JP2024075583A - Exterior material for power storage device, manufacturing method thereof, and power storage device - Google Patents

Abstract

To provide an exterior material for a power storage device that is composed of a laminate having at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order, and that exhibits high insulation properties after heat-sealing of the heat-sealable resin layer.SOLUTION: An exterior material 10 for a power storage device includes a laminate having at least a base layer 1, a barrier layer 3, an adhesive layer 5, and a heat-sealable resin layer 4 in this order, and the adhesive layer has a logarithmic decrement ΔE of 0.22 or less at 120°C in rigid pendulum measurement.SELECTED DRAWING: Figure 1

Description

This disclosure relates to an exterior material for an electricity storage device, a manufacturing method thereof, and an electricity storage device.

Various types of electricity storage devices have been developed, but in all electricity storage devices, exterior materials are essential components for sealing the electricity storage device elements such as electrodes and electrolytes. Traditionally, metal exterior materials have been widely used as exterior materials for electricity storage devices.

On the other hand, in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, and the like, there is a demand for electricity storage devices to have a variety of shapes, as well as to be thinner and lighter. However, the metallic exterior materials for electricity storage devices that have been widely used in the past have the disadvantage that they are difficult to keep up with the diversification of shapes, and there is also a limit to how much they can be made lighter.

In recent years, a film-like laminate in which a base layer, a barrier layer, and a heat-sealable resin layer are laminated in this order has been proposed as an exterior material for electricity storage devices that can be easily processed into a variety of shapes and can be made thinner and lighter (see, for example, Patent Document 1).

In such electrical storage device exterior materials, recesses are generally formed by cold forming, electrical storage device elements such as electrodes and electrolyte are placed in the space formed by the recesses, and the heat-sealable resin layer is heat-sealed to obtain an electrical storage device in which the electrical storage device elements are housed inside the electrical storage device exterior material.

JP 2008-287971 A

When sealing an electricity storage device element, a high temperature and high pressure are applied to the exterior material for the electricity storage device using a metal plate or the like to heat-seal the heat-sealable resin layer. However, when high temperature and high pressure are applied to the exterior material for the electricity storage device to heat-seal the heat-sealable resin layer, there is a problem that the insulating properties of the exterior material for the electricity storage device are reduced.

In this situation, the main objective of the present invention is to provide an exterior material for an electricity storage device that is composed of a laminate having at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order, and that exhibits high insulation properties after heat-sealing of the heat-sealable resin layer.

The inventors of the present disclosure conducted intensive research to solve the above problems. As a result, they discovered that an exterior material for an electricity storage device that is composed of a laminate having at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order, and in which the logarithmic decrement ΔE of the adhesive layer at 120°C in a rigid pendulum measurement is 0.22 or less, exhibits high insulation properties after the heat-sealable resin layer is heat-sealed.

The present disclosure has been completed based on these findings and through further investigations. That is, the present disclosure provides the invention of the following aspects.
The laminate is made of at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer, in this order.
The adhesive layer has a logarithmic decrement ΔE of 0.22 or less at 120° C. in a rigid pendulum measurement.

According to the present disclosure, it is possible to provide an exterior material for an electricity storage device that is composed of a laminate having at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order, and that exhibits high insulation properties after heat-sealing of the heat-sealable resin layer. In addition, according to the present disclosure, it is also possible to provide a manufacturing method for an exterior material for an electricity storage device, and an electricity storage device.

1 is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electricity storage device according to the present disclosure. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electricity storage device according to the present disclosure. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electricity storage device according to the present disclosure. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electricity storage device according to the present disclosure. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electricity storage device according to the present disclosure. FIG. 2 is a diagram for explaining a method for evaluating the insulating property of an exterior material for an electricity storage device. FIG. 1 is a schematic diagram for explaining a method for measuring a logarithmic decrement ΔE by rigid pendulum measurement.

The exterior material for an electric storage device disclosed herein is composed of a laminate having at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order, and the adhesive layer is characterized in that the logarithmic decrement ΔE at 120°C in a rigid pendulum measurement is 0.22 or less. The exterior material for an electric storage device disclosed herein has this configuration, and thus can exhibit high insulation after the heat-sealable resin layer is heat-sealed.

The exterior material for an electricity storage device disclosed herein is described in detail below. In this specification, the numerical range indicated by "-" means "greater than or equal to" or "less than or equal to." For example, the expression 2-15 mm means 2 mm or more and 15 mm or less.

1. Laminated structure of the exterior material for a power storage device The exterior material for a power storage device 10 of the present disclosure is composed of a laminate including at least a base layer 1, a barrier layer 3, an adhesive layer 5, and a heat-sealable resin layer 4 in this order, as shown in, for example, FIG. 1 to FIG. 5. In the exterior material for a power storage device 10, the base layer 1 is the outermost layer, and the heat-sealable resin layer 4 is the innermost layer. More specifically, in the exterior material for a power storage device 10 of the present disclosure, the heat-sealable resin layer 4 is composed of a single layer or multiple layers, and among the heat-sealable resin layers 4, the first heat-sealable resin layer 41 constitutes the surface of the laminate. FIGS. 1 to 3 show a laminated structure in which the heat-sealable resin layer 4 is composed of a single layer of the first heat-sealable resin layer 41, and the first heat-sealable resin layer 41 constitutes the surface of the laminate. 4 and 5 show a laminated structure in which the heat-fusible resin layer 4 is composed of a multi-layer (two layers) of a first heat-fusible resin layer 41 and a second heat-fusible resin layer 42, and the first heat-fusible resin layer 41 constitutes the surface of the laminate. As described later, the heat-fusible resin layer 4 may further include other heat-fusible resin layers, such as a third heat-fusible resin layer and a fourth heat-fusible resin layer, on the barrier layer 3 side of the second heat-fusible resin layer 42 in addition to the first heat-fusible resin layer 41 and the second heat-fusible resin layer 42.

When assembling an electricity storage device using the exterior material 10 for an electricity storage device and an electricity storage device element, the first heat-sealable resin layers 41 of the exterior material 10 for an electricity storage device are placed facing each other, and the electricity storage device element is housed in a space formed by heat-sealing the peripheral portions.

As shown in Figures 2 to 5, for example, the exterior material 10 for an electric storage device may have an adhesive layer 2 between the base layer 1 and the barrier layer 3, if necessary, for the purpose of increasing the adhesion between these layers. Also, as shown in Figure 5, a surface coating layer 6 or the like may be provided on the outside of the base layer 1 (the side opposite to the heat-sealable resin layer 4) if necessary.

The thickness of the laminate constituting the exterior material for electricity storage devices 10 is not particularly limited, but from the viewpoint of cost reduction and energy density improvement, it is preferably about 180 μm or less, about 155 μm or less, and from the viewpoint of maintaining the function of the exterior material for electricity storage devices to protect the electricity storage device elements, it is preferably about 35 μm or more, about 45 μm or more, about 60 μm or more, and preferred ranges include, for example, about 35 to 180 μm, about 35 to 155 μm, about 45 to 180 μm, about 45 to 155 μm, about 60 to 180 μm, and about 60 to 155 μm.

2. Layers forming the exterior material for an electricity storage device [Base material layer 1]
In the present disclosure, the substrate layer 1 is a layer provided for the purpose of exhibiting the function as a substrate of the exterior material for an electricity storage device, etc. The substrate layer 1 is located on the outer layer side of the exterior material for an electricity storage device.

There are no particular limitations on the material that forms the substrate layer 1, as long as it has the function of a substrate, i.e., at least insulating properties. The substrate layer 1 can be formed, for example, using a resin, which may contain additives as described below.

When the base layer 1 is made of a resin, the base layer 1 may be, for example, a resin film made of a resin, or may be formed by applying a resin. The resin film may be an unstretched film or a stretched film. Examples of stretched films include uniaxially stretched films and biaxially stretched films, and biaxially stretched films are preferred. Examples of stretching methods for forming biaxially stretched films include sequential biaxial stretching, inflation, and simultaneous biaxial stretching. Examples of methods for applying a resin include roll coating, gravure coating, and extrusion coating.

Examples of resins that form the base layer 1 include polyester, polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, and phenol resin, as well as modified versions of these resins. The resin that forms the base layer 1 may also be a copolymer of these resins, or a modified version of the copolymer. It may also be a mixture of these resins.

Among these, polyester and polyamide are preferred as the resin that forms the base layer 1.

Specific examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyesters. Examples of copolymer polyesters include copolymer polyesters in which ethylene terephthalate is the main repeating unit. Specific examples include copolymer polyesters in which ethylene terephthalate is the main repeating unit and is polymerized with ethylene isophthalate (hereinafter abbreviated as polyethylene (terephthalate/isophthalate)), polyethylene (terephthalate/adipate), polyethylene (terephthalate/sodium sulfoisophthalate), polyethylene (terephthalate/sodium isophthalate), polyethylene (terephthalate/phenyl-dicarboxylate), and polyethylene (terephthalate/decane dicarboxylate). These polyesters may be used alone or in combination of two or more.

Specific examples of polyamides include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (I represents isophthalic acid, T represents terephthalic acid) that contain structural units derived from terephthalic acid and/or isophthalic acid, and aromatic polyamides such as polyamide MXD6 (polymetaxylylene adipamide); alicyclic polyamides such as polyamide PACM6 (polybis(4-aminocyclohexyl)methane adipamide); polyamides copolymerized with lactam components or isocyanate components such as 4,4'-diphenylmethane diisocyanate; polyesteramide copolymers and polyetheresteramide copolymers that are copolymers of copolymerized polyamides with polyesters or polyalkylene ether glycols; and polyamides such as these copolymers. These polyamides may be used alone or in combination of two or more.

The substrate layer 1 preferably includes at least one of a polyester film, a polyamide film, and a polyolefin film, preferably includes at least one of a stretched polyester film, a stretched polyamide film, and a stretched polyolefin film, more preferably includes at least one of a stretched polyethylene terephthalate film, a stretched polybutylene terephthalate film, a stretched nylon film, and a stretched polypropylene film, and even more preferably includes at least one of a biaxially stretched polyethylene terephthalate film, a biaxially stretched polybutylene terephthalate film, a biaxially stretched nylon film, and a biaxially stretched polypropylene film.

The substrate layer 1 may be a single layer, or may be composed of two or more layers. When the substrate layer 1 is composed of two or more layers, the substrate layer 1 may be a laminate in which resin films are laminated with an adhesive or the like, or a laminate of resin films in which resins are co-extruded to form two or more layers. In addition, a laminate of resin films in which resins are co-extruded to form two or more layers may be used as the substrate layer 1 without being stretched, or may be uniaxially or biaxially stretched to form the substrate layer 1.

Specific examples of laminates of two or more resin films in the base layer 1 include a laminate of a polyester film and a nylon film, a laminate of two or more nylon films, and a laminate of two or more polyester films, and preferably a laminate of a stretched nylon film and a stretched polyester film, a laminate of two or more stretched nylon films, and a laminate of two or more stretched polyester films. For example, when the base layer 1 is a laminate of two resin films, a laminate of a polyester resin film and a polyester resin film, a laminate of a polyamide resin film and a polyamide resin film, or a laminate of a polyester resin film and a polyamide resin film is preferred, and a laminate of a polyethylene terephthalate film and a polyethylene terephthalate film, a laminate of a nylon film and a nylon film, or a laminate of a polyethylene terephthalate film and a nylon film is more preferred. In addition, when the base layer 1 is a laminate of two or more resin films, it is preferable that the polyester resin film is located in the outermost layer of the base layer 1, because the polyester resin is less likely to discolor when, for example, an electrolyte is attached to the surface.

