JP6943045B2 - Exterior material for power storage device and power storage device using it - Google Patents

Description

The present invention relates to an exterior material for a power storage device and a power storage device using the same.

As the power storage device, for example, 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 are known. Due to the miniaturization of mobile devices or the limitation of installation space, further miniaturization of power storage devices is required, and lithium ion batteries having high energy density are attracting attention. Conventionally, metal cans have been used as exterior materials used in lithium-ion batteries, but multilayer films that are lightweight, have high heat dissipation, and can be produced at low cost are now being used.

In a lithium ion battery using the above multilayer film as an exterior material, in order to prevent moisture from entering the inside, the battery contents (positive electrode, separator, negative electrode, electrolytic solution, etc.) are covered with an exterior material containing an aluminum foil layer. It has been adopted. A lithium-ion battery adopting such a configuration is called an aluminum laminate type lithium-ion battery.

In an aluminum-laminated lithium-ion battery, for example, a recess is formed in a part of the exterior material by cold molding, the battery contents are housed in the recess, and the remaining part of the exterior material is folded back to heat the edge portion. An embossed type lithium ion battery sealed with a seal is known (see, for example, Patent Document 1). In such a lithium-ion battery, the deeper the recess formed by cold molding, the more battery contents can be accommodated, so that the energy density can be increased.

Japanese Unexamined Patent Publication No. 2013-101765

However, when an exterior material for a power storage device is produced according to the material and the manufacturing method described in Patent Document 1 and an attempt is made to form a deep recess in the exterior material, the exterior material may be broken. Therefore, an object of the present invention is to provide an exterior material for a power storage device having excellent deep drawing moldability, and a power storage device using the same.

The present invention provides an exterior material for a power storage device having a structure in which at least a base material layer, an adhesive layer, a metal foil layer, a sealant adhesive layer and a sealant layer are laminated in this order.

^{In the exterior material for a power storage device, the adhesive layer has a yield stress of 3500 to 6500 N / cm 2} and 45 to 200% in the stress strain curve measured by a tensile test with a tensile speed of 6 mm / min. Has a breaking elongation rate of. Conventionally, the base material layer plays a role of protecting the metal foil layer during deep drawing, and the adhesive layer is mainly required to have adhesion between the base material layer and the metal foil layer. However, according to the present invention, since the adhesive layer has the above-mentioned yield stress and elongation at break, it is possible to obtain more excellent deep drawing moldability that could not be achieved only by improving the base material layer. Although it is not always clear why the adhesive layer has the yield stress and the elongation at break to improve the deep drawing moldability, the present inventors consider it as follows. That is, by making the above-mentioned physical properties of the adhesive layer closer to the same physical properties of the metal foil layer as compared with the conventional case, the behavior of the adhesive layer when stress is applied by deep drawing becomes closer to that of the metal foil layer, and even after deep drawing molding. It is considered that this is because the adhesive layer is easier to follow the metal foil layer.

It is preferable that the exterior material for a power storage device further includes an easy-adhesion-treated layer provided between the base material layer and the adhesive layer. As a result, the adhesion between the base material layer and the adhesive layer can be further improved, and the deep drawing moldability can be further improved.

In the exterior material for a power storage device, the easy-adhesion-treated layer may be a layer containing at least one resin selected from the group consisting of polyester resin, acrylic resin, polyurethane resin, epoxy resin and acrylic graft polyester resin. preferable. As a result, the adhesion between the base material layer and the adhesive layer can be further improved, and the deep drawing moldability can be further improved.

It is preferable that the exterior material for the power storage device further includes corrosion prevention treatment layers provided on both sides of the metal foil layer. Thereby, the adhesion between the base material layer and the metal foil layer can be further improved.

In the exterior material for a power storage device, the corrosion prevention treatment layer preferably contains a rare earth element oxide and phosphoric acid or phosphate. Thereby, the adhesion between the base material layer and the metal foil layer can be further improved.

In the exterior material for a power storage device, it is preferable that the rare earth element oxide is cerium oxide. Thereby, the adhesion between the base material layer and the metal foil layer can be further improved.

The present invention also includes a battery element including an electrode, a lead extending from the electrode, and a container for accommodating the battery element. The container has the sealant layer inside from the exterior material for a power storage device. Provided is a power storage device formed in such a manner. In such a power storage device, since the exterior material for the power storage device of the present invention is used as the container for accommodating the battery element, a deep recess can be formed in the container without causing breakage or the like.

According to the present invention, it is possible to provide an exterior material for a power storage device having excellent deep drawing moldability, and a power storage device using the same.

It is a schematic cross-sectional view of the exterior material for a power storage device which concerns on one Embodiment of this invention. This is an example of the stress-strain curve of the adhesive layer obtained by the tensile test. It is a figure which shows the embossing type exterior material obtained by using the exterior material for a power storage device which concerns on one Embodiment of this invention, (a) is the perspective view, (b) is the embossing shown in (a). It is a vertical cross-sectional view along the bb line of the type exterior material. It is a perspective view which shows the process of manufacturing a secondary battery using the exterior material for a power storage device which concerns on one Embodiment of this invention, (a) shows the state which prepared the exterior material for a power storage device, (b). Indicates a state in which an embossed exterior material for a power storage device and a battery element are prepared, and (c) shows a state in which a part of the exterior material for a power storage device is folded back and the end portion is melted. ) Indicates a state in which both sides of the folded portion are folded upward.

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 are designated by the same reference numerals, and duplicate description will be omitted.

[Exterior material for power storage device]
FIG. 1 is a cross-sectional view schematically showing an embodiment of an exterior material for a power storage device of the present invention. As shown in FIG. 1, the exterior material (exterior material for a power storage device) 10 of the present embodiment includes a base material layer 11 and an easy-adhesion-treated layer 12 provided on one surface side of the base material layer 11. The adhesive layer 13 provided on the side opposite to the base material layer 11 of the adhesive treatment layer 12 and the corrosion prevention treatment layers 15a and 15b provided on the opposite side of the adhesive layer 13 from the easy-adhesion treatment layer 12 are provided on both sides. The metal foil layer 14 to be provided, the sealant adhesive layer 16 provided on the side opposite to the adhesive layer 13 of the metal foil layer 14, and the sealant layer 17 provided on the side opposite to the metal foil layer 14 of the sealant adhesive layer 16. It is a laminated body in which these are sequentially laminated. Here, the corrosion prevention treatment layer 15a is provided on the surface of the metal foil layer 14 on the adhesive layer 13 side, and the corrosion prevention treatment layer 15b is provided on the surface of the metal foil layer 14 on the sealant adhesive layer 16 side. When the secondary battery is manufactured using the exterior material 10, the base material layer 11 is the outermost layer and the sealant layer 17 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 17 facing the inside of the power storage device. Hereinafter, each layer will be described.

(Base material layer 11)
The base material layer 11 imparts heat resistance in the sealing process when manufacturing a power storage device, and plays a role of suppressing the occurrence of breakage or pinholes that may occur during molding processing or distribution. In particular, in the case of an exterior material of a power storage device for large-scale applications, scratch resistance, chemical resistance, insulation and the like can be imparted.

The base material layer 11 is preferably a layer made of a resin film formed of an insulating resin. Examples of the resin film include polyester film, polyamide film, polypropylene film and the like. The base material layer 11 may be a single-layer film composed of any one of these resin films, or may be a laminated film composed of two or more of these resin films.

Among these films, the resin film used for the base material layer 11 is preferably a polyester film or a polyamide film because it is excellent in moldability. Examples of the polyester resin constituting the polyester film include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and copolymerized polyester. Examples of the polyamide resin constituting the polyamide film include nylon 6, nylon 6, 6, a copolymer of nylon 6 and nylon 6, 6, nylon 6, 10, polymethoxylylene adipamide (MXD6), and nylon 11. , Nylon 12 and the like.

As the resin film, any one obtained by either a uniaxial stretching method or a biaxial stretching method can be used, but a biaxially stretched film is preferable from the viewpoint of obtaining better deep drawing moldability. ..

Examples of the stretching method in the biaxially stretched film include a sequential biaxial stretching method, a tubular biaxial stretching method, and a simultaneous biaxial stretching method. The biaxially stretched film is preferably stretched by a tubular biaxial stretching method and a simultaneous biaxial stretching method from the viewpoint of obtaining more excellent deep drawing moldability.

The thickness of the base material layer 11 is preferably 6 to 40 μm, more preferably 10 to 30 μm. When the thickness of the base material layer 11 is 6 μm or more, the pinhole resistance and the insulating property of the exterior material 10 for the power storage device tend to be improved. When the thickness of the base material layer 11 is 40 μm or less, the total thickness of the exterior material 10 for the power storage device becomes large, and it becomes easy to avoid the situation where the electric capacity of the battery must be reduced.

(Easy Adhesive Treatment Layer 12)
The easy-adhesion-treated layer 12 is provided on one surface side of the base material layer 11 and is arranged between the base material layer 11 and the adhesive layer 13. The easy-adhesion-treated layer 12 is a layer for improving the adhesion between the base material layer 11 and the adhesive layer 13, and thus improving the adhesion between the base material layer 11 and the metal leaf layer 14. The easy-adhesion processing layer 12 may not be provided in the exterior material 10 for the power storage device. In that case, in order to improve the adhesion between the base material layer 11 and the adhesive layer 13, and eventually to improve the adhesion between the base material layer 11 and the metal leaf layer 14, the adhesive layer of the base material layer 11 is improved. The surface on the 13 side may be corona-treated.

