Exterior materials for energy storage devices and energy storage devices

Abstract

To provide an exterior material for a power storage device having excellent processability and puncture resistance.SOLUTION: An exterior material 1 for a power storage device according to the present invention includes a base material layer 51, a barrier layer 52 laminated inside the base material layer 51, and a sealant layer 53 laminated inside the barrier layer 52. The base material layer 51 is composed of a polyamide film. In the base material layer 51, the hot water shrinkage rate of TD and the hot water shrinkage rate of MD are both 2.0% to 5.0%, and the difference between the hot water shrinkage rate of TD and the hot water shrinkage rate of MD is 1.5% or less. The elastic modulus of TD and the elastic modulus of MD are both 1.5 GPa to 3 GPa, and at least one of the breaking strength of TD and the breaking strength of MD is 320 MPa or more.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This invention relates to an exterior material for a power storage device such as a battery and a capacitor used in a mobile terminal such as a smartphone or a tablet personal computer (tablet PC), as well as a battery and a capacitor used in a hybrid vehicle, an electric vehicle, etc., and a power storage device.

Background Art

[0002] Power storage devices are used as energy suppliers for mobile devices such as electric vehicles and hybrid vehicles, and portable devices such as power tools and mobile terminals. Such power storage devices are required to be lightweight and miniaturized in order to facilitate movement and carrying. Therefore, a metal can has been mainly used as the casing of the power storage device in the past. In recent years, however, a metal laminate material (exterior material) having a laminate of a base material layer, a barrier layer (metal foil layer) and a sealant layer as a basic configuration is often used.

[0003] Unlike stationary power storage devices, such non-stationary power storage devices such as mobile and portable types are highly likely to have their exterior materials damaged by vibration, external pressure, etc. Therefore, the exterior material is required to have the same mechanical strength as that of a metal can, particularly puncture resistance.

[0004] Conventionally, an aluminum foil has been used for the barrier layer as the exterior material. However, it has been difficult to obtain sufficient puncture resistance with a normal aluminum laminate material.

[0005] Therefore, in the power storage device shown in Patent Document 1 below, as the exterior material, a metal laminate material (stainless laminate material) in which the barrier layer is formed of a stainless foil (SUS foil) having higher rigidity than an aluminum foil is used to improve puncture resistance. Ne ート材)を用いることによって、突き刺し耐性を向上させるようにしている。

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-161362 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, because stainless steel foil has high rigidity, using stainless steel laminate as an exterior material for energy storage devices could lead to poor moldability (processability) of the exterior material, potentially resulting in reduced dimensional accuracy and decreased production efficiency.

[0008] This invention has been made in view of the above-mentioned problems, and aims to provide an exterior material for an energy storage device and an energy storage device that have excellent moldability and puncture resistance. [Means for solving the problem]

[0009] To solve the above problems, the present invention comprises the following means.

[0010] [1] An exterior material for an energy storage device comprising a base layer, a barrier layer laminated inside the base layer, and a sealant layer laminated inside the barrier layer, The aforementioned substrate layer is made of a polyamide film, The aforementioned substrate layer has a thermal shrinkage rate of 2.0% to 5.0% for both TD and MD. The difference between the thermal shrinkage rate of TD and the thermal shrinkage rate of MD in the aforementioned substrate layer is 1.5% or less. The aforementioned substrate layer has an elastic modulus of TD and an elastic modulus of MD, both of which are 1.5 GPa to 3 GPa. The aforementioned base material is characterized in that at least one of the breaking strength of TD and the breaking strength of MD is 320 MPa or higher.

[0011] [2] The exterior material for an energy storage device according to paragraph 1, wherein the base material layer has a thermal shrinkage rate of TD and a thermal shrinkage rate of MD of both 2.5% to 4.5%.

[0012] [3] The base material is an exterior material for an energy storage device according to paragraph 1 or 2, wherein the difference between the thermal shrinkage rate of TD and the thermal shrinkage rate of MD is 1.2% or less.

