JP7325926B2 - Battery packaging materials and batteries - Google Patents

Description

TECHNICAL FIELD The present invention relates to a battery packaging material and a battery.

Conventionally, various types of batteries have been developed, and in all batteries, packaging materials have become indispensable members for sealing battery elements such as electrodes and electrolytes. In the past, metal packaging materials were widely used for packaging batteries, but in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc., various shapes are required for batteries. At the same time, there is a demand for thinner and lighter products. However, metal battery packaging materials, which have been widely used in the past, have drawbacks in that it is difficult to follow the diversification of shapes and there is a limit to weight reduction.

Therefore, as a packaging material for batteries that can be easily processed into various shapes and that can realize thinness and weight reduction, a film-like laminate in which a substrate layer / metal foil layer / heat-fusible resin layer is laminated in order is proposed. has been proposed (see, for example, Patent Document 1). In such a film-like battery packaging material, the heat-sealable resin layers are opposed to each other and the peripheral edges are heat-sealed to seal the battery element.

More specifically, when a space for enclosing a battery element is provided in the battery packaging material, the heat-fusible resin layers are opposed to each other, and the peripheral edge portion other than the location serving as the injection port for enclosing the electrolyte solution. are heat-sealed to form a package having an injection port. Next, the electrolytic solution is injected into the package, the inlet portion is heat-sealed, the electrolytic solution permeates the battery element by heating or the like, and the inlet portion is heat-sealed again to manufacture the battery. .

JP 2008-287971 A

However, after heating the package into which the electrolytic solution has been injected to allow the electrolytic solution to permeate the battery element, if the inlet portion is heat-sealed again, the electrolytic solution will be released inside the heat-sealable resin layer into which the electrolytic solution has permeated. may foam, forming a portion where the heat-fusible resin layers are not completely adhered to each other. More specifically, in the battery manufacturing process, as shown in the schematic diagram of FIG. 11, a molded portion M for housing a battery element is formed in the battery packaging material 10 (FIG. 11a). Next, the center portion P of the battery packaging material is folded back to house the battery element C in the molded portion M (FIG. 11b). In this state, the heat-sealable resin layers are heat-sealed on two sides of the battery packaging material so that the terminals are exposed to the outside of the package (FIGS. 11c and 11d). Next, the electrolytic solution is injected from the opening (electrolytic solution injection port) on the remaining one side that is not heat-sealed (Fig. 11e), and this one side is heat-sealed to seal the package. (Fig. 11f). By heating in this state, the electrolytic solution permeates the battery element and the gas of the electrolytic solution is removed from the battery element. At this time, the gas of the electrolytic solution moves to the upper part of the forming part M. As shown in FIG. Furthermore, as shown in FIG. 11g, heat-sealing (heat-sealed portion S) is performed in the vicinity of the molding portion M, and the upper portion of the heat-sealed portion S is cut (chain double-dotted line of Q), thereby packaging. A battery in which a battery element is housed in a body is obtained. (In FIG. 11, one terminal protrudes in order to schematically show the battery element C, but normally a battery element with two protruding terminals is accommodated.) At this time, Since the part to be heat-sealed last is in a state where the electrolyte adheres or permeates, the electrolyte foams inside the heat-sealable resin layer in which the electrolyte permeates. , a portion where the heat-fusible resin layers are not completely adhered may be formed. In addition, the additive contained in the heat-fusible resin layer is deposited at the interface between the heat-fusible resin layers to form a portion where the heat-fusible resin layers are not completely bonded to each other. There is also Therefore, there is a problem that the sealing strength of the inlet portion of the package formed of the battery packaging material tends to be lower than the sealing strength of other portions.

Under such circumstances, the main object of the present invention is to provide a battery packaging material having high heat-sealing strength between heat-fusible resin layers permeated with an electrolytic solution. Another object of the present invention is to provide a battery using the battery packaging material.

The present inventors have made earnest studies to solve the above problems. As a result, a battery packaging material composed of a laminate comprising at least a substrate layer, a barrier layer, and a heat-fusible resin layer in this order, wherein the heat-fusible resin layer is composed of three or more layers. The three or more heat-fusible resin layers are composed of two or more types of resins, and include a layer composed of block polypropylene, and a layer composed of block polypropylene is located between the layer closest to the barrier layer and the outermost layer opposite to the barrier layer among the three or more heat-fusible resin layers. , the softening point of the layer located between the barrier layer and the layer composed of block polypropylene is lower than the softening point of the layer composed of block polypropylene, and the barrier layer and the layer composed of block polypropylene A battery packaging material that satisfies all the requirements that the distance in the thickness direction between the The cross-sectional structure of the heat-fusible resin layer has a special shape (specifically, in the cross-section of the heat-fused portion between the heat-fusible resin layers, the heat-fusible resin layer on one side is heat-fused on the other side. It was found that the heat-sealing strength between the heat-fusible resin layers permeated with the electrolytic solution is high.

The present invention has been completed through further studies based on these findings.

That is, the present invention provides inventions in the following aspects.
Section 1. A battery packaging material comprising a laminate comprising at least a substrate layer, a barrier layer, and a heat-fusible resin layer in this order,
The heat-fusible resin layer is composed of three or more layers,
The three or more heat-fusible resin layers are composed of two or more resins,
The three or more heat-fusible resin layers comprise layers made of block polypropylene,
Among the three or more heat-fusible resin layers, the layer made of block polypropylene is the layer closest to the barrier layer and the outermost layer on the side opposite to the barrier layer. It is located between the layers where
The softening point of the layer located between the barrier layer and the layer made of block polypropylene is lower than the softening point of the layer made of block polypropylene,
The battery packaging material, wherein the distance in the thickness direction between the barrier layer and the layer composed of the block polypropylene is 14 μm or more.
Section 2. Item 2. Item 1, wherein the heat-fusible resin layer has, in order from the barrier layer side, a layer made of random polypropylene, a layer made of block polypropylene, and a layer made of random polypropylene. packaging materials for batteries.
Item 3. Item 3. The battery packaging material according to Item 1 or 2, further comprising an adhesive layer between the barrier layer and the heat-fusible resin layer.
Section 4. Item 4. The battery packaging material according to any one of Items 1 to 3, wherein the adhesive layer is composed of acid-modified polyolefin or urethane resin.
Item 5. Item 5. A battery, wherein at least a positive electrode, a negative electrode, and a battery element are housed in a package formed of the battery packaging material according to any one of items 1 to 4.

The present invention provides a battery packaging material comprising a laminate comprising at least a substrate layer, a barrier layer, and a heat-fusible resin layer in this order, in which the heat-fusible resin layers are permeated with an electrolytic solution. It is possible to provide a battery packaging material having a high heat seal strength. Further, according to the present invention, it is possible to provide a battery using the battery packaging material.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the cross-sectional structure of the packaging material for batteries of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the cross-sectional structure of the packaging material for batteries of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the cross-sectional structure of the packaging material for batteries of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the cross-sectional structure of the packaging material for batteries of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the cross-sectional structure of the packaging material for batteries of this invention. It is a schematic diagram for demonstrating the measuring method of seal strength. It is a schematic diagram for demonstrating the measuring method of seal strength. In the cross section of the heat-sealed portion of the heat-sealable resin layers of the battery packaging material, the heat-sealable resin layer on one side protrudes toward the heat-sealable resin layer on the other side. It is a schematic diagram which shows an example of a state of becoming. 4 is a micrograph of a cross section of a heat-sealed portion between heat-sealable resin layers of the battery packaging material obtained in Example 2 (magnification: 20). 4 is a micrograph of a cross section of a heat-sealed portion between heat-sealable resin layers of the battery packaging material obtained in Comparative Example 1 (magnification: 20). FIG. 3 is a schematic diagram for explaining an example of a manufacturing process of a battery;

The battery packaging material of the present invention is a battery packaging material composed of a laminate comprising at least a substrate layer, a barrier layer, and a heat-fusible resin layer in this order, wherein the heat-fusible resin layer is , which is composed of three or more layers, the three or more heat-fusible resin layers are composed of two or more kinds of resins, and has a layer composed of block polypropylene; Among the three or more heat-fusible resin layers, the layer made of polypropylene is composed of a layer located closest to the barrier layer and a layer located on the outermost surface opposite to the barrier layer. The softening point of the layer located between the barrier layer and the layer composed of block polypropylene is lower than the softening point of the layer composed of block polypropylene, and the barrier layer and said block The distance in the thickness direction from the layer made of polypropylene is 14 μm or more. With such a structure, the battery packaging material of the present invention exhibits high heat sealing strength between the heat-fusible resin layers permeated with the electrolytic solution. The battery packaging material of the present invention will be described in detail below.

In this specification, the numerical range indicated by "-" means "more than" and "less than". For example, the notation of 2 to 15 mm means 2 mm or more and 15 mm or less.

