Exterior material for energy storage devices, method for manufacturing the same, and energy storage device

Abstract

To provide an exterior material for a power storage device, which is composed of a laminate including a base material layer, a barrier layer, and an inner layer in this order, and has excellent sealing performance in a high temperature environment.SOLUTION: An exterior material for a power storage device is composed of a laminate including at least a base material layer, a barrier layer, and an inner layer in this order, and the inner layer includes an adhesive layer and a heat-sealing resin layer from the barrier layer side. When the dynamic viscoelasticity measurement by tension is performed on the inner layer, the elongation rate at 80°C is 8.0% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to an exterior material for an energy storage device, a method for manufacturing the same, and an energy storage device. [Background technology]

[0002] While various types of energy storage devices have been developed, casing materials are essential components for sealing the device elements, such as electrodes and electrolytes, in all of them. Traditionally, metal casing materials have been widely used for energy storage devices.

[0003] On the other hand, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, and mobile phones, energy storage devices are required to come in a variety of shapes, as well as be thinner and lighter. However, conventional metal casing materials for energy storage devices have the drawback of being unable to keep up with the diversification of shapes, and also having limitations in terms of weight reduction.

[0004] Therefore, in recent years, a film-like laminate in which a base layer, barrier layer, adhesive layer, and heat-sealable resin layer are sequentially laminated has been proposed as an exterior material for energy storage devices that can be easily processed into various shapes and can achieve thinning and weight reduction (see, for example, Patent Document 1).

[0005] In such an exterior material for energy storage devices, recesses are generally formed by cold forming, and energy storage device elements such as electrodes and electrolytes are placed in the space formed by the recesses. By heat-sealing a heat-sealable resin layer, an energy storage device is obtained in which the energy storage device elements are housed inside the exterior material for the energy storage device. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2008-287971 [Patent Document 2] Japanese Patent Publication No. 2013-101778 [Overview of the project] [Problems that the invention aims to solve]

[0007] Depending on their application, energy storage devices may be exposed to high-temperature environments. For example, automotive energy storage devices are expected to be used in high-temperature environments. When energy storage devices are exposed to high temperatures, gas may be generated from the electrolyte and other materials contained inside the device, which can increase the internal pressure. Therefore, high sealing performance is required for energy storage devices in high-temperature environments.

[0008] However, in the aforementioned film-type exterior material for energy storage devices, the energy storage device elements are sealed by heat-sealing the heat-sealable resin layers together. In high-temperature environments, the adhesive layer and heat-sealable resin layer located inside the barrier layer tend to soften. Consequently, in high-temperature environments, if the internal pressure of the energy storage device increases, at least one of the adhesive layer and the heat-sealable resin layer may break, making it impossible to maintain the seal of the energy storage device elements by the exterior material.

[0009] Under these circumstances, the first embodiment of the present disclosure is an exterior material for an energy storage device comprising a laminate comprising at least a base layer, a barrier layer, and an inner layer in that order, and its main objective is to provide an exterior material for an energy storage device that has excellent sealing properties in high-temperature environments.

[0010] Furthermore, in the film-like exterior materials for energy storage devices described above, polypropylene resins such as acid-modified polypropylene may be used as the material for forming the adhesive layer that bonds the barrier layer and the heat-sealable resin layer. For example, when forming the adhesive layer with a polypropylene resin, polyethylene may be added to the polypropylene resin to improve processability and flexibility.

[0011] However, polypropylene resins and polyethylene do not have high compatibility. For example, when a small amount of polyethylene is added to a polypropylene resin and a heat-fusible resin layer is formed by melt extrusion molding, a sea-island structure is formed in which polyethylene islands are dispersed within the polypropylene resin sea (to observe this sea-island structure, the cross-section of the heat-fusible resin layer is stained with ruthenium tetroxide, and a cross-sectional image is obtained and observed using a scanning electron microscope).

[0012] When a large stress is applied to an exterior material for energy storage devices that has an adhesive layer exhibiting such a sea-island structure, the mechanical strength of the adhesive layer located inside the barrier layer tends to decrease. Consequently, when the internal pressure of the energy storage device increases in a high-temperature environment, the adhesive layer may break, and the exterior material for the energy storage device may not be able to maintain the seal on the energy storage device elements.

[0013] Under these circumstances, the second embodiment of the present disclosure is an exterior material for an energy storage device comprising a laminate comprising, in this order, at least a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer, and its main objective is to provide an exterior material for an energy storage device that has excellent sealing properties in high-temperature environments.

[0014] Furthermore, in the film-like exterior materials for energy storage devices described above, polyolefins such as polypropylene are sometimes used as the material for forming the heat-sealable resin layer. For example, when polypropylene is used to form the heat-sealable resin layer, polyethylene may be used in combination to improve processability and flexibility.

[0015] However, polypropylene and polyethylene do not have high compatibility. For example, when a small amount of polyethylene is added to polypropylene and a heat-fusible resin layer is formed by melt extrusion molding, a sea-island structure is formed in which polyethylene islands are dispersed within the polypropylene seas (to observe this sea-island structure, the cross-section of the heat-fusible resin layer is stained with ruthenium tetroxide, and a cross-sectional image is obtained and observed using a scanning electron microscope). Therefore, when the exterior material for energy storage devices is subjected to the aforementioned cold molding, the stress applied during molding can cause fine cracks to occur at the interface between the polypropylene and polyethylene portions of the heat-fusible resin layer, which can lead to whitening of the heat-fusible resin layer and a decrease in the insulation properties of the exterior material for energy storage devices.

[0016] For example, Patent Document 2 states that when the inner layer of a battery casing material is made of a mixture of polypropylene resin and polyethylene resin, the seal strength between heat-sealed inner layers can be controlled by controlling the size and number of "islands" by controlling the manufacturing conditions of the battery casing material, the thickness of the inner layer, and the mixing ratio of polypropylene resin and polyethylene resin. In a mixture with a sea-island structure, the particle size of the polyethylene resin, which is the size of the "island," is in the range of 0.5 to 5 μm (i.e., 0.196 to 19.6 μm). 2 It is stated that it is preferable that the degree is such.

[0017] However, the inventors of this disclosure have found that, as disclosed in Patent Document 2, conventional battery casing materials, which have polypropylene and polyethylene in the inner layer, have large polyethylene resin particles, and therefore cannot adequately suppress whitening and deterioration of insulation due to molding.

[0018] Under these circumstances, the third embodiment of the present disclosure primarily aims to provide an exterior material for energy storage devices comprising a heat-fusible resin layer containing polypropylene and polyethylene, wherein whitening and deterioration of insulation due to molding are suppressed. [Means for solving the problem]

[0019] The inventors of this disclosure have diligently studied to solve the problems of the invention according to the first embodiment described above. As a result, they have found that an exterior material for an energy storage device, comprising a laminate comprising at least a base layer, a barrier layer, and an inner layer in that order, exhibits excellent sealing performance in high-temperature environments if the inner layer has an elongation rate of 8.0% or less at 80°C when subjected to dynamic viscoelasticity measurement by tensile stress.

[0020] The first embodiment of this disclosure was completed by further consideration based on these findings. Specifically, the first embodiment of this disclosure provides the invention in the following aspects. It is composed of a laminate comprising, at least, a base layer, a barrier layer, and an inner layer in this order. The inner layer comprises, from the barrier layer side, an adhesive layer and a heat-fusible resin layer. An outer casing material for energy storage devices, wherein the inner layer exhibits an elongation rate of 8.0% or less at 80°C when subjected to dynamic viscoelasticity measurement by tensile stress.

[0021] The inventors of this disclosure have diligently studied to solve the problems of the invention according to the second embodiment described above. As a result, they found that the invention is composed of a laminate comprising, in this order, a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer, wherein the adhesive layer contains a polypropylene resin and polyethylene, and a sea-island structure is observed in a cross-sectional image obtained using a scanning electron microscope of the cross-section of the adhesive layer in a direction parallel to the TD (Transverse Direction) and in the thickness direction, wherein the cross-sectional image is obtained within the range from the surface of the adhesive layer on the barrier layer side to a portion with a thickness of 25%, when the thickness of the adhesive layer is set to 100%, and in the cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.25 μm² relative to the total number of island portions of the sea-island structure. 2 The proportion of the total number of islands less than 0.25 μm is 40% or more (i.e., [0.25 μm 2 We found that the exterior material for energy storage devices exhibits excellent sealing properties in high-temperature environments when the ratio of the total number of islands to the total number of islands is ≥ 40%.

[0022] The second embodiment of this disclosure was completed by further consideration based on these findings. Specifically, the second embodiment of this disclosure provides the invention in the following aspects. It is composed of a laminate comprising, at a minimum, a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer in this order. The adhesive layer contains a polypropylene resin and polyethylene. A sea-island structure was observed in the cross-sectional image obtained using a scanning electron microscope of the adhesive layer in a direction parallel to the TD and in the thickness direction. The aforementioned cross-sectional image is obtained within the range from the surface of the adhesive layer on the barrier layer side to the portion with a thickness of 25%, assuming the thickness of the adhesive layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.25 μm² relative to the total number of island portions. 2 An exterior material for energy storage devices in which the proportion of the total number of island portions less than 40% is 40% or more.

[0023] The inventors of this disclosure have diligently studied to solve the problems of the invention according to the third embodiment described above. As a result, the invention is composed of a laminate comprising, in order from the outside to the inside, at least a base layer, a barrier layer, and a heat-fusible resin layer, wherein the heat-fusible resin layer contains polypropylene and polyethylene, and a sea-island structure was observed in a cross-sectional image obtained using a scanning electron microscope of the cross-section of the heat-fusible resin layer in a direction parallel to the TD (Transverse Direction) and in the thickness direction, and in the cross-sectional image, the area of ​​the island portion of the sea-island structure was 0.02 μm² relative to the total number of island portions. 2 The proportion of the total number of islands listed below is 8 We found that exterior materials for energy storage devices, in which the content is 0.0% or more and at least one of an antioxidant and a radical scavenger is included in at least one of the layers inside the barrier layer, suppress whitening and deterioration of insulation due to molding. The cross-sectional image was obtained within the range from the surface opposite the barrier layer side of the heat-fusible resin layer to a thickness of 12.5%, when the total thickness of the layers located inside the barrier layer is taken as 100%. The direction of the heat-fusible resin layer MD and TD laminated in the laminate can generally be determined from the barrier layer described later. That is, in exterior materials for energy storage devices, the MD and TD of the barrier layer described later can generally be determined in the manufacturing process. For example, when the barrier layer is made of aluminum foil, linear lines called rolling marks are formed on the surface of the aluminum foil in the rolling direction (RD) of the aluminum foil. Since the rolling marks extend along the rolling direction, the rolling direction of the aluminum foil can be determined by observing the surface of the aluminum foil. Furthermore, in the manufacturing process of the laminate, the MD of the laminate and the RD of the aluminum foil generally coincide. Therefore, by observing the surface of the aluminum foil in the laminate and identifying the rolling direction (RD) of the aluminum foil, the MD of the laminate (i.e., the MD of the heat-fusible resin layer) can be determined. In addition, since the TD of the laminate is perpendicular to the MD of the laminate, the TD of the laminate (i.e., the TD of the heat-fusible resin layer) can also be determined.

[0024] A third embodiment of this disclosure was completed by further consideration based on these findings. Specifically, the third embodiment of this disclosure provides the invention in the following aspects. It is composed of a laminate comprising, from the outside to the inside, at least a base layer, a barrier layer, and a heat-sealable resin layer in this order. The heat-sealable resin layer contains polypropylene and polyethylene. A sea-island structure was observed in the cross-sectional image obtained using a scanning electron microscope of the heat-fusible resin layer in a direction parallel to TD and in the thickness direction. The aforementioned cross-sectional image is obtained within a range of 12.5% ​​thickness from the surface of the heat-fusible resin layer opposite the barrier layer, assuming that the total thickness of the layers located inside the barrier layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.02 μm² relative to the total number of island portions of the sea-island structure. 2 The proportion of the total number of the following island areas is 80.0% or more. An exterior material for an energy storage device, comprising at least one of the layers inside the barrier layer, containing at least one of an antioxidant and a radical scavenger. [Effects of the Invention]

[0025] According to the first embodiment of this disclosure, an exterior material for an energy storage device can be provided, comprising a laminate comprising at least a base layer, a barrier layer, and an inner layer in that order, which provides an exterior material for an energy storage device with excellent sealing properties in high-temperature environments. Furthermore, according to the first embodiment of this disclosure, a method for manufacturing an exterior material for an energy storage device and an energy storage device can also be provided.

[0026] Furthermore, according to a second embodiment of this disclosure, an exterior material for an energy storage device can be provided, comprising a laminate comprising at least a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer in this order, which provides an exterior material for an energy storage device with excellent sealing properties in high-temperature environments. Furthermore, according to a second embodiment of this disclosure, a method for manufacturing an exterior material for an energy storage device and an energy storage device can also be provided.

[0027] According to a third embodiment of this disclosure, an exterior material for an energy storage device can be provided, comprising a heat-fusible resin layer containing polypropylene and polyethylene, wherein whitening and deterioration of insulation due to molding are suppressed. Furthermore, according to a third embodiment of this disclosure, a method for manufacturing an exterior material for an energy storage device and an energy storage device can also be provided. [Brief explanation of the drawing]

[0028] [Figure 1]This is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an energy storage device according to the first embodiment of this disclosure. [Figure 2] This is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an energy storage device according to the first embodiment of this disclosure. [Figure 3] This is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an energy storage device according to the first embodiment of this disclosure. [Figure 4] This is a schematic diagram illustrating the method for preparing samples for creep testing in the examples. [Figure 5] This is a schematic diagram illustrating the method for conducting a creep test in the example. [Figure 6] This is a schematic diagram illustrating a method for housing an energy storage device element in a package formed from the exterior material for energy storage devices of the present disclosure. [Figure 7] This is a schematic diagram of a graph showing the relationship between elongation (%) and temperature (°C) obtained by dynamic viscoelasticity measurement. [Figure 8] This is a cross-sectional image (SEM image) in the thickness direction of the exterior material for the energy storage device of Example 1A after the creep test. [Figure 9] This is a cross-sectional image (SEM image) in the thickness direction of the exterior material for the energy storage device of Comparative Example 1A after the creep test. [Figure 10] This is a schematic diagram showing an example of the cross-sectional structure of the exterior material for an energy storage device according to the second embodiment. [Figure 11] This is a schematic diagram showing an example of the cross-sectional structure of the exterior material for an energy storage device according to the second embodiment. [Figure 12] This is a schematic diagram showing an example of the cross-sectional structure of the exterior material for an energy storage device according to the second embodiment. [Figure 13] This is a schematic diagram showing an example of the cross-sectional structure of the exterior material for an energy storage device according to the second embodiment. [Figure 14] This graph shows the relationship between the area of ​​the island portion (μm2) in the adhesive layer of Example 1B and the percentage (%) of the number of islands of each area relative to the total number of islands. [Figure 15]This graph shows the relationship between the area of ​​the island portion (μm2) in the adhesive layer of Example 2B and the percentage (%) of the number of islands of each area relative to the total number of islands. [Figure 16] This graph shows the relationship between the area of ​​the island portion (μm2) in the adhesive layer of Example 3B and the percentage (%) of the number of islands of each area relative to the total number of islands. [Figure 17] This graph shows the relationship between the area of ​​the island portion (μm2) in the adhesive layer of Example 4B and the percentage (%) of the number of islands of each area relative to the total number of islands. [Figure 18] This graph shows the relationship between the area of ​​the island portion (μm2) and the percentage of the number of islands of each area relative to the total number of islands in the adhesive layer of Comparative Example 1B. [Figure 19] This is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an energy storage device according to the third embodiment. [Figure 20] This is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an energy storage device according to the third embodiment. [Figure 21] This is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an energy storage device according to the third embodiment. [Figure 22] This is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an energy storage device according to the third embodiment. [Modes for carrying out the invention]

[0029] The exterior material for an energy storage device according to the first embodiment of this disclosure is composed of a laminate comprising, at least, a base layer, a barrier layer, and an inner layer in that order, and is characterized in that, when dynamic viscoelasticity measurement is performed by tension on the inner layer, the elongation rate at 80°C is 8.0% or less.

[0030] According to the exterior material for energy storage devices of the first embodiment of this disclosure, by having this configuration, when heat-sealable resin layers are heat-sealed together, the adhesion between the heat-sealable resin layers in a high-temperature environment is high, and excellent sealing performance can be achieved in a high-temperature environment.

[0031] An exterior material for an energy storage device according to a second embodiment of this disclosure is composed of a laminate comprising, in this order, at least a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer, wherein the adhesive layer contains a polypropylene resin and polyethylene, and a sea-island structure is observed in a cross-sectional image obtained using a scanning electron microscope of the cross-section of the adhesive layer in a direction parallel to the TD and in the thickness direction, wherein the cross-sectional image is obtained within the range from the surface of the adhesive layer on the barrier layer side to a portion with a thickness of 25%, when the thickness of the adhesive layer is set to 100%, and in the cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.25 μm² relative to the total number of island portions of the sea-island structure. 2 The present invention is characterized in that the proportion of the total number of island portions less than 40% is 40% or more. The exterior material for an energy storage device according to the second embodiment of this disclosure has excellent sealing properties in high-temperature environments due to having the above configuration.

[0032] The exterior material for an energy storage device according to the third embodiment of this disclosure is composed of a laminate comprising, in order from the outside to the inside, at least a base layer, a barrier layer, and a heat-fusible resin layer, wherein the heat-fusible resin layer contains polypropylene and polyethylene, and a sea-island structure is observed in a cross-sectional image obtained using a scanning electron microscope of the cross-section of the heat-fusible resin layer in a direction parallel to the TD and in the thickness direction, and the cross-sectional image is obtained within a range from the surface of the heat-fusible resin layer opposite the barrier layer side to a portion with a thickness of 12.5%, assuming that the total thickness of the layers located inside the barrier layer is 100%, and in the cross-sectional image, the area of ​​the island portion is 0.02 μm² relative to the total number of island portions of the sea-island structure. 2 The proportion of the total number of the following island portions is 80.0% or more, and at least one of the layers inside the barrier layer contains at least one of an antioxidant and a radical scavenger. According to the exterior material for energy storage devices of the third embodiment of this disclosure, having this configuration suppresses whitening due to molding and a decrease in insulation performance.

[0033] The exterior materials for energy storage devices described herein will be described in detail below. In this specification, numerical ranges indicated by "~" mean "greater than or equal to" and "less than or equal to". For example, the notation 2~15mm means 2mm or more and 15mm or less.

[0034] In the following description, any description of the disclosure that is specific to the first embodiment, the second embodiment, or the third embodiment will be clearly indicated. Unless otherwise specified, any description of the disclosure that is common to the first embodiment, the second embodiment, and the third embodiment will be described.

[0035] Furthermore, in the case of exterior materials for energy storage devices, the Machine Direction (MD) and Transverse Direction (TD) of the barrier layer 3, described later, can usually be determined during the manufacturing process. For example, if the barrier layer 3 is made of aluminum foil, linear lines called rolling marks are formed on the surface of the aluminum foil in the rolling direction (RD) of the aluminum foil. Since the rolling marks extend along the rolling direction, the rolling direction of the aluminum foil can be determined by observing the surface of the aluminum foil. Also, in the manufacturing process of a laminate, the MD of the laminate and the RD of the aluminum foil usually coincide, so by observing the surface of the aluminum foil in the laminate and determining the rolling direction (RD) of the aluminum foil, the MD of the laminate can be determined. In addition, since the TD of the laminate is perpendicular to the MD of the laminate, the TD of the laminate can also be determined.

[0036] Furthermore, if the MD of the exterior material for energy storage devices cannot be identified by the rolling marks of the aluminum alloy foil, it can be identified by the following method. One method for confirming the MD of the exterior material for energy storage devices is to observe the cross-section of the heat-fusible resin layer of the exterior material with an electron microscope and confirm the sea-island structure. In this method, the direction parallel to the cross-section where the average diameter of the island shapes perpendicular to the thickness direction of the heat-fusible resin layer is maximum can be determined as the MD. Specifically, the sea-island structure is confirmed by observing electron microscope images of each of the cross-sections in the longitudinal direction of the heat-fusible resin layer, and each of the cross-sections (a total of 10 cross-sections) from the direction parallel to the longitudinal cross-section, changing the angle by 10 degrees at a time, up to the direction perpendicular to the longitudinal cross-section. Next, the shape of each individual island is observed in each cross-section. For each island shape, the straight-line distance connecting the leftmost point perpendicular to the thickness direction of the heat-fusible resin layer and the rightmost point perpendicular to that point is defined as the diameter y. In each cross-section, the average of the top 20 diameters y of the island shapes, in descending order of diameter y, is calculated. The direction parallel to the cross-section where the average of the relevant diameter y of the island's shape was largest is determined to be the MD (Movement Direction).

[0037] 1. Laminated structure and physical properties of exterior materials for energy storage devices The exterior material 10 for a power storage device according to the first embodiment of this disclosure is composed of a laminate comprising a base layer 1, a barrier layer 3, and an inner layer (adhesive layer 5 and heat-fusible resin layer 4) in that order, as shown in Figure 1, for example. In the exterior material 10 for a power storage device, the base layer 1 is the outermost layer, and the heat-fusible resin layer 4 of the inner layer is the innermost layer. When assembling a power storage device using the exterior material 10 and a power storage device element, the power storage device element is housed in a space formed by heat-fussing the peripheral edges of the heat-fusible resin layers 4 of the exterior material 10 facing each other. In the laminate constituting the exterior material 10 for a power storage device according to the first embodiment of this disclosure, with respect to the barrier layer 3, the heat-fusible resin layer 4 side is inward of the barrier layer 3, and the base layer 1 side is outward of the barrier layer 3.

[0038] The exterior material 10 for the energy storage device according to the first embodiment may, for example, have an adhesive layer 2 between the base layer 1 and the barrier layer 3, as needed, for the purpose of improving the adhesion between these layers, as shown in Figures 2 and 3. Also, as shown in Figure 3, a surface coating layer 6 or the like may be provided on the outside of the base layer 1 (opposite the side from the heat-fusible resin layer 4), as needed.

[0039] Furthermore, the exterior material 10 for the energy storage device according to the second embodiment of this disclosure is composed of a laminate comprising a base layer 1, a barrier layer 3, an adhesive layer 5, and a heat-fusible resin layer 4 in that order, as shown in Figure 10, for example. In the exterior material 10 for the energy storage device, the base layer 1 is the outermost layer, and the heat-fusible resin layer 4 is the innermost layer. When assembling an energy storage device using the exterior material 10 and an energy storage device element, the energy storage device element is housed in a space formed by heat-fusing the peripheral edges of the heat-fusible resin layers 4 of the exterior material 10 facing each other.

[0040] The exterior material 10 for the energy storage device according to the second embodiment may, for example, have an adhesive layer 2 between the base layer 1 and the barrier layer 3, as needed, for the purpose of improving the adhesion between these layers, as shown in Figures 11 to 13. Also, as shown in Figure 13, a surface coating layer 6 or the like may be provided on the outside of the base layer 1 (opposite the side from the heat-fusible resin layer 4), as needed.

[0041] Furthermore, the exterior material 10 for the energy storage device according to the third embodiment of this disclosure is composed of a laminate comprising a base layer 1, a barrier layer 3, and a heat-sealable resin layer 4 in that order, as shown in Figure 19, for example. In the exterior material 10 for the energy storage device, the base layer 1 is the outermost layer, and the heat-sealable resin layer 4 is the innermost layer. When assembling an energy storage device using the exterior material 10 and an energy storage device element, the energy storage device element is housed in a space formed by heat-sealing the peripheral edges of the heat-sealable resin layers 4 of the exterior material 10 facing each other.

