Power storage device exterior material, power storage device exterior case, and power storage device

Abstract

A power storage device exterior material comprising a base material layer, a barrier layer, and a sealant layer laminated in the stated order, wherein the barrier layer is a metal layer formed of an aluminum alloy containing iron, and the conductivity of the metal layer is 54-60% IACS.

Description

Exterior materials for energy storage devices, exterior cases for energy storage devices, and energy storage devices 【0001】 This disclosure relates to exterior materials for energy storage devices, exterior cases for energy storage devices, and energy storage devices. 【0002】 In recent years, with the miniaturization and weight reduction of mobile electronic devices such as smartphones and tablet terminals, laminates consisting of a heat-resistant resin layer / adhesive layer / metal foil layer / adhesive layer / thermoplastic resin layer (internal sealant layer) are being used as the casing material for energy storage devices such as lithium-ion secondary batteries, lithium polymer secondary batteries, lithium-ion capacitors, and electric double-layer capacitors, instead of conventional metal cans. Furthermore, power supplies for electric vehicles, large power supplies for energy storage, and capacitors are increasingly being cased with laminates (casing materials) of the above configuration. The laminate is then formed into a three-dimensional shape, such as a roughly rectangular parallelepiped, by stretch molding or deep drawing. By forming it into such a three-dimensional shape, it is possible to secure a housing space for the main body of the energy storage device. At this time, higher moldability is required for devices that require high output, high capacity, etc., and devices that require flexible structural design. 【0003】 For example, Patent Document 1 proposes an exterior material for lithium-ion batteries having excellent moldability, in which at least a metal foil layer, a corrosion-preventive treatment layer, an adhesive resin layer, and a sealant layer are sequentially laminated on one side of a base layer. Furthermore, Patent Document 2 proposes a battery packaging material that is composed of a laminate comprising at least a surface coating layer, a base layer, an aluminum alloy foil, and a heat-sealable resin layer in this order, and is less prone to pinholes or cracks during molding and exhibits excellent moldability. 【0004】 Patent Document 1: Japanese Patent No. 6245335 Patent Document 2: Japanese Unexamined Patent Publication No. 2024-038176 【0005】 Patent documents 1 and 2 propose exterior materials and battery packaging materials for lithium-ion batteries that have excellent moldability, taking into consideration the base layer, aluminum alloy foil, etc. In addition to the methods described in these patent documents, it is desirable to improve the moldability of exterior materials for energy storage devices. 【0006】 This disclosure aims to provide an exterior material for energy storage devices having high moldability, as well as an exterior case for energy storage devices and an energy storage device using the aforementioned exterior material. 【0007】 The specific means for achieving the above objectives are as follows: <1> An exterior material for an energy storage device in which a base layer, a barrier layer, and a sealant layer are laminated in this order, the barrier layer is a metal layer made of an aluminum alloy containing iron, and the conductivity of the metal layer is 54% IACS to 60% IACS. <2> The exterior material for an energy storage device according to <1>, wherein the metal layer has an aluminum content of 98% by mass or more and an iron content of 0.7% by mass to 1.7% by mass. <3> The exterior material for an energy storage device according to <1> or <2>, wherein the metal layer has a content of silicon, copper, magnesium, and manganese, each independently less than 0.1% by mass. <4> The exterior material for an energy storage device according to any one of <1> to <3>, wherein the average crystal grain size of the alloy particles on the surface of the metal layer is 1 μm to 10 μm. <5> The exterior material for an energy storage device according to any one of <1> to <3>, wherein the average crystal grain size of the alloy particles on the surface of the metal layer is 1 μm to 6.5 μm. <6> The outer material for an energy storage device according to any one of <1> to <5>, wherein the thickness of the barrier layer is 25 μm to 120 μm. <7> The tensile strength of the barrier layer is 70 N / mm ２ ~150 N / mm ２ An exterior material for an energy storage device as described in any one of <1> to <6>. <8> An exterior case for an energy storage device, which is a molded body of the exterior material for an energy storage device as described in any one of <1> to <7>. <9> An energy storage device comprising: an energy storage device body; and an exterior member that houses the energy storage device body and includes the exterior material for an energy storage device as described in any one of <1> to <7>. 【0008】 According to this disclosure, it is possible to provide an exterior material for energy storage devices having high moldability, as well as an exterior case for energy storage devices and an energy storage device using the aforementioned exterior material for energy storage devices. 【0009】This is a schematic cross-sectional view showing an example of an exterior material for an energy storage device according to the present disclosure. This is a schematic cross-sectional view showing an example of an energy storage device. This is a schematic perspective view showing the components constituting the energy storage device of Figure 2 in a separated state. 【0010】 The present disclosure is described in detail below. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including elemental steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure. 