Resin film for terminals and method for selecting the same, and energy storage device

Abstract

To provide a resin film for a terminal which can achieve both seal strength under high temperature and initial seal strength at a sufficiently high level.SOLUTION: A resin film for a terminal is arranged so as to cover an outer peripheral surface of a part of a terminal electrically connected to a power storage device body in a power storage device including the power storage device body, and the terminal, and has a single layer structure or a multilayer structure, and includes a resin layer which has at least one sub-dispersion peak γ within a range of -130°C to -74°C of a profile of a loss tangent tanδ obtained by dynamic viscoelasticity measurement under a condition of 1.0 Hz, and contains a polyester-based resin or an amide-modified polyolefin-based resin.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a resin film for a terminal that is disposed so as to cover a part of the outer peripheral surface of a terminal in a power storage device including a power storage device main body and a terminal electrically connected to the power storage device main body, and a method for selecting the same. The present disclosure also relates to a power storage device using the resin film for a terminal.

Background Art

[0002] As power storage devices, for example, secondary batteries such as lithium ion batteries, nickel hydrogen batteries, and lead storage batteries, and electrochemical capacitors such as electric double layer capacitors are known. Further miniaturization of the power storage device is required due to miniaturization of portable devices or restrictions on installation space, and lithium ion batteries with high energy density have attracted attention. Conventionally, a metal can has been used as an exterior material for lithium ion batteries, but a multilayer film that is lightweight, has high heat dissipation, and can be manufactured at low cost is now being used.

[0003] A lithium ion battery using the multilayer film as an exterior material is called a laminated lithium ion battery. The exterior material covers the battery contents (positive electrode, separator, negative electrode, electrolyte, etc.) and prevents intrusion of moisture into the interior. A laminated lithium ion battery is manufactured, for example, by forming a recess by cold molding in a part of the exterior material, accommodating the battery contents in the recess, and folding back the remaining part of the exterior material and sealing the edge part by heat sealing (see, for example, Patent Document 1).

[0004] A laminated lithium ion battery includes a current extraction terminal (sometimes called a "tab lead"). For the purpose of improving the adhesion between the current extraction terminal and the exterior material, a resin film for a terminal (sometimes called a "tab sealant") may be disposed so as to cover a part of the outer periphery of the current extraction terminal (see, for example, Patent Documents 2 to 4).

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-101765 [Patent Document 2] Japanese Patent Publication No. 2008-4316 [Patent Document 3] Japanese Patent Publication No. 2010-218766 [Patent Document 4] Japanese Patent Publication No. 2009-259739 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, research and development is underway on a next-generation battery called a solid-state battery, which is considered the successor to lithium-ion batteries. Solid-state batteries are characterized by using a solid electrolyte instead of an organic electrolyte. While lithium-ion batteries cannot be used at temperatures higher than the boiling point of the electrolyte (around 80°C), solid-state batteries can be used at temperatures exceeding 100°C, and their lithium-ion conductivity can be increased by operating them at high temperatures (for example, 100-150°C).

[0007] However, when using the above-mentioned laminate as the outer material to manufacture a laminate-type all-solid-state battery, there is a risk that the sealing of the all-solid-state battery package may be insufficient due to the insufficient heat resistance of the terminal resin film.

[0008] This disclosure provides a resin film for terminals that can achieve sufficiently high levels of both sealing strength at high temperatures and initial sealing strength, and a method for selecting the same. Furthermore, this disclosure provides an energy storage device using the above-mentioned resin film for terminals. [Means for solving the problem]

[0009] A terminal resin film relating to one aspect of this disclosure is disposed to cover a portion of the outer surface of a terminal in an energy storage device comprising an energy storage device body and terminals electrically connected to the energy storage device body. This terminal resin film has a single-layer or multi-layer structure and comprises a resin layer having at least one subdispersion peak γ in the range of -130°C to -50°C in the profile of the loss tangent tanδ obtained by dynamic viscoelasticity measurement under conditions of 1.0 Hz.

[0010] The subdispersion peak γ is an indicator of the molecular motion of the resin material constituting the resin layer, and specifically, it is a parameter that reflects the local torsional motion of the main chain and the thermal motion of the entire side chain in the crystalline and amorphous parts of the resin material. According to the inventors' studies, a resin layer that satisfies the above requirements regarding the subdispersion peak γ contains a resin material that starts molecular motion at a relatively high temperature and is capable of exhibiting excellent sealing strength at high temperatures. Furthermore, a lower temperature at which the subdispersion peak γ appears indicates a more flexible resin layer, while a higher temperature indicates a more heat-resistant resin layer.

[0011] The resin layer described above preferably has at least one principal dispersion peak α in the 30°C to 130°C range of the tanδ profile. The principal dispersion peak α is a parameter that reflects the micro-Brownian motion of molecular chains in the amorphous region near the glass transition temperature (Tg) of the resin material contained in the resin layer. According to the inventors' studies, a resin layer that satisfies the above requirements regarding the principal dispersion peak α contains a resin material that begins molecular motion at a relatively low temperature (e.g., room temperature) and exhibits excellent flexibility. Therefore, the resin layer can exhibit even better seal strength (initial seal strength) in a room temperature environment. Note that the lower the temperature at which the principal dispersion peak α appears, the more flexible the resin layer is, and the higher the temperature, the more heat-resistant the resin layer is.

[0012] The resin layer described above preferably contains a plasticizer. By adjusting the plasticizer content in the resin layer, the temperature at which the sub-dispersion peak γ and the main dispersion peak α appear can be controlled. For example, by increasing the plasticizer content, the sub-dispersion peak γ and the main dispersion peak α can be shifted to lower temperatures.

[0013] The above-mentioned resin film for terminals preferably contains a hydrogen sulfide adsorbent. This hydrogen sulfide adsorbent may be contained in the resin layer, or, if the resin film for terminals has a multilayer structure, it may be contained in other layers. In all-solid-state batteries, for example, sulfide-based electrolytes, oxide-based electrolytes, or organic polymer-based electrolytes are used as the electrolyte. Of these, when a sulfide-based electrolyte is used, if moisture gets into the cell, hydrogen sulfide is generated, which raises concerns about a decrease in the adhesion between the outer surface of the terminal and the resin film for terminals. By containing a hydrogen sulfide adsorbent in the resin film for terminals, excellent seal strength can be maintained at room temperature and high temperatures even after exposure to hydrogen sulfide.

[0014] One aspect of this disclosure relates to a method for selecting a resin film for terminals, which is disposed to cover a portion of the outer surface of a terminal in an energy storage device comprising an energy storage device body and terminals electrically connected to the energy storage device body. This selection method includes the following steps. (A) A process of performing dynamic viscoelasticity measurement on the terminal resin film to be evaluated under the condition of 1.0 Hz. (B) A step to determine whether or not at least one subdispersion peak γ exists in the -130°C to -50°C range of the tanδ profile obtained by the above dynamic viscoelasticity measurement. [Effects of the Invention]

[0015] This disclosure provides a resin film for terminals that can achieve sufficiently high levels of both sealing strength at high temperatures and initial sealing strength, as well as a method for selecting the same. Furthermore, this disclosure provides an energy storage device using the above-mentioned resin film for terminals. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a perspective view showing an example of an all-solid-state battery. [Figure 2] Figure 2 is a schematic cross-sectional view showing an example of an exterior material for an energy storage device. [Figure 3]Figs. 3(a) to 3(c) are cross-sectional views schematically showing the configuration of the sealant layer provided in the exterior material for the power storage device. [Figure 4] Fig. 4 is a cross-sectional view taken along the line IV-IV shown in Fig. 1, and is a cross-sectional view schematically showing the configuration of the tabs (resin film for terminals and metal terminals) of the all-solid-state battery. [Figure 5] Figs. 5(a) to 5(c) are cross-sectional views schematically showing examples of the configuration of the resin film for terminals. [Figure 6] It is a plan view schematically showing the evaluation samples produced in the examples and comparative examples. [Embodiments for Carrying Out the Invention]

[0017] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. Also, the dimensional ratios in the drawings are not limited to the ratios shown in the figures.

