Exterior material for power storage device, manufacturing method thereof, and power storage device

Abstract

Provided is an exterior packaging material for an electricity storage device that is made of a laminate having at least a base layer containing a polyester film, a barrier layer, and a heat-sealable resin layer in this order, and that has excellent formability. [Solution] An exterior material for an electricity storage device, which is composed of a laminate having at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, the base layer including a polyester film, which has a work hardening index in both the longitudinal and transverse directions of 1.6 to 3.0, a difference between the work hardening indexes in the longitudinal and transverse directions of 0.5 or less, an intrinsic viscosity of 0.66 to 0.95, and a rigid amorphous content of 28% to 60%.

Description

[Technical Field]

[0001] The present disclosure relates to an exterior material for an electricity storage device, a method for producing the same, and an electricity storage device. [Background technology]

[0002] Various types of electricity storage devices have been developed, but in all of them, packaging materials (exterior materials) are essential components for sealing the electricity storage device elements such as electrodes and electrolytes. Conventionally, metal exterior materials have been widely used as exterior materials for electricity storage devices.

[0003] Meanwhile, in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc., electricity storage devices are being required to have a variety of shapes as well as to be thinner and lighter in weight. However, the metallic exterior materials for electricity storage devices that have been widely used in the past have the drawbacks of being difficult to keep up with the diversification of shapes and also having limitations on how much they can be made lighter.

[0004] Therefore, a film-like packaging material in which a substrate, an aluminum foil layer, and a heat-sealable resin layer are sequentially laminated has been proposed as a packaging material for an electricity storage device that can be easily processed into various shapes and can be made thinner and lighter (see, for example, Patent Document 1).

[0005] In such film-like packaging materials, recesses are generally formed by cold forming, and energy storage device elements such as electrodes and electrolyte are placed in the spaces formed by the recesses. The heat-sealable resin layers are then heat-sealed together to obtain an energy storage device in which the energy storage device elements are housed inside the packaging material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-287971 Summary of the Invention [Problem to be solved by the invention]

[0007] From the viewpoint of further increasing the energy density of the electricity storage device, it is required to form a deep recess in the film-like packaging material to accommodate the electricity storage device element. However, when the recess is formed by molding the film-like packaging material, there is a problem that cracks and pinholes are likely to occur.

[0008] Here, for example, polyamide film or polyester film is used as the base layer of the film-like packaging material, and it is preferable to use polyamide film in order to improve the formability of the packaging material.

[0009] However, while polyamide films have superior formability compared to polyester films, they are inferior in mechanical strength and insulation properties. Therefore, a technology is needed to improve the formability of exterior materials for electricity storage devices by using polyester films as the base layer.

[0010] A primary object of the present disclosure is to provide an exterior packaging material for an electricity storage device that is made of a laminate having at least a base layer containing a polyester film, a barrier layer, and a heat-sealable resin layer in this order, and that has excellent formability. [Means for solving the problem]

[0011] The inventors of the present disclosure conducted extensive studies to solve the above-mentioned problems, and as a result, they found that in a packaging material for an electricity storage device composed of a laminate including at least a base layer containing a polyester film, a barrier layer, and a heat-sealable resin layer in this order, the polyester film exhibits excellent formability by setting the strain hardening index in the longitudinal direction and the width direction, the difference between the strain hardening index in the longitudinal direction and the width direction, the intrinsic viscosity, and the rigid amorphous amount within specific ranges.

[0012] The present disclosure has been completed based on these findings and further investigations. That is, the present disclosure provides the inventions of the following aspects. The laminate is composed of at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, the substrate layer includes a polyester film, The polyester film is an exterior material for an electricity storage device, having a work-hardening index in both the longitudinal and transverse directions of 1.6 to 3.0, a difference between the work-hardening indexes in the longitudinal and transverse directions of 0.5 or less, an intrinsic viscosity of 0.66 to 0.95, and a rigid amorphous content of 28% to 60%. [Effects of the Invention]

[0013] According to the present disclosure, it is possible to provide a packaging material for an electricity storage device that is composed of a laminate having at least a base layer containing a polyester film, a barrier layer, and a heat-sealable resin layer in this order, and that has excellent formability. The present disclosure can also provide a method for manufacturing a packaging material for an electricity storage device, and an electricity storage device. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 2] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 3] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 4] 1 is a schematic diagram showing an example of a cross-sectional structure of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 5] FIG. 2 is a schematic diagram illustrating a method for housing an electricity storage device element in a package formed from the exterior packaging material for an electricity storage device of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] The packaging material for an electricity storage device of the present disclosure is composed of a laminate having at least a base layer, a barrier layer, and a heat-sealable resin layer, in this order, the base layer including a polyester film, characterized in that the polyester film has a work hardening index in both the longitudinal direction and the width direction of 1.6 to 3.0, a difference between the work hardening indexes in the longitudinal direction and the width direction of 0.5 or less, an intrinsic viscosity of 0.66 to 0.95, and a rigid amorphous amount of 28% to 60%. Due to this configuration, the packaging material for an electricity storage device of the present disclosure has excellent formability, despite the use of a base layer including a polyester film.

[0016] The packaging material for an electricity storage device of the present disclosure will be described in detail below. In this specification, a numerical range indicated by "to" means "not less than" or "not more than." For example, the expression "2 to 15 mm" means 2 mm or more and 15 mm or less.

[0017] In the packaging material for an electric storage device, the MD (Machine Direction) and TD (Transverse Direction) of the barrier layer described below can usually be determined during the manufacturing process. For example, when the barrier layer is made of a metal foil such as an aluminum alloy foil or a stainless steel foil, linear lines called rolling marks are formed on the surface of the metal foil in the rolling direction (RD) of the metal foil. Since the rolling marks extend along the rolling direction, the rolling direction of the metal foil can be determined by observing the surface of the metal foil. Furthermore, during the manufacturing process of a laminate, the MD of the laminate usually coincides with the RD of the metal foil. Therefore, the MD of the laminate can be identified by observing the surface of the metal foil of the laminate and identifying the rolling direction (RD) of the metal foil. Furthermore, since the TD of the laminate is perpendicular to the MD of the laminate, the TD of the laminate can also be identified.

[0018] Furthermore, when the MD of an electrical storage device packaging material cannot be identified due to rolling marks on a metal foil such as an aluminum alloy foil or a stainless steel foil, it can be identified by the following method. One method for confirming the MD of an electrical storage device packaging material is to observe the cross section of the heat-sealable resin layer of the electrical storage device packaging material using an electron microscope to confirm the sea-island structure. In this method, the direction parallel to the cross section in which the average diameter of the island shapes in the direction perpendicular to the thickness direction of the heat-sealable resin layer is largest can be determined as the MD. Specifically, the cross section in the longitudinal direction of the heat-sealable resin layer and each cross section at an angle of 10 degrees from the direction parallel to the longitudinal cross section up to the direction perpendicular to the longitudinal cross section (a total of 10 cross sections) are observed using an electron microscope to confirm the sea-island structure. Next, the shape of each individual island is observed in each cross section. For each island shape, the linear distance connecting the leftmost end in the direction perpendicular to the thickness direction of the heat-sealable resin layer to the rightmost end in the perpendicular direction is defined as the diameter y. For each cross section, the average of the 20 largest diameters y of the island shapes is calculated. The direction parallel to the cross section with the largest average diameter y of the island shapes is determined as MD.

[0019] 1.Layer structure of exterior materials for energy storage devices As shown in FIG. 1 , for example, the electrical storage device packaging material 10 of the present disclosure is composed of a laminate including a base material layer 1, a barrier layer 3, and a heat-sealable resin layer 4 in this order. In the electrical storage device packaging material 10, the base material layer 1 is the outermost layer, and the heat-sealable resin layer 4 is the innermost layer. When assembling an electrical storage device using the electrical storage device packaging material 10 and an electrical storage device element, the electrical storage device element is housed in a space formed by heat-sealing the peripheral portions of the electrical storage device packaging material 10 with the heat-sealable resin layers 4 of the electrical storage device packaging material 10 facing each other. In the laminate constituting the electrical storage device packaging material 10 of the present disclosure, with the barrier layer 3 as the reference, the heat-sealable resin layer 4 side relative to the barrier layer 3 is the inner side, and the base material layer 1 side relative to the barrier layer 3 is the outer side.

[0020] As shown in Figures 2 to 4, for example, the packaging material 10 for an electricity storage device may have an adhesive layer 2 between the base material layer 1 and the barrier layer 3, if necessary, for the purpose of increasing the adhesion between these layers. Furthermore, as shown in Figures 3 and 4, for example, the packaging material 10 for an electricity storage device may have an adhesive layer 5 between the barrier layer 3 and the heat-sealable resin layer 4, if necessary, for the purpose of increasing the adhesion between these layers. Furthermore, as shown in Figure 4, a surface coating layer 6 or the like may be provided on the outer side of the base material layer 1 (the side opposite to the heat-sealable resin layer 4 side), if necessary.

[0021] The thickness of the laminate constituting the electrical storage device packaging material 10 is not particularly limited, but from the viewpoints of cost reduction, energy density improvement, etc., it is preferably about 190 μm or less, about 155 μm or less, or about 120 μm or less. Furthermore, from the viewpoint of maintaining the function of the electrical storage device packaging material to protect the electrical storage device elements, the thickness of the laminate constituting the electrical storage device packaging material 10 is preferably about 35 μm or more, about 45 μm or more, or about 60 μm or more. Furthermore, preferred ranges for the laminate constituting the electrical storage device packaging material 10 include, for example, about 35 to 190 μm, about 35 to 155 μm, about 35 to 120 μm, about 45 to 190 μm, about 45 to 155 μm, about 45 to 120 μm, about 60 to 190 μm, about 60 to 155 μm, and about 60 to 120 μm, with about 60 to 155 μm being particularly preferred.

[0022] In the packaging material 10 for an electricity storage device, the ratio of the total thickness of the base material layer 1, the adhesive layer 2 (which is provided as needed), the barrier layer 3, the adhesive layer 5 (which is provided as needed), the heat-sealable resin layer 4, and the surface coating layer 6 (which is provided as needed) to the thickness (total thickness) of the laminate constituting the packaging material 10 for an electricity storage device is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. As a specific example, when the packaging material 10 for an electricity storage device of the present disclosure includes the base material layer 1, the adhesive layer 2, the barrier layer 3, the adhesive layer 5, and the heat-sealable resin layer 4, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the packaging material 10 for an electricity storage device is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. Furthermore, even when the packaging material 10 for an electricity storage device of the present disclosure is a laminate including a substrate layer 1, an adhesive layer 2, a barrier layer 3, and a heat-sealable resin layer 4, the ratio of the total thickness of these layers to the thickness (total thickness) of the laminate constituting the packaging material 10 for an electricity storage device can be, for example, 80% or more, preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

[0023] 2. Each layer that forms the exterior material for the energy storage device [Base material layer 1] In the present disclosure, the substrate layer 1 is a layer provided for the purpose of, for example, exhibiting the function as a substrate of the packaging material for an electricity storage device. The substrate layer 1 is located on the outer layer side of the packaging material for an electricity storage device. The substrate layer 1 may be the outermost layer (the layer that constitutes the outer surface), or, for example, when a surface coating layer 6 described below is provided, the surface coating layer 6 may be the outermost layer (the layer that constitutes the outer surface).

[0024] In the present disclosure, the base layer 1 includes a polyester film, and the polyester film is characterized by having a work-hardening index in both the longitudinal and width directions of 1.6 to 3.0, a difference between the work-hardening indexes in the longitudinal and width directions of 0.5 or less, an intrinsic viscosity of 0.66 to 0.95, and a rigid amorphous content of 28% to 60%.

[0025] The polyester film contained in the base layer 1 will be described in detail below.

[0026] In the present disclosure, the polyester film contained in the base layer 1 has a work hardening index of 1.6 or more and 3.0 or less in both the longitudinal and transverse directions. Here, the work hardening index is a value calculated from the stress at an elongation of 5% and the stress at an elongation of 60%, obtained from a tensile test determined by the method described in "(10) Work Hardening Index," an evaluation method in the Examples, which will be described later.

[0027] The laminate used in the packaging material for an electric storage device includes a substrate layer, a barrier layer, and a heat-sealable resin layer, and among these, the substrate layer tends to be designed to have the thinnest thickness. When the packaging material for an electric storage device is drawn, the neutral axis of the stress applied in the thickness direction is determined depending on the work-hardening state of each layer, and the position in the thickness direction where the stress is concentrated is determined. If the work-hardening state of the polyester film, i.e., the work-hardening index, is less than 1.6, the neutral axis will be biased toward the barrier layer and the heat-sealable resin layer, making it easier for stress to be applied unevenly to the barrier layer, resulting in fractures or pinholes in the barrier layer during drawing. For this reason, in the substrate layer 1 of the present disclosure, the polyester film must have a work-hardening index of at least 1.6. To prevent the neutral axis from being biased toward the outermost layer, the work-hardening index must be 3.0 or less in both the longitudinal and transverse directions.

[0028] In order to set the work hardening index of a polyester film in both the longitudinal and width directions to 1.6 or more and 3.0 or less, it is preferable that the breaking strength of the film in the longitudinal and width directions be 200 MPa or more. Here, the longitudinal and width directions of the film are determined by measuring the breaking strength in any one direction of the film (0°) and in directions at 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and 165° from that direction, and the direction with the highest breaking strength is defined as the width direction, and the direction perpendicular to the width direction is defined as the longitudinal direction.

