JP7631390B2 - Exterior material for power storage device and power storage device - Google Patents

Description

The present invention relates to exterior materials for electricity storage devices, such as batteries and capacitors used in mobile devices such as smartphones and tablets, and batteries and capacitors used in hybrid vehicles, electric vehicles, wind power generation, solar power generation, and nighttime electricity storage, and to electricity storage devices exteriorized with the exterior materials.

In recent years, as mobile electrical devices such as smartphones and tablet terminals have become thinner and lighter, a laminate consisting of a heat-resistant resin layer (base material layer), an outer adhesive layer, a metal foil layer, an inner adhesive layer, and a heat-sealable resin layer (inner sealant layer) has been used as the exterior material of the lithium ion secondary battery, lithium polymer secondary battery, lithium ion capacitor, electric double layer capacitor, and other power storage devices mounted on these devices instead of the conventional metal can (see Patent Document 1). In addition, power sources for electric vehicles, large power sources for power storage, capacitors, and the like are increasingly being exteriorized with the above-mentioned laminate (exterior material). The exterior material is molded into a three-dimensional shape such as a roughly rectangular parallelepiped shape by stretch molding or deep drawing. By molding into such a three-dimensional shape, it is possible to secure a storage space for accommodating the main body of the power storage device.

In addition, a configuration has been proposed in which a matte varnish layer is provided on the outside of the base material layer to protect the exterior material and improve formability (see Patent Document 2). Examples of the matte varnish layer include matte varnishes made by adding an appropriate amount of inorganic matting agents such as silica and kaolin to olefin-based or alkyd-based synthetic resins such as cellulose-based, polyamide-based, vinyl chloride-vinyl acetate-based, modified polyolefin-based, rubber-based, acrylic-based, and urethane-based (see Patent Document 2).

JP 2003-288865 A JP 2011-54563 A

However, when the above-mentioned conventional exterior materials are molded by stretch molding or other techniques to obtain an exterior case, there is a problem in that discoloration occurs on the surface of the exterior case.

In addition, conventional packaging materials have the problem of being prone to defects in appearance, such as scratches, due to rubbing during transportation, etc.

The present invention has been made in consideration of this technical background, and aims to provide an exterior material for an electricity storage device that has excellent abrasion resistance, excellent formability, and is less susceptible to discoloration due to molding, and an electricity storage device exteriorized with said exterior material.

To achieve the above objective, the present invention provides the following means:

[1] An exterior material for an electricity storage device, comprising a heat-resistant resin layer as an outer layer, a heat-sealable resin layer as an inner layer, and a metal foil layer disposed between the two layers,
A protective resin layer is laminated on the outer side of the heat-resistant resin layer,
the protective resin layer contains a resin and a spacer agent that is incompatible with the resin,
An exterior material for an electricity storage device, characterized in that a part of the spacer agent protrudes outward from a surface of the protective resin layer.

[2] The exterior material for a storage battery device according to the preceding paragraph 1, in which the spacer agent is contained in the protective resin layer in the form of an aggregate of a plurality of spacer agents.

[3] The exterior material for a storage battery device according to the preceding paragraph 2, in which the average particle size of each spacer agent constituting the aggregate is 1 μm to 20 μm.

[4] The exterior material for a power storage device according to the preceding paragraphs 2 or 3, wherein the average major axis of the spacer agent aggregates in the protective resin layer in a plan view is in the range of 10 μm to 120 μm.

[5] The exterior material for a storage battery device according to any one of items 2 to 4 above, in which the spacer agent aggregates protrude outward from the surface of the protective resin layer to a height of 1 μm or more.

[6] The exterior material for a power storage device according to any one of paragraphs 2 to 5 above, wherein the area of a protruding portion, in which the spacer agent aggregate protrudes outward from the surface of the protective resin layer to a height of 1 μm or more, in a plan view is 4% to 20% of the entire area of the protective resin layer in a plan view.

[7] The exterior material for a storage battery device according to any one of items 2 to 4 above, in which the spacer agent aggregates protrude outward from the surface of the protective resin layer to a height of 0.5 μm to 10 μm, and the average major axis of the spacer agent aggregates in the protective resin layer in a plan view is in the range of 10 μm to 120 μm.

[8] The exterior material for an electricity storage device according to any one of items 1 to 7 above, wherein the spacer agent is one or more spacer agents selected from the group consisting of waxes and polymer powders.

[9] The exterior material for a storage battery device according to any one of items 1 to 8 above, wherein the melting point of the spacer agent is 90°C to 350°C.

[10] The exterior material for a storage battery device according to any one of items 1 to 9 above, wherein the content of the spacer agent in the protective resin layer is 2% by mass to 20% by mass.

[11] The exterior material for an electricity storage device according to any one of items 1 to 10 above, wherein the resin is a reaction product resin between a polyol and a polyisocyanate.

[12] The exterior material for a storage battery device according to any one of items 1 to 11 above, wherein the protective resin layer further contains a matting agent made of fine particles, and the average major axis of the matting agent in the protective resin layer is in the range of 0.3 μm to 7 μm when viewed in plan.