【0011】 In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that are not clearly distinguishable from other processes, provided that the purpose of the process is achieved. In this disclosure, numerical ranges indicated using "~" include the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit of one numerical range may be replaced by the upper or lower limit of another numerical range described in stages. Also, in numerical ranges described in this disclosure, the upper or lower limit of that numerical range may be replaced by the values ​​shown in the examples. In this disclosure, each component may contain multiple types of the corresponding substance. When multiple types of the substance corresponding to each component are present in a composition, the content or amount of each component means the total content or amount of the multiple types of substances present in the composition, unless otherwise specified. In this disclosure, particles corresponding to each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value for a mixture of such multiple types of particles present in the composition, unless otherwise specified. In this disclosure, the thickness of the exterior material for the energy storage device or each layer can be measured by a scanning electron microscope (SEM). The thickness in this disclosure is the average value obtained when measured at five locations. 【0012】<Exterior material for energy storage devices> The exterior material for energy storage devices of this disclosure is an exterior material in which a base layer, a barrier layer, and a sealant layer are laminated in this order, the barrier layer is a metal layer made of an aluminum alloy containing iron, and the conductivity of the metal layer is 54% IACS to 60% IACS. 【0013】 The exterior material for energy storage devices disclosed herein has high moldability, and cracks, pinholes, etc., in the metal layer portion are less likely to occur during molding. The layer structure of the exterior material for energy storage devices will be described below. 【0014】 (Base Layer) The exterior material for the energy storage device comprises a base layer. The base layer is preferably formed of a heat-resistant resin layer. The heat-resistant resin is preferably a resin that does not melt at the heat-sealing temperature when the exterior material is heat-sealed. The heat-resistant resin is preferably a resin with a high melting point, for example, it is preferably higher than the melting point of each layer contained in the sealant layer, preferably 10°C or more higher than the melting point of the layer with the highest melting point among the layers contained in the sealant layer, and more preferably 20°C or more higher. 【0015】 Examples of base material layers include polyamide films such as nylon films and polyester films, and these films may be stretched films. Examples of stretched films include biaxially oriented polyamide films such as biaxially oriented nylon films, biaxially oriented polybutylene terephthalate (PBT) films, biaxially oriented polyethylene terephthalate (PET) films, and biaxially oriented polyethylene naphthalate (PEN) films. Examples of nylon films include nylon 6 films, nylon 6,6 films, and MXD nylon films. 【0016】 The base layer may be a single layer or a multilayer consisting of two or more layers. Examples of multilayers include polyester film / polyamide film (e.g., PET film / nylon film). 【0017】The thickness of the base layer may be 2 μm to 50 μm, 9 μm to 50 μm, or 10 μm to 30 μm. For example, if the base layer is a polyester film, its thickness may be 2 μm to 50 μm, and if the base layer is a nylon film, its thickness may be 7 μm to 50 μm. 【0018】 The tensile strength of the base layer (TD direction or MD direction), preferably the tensile strength of the nylon film, may be 150 MPa to 400 MPa or 200 MPa to 350 MPa. The MD / TD ratio of the tensile strength of the base layer may be 0.8 to 1.2 or 0.9 to 1.1. In this disclosure, the MD direction is the flow direction of the film roll, and the TD direction is the width direction of the film roll. 【0019】 <Method for Measuring Tensile Strength> The tensile strength of each base layer film used in the manufacture of exterior materials for energy storage devices, before lamination, shall be measured in accordance with JIS K7127:1999. Specifically, the tensile strength of a sample piece (a sample piece of the base layer film) shall be measured using a tensile testing machine under the following conditions: sample length 100 mm, sample width 15 mm, distance between scoring points 50 mm, and tensile speed 200 mm / min, so that the measurement direction in the TD and MD directions corresponds to the sample length. For example, a "Strograph (AGS-5kNX)" manufactured by Shimadzu Corporation may be used as the tensile testing machine. 【0020】 (Outer adhesive layer) An adhesive layer (also called an outer adhesive layer) may be provided between the substrate layer and the barrier layer described later, and the substrate layer and the barrier layer may be integrated via the outer adhesive layer. 【0021】 The adhesive constituting the outer adhesive layer is not particularly limited and includes, for example, thermosetting adhesives, photocuring adhesives, two-component curing adhesives, and non-crosslinking adhesives. The two-component curing adhesive is not particularly limited and includes, for example, olefin-based adhesives, epoxy-based adhesives, acrylic-based adhesives, and urethane-based adhesives. 【0022】In particular, the outer adhesive layer is preferably a layer formed by a two-component curing urethane adhesive. Examples of two-component curing urethane adhesives include adhesives composed of a first liquid consisting of one or more polyols selected from the group consisting of polyurethane polyols, polyester polyols, polyether polyols, and polyester urethane polyols, and a second liquid (curing agent) consisting of isocyanate. 