HK1191743A

HK1191743A - Cladding for lithium ion cell, lithium ion cell, and method for producing lithium ion cell

Info

Publication number: HK1191743A
Application number: HK14104983.5A
Authority: HK
Inventors: 铃田昌由; 谷口智昭
Original assignee: 凸版印刷株式会社
Priority date: 2011-05-11
Filing date: 2012-05-11
Publication date: 2014-08-01

Description

Outer packaging material for lithium ion battery, and method for manufacturing lithium ion battery

Technical Field

The present invention relates to an exterior material for a lithium ion battery, and a method for manufacturing a lithium ion battery.

This application is based on the priority claim of Japanese patent application No. 2011-.

Background

Currently, lithium ion secondary batteries that have high energy, can be made thinner and smaller are actively being researched and developed as consumer secondary batteries that are used in personal computers, portable terminal devices such as cellular phones, video cameras, and the like. As an outer package for a lithium ion battery (hereinafter, sometimes simply referred to as "outer package"), a molded product obtained by deep-drawing a multilayer laminated film (for example, a structure such as a heat-resistant base material layer/aluminum foil layer/sealant (hot-melt film) layer) by cold forming (deep-drawing molding) has been used, because of the advantages of light weight and freely selectable battery shape, instead of a conventional metal can. Further, from the viewpoint of not only high flexibility of battery shape but also light weight, high heat dissipation and low cost, application of the exterior material using the laminate film to a battery (battery) of a hybrid vehicle or an electric vehicle, which has been developed remarkably in recent years and has a small environmental load, has been attempted.

A lithium ion battery using a laminate film type outer package is formed by storing a positive electrode material, a negative electrode material, and a separator in the deep-drawn molded product as a battery main body part, storing an electrolyte layer made of an electrolyte solution in which a lithium salt is dissolved in an aprotic solvent (propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, or the like), or a polymer gel impregnated with the electrolyte solution, and heat-sealing the deep-drawn molded product by a heat sealing method.

The electrolyte has high permeability to the sealant layer. Therefore, there is a problem in that the permeated electrolyte reduces the lamination strength between the aluminum foil layer and the sealant layer to eventually cause leakage of the electrolyte. Further, LiPF as an electrolyte₆、LiBF₄Such lithium salts generate hydrofluoric acid by hydrolysis reaction, and thus cause corrosion of the metal surface and decrease in the lamination strength between the layers of the laminated film. Therefore, the outer packaging material is required to have the performance of preventing corrosion of the electrolyte and hydrofluoric acid.

As a method for imparting corrosion resistance to an electrolytic solution or hydrofluoric acid, a method of performing chromate treatment using hexavalent chromium on the surface of an aluminum foil is known. However, hexavalent chromium has been treated as a harmful substance to the environment, as in Rohs (directive on restriction of use of certain harmful components in electronic and electric appliances) restriction directive in europe, REACH (registration, evaluation, authorization, and restriction of chemicals) restriction directive, and thus, chromate treatment using trivalent chromium is currently being carried out. However, in the future, there is a possibility that a comprehensive chromium elimination action will be taken due to the use of hexavalent chromium as a starting material in obtaining trivalent chromium. In particular, from the viewpoint of application to electric vehicles which may be environmentally affected, it is important to provide a method for imparting corrosion resistance to an electrolyte or hydrofluoric acid so as to completely eliminate the treatment with a chromium compound.

On the other hand, the outer packaging material is required to have excellent moldability. That is, from the viewpoint of determining how the energy density can be determined by how the cell and the electrolyte can be housed in the lithium ion battery, in order to increase the amount of the cell and the electrolyte housed, it is required to further increase the molding depth when the exterior material is molded into the battery shape.

In general, the outer package is molded by cold molding (deep drawing) using a die, and in this case, if the molding depth is too deep, cracks or pinholes are generated in a portion stretched by the molding, and the reliability of the battery as a result is lost. Therefore, it becomes important how the forming depth can be deepened in a manner not to impair reliability.

In particular, in large-scale applications such as electric vehicles, there is a demand for further improvement in energy density from the viewpoint of battery performance, which is called acquisition of a large current. On the other hand, excellent reliability and long-term storage stability are also required.

