JP2024056802A - Exterior material for power storage device, manufacturing method thereof, and power storage device - Google Patents

Abstract

To provide an exterior packaging material for a power storage device, in which a matte design due to a surface coating layer containing a filler is prevented from being damaged by heat sealing.SOLUTION: An exterior material for a power storage device is composed of a laminate including, in order from the outside, at least a surface coating layer, a base material layer, a barrier layer, and a heat-fusible resin layer, and the surface coating layer includes a resin and a filler, and the hardness of the outer surface of the surface coating layer measured by a nanoindentation method in a 190°C environment is 14.5 MPa or more.SELECTED DRAWING: None

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, generally, recesses are 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 (thermally 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

In exterior materials for power storage devices that are composed of film-like laminates, a surface coating layer containing a filler may be provided on the outside of the base layer to give the outer surface a matte design.

However, when sealing an electricity storage device element using an exterior material for an electricity storage device, if a heat-sealing member (e.g., a metal heat seal bar) is used to apply heat and pressure from above the surface coating layer to heat-seal the heat-sealable resin layer, the uneven surface of the surface coating layer formed by the filler is crushed, resulting in a problem that the matte design of the heat-sealed portion is lost.

Under these circumstances, the main objective of the present disclosure is to provide an exterior material for an electricity storage device in which the matte design of the surface coating layer containing a filler is prevented from being damaged by heat sealing.

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 composed of a laminate including, in order from the outside, at least a surface coating layer, a base material layer, a barrier layer, and a heat-sealable resin layer, in which the surface coating layer contains a resin and a filler, and in which the hardness of the outer surface of the surface coating layer measured by the nanoindentation method in a 190°C environment is 14.5 MPa or more, suppresses the matte design provided by the surface coating layer containing the filler from being damaged by heat sealing.

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 includes, in order from the outside, at least a surface coating layer, a base layer, a barrier layer, and a heat-sealable resin layer,
The surface coating layer includes a resin and a filler,
An exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment.

According to the present disclosure, it is possible to provide an exterior material for an electricity storage device in which the matte design of the surface coating layer containing the filler is prevented from being damaged by heat sealing. In addition, according to the present disclosure, it is also possible to provide a manufacturing method for the exterior material for an electricity storage device, and an electricity storage device using the exterior material for 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. FIG. 1 is a schematic diagram for explaining a method for evaluating a matte finish design after heat sealing.

The exterior material for an electric storage device disclosed herein is composed of a laminate including, in order from the outside, at least a surface coating layer, a base material layer, a barrier layer, and a heat-sealable resin layer, and the surface coating layer contains a resin and a filler, and is characterized in that the hardness of the outer surface of the surface coating layer measured by a nanoindentation method in a 190°C environment is 14.5 MPa or more. By having this configuration, the exterior material for an electric storage device disclosed herein is prevented from damaging the matte design provided by the surface coating layer containing the filler due to heat sealing.

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 and physical properties of the exterior material for an electric storage device The exterior material for an electric storage device 10 of the present disclosure is composed of a laminate including, in order from the outside, a surface coating layer 6, a base material layer 1, a barrier layer 3, and a heat-sealable resin layer 4, as shown in, for example, FIG. 1 to FIG. 3. In the exterior material for an electric storage device 10, the surface coating layer 6 is the outermost layer, and the heat-sealable resin layer 4 is the innermost layer. When assembling an electric storage device using the exterior material for an electric storage device 10 and an electric storage device element, the heat-sealable resin layers 4 of the exterior material for an electric storage device 10 are opposed to each other, and the electric storage device element is accommodated in a space formed by heat-sealing the periphery. In the laminate constituting the exterior material for an electric storage device 10 of the present disclosure, the barrier layer 3 is used as a reference, and the heat-sealable resin layer 4 side is the inner side relative to the barrier layer 3, and the surface coating layer 6 side is the outer side relative to the barrier layer 3.

As shown in Figs. 2 and 3, the exterior material 10 for an electrical 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. In addition, although not shown, a colored layer may be provided between the base layer 1 and the barrier layer 3. In addition, as shown in Fig. 3, for example, an adhesive layer 5 may be provided between the barrier layer 3 and the heat-sealable resin layer 4, if necessary, for the purpose of increasing the adhesion between these layers.

The thickness of the laminate constituting the exterior material for electricity storage devices 10 is not particularly limited, but from the viewpoints of cost reduction and energy density improvement, the upper limit is preferably about 180 μm or less, about 160 μm or less, about 155 μm or less, about 140 μm or less, about 130 μm or less, and about 120 μm or less, and from the viewpoints of maintaining the function of the exterior material for electricity storage devices to protect the electricity storage device elements, the lower limit is preferably about 35 μm or more, about 45 μm or more, about 60 μm or more, and about 80 μm or more, and preferred ranges are, for example, about 35 to 180 μm, 35 to 1 Examples of the thickness include about 60 μm, about 35 to 155 μm, about 35 to 140 μm, about 35 to 130 μm, about 35 to 120 μm, about 45 to 180 μm, about 45 to 160 μm, about 45 to 155 μm, about 45 to 140 μm, about 45 to 130 μm, about 45 to 120 μm, about 60 to 180 μm, about 60 to 160 μm, about 60 to 155 μm, about 60 to 140 μm, about 60 to 130 μm, about 60 to 120 μm, about 80 to 180 μm, about 80 to 160 μm, about 80 to 155 μm, about 80 to 140 μm, about 80 to 130 μm, and about 80 to 120 μm. Among these, about 80 to 130 μm is particularly preferable.

In the exterior material 10 for an electric storage device disclosed herein, the hardness of the outer surface of the surface coating layer 6 is 14.5 MPa or more when measured by nanoindentation in a 190°C environment. In the exterior material 10 for an electric storage device, the surface coating layer 6 has the above-mentioned hardness in a very high-temperature environment of 190°C, which prevents the matte design of the surface coating layer 6 containing the filler from being damaged by heat sealing.

