Exterior material for electric power storage device, and electric power storage device

Abstract

Disclosed is an exterior material for use in an electric power storage device. The exterior material comprises a base material layer, a barrier layer, and a sealant layer in the given order. The sealant layer has an outermost layer on the side opposite to the barrier layer, and the outermost layer contains a polyester resin. The melting point of the outermost layer is 190–258°C, and the crystallinity is 33% or less.

Description

Exterior materials for energy storage devices and energy storage devices

[0001] This disclosure relates to an exterior material for an energy storage device and an energy storage device.

[0002] Solid-state batteries are known as energy storage devices. Compared to current liquid-type LIBs (operating temperature range: -40°C to 60°C), solid-state batteries do not require cooling and can therefore be used over a wide temperature range. Until now, solid-state batteries were assumed to be used at temperatures below 150°C, so the use of polypropylene resin (melting point: approximately 160°C) for the sealant layer of the outer material was being considered.

[0003] However, in recent years, in all-solid-state batteries, phenomena such as thermal runaway can occur, where, for example, the negative and positive electrodes conduct electricity, causing a localized current to flow in a part of the battery and generating uncontrollable heat. In such cases, the temperature of the sealant layer can reach 170°C or higher. Therefore, it has been found that polypropylene resins cannot satisfy the sufficient heat resistance requirements (sealing properties) for the sealant layer.

[0004] Therefore, instead of using polypropylene resin, there is consideration to using polyester resin, which has higher heat resistance (higher melting point) than polypropylene resin, in the sealant layer. For example, Patent Document 1 below discloses an exterior material for an energy storage device, which is composed of a laminate comprising a base layer, a barrier layer, and a heat-sealable resin layer in that order, wherein the heat-sealable resin layer includes a film, and the film is formed of a resin containing three or more constituent units, and the film has a melting peak temperature of 170°C or higher.

[0005] Patent No. 7355274

[0006] However, although the exterior material described in Patent Document 1 above has excellent sealing properties at room temperature, there was room for improvement in terms of sealing properties at 170°C.

[0007] Therefore, the purpose of this disclosure is to provide an exterior material for an energy storage device and an energy storage device that can have excellent sealing properties at room temperature and at 170°C.

[0008] The inventors of this disclosure, in order to solve the above problems, have diligently conducted research focusing on indicators related to the crystallinity of the sealant layer (melting point, degree of crystallinity, crystallization temperature, etc.) and have found that the above problems can be solved by setting the melting point and degree of crystallinity of the sealant layer to specific ranges, which has led to this disclosure. That is, one aspect of this disclosure is an exterior material for use in an energy storage device, comprising a base layer, a barrier layer, and a sealant layer in that order, wherein the sealant layer has an outermost layer on the side opposite to the barrier layer, the outermost layer contains a polyester resin, the melting point of the outermost layer is 190°C or more and 258°C or less, and the degree of crystallinity is 33% or less.

[0009] The above-mentioned exterior material can exhibit excellent sealing properties at room temperature and at 170°C. The inventors of this disclosure surmise the following as to why such effects are achieved: That is, because the melting point of the outermost layer is 258°C or lower and the degree of crystallinity is 33% or lower, the polyester resin melts sufficiently and becomes more fluid during heat sealing of the exterior material, and the molecules become entangled with each other, so that the sealant layer can exhibit excellent sealing properties at room temperature and at 170°C. In addition, because the melting point of the outermost layer is 190°C or higher, the molecular motion of the polyester resin does not become too large, and melting is suppressed, so that the sealant layer can exhibit excellent sealing properties even at 170°C.

[0010] In the above-mentioned exterior material for energy storage devices, it is preferable that the outermost layer has a crystallization temperature of 190°C or lower, or that no crystallization peak can be observed. Under room temperature conditions, if the crystallinity of the outermost layer is 190°C or lower, or if no crystallization peak can be observed, the polyester resin is less likely to crystallize, resulting in lower crystallinity, which can improve the impact resistance of the sealant layer.

[0011] In the above-mentioned exterior material for energy storage devices, when the outermost layer is formed by folding and overlapping the exterior material so that the sealant layers face each other, and then heat-sealing the overlapping portion under the conditions of a temperature of 280°C, a pressure of 0.5 MPa, and 5 seconds, it is preferable that the cold crystallization temperature of the sealant layer in the sealed portion be between 120°C and 190°C. By having a cold crystallization temperature of 120°C or higher and 190°C or lower in the sealed portion, crystallization is less likely to progress during heat cycle tests between 100°C and -40°C, and a decrease in seal strength at room temperature is suppressed. Furthermore, crystallization does not progress rapidly until the sealed portion reaches a temperature of 120°C, and the impact resistance of the sealant layer can be maintained. In addition, since crystallization progresses when the sealed portion reaches a temperature of 120°C or higher, the melting point of the polyester resin increases in a 170°C environment, making it less likely to melt and thus suppressing a decrease in sealing performance.

[0012] In the above-mentioned exterior material for energy storage devices, it is preferable that the polyester resin in the sealant layer consists of a crystalline resin and an amorphous resin. In this case, including a crystalline resin in the polyester resin improves the heat resistance of the sealant layer, while including an amorphous resin improves the fluidity of the polyester resin during heat sealing of the exterior material and the impact resistance of the sealant layer.

[0013] In the above-mentioned exterior material for energy storage devices, if the polyester resin of the sealant layer consists of a crystalline resin and an amorphous resin, it is preferable that the amorphous resin has constituent units derived from the acid component constituting the crystalline resin and constituent units derived from the glycol component. When the polyester resin of the sealant layer consists of a crystalline resin and an amorphous resin, and the amorphous resin has constituent units derived from the acid component constituting the crystalline resin and constituent units derived from the glycol component, the compatibility between the crystalline resin and the amorphous resin is increased, making it difficult for the crystalline resin and the amorphous resin to separate, and suppressing a decrease in the strength of the sealant layer. Furthermore, by including a crystalline resin in the polyester resin of the sealant layer, the heat resistance of the sealant layer is improved, while by including an amorphous resin in the polyester resin, the fluidity of the polyester resin during heat sealing of the exterior material and the impact resistance of the sealant layer can also be improved.

[0014] In the above-mentioned exterior material for energy storage devices, it is preferable that the constituent units derived from the acid component constituting the crystalline resin include constituent units derived from two or more acid components. In this case, the exterior material is more likely to have better sealing properties at room temperature and at 170°C.

[0015] In the above-mentioned exterior material for energy storage devices, it is preferable that the constituent units derived from the acid component constituting the crystalline resin include constituent units derived from terephthalic acid and constituent units derived from isophthalic acid. In this case, the exterior material is more likely to have better sealing properties at room temperature and at 170°C.

[0016] In the above-mentioned exterior material for energy storage devices, it is preferable that the proportion of the crystalline resin in the total 100% by mass of the crystalline resin and the amorphous resin is 70% by mass or more. In this case, the exterior material is more likely to have better sealing properties at room temperature and at 170°C.

[0017] In the above-mentioned exterior material for energy storage devices, when the outermost layer is formed by folding and overlapping the exterior material so that the sealant layers face each other, and then heat-sealing the overlapping portion under the conditions of a temperature of 280°C, a pressure of 0.5 MPa, and 5 seconds, it is preferable that the ratio of the crystallinity of the sealant layer in the unsealed portion to the crystallinity of the sealant layer in the sealed portion is 0.3 or more and 2.0 or less. In this case, the difference between the crystallinity (hardness) of the sealant layer in the sealed portion and the crystallinity of the sealant layer in the unsealed portion becomes smaller, so when stress is applied in the sealed portion to peel the sealant layers apart, excessive stress is less likely to be applied to the boundary between the sealed portion and the unsealed portion, the seal strength of the sealed portion is less likely to decrease, and a decrease in sealing performance can be suppressed.

[0018] In the above-mentioned exterior material for energy storage devices, when the outermost layer is formed by folding and overlapping the exterior material so that the sealant layers face each other, and then heat-sealing the overlapping portion at a temperature of 280°C, a pressure of 0.5 MPa, and for 5 seconds to form a sealed portion and an unsealed portion, it is preferable that the ratio of the crystallinity of the outermost layer in the unsealed portion to the crystallinity of the outermost layer in the sealed portion is 0.7 or more and 1.3 or less. In this case, the exterior material is more likely to have better sealing properties at room temperature and at 170°C. It is preferable that the crystallinity of the outermost layer is 3% or more and 20% or less. In this case, the exterior material is more likely to have better sealing properties at room temperature and at 170°C. In the above-mentioned exterior material for energy storage devices, the outermost layer has a crystallization temperature of 190°C or lower, and when the exterior material is folded and stacked so that the sealant layers face each other, and a heat seal is performed on the overlapping portion under the conditions of a temperature of 280°C, a pressure of 0.5 MPa, and 5 seconds to form a sealed portion and an unsealed portion, it is possible to set the cold crystallization temperature of the outermost layer in the sealed portion to 120°C or higher and 190°C or lower, and the ratio of the crystallization degree of the outermost layer in the unsealed portion to the crystallization degree of the outermost layer in the sealed portion to 0.7 or higher and 1.3 or lower. It is possible to do so, and it is preferable that the polyester resin of the sealant layer consists of a crystalline resin and an amorphous resin, the amorphous resin has constituent units derived from the acid component constituting the crystalline resin and constituent units derived from the glycol component, the constituent units derived from the acid component constituting the crystalline resin include constituent units derived from terephthalic acid and constituent units derived from isophthalic acid, the proportion of the crystalline resin in the total 100% by mass of the crystalline resin and the amorphous resin is 70% by mass or more, and the degree of crystallinity of the outermost layer is 3% or more and 20% or less. In this case, the exterior material can have even better sealing properties at room temperature and at 170°C.