[0042] The exterior material 10 for the energy storage device according to the third embodiment may, for example as shown in Figures 20 to 22, have an adhesive layer 2 between the base layer 1 and the barrier layer 3, if necessary, for the purpose of improving the adhesion between these layers. Also, for example as shown in Figures 21 and 22, an adhesive layer 5 may be provided between the barrier layer 3 and the heat-fusible resin layer 4, if necessary, for the purpose of improving the adhesion between these layers. Furthermore, as shown in Figure 22, a surface coating layer 6 or the like may be provided on the outside of the base layer 1 (opposite the heat-fusible resin layer 4 side), if necessary.

[0043] Furthermore, the exterior material 10 for the energy storage device according to the third embodiment of this disclosure is composed of a laminate comprising a base layer 1, a barrier layer 3, and a heat-sealable resin layer 4 in that order, as shown in Figure 19, for example. In the exterior material 10 for the energy storage device, the base layer 1 is the outermost layer, and the heat-sealable resin layer 4 is the innermost layer. When assembling an energy storage device using the exterior material 10 and an energy storage device element, the energy storage device element is housed in a space formed by heat-sealing the peripheral edges of the heat-sealable resin layers 4 of the exterior material 10 facing each other.

[0044] The exterior material 10 for the energy storage device according to the third embodiment may, for example as shown in Figures 20 to 22, have an adhesive layer 2 between the base layer 1 and the barrier layer 3, if necessary, for the purpose of improving the adhesion between these layers. Also, for example as shown in Figures 21 and 22, an adhesive layer 5 may be provided between the barrier layer 3 and the heat-fusible resin layer 4, if necessary, for the purpose of improving the adhesion between these layers. Furthermore, as shown in Figure 22, a surface coating layer 6 or the like may be provided on the outside of the base layer 1 (opposite the heat-fusible resin layer 4 side), if necessary.

[0045] In this disclosure, the thickness of the laminate constituting the exterior material 10 for energy storage devices is not particularly limited, but from the viewpoint of cost reduction and improvement of energy density, for example, it can be about 190 μm or less, preferably about 180 μm or less, about 155 μm or less, or about 120 μm or less. Furthermore, from the viewpoint of maintaining the function of the exterior material for energy storage devices, which is to protect the energy storage device elements, the thickness of the laminate constituting the exterior material 10 for energy storage devices can be preferably about 35 μm or more, about 45 μm or more, or about 60 μm or more. Furthermore, preferred ranges for the laminate constituting the outer casing material 10 for the energy storage device include, for example, approximately 35-190 μm, 35-180 μm, 35-155 μm, 35-120 μm, 45-190 μm, 45-180 μm, 45-155 μm, 45-120 μm, 60-190 μm, 60-180 μm, 60-155 μm, and 60-120 μm, with approximately 60-155 μm being particularly preferred.

[0046] In the exterior material 10 for energy storage devices according to the first embodiment of this disclosure, the ratio of the total thickness of the base layer 1, the adhesive layer 2 (optionally provided), the barrier layer 3, the inner layer (adhesive layer 5, heat-fusible resin layer 4), and the surface coating layer 6 (optionally provided) to the thickness (total thickness) of the laminate constituting the exterior material 10 for energy storage devices is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. Specifically, when the exterior material 10 for energy storage devices according to the first embodiment of this disclosure includes a base layer 1, an adhesive layer 2, a barrier layer 3, and an inner layer (adhesive layer 5 and heat-fusible resin layer 4), the ratio of the total thickness of each of these layers to the thickness (total thickness) of the laminate constituting the exterior material 10 for energy storage devices is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

[0047] Furthermore, in the exterior material 10 for energy storage devices according to the second embodiment of this disclosure, the ratio of the total thickness of the base layer 1, the adhesive layer 2 (optionally provided), the barrier layer 3, the adhesive layer 5, the heat-fusible resin layer 4, and the surface coating layer 6 (optionally provided) to the thickness (total thickness) of the laminate constituting the exterior material 10 for energy storage devices is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. Specifically, when the exterior material 10 for energy storage devices according to the second embodiment of this disclosure includes a base layer 1, an adhesive layer 2, a barrier layer 3, an adhesive layer 5, and a heat-fusible resin layer 4, the ratio of the total thickness of each of these layers to the thickness (total thickness) of the laminate constituting the exterior material 10 for energy storage devices is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

[0048] In the exterior material 10 for energy storage devices according to the third embodiment of this disclosure, the ratio of the total thickness of the base layer 1, optionally provided adhesive layer 2, barrier layer 3, optionally provided adhesive layer 5, heat-fusible resin layer 4, and optionally provided surface coating layer 6 to the thickness (total thickness) of the laminate constituting the exterior material 10 for energy storage devices is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. Specifically, if the exterior material 10 for energy storage devices according to the third embodiment of this disclosure includes a base layer 1, an adhesive layer 2, a barrier layer 3, an adhesive layer 5, and a heat-fusible resin layer 4, the ratio of the total thickness of each of these layers to the thickness (total thickness) of the laminate constituting the exterior material 10 for energy storage devices is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

[0049] The exterior material 10 for an energy storage device according to the first embodiment of this disclosure has an elongation rate of 8.0% or less at 80°C when dynamic viscoelasticity measurement is performed on the inner layer by tension. The method for measuring the elongation rate by dynamic viscoelasticity measurement is as follows. The lower the elongation rate obtained by this dynamic viscoelasticity measurement, the higher the crystallinity of the inner layer (adhesive layer 5 and heat-fusible resin layer 4), and the more the softening of the inner layer is suppressed, thus improving the sealing performance against internal stress in high-temperature environments.

[0050] <Dynamic Viscoelasticity (DMA) Measurement> For the exterior material for energy storage devices, a sample is prepared from the inner layer and dynamic viscoelasticity measurements are performed. Specifically, the barrier layer of the exterior material for energy storage devices is dissolved by immersing it in a 10% hydrochloric acid aqueous solution for 24 hours to obtain the inner layer (a laminate of an adhesive layer and a heat-fusible resin layer). This inner layer is a laminate composed only of the adhesive layer 5 and the heat-fusible resin layer 4, with the layers on the barrier layer side of the adhesive layer of the exterior material for energy storage devices (i.e., the barrier layer 3, adhesive layer 2 if necessary, base layer 1, surface coating layer 6 if necessary, etc.) removed. Next, this inner layer is washed with water, dried, and cut into pieces 5 mm wide and 10 mm long to obtain a sample. Then, dynamic viscoelasticity measurements are performed on the obtained sample using a dynamic viscoelasticity measuring device (for example, product name Rheogel-E4000 manufactured by UBM Co., Ltd.) under the following measurement conditions.

[0051] (Measurement conditions) Sample width 5mm Starting temperature 30℃ End temperature 160℃ Heating rate: 2°C / min Static load 50g Distance between test holders (distance between chucks): 10 mm Chuck pull Software used for measurement: RheoStation (ver7) Step temperature 1°C Waveform: Sine wave, 10Hz, distortion 10μm, distortion control (automatic adjustment) Measuring jig: tensile To prevent the sample from fracturing and making measurement impossible, the load is controlled at a constant level until the elongation reaches 10%. After the elongation reaches 10%, the load control is stopped, and the sample is then stretched by 20 μm for every 1°C increase.

[0052] The elongation rate at 80°C mentioned above may be 8.0% or less, but from the viewpoint of further improving the airtightness of the exterior material for energy storage devices in high-temperature environments, it is preferably about 7.0% or less, more preferably about 6.0% or less, and even more preferably about 5.5% or less. The elongation rate at 80°C mentioned above may also be, for example, about 0.0% or more, about 1.0% or more, about 2.0% or more, etc. The preferred range for the elongation rate at 80°C mentioned above is about 0.0 to 8.0%, about 0.0 to 7.0%, about 0.0 to 6.0%, about 0.0 to 5.5%, about 1.0 to 8.0%, about 1.0 to 7.0%, about 1.0 to 6.0%, about 1.0 to 5.5%, about 2.0 to 8.0%, about 2.0 to 7.0%, about 2.0 to 6.0%, about 2.0 to 5.5%, and about 3.7 to 4.7%.

[0053] In the exterior material for energy storage devices according to the first embodiment of this disclosure, one suitable example for setting the elongation rate at 80°C in the dynamic viscoelasticity measurement of the inner layer by tension to 8.0% or less is to increase the crystallinity of the adhesive layer and the heat-fusible resin layer. Specifically, when manufacturing the exterior material for energy storage devices, the adhesive layer and the heat-fusible resin layer are formed by melt extrusion molding, cooled, and then reheated to a temperature above the melting point of the adhesive layer and the heat-fusible resin layer, and then cooled again. Furthermore, the cooling rate after reheating is preferably set so that the temperature drop from the start of cooling to 60°C or less, more preferably to 50°C or less, and even more preferably to 45°C or less for the first 3 seconds, thereby controlling the initial cooling conditions to very slow cooling conditions and promoting the crystal growth of the resin in the adhesive layer and the heat-fusible resin layer. For example, by forming the adhesive layer and the heat-fusible resin layer using such a method, the crystallinity of the adhesive layer and the heat-fusible resin layer is increased, and the sealing performance in high-temperature environments is improved.

[0054] Furthermore, the elongation rate of the inner layer at 110°C, as measured by the dynamic viscoelasticity measurement described above, is not particularly limited, but from the viewpoint of further improving the sealing performance of the exterior material for energy storage devices in high-temperature environments, it is preferably about 15.0% or less, more preferably about 14.0% or less, and even more preferably 13.5% or less. In addition, the elongation rate at 110°C may be, for example, about 5.0% or more, about 6.0% or more, about 7.0% or more, about 8.0% or more, etc. The preferred ranges for the elongation rate at 110°C are approximately 5.0-15.0%, 5.0-14.0%, 5.0-13.5%, 6.0-15.0%, 6.0-14.0%, 6.0-13.5%, 7.0-15.0%, 7.0-14.0%, 7.0-13.5%, 8.0-15.0%, 8.0-14.0%, 8.0-13.5%, and 10.0-13.0%.

[0055] In the exterior material for an energy storage device according to the first embodiment of this disclosure, the method for setting the elongation rate at 110°C in the dynamic viscoelasticity measurement by tension of the inner layer to 15.0% or less is the method described above for setting the elongation rate at 80°C in the dynamic viscoelasticity measurement by tension to 8.0% or less (i.e., the very slow cooling conditions immediately after the post-heating process described above).

[0056] Furthermore, in the exterior material for energy storage devices according to the first embodiment of this disclosure, in the graph showing the relationship between elongation (%) and temperature (°C) obtained by the dynamic viscoelasticity measurement described above, the temperature at which the elongation is 10% is not particularly limited, but from the viewpoint of further improving the sealing performance of the exterior material for energy storage devices in high-temperature environments, it is preferably 85°C or higher, more preferably 90°C or higher, even more preferably 100°C or higher, and particularly preferably 105°C or higher. Also, such temperatures are, for example, 130°C or lower, 120°C or lower, 110°C or lower, etc. The preferred temperature ranges are approximately 85-130°C, 85-120°C, 85-110°C, 90-130°C, 90-120°C, 90-110°C, 100-130°C, 100-120°C, 100-110°C, 105-130°C, 105-120°C, and 105-110°C. The temperature at which the elongation rate is 10% is, for example, the temperature at position I in the schematic diagram of Figure 7, and at temperatures higher than position I, the graph becomes a straight line.

[0057] In the exterior material for an energy storage device according to the first embodiment of this disclosure, a method for setting the temperature to 85°C or higher can be the method of setting the elongation rate at 80°C in the dynamic viscoelasticity measurement by tensile stress described above to 8.0% or less (i.e., very slow cooling conditions immediately after the post-heating process described above).

[0058] 2. Each layer forming the exterior material for the energy storage device [Base material layer 1] In this disclosure, the base material layer 1 is a layer provided for purposes such as enabling it to function as a base material for the exterior material of an energy storage device. The base material layer 1 is located on the outer layer side of the exterior material for the energy storage device.

[0059] The material forming the base layer 1 is not particularly limited, as long as it has the function of a base material, that is, at least insulating properties. The base layer 1 can be formed using, for example, a resin, and the resin may contain additives described later.

[0060] When the base layer 1 is formed of resin, the base layer 1 may be, for example, a resin film formed of resin, or a film formed by coating with resin. The resin film may be an unstretched film or a stretched film. Examples of stretched films include uniaxially stretched films and biaxially stretched films, with biaxially stretched films being preferred. Examples of stretching methods for forming a biaxially stretched film include sequential biaxial stretching, inflation stretching, and simultaneous biaxial stretching. Examples of resin coating methods include roll coating, gravure coating, and extrusion coating.

[0061] Examples of resins that form the base layer 1 include polyester, polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicon resin, phenolic resin, and modified versions of these resins. Furthermore, the resin forming the base layer 1 may be a copolymer of these resins, or a modified version of such copolymer. It may also be a mixture of these resins.

[0062] Among these, polyester and polyamide are preferred as resins for forming the base layer 1.

[0063] Examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymerized polyesters. Examples of copolymerized polyesters include copolymerized polyesters with ethylene terephthalate as the main repeating unit. Specifically, examples include copolymerized polyesters polymerized with ethylene isophthalate using ethylene terephthalate as the main repeating unit (hereinafter abbreviated as polyethylene(terephthalate / isophthalate)), polyethylene(terephthalate / adipate), polyethylene(terephthalate / sodium sulfoisophthalate), polyethylene(terephthalate / sodium isophthalate), polyethylene(terephthalate / phenyl-dicarboxylate), and polyethylene(terephthalate / decanedicarboxylate). These polyesters may be used individually or in combination of two or more types.

[0064] Furthermore, polyamides specifically include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (where I represents isophthalic acid and T represents terephthalic acid), which contain constituent units derived from terephthalic acid and / or isophthalic acid; aromatic polyamides such as polyamide MXD6 (polymetaxylylene adipamide); alicyclic polyamides such as polyamide PACM6 (polybis(4-aminocyclohexyl)methaneadipamide); and lactam components and 4,4'-diphenylmethane-diisocyane Examples of polyamides include polyamides obtained by copolymerizing isocyanate components such as phosphate, polyesteramide copolymers and polyether esteramide copolymers which are copolymers of copolymerized polyamides with polyester or polyalkylene ether glycol; and these copolymers. These polyamides may be used individually or in combination of two or more types.

[0065] The base layer 1 preferably contains at least one of polyester film, polyamide film, and polyolefin film, preferably at least one of stretched polyester film, stretched polyamide film, and stretched polyolefin film, more preferably at least one of stretched polyethylene terephthalate film, stretched polybutylene terephthalate film, stretched nylon film, and stretched polypropylene film, and even more preferably at least one of biaxially oriented polyethylene terephthalate film, biaxially oriented polybutylene terephthalate film, biaxially oriented nylon film, and biaxially oriented polypropylene film.

[0066] The base layer 1 may be a single layer or may consist of two or more layers. If the base layer 1 consists of two or more layers, the base layer 1 may be a laminate formed by laminating resin films with an adhesive, or it may be a laminate of two or more resin films formed by co-extruding resin. Furthermore, the laminate of two or more resin films formed by co-extruding resin may be used as the base layer 1 in its unstretched state, or it may be used as the base layer 1 after uniaxial stretching or biaxial stretching.

[0067] Specific examples of a laminate of two or more resin films in the base layer 1 include a laminate of polyester film and nylon film, a laminate of two or more nylon films, and a laminate of two or more polyester films. Preferably, a laminate of stretched nylon film and stretched polyester film, a laminate of two or more stretched nylon films, and a laminate of two or more stretched polyester films are preferred. For example, when the base layer 1 is a laminate of two resin films, a laminate of polyester resin film and polyester resin film, a laminate of polyamide resin film and polyamide resin film, or a laminate of polyester resin film and polyamide resin film is preferred, and a laminate of polyethylene terephthalate film and polyethylene terephthalate film, a laminate of nylon film and nylon film, or a laminate of polyethylene terephthalate film and nylon film is more preferred. Furthermore, since polyester resin is less likely to discolor when an electrolyte adheres to its surface, for example, when the base layer 1 is a laminate of two or more resin films, it is preferable that the polyester resin film be located in the outermost layer of the base layer 1.

[0068] If the base layer 1 is a laminate of two or more resin films, the two or more resin films may be laminated with an adhesive in between. Preferred adhesives include those similar to those exemplified in adhesive layer 2 described later. The method for laminating the two or more resin films is not particularly limited, and known methods can be used, such as dry lamination, sandwich lamination, extrusion lamination, and thermal lamination, with dry lamination being preferred. When laminating by dry lamination, it is preferable to use a polyurethane adhesive. In this case, the thickness of the adhesive is, for example, about 2 to 5 μm. Alternatively, an anchor coat layer may be formed on the resin film and laminated. The anchor coat layer is similar to the adhesive exemplified in adhesive layer 2 described later. In this case, the thickness of the anchor coat layer is, for example, about 0.01 to 1.0 μm.

[0069] Furthermore, at least one of the surface and interior of the base layer 1 may contain additives such as lubricants, flame retardants, antiblocking agents, antioxidants, light stabilizers, tackifiers, and antistatic agents. Only one type of additive may be used, or two or more types may be mixed and used.

[0070] In this disclosure, from the viewpoint of improving the moldability of the exterior material for energy storage devices, it is preferable that a lubricant be present on the surface of the base layer 1. The lubricant is not particularly limited, but amide lubricants are preferred. Specific examples of amide lubricants 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 saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearate amide, N-stearyl oleic acid amide, N-oleyl stearate amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearate amide. Specific examples of saturated fatty acid bisamides include methylenebisstearate, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearate, ethylenebishydroxystearate, ethylenebisbehenamide, hexamethylenebisstearate, hexamethylenebisbehenamide, hexamethylenehydroxystearate, N,N'-distearyladipamide, and N,N'-distearylsebacinamide. Specific examples of unsaturated fatty acid bisamides include ethylenebisoleamide, ethylenebiserucamide, hexamethylenebisoleamide, N,N'-dioleyladipamide, and N,N'-dioleylsebacinamide. Specific examples of fatty acid ester amides include stearamidoethylstearate. Specific examples of aromatic bisamides include m-xylylenebisstearate, m-xylylenebishydroxystearate, and N,N'-distearyl isophthalamide. The lubricant may be used alone or in combination of two or more types.

[0071] When a lubricant is present on the surface of the base material layer 1, its amount of presence is not particularly limited, but preferably about 3 mg / m 2 or more, more preferably 4 to 15 mg / m 2 or so, even more preferably 5 to 14 mg / m 2 or so.

[0072] The lubricant present on the surface of the base material layer 1 may be one obtained by exuding the lubricant contained in the resin constituting the base material layer 1, or may be one obtained by applying a lubricant to the surface of the base material layer 1.

[0073] Regarding the thickness of the base material layer 1, it is not particularly limited as long as it exhibits the function as a base material. For example, it is about 3 to 50 μm, preferably about 10 to 35 μm. When the base material layer 1 is a laminate of two or more resin films, the thickness of each resin film constituting each layer is preferably about 2 to 25 μm, respectively.

[0074] [Adhesive layer 2] In the exterior material for a power storage device of the present disclosure, the adhesive layer 2 is a layer provided between them as needed for the purpose of enhancing the adhesiveness between the base material layer 1 and the barrier layer 3.

[0075] The adhesive layer 2 is formed of an adhesive capable of adhering the base material layer 1 and the barrier layer 3. The adhesive used for forming the adhesive layer 2 is not limited, and it may be any of a chemical reaction type, a solvent volatilization type, a hot melt type, a hot press type, etc. Also, it may be a two-component curing adhesive (two-component adhesive), a one-component curing adhesive (one-component adhesive), or a resin without a curing reaction. Further, the adhesive layer 2 may be a single layer or a multi-layer.

[0076] Specifically, adhesive components included in adhesives include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, copolymerized polyester; polyethers; polyurethanes; epoxy resins; phenolic resins; polyamides such as nylon 6, nylon 66, nylon 12, copolymerized polyamides; polyolefin resins such as polyolefins, cyclic polyolefins, acid-modified polyolefins, and acid-modified cyclic polyolefins; polyvinyl acetate; cellulose; (meth)acrylic resins; polyimides; polycarbonates; amino resins such as urea resins and melamine resins; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; and silicone resins. These adhesive components may be used individually or in combination of two or more. Among these adhesive components, polyurethane adhesives are particularly preferred. Furthermore, the adhesive strength of these adhesive resins can be increased by using an appropriate curing agent. The curing agent is selected appropriately from polyisocyanates, polyfunctional epoxy resins, oxazoline group-containing polymers, polyamine resins, acid anhydrides, etc., depending on the functional groups of the adhesive components.

[0077] Examples of polyurethane adhesives include polyurethane adhesives comprising a main component containing a polyol compound and a curing agent containing an isocyanate compound. Preferably, two-component curing polyurethane adhesives are used, with a polyol such as polyester polyol, polyether polyol, and acrylic polyol as the main component and an aromatic or aliphatic polyisocyanate as the curing agent. Furthermore, it is preferable to use a polyester polyol as the polyol compound, which has hydroxyl groups not only at the terminals of the repeating units but also in the side chains. Examples of curing agents include aliphatic, alicyclic, aromatic, and aromaticaliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Furthermore, examples include polyfunctional isocyanate modified products derived from one or more of these diisocyanates. Polyisocyanate compounds can also be used as polymers (e.g., trimers). Such polymers include adducts, biuretes, and nurates. The adhesive layer 2 is formed from a polyurethane adhesive, providing excellent electrolyte resistance to the exterior material for energy storage devices, and preventing the substrate layer 1 from peeling off even if electrolyte adheres to the sides.

[0078] Furthermore, the adhesive layer 2 may contain other components as long as they do not impair adhesion, and may include colorants, thermoplastic elastomers, tackifiers, fillers, etc. The inclusion of a colorant in the adhesive layer 2 allows for the coloring of the exterior material for energy storage devices. Known colorants such as pigments and dyes can be used. Additionally, only one type of colorant may be used, or two or more types may be mixed.

[0079] The type of pigment is not particularly limited, as long as it does not impair the adhesion of adhesive layer 2. Examples of organic pigments include azo, phthalocyanine, quinacridone, anthraquinone, dioxazine, indigothioindigo, perinone-perylene, isoindorenine, and benzimidazolon pigments. Examples of inorganic pigments include carbon black, titanium dioxide, cadmium, lead, chromium oxide, and iron pigments. Other examples include fine mica powder and fish scale foil.

[0080] Among colorants, carbon black is preferred for, for example, to give the exterior material of an energy storage device a black appearance.

[0081] The average particle size of the pigment is not particularly limited, but for example, it can be about 0.05 to 5 μm, preferably about 0.08 to 2 μm. The average particle size of the pigment is the median diameter measured by a laser diffraction / scattering particle size distribution analyzer.

[0082] The pigment content in the adhesive layer 2 is not particularly limited as long as the exterior material for the energy storage device is colored, and for example, it is about 5 to 60% by mass, preferably 10 to 40% by mass.

[0083] The thickness of the adhesive layer 2 is not particularly limited as long as it can bond the substrate layer 1 and the barrier layer 3, but for example, it is about 1 μm or more and about 2 μm or more. Also, the thickness of the adhesive layer 2 is, for example, about 10 μm or less and about 5 μm or less. Furthermore, preferred ranges for the thickness of the adhesive layer 2 include about 1 to 10 μm, about 1 to 5 μm, about 2 to 10 μm, and about 2 to 5 μm.

[0084] [Colored layer] The colored layer is a layer provided between the base layer 1 and the barrier layer 3 as needed (not shown in the figure). If an adhesive layer 2 is present, the colored layer may be provided between the base layer 1 and the adhesive layer 2, and between the adhesive layer 2 and the barrier layer 3. Alternatively, the colored layer may be provided on the outside of the base layer 1. By providing a colored layer, the exterior material for the energy storage device can be colored.

[0085] The colored layer can be formed, for example, by applying an ink containing a coloring agent to the surface of the substrate layer 1 or the surface of the barrier layer 3. Known coloring agents such as pigments and dyes can be used. In addition, only one type of coloring agent may be used, or two or more types may be mixed and used.

[0086] Specific examples of colorants included in the colored layer are the same as those exemplified in the [Adhesive Layer 2] section.