【0023】 The thickness of the outer adhesive layer may be 1 μm to 5 μm, or 2 μm to 5 μm. In particular, from the viewpoint of thinning and lightening the packaging material, a thickness of 1 μm to 3 μm is preferred for the outer adhesive layer. 【0024】 The outer adhesive layer may be a single layer or a multilayer of two or more layers. If it is a multilayer, for example, it may be a combination of an adhesive layer containing a colorant and an adhesive layer without a colorant. 【0025】 (Barrier Layer) The exterior material for energy storage devices is equipped with a barrier layer. The barrier layer is a metal layer made of an aluminum alloy containing iron, and the conductivity of the metal layer is 54% IACS to 60% IACS. The barrier layer plays a role in providing the exterior material with gas barrier properties that suppress the intrusion of oxygen, moisture, etc. 【0026】 The metal layer is not particularly limited and can include aluminum foil, aluminum vapor-deposited film, etc. The metal layer may be a single layer or a multilayer of two or more layers. 【0027】The conductivity of the metal layer is 54% IACS to 60% IACS, but may also be 55% IACS to 59% IACS, or 56% IACS to 58% IACS. The conductivity of the metal layer can be determined by measuring the electrical resistance using a resistance meter and the DC four-terminal method, in accordance with JIS C2525:1999. Specifically, first, the metal layer is cut to a width of 3 mm and a length of 80 mm, Ni wire is spot-welded to both ends, and the electrical resistance is measured using the four-terminal method. The resistance R of the test piece is determined from the current I flowing through the sample and the potential difference V between the voltage terminals, using the formula R = V / I. The current I is determined from the voltage drop across a standard resistor (0.1 Ω) connected in series with the test piece. The voltage drops across the test piece and the standard resistor, and the electromotive force of the R thermocouple are determined using a digital multimeter with a detection sensitivity of ±0.1 μV. The conductivity is determined by the following formula. Volume resistance ρ = R (A / L) Electrical conductivity γ (%IACS) = {1.7241 [μΩ・cm] / Volume resistance ρ [μΩ・cm]}×100 A: Sample cross-sectional area [cm ２ ] L: Length of measuring part [cm ２ 1.7241 [μΩ・cm]: Volume resistivity of standard soft copper 【0028】 The metal layer is a layer made of an aluminum alloy containing iron, and contains at least iron and aluminum. The metal layer may also contain components other than iron and aluminum, for example, it may or may not contain silicon, copper, manganese, magnesium, zinc, chromium, titanium, or other components, each independently. 【0029】 In the metal layer, aluminum may be the main component, and the aluminum content may be 95% by mass or more, 96% by mass or more, 97% by mass or more, 98% by mass or more, or 98.2% by mass or more. In the metal layer, the aluminum content may be 99.5% by mass or less, or 99% by mass or less. 【0030】 In the metal layer, the iron content may be 0.3% to 3% by mass, 0.5% to 2% by mass, 0.7% to 1.7% by mass, or 0.8% to 1.5% by mass. 【0031】 In the metal layer, the contents of silicon, copper, magnesium, and manganese may each independently be 1% by mass or less, may be 0.2% by mass or less, may be less than 0.1% by mass, or may be 0.05% by mass or less. The metal layer may or may not contain silicon, copper, magnesium, and manganese, respectively. When the metal layer contains silicon, copper, magnesium, or manganese, the contents of silicon, copper, magnesium, and manganese may each independently be 0.001% by mass or more. 【0032】 As an example, in the metal layer, the content of silicon may be 0.2% by mass or less, may be less than 0.1% by mass, or may be 0.08% by mass or less. Also, the content of silicon may be 0.01% by mass or more, or may be 0.03% by mass or more. 【0033】 As an example, in the metal layer, the contents of copper, magnesium, and manganese may each independently be 0.2% by mass or less, may be less than 0.1% by mass, may be 0.05% by mass or less, or may be 0.03% by mass or less. 【0034】 The metal layer may or may not contain components other than iron, aluminum, silicon, copper, magnesium, and manganese. For example, in the metal layer, the contents of zinc, chromium, or titanium may each independently be 1% by mass or less, may be 0.2% by mass or less, may be less than 0.1% by mass, may be 0.05% by mass or less, or may be 0.03% by mass or less. 【0035】The average crystal grain size of the alloy particles on the surface of the metal layer may be 1 μm to 10 μm, may be 1 μm to 6.5 μm, may be 2 μm to 5 μm, or may be 3 μm to 5 μm from the viewpoint of formability. A sample with a total width of 500 mm wide is taken from the metal layer, and further cut into cut samples of a size that is easy to polish from both ends (W, D) and the central part (C) in the width direction. The cut samples are embedded in resin and buffed using a rotary polishing machine. The polished aluminum foil sample is macro-etched by a known anodic oxidation method. The sample anodized in this way is observed with a polarized light microscope, and the crystal grain size is measured. At 200-fold magnification, a measurement area of 100 μmφ is set, and the number of crystal grains contained therein is counted. Note that if there is exactly one crystal grain in the measurement area, it is counted as 1, and if it is hanging on the edge of the measurement area, it is counted as 1 / 2. Assuming that n crystal grains are in an area of 100 μmφ, the average crystal grain size r is obtained by the following formula. [Formula 1] π(50) ２ / n = πr ２ [Formula 2] r = [(50) ２ / n] １／２ 【0036】 The thickness of the barrier layer may be 25 μm to 120 μm, may be 30 μm to 100 μm, or may be 30 μm to 80 μm from the viewpoint of suppressing pinhole generation during rolling and formability. 