Pouch film for secondary batteries and pouch-type secondary battery having same applied thereto

Abstract

Disclosed are a pouch film for secondary batteries and a pouch-type secondary battery having same applied thereto. The disclosed pouch film for secondary batteries may comprise: a metal barrier layer; and a sealant layer bonded to the metal barrier layer with an adhesive layer interposed therebetween, wherein the sealant layer may comprise: a first skin layer; a second skin layer; and a main layer interposed therebetween, and the first skin layer, the main layer, and the second skin layer may be sequentially disposed in a direction away from the metal barrier layer. Each of the first skin layer, the main layer, and the second skin layer may be composed of a polymer-based material containing an elastomer, and the elastomer content in the main layer may be higher than that in each of the first and second skin layers.

Description

Pouch film for secondary batteries and pouch-type secondary batteries using the same

[0001] The present invention relates to materials / members related to secondary batteries and secondary batteries using the same, and more specifically, to a pouch film for secondary batteries and a pouch-type secondary battery using the same.

[0002] The national research and development projects that supported this invention are as follows.

[0003] Assignment ID 1415185612

[0004] Assignment number 20022450

[0005] Ministry of Trade, Industry and Energy

[0006] Project Management Agency Name: Korea Institute of Industrial Technology Planning and Evaluation

[0007] Research Project Name: Materials, Components, and Package Type (Leading Company)

[0008] Research Project Name: Development of a Next-Generation Secondary Battery Pouch Capable of Twice Higher Adhesive Strength (60℃)

[0009] Contribution rate 1 / 1

[0010] Project execution organization name: Yulchon Chemical Co., Ltd.

[0011] Research period: January 1, 2023 - December 31, 2023

[0012] Assignment ID 2410004468

[0013] Assignment number 20022450

[0014] Ministry of Trade, Industry and Energy

[0015] Project Management Agency Name: Korea Institute of Industrial Technology Planning and Evaluation

[0016] Research Project Name: Materials and Components Technology Development (Leading Company)

[0017] Research Project Name: Development of a Next-Generation Secondary Battery Pouch Capable of Twice Higher Adhesive Strength (60℃)

[0018] Project execution organization name: Yulchon Chemical Co., Ltd.

[0019] Research period: January 1, 2024 - December 31, 2024

[0020] Pouch-type secondary batteries can have a structure in which an electrode assembly and electrolyte are sealed within a pouch made of thin, flexible plastic film and metal foil. Unlike traditional cylindrical or prismatic batteries, this pouch-type battery structure does not use a metal case, making it much lighter and more versatile in design. Pouch-type batteries can have a structure that improves internal space efficiency by stacking materials in layers rather than using a winding jelly roll. They are also easy to manufacture in various sizes and shapes, and can even be bent or folded, offering advantages such as high space efficiency, high energy density, and high design flexibility. This makes pouch-type secondary batteries useful for various devices such as electric vehicles, smartphones, and laptops.

[0021] In the manufacturing of pouch-type secondary batteries, the pouch film can be a key material component as a packaging material that wraps, protects, and seals the battery's internal components. Pouch films for secondary batteries typically consist of a sealant layer, a metal barrier layer, and an outer film. The metal barrier layer can protect the battery cell from oxygen, moisture, and other environmental factors, and may require high barrier performance and formability. The sealant layer, which provides sealing and comes into direct contact with the electrolyte, must have excellent resistance to chemical corrosion or damage caused by the electrolyte. The outer film may require abrasion resistance, moisture permeability, and chemical resistance to protect the battery cell from the external environment.

[0022] The pouch film plays a key role in ensuring the safety and reliability of secondary batteries. Therefore, strong adhesion between the barrier layer and the sealant layer, as well as high chemical resistance, durability, and heat resistance of the sealant layer, are required. In particular, the sealant layer must maintain high chemical resistance and durability even in electrolyte and high-temperature environments. Furthermore, after the sealing step by bonding the pouch films, the joint must have a peel strength (peel strength between the pouch films) exceeding the standard level (spec) and the peeling phenomenon that exposes the metallic barrier layer must be prevented. If the metallic barrier layer is exposed due to peeling after the sealing step, it can cause significant problems for the battery cell as the barrier layer is exposed to the electrolyte.

[0023] Recently, as the size and capacity of secondary batteries have increased and their exposure to high-temperature environments has increased, the physical properties required for pouch films for secondary batteries have become increasingly stringent. Therefore, to enhance the safety and reliability of secondary batteries, there is a growing need to develop pouch films that can satisfy both the physical properties required for the pouch film itself in electrolyte and high-temperature environments, as well as the physical properties required for the pouch film assembly after the sealing step.

[0024] The technical problem to be achieved by the present invention is to provide a pouch film for a secondary battery that can improve the safety and reliability of the secondary battery.

[0025] In addition, the technical problem to be achieved by the present invention is to provide a pouch film for a secondary battery having excellent chemical resistance, heat resistance, peeling resistance, and durability.

[0026] In addition, the technical problem to be achieved by the present invention is to provide a pouch film for a secondary battery that can satisfy both the physical property requirements required of the pouch film itself in an electrolyte environment and a high-temperature environment and the physical property requirements required of the pouch film joint after the sealing step.

[0027] In addition, the technical problem to be achieved by the present invention is to provide a pouch-type secondary battery using the above-described pouch film for secondary batteries.

[0028] The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be understood by those skilled in the art from the description below.

[0029] According to one embodiment of the present invention, a pouch film for a secondary battery is provided, comprising: a metal barrier layer; and a sealant layer bonded to the metal barrier layer with an adhesive layer therebetween; wherein the sealant layer includes a first skin layer, a second skin layer, and a main layer disposed therebetween, wherein the first skin layer, the main layer, and the second skin layer are sequentially disposed from a side where the metal barrier layer is disposed, and wherein each of the first skin layer, the main layer, and the second skin layer is composed of a polymer-based material including an elastomer, and wherein the elastomer content of the main layer is higher than the elastomer content of each of the first and second skin layers.

[0030] The ratio (A:B) of the elastomer content (A) of the main layer and the elastomer content (B) of the first skin layer may be in the range of about 1:0.67 to 0.74.

[0031] The ratio (A:C) of the elastomer content (A) of the main layer and the elastomer content (C) of the second skin layer may be in the range of about 1:0.67 to 0.74.

[0032] The ratio (A:B:C) of the elastomer content (A) of the main layer, the elastomer content (B) of the first skin layer, and the elastomer content (C) of the second skin layer may be in the range of about 1:0.67∼0.74:0.67∼0.74.

[0033] The elastomer content of the main layer may be in the range of about 10 to 15 wt%, the elastomer content of the first skin layer may be in the range of about 6.7 to 10.8 wt%, and the elastomer content of the second skin layer may be in the range of about 6.7 to 10.8 wt%.

[0034] The sum of the elastomer content of the main layer, the elastomer content of the first skin layer, and the elastomer content of the second skin layer may be in the range of about 26 to 37 wt%.

[0035] Each of the first skin layer, the main layer, and the second skin layer may include a polypropylene-based material as a main component.

[0036] The above polypropylene-based material may be CPP (cast polypropylene), but is not limited thereto, and various other materials may be possible.

[0037] The above metal barrier layer may include stainless steel (SUS).

[0038] The above metal barrier layer may be composed of stainless steel (SUS) having a thermal conductivity of about 15 W / mㆍk or more.

[0039] The above adhesive layer may have a melting temperature (Tm) of about 140°C or higher.

[0040] The ratio (A:B:C) of the elastomer content (A) of the main layer, the elastomer content (B) of the first skin layer, and the elastomer content (C) of the second skin layer may be in the range of about 1:0.67∼0.74:0.67∼0.74, the metal barrier layer may be composed of stainless steel (SUS) having a thermal conductivity of about 15 W / mㆍk or more, and the adhesive layer may have a melting temperature (Tm) of about 140°C or more.

[0041] An outer layer bonded to the metal barrier layer may be further provided, and the metal barrier layer may be disposed between the outer layer and the sealant layer.

[0042] According to another embodiment of the present invention, a pouch-type secondary battery is provided to which the aforementioned pouch film for secondary batteries is applied.

[0043] According to embodiments of the present invention, a pouch film for secondary batteries can be realized that can improve the safety and reliability of secondary batteries. According to embodiments of the present invention, a pouch film for secondary batteries can be realized that has excellent chemical resistance, heat resistance, peel resistance, and durability.

[0044] In particular, according to embodiments of the present invention, a pouch film for a secondary battery can be implemented that can satisfy both the physical property requirements required for the pouch film itself in an electrolyte environment and a high-temperature environment, and the physical property requirements required for the pouch film joint after the sealing step. The pouch film for a secondary battery according to embodiments can satisfy the physical property requirements required for a peeling test for the pouch film itself under electrolyte immersion and high-temperature conditions, and the physical property requirements required for a peeling test between pouch films after the sealing step.

