JP7205547B2 - Aluminum alloy foil, exterior material for power storage device, method for producing the same, and power storage device - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to an aluminum alloy foil, an exterior material for an electricity storage device, a method for manufacturing the same, and an electricity storage device.

BACKGROUND ART Conventionally, various types of electricity storage devices have been developed. In all electricity storage devices, packaging materials (exterior materials) are indispensable members for sealing electricity storage device elements such as electrodes and electrolytes. Conventionally, metal exterior materials have been frequently used as exterior materials for power storage devices.

On the other hand, in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc., power storage devices are required to have various shapes, and are required to be thinner and lighter. However, conventionally widely used metallic exterior materials for electric storage devices have the drawback that it is difficult to follow the diversification of shapes and that there is a limit to weight reduction.

Therefore, in recent years, film-type materials in which a base material/an aluminum alloy foil layer/a heat-sealable resin layer are sequentially laminated have been developed as exterior materials for power storage devices, which can be easily processed into various shapes and can be made thinner and lighter. has been proposed (see Patent Document 1, for example).

In such a film-like exterior material, a recess is generally formed by cold forming, and an electricity storage device element such as an electrode or an electrolytic solution is placed in the space formed by the recess, and a heat-sealable resin is placed in the space formed by the recess. By heat-sealing the layers together, an electricity storage device in which the electricity storage device element is accommodated inside the exterior material is obtained.

JP 2008-287971 A

In the process of molding the power storage device exterior material, the process of housing the power storage device element in the power storage device exterior material and heat-sealing it, and the process of bending the heat-sealed portion, the external terminal and the power storage device exterior material are separated. Short-circuiting with the aluminum alloy foil through foreign matter, or short-circuiting between the external terminal and the aluminum alloy foil of the exterior material for the electricity storage device due to uneven pressure during heat sealing, and heat sealing located in the innermost layer When fine cracks or pinholes occur in the heat-sealable resin layer, electricity flows between the aluminum alloy foil of the exterior material for the storage device and the external terminal through the electrolyte that permeates the heat-sealable resin layer. may corrode (in particular, if the aluminum alloy foil and the negative electrode terminal are short-circuited through the electrolyte, the aluminum alloy foil is likely to corrode). Corrosion of the aluminum alloy foil causes problems such as expansion of the aluminum alloy foil, leading to deterioration of the performance of the electricity storage device.

Under such circumstances, the present disclosure aims to provide an aluminum alloy foil for use as an exterior material for an electricity storage device, which effectively suppresses corrosion when electricity is applied in a state where an electrolytic solution is attached. and Another object of the present disclosure is to provide an exterior material for an electricity storage device using the aluminum alloy foil, a method for manufacturing the exterior material for an electricity storage device, and an electricity storage device.

The inventors of the present disclosure conducted extensive studies to solve the above problems. As a result, the composition of the aluminum alloy foil was repeatedly studied, and it was found that by setting the Mg content within a predetermined range, corrosion was effectively suppressed when electricity was applied while the electrolyte solution was adhered. Found it.

The present disclosure has been completed through further studies based on these findings. That is, the present disclosure provides inventions in the following aspects.
An aluminum alloy foil for use as an exterior material for an electricity storage device, having a Mg content of 0.20% by mass or more and 5.50% by mass or less.

Advantageous Effects of Invention According to the present disclosure, it is possible to provide an aluminum alloy foil for use as an exterior material for an electricity storage device, which effectively suppresses corrosion when electricity is applied while an electrolytic solution is attached. Further, according to the present disclosure, it is possible to provide an exterior material for an electricity storage device using the aluminum alloy foil, a method for manufacturing the exterior material for an electricity storage device, and an electricity storage device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electricity storage device of the present disclosure; BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electricity storage device of the present disclosure; BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electricity storage device of the present disclosure; BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electricity storage device of the present disclosure; 4 is a microscope image of the surface of the folding intersection of the exterior material for an electricity storage device of Example 1, observed after corrosion resistance evaluation. 4 is a microscope image of the folding intersection surface of the exterior material for an electricity storage device of Example 2, observed after corrosion resistance evaluation. 4 is a microscope image of the surface of the folding intersection of the exterior material for an electricity storage device of Comparative Example 1, observed after corrosion resistance evaluation. 10 is a microscope image of the surface of the folding intersection of the exterior material for an electricity storage device of Comparative Example 2, observed after corrosion resistance evaluation. It is a schematic diagram for demonstrating the corrosion-resistant evaluation method in an Example. It is a schematic diagram for demonstrating the measuring method of seal strength. It is a schematic diagram for demonstrating the measuring method of seal strength. It is a schematic diagram for demonstrating the measuring method of seal strength. FIG. 4 is a schematic diagram for explaining a method of measuring logarithmic decrement ΔE by rigid pendulum measurement; It is a schematic diagram for demonstrating the measuring method of seal strength. It is the figure which showed typically the temperature difference _T1 and the temperature difference _T2 in differential scanning calorimetry. FIG. 3 is a schematic diagram showing crystal grains and second phase particles in a cross section in the thickness direction of an aluminum alloy foil.

The aluminum alloy foil of the present disclosure is characterized by being an aluminum alloy foil for use as an exterior material for an electricity storage device, having a Mg content of 0.20% by mass or more and 5.50% by mass or less. According to the aluminum alloy foil of the present disclosure, by having this configuration, corrosion is effectively suppressed when electricity is applied while the electrolytic solution is adhered. Therefore, the exterior material for a power storage device using the aluminum alloy foil of the present disclosure effectively suppresses corrosion of the aluminum alloy foil.

The aluminum alloy foil, the exterior material for an electricity storage device, the manufacturing method thereof, and the electricity storage device of the present disclosure will be described in detail below. In this specification, the numerical range indicated by "-" means "more than" and "less than". For example, the notation of 2 to 15 mm means 2 mm or more and 15 mm or less.

1. Aluminum Alloy Foil The aluminum alloy foil of the present disclosure has a Mg content of 0.20% by mass or more and 5.50% by mass or less, and is characterized by being used as an exterior material for an electric storage device. The exterior material for a power storage device that can use the aluminum alloy foil of the present disclosure is not particularly limited, and the aluminum alloy foil of the present disclosure includes at least a base layer, a barrier layer, and a heat-fusible resin layer. It can be suitably used as a barrier layer of an exterior material for an electric storage device. A specific example of the exterior material for an electricity storage device using the aluminum alloy foil of the present disclosure will be described in detail in the section "2. Exterior material for an electricity storage device."

The aluminum alloy foil of the present disclosure has a Mg (magnesium) content of 0.20% by mass or more and 5.50% by mass or less. The main component of the aluminum alloy foil of the present disclosure is Al (aluminum), and specifically 93.65% by mass or more is composed 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, and still more preferably 0.20% by mass or more and 3.00% by mass. % or less, more preferably 0.20 mass % or more and 2.50 mass % or less, particularly preferably 0.20 mass % or more and 2.20 mass % or less.

The aluminum alloy foil of the present disclosure may contain components other than Mg and Al. Other components include, for example, Si (silicon), Fe (iron), Cu (copper), Mn (manganese), Cr (chromium), Zn (zinc), and unavoidable impurities. The other component may be of one type or two or more types.

From the viewpoint of providing an aluminum alloy foil that effectively suppresses corrosion when electricity is applied while the electrolyte is attached, the aluminum alloy foil of the present disclosure has a Si content of 0.40% by mass or less and an Fe content. Cu content is 0.20 mass% or less, Mn content is 1.00 mass% or less, Cr content is 0.50 mass% or less, Zn content is 0.25 mass% % or less, and other unavoidable impurities are preferably 0.05% by mass or less individually and 0.15% by mass or less in total, with the balance being Al. The aluminum alloy foil having such a composition has the same composition as the aluminum alloy having the composition of alloy number A5000 series aluminum of JIS H4000: 2014, and is subjected to, for example, melting and homogenization treatment in the same manner as a known aluminum alloy foil manufacturing method. , hot rolling, cold rolling, intermediate annealing, cold rolling, and final annealing. For the manufacturing conditions of the aluminum alloy foil, for example, the description in Japanese Patent Application Laid-Open No. 2005-163077 can be referred to. Further, the analysis of each chemical component contained in the aluminum alloy foil is performed by the analytical test specified in JIS H4160-1994.

In the present disclosure, as shown in the schematic diagram of FIG. 16, in the cross section in the thickness direction of the aluminum alloy foil, for any 100 second phase particles 3b within the field of view of the optical microscope, the individual second phase particles 3b When the straight line distance connecting the leftmost end in the direction perpendicular to the thickness direction and the rightmost end in the direction perpendicular to the thickness direction is defined as diameter y, the top 20 second phase particles 3b in descending order of diameter y The average diameter y is preferably 10.0 μm or less. As a result, although the aluminum alloy foil has a very thin thickness of, for example, about 85 μm or less, further about 50 μm or less, further about 40 μm or less, further about 35 μm or less, the aluminum alloy foil can be used as an exterior for an electricity storage device. Pinholes and cracks are less likely to occur when laminated on a material and molded, and the exterior material for an electric storage device can be provided with excellent moldability. Furthermore, in the present disclosure, the average diameter y of the second phase particles 3b in the aluminum alloy foil is 10.0 μm or less, so that the thickness of the aluminum alloy foil is, for example, about 85 μm or less, further about 50 μm or less, and further It is about 40 μm or less, further about 35 μm or less, and even when the total thickness of the exterior material for an electric storage device is as thin as the thickness described later, pinholes and cracks are unlikely to occur during molding, and excellent moldability. It has

In addition, from the viewpoint of improving moldability, the average diameter y is more preferably about 1.0 to 8.0 μm, more preferably about 1.0 to 6.0 μm. Since FIG. 16 is a schematic diagram, drawing is omitted and 100 second phase particles 3b are not drawn.

In the present disclosure, the second phase particles contained in the aluminum alloy foil refer to intermetallic compound particles that exist in the aluminum alloy, and include crystallized phases that are separated by rolling and precipitation that precipitates during homogenization treatment and annealing. phase particles.

When observing a cross-section in the thickness direction of an aluminum alloy foil with a scanning electron microscope (SEM), a crystal grain usually draws a boundary line in contact with a plurality of crystals. In contrast, second phase particles are usually single crystal boundaries. In addition, since the crystal grains and the second phase particles have different phases, they are characterized by different colors on the SEM image. Furthermore, when a cross section in the thickness direction of the aluminum alloy foil 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, so observation is easy. become.

The average crystal grain size of 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, from the viewpoint of improving formability. is mentioned. Since 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 the above value, the moldability of the exterior material for an electricity storage device described later is further improved. can be enhanced.

In the present disclosure, the average crystal grain size in the aluminum alloy foil is obtained by observing a cross section of the aluminum alloy foil in the thickness direction with a scanning electron microscope (SEM), and 100 aluminum alloy crystal grains 3a located within the field of view. As shown in the schematic diagram of FIG. 16, when the straight line distance connecting the leftmost end of each crystal grain in the direction perpendicular to the thickness direction and the rightmost end in the direction perpendicular to the thickness direction is taken as the maximum diameter x, 100 It means the average value of the maximum diameter x of individual crystal grains. Since FIG. 16 is a schematic diagram, drawing is omitted and 100 crystal grains 3a are not drawn.

The thickness of the aluminum alloy foil should exhibit at least a function as a barrier layer that suppresses the infiltration of moisture in the exterior material for an electric storage device. 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, particularly preferably about 35 μm or less, and the lower limit is preferably about 10 μm or more, more preferably about 20 μm or more, and more preferably about 25 μm or more. , 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, about 25 to 35 μm is mentioned.

