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

Abstract

To provide an exterior material for a power storage device that has high sealing strength and is capable of suppressing the generation of bubbles.SOLUTION: An exterior material for a power storage device includes a substrate layer, a barrier layer, an adhesive layer, and a sealant layer laminated in this order, and at least one of the adhesive and sealant layers has a swelling degree of 12% to 40% when exposed to an electrolyte solution, which is a mixture of diethyl carbonate (DEC) and propyl propionate (PrPr) in a 1:1 (mass ratio).SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In recent years, with the thinning and weight reduction of mobile electric devices such as smartphones and tablet terminals, as an exterior material for power storage devices such as lithium-ion secondary batteries, lithium polymer secondary batteries, lithium-ion capacitors, and electric double-layer capacitors mounted on these devices, instead of conventional metal cans, a laminate composed of a heat-resistant resin layer / adhesive layer / metal foil layer / adhesive layer / thermoplastic resin layer (inner sealant layer) is used. In addition, power sources for electric vehicles, large power sources for power storage applications, capacitors, etc. are also increasingly being externally packaged with the laminate (exterior material) having the above configuration. By performing bulging molding or deep drawing molding on the laminate, 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 power storage device main body can be secured.

[0003] In order to be formed into such a three-dimensional shape in a good state without pinholes, breaks, etc., it is required to improve the slipperiness of the surface of the inner sealant layer. As a method for improving the slipperiness of the surface of the inner sealant layer, adding an antiblocking agent to the inner sealant layer can be mentioned. However, if an excessive amount of antiblocking agent is added to the inner sealant layer, the inner sealant layer is likely to become cloudy, and due to the cloudiness of the sealant layer, there is a problem that it is easy to overlook delamination in the exterior material during quality inspection.

[0004] In Patent Document 1, an exterior material for a power storage device has been proposed that can ensure good slidability during molding, ensure good moldability, and suppress cloudiness in the exterior material.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent No. 6936093 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] For example, a power storage device is obtained by joining an inner sealant layer by heat sealing with a power storage device main body portion housed in an outer case obtained by molding an exterior material for a power storage device as described in Patent Document 1. In the power storage device, in order to enhance rapid chargeability, an electrolytic solution having a high ratio of a low-viscosity solvent may be employed. However, when a low-viscosity solvent is used, there is a risk that the seal strength of the heat-sealed portion decreases and the reliability of the heat seal deteriorates.

[0007] Furthermore, when a low-viscosity solvent is used, bubbles are likely to be generated due to volatilization of the electrolytic solution or the like at the heat-sealed portion, which may cause deterioration of the appearance of the heat-sealed portion and a decrease in the reliability of the heat seal.

[0008] From the above points, there is a demand for an exterior material for a power storage device having a high seal strength and capable of suppressing bubble generation.

[0009] An object of the present disclosure is to provide an exterior material for a power storage device having a high seal strength and capable of suppressing bubble generation, a sealant film, an outer case for a power storage device using the above-described exterior material for a power storage device, and a power storage device. [Means for Solving the Problems]

[0010] Specific means for achieving the above problems are as follows. <1> A base material layer, a barrier layer, an adhesive layer, and a sealant layer are laminated in this order. At least one layer included in the adhesive layer and the sealant layer is an exterior material for a power storage device which is a layer satisfying a swelling degree of 12% to 40% with respect to an electrolytic solution that is a mixed solution of diethyl carbonate (DEC) / propyl propionate (PrPr) = 1:1 (mass ratio). <2> The sealant layer includes at least two heat-sealable resin layers. The outermost layer on the side opposite to the barrier layer in the sealant layer is an exterior material for a power storage device according to <1>, which is a layer satisfying a swelling degree of less than 15% with respect to the electrolytic solution. <3> The sealant layer includes a first heat-sealable resin layer, a second heat-sealable resin layer, and a third heat-sealable resin layer in this order from the barrier layer side, and the second heat-sealable resin layer is an exterior material for a power storage device according to <1>, which is a layer satisfying a swelling degree of 12% to 40% with respect to the electrolytic solution. <4> At least one layer included in the adhesive layer and the sealant layer, and the thickness of the layer satisfying a swelling degree of 12% to 40% with respect to the electrolytic solution is 5 μm or more, which is an exterior material for a power storage device according to <1>. <5> The sealant layer includes propylene resin as a main component, which is an exterior material for a power storage device according to <1>. <6> A sealant film including a layer satisfying a swelling degree of 12% to 40% with respect to an electrolytic solution that is a mixed solution of diethyl carbonate (DEC) / propyl propionate (PrPr) = 1:1 (mass ratio). <7> A sealant film according to <6>, including a first heat-sealable resin layer, a second heat-sealable resin layer, and a third heat-sealable resin layer in this order, and the second heat-sealable resin layer is a layer satisfying a swelling degree of 12% to 40% with respect to the electrolytic solution. <8> A sealant film according to <6> or <7> for use in manufacturing an exterior material for a power storage device. <9> An exterior case for a power storage device, which is a molded body of an exterior material for a power storage device according to any one of <1> to <5>. <10> A power storage device main body, An exterior member that houses the power storage device main body and includes an exterior material for a power storage device according to any one of <1> to <5>. A power storage device comprising the same.

Advantages of the Invention

[0011] According to the present disclosure, it is possible to provide an exterior material for a power storage device having high sealing strength and capable of suppressing the generation of air bubbles, a sealing film, an exterior case for a power storage device using the above-described exterior material for a power storage device, and a power storage device.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0013] Hereinafter, the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the present disclosure.

