054] According to one embodiment of the present invention, the first sealant layer may have a melting point of 145°C or higher. As a specific example, the first sealant layer may have a melting point of 145°C or higher, 146°C or higher, 147°C or higher, 148°C or higher, 149°C or higher, 150°C or higher, 151°C or higher, 152°C or higher, 153°C or higher, 154°C or higher, 155°C or higher, 156°C or higher, 157°C or higher, 158°C or higher, 159°C or higher, or 160°C or higher. The upper limit may be 180°C or less, 179°C or less, 178°C or less, 177°C or less, 176°C or less, 175°C or less, 174°C or less, 173°C or less, 172°C or less, 171°C or less, 170°C or less, 169°C or less, 168°C or less, 167°C or less, 166°C or less, 165°C or less, 164°C or less, 163°C or less, 162°C or less, 161°C or less, or 160°C or less.

[0055] According to one embodiment of the present invention, the second sealant layer may have a melting point of 150°C or less. As a specific example, the second sealant layer may have a melting point of 150°C or less, 149°C or less, 148°C or less, 147°C or less, 146°C or less, 145°C or less, 144°C or less, 143°C or less, 142°C or less, 141°C or less, 140°C or less, 139°C or less, or 138°C or less. The lower limit may be 120°C or higher, 121°C or higher, 122°C or higher, 123°C or higher, 124°C or higher, 125°C or higher, 126°C or higher, 127°C or higher, 128°C or higher, 129°C or higher, 130°C or higher, 131°C or higher, 132°C or higher, 133°C or higher, 134°C or higher, 135°C or higher, 136°C or higher, 137°C or higher, or 138°C or higher.

[0056] According to one embodiment of the present invention, the first sealant layer may have a crystallization temperature of 92°C or higher. The crystallization temperature refers to a temperature at which a liquid or amorphous state changes into a solid crystal structure, and the crystallization temperature may affect the formation of a uniform sealing shape during the sealing process. As a specific example, the first sealant layer may have a crystallization temperature of 92°C or higher, 93°C or higher, 94°C or higher, 95°C or higher, 96°C or higher, 97°C or higher, 98°C or higher, 99°C or higher, 100°C or higher, 101°C or higher, 102°C or higher, 103°C or higher, 104°C or higher, 105°C or higher, 106°C or higher, 107°C or higher, 108°C or higher, 109°C or higher, or 110°C or higher. The upper limit may be 140°C or less, 139°C or less, 138°C or less, 137°C or less, 136°C or less, 135°C or less, 134°C or less, 133°C or less, 132°C or less, 131°C or less, 130°C or less, 129°C or less, 128°C or less, 127°C or less, 126°C or less, 125°C or less, 124°C or less, 123°C or less, 122°C or less, 121°C or less, 120°C or less, 119°C or less, 118°C or less, 117°C or less, 116°C or less, or 115°C or less. Here, the crystallization temperature may be measured using a differential scanning calorimeter (DSC). Specifically, the crystallization temperature can be measured after the DSC reaches equilibrium at 25°C, then increases the temperature by 10°C per minute to 200°C, and then decreases the temperature by 10°C per minute to 25°C. At this time, the crystallization temperature can be obtained from the maximum point of the exothermic peak from the temperature change that occurs while decreasing the temperature.

[0057] According to one embodiment of the present invention, the second sealant layer may have a crystallization temperature of 100°C or lower. As a specific example, the second sealant layer may have a crystallization temperature of 100°C or lower, 99°C or lower, 98°C or lower, 97°C or lower, 96°C or lower, or 95°C or lower. The lower limit may be 80°C or higher, 81°C or higher, 82°C or higher, 83°C or higher, 84°C or higher, 85°C or higher, 86°C or higher, 87°C or higher, 88°C or higher, 89°C or higher, 90°C or higher, 91°C or higher, 92°C or higher, 93°C or higher, 94°C or higher, or 95°C or higher.

[0058] According to one embodiment of the present invention, when the crystallization temperature of the first sealant layer and the second sealant layer, particularly the second sealant layer, is controlled as described above, the crystallization time of the first sealant layer and / or the second sealant layer in an unsealed area during sealing can be controlled to prevent the occurrence of an unmelted area.

[0059] According to one embodiment of the present invention, the melting index of the first sealant layer may be equal to or greater than the melting index of the second sealant layer.

