Adhesive film, electricity storage device, and method for manufacturing electricity storage device

Abstract

Provided is an adhesive film that is interposed between heat-sealable resin layers in the heat-sealed portion of the exterior material of an electricity storage device, and that seals the electricity storage device until the electricity storage device reaches a high temperature (for example, about 100°C to 125°C), and when the electricity storage device reaches the high temperature (for example, about 100°C to 125°C), the electricity storage device is opened at the position of the adhesive film between the heat-sealable resin layers, allowing gas generated inside the electricity storage device to be released to the outside. An adhesive film for use in an electricity storage device, comprising: The electricity storage device has a structure in which an electricity storage device element is housed in a package formed from an exterior packaging material for an electricity storage device, The packaging material for an electricity storage device is composed of a laminate including at least a base layer, a barrier layer, and a heat-sealable resin layer in this order from the outside, the heat-fusible resin layers of the electrical storage device packaging material are heat-fused together to house the electrical storage device element in the packaging body; the adhesive film is used so as to be interposed between the heat-fusible resin layers at positions where the heat-fusible resin layers are heat-fused to each other, The adhesive film has a multilayer structure, The adhesive film includes at least one resin layer L having a melting peak temperature that is 5° C. or more lower than that of the heat-fusible resin layer of the packaging material for an electricity storage device.

Description

[Technical Field]

[0001] The present disclosure relates to an adhesive film, an electricity storage device, and a method for manufacturing an electricity storage device. [Background technology]

[0002] Various types of electricity storage devices have been developed to date, and in all electricity storage devices, exterior materials for electricity storage devices have become essential components for sealing electricity storage device elements such as electrodes and electrolytes. Metal exterior materials for electricity storage devices have traditionally been widely used as exterior materials for electricity storage devices. However, in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, and the like, electricity storage devices are being required to have a variety of shapes, as well as to be thinner and lighter. However, the metal exterior materials for electricity storage devices that have traditionally been widely used have the drawbacks of being difficult to keep up with the diversification of shapes and also having limitations on how much they can be made lighter.

[0003] Therefore, in recent years, a laminate sheet in which a base layer / adhesive layer / barrier layer / thermal adhesive resin layer are laminated in this order has been proposed as an electrical storage device packaging material that can be easily processed into a variety of shapes and can achieve thinning and weight reduction. When such a laminate film-like electrical storage device packaging material is used, the electrical storage device elements are sealed in the electrical storage device packaging material by heat-sealing the peripheral edge of the electrical storage device packaging material with the innermost thermal adhesive resin layers facing each other. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-79638 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-8616 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, in recent years, as smartphones have become capable of high-speed, large-capacity data communication, the amount of electricity consumed has increased, and studies are being conducted to increase the capacity of power storage devices. However, increasing the capacity of batteries is accompanied by an increase in the container size and the amount of reactive substances, which increases the amount of gas generated when the power storage device experiences thermal runaway (i.e., when the power storage device becomes too hot), and increases the risk of explosion due to an increase in the internal pressure of the power storage device. Power storage devices that use metal exterior materials (such as metal can batteries) are equipped with a safety valve to ensure safety when gas is generated (see Patent Document 2).

[0006] However, it is difficult to install such a safety valve in an electricity storage device that uses a laminated film exterior material, and preventing the expansion of the electricity storage device due to gas generated inside the device when it becomes hot becomes a challenge.

[0007] Under these circumstances, a main object of the present disclosure is to provide an adhesive film that is interposed between heat-sealable resin layers in a heat-sealed portion of an exterior material of an electricity storage device, and that seals the electricity storage device until the electricity storage device reaches a high temperature (for example, about 100°C to 125°C), and when the electricity storage device reaches this high temperature (for example, about 100°C to 125°C), the electricity storage device is opened at the position of the adhesive film between the heat-sealable resin layers, allowing gas generated inside the electricity storage device to be released to the outside. Another object of the present disclosure is to provide an electricity storage device and a method for manufacturing the electricity storage device that utilizes this adhesive film. [Means for solving the problem]

[0008] The inventors of the present disclosure conducted extensive research to solve the above-mentioned problems. As a result, they found that by interposing an adhesive film having a resin layer L whose melting peak temperature is lower by a predetermined value or more than that of the heat-sealable resin layer of the electrical storage device packaging material between the heat-sealable resin layers of the electrical storage device packaging material in the heat-sealable portion of the electrical storage device, the electrical storage device can be sealed until the electrical storage device reaches a high temperature (for example, about 100°C to 125°C), and when the electrical storage device reaches this high temperature (for example, about 100°C to 125°C), the electrical storage device can be opened at the position of the adhesive film between the heat-sealable resin layers, allowing gas generated inside the electrical storage device to be released to the outside. The present disclosure was completed through further research based on this finding.

[0009] That is, the present disclosure provides the inventions of the following aspects. An adhesive film for use in an electricity storage device, The electricity storage device has a structure in which an electricity storage device element is housed in a package formed from an exterior packaging material for an electricity storage device, The packaging material for an electricity storage device is composed of a laminate including at least a base layer, a barrier layer, and a heat-sealable resin layer in this order from the outside, the heat-fusible resin layers of the electrical storage device packaging material are heat-fused together to house the electrical storage device element in the packaging body; the adhesive film is used so as to be interposed between the heat-fusible resin layers at positions where the heat-fusible resin layers are heat-fused to each other, The adhesive film has a multilayer structure, The adhesive film includes at least one resin layer L having a melting peak temperature that is 5° C. or more lower than that of the heat-fusible resin layer of the packaging material for an electricity storage device. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide an adhesive film that is interposed between heat-sealable resin layers in a heat-sealed portion of an exterior material of an electricity storage device, and that seals the electricity storage device until the electricity storage device reaches a high temperature (for example, about 100°C to 125°C), and when the electricity storage device reaches this high temperature (for example, about 100°C to 125°C), the electricity storage device is opened at the position of the adhesive film between the heat-sealable resin layers, allowing gas generated inside the electricity storage device to be released to the outside. Furthermore, the present disclosure can also provide an electricity storage device and a method for manufacturing the electricity storage device that use this adhesive film. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic plan view of an electricity storage device according to the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view taken along line AA' in FIG. [Figure 3] 1 is a schematic cross-sectional view of an example of an adhesive film of the present disclosure. [Figure 4] 1 is a schematic cross-sectional view of an example of an adhesive film of the present disclosure. [Figure 5] 1 is a schematic cross-sectional view of an example of an adhesive film of the present disclosure. [Figure 6] 1 is a schematic cross-sectional view of an example of an adhesive film of the present disclosure. [Figure 7] 1 is a schematic cross-sectional view of an example of an adhesive film of the present disclosure. [Figure 8] 1 is a schematic cross-sectional view of an exterior packaging material for an electricity storage device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] The adhesive film of the present disclosure is an adhesive film used in an electricity storage device, and the electricity storage device has a structure in which an electricity storage device element is housed in a packaging body formed from an exterior material for an electricity storage device, and the exterior material for an electricity storage device is composed of a laminate having, from the outside, at least a base material layer, a barrier layer, and a heat-sealable resin layer in this order, and the electricity storage device element is housed in the packaging body by heat-sealing the heat-sealable resin layers of the exterior material for an electricity storage device to each other, and the adhesive film is used so as to be interposed between the heat-sealable resin layers at a position where the heat-sealable resin layers are heat-sealed to each other, and the adhesive film has a multilayer structure and is characterized in that it includes at least one resin layer L having a melting peak temperature that is 5°C or more lower than that of the heat-sealable resin layer of the exterior material for an electricity storage device.

[0013] Because the adhesive film of the present disclosure has these characteristics, the energy storage device is sealed until it reaches a high temperature (for example, about 100°C to 125°C), and when the energy storage device reaches that high temperature (for example, about 100°C to 125°C), the energy storage device opens at the position of the adhesive film between the heat-sealable resin layers, allowing gas generated inside the energy storage device to be released to the outside.

[0014] The electricity storage device of the present disclosure is also an electricity storage device having a structure in which an electricity storage device element is housed in a packaging body formed from an exterior material for an electricity storage device, and the exterior material for an electricity storage device is composed of a laminate having, from the outside, at least a base material layer, a barrier layer, and a heat-sealable resin layer in this order, and the electricity storage device element is housed in the packaging body by heat-sealing the heat-sealable resin layers of the exterior material for an electricity storage device to each other, and an adhesive film is arranged so as to be interposed between the heat-sealable resin layers at a position where the heat-sealable resin layers are heat-sealed to each other, the adhesive film has a multilayer structure, and the adhesive film is characterized in that it includes at least one resin layer L having a melting peak temperature that is 5°C or more lower than that of the heat-sealable resin layer of the exterior material for an electricity storage device.

[0015] That is, the energy storage device of the present disclosure utilizes the adhesive film of the present disclosure, and the energy storage device is sealed until it reaches a high temperature (for example, about 100°C to 125°C), and when it reaches that high temperature (for example, about 100°C to 125°C), the energy storage device opens at the position of the adhesive film between the heat-sealable resin layers, allowing gas generated inside the energy storage device to be released to the outside.

[0016] The adhesive film and its manufacturing method, and the electricity storage device and its manufacturing method according to the present disclosure will be described in detail below.

[0017] In this specification, numerical ranges indicated with "to" mean "greater than or equal to" or "less than or equal to." For example, the expression 2 to 15 mm means 2 mm or greater and 15 mm or less.

