CN116745874A

CN116745874A - Outer packaging material for power storage device and power storage device

Info

Publication number: CN116745874A
Application number: CN202180083659.6A
Authority: CN
Inventors: 中嶋大介; 南崛勇二
Original assignee: Lesonac Packaging Co ltd
Current assignee: Lesonac Packaging Co ltd
Priority date: 2020-12-16
Filing date: 2021-12-13
Publication date: 2023-09-12

Abstract

The application provides an outer packaging material for an electric storage device, which has excellent processability and puncture resistance. The present application is directed to an exterior material 1 for a power storage device, which comprises a base layer 51, a barrier layer 52 laminated on the inner side of the base layer 51, and a sealant layer 53 laminated on the inner side of the barrier layer 52. The base material layer 51 is made of a polyamide film. The heat shrinkage of the base material layer 51 in TD and MD is 2.0% to 5.0%, the difference between the heat shrinkage of TD and MD is 1.5% or less, the elastic modulus of TD and MD are 1.5GPa to 3GPa, and at least one of the breaking strength of TD and the breaking strength of MD is 320MPa or more.

Description

Outer packaging material for power storage device and power storage device

Technical Field

The present application relates to an exterior material for a battery and a capacitor used in a portable terminal such as a smart phone and a tablet personal computer (tablet PC), and an electrical storage device such as a battery and a capacitor used in a hybrid car, an electric car, and the like, and an electrical storage device.

Background

The power storage device is used as an energy supply for mobile devices such as electric vehicles and hybrid vehicles, and as an energy supply for mobile devices such as electric tools and mobile terminals. In order to facilitate movement and portability of such a power storage device, it is required to be lightweight and compact. Therefore, although a metal can has been mainly used as a case for an electric storage device, in recent years, a metal laminate (outer package) having a laminate of a base layer, a barrier layer (metal foil layer), and a sealant layer as a basic structure has been often used.

Unlike the stationary type, such a movable type, portable type, or other non-stationary type power storage device has a high possibility of breakage of the outer package material due to vibration, external pressure, or the like, and therefore the outer package material is also required to have the same mechanical strength, particularly puncture resistance, as the metal can.

Conventionally, aluminum foil has been used as an exterior material for a barrier layer, but it has been difficult to obtain sufficient puncture resistance in a general aluminum laminate.

Accordingly, in the power storage device shown in patent document 1 below, the puncture resistance is improved by using, as an exterior material, a metal laminate (stainless steel laminate) in which the barrier layer is formed of a stainless steel foil (SUS foil) having higher rigidity than the aluminum foil.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2020-161362

Disclosure of Invention

Problems to be solved by the application

However, since the stainless steel foil has high rigidity, when the stainless steel laminate is used as an exterior material for an electric storage device, the formability (workability) of the exterior material may be deteriorated, which may lead to a decrease in dimensional accuracy and a decrease in production efficiency.

The preferred embodiments of the present application have been made in view of the above and/or other problems in the related art. The preferred embodiments of the present application can significantly improve upon existing methods and/or apparatus.

The present application has been made in view of the above-described problems, and an object thereof is to provide an exterior material for an electric storage device and an electric storage device which are excellent in moldability and puncture resistance.

Other objects and advantages of the present application will become apparent from the following preferred embodiments.

Means for solving the problems

In order to solve the above problems, the present application includes the following means.

[1] An exterior material for an electric storage device comprising a base layer, a barrier layer laminated on the inner side of the base layer, and a sealant layer laminated on the inner side of the barrier layer, characterized in that,

the base material layer is composed of a polyamide film,

the heat shrinkage of TD and MD of the base material layer is 2.0-5.0%,

the difference between the heat shrinkage of TD and the heat shrinkage of MD of the base material layer is 1.5% or less,

the elastic modulus of TD and MD of the base material layer are 1.5 GPa-3 GPa,

at least any one of the fracture strength of TD and the fracture strength of MD of the substrate layer is 320MPa or more.

[2] The exterior material for a power storage device according to item 1, wherein the heat shrinkage ratio of TD and the heat shrinkage ratio of MD of the base material layer are each 2.5 to 4.5.

[3] The exterior material for an electric storage device according to the foregoing item 1 or 2, wherein a difference between the heat shrinkage rate of TD of the base material layer and the heat shrinkage rate of MD is 1.2% or less.