[0045] By applying the pouch film for secondary batteries according to the embodiments, a pouch-type secondary battery having excellent stability, reliability, and durability can be manufactured.

[0046] However, the effects of the present invention are not limited to the above effects, and can be expanded in various ways without departing from the technical spirit and scope of the present invention.

[0047] FIG. 1 is a cross-sectional view showing a pouch film for a secondary battery according to one embodiment of the present invention.

[0048] FIG. 2 is a drawing exemplarily showing a test method for a pouch film for a secondary battery according to one embodiment of the present invention.

[0049] FIG. 3 is a cross-sectional view illustrating a peeling pattern corresponding to an OK case in an electrolyte immersion and high-temperature condition peeling test (first test) for a pouch film for a secondary battery according to one embodiment of the present invention.

[0050] Figures 4 and 5 are cross-sectional views illustrating the peeling pattern corresponding to an unsuitable (NG) case in an electrolyte immersion and high-temperature condition peeling test (first test) for a pouch film for a secondary battery.

[0051] Figure 6 is a photographic image showing a case where a peeling phenomenon occurred, which corresponds to an unsuitable (NG) case, in an electrolyte immersion and high-temperature condition peeling test (first test) for a pouch film for a secondary battery.

[0052] FIG. 7 is a photographic image showing a case in which peeling occurred in an acceptable (OK) case in an electrolyte immersion and high-temperature condition peeling test (first test) for a pouch film for a secondary battery according to one embodiment of the present invention.

[0053] FIG. 8 and FIG. 9 are cross-sectional views illustrating a peeling pattern corresponding to an OK case in a peeling test (second test) between pouch films after sealing for a pouch film for a secondary battery according to one embodiment of the present invention.

[0054] Figures 10 and 11 are cross-sectional views illustrating the peeling pattern corresponding to an unsuitable (NG) case in a peeling test (second test) between pouch films after sealing for a pouch film for a secondary battery.

[0055] Fig. 12 is a cross-sectional view showing a pouch film for a secondary battery according to an embodiment of the present invention.

[0056] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0057] The embodiments of the present invention described below are provided to more clearly explain the present invention to a person having ordinary skill in the art, and the scope of the present invention is not limited by the following embodiments, and the following embodiments can be modified in various other forms.

[0058] The terminology used herein is used to describe particular embodiments and is not intended to limit the present invention. The singular forms used herein may include the plural forms unless the context clearly dictates otherwise. In addition, the terms "comprise" and / or "comprising" used herein specify the presence of a stated feature, step, number, operation, element, element, and / or group thereof, but do not exclude the presence or addition of one or more other features, steps, numbers, operations, elements, elements, and / or groups thereof. In addition, the term "connected" used herein not only means that certain elements are directly connected, but also includes a concept that indirectly connects elements by interposing another element between them.

[0059] In addition, when it is said in this specification that a certain element is located "on" another element, this includes not only cases where a certain element is in contact with another element, but also cases where another element exists between the two elements. The term "and / or" as used in this specification includes any one of the listed items and any and all combinations of one or more of them. In addition, terms of degree such as "about", "substantially", etc. as used in this specification are used to mean a range of or close to the numerical value or degree, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly using the disclosure that mentions exact or absolute numbers provided to help the understanding of this specification.

[0060] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The sizes and thicknesses of areas or parts illustrated in the attached drawings may be somewhat exaggerated for clarity and convenience of explanation. Like reference numbers designate like components throughout the detailed description.

[0061] FIG. 1 is a cross-sectional view showing a pouch film for a secondary battery according to one embodiment of the present invention.

[0062] Referring to FIG. 1, a pouch film for a secondary battery according to an embodiment of the present invention may include a metal barrier layer (100) and a sealant layer (200) bonded to the metal barrier layer (100) with an adhesive layer (150) interposed therebetween. The adhesive layer (150) may be provided on one surface of the metal barrier layer (100), and the sealant layer (200) may be bonded to one surface of the metal barrier layer (100) under the interposition of the adhesive layer (150). An adhesive layer (150) may be disposed between the metal barrier layer (100) and the sealant layer (200) to bond them to each other.

[0063] The metal barrier layer (100) may include, for example, stainless steel (SUS) or be composed of stainless steel (SUS). Stainless steel (SUS) may have a higher elongation than aluminum (Al) and may have different physical properties from aluminum (Al). In this regard, when stainless steel (SUS) is applied to the metal barrier layer (100), the sealant layer (200) needs to be configured differently from when aluminum (Al) is used. In addition, when stainless steel (SUS) is applied to the metal barrier layer (100), the SDL (solvent-dry lamination) method may be used for applying an adhesive for forming the adhesive layer (150). In addition, the extrusion lamination method or the EC (extrusion coating) method may be applied.

[0064] The SDL method is a method of bonding a metal layer on a non-stretched polypropylene (CPP) layer using a solvent-based adhesive and drying the solvent-based adhesive, so that the sealant layer manufactured thereby is composed of a CPP layer. On the other hand, the extrusion lamination method is a method of extruding polypropylene resin when bonding polypropylene, which is mainly used for the sealant layer, particularly non-stretched polypropylene (CPP), to a metal layer, so that the sealant layer is composed of an extruded polypropylene (PP) layer and a CPP layer. In addition, the EC method is not a method of bonding (laminating) a sealing resin layer or film such as a polypropylene-based resin layer with a metal barrier layer, unlike extrusion lamination or SDL (solvent-dry lamination), but is a method of forming a sealant layer when manufacturing a cell pouch film by directly extruding (or co-extruding) a polyolefin-based resin, preferably a polypropylene-based resin, onto a metal barrier layer. As a result, the sealant layer is formed by extrusion layers, for example, an extrusion polypropylene layer. This EC sealant layer may also be formed by co-extrusion of a first extrusion layer, a second extrusion layer, and a third extrusion layer.

[0065] In the embodiment of the present invention, the composition of the metal barrier layer (100) is not limited to that described above. In other embodiments, a metal other than stainless steel (SUS) may be applied to the metal barrier layer (100). For example, the metal barrier layer (100) may be configured to include at least one of stainless steel (SUS), aluminum (Al), titanium (Ti), nickel (Ni), and copper (Cu). The metal barrier layer (100) may include an alloy or have a laminated structure. The metal barrier layer (100) may have a thickness of about 1 ㎛ to 100 ㎛. The metal barrier layer (100) may be a type of thin film or foil. The thickness of the metal barrier layer (100) may be, as a non-limiting example, about 40 ㎛ to 80 ㎛. Depending on the thickness of the metal barrier layer (100), the physical properties of the pouch film, such as barrier characteristics and tensile strength, may be controlled.

[0066] The sealant layer (200) may have a multi-layer structure in terms of diversifying functions. For example, in the case of a 3-layer structure, the main layer (220) is designed in consideration of the influence on the overall physical properties of the sealant layer. It may be designed to have a desired elongation and rigidity to improve formability, or an appropriate degree of crystallinity to increase insulation. In addition, the first skin layer (210) is designed to improve adhesion with a surface treatment agent or adhesive, and the second skin layer (230) is designed to have an appropriate melting temperature to ensure good sealing. For example, the melting temperature of the second skin layer (230) may be designed to be lower than that of the main layer (220), or similarly designed, to control the induction of interfacial peeling, thereby improving the high-temperature stability of the cell pouch film.

[0067] In an embodiment of the present invention, the sealant layer (200) may include a first skin layer (210), a second skin layer (230), and a main layer (220) disposed therebetween. The first skin layer (210), the main layer (220), and the second skin layer (230) may be sequentially disposed from the side where the metal barrier layer (100) is disposed. In other words, the first skin layer (210), the main layer (220), and the second skin layer (230) may be sequentially disposed from one side of the adhesive layer (150). The first skin layer (210) may be adjacent to the metal barrier layer (100), and the second skin layer (230) may be in contact with the electrolyte. The sealant layer (200) may have a three-layer structure including the first skin layer (210), the main layer (220), and the second skin layer (230). For example, the sealant layer (200) can be formed as a three-layer film in which the main layer (220) is positioned between two skin layers (210, 230) by using a method of melt-extruding the raw material composition.