When the base layer 1 is a laminate of two or more resin films, the two or more resin films may be laminated via an adhesive. Preferred adhesives include those similar to those exemplified in the adhesive layer 2 described below. The method for laminating two or more resin films is not particularly limited, and known methods can be used, such as dry lamination, sandwich lamination, extrusion lamination, and thermal lamination, and preferably dry lamination. When laminating by the dry lamination method, it is preferable to use a polyurethane adhesive as the adhesive. In this case, the thickness of the adhesive is, for example, about 2 to 5 μm. Alternatively, an anchor coat layer may be formed on the resin film and laminated. The anchor coat layer may be the same as the adhesive exemplified in the adhesive layer 2 described below. In this case, the thickness of the anchor coat layer is, for example, about 0.01 to 1.0 μm.

Additives such as lubricants, flame retardants, antiblocking agents, antioxidants, light stabilizers, tackifiers, and antistatic agents may be present on at least one of the surface and interior of the base layer 1. Only one type of additive may be used, or two or more types may be mixed together.

In the present disclosure, from the viewpoint of improving the formability of the exterior material for a power storage device, it is preferable that a lubricant is present on the surface of the base material layer 1. The lubricant is not particularly limited, but is preferably an amide-based lubricant. Specific examples of amide-based lubricants include, for example, saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Specific examples of saturated fatty acid amides include lauric acid amides, palmitic acid amides, stearic acid amides, behenic acid amides, and hydroxystearic acid amides. Specific examples of unsaturated fatty acid amides include oleic acid amides and erucic acid amides. Specific examples of substituted amides include N-oleyl palmitic acid amides, N-stearyl stearic acid amides, N-stearyl oleic acid amides, N-oleyl stearic acid amides, and N-stearyl erucic acid amides. Specific examples of methylol amides include methylol stearic acid amides. Specific examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipic acid amide, N,N'-distearyl sebacic acid amide, etc. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipic acid amide, N,N'-dioleyl sebacic acid amide, etc. Specific examples of fatty acid ester amides include stearamide ethyl stearate, etc. Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, and N,N'-distearylisophthalic acid amide. The lubricant may be used alone or in combination of two or more types.

When a lubricant is present on the surface of the base layer 1, the amount of the lubricant present is not particularly limited, but is preferably about 3 mg/ ^m2 or more, more preferably about 4 to 15 mg/ ^m2 , and even more preferably about 5 to 14 mg/ ^m2 .

The lubricant present on the surface of the base layer 1 may be a lubricant exuded from the resin that constitutes the base layer 1, or a lubricant applied to the surface of the base layer 1.

The thickness of the substrate layer 1 is not particularly limited as long as it functions as a substrate, but may be, for example, about 3 to 50 μm, and preferably about 10 to 35 μm. When the substrate layer 1 is a laminate of two or more resin films, the thickness of each of the resin films constituting each layer may be, for example, about 2 to 35 μm, and preferably about 2 to 25 μm.

[Adhesive layer 2]
In the exterior material for an electricity storage device of the present disclosure, the adhesive layer 2 is a layer that is provided between the base layer 1 and the barrier layer 3 as necessary for the purpose of increasing the adhesion between them.

The adhesive layer 2 is formed from an adhesive capable of bonding the base layer 1 and the barrier layer 3. There are no limitations on the adhesive used to form the adhesive layer 2, and it may be any of a chemical reaction type, a solvent volatilization type, a hot melt type, a hot pressure type, etc. It may also be a two-component curing adhesive (two-component adhesive), a one-component curing adhesive (one-component adhesive), or a resin that does not involve a curing reaction. The adhesive layer 2 may be a single layer or multiple layers.

Specific examples of adhesive components contained in the adhesive include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyesters; polyethers; polyurethanes; epoxy resins; phenolic resins; polyamides such as nylon 6, nylon 66, nylon 12, and copolymer polyamides; polyolefin resins such as polyolefins, cyclic polyolefins, acid-modified polyolefins, and acid-modified cyclic polyolefins; polyvinyl acetate; cellulose; (meth)acrylic resins; polyimides; polycarbonates; amino resins such as urea resins and melamine resins; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; and silicone resins. These adhesive components may be used alone or in combination of two or more. Among these adhesive components, polyurethane adhesives are preferred. In addition, the adhesive strength of these adhesive resins can be increased by using an appropriate curing agent in combination. The curing agent is selected from polyisocyanates, multifunctional epoxy resins, oxazoline group-containing polymers, polyamine resins, acid anhydrides, and the like, depending on the functional groups of the adhesive components.

The polyurethane adhesive may be, for example, a polyurethane adhesive containing a base agent containing a polyol compound and a curing agent containing an isocyanate compound. A two-component curing type polyurethane adhesive is preferably used, in which a polyol such as polyester polyol, polyether polyol, or acrylic polyol is used as the base agent, and an aromatic or aliphatic polyisocyanate is used as the curing agent. In addition, it is preferable to use a polyester polyol having a hydroxyl group on the side chain in addition to the terminal hydroxyl group of the repeating unit, as the polyol compound. Since the adhesive layer 2 is formed from a polyurethane adhesive, the exterior material for the electricity storage device is given excellent electrolyte resistance, and the base material layer 1 is prevented from peeling off even if the electrolyte adheres to the side surface.

In addition, the adhesive layer 2 may contain other components as long as they do not impair adhesion, and may contain colorants, thermoplastic elastomers, tackifiers, fillers, etc. By including a colorant in the adhesive layer 2, the exterior material for the power storage device can be colored. As the colorant, known colorants such as pigments and dyes can be used. In addition, only one type of colorant may be used, or two or more types may be mixed together.

There are no particular limitations on the type of pigment, so long as it does not impair the adhesiveness of the adhesive layer 2. Examples of organic pigments include azo-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigothioindigo-based, perinone-perylene-based, isoindolenine-based, and benzimidazolone-based pigments, while examples of inorganic pigments include carbon black-based, titanium oxide-based, cadmium-based, lead-based, chromium oxide-based, and iron-based pigments, as well as finely powdered mica and fish scale foil.

Among colorants, carbon black is preferred, for example to give the exterior material for an electricity storage device a black appearance.

The average particle size of the pigment is not particularly limited, and may be, for example, about 0.05 to 5 μm, and preferably about 0.08 to 2 μm. The average particle size of the pigment is the median size measured with a laser diffraction/scattering type particle size distribution measuring device.

The content of the pigment in the adhesive layer 2 is not particularly limited as long as the exterior material for the electricity storage device is colored, and may be, for example, about 5 to 60% by mass, and preferably 10 to 40% by mass.

The thickness of the adhesive layer 2 is not particularly limited as long as it can bond the base layer 1 and the barrier layer 3, but examples of the thickness include about 1 μm or more, about 2 μm or more, and about 10 μm or less, and about 5 μm or less. Preferred ranges include about 1 to 10 μm, about 1 to 5 μm, about 2 to 10 μm, and about 2 to 5 μm.

[Colored layer]
The colored layer is a layer (not shown) that is provided between the base material layer 1 and the barrier layer 3 as necessary. When the adhesive layer 2 is provided, a colored layer may be provided between the base material layer 1 and the adhesive layer 2, or between the adhesive layer 2 and the barrier layer 3. In addition, a colored layer may be provided on the outside of the base material layer 1. By providing a colored layer, the exterior material for an electricity storage device can be colored.

The colored layer can be formed, for example, by applying an ink containing a colorant to the surface of the base layer 1, the surface of the adhesive layer 2, or the surface of the barrier layer 3. As the colorant, known pigments, dyes, and the like can be used. Furthermore, only one type of colorant may be used, or two or more types may be mixed together.

Specific examples of colorants contained in the colored layer include those listed in the [Adhesive layer 2] section.

[Barrier layer 3]
In the packaging material for an electricity storage device, the barrier layer 3 is a layer that at least prevents the infiltration of moisture.

Examples of the barrier layer 3 include metal foils, vapor deposition films, and resin layers having barrier properties. Examples of vapor deposition films include metal vapor deposition films, inorganic oxide vapor deposition films, and carbon-containing inorganic oxide vapor deposition films. Examples of the resin layer include fluorine-containing resins such as polyvinylidene chloride, polymers mainly composed of chlorotrifluoroethylene (CTFE), polymers mainly composed of tetrafluoroethylene (TFE), polymers having fluoroalkyl groups, and polymers mainly composed of fluoroalkyl units, and ethylene-vinyl alcohol copolymers. Examples of the barrier layer 3 include resin films having at least one layer of these vapor deposition films and resin layers. The barrier layer 3 may be provided in multiple layers. It is preferable that the barrier layer 3 includes a layer composed of a metal material. Specific examples of the metal material constituting the barrier layer 3 include aluminum alloys, stainless steel, titanium steel, and steel plates. When used as a metal foil, it is preferable that the barrier layer 3 includes at least one of aluminum alloy foil and stainless steel foil.

From the viewpoint of improving the formability of the exterior material for an electric storage device, the aluminum alloy foil is preferably a soft aluminum alloy foil made of, for example, an annealed aluminum alloy, and from the viewpoint of further improving the formability, the aluminum alloy foil is preferably an iron-containing aluminum alloy foil. In the iron-containing aluminum alloy foil (100 mass%), the iron content is preferably 0.1 to 9.0 mass%, and more preferably 0.5 to 2.0 mass%. By having an iron content of 0.1 mass% or more, an exterior material for an electric storage device having better formability can be obtained. By having an iron content of 9.0 mass% or less, an exterior material for an electric storage device having better flexibility can be obtained. Examples of soft aluminum alloy foils include aluminum alloy foils having a composition specified in JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, or JIS H4000:2014 A8079P-O. Silicon, magnesium, copper, manganese, etc. may also be added as necessary. Softening can be achieved by annealing or the like.

Examples of stainless steel foil include austenitic, ferritic, austenitic-ferritic, martensitic, and precipitation hardened stainless steel foils. From the viewpoint of providing an exterior material for an electricity storage device with excellent formability, it is preferable that the stainless steel foil is made of austenitic stainless steel.

Specific examples of austenitic stainless steels that make up the stainless steel foil include SUS304, SUS301, and SUS316L, with SUS304 being particularly preferred.

In the case of a metal foil, the thickness of the barrier layer 3 is sufficient to at least function as a barrier layer that prevents moisture from penetrating, and may be, for example, about 9 to 200 μm. The thickness of the barrier layer 3 is, for example, preferably about 85 μm or less, more preferably about 50 μm or less, even more preferably about 40 μm or less, and particularly preferably about 35 μm or less, and is preferably about 10 μm or more, even more preferably about 20 μm or more, and more preferably about 25 μm or more. Preferred ranges of the thickness include about 10 to 85 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 35 μm, about 20 to 85 μm, about 20 to 50 μm, about 20 to 40 μm, about 20 to 35 μm, about 25 to 85 μm, about 25 to 50 μm, about 25 to 40 μm, and about 25 to 35 μm. When the barrier layer 3 is made of an aluminum alloy foil, the above-mentioned range is particularly preferable. In particular, when the barrier layer 3 is made of stainless steel foil, the thickness of the stainless steel foil is preferably about 60 μm or less, more preferably about 50 μm or less, even more preferably about 40 μm or less, even more preferably about 30 μm or less, and particularly preferably about 25 μm or less, and is preferably about 10 μm or more, more preferably about 15 μm or more. Preferred thickness ranges include about 10 to 60 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 30 μm, about 10 to 25 μm, about 15 to 60 μm, about 15 to 50 μm, about 15 to 40 μm, about 15 to 30 μm, and about 15 to 25 μm.

