Outer packaging material for power storage device, and power storage device

Abstract

The invention relates to an outer packaging material for a power storage device and the power storage device. The outer packaging material (1) for power storage devices comprises a polyamide resin layer (2) as an outer layer, a polyolefin resin layer (3) as an inner layer, and an aluminum foil layer (4) disposed between the two layers, the thickness of the outer packaging material (1) for power storage devices is 90 [mu] m or less, the breaking strain energy of the outer packaging material for power storage devices is 60 MJ / m3 or more, and the thickness of the outer packaging material (1) for power storage devices is 90 [mu] m or less. The fracture strain energy is obtained from a tensile stress-strain curve obtained by a tensile test. As a result, it is possible to provide a thin and lightweight outer packaging material for power storage devices, which is capable of ensuring excellent moldability even when molded deep, and which has high strength and excellent impact resistance.

Description

[0001] This application is a divisional application of the invention patent application filed on February 28, 2017, with application number 201710116517.0 and invention title "Outer Packaging Material for Energy Storage Equipment and Energy Storage Equipment". Technical Field

[0002] This invention relates to outer packaging materials for batteries and capacitors used in portable devices such as smartphones and tablets, and for batteries and capacitors used in hybrid electric vehicles, electric vehicles, wind power generation, solar power generation, and nighttime electricity storage devices, as well as storage devices packaged using the outer packaging materials.

[0003] It should be noted that in the claims and description of this application, the term "tensile breaking strength" means the tensile breaking strength determined by preparing a Type 2 test piece (15 mm wide) according to JIS K7127-1999 (Test Methods for Tensile Properties, Part 3), with a fixture spacing of 100 mm, a mark spacing of 50 mm, and a tensile speed of 100 mm / min.

[0004] Furthermore, in the claims and description of this application, the term "tensile breaking elongation" means the tensile breaking elongation determined by preparing a type 2 test piece (with a specimen width of 15 mm) according to JIS K7127-1999 (Test Methods for Tensile Properties, Part 3), with a fixture spacing of 100 mm, a mark spacing of 50 mm, and a tensile speed of 100 mm / min.

[0005] Furthermore, in the claims and description of this application, the term "fracture strain energy" means the fracture strain energy (energy per unit volume) obtained by preparing a type 2 test specimen (15 mm wide) according to JISK7127-1999 (Test Methods for Tensile Properties, Part 3), measuring the tensile stress-strain curve obtained under the conditions of 100 mm between clamps, 50 mm between marks, and a tensile speed of 100 mm / min, and calculating the area under the curve (the curve from the start of tension until fracture) in the tensile stress-strain curve.

[0006] In addition, in the claims and description of this application, the term "aluminum" is used to include aluminum and its alloys. Background Technology

[0007] In recent years, with the trend towards thinner and lighter mobile electronic devices such as smartphones and tablets, laminates formed from heat-resistant resin layers, adhesive layers, metal foil layers, adhesive layers, and thermoplastic resin layers have been used instead of traditional metal cans as outer packaging materials for energy storage devices such as lithium-ion secondary batteries, lithium polymer secondary batteries, lithium-ion capacitors, and double-layer capacitors mounted on these devices (see Patent Document 1). Typically, these laminates are stretched or deep-drawn to form a roughly rectangular or other three-dimensional shape. Furthermore, the use of these laminates (outer packaging materials) to package power supplies for electric vehicles, large power supplies for energy storage, capacitors, and the like is also gradually increasing.

[0008] Patent Document 1: Japanese Patent Application Publication No. 2005-22336 Summary of the Invention

[0009] On the other hand, in recent years, the aforementioned mobile power equipment has continued to become thinner and lighter. As the energy storage equipment installed in them, it is also required to become thinner and lighter. In response to this demand, the outer packaging materials for energy storage equipment are constantly being developed to achieve thinner and lighter designs.

[0010] In response to the aforementioned requirements for thinner and lighter materials, when the outer packaging material is designed to be thinner, problems such as cracking occur when deep forming is performed during stretching and deep forming, resulting in the problem that good forming can only be achieved at a shallow depth.

[0011] The present invention was made in view of the above-mentioned technical background, and its purpose is to provide a thin-walled, lightweight outer packaging material for energy storage devices. The outer packaging material for energy storage devices can ensure excellent formability even when deeply molded, and has high strength and excellent impact resistance.

[0012] To achieve the above objectives, the present invention provides the following means.