[0068] In an embodiment of the present invention, the sealant layer (200) is supplied in a film form and formed by SDL method by being combined (i.e., laminated) with the metal barrier layer (100). The sealant layer (200) film can be formed into a three-layer structure, for example, by co-extrusion method. That is, the sealant layer (200) can be formed by simultaneously extruding the resins that are the raw materials of the first skin layer (210), the main layer (220), and the second skin layer (230) at high temperature to form a multi-layered film. In addition, the metal barrier layer (100) and the sealant layer (200) can be combined (i.e., laminated) with each other by SDL method. In other words, the sealant layer (200) can be combined (i.e., laminated) with the metal barrier layer (100) by the adhesive layer (150), i.e., the adhesive layer. In another embodiment, the sealant layer (200) may be formed by an extrusion lamination method. The extrusion layer is formed by a co-extrusion method, and a polypropylene film having a three-layer structure is formed by laminating (i.e., laminating). In this way, co-extrusion methods, film lamination, and extrusion lamination, etc. may be used in the process of forming the pouch film. However, the above-described methods are merely exemplary, and the embodiments of the present invention are not limited thereto. The first skin layer (210) may be referred to as a first auxiliary layer or a first sub-layer, and similarly, the second skin layer (230) may be referred to as a second auxiliary layer or a second sub-layer. The main layer (220) may be referred to as an intermediate layer or a core layer.

[0069] Each of the first skin layer (210), the main layer (220), and the second skin layer (230) may be composed of a polyolefin-based resin including an elastomer. The polyolefin-based resin has excellent electrolyte resistance and excellent insulation properties, and accordingly, the sealant layer including the polyolefin-based resin may also have excellent electrolyte resistance and excellent insulation properties derived from the polyolefin-based resin.

[0070] The polyolefin-based resin may include, for example, a polyolefin derived from an olefin or a derivative thereof, a copolymer thereof, or a blend comprising at least one of the foregoing. For example, the polyolefin-based resin layer may include at least one selected from the group consisting of polyethylene, polypropylene, polybutylene, a copolymer derived from a monomer derived from ethylene and / or propylene and a monomer derived from an alpha-olefin, or a blend thereof.

[0071] Each of the first skin layer (210), the main layer (220), and the second skin layer (230) may be composed of a polyolefin resin and may also include an elastomer. Here, the elastomer may be a type of additive or auxiliary material. In an embodiment of the present invention, the elastomer content of the main layer (220) may be higher than the elastomer content of each of the first and second skin layers (210, 230).

[0072] The above sealant layer can form a sealing portion by thermal bonding (e.g., applying heat and pressure to the sealant layers that are in contact with each other to bond them). Therefore, by using this, the sealant layer of the secondary battery outer pouch film can be thermally bonded to form a sealing portion, thereby sealing the battery main body.

[0073] The polypropylene-based material may be, for example, CPP (cast polypropylene), but is not limited thereto, and various other materials may be possible. As non-limiting examples, in some cases, the polypropylene-based material may be OPP (oriented polypropylene), BOPP (biaxially oriented polypropylene), MOPP (monoaxially oriented polypropylene), etc.

[0074] The pouch film according to an embodiment of the present invention can have excellent electrolyte resistance properties (i.e., chemical resistance), heat resistance, peel resistance, and durability. This will be described in more detail later.

[0075] According to one embodiment, each of the first skin layer (210), the main layer (220), and the second skin layer (230) may include a polypropylene-based material as a main component (main constituent material). For example, the polypropylene-based material content of the main layer (220) may be about 50 to 90 wt%. The polypropylene-based material content of the first skin layer (210) may be about 50 to 94 wt%. The polypropylene-based material content of the second skin layer (230) may be about 50 to 94 wt%. The polypropylene-based material content of the main layer (220) may be lower than the polypropylene-based material content of each of the first and second skin layers (210, 230). The polypropylene-based material may be, for example, CPP (cast polypropylene). In this case, each of the first skin layer (210), the main layer (220), and the second skin layer (230) may be a polymer film containing CPP as a main component. The first skin layer (210) may be a CPP-based first skin layer, the main layer (220) may be a CPP-based main layer, and the second skin layer (230) may be a CPP-based second skin layer.

[0076] For example, the first skin layer (210) may include random polypropylene (rPP), ter-polypropylene (ter-PP), and block polypropylene (bPP) as a matrix, and may include an elastomer, a slip agent, etc. as additives thereto. The random polypropylene (rPP) may be formed of a random copolymer of a propylene monomer and a small amount of another olefin monomer, and may have superior impact strength and flexibility compared to homo polypropylene resin, and may exhibit transparency due to a small amount of crystals that cause light scattering. For example, the random polypropylene (rPP) may be, but is not limited to, a propylene-ethylene random copolymer or a propylene-1-butene random copolymer. The ter-polypropylene (ter-PP) may be a random copolymer of a propylene monomer and a small amount of two other olefin monomers, and may have excellent tensile strength. For example, the ter-polypropylene (ter-PP) may be, but is not limited to, a propylene-ethylene-1-butene random terpolymer. The block polypropylene (bPP) has a block structure of polypropylene, in which other monomer blocks are regularly arranged between polypropylene chains, and thus may have excellent heat sealability, chemical resistance, flexibility, and durability.

[0077] The weight of the polypropylene including the random polypropylene, tertiary polypropylene, and block polypropylene in the first skin layer (210) may be about 50 to 94 wt% or about 50 to 90 wt% based on the total weight of the first skin layer (210). If the polypropylene content exceeds about 94 wt% or about 90 wt%, a whitening phenomenon may occur when the pouch film is stretched, and if it is less than about 50 wt%, the elastomer content relatively increases, thereby improving low-temperature sealing properties but deteriorating high-temperature stability and chemical resistance.

[0078] The main layer (220) may include homo-polypropylene and block polypropylene. When ter-polypropylene or random polypropylene is applied to the main layer (220), it may be susceptible to swelling caused by the electrolyte, and mechanical properties such as tensile strength and rigidity may deteriorate. An elastomer, a slip agent, etc. may be used as an additive in the main layer (220). The homo-polypropylene may be composed of a single bond of propylene only, and may have a molecular weight distribution in which the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) is about 5.0 or less. The homo-polypropylene may have a melting temperature (Tm) of about 150°C or more or about 160°C or more for heat resistance.

[0079] The weight of polypropylene including homo polypropylene and block polypropylene in the main layer (220) may be about 50 to 90 wt% based on the total weight of the main layer (220), and at this time, the content of the homo polypropylene may not exceed about 50 wt%. If the polypropylene content exceeds 90 wt% or the homo polypropylene content exceeds about 50 wt%, a whitening phenomenon may occur during stretching of the pouch film, and if the polypropylene content is too low, the elastomer content relatively increases, thereby improving low-temperature sealing properties but deteriorating high-temperature stability and chemical resistance.

[0080] The second skin layer (230) may be a layer that comes into direct contact with the electrolyte, and one or more of homopolypropylene, random polypropylene, tertiary polypropylene, and block polypropylene may be applied to the second skin layer (230) to improve chemical resistance. As a specific example, the second skin layer (230) may include homopolypropylene, random polypropylene, tertiary polypropylene, and block polypropylene. Alternatively, the second skin layer (230) may include homopolypropylene and block polypropylene. As additives therefor, elastomers, slip agents, and the like may be used.

[0081] In the second skin layer (230), the weight of polypropylene including homo polypropylene, random polypropylene, tertiary polypropylene, and block polypropylene (or polypropylene including homo polypropylene and block polypropylene) may be about 50 to 94 wt% or about 50 to 90 wt% based on the total weight of the second skin layer (230). At this time, the content of homo polypropylene may not exceed about 50 wt%. If the polypropylene content exceeds about 94 wt% or about 90 wt% or the homo polypropylene content exceeds about 50 wt%, a whitening phenomenon may occur during stretching of the pouch film, and if it is less than about 50 wt%, the elastomer content relatively increases, thereby improving low-temperature sealing properties, but deteriorating high-temperature stability and chemical resistance.

[0082] The above elastomer may be added to the first skin layer (210), the main layer (220), and the second skin layer (230) to secure formability, sealing properties, etc. The elastomer may include at least one selected from the group consisting of thermoplastic polyolefin elastomer (TPO), reactor-made thermoplastic olefin (RTPO), and thermoplastic polyurethane (TPU). Here, the thermoplastic polyolefin elastomer (TPO) may include, for example, ethylene propylene rubber (EPR), ethylene butene rubber (EBR), linear low density polyethylene (LLDPE)-based elastomer, etc.

[0083] The material composition of the first skin layer (210), the main layer (220), and the second skin layer (230) is not limited to the above-described material composition and may vary depending on the case. The first skin layer (210) may be composed of various materials depending on the application target, size, use, etc. of the pouch film. For example, in order to protect the main layer (220), improve aesthetics, etc., various polymers such as polypropylene, polyethylene, high-density polyethylene (HDPE), or a combination thereof may be used in the first skin layer (210).

