JP7240081B2 - Exterior material for power storage device and method for manufacturing exterior material for power storage device - Google Patents

Description

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

As power storage devices, for example, secondary batteries such as lithium-ion batteries, nickel-hydrogen batteries, and lead-acid batteries, and electrochemical capacitors such as electric double-layer capacitors are known. There is a demand for further miniaturization of power storage devices due to the miniaturization of mobile devices, the limitation of installation space, and the like, 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 multi-layer films, which are lightweight, have high heat dissipation properties, and can be produced at low cost, are now being used.

In a lithium-ion battery that uses the multilayer film as an exterior material, in order to prevent moisture from penetrating into the interior, the battery contents (positive electrode, separator, negative electrode, electrolyte, etc.) are covered with an exterior material containing an aluminum foil layer. Adopted. A lithium ion battery having such a configuration is called an aluminum laminate type lithium ion battery.

For aluminum laminate type lithium ion batteries, for example, a recess is formed in a part of the exterior material by cold molding, the contents of the battery are accommodated in the recess, and the remaining part of the exterior material is folded back to heat the edge part. An embossed type lithium ion battery sealed with a seal is known. (See Patent Document 1, for example). In such a lithium-ion battery, the deeper the recess formed by cold molding, the more battery contents can be accommodated, so the energy density can be increased.

JP 2013-101765 A

However, with the material and manufacturing method described in Patent Document 1, there are cases where it cannot be said that the workability is sufficient, such as the lamination of the metal foil layer and the sealant layer and the winding after lamination cannot be performed appropriately. Further, if a deep concave portion is formed in the obtained exterior material, the exterior material may be broken.

The present invention has been made in view of the above circumstances, and aims to provide an exterior material for a power storage device that is excellent in processability during fabrication and deep drawability after fabrication, and a method for manufacturing the exterior material for a power storage device. aim.

The present invention has a structure in which at least a substrate layer, an adhesive layer, a metal foil layer, a sealant adhesive layer and a sealant layer are laminated in this order, and the substrate layer has a thickness of 50% after heat treatment at 160 to 200°C. Provided is an exterior material for a power storage device comprising a polyester film having a % elongation stress value of 100 to 180 MPa and a thermal shrinkage of 1 to 15%.
Stress value at 50% elongation: Tensile test for four directions (0° (MD), 45°, 90° (TD), 135°) of the base layer (specimen shape: No. 5 type specified in JIS K7127 dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min, temperature: 23° C.).
Thermal shrinkage rate: An average value of shrinkage rates before and after heat treatment in four directions (0° (MD), 45°, 90° (TD), and 135°) of the base material layer.

Some of the processes for manufacturing an exterior material for a power storage device require a lamination process in order to laminate a plurality of layers. At this time, the heat applied during lamination or the heat applied during drying of the adhesive generally causes thermal deterioration of the base material layer, which may cause breakage during draw molding. On the other hand, even in the case of a base material layer that is rigid enough not to cause thermal deterioration due to the heat applied during lamination or the heat applied during drying of the adhesive, there is a risk of tearing during draw molding. Further, even if the drawability is excellent, there are cases where the workability is not sufficient, for example, lamination of the metal foil layer and the sealant layer or winding after lamination cannot be performed properly. The present invention solves these problems.

In the power storage device exterior material, the polyester film preferably has a thermal shrinkage of 1 to 5% after heat treatment at 160°C. This makes it easier to further improve the processability during production and the deep drawability after production.

It is preferable that the power storage device exterior material further includes an easy-adhesion treatment layer provided between the base material layer and the adhesive layer. Thereby, the adhesion between the base layer and the adhesive layer can be further improved, and the deep drawability can be further improved.

In the power storage device exterior material, the easy-adhesion treatment layer is a layer containing at least one resin selected from the group consisting of polyester resins, acrylic resins, polyurethane resins, epoxy resins, and acrylic-grafted polyester resins. preferable. Thereby, the adhesion between the base layer and the adhesive layer can be further improved, and the deep drawability can be further improved.

It is preferable that the power storage device exterior material further includes corrosion prevention treatment layers provided on both surfaces of the metal foil layer. Thereby, the adhesion between the base material layer and the metal foil layer can be further improved.

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

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

In the power storage device exterior material, the coating layer preferably has a thickness of 0.05 to 3 μm. Thereby, even if a coating layer is provided, it becomes easy to suppress the deterioration of drawability.

The present invention also includes a step of bonding a base material layer to one surface of a metal foil layer via an adhesive layer, and a sealant layer to a surface opposite to the adhesive layer of the metal foil layer via a sealant adhesive layer. The base layer is made of a polyester film having a stress value at 50% elongation of 100 to 180 MPa and a heat shrinkage 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 for four directions (0° (MD), 45°, 90° (TD), 135°) of the base layer (specimen shape: No. 5 type specified in JIS K7127 dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min, temperature: 23° C.).
Thermal shrinkage rate: An average value of shrinkage rates before and after heat treatment in four directions (0° (MD), 45°, 90° (TD), and 135°) of the base material layer.

ADVANTAGE OF THE INVENTION According to this invention, the exterior material for electrical storage apparatuses which is excellent in the processability at the time of manufacture, and the deep drawing moldability after manufacture, and the manufacturing method of the exterior material for electrical storage apparatuses can be provided.

1 is a schematic cross-sectional view of an exterior material for a power storage device according to an embodiment of the present invention; FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the embossing type exterior material obtained using the exterior material for electrical storage apparatuses which concerns on one Embodiment of this invention, (a) is the perspective view, (b) is embossing shown in (a). FIG. 2 is a vertical cross-sectional view of the type armor along line bb; FIG. 2A is a perspective view showing a process of manufacturing a secondary battery using an exterior material for a power storage device according to an embodiment of the present invention, where (a) shows a state in which the exterior material for a power storage device is prepared; (c) shows a state in which an embossed exterior material for a power storage device and a battery element are prepared; ) shows a state in which both sides of the folded portion are folded upward.

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

[Exterior material for power storage device]
FIG. 1 is a cross-sectional view schematically showing one embodiment of the exterior material for a power storage device of the present invention. As shown in FIG. 1, an exterior material (exterior material for a power storage device) 10 of the present embodiment includes a base layer 11, an easy-adhesion treatment layer 12 provided on one side of the base layer 11, An adhesion layer 13 provided on the opposite side of the easy-adhesion treatment layer 12 to the base material layer 11, and an anti-corrosion treatment layer 15a provided on both sides of the adhesion layer 13 on the opposite side to the easy-adhesion treatment layer 12. and 15b, a sealant adhesion layer 16 provided on the side of the metal foil layer 14 opposite to the adhesion layer 13, and a sealant adhesion layer 16 provided on the side opposite to the metal foil layer 14. and the sealant layer 17 are sequentially laminated. 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 adhesion layer 16 side. The exterior material 10 may further have a coating layer 18 on the opposite side of the substrate layer 11 from the easy adhesion treatment layer 12 . The exterior material 10 has the base material layer 11 (or the coating layer 18) as the outermost layer and the sealant layer 17 as the innermost layer. That is, the exterior material 10 is used with the base material 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 described below.

(Base material layer 11)
The base material layer 11 provides the exterior material 10 with heat resistance in a pressurized heat-sealing process, which will be described later, when manufacturing the power storage device and electrolyte resistance against electrolyte leaking from another power storage device, and is processed or processed. It is a layer for suppressing the occurrence of pinholes that may occur during distribution.

The base material layer 11 is made of a polyester film having a stress value of 100 to 180 MPa at 50% elongation and a heat shrinkage of 1 to 15% after heat treatment at 160 to 200° C., as shown below.
Stress value at 50% elongation: Tensile test for four directions (0° (MD), 45°, 90° (TD), 135°) of the base layer (specimen shape: No. 5 type specified in JIS K7127 dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min, temperature: 23° C.).
Thermal shrinkage rate: An average value of shrinkage rates before and after heat treatment in four directions (0° (MD), 45°, 90° (TD), and 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, the substrate 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. After that, a tensile test (specimen shape: specified in JIS K7127) at 23 ° C. (room temperature) in 4 directions (0 ° (MD), 45 °, 90 ° (TD), 135 °) of the base layer No. 5 dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min). By averaging the measurement results in four directions, the stress value at 50% elongation is calculated.

