Aluminum alloy foil, exterior material for power storage device, manufacturing method thereof, and power storage device

Abstract

Provided is an aluminum alloy foil for use as an exterior material for an electricity storage device, which is effectively inhibited from corrosion when electricity is passed through it with an electrolyte attached thereto. [Solution] The aluminum alloy foil for use as a packaging material for an electricity storage device has a Mg content of 0.20 mass % or more and 5.50 mass % or less.

Description

[Technical Field]

[0001] The present disclosure relates to an aluminum alloy foil, an exterior material for an electricity storage device, a manufacturing method thereof, and an electricity storage device. [Background technology]

[0002] Various types of electricity storage devices have been developed, but in all of them, packaging materials (exterior materials) are essential components for sealing the electricity storage device elements such as electrodes and electrolytes. Conventionally, metal exterior materials have been widely used as exterior materials for electricity storage devices.

[0003] Meanwhile, in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc., electricity storage devices are being required to have a variety of shapes as well as to be thinner and lighter in weight. However, the metallic exterior materials for electricity storage devices that have been widely used in the past have the drawbacks of being difficult to keep up with the diversification of shapes and also having limitations on how much they can be made lighter.

[0004] Therefore, in recent years, a film-like packaging material in which a substrate / aluminum alloy foil layer / thermally adhesive resin layer are sequentially laminated has been proposed as a packaging material for an electricity storage device that can be easily processed into various shapes and can be made thinner and lighter (see, for example, Patent Document 1).

[0005] In such film-like packaging materials, recesses are generally formed by cold forming, and energy storage device elements such as electrodes and electrolyte are placed in the spaces formed by the recesses. The heat-sealable resin layers are then heat-sealed together to obtain an energy storage device in which the energy storage device elements are housed inside the packaging material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-287971 Summary of the Invention [Problem to be solved by the invention]

[0007] During processes such as the molding process for the electrical storage device packaging material, the process of housing an electrical storage device element in the electrical storage device packaging material and heat-sealing it, and the process of folding the heat-sealed portion, if a short circuit occurs between the external terminal and the aluminum alloy foil of the electrical storage device packaging material via a foreign object, or if uneven pressure during heat-sealing causes the external terminal and the aluminum alloy foil of the electrical storage device packaging material to come into close proximity or contact with each other, and if fine cracks or pinholes occur in the innermost heat-sealing resin layer, current may flow between the aluminum alloy foil of the electrical storage device packaging material and the external terminal via the electrolyte that has permeated the heat-sealing resin layer, potentially corroding the aluminum alloy foil (particularly, if the aluminum alloy foil and the negative electrode terminal are short-circuited via the electrolyte, the aluminum alloy foil is likely to corrode). Corrosion of the aluminum alloy foil can cause problems such as expansion of the aluminum alloy foil, leading to deterioration of the performance of the electrical storage device.

[0008] Under these circumstances, an object of the present disclosure is to provide an aluminum alloy foil for use in a packaging material for an electricity storage device, which effectively inhibits corrosion when electricity is passed through the foil with an electrolyte attached. Another object of the present disclosure is to provide a packaging material for an electricity storage device using the aluminum alloy foil, a method for manufacturing the packaging material for an electricity storage device, and an electricity storage device. [Means for solving the problem]

[0009] The inventors of the present disclosure have conducted extensive research to solve the above problems, and as a result, have found that by setting the Mg content within a predetermined range, corrosion can be effectively suppressed when current is passed through the aluminum alloy foil with an electrolyte attached thereto.

[0010] The present disclosure has been completed based on these findings and further investigations. That is, the present disclosure provides the inventions of the following aspects. 1. An aluminum alloy foil for use as a packaging material for an electricity storage device, having a Mg content of 0.20% by mass or more and 5.50% by mass or less. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide an aluminum alloy foil for use in a packaging material for an electricity storage device, in which corrosion is effectively suppressed when current is passed through the foil with an electrolyte solution attached. The present disclosure also makes it possible to provide a packaging material for an electricity storage device using the aluminum alloy foil, a method for manufacturing the packaging material for an electricity storage device, and an electricity storage device. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 2] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 3] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 4] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 5] 1 is a microscope image of the surface of a folded intersection of the exterior material for an electricity storage device of Example 1, observed after evaluating corrosion resistance. [Figure 6] 10 is a microscope image of the surface of the folded intersection of the exterior material for an electricity storage device of Example 2, observed after evaluating corrosion resistance. [Figure 7] 1 is a microscope image of the surface of a folded intersection of the exterior material for an electricity storage device of Comparative Example 1, observed after evaluating corrosion resistance. [Figure 8] 10 is a microscope image of the surface of a folded intersection of the exterior material for an electricity storage device of Comparative Example 2, observed after evaluating corrosion resistance. [Figure 9] FIG. 2 is a schematic diagram for explaining a method for evaluating corrosion resistance in the examples. [Figure 10]FIG. 2 is a schematic diagram for explaining a method for measuring seal strength. [Figure 11] FIG. 2 is a schematic diagram for explaining a method for measuring seal strength. [Figure 12] FIG. 2 is a schematic diagram for explaining a method for measuring seal strength. [Figure 13] FIG. 1 is a schematic diagram for explaining a method for measuring a logarithmic decrement ΔE by rigid pendulum measurement. [Figure 14] FIG. 2 is a schematic diagram for explaining a method for measuring seal strength. [Figure 15] FIG. 2 is a diagram schematically showing the temperature difference T1 and the temperature difference T2 in differential scanning calorimetry. [Figure 16] FIG. 2 is a schematic diagram showing crystal grains and second-phase particles in a cross section of an aluminum alloy foil in the thickness direction. DETAILED DESCRIPTION OF THE INVENTION

[0013] The aluminum alloy foil of the present disclosure is characterized in that it is an aluminum alloy foil for use in a packaging material for an electricity storage device, having a Mg content of 0.20 mass% or more and 5.50 mass% or less. The aluminum alloy foil of the present disclosure has this configuration, which effectively suppresses corrosion when current is passed through the foil with an electrolyte attached. Therefore, a packaging material for an electricity storage device using the aluminum alloy foil of the present disclosure effectively suppresses corrosion of the aluminum alloy foil.

[0014] The aluminum alloy foil, the packaging material for an electricity storage device, the manufacturing method thereof, and the electricity storage device according to the present disclosure will be described in detail below. In this specification, a numerical range indicated by "to" means "not less than" or "not more than." For example, the expression "2 to 15 mm" means 2 mm or more and 15 mm or less.

[0015] 1. Aluminum alloy foil The aluminum alloy foil of the present disclosure is characterized in that it has a Mg content of 0.20% by mass or more and 5.50% by mass or less and is used as an exterior packaging material for an electricity storage device. The exterior packaging material for an electricity storage device in which the aluminum alloy foil of the present disclosure can be used is not particularly limited, and the aluminum alloy foil of the present disclosure can be suitably used as the barrier layer of an exterior packaging material for an electricity storage device that includes at least a substrate layer, a barrier layer, and a heat-sealable resin layer. Specific examples of exterior packaging materials for electricity storage devices that use the aluminum alloy foil of the present disclosure will be described in detail in the section "2. Exterior packaging material for electricity storage device."

[0016] The aluminum alloy foil of the present disclosure has an Mg (magnesium) content of 0.20% by mass or more and 5.50% by mass or less. The aluminum alloy foil of the present disclosure is mainly composed of Al (aluminum), and specifically, 93.65% by mass or more of aluminum. The Mg content is preferably 0.20% by mass or more and 5.00% by mass or less, more preferably 0.20% by mass or more and 4.00% by mass or less, even more preferably 0.20% by mass or more and 3.00% by mass or less, still more preferably 0.20% by mass or more and 2.50% by mass or less, and particularly preferably 0.20% by mass or more and 2.20% by mass or less.

[0017] The aluminum alloy foil of the present disclosure may contain other components in addition to Mg and Al. Examples of other components include Si (silicon), Fe (iron), Cu (copper), Mn (manganese), Cr (chromium), Zn (zinc), and inevitable impurities. The other components may be one type or two or more types.

[0018] From the viewpoint of obtaining an aluminum alloy foil that effectively suppresses corrosion when current is applied with an electrolyte attached, the aluminum alloy foil of the present disclosure preferably has a Si content of 0.40 mass% or less, an Fe content of 0.70 mass% or less, a Cu content of 0.20 mass% or less, an Mn content of 1.00 mass% or less, a Cr content of 0.50 mass% or less, and a Zn content of 0.25 mass% or less, and other inevitable impurities each of which is 0.05 mass% or less and a total of 0.15 mass% or less, with the balance being Al. An aluminum alloy foil having such a composition is similar to an aluminum alloy having the composition of alloy number A5000 series aluminum in JIS H4000:2014, and can be produced in the same manner as known aluminum alloy foils, for example, through the steps of melting, homogenization, hot rolling, cold rolling, intermediate annealing, cold rolling, and final annealing. The manufacturing conditions of the aluminum alloy foil can be found, for example, in JP-A No. 2005-163077, etc. Analysis of each chemical component contained in the aluminum alloy foil is carried out by analytical tests specified in JIS H4160-1994.

[0019] In the present disclosure, as shown in the schematic diagram of Fig. 16, when any 100 second phase particles 3b within the field of view of an optical microscope are examined in a cross section of the aluminum alloy foil in the thickness direction, and the linear distance connecting the leftmost end of each second phase particle 3b in the direction perpendicular to the thickness direction to the rightmost end in the direction perpendicular to the thickness direction is defined as diameter y, the average diameter y of the top 20 second phase particles 3b in descending order of diameter y is preferably 10.0 µm or less. This makes it possible to provide an aluminum alloy foil with excellent formability, even if it is an extremely thin aluminum alloy foil with a thickness of, for example, about 85 µm or less, further about 50 µm or less, further about 40 µm or less, or even about 35 µm or less, when the aluminum alloy foil is laminated on an outer casing material for an electricity storage device and molded, with pinholes and cracks unlikely to occur. Furthermore, in the present disclosure, since the average diameter y of the second phase particles 3b in the aluminum alloy foil is 10.0 μm or less, the thickness of the aluminum alloy foil is, for example, about 85 μm or less, further about 50 μm or less, further about 40 μm or less, or even about 35 μm or less, and even when the total thickness of the exterior material for an electricity storage device is as thin as, for example, a thickness described below, pinholes and cracks are unlikely to occur during molding, and the exterior material has excellent moldability.

[0020] From the viewpoint of further improving moldability, the average diameter y is more preferably about 1.0 to 8.0 μm, and even more preferably about 1.0 to 6.0 μm. Note that, because Fig. 16 is a schematic diagram, the drawing is omitted and not all 100 second-phase particles 3b are depicted.

[0021] In the present disclosure, the second phase particles contained in the aluminum alloy foil refer to intermetallic compound particles present in the aluminum alloy, and are crystallized phase particles separated by rolling or precipitated phase particles precipitated during homogenization treatment or annealing.

[0022] When a cross section of an aluminum alloy foil in the thickness direction is observed with a scanning electron microscope (SEM), crystal grains usually have boundaries where multiple crystals meet. In contrast, second-phase particles usually have boundaries that form a single crystal. Furthermore, because the crystal grains and second-phase particles are in different phases, they are characterized by different colors in SEM images. Furthermore, when a cross section of an aluminum alloy foil in the thickness direction is observed with an optical microscope, only the second-phase particles appear black due to the difference in phase between the crystal grains and the second-phase particles, making observation easier.

[0023] From the viewpoint of further improving formability, the average crystal grain size in the aluminum alloy foil is preferably 20.0 μm or less, more preferably about 1.0 to 15.0 μm, and even more preferably about 1.0 to 10.0 μm. When the average crystal grain size in the aluminum alloy foil is 20.0 μm or less and the diameter y of the second-phase particles 3b is within the above range, the formability of the packaging material for an electricity storage device, which will be described later, can be further improved.