[0013] "4] The base material is an exterior material for an energy storage device according to any one of paragraphs 1 to 3 above, wherein the elastic modulus of TD and the elastic modulus of MD are both 2.0 GPa to 2.5 GPa."

[0014] [5] The base material layer is an exterior material for an energy storage device according to any one of paragraphs 1 to 4 above, wherein at least one of the breaking strength of TD and the breaking strength of MD is 400 MPa or less.

[0015] [6] The main body of the energy storage device, The exterior material is as described in any one of paragraphs 1 to 5 above, An energy storage device characterized in that the main body of the energy storage device is enclosed with the exterior material. [Effects of the Invention]

[0016] According to the exterior material for energy storage devices of the invention [1], the base material layer arranged on the outer surface is made of a unique polyamide film, so it has appropriate flexibility and can maintain the desired strength. Furthermore, because the difference in the thermal shrinkage rate between MD and TD of the base material layer is small, it can efficiently distribute forces from external pressure. Moreover, since the base material layer has a predetermined breaking strength, it can reliably maintain sufficient strength. Therefore, the exterior material for energy storage devices of the present invention has excellent moldability and sufficient puncture resistance.

[0017] According to the exterior material for energy storage devices of inventions [2] to [5], the above effects can be obtained even more reliably.

[0018] According to the energy storage device of the invention [6], since it is manufactured using the exterior material of the above invention, the same effects as above can be obtained. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a side sectional view showing the power storage device which is an embodiment of this invention. [Figure 2] Figure 2 is a perspective view showing the power storage device of the embodiment disassembled. [Figure 3] Figure 3 is a schematic sectional view schematically showing the exterior material of the power storage device of the embodiment. [Figure 4] Figure 4 is a schematic diagram for explaining MD and TD in the resin film.

Embodiments for Carrying Out the Invention

[0020] Figure 1 is a side sectional view showing the power storage device which is an embodiment of this invention, and Figure 2 is a perspective view showing the power storage device of the embodiment disassembled.

[0021] As shown in both figures, the power storage device of the present embodiment includes a casing (container) 11 as an outer package and a power storage device main body 10 such as an electrochemical element housed inside the casing 11.

[0022] The casing 11 is composed of a tray member 2 having a rectangular shape in plan view formed by the exterior material 1 and a cover member 3 having a rectangular shape in plan view formed by the exterior material 1.

[0023] [[ID= thirty-one]] The tray member 2 is composed of a molded product formed by molding the exterior material 1 using a technique such as deep drawing. The tray member 2 has a concave portion 21 having a rectangular shape in plan view formed by recessing the entire intermediate region except the outer peripheral edge portion downward, and a flange portion 22 protruding outward is integrally formed on the outer periphery of the opening edge portion of the concave portion 21.

[0024] The cover member 3 is composed of the exterior material 1 formed in a sheet shape. The cover member 3 has a flange portion 32 whose outer peripheral edge portion corresponds to the flange portion 22 of the tray member 2.

[0025] The outer packaging material 1, which serves as both the tray member 2 and the cover member 3, is made of an outer packaging laminate, which is a flexible and pliable laminate sheet or film.

[0026] Furthermore, the energy storage device body 10 is not particularly limited, but examples include a battery body, a capacitor body, a capacitor body, etc. The energy storage device body 10 is formed in a shape that corresponds to the recessed portion 21 of the tray member 2.

[0027] As will be described later, with the energy storage device body 10 housed in the recessed portion 21, the cover member 3 is placed on the tray member 2 so as to cover the recessed portion 21, and the flange portions 22 and 32 of the tray member 2 and the cover member 3 are heat-fused together to form the energy storage device of this embodiment.

[0028] Although not shown in the diagram, one end (inner end) of the tab lead is connected to the main body of the energy storage device 10, while the other end (outer end) is extended to the outside of the energy storage device, allowing electricity to be supplied to and supplied from the main body of the energy storage device 10 via the tab lead.

