Electrolyte-sealing film for metal bonding, electrolyte-sealing multilayer film for metal bonding, and battery

Abstract

Provided are: an electrolyte-sealing film for metal bonding, which contains an acid-modified polyethylene, which exhibits a heat of fusion measured by a differential scanning calorimeter of 130 J / g to 160 J / g, which has a Young's modulus of 200 MPa to 500 MPa, and which has a density of 0.920 g / cm3 to 0.934 g / cm3; an electrolyte-sealing multilayer film for metal bonding, comprising a core layer and a skin layer on both sides of the core layer, wherein the skin layer is the electrolyte-sealing film for metal bonding, and the thickness of the skin layer is 10 μm or more; and a battery using the electrolyte-sealing film and the electrolyte-sealing multilayer film.

Description

Electrolyte sealing film for metal adhesion, electrolyte sealing multilayer film for metal adhesion, and battery

[0001] The present disclosure relates to an electrolyte sealing film for metal bonding, an electrolyte sealing multilayer film for metal bonding, and a battery.

[0002] In recent years, research and development of nonaqueous electrolyte secondary batteries for use in portable devices, electric bicycles, hybrid vehicles, electric vehicles, and home energy storage has been actively pursued. Against this background, bipolar batteries such as those described in Patent Document 1 have been developed with the aim of improving power density and energy density. In bipolar batteries, a sealant is typically disposed around the outer periphery of each cell layer to prevent electrolyte leakage from one cell layer to the outside, contact with the electrolyte in another cell layer, and the resulting short circuit. Patent Document 2 proposes an acrylic resin sealant, and Patent Document 3 proposes an epoxy-graft-modified polyolefin resin sealant.

[0003] JP 2004-171955 A JP 2012-150900 A JP 2013-37946 A

[0004] However, the sealing materials described in Patent Documents 2 and 3 do not have sufficient sealing properties against the electrolyte. Furthermore, when a polyolefin resin is used, there is a possibility that wrinkles will occur in the current collecting foil due to thermal shrinkage after heat sealing.

[0005] The problem to be solved by the present disclosure is to provide an electrolyte sealing film for metal adhesion that has excellent sealing properties against an electrolyte and excellent wrinkle suppression properties. Another problem to be solved by the present disclosure is to provide an electrolyte sealing multilayer film for metal adhesion that has excellent sealing properties against an electrolyte and excellent wrinkle suppression properties. Yet another problem to be solved by the present disclosure is to provide the electrolyte sealing film for metal adhesion or a battery using the electrolyte sealing multilayer film for metal adhesion.

[0006] Specific means for solving the above problems include the following aspects: <1> A polymer having a heat of fusion of 130 J / g to 160 J / g as measured by a differential scanning calorimeter, a Young's modulus of 200 MPa to 500 MPa, and a density of 0.925 g / cm ３ ~0.934g / cm ３ <2> The electrolyte sealing film for metal bonding according to <1>, which is for bonding copper foil and aluminum foil. <3> An electrolyte sealing multilayer film for metal bonding, which has a core layer and skin layers on both sides of the core layer, the skin layers being the electrolyte sealing film for metal bonding according to <1> or <2>, and the thickness of the skin layers is 10 μm or more. <4> The core layer has a density of 0.90 g / cm ３ ~0.93 g / cm ３ <5> The electrolyte solution sealing multilayer film for metal adhesion according to <3>, which contains polyethylene represented by the formula (I). <6> The electrolyte solution sealing multilayer film for metal adhesion according to <3> or <4>, which is for bonding copper foil and aluminum foil. <7> A battery having, as an electrolyte solution sealant, the electrolyte solution sealing multilayer film for metal adhesion according to <1> or <2>, or the electrolyte solution sealing multilayer film for metal adhesion according to any one of <3> to <5>.

[0007] According to the present disclosure, there is provided an electrolyte sealing film for metal adhesion that has excellent sealing properties against an electrolyte solution and excellent wrinkle suppression properties. Also according to the present disclosure, there is provided an electrolyte sealing multilayer film for metal adhesion that has excellent sealing properties against an electrolyte solution and excellent wrinkle suppression properties. Furthermore, according to the present disclosure, there is provided a battery using the electrolyte sealing film for metal adhesion or the electrolyte sealing multilayer film for metal adhesion.