[0084] The sealant layer (200) may have a thickness of, for example, about 20 ㎛ to 200 ㎛. The first skin layer (210) may have a thickness corresponding to about 10 to 20% of the thickness of the entire sealant layer (200) to secure adhesion to metal. The main layer (220) may have a thickness corresponding to about 50 to 80% of the thickness of the entire sealant layer (200) to secure at least mechanical rigidity, high-temperature stability, chemical resistance, etc. The second skin layer (230) may have a thickness corresponding to about 10 to 20% of the thickness of the entire sealant layer (200) to secure adhesion and electrolyte resistance (electrolyte resistance characteristics). However, the appropriate thickness range of the sealant layer (200) and the thickness range of the layers (210, 220, 230) constituting the sealant layer (200) are not limited to the above-described range and may vary depending on the case.

[0085] According to one embodiment, the ratio (A:B) of the elastomer content (A) of the main layer (220) and the elastomer content (B) of the first skin layer (210) may be in the range of about 1:0.67 to 0.74. In addition, the ratio (A:C) of the elastomer content (A) of the main layer (220) and the elastomer content (C) of the second skin layer (230) may be in the range of about 1:0.67 to 0.74. The ratio (A:B:C) of the elastomer content (A) of the main layer (220), the elastomer content (B) of the first skin layer (210), and the elastomer content (C) of the second skin layer (230) may be in the range of about 1:0.67 to 0.74:0.67 to 0.74. The elastomer content of the main layer (220) may be higher than the elastomer content of each of the first and second skin layers (210, 220), but may preferably have an appropriate difference. When these conditions are satisfied, the chemical resistance, heat resistance, peeling resistance, durability, sealing properties, etc. of the pouch film according to the embodiment may be improved. Depending on the elastomer content (content ratio) conditions of the first skin layer (210), the main layer (220), and the second skin layer (230), the electrolyte resistance characteristics, high temperature resistance, peeling behavior, etc. of the pouch film may vary. This will be described in more detail later based on specific experimental results.

[0086] As a specific example, the elastomer content of the main layer (220) may be in the range of about 10 to 15 wt%, the elastomer content of the first skin layer (210) may be in the range of about 6.7 to 10.8 wt%, and the elastomer content of the second skin layer (230) may be in the range of about 6.7 to 10.8 wt%. Under these content range conditions, the ratio (A:B:C) of the elastomer content (A) of the main layer (220), the elastomer content (B) of the first skin layer (210), and the elastomer content (C) of the second skin layer (230) may satisfy the condition of 1:0.67 to 0.74:0.67 to 0.74. However, the elastomer content range conditions of the respective layers (210, 220, 230) described above are exemplary and may vary depending on the case.

[0087] According to one embodiment, the sum of the elastomer content of the main layer (220), the elastomer content of the first skin layer (210), and the elastomer content of the second skin layer (230) may be in the range of about 26 to 37 wt%. If the sum of the elastomer contents is less than about 26 wt%, the moldability of the sealant layer (200) may be reduced. If the sum of the elastomer contents exceeds about 37 wt%, the insulation resistance of the sealant layer (200) may be reduced. Therefore, it may be preferable that the sum of the elastomer contents in the sealant layer (200) be in the range of about 26 to 37 wt%. This will be described in more detail later based on specific experimental results.

[0088] Meanwhile, in an embodiment of the present invention, the metal barrier layer (100) may be made of or include stainless steel (SUS) having a thermal conductivity of about 15 W / mㆍk or more. For example, when the metal barrier layer (100) is made of stainless steel (SUS), its thermal conductivity may be about 15 W / mㆍk or more. The thermal conductivity of the stainless steel (SUS) applied in the embodiment may be about 15 to 30 W / mㆍk or about 15 to 25 W / mㆍk. The thermal conductivity of stainless steel (SUS) may vary depending on the type, and in an embodiment of the present invention, stainless steel (SUS) having a thermal conductivity of about 15 W / mㆍk or more may be used. In this case, the characteristics of the pouch film, such as chemical resistance, heat resistance, peeling resistance, durability, and sealing property, may be improved. This will be described in more detail later based on specific experimental results.

[0089] The adhesive layer (150) may serve to strengthen the adhesive strength between the metal barrier layer (100) and the sealant layer (200). The adhesive layer (150) may be formed of, for example, a polyurethane-based two-component curable composition, and may have excellent thermal stability by maintaining sterility through heating and sterilization after sealing the packaging material. More specifically, the adhesive layer (150) may be composed of a subject matter including a polyurethane resin and a curing agent including an isocyanate. The subject matter including a polyurethane resin and the curing agent including an isocyanate may be mixed in a wt% of, for example, about 95:5 to 70:30 to provide a fast curing speed and strong adhesive strength. The mixing ratio of the subject matter and the curing agent may be about 90:10 to 80:20.

[0090] The thickness of the adhesive layer (150) may vary depending on the thicknesses of the metal barrier layer (100) and the sealant layer (200), and as a non-limiting example, may be about 0.1 µm to 30 µm. As a more specific example, the thickness of the adhesive layer (150) may be about 0.5 µm to 10 µm or about 1 µm to 5 µm. Within the aforementioned thickness range, the adhesive strength between the metal barrier layer (100) and the sealant layer (200) can be effectively secured.

[0091] According to one embodiment, the adhesive layer (150) may have a melting temperature (Tm) of about 140°C or higher. The melting temperature (Tm) of the adhesive layer (150) may be, for example, about 140°C to 200°C or about 140°C to 180°C. When these conditions are satisfied, the characteristics of the pouch film according to the embodiment, such as chemical resistance, heat resistance, peel resistance, peel strength, and durability, may be improved. This will be described in more detail later based on specific experimental results.

[0092] A pouch film for a secondary battery according to an embodiment of the present invention can have excellent chemical resistance, heat resistance, peeling resistance, and durability in an electrolyte exposure environment and a high-temperature environment. In addition, after a sealing step of joining two pouch films for a secondary battery, a pouch film assembly formed by joining can have a peel strength (peel strength between pouch films) higher than a reference level (specification), and a peeling phenomenon in which a metal barrier layer is exposed in a peel test can be prevented. Therefore, according to an embodiment of the present invention, a pouch film for a secondary battery can be realized that can satisfy both the physical property requirements required for the pouch film itself in an electrolyte environment and a high-temperature environment, and the physical property requirements required for the pouch film assembly after the sealing step.

[0093] Two testing methods that can be performed on pouch films for secondary batteries are described below.

[0094] < Test Method 1 >: After immersing the pouch film for secondary batteries in the electrolyte for a predetermined period of time, the pouch film for secondary batteries is taken out of the electrolyte and placed in a high-temperature chamber, and the peel strength between the metal barrier layer and the sealant layer can be measured within the high-temperature chamber. For example, a sample of the pouch film for secondary batteries cut to a size of 25 mm × 150 mm is immersed (impregnated) in an electrolyte (standard electrolyte) at a temperature of 85°C±2°C for 1 day (i.e., 24 hours), and then the film sample is taken out of the electrolyte and placed in a high-temperature chamber at 80°C, left there for 5 minutes, and then the peel strength between the metal barrier layer and the sealant layer can be measured within the high-temperature chamber using a UTM (universal testing machine). When measuring, the sample is measured within 1 hour after being taken out of the electrolyte. The full scale of the tensile strength tester can be set to about 50% higher than the expected strength of the sample. This test measures the chemical resistance (electrolyte resistance characteristics), heat resistance (temperature resistance), and peel strength (peel strength between the metal barrier layer and the sealant layer) of the pouch film. Peeling must occur between the metal barrier layer and the sealant layer, and peeling in the middle (interlayer) of the sealant layer must be prevented. Peeling only between the metal barrier layer and the sealant layer is acceptable (OK), and peeling in the middle (interlayer) of the sealant layer is not acceptable (NG = no good). The peel strength between the metal barrier layer and the sealant layer must be at a predetermined level (e.g., 15 N / 15 mm) or higher. The above-mentioned test can be referred to as the 'first test', and it can be a peel test for the pouch film itself under electrolyte immersion and high-temperature conditions.

[0095] <Second Test Method>: After thermal bonding between the sealant layers of the pouch film for secondary batteries, the peel strength between them can be measured. After cutting a pouch film sample to a size of about 15 mm Х 150 mm and sealing it with the sealant layers in contact, the peel strength of the sealing surface, i.e., the peel strength between the sealant layers, can be measured using a tensile strength tester (i.e., UTM device). Here, the sealing conditions (i.e., the thermal bonding conditions) may be a temperature of 180°C±2°C, a pressure of 30 kgf / cm2, and a time of 3.0 seconds. The peel strength of the sealing surface can be measured using a tensile strength tester. The measurement can be performed with the full scale of the tensile strength tester set to about 50% higher than the expected strength of the sample. At this time, the unbonded first sample portion and the unbonded second sample portion may be fixed to a tensile strength tester (i.e., UTM device), respectively, and then the test may be performed. The pouch film joint formed by the bonding must have a peel strength (peel strength between pouch films) higher than the reference level (spec), and the peeling phenomenon that exposes the metal barrier layer must be prevented in the peeling test. If peeling occurs on the inner side of the sealant layer, including the upper or lower surface of the main layer, it is acceptable (OK), and if peeling occurs that exposes the metal barrier layer, it is unacceptable (NG). The above-described test may be referred to as a 'second test', and this may be a peeling test between pouch films after the sealing step. The above-described second test method is exemplarily illustrated in FIG. 2, but the embodiments of the present invention are not limited thereto.