[0029] Figure 3 is a schematic cross-sectional view illustrating the basic structure of the outer laminate material constituting the exterior material 1 in this embodiment. As shown in the figure, the exterior material 1 (laminate material) used in this embodiment comprises a base layer 51, a barrier layer (metal foil layer) 52 bonded to one surface (inner surface) of the base layer 51 via an adhesive layer 61, and a sealant layer (heat-fusible resin layer) 53 bonded to one surface (inner surface) of the metal foil layer 52 via the adhesive layer 62.

[0030] In this embodiment, the base layer 51 is made of a polyamide film.

[0031] As the polyamide film, it is preferable to use a biaxially oriented film such as nylon 6, nylon 6,6, or MXD nylon. In this embodiment, it is preferable to use simultaneous stretching and sequential stretching as the manufacturing method for the biaxially oriented film.

[0032] In this embodiment, the base layer 51 has a shared thermal shrinkage rate for both TD and MD. 2 It needs to be adjusted to between 0.0% and 5.0%, preferably between 2.5% and 4.5%.

[0033] Here, as shown in Figure 4, "MD" refers to the molding direction (resin flow direction) of the resin film F, and "TD" refers to the direction perpendicular to MD.

[0034] Furthermore, the hot water shrinkage rate is the dimensional change rate in the shrinkage direction (stretching direction) before and after immersion of a film (object being measured) in 100°C hot water for 5 minutes. For example, if the dimension in the shrinkage direction (MD or TD) before hot water immersion is "X" and the dimension in the shrinkage direction (MD or TD) after hot water immersion is "Y", the hot water shrinkage rate (%) in the shrinkage direction (MD or TD) can be calculated using the relationship {(XY) / X} × 100.

[0035] In this invention, it is preferable to use the average value of the hot water shrinkage rate (average hot water shrinkage rate) as the "hot water shrinkage rate" that indicates the characteristic value of the polyamide film. In this invention, the average hot water shrinkage rate is the average value of the hot water shrinkage rates at three points: two points at both ends and one point in the center, for one direction of the sheet (film) to be measured. However, in this invention, depending on the size of the energy storage device body 10, it may be preferable to use the hot water shrinkage rate measured at a specific location (hot water shrinkage rate at a reference position) rather than the average value as the "hot water shrinkage rate" that indicates the characteristic value of the polyamide film. contraction It is also possible to use a rate.

[0036] In this embodiment, since the hot water shrinkage rates of TD and MD are 2.0% or more, they possess appropriate flexibility, ensuring good moldability as the base layer 51. Furthermore, since they are 5.0% or less, the base layer 51 avoids excessive flexibility and maintains the desired strength.

[0037] Furthermore, in this embodiment, the difference between the hot water shrinkage rate of MD and the hot water shrinkage rate of TD of the base layer 51 needs to be adjusted to 1.5% or less, preferably to 1.2% or less. Specifically, when the average hot water shrinkage rate of MD is "MDz" and the hot water shrinkage rate of TD is "TDz", the relationship |MDz-TDz|≦1.5% needs to be satisfied, preferably |MDz-TDz|≦1.2%. % It's best to adjust it.

[0038] In other words, in this embodiment, since the difference in the thermal shrinkage rates of TD and MD is adjusted to within the specified range described above, it becomes possible to efficiently distribute the force from external pressure, and the desired strength can be reliably maintained for the base layer 51.

[0039] In this embodiment, it is necessary to adjust both the elastic modulus of the MD and the elastic modulus of the TD of the base layer 51 to 1.5 GPa to 3 GPa, and preferably to 2.0 GPa to 2.5 GPa.

[0040] In other words, when the moduli of elasticity of TD and MD are adjusted to within the above-mentioned specific range, the base layer 51 can more reliably maintain appropriate flexibility and strength.

[0041] In this embodiment, it is necessary to adjust at least one of the tensile strengths of the TD and MD in the base layer 51 to 320 MPa or higher, and preferably to 400 MPa or lower.