[0018] 1. Adhesive film The adhesive film of the present disclosure is an adhesive film used in an electricity storage device. The adhesive film of the present disclosure is used so as to be interposed between heat-sealable resin layers at a position where the heat-sealable resin layers of the electricity storage device packaging material are heat-sealed to each other. For example, as shown in FIGS. 1 and 2, in an electricity storage device 10 of the present disclosure, an adhesive film 1 of the present disclosure is interposed between opposing heat-sealable resin layers at a peripheral portion 3a of the electricity storage device packaging material 3 where the heat-sealable resin layers are heat-sealed to each other to seal an electricity storage device element 4. The adhesive film and the heat-sealable resin layers on both sides thereof are heat-sealed when the electricity storage device packaging material 3 seals the electricity storage device element 4. That is, both sides of the adhesive film can be heat-sealed to the heat-sealable resin layers.

[0019] The adhesive film 1 of the present disclosure seals the electricity storage device 10 until the device reaches a high temperature (for example, about 100°C to 125°C), and when the device reaches this high temperature (for example, about 100°C to 125°C), the device opens at the position of the adhesive film between the heat-sealable resin layers, allowing gas generated inside the device to be released to the outside. By arranging the adhesive film 1 at a portion of the position where the heat-sealable resin layers of the exterior material for an electricity storage device are heat-sealed, gas can be selectively released to the outside from the specific position where the adhesive film 1 is arranged. In other words, the position from which gas is released can be set to any position in the heat-sealed portion between the heat-sealable resin layers.

[0020] The position at which the adhesive film of the present disclosure is disposed is not particularly limited as long as it is a position at which the heat-sealable resin layers of the electrical storage device packaging material are heat-sealed to each other, and for example, if the electrical storage device is rectangular in plan view, the adhesive film can be disposed on either the long side or the short side of the heat-sealed peripheral portion 3a of the electrical storage device packaging material 3. Furthermore, the adhesive film of the present disclosure may be disposed in at least one position among the positions at which the heat-sealable resin layers of the electrical storage device packaging material are heat-sealed to each other, but may be disposed in two or more positions.

[0021] The size of the adhesive film is not particularly limited as long as the gas is appropriately released when the package is opened. For example, as shown in Fig. 1, when the power storage device is rectangular in plan view and the adhesive film is arranged along one side of the rectangle (in the example of Fig. 1, the adhesive film is arranged along the z direction), the ratio of the length of the adhesive film to the length of the side can be about 3 to 98%. Furthermore, the size of the adhesive film in the width direction (the direction perpendicular to the length direction and thickness direction, which is the direction along the x direction in the example of Fig. 1) can be about 20 to 300%, with the size of the adhesive film in the length direction being 100%.

[0022] In the electricity storage device 10, the metal terminal 2 is electrically connected to the electricity storage device element 4 and protrudes outside the electricity storage device packaging material 3. The adhesive film of the present disclosure is preferably disposed so as not to be located between the metal terminal 2 and the electricity storage device packaging material 3 (thermally adhesive resin layer). Furthermore, the adhesive film 1 of the present disclosure preferably does not come into contact with the metal terminal 2.

[0023] As shown in Figures 3 to 7, the adhesive film 1 of the present disclosure has a multilayer structure and includes at least one resin layer L having a melting peak temperature that is 5°C or more lower than that of the heat-sealable resin layer 35 of the packaging material 3 for an electricity storage device. In the schematic diagrams of Figures 3 to 7, at least the first layer 11 corresponds to the resin layer L, but the adhesive film 1 may include two or more layers that correspond to the resin layer L. The resin layer L has a melting peak temperature that is 5°C or more lower than that of the heat-sealable resin layer 35 of the packaging material 3 for an electricity storage device. Therefore, by interposing an adhesive film between the heat-sealable resin layers in the heat-sealed portion of the packaging material for the electricity storage device, the electricity storage device is sealed until the electricity storage device reaches a high temperature (for example, about 100°C to 1255°C). When the electricity storage device reaches that high temperature (for example, about 100°C to 125°C), the electricity storage device is opened at the position of the adhesive film 1 between the heat-sealable resin layers (particularly at the position of the resin layer L), allowing gas generated inside the electricity storage device to be released to the outside.

[0024] In the adhesive film 1 of the present disclosure, at least the first layer 11 is a layer corresponding to the resin layer L. Examples of the laminated structure of the adhesive film 1 of the present disclosure include a two-layer structure in which the first layer 11 and the second layer 12 are laminated in this order (see FIG. 3); a three-layer structure in which the second layer 12, the first layer 11, and the third layer 13 are laminated in this order (see FIG. 4); a three-layer structure in which the first layer 11, the second layer 12, and the third layer 13 are laminated in this order (see FIG. 5); a four-layer structure in which the first layer 11, the second layer 12, the third layer 13, and the fourth layer 14 are laminated in this order (see FIG. 6); and a four-layer structure in which the second layer 12, the first layer 11, the third layer 13, and the fourth layer 14 are laminated in this order (see FIG. 7).

[0025] In the adhesive film 1 of the present disclosure, at least one of the layers other than the first layer 11 (other layers described below) may also correspond to the resin layer L. For example, at least one of the second layer 12, third layer 13, and fourth layer 14 in FIGS. 3 to 7 may also correspond to the resin layer L. However, in the adhesive film 1 of the present disclosure, by providing a layer having a higher peak melting temperature than the resin layer L (for example, a layer having a higher peak melting temperature than the resin layer L), it becomes easier to design the resin layer L to be thinner. Reducing the thickness of the resin layer L has the advantage of easing gas release when the electricity storage device is opened. In this way, the adhesive film 1 of the present disclosure has a multilayer structure including the resin layer L, whose peak melting temperature is set in relation to the heat-sealable resin layer 35 of the packaging material 3 for an electricity storage device, and other layers, enabling various functional designs.

[0026] As will be described later, from the viewpoint of more suitably exerting the effects of the present disclosure, it is desirable that the layers other than the resin layer L have a higher peak melting temperature than the resin layer L. The adhesive film 1 of the present disclosure includes at least one resin layer L having a peak melting temperature that is 5°C or more lower than the heat-sealable resin layer of the electrical storage device packaging material, and therefore in an electrical storage device 10 to which the adhesive film of the present disclosure is applied, the peak melting temperature of the heat-sealable resin layer 35 of the electrical storage device packaging material 3 is higher than the peak melting temperature of the resin layer L by 5°C or more.

[0027] From the viewpoint of optimally exerting the effects of the present disclosure, the adhesive film 1 of the present disclosure has a total thickness of, for example, about 5 μm or more, preferably about 20 μm or more, and more preferably about 30 μm or more. The adhesive film 1 of the present disclosure has a total thickness of, for example, about 500 μm or less, preferably about 200 μm or less, and more preferably 180 μm or less. Preferred ranges for the total thickness of the adhesive film 1 of the present disclosure include about 5 to 500 μm, about 5 to 200 μm, about 5 to 180 μm, about 20 to 500 μm, about 20 to 200 μm, about 20 to 180 μm, about 30 to 500 μm, about 30 to 200 μm, and about 30 to 180 μm. As a more specific example, when the adhesive film 1 of the present disclosure is used in a consumer electricity storage device, the total thickness is preferably about 60 to 100 μm, and when it is used in an in-vehicle electricity storage device, the total thickness is preferably about 100 to 200 μm.

[0028] The materials and thicknesses of the resin layer L (first layer 11) and other layers (for example, second layer 12, third layer 13, fourth layer 14, etc.) included in the adhesive film 1 of the present disclosure will be described in detail below.

[0029] [First layer 11 (resin layer L)] In the adhesive film 1 of the present disclosure, the first layer 11 is a layer corresponding to the resin layer L having a melting peak temperature that is 5° C. or more lower than that of the heat-sealable resin layer 35 of the packaging material 3 for an electricity storage device.

[0030] The material constituting the resin layer L is not particularly limited as long as it has a melting peak temperature at least 5°C lower than that of the heat-sealable resin layer 35 of the electrical storage device packaging material 3. The resin layer L is preferably a layer containing a polyolefin-based resin (i.e., having a polyolefin skeleton), and more preferably a layer formed of a polyolefin-based resin. Examples of polyolefin-based resins include polyolefins such as polyethylene and polypropylene. The polyolefin-based resin may also be a resin obtained by acid-modifying a polyolefin (acid-modified polyolefin). The acid-modified polyolefin is not particularly limited as long as it is an acid-modified polyolefin, but preferably includes a polyolefin graft-modified with an unsaturated carboxylic acid or anhydride thereof, such as acid-modified polyethylene or acid-modified polypropylene.

[0031] Examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); and ethylene-butene-propylene terpolymers. Among these polyolefins, polyethylene and polypropylene are preferred.

[0032] The polyolefin may also be a cyclic polyolefin. Cyclic polyolefins are copolymers of olefins and cyclic monomers, and examples of olefins constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, and isoprene. Examples of cyclic monomers constituting the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, cyclic alkenes are preferred, and norbornene is more preferred. Styrene is also an example of a constituting monomer.

[0033] In the acid-modified polyolefin, the polyolefin to be acid-modified is preferably the polyolefin described above. For example, the carboxylic acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin with an α,β-unsaturated carboxylic acid or an anhydride thereof in place of an α,β-unsaturated carboxylic acid or an anhydride thereof, or by block polymerization or graft polymerization of the cyclic polyolefin with an α,β-unsaturated carboxylic acid or an anhydride thereof.

[0034] Examples of carboxylic acids or anhydrides thereof used for acid modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride. When a polyolefin resin is analyzed by infrared spectroscopy, a peak derived from maleic anhydride is preferably detected. For example, when a maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak derived from maleic anhydride is detected at a wave number of 1760 cm. -1 Near and wave number 1780cm -1 A peak derived from maleic anhydride is detected around 1000 Hz. In other words, in this case, when the polyolefin resin is measured by infrared spectroscopy, a peak derived from maleic anhydride is detected. However, if the degree of acid modification is low, the peak becomes small and may not be detected. In that case, analysis can be performed by nuclear magnetic resonance spectroscopy.