[0024] In the present disclosure, the average crystal grain size in an aluminum alloy foil is determined by observing a cross section of the aluminum alloy foil in the thickness direction with a scanning electron microscope (SEM), and for 100 aluminum alloy crystal grains 3a located within the field of view, the maximum diameter x is defined as the linear distance connecting the leftmost end of each crystal grain in the direction perpendicular to the thickness direction to the rightmost end of each crystal grain in the direction perpendicular to the thickness direction, as shown in the schematic diagram of Fig. 16. Note that, because Fig. 16 is a schematic diagram, the drawing of all 100 crystal grains 3a is omitted, and the drawing of all 100 crystal grains 3a is not performed.

[0025] The thickness of the aluminum alloy foil in the packaging material for an electricity storage device may be such that it at least functions as a barrier layer that prevents moisture from penetrating, with the lower limit being about 9 μm or more and the upper limit being about 200 μm or less. From the viewpoint of reducing the thickness of the exterior material for an electricity storage device, the upper limit of the thickness of the aluminum alloy foil 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 the lower limit is preferably about 10 μm or more, even more preferably about 20 μm or more, and more preferably about 25 μm or more. Preferred ranges for the thickness include about 10 to 85 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 35 μm, about 20 to 85 μm, about 20 to 50 μm, about 20 to 40 μm, about 20 to 35 μm, about 25 to 85 μm, about 25 to 50 μm, about 25 to 40 μm, and about 25 to 35 μm.

[0026] Furthermore, it is preferable that at least one side of the aluminum alloy foil be provided with a corrosion-resistant coating to prevent dissolution and corrosion of the aluminum alloy foil. The aluminum alloy foil may be provided with a corrosion-resistant coating on both sides. Here, the corrosion-resistant coating refers to a thin film formed on the surface of the aluminum alloy foil by, for example, a hydrothermal treatment such as boehmite treatment, a chemical conversion treatment, anodizing treatment, a plating treatment with nickel or chromium, or a corrosion prevention treatment such as applying a coating agent, to provide the aluminum alloy foil with corrosion resistance (e.g., acid resistance, alkali resistance, etc.). Specifically, the corrosion-resistant coating refers to a coating that improves the acid resistance of the aluminum alloy foil (acid-resistant coating), a coating that improves the alkali resistance of the aluminum alloy foil (alkali-resistant coating), etc. The treatment for forming the corrosion-resistant coating may be one type or a combination of two or more types. Furthermore, not only one layer but also multiple layers can be formed. Furthermore, among these treatments, the hydrothermal treatment and anodizing treatment are treatments in which the metal foil surface is dissolved by a treatment agent to form a metal compound with excellent corrosion resistance. These treatments may be included in the definition of chemical conversion treatment. When an aluminum alloy foil is provided with a corrosion-resistant coating, the aluminum alloy foil includes the corrosion-resistant coating.

[0027] The corrosion-resistant coating prevents delamination between the aluminum alloy foil and the base layer during molding of the exterior material for an electricity storage device, prevents dissolution and corrosion of the aluminum alloy foil surface and dissolution and corrosion of aluminum oxide present on the aluminum alloy foil surface due to hydrogen fluoride produced by the reaction between the electrolyte and water, and improves the adhesion (wettability) of the aluminum alloy foil surface, thereby preventing delamination between the base layer and the aluminum alloy foil during heat sealing and between the base layer and the aluminum alloy foil during molding.

[0028] Various corrosion-resistant coatings formed by chemical conversion treatments are known, including corrosion-resistant coatings containing at least one of phosphates, chromates, fluorides, triazine thiol compounds, and rare earth oxides. Examples of chemical conversion treatments using phosphates and chromates include chromate chromate treatment, phosphate chromate treatment, phosphate-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 acetylacetate, 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 paint-on chromate treatment, with paint-on chromate treatment being preferred. This paint-type chromate treatment involves first degreasing at least the inner surface of a barrier layer (e.g., an aluminum alloy foil) using a well-known method such as alkali immersion, electrolytic cleaning, acid pickling, electrolytic pickling, or acid activation, and then coating the degreased surface with a treatment solution primarily 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 solution primarily composed of a nonmetallic phosphate and a mixture of these nonmetallic salts, or a mixture of these with a synthetic resin, using a well-known coating method such as roll coating, gravure printing, or immersion, followed by drying. The treatment solution can be, for example, water, alcoholic solvents, hydrocarbon solvents, ketone solvents, ester solvents, or ether solvents, with water being preferred. The resin component used here may be a polymer such as a phenolic resin or an acrylic resin, or may be a chromate treatment using an aminated phenol polymer having repeating units represented by the following general formulas (1) to (4): In the aminated phenol 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 types.The acrylic resin is preferably polyacrylic acid, an acrylic acid methacrylic acid ester copolymer, an acrylic acid maleic acid copolymer, an acrylic acid styrene copolymer, or a derivative thereof such as a sodium salt, an ammonium salt, or an amine salt. A derivative of polyacrylic acid, such as an ammonium salt, a sodium salt, or an amine salt of polyacrylic acid, is particularly preferred. In the present disclosure, polyacrylic acid refers to a polymer of acrylic acid. The acrylic resin is also preferably a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic acid anhydride, or an ammonium salt, a sodium salt, or an amine salt of a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic acid anhydride. Only one type of acrylic resin may be used, or two or more types may be mixed and used.

[0029] [ka]

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] In the general formulas (1) to (4), X represents a hydrogen atom, a hydroxy group, an alkyl group, a hydroxyalkyl group, an allyl group, or a benzyl group. 1 and R 2 are the same or different and represent a hydroxy group, an alkyl group, or a hydroxyalkyl group. 1 and R 2Examples of the alkyl group represented by X and R include linear or branched alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl. 1 and R 2 Examples of the hydroxyalkyl group represented by the formula (1) include a linear or branched alkyl group having 1 to 4 carbon atoms 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. 1 and R 2 The alkyl group and hydroxyalkyl group represented by the formula (I) may be the same or different. In the 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 repeating units represented by the 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 can be prepared, for example, by polycondensing a phenol compound or a naphthol compound with formaldehyde to produce a polymer comprising repeating units represented by the formula (I) or (III), and then polycondensing the polymer with formaldehyde and an amine (R 1 R 2 NH) to the functional group (-CHNR 1 R 2 The aminated phenol polymers can be used singly or in combination of two or more.

[0034] Another example of a corrosion-resistant coating is a thin film formed by a coating-type corrosion prevention treatment in which a coating agent containing at least one selected from the group consisting of a rare earth element oxide sol, an anionic polymer, and a cationic polymer is applied. The coating agent may further contain phosphoric acid or a phosphate salt, 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, with cerium oxide being preferred from the perspective of further improving adhesion. The rare earth element oxide contained in the corrosion-resistant coating can be used alone or in combination of two or more. The liquid dispersion medium for the rare earth element oxide sol can be various solvents such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, with water being preferred. Preferred examples of cationic polymers include polyethyleneimine, ionic polymer complexes composed of polyethyleneimine and a polymer having a carboxylic acid, primary amine-grafted acrylic resins in which a primary amine is graft-polymerized onto an acrylic backbone, polyallylamine or its derivatives, and aminated phenols. Preferred anionic polymers are poly(meth)acrylic acid or its salts, or copolymers primarily composed of (meth)acrylic acid or its salts. The crosslinking agent is preferably at least one selected from the group consisting of a compound having a functional group selected from an isocyanate group, a glycidyl group, a carboxyl group, and an oxazoline group, and a silane coupling agent. The phosphoric acid or phosphoric acid salt is preferably a condensed phosphoric acid or a condensed phosphate salt.

[0035] An 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 a barrier layer and baking the coating at 150°C or higher.

[0036] The corrosion-resistant coating may have a laminated structure, if necessary, by further laminating at least one of a cationic polymer and an anionic polymer, such as those mentioned above.

[0037] The composition of the corrosion-resistant film can be analyzed using, for example, time-of-flight secondary ion mass spectrometry.

[0038] The amount of corrosion-resistant film formed on the surface of the aluminum alloy foil in the chemical conversion treatment is not particularly limited. For example, in the case of a coating-type chromate treatment, the amount of the corrosion-resistant film formed on the surface of the aluminum alloy foil is 2 It is desirable that the chromate compound is contained in an amount, in terms of chromium, of about 0.5 to 50 mg, preferably about 1.0 to 40 mg, the phosphorus compound in terms of phosphorus, and the aminated phenol polymer in an amount, in terms of phosphorus, of about 1.0 to 200 mg, preferably about 5.0 to 150 mg, per unit area.

[0039] The thickness of the corrosion-resistant coating 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 strength of the coating and the adhesive strength with the barrier layer or the thermally adhesive resin layer. The thickness of the corrosion-resistant coating can be measured by observation with a transmission electron microscope, or by a combination of observation with a transmission electron microscope and energy dispersive X-ray spectroscopy or electron energy loss spectroscopy. Analysis of the composition of the corrosion-resistant coating using time-of-flight secondary ion mass spectrometry can reveal the thickness of the corrosion-resistant coating, for example, by measuring the thickness of the coating with secondary ions consisting of Ce, P, and O (e.g., Ce2PO4 + , CePO4 - At least one of the following ions may be present: Cr, P, and O secondary ions (e.g., CrPO2 + , CrPO4 - Peaks derived from at least one of the above are detected.

[0040] The chemical conversion treatment is carried out by applying a solution containing a compound used to form a corrosion-resistant coating to the surface of an aluminum alloy foil by bar coating, roll coating, gravure coating, immersion, or other methods, and then heating the aluminum alloy foil to a temperature of approximately 70 to 200°C. Furthermore, before subjecting the aluminum alloy foil to the chemical conversion treatment, the aluminum alloy foil may be subjected to a degreasing treatment using an alkali immersion method, electrolytic cleaning, acid cleaning, electrolytic acid cleaning, or other methods. By performing such a degreasing treatment, the chemical conversion treatment of the surface of the aluminum alloy foil can be carried out more efficiently. Furthermore, by using an acid degreasing agent prepared by dissolving a fluorine-containing compound in an inorganic acid for the degreasing treatment, not only the metal foil can be degreased but also a passive metal fluoride can be formed. In such cases, only the degreasing treatment may be performed.

[0041] 2. Exterior materials for energy storage devices As shown in Figures 1 to 4, for example, an electrical storage device packaging material 10 of the present disclosure is composed of a laminate including at least a base material layer 1, a barrier layer 3, and a heat-sealable resin layer 4 in this order. In the electrical storage device packaging material 10, the base material layer 1 is the outermost layer, and the heat-sealable resin layer 4 is the innermost layer. When assembling an electrical storage device using the electrical storage device packaging material 10 and an electrical storage device element, the electrical storage device element is housed in a space formed by heat-sealing the peripheral portions of the electrical storage device packaging material 10 with the heat-sealable resin layers 4 facing each other.

[0042] The barrier layer 3 of the packaging material for an electricity storage device of the present disclosure contains the aluminum alloy foil of the present disclosure. That is, the barrier layer 3 of the packaging material for an electricity storage device of the present disclosure can be composed of the aluminum alloy foil of the present disclosure. The packaging material for an electricity storage device of the present disclosure using the aluminum alloy foil of the present disclosure effectively suppresses corrosion of the aluminum alloy foil.

[0043] As shown in Figures 2 to 4, for example, the packaging material 10 for an electricity storage device may have an adhesive layer 2 between the base material layer 1 and the barrier layer 3, if necessary, for the purpose of increasing the adhesion between these layers. Furthermore, as shown in Figures 3 and 4, for example, the packaging material 10 for an electricity storage device may have an adhesive layer 5 between the barrier layer 3 and the heat-sealable resin layer 4, if necessary, for the purpose of increasing the adhesion between these layers. Furthermore, as shown in Figure 4, a surface coating layer 6 or the like may be provided on the outer side of the base material layer 1 (the side opposite to the heat-sealable resin layer 4 side), if necessary.