【0037】 The tensile strength of the barrier layer is 70 N / mm ２ to 150 N / mm ２ from the viewpoint of suppressing pinhole generation during rolling and formability, may be 80 N / mm ２ to 140 N / mm ２ or may be 80 N / mm ２ to 120 N / mm ２This may also be the case. The tensile strength of the barrier layer can be measured, for example, as follows: First, the material is cut into strips 200 mm long and 15 mm wide so that the tensile direction is parallel to the rolling direction (MD direction). Next, the tensile strength (0.2% yield strength) is measured by performing a tensile test using a tensile testing machine (for example, a Shimadzu Strograph (AGS-5kNX)) under tensile conditions of a moving speed of 10 mm / min and a chuck distance of 100 mm until fracture occurs. 【0038】 In the metal layer, a base layer may be provided on at least one of the surfaces facing the substrate layer and the sealant layer. The presence of a base layer makes it difficult for the metal layer to peel off adjacent layers (e.g., adhesive layers). The base layer is formed by applying a silane coupling agent, chemical conversion treatment (described later), or the like to the surface of the metal layer. 【0039】 The thickness of the base layer is not particularly limited and may be 0.01 μm to 1 μm from the viewpoint of the adhesive strength between the metal layer, such as the adhesive layer, and the adjacent layer. 【0040】 The metal layer may have a chemical treatment applied to at least one of its surfaces, the substrate layer side and the sealant layer side, and may, for example, have a corrosion-preventive layer. By providing a corrosion-preventive layer, corrosion of the metal layer surface by its contents (such as the electrolyte of a battery) can be suppressed. 【0041】 Chemical treatments include chromic acid treatment, chromate phosphate treatment, zinc phosphate treatment, non-chromate treatment using zirconium, titanium, etc. as chromium substitute metal components, and formation of an oxide film by boehmite treatment. 【0042】For example, a corrosion-preventive layer may be formed by chemical conversion treatment on a metal layer by the following processes: For example, chemical conversion treatment is performed by coating the surface of a degreased metal layer with any of the following aqueous solutions: 1) an aqueous solution of a mixture containing phosphoric acid, chromic acid, and at least one compound selected from the group consisting of metal salts of fluoride and nonmetallic salts of fluoride; 2) an aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, and at least one compound selected from the group consisting of chromic acid and chromium(III) salts; 3) an aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, at least one compound selected from the group consisting of chromic acid and chromium(III) salts, and at least one compound selected from the group consisting of metal salts of fluoride and nonmetallic salts of fluoride; and then drying the solution. 【0043】 The chemical conversion coating formed by the chemical conversion treatment has a chromium content of 0.1 mg / m² (per side). 2 ~50 mg / m² 2 Preferably, 2 mg / m² 2 ~20 mg / m² 2 This is preferable. 【0044】 Next, when the metal layer is aluminum foil, a method for manufacturing aluminum foil will be described. The method for manufacturing aluminum foil may include the steps of preparing aluminum ingot, various additive metal elements, or an aluminum master alloy containing them, heating them to produce molten aluminum alloy, casting the molten aluminum alloy to produce an ingot, rolling the ingot into foil, and performing final annealing (FA). 【0045】Aluminum ingots, various additive metal elements, or aluminum master alloys containing them are prepared and heated at 680°C to 1000°C to produce molten aluminum alloy. Next, the molten metal is cast to produce ingots. This casting method can be a known method, such as DC casting (Direct Chill Casting) for casting slabs, or CC casting (Continuous Casting) for directly casting coils of aluminum plates. The obtained ingots may be rolled (for example, cold rolling) to form aluminum foil of a predetermined thickness, and if necessary, final annealing (FA) may be performed to produce aluminum foil. 【0046】 The resulting ingot is cold-rolled into rolled foil of a predetermined thickness. Homogenization and hot rolling may be performed before cold rolling as needed, and intermediate annealing (IA) may be performed during the cold-rolling process as needed. 【0047】 In the manufacturing method of aluminum foil, the homogenization heat treatment process and hot rolling are optional, but if segregation of the cast structure is a concern, they may be performed within a range that does not affect the properties of the aluminum foil, specifically between 450°C and 600°C. For the sake of production efficiency, the heat treatment time for the homogenization heat treatment process should preferably be 20 hours or less. 【0048】 In the manufacturing method of aluminum foil, an intermediate annealing (IA) step may or may not be included, but it may be performed at a temperature of 500°C or lower, within a range that does not affect the properties of the aluminum foil, for the purpose of improving rollability. For production efficiency, a heat treatment time of 20 hours or less is desirable. 【0049】 In the method for manufacturing aluminum foil, a final annealing (FA) step is performed as needed to remove rolling oil adhering during rolling and to temper the foil. The final annealing step is performed, for example, in an air atmosphere or an inert gas atmosphere at 180°C to 350°C. 【0050】 (Inner adhesive layer) An adhesive layer (also called an inner adhesive layer) may be provided between the barrier layer and the sealant layer described later, and the barrier layer and the sealant layer may be integrated via the inner adhesive layer. 