Adhesive Film for Metal Terminals, Method for Manufacturing Adhesive Film for Metal Terminals, Metal Terminal with Adhesive Film for Metal Terminals, Power Storage Device, and Method for Manufacturing Power Storage Device

Abstract

To provide a metal terminal adhesive film excellent in heat resistance and sealability.SOLUTION: Provided is a metal terminal adhesive film interposed between a metal terminal electrically connected with an electrode of a power storage device element and a power storage device sheath material for encapsulating the power storage device element. The metal terminal adhesive film is configured by a laminate at least comprising a polyester resin layer, an imine-modified polyolefin resin layer, and a polyolefin resin layer in this order.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to an adhesive film for metal terminals, a method for manufacturing the adhesive film for metal terminals, a metal terminal with the adhesive film for metal terminals, a power storage device, and a method for manufacturing the 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 the power storage device is an essential member for sealing power storage device elements such as electrodes and electrolytes. Conventionally, a metal exterior material for the power storage device has been frequently used as the exterior material for the power storage device. However, in recent years, with the improvement in performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc., the power storage device is required to have various shapes, and also to be thinned and lightened. However, the conventionally frequently used metal exterior material for the power storage device has the disadvantages 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 the power storage device 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 laminated film-shaped exterior material for the power storage device, with the heat-sealable resin layers located in the innermost layer of the exterior material for the power storage device facing each other, the peripheral portion of the exterior material for the power storage device is heat-sealed by heat sealing, whereby the power storage device element is sealed by the exterior material for the power storage device.

[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 between the heat-fusible resin layers. Since the metal terminals and the heat-fusible resin layers 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 layers.

[0005] For this reason, an adhesive film may be disposed between the metal terminals and the heat-fusible resin layers for the purpose of enhancing their adhesion. Examples of such an adhesive film include those described in Patent Document 1.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The adhesive film disposed between the metal terminals and the heat-fusible resin layers is heat-sealed at high temperature and high pressure between the exterior material for the power storage device and the metal terminals, and thus heat resistance and sealing properties are required.

[0008] As a power storage device using an adhesive film, those containing an electrolytic solution such as a lithium-ion battery are common, but all-solid-state batteries with a solid electrolyte as the electrolyte are also known. Since the electrolyte of an all-solid-state battery is solid, rapid charging at high temperatures is possible compared to power storage devices using an electrolytic solution, and use in a higher temperature environment is assumed compared to lithium-ion batteries and the like.

[0009] In addition, in the manufacturing process of all-solid-state batteries, for the purpose of increasing the ionic conductivity of the solid electrolyte, etc., the cells may be pressed at high temperature and high pressure (for example, a temperature of 120°C to 150°C and a pressure of about 100 MPa) with metal terminals attached, so there is a risk that the metal terminal portions reach high temperatures. Therefore, when applying the above-described adhesive film to all-solid-state batteries, particularly excellent heat-resistant sealing properties are required.

[0010] Moreover, not only all-solid-state batteries, but for example, when a power storage device is rapidly charged and discharged, the temperature of the metal terminals may reach about 150°C due to resistive heating. Therefore, it is desirable to impart excellent heat resistance and sealing properties to the adhesive films used in various power storage devices.

[0011] In order to enhance the heat resistance of the adhesive film, for example, a resin film with a high melting point such as a polyester film may be used as the adhesive film. However, the polyester film has low adhesion to metal terminals. Further, in order to adhere the polyester film to the metal terminals, it is necessary to heat at a very high temperature (for example, 160°C or higher) for a long time, and the sealing properties are not good.

[0012] Under such circumstances, the main object of the present disclosure is to provide an adhesive film for metal terminals having excellent heat resistance and sealing properties. Further, the present disclosure also aims to provide a method for manufacturing the adhesive film for metal terminals, a metal terminal with an adhesive film for metal terminals using the adhesive film for metal terminals, a power storage device using the adhesive film for metal terminals, and a method for manufacturing the power storage device.

Means for Solving the Problems

[0013] The inventors of the present disclosure have conducted intensive studies to solve the above problems. As a result, in the 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, it has been found that the adhesive film for metal terminals exhibits excellent heat resistance and sealing properties by being composed of a laminate including at least a polyester resin layer, an imine-modified polyolefin resin layer, and a polyolefin resin layer in this order. The present disclosure has been completed by further studies based on such findings.

[0014] That is, the present disclosure provides an invention in the following aspects. 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 the power storage device that seals the power storage device element, wherein the adhesive film for metal terminals is composed of a laminate including at least a polyester resin layer, an imine-modified polyolefin resin layer, and a polyolefin resin layer in this order.

Advantages of the Invention

[0015] According to the present disclosure, there can be provided 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 the power storage device that seals the power storage device element, the adhesive film for metal terminals having excellent heat resistance and sealing properties. Furthermore, the present disclosure can also provide a metal terminal with an adhesive film for metal terminals, a power storage device, and a method for manufacturing the power storage device.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0017] 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, and the adhesive film for metal terminals is composed of a laminate including at least a polyester-based resin layer, an imine-modified polyolefin-based resin layer, and a polyolefin-based resin layer in this order.

[0018] Since the adhesive film for metal terminals of the present disclosure has such characteristics, the adhesive film for metal terminals exhibits excellent heat resistance and sealing property. In the present disclosure, the fact that the adhesive film for metal terminals exhibits excellent heat resistance specifically means that when the adhesive film for metal terminals is adhered to the metal terminal and placed in a high-temperature environment (for example, 150 ° C), the sealing strength with the exterior material for the power storage device is high. Further, in the present disclosure, the fact that the adhesive film for metal terminals exhibits excellent sealing property means that when the adhesive film for metal terminals is heat-sealed at a temperature of about 170 to 210 ° C, the shape change due to the heat shrinkage of the adhesive film for metal terminals is small, and it is difficult to form a gap around the metal terminal due to heat-sealing along the shape of the metal terminal. The specific evaluation method is as described in the examples, for example.

[0019] Further, 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.

[0020] Hereinafter, the adhesive film for the metal terminal of the present disclosure, its manufacturing method, the energy storage device, and its manufacturing method will be described in detail.

[0021] In this specification, for a numerical range, 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.

[0022] Also, as a method for confirming the MD of the adhesive film for the metal terminal, there is a method of observing the cross-section of the adhesive film for the metal terminal (for example, the cross-section of the polyester-based resin layer, the imine-modified polyolefin-based resin layer, and the polyolefin-based resin layer) with an electron microscope to confirm the sea-island structure. In this method, the direction parallel to the cross-section where the average of the diameters of the island shapes in the direction perpendicular to the thickness direction of the adhesive film for the metal terminal is the largest can be determined as the MD. Specifically, the cross-section in the length direction of the adhesive film for the metal terminal and the direction parallel to the cross-section in the length direction are each changed by an angle of 10 degrees, and for each cross-section (a total of 10 cross-sections) up to the direction perpendicular to the cross-section in the length direction, the sea-island structure is observed by an electron micrograph. Next, in each cross-section, the shape of each individual island is observed. Regarding the shape of each individual island, the straight-line distance connecting the leftmost end and the rightmost end in the direction perpendicular to the thickness direction of the adhesive film for the metal terminal is defined as the diameter y. In each cross-section, the average of the top 20 diameters y in descending order of the diameter y of the island shape is calculated. The direction parallel to the cross-section where the average of the diameter y of the island shape is the largest is determined as the MD. Also, for example, the thermal shrinkage rate after leaving the adhesive film for the metal terminal in an environment of 150°C for 2 minutes can be measured, and the direction with the larger shrinkage rate can be determined as the MD.

[0023] 1. Adhesive film for metal terminals The adhesive film for metal terminals of the present disclosure is 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. Specifically, as shown in FIGS. 1 to 3, for example, the adhesive film 1 for metal terminals of the present disclosure is interposed between a metal terminal 2 electrically connected to an electrode of a power storage device element 4 and an exterior material 3 for a power storage device that seals the power storage device element 4. Further, the metal terminal 2 protrudes outside the exterior material 3 for a power storage device, and is sandwiched between the exterior material 3 for a power storage device and the exterior material 3 for a power storage device at the peripheral edge 3a of the heat-sealed exterior material 3 for a power storage device via the adhesive film 1 for metal terminals.

[0024] As described above, for example, it is assumed that the temperature will reach about 150°C during the heat pressing process in the manufacturing process of all-solid-state batteries or during rapid charging, and about 150°C is required as the durable temperature. Therefore, it is necessary to use a heat-sealable resin layer having a melting point of 150°C or higher for the exterior material 3 for a power storage device. When heat-sealing the sides formed by the exterior materials for a power storage device, the heating temperature is usually in the range of about 160 to 250°C, and the pressure is usually in the range of about 0.5 to 2.0 MPa. A flat metal sealing bar is used for sealing. For the sides where the metal terminal and the exterior material for a power storage device are heat-sealed via the adhesive film for metal terminals, similarly, the temperature is usually in the range of about 160 to 250°C, and the pressure is usually in the range of about 0.5 to 2.0 MPa. If necessary, a stepped metal sealing head with a step provided to adjust the difference due to the thickness of the metal terminal or the adhesive film for metal terminals at the corresponding part of the sealing head is used for sealing.

[0025]

[0026] ​The temporary bonding process is a process of temporarily fixing and degassing the adhesive film for metal terminals to the metal terminals. The main bonding process is a process of bonding the adhesive film for metal terminals to the metal terminals by performing heating and pressurization one or more times under higher temperature conditions than the temporary bonding process.

[0027] The temporary bonding process of the adhesive film for metal terminals to the metal terminals is performed, for example, under conditions of about 1 to 2 times with a metal sealing head coated with a heat-resistant rubber having a temperature of about 160 to 230 °C, a pressure of about 0.1 to 0.5 MPa, a time of about 10 to 20 seconds, a hardness of about 20 to 50, and a thickness of about 2 to 5 mm.

