Exterior material for power storage device, exterior case for power storage device, and power storage device

Abstract

This exterior material for a power storage device includes a base material layer, a barrier layer, and a heat-fusible resin layer, in the given order. The base material layer includes a layer A having an F-5 value, as determined from a tensile test, of 105 MPa or less.

Description

Exterior material for a power storage device, exterior case for a power storage device, and power storage device

[0001] The present disclosure relates to an exterior material for a power storage device, an exterior case for a power storage device, and a power storage device.

[0002] Power storage devices are used as energy suppliers for mobile devices such as electric vehicles and hybrid vehicles, and for portable devices such as power tools and mobile terminals. Conventionally, metal cans have been mainly used as the casings of power storage devices. However, in order to facilitate movement and carrying, there is a demand for weight reduction and miniaturization of power storage devices. Therefore, as the casing of a power storage device, an exterior material (also referred to as a laminate material) having a base material layer, a barrier layer, and a heat-sealable resin layer (also referred to as a sealant layer) in this order is often used.

[0003] The above-mentioned exterior material is arranged so that the heat-sealable resin layers face each other, sandwiches the main body part of the power storage device, and heat-seals the heat-sealable resin layers at the outer edge part of the exterior material, thereby accommodating and enclosing the main body part of the power storage device in the exterior material (see, for example, Patent Document 1).

[0004] In addition, power sources such as electric vehicles, large-scale power sources for power storage applications, capacitors, etc. are also increasingly being enclosed with exterior materials having the above structure. By forming the exterior material through processes such as overhanging molding and deep drawing molding, it is formed into a three-dimensional shape such as a substantially rectangular parallelepiped shape. By forming such a three-dimensional shape, a storage space for accommodating the main body part of the power storage device can be secured.

[0005] For example, Patent Document 2 discloses a laminated material for a secondary battery container, which is an A / B / C / D laminate in which at least one film (A) selected from polyethylene terephthalate, polyethylene naphthalate, and polylactic acid, a nylon 6 film (B), aluminum foil (C), and a polypropylene film (D) are laminated in this order, wherein B and D are unstretched films, a modified polyolefin layer is provided between C and D, and D contains 0.1 to 20 ppm by weight of at least one selected from erucic acid amide, oleic acid amide, stearic acid amide, and ethylenebisoleic acid amide.

[0006] Japanese Patent Publication No. 2023-89020, Japanese Patent No. 5453680

[0007] As the size of the main body of the energy storage device being housed increases, it is necessary to increase the molding depth of the outer material. However, increasing the molding depth stretches the outer material, causing excessive distortion and making it prone to defects such as pinholes and cracks.

[0008] Therefore, the present disclosure aims to provide an exterior material for energy storage devices, an exterior case for energy storage devices, and an energy storage device using the same, in which the occurrence of pinholes and cracks is suppressed even when the molding depth is increased.

[0009] This disclosure includes the following embodiments: <1> An exterior material for an energy storage device comprising a base layer, a barrier layer, and a heat-fusible resin layer in that order, wherein the base layer is composed of two or more layers, and the outermost layer of the base layer has an F-5 value of 105 MPa or less obtained by a tensile test. <2> The exterior material for an energy storage device according to <1>, wherein the outermost layer contains polyester. <3> An exterior material for an energy storage device comprising a base layer, a barrier layer, and a heat-fusible resin layer in that order, wherein the base layer includes a layer A that has an F-5 value of 105 MPa or less obtained by a tensile test and contains polyester. <4> The exterior material for an energy storage device according to any one of <1> to <3>, wherein the base layer is composed of two or more layers, and another layer B other than the outermost layer or layer A is positioned closer to the barrier layer than the outermost layer or layer A. <5> The exterior material for an energy storage device according to <4>, wherein the thickness of layer B is 20 μm or more. <6> An exterior material for an energy storage device according to <4> or <5>, wherein the layer B contains polyamide. <7> An exterior material for an energy storage device according to any one of <1> to <6>, wherein the thickness of the barrier layer is 50 μm or more. <8> An exterior case for an energy storage device, which is a molded body of the exterior material for an energy storage device according to any one of <1> to <7>. <9> An energy storage device comprising an energy storage device body and an exterior member containing the exterior material for an energy storage device according to any one of <1> to <7>, wherein the energy storage device body is exteriorized by the exterior member.

[0010] According to this disclosure, an exterior material for an energy storage device, an exterior case for an energy storage device, and an energy storage device using the same are provided, which suppress the occurrence of pinholes and cracks even when the molding depth is increased.