The easy-adhesion-treated layer 12 is preferably a layer containing at least one resin selected from the group consisting of polyester resin, acrylic resin, polyurethane resin, epoxy resin and acrylic graft polyester resin. The easy-adhesion-treated layer 12 has, for example, at least one resin selected from the group consisting of polyester resin, acrylic resin, polyurethane resin, epoxy resin and acrylic graft polyester resin on one surface of the base material layer 11. It can be formed by applying a coating agent as a main component.

<Polyester resin>
As the polyester resin, a copolymerized polyester in which a copolymerization component is introduced to lower the glass transition temperature is preferable from the viewpoint of adhesiveness. The copolymerized polyester is preferably water-soluble or water-dispersible from the viewpoint of coatability. As such a copolymerized polyester, a copolymerized polyester in which at least one group selected from the group consisting of a sulfonic acid group or an alkali metal base thereof is bonded (hereinafter, referred to as “sulfonic acid group-containing copolymerized polyester”) is used. It is preferable to use it.

Here, the sulfonic acid group-containing copolymerized polyester means a polyester in which at least one group selected from the group consisting of a sulfonic acid group or an alkali metal base thereof is bonded to a part of a dicarboxylic acid component or a glycol component. , A copolymerization prepared by using an aromatic dicarboxylic acid component containing at least one group selected from the group consisting of a sulfonic acid group or an alkali metal base thereof at a ratio of 2 to 10 mol% with respect to the total acid component. Polyester is preferred.

As an example of such a dicarboxylic acid, 5-sodium sulfoisophthalic acid is suitable. In this case, as other dicarboxylic acid components, terephthalic acid, isophthalic acid, phthalic acid, p-β-oxyethoxybenzoic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dicarboxydiphenyl, 4,4' -Dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, cyclohexane-1,4-dicarboxylic acid and the like can be mentioned.

Ethylene glycol is mainly used as a glycol component for producing a sulfonic acid group-containing copolymerized polyester, and in addition to this, ethylene oxide addition of propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, and bisphenol A is used. A product, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, or the like can be used. Above all, it is preferable to use ethylene glycol, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol or the like as a copolymerization component in that compatibility with polystyrene sulfonate is improved.

Further, as the polyester resin, a modified polyester copolymer, for example, a block copolymer modified with polyester, urethane, epoxy or the like, a graft copolymer or the like may be used. In the present embodiment, in order to improve the adhesion between the easy-adhesion-treated layer 12, the base material layer 11 and the adhesive layer 13, the easy-adhesion-treated layer 12 may further contain a resin other than the polyester resin. Examples of such a resin include urethane resin and acrylic resin.

<Acrylic resin>
Examples of the monomer components constituting the acrylic resin include alkyl acrylates and alkyl methacrylates (alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2). -Ethylhexyl group, lauryl group, stearyl group, etc.); Hydroxy group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate; acrylamide, methacrylicamide, Amids such as N-methylacrylamide, N-methylmethacrylate, N-methylolacrylamide, N-methylolmethacrylate, N, N-dimethylolacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylate, N-phenylacrylamide, etc. Group-containing monomer; Amino group-containing monomer such as N, N-diethylaminoethyl acrylate, N, N-diethylaminoethyl methacrylate; Epoxy group-containing monomer such as glycidyl acrylate and glycidyl methacrylate; Acrylic acid, methacrylic acid and salts thereof (lithium salt). , Sodium salt, potassium salt, etc.) or other carboxyl groups, or monomers containing the salts and the like can be used. One of these may be used alone, or two or more thereof may be used for copolymerization. Furthermore, these can be used in combination with other monomers other than the above.

Other monomers include, for example, epoxy group-containing monomers such as allylglycidyl ether; sulfonic acid groups such as styrene sulfonic acid, vinyl sulfonic acid and salts thereof (lithium salt, sodium salt, potassium salt, ammonium salt, etc.) or sulfonic acid groups thereof. Salt-containing monomers; sulphonic acid, itaconic acid, maleic acid, fumaric acid, and monomers containing carboxyl groups such as their salts (lithium salt, sodium salt, potassium salt, ammonium salt, etc.) or salts thereof; maleine anhydride Monomers containing acid anhydrides such as acids and itaconic anhydride; vinyl isocyanate, allylisocyanate, styrene, vinylmethyl ether, vinyl ethyl ether, vinyltris alkoxysilane, alkylmaleic acid monoester, alkyl fumolic acid monoester, acrylonitrile, Methacylonitrile, alkylitaconic acid monoester, vinylidene chloride, vinyl acetate, vinyl chloride and the like can be used. Further, as the acrylic resin, a modified acrylic copolymer, for example, a block copolymer modified with polyester, urethane, epoxy or the like, a graft copolymer or the like may be used.

The glass transition point (Tg) of the acrylic resin used in the present embodiment is not particularly limited, but is preferably 0 to 90 ° C, more preferably 10 to 80 ° C. If the Tg is low, the adhesion under high temperature and high humidity may decrease, and if the Tg is high, cracks may occur during stretching. Therefore, from the viewpoint of suppressing these, the Tg of the acrylic resin should be within the above range. Is preferable.

The weight average molecular weight of the acrylic resin used in the present embodiment is preferably 100,000 or more, more preferably 300,000 or more. If the weight average molecular weight is low, the moist heat resistance may decrease. In the present embodiment, in order to improve the adhesion between the easy-adhesion-treated layer 12, the base material layer 11 and the adhesive layer 13, the easy-adhesion-treated layer 12 may further contain a resin other than the acrylic resin. Examples of such a resin include polyester resin and urethane resin.

<Polyurethane resin>
As the polyurethane resin, a water-based polyurethane resin is preferable. As the water-based polyurethane resin, a self-emulsifying type is preferable because of its small particle size and good stability. The particle size of the aqueous polyurethane resin is preferably about 10 to 100 nm. The water-based polyurethane resin used in this embodiment preferably has a glass transition point (Tg) of 40 ° C to 150 ° C. When Tg is 40 ° C. or higher, it tends to be possible to sufficiently suppress the occurrence of blocking when winding into a roll after coating. On the other hand, if Tg is too high than the drying temperature after coating, it is difficult to form a uniform film, so Tg is preferably 150 ° C. or lower.

Further, in the present embodiment, a cross-linking agent may be used together with the water-based polyurethane resin. As the cross-linking agent for the water-based polyurethane, a general-purpose water-soluble cross-linking agent such as a water-soluble epoxy compound can be used. A water-soluble epoxy compound is a compound that is soluble in water and has two or more epoxy groups. Examples of the water-soluble epoxy compound include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,4-butanediol, 1,6-hexanediol, and neo. A polyepoxy compound obtained by etherification of 1 mol of glycols such as pentylene glycol and 2 mol of epichlorohydrin, and an ester of 1 mol of dicarboxylic acids such as phthalic acid, terephthalic acid, adipic acid and oxalic acid and 2 mol of epichlorohydrin. Examples thereof include diepylene compounds obtained by chemical conversion. However, the water-soluble epoxy compound is not limited to these.

These water-soluble cross-linking agents crosslink with the water-based polyurethane resin to improve the water resistance and solvent resistance of the coating film, and also to improve the adhesion between the easy-adhesion treatment layer 12, the base material layer 11 and the adhesive layer 13. Contribute. In the present embodiment, a resin other than the urethane resin may be further contained in order to improve the adhesion between the easy-adhesion-treated layer 12, the base material layer 11 and the adhesive layer 13. Examples of such a resin include polyester resin and acrylic resin.

Further, the easy-adhesion-treated layer 12 may be configured to contain, for example, the above-mentioned resin as a main component and a curing agent such as a polyfunctional isocyanate, a polyfunctional glycidyl compound, and a melamine-based compound. As described above, by including the above resin as the main component and a curing agent such as a polyfunctional isocyanate, a polyfunctional glycidyl compound, and a melamine-based compound, it is possible to incorporate a crosslinked structure, so that strong and easy adhesion can be achieved. The processing layer 12 can be configured.

The thickness of the easy-adhesion-treated layer 12 is preferably 0.02 to 0.5 μm, more preferably 0.04 to 0.3 μm. When the thickness of the easy-adhesion-treated layer 12 is 0.02 μm or more, a uniform easy-adhesion-treated layer 12 is likely to be formed, and a more sufficient easy-adhesion effect tends to be obtained. On the other hand, when the thickness of the easy-adhesion-treated layer 12 is 0.5 μm or less, the deep drawing moldability of the exterior material 10 tends to be further improved.

(Adhesive layer 13)
The adhesive layer 13 is a layer that adheres the base material layer 11 and the metal foil layer 14. The adhesive layer 13 adheres to the base material layer 11 via the easy-adhesion-treated layer 12. The adhesive layer 13 has an adhesive force necessary for firmly adhering the base material layer 11 and the metal foil layer 14, and the metal foil layer 14 is broken by the base material layer 11 during cold molding. It also has followability for suppressing this (performance for reliably forming the adhesive layer 13 on the member without peeling even if the member is deformed or expanded / contracted).

