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 which has high seal strength and can suppress air bubble generation.SOLUTION: An exterior material for a power storage device is formed by stacking a base material layer, a barrier layer and a sealant layer in this order, wherein the sealant layer includes an A layer, a B layer and a C layer in this order when being viewed from the base material layer side, the A layer contains a propylene resin A which is a random copolymer of propylene, and other copolymerization component excluding the propylene as a main component, the B layer contains a propylene resin B containing a rubber phase which is a copolymer of ethylene and α-olefin having 3 to 10 carbon atoms as a main component, the C layer contains a propylene resin C which is a random copolymer of propylene and other copolymerization component excluding the propylene as a main component. A percentage content of the rubber phase in the propylene resin B is 20 mass% to 40 mass%, the C layer further contains incompatible particles, and a percentage content of the incompatible particles in the C layer is 1,000 ppm to 4,000 ppm.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 main body of the power storage device can be secured.

[0003] In order to be formed into such a three-dimensional shape in good condition 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 (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 and good moldability, and can 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 accommodated in an outer case formed 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 with a high ratio of low-viscosity solvent may be employed. The low-viscosity solvent has high permeability to the sealant layer, and the degree of swelling of the sealant layer increases. As a result, the seal strength of the heat-sealed portion may decrease, and the reliability of the heat seal may decline.

[0007] Furthermore, when the electrolytic solution penetrates into the sealant layer, 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 that has high seal strength and can suppress the generation of bubbles.

[0009] An object of the present disclosure is to provide an exterior material for a power storage device, a sealant film, an outer case for a power storage device, and a power storage device that have high seal strength and can suppress the generation of bubbles. [Means for Solving the Problems]

[0010] Specific means for achieving the above problems are as follows. <1> A base material layer, a barrier layer, and a sealant layer are laminated in this order, the sealant layer includes an A layer, a B layer, and a C layer in this order when viewed from the base material layer side, The A layer mainly contains a propylene resin A which is a random copolymer of propylene and other copolymerization components excluding propylene. The B layer mainly contains a propylene resin B containing a rubber phase which is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms. The C layer mainly contains a propylene resin C which is a random copolymer of propylene and other copolymerization components excluding propylene. The content ratio of the rubber phase in the propylene resin B is 20% by mass to 40% by mass. The C layer further contains incompatible particles, and the content ratio of the incompatible particles in the C layer is 1000 ppm to 4000 ppm. An exterior material for a power storage device. <2> The ratio of the thickness of the B layer to the thickness of the sealant layer is 50% or more. The exterior material for a power storage device according to <1>. <3> The incompatible particles include silica particles. The exterior material for a power storage device according to <1> or <2>. <4> It includes an A layer, a B layer, and a C layer in this order. The A layer mainly contains a propylene resin A which is a random copolymer of propylene and other copolymerization components excluding propylene. The B layer mainly contains a propylene resin B containing a rubber phase which is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms. The C layer mainly contains a propylene resin C which is a random copolymer of propylene and other copolymerization components excluding propylene. The content ratio of the rubber phase in the propylene resin B is 20% by mass to 40% by mass. The C layer further contains incompatible particles, and the content ratio of the incompatible particles in the C layer is 1000 ppm to 4000 ppm. A sealant film. <5> A sealant film according to <4> for use in the manufacture of an exterior material for a power storage device. <6> 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 <1> to <3>. <7> A power storage device main body, An exterior member that houses the main body of the power storage device and includes an exterior material for a power storage device according to any one of <1> to <3>, 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, a sealing film, an exterior case for a power storage device, and a power storage device that have high sealing strength and can suppress the generation of air bubbles.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

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. Also, 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 a value for a mixture of the plurality of types of particles present in the composition, unless otherwise specified.