In addition, when the barrier layer 3 is a metal foil, it is preferable to provide a corrosion-resistant film at least on the surface opposite to the base layer in order to prevent dissolution and corrosion. The barrier layer 3 may be provided with a corrosion-resistant film on both sides. Here, the corrosion-resistant film refers to a thin film that is provided with corrosion resistance (e.g., acid resistance, alkali resistance, etc.) by performing, for example, hydrothermal transformation treatment such as boehmite treatment, chemical conversion treatment, anodizing treatment, plating treatment such as nickel or chromium, or corrosion prevention treatment by applying a coating agent on the surface of the barrier layer. Specifically, the corrosion-resistant film means a film that improves the acid resistance of the barrier layer (acid-resistant film), a film that improves the alkali resistance of the barrier layer (alkali-resistant film), etc. As a treatment for forming a corrosion-resistant film, one type may be performed, or two or more types may be combined. In addition to one layer, it is also possible to form a multi-layered film. Furthermore, among these treatments, hydrothermal transformation treatment and anodizing treatment are treatments in which the metal foil surface is dissolved by a treatment agent to form a metal compound with excellent corrosion resistance. These treatments may also be included in the definition of chemical conversion treatment. Also, if the barrier layer 3 has a corrosion-resistant coating, the corrosion-resistant coating is included in the barrier layer 3.

The corrosion-resistant coating prevents delamination between the barrier layer (e.g., aluminum alloy foil) and the base layer during molding of the exterior material for the power storage device, prevents dissolution and corrosion of the barrier layer surface due to hydrogen fluoride produced by the reaction between the electrolyte and water, and in particular prevents dissolution and corrosion of aluminum oxide present on the barrier layer surface when the barrier layer is an aluminum alloy foil, and improves the adhesion (wettability) of the barrier layer surface, preventing delamination between the base layer and barrier layer during heat sealing and between the base layer and barrier layer during molding.

Various corrosion-resistant films formed by chemical conversion treatments are known, including mainly corrosion-resistant films containing at least one of phosphates, chromates, fluorides, triazine thiol compounds, and rare earth oxides. Chemical conversion treatments using phosphates and chromates include, for example, chromate chromate treatment, phosphoric acid chromate treatment, phosphoric acid-chromate treatment, and chromate treatment. Examples of chromium compounds used in these treatments include chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromate acetyl acetate, chromium chloride, and potassium chromium sulfate. Examples of phosphorus compounds used in these treatments include sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphoric acid. Examples of chromate treatments include etching chromate treatment, electrolytic chromate treatment, and coating-type chromate treatment, with coating-type chromate treatment being preferred. In this coating-type chromate treatment, at least the inner surface of a barrier layer (e.g., an aluminum alloy foil) is first degreased by a known method such as an alkali immersion method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or an acid activation method, and then a treatment liquid mainly composed of a metal phosphate such as Cr (chromium) phosphate, Ti (titanium) phosphate, Zr (zirconium) phosphate, or Zn (zinc) phosphate, or a mixture of these metal salts, or a treatment liquid mainly composed of a nonmetallic phosphate and a mixture of these nonmetallic salts, or a treatment liquid composed of a mixture of these with a synthetic resin, or the like, is applied to the degreased surface by a known coating method such as a roll coating method, a gravure printing method, a dipping method, or the like, and then dried. As the treatment liquid, various solvents such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents can be used, and water is preferred. The resin component used here may be a polymer such as a phenolic resin or an acrylic resin, and may be a chromate treatment using an aminated phenolic polymer having a repeating unit represented by the following general formulas (1) to (4). In the aminated phenolic polymer, the repeating units represented by the following general formulas (1) to (4) may be contained alone or in any combination of two or more. The acrylic resin is preferably polyacrylic acid, acrylic acid methacrylic acid ester copolymer, acrylic acid maleic acid copolymer, acrylic acid styrene copolymer, or a derivative thereof such as a sodium salt, an ammonium salt, or an amine salt. In particular, a derivative of polyacrylic acid such as an ammonium salt, a sodium salt, or an amine salt of polyacrylic acid is preferable. In the present disclosure, polyacrylic acid means a polymer of acrylic acid. The acrylic resin is also preferably a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic anhydride, and is also preferably an ammonium salt, a sodium salt, or an amine salt of a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic anhydride. Only one type of acrylic resin may be used, or two or more types may be mixed together.

In the general formulae (1) to (4), X represents a hydrogen atom, a hydroxy group, an alkyl group, a hydroxyalkyl group, an allyl group, or a benzyl group. R ¹ and R ² may be the same or different and represent a hydroxy group, an alkyl group, or a hydroxyalkyl group. In the general formulae (1) to (4), examples of the alkyl group represented by X, R ¹ , and R ² include linear or branched alkyl groups having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. Examples of the hydroxyalkyl group represented by X, R ¹ , and R ² include linear or branched alkyl groups having 1 to 4 carbon atoms and substituted with one hydroxy group, such as a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, a 1-hydroxybutyl group, a 2-hydroxybutyl group, a 3-hydroxybutyl group, and a 4-hydroxybutyl group. In the general formulae (1) to (4), the alkyl groups and hydroxyalkyl groups represented by X, R ¹ , and R ² may be the same or different. In the general formulae (1) to (4), X is preferably a hydrogen atom, a hydroxy group, or a hydroxyalkyl group. The number average molecular weight of the aminated phenol polymer having the repeating units represented by the general formulae (1) to (4) is preferably about 500 to 1,000,000, for example, and more preferably about 1,000 to 20,000. The aminated phenol polymer is produced, for example, by polycondensing a phenol compound or a naphthol compound with formaldehyde to produce a polymer consisting of the repeating units represented by the general formula (1) or (3), and then introducing a functional group (-CH ₂ NR ¹ R ² ) into the polymer obtained above using formaldehyde and an amine (R ¹ R ² NH). The aminated phenol polymer may be used alone or in combination of two or more types.

Other examples of corrosion-resistant films include thin films formed by a coating-type corrosion prevention treatment in which a coating agent containing at least one selected from the group consisting of rare earth element oxide sol, anionic polymer, and cationic polymer is applied. The coating agent may further contain phosphoric acid or phosphate, and a crosslinking agent for crosslinking the polymer. The rare earth element oxide sol has rare earth element oxide fine particles (e.g., particles with an average particle size of 100 nm or less) dispersed in a liquid dispersion medium. Examples of rare earth element oxides include cerium oxide, yttrium oxide, neodymium oxide, and lanthanum oxide, and cerium oxide is preferred from the viewpoint of further improving adhesion. The rare earth element oxide contained in the corrosion-resistant film can be used alone or in combination of two or more types. Examples of liquid dispersion media for the rare earth element oxide sol include various solvents such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, and water is preferred. As the cationic polymer, for example, polyethyleneimine, an ionic polymer complex consisting of a polymer having polyethyleneimine and a carboxylic acid, a primary amine grafted acrylic resin in which a primary amine is graft-polymerized to an acrylic main skeleton, polyallylamine or a derivative thereof, aminated phenol, etc. are preferable. In addition, as the anionic polymer, poly(meth)acrylic acid or a salt thereof, or a copolymer mainly composed of (meth)acrylic acid or a salt thereof is preferable. In addition, it is preferable that the crosslinking agent is at least one selected from the group consisting of a compound having any one of the functional groups of an isocyanate group, a glycidyl group, a carboxyl group, and an oxazoline group, and a silane coupling agent. In addition, it is preferable that the phosphoric acid or the phosphoric acid salt is a condensed phosphoric acid or a condensed phosphate salt.

One example of a corrosion-resistant coating is one formed by applying a solution of fine particles of metal oxides such as aluminum oxide, titanium oxide, cerium oxide, and tin oxide, or barium sulfate dispersed in phosphoric acid to the surface of the barrier layer and baking the coating at 150°C or higher.

If necessary, the corrosion-resistant coating may have a laminated structure in which at least one of a cationic polymer and an anionic polymer is further laminated. Examples of the cationic polymer and anionic polymer include those described above.

The composition of the corrosion-resistant coating can be analyzed, for example, using time-of-flight secondary ion mass spectrometry.

The amount of the corrosion-resistant coating formed on the surface of the barrier layer 3 in the chemical conversion treatment is not particularly limited, but for example, in the case of performing a coating-type chromate treatment, it is desirable for the chromate compound to be contained in an amount, calculated as chromium, of about 0.5 to 50 mg, preferably about 1.0 to 40 mg, per 1 m2 of the surface of the barrier layer ³ , of a phosphorus compound, calculated as phosphorus, of about 0.5 to 50 mg, preferably about 1.0 to 40 mg, and of an aminated phenol polymer, calculated as phosphorus, of about 1.0 to 200 mg, preferably about 5.0 to 150 mg.

The thickness of the corrosion-resistant film is not particularly limited, but is preferably about 1 nm to 20 μm, more preferably about 1 nm to 100 nm, and even more preferably about 1 nm to 50 nm, from the viewpoint of the cohesive force of the film and the adhesive force with the barrier layer and the heat-sealable resin layer. The thickness of the corrosion-resistant film can be measured by observation with a transmission electron microscope, or a combination of observation with a transmission electron microscope and energy dispersive X-ray spectroscopy or electron energy loss spectroscopy. By analyzing the composition of the corrosion-resistant film using time-of-flight secondary ion mass spectrometry, for example, peaks derived from secondary ions composed of Ce, P, and O (for example, at least one of Ce ₂ PO ₄ ⁺ and CePO ₄ ^- ) or secondary ions composed of Cr, P, and O (for example, at least one of CrPO ₂ ⁺ and CrPO ₄ ^- ) are detected.

The chemical conversion treatment is carried out by applying a solution containing a compound used to form a corrosion-resistant film to the surface of the barrier layer by a bar coating method, a roll coating method, a gravure coating method, a dipping method, or the like, and then heating the barrier layer so that the temperature of the barrier layer is about 70 to 200°C. In addition, before applying the chemical conversion treatment to the barrier layer, the barrier layer may be subjected to a degreasing treatment by an alkali dipping method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or the like. By carrying out the degreasing treatment in this manner, the chemical conversion treatment of the surface of the barrier layer can be carried out more efficiently. In addition, by using an acid degreasing agent in which a fluorine-containing compound is dissolved in an inorganic acid for the degreasing treatment, it is possible to not only degrease the metal foil but also form a fluoride of the metal, which is a passive state, and in such a case, only the degreasing treatment may be carried out.

[Heat-fusible resin layer 4]
In the exterior packaging material for an electric storage device of the present disclosure, the heat-sealable resin layer 4 corresponds to the innermost layer, and is a layer (sealant layer) that exhibits the function of sealing the electric storage device element by heat-sealing the heat-sealable resin layer when assembling the electric storage device. In the exterior packaging material for an electric storage device 10 of the present disclosure, the heat-sealable resin layer 4 is composed of a single layer or multiple layers, and among the heat-sealable resin layers 4, the first heat-sealable resin layer 41 constitutes the surface of the laminate. Therefore, the first heat-sealable resin layer 41 is heat-sealed to seal the electric storage device element when assembling the electric storage device.

