Packaging material for battery

Abstract

Disclosed is a packaging material for a battery, comprising a stacked structure of: an outer layer consisting of a heat-resistant resin film; a barrier layer including metal foil; and an inner layer consisting of a composition including a thermoplastic polyolefin, wherein excellent adhesive strength is imparted to an adhesive layer stacked between the barrier layer and the inner layer, thereby securing stability. The present invention provides a packaging material for a battery, comprising a stacked structure of: an outer layer consisting of a heat-resistant resin film; a barrier layer including metal foil; and an inner layer consisting of a composition including a thermoplastic polyolefin, wherein an adhesive layer is further stacked between the barrier layer and the inner layer, and the adhesive layer includes 30-70 wt% of polypropylene, 5-30 wt% of polyethylene, 20-50 wt% of a propylene-based elastomer, and 1-15 wt% of acid-modified polypropylene.

Description

Packaging materials for batteries

[0001] The present invention relates to a battery packaging material, and more particularly, to a battery packaging material having a structure in which an outer layer, a barrier layer including a metal foil, and an inner layer are laminated.

[0002] This application claims priority to and the benefit of Republic of Korea Patent Application No. 10-2023-0171592, filed November 30, 2023, which is incorporated herein by reference in its entirety.

[0003] A secondary battery is a device that converts external electrical energy into chemical energy, stores electricity, and then converts the chemical energy back into electrical energy and supplies it when needed. It usually refers to a lithium secondary battery and is used in portable terminal devices such as laptops, smartphones, tablet PCs, and video cameras, electric vehicles including hybrid cars, smart grids for energy storage, robots, satellites, etc.

[0004] The packaging material used in these secondary batteries is an external material that stores the components inside the battery and protects the battery cells from external impact, and is an important component material that determines the life characteristics and operational sustainability of the battery.

[0005] Conventionally used secondary battery packaging materials include cylindrical (=can), square, and pouch types, each with their own advantages and disadvantages. First, cylindrical packaging can be mass-produced in standardized sizes and offers cost advantages, but it suffers from poor space efficiency during stacking. Second, square packaging, while more space-efficient and lightweight than cylindrical packaging, suffers from difficulties in heat management and higher production costs compared to cylindrical packaging. Pouch packaging, unlike the aforementioned two types, offers the advantages of flexible shape modification, lightweight design, high space utilization, and superior packaging efficiency.

[0006] Pouches for secondary batteries, for example, are largely composed of an outer layer, a barrier layer, and an inner layer (heat-sealing layer), and are multilayered with separate adhesive layers between each layer. The inner layer acts as a sealant when producing a multilayer film into a pouch shape, and must have heat-sealing properties, so it is a polyolefin film layer composed of polyethylene (PE), polypropylene (PP), or a copolymer of these. In addition, for the barrier layer, a metal foil layer of aluminum is mainly used as a base material to provide not only mechanical strength but also moisture and oxygen barrier properties. In addition, functional polymer films such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), nylon, and liquid crystal polymer (LCP) are used as film materials for the outer layer because they have excellent pinhole resistance, gas barrier properties, heat resistance, and mechanical strength.

[0007] In this way, cell pouches (packaging materials in the form of pouches) have advantages in terms of shape diversification and lightweight compared to conventional cylindrical and can-shaped ones. However, since they are made of soft multilayer film material and used as packaging materials, they can be damaged by various factors during various processes. For example, when storing the electrode assembly inside the pouch, protruding parts such as electrode tabs or electrode leads can cause damage such as cracks in the inner layer of the pouch. In addition, the heat applied during the sealing (heat sealing) process to manufacture the pouch can cause pinholes or internal damage to the pouch, causing cracks. If the aluminum layer is exposed due to such damage, a side reaction occurs due to its reactivity with the electrolyte. The aluminum layer exposed to the electrolyte can corrode due to a chemical reaction between the electrolyte and oxygen or moisture that has penetrated or diffused into the battery. This can generate corrosive gases, causing swelling that expands the inside of the battery. Specifically, lithium hexafluorophosphate (LiPF6) can react with water and oxygen to produce hydrofluoric acid (HF), a corrosive gas. This hydrofluoric acid can react with aluminum, causing a rapid exothermic reaction. Furthermore, if it is adsorbed onto the aluminum surface and penetrates into the tissue through a secondary reaction, the tissue becomes more brittle, causing cracks in the pouch film even from a minor impact. This can lead to electrolyte leakage, which can cause a reaction between lithium and the atmosphere, potentially leading to a fire.

