Jacket material for power storage device, jacket case for the power storage device, and the power storage device

Abstract

To provide a jacket material for a power storage device, capable of suppressing a curl of a flange part.SOLUTION: A jacket material 1 for a power storage device, is formed by laminating, in order from an outside to an inside, at least a base material layer 2, a barrier layer 3, and a heat-seal property resin layer 4. When a thickness of the heat-seal property resin layer 4 is a (a unit: μm), and an extension of a TD direction in a weight 2 N in a tension test that the heat-seal property resin layer 4 is measured under the following test condition as a compliance to JIS K7127 is b (a unit: %), and a value of a×b / 100 is a c value, the c value is 0.25 μm or more. However, the test condition is that a test piece width of 15 mm×a distance between marked lines of 100 mm (a test piece length is 180 mm), and a test speed of 100 mm / min.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In power storage devices (such as lithium-ion secondary batteries, all-solid-state batteries, various capacitors, etc.) used in large batteries (for vehicles, stationary types, etc.), small batteries (for notebook computers, mobile phones, cameras, etc.), etc., the power storage device body (such as a battery body) is externally covered with an exterior material. As this exterior material, an exterior material made of a metal-resin laminate material in which resin films are laminated on the inner surface and the outer surface of a metal foil, respectively, is used. In this exterior material, the outer layer laminated on the outer surface side of the metal foil is called a base material layer, and the innermost layer laminated on the inner surface side of the metal foil constitutes a heat-sealing resin layer as a sealant layer. The heat-sealing resin of the heat-sealing resin layer generally consists of a thermoplastic resin.

[0003] When manufacturing an exterior case for a power storage device with this exterior material, the exterior material is cut into blanks (workpieces to be processed) of a predetermined shape and size, and these blanks are press-processed into a container shape to manufacture the exterior case body. Generally, deep drawing forming is used as the press process.

[0004] During deep drawing forming, the outer peripheral portion of the blank is pressed by a blank holder (wrinkle suppressing member) to form the flange portion of the exterior case body. However, since the processing stress escapes to the flange portion during the forming process, curl is likely to occur in the flange portion. The curl generated in the flange portion causes misalignment and grasping failure in automatic conveyance using a robot arm or a suction cup.

[0005] Various measures for suppressing the curl generated in the flange portion have been proposed (Patent Documents 1-5).

[0006] Patent Document 1 proposes to define the thicknesses of the respective layers constituting the exterior material and the total thickness. Patent Document 2 proposes to define the thickness of the adhesive layer and the thickness of the sealant layer, and to set the total thickness of the adhesive layer and the sealant layer to be 3 times or more the thickness of the base material layer. Patent Document 3 proposes to satisfy a predetermined relationship regarding the stress at 10% elongation in the MD direction and TD direction of the exterior material and the stress at 10% elongation in the MD direction and TD direction of the base material layer. Patent Document 4 proposes that the ratio of the intensities of two predetermined absorption peaks in the infrared absorption spectrum of the polyester film constituting the base material layer is within a predetermined range. Patent Document 5 proposes to define the thickness of the exterior material and that the product of the stress value and the thickness at 10% elongation of the heat-sealable resin layer is a predetermined value or more.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0008] Thus, in order to suppress the curl generated in the flange portion, the inventor focused on the fact that the layer with the largest deformation in the deformation of the exterior material at the die shoulder, which has the greatest influence on the curl during the molding process, is the heat-sealable resin layer, examined the suppression of curl by the heat-sealable resin layer, and completed the present invention.

[0009] That is, the present invention has been made by the inventors paying attention to characteristics different from those of the exterior material proposed in the above patent document. An object of the present invention is to provide an exterior material for a power storage device capable of suppressing curling of a flange portion. Another object of the present invention is to provide an exterior case for a power storage device in which curling of the flange portion is suppressed and a power storage device including the exterior case.

Means for Solving the Problems

[0010] The present invention provides the following means.

[0011] 1) An exterior material for a power storage device in which at least a base material layer, a barrier layer, and a heat-sealable resin layer are laminated in order from the outside to the inside, wherein the thickness of the heat-sealable resin layer is a (unit: μm), and in a tensile test measured under the following test conditions in accordance with JIS K7127, the elongation in the TD direction at a load of 2 N is b (unit: %), and when the value of a × b / 100 is defined as the c value, an exterior material for a power storage device in which the c value is 0.25 μm or more. However, the test conditions are as follows. Test piece width 15 mm × gauge length 100 mm (test piece length 180 mm) Test speed 100 mm / min.

