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

Abstract

To provide an exterior material for energy storage devices with excellent moldability. [Solution] An exterior material for an energy storage device, comprising a laminate comprising at least a base material layer, a barrier layer, and a heat-fusible resin layer in this order, wherein the base material layer has a principal axis orientation within the range of 90° ± 30° as measured by the following measurement method. [Measurement Method] Using a principal axis orientation measuring device equipped with a camera and a light source, the camera of the measuring device, the base material layer, and the light source are positioned in a straight line, the base material layer is placed between the camera and the light source, and the base material layer is positioned such that the TD direction of the base material layer is 0° and the MD direction of the base material layer is 90°, the light from the light source is shone in the thickness direction of the base material layer to measure the principal axis orientation of the base material layer.

Description

[Technical Field]

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

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

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

[0004] Therefore, conventionally, a film-like exterior material has been proposed for energy storage devices in which a base material, an aluminum foil layer, and a heat-sealable resin layer are sequentially laminated, as it is easy to process into various shapes and can achieve thinning and weight reduction (see, for example, Patent Document 1).

[0005] In such film-like exterior materials, recesses are generally formed by cold forming, and energy storage device elements such as electrodes and electrolytes are placed in the spaces formed by these recesses. By heat-sealing the heat-sealable resin layers together, an energy storage device is obtained in which the energy storage device elements are housed inside the exterior material. [Prior art documents] [Patent Documents]

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

[0007] In recent years, there has been a demand for even thinner film-like exterior materials. Furthermore, from the perspective of further increasing the energy density of energy storage devices, there is also a demand for creating deeper recesses in the exterior materials.

[0008] However, when forming a film-like outer material for energy storage devices to create recesses that house the energy storage device elements, there is a problem that cracks and pinholes are prone to occur.

[0009] The main objective of this disclosure is to provide an exterior material for an energy storage device that has excellent moldability, comprising a laminate comprising at least a base layer, a barrier layer, and a heat-fusible resin layer in that order. [Means for solving the problem]

[0010] The inventors of this disclosure have diligently studied to solve the aforementioned problems. As a result, they have found that an exterior material for an energy storage device, comprising a laminate comprising at least a base layer, a barrier layer, and a heat-fusible resin layer in that order, wherein the base layer has a principal axis orientation within the range of 90°±30° as measured by the following measurement method, has excellent moldability. [Measurement method] Using a principal axis orientation measuring device equipped with a camera and a light source, the camera of the measuring device, the base material layer of the exterior material for the energy storage device, and the light source of the measuring device are positioned in a straight line, the base material layer is placed between the camera and the light source, and the base material layer is positioned such that the TD direction of the base material layer is 0° and the MD direction of the base material layer is 90°, the light from the light source is irradiated in the thickness direction of the base material layer to measure the principal axis orientation of the base material layer.

[0011] To improve the moldability of exterior materials for energy storage devices, the base layer is sometimes selected based on the tensile breaking strength (MPa) of the film used for the base layer. However, especially when the thickness of the base layer is thin, the difference in tensile force (N) of the base layer becomes small, and it is difficult to find a clear correlation between the tensile breaking strength of the base layer and the moldability of the exterior material for energy storage devices. In contrast, the inventors of this disclosure have found that even in such cases, if the principal axis orientation of the base layer is within the predetermined range, a clear correlation can be found between the physical properties of the base layer and the moldability of the exterior material for energy storage devices. Furthermore, while the measurement test for tensile breaking strength is a destructive test, the measurement test for principal axis orientation is a non-destructive test, which has the advantage of allowing selection of the base layer without destroying it.

[0012] This disclosure is the result of further consideration based on these findings. Specifically, this disclosure provides inventions in the following embodiments. It is composed of a laminate comprising, at least, a base layer, a barrier layer, and a heat-sealable resin layer in this order. The aforementioned base material is an exterior material for an energy storage device, wherein the principal axis orientation, as measured by the following measurement method, is within the range of 90° ± 30°. [Measurement method] Using a principal axis orientation measuring device equipped with a camera and a light source, the camera of the measuring device, the substrate layer, and the light source are positioned in a straight line, the substrate layer is placed between the camera and the light source, and the substrate layer is positioned such that the TD direction of the substrate layer is 0° and the MD direction of the substrate layer is 90°, the principal axis orientation of the substrate layer is measured by irradiating the substrate layer with light from the light source in the thickness direction. [Effects of the Invention]

[0013] According to this disclosure, it is possible to provide an exterior material for an energy storage device that comprises a laminate comprising at least a base layer, a barrier layer, and a heat-fusible resin layer in this order, and which has excellent moldability. Furthermore, according to this disclosure, it is also possible to provide a method for manufacturing an exterior material for an energy storage device and an energy storage device. [Brief explanation of the drawing]

[0014] [Figure 1] It is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electric storage device of the present disclosure. [Figure 2] It is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electric storage device of the present disclosure. [Figure 3] It is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electric storage device of the present disclosure. [Figure 4] It is a schematic diagram showing an example of a cross-sectional structure of an exterior material for an electric storage device of the present disclosure. [Figure 5] It is a schematic diagram for explaining a method of accommodating an electric storage device element in a package formed of an exterior material for an electric storage device of the present disclosure. [Figure 6] It is a schematic diagram (perspective view) for explaining a method of measuring the spindle orientation. [Figure 7] It is a schematic diagram (side view) for explaining a method of measuring the spindle orientation. [Figure 8] It is a schematic diagram (plan view) for explaining a method of measuring the spindle orientation.

Embodiments for Carrying Out the Invention

[0015] The exterior material for an electric storage device of the present disclosure is composed of a laminate including at least a base material layer, a barrier layer, and a heat-sealable resin layer in this order, and the base material layer is characterized in that the spindle orientation measured by the following measurement method is within the range of 90° ± 30°. The exterior material for an electric storage device of the present disclosure has excellent moldability by having such a configuration. [Measurement Method] Using a spindle orientation measuring device equipped with a camera and a light source, the base material layer is arranged between the camera and the light source such that the camera, the base material layer, and the light source of the measuring device are located on a straight line. When the base material layer is arranged such that the TD direction of the base material layer is the 0° direction and the MD direction of the base material layer is the 90° direction, the light of the light source is irradiated in the thickness direction of the base material layer to measure the spindle orientation of the base material layer.

[0016] The exterior materials for energy storage devices described herein will be described in detail below. In this specification, numerical ranges indicated by "~" mean "greater than or equal to" and "less than or equal to". For example, the notation 2~15mm means 2mm or more and 15mm or less.

[0017] Furthermore, in the case of exterior materials for energy storage devices, the Machine Direction (MD) and Transverse Direction (TD) of the barrier layer 3 described later can usually be determined during the manufacturing process. For example, when the barrier layer 3 is composed of metal foil such as aluminum alloy foil or stainless steel foil, linear lines called rolling marks are formed on the surface of the metal foil in the rolling direction (RD) of the metal foil. Since the rolling marks extend along the rolling direction, the rolling direction of the metal foil can be determined by observing the surface of the metal foil. Also, in the manufacturing process of a laminate, the MD of the laminate and the RD of the metal foil usually coincide, so the MD of the laminate can be determined by observing the surface of the metal foil in the laminate and identifying the rolling direction (RD) of the metal foil. In addition, since the TD of the laminate is perpendicular to the MD of the laminate, the TD of the laminate can also be determined.

[0018] Furthermore, if the MD of the exterior material for energy storage devices cannot be identified by the rolling marks of metal foils such as aluminum alloy foil or stainless steel foil, it can be identified by the following method. One method for confirming the MD of the exterior material for energy storage devices is to observe the cross-section of the heat-fusible resin layer of the exterior material of the energy storage device with an electron microscope and confirm the sea-island structure. In this method, the direction parallel to the cross-section where the average diameter of the island shapes perpendicular to the thickness direction of the heat-fusible resin layer is maximum can be determined as the MD. Specifically, the sea-island structure is confirmed by observing each of the cross-sections (a total of 10 cross-sections) in the longitudinal direction of the heat-fusible resin layer, and each of the cross-sections perpendicular to the longitudinal direction, by changing the angle by 10 degrees from the direction parallel to the longitudinal cross-section. Next, the shape of each individual island is observed in each cross-section. For the shape of each island, the straight-line distance connecting the leftmost point perpendicular to the thickness direction of the heat-fusible resin layer and the rightmost point perpendicular to that point is defined as the diameter y. For each cross-section, the average of the top 20 diameters y of the island shape, ordered from largest to smallest, is calculated. The direction parallel to the cross-section with the largest average diameter y of the island shape is determined to be the MD (Movement Direction).

[0019] 1. Laminated structure of exterior material for energy storage devices The exterior material 10 for energy storage devices of this disclosure is composed of a laminate comprising a base layer 1, a barrier layer 3, and a heat-fusible resin layer 4 in that order, as shown in Figure 1, for example. In the exterior material 10 for energy storage devices, the base layer 1 is the outermost layer, and the heat-fusible resin layer 4 is the innermost layer. When assembling an energy storage device using the exterior material 10 and an energy storage device element, the energy storage device element is housed in a space formed by heat-fussing the peripheral edges of the heat-fusible resin layers 4 of the exterior material 10 facing each other. In the laminate constituting the exterior material 10 for energy storage devices of this disclosure, with respect to the barrier layer 3, the heat-fusible resin layer 4 side is inward of the barrier layer 3, and the base layer 1 side is outward of the barrier layer 3.

[0020] The exterior material 10 for the energy storage device may, for example, have an adhesive layer 2 between the base layer 1 and the barrier layer 3, as needed, for the purpose of improving the adhesion between these layers, as shown in Figures 2 to 4. Also, as shown in Figures 3 and 4, an adhesive layer 5 may, as needed, have an adhesive layer 5 between the barrier layer 3 and the heat-fusible resin layer 4, for the purpose of improving the adhesion between these layers. Furthermore, as shown in Figure 4, a surface coating layer 6 or the like may be provided on the outside of the base layer 1 (opposite the heat-fusible resin layer 4 side), as needed.

[0021] The thickness of the laminate constituting the exterior material 10 for energy storage devices is not particularly limited, but from the viewpoint of cost reduction and improvement of energy density, for example, it can be about 190 μm or less, preferably about 180 μm or less, about 155 μm or less, about 120 μm or less, or about 100 μm or less. Furthermore, from the viewpoint of maintaining the function of the exterior material for energy storage devices, which is to protect the energy storage device elements, the thickness of the laminate constituting the exterior material 10 for energy storage devices can be preferably about 35 μm or more, about 45 μm or more, or about 60 μm or more. Furthermore, preferred ranges for the laminate constituting the outer casing material 10 for the energy storage device include, for example, approximately 35-190 μm, 35-180 μm, 35-155 μm, 35-120 μm, 35-100 μm, 45-190 μm, 45-180 μm, 45-155 μm, 45-120 μm, 45-100 μm, 60-190 μm, 60-180 μm, 60-155 μm, 60-120 μm, and 60-100 μm, with approximately 60-100 μm being particularly preferred.

