JP6728600B2 - Power storage device exterior material - Google Patents

Description

The present invention relates to a power storage device exterior material.

Known power storage devices include, for example, secondary batteries such as lithium ion batteries, nickel hydrogen batteries, and lead storage batteries, and electrochemical capacitors such as electric double layer capacitors. Due to the downsizing of portable devices, the limitation of installation space, and the like, further downsizing of power storage devices is required, and lithium ion batteries with high energy density are drawing attention. Conventionally, a metal can has been used as an exterior material used in a lithium-ion battery, but it is a multi-layer film that is lightweight, has high heat dissipation, and can be produced at low cost (for example, base material layer/metal foil layer/ A structure such as a sealant layer is used (for example, Patent Document 1).

JP, 2013-157287, A

By the way, as one of the means for realizing the thinning of the exterior material for a power storage device, there is a thinning of the sealant layer. However, when the sealant layer is thinned according to the conventional technique of Patent Document 1 or the like, the distance between the tab lead and the metal layer tends to be close to each other when the top seal is applied, which may cause a short circuit. Also, due to the progress of thinner layers, fluctuations in the layer thickness due to the flow of resin on the sealant layer side during heat sealing (top seal, side seal, and degassing heat seal) are likely to occur, which easily causes a short circuit. It is also possible to do. It should be noted that the top seal here is to heat-seal the place where the tab lead is sandwiched, the side seal is to be heat-sealed at other places, and the degassing heat-seal is to be heat-sealed into a bag shape. After injecting the electrolytic solution into the outer packaging material, for example, heat-sealing the central portion of the outer packaging material, respectively.

Therefore, in view of the above circumstances, an object of the present invention is to provide an exterior material for a power storage device that can maintain good insulation even when the sealant layer is thin.

In order to achieve the above object, the present invention comprises at least a base material layer, an adhesive layer, a metal foil layer and a sealant layer, the sealant layer contains an inorganic filler, and in a cross section along the laminating direction, a sealant. Provided is an exterior material for a power storage device, in which the proportion of the inorganic filler in the total layer thickness is 5 to 50%. This makes it possible to maintain good insulation even when the sealant layer is thin.

In the present invention, the content of the inorganic filler is preferably 5 to 35 mass% based on the total mass of the sealant layer. This makes it easy for the inorganic filler to sufficiently serve as a spacer, and also to prevent the decrease in adhesiveness.

The sealant layer is composed of two or more layers, and it is preferable that at least one layer of them does not contain the inorganic filler. Regarding the layer to which the inorganic filler is not added, it is possible to suppress the deterioration of the original properties of the sealant layer due to the inclusion of the inorganic filler.

The thickness of the layer containing the inorganic filler is preferably 50% or more with respect to the total thickness of the sealant layer. Outside this range, when heat or pressure is applied during heat sealing, resin flow tends to occur and a short circuit tends to occur.

In the sealant layer, it is preferable that the layer containing the inorganic filler is sandwiched between the layers not containing the inorganic filler. Thereby, the insulating property can be exhibited without impairing the adhesiveness with the metal foil layer 13 and the heat seal property.

The layer containing the inorganic filler is preferably a layer made of acid-modified polyolefin. As a result, the adhesiveness with the inorganic filler is enhanced, and it is easy to ensure low fluidity even when heat or pressure is applied during heat sealing.

The inorganic filler is preferably surface-treated. As a result, the adhesion between the resin forming the sealant layer and the inorganic filler is enhanced, and the resin fluidity during melting can be further reduced.

According to the present invention, it is possible to provide an outer casing material for a power storage device that can maintain good insulation even when the sealant layer is thin. In addition, according to the present invention, even when the sealant layer has a thickness of 35 μm or less, not only the occurrence of a short circuit in the top seal, the side seal, and the degassing heat seal is suppressed, but also the laminating strength and the seal required for the sealant layer are obtained. It is possible to provide an exterior material that does not cause a decrease in strength.

1 is a schematic cross-sectional view of a power storage device exterior material according to an embodiment of the present invention. It is a schematic sectional drawing of the exterior material for electrical storage devices which concerns on other embodiment of this invention. It is a schematic diagram explaining the calculation method of the ratio which the inorganic filler occupies with respect to the total thickness of the sealant layer. FIG. 5 is a schematic diagram illustrating a method of manufacturing an evaluation sample in an example. FIG. 5 is a schematic diagram illustrating a method of manufacturing an evaluation sample in an example. FIG. 5 is a schematic diagram illustrating a method of manufacturing an evaluation sample in an example.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts will be denoted by the same reference symbols, without redundant description. Further, the dimensional ratio of the drawings is not limited to the illustrated ratio.

[Exterior material for power storage device]
FIG. 1 is a cross-sectional view schematically showing an embodiment of a power storage device exterior material of the present invention. As shown in FIG. 1, an exterior material (exterior material for a power storage device) 10 of the present embodiment includes a base material layer 11 and a first adhesive layer 12 formed on one surface of the base material layer 11. And a metal foil layer 13 formed on the surface of the first adhesive layer 12 opposite to the base material layer 11, and a surface of the metal foil layer 13 opposite to the first adhesive layer 12. And a sealant layer 15 formed on the surface of the corrosion prevention treated layer 14 opposite to the metal foil layer 13 are sequentially laminated. In the exterior material 10, the base material layer 11 is the outermost layer and the sealant layer 15 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 15 facing the inside of the power storage device. Each layer will be described below.

<Base material layer 11>
The base material layer 11 is provided for the purpose of imparting heat resistance in a sealing step during manufacturing of a power storage device and as a measure against pinholes that may occur during processing or distribution, and it is preferable to use a resin layer having an insulating property. As such a resin layer, for example, a stretched or unstretched film such as a polyester film, a polyamide film, or a polypropylene film can be used as a single layer or a multilayer film in which two or more layers are laminated. More specifically, a polyethylene terephthalate film (PET) and a nylon film (Ny) can be coextruded using an adhesive resin, and then a coextruded multilayer stretched film subjected to a stretching treatment can be used.

6-40 micrometers is preferable and, as for the thickness of the base material layer 11, 10-25 micrometers is more preferable. When the thickness of the base material layer 11 is 6 μm or more, there is a tendency that the pinhole resistance and the insulating property of the power storage device exterior material 10 can be improved.

<First adhesive layer 12>
The first adhesive layer 12 is a layer that bonds the base material layer 11 and the metal foil layer 13 together. As a material forming the first adhesive layer 12, specifically, for example, polyurethane obtained by reacting a base compound such as polyester polyol, polyether polyol, acryl polyol, carbonate polyol with a bifunctional or higher functional isocyanate compound. Resin etc. are mentioned.

Polyester polyols are aliphatic succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, brassylic acid, etc.; aromatic dibases such as isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, etc. One or more acids and aliphatic type such as ethylene glycol, propylene glycol, butanediol, neopentyl glycol, methylpentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, dodecanediol; cyclohexanediol, hydrogenation And an alicyclic system such as xylylene glycol, and one or more aromatic diols such as xylylene glycol.

Further, as the polyester polyol, hydroxyl groups at both terminals of the polyester polyol obtained by using the above-mentioned dibasic acid and diol, for example, 2,4- or 2,6-tolylene diisocyanate, xylylene diisocyanate, 4, 4'-diphenylmethane diisocyanate, methylene diisocyanate, isopropylene diisocyanate, lysine diisocyanate, 2,2,4- or 2,4,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, 4 , 4'-dicyclohexylmethane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, or a simple substance of an isocyanate compound, or an adduct body, burette body, or isocyanurate body composed of at least one of the above isocyanate compounds. Examples of the polyester urethane polyol include a chain-extended polyester urethane polyol.

As the polyether polyol, it is possible to use ether-based polyols such as polyethylene glycol and polypropylene glycol, and polyether urethane polyol obtained by reacting the above-mentioned isocyanate compound as a chain extender.

As the acrylic polyol, it is possible to use an acrylic resin polymerized using the above-mentioned acrylic monomer.