[4] The exterior material for power storage devices according to any one of the above 1 to 3, wherein the elastic modulus of TD and the elastic modulus of MD of the base material layer are each 2.0GPa to 2.5GPa.

[5] The outer package material for a power storage device according to any one of the above 1 to 4, wherein at least one of the fracture strength of TD and the fracture strength of MD of the base material layer is 400MPa or less.

[6] An electricity storage device is characterized by comprising:

a power storage device main body portion; and

the outer packaging material according to any one of the preceding items 1 to 5,

the power storage device main body is externally coated with the external coating material.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the outer packaging material for a power storage device of the application [1], the base material layer disposed on the outer surface side is made of a specific polyamide film, and therefore has appropriate flexibility and can maintain a desired strength. Further, since the difference in hot water shrinkage rate between MD and TD of the base material layer is small, the force from the external pressure can be efficiently dispersed. Further, since the base material layer further has a predetermined breaking strength, a sufficient strength can be reliably maintained. Therefore, the exterior material for a power storage device of the present application is excellent in moldability and has sufficient puncture resistance.

According to the outer packaging material for electric storage devices of the applications [2] to [5], the above-described effects can be obtained more reliably.

According to the power storage device of the application [6], since the power storage device is manufactured using the outer packaging material of the application, the same effects as those described above can be obtained.

Drawings

Fig. 1 is a side cross-sectional view showing an electric storage device according to an embodiment of the present application.

Fig. 2 is a perspective view of the power storage device according to the embodiment shown in an exploded manner.

Fig. 3 is a schematic cross-sectional view schematically showing an outer package material of the power storage device according to the embodiment.

Fig. 4 is a schematic diagram for explaining MD and TD of a resin film.

Detailed Description

Fig. 1 is a side sectional view showing an electric storage device as an embodiment of the present application, and fig. 2 is a perspective view showing the electric storage device of the embodiment in an exploded manner.

As shown in both figures, the power storage device of the present embodiment includes: a case (container) 11 as an exterior body; and a power storage device main body 10 such as an electrochemical element housed in the case 11.

The case 11 is composed of a disc member 2 and a cover member 3, wherein the disc member 2 is formed of the outer material 1 and is rectangular in plan view, and the cover member 3 is formed of the outer material 1 and is rectangular in plan view.

The disc member 2 is formed of a molded product obtained by molding the outer package 1 by deep drawing or the like. The disc member 2 is formed such that the entire intermediate region except the outer peripheral edge portion is recessed downward to form a recessed portion 21 having a rectangular shape in a plan view, and a flange portion 22 protruding outward is integrally formed on the outer periphery of the opening edge portion of the recessed portion 21.

The cover member 3 is formed of the outer material 1 formed in a sheet shape. In the cover member 3, the outer peripheral edge portion is configured as a flange portion 32 corresponding to the flange portion 22 of the disk member 2.

The outer package 1 serving as the disc member 2 and the cover member 3 is composed of an outer package laminate which is a laminate sheet or film having flexibility and pliability.

The power storage device main body 10 is not particularly limited, and a battery main body, a capacitor main body, and the like can be exemplified. The power storage device main body 10 is formed in a shape corresponding to the concave portion 21 of the disk member 2.

As will be described later, the power storage device according to the present embodiment is formed by disposing the cover member 3 on the plate-like member 2 so as to cover the recess 21 in a state where the power storage device main body 10 is accommodated in the recess 21, and thermally welding the flange portions 22 and 32 of the plate-like member 2 and the cover member 3 to each other.

Although not shown, one end (inner end) of a tab (tab lead) is connected to the power storage device main body 10, and the other end (outer end) is arranged in a state of being led out to the outside of the power storage device, and electric power can be output and input to and from the power storage device main body 10 via the tab.

Fig. 3 is a schematic cross-sectional view schematically showing the basic structure of the outer packaging laminate constituting the outer packaging material 1 in the present embodiment. As shown in the figure, the outer package 1 (laminate) used in the present embodiment includes: a base material layer 51; a barrier layer (metal foil layer) 52 bonded to one surface (inner surface) of the base material 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 an adhesive layer 62.

In the present embodiment, the base material layer 51 is made of a polyamide film.

