CN117136458A

CN117136458A - Outer packaging material for electric storage device, method for producing same, and electric storage device

Info

Publication number: CN117136458A
Application number: CN202280026614.XA
Authority: CN
Inventors: 村泽宪
Original assignee: Dai Nippon Printing Co Ltd
Current assignee: Dai Nippon Printing Co Ltd
Priority date: 2021-04-02
Filing date: 2022-03-28
Publication date: 2023-11-28

Abstract

An exterior material for an electric storage device, which comprises a laminate comprising at least a base layer, a barrier layer, and a thermally fusible resin layer in this order, wherein the thermally fusible resin layer has a molecular weight of 15 ten thousand or more at the peak of a differential molecular weight distribution curve measured by high-temperature gel permeation chromatography.

Description

Outer packaging material for electric storage device, method for producing same, and electric storage device

Technical Field

The present invention relates to an exterior material for an electric storage device, a method for producing the same, and an electric storage device.

Background

Various types of power storage devices have been developed in the past, but in all of the power storage devices, an exterior material is an indispensable component for sealing power storage device elements such as electrodes and electrolytes. Conventionally, as an exterior material for a power storage device, a metal exterior material has been used in many cases.

On the other hand, in recent years, with the increase in performance of electric vehicles, hybrid electric vehicles, personal computers, video cameras, cellular phones, and the like, various shapes are demanded for power storage devices, and thinning and weight saving are demanded. However, conventionally used outer packaging materials for power storage devices made of metal have had drawbacks in that it is difficult to cope with the diversification of shapes, and weight reduction is limited.

Therefore, conventionally, as an exterior material for an electric storage device which is easily processed into various shapes and can be thinned and reduced in weight, a film-like laminate in which a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer are laminated in this order has been proposed (for example, refer to patent document 1).

In such an exterior material for power storage devices, a recess is generally formed by cold rolling, a power storage device element such as an electrode or an electrolyte is disposed in a space formed by the recess, and a heat-fusible resin layer is heat-fused to obtain a power storage device in which the power storage device element is housed inside the exterior material for power storage devices.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2008-287971

Patent document 2: japanese patent laid-open No. 2002-8616

Disclosure of Invention

Technical problem to be solved by the invention

In recent years, with the high-speed and large-capacity data communication of smart phones, the amount of consumed power has also increased, and the increase in capacity of power storage devices has been studied. However, the increase in capacity of the battery is accompanied by an increase in the size of the container and an increase in the reactive substance, and the amount of gas generated when the power storage device is thermally out of control (i.e., the height Wen Huashi of the power storage device) is also increased, which increases the risk of explosion associated with an increase in the internal pressure of the power storage device. In an electric storage device (for example, a metal can battery) using a metal outer package, safety at the time of gas generation is ensured by attaching a safety valve (see patent document 2).

However, in the case of an electric storage device using a laminated film-like outer packaging material, it is difficult to install such a safety valve, and it is difficult to avoid a problem of expansion of the electric storage device due to gas generated inside the electric storage device that becomes high temperature.

As a method of avoiding expansion of the power storage device due to gas generated inside the power storage device at a high temperature, it is conceivable to design the melting point of the resin used to form the heat-fusible resin layer to be low so as to be easily unsealed from the position of the heat-fusible resin layer. In addition, there is an advantage in that the time taken for the step of heat-sealing the heat-sealable resin layer can be shortened by lowering the melting point of the resin used to form the heat-sealable resin layer.

However, since the power storage device is exposed to high temperature (for example, about 100 ℃) due to heating in the baking step in the manufacturing step of the power storage device, when the melting point of the resin for forming the heat-fusible resin layer is lowered, there is a possibility that the outer packaging material for the power storage device is unsealed by heat and generated gas in the baking step, which is a stable region (110 ℃ or less) where the battery does not start thermal runaway.

Under such circumstances, a main object of the present invention is to provide an exterior material for an electric storage device, which is composed of a laminate comprising at least a base layer, a barrier layer, and a heat-fusible resin layer in this order, wherein the electric storage device can be sealed with the exterior material for an electric storage device before reaching a high temperature (for example, about 100 ℃).

Means for solving the technical problems

The present inventors have conducted intensive studies to solve the above-described problems. As a result, it has been found that an exterior material for an electric storage device, which is composed of at least a laminate comprising a base layer, a barrier layer, and a thermally fusible resin layer in this order, and which has a differential molecular weight distribution curve (a differential molecular weight distribution curve having a molecular weight (logarithmic value) as the horizontal axis and a concentration fraction of molecular weight as the vertical axis) measured by high-temperature gel permeation chromatography of the thermally fusible resin layer, has a peak molecular weight of 15 ten thousand or more, can be suitably sealed before the electric storage device reaches a high temperature (for example, about 100 ℃).

The present invention has been completed based on these findings by further repeated studies. That is, the present invention provides the following aspects.

The present invention also provides the following aspects.

An exterior material for an electric storage device, which comprises a laminate comprising at least a base layer, a barrier layer, and a heat-fusible resin layer in this order, wherein the Vickers hardness measured by pressing a Vickers indenter from the surface of the exterior material for an electric storage device on the heat-fusible resin layer side in the thickness direction to a depth of 1 [ mu ] m is 10.0MPa or more at a measurement temperature of 100 ℃ based on an indentation method.

Effects of the invention

The present invention can provide an exterior material for an electric storage device, which is composed of a laminate comprising at least a base layer, a barrier layer, and a heat-fusible resin layer in this order, and which can suitably seal an electric storage device element before the electric storage device reaches a high temperature (for example, about 100 ℃). Further, according to the present invention, a method for producing an exterior material for an electric storage device and an electric storage device can be provided.

Drawings

Fig. 1 is a schematic view showing an example of a cross-sectional structure of an exterior material for a power storage device according to the present invention.

Fig. 2 is a schematic diagram showing an example of a cross-sectional structure of the outer package material for a power storage device according to the present invention.

Fig. 3 is a schematic view showing an example of a cross-sectional structure of the outer package material for a power storage device according to the present invention.

Fig. 4 is a schematic view for explaining a method of housing an electric storage device element in a package formed of the outer packaging material for an electric storage device of the present invention.

Fig. 5 is a schematic diagram for explaining a measurement method of heat seal strength.

Fig. 6 is a schematic diagram for explaining a measurement method of heat seal strength.

Fig. 7 is a schematic diagram for explaining a measurement method of the softening point.

FIG. 8 is a schematic representation of a differential molecular weight distribution curve.

Detailed Description

The outer packaging material for the power storage device is characterized by comprising a laminate body which at least comprises a base material layer, a barrier layer and a heat-fusible resin layer in sequence, wherein the molecular weight of the peak value of a differential molecular weight distribution curve measured by using high-temperature gel permeation chromatography of the heat-fusible resin layer is more than 15 ten thousand. By providing this feature, the exterior material for an electric storage device according to the present invention can adequately seal the electric storage device element before the electric storage device reaches a high temperature (for example, about 100 ℃).

The present invention also provides an exterior material for an electric storage device, which comprises a laminate including at least a base layer, a barrier layer, and a heat-fusible resin layer in this order, wherein a vickers indenter is pressed from a surface of the exterior material for an electric storage device on the heat-fusible resin layer side to a depth of 1 [ mu ] m in the thickness direction at a measurement temperature of 100 ℃ by an indentation method, and wherein the hardness of 10.0MPa or more is measured. The exterior material for power storage devices can also suitably seal the power storage device element before the power storage device reaches a high temperature (for example, about 100 ℃). In the exterior material for an electric storage device, the peak molecular weight of the differential molecular weight distribution curve measured by high temperature gel permeation chromatography of the heat-fusible resin layer is not required to be 15 ten thousand or more, and preferably 15 ten thousand or more. In the following description, the exterior material for an electric storage device is the same as the exterior material for an electric storage device of the present invention described above in which the molecular weight of the peak of the differential molecular weight distribution curve measured by high temperature gel permeation chromatography of the heat-fusible resin layer is 15 ten thousand or more, except that the molecular weight of the peak of the differential molecular weight distribution curve measured by high temperature gel permeation chromatography of the heat-fusible resin layer is not necessarily 15 ten thousand or more, and therefore, a detailed description thereof is omitted.

Hereinafter, the exterior material for a power storage device according to the present invention will be described in detail. In the present invention, the numerical range indicated by "to" means "above" and "below". For example, the expression of 2 to 15mm means 2mm to 15 mm.

In addition, in the exterior material for the power storage device, the barrier layer 3 described later can be generally distinguished between MD (Machine Direction: machine direction, longitudinal direction) and TD (Transverse Direction: transverse direction) during the production process. For example, when the barrier layer 3 is made of a metal foil such as an aluminum alloy foil or a stainless steel foil, linear streaks called rolling marks are formed on the surface of the metal foil in the rolling direction (RD: rolling Direction) of the metal foil. Since the rolling mark extends along the rolling direction, the rolling direction of the metal foil can be grasped by observing the surface of the metal foil. Further, in the process of manufacturing the laminate, since the MD of the laminate is generally identical to the RD of the metal foil, the MD of the laminate can be determined by observing the surface of the metal foil of the laminate to determine the Rolling Direction (RD) of the metal foil. Further, the TD of the laminate is perpendicular to the MD of the laminate, and thus the TD of the laminate can be determined.

In addition, when the MD of the exterior material for the power storage device cannot be determined by using the rolling marks of the metal foil such as the aluminum alloy foil or the stainless steel foil, the MD can be determined by the following method. As a method for confirming MD of the exterior material for the power storage device, there is a method for confirming island structure by observing a cross section of the heat-fusible resin layer of the exterior material for the power storage device with an electron microscope. In this method, the MD can be determined as a direction parallel to a cross section where the average value of the diameters of the island shapes in the direction perpendicular to the thickness direction of the heat-fusible resin layer is largest. Specifically, the island structure was confirmed by observation of each of the cross section in the longitudinal direction of the heat-fusible resin layer and each of the cross sections (total 10 cross sections) from the direction parallel to the cross section in the longitudinal direction, each of which was changed by an angle of 10 degrees to the direction perpendicular to the cross section in the longitudinal direction, by electron microscopic photographs. Next, the shape of each island was observed in each section. For each island shape, a straight line distance connecting the leftmost end in the direction perpendicular to the thickness direction of the heat-fusible resin layer and the rightmost end in the perpendicular direction is set as a diameter y. In each section, the average value of the first 20 diameters y is calculated in order of the diameter y of the island shape from large to small. The direction parallel to the cross section where the average value of the diameter y of the island shape is largest is determined as MD.

1. Laminate structure and physical properties of exterior material for power storage device

As shown in fig. 1 to 3, for example, the exterior material 10 for a power storage device of the present invention is composed of a laminate including at least a base material layer 1, a barrier layer 3, and a heat-fusible resin layer 4 in this order. In the exterior material 10 for an electric storage device, the base material layer 1 is the outermost layer side, and the heat-fusible resin layer 4 is the innermost layer. When the power storage device is assembled using the power storage device exterior material 10 and the power storage device element, the power storage device element is housed in a space formed by thermally welding the peripheral edge portions in a state where the thermally-weldable resin layers 4 of the power storage device exterior material 10 are opposed to each other. In the laminate constituting the exterior material 10 for a power storage device of the present invention, the heat-fusible resin layer 4 is located further inside than the barrier layer 3, and the base material layer 1 is located further outside than the barrier layer 3, with reference to the barrier layer 3.

As shown in fig. 2 and 3, for example, the outer packaging material 10 for the power storage device may have an adhesive layer 2 between the base layer 1 and the barrier layer 3, if necessary, for the purpose of improving adhesion between these layers, or the like. As shown in fig. 2 and 3, an adhesive layer 5 may be provided between the barrier layer 3 and the heat-fusible resin layer 4 as needed for the purpose of improving the adhesion between these layers. As shown in fig. 3, a surface coating layer 6 or the like may be provided on the outer side (the side opposite to the heat-fusible resin layer 4) of the base material layer 1 as needed.

The thickness of the laminate constituting the exterior material 10 for a power storage device is not particularly limited, and may be, for example, about 190 μm or less, preferably about 180 μm or less, about 155 μm or less, or about 120 μm or less, from the viewpoints of cost reduction, energy density improvement, and the like. The thickness of the laminate constituting the exterior material 10 for electric storage devices is preferably about 35 μm or more, about 45 μm or more, or about 60 μm or more from the viewpoint of maintaining the function of the exterior material for electric storage devices in protecting the electric storage device elements. Further, preferable ranges of the laminate constituting the exterior material 10 for a power storage device include, for example, about 35 to 190 μm, about 35 to 180 μm, about 35 to 155 μm, about 35 to 120 μm, about 45 to 190 μm, about 45 to 180 μm, about 45 to 155 μm, about 45 to 120 μm, about 60 to 190 μm, about 60 to 180 μm, about 60 to 155 μm, about 60 to 120 μm, and particularly about 60 to 155 μm.