[13] An exterior case for an electricity storage device, comprising a molded article of the exterior material for an electricity storage device described in any one of items 1 to 12 above.

[14] A main body of an electricity storage device;
an exterior member made of the exterior material for an electricity storage device according to any one of items 1 to 12 and/or the exterior case for an electricity storage device according to item 13,
The power storage device, wherein the power storage device main body is exteriorly covered with the exterior member.

In the invention of [1], the protective resin layer provided on the outer side of the heat-resistant resin layer contains a resin and a spacer agent that is not compatible with the resin, and a part of the spacer agent (including aggregates) protrudes outward from the surface of the protective resin layer, so that the exterior material for an electric storage device of the present invention has excellent abrasion resistance. In addition, when molding the exterior material for an electric storage device of the present invention, the part of the spacer agent (including aggregates) protrudes outward from the surface of the protective resin layer, which prevents the molding surface of the mold from coming into direct contact with the protective resin layer, so that the exterior material has excellent moldability and is less likely to discolor.

In the invention of [2], the spacer agent is contained in the protective resin layer in the form of an aggregate of multiple spacer agents, so that when the molding surface of the mold and the spacer agent aggregate (the protruding portion of the aggregate) come into contact, the aggregate crumbles easily and has good slip properties, further improving moldability.

In the invention of [3], the average particle size of each spacer agent constituting the aggregate is 5 μm to 10 μm, so that the aggregate crumbles more easily when it comes into contact with the molding surface of the mold, and the slipperiness can be further improved.

In the invention of [4], the average major axis of the spacer agent aggregates in the protective resin layer in a plan view is in the range of 30 μm to 120 μm, so that direct contact between the molding surface of the mold and the protective resin layer can be sufficiently prevented.

In the invention of [5], the spacer agent aggregates protrude outward from the surface of the protective resin layer to a height of 1 μm or more, which further improves the scratch resistance of the exterior material and further prevents discoloration due to molding in the molded exterior material.

In the invention [6], direct contact between the molding surface of the mold and the protective resin layer can be more sufficiently prevented.

In the invention of [7], direct contact between the molding surface of the mold and the protective resin layer can be more sufficiently prevented.

In the invention of [8], the specific spacer agent is used, so that the spacer agent (including spacer agent aggregates) has good dispersibility in the protective resin layer, and outward protrusions can be formed uniformly from the surface of the protective resin layer, so that excellent abrasion resistance and excellent moldability can be stably ensured.

In the invention of [9], the melting point of the spacer agent is 90°C to 180°C, so the protective resin layer can be formed without the spacer agent melting during drying when the protective resin layer is formed, and the shape of the spacer agent can be maintained when the battery element is heat sealed with an exterior material.

In the invention of [10], the content of the spacer agent in the protective resin layer is 2% by mass to 20% by mass. When the content is 2% by mass or more, excellent abrasion resistance and excellent moldability can be sufficiently ensured, and when the content is 20% by mass or less, the protective function of the protective resin layer can be sufficiently exhibited.

The invention [11] can further improve the chemical resistance (solvent resistance, acid resistance, etc.) of the exterior material.

In the invention of [12], the protective resin layer further contains a matting agent consisting of fine particles, and the average major axis of the matting agent in the protective resin layer is in the range of 0.3 μm to 7 μm when viewed in plan, so that the matte appearance can be easily adjusted and the desired appearance can be reliably achieved.

The invention of [13] provides an exterior case for an electricity storage device that is excellent in abrasion resistance and is well-formed and does not discolor.

The invention [14] provides an electricity storage device that is exterior-covered with an exterior member that has excellent abrasion resistance.

1 is a cross-sectional view showing one embodiment of an exterior material for an electricity storage device according to the present invention. FIG. 2 is an enlarged schematic cross-sectional view of a portion of the outer layer and the protective layer. 1 is a cross-sectional view showing one embodiment of an electricity storage device according to the present invention.

1 shows one embodiment of the exterior material 1 for a power storage device according to the present invention. In this exterior material 1 for a power storage device, a heat-resistant resin layer (outer layer) 2 is laminated and integrated on one surface (upper surface) of a metal foil layer 4 via a first adhesive layer 5, and a heat-sealable resin layer (inner layer) 3 is laminated and integrated on the other surface (lower surface) of the metal foil layer 4 via a second adhesive layer 6, and a protective resin layer 7 is laminated on the outside of the heat-resistant resin layer 2 (on the side opposite the metal foil layer 4 side in the heat-resistant resin layer 2). In this embodiment, the protective resin layer 7 is laminated directly on the outer surface of the heat-resistant resin layer 2 (on the side opposite the metal foil layer 4 side in the heat-resistant resin layer 2) (see FIG. 1). In this embodiment, a resin composition is applied directly to the outer surface of the heat-resistant resin layer 2 by a gravure coating method, and the protective resin layer 7 is laminated.