[0018] [Power storage device] Fig. 1 is a perspective view showing the schematic configuration of the power storage device according to the present embodiment. In Fig. 1, as an example of the power storage device 100, an all-solid-state battery is illustrated for the following description. Note that the power storage device having the configuration shown in Fig. 1 may be called a battery pack or a battery cell.

[0019] The power storage device 100 is an all-solid-state battery, and includes a power storage device main body 50, an exterior material 10, a pair of metal terminals 30, and a resin film for terminals 40 (tab sealant). The power storage device main body 50 is a battery main body that performs charge and discharge. The exterior material 10 covers the surface of the power storage device main body 50 and is arranged so as to contact a part of the resin film for terminals 40.

[0020] [Exterior material] Figure 2 is a cross-sectional view showing an example of a cross-section of the exterior material 10. The exterior material 10 has a multilayer structure comprising, from the outside to the inside (towards the main body 50 of the energy storage device), a base material layer 11, a first adhesive layer 12, a barrier layer 13, a corrosion prevention treatment layer 14, a second adhesive layer 17, and a sealant layer 16 in this order.

[0021] (Sealant layer) The sealant layer 16 is a layer that provides heat sealing properties to the exterior material 10, and is placed on the inside and heat-sealed (heat-fused) during the assembly of the energy storage device.

[0022] As the sealant layer 16, thermoplastic resins such as polyolefin, polyamide, polyester, polycarbonate, polyphenylene ether, polyacetal, polystyrene, polyvinyl chloride, and polyvinyl acetate can be used, and from the viewpoint of heat resistance and sealing suitability, polyolefin, polyamide, and polyester are preferred. When directly laminating to the barrier layer without an adhesive, it is preferable to use a material in which at least one layer in contact with the barrier layer has been modified with an acid or glycidyl.

[0023] Examples of polyolefin resins include low-density, medium-density, and high-density polyethylene; ethylene-α-olefin copolymers; polypropylene; and propylene-α-olefin copolymers. When polyolefin resins are copolymers, they may be block copolymers or random copolymers.

[0024] Examples of polyester resins include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). These polyester resins may be used individually or in combination of two or more. Alternatively, a copolymer of any acid and glycol may be used.

[0025] To impart sealing properties, heat resistance, and other functionalities, for example, antioxidants, slip agents, flame retardants, antiblocking agents, light stabilizers, dehydrating agents, tackifiers, crystal nucleating agents, plasticizers, etc., may be added.

[0026] The peak melting temperature of the sealant layer varies depending on the application, but for exterior materials for all-solid-state batteries, it is preferably between 160 and 280°C because it improves heat resistance.

[0027] Preferably, the sealant layer 16 has at least one sub-dispersion peak γ in the range of -130°C to -50°C in the profile of the loss tangent tanδ obtained by dynamic viscoelasticity measurement under conditions of 1.0 Hz. When the sealant layer 16 satisfies this condition, the exterior material 10 can achieve sufficiently high levels of both high-temperature sealing strength and initial sealing strength (sealing strength at room temperature). From the viewpoint of sealing strength at room temperature and high temperatures, the temperature range in which the sub-dispersion peak γ exists is more preferably -120°C to -60°C, and even more preferably -110°C to -70°C. If the temperature in which the sub-dispersion peak γ exists is below -130°C, the heat resistance of the sealant layer 16 will be poor, and the sealing strength at high temperatures may be insufficient. On the other hand, if the temperature in which the sub-dispersion peak γ exists exceeds -50°C, the flexibility of the sealant layer 16 will be poor, and the sealing strength at room temperature may be insufficient.

[0028] The above tanδ can be calculated, for example, by immersing the exterior material in an aqueous sodium hydroxide solution to dissolve the barrier layer (metal foil) and extracting a film consisting only of the sealant layer. The extracted film is then measured using a dynamic viscoelasticity device (manufactured by SII, product name: DMS6100) in accordance with JIS K7244-4 under the following conditions, and the loss tangent tanδ can be calculated from the loss modulus E'' and storage modulus E'. • Peeling mode: Tension • Heating rate: 2°C / min Temperature range: -150 to 150°C • Frequency: 1.0Hz

[0029] The sealant layer 16 preferably has at least one main dispersion peak α in the 30°C to 130°C range of the tanδ profile. When the sealant layer 16 satisfies this condition, the exterior material 10 exhibits even better initial seal strength (seal strength at room temperature). From the viewpoint of seal strength at room temperature, the temperature range in which the main dispersion peak α exists is preferably 40°C to 110°C, and more preferably 50°C to 100°C. If the temperature in which the main dispersion peak α exists is below 30°C, the heat resistance of the sealant layer 16 tends to be poor, resulting in insufficient seal strength at high temperatures. On the other hand, if the temperature in which the main dispersion peak α exists exceeds 130°C, the flexibility of the sealant layer 16 tends to be poor, resulting in insufficient seal strength at room temperature.

[0030] The temperature at which the sub-dispersion peak γ and main dispersion peak α of the sealant layer 16 appear can be controlled, for example, by the structure of the base resin material contained in the sealant layer 16, the stretch ratio of the sealant layer 16, or the amount of additives (e.g., plasticizers) included. The sealant layer 16 may contain additives as needed. Examples of additives include plasticizers, antioxidants, slip agents, flame retardants, AB agents, light stabilizers, dehydrating agents, and tackifiers.

[0031] Examples of base resin materials included in the sealant layer 16 include polyester-based, polyolefin-based, or polyamide-based resins.

[0032] Polyester resins can be obtained by copolymerizing an acid component and a glycol component. Examples of acid components include phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, and sebacic acid. Examples of glycol components include ethylene glycol, butanediol, pentanediol, hexanediol, neopentyl glycol, diethylene glycol, polytetramethylene glycol, cyclohexanedimethanol, and propanediol. According to the inventors' studies, general PET (a copolymer of terephthalic acid and ethylene glycol) has a sub-dispersion peak γ outside the range of -130°C to -50°C, resulting in insufficient seal strength at room temperature. When a plasticizer is not incorporated into the sealant layer 16, it is preferable that the sealant layer 16 contains a polyester resin in which two or more glycol components are copolymerized with one acid component.

[0033] Polyolefin resins include polyethylene and polypropylene resins. Since commonly used polyolefin resins have poor heat resistance, it is preferable to use polyethylene or polypropylene that have been modified with amides or the like.

[0034] Examples of polyamide resins include nylon 6 and nylon 6,6.