[0012] 2) The exterior material for a power storage device according to item 1 above, wherein the c value is in the range of 0.25 μm to 0.30 μm.

[0013] 3) The exterior material for a power storage device according to item 1 or 2 above, wherein a is in the range of 20 μm to 130 μm.

[0014] 4) The exterior material for a power storage device according to any one of claims 1 to 3, wherein b is in the range of 0.2% to 1.3%.

[0015] 5) An exterior case for a power storage device formed of the exterior material for a power storage device according to any one of items 1 to 4 above.

[0016] 6) A power storage device in which a power storage device main body is housed in an exterior case for a power storage device formed of the exterior material for a power storage device according to any one of 1 to 4 in the preceding paragraph.

Advantages of the Invention

[0017] The present invention has the following effects.

[0018] In the preceding paragraph 1, since the c value is 0.25 μm or more, it is possible to suppress the curl generated in the flange portion during the molding process of the exterior material.

[0019] In the preceding paragraph 2, since the c value is within a predetermined range, it is possible to surely suppress the curl of the flange portion.

[0020] In the preceding paragraph 3, since a is within a predetermined range, it is possible to surely suppress the curl of the flange portion.

[0021] In the preceding paragraph 4, since b is within a predetermined range, it is possible to surely suppress the curl of the flange portion.

[0022] In the preceding paragraph 5, it is possible to provide an exterior case for a power storage device in which the curl of the flange portion is suppressed.

[0023] In the preceding paragraph 6, it is possible to provide a power storage device including an exterior case for a power storage device in which the curl of the flange portion is suppressed.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

BEST MODE FOR CARRYING OUT THE INVENTION

[0025] An embodiment of the present invention will be described below with reference to the drawings.

[0026] As shown in FIG. 1, an exterior material 1 for a power storage device according to an embodiment of the present invention is composed of a sheet-like laminate in which at least a base material layer 2, a barrier layer 3, and a heat-sealable resin layer 4 are laminated in order from the outside to the inside. That is, the exterior material 1 includes a base material layer 2 as an outer layer, a heat-sealable resin layer 4 as an inner layer (specifically, the innermost layer), and a barrier layer 3 as an intermediate layer disposed between the base material layer 2 and the heat-sealable resin layer 4 in a laminated state. In the figure, reference numeral "1a" is the inner surface of the exterior material 1, and reference numeral "1b" is the outer surface of the exterior material 1.

[0027] The base material layer 2 and the barrier layer 3 are bonded together via an outer adhesive layer 5, and the barrier layer 3 and the heat-sealable resin layer 4 are bonded together via an inner adhesive layer 6. Therefore, the base material layer 2, the barrier layer 3, and the heat-sealable resin layer 4 are integrally bonded. The barrier layer 3 has a metal foil layer 3A, and specifically, the barrier layer 3 is composed of the metal foil layer 3A.

[0028] The exterior material 1 is used for the exterior of the power storage device 30 as shown in FIG. 2. The power storage device 30 is, for example, a battery 30A such as a lithium ion secondary battery or a all-solid-state battery.

[0029] The battery 30A as the power storage device 30 includes a battery body 31A as the power storage device body 31 and an exterior case 20 that externally wraps the battery body 31A in a surrounding state. The exterior case 20 includes an exterior case body 21 in the shape of a container with one side open (specifically, a rectangular container shape), and a flat exterior lid 26 that closes the opening of the exterior case body 21.

[0030] The exterior case body 21 is formed by deep drawing processing of an exterior material 1 into a container shape (specifically, a rectangular container shape) with its inner surface 1a facing inward. Therefore, the exterior case body 21 is made of a deep drawn product of the exterior material 1. The battery body 31A is housed in the container portion (specifically, the rectangular container portion) 22 of the exterior case body 21. The container portion 22 has a bottom wall 23 and a peripheral wall 24, and a flange portion 25 as a joining planned portion is bent outwardly from the upper end of the peripheral wall 24.

[0031] The exterior lid 26 is used in a flat state without being formed from the exterior material 1, and the outer peripheral portion 27 of the exterior lid 26 is the joining planned portion of the exterior lid 26.

[0032] In the battery 30A, with the battery body 31A housed in the container portion 22 of the exterior case body 21, the exterior lid 26 is disposed on the exterior case body 21 so as to close the opening of the exterior case body 21 with its inner surface 1a facing the battery body 31A side. And the heat - fusible resin layer 4 of the flange portion 25 of the exterior case body 21 and the heat - fusible resin layer 4 of the outer peripheral portion 27 of the exterior lid 26 are heat - fused (joined) in a sealed state by heat sealing. Thereby, the battery 30A in a state where the entire battery body 31A is externally wrapped by the exterior case 20 is configured.

