Resin film for power storage device and the power storage device

Abstract

To provide a resin film for a power storage device, comprising an excellent insulation quality, and capable of suppressing an immersion of water into a power storage device element.SOLUTION: A resin film for a power storage device is constructed by two or more layers, and the two or more layers contains: at least one layer A of which a percentage content of a water absorption is 5 mass% or more; and at least one layer B of which the percentage content of the water absorption is less than 5 mass%.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a resin film for an electricity storage device and an electricity storage device. [Background technology]

[0002] Conventionally, various types of electricity storage devices have been developed, and in all electricity storage devices, exterior materials are essential components for sealing electricity storage device elements such as electrodes, electrolytes, etc. Conventionally, metallic exterior materials have been widely used as exterior materials for electricity storage devices.

[0003] Meanwhile, in recent years, various shapes as well as thinner and lighter weight are required for electricity storage devices along with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc. However, the metallic exterior materials for electricity storage devices that have been widely used in the past have the drawbacks of being difficult to keep up with the diversification of shapes and also having limitations in terms of weight reduction.

[0004] In view of this, a film-like laminate in which a base layer / barrier layer / adhesive layer / thermally adhesive resin layer are laminated in this order has been proposed as an exterior material for an electricity storage device that can be easily processed into a variety of shapes and can be made thin and lightweight (see, for example, Patent Document 1).

[0005] In such an exterior material for an electricity storage device, a recess is generally formed by cold forming, and electricity storage device elements such as electrodes and an electrolyte are placed in the space formed by the recess, and the heat-sealable resin layer is then heat-sealed to obtain an electricity storage device in which the electricity storage device elements are housed inside the exterior material for an electricity storage device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2008-287971 A Summary of the Invention [Problem to be solved by the invention]

[0007] If moisture penetrates into the inside of the electricity storage device element, the performance of the electricity storage device will deteriorate, so for example, when the above-mentioned film-like laminate is used as an exterior material, a barrier layer (for example, made of metal foil) is provided. By providing the barrier layer, it is possible to suppress the penetration of moisture from the outside of the barrier layer.

[0008] However, when the heat-sealable resin layer of the exterior material is heat-sealed to seal the electricity storage device element, the end faces of the heat-sealable resin layer are exposed to the outside, and there is a risk of moisture penetrating from the end faces of the heat-sealable resin layer.

[0009] Furthermore, if the heat-sealable resin layer of the exterior material absorbs water before the electricity storage device element is sealed with the exterior material, there is a risk that the moisture in the heat-sealable resin layer will penetrate into the electricity storage device element after the electricity storage device element is sealed.

[0010] Furthermore, some of the materials used in electricity storage devices are required to have excellent insulating properties.

[0011] Under these circumstances, a main object of the present disclosure is to provide a resin film for an electricity storage device that has excellent insulating properties and suppresses the penetration of moisture into the interior of an electricity storage device element. [Means for solving the problem]

[0012] The inventors of the present disclosure conducted intensive research to solve the above problems, and as a result, found that by configuring a resin film for an electricity storage device with two or more layers, and setting the content of a water absorbing agent in at least one of the two or more layers to 5 mass % or more and the content of a water absorbing agent in at least one of the two or more layers to less than 5 mass %, it is possible to suppress the intrusion of moisture into the interior of an electricity storage device element while providing excellent insulation.

[0013] The present disclosure has been completed based on these findings and through further investigations. That is, the present disclosure provides the invention of the following aspects. A resin film for an electricity storage device, The resin film for an electricity storage device is composed of two or more layers, The two or more layers include at least one layer A having a water absorbing agent content of 5% by mass or more, and at least one layer B having a water absorbing agent content of less than 5% by mass. Effect of the Invention

[0014] According to the present disclosure, it is possible to provide a resin film for an electricity storage device that has excellent insulating properties and suppresses the intrusion of moisture into the interior of an electricity storage device element. In addition, according to the present disclosure, it is also possible to provide an electricity storage device using the technology. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic diagram showing an example of a cross-sectional structure of a resin film for an electricity storage device according to the present disclosure. [Diagram 2] 1 is a schematic diagram showing an example of a cross-sectional structure of a resin film for an electricity storage device according to the present disclosure. [Diagram 3] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electricity storage device according to the present disclosure. [Figure 4] 1 is a schematic diagram showing an example of a cross-sectional structure of an electricity storage device according to the present disclosure. [Diagram 5] 1 is a schematic diagram showing an example of a cross-sectional structure of an electricity storage device according to the present disclosure. [Figure 6] 1 is a schematic diagram showing an example of a cross-sectional structure of an electricity storage device according to the present disclosure. [Figure 7] 1 is a schematic diagram showing an example of a cross-sectional structure of an electricity storage device according to the present disclosure. [Figure 8] 1 is a schematic diagram showing an example of a cross-sectional structure of an electricity storage device according to the present disclosure. [Figure 9] 1 is a schematic diagram showing an example of a cross-sectional structure of an electricity storage device according to the present disclosure. [Figure 10] 1 is a schematic perspective view illustrating an example of an electricity storage device according to the present disclosure. [Figure 11] 1 is a schematic diagram showing an example of a cross-sectional structure of an electricity storage device according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The resin film for an electricity storage device according to the present disclosure is configured with two or more layers, and the two or more layers are characterized in that they include at least one layer A having a water absorbing agent content of 5% by mass or more and at least one layer B having a water absorbing agent content of less than 5% by mass. By virtue of having such a configuration, the resin film for an electricity storage device according to the present disclosure has excellent insulating properties and can suppress the penetration of moisture into the interior of an electricity storage device element.

[0017] The resin film for an electricity storage device according to the present disclosure will be described in detail below. In the present disclosure, a numerical range indicated by "to" means "not less than" or "not more than." For example, the expression "2 to 15 mm" means 2 mm or more and 15 mm or less.

[0018] As a method for confirming the MD of the resin film for an electricity storage device, there is a method for confirming the sea-island structure by observing a cross section of the resin film for an electricity storage device (for example, a cross section of an acid-modified polyolefin layer or a polyolefin layer) with an electron microscope. In this method, the direction parallel to the cross section in which the average diameter of the shape of the islands in the direction perpendicular to the thickness direction of the resin film for an electricity storage device is the largest can be determined as the MD. Specifically, the cross section in the length direction of the resin film for an electricity storage device and each cross section (a total of 10 cross sections) in a direction perpendicular to the cross section in the length direction, which are changed in angle by 10 degrees each, are observed with an electron microscope to confirm the sea-island structure. Next, the shape of each individual island is observed in each cross section. For each island shape, the straight line distance connecting the leftmost end in the direction perpendicular to the thickness direction of the resin film for an electricity storage device and the rightmost end in the perpendicular direction is defined as the diameter y. In each cross section, the average of the diameters y of the top 20 island shapes in descending order of the diameter y is calculated. The direction parallel to the cross section in which the average diameter y of the island shape is the largest is determined as the MD. Alternatively, for example, the resin film for an electricity storage device may be left in an environment of 150°C for 2 minutes, and the thermal shrinkage rate after that may be measured, and the direction with the larger shrinkage rate may be determined as the MD.

[0019] 1. Resin films for energy storage devices The resin film for an electricity storage device of the present disclosure is composed of two or more layers. The two or more layers include at least one layer A having a water absorbing agent content of 5% by mass or more and at least one layer B having a water absorbing agent content of less than 5% by mass. In Fig. 1 and Fig. 2, of the two or more layers, the layer A having a water absorbing agent content of 5% by mass or more is referred to as the first layer 11, and the layer B having a water absorbing agent content of less than 5% by mass is referred to as the second layer 12. In Fig. 2, the third layer 13 is referred to as the layer B having a water absorbing agent content of less than 5% by mass.

[0020] The resin film for an electric storage device according to the present disclosure has excellent insulating properties and can suppress the intrusion of moisture into the inside of an electric storage device element, and therefore can be suitably used as a resin film for an electric storage device. For example, the resin film for an electric storage device 1 is suitable for use in the following applications: 1) an application in which it is disposed between an exterior material for an electric storage device and an electric storage device element; 2) an application in which it is used as a heat-sealable resin layer of an exterior material for an electric storage device; 3) an application in which it is used as an adhesive layer between a barrier layer and a heat-sealable resin layer of an exterior material for an electric storage device; or 4) an application in which it is used as an adhesive film for a metal terminal interposed between a metal terminal electrically connected to an electrode of an electric storage device element and an exterior material for an electric storage device that seals the electric storage device element. Furthermore, the resin film for an electric storage device according to the present disclosure can also be used to be interposed between the heat-sealable resin layers at a position where the heat-sealable resin layers of the exterior material for an electric storage device are heat-sealed to each other.

[0021] 1) In applications in which it is disposed between an exterior material for an electricity storage device and an electricity storage device element, the resin film for an electricity storage device 1 of the present disclosure is disposed between an exterior material 3 of an electricity storage device 10 and an electricity storage device element 4, as shown in the schematic diagrams of Figures 5 to 9.

[0022] As described above, if moisture penetrates into the inside of the electricity storage device element, the performance of the electricity storage device deteriorates, so a barrier layer (for example, made of metal foil) is provided on the film-like exterior material. By providing the barrier layer, it is possible to suppress the penetration of moisture from the outside of the barrier layer. However, when the heat-sealable resin layer of the exterior material is heat-sealed to seal the electricity storage device element, the end face of the heat-sealable resin layer is exposed to the outside, so there is a risk of moisture penetrating from the end face of the heat-sealable resin layer. In addition, if the heat-sealable resin layer of the exterior material absorbs water before sealing the electricity storage device element with the exterior material, there is also a risk that the moisture in the heat-sealable resin layer will penetrate into the electricity storage device element after sealing the electricity storage device element.

[0023] In contrast, by disposing the resin film for an electricity storage device 1 of the present disclosure between the exterior material 3 and the electricity storage device element 4 of the electricity storage device 10, it is possible to effectively prevent moisture from penetrating from the end of the heat-sealable resin layer of the exterior material, and prevent moisture contained in the heat-sealable resin layer of the exterior material from penetrating into the electricity storage device element. That is, since the resin film for an electricity storage device 1 of the present disclosure contains a water absorbing agent, the resin film for an electricity storage device 1 absorbs and retains moisture that has penetrated from the heat-sealable resin layer of the exterior material, thereby preventing moisture from reaching the electricity storage device element 4. Furthermore, since the resin film for an electricity storage device 1 of the present disclosure includes layer B having a water absorbing agent content of less than 5% by mass, it is possible to ensure excellent insulation.

[0024] In an application in which the resin film 1 for an electricity storage device of the present disclosure is used as 2) a heat-sealable resin layer of an exterior material for an electricity storage device, the resin film 1 for an electricity storage device of the present disclosure is used as a heat-sealable resin layer 35 of an exterior material for an electricity storage device 3 composed of a laminate having at least a base layer 31, a barrier layer 33, and a heat-sealable resin layer 35 in this order, as shown in Fig. 3. In an application in which the resin film 1 for an electricity storage device of the present disclosure is used as 3) an adhesive layer between a barrier layer and a heat-sealable resin layer of an exterior material for an electricity storage device, the resin film 1 for an electricity storage device of the present disclosure is used as an adhesive layer 34 of an exterior material for an electricity storage device 3 composed of a laminate having at least a base layer 31, a barrier layer 33, an adhesive layer 34, and a heat-sealable resin layer 35 in this order, as shown in Fig. 3.