[0042] In other words, if the tensile strengths of TD and MD are adjusted to within the specified range described above, the desired strength can be obtained more reliably as the base layer 51.

[0043] By using a polyamide film with the above-mentioned properties for the base layer 51, an exterior material 1 with good moldability and sufficient puncture resistance can be obtained.

[0044] In this embodiment, it is preferable to adjust the polyamide resin content of the film constituting the base layer 51 to 90 wt% to 100 wt%, preferably to 95 wt% to 100 wt%, and more preferably to 98% to 100 wt%.

[0045] Furthermore, in this embodiment, it is preferable to adjust the number average molecular weight of the nylon polyamide film constituting the base layer 51 to 15,000 to 30,000, more preferably to 20,000 to 30,000, and particularly preferably to 20,000 to 25,000.

[0046] In other words, if the number-average molecular weight of the nylon used as the base layer 51 is 15,000 or more, the base layer 51 becomes less prone to tearing, and if the molecular weight is 40,000 or less, the flexibility of the base layer 51 can be maintained, making it less prone to cracking.

[0047] In this embodiment, it is preferable to adjust the relative viscosity of the polyamide film as the base layer 51 to 2.9 to 3.1. That is, when the relative viscosity is adjusted to the above specific range, strength and flexibility can be more effectively imparted to the base layer 51, and an exterior material 1 with good moldability and high puncture resistance can be reliably obtained.

[0048] In this embodiment, the puncture strength of the exterior material 1 is preferably in the range of 22N to 30N, more preferably 24N to 30N, and even more preferably 26N to 30N.

[0049] In this embodiment, the thickness of the base layer 51 (polyamide film) is preferably adjusted to 9 μm to 25 μm, more preferably to 12 μm to 25 μm, and even more preferably to 17 μm to 23 μm. The thickness error of the polyamide film should be adjusted to within 1 μm.

[0050] Here, the distribution of the hot water shrinkage rate in the polyamide film of this embodiment will be explained. First, in a square polyamide film, the hot water shrinkage rate at three points along both sides and the center line in the vertical direction (MD) is defined as the fixed-point hot water shrinkage rate at three points along MD, and the hot water shrinkage rate at three points along both sides and the center line in the horizontal direction (TD) is defined as the fixed-point hot water shrinkage rate at three points along TD. contraction Fixed point hydrothermal water at three points: rate and TD contraction It is preferable to use a film in which the difference between the maximum fixed-point hot water shrinkage rate and the minimum fixed-point hot water shrinkage rate among a total of six fixed-point hot water shrinkage rates is adjusted to 2.5 or less.

[0051] The average of the three fixed-point hydrothermal contraction rates for MD corresponds to the average hydrothermal contraction rate for MD, and the average of the three hydrothermal contraction rates for TD corresponds to the average hydrothermal contraction rate for TD.

[0052] In Figure 4, the three regions indicated by the dashed lines are all square regions of the polyamide film (base layer 51) of the same size. When these square regions satisfy the above-mentioned distribution conditions for the thermal shrinkage rate, the uneven distribution of flexibility is suppressed throughout the entire base layer 51. As a result, even if external stress is applied, it is distributed throughout the entire base layer 51, making it less likely to tear and thus reliably improving its strength.

[0053] In this embodiment, the base layer 51 is formed from a polyamide film, but other layers may be laminated onto the base layer 51.

[0054] For example, a biaxially oriented polyamide film (such as nylon 6, nylon 6,6, or MXD nylon) or a biaxially oriented polyester film (such as polybutylene terephthalate (PBT), polyethylene terephthalate (PET), or polyethylene naphthalate (PEN)) may be laminated onto the base layer 51.

[0055] Furthermore, it is preferable to use a resin for the base layer 51 that has a melting point at least 10°C higher than all the resins constituting the sealant layer 53, and more preferably a resin that has a melting point at least 20°C higher. In other words, when this configuration is adopted, adverse effects of heat on the base layer 51 can be avoided when heat-sealing the sealant layer 53.