Moreover, in order to prevent dissolution and corrosion of the aluminum alloy foil, it is preferable that at least one surface of the aluminum alloy foil is provided with a corrosion-resistant film. The aluminum alloy foil may be provided with a corrosion resistant coating on both sides. Here, the corrosion-resistant film includes, for example, hydrothermal transformation treatment such as boehmite treatment, chemical conversion treatment, anodizing treatment, plating treatment such as nickel and chromium, and corrosion prevention treatment such as coating with a coating agent on aluminum alloy foil. A thin film applied to the surface of the aluminum alloy foil to provide corrosion resistance (for example, acid resistance, alkali resistance, etc.). The corrosion-resistant film specifically means a film that improves the acid resistance of the aluminum alloy foil (acid-resistant film), a film that improves the alkali resistance of the aluminum alloy foil (alkali-resistant film), and the like. As the treatment for forming the corrosion-resistant film, one type may be performed, or two or more types may be used in combination. Also, not only one layer but also multiple layers can be used. Furthermore, among these treatments, the hydrothermal transformation treatment and the anodizing treatment are treatments in which the surface of the metal foil is dissolved with a treating agent to form a metal compound having excellent corrosion resistance. These treatments are sometimes included in the definition of chemical conversion treatment. When the aluminum alloy foil has a corrosion-resistant film, the aluminum alloy foil includes the corrosion-resistant film.

The corrosion-resistant film prevents delamination between the aluminum alloy foil and the substrate layer during the molding of the exterior material for an electric storage device. Prevents dissolution, corrosion, and dissolution and corrosion of aluminum oxide present on the surface of the aluminum alloy foil, and improves the adhesiveness (wettability) of the surface of the aluminum alloy foil. The effect of preventing delamination with the foil and preventing delamination between the base material layer and the aluminum alloy foil during molding is shown.

Various types of corrosion-resistant coatings formed by chemical conversion treatment are known, and are mainly composed of at least one of phosphates, chromates, fluorides, triazinethiol compounds, and rare earth oxides. and corrosion-resistant coatings containing. Examples of chemical conversion treatments using phosphate and chromate include chromic acid chromate treatment, phosphoric acid chromate treatment, phosphoric acid-chromate treatment, and chromate treatment. Examples of compounds include chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromium acetyl acetate, chromium chloride, potassium chromium sulfate, and the like. Phosphorus compounds used for these treatments include sodium phosphate, potassium phosphate, ammonium phosphate, polyphosphoric acid, and the like. Examples of the chromate treatment include etching chromate treatment, electrolytic chromate treatment, coating-type chromate treatment, etc., and coating-type chromate treatment is preferred. In this coating-type chromate treatment, at least the inner layer side surface of the barrier layer (for example, aluminum alloy foil) is first subjected to a well-known method such as an alkali immersion method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, an acid activation method, or the like. After degreasing by a treatment method, metal phosphate such as Cr (chromium) phosphate, Ti (titanium) phosphate, Zr (zirconium) phosphate, Zn (zinc) phosphate is applied to the degreased surface. A processing solution mainly composed of a salt and a mixture of these metal salts, a processing solution mainly composed of a non-metal phosphate salt and a mixture of these non-metal salts, or a mixture of these and a synthetic resin. This is a treatment in which a treatment liquid composed of a mixture is applied by a well-known coating method such as a roll coating method, a gravure printing method, or an immersion method, and then dried. Various solvents such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents can be used as the treatment liquid, and water is preferred. In addition, the resin component used at this time includes polymers such as phenolic resins and acrylic resins. and the chromate treatment used. In the aminated phenol polymer, the repeating units represented by the following general formulas (1) to (4) may be contained singly or in any combination of two or more. good too. The acrylic resin is polyacrylic acid, acrylic acid methacrylic acid ester copolymer, acrylic acid maleic acid copolymer, acrylic acid styrene copolymer, or derivatives thereof such as sodium salts, ammonium salts, and amine salts. is preferred. In particular, derivatives of polyacrylic acid such as ammonium salt, sodium salt or amine salt of polyacrylic acid are preferred. In the present disclosure, polyacrylic acid means a polymer of acrylic acid. Further, the acrylic resin is preferably a copolymer of acrylic acid and dicarboxylic acid or dicarboxylic anhydride, and the ammonium salt, sodium salt, Alternatively, it is also preferably an amine salt. Only one type of acrylic resin may be used, or two or more types may be mixed and used.

In general formulas (1) to (4), X represents a hydrogen atom, hydroxy group, alkyl group, hydroxyalkyl group, allyl group or benzyl group. R ¹ and R ² are the same or different and represent a hydroxy group, an alkyl group or a hydroxyalkyl group. Examples of alkyl groups represented by X, R ¹ and R ² in general formulas (1) to (4) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, A linear or branched alkyl group having 1 to 4 carbon atoms such as a tert-butyl group can be mentioned. Examples of hydroxyalkyl groups represented by X, R ¹ and R ² include hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, 1-hydroxypropyl group, 2-hydroxypropyl group, 3- A straight or branched chain having 1 to 4 carbon atoms substituted with one hydroxy group such as hydroxypropyl group, 1-hydroxybutyl group, 2-hydroxybutyl group, 3-hydroxybutyl group and 4-hydroxybutyl group An alkyl group is mentioned. In general formulas (1) to (4), the alkyl groups and hydroxyalkyl groups represented by X, R ¹ and R ² may be the same or different. In general formulas (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 formulas (1) to (4) is, for example, preferably about 500 to 1,000,000, more preferably about 1,000 to 20,000. more preferred. The aminated phenol polymer is produced by, for example, polycondensing a phenol compound or naphthol compound and formaldehyde to produce a polymer comprising repeating units represented by the general formula (I) or general formula (III), followed by formaldehyde. and an amine (R ¹ R ² NH) to introduce a functional group (--CH ₂ NR ¹ R ² ) into the polymer obtained above. An aminated phenol polymer is used individually by 1 type or in mixture of 2 or more types.

Another example of the corrosion-resistant film is formed by a coating-type corrosion prevention treatment in which a coating agent containing at least one selected from the group consisting of rare earth element oxide sol, anionic polymer, and cationic polymer is applied. A thin film that is The coating agent may further contain phosphoric acid or a phosphate, a cross-linking agent for cross-linking the polymer. In the rare earth element oxide sol, rare earth element oxide fine particles (for example, particles having an average particle size of 100 nm or less) are dispersed in a liquid dispersion medium. Examples of rare earth element oxides include cerium oxide, yttrium oxide, neodymium oxide, and lanthanum oxide, and cerium oxide is preferable from the viewpoint of further improving adhesion. The rare earth element oxides contained in the corrosion-resistant coating can be used singly or in combination of two or more. As the liquid dispersion medium for the rare earth element oxide sol, various solvents such as water, alcohol solvents, hydrocarbon solvents, ketone solvents, ester solvents, and ether solvents can be used, with water being preferred. Examples of the cationic polymer include polyethyleneimine, an ionic polymer complex composed of a polymer containing polyethyleneimine and carboxylic acid, a primary amine-grafted acrylic resin obtained by graft-polymerizing a primary amine to an acrylic backbone, polyallylamine, or a derivative thereof. , aminated phenols and the like are preferred. The anionic polymer is preferably poly(meth)acrylic acid or a salt thereof, or a copolymer containing (meth)acrylic acid or a salt thereof as a main component. Moreover, the cross-linking agent is preferably at least one selected from the group consisting of a compound having a functional group such as an isocyanate group, a glycidyl group, a carboxyl group, or an oxazoline group, and a silane coupling agent. Further, the phosphoric acid or phosphate is preferably condensed phosphoric acid or condensed phosphate.

As an example of the corrosion-resistant film, fine particles of metal oxides such as aluminum oxide, titanium oxide, cerium oxide, and tin oxide, and barium sulfate are dispersed in phosphoric acid, which is applied to the surface of the barrier layer. C. or more, and those formed by performing baking processing are mentioned.

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

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

The amount of the corrosion ^- resistant film formed on the surface of the aluminum alloy foil in the chemical conversion treatment is not particularly limited. is about 0.5 to 50 mg, preferably about 1.0 to 40 mg in terms of chromium, the phosphorus compound is about 0.5 to 50 mg, preferably about 1.0 to 40 mg in terms of phosphorus, and aminated phenol polymer is contained in a ratio of, for example, about 1.0 to 200 mg, preferably about 5.0 to 150 mg.

The thickness of the corrosion-resistant coating is not particularly limited, but is preferably about 1 nm to 20 μm, more preferably 1 nm to 100 nm, from the viewpoint of cohesion of the coating and adhesion to the barrier layer and the heat-sealable resin layer. about 1 nm to 50 nm, more preferably about 1 nm to 50 nm. The thickness of the corrosion-resistant film 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 beam energy loss spectroscopy. By analysis of the composition of the corrosion-resistant coating using time-of-flight secondary ion mass spectrometry, for example, secondary ions composed of Ce, P and O (for example, at least one of Ce ₂ PO ₄ ⁺ and CePO ₄ ⁻ species) and, for example, secondary ions composed of Cr, P, and O (eg, at least one of CrPO ₂ ⁺ and CrPO ₄ ⁻ ) are detected.

In the chemical conversion treatment, a solution containing a compound used for forming a corrosion-resistant film is applied to the surface of the aluminum alloy foil by a bar coating method, a roll coating method, a gravure coating method, an immersion method, or the like. is carried out by heating so that the temperature of is about 70 to 200°C. In addition, before the aluminum alloy foil is subjected to the chemical conversion treatment, the aluminum alloy foil may be previously subjected to degreasing treatment by an alkali immersion method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or the like. By performing the degreasing treatment in this way, it becomes possible to perform the chemical conversion treatment on the surface of the aluminum alloy foil more efficiently. In addition, by using an acid degreasing agent obtained by dissolving a fluorine-containing compound in an inorganic acid for degreasing treatment, it is possible to form not only the degreasing effect of the metal foil but also the passive metal fluoride. In such cases, only degreasing treatment may be performed.

2. Exterior Material for Electricity Storage Device The exterior material 10 for an electricity storage device of the present disclosure includes at least a base material layer 1, a barrier layer 3, and a heat-fusible resin layer 4 in this order, as shown in FIGS. 1 to 4, for example. It is composed of a laminate. In the power storage device exterior material 10, the base material layer 1 is the outermost layer, and the heat-fusible resin layer 4 is the innermost layer. When an electricity storage device is assembled using the electricity storage device exterior material 10 and an electricity storage device element, the heat-sealable resin layers 4 of the electricity storage device exterior material 10 face each other, and the peripheral edges are heat-sealed. The electricity storage device element is accommodated in the space formed by .

The barrier layer 3 of the power storage device exterior material of the present disclosure contains the aluminum alloy foil of the present disclosure. That is, the barrier layer 3 of the power storage device exterior material of the present disclosure can be made of the aluminum alloy foil of the present disclosure. The exterior material for a power storage device of the present disclosure using the aluminum alloy foil of the present disclosure effectively suppresses corrosion of the aluminum alloy foil.

For example, as shown in FIGS. 2 to 4, the electrical storage device exterior material 10 is provided between the base material layer 1 and the barrier layer 3 for the purpose of improving the adhesion between these layers, if necessary. It may have an adhesive layer 2 . For example, as shown in FIGS. 3 and 4, an adhesive layer 5 may optionally be provided between the barrier layer 3 and the heat-fusible resin layer 4 for the purpose of enhancing the adhesion between these layers. may have Further, as shown in FIG. 4, a surface coating layer 6 or the like may be provided on the outside of the base material layer 1 (on the side opposite to the heat-fusible resin layer 4 side), if necessary.

The thickness of the laminate constituting the power storage device exterior material 10 is not particularly limited, but the upper limit is, for example, 300 μm or less, preferably about 180 μm or less, and about 155 μm or less from the viewpoint of cost reduction, energy density improvement, and the like. , about 120 μm or less, and the lower limit is preferably about 35 μm or more, about 45 μm or more, about 60 μm or more from the viewpoint of maintaining the function of the electricity storage device exterior material to protect the electricity storage device element, Preferred ranges are, 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, 60 to 120 μm. degree.

In the electrical storage device exterior material, the barrier layer 3, which will be described later, can usually be discriminated between MD (Machine Direction) and TD (Transverse Direction) in 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. ing. Since the rolling marks extend along the rolling direction, the rolling direction of the aluminum alloy foil can be grasped by observing the surface of the aluminum alloy foil. In the manufacturing process of the laminate, the MD of the laminate usually matches the RD of the aluminum alloy foil. By specifying the MD of the laminate can be specified. Moreover, since the TD of the laminate is perpendicular to the MD of the laminate, the TD of the laminate can also be specified.