【0051】The adhesive constituting the inner adhesive layer is not particularly limited and includes polyurethane resins, acrylic resins, epoxy resins, polyolefin resins, elastomer resins, fluororesins, or adhesives containing one or more acid-modified polypropylene resins. In particular, adhesives made of polyolefin composite resins with acid-modified polyolefin (for example, acid-modified polypropylene resin) as the main component are more preferred. 【0052】 The thickness of the inner adhesive layer may be 1 μm to 5 μm, or 2 μm to 5 μm. If the inner adhesive layer is composed of an adhesive containing an acid-modified polyolefin resin such as an acid-modified polypropylene resin (e.g., ethylene-propylene random copolymer and ethylene-propylene block copolymer), the thickness of the inner adhesive layer may be 5 μm to 20 μm, or 12 μm to 20 μm. 【0053】 (Sealant layer) The exterior material for the energy storage device includes a sealant layer. The sealant layer is a layer that provides heat-sealability to the exterior material. The sealant layer may include at least one heat-sealable resin layer, and may include two or three heat-sealable resin layers. 【0054】 The sealant layer (for example, a heat-fusible resin layer) contains a heat-fusible resin and may optionally contain a lubricant, miscible particles, other components described later, etc. 【0055】 The heat-fusible resin is selected to have a melting point below the heat-fussing temperature so that it melts at the heat-fussing temperature. The heat-fusible resin is not particularly limited as long as it has the above melting point, but it is preferably at least one selected from the group consisting of ethylene resin, propylene resin, olefin resin, acid-modified products thereof, and ionomers. 【0056】 The sealant layer (for example, a heat-fusible resin layer) preferably contains propylene resin as its main component. In this disclosure, "contained as a main component" means that the proportion of the relevant component is the largest in each layer, for example, that the content of the relevant component is 50% by mass or more of the total layer. 【0057】The propylene resin may be a propylene homopolymer, a block copolymer of propylene and another copolymer component other than propylene, or a random copolymer of propylene and another copolymer component other than propylene. It may also be a propylene homopolymer, a random copolymer of propylene and at least one monomer selected from the group consisting of ethylene and α-olefins having 4 or more carbon atoms, or a block copolymer of propylene and at least one monomer selected from the group consisting of ethylene and α-olefins having 4 or more carbon atoms. Examples of other copolymer components other than propylene include ethylene, α-olefins having 4 or more carbon atoms, and butadiene. Examples of α-olefins having 4 or more carbon atoms include 1-butene, 1-hexene, 1-pentene, and 4-methyl-1-pentene. 【0058】 The sealant layer (for example, a heat-sealable resin layer) may be an unoriented film, or it may be a CPP (cast polypropylene) film, an IPP (inflated polypropylene) film, or the like. 【0059】 The sealant layer may be a three-layer co-extruded CPP film, for example, with an hPP (propylene homopolymer) layer or a bPP (propylene block copolymer) layer as an intermediate layer, and rPP (propylene random copolymer) layers arranged in front of and behind it (the laminate layer and the seal layer), from the viewpoint of heat sealability, delamination resistance, and insulation. 【0060】 The sealant layer (for example, a heat-fusible resin layer) may contain components other than resin (other components). Examples of other components include antioxidants, plasticizers, ultraviolet absorbers, antifungal agents, colorants (pigments, dyes, etc.), antistatic agents, rust inhibitors, hygroscopic agents, oxygen absorbers, etc. Examples of plasticizers are not particularly limited and include glycerin fatty acid ester monoglycerides, glycerin fatty acid ester acetylated monoglycerides, glycerin fatty acid ester organic acid monoglycerides, glycerin fatty acid ester medium-chain fatty acid triglycerides, polyglycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, special fatty acid esters, and higher alcohol fatty acid esters. 【0061】 The sealant layer (for example, a heat-fusible resin layer) may further contain a lubricant or an antiblocking agent. 【0062】 The lubricant is not particularly limited, and examples include fatty acid amides. Examples of fatty acid amides are not particularly limited, and include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, aromatic bisamides, etc. One lubricant may be used alone, or two or more may be used together. 【0063】 Examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearate amide, N-stearyl oleic acid amide, N-oleyl stearate amide, and N-stearyl erucic acid amide. Examples of methylolamides include methylol stearate amide. Examples of saturated fatty acid bisamides include methylene bis-stearate amide, ethylene bis-capric acid amide, ethylene bis-lauric acid amide, ethylene bis-stearate amide, ethylene bis-hydroxystearic acid amide, ethylene bis-behenic acid amide, hexamethylene bis-stearate amide, hexamethylene bis-behenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipic acid amide, and N,N'-distearyl sebacinic acid amide. Examples of unsaturated fatty acid bisamides include ethylene bisoleamide, ethylene biserucamide, hexamethylene bisoleamide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacinamide. Examples of fatty acid ester amides include stearamidoethyl stearate. Examples of aromatic bisamides include m-xylylene bisstearate, m-xylylene bishydroxystearate, and N,N'-cystearyl isophthalamide. 【0064】 Examples of antiblocking agents include silica, acrylic resin beads, aluminum silicate, calcium carbonate, barium carbonate, titanium dioxide, talc, and kaolin. One antiblocking agent may be used alone, or two or more may be used together. 