[0033] Note that the reference numeral "28" in FIG. 2 indicates the heat-sealed portion (heat-sealing portion) between the heat-sealable resin layer 4 of the flange portion 25 of the outer case body 21 and the heat-sealable resin layer 4 of the outer peripheral portion 27 of the outer lid 26. A tab lead (not shown) connected to the battery body 31A is sandwiched between the flange portion 25 of the outer case body 21 and the outer peripheral portion 27 of the outer lid 26 and is led out to the outside of the outer case 20 through the space between the flange portion 25 of the outer case body 21 and the outer peripheral portion 27 of the outer lid 26 from the battery body 31A.

[0034] The method of manufacturing the outer case body 21 with the outer packaging material 1 is as follows.

[0035] The outer packaging material 1 is cut into a blank (workpiece) 1A of a predetermined shape and size (see FIG. 5). The shape of the blank 1A is, for example, a rectangular shape. Then, as shown in FIG. 3, the blank 1A is deep-drawn into a container shape to manufacture the outer case body 21.

[0036] That is, when deep-drawing the blank 1A, the blank 1A is placed on the die 51 equipped in the deep-drawing machine 50 with its inner layer side (the heat-sealable resin layer 4 side) facing upward, and the flange portion 25 formed by the outer peripheral portion of the blank 1A is pressed from above by a blank holder (wrinkle suppressing member) 52, and the flange portion 25 is sandwiched and held between the die 51 and the blank holder 52. In this state, when the punch 53 moves downward, the substantially central portion of the blank 1A is pressed and deformed downward by the punch 53, and the blank 1A is formed into a container shape. Then, the sandwiching of the flange portion 25 by the die 51 and the blank holder 52 is released, and the blank 1A is taken out from the die 51.

[0037] During this molding process, due to the processing stress relieved in the flange portion 25, curling is likely to occur in the flange portion 25 as shown in FIGS. 6 and 7. Regarding the direction of curling occurring in the flange portion 25, in the present embodiment, when the flange portion 25 curls toward the outer surface 1b side (substrate layer 2 side) of the exterior material 1 (blank 1A) as shown in FIG. 6, it is defined as “+” (positive), and when the flange portion 25 curls toward the inner surface 1a side (heat-sealable resin layer 4 side) of the exterior material 1 (blank 1A) as shown in FIG. 7, it is defined as “−” (negative).

[0038] As shown in FIG. 4, in the deformation of the exterior material 1 (blank 1A) at the die shoulder 51a that most affects curling during this molding process, the layer with the largest deformation among the plurality of layers constituting the exterior material 1 is the heat-sealable resin layer 4. In the same figure, chemical conversion films (see FIG. 1, 3a) formed on both the inner and outer surfaces of the metal foil layer 3A, which will be described later, are not shown.

[0039] In order to suppress curling occurring in the flange portion 25, the properties of the heat-sealable resin layer 4 are set as follows.

[0040] Let the thickness of the heat-sealable resin layer 4 be a (unit: μm), and in a tensile test measured under the following test conditions in accordance with JIS (Japanese Industrial Standards) K7127:1999), let the elongation in the TD direction at a load of 2 N be b (unit: %), and the value of a×b / 100 be the c value. The test conditions are as follows.

[0041] (Test Conditions) · Test piece width 15 mm × gauge length 100 mm (test piece length 180 mm) · Test speed 100 mm / min.

[0042] Also, the test piece type is “2”.

[0043] Note that the TD direction (Transverse Direction) of the heat-sealable resin layer 4 means a direction perpendicular to the MD direction (Machine Direction) of the heat-sealable resin layer 4.

[0044] The change in the resistance of the heat - fusible resin layer 4 to external stress (hereinafter referred to as resistance) due to the increase or decrease in the thickness of the heat - fusible resin layer 4 and the elongation in the elastic deformation range (i.e., before the yield point) of the heat - fusible resin layer 4 mutually affect the force with which the heat - fusible resin layer 4 tries to return to its original state (i.e., the elastic restoring force of the heat - fusible resin layer 4). Therefore, the spring - back amount of the heat - fusible resin layer 4 can be estimated by the product value of the two parameters, the thickness and the elongation, of the heat - fusible resin layer 4.