[0025] As described above, when the heat-sealable resin layer of the exterior material is heat-sealed to seal the electricity storage device element, the end face of the heat-sealable resin layer is exposed to the outside, and therefore moisture may penetrate from the end face of the heat-sealable resin layer. In addition, if the heat-sealable resin layer of the exterior material absorbs water before sealing the electricity storage device element with the exterior material, moisture in the heat-sealable resin layer may penetrate into the electricity storage device element after sealing the electricity storage device element. The same applies to the adhesive layer located between the barrier layer and the heat-sealable resin layer.

[0026] In contrast, by using the resin film for an electricity storage device 1 of the present disclosure as the heat-sealable resin layer or adhesive layer of the exterior material 3, it is possible to effectively suppress the intrusion of moisture from the end of the heat-sealable resin layer of the exterior material, and the intrusion of moisture contained in the heat-sealable resin layer or adhesive layer of the exterior material into the electricity storage device element. That is, since the resin film for an electricity storage device 1 of the present disclosure contains a water absorbing agent, the resin film for an electricity storage device 1 absorbs and retains moisture that has infiltrated from the heat-sealable resin layer of the exterior material, thereby suppressing the moisture from reaching the electricity storage device element 4. Furthermore, since the resin film for an electricity storage device 1 of the present disclosure includes layer B having a content of water absorbing agent of less than 5% by mass, it is possible to ensure excellent insulation.

[0027] In addition, in an application in which the resin film for an electricity storage device 1 of the present disclosure is used as an adhesive film for a metal terminal interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that encapsulates the electricity storage device element, as shown in Figure 4, the resin film for an electricity storage device 1 is used as an adhesive film for a metal terminal 21.

[0028] Since the end faces of the adhesive film for metal terminals are exposed to the outside, there is a risk that moisture may penetrate through the end faces of the adhesive film for metal terminals. In addition, if the adhesive film for metal terminals absorbs water before being interposed between the metal terminal and the exterior material for a power storage device, there is a risk that the moisture in the adhesive film for metal terminals may penetrate into the power storage device element after the adhesive film for metal terminals is interposed between the metal terminal and the exterior material for a power storage device.

[0029] In contrast, by using the resin film for an electricity storage device 1 of the present disclosure as an adhesive film for a metal terminal, it is possible to effectively suppress the infiltration of moisture from the end of the adhesive film for a metal terminal and the infiltration of moisture contained in the adhesive film for a metal terminal. That is, since the resin film for an electricity storage device 1 of the present disclosure contains a water absorbing agent, the resin film for an electricity storage device 1 absorbs and retains moisture that has infiltrated from the adhesive film for a metal terminal, thereby suppressing the moisture from reaching the electricity storage device element 4. Furthermore, since the resin film for an electricity storage device 1 of the present disclosure includes a layer B having a water absorbing agent content of less than 5 mass %, it is possible to ensure excellent insulation properties.

[0030] In the present disclosure, the moisture to be absorbed is gaseous and / or liquid moisture, which generates various outgases when absorbed, for example, in a solid electrolyte type lithium ion battery.

[0031] As shown in, for example, FIG. 4 to FIG. 11, the electricity storage device 10 has a structure in which an electricity storage device element 4 is sealed with an exterior material 3. The metal terminal 2 protrudes to the outside of the exterior material 3. The metal terminal 2 is connected to each of the positive and negative electrodes of the electricity storage device element 4. An adhesive film 21 for metal terminals is disposed between the metal terminal 2 and the exterior material 3, and the adhesion between the metal terminal 2 and the heat-sealable resin layer 35 of the exterior material is enhanced. The electricity storage device 10 is sealed by covering the electricity storage device element 4 with the exterior material 3 so that a flange portion (peripheral portion 3a of the exterior material 3) of the exterior material 3 can be formed on the periphery of the electricity storage device element 4, and heat-sealing the flange portion of the exterior material 3 to seal it. When the electricity storage device element 4 is housed using the exterior material 3, the exterior material 3 is used so that the heat-sealable resin layer 35 of the exterior material 3 faces inside (the surface in contact with the electricity storage device element 4). When the resin film 1 for an electrical storage device according to the present disclosure is used as an adhesive film for a metal terminal, for example, the adhesive film for a metal terminal is colored, so that the adhesive film for a metal terminal can be positioned with high positional accuracy between the metal terminal and the exterior material for an electrical storage device. In addition, the layer constituting the surface of the adhesive film for a metal terminal on the metal terminal side is preferably composed of an acid-modified polyolefin. This makes it possible to increase the adhesion of the adhesive film for a metal terminal to the metal terminal.

[0032] 10 and 11, the exterior material 3 is wrapped (wrapped around the body) around the electricity storage device element 4 (rectangular parallelepiped shape in FIG. 10 and FIG. 11) with the heat-sealable resin layer of the exterior material 3 for the electricity storage device facing inward, and the heat-sealable resin layers are heat-sealed to form a heat-sealed portion 70, and a lid body 60 is arranged to close the openings at both ends. Between the lid body 60 of the exterior material 3 for the electricity storage device and the electricity storage device element 4, the resin film for the electricity storage device 1 of the present disclosure may be arranged between the exterior material 3 for the electricity storage device that wraps the resin film for the electricity storage device and the electricity storage device element 4. In this case, the lid body 60 constitutes a part of the exterior material 3 for the electricity storage device, and the resin film for the electricity storage device 1 of the present disclosure is arranged between the exterior material 3 and the electricity storage device element 4. The lid body 60 may be composed of one member or may be composed of multiple members.

[0033] In the above-mentioned 1) use in which the resin film for an electricity storage device is disposed between the exterior material for an electricity storage device and an electricity storage device element, the resin film for an electricity storage device 1 of the present disclosure may be located over the entire surface of the exterior material 3 on the electricity storage device element 4 side (the heat-sealable resin layer 35 side), or may be located over a portion of the surface of the electricity storage device element 4 side (the heat-sealable resin layer 35 side). From the viewpoint of suitably exerting the effects of the present disclosure, the resin film for an electricity storage device 1 is preferably located between the exterior material 3 of the electricity storage device 10 and the electricity storage device element 4 so as to be located over the entire surface of the exterior material 3 on the electricity storage device element 4 side (the heat-sealable resin layer 35 side) (see schematic diagrams of FIGS. 5 to 9). For example, as shown in Fig. 5, the resin film for an electricity storage device 1 may be disposed only between the exterior material for an electricity storage device 3 and the electricity storage device element 4, or as shown in Fig. 6, the resin film for an electricity storage device 1 may be disposed between the peripheral portion 3a (heat-sealed portion) of the exterior material for an electricity storage device 3 and the electricity storage device element 4, or as shown in Fig. 7, the electricity storage device element 4 may be covered with the resin film for an electricity storage device 1, or as shown in Fig. 8, a part of the surface of the metal terminal 2 may be further covered with the resin film for an electricity storage device 1. Furthermore, as shown in Fig. 9, the resin film for an electricity storage device 1 of the present disclosure may be disposed between the exterior material 3 and the electricity storage device element 4 of an electricity storage device 10 such that the electricity storage device element 4 is sealed with the resin film for an electricity storage device 1. The resin film for an electricity storage device 1 may be present between the exterior material 3 and the metal terminal 2 and heat-sealed.

[0034] When the resin film for an electricity storage device 1 is located at a flange portion (peripheral edge portion 3a of the exterior material 3) of the exterior material 3, the resin film for an electricity storage device 1 preferably has heat adhesion. For example, in the schematic diagram of Fig. 9, the resin film for an electricity storage device 1 is located at a flange portion to which the exterior material 3 is heat-sealed, and therefore the resin film for an electricity storage device 1 preferably has heat adhesion to the heat-sealable resin layer 35 and the adhesive film for metal terminal 21. In addition, the resin films for an electricity storage device 1 preferably have heat adhesion to each other.

[0035] In the resin film for an electricity storage device 1 of the present disclosure, Layer A having a water absorbing agent content of 5% by mass or more may be a single layer or multiple layers, preferably a single layer. Layer B having a water absorbing agent content of less than 5% by mass may be a single layer or multiple layers.

[0036] The resin film for an electricity storage device 1 of the present disclosure is composed of two or more layers, as shown in, for example, Figures 1 and 2. Figure 1 shows the resin film for an electricity storage device 1 composed of a two-layer laminate in which a first layer 11 and a second layer 12 are laminated, and Figure 2 shows the resin film for an electricity storage device 1 composed of a three-layer laminate in which a second layer 12, a first layer 11, and a third layer 13 are laminated in this order. As described above, in Figures 1 and 2, the first layer 11 is layer A having a water absorbing agent content of 5 mass% or more, and the second layer 12 and the third layer 13 are layer B having a water absorbing agent content of less than 5 mass%.

[0037] In the present disclosure, a layer containing a water absorbing agent may be referred to as a "water absorbing layer". That is, in the present disclosure, layer A (first layer 11) having a water absorbing agent content of 5% by mass or more is a water absorbing layer, and layer B (second layer 12 and third layer 13) having a water absorbing agent content of less than 5% by mass is also a water absorbing layer when it contains a water absorbing agent. A specific example of the laminated structure of the resin film for an electrical storage device 1 is a laminated structure in which the first layer 11 is a water absorbing layer and the second layer 12 is a layer not containing a water absorbing agent in FIG. 1. Another example is a laminated structure in which the first layer 11 located in the middle is a water absorbing layer and the second layer 12 and third layer 13 located on the surface are layers not containing a water absorbing agent in FIG. 2.

[0038] In the present disclosure, the two or more layers of the resin film for an electricity storage device may include at least one layer A having a water absorbing agent content of 5% by mass or more and at least one layer B having a water absorbing agent content of less than 5% by mass. From the viewpoint of more suitably exerting the effects of the present disclosure, the content of the water absorbing agent in Layer A is preferably about 10% by mass or more, more preferably about 15% by mass or more, and also preferably about 50% by mass or less, more preferably about 40% by mass or less, and even more preferably about 30% by mass or less. Preferred ranges include about 5 to 50% by mass, about 5 to 40% by mass, about 5 to 30% by mass, about 10 to 50% by mass, about 10 to 40% by mass, about 10 to 30% by mass, about 15 to 50% by mass, about 15 to 40% by mass, and about 15 to 30% by mass. If the content of the water-absorbing agent in Layer A exceeds 50% by mass, there is a concern that a film formation defect, a decrease in interlayer adhesion, and a decrease in laminate strength or seal strength may occur due to the generation of foreign matter in Layer A. On the other hand, if the content of the water-absorbing agent is 5% or less, sufficient water absorption cannot be exhibited.

