JP6738189B2 - Exterior material for power storage device and power storage device - Google Patents

Description

INDUSTRIAL APPLICABILITY The present invention relates to a storage device such as a battery or a capacitor used for a mobile device such as a smartphone or a tablet, a hybrid vehicle, an electric vehicle, wind power generation, solar power generation, a battery or a capacitor used for storing electricity at night. The present invention relates to a packaging material and a power storage device packaged with the packaging material.

In recent years, as mobile electric devices such as smartphones and tablet terminals have become thinner and lighter, the storage devices such as lithium-ion secondary batteries, lithium-polymer secondary batteries, lithium-ion capacitors, and electric double-layer capacitors have been installed in these devices. As the exterior material, a laminate (laminate exterior material) composed of a heat resistant resin layer/adhesive layer/metal foil layer/adhesive layer/thermoplastic resin layer is used instead of the conventional metal can (patented patent). Reference 1). Power sources for electric vehicles, large-scale power sources for storage of electricity, capacitors, and the like are increasingly being packaged with the laminate (exterior material) having the above configuration.

JP, 2007-163310, A

However, the above conventional technique (the exterior material described in Patent Document 1) has the following problems. That is, when the battery or the like is packaged, the sealant layers of the package material are heat-sealed to each other for sealing, and if foreign matter (electrode active material, electrolyte, etc.) is attached to the surface of this sealant layer, There was a surface where the heat-sealed portion became thin and it was difficult to secure sufficient insulation in the heat-sealed portion. In particular, the tab portion is likely to have insufficient insulation, which may cause a short circuit.

The present invention has been made in view of such a technical background, and it is possible to suppress the outflow of the sealant layer at the time of heat-sealing the sealant layers and ensure sufficient insulation in the heat seal portion, Provided is an exterior material for an electricity storage device that can secure a sufficient sealing strength.

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

[1] An exterior material for an electricity storage device, which includes a metal foil layer and a sealant layer laminated on one surface of the metal foil layer,
The sealant layer comprises a first low melting point layer made of a thermoplastic resin forming an outermost layer on the metal foil layer side in the sealant layer, and a heat forming an outermost layer on the side opposite to the metal foil layer side in the sealant layer. A second low melting point layer made of a plastic resin, and a high melting point intermediate layer made of a thermoplastic resin disposed between the first low melting point layer and the second low melting point layer,
The melting point of the high melting point intermediate layer is 120° C. to 180° C.,
The melting point of the first low melting point layer and the melting point of the second low melting point layer are lower than the melting point of the high melting point intermediate layer,
The high melting point intermediate layer has a thickness of 20 μm or more,
When the thickness of the high melting point intermediate layer is "X" and the thickness of the sealant layer is "Y", 0.50Y ≤ X ≤ 0.99Y
An outer casing material for an electricity storage device, characterized in that

[2] The outer packaging material for an electricity storage device according to the above item 1, wherein the first low melting point layer has a thickness of 0.5 μm or more and the second low melting point layer has a thickness of 1 μm or more.

[3] The melting point of the high melting point intermediate layer is higher than the melting point of the first low melting point layer by 20° C. or more, and the melting point of the high melting point intermediate layer is higher than the melting point of the second low melting point layer by 20° C. or more. The exterior material for an electricity storage device according to 2.

[4] The thermoplastic resin forming the high melting point intermediate layer is an ethylene-propylene block copolymer resin having a weight average molecular weight of 200,000 to 800,000.
The thermoplastic resin forming the first low melting point layer and the thermoplastic resin forming the second low melting point layer are ethylene-propylene random copolymer resins having a weight average molecular weight of 10,000 to 200,000. The outer packaging material for an electricity storage device according to any one of the preceding items 1 to 3.

[5] The exterior material for an electricity storage device according to any one of the above items 1 to 4, wherein a heat resistant resin layer is laminated on the other surface of the metal foil layer with an outer adhesive layer interposed therebetween.

[6] A power storage device body,
An outer storage material for an electricity storage device according to any one of the preceding items 1 to 5,
An electricity storage device, wherein the electricity storage device body is covered with the exterior material.

