JP7377417B2 - Exterior material for power storage device and method for manufacturing exterior material for power storage device - Google Patents

Description

The present invention relates to an exterior packaging material for a power storage device and a method for manufacturing the exterior packaging material for a power storage device.

As power storage devices, for example, secondary batteries such as lithium ion batteries, nickel hydride batteries, and lead storage batteries, and electrochemical capacitors such as electric double layer capacitors are known. BACKGROUND ART Due to the miniaturization of portable devices and the limitations on installation space, there is a demand for further miniaturization of power storage devices, and lithium ion batteries with high energy density are attracting attention. Conventionally, metal cans have been used as exterior materials for lithium ion batteries, but multilayer films are now being used because they are lightweight, have high heat dissipation properties, and can be manufactured at low cost.

Lithium-ion batteries that use the above multilayer film as an exterior material have a structure in which the battery contents (positive electrode, separator, negative electrode, electrolyte, etc.) are covered with an exterior material that includes an aluminum foil layer to prevent moisture from entering the interior. It has been adopted. A lithium ion battery employing such a configuration is called an aluminum laminate type lithium ion battery.

For example, in an aluminum laminate type lithium-ion battery, a recess is formed in a part of the exterior material by cold molding, the battery contents are stored in the recess, and the remaining part of the exterior material is folded back and the edges are heated. Embossed type lithium ion batteries sealed with a seal are known. (For example, see Patent Document 1). In such a lithium ion battery, the deeper the recess formed by cold molding, the more battery contents can be accommodated, and therefore the energy density can be increased.

Japanese Patent Application Publication No. 2013-101765

However, the material and manufacturing method described in Patent Document 1 may not have sufficient processing suitability, such as the inability to properly bond the metal foil layer and the sealant layer or to take up the material after bonding. Furthermore, when attempting to form a deep recess in the obtained exterior material, the exterior material may break.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an exterior material for a power storage device that is excellent in processing suitability during production and deep drawing formability after production, and a method for manufacturing the exterior material for a power storage device. purpose.

The present invention has a structure in which at least a base material layer, an adhesive layer, a metal foil layer, a sealant adhesive layer, and a sealant layer are laminated in this order, and the base material layer has a Provided is an exterior material for a power storage device, which is made of a polyester film having a stress value at % elongation of 100 to 180 MPa and a heat shrinkage rate of 1 to 15%.
Stress value at 50% elongation: Tensile test in four directions (0° (MD), 45°, 90° (TD), 135°) of the base material layer (test piece shape: No. 5 type specified in JIS K7127) This is the average value of the stress values when a dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min, temperature: 23° C.) was performed.
Heat shrinkage rate: This is the average value of shrinkage rates before and after heat treatment in four directions (0° (MD), 45°, 90° (TD), 135°) of the base material layer.

Some manufacturing processes for exterior materials for power storage devices require a lamination process in order to laminate a plurality of layers. At this time, the base material layer generally undergoes thermal deterioration due to the heat applied during lamination or the heat applied during drying of the adhesive, and tearing may occur when drawing is performed. On the other hand, even in the case of a base material layer that is so rigid that it hardly suffers from thermal deterioration due to the heat applied during lamination or the heat applied during drying of the adhesive, there is a risk that tearing will occur when drawing is performed. Furthermore, even if the drawability is excellent, the processability may not be sufficient, such as the inability to properly bond the metal foil layer and the sealant layer together or to properly wind up the material after bonding. The present invention solves these problems.

In the above exterior material for a power storage device, the polyester film preferably has a heat shrinkage rate of 1 to 5% after heat treatment at 160°C. This makes it easier to further improve processing suitability during production and deep drawing formability after production.

Preferably, the exterior material for a power storage device further includes an adhesion-facilitating layer provided between the base layer and the adhesive layer. Thereby, the adhesion between the base material layer and the adhesive layer can be further improved, and the deep drawing formability can be further improved.

In the above-mentioned exterior material for a power storage device, the easy-adhesion treatment layer may be a layer containing at least one resin selected from the group consisting of polyester resin, acrylic resin, polyurethane resin, epoxy resin, and acrylic graft polyester resin. preferable. Thereby, the adhesion between the base material layer and the adhesive layer can be further improved, and the deep drawing formability can be further improved.

Preferably, the exterior material for a power storage device further includes corrosion prevention treatment layers provided on both sides of the metal foil layer. Thereby, the adhesion between the base material layer and the metal foil layer can be further improved.

In the exterior material for a power storage device, the corrosion prevention treatment layer preferably contains a rare earth element oxide and phosphoric acid or a phosphate. Thereby, the adhesion between the base material layer and the metal foil layer can be further improved.

The exterior material for a power storage device may have a structure in which a coating layer is further laminated on the base layer. This improves adhesion to the acrylic PSA tape.

In the exterior material for a power storage device, the coating layer preferably contains at least one resin selected from the group consisting of acrylic resins and polyester resins. This further improves the adhesion with the acrylic PSA tape.

In the above-mentioned exterior material for a power storage device, the thickness of the coating layer is preferably 0.05 to 3 μm. Thereby, even if a coating layer is provided, deterioration in drawing formability can be easily suppressed.

The present invention also includes a step of bonding a base material layer to one side of the metal foil layer via an adhesive layer, and a sealant layer to the opposite side of the metal foil layer from the adhesive layer via a sealant adhesive layer. The base layer is made of a polyester film having a stress value of 100 to 180 MPa at 50% elongation and a heat shrinkage rate of 1 to 15% after heat treatment at 160 to 200°C. , provides a method for manufacturing an exterior material for a power storage device.
Stress value at 50% elongation: Tensile test in four directions (0° (MD), 45°, 90° (TD), 135°) of the base material layer (test piece shape: No. 5 type specified in JIS K7127) This is the average value of the stress values when a dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min, temperature: 23° C.) was performed.
Heat shrinkage rate: This is the average value of shrinkage rates before and after heat treatment in four directions (0° (MD), 45°, 90° (TD), 135°) of the base material layer.

According to the present invention, it is possible to provide an exterior material for a power storage device that is excellent in processability during production and deep drawing formability after production, and a method for manufacturing the exterior material for a power storage device.

FIG. 1 is a schematic cross-sectional view of an exterior material for a power storage device according to an embodiment of the present invention. 1 is a diagram showing an embossed type exterior material obtained using the exterior material for a power storage device according to an embodiment of the present invention, (a) is a perspective view thereof, and (b) is an embossed exterior material shown in (a). FIG. 3 is a vertical cross-sectional view of the type exterior material taken along line bb. FIG. 2 is a perspective view showing a process of manufacturing a secondary battery using the exterior material for a power storage device according to an embodiment of the present invention, in which (a) shows a state in which the exterior material for a power storage device is prepared, and (b) (c) shows a state in which an embossed exterior material for a power storage device and a battery element are prepared, (c) shows a state in which a part of the exterior material for a power storage device is folded back and the ends are melted, and (d) ) indicates that both sides of the folded part are folded upward.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations will be omitted.

[Exterior material for power storage device]
FIG. 1 is a cross-sectional view schematically showing an embodiment of the exterior material for a power storage device of the present invention. As shown in FIG. 1, the exterior material (exterior material for power storage device) 10 of this embodiment includes a base material layer 11, an easy-to-adhesion treatment layer 12 provided on one surface of the base material layer 11, An adhesive layer 13 provided on the opposite side of the adhesive layer 12 from the base layer 11, and a corrosion prevention treatment layer 15a on both sides provided on the opposite side of the adhesive layer 13 from the adhesive layer 12. and 15b, a sealant adhesive layer 16 provided on the side opposite to the adhesive layer 13 of the metal foil layer 14, and a sealant adhesive layer 16 provided on the side opposite to the metal foil layer 14 of the sealant adhesive layer 16. This is a laminate in which a sealant layer 17 and a sealant layer 17 are sequentially stacked. Here, the corrosion prevention treatment layer 15a is provided on the surface of the metal foil layer 14 on the adhesive layer 13 side, and the corrosion prevention treatment layer 15b is provided on the surface of the metal foil layer 14 on the sealant adhesive layer 16 side. The exterior material 10 may further include a coating layer 18 on the side of the base layer 11 opposite to the adhesion-promoting layer 12. In the exterior material 10, the base material layer 11 (or coating layer 18) is the outermost layer, and the sealant layer 17 is the innermost layer. That is, the exterior material 10 is used with the base layer 11 facing the outside of the power storage device and the sealant layer 17 facing the inside of the power storage device. Each layer will be explained below.

(Base material layer 11)
The base material layer 11 provides the exterior material 10 with heat resistance in the pressurized heat fusion process described below when manufacturing the power storage device and electrolyte resistance against electrolyte leaked from other power storage devices, and is suitable for processing or This layer is intended to suppress the occurrence of pinholes that may occur during distribution.

The base layer 11 is made of a polyester film having a stress value at 50% elongation of 100 to 180 MPa and a heat shrinkage rate of 1 to 15% after heat treatment at 160 to 200° C., as shown below.
Stress value at 50% elongation: Tensile test in four directions (0° (MD), 45°, 90° (TD), 135°) of the base material layer (test piece shape: No. 5 type specified in JIS K7127) This is the average value of the stress values when a dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min, temperature: 23° C.) was performed.
Heat shrinkage rate: This is the average value of shrinkage rates before and after heat treatment in four directions (0° (MD), 45°, 90° (TD), 135°) of the base material layer.

Specifically, the stress value at 50% elongation (F50 stress value) of the base material layer 11 can be measured as follows. That is, a base material layer cut into A4 size is heated for 30 minutes in an oven maintained at an arbitrary heat treatment temperature within the range of 160 to 200°C. Thereafter, a tensile test (specimen shape: specified in JIS K7127) was conducted at 23°C (room temperature) in four directions (0° (MD), 45°, 90° (TD), 135°) of the base material layer. No. 5 dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min). Then, by averaging the measurement results in the four directions, the stress value at 50% elongation is calculated.

Note that the longitudinal direction and the lateral direction of the base material layer are made to correspond to the MD direction (machine feeding direction) and TD direction (perpendicular direction to the MD direction) of the base material layer original fabric, respectively. That is, when the base material layer 11 is made of a biaxially stretched film, the longitudinal direction and the transverse direction of the test piece each correspond to one of the two stretching directions of the film.

Since the stress value at 50% elongation of the base layer 11 measured as described above is in the range of 100 to 180 MPa, it has excellent processing suitability and allows deep drawing even after heat treatment. From this point of view, it is preferable that the stress value of the base layer 11 at 50% elongation is 110 to 170 MPa.

Specifically, the thermal shrinkage rate of the base material layer 11 can be measured as follows. That is, a base material layer cut into A4 size at 23°C is heated for 30 minutes in an oven maintained at an arbitrary heat treatment temperature within the range of 160 to 200°C. Thereafter, the length of the base material layer in four directions (0° (MD), 45°, 90° (TD), 135°) at 23° C. is measured. Then, the heat shrinkage rate is calculated by calculating the heat shrinkage rate in each direction according to the following formula and taking the average value.
Heat shrinkage rate (%) = [{Length in each direction measured before heat treatment (A4 size) - Length in each direction measured after heat treatment}/Length in each direction measured before heat treatment] × 100

Since the heat shrinkage rate of the base material layer 11 measured as described above is in the range of 1 to 15%, it becomes possible to appropriately bond the metal foil layer and the sealant layer and to properly roll the metal foil layer and the sealant layer after bonding. It is possible to obtain an exterior material that has excellent processing suitability and also has good moldability. From this point of view, the heat shrinkage rate of the base layer 11 is preferably 1 to 8%.