【0065】 The average particle size of the antiblocking agent may be 0.1 μm to 10 μm, or 1 μm to 5 μm. When the average particle size of the antiblocking agent is 0.1 μm or larger, it tends to function well as an antiblocking agent, and when the average particle size of the antiblocking agent is 10 μm or smaller, it tends to suppress the generation of bubbles due to the evaporation of the electrolyte, etc. The average particle size of the antiblocking agent can be measured by observing and measuring the cross-section of the sealant layer with a scanning electron microscope. Specifically, the sealant layer is embedded in a transparent epoxy resin, polished with a polisher, slurry, etc., and the cross-section of the sealant layer is observed and the particle size is measured. The average particle size is the arithmetic mean of the particle sizes of 50 antiblocking agents. 【0066】 If the sealant layer contains an antiblocking agent, the antiblocking agent content may be 100 ppm to 5000 ppm, 500 ppm to 4000 ppm, or 1000 ppm to 3000 ppm. 【0067】 The thickness of the sealant layer may be 20 μm to 120 μm, 20 μm to 100 μm, or 30 μm to 50 μm. If the sealant layer consists of multiple layers, the thickness of the sealant layer refers to the total thickness of those multiple layers. 【0068】 An example of an exterior material for an energy storage device according to this disclosure is shown below with reference to Figure 1. Figure 1 is a schematic cross-sectional view showing an example of an exterior material for an energy storage device according to this disclosure. 【0069】The exterior material 10 for the energy storage device shown in Figure 1 includes a base layer 1, a barrier layer 2, and a sealant layer 3 in that order. An outer adhesive layer 4 is provided between the base layer 1 and the barrier layer 2, and an inner adhesive layer 5 is provided between the barrier layer 2 and the sealant layer 3. 【0070】 <Method for Manufacturing the Exterior Material for Energy Storage Devices> The method for manufacturing the exterior material for energy storage devices is not particularly limited as long as the above-described exterior material for energy storage devices can be obtained. As an example of a method for manufacturing the exterior material for energy storage devices, the method for manufacturing the exterior material 10 for energy storage devices shown in Figure 1 will be described below. Note that the sizes of the components in each figure are conceptual, and the relative relationships of the sizes between components are not limited thereto. Also, components having substantially the same function are given the same reference numeral throughout all drawings, and redundant explanations may be omitted. 【0071】 A laminate A is prepared in which a base layer 1, an outer adhesive layer 4, and a barrier layer 2 are laminated in this order. Laminate A can be manufactured by a dry lamination method in which an adhesive component for forming the outer adhesive layer 4 is applied to the base layer 1 or the barrier layer 2 by gravure coating, roll coating, etc., and after drying, the barrier layer 2 or the base layer 1 is laminated on top of it. If the adhesive component is a curable resin, the outer adhesive layer 4 is cured by heating or the like after the barrier layer 2 or the base layer 1 is laminated onto the outer adhesive layer 4. 【0072】 Next, a sealant layer 3 is provided on the barrier layer 2 of the laminate A. The sealant layer 3 may be formed in advance on a resin film and placed on the barrier layer 2 (first method), or the resin material for forming the sealant layer 3 may be applied to the barrier layer 2 by extrusion molding, coating, etc. to form the sealant layer 3 (second method). In the first method, if the sealant layer is a multilayer laminate, the multilayer laminate can be manufactured by co-extrusion or the like. 【0073】 In the first method, the barrier layer 2 and the sealant layer 3 are bonded together by the inner adhesive layer 5. In the second method, the inner adhesive layer 5 may be omitted or may be provided. 【0074】When an inner adhesive layer 5 is provided between the barrier layer 2 and the sealant layer 3, the inner adhesive layer 5 and the sealant layer 3 can be laminated by methods such as extrusion lamination, thermal lamination, sandwich lamination, and dry lamination. Examples of extrusion lamination include methods in which the inner adhesive layer 5 and the sealant layer 3 are laminated by extruding them onto the barrier layer 2 of laminate A (co-extrusion lamination, tandem lamination). Examples of thermal lamination include methods in which a laminate B of the inner adhesive layer 5 and the sealant layer 3 is formed separately and laminated so that the inner adhesive layer 5 of laminate B and the barrier layer 2 of laminate A face each other, and methods in which a laminate C with the inner adhesive layer 5 is formed on the barrier layer 2 of laminate A and the inner adhesive layer 5 and sealant layer 3 of laminate C are laminated. Examples of sandwich lamination include methods in which a molten inner adhesive layer 5 is poured between the barrier layer 2 of laminate A and the sealant layer 3 that has been formed in advance into a film. An adhesive resin, such as an acid-modified polyolefin adhesive, may be poured between the barrier layer 2 of the laminate A and the sealant layer 3, which is formed in advance as a film, to create a sandwich laminate. After this, the layers may be heated with a heat-bonding roll to bond the barrier layer 2 and the sealant layer 3 via the inner adhesive layer 5 (heat-bonding resin). As a dry lamination method, an adhesive component for forming the inner adhesive layer 5 is solution-coated onto the barrier layer 2 of the laminate A, dried or baked, and the sealant layer 3, which is formed in advance as a film, is laminated onto this inner adhesive layer 5. 