In the exterior material 10 for an electric storage device, the ratio of the total thickness of the base material layer 1, the adhesive layer 2, the barrier layer 3, the adhesive layer 5, the heat-fusible resin layer 4, and the surface covering layer 6, which are provided as needed, to the thickness (total thickness) of the laminate constituting the exterior material 10 for an electric storage device is preferably 90% or more, more preferably 95% or more, and still more preferably 98% or more. As a specific example, in the case where the exterior material 10 for an electric storage device according to the present invention includes the base material layer 1, the adhesive layer 2, the barrier layer 3, the adhesive layer 5, and the heat-fusible resin layer 4, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the exterior material 10 for an electric storage device is preferably 90% or more, more preferably 95% or more, and still more preferably 98% or more.

From the standpoint of more suitably exhibiting the effects of the present invention, the heat seal strength of the outer package for an electric storage device of the present invention is preferably about 50N/15mm or more, more preferably about 60N/15mm or more, and even more preferably about 70N/15mm or more at a measurement temperature of 100℃in the measurement of the heat seal strength described later. From the same viewpoint, the heat seal strength is preferably about 100N/15mm or less, more preferably about 90N/15mm or less. The preferable range of the heat seal strength is about 50 to 100N/15mm, about 50 to 90N/15mm, about 60 to 100N/15mm, about 60 to 90N/15mm, about 70 to 100N/15mm, about 70 to 90N/15 mm.

In the outer packaging material for an electric storage device of the present invention, the heat seal strength at a measurement temperature of 110℃is preferably about 35N/15mm or more, more preferably about 40N/15mm or more, and still more preferably about 50N/15mm or more, in terms of more suitably exhibiting the effects of the present invention, in the measurement of the heat seal strength described later. From the same viewpoint, the heat seal strength is preferably about 80N/15mm or less, more preferably about 75N/15mm or less, and still more preferably about 70N/15mm or less. The preferable range of the heat seal strength is about 35 to 80N/15mm, about 35 to 75N/15mm, about 35 to 70N/15mm, about 40 to 80N/15mm, about 40 to 75N/15mm, about 40 to 70N/15mm, about 50 to 80N/15mm, about 50 to 75N/15mm, about 50 to 70N/15 mm.

In the case of measuring the heat seal strength of the outer package for an electric storage device of the present invention, which will be described later, the heat seal strength at a measurement temperature of 120℃is preferably about 2N/15mm or more, more preferably about 5N/15mm or more, and still more preferably about 10N/15mm or less, from the viewpoint of more suitably exhibiting the effects of the present invention. From the same viewpoint, the heat seal strength is preferably about 70N/15mm or less, more preferably about 60N/15mm or less. The preferable range of the heat seal strength is about 2 to 70N/15mm, about 2 to 60N/15mm, about 5 to 70N/15mm, about 5 to 60N/15mm, about 10 to 70N/15mm, about 10 to 60N/15 mm.

The measurement method of the heat seal strength is as follows.

(measurement of Heat seal Strength)

According to JIS K7127:1999, the heat seal strength was measured at each measured temperature (sample temperature) (e.g., 25 ℃, 100 ℃, 110 ℃, 120 ℃). As a test piece, an outer package for an electric storage device cut into a long strip shape having a width of 15mm in the TD direction was prepared. Specifically, as shown in fig. 5, first, the exterior material for the power storage device is cut into pieces of 60mm (TD direction) ×200mm (MD direction) (a of fig. 5). Next, the outer package material for the power storage device is folded in half in the MD direction at the position of the crease P (middle in the MD direction) so that the heat-fusible resin layers face each other (b in fig. 5). The heat-sealable resin layers were heat-sealed to each other at a seal width of 7mm, a temperature of 190℃and a surface pressure of 1.0MPa for 3 seconds on the inner side in the MD direction about 10mm from the crease P (c in FIG. 5). In fig. 5 c, the hatched portion S is a heat-sealed portion. Next, the sample was cut in the MD direction (cut at the position of the two-dot chain line in d in fig. 5) so that the width in the TD direction was 15mm, and a measurement sample was obtained (e in fig. 5). Next, the measurement sample 13 was left at each measurement temperature for 2 minutes, and the heat-sealable resin layer of the heat-sealed portion (heat-sealed portion) was peeled off at a speed of 300 mm/min in each measurement temperature environment by a tensile tester (for example, AG-Xplus (trade name) manufactured by shimadzu corporation) (fig. 6). The maximum strength at peeling was taken as the heat seal strength (N/15 mm). The distance between chucks was 50mm. Specific examples are shown in the examples.

From the viewpoint of more suitably exhibiting the effects of the present invention, the vickers hardness measured by pressing the vickers indenter from the surface of the heat-fusible resin layer 4 side of the outer packaging material 10 for a power storage device of the present invention to a depth of 1 μm in the thickness direction at a measurement temperature (sample temperature) of 100 ℃ based on the indentation method is preferably 10.0MPa or more, more preferably 11.0MPa or more, and still more preferably 12.0MPa or more. From the same viewpoint, the mahalanobis hardness is preferably 25.0MPa or less, more preferably 20.0MPa or less. Preferable ranges of the Marsh hardness include about 10.0 to 25.0MPa, about 10.0 to 20.0MPa, about 11.0 to 25.0MPa, about 11.0 to 20.0MPa, about 12.0 to 25.0MPa, and about 12.0 to 20.0 MPa. By setting the mahalanobis hardness at 100 ℃ to the above range, even when the internal pressure starts to rise due to the generation of gas from the inside of the power storage device by heat, the heat-fusible resin layer is less likely to move, and opening at an unexpected temperature can be prevented, and opening of the exterior material for the power storage device due to gas generated by heating in a baking step in the manufacturing process of the power storage device can be more appropriately prevented. The method for measuring the hardness of Martin is as follows.

(measurement of Martin hardness)

The vickers indenter was pressed to a depth of 1 μm in the thickness direction from the surface of the heat-fusible resin layer side of the exterior material for the power storage device at a measurement temperature (sample temperature) of 100 ℃ based on the indentation method, and the mahalanobis hardness was measured. The measurement conditions are as follows. The mahalanobis hardness is calculated from the load-displacement curve obtained by pressing in the vickers indenter. As the measurement value, an average value obtained for the surface 10 on the heat-fusible resin layer side was used. Marsh hardness by calculating the surface area A (mm) of the indenter at the maximum indentation depth of the Vickers indenter ² ) And dividing the maximum load F (N) by the surface area A (mm) ² ) (F/A) and the result was obtained. As the measuring device, for example, PICODENTER HM-500 manufactured by Fischer Instruments is used. For example, a measurement sample was prepared by bonding an exterior material for an electric storage device to one surface of a slide glass (76 mm. Times.26 mm. Times.1 mm) to which a double-sided adhesive tape was attached so that the side of the heat-fusible resin layer was the opposite side of the slide glass. Next, a heating table was set on the ultra-fine durometer equipped with the vickers indenter, the table temperature was set to 110 ℃, and the sample was heated for 5 minutes. Next, the surface hardness of the surface of the measurement sample on the heat-fusible resin layer side was measured.

< measurement Condition >)

Pressure head: vickers hardness (face angle 136 degree of front end portion of rectangular pyramid)

Measurement temperature (sample temperature): 100 DEG C

Table temperature: 110 DEG C

Speed: 1.000 μm/10 seconds

Depth of measurement: 1.0 μm

Hold time: 5 seconds

Speed of recovery from indentation: 1.000 μm/10 seconds

2. Layers forming an exterior material for an electric storage device

[ substrate layer 1]

In the present invention, the base material layer 1 is a layer provided for the purpose of functioning as a base material of an outer package material for an electric storage device, and the like. The base material layer 1 is located on the outer layer side of the outer package material for the power storage device.

The material for forming the base material layer 1 is not particularly limited, as long as it has a function as a base material, that is, at least insulation property. The base material layer 1 may be formed using, for example, a resin, and the resin may contain additives described later.

When the base material layer 1 is formed of a resin, the base material layer 1 may be a resin film formed of a resin, or may be formed by coating a resin. The resin film may be an unstretched film or a stretched film. The stretched film may be a uniaxially stretched film or a biaxially stretched film, and is preferably a biaxially stretched film. Examples of the stretching method for forming the biaxially stretched film include a sequential biaxial stretching method, a inflation method, and a simultaneous biaxial stretching method. Examples of the method for coating the resin include a roll coating method, a gravure coating method, and an extrusion coating method.

Examples of the resin forming the base layer 1 include resins such as polyesters, polyamides, polyolefins, epoxy resins, acrylic resins, fluorine resins, polyurethanes, silicone resins, and phenolic resins, and modified products of these resins. The resin forming the base layer 1 may be a copolymer of these resins or a modified product of the copolymer. In addition, a mixture of these resins may be used.

Among these, the resin forming the base material layer 1 is preferably polyester or polyamide.

Specific examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolyesters. Further, as the copolyester, a copolyester having ethylene terephthalate as a main unit, and the like can be mentioned. Specifically, there may be mentioned: a copolymer polyester obtained by polymerizing a main body of a repeating unit of ethylene terephthalate and ethylene isophthalate (hereinafter referred to simply as poly (terephthalic acid/isophthalic acid) ethylene ester), poly (terephthalic acid/adipic acid) ethylene ester, poly (terephthalic acid/sodium sulfoisophthalate) ethylene ester, poly (terephthalic acid/sodium isophthalate) ethylene ester, poly (terephthalic acid/phenyl-dicarboxylic acid) ethylene ester, poly (terephthalic acid/decanedicarboxylic acid) ethylene ester, and the like. These polyesters may be used alone or in combination of 1 or more than 2.

Specific examples of the polyamide include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; polyamides containing an aromatic group such as hexamethylenediamine-isophthalic acid-terephthalic acid copolyamide (such as nylon 6I, nylon 6T, nylon 6IT, nylon 6I6T (I represents isophthalic acid, T represents terephthalic acid)) and polyamide MXD6 (poly (m-xylylene adipamide)) containing structural units derived from terephthalic acid and/or isophthalic acid; alicyclic polyamides such as polyamide PACM6 (poly (4-aminocyclohexyl) methane adipoamide); polyamide obtained by copolymerizing a lactam component or an isocyanate component such as 4,4' -diphenylmethane-diisocyanate, and a polyester amide copolymer and a polyether ester amide copolymer which are copolymers of a copolyamide and a polyester or a polyalkylene ether glycol; polyamides such as copolymers thereof. These polyamides may be used alone or in combination of 1 or more than 2.

The substrate layer 1 preferably contains at least 1 of a polyester film, a polyamide film, and a polyolefin film, preferably contains at least 1 of a stretched polyester film, a stretched polyamide film, and a stretched polyolefin film, further preferably contains at least 1 of a stretched polyethylene terephthalate film, a stretched polybutylene terephthalate film, a stretched nylon film, and a stretched polypropylene film, further preferably contains at least 1 of a biaxially stretched polyethylene terephthalate film, a biaxially stretched polybutylene terephthalate film, a biaxially stretched nylon film, and a biaxially stretched polypropylene film.

The base material layer 1 may be a single layer or may be composed of 2 or more layers. When the base material layer 1 is composed of 2 or more layers, the base material layer 1 may be a laminate in which resin films are laminated with an adhesive or the like, or may be a laminate in which resin films are formed by coextrusion of 2 or more layers. The laminate of 2 or more resin films obtained by coextrusion of the resins may be used as the base layer 1 in an unstretched state, or may be uniaxially stretched or biaxially stretched to be used as the base layer 1.

Specific examples of the laminate of 2 or more resin films in the base layer 1 include a laminate of a polyester film and a nylon film, a laminate of 2 or more nylon films, a laminate of 2 or more polyester films, and the like, and a laminate of a stretched nylon film and a stretched polyester film, a laminate of 2 or more stretched nylon films, and a laminate of 2 or more stretched polyester films are preferable. For example, when the base material layer 1 is a laminate of 2 resin films, a laminate of a polyester resin film and a polyester resin film, a laminate of a polyamide resin film and a polyamide resin film, or a laminate of a polyester resin film and a polyamide resin film is preferable, and a laminate of a polyethylene terephthalate film and a polyethylene terephthalate film, a laminate of a nylon film and a nylon film, or a laminate of a polyethylene terephthalate film and a nylon film is more preferable. Further, since the polyester resin is less likely to be discolored when the electrolyte is adhered to the surface, for example, in the case where the base layer 1 is a laminate of 2 or more resin films, it is preferable that the polyester resin film is located at the outermost layer of the base layer 1.