[0022] In the exterior material 10 for energy storage devices, the ratio of the total thickness of the base layer 1, the adhesive layer 2 (optionally provided), the barrier layer 3, the adhesive layer 5 (optionally provided), the heat-fusible resin layer 4, and the surface coating layer 6 (optionally provided) to the thickness (total thickness) of the laminate constituting the exterior material 10 for energy storage devices is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. For example, if the exterior material 10 for energy storage devices of this disclosure includes a base layer 1, an adhesive layer 2, a barrier layer 3, an adhesive layer 5, and a heat-fusible resin layer 4, the ratio of the total thickness of each of these layers to the thickness (total thickness) of the laminate constituting the exterior material 10 for energy storage devices is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. Furthermore, even if the exterior material 10 for energy storage devices of this disclosure is a laminate comprising a base layer 1, an adhesive layer 2, a barrier layer 3, and a heat-fusible resin layer 4, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the exterior material 10 for energy storage devices can be, for example, 80% or more, preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

[0023] 2. Each layer forming the exterior material for the energy storage device [Base material layer 1] In this disclosure, the base layer 1 is a layer provided for purposes such as enabling it to function as a base material for the exterior material of an energy storage device. The base layer 1 is located on the outer layer side of the exterior material for an energy storage device. The base layer 1 may be the outermost layer (a layer constituting the outer surface), or, for example, if a surface coating layer 6 described later is provided, the surface coating layer 6 may be the outermost layer (a layer constituting the outer surface).

[0024] In this disclosure, the base material layer 1 is characterized in that a predetermined principal axis orientation is within the range of 90° ± 30°. That is, as shown in the schematic diagrams of Figures 6 to 8, the base material layer 1 of the exterior material for the energy storage device and the camera C of the principal axis orientation measuring device are positioned in a straight line, and the base material layer 1 is placed between the camera C and the light source LS of the principal axis orientation measuring device, and the base material layer 1 is positioned such that the TD direction of the base material layer 1 is in the 0° direction and the MD direction of the base material layer 1 is in the 90° direction, and the principal axis orientation of the base material layer 1, measured by irradiating the thickness direction (z direction) of the base material layer 1 with light L from the light source LS, is within the range of 90° ± 30° (i.e., 60 to 120°). From the viewpoint of more favorably achieving the effects of the present invention, the principal axis orientation of the base material layer 1 is preferably within the range of 90°±25° (i.e., 65~115°), more preferably within the range of 90°±20° (i.e., 70~110°), even more preferably within the range of 90°±15° (i.e., 75~105°), even more preferably within the range of 90°±10° (i.e., 80~100°), and even more preferably within the range of 90°±5° (i.e., 85~95°). The method for measuring the principal axis orientation of the base material layer 1 is as follows.

[0025] <Measurement of the principal axis orientation> For the base layer (the resin film constituting the base layer), as shown in the schematic diagrams in Figures 6 to 8, a principal axis orientation measuring device equipped with a camera C and a light source LS was used. The camera C of the measuring device, the base layer 1, and the light source LS were positioned in a straight line, and the base layer 1 was placed between the camera C and the light source LS. The TD direction of the base layer 1 was set to 0°, and the MD direction of the base layer 1 was set to 90°. The measurement was performed by irradiating the base layer 1 in the thickness direction D with light L from the light source LS. As shown in the schematic diagrams in Figures 6 and 7, during the measurement, light L was irradiated from the light source placed on the back side of the base layer 1 in the thickness direction (z direction) of the base layer 1. A transparent glass plate G was placed on top of the base layer 1 (on the camera C side) to ensure that no wrinkles were formed on the surface of the base layer 1 during the measurement. Furthermore, although not shown in Figures 6 to 8, the substrate layer 1 and the glass plate G are arranged in order on a plate with an opening at the position where light is irradiated onto the substrate layer 1, and the measurement is performed so that light L passes through the substrate layer 1 and the glass plate G through the opening in the plate. The specific measurement conditions are as follows. When measuring the principal axis orientation of the substrate layer 1 by obtaining the substrate layer (the resin film constituting the substrate layer) from an energy storage device or an exterior material for an energy storage device, the exterior material for the energy storage device is obtained from the top or bottom surface, rather than from the heat-sealed part or side of the energy storage device, to prepare the sample. In this disclosure, the principal axis orientation of the substrate layer is the leading axis. (Measurement conditions) Measurement device: For example, a high-speed polarization imaging device (CRYSTA PI-5) manufactured by Photron Corporation. Analysis software: For example, KAMAKIRI Offline Basic Software Ver: 1.5.0.1 Measurement sample: Prepare the sample by cutting the substrate layer to a size such as A4 (TD210mm x MD300mm). Measurement wavelength (camera side): 520~570nm (The camera, which receives light transmitted through the film, detects light with a wavelength of 520~570nm) Light source: White LED light (The measurement sample is positioned so that the extension of the light source coincides with the thickness direction of the substrate layer, and the camera is positioned on the extension of the light source.)

[0026] The mechanism by which the moldability of the exterior material 10 for energy storage devices is improved by having a predetermined principal axis orientation of the base layer 1 within the range of 90°±30° can be considered as follows. In other words, the molding of the exterior material for energy storage devices is generally performed by cold forming using a mold to create a rectangular molded portion (recess) with sides parallel to the MD direction. Here, within the circumference of the edge of the molded portion, the area that is stretched the most is the side portion of the rectangle, while the corner portion (around 45°) is stretched less. When the principal axis orientation of the base layer is 90°±30°, it is considered that the molecular orientation of the base layer is relatively aligned along the MD direction. For this reason, when molding the exterior material for energy storage devices, the resistance to stretching of the edge portion of the rectangular side portion, which is stretched the most, becomes stronger, and it is considered that pinholes are less likely to be formed. On the other hand, when the principal axis orientation of the base layer exceeds 90°±30°, it is considered that the molecular orientation of the base layer is relatively aligned in the direction of 45° oblique to the MD direction. Therefore, during the molding of the exterior material for energy storage devices, resistance to stretching is stronger only at the edges of the corner sections where the stretching area is small, while resistance to stretching is weaker at the edges of the sides of the rectangle, making it easier for pinholes to form.

[0027] Furthermore, in measuring the principal axis orientation of the substrate layer 1, the phase difference of the substrate layer 1 can also be measured. From the viewpoint of more favorably achieving the effects of the present invention, the phase difference of the substrate layer 1 is preferably about 210 nm or less, more preferably about 200 nm or less, even more preferably about 150 nm or less, even more preferably about 100 nm or less, and even more preferably about 80 nm or less. Also, the phase difference of the substrate layer 1 is, for example, about 30 nm or more, about 50 nm or more, etc. Preferred ranges for the phase difference of the substrate layer 1 are about 30 to 210 nm, about 30 to 200 nm, about 30 to 150 nm, about 30 to 100 nm, about 30 to 80 nm, about 50 to 210 nm, about 50 to 200 nm, about 50 to 150 nm, about 50 to 100 nm, and about 50 to 80 nm.

[0028] To set the principal axis orientation and phase difference of the base layer 1 to the aforementioned values, for example, the material, thickness, and various physical properties of the base layer 1 may be adjusted. If the base layer 1 is formed from a resin film, the manufacturing conditions such as the stretching method of the resin film (e.g., inflation method, tenter method), stretching ratio, stretching speed, cooling temperature, and heat setting temperature may be adjusted. These adjustments can be made based on known technologies. For example, since the principal axis orientation of the base layer 1 corresponds to the direction of high crystallinity of the resin, when using a resin film manufactured by a predetermined stretching method as a base layer by cutting it to a predetermined size, it is also effective to select the cutting position from the resin film so that the crystal orientation is aligned and use that as the base layer 1.

[0029] The material forming the base layer 1 is not particularly limited, as long as it has the function of a base material, that is, at least insulating properties, and satisfies the aforementioned principal axis orientation. The base layer 1 can be formed using, for example, a resin, and the resin may contain additives described later.

[0030] The base layer 1 may be, for example, a resin film formed from a resin, or a film formed by coating a resin. The resin film may be an unstretched film or a stretched film. Examples of stretched films include uniaxially stretched films and biaxially stretched films, with biaxially stretched films being preferred. Examples of stretching methods for forming a biaxially stretched film include sequential biaxial stretching, inflation stretching, and simultaneous biaxial stretching. Examples of resin coating methods include roll coating, gravure coating, and extrusion coating.

[0031] Examples of resins that form the base layer 1 include polyester, polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicon resin, phenolic resin, and modified versions of these resins. Furthermore, the resin forming the base layer 1 may be a copolymer of these resins, or a modified version of such copolymer. It may also be a mixture of these resins.

[0032] Among these, the resins used to form the base layer 1 are preferably polyester and polyamide, and particularly preferably polyamide.

[0033] Examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymerized polyesters. Examples of copolymerized polyesters include copolymerized polyesters with ethylene terephthalate as the main repeating unit. Specifically, examples include copolymerized polyesters polymerized with ethylene isophthalate using ethylene terephthalate as the main repeating unit (hereinafter abbreviated as polyethylene(terephthalate / isophthalate)), polyethylene(terephthalate / adipate), polyethylene(terephthalate / sodium sulfoisophthalate), polyethylene(terephthalate / sodium isophthalate), polyethylene(terephthalate / phenyl-dicarboxylate), and polyethylene(terephthalate / decanedicarboxylate). These polyesters may be used individually or in combination of two or more types.

[0034] Furthermore, specific examples of polyamides include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (where I represents isophthalic acid and T represents terephthalic acid), which contain constituent units derived from terephthalic acid and / or isophthalic acid; aromatic polyamides such as polyamide MXD6 (polymetaxylylene adipamide); alicyclic polyamides such as polyamide PACM6 (polybis(4-aminocyclohexyl)methaneadipamide); polyamides copolymerized with lactam components or isocyanate components such as 4,4'-diphenylmethane-diisocyanate; polyesteramide copolymers and polyether esteramide copolymers, which are copolymers of copolymerized polyamides with polyester or polyalkylene ether glycol; and other polymers of these polyamides. These polyamides may be used individually or in combination of two or more types.

[0035] The base layer 1 preferably contains at least one of polyester film, polyamide film, and polyolefin film; more preferably contains at least one of stretched polyester film, stretched polyamide film, and stretched polyolefin film; more preferably contains at least one of stretched polyethylene terephthalate film, stretched polybutylene terephthalate film, stretched nylon film, and stretched polypropylene film; and even more preferably contains at least one of biaxially oriented polyethylene terephthalate film, biaxially oriented polybutylene terephthalate film, biaxially oriented nylon film, and biaxially oriented polypropylene film. From the viewpoint of more favorably achieving the effects of the present invention, it is particularly preferable that the base layer 1 is composed of a biaxially oriented nylon film.