The base material layer 11 preferably has a heat shrinkage rate of 1 to 5% after heat treatment at 160°C. As a result, it is possible to obtain an exterior material with better processing suitability. From this point of view, the heat shrinkage rate is preferably 1 to 4%.

The polyester resin constituting the polyester film of the base layer 11 can be used without any particular restriction as long as it satisfies the above characteristics, but examples include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. , copolymerized polyester, and the like. Among these, copolymerized polyester can be preferably used from the viewpoint of excellent deep drawing formability.

The polyester film obtained by either simultaneous stretching or biaxial stretching can be used, but from the viewpoint of obtaining better deep drawing formability, a biaxially stretched polyester film is preferable. preferable.

Examples of stretching methods for biaxially stretched films include sequential biaxial stretching, tubular biaxial stretching, and simultaneous biaxial stretching. The biaxially stretched film is preferably one stretched by a tubular biaxial stretching method or a simultaneous biaxial stretching method from the viewpoint of obtaining better deep drawing formability.

The thickness of the base material layer 11 is preferably 6 to 40 μm, more preferably 10 to 30 μm. When the thickness of the base material layer 11 is 6 μm or more, there is a tendency that the pinhole resistance and insulation properties of the exterior material 10 for a power storage device can be improved. If the thickness of the base material layer 11 exceeds 40 μm, the total thickness of the power storage device exterior material 10 becomes large, which is not desirable because the electric capacity of the battery may have to be reduced.

(Easy adhesion treatment layer 12)
The easy-adhesion treatment layer 12 is provided on one side of the base layer 11 and is arranged between the base layer 11 and the adhesive layer 13. The adhesion-facilitating layer 12 is a layer for improving the adhesion between the base material layer 11 and the adhesive layer 13, and further improving the adhesion between the base material layer 11 and the metal foil layer 14. In the exterior material 10 for a power storage device, the easy-adhesion treatment layer 12 may not be provided. In that case, in order to improve the adhesion between the base material layer 11 and the adhesive layer 13 and further improve the adhesion between the base material layer 11 and the metal foil layer 14, the adhesive layer of the base material layer 11 is The surface on the 13 side may be subjected to corona treatment.

The easy-adhesion treatment layer 12 is preferably a layer containing at least one resin selected from the group consisting of polyester resin, acrylic resin, polyurethane resin, epoxy resin, and acrylic graft polyester resin. The adhesion-promoting layer 12 includes, for example, at least one resin selected from the group consisting of polyester resin, acrylic resin, polyurethane resin, epoxy resin, and acrylic graft polyester resin on one surface of the base material layer 11. It can be formed by applying a coating agent as the main component.

<Polyester resin>
From the viewpoint of adhesive properties, the polyester resin is preferably a copolymerized polyester in which a copolymerized component is introduced to lower the glass transition temperature. The copolymerized polyester is preferably water-soluble or water-dispersible from the viewpoint of coatability. Such copolyesters include copolyesters to which at least one group selected from the group consisting of sulfonic acid groups or their alkali metal bases are bonded (hereinafter referred to as "sulfonic acid group-containing copolyesters"). It is preferable to use

Here, the sulfonic acid group-containing copolyester refers to a polyester in which at least one group selected from the group consisting of a sulfonic acid group or its alkali metal base is bonded to a part of a dicarboxylic acid component or a glycol component, and among them, , a copolymer prepared by using an aromatic dicarboxylic acid component containing at least one group selected from the group consisting of sulfonic acid groups or their alkali metal bases in a proportion of 2 to 10 mol % based on the total acid components. Polyester is preferred.

A suitable example of such a dicarboxylic acid is 5-sodium sulfoisophthalic acid. In this case, other dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, p-β-oxyethoxybenzoic acid, 2,6-naphthalene dicarboxylic acid, 4,4'-dicarboxydiphenyl, 4,4' -dicarboxybenzophenone, bis(4-carboxyphenyl)ethane, adipic acid, sebacic acid, cyclohexane-1,4-dicarboxylic acid and the like.

Ethylene glycol is mainly used as the glycol component for producing the sulfonic acid group-containing copolyester, and in addition, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, and ethylene oxide addition of bisphenol A are used. Polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. can be used. Among them, it is preferable to use ethylene glycol, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, etc. as a copolymerization component since the compatibility with the polystyrene sulfonate is improved.

Furthermore, as the polyester resin, modified polyester copolymers such as block copolymers and graft copolymers modified with polyester, urethane, epoxy, etc. may be used. In this embodiment, in order to improve the adhesion between the adhesive layer 12 and the base layer 11 and adhesive layer 13, the adhesive layer 12 may further contain a resin other than the polyester resin. Examples of such resins include urethane resins and acrylic resins.

<Acrylic resin>
Examples of monomer components constituting the acrylic resin include alkyl acrylate, alkyl methacrylate (alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, - ethylhexyl group, lauryl group, stearyl group, cyclohexyl group, phenyl group, benzyl group, phenylethyl group, etc.); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl Hydroxy group-containing monomers such as methacrylate; acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N,N-dimethylolacrylamide, N-methoxymethylacrylamide, N - Amide group-containing monomers such as methoxymethylmethacrylamide and N-phenylacrylamide; Amino group-containing monomers such as N,N-diethylaminoethyl acrylate and N,N-diethylaminoethyl methacrylate;Epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate Monomers containing carboxyl groups or salts thereof such as acrylic acid, methacrylic acid, and salts thereof (lithium salt, sodium salt, potassium salt, etc.) can be used. These may be used alone or in combination of two or more. Furthermore, these can be used in combination with other monomers other than those mentioned above.

Examples of other monomers include epoxy group-containing monomers such as allyl glycidyl ether; sulfonic acid groups such as styrene sulfonic acid, vinyl sulfonic acid, and their salts (lithium salt, sodium salt, potassium salt, ammonium salt, etc.); Monomers containing salts; monomers containing carboxyl groups or their salts such as crotonic acid, itaconic acid, maleic acid, fumaric acid, and their salts (lithium salts, sodium salts, potassium salts, ammonium salts, etc.); maleic anhydride Monomers containing acids and acid anhydrides such as itaconic anhydride; vinyl isocyanate, allyl isocyanate, styrene, vinyl methyl ether, vinyl ethyl ether, vinyl tris alkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, acrylonitrile, Methacrylonitrile, alkyl itaconic acid monoester, vinylidene chloride, vinyl acetate, vinyl chloride, etc. can be used. Furthermore, as the acrylic resin, modified acrylic copolymers such as block copolymers and graft copolymers modified with polyester, urethane, epoxy, etc. may be used.

The glass transition point (Tg) of the acrylic resin used in this embodiment is not particularly limited, but is preferably 0 to 90°C, more preferably 10 to 80°C. If the Tg is low, adhesion may decrease under high temperature and high humidity conditions, and if it is high, cracks may occur during stretching, so from the viewpoint of suppressing these, the Tg of the acrylic resin should be within the above range. is preferred.

Further, the weight average molecular weight of the acrylic resin used in this embodiment is preferably 100,000 or more, more preferably 300,000 or more. If the weight average molecular weight is low, the heat and humidity resistance may decrease. In this embodiment, in order to improve the adhesion between the adhesive layer 12 and the base layer 11 and adhesive layer 13, the adhesive layer 12 may further contain a resin other than the acrylic resin. Examples of such resins include polyester resins and urethane resins.

<Polyurethane resin>
As the polyurethane resin, a water-based polyurethane resin is preferable. As the water-based polyurethane resin, a self-emulsifying type is preferable because it has a small particle size and good stability. The particle size of the water-based polyurethane resin is preferably about 10 to 100 nm. The water-based polyurethane resin used in this embodiment preferably has a glass transition point (Tg) of 40°C to 150°C. When the Tg is 40° C. or higher, there is a tendency to sufficiently suppress the occurrence of blocking when winding up into a roll after coating. On the other hand, if the Tg is too high than the drying temperature after coating, it will be difficult to form a uniform film, so the Tg is preferably 150° C. or less.

Further, in this embodiment, a crosslinking agent may be used together with the water-based polyurethane resin. As a crosslinking agent for water-based polyurethane, a general-purpose water-soluble crosslinking agent such as a water-soluble epoxy compound can be used. A water-soluble epoxy compound is a compound that is soluble in water and has two or more epoxy groups. Examples of water-soluble epoxy compounds include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,4-butanediol, 1,6-hexanediol, Polyepoxy compounds obtained by etherification of 1 mole of glycols such as pentyl glycol and 2 moles of epichlorohydrin, and esters of 1 mole of dicarboxylic acids such as phthalic acid, terephthalic acid, adipic acid, oxalic acid and 2 moles of epichlorohydrin. Examples include diepoxy compounds obtained by chemical reaction. However, the water-soluble epoxy compound is not limited to these.

These water-soluble crosslinking agents crosslink with the water-based polyurethane resin, improve the water resistance and solvent resistance of the coating film, and also improve the adhesion between the adhesion-promoting layer 12, the base material layer 11, and the adhesive layer 13. Contribute. In this embodiment, a resin other than the urethane resin may be further contained in order to improve the adhesion between the adhesion-promoting layer 12 and the base layer 11 and adhesive layer 13. Examples of such resins include polyester resins and acrylic resins.

Further, the adhesion-promoting layer 12 may be configured to include, for example, the resin as the main component and a curing agent such as a polyfunctional isocyanate, a polyfunctional glycidyl compound, or a melamine compound. In this way, by including the above-mentioned resin as the main component and a curing agent such as a polyfunctional isocyanate, a polyfunctional glycidyl compound, or a melamine compound, it is possible to incorporate a crosslinked structure, resulting in strong and easy adhesion. A processing layer 12 can be configured.

The coating agent used to form the adhesion-promoting layer 12 may be solvent-based or water-based. The dispersion type (dispersion) using a water-based main agent has a large molecular weight, improves intermolecular cohesive force, and is effective in improving the adhesion between the adhesion-promoting layer 12, the base material layer 11, and the adhesive layer 13. be.

The thickness of the adhesion-promoting layer 12 is preferably 0.02 to 0.5 μm, more preferably 0.04 to 0.3 μm. When the thickness of the adhesive-facilitating layer 12 is 0.02 μm or more, it is easy to form a uniform adhesive-facilitating layer 12, and a more sufficient adhesive-facilitating effect tends to be obtained. On the other hand, when the thickness of the easy-adhesion treatment layer 12 is 0.5 μm or less, there is a tendency that the deep drawing formability of the exterior material 10 can be further improved.

(Adhesive layer 13)
The adhesive layer 13 is a layer that adheres the base material layer 11 and the metal foil layer 14. The adhesive layer 13 is bonded to the base material layer 11 via the adhesion-facilitating layer 12 . The adhesive layer 13 has the adhesion force necessary to firmly adhere the base material layer 11 and the metal foil layer 14, and also prevents the metal foil layer 14 from being broken by the base material layer 11 during cold molding. It also has followability (ability to reliably form the adhesive layer 13 on the member without peeling even if the member is deformed/expanded/contracted) to suppress this.

