Adhesive film for metal terminals, method for manufacturing an adhesive film for metal terminals, metal terminals with an adhesive film for metal terminals, a power storage device using the adhesive film for metal terminals, and method for manufacturing a power storage device

Abstract

To provide an adhesive film for a metal terminal, which is superior in the adhesion of an adhesiveness film to a metal terminal by heat seal.SOLUTION: An adhesive film for a metal terminal is composed of a laminate including: a first polyolefin layer disposed on a metal terminal side; a base material; and a second polyolefin layer for a power storage device, which is disposed on an exterior material side in this order. As to a section of the first polyolefin layer in a direction in parallel with TD and a thickness direction, a sea island structure is observed in a sectional image taken by a field-emission type scanning electron microscope. The sectional image is one taken within a range of a part ranging from a surface on a side opposite to a base material-side surface to a thickness of 30% on the assumption that a thickness of the first polyolefin layer is 100%. In the sectional image of the adhesive film for a metal terminal after heating the adhesive film at a temperature of 190°C under a surface pressure of 0.016 MPa for 12 seconds, the percentage of a total area of island portions of the sea island structure is 25.0% or more and 35.0% or less.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

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

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

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

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

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Such an adhesive film is required to have excellent adhesion to the metal terminal when heat-sealed.

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

[0009] However, the adhesion of conventional adhesive films to metal terminals when in contact with an electrolytic solution has not been sufficiently studied. The inventors of the present disclosure, in addition to the excellent adhesion of the adhesive film to the metal terminals by heat sealing, pursued the suppression of a decrease in adhesion to the metal terminals when an electrolytic solution adheres to the adhesive film adhered to the metal terminals.

[0010] The main object of the present disclosure is to provide an adhesive film for metal terminals that has excellent adhesion to metal terminals by heat sealing, and further, even when an electrolytic solution adheres to the adhesive film adhered to the metal terminals, a decrease in adhesion to the metal terminals is preferably suppressed. 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 using the adhesive film for metal terminals, a power storage device using the adhesive film for metal terminals, and a method for manufacturing the power storage device.

Means for Solving the Problems

[0011] The inventors of the present disclosure conducted intensive studies to solve the above problems. As a result, an adhesive film for metal terminals composed of a laminate including a first polyolefin layer disposed on the metal terminal side, a base material, and a second polyolefin layer disposed on the side of the exterior material for the power storage device in this order. When the adhesive film for metal terminals is left standing for 12 seconds in a heating and pressurizing environment at a temperature of 190°C and a surface pressure of 0.016 MPa, and further left standing for 1 hour in an environment at a temperature of 25°C (general heating conditions during heat sealing), in the cross-sectional image of the surface portion on the metal terminal side of the first polyolefin layer, when the ratio of the total area of the island portions of the sea-island structure is within a predetermined range, the adhesive film has excellent adhesion to the metal terminals by heat sealing, and further, even when an electrolytic solution adheres to the adhesive film adhered to the metal terminals by heat sealing, a decrease in adhesion to the metal terminals is preferably suppressed. The present disclosure was completed by further studies based on such findings.

[0012] That is, the present disclosure provides an invention in the following aspects. An adhesive film for a metal terminal interposed between a metal terminal electrically connected to an electrode of a power storage device element and an exterior material for a power storage device that seals the power storage device element, The adhesive film for a metal terminal is composed of a laminate including a first polyolefin layer disposed on the metal terminal side, a base material, and a second polyolefin layer disposed on the exterior material side for the power storage device in this order. For a cross-section in a direction parallel to the TD (Transverse Direction) of the first polyolefin layer and in the thickness direction, a sea-island structure is observed in a cross-sectional image obtained using a field emission scanning electron microscope. The cross-sectional image is a cross-sectional image obtained within a range up to a portion having a thickness of 30% from the surface opposite to the surface on the base material side when the thickness of the first polyolefin layer is taken as 100%. In the cross-sectional image after the adhesive film for a metal terminal is allowed to stand for 12 seconds in a heating and pressurizing environment at a temperature of 190 ° C and a surface pressure of 0.016 MPa, and further allowed to stand for 1 hour in an environment at a temperature of 25 ° C, 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. An adhesive film for a metal terminal.

Advantages of the Invention

[0013] According to the present disclosure, it is possible to provide an adhesive film for a metal terminal that is excellent in adhesion to a metal terminal by heat sealing, and further, even when an electrolytic solution adheres to the adhesive film adhered to the metal terminal by heat sealing, a decrease in adhesion to the metal terminal is preferably suppressed. Furthermore, an object of the present disclosure is also to provide a method for manufacturing the adhesive film for a metal terminal, a metal terminal with an adhesive film for a metal terminal using the adhesive film for a metal terminal, a power storage device using the adhesive film for a metal terminal, and a method for manufacturing the power storage device.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

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Figure 8

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Figure 11

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Figure 14

Embodiments for Carrying Out the Invention

[0015] The adhesive film for metal terminals of the present disclosure is an adhesive film for metal terminals interposed between a metal terminal electrically connected to an electrode of a power storage device element and an exterior material for a power storage device that seals the power storage device element. The adhesive film for metal terminals is composed of a laminate including a first polyolefin layer disposed on the metal terminal side, a base material, and a second polyolefin layer disposed on the exterior material side of the power storage device in this order. Regarding a cross-section in a direction parallel to TD and in the thickness direction of the first polyolefin layer, an island structure is observed in a cross-sectional image obtained using a field emission scanning electron microscope. The cross-sectional image is a cross-sectional image obtained within a range up to a portion having a thickness of 30% from the surface opposite to the surface on the base material side when the thickness of the first polyolefin layer is taken as 100%. In the cross-sectional image after heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the ratio of the total area of the island portions of the island structure is 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 disposed on the metal terminal side (specifically, a cross-sectional image obtained within a range up to a portion having a thickness of 30% from the surface opposite to the surface on the base material side when the thickness of the first polyolefin layer is taken as 100%). In the cross-sectional image after heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the ratio of the total area of the island portions of the island structure is set to 25.0% or more and 35.0% or less. Therefore, the adhesive film has excellent adhesion to the metal terminals by heat sealing. Furthermore, even when an electrolytic solution adheres to the adhesive film adhered to the metal terminals by heat sealing, a decrease in adhesion to the metal terminals is preferably suppressed.

[0017] Further, the energy storage device of the present disclosure includes at least an energy storage device element including a positive electrode, a negative electrode, and an electrolyte, an exterior material for the energy storage device that seals the energy storage device element, and metal terminals that are electrically connected to each of the positive electrode and the negative electrode and protrude outside the exterior material for the energy storage device, and is characterized in that the adhesive film for the metal terminal of the present disclosure is interposed between the metal terminal and the exterior material for the energy storage device. Hereinafter, the adhesive film for the metal terminal of the present disclosure, its manufacturing method, the energy storage device using the adhesive film for the metal terminal, and its manufacturing method will be described in detail.

[0018] In addition, in this specification, for numerical ranges, the numerical range indicated by "~" means "or more" and "or less". For example, the notation of 2~15 mm means 2 mm or more and 15 mm or less.

[0019] Also, as a method for confirming the MD of the adhesive film for the metal terminal, there is a method of observing the cross-section of the adhesive film for the metal terminal (for example, the cross-section of the first polyolefin layer, the base material, or the second polyolefin layer) with an electron microscope to confirm the sea-island structure. In this method, the direction parallel to the cross-section where the average of the diameters of the island shapes in the direction perpendicular to the thickness direction of the adhesive film for the metal terminal is the largest can be determined as the MD. Specifically, the cross-section in the length direction of the adhesive film for the metal terminal and the direction parallel to the cross-section in the length direction are changed by an angle of 10 degrees each, and for each cross-section (a total of 10 cross-sections) from the cross-section in the length direction to the direction perpendicular to the cross-section in the length direction, the sea-island structure is observed by an electron micrograph. Next, in each cross-section, the shape of each individual island is observed. For the shape of each individual island, the straight-line distance connecting the leftmost end in the direction perpendicular to the thickness direction of the adhesive film for the metal terminal and the rightmost end in the perpendicular direction is defined as the diameter y. In each cross-section, the average of the top 20 diameters y in descending order of the diameter y of the island shape is calculated. The direction parallel to the cross-section where the average of the diameter y of the island shape is the largest is determined as the MD.

[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 a power storage device element and an exterior material for a power storage device that seals the power storage device element. Specifically, as shown in FIGS. 1 to 3, for example, the adhesive film 1 for metal terminals of the present disclosure is interposed between a metal terminal 2 electrically connected to an electrode of a power storage device element 4 and an exterior material 3 for a power storage device that seals the power storage device element 4. Further, the metal terminal 2 protrudes outside the exterior material 3 for a power storage device, and at the peripheral edge portion 3a of the heat-sealed exterior material 3 for a power storage device, it is sandwiched between the exterior material 3 for a power storage device via the adhesive film 1 for metal terminals. In the present disclosure, the heating temperature when heat-sealing the exterior material for a power storage device is usually in the range of about 160 to 190°C, and the pressure is usually in the range of about 1.0 to 2.0 MPa. In the step of bonding the metal terminal and the exterior material for a power storage device via the adhesive film, for example, multiple times of heating and pressurization are generally performed, such as a temporary bonding step to the metal terminal and a main bonding step. The temporary bonding step is a step of temporarily fixing the adhesive film to the metal terminal and removing air bubbles, and the main bonding step is a step of performing heating and pressurization one or more times under higher temperature conditions than the temporary bonding step to bond the adhesive film to the metal terminal. The temporary bonding step of the adhesive film for metal terminals to the metal terminal is performed, for example, under conditions of a temperature of about 140 to 160°C, a pressure of about 0.01 to 1.0 MPa, a time of about 3 to 15 seconds, and a number of times of about 3 to 6 times. The main bonding step is performed, for example, under conditions of a temperature of about 160 to 240°C, a pressure of about 0.01 to 1.0 MPa, a time of about 3 to 15 seconds, and a number of times of about 1 to 3 times.