The hardness measured by the nanoindentation method in a 190°C environment may be 14.5 MPa or more, but from the viewpoint of more effectively preventing the matte design from being damaged by heat sealing (hereinafter sometimes referred to as the viewpoint of the matte design), it is preferably about 18 MPa or more, and also preferably about 150 MPa or less, more preferably about 120 MPa or less, and preferred ranges include about 15 to 150 MPa, about 15 to 120 MPa, about 18 to 150 MPa, and about 18 to 120 MPa. Among these, about 18 to 120 MPa is particularly preferred. The hardness measured by the nanoindentation method in a 190°C environment is measured as follows.

[Hardness measured by nanoindentation method in 190°C environment]
The hardness is measured using a nanoindenter (for example, HYSITRON's "TI950 TriboIndenter"). A Berkovich indenter (for example, TI-0064) is used as the indenter of the nanoindenter. First, in a relative humidity of 50% and a temperature of 190° C., the indenter is applied to the surface of the surface coating layer of the exterior material for an electrical storage device (the surface where the measurement target is exposed, and perpendicular to the thickness direction of each layer) from a direction parallel to the thickness direction, and the indenter is pressed into the surface coating layer from the surface to a load of 25 μN over 10 seconds, and the state is maintained for 15 seconds, and then the load is removed over 10 seconds. The average value of N=5 measured by shifting the measurement point is taken as the hardness. The surface into which the indenter is pressed is the part exposed on the surface of the exterior material for an electrical storage device. The sample is fixed using a commercially available instant adhesive. In the cross-sectional structures of the exterior packaging material for an electricity storage device according to the present disclosure in Figs. 1 to 3, the up-down direction corresponds to the thickness direction of each layer.

The hardness measured by nanoindentation in a 190°C environment can be adjusted by the composition (type and content of resin) of the resin composition forming the surface coating layer 6, the curing conditions, the molecular weight, the number of functional groups, the crosslinking density, the bulkiness of the substituents, etc.

In addition, from the viewpoint of achieving the above-mentioned matte design and further improving moldability at room temperature, the exterior material 10 for an electrical storage device of the present disclosure has a resin hardness of the surface coating layer 6, as measured by a nanoindentation method in a cross section in the thickness direction of the surface coating layer 6 in a 23°C environment, of preferably about 420.4 MPa or less, more preferably about 350.4 MPa or less, and even more preferably about 310.4 MPa or less, and also preferably about 25.5 MPa or more, more preferably about 50.0 MPa or more, and even more preferably about 100.0 MPa or more. More preferably, it is about 150.0 MPa or more, and preferred ranges include about 22.5 to 420.4 MPa, about 22.5 to 350.4 MPa, about 22.5 to 310.4 MPa, about 50.0 to 420.4 MPa, about 50.0 to 350.4 MPa, about 50.0 to 310.4 MPa, about 100.0 to 420.4 MPa, about 100.0 to 350.4 MPa, about 100.0 to 310.4 MPa, about 150.0 to 420.4 MPa, about 150.0 to 350.4 MPa, and about 150.0 to 310.4 MPa. Among these, about 150.0 to 310.4 MPa is particularly preferred. In the present invention, excellent formability means, more specifically, that the matte design of the surface coating layer is prevented from being damaged by molding the exterior material 10 for an electrical storage device, and that cracks and peeling of the surface coating layer due to room temperature molding are prevented. The hardness measured by the nanoindentation method in a 23°C environment is measured as follows.

[Hardness measured by nanoindentation method in a 23°C environment]
The hardness is measured using a nanoindenter (for example, HYSITRON's "TI950 TriboIndenter"). A Berkovich indenter (for example, TI-0039) is used as the indenter of the nanoindenter. First, in an environment of 50% relative humidity and 23°C, the indenter is applied to the surface of the surface coating layer of the exterior material for an electrical storage device (the surface where the surface coating layer is exposed, and the surface is parallel to the thickness direction of each layer (see thickness direction W in Figures 1 to 3)) from a direction perpendicular to the thickness direction, and the indenter is pressed into the surface coating layer from the surface up to a load of 50 μN over 10 seconds, and the state is maintained for 5 seconds, and then the load is removed over 10 seconds. The average value of N=5 measured at different measurement points is taken as the hardness. The surface into which the indenter is pressed is a resin portion where a cross section of the surface coating layer (cross section in the thickness direction of the surface coating layer) is exposed, the cross section being obtained by cutting the exterior material for an electricity storage device in the thickness direction so as to pass through the center (which may be near the center). The cutting is performed using a commercially available rotary microtome.

The hardness measured by nanoindentation in a 23°C environment can be adjusted by the composition (resin type, content) of the resin composition forming the surface coating layer 6, the curing conditions, molecular weight, number of functional groups, crosslinking density, bulkiness of the substituents, etc.

In addition, from the viewpoint of the above-mentioned matte design, in the exterior material 10 for an electric storage device of the present disclosure, the arithmetic average roughness Ra ₁ of the outer surface of the surface coating layer 6 is preferably about 0.30 μm or more, more preferably about 0.40 μm or more, and even more preferably 0.50 or more, and is preferably about 0.90 μm or less, more preferably about 0.80 μm or less, and even more preferably about 0.70 μm or less, and preferred ranges include about 0.30 to 0.90 μm, about 0.30 to 0.80 μm, about 0.30 to 0.70 μm, about 0.40 to 0.90 μm, about 0.40 to 0.80 μm, about 0.40 to 0.70 μm, about 0.50 to 0.90 μm, about 0.50 to 0.80 μm, and about 0.50 to 0.70 μm. Among these, about 0.50 to 0.70 μm is particularly preferred. In addition, the ratio Ra2/Ra1 of the arithmetic mean roughness Ra2 of the outer surface of the surface coating layer 6 after the outer surface of the surface coating layer 6 is heated and pressed using a stainless steel plate under conditions of a temperature of 190°C, a surface pressure of 0.5 MPa, and a time of 6 seconds to the arithmetic mean roughness _Ra1 of the outer surface of the surface coating layer ₆ before the outer surface of the surface coating _layer is heated and pressed is preferably 0.7 or more. The upper limit of _the ratio _Ra2 / _Ra1 is not particularly limited, and examples thereof include 1.0 and 0.95.