1. Laminate Structure and Physical Properties of Battery Packaging Material The battery packaging material 10 of the present invention comprises at least a substrate layer 1, a barrier layer 3, and a heat-fusible resin layer 4, as shown in FIGS. It is composed of laminates provided in this order. In the battery packaging material of the present invention, the substrate layer 1 is the outermost layer, and the heat-fusible resin layer 4 is the innermost layer. That is, when the battery is assembled, the heat-sealable resin layers 4 positioned at the periphery of the battery element are heat-sealed to seal the battery element, thereby sealing the battery element.

The battery packaging material 10 of the present invention may comprise an adhesive layer 2 between the base material layer 1 and the barrier layer 3, as shown in FIGS. 2 to 5, for example. Also, as shown in FIGS. 3 and 4, an adhesive layer 5 may be provided between the barrier layer 3 and the heat-fusible resin layer 4 . Furthermore, as shown in FIG. 4, a surface coating layer 6 may be provided on the outer side of the base material layer 1 (the side opposite to the heat-sealable resin layer 4), if necessary.

As will be described later, in the battery packaging material 10 of the present invention, the heat-fusible resin layer 4 is composed of three or more layers. 1 to 4, the heat-fusible resin layer 4 is divided into three layers: a barrier-side layer 41 located closest to the barrier layer 3, an intermediate layer 42, and a surface layer 43 located on the outermost surface. Fig. 3 shows a schematic diagram composed of layers; 5, the heat-fusible resin layer 4 includes a barrier-side layer 41 positioned closest to the barrier layer 3, an intermediate layer 42, a surface layer 43 positioned on the outermost surface, and a barrier-side layer 43 positioned on the outermost surface. It shows a schematic diagram made up of four layers with a layer 44 between 41 and an intermediate layer 42 .

The thickness of the laminate constituting the battery packaging material 10 of the present invention is not particularly limited. From the viewpoint of exhibiting high heat seal strength between the adhesive resin layers, the thickness is, for example, about 180 μm or less, preferably about 150 μm or less, more preferably about 60 to 180 μm, still more preferably about 60 to 150 μm.

In addition, the battery packaging material of the present invention can be used in an environment of 85 ° C. in an electrolytic solution (lithium hexafluorophosphate concentration is 1 mol / L, volume ratio of ethylene carbonate, diethyl carbonate and dimethyl carbonate is 1: 1 : 1 solution) for 24 hours, and then, with the electrolytic solution adhering to the surface of the heat-fusible resin layer, the heat-fusible resin layers are heated to 190°C in an environment of 25°C. It is preferable that the seal strength (N/15 mm) when the heat-sealed interface is peeled off under the conditions of a surface pressure of 1.0 MPa and a time of 3 seconds is about 90 N/15 mm or more, and about More preferably, it is 100 N/15 mm or more, and even more preferably about 120 N/15 mm or more. The upper limit of the seal strength (N/15mm) is, for example, about 200N/15mm. Specifically, the measurement of the seal strength after contact with the electrolytic solution is performed by the following method.

<Measurement of seal strength after contact with electrolyte>
The sealing strength of the battery packaging material in a 25° C. environment is measured as follows in accordance with JIS K7127:1999. Specifically, as shown in FIG. 6, first, each battery packaging material is cut into 100 mm (TD: Transverse Direction)×200 mm (MD: Machine Direction) (FIG. 6a). Next, the battery packaging material is folded back at the position of the center P (middle of the MD), and the heat-sealable resin layers on the two opposite sides are heat-sealed to form a bag (the shaded area in FIG. 6b is heat-sealed portion). Next, from the opening on one side that is not heat-sealed, the electrolytic solution (1:1:1 mixture of ethylene carbonate, diethyl carbonate, and dimethyl carbonate so that the concentration of _LiPF6 is 1 mol/L) is poured into the liquid. Dissolved electrolyte solution) is enclosed and stored in an environment of 85° C. for 24 hours to impregnate the heat-fusible resin layer with the electrolyte solution (FIG. 6c). Next, it is cut along the two-dot chain line in FIG. 6c to obtain strips, and the electrolyte is discharged (FIGS. 6c and 6d). The heat-fusible resin layers of the obtained strips were put together, and about 10 mm inside from the end of the MD, under the conditions of 25 ° C. environment, seal width 7 mm, temperature 190 ° C., surface pressure 1.0 MPa, 3 seconds. The heat-sealable resin layers are heat-sealed (FIG. 6e). In FIG. 6e, the hatched portion S is the heat-sealed portion. Next, the width of the TD is set to 15 mm, and a test piece is obtained by cutting along the MD (cutting along the two-dot chain line in Fig. 6e) (Fig. 6f). Next, the test piece 13 is left in a temperature environment of 25 ° C. for 2 minutes, and in a temperature environment of 25 ° C., a tensile tester (manufactured by Shimadzu Corporation, AG-Xplus (trade name)) is used to heat-seal the heat-sealed portion. The flexible resin layer is peeled off by 15 mm at a speed of 300 mm/min (Fig. 7). The maximum strength at the time of peeling is defined as the seal strength (N/15 mm). The chuck-to-chuck distance is 50 mm. In the measurement of the seal strength, the case where the test piece 13 is peeled off (broken) at the heat-sealed interface A shown in FIG. position), the test piece 13 may break. When the test piece 13 breaks, the breaking strength is taken as the seal strength. Here, MD is a direction parallel to the winding direction in manufacturing the packaging material, and TD is a direction perpendicular to the winding direction and the thickness direction of the packaging material.

2. Each layer forming the battery packaging material [base layer 1]
In the battery packaging material of the present invention, the substrate layer 1 is the outermost layer. The material forming the base material layer 1 is not particularly limited as long as it has insulating properties. Materials for forming the substrate layer 1 include, for example, polyester resins, polyamide resins, epoxy resins, acrylic resins, fluororesins, polyurethane resins, silicon resins, phenolic resins, polycarbonates, and resin films such as mixtures and copolymers thereof. is mentioned. Among these, polyester resins and polyamide resins are preferred, and biaxially stretched polyester resins and biaxially stretched polyamide resins are more preferred. Specific examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and copolymerized polyester. Specific examples of polyamide resins include nylon 6, nylon 66, copolymers of nylon 6 and nylon 66, nylon 6,10, and polyamide MXD6 (polymetaxylylene adipamide).

The substrate layer 1 may be formed of a single layer of resin film, but may be formed of two or more layers of resin film in order to improve pinhole resistance and insulation. Specific examples include a multilayer structure in which a polyester film and a nylon film are laminated, a multilayer structure in which a plurality of nylon films are laminated, a multilayer structure in which a plurality of polyester films are laminated, and the like. When the substrate layer 1 has a multilayer structure, a laminate of a biaxially stretched nylon film and a biaxially stretched polyester film, a laminate of a plurality of biaxially stretched nylon films, and a laminate of a plurality of biaxially stretched polyester films. body is preferred. For example, when the base material layer 1 is formed from two layers of resin films, a structure in which a polyester resin and a polyester resin are laminated, a structure in which a polyamide resin and a polyamide resin are laminated, or a structure in which a polyester resin and a polyamide resin are laminated. is preferred, and a structure in which polyethylene terephthalate and polyethylene terephthalate are laminated, a structure in which nylon and nylon are laminated, or a structure in which polyethylene terephthalate and nylon are laminated is more preferred. In addition, since the polyester resin does not easily discolor when the electrolytic solution adheres to the surface, it is preferable to laminate the base material layer 1 so that the polyester resin is positioned as the outermost layer in the laminate structure. When the substrate layer 1 has a multilayer structure, the thickness of each layer is preferably about 2 to 25 μm.

When the substrate layer 1 is formed of a multilayer resin film, two or more resin films may be laminated via an adhesive component such as an adhesive or an adhesive resin. are the same as those for the adhesive layer 2, which will be described later. The method for laminating two or more layers of resin films is not particularly limited, and known methods can be employed, such as a dry lamination method and a sandwich lamination method, preferably a dry lamination method. When laminating by a dry lamination method, it is preferable to use a urethane-based adhesive as the adhesive layer. At this time, the thickness of the adhesive layer is, for example, about 2 to 5 μm.

In the present invention, from the viewpoint of improving the moldability of the battery packaging material, it is preferable that the surface of the substrate layer 1 is coated with a lubricant. The lubricant is not particularly limited, but preferably includes an amide-based lubricant. Specific examples of the amide-based lubricant are the same as those exemplified for the heat-fusible resin layer 4 described later.

When a lubricant exists on the surface of the base material layer 1, its amount is not particularly limited, but in an environment with a temperature of 24° C. and a relative humidity of 60%, it is preferably about 3 mg/m ² or more, more preferably 4 to 4 mg/m 2 . About 15 mg/m ² , more preferably about 5 to 14 mg/m ² .

The base material layer 1 may contain a lubricant. Further, the lubricant present on the surface of the base material layer 1 may be obtained by exuding the lubricant contained in the resin constituting the base material layer 1, or may be obtained by coating the surface of the base material layer 1 with the lubricant. may be

The thickness of the base material layer 1 is not particularly limited as long as it functions as a base material.