The adhesive constituting the adhesive layer 13 is, for example, a two-component adhesive comprising a main agent made of a polyol such as polyester polyol, polyether polyol, or acrylic polyol, and a curing agent made of aromatic or aliphatic isocyanate. A curable polyurethane adhesive can be used. In the above adhesive, the molar ratio (=NCO/OH) of the isocyanate groups of the curing agent to the hydroxyl groups of the main ingredient is preferably 1 to 10, more preferably 2 to 5.

The above-mentioned polyurethane adhesive is aged for 4 days or more at 40° C. after coating, so that the reaction between the hydroxyl group of the main ingredient and the isocyanate group of the curing agent progresses, and the base material layer 11 and the metal foil layer 14 are aged. Enables stronger adhesion with

The thickness of the adhesive layer 13 is preferably 1 to 10 μm, more preferably 2 to 6 μm, from the viewpoint of obtaining desired adhesive strength, followability, processability, and the like.

(Metal foil layer 14)
Examples of the metal foil layer 14 include various metal foils such as aluminum and stainless steel, and from the viewpoint of processability such as moisture resistance and spreadability, and cost, the metal foil layer 14 is preferably an aluminum foil. Although the aluminum foil may be a general soft aluminum foil, it is preferably an aluminum foil containing iron because of its excellent pinhole resistance and extensibility during molding.

In aluminum foil containing iron (100% by mass), the iron content is preferably 0.1 to 9.0% by mass, more preferably 0.5 to 2.0% by mass. When the iron content is 0.1% by mass or more, it is possible to obtain the exterior material 10 having better pinhole resistance and spreadability. When the iron content is 9.0% by mass or less, it is possible to obtain the exterior material 10 with more excellent flexibility.

Further, as the aluminum foil, a soft aluminum foil subjected to annealing treatment (for example, an aluminum foil made of 8021 material or 8079 material according to JIS standards) is more preferable since it can impart desired ductility during molding.

The metal foil used for the metal foil layer 14 is preferably subjected to, for example, a degreasing treatment in order to obtain desired electrolyte resistance. Moreover, in order to simplify the manufacturing process, it is preferable that the surface of the metal foil is not etched. As the degreasing treatment, for example, wet type degreasing treatment or dry type degreasing treatment can be used, but dry type degreasing treatment is preferable from the viewpoint of simplifying the manufacturing process.

Examples of the dry type degreasing treatment include a method in which the degreasing treatment is carried out by prolonging the treatment time in the step of annealing the metal foil. Sufficient electrolyte resistance can be obtained even with a degreasing treatment performed simultaneously with the annealing treatment performed to soften the metal foil.

Further, as the dry type degreasing treatment, treatments other than the annealing treatment such as flame treatment and corona treatment may be used. Further, as the dry type degreasing treatment, for example, a degreasing treatment in which contaminants are oxidatively decomposed and removed using active oxygen generated when the metal foil is irradiated with ultraviolet rays of a specific wavelength may be used.

As the wet type degreasing treatment, for example, acid degreasing treatment, alkaline degreasing treatment, etc. can be used. As the acid used in the acid degreasing treatment, for example, inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid can be used. These acids may be used alone or in combination of two or more. Furthermore, as the alkali used in the alkaline degreasing treatment, for example, sodium hydroxide, which has a high etching effect, can be used. Alternatively, alkaline degreasing treatment may be performed using a weakly alkaline material and a material containing a surfactant or the like. The wet type degreasing treatment described above can be performed by, for example, a dipping method or a spray method.

The thickness of the metal foil layer 14 is preferably 9 to 200 μm, more preferably 15 to 150 μm, and even more preferably 15 to 100 μm from the viewpoint of barrier properties, pinhole resistance, and processability. preferable. When the thickness of the metal foil layer 14 is 9 μm or more, it becomes difficult to break even when stress is applied during molding. When the thickness of the metal foil layer 14 is 200 μm or less, an increase in the mass of the exterior material can be reduced, and a decrease in the weight energy density of the power storage device can be suppressed.

(Corrosion prevention treatment layers 15a, 15b)
The corrosion prevention treatment layers 15a and 15b play a role of suppressing corrosion of the metal foil layer 14 due to electrolyte solution or hydrofluoric acid generated by reaction between electrolyte solution and water. Furthermore, the corrosion prevention treatment layer 15a plays a role in increasing the adhesion between the metal foil layer 14 and the adhesive layer 13. Furthermore, the corrosion prevention treatment layer 15b plays a role in increasing the adhesion between the metal foil layer 14 and the sealant adhesive layer 16. The corrosion prevention treatment layer 15a and the corrosion prevention treatment layer 15b may have the same structure or may have different structures. Although FIG. 1 shows a case where the corrosion prevention treatment layer is formed on both sides of the metal foil layer 14, the corrosion prevention treatment layer may be formed on at least one side of the metal foil layer 14.

For example, the corrosion prevention treatment layers 15a, 15b may be formed by applying degreasing treatment, hydrothermal conversion treatment, anodization treatment, chemical conversion treatment, or a coating agent having corrosion prevention ability to the base material layer of the corrosion prevention treatment layers 15a, 15b. It can be formed by applying a coating-type corrosion prevention treatment or a combination of these treatments.

Among the above-mentioned treatments, degreasing treatment, hydrothermal denaturation treatment, anodization treatment, especially hydrothermal denaturation treatment and anodic oxidation treatment, dissolve the surface of the metal foil (aluminum foil) with a treatment agent and create a metal compound (aluminum foil) with excellent corrosion resistance. This process forms aluminum compounds (boehmite, alumite). Therefore, in some cases, such treatment is included in the definition of chemical conversion treatment in order to obtain a co-continuous structure from the metal foil layer 14 to the corrosion prevention treatment layers 15a and 15b.

Examples of the degreasing treatment include acid degreasing and alkaline degreasing. Examples of acid degreasing include methods using acid degreasing obtained by using the above-mentioned inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid alone or by mixing these. In addition, by using an acid degreasing agent prepared by dissolving a fluorine-containing compound such as monosodium ammonium difluoride in the above-mentioned inorganic acid, not only the degreasing effect of the metal foil layer 14 but also the fluoride of the passive metal can be removed. This is effective in terms of hydrofluoric acid resistance. Examples of alkaline degreasing include a method using sodium hydroxide or the like.

As the hydrothermal conversion treatment, for example, a boehmite treatment obtained by immersing the metal foil layer 14 in boiling water to which triethanolamine is added can be used. As the anodic oxidation treatment, for example, alumite treatment can be used. Further, as the chemical conversion treatment, for example, chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, or a combination of two or more of these treatments is used. be able to. These hydrothermal conversion treatments, anodization treatments, and chemical conversion treatments are preferably performed in advance by the above-mentioned degreasing treatment.

Note that the above-mentioned chemical conversion treatment is not limited to the wet method, and for example, a method of mixing a treatment agent used in these treatments with a resin component and applying the mixture may be used. Moreover, as the above-mentioned corrosion prevention treatment, a coating type chromate treatment is preferable from the viewpoint of maximizing the effect and waste liquid treatment.

The coating agent used for coating-type corrosion prevention treatment in which a coating agent having corrosion prevention performance is applied contains at least one member selected from the group consisting of a rare earth element oxide sol, an anionic polymer, and a cationic polymer. Examples include coating agents. In particular, a method using a coating agent containing a rare earth element oxide sol is preferred.

The method of using a coating agent containing a rare earth element oxide sol is a pure coating type corrosion prevention treatment, and by using this method, a corrosion prevention effect can be imparted to the metal foil layer 14 even with a general coating method. Is possible. Further, the layer formed using the rare earth element oxide sol has an effect of preventing corrosion of the metal foil layer 14 (inhibitor effect), and is also a suitable material from an environmental point of view.

The rare earth element oxide sol includes rare earth element oxide fine particles (for example, particles with an average particle size of 100 nm or less) dispersed in a liquid dispersion medium. Examples of rare earth element oxides include cerium oxide, yttrium oxide, neodymium oxide, and lanthanum oxide. Among them, cerium oxide is preferred. Thereby, the adhesion between the metal foil layer 14 can be further improved. As the liquid dispersion medium for the rare earth element oxide sol, various solvents such as water, alcohol solvents, hydrocarbon solvents, ketone solvents, ester solvents, and ether solvents can be used. Among them, water is preferred. The rare earth element oxides contained in the corrosion prevention treatment layers 15a and 15b can be used alone or in combination of two or more.

Rare earth element oxide sol uses inorganic acids such as nitric acid, hydrochloric acid, and phosphoric acid, and organic acids such as acetic acid, malic acid, ascorbic acid, and lactic acid as dispersion stabilizers to stabilize the dispersion of rare earth element oxide particles. It is preferable to contain acids, salts thereof, and the like. Among these dispersion stabilizers, it is particularly preferable to use phosphoric acid or a phosphate salt. This not only stabilizes the dispersion of rare earth element oxide particles, but also improves the adhesion between the metal foil layer 14 by utilizing the chelating ability of phosphoric acid, and improves the adhesion between the metal foil layer 14 and the Effects such as imparting electrolyte resistance by capturing metal ions eluted by the influence (forming passivity) and improving the cohesive strength of the rare earth element oxide layer due to the fact that dehydration condensation of phosphoric acid easily occurs even at low temperatures can be expected. Examples of the phosphoric acid or phosphate salt used as a dispersion stabilizer include orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, and alkali metal salts and ammonium salts thereof. Among these, condensed phosphoric acids such as trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, and ultrametaphosphoric acid, or their alkali metal salts and ammonium salts are preferable for exhibiting functions as exterior materials for lithium ion batteries. In particular, when considering dry film forming properties (drying ability, amount of heat) when forming a layer containing a rare earth oxide by various coating methods using a coating composition containing a rare earth oxide sol, the reactivity at low temperatures A sodium salt is preferred because it has excellent dehydration condensation properties at low temperatures. As the phosphate, water-soluble salts are preferred. The phosphoric acid or phosphate contained in the corrosion prevention treatment layers 15a, 15b can be used alone or in combination of two or more.

The amount of phosphoric acid or its salt blended in the rare earth element oxide sol is preferably 1 part by mass or more, more preferably 5 parts by mass or more, per 100 parts by mass of the rare earth element oxide. When the amount is 1 part by mass or more, the sol is well stabilized and it is easy to fulfill the function as an exterior material for a lithium ion battery. The upper limit for blending phosphoric acid or its salt with respect to 100 parts by mass of the rare earth element oxide may be within a range that does not cause a functional deterioration of the rare earth element oxide sol, and 100 parts by mass or less shall be added to 100 parts by mass of the rare earth element oxide. It is preferably 50 parts by mass or less, more preferably 20 parts by mass or less.

However, since the layer formed from the above-mentioned rare earth element oxide sol is an aggregate of inorganic particles, the cohesive force of the layer itself is low even after the dry curing process. Therefore, in order to compensate for the cohesive force of this layer, it is preferable to composite it with an anionic polymer.