[0039] In order to more suitably exert the effects of the present disclosure, the content of the water-absorbing agent in Layer B having a content of the water-absorbing agent of less than 5 mass% is preferably about 3 mass% or less, more preferably 0 mass%, and preferred ranges include about 0 to 5 mass%, and about 0 to 3 mass%, etc.

[0040] From the viewpoint of more suitably exerting the effects of the present disclosure, the thickness of the layer A having a water-absorbing agent content of 5 mass % or more is preferably about 3 μm or more, more preferably about 5 μm or more, even more preferably about 10 μm or more, and is preferably about 200 μm or less, more preferably about 150 μm or less, even more preferably about 100 μm or less. Preferred ranges include about 3 to 200 μm, about 3 to 150 μm, about 3 to 100 μm, about 5 to 200 μm, about 5 to 150 μm, about 5 to 100 μm, about 10 to 200 μm, about 10 to 150 μm, and about 10 to 100 μm.

[0041] Moreover, from the viewpoint of more suitably exerting the effects of the present disclosure (particularly, excellent insulation), the thickness of Layer B having a water-absorbing agent content of less than 5 mass % is preferably not less than about 3 μm, more preferably not less than about 5 μm, and even more preferably not less than about 10 μm, and is preferably not more than about 100 μm, more preferably not more than about 80 μm, and even more preferably not more than about 50 μm. Preferred ranges include about 3 to 100 μm, about 3 to 80 μm, about 3 to 50 μm, about 5 to 100 μm, about 5 to 80 μm, about 5 to 50 μm, about 10 to 100 μm, about 10 to 80 μm, and about 10 to 50 μm.

[0042] The total thickness of the resin film 1 for an electricity storage device is not particularly limited as long as the effects of the present invention are achieved, and is preferably about 10 μm or more, more preferably about 15 μm or more, and even more preferably about 20 μm or more, and is preferably about 1000 μm or less, more preferably about 900 μm or less, and even more preferably about 500 μm or less. Preferred ranges of the thickness include about 10 to 1000 μm, about 10 to 900 μm, about 10 to 500 μm, about 15 to 1000 μm, about 15 to 900 μm, about 15 to 500 μm, about 20 to 1000 μm, about 20 to 900 μm, and about 20 to 500 μm.

[0043] Furthermore, when the resin film 1 for an electricity storage device of the present disclosure is used as an adhesive film for a metal terminal, the total thickness may be within the above-mentioned range, but is preferably at least about 30 μm, more preferably at least about 50 μm, and even more preferably at least about 60 μm, and is preferably at most about 1000 μm, more preferably at most about 500 μm, and even more preferably at most about 300 μm. Preferred ranges include about 30 to 1000 μm, about 30 to 500 μm, about 30 to 300 μm, about 50 to 1000 μm, about 50 to 500 μm, about 50 to 300 μm, about 60 to 1000 μm, about 60 to 500 μm, and about 60 to 300 μm.

[0044] Furthermore, from the viewpoint of more suitably exerting the effects of the present disclosure, the ratio of the thickness of Layer B having a water absorbing agent content of less than 5 mass% to the total thickness of the resin film 1 for an electricity storage device (thickness of Layer B / total thickness) is preferably not more than about 0.80, more preferably not more than about 0.75, and even more preferably not more than about 0.50. The lower limit is, for example, about 0.01, about 0.05, and about 0.10. Preferred ranges include about 0.01 to 0.80, about 0.01 to 0.75, about 0.01 to 0.50, about 0.05 to 0.80, about 0.05 to 0.75, about 0.05 to 0.50, about 0.10 to 0.80, about 0.10 to 0.75, and about 0.10 to 0.50.

[0045] Of the two or more layers of the resin film for an electricity storage device 1, at least one layer preferably contains a heat-sealable resin. Furthermore, it is preferable that one or both sides of the resin film for an electricity storage device 1 have heat-sealability. For example, in the above-mentioned application 2) where the resin film for an electricity storage device is used as a heat-sealable resin layer of an exterior material for an electricity storage device, at least one side of the resin film for an electricity storage device 1 needs to have heat-sealability. It is particularly preferable that all layers of the resin film for an electricity storage device 1 contain a heat-sealable resin.

[0046] In the above-mentioned 1) application in which the resin film for an electricity storage device is disposed between an exterior material for an electricity storage device and an electricity storage device element, when the resin film for an electricity storage device 1 is located at the flange portion (peripheral portion 3a of the exterior material 3) of the exterior material 3, it is preferable to enhance the thermal adhesion of the resin film for an electricity storage device 1. For example, when the resin film for an electricity storage device 1 is composed of three or more layers, it is preferable that the layer located at the surface (the second layer 12 and the third layer 13 in FIG. 2) contains a thermal adhesion resin. In addition, from the viewpoint of suppressing the decrease in the thermal adhesion of the layer located at the surface, it is preferable that the layer located at the surface does not contain a water absorbing agent (particularly an inorganic water absorbing agent). In the electricity storage device, from the viewpoint of more suitably exerting the water absorption performance of the water absorption layer of the resin film for an electricity storage device 1, it is preferable that the water absorption layer is provided between the layers located at the surface. This is because if the water absorption layer is located at the surface, it absorbs moisture in the atmosphere before the electricity storage device is manufactured, and the water absorption performance of the water absorption layer is likely to decrease. In the electricity storage device, it is also preferable that the third layer 13 located on the side of the exterior material 3 is the water absorption layer. This is because the third layer 13 is close to the exterior material 3 and easily absorbs moisture that has infiltrated from the exterior material 3 side. In the electricity storage device, it is also preferable that the second layer 12 located on the side of the electricity storage device element 4 is the water absorption layer. This is because the second layer 12 is close to the electricity storage device element 4 and easily absorbs moisture contained in the electricity storage device element 4.

[0047] The resin contained in the resin film 1 for an electrical storage device is not particularly limited as long as it does not impair the effects of the present disclosure. For example, it is preferably a thermoplastic resin, and more preferably a heat-sealable resin. Specific examples of the resin include thermoplastic resins such as polyolefin, polyester, polyamide, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, and phenolic resin, and modified products of these resins. The resin forming the resin film 1 for an electrical storage device may be a copolymer of these resins or a modified product of the copolymer. Furthermore, it may be a mixture of these resins. Among these, heat-sealable resins such as polyolefin and polyester are preferred.

[0048] Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers 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 alone or in combination of two or more. Among these, polypropylene is particularly preferred because of its excellent thermal fusion properties. The polypropylene may be either random polypropylene or homopolypropylene, but random polypropylene is preferred from the viewpoint of water absorption speed and film-forming properties.

[0049] Specific examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymerized polyesters. Examples of copolymerized polyesters include copolymerized polyesters in which ethylene terephthalate is the main repeating unit. Specific examples of polyesters include copolymerized polyesters in which ethylene terephthalate is the main repeating unit and is polymerized with ethylene isophthalate (hereinafter, abbreviated as polyethylene (terephthalate / isophthalate)), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl-dicarboxylate), and polyethylene (terephthalate / decane dicarboxylate). These polyesters may be used alone or in combination of two or more. Among these, polybutylene terephthalate is particularly preferred from the viewpoint of increasing heat resistance and pressure resistance (for example, a decrease in insulation when sealing the electricity storage device element 4 with the exterior material 3 (due to crushing due to heat sealing)).

[0050] The resin contained in the resin film for an electrical storage device 1 may contain an elastomer. The elastomer plays a role of ensuring the durability of the resin film for an electrical storage device 1 in a high-temperature environment while increasing its flexibility. Preferred elastomers include at least one thermoplastic elastomer selected from polyesters, polyamides, polyurethanes, polyolefins, polystyrenes, and polyethers, or thermoplastic elastomers that are copolymers of these. In the resin film for an electrical storage device 1, the content of the elastomer is not particularly limited as long as it can ensure the durability of the resin film for an electrical storage device 1 in a high-temperature environment while increasing its flexibility, and is, for example, about 0.1% by mass or more, preferably about 0.5% by mass or more, more preferably about 1.0% by mass or more, and even more preferably about 3.0% by mass or more. The content is, for example, about 10.0% by mass or less, about 8.0% by mass or less, about 5.0% by mass or less, etc. Preferred ranges of the content include about 0.1 to 10.0 mass%, about 0.1 to 8.0 mass%, about 0.1 to 5.0 mass%, about 0.5 to 10.0 mass%, about 0.5 to 8.0 mass%, about 0.5 to 5.0 mass%, about 1.0 to 10.0 mass%, about 1.0 to 8.0 mass%, about 1.0 to 5.0 mass%, about 3.0 to 10.0 mass%, about 3.0 to 8.0 mass%, and about 3.0 to 5.0 mass%.

[0051] Examples of the resin content in the resin film 1 for electricity storage devices include 40.0 mass% or more, 45.0 mass% or more, 50.0 mass% or more, 55.0 mass% or more, 60.0 mass% or more, 65.0 mass% or more, 70.0 mass% or more, 75.0 mass% or more, 80.0 mass% or more, 85.0 mass% or more, 90.0 mass% or more, 95.0 mass% or more, 99.0 mass% or more, 99.5 mass% or more, and 99.9 mass% or more.

[0052] Furthermore, from the viewpoint of more suitably exerting the effects of the present disclosure, the content of the absorbent contained in the resin film for an electricity storage device is preferably 3 mass% or more, more preferably 6 mass% or more, and even more preferably 9 mass% or more, and is preferably 30 mass% or less, more preferably 25 mass% or less, and even more preferably 20 mass% or less. Preferred ranges include about 3 to 30 mass%, about 3 to 25 mass%, about 3 to 20 mass%, about 6 to 30 mass%, about 6 to 25 mass%, about 6 to 20 mass%, about 9 to 30 mass%, about 9 to 25 mass%, and about 9 to 20 mass%.

[0053] The water absorbing agent contained in the resin film 1 for a power storage device is not particularly limited as long as it is dispersed in the resin film and exhibits water absorption. For example, from the viewpoint of stability over time in the power storage device, an inorganic water absorbing agent can be suitably used. As the inorganic water absorbing agent, for example, an alkali metal compound, an alkaline earth metal compound, etc. are preferable. Specific examples of preferable inorganic water absorbing agents include calcium oxide, anhydrous magnesium sulfate, magnesium oxide, calcium chloride, zeolite, aluminum oxide, silica gel, alumina gel, and burnt alum. In general, among inorganic water absorbing agents, inorganic chemical water absorbing agents have a higher water absorbing effect than inorganic physical water absorbing agents, can reduce the content, and can easily achieve sufficient water absorption and heat fusion in a single layer. Among inorganic chemical water absorbing agents, calcium oxide, anhydrous magnesium sulfate, and magnesium oxide are particularly preferable because they have little re-release of moisture, high stability over time in a low humidity state in a package, and have an absolute drying effect. The bone-dry effect refers to the effect of absorbing water until the relative humidity is close to 0%, and the humidity control effect refers to the effect of absorbing water when the humidity is high and releasing moisture when the humidity is low, thereby keeping the humidity constant. In addition, when used in a high-temperature environment, such as an all-solid-state battery, an inorganic chemical absorbent with a high temperature range for re-releasing moisture is preferred.