[0045] The reason why the test load is 2 N in the above tensile test is that the elongation of the heat - fusible resin layer 4 surely occurs in the elastic deformation range, and the tensile stress estimated from the amount of drawing of the flange portion 25 generated during the deep - drawing forming process when manufacturing the outer case body 21 of a general shape and size by deep - drawing forming is approximately equivalent to the tensile stress acting on the test piece when the test load is 2 N.

[0046] In order to suppress the curl of the flange portion 25, it is preferable that the c value is 0.25 μm or more. In this case, the heat - fusible resin layer 4 has appropriate resistance and appropriate elongation. When this heat - fusible resin layer 4 is arranged at the position where the deformation at the die shoulder 51a is the largest during the forming process, even if curl occurs in the flange portion 25 during the forming process, the degree of curl is suppressed by the spring - back effect of the heat - fusible resin layer 4.

[0047] Furthermore, it is preferable that the c value is in the range of 0.25 μm to 0.30 μm. Since the c value is 0.30 μm or less, the heat - fusible resin layer 4 can maintain appropriate resistance and appropriate elongation. Therefore, the heat - fusible resin layer 4 can surely exhibit the spring - back effect and the degree of curl is surely suppressed.

[0048] The thickness a of the heat-sealing resin layer 4 is preferably in the range of 20 μm to 130 μm. When a is 20 μm or more, it is possible to surely suppress the occurrence of breakage and pinholes in the exterior material 1 (blank 1A) during the molding process. Therefore, the heat-sealing resin layer 4 can more surely exhibit the spring-back effect and the degree of curl is more surely suppressed. When a is 130 μm or less, it is possible to surely suppress the occurrence of cracks in the exterior material 1 (blank 1A). Therefore, the heat-sealing resin layer 4 can more surely exhibit the spring-back effect and the degree of curl is more surely suppressed. The particularly preferred lower limit of a is 40 μm, and the particularly preferred upper limit of a is 80 μm.

[0049] The elongation b of the heat-sealing resin layer 4 is preferably in the range of 0.2% to 1.3%. When b is 0.2% or more, it is possible to surely suppress the occurrence of cracks in the exterior material 1 (blank 1A) during the molding process. Therefore, the heat-sealing resin layer 4 can more surely exhibit the spring-back effect and the degree of curl is more surely suppressed. When b is 1.3% or less, the heat-sealing resin layer 4 can sufficiently obtain the elastic restoring force. Therefore, the heat-sealing resin layer 4 can more surely exhibit the spring-back effect and the degree of curl is more surely suppressed. The particularly preferred upper limit of b is 0.5%.

[0050] Regarding the measurement of the thickness a and elongation b of the heat-sealing resin layer 4, when the heat-sealing resin layer 4 is made of a heat-sealing resin film and is not yet adhered to the barrier layer 3, a test piece is sampled from the heat-sealing resin film before being adhered to the barrier layer 3, and the thickness a and elongation b are measured. When the heat-sealing resin film has been adhered to the barrier layer 3, after dissolving and removing the layers other than the heat-sealing resin film (barrier layer 3, inner adhesive layer 6, base material layer 2, outer adhesive layer 5, etc.) from the heat-sealing resin film with an acid, a solvent, etc., a test piece may be sampled from the heat-sealing resin film and the thickness a and elongation b may be measured.

[0051] Here, in the tensile test of measuring the heat-sealable resin layer 4 under the above test conditions, the elongation b in the TD direction at a load of 2 N is the elongation in the elastic deformation range of the heat-sealable resin layer 4.

[0052] The configuration of the exterior material 1 will be described in detail below with reference to FIG. 1.

[0053] (Heat-sealable resin layer 4) The heat-sealable resin layer 4 is made of, for example, a heat-sealable resin film.

[0054] The heat-sealable resin of the heat-sealable resin layer 4 (heat-sealable resin film) is made of a thermoplastic resin. The type of the heat-sealable resin is not limited. Representative heat-sealable resins include single substances and copolymers of polyolefin resins (e.g., polypropylene, polyethylene), and specifically, propylene-based resins such as cast polypropylene (CPP) and inflation polypropylene (IPP) can be mentioned. Further, as the propylene-based resin, in addition to a homopolymer of propylene (hPP), an ethylene-propylene copolymer containing ethylene and propylene as copolymer components can be exemplified. Examples of the ethylene-propylene copolymer include an ethylene-propylene block copolymer (bPP) and an ethylene-propylene random copolymer (rPP). As the heat-sealable resin layer 4, it is preferable to use an unstretched film (e.g., CPP film) of the above-described heat-sealable resin.

