HK1246003B - Cell packaging material, method for manufacturing same, and cell - Google Patents

Description

Battery packaging material, method for producing the same, and battery

Technical Field

The present invention relates to a battery packaging material, a method for producing the same, and a battery.

Background Art

Various types of batteries have been developed. These batteries require packaging materials to encapsulate battery elements, including electrodes and electrolytes. Metal packaging materials are commonly used as battery packaging materials.

In recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, computers, cameras, mobile phones, and other devices, there has been a demand for batteries with diverse shapes. Furthermore, batteries are being required to be thinner and lighter. However, conventional metal packaging materials are difficult to accommodate this diverse battery shape. Furthermore, since these packaging materials are made of metal, their lightweighting is limited.

Therefore, as a battery packaging material that can be easily processed into various shapes and can achieve thickness reduction and weight reduction, a film-shaped laminated body comprising a base material layer/metal layer/thermo-fusible resin layer laminated in this order has been proposed.

For example, Patent Document 1 discloses a battery case packaging material including a biaxially stretched polyamide film layer as an outer layer, an unstretched thermoplastic resin film layer as an inner layer, and an aluminum foil layer disposed between the two film layers.

In addition, Patent Document 2 discloses an exterior material for a lithium-ion battery, which is laminated in this order: a base layer, an adhesive layer, an aluminum foil layer provided with an anti-corrosion treatment layer, an adhesive resin layer, and a sealing layer provided on the side of the adhesive resin layer opposite to the above-mentioned base layer, wherein the adhesive resin layer contains an acid-modified polyolefin resin and an elastomer.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Laid-Open No. 2008-287971

Patent Document 2: Japanese Patent Application Laid-Open No. 2013-258162

Summary of the Invention

Technical problem to be solved by the invention

However, the inventors of the present invention have conducted intensive studies and have discovered a technical problem in that insulation and durability may be reduced when the battery packaging material disclosed in Patent Document 2 is used for batteries.

The inventors of the present invention conducted further in-depth research and discovered that during the battery manufacturing process, tiny foreign matter, such as fragments of electrode active material or electrode sheets, may adhere to the surface of the heat-fusible resin layer. Due to the heat and pressure of heat-sealing the battery element with the battery packaging material, the heat-fusible resin layer may become thinner in the area where the foreign matter adheres. For example, if the heat-fusible resin layer becomes thinner in areas where the heat-sealed layers are heat-sealed, the insulation and durability of the battery packaging material may become insufficient.

Furthermore, tiny foreign matter, such as fragments of electrode active material or electrode sheet, is conductive. If conductive foreign matter is present between the electrode sheet and the heat-fusible resin layer, the heat and pressure during heat sealing could cause the foreign matter to penetrate the heat-fusible resin layer and potentially lead to an electrical connection between the electrode sheet and the metal layer of the battery packaging material, resulting in a short circuit.

The present invention was completed in response to these problems. Specifically, the main object of the present invention is to provide a battery packaging material that exhibits high insulation and durability even when minute foreign matter, such as fragments of electrode active material or electrode sheet, is present in heat-sealed areas, such as the interface between heat-fusible resin layers or between an electrode sheet and a heat-fusible resin layer.

Methods used to solve technical problems

The inventors of the present invention conducted intensive research to address the above-mentioned technical problems. As a result, they discovered that by forming a battery packaging material into a laminate comprising at least a substrate layer, a metal layer, an adhesive layer, and a heat-fusible resin layer in this order, and comprising the adhesive layer comprising a resin composition comprising an acid-modified polyolefin with a melting point of 50-120°C and an epoxy resin with a weight-average molecular weight of 50-2000, a battery packaging material with excellent insulation and durability can be obtained. Furthermore, the inventors discovered that by forming a battery packaging material into a laminate comprising at least a substrate layer, a metal layer, an adhesive layer, and a heat-fusible resin layer in this order, and comprising the adhesive layer comprising a resin composition comprising an acid-modified polyolefin and an epoxy resin, when measuring probe displacement using a thermomechanical analyzer, when a probe is placed on the adhesive layer surface at an end of the battery packaging material and heated from 40°C to 220°C, the probe position does not decrease compared to the initial value, indicating that such a battery packaging material also exhibits excellent insulation and durability. The first invention of the present invention was developed based on this finding and further research.

That is, the first invention provides a battery packaging material, a method for producing the same, and a battery in the following embodiments.

Item 1A. A battery packaging material comprising a laminate comprising at least a base material layer, a metal layer, an adhesive layer, and a heat-fusible resin layer in this order,

The adhesive layer comprises a resin composition containing an acid-modified polyolefin and an epoxy resin,

In measuring probe displacement using a thermomechanical analyzer, the probe was placed on the adhesive layer surface at the end of the battery packaging material. When the probe was heated from 40°C to 220°C, the probe position did not drop from the initial value.

Item 2A. The battery packaging material according to Item 1A, wherein, in measurement of probe displacement using a thermomechanical analyzer, the probe is disposed on the surface of the adhesive layer at an end portion of the battery packaging material, and when the probe is heated from 40°C to 220°C, the amount of rise in the position of the probe when heated from 140°C to 220°C is greater than the amount of rise in the position of the probe when heated from 80°C to 120°C.

Item 3A. The battery packaging material according to Item 1A or 2A, wherein the adhesive layer comprises a resin composition comprising an acid-modified polyolefin having a melting point of 50° C. to 120° C. and an epoxy resin having a weight-average molecular weight of 50 to 2000.

Item 4A. A battery packaging material comprising a laminate comprising at least a base material layer, a metal layer, an adhesive layer, and a heat-fusible resin layer in this order,

The adhesive layer has a resin composition containing an acid-modified polyolefin having a melting point of 50° C. to 120° C. and an epoxy resin having a weight-average molecular weight of 50 to 2000.

Item 5A. The battery packaging material according to any one of Items 1A to 4A, wherein the adhesive layer has a solid content of 0.5 g/m ² or more and 10 g/m ² or less.

Item 6A. The battery packaging material according to any one of Items 1A to 5A, wherein the adhesive layer has a thickness of 0.6 μm to 9 μm.

Item 7A. The battery packaging material according to any one of Items 1A to 6A, wherein the adhesive layer contains 0.5 parts by mass to 20 parts by mass of the epoxy resin per 100 parts by mass of the acid-modified polyolefin.

Item 8A. The battery packaging material according to any one of Items 1A to 7A, wherein the adhesive layer has a melting temperature in the range of 180° C. to 260° C.

Item 9A. The battery packaging material according to any one of Items 1A to 8A, wherein the thickness of the thermally fusible resin layer is in a range of 10 μm to 40 μm.

Item 10A. The battery packaging material according to any one of Items 1A to 9A, wherein the surface of the thermally adhesive resin layer has fine irregularities.

Item 11A. A battery comprising a battery element including a positive electrode, a negative electrode, and an electrolyte housed in a packaging body formed of the battery packaging material according to any one of Items 1A to 10A.

Item 12A. A method for producing a battery packaging material, comprising a lamination step of obtaining a laminate having at least a base material layer, a metal layer, an adhesive layer, and a heat-fusible resin layer in this order,

The adhesive layer is formed by using a resin composition containing an acid-modified polyolefin and an epoxy resin.

The adhesive layer used is one that satisfies the following conditions: when the probe is placed on the adhesive layer surface at the end of the battery packaging material and heated from 40°C to 220°C, the probe position does not drop compared to the initial value during measurement of probe displacement using a thermomechanical analyzer.

Furthermore, the inventors of the present invention conducted further intensive research to address the aforementioned technical issues. As a result, they discovered that by forming a battery packaging material into a laminate comprising at least a base layer, a metal layer, a first insulating layer, a second insulating layer, and a heat-fusible resin layer in this order, and by setting the melting temperature of the first insulating layer to 200°C or higher and the melting temperature of the second insulating layer to lower than the melting temperature of the first insulating layer, a battery packaging material with high insulation properties and durability can be obtained. The second invention of the present invention was developed based on this finding and further research.

That is, the second invention provides a battery packaging material, a method for producing the same, and a battery in the following embodiments.

Item 1B. A battery packaging material comprising a laminate comprising at least a base material layer, a metal layer, a first insulating layer, a second insulating layer, and a heat-fusible resin layer in this order,

The melting temperature of the first insulating layer is above 200°C.

The melting temperature of the second insulating layer is lower than the melting temperature of the first insulating layer.

Item 2B. The battery packaging material according to Item 1B, wherein the first insulating layer is formed of an acid-modified polyolefin and an epoxy resin.

Item 3B. The battery packaging material according to Item 1B or 2B, wherein the second insulating layer is formed of polypropylene having a melting temperature of 150° C. or higher.

Item 4B. The battery packaging material according to any one of Items 1B to 3B, wherein the melting temperature of the heat-fusible resin layer is lower than the melting temperature of the second insulating layer.

Item 5B. The battery packaging material according to any one of Items 1B to 4B, wherein the first insulating layer and the second insulating layer are bonded to each other via an adhesive layer.

Item 6B. The battery packaging material according to any one of Items 1B to 5B, wherein the first insulating layer has a thickness of 10 μm or less.

Item 7B. The battery packaging material according to any one of Items 1B to 6B, wherein the second insulating layer has a thickness of 10 μm to 50 μm.

Item 8B. The battery packaging material according to any one of Items 5B to 7B, wherein the adhesive layer has a thickness of 20 μm or less.

Item 9B. The battery packaging material according to any one of Items 1B to 8B, wherein the thermally fusible resin layer is formed of a polyolefin.

Item 10B. The battery packaging material according to any one of Items 1B to 9B, wherein the surface of the thermally adhesive resin layer has fine irregularities.

Item 11B. The battery packaging material according to any one of Items 1B to 10B, wherein the heat-fusible resin layer is formed of a plurality of layers, and the innermost layer of the heat-fusible resin layer is formed by dry lamination or extrusion molding.

Item 12B. A battery formed by encapsulating a battery element including a positive electrode, a negative electrode, and an electrolyte in a packaging body formed from the battery packaging material according to any one of Items 1B to 11B.

Item 13B. A method for manufacturing a battery packaging material, comprising the steps of stacking at least a base material layer, a metal layer, a first insulating layer, a second insulating layer and a heat-fusible resin layer in sequence to obtain a laminate, wherein the melting temperature of the first insulating layer is set to be above 200°C, and the melting temperature of the second insulating layer is set to be lower than the melting temperature of the first insulating layer.

Effects of the Invention

The battery packaging material of the present invention can provide a battery packaging material with high insulation and durability, even when minute foreign matter, such as fragments of electrode active material or electrode sheets, is present in heat-sealed areas, such as the interface between heat-fusible resin layers or between an electrode sheet and a heat-fusible resin layer. In other words, by encapsulating battery elements with the battery packaging material of the present invention, the insulation and durability of the battery can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic cross-sectional view of an example of a battery packaging material according to the first invention.