[Adhesive layer 2]
In the battery packaging material 10 of the present invention, the adhesive layer 2 is a layer provided between the base material layer 1 and the barrier layer 3 as necessary in order to firmly bond them.

The adhesive layer 2 is made of an adhesive capable of bonding the base material layer 1 and the barrier layer 3 together. The adhesive used to form the adhesive layer 2 may be a two-component curing adhesive or a one-component curing adhesive. Furthermore, the adhesion mechanism of the adhesive used to form the adhesive layer 2 is not particularly limited, and may be any of chemical reaction type, solvent volatilization type, heat melting type, heat pressure type, and the like.

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, and copolymerized polyester; Polyurethane adhesive; Epoxy resin; Phenolic resin; Polyamide resin such as nylon 6, nylon 66, nylon 12, copolyamide; Polyolefin such as polyolefin, carboxylic acid-modified polyolefin, metal-modified polyolefin Resins, polyvinyl acetate resins; cellulose adhesives; (meth)acrylic resins; polycarbonates; polyimide resins; amino resins such as urea resins and melamine resins; Examples include silicone-based resins. These adhesive components may be used singly or in combination of two or more. Among these adhesive components, polyurethane-based adhesives are preferred.

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

[Barrier layer 3]
In the battery packaging material, the barrier layer 3 is a layer that has the function of improving the strength of the battery packaging material and also preventing water vapor, oxygen, light, etc. from entering the battery. The barrier layer 3 can be formed of a metal foil, a metal vapor deposition film, an inorganic oxide vapor deposition film, a carbon-containing inorganic oxide vapor deposition film, a film provided with these vapor deposition layers, or the like. Preferably. Specific examples of the metal that constitutes the barrier layer 3 include aluminum alloys, stainless steels, and titanium steels, with aluminum alloys and stainless steels being preferred.

The barrier layer 3 is preferably made of metal foil, and more preferably made of aluminum alloy foil or stainless steel foil.

As the aluminum alloy foil, from the viewpoint of preventing wrinkles and pinholes in the barrier layer 3 during molding of the battery packaging material, for example, a soft aluminum alloy foil made of an annealed aluminum alloy is used. It is more preferable to have Examples of soft aluminum alloy foils include JIS H4160: 1994 A8021H-O, JIS H4160: 1994 A8079H-O, JIS H4000: 2014 A8021P-O, and aluminum alloys having compositions specified by JIS H4000: 2014 A8079P-O. foil.

Further, examples of the stainless steel foil include austenitic stainless steel foil and ferritic stainless steel foil, from the viewpoint of preventing wrinkles and pinholes in the barrier layer 3 during molding of the battery packaging material. be done. The stainless steel foil is preferably made of austenitic stainless steel.

Specific examples of the austenitic stainless steel constituting the stainless steel foil include SUS304, SUS301, SUS316L, etc. Among these, SUS304 is particularly preferable.

The thickness of the barrier layer 3 is not particularly limited as long as it functions as a barrier layer against water vapor. The lower limit is preferably about 10 μm or more, and the thickness range is about 10 to 80 μm, preferably about 10 to 50 μm. In particular, when the barrier layer 3 is made of stainless steel foil, the upper limit of the thickness of the stainless steel foil is preferably about 85 μm or less, more preferably about 50 μm or less, and even more preferably about 40 μm or less. It is more preferably about 30 μm or less, particularly preferably about 25 μm or less, and the lower limit is about 10 μm or more. About 40 μm, more preferably about 10 to 30 μm, more preferably about 15 to 25 μm.

At least one surface, preferably both surfaces, of the barrier layer 3 is preferably subjected to a chemical conversion treatment in order to stabilize adhesion and prevent dissolution and corrosion. Here, chemical conversion treatment refers to treatment for forming an acid-resistant film on the surface of the barrier layer. When an acid-resistant film is formed on the surface of the barrier layer 3 of the present invention, the barrier layer 3 includes an acid-resistant film. Examples of chemical conversion treatments include chromate chromate using chromate compounds such as chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromate acetyl acetate, chromium chloride, and potassium chromium sulfate. Treatment; phosphate chromate treatment using a phosphoric acid compound such as sodium phosphate, potassium phosphate, ammonium phosphate, polyphosphoric acid; aminated phenol having repeating units represented by the following general formulas (1) to (4) Chromate treatment using a polymer and the like can be mentioned. In the aminated phenol polymer, the repeating units represented by the following general formulas (1) to (4) may be contained singly or in any combination of two or more. good too.

In general formulas (1) to (4), X represents a hydrogen atom, hydroxyl group, alkyl group, hydroxyalkyl group, allyl group or benzyl group. R ¹ and R ² are the same or different and represent a hydroxyl group, an alkyl group or a hydroxyalkyl group. Examples of alkyl groups represented by X, R ¹ and R ² in general formulas (1) to (4) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, A linear or branched alkyl group having 1 to 4 carbon atoms such as a tert-butyl group can be mentioned. Examples of hydroxyalkyl groups represented by X, R ¹ and R ² include hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, 1-hydroxypropyl group, 2-hydroxypropyl group, 3- straight or branched chain having 1 to 4 carbon atoms substituted with one hydroxyl group such as hydroxypropyl group, 1-hydroxybutyl group, 2-hydroxybutyl group, 3-hydroxybutyl group and 4-hydroxybutyl group; An alkyl group is mentioned. In general formulas (1) to (4), the alkyl groups and hydroxyalkyl groups represented by X, R ¹ and R ² may be the same or different. In general formulas (1) to (4), X is preferably a hydrogen atom, a hydroxyl group or a hydroxyalkyl group. The number average molecular weight of the aminated phenol polymer having repeating units represented by formulas (1) to (4) is, for example, preferably about 500 to 1,000,000, more preferably about 1,000 to 20,000. more preferred.

In addition, as a chemical conversion treatment method for imparting corrosion resistance to the barrier layer 3, fine particles of metal oxides such as aluminum oxide, titanium oxide, cerium oxide, and tin oxide, and barium sulfate are dispersed in phosphoric acid. A method of forming an acid-resistant film on the surface of the barrier layer 3 by performing a baking treatment at 150° C. or higher can be mentioned. A resin layer obtained by cross-linking a cationic polymer with a cross-linking agent may be further formed on the acid-resistant film. Examples of the cationic polymer include polyethyleneimine, an ionic polymer complex composed of a polymer containing polyethyleneimine and carboxylic acid, a primary amine-grafted acrylic resin obtained by graft-polymerizing a primary amine to an acrylic backbone, and polyallylamine. or derivatives thereof, aminophenol and the like. As these cationic polymers, only one type may be used, or two or more types may be used in combination. Examples of cross-linking agents include compounds having at least one functional group selected from the group consisting of isocyanate groups, glycidyl groups, carboxyl groups, and oxazoline groups, and silane coupling agents. As these cross-linking agents, only one type may be used, or two or more types may be used in combination.

As a specific method for providing an acid-resistant coating, for example, at least the inner layer side surface of an aluminum foil (barrier layer) is first subjected to an alkali immersion method, an electrolytic cleaning method, an acid cleaning method, or an electrolysis method. A degreasing treatment is performed by a well-known treatment method such as an acid cleaning method or an acid activation method, and then the degreased surface is coated with Cr (chromium) phosphate, Ti (titanium) phosphate, Zr (zirconium) phosphate, and phosphorus. A processing solution (aqueous solution) mainly composed of a metal phosphate salt such as Zn (zinc) acid salt and a mixture of these metal salts, or a non-metal phosphate and a mixture of these non-metal salts as a main component A treatment solution (aqueous solution), or a treatment solution (aqueous solution) consisting of a mixture of these and a water-based synthetic resin such as an acrylic resin, a phenolic resin, or a polyurethane resin is applied by a roll coating method, a gravure printing method, an immersion method, etc. An acid-resistant film can be formed by coating with a known coating method. For example, when treated with a Cr (chromium) phosphate salt-based treatment solution, CrPO ₄ (chromium phosphate), AlPO ₄ (aluminum phosphate), Al ₂ O ₃ (aluminum oxide), Al(OH) _x (water aluminum oxide), AlF _x (aluminum fluoride), etc., and when treated with a Zn (zinc) phosphate salt-based treatment solution, Zn ₂ PO ₄ 4H ₂ O (zinc phosphate hydrate ), AlPO ₄ (aluminum phosphate), Al ₂ O ₃ (aluminum oxide), Al(OH) _x (aluminum hydroxide), AlF _x (aluminum fluoride), and the like.

Further, as other specific examples of the method for providing the acid-resistant film, for example, at least the inner layer side surface of the aluminum foil is first subjected to an alkali immersion method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, an acid activated An acid-resistant film can be formed by performing a degreasing treatment by a well-known treatment method such as a degreasing method, and then subjecting the degreased surface to a well-known anodizing treatment.

Another example of the acid-resistant coating includes a coating of a phosphorus compound (eg, phosphate-based) and a chromium compound (eg, chromic acid-based). Phosphate type includes zinc phosphate, iron phosphate, manganese phosphate, calcium phosphate, chromium phosphate and the like, and chromic acid type includes chromium chromate and the like.

