Secondary battery pouch film with excellent high-temperature moldability, and manufacturing method therefor

Abstract

The present invention provides a secondary battery pouch film comprising: a metal barrier layer; a first adhesive layer formed on an upper surface of the metal barrier layer; a protective layer bonded to the upper surface of the metal barrier layer by means of the first adhesive layer; a second adhesive layer formed on a lower surface of the metal barrier layer; and an inner substrate layer bonded to the lower surface of the metal barrier layer by means of the second adhesive layer, wherein an amide-based lubricating coating layer is formed on an upper surface of the protective layer. In addition, the present invention provides a method for manufacturing the secondary battery pouch film, comprising the steps of: forming a first adhesive layer on an upper surface of a metal barrier layer; bonding a protective layer to the upper surface of the metal barrier layer by means of the first adhesive layer as an adhesive; forming a second adhesive layer on a lower surface of the metal barrier layer; bonding an inner substrate layer to the lower surface of the metal barrier layer by means of the second adhesive layer as an adhesive; and forming an amide-based lubricating coating layer on an upper surface of the protective layer.

Description

Pouch film for secondary batteries with excellent high-temperature moldability and method for manufacturing the same

[0001] The present invention relates to a pouch film for a secondary battery that improves high-temperature moldability by reducing the coefficient of friction of the surface of the protective layer, and a method for manufacturing the same.

[0002] Pouch-type lithium secondary batteries have a structure in which electrodes and an electrolyte are sealed inside a pouch made of a thin, flexible plastic film and a metal foil. This structure is widely used in various devices such as electric vehicles, smartphones, and laptops because it has the advantages of being lightweight, having high energy density, and being designable in various shapes.

[0003] Pouch film is used as the outer casing for such pouch-type lithium secondary batteries. As a critical component determining the safety and performance of lithium-ion batteries, typical pouch film has a multilayer structure and is mainly composed of an outermost protective layer, an adhesive layer, a barrier metal layer (aluminum), an adhesive layer, and an inner substrate layer.

[0004] PET (Polyethylene terephthalate) film is mainly used as the protective layer due to its excellent mechanical strength, chemical resistance, and other properties.

[0005] In the manufacturing process of a pouch-type lithium secondary battery, a press forming process is performed to create an internal space of the pouch, and Fig. 1 is an example diagram illustrating the press forming process of a pouch film for a secondary battery.

[0006] Referring to FIG. 1, when a pouch film (10) for a secondary battery is placed on a press bed (20) in which a concave portion (40) is formed at a high temperature of about 80°C and the pouch film (10) for a secondary battery is formed by applying pressure with a press slide (30), a strong frictional force may be generated at the parts (A, B) where the protective layer of the pouch film (10) for a secondary battery and the press bed (20) come into contact. In particular, the temperature around 80°C is close to the glass transition temperature of the PET film, so the mechanical strength of the PET film may decrease, making the PET film more vulnerable to friction with the press bed (20). This may cause the PET film to tear or its surface to be damaged, which may reduce the airtightness and durability of the pouch and cause defects.

[0007] Therefore, there is a need for a new solution that can effectively prevent damage caused by friction during the high-temperature molding process while maintaining the basic physical properties of PET films.

[0008] [National R&D projects that supported this invention]

[0009] [Project ID] 2410004468

[0010] [Assignment No.] 20022450

[0011] [Ministry Name] Ministry of Trade, Industry and Energy

[0012] [Project Management (Specialized) Agency Name] Korea Institute of Industrial Technology Planning and Evaluation

[0013] [Research Project Name] Development of Materials and Components Technology (Leading Company)

[0014] [Research Project Title] Development of a next-generation secondary battery pouch capable of achieving more than twice the adhesive strength (60)

[0015] [Research Period] 2024.01.01 ~ 2024.12.31

[0016] [Prior Art Literature]

[0017] [Patent Literature]

[0018] Republic of Korea Registered Patent No. 10-2662512

[0019] The problem that the present invention aims to solve is to resolve the issue of the pouch film tearing or its surface being damaged when forming the pouch film during the manufacturing process of a pouch-type lithium secondary battery by providing a pouch film for a secondary battery with improved high-temperature moldability by reducing the coefficient of friction of the surface of the protective layer and a method for manufacturing the same.

[0020] To solve the above problem, the present invention provides a pouch film for a secondary battery comprising a metal barrier layer, a first adhesive layer formed on the upper surface of the metal barrier layer, a protective layer adhered to the upper surface of the metal barrier layer by the first adhesive layer, a second adhesive layer formed on the lower surface of the metal barrier layer, and an internal substrate layer adhered to the lower surface of the metal barrier layer by the second adhesive layer, wherein an amide-based lubricating coating layer is formed on the upper surface of the protective layer.

