TW201810764A - Exterior material for power storage device, and power storage device - Google Patents

Abstract

To provide an exterior material for a power storage device, which enables the suppression of outflow of sealant layers in thermally fusing the sealant layers to each other, and which allows an adequate insulating property to be ensured in a thermally sealed part. An exterior material for a power storage device comprises: a metal foil layer 4; and a sealant layer 3 laminated on one face of the metal foil layer. The sealant layer 3 includes: a first low-melting point layer 7 made of a thermoplastic resin and forming an outermost layer on the metal foil layer side; a second low-melting point layer 8 made of a thermoplastic resin and forming an outermost layer on a side opposite to the metal foil layer; and a high-melting point intermediate layer 9 made of a thermoplastic resin and disposed 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 120-180 DEG C. The melting points of the first and second low-melting point layers are lower than that of the high-melting point intermediate layer. The high-melting point intermediate layer 9 has a thickness of 20 [mu]m or more. Supposing that the thickness of the high-melting point intermediate layer 9 is "X", and the thickness of the sealant layer 3 is "Y", the thicknesses are in the following relation: 0.50Y ≤ X ≤ 0.99Y.

Description

Exterior material for power storage device and power storage device

The present invention relates to the storage of batteries or capacitors used in portable devices such as smart phones and tablet computers, hybrid electric vehicles, electric vehicles, wind power generation, solar power generation, and batteries or capacitors used in electric power storage at night. An exterior material for a device and a power storage device that is exteriorized with the exterior material.

In recent years, with the reduction in thickness and weight of portable electric machines such as smart phones and tablet terminals, power storage for lithium-ion batteries, lithium polymer batteries, lithium-ion capacitors, and electric double-layer capacitors mounted on these devices has been carried out. The exterior of the device is currently using a laminated body (laminated exterior) made of a heat-resistant resin layer / adhesive layer / metal foil layer / adhesive layer / thermoplastic resin layer to replace the traditional metal can. (See Patent Document 1). Outer cases of power sources such as electric vehicles, large-scale power sources for storage, capacitors, and the like, which are composed of the above-mentioned laminated body (outer body), are gradually increasing.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2007-161310

However, the above-mentioned conventional technology (external materials described in Patent Document 1) has the following problems. That is, when external batteries are installed, the sealing layers of the external materials are heat-sealed with each other and sealed, but if foreign matter (electrode active material, electrolyte, etc.) adheres to the surface of this sealing layer, there is a heat-sealed portion. The thinned side makes it difficult to ensure sufficient insulation of the heat-sealed portion. In particular, the connecting piece part is easy to be insufficiently insulated, and may cause a short circuit.

The present invention is made in view of the above-mentioned technical background, and an object thereof is to provide an exterior material for a power storage device, which can suppress the outflow of a sealing layer that occurs when the sealing layers are thermally fused to each other, thereby ensuring that the thermally sealed portion has sufficient insulation. And ensure sufficient sealing strength.

To achieve the foregoing object, the present invention provides the following technical means.

[1] An exterior material for a power storage device is an exterior material for a power storage device that includes a metal foil layer and a sealing layer laminated on a surface on one side of the metal foil layer, and is characterized in that the sealing layer includes : The first low melting point layer is made of a thermoplastic resin constituting the outermost layer on the metal foil layer side of the sealing layer; the second low melting point layer is made of the outermost layer on the opposite side to the metal foil layer side of the sealing layer Made of a thermoplastic resin; and a high-melting intermediate layer made of a thermoplastic resin disposed between the first low-melting layer and the second low-melting layer; and the melting point of the high-melting intermediate layer is 120 ° C. ~ 180 ° C; the melting point of the first low-melting layer and the melting point of the second low-melting layer are lower than the melting point of the high-melting intermediate layer; the thickness of the high-melting intermediate layer is 20 μm or more; the foregoing high melting point The thickness of the intermediate layer is "X", and when the thickness of the aforementioned sealing layer is "Y", it satisfies 0.50Y ≦ X ≦ 0.999Y

Related person.

[2] The exterior material for a power storage device according to the item 1, wherein the thickness of the first low-melting layer is 0.5 μm or more, and the thickness of the second low-melting layer is 1 μm or more.

[3] The exterior material for a power storage device according to item 1 or 2, wherein the melting point of the high-melting intermediate layer is 20 ° C or more higher than the melting point of the first low-melting layer, and the melting point of the high-melting intermediate layer is It is 20 ° C or more higher than the melting point of the second low-melting layer.

[4] The exterior material for a power storage device according to any one of items 1 to 3 above, wherein the thermoplastic resin constituting the high-melting intermediate layer has a weight average molecular weight in a range of 200,000 to 800,000. An ethylene-propylene block copolymer resin; and the thermoplastic resin constituting the first low-melting layer and the thermoplastic resin constituting the second low-melting layer, each having a weight average molecular weight in a range of 10,000 to 200,000. Ethylene-propylene random copolymer resin.