In addition, as another example of the acid-resistant film, by forming an acid-resistant film of phosphorus compounds (phosphates, etc.), chromium compounds (chromates, etc.), fluorides, triazine thiol compounds, etc., Prevention of delamination between the aluminum and the base material layer, dissolution and corrosion of the aluminum surface, especially aluminum oxide present on the aluminum surface, due to the hydrogen fluoride generated by the reaction between the electrolyte and moisture. and improve the adhesion (wettability) of the aluminum surface, prevent delamination between the base layer and aluminum during heat sealing, and delaminate between the base layer and aluminum during press molding for embossed types. It shows the effect of preventing lamination. Among the substances that form an acid-resistant film, an aqueous solution composed of three components, phenolic resin, chromium (3) fluoride compound, and phosphoric acid, is applied to the surface of aluminum, followed by dry baking.

Further, the acid-resistant film includes a layer having cerium oxide, phosphoric acid or a phosphate, an anionic polymer, and a cross-linking agent that cross-links the anionic polymer, and the phosphoric acid or phosphate is the It may be blended in an amount of 1 to 100 parts by mass with respect to 100 parts by mass of cerium oxide. It is preferable that the acid-resistant film has a multilayer structure further including a layer having a cationic polymer and a cross-linking agent for cross-linking the cationic polymer.

Further, the anionic polymer is preferably poly(meth)acrylic acid or a salt thereof, or a copolymer containing (meth)acrylic acid or a salt thereof as a main component. Moreover, the cross-linking agent is preferably at least one selected from the group consisting of a compound having a functional group such as an isocyanate group, a glycidyl group, a carboxyl group, or an oxazoline group, and a silane coupling agent.

Further, the phosphoric acid or phosphate is preferably condensed phosphoric acid or condensed phosphate.

As for the chemical conversion treatment, only one type of chemical conversion treatment may be performed, or two or more types of chemical conversion treatments may be performed in combination. Furthermore, these chemical conversion treatments may be carried out using one compound alone, or may be carried out using a combination of two or more compounds. Among chemical conversion treatments, chromic acid chromate treatment and chromate treatment in which a chromic acid compound, a phosphoric acid compound, and an aminated phenol polymer are combined are preferable.

Specific examples of acid-resistant coatings include those containing at least one of phosphates, chromates, fluorides, and triazinethiol compounds. An acid-resistant film containing a cerium compound is also preferred. As the cerium compound, cerium oxide is preferred.

Further, specific examples of acid-resistant coatings include phosphate-based coatings, chromate-based coatings, fluoride-based coatings, and triazinethiol compound coatings. The acid-resistant coating may be one of these, or may be a combination of multiple types. Furthermore, as the acid-resistant film, after degreasing the chemically treated surface of the barrier layer, It may be formed of a different treatment liquid.

The composition of the acid-resistant coating can be analyzed using, for example, time-of-flight secondary ion mass spectrometry.

The amount of the acid-resistant film formed on the surface of the barrier layer 3 in the chemical conversion treatment is not particularly limited. About 0.5 to 50 mg, preferably about 1.0 to 40 mg, in terms of phosphorus compound, about 0.5 to 50 mg, preferably about 1.0 to 40 mg in terms of phosphorus, and aminated phenol polymer is 1.0 It is desired to be contained in a ratio of about 200 mg, preferably about 5.0 to 150 mg.

The thickness of the acid-resistant coating is not particularly limited, but is preferably about 1 nm to 20 μm, more preferably about 1 nm to 100 nm, from the viewpoint of cohesion of the coating and adhesion to the barrier layer and the heat-sealable resin layer. , and more preferably about 1 nm to 50 nm. The thickness of the acid-resistant film can be measured by observation with a transmission electron microscope, or by a combination of observation with a transmission electron microscope and energy dispersive X-ray spectroscopy or electron beam energy loss spectroscopy. By analysis of the composition of the acid-resistant film using time-of-flight secondary ion mass spectrometry, for example, secondary ions composed of Ce, P and O (for example, at least one of Ce ₂ PO ₄ ⁺ , CePO ₄ ⁻ ) and secondary ions composed of Cr, P, and O (eg, at least one of CrPO ₂ ⁺ and CrPO ₄ ⁻ ) are detected.

In the chemical conversion treatment, a solution containing a compound used for forming an acid-resistant film is applied to the surface of the barrier layer by a bar coating method, a roll coating method, a gravure coating method, an immersion method, or the like. It is carried out by heating to about 200°C. In addition, before the barrier layer is subjected to the chemical conversion treatment, the barrier layer may be previously subjected to a degreasing treatment by an alkali immersion method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or the like. By performing the degreasing treatment in this way, it becomes possible to perform the chemical conversion treatment on the surface of the barrier layer more efficiently.

[Heat-fusible resin layer 4]
In the battery packaging material of the present invention, the heat-fusible resin layer 4 corresponds to the innermost layer, and is a layer that seals the battery element by heat-fusibly bonding the heat-fusible resin layers to each other when the battery is assembled.

The heat-fusible resin layer 4 is composed of three or more layers. The three or more heat-fusible resin layers 4 are composed of two or more kinds of resins and have layers composed of block polypropylene. Furthermore, the layer composed of block polypropylene is positioned between the layer closest to the barrier layer 3 and the outermost layer among the three or more heat-fusible resin layers. are doing. Also, the softening point of the layer located between the barrier layer 3 and the layer made of block polypropylene is lower than the softening point of the layer made of block polypropylene. Further, the distance in the thickness direction between the barrier layer 3 and the layer made of block polypropylene is 14 μm or more.

In the battery packaging material 10 of the present invention, since the heat-fusible resin layer 4 satisfies all of these requirements, the heat-fusible resin layers are heat-sealed to each other under predetermined heat-sealing conditions. When the heat-sealable resin layers 4 are joined together, the heat-sealable resin layer 4 on one side of the cross-section of the heat-sealed portion (the cross section parallel to the width direction and the thickness direction of the heat-sealed portion) However, the shape protrudes toward the other heat-fusible resin layer 4 side, so that the heat-fusible resin layers permeated with the electrolytic solution can exhibit high heat-sealing strength. Specific conditions for thermal fusion bonding are the following conditions.

(Conditions for heat sealing)
An electrolytic solution is enclosed in a bag-shaped battery packaging material and stored in an environment of 85° C. for 24 hours to impregnate the heat-fusible resin layer with the electrolytic solution. Next, the battery packaging material impregnated with the electrolytic solution is superimposed so that the fusible resin layer sides face each other and are in contact with each other. Next, heat and pressure were applied from one base layer side of the battery packaging material to the other base layer side under conditions of 25° C. environment, width 7 mm, temperature 190° C., pressure 2.0 MPa, and pressure 2.0 MPa for 3 seconds. is added to heat-seal the heat-sealable resin layers to form a heat-sealed portion.

In the cross section of the heat-sealed portion of the heat-sealable resin layer 4 of the battery packaging material, the heat-sealable resin layer 4 on one side protrudes toward the heat-sealable resin layer 4 on the other side. For example, an example shown in the schematic diagram of FIG. 8 is given. In the cross-sectional view shown in FIG. 8, in the heat-sealed portion 40, the heat-sealable resin layer 4 described on the upper side is deformed so as to be curved by heat and pressure during heat-sealing, and It protrudes toward the heat-fusible resin layer 4 and has a meandering shape. On the other hand, the heat-fusible resin layer 4 described on the lower side was also deformed so as to be curved by the heat and pressure at the time of heat-sealing, protruded toward the heat-fusible resin layer 4 on the upper side, and meandered. It has a shape. As a result, the interface 4a between the heat-fusible resin layer 4 on one side and the heat-fusible resin layer 4 on the other side is formed in a meandering manner at the portion where the heat-fusible resin layer 4 protrudes. , the portion where the heat-fusible resin layers 4 are bonded to each other is larger than when the interface is not meandering. In the battery packaging material of the present invention, the heat-sealable resin layer 4 on one side protrudes toward the heat-sealable resin layer 4 on the other side. It is thought that the area of the interface 4a between the heat-fusible resin layer 4 and the heat-fusible resin layer 4 on the other side is increased, and the heat seal strength between the heat-fusible resin layers 4 permeated with the electrolytic solution is increased.

From the viewpoint of effectively increasing the heat seal strength between the heat-sealable resin layers 4 into which the electrolytic solution has permeated, the height h of the protruded portion of the heat-sealable resin layer 4 in the cross section is The thickness d of the heat-sealable resin layer 4 is preferably larger than the thickness d, and the height h is more preferably about 1.5 to 10 times the thickness d, and further preferably about 3 to 7 times the thickness d. preferable.

The three or more heat-fusible resin layers 4 are composed of two or more kinds of resins. Since the three or more heat-fusible resin layers 4 are formed of two or more kinds of resins having different fluidities, when the heat-fusible resin layers 4 are heat-sealed to each other, the heat-fusible resin The shape of the layer 4 is easily changed, and as a result, the heat-fusible resin layer 4 on one side is likely to form a shape that protrudes toward the heat-fusible resin layer 4 on the other side.