[0013] [1] An outer packaging material for an energy storage device, comprising a polyamide resin layer as an outer layer, a polyolefin resin layer as an inner layer, and an aluminum foil layer disposed between the two layers. The characteristic feature is that the thickness of the outer packaging material for the energy storage device is less than 90 μm, the tensile breaking strength of the outer packaging material for the energy storage device is more than 110 N / 15 mm width, and the tensile breaking elongation of the outer packaging material for the energy storage device is more than 90%.

[0014] [2] As described in item 1 above, for the outer packaging material of the energy storage device, when the thickness of the polyamide resin layer is set as "X" and the thickness of the aluminum foil layer is set as "Y", the following relationship holds: (X / Y) ≥ 0.6.

[0015] [3] The outer packaging material for the energy storage device as described in item 1 or 2 above, wherein the fracture strain energy of the outer packaging material for the energy storage device is 60 MJ / m. 3 The fracture strain energy mentioned above is obtained from the tensile stress-strain curve obtained through tensile testing.

[0016] [4] The outer packaging material for the storage device as described in any one of items 1 to 3 above, wherein when the thickness of the aluminum foil layer is set as "Y" and the thickness of the polyolefin resin layer is set as "V", the following relationship holds: (Y / V) ≥ 0.6.

[0017] [5] An energy storage device, characterized in that, The device comprises the main body of the energy storage equipment and the outer packaging material for the energy storage equipment as described in any one of items 1 to 4 above. The main body of the energy storage device is packaged using the aforementioned outer packaging material.

[0018] In the invention of [1], the tensile breaking strength of the outer packaging material for the energy storage device is 110 N / 15 mm or more, and the tensile breaking elongation of the outer packaging material for the energy storage device is 90% or more. Thus, even if the thickness of the outer packaging material is set to a thin wall of 90 μm or less, it is possible to provide an outer packaging material for the energy storage device that can ensure excellent formability even with deep molding, and has high strength and excellent impact resistance.

[0019] In the invention of [2], when the thickness of the polyamide resin layer is set as "X" and the thickness of the aluminum foil layer is set as "Y", the relationship (X / Y)≥0.6 holds true. Thus, even with deeper molding, excellent formability can be ensured and impact resistance can be improved.

[0020] In the invention of [3], the fracture strain energy of the outer packaging material for the energy storage device is 60 MJ / m. 3 In addition, even with deeper molding, excellent formability can be ensured, and impact resistance can be improved.

[0021] In the invention of [4], when the thickness of the aluminum foil layer is set as "Y" and the thickness of the polyolefin resin layer is set as "V", the relationship (Y / V) ≥ 0.6 is established. Thus, even with deeper molding, excellent formability can be ensured, and higher strength and further improved impact resistance can be achieved.

[0022] In the invention (energy storage device) of [5], an energy storage device is provided that is packaged with an outer packaging material, which is designed to be thin-walled, can be deeply molded without cracking or other problems, and has high strength and excellent impact resistance. Attached Figure Description

[0023] Figure 1 This is a cross-sectional view showing one embodiment of the outer packaging material for energy storage devices according to the present invention.

[0024] Figure 2 This is a cross-sectional view showing one embodiment of an energy storage device constructed using the energy storage device outer packaging material of the present invention.

[0025] Figure 3 These are tensile stress-strain curves (SS curves) obtained by tensile testing of the outer packaging materials for energy storage devices in Examples 1-4.

[0026] Figure 4 The tensile stress-strain curves (SS curves) of the outer packaging materials for energy storage devices in Comparative Examples 1 to 5 are obtained by tensile testing (for comparison purposes, the tensile stress-strain curve of Example 4 is also shown).

[0027] Explanation of reference numerals in the attached figures 1...Outer packaging materials for energy storage equipment 2... Polyamide resin layer (outer layer) 3... Polyolefin resin layer (inner layer) 4... Aluminum foil layer 5... First adhesive layer 6...Second adhesive layer 11……Molded shell 19……Main body of the energy storage equipment 20……Storage equipment Detailed Implementation

[0028] One embodiment of the outer packaging material 1 for the energy storage device of the present invention is shown in Figure 1 The outer packaging material 1 for the storage device is used for the casing of a lithium-ion secondary battery. That is, the outer packaging material 1 for the storage device can be formed, for example, by deep drawing, stretching, or other molding processes to produce a casing for a secondary battery.