[0029] To achieve a breaking strength of 200 MPa or more, polyester films should be stretched at a high ratio during production. Specifically, biaxial stretching is most preferable, and stretching is preferably performed sequentially or simultaneously at an areal stretch ratio of 11.0 times or more using a known method. If the work hardening index is less than 1.6, the drawability is poor. Furthermore, the higher the work hardening index, the greater the elastic deformation due to bending during draw forming, which tends to increase warpage after forming. For this reason, it is important to minimize the work hardening index depending on the required degree of warpage.

[0030] To more suitably exhibit the effects of the present invention, the polyester film preferably has a strain hardening index of 1.8 or more, more preferably 2.0 or more. The strain hardening index of the polyester film is preferably 2.9 or less. Preferred ranges for the strain hardening index of the polyester film include about 1.6 to 3.0, about 1.6 to 2.9, about 1.8 to 3.0, about 1.8 to 2.9, about 2.0 to 3.0, and about 2.0 to 2.9.

[0031] In the present disclosure, from the viewpoint of in-plane uniformity, the difference in work hardening index between the longitudinal direction and the width direction of the polyester film is 0.5 or less. If the difference in work hardening index between the longitudinal direction and the width direction exceeds 0.5, the in-plane uniformity is low, and the load is applied unevenly during drawing, causing local deformation and resulting in poor drawability. The difference in work hardening index is preferably 0.3 or less.

[0032] In the present disclosure, the breaking elongation of the polyester film in at least one of the longitudinal and width directions is preferably 100% or more. One of the deformation behaviors of materials during drawing is elongation. The greater the elongation of the film, the greater the element of elongation deformation in its deformation behavior, improving drawing processability. Therefore, the breaking elongation in at least one of the longitudinal and width directions is preferably 100% or more, and it is more preferable that both the longitudinal and width directions have breaking elongation of 100% or more. To achieve breaking elongation of 100% or more in the longitudinal and width directions, the stretching ratio in each direction can be adjusted to 4.0 times or less. A stretching ratio exceeding 4.0 times in any direction is advantageous in increasing the work hardening index, but the breaking elongation in that stretching direction may be 100% or less, potentially reducing drawing formability. The breaking elongation range of the polyester film in both the longitudinal and width directions is preferably approximately 110 to 150%. The breaking elongation of the polyester film is measured by the method described in the evaluation method "(6) Breaking elongation" in the Examples below.

[0033] In the present disclosure, the polyester film has a rigid amorphous content of 28% or more and 60% or less relative to the entire film. Here, the rigid amorphous content is a value measured by the method described in the evaluation method "(8) Rigid Amorphous Content" in the Examples below. Having the rigid amorphous content within this range enables the film to achieve particularly remarkable puncture resistance, a characteristic in the thickness direction. The drawing process performed on packaging materials for electrical storage devices generally involves fixing the four corners with a mold and drawing the film in the thickness direction. By controlling the rigid amorphous content relative to the entire film within this range, excellent drawing characteristics are achieved in the aforementioned drawing process. If the rigid amorphous content exceeds 60%, the amorphous component accounts for the majority of the film bulk composition, significantly reducing the dimensional stability of the film. On the other hand, if the rigid amorphous content is less than 28%, the film will exhibit poor puncture resistance, a characteristic in the thickness direction.

[0034] To more suitably exhibit the effects of the present invention, the rigid amorphous content of the polyester film is preferably 30% or more, more preferably 35% or more. The rigid amorphous content of the polyester film is preferably 58% or less, more preferably 55% or less, and even more preferably 53% or less. Preferred ranges for the rigid amorphous content of the polyester film include about 28 to 60%, about 28 to 58%, about 28 to 55%, about 28 to 53%, about 30 to 60%, about 30 to 58%, about 30 to 55%, about 30 to 53%, about 35 to 60%, about 35 to 58%, about 35 to 55%, and about 35 to 53%.

[0035] The film bulk state is determined by the crystallinity of the raw materials used as well as the film-forming conditions. For example, when using polyethylene terephthalate, a rigid amorphous content of 28% or more can be achieved by, for example, increasing the film's planar orientation coefficient (fn) to 0.165 or more. The film's planar orientation coefficient is measured using the method described in the evaluation method for the Examples below, "(5) Planar Orientation Coefficient (fn) of Polyester Film." Achieving a film planar orientation coefficient of 0.165 or more can be achieved by using an areal stretch ratio of 12.25 or more during biaxial stretching. Furthermore, it is preferable to control the rigid amorphous content by the heat treatment temperature after sequential biaxial stretching. It is important to keep the highest temperature applied during film formation (heat treatment temperature) below 200°C. While increasing the heat treatment temperature above 230°C also tends to increase the rigid amorphous content due to the initiation of resin melting, this also promotes thermal crystallization of the film, resulting in an increased crystallinity (described below), resulting in a film bulk composition with a higher crystallinity than rigid amorphous. For this reason, it is important that the heat treatment temperature is not more than 200° C. If the heat treatment temperature of the film is more than 200° C. and less than 230° C., the rigid amorphous amount may be less than 28%.

[0036] To more effectively achieve the effects of the present invention, the polyester film preferably has a crystallinity of 15% or more and 40% or less. The crystallinity can be controlled by orientation crystallization due to stretching or thermal crystallization, thereby increasing the mechanical strength of the film. A crystallinity of less than 15% may result in insufficient film plane orientation, making it impossible to control the work hardening index within the range of the present disclosure. A crystallinity of more than 15% and less than 40% may be impossible to achieve within the range of the present disclosure. A crystallinity of 15% or more and 40% or less can be achieved, for example, by using a homopolyester resin, adjusting the film plane orientation coefficient to 0.165 or more and 0.170 or less, and setting the heat treatment temperature to 150°C or more and 200°C or less. Other resins may also be mixed. The crystallinity of the polyester film is measured using the method described in the evaluation method "(7) Crystallinity" in the Examples below.

[0037] To more effectively achieve the effects of the present invention, the crystallinity of the polyester film is preferably 16% or more, more preferably 18% or more, and even more preferably 20% or more. The crystallinity of the polyester film is preferably 39% or less, more preferably 35% or less, and even more preferably 32% or less. Preferred ranges for the crystallinity of the polyester film include about 15 to 40%, about 15 to 39%, about 15 to 35%, about 15 to 32%, about 16 to 40%, about 16 to 39%, about 16 to 35%, about 16 to 32%, about 18 to 40%, about 18 to 39%, about 18 to 35%, about 18 to 32%, about 20 to 40%, about 20 to 39%, about 20 to 35%, and about 15 to 32%.

[0038] The polyester film has an intrinsic viscosity of 0.66 to 0.95. The intrinsic viscosity is measured by the method described in the evaluation method "(4) Intrinsic Viscosity" in the Examples below. An intrinsic viscosity within this range enhances molecular chain entanglement, resulting in deformation in the thickness direction, particularly puncture resistance. If the intrinsic viscosity is less than 0.66, the molecular chain entanglement is insufficient, making it difficult to achieve sufficient drawing processability. On the other hand, if the intrinsic viscosity exceeds 0.95, the filtration pressure during melt film formation increases, necessitating a reduced discharge rate, resulting in poor productivity. The intrinsic viscosity can be adjusted by the raw materials used in melt film formation. To increase the intrinsic viscosity of a film, it is recommended to increase the intrinsic viscosity of the raw materials used during film formation. Considering both the entanglement effect of molecular chains and productivity, the intrinsic viscosity is preferably 0.69 to 0.88.

[0039] To more effectively achieve the effects of the present invention, the 150°C heat shrinkage rate of the polyester film in both the longitudinal and transverse directions is preferably 3.5% to 14.0%. When a polyester film is used for the base layer 1 and a secondary processing step involving heating, such as a lamination step in which a molten resin is directly laminated onto a film and heat of about 150°C is applied, the 150°C heat shrinkage rate is preferably 3.5% or more to suppress wrinkling during extrusion lamination. On the other hand, if the heat shrinkage rate at the temperature applied during lamination exceeds 14%, the film may deform excessively during lamination due to heat shrinkage during lamination, causing problems. To achieve both wrinkling and thermal deformation during lamination, the 150°C heat shrinkage rate of the polyester film in both the longitudinal and transverse directions is preferably 10% or less. The 150°C heat shrinkage rate in the longitudinal and width directions can be controlled to 3.5% or more and 14.0% or less by setting the film area magnification to 12.25 times or more and by heat treating the film at a heat treatment temperature of 160°C or more and 200°C or less. The 150°C heat shrinkage rate in the longitudinal and width directions of a polyester film is measured by the method described in the evaluation method in the Examples below, "(11) 150°C heat shrinkage rate in the longitudinal and width directions of a polyester film."

[0040] To more effectively achieve the effects of the present invention, the polyester film preferably has a melting point (melting endothermic peak temperature (Tm)) determined by a differential scanning calorimeter of 235°C or higher. When a polyester film is used as the base layer of an exterior packaging material for an electricity storage device, the heat-sealable resin layers are heat-sealed together to form a container. For this reason, it is necessary to suppress melting of the exterior packaging material due to the heat of heat sealing. If the melting endothermic peak temperature Tm is lower than 235°C, the heating temperature during heat sealing must be lowered, which increases the time required to form a container by heat sealing, and as a result, mass productivity may be impaired. To achieve a melting endothermic peak temperature Tm of 235°C or higher, it is most preferable to use a homopolyester. From the viewpoint of processability of the polyester film, the melting point is preferably 320°C or lower. The melting point of the polyester film is measured by the method described in "(9) Glass transition temperature Tg, melting point (melting endothermic peak temperature Tm)" in the evaluation methods of the examples described below.

[0041] To more suitably exhibit the effects of the present invention, the polyester film has a melting point of preferably 238° C. or higher, more preferably 240° C. or higher, and even more preferably 245° C. or higher. The polyester film has a melting point of preferably 300° C. or lower, more preferably 290° C. or lower, and even more preferably 270° C. or lower. Preferred melting point ranges for the polyester film include about 235 to 320° C., about 235 to 300° C., about 235 to 290° C., about 235 to 270° C., about 238 to 320° C., about 238 to 300° C., about 238 to 290° C., about 238 to 270° C., about 240 to 320° C., about 240 to 300° C., about 240 to 290° C., about 240 to 270° C., about 245 to 320° C., about 245 to 300° C., about 245 to 290° C., and about 245 to 270° C.

[0042] Polyester films are primarily composed of polyester. Polyester is a general term for polymeric compounds in which the main bond in the main chain is an ester bond. Polyesters are typically obtained by polycondensation of dicarboxylic acids or their derivatives with diols or their derivatives, and electrolyte resistance can be achieved by using polyester as the primary component. In this disclosure, "primarily composed" refers to a ratio of 60% by mass to 100% by mass of the entire object, and refers to the ratio relative to the polyester film. Here, a dicarboxylic acid unit (structural unit) or a diol unit (structural unit) refers to a divalent organic group excluding the portion removed by polycondensation, and is represented by the following general formula: Dicarboxylic acid unit (structural unit): -CO-R-CO- Diol unit (structural unit): -O-R'―O- (wherein R and R' are divalent organic groups. R and R' may be the same or different.)

[0043] Examples of diols or derivatives thereof that can give polyesters include, in addition to ethylene glycol, aliphatic dihydroxy compounds such as 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and neopentyl glycol; polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; alicyclic dihydroxy compounds such as 1,4-cyclohexanedimethanol and spiroglycol; aromatic dihydroxy compounds such as bisphenol A and bisphenol S; and derivatives thereof.

[0044] In addition to terephthalic acid, dicarboxylic acids or their derivatives that can produce polyesters include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, and 5-sodiumsulfonedicarboxylic acid, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, and fumaric acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, and hydroxycarboxylic acids such as parahydroxybenzoic acid, as well as their derivatives. Examples of dicarboxylic acid derivatives include esters of dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethyl methyl terephthalate, dimethyl 2,6-naphthalenedicarboxylate, dimethyl isophthalate, dimethyl adipate, diethyl maleate, and dimethyl dimerate.

[0045] The polyester film may have a single layer structure or a multilayer structure of two or more layers. In the case of a multilayer structure, a symmetrical structure with a central layer as the base point, such as layer B / layer A / layer B, is preferred from the viewpoint of suppressing warpage after film formation. If warpage occurs after film formation, handling may be impaired in subsequent battery manufacturing processes. In addition, in the present disclosure, a five-layer structure, such as layer B / A / layer B / A / B, may also be used. In the case of a multilayer structure, a three-layer stack structure, such as layer B / A / B, is preferred from the viewpoint of warpage after film formation. In the present disclosure, a two-layer structure, such as layer A / layer B, which have different molecular orientations, may cause warpage immediately after film formation. However, an asymmetric structure, such as a two-layer structure, such as layer A / B, may also be used as long as it does not impair the effects of the present invention.

[0046] To improve drawability, the polyester film preferably has a dynamic friction coefficient μd of 0.3 or less on the die-side contact surface. By maintaining the dynamic friction coefficient within this range, deformation resistance during drawing is reduced, improving processability. The dynamic friction coefficient of the polyester film is measured using the method described in the evaluation method for the examples, "(12) Dynamic Friction Coefficient of Polyester Film," described later. While there are no particular limitations on how to achieve a dynamic friction coefficient of 0.3 or less, it is preferable for the outermost layer to contain 0.3% to 5% by mass of inorganic particles and / or organic particles with an average particle size of 0.005 μm to 10 μm. A more preferable range is 0.5% to 3% by mass. However, adding too many particles can reduce the breaking elongation of the packaging material. Therefore, it is important to add particles within a range that does not impair the effects of the present invention. In this disclosure, particles with an average primary particle size of 0.005 μm or more are used. The particle size referred to here refers to the number-average particle size, meaning the particle size observed within the cross section of the film. If the shape is not a perfect circle, the particle size is determined by converting it into a perfect circle of the same area. Here, the number average particle size Dn can be determined by the following steps (1) to (4).