[0087] [Barrier layer 3] In the exterior material for energy storage devices, the barrier layer 3 is a layer that at least prevents the intrusion of moisture.

[0088] Examples of barrier layer 3 include metal foil, vapor-deposited film, and resin layer with barrier properties. Examples of vapor-deposited films include metal vapor-deposited films, inorganic oxide vapor-deposited films, and carbon-containing inorganic oxide vapor-deposited films. Examples of resin layers include fluorine-containing resins such as polymers mainly composed of polyvinylidene chloride, chlorotrifluoroethylene (CTFE), polymers mainly composed of tetrafluoroethylene (TFE), polymers having fluoroalkyl groups, and polymers mainly composed of fluoroalkyl units, as well as ethylene vinyl alcohol copolymers. In addition, a resin film having at least one of these vapor-deposited films and resin layers can also be provided as barrier layer 3. Multiple layers of barrier layer 3 may be provided. It is preferable that barrier layer 3 includes a layer made of a metal material. Specific examples of metal materials constituting barrier layer 3 include aluminum alloy, stainless steel, titanium steel, and steel plates. When used as a metal foil, it is preferable that it includes at least one of aluminum alloy foil and stainless steel foil.

[0089] From the viewpoint of improving the formability of the exterior material for energy storage devices, the aluminum alloy foil is more preferably a soft aluminum alloy foil composed of, for example, an annealed aluminum alloy, and from the viewpoint of further improving formability, it is more preferably an aluminum alloy foil containing iron. In an iron-containing aluminum alloy foil (100% by mass), the iron content is preferably 0.1 to 9.0% by mass, and more preferably 0.5 to 2.0% by mass. By having an iron content of 0.1% by mass or more, an exterior material for energy storage devices with better formability can be obtained. By having an iron content of 9.0% by mass or less, an exterior material for energy storage devices with better flexibility can be obtained. Examples of soft aluminum alloy foils include aluminum alloy foils having compositions specified in JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, or JIS H4000:2014 A8079P-O. Silicon, magnesium, copper, manganese, etc., may also be added as needed. Softening can be achieved through annealing or other treatments.

[0090] Furthermore, examples of stainless steel foils include austenitic, ferritic, austenitic-ferritic, martensitic, and precipitation-hardening stainless steel foils. Moreover, from the viewpoint of providing an exterior material for energy storage devices with excellent formability, it is preferable that the stainless steel foil be made of austenitic stainless steel.

[0091] Specific examples of austenitic stainless steels that make up stainless steel foil include SUS304, SUS301, and SUS316L, with SUS304 being particularly preferred among these.

[0092] In the case of metal foil, the thickness of the barrier layer 3 should at least function as a barrier layer that prevents moisture from penetrating, for example, about 9 to 200 μm. The thickness of the barrier layer 3 is preferably about 85 μm or less, more preferably about 50 μm or less, even more preferably about 40 μm or less, and particularly preferably about 35 μm or less. Also, the thickness of the barrier layer 3 is preferably about 10 μm or more, even more preferably about 20 μm or more, and more preferably about 25 μm or more. Furthermore, preferred ranges for the thickness of the barrier layer 3 include 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. When the barrier layer 3 is made of aluminum alloy foil, the above-mentioned range is particularly preferred. Furthermore, when the barrier layer 3 is made of aluminum alloy foil, from the viewpoint of providing high formability and high rigidity to the exterior material 10 for the energy storage device, the thickness of the barrier layer 3 is preferably about 45 μm or more, more preferably about 50 μm or more, more preferably about 55 μm or more, preferably about 80 μm or less, more preferably 75 μm or less, and even more preferably 70 μm or less. Preferred ranges include about 45-80 μm, about 45-75 μm, about 45-70 μm, about 50-80 μm, about 50-75 μm, about 50-70 μm, about 55-80 μm, about 55-75 μm, and about 55-70 μm. By providing the exterior material 10 for the energy storage device with high formability, deep drawing can be facilitated, which can contribute to increasing the capacity of the energy storage device. Furthermore, as the capacity of the energy storage device increases, the weight of the energy storage device also increases. However, by increasing the rigidity of the exterior material 10 for the energy storage device, it is possible to contribute to the high airtightness of the energy storage device.

[0093] Furthermore, in particular when the barrier layer 3 is composed of stainless steel foil, the thickness of the stainless steel foil is preferably about 60 μm or less, more preferably about 50 μm or less, even more preferably about 40 μm or less, even more preferably about 30 μm or less, and especially preferably about 25 μm or less. Also, the thickness of the stainless steel foil is preferably about 10 μm or more, more preferably about 15 μm or more. Furthermore, preferred ranges for the thickness of the stainless steel foil include about 10 to 60 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 30 μm, about 10 to 25 μm, about 15 to 60 μm, about 15 to 50 μm, about 15 to 40 μm, about 15 to 30 μm, and about 15 to 25 μm.

[0094] Furthermore, if the barrier layer 3 is a metal foil, it is preferable to provide a corrosion-resistant coating on at least the side opposite to the substrate layer to prevent dissolution and corrosion. The barrier layer 3 may also have a corrosion-resistant coating on both sides. Here, a corrosion-resistant coating refers to a thin film that provides corrosion resistance (e.g., acid resistance, alkali resistance, etc.) to the barrier layer by performing treatments such as hot water modification treatment such as boehmite treatment, chemical conversion treatment, anodizing treatment, plating treatment with nickel or chromium, or corrosion prevention treatment by applying a coating agent to the surface of the barrier layer. Specifically, a corrosion-resistant coating means a coating that improves the acid resistance of the barrier layer (acid-resistant coating), a coating that improves the alkali resistance of the barrier layer (alkali-resistant coating), etc. One type of treatment may be performed to form the corrosion-resistant coating, or two or more types may be combined. In addition, it is possible to have multiple layers instead of just one. Furthermore, among these treatments, hot water modification treatment and anodizing treatment are treatments that dissolve the surface of the metal foil with a treatment agent and form a metal compound with excellent corrosion resistance. These processes may also be included in the definition of chemical conversion treatment. Furthermore, if barrier layer 3 has a corrosion-resistant coating, the barrier layer 3 includes the corrosion-resistant coating.

[0095] The corrosion-resistant coating prevents delamination between the barrier layer (e.g., aluminum alloy foil) and the base layer during the molding of exterior materials for energy storage devices. It also prevents dissolution and corrosion of the barrier layer surface due to hydrogen fluoride generated by the reaction of electrolyte and water, particularly the dissolution and corrosion of aluminum oxide present on the barrier layer surface when the barrier layer is aluminum alloy foil. Furthermore, it improves the adhesion (wettability) of the barrier layer surface, preventing delamination between the base layer and the barrier layer during heat sealing and molding.

[0096] Various corrosion-resistant coatings are known to be formed by chemical conversion treatments, mainly including corrosion-resistant coatings containing at least one of the following: phosphates, chromates, fluorides, triazinethiol compounds, and rare earth oxides. Examples of chemical conversion treatments using phosphates and chromates include chromate treatment, phosphate chromate treatment, phosphate-chromate treatment, and chromate treatment. Examples of chromium compounds used in these treatments include chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, acetyl acetate chromate, chromium chloride, and potassium chromium sulfate. Examples of phosphorus compounds used in these treatments include sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphate. Examples of chromate treatments include etching chromate treatment, electrolytic chromate treatment, and coating-type chromate treatment, with coating-type chromate treatment being preferred. This coating-type chromate treatment involves first degreasing at least the inner surface of a barrier layer (e.g., aluminum alloy foil) using a well-known treatment method such as alkaline immersion, electrolytic cleaning, acid cleaning, electrolytic acid cleaning, or acid activation. Then, a treatment solution mainly composed of metal phosphate salts such as chromium phosphate, titanium phosphate, zirconium phosphate, and zinc phosphate, or mixtures thereof, or a treatment solution mainly composed of nonmetallic phosphates and mixtures thereof, or a treatment solution consisting of a mixture of these with synthetic resins, etc., is applied to the degreased surface using a well-known coating method such as roll coating, gravure printing, or immersion, and then dried. Various solvents can be used as the treatment solution, such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, with water being preferred. Furthermore, examples of resin components used in this process include polymers such as phenolic resins and acrylic resins, and examples of chromate treatment using an amination phenol polymer having repeating units represented by the following general formulas (1) to (4). In this amination phenol polymer, the repeating units represented by the following general formulas (1) to (4) may be included individually or in any combination of two or more types.The acrylic resin is preferably polyacrylic acid, acrylate methacrylate copolymer, acrylate maleic acid copolymer, acrylate styrene copolymer, or derivatives thereof such as sodium salts, ammonium salts, or amine salts. Derivatives of polyacrylic acid, such as ammonium salts, sodium salts, or amine salts of polyacrylic acid, are particularly preferred. In this disclosure, polyacrylic acid means a polymer of acrylic acid. Furthermore, the acrylic resin is also preferably a copolymer of acrylic acid and a dicarboxylic acid or dicarboxylic acid anhydride, and also preferably an ammonium salt, sodium salt, or amine salt of a copolymer of acrylic acid and a dicarboxylic acid or dicarboxylic acid anhydride. Only one type of acrylic resin may be used, or two or more types may be mixed and used.

[0097] [ka]

[0098] [ka]

[0099] [ka]

[0100] [ka]

[0101] In general formulas (1) to (4), X represents a hydrogen atom, a hydroxyl group, an alkyl group, a hydroxyalkyl group, an allyl group, or a benzyl group. Also, R 1 and R 2 Each of these represents a hydroxyl group, an alkyl group, or a hydroxyalkyl group, either identical or different. In general formulas (1) to (4), X and R 1 and R 2Examples of alkyl groups represented by include linear or branched alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl groups. Also, X, R 1 and R 2 Examples of hydroxyalkyl groups represented by include linear or branched alkyl groups having 1 to 4 carbon atoms with one hydroxyl group substituted, such as hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, 1-hydroxypropyl group, 2-hydroxypropyl group, 3-hydroxypropyl group, 1-hydroxybutyl group, 2-hydroxybutyl group, 3-hydroxybutyl group, and 4-hydroxybutyl group. In general formulas (1) to (4), X and R 1 and R 2 The alkyl group and hydroxyalkyl group shown may be the same or different. In general formulas (1) to (4), X is preferably a hydrogen atom, a hydroxyl group, or a hydroxyalkyl group. The number-average molecular weight of the amination phenol polymer having repeating units represented by general formulas (1) to (4) is preferably about 500 to 1,000,000, and more preferably about 1,000 to 20,000. The amination phenol polymer is produced, for example, by polycondensing a phenol compound or naphthol compound with formaldehyde to produce a polymer consisting of repeating units represented by the above general formula (1) or general formula (3), and then adding formaldehyde and amine (R 1 R 2 Using NH) to form the functional group (-CH2NR 1 R 2 ) to be introduced into the polymer obtained above. It is manufactured by [method]. The amination phenol polymer is used alone or in a mixture of two or more types.

[0102] Another example of a corrosion-resistant coating is a thin film formed by a coating-type corrosion prevention treatment, which involves applying a coating agent containing at least one selected from the group consisting of rare earth element oxide sols, anionic polymers, and cationic polymers. The coating agent may further contain phosphoric acid or phosphate, and a crosslinking agent for crosslinking the polymer. In the rare earth element oxide sol, fine particles of rare earth element oxides (for example, particles with an average particle size of 100 nm or less) are dispersed in a liquid dispersion medium. Examples of rare earth element oxides include cerium oxide, yttrium oxide, neodymium oxide, and lanthanum oxide, with cerium oxide being preferred from the viewpoint of further improving adhesion. The rare earth element oxides contained in the corrosion-resistant coating can be used individually or in combination of two or more. Various solvents can be used as the liquid dispersion medium for the rare earth element oxide sol, such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, with water being preferred. Preferred cationic polymers include, for example, polyethyleneimine, ionic polymer complexes comprising polyethyleneimine and a polymer having a carboxylic acid, primary amine-grafted acrylic resins obtained by graft polymerization of a primary amine onto an acrylic main skeleton, polyallylamine or its derivatives, and amination phenols. Preferred anionic polymers are poly(meth)acrylic acid or its salts, or copolymers mainly composed of (meth)acrylic acid or its salts. Furthermore, the crosslinking agent is preferably at least one selected from the group consisting of a compound having one of the functional groups of isocyanate, glycidyl, carboxyl, or oxazoline, and a silane coupling agent. Additionally, the phosphoric acid or phosphate is preferably condensed phosphoric acid or condensed phosphate.

[0103] An example of a corrosion-resistant coating is one formed by dispersing metal oxides such as aluminum oxide, titanium oxide, cerium oxide, and tin oxide, or fine particles of barium sulfate, in phosphoric acid, applying this mixture to the surface of a barrier layer, and then baking it at a temperature of 150°C or higher.

[0104] The corrosion-resistant coating may, if necessary, be a laminated structure in which at least one of a cationic polymer and an anionic polymer is further laminated. Examples of cationic and anionic polymers include those mentioned above.

[0105] Furthermore, the composition of the corrosion-resistant coating can be analyzed, for example, using time-of-flight secondary ion mass spectrometry.

[0106] The amount of corrosion-resistant film to be formed on the surface of the barrier layer 3 in the chemical conversion treatment is not particularly limited, but for example, in the case of coating-type chromate treatment, the surface of the barrier layer 3 is 1 m 2 Each serving contains, for example, about 0.5 to 50 mg of chromium equivalent, preferably 1 It is desirable that the product contains approximately 0.0 to 40 mg of phosphorus compounds, for example, approximately 0.5 to 50 mg of phosphorus equivalent, preferably approximately 1.0 to 40 mg of aminophenol polymers, and for example, approximately 1.0 to 200 mg, preferably approximately 5.0 to 150 mg of aminophenol polymers.

[0107] The thickness of the corrosion-resistant coating is not particularly limited, but from the viewpoint of the cohesive force of the coating and the adhesion force with the barrier layer and the heat-fusible resin layer, it is preferably about 1 nm to 20 μm, more preferably about 1 nm to 100 nm, and even more preferably about 1 nm to 50 nm. The thickness of the corrosion-resistant coating 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 spectroscopy or electron beam energy loss spectroscopy. By analyzing the composition of the corrosion-resistant coating using time-of-flight secondary ion mass spectrometry, for example, secondary ions consisting of Ce, P, and O (e.g., Ce2PO4) can be identified. + , C epo4 - (at least one of the above), or, for example, a secondary ion consisting of Cr, P, and O (e.g., CrPO2) + , CrPO4 - Peaks originating from at least one of the following are detected.

[0108] The chemical conversion treatment is carried out by applying a solution containing compounds used to form a corrosion-resistant film to the surface of the barrier layer using methods such as bar coating, roll coating, gravure coating, or immersion, and then heating the barrier layer to a temperature of approximately 70-200°C. Alternatively, before applying the chemical conversion treatment to the barrier layer, it may be subjected to a degreasing treatment using methods such as alkaline immersion, electrolytic cleaning, acid cleaning, or electrolytic acid cleaning. This degreasing treatment makes it possible to perform the chemical conversion treatment on the surface of the barrier layer more efficiently. Furthermore, by using an acid degreasing agent, which is a fluorine-containing compound dissolved in an inorganic acid, it is possible to not only degrease the metal foil but also form a fluoride of the passive metal; in such cases, only the degreasing treatment may be performed.

[0109] [Thermal adhesive resin layer 4] In the exterior material for energy storage devices of this disclosure, the heat-sealable resin layer 4 included in the inner layer is the innermost layer and is a layer (sealant layer) that performs the function of sealing the energy storage device elements by heat-sealing the heat-sealable resin layers together during the assembly of the energy storage device.

[0110] In the first embodiment, the resin constituting the heat-fusible resin layer 4 is not particularly limited as long as it is heat-fusible and the elongation at 80°C when dynamic viscoelasticity measurement is performed by tensile stress on the inner layer is 8.0% or less, but a resin containing a polyolefin backbone, such as polyolefin or acid-modified polyolefin, is preferred. In the second embodiment, the resin constituting the heat-fusible resin layer 4 is not particularly limited as long as it is heat-fusible, but a resin containing a polyolefin backbone, such as polyolefin or acid-modified polyolefin, is preferred.

[0111] In this disclosure, the presence of a polyolefin backbone in the resin constituting the heat-fusible resin layer 4 can be analyzed, for example, by infrared spectroscopy or gas chromatography-mass spectrometry. Furthermore, when the resin constituting the heat-fusible resin layer 4 is analyzed by infrared spectroscopy, it is preferable that a peak originating from maleic anhydride is detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak at wavenumber 1760 cm⁻¹ is detected. -1 Nearby wave frequency 1780cm -1 A peak derived from maleic anhydride is detected in the vicinity. If the heat-fusible resin layer 4 is composed of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride will be detected when measured by infrared spectroscopy. However, if the degree of acid modification is low, the peak may become small and not be detected. In that case, analysis is possible by nuclear magnetic resonance spectroscopy.

[0112] In this disclosure, polyolefins specifically include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymer of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymer of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. Among these, polypropylene is preferred. When the polyolefin resin is a copolymer, it may be a block copolymer or a random copolymer. These polyolefin resins may be used individually or in combination of two or more.

[0113] Furthermore, in this disclosure, the polyolefin may be a cyclic polyolefin. A cyclic polyolefin is a copolymer of an olefin and a cyclic monomer. Examples of olefins that are constituent monomers of the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, isoprene, and the like. Examples of cyclic monomers that are constituent monomers of the cyclic polyolefin include cyclic alkenes such as norbornene; and cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, norbornadiene, and the like. Among these, cyclic alkenes are preferred, and norbornene is more preferred.

[0114] In this disclosure, acid-modified polyolefin is a polymer modified by block polymerization or graft polymerization of a polyolefin with an acid component. As the polyolefin to be acid-modified, the above-mentioned polyolefin, copolymers obtained by copolymerizing the above-mentioned polyolefin with a polar molecule such as acrylic acid or methacrylic acid, or polymers such as crosslinked polyolefins can also be used. Examples of acid components used for acid modification include carboxylic acids or their anhydrides, such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

[0115] In this disclosure, the acid-modified polyolefin may be an acid-modified cyclic polyolefin. An acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a portion of the monomers constituting a cyclic polyolefin with an acid component, or by block polymerization or graft polymerization of an acid component to a cyclic polyolefin. The cyclic polyolefin to be acid-modified is the same as described above. Furthermore, the acid component used for acid modification is the same as the acid component used for modifying the polyolefin described above.

[0116] In this disclosure, preferred acid-modified polyolefins include polyolefins modified with carboxylic acids or their anhydrides, polypropylenes modified with carboxylic acids or their anhydrides, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

[0117] In this disclosure, the heat-sealable resin layer 4 may be formed by a single resin or by a blended polymer of two or more resins. Furthermore, the heat-sealable resin layer 4 may be formed as a single layer or as two or more layers made of the same or different resins.

[0118] Furthermore, in this disclosure, the heat-fusible resin layer 4 may contain a lubricant or the like as needed. When the heat-fusible resin layer 4 contains a lubricant, the moldability of the exterior material for the energy storage device can be improved. The lubricant is not particularly limited, and known lubricants can be used. The lubricant may be used alone or in combination of two or more types.

[0119] The lubricant is not particularly limited, but amide-based lubricants are preferred. Specific examples of lubricants include those exemplified in base layer 1. The lubricant may be used alone or in combination of two or more types.

[0120] In this disclosure, when a lubricant is present on the surface of the heat-fusible resin layer 4, the amount present is not particularly limited, but from the viewpoint of improving the moldability of the exterior material for energy storage devices, it is preferably 10 to 50 mg / m². 2 To a certain extent, more preferably 15-40 mg / m² 2 The degree can be described as follows.

[0121] In this disclosure, the lubricant present on the surface of the heat-fusible resin layer 4 may be a lubricant contained in the resin constituting the heat-fusible resin layer 4 that has been exuded, or a lubricant may be applied to the surface of the heat-fusible resin layer 4.

[0122] Furthermore, in this disclosure, the thickness of the heat-fusible resin layer 4 is not particularly limited as long as the heat-fusible resin layers heat-fuse together to perform the function of sealing the energy storage device element, but for example, it can be about 100 μm or less, preferably about 85 μm or less, and more preferably about 15 to 85 μm.In this disclosure, for example, if the thickness of the adhesive layer 5 described later is 10 μm or more, the thickness of the heat-fusible resin layer 4 can be preferably about 85 μm or less, and more preferably about 15 to 45 μm.For example, if the thickness of the adhesive layer 5 described later is less than 10 μm or if the adhesive layer 5 is not provided, the thickness of the heat-fusible resin layer 4 can be preferably about 20 μm or more, and more preferably about 35 to 85 μm.

[0123] As described above, in the exterior material for energy storage devices according to the first embodiment of this disclosure, a suitable example for setting the elongation rate at 80°C in the dynamic viscoelasticity measurement of the inner layer by tension to 8.0% or less is to increase the crystallinity of the adhesive layer and the heat-fusible resin layer. It is desirable to control the initial cooling conditions after post-heating to very slow cooling conditions to promote the crystal growth of the resin in the adhesive layer and the heat-fusible resin layer. For example, by forming the heat-fusible resin layer using such a method, the crystallinity of the adhesive layer and the heat-fusible resin layer is increased, and the sealing performance in high-temperature environments is improved.

[0124] In the third embodiment, the heat-fusible resin layer 4 comprises polypropylene and polyethylene. In the exterior material for energy storage devices of the third embodiment of this disclosure, a sea-island structure is observed in the cross-sectional image obtained using a scanning electron microscope of the cross-section of the heat-fusible resin layer 4 in a direction parallel to TD and in the thickness direction y. The cross-sectional image is obtained within the range from the surface of the heat-fusible resin layer 4 opposite to the barrier layer 3 to a thickness of 12.5% ​​(the area enclosed by the dashed line in Figure 21), for example, as shown in the schematic diagram in Figure 21, when the total thickness of the layers located inside the barrier layer 3 is taken as 100%. The surface of the heat-fusible resin layer 4 opposite to the barrier layer 3 has a thickness of 0%. To explain with a specific example, as in Examples 1 and 2 described later, if the exterior material for an energy storage device is constructed by laminating a base layer (30 μm thick including the adhesive) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (40 μm) / heat-fusible resin layer (40 μm) in that order, then the layers located inside the barrier layer 3 are the adhesive layer (40 μm) and the heat-fusible resin layer (40 μm), and their combined thickness of 80 μm is considered 100%. Furthermore, the position of the heat-fusible resin layer 4 on the surface opposite to the barrier layer 3 is the inner surface (inner surface) of the exterior material for the energy storage device 10, and the thickness at this position is considered 0%. Then, a cross-sectional image is acquired using a scanning electron microscope within the range from the surface (0% thickness) to the position with a thickness of 12.5% ​​(i.e., with a total thickness of 80 μm as 100%, the position with a thickness of 12.5% ​​is the position where the thickness is 10 μm from the surface of the heat-fusible resin layer 4 opposite to the barrier layer 3 side toward the barrier layer 3 side).

[0125] The observation of a sea-island structure in a cross-sectional image means that the cross-sectional image shows both a sea portion and an island portion. As mentioned above, when a small amount of polyethylene is added to polypropylene and a heat-fusible resin layer is formed by melt extrusion molding, a sea-island structure is formed in which polyethylene islands are dispersed within the polypropylene sea portion. In other words, polyethylene is contained in the islands. To observe this sea-island structure, as described below, the cross-section of the heat-fusible resin layer is stained with ruthenium tetroxide or the like, and a cross-sectional image is acquired and observed using a scanning electron microscope.