[0055] In addition to the above, as the heat-sealable resin, polyamide resins (such as 6-nylon), polyester resins (such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT)), vinylidene chloride polymers (PVDC), vinylidene chloride-methyl acrylate copolymers, ethylene-vinylidene copolymers (EVOH), etc. can be used.

[0056] Furthermore, the heat-sealable resin layer 4 may be formed of either a single-layer film or a multi-layer (including multiple layers) film of a heat-sealable resin. The multi-layer film can be produced by co-extrusion or the like. When the heat-sealable resin is, for example, a polypropylene-based resin, as a multi-layer film, a three-layer film in which rPP films as coating layers are laminated and integrated on both sides of a bPP film as an intermediate layer (i.e., rPP / bPP / rPP film), a three-layer film in which rPP films as coating layers are laminated and integrated on both sides of an hPP film as an intermediate layer (i.e., rPP / hPP / rPP film), etc. are used.

[0057] The adjustment of the elongation b of the heat-sealable resin layer 4 can be performed by changing the thickness of the heat-sealable resin layer 4, changing the component ratio of the heat-sealable resin, or by controlling the molecular weight of the heat-sealable resin by changing the manufacturing method of the heat-sealable resin. For example, when using rPP as the heat-sealable resin, the elongation b can be adjusted by changing the ethylene content in the rPP. Also, when the heat-sealable resin layer 4 is composed of the above-mentioned three-layer film (such as rPP / bPP / rPP film, rPP / hPP / rPP film, etc.), the adjustment of the elongation b can be performed by changing the mixing ratio of ethylene and propylene or by changing the layer thickness ratio in the three-layer film.

[0058] (Base material layer 2) The base material layer 2 is preferably made of a heat-resistant resin film that does not melt at the heat-sealing temperature (heat-sealing temperature) when heat-sealing a predetermined portion of the exterior material 1 by heat-sealing. In particular, the heat-resistant resin of the heat-resistant resin film preferably has heat resistance with a melting point 10°C or more, preferably 20°C or more higher than the melting point of the heat-sealable resin of the heat-sealable resin layer 4.

[0059] Specifically, as the heat-resistant resin film, a biaxially stretched polyamide film, a biaxially stretched polyester film, a biaxially stretched polyolefin film, a polyimide film, etc. are used.

[0060] In the biaxially stretched polyamide film, examples of the polyamide film include a 6-nylon film, a 6,6-nylon film, etc. In the biaxially stretched polyester film, examples of the polyester film include a polyethylene terephthalate (PET) film, a polybutylene terephthalate (PBT) film, a polyethylene naphthalate (PEN) film, etc. Examples of the biaxially stretched polyolefin film include a biaxially stretched polypropylene (OPP) film, etc.

[0061] The thickness of the base material layer 2 is not limited, and it is preferably in the range of 6 μm to 50 μm. A particularly preferred lower limit of the thickness of the base material layer 2 is 9 μm, and a particularly preferred upper limit is 30 μm.

[0062] The base material layer 2 is generally composed of a single layer, but it may also be composed of multiple layers (e.g., polyester film / polyamide film). In the case of multiple layers, the multiple layers are generally laminated via an adhesive layer. If the multiple layers are, for example, resin layers of the same type, the multiple layers may be continuously laminated by coextrusion.

[0063] Further, the base material layer 2 is not limited to being composed of a heat-resistant resin film, and it may also be composed of a coat layer of a heat-resistant resin or a layer formed by combining a base material film and a coat layer.

[0064] When the base material layer 2 is composed of a coat layer, the material of the base material layer (coat layer) 2 is preferably a resin such as polyamide, polyester, epoxy resin, polyamideimide resin, etc., and fillers such as inorganic particles (e.g., silica particles, alumina particles, kaolin particles, calcium oxide particles, calcium carbonate particles, calcium sulfate particles, barium sulfate particles, calcium silicate particles) or lubricants may be added to the resin to improve heat resistance and slipperiness. Also, when the base material layer 2 is composed of a coat layer, its thickness is preferably in the range of 1 μm to 5 μm.

[0065] (Barrier layer 3) The barrier layer 3 has the role of imparting to the exterior material 1 the property of blocking oxygen and moisture (e.g., gas barrier property). The barrier layer 3 generally consists of a metal foil layer 3A. As the metal foil of the metal foil layer 3A, aluminum foil, iron foil (including stainless steel foil), copper foil, nickel foil, titanium foil, metal clad foil, etc. are used, and particularly aluminum foil, and among them, the O material of 1000 series or 8000 series aluminum foil defined in JIS H4160:2006 is preferably used.

