Sealing film, electrode lead wire member and battery

Abstract

A sealing film that seals between a metal first base and a second base, the sealing film being provided with a first adhesive layer that mainly contains an acid-modified polyolefin and that adheres to the first base, a second adhesive layer that mainly contains a polyolefin and that adheres to the second base, and a substrate layer provided between the first adhesive layer and the second adhesive layer. The substrate layer contains (A), (B), and (C). The ratio [(A) / (B) + (C)] is 90 / 10 to 20 / 80. The content ratio of (B) relative to the total amount of (A), (B), and (C) is 5 to 70 mass% inclusive, and the content ratio of (C) relative to the total amount of (A), (B), and (C) is 5 to 70 mass% inclusive.

Description

[Technical Field]

[0001] The present invention relates to a sealing film, an electrode lead wire member, and a battery. This application claims priority based on Japanese Patent Application No. 2020-107874, filed on June 23, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] In recent years, secondary batteries such as lithium ion batteries, capacitors, etc. have been attracting attention as storage batteries for storing electrical energy. Such batteries include, for example, a battery body, a container that houses the battery body, and electrode leads connected to the battery body.

[0003] The housing is made of a laminate for battery exterior packaging, which has excellent waterproofing and light-blocking properties. The laminate for battery exterior packaging is, for example, a laminate formed by laminating a base layer made of polyamide or the like and aluminum foil. The electrode lead wire is sealed in the housing with a portion including one end extended to the outside.

[0004] In the above-mentioned battery, if water gets into the container, the water may react with components in the electrolyte to produce hydrogen fluoride. Hydrogen fluoride may deteriorate the electrode lead wires and shorten the battery life. For this reason, it has been proposed to interpose a sealing film (resin film) between the container and the electrode lead wires (see, for example, Patent Document 1).

[0005] The sealing film bonds the electrode lead wire to the container and prevents a gap from forming between the container and the electrode lead wire, thereby preventing water from entering the container from the outside through the gap. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-73200 A Summary of the Invention [Problem to be solved by the invention]

[0007] The sealing film (hereinafter referred to as the sealing film) preferably has high adhesive strength to the electrode lead wire. In addition, the sealing film is required to maintain adhesive strength between the resin layers constituting the sealing film and to prevent peeling between the resin layers.

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a sealing film, an electrode lead wire member, and a battery that have high adhesive strength to an electrode lead wire, maintain adhesive strength between resin layers that constitute the sealing film, and can suppress peeling between the resin layers. [Means for solving the problem]

[0009] In order to solve the above problems, one aspect of the present invention includes the following aspects.

[0010] [1] A sealing film for sealing between a first substrate made of metal and a second substrate, the sealing film comprising: a first adhesive layer that mainly contains an acid-modified polyolefin and adheres to the first substrate; a second adhesive layer that mainly contains a polyolefin and adheres to the second substrate; and a base layer provided between the first adhesive layer and the second adhesive layer, the base layer comprising the following components (A), (B), and (C), and the total amount of the components (B) and (C) and the component (A) are Content of with ratio( A) / [ The ratio of the content of the component (B) to the total amount of the components (A), (B), and (C) is 5% by mass or more and 70% by mass or less, and the content of the component (C) to the total amount of the components (A), (B), and (C) is 5% by mass or more and 70% by mass or less. Component (B): a resin that constitutes the first adhesive layer. Component (C): a resin that constitutes the second adhesive layer. Component (A): A resin different from the components (B) and (C). [2] The sealing film according to [1], wherein the melting point of the component (A) is higher than the melting point of the resin constituting the first adhesive layer or the second adhesive layer. [3] The sealing film according to [1] or [2], wherein the polyolefin constituting the second adhesive layer includes an acid-modified polyolefin. [4] The component (A) contains a polypropylene resin having a melting point of 150°C or higher and 170°C or lower, and the resin constituting the second adhesive layer is a polypropylene resin having a melting point of 110°C or higher and 150°C or lower. P The sealing film according to any one of [1] to [3], which is propylene or acid-modified polypropylene. [5] The sealing film according to any one of [1] to [4], wherein the resin constituting the first adhesive layer is an acid-modified polypropylene having a melting point of 110°C or more and 150°C or less. [6] An electrode lead wire member comprising: the sealing film according to any one of [1] to [5]; and the first base which is an electrode lead wire extending in one direction. [7] A battery comprising the electrode lead member according to [6], a battery body to which the electrode lead is connected, and the second base which is a container for accommodating the battery body. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a sealing film, an electrode lead wire member, and a battery that have high adhesive strength to an electrode lead wire, maintain adhesive strength between resin layers that constitute the sealing film, and can suppress peeling between the resin layers. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view showing a sealing film of an embodiment. [Figure 2] FIG. 2 is a schematic perspective view showing an electrode lead wire member according to the embodiment. [Figure 3] 1 is a schematic perspective view showing a battery according to an embodiment. [Figure 4] 4 is a cross-sectional view taken along line II in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0013] The sealing film, electrode lead wire member, and battery according to the embodiment will be described below with reference to Figures 1 to 4. Note that the dimensions and ratios of components in the drawings may differ from the actual dimensions and ratios.

