JP7830833B2 - Exterior material for energy storage devices and energy storage devices using the same - Google Patents

Description

This disclosure relates to an exterior material for energy storage devices and an energy storage device using the same.

As energy storage devices, secondary batteries such as lithium-ion batteries, nickel-metal hydride batteries, and lead-acid batteries, as well as electrochemical capacitors such as electric double-layer capacitors, are well known. Due to the miniaturization of portable devices and limitations on installation space, further miniaturization of energy storage devices is required, and lithium-ion batteries, with their high energy density, are attracting attention. While metal cans were conventionally used as the casing material for lithium-ion batteries, multilayer films, which are lightweight, have high heat dissipation, and can be manufactured at low cost, are now being used.

Lithium-ion batteries using the above-mentioned multilayer film as the outer casing are called laminate-type lithium-ion batteries. The outer casing covers the battery components (positive electrode, separator, negative electrode, electrolyte, etc.), preventing moisture from entering the interior. Laminate-type lithium-ion batteries are manufactured, for example, by forming a recess in a portion of the outer casing by cold molding, housing the battery components within the recess, folding back the remaining portion of the outer casing, and sealing the edges with heat seal (see, for example, Patent Document 1).

Japanese Patent Publication No. 2013-101765

Incidentally, research and development is underway on a next-generation battery, known as a solid-state battery, as an alternative to lithium-ion batteries. Solid-state batteries are characterized by using a solid electrolyte instead of an organic electrolyte. While lithium-ion batteries cannot be used at temperatures higher than the boiling point of the electrolyte (around 80°C), solid-state batteries can be used at temperatures exceeding 100°C, and their operation at high temperatures (e.g., 100-150°C) can increase the conductivity of lithium ions. Furthermore, using solid-state batteries reduces the space and cost required for a cooling system.

However, the inventors have discovered that when a laminate-type all-solid-state battery is manufactured using the multilayer film described above as the outer casing material, operating the resulting all-solid-state battery in a high-temperature environment leads to a decrease in the insulation properties of the outer casing material, making it susceptible to dielectric breakdown due to voltage application. It should be noted that current lithium-ion batteries are not used at high temperatures due to the use of electrolytes, so the above problem with the outer casing material when used in high-temperature environments has not been recognized as an issue until now. Furthermore, since the extraction of high voltage through bipolarization is being considered for all-solid-state batteries, the importance of insulation properties in the outer casing material will increase even further.

Furthermore, development is underway on other energy storage devices, such as lithium-ion capacitors, that are capable of high-temperature operation, not just solid-state batteries. Therefore, the casing materials for energy storage devices must be designed to resist dielectric breakdown even when the device is used in high-temperature environments.

This disclosure was made in view of the above-mentioned problems, and aims to provide an exterior material for energy storage devices that is less prone to dielectric breakdown even in high-temperature environments (e.g., 150°C), and an energy storage device using the same.

To achieve the above objective, this disclosure provides an exterior material for an energy storage device having a structure in which at least a base layer, an outer adhesive layer, a barrier layer, and a sealant layer are laminated in this order, wherein the ratio of the volume resistivity of the base layer at a 23°C environment to the volume resistivity at a 150°C environment (volume resistivity at a 23°C environment / volume resistivity at a 150°C environment) is 1 × ^10⁻¹⁰ to 1 × ^10³ .

According to the above-described exterior material for energy storage devices, by keeping the ratio of the volume resistivity of the base layer at 23°C to its volume resistivity at 150°C (volume resistivity at 23°C / volume resistivity at 150°C) (hereinafter also referred to as the "resistivity change ratio") within the above range, it is possible to suppress the rapid decrease in the volume resistivity of the base layer due to rising temperature, thereby suppressing dielectric breakdown in high-temperature environments (e.g., 150°C). Here, if the decrease in the volume resistivity of the base layer due to rising temperature is rapid, an exterior material designed to ensure sufficient insulation below the boiling point temperature of the electrolyte in conventional lithium-ion batteries (approximately 80°C) will experience dielectric breakdown when used in high-temperature environments (e.g., 100-150°C). In contrast, by keeping the resistance change ratio of the base layer within the above range, an exterior material designed to ensure sufficient insulation below approximately 80°C can be used in high-temperature environments without experiencing dielectric breakdown.

In the above-mentioned exterior material for the energy storage device, the volume resistivity of the base layer at a 23°C environment may be 1 × ^10¹³ Ω·m or more. When the volume resistivity of the base layer at a 23°C environment is within the above range, and the resistance change ratio is within the above range, dielectric breakdown can be more sufficiently suppressed both when used at temperatures of approximately 80°C or below, and when used in high-temperature environments (for example, when used at 100 to 150°C).

In the above-mentioned exterior material for the energy storage device, the volume resistivity of the base layer at a 150°C environment may be 1 × ^10¹² Ω·m or more. When the volume resistivity of the base layer at a 150°C environment is within the above range, and the resistance change ratio is within the above range, dielectric breakdown can be more sufficiently suppressed both when used at temperatures of approximately 80°C or below, and when used in high-temperature environments (for example, when used at 100 to 150°C).

In the above-mentioned exterior material for energy storage devices, the thickness of the base material layer may be 35 μm or less, and the value obtained by multiplying the volume resistivity of the base material layer at a 150°C environment by the thickness of the base material layer may be 5 × ^10¹³ (Ω・m × μm) or more. By keeping the thickness of the base material layer within the above range, the occurrence of curling after molding of the exterior material can be suppressed, thereby preventing a decrease in handling performance during heat sealing performed in a subsequent process. Furthermore, by keeping the value obtained by multiplying the thickness of the base material layer by the volume resistivity at a 150°C environment within the above range, dielectric breakdown can be more sufficiently suppressed both when used at temperatures of approximately 80°C or below, and when used in high-temperature environments (for example, when used at 100 to 150°C).

In the above-described exterior material for the energy storage device, the base layer may be a biaxially oriented film. Using a biaxially oriented film for the base layer can further improve the moldability of the exterior material for the energy storage device.

In the above-described exterior material for the energy storage device, the base layer may be a semi-aromatic polyamide film. Semi-aromatic polyamide films tend to maintain the resistance change ratio, volume resistivity at 23°C, and volume resistivity at 150°C within the specific ranges described above. Therefore, by using a semi-aromatic polyamide film as the base layer, dielectric breakdown can be more effectively suppressed both when used at temperatures below approximately 80°C and when used in high-temperature environments (e.g., 100-150°C).