In the power storage device exterior material 10 of the present disclosure, a metal plate with a width of 7 mm was used to heat the test sample from both sides in the stacking direction at a temperature of 190 ° C., with the heat-fusible resin layers 4 facing each other. The heat-sealable resin layers 4 are heat-sealed by heating and pressurizing under conditions of a pressure of 2.0 MPa and a time of 3 seconds (see FIGS. 10 and 11), and then, as shown in FIG. Using a tensile tester so as to be peeled off, in an environment at a temperature of 25 ° C., a tensile speed of 300 mm / min, a peeling angle of 180 °, and a distance between chucks of 50 mm, for 1.5 seconds from the start of tensile strength measurement The maximum value of the tensile strength (seal strength) measured by separating the thermally fused interface is preferably 110 N/15 mm or more, 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 preferable 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.

Furthermore, in the power storage device exterior material 10 of the present disclosure, a metal plate with a width of 7 mm was used to heat the test sample in the stacking direction at a temperature of 190 ° C. with the heat-fusible resin layers 4 facing each other. , under the conditions of a surface pressure of 2.0 MPa and a time of 3 seconds, the heat-fusible resin layers 4 are heat-sealed (see FIGS. 10 and 11), and then, as shown in FIG. , T-shaped peeling, using a tensile tester, in an environment at a temperature of 140 ° C., under the conditions of a tensile speed of 300 mm / min, a peel angle of 180 °, and a distance between chucks of 50 mm, 1.5 from the start of tensile strength measurement The maximum value of the tensile strength (seal strength) measured by peeling the thermally fused interface for a second is preferably 3.0 N/15 mm or more, and more preferably 4.0 N/15 mm or more. more preferred. The upper limit of the tensile strength is, for example, about 5.0 N/15 mm or less, and preferable 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. Therefore, in the exterior material for the electricity storage device of the present disclosure, the tensile strength (seal strength) preferably satisfies the above values. 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.

As shown in the examples below, the tensile test at each temperature is performed in a constant temperature bath, and the test sample is attached to the chuck in the constant temperature bath at a predetermined temperature (25 ° C. or 140 ° C.) for 2 minutes. Hold and start measurement.

The seal strength after contact with the electrolyte solution The power storage device exterior material 10 of the present disclosure is tested in an environment of 85 ° C. in an electrolyte solution (lithium hexafluorophosphate concentration is 1 mol / l, ethylene carbonate and diethyl carbonate A solution of 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) was added with a power storage device exterior material 72 . After contacting for a period of time, the heat-fusible resin layers were heat-fused under conditions of a temperature of 190° C., a surface pressure of 2.0 MPa, and a time of 3 seconds in a state where the electrolytic solution adhered to the surface of the heat-fusible resin layer. It is preferable that the seal strength when peeling off the heat-sealed interface is 60% or more of the seal strength when not in contact with the electrolytic solution (seal strength retention rate is 60% or more). , more preferably 80% or more, and even more preferably 100%.

(Method for measuring retention rate of seal strength)
Based on the seal strength before contact with the electrolytic solution measured by the following method as a standard (100%), the retention rate (%) of the seal strength after contact with the electrolytic solution is calculated.

<Measurement of seal strength before contact with electrolyte>
Tensile strength (seal strength) is measured in the same manner as in <Measurement of seal strength after contact with electrolyte solution> described below, except that the electrolyte solution is not injected into the test sample. The maximum tensile strength until the heat-sealed portion is completely peeled off is defined as the seal strength before contact with the electrolyte.

<Measurement of seal strength after contact with electrolyte>
As shown in the schematic diagram of FIG. 14, the electrical storage device exterior material is cut into a rectangle having a width (x direction) of 100 mm and a length (z direction) of 200 mm to obtain a test sample (FIG. 14a). The test sample is folded at the center in the z-direction so that the heat-sealable resin layer side overlaps (Fig. 14b). Next, both ends of the folded test sample in the x direction are heat-sealed (temperature 190 ° C., surface pressure 2.0 MPa, time 3 seconds), and a bag shape having one opening E is formed (Fig. 14c). Next, an electrolytic solution (lithium hexafluorophosphate concentration is 1 mol/l, volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate is 1:1:1) from the opening E of the bag-shaped test sample. 1) is injected (Fig. 14d), and the end of the opening E is heat-sealed (temperature: 190°C, surface pressure: 2.0 MPa, time: 3 seconds) (Fig. 14e). Next, the folded portion of the bag-shaped test sample is turned downward and left at rest in an environment at a temperature of 85° C. for a predetermined storage time (time for contact with the electrolytic solution, such as 72 hours). The end of the test sample is then cut (Fig. 14e) to drain the electrolyte. Next, with the electrolytic solution adhering to the surface of the heat-fusible resin layer, the upper and lower surfaces of the test sample were sandwiched between metal plates (7 mm width), and the temperature was 190 ° C., the surface pressure was 1.0 MPa, and the time was 3 seconds. The heat-sealable resin layers are heat-sealed with each other (Fig. 14f). The test sample is then cut 15 mm wide with a double-edged sample cutter so that the seal strength at 15 mm wide (x-direction) can be measured (Fig. 14f,g). Next, using a tensile tester so as to form a T-shaped peel, peel off the heat-sealed interface under the conditions of a tensile speed of 300 mm / min, a peel angle of 180 °, and a distance between chucks of 50 mm in an environment at a temperature of 25 ° C. and measure the tensile strength (seal strength) (Fig. 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.

Each layer forming the exterior material for the electricity storage device [base layer 1]
In the present disclosure, the base material layer 1 is a layer provided for the purpose of exhibiting a function as a base material of an exterior material for an electric storage device. The base material layer 1 is located on the outer layer side of the exterior material for electrical storage devices.

The material forming the base material layer 1 is not particularly limited as long as it functions as a base material, that is, at least has insulating properties. The base material layer 1 can be formed using, for example, a resin, and the resin may contain additives described later.

When the substrate layer 1 is formed of resin, the substrate layer 1 may be, for example, a resin film formed of resin, or may be formed by applying 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 a biaxially stretched film include successive biaxial stretching, inflation, and simultaneous biaxial stretching. Methods for applying the resin include a roll coating method, a gravure coating method, an extrusion coating method, and the like.

Examples of the resin forming the base material layer 1 include resins such as polyester, polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicon resin, phenolic resin, and modified products of these resins. Further, the resin forming the base material layer 1 may be a copolymer of these resins or a modified product of the copolymer. Furthermore, it may be a mixture of these resins.

As resin which forms the base material layer 1, polyester and polyamide are preferably mentioned among these.

Specific examples of polyester include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymerized polyester. Examples of copolyester include copolyester having ethylene terephthalate as a main repeating unit. Specifically, copolymer polyester polymerized with ethylene isophthalate with ethylene terephthalate as the main repeating unit (hereinafter abbreviated after polyethylene (terephthalate / isophthalate)), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate/sodium isophthalate), polyethylene (terephthalate/phenyl-dicarboxylate), polyethylene (terephthalate/decanedicarboxylate), and the like. These polyesters may be used singly or in combination of two or more.

Further, as the polyamide, specifically, aliphatic polyamide such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, copolymer of nylon 6 and nylon 66; terephthalic acid and / or isophthalic acid Hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamide such as nylon 6I, nylon 6T, nylon 6IT, nylon 6I6T (I represents isophthalic acid, T represents terephthalic acid) containing structural units derived from, polyamide MXD6 (polymetallic Polyamides containing aromatics such as silylene adipamide); alicyclic polyamides such as polyamide PACM6 (polybis(4-aminocyclohexyl)methane adipamide); Copolymerized polyamides, polyesteramide copolymers and polyetheresteramide copolymers which are copolymers of copolymerized polyamides with polyesters or polyalkylene ether glycols; and polyamides such as these copolymers. These polyamides may be used singly or in combination of two or more.

The substrate layer 1 preferably includes at least one of a polyester film, a polyamide film, and a polyolefin film, preferably includes at least one of a stretched polyester film, a stretched polyamide film, and a stretched polyolefin film, More preferably, at least one of an oriented polyethylene terephthalate film, an oriented polybutylene terephthalate film, an oriented nylon film, and an oriented polypropylene film is included, and the biaxially oriented polyethylene terephthalate film, biaxially oriented polybutylene terephthalate film, and biaxially oriented nylon film , biaxially oriented polypropylene film.

The base material layer 1 may be a single layer, or may be composed of two or more layers. When the substrate layer 1 is composed of two or more layers, the substrate layer 1 may be a laminate obtained by laminating resin films with an adhesive or the like, or may be formed by co-extrusion of resin to form two or more layers. It may also be a laminate of resin films. A laminate of two or more resin films formed by coextrusion of resin may be used as the base material layer 1 without being stretched, or may be used as the base material layer 1 by being uniaxially or biaxially stretched.

Specific examples of the laminate of two or more resin films in the substrate layer 1 include a laminate of a polyester film and a nylon film, a laminate of nylon films of two or more layers, and a laminate of polyester films of two or more layers. etc., preferably a laminate of a stretched nylon film and a stretched polyester film, a laminate of two or more layers of stretched nylon films, and a laminate of two or more layers of stretched polyester films. For example, when the substrate layer 1 is a laminate of two layers of resin films, a laminate of polyester resin films and polyester resin films, a laminate of polyamide resin films and polyamide resin films, or a laminate of polyester resin films and polyamide resin films. A laminate is preferred, and 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. In addition, the polyester resin is resistant to discoloration when, for example, an electrolytic solution adheres to the surface. It is preferably located in the outermost layer.

When the substrate layer 1 is a laminate of two or more layers of resin films, the two or more layers of resin films may be laminated via an adhesive. Preferred adhesives are the same as those exemplified for the adhesive layer 2 described later. The method for laminating two or more layers of resin films is not particularly limited, and known methods can be employed. Examples thereof include dry lamination, sandwich lamination, extrusion lamination, thermal lamination, and the like. A lamination method is mentioned. When laminating by dry lamination, it is preferable to use a polyurethane adhesive as the adhesive. At this time, the thickness of the adhesive is, for example, about 2 to 5 μm. Alternatively, an anchor coat layer may be formed on the resin film and laminated. As the anchor coat layer, the same adhesives as those exemplified in the adhesive layer 2 described later can be used. At this time, the thickness of the anchor coat layer is, for example, about 0.01 to 1.0 μm.

At least one of the surface and the inside of the substrate layer 1 may contain additives such as lubricants, flame retardants, antiblocking agents, antioxidants, light stabilizers, tackifiers, and antistatic agents. good. Only one type of additive may be used, or two or more types may be mixed and used.

In the present disclosure, it is preferable that a lubricant exists on the surface of the base material layer 1 from the viewpoint of improving the moldability of the exterior material for an electricity storage device. The lubricant is not particularly limited, but preferably includes an amide-based lubricant. Specific examples of amide 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, N-stearyl erucic acid amide and the like. Further, specific examples of methylolamide include methylol stearamide. Specific examples of saturated fatty acid bisamides include methylenebisstearic acid amide, ethylenebiscapric acid amide, ethylenebislauric acid amide, ethylenebisstearic acid amide, ethylenebishydroxystearic acid amide, ethylenebisbehenic acid amide, hexamethylenebisstearin. acid amide, hexamethylenebisbehenamide, hexamethylenehydroxystearic acid amide, N,N'-distearyladipic acid amide, N,N'-distearylsebacic acid amide and the like. Specific examples of unsaturated fatty acid bisamides include ethylenebisoleic acid amide, ethylenebiserucic acid amide, hexamethylenebisoleic acid amide, N,N'-dioleyladipic acid amide, and N,N'-dioleylsebacic acid amide. etc. Specific examples of fatty acid ester amides include stearamide ethyl stearate. Further, specific examples of the aromatic bisamide include m-xylylenebisstearic acid amide, m-xylylenebishydroxystearic acid amide, N,N'-distearyl isophthalic acid amide and the like. Lubricants may be used singly or in combination of two or more.

When a lubricant exists on the surface of the base material layer 1, its amount is not particularly limited, but is preferably about 3 mg/m ² or more, more preferably about 4 to 15 mg/m ² , and still more preferably 5 to 14 mg. / m ² degree.