[0047] (1) First, a cross section of the film is cut using a microtome without crushing it in the thickness direction, and a magnified image is obtained using a scanning electron microscope. At this time, the cut is made parallel to the TD direction (transverse direction) of the film. (2) Next, for each particle observed in the cross section of the image, its cross-sectional area S is calculated, and the particle size d is calculated using the following formula. d=2×(S / π) 1 / 2 (3) Using the obtained particle diameter d and the number of resin particles n, Dn is calculated using the following formula. Dn=Σd / n where Σd is the sum of particle diameters within the observation surface, and n is the total number of particles within the observation surface. (4) The above (1) to (3) are carried out at five different locations, and the average value is the number-average particle size of the particles. 2 The above evaluation is carried out in the above areas.

[0048] Examples of inorganic particles that can be used include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, aluminum oxide, mica, kaolin, and clay. Examples of organic particles that can be used include particles containing styrene, silicone, acrylic acids, methacrylic acids, polyesters, and divinyl compounds. Among these, inorganic particles such as wet and dry silica, alumina, and calcium carbonate, and particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, and divinylbenzene are preferred. Furthermore, two or more of these inorganic and organic particles may be used in combination. It is also preferred to apply a roughening treatment, such as embossing or sandblasting, to the film surface to control the maximum surface height.

[0049] The thickness of the polyester film is preferably 9 μm or more and 30 μm or less from the viewpoint of molding conformability and warpage after molding when used as a base layer of an exterior material for an electricity storage device. It is most preferably 12 μm or more and 28 μm or less. Depending on the required drawing depth, a thickness of less than 9 μm may result in poor moldability, while a thickness of 30 μm or more may result in high rigidity and warpage after molding.

[0050] To improve adhesion to the adhesive layer, it is also preferable to subject the polyester film to surface treatments such as corona treatment, plasma treatment, ozone treatment, or the provision of an anchor coat layer. Methods for forming an anchor coat layer include coating the film surface with a resin (combined melt extrusion, hot melt coating, in-line coating using a solvent other than water, or a water-soluble and / or water-dispersible resin, or offline coating). Among these, the in-line coating method, in which a coating agent is applied to one side of the film before the completion of oriented crystallization, stretched in at least one direction, and heat-treated to complete the oriented crystallization, is preferred in terms of uniform coating formation and productivity. Furthermore, when providing an anchor coat layer, the resin is not particularly limited, but examples include acrylic resins, urethane resins, polyester resins, olefin resins, fluorine-based resins, vinyl resins, chlorine-based resins, styrene-based resins, various graft resins, epoxy resins, silicone resins, and the like, and mixtures of these resins can also be used. From the viewpoint of adhesion, polyester resins, acrylic resins, or urethane resins are preferred. When a polyester resin is used as an aqueous coating liquid, a water-soluble or water-dispersible polyester resin is used. To achieve this water solubility or water dispersion, it is preferable to copolymerize a compound containing a sulfonate group or a compound containing a carboxylate group. When an acrylic resin is used as an aqueous coating liquid, it must be dissolved or dispersed in water, and a surfactant (such as, but not limited to, a polyether compound) may be used as an emulsifier. To further improve adhesion, various crosslinking agents can be used in combination with the resin in the anchor coat layer. Melamine, epoxy, and oxazoline resins are commonly used as crosslinking agent resins.

[0051] In the present disclosure, the substrate layer 1 may include at least one layer of polyester film having the above-described properties, and may also include other layers. The materials for forming the other layers are not particularly limited as long as they function as a substrate, i.e., have at least insulating properties. The other layers may be formed using, for example, a resin, and the resin may contain the additives described below.

[0052] The other layer may be, for example, a resin film formed from a resin, or may be formed by applying a resin. The resin film may be an unstretched film or a stretched film. Examples of stretched films include uniaxially stretched films and biaxially stretched films, with biaxially stretched films being preferred. Examples of stretching methods for forming biaxially stretched films include sequential biaxial stretching, inflation, and simultaneous biaxial stretching. Examples of methods for applying a resin include roll coating, gravure coating, and extrusion coating.

[0053] Examples of resins for forming the other layers include polyamides, polyolefins, epoxy resins, acrylic resins, fluororesins, polyurethanes, silicone resins, and phenolic resins, as well as modified versions of these resins. Furthermore, the resins for forming the other layers may be copolymers of these resins or modified versions of the copolymers. Furthermore, they may be mixtures of these resins.

[0054] Among these, polyamide is preferably used as the resin for forming the other layer. That is, when the base layer 1 of the present disclosure further includes another layer different from a polyester film, the base layer 1 is preferably a laminate of a polyester film and a polyamide film.

[0055] Specific examples of polyamides include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (where I represents isophthalic acid and T represents terephthalic acid), which contain structural units derived from terephthalic acid and / or isophthalic acid; and aromatic polyamides such as polyamide MXD6 (polymetaxylylene adipamide); alicyclic polyamides such as polyamide PACM6 (polybis(4-aminocyclohexyl)methane adipamide); polyamides copolymerized with a lactam component or an isocyanate component such as 4,4'-diphenylmethane diisocyanate; polyesteramide copolymers and polyetheresteramide copolymers, which are copolymers of copolymerized polyamides with polyesters or polyalkylene ether glycols; and copolymers of these polyamides. These polyamides may be used singly or in combination of two or more.

[0056] The polyamide film is preferably a stretched polyamide film, more preferably a stretched nylon film, and even more preferably a biaxially stretched nylon film.

[0057] When the base material layer 1 is composed of two or more layers, the base material layer 1 may be a laminate in which each film is laminated with an adhesive or the like, or a laminate of two or more films formed by co-extrusion of resins. Furthermore, a laminate of two or more resin films formed by co-extrusion of resins may be used as the base material layer 1 without being stretched, or may be uniaxially or biaxially stretched to form the base material layer 1.

[0058] Since polyester is less likely to discolor when, for example, an electrolyte solution adheres to its surface, when the base layer 1 is a laminate of two or more resin films, it is preferable that the polyester film be located as the outermost layer of the base layer 1.

[0059] When the base layer 1 is a laminate of two or more resin film layers, the two or more resin film layers may be laminated via an adhesive. When the base layer 1 is a laminate of two or more resin film layers, at least one layer must have the above-mentioned major axis orientation. Preferred adhesives include those similar to those exemplified for the adhesive layer 2 described below. The method for laminating two or more resin film layers is not particularly limited, and known methods can be used, such as dry lamination, sandwich lamination, extrusion lamination, and thermal lamination, with dry lamination being preferred. When laminating using the dry lamination method, it is preferable to use a polyurethane adhesive as the adhesive. In this case, the thickness of the adhesive is, for example, about 2 to 5 μm. Furthermore, as described for the polyester film, an anchor coat layer may be formed on the resin film used for the base layer and then laminated. Examples of the anchor coat layer include those similar to those exemplified for the adhesive layer 2 described below. In this case, the thickness of the anchor coat layer is, for example, about 0.01 to 1.0 μm.

[0060] Furthermore, additives such as lubricants, flame retardants, antiblocking agents, antioxidants, light stabilizers, tackifiers, and antistatic agents may be present on at least one of the surface and the interior of the base material layer 1. Only one type of additive may be used, or two or more types may be mixed and used.

[0061] In the present disclosure, from the viewpoint of improving the formability of the exterior material for an electrical storage device, it is preferable that a lubricant be present on the surface of the base layer 1. The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Specific examples of methylolamides include methylol stearic acid amide. Specific examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipamide, and N,N'-distearyl sebacic acid amide. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacic acid amide. Specific examples of fatty acid ester amides include stearamidoethyl stearate. Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, N,N'-distearyl isophthalic acid amide, etc. The lubricants may be used singly or in combination of two or more.

[0062] When a lubricant is present on the surface of the base layer 1, the amount of the lubricant is not particularly limited, but is preferably about 3 mg / m 2 or more, more preferably 4 to 15 mg / m 2 approximately, more preferably 5 to 14 mg / m 2 The degree of

[0063] The lubricant present on the surface of the base layer 1 may be a lubricant exuded from the resin that constitutes the base layer 1, or a lubricant applied to the surface of the base layer 1.

[0064] The thickness of the substrate layer 1 is not particularly limited as long as it functions as a substrate, but from the viewpoint of more suitably achieving the effects of the present invention, it is preferably at least about 10 μm, more preferably at least about 15 μm. From the same viewpoint, it is preferably not more than about 60 μm, more preferably not more than about 50 μm, even more preferably not more than about 40 μm, even more preferably not more than about 30 μm, even more preferably not more than about 28 μm, and even more preferably not more than about 25 μm. Preferred ranges for the thickness of the substrate layer 1 include about 10 to 60 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 30 μm, about 10 to 28 μm, about 10 to 25 μm, about 15 to 60 μm, about 15 to 50 μm, about 15 to 40 μm, about 15 to 30 μm, about 15 to 28 μm, and about 15 to 25 μm. When the base layer 1 is a laminate of two or more resin films, the thickness of each resin film constituting each layer is preferably about 2 to 25 μm.

[0065] [Adhesive layer 2] In the packaging material for an electricity storage device of the present disclosure, the adhesive layer 2 is a layer that is provided between the base layer 1 and the barrier layer 3 as needed for the purpose of increasing the adhesion between them.

[0066] The adhesive layer 2 is formed from an adhesive capable of bonding the base material layer 1 and the barrier layer 3. There are no limitations on the adhesive used to form the adhesive layer 2, and it may be any of a chemical reaction type, a solvent evaporation type, a hot melt type, a hot pressure type, etc. It may also be a two-component curing adhesive (two-component adhesive), a one-component curing adhesive (one-component adhesive), or a resin that does not involve a curing reaction. The adhesive layer 2 may be a single layer or multiple layers.

[0067] Specific examples of adhesive components contained in the adhesive include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyesters; polyethers; polyurethanes; epoxy resins; phenolic resins; polyamides such as nylon 6, nylon 66, nylon 12, and copolymer polyamides; polyolefin-based resins such as polyolefins, cyclic polyolefins, acid-modified polyolefins, and acid-modified cyclic polyolefins; polyvinyl acetate; cellulose; (meth)acrylic resins; polyimides; polycarbonates; amino resins such as urea resins and melamine resins; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; and silicone resins. These adhesive components may be used alone or in combination. Among these adhesive components, polyurethane adhesives are preferred. Furthermore, the adhesive strength of these adhesive component resins can be increased by using an appropriate curing agent in combination. The curing agent is selected appropriately from polyisocyanates, multifunctional epoxy resins, oxazoline group-containing polymers, polyamine resins, acid anhydrides, and the like, depending on the functional groups of the adhesive components.

[0068] Examples of polyurethane adhesives include polyurethane adhesives containing a first part containing a polyol compound and a second part containing an isocyanate compound. Preferred examples include two-component curing polyurethane adhesives, with a polyol such as polyester polyol, polyether polyol, or acrylic polyol as the first part and an aromatic or aliphatic polyisocyanate as the second part. Examples of polyurethane adhesives include polyurethane adhesives containing a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance, and an isocyanate compound. Examples of polyurethane adhesives include polyurethane adhesives containing a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance, and a polyol compound. Examples of polyurethane adhesives include polyurethane adhesives obtained by reacting a polyurethane compound obtained by reacting a polyol compound with an isocyanate compound in advance with moisture, such as in the air, and curing the polyurethane compound. Polyol compounds preferably include polyester polyols having hydroxyl groups on the side chains in addition to terminal hydroxyl groups in the repeating units. Examples of the second part include aliphatic, alicyclic, aromatic, and araliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Other examples include polyfunctional isocyanate-modified products of one or more of these diisocyanates. Multimers (e.g., trimers) can also be used as polyisocyanate compounds. Examples of such multimers include adducts, biurets, and nurates. Forming the adhesive layer 2 using a polyurethane adhesive provides the electrical storage device exterior material with excellent electrolyte resistance, preventing peeling of the base layer 1 even when the side surface is coated with an electrolyte.

[0069] Furthermore, the adhesive layer 2 may contain other components as long as they do not impair adhesion, and may contain colorants, thermoplastic elastomers, tackifiers, fillers, and the like. When the adhesive layer 2 contains a colorant, the exterior material for an electricity storage device can be colored. Known colorants such as pigments and dyes can be used as the colorant. Furthermore, only one type of colorant may be used, or two or more types may be mixed together.

[0070] The type of pigment is not particularly limited as long as it does not impair the adhesiveness of the adhesive layer 2. Examples of organic pigments include azo-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigothioindigo-based, perinone-perylene-based, isoindolenine-based, and benzimidazolone-based pigments, while examples of inorganic pigments include carbon black-based, titanium oxide-based, cadmium-based, lead-based, chromium oxide-based, and iron-based pigments, and other examples include finely powdered mica and fish scale foil.

[0071] Among colorants, carbon black is preferred in order to give the exterior appearance of the electrical storage device packaging material a black color, for example.

[0072] The average particle size of the pigment is not particularly limited and may be, for example, about 0.05 to 5 μm, and preferably about 0.08 to 2 μm. The average particle size of the pigment is the median size measured with a laser diffraction / scattering particle size distribution measuring device.

[0073] The content of the pigment in the adhesive layer 2 is not particularly limited as long as it colors the packaging material for an electricity storage device, and may be, for example, about 5 to 60 mass %, and preferably 10 to 40 mass %.

[0074] The thickness of the adhesive layer 2 is not particularly limited as long as it can bond the base layer 1 and the barrier layer 3, but is, for example, about 1 μm or more, or about 2 μm or more. The thickness of the adhesive layer 2 is, for example, about 10 μm or less, or about 5 μm or less. Preferred ranges for the thickness of the adhesive layer 2 include about 1 to 10 μm, about 1 to 5 μm, about 2 to 10 μm, and about 2 to 5 μm.