[0008] In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. In the present disclosure, when a composition contains multiple substances corresponding to each component, the amount of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified. In the numerical ranges described in stages in the present disclosure, the upper or lower limit described in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. In the numerical ranges described in the present disclosure, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. In the present disclosure, a combination of preferred embodiments is a more preferred embodiment. In the description of a group (atomic group) in the present disclosure, a description that does not specify whether it is substituted or unsubstituted includes both unsubstituted and substituted groups. In the present disclosure, unless otherwise specified, each component may be used alone or in combination of two or more types.

[0009] (Electrolyte Sealing Film for Metal Adhesion) The electrolyte sealing film for metal adhesion according to the present disclosure has a heat of fusion of 130 J / g to 160 J / g as measured by a differential scanning calorimeter (DSC), a Young's modulus of 200 MPa to 500 MPa, and a density of 0.925 g / cm ３ ~0.934g / cm ３ The acid-modified polyethylene includes

[0010] As mentioned above, conventional sealing materials do not have sufficient sealing properties against the electrolyte. Furthermore, when a polyolefin resin is used as the sealing material, there is a possibility that wrinkles will occur in the current collecting foil due to thermal shrinkage after heat sealing. In view of the above circumstances, the present inventors have conducted detailed studies and have found that a current collecting foil with a heat of fusion of 130 J / g to 160 J / g, a Young's modulus of 200 MPa to 500 MPa, and a density of 0.925 g / cm is suitable for this purpose. ３ ~0.934g / cm ３By including the acid-modified polyethylene, the resin has a relatively high degree of crystallinity and is resistant to shrinkage due to heat, making it possible to obtain an electrolyte sealing film for metal adhesion that has excellent sealing properties against electrolyte and excellent wrinkle prevention properties.

[0011] The electrolyte sealing film for metal adhesion according to the present disclosure will be described in detail below.

[0012] <Acid-Modified Polyethylene> The electrolyte solution sealing film for metal adhesion according to the present disclosure contains acid-modified polyethylene. In this specification, "acid-modified polyethylene" may refer to polyethylene in which at least a portion thereof is acid-modified, or may contain a portion of unmodified polyethylene. The content of unmodified polyethylene in the acid-modified polyethylene is not particularly limited, and may be, for example, 50% by mass or less, or 20% by mass or less, or the acid-modified polyethylene may not contain unmodified polyethylene. Furthermore, the acid-modified polyethylene has a heat of fusion of 130 J / g to 160 J / g, a Young's modulus of 200 MPa to 500 MPa, and a density of 0.925 g / cm as measured by a differential scanning calorimeter (DSC). ３ ~0.934g / cm ３ is.

[0013] <<Heat of Fusion Measured by Differential Scanning Calorimetry (DSC)>> The acid-modified polyethylene has a heat of fusion measured by a differential scanning calorimetry (DSC) of 130 J / g to 160 J / g, and from the viewpoints of sealability against an electrolyte (hereinafter also referred to as "electrolyte resistance") and wrinkle suppression, the heat of fusion is preferably 140 J / g to 160 J / g, more preferably 145 J / g to 160 J / g, and particularly preferably 145 J / g to 155 J / g.

[0014] The heat of fusion of the resin in this disclosure is measured using a differential scanning calorimeter (DSC214 manufactured by NETZSCH). For acid-modified polyethylene, the measurement sample was heated to 200°C (1st heat) and held for 5 minutes, then cooled to -50°C at a rate of 10°C / min (1st cool), held for 5 minutes, and then heated from -50°C to 200°C at a rate of 10°C / min (2nd heat). The peak area value in the 2nd heat is taken as the heat of fusion (J / g). The analysis temperature range is -20°C to 140°C. For the acid-modified polypropylene, the measurement sample was heated to 240°C (1st heat) and held for 5 minutes, then cooled to 20°C at a rate of 10°C / min (1st cool), held for 5 minutes, and then heated from 20°C to 240°C at a rate of 10°C / min (2nd heat). The peak area value in the 2nd heat is taken as the heat of fusion (J / g). The analytical temperature range is 55°C to 170°C.

[0015] <<Young's Modulus>> The Young's modulus of the acid-modified polyethylene is 200 MPa to 500 MPa, and from the viewpoints of electrolyte resistance and wrinkle suppression, it is preferably 220 MPa to 500 MPa, more preferably 250 MPa to 500 MPa, and particularly preferably 250 MPa to 300 MPa.