[0036] The base layer 1 may be a single layer or may consist of two or more layers. If the base layer 1 consists of two or more layers, the base layer 1 may be a laminate formed by laminating resin films with an adhesive, or it may be a laminate of two or more resin films formed by co-extruding resin. Furthermore, the laminate of two or more resin films formed by co-extruding resin may be used as the base layer 1 in its unstretched state, or it may be used as the base layer 1 after uniaxial stretching or biaxial stretching.

[0037] Specific examples of a laminate of two or more resin films in the base layer 1 include a laminate of polyester film and nylon film, a laminate of two or more nylon films, and a laminate of two or more polyester films. Preferably, a laminate of stretched nylon film and stretched polyester film, a laminate of two or more stretched nylon films, and a laminate of two or more stretched polyester films are preferred. For example, when the base layer 1 is a laminate of two resin films, a laminate of polyester resin film and polyester resin film, a laminate of polyamide resin film and polyamide resin film, or a laminate of polyester resin film and polyamide resin film is preferred, and a laminate of polyethylene terephthalate film and polyethylene terephthalate film, a laminate of nylon film and nylon film, or a laminate of polyethylene terephthalate film and nylon film is more preferred. Furthermore, since polyester resin is less likely to discolor when an electrolyte adheres to its surface, for example, when the base layer 1 is a laminate of two or more resin films, it is preferable that the polyester resin film be located in the outermost layer of the base layer 1.

[0038] If the base layer 1 is a laminate of two or more resin films, the two or more resin films may be laminated with an adhesive in between. If the base layer 1 is a laminate of two or more resin films, it is sufficient that at least one layer has the principal axis orientation described above. Preferred adhesives are similar to those exemplified in adhesive layer 2 described later. The method for laminating the two or more resin films is not particularly limited, and known methods can be used, such as dry lamination, sandwich lamination, extrusion lamination, and thermal lamination, with dry lamination being preferred. When laminating by dry lamination, it is preferable to use a polyurethane adhesive. In this case, the thickness of the adhesive is, for example, about 2 to 5 μm. Alternatively, an anchor coat layer may be formed on the resin film and laminated. The anchor coat layer is similar to the adhesive exemplified in adhesive layer 2 described later. In this case, the thickness of the anchor coat layer is, for example, about 0.01 to 1.0 μm.

[0039] Furthermore, at least one of the surface and interior of the base layer 1 may contain additives such as lubricants, flame retardants, antiblocking agents, antioxidants, light stabilizers, tackifiers, and antistatic agents. Only one type of additive may be used, or two or more types may be mixed and used.

[0040] In this disclosure, from the viewpoint of improving the moldability of the exterior material for energy storage devices, it is preferable that a lubricant be present on the surface of the base layer 1. The lubricant is not particularly limited, but amide lubricants are preferred. Specific examples of amide lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearate amide, N-stearyl oleic acid amide, N-oleyl stearate amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearate amide. Specific examples of saturated fatty acid bisamides include methylenebisstearate, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearate, ethylenebishydroxystearate, ethylenebisbehenamide, hexamethylenebisstearate, hexamethylenebisbehenamide, hexamethylenehydroxystearate, N,N'-distearyladipamide, and N,N'-distearylsebacinamide. Specific examples of unsaturated fatty acid bisamides include ethylenebisoleamide, ethylenebiserucamide, hexamethylenebisoleamide, N,N'-dioleyladipamide, and N,N'-dioleylsebacinamide. Specific examples of fatty acid ester amides include stearamidoethylstearate. Specific examples of aromatic bisamides include m-xylylenebisstearate, m-xylylenebishydroxystearate, and N,N'-distearyl isophthalamide. The lubricant may be used alone or in combination of two or more types.

[0041] If a lubricant is present on the surface of the substrate layer 1, the amount present is not particularly limited, but preferably about 3 mg / m². 2 More preferably 4-15 mg / m² 2 To a certain extent, more preferably 5-14 mg / m² 2 The degree can be described as follows.

[0042] The lubricant present on the surface of the base layer 1 may be a lubricant contained in the resin constituting the base layer 1 that has seeped out, or a lubricant may be applied to the surface of the base layer 1.

[0043] The thickness of the base layer 1 is not particularly limited as long as it performs its function as a base material, but from the viewpoint of more favorably achieving the effects of the present invention, it is preferably about 10 μm or more, more preferably about 15 μm or more. From the same viewpoint, it is preferably about 50 μm or less, more preferably about 40 μm or less, even more preferably about 30 μm or less, even more preferably about 25 μm or less, and even more preferably about 20 μm or less. Preferred ranges for the thickness of the base layer 1 include about 10 to 50 μm, about 10 to 40 μm, about 10 to 30 μm, about 10 to 25 μm, about 10 to 20 μm, about 15 to 50 μm, about 15 to 40 μm, about 15 to 30 μm, about 15 to 25 μm, and about 15 to 20 μm. When the base layer 1 is a laminate of two or more resin films, the thickness of each resin film constituting each layer is preferably about 2 to 25 μm.

[0044] [Adhesive layer 2] In the exterior material for energy storage devices of this disclosure, the adhesive layer 2 is a layer provided between the substrate layer 1 and the barrier layer 3 as needed, for the purpose of improving the adhesion between them.

[0045] The adhesive layer 2 is formed by an adhesive capable of bonding the substrate layer 1 and the barrier layer 3. The adhesive used to form the adhesive layer 2 is not limited, but may be a chemical reaction type, solvent evaporation type, heat melt type, hot pressure type, etc. It may also be a two-component curing adhesive (two-part adhesive), a one-component curing adhesive (one-part adhesive), or a resin that does not undergo a curing reaction. Furthermore, the adhesive layer 2 may be a single layer or a multi-layer layer.

[0046] Specifically, adhesive components included in adhesives include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, copolymerized polyester; polyethers; polyurethanes; epoxy resins; phenolic resins; polyamides such as nylon 6, nylon 66, nylon 12, copolymerized polyamides; polyolefin resins such as polyolefins, cyclic polyolefins, acid-modified polyolefins, and acid-modified cyclic polyolefins; polyvinyl acetate; cellulose; (meth)acrylic resins; polyimides; polycarbonates; amino resins such as urea resins and melamine resins; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; and silicone resins. These adhesive components may be used individually or in combination of two or more. Among these adhesive components, polyurethane adhesives are particularly preferred. Furthermore, the adhesive strength of these adhesive resins can be increased by using an appropriate curing agent. The curing agent is selected appropriately from polyisocyanates, polyfunctional epoxy resins, oxazoline group-containing polymers, polyamine resins, acid anhydrides, etc., depending on the functional groups of the adhesive components.

[0047] Examples of polyurethane adhesives include polyurethane adhesives comprising a first agent containing a polyol compound and a second agent containing an isocyanate compound. Preferably, a two-component curing type polyurethane adhesive is used, in which a polyol such as polyester polyol, polyether polyol, and acrylic polyol is used as the first agent and an aromatic or aliphatic polyisocyanate is used as the second agent. Another example of a polyurethane adhesive is a polyurethane adhesive comprising a polyurethane compound obtained by pre-reacting a polyol compound with an isocyanate compound and an isocyanate compound. Another example of a polyurethane adhesive is a polyurethane adhesive comprising a polyurethane compound obtained by pre-reacting a polyol compound with an isocyanate compound and an isocyanate compound and an isocyanate compound. Another example of a polyurethane adhesive is a polyurethane adhesive obtained by curing a polyurethane compound obtained by pre-reacting a polyol compound with an isocyanate compound by reacting it with moisture such as air. As the polyol compound, it is preferable to use a polyester polyol having hydroxyl groups on the side chains in addition to the hydroxyl groups at the ends of the repeating units. Examples of the second agent are aliphatic, alicyclic, aromatic, and aromaticaliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Also, polyfunctional isocyanate modified compounds derived from one or more of these diisocyanates are used. Furthermore, polymers (e.g., trimers) can be used as polyisocyanate compounds. Examples of such polymers include adducts, biuretes, and nurates. The adhesive layer 2 is formed from a polyurethane adhesive, which provides excellent electrolyte resistance to the exterior material for energy storage devices, preventing peeling of the substrate layer 1 even if electrolyte adheres to the sides.

[0048] Furthermore, the adhesive layer 2 may contain other components as long as they do not impair adhesion, and may include colorants, thermoplastic elastomers, tackifiers, fillers, etc. The inclusion of a colorant in the adhesive layer 2 allows for the coloring of the exterior material for energy storage devices. Known colorants such as pigments and dyes can be used. Additionally, only one type of colorant may be used, or two or more types may be mixed.

[0049] The type of pigment is not particularly limited, as long as it does not impair the adhesion of adhesive layer 2. Examples of organic pigments include azo, phthalocyanine, quinacridone, anthraquinone, dioxazine, indigothioindigo, perinone-perylene, isoindorenine, and benzimidazolon pigments. Examples of inorganic pigments include carbon black, titanium dioxide, cadmium, lead, chromium oxide, and iron pigments. Other examples include fine mica powder and fish scale foil.

[0050] Among colorants, carbon black is preferred for, for example, to give the exterior material of an energy storage device a black appearance.

[0051] The average particle size of the pigment is not particularly limited, but for example, it can be about 0.05 to 5 μm, preferably about 0.08 to 2 μm. The average particle size of the pigment is the median diameter measured by a laser diffraction / scattering particle size distribution analyzer.

[0052] The pigment content in the adhesive layer 2 is not particularly limited as long as the exterior material for the energy storage device is colored, and for example, it is about 5 to 60% by mass, preferably 10 to 40% by mass.

[0053] The thickness of the adhesive layer 2 is not particularly limited as long as it can bond the substrate layer 1 and the barrier layer 3, but for example, it is about 1 μm or more and about 2 μm or more. Also, the thickness of the adhesive layer 2 is, for example, about 10 μm or less and about 5 μm or less. Furthermore, preferred ranges for the thickness of the adhesive layer 2 include about 1 to 10 μm, about 1 to 5 μm, about 2 to 10 μm, and about 2 to 5 μm.

[0054] [Colored layer] The colored layer is a layer provided between the base layer 1 and the barrier layer 3 as needed (not shown in the figure). If an adhesive layer 2 is present, the colored layer may be provided between the base layer 1 and the adhesive layer 2, and between the adhesive layer 2 and the barrier layer 3. Alternatively, the colored layer may be provided on the outside of the base layer 1. By providing a colored layer, the exterior material for the energy storage device can be colored.

[0055] The colored layer can be formed, for example, by applying an ink containing a coloring agent to the surface of the substrate layer 1 or the surface of the barrier layer 3. Known coloring agents such as pigments and dyes can be used. In addition, only one type of coloring agent may be used, or two or more types may be mixed and used.

[0056] Specific examples of colorants included in the colored layer are the same as those exemplified in the [Adhesive Layer 2] section.