[0126] In the exterior material for the energy storage device of the third embodiment, in the cross-sectional image of the heat-fusible resin layer 4, the area of ​​the island portion is 0.02 μm relative to the total number of island portions of the sea-island structure. 2 The following island areas The proportion of the total number is 80.0% or more. The exterior material for energy storage devices of the third embodiment has these characteristics, which suppresses whitening of the heat-fusible resin layer due to cold forming of the exterior material for energy storage devices and a decrease in the insulation properties of the exterior material for energy storage devices. In other words, in the exterior material for energy storage devices of the third embodiment of this disclosure, in the heat-fusible resin layer 4 containing polypropylene and polyethylene, of all island portions, the area is 0.02 μm 2 The following By setting a high proportion of the extremely fine island portions, the occurrence of fine cracks at the interface between the polypropylene and polyethylene portions of the heat-fusible resin layer is effectively suppressed. As a result, it is believed that whitening of the heat-fusible resin layer 4 due to cold forming of the exterior material for energy storage devices and a decrease in the insulation properties of the exterior material for energy storage devices are suppressed.

[0127] In the cross-sectional image of the heat-fusible resin layer 4 of the third embodiment, the area of ​​the island portion is 0.02 μm relative to the total number of island portions in the sea-island structure. 2 The percentage of the total number of island areas (0.02 μm) 2 The ratio of the total number of islands (total number of islands / total number of all islands) should be 80.0% or more, but from the viewpoint of more effectively suppressing the aforementioned whitening and decrease in insulation performance, it is preferably 90.0% or more, more preferably 95.0% or more. The ratio of the total number can be, for example, 100.0% or less, 99.0% or less, or 98.0% or less. A preferred range for the ratio of the total number can be, for example, around 80.0-100.0%, 80.0-99.0%, 80.0-98.0%, 90.0-100.0%, 90.0-99.0%, 90.0-98.0%, 95.0-100.0%, 95.0-99.0%, or 95.0-98.0%.

[0128] Furthermore, from the viewpoint of more effectively suppressing the aforementioned whitening and decrease in insulating properties, in the cross-sectional image of the heat-fusible resin layer 4 of the third embodiment, the area of ​​the island portion is 0.01 μm relative to the total number of island portions of the sea-island structure. 2 The percentage of the total number of island areas (0.01 μm) 2 The ratio of the total number of islands (total number of islands) is preferably 50.0% or more, more preferably 55.0% or more, and even more preferably 60.0% or more. The percentage of the total number is, for example, 80.0% or less, 75.0% or less, 70.0% or less, etc. A preferred range for the percentage of the total number is, for example, around 50.0-80.0%, around 50.0-75.0%, around 50.0-70.0%, around 55.0-80.0%, around 55.0-75.0%, around 55.0-70.0%, around 60.0-80.0%, around 60.0-75.0%, and around 60.0-70.0%.

[0129] Furthermore, from the viewpoint of more effectively suppressing the aforementioned whitening and decrease in insulating properties, in the cross-sectional image of the heat-fusible resin layer 4 of the third embodiment, the area of ​​the island portion of the island portion is 0.03 μm² relative to the total number of island portions of the sea-island structure. 2 The percentage of the total number of the following island areas (0.03 μm) 2 The ratio of the total number of islands (total number of islands / total number of all islands) is preferably 90.0% or more, more preferably 95.0% or more, and even more preferably 97.0% or more. The percentage of the total number is, for example, 100.0% or less, 99.0% or less, 98.0% or less, etc. A preferred range for the percentage of the total number is, for example, around 90.0-100.0%, around 90.0-99.0%, around 90.0-98.0%, around 95.0-100.0%, around 95.0-99.0%, around 95.0-98.0%, around 97.0-100.0%, around 97.0-99.0%, and around 97.0-98.0%.

[0130] Furthermore, from the viewpoint of more effectively suppressing the aforementioned whitening and decrease in insulating properties, in the cross-sectional image of the heat-fusible resin layer 4 of the third embodiment, the area of ​​the island portion is 0.30 μm relative to the total number of island portions of the sea-island structure. 2The percentage of the total number of the above island areas (0.30 μm 2 The ratio of the above-mentioned island units (total number of island units / total number of all island units) is preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.1% or less. The percentage of this total number is, for example, 0.0% or more.

[0131] Furthermore, from the viewpoint of more effectively suppressing the aforementioned whitening and decrease in insulating properties, in the cross-sectional image of the heat-fusible resin layer 4 of the third embodiment, the area of ​​the island portion of the island portion is 0.15 μm² relative to the total number of island portions of the sea-island structure. 2 The percentage of the total number of the above island areas (0.15 μm) 2 The ratio of the above-mentioned island units (total number of island units / total number of all island units) is preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.1% or less. The percentage of this total number is, for example, 0.0% or more.

[0132] Furthermore, from the viewpoint of more effectively suppressing the aforementioned whitening and decrease in insulating properties, in the cross-sectional image of the heat-fusible resin layer 4 of the third embodiment, the ratio of the total area of ​​the island portion of the sea-island structure to the area of ​​the measurement range of the cross-sectional image (total area of ​​the island portion / area of ​​the measurement range of the cross-sectional image) is preferably 12.0% or less, more preferably 5.0% or less, and even more preferably 1.0% or less. Examples of the ratio of the total area include 0.1% or more. Examples of a preferred range for the ratio of the total area include approximately 0.1 to 12.0%, approximately 0.1 to 5.0%, and approximately 0.1 to 1.0%.

[0133] In the third embodiment, the ratio of the total area of ​​the island portions of each area can be adjusted by adjusting the conditions for forming the heat-fusible resin layer 4, in addition to the blending ratio of polypropylene and polyethylene contained in the heat-fusible resin layer 4 (for example, if the heat-fusible resin layer 4 is formed by melt extrusion molding as described later, the cooling conditions of the heat-fusible resin layer by the cooling roll can be set to rapid cooling conditions (for example, setting the difference in surface temperature between the melt-extruded heat-fusible resin layer and the cooling roll to 70°C or higher) to suppress the crystal growth of polyethylene in polypropylene). Furthermore, the type and content of at least one of the antioxidant and radical scavenger contained in the heat-fusible resin layer 4 can also be used as one of the means to adjust the ratio of the total area of ​​the island portions of each area.

[0134] In the third embodiment, the method for measuring the proportion of the island area in a sea-island structure in a cross-sectional image of the heat-fusible resin layer 4 is as follows.

[0135] <Measurement of the ratio of island area and number of islands in a sea-island structure> The exterior material for the energy storage device is embedded in a thermosetting epoxy resin and cured. A cross-section parallel to the TD and in the thickness direction y is prepared using a commercially available rotary microtome (e.g., LEICA EM UC6) and a glass knife, and the cross-section is prepared at room temperature using the microtome. The thermosealable resin layer of the energy storage device exterior material, along with the embedding resin, is stained with ruthenium tetroxide for 3 hours. After staining, the resin expands, making it impossible to observe the sea-island structure near the cross-section, so the expanded portion is trimmed with the microtome. Then, a stained section about 100 nm thick is taken from the cross-section after cutting about 1 μm to 2 μm using a diamond knife and observed as follows. Cross-sectional images of the stained section are obtained using a field emission scanning electron microscope (e.g., Hitachi High-Technologies Corporation S-4800). As mentioned above, the cross-sectional image was obtained within a range from the surface opposite the barrier layer of the heat-fusible resin layer to a point with a thickness of 12.5% ​​when the total thickness of the layers located inside the barrier layer is taken as 100%. If a field emission scanning electron microscope, such as the Hitachi High-Technologies S-4800, is used, the measurement conditions are as follows: acceleration voltage: 30kV, emission current: 10μA, detector: transmission detector, tilt: none (0°), and observation magnification: 5000x. Next, using image processing software capable of binarizing cross-sectional images (for example, the image analysis software included with the Keyence VHX-5000 electron microscope), the island portion and the sea portion of the sea-island structure were binarized in the cross-sectional image. If using image processing software, for example, the image analysis software included with the Keyence VHX-5000 electron microscope, the measurement would start under the brightness (standard) setting of the image analysis software, with the extraction area (measurement range) set to rectangular (7 μm vertically, 13 μm horizontally), the imaging size to standard (1600 × 1200), the tilt angle to 0 degrees, the shooting mode to normal shooting, and the extraction target to "dark areas". Automatic measurement would then correct for any missing or extra areas, and the total area and number of extracted areas (islands) would be measured. At this time, the area and number of all islands present in the extraction area would be measured, respectively.Using the acquired data, the ratio of the total area of ​​all islands to the area of ​​the measurement range of the cross-sectional image (total area of ​​islands / area of ​​the measurement range of the cross-sectional image), and the area of ​​each island being 0.01 μm are calculated. 2 The percentage of the total number of island areas (0.01 μm) 2 (Total number of islands / Total number of all islands), 0.02 μm 2 The percentage of the total number of the following island areas (0.02μm 2 (Total number of islands / Total number of all islands), 0.03 μm 2 The percentage of the total number of the following island areas (0.03 μm) 2 (Total number of islands / Total number of all islands), 0.30 μm 2 The percentage of the total number of the above island areas (0.30 μm 2 (Total number of islands / Total number of all islands), 0.15 μm 2 The percentage of the total number of the above island areas (0.15 μm) 2 Calculate the total number of islands (as shown above) / the total number of all islands.

[0136] In the third embodiment, examples of polypropylene include homopolypropylene, block copolymers of polypropylene (e.g., propylene-ethylene block copolymer, propylene-butene block copolymer, propylene-ethylene-butene block copolymer, preferably propylene-ethylene block copolymer), random copolymers of polypropylene (e.g., propylene-ethylene random copolymer, propylene-butene random copolymer, propylene-ethylene-butene random copolymer, preferably propylene-ethylene random copolymer), and propylene-α-olefin copolymers. Examples of polyethylene include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ethylene-α-olefin copolymers. The polypropylene and polyethylene contained in the heat-fusible resin layer 4 may be one type or two or more types.

[0137] In the third embodiment, the heat-fusible resin layer 4 is preferably formed from a polypropylene resin composition containing 45% by mass or less of polyethylene. The polyethylene content in the heat-fusible resin layer 4 is such that, in the cross-sectional image, the area of ​​the island portion of the island is 0.02 μm² relative to the total number of island portions of the sea-island structure. 2 The percentage of the total number of islands listed below will be 80.0% or more. The polyethylene content is adjusted as follows: The polyethylene content is, for example, about 45% by mass or less, preferably about 30% by mass or less, more preferably about 20% by mass or less, and also preferably about 5% by mass or more, more preferably about 10% by mass or more. Preferred ranges include about 5-45% by mass, about 5-30% by mass, about 5-20% by mass, about 10-45% by mass, about 10-30% by mass, and about 10-20% by mass. The polypropylene content is, for example, 95% by mass or less, and 90% by mass or less. The polypropylene content is, for example, 55% by mass or more, 70% by mass or more, and 80% by mass or more. Preferred ranges for the polypropylene content include about 55-95% by mass, about 70-95% by mass, about 80-95% by mass, about 55-90% by mass, about 70-90% by mass, and about 80-90% by mass. Furthermore, the mass ratio of polypropylene to polyethylene in the polypropylene resin composition is preferably about 5 to 80 parts by mass, more preferably about 5 to 45 parts by mass, and even more preferably about 10 to 30 parts by mass of polyethylene per 100 parts by mass of polypropylene.

[0138] The heat-sealable resin layer 4 of the third embodiment may contain other resins in addition to polypropylene and polyethylene. Examples of other resins include the acid-modified polyolefins mentioned above.

[0139] In the third embodiment, the heat-fusible resin layer 4 may be formed as a single layer, or it may be formed as two or more layers of the same or different resins.

[0140] Furthermore, the thickness of the heat-fusible resin layer 4 is not particularly limited as long as the heat-fusible resin layers heat-fuse together to seal the energy storage device elements, but for example, it can be about 100 μm or less, preferably about 85 μm or less, and more preferably about 15 to 85 μm. For example, if the thickness of the adhesive layer 5 described later is 10 μm or more, the thickness of the heat-fusible resin layer 4 can be preferably about 85 μm or less, and more preferably about 15 to 45 μm. For example, if the thickness of the adhesive layer 5 described later is less than 10 μm or if the adhesive layer 5 is not provided, the thickness of the heat-fusible resin layer 4 can be preferably about 20 μm or more, and more preferably about 35 to 85 μm.

[0141] In the third embodiment, the heat-fusible resin layer 4 is preferably formed by melt extrusion molding. Furthermore, if there is an adhesive layer 5 described later, it is preferable that the adhesive layer 5 and the heat-fusible resin layer 4 are formed by melt co-extrusion molding. In the third embodiment of this disclosure, it is preferable to suppress the crystal growth of polyethylene in polypropylene by rapidly cooling the molten resin forming the heat-fusible resin layer 4, thereby reducing the area of ​​the islands in the cross-sectional image to 0.02 μm² relative to the total number of islands in the sea-island structure. 2 Below The proportion of the total number of islands in the lower section can be adjusted to be 80.0% or more. For example, as described above, while appropriately adjusting the mixing ratio of polypropylene and polyethylene contained in the heat-fusible resin layer 4, when forming the heat-fusible resin layer 4 by melt extrusion molding, the cooling conditions of the molten resin (molten resin forming the heat-fusible resin layer) by the cooling roll (a roll that cools the sheet formed from the molten resin while conveying it) can be set to rapid cooling conditions (for example, setting the difference in surface temperature between the melt-extruded heat-fusible resin layer and the cooling roll to 70°C or more) to suppress the crystal growth of polyethylene in polypropylene. As a result, in the cross-sectional image above, the proportion of the island sections with an area of ​​0.02 μm² relative to the total number of island sections in the sea-island structure is... 2The proportion of the total number of island areas can be adjusted to be 80.0% or more. Furthermore, as described above, the type and content of at least one of the antioxidant and radical scavenger contained in the heat-fusible resin layer 4 can also be used as one of the means to adjust the proportion of the total area of ​​the island areas in each area. When the adhesive layer 5 and the heat-fusible resin layer 4 are formed by melt co-extrusion molding, it is preferable that the thickness of the adhesive layer 5 be 15 to 45 μm and the thickness of the heat-fusible resin layer 4 be 15 to 45 μm.

[0142] [Adhesive layer 5] In the exterior material for energy storage devices of this disclosure, the adhesive layer 5 included in the inner layer is a layer provided between the barrier layer 3 (or corrosion-resistant film) and the heat-fusible resin layer 4 in order to firmly bond them together.

[0143] In the first embodiment of this disclosure, the adhesive layer 5 is formed of a resin capable of bonding the barrier layer 3 and the heat-fusible resin layer 4, and in which the inner layer exhibits an elongation of 8.0% or less at 80°C when dynamic viscoelasticity is measured by tensile stress. A thermoplastic resin is preferably used as the resin for forming the adhesive layer 5. The resin used for forming the adhesive layer 5 preferably contains a polyolefin skeleton, and examples include the polyolefin and acid-modified polyolefin exemplified in the heat-fusible resin layer 4 described above. On the other hand, from the viewpoint of firmly bonding the barrier layer 3 and the adhesive layer 5, it is preferable that the adhesive layer 5 contains an acid-modified polyolefin. Examples of acid-modified components include dicarboxylic acids such as maleic acid, itaconic acid, succinic acid, and adipic acid, their anhydrides, acrylic acid, and methacrylic acid, but maleic anhydride is most preferred in terms of ease of modification and versatility. Furthermore, from the viewpoint of heat resistance of the exterior material for energy storage devices, the olefin component is preferably a polypropylene-based resin, and it is most preferable that the adhesive layer 5 contains maleic anhydride-modified polypropylene.

[0144] In this disclosure, the presence of a polyolefin skeleton in the resin constituting the adhesive layer 5 can be analyzed by methods such as infrared spectroscopy and gas chromatography-mass spectrometry, and the analytical method is not particularly limited. Furthermore, the presence of an acid-modified polyolefin in the resin constituting the adhesive layer 5 can be analyzed by measuring maleic anhydride-modified polyolefin using infrared spectroscopy, for example, at a wavenumber of 1760 cm⁻¹. -1 Nearby wave frequency 1780cm -1 A peak originating from maleic anhydride is detected in the vicinity. However, if the degree of acid denaturation is low, the peak may become small and not be detected. In that case, analysis is possible by nuclear magnetic resonance spectroscopy.

[0145] In the first embodiment of this disclosure, 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. Alternatively, 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 range of 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, for example, by extrusion molding of the heat-fusible resin layer 4 and the adhesive layer 5.

[0146] In the first embodiment of this disclosure, from the viewpoint of further improving the airtightness of the exterior material for energy storage devices in high-temperature environments, the ratio of the thickness of the heat-fusible resin layer to the thickness of the adhesive layer 5 (thickness of the heat-fusible resin layer 4 / thickness of the adhesive layer 5) is preferably about 0.3 or more, more preferably about 0.4 or more. Also, from the same viewpoint, the ratio of said thickness is preferably about 2.0 or less, more preferably about 1.5 or less. The preferred range for the ratio of said thickness is about 0.3 to 2.0, about 0.3 to 1.5, about 0.4 to 2.0, about 0.4 to 1.5, and about 1.2 to 1.4.

[0147] Furthermore, as mentioned above, in the exterior material for energy storage devices according to the first embodiment of this disclosure, a suitable example for setting the elongation rate at 80°C in the dynamic viscoelasticity measurement of the inner layer by tension to 8.0% or less is to increase the crystallinity of the adhesive layer and the heat-fusible resin layer. It is desirable to control the initial cooling conditions after post-heating to very slow cooling conditions to promote the crystal growth of the resin in the adhesive layer and the heat-fusible resin layer. For example, by forming the heat-fusible resin layer using such a method, the crystallinity of the adhesive layer and the heat-fusible resin layer is increased, and the sealing performance in high-temperature environments is improved.

[0148] Furthermore, in the second embodiment of this disclosure, the adhesive layer 5 contains a polypropylene resin and polyethylene. In the exterior material for energy storage devices of the second embodiment, a sea-island structure is observed in the cross-sectional image obtained using a scanning electron microscope for a cross-section of the adhesive layer 5 in a direction parallel to TD and in the thickness direction y. The cross-sectional image is, for example, as shown in the schematic diagram of Figure 12, a cross-sectional image obtained within the range from the surface of the adhesive layer 5 on the barrier layer 3 side to a portion with a thickness of 25% (the area enclosed by the dashed line in Figure 12), when the total thickness of the adhesive layer 5 is set to 100%. The surface of the adhesive layer 5 on the barrier layer 3 side has a thickness of 0%. To explain with a specific example, for example, in the exterior material for energy storage devices in which a base layer (thickness 30 μm including adhesive) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (40 μm) / heat-fusible resin layer (40 μm) are laminated in order, as in Examples 1B to 3B described later, the thickness of the adhesive layer 5 of 40 μm is set to 100%. Furthermore, the position of the surface of the adhesive layer 5 on the barrier layer 3 side is, in other words, the position of the interface where the barrier layer 3 and the adhesive layer 5 are in contact in Figure 12, and the thickness at this position is set to 0%. Then, a cross-sectional image is acquired using a scanning electron microscope within the range from this surface (0% thickness) to the position with a thickness of 25% (i.e., with the thickness of the adhesive layer 5 being 40 μm as 100%, the position with a thickness of 25% is the position where the thickness is 10 μm from the surface of the adhesive layer 5 on the barrier layer 3 side toward the heat-fusible resin layer 4 side).

[0149] The observation of a sea-island structure in a cross-sectional image means that the cross-sectional image shows both a sea portion and an island portion. As mentioned above, when a small amount of polyethylene is added to a polypropylene resin and an adhesive layer is formed by melt extrusion molding, a sea-island structure is formed in which polyethylene islands are dispersed within the polypropylene resin sea portion. In other words, polyethylene is contained within these islands. To observe this sea-island structure, as described later, the cross-section of the adhesive layer 5 is stained with ruthenium tetroxide or the like, and a cross-sectional image is acquired and observed using a scanning electron microscope.

[0150] In the cross-sectional image of the adhesive layer 5 of the exterior material for the energy storage device of the second embodiment, the area of ​​the island portion of the island portion is 0.25 μm² relative to the total number of island portions of the sea-island structure. 2 The proportion of the total number of islands with an area of ​​less than 0.25 μm is 40% or more. The exterior material for energy storage devices of the second embodiment has these characteristics, thereby improving the sealing performance of the exterior material for energy storage devices in high-temperature environments. That is, in the exterior material for energy storage devices of the second embodiment of the present disclosure, in the adhesive layer 5 containing polypropylene resin and polyethylene, the proportion of the total number of islands with an area of ​​less than 0.25 μm is 40% or more. 2 The proportion of the total number of items occupying the minute island area of ​​less than 1 is set high. As a result, fine islands of polyethylene are dispersed within the polypropylene resin of the adhesive layer 5, suppressing the separation of the polypropylene resin and polyethylene. Therefore, even when the energy storage device is placed in a high-temperature environment and the internal pressure rises, causing significant stress on the exterior material for the energy storage device, the sealing performance can be maintained.

[0151] From the viewpoint of more favorably achieving the effects of the invention of the second embodiment, in the cross-sectional image of the adhesive layer 5, the area of ​​the island portion of the island portion relative to the total number of island portions of the sea-island structure is 0.25 μm. 2 Percentage of total number of islands less than 0.25 μm (0.25 μm) 2The ratio of the total number of islands (less than 1 / total number of all islands) is preferably about 41% or more, more preferably about 50% or more, even more preferably about 55% or more, even more preferably about 65% or more, and even more preferably about 75% or more. The ratio of the total number can be, for example, about 100% or less, about 99% or less, about 98% or less, about 90% or less, about 85% or less. A preferred range for the ratio of the total number can be, for example, around 40-100%, 40-99%, 40-98%, 40-90%, 40-85%, 41-100%, 41-99%, 41-98%, 41-90%, 41-85%, 50-100%, 50-99%, 50-98%, 50-90%, The following percentages can be cited: approximately 50-85%, 55-100%, 55-99%, 55-98%, 55-90%, 55-85%, 65-100%, 65-99%, 65-98%, 65-90%, 65-85%, 75-100%, 75-99%, 75-98%, 75-90%, and 75-85%.

[0152] Furthermore, from the viewpoint of more favorably achieving the effects of the invention of the second embodiment, in the cross-sectional image of the adhesive layer 5, the area of ​​the island portion is 0.15 μm relative to the total number of island portions of the sea-island structure. 2 Percentage of total number of island areas less than 0.15 μm (0.15 μm) 2 The ratio of the total number of islands (less than 1 / total number of all islands) is preferably about 10% or more, more preferably about 20% or more, even more preferably about 25% or more, even more preferably about 30% or more, even more preferably about 40% or more, even more preferably about 50% or more, and even more preferably about 60% or more. The ratio of the total number is, for example, about 85% or less, about 80% or less, etc. Preferred ranges for the ratio of the total number are, for example, about 10-85%, about 10-80%, about 20-85%, about 20-80%, about 25-85%, about 25-80%, about 30-85%, about 30-80%, about 40-85%, about 40-80%, about 50-85%, about 50-80%, about 60-85%, and about 60-80%.

[0153] Furthermore, from the viewpoint of more favorably achieving the effects of the invention of the second embodiment, in the cross-sectional image of the adhesive layer 5, the area of ​​the island portion is 0.10 μm relative to the total number of island portions of the sea-island structure. 2 Percentage of total number of island areas less than 0.10 μm (0.10 μm) 2 The ratio of the total number of islands (less than 1 / total number of all islands) is preferably about 10% or more, more preferably about 15% or more, even more preferably about 20% or more, even more preferably about 30% or more, even more preferably about 40% or more, and even more preferably about 50% or more. The ratio of the total number is, for example, about 80% or less, about 75% or less, etc. Preferred ranges for the ratio of the total number are, for example, about 10-60%, about 10-50%, about 15-60%, about 15-50%, about 20-60%, about 20-50%, about 30-60%, and about 30-50%.

[0154] Furthermore, from the viewpoint of more favorably achieving the effects of the invention of the second embodiment, in the cross-sectional image of the adhesive layer 5, the area of ​​the island portion is 1.50 μm relative to the total number of island portions of the sea-island structure. 2 The percentage of the total number of the above island areas (1.50 μm 2 The ratio of the above-mentioned island units (total number of island units / total number of all island units) is preferably about 10% or less, more preferably about 9% or less, even more preferably about 8% or less, and even more preferably about 5% or less. The percentage of the total number can be, for example, about 0% or more, about 1% or more, etc. A preferred range for the percentage of the total number can be, for example, about 0-10%, about 0-9%, about 0-8%, about 0-5%, about 1-10%, about 1-9%, about 1-8%, and about 1-5%.