2. Layers forming the exterior material for an electricity storage device [Surface coating layer 6]
The exterior material for an electricity storage device 10 of the present disclosure has a surface coating layer 6 on the outside of the base material layer 1 for the purpose of imparting a matte design to the outer surface of the exterior material for an electricity storage device 10. The surface coating layer 6 is a layer located as the outermost layer of the exterior material for an electricity storage device 10 when an electricity storage device is assembled using the exterior material for an electricity storage device 10.

The surface coating layer 6 contains a resin and a filler. Examples of the filler include inorganic fillers and organic fillers. The surface coating layer 6 may contain one type of filler or two or more types of fillers. It is also preferable to use inorganic fillers and organic fillers in combination. The shape of the filler is not particularly limited, and examples include spherical, fibrous, plate-like, amorphous, and scaly shapes.

The average particle diameter of the filler is not particularly limited, but from the viewpoint of providing the exterior material 10 for an electrical storage device with a matte design, it is, for example, about 0.01 to 5 μm. The average particle diameter of the filler is the median diameter measured with a laser diffraction/scattering type particle size distribution measuring device. The average particle diameter of the filler is preferably equal to or less than the thickness of the surface coating layer 6.

The inorganic filler is not particularly limited as long as it can give the surface coating layer 6 a matte finish, and examples of the inorganic filler include particles of silica, talc, 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, gold, aluminum, copper, nickel, and the like. Among these, silica particles are particularly preferred.

The organic filler is not particularly limited as long as it can give the surface coating layer 6 a matte finish, and examples of such fillers include particles of nylon, polyacrylate, polystyrene, polyethylene, benzoguanamine, or crosslinked products thereof.

In the measurement of the above-mentioned [hardness measured by nanoindentation in a 23°C environment], the hardness of the organic filler contained in the surface coating layer 6 can also be measured by pressing the indenter into the surface at a location where the organic filler is present and the cross section of the surface coating layer is exposed, obtained by cutting the exterior material for an electricity storage device in the thickness direction through the center (which may be near the center). From the viewpoint of the matte design and moldability, the hardness of the organic filler measured in this manner is preferably about 300.0 MPa or more, more preferably about 400.0 MPa or more, and also preferably about 1500.4 MPa or less, more preferably about 1000.4 MPa or less, and even more preferably about 600.4 MPa or less. Preferred ranges include about 300.0 to 1500.4 MPa, about 300.0 to 1000.4 MPa, about 300.0 to 600.4 MPa, about 400.0 to 1500.4 MPa, about 400.0 to 1000.4 MPa, and about 400.0 to 600.4 MPa. Of these, about 400.0 to 600.4 MPa is particularly preferred.

The amount of filler contained in the surface coating layer 6 is not particularly limited, as long as the hardness measured by the nanoindentation method in a 190°C environment is 14.5 MPa or more. However, the amount is preferably about 3 parts by mass or more, more preferably about 10 parts by mass or more, and is preferably about 30 parts by mass or less, more preferably about 20 parts by mass or less, relative to 100 parts by mass of the resin in the resin composition that forms the surface coating layer 6. Preferred ranges include about 3 to 30 parts by mass, about 3 to 20 parts by mass, about 10 to 30 parts by mass, and about 10 to 20 parts by mass.

The resin contained in the resin composition forming the surface coating layer 6 is not particularly limited, but is preferably a curable resin, as long as the hardness measured by the nanoindentation method in a 190°C environment is 14.5 MPa or more. In other words, the surface coating layer 6 is preferably composed of a cured product of a resin composition containing a curable resin and a filler.

The curable resin may be either a one-component curing type or a two-component curing type, but is preferably a two-component curing type. Examples of two-component curing resins include two-component curing polyurethane, two-component curing polyester, and two-component curing epoxy resin. Among these, two-component curing polyurethane is preferred.

Examples of two-component curing polyurethane include polyurethanes containing a base material containing a polyol compound and a curing agent containing an isocyanate compound. Two-component curing polyurethanes are preferably used in which a polyol such as polyester polyol, polyether polyol, and acrylic polyol is used as the base material, 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 hydroxyl group at the end of the repeating unit as the polyol compound. Examples of curing agents include aliphatic, alicyclic, aromatic, and araliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Further examples include polyfunctional isocyanate modified products made from one or more of these diisocyanates. Furthermore, polymers (e.g., trimers) can also be used as polyisocyanate compounds. Examples of such polymers include adducts, biurets, and nurates. Note that an aliphatic isocyanate compound refers to an isocyanate that has an aliphatic group and no aromatic ring, an alicyclic isocyanate compound refers to an isocyanate that has an alicyclic hydrocarbon group, and an aromatic isocyanate compound refers to an isocyanate that has an aromatic ring.

In the resin composition forming the surface coating layer 6, when the resin is a polyurethane containing a base agent containing a polyol compound and a curing agent containing an isocyanate compound, for example, the hardness measured by the nanoindentation method in a 190°C environment and a 23°C environment can be adjusted by adjusting the ratio of the base agent to the curing agent.