[0057] [Barrier layer 3] In the exterior material for energy storage devices, the barrier layer 3 is a layer that at least prevents the intrusion of moisture.

[0058] Examples of barrier layer 3 include metal foil, vapor-deposited film, and resin layer with barrier properties. Examples of vapor-deposited films include metal vapor-deposited films, inorganic oxide vapor-deposited films, and carbon-containing inorganic oxide vapor-deposited films. Examples of resin layers include fluorine-containing resins such as polymers mainly composed of polyvinylidene chloride, chlorotrifluoroethylene (CTFE), polymers mainly composed of tetrafluoroethylene (TFE), polymers having fluoroalkyl groups, and polymers mainly composed of fluoroalkyl units, as well as ethylene vinyl alcohol copolymers. In addition, a resin film having at least one of these vapor-deposited films and resin layers can also be provided as barrier layer 3. Multiple layers of barrier layer 3 may be provided. It is preferable that barrier layer 3 includes a layer made of a metal material. Specific examples of metal materials constituting barrier layer 3 include aluminum alloy, stainless steel, titanium steel, and steel plates. When used as a metal foil, it is preferable that it includes at least one of aluminum alloy foil and stainless steel foil.

[0059] From the viewpoint of improving the formability of the exterior material for energy storage devices, the aluminum alloy foil is more preferably a soft aluminum alloy foil composed of, for example, an annealed aluminum alloy, and from the viewpoint of further improving formability, it is more preferably an aluminum alloy foil containing iron. In an iron-containing aluminum alloy foil (100% by mass), the iron content is preferably 0.1 to 9.0% by mass, and more preferably 0.5 to 2.0% by mass. By having an iron content of 0.1% by mass or more, an exterior material for energy storage devices with better formability can be obtained. By having an iron content of 9.0% by mass or less, an exterior material for energy storage devices with better flexibility can be obtained. Examples of soft aluminum alloy foils include aluminum alloy foils having compositions specified in JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, or JIS H4000:2014 A8079P-O. Silicon, magnesium, copper, manganese, etc., may also be added as needed. Softening can be achieved through annealing or other treatments.

[0060] Furthermore, examples of stainless steel foils include austenitic, ferritic, austenitic-ferritic, martensitic, and precipitation-hardening stainless steel foils. Moreover, from the viewpoint of providing an exterior material for energy storage devices with excellent formability, it is preferable that the stainless steel foil be made of austenitic stainless steel.

[0061] Specific examples of austenitic stainless steels that make up stainless steel foil include SUS304, SUS301, and SUS316L, with SUS304 being particularly preferred among these.

[0062] In the case of metal foil, the thickness of the barrier layer 3 should at least function as a barrier layer that prevents moisture from penetrating, for example, about 9 to 200 μm. The thickness of the barrier layer 3 is preferably about 85 μm or less, more preferably about 50 μm or less, even more preferably about 40 μm or less, and particularly preferably about 35 μm or less. Also, the thickness of the barrier layer 3 is preferably about 10 μm or more, even more preferably about 20 μm or more, and more preferably about 25 μm or more. Furthermore, preferred ranges for the thickness of the barrier layer 3 include about 10 to 85 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 35 μm, about 20 to 85 μm, about 20 to 50 μm, about 20 to 40 μm, about 20 to 35 μm, about 25 to 85 μm, about 25 to 50 μm, about 25 to 40 μm, and about 25 to 35 μm. When the barrier layer 3 is made of aluminum alloy foil, the above range is particularly preferred. Furthermore, when the barrier layer 3 is made of stainless steel foil, the thickness of the stainless steel foil is preferably about 60 μm or less, more preferably about 50 μm or less, even more preferably about 40 μm or less, even more preferably about 30 μm or less, and particularly preferably about 25 μm or less. Also, the thickness of the stainless steel foil is preferably about 10 μm or more, more preferably about 15 μm or more. Furthermore, preferred ranges for the thickness of the stainless steel foil include about 10 to 60 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 30 μm, about 10 to 25 μm, about 15 to 60 μm, about 15 to 50 μm, about 15 to 40 μm, about 15 to 30 μm, and about 15 to 25 μm.

[0063] Furthermore, if the barrier layer 3 is a metal foil, it is preferable to provide a corrosion-resistant coating on at least the side opposite to the substrate layer to prevent dissolution and corrosion. The barrier layer 3 may also have a corrosion-resistant coating on both sides. Here, a corrosion-resistant coating refers to a thin film that provides corrosion resistance (e.g., acid resistance, alkali resistance, etc.) to the barrier layer by performing treatments such as hot water modification treatment such as boehmite treatment, chemical conversion treatment, anodizing treatment, plating treatment with nickel or chromium, or corrosion prevention treatment by applying a coating agent to the surface of the barrier layer. Specifically, a corrosion-resistant coating means a coating that improves the acid resistance of the barrier layer (acid-resistant coating), a coating that improves the alkali resistance of the barrier layer (alkali-resistant coating), etc. One type of treatment may be performed to form the corrosion-resistant coating, or two or more types may be combined. In addition, it is possible to have multiple layers instead of just one. Furthermore, among these treatments, hot water modification treatment and anodizing treatment are treatments that dissolve the surface of the metal foil with a treatment agent and form a metal compound with excellent corrosion resistance. These processes may also be included in the definition of chemical conversion treatment. Furthermore, if barrier layer 3 has a corrosion-resistant coating, the barrier layer 3 includes the corrosion-resistant coating.

[0064] The corrosion-resistant coating prevents delamination between the barrier layer (e.g., aluminum alloy foil) and the base layer during the molding of exterior materials for energy storage devices. It also prevents dissolution and corrosion of the barrier layer surface due to hydrogen fluoride generated by the reaction of electrolyte and water, particularly the dissolution and corrosion of aluminum oxide present on the barrier layer surface when the barrier layer is aluminum alloy foil. Furthermore, it improves the adhesion (wettability) of the barrier layer surface, preventing delamination between the base layer and the barrier layer during heat sealing and molding.

[0065] Various corrosion-resistant coatings are known to be formed by chemical conversion treatments, mainly including corrosion-resistant coatings containing at least one of the following: phosphates, chromates, fluorides, triazinethiol compounds, and rare earth oxides. Examples of chemical conversion treatments using phosphates and chromates include chromate treatment, phosphate chromate treatment, phosphate-chromate treatment, and chromate treatment. Examples of chromium compounds used in these treatments include chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, acetyl acetate chromate, chromium chloride, and potassium chromium sulfate. Examples of phosphorus compounds used in these treatments include sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphate. Examples of chromate treatments include etching chromate treatment, electrolytic chromate treatment, and coating-type chromate treatment, with coating-type chromate treatment being preferred. This coating-type chromate treatment involves first degreasing at least the inner surface of a barrier layer (e.g., aluminum alloy foil) using a well-known treatment method such as alkaline immersion, electrolytic cleaning, acid cleaning, electrolytic acid cleaning, or acid activation. Then, a treatment solution mainly composed of metal phosphate salts such as chromium phosphate, titanium phosphate, zirconium phosphate, and zinc phosphate, or mixtures thereof, or a treatment solution mainly composed of nonmetallic phosphates and mixtures thereof, or a treatment solution consisting of a mixture of these with synthetic resins, etc., is applied to the degreased surface using a well-known coating method such as roll coating, gravure printing, or immersion, and then dried. Various solvents can be used as the treatment solution, such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, with water being preferred. Furthermore, examples of resin components used in this process include polymers such as phenolic resins and acrylic resins, and examples of chromate treatment using an amination phenol polymer having repeating units represented by the following general formulas (1) to (4). In this amination phenol polymer, the repeating units represented by the following general formulas (1) to (4) may be included individually or in any combination of two or more types.The acrylic resin is preferably polyacrylic acid, acrylate methacrylate copolymer, acrylate maleic acid copolymer, acrylate styrene copolymer, or derivatives thereof such as sodium salts, ammonium salts, or amine salts. Derivatives of polyacrylic acid, such as ammonium salts, sodium salts, or amine salts of polyacrylic acid, are particularly preferred. In this disclosure, polyacrylic acid means a polymer of acrylic acid. Furthermore, the acrylic resin is also preferably a copolymer of acrylic acid and a dicarboxylic acid or dicarboxylic acid anhydride, and also preferably an ammonium salt, sodium salt, or amine salt of a copolymer of acrylic acid and a dicarboxylic acid or dicarboxylic acid anhydride. Only one type of acrylic resin may be used, or two or more types may be mixed and used.

[0066] [ka]

[0067] [ka]

[0068] [ka]

[0069] [ka]

[0070] In general formulas (1) to (4), X represents a hydrogen atom, a hydroxyl group, an alkyl group, a hydroxyalkyl group, an allyl group, or a benzyl group. Also, R 1 and R 2 Each of these represents a hydroxyl group, an alkyl group, or a hydroxyalkyl group, either identical or different. In general formulas (1) to (4), X and R 1 and R 2Examples of the alkyl group represented by [alkyl group] include linear or branched alkyl groups having 1 to 4 carbon atoms such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, etc. Also, X, R 1 and R 2 Examples of the hydroxyalkyl group represented by [hydroxyalkyl group] include linear or branched alkyl groups having 1 to 4 carbon atoms with one hydroxy group substituted, such as hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, 1-hydroxypropyl group, 2-hydroxypropyl group, 3-hydroxypropyl group, 1-hydroxybutyl group, 2-hydroxybutyl group, 3-hydroxybutyl group, 4-hydroxybutyl group, etc. In General Formulas (1) to (4), the alkyl groups and hydroxyalkyl groups represented by X, R 1 and R 2 may be the same or different from each other. In General Formulas (1) to (4), X is preferably a hydrogen atom, a hydroxy group or a hydroxyalkyl group. The number average molecular weight of the aminated phenol polymer having the repeating unit represented by General Formulas (1) to (4) is preferably about 500 to 1,000,000, and more preferably about 1,000 to 20,000. The aminated phenol polymer is produced, for example, by polycondensing a phenol compound or a naphthol compound and formaldehyde to produce a polymer composed of the repeating unit represented by the above General Formula (1) or General Formula (3), and then introducing a functional group (-CH2NR 1 R 2 ) into the polymer obtained above using formaldehyde and an amine (R 1 R 2 ). The aminated phenol polymer is used alone or in combination of two or more.