[0060] According to one embodiment of the present invention, the first sealant layer may have a melting index of 15 g / 10 min or more and 24 g / 10 min or less. As a specific example, the first sealant layer may have a melting index of 15 g / 10 min or more, 16 g / 10 min or more, 17 g / 10 min or more, 18 g / 10 min or more, 19 g / 10 min or more, or 20 g / 10 min or more. The upper limit may be 24 g / 10 min or less, 23 g / 10 min or less, 22 g / 10 min or less, 21 g / 10 min or less, 20 g / 10 min or less, 19 g / 10 min or less, 18 g / 10 min or less, 17 g / 10 min or less, or 16 g / 10 min or less.

[0061] According to one embodiment of the present invention, the second sealant layer may have a melting index of 3 g / 10 min or more and 15 g / 10 min or less. As a specific example, the second sealant layer may have a melting index of 3 g / 10 min or more, 4 g / 10 min or more, 5 g / 10 min or more, 6 g / 10 min or more, 7 g / 10 min or more, 8 g / 10 min or more, 9 g / 10 min or more, 10 g / 10 min or more, 11 g / 10 min or more, or 12 g / 10 min or more. The upper limit may be 15 g / 10 min or less, 14 g / 10 min or less, 13 g / 10 min or less, 12 g / 10 min or less, 11 g / 10 min or less, 10 g / 10 min or less, 9 g / 10 min or less, 8 g / 10 min or less, 7 g / 10 min or less, 6 g / 10 min or less, or 5 g / 10 min or less.

[0062] When the melting index of the first sealant layer and the second sealant layer satisfies the above range, high sealing strength can be achieved, and at the same time, the sealing process speed can be increased, and chemical resistance such as insulation resistance and electrolyte barrier properties can be improved.

[0063] According to one embodiment of the present invention, the first sealant layer has an upper yield strength of 12 N / mm. 2 Above, 20 N / mm 2 It may be as follows. As a specific example, the first sealant layer has an upper yield strength of 12 N / mm. 2 Above, 13 N / mm 2 Above, 14 N / mm 2 Above, 15 N / mm 2 Above, 16 N / mm 2 Above, 17 N / mm 2 or 18 N / mm 2 It may be ideal. The upper limit is 20 N / mm 2 Below, 19 N / mm 2 Below, 18 N / mm2 Below, 17 N / mm 2 Below, 16 N / mm 2 Below, 15 N / mm 2 Below, 14 N / mm 2 Below, 13 N / mm 2 or less, or 12 N / mm 2 It could be as follows:

[0064] According to one embodiment of the present invention, the second sealant layer has an upper yield strength of 12 N / mm. 2 Above, 20 N / mm 2 It may be as follows. As a specific example, the second sealant layer has an upper yield strength of 12 N / mm. 2 Above, 13 N / mm 2 Above, 14 N / mm 2 Above, 15 N / mm 2 or 16 N / mm 2 It may be ideal. The upper limit is 20 N / mm 2 Below, 19 N / mm 2 Below, 18 N / mm 2 Below, 17 N / mm 2 Below, 16 N / mm 2 or less, or 15 N / mm 2 It could be as follows:

[0065] When the yield strength of the first sealant layer and the second sealant layer satisfies the above range, the sealing strength can be increased, and at the same time, the chemical resistance such as insulation resistance and electrolyte blocking property can be improved, and the mechanical strength and durability of the sealing portion can be improved.

[0066] According to one embodiment of the present invention, the pouch laminate film may have a peel strength of 125 N / 15 mm or more of a lead tab film sealing portion formed by contacting at least one side of a lead tab film and the inner layer and then sealing them, and for specific examples, it may be 125 N / 15 mm or more, 126 N / 15 mm or more, 127 N / 15 mm or more, 128 N / 15 mm or more, 129 N / 15 mm or more, or 130 N / 15 mm or more. Since the peel strength indicates better as it is higher, the upper limit thereof is not particularly limited, but may be 200 N / 15 mm or less, 190 N / 15 mm or less, 180 N / 15 mm or less, 170 N / 15 mm or less, or 165 N / 15 mm or less, and excellent sealing force can be secured within this range.

[0067] According to one embodiment of the present invention, the outer layer is a layer located on the outer surface of the pouch outer material, and may include at least one selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber.

