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

Abstract

To provide an adhesive film for metal terminals which has excellent adhesion to metal terminals of an adhesive film when heat-sealed and in which a decrease in the adhesion is suppressed even if an electrolytic solution adheres to the adhesive film tightly adhered to the metal terminals.SOLUTION: There is provided 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 a power storage device exterior material. The adhesive film for metal terminals comprises a laminate including a first polyolefin layer disposed on a metal terminal side, a substrate, and a second polyolefin layer disposed on a power storage device exterior material side, in this order. A sea-island structure is observed in an electron microscope cross-sectional image of a cross-section of the first polyolefin layer in a direction parallel to a TD and in a thickness direction. In the cross-sectional image after the adhesive film for metal terminals is heated for 12 seconds at a temperature of 190°C and a surface pressure of 0.016 MPa, a ratio of the total area of island portions of the sea-island structure is 25.0-35.0%.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Various types of electricity storage devices have been developed to date, and in all electricity storage devices, exterior materials for electricity storage devices have become essential components for sealing electricity storage device elements such as electrodes and electrolytes. Metal exterior materials for electricity storage devices have traditionally been widely used as exterior materials for electricity storage devices. However, in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, and the like, electricity storage devices are being required to have a variety of shapes, as well as to be thinner and lighter. However, the metal exterior materials for electricity storage devices that have traditionally been widely used have the drawbacks of being difficult to keep up with the diversification of shapes and also having limitations on how much they can be made lighter.

[0003] Therefore, in recent years, a laminate sheet in which a base material layer / adhesive layer / barrier layer / thermal adhesive resin layer are laminated in this order has been proposed as an electrical storage device packaging material that can be easily processed into a variety of shapes and can achieve thinning and weight reduction. When such a film-like electrical storage device packaging material is used, the electrical storage device elements are sealed in the electrical storage device packaging material by heat-sealing the peripheral edge of the electrical storage device packaging material with the innermost thermal adhesive resin layers facing each other.

[0004] Metal terminals protrude from the heat-sealed portions of the exterior material for an electricity storage device, and the electricity storage device elements sealed with the exterior material for an electricity storage device are electrically connected to the outside via the metal terminals electrically connected to the electrodes of the electricity storage device elements. That is, the portions of the heat-sealed exterior material for an electricity storage device where the metal terminals are present are heat-sealed in a state where the metal terminals are sandwiched between the heat-sealable resin layers. Because the metal terminals and the heat-sealable resin layer are made of different materials, adhesion is likely to decrease at the interface between the metal terminals and the heat-sealable resin layer.

[0005] For this reason, an adhesive film is sometimes disposed between the metal terminal and the heat-sealable resin layer in order to improve adhesion between them, etc. Examples of such adhesive films include those described in Patent Document 1. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-79638 Summary of the Invention [Problem to be solved by the invention]

[0007] Such adhesive films are required to have excellent adhesion to metal terminals when heat-sealed.

[0008] Furthermore, the adhesive film is required to suitably prevent a decrease in adhesion to the metal terminal even when the adhesive film comes into contact with the electrolyte solution sealed in the packaging material.

[0009] However, conventional adhesive films have not been sufficiently studied in terms of their adhesion to metal terminals when contacted with an electrolyte solution, and the inventors of the present disclosure have sought to achieve not only excellent adhesion of the adhesive film to the metal terminal by heat sealing, but also to suppress a decrease in adhesion to the metal terminal when an electrolyte solution adheres to the adhesive film that has adhered to the metal terminal.

[0010] The present disclosure has as its main object the provision of an adhesive film for metal terminals that exhibits excellent adhesion to metal terminals by heat sealing and that, even when an electrolyte solution adheres to the adhesive film adhered to the metal terminal, suitably suppresses a decrease in adhesion to the metal terminal. The present disclosure also has as its main object the provision of a method for manufacturing the adhesive film for metal terminals, a metal terminal with an adhesive film for metal terminals that uses the adhesive film for metal terminals, an electricity storage device that uses the adhesive film for metal terminals, and a method for manufacturing the electricity storage device. [Means for solving the problem]

[0011] The inventors of the present disclosure conducted extensive research to solve the above-mentioned problems. As a result, they found that an adhesive film for metal terminals composed of a laminate including, in this order, a first polyolefin layer disposed on the metal terminal side, a substrate, and a second polyolefin layer disposed on the exterior material side for an electricity storage device, wherein the adhesive film for metal terminals is left standing in a heated and pressurized environment at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, and then further left standing in an environment at a temperature of 25°C for 1 hour (typical heating conditions for heat sealing), and in a cross-sectional image of the surface portion of the first polyolefin layer on the metal terminal side, the ratio of the total area of the islands in the sea-island structure is within a predetermined range, thereby providing excellent adhesion of the adhesive film to the metal terminal by heat sealing, and further, even when an electrolyte solution adheres to the adhesive film adhered to the metal terminal by heat sealing, a decrease in adhesion to the metal terminal is suitably suppressed. The present disclosure was completed through further research based on this finding.

[0012] That is, the present disclosure provides the inventions of the following aspects. An adhesive film for metal terminals, which is interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that seals the electricity storage device element, the adhesive film for metal terminal is composed of a laminate including, in this order, a first polyolefin layer disposed on the metal terminal side, a substrate, and a second polyolefin layer disposed on the exterior material side for the electricity storage device; a sea-island structure is observed in a cross-sectional image of the first polyolefin layer taken in a direction parallel to the transverse direction (TD) and in the thickness direction, the cross-sectional image being obtained using a field emission scanning electron microscope; the cross-sectional image is a cross-sectional image obtained within a range from the surface opposite to the surface on the substrate side to a portion that is 30% of the thickness of the first polyolefin layer, where the thickness of the first polyolefin layer is 100%, An adhesive film for metal terminals, wherein the adhesive film for metal terminals is left to stand for 12 seconds in a heated and pressurized environment at a temperature of 190°C and a surface pressure of 0.016 MPa, and then further left to stand for 1 hour in an environment at a temperature of 25°C, and in the cross-sectional image thereof, the proportion of the total area of the island portions of the sea-island structure is 25.0% or more and 35.0% or less. [Effects of the Invention]

[0013] According to the present disclosure, it is possible to provide an adhesive film for metal terminals that has excellent adhesion to metal terminals by heat sealing and that, even when an electrolyte solution adheres to the adhesive film that has been adhered to the metal terminal by heat sealing, suitably suppresses a decrease in adhesion to the metal terminal.Furthermore, 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 that uses the adhesive film for metal terminals, an electricity storage device that uses the adhesive film for metal terminals, and a method for manufacturing the electricity storage device. [Brief explanation of the drawings]

[0014] [Figure 1]FIG. 1 is a schematic plan view of an electricity storage device according to the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view taken along line AA' in FIG. [Figure 3] FIG. 2 is a schematic cross-sectional view taken along line BB' in FIG. [Figure 4] 1 is a schematic cross-sectional view of an adhesive film for metal terminals according to the present disclosure. [Figure 5] 1 is a schematic cross-sectional view of an adhesive film for metal terminals according to the present disclosure. [Figure 6] 1 is a schematic cross-sectional view of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 7] This is a schematic cross-sectional view of an adhesive film / metal terminal / adhesive film laminate (metal terminal with adhesive film for metal terminal) obtained in an example by sandwiching a metal terminal between two adhesive films and heat-sealing them. [Figure 8] This is a cross-sectional image (binarized using image processing software) obtained using a field emission scanning electron microscope of a cross section (surface portion on the metal terminal side (opposite the substrate)) of the first polyolefin layer of the adhesive film for metal terminals obtained in Example 1 in a direction parallel to the TD and in the thickness direction. The cross-sectional image was obtained within a range of 30% of the thickness from the surface opposite the substrate-side surface of the first polyolefin layer. The cross-sectional image on the left was taken before the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, and the cross-sectional image on the right was taken after the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. [Figure 9]These are cross-sectional images (binarized using image processing software) obtained using a field emission scanning electron microscope of a cross section (surface portion on the substrate side) of the first polyolefin layer of the adhesive film for metal terminals obtained in Example 1 in a direction parallel to the TD and in the thickness direction. The cross-sectional images were obtained within a range from the surface on the substrate side of the first polyolefin layer to 30% of the thickness. The cross-sectional image on the left was taken before the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, and the cross-sectional image on the right was taken after the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. [Figure 10] This is a cross-sectional image (binarized using image processing software) obtained using a field emission scanning electron microscope of a cross section (surface portion on the metal terminal side (opposite the substrate)) of the first polyolefin layer of the adhesive film for metal terminals obtained in Comparative Example 1 in a direction parallel to the TD and in the thickness direction. The cross-sectional image was obtained within a range of 30% of the thickness from the surface opposite the substrate-side surface of the first polyolefin layer. The cross-sectional image on the left was taken before the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, and the cross-sectional image on the right was taken after the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. [Figure 11] These are cross-sectional images (binarized using image processing software) obtained using a field emission scanning electron microscope of a cross section (surface portion on the substrate side) of the first polyolefin layer of the adhesive film for metal terminals obtained in Comparative Example 1 in a direction parallel to the TD and in the thickness direction. The cross-sectional images were obtained within a range from the surface on the substrate side of the first polyolefin layer to 30% of the thickness. The cross-sectional image on the left was taken before the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, and the cross-sectional image on the right was taken after the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. [Figure 12]These are cross-sectional images (binarized using image processing software) obtained using a field emission scanning electron microscope of a cross section (surface portion on the metal terminal side (opposite the substrate)) of the first polyolefin layer of the adhesive film for metal terminals obtained in Comparative Example 2 in a direction parallel to the TD and in the thickness direction. The cross-sectional images were obtained within a range of 30% of the thickness from the surface opposite the substrate-side surface of the first polyolefin layer. The cross-sectional image on the left was taken before the first polyolefin layer was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, and the cross-sectional image on the right was taken after the first polyolefin layer was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. [Figure 13] These are cross-sectional images (binarized using image processing software) obtained using a field emission scanning electron microscope of a cross section (surface portion on the substrate side) parallel to the TD and in the thickness direction of the first polyolefin layer of the adhesive film for metal terminals obtained in Comparative Example 2. The cross-sectional images were obtained within a range from the surface on the substrate side of the first polyolefin layer to 30% of the thickness. The cross-sectional image on the left was taken before the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, and the cross-sectional image on the right was taken after the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. [Figure 14] FIG. 2 is a schematic diagram showing MD, TD, and thickness direction (y) in a production line for an adhesive film for a metal terminal. DETAILED DESCRIPTION OF THE INVENTION

[0015] The adhesive film for metal terminal of the present disclosure is an adhesive film for metal terminal interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that seals the electricity storage device element, the adhesive film for metal terminal being composed of a laminate including, in this order, a first polyolefin layer disposed on the metal terminal side, a substrate, and a second polyolefin layer disposed on the exterior material for an electricity storage device, the adhesive film for metal terminal being characterized in that a sea-island structure is observed in a cross-sectional image obtained using a field emission scanning electron microscope of a cross-section of the first polyolefin layer in a direction parallel to the TD and in the thickness direction, the cross-sectional image being a cross-sectional image obtained within a range from the surface opposite the surface on the substrate side to a portion 30% of the thickness of the first polyolefin layer, where the thickness of the first polyolefin layer is taken as 100%, and the cross-sectional image after heating the adhesive film for metal terminal at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds has a ratio of the total area of the islands of the sea-island structure to 25.0% or more and 35.0% or less.

[0016] The adhesive film for metal terminals of the present disclosure is a cross-sectional image of the surface portion of the first polyolefin layer placed on the metal terminal side (specifically, a cross-sectional image obtained within a range of 30% of the thickness from the surface opposite the substrate side surface, assuming the thickness of the first polyolefin layer to be 100%), in which the proportion of the total area of the island portions of the sea-island structure is set to 25.0% or more and 35.0% or less in the cross-sectional image after the adhesive film for metal terminals is heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds.Therefore, the adhesive film has excellent adhesion to the metal terminal by heat sealing, and further, even if an electrolyte adheres to the adhesive film adhered to the metal terminal by heat sealing, a decrease in adhesion to the metal terminal is suitably suppressed.