The carbonate polyol can be obtained by reacting a carbonate compound and a diol. As the carbonate compound, dimethyl carbonate, diphenyl carbonate, ethylene carbonate or the like can be used. On the other hand, as the diol, ethylene glycol, propylene glycol, butanediol, neopentyl glycol, methylpentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, dodecanediol and other aliphatic diols; cyclohexanediol, water Examples thereof include alicyclic diols such as added xylylene glycol; carbonate polyols using a mixture of one or more aromatic diols such as xylylene glycol, or polycarbonate urethane polyols chain-extended with the above-mentioned isocyanate compounds.

The above-mentioned various polyols can be used alone or in combination of two or more, depending on the function and performance required for the exterior material. Further, by using the above-mentioned isocyanate compound as a curing agent for these base materials, it is possible to use it as a polyurethane adhesive.

Furthermore, for the purpose of promoting adhesion, a carbodiimide compound, an oxazoline compound, an epoxy compound, a phosphorus compound, a silane coupling agent and the like may be added to the above-mentioned polyurethane resin.

Examples of the carbodiimide compound 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'- Examples thereof include di-cyclohexylcarbodiimide and N,N′-di-p-toluylcarbodiimide.

Examples of the oxazoline compound include monooxazoline such as 2-oxazoline, 2-methyl-2-oxazoline, 2-phenyl-2-oxazoline, 2,5-dimethyl-2-oxazoline, and 2,4-diphenyl-2-oxazoline. Compound, 2,2'-(1,3-phenylene)-bis(2-oxazoline), 2,2'-(1,2-ethylene)-bis(2-oxazoline), 2,2'-(1, Examples thereof include dioxazoline compounds such as 4-butylene)-bis(2-oxazoline) and 2,2′-(1,4-phenylene)-bis(2-oxazoline).

Examples of the epoxy compound include diglycidyl ethers of aliphatic diols such as 1,6-hexanediol, neopentyl glycol and polyalkylene glycol, sorbitol, sorbitan, polyglycerol, pentaerythritol, diglycerol, glycerol and trimethylol. Polyglycidyl ethers of aliphatic polyols such as propane, polyglycidyl ethers of alicyclic polyols such as cyclohexanedimethanol, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, trimellitic acid, adipic acid, sebacic acid, etc. Diglycidyl or polyglycidyl esters of polyhydric carboxylic acids of the family, resorcinol, bis-(p-hydroxyphenyl)methane, 2,2-bis-(p-hydroxyphenyl)propane, tris-(p-hydroxyphenyl)methane , Diglycidyl ether or polyglycidyl ether of polyhydric phenol such as 1,1,2,2-tetrakis(p-hydroxyphenyl)ethane, N,N'-diglycidylaniline, N,N,N-diglycidyltoluidine, N,N,N',N'-N-glycidyl derivatives of amines such as tetraglycidyl-bis-(p-aminophenyl)methane, triglycidyl derivatives of aminofer, triglycidyl tris(2-hydroxyethyl)isocyanurate , Triglycidyl isocyanurate, orthocresol type epoxy, and phenol novolac type epoxy.

Examples of the phosphorus compound include tris(2,4-di-t-butylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)4,4′-biphenylenephosphonate, bis(2,2). 4-di-t-butylphenyl)pentaerythritol-di-phosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol-di-phosphite, 2,2-methylenebis(4,4) 6-di-t-butylphenyl)octyl phosphite, 4,4′-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl)phosphite, 1,1,3-tris(2- Methyl-4-ditridecylphosphite-5-t-butyl-phenyl)butane, tris(mixedmono and di-nonylphenyl)phosphite, tris(nonylphenyl)phosphite, 4,4'-isopropylidenebis( Phenyl-dialkyl phosphite) and the like.

Examples of the silane coupling agent include vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycine. Sidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N Various silane coupling agents such as -β(aminoethyl)-γ-aminopropyltrimethoxysilane can be used.

Further, other various additives and stabilizers may be added to the above-mentioned polyurethane resin depending on the performance required for the adhesive.

The thickness of the first adhesive layer 12 is not particularly limited, but from the viewpoint of obtaining desired adhesive strength, conformability, workability, etc., for example, 1 to 10 μm is preferable, and 3 to 7 μm. More preferable.

<Metal foil layer 13>
The metal foil layer 13 has a water vapor barrier property that prevents moisture from entering the inside of the power storage device. Further, the metal foil layer 13 has spreadability for deep drawing. As the metal foil layer 13, various metal foils such as aluminum and stainless steel can be used, and the aluminum foil is preferable in terms of mass (specific gravity), moisture resistance, processability and cost.

As the aluminum foil, a general soft aluminum foil can be used, but it is preferable to use an aluminum foil containing iron for the purpose of imparting further pinhole resistance and spreadability during molding. The content of iron in the aluminum foil is preferably 0.1 to 9.0 mass% and more preferably 0.5 to 2.0 mass% in 100 mass% of the aluminum foil. When the iron content is 0.1% by mass or more, the exterior material 10 having more excellent pinhole resistance and spreadability can be obtained. When the iron content is 9.0% by mass or less, the exterior material 10 having more excellent flexibility can be obtained.

Further, as the aluminum foil, a soft aluminum foil that has been subjected to an annealing treatment (for example, an aluminum foil made of 8021 material and 8079 material according to JIS standard) is more preferable because it can impart desired malleability during molding.

Although the thickness of the metal foil layer 13 is not particularly limited, it 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, but it is preferable to use a degreased aluminum foil from the viewpoint of imparting electrolytic solution resistance. The degreasing treatment can be roughly classified into a wet type and a dry type.

Examples of the wet type include acid degreasing and alkaline degreasing. Examples of the acid used for acid degreasing include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid. These inorganic acids may be used alone or in combination of two or more. .. Further, from the viewpoint of improving the etching effect of the aluminum foil, various metal salts serving as a supply source of Fe ions, Ce ions, etc. may be blended as necessary. Examples of the alkali used for alkali degreasing include strong etching types such as sodium hydroxide. Moreover, you may use the thing which mix|blended a weak alkaline type|system|group or a surfactant. The degreasing is performed by a dipping method or a spray method.

Examples of the dry type include a method of performing degreasing treatment in the step of annealing aluminum. In addition to degreasing treatment, flame treatment or corona treatment may be performed. Further, a degreasing treatment for oxidatively decomposing/removing pollutants by active oxygen generated by irradiating ultraviolet rays of a specific wavelength is also included.

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 due to hydrofluoric acid generated by the electrolytic solution or the reaction between the electrolytic solution and water. The corrosion prevention treatment layer 14 is formed by, for example, degreasing treatment, hot water conversion treatment, anodizing treatment, chemical conversion treatment, or a combination of these treatments. The anticorrosion treatment layer may be formed on the surface of the metal foil layer 13 on the first adhesive layer 12 side, or may be formed on both surfaces of the metal foil layer 13. When the corrosion prevention treatment layers are formed on both surfaces of the metal foil layer 13, the structures of both corrosion prevention treatment layers may be the same or different.

Examples of the degreasing treatment include acid degreasing and alkaline degreasing. Examples of the acid degreasing include a method of using an inorganic acid such as sulfuric acid, nitric acid, hydrochloric acid and hydrofluoric acid alone, or a method using a mixed solution thereof. Further, as the acid degreasing, by using an acid degreasing agent in which a fluorine-containing compound such as monosodium ammonium difluoride is dissolved with the above-mentioned inorganic acid, aluminum degreasing is performed especially when an aluminum foil is used for the metal foil layer 13. Not only the effect is obtained, but also a passive aluminum fluoride can be formed, which is effective in terms of hydrofluoric acid resistance. Examples of alkaline degreasing include a method using sodium hydroxide and the like.

Examples of the hot water conversion treatment include boehmite treatment in which an aluminum foil is dipped in boiling water containing triethanolamine.

Examples of the anodizing treatment include alumite treatment.