[0021] The adhesive film 1 for metal terminals of the present disclosure is provided to enhance the adhesion between the metal terminal 2 and the exterior material 3 for the power storage device. By enhancing the adhesion between the metal terminal 2 and the exterior material 3 for the power storage device, the sealing performance of the power storage device element 4 is improved. As described above, when heat-sealing the power storage device element 4, the metal terminal 2 electrically connected to the electrode of the power storage device element 4 protrudes outside the exterior material 3 for the power storage device, and the power storage device element is sealed. At this time, since the metal terminal 2 formed of metal and the heat-sealing resin layer 35 (a layer formed of a heat-sealing resin such as polyolefin) located in the innermost layer of the exterior material 3 for the power storage device are made of different materials, if such an adhesive film is not used, the sealing performance of the power storage device element tends to be low at the interface between the metal terminal 2 and the heat-sealing resin layer 35.

[0022] As shown in FIGS. 4 and 5, the adhesive film 1 for metal terminals of the present disclosure includes at least a configuration in which a first polyolefin layer 12a, a base material 11, and a second polyolefin layer 12b are laminated in this order. The first polyolefin layer 12a is disposed on the side of the metal terminal 2. Further, the second polyolefin layer 12b is disposed on the side of the exterior material 3 for the power 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.

[0023] In the adhesive film 1 for metal terminals of the present disclosure, the first polyolefin layer 12a and the second polyolefin layer 12b are each a layer containing a polyolefin resin. Examples of the polyolefin resin include polyolefin and acid-modified polyolefin. Among the polyolefin resins, the first polyolefin layer 12a preferably contains an acid-modified polyolefin, and more preferably is a layer formed of an acid-modified polyolefin. Also, among the polyolefin resins, the second polyolefin layer 12b preferably contains a polyolefin or an acid-modified polyolefin, more preferably contains a polyolefin, and even more preferably is a layer formed of a polyolefin. By making the resin forming the second polyolefin layer 12b disposed on the side of the exterior material 3 for a power storage device the same resin as the resin forming the heat-sealable resin layer 35 of the exterior material 3 for a power storage device, the adhesion between the adhesive film 1 for metal terminals of the present disclosure and the exterior material for a power storage device is enhanced.

[0024] Also, the base material 11 preferably contains a polyolefin resin, more preferably contains a polyolefin, and even more preferably is a layer formed of a polyolefin.

[0025] In the first polyolefin layer 12a, the second polyolefin layer 12b, and the base material 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 the polyolefin resins such as polyolefin and acid-modified polyolefin may contain known additives, fillers, pigments, etc. described later.

[0026] As a specific example of a preferred laminated structure of the adhesive film 1 for metal terminals of the present disclosure, a three-layer structure in which a first polyolefin layer formed of acid-modified polypropylene / a base material formed of polypropylene / a second polyolefin layer formed of polypropylene are laminated in this order; a three-layer structure in which a first polyolefin layer formed of acid-modified polypropylene / a base material formed of polypropylene / a second polyolefin layer formed of acid-modified polypropylene are laminated in this order, etc. are mentioned. Among these, a three-layer structure in which a first polyolefin layer formed of acid-modified polypropylene / a base material formed of polypropylene / a second polyolefin layer formed of polypropylene are laminated in this order is particularly preferred.

[0027] Details of the materials constituting the first polyolefin layer 12a, the second polyolefin layer 12b, and the base material 11 will be described later.

[0028] When the adhesive film 1 for metal terminals of the present disclosure is disposed between the metal terminal 2 of the power storage device 10 and the exterior member 3 for the power storage device, the surface of the metal terminal 2 constituted by metal and the heat-sealing resin layer 35 (a layer formed of a heat-sealing resin such as polyolefin) of the exterior member 3 for the power storage device are adhered via the adhesive film 1 for metal terminals. The first polyolefin layer 12a of the adhesive film 1 for metal terminals is disposed on the metal terminal 2 side, the second polyolefin layer 12b is disposed on the exterior member 3 side for the power storage device, the first polyolefin layer 12a is in close contact with the metal terminal 2, and the second polyolefin layer 12b is in close contact with the heat-sealing resin layer 35 of the exterior member 3 for the power storage device.

[0029] In the adhesive film 1 for metal terminals of the present disclosure, a sea-island structure is observed in a cross-sectional image obtained using a field emission scanning electron microscope for a cross-section in a direction parallel to the TD of the first polyolefin layer 12a and in the thickness direction. The cross-sectional image is a cross-sectional image obtained within a range from the surface opposite to the surface on the base material 11 side to the portion having a thickness of 30% when the thickness of the first polyolefin layer 12a is taken as 100%. Further, in the cross-sectional image obtained after heating the adhesive film for metal terminals at a temperature of 190° C. and a surface pressure of 0.016 MPa for 12 seconds, the ratio of the total area of the island portions of the sea-island structure is 25.0 to 35.0%. Regarding the method of heating the adhesive film for metal terminals at a temperature of 190° C. and a surface pressure of 0.016 MPa for 12 seconds, a method of heating with a hot plate heated to 190° C. for 12 seconds is adopted in the same manner as the measurement of the adhesion strength in the examples described later.

[0030] Incidentally, when the thickness of the first polyolefin layer 12a is taken as 100%, the range from the surface opposite to the surface on the base material 11 side to the portion having a thickness of 30% may be abbreviated as the surface portion on the side opposite to the surface on the base material 11 side of the first polyolefin layer 12a (or the surface portion on the side of the metal terminal 2 of the first polyolefin layer 12a). Similarly, when the thickness of the first polyolefin layer 12a is taken as 100%, the range from the surface on the base material 11 side to the portion having a thickness of 30% may be abbreviated as the surface portion on the base material 11 side of the first polyolefin layer 12a.

[0031] The ratio of the total area of the island portions of the sea-island structure may be in the range of 25.0 to 35.0%, but it is particularly excellent in the adhesion of the adhesive film by heat sealing to the metal terminals. Further, even when the electrolyte adheres to the adhesive film adhered to the metal terminals by heat sealing, the decrease in the adhesion to the metal terminals is more preferably suppressed. Therefore, the ratio of the total area of the island portions of the sea-island structure is preferably about 26.0% or more, more preferably about 28.0% or more. Also, the ratio of the total area of the island portions of the sea-island structure is preferably about 32.0% or less, more preferably about 30.0% or less. The preferable range of the ratio of the total area of the island portions of the sea-island structure is about 26.0 to 32.0%, about 26.0 to 30.0%, about 28.0 to 35.0%, about 28.0 to 32.0%, about 28.0 to 30.0%.

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

[0033] <Observation of the sea-island structure in the cross-sectional image> Embed an adhesive film for metal terminals in a thermosetting epoxy resin and cure it. Use a commercially available rotary microtome (for example, UC6 manufactured by LEICA) and a diamond knife to prepare a cross-section in the target direction (cross-section along TD). At this time, perform cross-section preparation at -70 °C using a cryomicrotome with liquid nitrogen. Stain the embedded resin with ruthenium tetroxide overnight. When stained, the polypropylene expands, so trim the expanded part with a microtome and cut forward 100 nm to 300 nm at a time in the MD direction. When a total of about 1 μm to 2 μm is cut, observe the exposed cross-section as follows. For the stained cross-section, observe with a field emission scanning electron microscope (for example, S-4800 TYPE1 manufactured by Hitachi High-Technologies Corporation, measurement conditions: 3 kV 20 mA High WD6 mm detector (Upper)) to obtain an image (magnification is 10,000 times). Note that the cross-section image is within the range from the surface portion on the metal terminal side of the first polyolefin layer (when the thickness of the first polyolefin layer is 100%, the portion with a thickness of 30% from the surface on the side opposite to the surface of the base material). See Figure 4.). In addition, for the surface portion on the base material side of the first polyolefin layer (within the range from the surface of the base material to the portion with a thickness of 30% when the thickness of the first polyolefin layer is 100%), a cross-section image can be obtained in the same way by changing the observation location. Next, use image processing software that can binarize the image (for example, image analysis software WinROOF (Ver7.4) manufactured by Mitani Shoji Co., Ltd.). For the image, binarize the island part and the sea part of the sea-island structure, and obtain the number of island parts, the ratio of the total area of the island parts (total area of the island parts / area of the measurement range of the image), the average particle diameter of the island parts, the particle diameter deviation σ of the island parts, and the roundness of the island parts, etc.