[0019] In the above-described exterior material for energy storage devices, it is preferable that the energy storage device is an all-solid-state battery. The above-described exterior material for energy storage devices can have excellent sealing properties at room temperature and at 170°C, and is therefore particularly useful as an exterior material for all-solid-state batteries that may be exposed to a 170°C environment due to thermal runaway.

[0020] Another aspect of this disclosure provides an energy storage device comprising an energy storage element and an outer bag for housing the energy storage element, wherein the outer bag has the outer material described above. With the above energy storage device, the outer material for the energy storage device can have excellent sealing properties at room temperature and at 170°C. Therefore, even if the temperature of the energy storage element of the energy storage device exceeds 170°C due to thermal runaway and the outer material is placed in an environment of 170°C, the deterioration of the sealing properties of the outer bag can be suppressed, and the deterioration of the performance of the energy storage device can be suppressed. The above energy storage device is useful when it is an all-solid-state battery. This is because when an energy storage device is an all-solid-state battery, it may be placed in an environment of 170°C due to thermal runaway.

[0021] According to this disclosure, an exterior material for an energy storage device and an energy storage device are provided that can have excellent sealing properties at room temperature and at 170°C.

[0022] Figure 1 is a schematic cross-sectional view showing one embodiment of the exterior material for an energy storage device according to the present disclosure. Figure 2 is a schematic cross-sectional view showing another embodiment of the exterior material according to the present disclosure. Figure 3 is a perspective view showing one embodiment of an energy storage device according to the present disclosure.

[0023] Preferred embodiments of this disclosure will be described in detail below, with appropriate reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. Furthermore, the dimensional ratios in the drawings are not limited to those shown.

[0024] [Exterior Material for Energy Storage Devices] Figure 1 is a schematic cross-sectional view showing one embodiment of the exterior material for energy storage devices of the present disclosure. As shown in Figure 1, the exterior material for energy storage devices (hereinafter also simply referred to as "exterior material") 10 of this embodiment is an exterior material used in an energy storage device, and comprises a base layer 11, a first adhesive layer 12a, a barrier layer 13, a second adhesive layer 12b, and a sealant layer 16 in this order. The barrier layer 13 has a main body portion 13a. The sealant layer 16 has an outermost layer 16a on the side opposite to the barrier layer 13, and the outermost layer 16a contains polyester resin, the melting point of the outermost layer 16a is 190°C or higher and 258°C or lower, and the degree of crystallinity is 33% or less. With this exterior material 10, it is possible to have excellent sealing properties in a room temperature environment and a 170°C environment.

[0025] The barrier layer 13 may further have a corrosion-preventive treatment layer 14a on the base material layer 11 side of the main body portion 13a, and a corrosion-preventive treatment layer 14b on the sealant layer 16 side of the main body portion 13a.

[0026] The following will provide a detailed explanation of each layer that makes up the exterior material 10.

[0027] <Base Layer> The base layer 11 provides heat resistance during the sealing process when manufacturing energy storage devices and plays a role in suppressing the occurrence of pinholes that may occur during molding and distribution. In particular, for exterior materials of large-scale energy storage devices, it can also provide scratch resistance, chemical resistance, and insulation.

[0028] The base layer 11 is preferably a layer formed of an insulating resin. Suitable resins include polyester resin, polyamide resin, polyimide resin, polyamide-imide resin, polyetherketone resin, polyphenylene sulfide resin, polyetherimide resin, polysulfone resin, fluororesin, phenolic resin, melamine resin, urethane resin, allyl resin, silicone resin, epoxy resin, furan resin, acetylcellulose resin, and the like.

[0029] Among these resins, polyester resins and polyamide resins are preferred as the base layer 11 due to their excellent moldability. Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Examples of polyamide resins include nylon 6, nylon 6,6, copolymers of nylon 6 and nylon 6,6, nylon 6, nylon 9T, nylon 10, polymetaxylylene adipamide (MXD6), nylon 11, nylon 12, etc.

[0030] The base layer 11 may be in the form of a stretched or unstretched film, or as a coating film. Furthermore, the base layer 11 may be a single layer or a multilayer. If the base layer 11 is a multilayer, it is constructed by laminating layers made of different resins. If the base layer 11 is in the form of a film, it can be a film produced by co-extrusion or lamination via an adhesive. If the base layer 11 is a coating film, it can be a coating film obtained by coating multiple times with a coating film-forming composition. The base layer 11 can also be a multilayer by combining a film and a coating film.

[0031] When the above-mentioned resin is used in film form, the base layer 11 is preferably a biaxially oriented film. In this case, the moldability of the outer packaging material 10 is improved. Examples of stretching methods for biaxially oriented films include sequential biaxial stretching, tubular biaxial stretching, and simultaneous biaxial stretching. From the viewpoint of obtaining better deep-draw moldability, the biaxially oriented film is preferably a film stretched by tubular biaxial stretching.

[0032] The thickness of the base layer 11 is preferably 6 to 100 μm, more preferably 10 to 75 μm, and even more preferably 10 to 50 μm. A base layer thickness of 6 μm or more tends to improve the pinhole resistance and insulation properties of the exterior material 10. A base layer thickness of 100 μm or less allows for a reduction in the total thickness of the exterior material 10.

[0033] Furthermore, it is preferable that the base layer 11 has a melting temperature higher than that of the sealant layer 16. If the sealant layer 16 has a multilayer structure, the melting temperature of the sealant layer 16 refers to the melting temperature of the layer with the highest melting temperature. By having the base layer 11 have a melting temperature higher than that of the sealant layer 16, it is possible to suppress deterioration of the appearance of the exterior material 10 due to the melting of the base layer 11 (outer layer) during heat sealing.

[0034] The melting temperature of the base layer 11 is preferably 290°C or higher. However, it is preferable that the melting temperature of the base layer 11 is 350°C or lower. Examples of resin films that can be used as the base layer 11 and have a melting temperature within the above range include nylon film, polyester film such as PET film, polyamide film, and polyphenylene sulfide film (PPS film). The base layer 11 may be made using a commercially available film, or it may be formed by coating (application and drying of a coating liquid). The base layer 11 may also be formed by coating with a thermosetting resin. Furthermore, the base layer 11 may contain various additives (for example, flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, tackifiers, etc.).

[0035] Melting temperature T of the base layer 11 １１ and the melting temperature T of the sealant layer 16 １６ The difference (T １１ -T １６ The temperature is preferably 20°C or higher. This temperature difference of 20°C or higher further effectively suppresses deterioration of the appearance of the exterior material 10 caused by heat sealing.

[0036] <First Adhesive Layer> The first adhesive layer 12a is a layer that adheres the base material layer 11 and the barrier layer 13. Specific examples of the material constituting the first adhesive layer 12a include polyurethane resin, which is a cured product of an adhesive composition containing a main agent and a curing agent. Examples of the main agent include polyols such as polyester polyol, polyether polyol, acrylic polyol, and carbonate polyol. The various polyols described above may be used alone or in combination of two or more thereof depending on the functions and performance required for the exterior material 10. In addition, as a material constituting the first adhesive layer 12a, other than the above, a material containing an epoxy resin as a main agent and blended with a curing agent can also be used.

[0037] The adhesive composition described above may further contain other various additives and stabilizers depending on the performance required for the first adhesive layer 12a.

[0038] The curing agent contained in the adhesive composition includes at least one polyfunctional isocyanate compound selected from the group consisting of alicyclic isocyanate multimers and isocyanate multimers having an aromatic ring in the molecular structure. Examples of the polyfunctional isocyanate compound include a nurate of isophorone diisocyanate, an adduct of tolylene diisocyanate, an adduct of hexamethylene diisocyanate, a biuret and a nurate of hexamethylene diisocyanate, a biuret and a nurate of tolylene diisocyanate, an adduct, a biuret and a nurate of diphenylmethane diisocyanate, and an adduct, a biuret and a nurate of xylylene diisocyanate.

[0039] As the curing agent, an alicyclic isocyanate multimer and an isocyanate multimer having an aromatic ring in the molecular structure may be used in combination. The combined use of these tends to further improve heat resistance.

