Exterior material for power storage device, power storage device, and method for manufacturing power storage device

Abstract

This exterior material for a power storage device comprises a barrier layer and a thermocompression bonding layer provided on one or both surfaces of the barrier layer. The thermocompression bonding layer includes a resin layer that does not melt at 250°C or less. The thermocompression bonding layer may include a resin layer containing a polyamide-imide resin, a polycarbonate resin, a polyethersulfone resin, or a polyarylate resin.

Description

Exterior material for power storage device, power storage device, and method for manufacturing power storage device

[0001] The present disclosure relates to an exterior packaging material for an electricity storage device, an electricity storage device, and a method for manufacturing an electricity storage device.

[0002] An electricity storage device element including electrodes and an electrolyte may be housed inside an exterior body formed of an exterior material including a barrier layer such as a metal foil (see, for example, Patent Document 1). The exterior body may be formed by fusing together heat-sealable resin layers.

[0003] Patent No. 6882617

[0004] In the case of an electricity storage device such as an all-solid-state battery, it is sometimes expected that the device will be used at higher temperatures (e.g., 200°C or higher) than a lithium-ion battery. The present disclosure relates to an exterior material that can adequately support the electricity storage device even at higher temperatures.

[0005] The present disclosure includes the following: [1] A packaging material for an electricity storage device, comprising: a barrier layer; and a thermocompression layer provided on one or both sides of the barrier layer, wherein the thermocompression layer includes a resin layer that does not melt at 250°C or less. [2] A packaging material for an electricity storage device, comprising: a barrier layer; and a thermocompression layer provided on one or both sides of the barrier layer, wherein the thermocompression layer includes a resin layer containing a polyamideimide resin, a polycarbonate resin, a polyethersulfone resin, or a polyarylate resin. [3] The packaging material for an electricity storage device according to [1] or [2], wherein the thermocompression layer includes a support film and two of the resin layers provided on both sides of the support film. [4] The packaging material for an electricity storage device according to any of [1] to [3], wherein one thermocompression layer is provided on one side of the barrier layer, and the packaging material further includes a base material layer provided on the side of the barrier layer opposite the thermocompression layer. [5] The packaging material for an electricity storage device according to any one of [1] to [3], wherein two thermocompression layers are provided on both sides of the barrier layer. [6] The packaging material for an electricity storage device according to [5], wherein the packaging material further comprises a base material layer, wherein one of the two thermocompression layers and the base material layer are provided in this order from the barrier layer side. [7] The packaging material for an electricity storage device according to [6], wherein the packaging material further comprises an additional barrier layer provided separately from the barrier layer, wherein one of the two thermocompression layers, the additional barrier layer, and the base material layer are provided in this order from the barrier layer side. [8] The packaging material for an electricity storage device according to [5], wherein the packaging material further comprises a base material layer, wherein the base material layer and one of the two thermocompression layers are provided in this order from the barrier layer side. [9] The packaging material for an electricity storage device according to any one of [1] to [8], wherein the packaging material is used to house an electricity storage device element containing a solid electrolyte.

[10] An electricity storage device comprising: an electricity storage device element; and an exterior body that houses the electricity storage device element, wherein the exterior body includes the exterior material for an electricity storage device according to any one of [1] to [8], and at least some of the thermocompression bonding layers of the exterior material for an electricity storage device are bonded to each other.

[11] The electricity storage device according to

[10] , wherein the electricity storage device includes a solid electrolyte.

[12] A method for producing an electricity storage device, comprising forming an exterior body to house an electricity storage device element, wherein the exterior body is formed by bonding at least some of the thermocompression bonding layers of the electricity storage device exterior material according to any one of [1] to [8] to each other by thermocompression bonding.

[13] The method according to

[12] , wherein the electricity storage device element contains a solid electrolyte.

[0006] It is possible to provide a packaging material that can adequately hold an electricity storage device even at higher temperatures (for example, 200° C. or higher).

[0007] Fig. 7 is a cross-sectional view showing an example of an exterior material. Fig. 8 is a cross-sectional view showing an example of a thermocompression bonding layer having a support film. Fig. 9 is a cross-sectional view showing an example of an exterior material. Fig. 10 is a cross-sectional view showing an example of an exterior material. Fig. 11 is a cross-sectional view showing an example of an exterior material. Fig. 12 is a plan view showing an example of an electricity storage device. Fig. 13 is an end view taken along line VIII-VIII in Fig. 7.

[0008] The present invention is not limited to the following examples.