[0028] The main bonding process aims at heat fusion between the adhesive film for metal terminals and the metal terminals. For example, it is performed under conditions of about 1 to 2 times with a metal sealing head coated with a heat-resistant rubber having a temperature of about 180 to 250 °C, a pressure of about 0.2 to 1.0 MPa, a time of about 10 to 20 seconds, a hardness of about 20 to 50, and a thickness of about 2 to 5 mm.

[0029] Also, if necessary, by providing a step for adjusting the difference due to the thickness of the metal terminals or the adhesive film for metal terminals at the corresponding part of the sealing head, it is possible to weld efficiently. Also, by providing an adhesive layer on the surface of the metal terminal side of the adhesive film for metal terminals, it is possible to bond the metal terminals and the adhesive film for metal terminals at a relatively low temperature.

[0030] For example, after laminating a thermosetting resin capable of bonding to metal in an incompletely cured state as an adhesive layer on the surface of the metal terminal side, heat-sealing the metal terminals and the adhesive film for metal terminals, and then curing by aging to provide heat resistance. The sealing conditions for the metal terminals and the adhesive film for metal terminals in this case are, for example, about 100 °C to 200 °C and a pressure of about 0.2 to 3.0 MPa, and the aging conditions are about 40 to 150 °C and several minutes to 5 days.

[0031] In addition, when the power storage device to which the adhesive film for metal terminals of the present disclosure is applied is an all-solid-state battery, particularly high temperature and high pressure are applied to the adhesive film for metal terminals. The method of attaching the adhesive film for metal terminals exemplified here is just an example and is not limited to a specific method. For example, the pressurization time and the like are appropriately adjusted according to the thickness of the adhesive film for metal terminals and the like.

[0032] 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 formed of different materials, if such an adhesive film is not used, the sealing performance of the power storage device element tends to be low at the interface between the metal terminal 2 and the heat-sealing resin layer 35.

[0033] As shown in Fig. 4, the adhesive film 1 for metal terminals of the present disclosure includes at least a configuration in which a polyester resin layer 11, an imine-modified polyolefin resin layer 13, and a polyolefin resin layer 12 are laminated in this order. In the adhesive film 1 for metal terminals in Fig. 4, the polyester resin layer 11 constitutes the surface on the side of the exterior material 3 for the power storage device, and the polyolefin resin layer 12 constitutes the surface on the side of the metal terminal 2. However, in the adhesive film 1 for metal terminals of the present disclosure, the polyester resin layer 11 and the polyolefin resin layer 12 do not necessarily have to constitute the surface of the adhesive film 1 for metal terminals respectively. In particular, when using the acid-modified polyolefin described later as the resin of the polyolefin resin layer 12, since the adhesiveness with the metal terminal 2 is good (the acid-modified polyolefin has a high affinity for metals), it is preferable for the polyolefin resin layer 12 to constitute the surface on the side of the metal terminal 2. However, for the polyester resin layer 11, since it mainly contributes to improving the heat resistance of the adhesive film 1 for metal terminals, it is also preferable for the polyester resin layer 11 to constitute the surface of the adhesive film 1 for metal terminals, and it is also preferable not to constitute the surface. For example, it is also preferable that both surfaces of the adhesive film 1 for metal terminals are constituted by the polyolefin resin layer 12.

[0034] Further, the adhesive film 1 for metal terminals may include only one layer each for the polyester resin layer 11, the imine-modified polyolefin resin layer 13, and the polyolefin resin layer 12, or may include two or more layers. Also, within the limit of not inhibiting the effects of the present disclosure, the adhesive film 1 for metal terminals may include layers different from these.

[0035] Further, it is preferable that the imine-modified polyolefin resin layer 13 is in contact with each of the polyester resin layer 11 and the polyolefin resin layer 12. This is because generally, the polyester resin and the polyolefin resin have low affinity, and it is difficult to bond the polyester resin and the polyolefin resin with a high adhesive force. The imine-modified polyolefin resin layer 13 can preferably function as a layer for bonding the polyester resin layer 11 and the polyolefin resin layer 12.

[0036] As specific examples of the laminated structure of the adhesive film 1 for metal terminals of the present disclosure, for example, a laminated structure in which a polyester resin layer 11 / an imine-modified polyolefin resin layer 13 / a polyolefin resin layer 12 are laminated in this order; a laminated structure in which a polyolefin resin layer 12 / an imine-modified polyolefin resin layer 13 / a polyester resin layer 11 / an imine-modified polyolefin resin layer 13 / a polyolefin resin layer 12 are laminated in this order; a laminated structure in which a polyester resin layer 11 / an imine-modified polyolefin resin layer 13 / a polyolefin resin layer 12 / a polyolefin resin layer 12 are laminated in this order, and the like can be mentioned. Among these, from the viewpoint of the adhesion between the exterior material 3 for the power storage device and the metal terminal 2 and the adhesive film 1 for metal terminals, a three-layer structure in which a polyester resin layer 11 / an imine-modified polyolefin resin layer 13 / a polyolefin resin layer 12 are laminated in this order is preferable.

[0037] In the adhesive film 1 for metal terminals of the present disclosure, the polyester resin layer 11 is a layer containing a polyester resin. As will be described later, among polyester resins, the polyester resin layer 11 preferably contains at least one of polyethylene terephthalate and polybutylene terephthalate as a resin.

[0038] In the adhesive film 1 for metal terminals of the present disclosure, the polyolefin-based resin layer 12 is a layer containing a polyolefin-based resin (that is, having a polyolefin backbone). Since it has excellent adhesion to the metal terminal 2, the polyolefin-based resin layer 12 preferably contains an acid-modified polyolefin-based resin as the resin. The resin contained in the polyolefin-based resin layer 12 is preferably an acid-modified polyolefin-based resin. The acid-modified polyolefin-based resin is a resin obtained by acid-modifying a polyolefin-based resin. Examples of the polyolefin-based resin to be acid-modified include polyethylene and polypropylene.

[0039] In the adhesive film 1 for metal terminals of the present disclosure, the imine-modified polyolefin-based resin layer 13 is a layer containing an imine-modified polyolefin-based resin. The imine-modified polyolefin-based resin is a resin obtained by imine-modifying a polyolefin-based resin. Examples of the polyolefin-based resin to be imine-modified include polyethylene and polypropylene.

[0040] 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 or polyester) of the exterior material 3 for the power storage device are adhered via the adhesive film 1 for metal terminals. For example, the polyolefin-based resin layer 12 side of the adhesive film 1 for metal terminals is disposed on the metal terminal 2 side, the polyester-based resin layer 11 side is disposed on the exterior material 3 side for the power storage device, the polyolefin-based resin layer 12 side is in close contact with the metal terminal 2, and the polyester-based resin layer 11 side is in close contact with the heat-sealing resin layer 35 of the exterior material 3 for the power storage device.

[0041] As the thickness (total thickness) of the laminate constituting the adhesive film 1 for metal terminals of the present disclosure, from the viewpoint of enhancing the followability to the shape of the metal terminal 2, it is, for example, about 50 μm or more, preferably about 60 μm or more, more preferably about 80 μm or more. Further, the total thickness of the adhesive film 1 for metal terminals of the present disclosure is preferably about 500 μm or less, more preferably about 200 μm or less, still more preferably about 180 μm or less. Preferred ranges of the total thickness of the adhesive film 1 for metal terminals of the present disclosure include about 50 to 500 μm, about 50 to 250 μm, about 50 to 200 μm, about 50 to 180 μm, about 60 to 500 μm, about 60 to 250 μm, about 60 to 200 μm, about 60 to 180 μm, about 80 to 500 μm, about 80 to 250 μm, about 80 to 200 μm, and about 80 to 180 μm. As a more specific example, for instance, when the adhesive film 1 for metal terminals of the present disclosure is used in a consumer-use power storage device, the total thickness is preferably about 60 to 100 μm, and when used in an in-vehicle power storage device, the total thickness is preferably about 100 to 200 μm.

[0042] Hereinafter, the materials, thicknesses, etc. of the polyester resin layer 11, the imine-modified polyolefin resin layer 13, and the polyolefin resin layer 12 will be described in detail.

[0043] As shown in FIG. 4, the adhesive film 1 for metal terminals of the present disclosure includes a polyester resin layer 11 on one surface side of the imine-modified polyolefin resin layer 13 and a polyolefin resin layer 12 on the other surface side. In the adhesive film 1 for metal terminals of the present disclosure, it is preferable that the polyester resin layer 11 side is disposed on the side of the exterior material 3 for the power storage device. Further, it is preferable that the polyolefin resin layer 12 side is disposed on the metal terminal 2 side.

[0044] In the adhesive film 1 for metal terminals of the present disclosure, a polyester-based resin layer 11 and a polyolefin-based resin layer 12 are located on the surfaces of both sides, respectively. As described above, in the adhesive film 1 for metal terminals in FIG. 4, the polyester-based resin layer 11 constitutes the surface on the side of the exterior material 3 for the power storage device, and the polyolefin-based resin layer 12 constitutes the surface on the side of the metal terminal 2. However, in the adhesive film 1 for metal terminals of the present disclosure, the polyester-based resin layer 11 and the polyolefin-based resin layer 12 do not necessarily have to constitute the surface of the adhesive film 1 for metal terminals, respectively. In particular, when an acid-modified polyolefin is used as the resin of the polyolefin-based resin layer 12, the adhesiveness with the metal terminal 2 is good (the acid-modified polyolefin has a high affinity for metals). Therefore, for the polyolefin-based resin layer 12, it is preferable to constitute the surface on the side of the metal terminal 2. However, for the polyester-based resin layer 11, since it mainly contributes to improving the heat resistance of the adhesive film 1 for metal terminals, it is also preferable that the polyester-based resin layer 11 constitutes the surface of the adhesive film 1 for metal terminals, and it is also preferable that it does not constitute the surface. For example, it is also preferable that both sides of the adhesive film 1 for metal terminals are constituted by the polyolefin-based resin layer 12. When the polyester-based resin layer 11 constitutes the surface of the adhesive film 1 for metal terminals on the side of the exterior material for the power storage device, since the polyester-based resin layer 11 has excellent heat resistance, when heat-sealing the exterior material for the power storage device, there is an advantage that the adhesive film 1 for metal terminals interposed between the metal terminal and the exterior material for the power storage device is not easily crushed.