[0021] In addition, the present invention provides a method for manufacturing a pouch film for a secondary battery, comprising the steps of preparing a metal barrier layer, forming a first adhesive layer on the upper surface of the metal barrier layer and adhering a protective layer, forming a second adhesive layer on the lower surface of the metal barrier layer and adhering an internal substrate layer, and forming an amide-based lubricating coating layer on the upper surface of the protective layer.

[0022] Through the pouch film for a secondary battery and the method for manufacturing the same according to the present invention, by using an amide-based lubricating coating layer to reduce the coefficient of friction between the protective layer and the press machine, the problem of the protective layer tearing or the surface being damaged when press molding in a high-temperature environment can be effectively reduced, and the low coefficient of friction of the lubricating coating layer can be maintained for a long period of time, thereby providing an advantageous effect for the storage and distribution of the pouch film for a secondary battery.

[0023] Figure 1 is an example diagram illustrating the press forming process of a pouch film for a secondary battery.

[0024] FIG. 2 shows the structure of a pouch film for a secondary battery according to one embodiment of the present invention.

[0025] Hereinafter, various embodiments of the present invention are described with reference to the accompanying drawings. The present invention is not limited to specific embodiments and should be understood to include various modifications, equivalents, and / or alternatives of the embodiments of the present invention. In relation to the description of the drawings, similar reference numerals may be used for similar components.

[0026] In this document, expressions such as "have," "can have," "include," or "can include" refer to the existence of the relevant feature (e.g., numerical values, functions, actions, or components, etc.) and do not exclude the existence of additional features.

[0027] In this document, expressions such as “A or B,” “at least one of A or / and B,” or “one or more of A or / and B” may include all possible combinations of items listed together. For example, “A or B,” “at least one of A and B,” or “at least one of A or B” may refer to cases including (1) at least one A, (2) at least one B, or (3) both at least one A and at least one B.

[0028] As used in this document, the expression "configured to" may be replaced, depending on the context, with, for example, "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."

[0029] The terms used in this document are used merely to describe specific embodiments and are not intended to limit the scope of other embodiments. Singular expressions may include plural expressions unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as generally understood by those skilled in the art described in this document. Terms used in this document that are defined in general dictionaries may be interpreted as having the same or similar meaning as they have in the context of the relevant technology, and are not to be interpreted in an ideal or overly formal sense unless explicitly defined in this document. In some cases, even terms defined in this document may not be interpreted to exclude the embodiments of this document.

[0030] The embodiments disclosed in this document are presented for the purpose of explaining and understanding the disclosed technical content and are not intended to limit the scope of the invention. Accordingly, the scope of this document should be interpreted to include all modifications or various other embodiments based on the technical concept of the invention.

[0031] Hereinafter, preferred embodiments of the present invention will be described in detail. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, and should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0032] Therefore, it should be understood that 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, and that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0033] Throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0034] The present invention will be described in detail below.

[0035] In this specification, the term "pouch" has the broadest meaning and includes all devices in which cell components, such as an anode, a cathode, and a separator, are impregnated with an electrolyte and housed therein, and which are processed into pocket or box shapes using a laminated film structure that takes into account gas barrier properties, flexibility, electrolyte resistance, and heat sealability to house said cell components.

[0036] A pouch-type secondary battery specifically refers to a lithium secondary battery, which has a polymer electrolyte and generates current through the movement of lithium ions, and refers to the use of a pouch film in which a polymer and a metal barrier layer are laminated as an outer material for packaging to protect such a secondary battery. This pouch film is configured with a metal barrier layer interposed therein to protect the battery cell, which consists of the electrode assembly and the electrolyte filled inside through a subsequent process, and to stably maintain the electrochemical properties of the cell, and a protective layer (external resin layer) may be formed on the metal barrier layer to protect the battery cell from external impact.

[0037]

[0038] FIG. 2 shows the structure of a pouch film for a secondary battery according to one embodiment of the present invention.

[0039] Referring to FIG. 2, the present invention provides a pouch film for a secondary battery comprising a metal barrier layer (1), a first adhesive layer (2) formed on the upper surface of the metal barrier layer (1), a protective layer (3) that is bonded to the upper surface of the metal barrier layer (1) by the first adhesive layer (2), a second adhesive layer (4) formed on the lower surface of the metal barrier layer (1), and an internal substrate layer (5) that is bonded to the lower surface of the metal barrier layer (1) by the second adhesive layer (4), wherein an amide-based lubricating coating layer (6) is formed on the upper surface of the protective layer (3).