[0044] The thickness of the laminate constituting the electrical storage device packaging material 10 is not particularly limited, but the upper limit, from the viewpoint of cost reduction, improving energy density, etc., is, for example, 300 μm or less, preferably about 180 μm or less, about 155 μm or less, or about 120 μm or less; and the lower limit, from the viewpoint of maintaining the function of the electrical storage device packaging material to protect the electrical storage device elements, is preferably about 35 μm or more, about 45 μm or more, or about 60 μm or more; preferred ranges include, for example, about 35 to 180 μm, about 35 to 155 μm, about 35 to 120 μm, about 45 to 180 μm, about 45 to 155 μm, about 45 to 120 μm, about 60 to 180 μm, about 60 to 155 μm, or about 60 to 120 μm.

[0045] In the packaging material for an electricity storage device, the MD (Machine Direction) and TD (Transverse Direction) of the barrier layer 3 described below can usually be determined during the manufacturing process. For example, when the barrier layer 3 is made of an aluminum alloy foil, linear streaks called rolling marks are formed on the surface of the aluminum alloy foil in the rolling direction (RD) of the aluminum alloy foil. Since the rolling marks extend along the rolling direction, the rolling direction of the aluminum alloy foil can be determined by observing the surface of the aluminum alloy foil. Furthermore, during the manufacturing process of a laminate, the MD of the laminate usually coincides with the RD of the aluminum alloy foil, so the MD of the laminate can be identified by observing the surface of the aluminum alloy foil and identifying the rolling direction (RD) of the aluminum alloy foil. Furthermore, since the TD of the laminate is perpendicular to the MD of the laminate, the TD of the laminate can also be identified.

[0046] In the packaging material 10 for an electricity storage device of the present disclosure, with the heat-sealable resin layers 4 facing each other, a 7 mm wide metal plate is used to heat and pressurize both sides of the test sample in the stacking direction under conditions of a temperature of 190°C, a surface pressure of 2.0 MPa, and a time of 3 seconds to heat-seal the heat-sealable resin layers 4 (see FIGS. 10 and 11 ). Next, as shown in FIG. 12 , the heat-sealed interfaces are peeled off in a T-peel manner using a tensile tester at a temperature of 25°C, a pulling speed of 300 mm / min, a peel angle of 180°, and a chuck distance of 50 mm for 1.5 seconds from the start of tensile strength measurement. The maximum tensile strength (seal strength) measured is preferably 110 N / 15 mm or more, and more preferably 120 N / 15 mm or more. The upper limit of the tensile strength is, for example, about 200 N / 15 mm or less, and preferred ranges include 110 to 200 N / 15 mm and 120 to 200 N / 15 mm. In order to set such a tensile strength, for example, the type, composition, molecular weight, etc. of the resin constituting the heat-fusible resin layer are adjusted.

[0047] Furthermore, in the exterior packaging material 10 for an electricity storage device of the present disclosure, with the heat-sealable resin layers 4 facing each other, heat and pressure are applied from both sides of the test sample in the stacking direction using 7 mm-wide metal plates under conditions of a temperature of 190°C, a surface pressure of 2.0 MPa, and a time of 3 seconds to heat-seal the heat-sealable resin layers 4 (see FIGS. 10 and 11 ). Next, as shown in FIG. 12 , the heat-sealed interfaces are peeled off in a T-peel manner using a tensile tester under conditions of a temperature of 140°C, a pulling speed of 300 mm / min, a peel angle of 180°, and a chuck distance of 50 mm for 1.5 seconds from the start of tensile strength measurement. The maximum tensile strength (seal strength) measured is preferably 3.0 N / 15 mm or more, and more preferably 4.0 N / 15 mm or more. The upper limit of the tensile strength is, for example, about 5.0 N / 15 mm or less, and preferred ranges include 3.0 to 5.0 N / 15 mm and 4.0 to 5.0 N / 15 mm. As described above, the heat resistance temperature of the separator inside the electricity storage device is generally around 120 to 140°C, so in the packaging material for an electricity storage device of the present disclosure, it is preferable that the maximum value of the tensile strength (sealing strength) in a high-temperature environment of 140°C satisfies the above value. In order to achieve such a tensile strength, for example, the type, composition, molecular weight, etc. of the resin constituting the heat-sealable resin layer are adjusted.

[0048] As shown in the examples below, the tensile tests at each temperature were carried out in a thermostatic chamber. Once the temperature had reached the specified value (25°C or 140°C), the test sample was attached to a chuck and held there for 2 minutes before starting the measurement.

[0049] Seal strength after contact with electrolyte Furthermore, the electrical storage device packaging material 10 of the present disclosure is prepared by contacting the electrical storage device packaging material with an electrolyte solution (a solution having a lithium hexafluorophosphate concentration of 1 mol / L and containing ethylene carbonate, diethyl carbonate, and dimethyl carbonate in a volume ratio of 1:1:1 (a solution obtained by mixing ethylene carbonate, diethyl carbonate, and dimethyl carbonate in a volume ratio of 1:1:1)) in an environment of 85°C for 72 hours, and then heat-sealing the heat-sealing resin layers together under conditions of a temperature of 190°C, a surface pressure of 2.0 MPa, and a time of 3 seconds with the electrolyte solution adhered to the surfaces of the heat-sealing resin layers, and the seal strength when the heat-sealed interface is peeled off is preferably 60% or more of the seal strength when not in contact with the electrolyte solution (seal strength retention rate of 60% or more), more preferably 80% or more, and even more preferably 100%.

[0050] (Method for measuring the retention rate of seal strength) The seal strength measured by the following method before contact with the electrolyte is taken as the reference (100%), and the retention rate (%) of the seal strength after contact with the electrolyte is calculated.

[0051] <Measurement of seal strength before contact with electrolyte> In the following <Measurement of seal strength after contact with electrolyte>, the tensile strength (seal strength) is measured in the same manner except that no electrolyte is injected into the test sample. The maximum tensile strength until the heat-sealed portion is completely peeled off is taken as the seal strength before contact with the electrolyte.

[0052] <Measurement of seal strength after contact with electrolyte> As shown in the schematic diagram of Figure 14, the packaging material for an energy storage device was cut into a rectangle with a width (x direction) of 100 mm and a length (z direction) of 200 mm to prepare a test sample (Figure 14a). The test sample was folded back at the center in the z direction so that the heat-sealable resin layer was overlapping (Figure 14b). Next, both ends of the folded test sample in the x direction were heat-sealed (temperature: 190°C, surface pressure: 2.0 MPa, time: 3 seconds) to form a bag-like shape with an opening E (Figure 14c). Next, 6 g of electrolyte (a solution of 1 mol / L lithium hexafluorophosphate in a 1:1:1 volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate) was injected through opening E of the bag-shaped test sample (Figure 14d), and the end of opening E was heat-sealed (temperature: 190°C, surface pressure: 2.0 MPa, time: 3 seconds) (Figure 14e). Next, the bag-shaped test sample was placed with the folded portion facing downwards and left at 85°C for a specified storage time (e.g., 72 hours, which is the time for contact with the electrolyte). The edge of the test sample was then cut (Figure 14e) to drain the electrolyte. Next, with the electrolyte still attached to the surface of the heat-sealable resin layer, the top and bottom of the test sample were sandwiched between metal plates (7 mm wide). The heat-sealable resin layers were then heat-sealed together at 190°C, a surface pressure of 1.0 MPa, and a time of 3 seconds (Figure 14f). Next, the test sample was cut into 15 mm wide pieces using a double-edged sample cutter (Figures 14f and 14g) so that the seal strength at a 15 mm width (x direction) could be measured. Next, the heat-sealed interface was peeled using a tensile tester at 25°C, a tensile speed of 300 mm / min, a peel angle of 180°, and a chuck distance of 50 mm, to measure the tensile strength (seal strength) (Figure 12). The maximum tensile strength until the heat-sealed portion is completely peeled off is defined as the seal strength after contact with the electrolyte.

[0053] Each layer that forms the exterior material for an electricity storage device [Base material layer 1] In the present disclosure, the substrate layer 1 is a layer provided for the purpose of allowing the packaging material for an electricity storage device to function as a substrate. The substrate layer 1 is located on the outer layer side of the packaging material for an electricity storage device.

[0054] There are no particular limitations on the material forming the base layer 1, as long as it functions as a base, i.e., has at least insulating properties. The base layer 1 can be formed using, for example, a resin, which may contain additives described below.

[0055] When the base layer 1 is formed of a resin, the base layer 1 may be, for example, a resin film formed 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, with biaxially stretched films being 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.

[0056] Examples of resins that form the base layer 1 include 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. Furthermore, it may also be a mixture of these resins.

[0057] Of these, preferred resins for forming the base layer 1 include polyester and polyamide.

[0058] 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 / decanedicarboxylate). These polyesters may be used alone or in combination of two or more.

[0059] 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 (where I represents isophthalic acid and T represents terephthalic acid), which 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 a lactam component or an isocyanate component such as 4,4'-diphenylmethane diisocyanate; polyesteramide copolymers and polyetheresteramide copolymers, which are copolymers of copolymerized polyamides with polyesters or polyalkylene ether glycols; and polyamides such as copolymers of these copolymers. These polyamides may be used singly or in combination of two or more.

[0060] The base 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 oriented polyethylene terephthalate film, a biaxially oriented polybutylene terephthalate film, a biaxially oriented nylon film, and a biaxially oriented polypropylene film.

[0061] The base material layer 1 may be a single layer, or may be composed of two or more layers. When the base material layer 1 is composed of two or more layers, the base material layer 1 may be a laminate in which resin films are laminated with an adhesive or the like, or a laminate of resin films formed by co-extrusion of resins into two or more layers. Furthermore, a laminate of resin films formed by co-extrusion of resins into two or more layers may be used as the base material layer 1 without being stretched, or may be uniaxially or biaxially stretched to form the base material layer 1.

[0062] Specific examples of laminates of two or more resin films in the base layer 1 include laminates of polyester film and nylon film, laminates of two or more nylon films, and laminates of two or more polyester films. Preferably, laminates of stretched nylon film and stretched polyester film, laminates of two or more stretched nylon films, and laminates of two or more stretched polyester films are preferred. For example, when the base layer 1 is a laminate of two resin films, a laminate of polyester resin film and polyester resin film, a laminate of polyamide resin film and polyamide resin film, or a laminate of polyester resin film and polyamide resin film is preferred. A laminate of polyethylene terephthalate film and polyethylene terephthalate film, a laminate of nylon film and nylon film, or a laminate of polyethylene terephthalate film and nylon film is more preferred. Furthermore, when the base layer 1 is a laminate of two or more resin films, it is preferred that the polyester resin film be located as the outermost layer of the base layer 1, because polyester resins are less likely to discolor when an electrolyte solution adheres to their surface.

[0063] When the base layer 1 is a laminate of two or more resin film layers, the two or more resin film layers may be laminated via an adhesive. Examples of preferred adhesives include the same adhesives as those exemplified for adhesive layer 2 described below. The method for laminating two or more resin film layers is not particularly limited, and known methods can be used, such as dry lamination, sandwich lamination, extrusion lamination, and thermal lamination, with dry lamination being preferred. When laminating by dry lamination, a polyurethane adhesive is preferably used as the adhesive. In this case, the thickness of the adhesive may be, for example, about 2 to 5 μm. Alternatively, an anchor coat layer may be formed on the resin film before lamination. Examples of the anchor coat layer include the same adhesives as those exemplified for adhesive layer 2 described below. In this case, the thickness of the anchor coat layer may be, for example, about 0.01 to 1.0 μm.

[0064] Furthermore, 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 the interior of the base material layer 1. Only one type of additive may be used, or two or more types may be mixed and used.

[0065] In the present disclosure, from the viewpoint of improving the formability of the exterior material for an electrical storage device, it is preferable that a lubricant be present on the surface of the base layer 1. The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, 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 amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearic acid amide. 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 adipamide, and N,N'-distearyl sebacic acid amide. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacic acid amide. Specific examples of fatty acid ester amides include stearamidoethyl stearate. Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, N,N'-distearyl isophthalic acid amide, etc. The lubricants may be used singly or in combination of two or more.

[0066] When a lubricant is present on the surface of the base layer 1, the amount of the lubricant is not particularly limited, but is preferably about 3 mg / m 2 or more, more preferably 4 to 15 mg / m 2 approximately, more preferably 5 to 14 mg / m 2 The degree of

[0067] The lubricant present on the surface of the base layer 1 may be a lubricant exuded from the resin that constitutes the base layer 1, or a lubricant applied to the surface of the base layer 1.