The vertical direction and the horizontal direction of the base material layer are made to match the MD direction (mechanical feed direction) and the TD direction (perpendicular to the MD direction) of the base material layer material, respectively. That is, when the substrate layer 11 is made of a biaxially stretched film, the longitudinal direction and the transverse direction of the test piece correspond to either one of the two stretching directions of the film.

When the stress value at 50% elongation of the base material layer 11 measured as described above is in the range of 100 to 180 MPa, the workability is excellent, and deep draw molding is possible even after the heat treatment. From this point of view, the stress value at 50% elongation of the base material layer 11 is preferably 110 to 170 MPa.

Specifically, the thermal shrinkage rate of the base material layer 11 can be measured as follows. That is, a substrate 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. After that, the lengths of the base material layer in four directions (0° (MD), 45°, 90° (TD), 135°) at 23°C are 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.
Thermal 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

Because the heat shrinkage rate of the base material layer 11 measured as described above is in the range of 1 to 15%, it is possible to appropriately bond the metal foil layer and the sealant layer and to wind them after bonding. An exterior material having excellent processability and good moldability can be obtained. From this point of view, the heat shrinkage rate of the base material layer 11 is preferably 1 to 8%.

The base layer 11 preferably has a thermal shrinkage rate of 1 to 5% after heat treatment at 160.degree. As a result, the exterior material can be made more excellent in processability. From this point of view, the heat shrinkage rate is preferably 1 to 4%.

As the polyester resin constituting the polyester film of the base material layer 11, any resin that satisfies the above properties can be used without particular limitation. , copolymerized polyester, and the like. Among these, copolyester can be preferably used from the viewpoint of excellent deep drawability.

As the polyester film, it is possible to use a film obtained by either simultaneous stretching or biaxial stretching. preferable.

Examples of the stretching method for the biaxially stretched film include successive biaxial stretching, tubular biaxial stretching, and simultaneous biaxial stretching. The biaxially stretched film is preferably stretched by a tubular biaxial stretching method and a simultaneous biaxial stretching method from the viewpoint of obtaining better deep drawability.

The thickness of the base material layer 11 is preferably 6-40 μm, more preferably 10-30 μm. When the thickness of the base material layer 11 is 6 μm or more, there is a tendency that the resistance to pinholes and the insulating 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 exterior material 10 for a power storage device increases, 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 substrate layer 11 and arranged between the substrate layer 11 and the adhesive layer 13 . The easy-adhesion treatment layer 12 is a layer for improving the adhesion between the base layer 11 and the adhesion layer 13 , and thus the adhesion between the base layer 11 and the metal foil layer 14 . The easy-adhesion treatment layer 12 may not be provided in the power storage device exterior material 10 . In that case, in order to improve the adhesion between the substrate layer 11 and the adhesion layer 13, and thus to improve the adhesion between the substrate layer 11 and the metal foil layer 14, the adhesion layer of the substrate layer 11 The 13 side surface may be corona treated.

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

<Polyester resin>
From the viewpoint of adhesiveness, the polyester resin is preferably a copolymerized polyester in which a copolymer component is introduced to lower the glass transition temperature. Copolyester is preferably water-soluble or water-dispersible from the viewpoint of coatability. Such a copolyester includes a copolyester to which at least one group selected from the group consisting of sulfonic acid groups or alkali metal bases thereof is bonded (hereinafter referred to as "sulfonic acid group-containing copolyester"). 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 sulfonic acid groups or alkali metal bases thereof is bonded to a part of a dicarboxylic acid component or a glycol component. A copolymer prepared by using an aromatic dicarboxylic acid component containing at least one group selected from the group consisting of sulfonic acid groups and alkali metal bases thereof in a proportion of 2 to 10 mol% of the total acid component 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-naphthalenedicarboxylic 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 a glycol component for producing a sulfonic acid group-containing copolyester, and propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, and bisphenol A added with ethylene oxide. 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 compatibility with polystyrene sulfonate is improved.

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

<Acrylic resin>
Monomer components constituting the acrylic resin include, for example, alkyl acrylates and alkyl methacrylates (as alkyl groups, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2 -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 methoxymethyl methacrylamide 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 ; a monomer containing a carboxyl group such as acrylic acid, methacrylic acid and salts thereof (lithium salt, sodium salt, potassium salt, etc.) or a salt thereof can be used. One of these may be used alone, or two or more thereof may be used for copolymerization. Furthermore, these can be used in combination with other monomers other than the above.

Other monomers include, for example, epoxy group-containing monomers such as allyl glycidyl ether; Monomers containing salts; Monomers containing carboxyl groups or salts thereof, such as crotonic acid, itaconic acid, maleic acid, fumaric acid, and salts thereof (lithium, sodium, potassium, ammonium salts, etc.); maleic anhydride Acids, acid anhydride-containing monomers such as itaconic anhydride; Methacrylonitrile, alkyl itaconic acid monoester, vinylidene chloride, vinyl acetate, vinyl chloride and the like can be used. As the acrylic resin, modified acrylic copolymers such as block copolymers and graft copolymers modified with polyester, urethane, epoxy, etc. may be used.

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

Moreover, the weight average molecular weight of the acrylic resin used in the present 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 deteriorate. In this embodiment, the easy adhesion treatment layer 12 may further contain a resin other than the acrylic resin in order to improve the adhesion between the easy adhesion treatment layer 12 and the substrate layer 11 and the adhesive layer 13 . Examples of such resins include polyester resins and urethane resins.

<Polyurethane resin>
A water-based polyurethane resin is preferable as the polyurethane resin. As the water-based polyurethane resin, a self-emulsifying type is preferable because of its 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. If the Tg is 40° C. or higher, there is a tendency to sufficiently suppress the occurrence of blocking when the coating is wound into a roll after coating. On the other hand, if the Tg is too higher than the drying temperature after coating, it is difficult to form a uniform film, so the Tg is preferably 150° C. or less.

Moreover, in this embodiment, a cross-linking agent may be used together with the water-based polyurethane resin. As a cross-linking agent for water-based polyurethane, a general-purpose water-soluble cross-linking 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, neo Polyepoxy compounds obtained by etherification of 1 mol of glycols such as pentyl glycol and 2 mols of epichlorohydrin, and esters of 1 mol of dicarboxylic acids such as phthalic acid, terephthalic acid, adipic acid and oxalic acid and 2 mols of epichlorohydrin and diepoxy compounds obtained by chemical conversion. However, water-soluble epoxy compounds are not limited to these.

These water-soluble cross-linking agents cross-link with the water-based polyurethane resin, improve the water resistance and solvent resistance of the coating film, and improve the adhesion between the easy-adhesion treatment layer 12 and the base layer 11 and the adhesive layer 13. contribute. In this embodiment, a resin other than urethane resin may be further contained in order to improve the adhesion between the easy-adhesion treatment layer 12 and the substrate layer 11 and adhesive layer 13 . Examples of such resins include polyester resins and acrylic resins.

Further, the easy-adhesion treatment layer 12 may be configured to contain, for example, the above-described resin as a main component and a curing agent such as a polyfunctional isocyanate, a polyfunctional glycidyl compound, or a melamine-based compound. In this way, by including the above-described 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 treatment layer 12 may be configured.

The coating agent used to form the easy-adhesion treatment layer 12 may be solvent-based or water-based. The dispersion type using a water-based main agent has a large molecular weight, improves the intermolecular cohesive force, and is effective for adhesion between the easy-adhesion treatment layer 12 and the substrate layer 11 and the adhesive layer 13 . be.

