JP7106844B2 - Exterior material for power storage device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an exterior material for a power storage device.

As power storage devices, for example, secondary batteries such as lithium-ion batteries, nickel-hydrogen batteries, and lead-acid batteries, and electrochemical capacitors such as electric double-layer capacitors are known. There is a demand for further miniaturization of power storage devices due to the miniaturization of mobile devices, the limitation of installation space, and the like, and lithium ion batteries with high energy density are attracting attention. Conventionally, metal cans have been used as exterior materials for lithium-ion batteries. A film configured like a sealant layer) has come to be used.

In a lithium ion battery using the multilayer film as an outer packaging material, a configuration is adopted in which the battery contents are covered with an outer packaging material containing an aluminum foil layer as a metal foil layer in order to prevent moisture from entering the battery. A lithium ion battery having such a configuration is called an aluminum laminate type lithium ion battery. Lithium-ion batteries contain a positive electrode, a negative electrode, a separator, and a lithium salt as an electrolyte in an aprotic solvent with penetrating power such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate. Included is an electrolyte layer consisting of a dissolved electrolyte or a polymer gel impregnated with the electrolyte.

For aluminum laminate type lithium ion batteries, for example, a recess is formed in a part of the exterior material by cold molding, the contents of the battery are accommodated in the recess, and the remaining part of the exterior material is folded back to heat the edge part. An embossed type lithium ion battery sealed with a seal is known. The exterior material that constitutes such a lithium-ion battery is required to exhibit stable sealing performance by heat sealing, and to prevent the deterioration of the lamination strength between the aluminum foil layer and the sealant layer due to the electrolytic solution in the battery contents. ing.

In addition, as smartphones, tablet PCs, and the like become thinner, a thin power storage device is required to be mounted. With the thinning of power storage devices, the base layer, metal foil layer, and sealant layer of the exterior material for power storage devices are becoming thinner. is a problem.

Therefore, for example, in Patent Document 1, by providing a heat-sealing layer (sealant layer) containing an adhesive polymethylpentene layer, the barrier layer and the tab of the exterior body are stabilized without short-circuiting due to the heat and pressure of the heat-sealing. There have been proposed sheathing materials that can be sealed by

JP-A-2002-245983

In the conventional exterior material as described in Patent Literature 1, measures are taken against deterioration in insulation due to contact between the tab lead and the metal foil layer. However, it is considered that another factor also exists in the deterioration of insulation. In order to accumulate energy as a lithium-ion battery, it is necessary to perform charging and discharging under predetermined conditions such as current value, voltage value, and environmental temperature to cause a chemical change (formation). This formation step is performed in the state of a temporary battery into which an electrolytic solution is injected. Then, the battery is once unsealed to remove the gas generated by chemical conversion and to replenish the electrolytic solution, and then the final sealing is performed to complete the battery. Since this final seal seals the portion once immersed in the electrolyte, it becomes a degassing seal (degassing heat seal) that performs heat sealing while the electrolyte is caught.

The present inventors' investigations so far have shown that deterioration of insulation is often caused by breakage of the sealant layer due to degassing heat sealing, and countermeasures against this are very important. Patent Literature 1 does not discuss destruction of the sealant layer due to degassing heat sealing.

In the degassing heat seal, when the exterior material containing the contents of the battery is heat-sealed, the electrolyte is bitten into the heat seal, so the electrolyte foams and the sealant layer may be destroyed. . Then, it is considered that the electrolytic solution enters from the broken portion of the sealant layer and comes into contact with the metal layer, thereby degrading the insulation.

Furthermore, since the deterioration of the insulation caused by the breakage of the sealant layer due to degassing heat sealing is easily affected by the thinning of the sealant layer, it will be necessary to take particular measures in the future to improve the insulation.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exterior material for a power storage device that can sufficiently maintain insulation after degassing heat sealing.

The present invention provides an exterior material for a power storage device, which comprises at least a base material layer, a metal foil layer provided with a corrosion prevention treatment layer on one or both surfaces, and a sealant layer in this order. In the exterior material, the sealant layer contains a polypropylene resin (A) and an incompatible component (B) that is incompatible with the polypropylene resin, and the region where the polypropylene resin (A) exists and the polypropylene It has a plurality of regions where the incompatible component (B) exists, surrounded by the system resin (A). Furthermore, the sealant layer has a cross section along the thickness direction and the MD direction, and the average length LA ^MD of the existing region of the incompatible component (B) in the MD direction is 190% of the power storage device exterior material. Ratio of the average length LAh ^MD in the MD direction of the region where the incompatible component (B) exists in the cross section along the thickness direction and the MD direction after heating at ° C. for 30 seconds (LAh ^MD /LA ^MD ) is 0.20 or greater. Hereinafter, this ratio (LAh ^MD /LA ^MD ) may be simply referred to as shrinkage ratio.

According to the exterior material for a power storage device, even when the sealant layer is thinned, it is possible to sufficiently maintain the insulating properties after the degassing heat sealing. The present inventors presume that the reason why the exterior material for a power storage device has such effects is as follows. At the time of degassing heat sealing, the sealant layer is swollen by the electrolyte, and heat sealing is performed in a state where the electrolyte is bitten. occur. The foaming of the electrolytic solution tends to form voids at the interface of the sea-island structure formed by the polypropylene resin (A) and the incompatible component (B) of the sealant layer, and the metal foil layer fills the voids inside the sealant layer. It is conceivable that the exposed portion of the metal foil layer is exposed to the electrolyte, and the electrolyte is brought into contact with the exposed portion of the metal foil layer, thereby degrading the insulation. In particular, when the sealant layer is thinned, the deformation of the sealant layer due to foaming increases with respect to the thickness, further increasing the possibility of insulation deterioration. As a result, in the present invention, the sealant layer includes a low shrinkage sealant layer having a certain or higher shrinkage ratio. In the exterior material having such a low-shrinkage sealant layer, the adhesion between the polypropylene-based resin (A) and the incompatible component (B) at the interface of the sea-island structure is high, and even when the electrolyte foams, the interface is maintained. It becomes difficult for voids, which are starting points, to occur. Therefore, in the exterior material for a power storage device according to the present invention, even when the sealant layer is thinned, it is possible to sufficiently maintain the insulating properties after the degassing heat sealing.

In the power storage device exterior material, the presence region of the incompatible component (B) in the cross section along the thickness direction and MD direction of the sealant layer after heating the power storage device exterior material at 190 ° C. for 30 seconds. , the ratio of the average length LAh ^MD in the MD direction to the average length LAh ^VD in the thickness direction (LAh ^MD /LAh ^VD ) is preferably 2.50 or more. When the presence region of the immiscible component (B) after heating satisfies the above conditions, the insulating property after degassing heat-sealing tends to be better maintained.

In the power storage device exterior material, the sealant layer may be composed of a plurality of layers, at least one of which may be the low-shrinkage sealant layer. In this case, the layer closest to the metal foil layer among the plurality of sealant layers is preferably the low-shrinkage sealant layer. Since the sealant layer closest to the metal foil layer is the low-shrinkage sealant layer, it tends to be easier to suppress deterioration in insulation after degassing heat sealing. Foaming of the electrolyte during degassing heat sealing often occurs in a portion of the sealant layer near the metal foil layer, and the layer closest to the metal foil layer has a large shrinkage ratio (incompatible component (B) shrinkage is small), it tends to be easier to suppress the deterioration of insulation more efficiently.

In the power storage device exterior material, the sealant layer may further contain a compatible elastomer (C) that is compatible with the polypropylene resin (A), and the compatible elastomer (C) is propylene-α olefin Copolymers can be included. By containing a compatible elastomer (C) compatible with the polypropylene resin (A) in the sealant layer, it is possible to impart flexibility to the sealant layer, and functions such as molding whitening suppression and impact resistance to the exterior material can be imparted, and the functionality as an exterior material can be improved.

Further, the sealant layer is composed of a plurality of layers, and in the layer closest to the metal foil layer, the polypropylene resin (A) may contain an acid-modified polypropylene, and the compatible elastomer (C) is atactic. Structured polypropylene or atactic structured propylene-alpha olefin copolymer may be included. According to such an exterior material for a power storage device, it becomes easier to maintain the adhesion between the sealant layer and the metal foil layer, preventing the occurrence of defective adhesion portions that cause foaming of the electrolytic solution, and degassing heat sealing. There is a tendency that it becomes easier to further suppress the deterioration of the insulation of the

The power storage device exterior material may further include an adhesive layer between the metal foil layer and the sealant layer, wherein the adhesive layer comprises an acid-modified polyolefin, a polyfunctional isocyanate compound, a glycidyl compound, a carboxy and at least one curing agent selected from the group consisting of a compound having a group, a compound having an oxazoline group, and a carbodiimide compound.

ADVANTAGE OF THE INVENTION According to this invention, the exterior material for electrical storage apparatuses which can fully maintain the insulation after degassing heat sealing can be provided.

1 is a schematic cross-sectional view of an exterior material for a power storage device according to an embodiment of the present invention; FIG. FIG. 4 is an enlarged cross-sectional view schematically showing the cross-sectional structure of the surface along the thickness direction and the MD direction of the sealant layer in the power storage device exterior material according to one embodiment of the present invention, where (a) is 190° C. for 30 seconds; It is a figure before heating, and (b) is a figure after heating at 190 degreeC for 30 seconds. 1 is a schematic cross-sectional view of an exterior material for a power storage device according to an embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of an exterior material for a power storage device according to an embodiment of the present invention; FIG. It is a schematic diagram explaining the preparation method of the evaluation sample in an Example. It is a schematic diagram explaining the preparation method of the evaluation sample in an Example. It is a schematic diagram explaining the preparation method of the evaluation sample in an Example. It is a schematic diagram explaining the preparation method of the evaluation sample in an Example. SEM images of a cross section along the VD direction (thickness direction) and MD direction of the sealant layer in the exterior material for a power storage device obtained in Example 7, and (a) is the image before heating at 190 ° C. for 30 seconds. and (b) is an image after heating at 190° C. for 30 seconds.

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted. Also, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[Exterior material for power storage device]
FIG. 1 is a cross-sectional view schematically showing one embodiment of the exterior material for a power storage device of the present invention. As shown in FIG. 1 , the exterior material (exterior material for power storage device) 10 of the present embodiment includes a base material layer 11 and an adhesive layer 12 (first adhesive layer) formed on one surface of the base material layer 11 . ), a metal foil layer 13 formed on the surface of the first adhesive layer 12 opposite to the base layer 11, and the first adhesive layer 13 of the metal foil layer 13 A corrosion prevention treatment layer 14 formed on the surface opposite to the adhesive layer 12 and an adhesive layer 17 (second adhesion) formed on the surface of the corrosion prevention treatment layer 14 opposite to the metal foil layer 13 ) and a sealant layer 16 formed on the opposite side of the second adhesive layer 17 from the anti-corrosion treatment layer 14 are sequentially laminated. In the exterior material 10, the base material layer 11 is the outermost layer, and the sealant layer 16 is the innermost layer. That is, the exterior material 10 is used with the base material layer 11 facing the outside of the power storage device and the sealant layer 16 facing the inside of the power storage device. Each layer constituting the exterior material 10 will be specifically described below.

<Base material layer 11>
The base material layer 11 is provided for the purpose of imparting heat resistance in the sealing process during the manufacture of the electric storage device and for countermeasures against pinholes that may occur during processing and distribution, and it is preferable to use an insulating resin layer. As such a resin layer, for example, stretched or unstretched films such as polyester film, polyamide film and polypropylene film can be used as a single layer or a multilayer film obtained by laminating two or more layers. It is also possible to use a co-extruded multi-layer stretched film obtained by co-extrusion of a polyethylene terephthalate film (PET) and a nylon film (Ny) using an adhesive resin and subsequent stretching treatment.

The base material layer 11 may be provided by directly coating on the metal foil layer 13 described below. In this case, the first adhesive layer 12, which will be described later, is unnecessary. As a method for forming the substrate layer by coating, a method of coating a resin coating liquid such as urethane resin, acrylic resin, or polyester resin and curing by ultraviolet irradiation, high-temperature heating, aging (curing) treatment, or the like can be employed. The coating method is not particularly limited, and various methods such as gravure coating, reverse coating, roll coating and bar coating can be employed.

The thickness of the substrate layer 11 is preferably 3-40 μm, more preferably 5-25 μm. When the thickness of the base material layer 11 is 3 μm or more, there is a tendency that the resistance to pinholes and the insulating properties of the exterior material 10 for a power storage device can be improved.

<First adhesive layer 12>
The first adhesive layer 12 is a layer that bonds the base layer 11 and the metal foil layer 13 together. Specific examples of the material that constitutes the first adhesive layer 12 include, for example, polyester polyol, polyether polyol, acrylic polyol, carbonate polyol, and the like. Resin etc. are mentioned.

The various polyols described above can be used alone or in combination of two or more according to the functions and performances required for the exterior material.

In addition, various other additives and stabilizers may be added to the polyurethane resin described above, depending on the performance required for the adhesive.

The thickness of the first adhesive layer 12 is not particularly limited, but is preferably 1 to 10 μm, and preferably 3 to 7 μm, from the viewpoint of obtaining desired adhesive strength, followability, workability, and the like. more preferred.
<Metal foil layer 13>
The metal foil layer 13 has a water vapor barrier property that prevents moisture from entering the power storage device. In addition, the metal foil layer 13 has extensibility for deep drawing. Various metal foils such as aluminum, stainless steel, and copper can be used as the metal foil layer 13, and aluminum foil is preferable in terms of mass (specific gravity), moisture resistance, workability, and cost.

As the aluminum foil, a soft aluminum foil that has been subjected to an annealing treatment can be preferably used because it can impart the desired ductility during molding. For this purpose, it is more preferable to use aluminum foil containing iron. The content of iron in the aluminum foil is preferably 0.1 to 9.0% by mass, more preferably 0.5 to 2.0% by mass, based on 100% by mass of the aluminum foil. When the iron content is 0.1% by mass or more, it is possible to obtain the exterior material 10 having more excellent pinhole resistance and extensibility. When the iron content is 9.0% by mass or less, it is possible to obtain the exterior material 10 that is more excellent in flexibility.

