JP7126405B2 - Exterior material for power storage device and power storage device - Google Patents

Description

The present invention is used for power storage devices such as batteries and capacitors used in mobile devices such as smartphones and tablets, hybrid vehicles, electric vehicles, wind power generation, solar power generation, and batteries and capacitors used for storing nighttime electricity. It relates to an exterior material and an electric storage device.

In the claims of the present application and in this specification, the term "light" is used to include not only visible light and ultraviolet light, but also X-rays.

In addition, in the scope of claims and this specification of the present application, the term "photopolymerization initiator" means a compound that generates any one of radicals, cations, and anions upon irradiation with light.

In addition, in the scope of claims and this specification of the present application, the term "phosphoric acid-containing (meth)acrylate" means "phosphoric acid-containing acrylate and/or phosphoric acid-containing methacrylate".

Lithium ion secondary batteries are widely used as power sources for, for example, notebook computers, video cameras, mobile phones, electric vehicles, and the like. As this lithium ion secondary battery, one having a configuration in which a battery main body (a main body including a positive electrode, a negative electrode, and an electrolyte) is surrounded by a case is used. As this case material (exterior material), there is known a structure in which an outer layer made of a heat-resistant resin film, an aluminum foil layer, and an inner layer made of a thermoplastic resin film are adhered and integrated in this order.

For example, a laminated packaging material comprising an inner layer made of a resin film, a first adhesive layer, a metal layer, a second adhesive layer, and an outer layer made of a resin film, wherein the first adhesive layer and the second adhesive A packaging material is known in which at least one of the agent layers is composed of an adhesive composition containing, as essential components, a resin having an active hydrogen group in a side chain, a polyfunctional isocyanate, and a polyfunctional amine compound (Patent Document 1). .

However, in the technique described in Patent Document 1, it is necessary to perform heat aging at 50° C. for 7 days in order to obtain the desired adhesive strength as an adhesive, which has resulted in a problem of poor productivity. However, there is also the problem of requiring large-scale equipment for heat aging. Furthermore, since a solvent is used, if the drying is insufficient, the solvent tends to remain, making it difficult to obtain sufficient adhesive strength.

Therefore, as a solution to such productivity problems, a technique is known in which the curing time is greatly shortened by using a UV curing resin adhesive, and the heat aging process is not required.

JP 2008-287971 A

However, in the latter technique using the UV curable resin adhesive, coating is performed by dissolving the adhesive in a solvent in order to form a uniform adhesive layer. A drying process was required. Furthermore, there is also a problem that the adhesive (photocurable resin adhesive) tends to protrude due to the pressure applied by a roll or the like when the resin film is attached to the adhesive application surface.

The present invention has been made in view of the above technical background, and provides an exterior material for an electricity storage device and an exterior case for an electricity storage device that are excellent in productivity, do not cause adhesive to protrude, and provide sufficient high-temperature lamination strength. intended to provide Another object of the present invention is to provide an electricity storage device that is covered with such an outer material and/or an outer case.

In order to achieve the above object, the present invention provides the following means.

[1] An exterior material for an electricity storage device, comprising a heat-resistant resin layer as an outer layer, a heat-fusible resin layer as an inner layer, and a metal foil layer disposed between these layers,
The metal foil layer and the heat-resistant resin layer are bonded via an outer adhesive layer, and the metal foil layer and the heat-fusible resin layer are bonded via an inner adhesive layer,
At least one adhesive layer of the outer adhesive layer and the inner adhesive layer is formed of a photocurable resin adhesive containing a main agent and at least two photopolymerization initiators,
Part or all of the light absorption wavelength band of one of the two photopolymerization initiators has a wavelength region that does not overlap with the light absorption wavelength band of the other photopolymerization initiator. An exterior material for an electricity storage device, characterized by:

[2] The electricity storage according to the preceding item 1, wherein the content of one of the two types of photopolymerization initiators in the photocurable resin adhesive is 0.2% by mass to 3% by mass. Exterior material for devices.

[3] The electricity storage according to the above item 2, wherein the content of the other one of the two photopolymerization initiators in the photocurable resin adhesive is 9% by mass to 20% by mass. Exterior material for devices.

[4] Among the two types of photopolymerization initiators, the peak value of the light absorption wavelength of one photopolymerization initiator is in the range of 200 nm or more and less than 300 nm, and the light absorption wavelength of the other one photopolymerization initiator. 4. The exterior material for an electricity storage device according to any one of 1 to 3 above, which has a peak value in the range of 300 nm or more and 400 nm or less.

[5] The photocurable resin adhesive contains two or more main agents,
Among the two types of photopolymerization initiators, one photopolymerization initiator (X) and another photopolymerization initiator (Y) are
First type: (X) is an anionic polymerization initiator/(Y) is a radical polymerization initiator Second type: (X) is an anionic polymerization initiator/(Y) is a cationic polymerization initiator Third type: (X) is a cationic polymerization initiator/(Y) is a radical polymerization initiator Any one of the combinations of the above three types of types 1 to 3 above 1 to 4. 2. The exterior material for an electricity storage device according to Item 1.

[6] An exterior case for an electricity storage device, comprising a molding of the exterior material according to any one of 1 to 5 above.

[7] an electricity storage device main body;
An exterior member comprising the exterior material according to any one of the preceding items 1 to 5 and/or the exterior case according to claim 6,
An electricity storage device, wherein the electricity storage device main body is covered with the exterior member.