[0014] <Sealing film> 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 10 of an embodiment.

[0015] 2, the electrode lead member 10 includes an electrode lead 11 and a sealing film 1. The electrode lead 11 is an example of a "first base."

[0016] As shown in FIG. 1, the sealing film 1 includes a first adhesive layer 2, a second adhesive layer 3, and a base layer 4. Any layer other than the first adhesive layer 2, the second adhesive layer 3, and the base layer 4 may be included as long as it does not impair the effects of the present invention.

[0017] [First adhesive layer] The first adhesive layer 2 is a layer that is fused (adhered) to the electrode lead wire 11 (see FIG. 2) by heating or pressurizing. The surface of the first adhesive layer 2 is one surface 1a of the sealing film 1. The first adhesive layer 2 is a resin layer that contains a resin.

[0018] The first adhesive layer 2 mainly contains an acid-modified polyolefin. The first adhesive layer 2 "mainly contains an acid-modified polyolefin" means that the content of the acid-modified polyolefin is the highest among the resins constituting the first adhesive layer 2.

[0019] The first adhesive layer 2 preferably contains 50% by mass or more (preferably more than 50% by mass) of acid-modified polyolefin relative to the total amount of the first adhesive layer 2. The first adhesive layer 2 preferably contains 80% by mass or more of acid-modified polyolefin relative to the total amount of the first adhesive layer 2.

[0020] The first adhesive layer 2 may contain 100% by mass of acid-modified polyolefin based on the total amount of the first adhesive layer 2. In one embodiment of the present invention, the first adhesive layer 2 "mainly contains an acid-modified polyolefin" means that the first adhesive layer 2 contains 80% by mass or more and 100% by mass or less of acid-modified polyolefin relative to the total amount of the first adhesive layer 2.

[0021] Examples of polyolefins that form the first adhesive layer 2 include polypropylene, polyethylene, poly-1-butene, and polyisobutylene. Among these, polypropylene is preferred because of its excellent flexibility. Hereinafter, polypropylene may be abbreviated as "PP."

[0022] The polyolefin may be a copolymer of propylene and ethylene (propylene-ethylene copolymer). Among them, a random copolymer of propylene and ethylene is preferable. The polyolefin may be a copolymer of propylene and an olefinic monomer. Examples of the olefinic monomer include 1-butene, isobutylene, and 1-hexene.

[0023] The acid-modified polyolefin is a polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof, and has an acid functional group such as a carboxy group or a carboxylic anhydride group in the polyolefin resin.

[0024] Acid-modified polyolefins can be obtained by modifying polyolefin resins with unsaturated carboxylic acids or their derivatives, copolymerizing acid functional group-containing monomers with olefins, etc. Use of acid-modified polyolefins can improve the adhesion of the first adhesive layer 2 to the electrode lead wire 11 (see FIG. 2).

[0025] The acid-modified polyolefin is preferably acid-modified polypropylene (acid-modified PP) because of its excellent heat resistance. Acid-modified PP is a polymer obtained by graft copolymerizing, for example, polypropylene or a propylene-ethylene copolymer with a monomer having a carboxy group.

[0026] Examples of the monomer 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.

[0027] Acid-modified PP includes ionomers in which the carboxylic acid groups of an acid-modified polymer of polypropylene or an acid-modified polymer of propylene-ethylene copolymer are neutralized with metal hydroxides, alkoxides, salts of lower fatty acids, or the like. The acid group of the acid-modified PP is preferably a maleic anhydride group, that is, the acid-modified PP is preferably maleic anhydride-modified PP.