[0035] From the viewpoint of adjusting the temperature at which the sub-dispersion peak γ and main dispersion peak α of the sealant layer 16 appear, it is preferable that the sealant layer 16 contains a plasticizer. For example, ester compounds can be used as plasticizers. Specific examples include glycol diesters, adipic acid esters, phthalic acid esters, diacetyl monoacylglycerol derivatives, and esters having an ether skeleton. Depending on the base resin material of the sealant layer 16, the plasticizer content of the sealant layer 16 is preferably 30% by mass or less, based on the mass of the sealant layer 16. If an excess of plasticizer is added to the sealant layer 16, the temperature at which the sub-dispersion peak γ and main dispersion peak α appear tends to decrease excessively, and the cohesive force tends to decrease.

[0036] The sealant layer 16 may be a single layer or a multilayer structure of two or more layers (see Figures 3(a) to 3(c)). When the sealant layer is a single layer, its thickness is preferably 10 to 300 μm, and more preferably 20 to 100 μm. A thickness of 10 μm or more of the sealant layer 16 makes it easier to ensure airtightness and insulation, while a thickness of 300 μm or less allows for sufficient cell volume.

[0037] Figure 3(b) is a schematic cross-sectional view showing a two-layer sealant layer 16. The sealant layer 16 shown in the figure has a first resin layer 16a and a second resin layer 16b formed on the inner surface of the first resin layer 16a. The first resin layer 16a may be made of a different material than the second resin layer 16b, or it may have a different thickness from the second resin layer 16b. The thicknesses of the first resin layer 16a and the second resin layer 16b may be, for example, 5 to 300 μm and 20 to 200 μm, respectively. As shown in Figure 3(c), the sealant layer 16 may have a three-layer structure and further include a third resin layer 16c.

[0038] When the electrolyte of an all-solid-state battery is a sulfide-based electrolyte, it is preferable that the sealant layer 16 contains a hydrogen sulfide adsorbent. By containing a hydrogen sulfide adsorbent in the sealant layer 16, excellent seal strength can be maintained at room temperature and high temperatures even after exposure to hydrogen sulfide. As the hydrogen sulfide adsorbent, any material having the ability to absorb or adsorb hydrogen sulfide can be used. Specific examples include zinc oxide, amorphous metal silicates, zirconium lanthanide element hydroxides, tetravalent metal phosphates, potassium permanganate, sodium permanganate, aluminum oxide, iron hydroxide, silver sulfate, silver acetate, isocyanate compounds, aluminum silicate, potassium aluminum sulfate, zeolites, activated carbon, amine compounds, and ionomers.

[0039] The hydrogen sulfide adsorbent content of the sealant layer 16 is preferably 1 to 50% by mass, more preferably 2 to 25% by mass, and even more preferably 5 to 15% by mass, based on the mass of the sealant layer 16. A hydrogen sulfide adsorption effect is achieved when the hydrogen sulfide adsorbent content of the sealant layer 16 is 1% by mass or more, while a content of 50% by mass or less allows for both adhesion and sealant suitability of the sealant layer 16. If the sealant layer 16 has a multilayer structure, all or some of the layers may contain the hydrogen sulfide adsorbent. While layers other than the sealant layer 16 in the exterior material 10 (for example, the second adhesive layer 17) may contain sulfide-based electrolytes, from the viewpoint of hydrogen sulfide adsorption content, it is preferable that at least the sealant layer 16 contains the hydrogen sulfide adsorbent.

[0040] (base material layer) The base layer 11 provides heat resistance during the sealing process when manufacturing energy storage devices and plays a role in suppressing the occurrence of pinholes that may occur during molding and distribution. In particular, for exterior materials of large-scale energy storage devices, it can also provide scratch resistance, chemical resistance, and insulation.

[0041] The base layer 11 is preferably a layer made of a resin film formed from an insulating resin. Examples of resin films include stretched or unstretched films such as polyester film, polyamide film, polypropylene film, and polyphenylene sulfide film. The base layer 11 may be a single-layer film made of any of these resin films, or it may be a laminated film made of two or more of these resin films.

[0042] Among these, polyester film and polyamide film are preferred as the base layer 11 due to their excellent moldability, and polyamide film is more preferred. These films are preferably biaxially oriented films. Examples of polyester resins constituting the polyester film include polyethylene terephthalate. Examples of polyamide resins constituting the polyamide film include nylon 6, nylon 6,6, copolymers of nylon 6 and nylon 6,6, nylon 6,10, polymetaxylylene adipamide (MXD6), nylon 11, nylon 12, etc. Among these, nylon 6 (ONy) is preferred from the viewpoint of excellent heat resistance, puncture strength, and impact strength.

[0043] Examples of stretching methods for biaxially oriented films include sequential biaxial stretching, tubular biaxial stretching, and simultaneous biaxial stretching. From the viewpoint of obtaining better deep-drawing properties, it is preferable that the biaxially oriented film is stretched by the tubular biaxial stretching method.

[0044] The thickness of the base layer 11 is preferably 6 to 40 μm, and more preferably 10 to 30 μm. A base layer thickness of 6 μm or more tends to improve the pinhole resistance and insulation properties of the exterior material 10. When the thickness of the base layer 11 exceeds 40 μm, the total thickness of the exterior material 10 tends to increase.

[0045] (First adhesive layer) The first adhesive layer 12 is a layer that adheres the base layer 11 and the barrier layer 13. Specific examples of materials constituting the first adhesive layer 12 include polyurethane resins obtained by reacting a bifunctional or more isocyanate compound with a main component such as polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol. The various polyols mentioned above can be used individually or in combination of two or more, depending on the functions and performance required for the exterior material. In addition, various other additives and stabilizers may be added to the polyurethane resin, depending on the performance required for the adhesive.

[0046] The thickness of the first adhesive layer 12 is not particularly limited, but from the viewpoint of obtaining desired adhesive strength, conformability, and processability, for example, 1 to 10 μm is preferred, and 3 to 7 μm is more preferred.

[0047] (Barrier layer) The barrier layer 13 has water vapor barrier properties that prevent moisture from entering the inside of the energy storage device. Furthermore, the barrier layer 13 is ductile for deep drawing. As the barrier layer 13, various metal foils such as aluminum, stainless steel, and copper, as well as metal vapor-deposited films, inorganic oxide vapor-deposited films, carbon-containing inorganic oxide vapor-deposited films, and films with these vapor-deposited films can be used. From the viewpoints of mass (specific gravity), moisture resistance, processability, and cost, metal foil is preferred, and aluminum foil is more preferred.

[0048] As for the aluminum foil, soft aluminum foil that has undergone annealing treatment is particularly preferred because it can provide the desired ductility during molding. However, it is even more preferable to use aluminum foil containing iron in order to provide further pinhole resistance and ductility during molding. The iron content in the aluminum foil is preferably 0.1 to 9.0% by mass, and more preferably 0.5 to 2.0% by mass, of 100% by mass of aluminum foil. By having an iron content of 0.1% by mass or more, an exterior material 10 with better pinhole resistance and ductility can be obtained. By having an iron content of 9.0% by mass or less, an exterior material 10 with better flexibility can be obtained. Untreated aluminum foil may be used, but it is preferable to use degreased aluminum foil. When degreasing the aluminum foil, the degreasing treatment may be applied to only one side of the aluminum foil, or to both sides.

[0049] The thickness of the barrier layer 13 is not particularly limited, but it is preferably 9 to 200 μm, and more preferably 15 to 100 μm, considering barrier properties, pinhole resistance, and processability.

[0050] (Corrosion-resistant treatment layer) The corrosion-preventive treatment layer 14 is a layer provided to prevent corrosion of the barrier layer 13. The corrosion-preventive treatment layer 14 can be formed, for example, by degreasing, hot water modification, anodizing, chemical conversion, or a combination of these treatments.