In addition, the above-mentioned heat-resistant base material layer is required to have excellent chemical resistance and scratch resistance for the outer packaging material. In view of moldability, a polyamide film is often used as the base material layer. However, the polyamide film is dissolved in an electrolyte containing a lithium salt. Therefore, if an error occurs during the production of the battery and the electrolyte adheres to the base material layer of the outer cover, the polyamide film is corroded, and the yield of the battery production is affected. In the electric vehicle application, a battery pack in which a plurality of battery cells are integrated is used to obtain output power. Due to vibration or the like during operation of the automobile, adjacent battery cells in the battery pack may rub against each other to damage the base material layer. Further, if the electrolyte leaks out under the influence of the damage, the electrolyte may adhere to other battery cells and damage the battery pack in a wide range.

Therefore, as an outer package having electrolyte resistance and scratch resistance on the surface of the base material layer, an outer package having the following structure is known.

(1) There is known an outer cover in which a first base film layer composed of a biaxially stretched polyethylene terephthalate film (hereinafter referred to as "biaxially stretched PET film") and a second base film layer composed of a biaxially stretched nylon film (hereinafter referred to as "biaxially stretched Ny film") are laminated in this order from the outside (patent document 1). The outer packaging material has the following structure: the biaxially stretched film is formed by laminating a biaxially stretched PET film having low moisture absorption, rigidity, abrasion resistance and heat resistance and a biaxially stretched Ny film having flexibility, puncture strength, bending strength and cold resistance by a known dry lamination method using a two-component curable polyurethane adhesive or the like. The outer packaging material having this structure has the characteristics of the film.

(2) There is known an exterior material in which a coating layer made of a specific resin such as polyvinylidene chloride or vinylidene chloride-vinyl chloride copolymer is formed on the surface side of a stretched film forming a base material layer (patent document 2). The stretched film is protected on the coating layer.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4559547

Patent document 2: japanese patent No. 3567229

Disclosure of Invention

Problems to be solved by the invention

However, the outer materials (1) and (2) have the following problems: the portion stretched by the molding process tends to return to its original shape, and the depth of the molding is substantially reduced or the shape is deformed.

The purpose of the present invention is to provide an exterior material for a lithium ion battery, which has excellent moldability, a performance of maintaining the shape after molding, electrolyte resistance, and scratch resistance, a lithium ion battery using the exterior material for a lithium ion battery, and a method for producing a lithium ion battery.

Means for solving the problems

In order to solve the above problems, the present invention adopts the following technical means.

An exterior material for a lithium ion battery according to a first aspect of the present invention includes: a substrate layer formed by biaxially stretching a multilayer coextruded film including a first thermoplastic resin layer having rigidity and chemical resistance and disposed on the outer side, a second thermoplastic resin layer having stress propagation properties and adhesiveness, and a third thermoplastic resin layer having toughness; a metal foil layer laminated on one surface of the base material layer; an anticorrosion treated layer laminated on the metal foil layer; an inner adhesive layer laminated on the corrosion-resistant treated layer; and a sealant layer laminated on the inner adhesive layer.

In the lithium ion battery outer package according to the first aspect of the present invention, the thickness of the first thermoplastic resin layer is preferably 1 μm or more and 10 μm or less, the thickness of the second thermoplastic resin layer is preferably 0.1 μm or more and 5 μm or less, and the thickness of the third thermoplastic resin layer is preferably 10 μm or more and 50 μm or less.

In the lithium ion battery outer covering material according to the first aspect of the present invention, it is preferable that the first thermoplastic resin layer is a layer containing an aromatic polyester resin; the second thermoplastic resin layer is a layer containing a modified thermoplastic resin obtained by graft modification of at least one unsaturated carboxylic acid derivative component selected from the group consisting of an unsaturated carboxylic acid, an anhydride of an unsaturated carboxylic acid, and an ester of an unsaturated carboxylic acid; the third thermoplastic resin layer is a layer containing a polyamide resin.

In the lithium ion battery outer packaging material according to the first aspect of the present invention, the first thermoplastic resin layer is preferably on the surface layer side of the base material layer.

