JP2024030096A - Film for sealing tab lead - Google Patents

Abstract

To provide a film for sealing a tab lead for bonding a sheath material to a tab lead which is excellent in electrolyte resistance in high temperature environment and has high rigidity.SOLUTION: A film for sealing a tab lead is composed of at least three layers in which a tab lead adhesive layer, an intermediate layer and a sheath material adhesive layer are stacked in this order. A content ratio of a propylene single polymer is 50-100 mass% with respect to 100 mass% of the intermediate layer, and a content ratio of a propylene-based resin selected from the group consisting of a copolymer of propylene and ethylene or α-olefin having 4 or more carbon atoms and acid-modified polypropylene is 0-50 mass%. The tab lead adhesive layer is acid-modified polypropylene, and the sheath material adhesive layer is the propylene-based resin. Here, a melting point measured according to JIS K 7121 of the acid-modified polypropylene is 140-150°C, and an MFR measured at 230°C and a load of 2.16 kg according to JIS K 7210-1 is 5.0-15 g/10 min.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a tab lead sealing film that adheres an exterior material and a tab lead in a battery packaged with an exterior material.

A tab lead is a lead wire for extracting electricity from inside a cell used in, for example, a lithium ion battery, a lithium ion capacitor, or the like. In recent years, laminated lithium ion batteries and capacitors are required to have larger battery capacities and outputs for electric vehicles, hybrid vehicles, and the like. In such laminated batteries and capacitors, in order to ensure sealing properties, electrolyte resistance, insulation properties, etc. around the tab lead, it is possible to use a tab lead sealing film that adheres the exterior material and the tab lead. Are known.

Patent Document 1 discloses an adhesive film for sealing the metal terminal portion of a lithium battery, and the film is a single-layer or multilayer polyolefin film in which the layer in contact with the metal terminal is an acid-modified polyolefin layer; It has been shown that at least one layer of the polyolefin film is of a filler-containing construction. Patent Document 2 discloses an adhesive sheet for sealing the metal terminal portion of a flat electrochemical cell, and the sheet covers both sides of an insulating particle dispersed layer made of an acid-modified polyolefin resin in which insulating particles are dispersed. , it is shown that the structure is coated with an acid-modified polyolefin resin. By using the film of Patent Document 1 and the sheet of Patent Document 2, it is possible to prevent a short circuit between the barrier layer made of metal foil such as aluminum of the package and the metal terminal, and to seal the package in a stable state. It has also been shown to have excellent properties.

Further, Patent Document 3 discloses a terminal adhesive tape that is made of a resin composition in which a propylene-based thermoplastic elastomer is blended with a propylene-based resin and has a crosslinked structure, and has a crosslinked structure that has a short circuit prevention effect. It has been shown to be constructed using active energy rays.

Japanese Patent Application Publication No. 2005-174825 JP2009-87628A Japanese Patent Application Publication No. 2014-63679

With the increase in battery capacity and output of lithium-ion batteries and capacitors, tab lead shapes are becoming thicker and wider, and in order to deal with the heat generated by this, a highly heat-resistant tab lead sealing film is required. ing. In addition, in order to fix such a thick and wide tab lead to the exterior material in a stable state while maintaining sealing performance, the tab lead sealing film is required to have not only flexibility but also rigidity. That is, the tab lead sealing film is required to have electrolyte resistance and high rigidity in a high temperature environment in addition to the conventional sealing properties around the tab lead, electrolyte resistance, insulation properties, etc. Although the adhesive films and the like of Patent Documents 1 to 3 have the effect of preventing short circuits with metal terminals, the electrolyte resistance and rigidity of the films in high-temperature environments were insufficient.

An object of the present invention is to provide a tab lead sealing film for bonding an exterior material and a tab lead, which has excellent electrolyte resistance in a high temperature environment and high rigidity.