[0068] According to one embodiment of the present invention, the outer layer may be composed of a laminate of two or more layers in terms of diversifying functions. As a specific example, the outer layer may include a surface protection layer and a stretching auxiliary layer. Here, the surface protection layer may be a layer constituting the outermost layer of the pouch laminate film, and may be a layer that primarily protects the pouch outer material from the external environment, and the stretching auxiliary layer may be a layer that assists in the adhesion of the surface protection layer and the barrier layer, and at the same time prevents the surface protection layer and the barrier layer from being separated from each other when being stretched.

[0069] According to one embodiment of the present invention, the surface protection layer may include at least one selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber. The components of the surface protection layer may be selected and used within a range of mechanical properties that do not impair durability, heat resistance, pinhole resistance, chemical resistance, and electrical insulation, which are functions of the surface protection layer of the pouch outer material. As a specific example, the surface protection layer may include polyethylene terephthalate, which has excellent durability, heat resistance, pinhole resistance, chemical resistance, and electrical insulation, and as a more specific example, it may be a membrane or film made of polyethylene terephthalate.

[0070] According to one embodiment of the present invention, the stretching auxiliary layer may include at least one selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber. The components of the stretching auxiliary layer may be selected and used within a range of mechanical properties that do not impair the function of the stretching auxiliary layer of the pouch outer cover. As a specific example, the stretching auxiliary layer may include nylon that is easily adhered to the surface protection layer and has similar behavior when stretched to the barrier layer, and as a more specific example, it may be a membrane or film made of nylon.

[0071] According to one embodiment of the present invention, the surface protective layer may have an average thickness of 10 μm or more and 20 μm or less. As a specific example, the surface protective layer may have an average thickness of 10 μm or more, 11 μm or more, or 12 μm or more, and may also have an average thickness of 20 μm or less, 19 μm or less, 18 μm or less, 17 μm or less, 16 μm or less, 15 μm or less, 14 μm or less, 13 μm or less, or 12 μm or less, and within this range, the surface protective effect can be secured while preventing the thickness of the secondary battery from becoming excessively thick due to the outer material.

[0072] According to one embodiment of the present invention, the stretching auxiliary layer may have an average thickness of 15 μm or more and 30 μm or less. As a specific example, the surface protection layer may have an average thickness of 15 μm or more, 16 μm or more, 17 μm or more, 18 μm or more, 19 μm or more, 20 μm or more, 21 μm or more, 22 μm or more, 23 μm or more, 24 μm or more, or 25 μm or more, and may also have an average thickness of 30 μm or less, 29 μm or less, 28 μm or less, 27 μm or less, 26 μm or less, or 25 μm or less, and within this range, when stretched with the barrier layer, the adhesive strength between the surface protection layer and the barrier layer can be further improved while ensuring a behavior similar to that of the barrier layer.

[0073] According to one embodiment of the present invention, the barrier layer is a layer located at the center of the pouch outer case, and may be a layer that secures the mechanical strength of the pouch outer case, and at the same time prevents the ingress and egress of gas, moisture, etc. into and out of the secondary battery, and in particular, may be a layer that prevents leakage of electrolyte in a secondary battery using a non-aqueous electrolyte. In order to perform the above-described function, the barrier layer may be a foil made of metal, and as a specific example, may include at least one selected from the group consisting of aluminum, iron, copper, and nickel.

[0074] According to one embodiment of the present invention, the barrier layer may comprise aluminum, from the viewpoint of ensuring mechanical strength suitable for a pouch outer material, preventing weight gain due to the pouch outer material, exhibiting excellent formability, and sufficiently securing its role as a barrier layer. As a more specific example, the barrier layer may be an aluminum foil.