In the invention [1], since the melting point of the high-melting-point intermediate layer is 120° C. to 180° C. and the low-melting-point layer exists outside the high-melting-point intermediate layer, heat is applied when the sealant layers are heat-sealed. Since the outflow of the high melting point intermediate layer at the seal portion can be suppressed, the thickness of the high melting point intermediate layer is 20 μm or more, and the relationship of 0.50Y≦X≦0.99Y is satisfied, the sealant layers are It is possible to suppress a decrease in wall thickness due to the outflow of the sealant layer when heat-sealing the resin, to ensure sufficient insulation in the heat-sealed portion, and to sufficiently prevent the occurrence of a short circuit. Further, since the first low melting point layer and the second low melting point layer having a melting point lower than that of the high melting point intermediate layer are arranged on both sides of the high melting point intermediate layer, when the sealant layers are heat-sealed to each other. In addition, good heat sealing can be performed without melting the high melting point intermediate layer, and seal bonding can be performed with sufficient sealing strength (sufficient sealing strength can be secured in the heat sealing portion).

In the invention [2], since the thickness of the first low melting point layer is 0.5 μm or more and the thickness of the second low melting point layer is 1 μm or more, when the sealant layers are heat-sealed together, Seal joining can be performed with sufficient sealing strength (more sufficient sealing strength can be secured in the heat-sealed portion).

In the invention [3], the melting point of the high melting point intermediate layer is higher than that of the first low melting point layer by 20° C. or more, and the melting point of the high melting point intermediate layer is higher than that of the second low melting point layer by 20° C. or more. Therefore, it is possible to sufficiently suppress the outflow of the sealant layer at the heat seal portion when the sealant layers are heat-sealed to each other, and it is possible to secure more sufficient insulation at the heat seal portion.

In the invention [4], since the thermoplastic resin constituting the high melting point intermediate layer is an ethylene-propylene block copolymer resin having a weight average molecular weight in the range of 200,000 to 800,000, the sealant layers are heated together. It is possible to more sufficiently suppress the outflow of the sealant layer at the heat-sealed portion when fusion-bonded, and it is possible to further improve the insulating property at the heat-sealed portion. In addition, since the thermoplastic resin forming the first and second low melting point layers is an ethylene-propylene random copolymer resin having a weight average molecular weight of 10,000 to 200,000, respectively, the sealant layers are heated to each other. At the time of fusion bonding, it is possible to perform seal joining with more sufficient sealing strength (more sufficient sealing strength can be secured in the heat-sealed portion).

In the invention [5], since the heat-resistant resin layer is laminated on the other surface of the metal foil layer via the outer adhesive layer, the insulation property on the other surface side of the metal foil layer can be sufficiently secured. The physical strength and impact resistance of the exterior material can be improved.

According to the invention [6] (electric storage device), there is provided an electric storage device in which the heat-sealed portion is joined with a sufficient seal strength, and the heat-sealed portion is covered with an exterior material that ensures sufficient insulation.

It is sectional drawing which shows one Embodiment of the exterior material for electrical storage devices which concerns on this invention. FIG. 1 is a cross-sectional view showing an embodiment of an electricity storage device configured by using an electricity storage device exterior material according to the present invention.

FIG. 1 shows one embodiment of the exterior material 1 for an electricity storage device according to the present invention. The exterior material 1 for an electricity storage device is used for a lithium ion secondary battery case. The exterior material 1 for the electricity storage device is used for forming such as deep drawing and overhang forming, and is used as a case of a secondary battery or the like. Further, the exterior material 1 for the electricity storage device can be used as a planar exterior material without being subjected to molding (see FIG. 2).

In the present embodiment, in the exterior material 1 for an electricity storage device, the sealant layer (inner layer) 3 is laminated and integrated on one surface of the metal foil layer 4 via the inner adhesive layer 6, and the metal foil layer The heat-resistant resin layer (outer layer) 2 is laminated and integrated on the other surface of 4 with an outer adhesive layer 5 interposed therebetween.

The sealant layer (thermoplastic resin layer) (inner layer) 3 has excellent chemical resistance against a highly corrosive electrolytic solution used in a lithium ion secondary battery or the like, and heats the exterior material. It plays a role of imparting a sealing property.

In the present invention, the sealant layer 3 is composed of the first low melting point layer 7 made of a thermoplastic resin that constitutes the outermost layer of the sealant layer 3 on the metal foil layer 4 side and the metal foil layer side of the sealant layer 3. A second low melting point layer 8 made of a thermoplastic resin forming the outermost layer on the opposite side, and a high melting point intermediate made of a thermoplastic resin arranged between the first low melting point layer 7 and the second low melting point layer 8. The melting point of the high melting point intermediate layer 9 is 120° C. to 180° C., and the melting point of the first low melting point layer 7 and the second low melting point layer 8 are included. Is lower than the melting point of the high-melting-point intermediate layer 9, the thickness of the high-melting-point intermediate layer is 20 μm or more, and the thickness of the high-melting-point intermediate layer 9 is “X”. When the thickness is “Y”, the relationship is 0.50Y≦X≦0.99Y.