FIG2 is a schematic cross-sectional view of an example of the battery packaging material according to the first invention.

FIG3 is a schematic cross-sectional view of an example of the battery packaging material according to the first invention.

FIG. 4 is a conceptual diagram of a change in the position of a probe during measurement of the displacement of the probe using a thermomechanical analyzer.

FIG. 5 is a schematic diagram for explaining the method of “durability evaluation” in Examples.

FIG. 6 is a schematic diagram for explaining a method of “evaluating insulation performance against foreign matter inclusion” in the examples.

7 is a graph showing the relationship between the heating temperature and the displacement of the probe position when a probe of a thermomechanical analyzer is placed on the surface of the adhesive layer at the end of the battery packaging material obtained in Example 10A and the probe is heated from 40° C. to 250° C.

8 is a graph showing the relationship between the heating temperature and the displacement of the probe position when a probe of a thermomechanical analyzer is placed on the adhesive layer surface of the end portion of the battery packaging material obtained in Comparative Example 11A and the probe is heated from 40° C. to 250° C.

FIG9 is a schematic cross-sectional view of an example of a battery packaging material according to the second invention.

FIG10 is a schematic cross-sectional view of an example of a battery packaging material according to the second invention.

FIG11 is a schematic cross-sectional view of an example of a battery packaging material according to the second invention.

FIG12 is a schematic cross-sectional view of an example of a battery packaging material according to the second invention.

DETAILED DESCRIPTION

In a first embodiment of the first invention, a battery packaging material is characterized by comprising a laminate comprising at least a base layer, a metal layer, an adhesive layer, and a heat-fusible resin layer in this order, wherein the adhesive layer comprises a resin composition comprising an acid-modified polyolefin having a melting point of 50-120°C and an epoxy resin having a weight-average molecular weight of 50-2000. Furthermore, in a second embodiment of the first invention, a battery packaging material is characterized by comprising a laminate comprising at least a base layer, a metal layer, an adhesive layer, and a heat-fusible resin layer in this order, wherein the adhesive layer comprises a resin composition comprising an acid-modified polyolefin and an epoxy resin. When measuring probe displacement using a thermomechanical analyzer, the probe is placed on the surface of the adhesive layer at an end of the battery packaging material, and when the probe is heated from 40°C to 220°C, the probe position does not decrease compared to an initial value. The battery packaging material of the present invention, its production method, and a battery of the present invention obtained by encapsulating a battery element with the battery packaging material of the present invention will be described in detail below with reference to Figures 1 to 3. In the following description, the contents that are not common to the first embodiment and the second embodiment are clearly indicated, and are common to the first embodiment unless otherwise specified.

The battery packaging material of the second invention is characterized by comprising a laminate comprising at least a base material layer, a metal layer, a first insulating layer, a second insulating layer, and a heat-fusible resin layer in this order, wherein the first insulating layer has a melting temperature of 200°C or higher, and the second insulating layer has a melting temperature lower than that of the first insulating layer. The battery packaging material of the present invention, its manufacturing method, and the battery of the second invention obtained by encapsulating a battery element with the battery packaging material of the second invention are described in detail below with reference to Figures 9 to 12 . In the following description, matters not common to the first and second inventions are explicitly indicated; unless otherwise noted, they are common. For example, the base material layer 1, adhesive layer 2, metal layer 3, and surface covering layer are common to the first and second inventions.

1. Laminated structure of battery packaging materials

As shown in Figure 1, the battery packaging material of the first invention comprises a laminate comprising at least a base layer 1, a metal layer 3, an adhesive layer 4, and a heat-fusible resin layer 5, in that order. In the battery packaging material of the first invention, the base layer 1 forms the outermost layer, and the heat-fusible resin layer 5 forms the innermost layer. In other words, during battery assembly, the heat-fusible resin layers 5 located at the edges of the battery element are heat-fused together, sealing the battery element and thereby encapsulating the battery element.

As shown in FIG. 2 , in the battery packaging material of the first invention, an adhesive layer 2 may be provided between the base material layer 1 and the metal layer 3 as needed for the purpose of improving the adhesion between them.

As shown in Figure 9, the battery packaging material of the second invention comprises a laminate comprising at least a base layer 1, a metal layer 3, a first insulating layer 51, a second insulating layer 52, and a heat-fusible resin layer 41, in that order. In the battery packaging material of the second invention, without a surface covering layer (described later), the base layer 1 serves as the outermost layer, and the heat-fusible resin layer 41 serves as the innermost layer. Specifically, during battery assembly, the heat-fusible resin layers 41 located at the edges of the battery element are heat-fused together, sealing the battery element and thereby encapsulating the battery element.

As shown in FIG10 , in the battery packaging material of the second invention, an adhesive layer 2 may be provided, if necessary, between the base material layer 1 and the metal layer 3 to improve adhesion therebetween. Furthermore, as shown in FIG11 and FIG12 , in the battery packaging material of the second invention, an adhesive layer 6 may be provided, if necessary, between the first insulating layer 51 and the second insulating layer 52 to improve adhesion therebetween. Furthermore, as shown in FIG12 , an adhesive layer 7 may be provided, if necessary, between the metal layer 3 and the first insulating layer 51 to improve adhesion therebetween.

2. Composition of each layer forming the battery packaging material

[Base material layer 1]

In the battery packaging material of the present invention, the substrate layer 1 is a layer located on the outermost side. There are no particular restrictions on the raw materials forming the substrate layer 1 as long as they have insulating properties. As raw materials forming the substrate layer 1, for example, resin films such as polyester resins, polyamide resins, epoxy resins, acrylic resins, fluororesins, polyurethane resins, silicone resins, phenolic resins, and mixtures or copolymers thereof can be cited. Among them, polyester resins and polyamide resins are preferred, and biaxially stretched polyester resins and biaxially stretched polyamide resins are more preferred. As polyester resins, specifically polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolyesters, polycarbonates, etc. can be cited. In addition, as polyamide resins, specifically nylon 6, nylon 6,6, copolymers of nylon 6 and nylon 6,6, nylon 6,10, poly(m-xylene adipamide) (MXD6), etc. can be cited.

The substrate layer 1 can be formed by a single layer of resin film, but in order to improve pinhole resistance and insulation, it can also be formed by two or more layers of resin film. Specifically, a multilayer structure obtained by laminating a polyester film with a nylon film, a multilayer structure obtained by laminating multiple layers of nylon films, a multilayer structure obtained by laminating multiple layers of polyester films, etc. can be cited. When the substrate layer 1 is a multilayer structure, preferably a laminate of a biaxially stretched nylon film and a biaxially stretched polyester film, a laminate obtained by laminating multiple layers of biaxially stretched nylon films, or a laminate obtained by laminating multiple layers of biaxially stretched polyester films. For example, when the substrate layer 1 is formed by two layers of resin film, preferably a structure obtained by laminating a polyester resin with a polyester resin, a structure obtained by laminating a polyamide resin with a polyamide resin, or a structure obtained by laminating a polyester resin with a polyamide resin, more preferably a structure obtained by laminating a polyethylene terephthalate with a polyethylene terephthalate, a structure obtained by laminating a nylon with a nylon, or a structure obtained by laminating a polyethylene terephthalate with a nylon. Furthermore, since polyester resin is less likely to discolor when, for example, an electrolyte solution adheres to the surface, in this laminated structure, the base layer 1 is preferably laminated so that the polyester resin is located as the outermost layer. When the base layer 1 has a multilayer structure, the thickness of each layer is preferably 2 μm or more and 25 μm or less.

When the substrate layer 1 is formed from a multilayer resin film, two or more resin film layers may be laminated together via an adhesive component such as an adhesive or adhesive resin. The type and amount of the adhesive component used are the same as those for the adhesive layer 2 described below. The method for laminating the two or more resin film layers is not particularly limited, and known methods can be employed. Examples include dry lamination and sandwich lamination, with dry lamination being preferred. When dry lamination is employed, a polyurethane adhesive is preferably used as the adhesive layer. In this case, the thickness of the adhesive layer may be, for example, between 2 μm and 5 μm.

The thickness of the base material layer 1 is not particularly limited as long as it can function as a base material layer, and can be, for example, about 4 μm to 50 μm, preferably about 10 μm to 35 μm.

[Adhesive layer 2]

In the battery packaging material of the present invention, the adhesive layer 2 is a layer provided between the base material layer 1 and the metal layer 3 as needed in order to firmly bond them together.

The adhesive layer 2 is formed from an adhesive capable of bonding the base material layer 1 to the metal layer 3. The adhesive used to form the adhesive layer 2 may be a two-component curing adhesive or a single-component curing adhesive. Furthermore, the adhesive used to form the adhesive layer 2 is not particularly limited in its bonding mechanism, and any bonding mechanism, such as a chemical reaction type, a solvent evaporation type, a hot melt type, or a hot press type, may be employed.

Specific examples of adhesive components that can be used to form the adhesive layer 2 include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, polycarbonate, and copolyesters; polyether adhesives; polyurethane adhesives; epoxy resins; phenolic resins; polyamide resins such as nylon 6, nylon 66, nylon 12, and copolyamides; polyolefin resins such as polyolefins, carboxylic acid-modified polyolefins, and metal-modified polyolefins; and polyvinyl acetate resins; cellulose adhesives; (meth)acrylic resins; polyimide resins; amino resins such as urea resins and melamine resins; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; and silicone resins. These adhesive components can be used alone or in combination of two or more. Among these adhesive components, polyurethane-based adhesives are preferably used.

The thickness of the adhesive layer 2 is not particularly limited as long as it can function as an adhesive layer, and can be, for example, about 1 μm to 10 μm, preferably about 2 μm to 5 μm.

[Metal layer 3]

In the battery packaging material, the metal layer 3 is a layer that improves the strength of the battery packaging material and functions as a barrier layer for preventing water vapor, oxygen, light, etc. from penetrating into the interior of the battery. Specific examples of the metal constituting the metal layer 3 include aluminum, stainless steel, titanium, etc., with aluminum being preferred. The metal layer 3 can be formed by metal foil or metal vapor deposition, and is preferably formed of metal foil, more preferably of aluminum foil. From the perspective of preventing wrinkles or pinholes from forming in the metal layer 3 during the manufacture of the battery packaging material, it is more preferably formed of soft aluminum foil such as annealed aluminum (JIS H4160A8021H-O, JIS H4160A8079H-O, JIS H4000: 2014A8021P-O, JIS H4000: 2014A8079P-O).

The thickness of the metal layer 3 is not particularly limited as long as it can function as a barrier layer for water vapor and the like, and may be, for example, approximately 10 μm to 50 μm, preferably approximately 10 μm to 35 μm.

