JP7613838B2 - Sealing film, electrode lead wire member and battery - Google Patents

Description

The present invention relates to a sealing film, an electrode lead wire member, and a battery.

In recent years, secondary batteries such as lithium-ion batteries and capacitors have been attracting attention as storage batteries for storing electrical energy.

As an example, these secondary batteries and capacitors use storage containers made of a laminate for battery exteriors that has excellent waterproofing and light-blocking properties. The laminate for battery exteriors is, for example, a laminate in which a base layer made of polyamide or polyester is laminated with aluminum foil. The electrode lead wires of the secondary batteries and capacitors connect the inside and outside of the storage container, and one end protrudes from the storage container and is sealed.

A known configuration for such secondary batteries and capacitors is to place a sealing film, which is a laminate of resin, between the container and the electrode lead wire. The sealing film prevents gaps from forming around the electrode lead wire. This prevents moisture from entering the secondary battery or capacitor from around the electrode lead wire.

JP 2003-7268 A

It is known that when moisture penetrates into the container of a secondary battery or capacitor, the water reacts with the electrolyte, causing degradation. To improve the reliability of secondary batteries and capacitors, there was a demand for a technology that would be more effective than current technologies for preventing moisture penetration.

The present invention has been made in consideration of these circumstances, and aims to provide a sealing film that is easy to seal and inhibits the intrusion of moisture. Another aim is to provide an electrode lead wire member having such a sealing film. Another aim is to provide a battery having such an electrode lead wire member.

To solve the above problems, one aspect of the present invention includes the following aspects:

[1] A sealing film having an electrode adhesive layer, a sealant layer, and an intermediate layer provided between the electrode adhesive layer and the sealant layer, the electrode adhesive layer and the sealant layer containing maleic anhydride modified polyolefin, the intermediate layer containing a fluororesin, and the thickness of the intermediate layer being 30% or more and 75% or less of the total thickness of the sealing film.

[2] The sealing film described in [1], wherein the thickness of the intermediate layer is equal to or greater than the thickness of the electrode adhesive layer.

[3] The sealing film according to [1] or [2], wherein the thickness of the intermediate layer is equal to or greater than the thickness of the sealant layer.

[4] The sealing film according to any one of [1] to [3], wherein the fluororesin is polychlorotrifluoroethylene.

[5] The sealing film according to any one of [1] to [4], wherein the sealant layer contains at least one of maleic anhydride modified polyethylene and maleic anhydride modified polypropylene.

[6] An electrode lead wire member having an electrode lead wire extending in one direction and a sealing film described in any one of [1] to [5].

[7] An electrode lead wire member according to [6], which has a pair of sealing films that sandwich the electrode lead wire, the pair of sealing films being in contact with each other with the electrode adhesive layers facing each other and in contact with the entire circumference of the electrode lead wire in the circumferential direction to cover the electrode lead wire.

[8] The electrode lead wire member according to [6] or [7], in which the electrode lead wire has a lead wire body and a surface treatment layer formed on the surface of the lead wire body, and the sealing film is provided in contact with the surface treatment layer in the electrode adhesive layer.

[9] A battery comprising an electrode lead wire member according to any one of [6] to [8].

According to the present invention, it is possible to provide a sealing film that is easy to seal and to easily prevent the intrusion of moisture. It is also possible to provide an electrode lead wire member having such a sealing film. Furthermore, it is possible to provide a battery having such an electrode lead wire member.

FIG. 1 is a schematic cross-sectional view showing a sealing film 1 of an embodiment. FIG. 2 is a schematic perspective view showing an electrode lead member according to the embodiment. FIG. 3 is a schematic perspective view showing the battery 100 of the embodiment. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is an explanatory diagram showing a method for producing the test piece used in the examples. FIG. 6 is an explanatory diagram showing a method for producing the test piece used in the examples. FIG. 7 is a cross-sectional view of a test piece used in the examples.

The sealing film, electrode lead wire member, and battery according to this embodiment will be described below with reference to Figures 1 to 4. Note that in all of the following drawings, the dimensions and ratios of each component have been appropriately changed to make the drawings easier to understand.