Examples of the anionic polymer include polymers having a carboxyl group, such as poly(meth)acrylic acid (or a salt thereof) or a copolymer copolymerized with poly(meth)acrylic acid as a main component. Copolymerization components of the copolymer include alkyl (meth)acrylate monomers (alkyl groups include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, (t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.); (meth)acrylamide, N-alkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide (alkyl groups include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.), N-alkoxy(meth)acrylamide, N,N- Amide group-containing monomers such as dialkoxy(meth)acrylamide, (alkoxy groups include methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), N-methylol(meth)acrylamide, N-phenyl(meth)acrylamide; Hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; glycidyl group-containing monomers such as glycidyl (meth)acrylate and allyl glycidyl ether; (meth)acryloxypropyltrimethoxysilane, ( Examples include silane-containing monomers such as meth)acryloxypropyl triethyl-xylan; and isocyanate group-containing monomers such as (meth)acryloxypropyl isocyanate. Also, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, maleic acid, alkyl maleic acid monoester, fumaric acid, alkyl fumaric acid monoester, itaconic acid, alkyl itaconic acid monoester, (meth)acrylonitrile, chloride. Examples include vinylidene, ethylene, propylene, vinyl chloride, vinyl acetate, and butadiene.

The anionic polymer plays a role in improving the stability of the corrosion prevention treatment layers 15a and 15b (oxide layers) obtained using the rare earth element oxide sol. This is due to the effect of protecting the hard and brittle oxide layer with the acrylic resin component and the effect of trapping ionic contamination (especially sodium ions) derived from phosphates contained in the rare earth oxide sol (cation catcher). achieved. In other words, if alkali metal ions such as sodium or alkaline earth metal ions are contained in the corrosion prevention treatment layers 15a and 15b obtained using the rare earth element oxide sol, the corrosion prevention treatment layers 15a and 15b obtained by using the rare earth element oxide sol contain, in particular, alkali metal ions such as sodium or alkaline earth metal ions. Corrosion prevention treatment layers 15a and 15b tend to deteriorate. Therefore, by immobilizing sodium ions and the like contained in the rare earth oxide sol with the anionic polymer, the resistance of the corrosion prevention treatment layers 15a and 15b is improved.

The corrosion prevention treatment layers 15a and 15b, which are a combination of anionic polymer and rare earth element oxide sol, have the same corrosion prevention performance as the corrosion prevention treatment layers 15a and 15b formed by subjecting the metal foil layer 14 to chromate treatment. The anionic polymer preferably has a crosslinked structure of essentially water-soluble polyanionic polymer. Examples of the crosslinking agent used to form this structure include compounds having an isocyanate group, a glycidyl group, a carboxyl group, and an oxazoline group. Furthermore, it is also possible to introduce a crosslinking site having a siloxane bond using a silane coupling agent.

Examples of the compound having an isocyanate group include diisocyanates such as tolylene diisocyanate, xylylene diisocyanate or a hydrogenated product thereof, hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate or a hydrogenated product thereof, and isophorone diisocyanate. or adducts obtained by reacting these isocyanates with polyhydric alcohols such as trimethylolpropane, biurets obtained by reacting them with water, or polysaccharides such as trimeric isocyanurates. Isocyanates; or block polyisocyanates obtained by blocking these polyisocyanates with alcohols, lactams, oximes, etc. can be mentioned.

Examples of compounds having a glycidyl group include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,4-butanediol, 1,6-hexanediol, Epoxy compounds made by reacting glycols such as neopentyl glycol with Epicorhydrin, and products made by reacting Epicorhydrin with polyhydric alcohols such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol, and sorbitol. Examples include epoxy compounds, epoxy compounds prepared by reacting dicarboxylic acids such as phthalic acid, terephthalic acid, oxalic acid, and adipic acid with epichlorohydrin.

Examples of compounds having a carboxyl group include various aliphatic or aromatic dicarboxylic acids, and it is also possible to use poly(meth)acrylic acid and alkali (earth) metal salts of poly(meth)acrylic acid. be.

As the compound having an oxazoline group, for example, when using a low molecular weight compound having two or more oxazoline units, or a polymerizable monomer such as isopropenyloxazoline, (meth)acrylic acid, (meth)acrylic acid alkyl ester Examples include compounds copolymerized with acrylic monomers such as hydroxyalkyl (meth)acrylate.

Examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloropropylmethoxysilane, Vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, and especially anionic In consideration of reactivity with reactive polymers, epoxysilane, aminosilane, and isocyanatesilane are preferred.

The amount of the crosslinking agent blended is preferably 1 to 50 parts by weight, more preferably 10 to 20 parts by weight, per 100 parts by weight of the anionic polymer. When the ratio of the crosslinking agent is 1 part by mass or more with respect to 100 parts by mass of the anionic polymer, a crosslinked structure is sufficiently easily formed. If the ratio of the crosslinking agent is 50 parts by mass or less with respect to 100 parts by mass of the anionic polymer, the pot life of the coating liquid will be improved.

The method of crosslinking the anionic polymer is not limited to the above-mentioned crosslinking agent, but may also be a method of forming ionic crosslinks using titanium or zirconium compounds. Furthermore, a coating composition forming the corrosion prevention treatment layer 15a may be applied to these materials.

In the corrosion prevention treatment layers 15a, 15b explained above, the corrosion prevention treatment layers 15a, 15b by chemical conversion treatment, typified by chromate treatment, are particularly treated with hydrofluoric acid, hydrochloric acid, nitric acid, etc. in order to form an inclined structure with the metal foil layer 14. The metal foil layer 14 is treated using a chemical conversion treatment agent containing , sulfuric acid, or a salt thereof, and then a chromium-based or non-chromium-based compound is applied to form a chemical conversion treatment layer on the metal foil layer 14. However, since the above-mentioned chemical conversion treatment uses an acid as a chemical conversion treatment agent, it is accompanied by deterioration of the working environment and corrosion of the coating equipment.

On the other hand, the coating type corrosion prevention treatment layers 15a and 15b described above do not need to form a sloped structure with respect to the metal foil layer 14, unlike a chemical conversion treatment typified by chromate treatment. Therefore, the properties of the coating agent are not limited by acidity, alkalinity, neutrality, etc., and a good working environment can be realized. In addition, coating-type corrosion prevention treatment layers 15a and 15b are preferred for chromate treatment using a chromium compound, from the viewpoint of environmental hygiene and the need for an alternative solution.

The corrosion prevention treatment layers 15a and 15b may have a laminated structure in which a cationic polymer is further laminated, if necessary. Examples of cationic polymers include polyethyleneimine, ionic polymer complexes consisting of polyethyleneimine and a polymer containing carboxylic acid, primary amine-grafted acrylic resins in which a primary amine is grafted onto an acrylic main skeleton, polyallylamine, or derivatives thereof. , aminophenol resin, etc.

Examples of the "polymer having a carboxylic acid" that forms an ionic polymer complex include polycarboxylic acid (salt), copolymer obtained by introducing a comonomer into polycarboxylic acid (salt), polysaccharide having a carboxy group, etc. It will be done. Examples of polycarboxylic acids (salts) include polyacrylic acid or ionic salts thereof. Examples of the polysaccharide having a carboxy group include carboxymethylcellulose or an ionic salt thereof. Examples of ionic salts include alkali metal salts and alkaline earth metal salts.

A primary amine graphed acrylic resin is a resin in which a primary amine is graphed on an acrylic main skeleton. Examples of the acrylic main skeleton include various monomers used in the above-mentioned acrylic polyols, such as poly(meth)acrylic acid. Examples of the primary amine to be graphed on the acrylic main skeleton include ethyleneimine.

As polyallylamine or its derivatives, it is possible to use homopolymers or copolymers of allylamine, allylamine amide sulfate, diallylamine, dimethylallylamine, etc. Furthermore, even if these amines are free, they can be treated with acetic acid or hydrochloric acid. It is also possible to use stabilized products. Furthermore, it is also possible to use maleic acid, sulfur dioxide, etc. as a copolymer component. Furthermore, it is also possible to use a type in which thermal crosslinkability is imparted by partially methoxylating a primary amine. These cationic polymers may be used alone or in combination of two or more. Among the above-mentioned cationic polymers, at least one selected from the group consisting of polyallylamine and its derivatives is preferred.

The cationic polymer is preferably used in combination with a crosslinking agent having a functional group capable of reacting with an amine/imine such as a carboxy group or a glycidyl group. As a crosslinking agent used in combination with a cationic polymer, a polymer having a carboxylic acid that forms an ionic polymer complex with polyethyleneimine can also be used, such as a polycarboxylic acid (salt) such as polyacrylic acid or an ionic salt thereof; Copolymers into which a comonomer has been introduced, polysaccharides having carboxy groups such as carboxymethyl cellulose or ionic salts thereof, and the like.

In this embodiment, a cationic polymer is also described as a component constituting the corrosion prevention treatment layers 15a and 15b. The reason for this is that after extensive research using various compounds to provide electrolyte resistance and hydrofluoric acid resistance required for exterior materials for lithium-ion batteries, we found that the cationic polymer itself also has electrolyte resistance and hydrofluoric acid resistance. This is because it was found to be a compound capable of imparting acidity. The reason for this is presumed to be that damage to the metal foil layer 14 is suppressed by trapping fluorine ions with cationic groups (anion catcher). Furthermore, cationic polymers are very preferable in terms of improving the adhesion between the corrosion prevention treatment layer 15b and the sealant adhesive layer 16. Further, since the cationic polymer is water-soluble like the anionic polymer described above, water resistance can be improved by forming a crosslinked structure using the above-mentioned crosslinking agent. As described above, since a crosslinked structure can be formed even when using a cationic polymer, when a rare earth oxide sol is used to form the corrosion prevention treatment layers 15a and 15b, an anionic polymer is used as the protective layer. Cationic polymers may be used instead.

From the above, examples of combinations of the above-mentioned coating type corrosion prevention treatments are: (1) Rare earth oxide sol only, (2) Anionic polymer only, (3) Cationic polymer only, (4) Rare earth oxide sol. Sol + anionic polymer (laminated composite), (5) rare earth oxide sol + cationic polymer (laminated composite), (6) (rare earth oxide sol + anionic polymer: laminated composite) / cationic polymer ( (7) (Rare earth oxide sol + cationic polymer: laminated composite)/anionic polymer (multilayer), and the like. Among them, (1) and (4) to (7) are preferred, and (4) to (7) are more preferred. Further, in the case of the corrosion prevention treatment layer 15a, (6) is particularly preferable because the corrosion prevention effect and the anchor effect (adhesion improvement effect) can be achieved in one layer. Moreover, in the case of the corrosion prevention treatment layer 15b, (6) and (7) are particularly preferable because the electrolyte resistance on the sealant layer 17 side is more easily maintained. However, this embodiment is not limited to the above combinations. For example, as an example of selecting a corrosion prevention treatment, cationic polymers are very preferable materials because they have good adhesion to the modified polyolefin resin mentioned in the explanation of the sealant adhesive layer 16, which will be described later. In the case where the layer 16 is made of a modified polyolefin resin, a design in which a cationic polymer is provided on the surface in contact with the sealant adhesive layer 16 (for example, structures such as structures (5) and (6)) is possible.