[0075] According to one embodiment of the present invention, the barrier layer may have an average thickness of 40 μm or more and 90 μm or less. As a specific example, the barrier layer may have an average thickness of 40 ㎛ or more, 41 ㎛ or more, 42 ㎛ or more, 43 ㎛ or more, 44 ㎛ or more, 45 ㎛ or more, 46 ㎛ or more, 47 ㎛ or more, 48 ㎛ or more, 49 ㎛ or more, 50 ㎛ or more, 51 ㎛ or more, 52 ㎛ or more, 53 ㎛ or more, 54 ㎛ or more, 55 ㎛ or more, 56 ㎛ or more, 57 ㎛ or more, 58 ㎛ or more, 59 ㎛ or more, or 60 ㎛ or more, and also 90 ㎛ or less, 89 ㎛ or less, 88 ㎛ or less, 87 ㎛ or less, 86 ㎛ or less, 85 ㎛ or less, 84 ㎛ or less, 83 ㎛ or less, 82 ㎛ or less, 81 ㎛ or less, 80 ㎛ or less, 79 ㎛ or less, 78 ㎛ or less, 77 ㎛ or less, 76 ㎛ or less, 75 ㎛ or less, 74 ㎛ or less, 73 ㎛ or less, 72 ㎛ or less, 71 ㎛ or less, 70 ㎛ or less, 69 ㎛ or less, 68 ㎛ or less, 67 ㎛ or less, 66 ㎛ or less, 65 ㎛ or less, 64 ㎛ or less, 63 ㎛ or less, 62 ㎛ or less, 61 ㎛ or less, or 60 ㎛ or less. When the barrier layer has an average thickness within the above range, the mechanical strength as a barrier layer can be secured while further improving the formability, and the thickness of the secondary battery can be prevented from being excessively thickened and the weight from increasing due to the outer material.

[0076] According to one embodiment of the present invention, the first sealant layer and the second sealant layer may be layers located on the inner surface of the pouch laminate film. The first sealant layer and the second sealant layer form a sealing portion formed between the pouch laminate film and between the lead tab film and the pouch laminate film, and are also layers that come into direct contact with the secondary battery accommodated inside the pouch outer case, so that they are required to have both heat sealability and formability, as well as electrolyte resistance and insulation resistance.

[0077] According to one embodiment of the present invention, the first sealant layer may be a layer that assists in adhesion between the barrier layer and the second sealant layer, while further enhancing the function as an inner layer, and the second sealant layer may be a layer that constitutes the innermost inner layer of the pouch laminate film, and may be a layer that seals and prevents leakage of a secondary battery, particularly a non-aqueous electrolyte.

[0078] According to one embodiment of the present invention, the first sealant layer may have an average thickness of 10 μm or more and 50 μm or less. As a specific example, the first sealant layer may have an average thickness of 10 µm or more, 11 µm or more, 12 µm or more, 13 µm or more, 14 µm or more, 15 µm or more, 16 µm or more, 17 µm or more, 18 µm or more, 19 µm or more, 20 µm or more, 21 µm or more, 22 µm or more, 23 µm or more, 24 µm or more, 25 µm or more, 26 µm or more, 27 µm or more, 28 µm or more, 29 µm or more, or 30 µm or more, and further, 50 µm or less, 49 µm or less, 48 ​​µm or less, 47 µm or less, 46 µm or less, 45 µm or less, 44 µm or less, 43 µm or less, 42 µm or less, 41 µm or less, 40 µm or less, It may be 39 ㎛ or less, 38 ㎛ or less, 37 ㎛ or less, 36 ㎛ or less, 35 ㎛ or less, 34 ㎛ or less, 33 ㎛ or less, 32 ㎛ or less, 31 ㎛ or less, or 30 ㎛ or less, and within this range, the sealing force can be further improved by sufficient adhesive force between the pouch outer material and the lead tab film.

[0079] According to one embodiment of the present invention, the second sealant layer may have an average thickness of 30 μm or more and 70 μm or less. As a specific example, the second sealant layer may have an average thickness of 30 ㎛ or more, 31 ㎛ or more, 32 ㎛ or more, 33 ㎛ or more, 34 ㎛ or more, 35 ㎛ or more, 36 ㎛ or more, 37 ㎛ or more, 38 ㎛ or more, 39 ㎛ or more, 40 ㎛ or more, 41 ㎛ or more, 42 ㎛ or more, 43 ㎛ or more, 44 ㎛ or more, 45 ㎛ or more, 46 ㎛ or more, 47 ㎛ or more, 48 ㎛ or more, 49 ㎛ or more, or 50 ㎛ or more, and further, 70 ㎛ or less, 69 ㎛ or less, 68 ㎛ or less, 67 ㎛ or less, 66 ㎛ or less, 65 ㎛ or less, 64 ㎛ or less, 63 ㎛ or less, 62 ㎛ or less, 61 ㎛ or less, 60 ㎛ or less, It may be 59 ㎛ or less, 58 ㎛ or less, 57 ㎛ or less, 56 ㎛ or less, 55 ㎛ or less, 54 ㎛ or less, 53 ㎛ or less, 52 ㎛ or less, 51 ㎛ or less, or 50 ㎛ or less, and within this range, the sealing force can be further improved by sufficient adhesive force between the pouch outer material and the lead tab film.