In addition, in order to stabilize adhesion, prevent dissolution or corrosion, etc., it is preferred to perform chemical surface treatment on at least one surface, preferably both surfaces, of the metal layer 3. Here, chemical surface treatment refers to a treatment for forming an acid-resistant coating on the surface of the metal layer. Examples of chemical surface treatment include: chromate treatment using chromic acid compounds such as chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, dihydrogen chromium phosphate, chromic acid acetoacetate, chromium chloride, and potassium chromium sulfate; chromate phosphate treatment using phosphoric acid compounds such as sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphoric acid; and chromate treatment using an aminophenol polymer having repeating units represented by the following general formulas (1) to (4). In the aminophenol polymer, the repeating units represented by the following general formulas (1) to (4) may be included alone or in any combination of two or more.

In the general formulae (1) to (4), X represents a hydrogen atom, a hydroxyl group, an alkyl group, a hydroxyalkyl group, an allyl group, or a benzyl group. Furthermore, R ¹ and R ² are the same or different and represent a hydroxyl group, an alkyl group, or a hydroxyalkyl group. In the general formulae (1) to (4), examples of the alkyl group represented by X, R ¹ , and R ² include linear or branched alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl. Furthermore, examples of the hydroxyalkyl group represented by X, R ¹ , and R ² include linear or branched alkyl groups having 1 to 4 carbon atoms substituted with one hydroxyl group, such as hydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl, 1-hydroxypropyl, 2-hydroxypropyl, 3-hydroxypropyl, 1-hydroxybutyl, 2-hydroxybutyl, 3-hydroxybutyl, and 4-hydroxybutyl. In general formulae (1) to (4), the alkyl and hydroxyalkyl groups represented by X, ^R1 , and ^R2 may be the same or different. In general formulae (1) to (4), X is preferably a hydrogen atom, a hydroxyl group, or a hydroxyalkyl group. The number average molecular weight of the aminophenol polymer having repeating units represented by general formulae (1) to (4) is preferably from 500 to 1,000,000, and more preferably from 1,000 to 20,000.

Another example of a chemical surface treatment method for imparting corrosion resistance to the metal layer 3 is a method in which a material containing fine particles of a metal oxide such as aluminum oxide, titanium oxide, cerium oxide, or tin oxide, or barium sulfate, dispersed in phosphoric acid is applied and sintered at a temperature above 150°C to form a corrosion-resistant layer on the surface of the metal layer 3. Furthermore, a resin layer formed by crosslinking a cationic polymer with a crosslinking agent may be formed on the corrosion-resistant layer. Examples of cationic polymers include polyethyleneimine, ionic polymer complexes formed from polyethyleneimine and a polymer having a carboxylic acid, primary amine-grafted acrylic resins formed by grafting a primary amine onto an acrylic acid backbone, polyallylamine or its derivatives, and aminophenol. These cationic polymers may be used singly or in combination. Examples of crosslinking agents include compounds having at least one functional group selected from isocyanate, glycidyl, carboxyl, and oxazoline groups, and silane coupling agents. These crosslinking agents may be used singly or in combination.

Chemical surface treatment can be carried out by only one chemical surface treatment, or by combining two or more chemical surface treatments. In addition, these chemical surface treatments can be carried out using one compound alone, or by combining two or more compounds. Among the chemical surface treatments, preferably chromic acid chromate treatment, or chromate treatment in which a chromic acid compound, a phosphoric acid compound, and an aminophenol polymer are combined, etc.

There is no particular limitation on the amount of the acid-resistant coating formed on the surface of the metal layer 3 during the chemical conversion surface treatment. For example, during the chromate treatment, the surface of the metal layer 3 preferably contains, per 1 m ² , a chromic acid compound in an amount of not less than about 0.5 mg and not more than about 50 mg, preferably not less than about 1.0 mg and not more than about 40 mg, calculated as chromium; a phosphorus compound in an amount of not less than about 0.5 mg and not more than about 50 mg, preferably not less than about 1.0 mg and not more than about 40 mg, calculated as phosphorus; and an aminophenol polymer in an amount of not less than about 1 mg and not more than about 200 mg, preferably not less than about 5.0 mg and not more than about 150 mg.

Chemical surface treatment is performed by applying a solution containing a compound for forming an acid-resistant coating to the surface of the metal layer using a bar coating method, a roll coating method, a gravure coating method, a dipping method, or the like, and then heating the metal layer to a temperature of about 70°C to about 200°C. Furthermore, before chemical surface treatment is performed on the metal layer, the metal layer may be degreased in advance using an alkali immersion method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or the like. By performing these degreasing treatments, the chemical surface treatment of the metal layer can be performed more efficiently.

[Adhesive layer 4]

In the first invention, the adhesive layer 4 is provided between the metal layer 3 and the thermally adhesive resin layer 5 in order to improve the insulation and durability of the battery packaging material.

In the first embodiment of the first invention, the adhesive layer 4 has a resin composition comprising an acid-modified polyolefin having a melting point of 50°C to 120°C and an epoxy resin having a weight-average molecular weight of 50 to 2000. The adhesive layer 4 is preferably formed from the resin composition. The adhesive layer 4 may contain additives such as an anti-blocking agent (silicon dioxide, etc.), and the additives, etc. may be contained in the resin composition. In addition, in the resin composition contained in the adhesive layer 4, the acid-modified polyolefin having a melting point of 50°C to 120°C serves as a main agent, and the epoxy resin having a weight-average molecular weight of 50 to 2000 functions as a curing agent. In the battery packaging material, the resin composition forms a cured product. In addition, in the second embodiment of the first invention, the adhesive layer 4 has a resin composition comprising an acid-modified polyolefin and an epoxy resin. In the resin composition contained in the adhesive layer 4 of the second embodiment, the acid-modified polyolefin serves as a main agent, and the epoxy resin serves as a curing agent. In the battery packaging material, the resin composition forms a cured product. In the second embodiment as well, the melting point of the acid-modified polyolefin is preferably 50° C. or higher and 120° C. or lower, and the weight average molecular weight of the epoxy resin is preferably 50 or higher and 2000 or lower.

For example, as shown in the schematic diagram of Figure 4 , when measuring the displacement of a probe using a thermomechanical analyzer, the thermomechanical analyzer probe 10 is first placed on the surface of the adhesive layer 4 at the end of the battery packaging material (measurement start A in Figure 4 ). The end in this case is the portion of the adhesive layer 4 exposed by cutting through the center of the battery packaging material in the thickness direction. Cutting can be performed using a commercially available rotary microtome, etc. When measuring the displacement of a battery packaging material used for batteries enclosing an electrolyte, etc., the measurement is performed on the portion of the battery packaging material where the heat-fusible resin layers are heat-fused to each other. An atomic force microscope equipped with an arm with a heating mechanism can be used as the thermomechanical analyzer. The tip radius of the probe 10 is set to 30 nm or less, the load applied to the probe 10 is a deviation of -4 V, and the heating rate is 5°C/minute. Next, when the probe is heated in this state, the heat from the probe causes the surface of the adhesive layer 4 to expand, as shown in Figure 4 B, pushing up the probe 10, and raising the position of the probe 10 compared to its initial value (the position when the probe temperature is 40°C). As the heating temperature rises further, the adhesive layer 4 softens, and as shown in FIG4C, the probe 10 pierces the adhesive layer 4, and the position of the probe 10 drops. In the measurement of probe displacement using a thermomechanical analyzer, the battery packaging material to be measured is at room temperature (25°C), and the probe, heated to 40°C, is placed on the surface of the adhesive layer 4 to begin the measurement.

In the battery packaging materials of the first and second embodiments of the first invention, from the perspective of further improving insulation and durability, it is preferred that the position of the probe 10 provided on the surface of the adhesive layer 4 does not drop compared to its initial value (the position when the probe temperature was 40°C) when the probe is heated from 40°C to 220°C (more preferably, from 40°C to 250°C). More preferably, the position of the probe 10 provided on the surface of the adhesive layer 4 does not drop when heated from 160°C to 200°C. The process of heat-sealing the heat-fusible resin layers of the battery packaging material to encapsulate the battery element is typically performed at a temperature of approximately 160°C to 200°C. Therefore, a battery packaging material in which the position of the probe 10 provided on the surface of the adhesive layer 4 does not drop when the probe is heated from 160°C to 200°C can exhibit particularly high insulation and durability.

From the same perspective, when measuring the displacement of the probe 10 using a thermomechanical analyzer, the probe 10 is placed on the surface of the adhesive layer 4 at the end of the battery packaging material, and the probe is heated from 40°C to 220°C (more preferably from 40°C to 250°C). Preferably, the amount of displacement of the probe 10 when heated from 140°C to 220°C is greater than the amount of displacement of the probe 10 when heated from 80°C to 120°C.

As described above, during the battery manufacturing process, tiny foreign matter such as fragments of electrode active material or electrode sheets may adhere to the surface of the heat-fusible resin layer. This can cause thin-walled areas or through-holes in the heat-fusible resin layer, leading to reduced insulation. In contrast, in the battery packaging material of the first embodiment of the first invention, since the adhesive layer 4 that bonds the metal layer 3 and the heat-fusible resin layer 5 comprises the resin composition having the specific composition described above, even when tiny foreign matter such as fragments of electrode active material or electrode sheets is present at the interface between the heat-fusible resin layers or in heat-sealed areas such as between the electrode sheet and the heat-fusible resin layer, the insulation and durability of the battery packaging material can be improved.

Furthermore, in the battery packaging material according to the second embodiment of the first invention, the adhesive layer 4 comprises a resin composition comprising an acid-modified polyolefin and an epoxy resin. Furthermore, in measuring probe displacement using a thermomechanical analyzer, when the probe is placed on the adhesive layer surface at an end of the battery packaging material and heated from 40°C to 220°C, the probe position does not deviate from its initial value. Consequently, as in the first embodiment, the insulation and durability of the battery packaging material can be improved.

In the first and second embodiments of the first invention, the acid-modified polyolefin is preferably a polyolefin modified with an unsaturated carboxylic acid or its anhydride. Furthermore, the acid-modified polyolefin may be further modified with a (meth)acrylate. The modified polyolefin further modified with a (meth)acrylate is a polyolefin obtained by acid-modifying the polyolefin with an unsaturated carboxylic acid or its anhydride and a (meth)acrylate. In the present invention, "(meth)acrylate" refers to "acrylate" or "methacrylate." The acid-modified polyolefin may be used alone or in combination of two or more.