[0035] The resin layer L may be formed of one type of resin component alone, or may be formed of a blend polymer combining two or more types of resin components. From the viewpoint of film formability of the resin layer L, it is preferable to form it of a blend polymer combining two or more types of resin components. When using a blend polymer, it is preferable that the resin layer L contains acid-modified polypropylene as the main component (50% by mass or more of a component) and 50% by mass or less of another resin (preferably polyethylene from the viewpoint of improving flexibility). On the other hand, from the viewpoint of improving the electrolyte resistance of the resin layer L, it is preferable that the resin layer L contains polypropylene or acid-modified polypropylene alone as the resin.

[0036] The resin layer L may also contain an adhesive component. Examples of the adhesive component include elastomer.

[0037] The elastomer is not particularly limited as long as it exhibits adhesiveness when blended with polyolefin, and for example, an elastomer made of a thermoplastic resin (thermoplastic elastomer) is preferred.

[0038] Preferred examples of the elastomer include styrene-based elastomers, olefin-based elastomers, acrylic-based elastomers, silicone-based elastomers, urethane-based elastomers, polyester-based elastomers, polyamide-based elastomers, rubber-based elastomers, etc. The elastomers may be used alone or in combination of two or more.

[0039] The type of styrene-based elastomer is not particularly limited, but specific examples include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, and styrene-ethylene-propylene-styrene block copolymer.

[0040] Examples of olefin elastomers include copolymers of α-olefins having 2 to 20 carbon atoms, such as ethylene, propylene, 1-butene, 1-hexene, and 4-methylpentene. Suitable examples include ethylene-propylene copolymer (EPR) and ethylene-propylene-diene copolymer (EPDM). Other examples include copolymers of α-olefins with non-conjugated dienes having 2 to 20 carbon atoms, such as dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylenenorbornene, ethylidenenorbornene, butadiene, and isoprene. Further examples include carboxy-modified nitrile rubber obtained by copolymerizing methacrylic acid with a butadiene-acrylonitrile copolymer.

[0041] Acrylic elastomers are primarily composed of acrylic esters, and specifically, ethyl acrylate, butyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, etc. are preferably used. Furthermore, glycidyl methacrylate, allyl glycidyl ether, etc. are used as crosslinking point monomers. Furthermore, acrylonitrile and ethylene can also be copolymerized. Specific examples include acrylonitrile-butyl acrylate copolymer, acrylonitrile-butyl acrylate-ethyl acrylate copolymer, acrylonitrile-butyl acrylate-glycidyl methacrylate copolymer, etc.

[0042] Silicone elastomers are those containing organopolysiloxane as a main component, and examples thereof include polydimethylsiloxane-based, polymethylphenylsiloxane-based, and polydiphenylsiloxane-based elastomers.

[0043] Urethane elastomers consist of structural units consisting of hard segments made of low molecular weight ethylene glycol and diisocyanate, and soft segments made of high molecular weight (long-chain) diols and diisocyanates. Examples of high molecular weight (long-chain) diols include polypropylene glycol, polytetramethylene oxide, poly(1,4-butylene adipate), poly(ethylene-1,4-butylene adipate), polycaprolactone, poly(1,6-hexylene carbonate), and poly(1,6-hexylene-neopentylene adipate).

[0044] Polyester elastomers are obtained by polycondensation of dicarboxylic acids or their derivatives with diol compounds or their derivatives. Specific examples of dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid, and aromatic dicarboxylic acids in which the hydrogen atoms of the aromatic nuclei are substituted with methyl groups, ethyl groups, phenyl groups, etc.; aliphatic dicarboxylic acids having 2 to 20 carbon atoms such as adipic acid, sebacic acid, and dodecanedicarboxylic acid; and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. These compounds can be used alone or in combination of two or more.

[0045] Specific examples of the diol compound include aliphatic diols and alicyclic diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, and 1,4-cyclohexanediol, as well as bisphenol A, bis-(4-hydroxyphenyl)-methane, bis-(4-hydroxy-3-methylphenyl)-propane, and resorcinol. These compounds can be used alone or in combination of two or more.

[0046] Examples of polyamide-based elastomers include block copolymers in which polyamide is used as a hard segment component and polybutadiene, butadiene-acrylonitrile copolymer, styrene-butadiene copolymer, polyisoprene, ethylene-propylene copolymer, polyether, polyester, polybutadiene, polycarbonate, polyacrylate, polymethacrylate, polyurethane, silicone rubber, or the like is used as a soft segment component.

[0047] An example of the rubber elastomer is polyisobutylene.

[0048] Among the elastomers, styrene-based elastomers and olefin-based elastomers are preferred, with styrene-based elastomers being particularly preferred.

[0049] The proportion of the elastomer contained in the resin layer L is not particularly limited, but is preferably about 50% by mass or less, more preferably about 10 to 50% by mass, and even more preferably about 10 to 40% by mass.

[0050] The melting peak temperature of the resin layer L may be at least 5°C lower than that of the heat-sealable resin layer 35 of the packaging material 3 for an electrical storage device, but from the viewpoint of more suitably exerting the effects of the present disclosure, it is preferably at least 10°C lower, more preferably at least 15°C lower, even more preferably at least 17°C lower, and even more preferably at least 20°C lower.

[0051] Furthermore, from the viewpoint of more suitably exerting the effects of the present disclosure, the melting peak temperature of the resin layer L is preferably about 100°C or higher, more preferably about 110°C or higher, even more preferably about 120°C or higher, and is preferably about 135°C or lower, even more preferably about 130°C or lower, with preferred ranges including about 100 to 135°C, about 100 to 130°C, about 110 to 135°C, and about 110 to 130°C.

[0052] In the present disclosure, the method for measuring the melting peak temperature is as follows.

[0053] <Measurement of melting peak temperature> The melting peak temperature of each resin is measured according to the JIS K7121:2012 (Method for measuring transition temperatures of plastics (JIS K7121:1987, Supplement 1)). Measurements are performed using a differential scanning calorimeter (e.g., DSC, TA Instruments Q200). The sample is held at -50°C for 15 minutes, then heated from -50°C to 210°C at a heating rate of 10°C / min. The first melting peak temperature, P (°C), is measured, and the sample is then held at 210°C for 10 minutes. The sample is then cooled from 210°C to -50°C at a heating rate of 10°C / min and held for 15 minutes. The sample is then heated from -50°C to 210°C at a heating rate of 10°C / min. The second melting peak temperature, Q (°C), is measured. The nitrogen gas flow rate is 50 ml / min. Using the above procedure, the melting peak temperature P (°C) measured the first time and the melting peak temperature Q (°C) measured the second time are determined, and the melting peak temperature measured the first time is designated as the melting peak temperature. When measuring a sample with a high melting peak temperature, measurements may be made in the range of -50°C to 500°C at the same heating rate.

[0054] Furthermore, from the viewpoint of more suitably achieving the effects of the present disclosure, the thickness of first layer 11 is preferably about 0.1 μm or more, more preferably about 1 μm or more, even more preferably about 3 μm or more, and is preferably about 500 μm or less, more preferably about 200 μm or less, even more preferably 100 μm or less. Preferred ranges for the thickness of first layer 11 include about 0.1 to 500 μm, and about 1 to 200 μm.

[0055] When a layer corresponding to the resin layer L (i.e., a layer having a melting peak temperature of 100°C or higher and 135°C or lower) is present in addition to the first layer 11 (for example, when at least one of the second layer 12, third layer 13, and fourth layer 14 described below corresponds to the resin layer L), the total thickness of the resin layers L included in the adhesive film 1 is preferably about 0.1 μm or higher, more preferably about 3 μm or higher, and even more preferably about 5 μm or higher, and is preferably about 500 μm or lower, more preferably about 200 μm or lower, and even more preferably about 100 μm or lower. Preferred ranges for the total thickness of the resin layers L include about 0.1 to 500 μm, about 0.1 to 200 μm, about 0.1 to 100 μm, about 3 to 500 μm, about 3 to 200 μm, about 3 to 10 μm, about 5 to 500 μm, about 5 to 200 μm, and about 5 to 100 μm.

[0056] In the present disclosure, from the viewpoint of more suitably exerting the effects of the present disclosure, the ratio of the thickness of the first layer 11 to the total thickness (100%) of the adhesive film 1 is preferably about 5% or more, more preferably about 10% or more, even more preferably about 15% or more, and is preferably about 95% or less, more preferably about 90% or less, even more preferably about 85% or less, with preferred ranges being approximately 5 to 95%, approximately 5 to 90%, approximately 5 to 85%, approximately 10 to 95%, approximately 10 to 90%, approximately 10 to 85%, approximately 15 to 95%, approximately 15 to 90%, and approximately 15 to 85%.

[0057] Furthermore, in addition to the first layer 11, when there is also a layer corresponding to the resin layer L (i.e., a layer having a melting peak temperature 5°C or more lower than that of the heat-sealable resin layer 35 of the packaging material 3 for an electrical storage device) (for example, when at least one of the second layer 12, third layer 13, and fourth layer 14 described below corresponds to the resin layer L), the proportion of the total thickness of the resin layer L to the total thickness (100%) of the adhesive film 1 is preferably about 5% or more, more preferably about 10% or more, even more preferably about 15% or more, and also preferably about 95% or less, more preferably about 90% or less, even more preferably about 85% or less, with preferred ranges being about 5 to 95%, about 5 to 90%, about 5 to 85%, about 10 to 95%, about 10 to 90%, about 10 to 85%, about 15 to 95%, about 15 to 90%, about 15 to 85%.

