Cell pouch film containing a surface treatment layer with adjusted capillary number and method for manufacturing the same

Abstract

To provide a cell pouch film containing a surface treatment layer with an adjusted capillary number, and a method for manufacturing the same. [Solution] A cell pouch film comprising a first resin layer, a metal layer, and a second resin layer, wherein a surface treatment layer is included between the first resin layer and the metal layer, and the capillary value of the surface treatment layer is set to 0.5 to 5. A cell pouch film comprising a first resin layer, a metal layer, and a second resin layer, comprising the steps of forming a surface treatment layer on the metal layer and forming a first resin layer on the surface treatment layer, wherein the capillary value of the surface treatment layer is set to 0.5 to 5.

Description

Technical Field

[0001] The present invention relates to a film for a cell pouch including a surface treatment layer with an adjusted capillary number and a method for manufacturing the same.

Background Art

[0002] A pouch-type lithium secondary battery has a structure in which an electrode and an electrolyte are placed in a pouch made of a thin and flexible plastic film and a metal foil and sealed. Such a structure has advantages of being light, having a high energy density, and being able to be designed in various forms, and is widely used in various devices such as electric vehicles, smartphones, and notebook personal computers.

[0003] As an exterior material for such a pouch-type lithium secondary battery, a cell pouch film is used. The cell pouch film is an important component that affects the safety and performance of a lithium-ion battery. A general cell pouch film has a multilayer structure and is mainly composed of a protective layer, a metal layer (aluminum), an adhesive layer, and an inner base material layer. Currently, one of the main problems in the manufacturing process of the cell pouch film is the generation of bubbles between the protective layer and the metal layer. Such bubbles can be generated by various factors. As environmental factors, changes in temperature and humidity can affect the viscosity of the adhesive and the coating performance. As material-related problems, dust, impurities, and inappropriate surface tension of the film can induce bubble formation. As adhesive-related problems, an inappropriately prepared adhesive or a viscosity outside the optimal range can cause coating non-uniformity. In the coating and drying process, an insufficient coating amount or a non-uniform distribution can trap air and form bubbles. Such bubbles can reduce the performance of the cell pouch film and, in the long term, can have a negative impact on the safety and life of the battery. Therefore, minimizing bubble generation is a very important issue in the manufacturing process of the cell pouch film.

[0004] To date, various methods have been attempted to solve these problems. For example, methods such as controlling the workplace environment, strengthening material quality control, optimizing adhesives, and improving coating precision have been used. However, each of these methods has its limitations and has not provided a complete solution.

[0005] Furthermore, this application is based on a national research and development project supporting the following invention. Issue-specific number: 2410004468 Assignment Number: 20022450 Department: Ministry of Trade, Industry and Energy Project management (specialized) organization name: Korea Industrial Technology Planning and Evaluation Service (Excellent Company) Research project name: Development of materials and component technologies Research Project Title: Development of Next-Generation Secondary Battery Pouches Capable of Achieving More Than Twice the Adhesion Strength (60) Project Implementation Organization: Yeoul Cheong Chemical Company, Limited Research period: 2024.01.01~2024.12.31 [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Registered Patent No. 10-2665240 of the Republic of Korea [Overview of the project] [Problems that the invention aims to solve]

[0007] The problem that this invention aims to solve is to improve the performance of a cell pouch film by providing a cell pouch film containing a surface treatment layer with an adjusted capillary number and a method for manufacturing the same. [Means for solving the problem]

[0008] To solve the aforementioned problems, the present invention provides a cell pouch film comprising a first resin layer, a metal layer, and a second resin layer, wherein a surface treatment layer is included between the first resin layer and the metal layer, and the capillary number value of the surface treatment layer is 0.5 to 5.