[0068] The thickness of the base layer 1 is not particularly limited as long as it functions as a base, but may be, for example, about 3 to 50 μm, and preferably about 10 to 35 μm. When the base layer 1 is a laminate of two or more resin films, the thickness of each resin film constituting each layer is preferably about 2 to 25 μm.

[0069] [Adhesive layer 2] In the packaging 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 needed for the purpose of increasing the adhesion between them.

[0070] The adhesive layer 2 is formed from an adhesive capable of bonding the base material 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 evaporation 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.

[0071] 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-based 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. Among these adhesive components, polyurethane adhesives are preferred. Furthermore, the adhesive strength of these adhesive component resins can be increased by using an appropriate curing agent in combination. The curing agent is selected appropriately 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.

[0072] Examples of polyurethane adhesives include polyurethane adhesives containing a base agent containing a polyol compound and a curing agent containing an isocyanate compound. Preferred examples include two-component curing polyurethane adhesives that use a polyol such as polyester polyol, polyether polyol, or acrylic polyol as the base agent and an aromatic or aliphatic polyisocyanate as the curing agent. Furthermore, as the polyol compound, it is preferable to use a polyester polyol that has hydroxyl groups on the side chain in addition to the terminal hydroxyl groups of the repeating unit. Forming the adhesive layer 2 from a polyurethane adhesive provides the electrical storage device exterior material with excellent electrolyte resistance, preventing peeling of the base layer 1 even when the electrolyte adheres to the side surface.

[0073] Furthermore, the adhesive layer 2 may contain other components as long as they do not impair adhesion, and may contain colorants, thermoplastic elastomers, tackifiers, fillers, and the like. When the adhesive layer 2 contains a colorant, the exterior material for an electricity storage device can be colored. 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.

[0074] The type of pigment is not particularly limited as 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, and other examples include finely powdered mica and fish scale foil.

[0075] Among colorants, carbon black is preferred in order to give the exterior appearance of the electrical storage device packaging material a black color, for example.

[0076] 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 particle size distribution measuring device.

[0077] The content of the pigment in the adhesive layer 2 is not particularly limited as long as it colors the packaging material for an electricity storage device, and may be, for example, about 5 to 60 mass %, and preferably 10 to 40 mass %.

[0078] 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 together, but the lower limit is, for example, about 1 μm or more, or about 2 μm or more, and the upper limit is about 10 μm or less, or about 5 μm or less, and preferred ranges are about 1 to 10 μm, about 1 to 5 μm, about 2 to 10 μm, or about 2 to 5 μm.

[0079] [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 needed. 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. Alternatively, a colored layer may be provided on the outside of the base material layer 1. By providing a colored layer, the packaging material for an electricity storage device can be colored.

[0080] The colored layer can be formed, for example, by applying ink containing a colorant to the surface of the base layer 1, the surface of the adhesive layer 2, or the surface of the barrier layer 3. Known colorants such as pigments and dyes can be used. Furthermore, only one type of colorant may be used, or two or more types may be mixed together.

[0081] Specific examples of the colorant contained in the colored layer include the same as those exemplified in the section [Adhesive layer 2].

[0082] [Barrier layer 3] In the packaging material for an electricity storage device, the barrier layer 3 is a layer that at least prevents the penetration of moisture.

[0083] The barrier layer 3 of the packaging material for an electricity storage device of the present disclosure contains the aluminum alloy foil of the present disclosure. That is, the barrier layer 3 of the packaging material for an electricity storage device of the present disclosure can be composed of the aluminum alloy foil of the present disclosure. Details of the aluminum alloy foil of the present disclosure are as described in the section "1. Aluminum alloy foil."

[0084] [Thermal adhesive resin layer 4] In the 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 together when the electricity storage device is assembled.

[0085] The resin constituting the heat-sealable resin layer 4 is not particularly limited as long as it is heat-sealable, but resins containing a polyolefin skeleton, such as polyolefin and acid-modified polyolefin, are preferred. The presence of a polyolefin skeleton in the resin constituting the heat-sealable resin layer 4 can be determined by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like. Furthermore, when the resin constituting the heat-sealable resin layer 4 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 at a wavenumber of 1760 cm. -1 Near and wave number 1780cm -1 A peak derived from maleic anhydride is detected around . When the thermally adhesive resin layer 4 is a layer made of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride is detected when measured by infrared spectroscopy. However, if the degree of acid modification is low, the peak becomes small and may not be detected. In such cases, analysis can be performed by nuclear magnetic resonance spectroscopy.

[0086] 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.

[0087] The polyolefin may also be a cyclic polyolefin. Cyclic polyolefins are copolymers of olefins and cyclic monomers, and examples of olefins constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, and isoprene. Examples of cyclic monomers constituting the cyclic polyolefin include cyclic alkenes such as norbornene; and cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these, preferred are cyclic alkenes, and more preferred are norbornene.

[0088] Acid-modified polyolefins are polymers modified by block polymerization or graft polymerization of polyolefins with an acid component. Examples of acid-modified polyolefins include the above-mentioned polyolefins, copolymers of the above-mentioned polyolefins with polar molecules such as acrylic acid or methacrylic acid, and crosslinked polyolefins. Examples of acid components used for acid modification include carboxylic acids or anhydrides thereof, such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

[0089] The acid-modified polyolefin may be an acid-modified cyclic polyolefin. The 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 onto the cyclic polyolefin. The acid-modified cyclic polyolefin 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.

[0090] Preferred acid-modified polyolefins include polyolefins modified with carboxylic acid or its anhydride, polypropylenes modified with carboxylic acid or its anhydride, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

[0091] The thermally adhesive 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 resins. Furthermore, the thermally adhesive 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.

[0092] Furthermore, the heat-sealable resin layer 4 may contain a lubricant, etc., as necessary. When the heat-sealable resin layer 4 contains a lubricant, the moldability of the electrical storage device packaging material can be improved. The lubricant is not particularly limited, and known lubricants can be used. The lubricants may be used alone or in combination of two or more.

[0093] The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of the lubricant include those exemplified for the base layer 1. The lubricant may be used alone or in combination of two or more.

[0094] When a lubricant is present on the surface of the heat-sealable resin layer 4, the amount of the lubricant is not particularly limited, but from the viewpoint of improving the formability of the electronic packaging material, it is preferably 10 to 50 mg / m 2 approximately, more preferably 15 to 40 mg / m 2 The degree of

[0095] The lubricant present on the surface of the heat-sealable resin layer 4 may be a lubricant exuded from the resin constituting the heat-sealable resin layer 4, or a lubricant applied to the surface of the heat-sealable resin layer 4.

[0096] The thickness of the heat-sealable resin layer 4 is not particularly limited as long as it can heat-seal the heat-sealable resin layers to each other and function 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.

[0097] Even when the thermally adhesive resin layers are contacted with an electrolyte solution in a high-temperature environment and the thermally adhesive resin layers are thermally fused together with the electrolyte solution adhering to the thermally adhesive resin layers, the thermal fusion exhibits even higher seal strength. When the temperature difference T1 and the temperature difference T2 are measured using the method described below, the value obtained by dividing the temperature difference T2 by the temperature difference T1 (the ratio T2 / T1) is preferably 0.55 or greater, and even more preferably 0.60 or greater. As can be seen from the measurement of the temperature differences T1 and T2 described below, the closer the ratio T2 / T1 is to the upper limit of 1.0, the smaller the change in the width between the start point (extrapolated melting onset temperature) and the end point (extrapolated melting end temperature) of the melting peak before and after contact with the electrolyte solution (see the schematic diagram in FIG. 15). That is, the value of T2 is usually equal to or less than the value of T1. The reason why the change in the range between the extrapolated melting onset temperature and the extrapolated melting end temperature of the melting peak becomes large is that the low molecular weight resin contained in the resin constituting the heat-fusible resin layer dissolves in the electrolyte when it comes into contact with the electrolyte, and the range between the extrapolated melting onset temperature and the extrapolated melting end temperature of the melting peak of the heat-fusible resin layer after coming into contact with the electrolyte becomes smaller than that before coming into contact with the electrolyte.One method for reducing the change in the range between the extrapolated melting onset temperature and the extrapolated melting end temperature of the melting peak is to adjust the proportion of the low molecular weight resin contained in the resin constituting the heat-fusible resin layer.

[0098] (Measurement of temperature difference T1) A DSC curve is obtained for the resin used in the heat-sealable resin layer of each of the above-mentioned packaging materials for an electric storage device using differential scanning calorimetry (DSC) in accordance with the provisions of JIS K7121: 2012. From the obtained DSC curve, the temperature difference T1 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat-sealable resin layer is measured.

[0099] (Measurement of temperature difference T2) The resin used for the heat-sealable resin layer was placed in an electrolyte solution containing 1 mol / L of lithium hexafluorophosphate and a 1:1:1 volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate in an 85°C environment for 72 hours, after which it was thoroughly dried. Next, a differential scanning calorimetry (DSC) curve was obtained for the dried polypropylene in accordance with JIS K7121:2012. From the obtained DSC curve, the temperature difference T2 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the dried heat-sealable resin layer was measured.

[0100] A commercially available differential scanning calorimeter can be used to measure the extrapolated melting onset temperature and extrapolated melting end temperature of the melting peak temperature. The DSC curve used is as follows: the test sample is held at -50°C for 10 minutes, then heated to 200°C at a heating rate of 10°C / min (first run), held at 200°C for 10 minutes, cooled to -50°C at a heating rate of -10°C / min, held at -50°C for 10 minutes, heated to 200°C at a heating rate of 10°C / min (second run), held at 200°C for 10 minutes, and then heated to 200°C for the second run. When measuring the temperature difference T1 and the temperature difference T2, the melting peak appearing in the range of 120 to 160°C in each DSC curve is analyzed, focusing on the melting peak with the largest difference in thermal energy input. Even if two or more overlapping peaks exist, only the melting peak with the largest difference in thermal energy input is analyzed.

[0101] The extrapolated melting onset temperature refers to the start point of the melting peak temperature and is the temperature at the intersection of a line drawn by extending the baseline on the low-temperature side (65-75°C) toward the high-temperature side and a tangent drawn at the point where the gradient is maximum on the curve on the low-temperature side of the melting peak where the difference in thermal energy input is maximum. The extrapolated melting end temperature refers to the end point of the melting peak temperature and is the temperature at the intersection of a line drawn by extending the baseline on the high-temperature side (170°C) toward the low-temperature side and a tangent drawn at the point where the gradient is maximum on the curve on the high-temperature side of the melting peak where the difference in thermal energy input is maximum.

[0102] In the packaging material for an electricity storage device according to the present disclosure, even when an electrolytic solution contacts the heat-sealable resin layer in a high-temperature environment and the heat-sealable resin layers are heat-sealed together with the electrolytic solution adhering to the heat-sealable resin layer, the value obtained by dividing the temperature difference T2 by the temperature difference T1 (ratio T2 / T1) is, for example, 0.55 or more, preferably 0.60 or more, more preferably 0.70 or more, and even more preferably 0.75 or more. Preferred ranges include about 0.55 to 1.0, about 0.60 to 1.0, about 0.70 to 1.0, and about 0.75 to 1.0. The upper limit is, for example, 1.0. To achieve such a ratio T2 / T1, for example, the type, composition, molecular weight, etc. of the resin constituting the heat-sealable resin layer 4 can be adjusted.

[0103] Furthermore, even when an electrolyte solution comes into contact with the heat-sealable resin layer in a high-temperature environment and the heat-sealable resin layers are heat-sealed together with the electrolyte solution adhering to the heat-sealable resin layer, from the viewpoint of exhibiting even higher seal strength by heat fusion, the absolute value |T2-T1| of the difference between the temperature difference T2 and the temperature difference T1 is, for example, about 15°C or less, preferably about 10°C or less, more preferably about 8°C or less, and even more preferably about 7.5°C or less. Preferred ranges include about 0 to 15°C, about 0 to 10°C, about 0 to 8°C, about 0 to 7.5°C, about 1 to 15°C, about 1 to 10°C, about 1 to 8°C, about 1 to 7.5°C, about 2 to 15°C, about 2 to 10°C, about 2 to 8°C, about 2 to 7.5°C, about 5 to 15°C, about 5 to 10°C, about 5 to 8°C, and about 5 to 7.5°C. The lower limit of the absolute value of the difference |T2-T1| is, for example, 0° C., 1° C., 2° C., or 5° C. In order to set the absolute value of the difference |T2-T1|, for example, the type, composition, molecular weight, etc. of the resin constituting the thermally adhesive resin layer 4 is adjusted.