Further, in the battery packaging material 10 of the present invention, the three or more heat-fusible resin layers 4 are provided with an intermediate layer 42 made of block polypropylene, as in the laminated structure shown in FIGS. and the intermediate layer 42 made of the block polypropylene includes a barrier-side layer 41 located closest to the barrier layer 3 among the three or more heat-fusible resin layers 4, and a barrier-side layer 41 on the outermost surface. It is positioned between the positioned surface layer 43 . Furthermore, the softening point of the barrier-side layer 41 positioned between the barrier layer 3 and the intermediate layer 42 made of block polypropylene is lower than the softening point of the intermediate layer 42 made of block polypropylene.

The softening point of the barrier-side layer 41 located closest to the barrier layer 3 is preferably about 60 to 100.degree. C., more preferably about 80 to 95.degree. The softening point of the intermediate layer 42 made of block polypropylene is preferably about 100 to 120.degree. C., more preferably about 105 to 115.degree. The softening point of the surface layer 43 located on the outermost surface is preferably about 60 to 100.degree. C., more preferably about 80 to 98.degree.

In addition, in the present invention, the softening point of the heat-fusible resin layer 4 is a value measured by the following measuring method.

(Method for measuring softening point)
Values were measured using a scanning thermal microscope (NanoTA manufactured by Anasys) under the conditions of a thermal probe cantilever model EX-AN2-200 and a heating rate of 5° C./s. The softening point is the peak top temperature.

The melting point of the barrier-side layer 41 located closest to the barrier layer 3 is preferably about 80 to 170.degree. C., more preferably about 120 to 160.degree. The melting point of the intermediate layer 42 made of block polypropylene is preferably about 120 to 180.degree. C., more preferably about 140 to 170.degree. The melting point of the surface layer 43 located on the outermost surface is preferably about 80 to 170.degree. C., more preferably about 120 to 160.degree. Melting points are values measured by differential scanning calorimetry (DSC).

The melt mass flow rate (MFR) at 230° C. of the barrier-side layer 41 located closest to the barrier layer 3 is preferably about 5 to 17 g/10 minutes, more preferably about 6 to 13 g/10 minutes. is mentioned. The MFR at 230° C. of the intermediate layer 42 made of block polypropylene is preferably about 1 to 10 g/10 minutes, more preferably about 2 to 6 g/10 minutes. The MFR at 230° C. of the surface layer 43 located on the outermost surface is preferably about 5 to 17 g/10 minutes, more preferably about 6 to 13 g/10 minutes. MFR is a value measured by a method conforming to JIS K 7210-1:2014.

Furthermore, the distance W in the thickness direction between the barrier layer 3 and the intermediate layer 42 made of block polypropylene is preferably 14 μm or more, more preferably 20 μm or more. The upper limit of the distance is preferably 30 μm or less, more preferably 25 μm or less. Preferred ranges for the distance include about 14 to 30 μm, about 20 to 30 μm, about 14 to 25 μm, and about 20 to 25 μm. When the distance is 14 μm or more, the heat-fusible resin layer 4 on one side can be suitably protruded to the other side.

The thickness of the barrier-side layer 41 located closest to the barrier layer 3 is preferably about 10-25 μm, more preferably about 12-20 μm. The thickness of the intermediate layer 42 made of block polypropylene is preferably about 15-75 μm, more preferably about 20-60 μm. The thickness of the surface layer 43 located on the outermost surface is preferably about 3 to 20 μm, more preferably about 3 to 15 μm.

The resin component used for each layer of the heat-fusible resin layer 4 is not particularly limited as long as it satisfies all the above-described requirements for the heat-fusible resin layer 4. Examples include polyolefin, cyclic polyolefin, acid Examples include modified polyolefins and acid-modified cyclic polyolefins. The resin constituting the heat-fusible resin layer 4 contains block polypropylene at least in the intermediate layer. Therefore, at least one resin constituting the heat-fusible resin layer 4 contains a polyolefin skeleton. Whether the resin constituting the heat-fusible resin layer 4 contains a polyolefin skeleton can be analyzed by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like, and the analysis method is not particularly limited. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, peaks derived from maleic anhydride are detected near wavenumbers of 1760 cm ⁻¹ and 1780 cm ⁻¹ . However, if the degree of acid denaturation is low, the peak may be too small to be detected. In that case, it can be analyzed by nuclear magnetic resonance spectroscopy.

Specific examples of the polyolefin include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; homopolypropylene; block copolymers of polypropylene (i.e., block polypropylene; block copolymers, block copolymers of propylene and butenes, etc.); Polymers (both block polypropylene and random polypropylene may be used) and the like. Among these polyolefins, polyethylene and polypropylene are preferred.

The cyclic polyolefin is a copolymer of an olefin and a cyclic monomer. Examples of the olefin, which is a constituent monomer of the cyclic polyolefin, include ethylene, propylene, 4-methyl-1-pentene, butadiene, and isoprene. . Examples of cyclic monomers constituting the cyclic polyolefin include cyclic alkenes such as norbornene; specific examples thereof include cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene and norbornadiene. Among these polyolefins, cyclic alkenes are preferred, and norbornene is more preferred.

The acid-modified polyolefin is a polymer modified by block polymerization or graft polymerization of the polyolefin with an acid component such as carboxylic acid. Acid components used for modification include, for example, carboxylic acids such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride and itaconic anhydride, and anhydrides thereof.

The acid-modified cyclic polyolefin is obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin with α,β-unsaturated carboxylic acid or its anhydride, or by copolymerizing α,β- It is a polymer obtained by block polymerization or graft polymerization of an unsaturated carboxylic acid or its anhydride. The carboxylic acid-modified cyclic polyolefin is the same as described above. The carboxylic acid used for modification is the same as the acid component used for modification of the polyolefin.

Among these resin components, polyolefin such as polypropylene and carboxylic acid-modified polyolefin are preferred; polypropylene and acid-modified polypropylene are more preferred.

The heat-fusible resin layer 4 may be formed of one resin component alone, or may be formed of a blend polymer in which two or more resin components are combined. Furthermore, the heat-fusible resin layer 4 may be composed of only one layer, or may be composed of two or more layers of the same or different resin components.

The heat-fusible resin layer 4 consists of random polypropylene as a barrier-side layer 41 positioned closest to the barrier layer 3, block propylene as an intermediate layer 42, and a surface layer 43 positioned on the outermost surface. Random polypropylene. As a specific layer structure of the heat-fusible resin layer 4, for example, in the laminated structures shown in FIGS. Random polypropylene as 41/block propylene as intermediate layer 42/random polypropylene as outermost surface layer 43 are laminated; for example, in the laminated structure shown in FIG. acid-modified polypropylene as the barrier-side layer 41 located on the side/random polypropylene as the layer 44 located between the barrier-side layer 41 and the intermediate layer 42/block propylene as the intermediate layer 42/located on the outermost surface For example, a four-layer structure in which random polypropylene is laminated as the surface layer 43 is provided. When the adhesive layer 5 to be described later is not provided, the barrier-side layer 41 is preferably made of the acid-modified polyolefin described above from the viewpoint of enhancing adhesion to the barrier layer 3 . The thickness of the layer 44 located between the barrier-side layer 41 and the intermediate layer 42 is preferably about 2-20 μm, more preferably about 4-12 μm. The softening point of the layer 44 located between the barrier-side layer 41 and the intermediate layer 42 is preferably about 80 to 120.degree. C., more preferably about 90 to 110.degree.

In the block polypropylene constituting the intermediate layer 42, the proportion of propylene units is preferably about 50 mol % to 99 mol %, more preferably about 80 mol % to 99 mol %. In the random polypropylene of the surface layer 43 or barrier-side layer 41, the proportion of propylene units is preferably about 50 mol % to 99 mol %, more preferably about 80 mol % to 99 mol %.

In the present invention, from the viewpoint of improving the moldability of the battery packaging material, it is preferable that a lubricant is adhered to the surface of the heat-fusible resin layer. The lubricant is not particularly limited, but preferably includes an amide-based lubricant. Specific examples of amide-based lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, and unsaturated fatty acid bisamides. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide and the like. Further, specific examples of methylolamide include methylol stearamide. Specific examples of saturated fatty acid bisamides include methylenebisstearic acid amide, ethylenebiscapric acid amide, ethylenebislauric acid amide, ethylenebisstearic acid amide, ethylenebishydroxystearic acid amide, ethylenebisbehenic acid amide, hexamethylenebisstearin. acid amide, hexamethylenebisbehenamide, hexamethylenehydroxystearic acid amide, N,N'-distearyladipic acid amide, N,N'-distearylsebacic acid amide and the like. Specific examples of unsaturated fatty acid bisamides include ethylenebisoleic acid amide, ethylenebiserucic acid amide, hexamethylenebisoleic acid amide, N,N'-dioleyladipic acid amide, and N,N'-dioleylsebacic acid amide. etc. Specific examples of fatty acid ester amides include stearamide ethyl stearate. Further, specific examples of the aromatic bisamide include m-xylylenebisstearic acid amide, m-xylylenebishydroxystearic acid amide, N,N'-distearylisophthalic acid amide and the like. Lubricants may be used singly or in combination of two or more.