[0028] The resin constituting the first adhesive layer is preferably an acid-modified polypropylene having a melting point of 110°C or higher and 150°C or lower. If the melting point of the resin constituting the first adhesive layer 2 is 110°C or higher, the first adhesive layer 2 is less likely to become excessively thin during thermocompression bonding, making it easier to ensure adhesive strength. If the melting point of the resin constituting the first adhesive layer 2 is 150°C or lower, the resin is more likely to flow during thermocompression bonding, allowing the resin to sufficiently wrap around the electrode lead wire 11 and making it easier to seal the entire periphery of the electrode lead wire 11.

[0029] When the "resin constituting the first adhesive layer 2" is a polymer alloy of two or more types of resin, the "melting point of the resin constituting the first adhesive layer 2" means the melting point of the polymer alloy constituting the first adhesive layer 2.

[0030] In the first adhesive layer 2, optional components other than the polyolefin include known additives such as stabilizers, antistatic agents, and colorants.

[0031] The thickness of the first adhesive layer 2 can be 5 to 90% and preferably 25 to 70% of the total thickness of the sealing film 1, where the total thickness of the sealing film 1 is 100. That is, the thickness of the first adhesive layer 2 can be 5 to 90% and preferably 25 to 70% of the total thickness of the sealing film 1. The ratio of the layer thicknesses when the total thickness of the sealing film 1 is 100 is referred to as the "thickness ratio."

[0032] When the thickness ratio of the first adhesive layer 2 is equal to or greater than the above lower limit, it is possible to ensure sufficient adhesive strength between the first adhesive layer 2 and the electrode lead wire 11. When the thickness ratio of the first adhesive layer 2 is equal to or less than the above upper limit, it is possible to impart sufficient thickness to the second adhesive layer 3 and the base material layer 4.

[0033] [Second adhesive layer] The second adhesive layer 3 is a layer that is fused (adhered) to the storage container by, for example, heating or pressurizing. The storage container is an example of a second substrate. The storage container will be described later. The surface of the second adhesive layer 3 is the other surface 1b of the sealing film 1. The second adhesive layer 3 is a resin layer containing a resin.

[0034] The second adhesive layer 3 mainly contains polyolefin. The second adhesive layer 3 "mainly contains polyolefin" means that, among the resins constituting the second adhesive layer 3, the content of polyolefin is the highest.

[0035] The second adhesive layer 3 preferably contains 50% by mass or more of polyolefin (preferably more than 50% by mass of polyolefin) relative to the total amount of the second adhesive layer 3. The second adhesive layer 3 preferably contains 80% by mass or more of polyolefin relative to the total amount of the second adhesive layer 3.

[0036] The second adhesive layer 3 may contain 100% by mass of acid-modified polyolefin based on the total amount of the second adhesive layer 3. In one embodiment of the present invention, the second adhesive layer 3 "mainly contains an acid-modified polyolefin" means that the second adhesive layer 3 contains 80% by mass or more and 100% by mass or less of acid-modified polyolefin relative to the total amount of the second adhesive layer 3.

[0037] Examples of polyolefins constituting the second adhesive layer 3 include polypropylene (PP), polyethylene, poly-1-butene, polyisobutylene, etc. Among these, PP is preferred because of its excellent flexibility.

[0038] The polyolefin may be a copolymer of propylene and ethylene (propylene-ethylene copolymer). Among them, a random copolymer of propylene and ethylene is preferred. The polyolefin may be a copolymer (for example, a random copolymer) of propylene and an olefinic monomer. Examples of the olefinic monomer include 1-butene, isobutylene, and 1-hexene.

[0039] The polyolefin constituting the second adhesive layer 3 may be an acid-modified polyolefin. 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 above as the material for the first adhesive layer 2 is preferably used.

[0040] Because of its excellent flexibility, a polymer obtained by acid-modifying a random copolymer of propylene and ethylene is preferred as the acid-modified PP constituting the second adhesive layer 3. Use of an acid-modified polyolefin facilitates increasing the adhesion of the second adhesive layer 3 to the storage container, which is the second substrate.

[0041] The second adhesive layer 3 may contain both acid-modified PP and acid-modified polyethylene. When the second adhesive layer 3 contains both acid-modified PP and acid-modified polyethylene, the melting point of the second adhesive layer 3 can be lowered, and the heating temperature when fusing the second adhesive layer 3 can be reduced. This makes it possible to prevent the first adhesive layer 2 from being deteriorated by high-temperature heating.