[0009] Fig. 1 is a cross-sectional view showing an example of an exterior packaging material. The exterior packaging material 10 shown in Fig. 1 is a sheet-like laminate having a base sheet 7 including a barrier layer 1 and a thermocompression layer 2 provided on one side of the base sheet 7 or one side of the barrier layer 1. The base sheet 7 is a laminate further including an adhesive layer 3 and a base layer 5. The base layer 5 is provided on the side of the barrier layer 1 opposite to the thermocompression layer 2. The barrier layer 1 and the base layer 5 are bonded together by an adhesive layer 3 interposed therebetween.

[0010] The barrier layer 1 is a layer that suppresses the transmission of moisture, oxygen, light, and the like. The barrier layer 1 may be a metal layer. The barrier layer 1 may be a metal layer containing one or more metals selected from aluminum, stainless steel, copper, nickel, and titanium. The barrier layer 1 may be a metal layer containing an alloy composed of two or more metals selected from these. The barrier layer 1 may be a metal foil, and in particular, may be an aluminum foil. The thickness of the barrier layer 1 may be, for example, 5 μm or more and 200 μm or less.

[0011] The thermocompression layer 2 includes a resin layer that can be thermocompression bonded. The resin layer of the thermocompression layer 2 is usually insulating. The packaging material 10 can form an exterior body that houses an electricity storage device element by thermocompression bonding between the thermocompression layers 2, by thermocompression bonding between the thermocompression layer 2 and another member, or by a combination of these. Generally, to form an exterior body or a package, resin layers that melt at a relatively low temperature are often heat-sealed together. In contrast, the packaging material 10 according to the present disclosure has a thermocompression layer 2 that includes a resin layer that can be bonded by thermocompression bonding at a relatively high temperature.

[0012] When a thermocompression layer is bonded to another component by thermocompression bonding, the resin layer of the thermocompression layer is heated to a rubbery state above its glass transition temperature and pressed against the other component. Typically, the resin layer is not completely crushed during thermocompression bonding and maintains its shape as a "layer." Therefore, the resin layer can be peeled off and re-thermocompressed depending on the usage conditions. The thermocompression layer acts as a buffer, reducing stress on the energy storage device and preventing damage such as tearing of the exterior material. On the other hand, when a resin layer is bonded to another component by thermal fusion, the resin layer is heated above its melting point and becomes liquid, and is pressed against the other component. Therefore, the resin layer often does not maintain its original shape as a "layer" after thermal fusion. In this respect, resin layers for thermal fusion bonding are distinguished from thermocompression layers.

[0013] The resin layer of the thermocompression bonding layer 2 according to one aspect of the present disclosure may contain, for example, one or more resins selected from polyamideimide resin, polycarbonate resin, polyethersulfone resin, and polyarylate resin. The resin layer of the thermocompression bonding layer 2 may contain a polyamideimide resin (particularly a thermoplastic polyamideimide resin). The polyamideimide resin may be polyetheramideimide.

[0014] An example of the polyamide-imide resin may be a resin produced by a polycondensation reaction between a diamine compound having two amino groups or a diisocyanate compound having two isocyanate groups and a compound having an acidic functional group.

[0015] From the viewpoint of improving heat resistance and chemical resistance, the diamine compound and diisocyanate compound may be compounds having an aromatic ring. Examples of diamine compounds having an aromatic ring include 1,3-bis(3-aminophenoxy)benzene and 2,2-bis[4-(4-aminophenoxy)phenyl]propane. From the viewpoint of improving the flexibility of the thermocompression bonding layer and adjusting the thermocompression bonding properties, the diamine compound may include a compound having an aromatic ring and 1,3-bis(3-aminopropyl)1,1,3,3-tetramethyldisiloxane.

[0016] The compound having an acidic functional group may be one or more selected from tricarboxylic acid anhydrides, acid halides of tricarboxylic acids, and tricarboxylic acids. These compounds may be used in combination with tetracarboxylic acid dianhydrides such as pyromellitic anhydride and biphenyltetracarboxylic acid dianhydride, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid.

[0017] The compound having an acidic functional group may be an acid halide of trimellitic anhydride, and examples thereof include trimellitic anhydride chloride represented by the following formula (I):

[0018] The polyamide-imide resin may contain a structural unit represented by the following formula (Ia):

[0019] The total amount of the diamine compounds or diisocyanate compounds may be 0.90 to 1.10 mol, 0.95 to 1.05 mol, or 0.97 to 1.03 mol per 1.00 mol of the total amount of the compounds having an acidic functional group. A polyamideimide resin produced at a ratio in this range is likely to form a uniform polymer structure, and as a result, the thermocompression bonded layer can have higher uniformity in terms of thermocompression bondability, heat resistance, chemical resistance, etc.

[0020] The content of these resins in the thermocompression layer 2 may be 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, or 95% by mass or more and 100% by mass or less, based on the mass of the thermocompression layer 2 or its resin layer.