[0040] From the viewpoint of further improving heat resistance, the adhesive composition preferably contains at least one polyol selected from the group consisting of polyester polyols, acrylic polyols, and polycarbonate diols. Among these, polyester polyols are more preferred from the viewpoint of further improving heat resistance.

[0041] In the adhesive composition, the ratio of the number of isocyanate groups in the polyfunctional isocyanate compound to the number of hydroxyl groups in the polyol (NCO / OH) may be 1.5 to 40.0 or 15.0 to 30.0. When this ratio is 1.5 or higher, the curing agents react with each other, and by-products such as urea resin and biuret resin are more easily formed. Since these by-products contain active hydrogen groups, they interact with the polar groups of adjacent layers, further improving the interfacial adhesion between the first adhesive layer 12a and the substrate layer 11 and barrier layer 13. As a result, the heat resistance of the exterior material 10 tends to improve. On the other hand, when the above ratio is 40.0 or lower, the laminate strength of the exterior material 10 can be further improved in both room temperature and high-temperature environments.

[0042] The thickness of the first adhesive layer 12a is not particularly limited, but from the viewpoint of obtaining desired adhesive strength, conformability, and processability, it is preferably 1 to 10 μm, and more preferably 2 to 7 μm.

[0043] The mass per unit area of ​​the first adhesive layer 12a is set to 2.0 to 6.0 g / m², from the viewpoint of ensuring superior laminate strength in both room temperature and high temperature environments, as well as obtaining superior deep-draw moldability. ２ It may be 2.5 to 5.0 g / m ２ It may also be 3.0 to 4.0 g / m ２ That's fine.

[0044] <Barrier Layer> The barrier layer 13 has water vapor barrier properties that prevent moisture from entering the inside of the energy storage device. The barrier layer 13 may also have ductility for deep drawing molding.

[0045] (Main body) The barrier layer 13 includes the main body 13a. As the main body 13a, for example, various metal foils such as aluminum, stainless steel, and copper, or metal vapor-deposited films, inorganic oxide vapor-deposited films, carbon-containing inorganic oxide vapor-deposited films, or films having these vapor-deposited films can be used. As films having vapor-deposited films, for example, aluminum vapor-deposited films and inorganic oxide vapor-deposited films can be used. As the main body 13a, metal foil is preferred in terms of mass (specific gravity), barrier properties such as moisture resistance, processability and cost, and aluminum foil or stainless steel foil is more preferred.

[0046] As the aluminum foil, soft aluminum foil that has undergone annealing treatment is particularly preferred because it can provide the desired ductility during molding. To further improve pinhole resistance and ductility during molding, it is even more preferable to use aluminum foil containing iron. The iron content in the aluminum foil is preferably 0.1 to 9.0% by mass, and more preferably 0.5 to 2.0% by mass, of 100% by mass of the aluminum foil. By having an iron content of 0.1% by mass or more, an exterior material 10 with superior pinhole resistance and ductility can be obtained. By having an iron content of 9.0% by mass or less, an exterior material 10 with superior flexibility can be obtained. As the aluminum foil, untreated aluminum foil may be used, but it is preferable to use degreased aluminum foil in order to provide corrosion resistance. When degreasing the aluminum foil, the degreasing treatment may be applied to only one side of the aluminum foil, or to both sides.

[0047] The thickness of the barrier layer 13 is not particularly limited, but is preferably 9 to 200 μm, and more preferably 15 to 100 μm, considering barrier properties, pinhole resistance, and processability.

[0048] (Corrosion Prevention Treatment Layers) The corrosion prevention treatment layers 14a and 14b are layers provided to prevent corrosion of the main body portion 13a of the barrier layer 13. The corrosion prevention treatment layer 14a plays a role in increasing the adhesion between the barrier layer 13 and the first adhesive layer 12a. For this reason, the corrosion prevention treatment layer 14a is in contact with the first adhesive layer 12a. The corrosion prevention treatment layer 14b plays a role in increasing the adhesion between the barrier layer 13 and the second adhesive layer 12b. For this reason, the corrosion prevention treatment layer 14b is in contact with the second adhesive layer 12b. The corrosion prevention treatment layers 14a and 14b may be layers with the same configuration or layers with different configurations.

[0049] The corrosion-preventive treatment layers 14a and 14b can be formed, for example, by performing a degreasing treatment, a hot water modification treatment, an anodizing treatment, a chemical conversion treatment, a coating-type corrosion-preventive treatment in which a coating agent having corrosion-preventive properties is applied to the main body portion 13a which serves as the base material for the corrosion-preventive treatment layers 14a and 14b, or a combination of these treatments.

[0050] Of the processes described above, degreasing, hydrothermal modification, and anodic oxidation, particularly hydrothermal modification and anodic oxidation, are processes that dissolve the surface of the metal foil (aluminum foil) with a treatment agent to form a metal compound (aluminum compound (boehmite, anodized aluminum)) with excellent corrosion resistance. For this reason, such processes are sometimes included in the definition of chemical conversion treatment in order to obtain a structure in which a co-continuous structure is formed from the main body 13a of the barrier layer 13 to the corrosion prevention treatment layers 14a and 14b.

[0051] Degreasing treatments include acid degreasing and alkaline degreasing. Acid degreasing can be performed using inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid individually, or using mixtures of these inorganic acids. Furthermore, by performing acid degreasing using an acid degreasing agent obtained by dissolving a fluorine-containing compound such as ammonium monohydrogen-difluoride in the above-mentioned inorganic acid, it is possible not only to degrease the main body portion 13a of the barrier layer 13 but also to form a fluoride of the passive metal, and such acid degreasing is effective in terms of hydrofluoric acid resistance. Alkaline degreasing can be performed using sodium hydroxide, etc.

[0052] As the hydrothermal conversion treatment described above, for example, boehmite treatment obtained by immersing the main body 13 in boiling water added with triethanolamine can be used. As the anodizing treatment described above, for example, alumite treatment can be used. As the chemical conversion treatment described above, for example, chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, or a treatment combining two or more of these may be used. The above-described degreasing treatment may be performed before these hydrothermal conversion treatment, anodizing treatment, and chemical conversion treatment.

[0053] It should be noted that the aforementioned chemical conversion treatment is not limited to wet methods, and for example, a method of mixing a treatment agent used in these treatments with a resin component and then applying the mixture may also be used. From the viewpoint of waste liquid treatment, coating-type chromate treatment may be mentioned as the aforementioned corrosion prevention treatment.

[0054] Examples of the coating agent used for coating-type corrosion prevention treatments include coating agents containing at least one selected from the group consisting of rare earth element oxide sols, anionic polymers, and cationic polymers.

[0055] The mass per unit area of the corrosion prevention treatment layers 14a, 14b is 0.005 g / m ２ or more and 0.200 g / m ２ or less, alternatively, it may be 0.010 g / m ２ or more and 0.100 g / m ２ or less. If the mass per unit area is 0.005 g / m ２ or more, good corrosion prevention function can be imparted to the barrier layer 13. Even if the mass per unit area exceeds 0.200 g / m ２ , the corrosion prevention function becomes saturated. Although the above content is described by mass per unit area, if the specific gravity of the corrosion prevention treatment layers 14a, 14b is known, it is also possible to obtain the thickness of the corrosion prevention treatment layers 14a, 14b by conversion therefrom.

[0056] The thickness of the corrosion-preventive treatment layers 14a and 14b may be, for example, 10 nm to 5 μm, or 20 nm to 500 nm, from the viewpoint of corrosion prevention function and anchor function.

[0057] From the viewpoint of adhesion between the sealant layer 16 and the barrier layer 13, the corrosion-preventive treatment layers 14a and 14b may, for example, contain cerium oxide, 1 to 100 parts by mass of phosphoric acid or phosphate per 100 parts by mass of cerium oxide, and a cationic polymer.

[0058] <Second Adhesive Layer> The second adhesive layer 12b is a layer that adheres the barrier layer 13 and the sealant layer 16. A general adhesive for adhering the barrier layer 13 and the sealant layer 16 can be used for the second adhesive layer 12b. The second adhesive layer 12b may be the same as or different from the first adhesive layer 12a.

[0059] The thickness of the second adhesive layer 12b is not particularly limited, but from the viewpoint of obtaining the desired adhesive strength and processability, it is preferably 1 to 10 μm, and more preferably 2 to 7 μm.

[0060] <Sealant Layer> The sealant layer 16 is a layer that provides heat sealing properties to the exterior material 10, and is placed on the inside and heat-sealed (heat-fused) during the assembly of the energy storage device. The sealant layer 16 has an outermost layer 16a on the opposite side of the barrier layer 13, and the outermost layer 16a contains polyester resin, the melting point of the outermost layer 16a is between 190°C and 258°C, and the degree of crystallinity is 33% or less.

