Adhesive film for metal terminal, metal terminal with adhesive film for metal terminal, power storage device using the adhesive film for metal terminal, and manufacturing method of power storage device

Abstract

To provide an adhesive film for a metal terminal which exhibits high adhesive strength to a metal terminal even when heated and pressurized a plurality of times before being bonded to the metal terminal.SOLUTION: An adhesive film for a metal terminal is interposed between a metal terminal electrically connected to an electrode of a power storage device element and an outer casing material for a power storage device which encapsulates the power storage device element. After being placed in a heating / pressurized environment at a temperature of 180°C and a surface pressure of 0.0067 MPa for 12 seconds, and then placed in an environment at a temperature of 25°C for one hour. The adhesive film for metal terminals has a modulus of elasticity in tension A of 490 MPa or higher in an environment of 25°C.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to an adhesive film for metal terminals, a metal terminal with an adhesive film for metal terminals, a power storage device using the adhesive film for metal terminals, and a method for manufacturing a power storage device.

Background Art

[0002] Conventionally, various types of power storage devices have been developed. In every power storage device, an exterior material for power storage devices is an essential member for sealing power storage device elements such as electrodes and electrolytes. Conventionally, a metal exterior material for power storage devices has been frequently used as the exterior material for power storage devices. However, in recent years, with the improvement of performance in electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc., power storage devices are required to have various shapes, and also to be thinned and lightened. However, the conventionally frequently used metal exterior material for power storage devices has the drawbacks that it is difficult to follow the diversification of shapes and there is also a limit to weight reduction.

[0003] Therefore, in recent years, as an exterior material for power storage devices that can be easily processed into various shapes and can achieve thinning and weight reduction, a laminated sheet in which a base material layer / an adhesive layer / a barrier layer / a heat-sealable resin layer are sequentially laminated has been proposed. When using such a film-like exterior material for power storage devices, with the heat-sealable resin layers located in the innermost layer of the exterior material for power storage devices facing each other, the peripheral portion of the exterior material for power storage devices is heat-sealed by heat sealing, whereby the power storage device elements are sealed by the exterior material for power storage devices.

[0004] Metal terminals protrude from the heat-sealed portion of the exterior material for the power storage device, and the power storage device element sealed by the exterior material for the power storage device is electrically connected to the outside by the metal terminals electrically connected to the electrodes of the power storage device element. That is, among the portions where the exterior material for the power storage device is heat-sealed, the portions where the metal terminals are present are heat-sealed in a state where the metal terminals are sandwiched by the heat-fusible resin layer. Since the metal terminals and the heat-fusible resin layer are made of different materials from each other, the adhesion is likely to decrease at the interface between the metal terminals and the heat-fusible resin layer.

[0005] For this reason, an adhesive film may be disposed between the metal terminals and the heat-fusible resin layer for the purpose of enhancing their adhesion.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Such an adhesive film is required to have high adhesion to the exterior material for the power storage device and the metal terminals.

[0008] Incidentally, in the step of bonding a metal terminal and an exterior member for a power storage device via an adhesive film, for example, it is common for heating and pressurization to be performed multiple times, such as in a temporary bonding step to the metal terminal and a main bonding step. The temporary bonding step is a step of temporarily fixing the adhesive film to the metal terminal and removing air bubbles, and the main bonding step is a step of heating and pressurizing one or more times under higher temperature conditions than the temporary bonding step to bond the adhesive film to the metal terminal. As a result of investigations by the present inventors, it has become clear that if heating and pressurization are performed on the adhesive film up to the main bonding step and further heating and pressurization are performed in the main bonding step, the adhesion strength of the adhesive film to the metal terminal may decrease due to the influence of multiple heating and pressurization. Depending on the degree of decrease in adhesion strength, the adhesion strength between the exterior member for a power storage device and the metal terminal via the adhesive film may become insufficient.

[0009] Under such circumstances, the main object of the present disclosure is to provide an adhesive film for a metal terminal that exhibits high adhesion strength to the metal terminal when multiple heating and pressurization are performed before being bonded to the metal terminal. Furthermore, it is also an object of the present disclosure to provide a metal terminal with an adhesive film for a metal terminal, a power storage device using the adhesive film for a metal terminal, and a method for manufacturing the power storage device.

Means for Solving the Problems

[0010] The inventors of the present disclosure conducted intensive studies to solve the above problems. As a result, after standing still for 12 seconds in a heating and pressurization environment of a temperature of 180°C and a surface pressure of 0.0067 MPa, and further standing still for 1 hour in an environment of a temperature of 25°C, it was found that an adhesive film for a metal terminal having a tensile elastic modulus measured in an environment of a temperature of 25°C equal to or higher than a predetermined value exhibits high adhesion strength to the metal terminal when multiple heating and pressurization are performed before being bonded to the metal terminal. The present disclosure was completed by further studies based on such findings.

[0011] That is, the present disclosure provides an invention in the following aspects. A pressure-sensitive adhesive film for a metal terminal interposed between a metal terminal electrically connected to an electrode of a power storage device element and an exterior material for a power storage device that seals the power storage device element, the pressure-sensitive adhesive film for a metal terminal has a tensile elastic modulus A measured in an environment of 25° C. of 490 MPa or more after being allowed to stand for 12 seconds in a heating and pressurizing environment of a temperature of 180° C. and a surface pressure of 0.0067 MPa and further being allowed to stand for 1 hour in an environment of 25° C.

Advantages of the Invention

[0012] According to the present disclosure, it is possible to provide a pressure-sensitive adhesive film for a metal terminal that exhibits high adhesion strength to a metal terminal when the metal terminal is heated and pressurized a plurality of times before being adhered thereto. Further, according to the present disclosure, it is also possible to provide a metal terminal with the pressure-sensitive adhesive film for a metal terminal, a power storage device using the pressure-sensitive adhesive film for a metal terminal, and a method for manufacturing a power storage device.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0014] The adhesive film for metal terminals of the present disclosure is an adhesive film for metal terminals interposed between a metal terminal electrically connected to an electrode of a power storage device element and an exterior material for a power storage device that seals the power storage device element. The adhesive film for metal terminals of the present disclosure is characterized in that the tensile elastic modulus A measured in an environment of 25°C is 490 MPa or more after being left standing for 12 seconds in a heating and pressurizing environment of a temperature of 180°C and a surface pressure of 0.0067 MPa, and further left standing for 1 hour in an environment of 25°C. The treatment of leaving standing for 12 seconds in a heating and pressurizing environment of a temperature of 180°C and a surface pressure of 0.0067 MPa is a treatment assuming the heat and pressure applied in the above-mentioned temporary adhesion step and main adhesion step.

[0015] According to the adhesive film for metal terminals of the present disclosure, since the tensile elastic modulus after the heating and pressurizing environment is set to 490 MPa or more, when heating and pressurizing are performed a plurality of times before being adhered to the metal terminal, high adhesion strength can be exhibited with respect to the metal terminal.

[0016] In addition, the energy storage device of the present disclosure includes at least an energy storage device element including a positive electrode, a negative electrode, and an electrolyte, an exterior material for the energy storage device that seals the energy storage device element, and metal terminals that are electrically connected to each of the positive electrode and the negative electrode and protrude outside the exterior material for the energy storage device, and is characterized in that the adhesive film for the metal terminal of the present disclosure is interposed between the metal terminal and the exterior material for the energy storage device. Hereinafter, the adhesive film for the metal terminal of the present disclosure, the energy storage device using the adhesive film for the metal terminal, and the manufacturing method of the energy storage device will be described in detail.

[0017] In this specification, for numerical ranges, the numerical range indicated by "~" means "above" and "below". For example, the notation of 2~15 mm means 2 mm or more and 15 mm or less.

[0018] 1. Adhesive film for metal terminals The adhesive film for the metal terminal of the present disclosure is interposed between a metal terminal electrically connected to an electrode of an energy storage device element and an exterior material for the energy storage device that seals the energy storage device element. Specifically, for example, as shown in FIGS. 1 to 3, the adhesive film 1 for the metal terminal of the present disclosure is interposed between a metal terminal 2 electrically connected to an electrode of an energy storage device element 4 and an exterior material 3 for the energy storage device that seals the energy storage device element 4. Further, the metal terminal 2 protrudes outside the exterior material 3 for the energy storage device, and is sandwiched between the exterior material 3 for the energy storage device and the adhesive film 1 for the metal terminal at the peripheral edge 3a of the heat-sealed exterior material 3 for the energy storage device. In the present disclosure, the heating temperature when heat-sealing the exterior material for the energy storage device is usually in the range of about 160 to 190°C, and the pressure is usually in the range of about 1.0 to 2.0 MPa. In addition, the temporary adhesion process of the adhesive film for the metal terminal to the metal terminal is performed, for example, under the conditions of a temperature of about 140 to 160°C, a pressure of about 0.01 to 1.0 MPa, a time of about 3 to 15 seconds, and a number of times of about 3 to 6 times. Further, the main adhesion process is performed, for example, under the conditions of a temperature of about 160 to 240°C, a pressure of about 0.01 to 1.0 MPa, a time of about 3 to 15 seconds, and a number of times of about 1 to 3 times.

[0019] The adhesive film 1 for metal terminals of the present disclosure is provided to enhance the adhesion between the metal terminal 2 and the exterior material 3 for the power storage device. By enhancing the adhesion between the metal terminal 2 and the exterior material 3 for the power storage device, the sealing performance of the power storage device element 4 is improved. As described above, when heat-sealing the power storage device element 4, the metal terminal 2 electrically connected to the electrode of the power storage device element 4 protrudes outside the exterior material 3 for the power storage device, and the power storage device element is sealed. At this time, since the metal terminal 2 formed of metal and the heat-sealing resin layer 35 (a layer formed of a heat-sealing resin such as polyolefin) located in the innermost layer of the exterior material 3 for the power storage device are made of different materials, if such an adhesive film is not used, the sealing performance of the power storage device element is likely to be low at the interface between the metal terminal 2 and the heat-sealing resin layer 35.

[0020] The adhesive film 1 for metal terminals of the present disclosure may be single-layered as shown in FIG. 4 or multi-layered as shown in FIGS. 5 to 7 as long as the tensile elastic modulus A described later is 490 MPa or more. The adhesive film 1 for metal terminals of the present disclosure is preferably multi-layered. When the adhesive film 1 for metal terminals of the present disclosure is multi-layered, as shown in FIGS. 5 to 7, it preferably includes a configuration in which at least the base material 11 and the first polyolefin layer 12a are laminated, and more preferably includes a configuration in which at least the first polyolefin layer 12a, the base material 11, and the second polyolefin layer 12b are laminated in this order as shown in FIGS. 6 and 7. Further, in the adhesive film 1 for metal terminals of the present disclosure, it is preferable that the first polyolefin layer 12a and the second polyolefin layer 12b are respectively located on the surfaces on both sides.

[0021] In the adhesive film 1 for metal terminals of the present disclosure, it is preferable that at least one of the first polyolefin layer 12a and the second polyolefin layer 12b contains an acid-modified polyolefin, and it is more preferable that both the first polyolefin layer 12a and the second polyolefin layer 12b contain an acid-modified polyolefin. Further, the base material 11 preferably contains a polyolefin. As will be described later, each of the first polyolefin layer 12a and the second polyolefin layer 12b is preferably an acid-modified polypropylene layer formed of acid-modified polypropylene. Also, the base material 11 is preferably a polypropylene layer formed of polypropylene.