When the heat-sealable resin layer 4 is composed of a single layer, the heat-sealable resin layer 4 constitutes the first heat-sealable resin layer 41. Figures 1 to 3 show a laminated structure in which the heat-sealable resin layer 4 is composed of a single layer of the first heat-sealable resin layer 41, and the first heat-sealable resin layer 41 constitutes the surface of the laminate.

When the heat-sealable resin layer 4 is composed of multiple layers, it has at least a first heat-sealable resin layer 41 and a second heat-sealable resin layer 42, in that order from the surface side of the laminate constituting the exterior material 10 for an electrical storage device. Figures 4 and 5 show a laminated structure in which the heat-sealable resin layer 4 is composed of multiple layers (two layers) of the first heat-sealable resin layer 41 and the second heat-sealable resin layer 42, and the first heat-sealable resin layer 41 constitutes the surface of the laminate.

When the heat-sealable resin layer 4 is composed of multiple layers, the heat-sealable resin layer 4 may further include a third heat-sealable resin layer, a fourth heat-sealable resin layer, etc. on the barrier layer 3 side of the second heat-sealable resin layer 42 in addition to the first heat-sealable resin layer 41 and the second heat-sealable resin layer 42. When the heat-sealable resin layer 4 is composed of multiple layers, the heat-sealable resin layer 4 is preferably composed of two layers, the first heat-sealable resin layer 41 and the second heat-sealable resin layer 42.

The resin constituting the first heat-sealable resin layer 41 is preferably a resin containing a polyolefin skeleton, such as polyolefin or acid-modified polyolefin. The resin constituting the first heat-sealable resin layer 41 can be analyzed to contain a polyolefin skeleton, for example, by infrared spectroscopy, gas chromatography mass spectrometry, or the like. In addition, when the resin constituting the first heat-sealable resin layer 41 is analyzed by infrared spectroscopy, it is preferable that a peak derived from maleic anhydride is detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak derived from maleic anhydride is detected near the wave number 1760 cm ^-1 and near the wave number 1780 cm ^-1 . When the first heat-sealable resin layer 41 is a layer composed of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride is detected by infrared spectroscopy. However, if the degree of acid modification is low, the peak may be small and not detected. In that case, it can be analyzed by nuclear magnetic resonance spectroscopy.

Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. Among these, polypropylene is preferred. When the polyolefin resin is a copolymer, it may be a block copolymer or a random copolymer. These polyolefin resins may be used alone or in combination of two or more types.

The polyolefin may be a cyclic polyolefin. A cyclic polyolefin is a copolymer of an olefin and a cyclic monomer. Examples of the olefin that is a constituent monomer of the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, and isoprene. Examples of the cyclic monomer that is a constituent monomer of the cyclic polyolefin include cyclic alkenes such as norbornene; and cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these, cyclic alkenes are preferred, and norbornene is more preferred.

An acid-modified polyolefin is a polymer modified by block polymerization or graft polymerization of a polyolefin with an acid component. The polyolefin to be acid-modified may be the above-mentioned polyolefin, a copolymer obtained by copolymerizing the above-mentioned polyolefin with a polar molecule such as acrylic acid or methacrylic acid, or a polymer such as a cross-linked polyolefin. In addition, examples of the acid component used for acid modification include carboxylic acids or anhydrides such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

The acid-modified polyolefin may be an acid-modified cyclic polyolefin. An acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin by replacing it with an acid component, or by block polymerizing or graft polymerizing an acid component to the cyclic polyolefin. The cyclic polyolefin to be acid-modified is the same as described above. The acid component used for the acid modification is the same as the acid component used for the modification of the polyolefin described above.

Preferred acid-modified polyolefins include polyolefins modified with carboxylic acids or their anhydrides, polypropylenes modified with carboxylic acids or their anhydrides, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

The first heat-sealable resin layer 41 may be formed from one type of resin alone, or may be formed from a blend polymer that combines two or more types of resin.

The first heat-sealable resin layer 41 constituting the surface preferably contains polyolefin. For example, in the exterior material 10 for an electric storage device of the present disclosure, when the heat-sealable resin layer 4 includes the first heat-sealable resin layer 41 and the second heat-sealable resin layer 42, it is preferable that the first heat-sealable resin layer 41 constituting the surface contains polyolefin, and the second heat-sealable resin layer 42 contains acid-modified polyolefin. In addition, in the exterior material 10 for an electric storage device of the present disclosure, when the adhesive layer 5 is included, it is preferable that the first heat-sealable resin layer 41 constituting the surface contains polyolefin, and the adhesive layer 5 contains acid-modified polyolefin. In addition, it is preferable that the adhesive layer 5 contains acid-modified polyolefin, the first heat-sealable resin layer contains polyolefin, and the second heat-sealable resin layer contains polyolefin, and it is more preferable that the adhesive layer 5 contains acid-modified polypropylene, the first heat-sealable resin layer contains polypropylene, and the second heat-sealable resin layer contains polypropylene.

The first heat-sealable resin layer 41 may also contain a lubricant, etc., if necessary. When the first heat-sealable resin layer 41 contains a lubricant, the moldability of the exterior material for the power storage device can be improved. There are no particular limitations on the lubricant, and any known lubricant can be used. The lubricant may be used alone or in combination of two or more types.

The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of the lubricant include those exemplified for the base layer 1. The lubricant may be used alone or in combination of two or more types.

When a lubricant is present on the surface of the first heat-sealable resin layer 41, the amount thereof is not particularly limited, but from the viewpoint of improving the formability of the exterior material for an electricity storage device, it is preferably about 10 to 50 mg/m ² , and more preferably about 15 to 40 mg/m ^2. Note that even when a lubricant is present on the surface of the first heat-sealable resin layer 41, the first heat-sealable resin layer 41 including the lubricant constitutes the surface of the exterior material for an electricity storage device 10.

The lubricant present on the surface of the first heat-sealable resin layer 41 may be a lubricant exuded from the resin that constitutes the first heat-sealable resin layer 41, or a lubricant applied to the surface of the first heat-sealable resin layer 41.

The thickness of the first heat-sealable resin layer 41 is not particularly limited as long as the heat-sealable resin layer functions to heat-seal the electricity storage device element.

From the viewpoint of achieving even higher insulation after the heat fusion of the heat fusion resin layer, the thickness of the first heat fusion resin layer 41 is preferably about 100 μm or less, about 85 μm or less, about 60 μm or less, and also 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, 40 μm or more. Preferred ranges include about 5 to 100 μm, about 5 to 85 μm, about 5 to 60 μm, about 10 to 100 μm, about 10 to 85 μm, about 10 to 60 μm, about 20 to 100 μm, about 20 to 85 μm, about 20 to 60 μm, about 30 to 100 μm, about 30 to 85 μm, about 30 to 60 μm, about 40 to 100 μm, about 40 to 85 μm, and about 40 to 60 μm.

Specifically, from the viewpoint of exhibiting even higher insulating properties after the heat-sealing of the heat-sealing resin layer, when the heat-sealing resin layer 4 is composed of a single layer of the first heat-sealing resin layer 41, the thickness of the first heat-sealing resin layer 41 is preferably about 100 μm or less, about 85 μm or less, about 60 μm or less, or about 25 μm or less, and also preferably 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more. Preferred ranges include , about 5 to 100 μm, about 5 to 85 μm, about 5 to 60 μm, about 5 to 25 μm, about 10 to 100 μm, about 10 to 85 μm, about 10 to 60 μm, about 10 to 25 μm, about 20 to 100 μm, about 20 to 85 μm, about 20 to 60 μm, about 20 to 25 μm, about 30 to 100 μm, about 30 to 85 μm, about 30 to 60 μm, about 40 to 100 μm, about 40 to 85 μm, and about 40 to 60 μm.

In addition, from the viewpoint of achieving even higher insulation after the heat fusion of the heat fusion resin layer, when the heat fusion resin layer 4 includes the first heat fusion resin layer 41 and the second heat fusion resin layer 42, the thickness of the first heat fusion resin layer 41 is preferably about 85 μm or less, about 60 μm or less, about 25 μm or less, and also 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, 40 μm or more, and preferred ranges include about 5 to 85 μm, about 5 to 60 μm, about 5 to 25 μm, about 10 to 85 μm, about 10 to 60 μm, about 10 to 25 μm, about 20 to 85 μm, about 20 to 60 μm, about 20 to 25 μm, about 30 to 85 μm, about 30 to 60 μm, about 40 to 85 μm, and about 40 to 60 μm.

When the thermally adhesive resin layer 4 includes the second thermally adhesive resin layer 42, the resin constituting the second thermally adhesive resin layer 42 is preferably a resin containing a polyolefin skeleton, such as polyolefin or acid-modified polyolefin. These resins are the same as those described for the first thermally adhesive resin layer 41. The resin constituting the second thermally adhesive resin layer 42 can be analyzed to contain a polyolefin skeleton, for example, by infrared spectroscopy, gas chromatography mass spectrometry, or the like. In addition, when the resin constituting the second thermally adhesive resin layer 42 is analyzed by infrared spectroscopy, it is preferable that a peak derived from maleic anhydride is detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak derived from maleic anhydride is detected near the wave number 1760 cm ^-1 and near the wave number 1780 cm ^-1 . When the second thermally adhesive resin layer 42 is a layer composed of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride is detected by infrared spectroscopy. However, if the degree of acid modification is low, the peak may be small and not detected. In that case, analysis can be performed by nuclear magnetic resonance spectroscopy.

The second heat-sealable resin layer 42 preferably contains a polyolefin. In the exterior material for an electric storage device of the present disclosure, when the heat-sealable resin layer 4 includes a first heat-sealable resin layer 41 and a second heat-sealable resin layer 42, it is preferable that the first heat-sealable resin layer 41 and the second heat-sealable resin layer 42 contain a polyolefin.

The thickness of the second heat-sealable resin layer 42 is not particularly limited as long as the heat-sealable resin layer 4 functions to heat-seal the electricity storage device element.

From the viewpoint of exhibiting higher insulation after the heat fusion of the heat fusion resin layer, the thickness of the second heat fusion resin layer 42 is preferably larger than the thickness of the first heat fusion resin layer 41. For the first heat fusion resin layer 41, a resin that flows easily at high temperatures is preferably used so as to have excellent heat fusion properties. By providing such a thickness relationship, the insulation of the exterior material for the electric storage device can be improved by thinning the first heat fusion resin layer 41, which is a part of the heat fusion resin layer 4 and is composed of a resin that flows easily. By appropriately adjusting the MFR, melting point, molecular weight, etc. of the resin that constitutes the first heat fusion resin layer 41, it is possible to make the first heat fusion resin layer 41 a resin layer that flows easily at high temperatures.

From the viewpoint of achieving even higher insulation after the heat fusion of the heat fusion resin layer, the thickness of the second heat fusion resin layer 42 is preferably about 100 μm or less, about 85 μm or less, about 60 μm or less, and also 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, 40 μm or more. Preferred ranges include about 5 to 100 μm, about 5 to 85 μm, about 5 to 60 μm, about 10 to 100 μm, about 10 to 85 μm, about 10 to 60 μm, about 20 to 100 μm, about 20 to 85 μm, about 20 to 60 μm, about 30 to 100 μm, about 30 to 85 μm, about 30 to 60 μm, about 40 to 100 μm, about 40 to 85 μm, and about 40 to 60 μm.