[0071] Another example of a corrosion-resistant coating is a thin film formed by a coating-type corrosion prevention treatment, which involves applying a coating agent containing at least one selected from the group consisting of rare earth element oxide sols, anionic polymers, and cationic polymers. The coating agent may further contain phosphoric acid or phosphate, and a crosslinking agent for crosslinking the polymer. In the rare earth element oxide sol, fine particles of rare earth element oxides (for example, particles with an average particle size of 100 nm or less) are dispersed in a liquid dispersion medium. Examples of rare earth element oxides include cerium oxide, yttrium oxide, neodymium oxide, and lanthanum oxide, with cerium oxide being preferred from the viewpoint of further improving adhesion. The rare earth element oxides contained in the corrosion-resistant coating can be used individually or in combination of two or more. Various solvents can be used as the liquid dispersion medium for the rare earth element oxide sol, such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, with water being preferred. Preferred cationic polymers include, for example, polyethyleneimine, ionic polymer complexes comprising polyethyleneimine and a polymer having a carboxylic acid, primary amine-grafted acrylic resins obtained by graft polymerization of a primary amine onto an acrylic main skeleton, polyallylamine or its derivatives, and amination phenols. Preferred anionic polymers are poly(meth)acrylic acid or its salts, or copolymers mainly composed of (meth)acrylic acid or its salts. Furthermore, the crosslinking agent is preferably at least one selected from the group consisting of a compound having one of the functional groups of isocyanate, glycidyl, carboxyl, or oxazoline, and a silane coupling agent. Additionally, the phosphoric acid or phosphate is preferably condensed phosphoric acid or condensed phosphate.

[0072] An example of a corrosion-resistant coating is one formed by dispersing metal oxides such as aluminum oxide, titanium oxide, cerium oxide, and tin oxide, or fine particles of barium sulfate, in phosphoric acid, applying this mixture to the surface of a barrier layer, and then baking it at a temperature of 150°C or higher.

[0073] The corrosion-resistant coating may, if necessary, be a laminated structure in which at least one of a cationic polymer and an anionic polymer is further laminated. Examples of cationic and anionic polymers include those mentioned above.

[0074] Furthermore, the composition of the corrosion-resistant coating can be analyzed, for example, using time-of-flight secondary ion mass spectrometry.

[0075] The amount of corrosion-resistant film to be formed on the surface of the barrier layer 3 in the chemical conversion treatment is not particularly limited, but for example, in the case of coating-type chromate treatment, the surface of the barrier layer 3 is 1 m 2 It is desirable that the product contains, for example, about 0.5 to 50 mg of chromium-based chromium, preferably about 1.0 to 40 mg of phosphorus-based chromium

[0076] The thickness of the corrosion-resistant coating is not particularly limited, but from the viewpoint of the cohesive force of the coating and the adhesion force with the barrier layer and the heat-fusible resin layer, it is preferably about 1 nm to 20 μm, more preferably about 1 nm to 100 nm, and even more preferably about 1 nm to 50 nm. The thickness of the corrosion-resistant coating can be measured by observation with a transmission electron microscope, or by a combination of observation with a transmission electron microscope and energy-dispersive X-ray spectroscopy or electron beam energy loss spectroscopy. By analyzing the composition of the corrosion-resistant coating using time-of-flight secondary ion mass spectrometry, for example, secondary ions consisting of Ce, P, and O (e.g., Ce2PO4) can be identified. + CePO4 - (at least one of the above), or, for example, a secondary ion consisting of Cr, P, and O (e.g., CrPO2) + , CrPO4 - Peaks originating from at least one of the following are detected.

[0077] The chemical conversion treatment is carried out by applying a solution containing compounds used to form a corrosion-resistant film to the surface of the barrier layer using methods such as bar coating, roll coating, gravure coating, or immersion, and then heating the barrier layer to a temperature of approximately 70-200°C. Alternatively, before applying the chemical conversion treatment to the barrier layer, it may be subjected to a degreasing treatment using methods such as alkaline immersion, electrolytic cleaning, acid cleaning, or electrolytic acid cleaning. This degreasing treatment makes it possible to perform the chemical conversion treatment on the surface of the barrier layer more efficiently. Furthermore, by using an acid degreasing agent, which is a fluorine-containing compound dissolved in an inorganic acid, it is possible to not only degrease the metal foil but also form a fluoride of the passive metal; in such cases, only the degreasing treatment may be performed.

[0078] [Thermal adhesive resin layer 4] In the exterior material for energy storage devices of this disclosure, the heat-sealable resin layer 4 is the innermost layer and is a layer (sealant layer) that performs the function of sealing the energy storage device elements by heat-sealing the heat-sealable resin layers together during the assembly of the energy storage device.

[0079] The resin constituting the heat-fusible resin layer 4 is not particularly limited as long as it is heat-fusible, but resins containing a polyolefin backbone, such as polyolefins and acid-modified polyolefins, are preferred. The presence of a polyolefin backbone in the resin constituting the heat-fusible resin layer 4 can be analyzed, for example, by infrared spectroscopy or gas chromatography-mass spectrometry. Furthermore, when the resin constituting the heat-fusible resin layer 4 is analyzed by infrared spectroscopy, it is preferable to detect a peak originating from maleic anhydride. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak originating from maleic anhydride is detected at wavenumber 1760 cm⁻¹. -1 Nearby wave frequency 1780cm -1 A peak derived from maleic anhydride is detected in the vicinity. If the heat-fusible resin layer 4 is composed of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride will be detected when measured by infrared spectroscopy. However, if the degree of acid modification is low, the peak may become small and not be detected. In that case, analysis is possible by nuclear magnetic resonance spectroscopy.

[0080] Examples of polyolefins include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymer of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymer of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. Among these, polypropylene is preferred. When polyolefin resins are copolymers, they may be block copolymers or random copolymers. These polyolefin resins may be used individually or in combination of two or more.

[0081] Furthermore, the polyolefin may be a cyclic polyolefin. A cyclic polyolefin is a copolymer of an olefin and a cyclic monomer. Examples of olefins that are constituent monomers of the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, isoprene, and the like. Examples of cyclic monomers that are constituent monomers of the cyclic polyolefin include cyclic alkenes such as norbornene; and cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, norbornadiene, and the like. Among these, cyclic alkenes are preferred, and norbornene is more preferred.

[0082] Acid-modified polyolefins are polymers obtained by modifying polyolefins through block polymerization or graft polymerization with an acid component. Examples of polyolefins that can be acid-modified include the aforementioned polyolefins, copolymers obtained by copolymerizing the aforementioned polyolefins with polar molecules such as acrylic acid or methacrylic acid, or polymers such as cross-linked polyolefins. Examples of acid components used for acid modification include carboxylic acids or their anhydrides, such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

[0083] Acid-modified polyolefins may also be acid-modified cyclic polyolefins. Acid-modified cyclic polyolefins are polymers obtained by copolymerizing a portion of the monomers constituting a cyclic polyolefin with an acid component, or by block polymerization or graft polymerization of an acid component to a cyclic polyolefin. The cyclic polyolefin to be acid-modified is the same as described above. Furthermore, the acid component used for acid modification is the same as the acid component used for modifying the polyolefin described above.

[0084] Preferred acid-modified polyolefins include polyolefins modified with carboxylic acids or their anhydrides, polypropylenes modified with carboxylic acids or their anhydrides, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

[0085] The heat-sealable resin layer 4 may be formed by a single resin or by a blended polymer of two or more resins. Furthermore, the heat-sealable resin layer 4 may be formed as a single layer or as two or more layers of the same or different resins.

[0086] Furthermore, the heat-fusible resin layer 4 may contain a lubricant or the like as needed. When the heat-fusible resin layer 4 contains a lubricant, the moldability of the exterior material for the energy storage device can be improved. The lubricant is not particularly limited, and known lubricants can be used. The lubricant may be used alone or in combination of two or more types.

[0087] The lubricant is not particularly limited, but amide-based lubricants are preferred. Specific examples of lubricants include those exemplified in base layer 1. The lubricant may be used alone or in combination of two or more types.

[0088] When a lubricant is present on the surface of the heat-fusible resin layer 4, the amount present is not particularly limited, but from the viewpoint of improving the moldability of the exterior material for energy storage devices, it is preferably 10 to 50 mg / m². 2 To a certain extent, more preferably 15-40 mg / m² 2 The degree can be described as follows.

[0089] The lubricant present on the surface of the heat-fusible resin layer 4 may be a lubricant contained in the resin constituting the heat-fusible resin layer 4 that has seeped out, or a lubricant may be applied to the surface of the heat-fusible resin layer 4.

[0090] Furthermore, the thickness of the heat-fusible resin layer 4 is not particularly limited as long as the heat-fusible resin layers heat-fuse together to seal the energy storage device elements, but for example, it can be about 100 μm or less, preferably about 85 μm or less, and more preferably about 15 to 85 μm. For example, if the thickness of the adhesive layer 5 described later is 10 μm or more, the thickness of the heat-fusible resin layer 4 can be preferably about 85 μm or less, and more preferably about 15 to 45 μm. For example, if the thickness of the adhesive layer 5 described later is less than 10 μm or if the adhesive layer 5 is not provided, the thickness of the heat-fusible resin layer 4 can be preferably about 20 μm or more, and more preferably about 35 to 85 μm.

[0091] [Adhesive layer 5] In the exterior material for energy storage devices of this disclosure, the adhesive layer 5 is provided between the barrier layer 3 (or corrosion-resistant coating) and the heat-fusible resin layer 4 as necessary in order to firmly bond them together. It is a layer.

[0092] The adhesive layer 5 is formed of a resin capable of bonding the barrier layer 3 and the heat-fusible resin layer 4. The resin used to form the adhesive layer 5 can be the same as the adhesive exemplified in the adhesive layer 2. Furthermore, from the viewpoint of firmly bonding the adhesive layer 5 to the heat-fusible resin layer 4, the resin used to form the adhesive layer 5 preferably contains a polyolefin skeleton, such as the polyolefin and acid-modified polyolefin exemplified in the heat-fusible resin layer 4. On the other hand, from the viewpoint of firmly bonding the barrier layer 3 and the adhesive layer 5, the adhesive layer 5 preferably contains an acid-modified polyolefin. Examples of acid-modified components include dicarboxylic acids such as maleic acid, itaconic acid, succinic acid, and adipic acid, their anhydrides, acrylic acid, and methacrylic acid, but maleic anhydride is most preferred in terms of ease of modification and versatility. Furthermore, from the viewpoint of heat resistance for the exterior material of the energy storage device, the olefin component is preferably a polypropylene-based resin, and the adhesive layer 5 most preferably contains maleic anhydride-modified polypropylene.

[0093] The presence of a polyolefin skeleton in the resin constituting the adhesive layer 5 can be analyzed by methods such as infrared spectroscopy and gas chromatography-mass spectrometry, and the analytical method is not particularly limited. Furthermore, the presence of an acid-modified polyolefin in the resin constituting the adhesive layer 5 can be determined, for example, by measuring maleic anhydride-modified polyolefin using infrared spectroscopy, at a wavenumber of 1760 cm⁻¹. -1 Nearby wave frequency 1780cm -1 A peak originating from maleic anhydride is detected in the vicinity. However, if the degree of acid denaturation is low, the peak may become small and not be detected. In that case, analysis is possible by nuclear magnetic resonance spectroscopy.