[0009] Furthermore, the present invention provides a method for manufacturing a cell pouch film comprising a first resin layer, a metal layer, and a second resin layer, the method comprising the steps of forming a surface treatment layer on the metal layer and forming the first resin layer on the surface treatment layer, wherein the capillary number of the surface treatment layer is 0.5 to 5. [Effects of the Invention]

[0010] Through the cell pouch film and its manufacturing method according to the present invention, the number of capillaries in the surface treatment layer contained between the first resin layer and the metal layer can be adjusted to effectively reduce the rate of bubble generation between the metal layer and the first resin layer. This reduction in bubbles can improve the peel strength and electrolyte resistance of the cell pouch film. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram illustrating pore formation in a cell pouch film according to one embodiment of the present invention. [Figure 2] These are photographs used to calculate the porosity of examples and comparative examples of the present invention. [Figure 3] These are photographs used to calculate the porosity of examples and comparative examples of the present invention. [Figure 4] These are photographs used to calculate the porosity of examples and comparative examples of the present invention. [Figure 5] These are photographs used to calculate the porosity of examples and comparative examples of the present invention. [Modes for carrying out the invention]

[0012] Various embodiments of the present invention are described below with reference to the accompanying drawings. The present invention is not limited to any particular embodiment and should be understood to include various modifications, equivalents, and / or alternatives to embodiments of the present invention. In connection with the description of the drawings, similar reference numerals may be used for similar components. In this document, expressions such as "possess," "may possess," "include," or "may include" refer to the existence of the relevant feature (e.g., numerical values, functions, operations, or components such as parts), and do not exclude the existence of additional features. In this document, expressions such as "A or B," "A or / and B, or one or more of A or / and B" can include all possible combinations of the items listed together. For example, "A or B," "A and B, or A or B, or at least one of A or B" can refer to any of the following: (1) including at least one A, (2) including at least one B, or (3) including at least one A and at least one B. The expression "configured to" as used in this document can be replaced with other expressions depending on the context, such as "suitable for," "having the capacity to," "designed to," "adapted to," "made to," or "capable of." The term "configured to" does not necessarily mean "specifically designed to." The terms used in this document are merely used to describe specific embodiments and may not be intended to limit the scope of other embodiments. Singular expressions may include plural expressions unless the context clearly has a different meaning. The terms used herein, including technical or scientific terms, can have the same meaning as generally understood by those with ordinary knowledge in the technical field described in this document. Among the terms used in this document, those defined in a general dictionary can be analyzed with the same or similar meaning as the meaning they have in the context of the related art, and unless clearly defined in this document, they are not analyzed in an ideal or overly formal sense. In some cases, even terms defined in this document cannot be analyzed so as to exclude the embodiments of this document. The embodiments disclosed in this document are presented for the purpose of explaining and understanding the disclosed technical content and do not limit the scope of the present invention. Therefore, the scope of this document includes all modifications or various other embodiments based on the technical idea of the present invention. Hereinafter, preferred embodiments of the present invention will be described in detail. Prior to this, the terms and words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings. Instead, in accordance with the principle that the inventor himself can appropriately define the concept of the terms in order to explain the invention in the best way, they are construed with the meanings and concepts corresponding to the technical idea of the present invention. Therefore, the configurations of the embodiments described in this specification are merely some of the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. So, at the time of this application, there may be various equivalents and modifications that can replace them. Throughout the specification, when a certain part "includes" a certain component, this means that, unless otherwise stated, it does not exclude other components but may further include other components. Hereinafter, the present invention will be specifically described.

[0013] In this specification, "cell" means a battery, and has the broadest meaning including all kinds of batteries such as secondary batteries like lithium ion batteries and lithium polymer batteries, and various batteries such as portable rechargeable batteries.

[0014] In this specification, "cell pouch" refers to an object in which cell components such as an anode, a cathode, and a separator are impregnated with an electrolyte solution and stored. In order to store the cell components, it has the broadest meaning including all objects processed in a bag form or a box form using a film with a laminated structure considering gas barrier properties, flexibility, electrolyte resistance, heat adhesiveness, etc.

[0015] The cell pouch type battery specifically refers to a lithium secondary battery, which has a polymer electrolyte and generates an electric current by the movement of lithium ions. It is said that a film for cell pouch in which a polymer and a metal are laminated is used as an exterior material for packaging to protect such a secondary battery. Such a film for cell pouch is configured in a form with a metal layer interposed to protect a battery cell composed of the electrode assembly and an electrolyte solution filled therein in a subsequent process, and to stably maintain the electrochemical properties of the cell, and a first resin layer (external resin layer) can be formed on the metal layer to protect the battery cell from external impacts.