[0042] The resin constituting the second adhesive layer is a polymer having a melting point of 110°C or more and 150°C or less. P Polypropylene or acid-modified polypropylene is preferred. If the melting point of the resin constituting the second adhesive layer 3 is 110°C or higher, the second adhesive layer 3 is less likely to become excessively thin during thermocompression bonding, making it easier to ensure adhesive strength. If the melting point of the resin constituting the second adhesive layer 3 is 150°C or lower, the resin is more likely to flow during thermocompression bonding, making it easier to seal the gap between the container and the electrode lead wire 11.

[0043] When the "resin constituting the second adhesive layer 3" is a polymer alloy of two or more types of resin, the "melting point of the resin constituting the second adhesive layer 3" means the melting point of the polymer alloy constituting the second adhesive layer 3.

[0044] In the second adhesive layer 3, optional components other than the acid-modified polyolefin include known additives such as stabilizers, antistatic agents, and colorants.

[0045] The thickness (thickness ratio) of the second adhesive layer 3 can be 5 to 90, and preferably 10 to 50, relative to the total thickness of the sealing film 1, which is 100. That is, the thickness of the second adhesive layer 3 can be 5 to 90% of the total thickness of the sealing film 1, and preferably 10 to 50%.

[0046] When the thickness ratio of the second adhesive layer 3 is equal to or greater than the above lower limit, it becomes easier to ensure sufficient adhesive strength between the second adhesive layer 3 and the storage container, which is the second substrate. When the thickness ratio of the second adhesive layer 3 is equal to or less than the above upper limit, it becomes possible to impart sufficient thickness to the first adhesive layer 2 and the base material layer 4. As a result, it becomes easier to increase the adhesive strength between the first adhesive layer 2 and the electrode lead wire 11.

[0047] [Base material layer] The base layer 4 is provided between the first adhesive layer 2 and the second adhesive layer 3 . The substrate layer 4 contains the following components (A), (B), and (C). Component (B): a resin that constitutes the first adhesive layer. Component (C): A resin that constitutes the second adhesive layer. Component (A): a resin different from components (B) and (C).

[0048] The total amount of components (B) and (C) and component (A) Content of Relative to ( A) / [ (B)+(C)] is 90 / 10 to 20 / 80. When the content ratio of component (A) is equal to or greater than the above lower limit, a sufficient thickness can be imparted to base material layer 4. As a result, the adhesive strength between first adhesive layer 2 and electrode lead wire 11 and the adhesive strength between second adhesive layer 3 and the container can both be increased.

[0049] The content of component (B) relative to the total amount of components (A), (B), and (C) is 5% by mass or more and 70% by mass or less. The content of component (C) relative to the total amount of components (A), (B), and (C) is 5% by mass or more and 70% by mass or less.

[0050] An example of the component (B) is the acid-modified polyolefin that constitutes the first adhesive layer. An example of the component (C) is the polyolefin that constitutes the second adhesive layer.

[0051] The resin constituting the base layer 4 contains the components (A), (B), and (C). Optional components other than the components (A), (B), and (C) may be contained within a range that does not impair the effects of this embodiment. In this embodiment, the resin constituting the base layer 4 preferably consists of the components (A), (B), and (C).

[0052] The inclusion of component (B) in the resin constituting the base material layer 4 facilitates improving the affinity between the base material layer 4 and the first adhesive layer 2. This facilitates maintaining the adhesive strength between the base material layer 4 and the first adhesive layer 2, thereby preventing peeling between the resins.

[0053] When the resin constituting the base material layer 4 contains the component (C), the affinity between the base material layer 4 and the second adhesive layer 3 is likely to be improved. This makes it easier to maintain the adhesive strength between the base material layer 4 and the second adhesive layer 3, and prevents the resins from peeling off from each other.

[0054] The content ratios of the (B) component and the (C) component in the resin constituting the base layer 4 may be the same or different. In this embodiment, from the viewpoint of maintaining the same adhesive strength between the first adhesive layer and the base layer, and the same adhesive strength between the second adhesive layer and the base layer, it is preferable that the content ratios of the (B) component and the (C) component are the same. Furthermore, the components (B) and (C) may be the same.