The thickness of the metal foil layer 13 is not particularly limited, but is preferably 9 to 200 μm, more preferably 15 to 100 μm, in consideration of barrier properties, pinhole resistance, and workability. .

When an aluminum foil is used for the metal foil layer 13, an untreated aluminum foil may be used as the aluminum foil, but it is preferable to use a degreased aluminum foil in terms of imparting electrolytic solution resistance.

When the aluminum foil is degreased, only one side of the aluminum foil may be degreased, or both sides may be degreased.

<Corrosion prevention treatment layer 14>
The corrosion prevention treatment layer 14 is a layer provided to prevent corrosion of the metal foil layer 13 by the electrolyte or hydrofluoric acid generated by the reaction between the electrolyte and water. The corrosion prevention treatment layer 14 is formed by, for example, degreasing treatment, hydrothermal transformation treatment, anodizing treatment, chemical conversion treatment, or a combination of these treatments.

Examples of the degreasing treatment include acid degreasing and alkaline degreasing. Examples of acid degreasing include a method using an inorganic acid such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid alone, or a mixed solution thereof. In addition, as acid degreasing, an acid degreasing agent obtained by dissolving a fluorine-containing compound such as monosodium ammonium difluoride in the inorganic acid is used. Not only is the effect obtained, but it is also possible to form passivated aluminum fluoride, which is effective in terms of resistance to hydrofluoric acid. Alkaline degreasing includes a method using sodium hydroxide or the like.

The hydrothermal modification treatment includes, for example, a boehmite treatment in which an aluminum foil is immersed in boiling water containing triethanolamine.

Examples of the anodizing treatment include alumite treatment.

Examples of the chemical conversion treatment include dipping type and coating type. Immersion-type chemical conversion treatments include, for example, chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, and various chemical conversion treatments consisting of mixed phases thereof. be done. On the other hand, as coating type chemical conversion treatment, there is a method of coating the metal foil layer 13 with a coating agent having anti-corrosion performance.

Among these anti-corrosion treatments, when at least a part of the anti-corrosion treatment layer is formed by any one of hydrothermal transformation treatment, anodizing treatment, and chemical conversion treatment, it is preferable to perform the above-described degreasing treatment in advance. If a degreased metal foil such as a metal foil that has undergone an annealing process is used as the metal foil layer 13, it is not necessary to perform another degreasing treatment when forming the corrosion prevention treatment layer .

The coating agent used for coating-type chemical conversion treatment preferably contains trivalent chromium. In addition, the coating agent may contain at least one polymer selected from the group consisting of cationic polymers and anionic polymers, which will be described later.

Among the above treatments, particularly in the hydrothermal transformation treatment and the anodizing treatment, the surface of the aluminum foil is dissolved by a treating agent to form an aluminum compound (boehmite, alumite) having excellent corrosion resistance. Therefore, since a co-continuous structure is formed from the metal foil layer 13 using aluminum foil to the corrosion prevention treatment layer 14, the above treatment is included in the definition of chemical conversion treatment. On the other hand, as will be described later, it is also possible to form the corrosion prevention treatment layer 14 only by a pure coating method, which is not included in the definition of chemical conversion treatment. As this method, for example, a rare earth element oxide sol such as cerium oxide having an average particle size of 100 nm or less is used as a material that has an aluminum corrosion prevention effect (inhibitor effect) and is also suitable from an environmental point of view. method to be used. By using this method, it is possible to impart a corrosion-preventing effect to a metal foil such as an aluminum foil even by a general coating method.

Examples of the sol of the rare earth element oxide include sol using various solvents such as water-based, alcohol-based, hydrocarbon-based, ketone-based, ester-based, and ether-based solvents. Among them, a water-based sol is preferable.

In order to stabilize the dispersion of the rare earth element oxide sol, inorganic acids such as nitric acid, hydrochloric acid and phosphoric acid or salts thereof, and organic acids such as acetic acid, malic acid, ascorbic acid and lactic acid are added to stabilize the dispersion. used as a modifier. Among these dispersion stabilizers, phosphoric acid in particular is used in the exterior material 10 to (1) stabilize the dispersion of the sol and (2) improve adhesion with the metal foil layer 13 by utilizing the aluminum chelating ability of phosphoric acid. , (3) Imparting electrolyte resistance by trapping aluminum ions eluted under the influence of hydrofluoric acid (passivation formation), (4) Corrosion prevention treatment layer 14 ( oxide layer), etc. are expected.

Examples of the phosphoric acid or salts thereof include orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, and alkali metal salts and ammonium salts thereof. Among them, condensed phosphoric acids such as trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, and ultrametaphosphoric acid, or alkali metal salts and ammonium salts thereof are preferable for exhibiting functions in the exterior material 10 . In addition, considering the dry film-forming properties (drying ability, heat quantity) when forming the corrosion prevention treatment layer 14 made of the rare earth element oxide by various coating methods using the sol of the rare earth element oxide, A sodium salt is more preferable from the point of being excellent in dehydration-condensation property. As the phosphate, a water-soluble salt is preferred.

The compounding ratio of phosphoric acid (or its salt) to the rare earth element oxide is preferably 1 to 100 parts by weight per 100 parts by weight of the rare earth element oxide. When the compounding ratio is 1 part by mass or more with respect to 100 parts by mass of the rare earth element oxide, the rare earth element oxide sol becomes more stable and the function of the exterior material 10 becomes better. The compounding ratio is more preferably 5 parts by mass or more with respect to 100 parts by mass of the rare earth element oxide. Further, when the compounding ratio is 100 parts by mass or less with respect to 100 parts by mass of the rare earth element oxide, the function of the rare earth element oxide sol is enhanced, and the performance of preventing the erosion of the electrolytic solution is excellent. The compounding ratio is more preferably 50 parts by mass or less, and even more preferably 20 parts by mass or less with respect to 100 parts by mass of the rare earth element oxide.

Since the corrosion prevention treatment layer 14 formed of the rare earth element oxide sol is an aggregate of inorganic particles, there is a possibility that the cohesion of the layer itself will be reduced even after the drying and curing process. Therefore, in this case, the corrosion prevention treatment layer 14 is preferably compounded with the following anionic polymer or cationic polymer in order to compensate for cohesive force.

The anionic polymer includes a polymer having a carboxy group, such as poly(meth)acrylic acid (or a salt thereof) or a copolymer containing poly(meth)acrylic acid as a main component. Copolymerization components of this copolymer include alkyl (meth)acrylate monomers (alkyl groups include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.); (meth)acrylamide, N-alkyl(meth)acrylamide, N,N-dialkyl(meth)acrylamide (as the alkyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.), N-alkoxy(meth)acrylamide, N,N-dialkoxy Amide group-containing monomers such as (meth)acrylamide, (alkoxy groups include methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), N-methylol (meth)acrylamide, N-phenyl (meth)acrylamide; hydroxyl group-containing monomers such as hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; glycidyl group-containing monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; (meth) acryloxypropyltrimethoxysilane, (meth) Silane-containing monomers such as acryloxypropyltriethoxylan; isocyanate group-containing monomers such as (meth)acryloxypropylisocyanate;

These anionic polymers serve to improve the stability of the corrosion prevention treatment layer 14 (oxide layer) obtained using the rare earth element oxide sol. This is due to the effect of protecting the hard and brittle oxide layer with the acrylic resin component and the effect of capturing ion contamination (especially sodium ions) derived from phosphate contained in the rare earth element oxide sol (cation catcher). achieved. In other words, if the corrosion prevention treatment layer 14 obtained using the rare earth element oxide sol contains alkali metal ions such as sodium or alkaline earth metal ions, corrosion can be prevented starting from the place containing the ions. The treated layer 14 is likely to deteriorate. Therefore, by fixing sodium ions and the like contained in the rare earth element oxide sol with an anionic polymer, the resistance of the corrosion prevention treatment layer 14 is improved.

The corrosion prevention treatment layer 14, which is a combination of an anionic polymer and a rare earth element oxide sol, has corrosion prevention performance equivalent to that of the corrosion prevention treatment layer 14 formed by subjecting an aluminum foil to chromate treatment. Preferably, the anionic polymer is a crosslinked structure of a polyanionic polymer that is essentially water soluble. Examples of cross-linking agents used for forming this structure include compounds having isocyanate groups, glycidyl groups, carboxy groups, and oxazoline groups.

Examples of compounds having an isocyanate group include diisocyanates such as tolylene diisocyanate, xylylene diisocyanate or hydrogenated products thereof, hexamethylene diisocyanate, 4,4′ diphenylmethane diisocyanate or hydrogenated products thereof, isophorone diisocyanate; Polyisocyanates such as an adduct obtained by reacting a class with a polyhydric alcohol such as trimethylolpropane, a biuret obtained by reacting with water, or an isocyanurate which is a trimer; or these poly Block polyisocyanates obtained by blocking isocyanates with alcohols, lactams, oximes and the like are included.

Examples of compounds having a glycidyl group include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,4-butanediol, 1,6-hexanediol, Glycols such as neopentyl glycol and epoxy compounds reacted with epichlorohydrin; polyhydric alcohols such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol and sorbitol, and epoxy compounds reacted with epichlorohydrin; phthalic acid, terephthalate Epoxy compounds obtained by reacting dicarboxylic acids such as acid, oxalic acid and adipic acid with epichlorohydrin, and the like.

Examples of compounds having a carboxy group include various aliphatic or aromatic dicarboxylic acids. Poly(meth)acrylic acid and alkali (earth) metal salts of poly(meth)acrylic acid may also be used.

As the compound having an oxazoline group, for example, when using a low-molecular compound having two or more oxazoline units, or a polymerizable monomer such as isopropenyloxazoline, (meth)acrylic acid, (meth)acrylic acid alkyl ester , hydroxyalkyl (meth)acrylate, and other acrylic monomers are copolymerized.

Also, an anionic polymer and a silane coupling agent are reacted, more specifically, a carboxyl group of the anionic polymer and a functional group of the silane coupling agent are selectively reacted, and the cross-linking point is a siloxane bond. good. In this case, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ -Mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, etc. can be used. Among them, epoxysilane, aminosilane, and isocyanatesilane are preferred, especially considering reactivity with anionic polymers or copolymers thereof.

The ratio of these cross-linking agents to the anionic polymer is preferably 1 to 50 parts by mass, more preferably 10 to 20 parts by mass, per 100 parts by mass of the anionic polymer. When the ratio of the cross-linking agent is 1 part by mass or more with respect to 100 parts by mass of the anionic polymer, a cross-linked structure is easily formed. If the ratio of the cross-linking agent is 50 parts by mass or less with respect to 100 parts by mass of the anionic polymer, the pot life of the coating liquid is improved.

The method of cross-linking the anionic polymer is not limited to the above-mentioned cross-linking agent, and may be a method of forming ionic cross-links using a titanium or zirconium compound.

Examples of cationic polymers include polymers having amines, such as polyethyleneimine, ionic polymer complexes composed of polymers having polyethyleneimine and carboxylic acid, primary amine-grafted acrylic resins in which primary amines are grafted to the main acrylic skeleton, Cationic polymers such as polyallylamine or derivatives thereof, and aminophenol can be used. Examples of polyallylamine include homopolymers or copolymers of allylamine, allylamineamide sulfate, diallylamine, dimethylallylamine, and the like. These amines may be free amines or stabilized with acetic acid or hydrochloric acid. Maleic acid, sulfur dioxide, etc. may also be used as copolymer components. Furthermore, a type in which a primary amine is partially methoxylated to impart thermal crosslinkability can also be used, and an aminophenol can also be used. Allylamine or derivatives thereof are particularly preferred.

The cationic polymer is preferably used in combination with a cross-linking agent having a functional group capable of reacting with an amine/imine such as a carboxyl group or a glycidyl group. As a cross-linking agent used in combination with a cationic polymer, a polymer having a carboxylic acid that forms an ionic polymer complex with polyethyleneimine can also be used. and polysaccharides having a carboxy group such as carboxymethyl cellulose or its ion salt.

In this embodiment, the cationic polymer is also described as one constituent element that constitutes the corrosion prevention treatment layer 14 . The reason for this is that as a result of intensive studies using various compounds in order to provide the electrolyte resistance and hydrofluoric acid resistance required for exterior materials for power storage devices, it was found that the cationic polymer itself also has electrolyte resistance and hydrofluoric acid resistance. This is because it has been found to be a compound that can be imparted. The reason for this is presumed to be that the aluminum foil is prevented from being damaged by capturing fluorine ions with cationic groups (anion catcher).

Cationic polymers are more preferred materials in terms of improved adhesion. Moreover, since the cationic polymer is also water-soluble like the anionic polymer, it is more preferable to impart water resistance by forming a crosslinked structure. As a cross-linking agent for forming a cross-linked structure in the cationic polymer, the cross-linking agent described in the section of the anionic polymer can be used. When a rare earth element oxide sol is used as the corrosion prevention treatment layer 14, a cationic polymer may be used as the protective layer instead of the anionic polymer.

Corrosion prevention treatment layer by chemical conversion treatment represented by chromate treatment uses phosphoric acid, hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, or a chemical conversion treatment agent containing these salts in order to form an inclined structure with the aluminum foil. Then, a chromium or non-chromium compound is allowed to act on the aluminum foil to form a chemical conversion layer on the aluminum foil. However, since the chemical conversion treatment uses an acid as a chemical conversion treatment agent, the working environment deteriorates and the coating equipment is corroded. On the other hand, unlike the chemical conversion treatment represented by chromate treatment, the coating-type corrosion prevention treatment layer 14 does not need to form an inclined structure on the metal foil layer 13 using aluminum foil. Therefore, the properties of the coating agent are not subject to restrictions such as acidity, alkalinity, neutrality, etc., and a good working environment can be realized. In addition, the chromate treatment using a chromium compound is preferably a coating type anti-corrosion treatment layer 14 from the point of view of environmental hygiene that alternatives are being sought.