The lubricant present on the surface of the substrate layer 1 may be obtained by exuding the lubricant contained in the resin constituting the substrate layer 1, or by coating the surface of the substrate layer 1 with the lubricant. may

The thickness of the base material layer 1 is not particularly limited as long as it functions as a base material. When the substrate 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.

[Adhesive layer 2]
In the power storage device exterior material of the present disclosure, the adhesive layer 2 is a layer provided between the base layer 1 and the barrier layer 3 as necessary for the purpose of enhancing the adhesiveness between them.

The adhesive layer 2 is made of an adhesive capable of bonding the base material layer 1 and the barrier layer 3 together. The adhesive used to form the adhesive layer 2 is not limited, but may be any of a chemical reaction type, a solvent volatilization type, a hot melt type, a hot pressure type, and the like. Further, it may be a two-liquid curing adhesive (two-liquid adhesive), a one-liquid curing adhesive (one-liquid adhesive), or a resin that does not involve a curing reaction. Further, the adhesive layer 2 may be a single layer or multiple layers.

Specific examples of the adhesive component contained in the adhesive include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymerized polyester; polyether; polyurethane; epoxy resin; Phenolic resins; polyamides such as nylon 6, nylon 66, nylon 12, and copolymerized polyamides; polyolefin resins such as polyolefins, cyclic polyolefins, acid-modified polyolefins, and acid-modified cyclic polyolefins; polyvinyl acetate; cellulose; (meth)acrylic resins; polyimide; polycarbonate; amino resin such as urea resin and melamine resin; rubber such as chloroprene rubber, nitrile rubber and styrene-butadiene rubber; These adhesive components may be used singly or in combination of two or more. Among these adhesive components, polyurethane adhesives are preferred. In addition, an appropriate curing agent can be used in combination with these adhesive component resins to increase the adhesive strength. The curing agent is selected from among polyisocyanates, polyfunctional epoxy resins, oxazoline group-containing polymers, polyamine resins, acid anhydrides, etc., depending on the functional groups of the adhesive component.

Examples of polyurethane adhesives include polyurethane adhesives containing a main agent containing a polyol compound and a curing agent containing an isocyanate compound. Two-component curing type polyurethane adhesives using polyols such as polyester polyols, polyether polyols, and acrylic polyols as main agents and aromatic or aliphatic polyisocyanates as curing agents are preferred. Moreover, as the polyol compound, it is preferable to use a polyester polyol having a hydroxyl group in a side chain in addition to the terminal hydroxyl group of the repeating unit. Since the adhesive layer 2 is formed of a polyurethane adhesive, the exterior material for an electric storage device is imparted with excellent electrolyte resistance, and even if the electrolyte adheres to the side surface, the base layer 1 is suppressed from being peeled off. .

Further, the adhesive layer 2 may contain other components as long as they do not impede adhesion, and may contain colorants, thermoplastic elastomers, tackifiers, fillers, and the like. Since the adhesive layer 2 contains a coloring agent, the exterior material for an electric storage device can be colored. Known substances such as pigments and dyes can be used as the colorant. In addition, only one type of colorant may be used, or two or more types may be mixed and used.

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. Examples of pigments include carbon black, titanium oxide, cadmium, lead, chromium oxide, and iron pigments, as well as fine powder of mica and fish scale foil.

Among the coloring agents, carbon black is preferable, for example, in order to make the external appearance of the exterior material for an electric storage device black.

The average particle size of the pigment is not particularly limited, and is, for example, approximately 0.05 to 5 μm, preferably approximately 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 analyzer.

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

The thickness of the adhesive layer 2 is not particularly limited as long as the substrate layer 1 and the barrier layer 3 can be adhered. , about 5 μm or less, and preferable ranges include about 1 to 10 μm, about 1 to 5 μm, about 2 to 10 μm, and about 2 to 5 μm.

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

The colored layer can be formed, for example, by applying ink containing a coloring agent to the surface of the substrate layer 1, the adhesive layer 2, or the barrier layer 3. Known substances such as pigments and dyes can be used as the colorant. In addition, only one type of colorant may be used, or two or more types may be mixed and used.

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

[Barrier layer 3]
In the power storage device exterior material, the barrier layer 3 is a layer that at least prevents permeation of moisture.

The barrier layer 3 of the power storage device exterior material of the present disclosure contains the aluminum alloy foil of the present disclosure. That is, the barrier layer 3 of the power storage device exterior material of the present disclosure can be made 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".

[Heat-fusible resin layer 4]
In the power storage device exterior material of the present disclosure, the heat-fusible resin layer 4 corresponds to the innermost layer, and has the function of sealing the power storage device element by heat-sealing the heat-fusible resin layers to each other when assembling the power storage device. It is a layer (sealant layer) that exhibits

The resin constituting the heat-fusible resin layer 4 is not particularly limited as long as it is heat-fusible, but resins containing polyolefin skeletons such as polyolefins and acid-modified polyolefins are preferable. The inclusion of a polyolefin skeleton in the resin constituting the heat-fusible resin layer 4 can be analyzed by, for example, infrared spectroscopy, gas chromatography-mass spectrometry, or the like. Further, when the resin constituting the heat-fusible resin layer 4 is analyzed by infrared spectroscopy, it is preferable that a peak derived from maleic anhydride is detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, peaks derived from maleic anhydride are detected near wavenumbers of 1760 cm ⁻¹ and 1780 cm ⁻¹ . In the case where the heat-fusible resin layer 4 is a layer composed of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride is detected when measured by infrared spectroscopy. However, if the degree of acid denaturation is low, the peak may be too small to be detected. In that case, it can be analyzed by nuclear magnetic resonance spectroscopy.

Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; block copolymers of ethylene), random copolymers of polypropylene (for example, random copolymers of propylene and ethylene); propylene-α-olefin copolymers; 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-based resins may be used alone or in combination of two or more.

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

Acid-modified polyolefin is a polymer modified by block polymerization or graft polymerization of polyolefin with an acid component. As the acid-modified polyolefin, the above polyolefin, a copolymer obtained by copolymerizing the above polyolefin with a polar molecule such as acrylic acid or methacrylic acid, or a polymer such as crosslinked polyolefin can be used. Examples of acid components used for acid modification include carboxylic acids such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride and itaconic anhydride, and anhydrides thereof.

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

Preferred acid-modified polyolefins include carboxylic acid- or anhydride-modified polyolefins, carboxylic acid- or anhydride-modified polypropylenes, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

The heat-fusible resin layer 4 may be formed of one type of resin alone, or may be formed of a blend polymer in which two or more types of resin are combined. Furthermore, the heat-fusible 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.

Moreover, the heat-fusible resin layer 4 may contain a lubricant or the like as necessary. When the heat-fusible resin layer 4 contains a lubricant, it is possible to improve the moldability of the power storage device exterior material. The lubricant is not particularly limited, and known lubricants can be used. Lubricants may be used singly or in combination of two or more.

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

When a lubricant exists on the surface of the heat-fusible resin layer 4, the amount of the lubricant is not particularly limited, but from the viewpoint of improving the moldability of the electronic packaging material, it is preferably about 10 to 50 mg/m ² , More preferably, it is about 15 to 40 mg/m ² .

The lubricant present on the surface of the heat-fusible resin layer 4 may be obtained by exuding the lubricant contained in the resin constituting the heat-fusible resin layer 4 . The surface may be coated with a lubricant.

The thickness of the heat-fusible resin layer 4 is not particularly limited as long as the heat-fusible resin layers are heat-sealed to each other to exhibit the function of sealing the electricity storage device element. About 85 μm or less, more preferably about 15 to 85 μm. For example, when the thickness of the adhesive layer 5 described later is 10 μm or more, the thickness of the heat-fusible resin layer 4 is preferably about 85 μm or less, more preferably about 15 to 45 μm. When the thickness of the adhesive layer 5 described later is less than 10 μm or when the adhesive layer 5 is not provided, the thickness of the heat-fusible resin layer 4 is preferably about 20 μm or more, more preferably 35 to 85 μm. degree.

Even if the heat-fusible resin layer is heat-sealed in a state where the electrolyte comes into contact with the heat-fusible resin layer in a high-temperature environment and the electrolyte adheres to the heat-fusible resin layer, From the viewpoint of exhibiting a higher seal strength, when the temperature difference T ₁ and the temperature difference T ₂ are measured by the following method, the value obtained by dividing the temperature difference T ₂ by the temperature difference T ₁ ( The ratio T ₂ /T ₁ ) is, for example, 0.55 or more, more preferably 0.60 or more. As can be understood from the measurement contents of the temperature differences T ₁ and T ₂ below, the closer the ratio T ₂ /T ₁ is to the upper limit of 1.0, the more the heat-fusible resin layer contacts the electrolytic solution. This means that the change in width between the start point (extrapolation melting start temperature) and the end point (extrapolation melting end temperature) of the melting peak before and after is small (see the schematic diagram of FIG. 15). That is, the value of T2 is typically _{less than} or equal to the value of T1. The reason for the large change in the width between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak is that the low-molecular-weight resin contained in the resin constituting the heat-sealable resin layer comes into contact with the electrolyte. As a result, the width of the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak of the heat-fusible resin layer after contact with the electrolyte is compared to before contact with the electrolyte. and become smaller. As one method for reducing the change in the width of the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak, the ratio of the low-molecular-weight resin contained in the resin constituting the heat-fusible resin layer can be adjusted.

(Measurement of temperature difference _T1 )
In accordance with JIS K7121:2012, differential scanning calorimetry (DSC) is used to obtain a DSC curve for the resin used for the heat-fusible resin layer of each of the above exterior materials for power storage devices. 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 _- fusible resin layer is measured.

₍ Measurement of temperature difference T2)
In an environment at a temperature of 85° C., the resin used for the heat-fusible resin layer was mixed with a lithium hexafluorophosphate concentration of 1 mol/l and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1. After standing for 72 hours in the electrolytic solution, which is the solution of No. 1, it is sufficiently dried. Next, a DSC curve is obtained for the dried polypropylene using differential scanning calorimetry (DSC) in accordance with JIS K7121:2012. Next, 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 heat _- fusible resin layer after drying is measured.

A commercially available differential scanning calorimeter can be used for measuring the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature. Further, as a DSC curve, after holding the test sample at -50 ° C. for 10 minutes, the temperature was raised to 200 ° C. at a temperature increase rate of 10 ° C./min (first time), and after holding at 200 ° C. for 10 minutes, the temperature decrease rate After the temperature was lowered to -50°C at -10°C/min and held at -50°C for 10 minutes, the temperature was raised to 200°C at a temperature increase rate of 10°C/min (second time) and held at 200°C for 10 minutes, A DSC curve when the temperature is raised to 200° C. for the second time is used. When measuring the temperature difference T ₁ and the temperature difference T ₂ , among the melting peaks appearing in the range of 120 to 160° C. in each DSC curve, analyze the melting peak with the largest difference in thermal energy input. conduct. Even if two or more peaks are overlapped, only the melting peak with the maximum difference in thermal energy input is analyzed.

In addition, the extrapolated melting start temperature means the start point of the melting peak temperature, and the difference between the straight line obtained by extending the baseline on the low temperature side (65 to 75 ° C.) to the high temperature side and the melting point where the difference between the thermal energy input is the maximum The temperature at the point of intersection with the tangent line drawn at the point where the gradient is maximum on the curve on the low temperature side of the peak. The extrapolated melting end temperature means the end point of the melting peak temperature. is the temperature at the point of intersection with the tangent line drawn at the point where the slope of the curve becomes maximum.

In the exterior material for a power storage device of the present disclosure, the heat-fusible resin layer is contacted with the electrolyte in a high-temperature environment, and the heat-fusible resin layers are heat-fused together in a state where the electrolyte adheres to the heat-fusible resin layer. From the viewpoint of exhibiting a higher seal strength by heat fusion even when the two are bonded together, the value obtained by dividing the temperature difference T ₂ by the temperature difference T ₁ (ratio T ₂ /T ₁ ) is as follows: For example, it is 0.55 or more, preferably 0.60 or more, more preferably 0.70 or more, and still more preferably 0.75 or more. About 1.0, about 0.70 to 1.0, and about 0.75 to 1.0 can be mentioned. Moreover, an upper limit is 1.0, for example. In order to set such a ratio T ₂ /T ₁ , for example, the type, composition, molecular weight, etc. of the resin forming the heat-fusible resin layer 4 are adjusted.