[0021] The resin layer of the thermocompression bonding layer 2 may contain additional components such as a colorant, a coupling agent, and a resin modifier, as necessary. From the viewpoint of appropriate physical properties of the resin layer, the content of the additional components may be 50 parts by mass or less per 100 parts by mass of the resin such as polyamideimide resin.

[0022] The coupling agent can contribute to improving heat resistance and adhesion to the support film or barrier layer. The coupling agent can be, for example, a silane coupling agent, a titanium coupling agent, an aluminum coupling agent, or a combination thereof, or may be a silane coupling agent. Examples of the silane coupling agent include vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, Sisilane, γ-mercaptopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltris[2-(2-methoxyethoxy)ethoxy]silane, N-methyl-3-aminopropyltrimethoxysilane, triaminopropyltrimethoxysilane, 3-4,5-dihydroimidazol-1-ylpropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyldimethoxysilane, 3-cyanopropyltriethoxysilane, hexamethyldisilazane, N,Examples of suitable silanes include O-bis(trimethylsilyl)acetamide, methyltrimethoxysilane, methyltriethoxysilane, ethyltrichlorosilane, n-propyltrimethoxysilane, isobutyltrimethoxysilane, amyltrichlorosilane, octyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, methyltri(methacryloyloxyethoxy)silane, methyltri(glycidyloxy)silane, N-β(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane, octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldichlorosilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropylmethyldiethoxysilane, trimethylsilyl isocyanate, dimethylsilyl isocyanate, methylsilyl triisocyanate, vinylsilyl triisocyanate, phenylsilyl triisocyanate, tetraisocyanate silane, and ethoxysilane isocyanate. The silane coupling agent may be one or more selected from these.

[0023] The thermocompression layer 2 according to one aspect of the present disclosure may include a resin layer that does not melt at 250°C or below. "Does not melt at 250°C or below" means, in other words, that the resin layer does not liquefy at 250°C. For example, if the melting point of the resin layer observed by differential scanning calorimetry exceeds 250°C, the resin layer can be considered not to melt at 250°C or below. Resin layers containing a resin selected from the polyamideimide resin, polycarbonate resin, polyethersulfone resin, and polyarylate resin already exemplified often do not melt at 250°C or below.

[0024] The thermocompression layer 2 may include a resin layer exhibiting a glass transition temperature of 140° C. or higher and 280° C. or lower. The glass transition temperature of the resin layer of the thermocompression layer 2 may be 150° C. or higher, 160° C. or higher, 170° C. or higher, 180° C. or higher, 190° C. or higher, or 200° C. or higher, or may be 270° C. or lower, 260° C. or lower, less than 260° C., 250° C. or lower, 240° C. or lower, or 230° C. or lower.

[0025] The thickness of the thermocompression bonding layer 2 or its resin layer may be, for example, 1 μm or more and 2000 μm or less. The thickness of the thermocompression bonding layer 2 or its resin layer may be 5 μm or more, or 10 μm or more, and may be 1000 μm or less, or 500 μm or less.

[0026] The thermocompression layer 2 may be a single resin layer capable of thermocompression bonding, or may be a laminate including a support film and a resin layer. FIG. 2 is a cross-sectional view showing an example of a thermocompression layer having a support film. The thermocompression layer 2 shown in FIG. 2 is a laminate including a support film 20 and two resin layers 2A and 2B provided on both sides of the support film 20. The support film 20 is provided between the two resin layers 2A and 2B. The resin layers 2A and 2B can each be a resin layer capable of thermocompression bonding similar to the thermocompression layer 2, which is a single resin layer. For example, in the packaging material 10 having the configuration of FIG. 1, the thermocompression layer 2, which is a single resin layer, can be replaced with the thermocompression layer 2 having a support film shown in FIG. 2.

[0027] The support film 20 can be a film having high heat resistance and sufficiently high adhesion to prevent peeling or swelling at the interface between the support film 20 and the resin layers 2A and 2B at high temperatures (e.g., 200°C). The glass transition temperature of the support film may be higher than the glass transition temperature of the thermocompression-bondable resin layers (resin layers 2A and 2B). The glass transition temperature of the support film 20 does not need to be detected. When the glass transition temperature of the support film 20 is detected, for example, the glass transition temperature of the support film 20 may be 200°C or higher, 250°C or higher, 260°C or higher, or 300°C or higher, or 400°C or lower, or 350°C or lower. The support film 20 may be a film containing at least one polymer selected from the group consisting of, for example, aromatic polyimide, aromatic polyamide, aromatic polyamideimide, aromatic polysulfone, aromatic polyethersulfone, polyphenylene sulfide, aromatic polyetherketone, polyarylate, aromatic polyetheretherketone, polyethylene naphthalate, and polyethylene terephthalate. From the viewpoints of heat resistance and adhesion to the resin layer at high temperatures, the support film 20 may be a polyimide film containing aromatic polyimide.