[0075] [Colored layer] The colored layer is a layer (not shown) that is provided between the base material layer 1 and the barrier layer 3 as needed. When the adhesive layer 2 is provided, a colored layer may be provided between the base material layer 1 and the adhesive layer 2, or between the adhesive layer 2 and the barrier layer 3. Alternatively, a colored layer may be provided on the outside of the base material layer 1. By providing a colored layer, the packaging material for an electricity storage device can be colored.

[0076] The colored layer can be formed, for example, by applying ink containing a colorant to the surface of the base layer 1 or the surface of the barrier layer 3. Known colorants such as pigments and dyes can be used as the colorant. Furthermore, only one type of colorant may be used, or two or more types may be mixed together.

[0077] Specific examples of the colorant contained in the colored layer include the same as those exemplified in the section [Adhesive layer 2].

[0078] [Barrier layer 3] In the packaging material for an electricity storage device, the barrier layer 3 is a layer that at least prevents the penetration of moisture.

[0079] Examples of the barrier layer 3 include metal foils, vapor-deposited films, and resin layers having barrier properties. Vapor-deposited films include metal vapor-deposited films, inorganic oxide vapor-deposited films, and carbon-containing inorganic oxide vapor-deposited films. Resin layers include fluorine-containing resins such as polyvinylidene chloride, polymers mainly composed of chlorotrifluoroethylene (CTFE), polymers mainly composed of tetrafluoroethylene (TFE), polymers having fluoroalkyl groups, and polymers mainly composed of fluoroalkyl units, as well as ethylene-vinyl alcohol copolymers. Examples of the barrier layer 3 also include resin films comprising at least one of these vapor-deposited films and resin layers. The barrier layer 3 may comprise multiple layers. The barrier layer 3 preferably includes a layer composed of a metal material. Specific examples of metal materials constituting the barrier layer 3 include aluminum alloys, stainless steel, titanium steel, and steel. When used as a metal foil, the barrier layer 3 preferably includes at least one of aluminum alloy foil and stainless steel foil.

[0080] From the viewpoint of improving the formability of the electrical storage device packaging material, the aluminum alloy foil is preferably a soft aluminum alloy foil made of, for example, an annealed aluminum alloy, and from the viewpoint of further improving formability, an iron-containing aluminum alloy foil is preferred. In the iron-containing aluminum alloy foil (100% by mass), the iron content is preferably 0.1 to 9.0% by mass, more preferably 0.5 to 2.0% by mass. By setting the iron content to 0.1% by mass or more, an electrical storage device packaging material with better formability can be obtained. By setting the iron content to 9.0% by mass or less, an electrical storage device packaging material with better flexibility can be obtained. Examples of soft aluminum alloy foils include aluminum alloy foils having a composition specified in JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, or JIS H4000:2014 A8079P-O. Silicon, magnesium, copper, manganese, etc. may be added as needed. Softening can be achieved by annealing or other methods.

[0081] Examples of stainless steel foil include austenitic, ferritic, austenitic-ferritic, martensitic, and precipitation hardened stainless steel foils. From the viewpoint of providing an exterior material for an electricity storage device that has excellent formability, the stainless steel foil is preferably made of austenitic stainless steel.

[0082] Specific examples of austenitic stainless steels that can be used to form the stainless steel foil include SUS304, SUS301, and SUS316L, with SUS304 being particularly preferred.

[0083] In the case of a metal foil, the thickness of the barrier layer 3 should be sufficient to at least function as a barrier layer that prevents moisture penetration, and may be, for example, approximately 9 to 200 μm. The thickness of the barrier layer 3 is preferably 100 μm or less, more preferably approximately 85 μm or less. The thickness of the barrier layer 3 is preferably approximately 25 μm or more, more preferably 30 μm or more. Preferred thickness ranges for the barrier layer 3 include approximately 25 to 100 μm, approximately 25 to 85 μm, approximately 30 to 100 μm, and approximately 30 to 85 μm. When the barrier layer 3 is made of an aluminum alloy foil, the above-mentioned ranges are particularly preferred. In particular, when the barrier layer 3 is made of a stainless steel foil, the thickness of the stainless steel foil is preferably approximately 60 μm or less, more preferably approximately 50 μm or less, even more preferably approximately 40 μm or less, even more preferably approximately 30 μm or less, and particularly preferably approximately 25 μm or less. The thickness of the stainless steel foil is preferably at least about 10 μm, more preferably at least about 15 μm. Preferred thickness ranges for the stainless steel foil include about 10 to 60 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 30 μm, about 10 to 25 μm, about 15 to 60 μm, about 15 to 50 μm, about 15 to 40 μm, about 15 to 30 μm, and about 15 to 25 μm.

[0084] Furthermore, when the barrier layer 3 is a metal foil, it is preferable that a corrosion-resistant coating be provided on at least the surface opposite the substrate layer to prevent dissolution and corrosion. The barrier layer 3 may be provided with a corrosion-resistant coating on both sides. Here, the corrosion-resistant coating refers to a thin film formed on the surface of the barrier layer by, for example, a hydrothermal conversion treatment such as boehmite treatment, a chemical conversion treatment, anodizing treatment, a nickel or chromium plating treatment, or a corrosion prevention treatment such as applying a coating agent, to provide the barrier layer with corrosion resistance (e.g., acid resistance, alkali resistance, etc.). Specifically, the corrosion-resistant coating refers to a coating that improves the acid resistance of the barrier layer (acid-resistant coating) or a coating that improves the alkali resistance of the barrier layer (alkali-resistant coating). The corrosion-resistant coating may be formed by one type of treatment or a combination of two or more types. Furthermore, not only one layer but also multiple layers can be formed. Furthermore, among these treatments, the hydrothermal conversion treatment and anodizing treatment are treatments that dissolve the metal foil surface with a treatment agent to form a metal compound with excellent corrosion resistance. These treatments may be included in the definition of chemical conversion treatment. In addition, when the barrier layer 3 is provided with a corrosion-resistant coating, the barrier layer 3 includes the corrosion-resistant coating.

[0085] The corrosion-resistant coating prevents delamination between the barrier layer (e.g., aluminum alloy foil) and the substrate layer during molding of the exterior packaging material for an electricity storage device, prevents dissolution and corrosion of the barrier layer surface due to hydrogen fluoride produced by the reaction between the electrolyte and water, and in particular prevents dissolution and corrosion of aluminum oxide present on the barrier layer surface when the barrier layer is an aluminum alloy foil, and also improves the adhesion (wettability) of the barrier layer surface, thereby preventing delamination between the substrate layer and the barrier layer during heat sealing and between the substrate layer and the barrier layer during molding.

[0086] Various corrosion-resistant coatings formed by chemical conversion treatments are known, including corrosion-resistant coatings containing at least one of phosphates, chromates, fluorides, triazine thiol compounds, and rare earth oxides. Examples of chemical conversion treatments using phosphates and chromates include chromate chromate treatment, phosphate chromate treatment, phosphate-chromate treatment, and chromate treatment. Examples of chromium compounds used in these treatments include chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromate acetylacetate, chromium chloride, and potassium chromium sulfate. Examples of phosphorus compounds used in these treatments include sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphoric acid. Examples of chromate treatments include etching chromate treatment, electrolytic chromate treatment, and paint-on chromate treatment, with paint-on chromate treatment being preferred. This paint-type chromate treatment involves first degreasing at least the inner surface of a barrier layer (e.g., an aluminum alloy foil) using a well-known method such as alkali immersion, electrolytic cleaning, acid pickling, electrolytic pickling, or acid activation, and then coating the degreased surface with a treatment solution primarily composed of a metal phosphate such as Cr (chromium) phosphate, Ti (titanium) phosphate, Zr (zirconium) phosphate, or Zn (zinc) phosphate, or a mixture of these metal salts, or a treatment solution primarily composed of a nonmetallic phosphate and a mixture of these nonmetallic salts, or a mixture of these with a synthetic resin, using a well-known coating method such as roll coating, gravure printing, or immersion, followed by drying. The treatment solution can be, for example, water, alcoholic solvents, hydrocarbon solvents, ketone solvents, ester solvents, or ether solvents, with water being preferred. The resin component used here may be a polymer such as a phenolic resin or an acrylic resin, or may be a chromate treatment using an aminated phenol polymer having repeating units represented by the following general formulas (1) to (4): In the aminated phenol polymer, the repeating units represented by the following general formulas (1) to (4) may be contained alone or in any combination of two or more types.The acrylic resin is preferably polyacrylic acid, an acrylic acid methacrylic acid ester copolymer, an acrylic acid maleic acid copolymer, an acrylic acid styrene copolymer, or a derivative thereof such as a sodium salt, an ammonium salt, or an amine salt. A derivative of polyacrylic acid, such as an ammonium salt, a sodium salt, or an amine salt of polyacrylic acid, is particularly preferred. In the present disclosure, polyacrylic acid refers to a polymer of acrylic acid. The acrylic resin is also preferably a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic acid anhydride, or an ammonium salt, a sodium salt, or an amine salt of a copolymer of acrylic acid and a dicarboxylic acid or a dicarboxylic acid anhydride. Only one type of acrylic resin may be used, or two or more types may be mixed and used.

[0087] [ka]

[0088] [ka]

[0089] [ka]

[0090] [ka]

[0091] In the general formulas (1) to (4), X represents a hydrogen atom, a hydroxy group, an alkyl group, a hydroxyalkyl group, an allyl group, or a benzyl group. 1 and R 2 are the same or different and represent a hydroxy group, an alkyl group, or a hydroxyalkyl group. 1 and R 2Examples of the alkyl group represented by X and R include linear or branched alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl. 1 and R 2 Examples of the hydroxyalkyl group represented by the formula (1) include a linear or branched alkyl group having 1 to 4 carbon atoms substituted with one hydroxy group, such as a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, a 1-hydroxybutyl group, a 2-hydroxybutyl group, a 3-hydroxybutyl group, and a 4-hydroxybutyl group. 1 and R 2 The alkyl group and hydroxyalkyl group represented by the formula (1) may be the same or different. In the formulas (1) to (4), X is preferably a hydrogen atom, a hydroxy group, or a hydroxyalkyl group. The number average molecular weight of the aminated phenol polymer having repeating units represented by the formulas (1) to (4) is preferably about 500 to 1,000,000, and more preferably about 1,000 to 20,000. The aminated phenol polymer can be prepared, for example, by polycondensing a phenol compound or a naphthol compound with formaldehyde to produce a polymer comprising repeating units represented by the formula (1) or (3), and then polycondensing the polymer with formaldehyde and an amine (R 1 R 2 NH) to the functional group (-CHNR 1 R 2 The aminated phenol polymers can be used singly or in combination of two or more.

[0092] Another example of a corrosion-resistant coating is a thin film formed by a coating-type corrosion prevention treatment in which a coating agent containing at least one selected from the group consisting of a rare earth element oxide sol, an anionic polymer, and a cationic polymer is applied. The coating agent may further contain phosphoric acid or a phosphate salt, and a crosslinking agent for crosslinking the polymer. The rare earth element oxide sol has rare earth element oxide fine particles (e.g., particles with an average particle size of 100 nm or less) dispersed in a liquid dispersion medium. Examples of rare earth element oxides include cerium oxide, yttrium oxide, neodymium oxide, and lanthanum oxide, with cerium oxide being preferred from the perspective of further improving adhesion. The rare earth element oxide contained in the corrosion-resistant coating can be used alone or in combination of two or more. The liquid dispersion medium for the rare earth element oxide sol can be various solvents such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents, with water being preferred. Preferred examples of cationic polymers include polyethyleneimine, ionic polymer complexes composed of polyethyleneimine and a polymer having a carboxylic acid, primary amine-grafted acrylic resins in which a primary amine is graft-polymerized onto an acrylic backbone, polyallylamine or its derivatives, and aminated phenols. Preferred anionic polymers are poly(meth)acrylic acid or its salts, or copolymers primarily composed of (meth)acrylic acid or its salts. The crosslinking agent is preferably at least one selected from the group consisting of a compound having a functional group selected from an isocyanate group, a glycidyl group, a carboxyl group, and an oxazoline group, and a silane coupling agent. The phosphoric acid or phosphoric acid salt is preferably a condensed phosphoric acid or a condensed phosphate salt.

[0093] An example of a corrosion-resistant coating is one formed by applying a solution of fine particles of metal oxides such as aluminum oxide, titanium oxide, cerium oxide, and tin oxide, or barium sulfate dispersed in phosphoric acid to the surface of a barrier layer and baking the coating at 150°C or higher.

[0094] The corrosion-resistant coating may have a laminated structure, if necessary, by further laminating at least one of a cationic polymer and an anionic polymer, such as those mentioned above.

[0095] The composition of the corrosion-resistant film can be analyzed using, for example, time-of-flight secondary ion mass spectrometry.

[0096] The amount of the corrosion-resistant film formed on the surface of the barrier layer 3 in the chemical conversion treatment is not particularly limited. For example, in the case of applying chromate treatment, the amount of the corrosion-resistant film formed on the surface of the barrier layer 3 is 2 It is desirable that the chromate compound is contained in an amount, in terms of chromium, of about 0.5 to 50 mg, preferably about 1.0 to 40 mg, the phosphorus compound in terms of phosphorus, and the aminated phenol polymer in an amount, in terms of phosphorus, of about 1.0 to 200 mg, preferably about 5.0 to 150 mg, per unit area.