[0051] Degreasing treatments include acid degreasing and alkaline degreasing. Acid degreasing methods include using inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid individually, or mixtures thereof. Furthermore, as an acid degreasing method, using an acid degreasing agent obtained by dissolving a fluorine-containing compound such as monosodium ammonium difluoride in the above inorganic acid not only provides a degreasing effect on aluminum, especially when aluminum foil is used in the barrier layer 13, but also allows the formation of a passive aluminum fluoride, which is effective in terms of hydrofluoric acid resistance. Alkaline degreasing methods include using sodium hydroxide, etc.

[0052] Examples of hydrothermal alteration treatments include the boehmite treatment, which involves immersing aluminum foil in boiling water to which triethanolamine has been added. Examples of anodizing treatments include the anodizing treatment.

[0053] Chemical treatments can be immersion-type or coating-type. Immersion-type chemical treatments include, for example, chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, or various chemical treatments consisting of mixed phases of these. On the other hand, a coating-type chemical treatment is a method of applying a coating agent having corrosion-preventive properties onto the barrier layer 13.

[0054] Of these corrosion prevention treatments, if at least a portion of the corrosion prevention treatment layer is formed by hot water modification, anodizing, or chemical conversion, it is preferable to perform the degreasing treatment described above beforehand. However, if a degreased metal foil, such as a metal foil that has undergone an annealing process, is used as the barrier layer 13, it is not necessary to perform degreasing treatment again when forming the corrosion prevention treatment layer 14.

[0055] The coating agent used in the coating-type chemical conversion treatment preferably contains trivalent chromium. The coating agent may also contain at least one polymer selected from the group consisting of cationic polymers and anionic polymers, as described later.

[0056] In particular, in the hydrothermal alteration treatment and anodic oxidation treatment described above, the surface of the aluminum foil is dissolved by the treatment agent, forming aluminum compounds (boehmite, anodized aluminum) with excellent corrosion resistance. As a result, a co-continuous structure is formed from the barrier layer 13 using aluminum foil to the corrosion-preventive treatment layer 14, and therefore the above treatment is included in the definition of chemical conversion treatment. On the other hand, as will be described later, it is also possible to form the corrosion-preventive treatment layer 14 using only a pure coating method, which is not included in the definition of chemical conversion treatment. One example of this method is to use a sol of a rare earth element oxide such as cerium oxide with an average particle size of 100 nm or less, as it has a corrosion-preventive effect on aluminum (inhibitor effect) and is also environmentally suitable. By using this method, it is possible to impart a corrosion-preventive effect to metal foils such as aluminum foil even with a general coating method.

[0057] Examples of sols for the rare earth element oxides mentioned above include sols using various solvents such as aqueous, alcohol, hydrocarbon, ketone, ester, and ether systems. Among these, aqueous sols are preferred. In order to stabilize the dispersion of the rare earth element oxide sols, inorganic acids or their salts, such as nitric acid, hydrochloric acid, and phosphoric acid, or organic acids such as acetic acid, malic acid, ascorbic acid, and lactic acid are usually used as dispersion stabilizers. Of these dispersion stabilizers, phosphoric acid in particular is expected to provide the following benefits in the exterior material 10: (1) stabilization of sol dispersion, (2) improved adhesion with the barrier layer 13 by utilizing the aluminum chelating ability of phosphoric acid, and (3) improved cohesive force of the corrosion prevention treatment layer 14 (oxide layer) due to the ease with which dehydration condensation of phosphoric acid occurs even at low temperatures.

[0058] The corrosion-preventive treatment layer 14 formed by the above-mentioned rare earth element oxide sol is an aggregate of inorganic particles, and therefore, even after the drying and curing process, the cohesive force of the layer itself may decrease. Therefore, in this case, it is preferable that the corrosion-preventive treatment layer is compounded with the following anionic polymer or cationic polymer to compensate for the cohesive force.

[0059] The corrosion-preventive treatment layer is not limited to the layer described above. For example, it may be formed using a treatment agent that combines a resin binder (such as aminophenol) with phosphoric acid and a chromium compound, as is known from the field of coating chromate. Using this treatment agent, a layer can be formed that possesses both corrosion-preventive properties and adhesion. Furthermore, although it is necessary to consider the stability of the coating liquid, a layer can be formed that possesses both corrosion-preventive properties and adhesion by using a coating agent that pre-mixes a rare earth element oxide sol with a polycationic polymer or a polyanionic polymer into a single liquefaction.

[0060] The mass per unit area of ​​the corrosion-preventive treatment layer is 0.005 to 0.200 g / m², regardless of whether it is a multilayer or single-layer structure. 2 Preferably, 0.010 to 0.100 g / m 2 A more preferable mass per unit area is 0.005 g / m². 2 If the above is true, it is easier to impart corrosion prevention functionality to the barrier layer 13. Also, the above mass per unit area is 0.200 g / m². 2 Even if the thickness exceeds a certain limit, the corrosion prevention function does not change significantly. On the other hand, when using rare earth element oxide sols, if the coating film is thick, the heat during drying may result in insufficient curing, potentially leading to a decrease in cohesive force. The thickness of the corrosion prevention treatment layer 14 can be calculated from its specific gravity.

[0061] The corrosion-preventive treatment layer may, from the viewpoint of adhesion between the sealant layer and the barrier layer, for example, contain cerium oxide, 1 to 100 parts by mass of phosphoric acid or phosphate per 100 parts by mass of cerium oxide, and a cationic polymer; it may be formed by applying a chemical conversion treatment to the barrier layer 13; or it may be formed by applying a chemical conversion treatment to the barrier layer and also contain a cationic polymer.

[0062] (Second adhesive layer) The second adhesive layer 17 is a layer that bonds the barrier layer 13, on which the corrosion-preventive treatment layer 14 is formed, to the sealant layer 16. A general adhesive for bonding the barrier layer 13 and the sealant layer 16 can be used for the second adhesive layer 17.

[0063] If the corrosion-preventive treatment layer 14 has a layer containing at least one polymer selected from the group consisting of cationic polymers and anionic polymers described above, it is preferable that the second adhesive layer 17 is a layer containing a compound that is reactive with the polymer contained in the corrosion-preventive treatment layer 14 (hereinafter also referred to as "reactive compound").

[0064] For example, if the corrosion-preventive treatment layer 14 contains a cationic polymer, the second adhesive layer 17 contains a compound that is reactive with the cationic polymer. If the corrosion-preventive treatment layer 14 contains an anionic polymer, the second adhesive layer 17 contains a compound that is reactive with the anionic polymer. Furthermore, if the corrosion-preventive treatment layer 14 contains both a cationic polymer and an anionic polymer, the second adhesive layer 17 contains a compound that is reactive with the cationic polymer and a compound that is reactive with the anionic polymer. However, the second adhesive layer 17 does not necessarily have to contain the above two types of compounds, and may contain a compound that is reactive with both the cationic polymer and the anionic polymer. Here, "reactive" means forming a covalent bond with the cationic polymer or the anionic polymer. The second adhesive layer 17 may further contain an acid-modified polyolefin resin.

[0065] Compounds that react with cationic polymers include at least one compound selected from the group consisting of polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxyl group, and compounds having an oxazoline group.