[0011] This is a schematic cross-sectional view showing an example of an exterior material for an energy storage device. This is a schematic cross-sectional view showing an example of an energy storage device. This is a schematic perspective view showing the components constituting the energy storage device in Figure 2, separated from each other.

[0012] The embodiments of this disclosure will be described in detail below. However, the embodiments of this disclosure are not limited to the embodiments described below. In the embodiments described below, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the embodiments of this disclosure. In numerical ranges indicated using "~" in this disclosure, the numerical values ​​before and after "~" are included as the minimum and maximum values, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Also, in numerical ranges described in this disclosure, the upper or lower limit of that numerical range may be replaced with the value shown in the example. In this disclosure, numerical ranges expressed using "greater than or equal to" are numerical ranges that include that number as the lower limit, and numerical ranges expressed using "less than or equal to" are numerical ranges that include that number as the upper limit. For example, the notation "2 mm or more" means a numerical range that includes 2 mm as the lower limit, and the notation "15 mm or less" means a numerical range that includes 15 mm as the upper limit. In this disclosure, each component may contain multiple types of the corresponding substance. If multiple types of the substance corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple types of substances present in the composition, unless otherwise specified. In this disclosure, each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified. In this disclosure, the term “layer” includes cases where the layer is formed over the entire region in which it exists, as well as cases where it is formed only on a part of the region in which it exists.

[0013] When describing embodiments in this disclosure with reference to the drawings, the configuration of such embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the components are not limited thereto.

[0014] In this disclosure, the thickness of each layer can be measured by a scanning electron microscope (SEM). The thickness in this disclosure is the average value obtained when measuring at five locations.

[0015] The F-5 value represents the force applied when the test specimen is stretched by 5%. It is close to the yield point and serves as an indicator of deformation beyond which stretching will occur. In this disclosure, the F-5 value is measured in accordance with JIS K 7127:1999. The test specimen is 15 mm wide and 150 mm long. The test specimen is fixed to a tensile testing machine with clamps, one end is fixed, and the other end is pulled. The tensile stress (F-5 value) at the point when the test specimen is stretched by 5% is read from the stress-strain curve. The gauge length is 50 mm, the tensile speed is 100 mm / min, and the test environment is 25°C.

[0016] <Exterior Material for Energy Storage Devices> The exterior material for energy storage devices of this disclosure (hereinafter sometimes abbreviated as "exterior material") comprises a base layer, a barrier layer, and a heat-fusible resin layer in that order, wherein the base layer includes a layer whose F-5 value obtained by a tensile test is 105 MPa or less. In the exterior material of the first embodiment, the base layer is composed of two or more layers, and the outermost layer of the base layer is the outermost layer, which has an F-5 value of 105 MPa or less. In the exterior material of the second embodiment, the layer with an F-5 value of 105 MPa or less includes polyester.

[0017] In other words, the exterior material of the first embodiment includes a base layer, a barrier layer, and a heat-fusible resin layer in that order, the base layer is composed of two or more layers, and the outermost layer of the base layer has an F-5 value of 105 MPa or less obtained by a tensile test. The exterior material of the second embodiment includes a base layer, a barrier layer, and a heat-fusible resin layer in that order, the base layer includes a layer A containing polyester, which has an F-5 value of 105 MPa or less obtained by a tensile test.

[0018] In the first embodiment, the outermost layer of the base material layer preferably contains polyester. In the second embodiment, the base material layer may consist of one layer A, or it may consist of two or more layers including other layers B. If the base material layer of the second embodiment includes other layers B, it is preferable that the other layers B be positioned closer to the barrier layer than layer A.

[0019] Exterior materials having the above configuration suppress the occurrence of pinholes and cracks even when the molding depth is increased. The reason for this is not clear, but it is presumed to be as follows: The base material layer, which is placed outside the barrier layer, is composed of a layer having an F-5 value of 105 MPa or less, which reduces the rigidity around the corners where the most strain occurs when the molding depth is increased. As a result, localized strain at the corners is suppressed, and consequently, the occurrence of pinholes and cracks is suppressed. Furthermore, it has been found that the F-5 value, which represents a low stress state where the elongation of the test piece is 5%, is particularly related to the occurrence of pinholes and cracks due to localized strain at the corners.

[0020] Furthermore, for layers with an F-5 value of 105 MPa or less, it is sufficient that the F-5 value is 105 MPa or less in at least one of the MD and TD layers.

[0021] Furthermore, in the case of exterior materials for energy storage devices, the Machine Direction (MD) and Transfer 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 made 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 of the laminate and determining 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.

[0022] 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 for energy storage devices 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 (Mid-Depth Direction).