[0097] The thickness of the corrosion-resistant coating is not particularly limited, but is preferably about 1 nm to 20 μm, more preferably about 1 nm to 100 nm, and even more preferably about 1 nm to 50 nm, from the viewpoint of the cohesive strength of the coating and the adhesive strength with the barrier layer or the thermally adhesive resin layer. The thickness of the corrosion-resistant coating can be measured by observation with a transmission electron microscope, or by a combination of observation with a transmission electron microscope and energy dispersive X-ray spectroscopy or electron energy loss spectroscopy. Analysis of the composition of the corrosion-resistant coating using time-of-flight secondary ion mass spectrometry can reveal the thickness of the corrosion-resistant coating, for example, by measuring the thickness of the coating with secondary ions consisting of Ce, P, and O (e.g., Ce2PO4 + , CePO4 - At least one of the following ions may be present: Cr, P, and O secondary ions (e.g., CrPO2 + , CrPO4 - Peaks derived from at least one of the above are detected.

[0098] The chemical conversion treatment is carried out by applying a solution containing a compound used to form a corrosion-resistant coating to the surface of the barrier layer by bar coating, roll coating, gravure coating, immersion, or other methods, and then heating the barrier layer to a temperature of approximately 70 to 200°C. Furthermore, before applying the chemical conversion treatment to the barrier layer, the barrier layer may be subjected to a degreasing treatment using an alkali immersion method, electrolytic cleaning, acid cleaning, electrolytic acid cleaning, or other methods. By performing such a degreasing treatment, the chemical conversion treatment of the surface of the barrier layer can be carried out more efficiently. Furthermore, using an acid degreasing agent prepared by dissolving a fluorine-containing compound in an inorganic acid for the degreasing treatment not only degreases the metal foil but also forms a passive metal fluoride. In such cases, only the degreasing treatment may be performed.

[0099] [Thermal adhesive resin layer 4] In the packaging material for an electricity storage device of the present disclosure, the heat-sealable resin layer 4 corresponds to the innermost layer and is a layer (sealant layer) that functions to seal the electricity storage device elements by heat-sealing the heat-sealable resin layers together when the electricity storage device is assembled.

[0100] The resin constituting the heat-sealable resin layer 4 is not particularly limited as long as it is heat-sealable. Examples of suitable resins include polyolefins such as homo- or block-type polypropylene, resins containing a polyolefin skeleton such as cyclic polyolefins, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, acrylic resins, polymethylpentene and its copolymers with α-olefins, fluororesins such as nylon 6, nylon 66, polyvinylidene chloride, polyphenylene sulfide, acetyl cellulose, ETFE, PCTFE, PFA, and FEP, and resins obtained by modifying these resins with maleic anhydride or acrylic acid (e.g., acid-modified polyolefins). These resins may be one type or two or more types. The presence of a polyolefin skeleton in the resin constituting the heat-sealable resin layer 4 can be determined by, for example, infrared spectroscopy or gas chromatography-mass spectrometry. When the resin constituting the heat-sealable resin layer 4 is analyzed by infrared spectroscopy, a peak derived from maleic anhydride is preferably detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, the wave number is 1760 cm -1 Near and wave number 1780cm -1 A peak derived from maleic anhydride is detected around . When the thermally adhesive resin layer 4 is a layer made of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride is detected when measured by infrared spectroscopy. However, if the degree of acid modification is low, the peak becomes small and may not be detected. In such cases, analysis can be performed by nuclear magnetic resonance spectroscopy.

[0101] Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); propylene-α-olefin copolymers; and ethylene-butene-propylene terpolymers. Among these, polypropylene is preferred. When the polyolefin resin is a copolymer, it may be a block copolymer or a random copolymer. These polyolefin resins may be used alone or in combination of two or more.

[0102] The polyolefin may also be a cyclic polyolefin. Cyclic polyolefins are copolymers of olefins and cyclic monomers, and examples of olefins constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, and isoprene. Examples of cyclic monomers constituting the cyclic polyolefin include cyclic alkenes such as norbornene; and cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these, preferred are cyclic alkenes, and more preferred are norbornene.

[0103] Acid-modified polyolefins are polymers modified by block polymerization or graft polymerization of polyolefins with an acid component. Examples of acid-modified polyolefins include the above-mentioned polyolefins, copolymers of the above-mentioned polyolefins with polar molecules such as acrylic acid or methacrylic acid, and crosslinked polyolefins. Examples of acid components used for acid modification include carboxylic acids or anhydrides thereof, such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

[0104] The acid-modified polyolefin may be an acid-modified cyclic polyolefin. The acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin by replacing it with an acid component, or by block polymerizing or graft polymerizing an acid component onto the cyclic polyolefin. The acid-modified cyclic polyolefin is the same as described above. The acid component used for the acid modification is the same as the acid component used for the modification of the polyolefin.

[0105] Preferred acid-modified polyolefins include polyolefins modified with carboxylic acid or its anhydride, polypropylenes modified with carboxylic acid or its anhydride, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

[0106] When the heat-sealable resin layer 4 is formed from a maleic anhydride-modified resin of block-type polypropylene, a maleic anhydride-modified resin of polymethylpentene or its copolymer with an α-olefin, a maleic anhydride-modified resin of a cyclic polyolefin, a fluororesin such as ETFE, PCTFE, PFA, or FEP, polyethylene terephthalate, or polybutylene terephthalate, the electrical storage device packaging material 10 of the present disclosure can exhibit high sealing strength in high-temperature environments when used in applications requiring heat resistance, such as batteries used at high temperatures (e.g., 80°C or higher). The polyethylene terephthalate and polybutylene terephthalate may be stretched or unstretched, and may contain an elastomer.

[0107] The polybutylene terephthalate film preferably contains an elastomer in addition to polybutylene terephthalate. The elastomer enhances the flexibility of the polybutylene terephthalate film while ensuring its durability in high-temperature environments. Preferred elastomers include at least one thermoplastic elastomer selected from polyesters, polyamides, polyurethanes, polyolefins, polystyrenes, polyethers, and acrylics, or thermoplastic elastomer copolymers thereof. More preferred examples include thermoplastic elastomers composed of block copolymers of polybutylene terephthalate and polyethers, and thermoplastic elastomers composed of α-olefin copolymers of polymethylpentene. The content of the elastomer in the heat-sealable resin layer 4 is not particularly limited, as long as it enhances the flexibility of the heat-sealable resin layer 4 while ensuring its excellent heat resistance and sealability. For example, the content may be about 0.1% by mass or more, preferably about 0.5% by mass or more, more preferably about 1.0% by mass or more, and even more preferably about 3.0% by mass or more. The content is, for example, about 10.0% by mass or less, about 8.0% by mass or less, about 5.0% by mass or less, etc. Preferred ranges of the content include about 0.1 to 10.0% by mass, about 0.1 to 8.0% by mass, about 0.1 to 5.0% by mass, about 0.5 to 10.0% by mass, about 0.5 to 8.0% by mass, about 0.5 to 5.0% by mass, about 1.0 to 10.0% by mass, about 1.0 to 8.0% by mass, about 1.0 to 5.0% by mass, about 3.0 to 10.0% by mass, about 3.0 to 8.0% by mass, and about 3.0 to 5.0% by mass.

[0108] The thermally adhesive resin layer 4 may be formed of one type of resin alone or may be formed of a blend polymer of two or more types of resins. Furthermore, the thermally adhesive resin layer 4 may be formed of only one layer, or may be formed of two or more layers of the same or different resins.

[0109] Furthermore, the heat-sealable resin layer 4 may contain a lubricant, etc., as necessary. When the heat-sealable resin layer 4 contains a lubricant, the moldability of the electrical storage device packaging material can be improved. The lubricant is not particularly limited, and known lubricants can be used. The lubricants may be used alone or in combination of two or more.

[0110] The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of the lubricant include those exemplified for the base layer 1. The lubricant may be used alone or in combination of two or more.

[0111] When a lubricant is present on the surface of the heat-sealable resin layer 4, the amount of the lubricant present is not particularly limited, but from the viewpoint of improving the formability of the packaging material for an electricity storage device, it is preferably 10 to 50 mg / m 2 approximately, more preferably 15 to 40 mg / m 2 The degree of

[0112] The lubricant present on the surface of the heat-sealable resin layer 4 may be a lubricant exuded from the resin constituting the heat-sealable resin layer 4, or a lubricant applied to the surface of the heat-sealable resin layer 4.

[0113] The thickness of the heat-sealable resin layer 4 is not particularly limited as long as it can heat-seal the heat-sealable resin layers to each other and function to seal the electricity storage device element, but may be, for example, about 100 μm or less, preferably about 85 μm or less, and more preferably about 15 to 85 μm. For example, when the thickness of the adhesive layer 5 described below is 10 μm or more, the thickness of the heat-sealable resin layer 4 is preferably about 85 μm or less, and more preferably about 15 to 45 μm. For example, when the thickness of the adhesive layer 5 described below is less than 10 μm or when the adhesive layer 5 is not provided, the thickness of the heat-sealable resin layer 4 is preferably about 20 μm or more, and more preferably about 35 to 85 μm.

[0114] [Adhesive layer 5] In the packaging material for an electricity storage device of the present disclosure, the adhesive layer 5 is a layer that is provided as needed between the barrier layer 3 (or corrosion-resistant film) and the heat-sealable resin layer 4 in order to firmly bond them together.

[0115] The adhesive layer 5 is formed of a resin capable of bonding the barrier layer 3 and the heat-sealable resin layer 4. Examples of resins that can be used to form the adhesive layer 5 include the same adhesives as those exemplified for the adhesive layer 2. From the viewpoint of firmly bonding the adhesive layer 5 and the heat-sealable resin layer 4, the resin used to form the adhesive layer 5 preferably contains a polyolefin skeleton, such as the polyolefins and acid-modified polyolefins exemplified for the heat-sealable resin layer 4. From the viewpoint of firmly bonding the barrier layer 3 and the adhesive layer 5, the adhesive layer 5 preferably contains an acid-modified polyolefin. Examples of acid-modified components include dicarboxylic acids such as maleic acid, itaconic acid, succinic acid, and adipic acid, as well as anhydrides thereof, acrylic acid, and methacrylic acid. However, from the viewpoints of ease of modification and versatility, maleic anhydride is most preferred. From the viewpoint of the heat resistance of the electrical storage device exterior material, the olefin component is preferably a polypropylene-based resin, and the adhesive layer 5 most preferably contains maleic anhydride-modified polypropylene.

[0116] The presence of a polyolefin skeleton in the resin constituting the adhesive layer 5 can be determined by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like, and the analysis method is not particularly limited. Furthermore, the presence of an acid-modified polyolefin in the resin constituting the adhesive layer 5 can be determined by, for example, measuring a maleic anhydride-modified polyolefin by infrared spectroscopy, and finding a peak at a wave number of 1760 cm -1 Near and wave number 1780cm -1 A peak derived from maleic anhydride is detected around this point. However, if the degree of acid modification is low, the peak may be small and not be detected. In this case, analysis can be performed using nuclear magnetic resonance spectroscopy.

[0117] Furthermore, from the viewpoint of ensuring durability such as heat resistance and resistance to contents of the packaging material for an electricity storage device, and of ensuring moldability while reducing the thickness, the adhesive layer 5 is more preferably a cured product of a resin composition containing an acid-modified polyolefin and a curing agent. Preferred examples of the acid-modified polyolefin include those mentioned above.

[0118] The adhesive layer 5 is preferably a cured product of a resin composition containing an acid-modified polyolefin and at least one selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and a compound having an epoxy group. It is particularly preferably a cured product of a resin composition containing an acid-modified polyolefin and at least one selected from the group consisting of a compound having an isocyanate group and a compound having an epoxy group. The adhesive layer 5 preferably contains at least one selected from the group consisting of polyurethane, polyester, and epoxy resin, and more preferably contains polyurethane and epoxy resin. Examples of polyesters include ester resins formed by the reaction of epoxy groups with maleic anhydride groups, and amide ester resins formed by the reaction of oxazoline groups with maleic anhydride groups. If unreacted components of a curing agent such as a compound having an isocyanate group, a compound having an oxazoline group, or an epoxy resin remain in the adhesive layer 5, the presence of the unreacted components can be confirmed by a method selected from the group consisting of infrared spectroscopy, Raman spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), and the like.

[0119] Furthermore, from the viewpoint of further enhancing the adhesion between the barrier layer 3 and the adhesive layer 5, the adhesive layer 5 is preferably a cured product of a resin composition containing a curing agent having at least one selected from the group consisting of an oxygen atom, a heterocycle, a C═N bond, and a COC bond. Examples of curing agents having a heterocycle include curing agents having an oxazoline group and curing agents having an epoxy group. Examples of curing agents having a C═N bond include curing agents having an oxazoline group and curing agents having an isocyanate group. Examples of curing agents having a COC bond include curing agents having an oxazoline group and curing agents having an epoxy group. Whether the adhesive layer 5 is a cured product of a resin composition containing such a curing agent can be confirmed by, for example, gas chromatography mass spectrometry (GCMS), infrared spectroscopy (IR), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), or other methods.

[0120] The compound having an isocyanate group is not particularly limited, but from the viewpoint of effectively improving the adhesion between the barrier layer 3 and the adhesive layer 5, a polyfunctional isocyanate compound is preferably used. The polyfunctional isocyanate compound is not particularly limited as long as it is a compound having two or more isocyanate groups. Specific examples of polyfunctional isocyanate curing agents include pentane diisocyanate (PDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymers or nurates thereof, mixtures of these, and copolymers with other polymers. Other examples include adducts, biurets, and isocyanurates.

[0121] The content of the compound having an isocyanate group in the adhesive layer 5 is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 0.5 to 40 mass %, of the resin composition constituting the adhesive layer 5. This can effectively improve the adhesion between the barrier layer 3 and the adhesive layer 5.