[0034] The binarized cross-sectional images in Example 1 and Comparative Examples 1 and 2 are shown in FIGS. 8 to 13, respectively. FIG. 8 shows the surface portion on the metal terminal side of the first polyolefin layer in Example 1, FIG. 9 shows the surface portion on the base material side of the first polyolefin layer in Example 1, FIG. 10 shows the surface portion on the metal terminal side of the first polyolefin layer in Comparative Example 1, FIG. 11 shows the surface portion on the base material side of the first polyolefin layer in Comparative Example 1, FIG. 12 shows the surface portion on the metal terminal side of the first polyolefin layer in Comparative Example 2, and FIG. 13 shows the surface portion on the base material side of the first polyolefin layer in Comparative Example 2. Further, in each of FIGS. 8 to 13, the left image is before heating the adhesive film for metal terminals at a temperature of 190° C. and a surface pressure of 0.016 MPa for 12 seconds, and the right image is after heating the adhesive film for metal terminals at a temperature of 190° C. and a surface pressure of 0.016 MPa for 12 seconds (in the same manner as the measurement of the adhesion strength described later, the adhesive film for metal terminals is heated at a surface pressure of 0.016 MPa for 12 seconds on a hot plate heated to 190° C. (heating is performed so that the first polyolefin layer side is on the hot plate side)). In this measurement, since the island portion was stained more than the sea portion, the island portion was observed to be brighter than the sea portion. [Image processing conditions] Image processing can be performed using the image analysis software ImageJ. Specifically, an SEM image is acquired as a digital file of a grayscale image (such as JPEG format), and processing is performed according to the following binarization processing procedure and parameters. Pixels with a tone (bright) above the threshold are output as 1, and pixels with a tone (dark) below the threshold are output as 0, and each is defined as an island portion and a sea portion. [Binarization processing] 1. Spike noise removal (Despeckle) 2. Removal of the contour of the island portion (Remove Outliers radius = 4 threshold = 1 which = Bright) 3. Removal of the contour of the sea portion (Remove Outliers radius = 4 threshold = 1 which = Dark) 4. Spike noise removal (Despeckle) 5. Gaussian blur in the X-axis (short side of the sample) direction (threshold = 3 pixels) 6. Contrast enhancement (saturated = 0.2) 7. Removal of the outline of the island part (Remove Outliers radius=4 threshold=1 which=Bright) 8. Removal of the outline of the sea part (Remove Outliers radius=4 threshold=1 which=Dark) 9. Otsu binarization

[0035] The average particle diameter of the above-mentioned island part is a value calculated from the maximum Feret diameter of the island part in the binarized image by the image analysis software ImageJ. Also, the particle diameter deviation σ of the above-mentioned island part is a value calculated by the standard deviation of the above average particle diameter. Further, the circularity of the above-mentioned island part is a value calculated by the difference in the radii of two concentric circles when the island part in the binarized image is sandwiched between two concentric geometric circles and the distance between the concentric circles is minimized by the image analysis software ImageJ.

[0036] The cross-sectional image is, for example, as shown in the schematic diagram of FIG. 4. When the total thickness of the first polyolefin layer 12a is taken as 100%, it is a cross-sectional image obtained within the range from the surface on the metal terminal side (opposite to the base material 11) to the portion with a thickness of 30% (the region with cross-hatching in FIG. 4). The surface of the first polyolefin layer 12a opposite to the base material 11 has a thickness of 0%. To explain with a specific example, for example, as in Example 1 described later, if it is an adhesive film for a metal terminal in which a first polyolefin layer (thickness 50 μm) / base material (thickness 50 μm) / second polyolefin layer (thickness 50 μm) are laminated in this order, the thickness of the first polyolefin layer of 50 μm is taken as 100%. Also, the thickness at the position of the surface of the first polyolefin layer 12a opposite to the base material 11 is taken as 0%. Then, within the range from the surface (thickness 0%) to the position with a thickness of 30% (that is, taking 50 μm as 100%, the position with a thickness of 30% is the position with a thickness of 15 μm from the surface on the side opposite to the base material layer of the first polyolefin layer toward the base material side), a cross-sectional image is obtained using a field emission scanning electron microscope.

[0037] Moreover, observing a sea-island structure in a cross-sectional image means observing a sea portion (sea part) and an island portion (island part) in the cross-sectional image. For example, as a resin composition for forming the first polyolefin layer 12a, when a small amount of polyethylene is added to acid-modified polypropylene and the first polyolefin layer 12a is formed by melt extrusion molding, a sea-island structure in which island portions of polyethylene are dispersed in the sea portion of acid-modified polypropylene is formed. In addition, 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 the adhesive film 1 for metal terminals of the present disclosure, in the cross-sectional image of the surface portion on the metal terminal side (specifically, the portion with a thickness of 30% from the surface on the metal terminal side (opposite to the base material 11)) after heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the ratio of the total area of the island portions of the sea-island structure is 25.0 to 35.0%. The adhesive film 1 for metal terminals of the present disclosure has such characteristics, so it has excellent adhesion to the metal terminals by heat sealing. Furthermore, even when an electrolytic solution adheres to the adhesive film adhered to the metal terminals by heat sealing, a decrease in adhesion to the metal terminals is preferably suppressed. More specifically, in the first polyolefin layer 12a disposed on the metal terminal side of the adhesive film 1 for metal terminals of the present disclosure, the total area of the island portions of the sea-island structure of the surface portion on the metal terminal 2 side (the island portions are mainly formed of polyethylene, which, for example, softens the first polyolefin layer 12a and improves adhesion, but is slightly inferior in electrolytic solution resistance) is set within an appropriate range of 25.0 to 35.0%. By doing so, while ensuring excellent adhesion to the metal terminals, penetration of the electrolytic solution is preferably suppressed. As a result, it is considered that a decrease in adhesion to the metal terminals when the electrolytic solution adheres is suppressed. The surface portion on the metal terminal side after heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds corresponds to the surface portion after the first polyolefin layer 12a is adhered to the metal terminal 2 by heat sealing. In the adhesive film 1 for metal terminals of the present disclosure, it can be said that the ratio of the total area of the island portions of the sea-island structure of the surface portion on the metal terminal 2 side after heat sealing of the first polyolefin layer 12a is set within an appropriate range of 25.0 to 35.0%.

[0039] Further, in the adhesive film 1 for metal terminals of the present disclosure, when the thickness of the first polyolefin layer 12a is taken as 100%, a cross-sectional image obtained within the range up to the surface portion on the base material 11 side (specifically, the portion having a thickness of 30% from the surface on the base material 11 side), and even in the cross-sectional image after heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, a sea-island structure is usually observed. The ratio of the total area of the island portions of the sea-island structure in the cross-sectional image of the surface portion on the base material 11 side is not particularly limited, but is preferably about 25.0% or more, more preferably about 30.0% or more. Also, the ratio of the total area of the island portions is preferably about 35.0% or less, more preferably about 33.0% or less. The preferable range of the ratio of the total area of the island portions is about 25.0 to 35.0%, about 25.0 to 33.0%, about 30.0 to 35.0%, or about 30.0 to 33.0%. Regarding the method of 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 for 12 seconds with a hot plate heated to 190°C is adopted in the same manner as the measurement of the adhesion strength in the examples described later.

[0040] In the adhesive film 1 for metal terminals of the present disclosure, for example, the ratio of the total area of the island portions of the sea-island structure in the cross-sectional image of the surface portion on the metal terminal 2 side after heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds may be smaller or larger than the ratio of the total area of the island portions of the sea-island structure in the cross-sectional image of the surface portion on the base material 11 side, but it is desirable that they are about the same. That is, in the adhesive film 1 for metal terminals of the present disclosure, the ratio of the total area of the island portions of the surface portion on the metal terminal 2 side may be smaller or larger than that of the surface portion on the base material 11 side, but it is desirable that they are about the same. Also, before and after heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the ratio of the total area of the island portions of the sea-island structure in the cross-sectional image of the surface portion on the metal terminal 2 side is preferably about the same, and the ratio of the total area of the island portions of the sea-island structure in the cross-sectional image of the surface portion on the base material 11 side is preferably about the same.