[0054] In the resin film 1 for an electricity storage device, the water absorbing agent contained in the water absorbing layer is preferably contained via a master batch obtained by melt blending the water absorbing agent with a resin. Specifically, the water absorbing agent is melt blended with a resin at a relatively high concentration to prepare a master batch. The obtained master batch is further mixed with a resin and formed into a film to form a water absorbing layer. The content of the water absorbing agent in the master batch is preferably about 20 to 90 mass %, more preferably about 30 to 70 mass %. Within the above range, it is easy to contain a necessary and sufficient amount of the water absorbing agent in the water absorbing layer in a dispersed state.

[0055] The resin film 1 for an electricity storage device may contain various plastic compounding agents and additives for the purpose of improving or modifying, for example, processability, heat resistance, weather resistance, mechanical properties, dimensional stability, oxidation resistance, slipperiness, release properties, flame retardancy, mold resistance, electrical properties, strength, etc. The content may be any amount ranging from a trace amount to several tens of percent depending on the purpose. In the above, examples of typical additives that may be contained include antiblocking agents, lubricants, crosslinking agents, antioxidants, ultraviolet absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, modifying resins, etc.

[0056] From the viewpoint of more suitably exerting the effects of the present disclosure (particularly, excellent insulation), the content of solid particles in layer A among two or more layers in the resin film for an electricity storage device 1 of the present disclosure is preferably about 10% by mass or more, more preferably about 15% by mass or more, and also preferably about 50% by mass or less, more preferably about 40% by mass or less, and even more preferably about 30% by mass or less, and preferable ranges include about 5 to 50% by mass, about 5 to 40% by mass, about 5 to 30% by mass, about 10 to 50% by mass, about 10 to 40% by mass, about 10 to 30% by mass, about 15 to 50% by mass, about 15 to 40% by mass, and about 15 to 30% by mass. In addition, layer B, which has a water absorbing agent content of less than 5% by mass, has a solid particle content of preferably less than about 5%, more preferably less than about 3% by mass, and even more preferably 0% by mass, and preferable ranges include about 0 to 5% by mass, about 0 to 3% by mass, and the like. As the solid particles, for example, some of the water absorbing agents exemplified above are solid particles, and also pigments (e.g., carbon black-based, titanium oxide-based, cadmium-based, lead-based, chromium oxide-based, iron-based, etc.), fillers (silica, etc.), etc. are also solid particles.

[0057] The resin film for an electricity storage device of the present disclosure has a dielectric breakdown strength after water absorption, measured by the following measurement method, of preferably about 40 kV / mm or more, more preferably about 50 to 200 kV / mm, and even more preferably about 50 to 150 kV / mm.

[0058] (Measurement of dielectric breakdown strength after water absorption) A 10 cm square resin film for a storage battery device is prepared and immersed in warm water at 80°C. The immersion is continued until the water absorbing agent in the resin film for a storage battery device absorbs 100% of the water, to obtain a resin film for a storage battery device after water absorption. The resin film is judged to have absorbed 100% of the water when there is no weight change due to immersion. The water absorption degree of the resin film for a storage battery device is calculated from the weight of the film before and after immersion. Next, the dielectric breakdown strength of the resin film for a storage battery device after water absorption is measured in accordance with the provisions of JIS C 2110-1:2016 under the following measurement conditions: air at 23°C, short-time voltage increase method (AC, 50Hz), voltage increase rate of 0.3kV / s, and electrodes of 25mmφ cylinder / 75mmφ cylinder. The measured value is the average value of 5 samples.

[0059] (Method of manufacturing resin film for power storage device) The method for producing the resin film 1 for an electricity storage device is not particularly limited as long as the resin film 1 for an electricity storage device can be obtained, and known or commonly used film-forming methods and lamination methods can be applied. The resin film 1 for an electricity storage device can be produced by known film-forming methods and / or lamination methods, such as an extrusion method or co-extrusion method, a cast molding method, a T-die method, a cutting method, or an inflation method. For example, films constituting each layer that have been produced in advance may be laminated via an adhesive layer, a molten resin composition may be laminated on a layer that has been produced in advance by extrusion or co-extrusion, a plurality of layers may be simultaneously produced and laminated by melt pressure bonding, or one or more resins may be applied and dried to coat another layer.

[0060] The layers constituting the resin film for an electricity storage device 1 can be laminated by extrusion or co-extrusion using an extrusion coating method, or can be laminated via an adhesive layer after film formation using an inflation method or casting method. Even in the case of the extrusion coating method, lamination can be performed via an adhesive layer as necessary. Alternatively, a film that has been previously formed can be laminated and bonded via an adhesive layer that has been laminated using an extrusion coating method, a dry lamination method, a non-solvent lamination method, or the like. Then, aging treatment can be performed as necessary.

[0061] For example, when laminating each layer by extrusion coating, first, the resin composition forming the layer is heated and melted, and then expanded and stretched in the required width direction by a T-die to be extruded or co-extruded in a curtain shape, and the molten resin is allowed to flow down onto the surface to be laminated, and is sandwiched between a rubber roll and a cooled metal roll, so that the layer can be formed, and the layer can be laminated and bonded to the surface to be laminated at the same time. When laminating by extrusion coating, the melt flow rate (MFR) of the resin component contained in each layer is preferably 0.2 to 50 g / 10 min, more preferably 0.5 to 30 g / 10 min. If the MFR is smaller or larger than the above range, the processability is likely to be poor. In this specification, the MFR is a value measured by a method based on JIS K7210.

[0062] When the inflation method is used, the melt flow rate (MFR) of the resin component contained in each layer is preferably 0.2 to 10 g / 10 min, more preferably 0.2 to 9.5 g / 10 min. If the MFR is smaller or larger than the above range, the processability is likely to be poor.

[0063] In addition, between the layers constituting the resin film for electric storage devices, a desired surface treatment can be applied in advance to the surface of each layer as necessary in order to improve adhesion. For example, a corona discharge treatment, an ozone treatment, a low-temperature plasma treatment using oxygen gas or nitrogen gas, a glow discharge treatment, an oxidation treatment using chemicals, etc., can be optionally applied to form a corona treatment layer, an ozone treatment layer, a plasma treatment layer, an oxidation treatment layer, etc. Alternatively, various coating layers such as a primer coating layer, an undercoat layer, an anchor coating layer, an adhesive layer, and a vapor deposition anchor coating layer can be optionally formed on the surface to form a surface treatment layer. For the various coating layers, for example, a resin composition containing a polyester resin, a polyamide resin, a polyurethane resin, an epoxy resin, a phenol resin, a (meth)acrylic resin, a polyvinyl acetate resin, a polyolefin resin such as polyethylene or polypropylene, or a copolymer or modified resin thereof, a cellulose resin, etc. as a vehicle as a main component can be used.

[0064] Each layer constituting the resin film for an electricity storage device can be further uniaxially or biaxially stretched, if necessary, by a conventionally known method using a tenter system, a tubular system or the like.

[0065] 2. Energy storage devices As described above, the electricity storage device 10 of the present disclosure has a structure in which the electricity storage device element 4 is sealed with the exterior material 3. The electricity storage device 10 is sealed by covering the electricity storage device element 4 with the exterior material 3 so that a flange portion (peripheral portion 3a of the exterior material 3) of the exterior material 3 can be formed around the periphery of the electricity storage device element 4, and then heat-sealing the flange portion of the exterior material 3 to form a hermetic seal.

[0066] In the electricity storage device 10 of the present disclosure, in the above-mentioned use 1) of being disposed between an exterior material for an electricity storage device and an electricity storage device element, the resin film for an electricity storage device 1 may be located over the entire surface of the exterior material 3 on the electricity storage device element 4 side (the heat-sealable resin layer 35 side), or may be located over a part of the surface of the electricity storage device element 4 side (the heat-sealable resin layer 35 side). From the viewpoint of suitably exerting the effects of the present disclosure, the resin film for an electricity storage device 1 is preferably located between the exterior material 3 and the electricity storage device element 4 of the electricity storage device 10 so as to be located over the entire surface of the exterior material 3 on the electricity storage device element 4 side (the heat-sealable resin layer 35 side) (see schematic diagrams of FIGS. 5 to 9). For example, as shown in Fig. 5, the resin film for an electricity storage device 1 may be disposed only between the exterior material for an electricity storage device 3 and the electricity storage device element 4, or as shown in Fig. 6, the resin film for an electricity storage device 1 may be disposed between the peripheral portion 3a (heat-sealed portion) of the exterior material for an electricity storage device 3 and the electricity storage device element 4, or as shown in Fig. 7, the electricity storage device element 4 may be covered with the resin film for an electricity storage device 1, or as shown in Fig. 8, a part of the surface of the metal terminal 2 may be further covered with the resin film for an electricity storage device 1. Furthermore, as shown in Fig. 9, the resin film for an electricity storage device 1 of the present disclosure may be disposed between the exterior material 3 and the electricity storage device element 4 of an electricity storage device 10 such that the electricity storage device element 4 is sealed with the resin film for an electricity storage device 1. The resin film for an electricity storage device 1 may be present between the exterior material 3 and the metal terminal 2 and heat-sealed.

[0067] Furthermore, in the electricity storage device 10 of the present disclosure, in the application 2) of being used as a heat-sealable resin layer of an exterior material for an electricity storage device as described above, the resin film 1 for an electricity storage device of the present disclosure is used as the heat-sealable resin layer 35 of the exterior material 3 for an electricity storage device which is composed of a laminate having at least a base layer 31, a barrier layer 33, and a heat-sealable resin layer 35 in this order, as shown in FIG. 3.

[0068] Furthermore, in the electricity storage device 10 of the present disclosure, in the application 4) described above in which the resin film for an electricity storage device 1 is used as an adhesive film for a metal terminal interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that encapsulates the electricity storage device element, as shown in FIG. 4, the resin film for an electricity storage device 1 is used as an adhesive film for a metal terminal 21.

[0069] [Exterior material 3] The exterior material 3 may be a metal can or a laminated film having a barrier layer. The exterior material 3 made of a laminated film may have a laminated structure consisting of a laminate having at least a base material layer 31, a barrier layer 33, and a heat-sealable resin layer 35 in this order. FIG. 3 shows an example of a cross-sectional structure of the exterior material 3, in which the base material layer 31, an adhesive layer 32 provided as needed, a barrier layer 33, an adhesive layer 34 provided as needed, and a heat-sealable resin layer 35 are laminated in this order. In the exterior material 3, the base material layer 31 is the outer layer side, and the heat-sealable resin layer 35 is the innermost layer. When assembling the electricity storage device, the heat-sealable resin layers 35 located on the periphery of the electricity storage device element 4 are brought into contact with each other and heat-sealed to seal the electricity storage device element 4, thereby sealing the electricity storage device element 4. Note that FIGS. 4 to 9 show the electricity storage device 10 in the case where an embossed type exterior material 3 formed by embossing or the like is used, but the exterior material 3 may be an unformed pouch type. The pouch type includes three-sided seal, four-sided seal, pillow type, etc., and any type may be used.