<Sealing film, electrode lead wire member>
Fig. 1 is a schematic cross-sectional view showing a sealing film 1 of the present embodiment. Fig. 2 is a schematic perspective view showing an electrode lead member of the present embodiment.

The sealing film 1 has an electrode adhesive layer 2 , a sealant layer 3 , and an intermediate layer 4 .
The electrode lead member 10 has an electrode lead 11 and a sealing film 1 .
The following explains each in order.

(Electrode Adhesive Layer)
The electrode adhesive layer 2 is a layer that is fused to the electrode lead wire 11 by application of heat and pressure. The surface of the electrode adhesive layer 2 is one surface 1 a of the sealing film 1.

The electrode adhesive layer 2 mainly contains an acid-modified polyolefin. In this specification, the electrode adhesive layer 2 "mainly contains an acid-modified polyolefin" means that the content of acid-modified polyolefin is the highest among the resins constituting the electrode adhesive layer 2. The electrode adhesive layer 2 preferably contains 50% by mass or more of acid-modified polyolefin based on the total amount of the electrode adhesive layer 2. The electrode adhesive layer 2 preferably contains 80% by mass or more of acid-modified polyolefin based on the total amount of the electrode adhesive layer 2.

Optional components in the electrode adhesive layer 2 other than the acid-modified polyolefin include known additives such as stabilizers, antistatic agents, and colorants.

As the acid-modified polyolefin, acid-modified polypropylene is preferred because of its excellent heat resistance. Hereinafter, polypropylene may be abbreviated as "PP."

Acid-modified PP is a polymer in which a monomer having a carboxy group is graft-copolymerized onto polypropylene or an ethylene-propylene copolymer. The ethylene-propylene copolymer is preferably a random copolymer or a block copolymer.

Monomers having a carboxy group include unsaturated carboxylic acids such as acrylic acid and methacrylic acid, unsaturated carboxylic acid esters such as ethyl acrylate, and acid anhydrides such as maleic anhydride.

Acid-modified PP includes ionomers in which the carboxylic acid groups of acid-modified polymers of polypropylene or acid-modified polymers of ethylene-propylene copolymers have been neutralized with metal hydroxides, alkoxides, salts of lower fatty acids, etc.

The acid group of the acid-modified PP is preferably a maleic anhydride group. In other words, the acid-modified PP is preferably maleic anhydride-modified PP.

The melting point of the resin constituting the electrode adhesive layer 2 is preferably 100°C or higher and 160°C or lower. When the "resin constituting the electrode adhesive layer 2" is a polymer alloy of two or more types of resin, the "melting point of the resin constituting the electrode adhesive layer 2" means the melting point of the polymer alloy constituting the electrode adhesive layer 2.

The melt flow rate (MFR) of the acid-modified polyolefin forming the electrode adhesive layer 2 is preferably 3 g/10 min or more and 30 g/10 min or less, and more preferably 5 g/10 min or more and 10 g/10 min or less.

If the MFR of the acid-modified polyolefin forming the electrode adhesive layer 2 is 3 g/10 min or more, the acid-modified polyolefin will sufficiently wrap around the electrode lead wire 11 during thermocompression bonding, making it easier to seal the periphery of the electrode lead wire 11.

When the MFR of the acid-modified polyolefin forming the electrode adhesive layer 2 is 30 g/10 min or less, the electrode adhesive layer 2 is less likely to become excessively thin during thermocompression bonding, making it easier to ensure adhesive strength.

It is preferable that the thickness of the electrode adhesive layer 2 is as thin as possible while still allowing thermocompression bonding with the electrode lead wire 11. For example, it is preferable that the thickness of the electrode adhesive layer 2 is 20 μm or more and 30 μm or less. When the thickness of the electrode adhesive layer 2 is 20 μm or more, sufficient adhesive strength between the electrode adhesive layer 2 and the electrode lead wire 11 can be ensured. When the thickness of the electrode adhesive layer 2 is 30 μm or less, it is easier to ensure the heat resistance of the sealing film 1.