Examples of the chemical conversion treatment include a dipping type and a coating type. Examples of the immersion type chemical conversion treatment include chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, or various chemical conversion treatments including a mixed phase thereof. To be On the other hand, examples of the coating type chemical conversion treatment include a method of coating a coating agent having a corrosion prevention property on the metal foil layer 13.

When at least a part of the corrosion prevention treatment layer is formed by any one of the hot water conversion treatment, the anodic oxidation treatment, and the chemical conversion treatment, it is preferable to perform the degreasing treatment described above in advance. When the degreasing-treated metal foil is used as the metal foil layer 13, it is not necessary to perform the degreasing treatment again in forming the corrosion prevention treatment layer.

The coating agent used for the coating type chemical conversion treatment preferably contains trivalent chromium. Further, the coating agent may contain at least one polymer selected from the group consisting of a cationic polymer and an anionic polymer described below.

Further, among the above treatments, particularly the hot water conversion treatment and the anodic oxidation treatment dissolve the aluminum foil surface with a treatment agent to form an aluminum compound (boehmite, alumite) having excellent corrosion resistance. Therefore, since the metal foil layer 13 using the aluminum foil and the corrosion prevention treatment layer 14 form a co-continuous structure, it is included in the definition of chemical conversion treatment, but is included in the definition of chemical conversion treatment as described later. It is also possible to form the anticorrosion treatment layer 14 only by a pure coating method. As this method, for example, a sol of a rare earth element-based oxide such as cerium oxide having an average particle diameter of 100 nm or less is used as a material having an aluminum corrosion inhibiting effect (inhibitor effect) and being environmentally preferable. The method of using is mentioned. By using this method, it becomes possible to impart a corrosion prevention effect to a metal foil such as an aluminum foil even by a general coating method.

Examples of the rare earth element-based oxide sol include sol using various solvents such as water-based, alcohol-based, hydrocarbon-based, ketone-based, ester-based, and ether-based solvents. Of these, an aqueous sol is preferable.

In the sol of the rare earth element-based oxide, in order to stabilize the dispersion, nitric acid, hydrochloric acid, an inorganic acid such as phosphoric acid or a salt thereof, acetic acid, malic acid, ascorbic acid, lactic acid, or another organic acid is dispersed. Used as a stabilizer. Of these dispersion stabilizers, phosphoric acid is especially (1) dispersion stabilization of the sol and (2) improvement of adhesion to the metal foil layer 13 using the aluminum chelate ability of phosphoric acid in the exterior material 10. , (3) Electrolytic solution resistance is imparted by capturing (passive formation) of aluminum ions eluted under the influence of hydrofluoric acid, and (4) Corrosion prevention treatment layer 14 due to dehydration condensation of phosphoric acid even at low temperature ( It is expected that the cohesive force of the oxide layer) will be improved.

Examples of the phosphoric acid or its salt include orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, or their alkali metal salts and ammonium salts. Of these, condensed phosphoric acid such as trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, and ultrametaphosphoric acid, or alkali metal salts or ammonium salts thereof are preferable for exhibiting functions in the exterior material 10. In addition, considering the dry film-forming properties (drying capacity, calorific value) when forming a corrosion prevention treatment layer composed of a rare earth oxide by various coating methods using the above rare earth oxide sol, dehydration condensation property at low temperature The sodium salt is more preferable because it is excellent in As the phosphate, a water-soluble salt is preferable.

The compounding ratio of phosphoric acid (or its salt) to the rare earth element oxide is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the rare earth element oxide. When the mixing 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 packaging material 10 becomes better. The mixing ratio is more preferably 5 parts by mass or more with respect to 100 parts by mass of the rare earth element oxide. When the mixing 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 erosion of the electrolytic solution is excellent. The mixing 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 oxide sol is an aggregate of inorganic particles, the cohesive force of the layer itself may be low 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 supplement the cohesive force.

Examples of the anionic polymer include a polymer having a carboxy group, and examples thereof include poly(meth)acrylic acid (or a salt thereof) or a copolymer obtained by copolymerizing poly(meth)acrylic acid as a main component. As a copolymerization component of this copolymer, an alkyl (meth)acrylate-based monomer (as the alkyl group, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an 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, a methyl group, an ethyl 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, (as an alkoxy group, a methoxy group, an ethoxy group, a butoxy group, an isobutoxy group, etc.), N-methylol (meth)acrylamide, N-phenyl (meth)acrylamide; Hydroxyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate and other hydroxyl group-containing monomers; glycidyl (meth)acrylate and allyl glycidyl ether and other glycidyl group-containing monomers; (meth)acryloxypropyltrimethoxysilane, (meth) Silane-containing monomers such as acryloxypropyltriethoxylane; isocyanate group-containing monomers such as (meth)acryloxypropylisocyanate.

These anionic polymers play a role of improving the stability of the corrosion prevention treatment layer 14 (oxide layer) obtained by using the rare earth element oxide sol. This is achieved by the effect of protecting the hard and brittle oxide layer with the acrylic resin component, and the effect of trapping the ion contamination (particularly sodium ion) derived from the phosphate contained in the rare earth oxide sol (cation catcher). To be done. That is, when the corrosion prevention treatment layer 14 obtained by using the rare earth oxide sol contains alkali metal ions such as sodium or alkaline earth metal ions, the corrosion prevention starts from the place containing these ions. The treatment layer 14 is likely to deteriorate. Therefore, by fixing the sodium ions contained in the rare earth oxide sol with the anionic polymer, the resistance of the corrosion prevention treatment layer 14 is improved.

The corrosion prevention treatment layer 14 in which the anionic polymer and the rare earth element oxide sol are combined has the same corrosion prevention performance as the corrosion prevention treatment layer 14 formed by subjecting the aluminum foil to the chromate treatment. The anionic polymer preferably has a crosslinked structure of a polyanionic polymer which is essentially water-soluble. Examples of the cross-linking agent used for forming this structure include compounds having an isocyanate group, a glycidyl group, a carboxy group, or an oxazoline group.

Examples of the compound having an isocyanate group include tolylene diisocyanate, xylylene diisocyanate or hydrogenated products thereof, hexamethylene diisocyanate, 4,4′ diphenylmethane diisocyanate or its hydrogenated products, diisocyanates such as isophorone diisocyanate; or these isocyanates. Polyisocyanates such as adducts obtained by reacting polyhydric alcohols such as trimethylolpropane with water, burettes obtained by reacting with water, or isocyanurates that are trimers; or these polyisocyanates. Examples thereof include blocked polyisocyanates obtained by blocking isocyanates with alcohols, lactams, oximes and the like.

Examples of the compound 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 that act on epichlorohydrin; polyhydric alcohols such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol and sorbitol, and epoxy compounds that act on epichlorohydrin; phthalic acid, terephthalate Examples thereof include epoxy compounds in which an acid, a dicarboxylic acid such as oxalic acid, and adipic acid, and epichlorohydrin are allowed to act.

Examples of the compound having a carboxy group include various aliphatic or aromatic dicarboxylic acids. Further, poly(meth)acrylic acid or an alkali (earth) metal salt of poly(meth)acrylic acid may be used.

As the compound having an oxazoline group, for example, a low molecular weight compound having two or more oxazoline units, or (meth)acrylic acid or (meth)acrylic acid alkyl ester when a polymerizable monomer such as isopropenyloxazoline is used And those obtained by copolymerizing acrylic monomers such as hydroxyalkyl (meth)acrylate.

Further, the anionic polymer may have a siloxane bond at a cross-linking point by selectively reacting an amine with a functional group like a silane coupling agent. 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 and the like can be used. Of these, epoxy silane, amino silane, and isocyanate silane are preferable in view of reactivity with anionic polymers or copolymers thereof.

The ratio of these crosslinking agents to the anionic polymer is preferably 1 to 50 parts by mass, and more preferably 10 to 20 parts by mass with respect to 100 parts by mass of the anionic polymer. When the ratio of the cross-linking agent is 1 part by mass or more based on 100 parts by mass of the anionic polymer, the cross-linked structure is easily formed sufficiently. When 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 the cationic polymer include polymers having amines, polyethyleneimine, ionic polymer complexes composed of polymers having polyethyleneimine and a carboxylic acid, primary amine-grafted acrylic resins obtained by grafting a primary amine onto an acrylic main skeleton, Examples thereof include polyallylamine, derivatives thereof, and cationic polymers such as aminophenol.