[0070] The thickness of the laminate constituting the exterior material 3 is not particularly limited, but the upper limit, from the viewpoints of cost reduction, energy density improvement, and the like, is, for example, about 190 μm or less, preferably about 180 μm or less, about 160 μm or less, about 155 μm or less, about 140 μm or less, about 130 μm or less, and about 120 μm or less. The lower limit, from the viewpoint of maintaining the function of the exterior material 3 to protect the electricity storage device element 4, is preferably about 35 μm or more, about 45 μm or more, about 60 μm or more, and about 80 μm or more. Preferred ranges include, for example, about 35 to 190 μm, about 35 to 180 μm, about 35 to 160 μm, and about 35 to 15 Approx. 5μm, approx. 35~140μm, approx. 35~130μm, approx. 35~120μm, approx. 45~190μm, approx. 45~180μm, 45~160μm degree, about 45-155μm, about 45-140μm, about 45-130μm, about 45-120μm, about 60-190μm, about 60-180μm, Examples of the thickness include about 60 to 160 μm, about 60 to 155 μm, about 60 to 140 μm, about 60 to 130 μm, about 60 to 120 μm, about 80 to 190 μm, about 80 to 180 μm, about 80 to 160 μm, about 80 to 155 μm, about 80 to 140 μm, about 80 to 130 μm, and about 80 to 120 μm.

[0071] Furthermore, the resin film for an electricity storage device 1 of the present disclosure can be suitably applied to an exterior material for an all-solid-state battery. The thickness of the laminate constituting the exterior material for an all-solid-state battery is not particularly limited, but from the viewpoints of cost reduction, energy density improvement, and the like, it is preferably about 10,000 μm or less, about 8,000 μm or less, or about 5,000 μm or less. From the viewpoint of maintaining the function of the exterior material for an all-solid-state battery, which is to protect the battery element, it is preferably about 1 00 μm or more, about 150 μm or more, and about 200 μm or more, and preferred ranges include, for example, about 100 to 10,000 μm, about 100 to 8,000 μm, about 100 to 5,000 μm, about 150 to 10,000 μm, about 150 to 8,000 μm, about 150 to 5,000 μm, about 200 to 10,000 μm, about 200 to 8,000 μm, and about 200 to 5,000 μm, and about 200 to 5,000 μm is particularly preferred.

[0072] (Base material layer 31) In the packaging material 3, the base material layer 31 is a layer that functions as a base material of the packaging material, and is a layer that forms the outermost layer side.

[0073] The material for forming the base layer 31 is not particularly limited, as long as it has insulating properties. Examples of materials for forming the base layer 31 include polyester, polyamide, epoxy, acrylic, fluororesin, polyurethane, silicone resin, phenol, polyetherimide, polyimide, and mixtures and copolymers thereof. Polyesters such as polyethylene terephthalate and polybutylene terephthalate have the advantage of being excellent in electrolyte resistance and being unlikely to cause whitening due to adhesion of electrolyte, and are preferably used as materials for forming the base layer 31. In addition, polyamide films have excellent stretchability and can prevent whitening due to resin cracking of the base layer 31 during molding, and are preferably used as materials for forming the base layer 31.

[0074] The base layer 31 may be formed of a uniaxially or biaxially stretched resin film, or may be formed of an unstretched resin film. Among them, a uniaxially or biaxially stretched resin film, especially a biaxially stretched resin film, is preferably used as the base layer 31 because its heat resistance is improved by oriented crystallization.

[0075] Among these, nylon, polyester, and more preferably biaxially oriented nylon and biaxially oriented polyester are preferably used as the resin film forming the base layer 31. In addition, since all-solid-state batteries are designed to withstand temperatures of 150° C. or higher, they are often sealed at high temperatures of 200° C. or higher, and biaxially oriented polyester is the most suitable.

[0076] The base layer 31 may be laminated with resin films of different materials in order to improve pinhole resistance and insulation when used as a package for a power storage device. Specifically, a multi-layer structure in which a polyester film and a nylon film are laminated, a multi-layer structure in which a biaxially oriented polyester and a biaxially oriented nylon are laminated, and the like may be mentioned. When the base layer 31 is made into a multi-layer structure, each resin film may be bonded via an adhesive, or may be directly laminated without an adhesive. When bonding without an adhesive, for example, a method of bonding in a hot melt state such as a co-extrusion method, a sand lamination method, or a thermal lamination method may be mentioned. For the above-mentioned high temperature sealing, it is desirable that at least the outermost layer is a biaxially oriented polyester.

[0077] The base layer 31 may be made to have low friction in order to improve formability. When making the base layer 31 low-friction, the coefficient of friction of the surface is not particularly limited, but may be, for example, 1.0 or less. To make the base layer 31 low-friction, for example, matte treatment, formation of a thin film layer of a slip agent, a combination of these, etc. may be used.

[0078] The thickness of the base layer 31 is, for example, about 3 μm or more, about 4 μm or more, about 5 μm or more, about 10 μm or more, about 15 μm or more, and about 100 μm or less, about 75 μm or less, about 50 μm or less, or about 30 μm or less, and preferable ranges are about 3 to 100 μm, about 3 to 75 μm, about 3 to 50 μm, about 3 to 30 μm, and about 4 to 100 μm. Examples of the thickness include about 4 to 75 μm, about 4 to 50 μm, about 3 to 30 μm, about 5 to 100 μm, about 5 to 75 μm, about 5 to 50 μm, about 5 to 30 μm, about 10 to 100 μm, about 10 to 75 μm, about 10 to 50 μm, about 10 to 30 μm, about 15 to 100 μm, about 15 to 75 μm, about 15 to 50 μm, and about 15 to 30 μm.

[0079] (Adhesive layer 32) In the packaging material 3, the adhesive layer 32 is a layer that is disposed on the base material layer 31 as necessary in order to impart adhesion to the base material layer 31. That is, the adhesive layer 32 is provided between the base material layer 31 and the barrier layer 33.

[0080] The adhesive layer 32 is formed of an adhesive capable of bonding the base material layer 31 and the barrier layer 33. The adhesive used to form the adhesive layer 32 may be a two-component curing adhesive or a one-component curing adhesive. The adhesion mechanism of the adhesive used to form the adhesive layer 32 is not particularly limited, and may be any of a chemical reaction type, a solvent volatilization type, a thermal melting type, a thermal pressure type, and the like.

[0081] The resin component of the adhesive that can be used to form the adhesive layer 32 is preferably a polyurethane-based two-component curing adhesive; or a blend resin of polyamide, polyester, or these with modified polyolefin, from the viewpoint of having excellent ductility, durability under high humidity conditions, yellowing prevention, and thermal degradation prevention during heat sealing, and of effectively suppressing a decrease in the laminate strength between the base layer 31 and the barrier layer 33 and preventing the occurrence of delamination.

[0082] The adhesive layer 32 may be multi-layered with different adhesive components. When the adhesive layer 32 is multi-layered with different adhesive components, it is preferable to select a resin having excellent adhesion to the base material layer 31 as the adhesive component arranged on the base material layer 31 side, and an adhesive component having excellent adhesion to the barrier layer 33 as the adhesive component arranged on the barrier layer 33 side, from the viewpoint of improving the laminate strength between the base material layer 31 and the barrier layer 33. When the adhesive layer 32 is multi-layered with different adhesive components, specifically, the adhesive component arranged on the barrier layer 33 side is preferably an acid-modified polyolefin, a metal-modified polyolefin, a mixed resin of a polyester and an acid-modified polyolefin, a resin containing a copolymerized polyester, an alicyclic isocyanate compound, or the like.

[0083] The thickness of the adhesive layer 32 is, for example, about 2 to 50 μm, and preferably about 3 to 25 μm.

[0084] (Barrier layer 33) In the exterior material, the barrier layer 33 is a layer that has the function of preventing water vapor, oxygen, light, and the like from penetrating into the inside of the electricity storage device element in addition to improving the strength of the exterior material. The barrier layer 33 is preferably a metal layer, that is, a layer formed of a metal. Specific examples of the metal constituting the barrier layer 33 include aluminum, stainless steel, and titanium, and aluminum is preferred. The barrier layer 33 can be formed, for example, of a metal foil, a metal vapor deposition film, an inorganic oxide vapor deposition film, a carbon-containing inorganic oxide vapor deposition film, or a film provided with these vapor deposition films, and is preferably formed of a metal foil, and more preferably formed of an aluminum foil. From the viewpoint of preventing the occurrence of wrinkles or pinholes in the barrier layer 33 during the production of the exterior material, it is more preferable that the barrier layer be formed from a soft aluminum foil such as annealed aluminum (JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, JIS H4000:2014 A8079P-O).

[0085] With regard to the thickness of the barrier layer 33, from the viewpoint of making the exterior material thin while making it difficult for pinholes to occur even when formed, the thickness is preferably about 10 to 200 μm, and more preferably about 20 to 100 μm. From the viewpoint of imparting high formability or high rigidity to the exterior material 3 for an electricity storage device, the thickness of the barrier layer 33 is preferably about 45 μm or more, more preferably about 50 μm or more, and is preferably about 85 μm or less, more preferably 75 μm or less. Preferred ranges include about 45 to 85 μm, about 45 to 75 μm, about 50 to 85 μm, and about 50 to 75 μm.

[0086] Moreover, it is preferable that at least one surface, and preferably both surfaces, of the barrier layer 33 are subjected to a chemical conversion treatment in order to stabilize adhesion, prevent dissolution or corrosion, etc. Here, the chemical conversion treatment refers to a treatment for forming a corrosion-resistant film on the surface of the barrier layer.

[0087] (adhesive layer 34) In the exterior packaging material 3, the adhesive layer 34 is a layer that is provided, if necessary, between the barrier layer 33 and the heat-sealable resin layer 35 in order to firmly bond the heat-sealable resin layer 35.

[0088] The adhesive layer 34 is formed of an adhesive capable of bonding the barrier layer 33 and the heat-fusible resin layer 35. The composition of the adhesive used to form the adhesive layer is not particularly limited, but examples thereof include an adhesive made of a polyester polyol compound and an alicyclic isocyanate compound.

[0089] The thickness of the adhesive layer 34 is, for example, about 1 to 40 μm, and preferably about 2 to 30 μm.

[0090] (Thermal adhesive resin layer 35) In the exterior packaging material 3, the heat-sealable resin layer 35 corresponds to the innermost layer, and is a layer that seals the electricity storage device elements by being heat-sealed to each other when the electricity storage device is assembled.

[0091] The resin component used in the heat-sealable resin layer 35 is not particularly limited as long as it is heat-sealable, but for example, in the case of an exterior material, polyolefin and cyclic polyolefin are generally used. In addition, in the application in which the resin film 1 for an electricity storage device of the present disclosure is used as the heat-sealable resin layer of the exterior material for an electricity storage device (2) described above, as shown in Fig. 3, the resin film 1 for an electricity storage device of the present disclosure is used as the heat-sealable resin layer 35 of the exterior material for an electricity storage device 3 composed of a laminate having at least a base layer 31, a barrier layer 33, and a heat-sealable resin layer 35 in this order.