[0094] Furthermore, from the viewpoint of ensuring durability such as heat resistance and resistance to contents of the exterior material for energy storage devices, as well as ensuring moldability while keeping the thickness thin, it is more preferable that the adhesive layer 5 is a cured product of a resin composition containing an acid-modified polyolefin and a curing agent. The above-mentioned products are examples of the acid-modified polyolefin.

[0095] Furthermore, the adhesive layer 5 is preferably a cured product of a resin composition comprising an acid-modified polyolefin and at least one selected from the group consisting of compounds having isocyanate groups, compounds having oxazoline groups, and compounds having epoxy groups, and is particularly preferably a cured product of a resin composition comprising an acid-modified polyolefin and at least one selected from the group consisting of compounds having isocyanate groups and compounds having epoxy groups. Furthermore, the adhesive layer 5 preferably contains at least one selected from the group consisting of polyurethane, polyester, and epoxy resin, and more preferably contains polyurethane and epoxy resin. As polyester, for example, ester resins produced by the reaction of epoxy groups and maleic anhydride groups, and amide ester resins produced by the reaction of oxazoline groups and maleic anhydride groups are preferred. If unreacted curing agents such as compounds having isocyanate groups, compounds having oxazoline groups, and epoxy resins remain in the adhesive layer 5, the presence of unreacted substances can be confirmed by methods selected from, for example, infrared spectroscopy, Raman spectroscopy, and time-of-flight secondary ion mass spectrometry (TOF-SIMS).

[0096] Furthermore, from the viewpoint of further improving the adhesion between the barrier layer 3 and the adhesive layer 5, it is preferable that the adhesive layer 5 is a cured product of a resin composition containing a curing agent having at least one selected from the group consisting of oxygen atoms, heterocyclic rings, C=N bonds, and COC bonds. Examples of curing agents having heterocyclic rings include curing agents having oxazoline groups and curing agents having epoxy groups. Examples of curing agents having C=N bonds include curing agents having oxazoline groups and curing agents having isocyanate groups. Examples of curing agents having COC bonds include curing agents having oxazoline groups and curing agents having epoxy groups. The fact that the adhesive layer 5 is a cured product of a resin composition containing these curing agents can be confirmed by methods such as gas chromatography-mass spectrometry (GCMS), infrared spectroscopy (IR), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and X-ray photoelectron spectroscopy (XPS).

[0097] While there are no particular limitations on the compound having an isocyanate group, polyfunctional isocyanate compounds are preferred from the viewpoint of effectively improving the adhesion between the barrier layer 3 and the adhesive layer 5. The polyfunctional isocyanate compound is not particularly limited as long as it is a compound having two or more isocyanate groups. Specific examples of polyfunctional isocyanate curing agents include pentane diisocyanate (PDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymerized or nurated versions thereof, mixtures thereof, and copolymers with other polymers. Adducts, burettes, and isocyanurates are also examples.

[0098] The content of the compound having an isocyanate group in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, of the resin composition constituting the adhesive layer 5. This effectively enhances the adhesion between the barrier layer 3 and the adhesive layer 5.

[0099] Compounds containing an oxazoline group are not particularly limited as long as they have an oxazoline skeleton. Specific examples of compounds containing an oxazoline group include those with a polystyrene main chain and those with an acrylic main chain. Commercially available examples include the Epocross series manufactured by Nippon Shokubai Co., Ltd.

[0100] The proportion of the compound having an oxazoline group in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, of the resin composition constituting the adhesive layer 5. This effectively enhances the adhesion between the barrier layer 3 and the adhesive layer 5.

[0101] Examples of compounds having epoxy groups include epoxy resins. The epoxy resin is not particularly limited as long as it is capable of forming a crosslinked structure by the epoxy groups present in the molecule; known epoxy resins can be used. The weight-average molecular weight of the epoxy resin is preferably around 50 to 2000, more preferably around 100 to 1000, and even more preferably around 200 to 800. In the first disclosure, the weight-average molecular weight of the epoxy resin is the value measured by gel permeation chromatography (GPC) under conditions using polystyrene as a standard sample.

[0102] Specific examples of epoxy resins include glycidyl ether derivatives of trimethylolpropane, bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, bisphenol F type glycidyl ether, novolac glycidyl ether, glycerin polyglycidyl ether, and polyglycerin polyglycidyl ether. Epoxy resins may be used individually or in combination of two or more types.

[0103] The proportion of epoxy resin in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, of the resin composition constituting the adhesive layer 5. This effectively enhances the adhesion between the barrier layer 3 and the adhesive layer 5.

[0104] The polyurethane is not particularly limited, and any known polyurethane can be used. The adhesive layer 5 may be, for example, a cured product of a two-component polyurethane.

[0105] The proportion of polyurethane in the adhesive layer 5 is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 40% by mass, of the resin composition constituting the adhesive layer 5. This effectively enhances the adhesion between the barrier layer 3 and the adhesive layer 5 in an atmosphere where components that induce corrosion of the barrier layer, such as electrolytes, are present.

[0106] Furthermore, if the adhesive layer 5 is a cured product of a resin composition containing at least one compound selected from the group consisting of compounds having isocyanate groups, compounds having oxazoline groups, and epoxy resins, and the acid-modified polyolefin, the acid-modified polyolefin functions as the main agent, and the compounds having isocyanate groups, compounds having oxazoline groups, and compounds having epoxy groups each function as curing agents.

[0107] The adhesive layer 5 may contain a modifier having a carbodiimide group.

[0108] The thickness of the adhesive layer 5 is preferably about 50 μm or less, about 40 μm or less, about 30 μm or less, about 20 μm or less, or about 5 μm or less. Alternatively, the thickness of the adhesive layer 5 is preferably about 0.1 μm or more, or about 0.5 μm or more. The range of the thickness of the adhesive layer 5 is preferably about 0.1 to 50 μm, about 0.1 to 40 μm, about 0.1 to 30 μm, about 0.1 to 20 μm, about 0.1 to 5 μm, about 0.5 to 50 μm, about 0.5 to 40 μm, about 0.5 to 30 μm, about 0.5 to 20 μm, or about 0.5 to 5 μm. More specifically, in the case of the adhesive exemplified in adhesive layer 2, or the cured product of acid-modified polyolefin and a curing agent, the thickness is preferably about 1 to 10 μm, more preferably about 1 to 5 μm. Furthermore, when using the resin exemplified in the heat-fusible resin layer 4, the thickness is preferably about 2 to 50 μm, more preferably about 10 to 40 μm. When the adhesive layer 5 is the adhesive exemplified in the adhesive layer 2, or a cured product of a resin composition containing an acid-modified polyolefin and a curing agent, the adhesive layer 5 can be formed, for example, by applying the resin composition and curing it by heating. Also, when using the resin exemplified in the heat-fusible resin layer 4, it can be formed, for example, by extrusion molding of the heat-fusible resin layer 4 and the adhesive layer 5.

[0109] [Surface coating layer 6] The exterior material for energy storage devices of this disclosure may optionally include a surface coating layer 6 on the base layer 1 (on the side opposite to the barrier layer 3 of the base layer 1) for the purpose of improving at least one of the following: aesthetics, electrolyte resistance, scratch resistance, and moldability. The surface coating layer 6 is the outermost layer of the exterior material for energy storage devices when the energy storage device is assembled using the exterior material for energy storage devices.

[0110] The surface coating layer 6 can be formed from a resin such as polyvinylidene chloride, polyester, polyurethane, acrylic resin, or epoxy resin.

[0111] If the resin forming the surface coating layer 6 is a curable resin, it may be either a one-component curable resin or a two-component curable resin, but is preferably a two-component curable resin. Examples of two-component curable resins include two-component curable polyurethane, two-component curable polyester, and two-component curable epoxy resin. Among these, two-component curable polyurethane is preferred.

[0112] Examples of two-component curable polyurethanes include polyurethanes comprising a first agent containing a polyol compound and a second agent containing an isocyanate compound. Preferably, two-component curable polyurethanes include those comprising a polyol such as polyester polyol, polyether polyol, and acrylic polyol as the first agent and an aromatic or aliphatic polyisocyanate as the second agent. Examples of polyurethanes include polyurethanes comprising a polyurethane compound obtained by reacting a polyol compound and an isocyanate compound in advance, and an isocyanate compound. Examples of polyurethanes include polyurethanes comprising a polyurethane compound obtained by reacting a polyol compound and an isocyanate compound in advance, and a polyol compound. Examples of polyurethanes include polyurethanes cured by reacting a polyurethane compound obtained by reacting a polyol compound and an isocyanate compound in advance with moisture such as air. As the polyol compound, it is preferable to use a polyester polyol having hydroxyl groups on the side chains in addition to the hydroxyl groups at the ends of the repeating units. Examples of the second agent include aliphatic, alicyclic, aromatic, and aromaticaliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Polyfunctional isocyanate modified compounds derived from one or more of these diisocyanates are also possible. Furthermore, polymers (e.g., trimers) can be used as polyisocyanate compounds. Examples of such polymers include adducts, biuretes, and nurates. Furthermore, aliphatic isocyanate compounds refer to isocyanates that have an aliphatic group and no aromatic ring, alicyclic isocyanate compounds refer to isocyanates that have an alicyclic hydrocarbon group, and aromatic isocyanate compounds refer to isocyanates that have an aromatic ring.The surface coating layer 6 is formed of polyurethane, which provides the exterior material for energy storage devices with excellent electrolyte resistance.

[0113] The surface coating layer 6 may contain, as necessary, additives such as the aforementioned lubricants, antiblocking agents, matting agents, flame retardants, antioxidants, tackifiers, and antistatic agents in at least one of its surface and interior, depending on the functionality to be provided to the surface coating layer 6 and its surface. Examples of additives include fine particles with an average particle size of about 0.5 nm to 5 μm. The average particle size of the additive is the median diameter measured by a laser diffraction / scattering particle size distribution analyzer.

[0114] The additive may be either inorganic or organic. Furthermore, there are no particular restrictions on the shape of the additive; examples include spherical, fibrous, plate-like, amorphous, or flaky forms.

[0115] Specific examples of additives include talc, silica, graphite, kaolin, montmorillonite, mica, hydrotalcite, silica gel, zeolite, aluminum hydroxide, magnesium hydroxide, zinc oxide, magnesium oxide, aluminum oxide, neodymium oxide, antimony oxide, titanium oxide, cerium oxide, calcium sulfate, barium sulfate, calcium carbonate, calcium silicate, lithium carbonate, calcium benzoate, calcium oxalate, magnesium stearate, alumina, carbon black, carbon nanotubes, high-melting-point nylon, acrylate resin, cross-linked acrylic, cross-linked styrene, cross-linked polyethylene, benzoguanamine, gold, aluminum, copper, and nickel. Additives may be used individually or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferred from the viewpoint of dispersion stability and cost. In addition, various surface treatments such as insulation treatment and high-dispersibility treatment may be applied to the surface of the additives.