At least one of the surface and the interior of the surface coating layer 6 may further contain additives such as lubricants, colorants, antiblocking agents, flame retardants, antioxidants, tackifiers, and antistatic agents, as described below, depending on the functionality to be provided to the surface of the surface coating layer 6.

When the surface coating layer 6 contains a colorant, known colorants such as pigments and dyes can be used as the colorant. 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 surface coating layer 6 include the same ones exemplified in the [Adhesive layer 2] column. Furthermore, the preferred content of the colorant contained in the surface coating layer 6 is also the same as the content described in the [Adhesive layer 2] column.

The method for forming the surface coating layer 6 is not particularly limited, and examples include a method of applying a resin composition 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.

From the viewpoint of the above-mentioned matte design, the thickness of the surface coating layer 6 is preferably 0.5 μm or more, more preferably 1 μm or more, and is preferably 10 μm or less, more preferably 5 μm or less, with preferred ranges being about 0.5 to 10 μm, about 0.5 to 5 μm, about 1 to 10 μm, and about 1 to 5 μm.

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 surface coating layer 6. 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 surface coating layer 6, 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 surface coating layer 6 may be a lubricant that has been exuded from the surface coating layer 6, or a lubricant that has been applied to the surface of the surface coating layer 6.

[Base layer 1]
In the present disclosure, the substrate layer 1 is a layer provided for the purpose of, for example, exhibiting the function as a substrate of the exterior material for an electricity storage device. The substrate layer 1 is located between the surface coating layer 6 and the barrier layer 3 of the exterior material for an electricity storage device 10. In addition, in the case where the adhesive layer 2 is provided, the substrate layer 1 is located between the surface coating layer 6 and the adhesive layer 2.

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 resins such as polyester, polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, and phenolic 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 copolymers of 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 preferred 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.

The thickness of the substrate layer 1 is not particularly limited as long as it functions as a substrate, but examples of the thickness include about 3 to 50 μm, about 3 to 35 μm, and about 3 to 25 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 is 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.

Examples of polyurethane adhesives include polyurethane adhesives containing a base agent containing a polyol compound and a curing agent containing an isocyanate compound. Two-part curing polyurethane adhesives are 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 hydroxyl group at the end of the repeating unit as the polyol compound. Examples of curing agents include aliphatic, alicyclic, aromatic, and araliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Further examples include polyfunctional isocyanate modified products made from one or more of these diisocyanates. Furthermore, a polymer (e.g., a trimer) can also be used as the polyisocyanate compound. Examples of such polymers include adducts, biurets, and nurates. The adhesive layer 2 is formed from a polyurethane adhesive, which gives the exterior material for the power storage device excellent electrolyte resistance, and prevents the base layer 1 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 the lower limit is, for example, about 1 μm or more, about 2 μm or more, the upper limit is about 10 μm or less, about 5 μm or less, and preferred ranges are 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. Also, 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 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 exemplified 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 the 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 suppressing the occurrence of pinholes and cracks during molding of the exterior material for electric storage devices, the aluminum alloy foil is preferably a soft aluminum alloy foil composed of, for example, an annealed aluminum alloy, and from the viewpoint of more effectively suppressing the occurrence of pinholes and cracks during molding, 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%, more preferably 0.5 to 2.0 mass%. By having an iron content of 0.1 mass% or more, it is possible to obtain an exterior material for electric storage devices in which the occurrence of pinholes and cracks during molding is effectively suppressed. By having an iron content of 9.0 mass% or less, it is possible to obtain an exterior material for electric storage devices with better flexibility. 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. Furthermore, from the viewpoint of suppressing the occurrence of pinholes and cracks during the molding of the exterior material for the electricity storage device, 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.

The thickness of the barrier layer 3, in the case of a metal foil, should be such that it at least functions as a barrier layer to prevent the penetration of moisture, and may be, for example, approximately 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 preferably about 10 μm or more, more preferably about 20 μm or more, and more preferably about 25 μm or more, with the thickness being preferably in the range of 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, with about 25 to 40 μm being particularly preferred. When the barrier layer 3 is made of an aluminum alloy foil, the above-mentioned range is particularly preferred. In particular, when the barrier layer 3 is made of stainless steel foil, the upper limit of 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 the lower limit 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 that at least the surface opposite to the base layer is provided with a corrosion-resistant film 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 by performing, for example, hydrothermal conversion 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. The treatment for forming the corrosion-resistant film may be one type, or two or more types may be combined. In addition, it is possible to form not only one layer but also multiple layers. Furthermore, among these treatments, hydrothermal conversion 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. Note that these treatments may be included in the definition of chemical conversion treatment. In addition, when the barrier layer 3 has a corrosion-resistant film, the corrosion-resistant film 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 consisting 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 and used.

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 a paint-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 electricity storage device of the present disclosure, the heat-sealable resin layer 4 corresponds to the innermost layer and is a layer (sealant layer) that functions to seal the electricity storage device elements by heat-sealing the heat-sealable resin layers to each other when the electricity storage device is assembled.

The resin constituting the heat-sealable resin layer 4 is not particularly limited as long as it is heat-sealable, but is preferably a resin containing a polyolefin skeleton such as polyolefin or acid-modified polyolefin. The resin constituting the heat-sealable resin layer 4 can be analyzed to contain a polyolefin skeleton, for example, by infrared spectroscopy, gas chromatography mass spectrometry, etc. In addition, when the resin constituting the heat-sealable resin layer 4 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 heat-sealable resin layer 4 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.

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 heat-sealable resin layer 4 may be formed of one type of resin alone, or may be formed of a blend polymer of two or more types of resin. Furthermore, the heat-sealable resin layer 4 may be formed of only one layer, or may be formed of two or more layers of the same or different resins.