In the case where the base material layer 1 is a laminate of 2 or more resin films, the 2 or more resin films may be laminated via an adhesive. The preferable adhesive is the same as the adhesive exemplified in the adhesive layer 2 described later. The method for laminating 2 or more resin films is not particularly limited, and known methods may be used, and examples thereof include a dry lamination method, a sandwich lamination method, an extrusion lamination method, and a thermal lamination method, and a dry lamination method is preferable. When the lamination is performed by a dry lamination method, a urethane adhesive is preferably used as the adhesive. In this case, the thickness of the adhesive may be, for example, about 2 to 5. Mu.m. In addition, an anchor coat layer may be formed and laminated on the resin film. The anchor coat layer may be the same as the adhesive exemplified in the adhesive layer 2 described later. In this case, the thickness of the anchor coat layer may be, for example, about 0.01 to 1.0. Mu.m.

In addition, additives such as lubricants, flame retardants, antiblocking agents, antioxidants, light stabilizers, tackifiers, antistatic agents, and the like may be present in at least one of the surface and the interior of the substrate layer 1. The additive may be used in an amount of 1 or 2 or more.

In the present invention, it is preferable that a lubricant is present on the surface of the base material layer 1 from the viewpoint of improving the formability of the exterior material for an electric storage device. The lubricant is not particularly limited, and an amide-based lubricant is preferable. Specific examples of the amide-based lubricant include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Specific examples of the saturated fatty acid amide include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of the unsaturated fatty acid amide include oleic acid amide and erucic acid amide. Specific examples of the substituted amide include N-oleyl palmitoyl amide, N-stearyl stearoyl amide, N-stearyl oleamide, N-oleyl stearoyl amide, and N-stearyl erucic amide. Specific examples of the methylol amide include methylol stearic acid amide and the like. Specific examples of the saturated fatty acid bisamide include methylene bisstearamide, ethylene bisdecanoamide, ethylene bislauramide, ethylene bisstearamide, ethylene bishydroxystearamide, ethylene bisbehenamide, hexamethylene bisstearamide, hexamethylene bisbehenamide, hexamethylene hydroxystearamide, N '-distearyl adipic acid amide, N' -distearyl sebacic acid amide and the like. Specific examples of the unsaturated fatty acid bisamide include ethylene bis-oleamide, ethylene bis-erucamide, hexamethylene bis-oleamide, N '-dioleyladipamide, and N, N' -dioleylsebacamide. Specific examples of the fatty acid ester amide include ethyl stearamide stearate and the like. Specific examples of the aromatic bisamide include m-xylylene bisstearamide, m-xylylene bishydroxystearamide, and N, N' -distearyl isophthalic acid amide. The lubricant may be used alone or in combination of 1 or more than 2.

In the case where a lubricant is present on the surface of the base material layer 1, the amount thereof is not particularly limited, and may be preferably about 3mg/m ² The above, more preferably 4 to 15mg/m ² About, more preferably 5 to 14mg/m ² Left and right.

The lubricant present on the surface of the base material layer 1 may be a lubricant obtained by bleeding out a lubricant contained in a resin constituting the base material layer 1, or may be a lubricant obtained by coating the surface of the base material layer 1.

The thickness of the base material layer 1 is not particularly limited as long as it can function as a base material, and examples thereof include about 3 to 50 μm, preferably about 10 to 35 μm. In the case where the base layer 1 is a laminate of 2 or more resin films, the thickness of each resin film constituting each layer is preferably about 2 to 25 μm.

[ adhesive layer 2]

In the outer packaging material for an electric storage device of the present invention, the adhesive layer 2 is a layer provided between the base layer 1 and the barrier layer 3 as needed in order to improve the adhesion therebetween.

The adhesive layer 2 is formed of an adhesive capable of adhering the base material layer 1 to the barrier layer 3. The adhesive used for forming the adhesive layer 2 is not limited, and may be any of a chemical reaction type, a solvent evaporation type, a hot melt type, a hot press type, and the like. The resin may be a two-part curable adhesive (two-part adhesive), a one-part curable adhesive (one-part adhesive), or a resin that does not undergo a curing reaction. The adhesive layer 2 may be a single layer or a plurality of layers.

Specific examples of the adhesive component contained in the adhesive include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolyesters; polyether; polyurethane; an epoxy resin; a phenolic resin; polyamides such as nylon 6, nylon 66, nylon 12, and copolyamide; polyolefin resins such as polyolefin, cyclic polyolefin, acid-modified polyolefin, and acid-modified cyclic polyolefin; polyvinyl acetate; cellulose; (meth) acrylic resin; polyimide; a polycarbonate; amino resins such as urea resin and melamine resin; chloroprene rubber, nitrile rubber, styrene-butadiene rubber, and other rubbers; silicone resins, and the like. These adhesive components may be used alone or in combination of at least 2. Among these adhesive components, polyurethane adhesives are preferable. In addition, these resins as the adhesive component may be used in combination with an appropriate curing agent to improve the adhesive strength. The curing agent may be selected from a polyisocyanate, a polyfunctional epoxy resin, an oxazoline group-containing polymer, a polyamine resin, an acid anhydride, and the like, as appropriate, depending on the functional group of the adhesive component.

Examples of the polyurethane adhesive include polyurethane adhesives containing the 1 st agent containing a polyol compound and the 2 nd agent containing an isocyanate compound. Preferably, a two-part curable polyurethane adhesive containing a polyol such as a polyester polyol, a polyether polyol, and an acrylic polyol as the 1 st agent and an aromatic or aliphatic polyisocyanate as the 2 nd agent is used. Further, examples of the urethane adhesive include urethane adhesives containing a urethane compound and an isocyanate compound, which are obtained by reacting a polyol compound with an isocyanate compound in advance. Further, examples of the urethane adhesive include a urethane adhesive containing a urethane compound obtained by reacting a polyol compound with an isocyanate compound in advance and a polyol compound. Examples of the urethane adhesive include urethane adhesives obtained by reacting a urethane compound obtained by previously reacting a polyol compound with an isocyanate compound with moisture such as air and curing the resultant. As the polyol compound, a polyester polyol having a hydroxyl group in a side chain in addition to the hydroxyl group at the terminal of the repeating unit is preferably used. The 2 nd agent may be an aliphatic, alicyclic, aromatic or araliphatic isocyanate compound. Examples of the isocyanate compound include Hexamethylene Diisocyanate (HDI), xylylene Diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6 XDI), hydrogenated MDI (H12 MDI), toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and Naphthalene Diisocyanate (NDI). Further, there may be mentioned 1 or 2 or more kinds of polyfunctional isocyanate-modified products derived from these diisocyanates. In addition, as the polyisocyanate compound, a polymer (for example, a trimer) may be used. Such polymers include adducts, biurets, and allophanates. Since the adhesive layer 2 is formed of the urethane adhesive, excellent electrolyte resistance can be imparted to the exterior material for the power storage device, and even if the electrolyte adheres to the side surface, peeling of the base material layer 1 can be suppressed.

The adhesive layer 2 may contain a colorant, a thermoplastic elastomer, a thickener, a filler, and the like, as long as the adhesion is not impaired, and other components may be added thereto. The outer packaging material for the power storage device can be colored by containing the colorant in the adhesive layer 2. As the colorant, known colorants such as pigments and dyes can be used. In addition, 1 kind of colorant may be used alone, or 2 or more kinds may be used in combination.

The type of pigment is not particularly limited as long as the adhesiveness of the adhesive layer 2 is not impaired. Examples of the organic pigment include pigments such as azo, phthalocyanine, quinacridone, anthraquinone, dioxazine, indigo thioindigo, viol-perylene, isoindoline, and benzimidazolone, examples of the inorganic pigment include pigments such as carbon black, titanium oxide, cadmium, lead, chromium oxide, and iron, and examples of the inorganic pigment include fine mica (mica) powder and fish scale foil.

Among the colorants, carbon black is preferable, for example, for making the appearance of the exterior material for the power storage device black.

The average particle diameter of the pigment is not particularly limited, and examples thereof include about 0.05 to 5. Mu.m, preferably about 0.08 to 2. Mu.m. Wherein the average particle diameter of the pigment is the median particle diameter measured by a laser diffraction/scattering type particle diameter distribution measuring device.

The content of the pigment in the adhesive layer 2 is not particularly limited as long as the exterior material for the power storage device can be colored, and may be, for example, about 5 to 60 mass%, preferably 10 to 40 mass%.

The thickness of the adhesive layer 2 is not particularly limited as long as it can bond the base material layer 1 and the barrier layer 3, and is, for example, about 1 μm or more and about 2 μm or more. The thickness of the adhesive layer 2 is, for example, about 10 μm or less and about 5 μm or less. The preferable range of the thickness of the adhesive layer 2 is about 1 to 10 μm, about 1 to 5 μm, about 2 to 10 μm, and about 2 to 5 μm.

[ coloring layer ]

The colored layer is a layer (not shown) provided between the base material layer 1 and the barrier layer 3 as needed. In the case of having the adhesive layer 2, a coloring layer may be provided between the base material layer 1 and the adhesive layer 2 and between the adhesive layer 2 and the barrier layer 3. Further, a coloring layer may be provided on the outer side of the base material layer 1. By providing the coloring layer, the exterior material for the power storage device can be colored.

The colored layer can be formed, for example, by applying an ink containing a colorant to the surface of the base material layer 1 or the surface of the barrier layer 3. As the colorant, known colorants such as pigments and dyes can be used. In addition, 1 kind of colorant may be used alone, or 2 or more kinds may be used in combination.

Specific examples of the colorant contained in the coloring layer include the same colorant as the colorant described in the item [ adhesive layer 2 ].

[ Barrier layer 3]

In the exterior material for the power storage device, the barrier layer 3 is a layer that inhibits at least the penetration of moisture.

Examples of the barrier layer 3 include a metal foil, a vapor deposited film, and a resin layer having barrier properties. Examples of the vapor-deposited film include metal vapor-deposited films, inorganic oxide vapor-deposited films, carbon-containing inorganic oxide vapor-deposited films, and the like, and examples of the resin layer include fluorine-containing resins such as polyvinylidene chloride, polymers containing Chlorotrifluoroethylene (CTFE) as a main component, polymers containing Tetrafluoroethylene (TFE) as a main component, polymers having fluoroalkyl groups, and polymers containing fluoroalkyl units as a main component, and ethylene-vinyl alcohol copolymers. The barrier layer 3 may be a resin film provided with at least 1 layer of these vapor deposited films and resin layers. The barrier layer 3 may be provided in multiple layers. The barrier layer 3 preferably comprises a layer composed of a metallic material. The metal material constituting the barrier layer 3 may be, specifically, an aluminum alloy, stainless steel, titanium steel, or steel sheet, and when used as a metal foil, it is preferable to include at least one of an aluminum alloy foil and a stainless steel foil.

The aluminum alloy foil is more preferably a soft aluminum alloy foil composed of an annealed aluminum alloy or the like, for example, from the viewpoint of improving the formability of the exterior material for the power storage device, and an aluminum alloy foil containing iron is preferable from the viewpoint of further improving the formability. In the aluminum alloy foil (100 mass%) containing iron, the content of iron is preferably 0.1 to 9.0 mass%, more preferably 0.5 to 2.0 mass%. By setting the iron content to 0.1 mass% or more, an exterior material for an electric storage device having more excellent formability can be obtained. By setting the iron content to 9.0 mass% or less, an outer package for a power storage device having more excellent flexibility can be obtained. Examples of the soft aluminum alloy foil include those having JIS H4160:1994A8021H-O, JIS H4160:1994A8079H-O, JIS H4000:2014A8021P-O or JIS H4000:2014A 8079P-O. Silicon, magnesium, copper, manganese, and the like may be added as necessary. The softening can be performed by annealing or the like.

Examples of the stainless steel foil include austenitic stainless steel foils, ferritic stainless steel foils, martensitic stainless steel foils, and precipitation hardening stainless steel foils. From the viewpoint of providing an exterior material for a power storage device having more excellent formability, the stainless steel foil is preferably made of austenitic stainless steel.