[0096] FIG. 3 is a cross-sectional view illustrating a peeling pattern corresponding to an OK case in an electrolyte immersion and high-temperature condition peeling test (the first test) for a pouch film for a secondary battery according to one embodiment of the present invention.

[0097] Referring to FIG. 3, in the electrolyte immersion and high-temperature condition peeling test (the first test above), it may be an OK case if peeling occurs only between the metal barrier layer (100) and the sealant layer (200). Through this, the peeling strength between the metal barrier layer (100) and the sealant layer (200) can be measured. Depending on the peeling, the first skin layer (210) may be separated from the adhesive layer (150), and the adhesive layer (150) may remain on one surface of the metal barrier layer (100). However, in some cases, peeling may occur between the metal barrier layer (100) and the sealant layer (200) as the adhesive layer (150) is separated from the metal barrier layer (100).

[0098] Figures 4 and 5 are cross-sectional views illustrating the peeling pattern corresponding to an unsuitable (NG) case in the electrolyte immersion and high-temperature condition peeling test (the first test above) for a pouch film for a secondary battery.

[0099] Referring to FIGS. 4 and 5, in the electrolyte immersion and high-temperature condition peeling test (the first test above), peeling occurring in the middle (interlayer) of the sealant layer (200) may be an unsuitable (NG) case. As in FIG. 4, peeling occurring between the first skin layer (210) and the main layer (220), or as in FIG. 5, peeling occurring between the main layer (220) and the second skin layer (230) may be an unsuitable (NG) case. If the sealant layer (200) does not have appropriate (sufficient) resistance characteristics for the electrolyte environment and high-temperature environment, peeling may occur in the middle (interlayer) of the sealant layer (200).

[0100] Figure 6 is a photographic image showing a case where a peeling phenomenon occurred, which corresponds to an unsuitable (NG) case, in an electrolyte immersion and high-temperature condition peeling test (the first test above) for a pouch film for a secondary battery.

[0101] Referring to Fig. 6, it can be confirmed that the sealant layer is separated (peeled) into two layer portions. Here, the sealant layer (1) represents the first layer portion of the sealant layer, and the sealant layer (2) represents the second layer portion of the same sealant layer.

[0102] FIG. 7 is a photographic image showing a case in which peeling occurred in an acceptable (OK) case in an electrolyte immersion and high-temperature condition peeling test (the first test) for a pouch film for a secondary battery according to one embodiment of the present invention.

[0103] Referring to Fig. 7, the sealant layer can be separated (peeled) from the metal barrier layer while maintaining its single layer structure. In other words, the phenomenon of the middle (interlayer) of the sealant layer being peeled off during the test may not occur.

[0104] FIG. 8 and FIG. 9 are cross-sectional views illustrating a peeling pattern corresponding to an OK case in a peeling test between pouch films (the second test) after sealing for a pouch film for a secondary battery according to one embodiment of the present invention.

[0105] Referring to FIGS. 8 and 9, after performing a sealing process for bonding two pouch films (F1, F2) for secondary batteries to each other, the peeling characteristics between the bonded pouch films (F1, F2) can be evaluated. At this time, it may be an OK case if peeling occurs on the inside of the sealant layer (200), including the upper or lower surface of the main layer (220). As in FIG. 8, peeling may occur between the first skin layer (210) and the main layer (220), or as in FIG. 9, peeling may occur between the second skin layer (230) and the main layer (220). After the sealing step, it may be preferable that peeling that exposes the metal barrier layer (100) does not occur in the peeling test between the pouch films.

[0106] Figures 10 and 11 are cross-sectional views illustrating the peeling pattern corresponding to an unsuitable (NG) case in a peeling test between pouch films after sealing for a pouch film for a secondary battery (the second test above).

[0107] Referring to FIGS. 10 and 11, in a test after the sealing step, a case where peeling occurs, exposing the metal barrier layer (100), may be an unsuitable (NG) case. A case where separation (peeling) occurs between the first skin layer (210) and the adhesive layer (150) (FIG. 10) or a case where separation (peeling) occurs between the metal barrier layer (100) and the adhesive layer (150) (FIG. 11) may both be considered cases where the metal barrier layer (100) is exposed and may be unsuitable. If the metal barrier layer (100) is exposed, the reliability of the secondary battery may be lowered, and damage and explosion of the secondary battery may occur, which may have a serious impact on safety.

[0108] Hereinafter, test results for pouch films according to specific examples and comparative examples will be described with reference to Tables 1 to 6, etc.

[0109] Table 1 below summarizes the results of the first and second tests on pouch films according to specific examples and comparative examples.

[0110] Elastomer content by layer (wt%) Electrolyte + high temperature condition peeling mode (1st test) Peeling mode after sealing (2nd test) Comparative example 1 Skin-1 layer 3% / Main layer 10% / Skin-2 layer 7% Peeling of Skin 1 and Main layer (NG) Main layer peeling (OK) Comparative example 2 Skin-1 layer 3.4% / Main layer 10% / Skin-2 layer 7% Peeling of Skin 1 and Main layer (NG) Main layer peeling (OK) Comparative example 3 Skin-1 layer 3.7% / Main layer 10% / Skin-2 layer 7% Peeling of Skin 1 and Main layer (NG) Main layer peeling (OK) Comparative example 4 Skin-1 layer 4% / Main layer 10% / Skin-2 layer 7% Peeling of Skin 1 and Main layer (NG) Main layer peeling (OK) Comparative example 5Skin-1 layer 4.4% / Main layer 10% / Skin-2 layer 7%Skin 1 and Main layer peeling (NG)Main layer peeling (OK)Comparative example 6Skin-1 layer 4.7% / Main layer 10% / Skin-2 layer 7%Skin 1 and Main layer peeling (NG)Main layer peeling (OK)Comparative example 7Skin-1 layer 5% / Main layer 10% / Skin-2 layer 7%Skin 1 and Main layer peeling (NG)Main layer peeling (OK)Comparative example 8Skin-1 layer 5.4% / Main layer 10% / Skin-2 layer 7%Skin 1 and Main layer peeling (NG)Main layer peeling (OK)Comparative example 9Skin-1 layer 5.7% / Main layer 10% / Skin-2 layer 7%Skin 1 and Main layer peeling (NG)Main layer peeling (OK) Comparative Example 10 Skin-1 layer 6% / Main layer 10% / Skin-2 layer 7% Peeling of Skin 1 and Main layer (NG) Peeling of Main layer (OK) Comparative Example 11 Skin-1 layer 6.4% / Main layer 10% / Skin-2 layer 7% Peeling of Skin 1 and Main layer (NG) Peeling of Main layer (OK) Example 1 Skin-1 layer 6.7% / Main layer 10% / Skin-2 layer 7%No delamination between layers (OK)Main layer delamination (OK)Example 2Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7%No delamination between layers (OK)Main layer delamination (OK)Example 3Skin-1 layer 7.4% / Main layer 10% / Skin-2 layer 7%No delamination between layers (OK)Main layer delamination (OK)Comparative example 12Skin-1 layer 7.7% / Main layer 10% / Skin-2 layer 7%No delamination between layers (OK)SUS surface exposed (NG)Comparative example 13Skin-1 layer 8% / Main layer 10% / Skin-2 layer 7%No delamination between layers (OK)SUS surface exposed (NG)Comparative example 14Skin-1 layer 8.4% / Main layer 10% / Skin-2 layer 7% No delamination between layers (OK) SUS surface exposed (NG) Comparative example 15 Skin-1 layer 8.7% / Main layer 10% / Skin-2 layer 7% No delamination between layers (OK) SUS surface exposed (NG).