Also, in a high-temperature environment, when the electrolyte comes into contact with the heat-fusible resin layer and the heat-fusible resin layers are heat-sealed while the electrolyte adheres to the heat-fusible resin layer, heat From the viewpoint of exhibiting _a higher seal strength by fusion, the absolute value of the difference |T _{2 −T 1} | Below, more preferably about 8° C. or less, more preferably about 7.5° C. or less. 5°C, 1-15°C, 1-10°C, 1-8°C, 1-7.5°C, 2-15°C, 2-10°C, 2-8°C, 2-8°C About 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 |T ₂ −T ₁ | is, for example, 0° C., 1° C., 2° C., 5° C., or the like. In order to set the absolute value of the difference to |T ₂ −T ₁ |, for example, the type, composition, molecular weight, etc. of the resin forming the heat-fusible resin layer 4 are adjusted.

Also, the temperature difference T ₁ is preferably about 29 to 38°C, more preferably about 32 to 36°C. The temperature difference T ₂ is preferably about 17-30°C, more preferably about 26-29°C. In order to set the temperature differences T ₁ and T ₂ as described above, for example, the kind, composition, molecular weight, etc. of the resin forming the heat-fusible resin layer 4 are adjusted.

[Adhesion layer 5]
In the power storage device exterior material of the present disclosure, the adhesive layer 5 is provided between the barrier layer 3 (or the corrosion-resistant film) and the heat-fusible resin layer 4 as necessary in order to firmly bond them. It is a layer that can be

The adhesive layer 5 is made of a resin capable of bonding the barrier layer 3 and the heat-fusible resin layer 4 together. As the resin used for forming the adhesive layer 5, for example, the same adhesives as those exemplified for the adhesive layer 2 can be used. The resin used to form the adhesive layer 5 preferably contains a polyolefin skeleton, and includes the polyolefins and acid-modified polyolefins exemplified for the heat-fusible resin layer 4 described above. Whether the resin constituting the adhesive layer 5 contains a polyolefin skeleton can be analyzed by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like, and the analysis method is not particularly limited. Further, when the resin forming the adhesive layer 5 is analyzed by infrared spectroscopy, it is preferable that a peak derived from maleic anhydride is detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, peaks derived from maleic anhydride are detected near wavenumbers of 1760 cm ⁻¹ and 1780 cm ⁻¹ . However, if the degree of acid denaturation is low, the peak may be too small to be detected. In that case, it can be analyzed by nuclear magnetic resonance spectroscopy.

From the viewpoint of firmly bonding the barrier layer 3 and the heat-fusible resin layer 4, the adhesive layer 5 preferably contains an acid-modified polyolefin. Particularly preferred acid-modified polyolefins are polyolefins modified with carboxylic acid or its anhydride, polypropylene modified with carboxylic acid or its anhydride, maleic anhydride-modified polyolefin, and maleic anhydride-modified polypropylene.

Furthermore, from the viewpoint of making the power storage device exterior material excellent in shape stability after molding while reducing the thickness of the power storage device exterior material, the adhesive layer 5 is made of a resin composition containing an acid-modified polyolefin and a curing agent. is more preferably a cured product of Preferred examples of the acid-modified polyolefin include those mentioned above.

Further, the adhesive layer 5 is a cured product of a resin composition containing 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. 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 is particularly preferred. Moreover, the adhesive layer 5 preferably contains at least one selected from the group consisting of polyurethane, polyester, and epoxy resin, and more preferably contains polyurethane and epoxy resin. As the polyester, for example, an amide ester resin is preferable. Amide ester resins are generally produced by the reaction of carboxyl groups and oxazoline groups. More preferably, the adhesive layer 5 is a cured product of a resin composition containing at least one of these resins and the acid-modified polyolefin. In the case where the adhesive layer 5 contains an isocyanate group-containing compound, an oxazoline group-containing compound, or an unreacted product of a curing agent such as an epoxy resin, the presence of the unreacted product can be detected by, for example, infrared spectroscopy, It can be confirmed by a method selected from Raman spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), and the like.

In addition, from the viewpoint of further increasing the adhesion between the barrier layer 3 and the adhesive layer 5, the adhesive layer 5 contains at least It is preferably a cured product of a resin composition containing one curing agent. The curing agent having a heterocyclic ring includes, for example, a curing agent having an oxazoline group, a curing agent having an epoxy group, and the like. Moreover, the curing agent having a C═N bond includes a curing agent having an oxazoline group, a curing agent having an isocyanate group, and the like. Further, examples of curing agents having a C—O—C bond include curing agents having an oxazoline group, curing agents having an epoxy group, and polyurethanes. The adhesive layer 5 is a cured product of a resin composition containing these curing agents, for example, gas chromatography mass spectrometry (GCMS), infrared spectroscopy (IR), time-of-flight secondary ion mass spectrometry (TOF -SIMS) and X-ray photoelectron spectroscopy (XPS).

The isocyanate group-containing compound is not particularly limited, but from the viewpoint of effectively increasing the adhesion between the barrier layer 3 and the adhesive layer 5, polyfunctional isocyanate compounds are preferred. 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), polymerization and nurate compounds, mixtures thereof, copolymers with other polymers, and the like. In addition, adducts, burettes, isocyanurates and the like are included.

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

The compound having an oxazoline group is not particularly limited as long as it is a compound having an oxazoline skeleton. Specific examples of compounds having an oxazoline group include those having a polystyrene main chain and those having an acrylic main chain. Moreover, as a commercial item, the Epocross series by Nippon Shokubai Co., Ltd. etc. are mentioned, for example.

The ratio of the compound having an oxazoline group in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, more preferably 0.5 to 40% by mass, in the resin composition constituting the adhesive layer 5. is more preferable. Thereby, the adhesion between the barrier layer 3 and the adhesive layer 5 can be effectively improved.

Examples of compounds having an epoxy group include epoxy resins. The epoxy resin is not particularly limited as long as it is a resin capable of forming a crosslinked structure with 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 2000, more preferably about 100 to 1000, still 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) using polystyrene as a standard sample.

Specific examples of epoxy resins include glycidyl ether derivatives of trimethylolpropane, bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, novolak glycidyl ether, glycerin polyglycidyl ether, polyglycerin polyglycidyl ether, and the like. An epoxy resin may be used individually by 1 type, and may be used in combination of 2 or more types.

The proportion of the epoxy resin in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, more preferably in the range of 0.5 to 40% by mass, in the resin composition constituting the adhesive layer 5. is more preferred. Thereby, the adhesion between the barrier layer 3 and the adhesive layer 5 can be effectively improved.

Polyurethane is not particularly limited, and known polyurethanes can be used. The adhesive layer 5 may be, for example, a cured product of two-component curing type polyurethane.

The proportion of polyurethane in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, more preferably in the range of 0.5 to 40% by mass, in the resin composition constituting the adhesive layer 5. more preferred. As a result, the adhesion between the barrier layer 3 and the adhesive layer 5 can be effectively enhanced in an atmosphere containing a component that induces corrosion of the barrier layer, such as an electrolytic solution.

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

The upper limit of the thickness of the adhesive layer 5 is preferably about 50 μm or less, about 40 μm or less, about 30 μm or less, about 20 μm or less, or about 5 μm or less, and the lower limit is preferably about 0.1 μm or more. , 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, 0 .1 to 5 μm, 0.5 to 50 μm, 0.5 to 40 μm, 0.5 to 30 μm, 0.5 to 20 μm, and 0.5 to 5 μm. More specifically, in the case of the adhesive exemplified for the adhesive layer 2 or the cured product of acid-modified polyolefin and curing agent, the thickness is preferably about 1 to 10 μm, more preferably about 1 to 5 μm. In the case of using the resin exemplified for the heat-fusible resin layer 4, the thickness is preferably about 2 to 50 μm, more preferably about 10 to 40 μm. When the adhesive layer 5 is the adhesive exemplified for the adhesive layer 2 or a cured product of a resin composition containing an acid-modified polyolefin and a curing agent, for example, the resin composition is applied and cured by heating or the like. Thus, the adhesive layer 5 can be formed. Further, when using the resin exemplified for the heat-fusible resin layer 4, the heat-fusible resin layer 4 and the adhesive layer 5 can be formed by extrusion molding, for example.

In the power storage device exterior material of the present disclosure, the adhesive layer 5 has a logarithmic attenuation rate 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 0.22 or less, more preferably 0.20 or less. In the present disclosure, the logarithmic decrement ΔE at 120 ° C. is, for example, 0.50 or less, 0.40 or less, 0.30 or less, 0.22 or less, 0.26 or less, and further 0.20 or less When the energy storage device element is sealed with the energy storage device exterior material, it effectively suppresses the crushing of the adhesive layer when the heat-sealable resin layers are heat-sealed to each other, and exhibits high sealing strength in high-temperature environments. be done.

The logarithmic decrement at 120° C. in the rigid body pendulum measurement is an index representing the hardness of the resin in a high temperature environment of 120° C. The smaller the logarithmic decrement, the higher the hardness of the resin. In the rigid pendulum measurement, the damping rate of the pendulum is measured when the temperature of the resin is raised from low to high. In the rigid pendulum measurement, generally, the edge portion is brought into contact with the surface of the object to be measured, and the object to be measured is vibrated by pendulum motion in the horizontal direction. In the power storage device exterior material of the present disclosure, the logarithmic decrement in a high temperature environment of 120 ° C. is, 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 By disposing the adhesive layer 5 having a hardness of .20 or less between the aluminum alloy foil and the heat-sealable resin layer 4, the adhesive layer 5 is not crushed (thinned) during heat-sealing of the exterior material for the electric storage device. ) is suppressed, and high seal strength can be exhibited in a high-temperature environment.

Note that the logarithmic decrement ΔE is calculated by the following formula.
ΔE=[ln(A1/A2)+ln(A2/A3)+...ln(An/An+1)]/n
A: amplitude n: wave number

In the power storage device exterior material of the present disclosure, the perspective of effectively suppressing crushing of the adhesive layer 5 when the heat-fusible resin layers 4 are heat-sealed to each other and exhibiting high seal strength in a high-temperature environment. Therefore, 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 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. In order to set the logarithmic attenuation rate ΔE, for example, the type, composition, molecular weight, etc. of the resin forming the adhesive layer 5 are adjusted.

In the measurement of the logarithmic decrement ΔE, a commercially available rigid pendulum type physical property tester was used, a cylindrical cylinder edge was used as the edge to be pressed against the adhesive layer 5, the initial amplitude was 0.3 degrees, and the temperature ranged from 30°C to 200°C. A rigid pendulum physical property test is performed on the adhesive layer 5 under the condition of a temperature increase rate of 3° C./min. Then, based on the logarithmic decrement at 120° C., the standard for the effect of suppressing crushing exhibited by the adhesive layer 5 and improving the seal strength by heat sealing in a high-temperature environment was determined. Regarding the adhesive layer for measuring the logarithmic decrement rate ΔE, the electrical storage device exterior material was immersed in 15% hydrochloric acid to dissolve the base material layer and the aluminum alloy foil, and only the adhesive layer and the heat-fusible resin layer were formed. Dry the sample thoroughly and use it as a measurement target.

Alternatively, the logarithmic decrement ΔE of the adhesive layer 5 can be measured by obtaining the exterior material for an electricity storage device from the electricity storage device. When the power storage device exterior material is obtained from the power storage device and the logarithmic decrement ΔE of the adhesive layer 5 is measured, a sample is cut from the top surface portion where the power storage device exterior material is not stretched by molding to be measured.

In addition, in the power storage device exterior material of the present disclosure, the heat-fusible resin layers of the laminate constituting the power storage device exterior material are opposed to each other, and the temperature is 190 ° C., the surface pressure is 0.5 MPa, and the time is 3 seconds. After being heated and pressurized in the stacking direction under the conditions, the residual ratio of the thickness of the adhesive layer is preferably 70% or more, preferably 80% or more, and the preferable range is 70 to 95%, 80 to 95%. 95%. In addition, the upper limit of the residual ratio of the thickness is, for example, about 95%. The remaining thickness ratio is a value measured by the following method. In order to set the remaining ratio of the thickness, for example, the type, composition, molecular weight, etc. of the resin forming the adhesive layer 5 are adjusted.