In the above embodiment, the sealant layer 3 has a three-layer laminated structure of the first low melting point layer 7/high melting point intermediate layer 9/second low melting point layer 8, but such a three layer laminated structure is particularly preferable. However, the structure is not limited to the above, as long as it includes at least the first low melting point layer 7, the high melting point intermediate layer 9, and the second low melting point layer 8, a four-layer laminated structure, a five-layer laminated structure, or 6 It may have a laminated structure of more than one layer.

The melting point of the high melting point intermediate layer 9 needs to be 120° C. to 180° C. When the temperature is lower than 120° C., when the sealant layers are heat-sealed together, the high-melting-point intermediate layer also easily flows out in the heat-sealed portion, so that it is difficult to secure sufficient insulation in the heat-sealed portion. On the other hand, if the melting point exceeds 180° C., it is necessary to raise the sealing temperature in order to heat-bond the sealant layers to each other, but if the sealing temperature is high, the electrolytic solution is affected by heat and easily decomposes. .. Among them, the melting point of the high melting point intermediate layer 9 is preferably 150°C to 170°C. The heat-sealing temperature at the time of heat-sealing the sealant layers is preferably set within the range of +10°C to +40°C with respect to the melting point of the high melting point intermediate layer 9.

The high melting point intermediate layer 9 needs to have a thickness of 20 μm or more. If the thickness is less than 20 μm, the thickness of the sealant layer 3 for ensuring sufficient insulation cannot be maintained (ensured) after heat sealing. Above all, the thickness of the high melting point intermediate layer 9 is preferably 20 μm to 30 μm. If the thickness of the high-melting-point intermediate layer 9 is too large, heat conduction during heat sealing may be reduced and seal bonding may not be sufficient. From this viewpoint, the thickness of the high-melting-point intermediate layer 9 may be reduced. It is preferable to set the thickness to 40 μm or less.

Further, when the thickness of the high melting point intermediate layer 9 is "X" and the thickness of the sealant layer 3 is "Y", the relationship of 0.50Y≤X≤0.99Y is established. When the thickness X of the high-melting-point intermediate layer 9 is less than 50% of the thickness Y of the sealant layer 3, the low-melting-point layer flows out too much when the sealant layers are heat-sealed, and after heat sealing. There is a risk that the distance between the insulating parts cannot be secured sufficiently. Further, when the thickness X of the high-melting-point intermediate layer 9 is 99% or more of the thickness Y of the sealant layer 3, it is said that seal joining cannot be performed with sufficient seal strength when heat-sealing the sealant layers. Cause problems. Above all, it is preferable that the constitution is such that 0.60Y≦X≦0.90Y.

The melting point of the high melting point intermediate layer 9 is higher than the melting point of the first low melting point layer 7 by 20° C. or more, and the melting point of the high melting point intermediate layer 9 is higher than the melting point of the second low melting point layer 8 by 20° C. or more. It is preferably configured. With such a configuration, it is possible to sufficiently suppress the outflow of the sealant layer 3 at the heat seal portion when the sealant layers are heat-sealed to each other. Among them, the melting point of the high melting point intermediate layer 9 is higher than the melting point of the first low melting point layer 7 by 25° C. to 35° C., and the melting point of the high melting point intermediate layer 9 is higher than the melting point of the second low melting point layer 8. It is preferable that the temperature is higher by 25°C to 35°C.

The melting point of the first low melting point layer 7 and the melting point of the second low melting point layer 8 are both preferably in the range of 90°C to 140°C.

The thermoplastic resin forming the first low melting point layer 7, the second low melting point layer 8 and the high melting point intermediate layer 9 is not particularly limited, but is preferably a non-stretched film. The thermoplastic resin is not particularly limited, but at least one thermoplastic resin selected from the group consisting of polyethylene, polypropylene, olefin copolymers, acid-modified products thereof and ionomers is used. Is preferred.

Among them, the thermoplastic resin constituting the high melting point intermediate layer 9 is preferably an ethylene-propylene block copolymer resin having a weight average molecular weight of 200,000 to 800,000. In this case, when the sealant layers are heat-sealed to each other, the outflow of the sealant layer at the heat seal portion can be more sufficiently suppressed.