[0155] The ratio of the total number of island areas in each area mentioned above can be achieved by adjusting the conditions for forming the adhesive layer 5, in addition to the mixing ratio of polypropylene resin and polyethylene contained in the adhesive layer 5. For example, as described later, by setting the temperature (temperature at which the pellets are melted and kneaded in a twin-screw extruder) when forming pellets in which polyethylene is uniformly dispersed in polypropylene resin into a film, and by shortening the time (residence time) from when the resin is melted until it is formed into a film, the aggregation of polyethylene in the polypropylene resin can be suppressed, resulting in a 0.25 μm 2 The formation of the aforementioned islands is suppressed. Furthermore, the ratio of the total number of islands in each area can be adjusted by including at least one selected from the group consisting of antioxidants and radical scavengers in the adhesive layer 5. In addition, the above values ​​can be adjusted by appropriately adjusting the type and content of the antioxidants and radical scavengers.

[0156] The method for measuring the total number of island areas in each area of ​​the sea-island structure in the cross-sectional image of adhesive layer 5 is as follows:

[0157] <Measurement of the ratio of island area and number of islands in a sea-island structure> The exterior material for the energy storage device is embedded in a thermosetting epoxy resin and cured. A cross-section parallel to the TD and in the thickness direction y is prepared using a commercially available rotary microtome (e.g., LEICA EM UC6) and a glass knife, and the cross-section is prepared at room temperature using the microtome. The adhesive layer of the exterior material for the energy storage device, along with the embedding resin, is stained with ruthenium tetroxide for 3 hours. After staining, the resin expands, making it impossible to observe the sea-island structure near the cross-section, so the expanded portion is trimmed with the microtome. Then, a stained section about 100 nm thick is taken from the cross-section after cutting by about 1 μm to 2 μm using a diamond knife and observed as follows. Cross-sectional images of the stained section are obtained using a field emission scanning electron microscope (e.g., Hitachi High-Technologies Corporation S-4800). As mentioned above, the cross-sectional image is obtained within the range from the surface on the barrier layer side of the adhesive layer to a thickness of 25%, assuming the total thickness of the adhesive layer is 100%. If a field emission scanning electron microscope, such as the Hitachi High-Technologies S-4800, is used, the measurement conditions are: acceleration voltage: 30kV, emission current: 10μA, detector: transmission detector, tilt: none (0°), and observation magnification: 5000x. Next, using image processing software capable of binarizing cross-sectional images (for example, the image analysis software included with the Keyence VHX-5000 electron microscope), the island portion and the sea portion of the sea-island structure are binarized in the cross-sectional image. If using image processing software, for example, the image analysis software included with the Keyence VHX-5000 electron microscope, specifically, measurement is started under the brightness (standard) conditions of the image analysis software, the extraction area (measurement range) is set to a rectangle (7 μm vertically, 13 μm horizontally), the imaging size is set to standard (1600 × 1200), the tilt angle is set to 0 degrees, the shooting mode is set to normal shooting, and the extraction target is set to "dark areas". Furthermore, automatic measurement corrects for missing or extra extraction areas, and the total area and total number of extracted areas (islands) are measured. At this time, the area and number of all islands present in the extraction area are measured, respectively. Using the acquired data, the area of ​​the islands (μm) is calculated. 2 ) and the relationship between the number of islands of that area and the ratio (%) of the total number of islands of all islands (for example, the above (0.25 μm 2(Total number of islands less than 0.20 μm / Total number of all islands), (0.20 μm) 2 (Total number of islands less than 0.10 μm / Total number of all islands), (0.10 μm) 2 Calculate the total number of islands less than 1 / 2 (total number of all islands), etc.

[0158] In the second embodiment, acid-modified polypropylene is preferred as the polypropylene resin because it exhibits excellent adhesion to the barrier layer 3 and the heat-fusible resin layer. Acid-modified polypropylene is a polymer obtained by modifying polypropylene by block polymerization or graft polymerization with an acid component.

[0159] In the second embodiment, the polypropylene to be acid-modified specifically includes polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymer of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymer of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. When the polyolefin resin is a copolymer, it may be a block copolymer or a random copolymer. These polyolefin resins may be used individually or in combination of two or more.

[0160] In the second embodiment, the acid-modified polypropylene may also be a copolymer obtained by copolymerizing the aforementioned polypropylene with a polar molecule such as acrylic acid or methacrylic acid, or a polymer such as crosslinked polypropylene. Examples of acid components used for acid modification include carboxylic acids or their anhydrides, such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

[0161] In the second embodiment, the acid-modified polypropylene may be acid-modified cyclic polypropylene. Acid-modified cyclic polypropylene is a polymer obtained by copolymerizing some of the monomers constituting cyclic polypropylene with an acid component, or by block polymerization or graft polymerization of an acid component to cyclic polypropylene. The cyclic polyolefin to be acid-modified is the same as described above. Furthermore, the acid component used for acid modification is the same as the acid component used for modifying polypropylene described above.

[0162] In the second embodiment, the acid-modified polypropylene is preferably polypropylene modified with a carboxylic acid or its anhydride, and more preferably maleic anhydride-modified polypropylene.

[0163] In the second embodiment, examples of polyethylene include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ethylene-α-olefin copolymer.

[0164] In the second embodiment, the adhesive layer 5 is preferably formed of a polypropylene resin composition containing a polypropylene resin and 45% by mass or less of polyethylene. The preferred polypropylene resin is as described above. The polyethylene content in the adhesive layer 5 is such that, in the cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.25 μm² relative to the total number of island portions of the sea-island structure. 2The proportion of the total number of islands less than 40% is adjusted to be 40% or more. The polyethylene content in the resin composition forming the adhesive layer is, for example, about 45% by mass or less, preferably about 30% by mass or less, preferably about 5% by mass or more, more preferably about 10% by mass or more, even more preferably about 15% by mass or more, and even more preferably 20% by mass or more. Preferred ranges include about 5-45% by mass, about 5-30% by mass, about 10-45% by mass, about 10-30% by mass, about 15-45% by mass, about 15-30% by mass, about 20-45% by mass, and about 20-30% by mass. The polypropylene resin content is, for example, 95% by mass or less, 90% by mass or less, 85% by mass or less, and 80% by mass or less. The polypropylene resin content is, for example, 55% by mass or more and 70% by mass or more. Preferred ranges for the polypropylene resin content include approximately 55-95% by mass, 55-90% by mass, 55-85% by mass, 55-80% by mass, 70-95% by mass, 70-90% by mass, 70-85% by mass, and 70-80% by mass. Furthermore, the mass ratio of polypropylene resin to polyethylene in the polypropylene resin composition forming the adhesive layer 5 is preferably about 5-80 parts by mass, more preferably about 5-45 parts by mass, and even more preferably about 10-30 parts by mass of polyethylene per 100 parts by mass of polypropylene resin.

[0165] In the second embodiment, the adhesive layer 5 may contain other resins in addition to the polypropylene resin and polyethylene. However, the total proportion of the polypropylene resin and polyethylene in the adhesive layer 5 is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. In particular, the total proportion of the acid-modified polypropylene and polyethylene in the adhesive layer 5 is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0166] In the second embodiment, the adhesive layer 5 is typically provided so as to be in contact with the barrier layer 3 (or corrosion-resistant coating) and is a single layer.

[0167] In the second embodiment, the thickness of the adhesive layer 5 is preferably about 80 μm or less, about 60 μm or less, or about 50 μm or less. Alternatively, the thickness of the adhesive layer 5 is preferably about 5 μm or more, about 10 μm or more, about 20 μm or more, or about 30 μm or more. The range of the thickness is preferably about 5 to 80 μm, about 5 to 60 μm, about 5 to 50 μm, about 10 to 80 μm, about 10 to 60 μm, about 10 to 50 μm, about 20 to 80 μm, about 20 to 60 μm, about 20 to 50 μm, about 30 to 80 μm, about 30 to 60 μm, or about 30 to 50 μm.

[0168] (Antioxidants and radical scavengers) In the second embodiment, the exterior material 10 for the energy storage device preferably contains at least one selected from the group consisting of antioxidants and radical scavengers in at least one of the layers inside the barrier layer 3, from the viewpoint of further improving airtightness in high-temperature environments. Examples of layers inside the barrier layer 3 (hereinafter sometimes referred to as "inner layer") include a heat-fusible resin layer 4 and an adhesive layer 5. Preferably, at least one selected from the group consisting of antioxidants and radical scavengers is included in at least one of the heat-fusible resin layer 4 and the adhesive layer 5. That is, at least one selected from the group consisting of antioxidants and radical scavengers may be included in both the heat-fusible resin layer 4 and the adhesive layer 5, or only in the heat-fusible resin layer 4, or only in the adhesive layer 5. In the second embodiment, an antioxidant may be added to suppress oxidation of the inner layer in the high-temperature environment when forming the inner layer. Also, in the second embodiment, a radical scavenger may be added to capture radicals generated in the inner layer in the high-temperature environment when forming the inner layer.

[0169] In the second embodiment, the antioxidant is not particularly limited, as long as it does not inhibit the effect of the second embodiment. Specific examples of antioxidants include tris(2,4-di-t-butylphenoxy)phosphine, 2,2-methylenebis(4,6-di-t-butylphenyl)-2-ethylhexyl phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenylditridecyl)phosphite, 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyl Phosphorus-based antioxidants such as rudibenz[d,f][1,3,2]dioxaphosfepine), tetrakis(2,4-di-t-butylphenyl)-4,4'-bisphenyldiphosphonite, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, tetrakis(methylene-3-(3,5-di-t-butyl-4 -Hydroxyphenyl)propionate)methane, 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 3,9-bis(2-(3-(3-t-butyl-4-hydroxy-5-methylphenyl) Examples of antioxidants include phenolic antioxidants such as lopionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro(5,5)undecane, and sulfur-based antioxidants such as tetrakis[methylene-3-(laurylthio)propionate]methane, dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, and distearyl-3,3'-thiodipropionate. The antioxidants contained in the layers inside barrier layer 3 may be one type or two or more types.

[0170] In the second embodiment, a compound represented by the following general formula (A) is preferably exemplified as the phosphorus-based antioxidant.

[0171] [ka]

[0172] The presence of the compound represented by general formula (A) in the inner layer can be confirmed using various analytical methods such as NMR.

[0173] In general formula (A), R 11 and R 12 Each of these is independently an alkyl group having 1 to 18 carbon atoms, or a phenyl group which may have substituents. Among these, R 11 and R 12 Each of these is preferably an optionally substituent phenyl group. The compound represented by general formula (A) contained in the inner layer may be one type or two or more types.

[0174] In general formula (A), R 11 and R 12 The phenyl group preferably has, independently, at least one group selected from the group consisting of C1 to C9 alkyl groups, C5 to C8 cycloalkyl groups, C6 to C12 alkylcycloalkyl groups, and C7 to C12 aralkyl groups as a substituent. Among these groups, it is preferable that the phenyl group has at least one of the C1 to C9 alkyl group and the C7 to C12 aralkyl group as a substituent. Furthermore, R 11 and R 12 The number of substituents on each phenyl group may be 1 to 5, but preferably 2 to 3.

[0175] Preferred specific examples of the compound represented by the general formula (A) include the compound represented by the following formula (A1) (bis(2,4-dicumylphenyl)pentaerythritol diphosphite) and the compound represented by the following formula (A2) (bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite).

[0176] [ka]

[0177] In the second embodiment, the inner layer is particularly preferably a compound represented by formula (A1) as the compound represented by general formula (A).

[0178] As described above, in the second embodiment, the heat-fusible resin layer 4 and the adhesive layer 5 may each be a single layer or multiple layers. When the heat-fusible resin layer 4 and the adhesive layer 5 are multiple layers, at least one of them may contain the compound represented by the general formula (A). For example, the compound represented by the general formula (A) may be contained in both the heat-fusible resin layer 4 and the adhesive layer 5, in only the heat-fusible resin layer 4, or in only the adhesive layer 5. By containing the compound represented by the general formula (A) in at least one of the layers constituting the inner layer, the resin forming the layer can be heated to a higher temperature than conventional methods (e.g., 300°C or higher) to form the layer, thereby shortening the lead time. Furthermore, degradation due to high temperatures is suppressed in the layer, and high insulation properties can be exhibited.

[0179] In energy storage devices, the inner layer comes into contact with the electrolyte, raising concerns about adverse effects from antioxidants contained in the inner layer leaching into the electrolyte. However, the compound represented by formula (A1) has low solubility in the electrolyte solvent, and even when added in large quantities to improve insulation, it is expected to have minimal adverse effects on the characteristics of the energy storage device. Examples of solvents for the electrolyte in energy storage devices include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC); linear carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dipropyl carbonate (DPC); aliphatic carboxylic acid esters such as methyl formate, methyl acetate, methyl propionate, and ethyl propionate; and γ-lactones such as γ-butyrolactone. Examples include linear ethers such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), and ethoxymethoxyethane (EME); cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; dimethyl sulfoxide; formamide; acetamide; dimethylformamide; dimethylacetamide; dioxolane; acetonitrile; trimethoxymethane; dioxolane derivatives; sulfolane; methylsulfolane; propylene carbonate derivatives; tetrahydrofuran derivatives; and dimethyl sulfoxide. These can be used individually or in combination of two or more. In particular, at least one of cyclic carbonates, linear carbonates, and aliphatic carboxylic acid esters is preferably used, and especially a mixed system of cyclic carbonates and linear carbonates, or a mixed system of cyclic carbonates, linear carbonates, and aliphatic carboxylic acid esters is preferably used.

[0180] In the inner layer, the antioxidant content in the layer containing the antioxidant is not particularly limited as long as it achieves the effect of the second embodiment, but is preferably about 0.01% by mass or more, more preferably about 0.03% by mass or more, and even more preferably about 0.05% by mass or more. Furthermore, the content is preferably about 2% by mass or less, more preferably about 1% by mass or less, and even more preferably about 0.5% by mass or less. Preferred ranges for the content include about 0.01 to 2% by mass, about 0.01 to 1% by mass, about 0.01 to 0.5% by mass, about 0.03 to 2% by mass, about 0.03 to 1% by mass, and about 0.03 to 0.5% by mass.

[0181] In the second embodiment, the inner layer may also contain a radical scavenger. The radical scavenger is not particularly limited, and examples include alkyl radical scavengers, alkoxy radical scavengers, and peroxy radical scavengers. Examples of alkyl radical scavengers include compounds having both an acrylate group and a phenolic hydroxyl group in the same molecule, and specific examples include 1'-hydroxy[2,2'-ethylidenebis[4,6-bis(1,1-dimethylpropyl)benzene]]-1-yl acrylate and 2-t-butyl-4-methyl-6-(2-hydroxy-3-t-butyl-5-methylbenzyl)phenyl acrylate. When a radical scavenger is included in the inner layer, there may be one type of radical scavenger or two or more types.

[0182] When a radical scavenger is included in the inner layer, the content of the radical scavenger in the layer containing the radical scavenger in the inner layer is not particularly limited as long as it does not produce the effects of the second embodiment described above. However, from the viewpoint of more favorably exhibiting the effects of the second embodiment, it is preferably about 0.01% by mass or more, more preferably about 0.03% by mass or more. Furthermore, the content is preferably about 0.5% by mass or less, more preferably about 0.3% by mass or less, and even more preferably about 0.2% by mass or less. Preferred ranges for the content include about 0.01 to 0.5% by mass, about 0.01 to 0.3% by mass, about 0.01 to 0.2% by mass, about 0.03 to 0.5% by mass, about 0.03 to 0.3% by mass, and about 0.03 to 0.2% by mass.

[0183] In the third embodiment, the adhesive layer 5 is formed of a resin capable of bonding the barrier layer 3 and the heat-fusible resin layer 4. The resin used to form the adhesive layer 5 can be the same as the adhesive exemplified in the adhesive layer 2. Preferably, the resin used to form the adhesive layer 5 contains a polyolefin skeleton, such as the polyolefin and acid-modified polyolefin exemplified in the heat-fusible resin layer 4. The presence of a polyolefin skeleton in the resin constituting the adhesive layer 5 can be analyzed by methods such as infrared spectroscopy and gas chromatography-mass spectrometry, and the analytical method is not particularly limited. Furthermore, when the resin constituting the adhesive layer 5 is analyzed by infrared spectroscopy, it is preferable that a peak originating from maleic anhydride is detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak originating from maleic anhydride is detected at wavenumber 1760 cm⁻¹. -1 Nearby wave frequency 1780cm -1 A peak originating from maleic anhydride is detected in the vicinity. However, if the degree of acid denaturation is low, the peak may become small and not be detected. In that case, analysis is possible by nuclear magnetic resonance spectroscopy.

[0184] In the third embodiment, from the viewpoint of firmly bonding the barrier layer 3 and the heat-fusible resin layer 4, the adhesive layer 5 preferably contains an acid-modified polyolefin. Particularly preferred as the acid-modified polyolefin are polyolefins modified with a carboxylic acid or its anhydride, polypropylenes modified with a carboxylic acid or its anhydride, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

[0185] Furthermore, in the third embodiment, from the viewpoint of reducing the thickness of the exterior material for the energy storage device while providing an exterior material for the energy storage device with excellent shape stability after molding, it is more preferable that the adhesive layer 5 is a cured product of a resin composition containing an acid-modified polyolefin and a curing agent. The above-mentioned examples are preferred as examples of acid-modified polyolefins.

[0186] In the third embodiment, the adhesive layer 5 is preferably a cured product of a resin composition comprising an acid-modified polyolefin and at least one selected from the group consisting of compounds having isocyanate groups, compounds having oxazoline groups, and compounds having epoxy groups, and is particularly preferably a cured product of a resin composition comprising an acid-modified polyolefin and at least one selected from the group consisting of compounds having isocyanate groups and compounds having epoxy groups. Furthermore, the adhesive layer 5 preferably contains at least one selected from the group consisting of polyurethane, polyester, and epoxy resin, and more preferably contains polyurethane and epoxy resin. As polyester, for example, amide ester resins are preferred. Amide ester resins are generally produced by the reaction of carboxyl groups and oxazoline groups. It is more preferable that the adhesive layer 5 is a cured product of a resin composition comprising at least one of these resins and the acid-modified polyolefin. Furthermore, if unreacted compounds containing isocyanate groups, compounds containing oxazoline groups, or curing agents such as epoxy resin remain in the adhesive layer 5, the presence of these unreacted compounds can be confirmed by methods selected from, for example, infrared spectroscopy, Raman spectroscopy, or time-of-flight secondary ion mass spectrometry (TOF-SIMS).

[0187] Furthermore, in the third embodiment, from the viewpoint of further improving the adhesion between the barrier layer 3 and the adhesive layer 5, it is preferable that the adhesive layer 5 is a cured product of a resin composition containing a curing agent having at least one selected from the group consisting of oxygen atoms, heterocyclic rings, C=N bonds, and COC bonds. Examples of curing agents having heterocyclic rings include curing agents having oxazoline groups and curing agents having epoxy groups. Examples of curing agents having C=N bonds include curing agents having oxazoline groups and curing agents having isocyanate groups. Examples of curing agents having COC bonds include curing agents having oxazoline groups, curing agents having epoxy groups, and polyurethane. The fact that the adhesive layer 5 is a cured product of a resin composition containing these curing agents can be confirmed by methods such as gas chromatography-mass spectrometry (GCMS), infrared spectroscopy (IR), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and X-ray photoelectron spectroscopy (XPS).

[0188] In the third embodiment, the compound having an isocyanate group is not particularly limited, but from the viewpoint of effectively improving the adhesion between the barrier layer 3 and the adhesive layer 5, a polyfunctional isocyanate compound is preferred. The polyfunctional isocyanate compound is not particularly limited as long as it is a compound having two or more isocyanate groups. Specific examples of polyfunctional isocyanate curing agents include pentane diisocyanate (PDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymerized or nurated versions thereof, mixtures thereof, and copolymers with other polymers. Also, adducts, burettes, and isocyanurates are examples.

[0189] In the third embodiment, the content of the compound having an isocyanate group in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, of the resin composition constituting the adhesive layer 5. This effectively enhances the adhesion between the barrier layer 3 and the adhesive layer 5.

[0190] In the third embodiment, the compound having an oxazoline group is not particularly limited as long as it is a compound having an oxazoline skeleton. Specific examples of compounds having an oxazoline group include those having a polystyrene main chain and those having an acrylic main chain. Commercial products include, for example, the Epocross series manufactured by Nippon Shokubai Co., Ltd.

[0191] In the third embodiment, the proportion of the compound having an oxazoline group in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, of the resin composition constituting the adhesive layer 5. This effectively enhances the adhesion between the barrier layer 3 and the adhesive layer 5.

[0192] In the third embodiment, the compound having epoxy groups is, for example, an epoxy resin. The epoxy resin is not particularly limited as long as it is a resin capable of forming a crosslinked structure by the epoxy groups present in the molecule, and known epoxy resins can be used. The weight-average molecular weight of the epoxy resin is preferably about 50 to 2000, more preferably about 100 to 1000, and even more preferably about 200 to 800. In the first disclosure, the weight-average molecular weight of the epoxy resin is the value measured by gel permeation chromatography (GPC) under conditions using polystyrene as a standard sample.

[0193] In the third embodiment, specific examples of epoxy resins include glycidyl ether derivatives of trimethylolpropane, bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, novolac glycidyl ether, glycerin polyglycidyl ether, and polyglycerin polyglycidyl ether. The epoxy resin may be used alone or in combination of two or more types.

[0194] In the third embodiment, the proportion of epoxy resin in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, of the resin composition constituting the adhesive layer 5. This effectively enhances the adhesion between the barrier layer 3 and the adhesive layer 5.

[0195] In the third embodiment, the polyurethane is not particularly limited, and known polyurethanes can be used. The adhesive layer 5 may be, for example, a cured product of a two-component curable polyurethane.

[0196] In the third embodiment, the proportion of polyurethane in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, of the resin composition constituting the adhesive layer 5. This effectively enhances the adhesion between the barrier layer 3 and the adhesive layer 5 in an atmosphere where components that induce corrosion of the barrier layer, such as electrolytes, are present.

[0197] In the third embodiment, if the adhesive layer 5 is a cured product of a resin composition comprising at least one selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and an epoxy resin, and the acid-modified polyolefin, the acid-modified polyolefin functions as the main agent, and the compound having an isocyanate group, the compound having an oxazoline group, and the compound having an epoxy group each function as a curing agent.

[0198] In the third embodiment, the thickness of the adhesive layer 5 is preferably about 50 μm or less, about 45 μm or less, about 30 μm or less, about 20 μm or less, and about 5 μm or less. Alternatively, the thickness of the adhesive layer 5 is preferably about 0.1 μm or more, about 0.5 μm or more, about 5 μm or more, about 10 μm or more, and about 15 μm or more. Preferably, the thickness range includes approximately 0.1 to 50 μm, 0.1 to 45 μm, 0.1 to 30 μm, 0.1 to 20 μm, 0.1 to 5 μm, 0.5 to 50 μm, 0.5 to 45 μm, 0.5 to 30 μm, 0.5 to 20 μm, 0.5 to 5 μm, 5 to 50 μm, 5 to 45 μm, 5 to 30 μm, 5 to 20 μm, 10 to 50 μm, 10 to 45 μm, 10 to 30 μm, 10 to 20 μm, 15 to 50 μm, 15 to 45 μm, 15 to 30 μm, and 15 to 20 μm.