[0080] According to one embodiment of the present invention, the pouch laminate film may have an average thickness of 170 μm or more and 200 μm or less. As a specific example, the pouch laminate film may have an average thickness of 170 ㎛ or more, 171 ㎛ or more, 172 ㎛ or more, 173 ㎛ or more, 174 ㎛ or more, 175 ㎛ or more, 176 ㎛ or more, 177 ㎛ or more, 178 ㎛ or more, 179 ㎛ or more, or 180 ㎛ or more, and may also have an average thickness of 200 ㎛ or less, 199 ㎛ or less, 198 ㎛ or less, 197 ㎛ or less, 196 ㎛ or less, 195 ㎛ or less, 194 ㎛ or less, 193 ㎛ or less, 192 ㎛ or less, 191 ㎛ or less, 190 ㎛ or less, 189 ㎛ or less, 188 ㎛ or less, 187 ㎛ or less, 186 ㎛ or less, or 185 ㎛ or less, and within this range, the secondary It is possible to protect the battery while preventing the secondary battery from becoming excessively thick due to the outer material.

[0081] The present invention provides a pouch outer material including the above pouch laminate film.

[0082] According to one embodiment of the present invention, the pouch outer case may include at least one of the upper film and the lower film constituting the pouch outer case, which may include the pouch laminate film, and preferably, both the upper film and the lower film constituting the pouch outer case may be the pouch laminate film.

[0083] According to one embodiment of the present invention, the pouch outer material can secure sealing force for a sealing portion for sealing between the upper film and the lower film by applying the pouch laminate film as the upper film and / or the lower film, respectively, and can also secure sealing force between the upper film and / or the lower film and the lead tab film.

[0084] According to one embodiment of the present invention, the pouch outer material may be manufactured by contacting at least one side of the lead tab film with the second sealant layer of the pouch laminate film, and then sealing the seal at a temperature of 200° C., for 1.5 seconds or more and 2.1 seconds or less, under a pressure of 0.1 MPa or more and 0.3 MPa or less, so that the thickness of the inner layer at the sealing portion becomes 70% of the thickness of the inner layer.

[0085]

[0086] The present invention provides a secondary battery including the above pouch outer material.

[0087] According to one embodiment of the present invention, the secondary battery may include the pouch outer case and an electrode assembly accommodated in the pouch outer case.

[0088] According to one embodiment of the present invention, the secondary battery may be a lithium secondary battery.

[0089] The secondary battery of the present invention includes a pouch-type secondary battery case including the battery main body and the pouch laminated film, and the battery main body 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 main body may include a negative electrode for a lithium secondary battery, a positive electrode for a lithium secondary battery, a separator, a current collector, and a liquid electrolyte and a solid electrolyte.

[0090] The above lithium secondary battery positive electrode can be used without limitation as long as it is one that is commonly used as a positive electrode of a lithium secondary battery. For example, the above lithium secondary battery positive electrode can be LiCoO2, LiMnO2, LiFeO2, Li(Ni x Mn y Co z )O2(X+Y+Z=1), LiNiCoAlO2, etc. may be included as positive active materials.

[0091] 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.

[0092] 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.

[0093] 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.

[0094]

[0095] 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.

[0096]

[0097] Examples and Comparative Examples

[0098] A pouch laminate film having a structure of surface protection layer (PET) / stretching auxiliary layer (nylon) / barrier layer (aluminum thin film) / first sealant layer / second sealant layer was manufactured.

[0099] Specifically, a laminated film of a polyethylene terephthalate (PET) film (thickness 12 ㎛) and a nylon (Ny) film (thickness 25 ㎛) inside thereof was used, aluminum was used as the barrier layer (thickness 60 ㎛), and the sealant layer (thickness 80 ㎛) was manufactured by using an extrusion lamination method to form a polypropylene extrusion coating (EC) layer (first sealant layer, thickness 30 ㎛) and a non-stretched polypropylene (CPP) layer (second sealant layer, thickness 50 ㎛). At this time, the type of polyolefin resin forming the matrix of the first sealant layer, the type of polyolefin resin forming the matrix of the second sealant layer, the crystallization temperature (Tc; ℃), the melting point (Tm; ℃), the melt index and the upper yield strength (N / mm) measured under the conditions of a temperature of 230 ℃ and a load of 2.16 kg by the ASTM D1238 method 2 , upper yield strength) are shown in Tables 1 to 4 below.