[0040] Each component of the present invention will be described in detail below.

[0041]

[0042] Since the protective layer (3) corresponds to a part that comes into direct contact with the hardware, it is preferable that it be a resin having insulating properties. Therefore, as the resin used for the protective layer (3), it is preferable to use a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymer polyester, or polycarbonate, or to use a polyamide resin. The protective layer (3) may be a single layer or a multilayer structure of two or more layers.

[0043] Specifically, polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), copolymer polyester, and polycarbonate (PC). Specifically, polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, polycarbonate, copolymer polyesters based on repeating units of ethylene terephthalate, copolymer polyesters based on repeating units of butylene terephthalate, etc.

[0044] In addition, copolymer polyesters based on ethylene terephthalate as the main repeating unit include, specifically, copolymer polyesters polymerized with ethylene isophthalate based on 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), polyethylene (terephthalate / decanedicarboxylate), etc.

[0045] In addition, copolymer polyesters based on butylene terephthalate as the main repeating unit include, specifically, copolymer polyesters polymerized with butylene isophthalate based on butylene terephthalate as the main repeating unit, polybutylene (terephthalate / adipate), polybutylene (terephthalate / sebacate), polybutylene (terephthalate / decandicarboxylate), polybutylene naphthalate, etc. These polyesters may be used individually or in combination of two or more types.

[0046] As polyamide resins, specifically, aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; aromatic polyamides such as hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, nylon 6I6T (where I represents isophthalic acid and T represents terephthalic acid) comprising constituent units derived from terephthalic acid and / or isophthalic acid, and polyamides comprising aromatics such as polymethaxyleneadipamide (MXD6); and alicyclic polyamides such as polyaminomethylcyclohexyladipamide (PACM6). Examples include polyamides copolymerized with lactam components or isocyanate components such as 4,4'-diphenylmethane-diisocyanate, polyesteramide copolymers or polyetheresteramide copolymers which are copolymers of copolymerized polyamides with polyesters or polyalkylene ether glycols; and these copolymers. This polyamide may be used in a single type or in combination of two or more types.

[0047] The thickness of the protective layer (3) is preferably 10 to 40 μm or more, and is particularly preferably 12 to 27 μm. If the above range is not satisfied, if it is less than 10 μm, the physical properties are poor and it tears easily, and if it exceeds 40 μm, there is a problem that the moldability is poor.

[0048]

[0049] The metal barrier layer (1) 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 metal thin film. Specifically, the metal barrier layer (1) may include 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.

[0050] The material of the metal barrier layer (1) is preferably aluminum or stainless steel. For the aluminum alloy, an alloy in which various metals and non-metals are added to pure aluminum can be used. The aluminum layer can preferably be a soft aluminum foil.

[0051] The above aluminum substrate may optionally be an alloy comprising an element 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.

[0052] The stainless steel mentioned above is an iron-based alloy that can be manufactured to possess properties suitable for specific applications through a combination of various elements. Iron (Fe) is the base element of stainless steel, forming the matrix of the alloy and providing structural strength and ductility. Chromium (Cr) is a key element of stainless steel; present in an amount of at least 10.5%, it forms a protective oxide film on the surface to prevent corrosion. Nickel (Ni) can improve strength, ductility, and toughness, and provide high-temperature resistance. Carbon (C) can play a role in increasing strength and hardness. Molybdenum (Mo) can enhance corrosion resistance, particularly in environments containing chlorides, and improve high-temperature strength and creep resistance. Manganese (Mn) improves strength and can serve as a substitute for nickel in some grades. Nitrogen (N) can help improve strength. Titanium (Ti) and niobium (Nb) can play a role in improving stability in certain grades.

[0053] The stainless steel mentioned above can be classified primarily into austenitic, ferritic, martensitic, and duplex types based on its metal structure. Austenitic stainless steel is the most widely used, with grades 304 and 316 being examples. 304 contains 18% chromium and 8% nickel, while 316 has higher corrosion resistance due to the addition of molybdenum. Ferritic stainless steel is widely used for cost-effectiveness due to its high chromium content and almost no nickel. Grade 430 is a representative 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.

[0054] The metal foil used in the metal barrier layer (1) may be etched or degreased on its surface to improve adhesion with the internal substrate layer described later, but this may be omitted to reduce the process speed.