In addition to the first heat-sealable resin layer 41 and the second heat-sealable resin layer 42, the heat-sealable resin layer 4 may further include other heat-sealable resin layers, such as a third heat-sealable resin layer and a fourth heat-sealable resin layer, on the barrier layer 3 side of the second heat-sealable resin layer 42. Examples of resins constituting the other heat-sealable resin layers include those described for the first heat-sealable resin layer 41. Examples of thicknesses of the other heat-sealable resin layers include those described for the second heat-sealable resin layer 42.

The total thickness of the heat-sealable resin layer 4 is preferably about 100 μm or less, about 85 μm or less, or about 60 μm or less, and also 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more. Preferred ranges include about 5 to 100 μm, about 5 to 85 μm, about 5 to 60 μm, about 10 to 100 μm, about 10 to 85 μm, about 10 to 60 μm, about 20 to 100 μm, about 20 to 85 μm, about 20 to 60 μm, about 30 to 100 μm, about 30 to 85 μm, about 30 to 60 μm, about 40 to 100 μm, about 40 to 85 μm, about 60 to 70 μm, and about 40 to 60 μm.

[Adhesive layer 5]
In the packaging material for an electricity storage device according to the present disclosure, the adhesive layer 5 is a layer provided between the barrier layer 3 (or the corrosion-resistant film) and the heat-sealable resin layer 4 in order to firmly bond them together.

The exterior material for an electricity storage device disclosed herein is characterized in that the logarithmic attenuation factor ΔE of the adhesive layer 5 at 120°C in a rigid pendulum measurement is 0.22 or less. In the present disclosure, the logarithmic attenuation factor ΔE at 120°C is 0.22 or less, so that the heat-sealable resin layer exhibits high insulation after heat fusion.

The logarithmic attenuation at 120°C in the rigid pendulum measurement is an index of the hardness of the resin in a high-temperature environment of 120°C, and the smaller the logarithmic attenuation, the higher the hardness of the resin. In the rigid pendulum measurement, the attenuation rate of the pendulum is measured when the temperature of the resin is raised from a low temperature to a high temperature. In the rigid pendulum measurement, the edge is generally brought into contact with the surface of the object to be measured, and the object is caused to swing left and right to vibrate. In the exterior material for the electric storage device of the present invention, a hard adhesive layer 5 with a logarithmic attenuation rate of 0.22 or less in a high-temperature environment of 120°C is disposed between the barrier layer 3 and the heat-sealable resin layer 4, thereby exhibiting high insulation after the heat-sealable resin layer is heat-sealed.

From the viewpoint of exhibiting high insulating properties after the heat-sealing resin layer is heat-sealed, the logarithmic decrement ΔE at 120°C is preferably about 0.10 or more, more preferably about 0.11 or more, and even more preferably about 0.12 or more, and is preferably about 0.20 or less, preferably about 0.18 or less, more preferably about 0.17 or less, and particularly preferably 0.16 or less. The preferred range is 0.10 or less. .10 to 0.22, about 0.10 to 0.20, about 0.10 to 0.18, about 0.10 to 0.17, about 0.11 to 0.22, about 0.11 to 0.20, about 0.11 to 0.18, about 0.11 to 0.17, about 0.11 to 0.16, about 0.12 to 0.22, about 0.12 to 0.20, about 0.12 to 0.18, about 0.12 to 0.17, and about 0.12 to 0.16.

The logarithmic decrement ΔE of the adhesive layer 5 can be adjusted, for example, by the melt mass flow rate (MFR), molecular weight, melting point, softening point, molecular weight distribution, degree of crystallinity, and type and amount of hardener of the resin constituting the adhesive layer 5.

The logarithmic decrement ΔE of the adhesive layer 5 is measured using a commercially available rigid pendulum type physical property tester, and a rigid pendulum physical property test is performed on the adhesive layer 5 under the conditions of a cylindrical cylinder edge as the edge pressed against the adhesive layer 5, an initial amplitude of 0.3 degrees, and a temperature rise rate of 3°C/min in the temperature range of 30°C to 200°C. Note that for the adhesive layer 5 for which the logarithmic decrement ΔE is measured, the exterior material for the power storage device is immersed in 15% hydrochloric acid, the base material layer and barrier layer are dissolved, and the sample is thoroughly dried and used as the measurement subject.

It is also possible to obtain the exterior material for an electricity storage device from the electricity storage device and measure the logarithmic decrement ΔE of the adhesive layer 5. When obtaining the exterior material for an electricity storage device from the electricity storage device and measuring the logarithmic decrement ΔE of the adhesive layer 5, a sample is cut out from the top surface portion where the exterior material for an electricity storage device has not been stretched by molding and used as the measurement subject.

The logarithmic attenuation rate ΔE is calculated by the following formula.
ΔE = [ln(A1/A2) + ln(A2/A3) + ... ln(An/An+1)] / n
A: Amplitude n: Wave number

The adhesive layer 5 is formed of a resin capable of bonding the barrier layer 3 and the heat-sealable resin layer 4. The resin used to form the adhesive layer 5 may be, for example, the same adhesive as that exemplified for the adhesive layer 2. The resin used to form the adhesive layer 5 preferably contains a polyolefin skeleton, and examples thereof include the polyolefin and acid-modified polyolefin exemplified for the first heat-sealable resin layer 41 described above. The resin constituting the adhesive layer 5 may contain a polyolefin skeleton, and the resin may be analyzed by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like, and the analysis method is not particularly limited. In addition, when the resin constituting the adhesive layer 5 is analyzed by infrared spectroscopy, a peak derived from maleic anhydride is preferably detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak derived from maleic anhydride is detected near a wave number of 1760 cm ^-1 and a wave number of 1780 cm ^-1 . However, if the degree of acid modification is low, the peak may be small and may not be detected. In that case, the resin may be analyzed by nuclear magnetic resonance spectroscopy.

The adhesive layer 5 can be formed from a thermoplastic resin or a cured product of a thermosetting resin, and is preferably formed from a thermoplastic resin.

From the viewpoint of firmly adhering the barrier layer 3 and the heat-sealable resin layer 4, the adhesive layer 5 preferably contains an acid-modified polyolefin. Particularly preferred examples of the acid-modified polyolefin include polyolefins modified with carboxylic acids or their anhydrides, polypropylenes modified with carboxylic acids or their anhydrides, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

From the viewpoint of reducing the thickness of the exterior material for an electric storage device while providing an exterior material for an electric storage device with excellent shape stability after molding, it is preferable that the adhesive layer 5 is a cured product of a resin composition containing an acid-modified polyolefin and a curing agent. Preferred examples of the acid-modified polyolefin include those mentioned above.

As described above, in the exterior material 10 for an electric storage device disclosed herein, it is preferable that the first heat-sealable resin layer 41 constituting the surface contains polyolefin, and the adhesive layer 5 contains acid-modified polyolefin.

The adhesive layer 5 is preferably a cured product of a resin composition containing an acid-modified polyolefin and at least one selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and a compound having an epoxy group, and is particularly preferably a cured product of a resin composition containing an acid-modified polyolefin and at least one selected from the group consisting of a compound having an isocyanate group and a compound having an epoxy group. The adhesive layer 5 is preferably at least one selected from the group consisting of polyurethane, polyester, and epoxy resin, and more preferably contains polyurethane and epoxy resin. As the polyester, for example, an amide ester resin is preferable. Amide ester resins are generally produced by the reaction of a carboxyl group and an oxazoline group. The adhesive layer 5 is more preferably a cured product of a resin composition containing at least one of these resins and the acid-modified polyolefin. In addition, if unreacted compounds having an isocyanate group, compounds having an oxazoline group, or curing agents such as epoxy resins remain in the adhesive layer 5, the presence of the unreacted compounds can be confirmed by a method selected from, for example, infrared spectroscopy, Raman spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), etc.

In order to further increase the adhesion between the barrier layer 3 and the adhesive layer 5, the adhesive layer 5 is preferably a cured product of a resin composition containing a curing agent having at least one selected from the group consisting of an oxygen atom, a heterocycle, a C=N bond, and a C-O-C bond. Examples of curing agents having a heterocycle include curing agents having an oxazoline group and curing agents having an epoxy group. Examples of curing agents having a C=N bond include curing agents having an oxazoline group and curing agents having an isocyanate group. Examples of curing agents having a C-O-C bond include curing agents having an oxazoline group, curing agents having an epoxy group, and polyurethane. The fact that the adhesive layer 5 is a cured product of a resin composition containing these curing agents can be confirmed by, for example, gas chromatography mass spectrometry (GCMS), infrared spectroscopy (IR), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), or other methods.

The compound having an isocyanate group is not particularly limited, but from the viewpoint of effectively increasing the adhesion between the barrier layer 3 and the adhesive layer 5, a polyfunctional isocyanate compound is preferably used. The polyfunctional isocyanate compound is not particularly limited as long as it has two or more isocyanate groups. Specific examples of polyfunctional isocyanate-based curing agents include pentane diisocyanate (PDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymerized or nurated versions of these, mixtures of these, and copolymers with other polymers. Other examples include adducts, biuret forms, and isocyanurates.

The content of the compound having an isocyanate group in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, in the resin composition constituting the adhesive layer 5. This effectively improves the adhesion between the barrier layer 3 and the adhesive layer 5.

The compound having an oxazoline group is not particularly limited as long as it has an oxazoline skeleton. Specific examples of compounds having an oxazoline group include those having a polystyrene main chain and those having an acrylic main chain. In addition, examples of commercially available products include the Epocross series manufactured by Nippon Shokubai Co., Ltd.

The proportion of the compound having an oxazoline group in the adhesive layer 5 is preferably in the range of 0.1 to 50 mass % in the resin composition constituting the adhesive layer 5, and more preferably in the range of 0.5 to 40 mass %. This effectively improves the adhesion between the barrier layer 3 and the adhesive layer 5.

An example of a compound having an epoxy group is an epoxy resin. The epoxy resin is not particularly limited as long as it is a resin capable of forming a crosslinked structure by the epoxy group present in the molecule, and any known epoxy resin can be used. The weight average molecular weight of the epoxy resin is preferably about 50 to 2000, more preferably about 100 to 1000, and even more preferably about 200 to 800. In this disclosure, the weight average molecular weight of the epoxy resin is a value measured by gel permeation chromatography (GPC) under conditions using polystyrene as a standard sample.

Specific examples of epoxy resins include glycidyl ether derivatives of trimethylolpropane, bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, novolac glycidyl ether, glycerin polyglycidyl ether, polyglycerin polyglycidyl ether, etc. One type of epoxy resin may be used alone, or two or more types may be used in combination.

The proportion of epoxy resin in the adhesive layer 5 is preferably in the range of 0.1 to 50 mass % in the resin composition constituting the adhesive layer 5, and more preferably in the range of 0.5 to 40 mass %. This effectively improves the adhesion between the barrier layer 3 and the adhesive layer 5.

There are no particular limitations on the polyurethane, and any known polyurethane can be used. The adhesive layer 5 may be, for example, a cured product of a two-component curing polyurethane.

The proportion of polyurethane in the adhesive layer 5 is preferably in the range of 0.1 to 50 mass % in the resin composition constituting the adhesive layer 5, and more preferably in the range of 0.5 to 40 mass %. This effectively improves the adhesion between the barrier layer 3 and the adhesive layer 5 in an atmosphere containing components that induce corrosion of the barrier layer, such as an electrolyte.

In addition, when the adhesive layer 5 is a cured product of a resin composition containing at least one selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and an epoxy resin, and the acid-modified polyolefin, the acid-modified polyolefin functions as a main agent, and the compound having an isocyanate group, the compound having an oxazoline group, and the compound having an epoxy group each function as a curing agent.