[0092] Specific examples of the polyolefin include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); and ethylene-butene-propylene terpolymers. Among these polyolefins, polyethylene and polypropylene are preferable.

[0093] The cyclic polyolefin is a copolymer of an olefin and a cyclic monomer, and examples of the olefins constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, and isoprene. Examples of the cyclic monomers constituting the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, preferred are cyclic alkenes, and more preferred are norbornene. Another example of the constituting monomer is styrene.

[0094] Among these resin components, preferred are crystalline or amorphous polyolefins, cyclic polyolefins, and blend polymers thereof; more preferred are polyethylene, polypropylene, copolymers of ethylene and norbornene, and blend polymers of two or more of these.

[0095] The thermally adhesive resin layer 35 may be formed of one type of resin component alone, or may be formed of a blend polymer of two or more types of resin components. Furthermore, the thermally adhesive resin layer 35 may be formed of only one layer, or may be formed of two or more layers of the same or different resin components.

[0096] The thickness of the heat-fusible resin layer 35 is not particularly limited, but may be about 2 to 2000 μm, preferably about 5 to 1000 μm, and more preferably about 10 to 500 μm.

[0097] Furthermore, the resin film for an electricity storage device 1 of the present disclosure can be suitably applied to an exterior material for an all-solid-state battery, and the melting point of the heat-sealable resin layer 35 of the exterior material for an all-solid-state battery is preferably 150 to 250°C, more preferably 180 to 270°C, even more preferably 200 to 270°C, and even more preferably 200 to 250°C.

[0098] In addition, examples of the resin contained in the heat-sealable resin layer 35 of the all-solid-state battery exterior packaging material include polyolefins such as polypropylene and polyethylene, acid-modified polyolefins such as acid-modified polypropylene and acid-modified polyethylene, and polybutylene terephthalate. Among these, polybutylene terephthalate has excellent heat resistance, so that in the all-solid-state battery exterior packaging material, the heat-sealable resin layer 35 is preferably formed of a polybutylene terephthalate film. In addition, by forming the heat-sealable resin layer 35 of a polybutylene terephthalate film, the adhesion with the resin film for an electricity storage device 1 of the present disclosure is also excellent. The polybutylene terephthalate film forming the heat-sealable resin layer 35 may be prepared by laminating a previously prepared polybutylene terephthalate film with the adhesive layer 34 to form the heat-sealable resin layer 35, or the resin forming the polybutylene terephthalate film may be melt-extruded to form a film and then laminated with the adhesive layer 34, or the resin forming the heat-sealable resin layer 35 and the resin forming the adhesive layer 34 may be co-extruded to form the film.

[0099] The polybutylene terephthalate film may be a stretched polybutylene terephthalate film or an unstretched polybutylene terephthalate film, and is preferably an unstretched polybutylene terephthalate film.

[0100] The polybutylene terephthalate film preferably further contains an elastomer in addition to polybutylene terephthalate. The elastomer plays a role of ensuring the durability of the polybutylene terephthalate film in a high-temperature environment while increasing its flexibility. Preferred elastomers include at least one thermoplastic elastomer selected from polyesters, polyamides, polyurethanes, polyolefins, polystyrenes, and polyethers, or thermoplastic elastomers that are copolymers of these. In the polybutylene terephthalate film, the content of the elastomer is not particularly limited as long as it can ensure the durability of the polybutylene terephthalate film in a high-temperature environment while increasing its flexibility, and is, for example, about 0.1% by mass or more, preferably about 0.5% by mass or more, more preferably about 1.0% by mass or more, and even more preferably about 3.0% by mass or more. The content is, for example, about 10.0% by mass or less, about 8.0% by mass or less, about 5.0% by mass or less, etc. Preferred ranges of the content include about 0.1 to 10.0 mass%, about 0.1 to 8.0 mass%, about 0.1 to 5.0 mass%, about 0.5 to 10.0 mass%, about 0.5 to 8.0 mass%, about 0.5 to 5.0 mass%, about 1.0 to 10.0 mass%, about 1.0 to 8.0 mass%, about 1.0 to 5.0 mass%, about 3.0 to 10.0 mass%, about 3.0 to 8.0 mass%, and about 3.0 to 5.0 mass%.

[0101] The heat-sealable resin layer 35 may be formed of only one layer, or may be formed of two or more layers of the same or different resins. When the heat-sealable resin layer 35 is formed of two or more layers, at least one layer is formed of a polybutylene terephthalate film, and the polybutylene terephthalate film is preferably the innermost layer of the all-solid-state battery exterior material. In addition, the layer that adheres to the adhesive layer 34 is preferably a polybutylene terephthalate film. When the heat-sealable resin layer 35 is formed of two or more layers, the layer that is not formed of a polybutylene terephthalate film may be, for example, a layer formed of a polyolefin such as polypropylene or polyethylene, or an acid-modified polyolefin such as acid-modified polypropylene or acid-modified polyethylene. However, since polyolefins and acid-modified polyolefins have lower durability in high-temperature environments compared to polybutylene terephthalate, the heat-sealable resin layer 35 is preferably composed of only a polybutylene terephthalate film.

[0102] The power storage device of the present disclosure is a power storage device such as a battery (including a condenser, a capacitor, etc.). The power storage device of the present disclosure may be either a primary battery or a secondary battery, but is preferably used in a secondary battery. The type of secondary battery is not particularly limited, and examples thereof include a lithium ion battery, a lithium ion polymer battery, an all-solid-state battery, a lead acid battery, a nickel-hydrogen battery, a nickel-cadmium battery, a nickel-iron battery, a nickel-zinc battery, a silver oxide-zinc battery, a metal-air battery, a polyvalent cation battery, a condenser, and a capacitor. Among these secondary batteries, examples of the power storage device of the present disclosure include a lithium ion battery, a lithium ion polymer battery, and an all-solid-state battery, and are particularly preferably used in an all-solid-state battery. EXAMPLES

[0103] 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.

[0104] <Production of resin films for power storage devices> Example 1 A random polypropylene film (water absorbing agent content 0 mass%, thickness 10 μm) was laminated on each side of a random polypropylene film (thickness 30 μm) containing 20 mass% calcium oxide (CaO) as a water absorbing agent, to produce a resin film for an electricity storage device having a three-layer structure of r-PP (water absorbing agent content 0 mass%, 10 μm) / r-PP (water absorbing agent content 20 mass%, 30 μm) / r-PP (water absorbing agent content 0 mass%, 10 μm).

[0105] Example 2 A random polypropylene film (water absorbing agent content 0 mass%, thickness 20 μm) was laminated on one side of a random polypropylene film (thickness 30 μm) containing 20 mass% CaO as a water absorbing agent, to produce a two-layered resin film for an electricity storage device of r-PP (water absorbing agent content 0 mass%, 20 μm) / r-PP (water absorbing agent content 20 mass%, 30 μm). The resin film for an electricity storage device of Example 2 is used such that the r-PP (water absorbing agent content 0 mass%, 20 μm) side is disposed on the exterior material side, and the r-PP (water absorbing agent content 20 mass%, 30 μm) is disposed on the electricity storage device element side.

[0106] Example 3 A resin film for an electricity storage device having a two-layer structure of r-PP (water absorbing agent content 20 mass% 30 μm) / r-PP (water absorbing agent content 0 mass% 20 μm) was manufactured by laminating a random polypropylene film (water absorbing agent content 0 mass% 30 μm) on one side of a random polypropylene film (thickness 30 μm) containing 20 mass% CaO as a water absorbing agent in the same manner as in Example 2. However, the resin film for an electricity storage device in Example 3 is used such that the r-PP (water absorbing agent content 0 mass% 20 μm) side is disposed on the electricity storage device element side, and the r-PP (water absorbing agent content 20 mass% 30 μm) is disposed on the exterior material side.

[0107] Example 4 A random polypropylene film (thickness 15 μm) containing 20 mass% CaO as a water absorbing agent was laminated on both sides of a random polypropylene film (water absorbing agent content 0 mass%, thickness 20 μm) to produce a resin film for an electricity storage device having a three-layer structure of r-PP (water absorbing agent content 20 mass%, 15 μm) / r-PP (water absorbing agent content 0 mass%, 20 μm) / r-PP (water absorbing agent content 20 mass%, 15 μm).

[0108] Example 5 A random polypropylene film (water absorbing agent content 0 mass%, thickness 10 μm) was laminated on both sides of a random polypropylene film (thickness 30 μm) containing 20 mass% CaO as a water absorbing agent and 5 mass% titanium oxide particles as solid particles, to produce a resin film for an electricity storage device having a three-layer structure of r-PP (water absorbing agent content 0 mass%, 10 μm) / r-PP (water absorbing agent content 20 mass%, 30 μm) / r-PP (water absorbing agent content 0 mass%, 10 μm).

[0109] Example 6 A polybutylene terephthalate film (water absorbing agent content 0 mass%, thickness 10 μm) was laminated on both sides of a polybutylene terephthalate film (thickness 30 μm) containing 20 mass% CaO as a water absorbing agent, to produce a resin film for an electricity storage device having a three-layer structure of PBT (water absorbing agent content 0 mass%, 10 μm) / PBT (water absorbing agent content 20 mass%, 30 μm) / PBT (water absorbing agent content 0 mass%, 10 μm).

[0110] Example 7 A resin film for an electric storage device was produced in the same manner as in Example 2, and this was used as a heat-sealable resin layer of an exterior material for an electric storage device. As the base material layer of the exterior material for an electric storage device, a polyethylene terephthalate film (thickness 25 μm or 12 μm) was subjected to corona treatment on the bonding surface side, and a nylon film (thickness 25 μm) was prepared. In addition, an aluminum alloy foil (JIS H4160:1994 A8021H-O, thickness 40 μm) was prepared as a barrier layer. In addition, the above-mentioned resin film for an electric storage device was used as a heat-sealable resin layer. Next, a two-liquid curing urethane adhesive (polyester polyol and alicyclic isocyanate compound) was used to produce a laminate in which a polyethylene terephthalate film and a nylon film, and a nylon film and a barrier layer were bonded together by a dry lamination method. Further, the barrier layer side of the obtained laminate was adhered to the resin film for the electric storage device by the dry lamination method using a two-liquid curing urethane adhesive (polyester polyol and alicyclic isocyanate compound), and the adhesive layer (4 μm) / resin film for the electric storage device was laminated on the barrier layer. Next, the obtained laminate was aged and heated to obtain an exterior material for the electric storage device consisting of a laminate in which the polyethylene terephthalate film / adhesive layer / nylon film / adhesive layer / barrier layer / adhesive layer / resin film for the electric storage device were laminated in this order. The heat-sealable resin layer is laminated in the order of r-PP (water absorbent content 20% by mass 30 μm) / r-PP (water absorbent content 0% by mass 20 μm) from the barrier layer side.