The heat-sealable resin layer 4 may also contain a lubricant, etc., if necessary. When the heat-sealable resin layer 4 contains a lubricant, the occurrence of pinholes and cracks during molding of the exterior material for the power storage device can be suppressed. 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 in 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 heat-fusible resin layer 4, the amount of the lubricant is not particularly limited, but from the viewpoint of suppressing the occurrence of pinholes and cracks during molding of the exterior material for an electricity storage device, the amount is preferably about 10 to 50 mg/ ^m2 , and more preferably about 15 to 40 mg/ ^m2 .

The lubricant present on the surface of the heat-sealable resin layer 4 may be a lubricant exuded from the resin that constitutes the heat-sealable resin layer 4, or a lubricant applied to the surface of the heat-sealable resin layer 4.

The thickness of the heat-sealable resin layer 4 is not particularly limited as long as the heat-sealable resin layers are heat-sealed to each other to seal the electricity storage device element, but may be, for example, about 100 μm or less, preferably about 85 μm or less, and more preferably about 15 to 85 μm. For example, when the thickness of the adhesive layer 5 described below is 10 μm or more, the thickness of the heat-sealable resin layer 4 is preferably about 85 μm or less, and more preferably about 15 to 45 μm. For example, when the thickness of the adhesive layer 5 described below is less than 10 μm or when the adhesive layer 5 is not provided, the thickness of the heat-sealable resin layer 4 is preferably about 20 μm or more, and more preferably about 35 to 85 μm.

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

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 heat-sealable resin layer 4. The resin constituting the adhesive layer 5 may contain a polyolefin skeleton, for example, by 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, it can be analyzed by nuclear magnetic resonance spectroscopy.

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.

Furthermore, from the viewpoint of making the electrical storage device exterior material thin while providing an electrical storage device exterior material with excellent shape stability after molding, it is more 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.

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 the first 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.

The upper limit of the thickness of the adhesive layer 5 is preferably about 50 μm or less, about 40 μm or less, about 30 μm or less, about 20 μm or less, or about 5 μm or less, and the lower limit is preferably about 0.1 μm or more, or about 0.5 μm or more. The thickness range is preferably 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 to 5 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, or about 0.5 to 5 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 about 1 to 5 μm. In addition, when the resin exemplified in the heat-fusible resin layer 4 is used, the thickness is preferably about 2 to 50 μm, more preferably about 10 to 40 μm. For example, when the adhesive layer 5 is formed from an acid-modified polyolefin, the thickness of the adhesive layer 5 is preferably about 2 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more. In addition, for example, when the adhesive layer 5 is formed from an acid-modified polyolefin, the thickness of the adhesive layer 5 is preferably about 50 μm or less, more preferably 40 μm or less. In addition, for example, when the adhesive layer 5 is formed from an acid-modified polyolefin, the preferred range of the thickness of the adhesive layer 5 is about 2 to 50 μm, about 2 to 40 μm, about 5 to 50 μm, about 5 to 40 μm, about 8 to 50 μm, or about 8 to 40 μm. In addition, when the adhesive layer 5 is an adhesive exemplified in the adhesive layer 2 or a 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 as the heat-sealable resin layer 4, the heat-sealable resin layer 4 and the adhesive layer 5 can be formed, for example, by extrusion molding.

3. Manufacturing method of the exterior material for a power storage device The manufacturing method of the exterior material for a power storage device is not particularly limited as long as a laminate is obtained by laminating each layer included in the exterior material for a power storage device of the present invention, and includes a method including a step of obtaining a laminate in which, from the outside, at least the surface coating layer 6, the base layer 1, the barrier layer 3, and the heat-sealable resin layer 4 are laminated. Specifically, the manufacturing method of the exterior material for a power storage device of the present disclosure includes a step of obtaining a laminate in which, from the outside, at least the surface coating layer 6, the base layer 1, the barrier layer 3, and the heat-sealable resin layer 4 are laminated, the surface coating layer 6 contains a resin and a filler, and the hardness of the outer surface of the surface coating layer 6 measured by the nanoindentation method in a 190° C. environment is 14.5 MPa or more.

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.

Next, a surface coating layer 6 is laminated on the surface of the substrate layer 1 opposite to the barrier layer 3. The surface coating layer 6 can be formed, for example, by applying the above-mentioned resin composition for forming the surface coating layer 6 to the surface of the substrate layer 1 and curing it. 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 forming the surface coating layer 6 on the surface of the substrate layer 1, the barrier layer 3 may be formed on the surface of the substrate layer 1 opposite to the surface coating layer 6.

As described above, a laminate is formed that includes, from the outside, the surface coating layer 6, the base layer 1, the adhesive layer 2 (optional), the barrier layer 3, the adhesive layer 5 (optional), and the heat-sealable resin layer 4. In order to strengthen the adhesion of the adhesive layer 2 and the adhesive layer 5 (optional), a heat treatment may be further performed. Also, as described above, a colored layer may be provided between the base layer 1 and the barrier layer 3.

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, suitable applications of the exterior material for an electric storage device of the present disclosure include 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]
A stretched nylon (ONy) film (thickness 15 μm) was prepared as the substrate layer. An aluminum foil (JIS H4160:1994 A8021H-O (thickness 35 μm)) was prepared as the barrier layer. Next, the barrier layer and the substrate layer were laminated by a dry lamination method using an adhesive (a two-liquid type urethane adhesive containing a colorant) described later, 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 a roll coating method so that the amount of chromium applied was 10 mg/m ² (dry mass), and baking.