[0104] The temperature difference T1 is preferably about 29 to 38° C., and more preferably about 32 to 36° C. The temperature difference T2 is preferably about 17 to 30° C., and more preferably about 26 to 29° C. In order to set such temperature differences T1 and T2, for example, the type, composition, molecular weight, etc. of the resin constituting the heat-fusible resin layer 4 are adjusted.

[0105] [Adhesive layer 5] In the packaging material for an electricity storage device of the present disclosure, the adhesive layer 5 is a layer that is provided as needed between the barrier layer 3 (or corrosion-resistant film) and the heat-sealable resin layer 4 in order to firmly bond them together.

[0106] The adhesive layer 5 is formed from 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 can be, for example, the same adhesive as exemplified for the adhesive layer 2. The resin used to form the adhesive layer 5 preferably contains a polyolefin skeleton, such as the polyolefins and acid-modified polyolefins exemplified for the heat-sealable resin layer 4. The presence of a polyolefin skeleton in the resin constituting the adhesive layer 5 can be determined by, for example, infrared spectroscopy or gas chromatography-mass spectrometry, and the analysis method is not particularly limited. Furthermore, 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 a maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak derived from maleic anhydride is detected at a wavenumber of 1760 cm. -1 Near and wave number 1780cm -1 A peak derived from maleic anhydride is detected around this point. However, if the degree of acid modification is low, the peak may be small and not be detected. In this case, analysis can be performed using nuclear magnetic resonance spectroscopy.

[0107] From the viewpoint of firmly bonding 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 acid or its anhydride, polypropylenes modified with carboxylic acid or its anhydride, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

[0108] Furthermore, from the viewpoint of reducing the thickness of the electrical storage device packaging material while providing an electrical storage device packaging material that has excellent shape stability after molding, the adhesive layer 5 is more preferably 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.

[0109] 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. It 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 preferably contains at least one selected from the group consisting of polyurethane, polyester, and epoxy resin, more preferably polyurethane and epoxy resin. A preferred polyester is, for example, an amide ester resin. Amide ester resins are generally produced by the reaction of a carboxyl group with 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 of curing agents such as compounds having an isocyanate group, compounds having an oxazoline group, and 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.

[0110] Furthermore, from the viewpoint of further enhancing 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 COC 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 COC bond include curing agents having an oxazoline group, curing agents having an epoxy group, and polyurethane. Whether the adhesive layer 5 is a cured product of a resin composition containing such a curing agent 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.

[0111] The compound having an isocyanate group is not particularly limited, but from the viewpoint of effectively improving 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 is a compound having two or more isocyanate groups. Specific examples of polyfunctional isocyanate curing agents include pentane diisocyanate (PDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymers or nurates thereof, mixtures of these, and copolymers with other polymers. Other examples include adducts, biuret compounds, and isocyanurates.

[0112] The content of the compound having an isocyanate group in the adhesive layer 5 is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 0.5 to 40 mass %, of the resin composition constituting the adhesive layer 5. This can effectively improve the adhesion between the barrier layer 3 and the adhesive layer 5.

[0113] The compound having an oxazoline group is not particularly limited as long as it is a compound having an oxazoline skeleton. Specific examples of the compound having an oxazoline group include those having a polystyrene main chain and those having an acrylic main chain. Examples of commercially available products include the Epocross series manufactured by Nippon Shokubai Co., Ltd.

[0114] 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 %, and more preferably in the range of 0.5 to 40 mass %, in the resin composition constituting the adhesive layer 5. This can effectively improve the adhesion between the barrier layer 3 and the adhesive layer 5.

[0115] 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 groups present in the molecule, and known epoxy resins can be used. The weight-average molecular weight of the epoxy resin is preferably about 50 to 2,000, more preferably about 100 to 1,000, and even more preferably about 200 to 800. In the present 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.

[0116] 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.

[0117] The proportion of the epoxy resin in the adhesive layer 5 is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 0.5 to 40 mass %, of the resin composition constituting the adhesive layer 5. This can effectively improve the adhesion between the barrier layer 3 and the adhesive layer 5.

[0118] The polyurethane is not particularly limited, and any known polyurethane can be used. The adhesive layer 5 may be, for example, a cured product of two-component curing polyurethane.

[0119] The proportion of polyurethane in adhesive layer 5 is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 0.5 to 40 mass %, of the resin composition constituting adhesive layer 5. This effectively improves the adhesion between barrier layer 3 and adhesive layer 5 in an atmosphere containing components that induce corrosion of the barrier layer, such as an electrolyte solution.

[0120] 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 the 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.

[0121] The upper limit of the thickness of 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, and 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 an adhesive such as those exemplified for adhesive layer 2 or a 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. Furthermore, when a resin exemplified for the heat-fusible resin layer 4 is used, the thickness is preferably about 2 to 50 μm, more preferably about 10 to 40 μm. When the adhesive layer 5 is an adhesive exemplified for the adhesive layer 2 or a cured product of a resin composition containing an acid-modified polyolefin and a curing agent, the adhesive layer 5 can be formed, for example, by applying the resin composition and curing it by heating or the like. When a resin exemplified for the heat-fusible resin layer 4 is used, the heat-fusible resin layer 4 and the adhesive layer 5 can be formed, for example, by extrusion molding.

[0122] In the packaging material for an electricity storage device according to the present disclosure, the adhesive layer 5 preferably has a logarithmic decrement ΔE at 120°C in rigid pendulum measurement of, for example, 0.50 or less, 0.40 or less, 0.30 or less, 0.26 or less, 0.22 or less, or even 0.20 or less. In the present disclosure, by having the logarithmic decrement ΔE at 120°C be, for example, 0.50 or less, 0.40 or less, 0.30 or less, 0.22 or less, 0.26 or less, or even 0.20 or less, when sealing an electricity storage device element with the packaging material for an electricity storage device, crushing of the adhesive layer when heat-fusible resin layers are heat-fused together is effectively suppressed, and high sealing strength in high-temperature environments is exhibited.

[0123] The logarithmic attenuation at 120°C in rigid pendulum measurement is an index of the hardness of a resin in a high-temperature environment of 120°C, with a smaller logarithmic attenuation indicating a higher resin hardness. In rigid pendulum measurement, the attenuation rate of a pendulum is measured as the resin temperature is increased from a low temperature to a high temperature. In rigid pendulum measurement, the edge of the measurement object is generally brought into contact with the surface of the object, and the object is caused to oscillate in a left-right direction, thereby vibrating the object. In the electrical storage device packaging material of the present disclosure, a hard adhesive layer 5 having a logarithmic attenuation rate of, for example, 0.50 or less, 0.40 or less, 0.30 or less, 0.26 or less, 0.22 or less, or even 0.20 or less in a high-temperature environment of 120°C is disposed between the aluminum alloy foil and the heat-sealable resin layer 4. This suppresses the collapse (thinning) of the adhesive layer 5 during heat fusion of the electrical storage device packaging material, and furthermore, allows the electrical storage device packaging material to exhibit high sealing strength in a high-temperature environment.

[0124] The logarithmic attenuation factor ΔE is calculated by the following formula: ΔE=[ln(A1 / A2)+ln(A2 / A3)+...ln(An / An+1)] / n A: Amplitude n: wave number

[0125] In the packaging material for an electricity storage device of the present disclosure, from the viewpoint of effectively suppressing crushing of the adhesive layer 5 when the heat-sealable resin layers 4 are heat-sealed together and further exhibiting high sealing strength in high-temperature environments, the logarithmic decrement ΔE at 120°C is, for example, about 0.10 to 0.50, about 0.10 to 0.40, about 0.10 to 0.30, preferably about 0.10 to 0.26, about 0.10 to 0.22, preferably about 0.10 to 0.20, and more preferably about 0.10 to 0.16. Note that in order to set the logarithmic decrement ΔE, for example, the type, composition, molecular weight, etc. of the resin constituting the adhesive layer 5 are adjusted.

[0126] In measuring the logarithmic decrement ΔE, a commercially available rigid pendulum physical property tester was used, and a rigid pendulum physical property test was performed on the adhesive layer 5 under the conditions of a cylindrical cylinder edge as the edge pressed against the adhesive layer 5, an initial amplitude of 0.3 degrees, a temperature range of 30°C to 200°C, and a heating rate of 3°C / min. Then, based on the logarithmic decrement at 120°C, standards were established for the effect of the adhesive layer 5 in suppressing collapse and improving seal strength by heat fusion in a high-temperature environment. Note that, for the adhesive layer for measuring the logarithmic decrement ΔE, the packaging material for an electricity storage device was immersed in 15% hydrochloric acid to dissolve the base layer and aluminum alloy foil, and the sample remaining only with the adhesive layer and heat-sealable resin layer was thoroughly dried and used as the measurement subject.

[0127] It is also possible to obtain the electrical storage device packaging material from the electrical storage device and measure the logarithmic decrement ΔE of the adhesive layer 5. When obtaining the electrical storage device packaging material from the electrical storage device and measuring the logarithmic decrement ΔE of the adhesive layer 5, a sample is cut out from the top surface portion of the electrical storage device packaging material that has not been stretched by molding and used as the measurement object.

[0128] Furthermore, in the packaging material for an electricity storage device of the present disclosure, after the heat-sealable resin layers of the laminates constituting the packaging material for an electricity storage device are placed face to face and heated and pressurized in the lamination direction under conditions of a temperature of 190°C, a surface pressure of 0.5 MPa, and a time of 3 seconds, the remaining thickness of the adhesive layer is preferably 70% or more, more preferably 80% or more, and preferred ranges include 70 to 95%, and 80 to 95%. The upper limit of the remaining thickness is, for example, about 95%. The remaining thickness is a value measured by the following method. To achieve the remaining thickness, for example, the type, composition, molecular weight, etc. of the resin constituting the adhesive layer 5 are adjusted.

[0129] <Measurement of remaining adhesive layer thickness> The casing material for an electric storage device is cut into a length of 150 mm and a width of 60 mm to prepare a test sample. Next, the heat-sealable resin layers of the test sample are placed facing each other. Next, in this state, a 7 mm wide metal plate is used to heat and pressurize both sides of the test sample in the stacking direction at a temperature of 190°C, a surface pressure of 0.5 MPa, and a time of 3 seconds to heat-seal the heat-sealable resin layers. Next, the heat-sealed portion of the test sample is cut in the stacking direction using a microtome, and the thickness of the adhesive layer is measured on the exposed cross section. The test sample before heat fusion is also cut in the stacking direction using a microtome in the same manner, and the thickness of the adhesive layer is measured on the exposed cross section. The ratio of the thickness of the adhesive layer after heat fusion to the thickness of the adhesive layer before heat fusion is calculated, and the remaining thickness (%) of the adhesive layer is measured. The thickness of the adhesive layer is measured near the edge of the casing material for an electric storage device, at a location where the thickness is constant.

[0130] It is also possible to obtain the exterior packaging material for an electricity storage device from the electricity storage device and measure the remaining proportion of the thickness of the adhesive layer 5. When obtaining the exterior packaging material for an electricity storage device from the electricity storage device and measuring the remaining proportion of the thickness of the adhesive layer 5, a sample is cut out from the top surface portion of the exterior packaging material for an electricity storage device that has not been stretched by molding and used as the measurement object.

[0131] The logarithmic decrement ΔE of the adhesive layer 5 can be adjusted by, for example, the melt mass flow rate (MFR), molecular weight, melting point, softening point, molecular weight distribution, crystallinity, etc. of the resin constituting the adhesive layer 5.