[0015] <Outer packaging material for power storage device> [First Embodiment] In the outer packaging material for a power storage device of the present disclosure (hereinafter, also simply referred to as "outer packaging material"), a base material layer, a barrier layer, and a sealant layer are laminated in this order. The sealant layer includes an A layer, a B layer, and a C layer in this order when viewed from the base material layer side. The A layer mainly contains a propylene resin A which is a random copolymer of propylene and other copolymerization components excluding propylene. The B layer mainly contains a propylene resin B containing a rubber phase which is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms. The C layer mainly contains a propylene resin C which is a random copolymer of propylene and other copolymerization components excluding propylene. The content rate of the rubber phase in the propylene resin B is 20% by mass to 40% by mass. The C layer further contains incompatible particles, and the content rate of the incompatible particles in the C layer is 1000 ppm to 4000 ppm.

[0016] By using the exterior material for a power storage device of the present disclosure, high sealing strength can be achieved and the generation of air bubbles can be suppressed. In the exterior material for a power storage device, when the content of the rubber phase in the propylene resin B is 20% by mass or more, the sealing strength of the sealant layer can be enhanced. When the content of the rubber phase in the propylene resin B is 40% by mass or less and the content of incompatible particles in the C layer is 1000 ppm or more, there is a tendency to suppress excessive penetration of the electrolytic solution into the sealant layer when a low-viscosity solvent is used in the electrolytic solution. As a result, the generation of air bubbles due to volatilization or the like can be suppressed. When the content of incompatible particles in the C layer is 4000 ppm or less, the amount of electrolytic solution adsorbed by the incompatible particles can be reduced, and as a result, the generation of air bubbles due to volatilization or the like can be suppressed.

[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. Thus, in order to achieve rapid chargeability, it is desirable to employ an electrolytic solution having a high ratio of a low-viscosity solvent. When such an electrolytic solution is used, since the low-viscosity solvent has high permeability to the sealant layer, the sealing strength of the heat-sealed portion may decrease, or air bubbles may easily 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, high sealing strength can be achieved and the generation of air bubbles can be suppressed, so that rapid 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-sealing temperature when heat-sealing the exterior material. As the heat-resistant resin, it is preferably a resin having a high melting point. For example, it is preferably higher than the melting point of each layer contained in the sealant layer, and preferably has a melting point 10°C or more higher than the melting point of the layer having the highest melting point among the layers contained in the sealant layer, and preferably has a melting point 20°C or more higher.

[0020] Examples of the base material layer include polyamide films such as nylon films, and 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 films, 6,6-nylon films, MXD-nylon films, etc.

[0021] The base material layer may be a single layer or a multilayer composed of two or more layers. Examples of the multilayer include polyester film / polyamide film (for example, 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, and 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 a barrier layer described later, 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 thereof include thermosetting adhesives. The thermosetting adhesive is not particularly limited, and examples thereof include olefin-based adhesives, epoxy-based adhesives, and acrylic-based adhesives. The thickness of the outer 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 outer adhesive layer is preferably 1 μm to 3 μm.

[0025] The outer adhesive layer may be a single layer or a multilayer of two or more layers. In the case of a multilayer, 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 of imparting gas barrier properties to suppress the intrusion of oxygen, moisture, etc. into the exterior material. The barrier layer is not particularly limited, and examples thereof 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 thereof 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 preferable. 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 layers 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] The thickness of the barrier layer may be 5 μm to 120 μm, or may be 10 μm to 80 μm, from the viewpoints of suppressing pinhole generation during rolling and formability.

[0029] The metal foil may be subjected to a 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 the 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 a 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) An aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, and at least one compound selected from the group consisting of chromic acid and chromium(III) salts 3) An aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, at least one compound selected from the group consisting of chromic acid and chromium(III) salts, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides After applying any 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 preferably has a chromium adhesion amount (per side) of 0.1 mg / m 2 to 50 mg / m 2 more preferably 2 mg / m 2 to 20 mg / m 2 is even 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 adhesive constituting the inner adhesive layer is not particularly limited, and examples thereof include thermosetting adhesives. The thermosetting adhesive is not particularly limited, and examples thereof include olefin-based adhesives, epoxy-based adhesives, and acrylic-based adhesives. 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.