[0061] (Polyester Resin) The polyester resin is not particularly limited as long as the melting point and crystallinity of the outermost layer 16a are within the above range. Examples of polyester resins include polyester resins containing constituent units derived from an acid component and constituent units derived from a glycol component. In other words, examples of polyester resins include polyester resins obtained by copolymerizing an acid component and a glycol component. Examples of acid components include phthalic acid, terephthalic acid, isophthalic acid, sodium sulfisophthalate, naphthalenedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, dimer acid, cyclohexanedicarboxylic acid, hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, etc. These may be used individually or in combination of two or more. Examples of glycol components include ethylene glycol, butanediol, pentanediol, hexanediol, neopentyl glycol, diethylene glycol, polytetramethylene glycol, cyclohexanedimethanol, propanediol, etc. The polyester resin may be a copolymerized polyester resin having constituent units derived from multiple types of acid components and constituent units derived from one type of glycol component, a copolymerized polyester resin having constituent units derived from one type of acid component and constituent units derived from multiple types of glycol components, or a copolymerized polyester resin having constituent units derived from multiple types of acid components and constituent units derived from multiple glycol components, or a mixed resin obtained by blending multiple types of polyester resins. Furthermore, it is preferable that the polyester resin consists of a crystalline resin and an amorphous resin. In this case, the inclusion of a crystalline resin in the polyester resin improves the heat resistance of the sealant layer 16, while the inclusion of an amorphous resin improves the fluidity of the polyester resin during heat sealing of the exterior material 10 and the impact resistance of the sealant layer 16. When the polyester resin consists of a crystalline resin and an amorphous resin, it is preferable that the amorphous resin has constituent units derived from acid components constituting the crystalline resin and constituent units derived from glycol components.In this case, the polyester resin of the sealant layer 16 consists of a crystalline resin and an amorphous resin, and the amorphous resin has constituent units derived from the acid component that makes up the crystalline resin and constituent units derived from the glycol component, which increases the compatibility between the crystalline resin and the amorphous resin, making it difficult for the crystalline resin and the amorphous resin to separate and suppressing a decrease in the strength of the sealant layer 16. Furthermore, by including a crystalline resin in the polyester resin of the sealant layer 16, the heat resistance of the sealant layer 16 is improved, while by including an amorphous resin, the fluidity of the polyester resin during heat sealing of the exterior material 10 and the impact resistance of the sealant layer 16 can also be improved. Here, it is preferable that the constituent units derived from the acid component that makes up the crystalline resin include constituent units derived from two or more types of acid components. In this case, the exterior material 10 is more likely to have better sealing properties at room temperature and at 170°C.

[0062] When the polyester resin consists of a crystalline resin and an amorphous resin, the proportion of crystalline resin in the total 100% by mass of the crystalline resin and amorphous resin is preferably 50% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, or 90% by mass or more. When the proportion of crystalline resin in the total 100% by mass of the crystalline resin and amorphous resin is 50% by mass or more (preferably 70% by mass or more), the exterior material 10 is more likely to have better sealing properties at room temperature and at 170°C. The proportion of crystalline resin in the total 100% by mass of the crystalline resin and amorphous resin is less than 100% by mass, but is preferably 98% by mass or less, 95% by mass or less, or 92% by mass or less.

[0063] (Additives) The outermost layer 16a may further contain additives as needed, such as crystal nucleating agents, crystallization inhibitors, antioxidants, hydrogen sulfide adsorbents, oxygen adsorbents, moisture adsorbents, slip agents, flame retardants, antiblocking agents (AB agents), light stabilizers, dehydrating agents, thickeners, and tackifiers. From the viewpoint of controlling the degree of crystallinity, at least one of a crystal nucleating agent (crystallization accelerator) and a crystallization inhibitor is preferred as an additive. Examples of crystal nucleating agents (crystallization accelerators) include metal benzoate salts, talc, metal oxalate salts, metal stearate salts, ionomers, kaolin, carbon black, metal oxides, metal sulfates, and silicon dioxide.

[0064] (Layer structure) The sealant layer 16 may be a single layer or a laminate of multiple layers. If the sealant layer 16 is a single layer, it will consist only of the outermost layer 16a. If the sealant layer 16 is a laminate of multiple layers, the layer furthest from the barrier layer 13 will be the outermost layer 16a. The melting points and crystallinity of the layers other than the outermost layer 16a may be within or outside the range of the melting point and crystallinity of the outermost layer 16a. For example, from the viewpoint of film formation, the laminate may consist of the layers other than the outermost layer 16a, and the outermost layer 16a, in this order from the barrier layer 13 side. Here, the melting points and crystallinity of the layers other than the outermost layer 16a are outside the range of the melting point and crystallinity of the outermost layer 16a. From the viewpoint of sealing performance, it is preferable that the melting points and crystallinity of all layers other than the outermost layer 16a are within the range of the melting point and crystallinity of the outermost layer 16a. If the sealant layer 16 is composed of a laminate of multiple layers, the sealant layer 16 may be manufactured by bonding each layer together with an adhesive after pre-forming each layer, by co-extrusion, or by extruding another layer onto a pre-formed layer.

[0065] (Melting Point) The melting point of the outermost layer 16a is 190°C or higher and 258°C or lower. Having a melting point of 258°C or lower for the outermost layer allows the polyester resin to melt sufficiently and flow easily during heat sealing of the exterior material 10, causing the molecules to intertwine. This enables the sealant layer 16 to have excellent sealing properties at room temperature and at 170°C. Furthermore, having a melting point of 190°C or higher for the outermost layer 16a prevents excessive molecular motion of the polyester resin, suppressing melting. This allows the sealant layer to have excellent sealing properties even at 170°C. The melting point of the outermost layer 16a is preferably 200°C or higher and 250°C or lower, and more preferably 210°C or higher and 240°C or lower.

[0066] (Crystallization) The crystallinity of the outermost layer 16a is 33% or less. When the crystallinity of the outermost layer 16a is 33% or less, the polyester resin melts sufficiently and flows easily when the exterior material 10 is heat-sealed, and the molecules intertwine, so that the sealant layer can have excellent sealing properties at room temperature and at 170°C. However, since the outermost layer 16a has a melting point, the crystallinity of the outermost layer 16a is greater than 0%. The crystallinity is preferably 25% or less, more preferably 20% or less, and particularly preferably 15% or less. The crystallinity may be 10% or less, 9% or less, or 8% or less. The crystallinity may be 3% or more, 5% or more, or 7% or more. The crystallinity may be greater than 0% and 25% or less, 3% or more and 20% or less, 5% or more and 15% or less, 5% or more and 10% or less, 7% or more and 9% or less, or 7% or more and 8% or less. When the outermost layer 16a is formed by folding and overlapping the exterior material 10 so that the sealant layers 16 face each other, and then heat-sealing the overlapping portion at a temperature of 280°C, a pressure of 0.5 MPa, and a time of 5 seconds to form a sealed portion and an unsealed portion, it is preferable that the ratio of the crystallinity of the outermost layer 16a in the unsealed portion to the crystallinity of the outermost layer 16a in the sealed portion (hereinafter also referred to as "crystallinity ratio R") be 0.3 or more and 2.0 or less. Preferably, the crystallinity ratio R is 0.5 or more and 1.5 or less, and more preferably 0.7 or more and 1.3 or less. Preferably, the crystallinity ratio R is 0.7 or more and 1.0 or less, and more preferably 0.8 or more and 1.0 or less. In this case, the exterior material is more likely to have better sealing properties at room temperature and at 170°C.

[0067] (Crystallization Temperature) The outermost layer 16a is a layer having a crystallization temperature of 190°C or lower. Under room temperature conditions, a crystallization temperature of 190°C or lower for the outermost layer 16a makes it difficult for the polyester resin to crystallize, resulting in low crystallinity, which can improve the impact resistance of the sealant layer 16. The crystallization temperature of the outermost layer 16a is preferably 175°C or lower, and more preferably 155°C or lower. The crystallization temperature of the outermost layer 16a is preferably 130°C or higher, and more preferably 140°C or higher. The outermost layer 16a may be a layer in which a crystallization peak (exothermic peak in crystallization) cannot be confirmed. Under room temperature conditions, the inability to confirm a crystallization peak in the outermost layer 16a makes it difficult for the polyester resin to crystallize, resulting in low crystallinity, which can improve the impact resistance of the sealant layer 16. Here, "no crystallization peak can be confirmed" means that, when the outermost layer 16a is held at 20°C for 10 minutes, heated from 20°C to 300°C at a heating rate of 10°C / min and held at 300°C for 10 minutes, and then cooled from 300°C to 20°C at a cooling rate of 10°C / min, no crystallization peak appearing above the baseline of the DSC curve can be confirmed, and more specifically, the crystallization peak is 5 mJ / mg or less.