[0116] The method for forming the surface coating layer 6 is not particularly limited, and for example, a method of applying a resin to form the surface coating layer 6 can be used. If an additive is to be incorporated into the surface coating layer 6, the resin mixed with the additive can be applied.

[0117] The thickness of the surface coating layer 6 is not particularly limited as long as it performs the above-mentioned functions as a surface coating layer 6, and for example, it can be about 0.5 to 10 μm, preferably about 1 to 5 μm.

[0118] 3. Method for manufacturing exterior materials for energy storage devices The method for manufacturing the exterior material for energy storage devices is not particularly limited, as long as a laminate is obtained by laminating each layer of the exterior material for energy storage devices of the present invention. At a minimum, a method is provided which involves laminating the base material layer 1, the barrier layer 3, and the heat-fusible resin layer 4 in this order. That is, the method for manufacturing the exterior material 10 for energy storage devices of the present disclosure includes at a minimum step of laminating the base material layer 1, the barrier layer 3, and the heat-fusible resin layer 4 in this order to obtain a laminate, and a principal axis orientation measuring device equipped with a camera and a light source is used, and the base material layer is placed between the camera and the light source so that the direction of the camera of the measuring device and the MD direction of the base material layer 1 coincide, and the principal axis orientation of the base material layer 1 is measured by irradiating the base material layer with light from the light source in the thickness direction, and is within the range of 90°±30°.

[0119] An example of a method for manufacturing the exterior material for energy storage devices of the present invention is as follows. First, a laminate (hereinafter sometimes referred to as "laminated body A") is formed by sequentially laminating a base material layer 1, an adhesive layer 2, and a barrier layer 3. Specifically, laminate A can be formed by a dry lamination method in which the adhesive used to form the adhesive layer 2 is applied to the base material layer 1 or, if necessary, to the barrier layer 3 whose surface has been chemically treated, using a coating method such as gravure coating or roll coating, and after drying, the barrier layer 3 or base material layer 1 is laminated and the adhesive layer 2 is cured.

[0120] Next, a heat-fusible resin layer 4 is laminated onto the barrier layer 3 of laminate A. When the heat-fusible resin layer 4 is directly laminated onto the barrier layer 3, the heat-fusible resin layer 4 can be laminated onto the barrier layer 3 of laminate A by methods such as thermal lamination or extrusion lamination. When an adhesive layer 5 is provided between the barrier layer 3 and the heat-fusible resin layer 4, for example, (1) a method of laminating the adhesive layer 5 and the heat-fusible resin layer 4 by extrusion onto the barrier layer 3 of laminate A (co-extrusion lamination method, tandem lamination method), (2) a method of forming a laminate in which the adhesive layer 5 and the heat-fusible resin layer 4 are laminated separately, and then laminating this onto the barrier layer 3 of laminate A by thermal lamination, or a method of forming a laminate in which the adhesive layer 5 is laminated onto the barrier layer 3 of laminate A, and then laminating this with the heat-fusible resin layer 4 by thermal lamination. (3) A method of lamination by pouring a molten adhesive layer 5 between the barrier layer 3 of the laminate A and the heat-fusible resin layer 4 which has been previously formed into a sheet, thereby bonding the laminate A and the heat-fusible resin layer 4 via the adhesive layer 5 (sandwich lamination method); (4) A method of lamination by applying an adhesive solution to the barrier layer 3 of the laminate A to form the adhesive layer 5, drying it, or even baking it, and then laminating the heat-fusible resin layer 4 which has been previously formed into a sheet, onto this adhesive layer 5.

[0121] When a surface coating layer 6 is provided, the surface coating layer 6 is laminated on the surface of the base layer 1 opposite to the barrier layer 3. The surface coating layer 6 can be formed, for example, by applying the resin used to form the surface coating layer 6 to the surface of the base layer 1. The order of the steps of laminating the barrier layer 3 to the surface of the base layer 1 and laminating the surface coating layer 6 to the surface of the base layer 1 is not particularly limited. For example, the surface coating layer 6 may be formed on the surface of the base layer 1, and then the barrier layer 3 may be formed on the surface of the base layer 1 opposite to the surface coating layer 6.

[0122] As described above, a laminate is formed comprising, as necessary, a surface coating layer 6, a base material layer 1, an adhesive layer 2 as necessary, a barrier layer 3, an adhesive layer 5 as necessary, and a heat-fusible resin layer 4 in this order. In order to strengthen the adhesion of the adhesive layer 2 and adhesive layer 5 as necessary, the laminate may be subjected to further heat treatment.

[0123] In exterior materials for energy storage devices, the processability of each layer constituting the laminate may be improved by subjecting it to surface activation treatments such as corona treatment, blast treatment, oxidation treatment, or ozone treatment, as needed. For example, by applying corona treatment to the surface of the substrate layer 1 opposite to the barrier layer 3, the printability of ink on the surface of the substrate layer 1 can be improved.

[0124] 4. Applications of exterior materials for energy storage devices The exterior material for energy storage devices of this disclosure is used in packaging for sealing and housing energy storage device elements such as a positive electrode, a negative electrode, and an electrolyte. That is, an energy storage device can be formed by housing energy storage device elements, which include at least a positive electrode, a negative electrode, and an electrolyte, in packaging formed from the exterior material for energy storage devices of this disclosure.

[0125] Specifically, an energy storage device is provided by covering an energy storage device element, which comprises at least a positive electrode, a negative electrode, and an electrolyte, with the energy storage device exterior material of this disclosure, such that a flange portion (an area where heat-sealable resin layers come into contact) is formed around the periphery of the energy storage device element, with the metal terminals connected to the positive electrode and negative electrode respectively protruding outward, and then heat-sealing the heat-sealable resin layers of the flange portion to seal it. When housing the energy storage device element in a package formed from the energy storage device exterior material of this disclosure, the package is formed such that the heat-sealable resin portion of the energy storage device exterior material of this disclosure faces inward (the surface in contact with the energy storage device element). The packaging can be formed by overlapping the heat-sealable resin layers of two energy storage device casing materials facing each other and heat-sealing the periphery of the overlapped casing materials. Alternatively, as shown in the example in Figure 5, one energy storage device casing material can be folded and overlapped, and the periphery can be heat-sealed to form the packaging. When folding and overlapping, as shown in the example in Figure 5, the edges other than the folded edge can be heat-sealed to form a three-sided seal, or the edges can be folded to form a flange and then sealed on all four sides. Furthermore, the energy storage device casing material may have a recess for housing the energy storage device element formed by deep drawing or stretch molding. As shown in the example in Figure 5, one energy storage device casing material may have a recess while the other does not, or the other energy storage device casing material may also have a recess.

[0126] The casing material for energy storage devices disclosed herein can be suitably used in energy storage devices such as batteries (including capacitors, capacitors, etc.). Furthermore, the casing material for energy storage devices disclosed herein can be used in either primary batteries or secondary batteries, but is preferably used in secondary batteries. The types of secondary batteries to which the casing material for energy storage devices disclosed herein can be applied are not particularly limited, and examples include lithium-ion batteries, lithium-ion polymer batteries, all-solid-state batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, capacitors, capacitors, etc. Among these secondary batteries, lithium-ion batteries and lithium-ion polymer batteries are particularly suitable applications for the casing material for energy storage devices disclosed herein. [Examples]

[0127] 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.

[0128] <Manufacturing of exterior materials for energy storage devices> Examples 1, 2, 5, 6, 8 and Comparative Example 1 A biaxially oriented nylon film (Ny, thickness 20 μm or 15 μm as described in Table 1) was prepared as the base layer, and aluminum foil (JIS H4160:1994 A8021H-O, thickness 35 μm) with a corrosion-resistant coating formed on both sides was prepared as the barrier layer. The base layers used in Examples 1, 2, 5, 6, 8 and Comparative Example 1 each had the principal axis orientation described in Table 1. The principal axis orientation of the base layer was measured by the method described below. Next, the base layer and the barrier layer were laminated by dry lamination using a two-component curing urethane adhesive (polyol compound and aromatic isocyanate compound), and an aging treatment was performed to produce a laminate consisting of a base layer (thickness 20 μm or 15 μm) / adhesive layer (thickness after curing 3 μm) / barrier layer (thickness 35 μm).

[0129] Next, a maleic anhydride-modified polypropylene (PPa, 15 μm thick) as an adhesive layer and a polypropylene (PP, 15 μm thick) as a heat-sealable resin layer were co-extruded onto the barrier layer of the obtained laminate to laminate the adhesive layer / heat-sealable resin layer on the barrier layer. Then, the obtained laminate was aged and heated to obtain an exterior material for energy storage devices (thickness shown in Table 1) in which a biaxially oriented nylon film / adhesive layer / barrier layer / adhesive layer / heat-sealable resin layer was laminated in this order.

[0130] Example 3 Except for setting the barrier layer thickness to 30 μm, the adhesive layer thickness to 14 μm, and the heat-sealable resin layer thickness to 10 μm, an exterior material for an energy storage device (with the thicknesses listed in Table 1) was obtained in the same manner as in Example 2, with a biaxially oriented nylon film / adhesive layer / barrier layer / adhesive layer / heat-sealable resin layer laminated in this order.

[0131] Example 4 Except for forming a surface coating layer (3 μm thick) as the outermost layer of the exterior material for energy storage devices using a two-component curable urethane resin (containing silica particles (matting agent), polyol compound, and aromatic isocyanate compound) on the surface of the base layer, and using a two-component curable urethane adhesive containing carbon black (containing carbon black, polyol compound, and aromatic isocyanate compound) to form the adhesive layer between the base layer and the barrier layer, an exterior material for energy storage devices (with the thickness shown in Table 1) was obtained in the same manner as in Example 3, with the surface coating layer / biaxially oriented nylon film / adhesive layer / barrier layer / adhesive layer / heat-fusible resin layer laminated in this order.

[0132] Example 7 Except for the following differences, an exterior material for an energy storage device (with thicknesses listed in Table 1) was obtained in the same manner as in Example 6, in which a surface coating layer (3 μm thick) was formed on the surface of the base layer using a two-component curable urethane resin (containing silica particles (matting agent), polyol compound, and aromatic isocyanate compound) as the outermost layer of the exterior material for an energy storage device; a two-component curable urethane adhesive containing carbon black (containing carbon black, polyol compound, and aromatic isocyanate compound) was used to form the adhesive layer between the base layer and the barrier layer; the thickness of the adhesive layer was set to 14 μm; and the thickness of the heat-sealable resin layer was set to 10 μm.

[0133] Furthermore, erucic acid amide was applied as a lubricant to the outer surface of the base material layer of each energy storage device's exterior material.