[0033] (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 includes layer A, layer B, and layer C in this order when viewed from the base material layer side. Therefore, the layers are arranged in the order of the base material layer, the barrier layer, the adhesive layer, layer A, layer B, and layer B. Note that the sealant layer may or may not include layers other than layer A, layer B, and layer C.

[0034] 〈Layer A〉 Layer A mainly contains a propylene resin A which is a random copolymer of propylene and other copolymerization components excluding propylene. In the present disclosure, "mainly contains" 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.

[0035] The MFR of the propylene resin A may be 10 g / 10 min or more, may be 10 g / 10 min to 25 g / 10 min, or may be 12 g / 10 min to 20 g / 10 min. In the present disclosure, MFR means the MFR (melt flow rate) measured under the conditions of a temperature of 230 °C and a load of 2.16 kg in accordance with JIS K7210-1999.

[0036] The melting point of propylene resin A may be 140°C or higher and less than 170°C, may be 140°C to 165°C, or may be 140°C to 155°C. In the present disclosure, the melting point means the melting peak temperature (melting point) measured using a differential scanning calorimeter under the condition of a heating rate of 10°C / min by the method defined in JIS K7121-1987 "Method for Measuring Transition Temperature of Plastics".

[0037] Propylene resin A is a random copolymer of propylene and other copolymerization components excluding propylene, and is preferably 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. Examples of other copolymerization components excluding propylene include ethylene, α-olefins having 4 or more carbon atoms, butadiene, etc. Examples of α-olefins having 4 or more carbon atoms include ethylene, 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, etc.

[0038] Among the resin components contained in the A layer, the content of propylene resin A is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, particularly preferably 80% by mass or more, extremely preferably 90% by mass or more, and may be 95% by mass or more, may be 98% by mass or more, or may be 99% by mass or more. The upper limit of the content of the aforementioned propylene resin A is not particularly limited and may be 100% by mass or less.

[0039] The A layer may contain a resin other than propylene resin A (also referred to as other resins). Examples of other resins include ethylene resins, olefin resins, and other resins.

[0040] The thickness of the A layer may be 2 μm to 15 μm, or may be 3 μm to 10 μm. The ratio of the thickness of the A layer to the thickness of the sealant layer may be 5% or more, may be 10% or more, may be 40% or less, or may be 30% or less.

[0041] The B layer mainly contains propylene resin B containing a rubber phase which is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms. The content of the rubber phase in propylene resin B is 20% to 40% by mass, and from the viewpoint of heat seal strength, it is preferably 25% to 40% by mass, and more preferably 30% to 40% by mass. The rubber phase in propylene resin B can be observed by a scanning electron microscope on the cross section of the sealant layer. For example, by observing a sea part mainly composed of polypropylene and an island part which is the rubber phase, the content of the rubber phase in propylene resin B can be determined from the area ratio of the rubber phase and the density of the polymers constituting the sea part and the island part.

[0042] The MFR of propylene resin B may be 1.0 g / 10 min to 5.0 g / 10 min, may be 1.5 g / 10 min to 5 g / 10 min, or may be 2.0 g / 10 min to 4.0 g / 10 min.

[0043] The melting point of propylene resin B may be 140 °C or higher and less than 170 °C, may be 145 °C to 165 °C, or may be 150 °C to 165 °C.

[0044] Propylene resin B is preferably a resin having a higher melting point than propylene resin A and propylene resin C described later. The melting point difference between propylene resin C and propylene resin A may be 1 °C to 30 °C, may be 5 °C to 30 °C, or may be 10 °C to 25 °C.

[0045] Propylene resin B is preferably a block copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, and more preferably a block copolymer of ethylene and propylene. Examples of the α-olefin having 3 to 10 carbon atoms include propylene, 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, and the like.

[0046] When propylene resin B is a block copolymer of ethylene and propylene, propylene resin B includes a sea portion mainly composed of polypropylene and an island portion composed of ethylene-propylene rubber, and the island portion corresponds to a rubber phase.