<Measurement of Remaining Ratio of Adhesive Layer Thickness>
A test sample is prepared by cutting the exterior material for an electric storage device into a length of 150 mm and a width of 60 mm. Next, the heat-fusible resin layers of the test sample are opposed to each other. Next, in that state, using a metal plate with a width of 7 mm, the test sample is heated and pressurized from both sides in the stacking direction under the conditions of a temperature of 190 ° C., a surface pressure of 0.5 MPa, and a time of 3 seconds, and heat-sealed. The flexible resin layers are heat-sealed to each other. 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 for the exposed cross section. Similarly, the test sample before heat-sealing is also cut in the stacking direction using a microtome, and the thickness of the adhesive layer is measured for the exposed cross section. The ratio of the thickness of the adhesive layer after heat-sealing to the thickness of the adhesive layer before heat-sealing is calculated, and the remaining ratio (%) of the thickness of the adhesive layer is measured. In addition, the thickness of the adhesive layer is measured at a portion where the thickness is constant in the vicinity of the end portion of the exterior material for an electric storage device.

Moreover, the residual ratio of the thickness of the adhesive layer 5 can also be measured by obtaining the exterior material for an electricity storage device from the electricity storage device. When obtaining the power storage device exterior material from the power storage device and measuring the residual ratio of the thickness of the adhesive layer 5, a sample is cut from the top surface portion where the power storage device exterior material is not stretched by molding and is used as a measurement target. .

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 forming the adhesive layer 5 .

[Surface coating layer 6]
For the purpose of at least one of improving design, electrolyte resistance, scratch resistance, moldability, etc., the exterior material for an electricity storage device of the present disclosure is provided on the base layer 1 (base layer 1 (the side opposite to the barrier layer 3) may be provided with a surface coating layer 6. The surface coating layer 6 is a layer positioned on the outermost layer side of the exterior material for an electricity storage device when an electricity storage device is assembled using the exterior material for an electricity storage device.

The surface coating layer 6 can be formed of resin such as polyvinylidene chloride, polyester, polyurethane, acrylic resin, and epoxy resin, for example.

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

Examples of two-liquid curable polyurethanes include polyurethanes containing a main agent containing a polyol compound and a curing agent containing an isocyanate compound. Preferable examples include two-component curing type polyurethanes using polyols such as polyester polyols, polyether polyols, and acrylic polyols as main agents and aromatic or aliphatic polyisocyanates as curing agents. Moreover, as the polyol compound, it is preferable to use a polyester polyol having a hydroxyl group in a side chain in addition to the terminal hydroxyl group of the repeating unit. Since the surface coating layer 6 is made of polyurethane, the exterior material for an electric storage device is imparted with excellent electrolyte resistance.

At least one of the surface and the inside of the surface coating layer 6 may be coated with the above-described lubricant or anti-rust agent as necessary depending on the functionality to be provided on the surface coating layer 6 and its surface. Additives such as blocking agents, matting agents, flame retardants, antioxidants, tackifiers and antistatic agents may be included. Examples of the additive include fine particles having an average particle size of about 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.

Additives may be either inorganic or organic. Also, the shape of the additive is not particularly limited, and examples thereof include spherical, fibrous, plate-like, amorphous, scale-like, and the like.

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, and 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 nanotube, high melting point nylon, acrylate resin, Crosslinked acrylic, crosslinked styrene, crosslinked polyethylene, benzoguanamine, gold, aluminum, copper, nickel, and the like. Additives may be used singly or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferred from the viewpoint of dispersion stability and cost. In addition, the additive may be subjected to various surface treatments such as insulation treatment and high-dispersion treatment.

A method for forming the surface coating layer 6 is not particularly limited, and an example thereof includes a method of applying a resin for forming the surface coating layer 6 . When adding additives to the surface coating layer 6, a resin mixed with the additives may be applied.

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

3. Method for producing an exterior material for an electricity storage device The method for producing an exterior material for an electricity storage device is not particularly limited as long as a laminate obtained by laminating each layer included in the exterior material for an electricity storage device of the present disclosure is obtained. A method including a step of laminating the layer 1, the barrier layer 3, and the heat-fusible resin layer 4 in this order may be mentioned. As described above, as the barrier layer 3, the aluminum alloy foil of the present disclosure can be used.

An example of the method for manufacturing the exterior material for an electricity storage device of the present disclosure is as follows. First, a layered body (hereinafter also referred to as "layered body A") is formed by laminating a substrate layer 1, an adhesive layer 2, and a barrier layer 3 in this order. Specifically, the laminate A is formed by applying an adhesive used for forming the adhesive layer 2 on the substrate layer 1 or on the barrier layer 3 whose surface is chemically treated as necessary, by a gravure coating method, It can be performed by a dry lamination method in which the barrier layer 3 or the substrate layer 1 is laminated and the adhesive layer 2 is cured after coating and drying by a coating method such as a roll coating method.

Next, on the barrier layer 3 of the laminate A, the heat-fusible resin layer 4 is laminated. When the heat-fusible resin layer 4 is directly laminated on the barrier layer 3, the heat-fusible resin layer 4 is laminated on the barrier layer 3 of the laminate A by a method such as thermal lamination or extrusion lamination. do it. When the adhesive layer 5 is provided between the barrier layer 3 and the heat-fusible resin layer 4, for example, (1) the adhesive layer 5 and the heat-fusible resin layer are placed on the barrier layer 3 of the laminate A. 4 (co-extrusion lamination method, tandem lamination method); A method of laminating on the barrier layer 3 of the laminate A by a thermal lamination method, or forming a laminate in which an adhesive layer 5 is laminated on the barrier layer 3 of the laminate A, and laminating this with a heat-fusible resin layer 4 by a thermal lamination method Lamination method (3) While pouring the melted adhesive layer 5 between the barrier layer 3 of the laminate A and the heat-fusible resin layer 4 formed into a sheet in advance, the adhesive layer 5 is interposed. (4) coating the barrier layer 3 of the laminate A with an adhesive for forming the adhesive layer 5 in solution, A drying method, a baking method, or the like is used to laminate the adhesive layer 5 , and a heat-fusible resin layer 4 that has been formed into a sheet in advance is laminated on the adhesive layer 5 .

When providing the surface coating layer 6 , the surface coating layer 6 is laminated on the surface of the substrate layer 1 opposite to the barrier layer 3 . The surface coating layer 6 can be formed, for example, by coating the surface of the substrate layer 1 with the above-described resin for forming the surface coating layer 6 . 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 forming the surface coating layer 6 on the surface of the substrate layer 1 , the barrier layer 3 may be formed on the surface of the substrate layer 1 opposite to the surface coating layer 6 .

Surface coating layer 6/base layer 1/optionally provided adhesive layer 2/barrier layer 3/optionally provided adhesive layer 5/thermal fusion bonding as described above A laminate having the flexible resin layer 4 in this order is formed, and in order to strengthen the adhesiveness of the adhesive layer 2 and the adhesive layer 5 provided as necessary, it may be further subjected to heat treatment.

In the exterior material for an electricity storage device, each layer constituting the laminate may be subjected to surface activation treatment such as corona treatment, blasting treatment, oxidation treatment, and ozone treatment to improve processability as necessary. . For example, by subjecting the surface of the substrate layer 1 opposite to the barrier layer 3 to corona treatment, the printability of the ink onto the surface of the substrate layer 1 can be improved.

4. Use of Power Storage Device Exterior Material The power storage device exterior material of the present disclosure is used in a packaging body for sealingly housing power storage device elements such as a positive electrode, a negative electrode, and an electrolyte. That is, an electricity storage device can be obtained by housing an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte in a package formed by the electricity storage device exterior material of the present disclosure.

Specifically, an electricity storage device element having at least a positive electrode, a negative electrode, and an electrolyte is placed in the exterior material for an electricity storage device of the present disclosure in a state in which metal terminals connected to the positive electrode and the negative electrode protrude outward. , covering the periphery of the electricity storage device element so as to form a flange portion (area where the heat-fusible resin layers contact each other), and heat-sealing the heat-fusible resin layers of the flange portion to seal. provides an electricity storage device using an exterior material for an electricity storage device. In addition, when housing an electricity storage device element in a package formed by the electricity storage device exterior material of the present disclosure, the heat-fusible resin portion of the electricity storage device exterior material of the present disclosure is on the inside (surface in contact with the electricity storage device element ) to form a package.

The power storage device exterior material of the present disclosure can be suitably used for power storage devices such as batteries (including capacitors, capacitors, etc.). Moreover, although the exterior material for an electricity storage device of the present disclosure may be used for either a primary battery or a secondary battery, it is preferably a secondary battery. The type of secondary battery to which the power storage device exterior material of the present disclosure is applied is not particularly limited. Cadmium storage batteries, nickel/iron storage batteries, nickel/zinc storage batteries, silver oxide/zinc storage batteries, metal-air batteries, polyvalent cation batteries, capacitors, capacitors, and the like. Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries can be mentioned as suitable targets for application of the power storage device exterior material of the present disclosure.

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

[Example 1]
<Production of aluminum alloy foil>
An aluminum alloy consisting of 0.10% by mass of Mn, 2.20% by mass of Mg, 0.40% by mass of Fe, 0.10% by mass of Cu, 0.00% by mass of Si, 0.00% by mass of Cr, 0.00% by mass of Zn, and the balance of Al is used. An aluminum alloy foil having a thickness of 40 μm was obtained through the steps of melting, homogenization, hot rolling, cold rolling, intermediate annealing, cold rolling, and final annealing in the same manner as in the known aluminum alloy manufacturing method. The obtained aluminum alloy foil has the composition described in Example 1 of Table 1. As for the manufacturing conditions of the aluminum alloy foil, for example, the description in Japanese Patent Application Laid-Open No. 2005-163077 can be referred to.

<Manufacturing exterior materials for power storage devices>
Polyethylene terephthalate film (12 μm)/adhesive layer (2-liquid curing type urethane adhesive (polyol compound and aromatic isocyanate compound), thickness 3 μm)/biaxially oriented nylon film (thickness 15 μm) are laminated in this order as a base layer. A laminated film was prepared. Next, on the biaxially stretched nylon film (thickness 15 μm) of the base layer, the aluminum alloy foil (having the composition shown in Table 1 and having a thickness 40 μm) was laminated by a dry lamination method. Specifically, on one side of an aluminum alloy foil having a corrosion-resistant film (acid-resistant film (a film formed by chromate treatment, the amount of chromium is 30 mg/m ² )) formed on both sides, a two-component curing type A urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to form an adhesive layer (thickness 3 μm after curing) on the aluminum alloy foil. Next, after laminating the adhesive layer on the aluminum alloy foil and the biaxially oriented nylon film, aging treatment was performed to prepare a laminate of base layer/adhesive layer/barrier layer. Next, a maleic anhydride-modified polypropylene (40 μm thick) as an adhesive layer and a polypropylene (40 μm thick) as a heat-fusible resin layer are co-extruded on the barrier layer of the resulting laminate. Thus, the adhesive layer/heat-fusible resin layer was laminated on the barrier layer. Next, by aging and heating the obtained laminate, 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-fusible resin layer (40 μm) were laminated in this order to obtain an exterior material for an electric storage device.

In Examples 1 and 2, the maleic anhydride-modified polypropylene used for the adhesive layer was different, and the logarithmic decrement ΔE at 120 ° C. shown in Table 3 (using a rigid pendulum type physical property tester measured value). Further, in Examples 1 and 2, the heat-fusible resin layer has a melting peak measured by the method described below by adjusting the amount of the low-molecular-weight component in the polypropylene. _The value ₍ T2 _/ T1) obtained by dividing the temperature difference T2 between the temperature start _point (extrapolation melting start temperature) and the end point (extrapolation melting end temperature) by the temperature difference T1 is adjusted. ing.

Lubricant layers were formed by allowing erucamide as a lubricant to exist on both surfaces of the exterior material for an electric storage device. The same applies to the following examples and comparative examples.