[0045] The adhesive film 1 for metal terminals may contain only one layer each of the polyester-based resin layer 11, the imine-modified polyolefin-based resin layer 13, and the polyolefin-based resin layer 12, or may contain two or more layers. Also, within the limit of not inhibiting the effects of the present disclosure, the adhesive film 1 for metal terminals may contain layers different from these.

[0046] [Polyester-based resin layer 11] The polyester-based resin layer 11 is a layer containing a polyester-based resin.

[0047] Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, copolyester, etc. Examples of the copolyester include copolyesters having ethylene terephthalate as the main repeating unit. Specifically, copolyester polymers obtained by polymerizing ethylene isophthalate with ethylene terephthalate as the main repeating unit (hereinafter abbreviated following polyethylene (terephthalate / isophthalate)), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl-dicarboxylate), polyethylene (terephthalate / decanedicarboxylate), etc. are included. These polyesters may be used alone or in combination of two or more.

[0048] The polyester resin layer 11 preferably contains at least one of polyethylene terephthalate and polybutylene terephthalate as the resin among the polyester resins. The resin contained in the polyester resin layer 11 is preferably at least one of polyethylene terephthalate and polybutylene terephthalate.

[0049] The polyester resin layer 11 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 polyester resin layer 11 may be formed of only one layer or may be formed of two or more layers with the same or different resin components.

[0050] The polyester resin layer 11 preferably contains a polyester resin and an elastomer. The elastomer contained in the polyester resin layer 11 may be any one that plays a role in enhancing the flexibility while ensuring the excellent heat resistance and sealing properties of the adhesive film 1 for metal terminals. Preferred elastomers include at least one or more thermoplastic elastomers selected from polyester-based, polyamide-based, polyurethane-based, polyolefin-based, polystyrene-based, polyether-based, and acrylic-based, or thermoplastic elastomers that are copolymers thereof. More preferably, there may be mentioned thermoplastic elastomers composed of a block copolymer of polybutylene terephthalate and polyether, thermoplastic elastomers composed of an α-olefin copolymer of polymethylpentene, etc. In the thermoplastic elastomer composed of a block copolymer of polybutylene terephthalate and polyether, examples of the polyether component include copolymers of terephthalic acid and polytetramethylene ether glycol. Also, preferred specific examples of polyether-based thermoplastic elastomers include polytetramethylene glycol and poly(ε-caprolactam). In the polyester resin layer 11, the content of the elastomer is not particularly limited as long as it can enhance the flexibility while ensuring the excellent heat resistance and sealing properties of the adhesive film 1 for metal terminals. For example, it is about 0.1 mass% or more, preferably about 0.5 mass% or more, more preferably about 1.0 mass% or more, and even more preferably about 3.0 mass% or more. Also, the content is, for example, about 10.0 mass% or less, about 8.0 mass% or less, about 5.0 mass% or less, etc. Preferred ranges of the content include about 0.1 to 10.0 mass%, about 0.1 to 8.0 mass%, about 0.1 to 5.0 mass%, about 0.5 to 10.0 mass%, about 0.5 to 8.0 mass%, about 0.5 to 5.0 mass%, about 1.0 to 10.0 mass%, about 1.0 to 8.0 mass%, about 1.0 to 5.0 mass%, about 3.0 to 10.0 mass%, about 3.0 to 8.0 mass%, about 3.0 to 5.0 mass%, etc.

[0051] The melting point of the polyester resin layer 11 is preferably 20°C or more higher than that of the polyolefin resin layer 12, more preferably 40°C or more higher, and even more preferably 60°C or more higher. The melting point of the polyester resin layer 11 is preferably 180°C or more, more preferably 190°C or more, and even more preferably 200°C or more, and is also preferably 240°C or less, more preferably 230°C or less, and even more preferably 220°C or less.

[0052] From the viewpoint of more suitably achieving the effects of the present disclosure, the thickness of the polyester resin layer 11 is preferably about 10 μm or more, more preferably about 15 μm or more, and even more preferably about 20 μm or more, and is also preferably about 60 μm or less, more preferably about 55 μm or less, and even more preferably 50 μm or less. Preferred ranges for the thickness of the polyester resin layer 11 include about 10 to 60 μm, about 10 to 55 μm, about 10 to 50 μm, about 15 to 60 μm, about 15 to 55 μm, about 15 to 50 μm, about 20 to 60 μm, about 20 to 55 μm, and about 20 to 50 μm.

[0053] In the present disclosure, from the viewpoint of more suitably exerting the effects of the present disclosure, the ratio of the thickness of the polyester resin layer 11 to the total thickness (100%) of the adhesive film 1 for metal terminals is preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more, and is also preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less.

[0054] [Polyolefin resin layer 12] In the adhesive film 1 for metal terminals of the present disclosure, the polyolefin resin layer 12 is a layer containing a polyolefin resin (that is, having a polyolefin backbone). Since it has excellent adhesion to metal terminals, the polyolefin resin layer 12 preferably contains an acid-modified polyolefin resin as the resin. The resin contained in the polyolefin resin layer 12 is preferably an acid-modified polyolefin resin. The acid-modified polyolefin resin is a resin obtained by acid-modifying a polyolefin resin. Examples of the polyolefin resin to be acid-modified include polyethylene and polypropylene.

[0055] Acid-modified polyolefin has a high affinity for metals. Therefore, in the adhesive film 1 for metal terminals of the present disclosure, by disposing the polyolefin resin layer 12 containing the acid-modified polyolefin resin on the side of the metal terminal 2, excellent adhesion can be exhibited at the interface between the adhesive film 1 for metal terminals and the metal terminal 2. In addition, since the polyolefin resin has excellent adhesion to the heat-sealing resin layer 35 (formed of polyolefin or the like) of the exterior material for the power storage device, by disposing the polyolefin resin layer 12 on the side of the heat-sealing resin layer 35 of the exterior material 3 for the power storage device, even better adhesion can be exhibited at the interface between the adhesive film 1 for metal terminals and the heat-sealing resin layer 35.

[0056] 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.

[0057] In the polyolefin resin layer 12, examples of the polyolefin (for the polyolefin resin layer 12, 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 (for example, block copolymers of propylene and ethylene), random copolymers of polypropylene (for example, random copolymers of propylene and ethylene); and terpolymers of ethylene-butene-propylene. Among these polyolefins, polyethylene and polypropylene are preferable, and polypropylene is particularly preferable. Among polypropylenes, homopolypropylene (that is, homopolymers of polypropylene) is preferably used in terms of excellent heat resistance. For example, in the case of an acid-modified polyolefin resin, it preferably contains acid-modified homopolypropylene in terms of excellent heat resistance, and it is more preferably formed of acid-modified homopolypropylene.

[0058] Further, the polyolefin 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 them with α,β-unsaturated carboxylic acid or its anhydride, or by block-polymerizing or graft-polymerizing α,β-unsaturated carboxylic acid or its anhydride onto the cyclic polyolefin.

[0059] 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. Further, 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 preferred, and norbornene is more preferred. Styrene is also included as a constituent monomer.

[0060] 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 polyolefin resin layer 12 is analyzed by infrared spectroscopy, it is preferable that a peak derived from maleic anhydride is detected. For example, when measuring 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 . That is, in this case, when the polyolefin resin layer 12 is measured by infrared spectroscopy, a peak derived from maleic anhydride is detected. 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.

[0061] The polyolefin resin layer 12 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 polyolefin resin layer 12 may be formed of only one layer, or may be formed of two or more layers with the same or different resin components. From the viewpoint of the film-forming property of the polyolefin resin layer 12, it is preferably formed of a blend polymer combining two or more resin components. When using a blend polymer, for the polyolefin resin layer 12, it is preferable to use acid-modified polypropylene as the main component (50% by mass or more of the components), and 50% by mass or less as other resins (preferably polyethylene from the viewpoint of improving flexibility). Also, for the polyolefin resin layer 12, it is preferable to use polypropylene as the main component (50% by mass or more of the components), and 50% by mass or less as other resins (preferably polyethylene from the viewpoint of improving flexibility). On the other hand, from the viewpoint of the electrolytic solution resistance of the polyolefin resin layer 12, the polyolefin resin layer 12 preferably contains acid-modified polypropylene alone as the resin, and the polyolefin resin layer 12 preferably contains polypropylene alone as the resin.

[0062] The melting point of the polyolefin resin layer 12 is preferably 155 °C or higher, more preferably 160 °C or higher, still more preferably 165 °C or higher, and is preferably 170 °C or lower, more preferably 165 °C or lower, still more preferably 160 °C or lower.

[0063] From the viewpoint of more preferably achieving the effects of the present disclosure, the thickness of the polyolefin resin layer 12 is preferably about 10 μm or more, more preferably about 15 μm or more, still more preferably about 20 μm or more, and is preferably about 120 μm or less, more preferably about 110 μm or less, still more preferably 100 μm or less, and even more preferably 80 μm or less. Preferred ranges of the thickness of the polyolefin resin layer 12 include about 10 to 120 μm, about 10 to 110 μm, about 10 to 100 μm, about 10 to 80 μm, about 15 to 120 μm, about 15 to 110 μm, about 15 to 100 μm, about 15 to 80 μm, about 20 to 120 μm, about 20 to 110 μm, 20 to 100 μm, and about 20 to 80 μm.