【0075】 <Outer Case for Energy Storage Device> The outer case for energy storage device described herein is a molded body of the outer material for energy storage device described above. The outer material for energy storage device may be formed by deep drawing, stretch molding, etc. An example of the shape of the outer case for energy storage device is the outer case 20 shown in Figures 2 and 3, which will be described later. 【0076】 <Energy Storage Device> The energy storage device of this disclosure comprises an energy storage device body and an exterior member that houses the energy storage device body and includes the exterior material for the energy storage device of this disclosure. The exterior member may include the exterior case for the energy storage device of this disclosure. 【0077】 An example of an energy storage device 100 constructed using the exterior material 10 for energy storage devices of this disclosure is shown in Figures 2 and 3. Figure 2 is a schematic cross-sectional view showing an example of an energy storage device. Figure 3 is a schematic perspective view showing the components constituting the energy storage device of Figure 2 separated. The energy storage device 100 is a lithium-ion secondary battery. 【0078】 In Figures 2 and 3, the exterior member 15 is composed of an exterior case 20, which is a molded exterior material 10, and a flat exterior material 10. The main body 110 of the energy storage device is housed in a recess in the exterior case 20. The flat exterior material 10 is positioned with the sealant layer 3 facing inward (downward in Figures 2 and 3), and the peripheral edge of the sealant layer 3 of the flat exterior material 10 and the sealant layer 3 of the flange portion (sealing peripheral edge portion) 37 of the exterior case 20 are sealed together by heat fusion (heat sealing). 【0079】 In Figure 2, reference numeral 39 denotes a heat-sealed portion where the peripheral edge of the exterior material 10 and the flange portion (sealing peripheral edge) 37 of the exterior case 20 are joined (welded). In the energy storage device 100, the tip of the tab lead connected to the main body portion 110 of the energy storage device is led out to the outside of the exterior member 15, but this is not shown in the figure. 【0080】 The main body 110 of the energy storage device is not particularly limited and may include a battery body, a capacitor body, a capacitor body, etc. 【0081】 From the viewpoint of ensuring a secure seal, the width of the heat-seal portion 39 is preferably set to 0.5 mm or more, and more preferably to 3 mm to 15 mm. 【0082】 The form of the exterior member 15 is not limited to Figures 2 and 3, and may be a pair of planar exterior members 10 with their edges heat-sealed, or a pair of exterior cases 20 with their edges heat-sealed. 【0083】 Next, examples of the present disclosure will be described, but the present disclosure is not particularly limited to those examples. 【0084】[Example 1] (Preparation of Aluminum Foil) The aluminum foil used in this example was prepared as follows. First, aluminum ingots, various additive metal elements, or aluminum master alloys containing them were prepared and heated at 680°C to 1000°C to produce molten aluminum alloy. Next, the molten metal was cast to produce an ingot. The obtained ingot was subjected to homogenization heat treatment and hot rolling. The homogenization heat treatment and hot rolling were carried out under conditions of 450°C to 600°C. Furthermore, the heat treatment time for the homogenization heat treatment process was set to 20 hours or less. After the homogenization treatment and hot rolling, cold rolling was performed to obtain aluminum foil with the thickness (40 μm) shown in Table 1. Aluminum foil was produced by the above operations. The content (mass %) of each component in the produced aluminum foil is as shown in Table 1. 【0085】 A chemical conversion treatment solution consisting of phosphoric acid, polyacrylic acid (acrylic resin), chromium(III) salt compound, water, and alcohol was applied to both sides of the prepared aluminum foil, and then dried at 180°C to form a chemical conversion film. The amount of chromium deposited on this chemical conversion film was 10 mg / m² per side. ２ That was the case. 【0086】 A 15 μm biaxially oriented nylon 6 film was dry-laminated to one side of the aluminum foil via a two-component curing urethane adhesive (4 μm). The biaxially oriented nylon 6 film had a tensile strength of 280 MPa in the TD direction and a tensile strength of 260 MPa in the MD direction. 【0087】 A 40 μm CPP film was dry-laminated to the other side of the aluminum foil via a two-component maleic acid-modified polypropylene adhesive (2 μm). 【0088】 The CPP film used was a 40 μm thick, three-layer co-extruded CPP film with a bPP intermediate layer (28 μm) and rPP layers (6 μm each) on either side (laminate layer and seal layer), containing erucic acid amide as a lubricant at a concentration of 1000 ppm. 【0089】A laminate consisting of a base layer (biaxially oriented nylon 6 film), an outer adhesive layer (urethane adhesive), a metal layer (aluminum foil), an inner adhesive layer (maleic acid-modified polypropylene adhesive), and a sealant layer (three-layer co-extruded CPP film) was subjected to heat aging treatment at 40°C for 10 days. This produced the exterior material for the energy storage device of Example 1. 【0090】 [Examples 2-8 and Comparative Examples 1-4] Aluminum foil was prepared in the same manner as in Example 1, except that the composition of the components used to prepare the molten aluminum alloy was changed. Using the aluminum foil prepared in each example or comparative example, an outer casing material for an energy storage device was prepared using the same procedure as in Example 1. The content (mass%) of each component in the aluminum foil prepared in each example or comparative example is shown in Table 1. 