(Sealant Layer)
The sealant layer 3 is a layer that is fused to, for example, a battery container by heating and pressurizing. The container will be described later. The surface of the sealant layer 3 is the other surface 1b of the sealing film 1.

The sealant layer 3 mainly contains an acid-modified polyolefin. In this specification, the term "mainly contains an acid-modified polyolefin" means that the resin constituting the sealant layer 3 has the highest content of acid-modified polyolefin. The sealant layer 3 preferably contains 50% by mass or more of acid-modified polyolefin based on the total amount of the sealant layer 3. The sealant layer 3 preferably contains 80% by mass or more of acid-modified polyolefin based on the total amount of the sealant layer 3.

Optional components in the sealant layer 3 other than the acid-modified polyolefin include known additives such as stabilizers, antistatic agents, and colorants.

As the acid-modified polyolefin, acid-modified PP is preferred because of its excellent heat resistance. As the acid-modified PP, the acid-modified PP exemplified as the material for the electrode adhesive layer 2 described above is preferably used. Among them, as the acid-modified PP, a polymer obtained by acid-modifying a random copolymer of ethylene and propylene is preferred because of its excellent flexibility.

In addition, it is preferable that the acid-modified polyolefin constituting the sealant layer 3 contains at least one of acid-modified PP and acid-modified polyethylene.

It is preferable that the sealant layer 3 contains acid-modified PP to increase the strength of the fusion points with the battery container. On the other hand, when the sealant layer 3 contains acid-modified PP, the melting point of the sealant layer 3 increases as the content of acid-modified PP increases. Therefore, if the content of acid-modified PP in the sealant layer 3 is too high, the heating temperature (heat seal temperature) when fusing the sealant layer 3 becomes too high, and there is a risk of deterioration of the electrode adhesive layer 2.

Therefore, it is more preferable that the sealant layer 3 contains both acid-modified PP and acid-modified polyethylene. This lowers the melting point of the sealant layer 3, lowers the heating temperature when fusing the sealant layer 3, and suppresses deterioration of the electrode adhesive layer 2.

The acid group of the acid-modified polyethylene is preferably a maleic anhydride group. In other words, the acid-modified polyethylene is preferably maleic anhydride-modified polyethylene.

In the resin constituting the sealant layer 3, the ratio of acid-modified PP to the total of acid-modified PP and acid-modified polyethylene is preferably 20% by mass or more and 80% by mass or less.

The melting point of the resin forming the sealant layer 3 is preferably 100°C or higher and 160°C or lower. When the "resin constituting the sealant layer 3" is a polymer alloy of two or more types of resin, the "melting point of the resin constituting the sealant layer 3" means the melting point of the polymer alloy constituting the sealant layer 3.

The MFR of the resin forming the sealant layer 3 is preferably 3 g/10 min or more and 30 g/10 min or less, and more preferably 5 g/10 min or more and 10 g/10 min or less. If the MFR of the resin forming the sealant layer 3 is within the above range, it is preferable because it makes it easier to manufacture the sealing film 1.

It is preferable that the thickness of the sealant layer 3 is as thin as possible while still allowing thermocompression bonding to the storage container. For example, it is preferable that the thickness of the sealant layer 3 is 20 μm or more and 40 μm or less. If the thickness of the sealant layer 3 is 20 μm or more, the fusion strength between the sealant layer 3 and the storage container may be reduced. If the thickness of the sealant layer 3 is greater than these ranges, the heat resistance of the sealing film 1 may be poor.

It is preferable that the sealant layer 3 has the same thickness as the electrode adhesive layer 2.

(Middle class)
The intermediate layer 4 is provided between the electrode adhesive layer 2 and the sealant layer 3 .

The intermediate layer 4 mainly contains fluororesin. In this specification, the intermediate layer 4 "mainly contains fluororesin" means that the content of fluororesin is the highest among the resins constituting the intermediate layer 4. The intermediate layer 4 preferably contains 50% by mass or more of fluororesin based on the total amount of the intermediate layer 4. The intermediate layer 4 preferably contains 80% by mass or more of fluororesin based on the total amount of the intermediate layer 4.