When a lubricant exists on the surface of the heat-sealable resin layer 4 ^, the amount of the lubricant is not particularly limited. is about 4 to 15 mg/m ² , more preferably about 5 to 14 mg/m ² .

The heat-fusible resin layer 4 may contain a lubricant. Further, the lubricant present on the surface of the heat-fusible resin layer 4 may be obtained by exuding the lubricant contained in the resin constituting the heat-fusible resin layer 4, or the heat-fusible resin layer. The surface of 4 may be coated with a lubricant.

The thickness of the heat-fusible resin layer 4 as a whole is not particularly limited as long as it functions as a heat-fusible resin layer. From the viewpoint of a battery packaging material having particularly high sealing strength, the lower limit is preferably about 10 μm or more, about 15 μm or more, about 20 μm or more, about 30 μm or more, and the upper limit is preferably about 90 μm or less, more preferably about 90 μm or less. about 80 μm or less. Preferred ranges for the thickness of the heat-fusible resin layer are about 10 to 90 μm, about 10 to 80 μm, about 15 to 90 μm, about 15 to 80 μm, about 20 to 90 μm, about 20 to 80 μm, about 30 to 90 μm, About 30 to 80 μm can be mentioned.

[Adhesion layer 5]
In the battery packaging material of the present invention, the adhesive layer 5 is a layer optionally provided between the barrier layer 3 and the heat-fusible resin layer 4 in order to firmly bond them.

The adhesive layer 5 is made of a resin capable of bonding the barrier layer 3 and the heat-fusible resin layer 4 together. As the resin used to form the adhesive layer 5, the same adhesives as those exemplified for the adhesive layer 2 can be used in terms of the adhesive mechanism, the types of adhesive components, and the like. As the resin used to form the adhesive layer 5, polyolefin-based resins such as polyolefins, cyclic polyolefins, carboxylic acid-modified polyolefins, and carboxylic acid-modified cyclic polyolefins exemplified for the heat-sealable resin layer 4 can also be used. . From the viewpoint of excellent adhesion between the barrier layer 3 and the heat-fusible resin layer 4, the polyolefin is preferably carboxylic acid-modified polyolefin, and particularly preferably carboxylic acid-modified polypropylene. That is, the resin forming the adhesive layer 5 may or may not contain a polyolefin skeleton, but preferably contains a polyolefin skeleton. Whether or not the resin constituting the adhesive layer 5 contains a polyolefin skeleton can be analyzed by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like, and the analysis method is not particularly limited. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, peaks derived from maleic anhydride are detected near wavenumbers of 1760 cm ⁻¹ and 1780 cm ⁻¹ . However, if the degree of acid denaturation is low, the peak may be too small to be detected. In that case, it can be analyzed by nuclear magnetic resonance spectroscopy.

Furthermore, from the viewpoint of making the battery packaging material excellent in shape stability after molding while reducing the thickness of the battery packaging material, the adhesive layer 5 is made of a resin composition containing an acid-modified polyolefin and a curing agent. It may be a cured product. As the acid-modified polyolefin, the same carboxylic acid-modified polyolefin and carboxylic acid-modified cyclic polyolefin exemplified for the heat-sealable resin layer 4 can be preferably exemplified.

Moreover, the curing agent is not particularly limited as long as it cures the acid-modified polyolefin. Examples of curing agents include epoxy-based curing agents, polyfunctional isocyanate-based curing agents, carbodiimide-based curing agents, and oxazoline-based curing agents.

The epoxy-based curing agent is not particularly limited as long as it is a compound having at least one epoxy group. Examples of epoxy-based curing agents include epoxy resins such as bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, novolac glycidyl ether, glycerin polyglycidyl ether, and polyglycerin polyglycidyl ether.

The polyfunctional isocyanate-based curing agent is not particularly limited as long as it is a compound having two or more isocyanate groups. Specific examples of polyfunctional isocyanate curing agents include isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymers and nurates thereof, and Mixtures and copolymers with other polymers may be mentioned.

The carbodiimide-based curing agent is not particularly limited as long as it is a compound having at least one carbodiimide group (-N=C=N-). As the carbodiimide curing agent, a polycarbodiimide compound having at least two carbodiimide groups is preferred.

The oxazoline-based curing agent is not particularly limited as long as it is a compound having an oxazoline skeleton. Specific examples of oxazoline-based curing agents include Epocross series manufactured by Nippon Shokubai Co., Ltd., and the like.

From the viewpoint of enhancing the adhesion between the barrier layer 3 and the heat-fusible resin layer 4 by the adhesive layer 5, the curing agent may be composed of two or more kinds of compounds.

The content of the curing agent in the resin composition forming the adhesive layer 5 is preferably in the range of about 0.1 to 50% by mass, more preferably in the range of about 0.1 to 30% by mass. More preferably, it is in the range of about 0.1 to 10% by mass.

The thickness of the adhesive layer 5 is not particularly limited as long as it functions as an adhesive layer. Up to about 5 μm can be mentioned. In the case of using the resin exemplified for the heat-fusible resin layer 4, the thickness is preferably about 2 to 50 μm, more preferably about 10 to 45 μm, and even more preferably about 20 to 45 μm. In the case of a cured product of an acid-modified polyolefin and a curing agent, the thickness is preferably about 30 μm or less, more preferably about 0.1 to 20 μm, still more preferably about 0.5 to 5 μm. When the adhesive layer 5 is a cured product of a resin composition containing an acid-modified polyolefin and a curing agent, the adhesive layer 5 can be formed by applying the resin composition and curing it by heating or the like.

[Surface coating layer 6]
In the battery packaging material of the present invention, for the purpose of improving design, electrolyte resistance, scratch resistance, moldability, etc., on the substrate layer 1 (barrier layer of the substrate layer 1) 3), a surface coating layer 6 may be provided, if necessary. The surface coating layer 6 is the outermost layer when the battery is assembled.

The surface coating layer 6 can be made of, for example, polyvinylidene chloride, polyester resin, urethane resin, acrylic resin, epoxy resin, or the like. Among these, the surface coating layer 6 is preferably formed of a two-liquid curing resin. Examples of the two-liquid curable resin forming the surface coating layer 6 include a two-liquid curable urethane resin, a two-liquid curable polyester resin, and a two-liquid curable epoxy resin. Further, the surface coating layer 6 may contain additives.

Examples of the additive include fine particles having a particle size of about 0.5 nm to 5 μm. The material of the additive is not particularly limited, but examples thereof include metals, metal oxides, inorganic substances and organic substances. The shape of the additive is also not particularly limited, but examples thereof include spherical, fibrous, plate-like, amorphous, and balloon-like shapes. Specific examples of additives include talc, silica, graphite, kaolin, montmorilloid, 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, alumina, carbon black, carbon nanotubes, high melting point nylon, crosslinked acrylic, crosslinked styrene, crosslinked polyethylene, benzoguanamine, gold, aluminum, copper, nickel, and the like. These additives may be used singly or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferred from the viewpoint of dispersion stability and cost. In addition, the additive may be subjected to various surface treatments such as insulation treatment and high-dispersion treatment.

The content of the additive in the surface coating layer is not particularly limited, but is preferably about 0.05 to 1.0% by mass, more preferably about 0.1 to 0.5% by mass.

A method for forming the surface coating layer 6 is not particularly limited, but for example, a method of coating one surface of the substrate layer 1 with a two-liquid curing resin that forms the surface coating layer 6 can be used. When an additive is blended, the additive may be added to the two-liquid curing resin, mixed, and then applied.

The thickness of the surface coating layer 6 is not particularly limited as long as it exhibits the above functions as the surface coating layer 6, and is, for example, approximately 0.5 to 10 μm, preferably approximately 1 to 5 μm.

3. Method for Producing Battery Packaging Material The method for producing the battery packaging material of the present invention is not particularly limited as long as a laminate obtained by laminating each layer having a predetermined composition can be obtained. That is, the method for producing a battery packaging material of the present invention includes at least a step of laminating a substrate layer, a barrier layer, and a heat-fusible resin layer in this order to obtain a laminate. As the heat-fusible resin layer, the heat-fusible resin layer described in the section [Heat-fusible resin layer 4] is used. The structure of each layer of the laminate is as described above.

An example of the method for producing the battery packaging material of the present invention is as follows. First, a layered body (hereinafter also referred to as "layered body A") is formed by laminating a substrate layer 1, an adhesive layer 2, and a barrier layer 3 in this order. Specifically, the laminate A is formed by applying an adhesive used for forming the adhesive layer 2 to the base material layer 1 or the barrier layer 3 whose surface is chemically treated as necessary, by gravure coating, roll After coating and drying by a coating method such as a coating method, the barrier layer 3 or the base material layer 1 is laminated and the adhesive layer 2 is cured by a dry lamination method.