The heat-resistant resin layer (outer layer) 2 is a component that is primarily responsible for ensuring good formability of the exterior material 1, that is, for preventing breakage due to necking of the metal foil during molding.

The heat-resistant resin constituting the heat-resistant resin layer (outer layer) 2 is a heat-resistant resin that does not melt at the heat-sealing temperature when the exterior material for an electrical storage device 1 is heat-sealed. As the heat-resistant resin, a heat-resistant resin having a melting point 10°C or more higher than the melting point of the resin constituting the heat-sealable resin layer 3 is preferably used, and a heat-resistant resin having a melting point 20°C or more higher than the melting point of the resin constituting the heat-sealable resin layer 3 is particularly preferably used.

The heat-resistant resin layer (outer layer) 2 is not particularly limited, but examples thereof include stretched polyamide films such as stretched nylon films, stretched polyester films, etc. Among them, it is particularly preferable to use biaxially stretched polyamide films such as biaxially stretched nylon films, biaxially stretched polybutylene terephthalate (PBT) films, biaxially stretched polyethylene terephthalate (PET) films, or biaxially stretched polyethylene naphthalate (PEN) films as the heat-resistant resin stretched film layer 2. It is also preferable to use a heat-resistant resin biaxially stretched film stretched by a simultaneous biaxial stretching method as the heat-resistant resin stretched film layer 2. The nylon is not particularly limited, but examples thereof include nylon 6, nylon 6,6, and nylon MXD. The heat-resistant resin layer 2 may be formed as a single layer (a single stretched film), or may be formed as a multilayer structure, for example, consisting of a stretched polyester film/stretched polyamide film (e.g., a multilayer structure consisting of a stretched PET film/stretched nylon film).

The heat-resistant resin layer (outer layer) 2 may be a resin layer formed by applying a heat-resistant resin.

The thickness of the heat-resistant resin layer 2 is preferably 12 μm to 50 μm. When a polyester resin is used, the thickness is preferably 12 μm to 50 μm, and when a nylon resin is used, the thickness is preferably 15 μm to 50 μm. By setting the thickness to above the preferred lower limit, sufficient strength for the exterior material 1 can be ensured, and by setting the thickness to below the preferred upper limit, stress during stretch molding or drawing can be reduced, improving formability.

In the present invention, a protective resin layer 7 must be laminated on the outside of the heat-resistant resin layer 2 (on the side of the heat-resistant resin layer 2 opposite the metal foil layer 4). The protective resin layer 7 contains a resin and a spacer agent 8 that is incompatible with the resin, and a part of the spacer agent 8 protrudes outward from the surface of the protective resin layer 7 (see FIG. 2).

In this embodiment, the spacer agent is dispersed in the protective resin layer 7 in the form of a plurality of spacer agent aggregates 8 (see FIG. 2). The average particle size of each spacer agent constituting the aggregates is preferably 1 μm to 20 μm, and more preferably 5 μm to 10 μm. The major axis of the spacer agent aggregates 8 in the protective resin layer 7 is preferably in the range of 10 μm to 120 μm. In particular, the major axis of the spacer agent aggregates 8 in the protective resin layer 7 is more preferably in the range of 40 μm to 70 μm, and even more preferably in the range of 50 μm to 60 μm.

The spacer agent 8 or spacer agent aggregate 8 preferably has a protruding height H of 1 μm or more protruding outward from the surface of the protective resin layer 7 (see FIG. 2). By having a protruding height H of 1 μm or more, the scratch resistance of the exterior material 1 can be further improved, and when the exterior material 1 is molded, the molding surface of the mold and the protective resin layer 7 are prevented from coming into direct contact with each other, resulting in excellent moldability and less discoloration of the molded exterior material. Of these, it is more preferable for the protruding height H to be in the range of 1.5 μm to 10.0 μm.

Furthermore, the planar area of the protruding portion where the spacer agent 8 and/or the spacer agent aggregates 8 protrude outward from the surface of the protective resin layer 7 to a protruding height of 1 μm or more is preferably 4% to 20% of the entire planar area of the protective resin layer 7, more preferably 6% to 15%, and particularly preferably 5% to 10%.

The resin constituting the protective resin layer 7 is not particularly limited, but it is preferable to use a reaction product resin between a polyol and a polyisocyanate. The polyol is not particularly limited, but examples thereof include polyester polyol, polyurethane polyol, polyether polyol, etc. The weight average molecular weight (Mw) of the polyol is preferably 3,000 to 50,000.

The polyisocyanate is not particularly limited, but examples thereof include tolylene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), a trimethylolpropane adduct of TDI, and a trimethylolpropane adduct of HMDI. Among them, it is preferable to use a trimethylolpropane adduct of TDI, a trimethylolpropane adduct of HMDI, or a mixture of a trimethylolpropane adduct of TDI and a trimethylolpropane adduct of HMDI as the polyisocyanate.