[0134] <Measurement of the principal axis orientation> For each example and comparative example, the biaxially oriented nylon film used as the base layer was measured using a principal axis orientation measuring device equipped with a camera C and a light source LS, as shown in the schematic diagrams in Figures 6 to 8. The camera C of the measuring device, the base layer 1, and the light source LS were positioned in a straight line, and the base layer 1 was placed between the camera C and the light source LS. The TD direction of the base layer 1 was set to 0°, and the MD direction of the base layer 1 was set to 90°. The measurement was performed by irradiating the base layer 1 in the thickness direction D with light L from the light source LS. As shown in the schematic diagrams in Figures 6 and 7, during the measurement, light was irradiated in the thickness direction of the biaxially oriented nylon film (base layer 1) from a light source placed on the back side of the biaxially oriented nylon film (opposite side from the camera C side). A transparent glass plate G was placed on top of the base layer 1 (on the camera C side) to prevent wrinkles from forming on the surface of the base layer 1 during the measurement. Furthermore, although not shown in Figures 6 to 8, the substrate layer 1 and the glass plate G were arranged in order on a plate with an opening provided at the position where light was irradiated onto the substrate layer 1, and the measurement was performed so that light L was transmitted through the substrate layer 1 and the glass plate G through the opening in the plate. The measurement results are shown in Table 1. The specific measurement conditions are as follows. (Measurement conditions) Measurement device: Polarization high-speed imaging device (CRYSTA PI-5) manufactured by Photron Co., Ltd. Analysis software: KAMAKIRI Offline Basic Software Ver: 1.5.0.1 Measurement sample: Prepare by cutting a biaxially oriented nylon film to A4 size (TD210mm x MD300mm). Measurement wavelength (camera side): 520~570nm (The camera, which receives light transmitted through the film, detects light with a wavelength of 520~570nm) Light source: White LED light (The measurement sample is positioned so that the extension of the light source coincides with the thickness direction of the substrate layer, and the camera is positioned on the extension of the light source.)

[0135] <Evaluation of moldability> The exterior material for the energy storage device was cut into a rectangle with a length (MD (Machine Direction)) of 90 mm and a width (TD (Transverse Direction)) of 150 mm to serve as a test sample. This sample was cold-formed (single-stage pull-in forming) for 10 samples each, using a rectangular molding die (female mold, surface: maximum height roughness (nominal value Rz) of 3.2 μm, corner radius 2.0 mm, edge radius 1.0 mm) with a bore diameter of 31.6 mm (MD direction) × 54.5 mm (TD direction), and a corresponding molding die (male mold, surface: maximum height roughness (nominal value Rz) of 1.6 μm, corner radius 2.0 mm, edge radius 1.0 mm) as specified in Table 2 of the comparative surface roughness standard specimens for JIS B 0659-1:2002 Annex 1 (Reference) At this time, the test sample was placed on the female mold so that the heat-fusible resin layer was positioned on the male mold side, and molding was performed. The clearance between the male and female molds was set to 0.3 mm. After cold molding, the samples were examined in a dark room using a penlight to check for pinholes or cracks in the aluminum alloy foil by light transmission. The deepest molding depth at which no pinholes or cracks occurred in any of the 10 samples was defined as A mm, and the number of samples at the shallowest molding depth at which pinholes or cracks occurred was defined as B. The value calculated using the following formula was rounded to two decimal places and defined as the limit molding depth for the exterior material of the energy storage device. The depth criteria were determined in four stages for the cases where the base layer thickness was 20 μm and 15 μm, respectively. The results are shown in Table 1. Limit molding depth = A mm + (0.5 mm / 10 pieces) × (10 pieces - B pieces)

[0136] (Moldability evaluation criteria when the substrate layer thickness is 20 μm) A1: The limit molding depth is 7.5 mm or more. B1: Limit molding depth is 7.0 mm or more and less than 7.5 mm C1: Limit molding depth is 6.5 mm or more and less than 7.0 mm D1: Limit molding depth is less than 6.5 mm

[0137] (Moldability evaluation criteria when the substrate layer thickness is 15 μm) A2: The limit molding depth is 6.5 mm or more. B2: Limit molding depth is 6.0 mm or more and less than 6.5 mm C2: Limit molding depth is 5.5 mm or more and less than 6.0 mm D2: Limit molding depth is less than 5.5 mm

[0138] [Table 1]

[0139] The exterior materials for energy storage devices in Examples 1 to 8 show that the predetermined principal axis orientation of the base layer is within the range of 90° ± 30°, and that they exhibit excellent moldability.

[0140] Furthermore, when the phase difference of the substrate layer was also measured during the measurement of the principal axis orientation, the phase difference for Example 1 was 72.9 nm, for Example 2 it was 196.4 nm, for Example 5 it was 205.1 nm, for Example 6 it was 49.8 nm, for Example 8 it was 123.7 nm, and for Comparative Example 1 it was 228.7 nm. This shows that even with a phase difference of 210 nm or less, the outer casing material for energy storage devices exhibits excellent moldability.

[0141] Furthermore, for reference, the tensile breaking strength (MPa) of the biaxially oriented nylon film used as the base layer in Example 1 and Comparative Example 1 was measured. The tensile breaking strength of Example 1 was 270 MPa in the MD direction and 300 MPa in the TD direction, while the tensile breaking strength of Comparative Example 1 was 284 MPa in the MD direction and 320 MPa in the TD direction. Although the base layer of Comparative Example 1 had a higher tensile breaking strength than the base layer of Example 1, the moldability of the exterior material for the energy storage device was inferior in Comparative Example 1 compared to Example 1.

[0142] As described above, this disclosure provides inventions in the following embodiments. Item 1. The laminate comprises at least a base layer, a barrier layer, and a heat-fusible resin layer in this order. The aforementioned base material is an exterior material for an energy storage device, wherein the principal axis orientation, as measured by the following measurement method, is within the range of 90° ± 30°. [Measurement method] Using a principal axis orientation measuring device equipped with a camera and a light source, the camera of the measuring device, the substrate layer, and the light source are positioned in a straight line, the substrate layer is placed between the camera and the light source, and the substrate layer is positioned such that the TD direction of the substrate layer is 0° and the MD direction of the substrate layer is 90°, the principal axis orientation of the substrate layer is measured by irradiating the substrate layer with light from the light source in the thickness direction. Item 2. The exterior material for an energy storage device according to Item 1, wherein the thickness of the base material layer is 10 μm or more and 30 μm or less. Item 3. The exterior material for an energy storage device according to Item 1 or 2, wherein the base layer comprises at least one of a polyamide film and a polyester film. Item 4. The outer material for an energy storage device according to any one of items 1 to 3, wherein the thickness of the laminate is 100 μm or less. Item 5. An energy storage device in which an energy storage device element comprising at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed from an outer casing material for an energy storage device as described in any of Items 1 to 4. Item 6. The process includes at least a step of laminating a substrate layer, a barrier layer, and a heat-fusible resin layer in this order to obtain a laminate, A method for manufacturing an exterior material for an energy storage device, wherein the base material layer has a principal axis orientation within the range of 90°±30°, as measured by the following measurement method. [Measurement method] Using a principal axis orientation measuring device equipped with a camera and a light source, the camera of the measuring device, the substrate layer, and the light source are positioned in a straight line, the substrate layer is placed between the camera and the light source, and the principal axis orientation of the substrate layer is measured by irradiating the substrate layer with light from the light source in the thickness direction, with the TD direction of the substrate layer being 0° and the MD direction of the substrate layer being 90°. Item 7. The laminate comprises at least a base layer, a barrier layer, and a heat-fusible resin layer in this order. The aforementioned substrate layer is an exterior material for an energy storage device, wherein the phase difference, as measured by the following measurement method, is 210 nm or less. [Measurement method] Using a principal axis orientation measuring device equipped with a camera and a light source, the camera of the measuring device, the substrate layer, and the light source are positioned in a straight line, the substrate layer is placed between the camera and the light source, and the substrate layer is positioned such that the TD direction of the substrate layer is 0° and the MD direction of the substrate layer is 90°. In this case, the light from the light source is irradiated in the thickness direction of the substrate layer to measure the phase difference of the substrate layer. [Explanation of Symbols]

[0143] 1 Base material layer 2 Adhesive layer 3. Barrier layer 4 Heat-fusible resin layer 5 Adhesive layer 6 Surface coating layer 10. Exterior materials for energy storage devices

Claims

1. It is composed of a laminate comprising, at least, a base layer, an adhesive layer, a barrier layer, and a heat-fusible resin layer in this order. The direction of the MD of the substrate layer and the direction of the MD of the laminate coincide. The aforementioned base material is an exterior material for an energy storage device, wherein the principal axis orientation, as measured by the following measurement method, is within the range of 90° ± 30°. [Measurement method] Using a principal axis orientation measuring device equipped with a camera and a light source, the camera of the measuring device, the substrate layer, and the light source are positioned in a straight line, the substrate layer is placed between the camera and the light source, and the substrate layer is positioned such that the direction of the TD of the substrate layer is 0° and the direction of the MD of the substrate layer is 90°, the principal axis orientation of the substrate layer is measured by irradiating the substrate layer with light from the light source in the thickness direction.

2. The exterior material for an energy storage device according to claim 1, further comprising a surface coating layer on the side of the base material layer opposite to the barrier layer side.

3. The exterior material for an energy storage device according to claim 2, wherein the surface coating layer contains silica.

4. The exterior material for an energy storage device according to claim 2, wherein the surface coating layer contains titanium oxide.

5. The exterior material for an energy storage device according to claim 2, wherein the surface coating layer contains kaolin.

6. The adhesive layer comprises a coloring agent, as described in any one of claims 1 to 5, for exterior material for energy storage devices.

7. An exterior material for an energy storage device according to any one of claims 1 to 6, further comprising a colored layer between the base material layer and the barrier layer.

8. The substrate layer contains polyamide, The exterior material for an energy storage device according to any one of claims 1 to 7, wherein the polyamide includes an aromatic polyamide.

9. The process includes at least a step of obtaining a laminate by laminating a base layer, an adhesive layer, a barrier layer, and a heat-fusible resin layer in this order, The direction of the MD of the substrate layer and the direction of the MD of the laminate coincide. A method for manufacturing an exterior material for an energy storage device, wherein the base material layer has a principal axis orientation within the range of 90° ± 30°, as measured by the following measurement method. [Measurement method] Using a principal axis orientation measuring device equipped with a camera and a light source, the camera of the measuring device, the substrate layer, and the light source are positioned in a straight line, the substrate layer is placed between the camera and the light source, and the substrate layer is positioned such that the direction of the TD of the substrate layer is 0° and the direction of the MD of the substrate layer is 90°, the principal axis orientation of the substrate layer is measured by irradiating the substrate layer with light from the light source in the thickness direction.

10. An adhesive layer is provided between the barrier layer and the heat-fusible resin layer. A method for manufacturing an exterior material for an energy storage device according to claim 9, wherein the adhesive layer and the heat-fusible resin layer are formed by a co-extrusion lamination method, a tandem lamination method, a thermal lamination method, a sandwich lamination method, or a method of laminating an adhesive for forming the adhesive layer on the barrier layer and then laminating the heat-fusible resin layer, which has been previously formed into a sheet, on the adhesive layer.

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