As a result of intensive study on the layer structure of the tab lead sealing film, the present inventors have developed a laminated film consisting of at least three layers, in which the tab lead adhesive layer, the intermediate layer, and the exterior material adhesive layer are laminated in this order. We have discovered that by using an intermediate layer as the main component and constructing each adhesive layer from a specific resin, it is possible to create a film that has excellent electrolyte resistance in high-temperature environments and high rigidity.

The present invention relates to the following [1] to [7].
[1] A tab lead sealing film for bonding the exterior packaging material and a tab lead in a battery packaged with an exterior material, the tab lead sealing film comprising a tab lead adhesive layer, an intermediate layer, and an exterior material adhesive layer in this order. A laminated film consisting of at least three layers,
The content of the propylene homopolymer is 50 to 100% by mass with respect to 100% by mass of the intermediate layer, and is selected from the group consisting of a copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms, and acid-modified polypropylene. The content of the propylene resin is 0 to 50% by mass; the tab lead adhesive layer is acid-modified polypropylene; the exterior material adhesive layer is the propylene resin;
Here, according to JIS K 7121, the acid-modified polypropylene has a melting point of 140°C to 150°C, measured at a temperature increase rate of 10°C/min in a nitrogen stream, and 230°C according to JIS K 7210-1. A tab lead sealing film having an MFR of 5.0 to 15 g/10 minutes, measured at ℃ and 2.16 kg load.
[2] The tab lead sealing film according to [1], wherein the propylene resin constituting the intermediate layer is a block copolymer of propylene and ethylene.
[3] According to JIS K 7121 of propylene homopolymer, the melting point measured in a nitrogen stream at a heating rate of 10 °C/min is 160 °C to 165 °C, and according to JIS K 7210-1, the melting point is 230 °C The tab lead sealing film according to [1] or [2], which has an MFR of 2.0 to 9.5 g/10 minutes as measured at °C and a load of 2.16 kg.
[4] The tab lead seal according to any one of [1] to [3], wherein the propylene resin constituting the exterior material adhesive layer is a random copolymer of propylene and ethylene or the acid-modified polypropylene. Stop film.
[5] The tab lead sealing film according to any one of [1] to [4], wherein the acid-modified polypropylene is maleic anhydride-modified polypropylene.
[6] The tab lead sealing film has a total thickness of 100 to 500 μm, and the intermediate layer has a thickness of 40% to 70% of the total thickness, according to any one of [1] to [5]. Tab lead sealing film.
[7] 10% elongation measured at a tensile rate of 200 mm/min at 23°C, 50% RH, in accordance with JIS K 6251-1, for a tab lead sealing film formed to a thickness of 100 μm using the T-die extrusion method. The tab lead sealing film according to any one of [1] to [6], which has a load of 23 to 31 N/10 mm.

According to the present invention, it is possible to provide a tab lead sealing film that has excellent electrolyte resistance in a high-temperature environment and has high rigidity.

FIG. 1 is a diagram showing an example of a laminate type battery or capacitor according to the present invention. FIG. 2 is a cross-sectional view (A side half) taken along the line A-A' in FIG. FIG. 3 is a diagram showing the layer structure of the tab lead sealing film of the present invention.

The tab lead sealing film of the present invention is a laminated film consisting of at least three layers, in which the tab lead adhesive layer, the intermediate layer, and the exterior material adhesive layer are laminated in this order; the content of propylene homopolymer is based on 100% by mass of the intermediate layer. The proportion is 50 to 100% by mass, and the content of a propylene resin selected from the group consisting of a copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms and acid-modified polypropylene is 0 to 50% by mass. The tab lead adhesive layer is acid-modified polypropylene; The exterior material adhesive layer is the propylene-based resin; Here, in accordance with JIS K 7121 for the acid-modified polypropylene, the heating rate is 10 in a nitrogen stream. The melting point measured in °C/min is 140°C to 150°C, and the MFR measured at 230°C and 2.16 kg load is 5.0 to 15 g/10 min in accordance with JIS K 7210-1. By setting the content of propylene homopolymer in the intermediate layer to 50 to 100% by mass, and each adhesive layer being composed of the above-mentioned resin, a film for tab lead sealing has excellent electrolyte resistance in high-temperature environments and high rigidity. It can be done.