[0028] The glass transition temperatures of the resin layer of the thermocompression bonding layer 2 and the support film can be glass transition temperatures measured using a thermomechanical analyzer on a strip-shaped test piece cut out from the resin layer or the support film and having a size of 2 mm wide x 25 mm long, under the following conditions: inter-chuck distance 10 mm, tensile mode, temperature range 30°C to 400°C, heating rate 10°C / min, and tensile load 98 mN.

[0029] The support film 20 may be surface-treated to sufficiently increase the adhesion of the support film 20. Examples of methods for treating the surface of the support film 20 include chemical treatments (alkali treatment, silane coupling treatment, etc.), physical treatments (sand mat treatment, etc.), plasma treatments, and corona treatments.

[0030] The thickness of the support film 20 is not particularly limited, but may be 100 μm or less, 50 μm or less, or 25 μm or less from the viewpoint of conformability to the shape of the electricity storage device element, etc. The thickness of the support film 20 may be 5 μm or more, or 10 μm or more. The thickness of the support film 20 may be 5 μm or more and 100 μm or less.

[0031] An adhesive layer may not be provided between the thermocompression layer 2 and the barrier layer 1. In this case, the thermocompression layer 2 and the barrier layer 1 (e.g., a metal foil) may be in direct contact with each other. For example, a resin layer containing a polyamide-imide resin easily adheres sufficiently to other layers such as a barrier layer even without an adhesive layer.

[0032] The substrate layer 5 can be a resin film that is typically used as a substrate layer for an exterior material for an electrical storage device, and is a resin film containing a resin (particularly a thermoplastic resin) different from the resin that constitutes the thermocompression bonding layer 2. The substrate layer 5 may be a single-layer or multi-layer resin film. For example, the substrate layer 5 may be a resin film containing polyamideimide, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, or a combination thereof. The thickness of the substrate layer 5 may be, for example, 5 μm or more and 50 μm or less.

[0033] The adhesive layer 3 is formed of any adhesive capable of bonding the barrier layer 1 and the base layer 5. For example, the adhesive layer 3 is formed of a curable adhesive such as an energy ray (UV, X-ray, etc.) curable adhesive. The adhesive layer forming the adhesive layer 3 may be a urethane adhesive, an olefin adhesive, an acrylic adhesive, or an epoxy adhesive. The thickness of the adhesive layer 3 may be, for example, 2 μm or more and 50 μm or less. The adhesive layer 3 may not be provided.

[0034] FIG. 3 is a cross-sectional view showing another example of an exterior packaging material. The exterior packaging material 10 shown in FIG. 3 has a barrier layer 1 and two thermocompression layers 2, 2' provided on both sides of the barrier layer 1. The barrier layer 1 is provided between the two thermocompression layers 2, 2'. In this case, the thermocompression layers 2, 2' can each be the same as the thermocompression layer 2 constituting the exterior packaging material 10 of FIG. 1. The two thermocompression layers 2, 2' constituting one exterior packaging material 10 can include resin layers containing the same or different resins. The thicknesses of the two thermocompression layers 2, 2' may be the same or different. When one or both of the thermocompression layers 2, 2' essentially function as a substrate layer, a substrate layer separate from the thermocompression layers may not be provided.

[0035] Fig. 4 is a cross-sectional view showing yet another example of an exterior packaging material. The exterior packaging material 10 shown in Fig. 4 differs from the exterior packaging material 10 of Fig. 3 in that it further includes an adhesive layer 3 and a base material layer 5. The adhesive layer 3 and base material layer 5 of Fig. 4 can be the same layers as the adhesive layer 3 and base material layer 5 constituting the exterior packaging material 10 of Fig. 1, respectively. One of the two thermocompression layers 2, 2', the thermocompression layer 2', and the base material layer 5 are provided in this order from the barrier layer 1 side. The thermocompression layer 2' and the base material layer 5 are bonded together by the adhesive layer 3 interposed therebetween. The adhesive layer 3 does not necessarily have to be provided.

[0036] FIG. 5 is also a cross-sectional view showing yet another example of an exterior packaging material. The exterior packaging material 10 shown in FIG. 5 differs from the exterior packaging material 10 shown in FIG. 4 in that it further includes an additional barrier layer 1' provided separately from the barrier layer 1. The additional barrier layer 1' is provided between one of the two thermocompression layers 2, 2' and the base material layer 5 (or adhesive layer 3). In other words, one of the two thermocompression layers 2, 2', the additional barrier layer 1', and the base material layer 5 are provided in this order from the barrier layer 1 side. The additional barrier layer 1' can be a layer similar to the barrier layer 1. The two barrier layers 1, 1' may be the same as or different from each other. The additional barrier layer 1' and the base material layer 5 are bonded together by an adhesive layer 3 interposed therebetween. The adhesive layer 3 may not be provided.