[0017] The present disclosure also provides an electricity storage device comprising at least an electricity storage device element having a positive electrode, a negative electrode, and an electrolyte, an exterior material for an electricity storage device that encapsulates the electricity storage device element, and metal terminals electrically connected to the positive electrode and the negative electrode, respectively, and protruding outside the exterior material for an electricity storage device, wherein the adhesive film for a metal terminal of the present disclosure is interposed between the metal terminal and the exterior material for an electricity storage device. The adhesive film for a metal terminal and a method for manufacturing the same of the present disclosure, and an electricity storage device using the adhesive film for a metal terminal and a method for manufacturing the same are described in detail below.

[0018] In this specification, numerical ranges indicated with "to" mean "greater than or equal to" or "less than or equal to." For example, the expression 2 to 15 mm means 2 mm or greater and 15 mm or less.

[0019] Another method for confirming the MD of an adhesive film for metal terminals is to observe a cross section of the adhesive film for metal terminals (e.g., a cross section of the first polyolefin layer, the substrate, or the second polyolefin layer) using an electron microscope to confirm the sea-island structure. In this method, the direction parallel to the cross section in which the average diameter of the island shapes in the direction perpendicular to the thickness direction of the adhesive film for metal terminals is the largest can be determined as the MD. Specifically, the sea-island structure is confirmed by observing, using an electron microscope, a cross section in the longitudinal direction of the adhesive film for metal terminals and each cross section at an angle of 10 degrees from the direction parallel to the cross section in the longitudinal direction up to the direction perpendicular to the cross section in the longitudinal direction (a total of 10 cross sections). Next, the shape of each individual island is observed in each cross section. For each island shape, the linear distance connecting the leftmost end in the direction perpendicular to the thickness direction of the adhesive film for metal terminals to the rightmost end in that vertical direction is defined as the diameter y. For each cross section, the average of the diameters y of the top 20 island shapes in order of largest diameter y is calculated. The direction parallel to the cross section where the average diameter y of the island shape was the largest was determined to be the MD.

[0020] 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 an electricity storage device element and an exterior material for an electricity storage device that seals the electricity storage device element. Specifically, as shown in Figures 1 to 3, for example, an adhesive film for metal terminal 1 of the present disclosure is interposed between a metal terminal 2 electrically connected to an electrode of an electricity storage device element 4 and an exterior material for an electricity storage device 3 that seals the electricity storage device element 4. The metal terminal 2 protrudes outside the exterior material for an electricity storage device 3 and is sandwiched between the exterior material for an electricity storage device 3, via the adhesive film for metal terminal 1, at a peripheral portion 3a of the heat-sealed exterior material for an electricity storage device 3. In the present disclosure, the heating temperature when heat-sealing the exterior material for an electricity storage device is typically in the range of about 160 to 190°C, and the pressure is typically in the range of about 1.0 to 2.0 MPa. In addition, in the process of bonding a metal terminal and an exterior material for an electricity storage device via an adhesive film, it is common to perform multiple cycles of heating and pressure, such as a temporary bonding process to the metal terminal and a main bonding process. The temporary bonding process is a process of temporarily attaching the adhesive film to the metal terminal and removing air bubbles, and the main bonding process is a process of bonding the adhesive film to the metal terminal by applying heat and pressure once or multiple times under higher temperature conditions than the temporary bonding process. The temporary bonding process of the adhesive film for a metal terminal to the metal terminal is performed, for example, at a temperature of about 140 to 160°C, at a pressure of about 0.01 to 1.0 MPa, for about 3 to 15 seconds, and about 3 to 6 cycles, while the main bonding process is performed, for example, at a temperature of about 160 to 240°C, at a pressure of about 0.01 to 1.0 MPa, for about 3 to 15 seconds, and about 1 to 3 cycles.

[0021] The adhesive film 1 for metal terminals of the present disclosure is provided to improve adhesion between the metal terminal 2 and the exterior packaging material 3 for an electricity storage device. Improved adhesion between the metal terminal 2 and the exterior packaging material 3 for an electricity storage device improves the sealing performance of the electricity storage device element 4. As described above, when the electricity storage device element 4 is heat-sealed, the electricity storage device element is sealed such that the metal terminal 2 electrically connected to the electrode of the electricity storage device element 4 protrudes outside the exterior packaging material 3 for an electricity storage device. At this time, the metal terminal 2 made of metal and the heat-sealable resin layer 35 (a layer made of a heat-sealable resin such as polyolefin) located in the innermost layer of the exterior packaging material 3 for an electricity storage device are made of different materials. Therefore, without using such an adhesive film, the sealing performance of the electricity storage device element is likely to be reduced at the interface between the metal terminal 2 and the heat-sealable resin layer 35.

[0022] As shown in Figures 4 and 5, the adhesive film 1 for metal terminals of the present disclosure has a configuration in which at least a first polyolefin layer 12a, a substrate 11, and a second polyolefin layer 12b are laminated in this order. The first polyolefin layer 12a is disposed on the metal terminal 2 side. The second polyolefin layer 12b is disposed on the electricity storage device exterior packaging material 3 side. In the adhesive film 1 for metal terminals of the present disclosure, the first polyolefin layer 12a and the second polyolefin layer 12b are located on the surfaces of both sides, respectively.

[0023] In the adhesive film for metal terminal 1 of the present disclosure, the first polyolefin layer 12a and the second polyolefin layer 12b are each a layer containing a polyolefin-based resin. Examples of polyolefin-based resins include polyolefin and acid-modified polyolefin. The first polyolefin layer 12a preferably contains an acid-modified polyolefin among polyolefin-based resins, and is more preferably a layer formed from an acid-modified polyolefin. The second polyolefin layer 12b preferably contains a polyolefin or an acid-modified polyolefin among polyolefin-based resins, and is more preferably a polyolefin, and is even more preferably a layer formed from a polyolefin. The resin forming the second polyolefin layer 12b disposed on the side of the electrical storage device sheathing material 3 is the same resin as the resin forming the heat-sealable resin layer 35 of the electrical storage device sheathing material 3, thereby improving adhesion between the adhesive film for metal terminal 1 of the present disclosure and the electrical storage device sheathing material.

[0024] Furthermore, the substrate 11 preferably contains a polyolefin resin, preferably contains a polyolefin, and more preferably is a layer formed of a polyolefin.

[0025] In the first polyolefin layer 12a, the second polyolefin layer 12b, and the substrate 11, the polyolefin resin is preferably a polypropylene resin, the polyolefin is preferably polypropylene, and the acid-modified polyolefin is preferably acid-modified polypropylene. Note that polyolefin resins such as polyolefins and acid-modified polyolefins may contain known additives, fillers, pigments, etc., which will be described later.

[0026] Specific examples of preferred laminate structures for the adhesive film 1 for metal terminals of the present disclosure include a three-layer structure in which a first polyolefin layer formed from acid-modified polypropylene / a base material formed from polypropylene / a second polyolefin layer formed from polypropylene are laminated in this order; a three-layer structure in which a first polyolefin layer formed from acid-modified polypropylene / a base material formed from polypropylene / a second polyolefin layer formed from acid-modified polypropylene are laminated in this order; and among these, a three-layer structure in which a first polyolefin layer formed from acid-modified polypropylene / a base material formed from polypropylene / a second polyolefin layer formed from polypropylene are laminated in this order is particularly preferred.

[0027] The materials constituting the first polyolefin layer 12a, the second polyolefin layer 12b and the substrate 11 will be described in detail below.

[0028] When the adhesive film 1 for metal terminals of the present disclosure is placed between the metal terminal 2 of the electricity storage device 10 and the exterior material 3 for electricity storage devices, the surface of the metal terminal 2 made of metal and the heat-sealable resin layer 35 (a layer formed of a heat-sealable resin such as polyolefin) of the exterior material 3 for electricity storage devices are bonded via the adhesive film 1 for metal terminals. The first polyolefin layer 12a of the adhesive film 1 for metal terminals is placed on the metal terminal 2 side, and the second polyolefin layer 12b is placed on the exterior material 3 for electricity storage devices, with the first polyolefin layer 12a in close contact with the metal terminal 2 and the second polyolefin layer 12b in close contact with the heat-sealable resin layer 35 of the exterior material 3 for electricity storage devices.

[0029] In the adhesive film for metal terminal 1 of the present disclosure, a sea-island structure is observed in a cross-sectional image of the first polyolefin layer 12a taken using a field emission scanning electron microscope in a cross section parallel to the TD and in the thickness direction. The cross-sectional image was taken within a range of 30% of the thickness of the first polyolefin layer 12a from the surface opposite the surface on the substrate 11 side, assuming the thickness of the first polyolefin layer 12a to be 100%. Furthermore, in the cross-sectional image taken after heating the adhesive film for metal terminal at 190°C and a surface pressure of 0.016 MPa for 12 seconds, the total area ratio of the islands in the sea-island structure is 25.0 to 35.0%. The adhesive film for metal terminal was heated at 190°C and a surface pressure of 0.016 MPa for 12 seconds using a hot plate heated to 190°C for 12 seconds, similar to the method used to measure adhesion strength in the Examples described below.

[0030] When the thickness of the first polyolefin layer 12a is taken as 100%, the area ranging from the surface opposite the surface on the substrate 11 side to a portion that is 30% of the thickness may be abbreviated as the surface portion of the first polyolefin layer 12a opposite the surface on the substrate 11 side (or the surface portion of the first polyolefin layer 12a on the metal terminal 2 side). Similarly, when the thickness of the first polyolefin layer 12a is taken as 100%, the area ranging from the surface on the substrate 11 side to a portion that is 30% of the thickness may be abbreviated as the surface portion of the first polyolefin layer 12a on the substrate 11 side.

[0031] The total area ratio of the islands in the sea-island structure may be in the range of 25.0 to 35.0%, but because this provides particularly excellent adhesion of the adhesive film to a metal terminal by heat sealing and more suitably prevents a decrease in adhesion to the metal terminal even when an electrolyte solution adheres to the adhesive film adhered to the metal terminal by heat sealing, the total area ratio of the islands in the sea-island structure is preferably about 26.0% or more, more preferably about 28.0% or more. The total area ratio of the islands in the sea-island structure is preferably about 32.0% or less, more preferably about 30.0% or less. Preferred ranges for the total area ratio of the islands in the sea-island structure are about 26.0 to 32.0%, about 26.0 to 30.0%, about 28.0 to 35.0%, about 28.0 to 32.0%, and about 28.0 to 30.0%.

[0032] The sea-island structure in the cross-sectional image of the first polyolefin layer is observed as follows.

[0033] <Observation of sea-island structure in cross-sectional images> The adhesive film for metal terminals is embedded in a thermosetting epoxy resin and allowed to harden. A cross section in the desired direction (along the transverse direction) is prepared using a commercially available rotary microtome (e.g., LEICA UC6) and a diamond knife. The cross section is prepared at -70°C using a cryomicrotome with liquid nitrogen. The embedded resin is then stained overnight with ruthenium tetroxide. Since the polypropylene expands upon staining, the expanded portion is trimmed with the microtome, cutting in 100-300 nm increments along the transverse direction until a total cut of 1-2 μm is achieved. The exposed cross section is then observed as follows: The stained cross section is then observed with a field-emission scanning electron microscope (e.g., Hitachi High-Technologies S-4800 TYPE1, measurement conditions: 3 kV, 20 mA, High WD, 6 mm detector (upper)) to obtain an image (10,000x magnification). The cross-sectional image is taken of the surface portion of the first polyolefin layer on the metal terminal side (within a range of 30% of the thickness from the surface opposite the substrate side, assuming the thickness of the first polyolefin layer to be 100%; see Figure 4). Cross-sectional images can also be taken of the surface portion of the first polyolefin layer on the substrate side (within a range of 30% of the thickness from the surface on the substrate side, assuming the thickness of the first polyolefin layer to be 100%) by changing the observation location. Next, image processing software capable of binarizing images (e.g., Mitani Corporation's image analysis software WinROOF (Ver. 7.4)) is used to binarize the island and sea portions of the sea-island structure, and the number of islands, the ratio of the total island area (total island area / area of the measurement range of the image), the average island particle size, the island particle size deviation σ, and the island circularity are determined.