[0041] Also, in the adhesive film 1 for metal terminals of the present disclosure, when the thickness of the first polyolefin layer 12a is taken as 100%, in the cross-sectional image obtained within the range up to the surface portion on the metal terminal 2 side (specifically, the portion with a thickness of 30% from the surface opposite to the base material 11), even in the cross-sectional image of 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, a sea-island structure is usually observed. The ratio of the total area of the island portions of 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 about 22.0% or more, more preferably about 24.0% or more. Also, the ratio of the total area of the island portions is preferably about 32.0% or less, more preferably about 28.0% or less. The preferable range of the ratio of the total area of the island portions is 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] Also, in the adhesive film 1 for metal terminals of the present disclosure, when the thickness of the first polyolefin layer 12a is taken as 100%, in the cross-sectional image obtained within the range up to the surface portion on the base material 11 side (specifically, the portion with a thickness of 30% from the surface on the base material 11 side), even in the cross-sectional image of the first polyolefin layer 12a before heating at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, a sea-island structure is usually observed. The ratio of the total area of the island portions of the sea-island structure in the cross-sectional image of the surface portion on the base material 11 side of the first polyolefin layer 12a before heating is not particularly limited, but is preferably about 26.0% or more, more preferably about 28.0% or more. Also, the ratio of the total area of the island portions is preferably about 35.0% or less, more preferably about 32.0% or less. The preferable range of the ratio of the total area of the island portions is 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] Also, in the adhesive film 1 for metal terminals of the present disclosure, in the cross-sectional image of the surface portion on the side of the metal terminal 2 after heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the average particle diameter of the island portions of the sea-island structure is preferably about 0.3 μm or more, more preferably about 0.4 μm or more. Further, the average particle diameter of the island portions is preferably about 0.6 μm or less, more preferably about 0.5 μm or less. Also, preferable ranges of the average particle diameter of the island portions 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] Also, in the adhesive film 1 for metal terminals of the present disclosure, in the cross-sectional image of the surface portion on the side of the base material 11 after heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the average particle diameter of the island portions of the sea-island structure is preferably about 0.3 μm or more, more preferably about 0.4 μm or more. Further, the average particle diameter of the island portions is preferably about 0.6 μm or less, more preferably about 0.5 μm or less. Also, preferable ranges of the average particle diameter of the island portions 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] Also, in the adhesive film 1 for metal terminals of the present disclosure, in the cross-sectional image of the surface portion on the side of the metal terminal 2 before heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the average particle diameter of the island portions of the sea-island structure is preferably about 0.2 μm or more, more preferably about 0.3 μm or more. Further, the average particle diameter of the island portions is preferably about 0.5 μm or less, more preferably about 0.4 μm or less. Also, preferable ranges of the average particle diameter of the island portions 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 1 for metal terminals of the present disclosure, in the cross-sectional image of the surface portion on the base material 11 side before heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the average particle diameter of the island portions of the sea-island structure is preferably about 0.3 μm or more, more preferably about 0.4 μm or more. Further, the average particle diameter of the island portions is preferably about 0.6 μm or less, more preferably about 0.5 μm or less. Further, preferable ranges of the average particle diameter of the island portions 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] Note that the average particle diameter of the island portions in the cross-sectional image is a value calculated by image analysis software ImageJ.

[0048] In the adhesive film 1 for metal terminals 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 terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the particle diameter deviation σ of the island portions of the sea-island structure is preferably 0.4 or less, more preferably about 0.3 or less. Further, the particle diameter deviation σ of the island portions is, for example, 0.1 or more. Further, preferable ranges of the particle diameter deviation σ of the island portions include about 0.1 to 0.4 and about 0.1 to 0.3.

[0049] In the adhesive film 1 for metal terminals of the present disclosure, in the cross-sectional image of the surface portion on the base material 11 side after heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the particle diameter deviation σ of the island portions of the sea-island structure is preferably 0.4 or less, more preferably about 0.3 or less. Further, the particle diameter deviation σ of the island portions is, for example, 0.1 or more. Further, preferable ranges of the particle diameter deviation σ of the island portions include about 0.1 to 0.4 and about 0.1 to 0.3.

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

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

[0052] Note that the particle size deviation σ of the island portion in the cross-sectional image is a value calculated by the image analysis software ImageJ.

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

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

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

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

[0057] Note that the roundness of the island portion in the cross-sectional image is a value calculated by the image analysis software ImageJ.

[0058] The ratio of the total area of the island portions, the average particle diameter of the island portions, the particle diameter deviation σ of the island portions, and the roundness of the island portions 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 can be adjusted by the composition, skeleton, dispersibility, molecular weight, melting point, MFR of the resin constituting the first polyolefin layer, and further, conditions such as T-die, inflation, etc. in the production of the adhesive film 1 for metal terminals (for example, extrusion width from the T-die, draw ratio, draw speed, heat treatment temperature, and further, line speed, cooling rate, extrusion temperature, etc.) and the like.

[0059] As the total thickness of the adhesive film 1 for metal terminals of the present disclosure, from the viewpoint of enhancing the adhesion to the above-described metal terminal 2 while preferably suppressing a decrease in adhesion due to the electrolytic solution, for example, it is 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 still more preferably about 150 μm or more. Further, the total thickness of the adhesive film 1 for metal terminals of the present disclosure is preferably about 200 μm or less, and more preferably 180 μm or less. Preferred ranges of the total thickness of the adhesive film 1 for metal terminals 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, for example, when the adhesive film 1 for metal terminals of the present disclosure is used in a consumer power storage device, the total thickness is preferably about 60 to 100 μm, and when used in an in-vehicle power storage device, the total thickness is preferably about 100 to 200 μm.

[0060] Hereinafter, the first polyolefin layer 12a, the second polyolefin layer 12b, and the base material 11 will be described in detail.

[0061] [First Polyolefin Layer 12a and Second Polyolefin Layer 12b] As shown in FIGS. 4 and 5, the adhesive film 1 for metal terminals of the present disclosure includes a first polyolefin layer 12a on one surface side of a base material 11 and a second polyolefin layer 12b on the other surface side. The first polyolefin layer 12a is disposed on the side of the metal terminal 2. Also, the second polyolefin layer 12b is disposed on the side of the exterior material 3 for the power 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 on both sides, respectively.

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

[0063] In the adhesive film 1 for metal terminals of the present disclosure, the first polyolefin layer 12a and the second polyolefin layer 12b are layers containing a polyolefin-based resin, respectively. Examples of the polyolefin-based resin include polyolefin and acid-modified polyolefin. The first polyolefin layer 12a preferably contains an acid-modified polyolefin among polyolefin-based resins, and more preferably is a layer formed of an acid-modified polyolefin. Also, the second polyolefin layer 12b preferably contains polyolefin or acid-modified polyolefin among polyolefin-based resins, more preferably contains polyolefin, and even more preferably is a layer formed of polyolefin. Acid-modified polyolefin has a high affinity for metals. Also, polyolefin has a high affinity for heat-fusible resins such as polyolefin. Therefore, in the adhesive film 1 for metal terminals of the present disclosure, by disposing the first polyolefin layer 12a formed of an acid-modified polyolefin on the side of the metal terminal 2, more excellent adhesion can be exhibited at the interface between the adhesive film 1 for metal terminals and the metal terminal 2. Also, by disposing the second polyolefin layer 12b formed of polyolefin on the side of the heat-fusible resin layer 35 of the exterior material 3 for the power storage device, more excellent adhesion can be exhibited at the interface between the adhesive film 1 for metal terminals and the heat-fusible resin layer 35.

[0064] As a specific example of a preferred laminated structure of the adhesive film 1 for a metal terminal of the present disclosure, there are a three-layer structure in which a first polyolefin layer formed of acid-modified polypropylene / a base material formed of polypropylene / a second polyolefin layer formed of polypropylene are laminated in this order; a three-layer structure in which a first polyolefin layer formed of acid-modified polypropylene / a base material formed of polypropylene / a second polyolefin layer formed of acid-modified polypropylene are laminated in this order, and among these, a three-layer structure in which a first polyolefin layer formed of acid-modified polypropylene / a base material formed of polypropylene / a second polyolefin layer formed of 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 preferably includes a polyolefin graft-modified with an unsaturated carboxylic acid or its anhydride.

[0066] Specific examples of the polyolefin to be acid-modified include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylene such as homopolypropylene, block copolymers of polypropylene (for example, block copolymers of propylene and ethylene), random copolymers of polypropylene (for example, random copolymers of propylene and ethylene); and terpolymers of ethylene-butene-propylene. Among these polyolefins, polyethylene and polypropylene are preferably used, and polypropylene is particularly preferably used.

[0067] In addition, the polyolefin to be acid-modified may be a cyclic polyolefin. For example, a carboxylic acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin by replacing it with an α,β-unsaturated carboxylic acid or its anhydride, or by block-polymerizing or graft-polymerizing an α,β-unsaturated carboxylic acid or its anhydride to the cyclic polyolefin.

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

[0069] Examples of the carboxylic acid or its anhydride used for acid modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, itaconic anhydride, and the like. When the first polyolefin layer 12a is analyzed by infrared spectroscopy, it is preferable that a peak derived from maleic anhydride is detected. For example, when measuring maleic anhydride-modified polyolefin by infrared spectroscopy, peaks derived from maleic anhydride are detected in the vicinity of a wave number of 1760 cm -1 and in the vicinity of a wave number of 1780 cm -1 . 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 not be detected. In that case, it can be analyzed 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 alone, or may also be formed of a blend polymer in which two or more resin components are combined. Further, the first polyolefin layer 12a and the second polyolefin layer 12b may each be formed of only one layer, or may be formed of two or more layers with the same or different resin components. From the viewpoint of film-forming properties of the first polyolefin layer 12a and the second polyolefin layer 12b, it is preferable that these layers are each formed of a blend polymer in which two or more resin components are combined. When using a blend polymer, for the first polyolefin layer 12a, it is preferable to use acid-modified polypropylene as the main component (component of 50% by mass or more), and 50% by mass or less as other resin (preferably polyethylene). Also, for the second polyolefin layer 12b, it is preferable to use polypropylene as the main component (component of 50% by mass or more), and 50% by mass or less as other resin (preferably polyethylene). On the other hand, from the viewpoint of electrolyte resistance of the first polyolefin layer 12a and the second polyolefin layer 12b, the first polyolefin layer 12a preferably contains acid-modified polypropylene alone as the resin, and the second polyolefin layer 12b preferably contains polypropylene alone as the resin.