In the above-described exterior material for the energy storage device, the outer adhesive layer may be formed using a polyester-urethane adhesive. By using a polyester-urethane adhesive for the outer adhesive layer, excellent adhesive strength can be maintained even in high-temperature environments (e.g., 150°C).

The above-mentioned exterior material for the energy storage device may also be used for all-solid-state batteries.

This disclosure also provides a power storage device comprising: a power storage device body; current extraction terminals extending from the power storage device body; and an exterior material for the power storage device according to this disclosure, which clamps the current extraction terminals and houses the power storage device body. The power storage device may be an all-solid-state battery.

According to this disclosure, it is possible to provide an exterior material for energy storage devices that is less prone to dielectric breakdown even in high-temperature environments (e.g., 150°C), and an energy storage device using the same.

This is a schematic cross-sectional view of an exterior material for an energy storage device according to one embodiment of the present disclosure. This is a schematic cross-sectional view of an exterior material for an energy storage device according to one embodiment of the present disclosure. This is a perspective view of a power storage device according to one embodiment of the present disclosure.

The following describes preferred embodiments of this disclosure in detail, with appropriate reference to the drawings. In the drawings, identical or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. Furthermore, the dimensional ratios in the drawings are not limited to those shown.

[Exterior material for energy storage devices]
Figure 1 is a schematic cross-sectional view showing one embodiment of the exterior material for an energy storage device according to the present disclosure. As shown in Figure 1, the exterior material (exterior material for an energy storage device) 10 of this embodiment is a laminate in which a base layer 11, an outer adhesive layer 12a provided on one side of the base layer 11, a barrier layer 13 provided on the side of the outer adhesive layer 12a opposite to the base layer 11 and having first and second corrosion-preventive treatment layers 14a and 14b on both sides, an inner adhesive layer 12b provided on the side of the barrier layer 13 opposite to the outer adhesive layer 12a, and a sealant layer 16 provided on the side of the inner adhesive layer 12b opposite to the barrier layer 13. Here, the first corrosion-preventive treatment layer 14a is provided on the side of the barrier layer 13 facing the base layer 11, and the second corrosion-preventive treatment layer 14b is provided on the side of the barrier layer 13 facing the sealant layer 16. In the exterior material 10, the base layer 11 is the outermost layer, and the sealant layer 16 is the innermost layer. That is, the exterior material 10 is used with the base layer 11 facing the outside of the energy storage device and the sealant layer 16 facing the inside of the energy storage device.

The following will provide a detailed explanation of each layer that makes up the exterior material 10.

<Base material layer 11>
The base layer 11 provides moldability and insulation to the exterior material 10. Furthermore, the base layer 11 provides heat resistance during the sealing process in the manufacturing of the energy storage device and suppresses the occurrence of pinholes that may occur during molding and distribution. Especially in the case of exterior materials for large-scale energy storage devices, it can also provide scratch resistance, chemical resistance, and insulation.

The ratio of the volume resistivity of the base layer 11 at a 23°C environment to the volume resistivity at a 150°C environment (volume resistivity at 23°C / volume resistivity at 150°C) is 1 × ^10⁻¹⁰ to 1 × ^10³ . The above ratio (resistivity change ratio) is preferably 1 × ^10⁻¹⁰ to 5 × ^10² , and more preferably 1 × ^10⁻¹⁰ to 1 × ^10² . By keeping the resistance change ratio below the above upper limit, it is possible to suppress the rapid decrease in the volume resistivity of the base layer 11 with increasing temperature, and to suppress dielectric breakdown in high-temperature environments (e.g., 150°C).

The base layer 11 preferably has a volume resistivity of 1 × ^10¹³ Ω·m or more at a 23°C environment, more preferably 5 × ^10¹³ Ω·m or more, and even more preferably 1 × ^10¹⁴ Ω·m or more. Furthermore, the upper limit of the volume resistivity of the base layer 11 at a 23°C environment is not particularly limited, but may be, for example, 1 × ^10¹⁶ Ω·m or less, 5 × ^10¹⁵ Ω·m or less, or 1 × ^10¹⁵ Ω·m or less. By having the volume resistivity of the base layer 11 at a 23°C environment be above the above lower limit, dielectric breakdown can be more sufficiently suppressed both when used at temperatures of around 80°C or below, and when used in high-temperature environments (for example, when used at 100 to 150°C).

The base layer 11 preferably has a volume resistivity of 1 × ^10¹² Ω·m or more at a 150°C environment, more preferably 5 × ^10¹² Ω·m or more, and even more preferably 1 × ^10¹³ Ω·m or more. Furthermore, the upper limit of the volume resistivity of the base layer 11 at a 150°C environment is not particularly limited, but may be, for example, 1 × ^10¹⁵ Ω·m or less, 5 × ^10¹⁴ Ω·m or less, or 1 × ^10¹⁴ Ω·m or less. By having the volume resistivity of the base layer 11 at a 150°C environment be above the above lower limit, dielectric breakdown can be more sufficiently suppressed both when used at around 80°C or below, and when used in a high-temperature environment (for example, when used at 100 to 150°C).

The volume resistivity of the substrate layer 11 can be measured in accordance with JIS K 6911 under conditions of 23°C, less than 20% relative humidity, or 150°C, with a voltage of 100V.

The base layer 11 is preferably a layer made of a resin film formed from an insulating resin.

The base layer 11 is preferably made of a semi-aromatic polyamide film, in order to satisfy the above-mentioned conditions for resistance change ratio and volume resistivity, and to ensure good moldability.

The semi-aromatic polyamide constituting the semi-aromatic polyamide film is a copolymer of a dicarboxylic acid component and a diamine component, and contains aromatic groups within either the dicarboxylic acid component or the diamine component. Semi-aromatic polyamides possess high heat resistance. Furthermore, they offer excellent moldability and dimensional stability. By using a semi-aromatic polyamide film as the base layer 11, it is possible to easily satisfy the aforementioned resistance change ratio and volume resistivity conditions, and to form an exterior material for energy storage devices that is less prone to dielectric breakdown even in high-temperature environments (e.g., 150°C).

The dicarboxylic acid component constituting the semi-aromatic polyamide is preferably terephthalic acid as the main component. Other dicarboxylic acid components include, for example, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, and octadecanediic acid; and aromatic dicarboxylic acids such as 1,4-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,2-naphthalenedicarboxylic acid, and isophthalic acid. These may be used individually or in combination of two or more. The proportion of terephthalic acid in the dicarboxylic acid component is preferably 60 to 100 mol%.

The diamine component constituting the semi-aromatic polyamide is preferably an aliphatic diamine having 4 to 15 carbon atoms. Examples of aliphatic diamines having 4 to 15 carbon atoms include 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 4-methyl-1,8-octanediamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, 1,13-tridecanediamine, 1,14-tetradecanediamine, and 1,15-pentadecanediamine. These may be used individually or in combination of two or more.