[8] A step of applying a photocurable resin composition containing a main agent and at least two photopolymerization initiators to one surface of a metal foil;
a step of irradiating light from the coated side of the metal foil;
a step of superimposing a resin film on the coated surface after the light irradiation to obtain a laminate;
irradiating the laminate with light from the resin film side,
Part or all of the light absorption wavelength band of one of the two photopolymerization initiators has a wavelength region that does not overlap with the light absorption wavelength band of the other photopolymerization initiator. A method for manufacturing an exterior material for an electricity storage device, characterized by:

[9] A first application step of applying a photocurable resin composition containing a main agent and at least two photopolymerization initiators to one surface of a metal foil;
a step of irradiating light from the coated side of the metal foil;
a step of superimposing a first resin film on the coated surface after the light irradiation to obtain a first laminate;
irradiating the first laminate with light from the first resin film side,
a second application step of applying a photocurable resin composition containing a main agent and at least two types of photopolymerization initiators to the other surface of the metal foil of the first laminate after the light irradiation;
A step of irradiating light from the application side of the first laminate;
a step of obtaining a second laminate by superimposing a second resin film on the coated surface of the first laminate after the light irradiation;
irradiating the second laminate with light from the second resin film side,
Part or all of the light absorption wavelength band of one of the two photopolymerization initiators in the first coating step does not overlap the light absorption wavelength band of the other photopolymerization initiator. has a wavelength range,
Part or all of the light absorption wavelength band of one of the two photopolymerization initiators in the second coating step does not overlap the light absorption wavelength band of the other photopolymerization initiator. A method for manufacturing an exterior material for an electric storage device, characterized by having a wavelength region.

In the invention [1], at least one of the outer adhesive layer and the inner adhesive layer is a photocurable resin adhesive containing a main agent and at least two photopolymerization initiators. formed, and among the two types of photopolymerization initiators, part or all of the light absorption wavelength band of one of the photopolymerization initiators has a wavelength region that does not overlap with the light absorption wavelength band of the other photopolymerization initiator Since the photocurable resin adhesive layer is formed by photocuring the adhesive in stages, the viscosity of the adhesive can be changed depending on the stage. It is possible to provide an exterior material for an electric storage device that does not cause the adhesive to protrude when the outer layer or the inner layer is laminated (overlapping) on the adhesive (layer) that has been subjected to the bonding, and that can provide sufficient lamination strength after lamination. . Moreover, it can be applied without a solvent, and there is no decrease in adhesive performance due to residual solvent.

In the invention of [2], the content of one of the two types of photopolymerization initiators in the photocurable resin adhesive is in the range of 0.2% by mass to 3% by mass. , by first irradiating such a low content photopolymerization initiator with light containing part or all of a wavelength region that does not overlap with the light absorption wavelength band of the other photopolymerization initiator, some The main agent polymerizes and becomes an appropriate viscosity (gel), and the adhesive (light-curing resin adhesive) does not protrude even when pressure is applied by rolls, etc., when pasting a resin film, and the adhesive is uniform. A thick adhesive layer is formed.

In the invention of [3], since the content of the other photopolymerization initiator in the photocurable resin adhesive is in the range of 9% by mass to 20% by mass, the following light irradiation sufficiently photocures It is possible to secure sufficient adhesive strength.

In the invention [4], 200 nm to 400 nm is an ultraviolet light region, and therefore, a curing reaction (photopolymerization reaction) by visible light does not occur. The adhesive (photocurable resin adhesive) does not protrude, and sufficient adhesive strength can be ensured.

In the invention [5], since it is composed of a combination of different polymerization systems (e.g. cationic polymerization initiator and main agent/radical polymerization initiator and main agent), one polymerization initiator (e.g. radical type) On the other hand, since only the main agent of the polymerization system (for example, a radical system) reacts, light containing the light absorption wavelength of one polymerization initiator (and a wavelength that does not overlap with the light absorption wavelength band of the other photopolymerization initiator By first irradiating with the light of the area), a part of the main agent polymerizes and becomes an appropriate viscosity (gel), and even if pressure is applied by rolls etc. when pasting the resin film, the adhesive (light curing resin adhesive) does not protrude, and an adhesive layer having a uniform thickness is formed. When the other polymerization initiator (e.g., cationic) is irradiated with light, the main agent (e.g., cationic) of the polymerization system reacts, so each main agent can be polymerized separately. can be made to the desired hardness.

In the invention [6], it is possible to provide an exterior case for an electric storage device which is excellent in productivity, does not cause the adhesive to protrude, and provides sufficient lamination strength.

According to the invention [7], it is possible to provide an electric storage device covered with an electric storage device covering material that is excellent in productivity, does not cause the adhesive to protrude, and provides sufficient lamination strength.

In the invention [8], at least one adhesive layer (the inner adhesive layer or the outer adhesive layer) can be formed by light irradiation, and no aging process is required, so productivity can be improved. Furthermore, by pre-curing the photocurable resin composition before superimposing the resin film, it becomes an appropriate viscosity (gel body). There is no protrusion of the agent (photocurable resin adhesive). Furthermore, by dividing the photo-curing into two stages in this way, curing strain is alleviated, and as a result, the adhesive strength is also improved. That is, it is possible to manufacture an exterior material for an electric storage device that is excellent in productivity, does not cause the adhesive to protrude, and provides sufficient high-temperature lamination strength.