Next, on the barrier layer 3 of the laminate A, the adhesive layer 5 and the heat-fusible resin layer 4 are laminated in this order. For example, (1) a method of laminating the adhesive layer 5 and the heat-fusible resin layer 4 on the barrier layer 3 of the laminate A by co-extrusion (co-extrusion lamination method); and a heat-fusible resin layer 4 are laminated, and this is laminated on the barrier layer 3 of the laminate A by a thermal lamination method. An adhesive for forming the layer 5 is applied by extrusion or solution coating, and laminated by a method such as drying at a high temperature or baking. A method of laminating by a thermal lamination method, (4) Bonding while pouring a melted adhesive layer 5 between the barrier layer 3 of the laminate A and the heat-fusible resin layer 4 previously formed into a sheet form. A method of laminating the laminate A and the heat-fusible resin layer 4 with the layer 5 interposed therebetween (sandwich lamination method) can be used.

When providing the surface coating layer 6 , the surface coating layer 6 is laminated on the surface of the substrate layer 1 opposite to the barrier layer 3 . The surface coating layer 6 can be formed, for example, by coating the surface of the substrate layer 1 with the above-described resin for forming the surface coating layer 6 . The order of the step of laminating the barrier layer 3 on the surface of the base material layer 1 and the step of laminating the surface coating layer 6 on the surface of the base material layer 1 is not particularly limited. For example, after forming the surface coating layer 6 on the surface of the substrate layer 1 , the barrier layer 3 may be formed on the surface of the substrate layer 1 opposite to the surface coating layer 6 .

Surface coating layer 6/base layer 1/adhesive layer 2 optionally provided/barrier layer 3/adhesive layer 5 optionally provided with surface chemical conversion treatment as described above / A laminated body consisting of the heat-fusible resin layer 4 is formed. You may use for heat processing, such as a formula. Conditions for such heat treatment include, for example, 150 to 250° C. for 1 to 5 minutes.

In the battery packaging material of the present invention, each layer constituting the laminate, if necessary, improves or stabilizes film formability, lamination processing, final product secondary processing (pouching, embossing) suitability, etc. For this purpose, surface activation treatment such as corona treatment, blast treatment, oxidation treatment and ozone treatment may be applied.

4. Use of Battery Packaging Material The battery packaging material of the present invention is used as a package for hermetically housing battery elements such as a positive electrode, a negative electrode and an electrolyte. That is, a battery can be made by housing a battery element comprising at least a positive electrode, a negative electrode, and an electrolyte in a package formed of the battery packaging material of the present invention.

Specifically, a battery element comprising at least a positive electrode, a negative electrode, and an electrolyte is wrapped in the battery packaging material of the present invention in a state in which metal terminals connected to the positive electrode and the negative electrode protrude outward. By covering the periphery of the element so as to form a flange portion (area where the heat-fusible resin layers contact each other), and sealing the heat-fusible resin layers of the flange portion by heat-sealing, A battery using the battery packaging material is provided. When a battery element is housed in a package formed of the battery packaging material of the present invention, the heat-sealable resin portion of the battery packaging material of the present invention should face the inside (the surface in contact with the battery element). to form a package.

The battery packaging material of the present invention may be used for either primary batteries or secondary batteries, preferably for secondary batteries. The type of secondary battery to which the battery packaging material of the present invention is applied is not particularly limited. Examples include iron storage batteries, nickel/zinc storage batteries, silver oxide/zinc storage batteries, metal-air batteries, polyvalent cation batteries, capacitors, capacitors, and the like. Among these secondary batteries, lithium-ion batteries and lithium-ion polymer batteries can be cited as suitable targets for application of the battery packaging material of the present invention.

In the battery packaging material of the present invention, the heat-fusible resin layer is brought into contact with the electrolyte in a high-temperature environment, and the heat-fusible resin layers are heat-sealed with the electrolyte adhered to the heat-fusible resin layer. High sealing strength is exhibited by heat fusion even when it is sealed. Therefore, the battery packaging material of the present invention can be particularly suitably used as a battery packaging material for vehicle batteries and mobile device batteries, which are subjected to an aging process in a high-temperature environment.

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

(Example 1)
A barrier layer made of an aluminum alloy foil (thickness: 35 μm) having both sides subjected to chemical conversion treatment was laminated by a dry lamination method on the surface of a biaxially oriented nylon film (thickness: 15 μm) as a base layer. Specifically, a two-component urethane adhesive (a polyol compound and an aromatic isocyanate compound) was applied to one side of the aluminum alloy foil to form an adhesive layer (3 μm thick) on the barrier layer. Next, after laminating the adhesive layer on the barrier layer and the substrate layer, an aging treatment was performed to prepare a laminate of substrate layer/adhesive layer/barrier layer. In addition, the chemical conversion treatment of the aluminum alloy foil was carried out by roll coating a treatment solution consisting of phenolic resin, chromium fluoride compound, and phosphoric acid so that the coating amount of chromium was 10 mg/m ² (dry weight). This was done by coating both sides of the foil and baking it.

Then, a maleic anhydride-modified polypropylene (PPa layer, melting point 160° C., softening point 95° C., melt mass flow rate at 230° C. 6 g/10 minutes, thickness 15 μm) was extruded in a molten state on the barrier layer of the laminate. By doing so, a barrier-side layer of the heat-fusible resin layer 4 was formed on the barrier layer. From above, random polypropylene (R-PP layer, melting point 140 ° C., softening point 98 ° C., melt mass flow rate at 230 ° C. 7 g / 10 minutes, 4.5 μm), block polypropylene (intermediate layer, B-PP layer, melting point 162°C, softening point 110°C, melt mass flow rate at 230°C 2 g/10 min, 21 μm), random polypropylene (surface layer, R-PP layer, melting point 140°C, softening point 98°C, melt mass flow rate at 230°C 7 g/10 min, 4.5 μm) are laminated in order by a sandwich lamination method to obtain four layers of the heat-fusible resin described in Table 1. A battery packaging material comprising a layer was obtained.

(Example 2)
In the same manner as in Example 1, a laminate of substrate layer/adhesive layer/barrier layer was produced. The chemical conversion treatment of the aluminum alloy foil was also carried out in the same manner as in Example 1. Next, the barrier layer side of the laminate, random polypropylene (barrier side layer, R-PP layer, melting point 140° C., softening point 98° C., melt mass flow rate at 230° C. 7 g/10 minutes, 12 μm), block polypropylene (Intermediate layer, B-PP layer, melting point 162 ° C., softening point 110 ° C., melt mass flow rate 2 g / 10 minutes at 230 ° C., 56 μm), random polypropylene (surface layer, R-PP layer, melting point 140 ° C., softening point A laminated film having a three-layer structure in which melt mass flow rate of 7 g/10 min at 98° C. and 230° C., 12 μm) was laminated in order was laminated by a dry lamination method. Specifically, a two-liquid curing polyolefin adhesive (acid-modified polyolefin compound and epoxy compound) was applied to one side of the aluminum alloy foil to form an adhesive layer (3 μm thick) on the barrier layer. . Next, after laminating the adhesive layer on the barrier layer and the laminated film having the three-layer structure, aging treatment was performed to obtain a battery packaging material having the laminated structure shown in Table 1.

(Comparative example 1)
In the same manner as in Example 1, a laminate of substrate layer/adhesive layer/barrier layer was produced. The chemical conversion treatment of the aluminum alloy foil was also carried out in the same manner as in Example 1. Next, on the barrier layer of the laminate, maleic anhydride-modified polypropylene (PPa layer, melting point 160° C., softening point 95° C., melt mass flow rate at 230° C. 6 g/10 minutes, thickness 40 μm) and random polypropylene ( R-PP layer, melting point 140 ° C., softening point 98 ° C., melt mass flow rate 7 g / 10 min at 230 ° C., 40 μm). An adhesive resin layer was formed to obtain a battery packaging material having the laminate structure shown in Table 1.

(Comparative example 2)
In the same manner as in Example 1, a laminate of substrate layer/adhesive layer/barrier layer was produced. The chemical conversion treatment of the aluminum alloy foil was also carried out in the same manner as in Example 1. Next, on the barrier layer of the laminate, maleic anhydride-modified polypropylene (PPa layer, melting point 160° C., softening point 95° C., melt mass flow rate at 230° C. 6 g/10 minutes, thickness 15 μm) and random polypropylene ( R-PP layer, melting point 140° C., softening point 98° C., melt mass flow rate 7 g/10 min at 230° C., 50 μm) and maleic anhydride-modified polypropylene (PPa layer, melting point 160° C., softening point 95° C., 230° C. A melt mass flow rate of 6 g / 10 minutes, a thickness of 15 μm) is co-extruded in this order to form a heat-fusible resin layer consisting of three layers, and the lamination shown in Table 1 A battery packaging material having the structure was obtained.