The thickness of the easy-adhesion treatment layer 12 is preferably 0.02 to 0.5 μm, more preferably 0.04 to 0.3 μm. When the thickness of the easy-adhesion treatment layer 12 is 0.02 μm or more, it is easy to form a uniform easy-adhesion treatment layer 12, and there is a tendency that a more sufficient adhesion-facilitating effect can 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 drawability of the exterior material 10 can be further improved.

(Adhesion layer 13)
The adhesive layer 13 is a layer that bonds the base material layer 11 and the metal foil layer 14 together. The adhesion layer 13 adheres to the base material layer 11 via the easy-adhesion treatment layer 12 . The adhesive layer 13 has adhesive strength necessary for firmly bonding the base material layer 11 and the metal foil layer 14 together, and the metal foil layer 14 is broken by the base material layer 11 during cold molding. It also has followability (performance for reliably forming the adhesive layer 13 on the member without peeling off even if the member is deformed or stretched) for suppressing this.

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

After coating, the polyurethane-based adhesive is aged, for example, at 40° C. for 4 days or more, so that the reaction between the hydroxyl group of the main agent and the isocyanate group of the curing agent proceeds, and the base material layer 11 and the metal foil layer 14 are formed. 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, workability, and the like.

(Metal foil layer 14)
Various metal foils such as aluminum and stainless steel can be used as the metal foil layer 14, and the metal foil layer 14 is preferably an aluminum foil in terms of workability such as moisture resistance and spreadability, and cost. The aluminum foil may be a general soft aluminum foil, but an iron-containing aluminum foil is preferable from the viewpoint of excellent pinhole resistance and spreadability during molding.

In the 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 more excellent pinhole resistance and extensibility. When the iron content is 9.0% by mass or less, it is possible to obtain the exterior material 10 that is more excellent in flexibility.

Further, as the aluminum foil, an annealed soft aluminum foil (for example, an aluminum foil made of JIS 8021 material or 8079 material) is more preferable because it can impart desired ductility during molding.

The metal foil used for the metal foil layer 14 is preferably degreased, for example, 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, a wet-type degreasing treatment or a dry-type degreasing treatment can be used, but from the viewpoint of simplifying the manufacturing process, the dry-type degreasing treatment is preferable.

As the dry type degreasing treatment, for example, there is a method of performing degreasing treatment by lengthening the treatment time in the step of annealing the metal foil. Sufficient electrolytic solution resistance can be obtained even by a degreasing treatment that is performed at the same time as the annealing treatment that is performed to soften the metal foil.

As the dry-type degreasing treatment, flame treatment, corona treatment, and the like, which are treatments other than the annealing treatment, may be used. Furthermore, as the dry type degreasing treatment, for example, a degreasing treatment in which contaminants are oxidatively decomposed and removed by 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, an acid degreasing treatment, an alkaline degreasing treatment, or the like can be used. As the acid used for the acid degreasing treatment, inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid and hydrofluoric acid can be used. These acids may be used individually by 1 type, and may use 2 or more types together. As the alkali used for the alkali degreasing treatment, for example, sodium hydroxide having a high etching effect can be used. 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, an immersion 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, even more preferably 15 to 100 μm, from the viewpoints of barrier properties, pinhole resistance, and workability. preferable. When the thickness of the metal foil layer 14 is 9 μm or more, it becomes difficult to break even if stress is applied during molding. By setting the thickness of the metal foil layer 14 to 200 μm or less, it is possible to reduce the increase in the mass of the exterior material and suppress the reduction in the weight energy density of the power storage device.

(Corrosion prevention treatment layers 15a and 15b)
The corrosion prevention treatment layers 15a and 15b play a role of suppressing corrosion of the metal foil layer 14 by the electrolyte or hydrofluoric acid generated by the reaction between the electrolyte and water. In addition, the corrosion prevention treatment layer 15a plays a role of enhancing adhesion between the metal foil layer 14 and the adhesive layer 13. FIG. In addition, the corrosion prevention treatment layer 15b plays a role of enhancing adhesion between the metal foil layer 14 and the sealant adhesion layer 16. As shown in FIG. The anti-corrosion treatment layer 15a and the anti-corrosion treatment layer 15b may be layers with the same composition or layers with different compositions. Although FIG. 1 shows the case where the corrosion prevention treatment layer is formed on both surfaces of the metal foil layer 14, the corrosion prevention treatment layer may be formed on at least one surface of the metal foil layer 14.

The corrosion prevention treatment layers 15a and 15b are applied, for example, to the base material of the corrosion prevention treatment layers 15a and 15b by degreasing treatment, hydrothermal transformation treatment, anodizing treatment, chemical conversion treatment, and a coating agent having corrosion prevention ability. can be formed by applying a coating type corrosion prevention treatment or a combination of these treatments.

Among the treatments described above, degreasing, hydrothermal denaturation, and anodizing, especially hydrothermal denaturation and anodizing, dissolve the surface of the metal foil (aluminum foil) with a treatment agent, resulting in a highly corrosion-resistant metal compound ( This is a process to form an aluminum compound (boehmite, alumite). Therefore, such a treatment is sometimes included in the definition of chemical conversion treatment in order to obtain a structure forming a co-continuous structure from the metal foil layer 14 to the corrosion prevention treatment layers 15a, 15b.

Examples of the degreasing treatment include acid degreasing and alkaline degreasing. Examples of acid degreasing include a method 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 them. As acid degreasing, an acid degreasing agent obtained by dissolving a fluorine-containing compound such as monosodium ammonium difluoride in the above-mentioned inorganic acid is used, so that not only the degreasing effect of the metal foil layer 14 but also the passive metal fluoride is used. can be formed, which is effective in terms of resistance to hydrofluoric acid. Alkaline degreasing includes a method using sodium hydroxide or the like.

As the hydrothermal transformation treatment, for example, a boehmite treatment obtained by immersing the metal foil layer 14 in boiling water containing triethanolamine can be used. As the anodizing treatment, for example, alumite treatment can be used. 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 transformation treatments, anodizing treatments, and chemical conversion treatments are preferably performed in advance with the above-described degreasing treatment.

The chemical conversion treatment is not limited to the wet method. For example, a method of mixing a treatment agent used for these treatments with a resin component and applying the mixture may be used. As the anti-corrosion treatment, coating-type chromate treatment is preferable from the viewpoint of maximizing the effect and treating the waste liquid.

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

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

In the rare earth element oxide sol, rare earth element oxide fine particles (for example, particles having an average particle size of 100 nm or less) are 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 preferable. Thereby, the adhesion with the metal foil layer 14 can be further improved. Various solvents such as water, alcohol solvents, hydrocarbon solvents, ketone solvents, ester solvents, and ether solvents can be used as the liquid dispersion medium for the rare earth element oxide sol. Among them, water is preferred. The rare earth element oxides contained in the corrosion prevention treatment layers 15a and 15b can be used singly or in combination of two or more.

In order to stabilize the dispersion of the rare earth element oxide particles, the rare earth element oxide sol contains 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. 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. This not only stabilizes the dispersion of the rare earth element oxide particles, but also improves the adhesion between the metal foil layer 14 and the hydrofluoric acid by utilizing the chelating ability of phosphoric acid in the application of the lithium ion battery exterior material. Effects such as imparting electrolyte resistance by trapping metal ions eluted under the influence (passivation formation) and improving the cohesive strength of the rare earth element oxide layer by facilitating dehydration condensation of phosphoric acid even at low temperatures can be expected. Phosphoric acid or a phosphate used as a dispersion stabilizer includes, for example, orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, alkali metal salts and ammonium salts thereof. Among them, condensed phosphoric acids such as trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, and ultrametaphosphoric acid, or alkali metal salts and ammonium salts thereof, are preferable for exhibiting functions as an exterior material for lithium ion batteries. In particular, considering the dry film-forming properties (drying ability, heat quantity) when forming a layer containing a rare earth oxide by various coating methods using a coating composition containing a rare earth element oxide sol, the reactivity at low temperatures is preferred, and sodium salts are preferred from the viewpoint of excellent dehydration condensation properties at low temperatures. As the phosphate, a water-soluble salt is preferred. The phosphoric acid or phosphate contained in the corrosion prevention treatment layers 15a and 15b can be used singly or in combination of two or more.