[0058] [Other layers (second layer 12, third layer 13, fourth layer 14, etc.)] The adhesive film 1 of the present disclosure has a multilayer structure and includes at least a second layer 12 as another layer in addition to the first layer 11. When the adhesive film 1 of the present disclosure has a two-layer structure, it is a laminate of the first layer 11 and the second layer 12. When it has a three-layer structure, it is a laminate of the first layer 11, the second layer 12, and the third layer 13. When it has a four-layer structure, it is a laminate of the first layer 11, the second layer 12, the third layer 13, and the fourth layer 14. When it has a five-layer structure, it is a laminate of the first layer 11, the second layer 12, the third layer 13, the fourth layer 14, and the fifth layer 15. The order in which the first layer 11 and the other layers are stacked is not particularly limited. The number of layers in the adhesive film 1 is not particularly limited, but is preferably 2 to 5 layers, or 2 to 4 layers, for example.

[0059] As described above, the adhesive film 1 of the present disclosure may include a layer corresponding to the resin layer L among the other layers. For example, at least one of the second layer 12, the third layer 13, and the fourth layer 14 in FIGS. 3 to 7 may also correspond to the resin layer L. Furthermore, at least one of the other layers may be a layer having a higher peak melting temperature than the resin layer L (a layer having a peak melting temperature not lower by 5° C. or more than the heat-sealable resin layer 35 of the electrical storage device packaging material 3). For example, by providing a layer having a higher peak melting temperature than the resin layer L (for example, a layer having a peak melting temperature not lower by 5° C. or more than the heat-sealable resin layer 35 of the electrical storage device packaging material 3 and not corresponding to the resin layer L (hereinafter, sometimes referred to as resin layer M)) in the adhesive film 1 of the present disclosure, it becomes easier to design the resin layer L to be thin.

[0060] In the other layers, the material constituting the resin layer L is not particularly limited as long as it has a melting peak temperature 5°C or more lower than that of the heat-sealable resin layer 35 of the electrical storage device packaging material 3, similarly to the first layer 11 described above, and is preferably a layer containing a polyolefin-based resin (i.e., having a polyolefin skeleton), more preferably a layer formed of a polyolefin-based resin. Specific examples of polyolefin-based resins are as exemplified for the first layer 11.

[0061] The material for forming the other layer is not particularly limited. Examples of materials for forming the other layer include polyolefin resins, polyamide resins, polyester resins, epoxy resins, acrylic resins, fluororesins, silicone resins, phenolic resins, polyetherimides, polyimides, polycarbonates, and mixtures or copolymers thereof. Among these, it is particularly preferable to include a polyolefin resin, and it is more preferable to include a layer formed from a polyolefin resin. Note that even if the material for forming the other layer is a polyolefin resin, the other layer can be a layer (resin layer M) having a higher melting peak temperature than the resin layer L.

[0062] Specific examples of polyamides include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (I represents isophthalic acid, T represents terephthalic acid) containing structural units derived from terephthalic acid and / or isophthalic acid; aromatic polyamides such as polymetaxylylene adipamide (MXD6); alicyclic polyamides such as polyaminomethylcyclohexyl adipamide (PACM6); and polyamides copolymerized with lactam components or isocyanate components such as 4,4'-diphenylmethane diisocyanate. Examples of the polyamide include a polyamide having a copolymer of ...

[0063] Specific examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, copolymer polyesters whose repeating units are mainly ethylene terephthalate, copolymer polyesters whose repeating units are mainly butylene terephthalate, etc. Specific examples of copolymer polyesters whose repeating units are mainly ethylene terephthalate include copolymer polyesters in which ethylene terephthalate is the main repeating unit and is polymerized with ethylene isophthalate (hereinafter abbreviated as polyethylene (terephthalate / isophthalate)), polyethylene (terephthalate / isophthalate), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl-dicarboxylate), polyethylene (terephthalate / decanedicarboxylate), etc. Specific examples of copolymer polyesters containing butylene terephthalate as the main repeating unit include copolymer polyesters in which butylene terephthalate is the main repeating unit and is polymerized with butylene isophthalate (hereinafter abbreviated as polybutylene (terephthalate / isophthalate)), polybutylene (terephthalate / adipate), polybutylene (terephthalate / sebacate), polybutylene (terephthalate / decanedicarboxylate), polybutylene naphthalate, etc. These polyesters may be used alone or in combination of two or more.

[0064] At least one of the other layers may be formed of a nonwoven fabric made of the above-mentioned resin. When formed of a nonwoven fabric, the nonwoven fabric is preferably made of the above-mentioned polyolefin resin, polyamide resin, or the like.

[0065] Among the layers included in the other layers, the layer (resin layer M) having a melting peak temperature that is not 5°C or more lower than that of the heat-sealable resin layer 35 of the packaging material 3 for an electricity storage device has a melting peak temperature of preferably about 140°C or higher, more preferably about 160°C or higher, even more preferably about 180°C or higher, and preferably about 500°C or lower, more preferably about 450°C or lower, and even more preferably about 350°C or lower. Preferred ranges include higher than 135°C and 500°C or lower, higher than 135°C and 450°C or lower, higher than 135°C and 350°C or lower, about 140 to 500°C, about 140 to 450°C, about 140 to 350°C, about 160 to 500°C, about 160 to 450°C, about 160 to 350°C, about 180 to 500°C, about 180 to 450°C, and about 180 to 350°C.

[0066] Furthermore, from the viewpoint of more suitably achieving the effects of the present disclosure, the total thickness of the other layers is preferably about 0.1 μm or more, more preferably about 1 μm or more, even more preferably about 5 μm or more, and is preferably about 500 μm or less, more preferably about 300 μm or less, even more preferably about 200 μm or less. Preferred ranges for the total thickness of the other layers include about 0.1 to 500 μm, about 0.1 to 300 μm, about 0.1 to 200 μm, about 1 to 500 μm, about 1 to 300 μm, about 1 to 200 μm, about 5 to 500 μm, about 5 to 300 μm, and about 5 to 200 μm.

[0067] If there is a layer corresponding to resin layer M among the other layers (for example, if at least one of the second layer 12, third layer 13, and fourth layer 14 described below corresponds to resin layer M), the total thickness of resin layer M contained in adhesive film 1 is preferably at least about 5%, more preferably at least about 10%, even more preferably at least about 15%, and is preferably at most about 95%, more preferably at most about 90%, even more preferably at most about 85%, with preferred ranges being 5 to 95% and 10 to 90%.

[0068] In the present disclosure, from the viewpoint of more suitably exerting the effects of the present disclosure, the ratio of the total thickness of the other layers to the total thickness (100%) of the adhesive film 1 is preferably about 5% or more, more preferably about 10% or more, even more preferably about 15% or more, and is preferably about 95% or less, more preferably about 90% or less, even more preferably about 85% or less, with preferred ranges being approximately 5 to 95%, approximately 5 to 90%, approximately 5 to 85%, approximately 10 to 95%, approximately 10 to 90%, approximately 10 to 85%, approximately 15 to 95%, approximately 15 to 90%, and approximately 15 to 85%.

[0069] Furthermore, when a layer corresponding to resin layer M is present among the other layers (for example, when at least one of the second layer 12, third layer 13, and fourth layer 14 described below corresponds to resin layer M), the ratio of the total thickness of resin layer M to the total thickness (100%) of adhesive film 1 is preferably about 5% or more, more preferably about 10% or more, even more preferably about 15% or more, and is preferably about 95% or less, more preferably about 90% or less, even more preferably about 85% or less, with preferred ranges being about 5 to 95%, about 5 to 90%, about 5 to 85%, about 10 to 95%, about 10 to 90%, about 10 to 85%, about 15 to 95%, about 15 to 90%, and about 15 to 85%.

[0070] (additives) At least one of the first layer 11 and the other layers may contain additives such as a colorant such as a pigment, a filler, and a lubricant in addition to the resin.

[0071] Various inorganic pigments can be used as the pigment. A specific example of the pigment is carbon (carbon, graphite), which is exemplified as a filler described below. Carbon (carbon, graphite) is a material generally used inside an electricity storage device, and can be suitably incorporated because there is no risk of it eluting into the electrolyte solution. Furthermore, the coloring effect is significant, and a sufficient coloring effect can be obtained with an amount added that does not impair adhesion. Furthermore, the coloring effect is not melted by heat, and the apparent melt viscosity of the added resin can be increased. Furthermore, the pressed portion can be prevented from becoming thin during thermal adhesion (heat sealing), thereby providing excellent sealing between the exterior material for an electricity storage device and the metal terminal.

[0072] When a pigment is added to at least one of the first layer 11 and the other layers, the amount of pigment added may be, for example, about 0.05 to 0.3 parts by mass, and preferably about 0.1 to 0.2 parts by mass, for each 100 parts by mass of the resin component of each layer of the adhesive film 1, when carbon black with a particle size of about 0.03 μm is used. When both a pigment and a filler are added to the adhesive film 1, the filler and the pigment may both be added to the same layer, but from the viewpoint of not impairing the heat-sealing properties of the adhesive film 1, it is preferable to add the filler and the pigment separately to different layers.

[0073] The particle size of the filler is in the range of about 0.1 to 35 μm, preferably about 5.0 to 30 μm, and more preferably about 10 to 25 μm. The content of the filler is in the range of about 5 to 30 parts by mass, and more preferably about 10 to 20 parts by mass, per 100 parts by mass of the resin component forming each layer of the adhesive film 1.