In the invention [9], since the inner adhesive layer and the outer adhesive layer can be formed by light irradiation, the productivity can be further improved, the adhesive does not protrude, and sufficient high-temperature lamination strength can be obtained. Can manufacture exterior materials for

1 is a cross-sectional view showing an embodiment of an exterior material for an electricity storage device according to the present invention; FIG. 1 is a cross-sectional view showing an embodiment of an electricity storage device according to the present invention; FIG. FIG. 3 is a perspective view showing an exterior material (planar one), an electricity storage device main body, and an exterior case (three-dimensional molded body) constituting the electricity storage device of FIG. 2 in a separated state before being heat-sealed. It is a figure which shows an example of the mutual relationship between the optical absorption spectrum of two types of photoinitiators, the wavelength of the 1st irradiation light, and the wavelength of the 2nd irradiation light. FIG. 10 is a diagram showing another example of the interrelationship; FIG. 10 is a diagram showing still another example of the mutual relationship; FIG. 10 is a diagram showing still another example of the mutual relationship;

FIG. 1 shows an embodiment of an exterior material 1 for an electric storage device according to the present invention. This exterior material 1 is used as an exterior material for a battery such as a lithium ion secondary battery. The exterior material 1 may be used as it is as the exterior material 1 without being molded (see FIG. 3), or may be used as the molded case 10 after being subjected to molding such as deep drawing and stretch molding. (see FIG. 3).

The power storage device exterior material 1 is formed by laminating and integrating a heat-resistant resin layer (outer layer) 2 on one surface (upper surface) of a metal foil layer 4 with an outer adhesive layer (first adhesive layer) 5 interposed therebetween. In addition, a heat-fusible resin layer (inner layer) 3 is laminated and integrated on the other surface (lower surface) of the metal foil layer 4 via an inner adhesive layer (second adhesive layer) 6. (see Figure 1).

In the present invention, the outer layer 2 is made of a heat-resistant resin layer. As the heat-resistant resin forming the heat-resistant resin layer 2, a heat-resistant resin that does not melt at the heat-sealing temperature at which the exterior material 1 is heat-sealed is used. As the heat-resistant resin, it is preferable to use a heat-resistant resin having a melting point higher than the melting point of the heat-fusible resin forming the heat-fusible resin layer 3 by 10°C or more. It is particularly preferable to use a heat-resistant resin having a melting point higher than °C.

The heat-resistant resin layer (outer layer) 2 is a member that mainly plays the role of ensuring good moldability as the exterior material 1, that is, mainly plays the role of preventing breakage due to necking of the aluminum foil during molding. It is.

Examples of the heat-resistant resin layer (outer layer) 2 include, but are not limited to, a stretched polyamide film such as a stretched nylon film, and a stretched polyester film. Among them, the heat-resistant resin layer 2 may be biaxially oriented polyamide film such as biaxially oriented nylon film, biaxially oriented polybutylene terephthalate (PBT) film, biaxially oriented polyethylene terephthalate (PET) film or biaxially oriented polyethylene film. It is particularly preferred to use phthalate (PEN) films, all of which have a hot water shrinkage of 1.5% to 12%. Moreover, as the heat-resistant resin layer 2, it is preferable to use a heat-resistant resin biaxially stretched film stretched by a simultaneous biaxial stretching method. Examples of the nylon include, but are not particularly limited to, 6 nylon, 6,6 nylon, MXD nylon, and the like. In addition, the heat-resistant resin film layer 2 may be formed of a single layer (single stretched film), or may be, for example, a multilayer made of stretched polyester film/stretched polyamide film (stretched PET film/stretched nylon film). It may be formed by a multilayer film or the like).

The thickness of the heat-resistant resin layer 2 is preferably 10 μm to 25 μm. Sufficient strength as an exterior material can be ensured by setting the value to the preferred lower limit value or more, and by setting the value to the preferred upper limit value or less, the stress during stretch forming or draw forming can be reduced to improve formability. can be done.

In the present invention, the metal foil layer 4 plays a role of imparting a gas barrier property to the exterior material 1 to prevent permeation of oxygen and moisture. Examples of the metal foil layer 4 include, but are not limited to, aluminum foil, copper foil, iron foil, etc. Aluminum foil is generally used. The thickness of the metal foil layer 4 is preferably 10 μm to 80 μm. When the thickness is 10 μm or more, it is possible to prevent the occurrence of pinholes during rolling when manufacturing the metal foil. be able to. Above all, it is particularly preferable that the thickness of the metal foil layer 4 is 10 μm to 40 μm.

Preferably, at least the inner surface of the metal foil layer 4 (the surface on the inner adhesive layer 6 side) is subjected to a chemical conversion treatment. Such chemical conversion treatment can sufficiently prevent the corrosion of the metal foil surface due to the contents (electrolyte solution of the battery, etc.). For example, the metal foil is chemically treated by the following treatment. That is, for example, on the surface of a metal foil that has been degreased,
1) phosphoric acid;
chromic acid;
2) an aqueous solution of a mixture containing at least one compound selected from the group consisting of metal salts of fluoride and non-metal salts of fluoride;
at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins and phenolic resins;
3) an aqueous solution of a mixture containing at least one compound selected from the group consisting of chromic acid and chromium (III) salts;
at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins and phenolic resins;
at least one compound selected from the group consisting of chromic acid and chromium (III) salts;
An aqueous solution of a mixture containing at least one compound selected from the group consisting of a metal salt of fluoride and a non-metallic salt of fluoride After applying any of the aqueous solutions of 1) to 3) above, dry By doing so, chemical conversion treatment is performed.

The chemical conversion film preferably has a chromium adhesion amount (per side) of 0.1 mg/m ² to 50 mg/m ² , particularly preferably 2 mg/m ² to 20 mg/m ² .

The heat-sealable resin layer (inner layer) 3 provides excellent chemical resistance against highly corrosive electrolyte solutions used in lithium-ion secondary batteries and the like, and heat-sealing properties of the exterior material. It plays the role of giving

The resin constituting the heat-fusible resin layer 3 is not particularly limited, but examples include polyethylene, polypropylene, ionomer, ethylene ethyl acrylate (EEA), ethylene methyl acrylate (EAA), and ethylene methacryl. Methyl acid resin (EMMA), ethylene-vinyl acetate copolymer resin (EVA), maleic anhydride-modified polypropylene, maleic anhydride-modified polyethylene and the like can be mentioned.