[0023] Figure 1 is a schematic cross-sectional view showing an example of an exterior material for an energy storage device. An example of the layer structure of the exterior material for an energy storage device will be explained with reference to Figure 1. The exterior material 1 for an energy storage device includes, in this order, a first base layer 2A, a second base layer 2B, a barrier layer 4, and a heat-fusible resin layer (sealant layer) 3. In Figure 1, the first base layer 2A corresponds to the outermost layer and layer A, and the second base layer 2B corresponds to layer B.

[0024] In Figure 1, a second substrate layer 2B is provided on one side of the barrier layer 4 via a first adhesive layer 5. Also in Figure 1, a heat-fusible resin layer 3 is provided on the other side of the barrier layer 4 via a second adhesive layer 6. Furthermore, in Figure 1, the first substrate layer 2A and the second substrate layer 2B are bonded together via a third adhesive layer 7.

[0025] (Base Layer) The F-5 value of the first base layer 2A is 105 MPa or less, preferably 90 MPa or less, more preferably 85 MPa or less, and even more preferably 80 MPa or less, from the viewpoint of suppressing the occurrence of pinholes and cracks when the molding depth is increased. The lower limit of the F-5 value of the first base layer 2A is not particularly limited, but the lower the value, the better.

[0026] The thickness of the first base material layer 2A is preferably 5 μm or more from the viewpoint of processability. The thickness of the first base material layer 2A is preferably 15 μm or less, more preferably 12 μm or less, and even more preferably 9 μm or less, from the viewpoint of suppressing the occurrence of pinholes and cracks when the molding depth is increased.

[0027] The first base material layer 2A is preferably made of a heat-resistant resin. In this disclosure, a heat-resistant resin is a resin that does not melt at the heat-sealing temperature when heat-sealing the exterior material 1. The heat-resistant resin is preferably one that has a melting point 10°C or more higher than the melting point of the heat-fusible resin layer 3, and more preferably one that has a melting point 20°C or more higher than the melting point of the heat-fusible resin layer 3.

[0028] From the viewpoint of solvent resistance of the exterior material surface, it is preferable that the first base layer 2A in the second embodiment of the exterior material contains polyester, and that the first base layer 2A in the first embodiment of the exterior material contains polyester. Examples of polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), and it is preferable to use PET or PBT. PET may be uniaxially oriented or biaxially oriented. From the viewpoint of solvent resistance, biaxially oriented PET is preferred. PBT is also preferably biaxially oriented from the viewpoint of solvent resistance.

[0029] The F-5 value of the second base material layer 2B is preferably 70 MPa or less, more preferably 60 MPa or less, even more preferably 55 MPa or less, and particularly preferably 50 MPa or less, from the viewpoint of suppressing the occurrence of pinholes and cracks when the molding depth is increased. The lower limit of the F-5 value of the second base material layer 2B is not particularly limited, but from the viewpoint of strength when stacking energy storage devices enclosed in outer materials, it is preferably 35 MPa or more, more preferably 40 MPa or more, and even more preferably 45 MPa or more.

[0030] The thickness of the second base material layer 2B is preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 30 μm or more, from the viewpoint of suppressing the occurrence of pinholes and cracks when the molding depth is increased. The thickness of the second base material layer 2B is preferably 50 μm or less, more preferably 45 μm or less, and even more preferably 40 μm or less, from the viewpoint of thermal conductivity during sealing.

[0031] The second base layer 2B is preferably made of a heat-resistant resin. The heat-resistant resin is preferably one that has a melting point 10°C or more higher than the melting point of the heat-fusible resin layer 3, and more preferably one that has a melting point 20°C or more higher than the melting point of the heat-fusible resin layer 3.

[0032] The second base layer 2B preferably contains polyamide, from the viewpoint of suppressing localized strain at the corners and preventing the occurrence of pinholes and cracks. Examples of polyamide include nylon, such as 6 nylon film, 6,6 nylon film, and MXD nylon film. The nylon may be uniaxially oriented or biaxially oriented. From the viewpoint of increasing strength, biaxially oriented nylon is preferred.

[0033] The ratio of the F-5 value of the first substrate layer 2A to the F-5 value of the second substrate layer 2B is preferably 1.90 or less, more preferably 1.80 or less, even more preferably 1.70 or less, particularly preferably 1.60 or less, and extremely preferably 1.50 or less. There is no particular lower limit to the ratio of the F-5 value of the first substrate layer 2A to the F-5 value of the second substrate layer 2B.

[0034] The ratio of the thickness of the first base layer 2A to the thickness of the second base layer 2B is preferably 0.90 or less, more preferably 0.80 or less, even more preferably 0.70 or less, particularly preferably 0.60 or less, and extremely preferably 0.50 or less. There is no particular lower limit to the ratio of the thickness of the first base layer 2A to the thickness of the second base layer 2B.