By containing fluororesin in the intermediate layer 4, the sealing film 1 becomes more effective at preventing moisture penetration.

The fluororesin used for the intermediate layer 4 is preferably polychlorotrifluoroethylene (PCTFE), which has excellent mechanical strength, gas barrier properties, moldability, etc.

The thickness of the intermediate layer 4 is 30% or more and 75% or less of the total thickness of the sealing film 1. The thickness of the intermediate layer 4 is preferably 33% or more of the total thickness of the sealing film 1. In addition, the thickness of the intermediate layer 4 is preferably 73% or less of the total thickness of the sealing film 1.

It is preferable that the thickness of the intermediate layer 4 is equal to or greater than the thickness of the electrode adhesive layer 2.

It is preferable that the thickness of the intermediate layer 4 is equal to or greater than the thickness of the sealant layer 3.

Specifically, the thickness of the intermediate layer 4 is preferably 30 μm or more and 120 μm or less.

<Electrode lead wire member>
2, the electrode lead member 10 has an electrode lead 11 and the above-mentioned sealing film 1. The electrode lead member 10 shown in FIG.

The pair of sealing films 1 are in contact with each other with their electrode adhesive layers 2 facing each other. In FIG. 2, the surfaces 1a on the electrode adhesive layer 2 side are in contact with each other.

The pair of sealing films 1 also contact the entire circumference of the electrode lead wire 11 and cover the electrode lead wire 11.

[Electrode lead wire]
The electrode lead wire 11 has a lead wire body 111 and a surface treatment layer 112 .

(Lead wire body)
The lead wire body 111 is conductive and connects the inside of the battery to the outside of the battery. Known metals such as aluminum, copper, nickel, iron, gold, platinum, and various alloys can be used as the material of the lead wire body 111. Among these materials, aluminum and copper are preferred because they have excellent conductivity and are cost-effective.

The surface of the lead wire body 111 may be nickel plated. The nickel plating of the lead wire body 111 may be electroplated using a Watts bath containing nickel sulfate, nickel chloride, boric acid, or the like as the main components. The nickel plating of the lead wire body 111 is preferably performed using a nickel sulfamate plating bath containing nickel sulfamate and boric acid as the main components. The plating film formed by this method has excellent flexibility and is less likely to crack.

The lead wire body 111 is preferably made of an aluminum plate or a nickel-plated copper plate.

(Surface treatment layer)
A corrosion-resistant surface treatment layer 112 may be formed on the surface of the lead body 111. In this specification, "corrosion resistance" refers to the property of being less susceptible to corrosion by the electrolyte inside the battery.

Examples of the surface treatment layer 112 include acid-resistant coatings made of materials such as phosphates, chromates, fluorides, or triazine thiol compounds. These acid-resistant coatings can be formed by subjecting the lead wire body 111 to chemical conversion treatment.

The surface treatment layer 112, which is an acid-resistant coating, prevents delamination between the lead wire body 111 and the sealing film 1. In addition, the surface treatment layer 112, which is an acid-resistant coating, suppresses dissolution or corrosion of the surface of the lead wire body 111 when the electrolyte used in the battery reacts with moisture to produce hydrogen fluoride. In particular, when the material forming the lead wire body 111 is aluminum, the surface treatment layer 112 suppresses dissolution and corrosion of aluminum oxide present on the surface of the lead wire body 111.

The surface treatment layer 112 is preferably a coating formed by a phosphate chromate treatment using three components: phenolic resin, chromium trifluoride, and phosphoric acid.

Alternatively, the surface treatment layer 112 is preferably a coating formed by treatment with a chemical conversion treatment agent containing a resin component containing at least a phenolic resin and a metal such as molybdenum, titanium, or zirconium, or a metal salt of molybdenum, titanium, or zirconium.

Known techniques can be used for the chemical conversion treatment method. For example, by immersing a metal in the above-mentioned chemical conversion treatment agent, a reaction between the metal and the chemical conversion treatment agent occurs on the metal surface, producing an insoluble product that adheres to the metal surface. The resulting insoluble product functions as the above-mentioned acid-resistant coating.