[0199] More specifically, in the third embodiment, when the adhesive is as exemplified in adhesive layer 2, or as a cured product of acid-modified polyolefin and a curing agent, the thickness is preferably about 1 to 10 μm, more preferably about 1 to 5 μm. Furthermore, when using the resin exemplified in heat-fusible resin layer 4 (such as acid-modified polyolefin), the thickness is preferably about 5 to 50 μm, 5 to 45 μm, 10 to 50 μm, 10 to 45 μm, 15 to 50 μm, or 15 to 45 μm. When the adhesive layer 5 is as exemplified in adhesive layer 2, or as a cured product of a resin composition containing acid-modified polyolefin and a curing agent, for example, the adhesive layer 5 can be formed by applying the resin composition and curing it by heating or the like. Furthermore, when using the resin exemplified in heat-fusible resin layer 4, for example, it can be suitably formed by melt co-extrusion molding of the heat-fusible resin layer 4 and the adhesive layer 5.

[0200] (Antioxidants and radical scavengers) The exterior material 10 for the energy storage device of the third embodiment contains at least one of an antioxidant and a radical scavenger in at least one of the layers inside the barrier layer 3. Examples of layers inside the barrier layer 3 (hereinafter sometimes referred to as the "inner layer") include a heat-fusible resin layer 4 and an adhesive layer 5. Preferably, at least one of the antioxidant and the radical scavenger is contained in at least one of the heat-fusible resin layer 4 and the adhesive layer 5. That is, the antioxidant and the radical scavenger may each be contained in both the heat-fusible resin layer 4 and the adhesive layer 5, or in only the heat-fusible resin layer 4, or in only the adhesive layer 5. In the third embodiment, the antioxidant is added to suppress oxidation of the inner layer in the high-temperature environment when forming the inner layer. Also in the third embodiment, the radical scavenger is added to capture radicals generated in the inner layer in the high-temperature environment when forming the inner layer.

[0201] In the third embodiment, the antioxidant is not particularly limited, as long as it does not inhibit the effect of the third embodiment. Specific examples of antioxidants include tris(2,4-di-t-butylphenoxy)phosphine, 2,2-methylenebis(4,6-di-t-butylphenyl)-2-ethylhexyl phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenylditridecyl)phosphite, 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyl Phosphorus-based antioxidants such as rudibenz[d,f][1,3,2]dioxaphosfepine), tetrakis(2,4-di-t-butylphenyl)-4,4'-bisphenyldiphosphonite, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, tetrakis(methylene-3-(3,5-di-t-butyl-4 -Hydroxyphenyl)propionate)methane, 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 3,9-bis(2-(3-(3-t-butyl-4-hydroxy-5-methylphenyl) Examples include phenolic antioxidants such as lopionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro(5,5)undecane, and sulfur-based antioxidants such as tetrakis[methylene-3-(laurylthio)propionate]methane, dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, and distearyl-3,3'-thiodipropionate. The antioxidants contained in the layers inside barrier layer 3 may be one type or two or more types.

[0202] In the third embodiment, a compound represented by the following general formula (A) is preferably exemplified as the phosphorus-based antioxidant.

[0203] [Chemical formula]

[0204] That the compound represented by the general formula (A) is contained in the inner layer can be confirmed by using various analytical methods such as NMR.

[0205] In the general formula (A), R 11 and R 12 are each independently an alkyl group having 1 to 18 carbon atoms or a phenyl group which may have a substituent. Among these, R 11 and R 12 are each preferably independently a phenyl group which may have a substituent. The compound represented by the general formula (A) contained in the inner layer may be one kind or two or more kinds.

[0206] In the general formula (A), the phenyl groups of R 11 and R 12 each preferably independently have, as a substituent, at least one group selected from the group consisting of an alkyl group having 1 to 9 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, an alkylcycloalkyl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms. Among these groups, the phenyl group preferably has at least one of an alkyl group having 1 to 9 carbon atoms and an aralkyl group having 7 to 12 carbon atoms as a substituent. Further, the number of substituents of the phenyl groups of R 11 and R 12 may each be 1 to 5, preferably 2 to 3.

[0207] Preferred specific examples of the compound represented by the general formula (A) include the compound represented by the following formula (A1) (bis(2,4-dicumylphenyl)pentaerythritol diphosphite) and the compound represented by the following formula (A2) (bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite).

[0208] [Chemistry]

[0209] In the third embodiment, it is particularly preferable that the inner layer contains the compound represented by the formula (A1) as the compound represented by the general formula (A).

[0210] As described above, in the third embodiment, the inner layer may be a single layer or a multilayer. When the inner layer is a multilayer, at least one layer contained in the inner layer may contain the compound represented by the general formula (A). For example, the compound represented by the general formula (A) may be contained in both the heat-sealing resin layer 4 and the adhesive layer 5, may be contained only in the heat-sealing resin layer 4, or may be contained only in the adhesive layer 5. By containing the compound represented by the general formula (A) in at least one of the layers constituting the inner layer, the resin forming the layer can be heated to a higher temperature (for example, 300 °C or higher) than before to form the layer, and the lead time can be shortened. Further, deterioration of the layer due to high temperature is suppressed, and high insulation properties can be exhibited.

[0211] In energy storage devices, the inner layer comes into contact with the electrolyte, raising concerns about adverse effects due to the leaching of antioxidants contained in the inner layer into the electrolyte. However, in the third embodiment, the compound represented by formula (A1) has low solubility in the electrolyte solvent, and even when a large amount is added to improve insulation, it is expected that the adverse effects on the characteristics of the energy storage device will be small. Examples of solvents for the electrolyte of the energy storage device include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC); linear carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dipropyl carbonate (DPC); aliphatic carboxylic acid esters such as methyl formate, methyl acetate, methyl propionate, and ethyl propionate; and γ-lactones such as γ-butyrolactone. Examples include linear ethers such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), and ethoxymethoxyethane (EME); cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; dimethyl sulfoxide; formamide; acetamide; dimethylformamide; dimethylacetamide; dioxolane; acetonitrile; trimethoxymethane; dioxolane derivatives; sulfolane; methylsulfolane; propylene carbonate derivatives; tetrahydrofuran derivatives; and dimethyl sulfoxide. These can be used individually or in combination of two or more. Among these, at least one of cyclic carbonates, linear carbonates, and aliphatic carboxylic acid esters is preferably used, and in particular, a mixed system of cyclic carbonates and linear carbonates, or a mixed system of cyclic carbonates, linear carbonates, and aliphatic carboxylic acid esters is preferably used.

[0212] In the inner layer, the antioxidant content in the layer containing the antioxidant is not particularly limited as long as it achieves the effect of the third embodiment, but is preferably about 0.01% by mass or more, more preferably about 0.03% by mass or more, and even more preferably about 0.05% by mass or more. Furthermore, the content is preferably about 2% by mass or less, more preferably about 1% by mass or less, and even more preferably about 0.5% by mass or less. Preferred ranges for the content include about 0.01 to 2% by mass, about 0.01 to 1% by mass, about 0.01 to 0.5% by mass, about 0.03 to 2% by mass, about 0.03 to 1% by mass, and about 0.03 to 0.5% by mass.

[0213] In the third embodiment, the inner layer may contain a radical scavenger. The radical scavenger is not particularly limited, and examples include alkyl radical scavengers, alkoxy radical scavengers, and peroxy radical scavengers. Examples of alkyl radical scavengers include compounds having both an acrylate group and a phenolic hydroxyl group in the same molecule, and specific examples include 1'-hydroxy[2,2'-ethylidenebis[4,6-bis(1,1-dimethylpropyl)benzene]]-1-yl acrylate and 2-t-butyl-4-methyl-6-(2-hydroxy-3-t-butyl-5-methylbenzyl)phenyl acrylate. When a radical scavenger is included in the inner layer, there may be one type of radical scavenger or two or more types.

[0214] When a radical scavenger is included in the inner layer, the content of the radical scavenger in the layer containing the radical scavenger in the inner layer is not particularly limited as long as it does not produce the effects of the third embodiment described above. However, from the viewpoint of more favorably exhibiting the effects of the third embodiment, it is preferably about 0.01% by mass or more, more preferably about 0.03% by mass or more. Furthermore, the content is preferably about 0.5% by mass or less, more preferably about 0.3% by mass or less, and even more preferably about 0.2% by mass or less. Preferred ranges for the content include about 0.01 to 0.5% by mass, about 0.01 to 0.3% by mass, about 0.01 to 0.2% by mass, about 0.03 to 0.5% by mass, about 0.03 to 0.3% by mass, and about 0.03 to 0.2% by mass.

[0215] [Surface coating layer 6] The exterior material for energy storage devices of this disclosure may optionally include a surface coating layer 6 on the base layer 1 (on the side opposite to the barrier layer 3 of the base layer 1) for the purpose of improving at least one of the following: aesthetics, electrolyte resistance, scratch resistance, and moldability. The surface coating layer 6 is the outermost layer of the exterior material for energy storage devices when the energy storage device is assembled using the exterior material for energy storage devices.

[0216] The surface coating layer 6 can be formed from a resin such as polyvinylidene chloride, polyester, polyurethane, acrylic resin, or epoxy resin.

[0217] If the resin forming the surface coating layer 6 is a curable resin, it may be either a one-component curable resin or a two-component curable resin, but is preferably a two-component curable resin. Examples of two-component curable resins include two-component curable polyurethane, two-component curable polyester, and two-component curable epoxy resin. Among these, two-component curable polyurethane is preferred.

[0218] Examples of two-component curable polyurethanes include polyurethanes comprising a main component containing a polyol compound and a curing agent containing an isocyanate compound. Preferably, two-component curable polyurethanes are those in which a polyol such as polyester polyol, polyether polyol, and acrylic polyol is the main component and an aromatic or aliphatic polyisocyanate is the curing agent. Furthermore, it is preferable to use a polyester polyol as the polyol compound, which has hydroxyl groups not only at the terminals of the repeating units but also in the side chains. Examples of curing agents include aliphatic, alicyclic, aromatic, and aromaticaliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Furthermore, examples include polyfunctional isocyanate modified products derived from one or more of these diisocyanates. Polyisocyanate compounds can also be used as polymers (e.g., trimers). Such polymers include adducts, biuretes, and nulates. Note that aliphatic isocyanate compounds refer to isocyanates having aliphatic groups and no aromatic rings, alicyclic isocyanate compounds refer to isocyanates having alicyclic hydrocarbon groups, and aromatic isocyanate compounds refer to isocyanates having aromatic rings. The surface coating layer 6 being made of polyurethane provides excellent electrolyte resistance to the exterior material for energy storage devices.

[0219] The surface coating layer 6 may contain, as necessary, additives such as the aforementioned lubricants, antiblocking agents, matting agents, flame retardants, antioxidants, tackifiers, and antistatic agents in at least one of its surface and interior, depending on the functionality to be provided to the surface coating layer 6 and its surface. Examples of additives include fine particles with an average particle size of about 0.5 nm to 5 μm. The average particle size of the additive is the median diameter measured by a laser diffraction / scattering particle size distribution analyzer.

[0220] The additive may be either inorganic or organic. Furthermore, there are no particular restrictions on the shape of the additive; examples include spherical, fibrous, plate-like, amorphous, or flaky forms.

[0221] Specific examples of 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, alumina, carbon black, carbon nanotubes, high-melting-point nylon, acrylate resin, cross-linked acrylic, cross-linked styrene, cross-linked polyethylene, benzoguanamine, gold, aluminum, copper, and nickel. Additives may be used individually or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferred from the viewpoint of dispersion stability and cost. In addition, various surface treatments such as insulation treatment and high-dispersibility treatment may be applied to the surface of the additives.

[0222] The method for forming the surface coating layer 6 is not particularly limited, and for example, a method of applying a resin to form the surface coating layer 6 can be used. If an additive is to be incorporated into the surface coating layer 6, the resin mixed with the additive can be applied.

[0223] The thickness of the surface coating layer 6 is not particularly limited as long as it performs the above-mentioned functions as a surface coating layer 6, and for example, it can be about 0.5 to 10 μm, preferably about 1 to 5 μm.

[0224] 3. Method for manufacturing exterior materials for energy storage devices The method for manufacturing an exterior material for energy storage devices is not particularly limited, as long as a laminate is obtained by laminating the layers of the exterior material for energy storage devices of this disclosure. At a minimum, a method is provided which involves laminating the base layer 1, the barrier layer 3, and the inner layers (adhesive layer 5 and heat-fusible resin layer 4) in this order.

[0225] In other words, the method for manufacturing an exterior material for an energy storage device according to the first embodiment includes a step of obtaining a laminate by laminating a base layer, a barrier layer, and an inner layer (adhesive layer and heat-fusible resin layer) in this order, and when dynamic viscoelasticity measurement is performed on the inner layer, the elongation rate at 80°C is 8.0% or less.

[0226] Furthermore, the method for manufacturing an exterior material for an energy storage device according to the second embodiment includes a step of obtaining a laminate by laminating a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer in this order, wherein the adhesive layer contains a polypropylene resin and polyethylene, and a sea-island structure is observed in a cross-sectional image obtained using a scanning electron microscope of the cross-section of the adhesive layer in a direction parallel to the TD and in the thickness direction, wherein the cross-sectional image is obtained within the range from the surface on the barrier layer side of the adhesive layer to a portion with a thickness of 25%, when the thickness of the adhesive layer is set to 100%, and in the cross-sectional image, the area of ​​the island portion is 0.25 μm² relative to the total number of island portions of the sea-island structure. 2 A method for manufacturing exterior material for energy storage devices, wherein the proportion of the total number of island portions less than 40% is 40% or more.

[0227] Moreover, the manufacturing method of the exterior material for a power storage device according to the third embodiment includes at least a step of obtaining a laminate by laminating a base material layer, a barrier layer, and a heat-sealable resin layer in this order. The heat-sealable resin layer contains polypropylene and polyethylene. Regarding the cross-section in the direction parallel to TD of the heat-sealable resin layer and in the thickness direction y, a sea-island structure is observed in the cross-sectional image obtained using a scanning electron microscope. In the cross-sectional image, the ratio of the following island portions to the total number of island portions of the sea-island structure is 80.0% or more, and at least one of the antioxidant and the radical scavenger is included in at least one layer inside the barrier layer. This is the manufacturing method of the exterior material for a power storage device. 2 The total number of the following island portions is 80.0% or more, and at least one of the antioxidant and the radical scavenger is included in at least one layer inside the barrier layer.

[0228] As an example of the manufacturing method of the exterior material for a power storage device of the present disclosure, it is as follows. First, a laminate (hereinafter, may also be referred to as "laminate A") in which a base material layer 1, an adhesive layer 2, and a barrier layer 3 are laminated in this order is formed. Specifically, the formation of laminate A is carried out by applying the adhesive used for forming the adhesive layer 2 on the base material layer 1 or, if necessary, on the barrier layer 3 whose surface has been chemical conversion treated, by a coating method such as a gravure coating method or a roll coating method, drying, and then laminating the barrier layer 3 or the base material layer 1 and curing the adhesive layer 2 by a dry lamination method.

[0229] Next, the inner layer (adhesive layer 5 and heat-fusible resin layer 4) is laminated onto the barrier layer 3 of laminate A. For example, (1) a method of laminating the adhesive layer 5 and heat-fusible resin layer 4 by extrusion onto the barrier layer 3 of laminate A (co-extrusion lamination method, tandem lamination method), (2) a method of separately forming a laminate in which the adhesive layer 5 and the heat-fusible resin layer 4 are laminated and then laminating this onto the barrier layer 3 of laminate A by thermal lamination, or a method of forming a laminate in which the adhesive layer 5 is laminated onto the barrier layer 3 of laminate A and then laminating this with the heat-fusible resin layer 4 by thermal lamination, (3) laminate (4) A method in which a molten adhesive layer 5 is poured between the barrier layer 3 of A and a heat-fusible resin layer 4 that has been previously formed into a sheet, thereby bonding the laminate A and the heat-fusible resin layer 4 via the adhesive layer 5 (sandwich lamination method), (5) a method in which an adhesive for forming the adhesive layer 5 is solution-coated onto the barrier layer 3 of the laminate A and dried, or further laminated by baking, and the heat-fusible resin layer 4 that has been previously formed into a sheet is laminated on this adhesive layer 5.

[0230] As described above, in the exterior material for energy storage devices according to the first embodiment of this disclosure, a suitable example for setting the elongation rate at 80°C in the dynamic viscoelasticity measurement of the inner layer by tension to 8.0% or less is to increase the crystallinity of the adhesive layer and the heat-fusible resin layer. For example, when manufacturing the exterior material for energy storage devices, the adhesive layer and the heat-fusible resin layer are formed by melt extrusion molding, cooled, and then reheated to a temperature above the melting point of the adhesive layer and the heat-fusible resin layer, and then cooled again. Furthermore, the cooling rate after reheating is preferably set so that the temperature drop from the start of cooling to 60°C or less, more preferably to 50°C or less, and even more preferably to 45°C or less for the first 3 seconds, thereby controlling the initial cooling conditions to very slow conditions and promoting crystal growth of the adhesive layer and the heat-fusible resin layer. For example, by forming the adhesive layer 5 and the heat-fusible resin layer 4 using such a method, the crystallinity of the adhesive layer and the heat-fusible resin layer is increased, and the sealing performance in high-temperature environments is improved. As mentioned above, the method of setting the elongation rate at 110°C to 15.0% or less in the dynamic viscoelasticity measurement by tensile stress, and the method of setting the temperature at which the elongation rate is 10% to 85°C or higher, can also be used to similarly enhance crystallinity.

[0231] When a surface coating layer 6 is provided, the surface coating layer 6 is laminated on the surface of the base layer 1 opposite to the barrier layer 3. The surface coating layer 6 can be formed, for example, by applying the resin used to form the surface coating layer 6 to the surface of the base layer 1. The order of the steps of laminating the barrier layer 3 to the surface of the base layer 1 and laminating the surface coating layer 6 to the surface of the base layer 1 is not particularly limited. For example, the surface coating layer 6 may be formed on the surface of the base layer 1, and then the barrier layer 3 may be formed on the surface of the base layer 1 opposite to the surface coating layer 6.

[0232] As described above, a laminate is formed comprising, as necessary, a surface coating layer 6, a base layer 1, an adhesive layer 2 as necessary, a barrier layer 3, an adhesive layer 5, and a heat-fusible resin layer 4 in this order. However, to further strengthen the adhesion of the adhesive layer 2 and adhesive layer 5, which are provided as necessary, the laminate may be subjected to heat treatment.

[0233] In exterior materials for energy storage devices, the processability of each layer constituting the laminate may be improved by subjecting it to surface activation treatments such as corona treatment, blast treatment, oxidation treatment, or ozone treatment, as needed. For example, by applying corona treatment to the surface of the substrate layer 1 opposite to the barrier layer 3, the printability of ink on the surface of the substrate layer 1 can be improved.

[0234] 4. Applications of exterior materials for energy storage devices The exterior material for energy storage devices of this disclosure is used in packaging for sealing and housing energy storage device elements such as a positive electrode, a negative electrode, and an electrolyte. That is, an energy storage device can be formed by housing energy storage device elements, which include at least a positive electrode, a negative electrode, and an electrolyte, in packaging formed from the exterior material for energy storage devices of this disclosure.

[0235] Specifically, an energy storage device is provided by covering an energy storage device element, which comprises at least a positive electrode, a negative electrode, and an electrolyte, with the energy storage device exterior material of this disclosure, such that a flange portion (an area where heat-sealable resin layers come into contact) is formed around the periphery of the energy storage device element, with the metal terminals connected to the positive electrode and negative electrode respectively protruding outward, and then heat-sealing the heat-sealable resin layers of the flange portion to seal it. When housing the energy storage device element in a package formed from the energy storage device exterior material of this disclosure, the package is formed such that the heat-sealable resin portion of the energy storage device exterior material of this disclosure faces inward (the surface in contact with the energy storage device element). The packaging can be formed by overlapping the heat-sealable resin layers of two energy storage device casing materials facing each other and heat-sealing the periphery of the overlapped casing materials. Alternatively, as shown in the example in Figure 6, one energy storage device casing material can be folded and overlapped, and the periphery can be heat-sealed to form the packaging. When folding and overlapping, as shown in the example in Figure 6, the edges other than the folded edge can be heat-sealed to form a three-sided seal, or the edges can be folded to form a flange and then sealed on all four sides. Furthermore, the energy storage device casing material may have a recess for housing the energy storage device element formed by deep drawing or stretch molding. As shown in the example in Figure 6, one energy storage device casing material may have a recess while the other does not, or the other energy storage device casing material may also have a recess.

[0236] The casing material for energy storage devices disclosed herein can be suitably used in energy storage devices such as batteries (including capacitors, capacitors, etc.). Furthermore, the casing material for energy storage devices disclosed herein can be used in either primary batteries or secondary batteries, but is preferably used in secondary batteries. The types of secondary batteries to which the casing material for energy storage devices disclosed herein can be applied are not particularly limited, and examples include lithium-ion batteries, lithium-ion polymer batteries, all-solid-state batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, capacitors, capacitors, etc. Among these secondary batteries, lithium-ion batteries and lithium-ion polymer batteries are particularly suitable applications for the casing material for energy storage devices disclosed herein. [Examples]

[0237] The present disclosure will be described in detail below with reference to examples and comparative examples. However, the present disclosure is not limited to the examples.

[0238] Examples 1A to 4A and Comparative Examples 1A to 2A below represent experimental results relating to the first embodiment of this disclosure. Examples 1B to 10B and Comparative Example 1A below represent experimental results relating to the second embodiment of this disclosure. Examples 1C to 10C and Comparative Examples 1C to 2C below represent experimental results relating to the third embodiment of this disclosure.

[0239] <Manufacturing of exterior materials for energy storage devices> Example 1A As the base layer, polyethylene terephthalate (PET) film (12 μm thick) and stretched nylon (ONy) film (15 μm thick) were prepared. A two-component urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to the PET film (3 μm thick) and bonded to the ONy film. As the barrier layer, aluminum foil (JIS H4160:1994 A8021H-O (40 μm thick)) was prepared. Next, the two-component urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to one side of the aluminum foil to form an adhesive layer (3 μm thick) on the barrier layer. Then, the adhesive layer on the barrier layer and the base layer (ONy film side) were laminated by dry lamination, and an aging treatment was performed to create a laminate of base layer / adhesive layer / barrier layer. Both sides of the aluminum foil were treated with chemical conversion treatment. The chemical conversion treatment of aluminum foil involves a treatment solution consisting of phenolic resin, chromium fluoride compound, and phosphoric acid, with a chromium coating amount of 10 mg / m². 2 This was achieved by applying the coating to both sides of the aluminum foil using the roll-coating method and then baking it to achieve the desired (dry mass).

[0240] Next, maleic anhydride-modified polypropylene as an adhesive layer (40 μm thick) and random polypropylene as a heat-fusible resin layer (40 μm thick) were laminated on top of the barrier layer of each laminate obtained above, thereby obtaining an exterior material for energy storage devices in which a base layer (30 μm thick including adhesive) / adhesive layer (3 μm) / barrier layer (40 μm) / inner layer (adhesive layer (40 μm) / heat-fusible resin layer (40 μm)) were laminated in that order.

[0241] When laminating an adhesive layer and a heat-fusible resin layer on a barrier layer, the resins constituting the adhesive layer and the heat-fusible resin layer were co-extruded onto the barrier layer while molten, cooled to about several tens of degrees Celsius, and then reheated to a temperature above the melting point of the adhesive layer and the heat-fusible resin layer (over 100 degrees Celsius), and then cooled again. The cooling rate after reheating was controlled to a temperature drop of 42 degrees Celsius for the first 3 seconds from the start of cooling, and the initial cooling conditions were controlled to be very slow to promote crystal growth in the adhesive layer and the heat-fusible resin layer.

[0242] Example 2A As the resin constituting the subsequent layer and the heat-sealing resin layer, except that a resin having a lower melt mass flow rate (MFR) than the resin used in Example 1A was used respectively, an exterior material for a power storage device was obtained in the same manner as in Example 1A.