[0014] In the present disclosure, the term "step" includes not only a step independent of other steps but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved. In the numerical range indicated by "~" in the present disclosure, the numerical values described before and after "~" are included as the minimum value and the maximum value, respectively. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Further, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. In the present disclosure, each component may contain a plurality of corresponding substances. When a plurality of substances corresponding to each component are present in the composition, the content rate or content of each component means the total content rate or content of the plurality of substances present in the composition, unless otherwise specified. In the present disclosure, the particles corresponding to each component may contain a plurality of types of particles. When a plurality of types of particles corresponding to each component are present in the composition, the particle diameter of each component means the value for the mixture of the plurality of types of particles present in the composition, unless otherwise specified.

[0015] <Outer packaging material for power storage device> The outer packaging material for a power storage device of the present disclosure includes a base material layer, a barrier layer, an adhesive layer, and a sealant layer in this order, and at least one layer included in the adhesive layer and the sealant layer is a layer in which the swelling degree of an electrolytic solution (hereinafter, also referred to as "specific electrolytic solution") that is a mixed solution of diethyl carbonate (DEC) / propyl propionate (PrPr) = 1:1 (mass ratio) satisfies 12% to 40%.

[0016] By using the outer packaging material for a power storage device of the present disclosure, high seal strength can be obtained and generation of air bubbles can be suppressed. By including at least one layer in the adhesive layer and the sealant layer that is a layer in which the swelling degree of the specific electrolytic solution satisfies 12% to 40%, the balance of the permeability of the electrolytic solution becomes good, and both high seal strength and suppression of air bubble generation can be achieved.

[0017] The exterior material for a power storage device of the present disclosure is preferably used in the manufacture of a power storage device that houses a power storage device main body capable of charging with a power of 18 W or more. In this way, in order to achieve fast charging performance, it is desirable to adopt an electrolytic solution with a high ratio of low-viscosity solvent. When using such an electrolytic solution, the sealing strength of the heat seal part may decrease, and bubbles are likely to be generated due to volatilization of the electrolytic solution or the like. On the other hand, by using the exterior material for a power storage device of the present disclosure, it has high sealing strength and can suppress the generation of bubbles, so fast charging using the power storage device is also possible.

[0018] Hereinafter, the layer structure of the exterior material for a power storage device will be described.

[0019] (Base material layer) The exterior material for a power storage device includes a base material layer. The base material layer is preferably formed of a heat-resistant resin layer. The heat-resistant resin is preferably a resin that does not melt at the heat seal temperature when heat-sealing the exterior material. The heat-resistant resin preferably has a high melting point. For example, it is preferably higher than the melting point of each layer included in the sealant layer, and preferably has a melting point 10 °C or higher, more preferably 20 °C or higher, than the melting point of the layer having the highest melting point among the layers included in the sealant layer.

[0020] Examples of the base material layer include polyamide films such as nylon films, polyester films, etc. These films may be stretched films. Examples of the stretched film include biaxially stretched polyamide films such as biaxially stretched nylon films, biaxially stretched polybutylene terephthalate (PBT) films, biaxially stretched polyethylene terephthalate (PET) films, biaxially stretched polyethylene naphthalate (PEN) films, etc. Examples of the nylon film include 6-nylon film, 6,6-nylon film, MXD-nylon film, etc.

[0021] The base material layer may be a single layer or a multi-layer composed of two or more layers. Examples of the multi-layer include a polyester film / polyamide film (e.g., PET film / nylon film).

[0022] The thickness of the base material layer may be 2 μm to 50 μm. For example, when the base material layer is a polyester film, its thickness may be 2 μm to 50 μm; when the base material layer is a nylon film, its thickness may be 7 μm to 50 μm.

[0023] (Outer adhesive layer) An adhesive layer (also referred to as an outer adhesive layer) may be provided between the base material layer and the barrier layer described below, and the base material layer and the barrier layer may be integrated via the outer adhesive layer.

[0024] The adhesive constituting the outer adhesive layer is not particularly limited, and examples include thermosetting adhesives. The thermosetting adhesive is not particularly limited, and examples include olefin-based adhesives, epoxy-based adhesives, acrylic-based adhesives, etc. The thickness of the outer adhesive layer may be 1 μm to 5 μm. Among them, from the perspective of thinning and lightening the packaging material, the thickness of the outer adhesive layer is preferably 1 μm to 3 μm.

[0025] The outer adhesive layer may be a single layer or a multi-layer of two or more layers. In the case of a multi-layer, for example, a combination of an adhesive layer containing a colorant and an adhesive layer not containing a colorant may be used.

[0026] (Barrier layer) The exterior material for the power storage device includes a barrier layer. The barrier layer plays a role in imparting gas barrier properties to the exterior material to suppress the intrusion of oxygen, moisture, etc. The barrier layer is not particularly limited, and examples include metal foils, vapor deposition films, resin layers, etc. Examples of the vapor deposition film include metal vapor deposition films, inorganic oxide vapor deposition films, carbon-containing inorganic oxide vapor deposition films, etc. The metal foil is not particularly limited, and examples include aluminum foil, SUS foil (stainless steel foil), Cu foil, Ni foil, Ti foil, etc. Among them, aluminum foil and SUS foil (stainless steel foil) are preferred. Examples of the resin used for the resin layer include fluorine-containing resins, ethylene-vinyl alcohol copolymers, etc. Examples of the fluorine-containing resin include polyvinylidene chloride, polymers mainly composed of chlorotrifluoroethylene (CTFE), polymers mainly composed of tetrafluoroethylene (TFE), polymers having a fluoroalkyl group, polymers mainly composed of fluoroalkyl units, etc.

[0027] The barrier layer 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. Examples of the laminate of different types of layers include a combination of a vapor deposition film and a resin layer.

[0028] From the viewpoints of suppressing the generation of pinholes during rolling and formability, the thickness of the barrier layer may be 5 μm to 120 μm, or may be 10 μm to 80 μm.