From the viewpoint of exhibiting high insulating properties after the heat-sealing of the heat-sealing resin layer, the total thickness of the adhesive layer 5 and the heat-sealing resin layer 4 is preferably about 50 μm or more, more preferably about 60 μm or more, and even more preferably about 70 μm or more, and is preferably about 120 μm or less, and more preferably about 100 μm or less, with preferred ranges being about 50 to 120 μm, about 50 to 100 μm, about 60 to 120 μm, about 60 to 100 μm, about 70 to 120 μm, and about 70 to 100 μm.

In addition, the preferred ratio between the thickness of the first heat-sealable resin layer 41 and the thickness of the second heat-sealable resin layer 42 is such that, when the thickness of the first heat-sealable resin layer 41 is 1.0, the thickness of the second heat-sealable resin layer 42 is preferably approximately 1.5 to 6.0, more preferably approximately 1.7 to 5.5, and even more preferably approximately 2.0 to 5.0. In addition, the preferred ratio of the thickness of the adhesive layer 5 to the thickness of the first heat-sealable resin layer 41 to the thickness of the second heat-sealable resin layer 42 is preferably such that, with the thickness of the first heat-sealable resin layer 41 being 1.0, the thickness of the adhesive layer 5 is about 0.5 to 3.0 and the thickness of the second heat-sealable resin layer 42 is about 1.5 to 6.0, more preferably the thickness of the adhesive layer 5 is about 0.7 to 2.3 and the thickness of the second heat-sealable resin layer 42 is about 1.7 to 5.5, and even more preferably the thickness of the adhesive layer 5 is about 1.0 to 2.0 and the thickness of the second heat-sealable resin layer 42 is about 2.0 to 5.0.

Specific examples of preferred ratios between the thickness of the first heat-sealable resin layer 41 and the thickness of the second heat-sealable resin layer 42 include, for example, when the thickness of the first heat-sealable resin layer 41 is 1.0, the thickness of the second heat-sealable resin layer 42 is 2.0, 2.7, 3.0, 4.0, 5.0, 6.0, etc. In addition, preferred specific examples of the thickness of the adhesive layer 5, the first heat-sealable resin layer 41, and the second heat-sealable resin layer 42 include a thickness of the adhesive layer 5 of 1.0 and a thickness of the second heat-sealable resin layer 42 of 2.0, a thickness of the adhesive layer 5 of 1.7 and a thickness of the second heat-sealable resin layer 42 of 2.7, a thickness of the adhesive layer 5 of 1.3 and a thickness of the second heat-sealable resin layer 42 of 3.0, and a thickness of the adhesive layer 5 of 2.0 and a thickness of the second heat-sealable resin layer 42 of 5.0.

From the viewpoint of exhibiting high insulation after the heat fusion of the heat fusion resin layer, the thickness of the adhesive layer 5 may be greater than the thickness of the first heat fusion resin layer 41. For example, when the heat fusion resin layer 4 is composed of a single layer of the first heat fusion resin layer 41, the thickness of the adhesive layer 5 is preferably equal to or greater than the thickness of the first heat fusion resin layer 41. The first heat fusion resin layer 41 is preferably made of a resin that flows more easily at high temperatures than the adhesive layer 5 so as to have excellent heat fusion properties. By providing such a thickness relationship, the first heat fusion resin layer 41, which is a part of the heat fusion resin layer 4 and is made of a resin that flows easily, can be made thin, thereby increasing the insulation of the exterior material for the electric storage device. By appropriately adjusting the MFR, melting point, molecular weight, etc. of the resin that constitutes the first heat fusion resin layer 41, it is possible to make the first heat fusion resin layer 41 a resin layer that flows easily at high temperatures.

In addition, in the exterior material for an electric storage device 10 of the present disclosure, when the heat-sealable resin layer 4 includes a first heat-sealable resin layer 41 and a second heat-sealable resin layer 42, it is preferable that the thickness of the second heat-sealable resin layer 42 is greater than the thickness of the adhesive layer 5. Since the second heat-sealable resin layer 42 has better moisture barrier properties than the adhesive layer 5 that contributes to adhesion, providing such a thickness relationship can improve the moisture barrier properties of the exterior material for an electric storage device.

From the viewpoint of exhibiting high insulating properties after heat fusion of the heat-sealable resin layer, it is preferable that the thickness of the second heat-sealable resin layer 42 is greater than the thickness of the adhesive layer 5, and that the thickness of the adhesive layer 5 is greater than the thickness of the first heat-sealable resin layer 41.

The thickness of the adhesive layer 5 is preferably about 60 μm or less, about 50 μm or less, about 40 μm or less, about 30 μm or less, about 20 μm or less, about 10 μm or less, about 8 μm or less, about 5 μm or less, about 3 μm or less, and preferably about 0.1 μm or more, about 0.5 μm or more, about 5 μm or more, about 10 μm or more, about 20 μm or more. The thickness range is preferably about 0.1 to 60 μm, about 0.1 to 50 μm, about 0.1 to 40 μm, about 0.1 to 30 μm, about 0.1 to 20 μm, about 0.1 μm to 10 μm, or about 0.1 to 8 μm. , about 0.1 to 5 μm, about 0.1 to 3 μm, about 0.5 to 60 μm, about 0.5 to 50 μm, about 0.5 to 40 μm, about 0.5 to 30 μm, about 0.5 to 20 μm, about 0.5 μm to 10 μm, about 0.5 to 8 μm, about 0.5 to 5 μm, about 0.5 to 3 μm, about 5 to 60 μm, about 5 to 50 μm, about 5 to 40 μm, about 5 to 30 μm, about 5 to 20 μm, about 5 μm to 10 μm, about 5 to 8 μm, about 10 to 60 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 30 μm, and about 10 to 20 μm. More specifically, in the case of the adhesive layer 2 or the cured product of an acid-modified polyolefin and a curing agent, the thickness is preferably about 1 to 10 μm, more preferably 1 μm or more and less than 10 μm, even more preferably about 1 to 8 μm, even more preferably about 1 to 5 μm, and even more preferably about 1 to 3 μm. In addition, in the case of using the resin exemplified in the first heat-sealable resin layer 41, the thickness is preferably about 2 to 60 μm, about 2 to 50 μm, about 10 to 60 μm, about 10 to 50 μm, about 10 to 30 μm, about 20 to 60 μm, about 20 to 50 μm, and about 20 to 30 μm. In addition, in the case of the adhesive layer 5 being the adhesive layer 2 or the cured product of a resin composition containing an acid-modified polyolefin and a curing agent, for example, the adhesive layer 5 can be formed by applying the resin composition and curing it by heating or the like. In addition, when using the resin exemplified for the first heat-sealable resin layer 41, it can be formed, for example, by extrusion molding of the heat-sealable resin layer 4 and the adhesive layer 5.

Specific examples of preferred laminated structures on the side of the barrier layer 3 opposite the substrate layer 1 side in the exterior material 10 for an electric storage device of the present disclosure include, in order from the barrier layer 3 side, a laminated structure in which an adhesive layer 5 having a thickness of about 20 to 60 μm and a first heat-sealable resin layer 41 having a thickness of about 20 to 50 μm are laminated; a laminated structure in which an adhesive layer 5 having a thickness of about 20 to 60 μm and a first heat-sealable resin layer 41 having a thickness of about 20 to 40 μm are laminated; a laminated structure in which an adhesive layer 5 having a thickness of about 5 to 30 μm, a second heat-sealable resin layer 42 having a thickness of about 30 to 80 μm, and a first heat-sealable resin layer 41 having a thickness of about 5 to 25 μm are laminated; and a laminated structure in which an adhesive layer 5 having a thickness of about 5 to 20 μm, a second heat-sealable resin layer 42 having a thickness of about 40 to 80 μm, and a first heat-sealable resin layer 41 having a thickness of about 5 to 25 μm are laminated.

[Surface coating layer 6]
The exterior material for an electricity storage device according to the present disclosure may, if necessary, have a surface coating layer 6 on the substrate layer 1 (the side of the substrate layer 1 opposite to the barrier layer 3) for the purpose of improving at least one of design, electrolyte resistance, scratch resistance, formability, etc. The surface coating layer 6 is a layer located on the outermost layer side of the exterior material for an electricity storage device when an electricity storage device is assembled using the exterior material for an electricity storage device.

The surface coating layer 6 can be formed from a resin such as polyvinylidene chloride, polyester, polyurethane, acrylic resin, or epoxy resin.

When the resin forming the surface coating layer 6 is a curable resin, the resin may be either a one-component curable type or a two-component curable type, but is preferably a two-component curable type. Examples of two-component curable resins include two-component curable polyurethane, two-component curable polyester, and two-component curable epoxy resin. Among these, two-component curable polyurethane is preferred.

Examples of two-component curing polyurethanes include polyurethanes containing a base agent containing a polyol compound and a curing agent containing an isocyanate compound. Preferred examples include two-component curing polyurethanes that use a polyol such as polyester polyol, polyether polyol, or acrylic polyol as the base agent and an aromatic or aliphatic polyisocyanate as the curing agent. In addition, it is preferable to use a polyester polyol that has hydroxyl groups on the side chain in addition to the terminal hydroxyl groups of the repeating unit as the polyol compound. Since the surface coating layer 6 is formed from polyurethane, excellent electrolyte resistance is imparted to the exterior material for the electricity storage device.

At least one of the surface and the interior of the surface coating layer 6 may contain additives such as the above-mentioned lubricants, antiblocking agents, matting agents, flame retardants, antioxidants, tackifiers, and antistatic agents, depending on the functionality to be provided to the surface of the surface coating layer 6 and its surface, as necessary. Examples of additives include fine particles with an average particle size of about 0.5 nm to 5 μm. The average particle size of the additive is the median size measured by a laser diffraction/scattering type particle size distribution measuring device.

The additives may be either inorganic or organic. There are also no particular limitations on the shape of the additives, and examples of such shapes include spherical, fibrous, plate-like, amorphous, and scaly.

Specific examples of additives include talc, silica, graphite, kaolin, montmorillonite, mica, hydrotalcite, silica gel, zeolite, aluminum hydroxide, magnesium hydroxide, zinc oxide, magnesium oxide, aluminum oxide, neodymium oxide, antimony oxide, titanium oxide, cerium oxide, calcium sulfate, barium sulfate, calcium carbonate, calcium silicate, lithium carbonate, calcium benzoate, calcium oxalate, magnesium stearate, alumina, carbon black, carbon nanotubes, high melting point nylon, acrylate resin, cross-linked acrylic, cross-linked styrene, cross-linked polyethylene, benzoguanamine, gold, aluminum, copper, nickel, etc. The additives may be used alone or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferable from the viewpoint of dispersion stability and cost. In addition, the additives may be subjected to various surface treatments such as insulation treatment and high dispersibility treatment.

The method for forming the surface coating layer 6 is not particularly limited, and examples include a method of applying a resin that forms the surface coating layer 6. When an additive is added to the surface coating layer 6, a resin mixed with the additive may be applied.

The thickness of the surface coating layer 6 is not particularly limited as long as it exhibits the above-mentioned functions of the surface coating layer 6, and may be, for example, about 0.5 to 10 μm, and preferably about 1 to 5 μm.