[0047] Among the resin components contained in the B layer, the content of propylene resin B is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, particularly preferably 80% by mass or more, extremely preferably 90% by mass or more, and may be 95% by mass or more, may be 98% by mass or more, or may be 99% by mass or more. The upper limit of the content of the aforementioned propylene resin B is not particularly limited and may be 100% by mass or less.

[0048] The thickness of the B layer may be 10 μm to 30 μm, or may be 15 μm to 25 μm. The ratio of the thickness of the B layer to the thickness of the sealant layer may be 20% or more, may be 40% or more, may be 50% or more, and may be 90% or less, may be 80% or less, or may be 70% or less.

[0049] 〈C layer〉 The C layer mainly contains propylene resin C which is a random copolymer of propylene and other copolymerization components excluding propylene. The C layer further contains incompatible particles, and the content of the incompatible particles in the C layer is 1000 ppm to 4000 ppm.

[0050] The MFR of propylene resin C may be 10 g / 10 min or more, may be 10 g / 10 min to 20 g / 10 min, or may be 10 g / 10 min to 18 g / 10 min.

[0051] The MFR of propylene resin C is preferably not more than the MFR of propylene resin A. Thereby, the fluidity of the A layer containing propylene resin A becomes the same as or higher than the fluidity of the C layer containing propylene resin C, and the fluidity of the entire sealant layer tends to be good. The difference (MFR1 - MFR2) between the MFR (MFR1) of propylene resin A and the MFR (MFR2) of propylene resin C may be from 0 g / 10 min to 10 g / 10 min, or may be from 0 g / 10 min to 5 g / 10 min.

[0052] The melting point of propylene resin C may be from 100°C to 140°C, may be from 110°C to 140°C, or may be from 120°C to 140°C.

[0053] Propylene resin C is a resin having a lower melting point than propylene resin A, and the difference in melting point between propylene resin A and propylene resin C may be from 5°C to 50°C, may be from 10°C to 40°C, or may be from 12°C to 30°C.

[0054] Propylene resin C is a random copolymer of propylene and other copolymerization components excluding propylene, and is preferably 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. Examples of other copolymerization components excluding propylene include ethylene, α-olefins having 4 or more carbon atoms, butadiene, etc. Examples of α-olefins having 4 or more carbon atoms include ethylene, 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, etc.

[0055] Among the resin components contained in the C layer, the content of propylene resin C is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, particularly preferably 80% by mass or more, extremely preferably 90% by mass or more, and may be 95% by mass or more, may be 98% by mass or more, or may be 99% by mass or more. The upper limit of the content of the aforementioned propylene resin C is not particularly limited and may be 100% by mass or less.

[0056] The C layer may contain a resin other than propylene resin C (also referred to as other resins). Examples of other resins include ethylene resins, olefin resins, and other resins.

[0057] The thickness of the C layer may be 5 μm to 30 μm, or may be 3 μm to 10 μm. The ratio of the thickness of the C layer to the thickness of the sealant layer may be 5% or more, may be 10% or more, may be 40% or less, or may be 30% or less.

[0058] Propylene resin A and propylene resin C can be produced, for example, by reacting propylene with other copolymerization components other than propylene in the presence of a metallocene catalyst. By adjusting the reaction time, the amount of catalyst, the composition ratio of raw materials, etc., the MFR, melting point, etc. of propylene resin A and propylene resin C can be adjusted. For example, by increasing the ratio of other copolymerization components (for example, ethylene) other than propylene relative to propylene, the melting point of the obtained propylene resin tends to be lower.

[0059] The A layer, B layer, C layer and other layers provided as necessary in the sealant layer may contain components other than resins such as propylene resin (other components). Examples of 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 include glycerin fatty acid ester monoglyceride, glycerin fatty acid ester acetylated monoglyceride, glycerin fatty acid ester organic acid monoglyceride, glycerin fatty acid ester medium-chain fatty acid triglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, special fatty acid ester, higher alcohol fatty acid ester, etc.