FIG. 1 is a diagram showing an example of a laminate type battery or capacitor according to the present invention. A laminate type battery or capacitor is a multilayer film in which at least a metal foil layer and a heat seal layer are laminated, and a laminated electrode group in which a positive electrode plate and a negative electrode plate are laminated with a separator interposed therebetween, and an electrolyte (none of which are shown). The tab lead 9 connected to the positive electrode plate and the tab lead 10 connected to the negative electrode plate are taken out while being hermetically sealed with the heat seal layer of the outer packaging material 3 via the tab lead sealing film 2. It consists of One end of the lead conductor 1 in the vertical direction is exposed to the outside from the sheathing material 3 and serves as a connection terminal to an external device, etc., and the other end is connected to the electrode plate lead of the battery within the sheathing material 3. It is considered as a department. Note that the vertical direction of the lead conductor means the direction of the lead conductor exposed to the outside from the exterior material to serve as a connection terminal to an external device or the like. The thickness direction of a lead conductor is perpendicular to the longitudinal direction of the lead conductor and means the direction in which the thickness is smallest, and the width direction of the lead conductor is perpendicular to the longitudinal direction of the lead conductor and means the direction in which the thickness It means direction, not direction.

The exterior material 3 serves as an exterior case for a laminated battery or capacitor. The multilayer film used for the exterior material 3 is a film in which at least a metal foil layer and a heat seal layer are laminated. The multilayer film may have a protective layer on the side of the metal foil layer opposite to the heat seal layer. The exterior material 3 is sealed in a bag shape by, for example, bonding the peripheral heat-seal layers of two rectangular multilayer films together by thermal fusion. The tab leads 9 and 10 are thermally fused to the heat seal layer of the multilayer film through the tab lead sealing film 2, thereby sealing the tab leads 9 and 10 and the multilayer film.

FIG. 2 is a cross-sectional view taken along the line A-A' in FIG. 1 (A-side half). The tab lead sealing film 2 is heat-sealed so as to cover the outer periphery of a part of the longitudinal region of the strip-shaped lead conductor 1, excluding the region including both longitudinal ends. The tab lead sealing film 2 also has the function of insulating the lead conductor 1 and the metal foil layer in the multilayer film constituting the exterior material 3.

FIG. 3 is a diagram showing the layer structure of the tab lead sealing film of the present invention. The intermediate layer 11 is a layer that mainly functions to improve the rigidity and electrolyte resistance of the film. A tab lead adhesive layer 12 is laminated on one surface of the intermediate layer 11, and an exterior material adhesive layer 13 is laminated on the other surface of the intermediate layer 11. The tab lead adhesive layer 12 is thermally bonded to the tab leads 9 and 10, and the exterior material adhesive layer 13 is thermally bonded to the heat seal layer of the multilayer film 1.

The intermediate layer 11, the tab lead adhesive layer 12, and the exterior material adhesive layer 13 may contain a filler such as silica or aluminum oxide, but from the viewpoint of film formability of each layer, uniform dispersibility of the filler, and cost, it is preferable not to use the filler. Preferably, it does not substantially contain it. In the present invention, "substantially free" means that the content of filler in 100% by mass of each layer is less than 1.0% by mass, preferably less than 0.5% by mass, more preferably less than 0.5% by mass. is less than 0.1% by mass.