[0066] Examples of these polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxyl group, and compounds having an oxazoline group include the polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxyl group, and compounds having an oxazoline group that were previously exemplified as crosslinking agents for creating a crosslinked structure of cationic polymers. Among these, polyfunctional isocyanate compounds are preferred because they have high reactivity with cationic polymers and readily form crosslinked structures.

[0067] Compounds that react with anionic polymers include at least one compound selected from the group consisting of glycidyl compounds and compounds having an oxazoline group. Examples of these glycidyl compounds and compounds having an oxazoline group include the glycidyl compounds and compounds having an oxazoline group that were previously exemplified as crosslinking agents for creating a crosslinked structure of cationic polymers. Among these, glycidyl compounds are preferred due to their high reactivity with anionic polymers.

[0068] When the second adhesive layer 17 contains an acid-modified polyolefin resin, it is preferable that the reactive compound is also reactive with the acidic groups in the acid-modified polyolefin resin (i.e., forms a covalent bond with the acidic groups). This further improves adhesion to the corrosion-preventive treatment layer 14. In addition, the acid-modified polyolefin resin becomes a cross-linked structure, further improving the solvent resistance of the exterior material 10.

[0069] The content of the reactive compound is preferably equal to or 10 times the amount of the acidic groups in the acid-modified polyolefin resin. If the amount is equal to or greater than the amount, the reactive compound will react sufficiently with the acidic groups in the acid-modified polyolefin resin. On the other hand, if the amount exceeds 10 times the amount, the crosslinking reaction with the acid-modified polyolefin resin will be sufficiently saturated, and unreacted material will be present, raising concerns about a decrease in various performance characteristics. Therefore, for example, the content of the reactive compound is preferably 5 to 20 parts by mass (solid content ratio) per 100 parts by mass of the acid-modified polyolefin resin.

[0070] Acid-modified polyolefin resins are polyolefin resins into which acidic groups have been introduced. Examples of acidic groups include carboxyl groups, sulfonic acid groups, and acid anhydride groups, with maleic anhydride groups and (meth)acrylic acid groups being particularly preferred. As an acid-modified polyolefin resin, for example, the same type as the modified polyolefin resin used in the sealant layer 16 can be used.

[0071] The second adhesive layer 17 may contain various additives such as flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, and tackifiers.

[0072] Examples of adhesives that form the second adhesive layer 17 include polyurethane resins obtained by reacting a difunctional or more isocyanate compound with a main component such as polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol, and epoxy resins obtained by reacting an amine compound with a main component having epoxy groups, which are preferred from the viewpoint of heat resistance.

[0073] The thickness of the second adhesive layer 17 is not particularly limited, but from the viewpoint of obtaining the desired adhesive strength and processability, it is preferably 1 to 10 μm, and more preferably 2 to 7 μm.

[0074] [Metal terminal] Figure 4 is a cross-sectional view of the resin film and metal terminals for the terminals shown in Figure 1, in the direction of the IV-IV line. Of the pair of metal terminals 30, 30, one metal terminal 30 is electrically connected to the positive terminal of the energy storage device body 50, and the other metal terminal 30 is electrically connected to the negative terminal of the energy storage device body 50. The pair of metal terminals 30, 30 extend from the energy storage device body 50 to the outside of the exterior material 10. The shape of the pair of metal terminals 30, 30 can be, for example, a flat plate shape.

[0075] The material for the metal terminal 30 can be any metal. The metal used for the metal terminal 30 should be determined considering the structure of the energy storage device body 50 and the materials of its components. For example, if the energy storage device 100 is an all-solid-state battery, it is preferable to use aluminum for the metal terminal 30 connected to the positive electrode of the energy storage device body 50. For the metal terminal 30 connected to the negative electrode of the energy storage device body 50, it is preferable to use copper with a nickel plating layer formed on its surface, or nickel.

[0076] The thickness of the metal terminals 30 depends on the size and capacity of the solid-state battery. For small solid-state batteries, the thickness of the metal terminals 30 should be, for example, 50 μm or more. For large solid-state batteries used in energy storage and automotive applications, the thickness of the metal terminals 30 can be appropriately set within a range of, for example, 100 to 500 μm.

[0077] [Resin film for terminals] As shown in Figure 4, the terminal resin film 40 is positioned to cover a portion of the outer surface of the metal terminal 30. By positioning the terminal resin film 40 between the metal terminal 30 and the exterior material 10, the sealing and insulating properties of the energy storage device 100 can be further enhanced. The terminal resin film 40 has heat resistance equivalent to or exceeding that of the sealant layer 16 and the base material layer 11 described above.

[0078] The terminal resin film 40 comprises a resin layer 40a having at least one subdispersion peak γ in the range of -130°C to -50°C in the profile of the loss tangent tanδ obtained by dynamic viscoelasticity measurement under conditions of 1.0 Hz. The terminal resin film 40 has a single-layer structure or a multilayer structure. If the terminal resin film 40 has a single-layer structure, the terminal resin film 40 consists of a resin layer 40a (see Figure 5(a)). If the terminal resin film 40 has a multilayer structure, the terminal resin film 40 only needs to include at least one resin layer (resin layer 40a) that satisfies the above conditions (see Figures 5(b) and 5(c)). In the case of the terminal resin film 40 having a multilayer structure, it is preferable that all layers are made of the same resin material from the viewpoint of adhesion between adjacent layers.

[0079] By providing the resin layer 40a in the terminal resin film 40, the terminal resin film 40 can achieve sufficiently high levels of both high-temperature sealing strength and initial sealing strength (sealing strength at room temperature). The temperature range in which the sub-dispersion peak γ exists is preferably -120°C to -60°C, and more preferably -110°C to -70°C, from the viewpoint of sealing strength at room temperature and high temperatures. If the temperature in which the sub-dispersion peak γ exists is below -130°C, the heat resistance of the resin layer 40a will be poor, and the sealing strength at high temperatures may be insufficient. On the other hand, if the temperature in which the sub-dispersion peak γ exists exceeds -50°C, the flexibility of the resin layer 40a will be poor, and the sealing strength at room temperature may be insufficient.

[0080] The above tanδ can be calculated, for example, by measuring the terminal resin film 40 in accordance with JIS K7244-4 using a dynamic viscoelastic device (manufactured by SII, product name: DMS6100) under the following conditions, and from the loss modulus E'' and storage modulus E', as the loss tangent tanδ. • Peeling mode: Tension • Heating rate: 2°C / min Temperature range: -150 to 150°C • Frequency: 1.0Hz

[0081] Preferably, the resin layer 40a has at least one main dispersion peak α in the 30°C to 130°C range of the tanδ profile. When the resin layer 40a satisfies this condition, the terminal resin film 40 exhibits even better initial seal strength (seal strength at room temperature). From the viewpoint of seal strength at room temperature, the temperature range in which the main dispersion peak α exists is preferably 40°C to 110°C, and more preferably 50°C to 100°C. If the temperature in which the main dispersion peak α exists is below 30°C, the heat resistance of the resin layer 40a tends to be poor, resulting in insufficient seal strength at high temperatures. On the other hand, if the temperature in which the main dispersion peak α exists exceeds 130°C, the flexibility of the resin layer 40a tends to be poor, resulting in insufficient seal strength at room temperature.