[0016] The film for cell pouch is joined at the outer peripheral surface portion by heat fusion or the like between an upper film for cell pouch and a lower film for cell pouch, and a second resin layer (adhesive resin layer) may be formed between the lower surface of the upper film for cell pouch and the upper surface of the lower film for cell pouch for adhesion between the interfaces.

[0017] The present invention provides a film for cell pouch including a first resin layer, a metal layer, and a second resin layer, wherein a surface treatment layer is included between the first resin layer and the metal layer, and the capillary number value of the surface treatment layer is 0.5 to 5. The components of the present invention will be described in detail below.

[0018] In the method for manufacturing a cell pouch film of the present invention, the first resin layer corresponds to the part that comes into direct contact with the hardware, and therefore it is preferable that the resin is insulating. For this reason, it is preferable to use at least one of polyester resin or polyamide resin as the resin used for the first resin layer. The first resin layer may be a single layer or may be formed as a multilayer.

[0019] Examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), copolymer polyesters, and polycarbonate (PC). Examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, polycarbonate, copolymer polyesters mainly composed of repeating units of ethylene terephthalate, and copolymer polyesters mainly composed of repeating units of butylene terephthalate.

[0020] Furthermore, specific examples of copolymer polyesters with ethylene terephthalate as the main repeating unit include copolymer polyesters polymerized with ethylene isophthalate using ethylene terephthalate as the main repeating unit, polyethylene (terephthalate / isophthalate), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl dicarboxylate), and polyethylene (terephthalate / decanedicarboxylate).

[0021] Furthermore, specific examples of copolymer polyesters using butylene terephthalate as the main repeating unit include copolymer polyesters polymerized with butylene isophthalate using butylene terephthalate as the main repeating unit, polybutylene (terephthalate / adipate), polybutylene (terephthalate / sevacate), polybutylene (terephthalate / decanedicarboxylate), and polybutylene naphthalate. These polyesters may be used individually or in combination of two or more.

[0022] Examples of polyamide resins include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (where I is isophthalic acid and T is terephthalic acid), which contain constituent units derived from terephthalic acid and / or isophthalic acid; aromatic polyamides such as polymetaxylene adipamide (MXD6); alicyclic polyamides such as polyaminomethylcyclohexyl adipamide (PACM6); polyamides copolymerized with lactam components or isocyanate components such as 4,4'-diphenylmethane-diisocyanate; polyesteramide copolymers and polyether esteramide copolymers, which are copolymers of copolymerized polyamides with polyester or polyalkylene etherglycols; and copolymers thereof. These polyamides may be used individually or in combination of two or more. If the thickness of the first resin layer is less than the aforementioned range, it will have inferior physical properties and will easily break, and if it exceeds the aforementioned range, it will have the problem of having poor moldability.

[0023] The first resin layer may optionally be multilayered. For example, a polyester resin layer can be formed on the outermost edge of the cell pouch film, and a polyamide resin layer can be formed inside the polyester resin layer.

[0024] The thickness of the first resin layer may be 10 to 30 μm if it is a single layer. For example, the thickness of the first resin layer may be 10 μm or more, 11 μm or more, 12 μm or more, 13 μm or more, 14 μm or more, 15 μm or more, 30 μm or less, 29 μm or less, 28 μm or less, 27 μm or less, 26 μm or less, or 25 μm or less. If the first resin layer is a multilayer of two or more layers, the thickness may be 20 to 55 μm. For example, if the first resin layer is a multilayer of two or more layers, the thickness may be 20 μm or more, 21 μm or more, 22 μm or more, 23 μm or more, 25 μm or more, 26 μm or more, 27 μm or more, 28 μm or more, 29 μm or more, 30 μm or more, 50 μm or less, 49 μm or less, 48 ​​μm or less, 47 μm or less, 46 μm or less, 45 μm or less, 44 μm or less, 43 μm or less, 42 μm or less, 41 μm or less, or 40 μm or less.

[0025] The aforementioned metal layer is used as a barrier layer to prevent the penetration of oxygen or moisture from the outside, and may be in the form of a thin metal film. Specifically, the aforementioned metal layer may contain one or more materials selected from the group consisting of aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), stainless steel (SUS), tin (Sn), zinc (Zn), indium (In), tungsten (W), titanium (Ti), and invar (INVAR).