A lithium ion battery of a second aspect of the present invention includes: a container body formed of the outer package material for a lithium ion battery according to the first aspect; a battery component which is accommodated in the container body in a manner that a part of a sheet body (tab: a lug) is exposed to the outside; and an electrolyte contained in the container body together with the battery component. The container body has a concave portion formed in the lithium ion battery outer packaging material by cold forming, the container body is formed into a container shape in which the sealant layer is disposed inside the container body, and the battery component and the electrolyte solution are sealed by heat-sealing edge portions where the sealant layers are in contact with each other in a state in which the battery component and the electrolyte solution are housed in the concave portion.

A method for manufacturing a lithium ion battery according to a third aspect of the present invention is a method for manufacturing a lithium ion battery, comprising preparing the outer package for a lithium ion battery according to the first aspect; forming a concave portion (Y1) in the exterior material for a lithium ion battery by cold molding; accommodating a battery component in the recess so that a part of the sheet is exposed to the outside of the recess, forming the lithium ion battery exterior material into a container shape, and heat-sealing the edge portions so that openings are formed at the edge portions where the sealant layers are in contact with each other (Y2); injecting an electrolyte into the recess through the opening; and heat-sealing the rim portion in such a manner as to close the opening to perform encapsulation (Y3).

Effects of the invention

The exterior material for a lithium ion battery according to the first aspect of the present invention has excellent moldability, a property of retaining a shape after molding, electrolyte solution resistance, and scratch resistance.

The lithium ion battery according to the second aspect of the present invention has a container body formed by molding the outer covering material for a lithium ion battery in a predetermined shape, and has excellent electrolyte solution resistance and scratch resistance.

In addition, according to the method for manufacturing a lithium ion battery of the third aspect of the present invention, it is possible to manufacture a lithium ion battery having excellent electrolyte solution resistance and scratch resistance by molding the exterior material for a lithium ion battery into a container body in a predetermined shape.

Drawings

Fig. 1 is a cross-sectional view showing an example of an outer package for a lithium ion battery according to an embodiment of the present invention.

Fig. 2 is a perspective view showing one example of a lithium ion battery according to an embodiment of the present invention.

Fig. 3A is a perspective view showing a manufacturing process of the lithium ion battery of fig. 2.

Fig. 3B is a perspective view illustrating a manufacturing process of the lithium ion battery of fig. 2.

Fig. 3C is a perspective view showing a manufacturing process of the lithium ion battery of fig. 2.

Fig. 4 is a sectional view illustrating a method of evaluating curling properties in the example.

Detailed Description

< packaging Material for lithium ion Battery >

Next, a detailed description will be given of an example of an embodiment of the lithium ion battery outer package of the present invention.

As shown in fig. 1, an exterior material 1 for a lithium ion battery (hereinafter referred to as "exterior material 1") according to the present embodiment is a laminate in which an outer adhesive layer 14, a metal foil layer 15, an anticorrosion treatment layer 16, an inner adhesive layer 17, and a sealant layer 18 are laminated in this order on one surface side (one surface) of a base material layer 10. Outer package 1 is used with base layer 10 as the outermost layer and sealant layer 18 as the innermost layer.

[ base Material layer 10]

The base layer 10 is a layer composed of a film (hereinafter referred to as "film (a)") obtained by biaxially stretching a multilayer coextruded film, and the multilayer coextruded film includes: a thermoplastic resin layer (a) 11 (first thermoplastic resin layer) having rigidity and chemical resistance and disposed on the outside, a thermoplastic resin layer (b) 12 (second thermoplastic resin layer) having stress propagation properties and adhesiveness, and a thermoplastic resin layer (c) 13 (third thermoplastic resin layer) having toughness. Since the base layer 10 is formed of the film (a), the exterior material 1 having both excellent moldability and a property of maintaining the shape after molding processing, and excellent electrolyte solution resistance and scratch resistance is formed.

(thermoplastic resin layer (a) 11)

The thermoplastic resin layer (a) 11 functions as follows: heat resistance is imparted to outer package 1 in the sealing step in the production of a lithium ion battery, and a pinhole phenomenon that may occur during processing and distribution is suppressed. In addition, the electrolyte solution is provided with tolerance, and the occurrence of appearance defect phenomenon is restrained when the electrolyte solution is attached in the electrolyte solution injection process when the lithium ion battery is manufactured.