[0035] The total thickness of the first base layer 2A and the second base layer 2B is preferably 25 μm to 55 μm, preferably 30 μm to 50 μm, and preferably 35 μm to 45 μm. Setting it above the lower limit tends to further suppress the occurrence of pinholes and cracks when the molding depth is increased. Setting it below the upper limit tends to allow heat to be transferred more easily during sealing, thus lowering the sealing temperature and shortening the sealing time.

[0036] (Barrier Layer) The barrier layer 4 plays a role in providing gas barrier properties to the exterior material 1, preventing the intrusion of oxygen and moisture. The barrier layer 4 is not particularly limited and can be a metal foil, a vapor-deposited film, a resin layer, etc. 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 resins used in the resin layer include fluorine-containing resins and ethylene vinyl alcohol copolymers. Examples of fluorine-containing resins include polymers mainly composed of polyvinylidene chloride and chlorotrifluoroethylene (CTFE), polymers mainly composed of tetrafluoroethylene (TFE), polymers having fluoroalkyl groups, and polymers mainly composed of fluoroalkyl units.

[0037] The barrier layer 4 may be a single layer or a multilayer of two or more layers. In the case of a multilayer, it may be a laminate of the same type of layer or a laminate of different types of layers. An example of a laminate of different types of layers is a combination of a vapor-deposited film and a resin layer.

[0038] Among the above, it is preferable that the barrier layer 4 includes a layer made of a metallic material. Examples of metallic materials constituting the barrier layer 4 include aluminum alloy, stainless steel, copper, nickel, titanium steel, and steel sheet. When used as a metallic foil, it is preferable that it includes at least one of aluminum alloy foil and stainless steel foil.

[0039] The thickness of the barrier layer 4 can be set as appropriate, preferably 5 μm or more, more preferably 10 μm or more, even more preferably 50 μm or more, particularly preferably 58 μm or more, and most preferably 70 μm or more. When the thickness of the barrier layer 4 is equal to or greater than the above lower limit, the occurrence of pinholes during rolling tends to be prevented when the barrier layer 4 is a metal foil. In the case of the exterior material of this disclosure, even if the barrier layer 4 is made thicker, such as 50 μm or more, it is possible to suppress the occurrence of pinholes and cracks when the molding depth is increased.

[0040] Furthermore, the thickness of the barrier layer 4 is preferably 150 μm or less, and more preferably 100 μm or less. When the thickness of the barrier layer 4 is below the above upper limit, the stress during molding such as stretch molding and deep drawing can be reduced, and the occurrence of pinholes and cracks when the molding depth is increased tends to be further suppressed.

[0041] When using a metal foil, from the perspective of preventing surface corrosion, the metal foil may be subjected to a chemical conversion treatment, and it is preferable that the chemical conversion treatment is performed at least on the surface on the side of the heat-sealable resin layer. Examples of the chemical treatment method include the following. For example, after applying any one of the aqueous solutions of 1) to 3) below to the surface of the degreased metal foil and then drying, a chemical conversion treatment is performed. 1) An aqueous solution containing phosphoric acid, chromic acid, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides. 2) An aqueous solution containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, and at least one compound selected from the group consisting of chromic acid and chromium (III) salts. 3) An aqueous solution containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, at least one compound selected from the group consisting of chromic acid and chromium (III) salts, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides.

[0042] The chemical conversion film formed by the chemical conversion treatment preferably has a chromium adhesion amount (per side) of 0.1 mg / m ２ to 50 mg / m ２ and particularly preferably 2 mg / m ２ to 20 mg / m ２ is preferred.

[0043] (Heat-sealable resin layer) The heat-sealable resin layer 3 serves to impart heat-sealing properties to the exterior material. The heat-sealable resin layer 3 contains a heat-sealable resin. The heat-sealable resin is selected such that it melts at the heat-sealing temperature, and a resin with a melting point below the heat-sealing temperature is chosen. The heat-sealable resin is not particularly limited as long as it has the above melting point, and it is preferably at least one selected from the group consisting of polyethylene, polypropylene, olefin copolymers, acid-modified products thereof, and ionomers. Polyolefin resins are preferred, and polyethylene resins or polypropylene resins can be exemplified, with propylene resins being particularly preferred. As propylene resins, unstretched films such as cast polypropylene (CPP) and inflation polypropylene (IPP) are preferred. As the propylene resin, in addition to a homopolymer of propylene (hPP), an ethylene-propylene copolymer containing ethylene and propylene as copolymerization components can be exemplified. The ethylene-propylene copolymer may be either a random copolymer (rPP) or a block copolymer (bPP).