The acid-modified polyolefin is not particularly limited as long as it is a resin containing at least an olefin as a monomer unit. The polyolefin can be composed of, for example, at least one of polyethylene and polypropylene, and is preferably composed of polypropylene. Polyethylene can be composed of, for example, at least one of homopolyethylene and an ethylene copolymer. Polypropylene can be composed of, for example, at least one of homopolypropylene and a propylene copolymer. Examples of propylene copolymers include copolymers of propylene and other olefins such as ethylene-propylene copolymers, propylene-butene copolymers, and ethylene-propylene-butene copolymers. From the perspective of further improving the insulation and durability of battery packaging materials, the proportion of propylene units contained in polypropylene is preferably between 50 mol% and 100 mol%, more preferably between 80 mol% and 100 mol%. In addition, from the perspective of further improving the insulation and durability of battery packaging materials, the proportion of ethylene units contained in polyethylene is preferably between 50 mol% and 100 mol%, more preferably between 80 mol% and 100 mol%. The ethylene copolymer and the propylene copolymer can each be a random copolymer or a block copolymer. The ethylene copolymer and the propylene copolymer may be crystalline or amorphous, or may be a copolymer or a mixture thereof. The polyolefin may be composed of one homopolymer or copolymer, or may be composed of two or more homopolymers or copolymers.

Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, and crotonic acid. Acid anhydrides are preferably anhydrides of the unsaturated carboxylic acids exemplified above, with maleic anhydride and itaconic anhydride being more preferred. The acid-modified polyolefin may be modified with a single unsaturated carboxylic acid or its anhydride, or may be modified with two or more unsaturated carboxylic acids or their anhydrides.

Examples of (meth)acrylates include esters of (meth)acrylic acid and alcohols having 1 to 30 carbon atoms, preferably esters of (meth)acrylic acid and alcohols having 1 to 20 carbon atoms. Specific examples of (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. In the modification of polyolefins, the (meth)acrylates may be used alone or in combination of two or more.

The proportion of the unsaturated carboxylic acid or its anhydride in the acid-modified polyolefin is preferably from 0.1% to 30% by mass, more preferably from 0.1% to 20% by mass. By setting it within this range, the insulation and durability of the battery packaging material can be further improved.

The ratio of (meth)acrylate in the acid-modified polyolefin is preferably from 0.1% to 40% by mass, more preferably from 0.1% to 30% by mass. By setting the ratio within this range, the insulation and durability of the battery packaging material can be further improved.

The weight-average molecular weight of the acid-modified polyolefin is preferably from about 6,000 to about 200,000, more preferably from about 8,000 to about 150,000. In the present invention, the weight-average molecular weight of the acid-modified polyolefin is a value measured by gel permeation chromatography (GPC) using polystyrene as a standard sample. The melting point of the acid-modified polyolefin is preferably from about 50°C to about 120°C, more preferably from about 50°C to about 100°C. In the present invention, the melting point of the acid-modified polyolefin refers to the endothermic peak temperature in differential scanning calorimetry.

In the acid-modified polyolefin, the modification method of the polyolefin is not particularly limited, and for example, any method that can copolymerize the polyolefin with an unsaturated carboxylic acid or its anhydride, or a (meth)acrylate, may be used. Examples of such copolymerization include random copolymerization, block copolymerization, and graft copolymerization (graft modification), with graft copolymerization being preferred.

As the epoxy resin, there is no particular limitation as long as it is a resin that can form a cross-linked structure through the epoxy groups present in the molecule, and known epoxy resins can be used. In the first embodiment of the first invention, the weight average molecular weight of the epoxy resin is in the range of 50 to 2000. In the first and second embodiments, from the viewpoint of further improving the insulation and durability of the battery packaging material, the weight average molecular weight of the epoxy resin is preferably about 100 to 1000, and more preferably about 200 to 800. In the present invention, the weight average molecular weight of the epoxy resin is a value measured by gel permeation chromatography (GPC) under the condition of using polystyrene as a standard sample.

Specific examples of epoxy resins include bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, novolac glycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, etc. The epoxy resins may be used alone or in combination of two or more.

The proportion of the epoxy resin in the adhesive layer 4 is preferably in the range of 0.5 to 20 parts by mass, and more preferably in the range of 1 to 10 parts by mass, relative to 100 parts by mass of the acid-modified polyolefin. This can further improve the insulation properties and durability of the battery packaging material.

The melting temperature of the adhesive layer 4 is preferably between 180°C and 260°C, and more preferably between 200°C and 240°C. The melting temperature of the adhesive layer 4 is a value measured according to the method specified in JIS K7196:2012, "Softening Temperature Test Method by Thermomechanical Analysis of Thermoplastic Film and Sheet," specifically, the method described in the Examples. The penetration temperature is defined as the melting temperature.

The solid content of the adhesive layer 4 is not particularly limited. From the perspective of further improving insulation and durability, it is preferably from 0.5 g/ ^m² to 10 g/ ^m² , and more preferably from 0.8 g/ ^m² to 5.2 g/ ^m² . From the same perspective, the thickness of the adhesive layer 4 is preferably from 0.6 μm to 11 μm, and more preferably from 0.9 μm to 5.8 μm.

[Thermal-adhesive resin layer 5]

In the battery packaging material of the first invention, the heat-fusible resin layer 5 corresponds to the innermost layer and is a layer in which the heat-fusible resin layers are heat-fused to each other during battery assembly to seal the battery element.

The resin component used for the heat-fusible resin layer 5 of the first invention is not particularly limited as long as it can be heat-fusible, and examples thereof include polyolefins and acid-modified polyolefins.

Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); and terpolymers of ethylene-butene-propylene. Among these polyolefins, polyethylene and polypropylene are preferred, and polypropylene is more preferred.

The polyolefin may also be a cyclic polyolefin. Cyclic polyolefins are copolymers of olefins and cyclic monomers. Examples of olefins constituting cyclic polyolefins include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, and isoprene. Examples of cyclic monomers constituting cyclic polyolefins include cyclic olefins such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, cyclic olefins are preferred, and norbornene is more preferred.

Acid-modified polyolefins are polymers obtained by block-polymerizing or graft-polymerizing the above-mentioned polyolefins with carboxylic acids, etc. Examples of the carboxylic acids used for modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

The acid-modified polyolefin may also be an acid-modified cyclic polyolefin. Acid-modified cyclic polyolefins are polymers obtained by copolymerizing a portion of the monomers constituting the cyclic polyolefin with an α,β-unsaturated carboxylic acid or its anhydride, or by block or graft polymerization of an α,β-unsaturated carboxylic acid or its anhydride with a cyclic polyolefin. The acid-modified cyclic polyolefin is the same as described above. The carboxylic acid used for modification is the same as that used for modifying the acid-modified cyclic olefin copolymer.

Among these resin components, polyolefins are preferred; propylene copolymers are further preferred. Examples of propylene copolymers include copolymers of propylene and other olefins, such as ethylene-propylene copolymers, propylene-butene copolymers, and ethylene-propylene-butene copolymers. From the perspective of further improving the insulation and durability of battery packaging materials, the proportion of propylene units contained in polypropylene is preferably from 50 mol% to 100 mol%, more preferably from 80 mol% to 100 mol%. In addition, from the perspective of further improving the insulation and durability of battery packaging materials, the proportion of ethylene units contained in polyethylene is preferably from 50 mol% to 100 mol%, more preferably from 80 mol% to 100 mol%. The ethylene copolymer and the propylene copolymer may be either random copolymers or block copolymers, and are preferably random propylene copolymers.

The heat-fusible resin layer 5 of the first invention preferably comprises polypropylene, and more preferably comprises a layer formed of polypropylene. The heat-fusible resin layer 5 may be formed from a single resin component alone, or from a polymer blend obtained by combining two or more resin components. Furthermore, the heat-fusible resin layer 5 may be formed from a single layer, or from two or more layers formed from the same or different resin components.

When the heat-adhesive resin layer 5 of the first invention is formed of multiple layers, the innermost layer (opposite to the metal layer 3) of the heat-adhesive resin layer 5 is preferably formed by dry lamination or extrusion molding. This can further improve insulation and moldability.

The heat-fusible resin layer 5 of the first invention preferably has fine irregularities on its surface (the surface on the innermost layer side). This can further improve the moldability. Among them, as a method for forming fine irregularities on the surface of the heat-fusible resin layer 5, there are a method of adding a roughening agent exemplified in the surface covering layer described later to the heat-fusible resin layer 5, a method of bringing a cooling roller having irregularities into contact with the surface to perform shaping, and the like. As the fine irregularities, the ten-point average roughness of the surface of the heat-fusible resin layer 5 is preferably 0.3 μm to 35 μm, more preferably 0.3 μm to 10 μm, and even more preferably 0.5 μm to 2 μm. The ten-point average roughness is a value measured according to the method specified in JIS B0601:1994 using a KEYENCE laser microscope VK-9710 under measurement conditions with a 50x objective lens and no cutoff.

In addition, the thickness of the heat-fusible resin layer 5 of the first invention is not particularly limited as long as it can function as a heat-fusible resin layer. From the perspective of further improving insulation and durability, for example, it can be 10 μm to 40 μm, and preferably 15 μm to 40 μm.

[First Insulating Layer 51]

In the second invention, the first insulating layer 51 is provided between the metal layer 3 and the heat-fusible resin layer 41, along with the second insulating layer 52 (described later), to improve the insulation and durability of the battery packaging material. The first insulating layer 51 is laminated on the metal layer 3 side, and the second insulating layer 52 is laminated on the heat-fusible resin layer 41 side.

The melting temperature of the first insulating layer 51 is 200°C or higher. In the battery packaging material of the second invention, by including the first insulating layer 51 having such a high melting temperature and the second insulating layer 52 having a lower melting temperature than the first insulating layer 51, the insulation properties and durability of the battery packaging material can be improved even when tiny foreign matter such as fragments of electrode active material or electrode sheet is present in heat-sealed areas such as the interface between the heat-fusible resin layers or between the electrode sheet and the heat-fusible resin layer.

The melting temperature of the first insulating layer 51 is not particularly limited as long as it is 200°C or higher. Preferably, it is approximately 200°C or higher and 260°C or lower, and more preferably, approximately 200°C or higher and 240°C or lower. In the second invention, the melting temperature is a value measured according to the method specified in JIS K7196:2012, "Softening Temperature Test Method by Thermomechanical Analysis of Thermoplastic Film and Sheet," specifically, the method described in the Examples. The penetration temperature is defined as the melting temperature.