[0008] Due to these factors, packaging materials for cell pouches require various properties, such as mechanical flexibility and strength, high barrier properties, heat seal strength, chemical resistance to electrolytes (electrolysis resistance), electrical insulation, and thermal stability.

[0009] Currently, Japanese companies hold over 70% of the global market for cell pouch films, and domestic secondary battery manufacturers also rely heavily on Japanese products. Given this high dependence on imported secondary battery materials, domestic production of pouch materials is urgently needed. However, research on the inner layer (heat sealing layer) of pouch films, particularly the adhesive between the inner layer (heat sealing layer) and the barrier layer (aluminum layer), is hampered by the difficulty of technological development.

[0010] Accordingly, the present invention provides a battery packaging material having a laminated structure comprising an outer layer made of a heat-resistant resin film; a barrier layer including a metal foil; and an inner layer made of a composition including a thermoplastic polyolefin, wherein the battery packaging material has excellent adhesive strength and thus ensures stability by imparting an adhesive layer laminated between the barrier layer and the inner layer.

[0011] In order to solve the above problem, the present invention provides a battery packaging material comprising a laminated structure of an outer layer made of a heat-resistant resin film; a barrier layer including a metal foil; and an inner layer made of a composition including a thermoplastic polyolefin, wherein a first adhesive layer is further laminated between the barrier layer and the inner layer, and the first adhesive layer comprises 30 to 70 wt% of polypropylene, 5 to 30 wt% of polyethylene, 20 to 50 wt% of a propylene-based elastomer, and 1 to 15 wt% of an acid-modified polypropylene.

[0012] In addition, the metal foil provides a battery packaging material characterized in that it includes at least one metal selected from the group consisting of aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), tin (Sn), zinc (Zn), indium (In), and tungsten (W).

[0013] In addition, the above acid-modified polypropylene provides a battery packaging material characterized in that the maleic anhydride graft content is 0.1 to 10 wt%.

[0014] In addition, the propylene-based elastomer provides a battery packaging material characterized by having a melting point of 140°C or lower.

[0015] In addition, the propylene-based elastomer is a propylene-alpha olefin copolymer, and provides a battery packaging material characterized in that it includes a first propylene-based elastomer having an ethylene comonomer content of 5 to 25 wt% and a second propylene-based elastomer having a 1-butene comonomer content of 20 to 40 wt%.

[0016] In addition, a battery packaging material is provided, characterized in that the thickness of the outer layer is 10 to 40 ㎛; the thickness of the barrier layer is 25 to 50 ㎛; the thickness of the first adhesive layer is 25 to 50 ㎛; and the thickness of the inner layer is 25 to 50 ㎛.

[0017] In addition, the packaging material provides a battery packaging material characterized in that the peel strength of the interface between the aluminum foil and the first adhesive layer before and after electrolyte immersion, measured according to the following method, is 8 N / 15 mm or more.

[0018] [Method for measuring the peel strength of the aluminum foil and the first adhesive layer interface before electrolyte immersion]

[0019] After aging a film in which PET (12 ㎛ thick), a second adhesive layer (3 ㎛ thick), Nylon (15 ㎛ thick), a second adhesive layer (3 ㎛ thick), an aluminum foil (40 ㎛ thick), the first adhesive layer (40 ㎛ thick), and a PP inner layer (40 ㎛ thick) were laminated for 1 day under constant temperature and humidity conditions, a sample cut to 100 mm in length and 15 mm in width was measured for the T-shaped peel strength of the interface between the aluminum foil and the first adhesive layer at a test speed of 50 mm / min at 23°C using a measuring device (universal testing machine, Instron);

[0020] [Method for measuring the peel strength between the aluminum foil and the first adhesive layer after electrolyte immersion]

[0021] After maturing the above laminated film under constant temperature and humidity conditions for one day, the first sample cut to 150 mm in length and 17 mm in width was immersed in an electrolyte (EC / EMC / DMC=3 / 3 / 4 v / v composition) at 85°C for one day, and the second sample cut to 100 mm in length and 15 mm in width was measured for the T-shaped peel strength of the interface between the aluminum foil and the first adhesive layer using a measuring device (universal testing machine, Instron) at a test speed of 50 mm / min at 23°C.