Next, maleic anhydride modified polypropylene as an adhesive layer (thickness 20 μm) and random polypropylene as a heat-sealable resin layer (thickness 20 μm) were co-extruded onto the barrier layer of each of the laminates obtained above, thereby laminating an adhesive layer/heat-sealable resin layer on the barrier layer. Furthermore, the following resin composition 1 was applied to the surface of the substrate layer of the obtained laminate to a thickness of 3 μm, and cured under the formation conditions of a temperature of 40°C to 100°C for 3 days to form a matte surface coating layer, and an exterior material for a power storage device was obtained consisting of a laminate (total thickness 96 μm) in which, from the outside, the surface coating layer (3 μm)/substrate layer (thickness 15 μm)/adhesive layer (3 μm)/barrier layer (35 μm)/adhesive layer (20 μm)/heat-sealable resin layer (20 μm) were laminated.

[Example 2]
An exterior material for an electricity storage device was obtained in the same manner as in Example 1, except that in forming the surface coating layer, the following resin composition 2 was used instead of resin composition 1 to form the surface coating layer.

[Example 3]
An exterior material for a power storage device was obtained in the same manner as in Example 1, except that in forming the surface coating layer, the following resin composition 3 was used instead of resin composition 1 to form the surface coating layer.

[Example 4]
An exterior material for an electricity storage device was obtained in the same manner as in Example 1, except that in forming the surface coating layer, the following resin composition 4 was used instead of resin composition 1 to form the surface coating layer.

[Example 5]
An exterior material for an electricity storage device was obtained in the same manner as in Example 1, except that in forming the surface coating layer, the following resin composition 5 was used instead of resin composition 1 to form the surface coating layer.

[Example 6]
An exterior material for an electricity storage device was obtained in the same manner as in Example 1, except that in forming the surface coating layer, the following resin composition 6 was used instead of resin composition 1 to form the surface coating layer.

[Comparative Example 1]
An exterior material for an electricity storage device was obtained in the same manner as in Example 1, except that in forming the surface coating layer, the following resin composition 7 was used instead of resin composition 1 to form the surface coating layer.

<Resin composition used in forming surface coating layer and forming conditions>
(Resin Composition 1 (Used in Example 1))
A resin composition containing a resin (polyurethane formed from a mixture of two types of polyol compounds and an aromatic isocyanate compound), an inorganic filler (silica particles, average particle size 1 μm), an organic filler (average particle size 2 μm), and an olefin wax.

(Resin Composition 2 (Used in Example 2))
A resin composition containing a resin (polyurethane formed from a mixture of two types of polyol compounds and an aliphatic isocyanate compound), an inorganic filler (silica particles, average particle size 1 μm), an organic filler (average particle size 2 μm), and an olefin wax.

Resin Composition 3 (Used in Example 3)
A resin composition containing a resin (polyurethane formed from a mixture of two types of polyol compounds and an aromatic isocyanate compound (the blending ratio of the two types of polyol compounds was changed from that of resin composition 1)), an inorganic filler (silica particles, average particle diameter 1 μm), an organic filler (average particle diameter 2 μm), and an olefin wax.

Resin Composition 4 (Used in Example 4)
A resin composition in which the content of the olefin wax in the resin composition of Example 3 is ¼

Resin Composition 5 (Used in Example 5)
A resin composition in which the content of the olefin wax in the resin composition of Example 3 is 1/8

Resin Composition 6 (Used in Example 6)
Resin composition of Example 3 containing no olefin wax

(Resin Composition 7 (Used in Comparative Example 1))
A resin composition comprising 100 parts by mass of a resin (polyurethane formed from a mixture of one type of polyol compound and an aliphatic isocyanate compound), 10 parts by mass of an inorganic filler (barium sulfate particles, average particle diameter 1 μm), and an organic filler (average particle diameter 2 μm).

[Hardness measured by nanoindentation method in 190°C environment]
The hardness was measured using a nanoindenter (HYSITRON's "TI950 TriboIndenter"). A Berkovich indenter (TI-0064) was used as the indenter of the nanoindenter. First, in a relative humidity of 50% and a temperature of 190° C., the indenter was applied to the surface of the surface coating layer of the exterior material for a power storage device (the surface on which the measurement target is exposed, perpendicular to the thickness direction of each layer) from a direction parallel to the thickness direction, and the indenter was pressed into the surface coating layer from the surface to a load of 25 μN over 10 seconds, and the state was held for 15 seconds, and then the load was removed over 10 seconds. The average value of N=5 measured by shifting the measurement point was taken as the hardness. The results are shown in Table 1. The surface into which the indenter was pressed was the part exposed on the surface of the exterior material for a power storage device. The sample was fixed using a commercially available instant adhesive. The measurement results were rounded off to one decimal place.

[Hardness measured by nanoindentation method in a 23°C environment]
The hardness was measured using a nanoindenter (HYSITRON's "TI950 TriboIndenter"). A Berkovich indenter (TI-0039) was used as the indenter of the nanoindenter. First, in a relative humidity of 50% and a temperature of 23° C., the indenter was applied to the surface of the surface coating layer of the electrical storage device exterior material (the surface on which the surface coating layer is exposed, which is parallel to the thickness direction of each layer) from a direction perpendicular to the thickness direction, and the indenter was pressed into the surface coating layer from the surface to a load of 50 μN over 10 seconds, and the state was held for 5 seconds, and then the load was removed over 10 seconds. The average value of N=5 measured by shifting the measurement point was taken as the hardness. The results are shown in Table 1. The surface into which the indenter was pressed was a resin portion in which a cross section of the surface coating layer (a cross section in the thickness direction of the surface coating layer) was exposed, obtained by cutting the electrical storage device exterior material in the thickness direction so as to pass through the center (which may be near the center). In addition, in measuring the hardness of the surface coating layer, the portion where the indenter was pressed was a portion (resin portion) where no filler was present on the surface of the surface coating layer. The measurement results were rounded off to the nearest tenth. The organic filler contained in the surface coating layers of Examples 1-6 and Comparative Example 1 was the same, and the hardness of the surface coating layer of Example 2 measured by pressing the indenter into the portion where the organic filler was present was 496.1 MPa. Cutting was performed using a commercially available rotary microtome. The measurement results were rounded off to the nearest tenth.