The mixing amount of phosphoric acid or a salt thereof in the rare earth element oxide sol is preferably 1 part by mass or more, more preferably 5 parts by mass or more with respect to 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 the function as an exterior material for a lithium ion battery is easily satisfied. The upper limit of the amount of phosphoric acid or a salt thereof added to 100 parts by mass of the rare earth element oxide may be within a range that does not cause deterioration in the function of the rare earth element oxide sol. It is preferably 50 parts by mass or less, more preferably 20 parts by mass or less.

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

The anionic polymer includes a polymer having a carboxy group, such as poly(meth)acrylic acid (or a salt thereof) or a copolymer containing 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 (as the alkyl 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, ( silane-containing monomers such as meth)acryloxypropyltriethoxylan; and isocyanate group-containing monomers such as (meth)acryloxypropylisocyanate. In addition, 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 vinylidene, ethylene, propylene, vinyl chloride, vinyl acetate, butadiene, and the like;

The anionic polymer plays a role of 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 capturing ion contamination (especially sodium ions) derived from phosphate contained in the rare earth oxide sol (cation catcher). achieved. In other words, if the corrosion prevention treatment layers 15a and 15b obtained using the rare earth element oxide sol contain alkali metal ions such as sodium or alkaline earth metal ions, the area containing the ions becomes the starting point. Corrosion prevention treatment layers 15a and 15b are likely to deteriorate. Therefore, by fixing the sodium ions and the like contained in the rare earth oxide sol with an anionic polymer, the resistance of the corrosion prevention treatment layers 15a and 15b is improved.

The anti-corrosion treatment layers 15a, 15b combined with the anionic polymer and the rare earth element oxide sol have the same anti-corrosion performance as the anti-corrosion treatment layers 15a, 15b formed by subjecting the metal foil layer 14 to chromate treatment. The anionic polymer is preferably a crosslinked structure of a polyanionic polymer that is essentially water-soluble. Examples of cross-linking agents used for forming the structure include compounds having isocyanate groups, glycidyl groups, carboxy groups, and oxazoline groups. Furthermore, it is also possible to introduce a cross-linking site having a siloxane bond using a silane coupling agent.

Examples of compounds having an isocyanate group include diisocyanates such as tolylene diisocyanate, xylylene diisocyanate or hydrogenated products thereof, hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate or its hydrogenated products, and isophorone diisocyanate. or polyhydric compounds such as adducts obtained by reacting these isocyanates with polyhydric alcohols such as trimethylolpropane, biurets obtained by reacting them with water, or isocyanurates which are trimers. isocyanates; or block polyisocyanates obtained by blocking these polyisocyanates with alcohols, lactams, oximes and the like.

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 with glycols such as neopentyl glycol and epichlorohydrin, polyhydric alcohols such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol and sorbitol with epichlorohydrin Epoxy compounds, epoxy compounds obtained by reacting dicarboxylic acids such as epoxy compounds, phthalic acid, terephthalic acid, oxalic acid and adipic acid with epichlorohydrin, and the like.

Examples of compounds having a carboxy group include various aliphatic or aromatic dicarboxylic acids, and poly(meth)acrylic acid and alkali (earth) metal salts of poly(meth)acrylic acid can also be used. be.

As the compound having an oxazoline group, for example, when using a low-molecular compound having two or more oxazoline units, or a polymerizable monomer such as isopropenyloxazoline, (meth)acrylic acid, (meth)acrylic acid alkyl ester , hydroxyalkyl (meth)acrylates and other acrylic monomers are copolymerized.

Silane coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl)-γ-aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, especially the anionic Epoxysilane, aminosilane, and isocyanate silane are preferred in consideration of reactivity with the curable polymer.

The amount of the cross-linking agent is preferably 1 to 50 parts by mass, more preferably 10 to 20 parts by mass, per 100 parts by mass of the anionic polymer. When the ratio of the cross-linking agent is 1 part by mass or more with respect to 100 parts by mass of the anionic polymer, the cross-linked structure is sufficiently easily formed. If the ratio of the cross-linking 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 is improved.

The method for cross-linking the anionic polymer is not limited to the above-described cross-linking agent, and may be a method of forming ionic cross-links using a titanium or zirconium compound. Moreover, these materials may be applied with a coating composition that forms the corrosion prevention treatment layer 15a.

In the corrosion prevention treatment layers 15a and 15b described above, the corrosion prevention treatment layers 15a and 15b by chemical conversion treatment represented by chromate treatment form a sloped structure with the metal foil layer 14. The metal foil layer 14 is treated with 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 chemical conversion treatment uses an acid as a chemical conversion treatment agent, the working environment deteriorates and the coating equipment is corroded.

On the other hand, the coating-type corrosion prevention treatment layers 15a and 15b do not need to form an inclined structure on the metal foil layer 14, unlike the chemical conversion treatment represented by chromate treatment. Therefore, the properties of the coating agent are not subject to restrictions such as acidity, alkalinity, neutrality, etc., and a good working environment can be realized. In addition, the coating-type corrosion prevention treatment layers 15a and 15b are preferable from the point that alternatives to the chromate treatment using a chromium compound are required from the standpoint of environmental hygiene.

The corrosion prevention treatment layers 15a and 15b may have a laminated structure in which a cationic polymer is further laminated as necessary. Examples of cationic polymers include polyethyleneimine, ionic polymer complexes composed of polyethyleneimine and a polymer having a carboxylic acid, primary amine-grafted acrylic resins in which primary amines are grafted onto the main acrylic skeleton, polyallylamine, or derivatives thereof. , aminophenol resin and the like.

Examples of the "polymer having a carboxylic acid" that forms an ionic polymer complex include polycarboxylic acids (salts), copolymers obtained by introducing comonomers into polycarboxylic acids (salts), polysaccharides having a carboxy group, and the like. be done. Polycarboxylic acid (salt) includes, for example, polyacrylic acid or its ion salt. Polysaccharides having a carboxy group include, for example, carboxymethyl cellulose and ionic salts thereof. Examples of ionic salts include alkali metal salts and alkaline earth metal salts.

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

As polyallylamine or its derivatives, homopolymers or copolymers such as allylamine, allylamineamide sulfate, diallylamine, and dimethylallylamine can be used. Stabilized products can also be used. Further, 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 singly or in combination of two or more. As the cationic polymer, among the above, at least one selected from the group consisting of polyallylamine and derivatives thereof is preferable.

The cationic polymer is preferably used in combination with a cross-linking agent having a functional group capable of reacting with an amine/imine such as a carboxy group or glycidyl group. As a cross-linking 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. and polysaccharides having a carboxy group such as carboxymethyl cellulose or an ion salt thereof.

In the present embodiment, the cationic polymer is also described as one component constituting the corrosion prevention treatment layers 15a and 15b. The reason for this is that as a result of intensive studies using various compounds to provide the electrolyte resistance and hydrofluoric acid resistance required for exterior materials for lithium-ion batteries, it was 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 the metal foil layer 14 is prevented from being damaged by capturing fluorine ions with cationic groups (anion catcher). Cationic polymers are also very preferable in terms of improving the adhesion between the corrosion prevention treatment layer 15b and the sealant adhesion layer 16 . In addition, 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-described crosslinking agent. Thus, since a crosslinked structure can be formed even by 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 can be used as a protective layer. Cationic polymers may be used instead.

From the above contents, as examples of combination of the coating type corrosion prevention treatments described above, (1) rare earth oxide sol only, (2) anionic polymer only, (3) cationic polymer only, (4) rare earth oxide 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 ( multilayer), (7) (rare earth oxide sol + cationic polymer: lamination and composite)/anionic polymer (multilayer), and the like. Among them, (1) and (4) to (7) are preferred, and (4) to (7) are more preferred. 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 realized with a single 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 can be more easily maintained. However, this embodiment is not limited to the above combinations. For example, as an example of the selection of corrosion prevention treatment, the cationic polymer is a very preferable material in that it has good adhesion to the modified polyolefin resin mentioned in the explanation of the sealant adhesion layer 16, which will be described later. When the layer 16 is composed of a modified polyolefin resin, a design is possible in which a cationic polymer is provided on the surface in contact with the sealant adhesive layer 16 (for example, configurations (5) and (6)).