[0071] Furthermore, the first polyolefin layer 12a and the second polyolefin layer 12b may each contain a filler as required. By the first polyolefin layer 12a and the second polyolefin layer 12b containing a filler, since the filler functions as a spacer, it becomes possible to effectively suppress a short circuit between the metal terminal 2 and the barrier layer 33 of the exterior material 3 for the power storage device. Examples of the particle size of the filler include a range of about 0.1 to 35 μm, preferably about 5.0 to 30 μm, and more preferably about 10 to 25 μm. Also, examples of the content of the filler include about 5 to 30 parts by mass, more preferably about 10 to 20 parts by mass, respectively, with respect to 100 parts by mass of the resin component forming the first polyolefin layer 12a and the second polyolefin layer 12b.

[0072] As the filler, either an inorganic filler or an organic filler can be used. Examples of the inorganic filler include carbon (carbon, graphite), silica, aluminum oxide, barium titanate, iron oxide, silicon carbide, zirconium oxide, zirconium silicate, magnesium oxide, titanium oxide, calcium aluminate, calcium hydroxide, aluminum hydroxide, magnesium hydroxide, calcium carbonate, and the like. Examples of the organic filler include fluororesin, phenol resin, urea resin, epoxy resin, acrylic resin, benzoguanamine-formaldehyde condensate, melamine-formaldehyde condensate, polymethyl methacrylate cross-linked product, polyethylene cross-linked product, and the like. From the viewpoints of shape stability, rigidity, and resistance to the content, aluminum oxide, silica, fluororesin, acrylic resin, and benzoguanamine-formaldehyde condensate are preferable, and among them, spherical aluminum oxide and silica are more preferable. As a method for mixing the filler into the resin components forming the first polyolefin layer 12a and the second polyolefin layer 12b, a method of melt-blending both in advance with a Banbury mixer or the like to form a masterbatch and then setting it to a predetermined mixing ratio, a method of directly mixing with the resin components, or the like can be adopted.

[0073] In addition, the first polyolefin layer 12a and the second polyolefin layer 12b may each contain a pigment as required. As the pigment, various inorganic pigments can be used. As a specific example of the pigment, carbon (carbon, graphite) exemplified as the above filler can be preferably exemplified. Carbon (carbon, graphite) is a material generally used inside the power storage device and has no risk of elution into the electrolyte. Further, a sufficient coloring effect can be obtained at an addition amount that does not inhibit the adhesiveness with a large coloring effect, it does not melt with heat, and the apparent melt viscosity of the added resin can be increased. Furthermore, it can prevent the pressure-applied portion from becoming thin during heat adhesion (heat sealing), and can impart excellent sealing performance between the exterior material for the power storage device and the metal terminal.

[0074] When adding a pigment to the first polyolefin layer 12a and the second polyolefin layer 12b, for example, when using carbon black with a particle size of about 0.03 μm, the addition amount is about 0.05 to 0.3 parts by mass, preferably about 0.1 to 0.2 parts by mass, respectively, based on 100 parts by mass of the resin component forming the first polyolefin layer 12a and the second polyolefin layer 12b. By adding a pigment to the first polyolefin layer 12a and the second polyolefin layer 12b, the presence or absence of the adhesive film 1 for metal terminals can be made detectable by a sensor or visually inspectable. It is particularly preferable that the first polyolefin layer 12a contains 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 the second polyolefin layer 12b, but from the viewpoint of not inhibiting the heat fusion property of the adhesive film 1 for metal terminals, it is preferable to add the filler and the pigment separately to the first polyolefin layer 12a and the second polyolefin layer 12b.

[0075] The thicknesses of the first polyolefin layer 12a and the second polyolefin layer 12b are each preferably about 10 μm or more, more preferably about 15 μm or more, still more preferably about 20 μm or more, and even more preferably about 30 μm or more, from the viewpoint of enhancing the adhesion to the metal terminal 2 described above and suitably suppressing the decrease in adhesion due to the electrolytic solution. Also, for example, they are about 80 μm or less, preferably about 60 μm or less, and more preferably about 50 μm or less. Preferred ranges for the thicknesses of the first polyolefin layer 12a and the second polyolefin layer 12b are 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, for instance, when the adhesive film 1 for metal terminals of the present disclosure is used in a consumer power storage device, the thicknesses of the first polyolefin layer 12a and the second polyolefin layer 12b are each preferably about 10 to 30 μm, and when used in an in-vehicle power storage device, they are each preferably about 30 to 80 μm.

[0076] The ratio of the thickness of the base material 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, still more preferably 0.5 or more, and also preferably about 1.0 or less, more preferably about 0.8 or less, from the viewpoint of enhancing the adhesion to the metal terminal 2 described above and suitably suppressing the decrease in adhesion due to the electrolytic solution. 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] Also, taking the total thickness of the adhesive film 1 for metal terminals as 100%, the ratio of the total thickness of the first polyolefin layer 12a and the second polyolefin layer 12b is preferably about 30 to 80%, and more preferably about 50 to 70%.

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

[0079] The material for forming the base material 11 is not particularly limited. Examples of the material for forming the base material 11 include polyolefin resins, polyamide resins, polyester resins, epoxy resins, acrylic resins, fluorine resins, silicone resins, phenol resins, polyetherimide, polyimide, polycarbonate, and mixtures and copolymers thereof. Among these, polyolefin resins are particularly preferred. That is, the material for forming the base material 11 is preferably a resin containing a polyolefin backbone such as polyolefin and acid-modified polyolefin. Whether the resin constituting the base material 11 contains a polyolefin backbone can be analyzed by, for example, infrared spectroscopy, gas chromatography-mass spectrometry, etc.

[0080] As described above, the base material 11 preferably contains a polyolefin resin, preferably contains polyolefin, and more preferably is a layer formed of polyolefin. Specific examples of the polyolefin include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylene such as homopolypropylene, block copolymers of polypropylene (for example, block copolymers of propylene and ethylene), and random copolymers of polypropylene (for example, random copolymers of propylene and ethylene); and terpolymers of ethylene-butene-propylene. Among these polyolefins, polyethylene and polypropylene are preferably mentioned, and polypropylene is more preferably mentioned. Further, since it has excellent electrolytic solution resistance, the base material 11 preferably contains homopolypropylene, and it is particularly preferred that it is formed of homopolypropylene.

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

[0082] Examples of the polyester include, specifically, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, a copolymer polyester having ethylene terephthalate as a main repeating unit, a copolymer polyester having butylene terephthalate as a main repeating unit, and the like. In addition, examples of the copolymer polyester having ethylene terephthalate as a main repeating unit include, specifically, a copolymer polyester obtained by polymerizing ethylene isophthalate with ethylene terephthalate as a main repeating unit (hereinafter abbreviated following polyethylene(terephthalate / isophthalate)), polyethylene(terephthalate / isophthalate), polyethylene(terephthalate / adipate), polyethylene(terephthalate / sodium sulfoisophthalate), polyethylene(terephthalate / sodium isophthalate), polyethylene(terephthalate / phenyl-dicarboxylate), polyethylene(terephthalate / decanedicarboxylate), and the like. Further, examples of the copolymer polyester having butylene terephthalate as a main repeating unit include, specifically, a copolymer polyester obtained by polymerizing butylene isophthalate with butylene terephthalate as a main repeating unit (hereinafter abbreviated following polybutylene(terephthalate / isophthalate)), polybutylene(terephthalate / adipate), polybutylene(terephthalate / sebacate), polybutylene(terephthalate / decanedicarboxylate), polybutylene naphthalate, and the like. These polyesters may be used alone or in combination of two or more.

[0083] In addition, the base material 11 may be formed of a nonwoven fabric made of the above resin. When the base material 11 is a nonwoven fabric, it is preferably composed of the aforementioned polyolefin resin, polyamide resin, or the like.

[0084] In addition, by blending a colorant into the base material 11, the base material 11 can also be made into a layer containing the colorant. Also, a resin with low transparency can be selected to adjust the light transmittance. When the base material 11 is a film, a colored film or a film with low transparency can also be used. Further, when the base material 11 is a nonwoven fabric, a nonwoven fabric using fibers or a binder containing a colorant or a nonwoven fabric with low transparency can be used.

[0085] When the base material 11 is composed of a resin film, known adhesion-promoting means such as corona discharge treatment, ozone treatment, plasma treatment, etc. may be applied to the surface of the base material 11 as necessary.

[0086] From the viewpoint of enhancing the adhesion to the metal terminal 2 described above while preferably suppressing the decrease in adhesion due to the electrolytic solution, the thickness of the base material 11 is, for example, about 100 μm or less, preferably about 60 μm or less, more preferably about 55 μm or less. Also, the thickness of the base material 11 is preferably about 20 μm or more, more preferably about 30 μm or more, still more preferably about 40 μm or more. Preferred ranges of the thickness of the base material 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, for instance, when the adhesive film 1 for metal terminals of the present disclosure is used in a consumer storage device, the thickness of the base material 11 is preferably about 30 to 55 μm, and when used in an in-vehicle storage device, it is preferably about 40 to 100 μm, respectively.