[0056] In this embodiment, it is preferable to apply an easy-adhesion treatment to the bonding surface of the base layer 51 with the barrier layer 52 to form an easy-adhesion layer. Specifically, an easy-adhesion layer is formed by applying an aqueous emulsion (water-based emulsion) of one or more resins selected from the group consisting of epoxy resin, urethane resin, acrylic ester resin, methacrylic ester resin, polyester resin, and polyethyleneimine resin to the bonding surface and drying it. The amount of this easy-adhesion layer formed is 0.01 g / m². 2 ~0.5g / m 2 It's best to set it to that.

[0057] By applying an easy-adhesion treatment to the base layer 51 in this way, sufficient adhesive strength with the barrier layer 52 can be ensured.

[0058] The barrier layer 52 is preferably composed of a metal foil layer such as aluminum foil, copper foil, stainless steel foil, titanium foil, nickel foil, or cladding material.

[0059] The thickness of the barrier layer 52 should be set to 20 μm to 100 μm. Furthermore, by applying a surface treatment such as chemical conversion treatment to the barrier layer 52, corrosion of the barrier layer 52 and improvement of adhesion with the resin can be achieved.

[0060] For the sealant layer 53, it is preferable to use an unstretched film of a polyolefin resin such as polypropylene or polyethylene.

[0061] The thickness of this sealant layer 53 should ideally be set to 20 μm to 100 μm.

[0062] Furthermore, as the adhesive layer 61 for bonding the base layer 51 and the barrier layer 52, an adhesive layer formed from a two-component curing adhesive can be used. For example, a two-component curing adhesive consisting of a first liquid made from one or more polyols selected from the group consisting of polyurethane polyols, polyester polyols, polyether polyols, and polyester urethane polyols, and a second liquid (curing agent) made from isocyanate can be suitably used.

[0063] The thickness of this adhesive layer 61 should ideally be set to 2 μm to 5 μm.

[0064] Furthermore, as the adhesive layer 62 for bonding the barrier layer 52 and the sealant layer 53, it is preferable to use an adhesive containing one or more of the following: polyurethane resin, acrylic resin, epoxy resin, polyolefin resin, elastomer resin, fluororesin, or acid-modified polypropylene resin. In particular, it is more preferable to use an adhesive made of a polyurethane composite resin with acid-modified polyolefin as the main component.

[0065] The thickness of this adhesive layer 62 should ideally be set to 2 μm to 5 μm.

[0066] As described above, in this embodiment, the tray member 2 and the cover member 3 are made of the exterior material 1 having the above configuration.

[0067] When forming the recessed portion 21 of the tray member 2, the shorter side of the molded tray member 2 is the base material layer of the outer material 1. 51 By aligning the polyamide film with the side that has a higher thermal shrinkage rate, good moldability can be obtained. For example, the base layer of exterior material 1 51 If the MD in the region has a higher thermal shrinkage rate than the TD, when forming the tray member 2 as shown in Figure 2, the short side direction A and the base material layer 51 By aligning the MD of the tray member 2 and aligning the long side direction B with the TD of the base layer, good moldability can be obtained.

[0068] In this embodiment, when assembling the tray member 2, cover member 3, and energy storage device body 10, the energy storage device body 10 is housed in the recessed portion 21 of the tray member 2, and the cover member 3 is placed on the tray member 2 so as to close the opening of the recessed portion 21, thereby producing a provisional assembly of the energy storage device.

[0069] By heating the tray member 2 and cover member 3 in this temporary assembly while sandwiching their respective flange portions 22 and 32, the sealant layers 53 of each flange portion 22 and 32 are heat-fused (heat-bonded). This creates an energy storage device in which the energy storage device body 10 is sealed inside a casing 11 made of the tray member 2 and cover member 3.