Semi-aromatic polyamides may also be copolymerized with lactams such as ε-caprolactam, ζ-enanthractam, η-capryllactam, and ω-laurolactam.

The melting point (Tm) of the semi-aromatic polyamide is preferably 30°C or more higher than the melting point of the sealant layer 16, from the viewpoint of heat resistance during heat sealing. The melting point of the semi-aromatic polyamide may be, for example, 280 to 350°C. The types of monomers constituting the semi-aromatic polyamide and the copolymerization ratio are preferably adjusted so that the melting point of the semi-aromatic polyamide falls within the above range.

The resin film constituting the base layer 11, such as the semi-aromatic polyamide film described above, may be either a stretched or unstretched film, but it is preferable to be a biaxially oriented film because it is easier to obtain good moldability. Examples of stretching methods for biaxially oriented films include sequential biaxial stretching, tubular biaxial stretching, and simultaneous biaxial stretching. Since biaxially oriented films are easier to obtain with better moldability, it is preferable that they are stretched by simultaneous biaxial stretching or tubular biaxial stretching.

The base layer 11 may be a single-layer film composed of one type of resin film, or it may be a laminated film composed of two or more types of resin films.

The glass transition temperature (Tg) of the substrate layer 11 is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 115°C or higher. A Tg of 100°C or higher for the substrate layer 11 allows for more effective suppression of dielectric breakdown during use in high-temperature environments (e.g., at 100-150°C). While there is no particular upper limit to the Tg of the substrate layer 11, it may be, for example, 400°C or lower.

The thickness of the base layer 11 is preferably 5 μm or more, more preferably 6 μm or more, even more preferably 10 μm or more, and particularly preferably 12 μm or more. Furthermore, the thickness of the base layer 11 is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 35 μm or less, and particularly preferably 30 μm or less. A base layer thickness of 5 μm or more tends to improve the pinhole resistance and insulation properties of the energy storage device exterior material 10. A base layer thickness exceeding 50 μm is undesirable because it increases the total thickness of the energy storage device exterior material 10, potentially requiring a reduction in the battery's electrical capacity. Additionally, a base layer thickness of 50 μm or less suppresses curling of the energy storage device exterior material 10 after molding, thereby preventing a decrease in handling performance during subsequent heat sealing processes.

The volume resistivity of the base layer 11 at a 150°C environment multiplied by the thickness of the base layer 11 is preferably 5 × ^10¹³ (Ω·m × μm) or more, more preferably 1 × ^10¹⁴ (Ω·m × μm) or more, and even more preferably 2 × ^10¹⁴ (Ω·m × μm) or more. Furthermore, the value obtained by multiplying the volume resistivity of the base layer 11 at a 150°C environment by the thickness of the base layer 11 may be 1 × ^10¹⁶ (Ω·m × μm) or less, or 5 × ^10¹⁵ (Ω·m × μm) or less. If this value is above the above lower limit, dielectric breakdown can be more sufficiently suppressed both when used at temperatures below approximately 80°C and when used in high-temperature environments (for example, when used at 100 to 150°C).

<Outer adhesive layer 12a>
The outer adhesive layer 12a is a layer that adheres the base layer 11 and the barrier layer 13. Specific examples of materials constituting the outer adhesive layer 12a include polyurethane resins obtained by reacting a main component such as polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol with a bifunctional or higher isocyanate compound (polyfunctional isocyanate compound). Among polyurethane resins, polyester urethane resins using a polyester polyol and a bifunctional or higher isocyanate compound are preferred because they more effectively suppress the decrease in peel strength under high-temperature conditions.

The various polyols described above can be used individually or in combination of two or more, depending on the functions and performance required for the exterior material.

Furthermore, depending on the required performance of the adhesive, various other additives and stabilizers may be blended into the polyurethane resin described above.

In the polyurethane adhesive used to form the outer adhesive layer 12a containing the polyurethane resin described above, the ratio (NCO/OH) of isocyanate groups in the polyfunctional isocyanate compound to the number of hydroxyl groups in the polyol may be 2 to 60, 5 to 50, or 10 to 40. If this ratio is 2 or higher, the adhesive strength between the substrate layer 11 and the barrier layer 13 in a high-temperature environment (e.g., 150°C) can be further improved, and the lifting of the substrate layer 11 from the barrier layer 13 in a high-temperature environment can be further suppressed. If the above ratio is 60 or lower, it is possible to prevent excessive residue of unreacted hydroxyl groups, and the adhesive strength between the substrate layer 11 and the barrier layer 13 can be further improved in both room temperature and high-temperature environments. The heat resistance of the cured polyurethane adhesive (outer adhesive layer 12a) is improved by urea and biuret generated by the reaction of trace amounts of water in the air or adhesive with the polyfunctional isocyanate compound. Therefore, the more polyfunctional isocyanate compounds there are, the more these units increase, which in turn raises the Tg (transition time) and improves heat resistance.

The thickness of the outer adhesive layer 12a is not particularly limited, but from the viewpoint of obtaining desired adhesive strength, conformability, and processability, for example, 1 to 10 μm is preferred, and 3 to 7 μm is more preferred. When the thickness of the outer adhesive layer 12a is 1 μm or more, high adhesive strength is easily obtained, and stress relief of shear forces generated during thermal expansion of the base layer 11 and barrier layer 13 in high-temperature environments is facilitated. On the other hand, when the thickness of the outer adhesive layer is 10 μm or less, the moldability of the exterior material can be further improved.

<Barrier layer 13>
The barrier layer 13 has water vapor barrier properties that prevent moisture from entering the inside of the energy storage device. The barrier layer 13 may also have ductility for deep drawing. As the barrier layer 13, for example, various metal foils such as aluminum, stainless steel, and copper, or metal vapor-deposited films, inorganic oxide vapor-deposited films, carbon-containing inorganic oxide vapor-deposited films, or films provided with these vapor-deposited films can be used. As films provided with vapor-deposited films, for example, aluminum vapor-deposited films and inorganic oxide vapor-deposited films can be used. These can be used individually or in combination of two or more types. As the barrier layer 13, metal foil is preferred in terms of mass (specific gravity), moisture resistance, processability, and cost, and aluminum foil is more preferred.