[0016] The Young's modulus of the resin in this disclosure is measured using a tensile tester (AG-Xplus manufactured by Shimadzu Corporation). The test sample is a dumbbell type 3 according to JIS K6251 (2017), with a gauge length of 20 mm, a tensile speed of 50 mm / min, and a temperature of 25°C. The Young's modulus is the slope of the stress-strain curve for strains in the range of 0.5% to 1%. Measurements are performed three times and the average value is calculated.

[0017] <<Density>> The density of the acid-modified polyethylene is 0.925 g / cm ３ ~0.934g / cm ３ From the viewpoint of electrolyte resistance and wrinkle suppression, 0.927 g / cm ３ ~0.933g / cm ３ and preferably 0.928 g / cm ３ ~0.932g / cm ３More preferably, it is 0.929 g / cm ３ ~0.931g / cm ３ It is particularly preferred that:

[0018] The density of the resin in the present disclosure is measured at a temperature of 25°C in accordance with JIS K7112 (1999): Method A (water displacement method).

[0019] <<Melt Flow Rate (MFR)>> From the viewpoint of moldability, the melt flow rate (MFR) of the acid-modified polyethylene is preferably 0.01 g / 10 min to 5 g / 10 min, more preferably 0.05 g / 10 min to 4 g / 10 min, and particularly preferably 0.1 g / 10 min to 3 g / 10 min.

[0020] The MFR of the resins in the present disclosure is measured in accordance with JIS K7210 (2014): Method A (mass measurement method) at a temperature of 190°C and a load of 2.16 kgf for acid-modified polyethylene, and at a temperature of 230°C and a load of 2.16 kgf for acid-modified polypropylene.

[0021] <<Acid Value>> From the viewpoints of electrolyte resistance and wrinkle suppression, the acid value of the acid-modified polyethylene is preferably 2.0 mgKOH / g to 10 mgKOH / g, more preferably 2.5 mgKOH / g to 8 mgKOH / g, and particularly preferably 3.0 mgKOH / g to 4.5 mgKOH / g.

[0022] The acid value of the resin according to the present disclosure is measured by the following method. Approximately 0.5 g to 0.6 g of sample is weighed into a 100 mL flask, 70 mL of xylene solvent is added, and the sample is completely dissolved by stirring in a 60°C oil bath for 30 minutes. After cooling to room temperature (25°C, same below) (no precipitate remains), indicator titration is performed. Since potassium hydroxide does not dissolve in benzyl alcohol, a sodium hydroxide benzyl alcohol solution was used as the titrant, and the results are calculated as the KOH equivalent (the value multiplied by the molecular weight of 56.11).

[0023] <<Melting Point>> From the viewpoints of electrolyte resistance and wrinkle suppression, the melting point of the acid-modified polyethylene is preferably 110°C to 160°C, more preferably 115°C to 150°C, and particularly preferably 120°C to 140°C.

[0024] The melting point of the resin in the present disclosure is measured in the same manner as in the measurement of the heat of fusion of the resin using a differential scanning calorimeter described above, and the melting peak temperature in the second heat is taken as the melting point.

[0025] The acid-modified polyethylene may be, for example, polyethylene modified with an α,β-unsaturated carboxylic acid or a derivative thereof. The acid-modified polyethylene may be used alone or in combination of two or more kinds.

[0026] Examples of α,β-unsaturated carboxylic acids or derivatives thereof include unsaturated polycarboxylic acids such as maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, aconitic acid, phthalic acid, trimellitic acid, and norbornene dicarboxylic acid, and derivatives thereof (e.g., acid anhydrides, acid halides, amides, imides, and esters). Among these, itaconic anhydride and / or maleic anhydride are preferred in terms of the adhesiveness, handleability, and cost of the acid-modified polyolefin resin. The α,β-unsaturated carboxylic acids and derivatives thereof may be used alone or in combination of two or more.

[0027] From the viewpoint of adhesiveness, the graft mass of the α,β-unsaturated carboxylic acid and its derivative in the acid-modified polyethylene is preferably 0.1% by mass to 20% by mass, and more preferably 1% by mass to 10% by mass, based on 100% by mass of the acid-modified polyolefin resin. The graft mass (% by mass) of the α,β-unsaturated carboxylic acid and its derivative can be measured by a known method. For example, it can be determined by alkali titration or Fourier transform infrared spectroscopy.

[0028] Usable graft components include, for example, (meth)acrylic acid, (meth)acrylic acid esters, glycidyl (meth)acrylate, isocyanate-containing (meth)acrylic acid, and other copolymerizable unsaturated monomers such as styrene, cyclohexyl vinyl ether, and dicyclopentadiene. The combined use of these monomers can further improve adhesiveness, solubility in solvents, and the graft rate of the α,β-unsaturated carboxylic acid and its derivatives. It is preferable that the amount of these monomers used does not exceed the total graft amount of the α,β-unsaturated carboxylic acid and its derivatives.