[0022] Specific examples of the preferable laminated structure of the adhesive film 1 for metal terminals of the present disclosure include a two-layer structure of an acid-modified polypropylene layer / a polypropylene layer; a three-layer structure in which an acid-modified polypropylene layer / a polypropylene layer / an acid-modified polypropylene layer are laminated in this order; a five-layer structure in which an acid-modified polypropylene layer / a polypropylene layer / an acid-modified polypropylene layer / a polypropylene layer / an acid-modified polypropylene layer are laminated in this order, etc. Among these, a two-layer structure of an acid-modified polypropylene layer / a polypropylene layer; a three-layer structure in which an acid-modified polypropylene layer / a polypropylene layer / an acid-modified polypropylene layer are laminated in this order are more preferable, and a three-layer structure in which an acid-modified polypropylene layer / a polypropylene layer / an acid-modified polypropylene layer are laminated in this order is particularly preferable.

[0023] When the adhesive film 1 for metal terminals of the present disclosure is disposed between the metal terminal 2 of the power storage device 10 and the exterior material 3 for the power storage device, the surface of the metal terminal 2 made of metal and the heat-sealing resin layer 35 (a layer formed of a heat-sealing resin such as polyolefin) of the exterior material 3 for the power storage device are adhered via the adhesive film 1 for metal terminals.

[0024] The adhesive film 1 for metal terminals of the present disclosure has a tensile elastic modulus A measured at a temperature of 25°C, which is 490 MPa or more after standing for 12 seconds in a heating and pressurizing environment at a temperature of 180°C and a surface pressure of 0.0067 MPa, and further standing for 1 hour in an environment at a temperature of 25°C. From the viewpoint of exhibiting higher adhesion strength to the metal terminals when heated and pressurized multiple times before being adhered to the metal terminals, the tensile elastic modulus A is preferably about 520 MPa or more, more preferably about 550 MPa or more, still more preferably about 569 MPa or more, and still more preferably about 573 MPa or more. Regarding the upper limit of the tensile elastic modulus A, about 850 MPa or less is mentioned, and from the viewpoint of increasing the impact absorption energy described later, it is preferably about 800 MPa or less. From the viewpoint of obtaining an adhesive film 1 for metal terminals that is more excellent in flexibility (having good evaluation in the bending test described later), it is preferably about 680 MPa or less, more preferably about 610 MPa or less. Preferred ranges of the tensile elastic modulus A include about 490 to 850 MPa, about 490 to 800 MPa, about 490 to 680 MPa, about 490 to 610 MPa, about 520 to 850 MPa, about 520 to 800 MPa, about 520 to 680 MPa, about 520 to 610 MPa, about 550 to 850 MPa, about 550 to 800 MPa, about 550 to 680 MPa, about 550 to 610 MPa, about 569 to 850 MPa, about 569 to 800 MPa, about 569 to 680 MPa, about 569 to 610 MPa, about 573 to 850 MPa, about 573 to 800 MPa, about 573 to 680 MPa, about 573 to 610 MPa. From the viewpoint of obtaining an adhesive film 1 for metal terminals that exhibits high adhesion strength to the metal terminals and is overall good in terms of flexibility, rate of change in thickness, and impact absorption energy described later, the overall preferred range of the tensile elastic modulus A is about 500 to 550 MPa. The measuring method of the tensile elastic modulus A is as follows.

[0025] <Tensile elastic modulus A after heating and pressurizing> Under the conditions of a temperature of 180 °C and a surface pressure of 0.0067 MPa for 12 seconds, the tensile elastic modulus after heating and pressing is measured according to the following procedure. First, the adhesive film for metal terminals is cut into strips with a width (TD) of 15 mm and a length (MD) of 50 mm. Note that the MD and TD of the adhesive film for metal terminals can be determined by observing the sea-island structure of the cross-section in the thickness direction of the adhesive film for metal terminals. The shape of the islands observed in the cross-section in the MD direction is generally elongated compared to the cross-section in the TD direction. Next, with two tetrafluoroethylene-ethylene copolymer films (ETFE films, thickness 100 μm) sandwiching the adhesive film for metal terminals, it is placed on a hot plate heated to 180 °C, and a 500 g weight with a sponge is placed on it. After standing for 12 seconds, it is immediately left standing in an environment of 25 °C under atmospheric pressure for 1 hour to obtain a test piece. Next, in an environment of 25 °C under atmospheric pressure, using a tensilon universal material testing machine (for example, RTG-1210 manufactured by A&D Company), under the conditions of a tensile speed of 300 mm / min and a chuck distance of 30 mm, the stress-strain curve of the test piece is obtained, and the tensile elastic modulus A of the adhesive film for metal terminals after heating and pressing is determined from the slope of the straight line connecting two points with strains of 0.05% and 0.25%.

[0026] Before being exposed to a heat and pressure environment, the adhesive film 1 for metal terminals of the present disclosure has a tensile elastic modulus B measured in an environment at a temperature of 25°C, for example, of about 900 MPa or less, and preferably about 700 MPa or less from the viewpoint of obtaining an adhesive film 1 for metal terminals having excellent flexibility (good evaluation in the bending test described later). Further, from the viewpoint of increasing the stiffness of the adhesive film 1 for metal terminals and facilitating alignment with the metal terminals, the tensile elastic modulus B is preferably about 400 MPa or more. Preferred ranges of the tensile elastic modulus B include about 400 to 900 MPa and about 400 to 700 MPa, and among these, about 400 to 700 MPa is particularly preferred. From the viewpoint of obtaining an adhesive film 1 for metal terminals that exhibits high adhesion strength to the metal terminals and is overall good in terms of flexibility, rate of change in thickness, and impact absorption energy described later, the overall preferred range of the tensile elastic modulus B is 420 to 600 MPa, and more preferably 420 to 480 MPa. The method for measuring the tensile elastic modulus B is as follows.

[0027] <Tensile elastic modulus B before heating and pressurization> In accordance with the provisions of JIS K7161-1 (ISO527-1), measure the tensile elastic modulus B of the adhesive film for metal terminals (the adhesive film for metal terminals before performing the heating and pressurization in the <tensile elastic modulus A after heating and pressurization> described above) in a 25°C environment. Specifically, cut the adhesive film for metal terminals into a strip shape with a width (TD) of 15 mm and a length (MD) of 50 mm. Next, for the adhesive film for metal terminals, in a 25°C environment, using a tensilon universal material testing machine (for example, RTG-1210 manufactured by A&D Company), obtain the stress-strain curve of the test piece under the conditions of a tensile speed of 300 mm / min and a chuck distance of 30 mm, and determine the tensile elastic modulus B of the adhesive film for metal terminals before heating and pressurization from the slope of the straight line connecting two points of strain of 0.05% and 0.25%.

[0028] The tensile elastic modulus of the adhesive film 1 for metal terminals of the present disclosure can be adjusted by the laminate structure, melting point, MFR, thickness, thickness ratio of each layer, and further conditions such as T-die, inflation, etc. in the production of the adhesive film 1 for metal terminals (for example, extrusion width from the T-die, draw ratio, draw speed, heat treatment temperature, etc.).

[0029] From the viewpoint of obtaining an adhesive film 1 for metal terminals with excellent flexibility (good evaluation in the bending test described later), the difference in tensile elastic modulus, calculated by subtracting the value of the tensile elastic modulus B from the value of the tensile elastic modulus A of the adhesive film 1 for metal terminals of the present disclosure, is, for example, -250 to 200 MPa. From the viewpoint of exhibiting higher adhesion strength to the metal terminal when multiple heating and pressurization are performed before adhesion to the metal terminal, it is preferable that this difference is large, preferably 5 MPa or more, more preferably 20 MPa or more, and even more preferably 40 MPa or more. The upper limit of the difference in tensile elastic modulus is generally 120 MPa or less. Preferred ranges of the difference in tensile elastic modulus include about 5 to 120 MPa, about 20 to 120 MPa, and about 40 to 120 MPa. As the difference in tensile elastic modulus, from the viewpoint of obtaining an adhesive film 1 for metal terminals that exhibits high adhesion strength to the metal terminal and is overall good in terms of flexibility, rate of change in thickness, and impact absorption energy described later, the overall preferred range is about 40 to 75 MPa.

[0030] When multiple heatings and pressings are performed before being adhered to the metal terminal, from the viewpoint of exhibiting higher adhesion strength to the metal terminal, the adhesive film 1 for metal terminals of the present disclosure is a method compliant with the provisions of JIS K7127, and is obtained by performing a tensile test under the conditions of a temperature of 25°C, a tensile speed of 175 mm / min, and a chuck distance of 30 mm. The yield point stress obtained from the graph (stress-strain curve) showing the relationship between stress (MPa) and strain (mm) is preferably 17.0 MPa or more, more preferably 18.0 MPa or more, and is preferably 28.0 MPa or less, more preferably 26.0 MPa or less. The preferable range of the yield point stress includes about 17.0 to 28.0 MPa, about 17.0 to 26.0 MPa, about 18.0 to 28.0 MPa, about 18.0 to 26.0 MPa. Among these, about 18.0 to 26.0 MPa is particularly preferable. Further, the preferable range of the yield point stress in terms of overall adhesion, flexibility, and followability is about 17.0 to 18.0 MPa. The method for measuring the yield point stress is as follows.

[0031] <Yield point stress after heating and pressing> Based on the method compliant with the provisions of JIS K7127, the stress (yield point stress) at the yield point L (see the schematic diagram in FIG. 9) is obtained from the stress-strain curve obtained by performing a tensile test under the conditions of a temperature of 25°C, a tensile speed of 175 mm / min, and a chuck distance of 30 mm.

[0032] The yield point stress of the adhesive film 1 for metal terminals of the present disclosure can be adjusted by the laminated structure, the melting point of each layer, MFR, thickness, thickness ratio, and further, conditions such as T-die, inflation, etc. (for example, extrusion width from the T-die, draw ratio, draw speed, heat treatment temperature, etc.) in the production of the adhesive film 1 for metal terminals.

[0033] In addition, for the adhesive film 1 for metal terminals of the present disclosure, the rate of change in thickness before and after heating and pressing under the conditions of a temperature of 180°C and a surface pressure of 0.0067 MPa for 12 seconds is preferably close to 100% (that is, the change in thickness before and after heating and pressing is small or there is no change), specifically preferably 90 to 100%, more preferably 95 to 100%, and even more preferably 96 to 100%. When the rate of change in thickness is within these ranges, when the adhesive film 1 for metal terminals is thermally fused to the exterior material 10 for the power storage device, a large change in the thickness of the adhesive film 1 for metal terminals is suppressed, and voids are prevented from occurring between them. The rate of change in thickness is calculated by the formula: (thickness of the adhesive film for metal terminals after heating and pressing) / (thickness of the adhesive film for metal terminals before heating and pressing) × 100.

[0034] In addition, the impact absorption energy calculated from the area of the portion surrounded by the stress-strain curve obtained with the <tensile elastic modulus A after heating and pressing> is preferably about 90 MPa or more, more preferably about 140 MPa or more, and preferably about 400 MPa or less, more preferably about 300 MPa or less. A preferable range is about 90 to 400 MPa. A material with a small value of impact absorption energy is likely to break without significant deformation, and a material with a large value of impact absorption energy can be said to be a material that deforms greatly before breaking and is tough and does not easily crack.

[0035] The total thickness of the adhesive film 1 for metal terminals of the present disclosure is, from the viewpoint of enhancing the followability to the shape of the metal terminal 2, for example, about 120 μm or more, preferably about 140 μm or more, more preferably about 150 μm or more. Regarding the upper limit of the total thickness of the adhesive film 1 for metal terminals of the present disclosure, for example, about 200 μm can be mentioned. Preferred ranges of the total thickness of the adhesive film 1 for metal terminals of the present disclosure include about 120 to 200 μm, about 140 to 200 μm, and about 150 to 200 μm. Further, from the viewpoint of obtaining an adhesive film 1 for metal terminals that exhibits high adhesion strength to the metal terminal and is overall good in terms of flexibility, rate of change in thickness, and impact absorption energy, particularly preferably about 145 to 155 μm can be mentioned.