[0029] Figure 1 The outer packaging material 1 for the energy storage device shown comprises the following components: a polyamide resin layer (outer layer) 2 is integrally laminated on one side of the aluminum foil layer 4 through a first adhesive layer 5, and a polyolefin resin layer (inner layer) 3 is integrally laminated on the other side of the aluminum foil layer 4 through a second adhesive layer 6.

[0030] For the outer packaging material 1 for the energy storage device of the present invention, the thickness (total thickness) of the outer packaging material 1 for the energy storage device is 90 μm or less, the tensile breaking strength of the outer packaging material for the energy storage device is 110 N / 15 mm or more, and the tensile breaking elongation of the outer packaging material for the energy storage device is 90% or more.

[0031] According to the present invention, the tensile breaking strength of the outer packaging material for energy storage devices is 110 N / 15 mm or more, and the tensile breaking elongation is 90% or more. Thus, even if the thickness of the outer packaging material is designed to be thin-walled at 90 μm or less, an outer packaging material for energy storage devices can be provided that ensures excellent formability even with deep molding, and also has high strength and excellent impact resistance.

[0032] The tensile breaking strength of the outer packaging material for the aforementioned energy storage equipment is preferably 115 N / 15 mm width or higher, more preferably 120 N / 15 mm width or higher. Particularly preferred is the tensile breaking strength of the outer packaging material for the aforementioned energy storage equipment, which is in the range of 120 N / 15 mm width to 180 N / 15 mm width.

[0033] The tensile breaking elongation of the outer packaging material for the above-mentioned energy storage equipment is preferably 120% or more, and more preferably 120% to 200%.

[0034] In this invention, when the thickness of the polyamide resin layer 2 is set as "X" and the thickness of the aluminum foil layer 4 is set as "Y", the following relationship is preferably satisfied: (X / Y) ≥ 0.6.

[0035] At this point, even with deeper molding, excellent formability can be ensured, and impact resistance can be improved. Among these, a configuration in which the relationship (X / Y) ≥ 0.8 holds is more preferred, and a configuration in which the relationship (X / Y) ≥ 1.0 holds is particularly preferred.

[0036] Furthermore, when the thickness of the aluminum foil layer 4 is set to "Y" and the thickness of the polyolefin resin layer 3 is set to "V", the following relationship is preferred: (Y / V) ≥ 0.6.

[0037] At this point, even with deeper molding, excellent formability can be ensured, and higher strength and further improved impact resistance can be achieved. Among these, a configuration in which the relationship (Y / V) ≥ 0.8 holds is more preferred, and a configuration in which the relationship (Y / V) ≥ 1.0 holds is particularly preferred.

[0038] Furthermore, a configuration in which the relationship X≥Y≥V holds is preferred. In this case, even with deeper molding, excellent formability can be ensured.

[0039] Furthermore, the fracture strain energy of the outer packaging material for the aforementioned energy storage equipment is preferably 60 MJ (megajoules) / m. 3 The fracture strain energy mentioned above is obtained from the tensile stress-strain curve obtained through tensile testing. In this case, even with deeper molding, excellent formability can be ensured, and impact resistance can be improved.

[0040] In this invention, there are no particular limitations on the polyamide resin layer (outer layer) 2 described above. For example, polyamide films such as nylon films can be used, and stretched films using these films are preferred. Specifically, a biaxially stretched polyamide film such as a biaxially stretched nylon film is preferred as the polyamide resin layer (outer layer) 2. Furthermore, a simultaneously biaxially stretched polyamide film such as a biaxially stretched nylon film is particularly preferred. There are no particular limitations on the nylon film described above; for example, 6-nylon films, 6,6-nylon films, MXD nylon films, etc., can be used.

[0041] The thickness of the polyamide resin layer 2 is preferably set to 15 μm to 40 μm. More preferably, the thickness of the polyamide resin layer 2 is set to 20 μm to 40 μm.

[0042] The hot water shrinkage rate of the polyamide film used for the polyamide resin layer 2 is preferably 2.5% to 10%. This allows for deeper molding. Furthermore, it is preferable to use a biaxially stretched polyamide film with a ratio (MD / TD) of "hot water shrinkage rate in the M direction" to "hot water shrinkage rate in the T direction" in the range of 0.8 to 1.2. When the structure uses a ratio (MD / TD) in the range of 0.8 to 1.2, an outer packaging material with particularly good formability can be obtained. It should be noted that "M direction" refers to the "mechanical travel direction," and "T direction" refers to the "direction perpendicular to the M direction (mechanical travel direction)." The following meanings are the same.