The thickness of the heat-fusible resin layer 3 is preferably set to 10 μm to 100 μm. By setting the thickness to 10 μm or more, sufficient heat seal strength can be ensured, and setting the thickness to 100 μm or less contributes to thinning and weight reduction. Above all, it is more preferable to set the thickness of the heat-fusible resin layer 3 to 10 μm to 80 μm. The heat-fusible resin layer 3 is preferably formed of a heat-fusible resin unstretched film layer, and the heat-fusible resin layer 3 may be a single layer or multiple layers. It can be.

In the present invention, at least one of the outer adhesive layer 5 and the inner adhesive layer 6 is formed of a photocurable resin adhesive (a cured film of a photocurable resin composition). As the photocurable resin adhesive, a photocurable resin adhesive containing a main agent and at least two types of photopolymerization initiators is used. Part or all of the light absorption wavelength band of one of the two photopolymerization initiators has a wavelength region that does not overlap with the light absorption wavelength band of the other photopolymerization initiator. .

Examples of the base resin include, but are not limited to, acrylate resins, vinyl ether resins, and epoxy resins. Although the acrylate resin is not particularly limited, it is preferable to use, for example, at least one resin selected from the group consisting of urethane acrylate resins, epoxy acrylate resins and polyester acrylate resins. The viscosity (25° C.) of the main agent before curing is preferably 500 cP to 10000 cP. The viscosity (25° C.) is measured with a digital viscometer DV-E manufactured by Eko Seiki Co., Ltd. in accordance with JIS Z8803-2011. The content of the main agent in the photocurable resin adhesive is preferably 70% by mass to 90% by mass, in which case the adhesive strength can be further improved.

The two types of photopolymerization initiators (in a relationship in which part or all of the light absorption wavelength band of one photopolymerization initiator has a wavelength region that does not overlap with the light absorption wavelength band of the other photopolymerization initiator As two types of photopolymerization initiators), the absolute value of the difference between the peak value of the light absorption wavelength of one photopolymerization initiator and the peak value of the light absorption wavelength of the other photopolymerization initiator is 50 nm or more. It is preferably 100 nm or more, more preferably 100 nm or more.

The two types of photopolymerization initiators (in a relationship in which part or all of the light absorption wavelength band of one photopolymerization initiator has a wavelength region that does not overlap with the light absorption wavelength band of the other photopolymerization initiator As two types of photopolymerization initiators), the peak value of the light absorption wavelength of one photopolymerization initiator is in the range of 200 nm or more and less than 300 nm, and the peak value of the light absorption wavelength of the other one photopolymerization initiator is preferably in the range of 300 nm or more and 400 nm or less. In this case, 200 nm to 400 nm is an ultraviolet light region, and therefore, a curing reaction (photopolymerization reaction) by visible light does not occur. , the adhesive (photocurable resin adhesive) does not protrude, and sufficient adhesive strength can be ensured. At this time, the absolute value of the difference between the peak value of the light absorption wavelength of one photopolymerization initiator and the peak value of the light absorption wavelength of the other photopolymerization initiator is preferably 50 nm to 150 nm.

Examples of the photopolymerization initiator include, but are not limited to, radical polymerization initiators, cationic polymerization initiators, and anionic polymerization initiators. Examples of the radical polymerization initiator include, but are not limited to, benzophenone, benzoin alkyl ether (benzoethyl ether, benzobutyl ether, etc.), benzyl dimethyl ketal, and the like.

Examples of the cationic polymerization initiator include, but are not limited to, onium salts. Examples of the onium salt include, but are not limited to, sulfonium salts, iodonium salts, bromonium salts, diazonium salts, and chloronium salts.

Examples of the sulfonium salt include, but are not limited to, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, 4,4′-bis[ diphenylsulfonio]diphenylsulfide-bishexafluorophosphate, 4,4′-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide-bishexafluoroantimonate, 4,4′-bis[di(β- Hydroxyethoxy)phenylsulfonio]diphenylsulfide-bishexafluorophosphate, 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone hexafluoroantimonate, 7-[di(p-toluyl)sulfonio]-2- Isopropylthioxanthone tetrakis(pentafluorophenyl)borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide-hexafluorophosphate, 4-(p-ter-butylphenylcarbonyl)-4'-diphenylsulfonio-diphenylsulfide -hexafluoroantimonate, 4-(p-ter-butylphenylcarbonyl)-4′-di(p-toluyl)sulfonio-diphenylsulfide-tetrakis(pentafluorophenyl)borate, triphenylsulfonium bromide and the like. Examples of the iodonium salt include, but are not limited to, diphenyliodonium tetrakis(pentafluorophenyl)borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di(4-nonylphenyl)iodonium hexafluoro phosphate and the like.

Examples of the anionic polymerization initiator include, but are not limited to, acetophenone o-benzoyloxime, 1,2-bis(4-methoxyphenyl)-2-oxoethyl cyclohexylcarbamate, nifedipine, cyclohexylcarbamate. 2-nitrobenzyl, 1,5,7-triazabicyclo[4.4.0]dec-5-ene 2-(9-oxoxanthen-2-yl)propionate and the like.

The photocurable resin adhesive contains, in addition to the main agent and the photopolymerization initiator, one or more selected from the group consisting of silane coupling agents, acid anhydrides and phosphoric acid-containing (meth)acrylates. It preferably contains a compound of In this case, the bonding strength (adhesive strength) between the metal foil 4 and the resin films 2 and 3 can be improved.