The spacer agent 8 is preferably, but not limited to, one or more spacer agents selected from the group consisting of waxes and polymer powders. The waxes are not particularly limited, but examples thereof include paraffin wax, microcrystalline wax, hydrocarbon wax, low molecular weight polyethylene wax, etc. The polymer powder is not particularly limited, but examples thereof include ultra-high molecular weight polyethylene powder, polyethylene powder, low molecular weight polyethylene powder, polypropylene powder, low molecular weight polypropylene powder, etc.

The weight average molecular weight (simply "molecular weight" when there is no molecular weight distribution) of the spacer agent 8 is preferably 100 to 6,000,000, more preferably in the range of 1000 to 8000, and particularly preferably in the range of 1000 to 6000.

The melting point of the spacer agent 8 is preferably 50°C to 350°C, more preferably 50°C to 180°C, and particularly preferably 90°C to 160°C.

The density of the spacer agent 8 is preferably 0.85 g/cm ³ to 3.0 g/cm ³ , and more preferably 0.88 g/cm ³ to 2.3 g/cm ³ .

The content of the spacer agent in the protective resin layer 7 is preferably 2% by mass to 20% by mass. When the content is 2% by mass or more, excellent abrasion resistance and excellent moldability can be sufficiently ensured, and when the content is 20% by mass or less, the protective function of the protective resin layer can be sufficiently exhibited. In particular, the content of the spacer agent in the protective resin layer 7 is preferably 5% by mass to 15% by mass. Also, the content of the resin in the protective resin layer 7 is preferably 60% by mass to 98% by mass.

The protective resin layer 7 may further contain a matting agent made of fine particles. In this case, it is preferable that the average value of the major axis of the matting agent in the protective resin layer 7 is in the range of 0.3 μm to 7 μm in a plan view of the protective resin layer 7. The matting agent is a fine particle that forms an uneven shape on the surface of the protective resin layer 7 and diffuses light, thereby reducing the glossiness of the surface of the protective resin layer 7 and forming an appearance with a calm texture. The matting agent is not particularly limited, but examples thereof include inorganic fine particles (e.g., barium sulfate fine particles, silica fine particles, etc.), resin beads (e.g., acrylic resin beads, styrene resin beads, etc.), etc. It is particularly preferable that the average particle diameter of the matting agent is in the range of 0.5 μm to 5 μm. When barium sulfate fine particles are used as the matting agent, it is preferable to use barium sulfate fine particles having an average particle diameter of 0.3 μm to 3 μm. Also, when acrylic resin beads are used as the matting agent, it is preferable to use acrylic resin beads having an average particle diameter of 3 μm to 5 μm.

The thickness of the protective resin layer 7 (thickness after drying; excluding the protruding parts of the spacer agent) is preferably 0.5 μm to 10 μm.

The method for forming the protective resin layer 7 is not particularly limited, but for example, the protective resin layer 7 can be formed by applying an aqueous emulsion (water-based emulsion) containing the above resin and the spacer agent 8 to the surface of the heat-resistant resin layer 2 and drying it. The application method is not particularly limited, but examples include a spray coating method, a gravure roll coating method, a reverse roll coating method, and a lip coating method.

The heat-sealable resin layer (inner layer) 3 provides excellent chemical resistance against highly corrosive electrolytes used in lithium-ion secondary batteries and the like, and also provides the exterior material with heat sealability.

The heat-sealable resin layer 3 is not particularly limited, but is preferably a thermoplastic resin unstretched film layer. The thermoplastic resin unstretched film layer 3 is not particularly limited, but is preferably composed of an unstretched film made of at least one thermoplastic resin selected from the group consisting of polyethylene, polypropylene, olefin copolymers, acid-modified products thereof, and ionomers.

The thickness of the heat-sealable resin layer 3 is preferably set to 20 μm to 80 μm. By setting the thickness to 20 μm or more, the occurrence of pinholes can be sufficiently prevented, and by setting the thickness to 80 μm or less, the amount of resin used can be reduced, thereby reducing costs. In particular, the thickness of the heat-sealable resin layer 3 is preferably set to 30 μm to 50 μm. The heat-sealable resin layer 3 may be a single layer or multiple layers.

A lubricant is usually added to the heat-sealable resin layer 3. The addition of the lubricant can improve moldability during molding. The lubricant content in the heat-sealable resin layer 3 is preferably set in the range of 200 ppm to 5000 ppm.

The lubricant is not particularly limited, but examples thereof include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides.

The metal foil layer 4 serves to provide the exterior material 1 with gas barrier properties that prevent the intrusion of oxygen and moisture. The metal foil layer 4 is not particularly limited, but examples include aluminum foil and copper foil, with aluminum foil being commonly used. The thickness of the metal foil layer 4 is preferably 20 μm to 100 μm. Having a thickness of 20 μm or more can prevent the occurrence of pinholes during rolling when manufacturing the metal foil, while having a thickness of 100 μm or less can reduce stress during stretch forming and drawing, improving formability.