[0022] According to the present invention, a battery packaging material comprising a laminated structure of an outer layer made of a heat-resistant resin film; a barrier layer including a metal foil; and an inner layer made of a composition including a thermoplastic polyolefin; wherein an adhesive layer laminated between the barrier layer and the inner layer is made of a polypropylene-based resin, and is composed of polyethylene, a propylene-based elastomer, and an acid-modified polypropylene in a specific composition, thereby improving adhesive strength to secure stability, and further improving formability in post-processing, can be provided.

[0023] Hereinafter, the present invention will be described in detail through preferred embodiments. Prior to this, it should be noted that the terms and words used in this specification and claims should not be interpreted as limited to their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concept of a term to best explain his or her invention, they should be interpreted as meanings and concepts that conform to the technical concept of the present invention. Therefore, the configuration of the embodiments described in this specification is only the most preferred embodiment of the present invention and does not represent the entire technical concept of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as of the time of filing this application.

[0024]

[0025] The present invention discloses a packaging material for a lithium battery, comprising a laminated structure of an outer layer made of a heat-resistant resin film; a barrier layer including a metal foil; and an inner layer made of a composition including a thermoplastic polyolefin, wherein a first adhesive layer is further laminated between the barrier layer and the inner layer, and the first adhesive layer comprises 30 to 70 wt% of polypropylene, 5 to 30 wt% of polyethylene, 20 to 50 wt% of a propylene-based elastomer, and 1 to 15 wt% of an acid-modified polypropylene.

[0026] The above outer layer is the outermost layer of a lithium battery packaging material that can be exposed to the outside and is provided on a barrier layer including a metal foil, and is preferably formed using a material that has wear resistance, heat resistance, cold resistance, pinhole resistance, insulation, chemical resistance, moldability, etc. so as to protect the barrier layer including the metal foil. The outer layer made of such a heat-resistant resin film may include a polyamide-based resin or a polyester-based resin. The polyamide-based resin may be nylon, which has a high elongation and is thus advantageous for molding, and the polyester-based resin may be polybutylene terephthalate (PBT) or polyethylene terephthalate (PET), which can implement high chemical resistance, pinhole resistance, insulation, mechanical strength, etc.

[0027] The outer layer may have a thickness of about 10 to 40 ㎛, taking into consideration sufficient wear resistance, heat resistance, pinhole resistance, chemical resistance, formability, insulation, etc. If the thickness of the outer layer is too thin, the formability of the battery packaging material may be reduced due to insufficient strength of the outer layer. On the other hand, if it is too thick, the inner layer and the barrier layer including the metal foil provided under the outer layer must be implemented with a relatively thin thickness, so problems such as reduced thermal bonding strength and reduced peel strength between each layer may occur in the battery packaging material. However, the thickness of the outer layer is not limited to the above range, and may have an appropriate thickness depending on the purpose of the cell pouch to be implemented, for example, a thin-film cell pouch implemented with a total thickness of about 88 ㎛, a general cell pouch implemented with a total thickness of about 113 ㎛, or a medium- to large-sized cell pouch implemented with a total thickness of about 153 ㎛.