[0055] A corrosion-prevention treatment layer (not shown) may be additionally formed on the metal barrier layer (1). The corrosion-prevention treatment layer is basically a layer formed to prevent corrosion of the aluminum foil layer by an electrolyte or hydrofluoric acid.

[0056] As corrosion prevention treatments, examples include degreasing treatment, hydrothermal modification treatment, anodic oxidation treatment, chemical treatment, a coating-type corrosion prevention treatment in which a coating agent having corrosion prevention performance is applied, or a combination of two or more of these treatments.

[0057] Considering processability, oxygen and moisture blocking properties, etc., the thickness of the metal barrier layer (1) is preferably 10 to 100 μm, and more preferably 30 to 80 μm. If the above range is not satisfied, if it is less than 10 μm, it tears easily, and the electrostatic resistance and insulation properties decrease, and if it exceeds 100 μm, there is a problem of reduced moldability.

[0058]

[0059] The inner substrate layer (5) may comprise a resin or derivative thereof comprising one or more selected from the group consisting of polypropylene (PP) resin, polyethylene (PE) resin, ethylene vinyl acetate (EVA) resin, ethylene / propylene copolymer resin and ethylene / propylene / butadiene terpolymer resin.

[0060] The inner substrate layer (5) corresponds to the innermost layer, and when assembling the battery, the upper pouch film and the lower pouch film are joined by heat fusion, etc. At this time, the inner substrate layer of the upper pouch film and the inner substrate layer of the lower pouch film are joined by heat fusion, thereby sealing the battery element. The inner substrate layer (5) may be a single layer or a multi-layer structure of two or more layers.

[0061] The inner substrate layer (5) may be composed of a resin layer comprising one or more selected from the group consisting of polyolefin-based, polybutylene-based, ethylene copolymer, propylene copolymer, polyester-based, polyamide-based, polycarbonate-based, fluorine-based, silicone-based, cyclic polyolefin, carboxylic acid modified cyclic polyolefin, acrylic-based, ethylene-propylene-diene-monomer rubber (EPDM), and polyolefin ketone copolymer, provided that heat fusion is possible, although not particularly limited thereto. Preferably, it may be composed of a polyolefin-based resin layer, a polyolefin ketone, and an elastomer mixed resin layer.

[0062] Specific examples of the above polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); and ternary copolymers of ethylene-butene-propylene. Among these polyolefins, polyethylene or polypropylene is preferably used. In addition, the polypropylene may be unoriented polypropylene (cPP). When a polyolefin such as polyethylene or polypropylene is used in the inner substrate layer (5), it may have physical properties required as a packaging material for secondary batteries, such as good heat sealability, moisture resistance, and heat resistance.

[0063] The thickness of the inner substrate layer (5) is preferably 20 to 100 μm, and more preferably 40 to 90 μm, considering moldability, insulation, and electrolyte resistance. If the above range is not satisfied, problems may arise such as reduced moldability, insulation, and electrolyte resistance.

[0064]

[0065] The first adhesive layer (2) is intended to increase the adhesion between the protective layer (3) and the metal barrier layer (1). In order to improve the adhesive stability between the protective layer (3) and the metal barrier layer (1) and to suppress the formation of bubbles, it is preferable that the protective layer (3) be formed after the first adhesive layer (2) is formed on the metal barrier layer (1).

[0066] The first adhesive layer (2) may be formed from a composition comprising a main component, a curing agent, and a solvent.

[0067] The above subject may include polyester resin or 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.

[0068] In addition, specifically, the above polyurethane resin may include one or more selected from the group consisting of acrylic polyol, polyester polyol, polyether polyol, caprolactone polyol, polybutadiene polyol, and polyacrylate polyol.

[0069] The above curing agent may be an isocyanate-based compound, and specifically, examples of isocyanate-based compounds include polyisocyanates, their adducts, their isocyanurate modifieds, their carbodiimide modifieds, their allophanate modifieds, their biuret modifieds, etc. The above polyisocyanates include, specifically, aromatic diisocyanates such as diphenylmethane diisocyanate (MDI), polyphenylmethane diisocyanate (polymeric MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), bis(4-isocyanatecyclohexyl)methane (H12MDI), isophorone diisocyanate (IPDI), 1,5-naphthalene diisocyanate (1,5-NDI), 3,3'-dimethyl-4,4'-diphenylene diisocyanate (TODI), and xylene diisocyanate (XDI); and aliphatic diisocyanates such as tramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and isophorone diisocyanate; Examples include cycloaliphatic diisocyanates such as 4,4'-methylenebis(cyclohexyl isocyanate) and isophorone diisocyanate.