[0074] The filler may be either inorganic or organic. Examples of inorganic fillers include carbon (carbon, graphite), silica, aluminum oxide, barium titanate, iron oxide, silicon carbide, zirconium oxide, zirconium silicate, magnesium oxide, titanium oxide, calcium aluminate, calcium hydroxide, aluminum hydroxide, magnesium hydroxide, and calcium carbonate. Examples of organic fillers include fluororesins, phenolic resins, urea resins, epoxy resins, acrylic resins, benzoguanamine-formaldehyde condensates, melamine-formaldehyde condensates, cross-linked polymethyl methacrylates, and cross-linked polyethylenes. From the standpoints of shape stability, rigidity, and content resistance, aluminum oxide, silica, fluororesins, acrylic resins, and benzoguanamine-formaldehyde condensates are preferred, with spherical aluminum oxide and silica being particularly preferred. Methods for mixing the filler into the resin components that form each layer of the adhesive film 1 include melt-blending the two in advance using a Banbury mixer or the like to form a masterbatch and then mixing it in a predetermined ratio, or directly mixing it with the resin components.

[0075] From the viewpoint of improving the sealing property of the electricity storage device of the present disclosure, a lubricant may be contained in each of the layers constituting the surface of the adhesive film 1. The concentration of the lubricant is preferably 2000 ppm or less, more preferably 1500 ppm or less, and even more preferably 1000 ppm or less, and is preferably 200 ppm or more, more preferably 500 ppm or more, with preferred ranges being about 200 to 2000 ppm, about 200 to 1500 ppm, about 200 to 1000 ppm, about 500 to 2000 ppm, about 500 to 1500 ppm, and about 500 to 1000 ppm.

[0076] The lubricant is not particularly limited, but preferably includes amide-based lubricants. Specific examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearic acid amide. Specific examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipamide, and N,N'-distearyl sebacic acid amide. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacic acid amide. Specific examples of fatty acid ester amides include stearamidoethyl stearate. Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, N,N'-distearyl isophthalic acid amide, etc. The lubricants may be used singly or in combination of two or more.

[0077] When the layers constituting the adhesive film 1 are composed of resin films, the surfaces of these layers may be subjected to known adhesion-improving means such as corona discharge treatment, ozone treatment, or plasma treatment, if necessary.

[0078] In producing the adhesive film 1 of the present disclosure, lamination of each layer can be carried out by a known method such as extrusion lamination, T-die lamination, inflation lamination, or thermal lamination.

[0079] [Exterior materials for energy storage devices 3] The electrical storage device packaging material 3 may have a laminated structure including at least a substrate layer 31, a barrier layer 33, and a heat-sealable resin layer 35, in this order. FIG. 8 shows an example of the cross-sectional structure of the electrical storage device packaging material 3, in which the substrate layer 31, an optional adhesive layer 32, a barrier layer 33, an optional adhesive layer 34, and a heat-sealable resin layer 35 are laminated in this order. In the electrical storage device packaging material 3, the substrate layer 31 is the outer layer, and the heat-sealable resin layer 35 is the innermost layer. During assembly of the electrical storage device, the electrical storage device elements 4 are sealed by bringing the heat-sealable resin layers 35 located on the periphery of the electrical storage device elements 4 into contact with each other and heat-sealing them, thereby sealing the electrical storage device elements 4. While FIGS. 1 and 2 illustrate an electrical storage device 10 using an embossed type electrical storage device packaging material 3 formed by embossing or the like, the electrical storage device packaging material 3 may be an unformed pouch type. The pouch type includes three-sided seal, four-sided seal, pillow type, etc., and any type may be used.

[0080] The thickness of the laminate constituting the electricity storage device packaging material 3 is not particularly limited, but from the viewpoints of cost reduction, improving energy density, and the like, the upper limit is preferably about 180 μm or less, about 160 μm or less, about 155 μm or less, about 140 μm or less, about 130 μm or less, or about 120 μm or less, and from the viewpoint of maintaining the function of the electricity storage device packaging material 3 to protect the electricity storage device elements 4, the lower limit is preferably about 35 μm or more, about 45 μm or more, about 60 μm or more, or about 80 μm or more, and preferred ranges are, for example, about 35 to 180 μm, 35 to 1 Examples include about 60 μm, about 35 to 155 μm, about 35 to 140 μm, about 35 to 130 μm, about 35 to 120 μm, about 45 to 180 μm, about 45 to 160 μm, about 45 to 155 μm, about 45 to 140 μm, about 45 to 130 μm, about 45 to 120 μm, about 60 to 180 μm, about 60 to 160 μm, about 60 to 155 μm, about 60 to 140 μm, about 60 to 130 μm, about 60 to 120 μm, about 80 to 180 μm, about 80 to 160 μm, about 80 to 155 μm, about 80 to 140 μm, about 80 to 130 μm, and about 80 to 120 μm.

[0081] Furthermore, the adhesive film 1 of the present disclosure can be suitably applied to an exterior material for an all-solid-state battery. The thickness of the laminate constituting the exterior material for an all-solid-state battery is not particularly limited, but from the viewpoints of cost reduction, improving energy density, etc., it is preferably about 10,000 μm or less, about 8,000 μm or less, or about 5,000 μm or less, and from the viewpoint of maintaining the function of the exterior material for an all-solid-state battery, which is to protect the battery element, it is preferably about 100 μm or less. Examples of preferred ranges include about 100 to 10,000 μm, about 100 to 8,000 μm, about 100 to 5,000 μm, about 150 to 10,000 μm, about 150 to 8,000 μm, about 150 to 5,000 μm, about 200 to 10,000 μm, about 200 to 8,000 μm, and about 200 to 5,000 μm, with about 100 to 500 μm being particularly preferred.

[0082] (Base material layer 31) In the packaging material 3 for an electricity storage device, the base material layer 31 is a layer that functions as the base material of the packaging material for an electricity storage device, and is a layer that forms the outermost layer side.

[0083] The material for forming the base layer 31 is not particularly limited, as long as it has insulating properties. Examples of materials for forming the base layer 31 include polyester, polyamide, epoxy, acrylic, fluororesin, polyurethane, silicone resin, phenol, polyetherimide, polyimide, and mixtures or copolymers thereof. Polyesters such as polyethylene terephthalate and polybutylene terephthalate have the advantage of being highly resistant to electrolyte and being less susceptible to whitening due to adhesion of electrolyte, and are therefore preferably used as materials for forming the base layer 31. Furthermore, polyamide film has excellent stretchability and can prevent whitening due to resin cracking of the base layer 31 during molding, and is therefore preferably used as materials for forming the base layer 31.

[0084] The base layer 31 may be formed of a uniaxially or biaxially stretched resin film, or may be formed of an unstretched resin film. Among them, a uniaxially or biaxially stretched resin film, especially a biaxially stretched resin film, is preferably used as the base layer 31 because its heat resistance is improved by oriented crystallization.

[0085] Among these, nylon and polyester are preferred, and biaxially oriented nylon and biaxially oriented polyester are more preferred as the resin film forming the base layer 31. In addition, all-solid-state batteries are designed to withstand temperatures of 150°C or higher, so they are often sealed at high temperatures of 200°C or higher, and biaxially oriented polyester is the most suitable.

[0086] The base layer 31 can be formed by laminating resin films made of different materials to improve pinhole resistance and insulation when used as a package for an electricity storage device. Specific examples include a multilayer structure in which a polyester film and a nylon film are laminated together, or a multilayer structure in which a biaxially oriented polyester film and a biaxially oriented nylon film are laminated together. When the base layer 31 has a multilayer structure, the resin films may be bonded together via an adhesive, or may be directly laminated together without an adhesive. Bonding without an adhesive can be achieved by, for example, a method of bonding in a hot-melt state, such as coextrusion, sand lamination, or thermal lamination. For the high-temperature sealing described above, it is desirable that at least the outermost layer be made of biaxially oriented polyester.

[0087] The base layer 31 may be made low-friction to improve formability. When making the base layer 31 low-friction, the coefficient of friction of the surface is not particularly limited, but may be, for example, 1.0 or less. To make the base layer 31 low-friction, for example, matte treatment, formation of a thin film layer of a slip agent, or a combination thereof may be used.

[0088] The thickness of the base layer 31 is, for example, about 10 to 50 μm, and preferably about 15 to 30 μm.

[0089] (Adhesive layer 32) In the packaging material 3 for an electricity storage device, the adhesive layer 32 is a layer that is disposed on the base material layer 31 as necessary in order to impart adhesion to the base material layer 31. In other words, the adhesive layer 32 is provided between the base material layer 31 and the barrier layer 33.

[0090] The adhesive layer 32 is formed of an adhesive capable of bonding the base material layer 31 and the barrier layer 33. The adhesive used to form the adhesive layer 32 may be a two-component curing adhesive or a one-component curing adhesive. The bonding mechanism of the adhesive used to form the adhesive layer 32 is not particularly limited, and may be any of a chemical reaction type, a solvent volatilization type, a hot melt type, a hot pressure type, or the like.

[0091] The resin component of the adhesive that can be used to form the adhesive layer 32 is preferably a polyurethane-based two-component curing adhesive; polyamide, polyester, or a blend resin of these with modified polyolefin, from the viewpoint of having excellent ductility, durability under high humidity conditions, yellowing prevention, and thermal degradation prevention during heat sealing, and effectively suppressing a decrease in the laminate strength between the base layer 31 and the barrier layer 33 and preventing delamination.