Specific examples of austenitic stainless steel constituting the stainless steel foil include SUS304, SUS301, SUS316L, and the like, and among these, SUS304 is particularly preferred.

In the case of the metal foil, the thickness of the barrier layer 3 may be, for example, about 9 to 200 μm as long as it can function as a barrier layer that at least inhibits the penetration of moisture. The thickness of the barrier layer 3 is preferably about 85 μm or less, more preferably about 50 μm or less, further preferably about 40 μm or less, and particularly preferably about 35 μm or less. The thickness of the barrier layer 3 is preferably about 10 μm or more, more preferably about 20 μm or more, and even more preferably about 25 μm or more. The preferable range of the thickness of the barrier layer 3 includes about 10 to 85 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 35 μm, about 20 to 85 μm, about 20 to 50 μm, about 20 to 40 μm, about 20 to 35 μm, about 25 to 85 μm, about 25 to 50 μm, about 25 to 40 μm, and about 25 to 35 μm. In the case where the barrier layer 3 is made of an aluminum alloy foil, the above-described range is particularly preferable. In particular, when the barrier layer 3 is made of a stainless steel foil, the thickness of the stainless steel foil is preferably about 60 μm or less, more preferably about 50 μm or less, still more preferably about 40 μm or less, still more preferably about 30 μm or less, and particularly preferably about 25 μm or less. The thickness of the stainless steel foil is preferably about 10 μm or more, more preferably about 15 μm or more. The preferable range of the thickness of the stainless steel foil is about 10 to 60. Mu.m, about 10 to 50. Mu.m, about 10 to 40. Mu.m, about 10 to 30. Mu.m, about 10 to 25. Mu.m, about 15 to 60. Mu.m, about 15 to 50. Mu.m, about 15 to 40. Mu.m, about 15 to 30. Mu.m, and about 15 to 25. Mu.m.

In addition, when the barrier layer 3 is a metal foil, it is preferable that at least the surface opposite to the base layer has a corrosion-resistant film for preventing dissolution, corrosion, and the like. The barrier layer 3 may have a corrosion-resistant film on both sides. Here, the corrosion-resistant film is a film obtained by subjecting the surface of the barrier layer to a hot water modification treatment such as boehmite treatment, a chemical conversion treatment, an anodic oxidation treatment, a plating treatment such as nickel or chromium, or an anticorrosive treatment with a coating agent to impart corrosion resistance (for example, acid resistance, alkali resistance, etc.) to the barrier layer. The corrosion-resistant film specifically refers to a film that improves the acid resistance of the barrier layer (acid-resistant film), a film that improves the alkali resistance of the barrier layer (alkali-resistant film), and the like. As the treatment for forming the corrosion-resistant film, 1 kind may be performed, or 2 or more kinds may be performed in combination. In addition, it is also possible to build up a plurality of layers instead of just 1 layer. Among these treatments, the hot water modification treatment and the anodic oxidation treatment are treatments in which the surface of the metal foil is dissolved by a treating agent to form a metal compound excellent in corrosion resistance. In addition, these treatments are sometimes included in the definition of chemical conversion treatment. In addition, in the case where the barrier layer 3 has a corrosion-resistant film, the corrosion-resistant film is included as the barrier layer 3.

The corrosion-resistant film can exhibit the following effects when molded into an exterior material for an electric storage device: the separation (degradation) between the barrier layer (for example, aluminum alloy foil) and the base material layer is prevented, and dissolution and corrosion of the surface of the barrier layer due to hydrogen fluoride generated by the reaction of the electrolyte and moisture are prevented, and particularly, in the case where the barrier layer is aluminum alloy foil, dissolution and corrosion of alumina present on the surface of the barrier layer are prevented, and the adhesiveness (wettability) of the surface of the barrier layer is improved, and delamination of the base material layer and the barrier layer at the time of heat sealing and delamination of the base material layer and the barrier layer at the time of molding are prevented.

As the corrosion-resistant film formed by the chemical conversion treatment, various corrosion-resistant films are known, and mainly, corrosion-resistant films containing at least 1 of phosphate, chromate, fluoride, triazinethiol compound, and rare earth oxide, and the like are exemplified. Examples of the chemical conversion treatment using phosphate or chromate include chromate treatment, phosphate-chromate treatment, and examples of the chromium compound used in these treatments include chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium hydrogen phosphate, chromic acid acetoacetate, chromium chloride, and potassium chromium sulfate. The phosphorus compounds used in these treatments include sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphoric acid. Examples of the chromate treatment include etching chromate treatment, electrolytic chromate treatment, and coating chromate treatment is preferable. The coating type chromate treatment is as follows: first, a surface of at least an inner layer side of a barrier layer (for example, an aluminum alloy foil) is subjected to degreasing treatment by a known treatment method such as an alkali dipping method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or an acid activation method, and then a treatment liquid containing a metal phosphate such as Cr (chromium) salt, ti (titanium) phosphate, zr (zirconium) phosphate, zn (zinc) phosphate, or a mixture of a non-metal phosphate and a non-metal salt, or a treatment liquid composed of a mixture of these non-metal salts and a synthetic resin, or the like is coated on the degreased treatment surface by a known coating method such as a roll coating method, a gravure printing method, or an immersion method, and dried. For example, various solvents such as water, alcohol solvents, hydrocarbon solvents, ketone solvents, ester solvents, and ether solvents can be used as the treatment liquid, and water is preferable. The resin component used in this case may be a polymer such as a phenol resin or an acrylic resin, or a chromate treatment using an aminated phenolic polymer having a repeating unit represented by the following general formulae (1) to (4). In the aminated phenol polymer, 1 or 2 or more kinds of repeating units represented by the following general formulae (1) to (4) may be contained alone or in any combination. The acrylic resin is preferably polyacrylic acid, acrylic acid methacrylate copolymer, acrylic acid maleic acid copolymer, acrylic styrene copolymer or their derivatives such as sodium salt, ammonium salt, amine salt, etc. Particularly preferred are derivatives of polyacrylic acid such as ammonium salts, sodium salts, or amine salts of polyacrylic acid. In the present invention, polyacrylic acid refers to a polymer of acrylic acid. The acrylic resin is also preferably a copolymer of acrylic acid and a dicarboxylic acid or dicarboxylic anhydride, and is also preferably an ammonium salt, sodium salt or amine salt of a copolymer of acrylic acid and a dicarboxylic acid or dicarboxylic anhydride. The acrylic resin may be used in an amount of 1 or 2 or more.

In the general formulae (1) to (4), X represents a hydrogen atom, a hydroxyl group, an alkyl group, a hydroxyalkyl group, an allyl group or a benzyl group. In addition, R ¹ And R is ² Each identical or different, represents a hydroxyl group, an alkyl group or a hydroxyalkyl group. In the general formulae (1) to (4), X, R is ¹ And R is ² Examples of the alkyl group include straight-chain or branched alkyl groups having 1 to 4 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl. In addition, as X, R ¹ And R is ² Examples of the hydroxyalkyl group include straight-chain or branched alkyl groups having 1 to 4 carbon atoms, in which 1 hydroxyl group is substituted, such as hydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl, 1-hydroxypropyl, 2-hydroxypropyl, 3-hydroxypropyl, 1-hydroxybutyl, 2-hydroxybutyl, 3-hydroxybutyl, and 4-hydroxybutyl. X, R in the general formulae (1) to (4) ¹ And R is ² The alkyl and hydroxyalkyl groups shown may be the same or different from each other. In the general formulae (1) to (4), X is preferably a hydrogen atom, a hydroxyl group or a hydroxyalkyl group. The number average molecular weight of the aminated phenol polymer having the repeating units represented by the general formulae (1) to (4) is, for example, preferably about 500 to 100 ten thousand, more preferably about 1000 to 2 ten thousand. The aminated phenol polymer can be produced, for example, by polycondensing a phenol compound or a naphthol compound with formaldehyde to produce a polymer comprising a repeating unit represented by the above general formula (1) or general formula (3), followed by using formaldehyde and an amine (R) ¹ R ² NH) functional group (-CH) ₂ NR ¹ R ² ) Is introduced into the polymer obtained above. The aminated phenolic polymer may be used alone or in combination of 1 or more than 2 kinds.

As another example of the corrosion-resistant film, a film formed by a coating type corrosion-resistant treatment by coating a coating agent containing at least 1 kind selected from rare earth element oxide sol, anionic polymer, and cationic polymer is given. The coating agent may further comprise phosphoric acid or phosphate, and a crosslinking agent for crosslinking the polymer. In the rare earth element oxide sol, microparticles (for example, particles having an average particle diameter of 100nm or less) of the rare earth element oxide are dispersed in a liquid dispersion medium. Examples of the rare earth element oxide include cerium oxide, yttrium oxide, neodymium oxide, lanthanum oxide, and the like, and cerium oxide is preferable from the viewpoint of further improving adhesion. The rare earth element oxide contained in the corrosion-resistant film may be used alone or in combination of 1 or more than 2. As the liquid dispersion medium of the rare earth element oxide sol, various solvents such as water, alcohol solvents, hydrocarbon solvents, ketone solvents, ester solvents, ether solvents, and the like can be used, and water is preferable. Examples of the cationic polymer include polyethyleneimine, an ionic polymer complex composed of polyethyleneimine and a polymer having a carboxylic acid, a primary amine-grafted acrylic resin having a primary amine grafted and polymerized on an acrylic main skeleton, polyallylamine or a derivative thereof, and an aminated phenol. The anionic polymer is preferably poly (meth) acrylic acid or a salt thereof, or a copolymer containing (meth) acrylic acid or a salt thereof as a main component. The crosslinking agent is preferably at least 1 kind selected from the group consisting of a compound having any one of an isocyanate group, a glycidyl group, a carboxyl group, and an oxazoline group, and a silane coupling agent. The phosphoric acid or phosphate is preferably a condensed phosphoric acid or a condensed phosphate.

As an example of the corrosion-resistant film, a corrosion-resistant film formed by applying a material in which microparticles of metal oxides such as aluminum oxide, titanium oxide, cerium oxide, and tin oxide and barium sulfate are dispersed in phosphoric acid to the surface of the barrier layer, and performing a sintering treatment at 150 ℃.

The corrosion-resistant film may be formed in a laminated structure in which at least one of a cationic polymer and an anionic polymer is further laminated as necessary. Examples of the cationic polymer and the anionic polymer include those described above.

The composition of the corrosion-resistant film can be analyzed by, for example, time-of-flight secondary ion mass spectrometry.

The amount of the corrosion-resistant film formed on the surface of the barrier layer 3 in the chemical conversion treatment is not particularly limited, for example, in the case of performing the coating type chromate treatmentIn this case, it is preferable that the barrier layer 3 is formed every 1m ² On the surface, the content ratio of the chromic acid compound is, for example, about 0.5 to 50mg, preferably about 1.0 to 40mg in terms of chromium, the content ratio of the phosphorus compound is, for example, about 0.5 to 50mg, preferably about 1.0 to 40mg in terms of phosphorus, and the content ratio of the aminated phenolic polymer is, for example, about 1.0 to 200mg, preferably about 5.0 to 150 mg.

The thickness of the corrosion-resistant film is not particularly limited, and from the viewpoints of the cohesive force of the film and the adhesive force with the barrier layer or the heat-fusible resin layer, it is preferably about 1nm to 20. Mu.m, more preferably about 1nm to 100nm, and still more preferably about 1nm to 50 nm. The thickness of the corrosion-resistant film can be measured by observation with a transmission electron microscope or by a combination of observation with a transmission electron microscope and energy-dispersive X-ray spectrometry or electron beam energy loss spectrometry. By analysis of the composition of the corrosion-resistant film using time-of-flight secondary ion mass spectrometry, secondary ions (e.g., ce ₂ PO ₄ ⁺ 、CePO ₄ ^- Etc.), for example, secondary ions composed of Cr, P and O (e.g., crPO ₂ ⁺ 、CrPO ₄ ^- At least 1) of the above, etc.).

The chemical conversion treatment may be performed as follows: the solution containing the compound for forming the corrosion-resistant film is applied to the surface of the barrier layer by a bar coating method, a roll coating method, a gravure coating method, a dipping method, or the like, and then heated so that the temperature of the barrier layer becomes about 70 to 200 ℃. The barrier layer may be subjected to degreasing treatment by an alkali dipping method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or the like, before the chemical conversion treatment is performed on the barrier layer. By performing the degreasing treatment in this way, the chemical conversion treatment of the surface of the barrier layer can be performed more efficiently. In addition, by using an acid degreasing agent obtained by dissolving a fluorine-containing compound with an inorganic acid in the degreasing treatment, not only the degreasing effect of the metal foil but also the formation of a passive metal fluoride can be performed, and in such a case, only the degreasing treatment can be performed.