The thermoplastic resin forming the first low melting point layer 7 and the thermoplastic resin forming the second low melting point layer 8 are ethylene-propylene random copolymers having a weight average molecular weight of 10,000 to 200,000. It is preferably a polymer resin. In this case, when the sealant layers are heat-sealed to each other, the seal joining can be performed with more sufficient seal strength. For example, the first low melting point layer 7 is formed of an ethylene-propylene random copolymer resin having a weight average molecular weight of 100,000, and the second low melting point layer 8 is an ethylene-propylene random copolymer having a weight average molecular weight of 70,000. The structure formed of a copolymer resin and the first low melting point layer 7 and the second low melting point layer 8 were both formed of an ethylene-propylene random copolymer resin having a weight average molecular weight of 120,000. The configuration etc. can be illustrated.

Further, it is preferable to adopt a configuration in which the thickness of the first low melting point layer 7 is 0.5 μm or more and the thickness of the second low melting point layer 8 is 1 μm or more, and such a configuration is adopted. In this case, when the sealant layers are heat-sealed to each other, a sufficient seal strength can be secured and the seal joining can be performed. Among them, the thickness of the first low melting point layer 7 is particularly preferably 1 μm to 10 μm. The thickness of the second low melting point layer 8 is particularly preferably 1 μm to 10 μm.

The thickness (total thickness) of the sealant layer 3 is preferably set to 21 μm to 40 μm. When the thickness is 21 μm or more, generation of pinholes can be sufficiently prevented, and when the thickness is 40 μm or less, the amount of resin used can be reduced and the cost can be reduced. Above all, the thickness of the sealant layer 3 is particularly preferably set to 25 μm to 35 μm.

The metal foil layer 4 plays a role of imparting a gas barrier property to the exterior material 1 to prevent oxygen and moisture from entering. The metal foil layer 4 is not particularly limited, but examples thereof include aluminum foil, SUS foil (stainless steel foil), copper foil, and the like, and aluminum foil is generally used. The thickness of the metal foil layer 4 is preferably 10 μm to 100 μm. When it is 10 μm or more, pinholes can be prevented from being generated during rolling when manufacturing a metal foil, and when it is 100 μm or less, stress at the time of forming such as overhang forming and draw forming can be reduced to improve formability. be able to. Above all, the thickness of the metal foil layer 4 is particularly preferably 20 μm to 50 μm.

It is preferable that at least the inner surface (the surface on the inner adhesive layer 6 side) of the metal foil layer 4 is subjected to a chemical conversion treatment. By performing such a chemical conversion treatment, it is possible to sufficiently prevent the corrosion of the surface of the metal foil due to the contents (such as the electrolytic solution of the battery). For example, the metal foil is subjected to chemical conversion treatment by the following treatment. That is, for example, on the surface of the degreased metal foil,
1) phosphoric acid,
Chromic acid,
An aqueous solution of a mixture containing at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides 2) phosphoric acid;
At least one resin selected from the group consisting of acrylic resins, chitosan derivative resins and phenolic resins;
An aqueous solution of a mixture containing at least one compound selected from the group consisting of chromic acid and chromium (III) salts, 3) phosphoric acid, and
At least one resin selected from the group consisting of acrylic resins, chitosan derivative resins and phenolic resins;
At least one compound selected from the group consisting of chromic acid and chromium (III) salts;
Aqueous solution of mixture containing at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides, and applied with an aqueous solution of any one of the above 1) to 3), and then dried. By doing so, chemical conversion treatment is performed.

The conversion coating, chromium coating weight preferably is 0.1mg / m ² ~50mg / m ² as a (per one surface), in particular 2mg / m ² ~20mg / m 2 preferred.

In the present invention, the heat-resistant resin layer 2 is not an essential constituent layer, but the heat-resistant resin layer 2 is laminated on the other surface of the metal foil layer 4 with the outer adhesive layer 5 interposed therebetween. Preferably (see FIG. 1). By providing such a heat-resistant resin layer 2, it is possible to sufficiently secure the insulating property on the other surface side of the metal foil layer 4, and to improve the physical strength and impact resistance of the exterior material 1.

As the heat-resistant resin that constitutes the heat-resistant resin layer (outer layer) 2, a heat-resistant resin that does not melt at the heat-sealing temperature when the exterior material is heat-sealed is used. As the heat-resistant resin, it is preferable to use a heat-resistant resin having a melting point higher than the melting point of the high-melting-point intermediate layer 9 constituting the sealant layer 3 by 10° C. or more, and a melting point higher than the melting point of the high-melting-point intermediate layer 9 by 20° C. or more. It is particularly preferable to use a heat resistant resin having