[5] The exterior material for a power storage device according to any one of the preceding paragraphs 1 to 4, wherein the other surface of the metal foil layer is laminated with a heat-resistant resin through an outer adhesive layer. Floor.

[6] A power storage device comprising a power storage device body portion and the exterior material for a power storage device according to any one of the preceding items 1 to 5, and the power storage device body portion is provided by the exterior material Outfitters.

According to the invention of [1], since the melting point of the high-melting intermediate layer is 120 ° C to 180 ° C, and a low-melting layer exists outside the high-melting intermediate layer, the high-melting intermediate layer can be suppressed when the sealing layers are thermally fused to each other. The layer flows out from the heat-sealed portion, and since the thickness of the high-melting intermediate layer is 20 μm or more and satisfies the relationship of 0.50Y ≦ X ≦ 0.999Y, the leakage of the sealing layer caused by the heat-sealing of the sealing layers to each other can be suppressed. The thickness is reduced, so that the heat-sealed portion can be sufficiently insulated to sufficiently prevent a short circuit from occurring. In addition, since both sides of the above-mentioned high-melting intermediate layer are provided with a first low-melting layer and a second low-melting layer having a low-melting and low-melting intermediate layer, the sealing layer is high when the sealing layers are thermally fused to each other. The melting point intermediate layer does not melt, and can perform good heat-sealing and hermetic bonding with sufficient sealing strength (to ensure that the heat-sealed portion has sufficient sealing strength).

According to the invention of [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 sealing layers are thermally fused to each other, the sealing strength can be more sufficient. Sealed joint (ensures better sealing strength of the heat-sealed part).

According to the invention of [3], since the melting point of the high-melting intermediate layer is lower than that of the first layer The melting point layer has a higher melting point of 20 ° C or higher, and the melting point of the high-melting intermediate layer is higher than the melting point of the second low-melting layer by 20 ° C or more. Therefore, when the sealing layers are thermally fused to each other, the sealing layer can be sufficiently suppressed from being heat-sealed. The part is flowed out, so that the heat-sealed part can be more fully insulated.

According to the invention of [4], since the thermoplastic resin constituting the high-melting intermediate layer is an ethylene-propylene block copolymer resin having a weight-average molecular weight in a range of 200,000 to 800,000, the sealing layers are melted with each other. At this time, the sealing layer can be more sufficiently prevented from flowing out of the heat-sealed portion, thereby further improving the insulation of the heat-sealed portion. In addition, since the thermoplastic resins constituting the first and second low-melting layers are individually ethylene-propylene random copolymer resins having a weight-average molecular weight in the range of 10,000 to 200,000, the sealing layers are melted with each other. At this time, it is possible to have a further sufficient sealing strength to seal the joint (to ensure that the heat-sealed portion has more sufficient sealing strength).

According to the invention of [5], since the surface on the other side of the metal foil layer is laminated with the heat-resistant resin through the outer adhesive layer, the insulation on the surface side of the other side of the metal foil layer can be sufficiently ensured. Improve the physical strength and impact resistance of exterior materials.

According to the invention (electric storage device) of [6], it is possible to provide a power storage device in which the heat-sealed portion is joined with sufficient sealing strength, and the heat-sealed portion is provided with an exterior material having sufficient insulation properties.

1‧‧‧ Exterior materials for power storage devices

2‧‧‧ heat-resistant resin layer (outer layer)

3‧‧‧Sealing layer (inner layer)

4‧‧‧ metal foil layer

5‧‧‧ outside adhesive layer

6‧‧‧ inside adhesive layer

7‧‧‧The first low melting layer

8‧‧‧ 2nd low melting point layer

9‧‧‧ high-melting intermediate layer

11‧‧‧Shape

19‧‧‧ Power storage device body

20‧‧‧ Power storage device

FIG. 1 is a cross-sectional view showing an embodiment of an exterior material for a power storage device according to the present invention.

[Fig. 2] Shows one of the power storage devices constituted by using the exterior material for a power storage device of the present invention Sectional view of implementation type.

One embodiment of an exterior material 1 for a power storage device according to the present invention is shown in FIG. 1. This exterior material 1 for a power storage device is intended for use as a lithium ion battery case. The exterior material 1 for a power storage device can be formed, for example, by deep-stretch forming, bulging, or the like, and can be used as a battery case or the like. In addition, the said exterior material 1 for electrical storage devices can also be used as a planar exterior material which is not shape | molded (refer FIG. 2).

In this embodiment, the aforementioned exterior material 1 for a power storage device is integrated by laminating a surface on one side of the metal foil layer 4 with an inner adhesive layer 6 and a sealing layer (inner layer) 3, and the aforementioned metal foil is integrated. The surface on the other side of the layer 4 is formed by laminating and integrating the outer adhesive layer 5 and the heat-resistant resin layer (outer layer) 2.