It is preferable that at least the inner surface 4a (the surface on the second adhesive layer 6 side) of the metal foil layer 4 is subjected to a chemical conversion treatment. By performing such a chemical conversion treatment, corrosion of the metal foil surface due to the contents (battery electrolyte, food, medicine, etc.) can be sufficiently prevented. For example, the chemical conversion treatment is performed on the metal foil by carrying out the following treatment. That is, for example, the surface of the metal foil that has been subjected to a degreasing treatment is subjected to the following treatment.
The chemical conversion treatment is carried out by applying and then drying either of the following: 1) an aqueous solution consisting of a mixture of phosphoric acid, chromic acid, and a metal salt of a fluoride; 2) an aqueous solution consisting of a mixture of phosphoric acid, chromic acid, a metal salt of a fluoride, and a non-metal salt; or 3) an aqueous solution consisting of a mixture of an acrylic resin and/or a phenolic resin, phosphoric acid, chromic acid, and a metal salt of a fluoride.

The first adhesive layer (outer adhesive layer) 5 is not particularly limited, and examples thereof include an adhesive layer formed by a two-liquid reactive adhesive. Examples of the two-liquid reactive adhesive include a two-liquid reactive adhesive composed of a first liquid consisting of one or more polyols selected from the group consisting of polyurethane polyols, polyester polyols, and polyether polyols, and a second liquid (curing agent) consisting of polyisocyanate. The first adhesive layer 5 is formed, for example, by applying an adhesive such as the two-liquid reactive adhesive to the "upper surface of the metal foil layer 4" and/or the "lower surface of the heat-resistant resin layer 2" by a method such as gravure coating.

The second adhesive layer (inner adhesive layer) 6 is not particularly limited, but examples include adhesive layers formed from polyurethane adhesives, acrylic adhesives, epoxy adhesives, polyolefin adhesives, elastomer adhesives, fluorine adhesives, etc. Among them, it is preferable to use a two-liquid reactive adhesive consisting of a first liquid made of an acid-modified olefin resin (maleic anhydride-modified polypropylene, maleic anhydride-modified polyethylene, etc.) and a second liquid (curing agent) made of polyisocyanate, in which case the electrolyte resistance and water vapor barrier properties of the exterior material 1 can be further improved.

In the above embodiment, a configuration is adopted in which the first adhesive layer 5 and the second adhesive layer 6 are provided, but neither of these layers 5, 6 is a required constituent layer, and a configuration without these layers can also be adopted.

Thus, by forming (deep drawing, stretch forming, etc.) the exterior material 1 for an electricity storage device according to the present invention, an exterior case 1A for an electricity storage device as shown in FIG. 3 can be obtained. The shape of the exterior case 1A for an electricity storage device is not particularly limited, but examples include a substantially rectangular parallelepiped shape with one surface (top surface) open as shown in FIG. 3.

Next, one embodiment of the electric storage device 30 according to the present invention is shown in FIG. 3. As shown in FIG. 3, an electric storage device main body 31 having a substantially rectangular parallelepiped shape is accommodated in the accommodation recess of the exterior case 1A obtained by molding the exterior material for an electric storage device 1 of the present invention, and the exterior material for an electric storage device 1 of the present invention is placed on top of the electric storage device main body 31 with its inner layer 3 side facing inward (lower side), and the peripheral portion of the inner layer 3 of the planar exterior material 1 and the inner layer 3 of the flange portion (sealing peripheral portion) 29 of the exterior case 1A are sealed and joined by heat sealing to form the electric storage device 30 of the present invention.

In FIG. 4, 39 is a heat-sealed portion where the peripheral portion of the exterior material 1 and the flange portion (sealing peripheral portion) 29 of the exterior case 1A are joined (welded).

The electric storage device main body 31 is not particularly limited, but examples thereof include a battery main body, a capacitor main body, a condenser main body, etc.

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

<Spacer agent used>
(Polyethylene wax A)
Polyethylene wax (waxes) having an average particle size of 9 μm, a weight average molecular weight (Mw) of 3000, a melting point of 120° C., and a density of 0.96 g/cm ³
(Polyethylene wax B)
Polyethylene wax (waxes) having an average particle size of 12 μm, a weight average molecular weight (Mw) of 4000, a melting point of 128° C., and a density of 0.98 g/cm ³
(Polyethylene wax C)
Polyethylene wax (waxes) having an average particle size of 5 μm, a weight average molecular weight (Mw) of 6000, a melting point of 116° C., and a density of 0.95 g/cm ³
(PTFE wax D)
Polytetrafluoroethylene (PTFE) wax (waxes) having an average particle size of 2 μm, a weight average molecular weight (Mw) of 5000, a melting point of 320° C., and a density of 2.10 g/cm ³
(Low molecular weight polyethylene powder)
Low molecular weight polyethylene (PE) powder (low molecular weight polypropylene powder) having an average particle size of 20 μm, a weight average molecular weight (Mw) of 8500, a melting point of 121° C., and a density of 0.94 g/cm ³
Low molecular weight polypropylene (PP) powder having an average particle size of 15 μm, a weight average molecular weight (Mw) of 7000, a melting point of 145° C., and a density of 0.89 g/cm ³ .