The cationic polymer is preferably used in combination with a crosslinking agent having a functional group capable of reacting with an amine/imine such as a carboxy group or a glycidyl group. As the cross-linking agent used in combination with the cationic polymer, a polymer having a carboxylic acid which forms an ionic polymer complex with polyethyleneimine can also be used, and examples thereof include polycarboxylic acid (salt) such as polyacrylic acid or its ionic salt, or Examples thereof include a copolymer having a comonomer introduced thereinto, a carboxy group-containing polysaccharide such as carboxymethyl cellulose or an ionic salt thereof, and the like. Examples of polyallylamine include homopolymers or copolymers of allylamine, allylamine amide sulfate, diallylamine, dimethylallylamine and the like. These amines may be free amines or may be stabilized with acetic acid or hydrochloric acid. Further, maleic acid, sulfur dioxide or the like may be used as the copolymer component. Further, a type in which thermal crosslinkability is imparted by partially methoxylating a primary amine can be used, and aminophenol can also be used. Particularly, allylamine or its derivative is preferable.

In the present embodiment, the cationic polymer is also described as one constituent element of the corrosion prevention treatment layer 14. The reason for this is that as a result of extensive studies using various compounds for imparting the electrolyte resistance and hydrofluoric acid resistance required for exterior materials for power storage devices, the cationic polymer itself also shows electrolyte resistance and hydrofluoric acid resistance. This is because it has been found that the compound can be added. It is presumed that this is because the aluminum ion is suppressed from being damaged by capturing the fluorine ion with the cationic group (anion catcher).

Cationic polymers are more preferred materials in terms of improved adhesion. Further, since the cationic polymer is also water-soluble like the above-mentioned anionic polymer, it is more preferable to form a crosslinked structure to impart water resistance. As the cross-linking agent for forming the 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 oxide sol is used as the anticorrosion treatment layer, a cationic polymer may be used instead of the anionic polymer as the protective layer.

The corrosion prevention treatment layer 14 by chemical conversion treatment typified by chromate treatment is used to form an inclined structure with an aluminum foil. Therefore, a chemical conversion treatment agent containing hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid or a salt thereof is used to form an aluminum alloy. The foil is treated, and then a chromium or non-chromium compound is allowed to act on the foil to form a chemical conversion treatment layer on the aluminum foil. However, since the above chemical conversion treatment uses an acid as the chemical conversion treatment agent, it causes deterioration of the working environment and corrosion of the coating apparatus. On the other hand, unlike the chemical conversion treatment represented by the chromate treatment, the coating type corrosion prevention treatment layer 14 described above does not need to form a tilted structure with respect to the metal foil layer 13 using an aluminum foil. Therefore, the properties of the coating agent are not restricted by acidity, alkalinity, neutrality and the like, and a good working environment can be realized. In addition, the chromate treatment using a chromium compound is preferably the coating type corrosion prevention treatment layer 14 from the viewpoint that an alternative is required in view of environmental hygiene.

From the above contents, as examples of the combination of the above-mentioned coating type corrosion prevention treatments, (1) rare earth oxide sol only, (2) anionic polymer only, (3) cationic polymer only, (4) rare earth oxide Sol + anionic polymer (laminated composite), (5) rare earth oxide sol + cationic polymer (laminated composite), (6) (rare earth oxide sol + anionic polymer: laminated composite)/cationic polymer ( Multi-layer), (7) (rare earth oxide sol+cationic polymer: laminated composite)/anionic polymer (multi-layer), and the like. Among them, (1) and (4) to (7) are preferable, and (4) to (7) are particularly preferable. However, the present embodiment is not limited to the above combination. For example, as a case of selecting a corrosion prevention treatment, a cationic polymer is also very good in that it has good adhesiveness with a modified polyolefin resin which will be mentioned in the description of the sealant adhesive layer (sealant layer or second adhesive layer) described later. In the case where the sealant adhesive layer is composed of the modified polyolefin resin, a cationic polymer is provided on the surface in contact with the sealant adhesive layer (for example, the constitutions (5) and (6), etc.) because it is a preferable material for Such a design is possible.

Further, the corrosion prevention treatment layer 14 is not limited to the above-mentioned layers. For example, it may be formed by using a treating agent in which phosphoric acid and a chromium compound are mixed with a resin binder (aminophenol or the like) as in the case of coating type chromate which is a known technique. By using this treating agent, it is possible to form a layer having both the corrosion prevention function and the adhesiveness. In addition, although it is necessary to consider the stability of the coating liquid, both the corrosion prevention function and the adhesiveness can be obtained by using a coating agent in which the rare earth oxide sol and the polycationic polymer or the polyanionic polymer are previously liquefied. It can be a combined layer.

Mass per unit area of the corrosion prevention treatment layer 14 is a multilayer structure, it is either single-layer structure, preferably ^{0.005~0.200g / m 2, 0.010~0.100g / m} 2 Gayori preferable. When the mass per unit area is 0.005 g/m ² or more, the metal foil layer 13 is likely to have a corrosion prevention function. Further, 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 oxide sol is used, if the coating film is thick, curing due to heat during drying becomes insufficient, which may lead to a decrease in cohesive force. The thickness of the corrosion prevention treatment layer 14 can be converted from its specific gravity.

<Sealant layer 15>
The sealant layer 15 is a layer that imparts sealing properties by heat sealing to the exterior material 10. Examples of the material forming the sealant layer 15 include a polyolefin resin or an acid-modified polyolefin resin. When the sealant layer 15 is a single layer in the case of the exterior material 10 (that is, a configuration without the second adhesive layer 17 described later: thermal lamination), an acid-modified polyolefin resin (SPP) is used. Is preferred. Further, even when the sealant layer 15 has a multi-layer structure, it is preferable to use an acid-modified polyolefin resin on at least the outermost layer side that is in contact with the metal foil layer 13, but in the other layers, the polyolefin resin and the acid-modified polyolefin resin are used. Any of the polyolefin resins may be used. On the other hand, in the case of the exterior material 20 described later (that is, the configuration having the second adhesive layer 17: dry lamination), all layers are used regardless of the layer configuration (single layer or multiple layers) of the sealant layer 15. In the above, either a polyolefin resin or an acid-modified polyolefin resin may be used.

The acid-modified polyolefin resin is a resin obtained by introducing an acidic group into the polyolefin resin. Examples of the acidic group include a carboxy group and a sulfonic acid group, and a carboxy group is particularly preferable. Examples of the acid-modified polyolefin resin in which a carboxy group is introduced into a polyolefin resin include, for example, an unsaturated carboxylic acid or an acid anhydride thereof, or an unsaturated carboxylic acid or an ester of an acid anhydride thereof in the presence of a radical initiator with respect to the polyolefin resin. An acid-modified polyolefin resin obtained by graft modification below may be mentioned. Hereinafter, the unsaturated carboxylic acid or its acid anhydride and the ester of the unsaturated carboxylic acid or its acid anhydride may be collectively referred to as a graft compound.

Examples of the polyolefin resin include low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-α-olefin copolymer, homopolypropylene, block polypropylene, random polypropylene and propylene-α-olefin copolymer.

As the unsaturated carboxylic acid, 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, etc. Are listed. As the acid anhydride of the unsaturated carboxylic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylic anhydride And so on. As the ester of unsaturated carboxylic acid or its acid anhydride, methyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dimethyl maleate, monomethyl maleate, diethyl fumarate, dimethyl itaconate, diethyl citracone, Examples include dimethyl tetrahydrophthalic anhydride, dimethyl bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylate, and the like.