The sealing layer (thermoplastic resin layer) (inner layer) 3 has excellent chemical resistance to a corrosive electrolytic solution used in a lithium-ion battery, and also serves to impart heat-sealing properties to exterior materials.

In the present invention, the sealing layer 3 includes a first low-melting layer 7 made of a thermoplastic resin constituting an outermost layer on the metal foil layer 4 side of the sealing layer 3, and a second low-melting layer 8, It is made of a thermoplastic resin constituting the outermost layer on the side opposite to the metal foil layer side of the sealing layer 3; and a high-melting intermediate layer 9 is disposed on the first low-melting layer 7 and the second low-melting layer 8 It is made of thermoplastic resin (see Figure 1), and the melting point of the high-melting intermediate layer 9 is 120 ° C to 180 ° C, the melting point of the first low-melting layer 7 and the melting point of the second low-melting layer 8 The melting point is lower than the melting point of the high-melting intermediate layer 9 The thickness of the dot intermediate layer is 20 μm or more, and the thickness of the high-melting intermediate layer 9 is “X”, and the thickness of the aforementioned sealing layer 3 is “Y”, which satisfies the relationship of 0.50Y ≦ X ≦ 0.999Y. .

Moreover, in the above-mentioned embodiment, although the sealing layer 3 is a three-layer laminated structure of the first low-melting layer 7 / high-melting intermediate layer 9 / second low-melting layer 8 described above, it is not particularly limited to such a three-layer structure. The laminated structure may be a structure including at least the first low-melting layer 7, the high-melting intermediate layer 9, and the second low-melting layer 8, regardless of a four-layer structure, a five-layer structure, or a six-layer structure. Any of the above laminated structures may be used.

The melting point of the aforementioned high-melting intermediate layer 9 must be 120 ° C to 180 ° C. When the temperature is lower than 120 ° C, the high-melting intermediate layer in the heat-sealed portion also easily flows out when the sealing layers are thermally fused to each other, so it is difficult to ensure that the heat-sealed portion has sufficient insulation. On the other hand, if the melting point exceeds 180 ° C, the sealing temperature for heat-sealing the sealing layers with each other must be extremely high. However, when the sealing temperature is high, the electrolyte is affected by heat and easily decomposed. Among them, the melting point of the high-melting intermediate layer 9 is preferably 150 ° C to 170 ° C. The heat-sealing temperature when the sealing layers are thermally fused to each other is preferably set to a range of + 10 ° C to + 40 ° C relative to the melting point of the high-melting intermediate layer 9.

The thickness of the high-melting intermediate layer 9 must be 20 μm or more. If it is less than 20 μm, the thickness of the sealing layer 3 for ensuring sufficient insulation cannot be maintained (guaranteed) after heat sealing. The thickness of the high-melting intermediate layer 9 is preferably 20 μm to 30 μm. In addition, if the thickness of the high-melting intermediate layer 9 is too large, there is a possibility that the heat conduction during heat sealing is reduced and the sealing cannot be sufficiently sealed. From this viewpoint, the thickness of the high-melting intermediate layer 9 is preferably set to 40 μm or less.

In addition, when the thickness of the high-melting intermediate layer 9 is "X" and the thickness of the sealing layer 3 is "Y", it has a configuration satisfying the relationship of 0.50Y ≦ X ≦ 0.999Y. If the thickness X of the high-melting intermediate layer 9 is less than 50% of the thickness Y of the sealing layer 3, when the sealing layers are thermally fused to each other, the low-melting layer may excessively flow out, which may not fully ensure the insulation portion after heat sealing. Doubts about distance. In addition, if the thickness X of the high-melting-point intermediate layer 9 is more than 99% of the thickness Y of the sealing layer 3, when the sealing layers are thermally fused to each other, there is a problem that sealing joints cannot be performed with sufficient sealing strength. Among them, a structure that satisfies the relationship of 0.60Y ≦ X ≦ 0.90Y is preferred.

The melting point of the high-melting intermediate layer 9 is more than 20 ° C higher than the melting point of the first low-melting layer 7, and the melting point of the high-melting intermediate layer 9 is 20 ° C or more higher than the melting point of the second low-melting layer 8. The composition is better. With such a configuration, when the sealing layers are thermally fused to each other, it is possible to sufficiently suppress the sealing layer 3 from flowing out of the heat-sealed portion. The melting point of the high-melting intermediate layer 9 is 25 ° C to 35 ° C higher than the melting point of the first low-melting layer 7, and the melting point of the high-melting intermediate layer 9 is higher than the melting point of the second low-melting layer 8. A composition with a temperature between 25 ° C and 35 ° C is preferred.