As the polyamide film, biaxially stretched films such as nylon 6,6 and MXD nylon are preferably used. In the present embodiment, simultaneous stretching and sequential stretching are preferably used as the production method of the biaxially stretched film.

In the present embodiment, the heat shrinkage of the TD and the heat shrinkage of the MD of the base material layer 51 are each required to be adjusted to 2.0% to 5.0%, preferably 2.5% to 4.5%.

Here, as shown in fig. 4, "MD" means a molding direction of the resin film F (a resin flow direction), and "TD" means a direction orthogonal to the MD.

The hot water shrinkage refers to a dimensional change in the shrinkage direction (stretching direction) before and after immersing a film (object to be measured) in hot water at 100 ℃ for 5 minutes. For example, when 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 (%) in the shrinkage direction (MD or TD) is determined from the relational expression { (X-Y)/X } ×100.

In the present application, as the "hot water shrinkage" indicating the characteristic value of the polyamide film, an average value of the hot water shrinkage (average hot water shrinkage) is preferably used. In the present application, the average hot water shrinkage refers to an average value of hot water shrinkage at 3 points, which is the hot water shrinkage at 2 points at the both ends and the hot water shrinkage at 1 point at the center, with respect to one direction of a sheet (film) to be measured, as will be described later. Of course, in the present application, the "hot water shrinkage" indicating the characteristic value of the polyamide film may be the hot water shrinkage measured at a specific position (the hot water absorption rate at the reference position) instead of the average value, depending on the size of the power storage device main body 10.

In the present embodiment, since the heat shrinkage ratio of TD and MD is 2.0% or more, the substrate layer 51 has moderate flexibility, and good moldability can be ensured. Further, since the base material layer 51 is 5.0% or less, excessive flexibility can be avoided, and the desired strength can be maintained.

In the present embodiment, the difference between the heat shrinkage in MD and the heat shrinkage in TD of the base material layer 51 needs to be adjusted to 1.5% or less, preferably 1.2% or less. Specifically, when the average hot water shrinkage in the MD is "MDz" and the hot water shrinkage in the TD is "TDz", it is necessary to satisfy the relation of | MDz-TDz | 1.5%, and it is preferable to adjust the relation to be | MDz-TDz | 1.2% or less.

That is, in the present embodiment, since the difference in hot water shrinkage rates of TD and MD is adjusted to be within the above-described specific range, the force from the external pressure can be efficiently dispersed, and the desired strength can be reliably maintained as the base material layer 51.

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

That is, when the modulus of elasticity of the TD and MD is adjusted within the above specific range, the substrate layer 51 can maintain proper flexibility and strength more reliably.

In the present embodiment, it is necessary to adjust at least either the TD breaking strength or the MD breaking strength of the base material layer 51 to 320MPa or more, preferably 400MPa or less.

That is, when the fracture strength of TD and MD is adjusted to be within the above specific range, the desired strength can be obtained even more reliably as the base material layer 51.

By using a polyamide film having the above characteristics for the base material layer 51 in this manner, the outer package 1 having good moldability and sufficient puncture resistance can be obtained.

In the present embodiment, the polyamide resin content of the film constituting the base layer 51 is preferably adjusted to 90 to 100wt%, more preferably 95 to 100wt%, and even more preferably 98 to 100 wt%.

In the present embodiment, the number average molecular weight of nylon as the polyamide film constituting the base layer 51 is preferably adjusted to 15000 to 30000, more preferably 20000 to 30000, and particularly preferably 20000 to 25000.

That is, when the number average molecular weight of nylon as the base material layer 51 is 15000 or more, the base material layer 51 is less likely to be broken, and when the molecular weight is 40000 or less, the flexibility of the base material layer 51 can be maintained, and breakage is less likely to occur.

In the present embodiment, the relative viscosity of the polyamide film as the base layer 51 is preferably adjusted 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 material layer 51, and a material having good moldability and high puncture resistance can be reliably obtained as the outer package 1.

Here, in the present embodiment, the puncture strength of the outer material 1 is preferably in the range of 22N to 30N, more preferably 24N to 30N, and even more preferably 26N to 30N.

In the present embodiment, the thickness of the base material layer 51 (polyamide film) is preferably adjusted to 9 μm to 25. Mu.m, more preferably 12 μm to 25. Mu.m, and still more preferably 17 μm to 23. Mu.m. The thickness of the polyamide film is preferably adjusted to be within 1. Mu.m.