However, the corrosion prevention treatment layers 15a and 15b are not limited to the layers described above. For example, it may be formed using a resin binder (such as aminophenol resin) mixed with phosphoric acid and a chromium compound, as in the case of coating type chromate, which is a known technique. By using this treatment agent, it becomes possible to form a layer that has both corrosion prevention function and adhesion. In addition, in order to improve adhesion to the above-mentioned chemical conversion treatment layer (a layer formed by degreasing treatment, hydrothermal conversion treatment, anodizing treatment, chemical conversion treatment, or a combination of these treatments), the above-mentioned cationic It is also possible to carry out multiple treatments using polymers and/or anionic polymers, or to laminate cationic and/or anionic polymers in multilayer structures for combinations of these treatments. In addition, although it is necessary to consider the stability of the coating liquid, corrosion prevention function can be achieved by using a coating agent obtained by preparing the above-mentioned rare earth oxide sol and cationic polymer or anionic polymer into one liquid. It is possible to form a layer that has both adhesion and adhesion.

The mass per unit area of the corrosion prevention treatment layers 15a and 15b is preferably within the range of 0.005 to 0.200 g/m ² , more preferably within the range of 0.010 to 0.100 g/m ² . If it is 0.005 g/m ² or more, it is easy to provide the metal foil layer 14 with a corrosion prevention function. Further, even if the mass per unit area exceeds 0.200 g/m ² , the corrosion prevention function is saturated and does not change much. On the other hand, when a rare earth oxide sol is used, if the coating film is thick, curing by heat during drying may be insufficient, which may lead to a decrease in cohesive force. Note that although the above content is described in terms of mass per unit area, if the specific gravity is known, it is also possible to convert the thickness from there.

The thickness of the corrosion prevention treatment layers 15a and 15b is preferably, for example, 10 nm to 5 μm, more preferably 20 to 500 nm, from the viewpoint of corrosion prevention function and anchor function.

(Sealant adhesive layer 16)
The sealant adhesive layer 16 is a layer that adheres the metal foil layer 14 on which the corrosion prevention treatment layer 15b is formed and the sealant layer 17. The exterior material 10 can be roughly divided into a heat laminated structure and a dry laminated structure depending on the adhesive component forming the sealant adhesive layer 16.

The adhesive component forming the sealant adhesive layer 16 in the thermally laminated structure is preferably an acid-modified polyolefin resin obtained by graft-modifying a polyolefin resin with an acid. Since the acid-modified polyolefin resin has a polar group introduced into a part of the non-polar polyolefin resin, the sealant layer 17 when composed of a non-polar polyolefin resin film, etc. has polarity. It is possible to firmly adhere to both the corrosion prevention treatment layer 15b, which is often the case. In addition, by using acid-modified polyolefin resin, the resistance of the exterior material 10 to contents such as electrolyte is improved, and even if hydrofluoric acid is generated inside the battery, the adhesion strength decreases due to deterioration of the sealant adhesive layer 16. Easy to prevent.

Examples of the polyolefin resin of the acid-modified polyolefin resin include low density, medium density and high density polyethylene; ethylene-α olefin copolymer; polypropylene; and propylene-α olefin copolymer. The polyolefin resin in the case of a copolymer may be a block copolymer or a random copolymer. Further, as the polyolefin resin, a copolymer obtained by copolymerizing the above-mentioned materials with a polar molecule such as acrylic acid or methacrylic acid, or a polymer such as crosslinked polyolefin can also be used. Examples of acids that modify polyolefin resins include carboxylic acids, epoxy compounds, acid anhydrides, and the like, with maleic anhydride being preferred. The number of acid-modified polyolefin resins used in the sealant adhesive layer 16 may be one type or two or more types.

The heat laminated sealant adhesive layer 16 can be formed by extruding the adhesive component described above using an extrusion device. The thickness of the sealant adhesive layer 16 in thermal laminate construction is preferably between 2 and 50 μm.

Examples of the adhesive component forming the sealant adhesive layer 16 having a dry laminated structure include the same adhesives as those mentioned for the adhesive layer 13. In this case, in order to suppress swelling caused by the electrolyte and hydrolysis caused by hydrofluoric acid, it is necessary to design the composition of the adhesive so that it is a main component with a skeleton that is difficult to hydrolyze and can improve the crosslink density. preferable.

In order to improve the crosslinking density, for example, dimeric fatty acids, esters or hydrogenated products of dimer fatty acids, reduced glycols of dimer fatty acids, and reduced glycols of esters or hydrogenated products of dimer fatty acids may be added to the adhesive. The above-mentioned dimer fatty acid is an acid obtained by dimerizing various unsaturated fatty acids, and its structure can be exemplified by an acyclic type, a monocyclic type, a polycyclic type, and an aromatic ring type.

The fatty acid that is the starting material for the dimeric fatty acid is not particularly limited. Furthermore, a dibasic acid such as that used in ordinary polyester polyols may be introduced using such a dimer fatty acid as an essential component. As a curing agent for the main component constituting the sealant adhesive layer 16, it is possible to use, for example, an isocyanate compound that can also be used as a chain extender for polyester polyol. This increases the crosslinking density of the adhesive coating, leading to improved solubility and swelling properties, and can also be expected to improve adhesion to substrates by increasing the urethane group concentration.

The sealant adhesive layer 16 having a dry lamination structure has highly hydrolyzable bonding parts such as ester groups and urethane groups, so for applications where higher reliability is required, a heat lamination structure is used as the sealant adhesive layer 16. It is preferable to use an adhesive component of For example, the sealant adhesive layer 16 is formed by blending the above-mentioned curing agents into a coating liquid in which acid-modified polyolefin resin is dissolved or dispersed in a solvent such as toluene or methylcyclohexane (MCH), and then applied and dried. do.

When the sealant adhesive layer 16 is formed by extrusion molding, the adhesive resin tends to be oriented in the MD direction (extrusion direction) due to stress generated during extrusion molding. In this case, an elastomer may be added to the sealant adhesive layer 16 in order to alleviate the anisotropy of the sealant adhesive layer 16. As the elastomer to be added to the sealant adhesive layer 16, for example, olefin elastomer, styrene elastomer, etc. can be used.

The average particle size of the elastomer is preferably a particle size that can improve the compatibility between the elastomer and the adhesive resin and improve the effect of mitigating the anisotropy of the sealant adhesive layer 16. Specifically, the average particle size of the elastomer is preferably 200 nm or less, for example.

The average particle size of the elastomer can be determined, for example, by taking an enlarged photograph of the cross section of the elastomer composition using an electron microscope, and then measuring the average particle size of the dispersed crosslinked rubber component by image analysis. . The above elastomers may be used alone or in combination of two or more.

When blending an elastomer into the sealant adhesive layer 16, the amount of the elastomer added to the sealant adhesive layer 16 (100% by mass) is, for example, preferably 1 to 25% by mass, more preferably 10 to 20% by mass. When the content of the elastomer is 1% by mass or more, the compatibility with the adhesive resin is improved, and the effect of alleviating the anisotropy of the sealant adhesive layer 16 tends to be improved. Further, by setting the blending amount of the elastomer to 25% by mass or less, the effect of suppressing swelling of the sealant adhesive layer 16 by the electrolytic solution tends to be improved.

As the sealant adhesive layer 16, for example, a dispersion type adhesive resin liquid in which an adhesive resin is dispersed in an organic solvent may be used.

The thickness of the sealant adhesive layer 16 is preferably 2 to 50 μm, more preferably 20 to 40 μm in the case of a thermally laminated configuration. When the thickness of the sealant adhesive layer 16 is 2 μm or more, it is easy to obtain sufficient adhesive strength between the metal foil layer 14 and the sealant layer 17, and when the thickness is 50 μm or less, it is easy to obtain a sufficient adhesive strength between the metal foil layer 14 and the sealant layer 17. It is possible to easily reduce the amount of water that enters. Further, the thickness of the sealant adhesive layer 16 is preferably 1 to 5 μm in the case of a dry laminate structure. When the thickness of the sealant adhesive layer 16 is 1 μm or more, sufficient adhesive strength between the metal foil layer 14 and the sealant layer 17 can be easily obtained, and when the thickness is 5 μm or less, cracking of the sealant adhesive layer 16 can be prevented. Can be suppressed.

(Sealant layer 17)
The sealant layer 17 is a layer that provides heat-sealing sealing properties to the exterior material 10, and is a layer that is placed inside and heat-sealed when the power storage device is assembled. Examples of the sealant layer 17 include a resin film made of a polyolefin resin or an acid-modified polyolefin resin obtained by graft-modifying a polyolefin resin with an acid such as maleic anhydride. Among these, polyolefin resins are preferred, and polyolefin resins are preferred because they have improved water vapor barrier properties and can form a power storage device without being crushed excessively by heat sealing, and polypropylene is particularly preferred.

Examples of the polyolefin resin include low-density, medium-density, and high-density polyethylene; ethylene-α-olefin copolymer; polypropylene; and propylene-α-olefin copolymer. The polyolefin resin in the case of a copolymer may be a block copolymer or a random copolymer. These polyolefin resins may be used alone or in combination of two or more.

In addition, each of the above types of polypropylene, that is, random polypropylene, homopolypropylene, and block polypropylene, includes low-crystalline ethylene-butene copolymers, low-crystalline propylene-butene copolymers, and three types of ethylene, butene, and propylene. A terpolymer made of a component copolymer, an anti-blocking agent (AB agent) such as silica, zeolite, or acrylic resin beads, a fatty acid amide-based slip agent, etc. may be added.

Examples of the acid-modified polyolefin resin include the same resins as those listed for the sealant adhesive layer 16.

The sealant layer 17 may be a single layer film or a multilayer film, and may be selected depending on the required function. For example, in terms of providing moisture resistance, a multilayer film in which a resin such as an ethylene-cyclic olefin copolymer and polymethylpentene is interposed can be used.

Further, the sealant layer 17 may contain various additives such as a flame retardant, a slip agent, an anti-blocking agent, an antioxidant, a light stabilizer, and a tackifier.

When a heat-fusible film formed by extrusion molding is used as the sealant layer 17, the heat-fusible film tends to be oriented in the extrusion direction. Therefore, from the viewpoint of alleviating the anisotropy of the sealant layer 17 due to orientation, an elastomer may be added to the heat-fusible film. Thereby, whitening of the sealant layer 17 can be suppressed when forming the concave portion by cold molding the exterior material 10 for a power storage device.

As the elastomer constituting the sealant layer 17, for example, the same material as the elastomer exemplified as the elastomer constituting the sealant adhesive layer 16 can be used. When the sealant layer 17 has a multilayer film structure, at least one layer of the plurality of layers constituting the multilayer film structure may contain an elastomer. For example, if the sealant layer 17 has a three-layer laminated structure consisting of a laminated random polypropylene layer/block polypropylene layer/random polypropylene layer, the elastomer may be blended only in the block polypropylene layer or only in the random polypropylene layer. It may be blended or may be blended into both the random polypropylene layer and the block polypropylene layer.