[Evaluation of matte finish design after heat sealing]
As shown in the schematic diagram of FIG. 4, each electrical storage device exterior material was cut to 60 mm (TD direction) x 200 mm (MD direction) (FIG. 4a). Next, the electrical storage device exterior material was folded in half in the MD direction at the fold P (middle of the MD direction) so that the thermally adhesive resin layers faced each other (FIG. 4b). Next, the thermally adhesive resin layers were heat-sealed together at a heat seal width of 7 mm (a 7 mm wide stainless steel plate was used as the heat seal bar) about 10 mm inside in the MD direction under conditions of a temperature of 210°C, a surface pressure of 0.5 MPa, and 6 seconds (FIG. 4c). The shaded area S is the heat-sealed area. The difference in surface gloss between the shaded area and the area other than the shaded area was visually confirmed, and the matte design after heat sealing was evaluated according to the following criteria. The results are shown in Table 1.
A: In the heat sealed portion, the matte design before heat sealing was well maintained.
B: The heat sealed portion was glossy depending on the angle from which it was viewed, and the matte design before the heat sealing was somewhat diminished.
C: The heat sealed portion was glossy, and the matte design before the heat sealing was damaged.

[Measurement of arithmetic mean roughness _Ra1 , _Ra2 ]
For each electrical storage device exterior material before and after the above-mentioned [Evaluation of matte design after heat sealing], the arithmetic mean roughness _Ra1 of the surface coating layer (part to be heat sealed) before heat sealing of the surface coating layer and the arithmetic mean roughness _Ra2 of the heat sealed part of the surface coating layer after heat sealing were measured using an optical surface texture measuring instrument (New View 7300 manufactured by Zygo Corporation). The values of the arithmetic mean roughnesses _Ra1 and _Ra2 , and their ratio _Ra2 / _Ra1 (rate of change) are shown in Table 1.

[Moldability]
Each electrical storage device exterior material was cut into a rectangle with a length (MD) of 90 mm and a width (TD) of 150 mm to prepare a test sample. 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. The test sample was placed in a 25°C environment in a rectangular molding die (female die, the surface has a maximum height roughness (nominal value of Rz) of 3.2 μm as specified in Table 2 of the comparative surface roughness standard piece in JIS B 0659-1:2002 Annex 1 (Reference), corner R2.0 mm, ridgeline R1.0 mm) with an aperture of 31.6 mm (MD) x 54.5 mm (TD) and a corresponding molding die (male die, the surface of the ridgeline portion has a maximum height roughness (nominal value of Rz) of 1.6 μm as specified in Table 2 of the comparative surface roughness standard piece in JIS B 0659-1:2002 Annex 1 (Reference), corner R2.0 mm, ridgeline R1.0 mm). The maximum height roughness (nominal value of Rz) specified in Table 2 of the comparative surface roughness standard piece is 3.2 μm. Using a corner R2.0 mm, ridge R1.0 mm), cold molding (one-stage drawing molding) was performed on 10 test samples at a molding depth of 5 mm with a pressing pressure (surface pressure) of 0.9 MPa. At this time, the test sample was placed on a female mold so that the heat-fusible resin layer side was located on the male mold side and molding was performed. In addition, the clearance between the male mold and the female mold was 0.3 mm. For the test samples after cold molding, the matte design after molding was evaluated according to the following criteria. Note that the following criteria for evaluation A-C were applied when 6 or more (more than half) of the 10 test samples met these evaluation criteria. The results are shown in Table 1.
A: The matte design was well maintained even after molding, and there was no cracking or peeling of the surface coating layer.
B: After molding, the surface coating layer was not cracked or peeled off, but the surface of the surface coating layer became glossy, damaging the matte design.
C: After molding, gloss appeared on the surface of the surface coating layer, impairing the matte design, and furthermore cracks and peeling occurred in the surface coating layer.

The exterior material for an electricity storage device of Example 1-6 has a surface coating layer containing a resin and a filler, and the hardness of the outer surface of the surface coating layer measured by the nanoindentation method in a 190°C environment is 14.5 MPa or more. The exterior material for an electricity storage device of Example 1-6 prevents the matte design provided by the surface coating layer containing the filler from being damaged by heat sealing.

As described above, the present disclosure provides the following aspects of the invention.
Item 1. The laminate includes, in order from the outside, at least a surface coating layer, a base layer, a barrier layer, and a heat-sealable resin layer;
The surface coating layer includes a resin and a filler,
An exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment.
Item 2. The exterior material for a storage battery device according to Item 1, wherein a hardness of the resin of the surface coating layer is 420.4 MPa or less as measured by a nanoindentation method on a cross section in a thickness direction of the surface coating layer in a 23° C. environment.
Item 3. The exterior material for a storage battery device according to Item 1 or 2, wherein the hardness of the filler in the surface coating layer is 300.0 MPa or more as measured by a nanoindentation method on a cross section in a thickness direction of the surface coating layer in a 23° C. environment.
Item 4. The exterior material for an electricity storage device according to any one of Items 1 to 3, wherein the arithmetic mean roughness Ra ₁ of the outer surface of the surface coating layer is 0.3 μm or more.
Item 5. The exterior material for an electricity storage device according to any one of Items 1 to 4, wherein a ratio Ra 2 /Ra 1 of an arithmetic mean roughness Ra ₂ of the outer surface of the surface coating layer after the outer surface of the surface coating layer is heated and pressed using a stainless steel plate under conditions of a _temperature of 190° C., a surface pressure of _0.5 MPa, and a time period of 6 seconds to an arithmetic mean roughness Ra ₁ of the outer surface of the surface coating layer before the outer surface of the surface coating layer is heated and pressed is 0.7 or more.
Item 6. The exterior material for an electricity storage device according to any one of Items 1 to 5, further comprising an adhesive layer between the base layer and the barrier layer.
Item 7. The exterior material for an electricity storage device according to Item 6, wherein the adhesive layer is colored.
Item 8. The exterior material for an electricity storage device according to any one of Items 1 to 7, further comprising a colored layer between the base layer and the barrier layer.
Item 9. A method for producing an exterior material for an electricity storage device, comprising:
The method includes a step of obtaining a laminate in which at least a surface coating layer, a base layer, a barrier layer, and a thermally adhesive resin layer are laminated in this order from the outside,
The surface coating layer includes a resin and a filler,
A method for producing an exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment.
Item 10. 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 8.