Here, the distribution of the hot water shrinkage rate in the polyamide film of the present embodiment will be described. First, in a square polyamide film, when the heat shrinkage rate at both sides of the Machine Direction (MD) and at the center line 3 is set to the fixed point heat shrinkage rate at 3 points of the MD and the heat shrinkage rate at both sides of the Transverse Direction (TD) and at the center line 3 is set to the fixed point heat shrinkage rate at 3 points of the TD, it is preferable that the difference between the maximum fixed point heat shrinkage rate and the minimum fixed point heat shrinkage rate is adjusted to 2.5 or less, out of the fixed point heat shrinkage rates of the total 6 points of the fixed point heat absorption rate at 3 points of the MD and the fixed point heat absorption rate at 3 points of the TD.

The average value of the fixed-point hot-water shrinkage at 3 points in the MD corresponds to the average hot-water shrinkage in the MD, and the average value of the hot-water shrinkage at 3 points in the TD corresponds to the average hot-water shrinkage in the TD.

Here, 3 regions shown by the broken lines in fig. 4 are square regions of the polyamide film (base material layer 51) having the same size, and when the square regions satisfy the above distribution condition of the hot water shrinkage, unevenness in flexibility is suppressed in the entire region of the base material layer 51, and therefore, even if external stress is applied, the regions are dispersed throughout the base material layer 51, and breakage is less likely to occur, so that the strength can be reliably improved.

In the present embodiment, the base layer 51 is formed of a polyamide film, but other layers may be laminated on the base layer 51.

For example, a biaxially stretched polyamide film (nylon 6, MXD nylon, etc.), a biaxially stretched polyester film (polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc. may be laminated on the base layer 51.

The base material layer 51 is preferably a resin having a melting point higher by 10 ℃ or more than that of all the resins constituting the sealant layer 53, and more preferably a resin having a melting point higher by 20 ℃ or more. That is, in the case of this configuration, adverse effects of heat on the base material layer 51 can be avoided when the sealant layer 53 is thermally welded.

In the present embodiment, it is preferable to form an easy-to-adhere layer by applying an easy-to-adhere treatment to the surface of the base material layer 51 to be adhered to the barrier layer 52. That is, the adhesive surface is coated with 1 or 2 or more kinds of resins selected from the group consisting of epoxy resin, urethane resin, acrylate resin, methacrylate resin, polyester resin and polyethyleneimine resinThe aqueous emulsion (aqueous emulsion) is dried to form an easily adhesive layer. The formation amount of the easy-to-adhere layer was set to 0.01g/m ² ～0.5g/m ² Preferably, the method comprises the steps of.

By applying the easy-to-adhere treatment to the base material layer 51 in this manner, the adhesive strength with the barrier layer 52 can be sufficiently ensured.

The barrier layer 52 is preferably formed of a metal foil layer such as aluminum foil, copper foil, stainless steel foil, titanium foil, nickel foil, or clad material.

The thickness of the barrier layer 52 is preferably set to 20 μm to 100 μm. Further, by subjecting the barrier layer 52 to a base treatment (surface treatment) such as a chemical conversion treatment in advance, corrosion resistance of the barrier layer 52, improvement of adhesion to a resin, and the like can be achieved.

As the sealant layer 53, an unstretched film of a polyolefin resin such as polypropylene or polyethylene is preferably used.

The thickness of the sealant layer 53 is preferably set to 20 μm to 100 μm.

As the adhesive layer 61 for bonding the base material layer 51 and the barrier layer 52, an adhesive layer formed of a 2-liquid curable adhesive can be used. For example, a 2-liquid curable adhesive or the like composed of a 1 st liquid containing 1 or 2 or more kinds of polyols selected from the group consisting of polyurethane polyols, polyester polyols, polyether polyols and polyester urethane polyols and a 2 nd liquid (curing agent) formed of isocyanate can be preferably used.

The thickness of the adhesive layer 61 is preferably set to 2 μm to 5 μm.