[0034] The binarized cross-sectional images of Example 1 and Comparative Examples 1 and 2 are shown in Figures 8 to 13, respectively. Figure 8 shows the surface portion of the first polyolefin layer on the metal terminal side of Example 1, Figure 9 shows the surface portion of the first polyolefin layer on the substrate side of Example 1, Figure 10 shows the surface portion of the first polyolefin layer on the metal terminal side of Comparative Example 1, Figure 11 shows the surface portion of the first polyolefin layer on the substrate side of Comparative Example 1, Figure 12 shows the surface portion of the first polyolefin layer on the metal terminal side of Comparative Example 2, and Figure 13 shows the surface portion of the first polyolefin layer on the substrate side of Comparative Example 2. 8 to 13, the image on the left is before the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, and the image on the right is after the adhesive film for metal terminals was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds (similar to the measurement of adhesion strength described below, after the adhesive film for metal terminals was heated on a hot plate heated to 190°C for 12 seconds under the condition of a surface pressure of 0.016 MPa (heated so that the first polyolefin layer side was facing the hot plate)). Note that in this measurement, the island parts were dyed more than the sea part, and therefore appeared brighter than the sea part. [Image processing conditions] Image processing can be performed using the image analysis software ImageJ. Specifically, SEM images are acquired as digital files of grayscale images (e.g., JPEG format) and processed according to the binarization procedure and parameters below, with pixels above a threshold (bright) being output as 1 and pixels below the threshold (dark) as 0, defining them as island and sea regions, respectively. <Binarization processing> 1. Spike noise removal (Despeckle) 2. Remove island contours (Remove Outliers radius=4 threshold=1 which=Bright) 3. Remove Outliers radius=4 threshold=1 which=Dark 4. Spike noise removal (Despeckle) 5. Gaussian blur along the X axis (shorter side of the sample) (threshold = 3 pixels) 6. Contrast Enhancement (saturated = 0.2) 7.Remove Outliers radius=4 threshold=1 which=Bright 8. Remove Outliers radius=4 threshold=1 which=Dark 9. Otsu's Binarization

[0035] The average particle size of the islands is a value calculated from the maximum Feret's diameter of the islands in an image after binarization using the image analysis software ImageJ. The particle size deviation σ of the islands is a value calculated from the standard deviation of the average particle size. The circularity of the islands is a value calculated from the difference in radii of two concentric circles when the island in the image after binarization using the image analysis software ImageJ is sandwiched between two concentric circles with the smallest distance between the concentric circles.

[0036] The cross-sectional image is a cross-sectional image acquired within a range (cross-hatched area in FIG. 4) from the surface on the metal terminal side (opposite the substrate 11) to 30% of the thickness, assuming the total thickness of the first polyolefin layer 12a to be 100%, as shown in the schematic diagram of FIG. 4. The surface of the first polyolefin layer 12a opposite the substrate 11 is considered to have a thickness of 0%. To give a specific example, in the case of an adhesive film for metal terminals in which a first polyolefin layer (thickness 50 μm), a substrate (thickness 50 μm), and a second polyolefin layer (thickness 50 μm) are laminated in this order, as in Example 1 described below, the thickness of the first polyolefin layer, 50 μm, is considered to be 100%. The thickness of the surface of the first polyolefin layer 12a opposite the substrate 11 is considered to be 0%. Then, a cross-sectional image is obtained using a field emission scanning electron microscope within the range from the surface (0% thickness) to the 30% thickness position (i.e., if 50 μm is 100%, the 30% thickness position is the position 15 μm thick from the surface of the first polyolefin layer opposite the substrate layer side toward the substrate side).

[0037] Furthermore, "a sea-island structure is observed in a cross-sectional image" means that a sea portion (sea part) and island portions (island parts) are observed in the cross-sectional image. For example, when a small amount of polyethylene is added to acid-modified polypropylene as a resin composition forming the first polyolefin layer 12a and the first polyolefin layer 12a is formed by melt extrusion molding, a sea-island structure is formed in which polyethylene islands are dispersed in a sea portion of the acid-modified polypropylene. To observe the sea-island structure, as described above, the cross-section of the first polyolefin layer 12a is stained with ruthenium tetroxide or the like, and a cross-sectional image is obtained and observed using a field emission scanning electron microscope.

[0038] In adhesive film 1 for metal terminal of the present disclosure, the proportion of the total area of the islands in the sea-island structure is 25.0 to 35.0% in the cross-sectional image of the surface portion on the metal terminal side (specifically, the portion 30% of the thickness from the surface on the metal terminal side (the side opposite to substrate 11)) after heating the adhesive film for metal terminal at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. Because adhesive film 1 for metal terminal of the present disclosure has these characteristics, it has excellent adhesion to the metal terminal by heat sealing, and further, even when an electrolyte adheres to the adhesive film adhered to the metal terminal by heat sealing, a decrease in adhesion to the metal terminal is suitably suppressed. More specifically, in the first polyolefin layer 12a arranged on the metal terminal side of the adhesive film for metal terminal 1 of the present disclosure, the total area of the islands of the sea-island structure on the surface portion on the metal terminal 2 side (the islands are, for example, formed mainly of polyethylene, which makes the first polyolefin layer 12a flexible and improves adhesion but is somewhat inferior in electrolyte resistance) is set to an appropriate range of 25.0 to 35.0%, thereby ensuring excellent adhesion to the metal terminal while suitably suppressing penetration of the electrolyte, and as a result, it is thought that a decrease in adhesion to the metal terminal when the electrolyte adheres is suppressed. The surface portion of the adhesive film for metal terminals on the metal terminal side after heating for 12 seconds at a temperature of 190°C and a surface pressure of 0.016 MPa corresponds to the surface portion after the first polyolefin layer 12a has been adhered to the metal terminal 2 by heat sealing, and it can be said that in the adhesive film for metal terminals 1 of the present disclosure, the proportion of the total area of the island portions of the sea-island structure on the surface portion of the first polyolefin layer 12a on the metal terminal 2 side after heat sealing is set to an appropriate range of 25.0 to 35.0%.

[0039] Furthermore, in the adhesive film for metal terminal 1 of the present disclosure, when the thickness of the first polyolefin layer 12a is taken as 100%, a sea-island structure is usually observed in a cross-sectional image taken within the surface portion on the substrate 11 side (specifically, a portion 30% of the thickness from the surface on the substrate 11 side) after heating the adhesive film for metal terminal at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. The proportion of the total area of the islands in the sea-island structure in the cross-sectional image of the surface portion on the substrate 11 side is not particularly limited, but is preferably at least about 25.0%, more preferably at least about 30.0%. The proportion of the total area of the islands is preferably no more than about 35.0%, more preferably no more than about 33.0%. The preferred ranges for the proportion of the total area of the islands are approximately 25.0 to 35.0%, approximately 25.0 to 33.0%, approximately 30.0 to 35.0%, and approximately 30.0 to 33.0%. As for the method for heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, as described above, a method of heating on a hot plate heated to 190°C for 12 seconds is adopted, similar to the measurement of adhesion strength in the examples described below.

[0040] In the adhesive film 1 for metal terminals of the present disclosure, for example, after heating the adhesive film 1 for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the proportion of the total area of the islands of the sea-island structure in the cross-sectional image of the surface portion facing the metal terminal 2 may be smaller or larger than, but preferably similar to, the proportion of the total area of the islands of the sea-island structure in the cross-sectional image of the surface portion facing the substrate 11. That is, in the adhesive film 1 for metal terminals of the present disclosure, the proportion of the total area of the islands of the surface portion facing the metal terminal 2 may be smaller or larger than, but preferably similar to, the proportion of the total area of the islands of the sea-island structure in the cross-sectional image of the surface portion facing the substrate 11. Furthermore, it is preferable that the proportion of the total area of the islands of the sea-island structure in the cross-sectional image of the surface portion facing the metal terminal 2 is similar before and after heating the adhesive film 1 for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, and that the proportion of the total area of the islands of the sea-island structure in the cross-sectional image of the surface portion facing the substrate 11 is similar.

[0041] Furthermore, in the adhesive film for metal terminal 1 of the present disclosure, when the thickness of the first polyolefin layer 12a is taken as 100%, a sea-island structure is typically observed in a cross-sectional image taken within the surface portion on the metal terminal 2 side (specifically, the portion 30% of the thickness from the surface opposite the substrate 11), before the adhesive film for metal terminal is heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. The proportion of the total area of the islands in the sea-island structure in the cross-sectional image of the surface portion on the metal terminal 2 side of the first polyolefin layer 12a before heating is not particularly limited, but is preferably at least about 22.0%, more preferably at least about 24.0%. The proportion of the total area of the islands is preferably at most about 32.0%, more preferably at most about 28.0%. The proportion of the total area of the island portions is preferably in the range of about 22.0 to 32.0%, about 22.0 to 28.0%, about 24.0 to 32.0%, or about 24.0 to 28.0%.

[0042] Furthermore, in the adhesive film for metal terminal 1 of the present disclosure, when the thickness of the first polyolefin layer 12a is taken as 100%, a sea-island structure is typically observed in a cross-sectional image taken within the surface portion on the substrate 11 side (specifically, the portion 30% of the thickness from the surface on the substrate 11 side) before the first polyolefin layer 12a is heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. The proportion of the total area of the islands in the sea-island structure in the cross-sectional image of the surface portion on the substrate 11 side of the first polyolefin layer 12a before heating is not particularly limited, but is preferably at least about 26.0%, more preferably at least about 28.0%. Furthermore, the proportion of the total area of the islands is preferably at most about 35.0%, more preferably at most about 32.0%. The proportion of the total area of the island portions is preferably in the range of about 26.0 to 35.0%, about 26.0 to 32.0%, about 28.0 to 35.0%, or about 28.0 to 32.0%.

[0043] In the adhesive film for metal terminal 1 of the present disclosure, the average particle size of the islands in the sea-island structure is preferably about 0.3 μm or more, more preferably about 0.4 μm or more, in the cross-sectional image of the surface portion facing the metal terminal 2 after heating the adhesive film for metal terminal 1 at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. The average particle size of the islands is preferably about 0.6 μm or less, more preferably about 0.5 μm or less. Preferred ranges for the average particle size of the islands include about 0.3 to 0.6 μm, about 0.3 to 0.5 μm, about 0.4 to 0.6 μm, and about 0.4 to 0.5 μm.

[0044] In the adhesive film for metal terminal 1 of the present disclosure, the average particle size of the islands in the sea-island structure is preferably about 0.3 μm or more, more preferably about 0.4 μm or more, in the cross-sectional image of the surface portion on the substrate 11 side after heating the adhesive film for metal terminal 1 at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds. The average particle size of the islands is preferably about 0.6 μm or less, more preferably about 0.5 μm or less. Preferred ranges for the average particle size of the islands include about 0.3 to 0.6 μm, about 0.3 to 0.5 μm, about 0.4 to 0.6 μm, and about 0.4 to 0.5 μm.

[0045] In the adhesive film for metal terminal 1 of the present disclosure, in the cross-sectional image of the surface portion facing the metal terminal 2 before heating the adhesive film for metal terminal 1 at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the average particle size of the islands in the sea-island structure is preferably about 0.2 μm or more, more preferably about 0.3 μm or more. The average particle size of the islands is preferably about 0.5 μm or less, more preferably about 0.4 μm or less. Preferred ranges for the average particle size of the islands include about 0.2 to 0.5 μm, about 0.2 to 0.4 μm, about 0.3 to 0.5 μm, and about 0.3 to 0.4 μm.

[0046] In the adhesive film for metal terminal 1 of the present disclosure, in the cross-sectional image of the surface portion on the substrate 11 side before heating the adhesive film for metal terminal at 190°C and a surface pressure of 0.016 MPa for 12 seconds, the average particle size of the islands in the sea-island structure is preferably about 0.3 μm or more, more preferably about 0.4 μm or more. The average particle size of the islands is preferably about 0.6 μm or less, more preferably about 0.5 μm or less. Preferred ranges for the average particle size of the islands include about 0.3 to 0.6 μm, about 0.3 to 0.5 μm, about 0.4 to 0.6 μm, and about 0.4 to 0.5 μm.