[0029] The metal foil may be subjected to chemical conversion treatment on at least one of the surface on the base material layer side and the surface on the adhesive layer side, and for example, may have a corrosion prevention layer. By providing a corrosion prevention layer, corrosion of the metal foil surface by the contents (such as the electrolyte of the battery) can be suppressed. For example, the metal foil may be subjected to chemical conversion treatment to form a corrosion prevention layer by performing the following treatment. For example, on the surface of the degreased metal foil, 1) An aqueous solution of a mixture 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) Phosphoric acid, and At least one resin selected from the group consisting of an acrylic resin, a chitosan derivative resin, and a phenolic resin, and at least one compound selected from the group consisting of chromic acid and chromium (III) salts, an aqueous solution of a mixture containing the same 3) Phosphoric acid, At least one resin selected from the group consisting of an acrylic resin, a chitosan derivative resin, and a phenolic resin, and 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 a metal salt of fluoride and a non-metal salt of fluoride, an aqueous solution of a mixture containing the same After applying any one of the aqueous solutions of 1) to 3) above and drying, a chemical conversion treatment is performed.

[0030] The chemical conversion film formed by the chemical conversion treatment has a chromium adhesion amount (per side) of 0.1 mg / m 2 ~50 mg / m 2 is preferable, and 2 mg / m 2 ~20 mg / m 2 is more preferable.

[0031] (Inner adhesive layer) An adhesive layer (also referred to as an inner adhesive layer) may be provided between the barrier layer and the sealant layer described later, and the barrier layer and the sealant layer may be integrated via the inner adhesive layer.

[0032] The inner adhesive layer may be a layer in which the swelling degree of a specific electrolyte satisfies 12% to 40%, or may be a layer in which the swelling degree satisfies 15% to 35%. When the inner adhesive layer includes a layer in which the swelling degree of a specific electrolyte satisfies 12% to 40% (hereinafter, also referred to as a specific layer 1), the thickness of the specific layer 1 may be 5 μm or more, may be 10 μm to 30 μm, or may be 12 μm to 20 μm.

[0033] In the present disclosure, the swelling degree of a specific electrolytic solution is measured as follows. First, a test piece having the same composition as each corresponding layer (for example, a test piece of 50 μm × 80 mm × 80 mm) is immersed in a specific electrolytic solution under the conditions of 85°C for 24 hours, and the immersed test piece is dried at 40°C for 24 hours. Then, the mass of the immersed test piece and the mass of the dried test piece are measured using an electronic balance, and the swelling degree (%) is determined by the following formula. Swelling degree (%) = [(mass after immersion - mass after drying) / mass after drying] × 100

[0034] The adhesive constituting the inner adhesive layer is not particularly limited, and examples thereof include thermosetting adhesives and the adhesives of the present disclosure used for forming the aforementioned outer adhesive layer. The thermosetting adhesive is not particularly limited, and examples thereof include olefin-based adhesives, epoxy-based adhesives, acrylic-based adhesives, and acid-modified polyolefin-based adhesives such as maleic anhydride-modified polypropylene.

[0035] The thickness of the inner adhesive layer may be 1 μm to 5 μm. Among them, from the viewpoints of thinning and weight reduction of the packaging material, the thickness of the inner adhesive layer is preferably 1 μm to 3 μm. When the inner adhesive layer is composed of an acid-modified polyolefin-based adhesive such as acid-modified polypropylene (for example, ethylene-propylene random copolymer and ethylene-propylene block copolymer), the thickness of the inner adhesive layer may be 10 μm to 30 μm, or may be 12 μm to 20 μm.

[0036] (Sealant layer) The exterior material for a power storage device includes a sealant layer. The sealant layer is a layer that plays a role of imparting heat sealability to the exterior material. The sealant layer may include at least one heat-sealing resin layer, or may include two or three heat-sealing resin layers.

[0037] The sealant layer may include a layer in which the swelling degree of a specific electrolyte solution satisfies 12% to 40%, or may include a layer in which the swelling degree satisfies 15% to 35%. When the sealant layer includes a layer in which the swelling degree of a specific electrolyte solution satisfies 12% to 40% (hereinafter, also referred to as a specific layer 2), the thickness of the specific layer 2 may be 5 μm or more, may be 10 μm to 30 μm, or may be 12 μm to 20 μm.

[0038] When the sealant layer includes at least two thermally fusible resin layers, the outermost layer on the side opposite to the barrier layer in the sealant layer is preferably a layer in which the swelling degree of a specific electrolyte solution is less than 15%, more preferably a layer in which the swelling degree of a specific electrolyte solution is 12% or less, and even more preferably a layer in which the swelling degree of a specific electrolyte solution is 10% or less. Due to the low swelling degree in the aforementioned outermost layer, the generation of bubbles tends to be preferably suppressed.

[0039] The sealant layer may include a first thermally fusible resin layer, a second thermally fusible resin layer, and a third thermally fusible resin layer in this order from the barrier layer side. The second thermally fusible resin layer is preferably a layer in which the swelling degree of a specific electrolyte solution satisfies 12% to 40%, and more preferably a layer in which the swelling degree satisfies 15% to 35%. When the swelling degree of the specific electrolyte solution in the second thermally fusible resin layer is 12% or more, the permeability of the electrolyte solution becomes good, and the seal strength of the sealant layer can be preferably increased. When the swelling degree of the specific electrolyte solution in the second thermally fusible resin layer is 40% or less, the permeability of the electrolyte solution does not become too high, and the generation of bubbles can be preferably suppressed.

[0040] The sealant layer (for example, a thermally fusible resin layer) includes a thermally fusible resin and may optionally include a lubricant, incompatible particles, and other components described later.