At the end 1c of the sealing film 1 of the electrode lead wire member 10 as described above, the intermediate layer 4 having a fluororesin that is difficult for moisture to permeate is exposed over 30% to 75% of the entire thickness of the sealing film 1. In other words, in an area of 30% to 75% of the entire end 1c of the sealing film 1, the intrusion of moisture into the sealing film 1 is suppressed.

In addition, in 67% or less of the area of the end 1c of the sealing film 1, excluding the area corresponding to the intermediate layer 4, moisture may penetrate into the sealing film 1. Here, since the intermediate layer 4 is located between the electrode adhesive layer 2 and the sealant layer 3, the area through which moisture can penetrate into the sealing film 1 is divided into two, making it narrower. Therefore, moisture is less likely to penetrate from the end 1c of the sealing film 1 in the direction of the arrow indicated by the symbol X.

Furthermore, the sealing film 1 contains an acid-modified polyolefin as a material for forming the electrode adhesive layer 2. Therefore, the electrode adhesive layer 2 is easily heat-sealed to the electrode lead wire 11, and the interface between the electrode lead wire 11 and the sealing film 1 is easily sealed.

The sealing film 1 contains an acid-modified polyolefin as a material for forming the sealant layer 3. Therefore, the sealant layer 3 is easily heat-sealed with the resin material constituting the battery container, and easily seals the interface between the container and the sealing film 1.

As a result, the sealing film 1 of this embodiment is a sealing film that is easy to seal and prevents moisture from entering.

In addition, since the electrode lead wire member 10 of this embodiment includes the sealing film 1, it is an electrode lead wire member that is easy to seal and easily prevents moisture from entering.

<Batteries>
3 is a schematic perspective view showing the battery 100 of this embodiment. The battery 100 has the electrode lead member 10 of this embodiment described above, a container 20, and a lithium ion battery 30.

The storage container 20 has a container body 21 and a lid 22.

The container body 21 is obtained by drawing a laminate for battery exterior packaging. The container body 21 has a recess 21a for accommodating the lithium ion battery 30.
The laminate for battery exterior packaging will be described later.

The lid 22 is made of a laminate for battery exterior packaging and has a planar area equivalent to that of the container body 21.

The storage container 20 is formed by overlapping the container body 21 and the lid 22 and heat sealing the four edges 25.

The container body 21 and the lid 22 may be molded as a single unit. Specifically, a rectangular laminate for battery exterior packaging is prepared, and a recess is formed by drawing one end side of the center in the longitudinal direction, to form a member in which the container body 21 and the lid 22 are molded as a single unit. Such a member can be formed into the storage container 20 by folding the laminate for battery exterior packaging from the center in the longitudinal direction to close the recess, and heat sealing the four edges.

FIG. 4 is a cross-sectional view taken along line IV-IV in FIG.
The laminate for battery exterior, which is the material of the container body 21 and the lid 22 , has a metal foil 201 , a sealant layer 202 provided on one side of the metal foil 201 , and a film substrate 203 provided on the other side of the metal foil 201 .

That is, the container body 21 and the lid 22 each have a metal foil 201, a sealant layer 202, and a film substrate 203.

The metal foil 201 may be aluminum foil, stainless steel foil, copper foil, iron foil, etc. The metal foil 201 may be subjected to a base treatment such as a chemical conversion treatment.

The sealant layer 202 is in contact with the sealant layer 3 of the sealing film 1 and is heat-sealed.

The resin forming the sealant layer 202 is selected from those that can be fused to the sealing film 1. Examples of resins that form the sealant layer 202 include polypropylene-based resins, and polypropylene homopolymers and copolymers of polypropylene and ethylene can be used.

Polyethylene resins that can be used include low-density polyethylene and linear low-density polyethylene.

There are no particular limitations on the resin that constitutes the film substrate 203, but polyamide, polyethylene terephthalate (PET), phenolic resin, polypropylene, and other resins with high strength are preferably used.