Example 1
A resin composition A for forming a protective resin layer was obtained by mixing 100 parts by mass of a polyester polyol having a weight average molecular weight (Mw) of 9,800, 15 parts by mass of a trimethylolpropane adduct of hexamethylene diisocyanate (a TMP adduct of HMDI) as a polyisocyanate, 5 parts by mass of the above-mentioned polyethylene wax A (waxes) as a spacer agent, 12 parts by mass of acrylic resin beads having an average particle diameter of 2 μm as a first matting agent, 3 parts by mass of barium sulfate having an average particle diameter of 0.8 μm as a second matting agent, and 200 parts by mass of a mixed solvent of toluene and methyl ethyl ketone (100 parts by mass of toluene + 100 parts by mass of methyl ethyl ketone).

In this resin composition A for forming a protective resin layer, the ratio of NCO of the polyisocyanate to OH of the polyester polyol (NCO/OH) was 1.8.

Next, the above-mentioned resin composition A for forming a protective resin layer was applied by gravure roll coating to one side of a biaxially oriented nylon (nylon 6) film 2 having a thickness of 15 μm obtained by stretching using the simultaneous biaxial stretching method, and then dried. The film was then left in an environment of 60° C. for 3 days to allow the curing reaction to proceed, thereby forming a protective resin layer 7 having a formation amount of 2.5 g/ ^m2 .

On the other hand, a chemical conversion treatment solution consisting of polyacrylic acid, metal chromate, phosphoric acid, water, and isopropyl alcohol (IPA) was applied to both sides of an aluminum foil 4 (O material defined in JIS A8021) having a thickness of 35 μm, and dried at 180° C. until the amount of chromium deposited was 10 mg/m ² .

Next, the other side of the biaxially oriented nylon film 2 (the side opposite to the side on which the protective resin layer 7 is formed) is bonded to one side of the chemically treated aluminum foil 4 via a two-component curing polyester-based polyurethane outer adhesive 5 containing polyester polyol and a trimethylolpropane adduct of tolylene diisocyanate (TMP adduct of TDI), and then a 30 μm-thick unstretched polypropylene film (heat-sealable resin layer) 3 is bonded to the other side 4a of the aluminum foil 4 via a two-component curing inner adhesive 6 containing maleic anhydride-modified polypropylene and hexamethylene diisocyanate (HMDI), and then the material is left in a 40° C. environment for 5 days to obtain the exterior material 1 for a power storage device shown in FIG. 1.

A three-layer laminate film of 4 μm random polypropylene layer (erucic acid amide content 1000 ppm, silica fine particle content 5000 ppm)/22 μm block polypropylene layer (erucic acid amide content 2000 ppm)/4 μm random polypropylene layer (erucic acid amide content 1000 ppm, silica fine particle content 5000 ppm) was used as the unstretched polypropylene film 3. The coating amount of the outer adhesive 5 was set to 3 g/ ^m2 , and the coating amount of the inner adhesive 6 was set to 3 g/ ^m2 .

Example 2
An exterior material 1 for a power storage device shown in FIG. 1 was obtained in the same manner as in Example 1, except that the blending amount of polyethylene wax A (waxes) in the resin composition for forming a protective resin layer was changed to 10 parts by mass.

Example 3
An exterior material 1 for a power storage device shown in FIG. 1 was obtained in the same manner as in Example 1, except that the blending amount of polyethylene wax A (waxes) in the resin composition for forming a protective resin layer was changed to 15 parts by mass.

Example 4
An exterior material for a power storage device 1 shown in FIG. 1 was obtained in the same manner as in Example 2, except that, as the polyisocyanate, "8 parts by mass of a trimethylolpropane adduct of hexamethylene diisocyanate (TMP adduct of HMDI) and 7 parts by mass of a trimethylolpropane adduct of tolylene diisocyanate (TMP adduct of TDI)" was used instead of 15 parts by mass of a trimethylolpropane adduct of hexamethylene diisocyanate (TMP adduct of HMDI).

Example 5
An exterior material for a power storage device 1 shown in FIG. 1 was obtained in the same manner as in Example 4, except that 100 parts by mass of a polyurethane polyol having a weight average molecular weight (Mw) of 14,500 was used instead of 100 parts by mass of a polyester polyol having a Mw of 9,800, and 10 parts by mass of the polyethylene wax B (waxes) was used instead of 10 parts by mass of “polyethylene wax A”.

Example 6
An exterior material for a power storage device 1 shown in FIG. 1 was obtained in the same manner as in Example 4, except that 5 parts by mass of the PTFE wax D (waxes) was used instead of 10 parts by mass of "polyethylene wax A".

Example 7
An exterior material for a power storage device 1 shown in FIG. 1 was obtained in the same manner as in Example 5, except that 5 parts by mass of the PTFE wax D (waxes) was used instead of 10 parts by mass of "polyethylene wax B".