The thermoplastic resin layer (a) 11 is preferably a layer containing an aromatic polyester resin. The aromatic polyester resin satisfies the rigidity and chemical resistance required for the thermoplastic resin layer (a). Examples of the aromatic polyester resin include polyester resins obtained by polymerizing or copolymerizing at least one aromatic dibasic acid and at least one glycol.

Examples of the aromatic dibasic acid include isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid.

Examples of the diols include: aliphatic diols such as ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, methylpentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, and dodecanediol; alicyclic diols such as cyclohexanediol and hydrogenated xylylene glycol; aromatic diols such as benzenedimethanol.

The aromatic polyester resin may be a resin obtained by copolymerizing at least one aliphatic dibasic acid. Examples of the aliphatic dibasic acid include: and aliphatic dibasic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and brassylic acid.

Specific examples of the aromatic polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN). Among them, polyethylene terephthalate is preferable.

The thermoplastic resin layer (a) 11 may be a layer containing a polycarbonate resin or a fluororesin. The polycarbonate resin or the fluororesin satisfies the rigidity and chemical resistance required for the thermoplastic resin layer (a).

The thermoplastic resin layer (a) 11 may contain, as a soft component, an ethylene copolymer resin obtained by copolymerizing maleic anhydride or an aliphatic polyester resin. This can provide more excellent moldability.

The ethylene copolymer resin obtained by copolymerizing maleic anhydride is, for example, an ethylene- α, β unsaturated carboxylic acid alkyl ester-maleic anhydride copolymer. Examples of the α, β unsaturated carboxylic acid alkyl ester include those obtained by esterifying an α, β unsaturated carboxylic acid with an alcohol having an alkyl group having 1 to 4 carbon atoms. Examples of the α, β unsaturated carboxylic acid include: a monocarboxylic acid or a dicarboxylic acid having 3 to 8 carbon atoms, or a metal salt or an acid anhydride thereof. Specific examples thereof include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and maleic anhydride. Examples of commercially available products include "レクスパール (Rexpearl)" (trade name) manufactured by Japan ポリエチレン corporation (Japan Polyethylene Corp.).

Examples of the aliphatic polyester resin include polycaprolactone and the like, and examples of commercially available products include "プラクセル (Placcel)" (trade name) manufactured by celluloid Chemical Industries Ltd.

In addition, various rubber components such as various polyester elastomers, olefin elastomers, polyamide elastomers, and the like may be blended in the thermoplastic resin layer (a) 11 in order to obtain other modification effects.

In addition, various additives such as a lubricant, an antistatic agent, an antiblocking agent, and inorganic fine particles may be added to the thermoplastic resin layer (a) 11 as needed.

From the viewpoint of obtaining excellent electrolyte resistance, scratch resistance, and heat resistance, the thickness of the thermoplastic resin layer (a) 11 is preferably 1 μm or more, and more preferably 3 μm or more. The thickness of the thermoplastic resin layer (a) 11 is preferably 10 μm or less, more preferably 7 μm or less, from the viewpoint of excellent moldability and excellent performance of retaining the shape after molding.

(thermoplastic resin layer (b) 12)

The thermoplastic resin (b) 12 preferably contains a layer of a modified thermoplastic resin obtained by graft modification of at least one unsaturated carboxylic acid derivative component selected from the group consisting of an unsaturated carboxylic acid, an anhydride of an unsaturated carboxylic acid, and an ester of an unsaturated carboxylic acid. The modified thermoplastic resin satisfies the stress propagation property and the adhesiveness required for the thermoplastic resin layer (b). The modified thermoplastic resin is a material having higher rigidity and higher hardness than the two-component curable polyurethane adhesive, and can efficiently transmit stress during molding.