[0060] The A layer, B layer, C layer and other layers provided as necessary in the sealant 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, and the like.

[0061] The lubricant may be contained in any layer in the sealant layer or may not be contained.

[0062] Layer C in the sealant layer contains incompatible particles. Layer A, layer B, and other layers provided as necessary in the sealant layer may further contain incompatible particles.

[0063] The incompatible particles may be inorganic particles, organic particles, metal particles, composite particles thereof, or the like. 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.

[0064] Examples of the inorganic particles include inorganic oxide particles (such as silica particles, alumina particles, and titanium oxide particles), inorganic carbonate particles (such as calcium carbonate particles and barium carbonate particles), and inorganic silicate particles (such as aluminum silicate particles, talc particles, and kaolin particles). Among them, silica particles are preferable from the viewpoint of the balance between the antiblocking effect and the suppression of bubbles.

[0065] Examples of the organic particles include acrylic resin particles, polyolefin resin particles (such as polyethylene resin particles and polypropylene resin particles), and polystyrene resin particles.

[0066] The content rate of the incompatible particles in the C layer is from 1000 ppm to 4000 ppm, preferably from 1000 ppm to 3500 ppm, and more preferably from 1000 ppm to 3000 ppm.

[0067] The average particle diameter of the incompatible particles may be from 0.1 μm to 4.5 μm, or may be from 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 anti-blocking agent tends to be exerted, 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.

[0068] Hereinafter, an example of the exterior material for a power storage device of the present disclosure will be described with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view showing an example of the exterior material for a power storage device of the present disclosure. The exterior material 1 for a power storage device includes a base material layer 2, a barrier layer 4, and a sealant layer 3 in this order. The sealant layer 3 includes an A layer 7, a B layer 8, and a C 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 A layer 7.

[0069] <Manufacturing method of the exterior material for a 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.

[0070] 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 is 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.

[0071] Next, a sealant layer 3 is provided on the barrier layer 4 of the laminate A. The sealant layer 3 may be formed by disposing a resin film previously formed on the barrier layer 4 (first method), or a resin material for forming the sealant layer 3 (propylene resins A to C or resin compositions A to C containing propylene resins A to C as main components respectively) may be applied on the barrier layer 4 by extrusion molding, coating, etc. to form the sealant layer 3 (second method). In the first method, the resin film which is a multi-layer laminate such as the A layer 7, the B layer 8, and the C layer 9 can be produced by a co-extrusion method or the like.

[0072] 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.

[0073] When an 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. Examples of the extrusion lamination method include a method of laminating by extruding an inner adhesive layer 6 and a sealant layer (A layer, B layer 8, and C layer 9) on the barrier layer 4 of the laminate A (co-extrusion lamination method, tandem lamination method), etc. As the thermal lamination method, a method of separately forming a laminate B of the inner adhesive layer 6 and the sealant layer 3, and laminating the inner adhesive layer 6 of the laminate B and the barrier layer 4 of the laminate A so as to face each other, a laminate C having an inner adhesive layer 6 on the barrier layer 4 of the laminate A is formed, and the inner adhesive layer 6 of the laminate C and the sealant layer 3 are laminated, etc. may be mentioned. As the sandwich lamination method, 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. may be mentioned. As the dry lamination method, a method of solution coating an adhesive component for forming the 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. may be mentioned.

[0074] <Sealant film> The sealant film of the present disclosure includes an A layer, a B layer, and a C layer in this order. The A layer mainly contains a propylene resin A which is a random copolymer of propylene and other copolymerization components other than propylene. The B layer mainly contains a propylene resin B containing a rubber phase which is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms. The C layer mainly contains a propylene resin C which is a random copolymer of propylene and other copolymerization components other than propylene. The content of the rubber phase in the propylene resin B is 20% by mass to 40% by mass. The C layer further contains incompatible particles, and the content of the incompatible particles in the C layer is 1000 ppm to 4000 ppm. A preferred form of the sealant film of the present disclosure is the same as the preferred form of the exterior material for a power storage device of the present disclosure.