[ Heat-fusible resin layer 4]

In the exterior material for an electric storage device according to the present invention, the heat-fusible resin layer 4 corresponds to the innermost layer, and is a layer (sealing layer) that functions to seal the electric storage device element by heat-fusing the heat-fusible resin layers to each other when the electric storage device is assembled.

In the present invention, the molecular weight of the peak of the differential molecular weight distribution curve measured by high temperature gel permeation chromatography (the molecular weight obtained by differentiating the concentration fraction by the logarithmic value of the molecular weight) of the heat-fusible resin layer 4 is 15.0 ten thousand or more. From the viewpoint of further suitably exhibiting the effects of the present invention, the molecular weight is preferably about 16.0 ten thousand or more, more preferably about 16.5 ten thousand or more, and even more preferably about 17.0 ten thousand or more. The molecular weight is, for example, about 25.0 ten thousand or less, about 22.0 ten thousand or less, about 20.0 ten thousand or less, 19.8 ten thousand or less, or the like. The preferred range of molecular weights is 15.0 to 25.0 Mo Zuo, 15.0 to 22.0 Mo Zuo, 15.0 to 20.0 Mo Zuo, 15.0 to 19.8 Mo Zuo, 16.0 to 25.0 Mo Zuo, 16.0 to 22.0 Mo Zuo, 16.0 to 20.0 Mo Zuo, 16.0 to 19.8 Mo Zuo, 16.5 to 25.0 Mo Zuo, 16.5 to 22.0 Mo Zuo, 16.5 to 20.0 Mo Zuo, 16.5 to 19.8 Mo Zuo, 17.0 to 25.0 Mo Zuo, 17.0 to 22.0 Mo Zuo, 17.0 to 20.0 Mo Zuo, 17.0 to 19.8 Mo Zuo. By setting the molecular weight to about 15.0 ten thousand or more, the power storage device can be sealed more appropriately with the outer packaging material for the power storage device before the power storage device reaches a high temperature (for example, about 100 ℃). In addition, as characteristics concerning the molecular weight of the resin, a number average molecular weight (Mn), a weight average molecular weight (Mw), mw/Mn, and the like are often used. However, as a result of the studies by the inventors of the present invention, no clear correlation was found between the case where the power storage device could be sealed appropriately with the power storage device exterior material and the case where the power storage device could not be sealed appropriately with the power storage device exterior material. As in the present invention, a clear correlation was found between the peak of the differential molecular weight distribution curve and the sealability.

(measurement of molecular weight at peak of differential molecular weight distribution curve)

The heat-fusible resin layer was obtained as a measurement sample from the exterior material for the power storage device. For each measurement sample, the concentration fractions of each molecular weight were sequentially accumulated using high temperature gel permeation chromatography (for example, SSC-7120HT-GPC System manufactured by high temperature GPC, sensoScientific Co.) under the following measurement conditions, and an integrated molecular weight distribution curve was obtained. A differential molecular weight distribution curve is obtained by obtaining differential values of curves at respective molecular weights, and a molecular weight having a peak value of a vertical axis (concentration fraction: dw/d (Log (M))) is obtained. As shown in the schematic diagram of fig. 8, the differential molecular weight distribution curve is a graph in which the horizontal axis represents the molecular weight and the vertical axis represents the value obtained by differentiating the concentration fraction by the logarithmic value of the molecular weight. The molecular weight at the position where the concentration fraction is highest, which is obtained by differentiating the concentration fraction by the logarithmic value of the molecular weight, is the molecular weight of the peak of the differentiated molecular weight distribution curve (refer to the position of P in fig. 8).

< measurement Condition >)

(pretreatment)

The measurement sample was dissolved with a solvent (o-dichlorobenzene at 145 ℃).

The resulting solution was allowed to stand for 1 hour and stirred for another 1 hour.

Next, the solution was pressure-filtered with a membrane filter having a filter pore size of 1.0 μm and 0.5. Mu.m.

(measurement)

By the pretreatment, a sample obtained by dissolving a measurement sample in a solvent (o-dichlorobenzene) was prepared, and a differential molecular weight distribution curve was obtained by high temperature gel permeation chromatography (SSC-7120 HT-GPC System manufactured by high temperature GPC, sensoScientific Co.). The sample was injected in an amount of 300. Mu.L, the column was HT-G, the column temperature was 145℃and the mobile phase was o-dichlorobenzene (containing 0.025% by mass of BHT (butylated hydroxytoluene)), the flow rate was 1.0mL/min, the detector was a differential refractometer, the molecular weight was corrected as polystyrene, and the molecular weight range of the object was 1,000 ～ 20,000,000.

In the present invention, the TL value of the heat-fusible resin layer 4 described below is preferably 2.80 or less, more preferably 2.50 or less, and even more preferably 2.00 or less. The lower limit of the TL value described below is 1.00 or more. The TL value of the heat-fusible resin layer 4 is small, and thus, a curve from the concentration fraction of the highest molecular weight to the concentration fraction of the low molecular weight (specifically, 12 ten thousand molecular weight) resin in the resin contained in the heat-fusible resin layer 4 becomes gentle, and there is an advantage that when the outer package material for power storage devices of the size used for each power storage device is cut out from the outer package material for power storage devices of a large area, variation in heat sealing strength of the outer package material for each power storage device is small.

< calculation of TL value >)

In the above (measurement of the molecular weight of the peak of the differential molecular weight distribution curve), in the differential molecular weight distribution curve having the molecular weight (logarithmic value) as the horizontal axis and the concentration fraction of the molecular weight as the vertical axis, a value (referred to as TL value) obtained by dividing the concentration fraction of the molecular weight having the concentration fraction of the peak by the concentration fraction of the molecular weight 12 ten thousand lower than the molecular weight having the concentration fraction of the peak is calculated. That is, the TL value is calculated by the following formula.

TL value = (concentration fraction of molecular weight at peak value)/(concentration fraction of molecular weight 12 ten thousand lower than molecular weight at peak value)

In the exterior material for an electric storage device according to the present invention, the heat-fusible resin layer 4 preferably has a melting peak temperature of 130 ℃ or lower, from the viewpoint of more suitably exhibiting the effects of the present invention. From the same viewpoint, the melting peak temperature is preferably about 100 ℃ or higher, more preferably about 110 ℃ or higher, further preferably about 120 ℃ or higher, and further preferably about 150 ℃ or lower, more preferably about 145 ℃ or lower, further preferably about 138 ℃ or lower, further preferably about 128 ℃ or lower. The preferable range of the melting peak temperature is about 100 to 150 ℃, about 100 to 145 ℃, about 100 to 138 ℃, about 100 to 130 ℃, about 100 to 128 ℃, about 110 to 150 ℃, about 110 to 145 ℃, about 110 to 138 ℃, about 110 to 130 ℃, about 110 to 128 ℃, about 120 to 150 ℃, about 120 to 145 ℃, about 120 to 138 ℃, about 120 to 130 ℃ and about 120 to 138 ℃. The number of melting peak temperatures may be 1 or more. For example, a melting peak temperature of 130 ℃ or lower may be observed in the heat-fusible resin layer 4, or a melting peak temperature exceeding 130 ℃ may be observed. From the viewpoint of better exhibiting the effects of the present invention, the melting peak temperature observed in the heat-fusible resin layer 4 is preferably 145 ℃ or less in total. The melting peak temperature was measured as follows.

(measurement of melting Peak temperature)

The heat-fusible resin layer was obtained as a measurement sample from the exterior material for the power storage device. For the measurement sample, the test piece was prepared according to JIS K7121:2012 The melting peak temperature was measured by the regulation of (plastics transition temperature measurement method (JIS K7121: supplement 1 of 1987)). Measurement is performed using a differential scanning calorimeter (DSC, such as differential scanning calorimeter Q200 manufactured by taiinstruments).

In the outer packaging material for an electric storage device according to the present invention, the difference between the melting peak temperature and the softening point of the heat-fusible resin layer 4 is preferably about 30 ℃ or less, more preferably about 20 ℃ or less, still more preferably about 10 ℃ or less, and still more preferably about 5 ℃ or less, from the viewpoint of more suitably exhibiting the effects of the present invention. The preferable range of the difference is about 0 to 30 ℃, about 0 to 20 ℃, about 0 to 10 ℃ and about 0 to 5 ℃. In general, resins exceeding the glass transition point have a tendency to soften gradually as the temperature increases. When the temperature of the resin exceeds the melting point, the physical properties of the resin change rapidly, and the sealing strength at the melting point becomes a very small value, but the sealing strength of the heat-fusible resin layer tends to gradually decrease even in the course of gradual softening of the resin. When softening of the resin proceeds at a temperature substantially lower than the melting point, there is a possibility that the exterior material for the power storage device is unsealed at a temperature lower than the desired temperature. Therefore, the difference between the melting peak temperature and the softening point of the heat-fusible resin layer 4 preferably satisfies the above condition, and the difference is preferably as small as possible. The melting peak temperature and softening point of the heat-fusible resin layer 4 are measured as follows.

(measurement of softening Point)

As shown in a conceptual diagram of fig. 7, for example, first, a probe 11 is provided on the surface of the heat-fusible resin layer 4 in the cross section of the exterior material for the power storage device (measurement start a of fig. 7). The cross section at this time is a portion where the cross section of the heat-fusible resin layer 4 is exposed, which is obtained by cutting in the thickness direction of the exterior material for the power storage device. The probe arrangement position 4a is shown in fig. 7. The cutting can be performed by using a commercially available rotary slicer or the like. In addition, in the case of measuring the displacement amount of the exterior material for the power storage device used in the battery in which the electrolyte or the like is enclosed, the portion of the exterior material for the power storage device where the heat-fusible resin layer is not fused is cut in the thickness direction and measured in the same manner as in the above method. As AN atomic force microscope to which a cantilever having a heating mechanism can be attached, for example, AN afm plus system manufactured by ANASYS INSTRUMENTS can be used, and as a probe, a cantilever thermamever AN2-200 (spring constant 0.5 to 3N/m) manufactured by ANASYS INSTRUMENTS can be used. The radius of the tip of the probe 11 was 30nm or less, the set value of Deflection (Deflection) of the probe 11 was-4V, and the temperature rise rate was 5 ℃/min. Then, when the probe is heated in this state, the surface of the heat-fusible resin layer 4 expands due to heat from the probe, as shown in fig. 7B, and the probe 11 is pushed upward, and the position of the probe 11 rises from the initial value (the position at which the temperature of the probe is 40 ℃). When the heating temperature further increases, the heat-fusible resin layer 4 is softened, and as shown in fig. 7C, the probe 11 penetrates the heat-fusible resin layer 4, and the position of the probe 11 is lowered. The temperature at which the position is lowered (the point of change at which the position is lowered from the rise) is taken as the softening point of the exterior material for the power storage device. Further, the outer package for the power storage device, which is the object of measurement, was set at room temperature (25 ℃) and a probe heated to 40 ℃ was placed on the surface of the heat-fusible resin layer 4, and measurement was started.

The resin constituting the heat-fusible resin layer 4 is not particularly limited as long as it can be heat-fused, and a resin containing a polyolefin skeleton such as polyolefin or acid-modified polyolefin is preferable. The resin constituting the heat-fusible resin layer 4 may contain a polyolefin skeleton and may be prepared by infrared spectroscopy or gas chromatographySpectrometry, and the like. In addition, it is preferable that the peak derived from maleic anhydride can be detected when the resin constituting the heat-fusible resin layer 4 is analyzed by infrared spectroscopy. For example, when the maleic anhydride-modified polyolefin is measured by infrared spectrometry, it can be measured at a wave number of 1760cm ^-1 Nearby sum wave number 1780cm ^-1 The vicinity of the reaction vessel detected a peak derived from maleic anhydride. When the heat-fusible resin layer 4 is a layer made of a maleic anhydride-modified polyolefin, a peak derived from maleic anhydride can be detected when measured by infrared spectroscopy. However, when the degree of acid modification is low, the peak may be small and undetectable. In such a case, analysis can be performed using nuclear magnetic resonance spectroscopy.