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

The thermoplastic resin forming the first low-melting layer 7, the second low-melting layer 8, and the high-melting intermediate layer 9 is not particularly limited, but is preferably an unstretched film. Although the thermoplastic resin is not particularly limited, it is preferable to use at least one thermoplastic resin selected from the group consisting of polyethylene, polypropylene, and olefin-based copolymers, and acid-denatured products and ionomers thereof.

Among them, the thermoplastic resin constituting the high-melting intermediate layer 9 has a flat weight. An ethylene-propylene block copolymer resin having an average molecular weight in the range of 200,000 to 800,000 is preferable. In this case, when the sealing layers are thermally fused to each other, it is possible to sufficiently suppress the sealing layer from flowing out of the heat-sealed portion.

The thermoplastic resin constituting the first low-melting layer 7 and the thermoplastic resin constituting the second low-melting layer 8 are ethylene-propylene random copolymers having a weight average molecular weight in the range of 10,000 to 200,000. Resin is preferred. In this case, when the sealing layers are thermally fused to each other, the sealing joint can be further sealed with sufficient sealing strength. For example, the first low melting point layer 7 may be 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 may be formed of an ethylene-propylene random copolymer resin having a weight average molecular weight of 70,000. The composition of the propylene random copolymer resin, or the first low-melting layer 7 and the second low-melting layer 8 are each formed of an ethylene-propylene random copolymer resin having a weight average molecular weight of 120,000. The structure and the like are exemplified.

The thickness of the first low-melting layer 7 is 0.5 μm or more, and the thickness of the second low-melting layer 8 is 1 μm or more. In such a configuration, the sealing layers are heat-fused with each other. In this case, it is possible to ensure a sufficient sealing strength and seal the joint. The thickness of the first low-melting layer 7 is particularly preferably 1 μm to 10 μm. The thickness of the second low-melting layer 8 is particularly preferably 1 μm to 10 μm.

The thickness (the entire thickness) of the sealing layer 3 is preferably set to 21 μm to 40 μm. When it is 21 μm or more, the occurrence of pinholes can be fully prevented, and when it is set to 40 μm or less, the amount of resin used can be reduced to achieve cost reduction. The thickness of the sealing layer 3 is particularly preferably set to 25 μm to 35 μm.

The metal foil layer 4 is a gas that imparts to the exterior material 1 to prevent the intrusion of oxygen or moisture. The role of body barrier. The metal foil layer 4 is not particularly limited, and examples thereof include aluminum foil, SUS foil (stainless steel foil), and copper foil. Generally, aluminum foil is used. The thickness of the metal foil layer 4 is preferably 10 μm to 100 μm. 10 μm or more can prevent the occurrence of pinholes in the metal foil during pressure delay, and 100 μm or less can reduce the stress during forming such as bulging and deep forming and improve the formability. 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 chemical conversion treatment. By applying such a chemical conversion treatment, it is possible to sufficiently prevent the corrosion of the surface of the metal foil caused by the contents (the electrolyte of the battery, etc.). For example, the metal foil may be subjected to a chemical conversion treatment by the following treatment. That is, for example, on the surface of a metal foil subjected to degreasing treatment, a chemical treatment is applied after applying an aqueous solution of any one of the following 1) to 3) and then drying: 1) containing phosphoric acid, chromic acid, And a mixture of at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides; 2) containing phosphoric acid, selected from acrylic resins, chitosan derivative resins, and phenol resins; An aqueous solution of a mixture of at least one resin in the group and at least one compound selected from the group consisting of chromic acid and chromium (III) salts. 3) a resin containing phosphoric acid, at least one selected from the group consisting of an acrylic resin, a chitosan derivative resin, and a phenol resin, An aqueous solution of a mixture of at least one compound selected from the group consisting of chromic acid and chromium (III) salts, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides.

In the aforementioned chemical conversion film, the chromium adhesion amount (one side) is preferably 0.1 mg / m ² to 50 mg / m ² , and 2 mg / m ² to 20 mg / m ² is particularly preferred.

In the present invention, the heat-resistant resin layer 2 is not an essential constituent layer, but a structure in which the other surface of the metal foil layer 4 is laminated with the outer adhesive layer 5 and the heat-resistant resin layer 2 is preferable ( (See Figure 1). By providing such a heat-resistant resin layer 2, the insulation on the other side of the metal foil layer 4 can be sufficiently ensured, and the physical strength and impact resistance of the exterior material 1 can be improved.

The heat-resistant resin constituting the heat-resistant resin layer (outer layer) 2 is a heat-resistant resin that does not melt due to the heat-sealing temperature during heat-sealing. The heat-resistant resin is preferably a heat-resistant resin having a high melting point higher than the melting point of the high-melting intermediate layer 9 constituting the sealing layer 3 by 10 ° C or higher, and a resin having a higher melting point of the intermediate layer 9 having a higher melting point by 20 ° C or higher. A high-melting heat-resistant resin is particularly preferred.