[0044] Also, the heat-sealable resin layer 3 may be a single layer or a multi-layer. The multi-layer film constituting the multi-layer heat-sealable resin layer can be produced by coextrusion or the like. The multi-layer film may have two or more layers, and a three-layer multi-layer film is preferred. Among the various propylene resin films described above, a three-layer coextruded CPP film with hPP or bPP as the intermediate layer and rPP layers arranged on both outer sides of the intermediate layer is recommended in terms of excellent heat-sealing properties, delamination resistance, and insulation properties.

[0045] The thickness of the heat-sealable resin layer 3 is preferably 20 μm to 150 μm, and more preferably 30 μm to 100 μm. The total thickness of the multi-layer film is also preferably within the above range. The preferred thickness ratio of each layer of the three-layer film is, when the total thickness is 10, the layer on the side of the second adhesive layer 6: intermediate layer: outer layer (the innermost layer when assembling the exterior case) = 1 to 3: 4 to 8: 1 to 3.

[0046] Furthermore, a fatty acid amide-based lubricant may be added to the heat-fusible resin layer 3 to improve the slipperiness of the exterior material 1. The lubricant content in the heat-fusible resin layer 3 is preferably 500 ppm to 4000 ppm by mass.

[0047] The heat-fusible resin layer 3 may be applied using a resin film that has been formed in advance (the first method described later). The resin film used as the heat-fusible resin layer 3 may be a heat-fusible unstretched resin film layer. On the other hand, the heat-fusible resin that forms the heat-fusible resin layer 3 may be applied to the surface of the barrier layer 4 or the second adhesive layer 6 by extrusion molding, coating, etc. (the second method described later).

[0048] (First adhesive layer) The adhesive used in the first adhesive layer 5 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 first adhesive layer 5 may be a single layer or a multilayer layer of two or more layers.

[0049] Adhesive components include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymerized polyester; polyethers; polyurethanes; polyester polyurethanes; polyether polyurethanes; epoxy resins; phenolic resins; polyamides such as nylon 6, nylon 66, nylon 12, and 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. Adhesive components in thermosetting adhesives include polyolefin resins, epoxy resins, and (meth)acrylic resins. The adhesive components may be present individually or in combination of two or more types.

[0050] The first adhesive layer 5 may contain other components, such as colorants, thermoplastic elastomers, tackifiers, and fillers. Including a colorant in the first adhesive layer 5 yields a colored exterior material for energy storage devices. Known colorants such as pigments and dyes can be used. Furthermore, the colorant may be present alone or in combination of two or more types.

[0051] The thickness of the first adhesive layer 5 is preferably set to 1 μm to 5 μm, and more preferably to 1 μm to 3 μm from the viewpoint of thinning and lightening the exterior material 1.

[0052] (Second adhesive layer) The adhesive used in the second adhesive layer 6 is not particularly limited, and examples include the adhesives described in the first adhesive layer 5. In addition to the adhesives described in the first adhesive layer 5, other examples include polyolefin resins such as polyolefins, carboxylic acid-modified polyolefins, and metal-modified polyolefins, polyvinyl acetate resins, (meth)acrylic resins, and amino resins. These adhesives may be used individually or in combination of two or more types.

[0053] The thickness of the second adhesive layer 6 is preferably set to 1 μm to 5 μm, and more preferably to 1 μm to 3 μm from the viewpoint of thinning and lightening the exterior material 1. As described later in the method for manufacturing the exterior material for energy storage devices, the second adhesive layer 6 may be omitted depending on the method for forming the heat-fusible resin layer.

[0054] (Third Adhesive Layer) The adhesive used in the third adhesive layer 7 is not particularly limited, and examples include the adhesives described in the first adhesive layer 5. Preferably, the adhesive used in the third adhesive layer 7 is a cured product of an adhesive that uses one or more resins selected from polyurethane resins, polyester polyurethane resins, polyether polyurethane resins, polyether resins, and polyester resins as the main component and a polyfunctional isocyanate as the curing agent. Epoxy adhesives, acrylic adhesives, polyesteramide adhesives, or polyamide adhesives may also be used.

[0055] Examples of polyfunctional isocyanates include aromatic polyfunctional isocyanates, aliphatic polyfunctional isocyanates having an aromatic ring, and aliphatic polyfunctional isocyanates. Aromatic polyfunctional isocyanates are not particularly limited, but examples include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and triphenylmethane triisocyanate. Aliphatic polyfunctional isocyanates having an aromatic ring are not particularly limited, but examples include xylylene diisocyanate (XDI) and tetramethylxylylene diisocyanate (TMXDI). Aliphatic polyfunctional isocyanates are not particularly limited, but examples include hexamethylene diisocyanate (HDI).