[0082] The temperature at which the sub-dispersion peak γ and the main dispersion peak α of the resin layer 40a appear can be controlled, for example, by the structure of the base resin material contained in the resin layer 40a, the stretch ratio of the resin layer 40a, or the amount of additives (e.g., plasticizers) blended. The resin layer 40a may contain additives as needed. Examples of additives include plasticizers, antioxidants, slip agents, flame retardants, AB agents, light stabilizers, dehydrating agents, and tackifiers.

[0083] Examples of base resin materials included in the terminal resin film 40 include polyester-based, polyolefin-based, or polyamide-based resins.

[0084] Polyester resins can be obtained by copolymerizing an acid component and a glycol component. Examples of acid components include phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, and sebacic acid. Examples of glycol components include ethylene glycol, butanediol, pentanediol, hexanediol, neopentyl glycol, diethylene glycol, polytetramethylene glycol, cyclohexanedimethanol, and propanediol. According to the inventors' studies, general PET (a copolymer of terephthalic acid and ethylene glycol) has a sub-dispersion peak γ outside the range of -130°C to -50°C, resulting in insufficient seal strength at room temperature. When a plasticizer is not incorporated into the resin layer 40a, it is preferable that the resin layer 40a contains a polyester resin in which two or more glycol components are copolymerized with one acid component.

[0085] Polyolefin resins include polyethylene and polypropylene resins. Generally, polyolefin resins have poor heat resistance, so it is preferable to use polyethylene or polypropylene that has been modified with amides or the like. Furthermore, from the viewpoint of adhesion between the metal terminal 30 and the terminal resin film 40, it is preferable to use a polyolefin that has been acid-modified with carboxylic acid or maleic anhydride, or amide-modified, as the base resin material of the terminal resin film 40.

[0086] Examples of polyamide resins include nylon 6 and nylon 6,6.

[0087] From the viewpoint of adjusting the temperature at which the sub-dispersion peak γ and main dispersion peak α of the resin layer 40a appear, it is preferable that the resin layer 40a contains a plasticizer. For example, ester compounds can be used as plasticizers. Specific examples include glycol diesters, adipic acid esters, phthalic acid esters, diacetyl monoacylglycerol derivatives, and esters having an ether skeleton. Depending on the base resin material of the resin layer 40a, the plasticizer content of the resin layer 40a is preferably 30% by mass or less, based on the mass of the resin layer 40a. If an excess of plasticizer is blended into the resin layer 40a, the temperature at which the sub-dispersion peak γ and main dispersion peak α appear tends to decrease excessively, and the cohesive force tends to decrease.

[0088] If the terminal resin film 40 has a multilayer structure, the resin layer 40a may be positioned on the side that contacts the metal terminal 30 or on the side that contacts the outer casing material 10. If the terminal resin film 40 consists of three or more layers, the resin layer 40a may be positioned between the resin layer 40b and the resin layer 40c (see Figure 5(c)).

[0089] The thickness of the terminal resin film 40 is preferably 15 μm or more, more preferably 30 to 300 μm, and even more preferably 50 to 200 μm, from the viewpoint of embedding and insulation properties.

[0090] When the electrolyte of an all-solid-state battery is a sulfide-based electrolyte, it is preferable that the terminal resin film 40 contains a hydrogen sulfide adsorbent. By containing a hydrogen sulfide adsorbent in the terminal resin film 40, excellent seal strength can be maintained at room temperature and high temperatures even after exposure to hydrogen sulfide. The above-mentioned substances are examples of hydrogen sulfide adsorbents.

[0091] The hydrogen sulfide adsorbent content of the terminal resin film 40 is preferably 1 to 50% by mass, more preferably 2 to 25% by mass, and even more preferably 5 to 15% by mass, based on the mass of the terminal resin film 40. A hydrogen sulfide adsorbent content of 1% by mass or more in the terminal resin film 40 allows for hydrogen sulfide absorption or adsorption, while a content of 50% by mass or less ensures both adhesion and sealant suitability of the terminal resin film 40. When the terminal resin film 40 has a multilayer structure, from the viewpoint of adhesion to the metal terminal 30, it is preferable that the layer in contact with the metal terminal 30 does not contain the hydrogen sulfide adsorbent. That is, it is preferable that the layer in contact with the exterior material 10 (for example, the resin layer 40a in Figure 5(b) or the resin layers 40a and 40c in Figure 5(c)) contains the hydrogen sulfide adsorbent, and when the terminal resin film 40 consists of three or more layers, it is preferable that the intermediate layer (for example, the resin layer 40a in Figure 5(c)) contains the hydrogen sulfide adsorbent.

[0092] Although embodiments of the present disclosure have been described in detail above, the present invention is not limited to the above embodiments, and various modifications and changes are possible within the scope of the gist of the present disclosure as described in the claims. For example, in the above embodiments, an example was given in which the corrosion prevention treatment layer 14 is provided only on one surface of the barrier layer 13 (the side with the second adhesive layer 17), but the corrosion prevention treatment layer 14 may also be provided on the other surface of the barrier layer 13 (the side with the first adhesive layer 12). Also, for example, if the sealant layer 16 is attached to the barrier layer 13 by thermal lamination, the second adhesive layer 17 may be omitted. If the base material layer 11 is provided by coating or paint, the first adhesive layer 12 may be omitted. In the above embodiments, an electro-solid-state battery was given as an example of an energy storage device to which the exterior material 10 is applied, but the exterior material 10 may also be applied to other energy storage devices (for example, lithium-ion batteries).

[0093] A method for selecting a terminal resin film may be implemented based on the contents of the above embodiment. That is, this selection method is for selecting a terminal resin film to be placed so as to cover a part of the outer surface of a terminal in an energy storage device comprising an energy storage device body and terminals electrically connected to the energy storage device body, and may include (A) a step of performing a dynamic viscoelasticity measurement on the terminal resin film to be evaluated under the condition of 1.0 Hz, and (B) a step of determining whether or not there is at least one subdispersion peak γ in the range of -130°C to -50°C in the tanδ profile obtained by the dynamic viscoelasticity measurement. The matters described in the above embodiment may be appropriately applied to this selection method. [Examples]

[0094] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to the following examples.

[0095] [Materials used] The following materials were prepared to produce the resin films for terminals according to the examples and comparative examples. [Base resin material] • Polyester resin 1: Copolymer of terephthalic acid as the acid component and ethylene glycol as the glycol component. • Polyester resin 2: Copolymer of terephthalic acid as the acid component and ethylene glycol and butanediol as the glycol components. • Polyester resin 3: Copolymer of terephthalic acid and isophthalic acid as acid components and ethylene glycol, butanediol, and neopentyl glycol as glycol components. • Polyester resin 4: Copolymer of terephthalic acid as the acid component and ethylene glycol and 1,4-cyclohexanedimethanol as the glycol components. • Polyester resin 5: Copolymer of terephthalic acid and isophthalic acid as acid components and butanediol and hexanediol as glycol components • Polyester resin 6: A copolymer of terephthalic acid and isophthalic acid as acidic components, and butanediol and hexanediol as glycol components (with a higher proportion of butanediol than polyester resin 5). • Polyester resin 7: Copolymer of naphthalenedicarboxylic acid as the acid component and 1,4-cyclohexanedimethanol as the glycol component. • Polyester resin 8: Copolymer of terephthalic acid and isophthalic acid as acid components and ethylene glycol and hexanediol as glycol components. • Polyolefin resin 1: Amide-modified polyethylene • Polyolefin resin 2: Random polypropylene [Plasticizer] Glycol diester: 10 parts by mass were added as needed per 100 parts by mass of the base resin material. [Hydrogen sulfide absorbent] • Zinc oxide: 3 parts by mass were added as needed per 100 parts by mass of the base resin material.