[0122] The compound having an oxazoline group is not particularly limited as long as it is a compound having an oxazoline skeleton. Specific examples of the compound having an oxazoline group include those having a polystyrene main chain and those having an acrylic main chain. Examples of commercially available products include the Epocross series manufactured by Nippon Shokubai Co., Ltd.

[0123] The proportion of the compound having an oxazoline group in the adhesive layer 5 is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 0.5 to 40 mass %, in the resin composition constituting the adhesive layer 5. This can effectively improve the adhesion between the barrier layer 3 and the adhesive layer 5.

[0124] An example of a compound having an epoxy group is an epoxy resin. The epoxy resin is not particularly limited as long as it is a resin capable of forming a crosslinked structure by the epoxy groups present in the molecule, and known epoxy resins can be used. The weight-average molecular weight of the epoxy resin is preferably about 50 to 2,000, more preferably about 100 to 1,000, and even more preferably about 200 to 800. In the first disclosure, the weight-average molecular weight of the epoxy resin is a value measured by gel permeation chromatography (GPC) under conditions using polystyrene as a standard sample.

[0125] Specific examples of epoxy resins include glycidyl ether derivatives of trimethylolpropane, bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, bisphenol F glycidyl ether, novolac glycidyl ether, glycerin polyglycidyl ether, polyglycerin polyglycidyl ether, etc. One type of epoxy resin may be used alone, or two or more types may be used in combination.

[0126] The proportion of the epoxy resin in the adhesive layer 5 is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 0.5 to 40 mass %, of the resin composition constituting the adhesive layer 5. This can effectively improve the adhesion between the barrier layer 3 and the adhesive layer 5.

[0127] The polyurethane is not particularly limited, and any known polyurethane can be used. The adhesive layer 5 may be, for example, a cured product of two-component curing polyurethane.

[0128] The proportion of polyurethane in adhesive layer 5 is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 0.5 to 40 mass %, of the resin composition constituting adhesive layer 5. This effectively improves the adhesion between barrier layer 3 and adhesive layer 5 in an atmosphere containing components that induce corrosion of the barrier layer, such as an electrolyte solution.

[0129] In addition, when the adhesive layer 5 is a cured product of a resin composition containing at least one selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and an epoxy resin, and the acid-modified polyolefin, the acid-modified polyolefin functions as the main agent, and the compound having an isocyanate group, the compound having an oxazoline group, and the compound having an epoxy group each function as a curing agent.

[0130] The adhesive layer 5 may contain a modifier having a carbodiimide group.

[0131] The thickness of the adhesive layer 5 is preferably about 50 μm or less, about 40 μm or less, about 30 μm or less, about 20 μm or less, or about 5 μm or less. The thickness of the adhesive layer 5 is preferably about 0.1 μm or more, or about 0.5 μm or more. The thickness of the adhesive layer 5 is preferably about 0.1 to 50 μm, about 0.1 to 40 μm, about 0.1 to 30 μm, about 0.1 to 20 μm, about 0.1 to 5 μm, about 0.5 to 50 μm, about 0.5 to 40 μm, about 0.5 to 30 μm, about 0.5 to 20 μm, or about 0.5 to 5 μm. More specifically, in the case of adhesives such as those exemplified for the adhesive layer 2 or a cured product of an acid-modified polyolefin and a curing agent, the thickness is preferably about 1 to 10 μm, and more preferably about 1 to 5 μm. Furthermore, when a resin exemplified for the heat-fusible resin layer 4 is used, the thickness is preferably about 2 to 50 μm, more preferably about 10 to 40 μm. When the adhesive layer 5 is an adhesive exemplified for the adhesive layer 2 or a cured product of a resin composition containing an acid-modified polyolefin and a curing agent, the adhesive layer 5 can be formed, for example, by applying the resin composition and curing it by heating or the like. When a resin exemplified for the heat-fusible resin layer 4 is used, the heat-fusible resin layer 4 and the adhesive layer 5 can be formed, for example, by extrusion molding.

[0132] [Surface coating layer 6] The packaging material for an electricity storage device according to the present disclosure may have a surface coating layer 6 on the substrate layer 1 (the side of the substrate layer 1 opposite to the barrier layer 3) as needed, for the purpose of improving at least one of design, electrolyte resistance, scratch resistance, formability, etc. The surface coating layer 6 is a layer located on the outermost layer side of the packaging material for an electricity storage device when an electricity storage device is assembled using the packaging material for an electricity storage device.

[0133] The surface coating layer 6 can be formed from a resin such as polyvinylidene chloride, polyester, polyurethane, acrylic resin, or epoxy resin.

[0134] When the resin forming the surface coating layer 6 is a curable resin, the resin may be either a one-component curable resin or a two-component curable resin, but is preferably a two-component curable resin. Examples of two-component curable resins include two-component curable polyurethane, two-component curable polyester, and two-component curable epoxy resin. Among these, two-component curable polyurethane is preferred.

[0135] Examples of two-component curing polyurethanes include polyurethanes containing a first component containing a polyol compound and a second component containing an isocyanate compound. Preferred examples of two-component curing polyurethanes include those containing a polyol, such as polyester polyol, polyether polyol, or acrylic polyol, as the first component and an aromatic or aliphatic polyisocyanate as the second component. Examples of polyurethanes include polyurethane compounds prepared by reacting a polyol compound with an isocyanate compound in advance, and polyurethanes containing an isocyanate compound. Examples of polyurethanes include polyurethane compounds prepared by reacting a polyol compound with an isocyanate compound in advance, and polyurethanes containing a polyol compound. Examples of polyurethanes include polyurethanes prepared by reacting a polyol compound with an isocyanate compound in advance and curing the polyurethane compound with moisture, such as in the air. Polyol compounds preferably include polyester polyols having hydroxyl groups on the side chains in addition to terminal hydroxyl groups in the repeating units. Examples of the second component include aliphatic, alicyclic, aromatic, and araliphatic isocyanate compounds. Examples of isocyanate compounds include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and naphthalene diisocyanate (NDI). Also included are polyfunctional isocyanate-modified compounds of one or more of these diisocyanates. Furthermore, polymers (e.g., trimers) can also be used as polyisocyanate compounds. Examples of such polymers include adducts, biurets, and nurates. It should be noted that an aliphatic isocyanate compound refers to an isocyanate that has an aliphatic group but does not have an aromatic ring, an alicyclic isocyanate compound refers to an isocyanate that has an alicyclic hydrocarbon group, and an aromatic isocyanate compound refers to an isocyanate that has an aromatic ring.The surface coating layer 6 is formed from polyurethane, and thus the exterior packaging material for an electricity storage device is endowed with excellent resistance to an electrolyte solution.

[0136] The surface coating layer 6 may contain additives such as the aforementioned lubricants, antiblocking agents, matting agents, flame retardants, antioxidants, tackifiers, and antistatic agents, at least on the surface and / or inside of the surface coating layer 6, as needed, depending on the functionality to be imparted to the surface of the surface coating layer 6. Examples of additives include fine particles with an average particle size of approximately 0.5 nm to 5 μm. The average particle size of the additive is the median size measured with a laser diffraction / scattering particle size distribution analyzer.

[0137] The additive may be either inorganic or organic. The shape of the additive is not particularly limited, and examples thereof include spherical, fibrous, plate-like, amorphous, and scaly shapes.

[0138] Specific examples of additives include talc, silica, graphite, kaolin, montmorillonite, mica, hydrotalcite, silica gel, zeolite, aluminum hydroxide, magnesium hydroxide, zinc oxide, magnesium oxide, aluminum oxide, neodymium oxide, antimony oxide, titanium oxide, cerium oxide, calcium sulfate, barium sulfate, calcium carbonate, calcium silicate, lithium carbonate, calcium benzoate, calcium oxalate, magnesium stearate, alumina, carbon black, carbon nanotubes, high-melting-point nylon, acrylate resin, crosslinked acrylic, crosslinked styrene, crosslinked polyethylene, benzoguanamine, gold, aluminum, copper, and nickel. The additives may be used alone or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferred from the viewpoints of dispersion stability, cost, and the like. The additives may also be subjected to various surface treatments, such as insulation treatment and high-dispersibility treatment.

[0139] The method for forming the surface coating layer 6 is not particularly limited, and examples thereof include a method of applying a resin to form the surface coating layer 6. When an additive is blended into the surface coating layer 6, a resin mixed with the additive may be applied.

[0140] The thickness of the surface coating layer 6 is not particularly limited as long as the surface coating layer 6 exhibits the above-mentioned functions, and may be, for example, about 0.5 to 10 μm, and preferably about 1 to 5 μm.

[0141] 3. Manufacturing method for exterior materials for power storage devices The method for producing the electrical storage device packaging material is not particularly limited as long as it can produce a laminate in which the layers of the electrical storage device packaging material of the present disclosure are laminated, and examples include a method including a step of laminating at least a base material layer 1, a barrier layer 3, and a heat-sealable resin layer 4 in this order. That is, the method for producing the electrical storage device packaging material 10 of the present disclosure is composed of a laminate including at least a base material layer, a barrier layer, and a heat-sealable resin layer in this order, and the base material layer includes a polyester film, and the polyester film has a work-hardening index in both the longitudinal direction and the width direction of 1.6 or more and 3.0 or less and a difference between the work-hardening indexes in the longitudinal direction and the width direction of 0.5 or less, an intrinsic viscosity of 0.66 or more and 0.95 or less, and a rigid amorphous amount of 28% or more and 60% or less.

[0142] An example of a method for manufacturing an exterior material for an electricity storage device according to the present disclosure is as follows: First, a laminate (hereinafter, sometimes referred to as "laminate A") is formed in which a base layer 1, an adhesive layer 2, and a barrier layer 3 are laminated in this order. Specifically, laminate A can be formed by a dry lamination method in which an adhesive used to form adhesive layer 2 is applied to base layer 1 or to barrier layer 3, the surface of which has been chemically treated as necessary, by a coating method such as gravure coating or roll coating, and then dried, followed by laminating the barrier layer 3 or base layer 1 and curing the adhesive layer 2.

[0143] Next, a heat-sealable resin layer 4 is laminated on the barrier layer 3 of the laminate A. When the heat-sealable resin layer 4 is laminated directly on the barrier layer 3, the heat-sealable resin layer 4 may be laminated on the barrier layer 3 of the laminate A by a method such as thermal lamination or extrusion lamination. When an adhesive layer 5 is provided between the barrier layer 3 and the heat-sealable resin layer 4, for example, (1) a method of laminating the adhesive layer 5 and the heat-sealable resin layer 4 by extruding them onto the barrier layer 3 of the laminate A (co-extrusion lamination, tandem lamination), (2) a method of separately forming a laminate in which the adhesive layer 5 and the heat-sealable resin layer 4 are laminated, and laminating this on the barrier layer 3 of the laminate A by a thermal lamination, or a method of forming a laminate in which the adhesive layer 5 is laminated on the barrier layer 3 of the laminate A, and laminating this on the heat-sealable resin layer 4 by a thermal lamination. (3) a method (sandwich lamination method) in which a molten adhesive layer 5 is poured between the barrier layer 3 of the laminate A and a heat-sealable resin layer 4 previously formed into a sheet, and the laminate A and the heat-sealable resin layer 4 are bonded together via the adhesive layer 5; (4) a method in which an adhesive for forming the adhesive layer 5 is solution-coated on the barrier layer 3 of the laminate A, followed by drying or baking, and then the heat-sealable resin layer 4 previously formed into a sheet is laminated on the adhesive layer 5.

[0144] When the surface coating layer 6 is provided, the surface coating layer 6 is laminated on the surface of the base material layer 1 opposite to the barrier layer 3. The surface coating layer 6 can be formed, for example, by applying the above-mentioned resin for forming the surface coating layer 6 to the surface of the base material layer 1. The order of the step of laminating the barrier layer 3 on the surface of the base material layer 1 and the step of laminating the surface coating layer 6 on the surface of the base material layer 1 is not particularly limited. For example, after the surface coating layer 6 is formed on the surface of the base material layer 1, the barrier layer 3 may be formed on the surface of the base material layer 1 opposite to the surface coating layer 6.

[0145] As described above, a laminate is formed which includes the optional surface coating layer 6 / substrate layer 1 / optional adhesive layer 2 / barrier layer 3 / optional adhesive layer 5 / thermally adhesive resin layer 4 in this order, and in order to strengthen the adhesion of the optional adhesive layer 2 and adhesive layer 5, the laminate may be further subjected to a heat treatment.

[0146] In the packaging material for an electricity storage device, each layer constituting the laminate may be subjected to a surface activation treatment such as corona treatment, blast treatment, oxidation treatment, ozone treatment, etc., as needed to improve processability. For example, by subjecting the surface of the base layer 1 opposite to the barrier layer 3 to corona treatment, the printability of ink on the surface of the base layer 1 can be improved.

[0147] 4. Applications of exterior materials for energy storage devices The exterior packaging material for an electricity storage device according to the present disclosure is used in a package for hermetically housing an electricity storage device element such as a positive electrode, a negative electrode, an electrolyte, etc. That is, an electricity storage device can be formed by housing an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte in a package formed from the exterior packaging material for an electricity storage device according to the present disclosure.