Specifically, the polyolefin may be exemplified by: polyethylene such as low density polyethylene, medium density polyethylene, high density polyethylene and linear low density polyethylene; ethylene-alpha olefin copolymers; polypropylene such as homopolypropylene, a block copolymer of polypropylene (e.g., a block copolymer of propylene and ethylene), and a random copolymer of polypropylene (e.g., a random copolymer of propylene and ethylene); propylene-alpha olefin copolymers; ethylene-butene-propylene terpolymers, and the like. Among them, polypropylene is preferable. The polyolefin resin in the case of a copolymer may be a block copolymer or a random copolymer. These polyolefin resins may be used singly or in combination of 1 or 2 or more.

In addition, the polyolefin may be a cyclic polyolefin. The cyclic polyolefin is a copolymer of an olefin and a cyclic monomer, and examples of the olefin which is a constituent monomer of the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, isoprene, and the like. Examples of the cyclic monomer that is a constituent monomer of the cyclic polyolefin include: cyclic olefins such as norbornene; cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, norbornadiene, and the like. Among them, cyclic olefins are preferable, and norbornene is more preferable.

The acid-modified polyolefin is a polymer modified by block polymerization or graft polymerization of a polyolefin with an acid component. As the polyolefin modified with an acid, the above-mentioned polyolefin, a copolymer obtained by copolymerizing a polar molecule such as acrylic acid or methacrylic acid with the above-mentioned polyolefin, a polymer such as a crosslinked polyolefin, or the like can be used. Examples of the acid component used for acid modification include carboxylic acids such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride and itaconic anhydride, and anhydrides thereof.

The acid-modified polyolefin may also be an acid-modified cyclic polyolefin. The acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of monomers constituting the cyclic polyolefin with an acid component, or a polymer obtained by block polymerizing or graft polymerizing an acid component and the cyclic polyolefin. The cyclic polyolefin modified with an acid is the same as described above. The acid component used for the acid modification is the same as that used for the modification of the polyolefin described above.

Preferred examples of the acid-modified polyolefin include a polyolefin modified with a carboxylic acid or an anhydride thereof, a polypropylene modified with a carboxylic acid or an anhydride thereof, a maleic anhydride-modified polyolefin, and a maleic anhydride-modified polypropylene.

The heat-fusible resin layer 4 may be formed of 1 resin alone or a polymer blend obtained by combining 2 or more resins. The heat-fusible resin layer 4 may be formed of only 1 layer, or may be formed of 2 or more layers using the same or different resins.

The heat-fusible resin layer 4 may contain a lubricant or the like as necessary. When the heat-fusible resin layer 4 contains a lubricant, the formability of the exterior material for the power storage device can be improved. The lubricant is not particularly limited, and a known lubricant may be used. The lubricant may be used alone or in combination of 1 or more than 2.

The lubricant is not particularly limited, and an amide-based lubricant is preferable. Specific examples of the lubricant include the lubricants exemplified in the base material layer 1. The lubricant may be used alone or in combination of 1 or more than 2.

On the surface of the heat-fusible resin layer 4 In the case of the lubricant, the amount of the lubricant to be present is not particularly limited, but from the viewpoint of improving the formability of the exterior material for an electric storage device, it is preferable to include 10 to 50mg/m ² About, more preferably 15 to 40mg/m ² Left and right.

The lubricant present on the surface of the heat-fusible resin layer 4 may be a lubricant obtained by bleeding out a lubricant contained in a resin constituting the heat-fusible resin layer 4, or may be a lubricant obtained by applying a lubricant to the surface of the heat-fusible resin layer 4.

The thickness of the heat-fusible resin layer 4 is not particularly limited as long as it can exert a function of sealing the power storage device element by heat-fusing the heat-fusible resin layers to each other, and examples thereof include about 100 μm or less, preferably about 85 μm or less, and more preferably about 15 to 85 μm. In addition, for example, when the thickness of the adhesive layer 5 to be described later is 10 μm or more, the thickness of the heat-fusible resin layer 4 is preferably about 85 μm or less, more preferably about 15 to 45 μm, and for example, when the thickness of the adhesive layer 5 to be described later is less than 10 μm or when the adhesive layer 5 is not provided, the thickness of the heat-fusible resin layer 4 is preferably about 20 μm or more, more preferably about 35 to 85 μm.

[ adhesive layer 5]

In the outer packaging material for a power storage device of the present invention, the adhesive layer 5 is a layer provided between the barrier layer 3 (or the corrosion-resistant film) and the heat-fusible resin layer 4 as needed to firmly adhere them.

From the viewpoint of more suitably exhibiting the effect of the present invention, the melting peak of the adhesive layer 5 is preferably in the range of about 120 ℃ or higher, more preferably about 130 ℃ or higher, more preferably about 140 ℃ or higher, still more preferably about 150 ℃ or higher, and further preferably about 170 ℃ or lower, more preferably 150 ℃ or lower, and preferably in the range of about 120 to 170 ℃, about 120 to 150 ℃, about 130 to 170 ℃, about 130 to 150 ℃, about 140 to 170 ℃, about 140 to 150 ℃ or about 150 to 170 ℃. The number of melting peak temperatures may be 1 or more. In addition, a melting peak temperature outside the range of 120 to 170 ℃ may be observed in the adhesive layer 5. However, from the viewpoint of more suitably exhibiting the effects of the present invention, the melting peak temperature observed in the adhesive layer 5 is preferably all in the range of 120 to 170 ℃. The melting peak temperature was measured by the method described in one of the above (melting peak temperature) except that the adhesive layer was obtained as a measurement sample from the exterior material for the power storage device.

The adhesive layer 5 is formed of a resin capable of adhering the barrier layer 3 to the heat-fusible resin layer 4. As the resin for forming the adhesive layer 5, a thermoplastic resin can be preferably used. The resin used to form the adhesive layer 5 preferably includes a polyolefin skeleton, and examples thereof include the polyolefin and the acid-modified polyolefin exemplified in the heat-fusible resin layer 4. On the other hand, from the viewpoint of firmly adhering the barrier layer 3 and the adhesive layer 5, the adhesive layer 5 preferably contains an acid-modified polyolefin. Examples of the acid-modifying component include dicarboxylic acids such as maleic acid, itaconic acid, succinic acid and adipic acid, anhydrides thereof, acrylic acid, methacrylic acid and the like, and maleic anhydride is most preferable from the viewpoints of ease of modification, versatility and the like. In addition, from the viewpoint of heat resistance of the exterior material for the power storage device, the olefin component is preferably a polypropylene resin, and the adhesive layer 5 most preferably contains maleic anhydride-modified polypropylene.

The resin constituting the adhesive layer 5 includes a polyolefin skeleton, and can be analyzed by, for example, infrared spectrometry, gas chromatography mass spectrometry, or the like, and the analysis method is not particularly limited. In addition, when the resin constituting the adhesive layer 5 contains an acid-modified polyolefin, for example, when the maleic anhydride-modified polyolefin is measured by infrared spectroscopy, the resin can be used at a wave number of 1760cm ^-1 Nearby sum wave number 1780cm ^-1 The vicinity of the reaction vessel detected a peak derived from maleic anhydride. However, when the degree of acid modification is low, the peak may be small and undetectable. In such a case, analysis can be performed using nuclear magnetic resonance spectroscopy.

The thickness of the adhesive layer 5 is preferably about 60 μm or less, about 50 μm or less, or about 45 μm or less. The thickness of the adhesive layer 5 is preferably about 10 μm or more, about 20 μm or more, about 25 μm or more, or about 30 μm or more. The thickness of the adhesive layer 5 is preferably about 10 to 60 μm, about 10 to 50 μm, about 10 to 45 μm, about 20 to 60 μm, about 20 to 50 μm, about 20 to 45 μm, about 25 to 60 μm, about 25 to 50 μm, about 25 to 45 μm, about 30 to 60 μm, about 30 to 50 μm, or about 30 to 45 μm. The adhesive layer 5 can be formed by, for example, extrusion molding of the heat-fusible resin layer 4 and the adhesive layer 5.

[ surface coating 6]

The exterior material for a power storage device of the present invention may have a surface coating layer 6 on the base material layer 1 (on the side of the base material layer 1 opposite to the barrier layer 3) as needed for the purpose of improving at least one of design properties, electrolyte resistance, damage resistance, formability, and the like. The surface coating layer 6 is a layer located on the outermost layer side of the exterior material for the power storage device when the power storage device is assembled using the exterior material for the power storage device.

The surface coating layer 6 may be formed of, for example, a resin such as polyvinylidene chloride, polyester, polyurethane, acrylic resin, or epoxy resin.

In the case where the resin forming the surface coating layer 6 is a curable resin, the resin may be either one-liquid curable or two-liquid curable, and is preferably two-liquid curable. Examples of the two-part curable resin include two-part curable polyurethane, two-part curable polyester, and two-part curable epoxy resin. Among them, two-liquid curable polyurethane is preferable.

Examples of the two-part curable polyurethane include a polyurethane containing a 1 st part containing a polyol compound and a 2 nd part containing an isocyanate compound. Preferably, a two-part curable polyurethane comprising a polyol such as a polyester polyol, a polyether polyol, and an acrylic polyol as the 1 st part and an aromatic or aliphatic polyisocyanate as the 2 nd part is used. Examples of the polyurethane include a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance, and a polyurethane containing an isocyanate compound. Examples of the polyurethane include a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance, and a polyurethane containing a polyol compound. Examples of the polyurethane include a polyurethane obtained by reacting a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance with moisture such as air and curing the polyurethane compound. As the polyol compound, a polyester polyol having a hydroxyl group in a side chain in addition to the hydroxyl group at the terminal of the repeating unit is preferably used. The 2 nd agent may be an aliphatic, alicyclic, aromatic or araliphatic isocyanate compound. Examples of the isocyanate compound include Hexamethylene Diisocyanate (HDI), xylylene Diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6 XDI), hydrogenated MDI (H12 MDI), toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and Naphthalene Diisocyanate (NDI). Further, there may be mentioned 1 or 2 or more kinds of polyfunctional isocyanate-modified products derived from these diisocyanates. In addition, as the polyisocyanate compound, a polymer (for example, a trimer) may be used. Such polymers include adducts, biurets, and allophanates. The aliphatic isocyanate compound is an isocyanate having an aliphatic group and no aromatic ring, the alicyclic isocyanate compound is an isocyanate having an alicyclic hydrocarbon group, and the aromatic isocyanate compound is an isocyanate having an aromatic ring. The surface coating layer 6 is made of polyurethane, so that excellent electrolyte resistance can be imparted to the exterior material for the power storage device.

The surface coating layer 6 may contain additives such as the above-mentioned lubricants, antiblocking agents, matting agents, flame retardants, antioxidants, tackifiers, antistatic agents, and the like as needed, depending on the functionality and the like to be provided on the surface of the surface coating layer 6 or its surface, at least one of the surface and the inside of the surface coating layer 6. Examples of the additive include microparticles having an average particle diameter of about 0.5nm to 5. Mu.m. The average particle diameter of the additive is the median particle diameter measured by a laser diffraction/scattering type particle diameter distribution measuring device.

The additive may be any one of an inorganic substance and an organic substance. The shape of the additive is not particularly limited, and examples thereof include spherical, fibrous, plate-like, amorphous, and scaly.

Specific examples of the additives include talc, silica, graphite, kaolin, montmorillonite, mica, hydrotalcite, silica gel, zeolite, aluminum hydroxide, magnesium hydroxide, zinc oxide, magnesium oxide, aluminum oxide, neodymium oxide, antimony oxide, titanium oxide, cerium oxide, calcium sulfate, barium sulfate, calcium carbonate, calcium silicate, lithium carbonate, calcium benzoate, calcium oxalate, magnesium stearate, aluminum oxide, carbon black, carbon nanotubes, high melting nylon, acrylate resin, crosslinked acrylic acid, crosslinked styrene, crosslinked polyethylene, benzoguanamine, gold, aluminum, copper, nickel, and the like. The additive may be used alone or in combination of 1 or more than 2. Among these additives, silica, barium sulfate, and titanium oxide are preferable from the viewpoints of dispersion stability, cost, and the like. The surface of the additive may be subjected to various surface treatments such as an insulating treatment and a high dispersibility treatment.

The method for forming the surface coating layer 6 is not particularly limited, and examples thereof include a method of applying a resin for forming the surface coating layer 6. When the additive is blended in the surface coating layer 6, the resin mixed with the additive may be applied.

The thickness of the surface coating layer 6 is not particularly limited as long as the above-mentioned functions as the surface coating layer 6 can be exhibited, and examples thereof include about 0.5 to 10 μm, and preferably about 1 to 5 μm.