[0043] It should be noted that the so-called "hot water shrinkage rate" refers to the dimensional change rate of the test piece (10cm×10cm) of polyamide resin stretch film before and after immersion in hot water at 95℃ for 30 minutes in the stretching direction, which can be calculated by the following formula.

[0044] Hot water shrinkage rate (%) = {(EF) / E} × 100 E: Dimension in the stretching direction before impregnation treatment F: Dimension in the stretching direction after impregnation treatment.

[0045] It should be noted that when using biaxially stretched membranes, the hot water shrinkage rate is the average of the dimensional change rates in both stretching directions.

[0046] The hot water shrinkage rate of the polyamide resin stretch film can be controlled, for example, by adjusting the heat-fixing temperature during the stretching process.

[0047] The tensile breaking strength of the polyamide film used for the polyamide resin layer 2 is preferably 50 N / 15 mm width or more, more preferably 60 N / 15 mm width or more, and particularly preferably 90 N / 15 mm width or more. Furthermore, it is preferable that the ratio of "tensile breaking strength of the polyamide film in the M direction" to "tensile breaking strength of the polyamide film in the T direction" is in the range of 0.8 to 1.2, which allows for deeper molding.

[0048] The tensile elongation at break of the polyamide film used for the polyamide resin layer 2 is preferably 70% or more, more preferably 80% or more, and particularly preferably 120% or more. Furthermore, it is preferable that the ratio of "tensile elongation at break in the M direction of the polyamide film" to "tensile elongation at break in the T direction of the polyamide film" is in the range of 0.8 to 1.2, which achieves the effect of high strength and the ability to perform deeper molding.

[0049] The aluminum foil layer 4 serves to provide gas barrier properties (preventing the intrusion of oxygen and moisture) to the outer packaging material 1. The aluminum foil layer 4 is preferably made of an Al-Fe based annealed material. The thickness of the aluminum foil layer 4 is preferably 10 μm to 35 μm, more preferably 15 μm to 35 μm.

[0050] For the aluminum foil layer 4 described above, it is preferable to perform a chemical conversion treatment on at least the inner surface (the surface on the side of the second adhesive layer 6; the surface on the side of the polyolefin resin layer 3). By performing such a chemical conversion treatment, corrosion of the metal foil surface caused by the contents (electrolyte of the battery, etc.) can be sufficiently prevented. For example, the metal foil is chemically converted by performing the following treatment: That is, for example, by coating the surface of the degreased metal foil with any one of the aqueous solutions 1) to 3) below and then drying it, thereby performing the chemical conversion treatment: 1) Contains phosphoric acid; Chromic acid; and An aqueous solution of a mixture of at least one compound selected from the group consisting of metal salts of fluorides and nonmetal salts of fluorides. 2) Contains phosphoric acid; At least one resin selected from the group consisting of acrylic resins, deacetylated chitosan derivative resins, and phenolic resins; and An aqueous solution of a mixture of at least one compound selected from the group consisting of chromic acid and chromium (III) salts 3) Contains phosphoric acid; The resin is selected from at least one resin in the group consisting of acrylic resins, deacetylated chitosan derivative resins and phenolic resins; At least one compound selected from the group consisting of chromic acid and chromium (III) salts; and An aqueous solution of a mixture of at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides.

[0051] Regarding the chemical conversion coating, the preferred chromium adhesion amount (per single side) is 0.1 mg / m². 2 ~50 mg / m 2 2 mg / m 2 ~20 mg / m 2 .

[0052] As for the aforementioned polyolefin resin layer (inner layer) 3, it not only possesses excellent chemical resistance to highly corrosive electrolytes used in lithium-ion secondary batteries, but also serves to impart heat-sealing properties to the outer packaging material.

[0053] There are no particular limitations on the polyolefin resin layer 3 described above, but an unstretched (non-stretched) polyolefin resin film layer is preferred. There are no particular limitations on the polyolefin resin 3 described above, and examples include ethylene-propylene random copolymer resins and ethylene-propylene block copolymer resins.

[0054] Preferably, the polyolefin resin layer 3 is formed of an unstretched film consisting of a random copolymer containing propylene and other copolymers (olefins) as copolymers, a block copolymer containing propylene and other copolymers (olefins) as copolymers, and another random copolymer containing propylene and other copolymers (olefins) as copolymers. Furthermore, the polyolefin resin layer 3 is particularly preferably formed of an unstretched film consisting of a three-layer laminate consisting of ethylene-propylene random copolymer resin, ethylene-propylene block copolymer resin, and ethylene-propylene random copolymer resin. Thus, the polyolefin resin layer 3 can be a single layer or multiple layers.