The proportion of the graft compound in the acid-modified polyolefin resin is preferably 0.2 to 100 parts by mass with respect to 100 parts by mass of the polyolefin resin. The temperature condition of the graft reaction is preferably 50 to 250°C, more preferably 60 to 200°C. Although the reaction time depends on the production method, in the case of the melt graft reaction using a twin-screw extruder, it is preferably within the residence time of the extruder. Specifically, it is preferably 2 to 30 minutes, more preferably 5 to 10 minutes. The graft reaction can be carried out under either normal pressure or pressure.

Examples of the radical initiator include organic peroxides. Examples of organic peroxides include alkyl peroxides, aryl peroxides, acyl peroxides, ketone peroxides, peroxyketals, peroxycarbonates, peroxyesters and hydroperoxides. These organic peroxides can be appropriately selected depending on the temperature conditions and the reaction time. In the case of the melt grafting reaction by the above-mentioned twin-screw extruder, alkyl peroxide, peroxyketal and peroxyester are preferable, and di-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butyl. More preferred is peroxy-hexyne-3, dicumyl peroxide.

As the acid-modified polyolefin resin, a polyolefin resin modified with maleic anhydride is preferable, and for example, “Admer” manufactured by Mitsui Chemicals, or “Modic” manufactured by Mitsubishi Chemical is suitable. Since such an acid-modified polyolefin resin component is excellent in reactivity with various metals and polymers having various functional groups, it is possible to impart adhesiveness to the sealant layer 15 by utilizing the reactivity, and the electrolytic solution resistant. It is possible to improve the property.

The sealant layer 15 contains an inorganic filler 16. The inorganic filler 16 has insulating properties, electrolytic solution resistance, heat resistance (heat countermeasure during heat sealing), hardness (pressure countermeasure during heat sealing), and acid resistance (reaction between the electrolytic solution and water). It is required to have characteristics such as (measures against hydrogen fluoride) and preferably further have thermal conductivity (low temperature heat sealing is possible and heat dissipation as a battery can be expected).

Examples of the inorganic filler 16 include aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, calcium carbonate, zirconium silicate, zinc oxide, titanium oxide, tin oxide, iron oxide, antimony oxide, boron nitride, aluminum nitride and silicon nitride. Examples include fillers that are composed. Among these, aluminum oxide or boron nitride is preferable from the viewpoint of electrolytic solution resistance, acid resistance, heat resistance, hardness, and thermal conductivity.

The inorganic filler 16 is defined as a term including both primary filler (single filler) and secondary filler (aggregated filler). The shape of the inorganic filler 16 (the shape of the single filler) is not particularly limited, and spherical, plate-shaped, needle-shaped, fiber, columnar, or amorphous fillers can be preferably used. For example, when a spherical filler is used as the inorganic filler 16, the average primary particle diameter can be about 0.5 to 20 μm.

It is more preferable that these inorganic fillers 16 are surface-treated. When the inorganic filler 16 is surface-treated with a silane coupling material or the like, the adhesiveness between the resin forming the sealant layer 15 and the inorganic filler 16 is increased, and the resin fluidity at the time of melting may be further reduced. it can. As a result, even if heat or pressure is applied during heat sealing, the flow of resin can be suppressed, which can prevent short circuits. In addition, the surface treatment further has a viewpoint that it is easy to prevent the inorganic filler 16 from falling off from the sealant layer 15.

In the present embodiment, the ratio of these inorganic fillers 16 to the total thickness of the sealant layer 15 is 5 to 50% in the cross section along the stacking direction of the power storage device exterior material. Thereby, even if the sealant layer 15 is thinned, it is possible to maintain good insulation. The reason will be briefly described below.

In general, the sealant layer 15 is melted or crushed by heat or pressure during heat sealing when manufacturing the power storage device. For example, in the top seal, the sealant layer 15 is melted or crushed, so that the distance between the tab lead and the metal layer becomes short, and a short circuit easily occurs. On the other hand, the presence of a predetermined amount of the inorganic filler 16 in the sealant layer 15 makes it difficult for the sealant layer 15 to be melted or crushed even if heat or pressure is applied, so that the tab lead and the metal layer have a certain amount or more. You can create a distance. This makes it possible to suppress the occurrence of short circuits.

Further, as the sealant layer 15 becomes thinner, the resistance of the single layer becomes smaller, so that the insulation is likely to be deteriorated even if the layer thickness changes or some cracks occur. In particular, it has been confirmed that a short circuit is considered to be influenced by the layer thickness variation during heat sealing (top seal, side seal and degassing heat seal). Therefore, by adding the inorganic filler 16, the filler plays a role of maintaining a gap, and the flow of the resin due to melting at the time of heat sealing can be suppressed by the intermolecular interaction, and a short circuit can be prevented. Becomes

If the ratio of the inorganic filler 16 to the total thickness of the sealant layer 15 is less than 5%, the role as a spacer becomes insufficient, and the tab lead and the metal layer may approach each other, which may cause a short circuit. On the other hand, if the ratio is more than 50%, the content of the filler is too large, so that it becomes difficult to form the sealant layer 15, and the contact area becomes small, so that the adhesiveness between the layers decreases. In addition, the heat seal strength is reduced. From such a viewpoint, the above ratio is more preferably 20 to 30%.

The content of the inorganic filler 16 is preferably 5 to 35 mass% based on the total mass of the sealant layer 15. When the content is less than 5% by mass, the role as a spacer becomes insufficient, and the tab lead and the metal layer come close to each other, which may cause a short circuit. Further, if the content is small, the viscosity of the sealant layer 15 tends to be low, and it tends to be difficult to control the fluidity. On the other hand, when the content is more than 35% by mass, the contact area becomes small and the adhesiveness is apt to decrease. In addition, the heat seal strength tends to decrease, and the viscosity of the sealant layer 15 becomes too high, so that the film forming processability tends to decrease. From such a viewpoint, the content of the inorganic filler 16 is more preferably 15 to 25% by mass.

The sealant layer 15 may be a single layer film or a multilayer film in which a plurality of layers are laminated. Depending on the required function, for example, a multilayer film having a resin such as an ethylene-cyclic olefin copolymer or polymethylpentene interposed may be used from the viewpoint of imparting moisture resistance.

In the present embodiment, it is preferable that the sealant layer 15 is composed of two or more layers, and at least one of the layers does not contain the inorganic filler 16. By constructing the sealant layer 15 with two or more layers, for the layer to which the inorganic filler 16 is not added, the original characteristics of the sealant layer 15 are not deteriorated due to the inclusion of the inorganic filler 16, Insulation can be exhibited.

The thickness of the layer containing the inorganic filler 16 is preferably 50% or more with respect to the total thickness of the sealant layer 15. If the thickness of the layer containing the inorganic filler is less than 50% of the total thickness of the sealant layer 15, the resin flow easily occurs when heat or pressure is applied during heat sealing, and a short circuit occurs. Tends to do. Therefore, the ratio is more preferably 60% or more. The upper limit of the ratio can be set to 90% in order to enjoy the above-described merits by forming the sealant layer 15 in multiple layers, that is, by providing the layer containing no inorganic filler.

When the sealant layer 15 is composed of two or more layers, the layer containing the inorganic filler 16 is sandwiched between the layers not containing the inorganic filler 16 (for example, the intermediate layer in the three-layer structure). That) is preferred. Thereby, the insulating property can be exhibited without impairing the adhesiveness with the metal foil layer 13 and the heat seal property. Note that, for example, when the sealant layer 15 having such a three-layer structure is used, the layer containing the inorganic filler 16 can be arranged on the outer layer side or the inner layer side as a matter of course, but in the former case, the metal foil layer 13 is used. There is a tendency that the adhesiveness to and tends to decrease, and in the latter case, the seal strength tends to decrease.

When the sealant layer 15 is composed of two or more layers, each layer can be independently formed by appropriately using each component described above. That is, for example, the resin material forming each layer may be the same or different, and the thickness of each layer may be the same or different. However, from the viewpoint of enhancing the adhesiveness with the inorganic filler 16 and easily ensuring low fluidity even when heat or pressure is applied during heat sealing, at least the layer containing the inorganic filler 16 is acid. It is preferably a layer made of modified polyolefin.