Examples of the silane coupling agent include, but are not limited to, methyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, and the like. is mentioned. Among them, as the silane coupling agent, it is preferable to use a silane coupling agent having a carbon-carbon double bond such as vinyltriethoxysilane and allyltrimethoxysilane. In this case, a radical polymerization reaction is particularly used. Bonding with the adhesive can be strengthened (adhesive strength of the adhesive layers 5 and 6 can be improved).

Examples of the acid anhydride include, but are not limited to, maleic anhydride, methyl maleic anhydride, itaconic anhydride, hymic anhydride, and methyl hymic anhydride. Among them, as the acid anhydride, it is preferable to use an acid anhydride having a carbon-carbon double bond such as maleic anhydride, and the acid anhydride having such a double bond further promotes the radical polymerization reaction. be able to.

The phosphoric acid-containing (meth)acrylate (monomer) is not particularly limited, and examples thereof include monomers such as acryloyloxyethyl acid phosphate and bis(2-(meth)acryloyloxyethyl) acid phosphate. .

The thickness (thickness after drying) of the outer adhesive layer 5 and the inner adhesive layer 6 is preferably set to 1 μm to 6 μm.

By molding (deep drawing, stretch molding, etc.) the exterior material 1 for an electricity storage device of the present invention, an exterior case 10 for an electricity storage device can be obtained (see FIG. 3). The exterior material 1 of the present invention can be used as it is without being subjected to molding (see FIG. 3).

FIG. 2 shows an embodiment of an electricity storage device 30 configured using the exterior material 1 of the present invention. This power storage device 30 is a lithium ion secondary battery. In this embodiment, as shown in FIGS. 2 and 3, an exterior member 15 is composed of a case 10 obtained by molding the exterior member 1 and a planar exterior member 1 that has not been subjected to molding. there is Thus, a substantially rectangular parallelepiped electricity storage device main body (electrochemical element or the like) 31 is accommodated in the accommodation recess of the molded case 10 obtained by molding the exterior material 1 of the present invention, and the electricity storage device main body 31 On top of this, the exterior material 1 of the present invention is arranged without molding with the inner layer 3 side facing inward (lower side), and the peripheral edge portion of the inner layer 3 of the planar exterior material 1 and the exterior The power storage device 30 of the present invention is configured by heat-sealing and sealing the flange portion (sealing peripheral portion) 29 of the case 10 with the inner layer 3 (see FIGS. 2 and 3). ). The inner surface of the housing recess of the exterior case 10 is an inner layer (thermal adhesive resin layer) 3, and the outer surface of the housing recess is an outer layer (heat-resistant resin layer) 2 ( See Figure 3).

In FIG. 2, reference numeral 39 denotes a heat-sealed portion where the peripheral edge portion of the exterior material 1 and the flange portion (sealing peripheral edge portion) 29 of the exterior case 10 are joined (fused). In addition, in the electricity storage device 30, the tip of the tab lead connected to the electricity storage device main body 31 is led out to the outside of the exterior member 15, but the illustration is omitted.

The electricity storage device main body 31 is not particularly limited, but examples thereof include a battery main body, a capacitor main body, and a capacitor main body.

The width of the heat seal portion 39 is preferably set to 0.5 mm or more. By setting the thickness to 0.5 mm or more, sealing can be reliably performed. Above all, it is preferable to set the width of the heat seal portion 39 to 3 mm to 15 mm.

In the above-described embodiment, the exterior member 15 is composed of the exterior case 10 obtained by molding the exterior member 1 and the planar exterior member 1 (see FIGS. 2 and 3). For example, the exterior member 15 may be composed of a pair of exterior materials 1 or may be composed of a pair of exterior cases 10 .

Next, a preferred example of a method for manufacturing the exterior material 1 for an electric storage device according to the present invention will be described. First, on one surface of the metal foil 4, a base material and at least two types of photopolymerization initiators (however, these two types of photopolymerization initiators are part of the light absorption wavelength band of one of the photopolymerization initiators or all of which have a wavelength region that does not overlap with the light absorption wavelength band of the other photopolymerization initiator). Next, the metal foil 4 is irradiated with light from the side coated with the composition. At this time, it is preferable to irradiate with light having a wavelength in the light absorption wavelength band of one photopolymerization initiator that does not overlap with the light absorption wavelength band of the other photopolymerization initiator. Next, the heat-resistant resin film 2 is overlaid on the composition coated surface after the light irradiation to obtain a first laminate. Then, the first laminate is irradiated with light from the heat-resistant resin film 2 side to sufficiently cure the photocurable resin composition, thereby forming the outer adhesive layer 5 . At this time, it is preferable to irradiate the other photopolymerization initiator with light that includes a part of the light absorption wavelength band of the other photopolymerization initiator.

Next, on the other surface of the metal foil of the first laminate after the light irradiation, a main agent and at least two types of photopolymerization initiators (however, these two types of photopolymerization initiators are one photopolymerization initiator Part or all of the light absorption wavelength band of the agent has a wavelength region that does not overlap with the light absorption wavelength band of the other photopolymerization initiator). After that, the first laminate is irradiated with light from the side coated with the composition. At this time, it is preferable to irradiate with light having a wavelength in the light absorption wavelength band of one photopolymerization initiator that does not overlap with the light absorption wavelength band of the other photopolymerization initiator. Next, a heat-fusible resin film 3 is overlaid on the composition coated surface after the light irradiation to obtain a second laminate. Next, the second laminate is irradiated with light from the heat-fusible resin film 3 side to sufficiently cure the photocurable resin composition to form the inner adhesive layer 6 . At this time, it is preferable to irradiate the other photopolymerization initiator with light that includes a part of the light absorption wavelength band of the other photopolymerization initiator.

Examples of the light include, but are not limited to, ultraviolet light, visible light, and X-rays.