The features of the adhesive layer 13 in this embodiment will be described with reference to the drawings. FIG. 2 is an example of the stress-strain curve of the adhesive layer obtained by the tensile test. The horizontal axis in FIG. 2 indicates the elongation rate (strain) (%), and is obtained as the ratio of the length of the adhesive layer stretched by the tensile test to the length of the adhesive layer before the tensile test. The vertical axis in FIG. 2 ^{indicates the stress (N / cm 2} ) per unit cross-sectional area of the adhesive layer in the tensile test, and is obtained from the load applied to the adhesive layer in the tensile test. In FIG. 2, the stress at the yield point Y is the yield stress σ _y , and the elongation rate at the fracture point F is the fracture elongation rate ε _f .

The adhesive layer 13 has a yield stress σ _y of ^{3500 to 6500 N / cm 2} in the stress strain curve measured in a tensile test with a tensile speed of 6 mm / min. The yield stress sigma _y of the adhesive layer 13, is preferably 4000 N / cm ² or more, more preferably 4400N / cm ² or more, and still more preferably 5000N / cm ² or more. Further, the yield stress σ _y of the adhesive layer 13 is preferably 6000 N / cm ² or less. When the yield stress σ _y is 3500 N / cm ² or more, the adhesive layer can withstand the shear stress applied during deep drawing and further suppress the peeling at the interface with the base material layer 11 or the metal foil layer 14. It is possible to improve the deep drawing moldability. Further, when the yield stress σ _y is within the above range, the deformation behavior of the adhesive layer 13 due to the stress during molding becomes close to that of the metal foil layer 14, and the adhesive layer 13 and the metal foil layer are formed during deep drawing molding. The generation of shear stress at the interface with 14 can be reduced, and excellent deep draw moldability can be easily obtained.

_{Further, the adhesive layer 13 has a breaking elongation rate ε f} of 45 to 200% in the stress-strain curve measured in a tensile test with a tensile speed of 6 mm / min. The elongation at break ε _f of the adhesive layer 13 is preferably 70% or more, and more preferably 100% or more. Further, the elongation at break ε _f of the adhesive layer 13 may be 150% or less, or 120% or less. When the elongation at break ε _f is within the above range, it is difficult to break even in deep drawing molding, and the moldability is more likely to be improved.

The adhesive constituting the adhesive layer 13 is a two-component adhesive having, for example, a main agent composed of a polyol such as a polyester polyol, a polyether polyol, and an acrylic polyol, and a curing agent composed of an aromatic-based or aliphatic-based isocyanate. A curable polyurethane adhesive can be used. In the above adhesive, the molar ratio (= NCO / OH) of the isocyanate group of the curing agent to the hydroxyl group of the main agent is preferably 1 to 10, and more preferably 2 to 5. The yield stress σ _y and the elongation at break ε _f of the adhesive layer 13 can be controlled by, for example, the compounding ratio of the main agent and the curing agent, the types of polyol and isocyanate, and the like.

After coating, the polyurethane adhesive is aged at 40 ° C. for 4 days or more, so that the reaction between the hydroxyl group of the main agent and the isocyanate group of the curing agent proceeds, and the base material layer 11 and the metal foil layer 14 Allows for stronger adhesion with.

The thickness of the adhesive layer 13 is preferably 1 to 10 μm, more preferably 2 to 6 μm, from the viewpoint of obtaining desired adhesive strength, followability, processability, and the like.

(Metal leaf layer 14)
Examples of the metal foil layer 14 include various metal foils such as aluminum and stainless steel, and the metal foil layer 14 is preferably an aluminum foil from the viewpoint of processability such as moisture resistance and ductility and cost. The aluminum foil may be a general soft aluminum foil, but is preferably an aluminum foil containing iron from the viewpoint of excellent pinhole resistance and ductility during molding.

In the iron-containing aluminum foil (100% by mass), the iron content is preferably 0.1 to 9.0% by mass, more preferably 0.5 to 2.0% by mass. When the iron content is 0.1% by mass or more, the exterior material 10 having more excellent pinhole resistance and ductility 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 annealed (for example, an aluminum foil made of 8021 material or 8079 material according to JIS standards) is more preferable from the viewpoint of imparting a desired ductility during molding.

The metal foil used for the metal foil layer 14 is preferably subjected to, for example, a degreasing treatment in order to obtain a desired electrolytic solution resistance. Further, in order to simplify the manufacturing process, the metal foil is preferably one whose surface is not etched. As the degreasing treatment, for example, a wet type degreasing treatment or a dry type degreasing treatment can be used, but a dry type degreasing treatment is preferable from the viewpoint of simplifying the manufacturing process.

Examples of the dry type degreasing treatment include a method of performing the degreasing treatment by lengthening the treatment time in the step of annealing the metal foil. Sufficient electrolytic solution resistance can be obtained even with the degreasing treatment performed at the same time as the annealing treatment performed to soften the metal foil.

Further, as the dry type degreasing treatment, treatments such as frame treatment and corona treatment, which are treatments other than the annealing treatment, may be used. Further, as the dry type degreasing treatment, for example, a degreasing treatment for oxidatively decomposing and removing contaminants by active oxygen generated when a metal foil is irradiated with ultraviolet rays having a specific wavelength may be used.

As the wet type degreasing treatment, for example, treatments such as acid degreasing treatment and alkaline degreasing treatment can be used. As the acid used for the acid degreasing treatment, for example, an inorganic acid such as sulfuric acid, nitric acid, hydrochloric acid, or hydrofluoric acid can be used. These acids may be used alone or in combination of two or more. Further, as the alkali used for the alkali degreasing treatment, for example, sodium hydroxide having a high etching effect can be used. Further, the alkaline degreasing treatment may be performed using a weak alkaline material and a material containing a surfactant or the like. The wet type degreasing treatment described above can be performed by, for example, a dipping method or a spraying method.

The thickness of the metal foil layer 14 is preferably 9 to 200 μm, more preferably 15 to 150 μm, and further preferably 15 to 100 μm from the viewpoint of barrier property, pinhole resistance and processability. preferable. When the thickness of the metal foil layer 14 is 9 μm or more, it is difficult to break even if stress is applied by the molding process. When the thickness of the metal foil layer 14 is 200 μm or less, the increase in the mass of the exterior material can be reduced, and the decrease in the weight energy density of the power storage device can be suppressed.

(Corrosion prevention treatment layers 15a, 15b)
The corrosion prevention treatment layers 15a and 15b play a role of suppressing corrosion of the metal foil layer 14 due to the electrolytic solution or hydrofluoric acid generated by the reaction between the electrolytic solution and water. Further, the corrosion prevention treatment layer 15a plays a role of enhancing the adhesion between the metal foil layer 14 and the adhesive layer 13. Further, the corrosion prevention treatment layer 15b plays a role of enhancing the adhesion between the metal foil layer 14 and the sealant adhesive layer 16. The corrosion prevention treatment layer 15a and the corrosion prevention treatment layer 15b may be layers having the same structure or different structures. Although FIG. 1 shows a case where the corrosion prevention treatment layer is formed on both surfaces of the metal foil layer 14, the corrosion prevention treatment layer may be formed on at least one surface of the metal foil layer 14.

The corrosion prevention treatment layers 15a and 15b are coating agents having, for example, degreasing treatment, hydrothermal transformation treatment, anodizing treatment, chemical conversion treatment, and corrosion prevention ability on the layers serving as the base material of the corrosion prevention treatment layers 15a and 15b. It can be formed by performing a coating type corrosion prevention treatment or a corrosion prevention treatment combining these treatments.

Of the above-mentioned treatments, the degreasing treatment, the hydrothermal transformation treatment, the anodizing treatment, particularly the hydrothermal modification treatment and the anodizing treatment dissolve the surface of the metal foil (aluminum foil) with a treatment agent and are excellent in corrosion resistance. This is a process for forming an aluminum compound (boehmite, alumite). Therefore, such a treatment may be included in the definition of chemical conversion treatment in order to obtain a structure forming a co-continuous structure from the metal foil layer 14 to the corrosion prevention treatment layers 15a and 15b.

Examples of the degreasing treatment include acid degreasing and alkaline degreasing. Examples of the acid degreasing include a method using acid degreasing obtained by using the above-mentioned inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid alone or in combination thereof. Further, as the acid degreasing, by using an acid degreasing agent in which a fluorine-containing compound such as monosodium difluoride is dissolved in the above-mentioned inorganic acid, not only the degreasing effect of the metal foil layer 14 but also the immobile metal fluoride is used. It is possible to form a fluorine, which is effective in terms of resistance to fluorine acidity. Examples of the alkaline degreasing include a method using sodium hydroxide and the like.

As the hot water transformation treatment, for example, a boehmite treatment obtained by immersing the metal leaf layer 14 in boiling water to which triethanolamine is added can be used. As the anodizing treatment, for example, an alumite treatment can be used. Further, as the chemical conversion treatment, for example, chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, or a treatment in which two or more of these are combined is used. be able to. In these hot water transformation treatments, anodizing treatments, and chemical conversion treatments, it is preferable to perform the above-mentioned degreasing treatment in advance.

The chemical conversion treatment is not limited to the wet method, and for example, a method in which a treatment agent used for these treatments is mixed with a resin component and applied may be used. Further, as the corrosion prevention treatment, a coating type chromate treatment is preferable from the viewpoint of maximizing the effect and waste liquid treatment.

The coating agent used for the coating type corrosion prevention treatment for applying a coating agent having anticorrosion performance contains at least one selected from the group consisting of rare earth element oxide sol, anionic polymer, and cationic polymer. Coating agents can be mentioned. In particular, a method using a coating agent containing a rare earth element oxide sol is preferable.