[0092] Furthermore, the adhesive layer 32 may be multi-layered with different adhesive components. When the adhesive layer 32 is multi-layered with different adhesive components, it is preferable to select a resin that has excellent adhesion to the base material layer 31 as the adhesive component disposed on the base material layer 31 side, and an adhesive component that has excellent adhesion to the barrier layer 33 as the adhesive component disposed on the barrier layer 33 side, from the viewpoint of improving the laminate strength between the base material layer 31 and the barrier layer 33. When the adhesive layer 32 is multi-layered with different adhesive components, specifically, preferred examples of the adhesive component disposed on the barrier layer 33 side include acid-modified polyolefin, metal-modified polyolefin, a mixed resin of polyester and acid-modified polyolefin, and a resin containing copolymer polyester.

[0093] The thickness of the adhesive layer 32 is, for example, about 2 to 50 μm, and preferably about 3 to 25 μm.

[0094] (Barrier layer 33) In the electrical storage device packaging material, the barrier layer 33 is a layer that not only improves the strength of the electrical storage device packaging material but also has the function of preventing water vapor, oxygen, light, and the like from penetrating into the electrical storage device. The barrier layer 33 is preferably a metal layer, i.e., a layer formed of a metal. Specific examples of metals constituting the barrier layer 33 include aluminum, stainless steel, and titanium, and aluminum is preferred. The barrier layer 33 can be formed, for example, from a metal foil, a metal vapor deposition film, an inorganic oxide vapor deposition film, a carbon-containing inorganic oxide vapor deposition film, or a film provided with any of these vapor deposition films. It is preferably formed from a metal foil, and more preferably from an aluminum foil. From the viewpoint of preventing the occurrence of wrinkles or pinholes in the barrier layer 33 during the production of the packaging material for an electricity storage device, it is more preferable that the barrier layer be formed from a soft aluminum foil such as annealed aluminum (JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, JIS H4000:2014 A8079P-O).

[0095] The thickness of the barrier layer 33 is preferably about 10 to 200 μm, more preferably about 20 to 100 μm, about 20 to 45 μm, about 45 to 65 μm, or about 65 to 85 μm, from the viewpoint of making the packaging material for an electricity storage device thinner while making it less likely to produce pinholes during molding.

[0096] Furthermore, it is preferable that at least one surface, and preferably both surfaces, of the barrier layer 33 be chemically treated to stabilize adhesion, prevent dissolution and corrosion, etc. Here, chemical treatment refers to a treatment for forming a corrosion-resistant film on the surface of the barrier layer.

[0097] (adhesive layer 34) In the packaging material 3 for an electricity storage device, the adhesive layer 34 is a layer that is provided as needed between the barrier layer 33 and the heat-sealable resin layer 35 in order to firmly bond the heat-sealable resin layer 35.

[0098] The adhesive layer 34 is formed of an adhesive capable of bonding the barrier layer 33 and the heat-fusible resin layer 35. The composition of the adhesive used to form the adhesive layer is not particularly limited, but examples thereof include an adhesive made of a polyester polyol compound and an alicyclic isocyanate compound.

[0099] The thickness of the adhesive layer 34 is, for example, about 1 to 40 μm, and preferably about 2 to 30 μm.

[0100] (Thermal adhesive resin layer 35) In the packaging material 3 for an electricity storage device, the heat-sealable resin layer 35 corresponds to the innermost layer, and is a layer that seals the electricity storage device elements by heat-sealing the heat-sealable resin layers together when assembling the electricity storage device.

[0101] The resin component used in the heat-sealable resin layer 35 is not particularly limited as long as it is heat-sealable, but for example, in the case of an exterior material for an electricity storage device, polyolefins and cyclic polyolefins are generally used.

[0102] Specific examples of the polyolefin include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); and ethylene-butene-propylene terpolymers. Among these polyolefins, polyethylene and polypropylene are preferred.

[0103] The cyclic polyolefin is a copolymer of an olefin and a cyclic monomer, and examples of the olefin constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, and isoprene. Examples of the cyclic monomer constituting the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, cyclic alkenes are preferred, and norbornene is more preferred. Styrene is also an example of a constituting monomer.

[0104] Among these resin components, preferred are crystalline or amorphous polyolefins, cyclic polyolefins, and blend polymers thereof; more preferred are polyethylene, polypropylene, copolymers of ethylene and norbornene, and blend polymers of two or more of these.

[0105] The heat-fusible resin layer 35 may be formed of one type of resin component alone, or may be formed of a blend polymer of two or more types of resin components. Furthermore, the heat-fusible resin layer 35 may be formed of only one layer, or may be formed of two or more layers of the same or different resin components.

[0106] The thickness of the heat-fusible resin layer 35 is not particularly limited, but may be about 2 to 2000 μm, preferably about 5 to 1000 μm, and more preferably about 10 to 500 μm.

[0107] As described above, the adhesive film 1 includes at least one resin layer L having a melting peak temperature 55°C or more lower than that of the heat-sealable resin layer 35. That is, the heat-sealable resin layer 35 of the electrical storage device packaging material 3 has a melting peak temperature 5°C or more higher than that of the resin layer L. The melting peak temperature of the heat-sealable resin layer 35 is preferably 110 to 250°C, more preferably 120 to 270°C, even more preferably 130 to 270°C, and even more preferably 140 to 250°C. As described above, from the viewpoint of more suitably exhibiting the effects of the present disclosure, the melting peak temperature of the resin layer L is preferably 10°C or more lower, more preferably 15°C or more lower, even more preferably 17°C or more lower, and even more preferably 20°C or more lower than the melting peak temperature of the heat-sealable resin layer 35 of the electrical storage device packaging material 3.

[0108] Examples of resins contained in the heat-sealable resin layer 35 of the all-solid-state battery casing material include polyolefins such as polypropylene and polyethylene, acid-modified polyolefins such as acid-modified polypropylene and acid-modified polyethylene, and polybutylene terephthalate. Among these, polybutylene terephthalate has excellent heat resistance, so in the all-solid-state battery casing material, the heat-sealable resin layer 35 is preferably formed from a polybutylene terephthalate film. Furthermore, forming the heat-sealable resin layer 35 from a polybutylene terephthalate film also provides excellent adhesion to the resin layer L of the adhesive film of the present disclosure. The polybutylene terephthalate film forming the heat-sealable resin layer 35 may be formed by laminating a previously prepared polybutylene terephthalate film with the adhesive layer 34, or the resin forming the polybutylene terephthalate film may be melt-extruded to form a film and then laminated with the adhesive layer 34.

[0109] The polybutylene terephthalate film may be a stretched polybutylene terephthalate film or an unstretched polybutylene terephthalate film, and is preferably an unstretched polybutylene terephthalate film.

[0110] The polybutylene terephthalate film preferably further contains an elastomer in addition to polybutylene terephthalate. The elastomer serves to ensure the durability of the polybutylene terephthalate film in high-temperature environments while increasing its flexibility. Preferred elastomers include at least one thermoplastic elastomer selected from polyesters, polyamides, polyurethanes, polyolefins, polystyrenes, and polyethers, or thermoplastic elastomer copolymers thereof. The content of the elastomer in the polybutylene terephthalate film is not particularly limited as long as it ensures the durability of the polybutylene terephthalate film in high-temperature environments while increasing its flexibility. For example, the content is about 0.1% by mass or more, preferably about 0.5% by mass or more, more preferably about 1.0% by mass or more, and even more preferably about 3.0% by mass or more. The content may be, for example, about 10.0% by mass or less, about 8.0% by mass or less, or about 5.0% by mass or less. Preferred ranges for the content include about 0.1 to 10.0 mass%, about 0.1 to 8.0 mass%, about 0.1 to 5.0 mass%, about 0.5 to 10.0 mass%, about 0.5 to 8.0 mass%, about 0.5 to 5.0 mass%, about 1.0 to 10.0 mass%, about 1.0 to 8.0 mass%, about 1.0 to 5.0 mass%, about 3.0 to 10.0 mass%, about 3.0 to 8.0 mass%, and about 3.0 to 5.0 mass%, etc.

[0111] The heat-sealable resin layer 35 may be formed of only one layer, or may be formed of two or more layers of the same or different resins. When the heat-sealable resin layer 35 is formed of two or more layers, at least one layer is formed of a polybutylene terephthalate film, and the polybutylene terephthalate film is preferably the innermost layer of the all-solid-state battery packaging material. Furthermore, the layer bonded to the adhesive layer 34 is preferably a polybutylene terephthalate film. When the heat-sealable resin layer 35 is formed of two or more layers, the layer not formed of a polybutylene terephthalate film may be formed of, for example, a polyolefin such as polypropylene or polyethylene, or an acid-modified polyolefin such as acid-modified polypropylene or acid-modified polyethylene. However, since polyolefins and acid-modified polyolefins have lower durability in high-temperature environments than polybutylene terephthalate, the heat-sealable resin layer 35 is preferably formed of only a polybutylene terephthalate film.

[0112] 2. Energy storage devices The electricity storage device 10 of the present disclosure is an electricity storage device having a structure in which an electricity storage device element 4 is housed in a package formed from an exterior packaging material 3 for an electricity storage device. The exterior packaging material 3 for an electricity storage device is composed of a laminate having, from the outside, at least a base material layer 31, a barrier layer 33, and a heat-sealable resin layer 35 in this order, and the electricity storage device element 4 is housed in the package by heat-sealing the heat-sealable resin layers 35 of the exterior packaging material 3 for an electricity storage device. An adhesive film 1 is disposed between the heat-sealable resin layers 35 at a position where the heat-sealable resin layers 35 are heat-sealed. As described above, the adhesive film 1 has a multilayer structure and includes at least one resin layer L having a melting peak temperature that is 5°C or more lower than that of the heat-sealable resin layer 35 of the exterior packaging material 3 for an electricity storage device. That is, the energy storage device 10 of the present disclosure can be manufactured by a method including a packaging step of placing an adhesive film 1 between the heat-sealable resin layers 35 of the energy storage device exterior material 3 at a position where the heat-sealable resin layers 35 are to be heat-sealed together, and then heat-sealing the heat-sealable resin layers 35 together via the adhesive film 1, thereby packaging the energy storage device element 4 in a packaging body.