[0056] The thickness of the third adhesive layer 7 is preferably set to 1 μm to 5 μm, and more preferably to 1 μm to 3 μm from the viewpoint of thinning and lightening the exterior material 1.

[0057] (Other components) The first base layer 2A, the second base layer 2B, and the heat-sealable resin layer 3 constituting the exterior material 1 for energy storage devices may further contain antioxidants, plasticizers, ultraviolet absorbers, antifungal agents, colorants (pigments, dyes, etc.), antistatic agents, rust inhibitors, hygroscopic agents, oxygen absorbers, etc. The plasticizer is not particularly limited and includes glycerin fatty acid ester monoglycerides, glycerin fatty acid ester acetylated monoglycerides, glycerin fatty acid ester organic acid monoglycerides, glycerin fatty acid ester medium-chain fatty acid triglycerides, polyglycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, special fatty acid esters, higher alcohol fatty acid esters, etc.

[0058] (Other layers) The surface of the first base material layer 2A opposite to the second base material layer 2B becomes the outermost surface of the exterior member when an exterior member is formed to surround the main body of the energy storage device. Therefore, a surface coating layer (not shown) may be provided as needed. The surface coating layer may be formed using a known coating agent or the like.

[0059] (Other layer configurations) In Figure 1, the base material is described as having a two-layer configuration, but the base material in the second embodiment may consist of only one layer of the first base material layer 2A, or it may consist of three or more layers.

[0060] (Applications) The exterior material for energy storage devices disclosed herein is also suitably used as an exterior material for lithium-ion secondary batteries. The exterior material for energy storage devices disclosed herein may be molded into an exterior case, and the main body of the energy storage device may be housed inside this exterior case. Alternatively, the exterior material for energy storage devices disclosed herein may be used without molding, with the main body of the energy storage device being fitted onto the exterior and its periphery being heat-sealed.

[0061] <Method for Manufacturing Outer Coverings for Energy Storage Devices> The method for manufacturing outer coverings for energy storage devices is not particularly limited as long as the above-described outer coverings for energy storage devices can be obtained. An example of a method for manufacturing outer coverings for energy storage devices is as follows.

[0062] A laminate A is produced by a dry lamination method in which an adhesive component for forming the first adhesive layer 5 is applied to the second base material layer 2B or barrier layer 4 by gravure coating, roll coating, etc., and after drying, the barrier layer 4 or the second base material layer 2B is laminated on top of it. If the adhesive component is a curable resin, the first adhesive layer 5 is cured by heating or the like after the barrier layer 4 or the second base material layer 2B is laminated onto the first adhesive layer 5.

[0063] Next, laminate B is produced by a dry lamination method in which an adhesive component for forming a third adhesive layer 7 is applied to the second base material layer 2B of laminate A by gravure coating, roll coating, or the like, and after drying, the first base material layer 2A is laminated on top of it.

[0064] Then, a heat-fusible resin layer 3 is provided on the barrier layer 4 of the laminate B. The heat-fusible resin layer 3 may be formed in advance as a resin film and placed on the barrier layer 4 (first method), or the heat-fusible resin that forms the heat-fusible resin layer 3 may be applied to the barrier layer 4 by extrusion molding, coating, etc. to form the heat-fusible resin layer 3 (second method).

[0065] In the first method, the barrier layer 4 and the heat-fusible resin layer 3 are bonded together by the second adhesive layer 6. In the second method, the second adhesive layer 6 may be omitted or may be provided.

[0066] When a second adhesive layer 6 is provided between the barrier layer 4 and the heat-fusible resin layer 3, the second adhesive layer 6 and the heat-fusible resin layer 3 can be laminated by methods such as extrusion lamination, thermal lamination, sandwich lamination, and dry lamination. Examples of extrusion lamination methods include laminating the second adhesive layer 6 and the heat-fusible resin layer 3 by extruding them onto the barrier layer 4 of the laminate B (co-extrusion lamination method, tandem lamination method, etc.). Examples of thermal lamination methods include forming a separate laminate C of the second adhesive layer 6 and the heat-fusible resin layer 3, and laminating them so that the second adhesive layer 6 of laminate C and the barrier layer 4 of laminate B face each other, or forming a laminate D with the second adhesive layer 6 on the barrier layer 4 of laminate B, and laminating the second adhesive layer 6 of laminate D with the heat-fusible resin layer 3. Sandwich lamination methods include pouring a molten second adhesive layer 6 between the barrier layer 4 of laminate B and a pre-formed heat-fusible resin layer 3 in film form. Dry lamination methods include solution coating of an adhesive component for forming the second adhesive layer 6 onto the barrier layer 4 of laminate B, drying or baking it, and then laminating the pre-formed heat-fusible resin layer 3 in film form onto this second adhesive layer 6.