From the above contents, as examples of combination of the coating type corrosion prevention treatment described above, (1) rare earth element oxide sol only, (2) anionic polymer only, (3) cationic polymer only, (4) rare earth element Oxide sol + anionic polymer (laminated composite), (5) rare earth element oxide sol + cationic polymer (laminated composite), (6) (rare earth element oxide sol + anionic polymer: laminated composite)/ Cationic polymer (multilayered), (7) (rare earth element oxide sol + cationic polymer: laminated composite)/anionic polymer (multilayered), and the like. Among them, (1) and (4) to (7) are preferred, and (4) to (7) are particularly preferred. However, this embodiment is not limited to the above combinations. For example, as an example of selecting a corrosion prevention treatment, a cationic polymer is a very preferable material in that it has good adhesion to the modified polyolefin resin mentioned in the explanation of the second adhesive layer or sealant layer to be described later. Therefore, when the second adhesive layer or sealant layer is composed of a modified polyolefin resin, a cationic polymer is provided on the surface in contact with the second adhesive layer or sealant layer (for example, configuration (5) and Configuration such as (6)) is possible.

Moreover, the corrosion prevention treatment layer 14 is not limited to the layers described above. For example, like coating-type chromate, which is a known technique, it may be formed using a treatment agent in which phosphoric acid and a chromium compound are blended in a resin binder (such as aminophenol). By using this treatment agent, it is possible to form a layer having both corrosion prevention function and adhesion. In addition, although it is necessary to consider the stability of the coating liquid, it is possible to achieve both corrosion prevention function and adhesion by using a coating agent in which the rare earth element oxide sol and polycationic polymer or polyanionic polymer are made into a single component in advance. It can be a layer that also has

The mass per unit area of the corrosion prevention treatment layer 14 is preferably 0.005 to 0.200 g/m ² , more preferably 0.010 to 0.100 g/m ² , regardless of whether it has a multilayer structure or a single layer structure. preferable. If the mass per unit area is 0.005 g/m ² or more, the metal foil layer 13 can easily be provided with a corrosion prevention function. Moreover, even if the mass per unit area exceeds 0.200 g/m ² , the corrosion prevention function does not change much. On the other hand, when a rare earth element oxide sol is used, if the coating film is thick, curing by heat during drying becomes insufficient, which may lead to a decrease in cohesive strength. The thickness of the corrosion prevention treatment layer 14 can be converted from its specific gravity.

The corrosion prevention treatment layer 14 easily maintains the adhesion between the sealant layer and the metal foil layer, prevents the occurrence of foaming starting points in the electrolytic solution, and further suppresses the deterioration of the insulation after degassing heat sealing. From this point of view, for example, it may be an embodiment containing cerium oxide, 1 to 100 parts by mass of phosphoric acid or a phosphate with respect to 100 parts by mass of the cerium oxide, and a cationic polymer, and the metal foil layer 13 may be formed by chemical conversion treatment, or the metal foil layer 13 may be formed by chemical conversion treatment and contains a cationic polymer.

<Second Adhesive Layer 17>
The second adhesive layer 17 is a layer that bonds the metal foil layer 13 on which the corrosion prevention treatment layer 14 is formed and the sealant layer 16 . For the second adhesive layer 17, a general adhesive for bonding the metal foil layer and the sealant layer can be used.

When the corrosion prevention treatment layer 14 has a layer containing at least one polymer selected from the group consisting of the cationic polymers and anionic polymers described above, the second adhesive layer 17 is included in the corrosion prevention treatment layer 14. It is preferable that the layer contains a compound (hereinafter also referred to as a “reactive compound”) having reactivity with the above polymer.

For example, when the corrosion prevention treatment layer 14 contains a cationic polymer, the second adhesive layer 17 contains a compound reactive with the cationic polymer. When the corrosion prevention treatment layer 14 contains an anionic polymer, the second adhesive layer 17 contains a compound reactive with the anionic polymer. Further, when the corrosion prevention treatment layer 14 contains a cationic polymer and an anionic polymer, the second adhesive layer 17 contains a compound reactive with the cationic polymer and a compound reactive with the anionic polymer. . However, the second adhesive layer 17 does not necessarily contain the above two types of compounds, and may contain a compound reactive with both the cationic polymer and the anionic polymer. Here, "having reactivity" means forming a covalent bond with a cationic polymer or an anionic polymer. Moreover, the second adhesive layer 17 may further contain an acid-modified polyolefin resin.

Examples of the compound reactive with the cationic polymer include at least one compound selected from the group consisting of polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxy group, and compounds having an oxazoline group.

These polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxy group, and compounds having an oxazoline group include the polyfunctional isocyanate compounds, glycidyl compounds, and carboxy groups previously exemplified as cross-linking agents for forming the cationic polymer into a cross-linked structure. and a compound having an oxazoline group. Among these, polyfunctional isocyanate compounds are preferred because they are highly reactive with cationic polymers and tend to form a crosslinked structure.

The compound reactive with the anionic polymer includes at least one compound selected from the group consisting of glycidyl compounds and compounds having an oxazoline group. Examples of the glycidyl compound and the compound having an oxazoline group include the glycidyl compound and the compound having an oxazoline group exemplified above as a cross-linking agent for forming the cationic polymer into a cross-linked structure. Among these, glycidyl compounds are preferred because of their high reactivity with the anionic polymer.

When the second adhesive layer 17 contains an acid-modified polyolefin resin, the reactive compound preferably has reactivity with the acid groups in the acid-modified polyolefin resin (that is, forms covalent bonds with the acid groups). Thereby, the adhesiveness with the corrosion prevention treatment layer 14 is further enhanced. In addition, the acid-modified polyolefin resin becomes a crosslinked structure, and the solvent resistance of the exterior material 10 is further improved.

The content of the reactive compound is preferably equivalent to 10 times the amount of the acidic groups in the acid-modified polyolefin resin. If the amount is equal to or more, the reactive compound sufficiently reacts with the acidic groups in the acid-modified polyolefin resin. On the other hand, if the amount exceeds 10 equivalents, the cross-linking reaction with the acid-modified polyolefin resin is sufficiently saturated, so unreacted substances are present, and various performances may be deteriorated. Therefore, for example, the content of the reactive compound is preferably 5 to 20 parts by mass (solid content ratio) with respect to 100 parts by mass of the acid-modified polyolefin resin.

An acid-modified polyolefin resin is obtained by introducing an acidic group into a polyolefin resin. Examples of the acidic group include a carboxy group, a sulfonic acid group, an acid anhydride group and the like, and particularly preferred are a maleic anhydride group and a (meth)acrylic acid group. As the acid-modified polyolefin resin, for example, the same resin as the modified polyolefin resin (a) used for the first sealant layer 16a, which will be described later, can be used.

The second adhesive layer 17 may contain various additives such as flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers and tackifiers.

The second adhesive layer 17 includes, for example, an acid-modified polyolefin, a polyfunctional isocyanate compound, and a glycidyl compound, from the viewpoint of suppressing the deterioration of the laminate strength when the electrolytic solution is involved and from the viewpoint of further suppressing the deterioration of the insulation. , and at least one curing agent selected from the group consisting of a compound having a carboxy group, a compound having an oxazoline group, and a carbodiimide compound. Examples of carbodiimide compounds include N,N'-di-o-toluylcarbodiimide, N,N'-diphenylcarbodiimide, N,N'-di-2,6-dimethylphenylcarbodiimide, N,N'-bis (2,6-diisopropylphenyl)carbodiimide, N,N'-dioctyldecylcarbodiimide, N-triyl-N'-cyclohexylcarbodiimide, N,N'-di-2,2-di-t-butylphenylcarbodiimide, N- triyl-N'-phenylcarbodiimide, N,N'-di-p-nitrophenylcarbodiimide, N,N'-di-p-aminophenylcarbodiimide, N,N'-di-p-hydroxyphenylcarbodiimide, N,N '-di-cyclohexylcarbodiimide, N,N'-di-p-toluylcarbodiimide and the like.

As the adhesive for forming the second adhesive layer 17, for example, a polyurethane adhesive obtained by blending a polyester polyol composed of a hydrogenated dimer fatty acid and a diol with a polyisocyanate can be used.

The thickness of the second adhesive layer 17 is not particularly limited, but is preferably 1 to 10 μm, more preferably 3 to 7 μm, from the viewpoint of obtaining desired adhesive strength, workability, and the like.

<Sealant layer 16>
The sealant layer 16 is a layer that imparts sealing properties to the exterior material 10 by heat sealing. The sealant layer 16 contains a polypropylene-based resin (A) and an incompatible component (B) that is incompatible with the polypropylene-based resin. The sealant layer 16 may further contain a compatible elastomer (C) compatible with the polypropylene resin (A). Hereinafter, in some cases, the polypropylene resin (A) is referred to as "(A) component", and the incompatible component (B) that is incompatible with the (A) component is referred to as "(B) component". The compatible elastomer (C) compatible with the component (A) is sometimes referred to as "component (C)". Here, "not compatible with component (A)" and "incompatible with component (A)" (non-compatible type) are used in the polypropylene resin that constitutes component (A). It means that the dispersed phase size is 200 nm or more and less than 50 μm. Further, "compatible with component (A)" and "having compatibility with component (A)" (compatible system) mean that the dispersed phase size of 1 nm or more and 200 nm in the polypropylene resin constituting component (A) means to be distributed at less than

In the sealant layer 16, the incompatible component (B) preferably contains a compound (B1) having a compatible portion with the polypropylene resin (A). Hereinafter, the compound (B1) having a compatible part with the component (A) may be referred to as "compound (B1)" or "component (B1)". The immiscible component (B) may consist of compound (B1) alone.

A sea-island structure is formed in the sealant layer 16 by including the above component (A) and the above component (B) in the sealant layer 16 . That is, the sealant layer 16 has a region in which the polypropylene-based resin (A) exists and a region in which a plurality of incompatible components (B) exist surrounded by the polypropylene-based resin (A). Thereby, the seal strength after heat sealing can be improved. Further flexibility can be imparted to the sealant layer 16 by further including the above component (C) in the sealant layer 16 . Since the sealant layer 16 has flexibility, it is possible to impart functions such as mold whitening suppression, and it is possible to provide an exterior material with improved functionality.

FIG. 2 is an enlarged cross-sectional view schematically showing the cross-sectional structure of the surface along the VD direction and the MD direction of the sealant layer in the power storage device exterior material according to one embodiment of the present invention, (a) is 190 ° C. (b) is a diagram after heating at 190° C. for 30 seconds. The MD direction is the flow direction during formation of the sealant layer and corresponds to the so-called machine direction. Also, the VD direction indicates the thickness direction of the sealant layer 16 (or the stacking direction of the exterior material 10) and is perpendicular to the surface of the sealant layer including the MD direction. A direction perpendicular to the MD direction and the VD direction is sometimes called the TD direction, and this TD direction corresponds to the so-called transverse direction. The planes along the MD and TD directions are parallel to the plane of the sealant layer and perpendicular to the planes along the VD and MD directions.

In FIG. 2(a), the sealant layer 16 has a region 162 where the polypropylene resin (A) exists and a region 164 where a plurality of immiscible components (B) exist surrounded by the polypropylene resin (A). . The component (B) existing region 164 has a needle-like shape that is long in the MD direction of the sealant layer 16 and short in the VD direction. In FIG. 2A, the length LMD in the ^MD direction of the presence region 164 of the component (B) is much larger than the length LVD in the ^VD direction. The shape of the region 164 where the component (B) exists is derived from the method of forming the sealant layer 16 . The sealant layer 16 is formed by, for example, continuously supplying a dry-blended and melted resin composition for forming a sealant layer, and conveying or laminating the resin composition. When forming a thin layer such as a sealant layer, each material in the resin composition constitutes the sealant layer in a state of being thinly stretched in the MD direction. The formation speed (processing speed) of the sealant layer 16 can be, for example, 80 m/min or more from the viewpoint of productivity. When the formation speed of the sealant layer 16 is above a certain level in this way, the state in which each material is stretched in the MD direction becomes more conspicuous. When the (B) component dispersed in the (A) component is thinly stretched in the MD direction during the formation of the sealant layer 16, the (B) component has, for example, a plurality of elliptical shapes in cross sections along the MD and TD directions. , and these overlap in the VD direction. In cross sections along the VD direction and the MD direction of the sealant layer 16, the (B) component appears as the above-described acicular shape as the existence region 164 as shown in FIG. 2(a).

The average length LAMD in the ^MD direction of the component (B) existing region 164 may be, for example, 2.0 to 20.0 μm, or may be 3.0 to 15.0 μm. Also, the average length LA ^VD in the VD direction of the component (B) existing region 164 can be, for example, 0.1 to 1.0 μm. Note that the average lengths LA ^MD and LA ^VD of the component (B) existing regions 164 are obtained by measuring cross sections along the VD direction and the MD direction of the sealant layer 16 with a scanning electron microscope (SEM) or the like, using a magnification of about 3000. , and the lengths L ^MD and L ^VD of ten or more arbitrarily selected existence regions 164 are measured.

(B) The ratio of the average length LA ^MD in the MD direction to the average length LA ^VD in the VD direction of the component presence region 164 (LA ^MD /LA ^VD ) can be 10.0 or more; It may be 0 or more. That the average length of the component (B) existing region 164 satisfies the above ratio means that sufficient productivity is ensured in the formation of the sealant layer 16 .

The shape of component (B) that has been stretched as described above tends to be deformed into a spherical shape by heating. That is, when heated, the region where the component (B) exists, which is needle-shaped in the cross section along the VD and MD directions, tends to deform short in the MD direction and elongate in the VD direction. In other words, it can be said that the existing region of the component (B) is contracted in the MD direction. In FIG. 2(b), the sealant layer 16h shows the sealant layer after heating at 190° C. for 30 seconds. The sealant layer 16h after heating includes a region 162h where the polypropylene-based resin (A) after heating exists and a region 164h where a plurality of incompatible components (B) after heating exist which are surrounded by the polypropylene-based resin (A). have The component (B) existing region 164h is smaller in the MD direction and larger in the VD direction than the existing region 164 before heating.