3. Method for producing exterior material for power storage device

The method for producing the exterior material for an electric storage device is not particularly limited as long as a laminate in which the layers of the exterior material for an electric storage device of the present invention are laminated can be obtained, and a method including at least a step of laminating the base layer 1, the barrier layer 3, and the heat-fusible resin layer 4 in this order is exemplified. That is, the method for producing an exterior material for an electric storage device according to the present invention includes a step of laminating at least a base material layer, a barrier layer, and a heat-fusible resin layer in this order to obtain a laminate, wherein the heat-fusible resin layer of the exterior material for an electric storage device has a molecular weight of 15 ten thousand or more at a peak value of a differential molecular weight distribution curve measured by high-temperature gel permeation chromatography.

As an example of the method for producing the exterior material for an electric storage device according to the present invention, the following is given. First, a laminate (hereinafter, sometimes referred to as "laminate a") in which the base material layer 1, the adhesive layer 2, and the barrier layer 3 are laminated in this order is formed. The laminate a can be formed by specifically using the following dry lamination method: the adhesive for forming the adhesive layer 2 is applied to the base layer 1 or the barrier layer 3 whose surface is chemically converted as needed by a coating method such as a gravure coating method or a roll coating method, and dried, and then the barrier layer 3 or the base layer 1 is laminated and the adhesive layer 2 is cured.

Next, the heat-fusible resin layer 4 is laminated on the barrier layer 3 of the laminate a. In the case where the heat-fusible resin layer 4 is directly laminated on the barrier layer 3, the heat-fusible resin layer 4 may be laminated on the barrier layer 3 of the laminate a by a method such as a heat lamination method or an extrusion lamination method. In addition, when the adhesive layer 5 is provided between the barrier layer 3 and the heat-fusible resin layer 4, examples thereof include: (1) A method of extruding and laminating the adhesive layer 5 and the heat-fusible resin layer 4 on the barrier layer 3 of the laminate a (coextrusion lamination method, tandem lamination method); (2) A method of forming a laminate in which the adhesive layer 5 and the heat-fusible resin layer 4 are laminated, and laminating the laminate on the barrier layer 3 of the laminate a by a heat lamination method, or a method of forming a laminate in which the adhesive layer 5 is laminated on the barrier layer 3 of the laminate a, and laminating the laminate with the heat-fusible resin layer 4 by a heat lamination method; (3) A method (sandwich lamination method) of bonding the laminate a to the heat-fusible resin layer 4 via the adhesive layer 5 while flowing the molten adhesive layer 5 between the barrier layer 3 of the laminate a and the heat-fusible resin layer 4 previously formed into a sheet shape; (4) A method of applying and drying an adhesive solution for forming the adhesive layer 5 on the barrier layer 3 of the laminate a, a method of further sintering, and the like, and a method of laminating a heat-fusible resin layer 4 formed in advance in a sheet form on the adhesive layer 5.

In the case where the surface coating layer 6 is provided, the surface coating layer 6 is laminated on the surface of the base material layer 1 on the opposite side from the barrier layer 3. The surface coating layer 6 can be formed by, for example, applying the resin described above for forming the surface coating layer 6 to the surface of the base material layer 1. The order of the step of laminating the barrier layer 3 on the surface of the base material layer 1 and the step of laminating the surface coating layer 6 on the surface of the base material layer 1 is not particularly limited. For example, after the surface coating layer 6 is formed on the surface of the base material layer 1, the barrier layer 3 may be formed on the surface of the base material layer 1 opposite to the surface coating layer 6.

As described above, the laminate including the surface coating layer 6, the base material layer 1, the adhesive layer 2, the barrier layer 3, and the adhesive layer 5, and the heat-fusible resin layer 4 is formed in this order, and the heat treatment may be further performed to secure the adhesion between the adhesive layer 2 and the adhesive layer 5.

In the exterior material for the power storage device, each layer constituting the laminate may be subjected to surface activation treatment such as corona treatment, sandblasting treatment, oxidation treatment, ozone treatment, or the like as necessary to improve the processing suitability. For example, by performing corona treatment on the surface of the substrate layer 1 on the side opposite to the barrier layer 3, the printing suitability of the ink to the surface of the substrate layer 1 can be improved.

4. Use of outer packaging material for electric storage device

The exterior material for a power storage device of the present invention can be used for a package body in which power storage device elements such as a positive electrode, a negative electrode, and an electrolyte are sealed and stored. That is, the power storage device can be manufactured by housing a power storage device element including at least a positive electrode, a negative electrode, and an electrolyte in a package body formed of the outer package material for a power storage device of the present invention.

Specifically, by using the exterior material for an electric storage device according to the present invention, an electric storage device element including at least a positive electrode, a negative electrode, and an electrolyte is covered so that a flange portion (a region where heat-fusible resin layers contact each other) can be formed at the peripheral edge of the electric storage device element in a state where metal terminals connected to the positive electrode and the negative electrode, respectively, protrude to the outside, and the heat-fusible resin layers of the flange portion are heat-sealed to each other, whereby the electric storage device element can be sealed, and an electric storage device using the exterior material for an electric storage device can be provided. In the case where the power storage device element is housed in the package formed of the power storage device exterior material of the present invention, the package is formed such that the heat-fusible resin portion of the power storage device exterior material of the present invention is inside (the surface in contact with the power storage device element). The heat-fusible resin layers of the 2 exterior materials for power storage devices may be opposed to each other and superimposed, and the peripheral edge portions of the superimposed exterior materials for power storage devices may be heat-fused to form a package, or as in the example shown in fig. 4, the 1 exterior materials for power storage devices may be folded back and superimposed, and the peripheral edge portions may be heat-fused to form a package. In the case of folding back and overlapping, as in the example shown in fig. 4, the package may be formed by three-way sealing by heat welding the edges other than the folded back edges, or may be folded back so that the flange portion can be formed, and four-way sealing may be performed. In the exterior material for the power storage device, the recess for accommodating the power storage device element may be formed by deep drawing or protruding molding. As in the example shown in fig. 4, a recess may be provided in one outer package material for the power storage device, and a recess may not be provided in the other outer package material for the power storage device, or a recess may be provided in the other outer package material for the power storage device.

The exterior material for an electric storage device of the present invention can be suitably used for an electric storage device such as a battery (including a capacitor), a capacitor (capacitor), and the like. The exterior material for a power storage device of the present invention can be used for either a primary battery or a secondary battery, and is preferably used for a secondary battery. The type of secondary battery to which the exterior material for a power storage device of the present invention is applied is not particularly limited, and examples thereof include lithium ion batteries, lithium ion polymer batteries, all-solid batteries, lead storage batteries, nickel hydrogen storage batteries, nickel cadmium storage batteries, nickel iron storage batteries, nickel zinc storage batteries, silver zinc oxide storage batteries, metal air batteries, polyvalent cation batteries, capacitors (capacitors), and the like. Among these secondary batteries, preferred applications of the outer packaging material for a power storage device of the present invention include lithium ion batteries and lithium ion polymer batteries.

Example (example)

Hereinafter, examples and comparative examples are given to explain the present invention in detail. However, the present invention is not limited to the examples.

Production of exterior Material for electric storage device

Examples 1 to 4

As a base material layer, a stretched nylon (ONy) film (thickness 25 μm) was prepared. Further, as a barrier layer, an aluminum foil (JIS H4160:1994A8021H-O (thickness 40 μm)) was prepared. Next, a laminate of a base layer (thickness 25 μm)/an adhesive layer (thickness 3 μm after curing)/a barrier layer (thickness 40 μm) was produced by bonding the base layer and the barrier layer using a two-part urethane adhesive (a polyol compound and an aromatic isocyanate compound) by a dry lamination method and curing the resulting laminate. The chemical conversion treatment is performed on both sides of the aluminum foil. The chemical conversion treatment of the aluminum foil is performed as follows: the treatment liquid containing a phenol resin, a chromium fluoride compound and phosphoric acid was applied to both sides of the aluminum foil by a roll coating method so that the applied amount of chromium became 10mg/m ² (dry mass) and sintering.

Next, on the barrier layer of the laminate obtained above, maleic anhydride-modified polypropylene (PPa 1 or PPa2 in table 1, respectively) as an adhesive layer (thickness 23 μm) and atactic polypropylene (PP 1, PP2, PP3, or PP4 in table 1, respectively) as a heat-fusible resin layer (thickness 22 μm) were coextruded onto the barrier layer to obtain an exterior package for an electric storage device, in which a base layer (thickness 25 μm)/adhesive layer (3 μm)/barrier layer (40 μm)/adhesive layer (23 μm)/heat-fusible resin layer (22 μm) were laminated in this order.

In examples 1 to 4, random polypropylene PP1, PP2, PP3 or PP4 used in the heat-fusible resin layer was selected from those having a lower melting peak temperature and a higher molecular weight than the peak value of the differential molecular weight distribution curve than those used in the heat-fusible resin layer of the outer package, and when the heat-fusible resin layer was formed by coextrusion, coextrusion was performed under a temperature condition lower than usual to suppress thermal decomposition of the random polypropylene, thereby suppressing a decrease in the molecular weight of the peak value of the differential molecular weight distribution curve.

Comparative example 1

An exterior material for an electric storage device was obtained in the same manner as in example 1, except that the temperature at which maleic anhydride-modified polypropylene (PPa 1 in table 1, respectively) as an adhesive layer (thickness 23 μm) and atactic polypropylene (PP 1 in table 1, respectively) as a heat-fusible resin layer (thickness 22 μm) were coextruded onto the barrier layer was set to 30 ℃ higher than that of example 1, and a base layer (thickness 25 μm)/adhesive layer (3 μm)/barrier layer (40 μm)/adhesive layer (23 μm)/heat-fusible resin layer (22 μm) were laminated in this order.

Comparative example 2

An exterior material for an electric storage device was obtained in the same manner as in example 2, except that the temperature at which maleic anhydride-modified polypropylene (PPa 1 in table 1, respectively) as an adhesive layer (thickness 23 μm) and atactic polypropylene (PP 2 in table 1, respectively) as a heat-fusible resin layer (thickness 22 μm) were coextruded onto the barrier layer was set to 30 ℃ higher than that of example 2, and a base layer (thickness 25 μm)/adhesive layer (3 μm)/barrier layer (40 μm)/adhesive layer (23 μm)/heat-fusible resin layer (22 μm) were laminated in this order.

Melting peak temperatures of the adhesive layers or the heat-fusible resin layers of examples 1 to 4 and comparative examples 1 to 2 are shown in Table 1. The melting peak temperatures were measured by the following methods.

(measurement of melting Peak temperature)

The adhesive layer and the heat-fusible resin layer were obtained as measurement samples from the exterior material for the power storage device. For each measurement sample, the test piece was prepared according to JIS K7121:2012 The melting peak temperature was measured by the regulation of (plastics transition temperature measurement method (JIS K7121: supplement 1 of 1987)). The measurement was performed using a differential scanning calorimeter (DSC, differential scanning calorimeter Q200 manufactured by TA Instruments).

The heat-fusible resin layer was obtained as a measurement sample from the exterior material for the power storage device. For each measurement sample, the concentration fractions of each molecular weight were sequentially accumulated using high temperature gel permeation chromatography (SSC-7120 HT-GPC System manufactured by high temperature GPC, sensoScientific Co.) under the following measurement conditions, with the horizontal axis representing each molecular weight (logarithmic value), to obtain an integrated molecular weight distribution curve. A differential molecular weight distribution curve is obtained by obtaining differential values of curves at respective molecular weights, and a molecular weight having a peak value of a vertical axis (dw/d (Log (M))) is obtained. As shown in the schematic diagram of fig. 8, the differential molecular weight distribution curve is a graph in which the horizontal axis represents the molecular weight and the vertical axis represents the value obtained by differentiating the concentration fraction by the logarithmic value of the molecular weight. The molecular weight at the position where the concentration fraction is highest, which is obtained by differentiating the concentration fraction by the logarithmic value of the molecular weight, is the molecular weight of the peak of the differentiated molecular weight distribution curve (refer to the position of P in fig. 8).

< measurement Condition >)

(pretreatment)

(measurement)

< calculation of TL value >)

In the above (measurement of the molecular weight of the peak of the differential molecular weight distribution curve), in the differential molecular weight distribution curve having the molecular weight (logarithmic value) as the horizontal axis and the concentration fraction of the molecular weight as the vertical axis, a value (referred to as TL value) obtained by dividing the concentration fraction of the molecular weight having the concentration fraction of the peak by the concentration fraction of the molecular weight 12 ten thousand lower than the molecular weight having the concentration fraction of the peak is calculated. The results are shown in Table 1. It can be said that the smaller the TL value, the flatter the gradient of the concentration fraction curve from the concentration fraction of the highest molecular weight of the concentration fraction to the concentration fraction of the low molecular weight (specifically, 12 ten thousand lower molecular weight) resin. That is, the TL value is calculated by the following formula.