The heat resistant resin layer (outer layer) 2 is not particularly limited, but examples thereof include polyamide films such as nylon films, polyester films, polyolefin films and the like, and stretched films thereof are preferably used. Among them, as the heat resistant resin layer 2, biaxially stretched polyamide film such as biaxially stretched nylon film, biaxially stretched polybutylene terephthalate (PBT) film, biaxially stretched polyethylene terephthalate (PET) film, biaxially stretched polyethylene It is particularly preferable to use a phthalate (PEN) film or a biaxially oriented polypropylene film. The nylon film is not particularly limited, but examples thereof include 6 nylon film, 6,6 nylon film, MXD nylon film and the like. The heat-resistant resin layer 2 may be formed of a single layer, or may be formed of, for example, a multi-layer composed of a polyester film/a polyamide film (a multi-layer composed of a PET film/nylon film, etc.). Is also good. In the multilayer structure illustrated above, the polyester film is preferably arranged outside the polyamide film, and similarly, the PET film is preferably arranged outside the nylon film.

The heat-resistant resin layer 2 preferably has a thickness of 8 μm to 50 μm. By setting the above preferable lower limit value or more, sufficient strength as an exterior material can be secured, and by setting the above preferable upper limit value or less, stress at the time of forming such as overhang forming and drawing forming can be reduced to improve formability. Can be made. Above all, the thickness of the heat resistant resin layer 2 is particularly preferably 12 μm to 25 μm.

The outer adhesive layer 5 is not particularly limited, but examples thereof include a polyurethane adhesive layer, a polyester polyurethane adhesive layer, and a polyether polyurethane adhesive layer. The thickness of the outer adhesive layer 5 is preferably set to 1 μm to 5 μm. Above all, the thickness of the outer adhesive layer 5 is particularly preferably set to 1 μm to 3 μm from the viewpoint of reducing the thickness and weight of the exterior material.

The inner adhesive layer 6 is not particularly limited, and for example, those exemplified as the outer adhesive layer 5 can be used, but it is preferable to use a polyolefin-based adhesive that is less swelled by an electrolytic solution. preferable. The thickness of the inner adhesive layer 6 is preferably set to 1 μm to 5 μm. Above all, it is particularly preferable that the thickness of the inner adhesive layer 6 is set to 1 μm to 3 μm from the viewpoint of reducing the thickness and weight of the exterior material.

The thickness of the exterior material 1 for an electricity storage device of the present invention is preferably set to 60 μm to 160 μm.

A molding case (battery case or the like) can be obtained by molding (deep-drawing, overhang molding, or the like) the exterior material 1 of the present invention. The exterior material 1 of the present invention can be used as it is without being subjected to molding.

FIG. 2 shows an embodiment of an electricity storage device 20 configured by using the exterior material 1 of the present invention. The electricity storage device 20 is a lithium-ion secondary battery.

The battery 20 includes a bare cell 21 composed of a positive electrode active material, a negative electrode active material, a separator, and an electrolyte, tab leads 22 respectively connected to the positive electrode and the negative electrode, and the planar outer packaging material 1 that is not subjected to molding. And a molding case 11 having a housing recess 11b obtained by molding the exterior material 1 (see FIG. 2). The bare cell 21 and the tab lead 22 form a power storage device body 19.

The bare cell 21 and a part of the tab lead 22 are housed in the housing recess 11b of the molding case 11, the planar exterior material 1 is disposed on the molding case 11, and the peripheral portion of the exterior material 1 ( The inner layer 3) and the sealing peripheral edge 11a (the inner layer 3) of the molding case 11 are joined by heat sealing to form a heat-sealed portion (heat-sealed portion). A (battery) 20 is configured. The tip end of the tab lead 22 is led to the outside (see FIG. 2).

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

<Example 1>
A chemical conversion consisting of phosphoric acid, polyacrylic acid (acrylic resin), chromium (III) salt compound, water, and alcohol on both sides of a 35 μm thick aluminum foil (A8021 annealed aluminum foil specified in JIS H4160) 4. After applying the treatment liquid, it was dried at 180° C. to form a chemical conversion film. The amount of chromium deposited on this chemical conversion coating was 10 mg/m ² per side.

Next, a biaxially stretched 6-nylon film (outer layer) 2 having a thickness of 15 μm was dry-laminated on one surface of the chemical conversion-treated aluminum foil 4 via a two-component curing type urethane adhesive 5 ( Pasted together).