【0091】 (Measurement of Electrical Conductivity of Aluminum Foil) The electrical conductivity of the fabricated aluminum foil was measured by the following method. This measurement was performed in accordance with JIS C2525:1999, using a HIOKI RM3543 resistance meter and measuring electrical resistance using the DC four-terminal method. Specifically, the aluminum foil was first cut to a width of 3 mm and a length of 80 mm, Ni wire was spot-welded to both ends, and the electrical resistance was measured using the four-terminal method. The resistance R of the test piece was determined from the current I flowing through the sample and the potential difference V between the voltage terminals, using the formula R = V / I. The current I was determined from the voltage drop across a standard resistor (0.1 Ω) connected in series with the test piece. The voltage drops across the test piece and the standard resistor, and the electromotive force of the R thermocouple were determined using a digital multimeter with a detection sensitivity of ±0.1 μV. The electrical conductivity was calculated using the following formula. Volume resistance ρ = R (A / L) Electrical conductivity γ (%IACS) = {1.7241 [μΩ・cm] / Volume resistance ρ [μΩ・cm]}×100 A: Sample cross-sectional area [cm ２ ] L: Length of the measuring section [cm] 1.7241 [μΩ・cm]: Volume resistivity of standard soft copper 【0092】(Measurement of Average Crystal Grain Size) A sample measuring the total width × 500 mm width was taken from the fabricated aluminum foil, and then cut into easily polishable cut samples from both ends (W, D) and the center (C) in the width direction. The cut samples were embedded in resin and buffed using a rotary polishing machine. The polished aluminum foil samples were macro-etched using a known anodizing method. The anodized samples were observed with a polarizing microscope, and the crystal grain size was measured. A measurement area of ​​100 μmφ was set up at 200x magnification, and the number of crystal grains contained within it was counted. A crystal grain that was completely contained within the measurement area was counted as 1, and a crystal grain that was overlapping the edge of the measurement area was counted as 1 / 2. Assuming that there were n crystal grains in an area of ​​100 μmφ, the average crystal grain size r was calculated using the following formula: [Formula 1] π(50) ２ / n = πr ２ [Formula 2] r=[(50) ２ / n] １／２ 【0093】 (Measurement of Tensile Strength) The material was cut into strips 200 mm long and 15 mm wide so that the tensile direction was parallel to the rolling direction (MD direction). Tensile strength (0.2% yield strength) was measured by performing a tensile test using a Shimadzu Strograph (AGS-5kNX) at a travel speed of 10 mm / min and a chuck distance of 100 mm until fracture. The results are shown in Table 1. Table 1 shows the average value when the tensile strength was measured three times. 【0094】(Evaluation of Moldability) Moldability was evaluated by determining the molding depth as follows. Using a deep drawing molding tool manufactured by Amada Corporation, the exterior material for the energy storage device was deep-drawn into a rectangular parallelepiped shape with dimensions of 55 mm in length, 35 mm in width, and various depths, to obtain a molded case corresponding to the exterior case 20 shown in Figure 3. The moldability at four corners of the obtained molded case was evaluated based on the following criteria. The presence or absence of cracks and pinholes was examined using the light transmission method in a dark room. The results are shown in Table 1. If the evaluation is C or higher, it can be judged that the moldability is good. -Evaluation Criteria- A: No cracks or pinholes with a molding depth of 9 mm or more B: No cracks or pinholes with a molding depth of 8 mm or more and less than 9 mm C: No cracks or pinholes with a molding depth of 6 mm or more and less than 8 mm D: Cracks or pinholes present with a molding depth of less than 6 mm 【0095】 【0096】 As shown in Table 1, each embodiment showed better moldability than each comparative example. 【0097】 The disclosure of Japanese Patent Application No. 2024-212467, filed on December 5, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. An exterior material for an energy storage device, wherein a base layer, a barrier layer, and a sealant layer are laminated in this order, the barrier layer is a metal layer made of an aluminum alloy containing iron, and the conductivity of the metal layer is 54% IACS to 60% IACS.

2. The exterior material for an energy storage device according to claim 1, wherein the metal layer has an aluminum content of 98% by mass or more and an iron content of 0.7% by mass to 1.7% by mass.

3. The exterior material for an energy storage device according to claim 1, wherein the content of silicon, copper, magnesium, and manganese in the metal layer is independently less than 0.1% by mass.

4. The exterior material for an energy storage device according to claim 1, wherein the average crystal grain size of the alloy particles on the surface of the metal layer is 1 μm to 10 μm.

5. The exterior material for an energy storage device according to claim 1, wherein the average crystal grain size of the alloy particles on the surface of the metal layer is 1 μm to 6.5 μm.

6. The exterior material for an energy storage device according to claim 1, wherein the thickness of the barrier layer is 25 μm to 120 μm.

7. The tensile strength of the barrier layer is 70 N / mm². ２ ~150 N / mm ２ The exterior material for an energy storage device according to claim 1.

8. An outer case for an energy storage device, which is a molded body of an outer material for an energy storage device according to any one of claims 1 to 7.

9. An energy storage device comprising: an energy storage device main body; and an exterior member that houses the energy storage device main body and includes an exterior material for an energy storage device as described in any one of claims 1 to 7.

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