(Comparative Example 3)
In the same manner as in Example 1, a laminate of substrate layer/adhesive layer/barrier layer was produced. The chemical conversion treatment of the aluminum alloy foil was also carried out in the same manner as in Example 1. Next, the barrier layer side of the laminate, random polypropylene (R-PP layer, melting point 140 ° C., softening point 98 ° C., melt mass flow rate 7 g / 10 minutes at 230 ° C., 4.5 μm), block polypropylene (B - PP layer, melting point 162°C, softening point 110°C, melt mass flow rate 2 g/10 min at 230°C, 21 μm), random polypropylene (R-PP layer, melting point 140°C, softening point 98°C, melt at 230°C 4.5 μm at a mass flow rate of 7 g/10 min) was laminated in order by a dry lamination method. Specifically, a two-component curing type polyolefin adhesive (acid-modified polyolefin compound and epoxy compound) was applied to one side of the aluminum alloy foil, and an adhesive layer (softening point 70°C, thickness 3 μm) was formed. Next, after laminating the adhesive layer on the barrier layer and the laminated film having the three-layer structure, aging treatment was performed to obtain a battery packaging material having the laminated structure shown in Table 1.

<Observation of the cross-sectional structure of the heat-sealed part>
Each battery packaging material was folded back at the center with the heat-sealable resin layer on the inside, and two edges were heat-sealed to form a bag. Next, from the remaining unheat-sealed end (opening) of each bag-shaped battery packaging material, electrolytic solution (ethylene _carbonate , diethyl carbonate, An electrolyte dissolved in a liquid mixed with dimethyl carbonate at a ratio of 1:1:1 was poured, and the one side was heat-sealed to seal the electrolyte. Next, the heat-fusible resin layer was impregnated with the electrolytic solution by storing for 24 hours in an environment of 85°C. Next, one side of the end of the battery packaging material in the form of a bag is cut off, the cut off side is turned downward, and left to stand for 10 seconds to drain the electrolyte, and then the remaining two sides are sealed. cut off. Next, they were overlapped so that the heat-fusible resin layer sides faced each other and were in contact with each other. Next, in the peripheral portion of the battery packaging material, from one base layer side to the other base layer side, under a 25° C. environment, a width of 7 mm, a temperature of 190° C., a pressure of 2.0 MPa, and a pressure of 2.0 MPa for 3 seconds. By applying heat and pressure under the conditions of , the heat-sealable resin layers were heat-sealed to form the heat-sealed portion. Next, using a microtome, the heat-sealed portion was cut in the thickness direction, and the obtained cross section was observed with a microscope. Microscopic photographs of cross sections of Example 2 and Comparative Example 1 are shown in FIG. 9 (Example 2) and FIG. 10 (Comparative Example 1), respectively. Table 1 shows the evaluation of the cross-sectional structure of the heat-sealed portion. The microscope used was VK-9710 manufactured by Keyence Corporation.

<Measurement of seal strength>
In accordance with JIS K7127:1999, the sealing strength of the battery packaging material in a 25° C. environment was measured as follows. Specifically, as shown in FIG. 6, each battery packaging material was first cut into a size of 100 mm (TD: Transverse Direction)×200 mm (MD: Machine Direction) (FIG. 6a). Next, each battery packaging material is folded back at the position of the center P (middle of the MD), and the heat-sealable resin layers on the two sides facing each other are heat-sealed to form a bag (shaded area in FIG. 6b). is the heat-sealed portion). Next, from the opening on one side that is not heat-sealed, the electrolytic solution (1:1:1 mixture of ethylene carbonate, diethyl carbonate, and dimethyl carbonate so that the concentration of _LiPF6 is 1 mol/L) is poured into the liquid. The melted electrolyte solution) was enclosed and stored in an environment of 85° C. for 24 hours to impregnate the heat-fusible resin layer with the electrolyte solution (FIG. 6c). Next, it was cut at the position indicated by the two-dot chain line in FIG. 6c to obtain strips, and the electrolytic solution was discharged (FIGS. 6c and 6d). The heat-fusible resin layers of the obtained strip pieces were put together, and the heat-fusible resin was applied at a distance of about 10 mm from the end of the MD under the conditions of a seal width of 7 mm, a temperature of 190 ° C., a surface pressure of 1.0 MPa, and a surface pressure of 1.0 MPa for 3 seconds. The layers were heat-sealed together (Fig. 6e). In FIG. 6e, the hatched portion S is the heat-sealed portion. Next, the width of the TD was set to 15 mm, and a test piece was obtained by cutting in the MD (cutting at the position of the two-dot chain line in Fig. 6e) (Fig. 6f). Next, the test piece 13 is left in a temperature environment of 25 ° C. for 2 minutes, and in a temperature environment of 25 ° C., a tensile tester (manufactured by Shimadzu Corporation, AG-Xplus (trade name)) is used to heat-seal the heat-sealed portion. The flexible resin layer was peeled off by 15 mm at a speed of 300 mm/min (Fig. 7). The maximum strength at the time of peeling was defined as the seal strength (N/15 mm). The chuck-to-chuck distance is 50 mm. Table 1 shows the results. In the measurement of the seal strength, the case where the test piece 13 is peeled off (broken) at the heat-sealed interface A shown in FIG. position), the test piece 13 may break. When the test piece 13 was broken, the breaking strength was described in Table 1 as the seal strength. Here, MD is a direction parallel to the winding direction in manufacturing the packaging material, and TD is a direction perpendicular to the winding direction and the thickness direction of the packaging material.

In Table 1, ONy is a biaxially oriented nylon film, DL is an adhesive layer formed by a dry lamination method, ALM is an aluminum alloy foil, PPa is maleic anhydride-modified polypropylene, R-PP is random polypropylene, and B-PP is It stands for block polypropylene. Further, the numerical value behind each layer means the thickness (μm), for example, the notation “ONy15” means “15 μm thick biaxially stretched nylon film”.

In the battery packaging materials of Examples 1 and 2, among the heat-fusible resin layers composed of three or more layers, the layer composed of block polypropylene is the most barrier layer side of the heat-fusible resin layers. and the layer located on the outermost surface opposite to the barrier layer, the layer located between the barrier layer and the layer composed of block polypropylene is lower than the softening point of the layer made of block polypropylene, and the distance in the thickness direction between the barrier layer and the layer made of block polypropylene is 14 μm or more. In Examples 1 and 2, when the heat-fusible resin layers are superimposed so that the heat-fusible resin layers are in contact with each other, and the heat-fusible resin layers are heat-fused to each other, the width direction and the thickness direction of the heat-fusible part Observing the parallel cross section, the heat-fusible resin layer on one side has a shape protruding toward the heat-fusible resin layer on the other side, and the heat-fusible property in which the electrolytic solution permeates The heat seal strength between the resin layers was high.

On the other hand, in the battery packaging materials of Comparative Examples 1 to 3, the heat-fusible resin layer does not have such a specific structure. In Comparative Examples 1 to 3, when the heat-fusible resin layers are superimposed so that the heat-fusible resin layers are in contact with each other, and the heat-fusible resin layers are heat-fused to each other, the width direction and the thickness direction of the heat-fused portion Observing the parallel cross sections, when the heat-fusible resin layers are heat-fused, the interface is flat, and compared to Examples 1 and 2, the heat-fusible resin layers permeated with the electrolyte The heat seal strength of was low.

1 base material layer 2 adhesive layer 3 barrier layer 4 heat-fusible resin layer 5 adhesive layer 6 surface coating layer 10 battery packaging material 13 test piece 40 heat-fusible portion 41 barrier-side layer 42 intermediate layer 43 surface layer 44 barrier Layer 4a between the side layer and the intermediate layer Interface between the heat-fusible resin layer on one side and the heat-fusible resin layer on the other side

Claims (4)

A battery packaging material comprising a laminate comprising at least a substrate layer, a barrier layer, and a heat-fusible resin layer in this order,
The heat-fusible resin layer is composed of three or more layers,
The three or more heat-fusible resin layers are composed of two or more resins,
The three or more heat-fusible resin layers comprise layers made of block polypropylene,
Among the three or more heat-fusible resin layers, the layer made of block polypropylene is the layer closest to the barrier layer and the outermost layer on the side opposite to the barrier layer. It is located between the layers where
The softening point of the layer located between the barrier layer and the layer made of block polypropylene is lower than the softening point of the layer made of block polypropylene,
the distance in the thickness direction between the barrier layer and the layer made of block polypropylene is 20 μm or more;
An adhesive layer is provided between the barrier layer and the heat-fusible resin layer,
The battery packaging material, wherein the adhesive layer has a thickness of 1 μm or more and 5 μm or less. 2. The method according to claim 1, wherein the heat-fusible resin layer has, in order from the barrier layer side, a layer made of random polypropylene, a layer made of block polypropylene, and a layer made of random polypropylene. A packaging material for the described battery. 3. The battery packaging material according to claim 1, wherein said adhesive layer is made of acid-modified polyolefin or urethane resin. A battery, wherein at least a positive electrode, a negative electrode, and a battery element are housed in a package formed of the battery packaging material according to any one of claims 1 to 3.