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

[0088] Subsequently, the adhesion promoter layer 13 can be formed using known adhesion promoters such as isocyanate-based, polyethyleneimine-based, polyester-based, polyurethane-based, polybutadiene-based, etc. From the viewpoint of further improving the electrolytic solution resistance, among these, it is preferably formed by an isocyanate-based adhesion promoter. As the isocyanate-based adhesion promoter, those composed of isocyanate components selected from triisocyanate monomers and polymeric MDI are excellent in laminate strength and have little decrease in laminate strength after immersion in the electrolytic solution. In particular, it is particularly preferable to form it with an adhesion promoter composed of triphenylmethane-4,4',4"-triisocyanate which is a triisocyanate monomer or polymethylene polyphenyl polyisocyanate (NCO content is about 30%, viscosity is 200 to 700 mPa·s) which is polymeric MDI. Also, it is also preferable to form it with tris(p-isocyanatophenyl) thiophosphate which is a triisocyanate monomer or a two-component curable adhesion promoter mainly composed of a polyethyleneimine-based and using polycarbodiimide as a crosslinking agent.

[0089] The adhesion promoter layer 13 can be formed by applying and drying it by known coating methods such as the bar coating method, roll coating method, gravure coating method, etc. As the coating amount of the adhesion promoter, in the case of an adhesion promoter composed of triisocyanate, it is about 20 to 100 mg / m 2 or so, preferably about 40 to 60 mg / m 2 or so, in the case of an adhesion promoter composed of polymeric MDI, it is about 40 to 150 mg / m 2 or so, preferably about 60 to 100 mg / m 2 or so, and in the case of a two-component curable adhesion promoter mainly composed of a polyethyleneimine-based and using polycarbodiimide as a crosslinking agent, it is about 5 to 50 mg / m 2 or so, preferably about 10 to 30 mg / m 2 or so. Note that a triisocyanate monomer is a monomer having three isocyanate groups in one molecule, and polymeric MDI is a mixture of MDI and MDI oligomers polymerized from MDI and is represented by the following formula.

[0090] [Chemical formula]

[0091] The adhesive film 1 for metal terminals of the present disclosure can be manufactured, for example, by laminating a first polyolefin layer 12a and a second polyolefin layer 12b on both surfaces of a base material 11, respectively. The lamination of the base material 11 with the first polyolefin layer 12a and the second polyolefin layer 12b can be performed by a known method such as an extrusion lamination method or a thermal lamination method. Further, when laminating the base material 11 with the first and second polyolefin layers 12a and 12b via an adhesion promoter layer 13, for example, the adhesion promoter constituting the adhesion promoter layer 13 is applied and dried on the base material 11 by the above method, and the first polyolefin layer 12a and the second polyolefin layer 12b are laminated from above the adhesion promoter layer 13, respectively.

[0092] The method of interposing the adhesive film 1 for metal terminals between the metal terminal 2 and the exterior material 3 for the power storage device is not particularly limited. For example, as shown in FIGS. 1 to 3, at the portion where the metal terminal 2 is sandwiched by the exterior material 3 for the power storage device, the adhesive film 1 for metal terminals may be wound around the metal terminal 2. Further, although not shown, at the portion where the metal terminal 2 is sandwiched by the exterior material 3 for the power storage device, the adhesive film 1 for metal terminals may be 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 a power storage device. The metal terminal 2 (tab) is a conductive member electrically connected to an electrode (positive electrode or negative electrode) of a power storage device element 4 and is made of a metal material. The metal material constituting the metal terminal 2 is not particularly limited, and examples thereof include aluminum, nickel, copper, and the like. For example, the metal terminal 2 connected to the positive electrode of a lithium-ion power storage device is usually made of aluminum or the like. Also, the metal terminal 2 connected to the negative electrode of a lithium-ion power storage device is usually made of copper, nickel, or the like.

[0094] From the viewpoint of enhancing the electrolytic solution resistance, the surface of the metal terminal 2 is preferably subjected to a formation treatment. For example, when the metal terminal 2 is formed of aluminum, specific examples of the formation treatment include known methods for forming a corrosion-resistant film such as a phosphate, a chromate, a fluoride, and a triazine thiol compound. Among the methods for forming a corrosion-resistant film, a phosphating treatment using a composition composed of a phenol resin, a chromium(III) fluoride compound, and phosphoric acid is preferable.

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

[0096] [Exterior material 3 for power storage device] Examples of the exterior material 3 for the power storage device include those having a laminated structure composed of a laminate having at least a base material layer 31, a barrier layer 33, and a heat-sealable resin layer 35 in this order. Fig. 6 shows an example of the cross-sectional structure of the exterior material 3 for the power storage device, in which a base material layer 31, an adhesive layer 32 provided as necessary, a barrier layer 33, an adhesive layer 34 provided as necessary, and a heat-sealable resin layer 35 are laminated in this order. In the exterior material 3 for the power storage device, the base material layer 31 is on the outer layer side and the heat-sealable resin layer 35 is on the innermost layer. When assembling the power storage device, the power storage device element 4 is sealed by bringing the heat-sealable resin layers 35 located at the periphery of the power storage device element 4 into contact with each other and heat-sealing them. Figs. 1 to 3 illustrate the power storage device 10 when using an embossed type exterior material 3 for the power storage device formed by embossing or the like, but the exterior material 3 for the power storage device may be a non-formed pouch type. Note that there are various types of pouch types, such as three-sided seal, four-sided seal, and pillow type, and any type may be used.

[0097] The thickness of the laminate constituting the exterior material 3 for the power storage device is not particularly limited. However, regarding the upper limit, from the viewpoints of cost reduction, improvement of energy density, etc., it 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, about 120 μm or less. Regarding the lower limit, from the viewpoint of maintaining the function of the exterior material 3 for the power storage device to protect the power storage device element 4, it is preferably about 35 μm or more, about 45 μm or more, about 60 μm or more, about 80 μm or more. Regarding the preferable range, for example, about 35 to 190 μm, about 35 to 180 μm, about 35 to 160 μm, about 35 to 155 μm, about 35 to 140 μm, about 35 to 130 μm, about 35 to 120 μm, about 45 to 190 μm, about 45 to 180 μm, about 45 to 160 μm, about 45 to 155 μm, about 45 to 140 μm, about 45 to 130 μm, about 45 to 120 μm, about 60 to 190 μm, about 60 to 180 μm, about 60 to 160 μm, about 60 to 155 μm, about 60 to 140 μm, about 60 to 130 μm, about 60 to 120 μm, about 80 to 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, about 80 to 120 μm can be mentioned.

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

[0099] The material for forming the base material layer 31 is not particularly limited as long as it has insulation properties. Examples of the material for forming the base material layer 31 include polyester, polyamide, epoxy, acrylic, fluororesin, polyurethane, silicone resin, phenol, polyetherimide, polyimide, and mixtures or copolymers thereof. Polyesters such as polyethylene terephthalate and polybutylene terephthalate have excellent electrolyte resistance and the advantage that whitening and the like are less likely to occur due to the adhesion of the electrolyte, and are suitably used as the material for forming the base material layer 31. Also, polyamide films have excellent stretchability and can prevent the occurrence of whitening due to resin cracking of the base material layer 31 during molding, and are suitably used as the material for forming the base material layer 31.

[0100] The base material layer 31 may be formed of a uniaxially or biaxially stretched resin film, or may be formed of an unstretched resin film. Among them, uniaxially or biaxially stretched resin films, especially biaxially stretched resin films, are suitably used as the base material layer 31 because their heat resistance is improved by orientation crystallization.

[0101] Among these, preferred examples of the resin film for forming the base material layer 31 include nylon and polyester, and more preferably biaxially stretched nylon and biaxially stretched polyester.

[0102] In order to improve the pinhole resistance and insulation properties when the base material layer 31 is used as a package for a power storage device, it is also possible to laminate resin films of different materials. Specifically, examples include a multilayer structure in which a polyester film and a nylon film are laminated, and a multilayer structure in which biaxially stretched polyester and biaxially stretched nylon are laminated. When the base material layer 31 has a multilayer structure, the resin films may be adhered via an adhesive, or may be directly laminated without an adhesive. When adhering without an adhesive, examples of the method include methods of adhering in a heat-melt state such as coextrusion, sand lamination, and thermal lamination.

[0103] Further, the base material layer 31 may be made to have a reduced friction coefficient in order to improve its formability. When reducing the friction coefficient of the base material layer 31, the friction coefficient of its surface is not particularly limited, but for example, it may be 1.0 or less. To reduce the friction coefficient of the base material layer 31, for example, mat treatment, formation of a thin film layer of a slip agent, a combination of these, etc. can be mentioned.

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

[0105] (Adhesive layer 32) In the exterior material 3 for a power storage device, the adhesive layer 32 is a layer disposed on the base material layer 31 as necessary in order to impart adhesiveness to the base material layer 31. That is, the adhesive layer 32 is provided between the base material layer 31 and the barrier layer 33.

[0106] The adhesive layer 32 is formed of an adhesive that can adhere the base material layer 31 and the barrier layer 33. The adhesive used for forming the adhesive layer 32 may be a two-component curable adhesive or a one-component curable adhesive. Also, the adhesion mechanism of the adhesive used for forming the adhesive layer 32 is not particularly limited, and it may be any of a chemical reaction type, a solvent evaporation type, a hot melt type, a hot press type, etc.

[0107] As the resin component of the adhesive that can be used for forming the adhesive layer 32, it has excellent spreadability, durability under high humidity conditions, yellowing suppression effect, heat deterioration suppression effect during heat sealing, etc., and from the viewpoint of suppressing a decrease in the laminate strength between the base material layer 31 and the barrier layer 33 and effectively suppressing the occurrence of delamination, preferably a two-component curable polyurethane-based adhesive; a polyamide, a polyester, or a blend resin of these and a modified polyolefin can be mentioned.