Furthermore, a lubricant may be included in order to impart slipperiness to the sealant layer 17. As described above, since the sealant layer 17 contains a lubricant, when a recess is formed in the exterior material 10 for a power storage device by cold molding, the side or corner of the recess with a high elongation rate in the exterior material 10 for a power storage device This makes it possible to prevent the portion of the image from being stretched more than necessary. Thereby, separation between the metal foil layer 14 and the sealant adhesive layer 16 and occurrence of breakage and whitening due to cracks in the sealant layer 17 and the sealant adhesive layer 16 can be suppressed.

When the sealant layer 17 contains a lubricant, the content of the lubricant in the sealant layer 17 (100% by mass) is preferably 0.001 to 0.5% by mass. When the content of the lubricant is 0.001% by mass or more, there is a tendency that whitening of the sealant layer 17 during cold molding can be further suppressed. Moreover, when the content of the lubricant is 0.5% by mass or less, there is a tendency that a decrease in adhesion strength between the surface of the sealant layer 17 and the surface of the other layer in contact with the surface can be suppressed.

The thickness of the sealant layer 17 is preferably 10 to 100 μm, more preferably 20 to 60 μm. When the thickness of the sealant layer 17 is 10 μm or more, sufficient heat sealing strength can be obtained, and when the thickness is 100 μm or less, the amount of water vapor infiltrating from the edge of the exterior material can be reduced.

(Coating layer 18)
The coating layer 18 is a layer that provides the exterior material 10 with good adhesion to an acrylic PSA (Pressure Sensitive Adhesive) tape. Since a power storage device including the exterior material 10 as a container may be placed on a device via an acrylic PSA tape, the surface of the exterior material 10 (i.e., the surface on the base material layer 11 side) is in good contact with the tape. It is preferable to do so. Note that the acrylic PSA tape has an acrylic adhesive layer laminated on a base material such as a PET film. Examples of acrylic pressure-sensitive adhesives include those containing an acrylic copolymer having a hydroxyl group as a main ingredient and an isocyanate curing agent.

The coating layer 18 is preferably a layer containing at least one resin selected from the group consisting of acrylic resins and polyester resins.

Examples of monomer components constituting the acrylic resin include alkyl acrylate, alkyl methacrylate (alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, - ethylhexyl group, lauryl group, stearyl group, cyclohexyl group, phenyl group, benzyl group, phenylethyl group, etc.); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl Hydroxy group-containing monomers such as methacrylate; acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N,N-dimethylolacrylamide, N-methoxymethylacrylamide, N - Amide group-containing monomers such as methoxymethylmethacrylamide and N-phenylacrylamide; Amino group-containing monomers such as N,N-diethylaminoethyl acrylate and N,N-diethylaminoethyl methacrylate;Epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate Monomers containing carboxyl groups or salts thereof such as acrylic acid, methacrylic acid, and salts thereof (lithium salt, sodium salt, potassium salt, etc.) can be used. These may be used alone or in combination of two or more. Furthermore, these can be used in combination with other monomers other than those mentioned above.

Examples of other monomers include epoxy group-containing monomers such as allyl glycidyl ether; sulfonic acid groups such as styrene sulfonic acid, vinyl sulfonic acid, and their salts (lithium salt, sodium salt, potassium salt, ammonium salt, etc.); Monomers containing salts; monomers containing carboxyl groups or their salts such as crotonic acid, itaconic acid, maleic acid, fumaric acid, and their salts (lithium salts, sodium salts, potassium salts, ammonium salts, etc.); maleic anhydride Monomers containing acids and acid anhydrides such as itaconic anhydride; vinyl isocyanate, allyl isocyanate, styrene, vinyl methyl ether, vinyl ethyl ether, vinyl tris alkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, acrylonitrile, Methacrylonitrile, alkyl itaconic acid monoester, vinylidene chloride, vinyl acetate, vinyl chloride, etc. can be used. Furthermore, as the acrylic resin, modified acrylic copolymers such as block copolymers and graft copolymers modified with polyester, urethane, epoxy, etc. may be used.

As the polyester resin, a copolyester having a lower glass transition temperature by introducing a copolymer component is preferable. The copolymerized polyester is preferably water-soluble or water-dispersible from the viewpoint of coatability. Such copolyesters include copolyesters to which at least one group selected from the group consisting of sulfonic acid groups or their alkali metal bases are bonded (hereinafter referred to as "sulfonic acid group-containing copolyesters"). It is preferable to use

Here, the sulfonic acid group-containing copolyester refers to a polyester in which at least one group selected from the group consisting of a sulfonic acid group or its alkali metal base is bonded to a part of a dicarboxylic acid component or a glycol component, and among them, , a copolymer prepared by using an aromatic dicarboxylic acid component containing at least one group selected from the group consisting of sulfonic acid groups or their alkali metal bases in a proportion of 2 to 10 mol % based on the total acid components. Polyester is preferred.

A suitable example of such a dicarboxylic acid is 5-sodium sulfoisophthalic acid. In this case, other dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, p-β-oxyethoxybenzoic acid, 2,6-naphthalene dicarboxylic acid, 4,4'-dicarboxydiphenyl, 4,4' -dicarboxybenzophenone, bis(4-carboxyphenyl)ethane, adipic acid, sebacic acid, cyclohexane-1,4-dicarboxylic acid and the like.

Ethylene glycol is mainly used as the glycol component for producing the sulfonic acid group-containing copolyester, and in addition, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, and ethylene oxide addition of bisphenol A are used. Polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. can be used. Among them, it is preferable to use ethylene glycol, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, etc. as a copolymerization component since the compatibility with the polystyrene sulfonate is improved.

Acrylic resins and polyester resins may be used alone or in combination of two or more. Furthermore, these resins and curing agents exemplified below may be used in combination.

The curing agent is not particularly limited, but examples thereof include isocyanate curing agents. Isocyanates include aliphatic isocyanates and aromatic isocyanates, with aliphatic isocyanates being preferred. The aliphatic isocyanate curing agent is a bifunctional or more functional isocyanate compound that does not have an aromatic ring. Since it does not have an aromatic ring, the benzene ring does not turn into a quinoid due to ultraviolet rays, and yellowing can be suppressed, so it is suitable for the outermost layer such as a coating layer. Examples of aliphatic isocyanate curing agents include methylene diisocyanate, isopropylene diisocyanate, lysine diisocyanate, 2,2,4- or 2,4,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate. , 4,4'-dicyclohexylmethane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, and the like.

Among these, 1,6-hexamethylene diisocyanate and isophorone diisocyanate are preferred as the aliphatic isocyanate curing agent because they improve electrolyte resistance. In particular, 1,6-hexamethylene diisocyanate is preferred from the viewpoint of not only improving the self-healing performance of the curing agent but also having excellent reactivity between the isocyanate groups of the curing agent and the hydroxyl groups of acrylic resins and polyester resins. This also makes it possible to obtain excellent suitability for mass production.

Furthermore, by using an isocyanate adduct, biuret, or isocyanurate as a curing agent, the crosslinking density of the formed coating layer can be further improved, and excellent alcohol resistance and electrolyte resistance can be obtained.

The thickness of the coating layer 18 is preferably 0.05 to 3 μm. By having a thickness of the coating layer 18 of 0.05 μm or more, it is easy to obtain sufficient adhesion with the acrylic PSA tape, and by having a thickness of 3 μm or less, even if a coating layer is provided, there is no decrease in drawing formability. becomes easier to suppress.

[Manufacturing method of exterior material]
Next, a method for manufacturing the exterior material 10 will be explained. Note that the method for manufacturing the exterior material 10 is not limited to the following method.

Examples of the method for manufacturing the exterior material 10 include a method including the following steps S11 to S14.
Step S11: A step of forming a corrosion prevention treatment layer 15a on one surface of the metal foil layer 14, and forming a corrosion prevention treatment layer 15b on the other surface of the metal foil layer 14.
Step S12: A step of forming the adhesion-friendly treatment layer 12 on one surface of the base material layer 11 to obtain a laminate. Step S13: A step of bonding together the surface of the corrosion prevention treatment layer 15a opposite to the metal foil layer 14 and the surface of the laminate on the adhesion-promoting layer 12 side via the adhesive layer 13.
Step S14: A step of forming a sealant layer 17 on the opposite side of the metal foil layer 14 of the corrosion prevention treatment layer 15b via a sealant adhesive layer 16.
Step S15: A step of forming a coating layer 18 on the surface of the base material layer 11 opposite to the adhesion-promoting layer 12.

(Step S11)
In step S11, a corrosion prevention treatment layer 15a is formed on one surface of the metal foil layer 14, and a corrosion prevention treatment layer 15b is formed on the other surface of the metal foil layer 14. Corrosion prevention treatment layers 15a and 15b may be formed separately, or both may be formed at once. Specifically, for example, a corrosion prevention treatment agent (base material of the corrosion prevention treatment layer) is applied to both sides of the metal foil layer 14, and then drying, curing, and baking are performed sequentially to form the corrosion prevention treatment layer. 15a and 15b are formed at once. Further, a corrosion prevention treatment agent is applied to one side of the metal foil layer 14, and after drying, curing, and baking are performed sequentially to form a corrosion prevention treatment layer 15a, the same is applied to the other side of the metal foil layer 14. A corrosion prevention treatment layer 15b may also be formed. The order in which the corrosion prevention treatment layers 15a and 15b are formed is not particularly limited. Moreover, different corrosion prevention treatment agents may be used for the corrosion prevention treatment layer 15a and the corrosion prevention treatment layer 15b, or the same one may be used. As the above-mentioned corrosion prevention treatment agent, for example, a corrosion prevention treatment agent for coating type chromate treatment can be used. The method for applying the corrosion prevention treatment agent is not particularly limited, but examples include methods such as gravure coating, gravure reverse coating, roll coating, reverse roll coating, die coating, bar coating, kiss coating, and comma coating. can be used. Note that as the metal foil layer 14, an untreated metal foil layer may be used, or a metal foil layer that has been degreased by wet type degreasing treatment or dry type degreasing treatment may be used.

(Step S12)
In step S12, an easy-adhesion treatment layer 12 is formed on one surface of the base layer 11. Here, an in-line coating method will be described as an example of a method for forming the adhesion-promoting layer 12. First, an aqueous coating liquid containing a dispersion in which the above resin, which is the main component of the adhesion-promoting layer 12, is dispersed with a dispersant is prepared. Next, the aqueous coating liquid is applied to one surface of the thermoplastic resin film (base material of the base layer 11) before crystal orientation is completed. Next, the applied aqueous coating liquid is dried, and then the thermoplastic resin film is stretched in at least one direction.

Next, by completing the orientation of the thermoplastic resin film by heat treatment, a laminate in which the easy-adhesion treated layer 12 is formed on one surface of the base layer 11 is obtained. By forming the easy-adhesion treated layer 12 using such an in-line coating method, the adhesion between the base layer 11 and the easy-adhesion treated layer 12 is improved. Note that the method for forming the easy-adhesion treated layer 12 is not limited to the above method, and any method may be used. Moreover, the timing of forming the adhesion-promoting layer 12 is not limited to this embodiment.

(Step S13)
In step S13, the surface of the corrosion prevention treatment layer 15a opposite to the metal foil layer 14 and the surface of the laminate on the adhesion-promoting layer 12 side are dry laminated using an adhesive forming the adhesive layer 13. Can be pasted together using methods such as In step S13, aging (curing) treatment may be performed at room temperature to 100° C. to promote adhesion. The aging time is, for example, 1 to 10 days.