In the manufacturing method according to the above embodiment, the order of laminating the heat-resistant resin film 2 first and then the heat-fusible resin film 3 is adopted, but this order may be reversed. That is, the heat-sealable resin film 3 may be laminated first, and then the heat-resistant resin film 2 may be laminated.

In the above production method, the content of one of the two photopolymerization initiators in the photocurable resin composition is in the range of 0.2% by mass to 3% by mass. is preferred. By being in such a range, it is possible to first irradiate light with a wavelength that "does not overlap with the light absorption wavelength band of the other photopolymerization initiator" in the light absorption wavelength band of the photopolymerization initiator with a low content rate. Part of the main agent polymerizes and becomes a moderate viscosity (gel), and the adhesive (photocurable resin adhesive) protrudes even if pressure is applied by rolls etc. when pasting the resin film in the next process. There will be no

Further, the content of the other photopolymerization initiator of the two photopolymerization initiators in the photocurable resin composition is preferably in the range of 9% by mass to 20% by mass. By being in such a range, it is sufficiently photocured by light irradiation in the next step (irradiation of light containing light of a wavelength in a part of the light absorption wavelength band of the other one photopolymerization initiator). It is possible to secure sufficient adhesive strength.

In addition, the photocurable resin composition contains two or more main agents with different polymerization systems (for example, one is a radical polymerization system and the other is a cationic polymerization system), and among the two types of photopolymerization initiators, One photoinitiator (X) and another one photoinitiator (Y) are
First type: (X) is an anionic polymerization initiator/(Y) is a radical polymerization initiator Second type: (X) is an anionic polymerization initiator/(Y) is a cationic polymerization initiator Third type: (X) is a cationic polymerization initiator/(Y) is a radical polymerization initiator It is preferable to have a configuration in which any one of the three types of combinations of the first to third types is used. In this case, only the main agent (e.g., radical system) of the polymerization system polymerizes with respect to one polymerization initiator (e.g., radical system). By first irradiating light with a wavelength that does not overlap with the light absorption wavelength band of the initiator, a part of the main agent polymerizes and becomes a moderate viscosity (gel), and the pressure from rolls etc. when pasting the resin film. The adhesive (photocurable resin adhesive) does not protrude even when a load is applied, and an adhesive layer having a uniform thickness is formed. By irradiating the other polymerization initiator (e.g., cationic) with light (irradiating light containing light of a wavelength in a part of the light absorption wavelength band of the other photopolymerization initiator), the main agent (e.g., cationic) of the polymerization system is Since it polymerizes, it can be sufficiently photo-cured and sufficient adhesive strength can be secured.

4 to 7 show examples of the correlation between the light absorption spectra of the two types of photopolymerization initiators, the wavelength of the first irradiation light, and the wavelength of the second irradiation light in the present invention. In the examples of FIGS. 4 to 6, the photopolymerization initiator A has a “wavelength region that does not overlap” with the light absorption wavelength band of the other photopolymerization initiator B in part of the light absorption wavelength band (lower wavelength side). is doing. Then, as the first irradiation light, light in a partial wavelength band in the “non-overlapping wavelength region” is irradiated. As the second irradiation light, light having a wavelength close to the peak wavelength of the light absorption spectrum of the photopolymerization initiator B is irradiated.

Further, in the example of FIG. 7, the photopolymerization initiators A and B both have two light absorption peaks, and the photopolymerization initiator B is part of the light absorption wavelength band (high wavelength side). , and the light absorption wavelength band of the other photopolymerization initiator A and "a wavelength region that does not overlap". Then, as the first irradiation light, light in a partial wavelength band in the “non-overlapping wavelength region” is irradiated. Further, as the second irradiation light, a wavelength close to the peak wavelength on the lower wavelength side of the two peak wavelengths of the light absorption spectrum of the photopolymerization initiator B (and a wavelength lower than the light absorption wavelength band of the photopolymerization initiator B) wavelength deviating to the side) is irradiated (see FIG. 7).

4 to 7, the second irradiation light may be referred to as the "first irradiation light" and the first irradiation light may be referred to as the "second irradiation light", and the same effect as described above can be obtained. be done. It should be noted that the examples shown in FIGS. 4 to 7 are only examples of the corresponding relationships, and are not particularly limited to such relationships.

The above-described manufacturing method merely shows a preferred example, and the exterior material 1 for an electric storage device of the present invention is not particularly limited to one manufactured by the above-described manufacturing method.

Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

[Polymerization initiator used]
Isopropylthioxanthone: radical photopolymerization initiator, light absorption wavelength range: 320 nm to 460 nm
Triarylsulfonium tetrakis-(pentafluorophenyl)borate: cationic photopolymerization initiator, light absorption wavelength range: 350 nm to 420 nm
Benzophenone: Radical photopolymerization initiator, light absorption wavelength range: 250 nm to 360 nm
Phenyl (2,4,6-trimethylbenzoyl) lithium phosphinate ... Radical photopolymerization initiator, light absorption wavelength range: 350 nm to 500 nm
Benzoin isopropyl ether ... Radical photopolymerization initiator, light absorption wavelength range: 250 nm to 360 nm
<Example 1>
A chemical conversion treatment solution consisting of phosphoric acid, polyacrylic acid (acrylic resin), chromium (III) salt compound, water, and alcohol is applied to both sides of a 35 μm thick aluminum foil (A8079 aluminum foil specified in JIS H4160) 4. was applied and then dried at 180°C to form a chemical conversion film. The amount of chromium deposited on this chemical conversion film was 10 mg/m ² per side.