[0108] Further, the adhesive layer 32 may be laminated with different adhesive components. When laminating the adhesive layer 32 with different adhesive components, from the perspective of improving the lamination strength between the base material layer 31 and the barrier layer 33, a resin with excellent adhesiveness to the base material layer 31 is selected as the adhesive component arranged on the base material layer 31 side, and an adhesive component with excellent adhesiveness to the barrier layer 33 is selected as the adhesive component arranged on the barrier layer 33 side. When the adhesive layer 32 is laminated with different adhesive components, specifically, as the adhesive component arranged on the barrier layer 33 side, preferably, acid-modified polyolefin, metal-modified polyolefin, a mixed resin of polyester and acid-modified polyolefin, a resin containing copolymerized polyester, etc. may be mentioned.

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

[0110] (Barrier layer 33) In the exterior material for a power storage device, the barrier layer 33 is a layer having a function of preventing water vapor, oxygen, light, etc. from entering the inside of the power storage device in addition to improving the strength of the exterior material for a power storage device. The barrier layer 33 is preferably a metal layer, that is, a layer formed of a metal. Specifically, examples of the metal constituting the barrier layer 33 include aluminum, stainless steel, titanium, etc., and preferably aluminum. The barrier layer 33 can be formed, for example, by a metal foil, a metal vapor deposition film, an inorganic oxide vapor deposition film, a carbon-containing inorganic oxide vapor deposition film, a film provided with these vapor deposition films, etc., and it is preferably formed by a metal foil, and more preferably formed by an aluminum foil. From the perspective of preventing wrinkles and pinholes from occurring in the barrier layer 33 during the manufacture of the exterior material for a power storage device, the barrier layer is more preferably formed by 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] Regarding the thickness of the barrier layer 33, from the viewpoint of thinning the exterior material for the power storage device and making it difficult for pinholes to occur during molding, it is preferably about 10 to 200 μm, more preferably about 20 to 100 μm.

[0112] Further, the barrier layer 33 is preferably subjected to a chemical conversion treatment on at least one surface, preferably both surfaces, for the purpose of stabilizing adhesion, preventing dissolution and corrosion, etc. Here, the chemical conversion treatment refers to a treatment for forming a corrosion-resistant film on the surface of the barrier layer.

[0113] (Adhesive layer 34) In the exterior material 3 for the power storage device, the adhesive layer 34 is a layer provided between the barrier layer 33 and the heat-sealable resin layer 35 as needed in order to firmly adhere the heat-sealable resin layer 35.

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

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

[0116] (Heat-sealable resin layer 35) In the exterior material 3 for the power storage device, the heat-sealable resin layer 35 corresponds to the innermost layer and is a layer in which the heat-sealable resin layers are heat-sealed to seal the power storage device element during the assembly of the power storage device.

[0117] The resin component used for the heat-sealable resin layer 35 is not particularly limited as long as it can be heat-sealed, and examples thereof include polyolefin and cyclic polyolefin.

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

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

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

[0121] The heat-sealable resin layer 35 may be formed of a single resin component alone, or may be formed of a blend polymer combining two or more resin components. Further, the heat-sealable resin layer 35 may be formed of only one layer, but may also be formed of two or more layers of the same or different resin components. It is particularly preferable that the resins of the second polyolefin layer 12b and the heat-sealable resin layer 35 are the same, as the adhesion between these layers is improved.

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

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

[0124] Specifically, a power storage device element 4 including at least a positive electrode, a negative electrode, and an electrolyte is covered with an exterior material 3 for a power storage device with the metal terminals 2 connected to the positive electrode and the negative electrode protruding outside, and the adhesive film 1 for a metal terminal of the present disclosure is interposed between the metal terminal 2 and the heat-sealable resin layer 35. The peripheral edge of the power storage device element 4 is covered so that a flange portion of the exterior material for a power storage device (a region where the heat-sealable resin layers 35 contact each other, and the peripheral edge portion 3a of the exterior material for a power storage device) can be formed, and the heat-sealable resin layers 35 of the flange portion are heat-sealed and sealed, thereby providing a power storage device 10 using the exterior material 3 for a power storage device. When the power storage device element 4 is accommodated using the exterior material 3 for a power storage device, the heat-sealable resin layer 35 of the exterior material 3 for a power storage device is used so as to be on the inner side (the surface in contact with the power storage device element 4).

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

Examples

[0126] Examples and comparative examples are shown below to explain the present disclosure in detail. However, the present disclosure is not limited to the examples.

[0127] <Manufacture of Adhesive Film for Metal Terminals> Example 1 As the polyolefin for forming the first polyolefin layer, maleic anhydride-modified polypropylene (PPa) was used. As the polyolefin for forming the second polyolefin layer, polypropylene (PP) was used. As the base material, an unstretched polypropylene film (CPP, homopolypropylene, thickness 50 μm) was prepared. On one side of the base material (CPP), maleic anhydride-modified polypropylene (PPa) was extruded with a T-die extruder to form a first polyolefin layer (thickness 50 μm). On the other side of the base material (CPP), polypropylene (PP) was extruded with a T-die extruder to form a second polyolefin layer (thickness 50 μm). An adhesive film for metal terminals in which the first polyolefin layer (50 μm, PPa layer) / base material (50 μm, CPP layer) / second polyolefin layer (50 μm, PP layer) were laminated in order was obtained.

[0128] Comparative Example 1 As the polyolefin for forming the first polyolefin layer, maleic anhydride-modified polypropylene (PPa) was used. As the polyolefin for forming the second polyolefin layer, polypropylene (PP) was used. As the substrate, a polypropylene film (PP, thickness 30 μm) colored black with carbon black was prepared. Maleic anhydride-modified polypropylene (PPa) was extruded onto one side of the substrate (PP) using a T-die extruder to form the first polypropylene layer (thickness 50 μm). Polypropylene (PP) was extruded onto the other side of the substrate (PP) using a T-die extruder to form the second polypropylene layer (thickness 50 μm), and an adhesive film for metal terminals with the first polyolefin layer (50 μm, PPa layer) / substrate (30 μm, PP layer) / second polyolefin layer (20 μm, PP layer) laminated in sequence was obtained.

[0129] Comparative Example 2 As the polyolefin for forming the first polyolefin layer, maleic anhydride-modified polypropylene (PPa) was used. As the polyolefin for forming the second polyolefin layer, maleic anhydride-modified polypropylene (PPa) was used. As the substrate, polypropylene (PP) was prepared. Using the resin of each layer, multilayer air-cooled inflation molding was performed, and an adhesive film for metal terminals with the first polyolefin layer (25 μm, PPa layer) / substrate (50 μm, PP layer) / second polyolefin layer (25 μm, PPa layer) laminated in sequence was obtained.

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

[0131] <Observation of the island part in the sea-island structure> An adhesive film for metal terminals was embedded in a thermosetting epoxy resin and cured. Using a commercially available rotary microtome (UC6 manufactured by LEICA) and a diamond knife, a cross-section in the target direction (a cross-section parallel to the TD and in the thickness direction) was prepared. At that time, cryomicrotomy using liquid nitrogen was performed at -70 °C to prepare the cross-section. The embedded resin was stained with ruthenium tetroxide overnight. When stained, the polypropylene swells, so the swollen part was trimmed with a microtome and cut forward by 100 nm to 300 nm at a time in the MD direction. When a total of about 1 μm to 2 μm was cut, the exposed cross-section was observed as follows. For the stained cross-section, an image (magnification: 10,000 times) was acquired by observing with a field emission scanning electron microscope (S-4800 TYPE1 manufactured by Hitachi High-Technologies Corporation, measurement conditions: 3 kV 20 mA High WD6 mm detector (Upper)). The cross-section image is within the range from the surface portion on the metal terminal side of the first polyolefin layer (within the range from the surface on the side opposite to the substrate surface to the portion with a thickness of 30% when the thickness of the first polyolefin layer is 100%. Refer to Figure 4.) and the surface portion on the substrate side of the first polyolefin layer (within the range from the substrate surface to the portion with a thickness of 30% when the thickness of the first polyolefin layer is 100%). Next, using image processing software (image analysis software WinROOF (Ver7.4) manufactured by Mitani Corporation) that can binarize the image, for the said image, the island part and the sea part of the sea-island structure were binarized, and the number of island parts, the ratio of the total area of the island parts (total area of the island parts / area of the measurement range of the image), the average particle diameter of the island parts, the particle diameter deviation σ of the island parts, and the roundness of the island parts were obtained respectively. The results are shown in Tables 1 and 2. Table 1 is the measurement results for the sample after heating the adhesive film for metal terminals for 12 seconds using a hot plate heated to 190 °C in the same manner as <Measurement of the adhesion strength between the adhesive film for metal terminals and the metal terminal> described later, and Table 2 is the measurement results for the sample without performing the said heating.