The heat-resistant resin layer (outer layer) 2 is not particularly limited, and examples thereof include polyamide films such as nylon films, polyester films, and polyolefin films, and these stretched films can be suitably used. The heat-resistant resin layer 2 is a biaxially stretched polyamide film, a biaxially stretched polybutylene terephthalate (PBT) film, or a biaxially stretched polyterephthalic acid. Ethylene glycol (PET) film, biaxially stretched polyethylene naphthalate (PEN) film, and biaxially stretched polypropylene film are particularly preferred. The nylon film is not particularly limited, and examples thereof include 6 nylon films, 6,6 nylon films, and MXD nylon films. The heat-resistant resin layer 2 may be formed as a single layer, or may be formed, for example, as a multi-layer made of a polyester film / polyamide film (such as a multi-layer made of a PET film / nylon film). In the above-mentioned exemplified multi-layer structure, the polyester film is preferably disposed outside the polyamide film, and similarly, the PET film is disposed outside the nylon film.

The thickness of the heat-resistant resin layer 2 is preferably 8 μm to 50 μm. By setting it above the appropriate lower limit value, sufficient strength can be ensured as an exterior material, and by setting it below the appropriate upper limit value, molding stress such as bulging forming and strand forming can be reduced to improve formability. . 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, and examples thereof include a polyurethane adhesive layer, a polyester polyurethane adhesive layer, a polyether polyurethane adhesive layer, and the like. . The thickness of the outer adhesive layer 5 is preferably set to 1 μm to 5 μm. Among them, from the viewpoint of thinning and reducing the weight of the exterior material, the thickness of the outer adhesive layer 5 is particularly preferably set to 1 μm to 3 μm.

The inner adhesive layer 6 is not particularly limited. For example, the outer adhesive layer 5 may be exemplified as described above. However, it is preferable to use a polyolefin-based adhesive having less swelling due to an electrolytic solution. The thickness of the inner adhesive layer 6 is preferably set to 1 μm to 5 μm. Among them, from the viewpoint of thinning and reducing the weight of the exterior material, the thickness of the inner adhesive layer 6 is particularly preferably set to 1 μm to 3 μm.

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

By forming the exterior material 1 of the present invention (deep drawing, bulging) Etc.) to obtain a molded case (battery case, etc.). The exterior material 1 of the present invention may be used without being formed.

An embodiment of the power storage device 20 constructed using the exterior material 1 of the present invention is shown in FIG. 2. The power storage device 20 is a lithium-ion 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; a tab 22 that is individually connected to the positive electrode and the negative electrode; and the planar exterior material 1 that is not formed. And a molding case 11 in which the exterior material 1 is molded and has a receiving recess 11b (see FIG. 2). The bare cell 21 and the tab 22 constitute a power storage device body portion 19.

A part of the bare cell 21 and the connecting piece 22 are housed in the receiving recess 11 b of the molded case 11, the planar exterior material 1 is arranged on the molded case 11, and a peripheral edge portion of the exterior material 1 (Inner layer 3) and the sealing peripheral portion 11a (inner layer 3) of the molded case 11 are heat-sealed to form a heat-sealed portion (heat-sealed portion), thereby constituting the power storage device (battery) 20 described above. In addition, the tip end portion of the aforementioned tab 22 is led out to the outside (see FIG. 2).

[Example]

Next, specific embodiments of the present invention will be described, but the present invention is not limited to those embodiments.

<Example 1>

Apply a chemical conversion treatment solution containing phosphoric acid, polyacrylic acid (acrylic resin), chromium (III) salt compound, water, and ethanol to both sides of a 35 μm-thick aluminum foil (A8021 burnt aluminum foil specified in JIS H4160). , And dried at 180 ° C. to form a chemical conversion film. The amount of chromium adhered to the formed film was 10 mg / m ^{2 on} one side.

Next, on the side of the aluminum foil 4 that has undergone the chemical conversion treatment, a 2 layer hardened urethane-based adhesive 5 and a biaxially stretched 6 nylon film (outer layer) 2 with a thickness of 15 μm are formed as a dry layer. Press (fit).

Next, the first low-melting layer 7 having a thickness of 4.5 μm formed from an ethylene-propylene random copolymer having a melting point of 137 ° C. (with a weight average molecular weight of 150,000) using a T-type; and an ethylene-propylene block copolymer having a melting point of 163 ° C. Material (weight average molecular weight of 600,000) made of high-melting-point intermediate layer 9 with a thickness of 21 μm; ethylene-propylene random copolymer with a melting point of 137 ° C (weight average molecular weight of 150,000) was the second with a thickness of 4.5 μm The low-melting layer 8 was sequentially co-extruded in 3 layers to obtain these 30-layer sealing films (the first low-melting layer 7 / the high-melting intermediate layer 9 / the second low-melting layer 8) 3. The first low melting point layer 7 of the sealing film (inner layer) 3 is passed through a two-liquid curing type maleic acid-denatured polypropylene adhesive (the curing agent is a polyfunctional isocyanate) 6 and the dry-laminated aluminum foil 4 The other side is overlapped, dry lamination is carried out by sandwiching between a rubber pressure roller and a lamination roller heated to 100 ° C, and then cured at 40 ° C for 5 days (heating) to obtain FIG. 1 The exterior material 1 for a power storage device having a thickness of 86 μm having the structure shown.