[0070] In this energy storage device, the base material layer 51, which is arranged on the outer surface of the exterior material 1 in the casing 11, is made of a polyamide film in which the thermal shrinkage rate and elastic modulus of the medium-density (MD) and tangential (TD) are set within a specific range. Therefore, it has appropriate flexibility and can maintain the desired strength. Furthermore, because the difference in thermal shrinkage rate between the MD and TD of the base material layer 51 is set within a specific range, it can efficiently distribute forces from external pressure. Moreover, since the base material layer 51 has a predetermined breaking strength, it can reliably maintain sufficient strength. Accordingly, the exterior material 1 in the energy storage device of this embodiment has good moldability, excellent dimensional accuracy and dimensional stability, and sufficient puncture resistance, thus providing a high-quality energy storage device.

[0071] Furthermore, since the bonding surface of the base layer 51 to the barrier layer 52 is treated for easy adhesion, the two layers 51 and 52 can be bonded together with sufficient strength, and the base layer 51 and the barrier layer 52 are integrated. As a result, the base layer 51 is positioned in a stable state, which further improves moldability and puncture resistance.

[0072] In the above embodiment, the case in which a sheet-like exterior material 1 is used as the cover member 3 was described, but the present invention is not limited to this, and the cover member 3 may also be molded. For example, the cover member may be made of a molded product with a hat-shaped cross section in which the central part is formed to be concave (bulging) upward, and the outer edge of the hat-shaped cover member may be joined and integrated so as to cover the tray member as described above from above. Furthermore, in the present invention, a casing may be formed by overlapping two unmolded sheet-like exterior materials 1 so as to sandwich the energy storage device body and heat-sealing their outer edges.

[0073] Furthermore, while the above embodiment describes an example where two outer packaging materials (outer laminate materials) are used to form the casing, the invention is not limited to this. In the present invention, the number of outer packaging materials used to form the casing is not limited; it may be one, three or more, or any other number.

[0074] Furthermore, while this embodiment uses a three-layer exterior material, it is not limited to this, and in the present invention, an exterior material with four or more layers may be used. For example, another layer may be interposed between the base material layer and the barrier layer, or another layer may be interposed between the barrier layer and the sealant layer to create a structure of four or more layers. [Examples]

[0075] In this embodiment, exterior materials 1 for energy storage devices of Examples 1 to 7, which include the gist of the present invention, and exterior materials 1 and 2 for energy storage devices of Comparative Examples 1 to 3, which deviate from the gist of the present invention, were fabricated and various evaluations were performed.

[0076] <Example 1> Aluminum foil with a thickness of 35 μm (aluminum foil of alloy number A8079 as specified in JIS H4160) was prepared by applying a chemical conversion treatment solution consisting of polyacrylic acid, trivalent chromium compound, water, and alcohol to both sides of the aluminum foil as barrier layer 52, and drying it at 150°C to form a chemical conversion film on both sides. The amount of chromium deposited by this chemical conversion film was 5 mg / m² on one side. 2 That was the case.

[0077] Next, a two-component curing urethane adhesive is applied to one side (outer surface) of the chemically treated aluminum foil (barrier layer 52). Agent A 20 μm thick biaxially oriented nylon 6 (ONy) film was bonded to the base layer 51 via layer 61) by dry lamination. Details of this nylon film will be explained later.

[0078] Next, a 40 μm thick unoriented polypropylene (CPP) film, serving as the sealant layer 53, was placed on the other side (inner surface) of the dry-laminated aluminum foil (barrier layer 52) via a two-component curing maleic acid-modified polypropylene adhesive (adhesive layer 62). This film was then dry-laminated by sandwiching it between a rubber nip roll and a laminating roll heated to 100°C and pressing it together. Subsequently, the exterior material 1 for the energy storage device was obtained by aging (heating) it at 40°C for 10 days.