As for the aluminum foil, soft aluminum foil that has undergone annealing treatment is particularly preferred because it can impart the desired ductility during molding. However, it is even more preferable to use aluminum foil containing iron in order to further impart pinhole resistance and ductility during molding. The iron content in the aluminum foil is preferably 0.1 to 9.0% by mass, and more preferably 0.5 to 2.0% by mass, based on 100% by mass of the aluminum foil. An iron content of 0.1% by mass or more allows for the acquisition of an exterior material 10 with superior pinhole resistance and ductility. An iron content of 9.0% by mass or less allows for the acquisition of an exterior material 10 with superior flexibility. While untreated aluminum foil may be used, it is preferable to use degreased aluminum foil to impart corrosion resistance. When degreasing the aluminum foil, the degreasing treatment may be applied to only one side of the aluminum foil, or to both sides.

The thickness of the barrier layer 13 is not particularly limited, but it is preferably 9 to 200 μm, and more preferably 15 to 100 μm, considering barrier properties, pinhole resistance, and processability.

<First and second corrosion-preventive treatment layers 14a, 14b>
The first and second corrosion-preventive treatment layers 14a and 14b are layers provided to prevent corrosion of the metal foil (metal foil layer) and the like that which constitute the barrier layer 13. The first corrosion-preventive treatment layer 14a also plays a role in increasing the adhesion between the barrier layer 13 and the outer adhesive layer 12a. The second corrosion-preventive treatment layer 14b also plays a role in increasing the adhesion between the barrier layer 13 and the inner adhesive layer 12b. The first corrosion-preventive treatment layer 14a and the second corrosion-preventive treatment layer 14b may be layers with the same composition or layers with different compositions. The first and second corrosion-preventive treatment layers 14a and 14b (hereinafter also simply referred to as "corrosion-preventive treatment layers 14a and 14b") may be formed, for example, by degreasing, hot water modification, anodizing, chemical conversion, or a combination thereof.

Degreasing methods include acid degreasing and alkaline degreasing. Acid degreasing methods include using inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid individually, or mixtures thereof. Furthermore, using an acid degreasing agent prepared by dissolving a fluorine-containing compound such as monosodium ammonium difluoride in the above-mentioned inorganic acid is particularly effective when aluminum foil is used in the barrier layer 13. This not only provides a degreasing effect on the aluminum but also allows for the formation of a passive aluminum fluoride, which is beneficial in terms of corrosion resistance. Alkaline degreasing methods include using sodium hydroxide, etc.

One example of a hydrothermal alteration treatment is the boehmite treatment, which involves immersing aluminum foil in boiling water to which triethanolamine has been added.

An example of anodizing treatment is aluminum anodizing.

Chemical conversion treatments include immersion type and coating type. Examples of immersion type chemical conversion treatments include chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, or various chemical conversion treatments consisting of mixed phases of these. On the other hand, a coating type chemical conversion treatment involves applying a coating agent with corrosion-preventive properties onto the barrier layer 13.

When forming at least a portion of the corrosion-preventive treatment layer using one of these corrosion-preventive treatments—hot water modification, anodizing, or chemical conversion—it is preferable to perform the degreasing treatment described above beforehand. Furthermore, if a degreased metal foil, such as one that has undergone an annealing process, is used as the barrier layer 13, it is not necessary to perform degreasing treatment again when forming the corrosion-preventive treatment layers 14a and 14b.

The coating agent used in the coating-type chemical conversion treatment preferably contains trivalent chromium. Furthermore, the coating agent may also contain at least one polymer selected from the group consisting of cationic polymers and anionic polymers, as described later.

Furthermore, in particular, the hydrothermal modification and anodizing processes described above dissolve the surface of the aluminum foil using a treatment agent, forming aluminum compounds (boehmite, anodized aluminum) with excellent corrosion resistance. Therefore, a co-continuous structure is formed from the aluminum foil barrier layer 13 to the corrosion-preventive treatment layers 14a and 14b, and thus these processes are included in the definition of chemical conversion treatment. On the other hand, as will be described later, it is also possible to form the corrosion-preventive treatment layers 14a and 14b using only a pure coating method, which is not included in the definition of chemical conversion treatment. One example of this method is the use of a sol of a rare-earth element oxide, such as cerium oxide, with an average particle size of 100 nm or less, which has a corrosion-preventive effect (inhibitor effect) on aluminum and is also environmentally friendly. By using this method, it becomes possible to impart a corrosion-preventive effect to metal foils such as aluminum foil even with general coating methods.

Examples of sols for the above-mentioned rare earth element oxides include sols using various solvents such as aqueous, alcoholic, hydrocarbon, ketone, ester, and ether-based solvents. Among these, aqueous sols are preferred.

In the sols of the rare earth element oxides mentioned above, inorganic acids such as nitric acid, hydrochloric acid, and phosphoric acid, or their salts, and organic acids such as acetic acid, malic acid, ascorbic acid, and lactic acid are typically used as dispersion stabilizers to stabilize their dispersion. Among these dispersion stabilizers, phosphoric acid, in particular, is expected to provide the following benefits in the exterior material 10: (1) stabilization of sol dispersion, (2) improved adhesion with the barrier layer 13 utilizing the aluminum chelating ability of phosphoric acid, and (3) improved cohesiveness of the corrosion-preventive treatment layers 14a and 14b (oxide layers) due to the ease with which phosphoric acid undergoes dehydration condensation even at low temperatures.

The corrosion-preventive treatment layers 14a and 14b formed by the above-mentioned rare-earth element oxide sols are aggregates of inorganic particles, and therefore, even after the drying and curing process, the cohesive force of the layers themselves may decrease. Therefore, in this case, it is preferable that the corrosion-preventive treatment layers 14a and 14b are compounded with an anionic polymer or a cationic polymer to compensate for the reduced cohesive force.

Furthermore, the corrosion-preventive treatment layers 14a and 14b are not limited to the layers described above. For example, they may be formed using a treatment agent containing a resin binder (such as aminophenol) mixed with phosphoric acid and a chromium compound, similar to the known coating-type chromate. Using this treatment agent, a layer possessing both corrosion prevention and adhesion can be achieved. Additionally, although the stability of the coating solution must be considered, a coating agent pre-mixed with a rare-earth element oxide sol and a polycationic or polyanionic polymer can be used to create a layer possessing both corrosion prevention and adhesion.

The mass per unit area of the corrosion-preventive treatment layers 14a and 14b is preferably 0.005 to 0.200 g/ ^m² , and more preferably 0.010 to 0.100 g/ ^m² , regardless of whether it is a multilayer or single-layer structure. If the mass per unit area is 0.005 g/ ^m² or more, it is easier to impart corrosion prevention function to the barrier layer 13. Furthermore, even if the mass per unit area exceeds 0.200 g/ ^m² , the corrosion prevention function does not change much. On the other hand, when using rare earth element oxide sols, if the coating film is thick, the curing due to heat during drying may be insufficient, which may lead to a decrease in cohesive force. The thickness of the corrosion-preventive treatment layers 14a and 14b can be calculated from their specific gravity.