[0037] FIG. 6 is a cross-sectional view showing yet another example of an exterior packaging material. The exterior packaging material 10 shown in FIG. 6 has a barrier layer 1, two thermocompression layers 2 and 2', an adhesive layer 3, and a base material layer 5. The two thermocompression layers 2 and 2' are provided on both sides of the barrier layer 1. In other words, the barrier layer 1 is provided between the two thermocompression layers 2 and 2'. The base material layer 5 and one of the two thermocompression layers 2 and 2', the thermocompression layer 2', are provided in this order from the barrier layer 1 side. The barrier layer 1 and the base material layer 5 are bonded together by an adhesive layer 3 interposed therebetween. The adhesive layer 3 does not necessarily have to be provided. The barrier layer 1, the two thermocompression layers 2 and 2', the adhesive layer 3, and the base material layer 5 may be the same layers as the barrier layer 1, the thermocompression layers 2 and 2', the adhesive layer 3, and the base material layer 5 constituting the exterior packaging material of FIGS. 1 or 3 to 5, respectively. The thermocompression-bonded layer 2' of the packaging material 10 in Fig. 6 can also reinforce the function of the base material layer 5 as a base material layer. From this viewpoint, the glass transition temperature of the thermocompression-bonded layer 2' may be higher than the glass transition temperature of the thermocompression-bonded layer 2. The difference between the glass transition temperatures of the two may be 10°C or more, or 20°C or more.

[0038] The method for forming the thermocompression layer constituting the packaging material is not particularly limited. For example, a resin layer serving as a thermocompression layer can be formed by a method including applying a resin varnish for forming a thermocompression layer, which contains a resin or a precursor thereof for forming the thermocompression layer and a solvent, onto the barrier layer 1, and removing the solvent from the coating film. The coating film may be heated to remove the solvent. When producing a packaging material having two thermocompression layers, resin varnish may be applied to both sides of the barrier layer, and thermocompression layers may be formed on both sides of the barrier layer. When producing a packaging material having a thermocompression layer provided on a substrate layer, resin varnish may be applied to the substrate layer. A thermocompression layer containing a polyamide-imide resin may be formed by removing the solvent from a coating film of resin varnish containing a precursor of a polyimide-amide-imide resin (e.g., polyamic acid) and a solvent, and then imidizing the precursor to produce a polyamide-imide resin.

[0039] Examples of methods for applying the resin varnish include roll coating, reverse roll coating, gravure coating, bar coating, comma coating, die coating, and vacuum die coating.

[0040] The solvent of the resin varnish for forming the thermocompression bonding layer 2 or its resin layer may be, for example, N-methyl-2-pyrrolidone, dimethylacetamide, diethylene glycol dimethyl ether, tetrahydrofuran, cyclohexanone, methyl ethyl ketone, dimethylformamide, or a combination thereof. The resin varnish may further contain the above-mentioned additional components as necessary.

[0041] A thermocompression layer previously formed on any substrate film can also be used. In this case, the thermocompression layer formed on the substrate film can be laminated on one or both sides of the barrier layer. The thermocompression layer can be formed on the substrate film using the above-mentioned resin varnish. The substrate film may have a surface that has been subjected to a release treatment (e.g., silicone release treatment), and the above-mentioned resin varnish may be applied to that surface. A protective film may be provided on the surface of the thermocompression layer opposite to the substrate film.

[0042] Fig. 7 is a plan view showing an example of an electricity storage device having an exterior body formed from an exterior material. Fig. 8 is an end view taken along line VIII-VIII in Fig. 7. The electricity storage device 100 shown in Figs. 7 and 8 has an electricity storage device element 30, a connection terminal 31 connected to the electricity storage device element 30, and an exterior body 40 that houses the electricity storage device element 30. The exterior body 40 seals the electricity storage device element 30. The connection terminal 31 extends to the outside of the exterior body 40.

[0043] The exterior body 40 is formed, for example, by an exterior material 10 having a base sheet 7 including a barrier layer 1 and a thermocompression-bonded layer 2, as illustrated in Fig. 1 . The thermocompression-bonded layers 2 of the exterior material 10 are bonded to each other at a peripheral edge portion 40A of the exterior body 40. The connection terminal 31 may be sandwiched between the two thermocompression-bonded layers 2.

[0044] The electricity storage device element 30 can be any structure having an electricity storage function. For example, the electricity storage device element 30 may have a positive electrode, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode. The electrolyte may be a solid electrolyte, in which case the electricity storage device 100 can be an all-solid-state battery. All-solid-state batteries are sometimes required to have high durability even in high-temperature environments (e.g., 200°C or higher). If the exterior body 40 deforms at high temperatures, the electricity storage device element 30 may not be properly fixed. However, an exterior body 40 formed using an exterior material having a specific thermocompression bonding layer according to the present disclosure can properly hold the electricity storage device element 30 even in high-temperature environments.