[0055] The thickness of the polyolefin resin layer 3 is preferably set to 10 μm to 30 μm. More preferably, it is set to 15 μm to 30 μm.

[0056] There are no particular limitations on the first adhesive layer 5 mentioned above; for example, polyurethane adhesive layers, polyester polyurethane adhesive layers, polyether polyurethane adhesive layers, acrylic adhesive layers, etc., can be used. The thickness of the first adhesive layer 5 is preferably set to 1 μm to 5 μm. From the viewpoint of making the outer packaging material thinner and lighter, the thickness of the first adhesive layer 5 is particularly preferably set to 1 μm to 3 μm.

[0057] There are no particular limitations on the second adhesive layer 6 described above. For example, the adhesive layers listed as the first adhesive layer 5 can also be used, but it is preferable to use an acid-modified polyolefin adhesive that causes less swelling due to the electrolyte (as a curing agent, a polyfunctional isocyanate is preferred). The thickness of the second adhesive layer 6 is preferably set to 1 μm to 5 μm. From the viewpoint of thinning and lightweighting the outer packaging material, the thickness of the second adhesive layer 6 is particularly preferably set to 1 μm to 3 μm.

[0058] To achieve thinner walls, the thickness (total thickness) of the outer packaging material 1 for the aforementioned energy storage device is set to 90 μm or less. Preferably, the thickness of the outer packaging material 1 for the aforementioned energy storage device is set to 40 μm to 90 μm, and particularly preferably to 45 μm to 80 μm.

[0059] By molding the outer packaging material 1 of the energy storage device of the present invention (deep drawing, stretching, etc.), a molded shell (battery shell, etc.) can be obtained. It should be noted that the outer packaging material 1 of the present invention can also be used directly without molding.

[0060] An embodiment of the energy storage device 20 constructed using the energy storage device outer packaging material 1 of the present invention is shown in... Figure 2 The energy storage device 20 uses a lithium-ion secondary battery.

[0061] The battery 20 described above includes: an electrolyte 21, tabs 22, an unformed planar outer packaging material 1, and a molded shell 11 with a receiving recess 11b obtained by molding the outer packaging material 1 (see See). Figure 2 The electrolyte 21 and the tab 22 described above constitute the main body 19 of the energy storage device.

[0062] The electrolyte 21 and a portion of the tab 22 are housed within the receiving recess 11b of the molded housing 11. A planar outer packaging material 1 is positioned above the molded housing 11. The periphery (inner layer 3) of the outer packaging material 1 is joined and sealed to the sealing periphery 11a (inner layer 3) of the molded housing 11, thereby constituting the battery 20. It should be noted that the front end of the tab 22 is extended to the outside (see...). Figure 2 ).

[0063] Example The following describes specific embodiments of the present invention, but the present invention is not particularly limited to these embodiments.

[0064] <Example 1> An annealed aluminum foil (A8021 as specified in JIS H4160) with a thickness of 25 μm was coated on both sides with a chemical conversion treatment solution containing phosphoric acid, polyacrylic acid (acrylic resin), chromium (III) salt compound, water, and alcohol, and then dried at 180°C to form a chemical conversion coating. The chromium deposition on each side of the chemical conversion coating was 10 mg / m². 2 .

[0065] Next, on one side of the aluminum foil 4 that has undergone the above chemical conversion treatment, a 25 μm thick biaxially stretched 6 nylon film (outer layer) 2 is obtained by dry lamination (bonding) using a two-component curable polyester-polyurethane adhesive (main agent: polyester-polyurethane resin, curing agent: polyfunctional isocyanate) 5 and stretching using a simultaneous biaxial stretching method. The hot water shrinkage rate in the MD direction of the above-mentioned biaxially stretched 6 nylon film is 4.3%, and the ratio of the hot water shrinkage rate in the M direction to the hot water shrinkage rate in the T direction (MD / TD) of the above-mentioned biaxially stretched 6 nylon film is 1.0.