The method using a coating agent containing a rare earth element oxide sol is a pure coating type corrosion prevention treatment, and by using this method, the metal foil layer 14 is provided with a corrosion prevention effect even with a general coating method. It is possible. Further, the layer formed by using the rare earth element oxide sol has a corrosion preventing effect (inhibitor effect) of the metal foil layer 14, and is also a material suitable from an environmental aspect.

In the rare earth element oxide sol, fine particles of the rare earth element oxide (for example, particles having an average particle size of 100 nm or less) are dispersed in a liquid dispersion medium. Examples of rare earth element oxides include cerium oxide, yttrium oxide, neodium oxide, and lanthanum oxide. Of these, cerium oxide is preferable. Thereby, the adhesion between the metal foil layer 14 and the metal foil layer 14 can be further improved. As the liquid dispersion medium of the rare earth element oxide sol, for example, various solvents such as water, alcohol-based solvent, hydrocarbon-based solvent, ketone-based solvent, ester-based solvent, and ether-based solvent can be used. Of these, water is preferable. The rare earth element oxides contained in the corrosion prevention treatment layers 15a and 15b can be used alone or in combination of two or more.

Rare earth element oxide sol is an inorganic acid such as nitric acid, hydrochloric acid and phosphoric acid, and an organic acid such as acetic acid, malic acid, ascorbic acid and lactic acid as a dispersion stabilizer in order to stabilize the dispersion of rare earth element oxide particles. It is preferable to contain acids, salts thereof and the like. Of these dispersion stabilizers, it is particularly preferable to use phosphoric acid or phosphate. As a result, not only the dispersion stabilization of the rare earth element oxide particles, but also the improvement of the adhesion with the metal foil layer 14 by utilizing the chelating ability of phosphoric acid in the use of the exterior material for lithium ion batteries, and the improvement of the adhesion of hydrofluoric acid. It can be expected to have effects such as imparting electrolyte resistance by capturing (immobilizing) metal ions eluted due to the influence, and improving the cohesiveness of the rare earth element oxide layer by easily causing dehydration condensation of phosphoric acid even at low temperatures. .. Examples of phosphoric acid or phosphate used as the dispersion stabilizer include orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, alkali metal salts thereof, ammonium salts and the like. Among them, condensed phosphoric acids such as trimetaphosphoric acid, tetramethaphosphoric acid, hexametaphosphoric acid, and ultramethaphosphoric acid, or alkali metal salts and ammonium salts thereof are preferable for exhibiting the function as an exterior material for a lithium ion battery. In particular, considering the dry film-forming property (drying capacity, calorific value) when forming a layer containing a rare earth oxide by various coating methods using a coating composition containing a rare earth element oxide sol, reactivity at a low temperature is taken into consideration. A sodium salt is preferable because it is excellent in dehydration condensation property at low temperature. As the phosphate, a water-soluble salt is preferable. The phosphoric acid or phosphate contained in the corrosion prevention treatment layers 15a and 15b can be used alone or in combination of two or more.

The blending amount of phosphoric acid or a salt thereof in the rare earth element oxide sol is preferably 1 part by mass or more, more preferably 5 parts by mass or more, based on 100 parts by mass of the rare earth element oxide. When it is 1 part by mass or more, the sol is well stabilized and it is easy to satisfy the function as an exterior material for a lithium ion battery. The upper limit of the amount of phosphoric acid or a salt thereof with respect to 100 parts by mass of the rare earth element oxide may be a range that does not cause functional deterioration of the rare earth element oxide sol, and 100 parts by mass or less with respect to 100 parts by mass of the rare earth element oxide. Preferably, 50 parts by mass or less is more preferable, and 20 parts by mass or less is further preferable.

However, since the layer formed from the above-mentioned rare earth element oxide sol is an aggregate of inorganic particles, the cohesive force of the layer itself is low even after the drying cure step. Therefore, in order to supplement the cohesive force of this layer, it is preferable to combine it with an anionic polymer.

Examples of the anionic polymer include polymers 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 the copolymerization component of the 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, etc. t-Butyl group, 2-ethylhexyl group, cyclohexyl group, etc.); (meth) acrylamide, N-alkyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide (alkyl groups include methyl group, ethyl group, etc.) n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.), N-alkyl (meth) acrylamide, N, N-dialkoxy (Meta) acrylamide, (As alkoxy group, methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), N-methylol (meth) acrylamide, N-phenyl (meth) acrylamide and other amide group-containing monomers; 2- 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 acryloxypropyltrier xylan; and isociane group-containing monomers such as (meth) acryloxypropyl isocyane can be mentioned. Also, styrene, α-methylstyrene, vinylmethyl ether, vinylethyl ether, maleic acid, alkylmalic acid monoester, fumaric acid, alkylfumaric acid monoester, itaconic acid, alkylitaconic acid monoester, (meth) acrylonitrile, chloride. Examples thereof include vinylidene, ethylene, propylene, vinyl chloride, vinyl acetate and butadiene.

The anionic polymer plays a role of improving the stability of the corrosion prevention treatment layers 15a and 15b (oxide layers) obtained by using the rare earth element oxide sol. This is due to the effect of protecting the hard and brittle oxide layer with an acrylic resin component and the effect of capturing ion contamination (particularly sodium ions) derived from phosphate contained in the rare earth oxide sol (cation catcher). Achieved. That is, when the corrosion prevention treatment layers 15a and 15b obtained by using the rare earth element oxide sol contain alkali metal ions such as sodium or alkaline earth metal ions, the starting point is the place containing the ions. The corrosion prevention treatment layers 15a and 15b are likely to deteriorate. Therefore, by immobilizing sodium ions and the like contained in the rare earth oxide sol with the anionic polymer, the resistance of the corrosion prevention treatment layers 15a and 15b is improved.

The corrosion prevention treatment layers 15a and 15b in which the anionic polymer and the rare earth element oxide sol are combined have the same corrosion prevention performance as the corrosion prevention treatment layers 15a and 15b formed by subjecting the metal foil layer 14 to chromate treatment. The anionic polymer preferably has a structure in which an essentially water-soluble polyanionic polymer is crosslinked. Examples of the cross-linking agent used for forming the structure include compounds having an isociane group, a glycidyl group, a carboxy group, and an oxazoline group. Furthermore, it is also possible to introduce a crosslinked site having a siloxane bond by using a silane coupling agent.

Examples of the compound having an isocyanate group include diisocyanate such as tolylene diisocyanate, xylylene diisocyanate or a hydrogenated product thereof, hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate or a hydrogenated product thereof, and isophorone diisocyanate. Kind; or poly such as an adduct compound obtained by reacting these isocyanate compounds with a polyhydric alcohol such as trimethylolpropane, a burette compound obtained by reacting with water, or a trimeric isocyanate compound. Isocyanates; or blocked polyisocyanates obtained by blocking these polyisocyanates 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, and 1,6-hexanediol. Epoxy compounds in which glycols such as neopentyl glycol and epichlorohydrin are allowed to act, glycerin, polyglycerin, trimethylolpropane, pentaerythritol, sorbitol and other polyhydric alcohols and epoxy compounds in which epichlorohydrin is allowed to act, phthalic acid, terephthalic acid, Examples thereof include an epoxy compound obtained by reacting dicarboxylic acids such as oxalic acid and adipic acid with epichlorohydrin.

Examples of the compound having a carboxy group include various aliphatic or aromatic dicarboxylic acids, and it is also possible to use an alkali (earth) metal salt of poly (meth) acrylic acid and poly (meth) acrylic acid. be.

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

Examples of the silane coupling agent include γ-glycidoxypropyl lymethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and γ-chloropropylmethoxysilane. Vinyl trichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, and especially anion Considering the reactivity with the sex polymer, epoxysilane, aminosilane, and isocyanatesilane are preferable.

The blending amount of the cross-linking agent is preferably 1 to 50 parts by mass, 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 with respect to 100 parts by mass of the anionic polymer, the cross-linked structure is easily sufficiently formed. 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 for cross-linking the anionic polymer is not limited to the above-mentioned cross-linking agent, and may be a method for forming an ionic cross-link using a titanium or zirconium compound. Further, as these materials, a coating composition for forming the corrosion prevention treatment layer 15a may be applied.

In the corrosion prevention treatment layers 15a and 15b described above, the corrosion prevention treatment layers 15a and 15b by chemical conversion treatment represented by chromate treatment form an inclined structure with the metal foil layer 14, and therefore, in particular, hydrofluoric acid, hydrochloric acid, and nitric acid. The metal foil layer 14 is treated with a chemical conversion treatment agent containing sulfuric acid or salts thereof, and then a chromium-based or non-chromate-based compound is allowed to act to form the chemical conversion treatment layer on the metal foil layer 14. However, since the chemical conversion treatment uses an acid as the chemical conversion treatment agent, the working environment is deteriorated and the coating device is corroded.

On the other hand, the above-mentioned coating type corrosion prevention treatment layers 15a and 15b do not need to form an inclined structure with respect to the metal foil layer 14 unlike the chemical conversion treatment represented by the chromate treatment. Therefore, the properties of the coating agent are not restricted by acidity, alkalinity, neutrality, etc., and a good working environment can be realized. In addition, for the chromate treatment using a chromium compound, coating type corrosion prevention treatment layers 15a and 15b are preferable from the viewpoint that alternatives are required in terms of environmental hygiene.