As described above, during the battery manufacturing process, tiny foreign matter, such as electrode active material or fragments of electrode sheets, may adhere to the surface of the heat-fusible resin layer. This can cause thin-walled areas or through-holes in the heat-fusible resin layer, leading to reduced insulation. In contrast, the battery packaging material of the second invention comprises a first insulating layer 51 having a specific melting temperature and a second insulating layer 52 having a melting temperature lower than that temperature. This provides high mechanical strength against heat when heat is applied, such as during heat sealing, and offers high flexibility, effectively suppressing the formation of microcracks caused by stresses such as bending. Therefore, even in the case of microcracks that are prone to forming in thin-walled areas, through-holes caused by foreign matter, or voids caused by electrolyte foaming in the heat-fusible resin layer during heat sealing with electrolyte interposed, the first insulating layer 51 and the second insulating layer 52 prevent direct contact between the electrolyte and the metal layer, thereby protecting the metal layer 3. Furthermore, when foreign matter is caught in the heat-fusible resin layer 41, the combination of the first insulating layer 51 and the second insulating layer 52, which have both high heat resistance and high flexibility, can prevent the insulation of the battery packaging material from being degraded due to the foreign matter.

The resin forming the first insulating layer 51 is not particularly limited as long as it has the above-mentioned melting temperature. From the perspective of further improving insulation and durability by using it together with the second insulating layer 52, the first insulating layer 51 is preferably formed of acid-modified polyolefin and epoxy resin.

As the acid-modified polyolefin, a polyolefin modified with an unsaturated carboxylic acid or its anhydride is preferably used. Alternatively, the acid-modified polyolefin may be further modified with a (meth)acrylate. A modified polyolefin further modified with a (meth)acrylate is obtained by acid-modifying a polyolefin with an unsaturated carboxylic acid or its anhydride and a (meth)acrylate.

The acid-modified polyolefin is not particularly limited as long as it is a resin containing at least an olefin as a monomer unit. The polyolefin can be composed of, for example, at least one of polyethylene and polypropylene, and is preferably composed of polypropylene. Polyethylene can be composed of, for example, at least one of homopolyethylene and an ethylene copolymer. Polypropylene can be composed of, for example, at least one of homopolypropylene and a propylene copolymer. Examples of propylene copolymers include copolymers of propylene and other olefins such as ethylene-propylene copolymers, propylene-butene copolymers, and ethylene-propylene-butene copolymers. From the perspective of further improving the insulation and durability of battery packaging materials, the proportion of propylene units contained in polypropylene is preferably between 50 mol% and 100 mol%, more preferably between 80 mol% and 100 mol%. In addition, from the perspective of further improving the insulation and durability of battery packaging materials, the proportion of ethylene units contained in polyethylene is preferably between 50 mol% and 100 mol%, more preferably between 80 mol% and 100 mol%. The ethylene copolymer and the propylene copolymer can each be a random copolymer or a block copolymer. The ethylene copolymer and the propylene copolymer may be crystalline or amorphous, or may be a copolymer or a mixture thereof. The polyolefin may be composed of one homopolymer or copolymer, or may be composed of two or more homopolymers or copolymers.

Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, and crotonic acid. Acid anhydrides are preferably the anhydrides of the unsaturated carboxylic acids exemplified above, with maleic anhydride and itaconic anhydride being more preferred. The acid-modified polyolefin may be modified with a single unsaturated carboxylic acid or its anhydride, or may be modified with two or more unsaturated carboxylic acids or their anhydrides.

Examples of (meth)acrylates include esters of (meth)acrylic acid and alcohols having 1 to 30 carbon atoms, preferably esters of (meth)acrylic acid and alcohols having 1 to 20 carbon atoms. Specific examples of (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. In the modification of polyolefins, the (meth)acrylate may be used alone or in combination of two or more.

The proportion of the unsaturated carboxylic acid or its anhydride in the acid-modified polyolefin is preferably from 0.1% to 30% by mass, more preferably from 0.1% to 20% by mass. By setting it within this range, the insulation and durability of the battery packaging material can be further improved.

The ratio of (meth)acrylate in the acid-modified polyolefin is preferably from 0.1% to 40% by mass, more preferably from 0.1% to 30% by mass. By setting the ratio within this range, the insulation and durability of the battery packaging material can be further improved.

The weight-average molecular weight of the acid-modified polyolefin is preferably from about 6,000 to about 200,000, more preferably from about 8,000 to about 150,000. In the second invention, the weight-average molecular weight of the acid-modified polyolefin is a value measured by gel permeation chromatography (GPC) using polystyrene as a standard sample. The melting point of the acid-modified polyolefin is preferably from about 50°C to about 160°C, more preferably from about 50°C to about 120°C. In the second invention, the melting point of the acid-modified polyolefin refers to the endothermic peak temperature in differential scanning calorimetry.

In the acid-modified polyolefin, the modification method of the polyolefin is not particularly limited, and for example, an unsaturated carboxylic acid or its anhydride, or a (meth)acrylate can be copolymerized with the polyolefin. Examples of such copolymerization include random copolymerization, block copolymerization, and graft copolymerization (graft modification), with graft copolymerization being preferred.

The epoxy resin is not particularly limited as long as it can form a crosslinked structure due to epoxy groups present in the molecule, and a known epoxy resin can be used.

Specific examples of epoxy resins include bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, novolac glycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, etc. The epoxy resins may be used alone or in combination of two or more.

The proportion of the epoxy resin in the first insulating layer 51 is preferably in the range of 0.5 to 20 parts by mass, and more preferably in the range of 1 to 10 parts by mass, relative to 100 parts by mass of the acid-modified polyolefin. This can further improve the insulation properties and durability of the battery packaging material.

The thickness of the first insulating layer 51 is not particularly limited, but is preferably 10 μm or less, more preferably about 1 μm or more and about 5 μm or less, from the viewpoint of further improving insulation and durability together with the second insulating layer 52 .

[Second Insulating Layer 52]

In the second invention, the second insulating layer 52 is provided between the metal layer 3 and the heat-fusible resin layer 41 along with the first insulating layer 51 described above in order to improve the insulation and durability of the battery packaging material. The second insulating layer 52 is laminated on the heat-fusible resin layer 41 side, and the first insulating layer 51 is laminated on the metal layer 3 side.

The melting temperature of the second insulating layer 52 is lower than that of the first insulating layer 51. Since the melting temperature of the second insulating layer 52 is set lower than that of the first insulating layer 51, the first insulating layer 51 and the second insulating layer 52 together exhibit high durability and high flexibility, effectively preventing the degradation of the insulation properties of the battery packaging material due to foreign matter.

The melting temperature of the second insulating layer 52 is not particularly limited as long as it is lower than the melting temperature of the first insulating layer 51 , but is preferably 150° C. or higher, and more preferably about 150° C. or higher and 180° C. or lower.

The resin forming the second insulating layer 52 is not particularly limited as long as it has the above-mentioned melting temperature. From the viewpoint of further improving insulation and durability by using it together with the first insulating layer 51, the second insulating layer 52 is preferably formed of polyolefin.

Polyolefins are not particularly limited as long as they are resins containing at least an olefin as a monomer unit. Polyolefins can be composed of, for example, at least one of polyethylene and polypropylene, preferably polypropylene. Polyethylene can be composed of, for example, at least one of homopolyethylene and an ethylene copolymer. Polypropylene can be composed of, for example, at least one of homopolypropylene and a propylene copolymer. Examples of propylene copolymers include copolymers of propylene and other olefins such as ethylene-propylene copolymers, propylene-butene copolymers, and ethylene-propylene-butene copolymers. From the perspective of further improving the insulation and durability of battery packaging materials, the proportion of propylene units contained in polypropylene is preferably between 50 mol% and 100 mol%, more preferably between 80 mol% and 100 mol%. In addition, from the perspective of further improving the insulation and durability of battery packaging materials, the proportion of ethylene units contained in polyethylene is preferably between 50 mol% and 100 mol%, more preferably between 80 mol% and 100 mol%. The ethylene copolymer and the propylene copolymer can be either a random copolymer or a block copolymer, preferably a block propylene copolymer. The ethylene copolymer and the propylene copolymer may be crystalline or amorphous, or may be a copolymer or a mixture thereof. The polyolefin may be composed of one homopolymer or copolymer, or may be composed of two or more homopolymers or copolymers.

The melting point of the polyolefin is preferably about 120° C. to 180° C., more preferably about 140° C. to 180° C. In the second invention, the melting point of the polyolefin refers to the endothermic peak temperature in differential scanning calorimetry.

The thickness of the second insulating layer 52 is not particularly limited, but is preferably about 10 μm to 50 μm, more preferably about 15 μm to 40 μm, from the viewpoint of further improving insulation and durability together with the first insulating layer 51 .

[Adhesive layer 6]

In the second invention, the adhesive layer 6 is a layer provided between the first insulating layer 51 and the second insulating layer 52 as needed in order to improve the adhesion between these layers.

The adhesive layer 6 is formed of an adhesive capable of bonding the first insulating layer 51 and the second insulating layer 52. The resin forming the adhesive layer 6 is not particularly limited, but polyolefins are preferred. Examples of the polyolefin include those exemplified above for the second insulating layer 52. A random propylene copolymer is preferred as the polyolefin forming the adhesive layer 6.

The thickness of the adhesive layer 6 is not particularly limited as long as it can function as an adhesive layer, and can be, for example, 20 μm or less, preferably 2 μm or more and 10 μm or less.

[Adhesive layer 7]

In the battery packaging material of the second invention, the adhesive layer 7 is a layer provided between the metal layer 3 and the first insulating layer 51 as needed in order to firmly bond these layers.

The adhesive layer 7 is formed of an adhesive capable of bonding the metal layer 3 and the first insulating layer 51. The adhesive used to form the adhesive layer 7 has the same bonding mechanism, adhesive component types, and the like as those for the adhesive layer 2 described above. As the adhesive component used in the adhesive layer 7, preferably, an acid-modified polyolefin is used, more preferably, a carboxylic acid-modified polyolefin is used, and particularly preferably, a carboxylic acid-modified polypropylene is used.

The thickness of the adhesive layer 7 is not particularly limited as long as it can function as an adhesive layer, and can be, for example, about 1 μm to 10 μm, preferably about 1 μm to 5 μm.

[Thermal-adhesive resin layer 41]

In the battery packaging material of the second invention, the heat-fusible resin layer 41 corresponds to the innermost layer and is a layer in which the heat-fusible resin layers are heat-fused to each other during battery assembly to seal the battery element.

The resin component used for the heat-fusible resin layer 41 is not particularly limited as long as heat-fusible resin can be used, and examples thereof include polyolefins and acid-modified polyolefins.

Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); and terpolymers of ethylene-butene-propylene. Among these polyolefins, polyethylene and polypropylene are preferred, and polypropylene is more preferred.

The polyolefin may also be a cyclic polyolefin. Cyclic polyolefins are copolymers of olefins and cyclic monomers. Examples of olefins constituting cyclic polyolefins include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, and isoprene. Examples of cyclic monomers constituting cyclic polyolefins include cyclic olefins such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, cyclic olefins are preferred, and norbornene is more preferred.