REFERENCE SIGNS LIST 1 Base material layer 2 Adhesive layer 3 Barrier layer 4 Thermally adhesive resin layer 5 Adhesive layer 6 Surface coating layer 10 Exterior material for power storage device

Claims (18)

The laminate includes, in order from the outside, at least a surface coating layer, a base layer, a barrier layer, and a heat-sealable resin layer,
The surface coating layer includes a resin and a filler,
The surface coating layer contains a colorant,
An exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment. The laminate includes, in order from the outside, at least a surface coating layer, a base layer, a barrier layer, and a heat-sealable resin layer,
The surface coating layer includes a resin and a filler,
The surface coating layer contains titanium oxide,
An exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment. The laminate includes, in order from the outside, at least a surface coating layer, a base layer, a barrier layer, and a heat-sealable resin layer,
The surface coating layer includes a resin and a filler,
The surface coating layer contains silica,
An exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment. The laminate includes, in order from the outside, at least a surface coating layer, a base layer, a barrier layer, and a heat-sealable resin layer,
The surface coating layer includes a resin and a filler,
The surface coating layer contains kaolin,
An exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment. The laminate includes, in order from the outside, at least a surface coating layer, a base layer, a barrier layer, and a heat-sealable resin layer,
The surface coating layer includes a resin and a filler,
the surface coating layer contains at least two selected from the group consisting of silica, talc, 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, gold, aluminum, copper, and nickel;
An exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment. The exterior material for a power storage device according to any one of claims 1 to 5, wherein the hardness of the resin of the surface coating layer measured by nanoindentation method in a cross section in the thickness direction of the surface coating layer in a 23°C environment is 420.4 MPa or less. The exterior material for a storage battery device according to any one of claims 1 to 6, wherein the hardness of the filler in the surface coating layer, measured by nanoindentation method in a cross section in the thickness direction of the surface coating layer in a 23°C environment, is 300.0 MPa or more. The exterior material for an electricity storage device according to any one of claims 1 to 7, wherein the arithmetic mean roughness Ra ₁ of the outer surface of the surface coating layer is 0.3 µm or more. The exterior material for an electricity storage device according to any one of claims 1 to 8, wherein a ratio Ra 2 /Ra 1 of an arithmetic mean roughness Ra ₂ of the outer surface of the surface coating layer after the outer surface of the surface coating layer is heated and pressed using a stainless steel plate under conditions of a _temperature of 190°C, a surface pressure of 0.5 _MPa , and a time of 6 seconds to an arithmetic mean roughness Ra ₁ of the outer surface of the surface coating layer before the outer surface of the surface coating layer is heated and pressed is 0.7 or more. The exterior material for an electricity storage device according to any one of claims 1 to 9, comprising an adhesive layer between the base layer and the barrier layer. The exterior material for an electricity storage device according to claim 10, wherein the adhesive layer is colored. The exterior material for an electricity storage device according to any one of claims 1 to 11, which has a colored layer between the base layer and the barrier layer. A method for producing an exterior material for an electricity storage device, comprising:
The method includes a step of obtaining a laminate in which at least a surface coating layer, a base layer, a barrier layer, and a thermally adhesive resin layer are laminated in this order from the outside,
The surface coating layer includes a resin and a filler,
The surface coating layer contains a colorant,
A method for producing an exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment. A method for producing an exterior material for an electricity storage device, comprising:
The method includes a step of obtaining a laminate in which at least a surface coating layer, a base layer, a barrier layer, and a thermally adhesive resin layer are laminated in this order from the outside,
The surface coating layer includes a resin and a filler,
The surface coating layer contains titanium oxide,
A method for producing an exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment. A method for producing an exterior material for an electricity storage device, comprising:
The method includes a step of obtaining a laminate in which at least a surface coating layer, a base layer, a barrier layer, and a thermally adhesive resin layer are laminated in this order from the outside,
The surface coating layer includes a resin and a filler,
The surface coating layer contains silica,
A method for producing an exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment. A method for producing an exterior material for an electricity storage device, comprising:
The method includes a step of obtaining a laminate in which at least a surface coating layer, a base layer, a barrier layer, and a thermally adhesive resin layer are laminated in this order from the outside,
The surface coating layer includes a resin and a filler,
The surface coating layer contains kaolin,
A method for producing an exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment. A method for producing an exterior material for an electricity storage device, comprising:
The method includes a step of obtaining a laminate in which at least a surface coating layer, a base layer, a barrier layer, and a thermally adhesive resin layer are laminated in this order from the outside,
The surface coating layer includes a resin and a filler,
the surface coating layer contains at least two selected from the group consisting of silica, talc, 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, gold, aluminum, copper, and nickel;
A method for producing an exterior material for an electricity storage device, wherein the hardness of an outer surface of the surface coating layer is 14.5 MPa or more when measured by a nanoindentation method in a 190°C environment. An electricity storage device in which an electricity storage device element having 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 claims 1 to 12.