[0026] The material of the metal layer is preferably aluminum or stainless steel. For the aluminum alloy, alloys can be made by adding various metals and nonmetals to pure aluminum. The aluminum layer can preferably be made of soft aluminum foil.

[0027] The aluminum substrate may be an alloy selectively containing elements selected from the group consisting of silicon, boron, germanium, arsenic, antimony, copper, magnesium, manganese, zinc, lithium, iron, chromium, vanadium, titanium, bismuth, potassium, tin, lead, zirconium, nickel, cobalt, and combinations thereof.

[0028] Stainless steel is an iron-based alloy that can be manufactured to have properties suitable for specific applications through various combinations of elements. Iron (Fe) is the basic element of stainless steel, forming the matrix of the alloy and providing structural strength and flexibility. Chromium (Cr) is the core element of stainless steel, present in a minimum of 10.5% or more, forming a protective oxide film on the surface to prevent corrosion. Nickel (Ni) can improve strength, flexibility, and toughness, and provide high-temperature resistance. Carbon (C) can increase strength and hardness. Molybdenum (Mo) can enhance corrosion resistance, especially in chloride-containing environments, and improve high-temperature strength and creep resistance. Manganese (Mn) improves strength and can replace nickel in some grades. Nitrogen (N) can help improve strength. Titanium (Ti) and niobium (Nb) can improve stability in certain grades.

[0029] The aforementioned stainless steels can be classified mainly into austenitic, ferritic, martensitic, and duplex types based on their metallic structure. Austenitic stainless steel is the most widely used, with grades 304 and 316 being examples. Grade 304 contains 18% chromium and 8% nickel, while grade 316 has added molybdenum for even higher corrosion resistance. Ferritic stainless steel is widely used due to its high chromium content and low nickel content, making it cost-effective. Grade 430 is a typical example. Martensitic stainless steel can have its strength and hardness increased through heat treatment, with grades 410 and 420 being examples. Duplex stainless steel is characterized by a mixture of austenitic and ferritic structures, possessing both high strength and excellent corrosion resistance. Grades 2205 and 2507 are examples.

[0030] The metal foil used in the aforementioned metal layer may be etched or degreased on the surface to improve adhesion with the second resin layer, as described later, but this can be omitted to reduce process speed. The aforementioned metal layer is intended to prevent gas and water vapor from penetrating into the battery from the outside, and it is necessary that the metal layer is free from pinholes and unsuitable for processing (pouching, embossing).

[0031] The metal layer according to one embodiment of the present invention may satisfy at least one of the following conditions (1) to (3). (1) The surface roughness (Ra) value of the metal layer is 0.2 μm or more. (2) The surface roughness (Rt) value of the metal layer is 1.5 μm or more. (3) The surface roughness (Rz) value of the metal layer is 2.0 μm or greater.

[0032] The aforementioned surface roughness is an index that quantitatively indicates the state of fine irregularities on a surface. This means measuring and analyzing the degree of surface roughness caused by small deposits, crystals, curvature, etc., present on the surface. Surface roughness is expressed through various parameters, and the parameters of surface roughness refer to Ra (arithmetic mean roughness), Rt (overall height), and Rz (ten-point mean roughness).

[0033] The metal layer in the manufacturing of the cell pouch film can fall within the aforementioned surface roughness range. In the prior art, the smoother the surface of the metal layer of the cell pouch film, the lower the bubble generation rate was when bonding it with the first resin layer, as described later. However, this required additional steps for surface roughening or increased the cost of the metal layer during surface roughening. By incorporating the surface treatment layer according to one embodiment of the present invention onto the metal layer, the bubble generation rate can be dramatically reduced.

[0034] A corrosion-preventive treatment layer may be further formed on the metal layer. This corrosion-preventive treatment layer is basically formed to prevent corrosion of the aluminum foil layer by an electrolyte or hydrofluoric acid.

[0035] Examples of corrosion prevention treatments include degreasing, hydrothermal modification, anodizing, chemical conversion, coating-type corrosion prevention treatments involving the application of a coating agent with corrosion-preventive properties, or combinations of two or more of these treatments.