[0055] In this embodiment, preferred combinations of the content ratios (mass %) of the components (A), (B), and (C) are described below. (C) / (A) / (B)=5 / 90 / 5 (C) / (A) / (B)=10 / 80 / 10 (C) / (A) / (B)=15 / 70 / 15 (C) / (A) / (B)=20 / 60 / 20 (C) / (A) / (B)=25 / 50 / 25 (C) / (A) / (B)=30 / 40 / 30 (C) / (A) / (B)=35 / 30 / 35 (C) / (A) / (B)=40 / 20 / 40 (C) / (A) / (B)=60 / 20 / 20 (C) / (A) / (B)=70 / 20 / 10 (C) / (A) / (B)=20 / 20 / 60 (C) / (A) / (B)=10 / 20 / 70

[0056] Examples of polyolefins as component (A) include polypropylene (PP), polyethylene, poly-1-butene, polyisobutylene, etc., which are different from components (B) and (C). Of these, PP is preferred due to its excellent flexibility.

[0057] The polyolefin as component (A) may be a homopolymer of one type of olefin or a copolymer of two or more types of olefins. Examples of the homopolymer include a homopolymer of propylene (homoPP). Examples of the copolymer include a copolymer of propylene and an olefinic monomer (ethylene, 1-butene, isobutylene, 1-hexene, etc.), such as a propylene-ethylene copolymer.

[0058] The polyolefin used as component (A) is preferably an ICP (impact copolymer). ICPs have a phase-separated structure with a first phase and a second phase, such as an island-in-sea structure. The island-in-sea structure is a structure in which multiple islands, or "islands," are dispersed in a first phase, or "sea."

[0059] The first phase is composed of a homopolymer of an olefinic monomer such as propylene or ethylene.

[0060] The second phase is composed of a polymer different from the homopolymer that constitutes the first phase. The second phase contains, for example, a polymer of an olefin monomer such as propylene or ethylene, for example, ethylene propylene rubber (EPR). The second phase is composed, for example, of a main phase and a surface layer that covers the surface of the main phase. The main phase is composed, for example, of polyethylene. The surface layer is composed, for example, of EPR.

[0061] ICPs in which the homopolymer constituting the primary phase is homo-PP are called polypropylene ICPs or polypropylene dispersions. ICPs in which the homopolymer constituting the primary phase is homo-PP are called block PPs. ICPs are also called heterophasic copolymers or block copolymers.

[0062] The thickness (thickness ratio) of the base material layer 4 can be 5 to 90, and preferably 25 to 70, relative to the total thickness of the sealing film 1, which is 100. That is, the thickness of the base material layer 4 can be 5 to 90% of the total thickness of the sealing film 1, and preferably 25 to 70%. When the thickness ratio of the base material layer 4 is equal to or greater than the above lower limit, the resin does not flow too much and tends to exhibit the fluidity required during pressure bonding.

[0063] When the thickness ratio of the base material layer 4 is equal to or less than the upper limit, a sufficient thickness can be imparted to the first adhesive layer 2. This increases the adhesive strength between the first adhesive layer 2 and the electrode lead wire 11. Furthermore, when the thickness ratio of the base material layer 4 is equal to or less than 90, the fluidity of the resin does not decrease, and the fluidity of the resin during thermocompression bonding can be controlled within an appropriate range.

[0064] The component (A) contained in the base layer 4 preferably contains a polypropylene resin having a melting point of 150°C or higher and 170°C or lower. When the melting point of the component (A) contained in the base material layer 4 is 150° C. or higher, the sealing film 1 can be provided with heat resistance. When the melting point of the component (A) contained in the base material layer 4 is 170° C. or less, flexibility can be imparted to the sealing film 1. Therefore, gaps are less likely to occur between the electrode lead wire 11 and the sealing film 1.

[0065] The melting point M4 of component (A) contained in the base layer 4 is preferably higher than the melting point M2 of the resin constituting the first adhesive layer 2 or the melting point M3 of the resin constituting the second adhesive layer 3. That is, the melting point M4 is preferably higher than the melting point M2 or the melting point M3. It is desirable that the melting point M4 be higher than both the melting point M2 and the melting point M3. In one embodiment of the present invention, it is desirable that the melting point M4 be higher than at least one of the melting point M2 and the melting point M3.

[0066] The resin film constituting the base layer 4 can be obtained by melt-kneading the above components (A), (B) and (C) in a predetermined ratio, followed by extrusion molding.

[0067] <Electrode lead wire components> As shown in FIG. 2, the electrode lead member 10 has an electrode lead 11 and a pair of sealing films 1. The pair of sealing films 1 are disposed with the first adhesive layers 2 facing each other. The pair of sealing films 1 sandwich the electrode lead wire 11. The pair of sealing films 1 are in contact with areas corresponding to one surface and the other surface of the electrode lead wire 11, respectively. Therefore, the pair of sealing films 1 are in contact with the entire periphery of the electrode lead wire 11 as a whole.