[0047] The average particle size of the islands in the cross-sectional image is a value calculated using image analysis software ImageJ.

[0048] In the adhesive film for metal terminal 1 of the present disclosure, in the cross-sectional image of the surface portion on the metal terminal 2 side after heating the adhesive film for metal terminal 1 at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the particle size deviation σ of the islands in the sea-island structure is preferably 0.4 or less, more preferably about 0.3 or less. The particle size deviation σ of the islands is, for example, 0.1 or more. The particle size deviation σ of the islands is preferably in the range of about 0.1 to 0.4, or about 0.1 to 0.3.

[0049] In the adhesive film for metal terminal 1 of the present disclosure, the particle size deviation σ of the islands in the sea-island structure in the cross-sectional image of the surface portion on the substrate 11 side after heating the adhesive film for metal terminal at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds is preferably 0.4 or less, more preferably about 0.3 or less. The particle size deviation σ of the islands is, for example, 0.1 or more. The particle size deviation σ of the islands is preferably in the range of about 0.1 to 0.4, or about 0.1 to 0.3.

[0050] In the adhesive film for metal terminal 1 of the present disclosure, in the cross-sectional image of the surface portion facing the metal terminal 2 before heating the adhesive film for metal terminal at 190°C and a surface pressure of 0.016 MPa for 12 seconds, the particle size deviation σ of the islands in the sea-island structure is preferably 0.4 or less, more preferably about 0.3 or less. The particle size deviation σ of the islands is, for example, 0.1 or more. The particle size deviation σ of the islands is preferably in the range of about 0.1 to 0.4, or about 0.1 to 0.3.

[0051] In the adhesive film for metal terminal 1 of the present disclosure, in the cross-sectional image of the surface portion on the substrate 11 side before heating the adhesive film for metal terminal at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the particle size deviation σ of the islands in the sea-island structure is preferably 0.5 or less, more preferably about 0.4 or less. The particle size deviation σ of the islands is, for example, 0.1 or more. The particle size deviation σ of the islands is preferably in the range of about 0.1 to 0.5, or about 0.1 to 0.4.

[0052] The particle size deviation σ of the island in the cross-sectional image is a value calculated using image analysis software ImageJ.

[0053] In the adhesive film for metal terminal 1 of the present disclosure, the circularity of the islands in the sea-island structure in the cross-sectional image of the surface portion facing the metal terminal 2 after heating the adhesive film for metal terminal 1 at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds is preferably 0.75 or more, more preferably about 0.80 or more. The circularity of the islands is, for example, 0.95 or less. The circularity of the islands is preferably in the range of about 0.75 to 0.95, or about 0.80 to 0.95.

[0054] In the adhesive film for metal terminal 1 of the present disclosure, the circularity of the islands in the sea-island structure in the cross-sectional image of the surface portion on the substrate 11 side after heating the adhesive film for metal terminal at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds is preferably 0.72 or more, more preferably about 0.75 or more. The circularity of the islands is, for example, 0.95 or less. The circularity of the islands is preferably in the range of about 0.72 to 0.95, or about 0.75 to 0.95.

[0055] In the adhesive film for metal terminal 1 of the present disclosure, the circularity of the islands in the sea-island structure in the cross-sectional image of the surface portion facing the metal terminal 2 before heating the adhesive film for metal terminal 1 at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds is preferably 0.55 or more, more preferably about 0.60 or more. The circularity of the islands is, for example, 0.95 or less. The circularity of the islands is preferably in the range of about 0.55 to 0.95, or about 0.60 to 0.95.

[0056] In the adhesive film for metal terminal 1 of the present disclosure, the circularity of the islands in the sea-island structure in the cross-sectional image of the surface portion on the substrate 11 side before heating the adhesive film for metal terminal at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds is preferably 0.55 or more, more preferably about 0.60 or more. The circularity of the islands is, for example, 0.95 or less. The circularity of the islands is preferably in the range of about 0.55 to 0.95, or about 0.60 to 0.95.

[0057] The circularity of the island in the cross-sectional image is a value calculated using image analysis software ImageJ.

[0058] The proportion of the total area of the islands in the sea-island structure of the cross section of the first polyolefin layer of the adhesive film for metal terminals of the present disclosure, the average particle size of the islands, the particle size deviation σ of the islands, and the circularity of the islands can each be adjusted by the composition, skeleton, dispersibility, molecular weight, melting point, MFR of the resin constituting the first polyolefin layer, as well as conditions such as the T-die and inflation in the production of the adhesive film for metal terminals 1 (for example, the extrusion width from the T-die, stretching ratio, stretching speed, heat treatment temperature, and also the line speed during extrusion, cooling rate, extrusion temperature, etc.).

[0059] The total thickness of the adhesive film 1 for metal terminal of the present disclosure is, for example, about 60 μm or more, preferably about 80 μm or more, preferably about 100 μm or more, more preferably about 120 μm or more, and even more preferably about 150 μm or more, from the viewpoint of improving adhesion to the metal terminal 2 described above while suitably suppressing a decrease in adhesion due to the electrolyte. The total thickness of the adhesive film 1 for metal terminal of the present disclosure is preferably about 200 μm or less, more preferably 180 μm or less. Preferred ranges for the total thickness of the adhesive film 1 for metal terminal of the present disclosure include about 60 to 200 μm, about 60 to 180 μm, about 80 to 200 μm, about 80 to 180 μm, about 100 to 200 μm, about 100 to 180 μm, about 120 to 200 μm, about 120 to 180 μm, about 150 to 200 μm, and about 150 to 180 μm. As a more specific example, when the adhesive film 1 for metal terminals of the present disclosure is used in a consumer electricity storage device, the total thickness is preferably about 60 to 100 μm, and when it is used in an in-vehicle electricity storage device, the total thickness is preferably about 100 to 200 μm.

[0060] The first polyolefin layer 12a, the second polyolefin layer 12b, and the substrate 11 will be described in detail below.

[0061] [First Polyolefin Layer 12a and Second Polyolefin Layer 12b] As shown in Figures 4 and 5, the adhesive film 1 for metal terminals of the present disclosure comprises a first polyolefin layer 12a on one side of a substrate 11 and a second polyolefin layer 12b on the other side. The first polyolefin layer 12a is disposed on the metal terminal 2 side. The second polyolefin layer 12b is disposed on the exterior material 3 for an electricity storage device. In the adhesive film 1 for metal terminals of the present disclosure, the first polyolefin layer 12a and the second polyolefin layer 12b are located on the surfaces of both sides, respectively.

[0062] The sea-island structure in the cross-sectional image of the first polyolefin layer 12a disposed on the metal terminal 2 side has been described above.

[0063] In the adhesive film for metal terminal 1 of the present disclosure, the first polyolefin layer 12a and the second polyolefin layer 12b are each a layer containing a polyolefin-based resin. Examples of polyolefin-based resins include polyolefin and acid-modified polyolefin. The first polyolefin layer 12a preferably contains an acid-modified polyolefin among polyolefin-based resins, and is more preferably a layer formed from an acid-modified polyolefin. The second polyolefin layer 12b preferably contains a polyolefin or an acid-modified polyolefin among polyolefin-based resins, and is more preferably a polyolefin, and is even more preferably a layer formed from a polyolefin. Acid-modified polyolefins have a high affinity with metals. Polyolefins also have a high affinity with heat-sealable resins such as polyolefins. Therefore, in the adhesive film for metal terminal 1 of the present disclosure, by arranging the first polyolefin layer 12a formed from an acid-modified polyolefin on the metal terminal 2 side, even better adhesion can be achieved at the interface between the adhesive film for metal terminal 1 and the metal terminal 2. Furthermore, by placing the second polyolefin layer 12b formed from polyolefin on the heat-sealable resin layer 35 side of the packaging material 3 for an electrical storage device, even better adhesion can be achieved at the interface between the adhesive film 1 for metal terminals and the heat-sealable resin layer 35.

[0064] Specific examples of preferred laminate structures for the adhesive film 1 for metal terminals of the present disclosure include a three-layer structure in which a first polyolefin layer formed from acid-modified polypropylene / a base material formed from polypropylene / a second polyolefin layer formed from polypropylene are laminated in this order; a three-layer structure in which a first polyolefin layer formed from acid-modified polypropylene / a base material formed from polypropylene / a second polyolefin layer formed from acid-modified polypropylene are laminated in this order; and among these, a three-layer structure in which a first polyolefin layer formed from acid-modified polypropylene / a base material formed from polypropylene / a second polyolefin layer formed from polypropylene are laminated in this order is particularly preferred.

[0065] The acid-modified polyolefin is not particularly limited as long as it is an acid-modified polyolefin, but preferred examples include polyolefins graft-modified with an unsaturated carboxylic acid or an anhydride thereof.

[0066] Specific examples of acid-modified polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); and ethylene-butene-propylene terpolymers. Among these polyolefins, polyethylene and polypropylene are preferred, and polypropylene is particularly preferred.

[0067] The acid-modified polyolefin may be a cyclic polyolefin. For example, a carboxylic acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a cyclic polyolefin by substituting an α,β-unsaturated carboxylic acid or an anhydride thereof for some of the monomers constituting the cyclic polyolefin, or by block polymerizing or graft polymerizing an α,β-unsaturated carboxylic acid or an anhydride thereof with a cyclic polyolefin.

[0068] The acid-modified cyclic polyolefin is a copolymer of an olefin and a cyclic monomer, and examples of the olefin constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, and isoprene. Examples of the cyclic monomer constituting the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, preferred are cyclic alkenes, and more preferred are norbornene. Styrene is also an example of a constituting monomer.

[0069] Examples of carboxylic acids or anhydrides thereof used for acid modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride. When the first polyolefin layer 12a is analyzed by infrared spectroscopy, a peak derived from maleic anhydride is preferably detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak derived from maleic anhydride is detected at a wave number of 1760 cm. -1 Near and wave number 1780cm -1 A peak derived from maleic anhydride is detected near . When the first polyolefin layer 12a or the second polyolefin layer 12b is a layer composed of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride is detected when measured by infrared spectroscopy. However, if the degree of acid modification is low, the peak may become small and may not be detected. In such cases, analysis can be performed by nuclear magnetic resonance spectroscopy.

[0070] The first polyolefin layer 12a and the second polyolefin layer 12b may each be formed of a single resin component or a blend polymer of two or more resin components. Furthermore, the first polyolefin layer 12a and the second polyolefin layer 12b may each be formed of a single layer or two or more layers of the same or different resin components. From the viewpoint of film-forming properties of the first polyolefin layer 12a and the second polyolefin layer 12b, these layers are preferably formed of a blend polymer of two or more resin components. When a blend polymer is used, the first polyolefin layer 12a preferably contains acid-modified polypropylene as the main component (50% by mass or more) and 50% by mass or less of another resin (preferably polyethylene). The second polyolefin layer 12b preferably contains polypropylene as the main component (50% by mass or more) and 50% by mass or less of another resin (preferably polyethylene). On the other hand, from the viewpoint of the electrolyte resistance of the first polyolefin layer 12a and the second polyolefin layer 12b, it is preferable that the first polyolefin layer 12a contains only acid-modified polypropylene as the resin, and it is preferable that the second polyolefin layer 12b contains only polypropylene as the resin.

[0071] Furthermore, the first polyolefin layer 12a and the second polyolefin layer 12b may each contain a filler, if necessary. When the first polyolefin layer 12a and the second polyolefin layer 12b contain a filler, the filler functions as a spacer, making it possible to effectively prevent short circuits between the metal terminal 2 and the barrier layer 33 of the electrical storage device packaging material 3. The particle size of the filler is approximately 0.1 to 35 μm, preferably approximately 5.0 to 30 μm, and more preferably approximately 10 to 25 μm. The content of the filler is approximately 5 to 30 parts by mass, more preferably approximately 10 to 20 parts by mass, per 100 parts by mass of the resin components forming the first polyolefin layer 12a and the second polyolefin layer 12b, respectively.