[0068] (Cold Crystallization Temperature) The cold crystallization temperature is the temperature at which amorphous resin rapidly transforms into crystalline resin. When the outermost layer 16a is formed by folding and overlapping the exterior material 10 so that the sealant layers 16 face each other, and then heat-sealing the overlapping portion under the conditions of a temperature of 280°C, a pressure of 0.5 MPa, and 5 seconds, it is preferable that the cold crystallization temperature be between 120°C and 190°C. By having the cold crystallization temperature of the outermost layer 16a in the seal portion be between 120°C and 190°C, crystallization is less likely to progress rapidly during the heat cycle test from 100°C to -40°C, and the decrease in seal strength at room temperature is suppressed. Furthermore, crystallization does not progress rapidly until the seal portion reaches a temperature of 120°C, and the impact resistance of the sealant layer 16 can be maintained. In addition, since crystallization progresses when the seal portion reaches a temperature of 120°C or higher, the melting point of the polyester resin increases in a 170°C environment, making it less likely to melt and thus suppressing a decrease in sealing performance. The cold crystallization temperature is more preferably 135°C to 185°C, and particularly preferably 160°C to 180°C.

[0069] (Tg) The Tg (glass transition temperature) of the outermost layer 16a is not particularly limited, but from the viewpoint of seal strength (impact resistance) at room temperature, it is preferably 100°C or less, and from the viewpoint of seal strength (heat resistance) at 170°C, it is preferably 70°C or more.

[0070] (Adjustment of melting point, crystallinity, cold crystallization temperature, and crystallization temperature) The melting point, crystallinity, cold crystallization temperature, and crystallization temperature can be adjusted by the base resin, additives, heat treatment, stretching, etc. For example, with respect to the base resin, the melting point, crystallinity, cold crystallization temperature, and crystallization temperature can be adjusted by, for example, the type of acid component and glycol component, the polymerization form (copolymer or homopolymer), and the blending of multiple types of polyester resins. In particular, the crystallinity of the resulting base resin can be adjusted by adding a third component other than the acid component and glycol component. In particular, the crystallinity can be greatly reduced by adding the third component in an amount of 20 mol% or more and 80 mol% or less. With respect to additives, the melting point, crystallinity, cold crystallization temperature, and crystallization temperature can be adjusted by using crystal nucleating agents such as metal salts. With heat treatment, the amorphous resin changes into a crystalline resin by applying heat, so the melting point, crystallinity, cold crystallization temperature, and crystallization temperature can be adjusted. Regarding stretching, stretching causes molecules to orient themselves, making crystal formation easier, thus allowing for adjustment of the melting point, degree of crystallinity, cold crystallization temperature, and crystallization temperature.

[0071] (Thickness) The thickness of the sealant layer 16 is not particularly limited and may be, for example, 5 to 250 μm, but from the viewpoint of sealing performance, film formation performance, insulation performance and energy density, it is preferably 25 to 150 μm, and more preferably 40 to 100 μm. The sealant layer 16 may consist only of the outermost layer 16a, or it may consist of the outermost layer 16a and layers other than the outermost layer 16a. In this case, the sealant layer 16 may consist of layers other than the outermost layer 16a and the outermost layer 16a in order from the barrier layer 13 side. Here, if the laminate is composed of layers other than the outermost layer 16a whose melting point and crystallinity are outside the range of the melting point and crystallinity of the outermost layer 16a, it is preferable that the ratio of the thickness of the outermost layer 16a to the total thickness of the sealant layer 16 is 50% or more.

[0072] In the exterior material 10 for energy storage devices, the outermost layer 16a contains polyester resin, has a melting point of 190°C or higher and 258°C or lower, a degree of crystallinity of 3% or higher and 20% or lower, and a crystallization temperature of 190°C or lower. When the exterior material 10 is folded and stacked so that the sealant layers 16 face each other, and heat sealing is performed on the overlapping portion under the conditions of a temperature of 280°C, a pressure of 0.5 MPa, and 5 seconds to form a sealed portion and an unsealed portion, the cold crystallization temperature of the outermost layer 16a in the sealed portion is set to be 120°C or higher and 190°C or lower. It is possible to set the crystallinity ratio R to 0.7 or more and 1.3 or less, and it is preferable that the polyester resin consists of a crystalline resin and an amorphous resin, the amorphous resin has constituent units derived from the acid component constituting the crystalline resin and constituent units derived from the glycol component, the constituent units derived from the acid component constituting the crystalline resin include constituent units derived from terephthalic acid and constituent units derived from isophthalic acid, and the proportion of crystalline resin in the total of 100% by mass of the crystalline resin and amorphous resin is 70% by mass or more. In this case, the exterior material 10 can have even better sealing properties in a room temperature environment and a 170°C environment.

[0073] The melting point of the outermost layer 16a is preferably 200°C to 240°C, more preferably 210°C to 230°C.

[0074] The degree of crystallinity of the outermost layer 16a is preferably 3% to 15%, and more preferably 5% to 10%.

[0075] The crystallization temperature of the outermost layer 16a is preferably 175°C or lower, more preferably 155°C or lower. The crystallization temperature of the outermost layer 16a is preferably 130°C or higher, more preferably 140°C or higher.

[0076] The cold crystallization temperature is more preferably 135°C to 185°C, and particularly preferably 160°C to 180°C.

[0077] The degree of crystallinity ratio R is preferably 0.7 or more and 1.0 or less, and more preferably 0.8 or more and 1.0 or less. In this case, the exterior material is more likely to have better sealing properties at room temperature and at 170°C.

[0078] The proportion of crystalline resin in the total 100% by mass of crystalline resin and amorphous resin is more preferably 80% by mass or more, and particularly preferably 90% by mass or more. When the proportion of crystalline resin in the total 100% by mass of crystalline resin and amorphous resin is preferably 70% by mass or more, the exterior material 10 is more likely to have better sealing properties at room temperature and at 170°C.

[0079] Although preferred embodiments of the exterior material for energy storage devices of this embodiment have been described in detail above, this disclosure is not limited to the specific embodiments described above.

[0080] In the exterior material 10 shown in Figure 1, the barrier layer 13 and the sealant layer 16 are laminated using a second adhesive layer 12b. However, as shown in the exterior material 20 for the energy storage device in Figure 2, the barrier layer 13 and the sealant layer 16 may be directly laminated.

[0081] The exterior material for energy storage devices of this disclosure can be used as an exterior material for secondary batteries such as lithium-ion batteries, nickel-metal hydride batteries, and lead-acid batteries, as well as for electrochemical capacitors such as electric double-layer capacitors. However, since the exterior material 10 can have excellent sealing properties at room temperature and at 170°C, it is particularly useful as an exterior material for all-solid-state batteries that may be placed at 170°C due to thermal runaway.

[0082] [Energy Storage Device] Next, embodiments of the energy storage device of the present disclosure will be described. Figure 3 is a perspective view showing one embodiment of the energy storage device of the present disclosure. As shown in Figure 3, the all-solid-state battery 50 as an energy storage device comprises an energy storage element 52 and an outer bag 54 that houses the energy storage element 52. The all-solid-state battery 50 may further include two metal terminals (current extraction terminals) 53 for extracting current from the energy storage element 52 to the outside. The outer bag 54 has the outer material 10 described above and is used as a container for housing the energy storage element 52. In the outer material 10, the base layer 11 is oriented outwards from the outer bag 54, and the sealant layer 16 is oriented inwards from the outer bag 54 (towards the energy storage element 52). The outer bag 54 can be formed by folding one outer material 10 in half and heat-sealing the peripheral edge, or by overlapping two outer materials 10 and heat-sealing the peripheral edge. In the outer bag 54, the heat-sealed peripheral portion is the sealed portion 54a, and the remaining portion that is not heat-sealed is the non-heat-sealed portion 54b. The metal terminal 53 is sandwiched between the outer bag 54 with the sealant layer 16 on the inside. The metal terminal 53 may also be sandwiched between the outer bag 54 via a tab sealant. The metal terminal 53 is a part of the current collector that is exposed to the outside of the outer material 10, and is made of metal foil such as copper foil or aluminum foil.

[0083] The energy storage element 52 has a pair of electrodes and a solid electrolyte sandwiched between the pair of electrodes. One of the electrodes is the positive electrode and the other is the negative electrode. Examples of solid electrolytes include sulfide-based solid electrolytes and oxide-based solid electrolytes.

[0084] With the all-solid-state battery 50, the outer casing material 10 can have excellent sealing properties at room temperature and at 170°C. Therefore, even if the temperature of the energy storage element 52 of the all-solid-state battery 50 exceeds 170°C due to thermal runaway and the outer casing material 10 is placed in a 170°C environment, the deterioration of the sealing properties of the outer casing bag 54 can be suppressed, and the deterioration of the performance of the all-solid-state battery 50 can be suppressed.

[0085] In the case of the all-solid-state battery 50, the outer bag 54 may have an outer material 20 instead of the outer material 10.