[Middle layer]
In the present invention, the content of the propylene homopolymer is 50 to 100% by mass with respect to 100% by mass of the intermediate layer, and is made from a copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms and acid-modified polypropylene. The content of the propylene resin selected from the group consisting of (hereinafter also simply referred to as "propylene resin") is 0 to 50% by mass. By using such a middle tube layer, it is possible to obtain a tab lead sealing film that has excellent rigidity and electrolyte resistance in a high-temperature environment.
The intermediate layer is the main layer that provides electrolyte resistance in high temperature environments to the tab lead sealing film. Properties required to ensure electrolyte resistance in high-temperature environments include low swelling in electrolytes and rigidity at high temperatures. Propylene resins with higher crystallinity tend to have lower swelling properties with respect to electrolyte solutions. In addition, the deflection temperature under load of the resin (JIS K 6921-2) is cited as an index of rigidity at high temperatures. For example, assuming an environment where the temperature of the electrolyte is 85°C, the deflection temperature under load of the resin is 85°C. The temperature is preferably at least 100°C, more preferably at least 100°C. Propylene homopolymer has higher crystallinity than other propylene-based resins, and it is easy to set the deflection temperature under load to 85°C or higher. By setting the content to 50 to 100% by mass, electrolyte resistance in high-temperature environments can be achieved.
If the content of the propylene homopolymer is less than 50% by mass, the electrolyte resistance of the tab lead sealing film in a high-temperature environment will deteriorate. The content of the propylene homopolymer relative to 100% by mass of the intermediate layer is preferably 50 to 100% by mass, more preferably 70 to 100% by mass. Further, the content ratio of the propylene resin to 100% by mass of the intermediate layer is preferably 0 to 50% by mass, more preferably 0 to 30% by mass.

<Propylene homopolymer>
The propylene homopolymer can be obtained, for example, by a method of homopolymerizing propylene using a Ziegler-Natta catalyst, a metallocene catalyst, or the like. From the viewpoint of electrolyte resistance in high-temperature environments, the melting point of propylene homopolymer measured at a heating rate of 10°C/min in a nitrogen stream according to JIS K 7121 is 160 to 165°C. preferable. In the present invention, the melting point is the melting peak temperature in a differential scanning calorimeter (DSC) curve when a sample is heated from -50°C to 200°C at a rate of 10°C/min in a nitrogen stream. .

From the viewpoint of extrusion processability of the film, the melt flow rate (MFR) of propylene homopolymer measured at 230°C and 2.16 kg load according to JIS K 7210-1 is 2.0 to 9.5 g/ It is preferably 10 minutes, and more preferably 3.0 to 7.5 g/10 minutes.

Propylene homopolymers are commercially available, and examples include Sunallomer (registered trademark) PC600A and Sunallomer PL500A (both manufactured by Sunallomer Co., Ltd.).

<Propylene resin>
The propylene resin is selected from the group consisting of a copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms, and acid-modified polypropylene. A propylene resin is a polymer in which the proportion of propylene monomers in 100 mol% of all monomers constituting the copolymer is 50 mol% or more.

(Copolymer of propylene and ethylene or α-olefin having 4 or more carbon atoms)
A copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms can be produced using, for example, a Ziegler-Natta catalyst, a metallocene catalyst, or the like. Examples of the copolymer include propylene-ethylene copolymer, propylene-butene copolymer, propylene-ethylene-butene terpolymer, and the like. The copolymer may be a block copolymer or a random copolymer.

(Acid-modified polypropylene)
Examples of acid-modified polypropylene include polypropylene resins graft-modified with unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, etc.; copolymers of propylene with acrylic acid, methacrylic acid, etc.; metal-crosslinked polypropylene resins, and the like. The acid-modified polypropylene may be one copolymerized with ethylene or an α-olefin having 4 or more carbon atoms.

From the viewpoint of thermal adhesion, electrolyte resistance in high-temperature environments, and extrusion processability, the melting point of acid-modified polypropylene measured in accordance with JIS K 7121 at a temperature increase rate of 10°C/min in a nitrogen stream is 140. °C to 150 °C, and the MFR measured at 230 °C and a load of 2.16 kg according to JIS K 7210-1 is 5.0 to 15 g/10 minutes.

Among these, from the viewpoint of electrolyte resistance in a high-temperature environment, the propylene resin constituting the intermediate layer is preferably a block copolymer of propylene and ethylene. Block copolymers of propylene and ethylene are commercially available, such as Sunallomer (registered trademark) PC480A (manufactured by Sunallomer Co., Ltd.).