[0066] Next, a three-layer co-extrusion process is performed using a T-die, consisting of a 4 μm thick first resin layer formed from an ethylene-propylene random copolymer, a 17 μm thick second resin layer formed from an ethylene-propylene block copolymer resin, and another 4 μm thick first resin layer formed from an ethylene-propylene random copolymer. This yields a 25 μm thick sealing film (first resin layer / second resin layer / first resin layer) 3 formed by laminating the above three layers. Then, one side of the sealing film (inner layer) 3 is overlapped with the other side of the dry-laminated aluminum foil 4 through a two-component curable maleic acid modified polypropylene adhesive (curing agent is polyfunctional isocyanate) 6. Dry lamination is performed by clamping the film between a rubber clamping roller and a lamination roller heated to 100°C. The film is then aged (heated) at 50°C for 5 days to obtain a product with the following structure: Figure 1 The outer packaging material 1 for energy storage devices is shown with a thickness of 81 μm.

[0067] It should be noted that, as the above-mentioned two-component curing maleic acid modified polypropylene adhesive, an adhesive solution is prepared by mixing 100 parts by weight of maleic acid modified polypropylene (melting point 80℃, acid value 10 mgKOH / g) as the main agent, 8 parts by weight of 1,6-hexamethylene diisocyanate isocyanurate (NCO content: 20% by weight) as the curing agent, and a solvent. This adhesive solution is prepared such that the solid component coating amount is 2 g / m². 2 The coating is applied to the other side of the aluminum foil 4, heated and dried, and then overlapped with a first resin layer of the sealing film 3.

[0068] <Example 2> Instead of the 25 μm thick sealing film (a first resin layer with a thickness of 4 μm / a second resin layer with a thickness of 17 μm / a first resin layer with a thickness of 4 μm), a 20 μm thick sealing film (a first resin layer with a thickness of 3 μm / a second resin layer with a thickness of 14 μm / a first resin layer with a thickness of 3 μm) was used. Otherwise, the procedure was the same as in Example 1, resulting in a structure as described in Example 1. Figure 1 The outer packaging material 1 for energy storage devices shown has a thickness of 76 μm. It should be noted that the first resin used in Example 2 is the same as the first resin used in Example 1, and the second resin used in Example 2 is the same as the second resin used in Example 1. The same applies to the following examples and comparative examples.

[0069] <Example 3> As a biaxially stretched 6 nylon film (outer layer), a 2 μm thick black ink printing layer is laminated on one side (aluminum foil layer side), and a 2 μm thick surface coating formed by a two-component curable polyurethane resin (containing 12% by mass of silica with an average particle size of 4 μm and 8% by mass of acrylic resin beads with an average particle size of 3 μm) is laminated on the other side. Otherwise, the same procedure as in Example 1 is followed to obtain an outer packaging material 1 for energy storage devices with a thickness of 75 μm.

[0070] <Example 4> Except for using a 20 μm thick aluminum foil instead of a 25 μm thick aluminum foil, the procedure was the same as in Example 2, resulting in a structure as shown. Figure 1 The outer packaging material 1 for energy storage devices has a thickness of 71 μm, as shown.

[0071] <Comparative Example 1> A 40 μm thick aluminum foil was used instead of a 25 μm thick aluminum foil, and a 40 μm thick sealing film (a 6 μm thick first resin layer / a 28 μm thick second resin layer / a 6 μm thick first resin layer) was used instead of a 25 μm thick sealing film (a 4 μm thick first resin layer / a 17 μm thick second resin layer / a 4 μm thick first resin layer). Otherwise, the procedure was the same as in Example 1, and an outer packaging material for energy storage devices with a thickness of 111 μm was obtained.

[0072] <Comparative Example 2> A 15 μm thick biaxially stretched 6 nylon film (outer layer) was used instead of a 25 μm thick biaxially stretched 6 nylon film (outer layer), a 35 μm thick aluminum foil was used instead of a 25 μm thick aluminum foil, and a 30 μm thick sealing film (a 6 μm thick first resin layer / a 18 μm thick second resin layer / a 6 μm thick first resin layer) was used instead of a 25 μm thick sealing film (a 4 μm thick first resin layer / a 17 μm thick second resin layer / a 4 μm thick first resin layer). Otherwise, the procedure was the same as in Example 1 to obtain an outer packaging material for energy storage devices with a thickness of 86 μm.

[0073] <Comparative Example 3> A biaxially stretched 6 nylon film (outer layer) with a thickness of 15 μm was used instead of a biaxially stretched 6 nylon film (outer layer) with a thickness of 25 μm, and an aluminum foil with a thickness of 30 μm was used instead of an aluminum foil with a thickness of 25 μm. Otherwise, the same procedure as in Example 1 was followed to obtain an outer packaging material for energy storage devices with a thickness of 76 μm.