[0086] Furthermore, instead of the all-solid-state battery 50, secondary batteries such as lithium-ion batteries, nickel-metal hydride batteries, and lead-acid batteries, as well as electrochemical capacitors such as electric double-layer capacitors and semi-solid-state batteries can also be used as energy storage devices.

[0087] The outline of this disclosure is as follows: [1] An exterior material for use in an energy storage device, comprising a base layer, a barrier layer, and a sealant layer in this order, wherein the sealant layer has an outermost layer on the side opposite to the barrier layer, the outermost layer contains a polyester resin, the melting point of the outermost layer is 190°C or more and 258°C or less, and the degree of crystallinity is 33% or less. [2] The exterior material for an energy storage device according to [1], wherein the outermost layer has a crystallization temperature of 190°C or less or a crystallization peak cannot be confirmed. [3] The exterior material for an energy storage device according to [1] or [2], wherein when the exterior material is folded and overlapped so that the sealant layers face each other, and a heat seal is performed on the overlapping portion under the conditions of a temperature of 280°C, a pressure of 0.5 MPa, and 5 seconds to form a seal portion, the cold crystallization temperature of the outermost layer in the seal portion can be set to 120°C or more and 190°C or less. [4] An exterior material for an energy storage device according to any one of [1] to [3], wherein the polyester resin of the sealant layer comprises a crystalline resin and an amorphous resin. [5] An exterior material for an energy storage device according to [4], wherein the amorphous resin comprises constituent units derived from an acid component constituting the crystalline resin and constituent units derived from a glycol component. [6] An exterior material for an energy storage device according to [4] or [5], wherein the crystalline resin comprises constituent units derived from an acid component constituting the crystalline resin and constituent units derived from a glycol component. [7] An exterior material for an energy storage device according to [6], wherein the constituent units derived from an acid component constituting the crystalline resin are composed of constituent units derived from two or more acid components. [8] An exterior material for an energy storage device according to [7], wherein the constituent units derived from an acid component constituting the crystalline resin include constituent units derived from terephthalic acid and constituent units derived from isophthalic acid. [9] An exterior material for an energy storage device according to any one of [4] to [8], wherein the proportion of the crystalline resin in the total 100% by mass of the crystalline resin and the amorphous resin is 70% by mass or more.

[10] The exterior material for an energy storage device according to any one of [1] to [9], wherein the outermost layer is formed by folding and overlapping the exterior material so that the sealant layers face each other, and by heat sealing the overlapping portion at a temperature of 280°C, a pressure of 0.5 MPa, and a second of 5 seconds, thereby forming a sealed portion and an unsealed portion, wherein the ratio of the crystallinity of the outermost layer in the unsealed portion to the crystallinity of the outermost layer in the sealed portion is 0.3 or more and 2.0 or less.

[11] The exterior material for an energy storage device according to

[10] , wherein the outermost layer is formed by folding and overlapping the exterior material so that the sealant layers face each other, and by heat sealing the overlapping portion at a temperature of 280°C, a pressure of 0.5 MPa, and a second of 5 seconds, thereby forming a sealed portion and an unsealed portion, wherein the ratio of the crystallinity of the outermost layer in the unsealed portion to the crystallinity of the outermost layer in the sealed portion is 0.7 or more and 1.3 or less.

[12] The exterior material for an energy storage device according to any one of [1] to

[11] , wherein the crystallinity of the outermost layer is 3% or more and 20% or less.

[13] The outermost layer has a crystallization temperature of 190°C or less, and when the exterior material is folded and stacked so that the sealant layers face each other, and heat sealing is performed on the overlapping portion at a temperature of 280°C, a pressure of 0.5 MPa, and for 5 seconds to form a sealed portion and an unsealed portion, it is possible to set the cold crystallization temperature of the outermost layer in the sealed portion to 120°C or more and 190°C or less, the ratio of the degree of crystallization of the outermost layer in the unsealed portion to the degree of crystallization of the outermost layer in the sealed portion to 0.7 or more and 1.3 or less, the polyester resin of the sealant layer consists of a crystalline resin and an amorphous resin, the amorphous resin has constituent units derived from an acid component constituting the crystalline resin and constituent units derived from a glycol component, the constituent units derived from the acid component constituting the crystalline resin include constituent units derived from terephthalic acid and constituent units derived from isophthalic acid, and the proportion of the crystalline resin in the total of 100% by mass of the crystalline resin and the amorphous resin is 70% by mass or more. The exterior material for an energy storage device according to [1], wherein the crystallinity of the outermost layer is 3% or more and 20% or less.

[14] The exterior material for an energy storage device according to any one of [1] to

[13] , wherein the energy storage device is an all-solid-state battery.

[15] An energy storage device comprising an energy storage element and an outer bag for housing the energy storage element, wherein the outer bag has an outer material as described in any of [1] to

[13] .

[16] The energy storage device according to

[15] , which is an all-solid-state battery.

[0088] The present disclosure will be described in detail below using examples, but the present disclosure is not limited to the following examples.

[0089] [Materials Used] The materials used as the base layer, the first adhesive for forming the first adhesive layer, the second adhesive for forming the second adhesive layer, the material for forming the first corrosion-preventive treatment layer, the material for forming the second corrosion-preventive treatment layer, the metal foil, and the sealant layer are as follows.

[0090] <Substrate layer> PET: Biaxially oriented polyethylene terephthalate film with corona treatment on one side (thickness 25 μm, melting point 260°C)

[0091] <First adhesive for forming the first adhesive layer> An adhesive (first adhesive) prepared by blending a polyester polyol (manufactured by Showa Denko Materials Co., Ltd., product name: Teslac 2505-63, hydroxyl value: 7-11 mg KOH / g) and a nurate of isophorone diisocyanate (manufactured by Mitsui Chemicals, Inc., product name: Takenate 600) so that the NCO / OH ratio is 20.0, and diluting it with ethyl acetate to a solid content of 26% by mass.

[0092] <Second adhesive for forming the second adhesive layer> An adhesive (second adhesive) prepared by blending a polyester polyol (manufactured by Showa Denko Materials Co., Ltd., product name: Teslac 2505-63, hydroxyl value: 7-11 mg KOH / g) and a nurate of isophorone diisocyanate (manufactured by Mitsui Chemicals, Inc., product name: Takenate 600) so that the NCO / OH ratio is 20.0, and diluting it with ethyl acetate to a solid content of 26% by mass.

[0093] <Materials for forming the first corrosion-preventive treatment layer and materials for forming the second corrosion-preventive treatment layer> The materials for forming the first corrosion-preventive treatment layer and the materials for forming the second corrosion-preventive treatment layer are as follows (CL-1) and (CL-2). (CL-1): Sodium polyphosphate stabilized cerium oxide sol adjusted to a solid content concentration of 10% by mass using distilled water as the solvent. (CL-2): A composition adjusted to a solid content concentration of 5% by mass using distilled water as the solvent. The above sodium polyphosphate stabilized cerium oxide sol was obtained by blending 10 parts by mass of sodium phosphoric acid with 100 parts by mass of cerium oxide. In addition, in the above composition, the mass ratio of "polyallylamine (manufactured by Nitto Boseki Co., Ltd.)" and "polyglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation)" was 90:10.

[0094] <Metal foil (60 μm thickness)> Annealed and degreased soft aluminum foil (manufactured by Toyo Aluminum Co., Ltd., "8079 material")

[0095] <Sealant Layer> The base resins used to form the sealant layer are polyester resins A to H, polypropylene resin I, and polyester elastomer J, as shown in Table 1 below. In Table 1 below, "-" in the melting point column indicates that no melting peak was observed in the base resin, i.e., the base resin is an amorphous resin.

[0096]

[0097] (Examples 1, 4 and 5, Comparative Examples 1, 5, 6 and 8-10) First, a first corrosion-preventive treatment layer and a second corrosion-preventive treatment layer were formed on both sides of the metal foil, respectively, to create a barrier layer. Specifically, first, the above (CL-1) was applied to one side of the metal foil at a dry coating rate of 70 mg / m². ２ The material was coated using microgravure coating and then baked in a drying unit at 200°C. Next, (CL-2) was applied to the resulting layer at a dry coating rate of 20 mg / m². ２By applying a microgravure coating in this manner, a composite layer consisting of (CL-1) and (CL-2) was formed as the first corrosion-preventive treatment layer. Next, (CL-1) was applied to the other side of the metal foil at a dry coating rate of 70 mg / m². ２ The material was coated using microgravure coating and then baked in a drying unit at 200°C. Next, (CL-2) was applied to the resulting layer at a dry coating rate of 20 mg / m². ２ By applying a microgravure coating in this manner, a composite layer consisting of (CL-1) and (CL-2) was formed as the second corrosion-preventive treatment layer. In this way, a barrier layer was created. The above composite layer exhibits corrosion-preventive performance by combining two types, (CL-1) and (CL-2).