Next, a 4.5 μm thick first low melting point layer 7 made of an ethylene-propylene random copolymer having a melting point of 137° C. (weight average molecular weight of 150,000) and an ethylene-propylene block copolymer having a melting point of 163° C. ( A high melting point intermediate layer 9 having a weight average molecular weight of 600,000 and a thickness of 21 μm, and an ethylene-propylene random copolymer having a melting point of 137° C. (weight average molecular weight of 150,000) and a second thickness of 4.5 μm. The low melting point layer 8 is co-extruded using a T die so that three layers are laminated in this order, and a sealant film having a thickness of 30 μm is formed by laminating these three layers (first low melting point layer 7/high melting point 7). After obtaining the intermediate layer 9/second low melting point layer 8)3, the surface of the first low melting point layer 7 of the sealant film (inner layer) 3 is fixed to a two-component curing type maleic acid-modified polypropylene adhesive (where the curing agent is Polyfunctional isocyanate) 6 is put on the other surface of the aluminum foil 4 after the dry lamination, and the laminate is sandwiched between a rubber nip roll and a laminating roll heated to 100° C. and pressure-bonded to dry laminate. Then, after that, by aging (heating) at 40° C. for 5 days, a packaging material 1 for an electricity storage device having a structure shown in FIG. 1 and a thickness of 86 μm was obtained.

The high melting point intermediate layer (ethylene-propylene block copolymer) will be described in detail. The high melting point intermediate layer has a melting point of 163° C. and a crystal melting energy of 58 J/g. It is formed of a resin composition having a composition of 99% by mass, a melting point of 144° C., and a crystal melting energy of 19 J/g, which is 1% by mass of a second elastomer-modified olefin resin. Each of the first elastomer-modified olefin resin and the second elastomer-modified olefin resin is composed of an elastomer-modified homopolypropylene or/and an elastomer-modified random copolymer. The elastomer-modified random copolymer is an elastomer-modified random copolymer containing propylene and other copolymer components other than propylene as a copolymer component. When only the high melting point intermediate layer was observed by SEM (observation with a scanning electron microscope), it could be confirmed that the high melting point intermediate layer had a sea-island structure in which the elastomer component was an island.

The term "melting point" means a melting peak temperature measured by differential scanning calorimetry (DSC) according to JIS K7121-1987, and the term "crystal melting energy" complies with JIS K7122-1987. And the heat of fusion (crystal fusion energy) measured by differential scanning calorimetry (DSC).

Further, as the two-component curing type maleic acid-modified polypropylene adhesive, 100 parts by mass of maleic acid-modified polypropylene (melting point 80° C., acid value 10 mgKOH/g) as a main agent, hexamethylene diisocyanate isocyanurate as a curing agent (NCO content: 20% by mass) 8 parts by mass, and using an adhesive solution further mixed with a solvent, the adhesive solution is mixed with the aluminum foil 4 so that the solid content coating amount becomes 2 g/m ² . After coating on the other surface and heating and drying, it was laminated on the surface of the first low melting point layer 7 of the sealant film 3.

<Example 2>
As the sealant film, a low-density polyethylene (weight average molecular weight: 80,000) having a melting point of 115° C., a first low melting point layer 7 having a thickness of 3.75 μm, an ethylene-propylene block copolymer having a melting point of 142° C. (weight average molecular weight: A high melting point intermediate layer 9 having a thickness of 22.5 μm and a second low melting point layer 3 having a thickness of 3.75 μm and made of low density polyethylene (having a weight average molecular weight of 80,000) having a melting point of 115° C. Except for using the sealant film 3 having a thickness of 30 μm laminated in this order, an outer casing material 1 for an electricity storage device having a structure shown in FIG. 1 and having a thickness of 86 μm was obtained in the same manner as in Example 1.

<Example 3>
As a sealant film, a first low melting point layer 7 having a thickness of 1.5 μm and made of an ethylene-propylene random copolymer (weight average molecular weight: 120,000) having a melting point of 135° C., an ethylene-propylene block copolymer having a melting point of 161° C. A high-melting-point intermediate layer 9 having a thickness of 27 μm (weight average molecular weight of 500,000) and an ethylene-propylene random copolymer having a melting point of 135° C. (weight average molecular weight of 120,000) having a thickness of 1.5 μm. (2) Except for using the sealant film 3 having a thickness of 30 μm, which is formed by laminating the low melting point layers 8 in this order, the same procedure as in Example 1 was performed. Got

<Example 4>
As the sealant film, a first low melting point layer 7 having a thickness of 6 μm and comprising an ethylene-propylene random copolymer (weight average molecular weight: 150,000) having a melting point of 137° C., an ethylene-propylene block copolymer having a melting point of 163° C. (weight: 21 μm thick high melting point intermediate layer 9 having an average molecular weight of 600,000, and a second low melting point layer 3 μm thick made of an ethylene-propylene random copolymer having a melting point of 137° C. (weight average molecular weight of 150,000). The same procedure as in Example 1 was carried out except that the sealant film 3 having a thickness of 30 μm formed by laminating 8 in this order was used to obtain the exterior material 1 for an electricity storage device having a thickness shown in FIG. 1 and having a thickness of 86 μm.