[0079] The biaxially oriented nylon 6 film used as the base layer was produced by extruding nylon film using a T-die method and then stretching it using a tenter method. Furthermore, both sides of this nylon film used as the base layer were subjected to corona treatment. Additionally, if necessary, a coating solution containing acrylic ester resin and epoxy resin was applied to one side (inner surface) of the nylon film and dried to form an easy-adhesion layer (0.05 μm) (easy-adhesion treatment). When forming the easy-adhesion layer, the side on which the easy-adhesion layer was formed was bonded to the barrier layer 52.

[0080] [Table 1]

[0081] Table 1 shows the properties of the nylon film used as the base layer in Example 1. As shown in Table 1, the nylon film of Example 1 has a hot water shrinkage rate of 4.3% for TD and 3.4% for MD, a difference in hot water shrinkage rates between TD and MD (TD-MD) of 0.9%, an elastic modulus of 2.3 GPa for TD and 2.5 GPa for MD, a breaking strength of 345 MPa for TD and 282 MPa for MD, and a number-average molecular weight of 30,000 for the polyamide.

[0082] The remarks column in Table 1 indicates the thickness of the nylon film and whether or not an easy-adhesion layer is present. For example, in Example 1, "ONY20" indicates that the thickness of the nylon film is 20 μm, and "Easy-adhesion" indicates that an easy-adhesion layer is formed.

[0083] Here, the hot water shrinkage rate is the dimensional change rate in the stretching direction (shrinkage direction) of a nylon film test piece (1 cm × 1 cm) before and after immersion in 100°C hot water for 5 minutes, and can be calculated using the following formula.

[0084] Hydrothermal contraction rate (%) = {(XY) / X} × 100 X: Dimensions in the stretching direction (MD or TD) before immersion treatment Y: Dimension in the stretching direction (MD or TD) after immersion treatment. In this embodiment, a 1cm x 1cm test specimen is used to measure the hydrothermal fluid collection rate. However, the size of the test specimen is not particularly limited in this invention, and a test specimen of an appropriate size, such as 1cm to 10cm x 1cm to 10cm, can be used.

[0085] The elastic modulus (Young's modulus) of the core material was calculated from the "stress-strain curve (SS curve)" obtained by tensile testing a sample piece (a sample piece of film for the base layer) on a tensile testing machine under the conditions of a sample length of 100 mm, a sample width of 15 mm, a distance between test points of 50 mm, and a tensile speed of 200 mm / min, in accordance with JIS K7127 (1999). The "slope of the tangent to the straight portion" in the stress-strain curve is the Young's modulus. A Shimadzu Corporation "Strograph (AGS-5kNX)" was used as the tensile testing machine. The term "Young's modulus" above is synonymous with the Young's modulus defined in ASTM-D-882.

[0086] The tensile breaking strength is the breaking strength (unit: MPa) obtained by measuring under the conditions of a sample width of 15 mm, a distance between test points of 100 mm, and a tensile speed of 100 mm / min, in accordance with the tensile test of JIS K7127-1999.

[0087] The number-average molecular weight of polyamides was measured by gel permeation chromatography (GPC).

[0088] <Examples 2-7> A nylon film having the characteristics shown in Examples 2 to 7 of Table 1 was prepared. Using this nylon film, exterior material 1 of Examples 2 to 7 was manufactured in the same manner as described above. In Example 6, as shown in the remarks column of Table 1, a nylon film was used in which no easy-adhesion layer was formed and which had the same thickness as Example 3.

[0089] <Comparative Examples 1, 2> Comparative Examples 1 and 2: Nylon films having the properties shown in Table 1 were prepared. Exterior material 1 of Comparative Examples 1 and 2 was manufactured using these nylon films, in the same manner as described above.

[0090] <Evaluation of moldability> For the exterior material 1 of Examples 1-7 and Comparative Examples 1 and 2, deep drawing was performed using a deep drawing tool manufactured by Amada Co., Ltd. to form a rectangular recess measuring 55 mm in length and 35 mm in width in plan view. The presence or absence of pinholes and cracks in the corners of the resulting molded body was checked to determine the "maximum molding depth (mm)" at which such pinholes and cracks do not occur, and this was evaluated based on the following criteria. The presence or absence of cracks and pinholes was checked in a dark room using the light transmission method. Of the evaluation criteria described below, "◎" and "○" indicate a pass, and "×" indicates a fail.