[0111] Example 8 Two resin films for electricity storage devices were produced in the same manner as in Example 2, and these were used as adhesive films for metal terminals (length 10 mm, width 55 mm). At the center of the length of an aluminum metal terminal (length 60 mm, width 45 mm, thickness 400 μm), the metal terminal was sandwiched between two adhesive films for metal terminals so as to be perpendicular to the length direction, and the adhesive films for metal terminals were attached to the metal terminals by hot pressing from both sides (temperature 190° C., pressure 0.25 MPa, 16 seconds), thereby obtaining a metal terminal with an adhesive film for metal terminal. The adhesive films for metal terminals are laminated in the order of r-PP (water absorbent content 20% by mass, 30 μm) / r-PP (water absorbent content 0% by mass, 20 μm) from the metal terminal side.

[0112] Example 9 A random polypropylene film (water absorbing agent content 0 mass%, thickness 5 μm) was laminated on each side of a random polypropylene film (thickness 40 μm) containing 15 mass% calcium oxide (CaO) as a water absorbing agent, to produce a resin film for an electricity storage device having a three-layer structure of r-PP (water absorbing agent content 0 mass%, thickness 5 μm) / r-PP (water absorbing agent content 15 mass%, 40 μm) / r-PP (water absorbing agent content 0 mass%, 5 μm).

[0113] Example 10 A random polypropylene film (water absorbing agent content 0 mass%, thickness 90 μm) was laminated on one side of a random polypropylene film (thickness 30 μm) containing 20 mass% CaO as a water absorbing agent, to produce a two-layered resin film for an electricity storage device of r-PP (water absorbing agent content 0 mass%, 90 μm) / r-PP (water absorbing agent content 20 mass%, 30 μm). The resin film for an electricity storage device of Example 10 is used with the r-PP (water absorbing agent content 0 mass%, 90 μm) side disposed on the exterior material side, and the r-PP (water absorbing agent content 20 mass%, 30 μm) disposed on the electricity storage device element side.

[0114] Example 11 A random polypropylene film (water absorbing agent content 4 mass%, thickness 10 μm) containing 4 mass% calcium oxide (CaO) as a water absorbing agent was laminated on both sides of a random polypropylene film (thickness 30 μm) containing 17.4 mass% calcium oxide (CaO) as a water absorbing agent, to produce a resin film for an electricity storage device having a three-layer structure of r-PP (water absorbing agent content 4 mass%, 10 μm) / r-PP (water absorbing agent content 17.4 mass%, 30 μm) / r-PP (water absorbing agent content 4 mass%, 10 μm).

[0115] Example 12 A random polypropylene film (water absorbing agent content 20 mass % thickness 90 μm) containing 20 mass % CaO as a water absorbing agent was laminated on one side of a random polypropylene film (water absorbing agent content 0 mass % thickness 30 μm) to produce a two-layered resin film for an electricity storage device of r-PP (water absorbing agent content 20 mass % 90 μm) / r-PP (water absorbing agent content 0 mass % 30 μm). The resin film for an electricity storage device of Example 12 is used with the r-PP (water absorbing agent content 20 mass % 90 μm) side disposed on the exterior material side and the r-PP (water absorbing agent content 0 mass % 30 μm) disposed on the electricity storage device element side.

[0116] (Example 13) A random polypropylene film (water absorbing agent content 45 mass % thickness 30 μm) containing 45 mass % of CaO as a water absorbing agent was laminated on one side of a random polypropylene film (water absorbing agent content 0 mass % thickness 20 μm) to produce a two-layered resin film for an electricity storage device of r-PP (water absorbing agent content 45 mass % 30 μm) / r-PP (water absorbing agent content 0 mass % 20 μm). The resin film for an electricity storage device of Example 13 is used such that the r-PP (water absorbing agent content 45 mass % 30 μm) side is disposed on the exterior material side, and the r-PP (water absorbing agent content 0 mass % 20 μm) is disposed on the electricity storage device element side.

[0117] Example 14 A random polypropylene film (water absorbing agent content 0 mass%, thickness 10 μm) was laminated on both sides of a random polypropylene film (thickness 30 μm) containing 20 mass% magnesium oxide (MgO) as a water absorbing agent, to produce a resin film for an electricity storage device having a three-layer structure of r-PP (water absorbing agent content 0 mass%, thickness 10 μm) / r-PP (water absorbing agent content 20 mass%, 30 μm) / r-PP (water absorbing agent content 0 mass%, 10 μm).

[0118] Example 15 A random polypropylene film (water absorbing agent content 0 mass%, thickness 10 μm) was laminated on both sides of a random polypropylene film (thickness 30 μm) containing 20 mass% magnesium sulfate (MgSO4) as a water absorbing agent, to produce a resin film for an electricity storage device having a three-layer structure of r-PP (water absorbing agent content 0 mass%, thickness 10 μm) / r-PP (water absorbing agent content 20 mass%, 30 μm) / r-PP (water absorbing agent content 0 mass%, 10 μm).

[0119] Example 16 A maleic anhydride modified random polypropylene film (water absorbing agent content 0 mass% thickness 20 μm) was laminated on one side of a random polypropylene film (thickness 30 μm) containing 20 mass% CaO as a water absorbing agent, to produce a two-layered resin film for a power storage device of r-PPa (water absorbing agent content 0 mass% 20 μm) / r-PP (water absorbing agent content 20 mass% 30 μm). The resin film for a power storage device of Example 16 is an adhesive film for a metal terminal, and is used such that the r-PP (water absorbing agent content 20 mass% 30 μm) side is disposed on the exterior material side, and the r-PPa (water absorbing agent content 0 mass% 20 μm) side is disposed on the metal terminal side.

[0120] (Example 17) A maleic anhydride-modified homopolypropylene film (water absorbing agent content 0 mass%, thickness 20 μm) was laminated on one side of a homopolypropylene film (thickness 30 μm) containing 20 mass% CaO as a water absorbing agent, to produce a resin film for a power storage device having a two-layer structure of h-PPa (water absorbing agent content 0 mass%, 20 μm) / h-PP (water absorbing agent content 20 mass%, 30 μm). The resin film for a power storage device of Example 17 is an adhesive film for a metal terminal, and is used such that the h-PP (water absorbing agent content 20 mass%, 30 μm) side is disposed on the exterior material side, and the h-PPa (water absorbing agent content 0 mass%, 20 μm) side is disposed on the metal terminal side.

[0121] (Example 18) A maleic anhydride modified random polypropylene film (thickness 20 μm) containing 1 mass% CaO as a water absorbing agent was laminated on one side of a random polypropylene film (thickness 30 μm) containing 20 mass% CaO as a water absorbing agent to produce a two-layered resin film for a storage battery device of r-PPa (water absorbing agent content 1 mass% 20 μm) / r-PP (water absorbing agent content 20 mass% 30 μm). The resin film for a storage battery device of Example 18 is an adhesive film for a metal terminal, and is used by arranging the r-PP (water absorbing agent content 20 mass% 30 μm) side on the exterior material side and the r-PPa (water absorbing agent content 1 mass% 20 μm) on the metal terminal side.

[0122] (Example 19) A random polypropylene film (thickness 30 μm) containing 20 mass% calcium oxide (CaO) as a water absorbent was laminated on one side of the random polypropylene film (thickness 30 μm) containing 20 mass% calcium oxide (CaO) as a water absorbent, and a random polypropylene film (water absorbent content 0 mass% thickness 10 μm) was laminated on the other side to produce a three-layered resin film for a storage battery device of r-PPa (water absorbent content 0 mass% 10 μm) / r-PP (water absorbent content 20 mass% 30 μm) / r-PP (water absorbent content 0 mass% 10 μm). The resin film for a storage battery device of Example 19 is an adhesive film for a metal terminal, and is used by arranging the r-PP (water absorbent content 0 mass% 10 μm) side on the exterior material side and the r-PPa (water absorbent content 0 mass% 10 μm) on the metal terminal side.

[0123] (Example 20) A maleic anhydride-modified random polypropylene film (water absorbing agent content 0 mass% thickness 10 μm) containing a black pigment was laminated on one side of a homopolypropylene film (thickness 30 μm) containing 20 mass% calcium oxide (CaO) as a water absorbing agent, and a random polypropylene film (water absorbing agent content 0 mass% thickness 10 μm) was laminated on the other side to produce a three-layered resin film for a power storage device of black r-PPa (water absorbing agent content 0 mass% 10 μm) / h-PP (water absorbing agent content 20 mass% 30 μm) / r-PP (water absorbing agent content 0 mass% 10 μm). The resin film for a power storage device of Example 20 is an adhesive film for a metal terminal, and is used by arranging the black r-PPa (water absorbing agent content 0 mass% 10 μm) side on the metal terminal side and the r-PP (water absorbing agent content 0 mass% 10 μm) on the exterior material side.

[0124] Comparative Example 1 A random polypropylene film containing 12 mass % of CaO as a water absorbing agent (water absorbing agent content 12 mass %, 50 μm single layer configuration) was used as a resin film for an electricity storage device.

[0125] Comparative Example 2 A random polypropylene film (water absorbing agent content: 0 mass %; 50 μm; single layer structure) was used as a resin film for an electricity storage device.

[0126] Comparative Example 3 A random polypropylene film (thickness 30 μm) containing 12 mass% CaO as a water absorbing agent was laminated on both sides of the random polypropylene film (water absorbing agent content 12 mass%, thickness 10 μm) containing 12 mass% CaO, to produce a resin film for an electricity storage device having a three-layer structure of r-PP (water absorbing agent content 12 mass%, 10 μm) / r-PP (water absorbing agent content 12 mass%, 30 μm) / r-PP (water absorbing agent content 12 mass%, 10 μm).

[0127] <Evaluation of water absorption of resin film> A 10 cm square resin film (which was dried by leaving it in a vacuum oven (-50 MPa) for 24 hours immediately after production) was prepared and immersed in warm water at 80°C. The amount of water absorbed was calculated from the weight of the resin film before and after immersion, and the point at which the weight of the resin film did not change due to immersion was taken as the point at which the water absorbent in the resin film had absorbed 100% of the water. The weight increase per unit area at that time was taken as the water absorption performance (water release amount (g / m 2 The detection limit was 0.1 mg / m 2 The results are shown in Table 1. Moisture absorption capacity (g / m 2 ) = (Weight of resin film after immersion (g) - Weight of resin film before immersion (g)) / Area of ​​resin film after immersion (m 2 )

[0128] <Evaluation of the insulation properties of resin film after water absorption> The insulation was evaluated in accordance with the provisions of JIS C 2110-1:2016. Specifically, the test environment was air at 23°C, and the dielectric breakdown strength was measured for each of the five resin films after water absorption obtained in the above <Evaluation of water absorption of resin film>. Evaluation was made according to the following criteria based on the average value of the dielectric breakdown strength (dielectric breakdown voltage converted to unit thickness) of each of the five films. The results are shown in Table 1. The measurement conditions were as follows. Boost method: Short-time method (AC, 50Hz) Boost speed: 0.3kV / s Electrode: 25mmφ cylinder / 75mmφ cylinder Equipment: Dielectric breakdown test equipment YST-243-100RHO (Yamayo Tester Co., Ltd.) (Evaluation Criteria) A': Dielectric breakdown strength is 100kV / mm or more A: Dielectric breakdown strength is 50 kV / mm or more and less than 100 kV / mm B: Dielectric breakdown strength is 40 kV / mm or more and less than 50 kV / mm C: Dielectric breakdown strength is less than 40kV / mm

[0129] (Preparation of metal terminals with adhesive film for metal terminals) Using the adhesive films for metal terminals of Examples 8, 16 to 20, metal terminals with adhesive films for metal terminals were prepared. Aluminum alloy foil (JIS H4160:1994 A8079H-O) with a thickness of 400 μm×TD45 mm×MD60 mm was used as the metal terminal, and this was baked with a treatment agent consisting of three components, acrylic resin, chromium (III) nitrate compound, and phosphoric acid, so that the treatment layer was about 100 nm thick to prepare a surface-treated metal terminal. Next, two sheets of adhesive films for metal terminals cut to a size of TD10 mm×MD55 mm were prepared, and these two sheets of adhesive films for metal terminals were placed on both sides at a position 10 mm from the longitudinal end of the surface-treated metal terminal so that the widthwise centers of the surface-treated metal terminal and the surface-treated metal terminal were aligned. Next, the top and bottom were heat sealed under the conditions of 190℃ × 0.25MPa (surface pressure applied to the silicone rubber) × 16 seconds using a flat plate press with a metal head with 3.0mm thick silicone rubber with a hardness of 40 attached to the top and bottom, to prepare a metal terminal with an adhesive film for metal terminal, in which the adhesive film for metal terminal / surface-treated metal terminal / adhesive film for metal terminal were laminated in this order. At this time, the MD of the metal terminal and the MD of the adhesive film for metal terminal were arranged so as to be perpendicular to each other.