Next, 90.0 parts by mass of a urethane acrylate resin having two acryloyl groups, 0.5 parts by mass of isopropylthioxanthone, 7.5 parts by mass of benzophenone, and pentaerythritol triacrylate are applied to one surface of the chemically treated aluminum foil 4. A photocurable resin composition (outer adhesive) containing 1.5 parts by mass (polymerizable monomer) and 0.5 parts by mass of a silane coupling agent was applied so that the mass after drying was 4 g/m ² . The coated surface was irradiated with light having a wavelength of 405 nm so that the integrated light quantity was 300 mJ/cm ² (first light irradiation) to pre-cure the photocurable resin composition. Next, a biaxially stretched polyamide film 2 having a thickness of 15 μm was attached to the coated surface after the preliminary curing. Next, the laminated body after bonding is irradiated with light having a wavelength of 254 nm from the polyamide film 2 side so that the integrated light amount becomes 300 mJ / cm ² (second light irradiation) to sufficiently cure the photocurable resin composition. to obtain a first laminate.

Next, an acid-modified polyolefin adhesive (thermosetting inner adhesive) is applied to the other surface of the aluminum foil 4 in the first laminate, and dried. After bonding the oriented polypropylene film 3 to obtain a second laminate, the second laminate is left to stand in an environment of 40 ° C. for 9 days to perform a heat aging treatment to cure the thermosetting inner adhesive. An inner adhesive layer 6 was formed to obtain the exterior material 1 for an electric storage device having the structure shown in FIG.

<Example 2>
As an outer adhesive, 90.0 parts by mass of urethane acrylate resin having two acryloyl groups, 2.0 parts by mass of isopropylthioxanthone, 6.0 parts by mass of benzophenone, 1.5 parts by mass of pentaerythritol triacrylate (polymerizable monomer), A power storage device exterior material 1 having the configuration shown in FIG. 1 was obtained in the same manner as in Example 1, except that a photocurable resin composition containing 0.5 parts by mass of a silane coupling agent was used.

<Example 3>
As an outer adhesive, 90.0 parts by mass of urethane acrylate resin having two acryloyl groups, 0.1 parts by mass of isopropylthioxanthone, 7.9 parts by mass of benzophenone, 1.5 parts by mass of pentaerythritol triacrylate (polymerizable monomer), A power storage device exterior material 1 having the configuration shown in FIG. 1 was obtained in the same manner as in Example 1, except that a photocurable resin composition containing 0.5 parts by mass of a silane coupling agent was used.

<Example 4>
As an outer adhesive, 90.0 parts by mass of urethane acrylate resin having two acryloyl groups, 3.5 parts by mass of isopropylthioxanthone, 4.5 parts by mass of benzophenone, 1.5 parts by mass of pentaerythritol triacrylate (polymerizable monomer), A power storage device exterior material 1 having the configuration shown in FIG. 1 was obtained in the same manner as in Example 1, except that a photocurable resin composition containing 0.5 parts by mass of a silane coupling agent was used.

<Example 5>
As the outer adhesive, 80.0 parts by mass of urethane acrylate resin having two acryloyl groups, 10.0 parts by mass of vinyl ether resin, 6.0 parts by mass of triarylsulfonium tetrakis-(pentafluorophenyl)borate, and 2.0 parts by mass of benzophenone. part, pentaerythritol triacrylate (polymerizable monomer) 1.5 parts by mass, and a photocurable resin composition containing 0.5 parts by mass of a silane coupling agent. Example 1 except that irradiation was performed so that the integrated light amount was 300 mJ/cm ² , and the second light irradiation was performed by irradiating light with a wavelength of 365 nm so that the integrated light amount was 300 mJ/cm ² . In the same manner as above, an exterior material 1 for an electric storage device having the configuration shown in FIG. 1 was obtained.

<Example 6>
As the outer adhesive, 90.0 parts by mass of urethane acrylate resin having two acryloyl groups, 6.0 parts by mass of benzophenone, 2.0 parts by mass of phenyl (2,4,6-trimethylbenzoyl) lithium phosphinate, pentaerythritol tri A photocurable resin composition containing 1.5 parts by mass of an acrylate (polymerizable monomer) and 0.5 parts by mass of a silane coupling agent was used, and the first light irradiation was performed with light having a wavelength of 500 nm with an integrated light amount of 300 mJ/ cm ² , and in the second light irradiation, light with a wavelength of 254 nm was irradiated so that the integrated light amount was 300 mJ/cm ² . An exterior material 1 for an electric storage device having the configuration shown in FIG. 1 was obtained.

<Comparative Example 1>
As an outer adhesive, 90.0 parts by mass of urethane acrylate resin having two acryloyl groups, 6.0 parts by mass of benzophenone, 2.0 parts by mass of benzoin isopropyl ether, and 1.5 parts by mass of pentaerythritol triacrylate (polymerizable monomer) and a photocurable resin composition containing 0.5 parts by mass of a silane coupling agent was used in the same manner as in Example 5 to obtain an exterior material for an electric storage device.

<Comparative Example 2>
A chemically treated aluminum foil was obtained in the same manner as in Example 1. Next, 90.0 parts by mass of a urethane acrylate resin having two acryloyl groups, 8.0 parts by mass of benzophenone, and 1.5 parts by mass of pentaerythritol triacrylate (polymerizable monomer) were applied to one surface of the chemically treated aluminum foil 4. After applying a photocurable resin composition (outer adhesive) containing 0.5 parts by mass of a silane coupling agent so that the weight after drying is 4 g/m ² , A biaxially stretched polyamide film 2 having a thickness of 15 μm was laminated together (without irradiation). Next, the laminate after lamination is irradiated with light having a wavelength of 254 nm from the side of the polyamide film 2 so that the integrated amount of light becomes 350 mJ/cm ² to sufficiently cure the photocurable resin composition, thereby forming the first laminate. Obtained.