If necessary, the corrosion prevention treatment layers 15a and 15b may have a laminated structure in which a cationic polymer is further laminated. Examples of the cationic polymer include polyethyleneimine, an ionic polymer complex composed of polyethyleneimine and a polymer having a carboxylic acid, a primary amine graft acrylic resin in which a primary amine is graphed on the acrylic main skeleton, polyallylamine or a derivative thereof. , Aminophenol resin and the like.

Examples of the "polymer having a carboxylic acid" that forms an ionic polymer complex include polycarboxylic acid (salt), a copolymer in which a comonomer is introduced into the polycarboxylic acid (salt), and a polysaccharide having a carboxy group. Be done. Examples of the polycarboxylic acid (salt) include polyacrylic acid or an ionic salt thereof. Examples of the polysaccharide having a carboxy group include carboxymethyl cellulose or an ionic salt thereof. Examples of the ionic salt include alkali metal salts and alkaline earth metal salts.

The primary amine graph acrylic resin is a resin in which a primary amine is graphed on an acrylic main skeleton. Examples of the acrylic main skeleton include various monomers used in the above-mentioned acrylic polyols such as poly (meth) acrylic acid. Examples of the primary amine to be graphed on the acrylic main skeleton include ethyleneimine.

As the polyallylamine or a derivative thereof, homopolymers or copolymers such as allylamine, allylamine amide sulfate, diallylamine, and dimethylallylamine can be used, and further, these amines may be free amines using acetic acid or hydrochloric acid. Stabilized products can also be used. Further, it is also possible to use maleic acid, sulfur dioxide or the like as the copolymer component. Furthermore, it is also possible to use a type in which thermal crosslinkability is imparted by partially methoxylating a primary amine. These cationic polymers may be used alone or in combination of two or more. Among the above, as the cationic polymer, at least one selected from the group consisting of polyallylamine and its derivatives is preferable.

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 carboxy group and a glycidyl group. As the cross-linking agent used in combination with the cationic polymer, a polymer having a carboxylic acid forming an ionic polymer complex with polyethyleneimine can also be used, and for example, a polycarboxylic acid (salt) such as polyacrylic acid or an ionic salt thereof, or a polycarboxylic acid (salt) thereof. Examples thereof include a copolymer in which a comonomer is introduced into a polymer, a polysaccharide having a carboxy group such as carboxymethyl cellulose or an ionic salt thereof, and the like.

In this embodiment, the cationic polymer is also described as one component constituting the corrosion prevention treatment layers 15a and 15b. The reason for this is that as a result of diligent studies using various compounds to impart the electrolyte resistance and hydrofluoric acid resistance required for exterior materials for lithium-ion batteries, the cationic polymer itself also has electrolyte resistance and hydrofluoric acid resistance. This is because it was found to be a compound capable of imparting acidity. It is presumed that this factor is because the metal leaf layer 14 is suppressed from being damaged by capturing fluorine ions with a cationic group (anion catcher). The cationic polymer is also very preferable in terms of improving the adhesiveness between the corrosion prevention treatment layer 15b and the sealant adhesive layer 16. Further, since the cationic polymer is water-soluble like the anionic polymer described above, water resistance can be improved by forming a crosslinked structure using the above-mentioned crosslinking agent. As described above, since the crosslinked structure can be formed even by using the cationic polymer, when the rare earth oxide sol is used for forming the corrosion prevention treatment layers 15a and 15b, the anionic polymer is used as the protective layer thereof. A cationic polymer may be used instead.

From the above, as examples of the combination of coating type corrosion prevention treatments described above, (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 ( Multilayering), (7) (rare earth oxide sol + cationic polymer: laminated composite) / anionic polymer (multilayering), and the like. Among them, (1) and (4) to (7) are preferable, and (4) to (7) are more preferable. Further, in the case of the corrosion prevention treatment layer 15a, (6) is particularly preferable because the corrosion prevention effect and the anchor effect (adhesion improving effect) can be realized in one layer. Further, in the case of the corrosion prevention treatment layer 15b, (6) and (7) are particularly preferable because it becomes easier to maintain the electrolyte resistance on the sealant layer 17 side. However, this embodiment is not limited to the above combination. For example, as an example of selection of the corrosion prevention treatment, the cationic polymer is a very preferable material in that it has good adhesion to the modified polyolefin resin described in the description of the sealant adhesive layer 16 described later, and therefore the sealant is adhered. When the layer 16 is made of a modified polyolefin resin, it is possible to design such that a cationic polymer is provided on the surface in contact with the sealant adhesive layer 16 (for example, the configurations (5) and (6)).

However, the corrosion prevention treatment layers 15a and 15b are not limited to the above-mentioned layers. For example, it may be formed by using an agent in which a phosphoric acid and a chromium compound are mixed in a resin binder (aminophenol resin or the like), such as coating type chromate which is a known technique. By using the treatment agent, it is possible to form a layer having both a corrosion prevention function and adhesion. Further, in order to improve the adhesion to the above-mentioned chemical conversion treatment layer (layer formed by degreasing treatment, hydrothermal transformation treatment, anionization treatment, chemical conversion treatment, or a combination of these treatments), the above-mentioned cationic property It is also possible to perform complex treatments with polymers and / or anionic polymers, or to laminate cationic and / or anionic polymers as a multilayer structure for a combination of these treatments. In addition, although it is necessary to consider the stability of the coating liquid, a corrosion prevention function is used by using a coating agent obtained by preliminarily liquefying the above-mentioned rare earth oxide sol and a cationic polymer or an anionic polymer. It can be a layer having both adhesion and adhesion.

Corrosion treatment layer 15a, the mass per unit area of 15b is preferably in a range of 0.005~0.200g / ^{m 2,} the range of 0.010~0.100g / ^{m 2} is more preferable. If it is 0.005 g / m ² or more, it is easy to impart a corrosion prevention function to the metal foil layer 14. Further, even if the mass per unit area ^{exceeds 0.200 g / m 2} , the corrosion prevention function is saturated and does not change much. On the other hand, when a rare earth oxide sol is used, if the coating film is thick, the cure due to heat during drying becomes insufficient, and the cohesive force may decrease. In the above content, the mass per unit area is described, but if the specific gravity is known, the thickness can be converted from it.

The thickness of the corrosion prevention treatment layers 15a and 15b is preferably, for example, 10 nm to 5 μm, and more preferably 20 to 500 nm from the viewpoint of the corrosion prevention function and the function as an anchor.

(Sealant adhesive layer 16)
The sealant adhesive layer 16 is a layer for adhering the metal foil layer 14 on which the corrosion prevention treatment layer 15b is formed and the sealant layer 17. The exterior material 10 is roughly divided into a heat-laminated structure and a dry-laminated structure depending on the adhesive component forming the sealant adhesive layer 16.

The adhesive component forming the sealant adhesive layer 16 in the heat-laminated structure is preferably an acid-modified polyolefin-based resin obtained by graft-modifying a polyolefin-based resin with an acid. Since the acid-modified polyolefin-based resin has a polar group introduced into a part of the non-polar polyolefin-based resin, it has polarity with the sealant layer 17 when it is composed of a non-polar polyolefin-based resin film or the like. It can be firmly adhered to both of the corrosion prevention treatment layer 15b, which is often the case. Further, by using the acid-modified polyolefin resin, the resistance of the exterior material 10 to the contents such as the electrolytic solution is improved, and even if hydrofluoric acid is generated inside the battery, the adhesive force is lowered due to the deterioration of the sealant adhesive layer 16. Is easy to prevent.

Examples of the polyolefin-based resin of the acid-modified polyolefin-based resin include low-density, medium-density and high-density polyethylene; ethylene-α-olefin copolymer; polypropylene; and propylene-α-olefin copolymer. When it is a copolymer, the polyolefin resin may be a block copolymer or a random copolymer. Further, as the polyolefin resin, a copolymer obtained by copolymerizing the above-mentioned one with a polar molecule such as acrylic acid or methacrylic acid, or a polymer such as crosslinked polyolefin can also be used. Examples of the acid for modifying the polyolefin resin include carboxylic acids, epoxy compounds and acid anhydrides, and maleic anhydride is preferable. The acid-modified polyolefin-based resin used for the sealant adhesive layer 16 may be one type or two or more types.

The sealant adhesive layer 16 having a heat-laminated structure can be formed by extruding the adhesive component with an extrusion device. The thickness of the sealant adhesive layer 16 having a heat-laminated structure is preferably 2 to 50 μm.

Examples of the adhesive component forming the sealant adhesive layer 16 having a dry-laminated structure include the same adhesives as those mentioned in the adhesive layer 13. In this case, in order to suppress swelling due to the electrolytic solution and hydrolysis due to hydrolyzate, it is possible to design the composition of the adhesive so that it is the main component of the skeleton that is difficult to hydrolyze and the crosslink density can be improved. preferable.

When improving the cross-linking density, for example, dimer fatty acid, ester or hydrogenated dimer fatty acid, reduced glycol of dimer fatty acid, ester of dimer fatty acid or reduced glycol of hydrogenated material may be added to the adhesive. The dimer fatty acid is an acid obtained by dimerizing various unsaturated fatty acids, and examples of its structure include an acyclic type, a monocyclic type, a polycyclic type, and an aromatic ring type.