[0064] In the present disclosure, from the viewpoint of more preferably exerting the effects of the present disclosure, the ratio of the thickness of the polyolefin resin layer 12 to the total thickness (100%) of the adhesive film 1 for metal terminals is preferably 20% or more, more preferably 30% or more, still more preferably 40% or more, and is preferably 80% or less, more preferably 70% or less, still more preferably 60% or less.

[0065] [Imine-modified polyolefin resin layer 13] In the adhesive film 1 for metal terminals of the present disclosure, the imine-modified polyolefin resin layer 13 is a layer containing a polyolefin resin (that is, having a polyolefin backbone). The resin contained in the imine-modified polyolefin resin layer 13 is preferably an imine-modified polyolefin resin. The imine-modified polyolefin resin is a resin obtained by imine-modifying a polyolefin resin. Examples of the polyolefin resin to be imine-modified include polyethylene and polypropylene.

[0066] The imine modification is preferably obtained by subjecting a polyolefin to graft treatment with a polyimine compound having a plurality of imino groups in the presence of a radical generator. The imine-modified polyolefin is preferably imine-modified polypropylene obtained by graft-treating polypropylene imine.

[0067] The imine-modified polyolefin resin layer 13 preferably contacts each of the polyester resin layer 11 and the polyolefin resin layer 12. This is because generally, the polyester resin and the polyolefin resin have low affinity, and it is difficult to adhere the polyester resin and the polyolefin resin with a high adhesive force. The imine-modified polyolefin resin layer 13 can preferably function as a layer for adhering the polyester resin layer 11 and the polyolefin resin layer 12.

[0068] The imine-modified polyolefin resin layer 13 may 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 imine-modified polyolefin resin layer 13 may be formed of only one layer, or may be formed of two or more layers with the same or different resin components.

[0069] The melting point of the imine-modified polyolefin resin layer 13 is preferably 155 °C or higher, more preferably 160 °C or higher, still more preferably 165 °C or higher, and is preferably 170 °C or lower, more preferably 165 °C or lower, still more preferably 160 °C or lower.

[0070] From the viewpoint of more preferably achieving the effects of the present disclosure, the thickness of the imine-modified polyolefin resin layer 13 is preferably about 10 μm or more, more preferably about 15 μm or more, still more preferably about 20 μm or more, and is preferably about 60 μm or less, more preferably about 55 μm or less, still more preferably 50 μm or less. Preferred ranges of the thickness of the imine-modified polyolefin resin layer 13 include about 10 to 60 μm, about 10 to 55 μm, about 10 to 50 μm, about 15 to 60 μm, about 15 to 55 μm, about 15 to 50 μm, about 20 to 60 μm, about 20 to 55 μm, and about 20 to 50 μm, respectively.

[0071] In the present disclosure, from the perspective of more preferably exerting the effects of the present disclosure, the ratio of the thickness of the imine-modified polyolefin resin layer 13 to the total thickness (100%) of the adhesive film 1 for metal terminals is preferably 10% or more, more preferably 15% or more, still more preferably 20% or more, and is preferably 10% or less, more preferably 20% or less, still more preferably 30% or less.

[0072] (Additive) Further, the polyester resin layer 11, the polyolefin resin layer 12, and the imine-modified polyolefin resin layer 13 may each contain additives such as colorants such as pigments, fillers, and lubricants in addition to the resin.

[0073] As the pigment, various inorganic pigments can be used. Specific examples of the pigment can preferably be exemplified by carbon (carbon, graphite) exemplified as the filler described later. Note that carbon (carbon, graphite) is a material generally used inside the power storage device, and since there is no risk of elution into the electrolytic solution, it can be suitably blended when the polyolefin resin layer 12 is located on the metal terminal 2 side. In addition, an adequate coloring effect can be obtained with an addition amount that does not significantly inhibit the adhesiveness due to the large coloring effect, does not melt with heat, and can increase the apparent melt viscosity of the added resin. Further, it can prevent the pressure portion 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.

[0074] When adding a pigment to the polyester resin layer 11, the polyolefin resin layer 12, and the imine-modified polyolefin resin layer 13, 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 polyester resin layer 11, the polyolefin resin layer 12, and the imine-modified polyolefin resin layer 13. By adding a pigment to only one of the polyester resin layer 11 and the polyolefin resin layer 12 (preferably only the polyolefin resin layer 12), it becomes possible to easily distinguish between the metal terminal side surface and the surface of the exterior material for the power storage device. When adding both a pigment and a filler to the exterior material 3 for the power storage device, both the filler and the pigment may be added to the same polyester resin layer 11 or polyolefin resin layer 12. However, from the viewpoint of not inhibiting the heat fusion property of the adhesive film 1 for the metal terminal, it is preferable to add the filler and the pigment separately to the polyester resin layer 11 and the polyolefin resin layer 12.

[0075] Since at least one of the polyester resin layer 11, the polyolefin resin layer 12, and the imine-modified polyolefin resin layer 13 contains a filler, the filler functions as a spacer, so that 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. The particle size of the filler is in the range of about 0.1 to 35 μm, preferably about 5.0 to 30 μm, and more preferably about 10 to 25 μm. Also, the content of the filler is about 5 to 30 parts by mass, more preferably about 10 to 20 parts by mass, respectively, based on 100 parts by mass of the resin component forming the polyester resin layer 11, the polyolefin resin layer 12, and the imine-modified polyolefin resin layer 13.

[0076] As the filler, either an inorganic filler or an 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, and the like. Examples of the organic filler include fluororesin, phenol resin, urea resin, epoxy resin, acrylic resin, benzoguanamine-formaldehyde condensate, melamine-formaldehyde condensate, polymethyl methacrylate cross-linked product, polyethylene cross-linked product, and the like. 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 a method for mixing the filler into the resin components forming the polyester resin layer 11, the polyolefin resin layer 12, and the imine-modified polyolefin resin layer 13, a method of melt-blending both of them in a Banbury mixer or the like in advance to form a masterbatch and then setting it to a predetermined mixing ratio, a method of directly mixing with the resin components, or the like can be adopted.

[0077] From the viewpoint of enhancing the sealing performance of the power storage device of the present disclosure, it is preferable that the layers constituting the surface of the adhesive film 1 for metal terminals (for example, the polyester resin layer 11 and the polyolefin resin layer 12) each contain a lubricant. The concentration of the lubricant is preferably 2000 ppm or less, more preferably 1500 ppm or less, still more preferably 1000 ppm or less, and is also preferably 200 ppm or more, more preferably 500 ppm or more. The preferable range is about 200 to 2000 ppm, about 200 to 1500 ppm, about 200 to 1000 ppm, about 500 to 2000 ppm, about 500 to 1500 ppm, or about 500 to 1000 ppm.

[0078] The lubricant is not particularly limited, but preferably an amide-based lubricant. Specific examples of the amide-based lubricant include, for example, saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, aromatic bisamides, and the like. Specific examples of the saturated fatty acid amide include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, and the like. Specific examples of the unsaturated fatty acid amide include oleic acid amide, erucic acid amide, and the like. Specific examples of the substituted amide include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, and the like. Specific examples of the methylol amide include methylol stearic acid amide, and the like. Specific examples of the saturated fatty acid bisamide include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipic acid amide, N,N'-distearyl sebacic acid amide, and the like. Specific examples of the unsaturated fatty acid bisamide include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipic acid amide, N,N'-dioleyl sebacic acid amide, and the like. Specific examples of the fatty acid ester amide include stearoamide ethyl stearate, and the like. Specific examples of the aromatic bisamide include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, N,N'-distearyl isophthalic acid amide, and the like. The lubricant may be used alone or in combination of two or more kinds.

[0079] When the polyester resin layer 11, the polyolefin resin layer 12, and the imine-modified polyolefin resin layer 13 are each constituted by a resin film, known adhesion-aiding means such as corona discharge treatment, ozone treatment, plasma treatment, etc. may be applied to the surfaces of these layers as required.

[0080] The adhesive film 1 for metal terminals of the present disclosure can be manufactured, for example, by laminating the polyester resin layer 11 and the polyolefin resin layer 12 on the surface of the imine-modified polyolefin resin layer 13 respectively. The lamination of the imine-modified polyolefin resin layer 13 with the polyester resin layer 11 and the polyolefin resin layer 12 can be carried out by known methods such as the extrusion lamination method, the T-die method, the inflation method, the thermal lamination method, etc.

[0081] The method of interposing the adhesive film 1 for metal terminals between the metal terminal 2 and the exterior material 3 for the power storage device is not particularly limited. For example, as shown in FIGS. 1 to 3, at the portion where the metal terminal 2 is sandwiched by the exterior material 3 for the power storage device, the adhesive film 1 for metal terminals may be wound around the metal terminal 2. Also, although not shown, at the portion where the metal terminal 2 is sandwiched by the exterior material 3 for the power storage device, the adhesive film 1 for metal terminals may be disposed on both sides of the metal terminal 2 so as to cross the two metal terminals 2.

[0082] [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 composed 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 composed of aluminum or the like. Further, the metal terminal 2 connected to the negative electrode of a lithium-ion power storage device is usually composed of copper, nickel, or the like, and is composed of copper plated with nickel or a clad material of nickel and copper from the viewpoints of low resistance and prevention of surface deterioration.