However, the corrosion prevention treatment layers 15a and 15b are not limited to the layers described above. For example, like coating type chromate, which is a known technique, it may be formed using a resin binder (aminophenol resin or the like) mixed with phosphoric acid and a chromium compound. By using the treating agent, it becomes possible to form a layer having both corrosion prevention function and adhesion. In addition, in order to improve adhesion to the above-described chemical conversion treatment layer (a layer formed by degreasing treatment, hydrothermal transformation treatment, anodizing treatment, chemical conversion treatment, or a combination of these treatments), the above-described cationic It is also possible to apply multiple treatments using polymers and/or anionic polymers, or to laminate cationic polymers and/or anionic polymers as multilayer structures to combinations of these treatments. In addition, although it is necessary to consider the stability of the coating liquid, it is necessary to use a coating agent obtained by preliminarily combining the rare earth oxide sol and the cationic polymer or anionic polymer described above into a single component to prevent corrosion. It is possible to form a layer having both adhesiveness and adhesiveness.

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, the metal foil layer 14 can easily be provided with a corrosion prevention function. Moreover, 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 becomes insufficient, which may lead to a decrease in cohesive force. In the above description, the mass per unit area is used, but if the specific gravity is known, the thickness can be converted from the specific gravity.

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 adhesion 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 is broadly classified into a heat lamination structure and a dry lamination structure depending on the adhesive component forming the sealant adhesive layer 16 .

The adhesive component forming the sealant adhesive layer 16 in the thermal laminate 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 nonpolar polyolefin resin, the sealant layer 17 when it is composed of a nonpolar polyolefin resin film or the like has polarity. It can firmly adhere to both of the corrosion prevention treatment layers 15b, which are often used. In addition, by using an acid-modified polyolefin resin, the resistance to contents such as electrolyte solution of the exterior material 10 is improved, and even if hydrofluoric acid is generated inside the battery, the sealant adhesive layer 16 deteriorates, resulting in a decrease in adhesion. easy to prevent.

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

The heat-laminated sealant adhesive layer 16 can be formed by extruding the above adhesive component with an extrusion device. Preferably, the thickness of the sealant adhesive layer 16 in the thermal lamination configuration is between 2 and 50 μm.

As an adhesive component forming the sealant adhesive layer 16 having a dry laminate structure, for example, the same adhesives as those mentioned for the adhesive layer 13 can be used. In this case, in order to suppress swelling due to the electrolytic solution and hydrolysis due to hydrofluoric acid, it is possible to design the composition of the adhesive so that it has a main component with a structure that is difficult to hydrolyze and that can improve the crosslink density. preferable.

To improve the crosslink density, for example, dimer fatty acid, ester or hydrogenated product of dimer fatty acid, reduced glycol of dimer fatty acid, ester of dimer fatty acid or reduced glycol of hydrogenated product may be added to the adhesive. The dimer fatty acid is an acid obtained by dimerizing various unsaturated fatty acids, and examples of its structure include acyclic, monocyclic, polycyclic and aromatic ring types.

The fatty acid that is the starting material for the dimer fatty acid is not particularly limited. Moreover, 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 base material constituting the sealant adhesive layer 16, for example, an isocyanate compound that can also be used as a chain extender for polyester polyol can be used. As a result, the crosslink density of the adhesive coating increases, leading to improved solubility and swelling properties, and an increase in the concentration of urethane groups is expected to improve adhesiveness to substrates.

The sealant adhesive layer 16 having a dry laminate structure has a highly hydrolyzable bond such as an ester group and a urethane group. It is preferred to use an adhesive component of For example, an acid-modified polyolefin resin is dissolved or dispersed in a solvent such as toluene or methylcyclohexane (MCH), and the various curing agents described above are added to the coating liquid, which is then applied and dried to form the sealant adhesive layer 16. 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 compounded in the sealant adhesive layer 16, for example, an olefin-based elastomer, a styrene-based elastomer, or the like 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 can improve the effect of alleviating the anisotropy of the sealant adhesive layer 16 . Specifically, the average particle diameter of the elastomer is preferably 200 nm or less, for example.

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

When the elastomer is blended in 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. By setting the blending amount of the elastomer to 1% by mass or more, there is a tendency that the compatibility with the adhesive resin is improved and the effect of alleviating the anisotropy of the sealant adhesive layer 16 is improved. In addition, by setting the blending amount of the elastomer to 25% by mass or less, there is a tendency that the effect of suppressing the swelling of the sealant adhesion layer 16 due to the electrolytic solution is 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 thermal lamination. When the thickness of the sealant adhesive layer 16 is 2 μm or more, sufficient adhesive strength between the metal foil layer 14 and the sealant layer 17 can be easily obtained. It is possible to make it easier to reduce the amount of water that permeates. 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 imparts sealing properties to the exterior material 10 by means of heat sealing, and is a layer that is heat-sealed and arranged inside when the power storage device is assembled. As the sealant layer 17, a resin film made of a polyolefin resin or an acid-modified polyolefin resin obtained by graft-modifying an acid such as maleic anhydride to a polyolefin resin can be used. Among them, polyolefin-based resins are preferable because they can improve water vapor barrier properties and form a power storage device without being excessively crushed by heat sealing, and polypropylene is particularly preferable.

Polyolefin resins include, for example, low-density, medium-density and high-density polyethylene; ethylene-α-olefin copolymers; polypropylene; and propylene-α-olefin copolymers. When the polyolefin resin is a copolymer, it may be a block copolymer or a random copolymer. These polyolefin-based resins may be used alone or in combination of two or more.

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

As the acid-modified polyolefin resin, for example, the same resins as those mentioned for the sealant adhesive layer 16 can be used.

The sealant layer 17 may be a single-layer film or a multi-layer film, and may be selected according to the required functions. For example, from the viewpoint of imparting moisture resistance, a multi-layer film in which a resin such as an ethylene-cyclic olefin copolymer and polymethylpentene is interposed can be used.

The sealant layer 17 may also contain various additives such as flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers and tackifiers.

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 blended into the heat-fusible film. Thereby, whitening of the sealant layer 17 can be suppressed when the power storage device exterior material 10 is cold-molded to form the concave portion.

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

In addition, a lubricant may be contained in order to impart lubricity to the sealant layer 17 . In this way, since the sealant layer 17 contains a lubricant, when forming recesses in the power storage device exterior material 10 by cold molding, the sides or corners of the recesses having a high elongation rate in the power storage device exterior material 10 can be formed. It becomes possible to suppress that the portion that is to be stretched more than necessary. As a result, separation between the metal foil layer 14 and the sealant adhesive layer 16 and breakage and whitening due to cracks between the sealant layer 17 and the sealant adhesive layer 16 can be suppressed.

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

The thickness of the sealant layer 17 is preferably 10-100 μm, more preferably 20-60 μm. When the thickness of the sealant layer 17 is 10 μm or more, a sufficient heat-sealing strength can be obtained, and when it is 100 μm or less, the amount of water vapor entering from the ends 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 the power storage device including the exterior material 10 as a container may be placed on the device via the acrylic PSA tape, the surface of the exterior material 10 (that is, the surface on the base layer 11 side) is in good contact with the tape. preferably. The acrylic PSA tape is obtained by laminating an acrylic pressure-sensitive adhesive layer on a substrate such as a PET film. Examples of acrylic pressure-sensitive adhesives include those containing an acrylic copolymer having a hydroxyl group as a main component and an isocyanate-based 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.

Monomer components constituting the acrylic resin include, for example, alkyl acrylates and alkyl methacrylates (as alkyl groups, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2 -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 methoxymethyl methacrylamide 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 ; a monomer containing a carboxyl group such as acrylic acid, methacrylic acid and salts thereof (lithium salt, sodium salt, potassium salt, etc.) or a salt thereof can be used. One of these may be used alone, or two or more thereof may be used for copolymerization. Furthermore, these can be used in combination with other monomers other than the above.