The adhesive layer 62 for bonding the barrier layer 52 and the sealant layer 53 is preferably an adhesive containing 1 or more of a polyurethane resin, an acrylic resin, an epoxy resin, a polyolefin resin, an elastomer resin, a fluorine resin, and an acid-modified polypropylene resin, and more preferably an adhesive composed of a polyurethane composite resin containing an acid-modified polyolefin as a main component.

The thickness of the adhesive layer 62 is preferably set to 2 μm to 5 μm.

As described above, in the present embodiment, the outer material 1 configured as described above constitutes the disc member 2 and the cover member 3.

When the concave portion 21 of the disc member 2 is molded, good moldability can be obtained if the short side direction of the disc member 2 as a molded product is parallel to the side of the polyamide film as the base material layer of the outer package 1 where the hot water shrinkage rate is high. For example, when the heat shrinkage ratio in MD of the base material layer of the outer package 1 is higher than TD, when the disc member 2 shown in fig. 2 is molded, the disc member 2 is molded so that the short side direction a coincides with the MD of the base material layer and the long side direction B coincides with the TD of the base material layer, whereby good moldability can be obtained.

In the present embodiment, when the disk member 2, the cover member 3, and the power storage device main body 10 are assembled, the cover member 3 is disposed on the disk member 2 so as to close the opening of the recess 21 in a state in which the power storage device main body 10 is accommodated in the recess 21 of the disk member 2, and a power storage device temporary assembly in a temporary assembled state is produced.

The flange portions 22 and 32 of the disc member 2 and the cover member 3 in the temporary assembly are sandwiched between each other and heated, whereby the sealant layers 53 of the flange portions 22 and 32 are thermally welded (thermally bonded) to each other. Thus, the power storage device in which the power storage device main body 10 is sealed in the case 11 formed of the disk member 2 and the cover member 3 is produced.

In this power storage device, the base layer 51 disposed on the outer peripheral surface of the outer package 1 in the case 11 is made of a polyamide film having the hot water shrinkage and the elastic modulus set in specific ranges in MD and TD, and therefore has appropriate flexibility, and can maintain a desired strength. Further, since the difference in hot water shrinkage rate between the MD and the TD of the base material layer 51 is set within a specific range, the force from the external pressure can be dispersed efficiently. Further, since the base material layer 51 has a predetermined breaking strength, a sufficient strength can be reliably maintained. Therefore, the outer package 1 in the power storage device according to the present embodiment has good moldability, excellent dimensional accuracy and dimensional stability, and sufficient puncture resistance, and therefore can provide a high-quality power storage device.

Further, since the adhesion surface of the base material layer 51 and the barrier layer 52 is subjected to the easy adhesion treatment, the two layers 51 and 52 can be adhered to each other with sufficient strength, and the integration of the base material layer 51 and the barrier layer 52 can be achieved. Therefore, the base material layer 51 is arranged in a stable state, and thus the moldability and puncture resistance can be further improved.

In the above embodiment, the case where the sheet-shaped outer material 1 is used as the cover member 3 has been described, but the present application is not limited to this, and the cover member 3 may be molded. For example, the cover member may be formed of a molded product having a hat-shaped cross section in which the central portion is recessed upward (bulge-formed), and the outer peripheral edge portion may be joined and integrated so that the hat-shaped cover member covers the disk-shaped member from above. In the present application, the outer case may be formed by laminating 2 sheet-like outer materials 1 which are not molded so as to sandwich the power storage device main body, and heat-welding the outer peripheral edge portion thereof.

In the above embodiment, the case where 2 sheets of the outer package material (outer package laminate material) are used in forming the case has been described as an example, but the present application is not limited to this, and the number of sheets of the outer package material forming the case is not limited, and may be 1 sheet or 3 sheets or more.

In the present embodiment, the outer package having a 3-layer structure is used, but the present application is not limited thereto, and an outer package having a 4-layer structure or more may be used. For example, the separator may have 4 or more layers in which another layer is present between the base material layer and the barrier layer or another layer is present between the barrier layer and the sealant layer.

Examples

In this example, outer packaging materials 1 for power storage devices of examples 1 to 7 including the gist of the present application and outer packaging materials 1 and 2 for power storage devices of comparative examples 1 to 3 exceeding the gist of the present application were produced, and various evaluations were performed.