[0083] From the viewpoint of enhancing the electrolytic solution resistance, the surface of the metal terminal 2 is preferably 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 for forming a corrosion-resistant film such as a phosphate, a chromate, a fluoride, a triazine thiol compound, and an acrylate. Among the methods for 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, or a composition composed of three components of an acrylic resin, a chromium (III) nitrate compound, and phosphoric acid is preferable.

[0084] 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 4000 μm, more preferably about 60 to 3000 μm, and even more preferably about 70 to 1000 μm. Further, the length of the metal terminal 2 is preferably about 1 to 500 mm, more preferably about 3 to 300 mm. Further, the width of the metal terminal 2 is preferably about 1 to 200 mm, more preferably about 3 to 150 mm.

[0085] [Exterior material 3 for power storage device] Examples of the exterior material 3 for a 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. 5 shows, as an example of the cross-sectional structure of the exterior material 3 for a 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 a 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 on the periphery of the power storage device element 4 into contact with each other and heat-sealing them, and the power storage device element 4 is sealed. Figs. 1 to 3 illustrate the power storage device 10 when using an embossed type exterior material 3 for a power storage device formed by embossing or the like, but the exterior material 3 for a power storage device may be a non-formed pouch type. Note that, among pouch types, there are three-side seal, four-side seal, pillow type, etc., and any type may be used.

[0086] 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. For the preferable range, 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 can be mentioned.

[0087] In addition, the adhesive film 1 for the metal terminal of the present disclosure can be suitably applied to the exterior material for the all-solid-state battery. The thickness of the laminate constituting the exterior material for the all-solid-state battery is not particularly limited. However, from the viewpoints of cost reduction, improvement of energy density, etc., the upper limit is preferably about 10000 μm or less, about 8000 μm or less, about 5000 μm, about 500 μm or less. From the viewpoint of maintaining the function of the exterior material for the all-solid-state battery to protect the battery element, the lower limit is preferably about 100 μm or more, about 150 μm or more, about 200 μm or more. For the preferable range, for example, about 100 to 10000 μm, about 100 to 8000 μm, about 100 to 5000 μm, about 150 to 10000 μm, about 150 to 8000 μm, about 150 to 5000 μm, about 200 to 10000 μm, about 200 to 8000 μm, about 200 to 5000 μm, about 150 to 500 μm, about 200 to 500 μm can be mentioned, and particularly about 100 to 500 μm is preferable.

[0088] (Base material layer 31) In the exterior material 3 for a power storage device, the base material layer 31 is a layer that functions as the base material of the exterior material for a power storage device and is the layer that forms the outermost layer side.

[0089] 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 less likely to occur due to the adhesion of the electrolyte, and are preferably used as the material for forming the base material layer 31. Also, 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.

[0090] 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.

[0091] Among these, examples of the resin film for forming the base material layer 31 preferably include nylon and polyester, and more preferably biaxially stretched nylon and biaxially stretched polyester. Also, since all-solid-state batteries have a service temperature of 150°C or higher, they are often sealed at a high temperature of 200°C or higher, and biaxially stretched polyester is most suitable.

[0092] In order to improve the pinhole resistance and insulation performance when the substrate layer 31 is used as a package for a power 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, or a multilayer structure in which biaxially stretched polyester and biaxially stretched nylon are laminated. When the substrate layer 31 has a multilayer structure, the resin films may be adhered via an adhesive, or may be directly laminated without using an adhesive. When adhering without using an adhesive, for example, methods of adhering in a thermally melted state such as coextrusion method, sand laminate method, and thermal laminate method can be mentioned. For the above high-temperature sealing, it is desirable that at least the outermost layer is biaxially stretched polyester.

[0093] Also, the substrate layer 31 may be made to have a low friction coefficient in order to improve formability. When the substrate 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 substrate layer 31 have a low friction coefficient, for example, mat treatment, formation of a thin film layer of a slip agent, combinations thereof, etc. can be mentioned.

[0094] Regarding the thickness of the substrate layer 31, for example, it is about 10 to 50 μm, preferably about 15 to 30 μm.

[0095] (Adhesive layer 32) In the exterior material 3 for a power storage device, the adhesive layer 32 is a layer disposed on the substrate layer 31 as needed in order to impart adhesiveness to the substrate layer 31. That is, the adhesive layer 32 is provided between the substrate layer 31 and the barrier layer 33.

[0096] The adhesive layer 32 is formed of an adhesive that can adhere the substrate layer 31 and the barrier layer 33. The adhesive used for forming the adhesive layer 32 may be a two-component curing type adhesive or a one-component curing type adhesive. Also, the adhesion mechanism of the adhesive used for forming the adhesive layer 32 is not particularly limited, and any of chemical reaction type, solvent evaporation type, hot melt type, hot press type, etc. may be used.

[0097] As the resin component of the adhesive that can be used for forming the adhesive layer 32, from the viewpoints of excellent extensibility, durability under high humidity conditions, yellowing suppression effect, heat deterioration suppression effect during heat sealing, etc., and effectively suppressing the occurrence of delamination by suppressing a decrease in the lamination strength between the base material layer 31 and the barrier layer 33, preferably a two-component curable polyurethane-based adhesive; polyamide, polyester, or a blend resin of these and a modified polyolefin can be mentioned.

[0098] Also, the adhesive layer 32 may be laminated with different adhesive components. When the adhesive layer 32 is laminated with different adhesive components, from the viewpoint of improving the lamination 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 laminated with different adhesive components, specifically, as the adhesive component arranged on the barrier layer 33 side, preferably, acid-modified polyolefin, metal-modified polyolefin, a mixed resin of polyester and acid-modified polyolefin, a resin containing a copolymerized polyester, etc. can be mentioned.

[0099] Also, when the exterior material 3 for the power storage device is an exterior material for an all-solid-state battery, the adhesive layer 32 is preferably formed of a cured product of a resin composition containing at least one of polyester and polycarbonate and at least one of an alicyclic isocyanate compound and an aromatic isocyanate compound. Thereby, delamination between the above-mentioned barrier layer 33 and the heat-fusible resin layer 35 in a high-temperature environment of the exterior material for the all-solid-state battery is suppressed, and furthermore, high sealing strength can also be exhibited.

[0100] The polyester is preferably a polyester polyol. The polyester polyol is not particularly limited as long as it has an ester bond in the polymer main chain and has a plurality of hydroxyl groups at the terminals or side chains. Also, the polycarbonate is preferably a polycarbonate polyol. The polyester polyol is not particularly limited as long as it has a carbonate bond in the polymer main chain and has a plurality of hydroxyl groups at the terminals or side chains. The polyester is, for example, preferably a polyester obtained by previously reacting a polyester polyol with a polyisocyanate (such as a diisocyanate) to extend the urethane chain, or a polycarbonate obtained by previously reacting a polycarbonate polyol with a polyisocyanate (such as a diisocyanate) to extend the urethane chain. The polyester and polycarbonate contained in the resin composition forming the adhesive layer 5 may each be of one type or two or more types.

[0101] The alicyclic isocyanate compound is not particularly limited as long as it is a compound having an alicyclic structure and an isocyanate group. The alicyclic isocyanate compound preferably has two or more isocyanate groups. Specific examples of the alicyclic isocyanate compound include isophorone diisocyanate (IPDI), bis(4-isocyanatocyclohexyl)methane, 1,3-bis(isocyanatomethyl)cyclohexane, methylene bis(4,1-cyclohexylene) diisocyanate, etc., polymers or nurates thereof, mixtures thereof, copolymers with other polymers, etc. Also, adducts, burettes, isocyanurates, etc. are included. Also, the alicyclic isocyanate compound is preferably a polyol-modified polyisocyanate obtained by previously reacting an alicyclic isocyanate with a polyol (such as a polyester polyol). The alicyclic isocyanate compound contained in the resin composition forming the adhesive layer 5 may be of one type or two or more types.

[0102] Moreover, the aromatic isocyanate compound is not particularly limited as long as it is a compound having an aromatic ring and an isocyanate group. The aromatic isocyanate compound preferably has two or more isocyanate groups. Specific examples of the aromatic isocyanate compound include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), those obtained by polymerizing or nurating these, mixtures thereof, and copolymers with other polymers. Also, adducts, burettes, isocyanurates, etc. can be mentioned. Further, the aromatic isocyanate compound is preferably a polyol-modified polyisocyanate obtained by previously reacting an aromatic isocyanate with a polyol (for example, polyester polyol, etc.). The aromatic isocyanate compound contained in the resin composition forming the adhesive layer 5 may be one type or two or more types.

[0103] The resin composition forming the adhesive layer 32 may contain, for example, an alicyclic isocyanate compound and may not contain an aromatic isocyanate compound, or may contain, for example, an aromatic isocyanate compound and may not contain an alicyclic isocyanate compound, or may contain both an alicyclic isocyanate compound and an aromatic isocyanate compound. The resin composition forming the adhesive layer 32 preferably contains an aromatic isocyanate compound.

[0104] Regarding the content of the alicyclic isocyanate compound and the aromatic isocyanate compound in the adhesive layer 32, each is preferably in the range of 0.1 to 50% by mass, more preferably in the range of 0.5 to 40% by mass, in the resin composition constituting the adhesive layer 5. When the adhesive layer 5 contains both an alicyclic isocyanate compound and an aromatic isocyanate compound, the total content thereof is preferably in the range of 0.1 to 50% by mass, more preferably in the range of 0.5 to 40% by mass, in the resin composition constituting the adhesive layer 5.

[0105] Regarding the thickness of the adhesive layer 32, for example, it is about 2 to 50 μm, preferably about 3 to 25 μm.

[0106] (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, for example, by 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, soft aluminum foil such as annealed aluminum (JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, JIS H4000:2014 A8079P-O), etc. It is more preferably formed.

[0107] Regarding the thickness of the barrier layer 33, from the viewpoint of making it difficult for pinholes to occur even by molding while thinning the exterior material for the power storage device, it is preferably about 10 to 200 μm, and more preferably about 20 to 100 μm.