Other monomers include, for example, epoxy group-containing monomers such as allyl glycidyl ether; Monomers containing salts; Monomers containing carboxyl groups or salts thereof, such as crotonic acid, itaconic acid, maleic acid, fumaric acid, and salts thereof (lithium, sodium, potassium, ammonium salts, etc.); maleic anhydride Acids, acid anhydride-containing monomers such as itaconic anhydride; Methacrylonitrile, alkyl itaconic acid monoester, vinylidene chloride, vinyl acetate, vinyl chloride and the like can be used. 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, it is preferable to use a copolymerized polyester in which a copolymerization component is introduced to lower the glass transition temperature. Copolyester is preferably water-soluble or water-dispersible from the viewpoint of coatability. Such a copolyester includes a copolyester to which at least one group selected from the group consisting of sulfonic acid groups or alkali metal bases thereof is bonded (hereinafter referred to as "sulfonic acid group-containing copolyester"). 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 sulfonic acid groups or alkali metal bases thereof is bonded to a part of a dicarboxylic acid component or a glycol component. A copolymer prepared by using an aromatic dicarboxylic acid component containing at least one group selected from the group consisting of sulfonic acid groups and alkali metal bases thereof in a proportion of 2 to 10 mol% of the total acid component 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-naphthalenedicarboxylic 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 a glycol component for producing a sulfonic acid group-containing copolyester, and propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, and bisphenol A added with ethylene oxide. 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 compatibility with polystyrene sulfonate is improved.

The acrylic resin and polyester resin may be used alone or in combination of two or more. Further, these resins may be used in combination with curing agents exemplified below.

The curing agent is not particularly limited, and 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 higher isocyanate compound having no aromatic ring. Since it does not have an aromatic ring, quinoid formation of the benzene ring by ultraviolet rays does not occur, and yellowing can be suppressed. Therefore, it is suitable for the outermost layer such as a coating layer. 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, and isophorone diisocyanate. , 4,4′-dicyclohexylmethane diisocyanate, isopropylidene dicyclohexyl-4,4′-diisocyanate, and the like.

Among these, 1,6-hexamethylene diisocyanate and isophorone diisocyanate are preferable as the aliphatic isocyanate curing agent because they improve the electrolyte resistance. In particular, 1,6-hexamethylene diisocyanate is preferable from the viewpoint of improving the self-healing performance of the curing agent and having excellent reactivity between the isocyanate group of the curing agent and the hydroxyl groups of the acrylic resin and the polyester resin. This also makes it possible to obtain excellent suitability for mass production.

Further, by using an isocyanate adduct, buret or isocyanurate as a curing agent, the crosslink 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 0.05-3 μm. When the thickness of the coating layer 18 is 0.05 μm or more, it is easy to obtain sufficient adhesion to the acrylic PSA tape. becomes easier to suppress.

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

As a method for manufacturing the exterior material 10, for example, there is a method including the following steps S11 to S14.
Step S<b>11 : A step of forming a corrosion prevention treatment layer 15 a on one surface of the metal foil layer 14 and forming a corrosion prevention treatment layer 15 b on the other surface of the metal foil layer 14 .
Step S12: A step of forming an easy-adhesion treatment layer 12 on one surface of the base material layer 11 to obtain a laminate. Step S<b>13 : A step of bonding the surface of the corrosion prevention treatment layer 15 a opposite to the metal foil layer 14 and the surface of the laminate on the easy adhesion treatment layer 12 side via the adhesive layer 13 .
Step S14: A step of forming a sealant layer 17 on the surface of the corrosion prevention treatment layer 15b opposite to the metal foil layer 14 with the sealant adhesive layer 16 interposed therebetween.
Step S15: A step of forming a coating layer 18 on the surface of the substrate layer 11 opposite to the easy-adhesion treatment 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 . The corrosion prevention treatment layers 15a and 15b may be formed separately, respectively, 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 surfaces of the metal foil layer 14, and then drying, curing, and baking are sequentially performed to form the corrosion prevention treatment layer. 15a and 15b are formed at once. Also, a corrosion-inhibiting treatment agent is applied to one surface of the metal foil layer 14, followed by drying, curing, and baking in order to form the corrosion-inhibiting treatment layer 15a. A corrosion prevention treatment layer 15b may be formed. The order of forming the corrosion prevention treatment layers 15a and 15b is not particularly limited. In addition, different anti-corrosion treatment agents may be used for the anti-corrosion treatment layer 15a and the anti-corrosion treatment layer 15b, or the same anti-corrosion treatment agent may be used. As the anti-corrosion agent, for example, an anti-corrosion agent for coating type chromate treatment can be used. The method of applying the anti-corrosion treatment agent is not particularly limited, but examples include gravure coating, gravure reverse coating, roll coating, reverse roll coating, die coating, bar coating, kiss coating, comma coating, and the like. can be used. As the metal foil layer 14, an untreated metal foil layer may be used, or a metal foil layer degreased by wet type degreasing or dry type degreasing may be used.

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

Then, the orientation of the thermoplastic resin film is completed by heat treatment, thereby obtaining a laminate having the easy-adhesion treatment layer 12 formed on one surface of the substrate layer 11 . By forming the easy-adhesion treatment layer 12 using such an in-line coating method, the adhesion between the substrate layer 11 and the easy-adhesion treatment layer 12 is improved. In addition, any method may be used for the formation method of the easy-adhesion process layer 12, without being limited to the said method. Moreover, the timing of forming the easy-adhesion treatment layer 12 is not limited to the present 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 easy adhesion treatment layer 12 side are dry-laminated using an adhesive that forms the adhesion layer 13. can be pasted together by other methods. In step S13, aging (curing) treatment may be performed at room temperature to 100° C. in order to promote adhesion. Aging time is, for example, 1 to 10 days.

(Step S14)
After step S13, the substrate layer 11, the easy-adhesion treatment layer 12, the adhesion layer 13, the corrosion prevention treatment layer 15a, the metal foil layer 14, and the corrosion prevention treatment layer 15b of the laminate in which the corrosion prevention treatment layer 15b is 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, or the like, or may be laminated together with the sealant adhesive layer 16 by a coextrusion method. From the viewpoint of improving adhesiveness, the sealant layer 17 is preferably laminated by, for example, sandwich lamination, or laminated together with the sealant adhesive layer 16 by a coextrusion method, and more preferably laminated by sandwich lamination.

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

The exterior material 10 is obtained by the steps S11 to S15 described above. Note that the order of steps in the method for manufacturing the exterior material 10 is not limited to the method of sequentially performing the 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 having 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 holding the lead 2 and accommodating the battery element 1. The sealant layer 17 is formed inside. The container may be obtained by stacking two exterior materials with the sealant layers 17 facing each other and heat-sealing the peripheral edges of the stacked exterior materials 10, or by folding one exterior material. It may be obtained by superimposing and similarly heat-sealing the periphery of the exterior material 10 . Moreover, 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-hydrogen batteries, and lead-acid 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 leads 2 may be sandwiched by the exterior material 10 via a tab sealant.

[Method for manufacturing power storage device]
Next, a method for manufacturing a power storage device using the exterior material 10 described above will be described. Here, the case of manufacturing the secondary battery 40 using the embossed type packaging material 30 will be described as an example. 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 steps of manufacturing a single-sided molded battery using the exterior material 10. FIG. The secondary battery 40 is a double-side molded battery manufactured by providing two exterior materials such as the embossed exterior material 30 and bonding such exterior materials together while adjusting the alignment. good too. Also, the embossed type exterior material 30 may be formed using the exterior material 20 .