[0036] The thickness of the metal layer may be between 10 and 100 μm, taking into consideration processability, oxygen and moisture barrier properties, etc. For example, the thickness of the metal layer may be 10 μm or more, 11 μm or more, 12 μm or more, 13 μm or more, 14 μm or more, 15 μm or more, 16 μm or more, 20 μm or more, 21 μm or more, 25 μm or more, 100 μm or less, 90 μm or less, 85 μm or less, 80 μm or less, 75 μm or less, 70 μm or less, 69 μm or less, 68 μm or less, 67 μm or less, 66 μm or less, or 65 μm or less. If the thickness does not meet the above range, if it is less than 10 μm, it will easily break and will have poor electrolytic resistance and insulation properties, and if it exceeds 100 μm, there will be problems with poor moldability.

[0037] In the cell pouch film of the present invention, the second resin layer is the innermost layer and is a layer that seals the battery elements by being heat-welded to the other internal resin layers during battery assembly. The second resin layer may be a single layer or may be formed in multiple layers.

[0038] The second resin layer is not particularly limited as long as it is heat-weldable, but it may be composed of a resin layer containing one or more selected from the group consisting of polyolefins, polybutylenes, ethylene copolymers, propylene copolymers, polyesters, polyamides, polycarbonates, fluorine-based resins, silicone-based resins, cyclic polyolefins, carboxylic acid-modified cyclic polyolefins, acrylics, ethylene-propylene-diene-monomer rubber (EPDM), and polyolefin ketone copolymers.

[0039] Specific examples of the polyolefin system include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymer of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymer of propylene and ethylene); and ethylene-butene-propylene ternary copolymers. Among these polyolefins, polyethylene or polypropylene is preferred. The polypropylene may be unoriented polypropylene (cPP). When a polyolefin such as polyethylene or polypropylene is used in the internal resin layer, it can have the physical properties required for secondary battery packaging materials, such as good heat sealability, moisture resistance, and heat resistance.

[0040] The second resin layer may be selectively multilayered. For example, it may consist of an inner layer of extruded polypropylene (PP) with an outermost layer of unstretched polypropylene (cPP).

[0041] The thickness of the second resin layer may be 20 to 100 μm, taking into consideration moldability, insulation properties, and electrolyte resistance. For example, the thickness of the second resin layer may be 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 41 μm or more, 42 μm or more, 43 μm or more, 44 μm or more, 45 μm or more, 100 μm or less, 95 μm or less, 90 μm or less, 89 μm or less, 88 μm or less, 87 μm or less, 86 μm or less, or 85 μm or less. If the thickness does not meet the above range, problems may arise such as inferior moldability, insulation properties, and electrolyte resistance.

[0042] In one embodiment of the present invention, the surface treatment layer may be formed between the first resin layer and the metal layer. In order to improve the adhesive stability between the first resin layer and the metal layer and to suppress the formation of a bubble layer, it is preferable that the surface treatment layer is formed on the metal layer before the first resin layer is formed. The surface treatment layer may be formed from a surface treatment composition, which may contain a main agent, a curing agent, and a solvent.

[0043] The main component may include a polyester resin or a polyurethane resin. Specifically, the polyester resin may include one or more selected from the group consisting of unsaturated polyester resin, saturated polyester resin, ortho polyester resin, iso polyester resin, tere polyester resin, and hydroxyl-functional polyester resin.

[0044] Furthermore, the polyurethane resin may specifically include one or more selected from the group consisting of acrylic polyol, polyester polyol, polyether polyol, caprolactone polyol, polybutadiene polyol, and polyacrylate polyol.

[0045] The curing agent may be an isocyanate compound, and specifically, examples of isocyanate compounds include polyisocyanates, their adducts, their isocyanurate modified forms, their carbodiimide modified forms, their allophanate modified forms, and their biuret modified forms. Specifically, examples of polyisocyanates include diphenylmethane diisocyanate (MDI), polyphenylmethane diisocyanate (polymeric MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), bis(4-isocyanate cyclohexyl)methane (H12MDI), isophorone diisocyanate (IPDI), 1,5-naphthalene diisocyanate (1,5-NDI), and 3,3'-dimethyl-4. Examples include aromatic diisocyanates such as 4'-diphenylenediisocyanate (TODI) and xylenediisocyanate (XDI); aliphatic diisocyanates such as trimethylenediisocyanate, hexamethylenediisocyanate, trimethylhexamethylenediisocyanate, and isophorone diisocyanate; and ring-type diisocyanates such as 4,4'-methylenebis(cyclohexyl isocyanate) and isophorone diisocyanate.