[0045] The exterior body 40 may be formed by combining two or more exterior materials 10, or by folding a single exterior material 10. For example, the exterior body 40 can be formed by a method including bonding two thermocompression layers 2, which are arranged so as to face each other by overlapping the exterior materials 10 while accommodating the energy storage device element 30, by thermocompression bonding. The heating temperature for thermocompression bonding may be, for example, 180°C or higher and 400°C or lower. For thermocompression bonding, the overlapping exterior materials 10 may be heated while being pressed. In this case, the pressure applied to the pressed surfaces of the exterior materials may be 0.2 MPa or higher and 10 MPa or lower. The heating time may be, for example, 1 second or higher and 60 seconds or lower. The thermocompression layers 2 may be bonded to each other by thermocompression bonding multiple times (e.g., three times). The thermocompression layers 2 may not be bonded to each other along the entire periphery of the exterior body 40. The thermocompression layers 2 may be bonded to each other along part of the periphery of the exterior body 40 so that the energy storage device element 30 can be accommodated.

[0046] The present invention is not limited to the following examples. 1. Production of Exterior Materials for Examples A to E (1) Preparation of Film-Forming Resin Varnishes Resin Varnish A: In a 5-liter four-neck flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a fractionating column, 270.9 g (0.66 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 8.7 g (0.035 mol) of 1,3-bis(3-aminopropyl)-tetramethyldisiloxane were dissolved in 1950 g of N-methyl-2-pyrrolidone under a nitrogen atmosphere. The resulting solution was cooled to -10°C, and while maintaining that temperature, 149.5 g (0.71 mol) of trimellitic anhydride chloride was added. After the trimellitic anhydride chloride was dissolved, 100 g of triethylamine was added so that the temperature did not exceed 10°C. Polyamic acid was produced by reacting at room temperature for 3 hours. The solution was heated at 180°C for 5 hours to promote imidization, producing polyetheramideimide from the polyamic acid. The solution containing polyetheramideimide was poured into methanol. The precipitated solid was collected and dried. The dried solid was dissolved in N-methyl-2-pyrrolidone, and the solution was poured into methanol to precipitate the solid again. The solid was dried under reduced pressure to obtain a purified powdered polyetheramideimide A (thermoplastic polyamideimide resin). 120 g of this polyetheramideimide A and 3.6 g of a silane coupling agent (manufactured by Dow-Toray Industries, Inc., trade name: XIAMETER (registered trademark) OFS-6040 Silane) were dissolved in 280 g of N-methyl-2-pyrrolidone to obtain a resin varnish A for forming a thermocompression bonded layer.

[0047] Resin Varnish B: In a 5-liter four-neck flask equipped with a thermometer, stirrer, nitrogen inlet tube, and fractionating column, 258.6 g (0.63 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 67.0 g (0.27 mol) of 1,3-bis(3-aminopropyl)tetramethyldisiloxane were dissolved in 1550 g of N-methyl-2-pyrrolidone under a nitrogen atmosphere. The resulting solution was cooled to -10°C, and while maintaining that temperature, 187.3 g (0.89 mol) of trimellitic anhydride chloride was added. After the trimellitic anhydride chloride was dissolved, 100 g of triethylamine was added so that the temperature did not exceed 10°C. Polyamic acid was produced by a 3-hour reaction at room temperature. The solution was heated at 180°C for 5 hours to promote imidization, producing polyetheramideimide from the polyamic acid. The polyetheramideimide solution was then poured into methanol. The precipitated solid was collected and dried. The dried solid was dissolved in N-methyl-2-pyrrolidone, and the solution was poured into methanol to precipitate the solid again. The solid was dried under reduced pressure to obtain a purified powdered polyetheramideimide B (thermoplastic polyamideimide resin). 120 g of this polyetheramideimide B and 3.6 g of a silane coupling agent (manufactured by Dow-Toray Industries, Inc., trade name: XIAMETER (registered trademark) OFS-6040 Silane) were dissolved in 280 g of N-methyl-2-pyrrolidone to obtain a resin varnish B for forming a thermocompression layer.

[0048] Resin Varnish C Resin varnish C for forming a thermocompression layer was obtained by dissolving 18 g of polyetheramideimide A synthesized in the preparation of resin varnish A, 102 g of polyetheramideimide B synthesized for the preparation of resin varnish B, and 3.6 g of a silane coupling agent (manufactured by Dow-Toray Industries, Inc., trade name: XIAMETER (registered trademark) OFS-6040 Silane) in 280 g of N-methyl-2-pyrrolidone.