[0113] Specifically, an electricity storage device element 4 including at least a positive electrode, a negative electrode, and an electrolyte is covered with an exterior packaging material 3 for an electricity storage device, with metal terminals 2 connected to the positive and negative electrodes protruding outward, so that a flange portion of the exterior packaging material for an electricity storage device (a region where the heat-sealable resin layers 35 contact each other, i.e., the peripheral portion 3a of the exterior packaging material for an electricity storage device) can be formed around the periphery of the electricity storage device element 4, and the heat-sealable resin layers 35 of the flange portion are heat-sealed to seal them together. At this time, an adhesive film 1 is disposed between the heat-sealable resin layers 35 at a portion of the heat-sealed position and heat-sealed, thereby providing an electricity storage device 10 using the adhesive film 1. When the electricity storage device element 4 is housed using the exterior packaging material 3 for an electricity storage device, the exterior packaging material 3 for an electricity storage device is used so that the heat-sealable resin layer 35 of the exterior packaging material for an electricity storage device faces inside (the surface in contact with the electricity storage device element 4).

[0114] Details of the adhesive film 1 of the present disclosure used in the electricity storage device 10 of the present disclosure are as described above.

[0115] As described above, in the electricity storage device 10, the adhesive film 1 is disposed so as to be interposed between the heat-sealable resin layers 35 at a position where the heat-sealable resin layers 35 of the electricity storage device packaging material 3 are heat-sealed to each other. For example, as shown in Figures 1 and 2, in the electricity storage device 10 of the present disclosure, the adhesive film 1 of the present disclosure is interposed between the opposing heat-sealable resin layers at a position of the peripheral portion 3a of the electricity storage device packaging material 3 where the heat-sealable resin layers 35 are heat-sealed to seal the electricity storage device element 4. The adhesive film 1 and the heat-sealable resin layers 35 on both sides thereof are heat-sealed when the electricity storage device packaging material 3 is used to seal the electricity storage device element 4.

[0116] The electricity storage device 10 of the present disclosure is sealed until it reaches a high temperature (for example, about 100°C to 125°C). When the electricity storage device 10 reaches this high temperature (for example, about 100°C to 125°C), the electricity storage device 10 is opened at the position of the adhesive film 1 between the heat-sealable resin layers 35, and gas generated inside the electricity storage device 10 is released to the outside. The adhesive film 1 is disposed at a part of the position where the heat-sealable resin layers 35 of the electricity storage device packaging material 3 are heat-sealed, so that gas can be selectively released to the outside from the specific position where the adhesive film 1 is disposed. That is, in the electricity storage device 10 of the present disclosure, the position from which gas is released upon opening can be set to any position in the heat-sealed portion between the heat-sealable resin layers 35.

[0117] As described above, the position where the adhesive film 1 is arranged is not particularly limited as long as it is a position where the heat-sealable resin layers 35 of the electrical storage device packaging material 3 are heat-sealed to each other. For example, if the electrical storage device 10 has a rectangular shape in a plan view, the adhesive film 1 may be arranged on either the long side or the short side of the heat-sealed peripheral portion 3a of the electrical storage device packaging material 3. In addition, the adhesive film 1 is preferably arranged in a state where the adhesive film 1 is exposed inside the electrical storage device packaging material 3 (electricity storage device It is preferable that the heat-sealable resin layers 35 of the packaging material 3 for a power storage device are arranged in a manner such that the adhesive film 1 is not completely buried in the heat-sealed portions. The adhesive film 1 may be disposed at at least one of the positions where the three heat-fusible resin layers 35 are heat-fused together, but may be disposed at two or more positions.

[0118] Furthermore, as described above, in the electricity storage device 10 of the present disclosure, the size of the adhesive film 1 is not particularly limited as long as gas is appropriately released when the package is opened. For example, as shown in Fig. 1, when the electricity storage device 10 is rectangular in plan view and the adhesive film 1 is arranged along one side of the rectangle (in the example of Fig. 1, the adhesive film is arranged along the z direction), the ratio of the length of the adhesive film 1 to the length of the side can be approximately 3 to 98%. Furthermore, the size of the adhesive film 1 in the width direction (the direction perpendicular to the length direction and thickness direction, which is the direction along the x direction in the example of Fig. 1) can be approximately 20 to 300%, with the size of the adhesive film in the length direction being 100%.

[0119] In the electricity storage device 10, the metal terminal 2 is electrically connected to the electricity storage device element 4 and protrudes outside the electricity storage device packaging material 3. The adhesive film of the present disclosure is preferably arranged so as not to be located between the metal terminal 2 and the electricity storage device packaging material 3 (thermally adhesive resin layer 35). Furthermore, the adhesive film 1 of the present disclosure is preferably not in contact with the metal terminal 2.

[0120] The power storage device of the present disclosure can be a power storage device such as a battery (including a condenser, a capacitor, etc.). The power storage device of the present disclosure may be either a primary battery or a secondary battery, but is preferably a secondary battery. The type of secondary battery is not particularly limited, and examples include lithium ion batteries, lithium ion polymer batteries, all-solid-state batteries, lead acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, condensers, and capacitors. Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries are preferred. [Example]

[0121] The present disclosure will be described in detail below with reference to examples and comparative examples, but the present disclosure is not limited to the examples.

[0122] <Production of adhesive film> Example 1 Using an extruder and a T-die casting device, acid-modified polyethylene (melting peak temperature 122.7°C) containing a polyolefin-based elastomer (addition amount 10% by mass) as the first layer (resin layer L) and acid-modified polyethylene (melting peak temperature 120°C) as the second layer (resin layer L) were extruded to a thickness of 25 μm each, resulting in an adhesive film (total thickness 50 μm) in which the first layer (resin layer L PEa layer melting peak temperature 122.7°C, thickness 25 μm) / second layer (resin layer L PEa layer melting peak temperature 120°C, thickness 25 μm) were laminated in order.

[0123] Example 2 Using an extruder and a T-die casting machine, a polyethylene film (peak melting temperature 120°C, thickness 15μm) as the first layer (resin layer L) was extruded onto one side with polypropylene (peak melting temperature 140°C) as the second layer, and polypropylene (peak melting temperature 140°C) as the third layer on the other side, each to a thickness of 7.5μm, to obtain an adhesive film (total thickness 30μm) in which the second layer (PP layer, peak melting temperature 140°C, thickness 7.5μm) / first layer (resin layer L PE layer, peak melting temperature 120°C, thickness 15μm) / third layer (PP layer, peak melting temperature 140°C, thickness 7.5μm) were laminated in that order.

[0124] Example 3 Using an extruder and a T-die casting machine, a polyethylene film (peak melting temperature 110°C, thickness 15μm) as the first layer (resin layer L) was extruded onto one side with polypropylene (peak melting temperature 140°C) as the second layer, and polypropylene (peak melting temperature 140°C) as the third layer on the other side, each to a thickness of 7.5μm, to obtain an adhesive film (total thickness 30μm) in which the second layer (PP layer, peak melting temperature 140°C, thickness 7.5μm) / first layer (resin layer L PE layer, peak melting temperature 110°C, thickness 15μm) / third layer (PP layer, peak melting temperature 140°C, thickness 7.5μm) were laminated in that order.

[0125] Example 4 Using an extruder and a T-die casting machine, a maleic anhydride-modified polypropylene (peak melting temperature 140°C) was extruded onto one side of a polyethylene naphthalate film (peak melting temperature 265°C, thickness 12µm) as a third layer, and a maleic anhydride-modified polypropylene (peak melting temperature 140°C) was extruded onto the other side as a fourth layer, each to a thickness of 30µm. Furthermore, an acid-modified polyethylene (peak melting temperature 122.7°C) containing a polyolefin elastomer (addition amount 10% by mass) was extruded onto the surface of the second layer to a thickness of 33µm as a first layer (resin layer L), resulting in a first layer (resin layer L PEa layer peak melting temperature 122.7°C, thickness 33µm) / second layer (PPa layer peak melting temperature 140°C, thickness 30µm) / third layer (PEN layer peak melting temperature 265°C, thickness 12µm) / fourth layer (PPa layer An adhesive film (total thickness 100 μm) in which the laminated layers (melting peak temperature 140° C., thickness 30 μm) were laminated in this order was obtained.

[0126] Comparative Example 1 A single layer of polyethylene film (melting peak temperature 125°C, thickness 50 µm) was used as the adhesive film (total thickness 50 µm).

[0127] Comparative Example 2 A three-layer coextruded unstretched polypropylene film (CPP layer: polypropylene (peak melting temperature 140°C, thickness 10 μm) / polypropylene (peak melting temperature 140°C, thickness 20 μm) / polypropylene (peak melting temperature 140°C, thickness 10 μm)) was used as an adhesive film (total thickness 40 μm).

[0128] <Measurement of melting peak temperature> The melting peak temperature of each resin constituting the adhesive film was measured in accordance with the provisions of JIS K7121:2012 (Method for measuring transition temperatures of plastics (JIS K7121:1987, Supplement 1)). Measurements were performed using a differential scanning calorimeter (DSC, TA Instruments Q200). The measurement sample was held at -50°C for 15 minutes, then heated from -50°C to 210°C at a heating rate of 10°C / min. The first melting peak temperature P (°C) was measured, and then held at 210°C for 10 minutes. Next, the temperature was lowered from 210°C to -50°C at a heating rate of 10°C / min and held for 15 minutes. The second melting peak temperature Q (°C) was measured by heating from -50°C to 210°C at a heating rate of 10°C / min. The nitrogen gas flow rate was 50 ml / min. Using the above procedure, the melting peak temperature P (°C) measured the first time and the melting peak temperature Q (°C) measured the second time were determined, and the melting peak temperature measured the first time was designated as the melting peak temperature.