[0046] Specifically, examples of the adduct bodies include those obtained by adding trimethylolpropane, glycol, etc., to the polyisocyanate. Among these isocyanate compounds, polyisocyanates and their adduct bodies are preferred; more preferably aromatic diisocyanates, their adduct bodies, and their isocyanurate modified forms; more preferably MDI, polymeric MDI, TDI, their adduct bodies, and their isocyanurate modified forms; particularly preferred are adduct bodies of MDI, adduct bodies of TDI, polymeric MDI, and isocyanurate modified forms of TDI. These isocyanate compounds may be used individually or in combination of two or more. The solvent may include one or more compounds selected from the group consisting of acetate compounds, ketone compounds, and aromatic hydrocarbon compounds.

[0047] The acetate compound may include one or more selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, amyl acetate, hexyl acetate, isopropyl acetate, isobutyl acetate, glycol ether PM acetate, glycol ether EB acetate, and glycol ether DPM acetate.

[0048] The ketone compound may include one or more selected from the group consisting of methyl ethyl ketone (MEK), acetone, methyl isobutyl ketone (MIBK), cyclohexanone, diacetone alcohol, methyl isoamyl ketone, methyl n-amyl ketone, diethyl ketone, methyl n-propyl ketone, diisobutyl ketone, and methyl n-butyl ketone.

[0049] The aromatic hydrocarbon compound may include one or more selected from the group consisting of toluene, xylene, ortho-xylene, Solvarex 9A, Solvarex 10A, Solvarex 9LC, Solvarex 10LN, benzene, ethylbenzene, cumene, and styrene. The surface treatment composition may contain 50 to 70 parts by weight of the main component, 4 to 8 parts by weight of the curing agent, and 20 to 50 parts by weight of the solvent.

[0050] The thickness of the surface treatment layer may be 2 to 10 μm. For example, the thickness of the surface treatment layer may be 2 μm or more, 3 μm or more, 3.1 μm or more, 3.2 μm or more, 3.3 μm or more, 3.4 μm or more, 3.5 μm or more, 10 μm or less, 9 μm or less, 8 μm or less, 7 μm or less, or 5 μm or less. Only by being included within the above range can the capillary value be included within the range according to one embodiment of the present invention.

[0051] A surface treatment layer can be formed on the metal layer with the composition and content of the surface treatment composition described above. The capillary number of the formed surface treatment layer may be 0.5 to 5. For example, the capillary number of the surface treatment layer may be 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.1 or more, 1.2 or more, 5.0 or less, 4.5 or less, 4.4 or less, 4.3 or less, 4.2 or less, 4.1 or less, 4.0 or less, 3.9 or less, 3.8 or less, 3.7 or less, 3.6 or less, 3.5 or less, 3.4 or less, 3.3 or less, 3.2 or less, 3.1 or less, or 3.0 or less.

[0052] The capillary number is a dimensionless number used in fluid dynamics that indicates the relative importance of viscous force and surface tension. It is defined as the product of the fluid viscosity (μ) and the substrate velocity (V) divided by the surface tension (γ) (Ca = μV / γ), and is a numerical value that can play an important role in understanding and predicting fluid flow, especially fluid behavior at interfaces.

[0053] If the capillary value of the surface treatment layer according to one embodiment of the present invention is less than the range mentioned above, the fluidity of the surface treatment layer may increase too much, making it difficult to form a uniform coating layer. If it exceeds the range mentioned above, the viscosity of the surface treatment layer may become too high, causing non-uniformity of the treatment layer and reducing the adhesion strength to the first resin layer. Furthermore, non-uniformity may occur due to high surface tension, potentially leading to a high rate of bubble generation between the first resin layer and the metal layer.

[0054] In other words, by including the capillary value within the range described above, it is possible to provide sufficient time for air bubbles to escape when forming the surface treatment layer on the metal layer and the first resin layer, thereby significantly reducing the rate of air bubble generation.