Acid-modified polyolefins are polymers obtained by block-polymerizing or graft-polymerizing the above-mentioned polyolefins with carboxylic acids, etc. Examples of the carboxylic acids used for modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

The acid-modified polyolefin may also be an acid-modified cyclic polyolefin. Acid-modified cyclic polyolefins are polymers obtained by copolymerizing a portion of the monomers constituting the cyclic polyolefin with an α,β-unsaturated carboxylic acid or its anhydride, or by block polymerization or graft polymerization of an α,β-unsaturated carboxylic acid or its anhydride with a cyclic polyolefin. The acid-modified cyclic polyolefin is the same as described above. The carboxylic acid used for modification is the same as that used for modifying the acid-modified cyclic olefin copolymer.

Among these resin components, polyolefins are preferred; propylene copolymers are further preferred. Examples of propylene copolymers include copolymers of propylene and other olefins such as ethylene-propylene copolymers, propylene-butene copolymers, and ethylene-propylene-butene copolymers. From the perspective of further improving the insulation and durability of battery packaging materials, the proportion of propylene units contained in polypropylene is preferably between 50 mol% and 100 mol%, more preferably between 80 mol% and 100 mol%. In addition, from the perspective of further improving the insulation and durability of battery packaging materials, the proportion of ethylene units contained in polyethylene is preferably between 50 mol% and 100 mol%, more preferably between 80 mol% and 100 mol%. The ethylene copolymer and the propylene copolymer may be either random copolymers or block copolymers, and are preferably random propylene copolymers.

The heat-adhesive resin layer 41 may be formed from a single resin component or a polymer blend of two or more resin components. Furthermore, the heat-adhesive resin layer 41 may be formed from a single layer or from two or more layers of the same or different resin components.

When the heat-adhesive resin layer 41 is formed of multiple layers, the innermost layer (opposite to the metal layer 3) of the heat-adhesive resin layer 41 is preferably formed by dry lamination or extrusion molding. This can further improve insulation and moldability.

The melting temperature of the heat-adhesive resin layer 41 is preferably lower than that of the second insulating layer 52. The melting temperature of the heat-adhesive resin layer 41 is preferably about 80°C to 160°C, more preferably about 100°C to 140°C.

The heat-adhesive resin layer 41 preferably has fine irregularities on its surface (the innermost surface). This further improves moldability. Examples of methods for forming fine irregularities on the surface of the heat-adhesive resin layer 41 include adding a roughening agent, as exemplified in the surface coating layer described later, to the heat-adhesive resin layer 41, or contacting a cooling roller having irregularities with the surface to impart shape.

The thickness of the thermal adhesive resin layer 41 is not particularly limited as long as it can function as a thermal adhesive resin layer, and can be, for example, about 10 μm to 40 μm, preferably about 15 μm to 40 μm.

[Surface covering]

In the battery packaging material of the present invention, a surface covering layer (not shown) may be provided on the substrate layer 1 (on the side of the substrate layer 1 opposite to the metal layer 3) as needed to improve design, electrolyte resistance, friction resistance, and formability. The surface covering layer is the outermost layer when the battery is assembled.

The surface coating can be formed by polyvinylidene chloride, polyester resin, polyurethane resin, acrylic resin, epoxy resin, etc., for example. Wherein, the surface coating is preferably formed by two-liquid curing type resin. As the two-liquid curing type resin forming the surface coating, for example, two-liquid curing type polyurethane resin, two-liquid curing type polyester resin, two-liquid curing type epoxy resin, etc. can be listed. In addition, the surface coating can also be coordinated with a roughening agent.

As a roughening agent, for example, particles with a particle size of about 0.5 nm or more and about 5 μm or less can be listed. The material of the roughening agent is not particularly limited, for example, metals, metal oxides, inorganic substances, organic substances, etc. can be listed. In addition, the shape of the roughening agent is not particularly limited, for example, spherical, fibrous, plate-like, amorphous, hollow, etc. can be listed. As a roughening agent, specifically talc, silicon dioxide, graphite, kaolin, montmorillonite, montmorillonite, synthetic mica, hydrotalcite, silica gel, zeolite, aluminum hydroxide, magnesium hydroxide, zinc oxide, magnesium oxide, aluminum oxide, neodymium oxide, antimony oxide, titanium oxide, cerium oxide, calcium sulfate, barium sulfate, calcium carbonate, calcium silicate, lithium carbonate, calcium benzoate, calcium oxalate, magnesium stearate, aluminum oxide, carbon black, carbon nanotubes, high melting point nylon, cross-linked acrylic acid, cross-linked styrene, cross-linked polyethylene, benzoguanamine, gold, aluminum, copper, nickel, etc. These roughening agents can be used alone or in combination. Among these roughening agents, silicon dioxide, barium sulfate, and titanium oxide are preferred from the viewpoints of dispersion stability and cost, etc. The surface of the roughening agent may also be subjected to various surface treatments such as insulation treatment and high dispersibility treatment.

The method for forming the surface coating layer is not particularly limited, and an example thereof is a method of coating a two-component curable resin forming the surface coating layer on one surface of the base layer 1. When a roughening agent is added, the roughening agent can be added to the two-component curable resin, mixed, and then coated.

The thickness of the surface coating layer is not particularly limited as long as it can exhibit the above-mentioned function as the surface coating layer, and can be, for example, about 0.5 μm or less to about 10 μm or less, preferably about 1 μm or less to about 5 μm or less.

3. Method for manufacturing battery packaging materials

The method for producing the battery packaging material of the first invention is not particularly limited as long as a laminated body comprising layers of a predetermined composition can be obtained. The following method can be employed: The method includes a lamination step to obtain a laminated body comprising at least a base layer 1, a metal layer 3, an adhesive layer 4, and a heat-fusible resin layer 5 in this order, wherein the adhesive layer 4 is formed from a resin composition comprising an acid-modified polyolefin having a melting point of 50°C to 120°C and an epoxy resin having a weight-average molecular weight of 50 to 2000. Specifically, the layers described in "2. Formation of Layers of Battery Packaging Material" are used as the adhesive layer 4, and the layers are laminated to produce the battery packaging material of the present invention.

An example of a method for manufacturing a battery packaging material according to the first invention is as follows. First, a laminate (hereinafter sometimes referred to as "laminate A") is formed, comprising, in order, a substrate layer 1, an adhesive layer 2, and a metal layer 3. Specifically, laminate A can be formed by a dry lamination method as follows: an adhesive for forming the adhesive layer 2 is applied to the substrate layer 1 or, if necessary, the metal layer 3, which has undergone a chemical surface treatment, by a coating method such as extrusion, gravure coating, or roll coating, followed by drying. The metal layer 3 or the substrate layer 1 is then laminated and the adhesive layer 2 is cured.

Next, the adhesive layer 4 and the heat-adhesive resin layer 5 are laminated on the metal layer 3 of the laminate A. When laminating the adhesive layer 4 and the heat-fusible resin layer 5 on the metal layer 3, for example, the following methods can be cited: (1) a method of laminating the adhesive layer 4 and the heat-fusible resin layer 5 on the metal layer 3 of the laminate A by co-extrusion (coextrusion lamination method); (2) a method of laminating the laminate obtained by laminating the adhesive layer 4 and the heat-fusible resin layer 5 separately on the metal layer 3 of the laminate A by heat lamination; (3) a dry lamination method in which the resin composition for forming the adhesive layer 4 is applied to the metal layer 3 of the laminate A by a coating method such as gravure coating and roll coating and dried, and then the heat-fusible resin layer is laminated and the adhesive layer 4 is cured; (4) a method in which the molten adhesive layer 4 is flowed between the metal layer 3 of the laminate A and the heat-fusible resin layer 5 previously formed into a sheet, and the laminate A and the heat-fusible resin layer 5 are bonded to each other via the adhesive layer 4 (sandwich lamination method), etc. Among these methods, method (3) is preferred. When method (3) is employed, the resin composition forming the adhesive layer 4 is preferably laminated on the metal layer 3 and then dried at a temperature of 60°C to 120°C. When the heat-fusible resin layer is a multilayer layer, the innermost layer of the heat-fusible resin layer is preferably formed by dry lamination or extrusion molding.

When a surface covering layer is provided, the surface covering layer is laminated on the surface of the substrate layer 1 on the side opposite to the metal layer 3. The surface covering layer can be formed, for example, by coating the surface of the substrate layer 1 with the above-mentioned resin for forming the surface covering layer. The order of the steps of laminating the metal layer 3 on the surface of the substrate layer 1 and laminating the surface covering layer on the surface of the substrate layer 1 is not particularly limited. For example, the metal layer 3 may be formed on the surface of the substrate layer 1 on the side opposite to the surface covering layer after the surface covering layer is formed on the surface of the substrate layer 1.

As described above, a laminate is formed, which includes, in order, a surface covering layer (if desired), a base material layer 1, an adhesive layer 2 (if desired), a metal layer 3 (if desired with a chemically treated surface), an adhesive layer 4, and a heat-fusible resin layer 5. To strengthen the adhesion between the adhesive layer 2 and the adhesive layer 4 (if desired), a heat treatment using a hot roll contact method, hot air method, near-infrared radiation, or far-infrared radiation method may be further applied. For example, the heat treatment conditions include a temperature of 150°C to 250°C for 1 to 5 minutes.

Regarding the method for manufacturing the battery packaging material of the second invention, there are no particular restrictions as long as a laminated body composed of layers of a specified composition can be obtained. The following method can be used: it includes the steps of sequentially laminating at least a base material layer, a metal layer, a first insulating layer, a second insulating layer, and a heat-fusible resin layer to obtain a laminated body, the melting temperature of the first insulating layer is set to be above 200°C, and the melting temperature of the second insulating layer is set to be lower than the melting temperature of the first insulating layer.

That is, the battery packaging material of the second invention can be produced by using the layers described in “2. Formation of Each Layer of Battery Packaging Material” as the first insulating layer 51 and the second insulating layer 52 and laminating the layers.

An example of a method for manufacturing a battery packaging material according to the second invention is as follows. First, a laminate (hereinafter sometimes referred to as "laminate A") is formed, comprising, in order, a substrate layer 1, an adhesive layer 2, and a metal layer 3. Specifically, laminate A can be formed by a dry lamination method as follows: an adhesive for forming the adhesive layer 2 is applied to the substrate layer 1 or, if necessary, the metal layer 3, which has undergone a chemical surface treatment, by a coating method such as extrusion, gravure coating, or roll coating, followed by drying. The metal layer 3 or the substrate layer 1 is then laminated and the adhesive layer 2 is cured.