[0067] <Outer Case for Energy Storage Device> The outer case for energy storage device of this disclosure is a molded body of the outer material for energy storage device of this disclosure. The outer material for energy storage device may be formed by deep drawing, stretch molding, etc. An example of the shape of the outer case for energy storage device is the outer case 10 shown in Figures 2 and 3, which will be described later.

[0068] <Energy Storage Device> The energy storage device of this disclosure comprises an energy storage device body and an exterior member including an exterior material for the energy storage device of this disclosure, wherein the energy storage device body is enclosed by the exterior member. The exterior member may include an exterior case for the energy storage device of this disclosure.

[0069] An example of a power storage device 100 constructed using the exterior material 1 for power storage devices of this disclosure is shown in Figures 2 and 3. Figure 2 is a schematic cross-sectional view showing an example of a power storage device. Figure 3 is a schematic perspective view showing the components constituting the power storage device of Figure 2 separated. The power storage device 100 is a lithium-ion secondary battery.

[0070] In Figures 2 and 3, the exterior member 15 is composed of an exterior case 10, which is a molded exterior material 1, and a flat exterior material 1. The main body of the energy storage device (electrochemical element, etc.) 110 is housed in a recess in the exterior case 10. The flat exterior material 1 is positioned with the heat-sealable resin layer 3 facing inward (downward in Figures 2 and 3), and the peripheral edge of the heat-sealable resin layer 3 of the flat exterior material 1 and the heat-sealable resin layer 3 of the flange portion (sealing peripheral edge portion) 37 of the exterior case 10 are sealed by heat fusion (heat sealing).

[0071] In Figure 2, reference numeral 39 denotes a heat-sealed portion where the peripheral edge of the exterior material 1 and the flange portion (sealing peripheral edge) 37 of the exterior case 10 are joined (welded). In the energy storage device 100, the tip of the tab lead connected to the main body portion 110 of the energy storage device is led out to the outside of the exterior member 15, but this is not shown in the figure.

[0072] The main body 110 of the energy storage device is not particularly limited and may include a battery body, a capacitor body, a capacitor body, etc.

[0073] From the viewpoint of ensuring a secure seal, the width of the heat-seal portion 39 is preferably set to 0.5 mm or more, and more preferably to 3 mm to 15 mm.

[0074] The depth of the outer casing 10 may be 10 mm or more, or 15 mm or more. Even if the molding depth is increased, the occurrence of pinholes and cracks is suppressed when the outer casing material of this disclosure is used.

[0075] The embodiment will be described in detail below with reference to examples. However, this embodiment is not limited to the following examples.

[0076] Exterior materials 1 with the laminated configuration shown in Figure 1 were fabricated as Examples 1 to 41 and Comparative Examples 1 to 5. These exterior materials 1 all share the common feature of having the following layers laminated from the outside to the inside: a first base material 2A, a third adhesive layer 7, a second base material layer 2B, a first adhesive layer 5, a barrier layer 4, a second adhesive layer 6, and a heat-fusible resin layer 3. However, the F-5 value and thickness of the first base material layer 2A and the thickness of the second base material 2B differ. The F-5 values ​​of the first base material 2A and the second base material layer 2B were measured using MD (see Tables 1 to 3).

[0077] The materials common to the exterior materials in each example are as follows:

[0078] (Common materials) As the barrier layer 4, aluminum foil made of A8021-O as specified in JIS H4160, with thicknesses of 80 μm, 60 μm, and 50 μm was used. A chemical conversion treatment solution consisting of phosphoric acid, polyacrylic acid (acrylic resin), chromium (III) salt compound, water, and alcohol was applied to both sides of the aluminum foil, and then dried at 180°C to form a chemical conversion film. The amount of chromium deposited on this chemical conversion film was 10 mg / m² per side. ２ That is the case.

[0079] A biaxially oriented nylon 6 film with a thickness of 15 to 38 μm was used as the second base material layer 2B. Both sides of the biaxially oriented nylon 6 film were subjected to corona treatment.

[0080] A cast polypropylene (CPP) film with a thickness of 80 μm was used as the heat-sealable resin layer 3.

[0081] A two-component curing urethane adhesive was used as the first adhesive layer 5. An olefin-based adhesive was used as the second adhesive layer 6. A polyester urethane-based adhesive was used as the third adhesive layer 7.