[0068] The electrode lead wire 11 has a lead wire body 111 and a surface treatment layer 112. The electrode lead wire 11 extends linearly in one direction. The electrode lead wire 11 is made of metal.

[0069] The electrode lead wire 11 is conductive. The electrode lead wire 11 is electrically connected to the lithium ion battery 30 (see FIG. 3). The electrode lead wire 11 conducts electricity between the lithium ion battery 30 and an external device. Known metals such as aluminum, copper, nickel, iron, gold, platinum, and various alloys can be used as the material for the lead wire body 111. Among these, aluminum or copper is preferred because of its excellent conductivity and cost advantage.

[0070] The surface of the lead wire body 111 may be nickel-plated. The nickel plating of the lead wire body 111 may be formed by electroplating using a Watts bath containing nickel sulfate, nickel chloride, boric acid, or the like as its 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 its main components. The plating film formed by this method has excellent flexibility and is therefore less likely to crack. The lead wire body 111 is preferably an aluminum plate or a nickel-plated copper plate.

[0071] The surface treatment layer 112 is formed on the surface of the lead wire body 111. The surface treatment layer 112 is corrosion-resistant. "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 an acid-resistant coating made of a material such as a phosphate, a chromate, a fluoride, or a triazine thiol compound. The acid-resistant coating can be formed by subjecting the lead wire body 111 to a chemical conversion treatment.

[0072] 2, the surface treatment layer 112 is formed on a part of the surface of the lead wire body 111, but the surface treatment layer 112 may be formed on the entire surface area of ​​the lead wire body 111. Note that the electrode lead wire does not necessarily need to have a surface treatment layer formed thereon.

[0073] Since the first adhesive layer 2, the base material layer 4, and the second adhesive layer 3 of the sealing film 1 have the above-described configurations, the sealing film 1 has good adhesive strength to the electrode lead wire 11. Furthermore, the sealing film 1 can maintain the adhesive strength between the resin layers that constitute the sealing film, and can prevent the resin layers from peeling off from each other.

[0074] The sealing film 1 has good adhesive strength to the electrode lead wire 11, and therefore can prevent water from penetrating from the outside into the container. The sealing film 1 maintains adhesive strength between the resin layers constituting the sealing film and can prevent peeling of the resin layers, thereby realizing a battery 100 that is resistant to deterioration and highly reliable.

[0075] The sealing film 1 contains acid-modified polyolefin as a material for forming the first adhesive layer 2. Therefore, the first adhesive layer 2 is easily heat-sealed to the electrode lead wire 11, and can seal the interface between the electrode lead wire 11 and the sealing film 1. This makes it possible to prevent water from entering the container from the outside.

[0076] The sealing film 1 contains an acid-modified polyolefin as a material for forming the second adhesive layer 3. Therefore, the second adhesive layer 3 is easily heat-sealed with the resin material constituting the battery container, and the interface between the container and the sealing film 1 is easily sealed.

[0077] The electrode lead wire member 10 includes the sealing film 1, and therefore can prevent water from entering the container from the outside.

[0078] <Battery> FIG. 3 is a schematic perspective view showing the battery 100 of the embodiment. As shown in FIG. 3, the battery 100 includes the above-described electrode lead wire member 10, a container 20, and a lithium ion battery 30 (battery body).

[0079] The storage container 20 has a container body 21 and a lid 22. The storage container 20 is an example of a "second base." The container body 21 has a molded portion 21a that forms a recess for accommodating the lithium-ion battery 30. The container body 21 is obtained by drawing a laminate for battery exterior packaging. The lid 22 is made of the laminate for battery exterior packaging and has the same area in a plan view as the container body 21. The laminate for battery exterior packaging will be described later. The storage container 20 is formed by overlapping a container body 21 and a lid 22 and heat-sealing a peripheral edge 25 thereof.

[0080] FIG. 4 is a cross-sectional view taken along line II in FIG. As shown in Figure 4, the battery exterior laminate, which is the constituent material of the container body 21 and the lid 22, is a laminate in which a first film substrate 201, a second film substrate 202, a metal foil 203, and a sealant layer 204 are laminated in this order.