[0111] Referring to Table 1, only for Examples 1 to 3, both the first and second tests were evaluated as OK. In Example 1, the elastomer content of the first skin layer was 6.7 wt%, the elastomer content of the main layer was 10 wt%, and the elastomer content of the second skin layer was 7 wt%. In Example 2, the elastomer content of the first skin layer was 7 wt%, the elastomer content of the main layer was 10 wt%, and the elastomer content of the second skin layer was 7 wt%. In Example 3, the elastomer content of the first skin layer was 7.4 wt%, the elastomer content of the main layer was 10 wt%, and the elastomer content of the second skin layer was 7 wt%. At this time, the metal barrier layer was a SUS layer, and its thermal conductivity was 15 W / mㆍk or more. In all examples and comparative examples of Table 1, the formability and insulation resistance properties were evaluated as suitable. In the sealant layer, the first skin layer was configured so that the sum of random polypropylene, tert-polypropylene, and block polypropylene was in the range of 50 to 90 wt%, and an ethylene propylene rubber (EPR) series elastomer was used in an amount of a given wt% based on the total composition of the first skin layer. The main layer was configured so that the sum of homo polypropylene and block polypropylene was in the range of 10 to 90 wt%, and an ethylene propylene rubber (EPR) series elastomer was used in an amount of 10 wt%. The second skin layer was configured so that the sum of homo polypropylene, random polypropylene, tert-polypropylene, and block polypropylene (or, the sum of homo polypropylene and block polypropylene) was in the range of 10 to 90 wt%, and an ethylene propylene rubber (EPR) series elastomer was used in an amount of a given wt% based on the total composition of the second skin layer.

[0112] Meanwhile, in all examples and comparative examples of Table 1, the first skin layer, the main layer, and the second skin layer are all CPP-based films, which are the same in Tables 2 to 6 described below. In addition, in all examples and comparative examples, the thickness of the metal barrier layer was 60 μm, the thickness of the adhesive layer was 3.5 μm, and the thickness of the sealant layer was 80 μm, which are the same in Tables 2 to 6 described below.

[0113] Table 2 below summarizes the results of the first and second tests on pouch films according to specific examples and comparative examples.

[0114] Elastomer content by layer (wt%) Electrolyte + high temperature condition peeling mode (1st test) Peeling mode after sealing (2nd test) Comparative example 16 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 3.4% Peeling of Skin 2 and Main layer (NG) Main layer peeling (OK) Comparative example 17 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 3.7% Peeling of Skin 2 and Main layer (NG) Main layer peeling (OK) Comparative example 18 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 4% Peeling of Skin 2 and Main layer (NG) Main layer peeling (OK) Comparative example 19 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 4.4% Peeling of Skin 2 and Main layer (NG) Main layer peeling (OK) Comparative Example 20 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 4.7% Peeling of Skin 2 and Main layer (NG) Main layer peeling (OK) Comparative Example 21 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 5% Peeling of Skin 2 and Main layer (NG) Main layer peeling (OK) Comparative Example 22 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 5.4% Peeling of Skin 2 and Main layer (NG) Main layer peeling (OK) Comparative Example 23 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 5.7% Peeling of Skin 2 and Main layer (NG) Main layer peeling (OK) Comparative Example 24 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 6% Peeling of Skin 2 and Main layer (NG) Main layer peeling (OK) Comparative example 25 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 6.4% Peeling of Skin 2 and Main layers (NG) Main layer peeling (OK) Example 4 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 6.7%No delamination between layers (OK)Main layer delamination (OK)Example 5Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7%No delamination between layers (OK)Main layer delamination (OK)Example 6Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7.4%No delamination between layers (OK)Main layer delamination (OK)Comparative Example 26Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7.7%No delamination between layers (OK)SUS surface exposed (NG)Comparative Example 27Skin-1 layer 7% / Main layer 10% / Skin-2 layer 8%No delamination between layers (OK)SUS surface exposed (NG)Comparative Example 28Skin-1 layer 7% / Main layer 10% / Skin-2 layer 8.3%No delamination between layers (OK) SUS surface exposed (NG) Comparative example 29 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 8.7% No delamination between layers (OK) SUS surface exposed (NG).

[0115] Referring to Table 2, only for Examples 4 to 6, both the first and second tests were evaluated as OK. In Example 4, the elastomer content of the first skin layer was 7 wt%, the elastomer content of the main layer was 10 wt%, and the elastomer content of the second skin layer was 6.7 wt%. In Example 5, the elastomer content of the first skin layer was 7 wt%, the elastomer content of the main layer was 10 wt%, and the elastomer content of the second skin layer was 7 wt%. In Example 6, the elastomer content of the first skin layer was 7 wt%, the elastomer content of the main layer was 10 wt%, and the elastomer content of the second skin layer was 7.4 wt%. Example 5 may be substantially the same as Example 2. The metal barrier layer was a SUS layer, and its thermal conductivity was 15 W / m·k or higher. In all the examples and comparative examples in Table 2, the formability and insulation resistance characteristics were evaluated as suitable. Table 3 below summarizes the results of the first and second tests described above for pouch films according to specific examples and comparative examples.

[0116] Elastomer content by layer (wt%) Electrolyte + high temperature condition peeling mode (1st test) Peeling mode after sealing (2nd test) Formability Insulation resistance Comparative example 30 Skin-1 layer 7.04% / Main layer 11% / Skin-2 layer 7.7% Peeling of Skin 1 and Main layer (NG) Main layer peeling (OK) NG OK Example 7 Skin-1 layer 7.7% / Main layer 11% / Skin-2 layer 7.7% No peeling between layers (OK) Main layer peeling (OK) OK OK Comparative example 31 Skin-1 layer 8.47% / Main layer 11% / Skin-2 layer 7.7% No peeling between layers (OK) SUS surface exposed (NG) OK OK Comparative example 32 Skin-1 layer 7.68% / Main layer 12% / Skin-2 layer 8.4% Skin 1 and Main layer peeling (NG)Main layer peeling (OK)OKOKExample 8Skin-1 layer 8.4% / Main layer 12% / Skin-2 layer 8.4%No interlayer peeling (OK)Main layer peeling (OK)OKOKComparative example 33Skin-1 layer 9.24% / Main layer 12% / Skin-2 layer 8.4%No interlayer peeling (OK)SUS surface exposed (NG)OKOKComparative example 34Skin-1 layer 8.32% / Main layer 13% / Skin-2 layer 9.1%Skin 1 and Main layer peeling (NG)Main layer peeling (OK)OKOKExample 9Skin-1 layer 9.1% / Main layer 13% / Skin-2 layer 9.1%No interlayer peeling (OK)Main layer peeling (OK)OKOKComparative example 35Skin-1 layer 10.1% / Main layer 13% / Skin-2 layer 9.1% No delamination between layers (OK) SUS surface exposed (NG) OK OK Comparative example 36 Skin-1 layer 8.96% / Main layer 14% / Skin-2 layer 9.8% Peeling of Skin 1 and Main layers (NG) Main layer peeling (OK) OK OK Example 10 Skin-1 layer 9.8% / Main layer 14% / Skin-2 layer 9.8% No delamination between layers (OK) Main layer peeling (OK) OK OK Comparative example 37 Skin-1 layer 10.78% / Main layer 14% / Skin-2 layer 9.8%No delamination between layers (OK)SUS surface exposed (NG)OKOKComparative example 38Skin-1 layer 9.6% / Main layer 15% / Skin-2 layer 10.5%Skin 1 and Main layer delamination (NG)Main layer delamination (OK)OKOKExample 11Skin-1 layer 10.5% / Main layer 15% / Skin-2 layer 10.5%No delamination between layers (OK)Main layer delamination (OK)OKOKComparative example 39Skin-1 layer 11.55% / Main layer 15% / Skin-2 layer 10.5%No delamination between layers (OK)SUS surface exposed (NG)OKNG.

[0117] Referring to Table 3, in the case of Examples 7 to 11, both the first and second tests were evaluated as acceptable (OK). In Examples 7 to 11, the elastomer content of the first skin layer, the elastomer content of the main layer, and the elastomer content of the second skin layer can be confirmed, respectively. At this time, the metal barrier layer was a SUS layer, and its thermal conductivity was 15 W / mㆍk or more. In the case of Comparative Example 30, the sum of the elastomer content of the main layer, the elastomer content of the first skin layer, and the elastomer content of the second skin layer was 25.74 wt%, and at this time, the formability characteristics were inadequate. In the case of Comparative Example 39, the sum of the elastomer content of the main layer, the elastomer content of the first skin layer, and the elastomer content of the second skin layer was 37.05 wt%, and at this time, the insulation resistance characteristics were inadequate. If the total elastomer content in the sealant layer is too small, formability may be poor, and if it is too large, it may have a negative effect on insulation resistance characteristics. In an embodiment of the present invention, the total elastomer content of the main layer, the first skin layer, and the second skin layer may be, for example, in the range of about 26 to 37 wt%.

[0118] Table 4 below summarizes the results of the first and second tests on pouch films according to specific examples and comparative examples.