[0028] The barrier layer including the metal foil is intended to block the ingress of moisture or air from the outside and gas generated inside, and can be in contact with the inner layer and the first adhesive layer. The barrier layer including the metal foil may include a metal having gas barrier properties and moisture barrier properties, and may include, for example, one or more selected from the group consisting of aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), tin (Sn), zinc (Zn), indium (In), tungsten (W), etc. (a single metal or a mixture of single metals), or an alloy of two or more selected from these. As a preferred embodiment, the barrier layer including the metal foil may include aluminum (Al) or an aluminum alloy in consideration of all of the moisture barrier properties, the gas barrier properties, and the formability. The barrier layer including the metal foil may have a thickness of about 25 to 50 ㎛ in order to have a sufficient degree of gas barrier properties and moisture barrier properties. However, the thickness of the barrier layer including the metal foil is not limited thereto, and may have an appropriate thickness depending on the purpose of the cell pouch to be implemented, i.e., generally, a thin-film cell pouch implemented with a total thickness of about 88 ㎛, a general cell pouch implemented with a total thickness of about 113 ㎛, or a medium- to large-sized cell pouch implemented with a total thickness of about 153 ㎛.

[0029] It is preferable that the barrier layer including the metal foil be chemically treated on at least one side, preferably at least the inner layer side, and preferably both sides, to stabilize adhesion and prevent dissolution or corrosion. Here, chemically treating means forming an acid-resistant film on the surface of the barrier layer including the metal foil. Examples of the chemically treating include chromic acid chromate treatment using chromic acid compounds such as chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromate acetylacetate, chromium chloride, and potassium chromium sulfate; phosphoric acid chromate treatment using phosphoric acid compounds such as sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphoric acid; and chromate treatment using an aminated phenol polymer.

[0030] The inner layer is a layer made of a composition including thermoplastic polyolefin that comes into contact with the electrolyte of the battery, which corresponds to the innermost layer of the battery packaging material, and is subjected to thermal bonding for the purpose of sealing the battery.

[0031] That is, in the case of the inner layer, since it must have heat-adhesive properties as a layer that acts as a sealant when producing a multilayer film in the form of a pouch, it can be composed of polyolefins such as polyethylene (PE), polypropylene (PP), or copolymers thereof.

[0032] The inner layer may have a thickness of about 25 to 50 μm for sufficient thermal bonding characteristics, but is not limited thereto, and may have an appropriate thickness depending on the intended use of the cell pouch, for example, a thin-film cell pouch implemented with a total thickness of about 88 μm, a general-purpose cell pouch implemented with a total thickness of about 113 μm, or a medium- to large-sized cell pouch implemented with a total thickness of about 153 μm.

[0033] As a packaging material for secondary batteries, pouch-type materials use a soft pouch as a container, and thus may be damaged for various reasons during various processes. Therefore, the present invention provides a battery packaging material that ensures stability by imparting excellent adhesive strength to a first adhesive layer laminated between a barrier layer and an inner layer, wherein the first adhesive layer is composed of a polypropylene resin, and comprises polyethylene, a propylene elastomer, and an acid-modified polypropylene in a specific composition.

[0034] The type of polypropylene that serves as the base resin in the first adhesive layer is not particularly limited, and for example, a propylene homopolymer, a propylene-based binary copolymer, a propylene-based terpolymer, a propylene block copolymer, etc. can be used. Preferably, a copolymer of propylene and ethylene or one type of α-olefin other than propylene can be used, and more preferably, a terpolymer of propylene and ethylene and 1-butene can be used. At this time, when applied as a preferred propylene-based terpolymer, the ethylene and 1-butene contents can be 2 to 4 wt% and 2.5 to 4.5 wt%, respectively.

[0035] In the first adhesive layer, polypropylene may be included in an amount of 30 to 70 wt%, preferably 35 to 65 wt%, and more preferably 40 to 60 wt%. If the polypropylene content is less than 30 wt%, molding is difficult during film production and adhesion to a barrier layer including a metal foil is reduced, and if it exceeds 70 wt%, adhesion to a barrier layer including a metal foil is reduced.

[0036] Additionally, in the first adhesive layer, polyethylene plays a role in compensating for the neck-in phenomenon that occurs during extrusion molding.

[0037] The above polyethylene has a density of 0.900 to 0.940 g / cm, taking into account the compatibility and processability of the components constituting the first adhesive layer. 3, preferably 0.910 to 0.930 g / cm 3 , and a melting index (190℃, 2.16 kg load) of 5 to 20 g / 10min, preferably 10 to 15 g / 10min, can be used.