[0041] The heat-sealable resin is selected such that it melts at the heat-sealing temperature, and preferably has a melting point below the heat-sealing temperature. The heat-sealable resin is not particularly limited as long as it has the above melting point, and is preferably at least one selected from the group consisting of ethylene resins, propylene resins, olefin resins, acid-modified products thereof, and ionomers.

[0042] The sealant layer (for example, the heat-sealable resin layer) preferably contains a propylene resin as a main component. In the present disclosure, "containing as a main component" means that the proportion of the corresponding component is the largest in each layer. For example, it means that the content of the corresponding component is 50% by mass or more of the entire layer.

[0043] The propylene resin may be a block copolymer of propylene and other copolymerization components other than propylene, or a random copolymer of propylene and other copolymerization components other than propylene. It may also be a random copolymer of propylene and at least one monomer selected from the group consisting of ethylene and α-olefins having 4 or more carbon atoms, or a block copolymer of propylene and at least one monomer selected from the group consisting of ethylene and α-olefins having 4 or more carbon atoms. Examples of the other copolymerization components other than propylene include ethylene, α-olefins having 4 or more carbon atoms, and butadiene. Examples of the α-olefins having 4 or more carbon atoms include 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, and the like.

[0044] The sealant layer (for example, the heat-sealable resin layer) may contain components other than the resin (other components). Other components include antioxidants, plasticizers, ultraviolet absorbers, fungicides, colorants (pigments, dyes, etc.), antistatic agents, rust preventives, moisture absorbers, oxygen absorbers, etc. The plasticizer is not particularly limited, and examples thereof include glycerin fatty acid ester monoglyceride, acetylated monoglyceride of glycerin fatty acid ester, organic acid monoglyceride of glycerin fatty acid ester, medium-chain fatty acid triglyceride of glycerin fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, special fatty acid ester, higher alcohol fatty acid ester, etc.

[0045] The sealant layer (for example, a heat-sealable resin layer) may further contain a lubricant. The lubricant is not particularly limited, and examples thereof include fatty acid amides. The fatty acid amide is not particularly limited, and examples thereof include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, aromatic bisamides, etc.

[0046] The lubricant may be contained in any layer in the sealant layer or may not be contained.

[0047] The sealant layer (for example, a heat-sealable resin layer) may further contain incompatible particles.

[0048] The incompatible particles may be inorganic particles, organic particles, metal particles, composite particles thereof, etc. From the viewpoint of suppressing deformation due to heat during heat melting, the incompatible particles are preferably inorganic particles, metal particles, or composite particles thereof. From the viewpoints of ensuring the insulation function of the sealant layer and weight reduction, the incompatible particles are preferably inorganic particles, organic particles, or composite particles thereof. From these comprehensive viewpoints, it is more preferable that the incompatible particles contain inorganic particles. The incompatible particles may be used alone or in combination of two or more.

[0049] Examples of the inorganic particles include inorganic oxide particles (such as silica particles, alumina particles, titanium oxide particles, etc.), inorganic carbonate particles (such as calcium carbonate particles, barium carbonate particles, etc.), inorganic silicate particles (such as aluminum silicate particles, talc particles, kaolin particles, etc.). Among them, silica particles are preferred from the viewpoint of the balance between the antiblocking effect and the suppression of bubbles.

[0050] Examples of the organic particles include acrylic resin particles, polyolefin resin particles (such as polyethylene resin particles, polypropylene resin particles, etc.), polystyrene resin particles, and the like.

[0051] The average particle diameter of the incompatible particles may be 0.1 μm to 4.5 μm, or may be 0.5 μm to 4.0 μm. When the average particle diameter of the incompatible particles is 0.1 μm or more, the function as an antiblocking agent tends to be exhibited, and when the average particle diameter of the incompatible particles is 4.5 μm or less, the generation of bubbles due to the volatilization of the electrolytic solution or the like can be suppressed. The average particle diameter of the incompatible particles can also be measured by observing and actually measuring the cross section of the sealant layer with a scanning electron microscope. Specifically, the sealant layer is embedded in a transparent epoxy resin, polished with a polisher, slurry, etc., the cross section of the sealant layer is observed, and the particle diameter is measured. The average particle diameter is the arithmetic mean value of the particle diameters of 50 incompatible particles.

[0052] The outermost layer on the side opposite to the barrier layer in the sealant layer preferably contains incompatible particles. The content rate of the incompatible particles in the aforementioned outermost layer is preferably 1000 ppm to 4000 ppm, more preferably 1000 ppm to 3500 ppm, and still more preferably 1000 ppm to 3000 ppm.

[0053] When the sealant layer is a single-layer heat-sealable resin layer, the heat-sealable resin layer preferably contains, as a main component, a random copolymer of propylene and other copolymer components excluding propylene.

[0054] When the sealant layer is a single layer of heat-sealable resin layer, the thickness of the heat-sealable resin layer (for example, layer A in the examples) may be 2 μm to 15 μm, or may be 3 μm to 10 μm.

[0055] When the sealant layer is a two-layer heat-sealable resin layer, the heat-sealable resin layer on the barrier layer side (for example, layer A in the examples) is preferably a block copolymer of propylene and other copolymer components excluding propylene, and the heat-sealable resin layer on the side opposite to the barrier layer (for example, layer B in the examples) preferably contains a random copolymer of propylene and other copolymer components excluding propylene as a main component.

[0056] When the sealant layer is a two-layer heat-sealable resin layer, the thickness of the heat-sealable resin layer on the barrier layer side may be 10 μm to 30 μm, or may be 12 μm to 20 μm. The thickness of the heat-sealable resin layer on the side opposite to the barrier layer may be 2 μm to 15 μm, or may be 3 μm to 10 μm.