Various additives such as a flame retardant, a slip agent, an anti-blocking agent, an antioxidant, a light stabilizer, and a tackifier may be added to the sealant layer 15.

The thickness of the sealant layer 15 is preferably 10 to 100 μm, more preferably 20 to 50 μm. When the sealant layer 15 is composed of multiple layers, the total thickness (total thickness) of each layer is preferably within this range.

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

For example, although 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 sealant layer 15 side, the corrosion prevention treatment layer 14 is the first adhesive of the metal foil layer 13. It may be formed on the surface on the 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 metal foil layer 13 The structure of the corrosion prevention treatment layer 14 formed on the sealant layer 15 side may be the same or different.

In addition, in FIG. 1, the case where the metal foil layer 13 and the sealant layer 15 are directly laminated (via the corrosion prevention treatment layer 14) is shown, but like the case 20 of the power storage device shown in FIG. The metal foil layer 13 and the sealant layer 15 may be laminated using the second adhesive layer 17. Hereinafter, the second adhesive layer 17 will be described.

<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 15. For the second adhesive layer 17, a general adhesive for bonding the metal foil layer 13 and the sealant layer 15 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 above-mentioned cationic polymer and anionic polymer, the second adhesive layer 17 is included in the corrosion prevention treatment layer 14. It is preferably a layer containing a compound having reactivity with the polymer (hereinafter, also referred to as “reactive compound”).

For example, when the anticorrosion 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. When the anticorrosion 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 need to include the above-mentioned two types of compounds, and may include a compound that is 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 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 a polyfunctional isocyanate compound, a glycidyl compound, a compound having a carboxy group, and a compound having an oxazoline group.

As these polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxy group, and compounds having an oxazoline group, the polyfunctional isocyanate compounds, glycidyl compounds, and carboxy groups previously exemplified as a cross-linking agent for forming a cross-linked structure of a cationic polymer. And a compound having an oxazoline group. Among these, a polyfunctional isocyanate compound is preferable because it has high reactivity with a cationic polymer and easily forms a crosslinked structure.

Examples of the compound reactive with the anionic polymer include at least one compound selected from the group consisting of a glycidyl compound and a compound having an oxazoline group. Examples of the glycidyl compound and the oxazoline group-containing compound include the glycidyl compound and the oxazoline group-containing compound exemplified above as the crosslinking agent for forming the crosslinked structure of the cationic polymer. Among these, the glycidyl compound is preferable because of its 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 acidic group in the acid-modified polyolefin resin (that is, forms a covalent bond with the acidic group). Thereby, the adhesiveness with the anticorrosion treatment layer is further enhanced. In addition, the acid-modified polyolefin resin has a crosslinked structure, and the solvent resistance of the exterior material 10 is further improved.

The content of the reactive compound is preferably from 1 to 10 times the equivalent amount of the acidic group in the acid-modified polyolefin resin. When the amount is equal to or more than the equivalent amount, the reactive compound sufficiently reacts with the acidic group in the acid-modified polyolefin resin. On the other hand, if the amount exceeds 10 times the equivalent amount, the cross-linking structure with the acid-modified polyolefin resin becomes insufficient, and there is a concern that the physical properties such as the above-mentioned solvent resistance may deteriorate.

The acid-modified polyolefin resin is obtained by introducing an acidic group into a polyolefin resin. Examples of the acidic group include a carboxy group and a sulfonic acid group, and a carboxy group is particularly preferable. As the acid-modified polyolefin resin, the same ones as those exemplified as the modified polyolefin resin used for the sealant layer can be used.

The second adhesive layer 17 may be mixed with various additives such as a flame retardant, a slip agent, an anti-blocking agent, an antioxidant, a light stabilizer and a tackifier.

A general adhesive used for bonding the metal foil layer 13 and the sealant layer 15 may contain a silane coupling agent. This is because the addition of a silane coupling agent promotes adhesion and enhances adhesive strength. However, when an adhesive containing a silane coupling agent is used, components other than the silane coupling agent contained in the adhesive layer and the silane coupling agent may be subordinate depending on the type of functional group contained in the silane coupling agent. This may cause a reaction, which may adversely affect the intended cross-linking reaction. Therefore, it is preferable that the adhesive used for bonding the metal foil layer 13 and the sealant layer 15 does not contain a silane coupling agent.

When the second adhesive layer 17 contains the above-described reactive compound, a covalent bond is formed with the polymer in the corrosion prevention treatment layer 14, and the adhesion strength between the corrosion prevention treatment layer 14 and the second adhesive layer 17 is increased. Is improved. Therefore, it is not necessary to mix a silane coupling agent in the second adhesive layer 17 for the purpose of promoting adhesion, and the second adhesive layer 17 preferably does not contain a silane coupling agent.

The thickness of the second adhesive layer 17 is preferably 3 to 50 μm, more preferably 3 to 10 μm. When the thickness of the second adhesive layer 17 is at least the lower limit value, excellent adhesiveness is easily obtained. When the thickness of the second adhesive layer is less than or equal to the upper limit value, the amount of water permeated from the side end surface of the exterior material is reduced.

The configuration of the power storage device exterior material 20 other than the second adhesive layer 17 is the same as that of the power storage device exterior material 10. The thickness of the sealant layer 15 in the power storage device exterior material 20 is adjusted according to the thickness of the second adhesive layer 17. The thickness of the sealant layer 15 in the exterior material 20 for a power storage device is not particularly limited, but is, for example, preferably in the range of 5 to 100 μm, and more preferably in the range of 10 to 80 μm.

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

The manufacturing method of 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 laminating the base material layer 11 and the metal foil layer 13, and further laminating a sealant layer 15. Then, a schematic structure is provided including a step of producing a laminated body and a step of heat-treating the obtained laminated body, if necessary.

(Lamination process of the corrosion prevention treatment layer 14 on the metal foil layer 13)
This step is a step of forming the corrosion prevention treatment layer 14 on the metal foil layer 13. Examples of the method include, as described above, a method in which the metal foil layer 13 is subjected to degreasing treatment, hydrothermal conversion treatment, anodizing treatment, chemical conversion treatment, or a coating agent having a corrosion prevention property is applied. To be

When the corrosion prevention treatment layer 14 is a multi-layer, for example, a coating liquid (coating agent) forming the corrosion prevention treatment layer on the lower layer side (the metal foil layer 13 side) is applied to the metal foil layer 13 and baked. After forming the first layer by coating, the coating liquid (coating agent) that constitutes the upper corrosion preventing layer may be applied to the first layer and baked to form the second layer. The second layer can also be formed in the step of laminating the sealant layer 15 described below.

For degreasing treatment, spray method or dipping method, for hot water conversion treatment or anodizing treatment, dipping method, and for chemical conversion treatment, appropriately select dipping method, spraying method, coating method, etc. according to the type of chemical conversion treatment. You can do it.

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

As described above, the various treatments may be performed on both sides or one side of the metal foil layer 13, but in the case of the one-side treatment, it is preferable to apply the treatment surface to the side on which the sealant layer 15 is laminated. Note that the surface of the base material layer 11 may be subjected to the above treatment, if desired.

Any coating amount of the coating agent for forming the first layer and the second layer is preferably ^{0.005~0.200g / m 2, 0.010~0.100g / m} 2 is more preferable.

When dry curing is required, the base material temperature can be 60 to 300° C. depending on the drying conditions of the corrosion prevention treatment layer 14 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 material layer 11 with the first adhesive layer 12 interposed therebetween. As a method of bonding, a method such as dry lamination, non-solvent lamination, or wet lamination is used, and both materials are bonded with the material forming the first adhesive layer 12 described above. The first adhesive layer 12 is provided in a dry coating amount range of 1 to 10 g/m ² , and more preferably 3 to 7 g/m ² .

(Laminating step of sealant layer 15)
This step is a step of forming the sealant layer 15 on the corrosion prevention treatment layer 14 formed in the previous step. Examples of the method include a method of sand laminating the sealant layer 15 using an extrusion laminating machine. Further, the sealant layer 15 can be laminated by extruding the sealant layer 15 by a tandem laminating method or a coextrusion method.