[Tab lead adhesive layer]
The tab lead adhesive layer is an acid-modified polypropylene resin. By using acid-modified polypropylene resin in the tab lead adhesive layer, it is possible to obtain a tab lead sealing film that has excellent adhesion to the tab lead and electrolyte resistance. The tab lead adhesive layer may contain resins other than acid-modified polypropylene resin as long as the object of the present invention is not hindered. The content of the acid-modified polypropylene resin in 100% by mass of the tab lead adhesive layer is 90 to 100% by mass, preferably 95 to 100% by mass.

According to JIS K 7121, the melting point of acid-modified polypropylene measured at a heating rate of 10°C/min in a nitrogen stream is 140°C to 150°C, and according to JIS K 7210-1, the melting point is 140°C to 150°C. MFR measured at .16 kg load is 5.0-15 g/10 min. By setting the melting point and MFR of the acid-modified polypropylene within the above ranges, it is possible to obtain a tab lead sealing film that has excellent adhesiveness to the tab lead and electrolyte resistance in a high temperature environment. The acid-modified polypropylene preferably has a melting point of 140 to 148°C. The MFR of the acid-modified polypropylene is preferably 5.7 to 15 g/10 minutes.

As the acid-modified polypropylene, those exemplified for the intermediate layer can be used. Among these, maleic anhydride-modified polypropylene is preferred from the viewpoint of adhesion to tab lead and electrolyte resistance.

Acid-modified polypropylene is commercially available, such as Admer (registered trademark) QF551 (manufactured by Mitsui Chemicals, Inc., melting point: 145°C, MFR: 5.7 g/10 minutes), Admer (registered trademark) QE840 (Mitsui Chemicals, Inc.) Examples include Modic (registered trademark) P587 (manufactured by Mitsubishi Chemical Corporation, melting point: 148°C, MFR: 15g/10 minutes).

[Exterior material adhesive layer]
The exterior material adhesive layer is the propylene resin described above. By using the propylene-based resin in the exterior material adhesive layer, it is possible to obtain a tab lead sealing film with excellent adhesiveness to the exterior material. The exterior material adhesive layer may contain a resin other than the propylene-based resin as long as it does not impede the object of the present invention. The content of the propylene resin in 100% by mass of the exterior material adhesive layer is 90 to 100% by mass, preferably 95 to 100% by mass.

From the viewpoint of adhesion to the exterior material, the propylene resin constituting the exterior material adhesive layer is preferably a random copolymer of propylene and ethylene or the acid-modified polypropylene. In addition, in order to prevent poor adhesion to the tab lead due to mixing up the front and back sides of the tab lead sealing film, the exterior material adhesive layer is preferably made of the acid-modified polypropylene described above so as to be the same layer as the tab lead adhesive layer. More preferred. As the acid-modified polypropylene, those exemplified for the intermediate layer can be used. Among these, maleic anhydride-modified polypropylene is particularly preferred from the viewpoint of adhesion to exterior materials.

According to JIS K 7121, the melting point of acid-modified polypropylene measured at a heating rate of 10°C/min in a nitrogen stream is 140°C to 150°C, and according to JIS K 7210-1, the melting point is 230°C and 2°C. MFR measured at .16 kg load is 5.0-15 g/10 min. By setting the melting point and MFR of the acid-modified polypropylene within the above ranges, it is possible to obtain a tab lead sealing film with excellent adhesiveness to the exterior material. The acid-modified polypropylene preferably has a melting point of 140 to 148°C. The MFR of the acid-modified polypropylene is preferably 5.7 to 15 g/10 minutes.

Random copolymers of propylene and ethylene are commercially available, such as Sunallomer (registered trademark) PC540R (manufactured by Sunallomer Co., Ltd.).

[Other ingredients]
The intermediate layer, the tab lead adhesive layer, and the exterior material adhesive layer each contain additives such as heat stabilizers, antioxidants, ultraviolet absorbers, lubricants, and colorants such as pigments to the extent that they do not impede the purpose of the present invention. It's okay to stay.