[0074] <Comparative Example 4> A biaxially stretched 6 nylon film (outer layer) with a thickness of 15 μm was used instead of a biaxially stretched 6 nylon film (outer layer) with a thickness of 25 μm. Otherwise, the same procedure as in Example 1 was followed to obtain an outer packaging material for energy storage devices with a thickness of 71 μm.

[0075] <Comparative Example 5> A biaxially stretched 6 nylon film (outer layer) with a thickness of 12 μm was used instead of a biaxially stretched 6 nylon film (outer layer) with a thickness of 25 μm. Otherwise, the same procedure as in Example 1 was followed to obtain an outer packaging material for energy storage devices with a thickness of 66 μm.

[0076] The various physical properties of the outer packaging materials for energy storage devices obtained in the above embodiments and comparative examples were determined through the following operations. For each outer packaging material for energy storage devices, according to JIS K7127-1999 (-Test methods for tensile properties-Part 3: Test conditions for films and sheets), type 2 test pieces (sample width 15 mm) were prepared, and tensile tests were carried out under the conditions of 100 mm between clamps, 50 mm between marks, and a tensile speed of 100 mm / min. Tensile stress-strain curves (SS curves) were prepared, and the tensile breaking strength, tensile breaking elongation, and fracture strain energy were determined from the SS curves.

[0077] It should be noted that the above-mentioned "fracture strain energy" is the fracture strain energy (energy per unit volume) obtained by calculating the area under the curve (the curve from the start of tension until fracture) in the tensile stress-strain curve (SS curve) obtained above.

[0078] The tensile stress-strain (SS) curves obtained by tensile testing of the outer packaging materials for energy storage devices in Examples 1-4 are shown below. Figure 3 Furthermore, the tensile stress-strain (SS) curves obtained from tensile tests of the outer packaging materials of Comparative Examples 1-5 are shown below. Figure 4 .Should Figure 3 , Figure 4 In the figure, the vertical axis represents tensile stress (unit: N / 15 mm), and the horizontal axis represents strain (elongation) (unit: %).

[0079] The performance of the outer packaging materials for each energy storage device obtained through the above operations was evaluated based on the following evaluation method. The results are shown in Table 1. It should be noted that in Table 1, "aluminum foil layer" means "aluminum foil layer" (abbreviation).

[0080] <Evaluation of thinness> Packaging materials for energy storage devices with a thickness (total thickness) of less than 90 μm are evaluated as "○" (qualified), while materials with a thickness (total thickness) greater than 90 μm are evaluated as "×" (unqualified).

[0081] <Formability Evaluation Method> Using a stretch forming machine (product number: TP-25C-X2) manufactured by AMADA Co., Ltd., the outer packaging material was stretched to form an approximate cuboid shape of 54 mm long × 34 mm wide. That is, the stretch forming was performed by varying the forming depth. The corners of the resulting molded body were investigated for pinholes and cracks, and the "maximum forming depth (mm)" that did not produce such pinholes and cracks was investigated. The evaluation was based on the following criteria.

[0082] (Judgment Criteria) "○"... Maximum molding depth is 7 mm or more. “△”... The maximum forming depth is 5 mm or more but less than 7 mm. "×"……The maximum molding depth is less than 5 mm.

[0083] <Impact Resistance Evaluation Method> For each embodiment and comparative example, two rectangular outer packaging bodies were fabricated. The two outer packaging bodies were overlapped with their inner layers forming the inner side (internal side), leaving one gap, and then heat-sealed the three perimeter edges. Next, 5 mL of electrolyte was injected into the unsealed portion, and the unsealed portion was heat-sealed while still containing air to complete the sealing, thus obtaining a simulated battery. It should be noted that the following electrolyte was used: a mixed solvent obtained by combining ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in equal volume ratios was used as the electrolyte, and lithium hexafluorophosphate (LiPF6) was dissolved in the mixed solvent at a concentration of 1 mol / L. Ten simulated batteries were fabricated for each embodiment and comparative example.

[0084] Next, a 15 mm diameter cylindrical bar was placed on the upper surface (plane) of the simulated battery in a stable state, and then a 9 kg spherical metal weight was dropped onto the cylindrical bar. The impact resistance of the outer packaging material was evaluated based on the following criteria.