[0129] <Opening test method> A 121 μm thick exterior packaging material for an energy storage device was prepared, consisting of a substrate layer (PET (12 μm thick) / adhesive (2 μm thick) / nylon (15 μm thick)) / adhesive layer (2 μm thick) / barrier layer (aluminum alloy foil, 40 μm thick) / adhesive layer (maleic anhydride-modified polypropylene, 25 μm thick) / heat-sealable resin layer (polypropylene, melting peak temperature 140°C, 25 μm thick) laminated in this order. Two test pieces were cut to a size of 8 cm wide (z direction) x 19 cm long (x direction). Next, the heat-sealable resin layers of these two test pieces were stacked facing each other, forming a short side of 8 cm wide (z direction) and a long side of 19 cm long (x direction). A pair of overlapping test pieces was prepared. As shown in the schematic diagrams of FIGS. 1 and 2, an adhesive film was placed between the heat-sealable resin layers at the short side of the peripheral edge 3a where the heat-sealable resin layers of the electrical storage device packaging material were heat-sealed. The adhesive film measured 3 cm in width (z direction) × 1.5 cm in length (x direction). Although metal terminals are depicted in the schematic diagram of FIG. 1, no metal terminals were used in the unsealing test method. Furthermore, the adhesive film was positioned so that its width (z direction) and length (x direction) coincided with the test specimen. More specifically, the test specimen and the adhesive film were positioned so that their centers coincided in the width (z direction), and the adhesive film's bottom edge (x direction) was aligned with the 8 cm short side that was the bottom edge of the test specimen in the length (x direction). Next, the short side of the test piece of the electrical storage device packaging material, on which the adhesive film was placed, was heat-sealed to the opposing short side under conditions of a pressure of 0.5 MPa, a temperature of 190°C, and a seal width of 3 mm. At this time, both sides of the adhesive film were heat-sealed to the heat-sealable resin layer. A 0.8 cm margin not heat-sealed with the electrical storage device packaging material was left on both sides of the adhesive film. Furthermore, one long side of the test piece of the electrical storage device packaging material was heat-sealed in the same manner, resulting in a bag-shaped sample with the opposing short side and one long side heat-sealed, and the other long side, which was not heat-sealed, becoming an opening. 1 g of water was then poured into the bag-shaped sample, and the opening side (long side) was similarly heat-sealed to produce a water-tight test sample. A thermocouple was attached to the test sample, which was placed in an oven and heated from room temperature (25°C) at a heating rate of 6°C / min until the test sample temperature reached 140°C.The opening temperature was evaluated according to the following criteria, and the results are shown in Table 1. A: It was opened between 100℃ and 125℃. B: Opened at less than 100°C. C: Opened at over 125°C.

[0130] [Measurement of seal strength (at temperatures of 25°C, 60°C, 100°C, and 120°C)] The packaging material for an electricity storage device used in the above-mentioned "Opening Test Method" was cut to a size of 60 mm (Z direction) x 150 mm (X direction), then folded in half with the heat-sealable resin layer facing inward. An adhesive film (60 mm in Z direction, 15 mm in X direction) was sandwiched between the two pieces (at the folded portion). This state was heat-sealed at 240°C, 1.0 MPa, and 5 seconds using a 7 mm wide, upper and lower metal head sealer to prepare a test specimen. The resulting laminate was cut, and a 15 mm rectangular test specimen (with both sides of the adhesive film heat-sealed to the heat-sealable resin layer) was obtained from the center of the adhesive film sandwiched between the heat-sealable resin layers. The seal strength of the resulting test specimen was measured in accordance with JIS K7127:1999 at 25°C, 60°C, 100°C, and 120°C, as follows: Using a tensile tester equipped with a thermostatic chamber, one exterior material was chucked and pulled at a speed of 300 mm / min (chuck distance 50 mm) in each of the measurement environments of 25°C, 60°C, 100°C, or 120°C, and the seal strength (N / 15 mm) at each temperature was measured. The results are shown in Table 1. In addition, based on the seal strength (rounded value) at the measurement temperature of 60°C, the seal strength at 60°C was evaluated according to the following criteria. The results are shown in Table 1. A+:51N / 15mm or more A: 11N / 15mm or more and 50N / 15mm or less B: 10N / 15mm or less

[0131] [Table 1]

[0132] The adhesive films of Examples 1 to 4 have a multilayer structure and include layers (first layer (PEa layer) and second layer (PEa layer) in Example 1, first layer (PE layer) in Example 2, first layer (PE layer) in Example 3, and first layer (PEa layer) in Example 4) corresponding to the resin layer L having a melting peak temperature 5°C or more lower than that of the heat-sealable resin layer (melting peak of 140°C) of the packaging material for an electricity storage device. As is clear from the results of the unsealing temperature evaluation shown in Table 1, the adhesive films of Examples 1 to 4 seal the electricity storage device until the electricity storage device reaches a high temperature (for example, about 100°C to 125°C), and when the electricity storage device reaches that high temperature (for example, about 100°C to 125°C), the electricity storage device is unsealed at the position of the adhesive film between the heat-sealable resin layers, allowing gas generated inside the electricity storage device to be released to the outside.

[0133] In the opening test, when the adhesive films of Examples 1 to 4 were used, opening occurred at the position of the adhesive film in all cases.

[0134] As described above, the present disclosure provides the following aspects of the invention. Item 1. An adhesive film used in an electricity storage device, The electricity storage device has a structure in which an electricity storage device element is housed in a package formed from an exterior packaging material for an electricity storage device, The packaging material for an electricity storage device is composed of a laminate including at least a base layer, a barrier layer, and a heat-sealable resin layer in this order from the outside, the heat-fusible resin layers of the electrical storage device packaging material are heat-fused together to house the electrical storage device element in the packaging body; the adhesive film is used so as to be interposed between the heat-fusible resin layers at positions where the heat-fusible resin layers are heat-fused to each other, The adhesive film has a multilayer structure, The adhesive film includes at least one resin layer L having a melting peak temperature that is 5° C. or more lower than that of the heat-fusible resin layer of the packaging material for an electricity storage device. Item 2. The adhesive film according to Item 1, wherein the resin layer L has a melting peak temperature of 100°C or higher and 135°C or lower. Item 3. The adhesive film according to Item 1 or 2, wherein the resin layer L contains a polyolefin skeleton. Item 4. The adhesive film according to any one of Items 1 to 3, wherein the resin layer L has a thickness of 500 μm or less. Item 5. The adhesive film according to any one of Items 1 to 4, wherein the adhesive film has a thickness of 1 μm or more and 500 μm or less. Item 6. An electricity storage device having a structure in which an electricity storage device element is housed in a package formed from an exterior material for an electricity storage device, The packaging material for an electricity storage device is composed of a laminate including at least a base layer, a barrier layer, and a heat-sealable resin layer in this order from the outside, the heat-fusible resin layers of the exterior packaging material for an electricity storage device are heat-fused together to house the electricity storage device element in the packaging body, an adhesive film is disposed between the heat-fusible resin layers at a position where the heat-fusible resin layers are heat-fused to each other, so as to be interposed therebetween; The adhesive film has a multilayer structure, The adhesive film includes at least one resin layer L having a melting peak temperature that is 5° C. or more lower than that of the heat-fusible resin layer of the packaging material for an electricity storage device. Item 7. A method for manufacturing an electricity storage device having a structure in which an electricity storage device element is housed in a packaging body formed from an exterior material for an electricity storage device, The packaging material for an electricity storage device is composed of a laminate including at least a base layer, a barrier layer, and a heat-sealable resin layer in this order from the outside, the method includes a step of arranging an adhesive film between the heat-sealable resin layers at positions where the heat-sealable resin layers of the exterior packaging material for an electricity storage device are to be heat-sealed together, and heat-sealing the heat-sealable resin layers via the adhesive film, thereby accommodating the electricity storage device element in the packaging body, The adhesive film has a multilayer structure, The method for producing an electricity storage device, wherein the adhesive film includes at least one resin layer L having a melting peak temperature that is 5°C or more lower than that of the heat-fusible resin layer of the packaging material for an electricity storage device. [Explanation of symbols]

[0135] 1. Adhesive film 2 metal terminals 3. Exterior materials for energy storage devices 3a Peripheral part of the exterior material for the electricity storage device 4. Energy storage device elements 5. Adhesive film for metal terminals 10. Energy storage devices 11 1st layer (resin layer L) 12 2nd layer 13 3rd layer 14 4th layer 31 Base material layer 32 Adhesive layer 33 Barrier Layer 34 Adhesive layer 35 Heat-fusible resin layer

Claims

[Claim 1] An adhesive film for use in an electricity storage device, The electricity storage device has a structure in which an electricity storage device element is housed in a package formed from an exterior packaging material for an electricity storage device, The packaging material for an electricity storage device is composed of a laminate including at least a base layer, a barrier layer, and a heat-sealable resin layer in this order from the outside, the heat-fusible resin layers of the electrical storage device packaging material are heat-fused together to house the electrical storage device element in the packaging body; the adhesive film is used so as to be interposed between the heat-fusible resin layers at positions where the heat-fusible resin layers are heat-fused to each other, The adhesive film has a multilayer structure, The adhesive film includes at least one resin layer L having a melting peak temperature that is 5°C or more lower than that of the heat-fusible resin layer of the packaging material for an electricity storage device.

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