[0243] Example 3A As the base material layer, a polyethylene terephthalate (PET) film (thickness: 12 μm) and a stretched nylon (ONy) film (thickness: 25 μm) were prepared. A two-component urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to the PET film (3 μm) and adhered to the ONy film. Also, as the barrier layer, an aluminum foil (JIS H4160:1994 A8021H-O (thickness: 60 μm)) was prepared. Next, a two-component urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to one surface of the aluminum foil to form an adhesive layer (thickness: 3 μm) on the barrier layer. Then, after laminating the adhesive layer on the barrier layer and the base material layer (ONy film side) by the dry lamination method, an aging treatment was carried out to produce a laminate of the base material layer / adhesive layer / barrier layer. Chemical conversion treatment was applied to both surfaces of the aluminum foil. The chemical conversion treatment of the aluminum foil was carried out by applying a treatment liquid composed of a phenol resin, a chromium fluoride compound, and phosphoric acid to both surfaces of the aluminum foil by the roll coating method so that the coating amount of chromium was 10 mg / m 2 (dry mass), and baking.

[0244] Next, maleic anhydride-modified polypropylene as an adhesive layer (thickness: 40 μm) and random polypropylene as a heat-sealing resin layer (thickness: 40 μm) were laminated on the barrier layer of each laminate obtained above, and an exterior material for a power storage device in which the base material layer (including the adhesive, thickness: 40 μm) / adhesive layer (3 μm) / barrier layer (60 μm) / inner layer (adhesive layer (40 μm) / heat-sealing resin layer (40 μm)) were laminated in order was obtained.

[0245] When laminating an adhesive layer and a heat-fusible resin layer on a barrier layer, the resins constituting the adhesive layer and the heat-fusible resin layer were co-extruded onto the barrier layer while molten, cooled to about several tens of degrees Celsius, and then reheated to a temperature above the melting point of the adhesive layer and the heat-fusible resin layer (over 100 degrees Celsius), and then cooled again. The cooling rate after reheating was controlled to a temperature drop of 42 degrees Celsius for the first 3 seconds from the start of cooling, and the initial cooling conditions were controlled to be very slow to promote crystal growth in the adhesive layer and the heat-fusible resin layer.

[0246] Example 4A Except for using a resin with a lower melt mass flow rate (MFR) than the resin used in Example 1A as the resin constituting the adhesive layer and the heat-fusible resin layer, and using a propylene resin with a melt mass flow rate (MFR) between the adhesive layer and the heat-fusible resin layer, and laminating a propylene resin layer (second heat-fusible resin layer) between the adhesive layer (30 μm) and the heat-fusible resin layer (20 μm) as the inner layer, an exterior material for an energy storage device was obtained in the same manner as in Example 1A, with the following components laminated in order: base layer (thickness including adhesive: 30 μm) / adhesive layer (3 μm) / barrier layer (40 μm) / inner layer (adhesive layer (30 μm) / propylene resin layer (30 μm second heat-fusible resin layer) / heat-fusible resin layer (20 μm)).

[0247] Comparative Example 1A Except for not including a post-heating and subsequent cooling step when laminating the adhesive layer and the heat-fusible resin layer on top of the barrier layer, an exterior material for an energy storage device was obtained in the same manner as in Example 1A.

[0248] Comparative example 2A Except for laminating the adhesive layer and the heat-fusible resin layer on top of the barrier layer, the temperature drop during the 3 seconds from the start of cooling after post-heating was set to 90°C / 3 seconds, which can be considered a generally slow cooling condition, to obtain an exterior material for an energy storage device in the same manner as in Example 1A.

[0249] <Dynamic Viscoelasticity (DMA) Measurement> For each exterior material for energy storage devices obtained in the examples and comparative examples, samples were prepared from the inner layer and dynamic viscoelasticity measurements were performed. Specifically, the barrier layer of each exterior material for energy storage devices was dissolved by immersing it in a 10% hydrochloric acid aqueous solution for 24 hours to obtain the inner layer (a two-layer structure consisting of an adhesive layer and a heat-fusible resin layer). Next, this inner layer was washed with water, dried, and cut into strips 5 mm wide and 10 mm long to obtain samples. Then, dynamic viscoelasticity measurements were performed on each obtained sample using a dynamic viscoelasticity measuring device (product name Rheogel-E4000) manufactured by UBM Co., Ltd. under the following measurement conditions. The elongation rate (%) at 80°C and the elongation rate (%) at 110°C are shown in Table 1A. In addition, the temperature at an elongation rate of 10% is also shown in Table 1A in the graph showing the relationship between elongation rate and temperature obtained by the dynamic viscoelasticity measurement. For reference, a schematic diagram of the graph showing the relationship between elongation rate and temperature obtained by dynamic viscoelasticity measurement by tensile stress is shown in Figure 7. Point I in Figure 7 represents the point where the growth rate reached 10%.

[0250] (Measurement conditions) Sample width 5mm Starting temperature 30℃ End temperature 160℃ Heating rate: 2°C / min Static load 50g Distance between test holders (distance between chucks): 10 mm Chuck pull Software used for measurement: RheoStation (ver7) Step temperature 1°C Waveform: Sine wave, 10Hz Distortion 10μm, distortion control (automatic adjustment) Measuring jig: tensile The load was controlled at a constant level until the elongation reached 10%. After the elongation reached 10%, load control was stopped, and the material was then stretched by 20 μm for every 1°C increase.

[0251] <Creep test (evaluation of sealing performance in high-temperature environments)> In accordance with the provisions of JIS K7127:1999, creep tests were conducted on the exterior materials for energy storage devices in an 80°C environment as follows. As test specimens, the exterior materials for energy storage devices were prepared by cutting them into strips with a width of 15 mm in the TD direction. Specifically, as shown in Figure 4, first, each exterior material for energy storage devices was cut to 60 mm (TD direction) × 200 mm (MD direction) (Figure 4a). Next, the exterior material for energy storage devices was folded in half in the MD direction at the fold point P (midway in the MD direction) so that the heat-sealable resin layers faced each other (Figure 4b). The heat-sealable resin layers were heat-sealed together approximately 10 mm inward from the fold point P in the MD direction under the conditions of a seal width of 7 mm, a temperature of 190°C, a surface pressure of 0.6 MPa, and a duration of 3 seconds (Figure 4c). In Figure 4c, the shaded area S is the heat-sealed portion (sealed portion S). Next, the material was cut in the MD direction (at the position of the dashed line in Figure 4d) so that its width in the TD direction was 15 mm (Figure 4f). Then, using a BE-501 manufactured by Tester Industries, each of the obtained test pieces 13 was fixed at the top and a 2 kg weight W was suspended from the bottom in an 80°C environment, as shown in the schematic diagram in Figure 5, and the time until the seal portion S broke was measured. The results are shown in Table 1A.

[0252] For reference, cross-sectional images (SEM images) in the thickness direction of the exterior materials for energy storage devices of Example 1A and Comparative Example 1A after the creep test are shown in Figure 8 (Example 1A) and Figure 9 (Comparative Example 1A), respectively. From the image in Figure 9, it can be seen that the adhesive layer in Comparative Example 1A underwent cohesive failure after the creep test. It is thought that the adhesive layer in Comparative Example 1A underwent cohesive failure due to insufficient crystal growth.

[0253] [Table 1A]

[0254] As shown in Table 1A, the exterior material for energy storage devices of Examples 1A-4A exhibits an elongation rate of 8.0% or less at 80°C when dynamic viscoelasticity measurements are performed on the inner layer. The exterior material for energy storage devices of Examples 1A-4A is evaluated as having excellent sealing properties in high-temperature environments, as the time until the seal between the heat-fusible resin layers breaks down is very long in creep tests at 80°C.

[0255] Furthermore, the exterior material for the energy storage device in Comparative Example 2A was also cooled at a cooling rate of 90°C / 3 seconds, which is generally considered a slow cooling condition. As a result, it is thought that crystal growth progressed in the adhesive layer and the heat-fusible resin layer in Comparative Example 2A as well, and the time until the seal portion broke in the creep test at 80°C was relatively long at 43 hours. Although not as high as in Examples 1A-4A, the sealing performance was improved compared to Comparative Example 1A.

[0256] <Manufacturing of exterior materials for energy storage devices> Examples 1B, 2B and Comparative Example 1B Polyethylene terephthalate (PET) film (12 μm thick) and stretched nylon (ONy) film (15 μm thick) were prepared. The PET film and ONy film were bonded together with a two-component urethane adhesive (polyol compound and aromatic isocyanate compound) to form the base layer. Aluminum alloy foil (JIS H4160:1994 A8021H-O (40 μm thick)) was prepared as the barrier layer. Next, the aluminum alloy foil and the base layer (ONy film side) were laminated using a two-component urethane adhesive (polyol compound and aromatic isocyanate compound, cured thickness 3 μm) by dry lamination, and then an aging treatment was performed to create a laminate of base layer / adhesive layer / barrier layer. Both sides of the aluminum alloy foil were treated with a chemical conversion treatment. The chemical conversion treatment of the aluminum alloy foil involved a treatment solution consisting of phenolic resin, chromium fluoride compound, and phosphoric acid, with a chromium coating amount of 10 mg / m². 2 This was achieved by applying the coating to both sides of the aluminum alloy foil using the roll coating method and then baking it to achieve the desired (dry mass).

[0257] Next, on top of the barrier layer of each laminate obtained above, pellets of maleic anhydride-modified polypropylene resin (a composition of maleic anhydride-modified polypropylene and polyethylene) as an adhesive layer (thickness 40 μm) and pellets of random polypropylene resin (a composition of random polypropylene and polyethylene) as a heat-fusible resin layer (thickness 40 μm) are formed into films under the melt extrusion conditions described later (specifically, the pellets are melted and kneaded in a twin-screw extruder and extruded from a T-die to form a film), thereby laminating the adhesive layer and heat-fusible resin layer on top of the barrier layer, resulting in an exterior material for energy storage devices (total thickness 153 μm) in which a base layer (thickness 30 μm including adhesive) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (40 μm) / heat-fusible resin layer (40 μm) are laminated in that order.

[0258] In Examples 1B, 2B, and Comparative Example 1B, the same materials were used to constitute each layer, and the polyethylene content in the adhesive layer was approximately 25% by mass.

[0259] Example 3B Except for using resins with a lower melt mass flow rate (MFR) than those used in Example 1B as the resins constituting the adhesive layer and the heat-fusible resin layer, an exterior material for an energy storage device was obtained in the same manner as in Example 1B.

[0260] Example 4B Except for using resins with a lower melt mass flow rate (MFR) than the resin used in Example 1B as the resins constituting the adhesive layer and the heat-sealable resin layer, and setting the thickness of the adhesive layer to 30 μm and the thickness of the heat-sealable resin layer to 50 μm, an exterior material for an energy storage device was obtained in the same manner as in Example 1B.

[0261] Example 5B Except for using a 25 μm thick stretched nylon (ONy) film as the base layer and using aluminum alloy foil (JIS H4160:1994 A8021H-O (60 μm thick)) as the barrier layer, an exterior material for an energy storage device was obtained in the same manner as in Example 1B.

[0262] Example 6B Except for using melt extrusion condition B, described later, as the melt extrusion condition for forming the adhesive layer, an exterior material for an energy storage device was obtained in the same manner as in Example 5B.

[0263] Example 7B An exterior material for an energy storage device was obtained in the same manner as in Example 4B, except that the heat-fusible resin layer was constructed in a two-layer configuration, and the antioxidants and radical scavengers for the adhesive layer and the heat-fusible resin layer described later were used, the same resin as the adhesive layer in Example 4B was used as the resin constituting the adhesive layer, a resin with a lower elastic modulus than the heat-fusible resin layer in Example 4B was used as the resin constituting the heat-fusible resin layer in contact with the adhesive layer, and the same resin as the heat-fusible resin layer in Example 4B was used as the resin constituting the innermost heat-fusible resin layer.

[0264] Example 8B Except for using the antioxidants and radical scavengers described later for the adhesive layer and the heat-fusible resin layer, and employing melt extrusion condition B described later as the melt extrusion condition for the resin when forming the adhesive layer, an exterior material for an energy storage device was obtained in the same manner as in Example 7B.

[0265] Example 9B Except for using the antioxidants and radical scavengers described later for the adhesive layer and the heat-fusible resin layer, an exterior material for an energy storage device was obtained in the same manner as in Example 1B.

[0266] Example 10B Except for using melt extrusion condition B, described later, as the melt extrusion condition for forming the adhesive layer, an exterior material for an energy storage device was obtained in the same manner as in Example 9B.

[0267] (Melting extrusion conditions) The melt extrusion conditions for the resin when forming the adhesive layer by melt extrusion are as follows. The melt extrusion conditions used in the examples and comparative examples are shown in Table 1B. Melt extrusion condition A: The temperature during the melting and mixing of the resin is set to a low temperature (around 200-240°C), and the time until the resin is extruded from the T-die (residence time of the molten resin) is shortened compared to general conditions. Melt extrusion condition B: The temperature during melt mixing of the resin is set to a low temperature (approximately 240-260°C), and the time until the resin is extruded from the T-die (residence time of the molten resin) is set to be similar to that of general conditions. Melt extrusion condition C: The temperature during melt mixing of the resin is set to a high temperature (approximately 260-280°C), and the time until the resin is extruded from the T-die (residence time of the molten resin) is set to be similar to that of general conditions. Melt extrusion condition D: The temperature during the melting and mixing of the resin is set to a high temperature (approximately 260-280°C), and the time until the molten resin is extruded from the T-die (residence time of the molten resin) is shortened compared to general conditions.

[0268] <Measurement of the ratio of island area and number of islands in a sea-island structure> An outer casing material for an energy storage device was embedded in a thermosetting epoxy resin and cured. A cross-section parallel to the TD and in the thickness direction was prepared using a commercially available rotary microtome (LEICA EM UC6) and a glass knife, with the cross-section prepared at room temperature. The adhesive layer of the outer casing material for the energy storage device, along with the embedding resin, was stained with ruthenium tetroxide for 3 hours. Upon staining, the resin expanded, making it impossible to observe the sea-island structure near the cross-section, so the expanded portion was trimmed with the microtome. Then, a stained section approximately 100 nm thick was taken from the cross-section after cutting by 1 μm to 2 μm using a diamond knife and observed as follows. Cross-sectional images of the stained section were acquired using a field emission scanning electron microscope (Hitachi High-Technologies Corporation S-4800). Note that the cross-sectional image was acquired within the range from the surface on the barrier layer side of the adhesive layer to 25% thickness, assuming the adhesive layer thickness is 100%. The measurement conditions were: acceleration voltage: 30kV, emission current: 10μA, detector: transmission detector, tilt: none (0°), and observation magnification: 5000x. Next, using image processing software capable of binarizing cross-sectional images (image analysis software included with the Keyence VHX-5000 electron microscope), the island and sea portions of the sea-island structure were binarized in the cross-sectional image. Specifically, measurement was started with the brightness (standard) setting of the image analysis software, the extraction area (measurement range) was set to rectangular (7μm vertical, 13μm horizontal), the imaging size to standard (1600×1200), the tilt angle to 0 degrees, the shooting mode to normal shooting, and the extraction target to "dark areas". In addition, automatic measurement was used to correct for missing or extra extraction areas, and the total area and total number of extracted areas (islands) were measured. At this time, the area and number of all islands present in the extraction area were measured, respectively. Using the acquired data, the area of ​​the islands (μm) was calculated. 2 ) and the entire island The relationship between the number of island areas of that area and the total number of island areas (%) is shown in the bar graphs of Figures 14 (Example 1B), 15 (Example 2B), 16 (Example 3B), 17 (Example 4B), and 18 (Comparative Example 1B). In each bar graph of Figures 14 to 18, for example, an area of ​​0.1 μm 2The percentage (%) shown at the location represents the total number of islands, with an area of ​​0.10 μm, where 100% is the total number of islands. 2 This shows the percentage of island areas smaller than 0.25 μm. 2 The percentage (%) of the number shown at each location is calculated by setting the total number of island areas as 100%. Product is 0.20 μm 2 More than 0.25μm 2 This shows the percentage of island areas with an area of ​​less than 0.10 μm². 2 Percentage of islands with an area of ​​less than 0.15 μm² 2 Percentage of islands with an area of ​​less than 0.25 μm² 2 The percentage of islands with an area less than 1.50 μm², and the area of ​​islands with an area of ​​1.50 μm². 2 The percentage of each island shown above is presented in Table 1B. Note that in the bar graphs in Figures 14-18, the area is 2 μm². 2 It shows the value up to less than.

[0269] <Creep test (evaluation of sealing performance in high-temperature environments)> In accordance with the provisions of JIS K7127:1999, creep tests were conducted on the exterior materials for energy storage devices in an 80°C environment as follows. As test specimens, the exterior materials for energy storage devices were prepared by cutting them into strips with a width of 15 mm in the TD direction. Specifically, as shown in Figure 4, first, each exterior material for energy storage devices was cut to 60 mm (TD direction) × 200 mm (MD direction) (Figure 4a). Next, the exterior material for energy storage devices was folded in half in the MD direction at the fold point P (midway in the MD direction) so that the heat-sealable resin layers faced each other (Figure 4b). The heat-sealable resin layers were heat-sealed together approximately 10 mm inward from the fold point P in the MD direction under the conditions of a seal width of 7 mm, a temperature of 190°C, a surface pressure of 0.6 MPa, and a duration of 3 seconds (Figure 4c). In Figure 4c, the shaded area S is the heat-sealed portion (sealed portion S). Next, the material was cut in the MD direction (at the position of the dashed line in Figure 4d) so that its width in the TD direction was 15 mm (Figure 4e). Then, using a BE-501 manufactured by Tester Industries, each of the obtained test pieces 13 was fixed at the top and a 2 kg weight W was suspended from the bottom in an 80°C environment, as shown in the schematic diagram in Figure 5, and the time until the seal portion S broke was measured. The results are shown in Table 1B.

[0270] In Examples 7B to 10B, the types and concentrations of antioxidants and radical scavengers contained in the adhesive layer and the heat-fusible resin layer are as follows:

[0271] Examples 7B-8B: The adhesive layer and the heat-fusible resin layer contain a total of 0.4% by mass or less of tris(2,4-di-t-butylphenoxy)phosphine and tetrakis(methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

[0272] Examples 9B-10B: The adhesive layer and the heat-fusible resin layer contain a total of 0.6% by mass or less of bis(2,4-dicumylphenyl)pentaerythritol diphosphite, tris(2,4-di-t-butylphenoxy)phosphine, tetrakis(methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane, and 1'-hydroxy[2,2'-ethylidenebis[4,6-bis(1,1-dimethylpropyl)benzene]]-1-yl acrylate.

[0273] [Table 1B]

[0274] As is clear from the description in Table 1B, the exterior materials for energy storage devices in Examples 1B to 10B, in the cross-sectional image of the adhesive layer containing polypropylene resin and polyethylene, have a total number of island portions of the sea-island structure, with the area of ​​the island portions being 0.25 μm². 2 The proportion of the total number of islands smaller than 40% is 40%, and in the creep test at 80°C, the time until the seal area breaks is very long, indicating excellent sealing performance in high-temperature environments.

[0275] Furthermore, when the exterior material for the energy storage device was manufactured in the same manner as in Examples 1B, 2B and Comparative Example 1B, except that the melt extrusion condition D was used in the formation of the adhesive layer, the area of ​​the island portion of the sea-island structure was 0.25 μm² relative to the total number of island portions of the sea-island structure. 2 The proportion of the total number of islands smaller than 40% was below 40%, and in the creep test at 80°C, the time until the seal failed was shorter compared to Examples 1B to 10B.

[0276] <Manufacturing of exterior materials for energy storage devices> Examples 1C, 2C and Comparative Examples 1C, 2C Polyethylene terephthalate (PET) film (12 μm thick) and stretched nylon (ONy) film (15 μm thick) were prepared. A two-component urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to the PET film (3 μm thick) and bonded to the ONy film to form the base layer. Aluminum alloy foil (JIS H4160:1994 A8021H-O (40 μm thick)) was prepared as a barrier layer. Next, the two-component urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to one side of the aluminum alloy foil to form an adhesive layer (3 μm thick) on the barrier layer. Subsequently, the adhesive layer on the barrier layer and the base layer (ONy film side) were laminated using a dry lamination method, and then an aging treatment was performed to create a laminate of base layer / adhesive layer / barrier layer. Both sides of the aluminum alloy foil were treated with chemical conversion treatment. The chemical conversion treatment of aluminum alloy foil involves a treatment solution consisting of phenolic resin, chromium fluoride compound, and phosphoric acid, with a chromium coating amount of 10 mg / m². 2 Aluminum alloy foil is coated by roll coating method to achieve (dry mass) This was done by applying the coating to both sides and baking it.

[0277] Next, maleic anhydride-modified polypropylene as an adhesive layer (40 μm thick) and random polypropylene (a composition of random polypropylene and polyethylene) as a heat-fusible resin layer (40 μm thick) were melt-extruded onto the barrier layer of each laminate obtained above. The heat-fusible resin layer side was then cooled by contacting it with a cooling roll (using cooling conditions A or B described later), thereby laminating the adhesive layer and the heat-fusible resin layer on the barrier layer. This resulted in an exterior material for energy storage devices (total thickness 153 μm) in which a base layer (30 μm thick including adhesive) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (40 μm) / heat-fusible resin layer (40 μm) were laminated in that order. Example 2C had a lower polyethylene content in the heat-fusible resin layer compared to Example 1C. Comparative Example 1C had a higher polyethylene content in the heat-fusible resin layer compared to Example 1C. Comparative Example 2C used the same composition of the heat-fusible resin layer as Example 1C, but employed cooling condition B.

[0278] (Cooling conditions) The conditions for cooling the heat-fusible resin layer by bringing it into contact with a cooling roll are as follows. The cooling conditions used in the examples and comparative examples are shown in Table 1C. Cooling condition A: The temperature difference between the molten resin (the molten resin that forms the heat-fusible resin layer) obtained by molten co-extrusion and the surface temperature of the cooling roll is set to 70°C or more, and the molten resin is rapidly cooled to form the heat-fusible resin layer (conditions that suppress the crystal growth of polyethylene). Cooling condition B: The temperature difference between the molten resin (the molten resin forming the heat-fusible resin layer) obtained by molten co-extrusion and the surface temperature of the cooling roll is set to 50°C or less, allowing the molten resin to be cooled slowly to form the heat-fusible resin layer.

[0279] <Measurement of the ratio of island area and number of islands in a sea-island structure> An outer casing material for an energy storage device was embedded in a thermosetting epoxy resin and cured. A cross-section parallel to the TD and in the thickness direction was prepared using a commercially available rotary microtome (LEICA EM UC6) and a glass knife, with the cross-section preparation performed at room temperature. The thermosealable resin layer of the energy storage device outer casing material, along with the embedding resin, was stained with ruthenium tetroxide for 3 hours. Upon staining, the resin expanded, making it impossible to observe the sea-island structure near the cross-section, so the expanded portion was trimmed with the microtome. Then, a stained section approximately 100 nm thick was taken from the cross-section after cutting by 1 μm to 2 μm using a diamond knife and observed as follows. Cross-sectional images of the stained section were acquired using a field emission scanning electron microscope (Hitachi High-Technologies Corporation S-4800). The cross-sectional image was obtained within a range from the surface opposite the barrier layer to a point 12.5% ​​thick, assuming the total thickness of the layers located inside the barrier layer is 100%. The measurement conditions were: acceleration voltage: 30kV, emission current: 10μA, detector: transmission detector, tilt: none (0°), and observation magnification: 5000x. Next, using image processing software capable of binarizing cross-sectional images (image analysis software included with the Keyence VHX-5000 electron microscope), the island and sea portions of the sea-island structure were binarized in the cross-sectional image. Specifically, measurement was started with the brightness (standard) setting of the image analysis software, the extraction area (measurement range) was set to rectangular (7μm vertical, 13μm horizontal), the imaging size to standard (1600×1200), the tilt angle to 0 degrees, the shooting mode to normal shooting, and the extraction target to "dark areas". Furthermore, automatic measurement was used to correct for any missing or extra extracted areas, and the total area and number of extracted areas (islands) were measured. At this time, the area and number of all islands present in the extracted region were measured, respectively. Using the acquired data, the ratio of the total area of ​​all islands to the area of ​​the measurement range of the cross-sectional image (total area of ​​islands / area of ​​the measurement range of the cross-sectional image), and the area of ​​all islands, were calculated to be 0.01 μm. 2 The percentage of the total number of island areas (0.01 μm) 2 (Total number of islands / Total number of all islands), 0.02 μm 2 The percentage of the total number of island areas (0.02 μm)2 (Total number of islands / Total number of all islands), 0.03 μm 2 The percentage of the total number of the following island areas (0.03 μm) 2 (Total number of islands / Total number of all islands), 0.30 μm 2 The percentage of the total number of the above island areas (0.30 μm 2 (Total number of islands / Total number of all islands), 0.15 μm 2 The percentage of the total number of the above island areas (0.15 μm) 2 The total number of islands (as shown above / total number of all islands) was calculated. The results are shown in Table 1C.