Example 1 >

An aluminum foil having a thickness of 35 μm as the barrier layer 52 (aluminum foil of alloy No. a8079 defined by JIS H4160) was coated with a chemical conversion treatment liquid containing polyacrylic acid, trivalent chromium compound, water, and alcohol on both sides, and dried at 150 ℃. The chromium deposit amount based on the chemical conversion coating was 5mg/m on one side ² 。

Next, a biaxially stretched 6 nylon (ONy) film having a thickness of 20 μm as the base layer 51 was laminated on one surface (outer surface) of the aluminum foil (barrier layer 52) subjected to the chemical conversion treatment via a 2-liquid curable urethane adhesive (adhesive layer 61) by dry lamination. Details of the nylon film will be described later.

Next, an unstretched polypropylene (CPP) film having a thickness of 40 μm as the sealant layer 53 was laminated on the other surface (inner surface) of the dry-laminated aluminum foil (barrier layer 52) via a 2-liquid cured type maleic acid-modified polypropylene adhesive (adhesive layer 62), and was sandwiched between a rubber nip roller and a lamination roller heated to 100 ℃ to be pressure-bonded, thereby dry-laminated. Then, the outer package material 1 for the electric storage device was obtained by aging (heating) at 40℃for 10 days.

The biaxially stretched 6 nylon film as the base layer was obtained by stretching a nylon film extruded by a T-die method using a tenter (stretching). Further, both surfaces of the nylon film as the base layer were subjected to corona treatment. Further, a coating liquid containing an acrylic resin and an epoxy resin was applied to one surface (inner surface) of the nylon film as needed, and dried to form an adhesive layer (0.05 μm) (easy adhesion treatment). When the easy-to-adhere layer is formed, the surface on the side where the easy-to-adhere layer is formed is bonded to the barrier layer 52.

TABLE 1

The properties of the nylon film as the base material layer of example 1 are shown in table 1. As shown in table 1, the nylon film of example 1 had a hot water shrinkage of TD of 4.3%, a hot water shrinkage of MD of 3.4%, a difference in hot water shrinkage between TD and MD (TD-MD) of 0.9%, an elastic modulus of TD of 2.3gpa, an elastic modulus of MD of 2.5gpa, a breaking strength of TD of 345MPa, a breaking strength of MD of 282MPa, and a number average molecular weight of polyamide of 30000.

In the column for examination in table 1, the thickness of the nylon film and the presence or absence of the easy-to-adhere layer are described. For example, in example 1, "ONY20" means that the nylon film has a thickness of 20 μm, and "easy adhesion" means that an easy adhesion layer is formed.

The hot water shrinkage ratio was determined by the following equation, and the dimensional change ratio in the stretching direction (shrinkage direction) of a test piece (1 cm×1 cm) of a nylon film before and after immersion in hot water at 100 ℃ for 5 minutes was determined.

Hot water shrinkage (%) = { (X-Y)/X } ×100

X: dimension in the stretching direction (MD or TD) before the impregnation treatment

Y: dimension in the stretching direction (MD or TD) after the impregnation treatment

In the present example, the hot water collection rate was measured using a 1cm×1cm test piece, but in the present application, the size of the test piece is not particularly limited, and for example, a test piece having a suitable size of 1cm to 10cm×1cm to 10cm may be used.

The elastic modulus (Young's modulus) of the core material was measured by a tensile tester under conditions of a sample length of 100mm, a sample width of 15mm, a distance between evaluation points of 50mm, and a tensile speed of 200 mm/min, and the Young's modulus (unit: GPa) was calculated from the obtained "stress-strain curve (SS curve)", in accordance with JIS K7127 (1999). The "slope of the tangent to the straight line portion" in the stress-strain curve is Young's modulus. As a tensile tester, "Stroggraph (AGS-5 kNX)" manufactured by Shimadzu corporation was used. The term "Young's modulus" as defined by ASTM-D-882 is intended to be the same.

The tensile breaking strength is a breaking strength (unit: MPa) measured in accordance with the tensile test of JIS K7127-1999 under the conditions of a specimen width of 15mm, a distance between evaluation points of 100mm and a tensile speed of 100 mm/min.

The number average molecular weight of the polyamide is determined by Gel Permeation Chromatography (GPC).

Examples 2 to 7 >

Nylon films having the characteristics shown in examples 2 to 7 of table 1 were prepared. Using this nylon film, outer packaging material 1 of examples 2 to 7 was produced in the same manner as described above. In example 6, as shown in the spare column of table 1, a nylon film having the same thickness as that of example 3 and having no easy-to-adhere layer was used.