[0096] (Example 1) A single-layer resin film (thickness: 100 μm) for terminals was fabricated using the inflation method, consisting of the following resin composition. • Polyester resin 1:100 parts by mass • Plasticizer: 10 parts by mass • Hydrogen sulfide adsorbent: 3 parts by mass

[0097] (Example 2) A resin film for terminals (single layer, thickness: 100 μm) was prepared in the same manner as in Example 1, except that polyester resin 2 was used instead of polyester resin 1.

[0098] (Example 3) A single-layer resin film (thickness: 100 μm) for terminals was prepared in the same manner as in Example 1, except that a hydrogen sulfide adsorbent was not used.

[0099] (Example 4) A single-layer resin film (thickness: 100 μm) for terminals was fabricated using the inflation method, consisting of polyester resin 3.

[0100] (Example 5) A resin film for terminals (single layer, thickness: 100 μm) was prepared in the same manner as in Example 4, except that a plasticizer (10 parts by mass) and a hydrogen sulfide adsorbent (3 parts by mass) were added to the polyester resin 3.

[0101] (Example 6) A single-layer resin film (thickness: 100 μm) for terminals was fabricated using the inflation method, consisting of a polyester resin 4 and a hydrogen sulfide adsorbent (3 parts by mass).

[0102] (Example 7) A single-layer resin film (thickness: 100 μm) for terminals was prepared using the inflation method, consisting of a polyester resin 5 and a hydrogen sulfide adsorbent (3 parts by mass).

[0103] (Example 8) A single-layer resin film (thickness: 100 μm) for terminals was fabricated using the inflation method, consisting of a polyester resin 6 and a hydrogen sulfide adsorbent (3 parts by mass).

[0104] (Example 9) A single-layer resin film (thickness: 100 μm) for terminals was fabricated using the inflation method, consisting of a polyolefin resin 1 and a hydrogen sulfide adsorbent (3 parts by mass).

[0105] (Example 10) A two-layer resin film (50 μm / 50 μm) for terminals was fabricated using the inflation method. • Layer on the exterior material side: Polyester resin 1 and hydrogen sulfide adsorbent (3 parts by mass) • Layer on the metal terminal side: Polyester resin 7

[0106] (Example 11) A three-layer resin film for terminals (25 μm / 50 μm / 25 μm) was fabricated using the inflation method. • Layer on the exterior material side: Polyester resin 2, plasticizer (10 parts by mass), and hydrogen sulfide adsorbent (3 parts by mass) • Intermediate layer: Polyester resin 1, plasticizer (10 parts by mass), and hydrogen sulfide adsorbent (3 parts by mass) • Layer on the metal terminal side: Polyester resin 2 and plasticizer (10 parts by mass)

[0107] (Example 12) A three-layer resin film for terminals (25 μm / 50 μm / 25 μm) was fabricated using the inflation method. • Layer on the exterior material side: Polyester resin 1 and plasticizer (10 parts by mass) • Intermediate layer: Polyester resin 8 and hydrogen sulfide adsorbent (3 parts by mass) • Layer on the metal terminal side: Polyester resin 1 and plasticizer (10 parts by mass)

[0108] (Example 13) A two-layer resin film (50 μm / 50 μm) for terminals was fabricated using the inflation method. • Layer on the exterior material side: Polyester resin 1, plasticizer (10 parts by mass), and hydrogen sulfide adsorbent (3 parts by mass) • Layer on the metal terminal side: Polyester resin 8

[0109] (Example 14) A three-layer resin film for terminals (25 μm / 50 μm / 25 μm) was fabricated using the inflation method. • Exterior material side layer: Polyester resin 7 • Intermediate layer: Polyester resin 1, plasticizer (10 parts by mass), and hydrogen sulfide adsorbent (3 parts by mass) • Layer on the metal terminal side: Polyester resin 7

[0110] (Comparative Example 1) A single-layer resin film (thickness: 100 μm) for terminals was prepared using the inflation method, consisting of a polyester resin 7 and a hydrogen sulfide adsorbent (3 parts by mass).

[0111] (Comparative Example 2) A single-layer resin film (thickness: 100 μm) for terminals was fabricated using the inflation method, consisting of a polyester resin 1 and a hydrogen sulfide adsorbent (3 parts by mass).

[0112] (Comparative Example 3) A single-layer resin film (thickness: 100 μm) for terminals was prepared using the inflation method, consisting of a polyester resin 8 and a hydrogen sulfide adsorbent (3 parts by mass).

[0113] (Comparative Example 4) A single-layer, 100 μm thick resin film for terminals was fabricated using the inflation method, consisting of polyolefin resin 2.

[0114] (Comparative Example 5) A three-layer resin film for terminals (25 μm / 50 μm / 25 μm) was fabricated using the inflation method. • Exterior material side layer: Polyester resin 7 • Intermediate layer: Polyester resin 8 and hydrogen sulfide adsorbent (3 parts by mass) • Layer on the metal terminal side: Polyester resin 7

[0115] <Rating> The following evaluation tests were performed on the resin films for terminals obtained in the examples and comparative examples.

[0116] [Loss tangent tanδ of resin film for terminals] A resin film for terminals was cut to 10 mm (TD) x 30 mm (MD) to obtain test specimens. The test specimens were held with a chuck distance of 20 mm. Measurements were performed using a dynamic viscoelasticity analyzer (SII Corporation, product name: DMS6100) according to the method compliant with JIS K7244-4, under the following conditions, and the loss tangent tanδ was calculated from the loss modulus E'' and storage modulus E'. In addition, the temperature of the sub-dispersion peak γ and the temperature of the main dispersion peak α were determined from the obtained tanδ profile. The results are shown in Tables 1 to 3. • Peeling mode: Tension • Heating rate: 2°C / min Temperature range: -150 to 150°C • Frequency: 1.0Hz

[0117] [Initial seal strength] A chemically treated aluminum plate (50 mm x 50 mm) was prepared. On the other hand, a terminal resin film was cut to 50 mm (TD) x 100 mm (MD) to obtain a test specimen. This test specimen was folded in half, and the aluminum plate was placed in between. One side of the laminate (test specimen / aluminum plate / test specimen) was heat-sealed with a 10 mm wide sealing bar at 165°C, 0.6 MPa, and 10 seconds. After that, the heat-sealed portion was cut to a width of 15 mm to obtain a measurement sample (see Figure 6). The seal strength was measured at room temperature (23°C) with a peeling speed of 50 mm / min. Based on the results, the following criteria were used for evaluation. The results are shown in Tables 1-3. A: Burst intensity of 25N / 15mm or more B: Burst intensity of 20N / 15mm or more, and less than 25N / 15mm C: Burst intensity of 15N / 15mm or more, and less than 20N / 15mm D: Burst intensity less than 15N / 15mm

[0118] [High-temperature seal strength] A chemically treated aluminum plate (50 mm x 50 mm) was prepared. On the other hand, a terminal resin film was cut to 50 mm (TD) x 100 mm (MD) to obtain a test specimen. This test specimen was folded in half, and the aluminum plate was placed in between. One side of the laminate (test specimen / aluminum plate / test specimen) was heat-sealed with a 10 mm wide sealing bar at 165°C, 0.6 MPa, and for 10 seconds. After that, the heat-sealed portion was cut to a width of 15 mm, left to stand in a 150°C environment for 5 minutes, and then the seal strength was measured at a peeling speed of 50 mm / min in a 150°C environment. Based on the results, the following criteria were used for evaluation. The results are shown in Tables 1-3. A: Burst intensity of 15N / 15mm or more B: Burst intensity of 10N / 15mm or more, and less than 15N / 15mm C: Burst intensity of 5N / 15mm or more, and less than 10N / 15mm D: Burst intensity less than 5N / 15mm