The details of the high-melting intermediate layer (ethylene-propylene block copolymer) will be described. The high-melting intermediate layer is composed of 99% by mass of a first elastomer-modified olefin resin and a second elastomer-modified olefin resin. A 1% by mass resin composition is formed, and the melting point of the first elastomer-modified olefin-based resin is 163 ° C and the melting energy of crystal is 58 J / g; the melting point of the second elastomer-modified olefin-based resin is 144 ° C The crystal melting energy is 19 J / g. Either the first elastomer-denatured olefin-based resin or the second elastomer-denatured olefin-based resin is made of an elastomer-modified homopolypropylene or / and an elastomer-modified random copolymer. The aforementioned elastomer-denatured random copolymer refers to an elastomer-denatured body of a random copolymer containing propylene and copolymer components other than propylene. In addition, when only the high-melting intermediate layer was observed by SEM (observation with a scanning electron microscope), it was confirmed that the high-melting intermediate layer had an island structure having an island shape with an elastomer component.

The term "melting point" means the melting peak temperature measured by differential scanning calorimetry (DSC) based on JIS K7121-1987, and the term "crystallization melting energy" means the JIS K7122-1987 As a reference, the heat of fusion (crystal melting energy) measured by differential scanning calorimetry (DSC).

In addition, the aforementioned two-liquid curing type maleic acid modified polypropylene adhesive is used: 100 parts by mass of maleic acid modified polypropylene (melting point 80 ° C, acid value 10 mgKOH / g) as a main agent; Liuya as a curing agent 8 parts by mass of an isocyanurate body of methyl diisocyanate (NCO content rate: 20% by mass); a solvent-containing adhesive solution was further used to make the adhesive solution a solid content, and the coating amount was 2 g / m ² The surface coated on the other side of the aluminum foil 4 is heated and dried, and then overlaps with the first low-melting layer 7 surface of the sealing film 3.

<Example 2>

Except for the sealing film, the first low-melting layer 7 made of low-density polyethylene with a melting point of 115 ° C (weight-average molecular weight of 80,000) is 3.75 μm in thickness; the ethylene-propylene block copolymer having a melting point of 142 ° C (weight High-melting intermediate layer 9 with a thickness of 22.5 μm formed from an average molecular weight of 400,000; Second low-melting layer 8 with a thickness of 3.75 μm from a low-density polyethylene having a melting point of 115 ° C. (80,000 weight average molecular weight) according to Except for the sealing film 3 with a thickness of 30 μm, which was sequentially laminated, the rest was the same as in Example 1, and an exterior material 1 for a power storage device having a thickness of 86 μm and having a structure shown in FIG. 1 was obtained.

<Example 3>

Except for the sealing film, the first low-melting layer 7 having a thickness of 1.5 μm and an ethylene-propylene random copolymer having a melting point of 135 ° C (weight average molecular weight of 120,000); and an ethylene-propylene block copolymer having a melting point of 161 ° C Material (weight average molecular weight of 500,000) formed a high melting point intermediate layer 9 with a thickness of 27 μm; ethylene-propylene random copolymer with a melting point of 135 ° C. (weight average molecular weight of 120,000) formed a second layer with a thickness of 1.5 μm The low-melting-point layer 8 was sequentially laminated except for the sealing film 3 having a thickness of 30 μm, and the rest were the same as those in Example 1, and an exterior material 1 for a power storage device having a thickness of 86 μm and having the structure shown in FIG. 1 was obtained.

<Example 4>

Except for the sealing film, the first low-melting layer 7 having a thickness of 6 μm and 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 ( 21 μm high-melting intermediate layer 9 with a weight average molecular weight of 600,000); ethylene-propylene random copolymer with a melting point of 137 ° C (weight average molecular weight of 150,000) is a second low-melting layer with a thickness of 3 μm 8 Except that the sealing film 3 with a thickness of 30 μm was sequentially laminated, the rest were the same as in Example 1, and an exterior material 1 for a power storage device with a thickness of 86 μm and a structure shown in FIG. 1 was obtained.

<Example 5>

Except for the sealing film, the first low-melting layer 7 having a thickness of 3 μm and an ethylene-propylene random copolymer having a melting point of 137 ° C. (with a weight average molecular weight of 150,000); Weight average molecular weight is 600,00 0) A high-melting intermediate layer 9 having a thickness of 21 μm; a second low-melting layer 8 having a thickness of 6 μm and a thickness of 30 μm sequentially formed from an ethylene-propylene random copolymer having a melting point of 137 ° C. (weight average molecular weight of 150,000) Except for the sealing film 3, everything was the same as in Example 1 to obtain an exterior material 1 for a power storage device having a thickness of 86 μm and a structure shown in FIG. 1.