[0057] When the sealant layer includes a first heat-sealable resin layer, a second heat-sealable resin layer, and a third heat-sealable resin layer in this order from the barrier layer side, the first heat-sealable resin layer preferably contains a random copolymer of propylene and other copolymer components excluding propylene as a main component, the second heat-sealable resin layer preferably contains a block copolymer of propylene and other copolymer components excluding propylene as a main component, and the second heat-sealable resin layer preferably contains a random copolymer of propylene and other copolymer components excluding propylene as a main component.

[0058] The thickness of the first heat-sealable resin layer may be 5 μm to 15 μm, or may be 8 μm to 12 μm. The thickness of the second heat-sealable resin layer may be 10 μm to 30 μm, or may be 12 μm to 20 μm. The thickness of the third heat-sealable resin layer may be 2 μm to 15 μm, or may be 3 μm to 10 μm.

[0059] An example of the exterior material for a power storage device of the present disclosure will be described below with reference to FIGS. 1 to 3. FIGS. 1 to 3 are schematic cross-sectional views showing Examples 1 to 3 of the exterior material for a power storage device of the present disclosure.

[0060] The exterior material 1 for a power storage device shown in FIG. 1 includes a base material layer 2, a barrier layer 4, and a sealant layer 3 in this order. The sealant layer 3 includes a first heat-sealable resin layer 7, a second heat-sealable resin layer 8, and a third heat-sealable resin layer 9 in this order from the barrier layer 4 side. An outer adhesive layer 5 is provided between the base material layer 2 and the barrier layer 4, and an inner adhesive layer 6 is provided between the barrier layer 4 and the first heat-sealable resin layer 7. The second heat-sealable resin layer 8 is a layer in which the swelling degree of a specific electrolyte solution satisfies 12% to 40%, and the third heat-sealable resin layer 9 is a layer in which the swelling degree of a specific electrolyte solution satisfies less than 15%.

[0061] The exterior material 10 for a power storage device shown in FIG. 2 includes a base material layer 2, a barrier layer 4, and a sealant layer 13 in this order. The sealant layer 13 includes a first heat-sealable resin layer 17 and a second heat-sealable resin layer 18 in this order from the barrier layer 4 side. An outer adhesive layer 5 is provided between the base material layer 2 and the barrier layer 4, and an inner adhesive layer 6 is provided between the barrier layer 4 and the first heat-sealable resin layer 17. The first heat-sealable resin layer 17 is a layer in which the swelling degree of a specific electrolyte solution satisfies 12% to 40%, and the second heat-sealable resin layer 18 is a layer in which the swelling degree of a specific electrolyte solution satisfies less than 15%.

[0062] The exterior material 20 for a power storage device shown in FIG. 3 includes a base material layer 2, a barrier layer 4, and a sealant layer 27 in this order. The sealant layer 27 is a heat-sealable resin layer. An outer adhesive layer 5 is provided between the base material layer 2 and the barrier layer 4, and an inner adhesive layer 6 is provided between the barrier layer 4 and the sealant layer 27. The inner adhesive layer 6 is a layer in which the swelling degree of a specific electrolyte solution satisfies 12% to 40%, and the heat-sealable resin layer that is the sealant layer 27 is a layer in which the swelling degree of a specific electrolyte solution satisfies less than 15%.

[0063] <Manufacturing Method of Exterior Material for Power Storage Device> The manufacturing method of the exterior material for a power storage device is not particularly limited as long as the above-described exterior material for a power storage device can be obtained. As an example of the manufacturing method of the exterior material for a power storage device, the manufacturing method of the exterior material 1 for a power storage device shown in FIG. 1 will be described below.

[0064] Prepare a laminate A in which a base material layer 2, an outer adhesive layer 5, and a barrier layer 4 are laminated in this order. The laminate A can be produced by a dry lamination method in which an adhesive component for forming the outer adhesive layer 5 is applied to the base material layer 2 or the barrier layer 4 by a gravure coating method, a roll coating method, etc., dried, and then the barrier layer 4 or the base material layer 2 is laminated thereon. When the adhesive component is a curable resin, after laminating the barrier layer 4 or the base material layer 2 on the outer adhesive layer 5, the outer adhesive layer 5 is cured by heating or the like.

[0065] Next, a sealant layer 3 is provided on the barrier layer 4 of the laminate A. The sealant layer 3 may be a resin film previously formed and disposed on the barrier layer 4 (the first method), or a resin material for forming the sealant layer 3 may be applied on the barrier layer 4 by extrusion molding, coating, etc. to form the sealant layer 3 (the second method). In the first method, the resin film, which is a multi-layer laminate such as a first heat-sealable resin layer 7, a second heat-sealable resin layer 8, a third heat-sealable resin layer 9, etc., can be produced by a co-extrusion method or the like.

[0066] In the case of the first method, the barrier layer 4 and the sealant layer 3 are adhered by an inner adhesive layer 6. In the case of the second method, the inner adhesive layer 6 may be omitted or the inner adhesive layer 6 may be provided.