The modified thermoplastic resin is preferably a resin obtained by modifying a polyolefin-based resin, a styrene-based elastomer, or a polyester-based elastomer with the unsaturated carboxylic acid derivative component, from the viewpoint of having excellent stress propagation properties and adhesiveness. Hereinafter, a polyolefin-based resin graft-modified with an unsaturated carboxylic acid derivative component is referred to as an acid-modified polyolefin-based resin, a styrene-based elastomer resin graft-modified with an unsaturated carboxylic acid derivative component is referred to as an acid-modified styrene-based elastomer resin, and a polyester-based elastomer resin graft-modified with an unsaturated carboxylic acid derivative component is referred to as an acid-modified polyester-based elastomer resin.

Examples of the polyolefin-based resin in the acid-modified polyolefin-based resin include the following polymers: low density polyethylene, medium density polyethylene, high density polyethylene; ethylene-alpha olefin copolymers; homo, block or random polypropylene; propylene-alpha olefin copolymers; copolymers obtained by copolymerizing the above materials with polar molecules such as acrylic acid and methacrylic acid; a cross-linked polyolefin; and so on. The polyolefin-based resin may be used alone or in combination of two or more.

Examples of the styrene elastomer in the acid-modified styrene elastomer resin include: copolymers of styrene (hard block) with butadiene or isoprene or their hydrides (soft block), and the like.

Examples of the polyester elastomer in the acid-modified polyester elastomer resin include: copolymers of crystalline polyesters (hard segments) with polyalkylene ether glycols (soft segments), and the like.

Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, bicyclo [2,2,1] hept-2-ene-5, 6-dicarboxylic acid, and the like.

Examples of the acid anhydride of the unsaturated carboxylic acid include maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, bicyclo [2,2,1] hept-2-ene-5, 6-dicarboxylic anhydride, and the like.

Examples of the ester of an unsaturated carboxylic acid include esters of unsaturated carboxylic acids such as methyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dimethyl maleate, monomethyl maleate, diethyl fumarate, dimethyl itaconate, diethyl citraconate, dimethyl tetrahydrophthalate, and dimethyl bicyclo [2,2,1] hept-2-ene-5, 6-dicarboxylate.

As the modified thermoplastic resin, the following can be employed: 0.2 to 100 parts by mass of the unsaturated carboxylic acid derivative component is heated and reacted in the presence of a radical initiator with respect to 100 parts by mass of a thermoplastic resin as a matrix.

The reaction temperature is preferably 50 to 250 ℃, and more preferably 60 to 200 ℃. Although the reaction time is also limited by the production method, when the melt grafting reaction is carried out using a two-way extruder, the residence time in the extruder is preferably 2 minutes to 30 minutes, more preferably 5 minutes to 10 minutes. The modification reaction can be carried out under any of normal pressure and pressure.

Examples of the radical initiator used in the modification reaction include organic peroxides. As the organic peroxide, various materials can be selected depending on the temperature conditions and the reaction time, and examples thereof include: alkyl peroxides, aryl peroxides, acyl peroxides, ketone peroxides, peroxyketals, peroxycarbonates, peroxyesters, hydroperoxides, and the like. When the melt grafting reaction is carried out by the above-mentioned biaxial extruder, it is preferable to use an alkyl peroxide, a peroxyketal, or a peroxyester, and more preferably di-t-butyl peroxide, 2, 5-dimethyl-2, 5-di-t-butylperoxy-3-hexyne, or dicumyl peroxide.

As the acid-modified polyolefin-based resin, a polyolefin-based resin modified with maleic anhydride is representative, and examples thereof include: "アドマー (Admer)" (trade name) manufactured by Mitsui chemical corporation, "モディック (Modic)" (trade name) manufactured by Mitsubishi chemical corporation, "アドテックス (Adtex)" (trade name) manufactured by Japan Polyethylene corporation, and the like.

Examples of the acid-modified styrene-based elastomer include "タフテック (Tuftec)" (trade name) manufactured by AK エラストマー corporation and "クレイトン (Kraton)" (trade name) manufactured by クレイトンポリマー corporation.

The acid-modified polyester elastomer may be "プリマロイ (Primalloy)" (trade name) manufactured by mitsubishi chemical corporation.

Various additives such as a lubricant, an antistatic agent, an antiblocking agent, and inorganic fine particles may be added to the thermoplastic resin layer (b) 12 as needed.