[Example 2]
The composition of the aluminum alloy foil is Mn0.17% by mass, Mg0.20% by mass, Fe0.09% by mass, Cu0.00% by mass, Si0.00% by mass, Cr0.00% by mass, Zn0.00% by mass, Al balance An exterior material for an electricity storage device was obtained in the same manner as in Example 1, except for the above.

[Comparative Example 1]
The composition of the aluminum alloy foil is Mn0.00 mass%, Mg0.00 mass%, Fe1.20 mass%, Cu0.05 mass%, Si0.00 mass%, Cr0.00 mass%, Zn0.00 mass%, Al balance An exterior material for an electricity storage device was obtained in the same manner as in Example 1, except for the above.

[Comparative Example 2]
The composition of the aluminum alloy foil is Mn0.16% by mass, Mg0.10% by mass, Fe0.09% by mass, Cu0.00% by mass, Si0.00% by mass, Cr0.00% by mass, Zn0.00% by mass, Al balance An exterior material for an electricity storage device was obtained in the same manner as in Example 1, except for the above.

<Evaluation of corrosion resistance>
The exterior materials for electric storage devices used in Examples 1 and 2 and Comparative Examples 1 and 2 were cut into rectangles with a length of 50 mm and a width of 20 mm. Next, a polyethylene film with a width of 10 mm is heat-sealed to each side of the exterior material, excluding one short side, of the four edges of the exterior material, so that the inner surface of the rectangle overlaps with 5 mm. It was folded back at a position of 10 mm from the bottom in the direction, folded back in half in the direction in which the polyethylene films on the two long side end faces overlapped at the center in the width direction, and further pressed with 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 polygonal line in the width direction and the polygonal line in the length direction of the exterior material. The aluminum alloy foil was exposed for connection. Next, as shown in the schematic diagram of FIG. 9, the test sample exterior material is set as the working electrode, metallic lithium Li (diameter 15 mm × thickness 0.35 mm) is set as the counter electrode, and electrolyte solution X (1 mol / l LiPF ₆ and , ethylene carbonate, diethyl carbonate and dimethyl carbonate (mixture of 1:1:1 by volume). 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. Table 2 shows the results. Furthermore, the appearance of the exposed portion M of the obtained test sample was observed with a digital microscope (200x magnification). 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.

The aluminum alloy foils of Examples 1 and 2 had a Mg content of 2.20% by mass and 0.20% by mass, and as shown in Table 2, the total charge in the corrosion resistance evaluation was -6. The values are as small as 6×10 ³ C and −9.2×10 ³ C, and it can be seen that corrosion is effectively suppressed when electricity is applied while the electrolyte is adhered. In the microscope images (FIGS. 5 and 6) of the surfaces of the bending intersections of the exterior materials after the corrosion resistance evaluation in Examples 1 and 2, the corroded portions are very small. It can be seen that the exterior material is effectively inhibited from corroding when electricity is applied while the electrolyte is adhered. On the other hand, as shown in Table 2, the exterior materials of Comparative Examples 1 and 2 had large total charges of −2.1×10 ⁴ C and −1.8×10 ⁴ C in corrosion resistance evaluation. It can be seen that the effect of suppressing corrosion is inferior when electricity is applied while the electrolyte is adhered. Corrosion is observed in the microscope images (FIGS. 7 and 8) of the bending intersection surfaces of the exterior materials after the corrosion resistance evaluation of Comparative Examples 1 and 2. It can be seen that the material is inferior in the effect of suppressing corrosion.

<Measurement of Logarithmic Decay Rate ΔE of Adhesive Layer>
The exterior materials for an electricity storage device of Examples 1 and 2 obtained above were cut into a rectangle having a width (TD: Transverse Direction) of 15 mm and a length (MD: Machine Direction) of 150 mm, and a test sample (for an electricity storage device It was used as an exterior material 10). The MD of the power storage device exterior material corresponds to the rolling direction (RD) of the aluminum alloy foil, and the TD of the power storage device exterior material corresponds to the TD of the aluminum alloy foil. (RD) can be determined by the rolling grain. When the MD of the exterior material for an electric storage device cannot be specified by the rolling pattern of the aluminum alloy foil, it can be specified by the following method. As a method for confirming the MD of the exterior material for an electricity storage device, the cross section of the heat-fusible resin layer of the exterior material for the electricity storage device was observed with an electron microscope to confirm the sea-island structure. The direction parallel to the cross section in which the average diameter of the island shape in the direction was maximum can be determined as the MD. Specifically, the angle is changed by 10 degrees from the cross section in the length direction of the heat-fusible resin layer and the direction parallel to the cross section in the length direction, and each direction up to the direction perpendicular to the cross section in the length direction Each cross section (10 cross sections in total) is observed with an electron microscope to confirm the sea-island structure. Next, in each cross section, the shape of each individual island is observed. Regarding the shape of each island, the straight line distance connecting the leftmost end in the direction perpendicular to the thickness direction of the heat-fusible resin layer and the rightmost end in the perpendicular direction is defined as the diameter y. In each cross section, the average of the top 20 diameters y of the island shape is calculated in descending order of diameter y. The direction parallel to the cross section in which the average diameter y of the island shape is the largest is determined as the MD. FIG. 13 shows a schematic diagram for explaining the method of measuring the logarithmic decrement ΔE by rigid pendulum measurement. Using a rigid pendulum type physical property tester (model number: RPT-3000W manufactured by A&D Co., Ltd.), FRB-100 for the pendulum 30 frame, RBP-060 for the cylindrical cylinder edge 30a at the edge, cold A CHB-100, a vibration displacement detector 32 and a weight 33 were used for the block 31, and the initial amplitude was set to 0.3 degrees. Place the test sample on the cooling block 31 with the measurement surface (adhesive layer) facing upward, so that the axial direction of the cylindrical cylinder edge 30a with the pendulum 30 on the measurement surface is perpendicular to the MD direction of the test sample. installed. In addition, in order to prevent the test sample from floating or warping during measurement, the test sample was fixed on the cooling/heat block 31 by sticking a tape to a portion of the test sample that does not affect the measurement results. A cylindrical cylinder edge 30a was brought into contact with the surface of the adhesive layer. Next, the thermal block 31 was used to measure the logarithmic decrement ΔE of the adhesive layer in a temperature range of 30° C. to 200° C. at a heating rate of 3° C./min. The logarithmic decrement ΔE when the surface temperature of the adhesive layer of the test sample (electrical storage device exterior material 10) reached 120° C. was adopted. (The test sample that was measured once was not used, and the average value of three measurements (N = 3) was used using a newly cut sample.) Regarding the adhesive layer, the values obtained in Example 1 and the implementation obtained above were used. The exterior material for an electricity storage device of Example 2 was immersed in 15% hydrochloric acid to dissolve the base material layer and the aluminum alloy foil, and the test sample consisting of only the adhesive layer and the heat-fusible resin layer was sufficiently dried to obtain a logarithmic Attenuation rate ΔE was measured. Table 3 shows the logarithmic decrement ΔE at 120°C. (The logarithmic decrement ΔE is calculated by the following formula.)
ΔE=[ln(A1/A2)+ln(A2/A3)+. . . +ln(An/An+1)]/n
A: amplitude n: wave number

<Measurement of Remaining Ratio of Adhesive Layer Thickness>
The power storage device exterior materials of Examples 1 and 2 obtained above were cut into a length of 150 mm and a width of 60 mm to prepare a test sample (power storage device exterior material 10). Next, the heat-fusible resin layers of test samples of the same size made from the same exterior material for an electricity storage device were opposed to each other. Next, in that state, using a metal plate with a width of 7 mm, the test sample is heated from both sides in the stacking direction under the conditions of a temperature of 190 ° C., a surface pressure (0.5 MPa) shown in Table 3, and a time of 3 seconds. Pressurization was applied to heat-seal the heat-fusible 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 for the exposed cross section. A test sample before heat-sealing was similarly cut in the stacking direction using a microtome, and the thickness of the adhesive layer was measured for the exposed cross section. The ratio of the thickness of the adhesive layer after heat-sealing to the thickness of the adhesive layer before heat-sealing was calculated, and the residual ratio (%) of the thickness of the adhesive layer was measured. Table 3 shows the results.

<Measurement of seal strength in 25°C environment or 140°C environment>
The power storage device exterior materials of Examples 1 and 2 obtained above were cut into rectangles of 60 mm width×150 mm length to obtain test samples (power storage device exterior materials 10). Next, as shown in FIG. 10, the test sample was folded back at the center P in the length direction so that the heat-fusible resin layers faced each other. Next, using a metal plate 20 with a width of 7 mm, under the conditions of a surface pressure of 1.0 MPa, a time of 1 second, and 190 ° C., the test sample is 7 mm in the length direction (the width of the metal plate) and in the full width direction (i.e., 60 mm). , the heat-fusible resin layers were heat-sealed to each other. Next, using a double-edged sample cutter, a test sample was cut to a width of 15 mm as shown in FIG. In FIG. 11, S indicates the heat-sealed region. Next, as shown in FIG. 12, a tensile tester was used to create a T-shaped peel, in an environment at a temperature of 25 ° C. or at a temperature of 140 ° C., a tensile speed of 300 mm / min, a peel angle of 180 °, The heat-sealed interface is peeled off under the condition that the distance between chucks is 50 mm, and the maximum value of the peel strength (N/15 mm) for 1.5 seconds from the start of tensile strength measurement is calculated as the seal strength in the environment of 25 ° C. , the seal strength in a 140° C. environment. The tensile test at each temperature was performed in a constant temperature bath, and the test sample was attached to a chuck in the constant temperature bath at a predetermined temperature, held for 2 minutes, and then measured. Each seal strength is an average value (n=3) measured by similarly producing three test samples. Table 3 shows the results.

From the results shown in Table 3, the electrical storage device exterior materials of Examples 1 and 2 had 120 points in the rigid pendulum measurement of the adhesive layer located between the aluminum alloy foil and the heat-fusible resin layer. The logarithmic decrement ΔE at °C is 0.50 or less, effectively suppresses crushing of the adhesive layer when heat-sealing the heat-sealable resin layers, and exhibits high seal strength in a high-temperature environment. I know you do. Furthermore, the exterior material for an electricity storage device of Example 1 has a logarithmic attenuation rate ΔE of 0.20 or less, and the adhesive layer is more effectively crushed when the heat-fusible resin layers are heat-sealed to each other. It can be seen that it is suppressed and exhibits higher seal strength in high temperature environments.

<Measurement of extrapolated melting start temperature and extrapolated melting end temperature of melting peak temperature>
By the following method, the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the polypropylene used in the heat-fusible resin layer of the exterior material for the power storage device of Examples 1 and 2 were measured. Then, the temperature differences T ₁ and T ₂ between the extrapolated melting start temperature and the extrapolated melting end temperature are measured, and from the obtained temperature differences T ₁ and T ₂ , the ratio (T ₂ /T ₁ ) and the absolute value of the difference |T ₂ −T ₁ |. Table 4 shows the results.

(Measurement of temperature difference _T1 )
In accordance with the provisions of JIS K7121: 2012, using differential scanning calorimetry (DSC), the polypropylene used in the heat-fusible resin layer of the exterior material for the electricity storage device of Examples 1 and 2 above, A DSC curve was obtained. 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 _- fusible resin layer was measured.

₍ Measurement of temperature difference T2)
In an environment at a temperature of 85° C., the polypropylene used for the heat-fusible resin layer was mixed with a lithium hexafluorophosphate concentration of 1 mol/l and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1. After standing for 72 hours in the electrolytic solution, which is the solution of No. 1, it was sufficiently dried. Next, a DSC curve was obtained for the dried polypropylene using differential scanning calorimetry (DSC) in accordance with JIS K7121:2012. Next, 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 heat _- fusible resin layer after drying was measured.

In measuring the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature, Q200 manufactured by TA Instruments Co., Ltd. was used as a differential scanning calorimeter. Further, as a DSC curve, after holding the test sample at -50 ° C. for 10 minutes, the temperature was raised to 200 ° C. at a temperature increase rate of 10 ° C./min (first time), and after holding at 200 ° C. for 10 minutes, the temperature decrease rate The temperature was lowered to -50°C in -10°C minutes, held at -50°C for 10 minutes, then heated to 200°C at a rate of temperature increase of 10°C/minute (second time), held at 200°C for 10 minutes, and 2 A DSC curve when the temperature was raised to 200° C. for the first time was used. When measuring the temperature difference T ₁ and the temperature difference T ₂ , among the melting peaks appearing in the range of 120 to 160° C. in each DSC curve, analyze the melting peak with the largest difference in thermal energy input. went. Even when two or more peaks overlapped, only the melting peak with the maximum difference in thermal energy input was analyzed.