[0072] The filler may be either inorganic or organic. Examples of inorganic fillers 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, and calcium carbonate. Examples of organic fillers include fluororesins, phenolic resins, urea resins, epoxy resins, acrylic resins, benzoguanamine-formaldehyde condensates, melamine-formaldehyde condensates, cross-linked polymethyl methacrylates, and cross-linked polyethylenes. From the standpoints of shape stability, rigidity, and content resistance, aluminum oxide, silica, fluororesins, acrylic resins, and benzoguanamine-formaldehyde condensates are preferred, with spherical aluminum oxide and silica being particularly preferred. As a method for mixing the filler into the resin components forming the first polyolefin layer 12a and the second polyolefin layer 12b, a method in which the two are melt-blended in advance using a Banbury mixer or the like to form a masterbatch and then adjusted to a predetermined mixing ratio, or a method in which the filler is directly mixed with the resin components can be used.

[0073] The first polyolefin layer 12a and the second polyolefin layer 12b may each contain a pigment, if necessary. Various inorganic pigments can be used as the pigment. A specific example of the pigment is preferably carbon (carbon, graphite), which is one of the fillers exemplified above. Carbon (carbon, graphite) is a material commonly used inside electricity storage devices and is unlikely to leach into the electrolyte solution. Furthermore, the pigment has a significant coloring effect, and a sufficient coloring effect can be obtained with an amount that does not impair adhesion. Furthermore, the pigment does not melt due to heat, and the apparent melt viscosity of the added resin can be increased. Furthermore, the pigment can prevent the pressurized portion from becoming thin during thermal bonding (heat sealing), thereby providing excellent sealing between the electricity storage device exterior material and the metal terminal.

[0074] When a pigment is added to the first polyolefin layer 12a and the second polyolefin layer 12b, the amount of pigment added is, for example, about 0.05 to 0.3 parts by mass, preferably about 0.1 to 0.2 parts by mass, per 100 parts by mass of the resin components forming the first polyolefin layer 12a and the second polyolefin layer 12b when carbon black with a particle size of about 0.03 μm is used. By adding a pigment to the first polyolefin layer 12a and the second polyolefin layer 12b, the presence or absence of the adhesive film for metal terminal 1 can be detected by a sensor or visually inspected. It is particularly preferred that the first polyolefin layer 12a contain a pigment. When adding a filler and a pigment to the first polyolefin layer 12a and the second polyolefin layer 12b, the filler and the pigment may be added to the same first polyolefin layer 12a and second polyolefin layer 12b, but from the viewpoint of not impairing the thermal fusion properties of the adhesive film 1 for metal terminals, it is preferable to add the filler and the pigment separately to the first polyolefin layer 12a and the second polyolefin layer 12b.

[0075] The thickness of each of the first polyolefin layer 12a and the second polyolefin layer 12b is preferably about 10 μm or more, more preferably about 15 μm or more, even more preferably about 20 μm or more, and even more preferably about 30 μm or more, from the viewpoint of improving adhesion to the metal terminal 2 while suitably suppressing a decrease in adhesion due to the electrolyte, and is, for example, about 80 μm or less, preferably about 60 μm or less, and more preferably about 50 μm or less. Preferred thickness ranges for the first polyolefin layer 12a and the second polyolefin layer 12b include about 10 to 80 μm, about 10 to 60 μm, about 10 to 50 μm, about 15 to 80 μm, about 15 to 60 μm, about 15 to 50 μm, about 20 to 80 μm, about 20 to 60 μm, about 20 to 50 μm, about 30 to 80 μm, about 30 to 60 μm, and about 30 to 50 μm, respectively. As a more specific example, when the adhesive film for metal terminals 1 of the present disclosure is used in a consumer electricity storage device, the thickness of the first polyolefin layer 12a and the second polyolefin layer 12b is preferably about 10 to 30 μm each, and when used in an in-vehicle electricity storage device, the thickness of each is preferably about 30 to 80 μm.

[0076] The ratio of the thickness of the substrate 11 to the total thickness of the first polyolefin layer 12a and the second polyolefin layer 12b is preferably about 0.3 or more, more preferably about 0.4 or more, and even more preferably 0.5 or more, from the viewpoint of improving adhesion to the metal terminal 2 while suitably suppressing a decrease in adhesion due to the electrolyte, and is preferably about 1.0 or less, more preferably about 0.8 or less, and preferred ranges include about 0.3 to 1.0, about 0.3 to 0.8, about 0.4 to 1.0, about 0.4 to 0.8, about 0.5 to 1.0, and about 0.5 to 0.8.

[0077] Furthermore, the ratio of the total thickness of the adhesive film 1 for a metal terminal to 100% is preferably about 30 to 80%, and more preferably about 50 to 70%.

[0078] [Base material 11] In the adhesive film for a metal terminal 1, the substrate 11 is a layer that functions as a support for the adhesive film for a metal terminal 1.

[0079] The material forming the substrate 11 is not particularly limited. Examples of materials that can be used to form the substrate 11 include polyolefin resins, polyamide resins, polyester resins, epoxy resins, acrylic resins, fluororesins, silicone resins, phenolic resins, polyetherimides, polyimides, polycarbonates, and mixtures or copolymers thereof. Among these, polyolefin resins are particularly preferred. That is, the material forming the substrate 11 is preferably a resin containing a polyolefin skeleton, such as polyolefin or acid-modified polyolefin. Whether the resin constituting the substrate 11 contains a polyolefin skeleton can be determined by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like.

[0080] As described above, the substrate 11 preferably contains a polyolefin resin, preferably contains a polyolefin, and more preferably is a layer formed of a polyolefin. Specific examples of polyolefin include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylenes such as homopolypropylene, polypropylene block copolymers (e.g., propylene-ethylene block copolymers), and polypropylene random copolymers (e.g., propylene-ethylene random copolymers); and ethylene-butene-propylene terpolymers. Among these polyolefins, polyethylene and polypropylene are preferred, and polypropylene is more preferred. Furthermore, because of its excellent electrolyte resistance, the substrate 11 preferably contains homopolypropylene, and is particularly preferably formed of homopolypropylene.

[0081] Specific examples of polyamides include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (where I represents isophthalic acid and T represents terephthalic acid) containing structural units derived from terephthalic acid and / or isophthalic acid; aromatic polyamides such as polymetaxylylene adipamide (MXD6); alicyclic polyamides such as polyaminomethylcyclohexyl adipamide (PACM6); polyamides copolymerized with lactam components or isocyanate components such as 4,4'-diphenylmethane diisocyanate; polyesteramide copolymers and polyetheresteramide copolymers, which are copolymers of copolymerized polyamides with polyesters or polyalkylene ether glycols; and copolymers thereof. These polyamides may be used alone or in combination of two or more.

[0082] Specific examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, copolymer polyesters whose repeating units are mainly ethylene terephthalate, copolymer polyesters whose repeating units are mainly butylene terephthalate, etc. Specific examples of copolymer polyesters whose repeating units are mainly ethylene terephthalate include copolymer polyesters in which ethylene terephthalate is the main repeating unit and is polymerized with ethylene isophthalate (hereinafter abbreviated as polyethylene (terephthalate / isophthalate)), polyethylene (terephthalate / isophthalate), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl-dicarboxylate), polyethylene (terephthalate / decanedicarboxylate), etc. Specific examples of copolymer polyesters containing butylene terephthalate as the main repeating unit include copolymer polyesters in which butylene terephthalate is the main repeating unit and is polymerized with butylene isophthalate (hereinafter abbreviated as polybutylene (terephthalate / isophthalate)), polybutylene (terephthalate / adipate), polybutylene (terephthalate / sebacate), polybutylene (terephthalate / decanedicarboxylate), polybutylene naphthalate, etc. These polyesters may be used alone or in combination of two or more.

[0083] The substrate 11 may also be formed of a nonwoven fabric made of the above-mentioned resin. When the substrate 11 is a nonwoven fabric, the substrate 11 is preferably made of the above-mentioned polyolefin resin, polyamide resin, or the like.

[0084] Furthermore, by blending a colorant into the substrate 11, the substrate 11 can be made into a layer containing a colorant. Furthermore, light transmittance can be adjusted by selecting a resin with low transparency. When the substrate 11 is a film, a colored film or a film with low transparency can be used. When the substrate 11 is a nonwoven fabric, a nonwoven fabric using a fiber or binder containing a colorant or a nonwoven fabric with low transparency can be used.

[0085] When the substrate 11 is made of a resin film, the surface of the substrate 11 may be subjected to a known adhesion-facilitating treatment such as corona discharge treatment, ozone treatment, or plasma treatment, if necessary.

[0086] The thickness of the substrate 11 is, for example, about 100 μm or less, preferably about 60 μm or less, and more preferably about 55 μm or less, from the viewpoint of improving adhesion to the metal terminal 2 while suitably suppressing a decrease in adhesion due to the electrolyte. The thickness of the substrate 11 is preferably about 20 μm or more, more preferably about 30 μm or more, and even more preferably about 40 μm or more. Examples of preferred thickness ranges for the substrate 11 include about 20 to 100 μm, about 20 to 60 μm, about 20 to 55 μm, about 30 to 100 μm, about 30 to 60 μm, about 30 to 55 μm, about 40 to 100 μm, about 40 to 60 μm, and about 40 to 55 μm. As a more specific example, when the adhesive film 1 for metal terminals of the present disclosure is used in a consumer electricity storage device, the thickness of the substrate 11 is preferably about 30 to 55 μm, and when used in an in-vehicle electricity storage device, the thickness is preferably about 40 to 100 μm.

[0087] [Adhesion promoter layer 13] The adhesion promoter layer 13 is a layer that is provided as needed for the purpose of firmly adhering the substrate 11 to the first polyolefin layer 12a and the second polyolefin layer 12b (see FIG. 5). The adhesion promoter layer 13 may be provided on only one side between the substrate 11 and the first polyolefin layer 12a and the second polyolefin layer 12b, or on both sides.

[0088] The adhesion promoter layer 13 can be formed using known adhesion promoters such as isocyanate-based, polyethyleneimine-based, polyester-based, polyurethane-based, and polybutadiene-based. From the viewpoint of further improving electrolyte resistance, it is preferable to form the layer using an isocyanate-based adhesion promoter. Among the isocyanate-based adhesion promoters, those containing an isocyanate component selected from triisocyanate monomer and polymeric MDI provide excellent laminate strength and show little decrease in laminate strength after immersion in an electrolyte. It is particularly preferable to form the adhesive layer using an adhesion promoter made from triphenylmethane-4,4',4"-triisocyanate, a triisocyanate monomer, or polymethylene polyphenyl polyisocyanate, a polymeric MDI (NCO content of approximately 30%, viscosity of 200 to 700 mPa·s). It is also preferable to form the adhesive layer using tris(p-isocyanatephenyl)thiophosphate, a triisocyanate monomer, or a two-component curing adhesion promoter that uses a polyethyleneimine-based compound as the main component and polycarbodiimide as the crosslinking agent.

[0089] The adhesion promoter layer 13 can be formed by coating and drying using a known coating method such as bar coating, roll coating, or gravure coating. The amount of the adhesion promoter to be applied is 20 to 100 mg / m when the adhesion promoter is made of triisocyanate. 2 Approximately, preferably 40 to 60 mg / m 2 In the case of adhesion promoters made of polymeric MDI, the concentration is 40 to 150 mg / m 2 Approximately, preferably 60 to 100 mg / m 2 In the case of a two-component curing adhesion promoter that uses polyethyleneimine as the main component and polycarbodiimide as the crosslinking agent, the adhesive strength is about 5 to 50 mg / m 2 about 10 to 30 mg / m 2 Triisocyanate monomer is a monomer with three isocyanate groups in one molecule, and polymeric MDI is a mixture of MDI and MDI oligomers formed by polymerizing MDI, and is represented by the following formula:

[0090] [ka]

[0091] The adhesive film 1 for metal terminals of the present disclosure can be produced, for example, by laminating a first polyolefin layer 12a and a second polyolefin layer 12b, respectively, on both surfaces of a substrate 11. The substrate 11 and the first polyolefin layer 12a and the second polyolefin layer 12b can be laminated by known methods such as extrusion lamination or thermal lamination. When the substrate 11 and the first and second polyolefin layers 12a, 12b are laminated via an adhesion promoter layer 13, for example, the adhesion promoter that constitutes the adhesion promoter layer 13 can be applied to the substrate 11 by the above-mentioned method and dried, and the first polyolefin layer 12a and the second polyolefin layer 12b can be laminated on top of the adhesion promoter layer 13.