[0055] As shown in Figure 1, the bubbles 40 can occur between the metal layer 10 and the surface treatment layer 20, or between the surface treatment layer 20 and the first resin layer 30. The bubble generation rate can be calculated as "area of ​​bubbles generated / total area measured * 100 (%)". According to one embodiment of the present invention, the bubble generation rate can be less than 3%, preferably less than 2%, more preferably less than 1%, and particularly preferably less than 0.5%. If the bubble generation is reduced to below the above range, the adhesive surface between the first resin layer and the metal layer can be uniform, thereby improving the durability of the resulting cell pouch film. Furthermore, the present invention can provide the following manufacturing method in order to ensure the capillary values ​​described above.

[0056] Specifically, the method for manufacturing a cell pouch film of the present invention may include the steps of forming a surface treatment layer on the metal layer and forming the first resin layer on the surface treatment layer, in a cell pouch film comprising a first resin layer, a metal layer and a second resin layer.

[0057] Preferably, in order to ensure the capillary number, a heat treatment step may be further included after forming the surface treatment layer on the metal layer and before forming the first resin layer. Specifically, the heat treatment step may be carried out for 10 to 100 seconds at a temperature of 60 to 100°C after applying the surface treatment composition on the metal layer. Through the heat treatment, the substrate velocity, viscosity, and surface tension of the formed surface treatment layer can be adjusted, and in particular, heat treatment may be required to increase the viscosity value of the surface treatment composition, especially as a larger amount of solvent is included, in order to ensure an appropriate capillary number. Furthermore, the rate of bubble formation between the metal layer and the surface treatment layer can be reduced through the heat treatment step within the range described above. Through the heat treatment step within the range described above, the cell pouch film can be made to have high durability even under harsh conditions, such as 120°C high-temperature peel stability and long-term reliability evaluation.

[0058] The present invention will be described in detail below with reference to examples. However, the examples of the present invention can be modified into various other forms, and the scope of the present invention should not be interpreted as being limited to the examples detailed below. The examples of the present invention are provided to give a more complete explanation of the present invention to a person of average knowledge in the art.

[0059] Examples and Comparative Examples Example 1

[0060] A 4 μm thick surface treatment layer was formed on the first surface of a 60 μm thick aluminum foil as the metal layer, using a surface treatment composition with the composition, content, and conditions shown in Table 1. A 12 μm thick PET film and a 25 μm thick nylon film were bonded together as the first resin layer, and then the nylon film surface of the first resin layer and the first surface of the aluminum foil were bonded together using a solvent dry lamination method. A 30 μm thick extruded polypropylene (PP) and a 50 μm thick unoriented polypropylene (cPP) were bonded together as the second resin layer, with the extruded polypropylene (PP) and the second surface of the aluminum foil facing each other, using a sandwich lamination method to produce a cell pouch film.

[0061] Examples 2-10 and Comparative Examples 1-3

[0062] Examples 2-8 and Comparative Examples 1-3 were manufactured in the same manner as in Example 1, except that the conditions were different as shown in Table 1 below.

[0063] In Examples 6 to 8 below, the manufacturing process was the same as in Example 1, but after forming the surface treatment composition on the metal layer, heat treatment was performed at 70°C for 20 seconds. Thereafter, the first resin layer was formed.

[0064] [Table 1]

[0065] Experimental example Experimental Example 1: Evaluation of Bubble Generation Rate

[0066] The cell pouch films produced in the above examples and comparative examples were cut to a size of 15 mm x 25 mm, and then photographed with a Leica DM2700 P product to measure the rate of bubble formation. Figure 2 shows a photograph of Example 1, Figure 3 shows a photograph of Example 2, Figure 4 shows a photograph of Example 3, and Figure 5 shows a photograph of Comparative Example 1. Bubble area / Total measurement area * 100 (%)

[0067] Experimental Example 2: Long-term reliability evaluation

[0068] The long-term reliability of the manufactured examples and comparative examples was evaluated. To replace battery evaluation, which must be conducted for a minimum of 6 months to 10 years, the long-term reliability evaluation was performed under harsh conditions (85°C / 85RH%) for 4 weeks. First, each sample of the examples and comparative examples was molded to the same size using a test mold (16cm x 9cm) from Kurimura Chemical Co., Ltd. Ten of each molded sample were produced and then stored at 85°C / 85RH%, and the presence or absence of delamination between the metal layer (aluminum foil) and the first resin layer film was visually inspected. Samples showing lifting or delamination were marked as NG, and the number of deteriorated samples out of the 10 samples was counted.