[0029] The acid-modified polyolefin can be produced by a conventionally known graft polymerization method such as a melt-kneading method or a solution method. Examples of the method include a method in which unmodified polyethylene is melted, maleic anhydride and an organic peroxide are added thereto, and a graft reaction is carried out in the presence of radicals, and a method in which unmodified polyethylene is dissolved in a solvent to form a solution, and an α,β-unsaturated carboxylic acid or a derivative thereof and an organic peroxide are added thereto, and a graft reaction is carried out in the presence of radicals. For the melt-kneading method, a single-screw or twin-screw extruder, a Banbury mixer, a kneader, or the like can be used.

[0030] In producing the acid-modified polyethylene, a reaction aid for improving the grafting efficiency of the unsaturated carboxylic acid and a stabilizer for adjusting the resin stability can be further compounded depending on the purpose of use.

[0031] Examples of the reaction aid include styrene, o-methylstyrene, p-methylstyrene, α-methylstyrene, divinylbenzene, hexadiene, and dicyclopentadiene. Examples of the stabilizer include hydroquinone, benzoquinone, and nitrosophenylhydroxy compounds. Known organic peroxides can be used, such as benzoyl peroxide, dicumyl peroxide, lauroyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and cumene hydroperoxide.

[0032] The content of the acid-modified polyethylene in the electrolyte solution sealing film for metal adhesion is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

[0033] <Other Components> The electrolyte sealing film for metal bonding according to the present disclosure may contain other components in addition to the acid-modified polyethylene as needed, as long as the effects of the present disclosure are not affected. Examples of other components include known additives and other resin components, such as extender pigments, coloring pigments, dyes, antioxidants, plasticizers, lubricants, flame retardants, antistatic agents, UV absorbers, leveling agents, antifoaming agents, and thickeners. Furthermore, the content of other components in the electrolyte sealing film for metal bonding according to the present disclosure is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less, relative to the total mass of the film. It is particularly preferred that the film does not contain any other components.

[0034] Examples of other resin components include ethylene-α-olefin copolymers such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid ester copolymer, and ethylene-methacrylic acid ester copolymer; polyolefin resins such as polyethylene, polypropylene, and polybutene-1 resin; polyphenylene ether resins, polyamide resins such as nylon 6 and nylon 66; aramid resins; aromatic polyester resins such as polyethylene terephthalate and polybutylene terephthalate; aliphatic polyester resins such as polylactic acid, polybutylene succinate, and polycaprolactone; polycarbonate resins; polyarylate resins; modified polyphenylene oxide resins; polysulfone resins; polyphenylene sulfide resins; polyethersulfone resins; polyetherketone resins; polyetheretherketone resins; polyimide resins; polyoxymethylene homopolymers; and polyoxymethylene copolymers. Examples of the polymer include silicon-containing soft polymers such as oxymethylene resins, polymethyl methacrylate resins, dimethylpolysiloxanes, diphenylpolysiloxanes, and dihydroxypolysiloxanes, vinyl aromatic polymers such as polystyrene, ethylene-propylene copolymer rubber (EPM), ethylene-propylene-non-conjugated diene copolymer rubber (EPDM), ethylene-butene copolymer rubber (EBM), and ethylene-propylene-butene copolymer rubber, styrene-based elastomers such as styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, styrene-ethylene / butylene-styrene block copolymers, and styrene-ethylene / propylene-styrene block copolymers, polybutadiene, hydrogenated vinyl aromatic polymers, other hydrogenated vinyl aromatic block copolymers including hydrogenated styrene / butadiene or styrene / isoprene block copolymers, cycloolefin polymers, and cycloolefin copolymers. These may be used alone or in combination of two or more.

[0035] Examples of the antioxidant include phenolic antioxidants such as 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate, and tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane; sulfur-based antioxidants such as dilauryl-3,3'-thiodipropionate and dimyristyl-3,3'-dithiopropionate; and phosphorus-based antioxidants such as trisnonylphenyl phosphite and tris(2,4-di-t-butylphenyl)phosphite.