[0082] (Fabrication of exterior material) A first adhesive layer 5 with a thickness of 4 μm was formed on one side of the barrier layer 4 on which a chemical conversion film was formed, and the second base material layer 2B was dry laminated to obtain a first intermediate laminate. Furthermore, a third adhesive layer 7 with a thickness of 4 μm was formed on the surface of the second base material layer 2B of the first intermediate laminate, and the first base material layer 2A was dry laminated. After that, the second intermediate laminate was fabricated by aging at 60°C for 7 days.

[0083] A second adhesive layer 6 with a thickness of 3 μm was formed on the other side of the barrier layer 4 of the second intermediate laminate, and the heat-fusible resin layer 3 was dry-laminated. Then, it was aged at 40°C for 10 days to produce the exterior material.

[0084] (Evaluation of moldability) The fabricated exterior material was cut to 100 mm x 125 mm to be used as molding material. Then, using a punch (punch shape: 33 mm x 54 mm, corner radius: 2 mm, punch shoulder radius: 1.3 mm) and a die (die shape: die shoulder radius: 1 mm), deep drawing was performed using a press machine manufactured by Amada Corporation (model number: TP-25C-XZ). Deep drawing was performed by bringing the top surface of the punch into contact with the heat-fusible resin layer 3 of the molding material and causing the first base material layer 2A to protrude outwards, and the molding depth D was changed in increments of 0.5 mm.

[0085] Then, the corners of the molded product were illuminated and visually inspected for the presence or absence of light transmission due to pinholes and cracks. The maximum molding depth (mm) at which good molding without pinholes or cracks could be achieved was determined, and the moldability was evaluated based on the following criteria, with those meeting evaluation criteria A, B, and C being considered acceptable.

[0086] A: Maximum molding depth of 15 mm or more B: Maximum molding depth of 10 mm or more but less than 15 mm C: Maximum molding depth of 6 mm or more but less than 10 mm D: Maximum molding depth of less than 6 mm

[0087]

[0088]

[0089]

[0090] Examples 1 to 41 include a first base layer (outermost layer) with an F-5 value of 105 MPa or less, or a first base layer (outermost layer) with an F-5 value of 105 MPa or less and containing polyester. As shown in Tables 1 to 3, no pinholes or cracks occurred in Examples 1 to 41 even when the molding depth was 10 mm or more. In contrast, Comparative Examples 1 to 5 have a first base layer, which is the outermost layer of the base layer, with an F-5 value greater than 105 MPa, or a second base layer with an F-5 value of 105 MPa or less, but the second base layer does not contain polyester. In Comparative Examples 1 to 5, pinholes and cracks occurred when the molding depth was 10 mm or more.

[0091] The disclosure of Japanese Patent Application No. 2024-185286 is incorporated in its entirety by reference. All documents, patent applications, and technical standards in this disclosure are incorporated by reference to the same extent as if each individual document, patent application, and technical standard had been specifically and individually noted as being incorporated by reference.

[0092] 1. Exterior material for energy storage device 2A. First base layer 2B. Second base layer 3. Heat-fusible resin layer 4. Barrier layer 5. First adhesive layer 6. Second adhesive layer 7. Third adhesive layer 10. Exterior case 15. Exterior component 100. Energy storage device 110. Main body of energy storage device

Claims

1. An exterior material for an energy storage device, comprising a base layer, a barrier layer, and a heat-sealable resin layer in that order, wherein the base layer is composed of two or more layers, and the outermost layer of the base layer has an F-5 value of 105 MPa or less obtained by a tensile test.

2. The outermost layer comprises polyester, as described in claim 1, for the exterior material of an energy storage device.

3. An exterior material for an energy storage device, comprising a base layer, a barrier layer, and a heat-sealable resin layer in that order, wherein the base layer includes a polyester layer A having an F-5 value of 105 MPa or less obtained by a tensile test.

4. The exterior material for an energy storage device according to claim 1 or 3, wherein the base material layer is composed of two or more layers, and the outermost layer or another layer B other than layer A is positioned closer to the barrier layer than the outermost layer or layer A.

5. The exterior material for an energy storage device according to claim 4, wherein the thickness of layer B is 20 μm or more.

6. The exterior material for an energy storage device according to claim 4, wherein layer B contains polyamide.

7. The exterior material for an energy storage device according to claim 1 or claim 3, wherein the thickness of the barrier layer is 50 μm or more.

8. An outer case for an energy storage device, which is a molded body of the outer material for an energy storage device according to claim 1 or claim 3.

9. An energy storage device comprising: an energy storage device main body; and an exterior member including an exterior material for an energy storage device as described in claim 1 or claim 3, wherein the energy storage device main body is covered by the exterior member.

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