[0067] When the inner adhesive layer 6 is provided between the barrier layer 4 and the sealant layer 3, the inner adhesive layer 6 and the sealant layer 3 can be laminated by an extrusion lamination method, a thermal lamination method, a sandwich lamination method, a dry lamination method, etc. As the extrusion lamination method, there is a method of laminating by extruding an inner adhesive layer 6 and a sealant layer (a first heat-fusible resin layer 7, a second heat-fusible resin layer 8, and a third heat-fusible resin layer 9) onto the barrier layer 4 of the laminate A (co-extrusion lamination method, tandem lamination method), etc. As the thermal lamination method, separately, a laminate B of the inner adhesive layer 6 and the sealant layer 3 is formed, and a method of laminating so that the inner adhesive layer 6 of the laminate B and the barrier layer 4 of the laminate A face each other, a laminate C having an inner adhesive layer 6 is formed on the barrier layer 4 of the laminate A, and a method of laminating the inner adhesive layer 6 of the laminate C and the sealant layer 3, etc. are mentioned. As the sandwich lamination method, there is a method of pouring a molten inner adhesive layer 6 between the barrier layer 4 of the laminate A and the sealant layer 3 previously formed in a film shape, etc. An adhesive resin such as an acid-modified polyolefin-based adhesive is poured between the barrier layer 4 of the laminate A and the sealant layer 3 previously formed in a film shape, sandwich laminated, and then heated with a thermal adhesive roll to bond the barrier layer 4 and the sealant layer 3 via the inner adhesive layer 6 (thermal adhesive resin). As the dry lamination method, there is a method of solution coating an adhesive component for forming an inner adhesive layer 6 on the barrier layer 4 of the laminate A, drying or baking it, and laminating the sealant layer 3 previously formed in a film shape on this inner adhesive layer 6, etc.

[0068] <Sealant film> The sealant film of the present disclosure includes a layer in which the swelling degree of an electrolytic solution that is a mixed solution of diethyl carbonate (DEC) / propyl propionate (PrPr)=1:1 (mass ratio) satisfies 12% to 40%.

[0069] A preferred configuration of the sealant film of the present disclosure is the same as the preferred configuration of the sealant layer in the exterior material for a power storage device of the present disclosure described above.

[0070] The sealant film of the present disclosure may be used in the manufacture of an exterior material for a power storage device, for example, it may also be used in the manufacture of the sealant layer of an exterior material for a power storage device.

[0071] <Outer case for power storage device> The outer case for a power storage device according to the present disclosure is a molded body of the above-described outer material for a power storage device. The outer material for a power storage device may be molded by deep drawing molding, overhanging molding, or the like. Examples of the shape of the outer case for a power storage device include the outer cases 10 in FIGS. 4 and 5 described later.

[0072] <Power storage device> The power storage device according to the present disclosure includes a power storage device main body portion and an outer member that houses the power storage device main body portion and includes the above-described outer material for a power storage device according to the present disclosure. The outer member may be configured to include the outer case for a power storage device according to the present disclosure.

[0073] An example of a power storage device 100 configured using the outer material 1 for a power storage device according to the present disclosure is shown in FIGS. 4 and 5. FIG. 4 is a schematic cross-sectional view showing an example of the power storage device. FIG. 5 is a schematic perspective view showing the components constituting the power storage device of FIG. 4 in a separated state. The power storage device 100 is a lithium-ion secondary battery.

[0074] In FIGS. 4 and 5, an outer member 15 is constituted by an outer case 10 that is a molded body of the outer material 1 and a planar outer material 1. A power storage device main body portion 110 is housed in the housing recess of the outer case 10. Then, the planar outer material 1 is arranged with the sealant layer 3 side facing inward (downward in FIGS. 4 and 5), and the peripheral edge of the sealant layer 3 of the planar outer material 1 and the sealant layer 3 of the flange portion (sealing peripheral edge portion) 37 of the outer case 10 are sealed and joined by heat fusion (heat seal).

[0075] In FIG. 4, reference numeral 39 denotes a heat seal portion where the peripheral edge of the outer material 1 and the flange portion (sealing peripheral edge portion) 37 of the outer case 10 are joined (welded). In the power storage device 100, the tip of the tab lead connected to the power storage device main body portion 110 is led out to the outside of the outer member 15, but the illustration is omitted.

[0076] The power storage device main body 110 is not particularly limited, and examples thereof include a battery main body, a capacitor main body, a condenser main body, and the like.

[0077] From the viewpoint of ensuring sealing, the width of the heat seal portion 39 is preferably set to 0.5 mm or more, and more preferably set to 3 mm to 15 mm.

[0078] The form of the exterior member 15 is not limited to FIGS. 4 and 5, and the peripheries may be heat-sealed by a pair of planar exterior materials 1, or the peripheries may be heat-sealed by a pair of exterior cases 10.

Example

[0079] Next, examples of the present disclosure will be described, but the present disclosure is not particularly limited to these examples.

[0080] [Example 1] After applying a chemical conversion treatment liquid composed of phosphoric acid, polyacrylic acid (acrylic resin), chromium (III) salt compound, water, and alcohol to both sides of an aluminum foil with a thickness of 35 μm, drying was performed at 180 ° C. to form a chemical conversion film. The chromium adhesion amount of this chemical conversion film was 10 mg / m per side 2 was.

[0081] Next, a biaxially stretched 6-nylon film with a thickness of 15 μm was dry-laminated (bonded) to one surface of the chemically converted aluminum foil via a two-component curable urethane-based adhesive. Thereby, a laminate A in which a base material layer, an outer adhesive layer, and a barrier layer were laminated in this order was produced.

[0082] Next, a sealant film composed of an A layer containing propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles) was obtained.

[0083] An adhesive resin that is acid-modified polypropylene (ethylene-propylene random copolymer) was prepared. An adhesive resin was poured between the other surface of the aluminum foil and the A-layer surface of the sealant film, and after sandwich lamination, it was wound around a roll shaft after heating with a heat-sealing roll. After aging (heating) at 40 °C for 10 days, an exterior material for a power storage device was obtained by pulling it out from the roll shaft. The thickness of each layer is as shown in Table 1.

[0084] [Example 2] In the same manner as in Example 1, a laminate A in which a base material layer, an outer adhesive layer, and a barrier layer were laminated in this order was produced. Next, a sealant film was obtained, which consisted of an A layer containing propylene resin (ethylene-propylene block copolymer), 1000 ppm of erucic acid amide (lubricant), 50 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles), and a B layer containing propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles). An adhesive resin that is acid-modified polypropylene (ethylene-propylene block copolymer) was prepared. Using this adhesive resin, an exterior material for a power storage device was obtained in the same procedure as in Example 1. The thickness of each layer is as shown in Table 1.