<Example 6>

Except for the sealing film, the first low-melting layer 7 with a thickness of 4.5 μm formed from an ethylene-propylene random copolymer with a melting point of 137 ° C (weight average molecular weight of 150,000); and an ethylene-propylene block copolymer having a melting point of 152 ° C Material (weight average molecular weight of 400,000) made of high-melting intermediate layer 9 with a thickness of 21 μm; ethylene-propylene random copolymer with a melting point of 137 ° C. (weight average molecular weight of 150,000) was the second with a thickness of 4.5 μm The low-melting-point layer 8 was sequentially laminated except for the sealing film 3 having a thickness of 30 μm, and the rest were the same as those in Example 1, and an exterior material 1 for a power storage device having a thickness of 86 μm and having the structure shown in FIG. 1 was obtained.

<Comparative example 1>

Except for the sealing film, the first low-melting layer 7 having a thickness of 10.5 μm was formed using an ethylene-propylene random copolymer having a melting point of 140 ° C (weight average molecular weight of 140,000); and an ethylene-propylene block copolymer having a melting point of 163 ° C Material (weight average molecular weight of 600,000) made of high-melting-point intermediate layer 9 with a thickness of 9 μm; ethylene-propylene random copolymer with a melting point of 140 ° C. (weight average molecular weight of 140,000) of the second having a thickness of 10.5 μm The low-melting-point layer 8 was sequentially laminated except for the sealing film 3 having a thickness of 30 μm, and the rest were the same as those in Example 1 to obtain an exterior material for a power storage device having a thickness of 86 μm.

<Comparative example 2>

Except for sealing film, ethylene-propylene random copolymerization with melting point of 140 ℃ The first low melting point layer with a thickness of 15 μm formed by a polymer (weight average molecular weight of 140,000); the high melting point intermediate layer with a thickness of 15 μm formed by an ethylene-propylene block copolymer (weight average molecular weight of 450,000) having a melting point of 156 ° C Except that the sealing film with a thickness of 30 μm was sequentially laminated, the rest were the same as in Example 1, and an exterior material for a power storage device with a thickness of 86 μm was obtained. In the obtained exterior material for a storage device, the first low-melting layer constitutes the outermost layer on the metal foil layer side of the sealing layer.

<Comparative example 3>

Except for the sealing film, the first low-melting layer 7 with a thickness of 10.5 μm made of low-density polyethylene (having a weight-average molecular weight of 80,000) having a melting point of 115 ° C; and an ethylene-propylene block copolymer having a melting point of 142 ° C (weight High molecular weight intermediate layer 9 with a thickness of 9 μm formed from an average molecular weight of 400,000; Low density polyethylene with a melting point of 115 ° C (weight average molecular weight of 80,000) formed a second low melting point layer 8 with a thickness of 10.5 μm in order Except for the laminated sealing film 3 having a thickness of 30 μm, the rest were the same as in Example 1 to obtain an exterior material for a power storage device having a thickness of 86 μm.

Each of the obtained exterior materials for power storage devices was evaluated based on the following measurement methods. The results are shown in Table 1. In Table 1, X / Y means (thickness of the high-melting intermediate layer) ÷ (thickness of the sealing layer). In addition, in Table 1, the expression of "> 200MΩ" of the insulation resistance value indicates that the insulation resistance value is larger than 200MΩ.

<Insulation resistance measurement method>

The obtained exterior material for a power storage device was cut into two rectangular test pieces having a size of 100 mm in length × 15 mm in width. The pair of test pieces were brought into contact with each other and the sealing layers were overlapped, and a heat seal of a double-sided heating type was used to heat-seal the sealing layers with each other for 2 seconds under the conditions of a sealing width of 5 mm and 0.15 MPa. In addition, in Examples 1, 3 to 6, and Comparative Examples 1, 2, the heat-sealing temperature was set to 180 ° C, and the heat-sealing temperatures of Example 2 and Comparative Example 3 were set to 160 ° C (see Table 1).

Next, a conductive double-sided tape was individually attached to both ends in the longitudinal direction of the test piece to ensure conduction with the aluminum foil layer. The terminals of the insulation resistance measuring device (manufactured by Hitachi Denki Co., Ltd .; HIOKI3154) and the two-sided tape on both ends of the test piece in the longitudinal direction are connected to form a circuit, and a voltage is applied at 25V for 5 seconds to measure. Insulation resistance value.