[0091] ◎: No cracks or pinholes in molded depth of 7mm or more. ○: Molding depth of 5mm or more and less than 7mm, with no cracks or pinholes. ×: Cracks or pinholes present in molded depths of less than 5mm. The results of the moldability evaluation obtained in this way are shown in Table 1.

[0092] <Puncture Strength Test (Evaluation of Puncture Resistance)> The puncture strength is a value measured in accordance with JIS (Japanese Industrial Standards) Z1707:2019. That is, the puncture strength test was measured by the following procedure (1) to (3).

[0093] (1) The test specimens obtained from the exterior material 1 of each example and each comparative example are fixed with a jig, and a semicircular needle with a diameter of 1.0 mm and a tip shape radius of 0.5 mm is inserted at a test speed of 50 ± 5 mm / min, and the maximum force (N) until the needle penetrates is measured.

[0094] (2) The number of test specimens shall be five or more for each example and each comparative example, and shall be taken in an average manner across the entire width of the test specimen.

[0095] (3) If the test results depend on whether the film (test specimen) is penetrated from any side, the test shall be performed on each side. The reported values ​​shall be rounded to one decimal place.

[0096] The results of the puncture strength tests obtained in this way are shown in Table 1.

[0097] As is clear from the evaluation results above, the exterior material of the example received excellent evaluations in both moldability and puncture resistance. In contrast, the exterior material of the comparative example was inferior to the exterior material of the example in both moldability and puncture resistance. 。 [Explanation of Symbols]

[0098] 1: Exterior materials 10: Energy storage device unit 51: Base material layer 52: Barrier layer 53: Sealant layer

Claims

1. An exterior material for an energy storage device comprising a base layer, a barrier layer laminated inside the base layer, and a sealant layer laminated inside the barrier layer, The exterior material has a rectangular recess in plan view, having a short side direction and a long side direction, for housing the energy storage device body, and is formed such that the short side direction of the recess coincides with the MD of the base material layer and the long side direction of the recess coincides with the TD of the base material layer. The aforementioned substrate layer is made of a polyamide film, The aforementioned substrate layer has a thermal shrinkage rate of 2.0% to 5.0% for both TD and MD. The aforementioned substrate layer has a difference of 1.5% or less between the hot water shrinkage rate of TD and the hot water shrinkage rate of MD. The substrate layer has an elastic modulus of TD of 1.5 GPa to 2.3 GPa and an elastic modulus of MD of 2.0 GPa to 3 GPa, and the elastic modulus of TD is lower than the elastic modulus of MD. The aforementioned base layer is characterized in that at least one of the breaking strength of TD and MD is 320 MPa or higher, and the breaking strength of TD is higher than the breaking strength of MD.

2. The exterior material for an energy storage device according to claim 1, wherein the base material layer has a thermal shrinkage rate of TD and a thermal shrinkage rate of MD, both of which are 2.5% to 4.5%.

3. The exterior material for an energy storage device according to claim 1 or 2, wherein the difference between the thermal shrinkage rate of TD and the thermal shrinkage rate of MD in the base layer is 1.2% or less.

4. The exterior material for an energy storage device according to any one of claims 1 to 3, wherein the base layer has an elastic modulus of TD of 2.0 GPa to 2.3 GPa and an elastic modulus of MD of 2.0 GPa to 2.5 GPa.

5. The exterior material for an energy storage device according to any one of claims 1 to 4, wherein the base material layer has a breaking strength of TD and a breaking strength of MD of 400 MPa or less.

6. The main body of the energy storage device, The exterior material is as described in any one of claims 1 to 5, An energy storage device characterized in that the main body of the energy storage device is enclosed with the exterior material.

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