As shown in Figures 3 and 4, in the battery 100, the electrode lead wire member 10 is pulled out from the inside (recess 21a) of the storage container 20 to the outside of the storage container 20. In addition, the electrode lead wire member 10 is fused to the sealant layer 202 of the storage container 20 at the sealing film 1.

According to the battery 100 configured as described above, since the electrode lead wire member 10 has the above-mentioned sealing film 1, the intrusion of moisture from around the electrode lead wire 11 into the inside of the storage container 20 is suppressed. This results in a battery 100 that is less prone to deterioration and is highly reliable.

The above describes preferred embodiments of the present invention with reference to the attached drawings, but the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Using the resin described below, a sealing film was produced in which an electrode adhesive layer, an intermediate layer, and a sealant layer were laminated in this order. The resins that were the raw materials for each layer were separately heated and melted, and simultaneous multilayer film formation was performed using an extruder capable of simultaneous multilayer extrusion molding. Furthermore, the ends in the width direction of the obtained laminate were slit and cut off to produce the original rolls of sealing film for each Example and Comparative Example. The width of the original roll of sealing film was 250 mm.

Electrode adhesive layer: Maleic anhydride modified polypropylene (MFR 7.5 g/10 min, melting point 135° C.)
Middle layer: PCTFE (polychlorotetrafluoroethylene)
Sealant layer: 1:1 (mass ratio) blend of maleic anhydride polyethylene and maleic anhydride polypropylene

Maleic anhydride modified polypropylene is a polymer in which maleic anhydride is graft-polymerized onto a random copolymer of ethylene and propylene.

In the following examples and comparative examples, the following resins were used.
Maleic anhydride modified polypropylene: Admer QF060 (manufactured by Mitsui Chemicals, Inc.)
Maleic anhydride modified polyethylene: Admer NF518 (manufactured by Mitsui Chemicals, Inc.)
PCTFE: DF0050-C1 (manufactured by Daikin Industries, Ltd.)

The thickness of each layer of the sealing film produced is shown in Tables 1 and 2.

Sealing films were cut out from each of the obtained original sealing film rolls as follows, and each evaluation was performed.

<Preparation of electrode lead wire member>
Square aluminum foil and copper foil were used as electrode lead wires, each having dimensions of 50 mm width × 50 mm length × 300 μm thickness.

The copper foil was plated using a _plating bath with the following composition: Ni( _{NH2SO3 ) 2.4H2O} : 500 _g /l, _NiCl2.6H2O : 30 g/l, _H3BO3 : 50 g/l _, and sodium lauryl sulfate 5 ml/l. The plating conditions were a bath temperature of 50°C and a current density of 10 A/ ^dm2 .

A surface treatment layer made of glyceryl chitosan was formed by applying a surface treatment agent made of glyceryl chitosan dissolved in water to the surface of the two types of electrode lead wires and drying them. The thickness of the surface treatment layer was 0.8 μm.

Two rectangular pieces of sealing film measuring 15 mm wide and 60 mm long were cut out from each original sealing film roll. When cutting out the sealing film, the width direction of the original sealing film roll was aligned with the width direction of the sealing film to be cut out.

As shown in Fig. 5, a pair of sealing films 1A was placed over the electrode lead wire 11A and thermocompression bonded using a heat sealer at 190°C, 2 kgf/ ^cm2 , and 5 seconds. The sealing film 1A was oriented so that the electrode adhesive layer faced the electrode lead wire 11A. One of the pair of seal bars included in the heat sealer used was covered with an elastic body.

After thermocompression bonding, the front and back sides of the resulting laminate were switched and thermocompression bonded again under the above conditions to produce the electrode lead wire member 10A.

An electrode lead wire member using aluminum foil as the electrode lead wire 11A was used as sample A.
Also, sample B was an electrode lead wire member using nickel-plated copper foil as the electrode lead wire 11A.

<Preparation of Laminate for Battery Exterior>
A 12 μm thick biaxially oriented PET film, a 40 μm thick aluminum foil, and a 40 μm thick ethylene-propylene random copolymer film were dry laminated and cut into a square with each side measuring 100 mm to produce a laminate 200 for battery exterior packaging.