[0100]

[0101] Example 1234: 1st sealant layer matrix R-PP 1) H-PP 2) or B-PP 3) H-PP 2) or B-PP 3) H-PP 2) or B-PP 3) Tc94110≤110≤110≤Tm148160160160MFR20181919Yield strength151718182nd sealant layerMatrixR-PP 1) or T-PP 4) R-PP 1) or T-PP 4) R-PP 1) or T-PP 4) R-PP 1) or T-PP 4)Tc95≤100≤100≤100Tm138148138138MFR6755Upper yield strength16151616MFR1-MFR214111414UTS1-UTS2-12221) R-PP: Random polypropylene2) H-PP: Homo polypropylene3) B-PP: Block polypropylene4) T-PP: Terpolymer polypropylene

[0102] Comparison Example 12345 1st Sealant Layer Matrix R-PP 1) R-PP 1) R-PP 1) H-PP 2) or B-PP 3) H-PP 2) or B-PP 3) Tc909494110≤110≤Tm148148148160160MFR2028201212Yield strength1515131312Second sealant layerMatrixH-PP 2) or B-PP 3) R-PP 1) or T-PP 4) R-PP 1) or T-PP 4) R-PP 1) or T-PP 4) R-PP 1) or T-PP 4) Tc1139595≤100≤100Tm160138138138138MFR5261212Yield strength1716161519MFR1-MFR215261400UTS1-UTS2-2-1-3-2-71) R-PP: Random polypropylene2) H-PP: Homo polypropylene3) B-PP: Block polypropylene4) T-PP: Terpolymer polypropylene

[0103] Comparison Example 6789 1st Sealant Layer Matrix H-PP 2) or B-PP 3) H-PP 2) or B-PP 3) R-PP 1) or T-PP 4) R-PP 1) or T-PP 4)Tc110≤110≤≤110≤110Tm160160133148MFR12191612Yield strength201513172nd sealant layerMatrixR-PP 1) or T-PP 4) H-PP 2) or B-PP 3) H-PP 2) or B-PP 3) H-PP 2) or B-PP 3) Tc≤100110≤110≤110≤Tm138160160160MFR12555Upper yield strength13171717MFR1-MFR2014117UTS1-UTS27-2-401) R-PP: Random polypropylene2) H-PP: Homo polypropylene3) B-PP: Block polypropylene4) T-PP: Terpolymer polypropylene

[0104] Comparison Example 1011121314 1st Sealant Layer Matrix R-PP 1) or T-PP 4) R-PP 1) or T-PP 4) R-PP 1) or T-PP 4) R-PP 1) or T-PP 4) H-PP 2) or B-PP 3) Tc≤110≤110≤110≤110110≤Tm148148148148160MFR162020912Yield strength151515151512Second sealant layerMatrixH-PP 2) or B-PP 3) H-PP 2) or B-PP 3) H-PP 2) or B-PP 3) H-PP 2) or B-PP 3) R-PP 1) or T-PP 4Tc110≤110≤110≤110≤100Tm160160160160138MFR58101012Yield strength1716161715MFR1-MFR2111210-10UTS1-UTS2-2-1-1-2-31) R-PP: Random polypropylene2) H-PP: Homo polypropylene3) B-PP: Block polypropylene4) T-PP: Terpolymer polypropylene

[0105] Experimental Example 1

[0106] Using the above-mentioned manufactured pouch laminate film, the sealing strength was measured as follows, and the results are shown in Tables 5 to 8 below, along with the sealing initiation temperature (SIT; ℃).

[0107]

[0108] * Sealing Initiation Temperature (SIT; ℃): The sealing initiation temperature refers to the starting temperature at which the surface of the pouch film is bonded when heat is applied to the pouch film, and more specifically, it refers to the temperature at which the sealing strength (load) of the pouch film is 100 N / 15mm or more when measuring the sealing strength. The lower the sealing initiation temperature, the lower the temperature at which bonding can begin, and therefore, the lower the sealing initiation temperature can be advantageous for a fast sealing process (Sealing Tack Time) in a high temperature / high heat environment. The sealing initiation temperature was measured by measuring the sealing strength while increasing it by 10 ℃ from 150 ℃ and confirming that the temperature exceeded 100 N / 15mm.