[0092] The method for interposing the adhesive film 1 for a metal terminal between the metal terminal 2 and the exterior packaging material 3 for an electricity storage device is not particularly limited, and for example, as shown in Figures 1 to 3, the adhesive film 1 for a metal terminal may be wrapped around the metal terminal 2 in the portion where the metal terminal 2 is sandwiched by the exterior packaging material 3 for an electricity storage device. Furthermore, although not shown, in the portion where the metal terminal 2 is sandwiched by the exterior packaging material 3 for an electricity storage device, the adhesive film 1 for a metal terminal may be arranged on both sides of the metal terminal 2 so as to cross the two metal terminals 2.

[0093] [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 an electricity storage device. The metal terminal 2 (tab) is a conductive member electrically connected to an electrode (positive electrode or negative electrode) of an electricity storage device element 4, and is made of a metal material. The metal material constituting the metal terminal 2 is not particularly limited, and examples thereof include aluminum, nickel, copper, etc. For example, the metal terminal 2 connected to the positive electrode of a lithium ion electricity storage device is usually made of aluminum, etc. Furthermore, the metal terminal 2 connected to the negative electrode of a lithium ion electricity storage device is usually made of copper, nickel, etc.

[0094] To enhance electrolyte resistance, the surface of the metal terminal 2 is preferably subjected to a chemical conversion treatment. For example, when the metal terminal 2 is made of aluminum, specific examples of the chemical conversion treatment include known methods for forming a corrosion-resistant film using phosphates, chromates, fluorides, triazine thiol compounds, etc. Among the methods for forming a corrosion-resistant film, a preferred method is a phosphate chromate treatment using a compound consisting of three components: a phenolic resin, a chromium (III) fluoride compound, and phosphoric acid.

[0095] The size of the metal terminal 2 may be set appropriately depending on the size of the electricity storage device to be used. The thickness of the metal terminal 2 is preferably about 50 to 1000 μm, more preferably about 70 to 800 μm. The length of the metal terminal 2 is preferably about 1 to 200 mm, more preferably about 3 to 150 mm. The width of the metal terminal 2 is preferably about 1 to 200 mm, more preferably about 3 to 150 mm.

[0096] [Exterior materials for energy storage devices 3] The electrical storage device packaging material 3 may have a laminated structure including at least a substrate layer 31, a barrier layer 33, and a heat-sealable resin layer 35, in this order. FIG. 6 shows an example of the cross-sectional structure of the electrical storage device packaging material 3, in which the substrate layer 31, an optional adhesive layer 32, a barrier layer 33, an optional adhesive layer 34, and a heat-sealable resin layer 35 are laminated in this order. In the electrical storage device packaging material 3, the substrate layer 31 is the outer layer, and the heat-sealable resin layer 35 is the innermost layer. During assembly of the electrical storage device, the electrical storage device elements 4 are sealed by bringing the heat-sealable resin layers 35 located on the peripheries of the electrical storage device elements 4 into contact with each other and heat-sealing them, thereby sealing the electrical storage device elements 4. While FIGS. 1 to 3 illustrate an electrical storage device 10 using an embossed type electrical storage device packaging material 3 formed by embossing or the like, the electrical storage device packaging material 3 may be an unformed pouch type. The pouch type includes three-sided seal, four-sided seal, pillow type, etc., and any type may be used.

[0097] The thickness of the laminate constituting the electricity storage device packaging material 3 is not particularly limited, but the upper limit, from the viewpoints of cost reduction, energy density improvement, etc., is preferably about 190 μm or less, 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, or about 120 μm or less, and the lower limit, from the viewpoint of maintaining the function of the electricity storage device packaging material 3 to protect the electricity storage device elements 4, is preferably about 35 μm or more, about 45 μm or more, about 60 μm or more, or about 80 μm or more, and preferred ranges are, for example, about 35 to 190 μm, about 35 to 180 μm, or about 35 to 160 μm. , about 35-155μm, about 35-140μm, about 35-130μm, about 35-120μm, about 45-190μm, about 45-180μm, 45- Approx. 160μm, approx. 45~155μm, approx. 45~140μm, approx. 45~130μm, approx. 45~120μm, approx. 60~190μm, 60~180μm Examples include 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 190 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, and about 80 to 120 μm.

[0098] (Base material layer 31) In the packaging material 3 for an electricity storage device, the base material layer 31 is a layer that functions as the base material of the packaging material for an electricity storage device, and is a layer that forms the outermost layer side.

[0099] The material for forming the base layer 31 is not particularly limited, as long as it has insulating properties. Examples of materials for forming the base layer 31 include polyester, polyamide, epoxy, acrylic, fluororesin, polyurethane, silicone resin, phenol, polyetherimide, polyimide, and mixtures or copolymers thereof. Polyesters such as polyethylene terephthalate and polybutylene terephthalate have the advantage of being highly resistant to electrolyte and being less susceptible to whitening due to adhesion of electrolyte, and are therefore preferably used as materials for forming the base layer 31. Furthermore, polyamide film has excellent stretchability and can prevent whitening due to resin cracking of the base layer 31 during molding, and is therefore preferably used as materials for forming the base layer 31.

[0100] The base 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, especially a biaxially stretched resin film, is preferably used as the base layer 31 because its heat resistance is improved by oriented crystallization.

[0101] Among these, the resin film forming the base layer 31 is preferably nylon or polyester, and more preferably biaxially oriented nylon or biaxially oriented polyester.

[0102] The base material layer 31 may be formed by laminating resin films made of different materials to improve pinhole resistance and insulation when used as a package for an electricity storage device. Specific examples include a multilayer structure in which a polyester film and a nylon film are laminated together, or a multilayer structure in which a biaxially oriented polyester film and a biaxially oriented nylon film are laminated together. When the base material layer 31 has a multilayer structure, the resin films may be bonded together via an adhesive, or may be laminated together directly without an adhesive. When bonding without an adhesive, examples of methods that bond the films in a hot-melt state include coextrusion, sand lamination, and thermal lamination.

[0103] The base layer 31 may be made low-friction to improve formability. When making the base layer 31 low-friction, the coefficient of friction of the surface is not particularly limited, but may be, for example, 1.0 or less. To make the base layer 31 low-friction, for example, matte treatment, formation of a thin film layer of a slip agent, or a combination thereof may be used.

[0104] The thickness of the base layer 31 is, for example, about 10 to 50 μm, and preferably about 15 to 30 μm.

[0105] (Adhesive layer 32) In the packaging material 3 for an electricity storage device, the adhesive layer 32 is a layer that is disposed on the base material layer 31 as necessary in order to impart adhesion to the base material layer 31. In other words, the adhesive layer 32 is provided between the base material layer 31 and the barrier layer 33.

[0106] The adhesive layer 32 is formed of an adhesive capable of bonding the base material layer 31 and the barrier layer 33. The adhesive used to form the adhesive layer 32 may be a two-component curing adhesive or a one-component curing adhesive. The bonding mechanism of the adhesive used to form the adhesive layer 32 is not particularly limited, and may be any of a chemical reaction type, a solvent volatilization type, a hot melt type, a hot pressure type, or the like.

[0107] The resin component of the adhesive that can be used to form the adhesive layer 32 is preferably a polyurethane-based two-component curing adhesive; polyamide, polyester, or a blend resin of these with modified polyolefin, from the viewpoint of having excellent ductility, durability under high humidity conditions, yellowing prevention, and thermal degradation prevention during heat sealing, and effectively suppressing a decrease in the laminate strength between the base layer 31 and the barrier layer 33 and preventing delamination.

[0108] Furthermore, the adhesive layer 32 may be multi-layered with different adhesive components. When the adhesive layer 32 is multi-layered with different adhesive components, it is preferable to select a resin that has excellent adhesion to the base material layer 31 as the adhesive component disposed on the base material layer 31 side, and an adhesive component that has excellent adhesion to the barrier layer 33 as the adhesive component disposed on the barrier layer 33 side, from the viewpoint of improving the laminate strength between the base material layer 31 and the barrier layer 33. When the adhesive layer 32 is multi-layered with different adhesive components, specifically, preferred examples of the adhesive component disposed on the barrier layer 33 side include acid-modified polyolefin, metal-modified polyolefin, a mixed resin of polyester and acid-modified polyolefin, and a resin containing copolymer polyester.

[0109] The thickness of the adhesive layer 32 is, for example, about 2 to 50 μm, and preferably about 3 to 25 μm.

[0110] (Barrier layer 33) In the electrical storage device packaging material, the barrier layer 33 is a layer that not only improves the strength of the electrical storage device packaging material but also has the function of preventing water vapor, oxygen, light, and the like from penetrating into the electrical storage device. The barrier layer 33 is preferably a metal layer, i.e., a layer formed of a metal. Specific examples of metals constituting the barrier layer 33 include aluminum, stainless steel, and titanium, and aluminum is preferred. The barrier layer 33 can be formed, for example, from a metal foil, a metal vapor deposition film, an inorganic oxide vapor deposition film, a carbon-containing inorganic oxide vapor deposition film, or a film provided with any of these vapor deposition films. It is preferably formed from a metal foil, and more preferably from an aluminum foil. From the viewpoint of preventing the occurrence of wrinkles or pinholes in the barrier layer 33 during the production of the packaging material for an electricity storage device, it is more preferable that the barrier layer be formed from a 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).

[0111] The thickness of the barrier layer 33 is preferably about 10 to 200 μm, and more preferably about 20 to 100 μm, from the viewpoint of making the packaging material for an electricity storage device thinner and making it less likely to produce pinholes during molding.

[0112] Furthermore, it is preferable that at least one surface, and preferably both surfaces, of the barrier layer 33 be chemically treated to stabilize adhesion, prevent dissolution and corrosion, etc. Here, chemical treatment refers to a treatment for forming a corrosion-resistant film on the surface of the barrier layer.

[0113] (adhesive layer 34) In the packaging material 3 for an electricity storage device, the adhesive layer 34 is a layer that is provided as needed between the barrier layer 33 and the heat-sealable resin layer 35 in order to firmly bond the heat-sealable resin layer 35.

[0114] The adhesive layer 34 is formed of an adhesive capable of bonding the barrier layer 33 and the heat-sealable resin layer 35. The composition of the adhesive used to form the adhesive layer is not particularly limited, and examples thereof include a resin composition containing an acid-modified polyolefin. Examples of acid-modified polyolefins include the same as those exemplified for the first polyolefin layer 12a and the second polyolefin layer 12b.

[0115] The thickness of the adhesive layer 34 is, for example, about 1 to 40 μm, and preferably about 2 to 30 μm.

[0116] (Thermal adhesive resin layer 35) In the packaging material 3 for an electricity storage device, the heat-sealable resin layer 35 corresponds to the innermost layer, and is a layer that seals the electricity storage device elements by heat-sealing the heat-sealable resin layers together when assembling the electricity storage device.

[0117] The resin component used in the heat-fusible resin layer 35 is not particularly limited as long as it is heat-fusible, and examples thereof include polyolefins and cyclic polyolefins.

[0118] Specific examples of the polyolefin include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); and ethylene-butene-propylene terpolymers. Among these polyolefins, polyethylene and polypropylene are preferred.

[0119] The cyclic polyolefin is a copolymer of an olefin and a cyclic monomer, and examples of the olefin constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, and isoprene. Examples of the cyclic monomer constituting the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, cyclic alkenes are preferred, and norbornene is more preferred. Styrene is also an example of a constituting monomer.

[0120] Among these resin components, preferred are crystalline or amorphous polyolefins, cyclic polyolefins, and blend polymers thereof; more preferred are polyethylene, polypropylene, copolymers of ethylene and norbornene, and blend polymers of two or more of these.