[0108] Also, the barrier layer 33 is preferably subjected to 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.

[0109] (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-fusible resin layer 35 as necessary in order to firmly adhere the heat-fusible resin layer 35.

[0110] The subsequent layer 34 is formed by an adhesive capable of adhering the barrier layer 33 and the heat-sealable resin layer 35. The composition of the adhesive used for forming the adhesive layer is not particularly limited, and examples thereof include adhesives composed of a polyester polyol compound and an alicyclic isocyanate compound.

[0111] Further, it is also preferable that the adhesive layer 34 is a cured product of a resin composition containing an acid-modified polyolefin and at least one selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and a compound having an epoxy group. Particularly preferably, it is a cured product of a resin composition containing an acid-modified polyolefin and at least one selected from the group consisting of a compound having an isocyanate group and a compound having an epoxy group.

[0112] When the exterior material 3 for the power storage device is an exterior material for an all-solid-state battery, similar to the adhesive layer 32, the adhesive layer 34 is preferably formed by a cured product of a resin composition containing at least one of polyester and polycarbonate and at least one of an alicyclic isocyanate compound and an aromatic isocyanate compound.

[0113] Regarding the thickness of the adhesive layer 34, for example, it is about 1 to 40 μm, preferably about 2 to 30 μm.

[0114] (Heat-sealable resin layer 35) In the exterior material 3 for the power storage device, the heat-sealable resin layer 35 corresponds to the innermost layer and is a layer in which the heat-sealable resin layers are heat-sealed to seal the power storage device element during the assembly of the power storage device.

[0115] The resin component used for the heat-sealable resin layer 35 is not particularly limited as long as it is heat-sealable. For example, in the exterior material for the power storage device, generally, polyolefin and cyclic polyolefin are mentioned.

[0116] 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 used.

[0117] 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 preferably used, and norbornene is more preferably used. Styrene is also included as a constituent monomer.

[0118] Among these resin components, crystalline or amorphous polyolefins, cyclic polyolefins, and blend polymers thereof are preferably used; polyethylene, polypropylene, copolymers of ethylene and norbornene, and blend polymers of two or more of these are more preferably used.

[0119] 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, or may be formed of two or more layers of the same or different resin components.

[0120] Moreover, 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, more preferably about 10 to 500 μm.

[0121] In addition, the adhesive film 1 for metal terminals of the present disclosure can be particularly preferably applied to the exterior material for all-solid-state batteries. The melting point of the heat-sealable resin layer 35 of the exterior material for all-solid-state batteries is preferably 150 to 250 °C, more preferably 180 to 270 °C, still more preferably 200 to 270 °C, and even more preferably 200 to 250 °C.

[0122] Examples of the resin contained in the heat-sealable resin layer 35 of the exterior material for all-solid-state batteries include polyolefins such as polypropylene and polyethylene, acid-modified polyolefins such as acid-modified polypropylene and acid-modified polyethylene, and polybutylene terephthalate. Among these, polybutylene terephthalate is excellent in heat resistance. Therefore, in the exterior material for all-solid-state batteries, the heat-sealable resin layer 35 is preferably formed of a polybutylene terephthalate film. In addition, when the heat-sealable resin layer 35 is formed of a polybutylene terephthalate film, the adhesiveness with the resin layer of the adhesive film for metal terminals of the present disclosure is also excellent. The polybutylene terephthalate film for forming the heat-sealable resin layer 35 may be a pre-prepared polybutylene terephthalate film laminated with the adhesive layer 34 to form the heat-sealable resin layer 35, or the resin for forming the polybutylene terephthalate film may be melt-extruded into a film and laminated with the adhesive layer 34, or the adhesive layer 34 and polybutylene terephthalate may be co-extruded and laminated on the barrier layer 33.

[0123] The polybutylene terephthalate film may be a stretched polybutylene terephthalate film or an unstretched polybutylene terephthalate film, and it is preferably an unstretched polybutylene terephthalate film.

[0124] The polybutylene terephthalate film preferably contains, in addition to polybutylene terephthalate, an elastomer. The elastomer plays a role in enhancing the flexibility of the polybutylene terephthalate film while ensuring its durability in a high-temperature environment. Preferred elastomers include at least one or more thermoplastic elastomers selected from polyester-based, polyamide-based, polyurethane-based, polyolefin-based, polystyrene-based, and polyether-based, or thermoplastic elastomers that are copolymers thereof. In the polybutylene terephthalate film, the content of the elastomer is not particularly limited as long as it can enhance the flexibility while ensuring the durability of the polybutylene terephthalate film in a high-temperature environment. For example, it is about 0.1% by mass or more, preferably about 0.5% by mass or more, more preferably about 1.0% by mass or more, and even more preferably about 3.0% by mass or more. Also, the content is, for example, about 10.0% by mass or less, about 8.0% by mass or less, about 5.0% by mass or less, etc. Preferred ranges of the content include about 0.1 to 10.0% by mass, about 0.1 to 8.0% by mass, about 0.1 to 5.0% by mass, about 0.5 to 10.0% by mass, about 0.5 to 8.0% by mass, about 0.5 to 5.0% by mass, about 1.0 to 10.0% by mass, about 1.0 to 8.0% by mass, about 1.0 to 5.0% by mass, about 3.0 to 10.0% by mass, about 3.0 to 8.0% by mass, about 3.0 to 5.0% by mass, etc.

[0125] The heat-sealable resin layer 35 may be formed of only one layer, or may be formed of two or more layers of the same or different resins. When the heat-sealable resin layer 35 is formed of two or more layers, at least one layer is formed of a polybutylene terephthalate film, and the polybutylene terephthalate film is preferably the innermost layer of the exterior material for all-solid-state batteries. Also, the layer that adheres to the adhesive layer 34 is preferably a polybutylene terephthalate film. When the heat-sealable resin layer 35 is formed of two or more layers, for the layers not formed of the polybutylene terephthalate film, they may be layers formed of, for example, polyolefins such as polypropylene and polyethylene, or acid-modified polyolefins such as acid-modified polypropylene and acid-modified polyethylene. However, since polyolefins and acid-modified polyolefins have lower durability in a high-temperature environment compared to polybutylene terephthalate, the heat-sealable resin layer 35 is preferably composed of only the polybutylene terephthalate film.

[0126] 2. Energy storage device The power storage device 10 of the present disclosure includes at least a power storage device element 4 including a positive electrode, a negative electrode, and an electrolyte, an exterior material 3 for the power storage device that seals the power 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 power storage device. In the power storage device 10 of the present disclosure, the adhesive film 1 for metal terminals of the present disclosure is interposed between the metal terminal 2 and the exterior material 3 for the power storage device. That is, the power storage device 10 of the present disclosure can be manufactured by a method including a step of interposing the adhesive film 1 for metal terminals of the present disclosure between the metal terminal 2 and the exterior material 3 for the power storage device.

[0127] Specifically, a power storage device element 4 including at least a positive electrode, a negative electrode, and an electrolyte is coated with an exterior material 3 for a power storage device, with metal terminals 2 connected to each of the positive electrode and the negative electrode protruding outward. The adhesive film 1 for a metal terminal of the present disclosure is interposed between the metal terminal 2 and a heat-sealable resin layer 35, and the peripheral edge of the power storage device element 4 is coated so that a flange portion of the exterior material for a power storage device (a region where the heat-sealable resin layers 35 contact each other, i.e., the peripheral edge portion 3a of the exterior material for a power storage device) can be formed, and the heat-sealable resin layers 35 of the flange portion are heat-sealed and sealed, thereby providing a power storage device 10 using the exterior material 3 for a power storage device. When the power storage device element 4 is housed using the exterior material 3 for a power storage device, the heat-sealable resin layer 35 of the exterior material 3 for a power storage device is used so as to be on the inner side (the surface in contact with the power storage device element 4).

[0128] 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. There is no particular limitation on the type of secondary battery to which the exterior material for a power storage device of the present disclosure is applied. For example, lithium-ion batteries, lithium-ion polymer batteries, all-solid-state batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, capacitors, capacitors, etc. can be mentioned. Among these secondary batteries, lithium-ion batteries and lithium-ion polymer batteries can be mentioned as suitable application targets for the exterior material for a power storage device of the present disclosure.

[0129] Among these, the adhesive film 1 for a metal terminal of the present disclosure can be suitably applied to all-solid-state batteries.

Examples

[0130] Examples and comparative examples are shown below to explain the present disclosure in detail. However, the present disclosure is not limited to the examples.

[0131] <Manufacture of Adhesive Film for Metal Terminals> Example 1 Maleic anhydride-modified polypropylene (obtained by modifying homopolypropylene with maleic anhydride) that forms a polyolefin-based resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin-based resin layer, and polybutylene terephthalate (homo type) that forms a polyester-based resin layer were laminated in this order, and a laminate was manufactured by coextrusion molding. An adhesive film for metal terminals (thickness 100 μm) with a polyolefin-based resin layer (h-PPa layer, thickness 20 μm, melting point 165°C) / imine-modified polyolefin-based resin layer (r-IP layer, thickness 20 μm, melting point 141°C) / polyester-based resin layer (h-PBT layer, thickness 60 μm, melting point 224°C) laminated in order was obtained. The laminated structure of the adhesive film for metal terminals is shown in Table 1.