[0148] Specifically, an electricity storage device using the electricity storage device packaging material is provided by covering an electricity storage device element having at least a positive electrode, a negative electrode, and an electrolyte with the electricity storage device packaging material of the present disclosure in a state in which metal terminals connected to each of the positive electrode and the negative electrode protrude outward, so that a flange portion (a region where the heat-sealable resin layers contact each other) can be formed around the periphery of the electricity storage device element, and heat-sealing the heat-sealable resin layers of the flange portion to form a hermetic seal. Note that when an electricity storage device element is housed in a package formed from the electricity storage device packaging material of the present disclosure, the package is formed so that the heat-sealable resin portion of the electricity storage device packaging material of the present disclosure faces inside (the surface in contact with the electricity storage device element). A package may be formed by overlapping two electrical storage device exterior packaging materials with the heat-sealable resin layers facing each other and heat-sealing the peripheral portions of the overlapped electrical storage device exterior packaging materials. Alternatively, as shown in the example of FIG. 5, one electrical storage device exterior packaging material may be folded back and overlapped, and the peripheral portions may be heat-sealed to form a package. When folding back and overlapping, as shown in the example of FIG. 5, the sides other than the folded side may be heat-sealed to form a package with a three-sided seal, or the material may be folded back to form a flange and sealed on all four sides. Furthermore, a recess for accommodating an electrical storage device element may be formed in the electrical storage device exterior packaging material by deep drawing or bulging molding. As shown in the example of FIG. 5, one electrical storage device exterior packaging material may have a recess and the other electrical storage device exterior material may not have a recess, or the other electrical storage device exterior material may also have a recess.

[0149] The exterior material for an electricity storage device according to the present disclosure can be suitably used in electricity storage devices such as batteries (including condensers, capacitors, etc.). The exterior material for an electricity storage device according to the present disclosure may be used in either primary or secondary batteries, but is preferably used in secondary batteries. The type of secondary battery to which the exterior material for an electricity storage device according to the present disclosure is applied is not particularly limited, and examples include lithium ion batteries, lithium ion polymer batteries, all-solid-state batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, condensers, and capacitors. Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries are suitable applications for the exterior material for an electricity storage device according to the present disclosure. [Example]

[0150] The present disclosure will be described in detail below with reference to examples and comparative examples, but the present disclosure is not limited to the examples.

[0151] [Examples 1-13 and Comparative Examples 1-2] <Production and Evaluation of Polyester Film> Polyester films were produced and evaluated by the following methods.

[0152] (1) Polyester composition The polyester resin and film were dissolved in hexafluoroisopropanol (HFIP), 1 H-NMR and 13 The contents of each monomer residue and by-product diethylene glycol were quantified using C-NMR.

[0153] (2) Film thickness and layer thickness The thickness of the entire film was measured by cutting the film into 200 mm × 300 mm pieces using a dial gauge, measuring the thickness at five random locations on each sample, and averaging the results. The thickness of each layer of the film and packaging material was determined by embedding the sample in epoxy resin, cutting out the film cross section with a microtome, and observing the cross section at 5000x magnification with a transmission electron microscope (TEMH7100, manufactured by Hitachi, Ltd.).

[0154] (3) Longitudinal and transverse directions of polyester film In the present disclosure, the breaking strength of a film is measured in any one direction (0°) of the film and in directions at 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and 165° from that direction. The direction with the highest breaking strength is defined as the width direction, and the direction perpendicular to the width direction is defined as the longitudinal direction. The breaking strength can be obtained by the method described in "(6) Breaking Elongation." In "(6) Breaking Elongation," rectangular samples with long sides of 150 mm and short sides of 10 mm are cut out and measured. The long sides are cut out to match the 12 directions, i.e., any one direction (0°) of the film and 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and 165° from that direction.

[0155] (4) Intrinsic viscosity The solution viscosity of the polyester film was measured in orthochlorophenol at 25°C using an Ostwald viscometer, and the intrinsic viscosity was calculated from the solution viscosity. The unit of intrinsic viscosity is [dL / g]. The number n was set to 3, and the average value was used.

[0156] (5) Planar orientation coefficient fn of polyester film Using an Abbe refractometer, the layer whose plane orientation coefficient was to be measured (hereinafter referred to as the measurement layer) was adhered to the glass surface, and then the refractive indexes (Nx, Ny, Nz) in the a direction, b direction, and thickness direction were measured using sodium D line as a light source, and the plane orientation coefficient fn of the measurement layer was calculated using the following formula. Plane orientation coefficient fn=(Nx+Ny) / 2-Nz

[0157] (6) Breaking elongation The film was cut into rectangular samples measuring 150 mm in length and 10 mm in width in the longitudinal and transverse directions. Tensile tests were performed in the longitudinal and transverse directions of the film under conditions of 25°C and 63% RH using a tensile tester (Orientec Co., Ltd., automatic film strength and elongation measuring device "Tensilon AMF / RTA-100") at a crosshead speed of 300 mm / min, a width of 10 mm, and a sample length of 50 mm. The elongation at break was measured and used as the breaking elongation. The measurement was performed five times, and the average was used.

[0158] (7) Crystallinity In accordance with JIS K7122 (1999), a differential scanning calorimeter robot DSC-RDC220 manufactured by Seiko Electronics Co., Ltd. was used, and a "Disc Session" SSC / 5200 was used for data analysis. Five mg of film sample was placed on an aluminum tray and heated from room temperature to 300°C at a rate of 20°C / min, and held at 300°C for five minutes. The endothermic peak heat ΔHm, cold crystallization heat ΔHc, and heat of fusion of perfectly crystalline PET ΔHm0 (140.1 J / g) were used to calculate the heat of melting using the following formula: Crystallinity (%)=(ΔHm-ΔHc) / ΔHm0x100

[0159] (8) Rigid amorphous amount The rigid amorphous amount was calculated from the mobile amorphous amount and the degree of crystallinity obtained by the measurement using the following calculation formula. Rigid amorphous amount (%) = 100-(movable amorphous amount + crystallinity). The theoretical specific heat difference of completely amorphous polyethylene terephthalate = 0.4052 J / (g°C) In addition, in this disclosure, the theoretical value of the specific heat difference of a completely amorphous polyethylene terephthalate is referred to. The mobile amorphous amount was measured as follows: Using a temperature-modulated DSC manufactured by TA Instruments, 5 mg of sample was measured in a nitrogen atmosphere from 0°C to 150°C at a heating rate of 2°C / min, with a temperature modulation amplitude of ±1°C and a temperature modulation period of 60 seconds. The specific heat difference at the glass transition temperature obtained by the measurement was determined, and the amount was calculated using the following formula. Mobile amorphous amount (%) = (specific heat difference) / (theoretical specific heat difference of completely amorphous polyester) x 100 The theoretical specific heat difference of completely amorphous polyethylene terephthalate = 0.4052 J / (g°C) In addition, in the present disclosure, for those containing 70 mol % or more polyethylene terephthalate units, the theoretical value of the specific heat difference of a completely amorphous material of polyethylene terephthalate is referenced.

[0160] (9) Glass transition temperature Tg, melting point (melting endothermic peak temperature Tm) In accordance with JIS K7122 (1999), a differential scanning calorimeter (Seiko Instruments EXSTARDSC6220) was used to heat 3 mg of resin in a nitrogen atmosphere from 30°C to 300°C at a rate of 20°C / min. After holding at 300°C for 5 minutes, the temperature was lowered to 30°C at a rate of 40°C / min. After holding at 30°C for another 5 minutes, the temperature was raised from 30°C to 300°C at a rate of 20°C / min. The glass transition temperature obtained during this temperature increase was calculated using the following formula (i). Glass transition temperature = (extrapolated glass transition onset temperature + extrapolated glass transition finish temperature) / 2 (i) Here, the extrapolated glass transition onset temperature is the temperature at the intersection of a line drawn by extending the low-temperature baseline toward the high-temperature side and a tangent drawn at the point where the gradient of the step-change portion of the glass transition curve is maximum. The extrapolated glass transition end temperature is the temperature at the intersection of a line drawn by extending the high-temperature baseline toward the low-temperature side and a tangent drawn at the point where the gradient of the step-change portion of the glass transition curve is maximum. The peak top of the endothermic peak associated with the crystalline melting of the resin is defined as the melting point (melting endothermic peak temperature Tm).

[0161] (10) Work hardening index The film was cut into rectangular samples measuring 150 mm in length and 10 mm in width in the longitudinal and transverse directions. Tensile tests were performed in the longitudinal and transverse directions of the film under the conditions of 25°C and 63% RH using a tensile tester (Orientec Co., Ltd., automatic film strength and elongation measuring device "Tensilon AMF / RTA-100") at a crosshead speed of 300 mm / min, a width of 10 mm, and a sample length (gauge length) of 50 mm.0 (mm), length at 5% elongation is L 1 (mm), the nominal stress at 5% elongation is P 1 (MPa), and the length at 60% elongation is L 2 (mm), the nominal stress at 60% elongation is P 2 When the strain is expressed as (MPa), the true strain at 5% elongation is calculated from equation (1), the true strain at 60% elongation from equation (2), the true stress at 5% elongation from equation (3), and the true stress at 60% elongation from equation (4). The slope of the equation formed by taking the X axis as true strain and the Y axis as true stress from the values ​​obtained from (1) to (4) was taken as the work hardening index. Five measurements were taken in the longitudinal and transverse directions, and the average values ​​were used. True strain at 5% elongation = L n (L 1 / L 0 )···(1) True strain at 60% elongation = L n (L 2 / L 1 )···(2) True stress at 5% elongation = L n (P 1 (1+L n (L 1 / L 0 )))···(3) True stress at 60% elongation = L n (P 2 (1+L n (L 2 / L 1 )))···(4) ※L n :Natural logarithm

[0162] (11) Heat shrinkage rate of polyester film in the longitudinal and transverse directions at 150°C The film was cut into rectangular samples measuring 150 mm long and 10 mm wide in both the longitudinal and transverse directions. Marked lines were drawn on the samples at 100 mm intervals, and the samples were heat-treated by hanging a 3 g weight and placing them in a hot air oven heated to 150°C for 30 minutes. The distance between the marks after heat treatment was measured, and the heat shrinkage rate was calculated from the change in the distance between the marks before and after heating. Five samples were measured in both the longitudinal and transverse directions, and the average value was used for evaluation.

[0163] (12) Dynamic friction coefficient of polyester film Using a slip tester manufactured by Toyo Seiki Co., Ltd., the two surfaces of the film were rubbed together in accordance with JIS-K7125 (1999), and the stable region of the resistance value after the initial rise was measured, and this was taken as the coefficient of dynamic friction μd. The sample was a rectangle with a width of 80 mm and a length of 200 mm, and three sets (six pieces) were cut from the roll along the longitudinal direction of the rectangle. Three measurements were performed, and the average value was calculated.

[0164] (13) Wrinkles during extrusion lamination A 60,000 mm 2 piece was cut out from each of the exterior materials obtained by the method described in <Production of exterior materials for electricity storage devices> below. 2 The appearance of the range was visually inspected and judged as follows: ○: No wrinkles were observed on the entire film. △: Wrinkles less than 5 mm were observed. ×: Wrinkles of 5 mm or more were observed.

[0165] (Production of polyester film) The resins constituting the polyester films used for film formation were prepared by mixing the main raw materials, auxiliary raw materials, and particle masters in the types and proportions shown in Table 1 for each Example and Comparative Example. The main raw materials, auxiliary raw materials, and particle masters used in each Example and Comparative Example were prepared as follows: Polyester A Polyethylene terephthalate resin (intrinsic viscosity 0.72) containing 100 mol % terephthalic acid as the dicarboxylic acid component and 100 mol % ethylene glycol as the glycol component. Polyester B Polyethylene terephthalate resin (intrinsic viscosity 0.82) containing 100 mol % terephthalic acid as the dicarboxylic acid component and 100 mol % ethylene glycol as the glycol component. Polyester C Polyethylene terephthalate resin (intrinsic viscosity 0.92) containing 100 mol % terephthalic acid as the dicarboxylic acid component and 100 mol % ethylene glycol as the glycol component. Polyester D Polybutylene terephthalate resin (intrinsic viscosity 1.2) containing 100 mol % terephthalic acid as the dicarboxylic acid component and 100 mol % 1-4 butanediol as the glycol component. Polyester E Polyethylene terephthalate resin (intrinsic viscosity 0.65) containing 100 mol % terephthalic acid as the dicarboxylic acid component and 100 mol % ethylene glycol as the glycol component. Particle Master A Polyethylene terephthalate particle master containing aggregated silica particles with an average particle size of 1.2 μm at a particle concentration of 2% by mass in polyester A.

[0166] (Coating A) Acrylic resin consisting of a copolymer composition of methyl methacrylate / ethyl acrylate / acrylic acid / N-methylolacrylamide = 63 / 35 / 1 / 1% by mass: 3.00% by mass Melamine crosslinker: 0.75% by weight Colloidal silica particles (average particle size: 80 nm): 0.15% by mass Hexanol: 0.26% by mass Butyl cellosolve: 0.18% by mass ·Water: 95.66% by mass

[0167] Using an extruder, the polyester species and particle master listed in Table 1 were each dried in a vacuum dryer at 180°C for 4 hours to thoroughly remove moisture. The main and auxiliary materials and particle master listed in Table 1 were then loaded into the extruder and melted at 280°C. The resin melt extruded from the extruder and discharged from the die was cooled and solidified on a cast drum cooled to 25°C to obtain an unstretched sheet. The distance between the lip of the T-die and the cooling drum was set to 35 mm, and a 0.1 mm diameter wire electrode was used to apply an electrostatic voltage of 14 kV to the sheet, causing it to adhere to the cooling drum. The unstretched sheet passed through the cooling drum at a speed of 25 m / min, and the contact length of the unstretched sheet with the cooling drum was 2.5 m.