The corrosion-preventive treatment layers 14a and 14b may, from the viewpoint of facilitating adhesion between the sealant layer and the barrier layer, for example, contain cerium oxide, 1 to 100 parts by mass of phosphoric acid or phosphate per 100 parts by mass of cerium oxide, and a cationic polymer. Alternatively, they may be formed by applying a chemical conversion treatment to the barrier layer 13, or they may be formed by applying a chemical conversion treatment to the barrier layer 13 and also contain a cationic polymer.

<Inner adhesive layer 12b>
The inner adhesive layer 12b is a layer that bonds the barrier layer 13, on which the second corrosion-preventive treatment layer 14b is formed, to the sealant layer 16. A general adhesive for bonding the barrier layer and the sealant layer can be used for the inner adhesive layer 12b, for example, the same adhesive as that used for the outer adhesive layer 12a described above can be used.

The thickness of the inner adhesive layer 12b is not particularly limited, but from the viewpoint of obtaining the desired adhesive strength and processability, it is preferably 1 to 10 μm, and more preferably 3 to 7 μm.

<Sealant layer 16>
The sealant layer 16 is a layer that provides heat-sealing properties to the exterior material 10. Examples of sealant layers 16 include resin films made of polyolefin resin or polyester resin. The resins constituting these sealant layers 16 (hereinafter also referred to as "base resins") may be used individually or in combination of two or more types.

Examples of polyolefin resins include low-density, medium-density, or high-density polyethylene; ethylene-α-olefin copolymers; polypropylene; block or random copolymers containing propylene as a copolymer component; and propylene-α-olefin copolymers.

Examples of polyester resins include polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polyethylene naphthalate (PEN) resin, polybutylene naphthalate (PBN) resin, and copolymers thereof.

The sealant layer 16 may contain a polyolefin elastomer. The polyolefin elastomer may be compatible with the base resin described above, or it may not be compatible. It may contain both compatible polyolefin elastomers and incompatible polyolefin elastomers. "Compatible" means dispersed in the base resin with a dispersion phase size of 1 nm or more and less than 500 nm. "Incompatible" means dispersed in the base resin with a dispersion phase size of 500 nm or more and less than 20 μm.

When the base resin is a polypropylene-based resin, examples of compatible polyolefin elastomers include propylene-butene-1 random copolymers, and examples of incompatible polyolefin elastomers include ethylene-butene-1 random copolymers. Polyolefin elastomers can be used individually or in combination of two or more.

Furthermore, the sealant layer 16 may contain additives such as slip agents, antiblocking agents, antioxidants, light stabilizers, and flame retardants. The content of these additives is preferably 5 parts by mass or less, based on a total mass of 100 parts by mass of the sealant layer 16.

The thickness of the sealant layer 16 is not particularly limited, but from the viewpoint of achieving both thinness and improved heat seal strength in high-temperature environments, it is preferably in the range of 5 to 100 μm, more preferably in the range of 10 to 100 μm, and even more preferably in the range of 20 to 80 μm.

The sealant layer 16 may be either a single-layer film or a multi-layer film, and should be selected according to the required function.

While preferred embodiments of the exterior material for the energy storage device of this embodiment have been described in detail above, this disclosure is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of this disclosure as described in the claims.

For example, Figure 1 shows a case where corrosion-preventive treatment layers 14a and 14b are provided on both sides of the barrier layer 13. However, only one of the corrosion-preventive treatment layers 14a and 14b may be provided, or no corrosion-preventive treatment layer may be provided at all.

Figure 1 shows a case where the barrier layer 13 and sealant layer 16 are laminated using an inner adhesive layer 12b. However, as shown in Figure 2, the exterior material 20 for the energy storage device may be laminated using an adhesive resin layer 15. Furthermore, in the exterior material 20 for the energy storage device shown in Figure 2, an inner adhesive layer 12b may be provided between the barrier layer 13 and the adhesive resin layer 15.

<Adhesive resin layer 15>
The adhesive resin layer 15 is generally composed of an adhesive resin composition as the main component and additive components as needed. The adhesive resin composition is not particularly limited, but it is preferable that it contains a modified polyolefin resin.

The modified polyolefin resin is preferably a polyolefin resin that has been graft-modified with an unsaturated carboxylic acid, or an unsaturated carboxylic acid derivative derived from either its acid anhydride or ester.

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

The modified polyolefin resin is preferably a polyolefin resin modified with maleic anhydride. Suitable modified polyolefin resins include, for example, "Admer" manufactured by Mitsui Chemicals, Inc. and "Modic" manufactured by Mitsubishi Chemical Corporation. Such modified polyolefin resins exhibit excellent reactivity with various metals and polymers having various functional groups; therefore, this reactivity can be used to impart adhesion to the adhesive resin layer 15. Furthermore, the adhesive resin layer 15 may, as needed, contain various additives such as various compatible and incompatible elastomers, flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, and tackifiers.

The thickness of the adhesive resin layer 15 is not particularly limited, but from the viewpoint of stress relaxation and moisture permeability, it is preferable that it be the same as or less than that of the sealant layer 16.

Furthermore, in the exterior material 20 for the energy storage device, the total thickness of the adhesive resin layer 15 and the sealant layer 16 is preferably in the range of 5 to 100 μm, and more preferably in the range of 20 to 80 μm, from the viewpoint of achieving both thinness and improved heat seal strength in high-temperature environments.

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

The manufacturing method for the exterior material 10 of this embodiment generally includes the steps of: providing corrosion-preventive treatment layers 14a and 14b on the barrier layer 13; bonding the base layer 11 and the barrier layer 13 using an outer adhesive layer 12a; further laminating a sealant layer 16 via an inner adhesive layer 12b to create a laminate; and, if necessary, aging the obtained laminate.

(Lamination process of corrosion-preventive treatment layers 14a and 14b onto the barrier layer 13)
This process involves forming corrosion-preventive treatment layers 14a and 14b on the barrier layer 13. As described above, methods for this include degreasing, hot water modification, anodizing, chemical conversion, or applying a coating agent with corrosion-preventive properties to the barrier layer 13.

Furthermore, if the corrosion prevention treatment layers 14a and 14b are multi-layered, for example, the coating agent constituting the lower layer (barrier layer 13 side) of the corrosion prevention treatment layer can be applied to the barrier layer 13 and baked to form the first layer. Then, the coating agent constituting the upper layer of the corrosion prevention treatment layer can be applied to the first layer and baked to form the second layer.