[0049] Resin Varnish D: In a 5-liter four-neck flask equipped with a thermometer, stirrer, nitrogen inlet tube, and fractionating column, 235.3 g (0.80 mol) of 1,3-bis(3-aminophenoxy)benzene and 85.6 g (0.34 mol) of 1,3-bis(3-aminopropyl)tetramethyldisiloxane were dissolved in 1500 g of N-methyl-2-pyrrolidone under a nitrogen atmosphere. The resulting solution was cooled to -10°C, and while maintaining that temperature, 239.7 g (1.14 mol) of trimellitic anhydride chloride was added. After the trimellitic anhydride chloride had dissolved, 138.0 g (1.36 mol) of triethylamine was added so that the temperature did not exceed 10°C. Polyamic acid was produced by a 3-hour reaction at room temperature. The solution was heated at 180°C for 5 hours to promote imidization, producing polyetheramideimide from the polyamic acid. The polyetheramideimide solution was then poured into methanol. The precipitated solid was collected and dried. The dried solid was dissolved in N-methyl-2-pyrrolidone, and the solution was poured into methanol to precipitate the solid again. The solid was dried under reduced pressure to obtain a purified powdered polyetheramideimide D (thermoplastic polyamideimide resin). 120 g of this polyetheramideimide D and 6.0 g of a silane coupling agent (manufactured by Dow-Toray Industries, Inc., trade name: XIAMETER™ OFS-6040 Silane) were dissolved in 280 g of N-methyl-2-pyrrolidone to obtain a resin varnish D for forming a thermocompression bonded layer.

[0050] Resin Varnish E: In a 5-liter four-neck flask equipped with a thermometer, stirrer, nitrogen inlet tube, and fractionating column, 172.4 g (0.42 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 153.7 g (0.42 mol) of 4,4'-methylenebis(2,6-diisopropylaniline) were dissolved in 1550 g of N-methyl-2-pyrrolidone under a nitrogen atmosphere. The resulting solution was cooled to -10°C, and while maintaining that temperature, 174.7 g (0.83 mol) of trimellitic anhydride chloride was added. After the trimellitic anhydride chloride had dissolved, 130 g of triethylamine was added so that the temperature did not exceed 10°C. Polyamic acid was produced by a 3-hour reaction at room temperature. The solution was heated at 180°C for 5 hours to promote imidization, producing polyetheramideimide from the polyamic acid. The polyetheramideimide solution was then poured into methanol. The precipitated solid was collected and dried. The dried solid was dissolved in N-methyl-2-pyrrolidone, and the solution was poured into methanol to precipitate the solid again. The solid was dried under reduced pressure to obtain a purified powdered polyetheramideimide E (thermoplastic polyamideimide resin). 120 g of this polyetheramideimide E and 6.0 g of a silane coupling agent (manufactured by Dow-Toray Industries, Inc., trade name: XIAMETER (registered trademark) OFS-6040 Silane) were dissolved in 280 g of N-methyl-2-pyrrolidone to obtain a resin varnish E for forming a thermocompression bonded layer.

[0051] (2) Preparation of Exterior Materials Examples A to E Resin varnish A was applied to the matte, rough surface of aluminum foil (TY-X2 material 8079 manufactured by Toyo Aluminum K.K.). The coating was dried by heating at 100°C for 10 minutes and at 300°C for 10 minutes, forming a thermocompression layer with a thickness of approximately 40 μm on the aluminum foil. By the above method, an exterior material for evaluation of Example A, which is a sheet-like laminate having an aluminum foil (barrier layer) and a thermocompression layer, was prepared. Exterior materials for evaluation of Examples B, C, D, and E were prepared in the same manner, except that resin varnishes B, C, D, and E, respectively, were used.

[0052] 2. Evaluation (1) Appearance Change of Exterior Materials at High Temperatures Multiple strip-shaped test pieces, 10 mm wide and 50 mm long, were cut from each exterior material for evaluation. Two test pieces were attached together with the thermocompression-bonded layers facing each other. The formed laminate was thermocompressed under the conditions shown in Table 1 to bond the thermocompression-bonded layers together, producing an adhesive bond for evaluating appearance changes. The pressure (1 MPa) under the thermocompression bonding conditions shown in Table 1 is the pressure applied to the laminate. This adhesive bond was placed on a hot plate heated to 200°C, 220°C, or 250°C for 10 seconds. At this point, the adhesive bond was observed to determine whether or not there were any changes in appearance, such as swelling or wrinkles. As shown in Table 1, none of the adhesive bonded materials exhibited any changes in appearance, such as swelling or wrinkles, at high temperatures, confirming their excellent heat resistance.