The aluminum foil corresponds to the metal foil 201 described above. The random copolymer film corresponds to the sealant layer 202 described above. The PET film corresponds to the film substrate 203 described above.

<Fusion between electrode lead wire member and laminate for battery exterior>
For each of Sample A and Sample B, the sealant layer of the sealing film 1A and the random copolymer film (sealant layer) of the laminate for battery exterior packaging 200 were overlapped and heat sealed.

Specifically, as shown in FIG. 6, the electrode lead wire 11A of the electrode lead wire member 10A and two battery exterior laminates 200 were stacked with their centers aligned and their sides parallel to each other.

The portion of the electrode lead wire member 10A where the sealing film 1A was present was heat sealed on both sides of the battery exterior laminate 200 using a heat sealer under conditions of 190°C, 2 kgf/ ^cm2 , and 5 seconds, thereby obtaining a laminate in which the battery exterior laminate 200 was fused to both sides of the electrode lead wire member 10A.

<Measurement of Bonding Strength>
The resulting laminate was cut at the position indicated by the dashed line Y in Fig. 6 to prepare a test piece for measuring the bonding strength. Fig. 7 is a cross-sectional view of the test piece.

The 180-degree peel strength of the obtained test specimen was measured using an Instron tensile tester. The test specimen was held at the end α of the battery exterior laminate 200 farther from the electrode lead wire 11 and the end β of the electrode lead wire 11 farther from the sealing film 1 with the gripping parts of the tester, and pulled in the direction of the double-headed arrow A in FIG. 7 at a speed of 10 mm/min.

The peel strength was measured for each of the two battery exterior laminates 200.

Electrode lead wire members 10A in which both battery exterior laminates 200 had a peel strength of 100 N/30 mm or more were rated as good (◯), and others were rated as bad (×).

<Sealability test>
For each of samples A and B, a penetrant liquid prepared by dissolving a red dye in a hydrocarbon solvent was dropped onto the edge of the thermocompression bonded portion between the electrode lead wire 11A and the sealing film 1A. The penetrant liquid was dropped onto both sides in the width direction of the sealing film 1A.

After dripping the penetrant liquid, the electrode lead wire member 10A was observed from both the front and back sides through the sealing film 1. Samples in which penetration of the penetrant liquid from the edge of the electrode lead wire 11 to the interface between the electrode lead wire 11A and the sealing film 1A was not observed were rated as good (◯), and samples in which penetration was observed were rated as bad (×).

<Hardness test>
For each of the electrode lead wire members 10A of Examples 1 to 6 and Comparative Examples 1 to 4, the sealing film 1A protruding from the end of the electrode lead wire 11A was folded 180 degrees to one side (first time) along the end of the electrode lead wire 11, and then folded 180 degrees to the other side (second time), and the occurrence of whitening was observed. The location for observing whitening was the surface of the sealing film 1A that would be the front side when the sealing film 1A was folded the second time.

The state of whitening occurring on the sealing film 1 was observed and evaluated as ◯, Δ, or × as follows. The sealing film with the state of whitening of ◯ or Δ was evaluated as passing.
(Evaluation Criteria)
◯: No whitening is observed.
Δ: Whitening was observed in the folded portion, but the electrode lead wire was visible through the folded portion.
Furthermore, when the folded portion was observed under a magnification of 40 times with an optical microscope, no cracks were observed.
×: Falls under (1) or (2) below.
(1) The folded portion turns white, and the electrode lead wire cannot be seen through the folded portion.
(2) When the folded portion is observed under an optical microscope (magnification 40 times), cracks can be seen in the folded portion.

<Evaluation of Barrier Properties>
The water vapor permeability of each film was measured according to JIS K 7129-2 "Plastics - Films and sheets - Determination of water vapor permeability - Part 2: Infrared sensor method". If the water vapor permeability of the film is large, more water will penetrate into the battery through the film. Conversely, if the water vapor permeability is small, less water will penetrate into the battery.