The fatty acid that is the starting material of the dimer fatty acid is not particularly limited. In addition, diprotic acids such as those used in ordinary polyester polyols may be introduced with such dimer fatty acids as essential components. As a curing agent for the main agent constituting the sealant adhesive layer 16, for example, an isocyanate compound that can also be used as a chain extender for a polyester polyol can be used. As a result, the crosslink density of the adhesive coating film is increased, leading to improvement in solubility and swelling property, and an increase in urethane group concentration is expected to improve substrate adhesion.

Since the sealant adhesive layer 16 having a dry-laminated structure has highly hydrolyzable bonding portions such as an ester group and a urethane group, the sealant adhesive layer 16 has a heat-laminated structure for applications requiring higher reliability. It is preferable to use the adhesive component of. For example, an acid-modified polyolefin resin is dissolved or dispersed in a solvent such as toluene or methylcyclohexane (MCH), and various curing agents described above are mixed with the coating liquid, and the sealant adhesive layer 16 is formed by coating and drying. do.

When the sealant adhesive layer 16 is formed by extrusion molding, the adhesive resin tends to be oriented in the MD direction (extrusion direction) due to stress generated during extrusion molding or the like. In this case, an elastomer may be added to the sealant adhesive layer 16 in order to alleviate the anisotropy of the sealant adhesive layer 16. As the elastomer to be blended in the sealant adhesive layer 16, for example, an olefin-based elastomer, a styrene-based elastomer, or the like can be used.

The average particle size of the elastomer is preferably a particle size capable of improving the compatibility between the elastomer and the adhesive resin and improving the effect of alleviating the anisotropy of the sealant adhesive layer 16. Specifically, the average particle size of the elastomer is preferably 200 nm or less, for example.

The average particle size of the elastomer can be determined by, for example, taking an enlarged photograph of the cross section of the elastomer composition with an electron microscope and then measuring the average particle size of the dispersed crosslinked rubber components by image analysis. .. The above elastomer may be used alone or in combination of two or more.

When the elastomer is blended in the sealant adhesive layer 16, the blending amount of the elastomer added in the sealant adhesive layer 16 (100% by mass) is, for example, preferably 1 to 25% by mass, more preferably 10 to 20% by mass. By setting the blending amount of the elastomer to 1% by mass or more, the compatibility with the adhesive resin tends to be improved, and the effect of alleviating the anisotropy of the sealant adhesive layer 16 tends to be improved. Further, by setting the blending amount of the elastomer to 25% by mass or less, the effect of suppressing the swelling of the sealant adhesive layer 16 by the electrolytic solution tends to be improved.

As the sealant adhesive layer 16, for example, a dispersion type adhesive resin liquid in which an adhesive resin is dispersed in an organic solvent may be used.

The thickness of the sealant adhesive layer 16 is preferably 2 to 50 μm, more preferably 20 to 40 μm in the case of a heat-laminated structure. When the thickness of the sealant adhesive layer 16 is 2 μm or more, sufficient adhesive strength between the metal foil layer 14 and the sealant layer 17 can be easily obtained, and when it is 50 μm or less, the end face of the exterior material can be used as an internal battery element. It is possible to easily reduce the amount of water that infiltrates. The thickness of the sealant adhesive layer 16 is preferably 1 to 5 μm in the case of a dry laminate structure. When the thickness of the sealant adhesive layer 16 is 1 μm or more, sufficient adhesive strength between the metal foil layer 14 and the sealant layer 17 can be easily obtained, and when it is 5 μm or less, cracks in the sealant adhesive layer 16 occur. It can be suppressed.

(Sealant layer 17)
The sealant layer 17 is a layer that imparts sealing properties to the exterior material 10 by heat sealing, and is a layer that is arranged inside when the power storage device is assembled and is heat-sealed. Examples of the sealant layer 17 include a polyolefin-based resin or a resin film made of an acid-modified polyolefin-based resin obtained by graft-modifying an acid such as maleic anhydride to the polyolefin-based resin. Of these, polyolefin-based resins that improve the barrier property of water vapor and can form the form of the power storage device without being excessively crushed by heat sealing are preferable, and polypropylene is particularly preferable.

Examples of the polyolefin-based resin include low-density, medium-density and high-density polyethylene; ethylene-α-olefin copolymer; polypropylene; and propylene-α-olefin copolymer. When it is a copolymer, the polyolefin resin may be a block copolymer or a random copolymer. One type of these polyolefin resins may be used alone, or two or more types may be used in combination.

In addition, each of the above types of polypropylene, that is, random polypropylene, homopolypropylene, and block polypropylene, includes a low-crystalline ethylene-butene copolymer, a low-crystalline propylene-butene copolymer, and ethylene, butene, and propylene. An anti-blocking agent (AB agent) such as a tarpolymer composed of a component copolymer, silica, zeolite, or acrylic resin beads, a fatty acid amide-based slip agent, or the like may be added.

Examples of the acid-modified polyolefin-based resin include those similar to those mentioned in the sealant adhesive layer 16.

The sealant layer 17 may be a single-layer film or a multilayer film, and may be selected according to a required function. For example, in terms of imparting moisture resistance, a multilayer film in which a resin such as an ethylene-cyclic olefin copolymer and polymethylpentene is interposed can be used.

Further, the sealant layer 17 may contain various additives such as a flame retardant, a slip agent, an anti-blocking agent, an antioxidant, a light stabilizer and a tackifier.

When a heat-weldable film formed by extrusion molding is used as the sealant layer 17, there is a tendency for the heat-weldable film to be oriented in the extrusion direction. Therefore, from the viewpoint of alleviating the anisotropy of the sealant layer 17 due to orientation, an elastomer may be added to the heat-weldable film. As a result, it is possible to prevent the sealant layer 17 from whitening when the exterior material 10 for a power storage device is cold-molded to form a recess.

As the elastomer constituting the sealant layer 17, for example, the same material as the material exemplified as the elastomer constituting the sealant adhesive layer 16 can be used. When the sealant layer 17 has a multilayer film structure, at least one of the plurality of layers constituting the multilayer film structure may be configured to contain an elastomer. For example, in the case of a three-layer laminated structure consisting of a laminated random polypropylene layer / block polypropylene layer / random polypropylene layer as the sealant layer 17, the elastomer may be blended only in the block polypropylene layer or only in the random polypropylene layer. It may be blended, or it may be blended in both the random polypropylene layer and the block polypropylene layer.

Further, a lubricant may be contained in order to impart slipperiness to the sealant layer 17. As described above, when the sealant layer 17 contains the lubricant to form a recess in the exterior material 10 for the power storage device by cold molding, the side or corner of the recess having a high draw ratio in the exterior material 10 for the power storage device It is possible to prevent the portion to be stretched more than necessary. As a result, it is possible to prevent the metal foil layer 14 and the sealant adhesive layer 16 from peeling off, and the sealant layer 17 and the sealant adhesive layer 16 from being broken or whitened due to cracks.

When the sealant layer 17 contains a lubricant, the content of the lubricant in the sealant layer 17 (100% by mass) is preferably 0.001 to 0.5% by mass. When the content of the lubricant is 0.001% by mass or more, whitening of the sealant layer 17 tends to be more suppressed during cold molding. Further, when the content of the lubricant is 0.5% by mass or less, there is a tendency that a decrease in the adhesion strength between the surface of the sealant layer 17 and the surface of another layer in contact with the sealant layer 17 can be suppressed.

The thickness of the sealant layer 17 is preferably 10 to 100 μm, more preferably 20 to 60 μm. When the thickness of the sealant layer 17 is 10 μm or more, sufficient heat seal strength can be obtained, and when it is 100 μm or less, the amount of water vapor infiltrated from the end portion of the exterior material can be reduced.

[Manufacturing method of exterior materials]
Next, a method of manufacturing the exterior material 10 will be described. The method for manufacturing the exterior material 10 is not limited to the following methods.

Examples of the method for manufacturing the exterior material 10 include a method having the following steps S11 to S14.
Step S11: A step of forming a corrosion prevention treatment layer 15a on one surface of the metal foil layer 14 and forming a corrosion prevention treatment layer 15b on the other surface of the metal foil layer 14.
Step S12: A step of forming the easy-adhesion-treated layer 12 on one surface of the base material layer 11 to obtain a laminate.
Step S13: A step of bonding the surface of the corrosion prevention treatment layer 15a on the side opposite to the metal foil layer 14 and the surface of the laminated body on the side of the easy-adhesion treatment layer 12 via the adhesion layer 13.
Step S14: A step of forming the sealant layer 17 on the surface of the corrosion prevention treatment layer 15b opposite to the metal foil layer 14 via the sealant adhesive layer 16.

(Step S11)
In step S11, the corrosion prevention treatment layer 15a is formed on one surface of the metal foil layer 14, and the corrosion prevention treatment layer 15b is formed on the other surface of the metal foil layer 14. The corrosion prevention treatment layers 15a and 15b may be formed separately, or both may be formed at the same time. Specifically, for example, a corrosion prevention treatment agent (base material of the corrosion prevention treatment layer) is applied to both surfaces of the metal foil layer 14, and then drying, curing, and baking are sequentially performed to prevent the corrosion treatment layer. Form 15a and 15b at once. Further, a corrosion prevention treatment agent is applied to one surface of the metal foil layer 14, and drying, curing, and baking are sequentially performed to form the corrosion prevention treatment layer 15a, and then the other surface of the metal foil layer 14 is similarly applied. The corrosion prevention treatment layer 15b may be formed. The order of forming the corrosion prevention treatment layers 15a and 15b is not particularly limited. Further, as the corrosion prevention treatment agent, different ones may be used for the corrosion prevention treatment layer 15a and the corrosion prevention treatment layer 15b, or the same one may be used. As the corrosion prevention treatment agent, for example, a corrosion prevention treatment agent for coating type chromate treatment can be used. The method of applying the corrosion prevention treatment agent is not particularly limited, and for example, a gravure coating method, a gravure reverse coating method, a roll coating method, a reverse roll coating method, a die coating method, a bar coating method, a kiss coating method, a comma coating method, or the like. Can be used. As the metal foil layer 14, an untreated metal foil layer may be used, or a metal foil layer that has been degreased by a wet type degreasing treatment or a dry type degreasing treatment may be used.