In the power storage device exterior material 10 of the present embodiment, the sealant layer 16 includes a low-shrinkage sealant layer having a small degree of deformation and shrinkage. In the low-shrinkage sealant layer, as shown in FIG. 2(b), the ^MD -direction length LhMD of the component (B) existing region ^164h after heating is smaller than the length LMD before heating. However, the degree of shrinkage is small. Specifically, in the low-shrinkage sealant layer, the average length LAh ^MD in the MD direction of the existing region of the component (B) before heating in the cross section along the VD direction and the MD direction, along the VD direction and the MD direction The ratio (LAh ^MD /LA ^MD ) of the average length LAh ^MD in the MD direction of the existing region of the component (B) after heating in the cross section is 0.20 or more, preferably 0.30 or more, and more preferably is greater than or equal to 0.35. This ratio (LAh ^MD /LA ^MD ) is sometimes simply referred to as the shrinkage ratio. When the shrinkage ratio is 0.20 or more, the adhesion strength of the interface of the sea-island structure composed of the components (A) and (B) is high, and voids are less likely to form at the interface even when the electrolyte foams. , the deterioration of insulation after degassing heat sealing can be suppressed.

In the low shrinkage sealant layer, the average length LAh ^MD in the MD direction of the component (B) existing region 164h after heating can be, for example, 1.0 to 20.0 μm, and can be 2.0 to 15 0 μm. In addition, the average length LAh ^VD in the VD direction of the component (B) existing region 164h after heating can be, for example, 0.1 to 2.0 μm. Note that the average lengths LAh ^MD and LAh ^VD of the (B) component existing region 164 h after heating are obtained by scanning a cross section along the VD direction and the MD direction of the sealant layer 16 h after heating with a scanning electron microscope (SEM) or the like. It is an average value when the lengths Lh ^MD and Lh ^VD of ten or more arbitrarily selected existing regions 164 h are measured by observing at a magnification of about 3000 times.

In the low-shrinkage sealant layer, the ratio of the average length LAh ^MD in the MD direction to the average length LAh ^VD in the VD direction (LAh ^MD /LAh ^VD ) of the presence region 164h of the component (B) after heating is 2. It is preferably 0.50 or more, more preferably 3.00 or more, and even more preferably 5.00 or more. This ratio (LAh ^MD /LAh ^VD ) is sometimes simply referred to as the length-to-width ratio or aspect ratio. The fact that the average length of the region 164 in which component (B) exists after heating satisfies the above ratio means that the shape of component (B) stretched during the formation of the sealant layer is maintained even after heating, and the interface of the sea-island structure is maintained. This means that the adhesion strength is high, and as a result, even if the electrolytic solution foams, voids are less likely to occur at the interface, and there is a tendency to further suppress the deterioration of insulation after degassing heat sealing.

Examples of the sealant layer 16 are described below.

(Polypropylene resin (A))
The polypropylene-based resin (A) is a resin obtained from polymerized monomers containing propylene. Examples of the polypropylene-based resin (A) include homopolypropylene and random polypropylene. The polypropylene-based resin (A) is preferably random polypropylene, more preferably a propylene-ethylene random copolymer, from the viewpoint of the basic performance of the exterior material such as heat seal strength. Propylene-ethylene random copolymers are excellent in heat-sealing properties at low temperatures, and can improve sealing properties related to electrolytic solutions.

In the propylene-ethylene random copolymer, the ethylene content is preferably 0.1 to 10% by mass, more preferably 1 to 7% by mass, even more preferably 2 to 5% by mass. When the ethylene content is 0.1% by mass or more, the effect of lowering the melting point due to copolymerization of ethylene is sufficiently obtained, and the sealing properties related to the electrolytic solution can be further improved, and impact resistance can be obtained. , there is a tendency that the seal strength and molding whitening resistance can be improved. When the ethylene content is 10% by mass or less, it is possible to prevent the melting point from dropping too much, and there is a tendency to more sufficiently suppress the occurrence of excessively sealed portions. The ethylene content can be calculated from the mixing ratio of the monomers during polymerization.

The melting point of the propylene-ethylene random copolymer is preferably 120 to 145°C, more preferably 125 to 140°C. When the melting point is 120° C. or higher, there is a tendency that the generation of excessively sealed portions can be more sufficiently suppressed. When the melting point is 145° C. or less, there is a tendency that the sealing properties related to the electrolytic solution can be further improved.

The propylene-ethylene random copolymer may be acid-modified, for example, an acid-modified propylene-ethylene random copolymer graft-modified with maleic anhydride. By using the acid-modified propylene-ethylene random copolymer, the adhesiveness to the tab lead can be maintained even without the tab sealant.

The propylene-ethylene random copolymer can be used alone or in combination of two or more.

In the sealant layer 16, the content of component (A) may be 50 to 99% by mass, 50 to 95% by mass, or 50 to 85% by mass, based on the total solid content of the sealant layer 16. % by mass. When the content of the component (A) is 50% by mass or more, the effect of using the component (A) itself can improve the sealing properties. In addition, by making the content of component (A) 50% by mass or more, it is possible to prevent component (B) from being excessively present, so that a good sea-island structure can be easily formed, and a sealant layer can be formed. It is possible to suppress the deterioration of heat resistance and cohesion of No. 16. On the other hand, by setting the content of the component (A) to 99% by mass or less, the component (B) can be contained in an amount of 1% by mass or more, so that the seal strength and insulation can be improved by the component (B). can.

(Incompatible component (B))
Examples of the incompatible component (B) include graft copolymers, block copolymers and random copolymers. These copolymers have at least a portion incompatible with component (A).

The incompatible component (B) preferably contains a compound (B1) having a compatible portion with the polypropylene resin (A). By including the compound (B1) in the immiscible component (B), the shrinkage ratio of the sealant layer 16 can be improved, the adhesion strength at the interface of the sea-island structure can be improved, and the formation of voids caused by the foaming of the electrolytic solution can be improved. Since the formation is suppressed, the insulation can be further improved. In addition, the seal strength can be improved by improving the adhesion strength at the sea-island interface by the compound (B1). Such a compound (B1) can be obtained, for example, when the immiscible component (B) is a graft copolymer or block copolymer. Graft copolymers suitable as the compound (B1) include graft copolymers composed of a polyolefin main chain and polystyrene side chains, and graft copolymers composed of a polyolefin main chain and styrene-acrylonitrile copolymer side chains. etc. As the above-mentioned graft copolymer, for example, "Modiper" manufactured by NOF Corporation is suitable.

Examples of block copolymers suitable as the compound (B1) include a block copolymer having a block composed of a styrene unit and a block composed of an ethylene-butylene unit, and a block composed of a styrene unit and ethylene-butylene. A block copolymer having a block composed of a unit and a block composed of a crystalline olefin unit, a block copolymer having a block composed of a crystalline ethylene unit and a block composed of an ethylene-butylene unit , a block copolymer having a block composed of ethylene and a block composed of ethylene-octene 1, a block copolymer having a block composed of a propylene unit and a block composed of an ethylene unit, etc. is mentioned. For example, a block composed of propylene units is compatible with component (A), and a block composed of ethylene units is incompatible with component (A). Suitable block copolymers include, for example, "DYNARON" manufactured by JSR, "INTUNE" and "INFUSE" manufactured by DOW.

The immiscible component (B) may contain an immiscible elastomer. Examples of non-compatible elastomers include polyolefin elastomers containing α-olefins as comonomers. In particular, the use of the ethylene-α-olefin copolymer tends to impart functionality to the sealant layer 16 without lowering the electrolyte lamination strength or various seal strengths related to the electrolyte. The ethylene-α-olefin copolymer is obtained by copolymerizing ethylene with at least one α-olefin selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 1-octene and 4-methyl-1-pentene. An ethylene-butene-1 random copolymer obtained by copolymerizing ethylene with 1-butene can be preferably used. As the ethylene-α-olefin copolymer, "Tafmer" manufactured by Mitsui Chemicals, "Excellen" manufactured by Sumitomo Chemical Co., Ltd., etc. are suitable.

For the sealant layer 16, a dispersion in which the incompatible component (B) is dispersed in the polypropylene resin (A) is prepared, and by using the dispersion, the polypropylene resin (A) and the incompatible component (B) may contain Examples of such a dispersion include a dispersion in which an elastomer is finely dispersed in a polypropylene resin. When the sealant layer 16 contains the immiscible component (B) as a dispersion in which the polypropylene resin (A) is previously dispersed, the insulating properties and seal strength tend to be further improved. The incompatible component (B) in the dispersion preferably contains a graft copolymer or block copolymer. When the immiscible component (B) in the dispersion contains a graft copolymer or a block copolymer, there is a tendency that the adhesion at the sea-island interface can be further improved.

As the immiscible component (B), olefin-based and styrene-based materials have been described above, but from the viewpoint of electrolyte resistance, the immiscible component (B) is preferably an olefin-based material.

(Compatible elastomer (C))
Examples of compatible elastomers (C) include propylene-α-olefin copolymers. By using the propylene-α-olefin copolymer, functionality can be imparted to the sealant layer 16 without lowering the electrolytic solution lamination strength and various sealing strengths related to the electrolytic solution. The propylene-α-olefin copolymer is a compound obtained by copolymerizing propylene with an α-olefin selected from 1-butene, 1-pentene, 1-hexene, 1-octene and 4-methyl-1-pentene. A propylene-butene-1 random copolymer obtained by copolymerizing 1-butene can be preferably used.

The melting point of the polyolefin-based elastomer is preferably 150° C. or less, but from the viewpoint of suppressing excessively sealed portions, suppressing molding whitening, and improving sealing properties related to the electrolytic solution, it is preferably 60 to 120° C. , 65 to 90°C. A melting point of 150° C. or less can improve the sealing properties related to the electrolyte, especially the degassing heat seal strength. Further, when the melting point is 60° C. or higher, it is advantageous from the viewpoint of suppressing the generation of excessively sealed portions.

Polyolefin-based elastomers can be used singly or in combination of two or more.

In the sealant layer 16, the content of component (B) is preferably 1 to 40% by mass, more preferably 5 to 25% by mass, based on the total solid content of the sealant layer 16. When the content of component (B) is 1% by mass or more, impact resistance can be imparted to the sealant layer 16, and seal strength and insulation can be improved. On the other hand, by setting the content of the component (B) to 40% by mass or less, it becomes easier to form a favorable sea-island structure, and the cohesive force of the sealant layer 16 as a whole can be improved, thereby improving the seal strength and insulation properties. be able to. For convenience, the dispersion in which the elastomer is finely dispersed in the polypropylene resin is described as the incompatible component (B). ) component.

When the sealant layer 16 contains the (C) component, the content of the (C) component in the sealant layer 16 is preferably 5 to 30% by mass, based on the total solid content of the sealant layer 16, preferably 10 to 25 mass. % is more preferable. When the content of the component (C) is 5% by mass or more, the flexibility of the sealant layer 16 can be easily obtained, and functions such as molding whitening suppression can be imparted, and the exterior material with further improved functionality. can be provided. On the other hand, by setting the content of component (C) to 30% by mass or less, the cohesive force of the entire sealant layer 16 can be improved, and the seal strength and insulation can be improved.

Further, the content ratio (M _C /M _B ) of the compatible elastomer (C) to the incompatible component (B) is preferably 0.2 to 3.0, more preferably 0.3 to 2.0. .0 is more preferred. When the content ratio (M _C /M _B ) is within the above range, it becomes easier to improve the seal strength.

When the immiscible component (B) contains the compound (B1), the content of the compound (B1) in the sealant layer 16 is preferably 1 to 40% by mass based on the total amount of the sealant layer, and 2 to It is more preferably 25% by mass. When the content of the compound (B1) is 1% by mass or more, the adhesion strength at the sea-island interface can be easily improved, and the effect of improving the seal strength and insulation can be easily obtained. On the other hand, by setting the content of the compound (B1) to 40% by mass or less, it becomes easier to suppress deterioration in the cohesive force, seal strength, and insulation of the sealant layer 16 as a whole.

(Additional component)
The sealant layer 16 may further contain components other than the components (A) to (C) described above. As components other than components (A) to (C), other resins such as LDPE (low density polyethylene) may be added in order to improve handling and workability. The content of the other resin components to be added is preferably 10 parts by mass or less when the total mass of the sealant layer 16 is 100 parts by mass. Examples of components other than resins include slip agents, antiblocking agents, antioxidants, light stabilizers, and flame retardants. The content of components other than these resins is preferably 5 parts by mass or less when the total mass of the sealant layer 16 is 100 parts by mass.

The presence of α-olefin in the sealant layer 16 can be confirmed by attribution using FT-IR (Fourier transform infrared spectrophotometer). The α-olefin content was measured using the sealant layer 16 blended with a known amount of elastomer containing a known amount of α-olefin, and using the transmittance or absorbance of the characteristic absorption bands of components (A) to (C), a calibration curve was obtained. It is possible to check by creating Further, the α-olefin content of each of the immiscible component (B) and the compatible elastomer (C) was also similarly imaged in the characteristic absorption band of FT-IR, and microscopic FT-IR (transmission method) ) can be confirmed by mapping the absorption band attributed to butene-1. In addition to FT-IR, the presence and content of butene-1 can also be confirmed by measuring the sealant layer 16 with NMR.

The thickness of the sealant layer 16 is, for example, 5-100 μm. It may be 10 to 80 μm, 10 to 60 μm, 10 to 45 μm, or 30 μm or less from the demand for miniaturization of power storage devices. Even with such a thin film structure, the exterior material for a power storage device of the present embodiment can suppress deterioration in insulation after heat sealing, molding, and degassing heat sealing.

As described above, preferred embodiments of the exterior material for a power storage device of the present embodiment have been described in detail, but the present invention is not limited to such specific embodiments, and the present invention described within the scope of claims. Various modifications and changes are possible within the scope of the gist.