[Layer structure]
The tab lead sealing film is a laminated film consisting of at least three layers, in which a tab lead adhesive layer, an intermediate layer, and an exterior material adhesive layer are laminated in this order. The tab lead sealing film may contain layers other than these layers, and each layer may be composed of two or more layers having different formulations.

The thickness of the tab lead is preferably 0.2 mm or more and 1.0 mm or less. In addition, from the viewpoint of the end sealability of the tab lead sealing film with respect to the thickness of the tab lead and the end sealability of the exterior material with respect to the thickness of the tab lead with the sealing film, the total thickness of the sealing film is , preferably from 100 to 500 μm, more preferably from 100 to 400 μm, even more preferably from 100 to 200 μm. From the viewpoint of insulation of the sealing film, the thickness of the intermediate layer is preferably 40% to 70%, more preferably 50% to 70%, and 50% to 60% of the total thickness. It is more preferable that
From the viewpoint of thermal adhesion between the tab lead and the exterior material, the thickness of the tab lead adhesive layer and the exterior material adhesive layer is preferably 15 to 30%, more preferably 15 to 25%, of the total thickness. It is preferably 20 to 25%, and more preferably 20 to 25%.

[Method for manufacturing tab lead sealing film]
The tab lead sealing film can be manufactured as a three-layer film with a predetermined thickness by co-extruding three layers using a known co-extrusion method.

[Physical properties of tab lead sealing film]
From the viewpoint of film rigidity, a three-layer tab lead sealing film molded to a thickness of 100 μm by T-die extrusion was tested at a tensile rate of 200 mm/200 mm at 23°C and 50% RH in accordance with JIS K 6251-1. Preferably, the load at 10% elongation measured in minutes is 23 to 31 N/10 mm.

[Applications of tab lead sealing film]
The tab lead sealing film of the present invention has excellent adhesion and sealing properties to the tab lead and exterior material, as well as high rigidity and excellent electrolyte resistance at high temperatures. The tab lead sealing film can be suitably used for high capacity and high output laminate type batteries and capacitors, particularly lithium ion batteries and lithium ion capacitors.

Hereinafter, the present invention will be explained in more detail based on Examples and Comparative Examples.

[Raw materials used]
The raw materials used in the examples and comparative examples are as follows. In addition, the melting point of each resin is based on JIS K 7121, and is measured using a differential scanning calorimeter (DSC) when a sample is heated from -50°C to 200°C at a rate of 10°C/min in a nitrogen stream. It is the melting peak temperature in the DSC curve. Furthermore, the MFR of each resin is a value measured at 230° C. and a load of 2.16 kg in accordance with JIS K 7210-1.

<Acid-modified polypropylene>
(a-1) Maleic anhydride-modified polypropylene (manufactured by Mitsui Chemicals, Inc., Admer (registered trademark) QF551, melting point: 145°C, MFR: 5.7 g/10 minutes)
(a-2) Maleic anhydride-modified polypropylene (manufactured by Mitsui Chemicals, Inc., Admer (registered trademark) QE840, melting point: 140°C, MFR: 9.2 g/10 minutes)
(a-3) Maleic anhydride-modified polypropylene (manufactured by Mitsubishi Chemical Corporation, Modic (registered trademark) P587, melting point: 148°C, MFR: 15 g/10 minutes)
(a-4) Maleic anhydride-modified polypropylene (manufactured by Mitsui Chemicals, Admer (registered trademark) AT3401, melting point: 136°C, MFR: 8.0 g/10 minutes)
(a-5) Maleic anhydride-modified polypropylene (manufactured by Mitsui Chemicals, Admar (registered trademark) QF500, melting point: 165°C, MFR: 3.0 g/10 minutes)