[0053] (2) Glass Transition Temperature of Thermocompression Layer Resin varnish A, B, C, D, or E was applied to a peelable support film after drying. The coating was dried by heating at 100°C for 10 minutes and then at 300°C for 10 minutes, forming a thermocompression layer approximately 40 μm thick on the support film. A rectangular test piece measuring 2 mm wide x 25 mm long was cut from the thermocompression layer peeled from the support film. This test piece was attached to a chuck for measuring the tensile mode of a thermomechanical analyzer (TMA / SS7100, manufactured by Hitachi High-Tech Corporation). The chuck distance was 10 mm. Measurements were performed under the following conditions: a temperature range of 30°C to 300°C, a heating rate of 10°C / min, and a tensile load of 98 mN. From the measurement results, the glass transition temperatures of the thermocompression layers formed from resin varnish A, B, C, D, or E were determined. The measured glass transition temperatures are shown in Table 1.

[0054]

[0055] (3) Exterior Materials Having a Heat-Sealing Layer (Comparative Examples A and B) For comparison, exterior materials of Comparative Examples A and B, which are sheet-like laminates of aluminum foil and a heat-sealing layer (thickness: approximately 40 μm) containing polyethylene or polyethylene terephthalate, were prepared. From these exterior materials, multiple strip-shaped test pieces measuring 10 mm in width and 50 mm in length were cut. Two test pieces were attached together with the heat-sealing layers facing each other. The formed laminate was heat-sealed under the conditions shown in Table 2 to bond the heat-sealing layers together and produce an adhesive body for evaluating appearance changes. The pressure (1 MPa) under the heat-sealing conditions shown in Table 2 is the pressure applied to the laminate. The heat-sealing layer containing polyethylene melts at approximately 100°C. The heat-sealing layer containing polyethylene terephthalate resin melts at 250°C or below. The appearance changes at high temperatures of the adhesive bodies formed using the exterior materials of Comparative Examples A and B were evaluated using the same method as described above. As shown in Table 2, swelling or wrinkling was observed at temperatures as high as 200°C or higher.

[0056]

[0057] 1...barrier layer, 1'...additional barrier layer, 2, 2'...thermocompression layer, 3...adhesive layer, 5...substrate layer, 7...substrate sheet, 10...exterior material, 20...support film, 30...electricity storage device element, 31...connection terminal, 40...exterior body, 100...electricity storage device.

Claims

1. An exterior packaging material for an electricity storage device, comprising: a barrier layer; and a thermocompression layer provided on one or both sides of the barrier layer, wherein the thermocompression layer includes a resin layer that does not melt at 250°C or below.

2. An exterior packaging material for an electricity storage device, comprising: a barrier layer; and a thermocompression layer provided on one or both sides of the barrier layer, wherein the thermocompression layer comprises a resin layer containing a polyamideimide resin, a polycarbonate resin, a polyethersulfone resin, or a polyarylate resin.

3. The packaging material for an electricity storage device according to claim 1 or 2, wherein the thermocompression layer includes a support film and two of the resin layers provided on either side of the support film.

4. The packaging material for an electricity storage device according to claim 1 or 2, wherein one thermocompression layer is provided on one side of the barrier layer, and the packaging material further comprises a base material layer provided on the side of the barrier layer opposite the thermocompression layer.

5. The packaging material for an electricity storage device according to claim 1 or 2, wherein two of the thermocompression layers are provided on both sides of the barrier layer.

6. The packaging material for an electricity storage device according to claim 5, further comprising a base material layer, and one of the two thermocompression layers and the base material layer are provided in this order from the barrier layer side.

7. The packaging material for an electricity storage device according to claim 6, further comprising an additional barrier layer provided separately from the barrier layer, and one of the two thermocompression layers, the additional barrier layer, and the base material layer are provided in this order from the barrier layer side.

8. The packaging material for an electricity storage device according to claim 5, further comprising a base material layer, the base material layer and one of the two thermocompression layers being provided in this order from the barrier layer side.

9. The packaging material for an electricity storage device according to claim 1 or 2, which is used to house an electricity storage device element containing a solid electrolyte.

10. An electricity storage device comprising: an electricity storage device element; and an exterior body that houses the electricity storage device element, wherein the exterior body includes the exterior material for an electricity storage device according to claim 1 or 2, and at least some of the thermocompression layers of the exterior material for an electricity storage device are bonded to each other.

11. The electrical storage device according to claim 10, wherein the electrical storage device comprises a solid electrolyte.

12. A method for producing an electricity storage device, comprising forming an exterior body to house an electricity storage device element, wherein the exterior body is formed by bonding at least some of the thermocompression layers of the exterior material for an electricity storage device according to claim 1 or 2 to each other by thermocompression bonding.

13. The method of claim 12, wherein the electrical storage device element comprises a solid electrolyte.

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