[0070] Specifically, the above-mentioned adduct may be a polyisocyanate to which trimethylolpropane, glycol, etc., have been added. Among these isocyanate-based compounds, preferably polyisocyanates and their adducts; more preferably aromatic diisocyanates, their adducts, and their isocyanurate modifieds; even more preferably MDI, polymeric MDI, TDI, their adducts, and their isocyanurate modifieds; particularly preferably, MDI adducts, TDI adducts, polymeric MDI, and TDI isocyanurate modifieds. These isocyanate-based compounds may be used as a single type or in combination of two or more types.

[0071] The above solvent may include one or more selected from the group consisting of acetate compounds, ketone compounds and aromatic hydrocarbon compounds.

[0072] The above acetate-based 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.

[0073] The above ketone-based compounds 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.

[0074] The above 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.

[0075] The thickness of the first adhesive layer (2) is preferably 2 to 10 μm, and more preferably 3 to 5 μm, considering the adhesion with the protective layer and the thickness after molding. If the above range is not satisfied, the adhesion is reduced if it is less than 2 μm, and problems such as cracking may occur if it exceeds 10 μm.

[0076]

[0077] The second adhesive layer (4) is intended to increase the adhesion between the inner substrate layer (5) and the metal barrier layer (1), and the second adhesive layer (4) may be polyurethane, acid-modified polyolefin resin, or epoxy. Specific examples of the second adhesive (4) may include maleic anhydride polypropylene (MAHPP).

[0078] The second adhesive layer (4) is preferably 2 to 10 μm, and more preferably 3 to 5 μm, considering the adhesion with the inner substrate layer (5) and the thickness after molding. If the above range is not satisfied, the adhesion is reduced if it is less than 2 μm, and problems such as cracking may occur if it exceeds 5 μm. When laminating the inner substrate layer (5) and the metal barrier layer (1) using the second adhesive layer (4), there are no special limitations, but preferably, the lamination can be performed by laminating using a dry lamination method, a heat lamination method, or an extrusion lamination method.

[0079] The amide-based lubricating coating layer (6) is intended to prevent the surface of the protective layer (3) from being torn or damaged due to strong frictional force generated at the contact point between the protective layer (3) and the press bed when performing a press molding process at a high temperature of about 80°C by lowering the friction coefficient of the surface of the protective layer (3). It is required to have a low friction coefficient of 0.2 or less, maintain a low friction coefficient at high temperatures, and maintain long-term storage reliability in which the physical properties of the coating layer are maintained even during long-term storage.

[0080] The amide-based lubricating coating layer (6) can be formed by dissolving an amide-based lubricating composition in a solvent, coating it on a protective layer (3) using a known coating method, such as inline prestige coating, spin coating, bar coating, gravure coating, air knife coating, or roller coating, and then drying it at about 120 to 150°C for about 10 to 20 seconds. The coating thickness may be about 300 to 500 nm, and preferably about 400 to 500 nm. If the above range is not satisfied, there is a problem that the durability of the lubricating coating layer (6) may decrease if it is less than 300 nm, and the moldability may decrease if it exceeds 500 nm.

[0081] The above amide-based lubricating composition may include one or more selected from the group consisting of a saturated amide-based slip agent having 18 to 22 carbon atoms, an unsaturated amide-based slip agent having 20 to 24 carbon atoms, and a slip agent based on a dual amide structure.

[0082] The above saturated amide-based slip agent having 18 to 22 carbon atoms comprises stearamide, behenamide, or arachidamide, and the above unsaturated amide-based slip agent having 20 to 24 carbon atoms comprises erucamide, gadoleic amide, or selacholeic amide, and the above diamide structure-based slip agent comprises N,N'-bis-ethylene stearamide, N,N'-bis-ethylene oleamide, N,N'-bis-ethylene behenamide, N,N'-bis-ethylene erucamide, or N,N'-bis-propylene It may include stearamide (N,N'-bis propylene stearamide), N,N'-bis-butylene oleamide (N,N'-bis butylene oleamide), ethylene bis oleamide (EBO), or ethylene bis stearamide (EBS).

[0083] The above solvent may include organic solvents, alcohols, ketones, or esters, and specifically may include toluene, acetone, xylene, isopropanol, methanol, cyclohexanone, ethyl acetate, or butyl acetate, and preferably may include toluene.