[0036] <When the adhesive film for metal terminals of the present disclosure is a single layer> When the adhesive film 1 for metal terminals of the present disclosure is a single layer, the adhesive film 1 for metal terminals of the present disclosure is preferably composed of a first polyolefin layer 12a having the physical properties described above.

[0037] <When the adhesive film for metal terminals of the present disclosure is a multilayer> When the adhesive film 1 for metal terminals of the present disclosure is a multilayer, the adhesive film 1 for metal terminals of the present disclosure preferably includes a structure in which at least a base material 11 and a first polyolefin layer 12a are laminated, and is a laminate having the above-described characteristics. Preferably, it includes a structure in which at least a first polyolefin layer 12a, a base material 11, and a second polyolefin layer 12b are laminated in this order, and is a laminate having the above-described characteristics.

[0038] Hereinafter, the base material 11, the first polyolefin layer 12a, and the second polyolefin layer 12b will be described in detail.

[0039] [Base material 11] In the adhesive film 1 for metal terminals, the base material 11 is a layer that functions as a support for the adhesive film 1 for metal terminals and is provided as needed.

[0040] The material for forming the base material 11 is not particularly limited. Examples of the material for forming the base material 11 include polyolefins, polyamides, polyesters, epoxy resins, acrylic resins, fluororesins, silicone resins, phenolic resins, polyetherimides, polyimides, polycarbonates, and mixtures and copolymers thereof. Among these, polyolefins are particularly preferred. That is, the material for forming the base material 11 is preferably a resin containing a polyolefin backbone such as polyolefin and acid-modified polyolefin. Whether the resin constituting the base material 11 contains a polyolefin backbone can be analyzed, for example, by infrared spectroscopy, gas chromatography-mass spectrometry, etc.

[0041] Specific examples of the polyolefin include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylene such as homopolypropylene, block copolymers of polypropylene (for example, block copolymers of propylene and ethylene), and random copolymers of polypropylene (for example, random copolymers of propylene and ethylene); terpolymers of ethylene-butene-propylene; and the like. Among these polyolefins, polyethylene and polypropylene are preferably mentioned, and polypropylene is more preferably mentioned.

[0042] Examples of the polyamide 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) containing structural units derived from terephthalic acid and / or isophthalic acid, and polyamides containing aromatics such as polymetaxylylene adipamide (MXD6); alicyclic polyamides such as polyaminomethylcyclohexyl adipamide (PACM6); furthermore, polyamides copolymerized with lactam components or isocyanate components such as 4,4'-diphenylmethane-diisocyanate, and polyester amide copolymers and polyether ester amide copolymers that are copolymers of copolymer polyamides with polyesters or polyalkylene ether glycols; and these copolymers and the like. These polyamides may be used alone or in combination of two or more kinds.

[0043] Examples of the polyester include, specifically, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, a copolymer polyester having ethylene terephthalate as a main repeating unit, a copolymer polyester having butylene terephthalate as a main repeating unit, and the like. Further, examples of the copolymer polyester having ethylene terephthalate as a main repeating unit include, specifically, a copolymer polyester obtained by polymerizing ethylene isophthalate with ethylene terephthalate as a main repeating unit (hereinafter abbreviated following polyethylene(terephthalate / isophthalate)), polyethylene(terephthalate / isophthalate), polyethylene(terephthalate / adipate), polyethylene(terephthalate / sodium sulfoisophthalate), polyethylene(terephthalate / sodium isophthalate), polyethylene(terephthalate / phenyl-dicarboxylate), polyethylene(terephthalate / decanedicarboxylate), and the like. Further, examples of the copolymer polyester having butylene terephthalate as a main repeating unit include, specifically, a copolymer polyester obtained by polymerizing butylene isophthalate with butylene terephthalate as a main repeating unit (hereinafter abbreviated following polybutylene(terephthalate / isophthalate)), polybutylene(terephthalate / adipate), polybutylene(terephthalate / sebacate), polybutylene(terephthalate / decanedicarboxylate), polybutylene naphthalate, and the like. These polyesters may be used alone or in combination of two or more kinds.

[0044] Further, the base material 11 may be formed of a nonwoven fabric made of the above resin. When the base material 11 is a nonwoven fabric, the base material 11 is preferably composed of the aforementioned polyolefin, polyamide, or the like.

[0045] Further, by blending a colorant into the base material 11, the base material 11 can also be made into a layer containing the colorant. Also, a resin with low transparency can be selected to adjust the light transmittance. When the base material 11 is a film, a colored film or a film with low transparency can also be used. Further, when the base material 11 is a nonwoven fabric, a nonwoven fabric using fibers or a binder containing a colorant or a nonwoven fabric with low transparency can be used.

[0046] From the viewpoint of exhibiting higher adhesion strength to the metal terminal when the melt mass flow rate (MFR) of the base material 11 at 230°C satisfies the above-described characteristics and multiple heating and pressurization operations are performed until it is adhered to the metal terminal, it is preferably 8 g / 10 min or less, more preferably 4 g / 10 min or less. Also, from the viewpoint of obtaining an adhesive film 1 for metal terminals having excellent flexibility (good evaluation in the bending test described later), it is preferably 1 g / 10 min or more, more preferably 2 g / 10 min or more. Preferred ranges include about 1 to 8 g / 10 min, about 1 to 4 g / 10 min, about 2 to 8 g / 10 min, and about 2 to 4 g / 10 min. When the base material layer 11 is a polyolefin layer (a layer formed of polyolefin), it is particularly preferable that the MFR value of the polyolefin layer satisfies the above values. The melt mass flow rate (MFR) of the base material 11 is the value (g / 10 min) at 230°C measured in accordance with the provisions of JIS K7210-1:2014 (ISO 1133-1:2011).

[0047] Also, from the viewpoint of exhibiting higher adhesion strength to the metal terminal when the melting point of the base material 11 satisfies the above-described characteristics and multiple heating and pressurization operations are performed until it is adhered to the metal terminal, it is preferably 130°C or higher, more preferably 150°C or higher. Also, from the viewpoint of obtaining an adhesive film 1 for metal terminals having excellent flexibility (good evaluation in the bending test described later), it is preferably 190°C or lower, more preferably 170°C or lower. Preferred ranges include about 130 to 190°C and about 150 to 170°C. The melting point of the base material 11 is measured by the method described in the examples.

[0048] When the base material 11 is composed of a resin film, known adhesion - promoting means such as corona discharge treatment, ozone treatment, plasma treatment, etc. may be applied to the surface of the base material 11 as necessary.

[0049] Regarding the thickness of the base material 11, from the viewpoint of exhibiting higher adhesion strength to the metal terminal when multiple heating and pressing operations are performed until it is adhered to the metal terminal, it is preferably about 50 μm or more, more preferably about 60 μm or more, still more preferably about 80 μm or more, and even more preferably about 90 μm or more. Also, it is preferably about 150 μm or less, more preferably about 130 μm or less, still more preferably about 120 μm or less. Preferred ranges include about 50 - 150 μm, about 50 - 130 μm, about 50 - 120 μm, about 60 - 150 μm, about 60 - 130 μm, about 60 - 120 μm, about 80 - 150 μm, about 80 - 130 μm, about 80 - 120 μm, about 90 - 150 μm, about 90 - 130 μm, about 90 - 120 μm. Among these, about 90 - 120 μm is particularly preferred.

[0050] [First and Second Polyolefin Layers 12a, 12b] The adhesive film 1 for metal terminals of the present disclosure preferably includes a first polyolefin layer 12a. When the adhesive film 1 for metal terminals of the present disclosure is composed of a single layer, the adhesive film 1 for metal terminals is preferably composed of the first polyolefin layer 12a as shown in FIG. 4. Also, when the adhesive film 1 for metal terminals of the present disclosure is a multi - layer, it preferably includes a structure in which at least the base material 11 and the first polyolefin layer 12a are laminated. More preferably, as shown in FIGS. 6 and 7, it includes a structure in which at least the first polyolefin layer 12a, the base material 11, and the second polyolefin layer 12b are laminated in this order. Further, in the adhesive film 1 for metal terminals of the present disclosure, it is preferable that the first polyolefin layer 12a and the second polyolefin layer 12b are respectively located on the surfaces on both sides.

[0051] Further, at least one of the first polyolefin layer 12a and the second polyolefin layer 12b preferably contains an acid-modified polyolefin, and more preferably both the first polyolefin layer 12a and the second polyolefin layer 12b contain an acid-modified polyolefin. When at least one of the first and second polyolefin layers 12a and 12b is formed of an acid-modified polyolefin, there are cases where one of the first and second polyolefin layers 12a and 12b is formed of an acid-modified polyolefin and the other is formed of a polyolefin, and cases where both the first and second polyolefin layers 12a and 12b are formed of an acid-modified polyolefin. Acid-modified polyolefins have a high affinity with heat-sealable resins such as metals and polyolefins. Also, polyolefins have a high affinity with heat-sealable resins such as polyolefins. Therefore, in the adhesive film 1 for metal terminals of the present disclosure, by disposing the layer formed of an acid-modified polyolefin on the side of the metal terminal 2, excellent adhesion can be exhibited at the interface between the adhesive film 1 for metal terminals, the metal terminal 2, and the heat-sealable resin layer 35. Further, by disposing the layer formed of a polyolefin on the side of the heat-sealable resin layer 35 of the exterior material 10 for the power storage device, even more excellent adhesion can be exhibited at the interface between the adhesive film 1 for metal terminals and the heat-sealable resin layer 35.

[0052] The adhesive film 1 for metal terminals is preferably a laminate sequentially comprising a first polyolefin layer 12a, a base material 11, and a second polyolefin layer 12b. As shown in FIGS. 6 and 7, for example, the adhesive film 1 for metal terminals has a laminated structure in which the first polyolefin layer 12a / base material 11 / second polyolefin layer 12b are laminated in this order. As described above, the adhesive film 1 for metal terminals particularly preferably has a three-layer structure in which an acid-modified polypropylene layer / polypropylene layer / acid-modified polypropylene layer are laminated in this order, or a three-layer structure in which a polypropylene layer / polypropylene layer / acid-modified polypropylene layer are laminated in this order. When the adhesive film 1 for metal terminals has a three-layer structure in which a polypropylene layer / polypropylene layer / acid-modified polypropylene layer are laminated in this order, the acid-modified polypropylene layer constituting one surface is disposed on the side of the metal terminal 2, and the polypropylene layer constituting the other surface is disposed on the side of the heat-sealable resin layer 35 of the exterior material 10 for the power storage device. Thus, the adhesive film 1 for metal terminals can be particularly suitably adhered between the exterior material 10 for the power storage device and the metal terminal 2.

[0053] In the first and second polyolefin layers 12a and 12b, the acid-modified polyolefin is not particularly limited as long as it is an acid-modified polyolefin, but preferably includes a polyolefin graft-modified with an unsaturated carboxylic acid or its anhydride.

[0054] Specific examples of the polyolefin to be acid-modified include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylene 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); and terpolymers of ethylene-butene-propylene. Among these polyolefins, polyethylene and polypropylene are preferred.

[0055] Further, the polyolefin to be acid-modified may be a cyclic polyolefin. For example, a carboxylic acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin by replacing it with an α,β-unsaturated carboxylic acid or its anhydride, or by block-polymerizing or graft-polymerizing an α,β-unsaturated carboxylic acid or its anhydride to the cyclic polyolefin.