(Step S12)
In step S12, the easy-adhesion-treated layer 12 is formed on one surface of the base material layer 11. Here, an in-line coating method will be described as an example of a method for forming the easy-adhesion-treated layer 12. First, an aqueous coating liquid containing a dispersion in which the above resin, which is the main component of the easy-adhesion treatment layer 12, is dispersed with a dispersant is prepared. Next, the aqueous coating liquid is applied to one surface of the thermoplastic resin film (base material of the base material layer 11) before the crystal orientation is completed. Next, the applied aqueous coating liquid is dried, and then the thermoplastic resin film is stretched in at least the uniaxial direction.

Next, by completing the orientation of the thermoplastic resin film by heat treatment, a laminated body in which the easy-adhesion-treated layer 12 is formed on one surface of the base material layer 11 can be obtained. By forming the easy-adhesion-treated layer 12 by using such an in-line coating method, the adhesion between the base material layer 11 and the easy-adhesion-treated layer 12 is improved. The method for forming the easy-adhesion-treated layer 12 is not limited to the above method, and any method may be used. Further, the timing of forming the easy-adhesion-treated layer 12 is not limited to the present embodiment.

(Step S13)
In step S13, the surface of the corrosion prevention treatment layer 15a opposite to the metal foil layer 14 and the surface of the laminated body on the easy adhesion treatment layer 12 side are dry-laminated using an adhesive forming the adhesive layer 13. It can be pasted together by such methods. In step S13, an aging treatment is performed in the range of room temperature to 100 ° C. in order to promote adhesiveness. The aging time is, for example, 1 to 10 days. The temperature and time in the aging treatment are selected so that the adhesive constituting the adhesive layer 13 can be sufficiently cured. Therefore, the yield stress and the elongation at break of the adhesive layer 13 included in the exterior material 10 can be obtained by the above aging treatment.

(Step S14)
After the step S13, the corrosion prevention treatment layer 15b of the laminated body in which the base material layer 11, the easy adhesion treatment layer 12, the adhesion layer 13, the corrosion prevention treatment layer 15a, the metal foil layer 14 and the corrosion prevention treatment layer 15b are laminated in this order. The sealant layer 17 is formed on the surface opposite to the metal foil layer 14 via the sealant adhesive layer 16. The sealant layer 17 may be laminated by dry lamination, sandwich lamination or the like, or may be laminated together with the sealant adhesive layer 16 by a coextrusion method. From the viewpoint of improving the adhesiveness, the sealant layer 17 is preferably laminated by, for example, sandwich lamination, or is laminated together with the sealant adhesive layer 16 by a coextrusion method, and more preferably by sandwich lamination.

The exterior material 10 is obtained by the steps S11 to S14 described above. The process order of the method for manufacturing the exterior material 10 is not limited to the method in which the above steps S11 to S14 are sequentially performed. For example, the order of the steps to be carried out may be changed as appropriate, such as performing the step S12 and then the step S11.

[Power storage device]
Next, a power storage device including the exterior material 10 as a container will be described. The power storage device includes a battery element 1 including an electrode, a lead 2 extending from the electrode, and a container that sandwiches the lead 2 and houses the battery element 1. The sealant layer 17 is formed so as to be on the inside. The container may be obtained by stacking two exterior materials with the sealant layers 17 facing each other and heat-sealing the peripheral edges of the overlapped exterior materials 10, or by folding back one exterior material. It may be obtained by superimposing and heat-sealing the peripheral edge portion of the exterior material 10 in the same manner. Further, the power storage device may include the exterior material 20 as a container. Examples of the power storage device include secondary batteries such as lithium ion batteries, nickel hydrogen batteries, and lead storage batteries, and electrochemical capacitors such as electric double layer capacitors.

The lead 2 is sandwiched and sealed by an exterior material 10 that forms a container with the sealant layer 17 inside. The lead 2 may be sandwiched by the exterior material 10 via the tab sealant.

[Manufacturing method of power storage device]
Next, a method of manufacturing a power storage device using the above-mentioned exterior material 10 will be described. Here, a case where the secondary battery 40 is manufactured by using the embossed type exterior material 30 will be described as an example. FIG. 3 is a diagram showing the embossed type exterior material 30. FIGS. 4A to 4D are perspective views showing a manufacturing process of a one-sided molded battery using the exterior material 10. The secondary battery 40 is a double-sided molded battery manufactured by providing two exterior materials such as the embossed type exterior material 30 and laminating such exterior materials while adjusting the alignment. May be good. Further, the embossed type exterior material 30 may be formed by using the exterior material 20.

The secondary battery 40, which is a one-side molded processed battery, can be manufactured by, for example, the following steps S21 to S25.
Step S21: A step of preparing the exterior material 10, the battery element 1 including the electrodes, and the leads 2 extending from the electrodes.
Step S22: A step of forming a recess 32 for arranging the battery element 1 on one side of the exterior material 10 (see FIGS. 4A and 4B).
Step S23: The battery element 1 is arranged in the molding processing area (recess 32) of the embossed type exterior material 30, the embossed exterior material 30 is folded back and overlapped so that the lid 34 covers the recess 32, and extends from the battery element 1. A step of pressurizing and heat-sealing one side of the embossed type exterior material 30 so as to sandwich the lead 2 (see FIGS. 4 (b) and 4 (c)).
Step S24: One side other than the side holding the lead 2 is left, and the other side is pressure-heat fused. Then, the electrolytic solution is injected from the remaining side, and the one side remaining in the vacuum state is pressure-heat-sealed. Step to perform (see FIG. 4 (c)).
Step S25: A step of cutting the end of the pressure heat fusion side other than the side holding the lead 2 and bending it toward the molding processing area (recess 32) (see FIG. 4D).

(Step S21)
In step S21, the exterior material 10, the battery element 1 including the electrodes, and the leads 2 extending from the electrodes are prepared. The exterior material 10 is prepared based on the above-described embodiment. The battery element 1 and the lead 2 are not particularly limited, and known battery elements 1 and lead 2 can be used.

(Step S22)
In step S22, a recess 32 for arranging the battery element 1 is formed on the sealant layer 17 side of the exterior material 10. The planar shape of the recess 32 is a shape that matches the shape of the battery element 1, for example, a rectangular shape in a plan view. The recess 32 is formed by, for example, pressing a pressing member having a rectangular pressure surface against a part of the exterior material 10 in the thickness direction thereof. Further, the pressing position, that is, the recess 32 is formed at a position biased toward one end in the longitudinal direction of the exterior material 10 from the center of the exterior material 10 cut out in a rectangular shape. As a result, the other end side on which the recess 32 is not formed after the molding process can be folded back to form a lid (cover portion 34).

More specifically, as a method of forming the concave portion 32, a molding process using a mold (deep drawing molding) can be mentioned. As a molding method, a female mold and a male mold arranged so as to have a gap equal to or larger than the thickness of the exterior material 10 are used, and the male mold is pushed into the female mold together with the exterior material 10. Can be mentioned. By adjusting the pushing amount of the male die, the depth (deep drawing amount) of the recess 32 can be adjusted to a desired amount. By forming the recess 32 in the exterior material 10, the embossed type exterior material 30 can be obtained. The embossed type exterior material 30 has a shape as shown in FIG. 2, for example. Here, FIG. 3A is a perspective view of the embossed type exterior material 30, and FIG. 3B is a vertical cross section of the embossed type exterior material 30 shown in FIG. 3A along the line bb. It is a figure.

(Step S23)
In step S23, the battery element 1 composed of the positive electrode, the separator, the negative electrode, and the like is arranged in the molding processing area (recess 32) of the embossed type exterior material 30. Further, the leads 2 extending from the battery element 1 and joined to the positive electrode and the negative electrode, respectively, are pulled out from the molding processing area (recessed portion 32). After that, the embossed type exterior material 30 is folded back at substantially the center in the longitudinal direction, the sealant layers 17 are stacked so as to be inside, and one side of the embossed type exterior material 30 holding the lead 2 is pressure-heat fused. NS. Pressurized heat fusion is controlled under three conditions of temperature, pressure and time, and is appropriately set. The temperature of pressure heat fusion is preferably equal to or higher than the temperature at which the sealant layer 17 is melted.

The thickness of the sealant layer 17 before heat fusion is preferably 40 to 80% of the thickness of the lead 2. When the thickness of the sealant layer 17 is at least the above lower limit value, the heat-sealing resin tends to be able to sufficiently fill the lead 2 end portion, and when it is at least the above upper limit value, the exterior material 10 of the secondary battery 40 is used. The thickness of the end portion can be appropriately suppressed, and the amount of water infiltrated from the end portion of the exterior material 10 can be reduced.