[0130] <Adhesion evaluation of adhesive films for metal terminals> An exterior material for a power storage device (hereinafter, sometimes simply referred to as "exterior material") was produced. A base layer (thickness 30 μm) consisting of a polyethylene terephthalate film (thickness 12 μm) / adhesive layer (thickness 3 μm) / nylon film (thickness 15 μm) was laminated on an aluminum alloy foil (thickness 40 μm JIS H4160:1994 A8079H-O) by dry lamination, and a heat-sealing resin layer was laminated on the other surface by co-extrusion. Specifically, a two-liquid urethane adhesive (polyol compound and aromatic isocyanate compound) was applied on the nylon film, and an adhesive layer (thickness 3 μm) was formed on the nylon film. Next, the adhesive layer and a polyethylene terephthalate film were laminated on the nylon film to produce a base layer. Next, a two-liquid urethane adhesive (polyol compound and aromatic isocyanate compound) was applied on one surface of a barrier layer consisting of an aluminum alloy foil, and an adhesive layer (thickness 3 μm) was formed on the aluminum alloy foil. Next, the adhesive layer and the substrate layer with the nylon film side as the adhesive surface were laminated on the aluminum alloy foil, and then aging treatment was performed to produce a substrate layer / adhesive layer / barrier layer laminate. Next, an adhesive layer (40 μm thick, arranged on the metal layer side) made of maleic anhydride-modified polypropylene resin and a heat-sealable resin layer (40 μm thick, innermost layer) made of random polypropylene resin were co-extruded on the barrier layer of the laminate to laminate the adhesive layer / heat-sealable resin layer on the barrier layer, thereby obtaining an exterior material for a power storage device in which the substrate layer, adhesive layer, barrier layer, adhesive layer, and heat-sealable resin layer were laminated in this order.

[0131] Next, the exterior material was cut to a size of TD 60 mm and MD 200 mm, and the exterior material was placed facing each other with the heat-sealable resin layer on the inside, and the metal terminal with adhesive film for metal terminal obtained above was sandwiched between the opposing heat-sealable resin layers. At this time, the exterior material was laminated so that the MD and TD of the exterior material were aligned with the TD and MD directions of the metal terminal with adhesive film for metal terminal, respectively. In this state, the exterior material was heat-sealed using a heat seal tester under conditions of a width of 7 mm, 190 ° C. × 0.25 MPa × 16 seconds, and naturally cooled to 25 ° C. to obtain a laminate in which the exterior material and the adhesive film were heat-sealed. The 7 mm width is the MD direction of the exterior material. Note that these heat-sealing conditions are temperature conditions suitable for the resin used in the adhesive film for metal terminal. The heat-sealed portion of the obtained laminate is configured such that the exterior material / adhesive film for metal terminal / metal terminal / adhesive film for metal terminal / exterior material are laminated in this order. Next, the laminate was cut in a direction perpendicular to the 7 mm seal width to obtain a 15 mm wide sample. The sample was taken from the center of the laminate. The 15 mm width corresponds to the TD direction of the exterior material. Next, the exterior material on one side of the sample and the metal terminal were chucked, and the exterior material and metal terminal were pulled in the 180° direction at a speed of 50 mm / min to measure the seal strength. These measurements were performed in a 25°C, 50% humidity environment. The sealability against the metal terminal was evaluated according to the following criteria. The results are shown in Table 2. A: The seal strength is 20N / 15mm or more. B: The seal strength is 10N / 15mm or more and less than 20N / 15mm. C: The seal strength is less than 10N / 15mm.

[0132] [Table 1]

[0133] [Table 2]

[0134] As described above, the present disclosure provides the following aspects of the invention. Item 1. A resin film for an electricity storage device, The resin film for an electricity storage device is composed of two or more layers, The two or more layers include at least one layer A having a water absorbing agent content of 5% by mass or more, and at least one layer B having a water absorbing agent content of less than 5% by mass. Item 2. The resin film for an electricity storage device according to Item 1, wherein at least one of the Layers B has a water-absorbing agent content of 0%. Item 3. The resin film for an electricity storage device according to Item 1 or 2, wherein at least one of the two or more layers has a solid particle content of less than 5 mass %. Item 4. The resin film for an electricity storage device according to any one of Items 1 to 3, wherein the water absorbing agent includes an inorganic water absorbing agent. Item 5. The resin film for an electricity storage device according to any one of Items 1 to 4, wherein the water absorbing agent includes at least one selected from the group consisting of calcium oxide, anhydrous magnesium sulfate, magnesium oxide, calcium chloride, zeolite, aluminum oxide, silica gel, alumina gel, and calcined alum. Item 6. The resin film for an electricity storage device according to any one of Items 1 to 5, wherein at least one of the two or more layers contains a heat-sealable resin. Item 7. The resin film for an electricity storage device according to Item 6, wherein the heat-fusible resin contains at least one selected from the group consisting of polyesters and polyolefins. Item 8. The resin film for an electricity storage device according to any one of Items 1 to 7, wherein the resin film for an electricity storage device after absorbing water has a dielectric breakdown strength of 40 kV / mm or more, as measured by the following measurement method. (Measurement of dielectric breakdown strength after water absorption) A 10 cm square resin film for a storage battery device is prepared and immersed in warm water at 80°C. The immersion is continued until the water absorbing agent in the resin film for a storage battery device absorbs 100% of the water, to obtain a resin film for a storage battery device after absorbing water. The water absorption degree of the resin film for a storage battery device is calculated from the weight of the film before and after immersion. Next, the dielectric breakdown strength of the resin film for a storage battery device after absorbing water is measured in accordance with the provisions of JIS C 2110-1:2016 under the following measurement conditions: 23°C in air, short-time voltage increase method (AC, 50Hz), voltage increase rate of 0.3kV / s, and electrodes of 25mmφ cylinder / 75mmφ cylinder. The measured value is the average value measured for five samples. Item 9. The resin film for an electricity storage device according to any one of Items 1 to 8, wherein the resin film for an electricity storage device is 1) disposed between an exterior material for an electricity storage device and an electricity storage device element, 2) used as a heat-sealable resin layer of an exterior material for an electricity storage device, 3) used as an adhesive layer between a barrier layer and a heat-sealable resin layer of an exterior material for an electricity storage device, or 4) used as an adhesive film for a metal terminal interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that encapsulates the electricity storage device element. Item 10. An electricity storage device in which an electricity storage device element having at least a positive electrode, a negative electrode, and an electrolyte is housed in a packaging body formed from an exterior material, 10. An electricity storage device, comprising: an electricity storage device resin film according to any one of items 1 to 9 disposed between the exterior material and the electricity storage device. [Explanation of symbols]

[0135] 1. Resin films for energy storage devices 2 metal terminals 3 Exterior materials 3a Periphery of exterior material 4. Energy storage device elements 10. Energy storage devices 11 1st layer 12 2nd layer 13 3rd layer 21 Adhesive film for metal terminals 31 Base material layer 32 Adhesive layer 33 Barrier Layer 34 Adhesive layer 35 Heat-fusible resin layer

Claims

1. A resin film for an electricity storage device, The resin film for an electricity storage device is composed of two or more layers, the two or more layers include at least one layer A having a water absorbing agent content of 5 mass % or more, and at least one layer B having a water absorbing agent content of 1 mass % or more and less than 5 mass %.

2. 2 . The resin film for an electricity storage device according to claim 1 , wherein at least one of the two or more layers has a solid particle content of less than 5 mass %.

3. The resin film for an electricity storage device according to claim 1 , wherein the water absorbing agent comprises an inorganic water absorbing agent.

4. 3. The resin film for an electricity storage device according to claim 1, wherein the water absorbing agent comprises at least one selected from the group consisting of calcium oxide, anhydrous magnesium sulfate, magnesium oxide, calcium chloride, zeolite, aluminum oxide, silica gel, alumina gel, and calcined alum.

5. The resin film for an electricity storage device according to claim 1 , wherein at least one of the two or more layers contains a heat-sealable resin.

6. The resin film for an electricity storage device according to claim 5 , wherein the heat-fusible resin comprises at least one selected from the group consisting of polyesters and polyolefins.

7. 3. The resin film for an electricity storage device according to claim 1 or 2, wherein the resin film for an electricity storage device after absorbing water has a dielectric breakdown strength of 40 kV / mm or more, as measured by the following measurement method. (Measurement of dielectric breakdown strength after water absorption) A 10 cm square resin film for a storage battery device is prepared and immersed in warm water at 80°C. The immersion is continued until the water absorbing agent in the resin film for a storage battery device absorbs 100% of the water, to obtain a resin film for a storage battery device after absorbing water. The water absorption degree of the resin film for a storage battery device is calculated from the weight of the film before and after immersion. Next, the dielectric breakdown strength of the resin film for a storage battery device after absorbing water is measured in accordance with the provisions of JIS C 2110-1:2016 under the following measurement conditions: 23°C in air, short-time voltage increase method (AC, 50 Hz), voltage increase rate of 0.3 kV / s, and electrodes of 25 mmφ cylinder / 75 mmφ cylinder. The measured value is the average value measured for five samples.

8. 3) used as an adhesive layer between a barrier layer and a heat-sealable resin layer of an exterior material for an electricity storage device; or 4) used as an adhesive film for a metal terminal interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that seals the electricity storage device element.

9. An electricity storage device, comprising: an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte, the electricity storage device element being housed in a packaging body formed from an exterior material; An electricity storage device, comprising the resin film for an electricity storage device according to claim 1 or 2 disposed between the exterior material and the electricity storage device.

Images