Through this step, a laminate in which the respective layers are laminated in the order of base material layer 11/first adhesive layer 12/metal foil layer 13/corrosion prevention treatment layer 14/sealant layer 15 as shown in FIG. 1 is obtained. To be

Further, in the case of forming the multilayer anticorrosion treatment layer 14, if the extrusion laminating machine is provided with a unit capable of applying the anchor coat layer, the second layer of the anticorrosion treatment layer 14 is formed in the unit. May be applied.

(Heat treatment process)
This step is a step of heat-treating the laminated body. By heat-treating the laminate, the adhesion between the metal foil layer 13/corrosion prevention treatment layer 14/sealant layer 15 can be improved, and more excellent electrolytic solution resistance and hydrofluoric acid resistance can be imparted. Also, the effect of suppressing the crystallization of the sealant layer 15 and suppressing the occurrence of the whitening phenomenon during molding can be obtained. Therefore, in this step, it is preferable to perform heat treatment to the extent that crystallization of the sealant layer 15 is not promoted while improving the adhesion between the layers described above. The temperature of the heat treatment depends on the type of material forming the sealant layer 15 and the like, but as a guide, the heat treatment is performed such that the highest temperature reached of the laminate is 20 to 100° C. higher than the melting point of the sealant layer 15. Is preferable, and it is more preferable that the heat treatment is performed so as to be 20 to 60° C. higher than the melting point of the sealant layer 15. If the highest temperature reached of the laminate is below this range, crystal nuclei remain and crystallization is likely to be promoted. On the other hand, when the highest temperature reached of the laminate exceeds this range, for example, thermal expansion of the metal foil or thermal contraction of the base material layer after bonding may occur, which may deteriorate workability and characteristics. Therefore, the heat treatment time depends on the treatment temperature, but it is desirable to perform the heat treatment in a short time (for example, less than 30 seconds).

Further, it is preferable that the cooling is performed rapidly in order to suppress crystallization. The cooling rate is preferably about 50 to 100° C./sec.

In this way, the exterior material 10 of this embodiment as shown in FIG. 1 can be manufactured.

Next, an example of a method of manufacturing the exterior material 20 shown in FIG. 2 will be described. The manufacturing method of the exterior material 20 is not limited to the following method.

The manufacturing method of 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, and a second adhesive layer. The sealant layer 15 is further laminated via 17 to produce a laminated body, and if necessary, the obtained laminated body is subjected to an aging treatment. In addition, up to the step of bonding the base material layer 11 and the metal foil layer 13 can be performed in the same manner as the manufacturing method of the exterior material 10 described above.

(Lamination process of the second adhesive layer 17 and the sealant layer 15)
This step is a step of bonding the sealant layer 15 to the corrosion prevention treatment layer 14 side of the metal foil layer 13 via the second adhesive layer 17. A wet process can be used as a bonding method.

In the case of the wet process, the solution or dispersion liquid of the adhesive that constitutes the second adhesive layer 17 is applied on the corrosion prevention treatment layer 14, and the temperature is adjusted to a predetermined temperature (when the adhesive contains an acid-modified polyolefin resin). Is baked at a temperature above its melting point). Then, the sealant layer 15 is laminated to manufacture the exterior material 20. Examples of the coating method include the various coating methods exemplified above.

(Aging treatment process)
This step is a step of aging 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 15 can be promoted. The aging treatment can be performed in the range of room temperature to 100°C. The aging time is, for example, 1 to 10 days.

In this way, the exterior member 20 of this embodiment as shown in FIG. 2 can be manufactured.

The preferred embodiments of the exterior material for a power storage device and the manufacturing method thereof according to the present invention have been described above in detail, but the present invention is not limited to the specific embodiments and is described in the scope of claims. Further, various modifications and changes can be made within the scope of the present invention.

The packaging material for a power storage device of the present invention is suitable as a packaging material for a power storage device such as a secondary battery such as a lithium ion battery, a nickel hydrogen battery, and a lead storage battery, and an electrochemical capacitor such as an electric double layer capacitor. Can be used. Above all, the exterior material for a power storage device of the present invention is suitable as an exterior material for a lithium ion battery.

Hereinafter, the present invention will be described more specifically based on Examples, but the present invention is not limited to the following Examples.

[Materials used]
The 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 adhesive (manufactured by Toyo Ink Co., Ltd.) in which an adduct-based curing agent of tolylene diisocyanate was mixed with a polyester polyol-based main agent was used.

<Corrosion prevention treatment layer>
"Sodium polyphosphate-stabilized cerium oxide sol" adjusted to a solid content concentration of 10 mass% was used using distilled water as a solvent. The sodium polyphosphate-stabilized cerium oxide sol was obtained by mixing 10 parts by mass of Na salt of phosphoric acid with 100 parts by mass of cerium oxide.

<Metal foil layer (thickness 35 μm)>
A soft aluminum foil subjected to annealing degreasing treatment (“8079 material” manufactured by Toyo Aluminum Co., Ltd.) was used.

<Second adhesive layer (thickness 4 μm)>
An adhesive prepared by mixing 10 parts by mass (solid content ratio) of a polyisocyanate compound having an isocyanurate structure with 100 parts by mass of a maleic anhydride-modified polyolefin resin dissolved in toluene was used.

<Sealant layer (thickness is shown in the table)>
SPP: Maleic anhydride modified polypropylene (Mitsui Chemicals Admer)
PP: Polypropylene (Prime Polymer Pro Prime Polypro)

<Inorganic filler>
Aluminum oxide: manufactured by Denki Kagaku Kogyo (spherical)
Silicon Nitride: Made by Nippon Ceratech (Amorphous)
Boron Nitride: Sumitomo 3M (plate)
Silicon oxide: manufactured by Denki Kagaku Kogyo (spherical)
Titanium oxide: manufactured by Fuji Titanium Industry Co., Ltd. (spherical)
*Inorganic filler surface treatment: Silane coupling agent (Toray Dow Corning)

[ Reference Example 1] (sealant layer: thermal laminate)
Sodium polyphosphate-stabilized cerium oxide sol was applied to one surface 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. As a result, the first corrosion prevention treatment layer was formed on the metal foil layer.

Next, the other surface of the metal foil layer was also coated with sodium polyphosphate-stabilized cerium oxide sol by microgravure coating so that the dry coating amount was 70 mg/m ^2, and baked at 200° C. in a drying unit. gave. Thereby, the second corrosion prevention treatment layer was formed on the metal foil layer.

Next, the first corrosion prevention treatment layer side of the metal foil layer provided with the first and second corrosion prevention treatment layers was subjected to a dry lamination method using a polyurethane adhesive (first adhesive layer) as a base. I stuck it on the material layer. This was set in the unwinding part of the extrusion laminating machine, and the sealant layer (thickness 35 μm) of constitution-1 was laminated on the second corrosion prevention treated layer by coextrusion under the processing conditions of 290° C. and 100 m/min. did. Regarding the sealant layer, a desired layer was prepared in advance by using a twin-screw extruder, and was subjected to a water-cooling/pelletizing step and then used for the extrusion lamination. The composition of the sealant layer was as shown in Tables 1 and 2.

The laminate thus obtained is subjected to heat treatment by thermal lamination so that the maximum temperature reached by the laminate is 190° C., and the exterior material (base layer/first adhesive layer/first layer). Of (corrosion prevention treatment layer/metal foil layer/second corrosion prevention treatment layer/sealant layer).

[ Examples 6 to 24 , 28 to 31, Reference Examples 1 to 5, 25 to 27, Comparative Examples 1 to 3] (sealant layer: thermal laminate)
An exterior material was produced in the same manner as in Reference Example 1 except that the sealant layers having the configurations shown in Tables 1 and 2 were used instead of the sealant layer having the configuration-1.