Degreasing can be performed using either the spray method or the immersion method. Hot water modification and anodizing treatments can be performed using the immersion method. For chemical conversion treatments, the immersion method, spray method, coating method, etc., can be appropriately selected depending on the type of chemical conversion treatment.

Various methods can be used for applying coatings with corrosion-preventive properties, including gravure coating, reverse coating, roll coating, and bar coating.

As described above, the various treatments may be applied to either both sides or one side of the metal foil. However, in the case of single-sided treatment, it is preferable to apply the treatment to the side on which the sealant layer 16 is laminated. Furthermore, the above treatment may also be applied to the surface of the base layer 11, if required.

Furthermore, the amount of coating agent applied to form the first and second layers is preferably 0.005 to 0.200 g/ ^m² , and more preferably 0.010 to 0.100 g/ ^m² .

Furthermore, if drying and curing are required, the base material temperature can be set to a range of 60 to 300°C, depending on the drying conditions of the corrosion-preventive treatment layers 14a and 14b used.

(Bonding process between the base layer 11 and the barrier layer 13)
This process involves bonding a barrier layer 13, which is provided with corrosion-preventive treatment layers 14a and 14b, to a base material layer 11 via an outer adhesive layer 12a. The bonding method can be dry lamination, non-solvent lamination, or wet lamination, using the materials that constitute the outer adhesive layer 12a described above. The outer adhesive layer 12a is applied in a dry coating amount ranging from 1 to 10 g/ ^m² , more preferably from 2 to 7 g/ ^m² .

(Lamination process of inner adhesive layer 12b and sealant layer 16)
This process involves bonding the sealant layer 16 to the second corrosion-preventive treatment layer 14b side of the barrier layer 13 via the inner adhesive layer 12b. Methods of bonding include wet processes and dry lamination.

In the wet process, a solution or dispersion of the adhesive constituting the inner adhesive layer 12b is applied onto the second corrosion-preventive treatment layer 14b, and the solvent is evaporated at a predetermined temperature to form a dry film, or, if necessary, a baking treatment is performed after drying. Then, the sealant layer 16 is laminated to manufacture the exterior material 10. Various coating methods as exemplified above are examples of coating methods. The preferred dry application amount of the inner adhesive layer 12b is the same as that of the outer adhesive layer 12a.

In this case, the sealant layer 16 can be manufactured, for example, by a melt extrusion molding machine using a resin composition for forming a sealant layer containing the components of the sealant layer 16 described above. From the viewpoint of productivity, the processing speed of the melt extrusion molding machine can be set to 80 m/min or more.

(Aging process)
This process involves aging (curing) the laminate. Aging the laminate promotes adhesion between the barrier layer 13, the second corrosion-preventive treatment layer 14b, the inner adhesive layer 12b, and the sealant layer 16. The aging process can be carried out in a temperature range of room temperature to 100°C. The aging time is, for example, 1 to 10 days.

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

Next, an example of a manufacturing method for the exterior material 20 shown in Figure 2 will be described. Note that the manufacturing method for the exterior material 20 is not limited to the method described below.

The manufacturing method for the exterior material 20 of this embodiment generally includes the steps of: providing corrosion-preventive treatment layers 14a and 14b on the barrier layer 13; bonding the base layer 11 and the barrier layer 13 using an outer adhesive layer 12a; further laminating the adhesive resin layer 15 and the sealant layer 16 to create a laminate; and, if necessary, heat-treating the obtained laminate. Note that the steps up to bonding the base layer 11 and the barrier layer 13 can be carried out in the same manner as the manufacturing method for the exterior material 10 described above.

(Lamination process of adhesive resin layer 15 and sealant layer 16)
This step involves forming an adhesive resin layer 15 and a sealant layer 16 on the second corrosion-preventive treatment layer 14b formed in the previous step. One method for this is to sand-laminate the adhesive resin layer 15 together with the sealant layer 16 using an extrusion laminating machine. Furthermore, lamination is also possible by tandem lamination or co-extrusion, in which the adhesive resin layer 15 and the sealant layer 16 are extruded. In forming the adhesive resin layer 15 and the sealant layer 16, for example, each component is blended to satisfy the above-described configuration of the adhesive resin layer 15 and the sealant layer 16. The above-described sealant layer forming resin composition is used to form the sealant layer 16.

This process yields a laminate in which the layers are stacked in the following order, as shown in Figure 2: base layer 11 / outer adhesive layer 12a / first corrosion-preventive treatment layer 14a / barrier layer 13 / second corrosion-preventive treatment layer 14b / adhesive resin layer 15 / sealant layer 16.

The adhesive resin layer 15 may be laminated by directly extruding the dry-blended material, which has been mixed to the material composition described above, using an extrusion laminating machine. Alternatively, the adhesive resin layer 15 may be laminated by extruding the granulated material, which has been melt-blended using a melt-kneading device such as a single-screw extruder, twin-screw extruder, or Brabender mixer, using an extrusion laminating machine.

The sealant layer 16 may be laminated by directly extruding a dry-blended material, which has been prepared to match the material composition described above, using an extrusion laminating machine. Alternatively, the adhesive resin layer 15 and the sealant layer 16 may be laminated using a tandem lamination method or co-extrusion method, where granules are extruded using an extrusion laminating machine after melt blending with a melt-kneading device such as a single-screw extruder, twin-screw extruder, or Brabender mixer. Furthermore, a single sealant film may be prepared in advance as a cast film using the sealant layer forming resin composition, and this film may be laminated together with the adhesive resin by sand lamination. From the viewpoint of productivity, the formation speed (processing speed) of the adhesive resin layer 15 and the sealant layer 16 can be, for example, 80 m/min or more.

(Heat treatment process)
This process involves heat-treating the laminate. Heat-treating the laminate improves the adhesion between the barrier layer 13, the second corrosion-preventive treatment layer 14b, the adhesive resin layer 15, and the sealant layer 16. Preferably, the heat treatment is performed at a temperature at least equal to or greater than the melting point of the adhesive resin layer 15.

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

While preferred embodiments of the exterior material for energy storage devices described herein have been detailed, this disclosure is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of this disclosure as described in the claims.

The exterior material for energy storage devices disclosed herein can be suitably used as an exterior material for energy storage devices such as secondary batteries including lithium-ion batteries, nickel-metal hydride batteries, and lead-acid batteries, as well as electrochemical capacitors such as electric double-layer capacitors. In particular, the exterior material for energy storage devices disclosed herein is suitable as an exterior material for all-solid-state batteries using a solid electrolyte.