[0056] The cyclic polyolefin to be acid-modified is a copolymer of an olefin and a cyclic monomer. Examples of the olefin that is a constituent monomer of the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, isoprene, and the like. Examples of the cyclic monomer that is a constituent monomer of the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, norbornadiene, and the like. Among these polyolefins, cyclic alkenes are preferably used, and norbornene is more preferably used. Styrene may also be used as a constituent monomer.

[0057] Examples of the carboxylic acid or its anhydride used for acid modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, itaconic anhydride, and the like. When the first and second polyolefin layers 12a and 12b are each analyzed by infrared spectroscopy, it is preferable that a peak derived from maleic anhydride is detected. For example, when measuring a maleic anhydride-modified polyolefin by infrared spectroscopy, peaks derived from maleic anhydride are detected in the vicinity of a wave number of 1760 cm -1 and in the vicinity of a wave number of 1780 cm -1 . When the first and second polyolefin layers 12a and 12b are layers composed 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 may become small and not be detected. In that case, it can be analyzed by nuclear magnetic resonance spectroscopy.

[0058] When either one of the first and second polyolefin layers 12a and 12b is formed of a polyolefin, examples of the polyolefin include the same ones as those exemplified as the polyolefin to be acid-modified or the cyclic polyolefin to be acid-modified described above.

[0059] The first and second polyolefin layers 12a and 12b may each be formed of a single resin component alone, or may be formed of a blend polymer in which two or more resin components are combined. Further, the first and second polyolefin layers 12a and 12b may each be formed of only one layer, or may be formed of two or more layers with the same or different resin components.

[0060] Furthermore, the first and second polyolefin layers 12a and 12b may each contain a filler as needed. Since the filler functions as a spacer when the first and second polyolefin layers 12a and 12b contain the filler, it is possible to effectively suppress a short circuit between the metal terminal 2 and the barrier layer 33 of the exterior material 3 for the power storage device. Examples of the particle size of the filler include a range of about 0.1 to 35 μm, preferably about 5.0 to 30 μm, and more preferably about 10 to 25 μm. Also, examples of the content of the filler include about 5 to 30 parts by mass, more preferably about 10 to 20 parts by mass, respectively, with respect to 100 parts by mass of the resin component forming the first and second polyolefin layers 12a and 12b.

[0061] As the filler, either inorganic or organic filler can be used. Examples of the inorganic filler include carbon (carbon, graphite), silica, aluminum oxide, barium titanate, iron oxide, silicon carbide, zirconium oxide, zirconium silicate, magnesium oxide, titanium oxide, calcium aluminate, calcium hydroxide, aluminum hydroxide, magnesium hydroxide, calcium carbonate, etc. Examples of the organic filler include fluororesin, phenol resin, urea resin, epoxy resin, acrylic resin, benzoguanamine-formaldehyde condensate, melamine-formaldehyde condensate, polymethyl methacrylate crosslinked product, polyethylene crosslinked product, etc. From the viewpoints of shape stability, rigidity, and resistance to the content, aluminum oxide, silica, fluororesin, acrylic resin, and benzoguanamine-formaldehyde condensate are preferable, and among them, spherical aluminum oxide and silica are more preferable. As the method for mixing the filler into the resin components forming the first and second polyolefin layers 12a and 12b, a method of melt-blending the two in advance with a Banbury mixer or the like to make a masterbatch and then adjusting it to a predetermined mixing ratio, a method of directly mixing with the resin components, etc. can be adopted.

[0062] In addition, the first and second polyolefin layers 12a and 12b may each contain a pigment as necessary. As the pigment, various inorganic pigments can be used. As a specific example of the pigment, carbon (carbon, graphite) exemplified as the above filler can be preferably cited. Carbon (carbon, graphite) is a material generally used inside the power storage device and has no risk of elution into the electrolyte. Also, with an addition amount that provides a sufficient coloring effect without significantly inhibiting the adhesiveness due to a large coloring effect, it does not melt with heat and can increase the apparent melt viscosity of the added resin. Furthermore, it can prevent the pressure-applied part from becoming thin during heat adhesion (heat sealing), and can impart excellent sealing performance between the exterior material for the power storage device and the metal terminal.

[0063] When adding a pigment to the first and second polyolefin layers 12a and 12b, for example, when using carbon black with a particle size of about 0.03 μm, the addition amount is about 0.05 to 0.3 parts by mass, preferably about 0.1 to 0.2 parts by mass, respectively, based on 100 parts by mass of the resin component forming the first and second polyolefin layers 12a and 12b. By adding a pigment to the first and second polyolefin layers 12a and 12b, the presence or absence of the adhesive film 1 for metal terminals can be made detectable by a sensor or inspectable visually. When adding a filler and a pigment to the first and second polyolefin layers 12a and 12b, the filler and the pigment may be added to the same first and second polyolefin layers 12a and 12b, but from the viewpoint of not inhibiting the heat fusion property of the adhesive film 1 for metal terminals, it is preferable to add the filler and the pigment separately to the first and second polyolefin layers 12a and 12b.

[0064] The first and second polyolefin layers 12a and 12b can each be constituted by a polyolefin film or an acid-modified polyolefin film. When the first and second polyolefin layers 12a and 12b are constituted by a polyolefin film or an acid-modified polyolefin film, an adhesive film for metal terminals can be suitably manufactured by laminating a resin film formed of the above polyolefin or acid-modified polyolefin on the base material 11 using, for example, the dry lamination method. Also, an adhesive film for metal terminals can be suitably manufactured by extrusion-molding the resin constituting the first and second polyolefin layers 12a and 12b onto the base material 11.

[0065] The melt mass flow rate (MFR) of the first and second polyolefin layers 12a and 12b at 230°C is preferably about 5 g / 10 min or more, more preferably about 7 g / 10 min or more, still more preferably about 8 g / 10 min or more, from the viewpoint of enhancing the followability to the shape of the metal terminal while satisfying the above-described characteristics. Also, it is preferably about 11 g / 10 min or less, more preferably about 10 g / 10 min or less. Preferred ranges include about 5 to 11 g / 10 min, about 5 to 10 g / 10 min, about 7 to 11 g / 10 min, about 7 to 10 g / 10 min, about 8 to 11 g / 10 min, and about 8 to 10 g / 10 min. The melt mass flow rate (MFR) of the first and second polyolefin layers 12a and 12b is the value (g / 10 min) at 230°C measured in accordance with the provisions of JIS K7210-1:2014 (ISO 1133-1:2011). When at least one of the first and second polyolefin layers 12a and 12b is an acid-modified polyolefin layer, it is particularly preferable that the MFR value of the acid-modified polyolefin layer satisfies the above values.

[0066] Also, the melting point of the first and second polyolefin layers 12a and 12b is preferably about 120°C or higher, more preferably about 130°C or higher, from the viewpoint of enhancing the followability to the shape of the metal terminal while satisfying the above-described characteristics. Also, it is preferably about 160°C or lower, more preferably about 150°C or lower. Preferred ranges include about 120 to 160°C, about 120 to 150°C, about 130 to 160°C, and about 130 to 150°C. The melting point of the first and second polyolefin layers 12a and 12b is measured by the method described in the examples.

[0067] When laminating the first and second polyolefin layers 12a and 12b made of a resin film on the surface of the base material 11, known adhesion-promoting means such as corona discharge treatment, ozone treatment, and plasma treatment may be applied to the surfaces of the first and second polyolefin layers 12a and 12b on the side of the base material 11 as needed. In particular, due to the corona discharge treatment, the adhesion between the base material 11 and the first polyolefin layer 12a and the second polyolefin layer 12b is enhanced, and excellent sealing performance can be imparted between the exterior material for the power storage device and the metal terminal.

[0068] From the viewpoint of exhibiting higher adhesion strength to the metal terminal when multiple heating and pressurization operations are performed until the first and second polyolefin layers 12a and 12b are adhered to the metal terminal, the thickness of the first and second polyolefin layers 12a and 12b is preferably about 10 μm or more, more preferably about 15 μm or more, and is preferably about 50 μm or less, more preferably about 45 μm or less, and even more preferably 30 μm or less. Preferred ranges for the thickness of the first and second polyolefin layers 12a and 12b include about 10 to 50 μm, about 10 to 45 μm, about 10 to 30 μm, about 15 to 50 μm, about 15 to 45 μm, and about 10 to 30 μm, respectively. Among these, 10 to 30 μm is particularly preferred.

[0069] The ratio of the thickness of the base material 11 to the total thickness of the first and second polyolefin layers 12a and 12b is preferably about 0.7 or more, more preferably about 1.0 or more, from the viewpoint of exhibiting higher adhesion strength to the metal terminal when heating and pressing are performed a plurality of times until it is adhered to the metal terminal while satisfying the above-described characteristics. Also, it is preferably about 4.0 or less, more preferably about 2.0 or less. Preferred ranges include about 0.7 to 4.0, about 0.7 to 2.0, about 1.0 to 4.0, and about 1.0 to 2.0. Among these, about 1.0 to 4.0 is particularly preferable. In particular, when at least one of the first and second polyolefin layers 12a and 12b is an acid-modified polypropylene layer, when the ratio of the thickness of the acid-modified polypropylene layer in the adhesive film 1 for metal terminals satisfies these values, a decrease in water vapor barrier properties is suppressed. When the decrease in water vapor barrier properties is suppressed, a long life and long-term stability of the power storage device are expected. From such a viewpoint as well, the ratio is preferably the above upper limit.

[0070] Also, assuming the total thickness of the adhesive film 1 for metal terminals is 100%, the ratio of the total thickness of the first and second polyolefin layers 12a and 12b is preferably about 15 to 60%, more preferably about 20 to 40%.

[0071] [Adhesion promoter layer 13] The adhesion promoter layer 13 is a layer provided as necessary for the purpose of firmly adhering the base material 11 and the first and second polyolefin layers 12a and 12b (see FIG. 7). The adhesion promoter layer 13 may be provided only on one side between the base material 11 and the first and second polyolefin layers 12a and 12b, or may be provided on both sides.

[0072] Subsequently, the adhesion promoter layer 13 can be formed using known adhesion promoters such as isocyanate-based, polyethyleneimine-based, polyester-based, polyurethane-based, polybutadiene-based, etc. From the perspective of further improving the electrolytic solution resistance, among these, it is preferably formed by an isocyanate-based adhesion promoter. As the isocyanate-based adhesion promoter, those composed of isocyanate components selected from triisocyanate monomers and polymeric MDI are excellent in laminate strength and have little decrease in laminate strength after immersion in the electrolytic solution. In particular, it is particularly preferable to form it with an adhesion promoter composed of triphenylmethane-4,4',4"-triisocyanate which is a triisocyanate monomer or polymethylene polyphenyl polyisocyanate (NCO content is about 30%, viscosity is 200 - 700 mPa·s) which is polymeric MDI. Also, it is also preferable to form it with tris(p-isocyanatophenyl) thiophosphate which is a triisocyanate monomer or a two-component curing type adhesion promoter with polyethyleneimine-based as the main agent and polycarbodiimide as the crosslinking agent.

[0073] The adhesion promoter layer 13 can be formed by coating and drying using known coating methods such as bar coating method, roll coating method, gravure coating method, etc. As the coating amount of the adhesion promoter, in the case of an adhesion promoter composed of triisocyanate, it is about 20 - 100 mg / m 2 preferably about 40 - 60 mg / m 2 in the case of an adhesion promoter composed of polymeric MDI, it is about 40 - 150 mg / m 2 preferably about 60 - 100 mg / m 2 in the case of a two-component curing type adhesion promoter with polyethyleneimine-based as the main agent and polycarbodiimide as the crosslinking agent, it is about 5 - 50 mg / m 2 preferably about 10 - 30 mg / m 2 Note that a triisocyanate monomer is a monomer having 3 isocyanate groups in one molecule, and polymeric MDI is a mixture of MDI and MDI oligomers polymerized from MDI, and is represented by the following formula.