[0085] [Example 3] In the same manner as in Example 1, a laminate A in which a base material layer, an outer adhesive layer, and a barrier layer were laminated in this order was produced. Next, a sealant film was obtained, which consisted of an A layer containing propylene resin (ethylene-propylene block copolymer), 1000 ppm of erucic acid amide (lubricant), 50 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles), and a B layer containing propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles).

[0086] 100 parts by mass of maleic acid-modified polypropylene (melting point: 80 °C, acid value: 10 mgKOH / g) as the main agent, 8 parts by mass of an isocyanurate form of hexamethylene diisocyanate (NCO content: 20% by mass) as the curing agent, and further a solvent were mixed to prepare an adhesive solution. The adhesive solution was applied to the other surface of the aluminum foil, dried by heating, and then laminated on the A layer surface of the sealant film. Next, the laminate A with the sealant film laminated thereon was sandwiched between a rubber nip roll and a laminating roll heated to 100 °C and pressure-bonded by dry lamination, and wound around a roll shaft. After aging (heating) at 40 °C for 10 days, it was pulled out from the roll shaft to obtain an exterior material for a power storage device. The thickness of each layer is as shown in Table 1.

[0087] [Example 4] In the same manner as in Example 1, a laminate A in which a base material layer, an outer adhesive layer, and a barrier layer were laminated in this order was produced. Next, an A layer containing a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter: 1.0 μm; incompatible particles), a B layer containing a propylene resin (ethylene-propylene block copolymer), 1000 ppm of erucic acid amide (lubricant), and 50 ppm of silica particles (average particle diameter: 1.0 μm; incompatible particles), and a C layer containing a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter: 1.0 μm; incompatible particles) were co-extruded using a T-die so that these three layers were laminated in this order to obtain a sealant film in which these three layers were laminated. Using the adhesive solution prepared in Example 3, an exterior material for a power storage device was obtained in the same procedure as in Example 3. The thickness of each layer is as shown in Table 1.

[0088] [Example 5] In the same manner as in Example 1, a laminate A in which a base material layer, an outer adhesive layer, and a barrier layer were laminated in this order was produced. Next, an A layer containing a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles), a B layer containing a propylene resin (ethylene-propylene block copolymer), 1000 ppm of erucic acid amide (lubricant), and 50 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles), and a C layer containing a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles) were co-extruded using a T-die so that these three layers were laminated in this order, and a sealant film in which these three layers were laminated was obtained. The ethylene-propylene block copolymer constituting the B layer includes a sea portion mainly composed of polypropylene and an island portion (rubber phase) composed of ethylene-propylene rubber, and the amount of ethylene-propylene rubber is increased compared to Example 4. 100 parts by mass of maleic acid-modified polypropylene (melting point 80 °C, acid value 10 mgKOH / g) as the main agent, 8 parts by mass of an isocyanurate form of tolylene diisocyanate (NCO content: 20% by mass) as the curing agent, and further a solvent were mixed to prepare an adhesive solution. Using this adhesive solution, an exterior material for a power storage device was obtained in the same procedure as in Example 4. The thickness of each layer is as shown in Table 1.

[0089] [Example 6] In the same manner as in Example 1, a laminate A in which a base material layer, an outer adhesive layer, and a barrier layer were laminated in this order was produced. Next, an A layer containing a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles), a B layer containing a propylene resin (ethylene-propylene block copolymer), 1000 ppm of erucic acid amide (lubricant), and 50 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles), and a C layer containing a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles) were co-extruded using a T-die so that these three layers were laminated in this order to obtain a sealant film in which these three layers were laminated. The ethylene-propylene block copolymer constituting the B layer includes a sea portion mainly composed of polypropylene and an island portion (rubber phase) composed of ethylene-propylene rubber, and the amount of ethylene-propylene rubber is increased compared to Example 5. An exterior material for a power storage device was obtained in the same procedure as in Example 3 using the adhesive solution prepared in Example 3. The thickness of each layer is as shown in Table 1.

[0090] [Comparative Example 1] A laminate A in which a base material layer, an outer adhesive layer, and a barrier layer were laminated in this order was produced in the same manner as in Example 1. Next, a sealant film composed of an A layer containing a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles), and a B layer containing a propylene resin (ethylene-propylene block copolymer), 1000 ppm of erucic acid amide (lubricant), and 50 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles) was obtained. The ethylene-propylene block copolymer constituting the B layer includes a sea portion mainly composed of polypropylene and an island portion (rubber phase) composed of ethylene-propylene rubber, and the amount of ethylene-propylene rubber is increased compared to Example 6. An exterior material for a power storage device was obtained in the same procedure as in Example 3 using the adhesive solution prepared in Example 3. The thickness of each layer is as shown in Table 1.

[0091] [Comparative Example 2] In the same manner as in Example 1, a laminate A in which a base material layer, an outer adhesive layer, and a barrier layer were laminated in this order was produced. Next, an A layer containing a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles), a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles) A B layer, and a C layer containing a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles) were co-extruded using a T-die so that three layers were laminated in this order, and a sealant film in which these three layers were laminated was obtained.

[0092] [Comparative Example 3] In the same manner as in Example 1, a laminate A in which a base material layer, an outer adhesive layer, and a barrier layer were laminated in this order was produced. Next, a sealant film composed of an A layer containing a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles), and a B layer containing a propylene resin (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter 1.0 μm; incompatible particles) was obtained. Using the adhesive resin prepared in Example 2, an exterior material for a power storage device was obtained in the same procedure as in Example 1. The thickness of each layer is as shown in Table 1.