<Propylene homopolymer>
(h-1) Propylene homopolymer (manufactured by Sunallomer Co., Ltd., Sunallomer (registered trademark) PC600A, melting point: 162°C, MFR: 7.5g/10 minutes, deflection temperature under load (0.45MPa): 102°C (catalog value ))
(h-2) Propylene homopolymer (manufactured by Sunallomer Co., Ltd., Sunallomer (registered trademark) PL500A, melting point: 162°C, MFR: 3.0g/10 minutes, deflection temperature under load (0.45MPa): 96°C (catalog value ))

<Propylene-ethylene copolymer>
(b-1) Propylene-ethylene block copolymer (manufactured by Sunallomer Co., Ltd., Sunallomer (registered trademark) PC480A, melting point: 160°C, MFR: 2.0g/10 minutes, deflection temperature under load (0.45MPa): 83°C (Catalog value))
(r-1) Propylene-ethylene random copolymer (manufactured by Sunallomer Co., Ltd., Sunallomer (registered trademark) PC540R, melting point: 132°C, MFR: 5.3g/10 minutes, deflection temperature under load (0.45MPa): 59°C (Catalog value))

Example 1
Using a 3-layer T-die coextrusion molding machine, maleic anhydride-modified polypropylene (a-1) was used as the tab lead adhesive layer (25 μm), propylene homopolymer (h-1) was used as the intermediate layer (50 μm), and maleic anhydride was used as the exterior material adhesive layer. Modified polypropylene (a-1) of 25 μm was laminated in this order to obtain a tab lead sealing film consisting of three layers with a total thickness of 100 μm.
The die temperature during extrusion molding was 230 to 240°C for the tab lead adhesive layer, 250 to 270°C for the intermediate layer, and 230 to 240°C for the exterior material adhesive layer.

Examples 2 to 11 and Comparative Examples 1 to 7
A three-layer tab lead sealing film was obtained in the same manner as in Example 1, except that the formulations and thicknesses of the tab lead adhesive layer, intermediate layer, and exterior material adhesive layer were changed as shown in Table 1.

The evaluation method for the films of Examples and Comparative Examples is as follows.
<Load at 10% elongation>
Test pieces were prepared by punching out the films of Examples and Comparative Examples in the dumbbell shape specified in JIS K 6251-1. The test piece was stored in a 23° C. 50% RH environment for 24 hours. Thereafter, under the same conditions, the load at 10% elongation was measured at a tensile speed of 200 mm/min in accordance with JIS K 6251-1. The measurement was repeated five times, and the average value was taken as the load at 10% elongation. The results are shown in Table 1.

<Adhesion strength before and after immersion in electrolyte>
An aluminum plate (manufactured by UACJ Corporation, A1N30) with a length of 60 mm x width of 20 mm x thickness of 0.4 mm was subjected to trivalent chromate treatment. The thus obtained aluminum plate was used as an adherend, the adherend and the tab lead adhesive layer of the tab lead sealing film were placed facing each other, and a glass cloth of 80 μm thickness was placed between the upper and lower heat seal bars heated to 190°C. They were sandwiched between heat-resistant sheets and bonded under conditions of 0.6 MPa and 5 seconds.
The obtained adhesive test piece was immersed in a 1 mol/L LiPF ₆ electrolyte in ethylene carbonate: diethyl carbonate: dimethyl carbonate = 1:1:1 to which 1,000 ppm of distilled water was added, and placed in a constant temperature bath at 85 °C. After being left for 3 days, it was taken out from the constant temperature bath, and the adhesive test piece was washed with a dimethyl carbonate solution, then washed with water and dried.
An adhesion test piece that was not immersed in electrolyte (hereinafter referred to as "untreated") and an adhesion test piece that had been immersed in electrolyte were stored in an environment of 23°C and 50% RH for 24 hours, and under the same conditions, JIS K 6854. -2, the adhesive strength was measured at a tensile speed of 100 mm/min. The measurement was repeated five times, and the average value was taken as the adhesive strength. The results are shown in Table 1. Note that the film of Comparative Example 7 could not be adhered to the trivalent chromate-treated aluminum plate, so the electrolyte immersion test was not conducted.