Next, at least the first insulating layer 51, the second insulating layer 52, and the heat-fusible resin layer 4 are laminated on the metal layer 3 of the laminated body A. There are no limitations on the method for laminating the first insulating layer 51 and the second insulating layer 52 on the metal layer 3. For example, a method can be used in which the resin constituting the first insulating layer 51 and the resin constituting the second insulating layer 52 are sequentially coated on the metal layer 3. Alternatively, a resin film constituting the first insulating layer 51 and a resin film constituting the second insulating layer 52 can be laminated.

When an adhesive layer 6 is provided between the first insulating layer 51 and the second insulating layer 52, a resin constituting the adhesive layer 6 may be applied to the first adhesive layer 51 before laminating the second insulating layer 52. Alternatively, a film obtained by laminating the adhesive layer 6 on the second insulating layer 52 in advance may be laminated on the first insulating layer 51. Furthermore, when an adhesive layer 7 is provided between the metal layer 3 and the first adhesive layer 51, a resin constituting the adhesive layer 7 may be applied to the metal layer 3 before laminating the first insulating layer 51.

Finally, the heat-fusible resin layer 4 is laminated on the second insulating layer 52 to obtain the battery packaging material of the second invention. Alternatively, a two-layer resin film, formed by laminating the second insulating layer 52 and the heat-fusible resin layer 4, may be laminated on the first adhesive layer 51.

In the case where a surface covering layer is provided, the surface covering layer is laminated on the surface of the substrate layer 1 on the side opposite to the metal layer 3. The surface covering layer can be formed, for example, by applying the above-mentioned resin for forming the surface covering layer to the surface of the substrate layer 1. The order of the steps of laminating the metal layer 3 on the surface of the substrate layer 1 and laminating the surface covering layer on the surface of the substrate layer 1 is not particularly limited. For example, after forming the surface covering layer on the surface of the substrate layer 1, the metal layer 3 may be formed on the surface of the substrate layer 1 on the side opposite to the surface covering layer.

As described above, a laminate is formed comprising: a surface covering layer (if desired) / a base material layer 1 / an adhesive layer 2 / a metal layer 3 with a chemically treated surface (if desired) / an adhesive layer 7 (if desired) / a first insulating layer 51 / an adhesive layer 6 (if desired) / a second insulating layer 52 / a heat-fusible resin layer 4. To strengthen the adhesion between the adhesive layer 2 and the adhesive layer 5 (if desired), a heat treatment using a hot roller contact method, hot air method, near-infrared radiation, or far-infrared radiation method may be further applied. For example, the heat treatment conditions may be a temperature of 150°C to 250°C for 1 minute to 5 minutes.

In the battery packaging material of the present invention, each layer constituting the laminate may be subjected to a surface activation treatment such as corona discharge treatment, sandblasting, oxidation treatment, or ozone treatment, if necessary, in order to improve or stabilize film forming properties, lamination processing, and suitability for secondary processing (packaging, embossing) of the final product.

4. Application of battery packaging materials

The battery packaging material of the present invention is used as a packaging material for sealing and storing battery components such as a positive electrode, a negative electrode, and an electrolyte.

Specifically, the battery packaging material of the present invention is used to cover a battery element comprising at least a positive electrode, a negative electrode, and an electrolyte, with the metal terminals connected to the positive and negative electrodes protruding outward, in a manner that forms a flange portion (an area where the heat-fusible resin layers contact each other) at the edge of the battery element. The heat-fusible resin layers at the flange portion are heat-sealed to each other, thereby providing a battery using the battery packaging material. Furthermore, when the battery packaging material of the present invention is used to house the battery element, the heat-fusible resin portion of the battery packaging material of the present invention is positioned inward (the surface in contact with the battery element).

The battery packaging material of the present invention can be used for any type of primary battery or secondary battery, and is preferably used for secondary batteries. The type of secondary battery to which the battery packaging material of the present invention is applicable is not particularly limited, and examples thereof include lithium-ion batteries, lithium-ion polymer batteries, lead-acid batteries, nickel-hydrogen batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, multivalent cation batteries, capacitors, and the like. Among these secondary batteries, lithium-ion batteries and lithium-ion polymer batteries are suitable as suitable applications for the battery packaging material of the present invention.

Example

The present invention is described in detail below using examples and comparative examples. However, the present invention is not limited to the examples. The weight-average molecular weight of the resin is a value measured by gel permeation chromatography (GPC) using polystyrene as a standard sample. The melting temperature is the penetration temperature of the TMA needle penetration mode in accordance with JIS K7196:2012, using an EXSTAR6000 manufactured by Seiko Instruments. The melting point of the main agent of the adhesive layer is measured using a differential scanning calorimeter in accordance with JIS K7121:2012.

<Examples 1A to 12A and Comparative Examples 1A to 17A>

A metal layer comprising aluminum foil (35 μm thick) chemically surface treated on both sides was laminated onto a nylon film (25 μm thick) as a substrate layer using a dry lamination method. Specifically, a two-component polyurethane adhesive (polyol compound and aromatic isocyanate compound) was applied to one surface of the aluminum foil to form an adhesive layer (3 μm thick) on the metal layer. The adhesive layer on the metal layer and the substrate layer were then laminated and then aged at 40°C for 24 hours to produce a laminate of the substrate layer, adhesive layer, and metal layer. The chemical surface treatment of the aluminum foil used as the metal layer was performed by the following method: a treatment solution comprising a phenolic resin, a chromium fluoride compound, and phosphoric acid was applied to both sides of the aluminum foil using a roll coating method in such a manner that the chromium coating amount reached 10 mg/ ^m² (dry mass), and the film was sintered at a lamination temperature of 180°C or above for 20 seconds.

Next, a resin composition containing the main agent and curing agent described in Table 1A was applied to the other side surface of the metal layer of the obtained laminate in the coating amount (dry mass) described in Table 1A, and dried at 80°C for 60 seconds to form an adhesive layer. Next, a polypropylene film (thickness 35 μm) was laminated on the adhesive layer using a dry lamination method to form a heat-fusible resin layer. Through the above steps, in Examples 1A to 12A and Comparative Examples 1A to 16A, laminates having a base layer, an adhesive layer, a metal layer, an adhesive layer, and a heat-fusible resin layer were obtained in sequence. In Comparative Example 17, polypropylene was extruded on the metal layer to obtain a laminate having a base layer, an adhesive layer, a metal layer, and a heat-fusible resin layer in sequence. Each of the obtained laminates was aged at 70°C for 24 hours to obtain the battery packaging materials of Examples 1A to 12A and Comparative Examples 1A to 17A. The thickness of the adhesive layer calculated from the coating amount and density is shown in Table 1A.

Durability evaluation

Each of the battery packaging materials obtained above is cut into 60 mm (MD direction, longitudinal direction) × 150 mm (TD direction, transverse direction) as shown in the schematic diagram of Figure 5 (Figure 5(a)). Then, the cut battery packaging material is folded in half so that the heat-fusible resin layers are facing each other in the TD direction (Figure 5(b)). Then, the opposite side E in the TD direction and the side F in the MD direction are heat-fused (the width of the heat-fused part S is 7 mm) to produce a bag-shaped battery packaging material with one side open in the TD direction (Figure 5(c) opening G). The heat-fusion conditions are a temperature of 190°C, a surface pressure of 1.0 MPa, and a heating and pressing time of 3 seconds. Then, as shown in Figure 5(d), 3 g of electrolyte H is injected from the opening G. Then, the opening G is heat-fused with a width of 7 mm under the same conditions as above (Figure 5(e)). The electrolyte H is obtained by mixing lithium hexafluorophosphate with a solution of ethylene carbonate: diethyl carbonate: dimethyl carbonate at a volume ratio of 1:1:1. The battery packaging material is then placed in a constant temperature chamber at 85°C for 24 hours, with the opening G facing upward (as shown in Figure 5(e)).

Next, each battery packaging material was removed from the constant temperature layer. As shown in Figure 5(f), the side where the electrolyte H was injected was cut (at the dotted line in Figure 5(f)). The battery packaging material was then unsealed and the electrolyte H was removed (Figure 5(g)). Next, a portion of the battery packaging material with a width of 15 mm in the TD direction was cut into a rectangular shape (at the dotted line in Figure 5(h)), yielding a test piece T (Figure 5(i)). The thermally fusible resin layer and the metal layer of the resulting test piece T were peeled off. The thermally fusible resin layer and the metal layer were stretched at a rate of 50 mm/min using a tensile testing machine (Shimadzu Corporation, trade name AGS-50D), and the peel strength (N/15 mm) of the test piece was measured (peel strength after durability testing). Separately, the peel strength (peel strength before durability testing) of the test piece T obtained by cutting the battery packaging materials obtained in Examples 1A to 12A and Comparative Examples 1A to 17A into a width of 15 mm was similarly measured. The results are shown in Table 1A. However, when the thermally adhesive resin layer and the metal layer were peeled off, the adhesive layer between these layers was laminated on either or both of the thermally adhesive resin layer and the metal layer.

<Evaluation of insulation performance against foreign matter inclusion>

As shown in the schematic diagram of Figure 6 , each of the battery packaging materials obtained above was cut into a size of 60 mm (horizontally) x 150 mm (vertically) to obtain a test piece (Figure 6(a)). The test piece was then folded in half with its short sides facing each other, and the surfaces of the heat-fusible resin layers of the test piece were arranged so as to face each other. A wire M was then inserted between the opposing surfaces of the heat-fusible resin layers (Figure 6(b)). In this state, the heat-fusible resin layers were heat-sealed together using a heat sealer comprising a flat hot plate 7 mm wide in a direction perpendicular to the longitudinal direction of the battery packaging material (Figure 6(c), heat-fused portion S). Heat sealing was performed from above the portion where the wire M was located, thermally fusing the heat-fusible resin layer to the wire M. The positive electrode of the tester was then connected to the wire M, and the negative electrode was connected to one side of the battery packaging material. At this point, an alligator clip was inserted into the negative electrode of the tester, extending from the base material layer side of the electrode packaging material to the aluminum layer, electrically connecting the negative electrode of the tester to the aluminum foil. Next, a voltage of 100 V was applied between the testers, and the time (seconds) until a short circuit occurred was measured. The results are shown in Table 1A.

[Table 1A]

As shown in Table 1A, the battery packaging materials of Examples 1A to 12A, in which the adhesive layer disposed between the metal layer and the heat-fusible resin layer is formed from a resin composition comprising an acid-modified polyolefin with a melting point of 50°C to 120°C and an epoxy resin with a weight-average molecular weight of 50 to 2000, exhibit excellent durability and insulation. On the other hand, the battery packaging materials of Comparative Examples 1A to 4A, in which the melting point of the acid-modified polyolefin is outside the range of 50°C to 120°C, Comparative Examples 5A to 8A, in which the weight-average molecular weight of the epoxy resin is outside the range of 50 to 2000, Comparative Examples 9A to 12A, in which no epoxy resin is used as a curing agent, Comparative Examples 13A to 16A, in which no acid-modified polyolefin is used, and Comparative Example 17, in which no adhesive layer is provided, exhibit inferior insulation and generally lower durability compared to Examples 1A to 12A.