[0081] The resin that constitutes the first film substrate 201 and the second film substrate 202 is not particularly limited, but polyamide, polyethylene terephthalate (PET), phenolic resin, polypropylene, etc. are suitable. The metal foil 203 is preferably an aluminum foil, a stainless steel foil, a copper foil, an iron foil, or the like.

[0082] The sealant layer 204 is in contact with and heat-sealed to the second adhesive layer 3 of the sealing film 1. A resin that can be fused to the sealing film 1 is selected as the resin that constitutes the sealant layer 204. Examples of the resin that constitutes the sealant layer 204 include polypropylene-based resins and polyethylene-based resins. As the polypropylene-based resin, a polypropylene homopolymer, a propylene-ethylene copolymer, etc. may be used. As the polyethylene-based resin, low-density polyethylene, linear low-density polyethylene, etc. may also be used.

[0083] 3 and 4, in the battery 100, the electrode lead wire 11 is drawn from the lithium ion battery 30 inside the container 20 (inside the molded portion 21a) to the outside of the container 20. The electrode lead wire 11 is fused to the sealant layer 204 of the container 20 via the sealing film 1.

[0084] According to the battery 100, the electrode lead wire member 10 has the above-mentioned sealing film 1, which can prevent water from penetrating from the outside into the container, thereby realizing a battery 100 that is resistant to deterioration and highly reliable.

[0085] Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, 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. For example, the first adhesive layer and the second adhesive layer may contain a resin other than polyolefin. [Example]

[0086] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0087] <Preparation of sealing film> A sealing film in which a first adhesive layer, a base layer, and a second adhesive layer were laminated in this order was produced as follows. The resins that served as the raw materials for each layer were separately heated and melted, and a laminate was obtained by simultaneous multilayer film formation using an extruder capable of simultaneous multilayer extrusion molding. This laminate was cut to a predetermined size to obtain the sealing films of each example and comparative example. The sealing film was formed into a strip shape (width 15 mm, thickness 150 μm).

[0088] The constituent materials of the first adhesive layer, the base material layer, and the second adhesive layer are as follows. First adhesive layer: maleic anhydride-modified polypropylene (melting point 140°C). In Table 1, this is indicated as (B). Second adhesive layer: random copolymer of propylene and ethylene (melting point 140°C). In Table 1, this is indicated as (C). Base layer: a resin composed of the above (B), (C) and (A), where (A) is polypropylene ICP (melting point 161°C).

[0089] In Table 1, the blending ratios of (A), (B), and (C) are the blending ratios (% by mass) shown in brackets [ ].

[0090] The melting point M4 of polypropylene ICP, which is the resin constituting the base layer, is higher than the melting point M2 of the resin constituting the first adhesive layer and the melting point M3 of the resin constituting the second adhesive layer.

[0091] Maleic anhydride-modified polypropylene is a polymer obtained by graft-polymerizing maleic anhydride onto a random copolymer of propylene and ethylene. Polypropylene ICP has a structure in which the second phase is dispersed within the first phase (sea-island structure). The first phase is composed of homo-PP. The second phase contains ethylene-propylene rubber and polyethylene. Polypropylene ICP is a mixture containing PP, ethylene-propylene rubber, and polyethylene.

[0092] <Making electrode lead wires> An electrode lead wire was fabricated using a rectangular nickel-plated copper foil measuring 45 mm wide and 52 mm long, with a surface treatment layer formed on the surface of the lead wire body.

[0093] <Production of Laminate for Battery Enclosure> A 12 μm thick PET film, a 15 μm thick nylon film, a 40 μm thick aluminum foil, and an 80 μm thick PP film were laminated by dry lamination to obtain a laminate for battery exterior packaging.

[0094] The PET film, nylon film, aluminum foil, and PP film correspond to the first film substrate 201, the second film substrate 202, the metal foil 203, and the sealant layer 204, respectively (see FIG. 4).

[0095] <Measurement of interlayer peel strength> The 180-degree peel strength of the sealing film was measured using a testing machine (a tabletop precision universal testing machine manufactured by Shimadzu Corporation: Autograph AGS-500NX).

[0096] A cut (half cut) several tens of micrometers deep was made from the first adhesive layer side of the sealing film. A cutter blade was inserted between the layers of the measurement specimen, which was a laminate of the sealing film and the base film, and a part of the layer was peeled off. The end of the sealing film and the end of the base film were gripped with the gripping parts of the testing machine, and the sealing film and the base film were peeled off in such a manner that the peeled layers were peeled off at 180 degrees. The peeling speed was 50 mm / min.