In this example, the intrusion of moisture from the external environment through the end face of the sealing film was evaluated using the above evaluation method. The key to the moisture blocking performance from the end face is not the surface direction of the sealing film, but the barrier properties of the end face. The end face of the intermediate layer made of fluororesin can suppress the intrusion of moisture from the end face of the sealing film, so the degree of moisture intrusion from the end face of the sealing film is affected by the barrier properties of the electrode adhesive layer and the sealant layer.

When the electrode adhesive layer and the sealant layer are heat-sealed to their respective adherends, they are heated and melted to solidify. At this time, the thickness of each of the electrode adhesive layer and the sealant layer decreases, and the proportion of the electrode adhesive layer and the sealant layer in the overall thickness of the sealing film decreases. For this reason, it is believed that the thickness of the intermediate layer becomes dominant in preventing moisture penetration from the end surface of the sealing film.

In this example, the above evaluation method was adopted because it was thought that by measuring the water vapor barrier performance in the surface direction of the entire sealing film, it would be possible to discuss the intrusion of moisture from the edge direction in a pseudo manner.

The evaluation results are shown in Tables 3 and 4 below.

From Tables 1 and 2, it was confirmed that the basic bonding strength and sealing performance of the laminate film to which the electrodes were bonded were sufficient in Examples 1 to 6 and Comparative Examples 1 and 3. In Comparative Examples 2 and 4, the electrode adhesive layer and sealant layer were thin, so the bonding strength was insufficient.

The results of the hardness test were judged based on the degree of whitening, but there were no samples with a large amount of whitening.

Moreover, the measurement results of the water vapor transmission rate showed that the sealing films of Examples 1 to 6 had a water vapor transmission rate of less than 0.16 g/m ² ·day, indicating that the films had sufficient water vapor barrier performance.

On the other hand, the sealing films of Comparative Examples 1 and 3 had water vapor permeation rates exceeding 0.3 g/ ^m2 ·day, and were found to have poor water vapor barrier performance. In other words, the sealing films of Comparative Examples 1 and 3 suggest the possibility that a large amount of moisture may penetrate into the inside of the battery. Therefore, it can be determined that the sealing films of Comparative Examples 1 and 3 are unsuitable as battery components even though they have good bonding strength and sealing performance.

These results demonstrate that the present invention is useful.

1, 1A...sealing film, 1a, 1b...surface, 2...electrode adhesive layer, 3, 202...sealant layer, 4...intermediate layer, 10, 10A...electrode lead wire member, 11, 11A...electrode lead wire, 100...battery, 111...lead wire body, 112...surface treatment layer

Claims (9)

An electrode adhesive layer;
A sealant layer;
A sealing film having an intermediate layer provided between the electrode adhesive layer and the sealant layer,
the electrode adhesive layer and the sealant layer contain maleic anhydride modified polyolefin,
The intermediate layer contains a fluororesin,
The thickness of the intermediate layer is 30% or more and 75% or less of the total thickness of the sealing film,
The sealant layer comprises a sealing film containing both maleic anhydride modified polyethylene and maleic anhydride modified polypropylene in a mixed state . The sealing film according to claim 1, wherein the thickness of the intermediate layer is equal to or greater than the thickness of the electrode adhesive layer. The sealing film according to claim 1 or 2, wherein the thickness of the intermediate layer is equal to or greater than the thickness of the sealant layer. The sealing film according to any one of claims 1 to 3, wherein the fluororesin is polychlorotrifluoroethylene. The sealing film according to any one of claims 1 to 4, wherein the electrode adhesive layer and the sealant layer are made of different materials. An electrode lead wire extending in one direction;
An electrode lead member comprising the sealing film according to claim 1 . A pair of the sealing films sandwiching the electrode lead wire therebetween,
The electrode lead member according to claim 6 , wherein the pair of sealing films are in contact with each other such that the electrode adhesive layers face each other and are in contact with the entire circumferential circumference of the electrode lead wire to cover the electrode lead wire. The electrode lead wire includes a lead wire body and
a surface treatment layer formed on the surface of the lead wire body,
The electrode lead member according to claim 6 , wherein the sealing film is provided in the electrode adhesive layer so as to be in contact with the surface treatment layer. A battery comprising an electrode lead wire member according to any one of claims 6 to 8.

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