For example, FIG. 1 shows the case where the corrosion prevention treatment layer 14 is formed on the surface of the metal foil layer 13 on the side of the second adhesive layer 17 , but the corrosion prevention treatment layer 14 is formed on the second adhesive layer 17 side of the metal foil layer 13 . It may be formed on the surface of one adhesive layer 12 side, or may be formed on both surfaces of the metal foil layer 13 . When the corrosion prevention treatment layer 14 is formed on both surfaces of the metal foil layer 13, the structure of the corrosion prevention treatment layer 14 formed on the first adhesive layer 12 side of the metal foil layer 13 and the structure of the metal foil layer 13 The structure of the corrosion prevention treatment layer 14 formed on the second adhesive layer 17 side may be the same or different.

FIG. 1 shows the case where the metal foil layer 13 and the sealant layer 16 are laminated using the second adhesive layer 17, but the power storage device exterior material 20 shown in FIG. The sealant layer 16 may be formed directly on the metal foil layer 13 without interposing the second adhesive layer 17 as in the device exterior material 30 . On the other hand, the power storage device exterior material 20 shown in FIG. 3 and the power storage device exterior material 30 shown in FIG. .

FIG. 1 shows the case where the sealant layer 16 is formed of a single layer, but the sealant layer 16 may be formed like the power storage device exterior material 20 shown in FIG. 3 and the power storage device exterior material 30 shown in FIG. It may be formed from multiple layers of two or more layers. The configuration of each of the multiple layers forming the sealant layer 16 may be the same or different. When the sealant layer 16 is multi-layered, at least one of them is preferably a low-shrinkage sealant layer.

In the power storage device exterior material 20 shown in FIG. 3, the sealant layer 16 is composed of a first sealant layer 16a and a second sealant layer 16b. Here, the first sealant layer 16a is the outermost layer of the sealant layers, and the second sealant layer 16b is the innermost layer of the sealant layers. At least one layer selected from the group consisting of the first sealant layer 16a and the second sealant layer 16b is preferably a low-shrinkage sealant layer.

The second sealant layer 16b (innermost layer) can be formed, for example, using the same components as those of the sealant layer 16 in the exterior material 10 described above. When the second sealant layer 16b is a low-shrinkage sealant layer, it becomes easier to suppress the deterioration of the insulation when the electrolytic solution is involved.

The thickness of the second sealant layer 16b may be, for example, 5 to 100 μm, may be 10 to 60 μm from the viewpoint of thinning, may be 10 to 40 μm, or may be 10 to 30 μm. 20 μm or less.

The first sealant layer 16a (outermost layer, metal foil side layer) may be formed, for example, using the same components as the second sealant layer 16b, but in the first sealant layer 16a, for example In place of the same components as those of the second sealant layer 16b, it is preferable to use an adhesive component containing an additive component as necessary in consideration of aluminum treatment and adhesiveness. By using the above adhesive component as the first sealant layer 16a, the sealant layer can be formed on the metal foil layer without an adhesive layer. The first sealant layer 16a, like the second sealant layer 16b, contains components corresponding to the above components (A) and (B), so that the first sealant layer 16a forms a sea-island structure, and When the first sealant layer 16a is a low-shrinkage sealant layer, the adhesiveness of the sea-island interface can be improved, and the adhesiveness between the sealant layer and the metal foil layer can be easily maintained. It tends to prevent the occurrence of voids associated with degassing and further suppress the deterioration of insulation after degassing heat sealing.

The adhesive constituents in the first sealant layer 16a are not particularly limited, but the modified polypropylene resin (i) as the component (A) and the macrophase-separated thermoplastic elastomer (ii) as the component (B) ) component. Further, the additive component preferably contains an atactic structure polypropylene or an atactic structure propylene-α-olefin copolymer (iii). Each component will be described below.

(Modified polypropylene resin (i))
Modified polypropylene resin (i) is obtained by graft-modifying an unsaturated carboxylic acid derivative component derived from any of unsaturated carboxylic acid, unsaturated carboxylic acid anhydride, and unsaturated carboxylic acid ester to polypropylene resin. It is preferably a resin with

Examples of polypropylene-based resins include homopolypropylene and random polypropylene.

Compounds used for graft modification of these polypropylene resins include unsaturated carboxylic acid derivative components derived from any of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and unsaturated carboxylic acid esters. be done.

Specifically, examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, bicyclo[2,2,1]hept-2-ene-5, 6-dicarboxylic acid and the like.

Acid anhydrides of unsaturated carboxylic acids include, for example, maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylic anhydride. acid anhydrides of unsaturated carboxylic acids such as

Esters of unsaturated carboxylic acids include, for example, methyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dimethyl maleate, monomethyl maleate, diethyl fumarate, dimethyl itaconate, diethyl citraconate, tetrahydrophthalic anhydride. Esters of unsaturated carboxylic acids such as dimethyl and dimethyl bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylate are included.

The modified polypropylene resin (i) is obtained by graft polymerization (graft modification) of 0.2 to 100 parts by mass of the unsaturated carboxylic acid derivative component described above with respect to 100 parts by mass of the base polypropylene resin in the presence of a radical initiator. It can be manufactured by The reaction temperature for graft modification is preferably 50 to 250°C, more preferably 60 to 200°C. In addition, the reaction time is appropriately set according to the production method. minutes is more preferred. Graft modification can be carried out under normal pressure or pressurized conditions.

Radical initiators used for graft modification include organic peroxides such as alkyl peroxides, aryl peroxides, acyl peroxides, ketone peroxides, peroxyketals, peroxycarbonates, peroxyesters and hydroperoxides. be done.

These organic peroxides can be appropriately selected and used according to the reaction temperature and reaction time conditions described above. For example, in the case of melt graft polymerization using a twin-screw extruder, alkyl peroxides, peroxyketals, and peroxyesters are preferred, and specifically di-t-butyl peroxide, 2,5-dimethyl-2,5-di -t-butylperoxy-hexyne-3, dicumyl peroxide and the like are preferred.

Modified polypropylene resin (i) is preferably modified with maleic anhydride. Since such a modified polypropylene resin (i) is excellent in reactivity with various metals and polymers having various functional groups, the reactivity can be used to impart adhesion to the first sealant layer 16a. It is possible to improve the electrolytic solution resistance.

(Macrophase-separated thermoplastic elastomer (ii))
The macrophase-separated thermoplastic elastomer (ii) forms a macrophase-separated structure with a dispersed phase size of more than 200 nm and 50 μm or less in the modified polypropylene resin (i).

When the first sealant layer 16a contains the macrophase-separated thermoplastic elastomer (ii), the modified polypropylene resin (i) or the like, which can be the main component of the first sealant layer 16a, is laminated. viscoelastic adhesion can be imparted to the first sealant layer 16a. Therefore, the adhesion of the first sealant layer 16a is further improved, and the exterior material 20 having excellent electrolyte resistance is obtained. By containing the macrophase-separated thermoplastic elastomer (ii) in the first sealant layer 16a, the sealant layer 16 can be imparted with impact resistance, and seal strength and insulation can be improved.

The macrophase-separated thermoplastic elastomer (ii) exists in a sea-island pattern in the modified polypropylene resin (i), and when the dispersed phase size is 200 nm or less, it can improve viscoelastic adhesion. become difficult. On the other hand, when the dispersed phase size exceeds 50 μm, the modified polypropylene resin (i) and the macrophase-separated thermoplastic elastomer (ii) are essentially incompatible, so lamination suitability (processability) is significantly reduced. Along with this, the physical strength of the first sealant layer 16a tends to decrease. From the above, the dispersed phase size is preferably 500 nm to 10 μm.

Examples of such a macrophase-separated thermoplastic elastomer (ii) include, for example, ethylene mixed with an α-olefin selected from 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene. Examples include polymerized polyethylene-based thermoplastic elastomers.

In addition, as the macrophase-separated thermoplastic elastomer (ii), commercially available products can be used. etc. is suitable.

In the first sealant layer 16a, the content of the macrophase-separated thermoplastic elastomer (ii) relative to the modified polypropylene resin (i) is 1 to 40 parts by mass with respect to 100 parts by mass of the modified polypropylene resin (i). is preferred, and 5 to 30 parts by mass is more preferred. If the content of the macrophase-separated thermoplastic elastomer (ii) is less than 1 part by mass, no improvement in adhesion of the first sealant layer can be expected. On the other hand, when the content of the macrophase-separated thermoplastic elastomer (ii) exceeds 40 parts by mass, the modified polypropylene-based resin (i) and the macrophase-separated thermoplastic elastomer (ii) inherently have low compatibility, so processing The strength tends to decrease markedly. In addition, since the macrophase-separated thermoplastic elastomer (ii) is not a resin exhibiting adhesiveness, the adhesion of the first sealant layer 16a to other layers such as the second sealant layer 16b and the corrosion prevention treatment layer 14 is lowered. easier to do.

(Polypropylene with atactic structure or propylene-α-olefin copolymer with atactic structure (iii))
The first sealant layer 16a preferably contains an atactic structure polypropylene or an atactic structure propylene-α olefin copolymer (hereinafter simply referred to as “(iii) component”) as an additive component. Here, the (iii) component is a completely amorphous resin component. Flexibility can be imparted to the sealant layer 16 by the first sealant layer 16a containing the component (iii). Since the sealant layer 16 has flexibility, it is possible to provide the exterior material 10 with functions such as suppression of molding whitening, thereby providing an exterior material with improved functionality.

The first sealant layer 16a contains, as an additive component, a propylene-α-olefin copolymer having an isotactic structure corresponding to the component (C) in addition to the component (iii) described above to impart flexibility. It may contain further.

In the first sealant layer 16a, the total mass of the components (i) and (ii) may be, for example, 60% by mass or more and 95% by mass or less based on the total mass of the first sealant layer 16a. , 70% by mass or more and 90% by mass or less.

In the first sealant layer 16a, the mass of component (iii) is, for example, 5% by mass or more and 40% by mass or less based on the total mass of components (i), (ii), and (iii). is preferred. When the mass of component (iii) is 5% by mass or more based on the total mass of components (i), (ii), and (iii), the effect of adding the additive as described above is obtained. tend to be easier to obtain. On the other hand, when the mass of component (iii) is 40% by mass or less based on the total mass of components (i), (ii), and (iii), the second sealant layer 16b and the corrosion prevention treatment layer The adhesion of the first sealant layer 16a to other layers such as 14 tends to decrease. From these points of view, in the first sealant layer 16a, the total mass of components (i) and (ii) is based on the total mass of components (i), (ii), and (iii), for example, It is preferably 60 to 95% by mass.

As a method for analyzing the additive component (iii) in the first sealant layer 16a, for example, stereoregularity evaluation by nuclear magnetic resonance spectroscopy (NMR) can be used for quantitative determination.

The first sealant layer 16a includes, in addition to adhesive components (that is, modified polypropylene resin (i) and macrophase-separated thermoplastic elastomer (ii)) and additive components (that is, component (iii)), Various additives such as flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, tackifiers, etc. may be included depending on the application.

The thickness of the first sealant layer 16a is not particularly limited, but is preferably equal to or less than that of the second sealant layer 16b from the viewpoint of stress relaxation and moisture/electrolyte permeation.

Also, in the power storage device exterior material 20, the thickness of the sealant layer 16 (total thickness of the first sealant layer 16a and the second sealant layer 16b) is 10 to 80 μm from the viewpoint of thinning. 10 to 60 μm, 10 to 45 μm, or 30 μm or less. Even with such a thin film structure, the exterior material for a power storage device of the present embodiment can suppress deterioration in insulation after heat sealing, molding, and degassing heat sealing.

FIG. 3 shows the case where the sealant layer 16 is formed of two layers, but the sealant layer 16 may be formed of three layers like the power storage device exterior material 30 shown in FIG. 4 . In the power storage device exterior material 30 shown in FIG. 4, the sealant layer 16 is composed of a first sealant layer 16a, a second sealant layer 16b, and a third sealant layer 16c. Here, the first sealant layer 16a is the outermost layer (metal foil side layer) of the sealant layer, the third sealant layer 16c is the intermediate layer of the sealant layer, and the second sealant layer 16b is the sealant layer. It is the innermost layer. At least one layer selected from the group consisting of these three layers is preferably a low-shrinkage sealant layer.

Examples and preferred forms of the material constituting the first sealant layer 16 a of the power storage device exterior material 30 are the same as those of the first sealant layer 16 a of the power storage device exterior material 20 .

Exemplary and preferred forms of the materials constituting the second sealant layer 16 b and the third sealant layer 16 c of the power storage device exterior material 30 are the same as those of the second sealant layer 16 b of the power storage device exterior material 20 .

In the power storage device exterior material 30, the thickness of the first sealant layer 16a may be, for example, 2 to 30 μm, 5 to 20 μm, or 8 to 10 μm. The thickness of the sealant layer 16b may be, for example, 5 to 80 μm, 13 to 40 μm, or 15 to 20 μm, and the thickness of the third sealant layer 16c may be, for example, , 2 to 30 μm, 5 to 20 μm, or 8 to 10 μm.

Also in the power storage device exterior material 30, from the viewpoint of thinning, the thickness of the sealant layer 16 (the total thickness of the first sealant layer 16a, the second sealant layer 16b, and the third sealant layer 16c) is , 30 μm or less. Even with such a thin film structure, the exterior material for a power storage device of the present embodiment can suppress deterioration in insulation after heat sealing, molding, and degassing heat sealing.

When the sealant layer is composed of a plurality of layers as in the power storage device exterior materials 20 and 30, the first sealant layer 16a closest to the metal foil layer 13 is preferably a low-shrinkage sealant layer. Since the first sealant layer 16a is a low-shrinkage sealant layer, the adhesion strength at the sea-island interface can be improved, and the formation of voids due to foaming of the electrolytic solution can be suppressed. There is a tendency that later insulation can be further improved. Foaming of the electrolytic solution during degassing heat sealing often occurs in a portion of the sealant layer 16 near the metal foil layer 13, and the layer closest to the metal foil layer 13 is a low-shrinkage sealant layer, It tends to be easier to suppress the deterioration of insulation more efficiently.