Comparative example 1, 2 >

Nylon films having the characteristics shown in comparative examples 1 and 2 of table 1 were prepared. Outer packaging materials 1 of comparative examples 1 and 2 were produced in the same manner as described above except that the nylon film was used.

< evaluation of moldability >

The outer package materials 1 of examples 1 to 7 and comparative examples 1 and 2 were deep-drawn using a deep-drawing die manufactured by Amada co., ltd. To form a recess having a rectangular shape in plan view and a length of 55mm×width of 35 mm. Then, by checking the presence or absence of pinholes (pinholes) and cracks at the corners of the obtained molded article, the "maximum molding depth (mm)" at which such pinholes and cracks were not generated was examined, and evaluated based on the following determination criteria. In the evaluation, the presence or absence of a crack (crack) or pinhole was examined in a darkroom by a light transmission method. Evaluation criteria described belowIn "good" and "×", are->"O" is acceptable and "X" is unacceptable.

The molding depth is more than 7mm and no crack or pinhole exists

O: the molding depth is more than 5mm and less than 7mm, and has no crack and pinhole

X: the depth of the molding is less than 5mm and has cracks and pinholes

The results of evaluating the moldability obtained in this manner are shown in table 1.

< puncture Strength test (evaluation of puncture resistance) >)

Puncture strength is according to JIS (Japanese Industrial Standard) Z1707: 2019. That is, the puncture strength test was performed by the following steps (1) to (3).

(1) The test pieces obtained from the outer packages 1 of each example and each comparative example were fixed with a jig, a semicircular needle having a diameter of 1.0mm and a tip shape radius of 0.5mm was pierced at a test speed of 50.+ -. 5mm/min, and the maximum force (N) until penetration of the needle was measured.

(2) The number of test pieces was 5 or more in each of examples and comparative examples, and the test pieces were collected so as to be averaged over the entire width of the test piece.

(3) When the test result depends on which surface of the film (test piece) is penetrated, the operation is performed on each surface. The reported value is set to 1 bit after the decimal point.

The results of the puncture strength test obtained in this way are shown in table 1.

From the above evaluation results, it was found that the outer packaging material of examples was excellent in moldability and puncture resistance. In contrast, the outer packaging material of the comparative example was inferior in moldability and puncture resistance to the outer packaging material of the example.

The present application claims priority from japanese patent application No. 2020-208209 of japanese patent application filed at 12/16 of 2020 and from japanese patent application No. 2021-186839 of japanese patent application filed at 11/17 of 2021, the disclosure of which forms part of the present application directly.

The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention in the use of such equivalents of the features shown and described herein, it being recognized that various modifications are possible within the scope of the application as claimed.

Industrial applicability

The exterior material for a power storage device of the present application can be used for a power storage device such as a battery and a capacitor in a portable device or an electric vehicle.

Description of the reference numerals

1: outer packing material

10: power storage device body

51: substrate layer

52: barrier layer

53: sealant layer

Claims

1. An exterior material for an electric storage device comprising a base layer, a barrier layer laminated on the inner side of the base layer, and a sealant layer laminated on the inner side of the barrier layer, characterized in that,

the substrate layer is composed of a polyamide film,

the hot water shrinkage of TD and MD of the substrate layer are both 2.0-5.0%,

the elastic modulus of TD and MD of the substrate layer are 1.5 GPa-3 GPa,

at least one of the fracture strength of TD and the fracture strength of MD of the base material layer is 320MPa or more.

2. The exterior material for power storage devices according to claim 1, wherein the heat shrinkage of TD and the heat shrinkage of MD of the base material layer are each 2.5 to 4.5.

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

4. The exterior material for power storage devices according to any one of claims 1 to 3, wherein the modulus of elasticity of TD and the modulus of elasticity of MD of the base material layer are each 2.0GPa to 2.5GPa.

5. The exterior material for power storage devices according to any one of claims 1 to 4, wherein at least one of a fracture strength of TD and a fracture strength of MD of the base material layer is 400MPa or less.

6. An electricity storage device is characterized by comprising:

a power storage device main body portion; and

the outer packaging material according to claim 1 to 5,