[0036] Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and 2-[(2'-hydroxy-3',5'-bis(α,α-dimethylbenzyl)phenyl]-benzotriazole; benzophenone-based ultraviolet absorbers such as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone and 2-hydroxy-4-n-octylbenzophenone; and phenyl salicylate. Examples of the ultraviolet absorber include salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers such as ethyl-2-cyano-3,3-diphenylacrylate, oxalic anilide-based ultraviolet absorbers such as 2-ethoxy-2'-ethyl oxalic acid bisanilide, and hindered amine-based ultraviolet absorbers such as bis[2,2,6,6-tetramethyl-4-piperidine]sebacate and bis[N-methyl-2,2,6,6-tetramethyl-4-piperidinyl]sebacate.

[0037] Examples of the flame retardant include bromine-based flame retardants such as tetrabromobisphenol A, hexabromobenzene, decabromodiphenyl ether, hexabromocyclododecane, bis(pentabromophenyl)ethane, and bis(tetrabromophthalimide)ethane; aromatic phosphate ester-based flame retardants such as triphenyl phosphate, 2-ethylhexyl diphenyl phosphate, and cresyl diphenyl phosphate; aromatic condensed phosphate esters such as 1,3-phenylene bis(diphenyl phosphate), 1,3-phenylene bis(dixylenyl)phosphate, and bisphenol A bis(diphenyl phosphate); halogen-containing phosphate ester-based flame retardants such as tris(dichloropropyl)phosphate; red phosphorus-based flame retardants such as red phosphorus; inorganic flame retardants such as aluminum hydroxide, magnesium hydroxide, and antimony trioxide; silicon-based flame retardants; and boron-based flame retardants.

[0038] <Film Thickness> The thickness of the electrolyte sealing film for metal adhesion according to the present disclosure is not particularly limited, but from the viewpoints of electrolyte resistance and wrinkle suppression, it is preferably 10 μm to 500 μm, more preferably 20 μm to 300 μm, and particularly preferably 30 μm to 200 μm.

[0039] <Method for producing electrolyte sealing film for metal bonding> The method for producing the electrolyte sealing film for metal bonding according to the present disclosure is not particularly limited, and the film can be produced by a known method. Specifically, for example, the electrolyte sealing film for metal bonding according to the present disclosure can be produced by feeding acid-modified polyethylene to an extruder, extruding it through a T-die, and forming a film.

[0040] (Electrolyte-sealing multilayer film for metal bonding) The electrolyte-sealing multilayer film for metal bonding according to the present disclosure has a core layer and skin layers on both sides of the core layer, the skin layers being the electrolyte-sealing film for metal bonding according to the present disclosure, and the thickness of the skin layers being 10 μm or more. By providing a core layer by multilayering, it is possible to combine the properties of the resins in the core layer to impart required functions. For example, film stiffness, heat resistance, and reduced linear expansion coefficient. Furthermore, by multilayering, it is possible to create high-value-added products at low cost.

[0041] <Skin Layer> Preferred aspects of the skin layer in the electrolyte solution sealing multilayer film for metal adhesion according to the present disclosure are the same as the preferred aspects of the electrolyte solution sealing film for metal adhesion according to the present disclosure, except as described below. Furthermore, the two skin layers present on both sides of the core layer may be the same skin layer or different skin layers, but are preferably the same skin layer. The thickness of the skin layer is 10 μm or more, and from the viewpoints of electrolyte resistance and wrinkle suppression, it is preferably 10 μm to 200 μm, more preferably 20 μm to 100 μm, and particularly preferably 30 μm to 50 μm.

[0042] <Core Layer> From the viewpoints of adhesion to the skin layer, electrolyte resistance, and wrinkle suppression, the core layer is preferably a layer containing a resin, more preferably a layer containing polyolefin, and even more preferably a layer containing polyethylene, and has a density of 0.90 g / cm ３ ~0.93 g / cm ３ Examples of resins used in the core layer include polyolefins such as polyethylene and polypropylene, (meth)acrylic resins, diene resins, fluororesins, polyamides, polyimides, and polyurethanes, and from the viewpoints of adhesion to the skin layer, electrolyte resistance, and wrinkle suppression, polyolefins are preferred, and polyethylene is more preferred.

[0043] <<Melt Flow Rate (MFR)>> From the viewpoint of moldability, the melt flow rate (MFR) of the core layer is preferably 0.1 g / 10 min to 10 g / 10 min, more preferably 1 g / 10 min to 5 g / 10 min, and particularly preferably 2 g / 10 min to 4 g / 10 min.