[0074] [Chemical formula]

[0075] The adhesive film 1 for metal terminals of the present disclosure can be manufactured, for example, by laminating first and second polyolefin layers 12a and 12b on both surfaces of a base material 11, respectively. The lamination of the base material 11 and the first and second polyolefin layers 12a and 12b can be performed by a known method such as an extrusion lamination method or a thermal lamination method. Further, when the base material 11 and the first and second polyolefin layers 12a and 12 are laminated via an adhesion promoter layer 13, for example, the adhesion promoter constituting the adhesion promoter layer 13 is applied and dried on the base material 11 by the above method, and the first and second polyolefin layers 12a and 12b are laminated from above the adhesion promoter layer 13, respectively.

[0076] The method of interposing the adhesive film 1 for metal terminals between the metal terminal 2 and the exterior material 3 for a power storage device is not particularly limited. For example, as shown in FIGS. 1 to 3, in the portion where the metal terminal 2 is sandwiched by the exterior material 3 for a power storage device, the adhesive film 1 for metal terminals may be wound around the metal terminal 2. Although not shown, in the portion where the metal terminal 2 is sandwiched by the exterior material 3 for a power storage device, the adhesive film 1 for metal terminals may be arranged on both sides of the metal terminal 2 so as to cross the two metal terminals 2.

[0077] [Metal terminal 2] The adhesive film 1 for metal terminals of the present disclosure is used by being interposed between a metal terminal 2 and an exterior material 3 for a power storage device. The metal terminal 2 (tab) is a conductive member electrically connected to an electrode (positive electrode or negative electrode) of a power storage device element 4 and is made of a metal material. The metal material constituting the metal terminal 2 is not particularly limited, and examples thereof include aluminum, nickel, and copper. For example, the metal terminal 2 connected to the positive electrode of a lithium-ion power storage device is usually made of aluminum or the like. Also, the metal terminal 2 connected to the negative electrode of a lithium-ion power storage device is usually made of copper, nickel, or the like.

[0078] From the viewpoint of enhancing the electrolytic solution resistance, it is preferable that the surface of the metal terminal 2 is subjected to a formation treatment. For example, when the metal terminal 2 is formed of aluminum, specific examples of the formation treatment include known methods of forming a corrosion-resistant film such as a phosphate, a chromate, a fluoride, or a triazine thiol compound. Among the methods of forming a corrosion-resistant film, a phosphating treatment using a composition composed of three components of a phenol resin, a chromium(III) fluoride compound, and phosphoric acid is preferable.

[0079] The size of the metal terminal 2 may be appropriately set according to the size of the power storage device to be used and the like. The thickness of the metal terminal 2 is preferably about 50 to 1000 μm, more preferably about 70 to 800 μm. Also, the length of the metal terminal 2 is preferably about 1 to 200 mm, more preferably about 3 to 150 mm. Further, the width of the metal terminal 2 is preferably about 1 to 200 mm, more preferably about 3 to 150 mm.

[0080] [Exterior material 3 for power storage device] Examples of the exterior material 3 for the power storage device include those having a laminated structure composed of a laminate having at least a base material layer 31, a barrier layer 33, and a heat-sealable resin layer 35 in this order. Fig. 8 shows, as an example of the cross-sectional structure of the exterior material 3 for the power storage device, a mode in which a base material layer 31, an adhesive layer 32 provided as necessary, a barrier layer 33, an adhesive layer 34 provided as necessary, and a heat-sealable resin layer 35 are laminated in this order. In the exterior material 3 for the power storage device, the base material layer 31 is on the outer layer side and the heat-sealable resin layer 35 is on the innermost layer. When assembling the power storage device, the power storage device element 4 is sealed by bringing the heat-sealable resin layers 35 located at the peripheries of the power storage device element 4 into contact with each other and heat-sealing them. Figs. 1 to 3 illustrate the power storage device 10 when using the embossed type exterior material 3 for the power storage device formed by embossing or the like, but the exterior material 3 for the power storage device may be a non-formed pouch type. Note that among the pouch types, there are a three-side seal, a four-side seal, a pillow type, etc., and any type may be used.

[0081] The thickness of the laminate constituting the exterior material 3 for the power storage device is not particularly limited. However, from the viewpoints of cost reduction, improvement of energy density, etc., the upper limit is preferably about 180 μm or less, about 160 μm or less, about 155 μm or less, about 140 μm or less, about 130 μm or less, about 120 μm or less. From the viewpoint of maintaining the function of the exterior material 3 for the power storage device to protect the power storage device element 4, the lower limit is preferably about 35 μm or more, about 45 μm or more, about 60 μm or more, about 80 μm or more. Preferred ranges include, for example, about 35 to 180 μm, about 35 to 160 μm, about 35 to 155 μm, about 35 to 140 μm, about 35 to 130 μm, about 35 to 120 μm, about 45 to 180 μm, about 45 to 160 μm, about 45 to 155 μm, about 45 to 140 μm, about 45 to 130 μm, about 45 to 120 μm, about 60 to 180 μm, about 60 to 160 μm, about 60 to 155 μm, about 60 to 140 μm, about 60 to 130 μm, about 60 to 120 μm, about 80 to 180 μm, about 80 to 160 μm, about 80 to 155 μm, about 80 to 140 μm, about 80 to 130 μm, about 80 to 120 μm.

[0082] (Base material layer 31) In the exterior material 3 for the power storage device, the base material layer 31 is a layer that functions as the base material of the exterior material for the power storage device and is the layer that forms the outermost layer side.

[0083] The material for forming the base material layer 31 is not particularly limited as long as it has insulating properties. Examples of the material for forming the base material layer 31 include polyester, polyamide, epoxy, acrylic, fluororesin, polyurethane, silicone resin, phenol, polyetherimide, polyimide, and mixtures and copolymers thereof. Polyesters such as polyethylene terephthalate and polybutylene terephthalate have excellent electrolyte resistance and the advantage that whitening and the like are unlikely to occur due to the adhesion of the electrolyte, and are preferably used as the material for forming the base material layer 31. In addition, the polyamide film has excellent stretchability and can prevent the occurrence of whitening due to resin cracking of the base material layer 31 during molding, and is preferably used as the material for forming the base material layer 31.

[0084] The base material layer 31 may be formed of a uniaxially or biaxially stretched resin film, or may be formed of an unstretched resin film. Among them, a uniaxially or biaxially stretched resin film, particularly a biaxially stretched resin film, is preferably used as the base material layer 31 because its heat resistance is improved by orientation crystallization.

[0085] Among these, preferred examples of the resin film forming the base material layer 31 include nylon and polyester, and more preferably biaxially stretched nylon and biaxially stretched polyester.

[0086] In order to improve the pinhole resistance and insulation properties when the base material layer 31 is used as a package of the energy storage device, it is also possible to laminate resin films of different materials. Specifically, examples include a multilayer structure in which a polyester film and a nylon film are laminated, and a multilayer structure in which biaxially stretched polyester and biaxially stretched nylon are laminated. When the base material layer 31 has a multilayer structure, each resin film may be adhered via an adhesive, or may be directly laminated without an adhesive. When adhering without an adhesive, for example, methods of adhering in a thermally melted state such as a coextrusion method, a sand laminating method, and a thermal laminating method can be mentioned.

[0087] Also, the base material layer 31 may be made to have a low friction coefficient in order to improve its formability. When the base material layer 31 is made to have a low friction coefficient, the friction coefficient of its surface is not particularly limited, but for example, 1.0 or less can be mentioned. To make the base material layer 31 have a low friction coefficient, for example, mat treatment, formation of a thin film layer of a slip agent, and combinations thereof can be mentioned.

[0088] Regarding the thickness of the base material layer 31, for example, it is about 10 to 50 μm, preferably about 15 to 30 μm.

[0089] (Adhesive layer 32) In the exterior material 3 for a power storage device, the adhesive layer 32 is a layer disposed on the base material layer 31 as needed in order to impart adhesiveness to the base material layer 31. That is, the adhesive layer 32 is provided between the base material layer 31 and the barrier layer 33.

[0090] The adhesive layer 32 is formed of an adhesive capable of bonding the base material layer 31 and the barrier layer 33. The adhesive used for forming the adhesive layer 32 may be a two-component curable adhesive or a one-component curable adhesive. Also, the adhesion mechanism of the adhesive used for forming the adhesive layer 32 is not particularly limited, and any of a chemical reaction type, a solvent evaporation type, a hot melt type, a hot press type, etc. may be used.

[0091] As the resin component of the adhesive that can be used for forming the adhesive layer 32, it has excellent spreadability, durability under high humidity conditions, yellowing suppression effect, heat deterioration suppression effect during heat sealing, etc., and from the viewpoint of suppressing a decrease in the laminate strength between the base material layer 31 and the barrier layer 33 and effectively suppressing the occurrence of delamination, preferably a two-component curable polyurethane-based adhesive; polyamide, polyester, or a blend resin of these and a modified polyolefin can be mentioned.

[0092] Also, the adhesive layer 32 may be multi-layered with different adhesive components. When the adhesive layer 32 is multi-layered with different adhesive components, from the viewpoint of improving the laminate strength between the base material layer 31 and the barrier layer 33, a resin excellent in adhesiveness to the base material layer 31 is selected as the adhesive component arranged on the base material layer 31 side, and an adhesive component excellent in adhesiveness to the barrier layer 33 is selected as the adhesive component arranged on the barrier layer 33 side. When the adhesive layer 32 is multi-layered with different adhesive components, specifically, as the adhesive component arranged on the barrier layer 33 side, preferably, an acid-modified polyolefin, a metal-modified polyolefin, a mixed resin of polyester and an acid-modified polyolefin, a resin containing a copolymerized polyester, etc. can be mentioned.

[0093] Regarding the thickness of the adhesive layer 32, for example, it is about 2 to 50 μm, preferably about 3 to 25 μm.

[0094] (Barrier layer 33) In the exterior material for a power storage device, the barrier layer 33 is a layer that has a function of preventing water vapor, oxygen, light, etc. from entering the inside of the power storage device in addition to improving the strength of the exterior material for the power storage device. The barrier layer 33 is preferably a metal layer, that is, a layer formed of a metal. Specifically, examples of the metal constituting the barrier layer 33 include aluminum, stainless steel, titanium, etc., and preferably aluminum. The barrier layer 33 can be formed by, for example, a metal foil, a metal vapor deposition film, an inorganic oxide vapor deposition film, a carbon-containing inorganic oxide vapor deposition film, a film provided with these vapor deposition films, etc., and is preferably formed by a metal foil, and more preferably formed by an aluminum foil. From the viewpoint of preventing wrinkles and pinholes from occurring in the barrier layer 33 during the manufacture of the exterior material for the power storage device, the barrier layer is, for example, annealed aluminum (JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, JIS H4000:2014 A8079P-O), etc., and is more preferably formed by a soft aluminum foil.

[0095] Regarding the thickness of the barrier layer 33, from the viewpoint of making the exterior material for the power storage device thinner and making it difficult for pinholes to occur during molding, it is preferably about 10 to 200 μm, and more preferably about 20 to 100 μm.

[0096] Also, the barrier layer 33 is preferably subjected to a chemical conversion treatment on at least one surface, preferably both surfaces, for the purpose of stabilizing adhesion, preventing dissolution and corrosion, etc. Here, the chemical conversion treatment refers to a treatment for forming a corrosion-resistant film on the surface of the barrier layer.