Next, an acid-modified polyolefin adhesive (thermosetting inner adhesive) is applied to the other surface of the aluminum foil 4 in the first laminate, and dried. After bonding the oriented polypropylene film 3 to obtain a second laminate, the second laminate is left to stand in an environment of 40 ° C. for 9 days to perform a heat aging treatment to cure the thermosetting inner adhesive. An inner adhesive layer 6 was formed to obtain an exterior material for an electric storage device.

Each electrical storage device exterior material obtained as described above was evaluated based on the following measurement method and evaluation method.

<Laminate strength evaluation method>
A test piece with a width of 15 mm and a length of 150 mm was cut out from the obtained exterior material. was peeled off.

In accordance with JIS K6854-3 (1999), a strograph (AGS-5kNX) manufactured by Shimadzu Corporation was used to clamp and fix a laminate containing an aluminum foil with one chuck, and the other chuck was used for the peeling. The heat-resistant resin layer is sandwiched and fixed, and in this state, the peel strength is measured when T-shaped peeling is performed at a tensile speed of 100 mm / min. )”. The measurement results were evaluated based on the following criteria.
(criterion)
"◎" ... Lamination strength was "1.5 N / 15 mm width" or more (accepted)
"○" ... Lamination strength was "1.0 N / 15 mm width" or more and less than "1.5 N / 15 mm width" (accepted)
"x"... The laminate strength was less than "1.0 N/15 mm width" (failed).

<Applicability evaluation method>
The coatability of the photocurable resin composition was evaluated. Specifically, the uniformity of the coating film of the photocurable resin composition was examined, the variation in coating thickness was measured, and evaluation was made based on the following criteria.
(criterion)
"◎" ... There was no uncoated part in the coating film, the uniformity of the coating film was excellent, and the variation in the coating thickness was ± 20% or less "○" ... There was no uncoated part in the coating film, The uniformity of the coating was good, and the variation in the coating thickness was more than ± 20% and ± 30% or less. was over 30%.

<Protrusion prevention evaluation method>
In the obtained exterior material for an electricity storage device, it was examined whether or not the cured product of the photocurable resin composition protruded from the edge of the exterior material, and was evaluated based on the following criteria.
(criterion)
"◯": No protruding outward from the edge of the outer packaging material was observed in the cured product of the resin composition (appearance was good).
"X": The cured product of the resin composition protruded outward from the edge of the exterior material (defective appearance).

As is clear from the table, the exterior materials for electric storage devices of Examples 1 to 6 of the present invention are excellent in productivity because there is no drying step for the outer adhesive, sufficient lamination strength is obtained, and coatability is also good. It was good.

On the other hand, in Comparative Examples 1 and 2, which deviate from the defined scope of the claims of the present invention, at least one of the evaluations was "x" (inferior).

Specific examples of the exterior material for an electricity storage device according to the present invention include, for example,
・It is used as an exterior material for various storage devices such as storage devices such as lithium secondary batteries (lithium ion batteries, lithium polymer batteries, etc.), lithium ion capacitors, and electric double layer capacitors. Further, the power storage device according to the present invention includes all-solid-state batteries in addition to the power storage devices exemplified above.

1... Exterior material for power storage device 2... Heat-resistant resin layer (outer layer)
3... Heat-fusible resin layer (inner layer)
4 Metal foil layer 5 Outer adhesive layer 6 Inner adhesive layer 10 Exterior case (molded case)
15... Exterior member 30... Power storage device 31... Power storage device main body

Claims (6)

An exterior material for a power storage device, comprising a heat-resistant resin layer as an outer layer, a heat-sealable resin layer as an inner layer, and a metal foil layer disposed between these layers,
The metal foil layer and the heat-resistant resin layer are bonded via an outer adhesive layer, and the metal foil layer and the heat-fusible resin layer are bonded via an inner adhesive layer,
At least one adhesive layer of the outer adhesive layer and the inner adhesive layer is formed of a photocurable resin adhesive containing a main agent and at least two photopolymerization initiators,
Part or all of the light absorption wavelength band of one of the two photopolymerization initiators has a wavelength region that does not overlap with the light absorption wavelength band of the other photopolymerization initiator. ,
Among the two types of photopolymerization initiators, the peak value of the light absorption wavelength of one photopolymerization initiator is 20
In the range of 0 nm or more and less than 300 nm, the peak value of the light absorption wavelength of the other photopolymerization initiator
is in the range of 300 nm or more and 400 nm or less . The power storage device according to claim 1, wherein the content of one of the two photopolymerization initiators in the photocurable resin adhesive is 0.2% by mass to 3% by mass. Exterior material. The power storage device according to claim 2, wherein the content of the other photopolymerization initiator of the two photopolymerization initiators in the photocurable resin adhesive is 9% by mass to 20% by mass. Exterior material. The photocurable resin adhesive contains two or more main agents,
Among the two types of photopolymerization initiators, one photopolymerization initiator (X) and another photopolymerization initiator (Y) are
First type: (X) is an anionic polymerization initiator/(Y) is a radical polymerization initiator Second type: (X) is an anionic polymerization initiator/(Y) is a cationic polymerization initiator Third type: (X) is a cationic polymerization initiator/(Y) is a radical polymerization initiator, and any one combination of the above three types of types 1 to 3 is used. 2. The exterior material for an electricity storage device according to 1 or 2 above. An exterior case for an electricity storage device, comprising the molding of the exterior material according to any one of claims 1 to 4 . an electricity storage device main body;
An exterior member comprising the exterior material according to any one of claims 1 to 4 and / or the exterior case according to claim 5 ,
An electricity storage device, wherein the electricity storage device main body is covered with the exterior member.

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