[0168] Next, the unstretched sheet was preheated with a group of rolls heated to the temperature listed in Table 2, and then stretched in the longitudinal direction (machine direction) using heated rolls controlled to the temperature listed in Table 2 to the respective stretching ratios listed in Table 2. Then, the sheet was cooled with a group of rolls at a temperature of 25°C to obtain a uniaxially stretched film. This uniaxially stretched film was subjected to a corona discharge treatment in air, and coating agent A was mixed and ultrasonically dispersed to form an anchor coat layer on the treated surface, and the surface bonded to the cast was uniformly coated with a #4 metaling bar for surface treatment. Next, while holding both ends of the uniaxially stretched film with clips, it was introduced into a preheating zone in a tenter controlled to the temperature listed in Table 2, and subsequently stretched continuously in a heating zone maintained at the temperature listed in Table 2 in the direction perpendicular to the longitudinal direction (width direction) to the respective stretching ratios listed in Table 2. Subsequently, the film was subjected to a heat treatment for 20 seconds in the heat treatment zone of the tenter at the heat treatment temperature listed in Table 2, and then to a relaxation treatment at the relaxation temperature and the relaxation ratio listed in Table 2. The film was then uniformly and slowly cooled to obtain a polyester film having the thickness shown in Table 1. The properties of the polyester film are shown in Table 3.

[0169] <Manufacturing of exterior materials for energy storage devices> In Examples 1-12 and Comparative Examples 1-2, the polyester film obtained by the above method was used as the substrate layer, and packaging materials for electricity storage devices were produced according to the following procedure. Each polyester film (PET, thickness 25 μm) was prepared as the substrate layer, and aluminum foil (JIS H4160:1994 A8021H-O, thickness 40 μm) was prepared as the barrier layer, with corrosion-resistant coatings formed on both sides. Next, the substrate layer and barrier layer were laminated by dry lamination using a two-component curing urethane adhesive (polyol compound and aromatic isocyanate compound), and aging treatment was performed to produce a laminate of substrate layer (thickness 25 μm) / adhesive layer (thickness 3 μm after curing) / barrier layer (thickness 40 μm). In Example 13, a laminate film (PET / ONy) was used as a substrate layer, consisting of a resin film (polyethylene terephthalate film, 12 μm thick) obtained by the above method and a stretched nylon film (15 μm thick) laminated with a two-component curing urethane adhesive (polyol compound and aromatic isocyanate compound, 3 μm thick after curing). An exterior packaging material for an electricity storage device was manufactured using the following procedure. The laminate film (PET / ONy) was used as the substrate layer, and aluminum foil (JIS H4160:1994 A8021H-O, 40 μm thick) was used as a barrier layer with corrosion-resistant coatings formed on both sides. Next, the ONy side of the substrate layer and the barrier layer were laminated by dry lamination using the two-component curing urethane adhesive (polyol compound and aromatic isocyanate compound), and an aging treatment was performed to produce a laminate consisting of substrate layer (30 μm thick), adhesive layer (3 μm thick after curing), and barrier layer (40 μm thick).

[0170] Next, maleic anhydride-modified polypropylene (PPa, thickness 40 μm) as an adhesive layer and polypropylene (PP, thickness 40 μm) as a heat-sealable resin layer were co-extruded onto the barrier layer of the obtained laminate, thereby laminating an adhesive layer / heat-sealable resin layer on the barrier layer. Next, the obtained laminate was aged and heated to obtain an exterior packaging material for an electricity storage device in which polyester film / adhesive layer / barrier layer / adhesive layer / heat-sealable resin layer were laminated in this order.

[0171] The outer surface of the base material layer of each of the electrical storage device packaging materials was coated with erucic acid amide as a lubricant.

[0172] <Evaluation of formability> The exterior material for an electricity storage device was cut into a rectangle with a length (MD (Machine Direction)) of 90 mm and a width (TD (Transverse Direction)) of 150 mm to prepare a test sample. These samples were cold-formed (single-stage drawing) into a rectangular mold (female mold, surface roughness in maximum height (nominal Rz value) of 3.2 μm as specified in Table 2 of JIS B 0659-1:2002, Appendix 1 (Reference), surface roughness standard for comparison, with a corner radius of 2.0 mm and a ridge radius of 1.0 mm) with a press pressure (surface pressure) of 0.25 MPa, with the forming depth varied in 0.5 mm increments from 0.5 mm, for ten samples each. The test sample was placed on a female mold so that the heat-sealable resin layer was positioned on the male mold side. The clearance between the male and female molds was 0.3 mm. Molding was performed in a 25°C environment. After cold molding, the samples were irradiated with a penlight in a dark room to check for pinholes or cracks in the aluminum alloy foil by light transmission. The deepest molding depth at which no pinholes or cracks occurred in the aluminum alloy foil among the 10 samples was designated A mm, and the shallowest molding depth at which pinholes or other defects occurred in the aluminum alloy foil was designated B. The value calculated using the following formula was rounded to two decimal places to determine the limit molding depth of the exterior material for an energy storage device. The depth criteria for each were evaluated using the following four-point scale. The results are shown in Table 3. Limit forming depth = A mm + (0.5 mm / 10 pieces) x (10 pieces - B pieces)

[0173] (Formability evaluation criteria) S: Limit forming depth is 6.5 mm or more A: The limit forming depth is 6.0 mm or more and less than 6.5 mm B: Limit forming depth is 5.0 mm or more and less than 6.0 mm C: Limit forming depth is 4.5 mm or more and less than 5.0 mm D: Limit forming depth is less than 4.5 mm

[0174] [Table 1]

[0175] [Table 2]

[0176] [Table 3]

[0177] As described above, the present disclosure provides the following aspects of the invention. Item 1. The laminate is composed of at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, the substrate layer includes a polyester film, The polyester film is an exterior material for an electricity storage device, having a work-hardening index in both the longitudinal and transverse directions of 1.6 to 3.0, a difference between the work-hardening indexes in the longitudinal and transverse directions of 0.5 or less, an intrinsic viscosity of 0.66 to 0.95, and a rigid amorphous content of 28% to 60%. Item 2. The packaging material for an electricity storage device according to Item 1, wherein the polyester film has a thickness of 5 μm or more and 40 μm or less. Item 3. The packaging material for an electricity storage device according to Item 1 or 2, wherein the polyester film has a melting point of 235°C or higher. Item 4. The packaging material for an electricity storage device according to any one of Items 1 to 3, wherein the polyester film has a crystallinity of 15% or more and 40% or less. Item 5. The packaging material for an electricity storage device according to any one of Items 1 to 4, wherein the polyester film has a breaking elongation of 100% or more in at least one of the longitudinal direction and the width direction. Item 6. An electricity storage device, in which an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed from the exterior packaging material for an electricity storage device according to any one of Items 1 to 5. Item 7. The method includes a step of laminating at least a base layer, a barrier layer, and a heat-sealable resin layer in this order to obtain a laminate, the substrate layer includes a polyester film, The polyester film has a work hardening index in both the longitudinal and width directions of 1.6 to 3.0, a difference between the work hardening indexes in the longitudinal and width directions of 0.5 or less, an intrinsic viscosity of 0.66 to 0.95, and a rigid amorphous content of 28% to 60%. [Explanation of symbols]

[0178] 1 Base material layer 2 Adhesive layer 3 Barrier layer 4 Heat-fusible resin layer 5 Adhesive layer 6 Surface coating layer 10. Exterior materials for energy storage devices

Claims

1. The laminate is composed of at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, The thickness of the laminate is 190 μm or less (excluding 155 μm or less), or 155 μm or less, the substrate layer includes a polyester film, the polyester film has a work-hardening index in both the longitudinal direction and the width direction of 1.6 or more and 3.0 or less, and a difference between the work-hardening indexes in the longitudinal direction and the width direction of 0.5 or less (wherein the longitudinal direction and the width direction of the polyester film are determined by measuring the breaking strength in any one direction of the film (0°) and in directions at 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and 165° from that direction, and the direction with the highest breaking strength is defined as the width direction, and the direction perpendicular to the width direction is defined as the longitudinal direction), an intrinsic viscosity of 0.66 or more and 0.95 or less, and a rigid amorphous amount of 28% or more and 60% or less.

2. The laminate is composed of at least a substrate layer, a barrier layer, and a heat-sealable resin layer in this order, The thickness of the base layer is 60 μm or less (excluding 40 μm or less), or 40 μm or less, the substrate layer includes a polyester film, the polyester film has a work-hardening index in both the longitudinal direction and the width direction of 1.6 or more and 3.0 or less, and a difference between the work-hardening indexes in the longitudinal direction and the width direction of 0.5 or less (wherein the longitudinal direction and the width direction of the polyester film are determined by measuring the breaking strength in any one direction of the film (0°) and in directions at 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and 165° from that direction, and the direction with the highest breaking strength is defined as the width direction, and the direction perpendicular to the width direction is defined as the longitudinal direction), an intrinsic viscosity of 0.66 or more and 0.95 or less, and a rigid amorphous amount of 28% or more and 60% or less.

3. The laminate is composed of at least a substrate layer, a barrier layer, and a heat-sealable resin layer in this order, the substrate layer includes a polyester film, the base layer further includes another layer different from the polyester film, the resin forming the other layer includes polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, phenolic resin, or modified products of these resins; the polyester film has a work-hardening index in both the longitudinal direction and the width direction of 1.6 or more and 3.0 or less, and a difference between the work-hardening indexes in the longitudinal direction and the width direction of 0.5 or less (wherein the longitudinal direction and the width direction of the polyester film are determined by measuring the breaking strength in any one direction of the film (0°) and in directions at 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and 165° from that direction, and the direction with the highest breaking strength is defined as the width direction, and the direction perpendicular to the width direction is defined as the longitudinal direction), an intrinsic viscosity of 0.66 or more and 0.95 or less, and a rigid amorphous amount of 28% or more and 60% or less.

4. The laminate is composed of at least a substrate layer, a barrier layer, and a heat-sealable resin layer in this order, the thickness of the barrier layer is 200 μm or less (excluding 85 μm or less), or 85 μm or less; the substrate layer includes a polyester film, the polyester film has a work-hardening index in both the longitudinal direction and the width direction of 1.6 or more and 3.0 or less, and a difference between the work-hardening indexes in the longitudinal direction and the width direction of 0.5 or less (wherein the longitudinal direction and the width direction of the polyester film are determined by measuring the breaking strength in any one direction of the film (0°) and in directions at 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and 165° from that direction, and the direction with the highest breaking strength is defined as the width direction, and the direction perpendicular to the width direction is defined as the longitudinal direction), an intrinsic viscosity of 0.66 or more and 0.95 or less, and a rigid amorphous amount of 28% or more and 60% or less.

5. The laminate is composed of at least a substrate layer, a barrier layer, and a heat-sealable resin layer in this order, the barrier layer is made of stainless steel foil, the thickness of the barrier layer is 60 μm or less (excluding 40 μm or less), or 40 μm or less; the substrate layer includes a polyester film, the polyester film has a work-hardening index in both the longitudinal direction and the width direction of 1.6 or more and 3.0 or less, and a difference between the work-hardening indexes in the longitudinal direction and the width direction of 0.5 or less (wherein the longitudinal direction and the width direction of the polyester film are determined by measuring the breaking strength in any one direction of the film (0°) and in directions at 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and 165° from that direction, and the direction with the highest breaking strength is defined as the width direction, and the direction perpendicular to the width direction is defined as the longitudinal direction), an intrinsic viscosity of 0.66 or more and 0.95 or less, and a rigid amorphous amount of 28% or more and 60% or less.

6. A laminate comprising at least a substrate layer, an adhesive layer, a barrier layer, and a heat-sealable resin layer in this order, the adhesive layer includes a colorant; the substrate layer includes a polyester film, the polyester film has a work-hardening index in both the longitudinal direction and the width direction of 1.6 or more and 3.0 or less, and a difference between the work-hardening indexes in the longitudinal direction and the width direction of 0.5 or less (wherein the longitudinal direction and the width direction of the polyester film are determined by measuring the breaking strength in any one direction of the film (0°) and in directions at 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and 165° from that direction, and the direction with the highest breaking strength is defined as the width direction, and the direction perpendicular to the width direction is defined as the longitudinal direction), an intrinsic viscosity of 0.66 or more and 0.95 or less, and a rigid amorphous amount of 28% or more and 60% or less.

7. An exterior material for an electricity storage device described in any one of claims 1 to 6, wherein the thickness of the polyester film is 5 μm or more and 40 μm or less.

8. An exterior material for an electricity storage device described in any one of claims 1 to 7, wherein the melting point of the polyester film is 235°C or higher.

9. An exterior material for a storage battery device described in any one of claims 1 to 8, wherein the crystallinity of the polyester film is 15% or more and 40% or less.

10. An exterior material for a storage battery device described in any one of claims 1 to 9, wherein the breaking elongation in at least one of the longitudinal and transverse directions of the polyester film is 100% or more.

11. An electricity storage device, in which an electricity storage device element having at least a positive electrode, a negative electrode, and an electrolyte is housed in a packaging body formed from an exterior material for an electricity storage device described in any one of claims 1 to 10.

12. The method includes a step of laminating at least a substrate layer, a barrier layer, and a heat-sealable resin layer in this order to obtain a laminate, The thickness of the laminate is 190 μm or less (excluding 155 μm or less), or 155 μm or less, the substrate layer includes a polyester film, the polyester film has a work-hardening index in both the longitudinal direction and the width direction of 1.6 or more and 3.0 or less, and a difference between the work-hardening indexes in the longitudinal direction and the width direction of 0.5 or less (wherein the longitudinal direction and the width direction of the polyester film are determined by measuring the breaking strength in any one direction of the film (0°) and in directions at 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and 165° from that direction, and the direction with the highest breaking strength is defined as the width direction, and the direction perpendicular to the width direction is defined as the longitudinal direction), an intrinsic viscosity of 0.66 or more and 0.95 or less, and a rigid amorphous amount of 28% or more and 60% or less.

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