[0038] In the first adhesive layer, polyethylene may be contained in an amount of 5 to 30 wt%, preferably 5 to 25 wt%, and more preferably 10 to 20 wt%. If the polyethylene content is less than 5 wt%, the neck-in phenomenon occurs excessively during extrusion molding, and if it exceeds 30 wt%, the adhesion to the barrier layer including the metal foil is reduced.

[0039] In the first adhesive layer, the acid-modified polypropylene is a resin added to increase the adhesive strength between the barrier layer including the metal foil and the inner layer by imparting a polar group.

[0040] The above acid-modified polypropylene may be a modified polypropylene grafted with maleic anhydride, which is a polar functional group, in an amount of 0.1 to 10 wt%, preferably 2 to 5 wt%. If the maleic anhydride graft content of the modified polypropylene is less than 0.1 wt%, the adhesive strength with a barrier layer including a metal foil may be reduced, and if it exceeds 10 wt%, a large amount of polar functional groups may cause fish eye and generate low molecules, which may lower the surface tension after corona surface treatment, thereby reducing the adhesive strength with the barrier layer.

[0041] In the first adhesive layer, the acid-modified polypropylene may be included in an amount of 1 to 15 wt%, preferably 2 to 10 wt%, and more preferably 3 to 7 wt%. If the acid-modified polypropylene content is less than 1 wt%, the improvement in adhesion with the barrier layer may not be satisfactory, and if it exceeds 15 wt%, the adhesion with the barrier layer may also be reduced due to the large amount of polar functional groups.

[0042] In addition, the first adhesive layer includes a propylene-based elastomer to further enhance the adhesive strength between the barrier layer including the metal foil and the inner layer while reinforcing the soft properties of the multilayer film material pouch. Here, the use of an ethylene-based elastomer as the elastomer may be considered, but it has been confirmed that the adhesive strength is significantly improved when a propylene-based elastomer is employed in combination with other components constituting the first adhesive layer compared to when an ethylene-based elastomer is employed.

[0043] At this time, the propylene-based elastomer is preferably used with a melting point of 140°C or lower to increase productivity by exhibiting adhesive strength from a low temperature when producing packaging materials through a lamination process of the outer layer, barrier layer, and inner layer, and more preferably, it is preferably used with a melting point of 60 to 140°C, and even more preferably, it is preferably used with a melting point of 70 to 110°C.

[0044] In addition, the propylene-based elastomer may be used alone or in combination of two or more, and in the present invention, it was confirmed that the adhesive strength is maximized when two propylene-alpha olefin copolymers of a specific composition are mixed and used, including a first propylene-based elastomer having an ethylene comonomer content of 5 to 25 wt%, preferably 10 to 20 wt%, and a second propylene-based elastomer having a 1-butene comonomer content of 25 to 35 wt%. At this time, the density of the first propylene-based elastomer is 0.84 to 0.88 g / cm. 3 The density of the above two propylene-based elastomers may be 0.88 to 0.92 g / cm 3 It may be. In addition, it is most preferable that the melting point of the first propylene-based elastomer is 100 to 110°C, and it is most preferable that the melting point of the second propylene-based elastomer is 70 to 80°C.

[0045] In the first adhesive layer, the propylene-based elastomer may be included in an amount of 20 to 50 wt%, preferably 20 to 45 wt%, and more preferably 25 to 45 wt%. When the propylene-based elastomer content is less than 20 wt%, the effect of imparting soft properties to the packaging material and the degree of improvement in adhesion with the barrier layer are minimal, and when it exceeds 50 wt%, molding is difficult during film production and the degree of improvement in adhesion with the barrier layer including the metal foil is minimal. In addition, when the first propylene-based elastomer and the second propylene-based elastomer are mixed and used, it is preferable to use them in an amount of 10 to 25 wt%, and more preferably, it is possible to use them in an amount of 15 to 20 wt%, respectively.