[0085] (Judgment Criteria) "○"... Of the 10 simulated batteries, fewer than 3 had their outer packaging material damaged due to the falling weight. "△"... Of the 10 simulated batteries, 4 to 7 had their outer packaging damaged due to the falling weight. "×"... Of the 10 simulated batteries, 8 to 10 had their outer packaging materials damaged due to the falling of heavy objects.

[0086] <Comprehensive Judgment> Materials with all three evaluation results of "○" in the thinness evaluation, formability evaluation, and impact resistance evaluation are judged as "○" (excellent), and materials with any one of the evaluation results of "×" or "△" are judged as "×" (not good).

[0087] As can be seen from Table 1, the outer packaging materials for energy storage devices in Embodiments 1 to 4 of the present invention have a wall thickness of less than 90 μm, a large maximum molding depth, and can ensure excellent formability even with deep molding, as well as excellent impact resistance.

[0088] In contrast, regarding the outer packaging material of Comparative Example 1, where the thickness of the outer packaging material was set at 111 μm, although it exhibited excellent formability and impact resistance, the thickness of the outer packaging material at 111 μm could not meet the requirement for thinner walls. Furthermore, in Comparative Examples 2-5, which deviate from the scope of this invention, deeper molding resulted in poor molding and insufficient impact resistance.

[0089] Industrial availability The outer packaging material for energy storage devices of the present invention can be used as the outer packaging material for various energy storage devices. As a specific example of the energy storage device, for example: • Energy storage devices such as lithium secondary batteries (lithium-ion batteries, lithium polymer batteries, etc.); • Lithium-ion capacitors; • Electric double-layer capacitors; etc.

[0090] This application claims priority to Japanese Patent Application No. 2016-40083, filed on March 2, 2016, the disclosure of which forms a direct part of this application.

[0091] The terminology and descriptions used herein are for illustrative purposes only and are not intended to limit the invention. Any design modifications are permitted within the scope of the claims, provided they do not depart from their spirit.

Claims

1. An outer packaging material for an energy storage device, comprising a polyamide resin layer as an outer layer, a polyolefin resin layer as an inner layer, and an aluminum foil layer disposed between the two layers. Its features are, The thickness of the outer packaging material for the energy storage device is less than 90 μm, and the fracture strain energy of the outer packaging material for the energy storage device is 60 MJ / m. 3 The fracture strain energy mentioned above is obtained from the tensile stress-strain curve obtained through tensile testing.

2. The outer packaging material for energy storage devices as described in claim 1, wherein, The tensile breaking strength of the outer packaging material for the energy storage device is 110 N / 15 mm or more, and the tensile breaking elongation of the outer packaging material for the energy storage device is 90% or more.

3. The outer packaging material for energy storage devices as described in claim 1 or 2, wherein, When the thickness of the polyamide resin layer is set to "X" and the thickness of the aluminum foil layer is set to "Y", the following relationship holds: (X / Y) ≥ 0.

6.

4. The outer packaging material for energy storage devices as described in any one of claims 1 to 3, wherein, When the thickness of the aluminum foil layer is set to "Y" and the thickness of the polyolefin resin layer is set to "V", the following relationship holds true. (Y / V) ≥ 0.

6.

5. The outer packaging material for energy storage devices as described in any one of claims 1 to 4, wherein, The thickness of the polyamide resin layer is 20 μm to 40 μm, the thickness of the aluminum foil layer is 15 μm to 35 μm, and the thickness of the polyolefin resin layer is 15 μm to 30 μm.

6. The outer packaging material for energy storage equipment as described in any one of claims 1 to 5, wherein, The polyamide resin layer (outer layer) is composed of a biaxially stretched polyamide film. The biaxially stretched polyamide film has a hot water shrinkage rate of 2.5~10%, a hot water shrinkage rate in the M direction to the hot water shrinkage rate in the T direction of 0.8~1.2, a tensile breaking strength of 50 N / 15 mm or more, and a tensile breaking elongation of 70% or more.

7. The outer packaging material for energy storage devices as described in any one of claims 1 to 6, wherein, The polyamide resin layer (outer layer) is composed of a biaxially stretched polyamide film.

8. An energy storage device, characterized in that, It comprises the main body of the energy storage device and the outer packaging material for the energy storage device as described in any one of claims 1 to 7. The main body of the energy storage device is packaged using the aforementioned outer packaging material.

Images