In addition, the extrapolated melting start temperature means the start point of the melting peak temperature, and the difference between the straight line obtained by extending the baseline on the low temperature side (65 to 75 ° C.) to the high temperature side and the melting point where the difference between the thermal energy input is the maximum The temperature at the point of intersection with the tangent line drawn at the point where the slope of the curve on the low temperature side of the peak reaches its maximum. The extrapolated melting end temperature means the end point of the melting peak temperature. The temperature at the point of intersection with the tangent line drawn at the point where the slope of the curve becomes maximum.

<Measurement of seal strength before contact with electrolyte>
Tensile strength (seal strength) was measured in the same manner as in <Measurement of seal strength after contact with electrolyte solution> described below, except that the electrolyte solution was not injected into the test sample. The maximum tensile strength until the heat-sealed portion is completely peeled off is defined as the seal strength before contact with the electrolyte. In addition, in Table 5, the seal strength before contact with the electrolyte is described as the seal strength at 85° C. for 0 hours of contact with the electrolyte.

<Measurement of seal strength after contact with electrolyte>
As shown in the schematic diagram of FIG. 14, the exterior materials for power storage devices of Examples 1 and 2 obtained above were cut into rectangles with a width (x direction) of 100 mm and a length (z direction) of 200 mm. A test sample (electrical storage device exterior material 10) was used (Fig. 14a). The test sample (power storage device exterior material 10) was folded at the center in the z direction so that the heat-fusible resin layer side 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 having one opening E (Fig. 14c). Next, an electrolytic solution (lithium hexafluorophosphate concentration is 1 mol/l, volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate is 1:1:1) from the opening E of the bag-shaped test sample. 1) was injected (Fig. 14d), and the end of the opening E was heat-sealed (temperature: 190°C, surface pressure: 2.0 MPa, time: 3 seconds) (Fig. 14e). Next, the folded portion of the bag-shaped test sample was turned down and left at rest in an environment at a temperature of 85° C. for a predetermined storage time (0 hour, 24 hours, and 72 hours, which is the time of contact with the electrolytic solution). The end of the test sample was then cut (Fig. 14e) to drain the electrolyte. Next, with the electrolytic solution adhering to the surface of the heat-fusible resin layer, the upper and lower surfaces of the test sample were sandwiched between metal plates 20 (7 mm width), and the temperature was 190 ° C., the surface pressure was 1.0 MPa, and the time was 3 seconds. The heat-sealable resin layers were heat-sealed to each other under the conditions (Fig. 14f). The test samples were then cut with a double-edged sample cutter to a width of 15 mm (Fig. 14f,g) so that the seal strength at 15 mm in width (x-direction) could be measured. Next, a tensile tester (AGS-xplus (trade name) manufactured by Shimadzu Corporation) is used to form a T-shaped peel, in an environment at a temperature of 25 ° C., a tensile speed of 300 mm / min, a peel angle of 180 °, a chuck. The thermally fused interface was peeled off under the condition that the distance was 50 mm, and the tensile strength (seal strength) was measured (Fig. 12). The maximum tensile strength until the heat-sealed portion was completely peeled off (the distance until peeling was 7 mm, which is the width of the metal plate) was defined as the seal strength after contact with the electrolyte.

Table 5 shows the retention rate (%) of the seal strength after contact with the electrolyte, with the seal strength before contact with the electrolyte as the standard (100%).

From the results shown in Table 4, in the power storage device exterior materials of Examples 1 and 2, the value obtained by dividing the temperature difference T ₂ by the temperature difference T ₁ was 0.55 or more. Even if the electrolyte contacts the heat-fusible resin layer and the heat-fusible resin layers are heat-fused with the electrolyte adhered to the heat-fusible resin layer, the heat-fusible It can be seen that the seal strength is exhibited. Furthermore, in the exterior material for an electricity storage device of Example ₁ , the value obtained by dividing the temperature difference T2 by the temperature difference T1 is 0.60 or _more , and the heat-fusible resin layer has an electrolyte solution in a high-temperature environment. Even when the heat-sealable resin layers are heat-sealed with each other in contact with each other and the electrolyte adheres to the heat-sealable resin layer, it can be seen that a higher seal strength is exhibited by heat-sealing. .

As described above, the present disclosure provides inventions in the following aspects.
Section 1. An aluminum alloy foil for use as an exterior material for an electricity storage device, having a Mg content of 0.20% by mass or more and 5.50% by mass or less.
Section 2. Si content is 0.40% by mass or less, Fe content is 0.70% by mass or less, Cu content is 0.20% by mass or less, Mn content is 1.00% by mass or less, and Cr content is 0.00% by mass or less. 50% by mass or less, the Zn content is 0.25% by mass or less, the other inevitable impurities are individually 0.05% by mass or less and the total is 0.15% by mass or less, and the balance is Al. Item 1. The aluminum alloy foil according to item 1.
Item 3. Item 3. The aluminum alloy foil according to Item 1 or 2, having a thickness of 200 μm or less.
Section 4. Consists of a laminate comprising at least a substrate layer, a barrier layer, and a heat-fusible resin layer in this order,
An exterior 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. Item 5. According to Item 4, the temperature difference T ₁ and the temperature difference T ₂ are measured by the following method, and the value obtained by dividing the temperature difference T ₂ by the temperature difference T ₁ is 0.55 or more. Exterior material for power storage devices.
(Measurement of temperature difference _T1 )
_A 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)
In an environment at a temperature of 85° C., the heat-sealable resin layer was formed with a solution having a lithium hexafluorophosphate concentration of 1 mol/l and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1. After standing for 72 hours in the electrolytic solution, it is dried. A temperature difference T2 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat _- fusible 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 power storage device exterior material according to Item 4 or 5, wherein the adhesive layer has a logarithmic decrement ΔE of 0.50 or less at 120° C. in rigid pendulum measurement.
Item 7. An electricity storage device, wherein an electricity storage device element comprising at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed of the electricity storage device exterior material according to any one of Items 4 to 6.
Item 8. At least a step of laminating the substrate layer, the barrier layer, and the heat-fusible resin layer in this order to obtain a laminate,
A method for producing an exterior material for an electricity storage device, using the aluminum alloy foil according to any one of Items 1 to 3 as the barrier layer.

Reference Signs List 1 base material layer 2 adhesive layer 3 barrier layer 4 heat-fusible resin layer 5 adhesive layer 6 surface coating layer 10 exterior material for electric storage device

Claims (21)

Consists of a laminate comprising at least a substrate layer, a barrier layer, and a heat-fusible resin layer in this order,
The barrier layer is an aluminum alloy foil having a Mg content of 0.20% by mass or more and 5.50% by mass or less,
_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 )
_A 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)
In an environment at a temperature of 85° C., the heat-sealable resin layer was formed with a solution having a lithium hexafluorophosphate concentration of 1 mol/l and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1. After standing for 72 hours in the electrolytic solution, it is dried. A temperature difference T2 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat _- fusible resin layer after drying is measured by differential scanning calorimetry. The exterior material for an electricity storage device according to claim 1, wherein the aluminum alloy foil has an average crystal grain size of 20.0 µm or less and/or an average diameter y of the second phase particles of 10.0 µm 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, and a Mn content of 1.00% by mass or less. Cr content is 0.50% by mass or less, Zn content is 0.25% by mass or less, and other inevitable impurities are 0.05% by mass or less individually and 0.15% by mass or less in total, The exterior material for an electricity storage device according to claim 1 or 2, wherein the balance is Al. 4. The exterior material for an electricity storage device according to claim 1 , wherein said aluminum alloy foil has a thickness of 200 μm or less. An adhesive layer is provided between the aluminum alloy foil and the heat-sealable resin layer,
The power storage device exterior material according to any one of claims 1 to 4, wherein the adhesive layer has a logarithmic decrement ΔE of 0.50 or less at 120°C in rigid pendulum measurement. 6. Any one of claims 1 to 5, wherein the thickness of the laminate is 180 μm or less and the thickness of the laminate is 155 μm or less, or the thickness of the laminate is more than 155 μm and 180 μm or less. 2. The exterior material for an electricity storage device according to Item 1. The power storage device exterior material according to any one of claims 1 to 6, wherein two or more types of lubricants are present on at least one of the surface and the interior of the base material layer. At least one of the surface and the inside of the base material layer is selected from the group consisting of 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. The exterior material for an electricity storage device according to any one of claims 1 to 7, wherein at least two kinds of the material are present. The power storage device exterior material according to any one of claims 1 to 8, wherein a lubricant is present on the surface of the base material layer, and the amount of the lubricant present is 3 mg/m ² or more. Claims 1 to 9, wherein the thickness of the base layer is 50 µm or less and the thickness of the base layer is 35 µm or less, or the thickness of the base layer is more than 35 µm and 50 µm or less. The exterior material for an electricity storage device according to any one of the above. 11. Any one of claims 1 to 10, wherein the thickness of the barrier layer is 85 μm or less and the thickness of the barrier layer is 50 μm or less, or the thickness of the barrier layer is more than 50 μm and 85 μm or less. 2. The exterior material for an electricity storage device according to Item 1. The power storage device according to any one of claims 1 to 11, wherein the heat-fusible resin layer contains at least one selected from the group consisting of polyolefin, cyclic polyolefin, acid-modified polyolefin, and acid-modified cyclic polyolefin. exterior material. The exterior material for an electricity storage device according to any one of claims 1 to 12, wherein the heat-fusible resin layer is formed of a blend polymer in which two or more resins are combined. The exterior material for an electricity storage device according to any one of claims 1 to 13, wherein the heat-fusible resin layer is formed of two or more layers of the same or different resins. The power storage device exterior material according to any one of claims 1 to 14, wherein two or more types of lubricants are present on at least one of the surface and the inside of the heat-fusible resin layer. At least one of the surface and the inside of the heat-sealable resin layer is composed of saturated fatty acid amide, unsaturated fatty acid amide, substituted amide, methylolamide, saturated fatty acid bisamide, unsaturated fatty acid bisamide, fatty acid ester amide, and aromatic bisamide. The exterior material for an electricity storage device according to any one of claims 1 to 15, wherein at least one selected from the group is present. An adhesive layer is provided between the barrier layer and the heat-fusible resin layer,
The power storage device exterior material according to any one of claims 1 to 16, wherein the adhesive layer is made of a resin containing a polyolefin skeleton. An adhesive layer is provided between the barrier layer and the heat-fusible resin layer,
The power storage device exterior material according to any one of claims 1 to 17, wherein the adhesive layer contains at least one selected from the group consisting of polyolefin, cyclic polyolefin, acid-modified polyolefin, and acid-modified cyclic polyolefin. An electricity storage device, wherein an electricity storage device element comprising at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed of the electricity storage device exterior material according to any one of claims 1 to 18. At least a step of laminating the substrate layer, the barrier layer, and the heat-fusible resin layer in this order to obtain a laminate,
The barrier layer is an aluminum alloy foil having a Mg content of 0.20% by mass or more and 5.50% by mass or less,
_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 . manufacturing method.
(Measurement of temperature difference _T1 )
_A 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)
In an environment at a temperature of 85° C., the heat-sealable resin layer was formed with a solution having a lithium hexafluorophosphate concentration of 1 mol/l and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1. After standing for 72 hours in the electrolytic solution, it is dried. A temperature difference T2 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat _- fusible resin layer after drying is measured by differential scanning calorimetry. An adhesive layer is provided between the barrier layer and the heat-fusible resin layer,
The adhesive layer and the heat-fusible resin layer are formed by a coextrusion lamination method, a tandem lamination method, a thermal lamination method, a sandwich lamination method, or an adhesive for forming the adhesive layer on the barrier layer. 21. The method of manufacturing the exterior material for a power storage device according to claim 20, wherein the heat-fusible resin layer is formed by solution coating and then laminated on the adhesive layer in advance in the form of a sheet.

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