[0046] The first adhesive layer may have a thickness of about 25 to 50 μm in order to provide soft properties to the packaging material and sufficiently improve adhesive strength, but is not limited thereto, and may have an appropriate thickness depending on the intended use of the cell pouch, for example, a thin-film cell pouch implemented with a total thickness of about 88 μm, a general-purpose cell pouch implemented with a total thickness of about 113 μm, or a medium- to large-sized cell pouch implemented with a total thickness of about 153 μm.

[0047] Meanwhile, in the present invention, a second adhesive layer may be further formed to adhere the outer layer and the barrier layer including the metal foil. In this case, if the outer layer is composed of multiple layers, the second adhesive layer may be interposed between the outer layers.

[0048] The second adhesive layer is formed by an adhesive capable of bonding the outer layer and the barrier layer including the metal foil, and the adhesive used to form the second adhesive layer may be a two-component curing adhesive or a one-component curing adhesive. In addition, the bonding mechanism of the adhesive used to form the second adhesive layer is not particularly limited, and any one of a chemical reaction type, a solvent volatilization type, a heat melting type, a heat pressure type, etc. may be selected.

[0049] Examples of the resin component of the adhesive that can be used to form the second adhesive layer include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, polycarbonate, and copolymerized polyester; polyether adhesives; polyurethane adhesives; epoxy resins; phenol resin resins; polyamide resins such as nylon 6, nylon 66, nylon 12, and copolymerized polyamide; polyolefin resins such as polyolefin, acid-modified polyolefin, and metal-modified polyolefin; polyvinyl acetate resins; cellulose adhesives; (meth)acrylic resins; polyimide resins; amino resins such as urea resin and melamine resin; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; silicone resins; and fluorinated ethylene propylene copolymers. These adhesive components can be used alone or in combination of two or more.

[0050] The thickness of the second adhesive layer may be, for example, 2 to 10 μm.

[0051] The method for manufacturing a battery packaging material according to the present invention is not particularly limited as long as a laminate in which each layer having a predetermined composition is laminated can be obtained, but the following methods are exemplified.

[0052] First, a laminate (laminated body A) is formed by sequentially laminating an outer layer, a second adhesive layer, and a barrier layer including a metal foil. Specifically, the formation of laminated body A can be performed by a dry lamination method in which an adhesive used for forming the second adhesive layer is applied to a barrier layer including a metal foil having a surface treated with Mars using a coating method such as an extrusion method, a gravure coating method, a roll coating method, etc., and then the outer layer is laminated to harden the second adhesive layer.

[0053] Next, the inner layer is laminated on the barrier layer including the metal foil of laminate A. At this time, the first adhesive layer interposed between the barrier layer including the metal foil and the inner layer can be laminated, for example, by co-extruding the first adhesive layer and the inner layer on the barrier layer including the metal foil of laminate A (co-extrusion lamination method).

[0054] The battery packaging material according to the present invention comprises a first adhesive layer laminated between a barrier layer and an inner layer made of a polypropylene-based resin, and comprises polyethylene, a propylene-based elastomer, and an acid-modified polypropylene in a specific composition to enhance adhesive strength and ensure stability. Specifically, the battery packaging material according to the present invention may have an interface peel strength of 8 N / 15 mm or more between an aluminum foil and the first adhesive layer before and after electrolyte immersion, measured according to the following method, and may preferably be 11 N / 15 mm or more.

[0055] [Method for measuring the peel strength of the aluminum foil and the first adhesive layer interface before electrolyte immersion]

[0056] After aging a film in which PET (12 ㎛ thick), a second adhesive layer (3 ㎛ thick), Nylon (15 ㎛ thick), a second adhesive layer (3 ㎛ thick), an aluminum foil (40 ㎛ thick), the first adhesive layer (40 ㎛ thick), and a PP inner layer (40 ㎛ thick) were laminated for 1 day under constant temperature and humidity conditions, a sample cut to 100 mm in length and 15 mm in width was measured for the T-shaped peel strength of the interface between the aluminum foil and the first adhesive layer at a test speed of 50 mm / min at 23°C using a measuring device (universal testing machine, Instron);

[0057] [Method for measuring the peel strength between the aluminum foil and the first adhesive layer after electrolyte immersion]

[0058] After maturing the above laminated film under constant temperature and humidity conditions for one day, the first sample cut to 150 mm in length and 17 mm in width was immersed in an electrolyte (EC / EMC / DMC=3 / 3 / 4 v / v composition) at 85°C for one day, and the second sample cut to 100 mm in length and 15 mm in width was measured for the T-shaped peel strength of the interface between the aluminum foil and the first adhesive layer using a measuring device (universal testing machine, Instron) at a test speed of 50 mm / min at 23°C.