[Energy storage device]
Figure 3 is a perspective view showing one embodiment of a power storage device made using the exterior material described above. As shown in Figure 3, the power storage device 50 is composed of a battery element (power storage device body) 52, two metal terminals (current extraction terminals) 53 for extracting current from the battery element 52 to the outside, and an exterior material 10 that encloses the battery element 52 in an airtight state. The exterior material 10 is the exterior material 10 according to the embodiment described above. In the exterior material 10, the base material layer 11 is the outermost layer, and the sealant layer 16 is the innermost layer. That is, the exterior material 10 is constructed to enclose the battery element 52 inside by folding one laminate film in half and heat-sealing it, or by overlapping two laminate films and heat-sealing them, so that the base material layer 11 is on the outside side of the power storage device 50 and the sealant layer 16 is on the inside side of the power storage device 50. Note that in the power storage device 50, an exterior material 20 may be used instead of the exterior material 10.

The battery element 52 has an electrolyte interposed between the positive and negative electrodes. The metal terminal 53 is a portion of the current collector that is exposed to the outside of the outer casing 10, and is made of metal foil such as copper foil or aluminum foil.

The energy storage device 50 of this embodiment may be an all-solid-state battery. In this case, a solid electrolyte such as a sulfide-based solid electrolyte is used as the electrolyte of the battery element 52. Because the energy storage device 50 of this embodiment uses the exterior material 10 of this embodiment, even when used in a high-temperature environment (e.g., 150°C), it is possible to suppress the deterioration of the insulation properties of the exterior material 10 and the occurrence of dielectric breakdown.

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

[Materials used]
The materials used in the examples and comparative examples are shown below.

<Base material layer>
Semi-aromatic polyamide: Semi-aromatic polyamide film having the thickness and Tg shown in Table 1, produced by the film-forming method shown in Table 1. PET: Polyethylene terephthalate film having the thickness and Tg shown in Table 1, produced by the film-forming method shown in Table 1 (manufactured by Toray Industries, Inc., product names: Lumirror #25, #50).
PBT: Polybutylene terephthalate film (manufactured by Kojin Film & Chemicals, trade name: Boblet) produced by the film-forming method shown in Table 1, having the thickness and Tg shown in the same table.
Nylon 6: A nylon 6 film (manufactured by Unitika Corporation, product name: ON-U) produced by the film-forming method shown in Table 1, having the thickness and Tg shown in the same table.

<Outer adhesive layer (thickness: 5 μm)>
Polyester urethane: A polyester urethane adhesive was used, which was prepared by blending polyester polyol (manufactured by Toyo Morton Co., Ltd., product name: TMK-55) and isocyanate (TDI-Adduct, manufactured by Toyo Morton Co., Ltd., product name: CAT-10L) and diluting it with a solvent.
PO-based: A polyolefin adhesive was used, which was a mixture of Aurolene 350S (product name) manufactured by Nippon Paper Industries and DYNAGRAND CR-410B (product name) manufactured by Toyo Morton Co., Ltd., diluted with a solvent.

<First corrosion-preventive treatment layer (substrate layer side) and second corrosion-preventive treatment layer (sealant layer side)>
(CL-1): A "sodium polyphosphate stabilized cerium oxide sol" was used, which was prepared by using distilled water as the solvent and adjusting the solid content to 10% by mass. The sodium polyphosphate stabilized cerium oxide sol was obtained by mixing 10 parts by mass of sodium phosphoric acid with 100 parts by mass of cerium oxide.
(CL-2): A composition consisting of 90% by mass of "polyallylamine (manufactured by Nitto Boseki Co., Ltd.)" and 10% by mass of "polyglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation)" was used, adjusted to a solid content concentration of 5% by mass using distilled water as a solvent.

<Barrier layer (thickness: 40 μm)>
Annealed and degreased soft aluminum foil (manufactured by Toyo Aluminum Co., Ltd., "8079 material") was used.

<Adhesive resin layer (thickness: 27 μm)>
As the adhesive resin, a random polypropylene (PP)-based acid-modified polypropylene resin composition (manufactured by Mitsui Chemicals, Inc.) was used.

<Sealant layer (thickness 53 μm)>
A polypropylene-polyethylene random copolymer (manufactured by Prime Polymer, trade name: F744NP) was used as the resin composition for forming the sealant layer.

[Manufacturing of exterior materials]
(Example 1)
First, the barrier layer was provided with first and second corrosion-preventive treatment layers in the following procedure. Specifically, (CL-1) was applied to both surfaces of the barrier layer by direct gravure coating at a dry coating rate of 70 mg/ ^m² , and then baked in a drying unit at 200°C. Next, (CL-2) was applied to the resulting layer by direct gravure coating at a dry coating rate of 20 mg/ ^m² , thereby forming a composite layer consisting of (CL-1) and (CL-2) as the first and second corrosion-preventive treatment layers. This composite layer exhibits corrosion-preventive performance by combining the two types, (CL-1) and (CL-2).

Next, the first corrosion-preventive treatment layer side of the barrier layer, which had the first and second corrosion-preventive treatment layers, was bonded to the substrate layer using a polyester urethane adhesive (outer adhesive layer) by a dry lamination method. The lamination of the barrier layer and the substrate layer was performed by applying the polyester urethane adhesive to the surface of the barrier layer facing the first corrosion-preventive treatment layer, ensuring a cured thickness of 5 μm. After drying at 80°C for 30 seconds, it was laminated with the substrate layer and aged at 80°C for 120 hours.

Next, the laminate of the barrier layer and the base layer was set in the unwinding section of an extrusion laminating machine, and an adhesive resin layer (thickness 27 μm) and a sealant layer (thickness 53 μm) were laminated in this order by co-extrusion on the second corrosion-preventive treatment layer at processing conditions of 270°C and 80 m/min. The adhesive resin layer and sealant layer were prepared in advance using a twin-screw extruder as compounds of various materials, and after undergoing water cooling and pelletizing processes, were used for the above extrusion lamination.

The laminate obtained in this manner was heat-treated to a maximum temperature of 190°C to produce an exterior material (a laminate consisting of a base layer, an outer adhesive layer, a first corrosion-preventive treatment layer, a barrier layer, a second corrosion-preventive treatment layer, an adhesive resin layer, and a sealant layer).