The secondary battery 40, which is a single-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 electrodes, and the leads 2 extending from the electrodes.
Step S22: A step of forming a concave portion 32 for arranging the battery element 1 on one side of the packaging material 10 (see FIGS. 3(a) and 3(b)).
Step S23: The battery element 1 is placed in the molding area (recess 32) of the embossed exterior material 30, the embossed exterior material 30 is folded back so that the lid 34 covers the recess 32, and extends from the battery element 1. A step of pressurizing and heat-sealing one side of the embossed type packaging material 30 so as to sandwich the lead 2 (see FIGS. 3(b) and 3(c)).
Step S24: Leave one side other than the side where the lead 2 is sandwiched, press and heat-seal the other sides, then inject the electrolytic solution from the remaining side, and pressure-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 sandwiching the leads 2 and bending them toward the molding processing area (recess 32) (see FIG. 3(d)).

(Step S21)
In step S21, an exterior material 10, a battery element 1 including electrodes, and leads 2 extending from the electrodes are prepared. The exterior material 10 is prepared based on the embodiment described above. The battery element 1 and leads 2 are not particularly limited, and known battery elements 1 and leads 2 can be used.

(Step S22)
In step S<b>22 , recesses 32 for arranging battery elements 1 are formed on the sealant layer 17 side of exterior material 10 . The planar shape of the concave portion 32 is a shape that matches the shape of the battery element 1, for example, a rectangular shape in plan view. The concave portion 32 is formed by pressing a pressing member having, for example, a rectangular pressure surface against a portion of the exterior material 10 in its thickness direction. Further, the position to be pressed, that is, the recess 32 is formed at a position biased toward one end of the exterior material 10 in the longitudinal direction from the center of the exterior material 10 cut into a rectangular shape. As a result, after the molding process, the other end side where the concave portion 32 is not formed can be folded back to form a lid (lid portion 34).

A more specific method of forming the recess 32 is molding using a mold (deep drawing molding). As a molding method, a female mold and a male mold arranged to have a gap larger than the thickness of the exterior material 10 are used, and the male mold is pushed into the female mold together with the exterior material 10 . is mentioned. By adjusting the pushing amount of the male mold, the depth (deep drawing amount) of the concave portion 32 can be adjusted to a desired amount. The embossed type exterior material 30 is obtained by forming the concave portions 32 in the exterior material 10 . 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 along the bb line of the embossed type exterior material 30 shown in FIG. 2(a). It is a diagram.

(Step S23)
In step S<b>23 , the battery element 1 composed of a positive electrode, a separator, a negative electrode, and the like is placed in the molding processing area (concave portion 32 ) of the embossed 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 processing area (recess 32). After that, the embossed type exterior material 30 is folded back at approximately the center in the longitudinal direction, stacked so that the sealant layers 17 face each other inside, and one side of the embossed type exterior material 30 sandwiching the lead 2 is pressurized and heat-sealed. be. The pressurized heat fusion is controlled by three conditions of temperature, pressure and time, which are appropriately set. The temperature of the pressurized heat fusion is preferably higher than the temperature at which the sealant layer 17 is melted.

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 equal to or more than the above lower limit, there is a tendency that the heat-sealing resin can sufficiently fill the ends of the leads 2. The thickness of the end portion can be suppressed appropriately, and the amount of moisture entering from the end portion of the exterior material 10 can be reduced.

(Step S24)
In step S24, one side other than the side where the leads 2 are sandwiched is left, and the other sides are pressurized and heat-sealed. After that, an electrolytic solution is injected from the remaining one side, and the remaining one side is pressurized and heat-sealed in a vacuum state. The conditions for pressure heat fusion are the same as in step S23.

(Step S25)
The peripheral pressurized and heat-sealed edges other than the edges sandwiching the lead 2 are cut, and the sealant layer 17 protruding from the edges is removed. After that, the peripheral pressurized heat-sealed portion is folded back toward the molding processing area 32 to form the folded portion 42, whereby the secondary battery 40 is obtained.

Although preferred embodiments of the exterior material for a power storage device and the method for manufacturing a power storage device according to the present invention have been described 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 spirit of the invention as described.

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

(Preparation of base material layer)
As the substrate layer 11, a polyester film having the properties shown in Table 1 (each thickness: 25 μm) was prepared. In Table 1, the stress value at 50% elongation and thermal shrinkage were measured as follows.
Stress value at 50% elongation (F50 stress value): Each polyester film cut into A4 size was heated in an oven maintained at an arbitrary heat treatment temperature within the range of 160 to 200°C for 30 minutes. After that, a tensile test (specimen 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). By averaging the measurement results in four directions, the stress value at 50% elongation was calculated.
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. After that, the lengths of the polyester film in four directions (0° (MD), 45°, 90° (TD), 135°) at 23°C were 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.
Thermal 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)
A soft aluminum foil 8079 material (manufactured by Toyo Aluminum Co., Ltd.) having a thickness of 40 μm was prepared as the metal foil layer 14 . Then, a sodium polyphosphate-stabilized cerium oxide sol (corrosion prevention treatment agent) adjusted to a solid content concentration of 10% by mass using distilled water as a solvent was applied to both surfaces of the metal foil layer 14 by gravure coating. At this time, 10 parts by mass of phosphoric acid was added to 100 parts by mass of cerium oxide.

Next, after drying the applied sodium polyphosphate-stabilized cerium oxide sol, baking treatment is sequentially performed to form a corrosion prevention treatment layer 15a on one surface of the metal foil layer 14, and a corrosion prevention treatment layer 15a on the other surface. 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 substrate layer 11, and one side of the substrate layer 11 was subjected to corona treatment.

Next, a polyurethane-based adhesive was applied as the adhesive layer 13 to the surface of the corrosion prevention treatment layer 15 a of the metal foil layer 14 opposite to the metal foil layer 14 . Then, the metal foil layer 14 and the corona-treated surface of the substrate layer 11 were adhered via the adhesive layer 13 by a dry lamination method. After that, the structure composed of the substrate 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, thereby 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 serves as the base material of the sealant adhesive layer 16 . At this time, the thickness of the sealant adhesive layer 16 was set to 15 μm. Then, by a sandwich lamination method using a heat lamination device, a polyolefin film having a thickness of 30 μm (a non-oriented polypropylene film on the side of the sealant adhesion layer 16 of a non-stretched polypropylene film) is applied to the corrosion prevention treatment layer 15b via the sealant adhesion layer 16 to form the sealant layer 17. A film whose surface was corona-treated) was laminated at 160° C. (heat-press bonded). By winding this, a roll-shaped exterior material 10 for a power storage device was produced.

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

(Example 3)
Exterior material 10 for a power storage device was produced in the same manner as in Example 1, except that instead of subjecting one side of base layer 11 to corona treatment, easy-adhesion treatment layer 12 was formed on the surface of base layer 11 on the adhesive layer 13 side. was made. The easy-adhesion treatment layer 12 uses an in-line coating method to coat one side of the base material layer 11 with a coating agent that is the base material of the easy-adhesion treatment layer 12 prepared as follows and has a solid content of 0.1 g/m ^{2 .} It was formed by coating and drying. The easy-adhesion treatment layer 12 had a thickness of about 0.1 μm.
(Preparation of coating agent for forming easy-adhesion layer)
As a coating agent for forming an easy-adhesion treatment layer, a coating agent having the following composition was prepared.
Coating agent: Water-soluble polyester "Aron Melt PES-1000" manufactured by Toagosei Co., Ltd., self-emulsifying polyisocyanate "Aquanate 100" manufactured by Nihon Polyurethane Industry Co., Ltd. and spherical silica manufactured by Nippon Shokubai Chemical Industry Co., Ltd. Fine particles "Seahoster KE-P30" (average particle size 0.3 μm) were added at a compounding 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 the sodium polyphosphate-stabilized cerium oxide sol, chromate treatment was performed to form the corrosion prevention treatment layers 15a and 15b. An exterior material 10 for a power storage device was produced. The chromate treatment was carried out by coating both surfaces of the metal foil layer 14 with a treatment liquid comprising a phenolic resin, a chromium fluoride compound, and phosphoric acid to form a film, followed by baking.