[0132] [Surface coating layer 6] The packaging material for an electricity storage device according to the present disclosure may have a surface coating layer 6 on the substrate layer 1 (the side of the substrate layer 1 opposite to the barrier layer 3) as needed, for the purpose of improving at least one of design, electrolyte resistance, scratch resistance, formability, etc. The surface coating layer 6 is a layer located on the outermost layer side of the packaging material for an electricity storage device when an electricity storage device is assembled using the packaging material for an electricity storage device.

[0133] The surface coating layer 6 can be formed from a resin such as polyvinylidene chloride, polyester, polyurethane, acrylic resin, or epoxy resin.

[0134] When the resin forming the surface coating layer 6 is a curable resin, the resin may be either a one-component curable resin or a two-component curable resin, but is preferably a two-component curable resin. Examples of two-component curable resins include two-component curable polyurethane, two-component curable polyester, and two-component curable epoxy resin. Among these, two-component curable polyurethane is preferred.

[0135] Examples of two-component curing polyurethanes include polyurethanes containing a base agent containing a polyol compound and a curing agent containing an isocyanate compound. Preferred examples include two-component curing polyurethanes that use a polyol such as polyester polyol, polyether polyol, or acrylic polyol as the base agent and an aromatic or aliphatic polyisocyanate as the curing agent. Furthermore, it is preferable to use a polyester polyol that has hydroxyl groups on the side chain in addition to the terminal hydroxyl groups of the repeating unit as the polyol compound. Forming the surface coating layer 6 from polyurethane provides the electrical storage device exterior material with excellent electrolyte resistance.

[0136] The surface coating layer 6 may contain additives such as the aforementioned lubricants, antiblocking agents, matting agents, flame retardants, antioxidants, tackifiers, and antistatic agents, at least on the surface and / or inside of the surface coating layer 6, as needed, depending on the functionality to be imparted to the surface of the surface coating layer 6. Examples of additives include fine particles with an average particle size of approximately 0.5 nm to 5 μm. The average particle size of the additive is the median size measured with a laser diffraction / scattering particle size distribution analyzer.

[0137] The additive may be either inorganic or organic. The shape of the additive is not particularly limited, and examples thereof include spherical, fibrous, plate-like, amorphous, and scaly shapes.

[0138] Specific examples of additives include talc, silica, graphite, kaolin, montmorillonite, mica, hydrotalcite, silica gel, zeolite, aluminum hydroxide, magnesium hydroxide, zinc oxide, magnesium oxide, aluminum oxide, neodymium oxide, antimony oxide, titanium oxide, cerium oxide, calcium sulfate, barium sulfate, calcium carbonate, calcium silicate, lithium carbonate, calcium benzoate, calcium oxalate, magnesium stearate, alumina, carbon black, carbon nanotubes, high-melting-point nylon, acrylate resin, crosslinked acrylic, crosslinked styrene, crosslinked polyethylene, benzoguanamine, gold, aluminum, copper, and nickel. The additives may be used alone or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferred from the viewpoints of dispersion stability, cost, and the like. The additives may also be subjected to various surface treatments, such as insulation treatment and high-dispersibility treatment.

[0139] The method for forming the surface coating layer 6 is not particularly limited, and examples thereof include a method of applying a resin to form the surface coating layer 6. When an additive is blended into the surface coating layer 6, a resin mixed with the additive may be applied.

[0140] The thickness of the surface coating layer 6 is not particularly limited as long as the surface coating layer 6 exhibits the above-mentioned functions, and may be, for example, about 0.5 to 10 μm, and preferably about 1 to 5 μm.

[0141] 3. Manufacturing method for exterior materials for power storage devices The method for producing the packaging material for an electricity storage device is not particularly limited as long as a laminate is obtained in which the layers of the packaging material for an electricity storage device of the present disclosure are laminated, and an example is a method comprising a step of laminating at least a base layer 1, a barrier layer 3, and a heat-sealable resin layer 4 in this order. As described above, the aluminum alloy foil of the present disclosure can be used as the barrier layer 3.

[0142] An example of a method for manufacturing an exterior material for an electricity storage device according to the present disclosure 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, laminate A can be formed by a dry lamination method in which an adhesive used to form adhesive layer 2 is applied to base layer 1 or to 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, followed by laminating the barrier layer 3 or base layer 1 and curing the adhesive layer 2.

[0143] Next, a heat-sealable resin layer 4 is laminated on the barrier layer 3 of the laminate A. When the heat-sealable resin layer 4 is laminated directly 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 onto the barrier layer 3 of the laminate A (co-extrusion lamination, tandem lamination), (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, 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 on the heat-sealable resin layer 4 by a thermal lamination. (3) a method (sandwich lamination 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; (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, followed by drying or baking, and then the heat-sealable resin layer 4 previously formed into a sheet is laminated on the adhesive layer 5.

[0144] When the surface coating layer 6 is provided, the surface coating layer 6 is laminated on the surface of the base material layer 1 opposite to the barrier layer 3. The surface coating layer 6 can be formed, for example, by applying the above-mentioned resin for forming the surface coating layer 6 to the surface of the base material layer 1. The order of the step of laminating the barrier layer 3 on the surface of the base material layer 1 and the step of laminating the surface coating layer 6 on the surface of the base material layer 1 is not particularly limited. For example, after the surface coating layer 6 is formed on the surface of the base material layer 1, the barrier layer 3 may be formed on the surface of the base material layer 1 opposite to the surface coating layer 6.

[0145] As described above, a laminate is formed which includes the optional surface coating layer 6 / substrate layer 1 / optional adhesive layer 2 / barrier layer 3 / optional adhesive layer 5 / thermally adhesive resin layer 4 in this order, and in order to strengthen the adhesion of the optional adhesive layer 2 and adhesive layer 5, the laminate may be further subjected to a heat treatment.

[0146] In the packaging material for an electricity storage device, each layer constituting the laminate may be subjected to a surface activation treatment such as corona treatment, blast treatment, oxidation treatment, ozone treatment, etc., as needed to improve processability. For example, by subjecting the surface of the base layer 1 opposite to the barrier layer 3 to corona treatment, the printability of ink on the surface of the base layer 1 can be improved.

[0147] 4. Applications of exterior materials for energy storage devices The exterior packaging 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. That is, 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 packaging material for an electricity storage device according to the present disclosure.

[0148] Specifically, an electricity storage device using the electricity storage device packaging material is provided by covering an electricity storage device element having at least a positive electrode, a negative electrode, and an electrolyte with the electricity storage device packaging material of the present disclosure in a state in which metal terminals connected to each of the positive electrode and negative electrode protrude outward, so that a flange portion (a region where the heat-sealable resin layers contact each other) can be formed around the periphery of the electricity storage device element, and the heat-sealable resin layers of the flange portion are heat-sealed to form a hermetic seal. Note that when an electricity storage device element is housed in a package formed from the electricity storage device packaging material of the present disclosure, the package is formed so that the heat-sealable resin portion of the electricity storage device packaging material of the present disclosure faces inside (the surface that contacts the electricity storage device element).

[0149] The exterior material for an electricity storage device according to the present disclosure can be suitably used in electricity storage devices such as batteries (including condensers, capacitors, etc.). The exterior material for an electricity storage device according to the present disclosure may be used in either primary or secondary batteries, but is preferably used in secondary batteries. The type of secondary battery to which the exterior material for an electricity storage device according to the present disclosure is applied is not particularly limited, and examples include lithium ion batteries, lithium ion polymer batteries, all-solid-state batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, condensers, and capacitors. Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries are suitable applications for the exterior material for an electricity storage device according to the present disclosure. [Example]

[0150] The present disclosure will be described in detail below with reference to examples and comparative examples, but the present disclosure is not limited to the examples.

[0151] [Example 1] <Production of aluminum alloy foil> An aluminum alloy foil having a thickness of 40 μm was obtained using an aluminum alloy consisting of 0.10 mass% Mn, 2.20 mass% Mg, 0.40 mass% Fe, 0.10 mass% Cu, 0.00 mass% Si, 0.00 mass% Cr, 0.00 mass% Zn, and the remainder being Al. The aluminum alloy foil was subjected to the steps of melting, homogenization, hot rolling, cold rolling, intermediate annealing, cold rolling, and final annealing in the same manner as in known aluminum alloy manufacturing methods. The obtained aluminum alloy foil had the composition shown in Example 1 in Table 1. Regarding the manufacturing conditions of the aluminum alloy foil, reference can be made to, for example, the description in JP 2005-163077 A.

[0152] <Manufacturing of exterior materials for electricity storage devices> A laminated film was prepared in which a polyethylene terephthalate film (12 μm) was used as the substrate layer, an adhesive layer (two-component curing urethane adhesive (polyol compound and aromatic isocyanate compound), thickness 3 μm) and a biaxially oriented nylon film (thickness 15 μm) were laminated in this order. Next, a barrier layer made of the aluminum alloy foil (having the composition shown in Table 1 and a thickness of 40 μm) with corrosion-resistant coatings (acid-resistant coatings) formed on both sides was laminated on the biaxially oriented nylon film (thickness 15 μm) of the substrate layer by dry lamination. Specifically, a barrier layer made of the aluminum alloy foil (having the composition shown in Table 1 and a thickness of 40 μm) with corrosion-resistant coatings (acid-resistant coatings) formed on both sides (a coating formed by chromate treatment, with a chromium content of 30 mg / m) was laminated on the biaxially oriented nylon film (thickness 15 μm) of the substrate layer by dry lamination. 2 A two-component curing urethane adhesive (a polyol compound and an aromatic isocyanate compound) was applied to one side of the aluminum alloy foil on which the adhesive layer had been formed, forming an adhesive layer (3 μm thick after curing) on ​​the aluminum alloy foil. The adhesive layer on the aluminum alloy foil was then laminated with a biaxially oriented nylon film, and an aging treatment was then performed to produce a substrate layer / adhesive layer / barrier layer laminate. Next, maleic anhydride-modified polypropylene (40 μm thick) as an adhesive layer and polypropylene (40 μm thick) as a heat-sealable resin layer were co-extruded onto the barrier layer of the resulting laminate, thereby laminating an adhesive layer / heat-sealable resin layer on the barrier layer. Next, the obtained laminate was aged and heated to obtain an exterior material for an electricity storage device, in which polyethylene terephthalate film (12 μm) / adhesive layer (3 μm) / biaxially oriented nylon film (15 μm) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (40 μm) / heat-sealable resin layer (40 μm) were laminated in this order.

[0153] In Examples 1 and 2, the maleic anhydride-modified polypropylenes used in the adhesive layers were different from each other and had the logarithmic decrement ΔE at 120°C (values ​​measured using a rigid pendulum-type physical property tester) shown in Table 3. In addition, in Examples 1 and 2, the amount of low-molecular-weight components in the heat-sealable resin layers was adjusted to adjust the value (T2 / T1) obtained by dividing the temperature difference T2 between the start point (extrapolated melting start temperature) and end point (extrapolated melting end temperature) of the melting peak temperature of the heat-sealable resin layer by the temperature difference T1, as measured by the method described below.

[0154] Erucic acid amide was present as a lubricant on both sides of the electrical storage device packaging material to form a lubricant layer, which is the same in the following examples and comparative examples.

[0155] [Example 2] An exterior material for a power storage device was obtained in the same manner as in Example 1, except that the composition of the aluminum alloy foil was 0.17 mass% Mn, 0.20 mass% Mg, 0.09 mass% Fe, 0.00 mass% Cu, 0.00 mass% Si, 0.00 mass% Cr, 0.00 mass% Zn, and the remainder was Al.

[0156] [Comparative Example 1] An exterior material for a power storage device was obtained in the same manner as in Example 1, except that the composition of the aluminum alloy foil was 0.00 mass% Mn, 0.00 mass% Mg, 1.20 mass% Fe, 0.05 mass% Cu, 0.00 mass% Si, 0.00 mass% Cr, 0.00 mass% Zn, and the remainder was Al.

[0157] Comparative Example 2 An exterior material for a power storage device was obtained in the same manner as in Example 1, except that the composition of the aluminum alloy foil was 0.16 mass% Mn, 0.10 mass% Mg, 0.09 mass% Fe, 0.00 mass% Cu, 0.00 mass% Si, 0.00 mass% Cr, 0.00 mass% Zn, and the remainder was Al.