<Measurement of probe displacement using a thermomechanical analyzer>

A probe is set on the surface of the adhesive layer at the end of each battery packaging material obtained in Example 10A and Comparative Example 11A, and the probe is heated from 40°C to 250°C (heating rate 5°C/min, probe tip radius 30nm or less, and load applied to the probe is set to deflection -4V), and the displacement of the probe is measured. The curves showing the relationship between the heating temperature and the displacement of the probe position are shown in Figure 7 (Example 10A) and Figure 8 (Comparative Example 11A), respectively. The details of the measurement conditions are as follows. As a thermomechanical analysis device, an afm plus system manufactured by ANALYSIS INSTRUMENTS was used, and an arm Therma Lever was used as a probe. The three samples provided (polycaprolactam (melting point 55°C), polyethylene (melting point 116°C), and polyethylene terephthalate (melting point 235°C)) were used for calibration, and the applied voltage was set to 0.1-10V, the speed to 0.2V/second, and the deflection to -4V.

As shown in Figure 7 , when using the battery packaging material obtained in Example 10A, the probe position did not decrease compared to the initial value when heated from 40°C to 220°C using a thermomechanical analyzer. Furthermore, in Example 10A, the increase in the probe position when heated from 140°C to 220°C was greater than the increase in the probe position when heated from 80°C to 120°C. On the other hand, as shown in Figure 8 , when using the battery packaging material obtained in Comparative Example 11A, the probe position decreased compared to the initial value when heated from 40°C to 220°C using a thermomechanical analyzer.

<Examples 1B to 4B and Comparative Examples 1B to 4B>

A metal layer comprising aluminum foil (35 μm thick) chemically surface treated on both sides was laminated onto a nylon film (25 μm thick) as a substrate layer using a dry lamination method. Specifically, a two-component polyurethane adhesive (polyol compound and aromatic isocyanate compound) was applied to one surface of the aluminum foil to form an adhesive layer (3 μm thick) on the metal layer. Subsequently, the adhesive layer on the metal layer and the substrate layer were laminated and then aged at 40°C for 24 hours to produce a laminate of substrate layer/adhesive layer/metal layer. The chemical surface treatment of the aluminum foil used as the metal layer was performed as follows: a treatment solution comprising a phenolic resin, a chromium fluoride compound, and phosphoric acid was applied to both sides of the aluminum foil using a roller coating method in such a manner that the chromium coating amount reached 10 mg/m ² (dry mass), and the coating was sintered for 20 seconds at a lamination temperature of 180°C or above.

Next, the resin listed in Table 1B was applied at 2 g/ ^m² onto the other side of the metal layer of the resulting laminate and dried at 80°C to form a first insulating layer. Next, a second insulating layer and a heat-fusible resin layer, formed from the resin listed in Table 1B, were laminated onto the first insulating layer using dry lamination. The first and second insulating layers were laminated adjacent to each other. Comparative Example 1B did not include a second insulating layer. Furthermore, Comparative Example 2 did not include a first insulating layer. For Example 4B, an adhesive layer, a second insulating layer, and a heat-fusible resin layer were laminated onto the first insulating layer using dry lamination. The resins, thicknesses, and melting temperatures of each layer are shown in Table 1B. Through the above steps, in Examples 1B to 3B and Comparative Examples 3B to 4B, laminates were obtained, each consisting of a base material layer, adhesive layer, metal layer, first insulating layer, second insulating layer, and heat-fusible resin layer laminated in this order. In Example 4B, a laminate was obtained in which the following layers were stacked in order: base material layer/adhesive layer/metal layer/first insulating layer/adhesive layer/second insulating layer/thermo-fusible resin layer. In Comparative Example 1, a laminate was obtained in which the following layers were stacked in order: base material layer/adhesive layer/metal layer/first insulating layer/thermo-fusible resin layer. In Comparative Example 2, a laminate was obtained in which the following layers were stacked in order: base material layer/adhesive layer/metal layer/second insulating layer/thermo-fusible resin layer. The resulting laminates were aged at 70°C for 24 hours to produce the battery packaging materials of Examples 1B to 4B and Comparative Examples 1B to 4B.

Durability evaluation

The durability of each battery packaging material obtained in Examples 1B to 4B and Comparative Examples 1B to 4B was evaluated in the same manner as above. The results are shown in Table 1B.

<Evaluation of insulation performance against foreign matter inclusion>

The insulation properties of the battery packaging materials obtained in Examples 1B to 4B and Comparative Examples 1B to 4B against inclusion of foreign matter were evaluated in the same manner as above. The results are shown in Table 1B.

[Table 1B]

In Table 1B, acid-modified PP refers to maleic anhydride-modified polypropylene, random PP refers to random propylene copolymer, and block PP refers to block propylene copolymer.

As shown in Table 1B, the battery packaging materials of Examples 1B to 4B, which comprise a laminate comprising at least a base layer, a metal layer, a first insulating layer, a second insulating layer, and a heat-fusible resin layer in this order, and in which the melting temperature of the first insulating layer is 200°C or higher and the melting temperature of the second insulating layer is set lower than the melting temperature of the first insulating layer, exhibit excellent durability and insulation. On the other hand, the battery packaging material of Comparative Example 1, which lacks a second insulating layer, exhibits poor insulation. Furthermore, the battery packaging material of Comparative Example 2B, which lacks a first insulating layer, exhibits poor durability and insulation. Furthermore, the battery packaging materials of Comparative Examples 3B and 4B, which have both a first insulating layer and a second insulating layer but a melting temperature of the first insulating layer below 200°C, exhibit poor durability and insulation.

Explanation of symbols

1…base material layer; 2…adhesive layer; 3…metal layer; 4…adhesive layer; 5…thermo-meltable resin layer; 6…adhesive layer; 7…adhesive layer; 10…probe; 41…thermo-meltable resin layer; 51…first insulating layer; 52…second insulating layer.

Claims (20)

1. A packaging material for batteries, characterized in that: This includes a laminate comprising at least a substrate layer, a metal layer, an adhesive layer, and a thermoplastic resin layer in sequence. The adhesive layer comprises a resin composition including an acid-modified polyolefin with a melting point of 50°C to 120°C and an epoxy resin with a weight-average molecular weight of 50 to 2000. In the measurement of the displacement of the probe using a thermomechanical analysis apparatus, the probe is placed on the surface of the adhesive layer at the end of the battery packaging material. When the probe is heated from 40°C to 220°C, the position of the probe does not decrease compared to the initial value. 2. The battery packaging material as described in claim 1, characterized in that: In the measurement of the displacement of the probe using a thermomechanical analysis apparatus, the probe is disposed on the surface of the adhesive layer at the end of the battery packaging material. When the probe is heated from 40°C to 220°C, the increase in the position of the probe when heated from 140°C to 220°C is greater than the increase in the position of the probe when heated from 80°C to 120°C. 3. The battery packaging material as described in claim 1 or 2, characterized in that: The solid content of the adhesive layer is between 0.5 g/ ^m² and 10 g/ ^m² . 4. The battery packaging material as described in claim 1 or 2, characterized in that: The thickness of the adhesive layer is between 0.6 μm and 11 μm. 5. The battery packaging material as described in claim 1 or 2, characterized in that: The adhesive layer contains 0.5 to 20 parts by weight of epoxy resin relative to 100 parts by weight of acid-modified polyolefin. 6. The battery packaging material as described in claim 1 or 2, characterized in that: The melting temperature of the adhesive layer is in the range of 180°C to 260°C. 7. The battery packaging material as described in claim 1 or 2, characterized in that: The thickness of the heat-fusion resin layer is in the range of 10 μm to 40 μm. 8. The battery packaging material as described in claim 1 or 2, characterized in that: The surface of the heat-fusion resin layer has fine irregularities. 9. A method for manufacturing a battery packaging material, characterized in that: This includes a lamination process for obtaining a laminate comprising at least a substrate layer, a metal layer, an adhesive layer, and a thermoplastic resin layer in sequence. The adhesive layer is formed using a resin composition comprising an acid-modified polyolefin with a melting point of 50°C to 120°C and an epoxy resin with a weight-average molecular weight of 50 to 2000. As the adhesive layer, a layer that satisfies the following condition is used: when the displacement of the probe is measured using a thermomechanical analysis device, the probe is placed on the surface of the adhesive layer at the end of the battery packaging material, and when the probe is heated from 40°C to 220°C, the position of the probe does not decrease compared to the initial value. 10. A battery packaging material, characterized in that: It includes a laminate comprising at least a substrate layer, a metal layer, a first insulating layer, a second insulating layer, and a thermosetting resin layer in sequence. The melting temperature of the first insulating layer is above 200°C. The melting temperature of the second insulating layer is lower than that of the first insulating layer. The first insulating layer is formed of acid-modified polyolefin and epoxy resin. 11. The battery packaging material as described in claim 10, characterized in that: The second insulating layer is formed of polypropylene with a melting temperature of 150°C or higher. 12. The battery packaging material as described in claim 10 or 11, characterized in that: The melting temperature of the heat-fusion resin layer is lower than that of the second insulating layer. 13. The battery packaging material as described in claim 10 or 11, characterized in that: The first insulating layer and the second insulating layer are bonded together through an adhesive layer. 14. The battery packaging material as described in claim 10 or 11, characterized in that: The thickness of the first insulating layer is less than 10 μm. 15. The battery packaging material as described in claim 10 or 11, characterized in that: The thickness of the second insulating layer is more than 10 μm and less than 50 μm. 16. The battery packaging material as described in claim 13, characterized in that: The thickness of the adhesive layer is less than 20 μm. 17. The battery packaging material as described in claim 10 or 11, characterized in that: The heat-melting resin layer is formed of polyolefin. 18. The battery packaging material as described in claim 10 or 11, characterized in that: The surface of the heat-fusion resin layer has fine irregularities. 19. A method for manufacturing a battery packaging material, characterized in that: The process includes at least the step of sequentially stacking a substrate layer, a metal layer, a first insulating layer, a second insulating layer, and a thermosetting resin layer to obtain a laminate. The melting temperature of the first insulating layer is set to above 200°C. The melting temperature of the second insulating layer is set to be lower than that of the first insulating layer. The first insulating layer is formed of acid-modified polyolefin and epoxy resin. 20. A battery, characterized in that: A battery element having a positive electrode, a negative electrode, and an electrolyte is formed by encapsulating a battery packaging body made of the battery packaging material according to any one of claims 1 to 18.