[0097] (Adhesive layer 34) In the exterior material 3 for a power storage device, the adhesive layer 34 is a layer provided between the barrier layer 33 and the heat-sealable resin layer 35 as needed in order to firmly adhere the heat-sealable resin layer 35.

[0098] The subsequent layer 34 is formed by an adhesive capable of bonding the barrier layer 33 and the heat-fusible resin layer 35. The composition of the adhesive used for forming the adhesive layer is not particularly limited, and examples thereof include resin compositions containing acid-modified polyolefins. Examples of the acid-modified polyolefins can be the same ones as those exemplified for the first and second polyolefin layers 12a and 12b.

[0099] Regarding the thickness of the adhesive layer 34, for example, it is about 1 to 40 μm, preferably about 2 to 30 μm.

[0100] (Heat-fusible resin layer 35) In the exterior material 3 for the power storage device, the heat-fusible resin layer 35 corresponds to the innermost layer and is a layer in which the heat-fusible resin layers are heat-fused to seal the power storage device element during the assembly of the power storage device.

[0101] The resin component used for the heat-fusible resin layer 35 is not particularly limited as long as it can be heat-fused, and examples thereof include polyolefins and cyclic polyolefins.

[0102] Specific examples of the polyolefin include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylene 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); and terpolymers of ethylene-butene-propylene. Among these polyolefins, polyethylene and polypropylene are preferably mentioned.

[0103] The cyclic polyolefin is a copolymer of an olefin and a cyclic monomer. Examples of the olefin that is a constituent monomer of the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, isoprene, and the like. Examples of the cyclic monomer that is a constituent monomer of the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, cyclic alkenes are preferred, and norbornene is more preferred. Styrene is also included as a constituent monomer.

[0104] Among these resin components, crystalline or amorphous polyolefins, cyclic polyolefins, and blend polymers thereof are preferred; polyethylene, polypropylene, copolymers of ethylene and norbornene, and blend polymers of two or more of these are more preferred.

[0105] The heat-sealable resin layer 35 may be formed of a single resin component alone, or may be formed of a blend polymer combining two or more resin components. Further, the heat-sealable resin layer 35 may be formed of only one layer, but may also be formed of two or more layers of the same or different resin components.

[0106] Also, the thickness of the heat-sealable resin layer 35 is not particularly limited, but is about 2 to 2000 μm, preferably about 5 to 1000 μm, and more preferably about 10 to 500 μm.

[0107] 2. Energy storage device 10 The energy storage device 10 of the present disclosure includes at least an energy storage device element 4 including a positive electrode, a negative electrode, and an electrolyte, an exterior material 3 for the energy storage device that seals the energy storage device element 4, and metal terminals 2 that are electrically connected to the positive electrode and the negative electrode respectively and protrude outside the exterior material 3 for the energy storage device. In the energy storage device 10 of the present disclosure, the adhesive film 1 for the metal terminal of the present disclosure is interposed between the metal terminal 2 and the exterior material 3 for the energy storage device. That is, the energy storage device 10 of the present disclosure can be manufactured by a method including a step of interposing the adhesive film 1 for the metal terminal of the present disclosure between the metal terminal 2 and the exterior material 3 for the energy storage device.

[0108] Specifically, with an energy storage device element 4 including at least a positive electrode, a negative electrode, and an electrolyte, the adhesive film 1 for the metal terminal of the present disclosure is interposed between the metal terminal 2 and the heat-fusible resin layer 35 in a state where the metal terminals 2 connected to the positive electrode and the negative electrode respectively protrude outside, and the energy storage device element 4 is covered so that a flange portion of the exterior material for the energy storage device (a region where the heat-fusible resin layers 35 contact each other, and the peripheral portion 3a of the exterior material for the energy storage device) can be formed, and the heat-fusible resin layers 35 of the flange portion are heat-sealed and sealed, whereby the energy storage device 10 using the exterior material 3 for the energy storage device is provided. When the energy storage device element 4 is housed using the exterior material 3 for the energy storage device, the heat-fusible resin layer 35 of the exterior material 3 for the energy storage device is used so as to be on the inner side (the surface in contact with the energy storage device element 4).

[0109] The exterior material for a power storage device of the present disclosure can be suitably used for power storage devices such as batteries (including capacitors, capacitors, etc.). Further, the exterior material for a power storage device of the present disclosure can be used for either a primary battery or a secondary battery, but is preferably a secondary battery. The type of secondary battery to which the exterior material for a power storage device of 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-hydrogen storage batteries, nickel-cadmium storage batteries, nickel-iron storage batteries, nickel-zinc storage batteries, silver oxide-zinc storage batteries, metal-air batteries, polyvalent cation batteries, capacitors, capacitors, and the like. Among these secondary batteries, lithium-ion batteries and lithium-ion polymer batteries are mentioned as suitable application targets for the exterior material for a power storage device of the present disclosure.

Examples

[0110] Examples and comparative examples are shown below to explain the present disclosure in detail. However, the present disclosure is not limited to the examples.

[0111] Examples 1-16 and Comparative Examples 1-6 <Manufacture of Adhesive Film for Metal Terminals> A polypropylene layer having the melting point and MFR described in Table 1 and the thickness described in Table 2 was used as a base material (hereinafter sometimes referred to as "PP layer"). Also, maleic anhydride-modified polypropylene having the melting point and melt mass flow rate (MFR) described in Table 1 (hereinafter sometimes referred to as "PPa") was used as the first polyolefin layer (PPa layer) and the second polyolefin layer (PPa layer). For Examples 1 to 12 and Comparative Example 3, by using a T-die extruder to extrude two types of polypropylene and maleic anhydride-modified polypropylene in a three-layer extrusion, an adhesive film for metal terminals in which the PPa layer / PP layer / PPa layer was laminated in this order was obtained. Also, for Examples 13 to 16 and Comparative Examples 4 to 6, an adhesive film for metal terminals in which the PPa layer / PP layer / PPa layer was laminated in this order was obtained by the inflation method. Further, for Comparative Examples 1 and 2, maleic anhydride-modified polypropylene (PPa) was extruded on each side of a base material (PP layer) made of a polypropylene film (PP) using a T-die extruder, and an adhesive film for metal terminals in which the PPa layer / PP layer / PPa layer was laminated in this order was obtained. The thickness of each layer of the PPa layer / PP layer / PPa layer is as shown in Table 2.

[0112] Physical properties such as the tensile elastic modulus, yield stress at the lower yield point, water vapor barrier property, and rate of change in thickness of the adhesive film for metal terminals described in Table 2 were adjusted by the melting point, MFR, thickness, thickness ratio of the PPa layer and the PP layer, and further, conditions such as T-die and inflation in the production of the adhesive film for metal terminals 1 (for example, extrusion width from the T-die, draw ratio, draw speed, heat treatment temperature, etc.).

[0113] <Measurement of melting point> The melting points of the PP layer and the PPa layer described in Table 1 are the values measured by the following methods. The melting peak temperature was measured twice using a differential scanning calorimeter (DSC, Q200 differential scanning calorimeter manufactured by TA Instruments). Specifically, in accordance with the procedure of JIS K7121:2012 (Method for Measuring the Transition Temperature of Plastics (Addendum 1 to JIS K7121:1987)), by differential scanning calorimetry (DSC), the PP layer or the PPa layer was held at -20°C for 10 minutes, and then heated from -20°C to 250°C at a heating rate of 10°C / min to measure the first melting peak temperature P (°C). After that, it was held at 250°C for 10 minutes. Next, it was cooled from 250°C to -20°C at a cooling rate of 10°C / min and held for 10 minutes. Furthermore, it was heated from -20°C to 250°C at a heating rate of 10°C / min to measure the second melting peak temperature Q (°C). The flow rate of nitrogen gas was set to 50 ml / min. By the above procedure, the first measured melting peak temperature P (°C) and the second measured melting peak temperature Q (°C) were obtained, and the one with the maximum peak was taken as the melting point.

[0114] <Melt Mass Flow Rate (MFR)> The melt mass flow rates (MFR) of the PP layer and the PPa layer described in Table 1 are the values (g / 10 min) at 230°C measured in accordance with the provisions of JIS K7210-1:2014 (ISO 1133-1:2011).

[0115]

Table 1

[0116] <Tensile Modulus B before Heating and Pressurization> In accordance with the provisions of JIS K7161-1 (ISO527-1), the tensile modulus B of the adhesive film for metal terminals (the adhesive film for metal terminals before heat and pressure application in <Tensile Modulus A after Heat and Pressure Application> described below) at 25°C was measured. Specifically, each adhesive film for metal terminals obtained in the examples and comparative examples was cut into strips with a width (TD) of 15 mm and a length (MD) of 50 mm. Next, for the adhesive film for metal terminals, in an environment of 25°C, using a Tensilon universal material testing machine (RTG-1210 manufactured by A&D Company), under the conditions of a tensile speed of 300 mm / min and a chuck distance of 30 mm, the stress-strain curve of the test piece was obtained, and the tensile modulus B of the adhesive film for metal terminals before heat and pressure application was determined from the slope of the straight line connecting two points of strain 0.05% and 0.25%. The results are shown in Table 2.

[0117] <Tensile Modulus A after Heat and Pressure Application> Under the conditions of a temperature of 180°C and a surface pressure of 0.0067 MPa for 12 seconds, the tensile modulus after heat and pressure application was measured by the following procedure. First, each adhesive film for metal terminals obtained in the examples and comparative examples was cut into strips with a width (TD) of 15 mm and a length (MD) of 50 mm. Next, with the adhesive film for metal terminals sandwiched between two tetrafluoroethylene-ethylene copolymer films (ETFE films, thickness 100 μm), it was placed on a hot plate heated to 180°C, and a 500 g weight with a sponge was placed on it. After standing for 12 seconds, it was immediately left standing in an environment of 25°C under atmospheric pressure for 1 hour to obtain a test piece. Next, in an environment of 25°C under atmospheric pressure, using a Tensilon universal material testing machine (RTG-1210 manufactured by A&D Company), under the conditions of a tensile speed of 300 mm / min and a chuck distance of 30 mm, the stress-strain curve of the test piece was obtained, and the tensile modulus A of the adhesive film for metal terminals after heat and pressure application was determined from the slope of the straight line connecting two points of strain 0.05% and 0.25%. The results are shown in Table 2.

[0118] <Yield Stress after Heat and Pressure Application> A method in accordance with the provisions of JIS K7127, the stress (yield point stress) at the lower yield point L (see the schematic diagram in Fig. 9) was determined from the stress-strain curve obtained by performing a tensile test under the conditions of a temperature of 25°C, a tensile speed of 175 mm / min, and a chuck distance of 30 mm. The results are shown in Table 2.

[0119] <Water vapor barrier property (moisture content)> First, an exterior material for a power storage device (hereinafter, may be simply referred to as "exterior material") was produced by the following procedure. An aluminum alloy foil (thickness: 35 μm) was laminated on a base material layer (thickness: 25 μm) made of a nylon film by a dry lamination method. Specifically, a two-component urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to one surface of a barrier layer made of an aluminum alloy foil to form an adhesive layer (thickness: 3 μm) on the aluminum alloy foil. Next, after laminating the adhesive layer on the aluminum alloy foil and the base material layer, an aging treatment was performed to produce a laminate of the base material layer / adhesive layer / barrier layer. Next, an adhesive layer (thickness: 20 μm, arranged on the metal layer side) made of a maleic anhydride-modified polypropylene resin and a heat-sealable resin layer (thickness: 15 μm, innermost layer) made of a random polypropylene resin were co-extruded on the barrier layer of the laminate to laminate the adhesive layer / heat-sealable resin layer on the barrier layer. Next, the obtained laminate was heated at 190°C for 2 minutes to obtain an exterior material for a power storage device in which the base material layer, the adhesive layer, the barrier layer, the adhesive layer, and the heat-sealable resin layer were laminated in this order.