(Step S14)
After step S13, the corrosion prevention treatment layer 15b of the laminate in which the base material layer 11, the easy adhesion treatment layer 12, the adhesive layer 13, the corrosion prevention treatment layer 15a, the metal foil layer 14, and the corrosion prevention treatment layer 15b are laminated in this order. A sealant layer 17 is formed on the surface opposite to the metal foil layer 14 with a sealant adhesive layer 16 interposed therebetween. The sealant layer 17 may be laminated by dry lamination, sandwich lamination, etc., or may be laminated together with the sealant adhesive layer 16 by a coextrusion method. In order to improve adhesion, the sealant layer 17 is preferably laminated by sandwich lamination, or laminated together with the sealant adhesive layer 16 by a coextrusion method, and more preferably by sandwich lamination.

(Step S15)
After step S14, the base material layer 11, the easy-adhesion treatment layer 12, the adhesive layer 13, the corrosion prevention treatment layer 15a, the metal foil layer 14, the corrosion prevention treatment layer 15b, the sealant adhesive layer 16, and the sealant layer 17 were laminated in this order. A coating layer 18 is formed on the surface of the laminate opposite to the adhesion-promoting layer 12 of the base layer 11 . The forming method is not particularly limited, and examples thereof include gravure coating, gravure reverse coating, roll coating, reverse roll coating, die coating, bar coating, kiss coating, comma coating, and the like.

Through the steps S11 to S15 described above, the exterior material 10 is obtained. Note that the process order of the method for manufacturing the exterior material 10 is not limited to the method of sequentially performing the above steps S11 to S15. For example, the order of the steps to be performed may be changed as appropriate, such as performing step S12 and then performing step S11.

[Power storage device]
Next, a power storage device including the exterior material 10 as a container will be described. The power storage device includes a battery element 1 including an electrode, a lead 2 extending from the electrode, and a container that holds the lead 2 and accommodates the battery element 1, and the container includes: The sealant layer 17 is formed on the inside. The above-mentioned container may be obtained by overlapping two exterior materials with the sealant layers 17 facing each other and heat-sealing the peripheral edges of the overlapping exterior materials 10, or by folding one exterior material. It may also be obtained by overlapping and heat-sealing the peripheral edges of the exterior material 10 in the same manner. Further, the power storage device may include the exterior material 20 as a container. Examples of power storage devices include secondary batteries such as lithium ion batteries, nickel hydride batteries, and lead storage batteries, and electrochemical capacitors such as electric double layer capacitors.

The lead 2 is sandwiched and sealed by an exterior material 10 forming a container with a sealant layer 17 inside. The lead 2 may be held between the exterior materials 10 via a tab sealant.

[Method for manufacturing power storage device]
Next, a method for manufacturing a power storage device using the above-described exterior material 10 will be described. In addition, here, the case where the secondary battery 40 is manufactured using the embossed type exterior material 30 is mentioned as an example, and is demonstrated. FIG. 2 is a diagram showing the embossed type exterior material 30. As shown in FIG. (a) to (d) of FIG. 3 are perspective views showing the manufacturing process of a single-sided molded battery using the exterior material 10. The secondary battery 40 is a double-sided molded battery manufactured by providing two exterior materials such as the embossed type exterior material 30 and bonding these exterior materials together while adjusting the alignment. Good too. Further, the embossed type exterior material 30 may be formed using the exterior material 20.

The secondary battery 40, which is a one-sided molded battery, can be manufactured, for example, by the following steps S21 to S25.
Step S21: A step of preparing the exterior material 10, the battery element 1 including the electrode, and the lead 2 extending from the electrode.
Step S22: Step of forming a recess 32 for arranging the battery element 1 on one side of the exterior material 10 (see FIGS. 3(a) and 3(b)).
Step S23: Place the battery element 1 in the molding area (recess 32) of the embossed type exterior material 30, fold back and stack the embossed type exterior material 30 so that the lid 34 covers the recess 32, and extend from the battery element 1. A process of pressurizing and heat-sealing one side of the embossed type exterior material 30 so as to sandwich the leads 2 (see FIGS. 3(b) and 3(c)).
Step S24: Leave one side other than the side that holds the lead 2, press and heat seal the other sides, then inject the electrolyte from the remaining side, and press and heat seal the remaining side in a vacuum state. (see FIG. 3(c)).
Step S25: A step of cutting the edges of the pressurized and heat-sealed sides other than the sides that sandwich the lead 2 and bending them toward the molding area (recess 32) (see FIG. 3(d)).

(Step S21)
In step S21, the exterior material 10, the battery element 1 including the electrode, and the lead 2 extending from the electrode are prepared. The exterior material 10 is prepared based on the embodiment described above. There are no particular limitations on the battery element 1 and leads 2, and known battery elements 1 and leads 2 can be used.

(Step S22)
In step S22, a recess 32 for arranging the battery element 1 is formed on the sealant layer 17 side of the exterior material 10. The planar shape of the recess 32 is a shape that matches the shape of the battery element 1, for example, a rectangular shape in plan view. The recess 32 is formed, for example, by pressing a pressing member having a rectangular pressure surface against a portion of the exterior material 10 in the thickness direction thereof. Further, the position to be pressed, that is, the recess 32, is formed at a position that is biased toward one end of the exterior material 10 in the longitudinal direction from the center of the exterior material 10 cut out into a rectangle. Thereby, after the molding process, the other end side where the recess 32 is not formed can be folded back to form a lid (lid portion 34).

More specifically, a method for forming the recess 32 includes molding using a mold (deep drawing molding). The molding method uses a female mold and a male mold arranged to have a gap equal to or greater than the thickness of the exterior material 10, and presses the male mold together with the exterior material 10 into the female mold. can be mentioned. By adjusting the amount of depression of the male mold, the depth of the recess 32 (deep drawing amount) can be adjusted to a desired amount. By forming the recesses 32 in the exterior material 10, an embossed type exterior material 30 is obtained. This embossed type exterior material 30 has a shape as shown in FIG. 2, for example. Here, FIG. 2(a) is a perspective view of the embossed type exterior material 30, and FIG. 2(b) is a vertical cross section of the embossed type exterior material 30 shown in FIG. 2(a) along line bb. It is a diagram.

(Step S23)
In step S23, the battery element 1 composed of a positive electrode, a separator, a negative electrode, etc. is placed in the molding area (recess 32) of the embossed type exterior material 30. Further, the leads 2 extending from the battery element 1 and joined to the positive electrode and the negative electrode are pulled out from the molding area (recess 32). Thereafter, the embossed type exterior material 30 is folded back at approximately the center in the longitudinal direction, and is stacked so that the sealant layers 17 are on the inside, and one side of the embossed type exterior material 30 that sandwiches the lead 2 is heat-sealed under pressure. Ru. Pressure heat fusion is controlled by three conditions: temperature, pressure, and time, and is set appropriately. The temperature of the pressurized heat fusion is preferably higher than the temperature at which the sealant layer 17 is melted.

Note that the thickness of the sealant layer 17 before heat sealing is preferably 40 to 80% of the thickness of the lead 2. When the thickness of the sealant layer 17 is at least the above lower limit value, the heat-sealing resin tends to be able to sufficiently fill the ends of the leads 2, and when it is at most the above upper limit value, the outer casing material 10 of the secondary battery 40 The thickness of the end portion can be suppressed to an appropriate level, and the amount of moisture infiltrating from the end portion of the exterior material 10 can be reduced.

(Step S24)
In step S24, one side other than the side holding the lead 2 is left, and the other sides are pressurized and heat fused. After that, electrolyte is injected from the remaining side, and the remaining side is heat-sealed under pressure in a vacuum state. The conditions for pressure heat fusion are the same as in step S23.

(Step S25)
The edges of the peripheral pressurized and heat-sealed edges other than the edges that sandwich the leads 2 are cut, and the sealant layer 17 protruding from the edges is removed. Thereafter, the peripheral pressurized heat-sealed portion is folded back toward the molding area 32 to form a folded portion 42, thereby obtaining the secondary battery 40.

Although the preferred embodiments of the exterior material for a power storage device and the method of manufacturing a power storage device of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and is within the scope of the claims. Various modifications and changes are possible within the scope of the described gist of the invention.

EXAMPLES Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples.

(Preparation of base material layer)
As the base material layer 11, a polyester film (each having a thickness of 25 μm) having the characteristics shown in Table 1 was prepared. In Table 1, the stress value at 50% elongation and the heat shrinkage rate were each measured as follows.
Stress value at 50% elongation (F50 stress value): Each polyester film cut into A4 size was heated for 30 minutes in an oven maintained at an arbitrary heat treatment temperature within the range of 160 to 200°C. After that, the polyester film was subjected to a tensile test in four directions (0° (MD), 45°, 90° (TD), 135°) (test piece shape: No. 5 dumbbell shape specified in JIS K7127, chuck). distance: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min, temperature: 23°C). Then, the stress value at 50% elongation was calculated by averaging the measurement results in the four directions.
Heat shrinkage rate: Each polyester film cut into A4 size at 23°C was heated for 30 minutes in an oven maintained at an arbitrary heat treatment temperature within the range of 160 to 200°C. Thereafter, the length of the polyester film in four directions (0° (MD), 45°, 90° (TD), 135°) at 23° C. was measured. Then, the heat shrinkage rate was calculated by calculating the heat shrinkage rate in each direction according to the following formula and taking the average value.
Heat shrinkage rate (%) = [{Length in each direction measured before heat treatment (A4 size) - Length in each direction measured after heat treatment}/Length in each direction measured before heat treatment] × 100

(Example 1)
As the metal foil layer 14, a soft aluminum foil 8079 material (manufactured by Toyo Aluminum Co., Ltd.) having a thickness of 40 μm was prepared. Next, on both sides of the metal foil layer 14, a sodium polyphosphate stabilized cerium oxide sol (corrosion prevention treatment agent) using distilled water as a solvent and having a solid content concentration of 10% by mass was applied by gravure coating. At this time, the amount of phosphoric acid was 10 parts by mass with respect to 100 parts by mass of cerium oxide.

Next, after drying the applied sodium polyphosphate stabilized cerium oxide sol, a baking treatment is sequentially performed to form a corrosion prevention treatment layer 15a on one side of the metal foil layer 14, and a corrosion prevention treatment layer 15a on the other side. A treated layer 15b was formed. The baking conditions were a temperature of 150° C. and a processing time of 30 seconds.

Next, a polyester film shown in Table 1 was used as the base layer 11, and one side of the base layer 11 was subjected to corona treatment.

Next, a polyurethane adhesive was applied as the adhesive layer 13 to the surface of the corrosion prevention treated layer 15a of the metal foil layer 14 on the side opposite to the metal foil layer 14. Next, the metal foil layer 14 and the corona-treated surface of the base layer 11 were bonded together via the adhesive layer 13 by dry lamination. Thereafter, the structure consisting of the base material layer 11, the adhesive layer 13, the corrosion prevention treatment layer 15a, the metal foil layer 14, and the corrosion prevention treatment layer 15b is left in an atmosphere at a temperature of 60° C. for 6 days to undergo aging. Processed.