3. Manufacturing method of the exterior material for an electric storage device The manufacturing method of the exterior material for an electric storage device is not particularly limited as long as a laminate in which each layer included in the exterior material for an electric storage device of the present invention is laminated can be obtained, and an example of the manufacturing method includes a method including a step of laminating at least a base layer 1, a barrier layer 3, and a heat-sealable resin layer 4 in this order. In the manufacturing method of the exterior material for an electric storage device 10 of the present disclosure, the heat-sealable resin layer 4 is composed of a single layer or multiple layers, and the adhesive layer 5 has a logarithmic decrement ΔE of 0.22 or less at 120° C. in a rigid pendulum measurement. The details of the exterior material for an electric storage device 10 of the present disclosure are as described above.

An example of the manufacturing method of the exterior material for a power storage device of the present invention is as follows. First, a laminate (hereinafter, sometimes referred to as "laminate A") is formed in which a base layer 1, an adhesive layer 2, and a barrier layer 3 are laminated in this order. Specifically, the laminate A can be formed by a dry lamination method in which the adhesive used to form the adhesive layer 2 is applied to the base layer 1 or to the barrier layer 3, the surface of which has been chemically treated as necessary, by a coating method such as gravure coating or roll coating, and then dried, and the barrier layer 3 or base layer 1 is laminated and the adhesive layer 2 is cured.

Next, the heat-sealable resin layer 4 is laminated on the barrier layer 3 of the laminate A. When the heat-sealable resin layer 4 is directly laminated on the barrier layer 3, the heat-sealable resin layer 4 may be laminated on the barrier layer 3 of the laminate A by a method such as thermal lamination or extrusion lamination. When an adhesive layer 5 is provided between the barrier layer 3 and the heat-sealable resin layer 4, for example, (1) a method of laminating the adhesive layer 5 and the heat-sealable resin layer 4 by extruding them on the barrier layer 3 of the laminate A (co-extrusion lamination method, tandem lamination method), (2) a method of separately forming a laminate in which the adhesive layer 5 and the heat-sealable resin layer 4 are laminated, and laminating this on the barrier layer 3 of the laminate A by a thermal lamination method, or a method of forming a laminate in which the adhesive layer 5 is laminated on the barrier layer 3 of the laminate A, and laminating this with the heat-sealable resin layer 4 by a thermal lamination method. (3) a method in which a molten adhesive layer 5 is poured between the barrier layer 3 of the laminate A and a heat-sealable resin layer 4 previously formed into a sheet, and the laminate A and the heat-sealable resin layer 4 are bonded together via the adhesive layer 5 (sandwich lamination method); (4) a method in which an adhesive for forming the adhesive layer 5 is solution-coated on the barrier layer 3 of the laminate A, and then the adhesive is dried or baked, and the heat-sealable resin layer 4 previously formed into a sheet is laminated on the adhesive layer 5.

When the surface coating layer 6 is provided, the surface coating layer 6 is laminated on the surface of the substrate layer 1 opposite the barrier layer 3. The surface coating layer 6 can be formed, for example, by applying the above-mentioned resin that forms the surface coating layer 6 to the surface of the substrate layer 1. The order of the step of laminating the barrier layer 3 on the surface of the substrate layer 1 and the step of laminating the surface coating layer 6 on the surface of the substrate layer 1 is not particularly limited. For example, after the surface coating layer 6 is formed on the surface of the substrate layer 1, the barrier layer 3 may be formed on the surface of the substrate layer 1 opposite the surface coating layer 6.

As described above, a laminate is formed that includes, in this order, the optional surface coating layer 6, the substrate layer 1, the optional adhesive layer 2, the barrier layer 3, the adhesive layer 5, and the heat-sealable resin layer 4. In order to strengthen the adhesion of the optional adhesive layer 2 and the adhesive layer 5, the laminate may be subjected to a heat treatment.

In the exterior material for an electricity storage device, each layer constituting the laminate may be subjected to a surface activation treatment such as corona treatment, blast treatment, oxidation treatment, or ozone treatment, as necessary, to improve the suitability for processing. For example, by subjecting the surface of the base layer 1 opposite the barrier layer 3 to corona treatment, the printability of the ink on the surface of the base layer 1 can be improved.

The exterior material for an electricity storage device according to the present disclosure is used in a package for hermetically housing an electricity storage device element such as a positive electrode, a negative electrode, an electrolyte, etc. In other words, an electricity storage device can be formed by housing an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte in a package formed from the exterior material for an electricity storage device according to the present disclosure.

Specifically, an electricity storage device element having at least a positive electrode, a negative electrode, and an electrolyte is covered with the exterior material for an electricity storage device of the present disclosure in such a manner that a flange portion (a region where the heat-sealable resin layers contact each other) can be formed on the periphery of the electricity storage device element with the metal terminals connected to each of the positive electrode and negative electrode protruding outward, and the heat-sealable resin layers of the flange portion are heat-sealed to provide an electricity storage device using the exterior material for an electricity storage device. Note that when an electricity storage device element is housed in a package formed from the exterior material for an electricity storage device of the present disclosure, the package is formed so that the heat-sealable resin portion of the exterior material for an electricity storage device of the present disclosure faces inside (the surface in contact with the electricity storage device element).

The exterior material for an electric storage device of the present disclosure can be suitably used for an electric storage device such as a battery (including a condenser, a capacitor, etc.). The exterior material for an electric storage device of the present disclosure may be used for either a primary battery or a secondary battery, but is preferably a secondary battery. The type of secondary battery to which the exterior material for an electric storage device of the present disclosure is applied is not particularly limited, and examples thereof include lithium ion batteries, lithium ion polymer batteries, all-solid-state batteries, lead-acid batteries, nickel-hydrogen batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, condensers, capacitors, etc. Among these secondary batteries, the exterior material for an electric storage device of the present disclosure is suitably applied to lithium ion batteries and lithium ion polymer batteries.

The present disclosure will be described in detail below with reference to examples and comparative examples. However, the present disclosure is not limited to the examples.

<Production of exterior materials for power storage devices>
Example 1 and Comparative Example 1
As the substrate layer, a polyethylene terephthalate (PET) film (thickness 12 μm) and an oriented nylon (ONy) film (thickness 15 μm) were prepared, and a two-liquid type urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to the PET film (3 μm) and bonded to the ONy film. In addition, an aluminum foil (JIS H4160: 1994 A8021H-O (thickness 40 μm)) was prepared as the barrier layer. Next, a two-liquid type urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to one side of the aluminum foil to form an adhesive layer (thickness 3 μm) on the barrier layer. Next, the adhesive layer on the barrier layer and the substrate layer (ONy film side) were laminated by a dry lamination method, and then aging treatment was performed to produce a substrate layer/adhesive layer/barrier layer laminate. Both sides of the aluminum foil were subjected to a chemical conversion treatment. The chemical conversion treatment of the aluminum foil was performed by applying a treatment solution consisting of a phenolic resin, a chromium fluoride compound, and phosphoric acid to both sides of the aluminum foil by roll coating so that the amount of chromium applied was 10 mg/ ^m2 (dry mass), and then baking.

Next, on the barrier layer of each laminate obtained above, maleic anhydride modified polypropylene as an adhesive layer (thickness 20 μm), random polypropylene as a second heat-sealable resin layer (thickness 50 μm), and random polypropylene as a first heat-sealable resin layer (thickness 10 μm) were co-extruded to laminate the adhesive layer/second heat-sealable resin layer/first heat-sealable resin layer on the barrier layer, thereby obtaining an exterior material for a storage device in which the substrate layer (thickness 30 μm including adhesive)/adhesive layer (3 μm)/barrier layer (40 μm)/adhesive layer (20 μm)/second heat-sealable resin layer (50 μm)/first heat-sealable resin layer (10 μm) are laminated in this order. The adhesive layers of Example 1 and Comparative Example 1 each have the logarithmic attenuation factor ΔE at 120°C (value measured using a rigid pendulum type physical property tester) shown in Table 1.

Example 2 and Comparative Example 2
As the substrate layer, a polyethylene terephthalate (PET) film (thickness 12 μm) and an oriented nylon (ONy) film (thickness 15 μm) were prepared, and a two-liquid type urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to the PET film (3 μm) and bonded to the ONy film. In addition, an aluminum foil (JIS H4160: 1994 A8021H-O (thickness 40 μm)) was prepared as the barrier layer. Next, a two-liquid type urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to one side of the aluminum foil to form an adhesive layer (thickness 3 μm) on the barrier layer. Next, the adhesive layer on the barrier layer and the substrate layer (ONy film side) were laminated by a dry lamination method, and then aging treatment was performed to produce a substrate layer/adhesive layer/barrier layer laminate. Both sides of the aluminum foil were subjected to a chemical conversion treatment. The chemical conversion treatment of the aluminum foil was performed by applying a treatment solution consisting of a phenolic resin, a chromium fluoride compound, and phosphoric acid to both sides of the aluminum foil by roll coating so that the amount of chromium applied was 10 mg/ ^m2 (dry mass), and then baking.

Next, on the barrier layer of each laminate obtained above, maleic anhydride modified polypropylene as an adhesive layer (thickness 30 μm), random polypropylene as a second heat-sealable resin layer (thickness 40 μm), and random polypropylene as a first heat-sealable resin layer (thickness 10 μm) were co-extruded to laminate the adhesive layer/second heat-sealable resin layer/first heat-sealable resin layer on the barrier layer, thereby obtaining an exterior material for a storage device in which the base layer (thickness 30 μm including adhesive)/adhesive layer (3 μm)/barrier layer (40 μm)/adhesive layer (30 μm)/second heat-sealable resin layer (40 μm)/first heat-sealable resin layer (10 μm) are laminated in this order. The adhesive layers of Example 2 and Comparative Example 2 each have the logarithmic attenuation factor ΔE at 120°C (value measured using a rigid pendulum type physical property tester) shown in Table 1.

Example 3
As the substrate layer, a polyethylene terephthalate (PET) film (thickness 12 μm) and an oriented nylon (ONy) film (thickness 15 μm) were prepared, and a two-liquid type urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to the PET film (3 μm) and bonded to the ONy film. In addition, an aluminum foil (JIS H4160: 1994 A8021H-O (thickness 40 μm)) was prepared as the barrier layer. Next, a two-liquid type urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to one side of the aluminum foil to form an adhesive layer (thickness 3 μm) on the barrier layer. Next, the adhesive layer on the barrier layer and the substrate layer (ONy film side) were laminated by a dry lamination method, and then aging treatment was performed to produce a substrate layer/adhesive layer/barrier layer laminate. Both sides of the aluminum foil were subjected to a chemical conversion treatment. The chemical conversion treatment of the aluminum foil was performed by applying a treatment solution consisting of a phenolic resin, a chromium fluoride compound, and phosphoric acid to both sides of the aluminum foil by roll coating so that the amount of chromium applied was 10 mg/ ^m2 (dry mass), and then baking.

Next, on the barrier layer of each laminate obtained above, maleic anhydride modified polypropylene as an adhesive layer (thickness 10 μm), random polypropylene as a second heat-sealable resin layer (thickness 60 μm), and random polypropylene as a first heat-sealable resin layer (thickness 10 μm) were co-extruded to laminate the adhesive layer/second heat-sealable resin layer/first heat-sealable resin layer on the barrier layer, thereby obtaining an exterior material for a storage device in which the substrate layer (thickness 30 μm including adhesive)/adhesive layer (3 μm)/barrier layer (40 μm)/adhesive layer (10 μm)/second heat-sealable resin layer (60 μm)/first heat-sealable resin layer (10 μm) are laminated in this order. The adhesive layer of Example 3 has the logarithmic attenuation factor ΔE at 120°C (value measured using a rigid pendulum type physical property tester) shown in Table 1.