<Example 5>
As the sealant film, a first low melting point layer 7 having a thickness of 3 μm and made of an ethylene-propylene random copolymer (weight average molecular weight: 150,000) having a melting point of 137° C., an ethylene-propylene block copolymer having a melting point of 163° C. (weight: 21 μm thick high melting point intermediate layer 9 having an average molecular weight of 600,000 and a 6 μm thick second low melting point layer made of an ethylene-propylene random copolymer having a melting point of 137° C. (weight average molecular weight of 150,000). Except for using the sealant film 3 having a thickness of 30 μm formed by laminating 8 in this order, the exterior material 1 for an electricity storage device having a thickness shown in FIG. 1 and having a thickness of 86 μm was obtained in the same manner as in Example 1.

< Reference example >
As a sealant film, a first low melting point layer 7 having a thickness of 4.5 μm and made of an ethylene-propylene random copolymer having a melting point of 137° C. (weight average molecular weight of 150,000); an ethylene-propylene block copolymer having a melting point of 152° C. A high melting point intermediate layer 9 having a thickness (weight average molecular weight of 400,000) of 21 μm and an ethylene-propylene random copolymer having a melting point of 137° C. (weight average molecular weight of 150,000) having a thickness of 4.5 μm. (2) Except for using the sealant film 3 having a thickness of 30 μm, which is formed by laminating the low melting point layers 8 in this order, the same procedure as in Example 1 was performed. Got

<Comparative Example 1>
As the sealant film, a first low melting point layer 7 having a thickness of 10.5 μm and comprising an ethylene-propylene random copolymer having a melting point of 140° C. (weight average molecular weight 140,000), an ethylene-propylene block copolymer having a melting point of 163° C. A high-melting-point intermediate layer 9 having a thickness of 9 μm (having a weight-average molecular weight of 600,000) and an ethylene-propylene random copolymer having a melting point of 140° C. (weight-average molecular weight of 140,000) having a thickness of 10.5 μm. 2 An outer packaging material for an electricity storage device having a thickness of 86 μm was obtained in the same manner as in Example 1 except that the sealant film 3 having a thickness of 30 μm and having the low melting point layer 8 laminated in this order was used.

<Comparative example 2>
As the sealant film, a first low melting point layer having a thickness of 15 μm and comprising an ethylene-propylene random copolymer having a melting point of 140° C. (weight average molecular weight 140,000) and an ethylene-propylene block copolymer having a melting point of 156° C. (weight average A high-melting-point intermediate layer having a molecular weight of 450,000) having a thickness of 15 μm, and a sealant film having a thickness of 30 μm, which are laminated in this order, were used. A device exterior material was obtained. In addition, in the obtained exterior material for an electricity storage device, the first low melting point layer constitutes the outermost layer on the metal foil layer side in the sealant layer.

<Comparative example 3>
As the sealant film, a low-density polyethylene (weight average molecular weight: 80,000) having a melting point of 115° C., a first low melting point layer 7 having a thickness of 10.5 μm, an ethylene-propylene block copolymer having a melting point of 142° C. (weight average molecular weight: In the order of a high melting point intermediate layer 9 having a thickness of 9 μm and a second low melting point layer 8 having a thickness of 10.5 μm and made of low density polyethylene (weight average molecular weight: 80,000) having a melting point of 115° C. In the same manner as in Example 1 except that the sealant film 3 having a thickness of 30 μm laminated in step 1 was used, an outer casing material for an electricity storage device having a thickness of 86 μm was obtained.

Each of the electric storage device exterior materials obtained as described above was evaluated based on the following measurement method. The results are shown in Table 1. In Table 1, X/Y means (thickness of high melting point intermediate layer)/(thickness of sealant layer). Further, in Table 1, the notation “>200 MΩ” for the insulation resistance value indicates that the insulation resistance value is a value larger than 200 MΩ.

<Insulation resistance measurement method>
Two rectangular test pieces with a size of 100 mm in length and 15 mm in width are cut out from the obtained exterior material for an electricity storage device. The pair of test pieces were superposed so that the sealant layers contact each other, and the sealant layers were heat-sealed for 2 seconds under a condition of a seal width of 5 mm and 0.15 MPa with a double-sided heat sealer. In Examples 1, 3 to 6 and Comparative Examples 1 and 2, the heat sealing temperature was set to 180°C, and in Example 2 and Comparative Example 3, the heat sealing temperature was set to 160°C (see Table 1).