[0084] The above amide-based lubricating composition may include one or more selected from the group consisting of a saturated amide-based slip agent having 18 to 22 carbon atoms, an unsaturated amide-based slip agent having 20 to 24 carbon atoms, and a slip agent based on a dual amide structure. More specifically, it is preferable to include a saturated amide-based slip agent having 18 to 22 carbon atoms and an unsaturated amide-based slip agent having 20 to 24 carbon atoms together, and it is even more preferable to include a saturated amide-based slip agent having 18 to 22 carbon atoms and an unsaturated amide-based slip agent having 20 to 24 carbon atoms together in a weight ratio of 1:4. By including one or more selected from the group consisting of a saturated amide-based slip agent having 18 to 22 carbon atoms, an unsaturated amide-based slip agent having 20 to 24 carbon atoms, and a slip agent based on a dual amide structure, the above amide-based lubricating composition can have the effect of having a significantly low coefficient of friction at room temperature and high temperature, and excellent long-term storage reliability and heat resistance.

[0085] The above amide-based lubricating composition is preferably blended in a ratio of about 0.2 to 1 weight percent relative to the total weight of the solvent blended with the above solvent, more preferably in a ratio of 0.3 to 0.7 weight percent, and most preferably in a ratio of 0.5 to 0.6 weight percent. If the composition falls outside the above range, if it is blended in a ratio of less than 0.2 weight percent, the coefficient of friction is high, which may cause the protective layer to tear or break during the press molding process, resulting in poor moldability and reduced heat resistance, which may cause thermal deformation at high temperatures. If it is blended in a ratio exceeding 1 weight percent, it is difficult to coat the lubricating coating layer to have a uniform and smooth surface, which may cause defects in the pouch film for secondary batteries and may cause thermal deformation at high temperatures.

[0086]

[0087] In addition, the present invention can provide a method for manufacturing a pouch film for a secondary battery having the above characteristics.

[0088] Specifically, a method for manufacturing a pouch film for a secondary battery according to one embodiment of the present invention may include the steps of: forming a first adhesive layer on the upper surface of a metal barrier layer; attaching a protective layer to the upper surface of the metal barrier layer using the first adhesive layer as an adhesive; forming a second adhesive layer on the lower surface of the metal barrier layer; attaching an internal substrate layer to the lower surface of the metal barrier layer using the second adhesive layer as an adhesive; and forming an amide-based lubricating coating layer on the upper surface of the protective layer.

[0089]

[0090] Hereinafter, the present invention will be described in detail with reference to examples in order to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0091]

[0092] Examples and Comparative Examples

[0093] A film for a pouch was produced using a sandwich lamination method. As a protective layer, a PET film with a thickness of 12 μm was formed with an average thickness of 4 μm using a polyurethane-based adhesive, and a nylon film with a thickness of 25 μm was laminated. As a metal barrier layer, an adhesive layer with a thickness of 4 μm was formed on the first surface of an aluminum foil with a thickness of 60 μm using a polyurethane-based adhesive, and the laminated film was stacked with the nylon film and the aluminum foil facing each other. Then, an unoriented polypropylene (CPP) layer was adhered to the second surface (opposite to the first surface) of the aluminum layer using extruded polypropylene (PP), and an inner protective layer was formed to a thickness of 80 μm.

[0094] After that, an amide-based lubricating composition was prepared with the composition of Table 1 below and coated onto the upper surface of the PET film using an inline prestige coating method, and dried at a temperature of 150°C for 20 seconds to form an amide-based lubricating coating layer having the thickness of Table 1 below, thereby manufacturing a film for a pouch.

[0095]

[0096] Solvent (Toluene, wt%) Lubricant Composition (wt%) Coating Thickness (nm) Saturated amide-based slip agent with 18–22 carbon atoms (Behenamide) Unsaturated amide-based slip agent with 20–24 carbon atoms (Erucamid) Dual amide structure-based slip agent (N,N'-Bis-ethylene Stearamide) Amide-based slip agent with 12–16 carbon atoms (Lauramide) Silicone-based slip agent (Silicone Oil) Total Lubricant Composition (wt%) Example 1: 99.50.10.40000.5400 Example 2: 99.50.20.30000.5400 Example 3: 99.50.40.10000.5400 Example 4: 99.50.40.1000.5400 Example 599.500.10.4000.5400 Example 699.50.10.30.1000.5400 Example 799.500.50000.5400 Example 899.50.500000.5400 Example 999.5000.5000.5400 Comparative Example 198.50.510001.5400 Comparative Example 298.5010.5001.5400 Comparative Example 399.900.10000.1400 Comparative Example 499.50.10.40000.5200 Comparative Example 599.50.10.40000.5650 Comparative Example 699.50000.500.5400 Comparative Example 799.500000.50.5400

[0097] Experimental Example

[0098] Experimental Example 1: Measurement of Room Temperature Friction Coefficient

[0099] The friction coefficients of the pouch films prepared in Examples 1 to 9, Comparative Examples 1 to 3, and Comparative Examples 6 to 7 were measured at room temperature according to the ISO 8295 method, and the results are shown in Table 2 below. The measurement conditions were a sled weight of 200g, a measurement speed of 100 mm / min, a measurement distance of 100 mm, and 5 repetitions, and the average value was calculated.