[ Examples 37 to 40, Reference Examples 32 to 36 ] (sealant layer: dry laminate)
In the same manner as in Reference Example 1, a laminate of base material layer/first adhesive layer/first corrosion prevention treatment layer/metal foil layer/second corrosion prevention treatment layer was prepared. Next, an adhesive (second adhesive layer) is applied on the second corrosion prevention treatment layer by a dry coating method at a dry coating amount of 4 to 5 g/m ² , dried and formed into a film, and then a sealant. The layers were pasted. The adhesive-bonded surface of the sealant layer was corona treated. After that, aging is performed at 40° C. for 5 days, and an exterior material (base material layer/first adhesive layer/first corrosion prevention treatment layer/metal foil layer/second corrosion prevention treatment layer/second adhesion). An agent layer/sealant layer laminate) was produced.

In the table, the proportion of the inorganic filler in the total thickness of the sealant layer was calculated as shown in FIG.
First, a cross section of the sealant layer cut out along the stacking direction of the exterior material is photographed with a microscope and image processing is performed. At that time, a measurement point of n=1 is determined as an arbitrary starting point. Nine measuring points are provided in the surface direction at intervals of 0.1 mm from the starting point, and a total of 10 measuring points including the starting point are determined. Next, as shown in FIG. 3, for example, at the measurement point of n=1, the total thickness t of the sealant layer and the vertical cumulative length x+y of the inorganic filler (two at the measurement point of n=1) decide. Then, by calculating (x+y)/t×100(%), the proportion (length in the vertical direction) of the inorganic filler in the total thickness of the sealant layer at any measurement point of n=1 is measured. .. By performing this operation on the measurement points of n=2 to n=10 and obtaining the average value thereof, the proportion of the inorganic filler in the total thickness of the sealant layer can be determined.

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

(Electrolytic solution laminating strength)
A Teflon (registered trademark) container was filled with an electrolytic solution in which LiPF ₆ was added to a mixed solution of ethylene carbonate/diethyl carbonate/dimethyl carbonate=1/1/1 (mass ratio) so as to be 1 M, and the exterior material was filled therein. Was cut into a size of 15 mm×100 mm, and the sample was sealed and stored at 85° C. for 24 hours. After that, co-washing was performed, and the laminate strength (T-type peeling strength) between the metal foil layer/sealant layer or between the metal foil layer/second adhesive layer was measured using a tester (manufactured by INSTRON). The test was performed according to JIS K6854 in a 23° C., 50% RH atmosphere at a peeling speed of 50 mm/min. Based on the results, the following criteria were evaluated.
A: Laminate strength is more than 9N/15mm B: Laminate strength is 7N/15mm or more, 9N/15mm or less C: Laminate strength is 5N/15mm or more, less than 7N/15mm D: Laminate strength is less than 5N/15mm

(Electrolytic solution heat seal strength)
A sample obtained by cutting the outer casing material into 60 mm×120 mm was folded in two, and heat sealed at 190° C., 0.5 MPa, 3 sec with a seal bar having a side of 10 mm. After that, LiPF ₆ was added to a mixed solution of ethylene carbonate/diethyl carbonate/dimethyl carbonate=1/1/1 (mass ratio) so that the remaining 2 sides were heat-sealed into a bag shape so as to be 1M. The pouch in which 1 ml of the electrolyte was injected was stored at 60°C for 24 hours, the first side of the heat seal was cut into a width of 15 mm (see Fig. 4), and the seal strength (T-type peeling strength) was measured with a tester (INSTRON. (Manufactured by the company). The test was performed according to JIS K6854 in a 23° C., 50% RH atmosphere at a peeling speed of 50 mm/min. Based on the results, the following criteria were evaluated.
A: Seal strength is 80 N/15 mm or more, burst width is over 5 mm B: Seal strength is 80 N/15 mm or more, burst width is 3-5 mm
C: Seal strength is 60 N/15 mm or more and less than 80 N/15 mm D: Seal strength is less than 60 N/15 mm

(Degassing heat seal strength)
A sample obtained by cutting the outer packaging material into 75 mm×150 mm is folded in half into 37.5 mm×150 mm (see FIG. 5A), and then the 150 mm side and the 37.5 mm side are heat-sealed to form a bag. Then, in the pouch, 5 ml of an electrolytic solution prepared 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 and heat-sealed. After sealing and storing at 60° C. for 24 hours, the central part of the pouch was degassing heat-sealed at 190° C., 0.3 MPa, 2 sec (see FIG. 5B). In order to stabilize the seal part, after storing it at room temperature for 24 hours, the degassing seal part was cut into a width of 15 mm (see FIG. 5(c)), and the heat seal strength (T-type peel strength) was measured with a tester. (Manufactured by INSTRON). The test was performed according to JIS K6854 in a 23° C., 50% RH atmosphere at a peeling speed of 50 mm/min. Based on the results, the following criteria were evaluated.
A: Seal strength is 60 N/15 mm or more B: Seal strength is 40 N/15 mm or more, less than 60 N/15 mm C: Seal strength is 30 N/15 mm or more, less than 40 N/15 mm D: Seal strength is less than 30 N/15 mm

(Insulation performance)
A sample obtained by cutting the exterior material into 75 mm×150 mm was folded in half into 37.5 mm×150 mm. Then, the tab sealant and the tab were sandwiched, and top sealing (sealing pressure was controlled using a gap), and then side sealing was performed. After that, a part of the outer layer is shaved to expose the metal layer in order to contact the electrode, and then the tab (point A in FIG. 6A) and the exposed metal layer (point B in FIG. 6A) are formed. The electrodes were connected, 25 V was applied, and the resistance value was measured (insulation test 1).
Subsequently, 5 ml of the electrolytic solution was injected from the remaining one side and sealed by heat sealing. After storing at 60° C. for 24 hours, the central part of the pouch was degassing heat-sealed at 190° C., 0.3 MPa, 2 sec. In order to stabilize the seal part, after storing it at room temperature for 24 hours, connect the electrode to the tab (point A in FIG. 6(b)) and the exposed metal layer (point B in FIG. 6(b)), and apply 25V. Then, the resistance value was measured (insulation test 2).
Based on the results of the insulation tests 1 and 2, the following criteria were evaluated.
A: 200 MΩ or more B: 100 MΩ or more and 200 MΩ or less C: 30 MΩ or more and less than 100 MΩ D: less than 30 MΩ

(Comprehensive quality)
Table 3 shows the results of the above evaluations. In Table 3 below, when the evaluation results do not have D evaluation, it can be said that the overall quality is excellent.

As is clear from the results of Tables 1 to 3, with the outer casing material for a power storage device of the example, even when the sealant layer is thin, good insulation is achieved while achieving sufficient heat seal strength. It is understood that sex can be maintained. It is also understood that when the layer containing the inorganic filler is made of SPP and is the intermediate layer, good insulation can be maintained while maintaining particularly excellent laminating strength and sealing strength.

10, 20... Exterior material for electric storage device (exterior material), 11... Base material layer, 12... First adhesive layer, 13... Metal foil layer, 14... Corrosion prevention treatment layer, 15... Sealant layer, 16... Inorganic System filler, 17... Second adhesive layer.

Claims (5)

At least a base material layer, an adhesive layer, a metal foil layer and a sealant layer,
The sealant layer contains an inorganic filler, and in a cross section along the stacking direction, the proportion of the inorganic filler in the total thickness of the sealant layer is 5 to 50%,
The sealant layer is composed of two or more layers, at least one of which does not contain the inorganic filler,
A packaging material for a power storage device , wherein in the sealant layer, a layer containing the inorganic filler is sandwiched by layers not containing the inorganic filler . The exterior material for a power storage device according to claim 1, wherein the content of the inorganic filler is 5 to 35 mass% based on the total mass of the sealant layer. The outer casing material for a power storage device according to claim 1, wherein the thickness of the layer containing the inorganic filler is 50% or more with respect to the total thickness of the sealant layer. It said layer containing the inorganic filler is a layer made of acid-modified polyolefin resin and the inorganic filler, a power storage device for exterior materials of any one of claims 1-3. The inorganic filler is one that was treated surface, a power storage device for exterior materials of any one of claims 1-4.