[0066] The thickness of the barrier layer 3 (metal foil layer 3A) is not limited, and it is preferably in the range of 10 μm to 120 μm. The particularly preferred lower limit of the thickness of the barrier layer 3 is 35 μm, and the particularly preferred upper limit is 90 μm.

[0067] When the barrier layer 3 is the metal foil layer 3A, it is preferable that a base treatment film such as a chemical conversion film (3a, indicated by dot hatching) for enhancing corrosion resistance is formed on at least one of the inner surface and the outer surface of the metal foil layer 3A. The formation of the chemical conversion film 3a is performed by subjecting the surface of the metal foil of the metal foil layer 3A to, for example, chromate treatment or non-chromium type chemical conversion treatment using a zirconium compound or the like.

[0068] For example, in the case of chromate treatment, an aqueous solution of any one of the following mixtures 1) to 3) is applied to the surface of the degreased metal foil and then dried.

[0069] 1) A mixture of phosphoric acid, chromic acid, and at least one of a metal salt of fluoride and a non-metal salt of fluoride 2) A mixture of phosphoric acid, any one of an acrylic resin, a chitosan derivative resin, and a phenolic resin, and at least one of chromic acid and a chromium(III) salt 3) A mixture of phosphoric acid, any one of an acrylic resin, a chitosan derivative resin, and a phenolic resin, at least one of chromic acid and a chromium(III) salt, and at least one of a metal salt of fluoride and a non-metal salt of fluoride.

[0070] The chromium deposition amount of the formation film 3a is not limited, and it is preferably in the range of 0.1 mg / m 2 ~50 mg / m 2 and more preferably in the range of 2 mg / m 2 ~20 mg / m 2 .

[0071] (Outer adhesive layer 5) The outer adhesive layer 5 is a layer responsible for joining (adhering) the base material layer 2 and the barrier layer 3, and is interposed between the base material layer 2 and the barrier layer 3. The thickness of the outer adhesive layer 5 is not limited, and it is preferably in the range of 1 μm to 5 μm.

[0072] The type of the outer adhesive layer 5 is not limited, and examples thereof include an adhesive layer formed of a two-component curable adhesive. As the two-component curable adhesive, urethane resins, polyester polyurethane resins, polyether polyurethane resins, epoxy resins, etc. are used.

[0073] For example, as the two-component curable adhesive, a two-component curable adhesive composed of a first agent (main agent) composed of one or more polyols selected from the group consisting of polyurethane polyols, polyester polyols, polyether polyols, and polyester urethane polyols and a second liquid (curing agent) composed of isocyanate is used.

[0074] The method for joining (adhering) the base material layer 2 and the barrier layer 3 is not limited, and for example, a dry lamination method can be mentioned.

[0075] (Inner adhesive layer 6) The inner adhesive layer 6 has an adhesive component such as an adhesive or an adhesive resin interposed between the barrier layer 3 and the heat-fusible resin layer 4, and is a layer that joins (adheres) the barrier layer 3 and the heat-fusible resin layer 4 in a laminated state through this adhesive component. The thickness of the inner adhesive layer 6 is not limited, and it is preferably in the range of 2 μm to 30 μm.

[0076] The types of the adhesive and the adhesive resin of the inner adhesive layer 6 are not limited. For example, as the adhesive, an adhesive containing one or more of a polyurethane resin, an acrylic resin, an epoxy resin, a polyolefin resin, an elastomer resin, a fluorine resin, and an acid-modified polypropylene resin is used.

[0077] The method of joining (adhering) the barrier layer 3 and the heat-sealable resin layer 4 is not limited, and examples thereof include a dry lamination method and a heat lamination method.

[0078] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention.

[0079] For example, in the exterior material according to the present invention, the heat-sealable resin layer is not limited to being composed of a heat-sealable resin film. In addition, for example, a heat-sealable resin layer laminated on the inner surface side of the barrier layer by an extrusion lamination method may be used.

[0080] Furthermore, the exterior material according to the present invention is not limited to having a plurality of layers shown in FIG. 1. In addition, for example, a new layer may be added to the plurality of layers shown in FIG. 1 to add or improve the function of the exterior material.

Examples

[0081] Specific examples and comparative examples of the present invention are shown below. However, the present invention is not limited to the following examples.

[0082]

Table 1

[0083] In Examples 1 to 12 and Comparative Examples 1 to 3, the evaluation exterior material 1 was produced by the following method.