[0044] <<Melting Point>> From the viewpoints of electrolyte resistance and wrinkle suppression, the melting point of the core layer is preferably 80°C to 160°C, more preferably 95°C to 150°C, and particularly preferably 110°C to 140°C.

[0045] <<Density>> The density of the core layer is 0.88 g / cm from the viewpoints of electrolyte resistance and wrinkle suppression. ３ ~0.94 g / cm ３ It is preferable that the density is 0.90 g / cm ３ ~0.93 g / cm ３ More preferably, it is 0.91 g / cm ３ ~0.93 g / cm ３ It is particularly preferred that:

[0046] <<Core Layer Thickness>> The thickness of the core layer is not particularly limited, but from the viewpoints of electrolyte resistance and wrinkle suppression, it is preferably 30 μm to 500 μm, more preferably 50 μm to 300 μm, and particularly preferably 70 μm to 200 μm. Furthermore, the thickness of the core layer is preferably thicker than the thickness of the skin layer.

[0047] The content of the resin in the core layer, preferably the content of the polyolefin, is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

[0048] The core layer may contain other components besides the resin as needed, as long as the effects of the present disclosure are not affected. Examples of other components include the additives used in the electrolyte sealing film for metal adhesion according to the present disclosure.

[0049] <Thickness of electrolyte-sealing multilayer film for metal bonding> The thickness of the electrolyte-sealing multilayer film for metal bonding according to the present disclosure is not particularly limited, but from the viewpoints of electrolyte resistance and wrinkle suppression, it is preferably 50 μm to 500 μm, more preferably 70 μm to 400 μm, and particularly preferably 80 μm to 300 μm.

[0050] <Method for producing an electrolyte-sealing multilayer film for metal bonding> The method for producing the electrolyte-sealing multilayer film for metal bonding according to the present disclosure is not particularly limited, and can be produced by a known method. Specifically, for example, acid-modified polyethylene and a resin forming a core layer are fed into separate extruders, and co-extruded from a single T-die so that both skin layers are acid-modified polyethylene and the core layer is the resin, thereby forming a multilayer film, and the electrolyte-sealing film for metal bonding according to the present disclosure can be produced. Alternatively, the core layer may be produced, and skin layers may be attached to both sides of the core layer by crimping or the like.

[0051] <Uses> The electrolyte sealing film for metal adhesion and the electrolyte sealing multilayer film for metal adhesion according to the present disclosure can be suitably used in batteries, and particularly suitably used in bipolar batteries.

[0052] (Battery) The battery according to the present disclosure includes, as an electrolyte sealant, the electrolyte sealing film for metal bonding according to the present disclosure or the electrolyte sealing multilayer film for metal bonding according to the present disclosure. Examples of batteries include known batteries using electrolytes, but bipolar batteries are preferred from the viewpoint of further demonstrating the effects of the present disclosure. Also suitable are battery packs formed by connecting multiple bipolar batteries. A bipolar battery is formed by alternately stacking multiple bipolar electrodes, each having a positive electrode layer formed on one side of a current collector and a negative electrode layer formed on the other side, and an electrolyte layer that performs ion exchange between the bipolar electrodes. Examples of the electrolyte layer include a separator impregnated with electrolyte. In a bipolar battery, multiple unit cells, each consisting of a positive electrode layer, an electrolyte layer, and a negative electrode layer sandwiched between current collectors, are contained in a single package. If electrolyte leaks from one unit cell, it can cause a liquid short circuit (short circuit) with the other unit cells. To prevent this, an electrolyte sealant is provided for each unit cell. The current collector is preferably a metal foil such as copper foil or aluminum foil. The current collector, positive electrode, negative electrode, separator, electrolyte, exterior material, and the like used in the battery or bipolar battery according to the present disclosure are not particularly limited, and known materials can be used. Examples of bipolar batteries include those described in JP 2004-171955 A, JP 2012-150900 A, and JP 2013-37946 A.

[0053] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure. Unless otherwise specified, "%" is based on mass.