[0100]

[0101] Friction Coefficient Example 10.10 Example 20.12 Example 30.15 Example 40.16 Example 50.17 Example 60.14 Example 70.09 Example 80.16 Example 90.19 Comparative Example 10.21 Comparative Example 20.23 Comparative Example 30.39 Comparative Example 60.31 Comparative Example 70.40

[0102] Referring to Table 2 above, it was confirmed that the pouch films prepared in Examples 1 to 9 all had very low room temperature friction coefficients of less than 0.20, whereas the pouch films prepared in Comparative Examples 1 to 3 and 6 to 7 all had room temperature friction coefficients exceeding 0.20, and in particular, Comparative Examples 3 and 7 had significantly high friction coefficients.

[0103] Meanwhile, it was confirmed that the pouch films manufactured in Comparative Examples 1 and 2 had a surface of the lubricating coating layer that was not uniform and was not smooth, so the pouch films actually showed a surface condition close to a defect.

[0104]

[0105] Experimental Example 2: Friction Coefficient Long-term Storage Reliability

[0106] The pouch films prepared in Examples 1 to 9 and Comparative Examples 6 to 7 were stored at room temperature for one year, and then the friction coefficient was measured in the same manner as in Experimental Example 1, and the results are shown in Table 3 below.

[0107]

[0108] Friction coefficient measured immediately Friction coefficient measured after 1 year of storage Example 10.10 0.10 Example 20.12 0.12 Example 30.15 0.17 Example 40.16 0.17 Example 50.17 0.17 Example 60.14 0.14 Example 70.09 0.10 Example 80.16 0.18 Example 90.19 0.20 Comparative Example 60.31 0.33 Comparative Example 70.40 0.41

[0109] Referring to Table 3 above, it was confirmed that for all pouch films prepared in Examples 1 to 9 and Comparative Examples 6 to 7, the coefficient of friction after storage at room temperature for one year showed no change at all or only a slight increase.

[0110]

[0111] Experimental Example 3: Measurement of High-Temperature Friction Coefficient

[0112] The pouch films prepared in Examples 1 to 9 and Comparative Examples 6 to 7 were stored at 80°C for one week, and then the friction coefficient was measured in the same manner as in Experimental Example 1, and the results are shown in Table 4 below.

[0113]

[0114] Friction coefficient measured immediately Friction coefficient measured after storage at 80°C for 1 week Example 10.10 0.10 Example 20.12 0.14 Example 30.15 0.19 Example 40.16 0.17 Example 50.17 0.18 Example 60.14 0.15 Example 70.09 0.12 Example 80.16 0.18 Example 90.19 0.19 Comparative Example 60.31 0.42 Comparative Example 70.40 0.49

[0115] Referring to Table 4 above, it was confirmed that for the pouch films prepared in Examples 1 to 9, the coefficient of friction measured after storage at 80°C for one week showed no change at all or only a slight increase. However, for the pouch films prepared in Comparative Examples 6 to 7, it was confirmed that the coefficient of friction increased significantly after storage at 80°C for one week in all cases, indicating that the reliability of maintaining the coefficient of friction at high temperatures was low.

[0116]

[0117] Experimental Example 4: Moldability

[0118] The pouch films prepared in Examples 1 to 9 and Comparative Examples 1 to 7 were press-molded five times at 80°C to observe whether tearing of the protective layer occurred or if they were molded into the intended shape, and the results are shown in Table 5 below.

[0119]

[0120] Molding Observation Results Example 1: Not observed Example 2: Not observed Example 3: Not observed Example 4: Not observed Example 5: Not observed Example 6: Not observed Example 7: Not observed Example 8: Not observed Example 9: Not observed Comparative Example 1: Not observed Comparative Example 2: Not observed Comparative Example 3: Multiple tears in protective layer observed Comparative Example 4: Multiple tears in protective layer observed Comparative Example 5: Poor molding condition (failed to maintain intended shape) Comparative Example 6: Multiple tears in protective layer observed Comparative Example 7: Multiple tears in protective layer observed

[0121] Referring to Table 5 above, in the case of the pouch films prepared in Examples 1 to 9 and Comparative Examples 1 to 2, no phenomenon was found where the protective layer was torn or not formed into the intended shape during the molding process; however, in the case of the pouch films prepared in Comparative Examples 3 to 4 and 6 to 7, multiple torn areas were found in all of them, and in the case of Comparative Example 5, a phenomenon was found where the shape of the pouch film was not maintained after molding.