<Seal strength measurement method>

The exterior material was cut into a booklet shape having a width of 15 mm × a length of 100 mm to obtain a test piece. Two test pieces were prepared, and the inner layers of these two test pieces were placed inside and overlapped each other, and then they were heat-sealed across a width of 15 mm to form a heat-sealed portion (heat-sealed portion). The heat sealing is performed by using a heat sealing device (TP-701-A) manufactured by Tester Industries Co., Ltd. and heating at one side with a sealing pressure of 0.2 MPa (indicator pressure) for 2 seconds. In addition, for the test pieces of Examples 1, 3 to 6, and Comparative Examples 1, 2, the heat seal temperature was set to 180 ° C, and for the test pieces of Example 2 and Comparative Example 3, the heat seal temperature was set to 160 ° C. seal.

Next, using the JIS Z0238-1998 as a reference, the peel strength was measured for the two test pieces in which the heat sealing was completed. The two test pieces that were heat-sealed were fixed at both ends of the individual unsealed portions, and T-peeled (90-degree peeled) at a tensile speed (clamping moving speed) of 100 mm / minute to measure the peel strength. This was taken as the sealing strength (N / 15mm width).

It is clear from Table 1 that the insulation resistance value of the exterior materials for power storage devices according to Examples 1 to 6 of the present invention is a relatively large value, which can ensure that the heat-sealed portion has sufficient insulation.

In contrast, in Comparative Examples 1, 3 in which X / Y deviates from the specified range of the present invention, and Comparative Example 2 without a second low-melting layer, the insulation resistance value of either is small, and sufficient insulation cannot be secured. .

[Industrial availability]

As a specific example, the exterior material for a power storage device of the present invention can be used, for example:

‧Power storage devices such as lithium batteries (lithium ion batteries, lithium polymer batteries, etc.)

‧Lithium ion capacitor

‧Double layer capacitor

And other external storage materials. The power storage device of the present invention includes an all-solid-state battery in addition to the power storage device exemplified above.

This application is accompanied by the date of application on April 21, 2016 The priority claim No. 2016-85436 of this patent application, the disclosure of which directly constitutes a part of this application.

The terms and descriptions used herein are used to describe embodiments of the present invention, but the present invention is not limited thereto. Any equivalents of the characteristic matters disclosed and described in the present invention should not be excluded, and various modifications within the scope claimed by the present invention should also be understood as acceptable.

1‧‧‧ Exterior materials for power storage devices

2‧‧‧ heat-resistant resin layer (outer layer)

3‧‧‧Sealing layer (inner layer)

4‧‧‧ metal foil layer

5‧‧‧ outside adhesive layer

6‧‧‧ inside adhesive layer

7‧‧‧The first low melting layer

8‧‧‧ 2nd low melting point layer

9‧‧‧ high-melting intermediate layer

Claims (6)

An exterior material for a power storage device is an exterior material for a power storage device including a metal foil layer and a sealing layer laminated on a surface on one side of the metal foil layer, characterized in that the aforementioned sealing layer includes: the first The low melting point layer is made of a thermoplastic resin constituting the outermost layer on the metal foil layer side of the sealing layer; the second low melting point layer is made of the thermoplasticity constituting the outermost layer on the opposite side to the metal foil layer side of the sealing layer Made of resin; and a high-melting intermediate layer made of a thermoplastic resin disposed between the first low-melting layer and the second low-melting layer; and the melting point of the high-melting intermediate layer is 120 ° C to 180 ° C ; The melting point of the first low-melting layer and the melting point of the second low-melting layer are lower than the melting point of the high-melting intermediate layer; the thickness of the high-melting intermediate layer is 20 μm or more; When the thickness is "X" and the thickness of the aforementioned sealing layer is "Y", it is a relationship that satisfies 0.50Y ≦ X ≦ 0.999Y. The exterior material for a power storage device according to item 1 of the scope of the patent application, wherein 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. The exterior material for a power storage device according to item 1 or 2 of the scope of the patent application, wherein the melting point of the high-melting intermediate layer is 20 ° C or more higher than the melting point of the first low-melting layer, and the melting point of the high-melting intermediate layer is The melting point is 20 ° C or more higher than the melting point of the second low-melting layer. The exterior material for a power storage device as described in item 1 or 2 of the scope of patent application, wherein The thermoplastic resin of the high-melting intermediate layer is an ethylene-propylene block copolymer resin having a weight average molecular weight in the range of 200,000 to 800,000; and the thermoplastic resin constituting the first low-melting layer and the foregoing first 2 The thermoplastic resin of the low melting point layer is an ethylene-propylene random copolymer resin having a weight average molecular weight in the range of 10,000 to 200,000. The exterior material for a power storage device according to item 1 or 2 of the scope of patent application, wherein the other surface of the metal foil layer is laminated with an outer adhesive layer and a heat-resistant resin. A power storage device comprising a power storage device main body and an exterior material for a power storage device described in any one of claims 1 to 5 of the scope of patent application, and the power storage device main body is provided by the exterior material Outfitters.