Next, a conductive double-sided tape was attached to each of both ends of the test piece in the lengthwise direction to secure electrical continuity with the aluminum foil layer. After forming a circuit by connecting the terminals of the insulation resistance measuring device (manufactured by Hioki Electric Co.; product number HIOKI3154) and the double-sided tapes at both ends in the length direction of the test piece, voltage is applied under the condition of 25V for 5 seconds. Then, the insulation resistance value was measured.

<Seal strength measurement method>
A test piece is obtained by cutting the exterior material into a strip shape having a width of 15 mm and a length of 100 mm. Two test pieces were prepared, and these two test pieces were superposed on each other with their inner layers facing inward, and then heat-sealed on the entire surface over a width of 15 mm to form a heat-sealed portion (heat-sealed portion). ) Was formed. The heat-sealing was performed by using a heat-sealing device (TP-701-A) manufactured by Tester Sangyo Co., Ltd. and heating the one side for 2 seconds at a sealing pressure of 0.2 MPa (gauge display pressure). The heat-sealing temperature was set to 180° C. for the test pieces of Examples 1, 3 to 6 and Comparative Examples 1 and 2, and the heat-sealing temperature was set to 160° C. for the test pieces of Example 2 and Comparative Example 3. Then, heat sealing was performed.

Next, according to JIS Z0238-1998, the peel strength of the two heat-sealed test pieces was measured. Peel strength is measured by chucking both ends of each of the two heat-sealed test pieces, which are unsealed portions, and performing T-shaped peeling (90 degree peeling) at a pulling speed (grip moving speed) of 100 mm/min. This was taken as the sealing strength (N/15 mm width).

As is clear from Table 1, in the exterior materials for electricity storage devices of Examples 1 to 6 according to the present invention, the insulation resistance was a large value, and sufficient insulation could be secured in the heat-sealed portion.

On the other hand, in Comparative Examples 1 and 3 in which X/Y deviates from the specified range of the present invention, and Comparative Example 2 in which the second low melting point layer is not provided, the insulation resistance value is small, and sufficient insulation is obtained. I could not secure.

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

1... Exterior material for electricity storage device 2... Heat-resistant resin layer (outer layer)
3... Sealant layer (inner layer)
4... Metal foil layer 5... Outer adhesive layer 6... Inner adhesive layer 7... First low melting point layer 8... Second low melting point layer 9... High melting point intermediate layer 11... Molding case 19... Electric storage device body 20... Electric storage device

Claims (5)

A packaging material for an electricity storage device, comprising a metal foil layer and a sealant layer laminated on one surface of the metal foil layer,
The sealant layer comprises a first low melting point layer made of a thermoplastic resin forming an outermost layer on the metal foil layer side in the sealant layer, and a heat forming an outermost layer on the side opposite to the metal foil layer side in the sealant layer. A second low melting point layer made of a plastic resin, and a high melting point intermediate layer made of a thermoplastic resin disposed between the first low melting point layer and the second low melting point layer,
The melting point of the high melting point intermediate layer is 120° C. to 180° C.,
The melting point of the first low melting point layer and the melting point of the second low melting point layer are lower than the melting point of the high melting point intermediate layer,
The high melting point intermediate layer has a thickness of 20 μm or more,
When the thickness of the high melting point intermediate layer is "X" and the thickness of the sealant layer is "Y", 0.50Y ≤ X ≤ 0.99Y
There is of the relationship,
The melting point of the high melting point intermediate layer is 25° C. to 35° C. higher than the melting point of the first low melting point layer,
The exterior material for an electricity storage device, wherein the melting point of the high melting point intermediate layer is 25° C. to 35° C. higher than the melting point of the second low melting point layer. The outer packaging material for an electricity storage device according to claim 1, wherein the first low melting point layer has a thickness of 0.5 μm or more, and the second low melting point layer has a thickness of 1 μm or more. The thermoplastic resin constituting the high melting point intermediate layer is an ethylene-propylene block copolymer resin having a weight average molecular weight of 200,000 to 800,000,
The thermoplastic resin forming the first low melting point layer and the thermoplastic resin forming the second low melting point layer are ethylene-propylene random copolymer resins having a weight average molecular weight of 10,000 to 200,000. The exterior material for an electricity storage device according to claim 1 or 2. The exterior material for an electricity storage device according to any one of claims 1 to 3, wherein a heat resistant resin layer is laminated on the other surface of the metal foil layer via an outer adhesive layer. An electricity storage device body,
An exterior material for an electricity storage device according to any one of claims 1 to 4,
An electricity storage device, wherein the electricity storage device body is covered with the exterior material.

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