Also, the second sealant layer 16b or the third sealant layer 16c may be a low-shrinkage sealant layer. Since the second sealant layer 16b or the third sealant layer 16c is a low-shrinkage sealant layer, the adhesion strength of the sea-island interface formed by the components (A) and (B) can be improved, Since the formation of voids due to foaming is suppressed, the insulating properties can be further improved.

[Method for manufacturing exterior material]
Next, an example of a method for manufacturing the exterior material 10 shown in FIG. 1 will be described. Note that the method for manufacturing the exterior material 10 is not limited to the following method.

The method for manufacturing the exterior material 10 of the present embodiment includes a step of laminating the corrosion prevention treatment layer 14 on the metal foil layer 13, a step of bonding the base material layer 11 and the metal foil layer 13 together, and a second adhesive layer. It is roughly configured including a step of further laminating a sealant layer 16 via 17 to produce a laminated body, and a step of aging the obtained laminated body, if necessary.

(Lamination step of corrosion prevention treatment layer 14 on metal foil layer 13)
This step is a step of forming the corrosion prevention treatment layer 14 on the metal foil layer 13 . As the method, as described above, the metal foil layer 13 may be subjected to a degreasing treatment, a hydrothermal transformation treatment, an anodizing treatment, or a chemical conversion treatment, or a method of applying a coating agent having corrosion prevention performance. .

Further, when the corrosion prevention treatment layer 14 is multi-layered, for example, a coating liquid (coating agent) constituting the corrosion prevention treatment layer on the lower layer side (metal foil layer 13 side) is applied to the metal foil layer 13 and baked to form the second layer. After forming the first layer, a coating liquid (coating agent) that constitutes the upper corrosion prevention treatment layer may be applied to the first layer and baked to form the second layer.

For degreasing, the spray method or immersion method is used. For hydrothermal transformation treatment and anodizing treatment, the immersion method is used. For the chemical conversion treatment, the immersion method, spray method, coating method, etc. are appropriately selected according to the type of chemical conversion treatment. you can do it.

Various methods such as gravure coating, reverse coating, roll coating, and bar coating can be used as the coating method of the coating agent having anti-corrosion performance.

As described above, the various treatments may be performed on either one or both sides of the metal foil, but in the case of single-sided treatment, the treated side is preferably the side on which the second adhesive layer 17 is laminated. Note that the surface of the base layer 11 may also be subjected to the above-described treatment as required.

Also, the coating amount of the coating agent for forming the first layer and the second layer is preferably 0.005 to 0.200 g/m ² , more preferably 0.010 to 0.100 g/m ² .

Further, when dry curing is required, it can be carried out at a base material temperature of 60 to 300° C. depending on the drying conditions for the corrosion prevention treatment layer 14 to be used.

(Step of Bonding Base Material Layer 11 and Metal Foil Layer 13)
This step is a step of bonding the metal foil layer 13 provided with the corrosion prevention treatment layer 14 and the base layer 11 with the first adhesive layer 12 interposed therebetween. As a bonding method, dry lamination, non-solvent lamination, wet lamination, or the like is used, and both are bonded together using the material constituting the first adhesive layer 12 described above. The first adhesive layer 12 is provided in a dry coating amount of 1 to 10 g/m ² , more preferably 3 to 7 g/m ² .

(Step of Laminating Second Adhesive Layer 17 and Sealant Layer 16)
This step is a step of bonding the sealant layer 16 to the corrosion prevention treatment layer 14 side of the metal foil layer 13 via the second adhesive layer 17 . A wet process, a dry lamination, etc. are mentioned as the method of bonding.

In the case of a wet process, a solution or dispersion of an adhesive that constitutes the second adhesive layer 17 is applied onto the corrosion prevention treatment layer 14 and heated at a predetermined temperature (when the adhesive contains an acid-modified polyolefin resin, is a temperature above its melting point) to remove the solvent and form a dry film, or after the dry film is formed, a baking treatment is performed as necessary. After that, the sealant layer 16 is laminated to manufacture the exterior material 10 . Examples of the coating method include the various coating methods exemplified above.

In this case, the sealant layer 16 can be produced, for example, by a melt extruder. In the melt extruder, the processing speed can be 80 m/min or more from the viewpoint of productivity. The sealant layer 16 obtained under such conditions tends to have a structure in which the component (B) is stretched in the MD direction.

(Aging treatment process)
This step is a step of aging (curing) the laminate. By aging the laminate, the adhesion between the metal foil layer 13/corrosion prevention treatment layer 14/second adhesive layer 17/sealant layer 16 can be promoted. Aging treatment can be performed at room temperature to 100°C. Aging time is, for example, 1 to 10 days. The exterior material 10 (sealant layer 16) to be heated at 190° C. for 30 seconds as shown in FIG. 2 and described above may have undergone the above-described aging treatment.

Thus, the exterior material 10 of the present embodiment as shown in FIG. 1 can be manufactured.

Next, an example of a method for manufacturing the exterior material 20 shown in FIG. 3 will be described. Note that the method for manufacturing the exterior material 20 is not limited to the following method.

The method for manufacturing the exterior material 20 of the present embodiment includes a step of laminating the corrosion prevention treatment layer 14 on the metal foil layer 13, a step of bonding the base material layer 11 and the metal foil layer 13 together, and a step of forming the first sealant layer 16a. and the second sealant layer 16b are further laminated to form a laminate, and if necessary, the obtained laminate is heat-treated. The steps up to the step of bonding the base material layer 11 and the metal foil layer 13 together can be performed in the same manner as in the method for manufacturing the exterior material 10 described above.

(Lamination step of first sealant layer 16a and second sealant layer 16b)
This step is a step of forming a first sealant layer 16a and a second sealant layer 16b on the corrosion prevention treatment layer 14 formed in the previous step. As a method thereof, there is a method of sand laminating the first sealant layer 16a together with the second sealant layer 16b using an extrusion laminator. Furthermore, lamination is also possible by a tandem lamination method or a co-extrusion method in which the first sealant layer 16a and the second sealant layer 16b are extruded. In forming the first sealant layer 16a and the second sealant layer 16b, for example, each component is blended so as to satisfy the configurations of the first sealant layer 16a and the second sealant layer 16b described above.

Through this process, as shown in FIG. 3, the substrate layer 11/first adhesive layer 12/metal foil layer 13/corrosion prevention treatment layer 14/first sealant layer 16a/second sealant layer 16b are formed in this order. to obtain a laminate in which each layer is laminated.

The first sealant layer 16a may be formed by directly laminating dry-blended materials by an extrusion laminating machine so as to have the above-described material composition, or by using a single-screw extruder or twin-screw extruder in advance. Alternatively, the granulated first sealant layer 16a may be laminated using an extrusion laminator after being melt-blended using a melt-kneading device such as a Brabender mixer.

The second sealant layer 16b may be formed by directly laminating a dry-blended material by an extrusion laminator so as to have the material formulation composition described above as a component for forming the sealant layer, or by laminating in advance with a single-screw extruder. , a twin-screw extruder, a Brabender mixer, or another melt-kneading device to extrude the first sealant layer 16a and the second sealant layer 16b using an extrusion laminator. It may be laminated by a tandem lamination method or a coextrusion method. Alternatively, a sealant single film may be formed in advance as a cast film using the constituent components for forming the sealant layer, and this film may be laminated by a method of sandwich lamination with an adhesive resin, or an adhesive may be used. Lamination may be performed by a dry lamination method. The formation speed (processing speed) of the sealant layers 16a and 16b can be, for example, 80 m/min or more from the viewpoint of productivity. The sealant layers 16a and 16b obtained under such conditions tend to have a structure in which the component (B) is stretched in the MD direction.

(Heat treatment process)
This step is a step of heat-treating the laminate. By heat-treating the laminate, the adhesion between the metal foil layer 13/corrosion prevention treatment layer 14/first sealant layer 16a/second sealant layer 16b is improved, resulting in better electrolyte resistance and resistance. Hydrofluoric acid can be imparted. As a method of heat treatment, it is preferable to perform treatment at a temperature equal to or higher than the melting point of at least the first sealant layer 16a. Examples of the heat treatment include techniques such as oven heating, sandwiching between heated rolls (thermal lamination), and winding around heated rolls, but are not limited to these. The heat treatment time depends on the heat treatment method, temperature conditions, etc., depending on the performance (adhesion strength (laminate strength) between the metal foil layer 13 / corrosion prevention treatment layer 14 / first sealant layer 16a / second sealant layer 16b ) and productivity, it can be adjusted as appropriate. For example, when heat treatment is performed by sandwiching between heated rolls or winding around heated rolls, the heat treatment time is 0.5 seconds or more from the viewpoint of the above performance, and 1.0 second from the viewpoint of productivity. can be: Moreover, the exterior material 20 (sealant layer 16) when heated at 190° C. for 30 seconds as shown in FIG. 2 and described above may have undergone the above aging treatment or heat treatment.

In this way, the exterior material 20 of this embodiment as shown in FIG. 3 can be manufactured.

Next, an example of a method for manufacturing the exterior material 30 shown in FIG. 4 will be described. Note that the method for manufacturing the exterior material 30 is not limited to the following method.

The method for manufacturing the exterior material 30 of the present embodiment includes a step of laminating the corrosion prevention treatment layer 14 on the metal foil layer 13, a step of bonding the base material layer 11 and the metal foil layer 13 together, and a step of forming the first sealant layer 16a. , a step of further laminating the third sealant layer 16c and the second sealant layer 16b to produce a laminate, and, if necessary, a step of heat-treating the obtained laminate. .

(Lamination step of first sealant layer 16a, third sealant layer 16c and second sealant layer 16b)
This step is a step of forming a first sealant layer 16 a , a third sealant layer 16 c and a second sealant layer 16 b on the corrosion prevention treatment layer 14 . Examples of the method include a tandem lamination method and a co-extrusion method in which the first sealant layer 16a, the third sealant layer 16c and the second sealant layer 16b are extruded using an extrusion laminator. In this case, the dry-blended materials may be directly laminated by an extrusion lamination machine so as to have the above-described material formulation composition as the constituent components for forming the sealant layer, or may be laminated in advance by a single-screw extruder or a twin-screw extruder. , the granulated material after melt blending using a melt-kneading device such as a Brabender mixer, and the first sealant layer 16a, the third sealant layer 16c and the second sealant layer 16b with an extrusion laminator. It may be laminated by a tandem lamination method of extrusion or a co-extrusion method.

The third sealant layer 16c and the second sealant layer 16b may be formed by co-extrusion, and these films may be laminated together with the components for forming the first sealant layer 16a by sand lamination. The formation speed (processing speed) of the sealant layers 16a, 16b, 16c can be, for example, 80 m/min or more from the viewpoint of productivity. The sealant layers 16a, 16b, 16c obtained under such conditions tend to have a structure in which the component (B) is stretched in the MD direction. The method for manufacturing the exterior material 30 of the present embodiment may include the heat treatment process described above in the method for manufacturing the exterior material 20 . The heat treatment technique and conditions can be the same as those described above in the method of manufacturing the exterior material 20 .

In this way, the exterior material 30 of this embodiment as shown in FIG. 4 can be manufactured.

Preferred embodiments of the exterior material for a power storage device of the present invention have been described above in detail. Various modifications and changes are possible within the scope of the gist. For example, when manufacturing an exterior material for a power storage device that does not have the first adhesive layer 12, a resin material capable of forming the base material layer 11 is applied or coated onto the metal foil layer 13 as described above. Thus, the base material layer 11 may be formed. Further, in the above-described embodiments, it was explained that the region where the component (B) is present in the low-shrinkage sealant layer slightly shrinks when heated, but the low-shrinkage sealant layer may not shrink when heated. .

The power storage device exterior material of the present invention is suitable as, for example, a secondary battery such as a lithium ion battery, a nickel metal hydride battery, and a lead storage battery, and an electrical storage device such as an electrochemical capacitor such as an electric double layer capacitor. can be used. Among others, the exterior material for a power storage device of the present invention is suitable as an exterior material for a lithium ion battery.

EXAMPLES The present invention will be described in more detail based on examples below, but the present invention is not limited to the following examples.

[Materials used]
Materials used in Examples and Comparative Examples are shown below.
<Base material layer (thickness 15 μm)>
A nylon film (Ny) (manufactured by Toyobo Co., Ltd.) was used.

<First adhesive layer (thickness 4 μm)>
A polyurethane-based adhesive (manufactured by Toyo Ink Co., Ltd.) in which a tolylene diisocyanate adduct-based curing agent was blended with a polyester polyol-based main agent was used.

<First Corrosion Prevention Treated Layer (Base Layer Side) and Second Corrosion Prevention Treated Layer (Sealant Layer Side)>
(CL-1): "Sodium polyphosphate-stabilized cerium oxide sol" adjusted to a solid concentration of 10% by mass using distilled water as a solvent was used. The sodium polyphosphate-stabilized cerium oxide sol was obtained by blending 10 parts by mass of Na salt of phosphoric acid with 100 parts by mass of cerium oxide.
(CL-2): 90% by mass of “polyallylamine (manufactured by Nittobo Co., Ltd.)” adjusted to a solid content concentration of 5% by mass using distilled water as a solvent, and “polyglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation)” A composition consisting of 10% by weight was used.
(CL-3): Using an aqueous phosphoric acid solution with a concentration of 1% by mass as a solvent, chromium fluoride (CrF ₃ ) is added to a water-soluble phenolic resin (manufactured by Sumitomo Bakelite Co., Ltd.) adjusted to a solid content concentration of 1% by mass. The concentration of the chemical conversion treatment agent was adjusted so that the amount of Cr present in the dry film was 10 mg/m ² .

<Metal foil layer (thickness 35 μm)>
Annealed and degreased soft aluminum foil (“8079 material” manufactured by Toyo Aluminum Co., Ltd.) was used.