[0075] The sealant film of the present disclosure may be used for manufacturing an exterior material for a power storage device. For example, it may be used for manufacturing the sealant layer of an exterior material for a power storage device.

[0076] <Exterior case for power storage device> The exterior case for the power storage device of the present disclosure is a molded body of the aforementioned exterior material for the power storage device. The exterior material for the power storage device may be molded by deep drawing, protrusion molding, or the like. Examples of the shape of the exterior case for the power storage device include the exterior case 10 shown in FIGS. 2 and 3 described later.

[0077] <Power storage device> The power storage device of the present disclosure includes a power storage device main body portion and an exterior member that houses the power storage device main body portion and includes the aforementioned exterior material for the power storage device of the present disclosure. The exterior member may be configured to include the exterior case for the power storage device of the present disclosure.

[0078] An example of a power storage device 100 configured using the exterior material 1 for the power storage device of the present disclosure is shown in FIGS. 2 and 3. FIG. 2 is a schematic cross-sectional view showing an example of the power storage device. FIG. 3 is a schematic perspective view showing the components constituting the power storage device of FIG. 2 in a separated state. The power storage device 100 is a lithium-ion secondary battery.

[0079] In FIGS. 2 and 3, an exterior case 10 that is a molded body of the exterior material 1 and the planar exterior material 1 constitute an exterior member 15. The power storage device main body portion 110 is housed in the accommodation recess of the exterior case 10. Then, the planar exterior material 1 is arranged with the sealant layer 3 side facing inward (downward in FIGS. 2 and 3), and the peripheral edge of the sealant layer 3 of the planar exterior material 1 and the sealant layer 3 of the flange portion (sealing peripheral edge portion) 37 of the exterior case 10 are sealed and joined by heat fusion (heat seal).

[0080] In FIG. 2, reference numeral 39 is a heat seal portion where the peripheral edge of the exterior material 1 and the flange portion (sealing peripheral edge portion) 37 of the exterior 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 exterior member 15, but the illustration is omitted.

[0081] The power storage device main body portion 110 is not particularly limited, and examples include a battery main body portion, a capacitor main body portion, a condenser main body portion, and the like.

[0082] From the viewpoint of ensuring sealing, the width of the heat-sealing portion 39 is preferably set to 0.5 mm or more, and more preferably set to 3 mm to 15 mm.

[0083] The form of the exterior member 15 is not limited to FIGS. 2 and 3. The peripheries may be heat-sealed (heat-sealed) with a pair of planar exterior materials 1, or the peripheries may be heat-sealed (heat-sealed) with a pair of exterior cases 10.

Example

[0084] Next, examples of the present disclosure will be described, but the present disclosure is not particularly limited to these examples.

[0085] [Example 1] A chemical conversion treatment solution composed of phosphoric acid, polyacrylic acid (acrylic resin), chromium (III) salt compound, water, and alcohol was applied to both sides of an aluminum foil with a thickness of 35 μm, and then dried 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 It was.

[0086] Next, a biaxially stretched 6-nylon film with a thickness of 15 μm was dry-laminated (bonded) to one surface of the chemically treated 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.

[0087] Next, a 6-μm-thick A layer containing propylene resin A (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter: 2.0 μm; incompatible particles), a 18-μm-thick B layer containing propylene resin B (ethylene-propylene block copolymer, rubber phase content: 30% by mass), 1000 ppm of erucic acid amide (lubricant), and 50 ppm of silica particles (average particle diameter: 2.0 μm; incompatible particles), and a 6-μm-thick C layer containing propylene resin C (ethylene-propylene random copolymer), 1000 ppm of erucic acid amide (lubricant), and 2000 ppm of silica particles (average particle diameter: 2.0 μm; incompatible particles) were co-extruded using a T-die so that these three layers were laminated in this order to obtain a 30-μm-thick sealant film in which these three layers were laminated.