[0097] A peel strength of 20 N / 15 mm or more was judged as "OK" (good), indicating that peeling between the resins that make up the sealing film was suppressed. A peel strength of less than 20 N / 15 mm was judged as "NG" (poor), indicating that peeling between the resins that make up the sealing film was not suppressed.

[0098] <Measurement of adhesive strength to electrode lead wire> The adhesive strength of the sealing film to the electrode lead wire was measured as follows. The sealing film and the electrode lead wire were overlapped and heat-sealed to form a laminate, which was then cut into strips (10 mm wide x 120 mm long) to obtain test specimens. The heat-sealing conditions were 180°C, 0.5 MPa, and 10 seconds.

[0099] The 180-degree peel strength of this measurement specimen was measured using a testing machine (a table-top precision universal testing machine: Autograph AGS-500NX manufactured by Shimadzu Corporation) as follows.

[0100] The end of the sealing film and the end of the electrode lead wire were gripped by the gripping parts of the testing machine, and the sealing film was peeled from the electrode lead wire under the condition of 180-degree peeling at a peeling speed of 300 mm / min.

[0101] A peel strength of 20 N / 10 mm or more was judged as "OK" (good), indicating a high adhesive strength to the electrode lead wire. A peel strength of less than 20 N / 10 mm was judged as "NG" (poor), indicating a low adhesive strength to the electrode lead wire. The results are shown in Table 1.

[0102] [Table 1]

[0103] As shown in Table 1, in Comparative Examples 1 to 3, peeling occurred between the first adhesive layer and the base layer, or between the second adhesive layer and the base layer. In Comparative Example 4, although the resin layers did not peel off from each other, the adhesive strength to the electrode lead wire was low.

[0104] In contrast to this, it was found that in Examples 1 to 9, the adhesive strength to the electrode lead wire was high, and the adhesive strength between the layers was also high. [Explanation of symbols]

[0105] 1...sealing film, 2...first adhesive layer, 3...second adhesive layer, 4...base material layer, 10...electrode lead wire member, 11...electrode lead wire (first substrate), 20...container (second substrate), 30...lithium ion battery (battery body), 100...battery.

Claims

1. A sealing film for sealing between a first substrate and a second substrate made of metal, the sealing film comprising: a first adhesive layer that mainly contains an acid-modified polyolefin and adheres to the first substrate; a second adhesive layer that mainly contains a polyolefin and adheres to the second substrate; and a base layer provided between the first adhesive layer and the second adhesive layer, wherein the base layer comprises the following components (A), (B), and (C): the ratio (A) / [(B)+(C)] of the total amount of the component (B) and the component (C) to the content of the component (A) is 90 / 10 to 20 / 80; the content of the component (B) relative to the total amount of the components (A), (B), and (C) is 5% by mass or more and 70% by mass or less, the content of the component (C) relative to the total amount of the components (A), (B), and (C) is 5% by mass or more and 70% by mass or less, The melting point of the component (A) is higher than the melting point of the resin constituting the first adhesive layer or the second adhesive layer. Component (B): a resin that constitutes the first adhesive layer. Component (C): a resin that constitutes the second adhesive layer. Component (A): A resin different from the components (B) and (C).

2. The sealing film according to claim 1 , wherein the polyolefin constituting the second adhesive layer includes an acid-modified polyolefin.

3. The sealing film described in Claim 2, wherein the (A) component includes a polypropylene resin having a melting point of 150°C or more and 170°C or less, and the resin constituting the second adhesive layer is an acid-modified polypropylene having a melting point of 110°C or more and 150°C or less.

4. The component (A) includes a polypropylene resin having a melting point of 150°C or more and 170°C or less, and the resin constituting the second adhesive layer is polypropylene having a melting point of 110°C or more and 150°C or less or an acid-modified polypropylene having a melting point of 110°C or more and 150°C or less. The sealing film according to claim 1.

5. The sealing film according to any one of claims 1 to 4, wherein the resin constituting the first adhesive layer is an acid-modified polypropylene having a melting point of 110°C or higher and 150°C or lower.

6. An electrode lead wire member comprising: the sealing film according to any one of claims 1 to 5; and the first base body being an electrode lead wire extending in one direction.

7. A battery comprising: the electrode lead member according to claim 6; a battery body to which the electrode lead is connected; and the second base serving as a container for accommodating the battery body.

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