[0280] (Antioxidant) In the examples and comparative examples, the types and concentrations of antioxidants contained in the adhesive layer and the heat-fusible resin layer are as follows:

[0281] Example 1C: The adhesive layer and the heat-sealable resin layer contain a total of 0.4% by mass or less of tris(2,4-di-t-butylphenoxy)phosphine and tetrakis(methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane. Example 2C: The adhesive layer and the heat-fusible resin layer contain 0.4% by mass of tris(2,4-di-t-butylphenoxy)phosphine.

[0282] Comparative Example 1C: The adhesive layer and the heat-sealable resin layer contain a total of 0.4% by mass or less of tris(2,4-di-t-butylphenoxy)phosphine and tetrakis(methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane. Comparative Example 2C: The adhesive layer and the heat-sealable resin layer contain a total of 0.4% by mass or less of tris(2,4-di-t-butylphenoxy)phosphine and tetrakis(methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

[0283] <Whitening due to molding> Each exterior material for the energy storage device was cut into a rectangle with a length (MD: Machine Direction) of 90 mm and a width (TD) of 150 mm to serve as a test sample. The MD of the exterior material for the energy storage device corresponds to the rolling direction (RD) of the aluminum alloy foil, and the TD of the exterior material for the energy storage device corresponds to the TD of the aluminum alloy foil. This test sample was subjected to the following conditions at 25°C: a rectangular molding die (female mold, surface has a maximum height roughness (nominal value Rz) of 3.2 μm, as specified in Table 2 of the comparative surface roughness standard specimens in Annex 1 (Reference) of JIS B 0659-1:2002; corner radius 2.0 mm, edge radius 1.0 mm) and a corresponding molding die (male mold, surface of the edge has a maximum height roughness (nominal value Rz) of 1.6 μm, as specified in Table 2 of the comparative surface roughness standard specimens in Annex 1 (Reference) of JIS B 0659-1:2002; surface other than the edge has a maximum height roughness (nominal value Rz) of 1.6 μm. The maximum height roughness (nominal value of Rz) is 3.2 μm, as specified in Table 2 of the comparative surface roughness standard specimens. Cold forming (single-stage pull-in forming) was performed with a pressing pressure (surface pressure) of 0.1 MPa to achieve a molding depth of 6.0 mm using corner radius R2.0 mm and edge radius R1.0 mm. At this time, the test sample was placed on the female mold so that the heat-fusible resin layer side was located on the male mold side, and forming was performed. The clearance between the male and female molds was set to 0.3 mm. The heat-fusible resin layer of the molded test sample was visually observed to check for whitening. Samples with no whitening were rated A, those with slight whitening were rated B, and those with clear whitening were rated C. The results are shown in Table 1C. Note that the areas where whitening occurred were mainly around the side walls on the short side of the molded part.

[0284] <Insulating properties> The exterior material for the energy storage device was cut into sheet pieces measuring 160mm in length (MD) x 90mm in width (TD). Next, these sheet pieces were subjected to a 25°C environment using a rectangular molding die (female mold, surface has a maximum height roughness (nominal value of Rz) of 3.2 μm, as specified in Table 2 of the comparative surface roughness standard specimens in Annex 1 (Reference) of JIS B 0659-1:2002, corner R2.0 mm, ridge R1.0 mm) and a corresponding molding die (male mold, surface of the ridge has a maximum height roughness (nominal value of Rz) of 1.6 μm, as specified in Table 2 of the comparative surface roughness standard specimens in Annex 1 (Reference) of JIS B 0659-1:2002, and the surface other than the ridge has a maximum height roughness (nominal value of Rz) of 1.6 μm, as specified in Annex 1 (Reference) of JIS B 0659-1:2002 The maximum height roughness (nominal value of Rz) is 3.2 μm, as specified in Table 2 of the comparative surface roughness standard specimens. Cold forming (single-stage pull-in forming) was performed with a pressing pressure (surface pressure) of 0.1 MPa to achieve a molding depth of 3.0 mm using corner radius (R2.0 mm) and edge radius (R1.0 mm). Next, the molded sample piece was folded in half in the MD direction so that the heat-fusible resin layers faced each other, and the molded body was obtained by cutting the end on the MD side from the molded part to a width of 3 mm. The position of the molded part was such that the distance between the molded part and both ends of the TD of the sheet piece was 25 mm and 32 mm, respectively.

[0285] Next, a polyethylene terephthalate sheet (PET sheet) with a thickness of 3.0 mm, a length (MD) of 30.0 mm, and a width (TD) of 52.5 mm, and an aluminum terminal with a thickness of 70 μm, a length (MD) of 55 mm, and a width (TD) of 5 mm were prepared. A tab film (formed from maleic anhydride-modified polypropylene) with a thickness of 100 μm and a width of 10 mm was wrapped around the center of the aluminum terminal. Using paper tape, the aluminum terminal was attached to the MD end of the PET sheet, and the PET sheet was inserted into the molded part of the molded body as described above. At this time, the aluminum terminal protruded from the molded part to the outside of the molded body, and the tab film was positioned between the heat-sealable resin layers of the molded body. In this state, the edge of the molded body from which the aluminum terminal protruded was heat-sealed under the conditions of a width of 3 mm, a surface pressure of 4.0 MPa, a sealing temperature of 170°C, and a sealing time of 3.0 seconds. Next, one end perpendicular to the heat-sealed end was heat-sealed under the conditions of a width of 3 mm, a surface pressure of 1.0 MPa, a sealing temperature of 170°C, and a sealing time of 3.0 seconds to form a bag-like structure. Then, the bag-shaped molded body was stored in a dry room for one day. An electrolyte (prepared by mixing lithium hexafluoride phosphate to a concentration of 1 mol / L in a solution of ethylene carbonate:diethyl carbonate:dimethyl carbonate in a volume ratio of 1:1:1) was poured through the remaining open end (opening), and the opening was heat-sealed under the conditions of a width of 3 mm, a surface pressure of 1.0 MPa, a sealing temperature of 170°C, and a sealing time of 3.0 seconds to seal the electrolyte inside the molded body. Finally, with the heat-sealed end facing upwards, the molded body was stored in a 60°C environment for 6 hours. Next, between the last heat-sealed edge and the molded portion, heat-sealable resin layers were heat-sealed together along the molded portion under the conditions of a width of 3 mm, a surface pressure of 1.0 MPa, a sealing temperature of 170°C, and a sealing time of 3.0 seconds, to create a test sample in which the electrolyte was sealed into the molded portion.

[0286] Next, the insulation between the barrier layer of the test sample and the aluminum terminal was evaluated using a tester (HIOKI 3154 insulation resistance tester). First, 10 test samples were prepared. Next, one terminal of the tester was connected to the aluminum terminal of the test sample, and the other terminal was connected to the barrier layer of the exterior material for the energy storage device using alligator clips. Next, a voltage of 25V was applied between the testers, and samples with a resistance of 200MΩ or more after 10 seconds were judged as pass (OK), and samples with a resistance of less than 200MΩ after 10 seconds were judged as fail (NG). The number of failing (NG) test samples out of 10 test samples is shown in Table 1C.

[0287] [Table 1C]

[0288] As is clear from the description in Table 1C, the exterior material for the energy storage device in Examples 1C and 2C, in the cross-sectional image of the heat-sealable resin layer containing polypropylene and polyethylene, has an island structure where the area of ​​the island portion is 0.02 μm² relative to the total number of island portions. 2 The proportion of the total number of the following island-like structures is 80.0% or more, indicating that whitening and a decrease in insulation performance due to molding are effectively suppressed.

[0289] As described above, the first embodiment of this disclosure provides the invention in the following aspects. Item 1A. The laminate comprises at least a base layer, a barrier layer, and an inner layer in this order. The inner layer comprises, from the barrier layer side, an adhesive layer and a heat-fusible resin layer. An outer casing material for energy storage devices, wherein the inner layer exhibits an elongation rate of 8.0% or less at 80°C when subjected to dynamic viscoelasticity measurement by tensile stress. Item 2A. The exterior material for energy storage devices according to Item 1A, wherein, in the graph showing the relationship between elongation and temperature obtained by the dynamic viscoelasticity measurement, the temperature at an elongation of 10% is 85°C or higher. Item 3A. The exterior material for an energy storage device according to Item 1A or 2A, wherein the elongation at 110°C in the dynamic viscoelasticity measurement of the inner layer is 15.0% or less. Item 4A. An exterior material for an energy storage device according to any one of items A1 to 3A, wherein the ratio of the thickness of the heat-fusible resin layer to the thickness of the adhesive layer is 0.3 or more and 1.5 or less. Item 5A. The exterior material for an energy storage device according to any one of items 1A to 4A, wherein the adhesive layer is made of a thermoplastic resin. Item 6A. The process includes at least a step of obtaining a laminate by laminating a base layer, a barrier layer, and an inner layer in this order, The inner layer comprises, from the barrier layer side, an adhesive layer and a heat-fusible resin layer. A method for manufacturing an outer casing material for an energy storage device, wherein the inner layer exhibits an elongation rate of 8.0% or less at 80°C when subjected to dynamic viscoelasticity measurement by tensile stress. Item 7A. An energy storage device in which an energy storage device element comprising at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed from an outer casing material for energy storage devices as described in any one of items 1A to 5A.

[0290] Furthermore, a second embodiment of this disclosure provides the invention in the following manner. Item 1B. The laminate comprises, at least, a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer in this order. The adhesive layer contains a polypropylene resin and polyethylene. A sea-island structure was observed in the cross-sectional image obtained using a scanning electron microscope of the adhesive layer in a direction parallel to the TD and in the thickness direction. The aforementioned cross-sectional image is obtained within the range from the surface of the adhesive layer on the barrier layer side to the portion with a thickness of 25%, assuming the thickness of the adhesive layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.25 μm² relative to the total number of island portions. 2 An exterior material for energy storage devices in which the proportion of the total number of island portions less than 40% is 40% or more. Item 2B. In the cross-sectional image of the adhesive layer, the area of ​​the island portion of the sea-island structure is 1.50 μm² relative to the total number of island portions of the sea-island structure. 2 The exterior material for energy storage devices described in item 1, wherein the proportion of the total number of the above-mentioned island portions is 10% or less. Item 3B. In the cross-sectional image of the adhesive layer, the area of ​​the island portion of the sea-island structure is 0.15 μm² relative to the total number of island portions of the sea-island structure. 2 An exterior material for an energy storage device as described in item 1B or 2B, wherein the proportion of the total number of island portions less than 20% is 20% or more. Item 4B. In the cross-sectional image of the adhesive layer, the area of ​​the island portion of the sea-island structure is 0.10 μm² relative to the total number of island portions of the sea-island structure. 2 An exterior material for an energy storage device as described in item 1B or 2B, wherein the proportion of the total number of island portions less than 10% is 10% or more. Item 5B. The polypropylene resin in the adhesive layer is acid-modified polypropylene, the exterior material for an energy storage device according to any one of items 1B to 4B. Item 6B. An exterior material for an energy storage device according to any one of items 1B to 5B, wherein the thickness of the adhesive layer is 5 μm or more. Item 7B. The resin forming the heat-fusible resin layer comprises a polyolefin skeleton, the exterior material for an energy storage device according to any one of items 1B to 6B. Item 8B. An exterior material for an energy storage device according to any one of items 1B to 7B, wherein at least one of the layers inside the barrier layer contains at least one selected from the group consisting of antioxidants and radical scavengers. Item 9B. The exterior material for an energy storage device according to Item 8B, wherein the antioxidant is at least one selected from the group consisting of phosphorus-based antioxidants and phenol-based antioxidants. Item 10B. The exterior material for an energy storage device according to any one of items 1B to 9B, wherein the radical scavenger is an alkyl radical scavenger. Item 11B. The process includes a step of obtaining a laminate by laminating, from the outside to the inside, at least a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer in this order. The adhesive layer contains a polypropylene resin and polyethylene. A sea-island structure was observed in the cross-sectional image obtained using a scanning electron microscope of the adhesive layer in a direction parallel to the TD and in the thickness direction. The aforementioned cross-sectional image is obtained within the range from the surface of the adhesive layer on the barrier layer side to the portion with a thickness of 25%, assuming the thickness of the adhesive layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.25 μm² relative to the total number of island portions. 2 A method for manufacturing exterior material for energy storage devices, wherein the proportion of the total number of island portions less than 40% is 40% or more. Item 12B. An energy storage device in which an energy storage device element comprising at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed from an outer casing material for energy storage devices as described in any one of items 1B to 10B.

[0291] Furthermore, a third embodiment of this disclosure provides the invention in the following manner. Item 1C. The laminate comprises, from the outside to the inside, at least a base layer, a barrier layer, and a heat-fusible resin layer in this order. The heat-sealable resin layer contains polypropylene and polyethylene. A sea-island structure was observed in the cross-sectional image obtained using a scanning electron microscope of the heat-fusible resin layer in a direction parallel to TD and in the thickness direction. The aforementioned cross-sectional image is obtained within a range of 12.5% ​​thickness from the surface of the heat-fusible resin layer opposite the barrier layer, assuming that the total thickness of the layers located inside the barrier layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.02 μm² relative to the total number of island portions of the sea-island structure. 2 The proportion of the total number of the following island areas is 80.0% or more. An exterior material for an energy storage device, comprising at least one of the layers inside the barrier layer, containing at least one of an antioxidant and a radical scavenger. Item 2C. The exterior material for an energy storage device according to Item 1C, wherein the antioxidant is at least one selected from the group consisting of phosphorus-based antioxidants and phenol-based antioxidants. Item 3C. The exterior material for an energy storage device according to Item 1C or 2C, wherein the radical scavenger is an alkyl radical scavenger. Item 4C. An exterior material for an energy storage device according to any one of items 1C to 3C, wherein in the cross-sectional image of the heat-fusible resin layer, the ratio of the total area of ​​the island portion of the sea-island structure to the area of ​​the measurement range of the cross-sectional image is 12.0% or less. Section 5C. In the cross-sectional image of the heat-fusible resin layer, the area of ​​the island portion of the sea-island structure is 0.03 μm² relative to the total number of island portions of the sea-island structure. 2 An exterior material for an energy storage device as described in any one of items 1C to 4C, wherein the proportion of the total number of the following island sections is 90.0% or more. Section 6C. In the cross-sectional image of the heat-fusible resin layer, the area of ​​the island portion of the sea-island structure is 0.01 μm² relative to the total number of island portions of the sea-island structure. 2 An exterior material for an energy storage device as described in any one of items 1C to 5C, wherein the proportion of the total number of the following island sections is 50.0% or more. Section 7C. In the cross-sectional image of the heat-fusible resin layer, the area of ​​the island portion of the sea-island structure is 0.30 μm² relative to the total number of island portions of the sea-island structure. 2 An exterior material for an energy storage device as described in any one of items 1C to 6C, wherein the proportion of the total number of the above-mentioned island portions is 1.0% or less. Item 8C. An exterior material for an energy storage device according to any one of items 1C to 7C, comprising an adhesive layer between the barrier layer and the heat-fusible resin layer. Item 9C. The exterior material for an energy storage device according to Item 8C, wherein the thickness of the adhesive layer is 5 μm or more. Item 10C. The process includes a step of obtaining a laminate by laminating a base material layer, a barrier layer, and a heat-fusible resin layer in this order from the outside to the inside. The heat-sealable resin layer contains polypropylene and polyethylene. A sea-island structure was observed in the cross-sectional image obtained using a scanning electron microscope of the heat-fusible resin layer in a direction parallel to TD and in the thickness direction. The aforementioned cross-sectional image is obtained within a range of 12.5% ​​thickness from the surface of the heat-fusible resin layer opposite the barrier layer, assuming that the total thickness of the layers located inside the barrier layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.02 μm² relative to the total number of island portions of the sea-island structure. 2 The proportion of the total number of the following island areas is 80.0% or more. A method for manufacturing an exterior material for an energy storage device, comprising including at least one of an antioxidant and a radical scavenger in at least one of the layers inside the barrier layer. Item 11C. An energy storage device in which an energy storage device element comprising at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed from an outer casing material for energy storage devices as described in any one of items 1C to 9C. [Explanation of Symbols]

[0292] 1 Base material layer 2 Adhesive layer 3. Barrier layer 4 Heat-fusible resin layer 5 Adhesive layer 6 Surface coating layer 10. Exterior materials for energy storage devices

Claims

1. It is composed of a laminate comprising, at a minimum, a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer in this order. The aforementioned substrate layer is formed from two or more resin films. The adhesive layer contains a polypropylene resin and polyethylene. A sea-island structure was observed in the cross-sectional image obtained using a scanning electron microscope of the adhesive layer in a direction parallel to TD and in the thickness direction. The aforementioned cross-sectional image is obtained within the range from the surface of the adhesive layer on the barrier layer side to a portion with a thickness of 25%, assuming the thickness of the adhesive layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.25 μm, relative to the total number of island portions. 2 An exterior material for energy storage devices in which the proportion of the total number of island portions less than 40% is 40% or more.

2. It is composed of a laminate comprising, at a minimum, a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer in this order. The aforementioned base material layer is formed from a single layer of polyester film. The adhesive layer contains a polypropylene resin and polyethylene. A sea-island structure was observed in the cross-sectional image obtained using a scanning electron microscope of the adhesive layer in a direction parallel to TD and in the thickness direction. The aforementioned cross-sectional image is obtained within the range from the surface of the adhesive layer on the barrier layer side to a portion with a thickness of 25%, assuming the thickness of the adhesive layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.25 μm, relative to the total number of island portions. 2 An exterior material for energy storage devices in which the proportion of the total number of island portions less than 40% is 40% or more.

3. It is composed of a laminate comprising, at a minimum, a base layer, a barrier layer, an adhesive layer, and a heat-fusible resin layer in this order. The thickness of the barrier layer is 50 μm or more and 80 μm or less. The adhesive layer contains a polypropylene resin and polyethylene. A sea-island structure was observed in the cross-sectional image obtained using a scanning electron microscope of the adhesive layer in a direction parallel to TD and in the thickness direction. The aforementioned cross-sectional image is obtained within the range from the surface of the adhesive layer on the barrier layer side to a portion with a thickness of 25%, assuming the thickness of the adhesive layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.25 μm, relative to the total number of island portions. 2 An exterior material for energy storage devices in which the proportion of the total number of island portions less than 40% is 40% or more.

4. It is composed of a laminate comprising, from the outside to the inside, at least a base layer, a barrier layer, and a heat-sealable resin layer in this order. The aforementioned substrate layer is formed from two or more resin films. The heat-sealable resin layer contains polypropylene and polyethylene. A sea-island structure was observed in the cross-sectional image of the heat-fusible resin layer in the direction parallel to TD and in the thickness direction, obtained using a scanning electron microscope. The aforementioned cross-sectional image is obtained within a range of 12.5% ​​thickness from the surface of the heat-fusible resin layer opposite to the barrier layer, assuming that the total thickness of the layers located inside the barrier layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.02 μm, relative to the total number of island portions of the sea-island structure. 2 The proportion of the total number of the following island areas is 80.0% or more. An exterior material for an energy storage device, comprising at least one of the layers inside the barrier layer, containing at least one of an antioxidant and a radical scavenger.

5. It is composed of a laminate comprising, from the outside to the inside, at least a base layer, a barrier layer, and a heat-sealable resin layer in this order. The aforementioned base material layer is formed from a single layer of polyester film. The heat-sealable resin layer contains polypropylene and polyethylene. A sea-island structure was observed in the cross-sectional image of the heat-fusible resin layer in the direction parallel to TD and in the thickness direction, obtained using a scanning electron microscope. The aforementioned cross-sectional image is obtained within a range of 12.5% ​​thickness from the surface of the heat-fusible resin layer opposite to the barrier layer, assuming that the total thickness of the layers located inside the barrier layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.02 μm, relative to the total number of island portions of the sea-island structure. 2 The proportion of the total number of the following island areas is 80.0% or more. An exterior material for an energy storage device, comprising at least one of the layers inside the barrier layer, containing at least one of an antioxidant and a radical scavenger.

6. It is composed of a laminate comprising, from the outside to the inside, at least a base layer, a barrier layer, and a heat-sealable resin layer in this order. The thickness of the barrier layer is 50 μm or more and 80 μm or less. The heat-sealable resin layer contains polypropylene and polyethylene. A sea-island structure was observed in the cross-sectional image of the heat-fusible resin layer in the direction parallel to TD and in the thickness direction, obtained using a scanning electron microscope. The aforementioned cross-sectional image is obtained within a range of 12.5% ​​thickness from the surface of the heat-fusible resin layer opposite to the barrier layer, assuming that the total thickness of the layers located inside the barrier layer is 100%. In the aforementioned cross-sectional image, the area of ​​the island portion of the sea-island structure is 0.02 μm, relative to the total number of island portions of the sea-island structure. 2 The proportion of the total number of the following island areas is 80.0% or more. An exterior material for an energy storage device, comprising at least one of the layers inside the barrier layer, containing at least one of an antioxidant and a radical scavenger.

7. The exterior material for an energy storage device according to claim 1 or 4, wherein the thickness of the resin film constituting each layer of the base material is 2 μm or more and 25 μm or less.

8. In the cross-sectional image of the adhesive layer, the area of ​​the island portion of the sea-island structure is 1.50 μm² relative to the total number of island portions of the sea-island structure. 2 The exterior material for an energy storage device according to any one of claims 1 to 3, wherein the proportion of the total number of the above-mentioned island portions is 10% or less.

9. In the cross-sectional image of the adhesive layer, the area of ​​the island portion of the sea-island structure is 0.15 μm relative to the total number of island portions of the sea-island structure. 2 An exterior material for an energy storage device according to any one of claims 1 to 3, wherein the proportion of the total number of island portions less than 20% is 20% or more.

10. In the cross-sectional image of the adhesive layer, the ratio of the total number of island portions having an area of less than 0.10 μm 2 to the total number of island portions in the sea-island structure is 10% or more. The exterior material for a power storage device according to any one of claims 1 to 3.

11. The exterior material for an energy storage device according to any one of claims 4 to 6, wherein in the cross-sectional image of the heat-fusible resin layer, the ratio of the total area of ​​the island portion of the sea-island structure to the area of ​​the measurement range of the cross-sectional image is 12.0% or less.

12. In the cross-sectional image of the heat-fusible resin layer, the area of ​​the island portion of the sea-island structure is 0.03 μm. 2 An exterior material for an energy storage device according to any one of claims 4 to 6, wherein the proportion of the total number of the following island portions is 90.0% or more.

13. In the cross-sectional image of the heat-fusible resin layer, the area of ​​the island portion of the sea-island structure is 0.01 μm² relative to the total number of island portions. 2 An exterior material for an energy storage device according to any one of claims 4 to 6, wherein the proportion of the total number of the following island portions is 50.0% or more.

14. In the cross-sectional image of the heat-fusible resin layer, the area of ​​the island portion of the sea-island structure is 0.30 μm² relative to the total number of island portions. 2 The exterior material for an energy storage device according to any one of claims 4 to 6, wherein the proportion of the total number of the above-mentioned island portions is 1.0% or less.

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