[0069] Experimental Example 3: Evaluation of Peel Strength

[0070] The peel strength of the metal layer / first resin layer of the cell pouches manufactured in the above examples and comparative examples was measured at 25°C and 120°C using a chamber-type UTM machine in a high-temperature environment. The mean and standard deviation were calculated after 10 measurements.

[0071] Experimental Example 4: Evaluation of Coating Uniformity

[0072] The weight of the first resin layer per unit area of ​​the cell pouch film in the above examples and comparative examples was measured 10 times, and the mean and standard deviation were calculated. The results of Experimental Examples 1 to 4 are shown in Table 2.

[0073] [Table 2] [Explanation of Symbols]

[0074] 10: Metal layer 20: Surface treatment layer 30: 1st resin layer 40: Bubbles

Claims

1. A cell pouch film comprising a first resin layer, a metal layer, and a second resin layer, A surface treatment layer is included between the first resin layer and the metal layer. The capillary value of the surface treatment layer is 0.5 to 5. A film for cell pouches characterized by the following features.

2. The aforementioned metal layer meets the following conditions (1) to (3): (1) The surface roughness (Ra) value of the metal layer is 0.2 μm or greater. (2) The surface roughness (Rt) value of the metal layer is 1.5 μm or more. (3) Surface roughness (Rz) value of the metal layer is 2.0 μm or more. Satisfy at least one of the following conditions The film for cell pouches according to claim 1.

3. The rate of bubble generation between the first resin layer and the metal layer of the cell pouch film is less than 3%. The film for cell pouches according to claim 1.

4. The first resin layer comprises at least one of polyester resin or polyamide resin. The film for cell pouches according to claim 1.

5. The metal layer includes one or more selected from the group consisting of aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), stainless steel (SUS), tin (Sn), zinc (Zn), indium (In), tungsten (W), titanium (Ti), and Invar (INVAR). The film for cell pouches according to claim 1.

6. The second resin layer contains a resin selected from the group consisting of polyolefins, polybutylenes, ethylene copolymers, propylene copolymers, polyesters, polyamides, polycarbonates, fluorine-based resins, silicone-based resins, cyclic polyolefins, carboxylic acid-modified cyclic polyolefins, acrylics, ethylene-propylene-diene-monomer rubber (EPDM), and polyolefin ketone copolymers. The film for cell pouches according to claim 1.

7. The surface treatment layer is formed from a surface treatment composition. The film for cell pouches according to claim 1.

8. The surface treatment composition comprises a main component, a curing agent, and a solvent. The cell pouch film according to claim 7.

9. The main component includes a polyester resin or a polyurethane resin. The cell pouch film according to claim 8.

10. The curing agent includes an isocyanate compound. The cell pouch film according to claim 8.

11. The solvent comprises one or more compounds selected from the group consisting of acetate compounds, ketone compounds, and aromatic hydrocarbon compounds. The cell pouch film according to claim 8.

12. The surface treatment composition, Based on 50 to 70 parts by weight of the main component 4 to 8 parts by weight of the curing agent and The solvent comprises 20 to 50 parts by weight of the aforementioned solvent. The cell pouch film according to claim 8.

13. A cell pouch film comprising a first resin layer, a metal layer, and a second resin layer, The steps of forming a surface treatment layer on the metal layer and The step includes forming a first resin layer on the surface treatment layer, The capillary value of the surface treatment layer is 0.5 to 5. A method for manufacturing a film for cell pouches, characterized by the following:

14. The aforementioned surface treatment layer is formed from a surface treatment composition, The surface treatment composition comprises a main component, a curing agent, and a solvent. A method for manufacturing a cell pouch film according to claim 13.

15. The surface treatment composition, Based on 50 to 70 parts by weight of the main component 4 to 8 parts by weight of the curing agent and The solvent comprises 20 to 50 parts by weight of the aforementioned solvent. A method for manufacturing a cell pouch film according to claim 14.

16. The step of forming a surface treatment layer on the metal layer is: A surface treatment composition is applied to the metal layer. Perform heat treatment at a temperature of 60-100°C for 10-100 seconds. A method for manufacturing a cell pouch film according to claim 14.

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