(measurement of softening Point)

As shown in a conceptual diagram of fig. 7, for example, first, a probe 11 is provided on the surface of the heat-fusible resin layer 4 in the cross section of the exterior material for the power storage device (measurement start a of fig. 7). The cross section at this time is a portion where the cross section of the heat-fusible resin layer 4 is exposed, which is obtained by cutting in the thickness direction of the exterior material for the power storage device. The probe arrangement position 4a is shown in fig. 7. The cutting can be performed by using a commercially available rotary microtome. As AN atomic force microscope to which a cantilever having a heating mechanism can be attached, AN afm plus system manufactured by ANASYS INSTRUMENTS was used, and as a probe, a cantilever thermaLever AN2-200 (spring constant 0.5 to 3N/m) manufactured by ANASYS INSTRUMENTS was used. The radius of the tip of the probe 11 was 30nm or less, the set value of Deflection (Deflection) of the probe 11 was-4V, and the temperature rise rate was 5 ℃/min. Then, when the probe is heated in this state, the surface of the heat-fusible resin layer 4 expands due to heat from the probe, as shown in fig. 7B, and the probe 11 is pushed upward, and the position of the probe 11 rises from the initial value (the position at which the temperature of the probe is 40 ℃). When the heating temperature further increases, the heat-fusible resin layer 4 is softened, and as shown in fig. 7C, the probe 11 penetrates the heat-fusible resin layer 4, and the position of the probe 11 is lowered. The temperature at which the position is lowered (the point of change at which the position is lowered from the rise) is taken as the softening point of the exterior material for the power storage device. Further, the outer package for the power storage device, which is the object of measurement, was set at room temperature (25 ℃) and a probe heated to 40 ℃ was placed on the surface of the heat-fusible resin layer 4, and measurement was started.

In example 1, the difference between the melting peak temperature and the softening point of the heat-fusible resin layer was 3 ℃.

(measurement of Heat seal Strength)

According to JIS K7127:1999, the seal strength of the exterior material for the power storage device at each measured temperature (sample temperature) described in table 1 was measured as follows. As a test piece, an outer package for an electric storage device cut into a long strip shape having a width of 15mm in the TD direction was prepared. Specifically, as shown in fig. 5, first, each exterior material for power storage devices was cut into test pieces (a of fig. 5) of 60mm (TD direction) ×200mm (MD direction). At this time, 10 test pieces were obtained from 10 points (equal intervals) in the width direction of the outer package material for the power storage device (width 1000 mm), respectively. Next, the outer packaging material for the power storage device was folded in half in the MD direction at the position of the fold P (middle in the MD direction) so that the heat-fusible resin layers faced each other for each test piece (b in fig. 5). The heat-sealable resin layers were heat-sealed to each other at a seal width of 7mm, a temperature of 190℃and a surface pressure of 1.0MPa for 3 seconds on the inner side in the MD direction about 10mm from the crease P (c in FIG. 5). In fig. 5 c, the hatched portion S is a heat-sealed portion. Next, the sample was cut in the MD direction (cut at the position of the two-dot chain line in d in fig. 5) so that the width in the TD direction was 15mm, and a measurement sample was obtained (e in fig. 5). Next, the measurement sample 13 was left at each measurement temperature for 2 minutes, and the heat-sealable resin layer of the heat-sealed portion (heat-sealed portion) was peeled off at a rate of 300 mm/min in each measurement temperature environment by a tensile tester (AG-Xplus (trade name) manufactured by shimadzu corporation) (fig. 6). The maximum strength at peeling was taken as the heat seal strength (N/15 mm). The distance between chucks was 50mm. The resulting heat seal strength is shown in Table 1 as the average value of 10 measurement samples and the minimum value of 10 measurement samples, respectively. The results are shown in Table 1.

(measurement of Martin hardness)

The vickers indenter was press-fitted to a depth of 1 μm in the thickness direction from the surface of the heat-fusible resin layer side of the outer packaging material for each power storage device at a measurement temperature (sample temperature) of 100 ℃ based on the indentation method, and the mahalanobis hardness was measured. The measurement conditions are as follows. The mahalanobis hardness is calculated from the load-displacement curve obtained by pressing in the vickers indenter. As the measurement value, an average value obtained for the surface 10 on the heat-fusible resin layer side was used. Marsh hardness by calculating the surface area A (mm) of the indenter at the maximum indentation depth of the Vickers indenter ² ) And dividing the maximum load F (N) by the surface area A (mm) ² ) (F/A) and the result was obtained. The method for measuring the mahalanobis hardness of the surface of the heat-fusible resin layer is described in detail below. As a measuring device, PICODENTER HM-500 manufactured by Fischer Instruments was used. The exterior material for the power storage device was adhered to one surface of a slide glass (76 mm. Times.26 mm. Times.1 mm) to which a double-sided adhesive tape was attached, so that the side of the heat-fusible resin layer was the opposite side of the slide glass, to prepare a measurement sample. Next, a heating table was set on the ultra-fine durometer equipped with the vickers indenter, the table temperature was set to 110 ℃, and the sample was heated for 5 minutes. Next, the surface hardness of the surface of the measurement sample on the heat-fusible resin layer side was measured. The results are shown in Table 2.

< measurement Condition >)

Measurement temperature (sample temperature): 100 DEG C

Table temperature: 110 DEG C

Speed: 1.000 μm/10 seconds

Depth of measurement: 1.0 μm

Hold time: 5 seconds

Speed of recovery from indentation: 1.000 μm/10 seconds

TABLE 1

In Table 1, the expression "122/134" means that melting peak temperatures were observed at 122℃and 134 ℃.

TABLE 2

The peak molecular weight of the differential molecular weight distribution curve measured by high temperature gel permeation chromatography of the heat-fusible resin layer of the exterior material for power storage devices of examples 1 to 4 was 15 ten thousand or more. The exterior materials for electric storage devices of examples 1 to 4 had high heat sealing strength before the electric storage device reached a high temperature of 100℃and further 110℃in spite of the low melting point of the heat-fusible resin layer, and the exterior materials for electric storage devices had the contents properly sealed. It is also clear that the outer packaging materials for power storage devices of examples 1 to 4 have small differences between the average value and the minimum value of the heat seal strength at each measured temperature, and that the quality variation is small when the outer packaging materials for power storage devices are cut out and used.

As described above, the present invention provides the following means.

The exterior material for an electric storage device according to item 1, which comprises a laminate comprising at least a base layer, a barrier layer, and a thermally fusible resin layer in this order, wherein the thermally fusible resin layer has a molecular weight of 15 ten thousand or more at a peak value of a differential molecular weight distribution curve measured by high temperature gel permeation chromatography.

The exterior material for electric storage devices according to item 1, wherein the vickers indenter is pressed into the thickness direction from the surface of the exterior material for electric storage devices on the side of the heat-fusible resin layer to a depth of 1 μm at a measurement temperature of 100 ℃ based on an indentation method, and the mahalanobis hardness measured is 10.0MPa or more.

The exterior material for an electric storage device according to item 3 is composed of a laminate comprising at least a base layer, a barrier layer and a heat-fusible resin layer in this order, and has a hardness of 10.0MPa or more as measured by indentation at a measurement temperature of 100 ℃ by pressing a Vickers indenter from the surface of the exterior material for an electric storage device on the heat-fusible resin layer side to a depth of 1 [ mu ] m in the thickness direction.

The exterior material for a power storage device according to any one of items 1 to 3, wherein, in the differential molecular weight distribution curve having a logarithmic molecular weight on the horizontal axis and a concentration fraction of molecular weight on the vertical axis, the TL value calculated by dividing the concentration fraction of molecular weight having a peak concentration fraction by the concentration fraction of molecular weight 12 ten thousand lower than the molecular weight having a peak concentration fraction is 1.00 to 2.80.

The exterior material for a power storage device according to any one of items 1 to 4, wherein the heat-fusible resin layer has a melting peak temperature of 130 ℃ or lower.

The exterior material for an electric storage device according to any one of items 1 to 5, wherein the resin constituting the heat-fusible resin layer has a polyolefin skeleton.

The exterior material for an electric storage device according to any one of items 1 to 6, wherein the resin constituting the heat-fusible resin layer contains polypropylene.

The exterior material for an electric storage device according to any one of items 1 to 7, wherein an adhesive layer is provided between the barrier layer and the heat-fusible resin layer, and a resin constituting the adhesive layer has a polyolefin skeleton.

The exterior material for a power storage device according to item 8, wherein the adhesive layer has a melting peak observed in a range of 120 ℃ to 170 ℃.

Item 10. The exterior material for an electric storage device according to item 8 or 9, wherein the resin constituting the adhesive layer comprises acid-modified polypropylene.

The exterior material for an electric storage device according to any one of items 1 to 10, wherein a difference between a melting peak temperature and a softening point of the heat-fusible resin layer is 30 ℃ or less.

The method for producing an exterior material for an electric storage device according to item 12, comprising a step of laminating at least a base layer, a barrier layer, and a heat-fusible resin layer in this order to obtain a laminate, wherein the heat-fusible resin layer has a molecular weight of 15 ten thousand or more at a peak value of a differential molecular weight distribution curve measured by high-temperature gel permeation chromatography.

The electricity storage device according to item 13, wherein an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte is housed in the package formed of the outer packaging material for an electricity storage device according to any one of items 1 to 11.

Description of the reference numerals

1 a base material layer, 2 an adhesive layer, 3 a barrier layer, 4a heat-fusible resin layer, 4a probe arrangement position, 5 an adhesive layer, 6 a surface cover layer, 10 an outer package material for an electric storage device.

Claims

1. An exterior material for an electric storage device, characterized in that:

comprises a laminate comprising at least a base layer, a barrier layer and a heat-fusible resin layer in this order,

the peak molecular weight of the differential molecular weight distribution curve measured by high temperature gel permeation chromatography of the heat-fusible resin layer is 15 ten thousand or more.

2. The exterior material for an electric storage device according to claim 1, wherein:

The vickers indenter was press-fitted to a depth of 1 μm in the thickness direction from the surface of the heat-fusible resin layer side of the exterior material for the power storage device at a measurement temperature of 100 ℃ based on an indentation method, and the hardness of 10.0MPa or more was measured.

3. An exterior material for an electric storage device, characterized in that:

4. The exterior material for an electric storage device according to any one of claims 1 to 3, wherein:

in the differential molecular weight distribution curve having a molecular weight logarithmic value on the horizontal axis and a molecular weight concentration fraction on the vertical axis, the TL value calculated by dividing the molecular weight concentration fraction having a peak concentration fraction by the molecular weight concentration fraction 12 ten thousand lower than the molecular weight having a peak concentration fraction is 1.00 to 2.80.

5. The exterior material for an electric storage device according to any one of claims 1 to 4, wherein:

The heat-fusible resin layer has a melting peak temperature of 130 ℃ or lower.

6. The exterior material for an electric storage device according to any one of claims 1 to 5, wherein:

the resin constituting the heat-fusible resin layer has a polyolefin skeleton.

7. The exterior material for an electric storage device according to any one of claims 1 to 6, wherein:

the resin constituting the heat-fusible resin layer contains polypropylene.

8. The exterior material for an electric storage device according to any one of claims 1 to 7, characterized in that:

an adhesive layer is provided between the barrier layer and the heat-fusible resin layer,

the resin constituting the adhesive layer has a polyolefin skeleton.

9. The exterior material for an electric storage device according to claim 8, wherein:

the melting peak of the adhesive layer is observed in a range of 120 ℃ to 170 ℃.

10. The exterior material for an electric storage device according to claim 8 or 9, characterized in that:

the resin constituting the adhesive layer contains acid-modified polypropylene.

11. The exterior material for an electric storage device according to any one of claims 1 to 10, characterized in that:

the difference between the melting peak temperature and the softening point of the heat-fusible resin layer is 30 ℃ or less.

12. A method for producing an exterior material for an electric storage device, characterized by comprising:

comprises a step of laminating at least a base layer, a barrier layer and a heat-fusible resin layer in this order to obtain a laminate,

13. An electric storage device characterized in that:

the package formed of the exterior material for an electric storage device according to any one of claims 1 to 11, wherein an electric storage device element including at least a positive electrode, a negative electrode, and an electrolyte is housed.