Next, the sealant adhesive layer 16 was formed by extruding maleic anhydride-modified polypropylene (manufactured by Mitsui Chemicals, Inc., trade name: Admer), which is a base material of the sealant adhesive layer 16. At this time, the thickness of the sealant adhesive layer 16 was 15 μm. Then, by a sandwich lamination method using a thermal lamination device, a polyolefin film with a thickness of 30 μm that will become the sealant layer 17 (on the sealant adhesive layer 16 side of the unstretched polypropylene film) is attached to the corrosion prevention treatment layer 15b via the sealant adhesive layer 16. (a film whose surface had been corona-treated) were laminated together at 160° C. (bonded under heat and pressure). By winding this up, a roll-shaped exterior material 10 for a power storage device was produced.

(Example 2, Comparative Examples 1 to 6)
Exterior material 10 for a power storage device was produced in the same manner as in Example 1, except that the polyester film listed in Table 1 was used.

(Example 3)
Exterior material 10 for a power storage device was prepared in the same manner as in Example 1, except that instead of corona treatment on one side of base layer 11, easy-adhesion treatment layer 12 was formed on the surface of base layer 11 on the adhesive layer 13 side. was created. The easy-adhesion treatment layer 12 is prepared by coating one side of the base layer 11 with a coating agent, which will be the base material of the easy-adhesion treatment layer 12, prepared as follows, at a solid content of 0.1 g/m ² using an in-line coating method. It was formed by coating and drying. The thickness of the easy-adhesion treatment layer 12 was about 0.1 μm.
(Preparation of coating agent for forming adhesion treatment layer)
A coating agent having the following composition was prepared as a coating agent for forming an easy-adhesion treatment layer.
Coating agent: water-soluble polyester “Aronmelt PES-1000” manufactured by Toagosei Co., Ltd., self-emulsifying polyisocyanate “Aquanate 100” manufactured by Nippon Polyurethane Industries, Ltd., and true spherical silica manufactured by Nippon Shokubai Chemical Co., Ltd. Fine particles "Seahoster KE-P30" (average particle size 0.3 μm) were added at a blending ratio (mass ratio) of 95/5/0.5 and diluted with water.

(Example 4)
In the same manner as in Example 1, except that instead of forming the corrosion prevention treatment layers 15a and 15b using sodium polyphosphate stabilized cerium oxide sol, the corrosion prevention treatment layers 15a and 15b were formed by performing chromate treatment, Exterior material 10 for a power storage device was produced. The chromate treatment was performed by applying a treatment liquid consisting of a phenol resin, a chromium fluoride compound, and phosphoric acid to both surfaces of the metal foil layer 14 to form a film, and then baking the film.

(Examples 5-8, Comparative Examples 7-12)
A resin composition containing polyester polyol and an isocyanurate of IPDI as a curing agent is applied onto the base layer 11 and cured by heating, thereby forming a polyester resin with a thickness of 1.0 μm onto the base layer 11. Exterior material 10 for a power storage device was produced in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 6, respectively, except that a coating layer was formed.

(Examples 9 to 12, Comparative Examples 13 to 18)
A resin composition containing an acrylic polyol and an adduct of HDI as a curing agent is applied onto the base layer 11 and cured by heating. Exterior material 10 for a power storage device was produced in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 6, respectively, except that a coating layer was formed.

(Reference examples 1-2)
Exterior material 10 for a power storage device was produced in the same manner as in Examples 5 and 9, respectively, except that the thickness of the coating layer was 4.0 μm.

<Evaluation of processing suitability>
The sealant layer 17 was laminated to the corrosion prevention treatment layer 15b via the sealant adhesive layer 16 by a sandwich lamination method using a thermal lamination device, and the processing suitability for winding this was evaluated based on the following criteria.
A: Both lamination and winding were performed satisfactorily.
B: Lamination or winding could not be performed well.
C: Neither lamination nor winding could be performed well.

<Evaluation of molding depth>
Regarding the power storage device exterior material 10 produced in each Example and Comparative Example, the molding depth at which deep drawing was possible was evaluated by the following method. First, the power storage device exterior material 10 was placed in a molding device so that the sealant layer 17 faced upward. The molding depth of the molding device was set to 6.0 mm or 6.5 mm, and cold molding was performed in an environment with a room temperature of 23°C and a dew point temperature of -35°C. Note that the punch mold has a rectangular cross section of 70 mm x 80 mm, a punch radius (RP) of 1.00 mm on the bottom, and a punch corner radius (RCP) of 1.00 mm on the side. It was used. Further, the die used had a die radius (RD) of 1.00 mm on the upper surface of the opening. The presence or absence of breakage and pinholes in the cold-molded portion was visually confirmed while irradiating the exterior material 10 with a light, and the maximum value of the molding depth (molding limit) was evaluated based on the following criteria. The results are shown in Table 2.
A: Neither breakage nor pinholes occurred at a molding depth of 6.5 mm.
B: Although fractures or pinholes occurred at a molding depth of 6.5 mm, neither fractures nor pinholes occurred at a molding depth of 6.0 mm.
C: Breakage or pinholes occurred at a molding depth of 6.0 mm.

<Evaluation of interlayer adhesion>
The adhesion between the base material layer 11 and the metal foil layer 14 was evaluated using the following method for the exterior material 10 for a power storage device produced in each Example and Comparative Example. First, the power storage device exterior material 10 was placed in a molding device so that the sealant layer 17 faced upward. The molding depth of the molding device was set to 5 mm, and cold molding was performed in an environment with a room temperature of 23°C and a dew point temperature of -35°C. Note that the punch mold has a rectangular cross section of 70 mm x 80 mm, a punch radius (RP) of 1.00 mm on the bottom, and a punch corner radius (RCP) of 1.00 mm on the side. It was used. Further, the die used had a die radius (RD) of 1.00 mm on the upper surface of the opening.

Next, the cold-molded exterior material 10 was placed in a 100 mL beaker containing 30 mL of a 1M lithium hexafluorophosphate solution (solvent volume ratio = ethyl carbonate: dimethyl carbonate: dimethyl carbonate = 1:1:1). . Next, the beaker containing the exterior material 10 was sealed in a one-ton can and placed in a temperature environment of 40° C. for 2 hours, thereby exposing the exterior material 10 to the electrolytic solution. Thereafter, the packaging material 10 was taken out from the beaker inside the can and placed in an oven at 110°C, in an environment of 60°C and 95% humidity, or in hot water at 50°C. Then, the presence or absence of peeling between the base material layer 11 and the metal foil layer 14 of the exterior material 10 over time was visually confirmed, and peeling was confirmed between the base material layer 11 and the metal foil layer 14. The maximum value (unit: week) for the period during which no Based on the results, the adhesion between the base layer 11 and the metal foil layer 14 was evaluated using the following evaluation criteria. The results are shown in Table 2.
A: No peeling was observed even after 4 weeks.
B: Peeling was confirmed after 4 weeks.

<PSA tape adhesion>
The adhesion between the base layer 11 (or coating layer 18) and the acrylic PSA tape for the exterior material 10 for a power storage device produced in each Example and Comparative Example was evaluated by the following method. First, the exterior material 10 for a power storage device was attached to a support so that the base layer 11 (or coating layer 18) side was the top surface. Next, an acrylic PSA tape and a supporting aluminum foil for a peel test were pasted onto the base layer 11 (or coating layer 18) with a force of about 20N. After leaving this for about 1 hour, the peel strength (180 degree peeling, peeling speed: 50 mm/min) between the base material layer 11 (or coating layer 18) and the acrylic PSA tape was measured, and based on the following evaluation criteria. I made an evaluation. The results are shown in Table 2.
○: Peel strength was 10 N/15 mm or more.
×: Peel strength was less than 10 N/15 mm.

From the results shown in Table 2, it is understood that according to this example, it is possible to provide an exterior material for a power storage device that is excellent in processing suitability during production and deep drawing formability after production.

DESCRIPTION OF SYMBOLS 1...Battery element, 2...Lead, 10...Exterior material (exterior material for power storage device), 11...Base material layer, 12...Easy adhesion treatment layer, 13...Adhesive layer, 14...Metal foil layer, 15a, 15b...Corrosion Prevention treatment layer, 16... Sealant adhesion layer, 17... Sealant layer, 18... Coating layer, 30... Embossed type exterior material, 32... Molding area (recess), 34... Lid, 40... Secondary battery.

Claims (5)

It has a structure in which at least a base material layer, an adhesive layer, a metal foil layer, a sealant adhesive layer, and a sealant layer are laminated in this order,
The thickness of the base material layer is 6 to 40 μm, the thickness of the metal foil layer is 9 to 200 μm, and the thickness of the sealant layer is 10 to 100 μm,
the metal foil layer is aluminum foil,
An exterior material for a power storage device, wherein the base layer is made of a polyester film that satisfies the following conditions. <Conditions>
The stress value at 50% elongation after heat treatment at 160 to 200 °C is 100 to 180 MPa, the heat shrinkage rate after heat treatment at 160 to 200 °C is 1 to 15%, and after heat treatment at 200 °C A polyester film with a heat shrinkage rate of 7.8% or more. These heat treatments involve heating in an oven for 30 minutes.
Stress value at 50% elongation: Tensile test in four directions (0° (MD), 45°, 90° (TD), 135°) of the base material layer (test piece shape: No. 5 type specified in JIS K7127) This is the average value of the stress values when a dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min, temperature: 23° C.) was performed.
Heat shrinkage rate: This is the average value of shrinkage rates before and after heat treatment in four directions (0° (MD), 45°, 90° (TD), 135°) of the base material layer. The exterior material for a power storage device according to claim 1, wherein the polyester film has a heat shrinkage rate of 1 to 5% after heat treatment at 160°C. The exterior material for a power storage device according to claim 1 or 2, further comprising an adhesion-facilitating treatment layer provided between the base material layer and the adhesive layer. The exterior material for a power storage device according to any one of claims 1 to 3, further comprising a corrosion prevention treatment layer provided on both sides of the metal foil layer. Selecting a polyester film that satisfies the following conditions as the base layer, and bonding the base layer to one side of the metal foil layer via an adhesive layer, and the opposite side of the metal foil layer to the adhesive layer. forming a sealant layer on the surface via a sealant adhesive layer,
The thickness of the base material layer is 6 to 40 μm, the thickness of the metal foil layer is 9 to 200 μm, and the thickness of the sealant layer is 10 to 100 μm,
A method for manufacturing an exterior material for a power storage device, wherein the metal foil layer is an aluminum foil.
<Conditions>
The stress value at 50% elongation after heat treatment at 160 to 200 °C is 100 to 180 MPa, the heat shrinkage rate after heat treatment at 160 to 200 °C is 1 to 15%, and after heat treatment at 200 °C A polyester film with a heat shrinkage rate of 7.8% or more. These heat treatments involve heating in an oven for 30 minutes.
Stress value at 50% elongation: Tensile test in four directions (0° (MD), 45°, 90° (TD), 135°) of the base material layer (test piece shape: No. 5 type specified in JIS K7127) This is the average value of the stress values when a dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min, temperature: 23° C.) was performed.
Heat shrinkage rate: This is the average value of shrinkage rates before and after heat treatment in four directions (0° (MD), 45°, 90° (TD), 135°) of the base material layer.

Images