[0084] As the metal foil layer 3A constituting the barrier layer 3, an aluminum foil with a thickness of 35 μm was prepared. The material of the aluminum foil is the aluminum alloy symbol A8021-O material specified in JIS H4160:2006. Chemical conversion films 3a were formed on both the inner and outer surfaces of this aluminum foil. The formation of this chemical conversion film 3a was carried out by applying a chemical conversion treatment liquid composed of phosphoric acid, polyacrylic acid (acrylic resin), chromium(III) salt compound, water, and alcohol to both surfaces of the aluminum foil, and then drying at 180 °C. The chromium adhesion amount of the chemical conversion film 3a was 3 mg / m per one side of the aluminum foil. 2 It was.

[0085] Next, a two-component curable polyurethane-based adhesive as the adhesive of the outer adhesive layer 5 was applied to the outer surface of the aluminum foil, and a biaxially stretched 6-nylon film with a thickness of 25 μm as the base material layer 2 was laminated to the outer surface of the aluminum foil via this outer adhesive layer 5 by the dry lamination method. The thickness of the outer adhesive layer 5 was 2 μm.

[0086] Next, a two-component curable maleic acid-modified polypropylene adhesive as the adhesive of the inner adhesive layer 6 was applied to the inner surface of the aluminum foil, and a CPP film having the composition and thickness a described in the "Thermal fusion resin layer" column of Table 1 as the thermal fusion resin layer 4 was laminated to the inner surface of the aluminum foil via this inner adhesive layer 6. Thereby, a sheet-like laminate in which the biaxially stretched 6-nylon film layer (base material layer 2), the aluminum foil layer (metal foil layer 3A), and the CPP film layer (thermal fusion resin layer 4) were laminated and integrated was produced. The thickness of the inner adhesive layer 6 was 3 μm.

[0087] In addition, in the "Composition" column in the "Thermal fusion resin layer" column of the same table, the numerical value in parentheses means the thickness (unit: μm).

[0088] Next, the laminate was aged at 40 °C for 10 days to produce the exterior material 1 for evaluation.

[0089] (Tensile test) A test piece for a tensile test in the TD direction was taken from the CCP film used as the heat-sealing resin layer 4. In the test piece, the test piece width was 15 mm × the gauge length was 100 mm, and the test piece length was 180 mm, and the test piece type was "2". Then, using a "Strograph (AGS-5kNX)" manufactured by Shimadzu Corporation as a tensile testing machine, a tensile test was conducted on this test piece under the test conditions of a test speed of 100 mm / min and a load of 2 N in accordance with JIS K7127:1999, and the elongation b (unit: %) in the TD direction at a load of 2 N was measured. The results were described in the "Elongation b" column of Table 1. In the tensile test, the elongation b in the TD direction at a load of 2 N for all the test pieces occurred in the elastic deformation region.

[0090] Also, a c value (= a × b / 100) was calculated using the above thickness a and the above elongation b of the CPP film, and the results were described in the "c value" column of Table 1.

[0091] (Evaluation of curling property) The evaluation exterior material 1 was cut into a rectangular blank (workpiece to be processed) 1A with a length of 100 mm and a width of 150 mm shown in FIG. 5. Also, a die set for deep drawing forming including a die 51, a punch 53, and a blank holder 52 was attached to a servo press machine to form a deep drawing forming machine 50. Then, the blank 1A was placed on the die 51 with its inner layer side (the heat-sealing resin layer 4 side) facing upward, and the flange portion 25 formed by the outer peripheral portion of the blank 1A was held sandwiched between the die 51 and the blank holder 52 by pressing it from above with the blank holder 52. In this state, by lowering the punch, the central portion of the blank 1A was pressed and deformed downward by the punch 53 to form the blank 1A into a square container shape. Then, the clamping of the flange portion 25 by the die 51 and the blank holder 52 was released, and the blank 1A was taken out from the die 51 to manufacture the exterior case body 21.

[0092] Note that the portion 8 indicated by the cross-hatching in the blank 1A was the portion pressed by the punch 53 at the start of the above-described deep drawing forming process, and this portion 8 was a rectangular portion with a length of 33 mm and a width of 54 mm at the center of the blank 1A.

[0093] The outer case body 21 has a container part (specifically, a rectangular container part) 22 and a flange part 25 that bends outwardly and protrudingly from the upper end of the peripheral wall 24 of the container part 22. Regarding the dimensions of the container part 22, the bottom wall 23 was rectangular with a length of 33 mm in the vertical direction and 54 mm in the horizontal direction, and a depth of 5 mm.