[0109]

[0110] * Sealing strength (N / 15 mm): The pouch films of the examples and comparative examples were folded in half, pressed so that the thickness remaining ratio of the sealant layer including the first sealant layer and the second sealant layer was 70%, and cut to a width of 15 mm to prepare a specimen. The sealing strength was measured by peeling the interface between the first sealant layer and the second sealant layer of the manufactured specimen by 180° at a gauge distance of 30 mm and a peeling speed of 50 mm / min at room temperature (25 ℃) and high temperature (60 ℃) using a universal testing machine (UTM). Here, the sealing strength means the maximum value of the sealing strength shown in the sealing strength graph.

[0111]

[0112] Experimental Example 2

[0113] Using the pouch laminate film manufactured above, sealing was performed at a sealing temperature of 200°C so that the thickness remaining ratio of the sealant layer including the first sealant layer and the second sealant layer for the lead tab film and the pouch laminate film was 70%, and the tab sealing strength and sealing shape of the sealed portion manufactured by the sealing were measured and observed using the following method, and are shown together in Tables 5 to 8 below.

[0114] Here, the sealing shape was cut from the pouch outer material in a direction perpendicular to the manufactured lead tab film sealing portion, and epoxy molding and polishing were performed on the cross-section. Then, a cross-sectional analysis was performed on the lead tab film sealing portion and adjacent areas using an optical device, and observation was made through an optical image obtained from the optical device.

[0115]

[0116] * Tab sealing strength (N / 15 mm): Each lead tab film sealing section manufactured above was cut to a width of 15 mm to manufacture a specimen, and then the sealing strength of the sealing section was measured using a universal testing machine (UTM) at a gauge distance of 20 mm and a peeling speed of 50 mm / min. Here, the sealing strength refers to the maximum value of the sealing strength shown in the sealing strength graph.

[0117]

[0118] Experimental Example 3

[0119] The above-mentioned manufactured pouch laminate film was molded into 30 mm x 40 mm x 5 mm, and then dummy cells were manufactured through side sealing and tab sealing based on 2 ml of electrolyte. The number of samples was 10 per sample. After manufacturing the dummy cells, the resistance was measured when a voltage of 1 kV was applied after 24 hours at a temperature condition of 60 ℃, and the results are shown in Tables 5 to 8 below.

[0120] In addition, the number of times the insulation resistance became less than 1 G due to damage to the pouch laminate due to bending was confirmed and is shown in Tables 5 to 8 below.

[0121]

[0122] Classification Example 1234 Sealing strength 25 ℃ 130<130<130<130<60 ℃ 100<100<100<100 <SIT170180180180탭 실링 강도130130130130실링 모양양호양호양호양호절연저항1000 V100 G120 G120 G120 GBending100 회≤50 회80 회100 회≤

[0123] Classification Comparison Example 12345 Sealing strength 25 ℃ 130 < 130 < 110 110 110 60 ℃ 100 < 100 < 80 100 80 (NG) SIT 200 170 170 180 180 Tab sealing strength 110 130 110 130 120 Sealing shape Not melted Not melted Good Good Good Insulation resistance 1000 V80 G100 G100 G120 G100 GBending 50 times 100 times ≤ 100 times ≤ 50 times ≤ 50 times

[0124] Classification comparison example 6789 Sealing strength 25 ℃ 130 < 100 100 < 130 < 60 ℃ 100 < 40 (NG) ≤ 40 100 <SIT180205200200탭 실링 강도120100≤100130실링 모양양호미용융미용융미용융절연저항1000 V100 G180 G50 G50 GBending≤50 회≤10 회50 회50 회

[0125] Classification Comparison Example 10 1 1 1 2 1 3 1 4 Sealing Strength 25 ℃ 130 130 < 130 < 130 < 100 60 ℃ ≤ 40 100 100 100 60 SIT 200 200 200 200 180 Tab Sealing Strength 120 110 110 100 130 Sealing Shape Not Melted Not Melted Not Melted Not Melted Good Insulation Resistance 1000 V 50 G 50 G 20 G 80 G 100 GB Ending 50 times 50 times 50 times 50 times 100 times ≤

[0126] Referring to Tables 5 to 8 and FIGS. 1 and 2, it can be confirmed that the pouch laminate films of Examples 1 to 4 have excellent sealing strengths of 130 or higher at room temperature and 100 or higher at 60°C. In addition, sealing began stably at a temperature of 170-180°C, which is relatively low compared to the comparative examples, and the tab sealing strength was also excellent at 130, and it can be confirmed that the sealing shape was uniform without the polymer being pushed. It can also be confirmed that the insulation resistance characteristics were significantly superior to the comparative examples.