Example 8
An exterior material 1 for a storage battery device as shown in FIG. 1 was obtained in the same manner as in Example 7, except that, as the first matting agent, 12 parts by mass of urethane resin beads having an average particle diameter of 3 μm were used instead of 12 parts by mass of acrylic resin beads having an average particle diameter of 2 μm.

<Example 9>
An exterior material for a power storage device 1 shown in FIG. 1 was obtained in the same manner as in Example 8, except that 5 parts by mass of the above-mentioned "polyethylene wax C" was used instead of 5 parts by mass of "PTFE wax D".

Example 10
An exterior material for a power storage device 1 shown in FIG. 1 was obtained in the same manner as in Example 7, except that 3 parts by mass of the low-molecular-weight PE powder was used instead of 5 parts by mass of "PTFE wax D".

Example 11
An exterior material for a power storage device 1 shown in FIG. 1 was obtained in the same manner as in Example 7, except that 5 parts by mass of the low-molecular-weight PE powder was used instead of 5 parts by mass of "PTFE wax D".

Example 12
An exterior material for a power storage device 1 shown in FIG. 1 was obtained in the same manner as in Example 7, except that 3 parts by mass of the low-molecular-weight PP powder was used instead of 5 parts by mass of "PTFE wax D".

<Example 13>
An exterior material for a power storage device 1 shown in FIG. 1 was obtained in the same manner as in Example 7, except that 5 parts by mass of the low-molecular-weight PP powder was used instead of 5 parts by mass of "PTFE wax D".

<Example 14>
An outer casing material 1 for a power storage device shown in FIG. 1 was obtained in the same manner as in Example 1, except that 100 parts by mass of a polyurethane polyol having a weight average molecular weight (Mw) of 14,500 was used instead of 100 parts by mass of a polyester polyol having a Mw of 9,800, and 3 parts by mass of the low molecular weight PE powder was used instead of 5 parts by mass of “polyethylene wax A”.

Example 15
An exterior material 1 for a power storage device shown in FIG. 1 was obtained in the same manner as in Example 1, except that 100 parts by mass of a polyurethane polyol having a weight average molecular weight (Mw) of 14,500 was used instead of 100 parts by mass of a polyester polyol having a Mw of 9,800, and 3 parts by mass of the low molecular weight PP powder was used instead of 5 parts by mass of “polyethylene wax A”.

<Comparative Example 1>
An exterior material for an electricity storage device was obtained in the same manner as in Example 1, except that the resin composition for forming a protective resin layer was not blended with (contained) polyethylene wax A (spacer agent).

In addition, in Tables 1 and 2, the details (type, average particle size, amount) of the first and second matting agents have been omitted (these are listed in the Examples section above).

The exterior materials for electricity storage devices obtained as described above were evaluated according to the following evaluation methods. The results are shown in Tables 1 and 2.

The "protrusion height H (μm)" in Table 1 is the average protrusion height (protrusion height H) obtained by averaging the protrusion heights of 10 spacer agent aggregates protruding outward from the surface of the protective resin layer by observing the cross section of the exterior material for an electricity storage device (see Figure 2) with a SEM (scanning electron microscope).

In addition, in Table 1, the "area percentage (%) in plan view of protruding portions having a protruding height of 1 μm or more" means the area percentage calculated by observing a square region (2,500 ^μm2 ) of 50 μm length by 50 μm width on the surface of the protective resin layer side of the exterior material for an electrical storage device in plan view using an SEM (scanning electron microscope) and using the following formula: In other words, when the "plan view area of protruding portions having a protruding height of 1 μm or more where spacer agent aggregates protrude outward from the surface of the protective resin layer" calculated by the above planar observation using the SEM is "S ( ^μm2 )," this is the area percentage calculated by the following formula.

Area ratio (%) = (S/2500) x 100
In addition, the "longest diameter of the aggregate" in Table 1 is the average value (average long diameter of the spacer agent aggregates) obtained by observing the surface of the protective resin layer side of the exterior material for an electrical storage device in plan view using an SEM (scanning electron microscope), determining the long diameters (W) in plan view of 10 randomly selected spacer agent aggregates using this planar observation with the SEM (see Figure 2).

<Method for evaluating scratch resistance>
Using a Gakushin method friction fastness tester (with an aluminum jig with a load of 200 g) manufactured by Tester Sangyo Co., Ltd., the aluminum jig was brought back and forth in contact with the surface of the exterior material for a storage battery device (surface of protective resin layer 7) 10 times, and the presence or absence and the extent of scratches on the surface were then visually inspected, and the abrasion resistance was evaluated based on the following judgment criteria.
(Judgment criteria)
"◯": no scratches at all on the surface of the protective resin layer; "Δ": slight scratches were observed on the surface of the protective resin layer, but they were barely noticeable; "×": scratches were clearly observed on the surface of the protective resin layer.