As shown in Table 1, the content of the propylene homopolymer is 50 to 100% by mass with respect to 100% by mass of the intermediate layer, the tab lead adhesive layer is made of a specific acid-modified polyolefin, and the exterior material adhesive layer is made of ethylene-propylene. The tab lead sealing films of Examples 1 to 11, which are made of random copolymers or specific acid-modified polyolefins, have high rigidity and excellent adhesion before and after immersion in electrolyte.
From the comparison of Examples 1, 5, and 6, and the comparison of Examples 9 and 10, Examples 1 and 9, in which the intermediate layer was composed of only a propylene homopolymer, have much better rigidity and electrolyte resistance, and are preferable. .

Comparative Examples 1 to 3 and 6, in which the acid-modified polypropylene constituting each adhesive layer had a melting point of 136°C, were inferior in rigidity and adhesiveness before and after immersion in the electrolyte. Comparative Examples 4 and 5, in which the acid-modified polypropylene constituting each adhesive layer has a melting point of 140°C to 150°C, but the content of the propylene homopolymer in the intermediate layer is less than 50% by mass, have a high rigidity and an electrolytic solution. Poor adhesion before and after dipping. Comparative Example 7, in which the acid-modified polypropylene constituting each adhesive layer had a melting point of 165° C., could not be bonded to the trivalent chromate-treated aluminum plate.

The tab lead sealing film of the present invention can be suitably used for laminated lithium ion batteries and lithium ion capacitors.

1 Lead conductor 2 Tab lead sealing film 3 Exterior material (metal foil laminate multilayer film)
9 Tab lead on positive electrode side 10 Tab lead on negative electrode side 11 Intermediate layer 12 Tab lead adhesive layer 13 Exterior material adhesive layer

Claims (7)

A tab lead sealing film for bonding the exterior packaging material and a tab lead in a battery wrapped with an exterior packaging material, the film comprising:
The tab lead sealing film is a laminated film consisting of at least three layers, in which a tab lead adhesive layer, an intermediate layer, and an exterior material adhesive layer are laminated in this order,
The content of the propylene homopolymer is 50 to 100% by mass with respect to 100% by mass of the intermediate layer, and is selected from the group consisting of a copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms, and acid-modified polypropylene. The content of propylene resin is 0 to 50% by mass,
The tab lead adhesive layer is acid-modified polypropylene,
The exterior material adhesive layer is the propylene-based resin,
Here, according to JIS K 7121, the acid-modified polypropylene has a melting point of 140°C to 150°C, measured at a temperature increase rate of 10°C/min in a nitrogen stream, and 230°C according to JIS K 7210-1. A tab lead sealing film having an MFR of 5.0 to 15 g/10 minutes, measured at ℃ and 2.16 kg load. The tab lead sealing film according to claim 1, wherein the propylene resin constituting the intermediate layer is a block copolymer of propylene and ethylene. According to JIS K 7121, propylene homopolymer has a melting point of 160°C to 165°C measured at a heating rate of 10°C/min in a nitrogen stream, and 230°C and 2°C according to JIS K 7210-1. The tab lead sealing film according to claim 1 or 2, which has an MFR of 2.0 to 9.5 g/10 minutes measured at a load of 16 kg. The tab lead sealing film according to claim 1 or 2, wherein the propylene resin constituting the exterior material adhesive layer is a random copolymer of propylene and ethylene or the acid-modified polypropylene. The tab lead sealing film according to claim 1 or 2, wherein the acid-modified polypropylene is maleic anhydride-modified polypropylene. The tab lead sealing film according to claim 1 or 2, wherein the total thickness of the tab lead sealing film is 100 to 500 μm, and the thickness of the intermediate layer is 40% to 70% of the total thickness. The load at 10% elongation measured at a tensile rate of 200 mm/min at 23°C and 50% RH in accordance with JIS K 6251-1 for a tab lead sealing film molded to a thickness of 100 μm using the T-die extrusion method. The tab lead sealing film according to claim 1 or 2, wherein the tab lead sealing film is 23 to 31 N/10 mm.