[0127] On the other hand, in the case of Comparative Examples 1, 7, 8 and 10 to 13 where the crystallization temperature is high and the melting point of the first sealant layer is lower than that of the second sealant layer, the sealing area is not melted due to the difference in melting points, showing an uneven shape with an uneven appearance, and the tab sealing strength and insulation resistance are also at a low level.

[0128] In addition, in the case of Comparative Examples 1 to 6, 9, 13 and 14, where the difference in melting index and yield strength between the first sealant layer and the second sealant layer is outside the scope of the present invention, it can be confirmed that the sealing initiation temperature (SIT) is high, the sealing strength and the tab sealing strength are inferior, the sealing portion is not melted and shows an unbalanced shape as requested, and the insulation resistance characteristics are also inferior.

[0129]

[0130] Acknowledgement

[0131] The present invention is a result of the following task support.

[0132] [Project ID] 2410004468

[0133] [Assignment Number] 20022450

[0134] Ministry of Trade, Industry and Energy

[0135] [Name of Project Management (Specialist) Institution] Korea Institute of Industrial Technology Planning and Evaluation

[0136] [Research Project Name] Material and Components Technology Development (Leeum Company)

[0137] [Research Project Name] Development of a Next-Generation Secondary Battery Pouch Capable of Delivering More Than Double the Highest Adhesive Strength (60°C)

[0138] [Contribution rate] 1 / 1

[0139] [Name of Project Performing Organization] Yulchon Chemical Co., Ltd.

[0140] Research Period: January 1, 2024 - December 31, 2024

Claims

1. Contains an outer layer, a barrier layer, a first sealant layer, and a second sealant layer, The crystallization temperature of the second sealant layer is 100 ℃ or less, The melting point of the first sealant layer is higher than the melting point of the second sealant layer, The difference (MFR1-MFR2) between the melting index (MFR1) of the first sealant layer and the melting index (MFR2) of the second sealant layer is 10 g / 10 min or more and 20 g / 10 min or less, The difference (UTS1-UTS2) between the upper yield strength (UTS1) of the first sealant layer and the upper yield strength (UTS2) of the second sealant layer is -1 N / mm 2 More than 10 N / mm 2 A pouch laminate film having the following properties.

2. In claim 1, A pouch laminate film wherein the first sealant layer is at least one selected from the group consisting of random polypropylene, homo polypropylene, and block polypropylene.

3. In claim 1, A pouch laminate film wherein the second sealant layer is at least one selected from the group consisting of random polypropylene and terpolymer polypropylene.

4. In claim 1, A pouch laminate film wherein the melting point of the first sealant layer is 10° C. or higher than the melting point of the second sealant layer.

5. In claim 1, A pouch laminate film wherein the first sealant layer has a crystallization temperature of 92°C or higher.

6. In claim 1, A pouch laminate film wherein the first sealant layer has a melting point of 145°C or higher.

7. In claim 1, A pouch laminate film wherein the first sealant layer has a melting index of 15 g / 10 min or more and 24 g / 10 min or less.

8. In claim 1, The first sealant layer has a yield strength of 12 N / mm. 2 Above, 20 N / mm 2 A pouch laminate film having the following properties.

9. In claim 1, A pouch laminate film wherein the second sealant layer has a melting point of 150°C or less.

10. In claim 1, A pouch laminate film wherein the second sealant layer has a melting index of 3 g / 10 min or more and 15 g / 10 min or less.

11. In claim 1, The second sealant layer has a yield strength of 12 N / mm. 2 Above, 20 N / mm 2 A pouch laminate film having the following properties.

12. A pouch outer material comprising a pouch laminate film according to any one of claims 1 to 11.

13. A secondary battery comprising a pouch outer material according to claim 12.

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