[0132] Example 2 Maleic anhydride-modified polypropylene (obtained by modifying homopolypropylene with maleic anhydride) that forms a polyolefin-based resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin-based resin layer, and polybutylene terephthalate (homo type) that forms a polyester-based resin layer were laminated in this order, and a laminate was manufactured by coextrusion molding. An adhesive film for metal terminals (thickness 100 μm) with a polyolefin-based resin layer (h-PPa layer, thickness 30 μm, melting point 165°C) / imine-modified polyolefin-based resin layer (r-IP layer, thickness 30 μm, melting point 141°C) / polyester-based resin layer (h-PBT layer, thickness 40 μm, melting point 224°C) laminated in order was obtained. The laminated structure of the adhesive film for metal terminals is shown in Table 1.

[0133] Example 3 Maleic anhydride-modified polypropylene (homopolypropylene modified with maleic anhydride) that forms a polyolefin resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin resin layer, and polybutylene terephthalate (homotype) that forms a polyester resin layer were laminated in this order to produce a laminate by coextrusion molding. An adhesive film for metal terminals (thickness: 100 μm) with a polyolefin resin layer (h-PPa layer, thickness: 40 μm, melting point: 165°C) / imine-modified polyolefin resin layer (r-IP layer, thickness: 20 μm, melting point: 141°C) / polyester resin layer (h-PBT layer, thickness: 40 μm, melting point: 224°C) laminated in this order was obtained. The laminated structure of the adhesive film for metal terminals is shown in Table 1.

[0134] Example 4 Maleic anhydride-modified polypropylene (homopolypropylene modified with maleic anhydride) that forms a polyolefin resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin resin layer, and polybutylene terephthalate (homotype) that forms a polyester resin layer were laminated in this order to produce a laminate by coextrusion molding. An adhesive film for metal terminals (thickness: 100 μm) with a polyolefin resin layer (h-PPa layer, thickness: 60 μm, melting point: 165°C) / imine-modified polyolefin resin layer (r-IP layer, thickness: 20 μm, melting point: 141°C) / polyester resin layer (h-PBT layer, thickness: 20 μm, melting point: 224°C) laminated in this order was obtained. The laminated structure of the adhesive film for metal terminals is shown in Table 1.

[0135] Example 5 Maleic anhydride-modified polypropylene (modified homopolypropylene with maleic anhydride) forming a polyolefin resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin resin layer, and polybutylene terephthalate (copolymer type, copolymerized with polyester and polyether) forming a polyester resin layer were laminated in this order, and a laminate was produced by coextrusion molding. An adhesive film for metal terminals (thickness: 100 μm) with a polyolefin resin layer (h-PPa layer, thickness: 30 μm, melting point: 165 °C) / imine-modified polyolefin resin layer (r-IP layer, thickness: 30 μm, melting point: 141 °C) / polyester resin layer (copolymerized PBT layer, thickness: 40 μm, melting point: 213 °C) laminated in order was obtained. The laminated structure of the adhesive film for metal terminals is shown in Table 1.

[0136] Example 6 Maleic anhydride-modified polypropylene (modified homopolypropylene with maleic anhydride) forming a polyolefin resin layer, imine-modified polypropylene (homotype) as an imine-modified polyolefin resin layer, and polybutylene terephthalate (homotype) forming a polyester resin layer were laminated in this order, and a laminate was produced by coextrusion molding. An adhesive film for metal terminals (thickness: 100 μm) with a polyolefin resin layer (h-PPa layer, thickness: 30 μm, melting point: 165 °C) / imine-modified polyolefin resin layer (h-IP layer, thickness: 30 μm, melting point: 160 °C) / polyester resin layer (h-PBT layer, thickness: 40 μm, melting point: 224 °C) laminated in order was obtained. The laminated structure of the adhesive film for metal terminals is shown in Table 1.

[0137] Example 7 Maleic anhydride-modified polypropylene (homopolypropylene modified with maleic anhydride) that forms a polyolefin resin layer, polypropylene (homotype) that forms a polyolefin resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin resin layer, and polybutylene terephthalate (copolymer type) that forms a polyester resin layer were laminated in this order to produce a laminate by coextrusion molding. A pressure-sensitive adhesive film for metal terminals (thickness: 100 μm) with a laminated structure of polyolefin resin layer (h-PPa layer, thickness: 30 μm, melting point: 165°C) / polyolefin resin layer (h-PP layer, thickness: 10 μm, melting point: 165°C) / imine-modified polyolefin resin layer (r-IP layer, thickness: 20 μm, melting point: 141°C) / polyester resin layer (h-PBT layer, thickness: 40 μm, melting point: 224°C) laminated in this order was obtained. The laminated structure of the pressure-sensitive adhesive film for metal terminals is shown in Table 1.

[0138] Example 8 Maleic anhydride-modified polypropylene (homopolypropylene modified with maleic anhydride) that forms a polyolefin resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin resin layer, polybutylene terephthalate (homotype) that forms a polyester resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin resin layer, and maleic anhydride-modified polypropylene (homopolypropylene modified with maleic anhydride) that forms a polyolefin resin layer were laminated in this order to produce a laminate by coextrusion molding. A pressure-sensitive adhesive film for metal terminals (thickness: 100 μm) with a laminated structure of polyolefin resin layer (h-PPa layer, thickness: 20 μm, melting point: 165°C) / imine-modified polyolefin resin layer (r-IP layer, thickness: 10 μm, melting point: 141°C) / polyester resin layer (h-PBT layer, thickness: 40 μm, melting point: 224°C) / imine-modified polyolefin resin layer (r-IP layer, thickness: 10 μm, melting point: 141°C) / polyolefin resin layer (h-PPa layer, thickness: 20 μm, melting point: 165°C) laminated in this order was obtained. The laminated structure of the pressure-sensitive adhesive film for metal terminals is shown in Table 1.

[0139] Example 9 Maleic anhydride-modified polypropylene (homopolypropylene modified with maleic anhydride) forming a polyolefin resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin resin layer, polybutylene terephthalate (homotype) forming a polyester resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin resin layer, and polypropylene (homotype) forming a polyolefin resin layer were laminated in this order and produced by coextrusion molding to obtain an adhesive film for metal terminals (thickness: 100 μm) in which a polyolefin resin layer (h-PPa layer, thickness 20 μm, melting point 165 °C) / imine-modified polyolefin resin layer (r-IP layer, thickness 10 μm, melting point 141 °C) / polyester resin layer (h-PBT layer, thickness 40 μm, melting point 224 °C) / imine-modified polyolefin resin layer (r-IP layer, thickness 10 μm, melting point 141 °C) / polyolefin resin (h-PP layer, thickness 20 μm, melting point 165 °C) were laminated in order. The laminated structure of the adhesive film for metal terminals is shown in Table 1.

[0140] Example 10 Maleic anhydride-modified polypropylene (polypropylene modified with maleic anhydride) that forms a polyolefin resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin resin layer, polyethylene terephthalate that forms a polyester resin layer, imine-modified polypropylene (random type) as an imine-modified polyolefin resin layer, and polypropylene (homotype) that forms a polyolefin resin layer are laminated in this order by coextrusion molding to obtain an adhesive film for metal terminals (thickness 100 μm) in which a polyolefin resin layer (h-PPa layer, thickness 20 μm, melting point 165°C) / imine-modified polyolefin resin layer (r-IP layer, thickness 10 μm, melting point 141°C) / polyester resin layer (PET layer, thickness 40 μm, melting point 225°C) / imine-modified polyolefin resin layer (r-IP layer, thickness 10 μm, melting point 141°C) / polyolefin resin (h-PP layer, thickness 20 μm, melting point 165°C) are laminated in sequence. The laminated structure of the adhesive film for metal terminals is shown in Table 1.

[0141] Comparative Example 1 A maleic anhydride-modified random polypropylene film (random polypropylene modified with maleic anhydride) (thickness 80 μm, melting point 140°C, random type) that forms a polyolefin resin layer was prepared, and the single layer of the maleic anhydride-modified polypropylene film was used as an adhesive film for metal terminals.

[0142] Comparative Example 2 Using an extruder and a T-die casting device, maleic anhydride-modified polypropylene (random polypropylene modified with maleic anhydride) was extruded onto one side of a polypropylene film (80 μm thick, homotype), and maleic anhydride-modified polypropylene (random polypropylene modified with maleic anhydride) was extruded onto the other side at a temperature of 270°C. Respectively, an adhesive film for metal terminals (150 μm thick) with a laminated structure of polyolefin resin layer (r-PPa layer, 35 μm thick, melting point 140°C) / polyolefin resin layer (h-PP layer, 80 μm thick, melting point 165°C) / polyolefin resin layer (r-PPa layer, 35 μm thick, melting point 140°C) laminated in sequence was obtained. The laminated structure of the adhesive film for metal terminals is shown in Table 1.

[0143] Comparative Example 3 Using an extruder and a T-die casting device, maleic anhydride-modified polypropylene (homopolypropylene modified with maleic anhydride) was extruded onto one side of a polybutylene terephthalate film (50 μm thick, homotype) at a temperature of 165°C. Respectively, an adhesive film for metal terminals (100 μm thick) with a laminated structure of polyolefin resin layer (h-PPa layer, 50 μm thick, melting point 224°C) / polyester resin layer (h-PBT layer, 50 μm thick, melting point 224°C) laminated in sequence was obtained. The laminated structure of the adhesive film for metal terminals is shown in Table 1.

[0144] Comparative Example 4 A polybutylene terephthalate film (100 μm thick, melting point 225°C, homotype) was prepared, and the single layer of the polybutylene terephthalate film was used as an adhesive film for metal terminals.