[0093] [Heat Seal Evaluation] <Seal Strength Measurement> After cutting out two specimens with a width of 15 mm and a length of 200 mm from the obtained exterior material, while these two specimens were overlapped in a state where their inner sealant layers were in contact with each other, using a heat sealing device (TP-701-A) manufactured by Tester Sangyo Co., Ltd., heat sealing was performed by one-sided heating under the conditions of a heat sealing temperature of 200 °C, a seal pressure of 0.2 MPa (gauge display pressure), and a seal time of 2 seconds.

[0094] Next, for a pair of exterior materials in which the inner sealant layers were heat-sealed to each other as described above, in accordance with JIS K7127-1998, using a Strograph (tensile test device) (AGS-5kNX) manufactured by Shimadzu Access Co., Ltd., the peel strength when the exterior material (specimen) was peeled 180 degrees at a peeling speed of 100 mm / min with the inner sealant layers of the seal part in contact with each other was measured, and this was taken as the seal strength (N / 15 mm width).

[0095] [Presence or absence of bubbles] As shown in FIGS. 4 and 5, using an exterior material for a power storage device, an exterior case 10 and a planar exterior material 1 were prepared. Then, the power storage device main body 110 was housed in the housing recess of the exterior case 10, and the peripheral edge of the sealant layer 3 of the planar exterior material 1 and the sealant layer 3 of the flange part (sealing peripheral edge part) 37 of the exterior case 10 were seal-joined by heat fusion to obtain a power storage device 100. At this time, the conditions were a width of the heat seal part 39 of 5 mm, a heat seal temperature of 200 °C, a seal pressure of 0.2 MPa (gauge display pressure), and a seal time of 2 seconds. Also, the power storage device main body 110 was a lithium-ion secondary battery, and a mixed solution of ethylene carbonate / propylene carbonate / ethyl propionate / propyl propionate (EC / PC / EP / PP) = 10 / 15 / 10 / 65 (volume ratio) containing 1.0 M LiPF6 was used as the electrolytic solution. After storing the seal-joined power storage device 100 in an environment of 85 °C for 3 days, the presence or absence of bubble generation in the heat seal part 39 was confirmed. Specifically, the cross-section of the heat seal part 39 was observed using an optical microscope, and it was determined that there were bubbles when cavities were present, and no bubbles when cavities were not present.

[0096] [Derivation of Swelling Degree] A test piece having the same composition as each layer (layer A to layer C) of the adhesive layer or the sealant layer was immersed in the electrolyte, and the swelling degree of each layer was determined by measuring the mass change of the test piece. Specifically, a 50 μm × 80 mm × 80 mm test piece having the same composition as each layer (layer A to layer C) of the adhesive layer or the sealant layer, and an electrolyte which is a mixed solution of diethyl carbonate (DEC) / propyl propionate (PrPr) = 1:1 (mass ratio) were prepared. The test piece was immersed in the electrolyte under the conditions of 85°C for 24 hours, and the immersed test piece was dried at 40°C for 24 hours. Then, the mass of the immersed test piece and the mass of the dried test piece were measured using an electronic balance, and the swelling degree (%) was determined by the following formula. The results are shown in Table 1. Swelling degree (%) = [(mass after immersion - mass after drying) / mass after drying] × 100

[0097]

Table 1

[0098] As shown in Table 1, for the exterior materials for power storage devices of Examples 1 to 6, the seal strength was high and the generation of bubbles was suppressed.

Claims

1. A base material layer, a barrier layer, an adhesive layer, and a sealant layer are laminated in this order, and at least one layer included in the adhesive layer and the sealant layer is a layer that satisfies a swelling degree of 12% to 40% with respect to an electrolytic solution that is a mixed solution of diethyl carbonate (DEC) / propyl propionate (PrPr) = 1:1 (mass ratio). An exterior material for a power storage device.

2. The sealant layer includes at least two heat-sealable resin layers, and the outermost layer on the side opposite to the barrier layer in the sealant layer is a layer that satisfies a swelling degree of less than 15% with respect to the electrolytic solution. The exterior material for a power storage device according to Claim 1.

3. The sealant layer includes a first heat-sealable resin layer, a second heat-sealable resin layer, and a third heat-sealable resin layer in this order from the barrier layer side, and the second heat-sealable resin layer is a layer that satisfies a swelling degree of 12% to 40% with respect to the electrolytic solution. The exterior material for a power storage device according to Claim 1.

4. At least one layer included in the adhesive layer and the sealant layer, and the thickness of the layer that satisfies a swelling degree of 12% to 40% with respect to the electrolytic solution is 5 μm or more. The exterior material for a power storage device according to Claim 1.

5. The sealant layer includes a propylene resin as a main component. The exterior material for a power storage device according to Claim 1.

6. A sealant film including a layer that satisfies a swelling degree of 12% to 40% with respect to an electrolytic solution that is a mixed solution of diethyl carbonate (DEC) / propyl propionate (PrPr) = 1:1 (mass ratio).

7. Including a first heat-sealable resin layer, a second heat-sealable resin layer, and a third heat-sealable resin layer in this order, and the second heat-sealable resin layer is a layer that satisfies a swelling degree of 12% to 40% with respect to the electrolytic solution. The sealant film according to Claim 6.

8. The sealant film according to Claim 6 or Claim 7 for use in manufacturing an exterior material for a power storage device.

9. An exterior case for a power storage device, which is a molded body of the exterior material for a power storage device according to any one of Claims 1 to 5.

10. A power storage device main body, an exterior member that houses the power storage device main body and includes the exterior material for a power storage device according to any one of Claims 1 to 5, and a power storage device comprising the same.

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