[0094] Next, in order to examine the degree of curl generated in the flange part 25 of the outer case body 21, as shown in FIGS. 6 and 7, the outer case body 21 was placed on the horizontal and flat top surface 61 of the flat table 60 with the opening of its container part 22 facing downward, and the height h of the end P of the flange part 25 with the upper end position O of the peripheral wall 24 of the container part 22 as the reference height position was measured, and the result was described in the "curling property" column of Table 1.

[0095] Here, the definitions of "+" (positive) and "-" (negative) in the direction of curl generated in the flange part 25 are as described above. That is, as shown in FIG. 6, when the flange part 25 curls toward the outer surface 1b side (base material layer 2 side) of the exterior material 1 (blank 1A), it is defined as "+" (positive), and as shown in FIG. 7, when the flange part 25 curls toward the inner surface 1a side (heat-sealable resin layer 4 side) of the exterior material 1 (blank 1A), it is defined as "-" (negative). Also, the height h of the end P of the flange part 25 was taken as the curl amount h of the flange part 25.

[0096] The meanings of the symbols in the "curling property" column of the same table are as follows. Note that "A", "B", and "C" were regarded as passing for the evaluation of curling property, and "D" was regarded as failing.

[0097] A: -5 mm ≤ h ≤ 5 mm B: -6 mm ≤ h < -5 mm, or 5 mm < h ≤ 6 mm C: -7 mm ≤ h < -6 mm, or 6 mm < h ≤ 7 mm D: h < -7 mm, or 7 mm < h.

[0098] (Evaluation of formability) A press working machine manufactured by Amada Co., Ltd. was prepared as a deep drawing forming machine. Then, the outer case body 21 was manufactured by performing deep drawing forming on the blank 1A cut from the evaluation exterior material 1 using this press working machine while varying the forming depth. The bottom wall 23 of the container part 22 of the outer case body 21 had a rectangular shape with a length of 33 mm in the vertical direction and 54 mm in the horizontal direction.

[0099] The presence or absence of cracks and pinholes was examined by the light transmission method in a dark room at four corner parts of the outer case body 21, and the formability of the exterior material 1 was evaluated. The results were described in the "Formability" column of Table 1.

[0100] The meanings of the symbols in the "Formability" column of the same table are as follows. Note that "A" and "B" were regarded as passing for the evaluation of formability, and "C" was regarded as failing.

[0101] A: No cracks and pinholes with a maximum forming depth of 6 mm or more B: No cracks and pinholes with a maximum forming depth of 5 mm or more and less than 6 mm C: Cracks or / and pinholes with a maximum forming depth of less than 5 mm.

[0102] As can be seen from Table 1, for the exterior materials of Examples 1 to 12 where the c value is 0.25 μm or more, the "Curling property" column is either "A", "B", or "C", that is, the curl amount h of the flange part 25 is small, and thus it was confirmed that the curling of the flange part 25 is suppressed.

Industrial Applicability

[0103] The present invention can be used for an exterior material for a power storage device, an outer case for a power storage device, and a power storage device.

Explanation of Symbols

[0104] 1: Exterior material 1A: Blank 2: Base material layer 3: Barrier layer 3A: Metal foil layer 4: Heat-sealable resin layer 20: Exterior case 21: Exterior case main body 22: Container part 25: Flange part 26: Exterior lid 30: Power storage device 30A: Battery 51: Die 52: Flange holder 53: Punch

Claims

1. An exterior material for a power storage device in which a base material layer, a barrier layer, and a heat-sealable resin layer are laminated in order from the outside to the inside, wherein the thickness of the heat-sealable resin layer is a (unit: μm), and in a tensile test measured under the following test conditions in accordance with JIS K7127, the elongation in the TD direction at a load of 2 N is b (unit: %), and when the value of a×b / 100 is defined as the c value, An exterior material for a power storage device, wherein the c value is 0.25 μm or more. However, the test conditions are as follows. Test piece width 15 mm × gauge length 100 mm (test piece length 180 mm) Test speed 100 mm / min.

2. The exterior material for a power storage device according to claim 1, wherein the c value is in the range of 0.25 μm to 0.30 μm.

3. The exterior material for a power storage device according to claim 1 or 2, wherein a is in the range of 20 μm to 130 μm.

4. The exterior case for a power storage device formed of the exterior material for a power storage device according to claim 1 or 2.

5. A power storage device in which a power storage device body is housed in an exterior case for a power storage device formed of the exterior material for a power storage device according to claim 1 or 2.

6. A power storage device in which a power storage device body is housed in an exterior case for a power storage device formed of the exterior material for a power storage device according to claim 1 or 2.

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