[0088] 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 so that the solid content coating amount was 2 g / m 2 After being heated and dried, it was superposed on the A-layer surface of the sealant film. Next, the laminate A in which the sealant film was superposed was sandwiched between a rubber nip roll and a laminating roll heated to 100°C and pressure-bonded to perform dry lamination, and it was 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.

[0089] [Examples 2 to 6 and Comparative Examples 1 to 4] In Example 1, an exterior material for a power storage device was obtained in the same manner as in Example 1, except that the thicknesses of the A layer to the C layer, the rubber phase content of propylene resin B, the average particle diameter and content of the incompatible particles were changed as shown in Table 1.

[0090] [Heat Seal Evaluation] [Seal Strength Measurement] After cutting out two test pieces with a width of 15 mm and a length of 200 mm from the obtained exterior material, the two test pieces were overlapped so that their inner sealant layers contacted each other, and a heat sealing device (TP-701-A) manufactured by Tester Sangyo Co., Ltd. was used. 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.

[0091] 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 exterior material (test piece) was peeled at a peeling speed of 100 mm / min by 180 degrees with the inner sealant layers of the seal portion, and the peeling strength at this time was measured and taken as the seal strength (N / 15 mm width).

[0092] [Presence or absence of bubbles] As shown in FIGS. 2 and 3, 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 accommodated in the accommodation recess of the exterior case 10, and the peripheral portion of the sealant layer 3 of the planar exterior material 1 and the sealant layer 3 of the flange portion (sealing peripheral portion) 37 of the exterior case 10 were seal-bonded by heat fusion to obtain a power storage device 100. At this time, the width of the heat-sealed portion 39 was 5 mm, the heat-sealing temperature was 200 °C, the seal pressure was 0.2 MPa (gauge display pressure), and the seal time was 2 seconds. 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-bonded power storage device 100 in an environment of 85 °C for 3 days, the presence or absence of bubble generation in the heat-sealed portion 39 was confirmed. Specifically, the cross-section of the heat-sealed portion 39 was observed using an optical microscope, and when cavities were present, it was considered that there were bubbles, and when cavities were not present, it was considered that there were no bubbles.

[0093]

Table 1

[0094] As shown in Table 1, for the exterior materials for the power storage devices of Examples 1 to 6, the sealing strength was high and the generation of bubbles was suppressed.

Claims

1. A base material layer, a barrier layer, and a sealant layer are laminated in this order, the sealant layer includes an A layer, a B layer, and a C layer in this order when viewed from the base material layer side, the A layer mainly contains a propylene resin A which is a random copolymer of propylene and other copolymerization components excluding propylene, the B layer mainly contains a propylene resin B containing a rubber phase which is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, the C layer mainly contains a propylene resin C which is a random copolymer of propylene and other copolymerization components excluding propylene, the content rate of the rubber phase in the propylene resin B is 20 mass% to 40 mass%, the C layer further contains incompatible particles, and the content rate of the incompatible particles in the C layer is 1000 ppm to 4000 ppm. An exterior material for a power storage device.

2. The exterior material for a power storage device according to Claim 1, wherein the ratio of the thickness of the B layer to the thickness of the sealant layer is 50% or more.

3. The exterior material for a power storage device according to Claim 1, wherein the incompatible particles include silica particles.

4. It includes an A layer, a B layer, and a C layer in this order, the A layer mainly contains a propylene resin A which is a random copolymer of propylene and other copolymerization components excluding propylene, the B layer mainly contains a propylene resin B containing a rubber phase which is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, the C layer mainly contains a propylene resin C which is a random copolymer of propylene and other copolymerization components excluding propylene, the content rate of the rubber phase in the propylene resin B is 20 mass% to 40 mass%, the C layer further contains incompatible particles, and the content rate of the incompatible particles in the C layer is 1000 ppm to 4000 ppm. A sealant film.

5. The sealant film according to Claim 4 for use in manufacturing an exterior material for a power storage device.

6. 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 3.

7. A power storage device main body part, an exterior member that houses the power storage device main body part and includes the exterior material for a power storage device according to any one of Claims 1 to 3, and a power storage device provided with the same.

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