[0098] Next, using a dry lamination method, the first corrosion-preventive treatment layer of the barrier layer was bonded to the substrate layer using a first adhesive to form the first adhesive layer. Specifically, the first adhesive was applied to the first corrosion-preventive treatment layer so that its thickness after drying was 4 μm. Subsequently, the first adhesive was dried at 80°C for 1 minute, and then the substrate layer and the barrier layer were bonded together. After that, aging was performed at 80°C for 120 hours. In this way, the first laminate (substrate layer / first adhesive layer / barrier layer (first corrosion-preventive treatment layer / metal foil / second corrosion-preventive treatment layer)) was obtained.

[0099] Next, as the base resin used to form the sealant layer, the types of base resins shown in Tables 2, 4, or 5 were used in the proportions (mass%) shown in Tables 2, 4, or 5, and a sealant layer with a thickness of 50 μm was formed using the T-die method. Next, the second corrosion-preventive treatment layer of the barrier layer was bonded to the sealant layer using a second adhesive for forming the second adhesive layer by a dry lamination method. Specifically, the second adhesive was applied to the second corrosion-preventive treatment layer so that the thickness of the second adhesive after drying was 4 μm. Subsequently, the second adhesive was dried at 80°C for 1 minute, and then the sealant layer and the barrier layer were bonded together and aged at 80°C for 120 hours to obtain the second laminate. In this way, an exterior material (base material layer / first adhesive layer / barrier layer (first corrosion-preventive treatment layer / metal foil / second corrosion-preventive treatment layer) / second adhesive layer / sealant layer) consisting of the second laminate was obtained. In Tables 2-5, "Percentage" is indicated as "100%" when a single resin is used as the base resin, and the percentages are listed in the upper and lower rows respectively when a mixture of two types of resins is used as the base resin. Here, "%" represents "mass percent". Also, in Tables 2-5, "Crystalline resin / Amorphous resin" indicates the mass ratio of crystalline resin to amorphous resin in the base resin.

[0100] (Example 2) When forming the sealant layer, the base resin used was one of the types shown in Table 2 (polyester resin B) in the proportions shown in Table 2 (100% by mass) as the base resin used for forming the sealant layer, and kaolin was added as a crystal nucleating agent at a ratio of 0.1 parts by mass per 100 parts by mass of the base resin. Except for these differences, an exterior material (base layer / first adhesive layer / barrier layer (first corrosion prevention treatment layer / metal foil / second corrosion prevention treatment layer) / second adhesive layer / sealant layer) was obtained in the same manner as in Example 1.

[0101] (Examples 3, 6, 11 and Comparative Example 11) Except that when forming the sealant layer, the types of base resins shown in Tables 2, 3, or 5 were used as the base resin for forming the sealant layer, in the proportions shown in Tables 2, 3, or 5, respectively, to obtain an exterior material (base layer / first adhesive layer / barrier layer (first corrosion prevention treatment layer / metal foil / second corrosion prevention treatment layer) / second adhesive layer / sealant layer) in the same manner as in Example 1.

[0102] (Example 10) A first laminate (base layer / first adhesive layer / barrier layer (first corrosion-preventive treatment layer / metal foil / second corrosion-preventive treatment layer)) was obtained in the same manner as in Example 1. Next, a sealant layer was laminated onto the second corrosion-preventive treatment layer of the first laminate by extruding the types of base resins shown in Table 3 in the proportions shown in Table 3 using a thermal lamination method at 290°C from a T-die. In this way, an exterior material (base layer / first adhesive layer / barrier layer (first corrosion-preventive treatment layer / metal foil / second corrosion-preventive treatment layer / sealant layer)) was obtained. At this time, the thickness of the sealant layer was 50 μm.

[0103] (Example 7) An exterior material was obtained in the same manner as in Example 6, except that treatment 1 was performed on the second laminate. Here, treatment 1 refers to heat treatment in an oven at 180°C for 5 minutes.

[0104] (Example 8) An exterior material was obtained in the same manner as in Example 6, except that treatment 2 was performed on the second laminate of Example 7. Here, treatment 2 refers to heat treatment in an oven at 180°C for 5 minutes, folding and stacking the second laminate, and heat sealing the overlapping portion at a temperature of 280°C, a pressure of 0.5 MPa, and for 5 seconds to form a sealed portion, and then heat treatment again in an oven at 180°C for 5 minutes.

[0105] (Example 9) An exterior material was obtained in the same manner as in Example 6, except that treatment 3 was performed on the second laminate of Example 7. Here, treatment 3 refers to folding and stacking the second laminate, heat sealing the overlapping portion at a temperature of 280°C, a pressure of 0.5 MPa, and for 5 seconds to form a sealed portion, and then pressing a metal plate made of SUS against the sealed portion and performing heat treatment at 180°C for 5 minutes.

[0106] (Example 12) When forming the sealant layer, a second sealant layer was formed on top of a first sealant layer that had been prepared in advance to form a two-layer sealant layer, and the two-layer sealant layer was attached to the barrier layer with the first sealant layer facing the barrier layer side, in the same manner as in Example 1, to obtain an exterior material (base layer / first adhesive layer / barrier layer (first corrosion prevention treatment layer / metal foil / second corrosion prevention treatment layer) / second adhesive layer / sealant layer (first sealant layer / second sealant layer)). The first sealant layer was formed by forming a film using polyester resin A of the types shown in Table 3 in the proportions shown in Table 3 as the base resin, and then heat-treating it at 180°C for 5 minutes. The second sealant layer was formed by extrusion using a mixed resin obtained by mixing polyester resin D and polyester resin G of the types shown in Table 3 in the proportions shown in Table 3.

[0107] (Comparative Example 2) Except that the type of base resin was changed to the base resin shown in Table 4 and the second laminate was heat-treated in an oven at 180°C for 5 minutes (heat treatment 1), an exterior material was obtained in the same manner as in Example 1.

[0108] (Comparative Example 3) An exterior material was obtained in the same manner as in Example 1, except that treatment 1 was performed on the second laminate.

[0109] (Comparative Example 4) Except for changing the type of base resin to the base resin shown in Table 4 and performing treatment 1 on the second laminate, an exterior material was obtained in the same manner as in Example 10.

[0110] (Comparative Example 7) Except for changing the type of base resin to the base resin shown in Table 5 and performing treatment 1 on the second laminate, an exterior material was obtained in the same manner as in Example 1.

[0111] <Melting point, crystallization temperature, cold crystallization temperature, and degree of crystallinity> Samples cut from the outer packaging material obtained in the examples and comparative examples to a size of 120 mm (MD) x 60 mm (TD) were folded in half along the center line between a pair of opposing short sides. Subsequently, the ends of the sample located on the opposite side of the fold were heat-sealed with a 10 mm wide sealing bar at 280 °C / 0.5 MPa / 5 seconds to form a test specimen having a sealed portion and an unsealed portion with a length of 60 mm and a width of 10 mm.

[0112] (1) Melting point, crystallization temperature, cold crystallization temperature, and degree of crystallinity of the sealant layer in the unsealed portion (Melting point, crystallization temperature, and cold crystallization temperature) A portion was cut from the sealant layer in the unsealed portion of the above test specimen and designated as Sample A. The melting point, crystallization temperature, and cold crystallization temperature of Sample A were measured using a differential scanning calorimeter (DSC, differential scanning calorimeter manufactured by T.A. Instruments) according to the procedure of JIS K7121:2012 (Method for measuring the transition temperature of plastics (Supplement 1 of JIS K7121:1987)). Specifically, using differential scanning calorimeter (DSC), Sample A was held at 20°C for 10 minutes, then heated from 20°C to 300°C at a heating rate of 10°C / min, and the "cold crystallization temperature" and "melting point" were measured, after which it was held at 300°C for 10 minutes. In this case, the "cold crystallization temperature" was defined as the temperature at the maximum value of the cold crystallization peak (exothermic peak of cold crystallization) that appears above the baseline of the DSC curve (a curve showing the relationship between differential scanning heat (DSC) and temperature), and the "melting point" was defined as the temperature at the minimum value of the melting peak (endothermic peak of melting) that appears below the baseline of the DSC curve. Next, the temperature was lowered from 300°C to 20°C at a cooling rate of 10°C / min, and the "crystallization temperature" was measured and held for 10 minutes. In this case, the "crystallization temperature" was defined as the temperature at the maximum value of the crystallization peak that appears above the baseline of the DSC curve. If multiple peaks appeared in the DSC curve, the peak with the largest peak area was defined as the "peak". The results for the melting point and crystallization temperature are shown in Tables 2 to 5. For the crystallization temperature, if a crystallization peak could not be confirmed in the DSC curve, it was indicated as "Not Confirmable".