[0121] The heat-sealable resin layer 35 may be formed of a single resin component, or may be formed of a blend polymer of two or more resin components. 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. It is particularly preferred that the second polyolefin layer 12b and the heat-sealable resin layer 35 use the same resin, as this improves adhesion between these layers.

[0122] The thickness of the heat-fusible resin layer 35 is not particularly limited, but may be about 2 to 2000 μm, preferably about 5 to 1000 μm, and more preferably about 10 to 500 μm.

[0123] 2. Energy storage devices An electricity storage device 10 of the present disclosure comprises at least an electricity storage device element 4 having a positive electrode, a negative electrode, and an electrolyte, an exterior material for an electricity storage device 3 that seals the electricity storage device element 4, and metal terminals 2 that are electrically connected to the positive electrode and the negative electrode, respectively, and protrude to the outside of the exterior material for an electricity storage device 3. The electricity storage device 10 of the present disclosure is characterized in that an adhesive film for a metal terminal 1 of the present disclosure is interposed between the metal terminal 2 and the exterior material for an electricity storage device 3. In other words, the electricity storage device 10 of the present disclosure can be produced by a method that includes a step of interposing an adhesive film for a metal terminal 1 of the present disclosure between the metal terminal 2 and the exterior material for an electricity storage device 3.

[0124] Specifically, an electricity storage device element 4 including at least a positive electrode, a negative electrode, and an electrolyte is enclosed in an electricity storage device packaging material 3, with metal terminals 2 connected to the positive and negative electrodes protruding outward, and an adhesive film 1 for metal terminals of the present disclosure is interposed between the metal terminals 2 and a heat-sealable resin layer 35, and the electricity storage device element 4 is covered around its periphery so as to form a flange portion of the electricity storage device packaging material (a region where the heat-sealable resin layers 35 come into contact with each other, i.e., the peripheral portion 3a of the electricity storage device packaging material), and the heat-sealable resin layers 35 of the flange portion are heat-sealed to provide an electricity storage device 10 using the electricity storage device packaging material 3. When the electricity storage device element 4 is housed using the electricity storage device packaging material 3, the heat-sealable resin layer 35 of the electricity storage device packaging material 3 is used so that it faces inside (the surface in contact with the electricity storage device element 4).

[0125] The exterior material for an electricity storage device according to the present disclosure can be suitably used in electricity storage devices such as batteries (including condensers, capacitors, etc.). The exterior material for an electricity storage device according to the present disclosure may be used in either primary or secondary batteries, but is preferably used in secondary batteries. The type of secondary battery to which the exterior material for an electricity storage device according to the present disclosure is applied is not particularly limited, and examples include lithium ion batteries, lithium ion polymer batteries, all-solid-state batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, condensers, and capacitors. Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries are suitable applications for the exterior material for an electricity storage device according to the present disclosure. [Example]

[0126] The present disclosure will be described in detail below with reference to examples and comparative examples, but the present disclosure is not limited to the examples.

[0127] <Production of adhesive film for metal terminals> Example 1 A maleic anhydride-modified polypropylene (PPa) was used as the polyolefin for the first polyolefin layer, a polypropylene (PP) was used as the polyolefin for the second polyolefin layer, and an unstretched polypropylene film (CPP, homopolypropylene, 50 μm thick) was used as the substrate. The maleic anhydride-modified polypropylene (PPa) was extruded onto one side of the substrate (CPP) using a T-die extruder to form a first polyolefin layer (50 μm thick), and polypropylene (PP) was extruded onto the other side of the substrate (CPP) using a T-die extruder to form a second polyolefin layer (50 μm thick), resulting in an adhesive film for metal terminals in which the first polyolefin layer (50 μm, PPa layer), substrate (50 μm, CPP layer), and second polyolefin layer (50 μm, PP layer) were laminated in this order.

[0128] Comparative Example 1 The first polyolefin layer was made of maleic anhydride-modified polypropylene (PPa), the second polyolefin layer was made of polypropylene (PP), and the substrate was a polypropylene film (PP, thickness 30 μm) colored black with carbon black. The maleic anhydride-modified polypropylene (PPa) was extruded onto one side of the substrate (PP) using a T-die extruder to form a first polypropylene layer (thickness 50 μm). The other side of the substrate (PP) was extruded using a T-die extruder to form a second polypropylene layer (thickness 50 μm). This resulted in an adhesive film for metal terminals in which the first polyolefin layer (50 μm, PPa layer), substrate (30 μm, PP layer), and second polyolefin layer (20 μm, PP layer) were laminated in this order.

[0129] Comparative Example 2 The first polyolefin layer was maleic anhydride-modified polypropylene (PPa), the second polyolefin layer was maleic anhydride-modified polypropylene (PPa), and the substrate was polypropylene (PP). The resins for each layer were subjected to multi-layer air-cooled inflation molding to obtain an adhesive film for metal terminals, in which the first polyolefin layer (25 μm, PPa layer), the substrate (50 μm, PP layer), and the second polyolefin layer (25 μm, PPa layer) were laminated in this order.

[0130] The number of islands, the proportion of total area, the average particle size, the particle size deviation, and the circularity in the sea-island structure of the cross section of the first polyolefin layer of the adhesive film for metal terminal shown in Tables 1 and 2 can be adjusted by the composition, skeleton, dispersibility, molecular weight, melting point, MFR, and T-die and inflation conditions in the production of adhesive film for metal terminal 1 (for example, the extrusion width from the T-die, the stretching ratio, the stretching speed, the heat treatment temperature, the line speed during extrusion, the cooling speed, the extrusion temperature, etc.). In Example 1, the film was heated for 12 seconds on a hot plate heated to a temperature of 190°C (described below) (surface pressure: 0.016 MPa), and then naturally cooled to room temperature (25°C). The sea-island structure can also change depending on the cooling conditions after heating.

[0131] <Observation of islands in sea-island structures> The adhesive film for metal terminals was embedded in a thermosetting epoxy resin and cured. Cross sections in the desired direction (parallel to the TD and through the thickness direction) were prepared using a commercially available rotary microtome (LEICA UC6) and a diamond knife. The sections were then cryomicrotome-prepared at -70°C using liquid nitrogen. The embedded resin was stained overnight with ruthenium tetroxide. Since the polypropylene expanded upon staining, the expanded sections were trimmed with the microtome, cutting in 100-300 nm increments along the MD direction for a total of 1-2 μm. The exposed cross sections were then observed as follows. Images of the stained cross sections (10,000x magnification) were obtained using a field-emission scanning electron microscope (Hitachi High-Technologies S-4800 TYPE1, measurement conditions: 3 kV, 20 mA, High WD 6 mm, detector (upper)). Cross-sectional images were obtained for the surface portion of the first polyolefin layer on the metal terminal side (within the range of 30% of the thickness from the surface opposite the substrate side, assuming the thickness of the first polyolefin layer to be 100%; see Figure 4), and for the surface portion of the first polyolefin layer on the substrate side (within the range of 30% of the thickness from the surface on the substrate side, assuming the thickness of the first polyolefin layer to be 100%). Next, using image processing software capable of binarizing images (Mitani Corporation's image analysis software WinROOF (Ver. 7.4)), the island and sea portions of the sea-island structure of the image were binarized, and the number of island portions, the ratio of the total area of the island portions (total area of island portions / area of the measurement range of the image), the average particle size of the island portions, the particle size deviation σ of the island portions, and the circularity of the island portions were determined. The results are shown in Tables 1 and 2. Table 1 shows the measurement results for a sample after heating the adhesive film for metal terminals for 12 seconds using a hot plate heated to 190°C, as in <Measurement of adhesion strength between adhesive film for metal terminals and metal terminals> described below, and Table 2 shows the measurement results for a sample that was not heated.

[0132] 8 to 13 show binarized cross-sectional images of Example 1 and Comparative Examples 1 and 2, respectively. Fig. 8 shows the surface portion of the first polyolefin layer on the metal terminal side of Example 1, Fig. 9 shows the surface portion of the first polyolefin layer on the substrate side of Example 1, Fig. 10 shows the surface portion of the first polyolefin layer on the metal terminal side of Comparative Example 1, Fig. 11 shows the surface portion of the first polyolefin layer on the substrate side of Comparative Example 1, Fig. 12 shows the surface portion of the first polyolefin layer on the metal terminal side of Comparative Example 2, and Fig. 13 shows the surface portion of the first polyolefin layer on the substrate side of Comparative Example 2. In addition, in each of Figs. 8 to 13, the image on the left is the adhesive film for metal terminals before heating at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, and the image on the right is the adhesive film for metal terminals after heating at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds (after heating for 12 seconds on a hot plate heated to a temperature of 190°C and a surface pressure of 0.016 MPa, in the same manner as in the measurement of adhesion strength described below). In this measurement, the island portions were stained more than the sea portion, and therefore appeared brighter than the sea portion. [Image processing conditions] Image processing was performed using the image analysis software ImageJ. Specifically, SEM images were acquired as digital grayscale images (JPEG) and processed according to the binarization procedure and parameters below, with pixels above the threshold (bright) being output as 1 and pixels below the threshold (dark) as 0, defining them as island and sea regions, respectively. <Binarization processing> 1. Spike noise removal (Despeckle) 2. Remove island contours (Remove Outliers radius=4 threshold=1 which=Bright) 3. Remove Outliers radius=4 threshold=1 which=Dark 4. Spike noise removal (Despeckle) 5. Gaussian blur along the X axis (shorter side of the sample) (threshold = 3 pixels) 6. Contrast Enhancement (saturated = 0.2) 7.Remove Outliers radius=4 threshold=1 which=Bright 8. Remove Outliers radius=4 threshold=1 which=Dark 9. Otsu's Binarization

[0133] The average particle size of the islands is a value calculated from the maximum Feret's diameter of the islands in an image after binarization using the image analysis software ImageJ. The particle size deviation σ of the islands is a value calculated from the standard deviation of the average particle size. The circularity of the islands is a value calculated from the difference in radii of two concentric circles when the island in the image after binarization using the image analysis software ImageJ is sandwiched between two concentric circles with the smallest distance between the concentric circles.

[0134] <Measurement of adhesion strength between adhesive film for metal terminals and metal terminals> Aluminum (JIS H4160:1994 A8079H-O) measuring 50 mm in length, 22.5 mm in width, and 0.2 mm in thickness was prepared as the metal terminal. Each adhesive film for metal terminals obtained in the Examples and Comparative Examples was cut to a length of 45 mm and a width of 15 mm. The adhesive film for metal terminals was then placed on the metal terminal to obtain a metal terminal / adhesive film laminate. The metal terminals were laminated so that the longitudinal and lateral directions of the metal terminals coincided with the length and width directions of the adhesive film for metal terminals, respectively, and the centers of the metal terminal and adhesive film for metal terminals were aligned. The first polyolefin layer of the adhesive film for metal terminals was positioned on the metal terminal side. Next, a tetrafluoroethylene-ethylene copolymer film (ETFE film, 100 μm thick) was placed on top of the adhesive film for metal terminals of the laminate (covering the surface of the adhesive film for metal terminals with the ETFE film). This laminate was then placed on a hot plate heated to 190°C (with the metal terminal facing the hot plate), and a 500g sponge-attached weight was placed on top (surface pressure: 0.016 MPa). The laminate was then left to stand for 12 seconds to heat-seal the adhesive film to the metal terminal. The heat-sealed laminate was then allowed to cool naturally to 25°C. Next, the adhesive film for metal terminals was peeled from the metal terminal using a Tensilon universal material testing machine (RTG-1210, manufactured by A&D Co., Ltd.) at 25°C. The maximum strength at the time of peeling was recorded as the adhesion strength to the metal terminal (N / 15 mm). The peel speed was 50 mm / min, the peel angle was 180°, and the chuck distance was 30 mm. The average value was obtained from three measurements. The results are shown in Table 1. The treatment of leaving the board to stand for 12 seconds in a heated and pressurized environment at a temperature of 190°C and a surface pressure of 0.016 MPa is a treatment that simulates the heat and pressure applied in the temporary bonding process and the main bonding process.