[0054] <Acid-modified polyolefins used> The polyolefins used in the examples and comparative examples are shown below. All of these polyolefins were prepared by polymerization according to a conventional method. Note that all of the acid-modified polyolefins described below are maleic anhydride-modified polyolefins. mPE-1: MFR 0.3 g / 10 min, melting point 132°C, density 0.926 g / cm ３mPE-2: MFR 3.0 g / 10 min, melting point 125°C, density 0.929 g / cm ３ mPE-3: MFR 1.0 g / 10 min, melting point 124°C, density 0.928 g / cm ３ mPE-4: MFR 1.5 g / 10 min, melting point 128°C, density 0.937 g / cm ３ mPE-5: MFR 2.5 g / 10 min, melting point 122°C, density 0.918 g / cm ３ mPE-6: MFR 1.0 g / 10 min, melting point 116°C, density 0.900 g / cm ３ mPE-7: MFR 6.0 g / 10 min, melting point 104°C, density 0.896 g / cm ３ mPE-8: MFR 3.5 g / 10 min, melting point 119°C, density 0.900 g / cm ３ mPE-9: MFR 10 g / 10 min, melting point 98°C, density 0.880 g / cm ３ mPP-1: MFR 14 g / 10 min, melting point 157 ° C, density 0.898 g / cm ３ , acid-modified polypropylene with an acid value of 1.1 mg KOH / g.

[0055] (Examples 1 to 3 and Comparative Examples 1 to 7) <Production of Film> Each monolayer film was produced by the T-die method. Specifically, acid-modified polyethylene was supplied to an extruder and extruded through a T-die to form a monolayer film (100 μm). In Example 1, mPE-1 was used. In Example 2, mPE-2 was used. In Example 3, mPE-3 was used. In Comparative Example 1, mPE-4 was used. In Comparative Example 2, mPE-5 was used. In Comparative Example 3, mPE-6 was used. In Comparative Example 4, mPE-7 was used. In Comparative Example 5, mPE-8 was used. In Comparative Example 6, mPE-9 was used. In Comparative Example 7, mPP-1 was used.

[0056] (Examples 4 to 7) Each multilayer film was manufactured by a T-die coextrusion method. Specifically, acid-modified polyethylene and polyethylene were supplied to separate extruders and coextruded from a single T-die so that both skin layers were acid-modified polyethylene and the core layer was polyethylene, to produce a multilayer film (140 μm). In Examples 4 to 7, acid-modified polyethylene (mPE-2) was used for the skin layer. In Examples 4 and 5, acid-modified polyethylene (mPE-2) with an MFR of 2.1 g / 10 min, a melting point of 124°C, and a density of 0.927 g / cm was used for the core layer. ３ In Example 6, polyethylene (PE-1) having an MFR of 2.1 g / 10 min, a melting point of 123°C, and a density of 0.920 g / cm was used for the core layer. ３ In Example 7, polyethylene (PE-2) having an MFR of 3.5 g / 10 min, a melting point of 90°C, and a density of 0.898 g / cm was used for the core layer. ３ Polyethylene (PE-3) of 1000 kJ / cm2 was used. In Examples 4, 6, and 7, the layer thickness ratio was skin layer / core layer / skin layer = 30 μm / 80 μm / 30 μm. In Example 5, the layer thickness ratio was skin layer / core layer / skin layer = 10 μm / 120 μm / 10 μm.

[0057] <Acid Value Measurement> The acid value of the resin was measured using the following method. Approximately 0.5 g to 0.6 g of sample was weighed into a 100 mL flask, and 70 mL of xylene solvent was added. The sample was completely dissolved by stirring for 30 minutes in a 60°C oil bath, and then allowed to cool to room temperature (25°C, same below) (no precipitate was observed), after which an indicator titration was performed. Since potassium hydroxide does not dissolve in benzyl alcohol, a sodium hydroxide benzyl alcohol solution was used as the titrant, and the results were calculated as the KOH equivalent (the value multiplied by the molecular weight of 56.11).

[0058] <Measurement of Density> The density of the resin was measured at a temperature of 25°C in accordance with JIS K7112 (1999): Method A (water displacement method).

[0059] <Measurement of Melt Flow Rate (MFR)> The MFR of the resin was measured in accordance with JIS K7210 (2014): Method A (mass measurement method) at a temperature of 190°C and a load of 2.16 kgf for acid-modified polyethylene, and at a temperature of 230°C and a load of 2.16 kgf for acid-modified polypropylene.