(Step S24)
In step S24, pressure heat fusion is performed on the other side, leaving one side other than the side holding the lead 2. After that, the electrolytic solution is injected from the remaining side, and the remaining side is pressurized and heat-sealed in a vacuum state. The conditions for pressure heat fusion are the same as in step S23.

(Step S25)
The peripheral pressure heat-sealing side end portion other than the side sandwiching the lead 2 is cut, and the sealant layer 17 protruding from the end portion is removed. After that, the peripheral pressure heat-sealing portion is folded back toward the molding processing area 32 to form the folded-back portion 42, whereby the secondary battery 40 is obtained.

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

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

(Example 1)
In Example 1, the exterior material 10 for a power storage device was produced by the following method. First, as the metal foil layer 14, a soft aluminum foil 8079 material (manufactured by Toyo Aluminum Co., Ltd.) having a thickness of 40 μm was prepared. Next, on both sides of the metal foil layer 14, distilled water was used as a solvent and sodium polyphosphate stabilized cerium oxide sol (corrosion prevention treatment agent) adjusted to a solid content concentration of 10% by mass was applied by gravure coating. At this time, the amount of phosphoric acid was 10 parts by mass with respect to 100 parts by mass of cerium oxide.

Next, the applied sodium polyphosphate-stabilized cerium oxide sol is dried and then baked in sequence to form a corrosion prevention treatment layer 15a on one surface of the metal foil layer 14 and to prevent corrosion on the other surface. The treated layer 15b was formed. At this time, the baking conditions were a temperature of 150 ° C. and a treatment time of 30 seconds.

Next, as the base material layer 11, a polyester film having a thickness of 25 μm was used, and one side of the base material layer 11 was corona-treated.

Next, a polyurethane-based adhesive in which a main agent made of polyol and a curing agent made of isocyanate are mixed is applied as an adhesive layer 13 to the surface of the metal foil layer 14 on the opposite side of the corrosion prevention treatment layer 15a from the metal foil layer 14. bottom. Next, the metal foil layer 14 and the corona-treated surface of the base material layer 11 were adhered to each other via the adhesive layer 13 by a dry laminating method. After that, the structure composed of the base material layer 11, the adhesive layer 13, the corrosion prevention treatment layer 15a, the metal foil layer 14, and the corrosion prevention treatment layer 15b is left for 6 days in an atmosphere at a temperature of 60 ° C. for aging. Processed. The thickness of the adhesive layer 13 was 4 μm. Then, as shown below, an exterior material 10 for a power storage device having a heat-laminated structure was produced.

The sealant adhesive layer 16 was formed by extruding maleic anhydride-modified polypropylene (manufactured by Mitsui Chemicals, Inc., trade name: Admer), which is a base material of the sealant adhesive layer 16. At this time, the thickness of the sealant adhesive layer 16 was set to 15 μm. Then, by the sandwich lamination method, the surface on the sealant adhesive layer 16 side of the non-stretched polypropylene film having a thickness of 30 μm to be the sealant layer 17 was corona-treated on the corrosion prevention treatment layer 15b via the sealant adhesive layer 16. The film) was adhered (heat-bonded) at 160 ° C. As a result, the exterior material 10 for the power storage device was produced.

(Examples 2 to 4, Comparative Examples 1 to 5)
In the polyurethane-based adhesive forming the adhesive layer 13, the exterior material 10 for a power storage device was produced in the same manner as in Example 1 except that the mixing ratio of the main agent and the curing agent was changed.

(Example 5)
The exterior material 10 for a power storage device is the same as in the second embodiment, except that the easy-adhesion-treated layer 12 is formed on the surface of the base material layer 11 on the adhesive layer 13 side instead of corona-treating one side of the base material layer 11. Was produced. The easy-adhesion-treated layer 12 uses an in-line coating method to coat one side of the base material layer 11 with a coating agent as a base material of the easy-adhesion-treated layer 12 so that the solid content is 0.1 g / m ^2. Then, it was dried to form an easy-adhesion-treated layer 12 having a thickness of about 0.1 μm.

The coating agent prepared below was used as the coating agent for forming the easy-adhesion-treated layer.
Coating agent: Water-soluble polyester "Aronmelt PES-1000" manufactured by Toa Synthetic Co., Ltd., self-emulsifying polyisocyanate "Aquanate 100" manufactured by Nihon Polyurethane Industry Co., Ltd., and spherical silica manufactured by Nippon Catalytic Chemical Industry Co., Ltd. Fine particles "Seahoster KEP30" (average particle size 0.3 μm) were added at a blending ratio (mass ratio) of 95/5 / 0.5 and diluted with water.

(Example 6)
In the same manner as in Example 2, except that the corrosion prevention treatment layers 15a and 15b were formed by chromate treatment instead of forming the corrosion prevention treatment layers 15a and 15b using the sodium polyphosphate stabilized cerium oxide sol. An exterior material 10 for a power storage device was produced. The chromate treatment was carried out by applying a treatment liquid composed of a phenol resin, a chromium fluoride compound, and phosphoric acid on both surfaces of the metal foil layer 14, forming a film, and baking the metal foil layer 14.

<Measurement of yield stress and elongation at break>
By applying the polyurethane adhesive used for forming the adhesive layer 13 in each Example and Comparative Example on the AL plate so that the sample thickness is 4.0 μm, and leaving it at 60 ° C. for 6 days. Aging treatment was performed. The adhesive layer after aging was peeled off from the AL plate and cut into a width of 5 mm and a length of 20 mm to prepare a measurement sample. Grasp both ends of the measurement sample in the longitudinal direction with a jig, apply a tensile load to the measurement sample at a tensile speed of 6 mm / min using a tensile tester, and the relationship between the load value (stress value) and the amount of deformation (elongation). Was graphed (stress strain curve). Table 1 shows the results of reading the _{yield stress σ y} (N / cm ² ), which is the stress value at the yield point Y of the obtained stress strain curve, _{and the breaking elongation rate ε f} (%), which is the elongation rate at the breaking point F. show.

<Evaluation of molding depth>
With respect to the exterior material 10 for a power storage device produced in each Example and Comparative Example, the molding depth capable of deep drawing was evaluated by the following method. First, the exterior material 10 for the power storage device was arranged in the molding device so that the sealant layer 17 faces upward. The molding depth of the molding apparatus was set to 3.5 to 7.0 mm in every 0.05 mm, and cold molding was performed in an environment of room temperature of 23 ° C. and dew point temperature of −35 ° C. The punch die has a rectangular cross section of 70 mm × 80 mm, a punch radius (RP) of 1.00 mm on the bottom surface, and a punch corner radius (RCP) of 1.00 mm on the side surface. It was used. Further, as the die mold, a die having a 1.00 mm diradius (RD) on the upper surface of the opening was used. The presence or absence of breakage and pinholes in the cold-molded portion was visually confirmed while irradiating the exterior material 10 with light, and the maximum molding depth that could be deep-drawn without any breakage or pinholes. The value (molding limit) was calculated and evaluated according to the following criteria. Table 1 shows the molding limit and the evaluation result of moldability.
A: Molding limit is 5.50 mm or more B: Molding limit is 5.00 mm or more and less than 5.50 mm C: Molding limit is 4.40 mm or more and less than 5.00 mm D: Molding limit is less than 4.40 mm

From the results shown in Table 1, it can be understood that excellent deep drawing moldability was obtained in the examples. Further, it can be understood that further excellent deep drawing moldability was obtained by surface-treating the base material layer and the metal foil layer to improve the adhesion.

1 ... Battery element, 2 ... Lead, 10 ... Exterior material (exterior material for power storage device), 11 ... Base material layer, 12 ... Easy adhesive treatment layer, 13 ... Adhesive layer, 14 ... Metal foil layer, 15a, 15b ... Corrosion Prevention treatment layer, 16 ... Sealant adhesive layer, 17 ... Sealant layer, 30 ... Embossed type exterior material, 32 ... Molding area (recess), 34 ... Lid, 40 ... Secondary battery, Y ... Yield point, F ... Break point.

Claims (7)

An exterior material for a power storage device having a structure in which at least a base material layer, an adhesive layer, a metal foil layer, a sealant adhesive layer, and a sealant layer are laminated in this order.
The adhesive layer is formed of a two-component curable polyurethane adhesive having a main agent made of polyol and a curing agent made of isocyanate, and the stress measured in a tensile test with a tensile speed of 6 mm / min. An exterior material for a power storage device having a yield stress of 3500 to 6500 N / cm ^{2 and a breaking elongation of 45 to 200% in a strain curve.} The exterior material for a power storage device according to claim 1, further comprising an easy-adhesion-treated layer provided between the base material layer and the adhesive layer. The power storage device according to claim 2, wherein the easy-adhesion-treated layer is a layer containing at least one resin selected from the group consisting of a polyester resin, an acrylic resin, a polyurethane resin, an epoxy resin, and an acrylic graft polyester resin. Exterior material. The exterior material for a power storage device according to any one of claims 1 to 3, further comprising a corrosion prevention treatment layer provided on both sides of the metal foil layer. The exterior material for a power storage device according to claim 4, wherein the corrosion prevention treatment layer contains a rare earth element oxide and phosphoric acid or a phosphate. The exterior material for a power storage device according to claim 5, wherein the rare earth element oxide is cerium oxide. A battery element including an electrode, a lead extending from the electrode, and a container for accommodating the battery element are provided.
The container is formed from the exterior material for a power storage device according to any one of claims 1 to 6 so that the sealant layer is on the inside.

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