Example 4
An exterior material for a power storage device was obtained in the same manner as in Example 1, except that a polyethylene terephthalate (PET) film (thickness 25 μm) was used as the base material layer instead of a laminate of a polyethylene terephthalate (PET) film (thickness 12 μm) and an oriented nylon (ONy) film (thickness 15 μm). The exterior material was formed in the same manner as in Example 1, in which the base material layer (thickness 25 μm)/adhesive layer (3 μm)/barrier layer (40 μm)/adhesive layer (20 μm)/second heat-sealable resin layer (50 μm)/first heat-sealable resin layer (10 μm) were laminated in that order.

Example 5
An exterior material for a power storage device was obtained in the same manner as in Example 1, in which the base material layer (thickness 25 μm)/adhesive layer (3 μm)/barrier layer (40 μm)/adhesive layer (20 μm)/second heat-sealable resin layer (50 μm)/first heat-sealable resin layer (10 μm) were laminated in this order, except that a stretched nylon (ONy) film (thickness 25 μm) was used as the base material layer instead of a laminate of a polyethylene terephthalate (PET) film (thickness 12 μm) and a stretched nylon (ONy) film (thickness 15 μm).

Example 6 and Comparative Example 3
As the substrate layer, a polyethylene terephthalate (PET) film (thickness 12 μm) and an oriented nylon (ONy) film (thickness 15 μm) were prepared, and a two-liquid type urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to the PET film (3 μm) and bonded to the ONy film. In addition, an aluminum foil (JIS H4160: 1994 A8021H-O (thickness 40 μm)) was prepared as the barrier layer. Next, a two-liquid type urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to one side of the aluminum foil to form an adhesive layer (thickness 3 μm) on the barrier layer. Next, the adhesive layer on the barrier layer and the substrate layer (ONy film side) were laminated by a dry lamination method, and then aging treatment was performed to produce a substrate layer/adhesive layer/barrier layer laminate. Both sides of the aluminum foil were subjected to a chemical conversion treatment. The chemical conversion treatment of the aluminum foil was performed by applying a treatment solution consisting of a phenolic resin, a chromium fluoride compound, and phosphoric acid to both sides of the aluminum foil by roll coating so that the amount of chromium applied was 10 mg/ ^m2 (dry mass), and then baking.

Next, maleic anhydride modified polypropylene as an adhesive layer (40 μm thick) and random polypropylene as a first heat-sealable resin layer (40 μm thick) were co-extruded onto the barrier layer of each laminate obtained above, thereby laminating the adhesive layer/first heat-sealable resin layer on the barrier layer, thereby obtaining an exterior material for a storage device in which the substrate layer (30 μm thick including the adhesive)/adhesive layer (3 μm)/barrier layer (40 μm)/adhesive layer (40 μm)/first heat-sealable resin layer (40 μm) are laminated in this order. The adhesive layers of Example 6 and Comparative Example 3 each have the logarithmic attenuation factor ΔE at 120°C (value measured using a rigid pendulum type physical property tester) shown in Table 2.

<Measurement of logarithmic decrement ΔE of adhesive layer>
Each of the electrical storage device exterior materials obtained above was cut into a rectangle with a width (TD: transverse direction) of 15 mm and a length (MD: machine direction) of 45 mm to obtain a test sample (electrical storage device exterior material 10). The MD of the electrical storage device exterior material corresponds to the rolling direction (RD) of the aluminum alloy foil, and the TD of the electrical storage device exterior material corresponds to the TD of the aluminum alloy foil, and the rolling direction (RD) of the aluminum alloy foil can be determined from the rolling grain. When the MD of the electrical storage device exterior material cannot be specified from the rolling grain of the aluminum alloy foil, it can be specified by the following method. As a method for confirming the MD of the electrical storage device exterior material, a cross section of the heat-sealable resin layer of the electrical storage device exterior material is observed with an electron microscope to confirm the sea-island structure, and the direction parallel to the cross section in which the average diameter of the island shape in the direction perpendicular to the thickness direction of the heat-sealable resin layer is maximum can be determined as the MD. Specifically, the sea-island structure is confirmed by observing the cross section in the longitudinal direction of the heat-sealable resin layer and each cross section (total of 10 cross sections) at an angle of 10 degrees from the direction parallel to the cross section in the longitudinal direction to the direction perpendicular to the cross section in the longitudinal direction. Next, the shape of each island is observed in each cross section. The straight line distance connecting the leftmost end in the direction perpendicular to the thickness direction of the heat-sealable resin layer to the rightmost end in the perpendicular direction is defined as the diameter y. The average of the diameters y of the top 20 island shapes in order of the largest diameter y in each cross section is calculated. The direction parallel to the cross section with the largest average diameter y of the island shapes is determined as the MD. A schematic diagram for explaining the method of measuring the logarithmic decrement ΔE by rigid pendulum measurement is shown in FIG. 7. A rigid pendulum type physical property tester (model number: RPT-3000W manufactured by A & D Co., Ltd.) was used, FRB-100 was used for the frame of the pendulum 30, RBP-060 was used for the cylindrical cylinder edge 30a of the edge portion, CHB-100 was used for the cold block 31, and a vibration displacement detector 32 and a weight 33 were used, and the initial amplitude was set to 0.3 degrees. The measurement surface (adhesive layer) of the test sample was placed on the cold block 31 facing upward, and the axial direction of the cylindrical cylinder edge 30a with the pendulum 30 on the measurement surface was set so as to be perpendicular to the MD direction of the test sample. In addition, in order to prevent the test sample from floating or warping during measurement, tape was attached to a place on the cold block 31 that does not affect the measurement results of the test sample and fixed on the cold block 31. The cylindrical cylinder edge 30a was brought into contact with the surface of the adhesive layer. Next, the logarithmic decrement ΔE of the adhesive layer was measured using the cold block 31 at a temperature rise rate of 3 ° C. / min in the temperature range from 30 ° C. to 200 ° C. The logarithmic attenuation factor ΔE was adopted when the surface temperature of the adhesive layer of the test sample (electrical storage device exterior material 10) reached 120°C. (The test sample that had been measured once was not used, and the average value of measurements taken three times (N = 3) using newly cut samples was used.) For the adhesive layer, each of the electrical storage device exterior materials obtained above was immersed in 15% hydrochloric acid to dissolve the base material layer and aluminum foil, and the test sample consisting of only the adhesive layer and the heat-sealable resin layer was thoroughly dried to measure the logarithmic attenuation factor ΔE. The logarithmic attenuation factors ΔE at 120°C are shown in Tables 1 and 2, respectively. The logarithmic attenuation factor ΔE is calculated by the following formula.
ΔE=[ln(A1/A2)+ln(A2/A3)+. ． ． + ln(An/An+1)/n
A: Amplitude n: Wave number

[Insulation evaluation (wire short circuit test)]
As shown in FIG. 6, each of the exterior materials for power storage devices obtained in the above manufacturing examples was cut to prepare a strip of 40 mm wide x 100 mm long, which was used as a test sample (exterior material for power storage devices 10) (FIG. 6(a)). Meanwhile, a stainless steel wire 11 having a diameter of 25 μm and a length of 70 mm was placed in the center of the width direction of an aluminum plate 12 having a width of 30 mm, a length of 100 mm, and a thickness of 100 μm (FIG. 6(b)). Next, the heat-sealable resin layer side of the test sample and the wire 11 side of the aluminum plate 12 were placed so as to face each other (FIG. 6(c)). At this time, the center of the width direction of the test sample and the center of the width direction of the aluminum plate 12 were aligned. Next, the positive pole of the tester was connected to the aluminum plate 12, and the negative pole was connected to the test sample. For the negative pole of the tester, an alligator clip was clamped from the base layer side of the test sample to reach the barrier layer, and the negative pole of the tester and the barrier layer were electrically connected. The tester was prepared so that a continuity (short circuit) signal would be generated when the applied voltage was 100 V and the resistance was 200 MΩ or less. Next, a voltage of 100 V was applied between the testers, and the stainless steel wire 11 was interposed between the aluminum plate 12 and the test sample, and the wire was heat-sealed at 190° C., 1 MPa, and a width of 7 mm so as to be perpendicular to the wire (the shaded area in FIG. 6(c) is the heat-sealed area S), and the time until the short circuit signal was generated was measured. Five measurements were made, and the average value of the three points was calculated, excluding the longest and shortest points. The results are shown in Tables 1 and 2.

In Tables 1 and 2, DL indicates the adhesive that bonds the polyethylene terephthalate film and the stretched nylon film.

As is clear from the results shown in Tables 1 and 2, the electrical storage device packaging materials of Examples 1-6 have an adhesive layer bonding the barrier layer and the heat-sealable resin layer with a logarithmic decrement ΔE of 0.22 or less at 120°C, a long time until a short circuit occurs in a wire short circuit test, and high insulation is demonstrated after the heat-sealable resin layer is heat-sealed.

As described above, the present disclosure provides the following aspects of the invention.
Item 1. The laminate includes at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order.
The adhesive layer has a logarithmic decrement ΔE of 0.22 or less at 120° C. in a rigid pendulum measurement.
Item 2. The packaging material for an electricity storage device according to Item 1, wherein a total thickness of the adhesive layer and the heat-sealable resin layer is 50 μm or more.
Item 3. The exterior material for an electricity storage device according to Item 1 or 2, wherein a resin constituting the adhesive layer contains a polyolefin skeleton.
Item 4. The exterior material for an electricity storage device according to any one of Items 1 to 3, wherein the adhesive layer has a thickness of 50 μm or less.
Item 5. The thermally adhesive resin layer is composed of a single layer or multiple layers,
Item 5. The thickness of the adhesive layer is equal to or greater than the thickness of a first heat-sealable resin layer constituting the surface of the laminate, among the heat-sealable resin layers. The exterior material for a storage device according to any one of items 1 to 4.
Item 6. The packaging material for an electricity storage device according to Item 5, wherein the first heat-sealable resin layer has a thickness of 5 μm or more and 25 μm or less.
Item 7. The packaging material for an electricity storage device according to Item 5 or 6, wherein a lubricant is present on a surface of the first heat-sealable resin layer.
Item 8. The heat-sealable resin layer includes, in order from the surface side of the laminate, at least the first heat-sealable resin layer and the second heat-sealable resin layer,
Item 8. The electrical storage device packaging material according to any one of items 1 to 7, wherein the second heat-sealable resin layer has a thickness greater than a thickness of the adhesive layer.
Item 9. The packaging material for an electricity storage device according to Item 8, wherein a thickness of the second heat-sealable resin layer is greater than a thickness of the first heat-sealable resin layer.
Item 10. The method includes a step of laminating at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order to obtain a laminate,
The method for producing an exterior material for an electricity storage device, wherein the adhesive layer has a logarithmic decrement ΔE of 0.22 or less at 120° C. in a rigid pendulum measurement.
Item 11. An electricity storage device, in which an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed from the exterior material for an electricity storage device according to any one of Items 1 to 9.

Reference Signs List 1: Base material layer 2: Adhesive layer 3: Barrier layer 4: Heat-sealable resin layer 5: Adhesive layer 6: Surface coating layer 10: Exterior material for an electricity storage device 41: First heat-sealable resin layer 42: Second heat-sealable resin layer

Claims (1)

The laminate is made of at least a base layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer, in this order.
The adhesive layer has a logarithmic decrement ΔE of 0.22 or less at 120° C. in a rigid pendulum measurement.