[0059] Hereinafter, the present invention will be described in more detail through specific examples and comparative examples.

[0060]

[0061] Examples and Comparative Examples

[0062] Using the first adhesive layer resin of the composition shown in Table 1 below, a specimen was manufactured and its properties were measured according to the following method, and the results are shown in Table 1 below.

[0063] (1) Simple peel strength

[0064] Under conditions of 130 and 160℃, a specimen composed of an aluminum sheet (sheet, 1 mm thick) / first adhesive layer resin (150 ㎛ thick) / aluminum sheet (sheet, 1 mm thick) was manufactured using a press machine, and then the sample was cut to a length of 100 mm and a width of 15 mm. The T-shaped peel strength of the interface between the aluminum and the first adhesive layer was measured using a universal testing machine (Instron) at a test speed of 200 mm / min at 23℃.

[0065] (2) Method for measuring the peel strength of the aluminum foil and the first adhesive layer interface before electrolyte immersion

[0066] The temperature of the rear compression roll section of the coextrusion equipment was set to 140℃ and 160℃, and a film in which PET (12 ㎛ thick), a second adhesive layer (3 ㎛ thick), Nylon (15 ㎛ thick), a second adhesive layer (3 ㎛ thick), an aluminum foil (40 ㎛ thick), the first adhesive layer (40 ㎛ thick), and a PP inner layer (40 ㎛ thick) were laminated was aged for 1 day under constant temperature and humidity conditions. Then, a sample was cut to 100 mm in length and 15 mm in width, and the T-shaped peel strength of the interface between the aluminum foil and the first adhesive layer was measured at 23℃ at a test speed of 50 mm / min using a measuring device (universal testing machine, Instron).

[0067] (3) Method for measuring the peel strength of the aluminum foil and the first adhesive layer interface after electrolyte immersion

[0068] The temperature of the rear compression roll part of the coextrusion equipment was set to 160℃, and a film in which PET (12 ㎛ thick), a second adhesive layer (3 ㎛ thick), Nylon (15 ㎛ thick), a second adhesive layer (3 ㎛ thick), an aluminum foil (40 ㎛ thick), the first adhesive layer (40 ㎛ thick), and a PP inner layer (40 ㎛ thick) were laminated was aged under constant temperature and humidity conditions for 1 day, and then the first sample was cut to 150 mm in length and 17 mm in width. After immersing the sample in an electrolyte (EC / EMC / DMC=3 / 3 / 4 v / v composition) at 85℃ for 1 day, the second sample was cut to 100 mm in length and 15 mm in width, and the T-shaped peel strength of the interface between the aluminum foil and the first adhesive layer was measured at 23℃ at a test speed of 50 mm / min using a measuring device (universal testing machine, Instron). Here, EC stands for ethylene carbonate, EMC stands for ethylmethyl carbonate, and DMC stands for dimethyl carbonate.

[0069]

[0070]

[0071]

[0072] Referring to Table 1, it can be confirmed that the interface adhesive strength between the barrier layer and the first adhesive layer is significantly improved when the first adhesive layer laminated between the barrier layer and the inner layer is composed of a polypropylene-based resin according to the present invention, but is composed of polyethylene, a propylene-based elastomer, and an acid-modified polypropylene in a specific composition (Examples 1 to 4), and this effect is maximized when the propylene-based elastomer among the components constituting the first adhesive layer is composed of a specific mixed composition (Examples 1 and 2).