[0132] The binarized cross-sectional images in Example 1 and Comparative Examples 1 and 2 are shown in FIGS. 8 to 13, respectively. FIG. 8 shows the surface portion on the metal terminal side of the first polyolefin layer in Example 1, FIG. 9 shows the surface portion on the base material side of the first polyolefin layer in Example 1, FIG. 10 shows the surface portion on the metal terminal side of the first polyolefin layer in Comparative Example 1, FIG. 11 shows the surface portion on the base material side of the first polyolefin layer in Comparative Example 1, FIG. 12 shows the surface portion on the metal terminal side of the first polyolefin layer in Comparative Example 2, and FIG. 13 shows the surface portion on the base material side of the first polyolefin layer in the Comparative Example. Further, in each of FIGS. 8 to 13, the left image is before heating the adhesive film for metal terminals at a temperature of 190° C. and a surface pressure of 0.016 MPa for 12 seconds, and the right image is after heating the adhesive film for metal terminals 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 the measurement of the adhesion strength described later). In this measurement, since the island portion was stained more than the sea portion, the island portion was observed to be brighter than the sea portion. [Image Processing Conditions] The image processing was performed using the image analysis software ImageJ. Specifically, the SEM image was acquired as a digital file of a grayscale image (JPEG), and the processing was performed according to the following binarization processing procedure and parameters. Pixels with a tone (bright) above the threshold were set to 1, and pixels with a tone (dark) below the threshold were set to 0 and output, and each was defined as an island portion and a sea portion. [Binarization Processing] 1. Spike noise removal (Despeckle) 2. Removal of the contour of the island portion (Remove Outliers radius = 4 threshold = 1 which = Bright) 3. Removal of the contour of the sea portion (Remove Outliers radius = 4 threshold = 1 which = Dark) 4. Spike noise removal (Despeckle) 5. Gaussian blur in the X-axis (short side of the sample) direction (threshold = 3 pixels) 6. Contrast enhancement (saturated = 0.2) 7. Removal of Island Outliers (Remove Outliers radius=4 threshold=1 which=Bright) 8. Removal of Sea Outliers (Remove Outliers radius=4 threshold=1 which=Dark) 9. Otsu Binarization

[0133] The average particle size of the above-mentioned island part is a value calculated from the maximum Feret diameter of the island part in the binarized image by the image analysis software ImageJ. Also, the particle size deviation σ of the above-mentioned island part is a value calculated by the standard deviation of the above average particle size. Further, the circularity of the above-mentioned island part is a value calculated by the difference in the radii of two concentric circles when the island part in the binarized image is sandwiched between two concentric geometric circles and the distance between the concentric circles is minimized by the image analysis software ImageJ.

[0134] <Measurement of Adhesion Strength between Adhesive Film for Metal Terminals and Metal Terminals> As the metal terminal, aluminum (JIS H4160:1994 A8079H-O) with a length of 50 mm, a width of 22.5 mm, and a thickness of 0.2 mm was prepared. Also, each adhesive film for the metal terminal obtained in the examples and comparative examples was cut into a length of 45 mm and a width of 15 mm. Next, the adhesive film for the metal terminal was placed on the metal terminal to obtain a laminate of the metal terminal / adhesive film. At this time, the longitudinal and transverse directions of the metal terminal were made to coincide with the length and width directions of the adhesive film for the metal terminal, respectively, and they were laminated so that the centers of the metal terminal and the adhesive film for the metal terminal coincided. Also, the first polyolefin layer of the adhesive film for the metal terminal was disposed on the metal terminal side. Next, a tetrafluoroethylene-ethylene copolymer film (ETFE film, thickness 100 μm) was placed on the adhesive film for the metal terminal of the laminate (covering the surface of the adhesive film for the metal terminal with the ETFE film), and it was placed on a hot plate heated to 190°C (with the metal terminal on the hot plate side), and a 500 g weight with a sponge was placed on it (the surface pressure was 0.016 MPa), and it was left standing for 12 seconds to thermally fuse the adhesive film to the metal terminal. The laminate after thermal fusion was naturally cooled to 25°C. Next, in an environment of 25°C, the adhesive film for the metal terminal was peeled from the metal terminal using a tensilon universal material testing machine (RTG-1210 manufactured by A&D Company). The maximum strength at the time of peeling was defined as the adhesion strength (N / 15 mm) to the metal terminal. The peeling speed was 50 mm / min, the peeling angle was 180°, the distance between chucks was 30 mm, and the average value of three measurements was taken. The results are shown in Table 1. The treatment of leaving it standing for 12 seconds in a heating and pressurizing environment at a temperature of 190°C and a surface pressure of 0.016 MPa is a treatment assuming the heat and pressure applied in the above-mentioned preliminary adhesion step and main adhesion step.

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

[0136]

Table 1

[0137]

Table 2

[0138] The adhesive film for metal terminals of Example 1 is the cross-sectional image of the surface portion on the metal terminal side of the first polyolefin layer. In the cross-sectional image after heating the adhesive film for metal terminals at a temperature of 190°C and a surface pressure of 0.016 MPa for 12 seconds, the ratio of the total area of the island portions of the sea-island structure is set to 25.0 to 35.0%. The adhesive film for metal terminals of Example 1 is excellent in the adhesion of the adhesive film to the metal terminal by heat sealing. Furthermore, even when the electrolytic solution adheres to the adhesive film adhered to the metal terminal by heat sealing, the decrease in adhesion to the metal terminal is preferably suppressed.

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

Explanation of Signs

[0140] 1 Adhesive film for metal terminals 2 Metal terminals 3 Exterior material for power storage device 3a Peripheral portion of the exterior material for power storage device 4 Power storage device element 10 Power storage device 11 Base material 12a First polyolefin layer 12b Second polyolefin layer 13 Adhesion promoter layer 31 Base material layer 32 Adhesive layer 33 Barrier layer 34 Adhesion layer 35 Heat-sealable resin layer

Claims

1. An adhesive film for a metal terminal interposed between a metal terminal electrically connected to an electrode of a power storage device element and an exterior material for a power storage device that seals the power storage device element, wherein the adhesive film for a metal terminal is composed of a laminate including a first polyolefin layer disposed on the metal terminal side, a base material, and a second polyolefin layer disposed on the exterior material side for the power storage device, in this order, a sea-island structure is observed in a cross-sectional image obtained using a field emission scanning electron microscope for a cross-section in a direction parallel to TD and in the thickness direction of the first polyolefin layer, the cross-sectional image is a cross-sectional image obtained within a range from the surface on the side opposite to the surface on the base material side to a portion having a thickness of 30% when the thickness of the first polyolefin layer is taken as 100%, in the cross-sectional image when the adhesive film for a metal terminal is allowed to stand for 12 seconds in a heat and pressure environment of a temperature of 190 ° C and a surface pressure of 0.016 MPa and further allowed to stand for 1 hour in an environment of a temperature of 25 ° C, 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, an adhesive film for a metal terminal, wherein in the cross-sectional image, the particle size deviation of the island portions is 0.3 or less.

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

3. The adhesive film for a metal terminal according to claim 1 or 2, wherein in the cross-sectional image, the roundness of the island portions is 0.75 or more.

4. The adhesive film for a metal terminal 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 a metal terminal according to any one of claims 1 to 4, wherein the thickness of the base material is 60 μm or less.

6. The adhesive film for a metal terminal 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 a metal terminal according to any one of claims 1 to 6, wherein the thickness of the adhesive film for a 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 a metal terminal according to any one of claims 1 to 8, wherein the base material contains a polyolefin skeleton.

10. The base material is the adhesive film for metal terminals according to any one of claims 1 to 9, including homopolypropylene (however, excluding those in which the ratio of the total area of the island portions of the sea-island structure is 28.0% or more and 35.0% or less).

11. When the thickness of the first polyolefin layer is taken as 100%, it is the cross-sectional image obtained within the range up to the portion having a thickness of 30% from the surface opposite to the surface on the base material side in the cross-sectional image obtained by using a field emission scanning electron microscope for the cross-section in the direction parallel to TD and in the thickness direction of the first polyolefin layer. In the cross-sectional image when the adhesive film for metal terminals is allowed to stand still for 12 seconds in a heating and pressurizing environment at a temperature of 190 ° C and a surface pressure of 0.016 MPa, and further allowed to stand still 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 island portions of the sea-island structure is 28.0% or more and 35.0% or less.

12. A method for manufacturing an adhesive film for metal terminals, which is interposed between a metal terminal electrically connected to an electrode of a power storage device element and an exterior material for a power storage device that seals the power storage device element, The adhesive film for metal terminals is composed of a laminate including a first polyolefin layer disposed on the metal terminal side, a base material, and a second polyolefin layer disposed on the exterior material side for the power storage device, in this order. The method includes a step of obtaining a laminate including the first polyolefin layer, the base material, and the second polyolefin layer in this order. A sea-island structure is observed in the cross-sectional image obtained by using a field emission scanning electron microscope for the cross-section in the direction parallel to TD and in the thickness direction of the first polyolefin layer. The cross-sectional image is a cross-sectional image obtained within the range up to the portion having a thickness of 30% from the surface opposite to the surface on the base material side when the thickness of the first polyolefin layer is taken as 100%. In the cross-sectional image when the adhesive film for metal terminals is allowed to stand still for 12 seconds in a heating and pressurizing environment at a temperature of 190 ° C and a surface pressure of 0.016 MPa, and further allowed to stand still for 1 hour in an environment at a temperature of 25 ° C, 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. In the cross-sectional image, the particle size deviation of the island portions is 0.3 or less. A method for manufacturing an adhesive film for metal terminals.

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

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

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

Images