[0119] [Seal strength after hydrogen sulfide exposure (at room temperature)] A chemically treated aluminum plate (50 mm x 50 mm) was prepared. On the other hand, a terminal resin film was cut to 50 mm (TD) x 100 mm (MD) to obtain a test specimen. This test specimen was folded in half, and the aluminum plate was placed in between. One side of the laminate (test specimen / aluminum plate / test specimen) was heat-sealed with a 10 mm wide sealing bar at 165°C, 0.6 MPa, and 10 seconds. After that, the heat-sealed portion was cut to a width of 15 mm, and after standing for 72 hours in a room temperature environment with a hydrogen sulfide concentration of 20 ppm, the seal strength was measured at room temperature with a peeling speed of 50 mm / min. Based on the results, the following criteria were used for evaluation. The results are shown in Tables 1-3. A: Burst intensity of 25N / 15mm or more B: Burst intensity of 20N / 15mm or more, and less than 25N / 15mm C: Burst intensity of 15N / 15mm or more, and less than 20N / 15mm D: Burst intensity less than 15N / 15mm

[0120] [Seal strength after hydrogen sulfide exposure (at 150°C)] A chemically treated aluminum plate (50 mm x 50 mm) was prepared. On the other hand, a terminal resin film was cut to 50 mm (TD) x 100 mm (MD) to obtain a test specimen. This test specimen was folded in half, and the aluminum plate was placed in between. One side of the laminate (test specimen / aluminum plate / test specimen) was heat-sealed with a 10 mm wide sealing bar at 165°C, 0.6 MPa, and for 10 seconds. After that, the heat-sealed portion was cut to a width of 15 mm and left to stand for 72 hours in a room temperature environment with a hydrogen sulfide concentration of 20 ppm. After that, it was left to stand in a 150°C environment for 5 minutes, and then the seal strength was measured at a peeling speed of 50 mm / min in a 150°C environment. Based on the results, the following criteria were used for evaluation. The results are shown in Tables 1-3. A: Burst intensity of 15N / 15mm or more B: Burst intensity of 10N / 15mm or more, and less than 15N / 15mm C: Burst intensity of 5N / 15mm or more, and less than 10N / 15mm D: Burst intensity less than 5N / 15mm

[0121] [Table 1]

[0122] [Table 2]

[0123] [Table 3]

[0124] In Tables 1-3, those without a D in the evaluation results can be said to have excellent overall quality. Examples 1-14 received A-C ratings for seal strength. In contrast, Comparative Examples 1-5 had a D rating for some of their seal strength evaluations. Specifically, Comparative Example 1 received a D rating for seal strength at room temperature (initial and after hydrogen sulfide exposure). This is presumed to be because the temperature of the sub-dispersion peak γ was higher than the -130°C to -50°C range, and the temperature of the main dispersion peak α was also higher than the 30°C to 130°C range. Comparative Example 2 also received a D rating for seal strength at room temperature (initial and after hydrogen sulfide exposure). This is presumed to be because the temperature of the sub-dispersion peak γ was higher than the -130°C to -50°C range. Comparative Example 3 received a D rating for seal strength in a 150°C environment both before and after hydrogen sulfide exposure. This is presumed to be because the temperature of the sub-dispersion peak γ was lower than the -130°C to -50°C range. Comparative Example 4 also received a D rating for seal strength both before and after hydrogen sulfide exposure at a 150°C environment. This is presumed to be because the temperature of the sub-dispersion peak γ was lower than the -130°C to -50°C range, and the temperature of the main dispersion peak α was also lower than the 30°C to 130°C range. Comparative Example 5 also received a D rating for seal strength in all aspects. [Explanation of Symbols]

[0125] 10...Exterior material for energy storage device, 11...Base layer, 12...First adhesive layer, 13...Barrier layer, 14...Corrosion prevention treatment layer, 16...Sealant layer, 16a...First resin layer, 16b...Second resin layer, 16c...Third resin layer, 17...Second adhesive layer, 30...Metal terminal, 40...Resin film for terminal, 40a...Resin layer, 50...Energy storage device body, 100...Energy storage device

Claims

1. A resin film for a terminal, which is disposed to cover a part of the outer surface of a terminal in a power storage device comprising a power storage device body and terminals electrically connected to the power storage device body, The resin film for the terminal has a single-layer structure or a multi-layer structure. The resin layer comprises a profile of loss tangent tanδ obtained by dynamic viscoelastic measurement under conditions of 1.0 Hz, having at least one subdispersion peak γ in the range of -130°C to -74°C. A resin film for terminals, comprising a polyester resin or an amide-modified polyolefin resin in the aforementioned resin layer.

2. The resin film for terminals according to claim 1, wherein the resin layer has at least one main dispersion peak α in the 30°C to 130°C range of the tanδ profile.

3. The resin film for terminals according to claim 1 or 2, wherein the resin layer contains a plasticizer.

4. A resin film for terminals according to any one of claims 1 to 3, comprising a hydrogen sulfide adsorbent.

5. A method for selecting a resin film for a terminal, which is arranged to cover a part of the outer surface of a terminal in a power storage device comprising a power storage device body and terminals electrically connected to the power storage device body, The terminal resin film to be evaluated has a resin layer, The resin layer comprises a polyester resin or an amide-modified polyolefin resin. (A) A step of performing a dynamic viscoelasticity measurement on the resin layer of the terminal resin film to be evaluated under the condition of 1.0 Hz, (B) A step of determining whether or not there is at least one subdispersion peak γ in the range of -130°C to -74°C in the tanδ profile obtained by the dynamic viscoelasticity measurement, A method for selecting a resin film for terminals, including the following.

6. The main unit of the energy storage device, Terminals extending from the main body of the energy storage device, An exterior material that clamps the terminals and houses the main body of the energy storage device, A terminal resin film according to any one of claims 1 to 4, disposed between the terminal and the exterior material, A power storage device equipped with the following features.

7. The exterior material has a laminated structure comprising, in this order, at least a base layer, a barrier layer, and a sealant layer. The energy storage device according to claim 6, wherein the sealant layer has at least one subdispersion peak γ in the range of -130°C to -50°C in the profile of the loss tangent tanδ obtained by dynamic viscoelastic measurement under conditions of 1.0 Hz.

8. The energy storage device according to claim 7, wherein the sealant layer has at least one main dispersion peak α in the range of 30°C to 130°C of the tanδ profile.

9. The energy storage device according to claim 7 or 8, wherein the sealant layer contains a plasticizer.

10. The energy storage device according to any one of claims 7 to 9, wherein the sealant layer contains a hydrogen sulfide adsorbent.

11. The barrier layer and the sealant layer are further provided with an adhesive layer, The energy storage device according to any one of claims 7 to 10, wherein the adhesive layer contains a hydrogen sulfide adsorbent.

12. The energy storage device according to any one of claims 7 to 11, further comprising a corrosion-preventive treatment layer provided on at least one surface of the barrier layer.

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