[0113] (Degree of Crystallinity) For the sealant layer of the unsealed portion of the above test specimen, the total area (J / g) of each was calculated from the integral values ​​of the "cold crystallization peak" and the "melting peak" obtained as described above. Then, the degree of crystallinity A1 was calculated using the following formula. The results are shown in Tables 2 to 5. Degree of Crystallinity A1 (%) = 100 × (Total area of ​​melting peak (J / g) - Total area of ​​cold crystallization peak (J / g)) / 140 (J / g) ... (1) "140 (J / g)" is the complete melting energy of PET (polyethylene terephthalate). Note that the value of the complete melting energy (denominator) in the above formula (1) was the value of the complete melting energy of PET (polyethylene terephthalate), regardless of the type of base resin contained in the sealant layer.

[0114] (2) Melting point, crystallization temperature, cold crystallization temperature, and degree of crystallinity of the sealant layer of the seal portion A portion of the sealant layer of the above test specimen was cut out and designated as Sample B. The melting point, crystallization temperature, cold crystallization temperature, and degree of crystallinity A2 were then determined for Sample B in the same manner as above. The results for the cold crystallization temperature and the degree of crystallinity A2 of the seal portion are shown in Tables 2 to 5. For the cold crystallization temperature, if a cold crystallization peak could not be confirmed in the DSC curve, it was indicated as "Not confirmed".

[0115] (3) Crystallinity Ratio (A1 / A2) The crystallinity ratio was calculated from the crystallinity A1 and crystallinity A2 obtained as described above, based on the following formula: Crystallinity Ratio = Crystallinity A1 / Crystallinity A2 The results of the crystallinity ratio are shown in Tables 2 to 5. Note that if the crystallinity A2 is 0%, the crystallinity ratio is indicated as "-".

[0116] <Sealant Layer Sealing Performance> The burst strength of the sealant layer in the exterior materials obtained in Examples 1 to 12 and Comparative Examples 1 to 11 was used as an indicator of sealing performance, and samples for measuring the burst strength were prepared using the following procedure.

[0117] First, a sample cut from the prepared exterior material to a size of 120 mm (MD) x 60 mm (TD) was folded in half along the center line between two opposing short sides. Next, the ends of the sample on the opposite side of the fold were heat-sealed using a 10 mm wide sealing bar at 280°C / 0.5 MPa / 5 seconds, obtaining a sealed section and an unsealed section measuring 60 mm in length and 10 mm in width. Subsequently, a 60 mm (MD) x 10 mm (TD) section was cut out, including the longitudinal center (TD) of the sealed section, to prepare a sample for measuring seal strength. Two of these samples were prepared for each example and each comparative example.

[0118] The above sample was placed in a thermal shock chamber (TSA-103EL, manufactured by ESPEC Corporation). A heat cycle test was then performed on the sample under the following conditions. The starting temperature for the heat cycle test was 100°C. Temperature range: -40°C to 100°C Temperature transition period: 2 minutes Temperature holding period: 28 minutes Number of cycles: 600 (1 cycle: 100°C start → temperature transition (2 minutes) → -40°C hold (28 minutes) → temperature transition (2 minutes) → 100°C hold (28 minutes))

[0119] After conducting the heat cycle test described above, one of the two samples was mounted on a tensile testing machine (manufactured by Shimadzu Corporation). A T-shaped peel test was then performed at room temperature with a tensile speed of 50 mm / min to peel off the seal portion of the sample. Meanwhile, the other of the two samples was left to stand at 170°C for 5 minutes before being mounted on a tensile testing machine (manufactured by Shimadzu Corporation). A T-shaped peel test was then performed at 170°C with a tensile speed of 50 mm / min to peel off the seal portion of the sample. In this manner, the burst strength of the sealant layer during peeling was measured at room temperature and at 170°C. The sealing performance of the sealant layers obtained in Examples 1 to 12 and Comparative Examples 1 to 11 was evaluated based on the following evaluation criteria. The results are shown in Tables 6 to 7. If the evaluation result is "S", "A", "B", or "C", the sealant layer is evaluated to have excellent sealing performance. [Evaluation Criteria] S: Burst intensity of 30 N / 10 mm or more A: Burst intensity of 25 N / 10 mm or more and less than 30 N / 10 mm B: Burst intensity of 20 N / 10 mm or more and less than 25 N / 10 mm C: Burst intensity of 15 N / 10 mm or more and less than 20 N / 10 mm D: Burst intensity less than 15 N / 10 mm

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126] As shown in Tables 6-7, the sealing performance of the exterior materials in Examples 1-12 was evaluated as "S," "A," "B," or "C" at room temperature and 17°C. In contrast, the sealing performance of the exterior materials in Comparative Examples 1-11 was evaluated as "D" at least at 170°C. From the above, it was confirmed that the exterior materials of this disclosure can have excellent sealing performance even in a 170°C environment.

[0127] 10, 20...Outer packaging material, 11...Base layer, 13...Barrier layer, 16...Sealant layer, 16a...Outermost layer, 50...All-solid-state battery (energy storage device), 52...Energy storage element, 54...Outer bag, 54a...Sealed portion, 54b...Non-sealed portion.

Claims

1. An exterior material for use in an energy storage device, comprising a base layer, a barrier layer, and a sealant layer in that order, wherein the sealant layer has an outermost layer on the side opposite to the barrier layer, the outermost layer contains a polyester resin, the melting point of the outermost layer is 190°C or higher and 258°C or lower, and the degree of crystallinity is 33% or lower.

2. The outermost layer has a crystallization temperature of 190°C or lower, or a crystallization peak cannot be observed, as described in claim 1.

3. The exterior material for an energy storage device according to claim 1, wherein when the outermost layer is formed by folding and overlapping the exterior material so that the sealant layers face each other, and a heat seal is performed on the overlapping portion under the conditions of a temperature of 280°C, a pressure of 0.5 MPa, and 5 seconds, it is possible to set the cold crystallization temperature of the outermost layer in the seal portion to 120°C or more and 190°C or less.

4. The exterior material for an energy storage device according to claim 1, wherein the polyester resin of the sealant layer consists of a crystalline resin and an amorphous resin.

5. The exterior material for an energy storage device according to claim 4, wherein the amorphous resin has constituent units derived from the acid component constituting the crystalline resin and constituent units derived from the glycol component.

6. The exterior material for an energy storage device according to claim 5, wherein the constituent units derived from the acid component constituting the crystalline resin are composed of constituent units derived from two or more acid components.

7. The exterior material for an energy storage device according to claim 6, wherein the constituent units derived from the acid component constituting the crystalline resin include constituent units derived from terephthalic acid and constituent units derived from isophthalic acid.

8. The exterior material for an energy storage device according to claim 4, wherein the proportion of the crystalline resin in the total of 100% by mass of the crystalline resin and the amorphous resin is 70% by mass or more.

9. The exterior material for an energy storage device according to claim 1, wherein when the outermost layer is formed by folding and overlapping the exterior material so that the sealant layers face each other, and heat sealing is performed on the overlapping portion under the conditions of a temperature of 280°C, a pressure of 0.5 MPa, and 5 seconds, it is possible to set the ratio of the crystallinity of the outermost layer in the non-sealed portion to the crystallinity of the outermost layer in the sealed portion to 0.3 or more and 2.0 or less.

10. The exterior material for an energy storage device according to claim 9, wherein when the outermost layer is formed by folding and overlapping the exterior material so that the sealant layers face each other, and heat sealing is performed on the overlapping portion under the conditions of a temperature of 280°C, a pressure of 0.5 MPa, and 5 seconds to form a sealed portion and an unsealed portion, it is possible to set the ratio of the crystallinity of the outermost layer in the unsealed portion to the crystallinity of the outermost layer in the sealed portion to 0.7 or more and 1.3 or less.

11. The exterior material for an energy storage device according to claim 1, wherein the crystallinity of the outermost layer is 3% or more and 20% or less.

12. The outermost layer has a crystallization temperature of 190°C or less, and when the exterior material is folded and stacked so that the sealant layers face each other, and a heat seal is performed on the overlapping portion at a temperature of 280°C, a pressure of 0.5 MPa, and for 5 seconds to form a sealed portion and an unsealed portion, it is possible to set the cold crystallization temperature of the outermost layer in the sealed portion to 120°C or more and 190°C or less, and the ratio of the degree of crystallization of the outermost layer in the unsealed portion to the degree of crystallization of the outermost layer in the sealed portion to 0.7 or more and 1.3 or less, the polyester resin of the sealant layer consists of a crystalline resin and an amorphous resin, the amorphous resin has constituent units derived from acid components and constituent units derived from glycol components that constitute the crystalline resin, the proportion of the crystalline resin in the total of 100% by mass of the crystalline resin and the amorphous resin is 70% by mass or more, and the degree of crystallization of the outermost layer is 3% or more and 20% or less, as described in claim 1.

13. The exterior material for an energy storage device according to any one of claims 1 to 12, wherein the energy storage device is an all-solid-state battery.

14. An energy storage device comprising an energy storage element and an outer bag for housing the energy storage element, wherein the outer bag has an outer material as described in any one of claims 1 to 12.

15. The energy storage device according to claim 14, which is an all-solid-state battery.

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