[0060] <Measurement of Heat of Fusion and Melting Point> The heat of fusion of the resin was measured using a differential scanning calorimeter (DSC214 manufactured by NETZSCH). For acid-modified polyethylene, the measurement sample was heated to 200°C (1st heat) and held at that temperature for 5 minutes, then cooled to -50°C at a rate of 10°C / min (1st cool), held at that temperature for 5 minutes, and then heated from -50°C to 200°C at a rate of 10°C / min (2nd heat). The peak area value in the 2nd heat was taken as the heat of fusion (J / g). The analytical temperature range was -20°C to 140°C. For the acid-modified polypropylene, the measurement sample was heated to 240°C (1st heat) and held for 5 minutes, then cooled to 20°C at a rate of 10°C / min (1st cool), held for 5 minutes, and then heated from 20°C to 240°C at a rate of 10°C / min (2nd heat). The peak area value in the 2nd heat was taken as the heat of fusion (J / g). The analytical temperature range was 55°C to 170°C. The melting peak temperature in the 2nd heat was taken as the melting point of the resin.

[0061] <Measurement of Young's modulus> The Young's modulus of the resin was measured using a tensile tester (AG-Xplus manufactured by Shimadzu Corporation). The test sample was a dumbbell type 3 according to JIS K6251 (2017), with a gauge length of 20 mm, a tensile speed of 50 mm / min, and a temperature of 25°C. The Young's modulus was determined as the slope of the stress-strain curve for a strain in the range of 0.5% to 1%. The measurement was performed three times, and the average value was calculated.

[0062] <Evaluation of Electrolyte Resistance> The electrolyte resistance was evaluated by the following method. The film and copper foil (10 μm thick, manufactured by Shohoku Laminate Industry Co., Ltd.) of the adherend were cut to 50 mm × 30 mm, the film and the adherend were overlapped, and a 10 mm × 30 mm area was heat-sealed at a temperature of the melting point + 35°C using an impulse sealer to prepare a test piece. The prepared test piece was cut to 50 mm × 10 mm, placed in a resin bag laminated with aluminum foil, and placed in an electrolyte (1 M (= 1 mol / L) LiPF ６ A 1 / 1 / 1 volume % solution of ethylene carbonate (EC) / diethyl carbonate (DEC) / dimethyl carbonate (DMC) (manufactured by Kishida Chemical Co., Ltd.) was added and vacuum laminated. After heating at 60°C for 72 hours, the test piece was removed and the 180° peel strength was measured at room temperature with a tensile tester (AG-Xplus manufactured by Shimadzu Corporation) at a pulling rate of 10 mm / min. Higher strength indicates better electrolyte resistance. The evaluation criteria are as follows: A: Peel strength is 0.3 N / mm or more; F: Peel strength is less than 0.3 N / mm.

[0063] <Evaluation of curl (wrinkle suppression)> Curl was measured by the following method. The film and copper foil (35 μm, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) as the adherend were cut into 50 mm x 10 mm pieces, the film and the adherend were overlapped, and the entire surface was heat-sealed at a temperature of the melting point + 35°C using an impulse sealer to obtain a test piece. One long side of the test piece was pressed on a horizontal surface, and the height of the other long side from the horizontal surface was measured and taken as the curl. Small curl means that the thermal shrinkage of the film after heat sealing was small, which means that no wrinkles were generated and the film was excellent. The evaluation criteria are as follows: A: curl height less than 2.5 mm F: curl height 2.5 mm or more

[0064]

[0065] As shown in Table 1, the films of Examples 1 to 7 were superior to the films of Comparative Examples 1 to 7 in both sealing ability against the electrolyte and wrinkle suppression.

[0066] The disclosure of Japanese Patent Application No. 2023-217192, filed on December 22, 2023, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. The heat of fusion measured by a differential scanning calorimeter is 130 J / g to 160 J / g, the Young's modulus is 200 MPa to 500 MPa, and the density is 0.920 g / cm ３ ~0.934g / cm ３ An electrolyte sealing film for metal adhesion comprising an acid-modified polyethylene.

2. The electrolyte sealing film for metal bonding according to claim 1, which is for bonding copper foil and aluminum foil.

3. An electrolyte sealing multilayer film for metal adhesion, comprising a core layer and a skin layer on both sides of the core layer, the skin layer being the electrolyte sealing film for metal adhesion described in claim 1, and the thickness of the skin layer being 10 μm or more.

4. The core layer has a density of 0.895 g / cm ３ ~0.930g / cm ３ 4. The electrolyte sealing multi-layer film for metal adhesion according to claim 3, comprising polyethylene represented by the formula:

5. The electrolyte sealing multi-layer film for metal adhesion according to claim 3, which is for adhesion to copper foil and aluminum foil.

6. A battery having, as an electrolyte sealant, the electrolyte sealing film for metal adhesion according to claim 1 or 2, or the electrolyte sealing multilayer film for metal adhesion according to any one of claims 3 to 5.

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