(Examples 5-8, Comparative Examples 7-12)
A resin composition obtained by blending a polyester polyol with an isocyanurate of IPDI as a curing agent is applied onto the substrate layer 11 and cured by heating to form a polyester-based resin having a thickness of 1.0 μm on the substrate layer 11. Exterior materials 10 for power storage devices were 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 9-12, Comparative Examples 13-18)
A resin composition obtained by mixing an acrylic polyol with an adduct of HDI as a curing agent is applied onto the substrate layer 11 and cured by heating to form an acrylic resin having a thickness of 1.0 μm on the substrate layer 11. Exterior materials 10 for power storage devices were 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 and 2)
Exterior materials 10 for power storage devices were 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 suitability for processing>
The sealant layer 17 was adhered to the corrosion prevention treatment layer 15b via the sealant adhesive layer 16 by a sandwich lamination method using a thermal lamination apparatus, and the workability when winding this was evaluated according to the following criteria.
A: Both lamination and winding were performed well.
B: Lamination or winding could not be performed satisfactorily.
C: Both lamination and winding could not be performed satisfactorily.

<Evaluation of molding depth>
For the exterior material 10 for a power storage device produced in each example and comparative example, the molding depth that allows deep drawing molding was evaluated by the following method. First, the power storage device exterior material 10 was placed in a molding apparatus so that the sealant layer 17 faced upward. The molding depth of the molding apparatus was set to 6.0 mm or 6.5 mm, and cold molding was performed under an environment of room temperature of 23°C and dew point temperature of -35°C. The punch die 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. A die having a die radius (RD) of 1.00 mm on the upper surface of the opening was used. The presence or absence of breakage and pinholes in the cold-formed portion was visually confirmed while irradiating the exterior material 10 with light, and the maximum value of the forming depth (forming limit) was evaluated according to the following criteria. Table 2 shows the results.
A: Neither fracture nor pinhole occurred at a molding depth of 6.5 mm.
B: Breakage or pinholes occurred at a molding depth of 6.5 mm, but neither breakage nor pinholes occurred at a molding depth of 6.0 mm.
C: Fracture or pinhole occurred at 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 by the following method for the power storage device exterior material 10 produced in each of the examples and the comparative examples. First, the power storage device exterior material 10 was placed in a molding apparatus so that the sealant layer 17 faced upward. The molding depth of the molding apparatus was set to 5 mm, and cold molding was performed under an environment of room temperature of 23°C and dew point temperature of -35°C. The punch die 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. A die having a die radius (RD) of 1.00 mm on the upper surface of the opening was used.

Next, the cold-molded exterior material 10 was placed in a 100-mL beaker containing 30 mL of a 1 M lithium hexafluorophosphate solution (solvent volume ratio=ethyl carbonate:dimethyl carbonate:dimethyl carbonate=1:1:1). . Next, the beaker containing the packaging material 10 was enclosed in a 18-liter can and placed in a temperature environment of 40° C. for 2 hours, thereby exposing the packaging material 10 to the electrolytic solution. After that, the outer packaging material 10 was taken out from the beaker in the 18-liter can and placed in an oven at 110°C, in an environment with a temperature of 60°C and a humidity of 95%, or in warm water of 50°C. After that, the presence or absence of peeling between the base material layer 11 and the metal foil layer 14 of the exterior material 10 is visually checked, and peeling between the base material layer 11 and the metal foil layer 14 is confirmed. The maximum value (unit: weeks) of the period during which there was no Based on the results, the adhesion between the substrate layer 11 and the metal foil layer 14 was evaluated according to the following evaluation criteria. Table 2 shows the results.
A: No peeling was observed even after 4 weeks.
B: Peeling was confirmed after 4 weeks.

<PSA tape adhesion>
The adhesion between the base material layer 11 (or the coating layer 18) and the acrylic PSA tape was evaluated by the following method for the power storage device exterior material 10 produced in each example and comparative example. First, the power storage device exterior material 10 was attached to the support so that the substrate layer 11 (or the coating layer 18 ) side faced upward. Next, an acrylic PSA tape and a support aluminum foil for a peel test were attached to the substrate layer 11 (or the coating layer 18) with a force of about 20N. After allowing this to stand still for about 1 hour, the peel strength (180-degree peel, peel speed: 50 mm/min) between the base layer 11 (or coating layer 18) and the acrylic PSA tape was measured and measured according to the following evaluation criteria: made an evaluation. Table 2 shows the results.
◯: The peel strength was 10 N/15 mm or more.
x: The 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 processability during fabrication and deep drawability after fabrication.

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

Claims (10)

Having a structure in which at least a substrate layer, an adhesive layer, a metal foil layer, a sealant adhesive layer and a sealant layer are laminated in this order,
The base layer has a thickness of 6 to 40 μm, the metal foil layer has a thickness of 9 to 200 μm, the sealant layer has a thickness of 10 to 100 μm,
The metal foil layer is an aluminum foil,
The base material layer has a stress value at 50% elongation of 100 to 180 MPa after heat treatment at 160 to 200°C, a heat shrinkage rate of 1 to 15% after heat treatment at 160 to 200°C, and 200°C. An exterior material for a power storage device, comprising a biaxially stretched polyester film having a heat shrinkage of 7.8% or more after heat treatment at .
Stress value at 50% elongation: Tensile test for four directions (0° (MD), 45°, 90° (TD), 135°) of the base layer (specimen shape: No. 5 type specified in JIS K7127 dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min, temperature: 23° C.).
Thermal shrinkage rate: An average value of shrinkage rates before and after heat treatment in four directions (0° (MD), 45°, 90° (TD), and 135°) of the base material layer. 2. The exterior material for a power storage device according to claim 1, wherein said polyester film has a thermal shrinkage of 1 to 5% after heat treatment at 160.degree. 3. The exterior material for a power storage device according to claim 1, further comprising an easy-adhesion treatment layer provided between said base material layer and said adhesive layer. 4. The power storage device according to claim 3, wherein said easy-adhesion treatment layer is a layer containing at least one resin selected from the group consisting of polyester resins, acrylic resins, polyurethane resins, epoxy resins, and acrylic-grafted polyester resins. Exterior material. 5. The exterior material for a power storage device according to claim 1, further comprising anti-corrosion treatment layers provided on both sides of said metal foil layer. 6. The exterior material for a power storage device according to claim 5, wherein said corrosion prevention treatment layer contains a rare earth element oxide and phosphoric acid or a phosphate. 7. The exterior material for a power storage device according to claim 1, having a structure in which a coating layer is further laminated on the base material layer. 8. The exterior material for a power storage device according to claim 7, wherein said coating layer is a layer containing at least one resin selected from the group consisting of an acrylic resin and a polyester resin. 9. The exterior material for a power storage device according to claim 7, wherein said coating layer has a thickness of 0.05 to 3 μm. a step of bonding a substrate layer to one surface of a metal foil layer via an adhesive layer; and forming a sealant layer via a sealant adhesive layer on the surface of the metal foil layer opposite to the adhesive layer. process, comprising
The base layer has a thickness of 6 to 40 μm, the metal foil layer has a thickness of 9 to 200 μm, the sealant layer has a thickness of 10 to 100 μm,
The metal foil layer is an aluminum foil,
The base material layer has a stress value at 50% elongation of 100 to 180 MPa after heat treatment at 160 to 200°C, a heat shrinkage rate of 1 to 15% after heat treatment at 160 to 200°C, and 200°C. A method for producing an exterior material for a power storage device, comprising a biaxially stretched polyester film having a heat shrinkage of 7.8% or more after heat treatment in .
Stress value at 50% elongation: Tensile test for four directions (0° (MD), 45°, 90° (TD), 135°) of the base layer (specimen shape: No. 5 type specified in JIS K7127 dumbbell shape, distance between chucks: 75 mm, distance between gauges: 25 mm, test speed: 50 mm/min, temperature: 23° C.).
Thermal shrinkage rate: An average value of shrinkage rates before and after heat treatment in four directions (0° (MD), 45°, 90° (TD), and 135°) of the base material layer.

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