[0073] In this regard, it can be seen that in all cases where polyethylene and acid-modified polypropylene are not used, or where an ethylene-based elastomer is used (Comparative Examples 1 to 3), where the propylene-based elastomer content is below a certain level (Comparative Examples 6 to 8, 10), where the propylene-based elastomer content is below a certain level and acid-modified polypropylene is not used (Comparative Examples 4 and 5), where the propylene-based elastomer content is excessive (Comparative Example 9), and where the acid-modified polypropylene content is excessive (Comparative Example 11), peeling occurs at the interface between the barrier layer and the first adhesive layer, or the interfacial adhesive strength is significantly lower than that of the above examples.

[0074]

[0075] The preferred embodiments of the present invention have been described in detail above. The description of the present invention is provided for illustrative purposes only, and those skilled in the art will readily appreciate that other specific modifications can be readily made without altering the technical spirit or essential features of the present invention.

[0076] Accordingly, the scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning, scope and equivalent concepts of the claims should be interpreted as being included in the scope of the present invention.

Claims

1. A battery packaging material comprising a laminated structure of an outer layer made of a heat-resistant resin film; a barrier layer including a metal foil; and an inner layer made of a composition including a thermoplastic polyolefin; A first adhesive layer is further laminated between the above barrier layer and the inner layer, A battery packaging material, characterized in that the first adhesive layer comprises 30 to 70 wt% of polypropylene, 5 to 30 wt% of polyethylene, 20 to 50 wt% of propylene-based elastomer, and 1 to 15 wt% of acid-modified polypropylene.

2. In paragraph 1, A battery packaging material, characterized in that the metal foil comprises at least one metal selected from the group consisting of aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), tin (Sn), zinc (Zn), indium (In), and tungsten (W).

3. In paragraph 1, A battery packaging material, characterized in that the above acid-modified polypropylene has a maleic anhydride graft content of 0.1 to 10 wt%.

4. In paragraph 1, A battery packaging material, characterized in that the above propylene-based elastomer has a melting point of 140°C or lower.

5. In paragraph 1, A battery packaging material, characterized in that the propylene-based elastomer is a propylene-alpha olefin copolymer, and includes a first propylene-based elastomer having an ethylene comonomer content of 5 to 25 wt% and a second propylene-based elastomer having a 1-butene comonomer content of 20 to 40 wt%.

6. In paragraph 1, A battery packaging material, characterized in that the thickness of the outer layer is 10 to 40 ㎛; the thickness of the barrier layer is 25 to 50 ㎛; the thickness of the first adhesive layer is 25 to 50 ㎛; and the thickness of the inner layer is 25 to 50 ㎛.

7. In paragraph 1, The above packaging material is a battery packaging material characterized in that the peel strength between the aluminum foil and the first adhesive layer interface before and after electrolyte immersion measured by the following method is 8 N / 15 mm or more: [Method for Measuring the Peeling Strength of Aluminum Foil and First Adhesive Layer Interface Before Electrolyte Immersion] A film in which PET (12 ㎛ thick), a second adhesive layer (3 ㎛ thick), Nylon (15 ㎛ thick), a second adhesive layer (3 ㎛ thick), aluminum foil (40 ㎛ thick), the first adhesive layer (40 ㎛ thick), and a PP inner layer (40 ㎛ thick) are laminated is aged for 1 day under constant temperature and humidity conditions, and a sample is cut to a length of 100 mm and a width of 15 mm. The T-shaped peel strength of the interface between the aluminum foil and the first adhesive layer is measured at a test speed of 50 mm / min at 23°C using a measuring device (universal testing machine, Instron). [Method for measuring peel strength between aluminum foil and first adhesive layer interface after electrolyte immersion] After maturing the above laminated film under constant temperature and humidity conditions for one day, the first sample was cut to 150 mm in length and 17 mm in width, and the sample was immersed in an electrolyte (EC / EMC / DMC=3 / 3 / 4 v / v composition) at 85°C for one day, and the second sample was cut to 100 mm in length and 15 mm in width. The T-shaped peel strength of the interface between the aluminum foil and the first adhesive layer was measured at 23°C at a test speed of 50 mm / min using a measuring device (universal testing machine, Instron).

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