[0120] Next, as shown in the schematic diagram of FIG. 11, the obtained exterior material 3 was cut into a square with a length in the machine direction (MD) of 120 mm and a width in the transverse direction (TD) of 120 mm (FIG. 11a). Also, each adhesive film 1 for metal terminals obtained in the examples and comparative examples (hereinafter, may be simply referred to as "adhesive film") was cut into a rectangle with a length in the machine direction (MD) of 120 mm and a width in the transverse direction (TD) of 10 mm. With the heat-fusible resin layer on the inside, the exterior material 10 was bent in half in the longitudinal direction, and between them, two adhesive films for metal terminals were arranged so that the longitudinal and transverse directions were aligned, and a laminate in which the exterior material / adhesive film / adhesive film / exterior material was laminated in order was obtained (FIG. 11b). The adhesive films are arranged between the exterior materials 10 along the long side to be heat-sealed described later. Next, using a heat-sealing bar (stainless steel plate), at the positions of the long side and short side of the laminate, each layer of the laminate was heat-sealed to form a bag shape with one short side not heat-sealed. The heat-sealing conditions for the long side were as follows: using a heat-sealing bar with a width of 10 mm, a temperature of 190°C, a surface pressure of 1.0 MPa, for 3 seconds, once (s1 in FIG. 11c). For the short side, after heat-sealing once under the conditions of using a heat-sealing bar with a width of 7 m, a temperature of 190°C, a surface pressure of 2.0 MPa, and for 3 seconds, further, at a position 3 mm inside from the short side, using a heat-sealing bar with a width of 7 m, a temperature of 190°C, a surface pressure of 2.0 MPa, and for 3 seconds, heat-sealing was performed once. That is, for the short side 2, by shifting the position by 3 mm and heat-sealing twice, heat-sealing was performed so as to have a width of 10 mm (s2 in FIG. 11c). Next, the width of the heat-sealed portion in the long side direction was made 3 mm, and the heat-sealed portion was cut off along the long side direction and dried in a dry room for 1 day (FIG. 11d). Next, from the position of the short side that was not heat-sealed, about 3.0 g of a liquid of ethylene carbonate:diethyl carbonate:dimethyl carbonate = 1:1:1 (volume ratio) (moisture content 0%) was injected (FIG. 11e), and the short side that was not heat-sealed was also heat-sealed in the same manner as the above short side to form a sealed bag (FIG. 11f). This sealed bag was left standing in an environment of a temperature of 60°C and a relative humidity of 90% for 30 days, and then in a dry room, the moisture content of the liquid taken out from the sealed bag was measured by the Karl Fischer method. The results are shown in Table 2.

[0121] <Rate of change in thickness> Regarding the <tensile elastic modulus A after heating and pressurization>, for each adhesive film for metal terminals before and after heating and pressurization for 12 seconds under the conditions of a temperature of 180°C and a surface pressure of 0.0067 MPa, the rate of change in thickness was calculated from the formula of (thickness of the adhesive film for metal terminals after heating and pressurization) / (thickness of the adhesive film for metal terminals before heating and pressurization) × 100. The rate of change in thickness is the average value measured at three points in the MD direction of the adhesive film for metal terminals. The results are shown in Table 2.

[0122] <Measurement of Adhesion Strength between Adhesive Film for Metal Terminals and Metal Terminals> As the metal terminals, aluminum (JIS H4160:1994 A8079H-O) with a length of 50 mm, a width of 22.5 mm, and a thickness of 0.2 mm was prepared. Also, each adhesive film for metal terminals obtained in the examples and comparative examples was cut into a length of 45 mm and a width of 15 mm. Next, the adhesive film for metal terminals was placed on the metal terminals to obtain a laminate of metal terminals / adhesive film. At this time, the longitudinal and transverse directions of the metal terminals were made to coincide with the length and width directions of the adhesive film for metal terminals, respectively, and the laminate was made such that the centers of the metal terminals and the adhesive film for metal terminals coincided. Next, a tetrafluoroethylene-ethylene copolymer film (ETFE film, thickness 100 μm) was placed on the adhesive film for metal terminals of the laminate (covering the surface of the adhesive film for metal terminals with the ETFE film), and it was placed on a hot plate heated to 180°C (the metal terminals were on the hot plate side), and a 500 g weight with a sponge was placed on it, and it was left standing for 12 seconds to thermally fuse the adhesive film to the metal terminals (surface pressure 0.0067 MPa, contact area 300 mm 2)。The laminated body after heat fusion was naturally cooled to 25°C. Next, in an environment of 25°C, the adhesive film for metal terminals was peeled from the metal terminals using a Tensilon universal material testing machine (RTG-1210 manufactured by A&D Company). The maximum strength at the time of peeling was defined as the adhesion strength (N / 15 mm) to the metal terminals. The peeling speed was 175 mm / min, the peeling angle was 180°, the distance between chucks was 30 mm, and the average value of three measurements was taken. The treatment of standing still for 12 seconds in a heating and pressing environment at a temperature of 180°C and a surface pressure of 0.016 MPa was a treatment assuming the heat and pressure applied in the above-mentioned temporary adhesion step and main adhesion step. The results are shown in Table 2.

[0123] <Bending test> Each adhesive film for metal terminals obtained in the examples and comparative examples was cut into a size of 100 mm in the longitudinal direction (MD) and 15 mm in the transverse direction (TD). Using a mandrel testing machine (a metal rod with a diameter of 2 mm), it was wound around the adhesive film. At this time, it was wound so that the MD of the adhesive film for metal terminals was perpendicular to the metal rod of the mandrel testing machine. A bending test was performed in this state, and the adhesive film for metal terminals was visually observed and evaluated according to the following criteria. The results are shown in Table 2. A: There is no whitening in the wound part of the adhesive film for metal terminals, and it returns to its original shape after winding. B: There is no whitening in the wound part of the adhesive film for metal terminals, but it does not return to its original shape after winding and is curled. C: There is whitening in the wound part of the adhesive film for metal terminals.

[0124] <Followability evaluation 1 (adhesive film / metal terminal)> As the metal terminal, an aluminum foil (JIS H4160:1994 A8079H-O) with a thickness of 200 μm was prepared. Also, the adhesive films for each metal terminal obtained in the examples and comparative examples were prepared. Next, the metal terminal was sandwiched between two adhesive films to obtain a laminate of adhesive film / metal terminal / adhesive film. Next, while sandwiching the laminate with two tetrafluoroethylene-ethylene copolymer films (ETFE films, thickness 100 μm), it was placed on a hot plate heated to 180°C, and a 500 g weight with a sponge was placed on it, and left standing for 12 seconds to thermally fuse the adhesive film to the metal terminal (surface pressure 0.0067 MPa, contact area 300 mm 2 ). At this time, as shown in the schematic diagram of FIG. 10, the metal terminal was sandwiched by the adhesive film, so that the periphery of the metal terminal was covered by the adhesive film, and a portion where the two adhesive films were thermally fused to each other was formed. The laminate after thermal fusion was naturally cooled to 25°C, and the cross-section in the thickness direction was observed with a laser microscope, and the followability of the adhesive film for the metal terminal to the shape of the metal terminal was evaluated according to the following criteria. The results are shown in Table 2. A: There are no bubbles between the adhesive film for the metal terminal and the metal terminal B: There are no bubbles at the interface between the adhesive film for the metal terminal and the metal terminal, but there are bubbles in the adhesive film for the metal terminal in the vicinity of the interface C: There are bubbles at the interface between the adhesive film for the metal terminal and the metal terminal, and there are also bubbles in the adhesive film for the metal terminal in the vicinity of the interface

[0125] <Followability Evaluation 2 (Adhesive Film / Exterior Material)> First, in the same manner as the procedure described in the above-mentioned followability evaluation 1, a laminate of an adhesive film / metal terminal / adhesive film was produced. Next, the obtained laminate was sandwiched between two exterior materials, and in this state, using a heat-sealing tester, sealing was performed under the conditions of 180 °C, surface pressure of 1.0 MPa, and for 3 seconds, to obtain a laminate in which the exterior material and the adhesive film were heat-sealed together. The obtained laminate was naturally cooled to 25 °C, and the cross-section in the thickness direction was observed with a laser microscope, and the followability of the adhesive film for metal terminals to the shape of the exterior material of the power storage device was evaluated according to the following criteria. The results are shown in Table 2. A: There is no gap between the adhesive film for metal terminals and the exterior material of the power storage device B: There are fine gaps (with a diameter of 10 μm or less) between the adhesive film for metal terminals and the exterior material of the power storage device C: There are gaps (with a diameter exceeding 10 μm) between the adhesive film for metal terminals and the exterior material of the power storage device

[0126] <Impact absorption energy> The impact absorption energy was calculated from the area of the portion surrounded by the stress-strain curve obtained with the <tensile elastic modulus A after heating and pressurization>. The results are shown in Table 2.

[0127]

Table 2

[0128] In Table 2, the notation "-" means that it has not been measured.

[0129] The adhesive films for metal terminals of Examples 1 to 16 are adhesive films for metal terminals interposed between a metal terminal electrically connected to the electrode of the power storage device element and an exterior material of the power storage device for sealing the power storage device element, and the tensile elastic modulus A is 490 MPa or more. As is clear from the results shown in Table 2, the adhesive films for metal terminals of Examples 1 to 16 having such a configuration exhibit high adhesion strength to the metal terminals when multiple heating and pressurization are performed until they are adhered to the metal terminals.

[0130] In particular, the adhesive films for metal terminals in Examples 1 and 2 have a sufficient adhesion strength such that the adhesion strength is 45 N / 15 mm or more. Furthermore, they are also excellent in terms of flexibility (bending test), rate of change in thickness, and impact absorption energy. They have good adhesion, flexibility, rate of change in thickness, and impact absorption energy, and are adhesive films for metal terminals with an excellent balance of comprehensive properties. That is, in the adhesive film for metal terminals of the present disclosure, the tensile modulus A is about 500 to 550 MPa, the tensile modulus B is 420 to 480 MPa, the difference between the tensile moduli A and B is 40 to 75 MPa, the total thickness of the adhesive film for metal terminals is 145 to 155 μm, the thickness of the base material is 90 to 120 μm, the thicknesses of the first polyolefin layer and the second polyolefin layer are each 10 to 30 μm, and the ratio of the thickness of the base material to the total thickness of the first and second polyolefin layers is 1.0 to 4.0. As a result, it becomes an adhesive film for metal terminals with good adhesion, flexibility, rate of change in thickness, and impact absorption energy, and an excellent balance of comprehensive properties.

[0131] Example 17 <Manufacture of Adhesive Film for Metal Terminals> An unstretched polypropylene layer (hereinafter, may be referred to as "CPP layer") having the melting point and MFR described in Table 3 and the thickness described in Table 4 was used as the base material. Also, polypropylene (PP) having the melting point and melt mass flow rate (MFR) described in Table 3 was used as the first polyolefin layer (PP layer), and maleic anhydride-modified polypropylene (PPa) was used as the second polyolefin layer (PPa layer). Polypropylene (PP) and maleic anhydride-modified polypropylene (PPa) were extruded onto both sides of the base material made of the unstretched polypropylene film (CPP layer) one side at a time using a T-die extruder to obtain an adhesive film for metal terminals in which the PP layer / CPP layer / PPa layer were laminated in order. The thicknesses of each layer of the PP layer / CPP layer / PPa layer are as shown in Table 4.