[0145] [Measurement of seal strength in a 150°C environment (evaluation of heat resistance)] An outer packaging material for all-solid-state batteries (a laminated film in which a base material layer (polyethylene terephthalate (25 μm)) / an adhesive layer (urethane adhesive 3 μm) / an aluminum foil (40 μm) / an adhesive layer (urethane adhesive (3 μm)) / a heat-sealable resin layer (polybutylene terephthalate (25 μm)) are laminated in this order) was prepared and cut into a size of TD30×MD150 mm. Also, as a metal terminal with an adhesive film for metal terminals, an aluminum foil (JIS H4160:1994 A8079H-O) (TD22.5 mm, MD180 mm, thickness 400 μm) was prepared. Adhesive films for metal terminals (width (TD) 20 mm, length (MD) 165 mm) were respectively arranged on both sides of the metal terminal. At this time, the MD and TD of the metal terminal were respectively laminated so as to coincide with the length direction (MD) and width direction (TD) of the adhesive film, and the centers of the metal terminal and the adhesive film were made to coincide. Next, heat fusion was performed under the conditions of a temperature of 200 °C, a surface pressure of about 0.25 MPa, and 16 seconds to produce a laminate in which an adhesive film for metal terminals / metal terminal / adhesive film for metal terminals were laminated in this order. Further, the metal terminal with an adhesive film for metal terminals was equally divided into six parts in the length direction (MD) so that the width became 25 mm each. Next, the heat-sealable resin layers of the outer packaging material for all-solid-state batteries (outer packaging material) were made to face each other inside and the length direction (MD) was folded in half (TD30 mm×MD75 mm), and a metal terminal with an adhesive film for metal terminals (width 25 mm×length 20 mm) was sandwiched therebetween. At this time, the metal terminal with an adhesive film for metal terminals was sandwiched so that the MD of the adhesive film for metal terminals was orthogonal to the MD of the outer packaging material and abutted against the inner part of the fold of the outer packaging material. In this state, heat sealing was performed at 240 °C×1.0 MPa×12 seconds with a sealing machine having upper and lower metal heads with a width of 7 mm. The heat-sealed part of the obtained laminate has a structure in which the outer packaging material / adhesive film for metal terminals / metal terminal / adhesive film for metal terminals / outer packaging material are laminated in this order. Next, the laminate was cut in a direction perpendicular to the sealing width of 7 mm to obtain a sample with a width of 15 mm. At this time, the sample was obtained from the central part of the laminate. Next, the outer packaging material on one side of the sample and the metal terminal were chucked, and in an environment of 150 °C with a tensile tester equipped with a thermostatic bath, the outer packaging material and the metal terminal were pulled in the 180 °C direction at a speed of 300 mm / min, and the seal strength at 150 °C was measured.

[0146] [Evaluation of Sealing Property] <Followability to Metal Terminals> The adhesive film for metal terminals was cut into a size of 55 mm × 10 mm, and two pieces of the adhesive film for metal terminals were prepared. Also, a metal terminal made of aluminum alloy (width 45 mm, length 60 mm, thickness 400 μm) was prepared. As shown in the schematic diagram of Fig. 6, on both sides of the central position of the metal terminal, the polyolefin resin layer of the adhesive film for metal terminals was arranged on the metal terminal side, and a flat-plate press machine with a metal head pasted with silicon rubber having a thickness of 3.0 mm and a hardness of 40 on both the upper and lower sides was heat-sealed under the conditions of 200 °C × 0.25 MPa (surface pressure applied to the silicon rubber) × 12 seconds to prepare a metal terminal with an adhesive film for metal terminals. The metal terminal with an adhesive film for metal terminals was observed using a loupe (magnification 20 times), and the state around the metal terminal where the adhesive film for metal terminals was heat-fused was confirmed. The evaluation criteria are as follows. A: The adhesive film follows the shape of the metal terminal, and no gap is formed between the metal terminal and the adhesive film. B: The adhesive film generally follows the shape of the metal terminal, and the gap between the metal terminal and the adhesive film is slight. C: The followability of the adhesive film to the shape of the metal terminal is insufficient, and there is a large gap between the metal terminal and the adhesive film.

[0147] <Thermal Shrinkage of Adhesive Film> The adhesive film for metal terminals was cut into a size of 10 mm × 120 mm, and marking lines were made at intervals of 100 mm. Next, the adhesive film for metal terminals was hung in an oven at 190 °C and heated for 3 minutes, and then the length between the marking lines was measured. The length retention rate of the marking line interval (length after heating / length before heating) was calculated, and the suppression of thermal shrinkage was evaluated according to the following criteria. A: The length retention rate of the marking line interval is 0.7 or more, and the thermal shrinkage is sufficiently suppressed. C: The length retention rate of the marking line interval is less than 0.7, and the suppression of thermal shrinkage is insufficient.

[0148]

Table 1

[0149] In the laminate structure shown in Table 1, h-PPa is a homopolypropylene modified with maleic anhydride, r-PPa is a random polypropylene modified with maleic anhydride, h-IP is a homopolypropylene modified with imine, r-IP is a random polypropylene modified with imine, h-PBT means a homotype polybutylene terephthalate, and the numerical values in parentheses are thickness (μm).

[0150] As described above, the present disclosure provides an invention in the following aspects. Item 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, The adhesive film for a metal terminal is composed of a laminate including at least a polyester resin layer, an imine-modified polyolefin resin layer, and a polyolefin resin layer in this order. Item 2. The adhesive film for a metal terminal according to Item 1, wherein the polyolefin resin layer constitutes the surface of the adhesive film for a metal terminal on the metal terminal side. Item 3. The adhesive film for a metal terminal according to Item 1 or 2, wherein the melting point of the polyester resin layer is 20 °C or higher than the melting point of the polyolefin resin layer. Item 4. The adhesive film for a metal terminal according to any one of Items 1 to 3, wherein the polyester resin layer contains a polyester resin and an elastomer. Item 5. The adhesive film for a metal terminal according to any one of Items 1 to 4, wherein the melting point of the polyolefin resin layer is 155 °C or higher. Item 6. The adhesive film for a metal terminal according to any one of Items 1 to 5, wherein the melting point of the imine-modified polyolefin resin layer is 140 °C or higher. 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 50 μm or more and 500 μm or less. Item 8. The adhesive film for metal terminals according to any one of Items 1 to 7, wherein the exterior material for the power storage device is composed of a laminate including, at least from the outside, a base material layer, a barrier layer, and a heat-sealable resin layer in this order. Item 9. 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 8 is attached to the metal terminal. Item 10. A power storage device including at least a power storage device element including a positive electrode, a negative electrode, and an electrolyte, an exterior material for the power storage device for sealing the power storage device element, and metal terminals electrically connected to the positive electrode and the negative electrode respectively and protruding outside the exterior material for the power storage device, wherein the adhesive film for metal terminals according to any one of Items 1 to 8 is interposed between the metal terminal and the exterior material for the power storage device. Item 11. A method for manufacturing a power storage device including at least a power storage device element including a positive electrode, a negative electrode, and an electrolyte, an exterior material for the power storage device for sealing the power storage device element, and metal terminals electrically connected to the positive electrode and the negative electrode respectively and protruding outside the exterior material for the power storage device, the method including a step of interposing the adhesive film for metal terminals according to any one of Items 1 to 8 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. Item 12. A method for manufacturing 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 the power storage device for sealing the power storage device element, the method including obtaining an adhesive film for metal terminals composed of a laminate including at least a polyester resin layer, an imine-modified polyolefin resin layer, and a polyolefin resin layer in this order.

Explanation of Signs

[0151] 1 Adhesive film for metal terminals 2 Metal terminals 3 Exterior material for power storage devices 3a Peripheral part of the exterior material for power storage devices 4 Power storage device elements 10 Power storage devices 11 Polyester-based resin layer 12 Polyolefin-based resin layer 13 Imine-modified polyolefin-based resin layer 31 Base material layer 32 Adhesive layer 33 Barrier layer 34 Adhering 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 is composed of a laminate including at least a polyester resin layer, an imine-modified polyolefin resin layer, and a polyolefin resin layer in this order.

2. The adhesive film for a metal terminal according to claim 1, wherein the polyolefin resin layer constitutes the surface of the adhesive film for a metal terminal on the side of the metal terminal.

3. The adhesive film for a metal terminal according to claim 1 or 2, wherein the melting point of the polyester resin layer is 20 °C or higher than the melting point of the polyolefin resin layer.

4. The adhesive film for a metal terminal according to any one of claims 1 to 3, wherein the polyester resin layer contains a polyester resin and an elastomer.

5. The adhesive film for a metal terminal according to any one of claims 1 to 4, wherein the melting point of the polyolefin resin layer is 155 °C or higher.

6. The adhesive film for a metal terminal according to any one of claims 1 to 5, wherein the melting point of the imine-modified polyolefin resin layer is 140 °C or higher.

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 50 μm or more and 500 μm or less.

8. The adhesive film for a metal terminal according to any one of claims 1 to 7, wherein 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 from the outside.

9. A metal terminal with an adhesive film for a metal terminal, wherein the adhesive film for a metal terminal according to any one of claims 1 to 8 is attached to the metal terminal.

10. 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 a power storage device that seals the power storage device element, and the metal terminals electrically connected to the positive electrode and the negative electrode respectively and protruding outside the exterior material for a power storage device, wherein the adhesive film for a metal terminal according to any one of claims 1 to 8 is interposed between the metal terminal and the exterior material for a power storage device.

11. A method for manufacturing 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 for sealing the power storage device element; and metal terminals electrically connected to each of the positive electrode and the negative electrode and protruding outside the exterior material for the power storage device. A method for manufacturing a power storage device, comprising a step of interposing the adhesive film for metal terminals according to any one of claims 1 to 8 between the metal terminals 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.

12. A method for manufacturing an adhesive film for metal terminals, which is interposed between a metal terminal electrically connected to an electrode of a power storage device element and an exterior material for the power storage device for sealing the power storage device element. A method for manufacturing an adhesive film for metal terminals, comprising obtaining an adhesive film for metal terminals made of a laminate including at least a polyester resin layer, an imine-modified polyolefin resin layer, and a polyolefin resin layer in this order.

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