<Evaluation method for discoloration prevention>
A first exterior case for a power storage device (rectangular parallelepiped molded body with an open top) 1A having a rectangular parallelepiped shape of 55 mm long x 35 mm wide x 4 mm deep is obtained by applying a pressure of 0.3 MPa to the exterior material for a power storage device using an embossing machine (product number: TP-25C-X2) manufactured by Amada Co., Ltd. (see FIG. 3). Both sides of the first exterior case obtained were visually inspected for the presence or absence of discoloration and the degree of discoloration, and the discoloration prevention property was evaluated based on the following criteria. The evaluation results are shown in Table 2.

The exterior material for the power storage device was stretched in the same manner as above with a pressing pressure of 0.25 MPa to obtain a second exterior case for the power storage device (a rectangular solid molded body with an open top) 1A having a rectangular parallelepiped shape of 55 mm length x 35 mm width x 6 mm depth (see Figure 3). Both sides of the obtained second exterior case were visually inspected for the presence or absence of discoloration and the degree of discoloration, and the discoloration prevention properties were evaluated based on the following criteria. The evaluation results are shown in Table 2.

(Judgment criteria)
"◎": No discoloration was observed on either side of the exterior case before and after molding. "○": Extremely slight discoloration was observed on the surface of the protective resin layer side of the exterior case before and after molding, but it was at a level that did not cause any problems as a product. "△": Only slight discoloration was observed on the surface of the protective resin layer side of the exterior case before and after molding, and it was at a level that could be used as a product. "×": Clear discoloration was observed on the surface of the protective resin layer side of the exterior case before and after molding.

As is clear from the table, the electrical storage device exterior materials of Examples 1 to 15 according to the present invention have excellent abrasion resistance, and are less susceptible to discoloration due to molding, making them excellent in discoloration prevention properties.

In contrast, in Comparative Example 1, in which no spacer agent was added to the protective resin layer, the abrasion resistance was insufficient and the resistance to discoloration due to molding was poor.

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

1... Exterior material for power storage device 2... Heat-resistant resin layer (outer layer)
3... Heat-fusible resin layer (inner layer)
4... Metal foil layer 7... Protective resin layer 8... Spacer agent (spacer agent aggregate)
H: protruding height (protruding height of a part of the spacer agent from the surface of the protective resin layer)
W: major axis of spacer agent aggregate in plan view

Claims (13)

An exterior material for an electricity storage device, comprising: a heat-resistant resin layer as an outer layer; a heat-fusible resin layer as an inner layer; and a metal foil layer disposed between the two layers,
A protective resin layer is laminated on the outer side of the heat-resistant resin layer,
the protective resin layer contains a resin and a spacer agent that is incompatible with the resin,
a part of the spacer agent protrudes outward from a surface of the protective resin layer;
The spacer agent has an average particle size of 1 μm to 20 μm;
the thickness of the protective resin layer (thickness after drying; excluding the protruding portion of the spacer agent) is 0.5 μm to 10 μm,
The exterior material for an electricity storage device, wherein the spacer agent has a weight average molecular weight in the range of 1,000 to 8,000 . 2. The exterior material for an electricity storage device according to claim 1, wherein the spacer agent has a density of 0.85 g/cm ³ to 3.0 g/cm ³ . The exterior material for a storage battery device according to claim 1 or 2, wherein the spacer agent is contained in the protective resin layer in the form of an aggregate of a plurality of spacer agents. The exterior material for a power storage device according to claim 3, wherein the average major axis of the spacer agent aggregates in the protective resin layer in a plan view is in the range of 10 μm to 120 μm. The exterior material for a storage battery device according to claim 3 or 4, wherein the spacer agent aggregates protrude outward from the surface of the protective resin layer to a height of 1 μm or more. The exterior material for a power storage device according to any one of claims 3 to 5, wherein the area of a protruding portion, in which the spacer agent aggregate protrudes outward from the surface of the protective resin layer to a height of 1 μm or more, in a plan view is 4% to 20% of the entire area of the protective resin layer in a plan view. The exterior material for a storage battery device according to any one of claims 1 to 6, wherein the spacer agent is one or more types of spacer agents selected from the group consisting of waxes and polymer powders. The exterior material for a storage battery device according to any one of claims 1 to 7, wherein the melting point of the spacer agent is 90°C to 350°C. The exterior material for a storage battery device according to any one of claims 1 to 8, wherein the content of the spacer agent in the protective resin layer is 2% by mass to 20% by mass. The exterior material for an electricity storage device according to any one of claims 1 to 9, wherein the resin is a reaction product resin between a polyol and a polyisocyanate. The exterior material for a storage battery device according to any one of claims 1 to 10, wherein the protective resin layer further contains a matting agent made of fine particles, and the average major axis of the matting agent in the protective resin layer is in the range of 0.3 μm to 7 μm when viewed in plan of the protective resin layer. An exterior case for an electricity storage device, comprising a molded article of the exterior material for an electricity storage device according to any one of claims 1 to 11. A main body of the electricity storage device;
An exterior member comprising the exterior material for an electricity storage device according to any one of claims 1 to 11 and/or the exterior case for an electricity storage device according to claim 12,
The power storage device, wherein the power storage device main body is exteriorly covered with the exterior member.

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