[0119] Elastomer content by layer (wt%) Electrolyte + high temperature condition peeling mode (1st test) Peeling mode after sealing (2nd test) Formability Insulation resistance Example 12 Skin-1 layer 7.4% / Main layer 11% / Skin-2 layer 7.7% No interlayer peeling (OK) Main layer peeling (OK) OK OK Example 13 Skin-1 layer 7.7% / Main layer 11% / Skin-2 layer 7.4% No interlayer peeling (OK) Main layer peeling (OK) OK OK Example 14 Skin-1 layer 8% / Main layer 11% / Skin-2 layer 7.7% No interlayer peeling (OK) Main layer peeling (OK) OK OK Example 15 Skin-1 layer 7.7% / Main layer 11% / Skin-2 layer 8% No interlayer peeling (OK) Main layer peeling (OK)OKOKExample 16Skin-1 layer 8% / Main layer 12% / Skin-2 layer 8.4%No delamination between layers (OK)Main layer delamination (OK)OKOKExample 17Skin-1 layer 8.4% / Main layer 12% / Skin-2 layer 8%No delamination between layers (OK)Main layer delamination (OK)OKOKExample 18Skin-1 layer 8.7% / Main layer 12% / Skin-2 layer 8.4%No delamination between layers (OK)Main layer delamination (OK)OKOKExample 19Skin-1 layer 8.4% / Main layer 12% / Skin-2 layer 8.7%No delamination between layers (OK)Main layer delamination (OK)OKOKExample 20Skin-1 layer 8.8% / Main layer 13% / Skin-2 layer 9.1%No delamination between layers (OK) Main layer peeling (OK) OK OK Example 21 Skin-1 layer 9.1% / Main layer 13% / Skin-2 layer 8.8% No interlayer peeling (OK) Main layer peeling (OK) OK OK Example 22 Skin-1 layer 9.4% / Main layer 13% / Skin-2 layer 9.1% No interlayer peeling (OK) Main layer peeling (OK) OK OK Example 23 Skin-1 layer 9.1% / Main layer 13% / Skin-2 layer 9.4% No interlayer peeling (OK) Main layer peeling (OK) OK OK Example 24 Skin-1 layer 10.2% / Main layer 15% / Skin-2 layer 10.5%No interlayer delamination (OK)Main layer delamination (OK)OKOKExample 25Skin-1 layer 10.5% / Main layer 15% / Skin-2 layer 10.2%No interlayer delamination (OK)Main layer delamination (OK)OKOKExample 26Skin-1 layer 10.8% / Main layer 15% / Skin-2 layer 10.5%No interlayer delamination (OK)Main layer delamination (OK)OKOKExample 27Skin-1 layer 10.5% / Main layer 15% / Skin-2 layer 10.8%No interlayer delamination (OK)Main layer delamination (OK)OKOK.

[0120] Referring to Table 4, in the case of Examples 12 to 27, it was evaluated as suitable (OK) in both the first and second tests. In Examples 12 to 27, the elastomer content of the first skin layer, the elastomer content of the main layer, and the elastomer content of the second skin layer can be confirmed, respectively. At this time, the metal barrier layer was a SUS layer, and its thermal conductivity was 15 W / mㆍk or more. In all the examples of Table 4, the formability and insulation resistance characteristics were evaluated as suitable. In the results of Tables 1 to 4 described above, in the case of Examples 1 to 27, the ratio (A:B) of the elastomer content (A) of the main layer and the elastomer content (B) of the first skin layer can be in the range of about 1:0.67 to 0.74. In addition, the ratio (A:C) of the elastomer content (A) of the main layer and the elastomer content (C) of the second skin layer may be in the range of about 1:0.67∼0.74. The ratio (A:B:C) of the elastomer content (A) of the main layer, the elastomer content (B) of the first skin layer and the elastomer content (C) of the second skin layer may be in the range of about 1:0.67∼0.74:0.67∼0.74. When these conditions are satisfied, the chemical resistance, heat resistance, peeling resistance, durability, etc. of the pouch film according to the embodiment may be improved. In addition, for Examples 1 to 27, the elastomer content of the main layer may be in the range of about 10 to 15 wt%, the elastomer content of the first skin layer may be in the range of about 6.7 to 10.8 wt%, and the elastomer content of the second skin layer may be in the range of about 6.7 to 10.8 wt%. Under these content range conditions, the ratio (A:B:C) of the elastomer content (A) of the main layer, the elastomer content (B) of the first skin layer, and the elastomer content (C) of the second skin layer may satisfy the condition of 1:0.67 to 0.74:0.67 to 0.74. However, the elastomer content range conditions of the above-mentioned respective layers (main layer, first skin layer, second skin layer) may vary depending on the case.

[0121] Table 5 below summarizes the results of the first and second tests on pouch films according to specific examples and comparative examples. In Table 5, the influence of thermal conductivity was evaluated by conducting tests while varying the thermal conductivity of the SUS layer applied to the metal barrier layer.

[0122] Elastomer content by layer (wt%)SUS thermal conductivity (W / mㆍk)Electrolyte + high temperature condition peeling mode (1st test)Peeling mode after sealing (2nd test)Example 28Skin-1 layer 6.7% / Main layer 10% / Skin-2 layer 7%20No peeling between layers (OK)Main layer peeling (OK)Comparative example 40Skin-1 layer 6.7% / Main layer 10% / Skin-2 layer 7%10No peeling between layers (OK)No sealing (NG)Comparative example 41Skin-1 layer 6.7% / Main layer 10% / Skin-2 layer 7%13No peeling between layers (OK)No sealing (NG)Example 29Skin-1 layer 6.7% / Main layer 10% / Skin-2 layer 7%15No peeling between layers (OK)Main layer peeling (OK) Example 30 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7% 20 No delamination between layers (OK) Main layer delamination (OK) Comparative example 42 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7% 10 No delamination between layers (OK) No sealing (NG) Example 31 Skin-1 layer 7.4% / Main layer 10% / Skin-2 layer 7% 20 No delamination between layers (OK) Main layer delamination (OK) Comparative example 43 Skin-1 layer 7.4% / Main layer 10% / Skin-2 layer 7% 10 No delamination between layers (OK) No sealing (NG) Example 32 Skin-1 layer 7% / Main layer 10% / Skin-2 layer 6.7% 20 No delamination between layers (OK) Main layer delamination (OK) Comparative example 44 Skin-1st layer 7% / Main layer 10% / Skin-2nd layer 6.7% No delamination between layers (OK) No sealing (NG) Example 33 Skin-1st layer 7% / Main layer 10% / Skin-2nd layer 7% No delamination between layers (OK) Main layer delamination (OK) Comparative example 45 Skin-1st layer 7% / Main layer 10% / Skin-2nd layer 7% No delamination between layers (OK) No sealing (NG) Example 34 Skin-1st layer 7% / Main layer 10% / Skin-2nd layer 7.4%20No delamination between layers (OK)Main layer delamination (OK)Comparative example 46Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7.4%10No delamination between layers (OK)No sealing (NG)Comparative example 47Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7.4%13No delamination between layers (OK)No sealing (NG)Example 35Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7.4%15No delamination between layers (OK)Main layer delamination (OK).

[0123] Referring to Table 5, the metal barrier layer was a SUS layer, and in Examples 28 to 35, where the thermal conductivity of the SUS layer was 15 W / mㆍk or higher, both the first and second tests were evaluated as OK. Therefore, when the metal barrier layer is made of or includes stainless steel (SUS) having a thermal conductivity of 15 W / mㆍk or higher, more preferable test results can be obtained. The thermal conductivity of the stainless steel (SUS) applied to the examples may be about 15 to 30 W / mㆍk or about 15 to 25 W / mㆍk. In Examples 28 to 35, the elastomer content of the first skin layer, the elastomer content of the main layer, and the elastomer content of the second skin layer can be confirmed, respectively. Table 6 below summarizes the results of the first and second tests described above for pouch films according to specific examples and comparative examples. In Table 6, the influence of the melting temperature (Tm) of the adhesive layer was evaluated by performing tests while changing the melting temperature (Tm) of the adhesive layer.