[0158] [Table 1]

[0159] <Evaluation of corrosion resistance> The exterior packaging materials for electricity storage devices used in Examples 1 and 2 and Comparative Examples 1 and 2 were cut into rectangles measuring 50 mm long and 20 mm wide. Next, 10 mm-wide polyethylene film was attached to each of the four end faces of the exterior packaging material, except for one short side, so that each end face overlapped the inner surface of the rectangle by 5 mm. The end faces were then covered by heat welding. The film was then folded back at a position 10 mm from the bottom in the lengthwise direction, and further folded back in half at the center in the widthwise direction so that the polyethylene film on the two long side end faces overlapped. The film was then pressed at a pressure of 3 MPa to obtain a test sample. The corrosion resistance of the test sample was evaluated at the cross section formed by the widthwise and lengthwise fold lines of the exterior packaging material. At the end of the test sample that was not immersed in the electrolyte, aluminum alloy foil was exposed for connection to the working electrode. Next, as shown in the schematic diagram of FIG. 9, the test sample outer casing material was set as the working electrode, and metallic lithium Li (15 mm diameter × 0.35 mm thickness) was set as the counter electrode, and the test sample was immersed in electrolyte X (consisting of 1 mol / L LiPF6 and a mixed solution of ethylene carbonate, diethyl carbonate, and dimethyl carbonate (volume ratio 1:1:1)). In this state, a voltage of 0.1 V was applied for 24 hours in an environment of 20°C, and the total charge (C) was measured. The results are shown in Table 2. Furthermore, the appearance of the exposed portion M of the obtained test sample was observed with a digital microscope (magnification 200x). The obtained images are shown in FIG. 5 (Example 1), FIG. 6 (Example 2), FIG. 7 (Comparative Example 1), and FIG. 8 (Comparative Example 2), respectively.

[0160] [Table 2]

[0161] The aluminum alloy foils of Examples 1 and 2 had Mg contents of 2.20 mass% and 0.20 mass%, respectively, and as shown in Table 2, the total charge in the corrosion resistance evaluation was −6.6 × 10 3 C and -9.2 x 10 3C, which indicates that corrosion is effectively suppressed when current is passed through with the electrolyte attached. The corrosion areas are very small in the microscope images (FIGS. 5 and 6) of the folded intersection surfaces of the exterior packaging materials of Examples 1 and 2 after the corrosion resistance evaluation, which also indicates that corrosion is effectively suppressed in the exterior packaging materials of Examples 1 and 2 when current is passed through with the electrolyte attached. On the other hand, as shown in Table 2, the exterior packaging materials of Comparative Examples 1 and 2 had a total charge of -2.1 × 10 in the corrosion resistance evaluation. 4 C and -1.8 x 10 4 C, which is large, and it is clear that the corrosion-inhibiting effect is poor when current is passed through with the electrolyte attached. Corrosion is observed in the microscope images (FIGS. 7 and 8) of the folded intersection surfaces of the exterior packaging materials of Comparative Examples 1 and 2 after the corrosion resistance evaluation, and it is also clear that the exterior packaging materials of Comparative Examples 1 and 2 are poor in the corrosion-inhibiting effect.

[0162] <Measurement of the logarithmic decrement ΔE of the adhesive layer> The electrical storage device packaging materials of Examples 1 and 2 obtained above were cut into rectangles with a width (TD: Transverse Direction) of 15 mm and a length (MD: Machine Direction) of 150 mm to prepare test samples (electrical storage device packaging materials 10). The MD of the electrical storage device packaging material corresponds to the rolling direction (RD) of the aluminum alloy foil, and the TD of the electrical storage device packaging material corresponds to the TD of the aluminum alloy foil, and the rolling direction (RD) of the aluminum alloy foil can be determined from the rolling marks. When the MD of the electrical storage device packaging material cannot be identified from the rolling marks of the aluminum alloy foil, it can be identified by the following method. To confirm the MD of the electrical storage device packaging material, a cross section of the heat-sealable resin layer of the electrical storage device packaging material is observed with an electron microscope to confirm the sea-island structure, and the direction parallel to the cross section in which the average diameter of the island shapes in the direction perpendicular to the thickness direction of the heat-sealable resin layer is greatest can be determined to be the MD. Specifically, the sea-island structure is confirmed by observing electron microscope photographs of a cross section of the heat-sealable resin layer in the longitudinal direction and cross sections at angles of 10 degrees from the direction parallel to the longitudinal cross section, up to a direction perpendicular to the longitudinal cross section (a total of 10 cross sections). Next, the shape of each individual island is observed in each cross section. For each island shape, the linear distance connecting the leftmost end in the direction perpendicular to the thickness direction of the heat-sealable resin layer to the rightmost end in the same direction is defined as the diameter y. For each cross section, the average diameter y of the top 20 island shapes in descending order of diameter y is calculated. The direction parallel to the cross section with the largest average diameter y of the island shape is determined as MD. Figure 13 shows a schematic diagram illustrating the method for measuring the logarithmic decrement ΔE using rigid pendulum measurement. A rigid pendulum-type physical property tester (model number: RPT-3000W, manufactured by A&D Co., Ltd.) was used, with FRB-100 for the frame of the pendulum 30, RBP-060 for the cylindrical cylinder edge 30a of the edge part, CHB-100 for the cooling block 31, a vibration displacement detector 32, and a weight 33, and the initial amplitude was set to 0.3 degrees. The test sample was placed on the cooling block 31 with the measurement surface (adhesive layer) facing upward, and the cylindrical cylinder edge 30a with pendulum 30 attached was set on the measurement surface so that the axial direction was perpendicular to the MD direction of the test sample.To prevent the test sample from lifting or warping during measurement, tape was applied to a location on the test sample that would not affect the measurement results, and the test sample was fixed to a cooling block 31. The cylindrical cylinder edge 30a was placed in contact with the surface of the adhesive layer. Next, the logarithmic decrement ΔE of the adhesive layer was measured using the cooling block 31 at a temperature increase rate of 3°C / min over a temperature range from 30°C to 200°C. The logarithmic decrement ΔE was measured when the surface temperature of the adhesive layer of the test sample (electrical storage device packaging material 10) reached 120°C. (Test samples that had already been measured were not used; instead, three measurements (N=3) were performed using newly cut samples, and the average value was used.) For the adhesive layer, the electrical storage device packaging materials of Examples 1 and 2 obtained above were immersed in 15% hydrochloric acid to dissolve the base layer and aluminum alloy foil. The test samples, which consisted of only the adhesive layer and the heat-sealable resin layer, were thoroughly dried, and the logarithmic decrement ΔE was measured. Table 3 shows the logarithmic decrement ΔE at 120°C. (The logarithmic decrement ΔE is calculated using the following formula.) ΔE=[ln(A1 / A2)+ln(A2 / A3)+...+ln(An / An+1)] / n A: Amplitude n: wave number

[0163] <Measurement of remaining adhesive layer thickness> The electrical storage device packaging materials of Examples 1 and 2 obtained above were cut into a length of 150 mm and a width of 60 mm to prepare test samples (electrical storage device packaging materials 10). Next, the heat-sealable resin layers of test samples of the same size, prepared from the same electrical storage device packaging material, were placed face-to-face. Next, in this state, a 7 mm-wide metal plate was used to heat and pressurize both sides of the test sample in the stacking direction under conditions of a temperature of 190°C, a surface pressure (0.5 MPa) shown in Table 3, and a time of 3 seconds, thereby heat-sealing the heat-sealable resin layers. Next, the heat-sealed portion of the test sample was cut in the stacking direction using a microtome, and the thickness of the adhesive layer was measured on the exposed cross section. The test sample before heat fusion was also cut in the stacking direction using a microtome in the same manner, and the thickness of the adhesive layer was measured on the exposed cross section. The ratio of the thickness of the adhesive layer after heat fusion to the thickness of the adhesive layer before heat fusion was calculated, and the remaining thickness (%) of the adhesive layer was measured. The results are shown in Table 3.

[0164] <Seal strength measurement in a 25°C or 140°C environment> The electrical storage device packaging materials of Examples 1 and 2 obtained above were cut into rectangular shapes measuring 60 mm wide and 150 mm long to prepare test samples (electrical storage device packaging materials 10). Next, as shown in FIG. 10, the test samples were folded back at the center P in the longitudinal direction so that the heat-sealable resin layers faced each other. Next, using a 7 mm wide metal plate 20, the heat-sealable resin layers were heat-sealed together over 7 mm in the longitudinal direction (the width of the metal plate) and across the entire width direction (i.e., 60 mm) of the test samples under conditions of a surface pressure of 1.0 MPa, a time of 1 second, and 190°C. Next, using a double-edged sample cutter, the test samples were cut into 15 mm wide pieces, as shown in FIG. 11. In FIG. 11, the heat-sealed area is indicated by S. Next, as shown in Figure 12, the heat-sealed interface was peeled using a tensile tester at a temperature of 25°C or 140°C under conditions of a tensile speed of 300 mm / min, a peel angle of 180°, and a chuck distance of 50 mm, resulting in a T-peel pattern. The maximum peel strength (N / 15 mm) measured within 1.5 seconds from the start of tensile strength measurement was recorded as the seal strength at 25°C and at 140°C, respectively. The tensile tests at each temperature were performed in a thermostatic chamber. Once the temperature reached the designated temperature, the test sample was attached to a chuck and held there for 2 minutes before starting the measurement. Each seal strength was the average (n = 3) of three test samples prepared in the same manner. The results are shown in Table 3.

[0165] [Table 3]

[0166] From the results shown in Table 3, it can be seen that the logarithmic decrement ΔE at 120°C in rigid pendulum measurement of the adhesive layer located between the aluminum alloy foil and the heat-sealable resin layer in the packaging materials for electricity storage devices of Examples 1 and 2 is 0.50 or less, which means that crushing of the adhesive layer when the heat-sealable resin layers are heat-sealed to each other is effectively suppressed and high seal strength is exhibited in high-temperature environments. Furthermore, it can be seen that the logarithmic decrement ΔE of the packaging material for electricity storage devices of Example 1 is 0.20 or less, which means that crushing of the adhesive layer when the heat-sealable resin layers are heat-sealed to each other is more effectively suppressed and high seal strength is exhibited in high-temperature environments.

[0167] <Measurement of extrapolated melting onset temperature and extrapolated melting finish temperature from the melting peak temperature> Using the following method, the polypropylene used in the heat-sealable resin layer of the electrical storage device packaging materials of Examples 1 and 2 was measured for the extrapolated melting onset temperature and extrapolated melting end temperature of the melting peak temperature, and the temperature differences T1 and T2 between the extrapolated melting onset temperature and the extrapolated melting end temperature were measured. From the obtained temperature differences T1 and T2, the ratio (T2 / T1) and the absolute value of the difference |T2-T1| were calculated. The results are shown in Table 4.

[0168] (Measurement of temperature difference T1) In accordance with the provisions of JIS K7121:2012, differential scanning calorimetry (DSC) was used to obtain DSC curves for the polypropylene used in the heat-sealable resin layers of the exterior packaging materials for electricity storage devices of Examples 1 and 2. From the obtained DSC curves, the temperature difference T1 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat-sealable resin layer was measured.

[0169] (Measurement of temperature difference T2) The polypropylene used for the heat-sealable resin layer was placed in an electrolyte solution containing 1 mol / L of lithium hexafluorophosphate and a 1:1:1 volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate in an 85°C environment for 72 hours, and then thoroughly dried. Next, a differential scanning calorimetry (DSC) curve was obtained for the dried polypropylene in accordance with JIS K7121:2012. From the obtained DSC curve, the temperature difference T2 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the dried heat-sealable resin layer was measured.