[0135] <Adhesion strength after immersion in electrolyte> The adhesive film was heat-sealed to the metal terminal in the same manner as in the above-mentioned <Measurement of Adhesion Strength Between an Adhesive Film for Metal Terminal and a Metal Terminal>. The heat-sealed laminate was allowed to cool naturally to 25°C. Next, the resulting laminate was immersed in an 85°C electrolyte (obtained by mixing a solution of ethylene carbonate, diethyl carbonate, and dimethyl carbonate in a volume ratio of 1:1:1 with lithium hexafluorophosphate at 1 mol / L) for one day, then washed with water until the electrolyte and salt were thoroughly washed away, and then removed. Within one hour, the adhesive film for metal terminal was peeled from the metal terminal in the same manner as in the above-mentioned <Measurement of Adhesion Strength Between an Adhesive Film for Metal Terminal and a Metal Terminal>. The maximum strength at the time of peeling was taken as the adhesion strength to the metal terminal (N / 15 mm). The results are shown in Table 1.

[0136] [Table 1]

[0137] [Table 2]

[0138] In the adhesive film for metal terminal of Example 1, the cross-sectional image of the surface portion of the first polyolefin layer facing the metal terminal, which is the cross-sectional image after the adhesive film for metal terminal was heated at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, shows that the proportion of the total area of the islands in the sea-island structure is set to 25.0 to 35.0%. The adhesive film for metal terminal of Example 1 has excellent adhesion to the metal terminal by heat sealing, and further, even when an electrolyte solution adheres to the adhesive film adhered to the metal terminal by heat sealing, a decrease in adhesion to the metal terminal is suitably suppressed.

[0139] As described above, the present disclosure provides the following aspects of the invention. Item 1. An adhesive film for metal terminals that is interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that encapsulates the electricity storage device element, the adhesive film for metal terminal is composed of a laminate including, in this order, a first polyolefin layer disposed on the metal terminal side, a substrate, and a second polyolefin layer disposed on the exterior material side for the electricity storage device; a sea-island structure is observed in a cross-sectional image of the first polyolefin layer taken in a direction parallel to the TD and in the thickness direction, the cross-sectional image being obtained using a field emission scanning electron microscope; the cross-sectional image is a cross-sectional image obtained within a range from the surface opposite to the surface on the substrate side to a portion that is 30% of the thickness of the first polyolefin layer, where the thickness of the first polyolefin layer is 100%, An adhesive film for metal terminals, wherein the adhesive film for metal terminals is left to stand for 12 seconds in a heated and pressurized environment at a temperature of 190°C and a surface pressure of 0.016 MPa, and then further left to stand for 1 hour in an environment at a temperature of 25°C, and in the cross-sectional image thereof, the proportion of the total area of the island portions of the sea-island structure is 25.0% or more and 35.0% or less. Item 2. The adhesive film for a metal terminal according to Item 1, wherein the average particle size of the island portions in the cross-sectional image is 0.3 μm or more. Item 3. The adhesive film for metal terminal according to Item 1 or 2, wherein the particle size deviation of the island portions in the cross-sectional image is 0.3 or less. Item 4. The adhesive film for a metal terminal according to any one of Items 1 to 3, wherein the circularity of the island portion in the cross-sectional image is 0.75 or more. Item 5. The adhesive film for metal terminal according to any one of Items 1 to 4, wherein the thickness of the first polyolefin layer is 60 μm or less. Item 6. The adhesive film for a metal terminal according to any one of Items 1 to 5, wherein the thickness of the substrate is 60 μm or less. Item 7. The adhesive film for metal terminal according to any one of Items 1 to 6, wherein the second polyolefin layer has a thickness of 60 μm or less. Item 8. The adhesive film for a metal terminal according to any one of Items 1 to 7, wherein the adhesive film for a metal terminal has a thickness of 180 μm or less. Item 9. The adhesive film for a metal terminal according to any one of Items 1 to 8, wherein the first polyolefin layer contains a pigment. Item 10. The adhesive film for a metal terminal according to any one of Items 1 to 9, wherein the substrate includes a polyolefin skeleton. Item 11. A method for producing an adhesive film for a metal terminal, which is interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that encapsulates the electricity storage device element, comprising: the adhesive film for metal terminal is composed of a laminate including, in this order, a first polyolefin layer disposed on the metal terminal side, a substrate, and a second polyolefin layer disposed on the exterior material side for the electricity storage device; obtaining a laminate having the first polyolefin layer, the substrate, and the second polyolefin layer in this order, a sea-island structure is observed in a cross-sectional image of the first polyolefin layer taken in a direction parallel to the TD and in the thickness direction, the cross-sectional image being obtained using a field emission scanning electron microscope; the cross-sectional image is a cross-sectional image obtained within a range from the surface opposite to the surface on the substrate side to a portion that is 30% of the thickness of the first polyolefin layer, where the thickness of the first polyolefin layer is 100%, A method for producing an adhesive film for metal terminals, wherein the adhesive film for metal terminals is left to stand for 12 seconds in a heated and pressurized environment at a temperature of 190°C and a surface pressure of 0.016 MPa, and then further left to stand for 1 hour in an environment at a temperature of 25°C, and in the cross-sectional image thereof, the ratio of the total area of the island portions of the sea-island structure is 25.0% or more and 35.0% or less. Item 12. A metal terminal with an adhesive film for a metal terminal, comprising the adhesive film for a metal terminal according to any one of Items 1 to 10 attached to a metal terminal. Item 13. An electricity storage device including at least the electricity storage device element including a positive electrode, a negative electrode, and an electrolyte, the electricity storage device casing material that seals the electricity storage device element, and the metal terminals that are electrically connected to the positive electrode and the negative electrode, respectively, and that protrude outside the electricity storage device casing material, Item 11. An electricity storage device, wherein the adhesive film for a metal terminal according to any one of items 1 to 10 is interposed between the metal terminal and the exterior material for an electricity storage device. Item 14. A method for manufacturing an electricity storage device including at least an electricity storage device element including a positive electrode, a negative electrode, and an electrolyte, an exterior material for an electricity storage device that seals the electricity storage device element, and metal terminals that are electrically connected to the positive electrode and the negative electrode, respectively, and protrude outside the exterior material for an electricity storage device, A method for producing an electricity storage device, comprising a step of interposing the adhesive film for metal terminal according to any one of items 1 to 10 between the metal terminal and the exterior material for an electricity storage device, and sealing the electricity storage device element with the exterior material for an electricity storage device. [Explanation of symbols]

[0140] 1. Adhesive film for metal terminals 2 metal terminals 3. Exterior materials for energy storage devices 3a Peripheral part of the exterior material for the electricity storage device 4. Energy storage device elements 10. Energy storage devices 11 Base material 12a First polyolefin layer 12b Second polyolefin layer 13 Adhesion promoter layer 31 Base material layer 32 Adhesive layer 33 Barrier Layer 34 Adhesive layer 35 Heat-fusible resin layer

Claims

1. An adhesive film for metal terminals, which is interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that seals the electricity storage device element, the adhesive film for a metal terminal is composed of a laminate including, in this order, a first polyolefin layer disposed on the metal terminal side, a substrate, and a second polyolefin layer disposed on the electricity storage device exterior material side; a sea-island structure is observed in a cross-sectional image of the first polyolefin layer taken in a direction parallel to the TD and in the thickness direction, the cross-sectional image being obtained using a field emission scanning electron microscope; the cross-sectional image is a cross-sectional image obtained within a range from the surface opposite to the surface on the substrate side to a portion that is 30% of the thickness of the first polyolefin layer, where the thickness of the first polyolefin layer is 100%, the adhesive film for metal terminal is left to stand for 12 seconds in a heated and pressurized environment at a temperature of 190°C and a surface pressure of 0.016 MPa, and then further left to stand for 1 hour in an environment at a temperature of 25°C, and in the cross-sectional image, the ratio of the total area of the island parts of the sea-island structure is 25.0% or more and 35.0% or less; An adhesive film for a metal terminal, wherein the circularity of the island portion in the cross-sectional image is 0.75 or more.

2. The adhesive film for a metal terminal according to claim 1 , wherein the average particle diameter of the island portions in the cross-sectional image is 0.3 μm or more.

3. 3. The adhesive film for a metal terminal according to claim 1, wherein the circularity of the island portion in the cross-sectional image is 0.80 or more.

4. The adhesive film for metal terminals according to any one of claims 1 to 3, wherein the thickness of the first polyolefin layer is 60 µm or less.

5. The adhesive film for metal terminals according to any one of claims 1 to 4, wherein the thickness of the substrate is 60 µm or less.

6. The adhesive film for metal terminals according to any one of claims 1 to 5, wherein the thickness of the second polyolefin layer is 60 µm or less.

7. The adhesive film for metal terminal according to any one of claims 1 to 6, wherein the thickness of the adhesive film for metal terminal is 180 µm or less.

8. The adhesive film for a metal terminal according to any one of claims 1 to 7, wherein the first polyolefin layer contains a pigment.

9. The adhesive film for metal terminals according to any one of claims 1 to 8, wherein the substrate comprises a polyolefin skeleton.

10. An adhesive film for metal terminals according to any one of claims 1 to 9, wherein the substrate comprises homopolypropylene (excluding those in which the proportion of the total area of the island portions of the sea-island structure is 28.0% or more and 35.0% or less).

11. The cross-sectional image was obtained within a range of 30% of the thickness of the first polyolefin layer from the surface opposite the surface on the substrate side, assuming that the thickness of the first polyolefin layer is 100%, and the adhesive film for metal terminals was left to stand for 12 seconds in a heated and pressurized environment at a temperature of 190°C and a surface pressure of 0.016 MPa, and then further left to stand for 1 hour in an environment at a temperature of 25°C. The adhesive film for metal terminals according to any one of claims 1 to 9, wherein the ratio of the total area of the islands in the sea-island structure is 28.0% or more and 35.0% or less.

12. A method for producing an adhesive film for a metal terminal, which is interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that encapsulates the electricity storage device element, comprising: the adhesive film for a metal terminal is composed of a laminate including, in this order, a first polyolefin layer disposed on the metal terminal side, a substrate, and a second polyolefin layer disposed on the electricity storage device exterior material side; obtaining a laminate comprising the first polyolefin layer, the substrate, and the second polyolefin layer in this order; a sea-island structure is observed in a cross-sectional image of the first polyolefin layer taken in a direction parallel to the TD and in the thickness direction, the cross-sectional image being obtained using a field emission scanning electron microscope; the cross-sectional image is a cross-sectional image obtained within a range from the surface opposite to the surface on the substrate side to a portion that is 30% of the thickness of the first polyolefin layer, where the thickness of the first polyolefin layer is 100%, the adhesive film for metal terminal is left to stand for 12 seconds in a heated and pressurized environment at a temperature of 190°C and a surface pressure of 0.016 MPa, and then further left to stand for 1 hour in an environment at a temperature of 25°C, and in the cross-sectional image, the ratio of the total area of the island parts of the sea-island structure is 25.0% or more and 35.0% or less; In the cross-sectional image, the circularity of the island portion is 0.75 or more. A method for manufacturing an adhesive film for metal terminals.

13. A metal terminal with an adhesive film for a metal terminal, comprising the adhesive film for a metal terminal according to any one of claims 1 to 11 attached to a metal terminal.

14. an electricity storage device including at least an electricity storage device element including a positive electrode, a negative electrode, and an electrolyte; an exterior material for an electricity storage device that seals the electricity storage device element; and metal terminals that are electrically connected to the positive electrode and the negative electrode, respectively, and protrude outside the exterior material for an electricity storage device, An electricity storage device, comprising the adhesive film for metal terminals according to any one of claims 1 to 11 interposed between the metal terminals and the exterior material for electricity storage devices.

15. a manufacturing method for an electricity storage device including at least an electricity storage device element including a positive electrode, a negative electrode, and an electrolyte; an exterior material for an electricity storage device that seals the electricity storage device element; and metal terminals that are electrically connected to the positive electrode and the negative electrode, respectively, and protrude outside the exterior material for an electricity storage device, A method for manufacturing an electricity storage device, comprising a step of interposing the adhesive film for metal terminal according to any one of claims 1 to 11 between the metal terminal and the exterior material for an electricity storage device, and sealing the electricity storage device element with the exterior material for an electricity storage device.

Images