<Second adhesive layer (3 μm thick)>
As the adhesive for forming the second adhesive layer, the following adhesives a and b were prepared.
Adhesive a: An adhesive obtained by blending 10 parts by mass (solid content ratio) of a polyisocyanate compound having an isocyanurate structure with 100 parts by mass of an acid-modified polyolefin resin dissolved in toluene.
Adhesive b: A polyurethane-based adhesive obtained by blending a polyester polyol composed of a hydrogenated dimer fatty acid and a diol with a polyisocyanate so that the molar ratio (NCO/OH) is 2.

<Sealant layer>
The following materials were prepared as the components (A) to (C) constituting the base resin composition for forming the sealant layer.
((A) component)
Acid-modified PP: acid-modified polypropylene.
Random PP: propylene-ethylene random copolymer.
((B) component)
Ethylene-α-olefin copolymer: Ethylene-propylene copolymer elastomer having no compatibility with acid-modified PP and random PP (component (A)).
Ethylene-butene-1 random copolymer: Ethylene-butene-1 random copolymer elastomer incompatible with acid-modified PP and random PP (component (A)).
((B1) component)
Block copolymer 1: A block copolymer composed of crystalline ethylene units and ethylene-butylene units and having no compatibility with acid-modified PP and random PP (component (A)).
Block copolymer 2: A block copolymer composed of propylene units and ethylene units and having no compatibility with acid-modified PP and random PP (component (A)).
Graft copolymer: A graft copolymer composed of a polyolefin main chain and polystyrene side chains and having no compatibility with acid-modified PP and random PP (component (A)).
((C) component)
Atactic structure copolymer: A propylene-α olefin copolymer with an atactic structure compatible with acid-modified PP (component (A)).
Propylene-butene-1 random copolymer: A propylene-butene-1 random copolymer elastomer compatible with random PP (component (A)).

[Production of exterior material]
(Example 1)
First, the metal foil layer was provided with first and second corrosion prevention treatment layers by the following procedure. Specifically, (CL-1) was applied to both surfaces of the metal foil layer by microgravure coating so that the dry coating amount was 70 mg/m ² , and baked at 200° C. in a drying unit. Next, (CL-2) was applied onto the obtained layer by micro gravure coating so that the dry coating amount was 20 mg/m ² to obtain a composite of (CL-1) and (CL-2). The layers were formed as first and second corrosion control treatment layers. This composite layer exhibits anti-corrosion performance by combining two types (CL-1) and (CL-2).

Next, the metal foil layer provided with the first and second corrosion prevention treatment layers is dry-laminated on the side of the first corrosion prevention treatment layer, using a polyurethane adhesive (first adhesive layer). pasted on the material layer. This is set in the unwinding section of an extrusion laminating machine, and the material for the sealant layer is co-extruded on the second corrosion prevention treatment layer at 270 ° C. and 100 m / min. A layer (hereinafter also referred to as “AL side layer”) (8.3 μm thick) and the innermost layer (16.7 μm thick) were laminated in this order. For the AL side layer and the innermost layer, a compound of various materials was prepared in advance using a twin-screw extruder, and the compound was subjected to water cooling and pelletizing steps before being used in the extrusion laminate. For forming the AL side layer, acid-modified PP ((A) component, 55.0% by mass), ethylene-α olefin copolymer ((B) component, 20.0% by mass), and atactic structure copolymer A mixture of ((C) component, 25.0% by mass) was used. For forming the innermost layer, random PP (component (A), 63.6% by mass), ethylene-butene-1 random copolymer (component (B), 9.1% by mass), block copolymer 2 ( A mixture of component (B1), 9.1% by mass) and propylene-butene-1 random copolymer (component (C), 18.2% by mass) was used. The structure of each layer is also shown in Table 1 below. The numerical values in the sealant layer column in Table 1 indicate the content or thickness of each component in each layer or the entirety of the sealant layer.

The laminate thus obtained was wrapped around a roll heated to 190° C. and conveyed, so that the laminate was subjected to heat treatment at 190° C. for about 0.5 seconds. Laminate of material layer/first adhesive layer/first corrosion prevention treatment layer/metal foil layer/second corrosion prevention treatment layer/AL side layer (sealant layer 16a)/innermost layer (sealant layer 16b)) manufactured.

(Example 2)
For forming the AL side layer (sealant layer 16a), acid-modified PP (component (A), 50.0% by mass), ethylene-α olefin copolymer (component (B), 18.2% by mass), block copolymer Use of a mixture of polymer 2 (component (B1), 9.1% by mass) and atactic structure copolymer (component (C), 22.7% by mass), formation of the innermost layer (sealant layer 16b) To, random PP ((A) component, 70.0% by mass), ethylene-butene-1 random copolymer ((B) component, 10.0% by mass), and propylene-butene-1 random copolymer ( An exterior material of Example 2 was produced in the same manner as in Example 1, except that a mixture of component (C), 20.0% by mass) was used. The structure of each layer is also shown in Table 1 below.

(Example 3)
For forming the AL side layer (sealant layer 16a), acid-modified PP (component (A), 50.0% by mass), ethylene-α olefin copolymer (component (B), 18.2% by mass), block copolymer In the same manner as in Example 1, except that a mixture of polymer 2 (component (B1), 9.1% by mass) and atactic structure copolymer (component (C), 22.7% by mass) was used. , the exterior material of Example 3 was manufactured. The structure of each layer is also shown in Table 1 below.

(Example 4)
For forming the AL side layer (sealant layer 16a), acid-modified PP (component (A), 52.4% by mass), ethylene-α olefin copolymer (component (B), 19.0% by mass), block copolymer Use of a mixture of polymer 2 (component (B1), 4.8% by mass) and atactic structural copolymer (component (C), 23.8% by mass), formation of the innermost layer (sealant layer 16b) To, random PP ((A) component, 66.7% by mass), ethylene-butene-1 random copolymer ((B) component, 9.5% by mass), block copolymer 2 ((B1) component, 4.8% by mass), and a mixture of propylene-butene-1 random copolymer ((C) component, 19.0% by mass). Manufactured cladding. The structure of each layer is also shown in Table 1 below.

(Example 5)
For forming the AL side layer (sealant layer 16a), acid-modified PP (component (A), 54.4% by mass), ethylene-α olefin copolymer (component (B), 19.8% by mass), block copolymer Use of a mixture of polymer 2 ((B1) component, 1.0% by mass) and atactic structure copolymer ((C) component, 24.8% by mass), formation of the innermost layer (sealant layer 16b) To, random PP ((A) component, 69.3% by mass), ethylene-butene-1 random copolymer ((B) component, 9.9% by mass), block copolymer 2 ((B1) component, 1.0% by mass), and a mixture of propylene-butene-1 random copolymer ((C) component, 19.8% by mass). Manufactured cladding. The structure of each layer is also shown in Table 1 below.

(Example 6)
For forming the AL side layer (sealant layer 16a), acid-modified PP ((A) component, 55.0% by mass), block copolymer 2 ((B1) component, 20.0% by mass), and atactic structural co- A mixture of polymers ((C) component, 25.0% by mass) was used, and random PP ((A) component, 70.0% by mass) and block copolymerization were used to form the innermost layer (sealant layer 16b). Coalescence 2 ((B1) component, 10.0% by mass) and a mixture of propylene-butene-1 random copolymer ((C) component, 20.0% by mass) were used, except that Example 1 was used. In the same manner, an exterior material of Example 6 was produced. The structure of each layer is also shown in Table 1 below.

(Example 7)
For forming the innermost layer (sealant layer 16b), random PP ((A) component, 70.0% by mass), block copolymer 2 ((B1) component, 10.0% by mass), and propylene-butene-1 An exterior material of Example 7 was produced in the same manner as in Example 2, except that a mixture of random copolymers (component (C), 20.0% by mass) was used. The structure of each layer is also shown in Table 1 below.

(Example 8)
First, the metal foil layer was provided with the first and second corrosion prevention treatment layers by the following procedure. Specifically, (CL-3) was applied to both surfaces of the metal foil layer by microgravure coating so that the dry coating amount was 30 mg/m ² , and baked at 200° C. in a drying unit. Next, (CL-2) was applied onto the obtained layer by micro gravure coating so that the dry coating amount was 20 mg/m ² to obtain a composite of (CL-3) and (CL-2). The layers were formed as first and second corrosion control treatment layers. This composite layer exhibits anti-corrosion performance by combining two types of (CL-3) and (CL-2). An exterior material of Example 8 was manufactured in the same manner as in Example 7, except that the metal foil layer provided with the first and second anticorrosion treatment layers in this manner was used. The structure of each layer is also shown in Table 1 below.

(Example 9)
In the same manner as in Example 1, the metal foil layer was provided with the first and second corrosion prevention treatment layers. The first corrosion prevention treatment layer side of the metal foil layer provided with the first and second corrosion prevention treatment layers is dry-laminated to the base layer using a polyurethane adhesive (first adhesive layer). pasted. Next, the sealant layer 16 is formed by dry laminating the metal foil layer provided with the first and second corrosion prevention treatment layers on the side of the second corrosion prevention treatment layer using an adhesive a (second adhesive layer). (Innermost layer) (thickness: 25 μm), and the exterior material of Example 9 was produced. For forming the innermost layer (sealant layer 16), random PP ((A) component, 70.0% by mass), block copolymer 2 ((B1) component, 10.0% by mass), and propylene-butene- 1 random copolymer (component (C), 20.0% by mass) was used. The structure of each layer is also shown in Table 1 below.

(Example 10)
In the same manner as in Example 1, the metal foil layer was provided with the first and second corrosion prevention treatment layers. The first corrosion prevention treatment layer side of the metal foil layer provided with the first and second corrosion prevention treatment layers is dry-laminated to the base layer using a polyurethane adhesive (first adhesive layer). pasted. Next, a sealant layer 16 is formed by dry laminating the metal foil layer provided with the first and second corrosion prevention treatment layers on the side of the second corrosion prevention treatment layer using an adhesive b (second adhesive layer). (Innermost layer) (thickness: 25 μm), and the exterior material of Example 10 was produced. For forming the innermost layer (sealant layer 16), random PP ((A) component, 70.0% by mass), block copolymer 2 ((B1) component, 10.0% by mass), and propylene-butene- 1 random copolymer (component (C), 20.0% by mass) was used. The structure of each layer is also shown in Table 1 below.

(Example 11)
For forming the AL side layer (sealant layer 16a), acid-modified PP (component (A), 72.7% by mass), ethylene-α olefin copolymer (component (B), 18.2% by mass), and block A mixture of copolymer 2 ((B1) component, 9.1% by mass) was used, random PP ((A) component, 90.0% by mass) was used to form the innermost layer (sealant layer 16b), and An exterior material of Example 11 was produced in the same manner as in Example 1, except that a mixture of block copolymer 2 (component (B1), 10.0% by mass) was used. The structure of each layer is also shown in Table 1 below.

(Example 12)
For forming the AL side layer (sealant layer 16a), acid-modified PP (component (A), 50.0% by mass), ethylene-α olefin copolymer (component (B), 18.2% by mass), block copolymer Use of a mixture of polymer 1 (component (B1), 9.1% by mass) and atactic structural copolymer (component (C), 22.7% by mass), formation of the innermost layer (sealant layer 16b) To, random PP ((A) component, 70.0% by mass), ethylene-butene-1 random copolymer ((B) component, 9.1% by mass), block copolymer 2 ((B1) component, 9.1% by mass), and a mixture of propylene-butene-1 random copolymer ((C) component, 18.2% by mass). Manufactured cladding. The structure of each layer is also shown in Table 1 below.

(Example 13)
For forming the innermost layer (sealant layer 16b), random PP ((A) component, 70.0% by mass), block copolymer 2 ((B1) component, 10.0% by mass), and propylene-butene-1 An exterior material of Example 13 was produced in the same manner as in Example 12, except that a mixture of random copolymers (component (C), 20.0% by mass) was used. The structure of each layer is also shown in Table 1 below.

(Example 14)
For forming the AL side layer (sealant layer 16a), acid-modified PP ((A) component, 50.0% by mass), ethylene-α olefin copolymer ((B) component, 18.2% by mass), graft copolymer Use of a mixture of a polymer (component (B1), 9.1% by mass) and an atactic structure copolymer (component (C), 22.7% by mass), and formation of the innermost layer (sealant layer 16b) , random PP ((A) component, 70.0% by mass), graft copolymer ((B1) component, 10.0% by mass), and propylene-butene-1 random copolymer ((C) component, 20 .0% by mass), the exterior material of Example 12 was produced in the same manner as in Example 1, except that the mixture was used. The structure of each layer is also shown in Table 1 below.

(Comparative example 1)
For forming the AL side layer (sealant layer 16a), acid-modified PP (component (A), 52.0% by mass), ethylene-α olefin copolymer (component (B), 45.0% by mass), and atactic A mixture of structural copolymer (component (C), 3.0% by mass) was used, and random PP (component (A), 52.0% by mass) was used to form the innermost layer (sealant layer 16b), ethylene - Except for using a mixture of butene-1 random copolymer ((B) component, 45.0% by mass) and propylene-butene-1 random copolymer ((C) component, 3.0% by mass) manufactured an exterior material of Comparative Example 1 in the same manner as in Example 1. The structure of each layer is also shown in Table 1 below.

<Evaluation>
The following evaluation tests were performed on the exterior materials obtained in Examples and Comparative Examples.

(Shrinkage ratio and aspect ratio of component (B) existing area)
A part of the exterior material was cut and heated in an oven at 190° C. for 30 seconds to prepare a sample before heating and a sample after heating, which were sealed for cross-sectional observation. A range of 50 μm in the MD direction and 25 μm in the VD direction in the cross section along the VD direction and the MD direction of the sealant layer of the sample was observed with a scanning electron microscope (SEM), and any component (B) in the sample before heating Measure the length L ^MD in the MD direction of five or more existing regions and the length Lh ^MD in the MD direction of any five or more existing regions of the component (B) in the sample after heating, and average each The lengths LA ^MD and LAh ^MD were determined. Furthermore, from the calculated LA ^MD and LAh ^MD , the shrinkage ratio (LAh ^MD /LA ^MD ) of the existing region of component (B) before and after heating was calculated.