[0122] Experimental Example 5: Heat Resistance

[0123] The pouch films prepared in Examples 1 to 9, Comparative Examples 1 to 3 and 6 to 7 were placed in a high-temperature, high-pressure reactor and tested for 2 seconds at 225°C at a pressure of 0.3 MPa to observe whether thermal deformation occurred, and the results are shown in Table 6 below.

[0124]

[0125] Molding Observation Results Example 1: Not observed Example 2: Not observed Example 3: Not observed Example 4: Not observed Example 5: Not observed Example 6: Not observed Example 7: Not observed Example 8: Not observed Example 9: Not observed Comparative Example 1: Partial thermal deformation observed Comparative Example 2: Not observed Comparative Example 3: Multiple thermal deformation observed Comparative Example 6: Multiple thermal deformation observed Comparative Example 7: Multiple thermal deformation observed

[0126] Referring to Table 6 above, it was confirmed that the pouch films prepared in Examples 1 to 9 and Comparative Example 2 had relatively excellent thermal stability as no thermal deformation was observed, whereas the pouch films prepared in Comparative Examples 1, 3, 6 to 7 had some or many areas of thermal deformation, indicating poor thermal stability.

[0127] [Explanation of the symbol]

[0128] 1 : Metal barrier layer 2 : First adhesive layer

[0129] 3: Protective layer 4: Second adhesive layer

[0130] 5 : Internal substrate layer 6 : Amid-based lubricating coating layer

[0131] 10: Pouch film for secondary batteries 20: Press bed

[0132] 30: Press slide 40: Recess

Claims

Metal barrier layer; A first adhesive layer formed on the upper surface of the metal barrier layer; A protective layer that is bonded to the upper surface of the metal barrier layer by the first adhesive layer; A second adhesive layer formed on the lower surface of the metal barrier layer; and It includes an internal substrate layer that is bonded to the lower surface of the metal barrier layer by the second adhesive layer, A pouch film for a secondary battery, characterized in that an amide-based lubricating coating layer is formed on the upper surface of the above protective layer. In claim 1, A pouch film for a secondary battery, characterized in that the protective layer comprises one or more selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymer polyester, polycarbonate, and polyamide resin. In claim 1, A pouch film for a secondary battery, characterized in that the metal barrier layer comprises 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. In claim 1, A pouch film for a secondary battery, characterized in that the above amide-based lubricating coating layer comprises one or more selected from the group consisting of a saturated amide-based slip agent having 18 to 22 carbon atoms, an unsaturated amide-based slip agent having 20 to 24 carbon atoms, and a slip agent based on a dual amide structure. In claim 1, A pouch film for a secondary battery, characterized in that the above amide-based lubricating coating layer has a thickness of 300 to 500 nm. A step of forming a first adhesive layer on the upper surface of a metal barrier layer; A step of adhering a protective layer to the upper surface of the metal barrier layer using the first adhesive layer as an adhesive; A step of forming a second adhesive layer on the lower surface of the metal barrier layer; A step of bonding an internal substrate layer to the lower surface of the metal barrier layer using the second adhesive layer as an adhesive; and A method for manufacturing a pouch film for a secondary battery, characterized by including the step of forming an amide-based lubricating coating layer on the upper surface of the above protective layer. In claim 6, The step of forming the above amide-based lubricating coating layer is, A step of dissolving an amide-based lubricating composition in a solvent, comprising one or more selected from the group consisting of a saturated amide-based slip agent having 18 to 22 carbon atoms, an unsaturated amide-based slip agent having 20 to 24 carbon atoms, and a diamide structure-based slip agent; A step of coating an amide-based lubricating composition dissolved in the above solvent onto the upper surface of the protective layer; and A method for manufacturing a pouch film for a secondary battery, characterized by including a drying step. In claim 7, A method for manufacturing a pouch film for a secondary battery, characterized in that the above solvent comprises one or more selected from the group consisting of toluene, acetone, xylene, isopropanol, methanol, cyclohexanone, ethyl acetate, and butyl acetate. In claim 7, A method for manufacturing a pouch film for a secondary battery, characterized in that the above amide-based lubricating composition is blended in a ratio of about 0.2 to 1 weight percent relative to the total weight blended with the solvent.

Images