[0132] The physical properties such as the tensile elastic modulus, yield stress at the lower yield point, water vapor barrier property, and rate of change in thickness of the adhesive film for metal terminals described in Table 4 were adjusted by the melting points, MFRs, thicknesses, thickness ratios of the PP layer, PPa layer, and CPP layer, and further by the conditions of the T-die in the production of the adhesive film 1 for metal terminals (for example, the extrusion width from the T-die, draw ratio, draw speed, heat treatment temperature, etc.) in the same manner as in Examples 1 to 16.

[0133] Regarding the adhesive film for metal terminals of Example 17, in the same manner as in Examples 1 to 16, the tensile elastic modulus, yield stress after heating and pressing, impact absorption energy, water vapor barrier property, rate of change in thickness, bending test, and followability evaluations 1 and 2 were each conducted. The results are shown in Table 4.

[0134]

Table 3

[0135]

Table 4

[0136] Regarding the adhesive film for metal terminals of Example 17 as well, similar to Examples 1 to 16, it is an adhesive film for metal terminals interposed between a metal terminal electrically connected to the electrode of the power storage device element and an exterior material for the power storage device that seals the power storage device element, and the tensile elastic modulus A is 490 MPa or more. As is clear from the results shown in Table 4, the adhesive film for metal terminals of Example 17 having this configuration exhibits high adhesion strength to the metal terminal when multiple heating and pressing operations are performed until it is adhered to the metal terminal.

[0137] As described above, the present disclosure provides an invention in the following aspects. Item 1. An adhesive film for metal terminals interposed between a metal terminal electrically connected to the electrode of a power storage device element and an exterior material for the power storage device that seals the power storage device element, The adhesive film for metal terminals is an adhesive film for metal terminals that, after being left standing for 12 seconds in a heating and pressurizing environment at a temperature of 180°C and a surface pressure of 0.0067 MPa and then left standing for 1 hour in an environment at a temperature of 25°C, has a tensile elastic modulus A measured in an environment at a temperature of 25°C of 490 MPa or more. Item 2. The adhesive film for metal terminals according to Item 1, wherein the tensile elastic modulus B measured in an environment at a temperature of 25°C before the adhesive film for metal terminals is exposed to the heating and pressurizing environment is 700 MPa or less. Item 3. The adhesive film for metal terminals according to Item 2, wherein the difference in tensile elastic modulus, calculated by subtracting the value of the tensile elastic modulus B from the value of the tensile elastic modulus A, is 5 MPa or more. Item 4. The adhesive film for metal terminals according to any one of Items 1 to 3, wherein the tensile elastic modulus A is 680 MPa or less. Item 5. The adhesive film for metal terminals according to any one of Items 1 to 4, wherein the yield point stress obtained from a graph showing the relationship between stress (MPa) and strain (mm), which is obtained by performing a tensile test in accordance with the method specified in JIS K7127 under the conditions of a temperature of 25°C, a tensile speed of 175 mm / min, and a chuck distance of 30 mm, is 17.0 MPa or more. Item 6. The adhesive film for metal terminals according to any one of Items 1 to 5, wherein the rate of change in thickness calculated by the following formula before and after heating and pressurizing for 12 seconds under the conditions of a temperature of 180°C and a surface pressure of 0.0067 MPa is 90% or more and 100% or less. Rate of change in thickness = (thickness of the adhesive film for metal terminals after heating and pressurizing / thickness of the adhesive film for metal terminals before heating and pressurizing) × 100 Item 7. The adhesive film for metal terminals according to any one of Items 1 to 6, wherein the thickness of the adhesive film for metal terminals is 140 μm or more. Item 8. The adhesive film for metal terminals according to any one of Items 1 to 7, wherein the adhesive film for metal terminals is composed of a laminate including a first polyolefin layer, a base material, and a second polyolefin layer in this order. Item 9. The adhesive film for metal terminals according to item 8, wherein the ratio of the thickness of the base material to the total thickness of the first polyolefin layer and the second polyolefin layer is 0.7 or more and 4.0 or less. Item 10. The adhesive film for metal terminals according to item 8 or 9, wherein the thickness of the base material is 50 μm or more and 150 μm or less. Item 11. The adhesive film for metal terminals according to any one of items 8 to 10, wherein the thicknesses of the first polyolefin layer and the second polyolefin layer are each 10 μm or more and 50 μm or less. Item 12. The adhesive film for metal terminals according to any one of items 8 to 11, wherein the melt mass flow rate at 230 °C of at least one of the first polyolefin layer and the second polyolefin layer is 7.2 g / 10 min or more and 9.8 g / 10 min or less. Item 13. The adhesive film for metal terminals according to any one of items 8 to 12, wherein the melt mass flow rate at 230 °C of the base material is 1.8 g / 10 min or more and 5.0 g / 10 min or less. Item 14. The adhesive film for metal terminals according to any one of items 8 to 13, wherein the resin contained in the base material contains a polyolefin backbone. Item 15. The adhesive film for metal terminals according to any one of items 8 to 14, wherein the first polyolefin layer and the second polyolefin layer contain an acid-modified polyolefin. Item 16. The exterior material for a power storage device is composed of a laminate including at least a base material layer, a barrier layer, and a heat-sealable resin layer in this order, The adhesive film for metal terminals according to any one of items 1 to 15, wherein the adhesive film for metal terminals is interposed between the heat-sealable resin layer and the metal terminal. Item 17. A metal terminal with an adhesive film for metal terminals, wherein the adhesive film for metal terminals according to any one of items 1 to 16 is attached to the metal terminal. Item 18. A power storage device comprising at least the power storage device element including a positive electrode, a negative electrode, and an electrolyte, an exterior material for the power storage device that seals the power storage device element, and metal terminals that are electrically connected to each of the positive electrode and the negative electrode and protrude outside the exterior material for the power storage device, A power storage device, wherein an adhesive film for a metal terminal according to any one of Items 1 to 16 is interposed between the metal terminal and the exterior material for the power storage device. Item 19. A method for manufacturing a battery comprising at least the power storage device element including a positive electrode, a negative electrode, and an electrolyte, an exterior material for the power storage device that seals the power storage device element, and metal terminals that are electrically connected to each of the positive electrode and the negative electrode and protrude outside the exterior material for the power storage device, A method for manufacturing a power storage device, comprising a step of interposing an adhesive film for a metal terminal according to any one of Items 1 to 16 between the metal terminal and the exterior material for the power storage device and sealing the power storage device element with the exterior material for the power storage device.

Explanation of Reference Numerals

[0138] 1 Adhesive film for metal terminal 2 Metal terminal 3 Exterior material for power storage device 3a Peripheral portion of exterior material for power storage device 4 Power storage device element 10 Power storage device 11 Base material 12a First polyolefin layer 12b Second polyolefin layer 13 Adhesion promoter layer 31 Base material layer 32 Adhesive layer 33 Barrier layer 34 Adhesion layer 35 Heat-sealable resin layer

Claims

1. An adhesive film for a metal terminal interposed between a metal terminal electrically connected to an electrode of a power storage device element and an exterior material for a power storage device that seals the power storage device element, wherein the adhesive film for a metal terminal has a tensile elastic modulus A measured in an environment at 25°C of 490 MPa or more after being left standing for 12 seconds in a heating and pressing environment at a temperature of 180°C and a surface pressure of 0.0067 MPa, and then further left standing for 1 hour in an environment at 25°C. The adhesive film for a metal terminal.

2. The adhesive film for a metal terminal according to claim 1, wherein the adhesive film for a metal terminal has a tensile elastic modulus B measured in an environment at 25°C of 700 MPa or less before being exposed to the heating and pressing environment.

3. The adhesive film for a metal terminal according to claim 2, wherein the difference in tensile elastic modulus, calculated by subtracting the value of the tensile elastic modulus B from the value of the tensile elastic modulus A, is 5 MPa or more.

4. The adhesive film for a metal terminal according to any one of claims 1 to 3, wherein the adhesive film for a metal terminal has a tensile elastic modulus A of 680 MPa or less.

5. The adhesive film for a metal terminal according to any one of claims 1 to 4, wherein the adhesive film for a metal terminal is a method compliant with the provisions of JIS K7127, and the yield point stress obtained from a graph showing the relationship between stress (MPa) and strain (mm) obtained by conducting a tensile test under the conditions of a temperature of 25°C, a tensile speed of 175 mm / min, and a chuck distance of 30 mm is 17.0 MPa or more.

6. The adhesive film for a metal terminal according to any one of claims 1 to 5, wherein the rate of change in thickness calculated by the following formula before and after heating and pressing under the conditions of a temperature of 180°C and a surface pressure of 0.0067 MPa for 12 seconds is 90% or more and 100% or less. Rate of change in thickness = (thickness of the adhesive film for a metal terminal after heating and pressing / thickness of the adhesive film for a metal terminal before heating and pressing) × 100

7. The adhesive film for a metal terminal according to any one of claims 1 to 6, wherein the thickness of the adhesive film for a metal terminal is 140 μm or more.

8. The adhesive film for a metal terminal according to any one of claims 1 to 7, wherein the adhesive film for a metal terminal is composed of a laminate including a first polyolefin layer, a base material, and a second polyolefin layer in this order.

9. The ratio of the thickness of the base material to the total thickness of the first polyolefin layer and the second polyolefin layer is 0.7 or more and 4.0 or less. The adhesive film for metal terminals according to claim 8.

10. The thickness of the base material is 50 μm or more and 150 μm or less. The adhesive film for metal terminals according to claim 8 or 9.

11. The thicknesses of the first polyolefin layer and the second polyolefin layer are each 10 μm or more and 50 μm or less. The adhesive film for metal terminals according to any one of claims 8 to 10.

12. The melt mass flow rate at 230 °C of at least one of the first polyolefin layer and the second polyolefin layer is 7.2 g / 10 min or more and 9.8 g / 10 min or less. The adhesive film for metal terminals according to any one of claims 8 to 11.

13. The melt mass flow rate at 230 °C of the base material is 1.8 g / 10 min or more and 5.0 g / 10 min or less. The adhesive film for metal terminals according to any one of claims 8 to 12.

14. The resin contained in the base material contains a polyolefin backbone. The adhesive film for metal terminals according to any one of claims 8 to 13.

15. The first polyolefin layer and the second polyolefin layer contain an acid-modified polyolefin. The adhesive film for metal terminals according to any one of claims 8 to 14.

16. The exterior material for the power storage device is composed of a laminate including at least a base material layer, a barrier layer, and a heat-sealable resin layer in this order. The adhesive film for metal terminals is interposed between the heat-sealable resin layer and the metal terminal. The adhesive film for metal terminals according to any one of claims 1 to 15.

17. A metal terminal with an adhesive film for metal terminals, wherein the adhesive film for metal terminals according to any one of claims 1 to 16 is attached to the metal terminal.

18. A power storage device including at least a power storage device element having a positive electrode, a negative electrode, and an electrolyte, an exterior material for the power storage device that seals the power storage device element, and the metal terminals that are electrically connected to the positive electrode and the negative electrode respectively and protrude outside the exterior material for the power storage device. The adhesive film for metal terminals according to any one of claims 1 to 16 is interposed between the metal terminal and the exterior material for the power storage device. The power storage device.

19. A method for manufacturing a battery, comprising at least: the power storage device element including a positive electrode, a negative electrode, and an electrolyte; an exterior material for the power storage device that seals the power storage device element; and metal terminals that are electrically connected to the positive electrode and the negative electrode respectively and protrude outside the exterior material for the power storage device, the method for manufacturing a power storage device including a step of sealing the power storage device element with the exterior material for the power storage device with the adhesive film for metal terminals according to any one of claims 1 to 16 interposed between the metal terminals and the exterior material for the power storage device.

Images