In addition, the range of 50 μm in the MD direction and 25 μm in the VD direction in the cross section along the VD direction and the MD direction of the sealant layer of the sample after heating was observed with an SEM, and any five or more existing regions of the component (B) MD direction length Lh ^MD and VD direction length Lh ^VD were measured, and each average length LAh ^MD and LAh ^VD were calculated|required. Furthermore, the aspect ratio (LAh ^MD /LAh ^VD ) of the existing region of the component (B) was calculated from the calculated LAh ^MD and LAh ^VD .

(seal strength)
A sample obtained by cutting the exterior material to 60 mm×120 mm was folded in two, and one side was heat sealed at 190° C., 0.5 MPa, and 3 seconds with a seal bar having a width of 10 mm. After storing the heat-sealed sample at room temperature for 24 hours, the first side of the heat-sealing was cut to a width of 15 mm (see FIG. 5), and the seal strength (T-peel strength) was measured using a tester (manufactured by INSTRON). measured continuously. The test was conducted in accordance with JIS K6854 at a peeling rate of 50 mm/min under an atmosphere of 23° C. and 50% RH. The seal strength was evaluated according to the following criteria based on the measurement results of the initial maximum seal strength (burst strength) after the start of peeling.
S: Burst strength of 60 N/15 mm or more A: Burst strength of 50 N/15 mm or more and less than 60 N/15 mm B: Burst strength of 40 N/15 mm or more and less than 50 N/15 mm C: Burst strength of 35 N/15 mm or more and 40 N/15 mm Less than D: Burst strength less than 35 N/15 mm

(Electrolyte lamination strength)
A Teflon (registered trademark) container is filled with an electrolytic solution obtained by adding LiPF ₆ to a mixed solution of ethylene carbonate / diethyl carbonate / dimethyl carbonate = 1/1/1 (mass ratio) so that it becomes 1 M, and an exterior material is placed therein. was cut into 15 mm×100 mm, and stored at 85° C. for 24 hours after sealing. Then, it was co-washed, and the laminate strength (T-peel strength) between the metal foil layer and the sealant layer was measured using a tester (manufactured by INSTRON). The test was conducted in accordance with JIS K6854 at a peeling rate of 50 mm/min under an atmosphere of 23° C. and 50% RH. Based on the results, evaluation was made according to the following criteria.
A: Laminate strength is over 7N/15mm B: Laminate strength is 6N/15mm or more and 7N/15mm or less C: Lamination strength is 5N/15mm or more and less than 6N/15mm D: Lamination strength is less than 5N/15mm

(Electrolyte heat seal strength)
A sample cut into 60 mm × 120 mm of the exterior material is folded in two with the sealant layer inside, and one side is heat sealed at 190 ° C., 0.5 MPa, 3 seconds with a seal bar with a width of 10 mm to form a heat sealed part. did. After that, LiPF ₆ was added to a mixed solution of ethylene carbonate/diethyl carbonate/dimethyl carbonate = 1/1/1 (mass ratio) to a bag-shaped exterior material by heat-sealing the remaining two sides so that the concentration became 1M. After storing the pouch into which 2 ml of the electrolytic solution was injected at 60 ° C. for 24 hours, the first heat-sealed side was cut to a width of 15 mm (see FIG. 6), and one end of the heat-sealed portion (the end that was in contact with the electrolytic solution Part), the seal strength (T-type peel strength) was continuously measured using a tester (manufactured by INSTRON). The test was conducted in accordance with JIS K6854 at a peeling rate of 50 mm/min under an atmosphere of 23° C. and 50% RH. Based on the burst strength obtained in the same manner as for the "seal strength" item, evaluation was made according to the following criteria.
S: burst strength of 50 N/15 mm or more A: burst strength of 45 N/15 mm or more and less than 50 N/15 mm B: burst strength of 35 N/15 mm or more and less than 45 N/15 mm C: burst strength of 25 N/15 mm or more and 35 N/15 mm Less than D: Burst strength less than 25 N/15 mm

(Degassing heat seal strength (degas heat seal strength))
A sample of the exterior material cut to 75 mm × 150 mm was folded in half to 37.5 mm × 150 mm with the sealant layer on the inside (see Fig. 7 (a)), and one of the 150 mm side and the 37.5 mm side was heat-sealed. and made bags. After that, 5 ml of an electrolytic solution obtained by adding LiPF ₆ to 1 M to a mixed solution of ethylene carbonate/diethyl carbonate/dimethyl carbonate = 1/1/1 (mass ratio) was injected into the pouch, and The other side was heat-sealed to obtain a pouch sealed by the seal portion DS1. Next, after storing this pouch at 60° C. for 24 hours, the central portion of the pouch containing the electrolyte was heat-sealed with a seal bar of 10 mm width at 190° C. at 0.3 MPa for 2 seconds (degassing heat sealing part DS2, see FIG. 7(b)). In order to stabilize the seal portion, after storage at room temperature for 24 hours, the area including the degassing heat seal portion DS2 was cut to a width of 15 mm (see FIG. 7(c)), and one end of the degassing heat seal portion ( The seal strength (T-type peel strength) was measured from the end on the side in contact with the electrolytic solution using a tester (manufactured by INSTRON). The test was conducted in accordance with JIS K6854 at a peeling rate of 50 mm/min under an atmosphere of 23° C. and 50% RH. Based on the burst strength obtained in the same manner as for the "seal strength" item, evaluation was made according to the following criteria.
S: burst strength of 45 N/15 mm or more A: burst strength of 40 N/15 mm or more and less than 45 N/15 mm B: burst strength of 30 N/15 mm or more and less than 40 N/15 mm C: burst strength of 20 N/15 mm or more and 30 N/15 mm Less than D: Burst strength less than 20 N / 15 mm

(Insulation after degassing heat sealing (degassing insulation))
A sample 40 obtained by cutting the exterior material to 120 mm × 200 mm was set in a cold molding mold so that the sealant layer was in contact with the convex part of the molding machine, and deep drawing was performed to 2.0 mm at a molding speed of 15 mm / sec. After forming the deep-drawn portion 41, it was folded in two to 120 mm×100 mm (see FIG. 8(a)). Next, with the tab 42 and the tab sealant 43 sandwiched between them, the 100 mm upper side portion 44 was heat-sealed (see FIG. 8B), and then the 120 mm side portion 45 was heat-sealed to form a bag. (See FIG. 8(c)). After that, in order to make contact with the electrode, part of the outer layer of the sample 40 was shaved to form an exposed portion 46 of the metal foil layer (see FIG. 8(d)). Next, 5 ml of an electrolytic solution obtained by adding LiPF ₆ to 1 M to a mixed solution of ethylene carbonate/diethyl carbonate/dimethyl carbonate = 1/1/1 (mass ratio) was poured into the pouch, and the lower side of 100 mm was poured. 47 was sealed by heat sealing (see FIG. 8(e)). After that, the pouch was placed flat and left at 60° C. for 24 hours, and the portion 48 inside the heat-sealed lower side portion 47 was placed at 190° C. under 0.3 MPa (surface pressure) with the electrolyte solution being caught. ), degassing heat-sealed in 2 seconds (see FIG. 8(f)). Next, electrodes 49a and 49b are connected to the tab 42 and the exposed portion 46 of the metal foil layer, respectively, and a voltage of 25 V is applied using a withstand voltage/insulation resistance tester (manufactured by KIKUSUI, "TOS9201"). was measured (see FIG. 8(g)). For the samples whose resistance value was less than 15 MΩ, 25 V was continuously applied for 2 hours to identify the portion of the insulation deterioration. By applying voltage for a long period of time, the reaction product between the metal foil and the electrolyte is deposited from the location where the insulation is lowered, so the location where the insulation is lowered can be identified. The mold used had a molding area of 80 mm×70 mm (rectangular cylindrical shape) and a punch corner radius (RCP) of 1.0 mm. Based on the results, evaluation was made according to the following criteria.
A: Resistance value of 200 MΩ or more B: Resistance value of 100 MΩ or more and less than 200 MΩ C: Resistance value of 15 MΩ or more and less than 100 MΩ D: Resistance value of less than 15 MΩ

The results of the shrinkage ratio and aspect ratio of the component (B), seal strength, electrolyte lamination strength, electrolyte seal strength, degassing heat seal strength, and degassing insulation evaluated as described above are based on the entire sealant layer. The contents of component (B) and component (C) are shown in Table 2 below. In Table 2 below, it can be said that the overall quality is excellent if there is no D rating in each evaluation result.

9 is an SEM image of a cross section along the VD direction and the MD direction of the sealant layer in the exterior material for a power storage device obtained in Example 7, and (a) is an image before heating at 190° C. for 30 seconds. and (b) is an image after heating at 190° C. for 30 seconds. The layers confirmed in FIG. 9(a) are, from the top, the metal foil layer 13, the AL side layer (sealant layer 16a) before heating, and the innermost layer (sealant layer 16b) before heating. From FIG. 9(a) showing the cross section before heating, the AL-side layer and the innermost layer have regions 162a and 162b where the component (A) is present in gray and the region where the component (B) is present in white. 164a and 164b can be confirmed. From FIG. 9A, it can be confirmed that the existing regions 164a and 164b of the (B) component are stretched in the MD direction. Each layer confirmed in FIG. 9(b) is the metal foil layer 13 from the top, the AL side layer after heating (sealant layer 16ha after heating), and the innermost layer after heating (sealant layer 16hb after heating). . From FIG. 9(b) showing the cross section after heating, the AL-side layer 16ha and the innermost layer 16hb have regions 162ha and 162hb where component (A) is present, indicated in gray, and component (B), indicated in white. Existence areas 164ha and 164hb can be confirmed. Further, comparing FIG. 9(a) and FIG. 9(b), it can be confirmed that the existing regions 164ha and 164hb of the component (B) after heating are slightly shrunk in the MD direction compared to before heating. However, the shrinkage ratio is as large as 0.63, and it can be said that the degree of shrinkage is small.

In addition, as is clear from the results shown in Table 2, the power storage device exterior materials obtained in Examples 1 to 14 have a low-shrinkage sealant layer having a shrinkage rate of 0.20 or more. It was also confirmed that the insulating property after degassing heat sealing is excellent. Furthermore, it was confirmed that the exterior materials of Examples 1 to 14 had sufficient performance in electrolyte lamination strength, electrolyte heat seal strength, and degassing heat seal strength. On the other hand, it was confirmed that the exterior material of Comparative Example 1 was inferior in sealing strength and insulation.

DESCRIPTION OF SYMBOLS 10, 20, 30... Exterior material for electrical storage apparatus 11... Base material layer 12... First adhesive layer 13... Metal foil layer 14... Corrosion prevention treatment layer 16... Sealant layer 16a... First layer Sealant layer 16b...Second sealant layer 16c...Third sealant layer 16h...Sealant layer after heating 17...Second adhesive layer 162...Polypropylene-based resin existing region 164...Incompatible system Component existence region 164h: Incompatible component existence region after heating DS1: Sealing portion DS2: Degassing heat sealing portion.

Claims (8)

An exterior material for a power storage device, comprising at least a base material layer, a metal foil layer provided with a corrosion prevention treatment layer on one or both surfaces, and a sealant layer in this order,
The sealant layer contains a polypropylene-based resin (A) and an incompatible component (B) that is incompatible with the polypropylene-based resin, and the existing region of the polypropylene-based resin (A) and the polypropylene-based resin (A) and a region where a plurality of the immiscible components (B) are present surrounded by
The incompatible component (B) contains a compound (B1) having a compatible portion with the polypropylene resin (A),
The sealant layer has an average length LA in the MD direction of the region where the incompatible component (B) exists in the cross section along the thickness direction and the MD direction^MD, the average length LAh in the MD direction of the existing region of the incompatible component (B) in the cross section along the thickness direction and the MD direction after heating the power storage device exterior material at 190 ° C. for 30 seconds^MDratio (LAh^MD/LA^MD) is 0.20 or more. Average in the thickness direction of the existing region of the incompatible component (B) in the cross section along the thickness direction and the MD direction of the sealant layer after heating the power storage device exterior material at 190 ° C. for 30 seconds The exterior material for a power storage device according to claim 1, wherein a ratio ( ^LAhMD / ^LAhVD ) of the average length ^LAhMD in the ^MD direction to the length LAhVD is 2.50 or more. 3. The exterior material for a power storage device according to claim 1, wherein said sealant layer comprises a plurality of layers, at least one of which is said low-shrinkage sealant layer. 4. The exterior material for a power storage device according to claim 1, wherein said sealant layer is composed of a plurality of layers, of which the layer closest to said metal foil layer is said low-shrinkage sealant layer. The sealant layer further contains a compatible elastomer (C) compatible with the polypropylene resin (A),
5. The exterior material for a power storage device according to claim 1, wherein said compatible elastomer (C) contains a propylene-α-olefin copolymer. The sealant layer further contains a compatible elastomer (C) compatible with the polypropylene resin (A),
The sealant layer consists of a plurality of layers, and in the layer closest to the metal foil layer,
The polypropylene-based resin (A) contains an acid-modified polypropylene,
5. The exterior material for a power storage device according to claim 1, wherein said compatible elastomer (C) comprises polypropylene having an atactic structure or a propylene-α-olefin copolymer having an atactic structure. further comprising an adhesive layer between the metal foil layer and the sealant layer;
The adhesive layer comprises an acid-modified polyolefin, and at least one curing agent selected from the group consisting of a polyfunctional isocyanate compound, a glycidyl compound, a compound having a carboxy group, a compound having an oxazoline group, and a carbodiimide compound. The exterior material for a power storage device according to any one of claims 1 to 4, containing the power storage device. The exterior material for a power storage device according to any one of claims 1 to 7, wherein the compound (B1) is a graft copolymer or a block copolymer.

Images