(Examples 2-3 and Comparative Examples 1-5)
Except for changing the configuration of the base layer and/or outer adhesive layer as shown in Table 1, the exterior materials of Examples 2-3 and Comparative Examples 1-5 (laminated structures of base layer/outer adhesive layer/first corrosion-preventive treatment layer/barrier layer/second corrosion-preventive treatment layer/adhesive resin layer/sealant layer) were prepared in the same manner as in Example 1. When "PO-based" was used as the outer adhesive layer, the conditions for lamination between the barrier layer and the base layer were changed to drying at 100°C for 30 seconds and aging at 40°C for 120 hours.

[Measurement of volume resistivity]
The volume resistivity of the substrate layers used in the examples and comparative examples was measured in accordance with JIS K 6911 under conditions of 23°C, relative humidity of 20% RH or less, or 150°C, and a voltage of 100V. Furthermore, the resistance change ratio (volume resistivity at 23°C / volume resistivity at 150°C) was calculated from the volume resistivity at 23°C and 150°C. These results are shown in Table 1.

[Measurement of dielectric breakdown voltage]
The exterior materials obtained in the examples and comparative examples were cut into 100 mm x 100 mm pieces to prepare test specimens. The dielectric breakdown voltage (AC, 50 Hz) perpendicular to the surface of these test specimens was measured in accordance with JIS C2110-1. The details of the test conditions are as follows. A measured dielectric breakdown voltage of 8 kV or higher was classified as "A", a voltage between 7 kV and 8 kV was classified as "B", and a voltage below 7 kV was classified as "C". The results are shown in Table 1.
(Test conditions)
Number of test specimens: 3 Test temperature: 150°C
Ambient medium: Oil Electrode shape: 25 mm diameter cylinder / 25 mm diameter cylinder Pressure boosting method: Short-time test Pressure boosting rate: 0.5 kV/sec

[Evaluation of moldability]
The exterior materials obtained in the examples and comparative examples were cut into rectangular shapes measuring 120 mm in the TD direction and 200 mm in the MD direction, and placed in a molding apparatus with the sealant layer facing upwards. The molding depth of the molding apparatus was set to 5.0 mm, the holding pressure to 0.8 MPa, and cold molding was performed in an environment with a room temperature of 23°C and a dew point of -35°C. The punch die used had a rectangular cross-section of 80 mm x 70 mm, a punch radius (RP) of 1 mm on the bottom surface, and a punch corner radius (RCP) of 1 mm on the side surface. The die die used had a die radius (RD) of 1 mm on the upper surface of the opening. The clearance between the punch die and the die die was set to 170 μm. The molding area was approximately the center of one half of the cut exterior material, divided approximately in the middle of the longitudinal direction (MD direction), and the longitudinal direction of the punch die was aligned with the TD direction of the exterior material.

Ten samples were prepared by deep drawing under the above conditions, and (a) the presence or absence of pinholes and cracks, and (b) the presence or absence of curling after molding were observed and judged based on the following criteria.
(a) Presence or absence of pinholes and cracks A: No pinholes or cracks in any of the samples B: No pinholes or cracks in 80% to less than 100% of the samples C: Less than 80% of the samples are free of pinholes and cracks (b) Presence or absence of curling after molding A: The unmolded portion does not curl, or even if it curls, the tip of the unmolded portion does not complete a full rotation C: The tip of the unmolded portion curls to complete one or more rotations Based on the evaluation results of (a) and (b) above, the moldability of the exterior material was determined according to the following criteria. The results are shown in Table 1.
A: Both evaluation results in (a) and (b) above are judged as "A" B: The evaluation result in (a) above is judged as "B" and the evaluation result in (b) above is judged as "A" C: At least one of the evaluation results in (a) and (b) above is judged as "C"

[Measurement of peel strength]
The exterior materials obtained in the examples and comparative examples were cut into specimens measuring 15 mm in width and 100 mm in length to prepare test pieces. The peel strength between the base layer and the barrier layer of these test pieces was measured under a 150°C environment. The measurement was performed using a T-shaped peel test with a tensile testing machine (manufactured by Shimadzu Corporation) at a tensile speed of 50 mm/min. Based on the obtained results, the peel strength under a 150°C environment was evaluated according to the evaluation criteria below. The results are shown in Table 1.
A: Peel strength of 1 N/15 mm or more C: Peel strength of less than 1 N/15 mm

10, 20... Exterior material for energy storage device, 11... Base material layer, 12a... Outer adhesive layer, 12b... Inner adhesive layer, 13... Barrier layer, 14a... First corrosion prevention treatment layer, 14b... Second corrosion prevention treatment layer, 15... Adhesive resin layer, 16... Sealant layer, 50... Energy storage device, 52... Battery element, 53... Metal terminal.

Claims (10)

An exterior material for an energy storage device having a structure in which at least a base layer, an outer adhesive layer, a barrier layer, and a sealant layer are laminated in this order,
The ratio of the volume resistivity of the substrate layer at 23°C to the volume resistivity at 150°C (volume resistivity at 23°C / volume resistivity at 150°C) is 1 × ^10⁰ to 1 × ^10³ .
An exterior material for an energy storage device, wherein the substrate layer is a semi-aromatic polyamide film having a glass transition temperature of 110°C or higher . The exterior material for an energy storage device according to claim 1, wherein the volume resistivity of the base layer at a 23°C environment is 1 × ^10¹³ Ω·m or more. The exterior material for an energy storage device according to claim 1 or 2, wherein the volume resistivity of the base layer in a 150°C environment is 1 × ^10¹² Ω·m or more. The thickness of the aforementioned substrate layer is 35 μm or less.
An exterior material for an energy storage device according to any one of claims 1 to 3, wherein the value obtained by multiplying the volume resistivity of the base material layer at a 150°C environment by the thickness of the base material layer is 5 × ^10¹³ (Ω·m × μm) or more. The exterior material for an energy storage device according to any one of claims 1 to 4, wherein the base material layer is a biaxially stretched film. The exterior material for a power storage device according to any one of claims 1 to 5, wherein the outer adhesive layer is a layer formed using a polyester urethane adhesive. An exterior material for an energy storage device according to any one of claims 1 to 6, for use with all-solid-state batteries. The exterior material for an energy storage device according to any one of claims 1 to 7, wherein the ratio of the volume resistivity of the base layer at a 23°C environment to the volume resistivity at a 150°C environment (volume resistivity at a 23°C environment / volume resistivity at a 150°C environment) is 1 × ^10⁻⁵ to 1 × ^10⁻² . The main unit of the energy storage device,
Current extraction terminals extending from the main body of the aforementioned energy storage device,
An exterior material for a power storage device according to any one of claims 1 to 8, which clamps the current extraction terminal and houses the power storage device body,
A power storage device equipped with the following features. The energy storage device according to claim 9, which is an all-solid-state battery.