[0124] Classification Adhesive Tm / Elastomer content (wt%) for each layer Electrolyte + high temperature condition peeling mode (1st test) Peeling strength (N / 15mm) Peeling mode after sealing (2nd test) Comparative example 48 SUS Metal / Adhesive Tm 120 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 3% Peeling of Skin 2 and Main layers (NG) 13 (NG) Peeling of Main layer (OK) Comparative example 49 SUS Metal / Adhesive Tm 120 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7% No peeling between layers (OK) 13 (NG) Peeling of Main layer (OK) Comparative example 50 SUS Metal / Adhesive Tm 130 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7% No peeling between layers (OK) 14 (NG) Peeling of Main layer (OK) Comparative Example 51 SUS Metal / Adhesive Tm 140 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 3% Peeling of Skin 2 and Main layer (NG) 17 Main layer peeling (OK) Example 36 SUS Metal / Adhesive Tm 140 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7% No delamination between layers (OK) 17 Main layer peeling (OK) Comparative Example 52 SUS Metal / Adhesive Tm 140 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 8% No delamination between layers (OK) 17 SUS surface exposed (NG) Comparative Example 53 SUS Metal / Adhesive Tm 160 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 3% Peeling of Skin 2 and Main layer (NG) 18 Main layer peeling (OK) Example 37 SUS Metal / Adhesive Tm 160 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7% No delamination between layers (OK) 18 Main layer delamination (OK) Comparative example 54 SUS Metal / Adhesive Tm 160 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 8% No delamination between layers (OK) 18 SUS surface exposed (NG) Comparative example 55 SUS Metal / Adhesive Tm 180 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer3%Skin 2 and Main layer peeling (NG)20Main layer peeling (OK)Example 38SUS Metal / Adhesive Tm 180 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 7%No interlayer peeling (OK)20Main layer peeling (OK)Comparative Example 56SUS Metal / Adhesive Tm 180 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 8%No interlayer peeling (OK)20SUS surface exposed (NG)Comparative Example 57SUS Metal / Adhesive Tm 200 / Skin-1 layer 7% / Main layer 10% / Skin-2 layer 8%No interlayer peeling (OK)14 (NG)SUS surface exposed (NG)

[0125] Referring to Table 6, in the case of Examples 36 to 38, where the melting temperature (Tm) of the adhesive layer (adhesive) was 140°C or higher, the peel strength condition was satisfied and it was evaluated as OK in both the first and second tests. Here, the peel strength refers to the peel strength in the first test, i.e., the peel strength between the metal barrier layer and the sealant layer, and a case where it is 15 N / 15 mm or higher may be considered OK. In the case of Comparative Examples 49 and 50, it was confirmed that the melting temperature (Tm) of the adhesive layer (adhesive) was lower than 140°C, and in this case, the peel strength condition was not satisfied. In the pouch film according to the embodiment of the present invention, the melting temperature (Tm) of the adhesive layer may be preferably 140°C or higher. The melting temperature (Tm) of the adhesive layer may be, for example, about 140°C to 200°C or about 140°C to 180°C. In Table 6, the metal barrier layer was a SUS layer, and its thermal conductivity was 15 W / mㆍk or more. Fig. 12 is a cross-sectional view showing a pouch film for a secondary battery according to an embodiment of the present invention.

[0126] Referring to FIG. 12, the pouch film for a secondary battery according to an embodiment of the present invention may further include an outer layer (300) bonded to a metal barrier layer (100). The metal barrier layer (100) may be disposed between the outer layer (300) and a sealant layer (200). In addition, the pouch film for a secondary battery may further include an adhesive layer (250) disposed between the metal barrier layer (100) and the outer layer (300). The adhesive layer (150) between the metal barrier layer (100) and the sealant layer (200) may be referred to as a first adhesive layer, and the adhesive layer (250) between the metal barrier layer (100) and the outer layer (300) may be referred to as a second adhesive layer.

[0127] The outer layer (300) may be disposed on the outside of the pouch film, and may be composed of one or more materials selected from, but not limited to, nylon, a laminated film of nylon and PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PP (polypropylene), etc. The outer layer (300) may have a single-layer or multi-layer structure. The thickness of the outer layer (300) may be, for example, about 1 ㎛ to 100 ㎛. If the outer layer (300) is too thin, it may be difficult to secure sufficient mechanical strength or the formability may be reduced, and if the outer layer (300) is too thick, it may not be preferable in terms of insulation breakdown voltage requirements, etc. As a non-limiting example, the thickness of the outer layer (300) may be about 5 ㎛ to 50 ㎛ or about 10 ㎛ to 30 ㎛.

[0128] According to an embodiment of the present invention, a pouch-type secondary battery to which the aforementioned pouch film for secondary batteries is applied can be provided. The remaining configuration of the pouch-type secondary battery, excluding the configuration of the pouch film, can follow the configuration of a typical secondary battery. The pouch-type secondary battery can be, for example, a lithium ion battery. However, the type of the pouch-type secondary battery is not limited to a lithium ion battery and can vary widely. The pouch film according to the embodiments can be applied to all secondary batteries that can be manufactured in a pouch form.

[0129] According to the embodiments of the present invention described above, a pouch film for a secondary battery can be implemented that can improve the safety and reliability of the secondary battery. According to the embodiments of the present invention, a pouch film for a secondary battery having excellent chemical resistance, heat resistance, peeling resistance, and durability can be implemented. In particular, according to the embodiments of the present invention, a pouch film for a secondary battery can be implemented that can satisfy both the physical property requirements required for the pouch film itself in an electrolyte environment and a high-temperature environment, and the physical property requirements required for the pouch film joint after the sealing step. The pouch film for a secondary battery according to the embodiments can satisfy the physical property requirements required in a peeling test for the pouch film itself under electrolyte immersion and high-temperature conditions, and the physical property requirements required in a peeling test between pouch films after the sealing step. By applying the pouch film for a secondary battery according to the embodiments, a pouch-type secondary battery having excellent stability, reliability, and durability can be manufactured.

[0130] In this specification, preferred embodiments of the present invention have been disclosed, and although specific terms have been used, they have been used only in a general sense to easily explain the technical contents of the present invention and to help the understanding of the invention, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of ​​the present invention are possible in addition to the embodiments disclosed herein. Those skilled in the art will appreciate that the pouch film for secondary batteries according to the embodiments described with reference to FIGS. 1 to 12, pouch-type secondary batteries using the same, and related methods can be variously substituted, changed, and modified without departing from the technical idea of ​​the present invention. Therefore, the scope of the invention should not be defined by the described embodiments, but by the technical idea described in the claims.

Claims

1. Metal barrier layer; and A sealant layer bonded to the metal barrier layer with an adhesive layer between them; The above sealant layer includes a first skin layer, a second skin layer, and a main layer disposed between them, From the side where the metal barrier layer is arranged, the first skin layer, the main layer, and the second skin layer are arranged sequentially. Each of the first skin layer, the main layer and the second skin layer is composed of a polymer material including an elastomer, A pouch film for a secondary battery, wherein the elastomer content of the main layer is higher than the elastomer content of each of the first and second skin layers.

2. In paragraph 1, A pouch film for a secondary battery, wherein the ratio (A:B) of the elastomer content (A) of the main layer and the elastomer content (B) of the first skin layer is in the range of 1:0.67 to 0.

74.

3. In paragraph 1, A pouch film for a secondary battery, wherein the ratio (A:C) of the elastomer content (A) of the main layer and the elastomer content (C) of the second skin layer is in the range of 1:0.67 to 0.

74.

4. In paragraph 1, A pouch film for a secondary battery, wherein the ratio (A:B:C) of the elastomer content (A) of the main layer, the elastomer content (B) of the first skin layer, and the elastomer content (C) of the second skin layer is in the range of 1:0.67∼0.74:0.67∼0.

74.

5. In paragraph 1, The elastomer content of the above main layer is in the range of 10 to 15 wt%, The elastomer content of the first skin layer is in the range of 6.7 to 10.8 wt%, A pouch film for a secondary battery, wherein the elastomer content of the second skin layer is in the range of 6.7 to 10.8 wt%.

6. In paragraph 1, A pouch film for a secondary battery, wherein the sum of the elastomer content of the main layer, the elastomer content of the first skin layer, and the elastomer content of the second skin layer is in the range of 26 to 37 wt%.

7. In paragraph 1, A pouch film for a secondary battery, wherein each of the first skin layer, the main layer, and the second skin layer contains a polypropylene-based material as a main component.

8. In paragraph 7, The above polypropylene material is a pouch film for secondary batteries, which is CPP (cast polypropylene).

9. In paragraph 1, The above metal barrier layer is a pouch film for a secondary battery including stainless steel (SUS).

10. In paragraph 1, The above metal barrier layer is a pouch film for secondary batteries made of stainless steel (SUS) having a thermal conductivity of 15 W / mㆍk or more.

11. In paragraph 1, A pouch film for a secondary battery, wherein the adhesive layer has a melting temperature (Tm) of 140°C or higher.

12. In paragraph 1, The ratio (A:B:C) of the elastomer content (A) of the main layer, the elastomer content (B) of the first skin layer, and the elastomer content (C) of the second skin layer is in the range of 1:0.67∼0.74:0.67∼0.74, The above metal barrier layer is composed of stainless steel (SUS) having a thermal conductivity of 15 W / mㆍk or more. A pouch film for a secondary battery, wherein the adhesive layer has a melting temperature (Tm) of 140°C or higher.

13. In paragraph 1, A pouch film for a secondary battery further comprising an outer layer bonded to the metal barrier layer, wherein the metal barrier layer is disposed between the outer layer and the sealant layer.

14. A pouch-type secondary battery to which is applied the pouch film for secondary batteries according to any one of claims 1 to 13.

Images