[0170] To measure the extrapolated melting start temperature and extrapolated melting end temperature of the melting peak temperature, a TA Instruments Q200 differential scanning calorimeter was used. The DSC curve was obtained by holding the test sample at -50 ° C for 10 minutes, then heating it to 200 ° C at a heating rate of 10 ° C / min (first time), holding it at 200 ° C for 10 minutes, then cooling it to -50 ° C at a heating rate of -10 ° C / min, holding it at -50 ° C for 10 minutes, then heating it to 200 ° C at a heating rate of 10 ° C / min (second time), holding it at 200 ° C for 10 minutes, and then heating it to 200 ° C for the second time. The DSC curve was used. Furthermore, when measuring the temperature difference T1 and the temperature difference T2, the melting peaks appearing in the range of 120 to 160 ° C in each DSC curve were analyzed for the melting peaks with the largest difference in thermal energy input. Even when two or more overlapping peaks existed, only the melting peak with the largest difference in thermal energy input was analyzed.

[0171] The extrapolated melting onset temperature refers to the start point of the melting peak temperature and is the temperature at the intersection of a line drawn by extending the baseline on the low-temperature side (65-75°C) toward the high-temperature side and a tangent drawn at the point where the gradient is maximum on the curve on the low-temperature side of the melting peak where the difference in thermal energy input is maximum. The extrapolated melting end temperature refers to the end point of the melting peak temperature and is the temperature at the intersection of a line drawn by extending the baseline on the high-temperature side (170°C) toward the low-temperature side and a tangent drawn at the point where the gradient is maximum on the curve on the high-temperature side of the melting peak where the difference in thermal energy input is maximum.

[0172] <Measurement of seal strength before contact with electrolyte> In the following "Measurement of Seal Strength After Contact with Electrolyte," tensile strength (seal strength) was measured in the same manner, except that no electrolyte was injected into the test sample. The maximum tensile strength until the heat-sealed portion was completely peeled off was taken as the seal strength before contact with the electrolyte. In Table 5, the seal strength before contact with the electrolyte is shown as the seal strength when the contact time with the electrolyte at 85°C was 0 hours.

[0173] <Measurement of seal strength after contact with electrolyte> As shown in the schematic diagram of Fig. 14, the electrical storage device packaging materials of Examples 1 and 2 obtained above were cut into a rectangle with a width (x direction) of 100 mm and a length (z direction) of 200 mm to prepare a test sample (electrical storage device packaging material 10) (Fig. 14a). The test sample (electrical storage device packaging material 10) was folded back at the center in the z direction so that the heat-sealable resin layer sides overlapped (Fig. 14b). Next, both ends of the folded test sample in the x direction were heat-sealed (temperature 190°C, surface pressure 2.0 MPa, time 3 seconds) to form a bag shape with one opening E (Fig. 14c). Next, 6 g of electrolyte (a solution containing 1 mol / L lithium hexafluorophosphate and a 1:1:1 volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate) was injected through opening E of the bag-shaped test sample (Fig. 14d), and the edge of opening E was heat-sealed (temperature: 190°C, surface pressure: 2.0 MPa, time: 3 seconds) (Fig. 14e). Next, the bag-shaped test sample was placed with the folded-over portion facing downwards in an environment at 85°C for the specified storage times (time in contact with the electrolyte: 0, 24, or 72 hours). Next, the edge of the test sample was cut (Fig. 14e), and the electrolyte was drained. Next, with the electrolyte attached to the surface of the heat-sealable resin layer, the top and bottom surfaces of the test sample were sandwiched between metal plates 20 (7 mm wide). The heat-sealable resin layers were heat-sealed together at a temperature of 190°C, a surface pressure of 1.0 MPa, and a time of 3 seconds (Figure 14f). Next, the test sample was cut into 15 mm wide pieces using a double-edged sample cutter so that the seal strength could be measured across a 15 mm width (x direction) (Figures 14f and 14g). Next, the heat-sealed interface was peeled using a tensile tester (Shimadzu Corporation, AGS-xplus (trade name)) at a temperature of 25°C under the following conditions: a pulling speed of 300 mm / min, a peel angle of 180°, and a chuck distance of 50 mm. The tensile strength (seal strength) was measured by peeling the heat-sealed interface at a temperature of 25°C using a tensile tester (Shimadzu Corporation, AGS-xplus (trade name)) at a pulling speed of 300 mm / min, a peel angle of 180°, and a chuck distance of 50 mm (Figure 12). The maximum tensile strength until the heat-sealed portion was completely peeled (the distance until peeling was 7 mm, the width of the metal plate) was defined as the seal strength after contact with the electrolyte.

[0174] Table 5 shows the retention rate (%) of the seal strength after contact with the electrolyte, with the seal strength before contact with the electrolyte taken as the reference (100%).

[0175] [Table 4]

[0176] [Table 5]

[0177] From the results shown in Table 4, it can be seen that the value obtained by dividing the temperature difference T2 by the temperature difference T1 for the electrical storage device packaging materials of Examples 1 and 2 is 0.55 or more, and that high sealing strength is exhibited by heat fusion even when an electrolytic solution comes into contact with the thermally adhesive resin layer in a high-temperature environment and the thermally adhesive resin layers are heat-fused together with the electrolytic solution adhering to the thermally adhesive resin layer. Furthermore, it can be seen that the value obtained by dividing the temperature difference T2 by the temperature difference T1 for the electrical storage device packaging material of Example 1 is 0.60 or more, and that higher sealing strength is exhibited by heat fusion even when an electrolytic solution comes into contact with the thermally adhesive resin layer in a high-temperature environment and the thermally adhesive resin layers are heat-fused together with the electrolytic solution adhering to the thermally adhesive resin layer.

[0178] As described above, the present disclosure provides the following aspects of the invention. Item 1. An aluminum alloy foil for use as a packaging material for an electricity storage device, having a Mg content of 0.20% by mass or more and 5.50% by mass or less. Item 2. The aluminum alloy foil according to Item 1, wherein the Si content is 0.40% by mass or less, the Fe content is 0.70% by mass or less, the Cu content is 0.20% by mass or less, the Mn content is 1.00% by mass or less, the Cr content is 0.50% by mass or less, the Zn content is 0.25% by mass or less, and other unavoidable impurities are each 0.05% by mass or less and 0.15% by mass or less in total, with the balance being Al. Item 3. The aluminum alloy foil according to Item 1 or 2, having a thickness of 200 μm or less. Item 4. The laminate is composed of at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, Item 4. An exterior packaging material for an electricity storage device, wherein the barrier layer comprises the aluminum alloy foil according to any one of items 1 to 3. Item 5. The packaging material for an electricity storage device according to Item 4, wherein the temperature difference T1 and the temperature difference T2 are measured by the following method, and the value obtained by dividing the temperature difference T2 by the temperature difference T1 is 0.55 or more. (Measurement of temperature difference T1) The temperature difference T1 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat-fusible resin layer is measured by differential scanning calorimetry. (Measurement of temperature difference T2) The heat-sealable resin layer is left to stand in an electrolyte solution of 1 mol / L lithium hexafluorophosphate and a 1:1:1 volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate in an 85°C environment for 72 hours, and then dried. The temperature difference T2 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat-sealable resin layer after drying is measured by differential scanning calorimetry. Item 6. An adhesive layer is provided between the aluminum alloy foil and the heat-sealable resin layer, Item 6. The packaging material for an electricity storage device according to Item 4 or 5, wherein the adhesive layer has a logarithmic decrement ΔE of 0.50 or less at 120°C in a rigid pendulum measurement. Item 7. 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 packaging material for an electricity storage device according to any one of Items 4 to 6. Item 8. The method includes a step of laminating at least a base layer, a barrier layer, and a heat-sealable resin layer in this order to obtain a laminate, Item 4. A method for producing an exterior packaging material for an electricity storage device, using the aluminum alloy foil according to any one of items 1 to 3 as the barrier layer. [Explanation of symbols]

[0179] 1 Base material layer 2 Adhesive layer 3 Barrier layer 4 Heat-fusible resin layer 5 Adhesive layer 6 Surface coating layer 10. Exterior materials for energy storage devices

Claims

1. The laminate is composed of at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, the barrier layer includes an aluminum alloy foil having a Mg content of 0.20 mass% or more and 5.50 mass% or less, The aluminum alloy foil has a Si content of 0.40% by mass or less, an Fe content of 0.70% by mass or less, a Cu content of 0.20% by mass or less, an Mn content of 1.00% by mass or less, a Cr content of 0.50% by mass or less, a Zn content of 0.25% by mass or less, other inevitable impurities each of which is 0.05% by mass or less and a total of 0.15% by mass or less, with the balance being Al and Mg, The aluminum alloy foil has an average crystal grain size of 20.0 μm or less, and / or an average diameter y of second-phase particles of 10.0 μm or less, The average crystal grain size is an average value of the maximum diameters x of 100 crystal grains when a cross section of an aluminum alloy foil in the thickness direction is observed with a scanning electron microscope (SEM) and the linear distance connecting the leftmost end of each crystal grain in the direction perpendicular to the thickness direction to the rightmost end of each crystal grain in the direction perpendicular to the thickness direction is defined as the maximum diameter x of the 100 crystal grains located within the field of view, the average diameter y of the second-phase particles is the average of the diameters y of the second-phase particles that are top 20 in terms of the largest diameter y, when the diameter y is defined as the linear distance connecting the leftmost end of each second-phase particle in a direction perpendicular to the thickness direction to the rightmost end of each second-phase particle in a direction perpendicular to the thickness direction, for any 100 second-phase particles within the field of view of an optical microscope.

2. The packaging material for an electricity storage device according to claim 1 , wherein the aluminum alloy foil has a manganese content of 0.17 mass % or less.

3. The temperature difference T 1 and temperature difference T 2 The temperature difference T 2 The temperature difference T 1 The packaging material for an electricity storage device according to claim 2 , wherein a value obtained by dividing by 0.55 or more is 0.55 or more. (Temperature difference T 1 Measurement of The temperature difference T between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat-fusible resin layer is measured by differential scanning calorimetry. 1 Measure. (Temperature difference T 2 Measurement of The heat-sealable resin layer is left standing for 72 hours in an electrolyte solution containing lithium hexafluorophosphate at a concentration of 1 mol / L and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1 in an environment at a temperature of 85°C, and then dried. The temperature difference T between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat-sealable resin layer after drying is measured by differential scanning calorimetry. 2 Measure.

4. an adhesive layer is provided between the aluminum alloy foil and the heat-sealable resin layer, The packaging material for an electricity storage device according to any one of claims 1 to 3, wherein the adhesive layer has a logarithmic decrement ΔE of 0.50 or less at 120°C in rigid pendulum measurement.

5. An electricity storage device, wherein 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 packaging material for an electricity storage device according to any one of claims 1 to 4.

6. The method includes a step of laminating at least a base layer, a barrier layer, and a heat-sealable resin layer in this order to obtain a laminate, the barrier layer includes an aluminum alloy foil having a Mg content of 0.20 mass% or more and 5.50 mass% or less, The aluminum alloy foil has a Si content of 0.40% by mass or less, an Fe content of 0.70% by mass or less, a Cu content of 0.20% by mass or less, an Mn content of 1.00% by mass or less, a Cr content of 0.50% by mass or less, a Zn content of 0.25% by mass or less, other inevitable impurities each of which is 0.05% by mass or less and a total of 0.15% by mass or less, with the balance being Al and Mg, The aluminum alloy foil has an average crystal grain size of 20.0 μm or less, and / or an average diameter y of second-phase particles of 10.0 μm or less, The average crystal grain size is an average value of the maximum diameters x of 100 crystal grains when a cross section of an aluminum alloy foil in the thickness direction is observed with a scanning electron microscope (SEM) and the linear distance connecting the leftmost end of each crystal grain in the direction perpendicular to the thickness direction to the rightmost end of each crystal grain in the direction perpendicular to the thickness direction is defined as the maximum diameter x of the 100 crystal grains located within the field of view, the average diameter y of the second-phase particles is the average of diameters y of 20 second-phase particles that are ranked in order of largest diameter y, where y is the linear distance connecting the leftmost end, in a direction perpendicular to the thickness direction, of each of the second-phase particles selected from any 100 second-phase particles within the field of view of an optical microscope, and the rightmost end, in the direction perpendicular to the thickness direction, of each of the second-phase particles.

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