From the viewpoint of increasing the adhesiveness between the thermoplastic resin layer (a) 11 and the thermoplastic resin layer (c) 13, the thickness of the thermoplastic resin layer (b) 12 is preferably 0.1 μm or more, and more preferably 0.5 μm or more. From the viewpoint of improving the stress propagation property and the moldability, the thickness of the thermoplastic resin layer (b) 12 is preferably 5 μm or less, more preferably 3 μm or less.

(thermoplastic resin layer (c) 13)

The thermoplastic resin layer (c) 13 plays a role of imparting toughness and improving the moldability of the exterior material 1. In addition, flexibility, puncture resistance, and cold resistance are imparted.

The thermoplastic resin layer (c) 13 is preferably a layer containing a polyamide resin. The polyamide resin satisfies toughness required for the thermoplastic resin layer (c).

Examples of the polyamide resin include: poly-epsilon-caprolactam (nylon 6), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebacamide (nylon 610), polyundecanoamide (nylon 11), polydodecanoamide (nylon 12), poly m-xylylene adipamide (MXD 6), and copolymers thereof. Among them, nylon 6 and nylon 66 are preferable.

The thermoplastic resin layer (c) 13 may contain an ethylene copolymer resin obtained by copolymerizing maleic anhydride or an aliphatic polyester resin, as described in the description of the thermoplastic resin layer (a) 11. This can provide more excellent moldability. In addition, various rubber components such as various polyester elastomers, olefin elastomers, polyamide elastomers, and the like may be blended in order to obtain other modification effects.

Various additives such as a lubricant, an antistatic agent, an antiblocking agent, and inorganic fine particles may be added to the thermoplastic resin layer (c) 13 as needed.

From the viewpoint of obtaining excellent moldability, the thickness of the thermoplastic resin layer (c) 13 is preferably 10 μm or more, more preferably 15 μm or more. In view of economy and the thickness of the laminate required by the lithium ion battery market, the thickness of the thermoplastic resin layer (c) 13 is preferably 50 μm or less, and more preferably 35 μm or less.

In the structure of the outer wrapper 1, the base layer 10 is formed of a film (a) obtained by biaxially stretching a multilayer coextruded film having a thermoplastic resin layer (a) 11, a thermoplastic resin layer (b) 12 and a thermoplastic resin layer (c) 13 disposed on the outer side. Therefore, excellent moldability and property of maintaining the shape after molding processing, and excellent electrolyte resistance and scratch resistance are obtained. The main reason for obtaining such an effect is as follows.

In cold forming, it is important that the outer jacket material is formed with a sufficient drawing depth, and it is important that the outer jacket material does not return to its original shape after the forming process, and therefore, it is necessary to deep-draw the base layer and the metal foil layer in a plastic deformation region exceeding the yield point during drawing. However, the outer cover material of patent document 1 in which the biaxially stretched PET film and the biaxially stretched Ny film are bonded by an adhesive is considered to be in the following cases: the adhesive layer absorbs and relaxes the stress during molding, and thereby the biaxially stretched PET film is molded particularly in an elastic deformation region not exceeding the yield point or a region in the vicinity of the yield point (transition region from elastic deformation to plastic deformation). Thus, it is believed that: residual stress is accumulated in the biaxially stretched PET film or biaxially stretched Ny film, and the outer cover material after molding tends to return to its original shape or warp at portions other than the recessed portions. In particular, biaxially stretched PET films are less likely to undergo plastic deformation than metal foils and biaxially stretched Ny films, and the adhesive layer has a large influence on the stress transmission properties. Further, since the laminated biaxially stretched PET film and biaxially stretched Ny film are produced separately, the stretching conditions are not completely the same, and the stress characteristics are not the same. In a laminated film obtained by laminating films having different stress characteristics, the stress characteristics at the time of molding are not uniform, and the performance of maintaining the shape after molding is also deteriorated.

On the other hand, since the film (a) of the base material layer 10 in the outer package 1 has the thermoplastic resin layer (a) 11 on the outer side, excellent electrolyte solution resistance and scratch resistance are obtained. Further, by providing the thermoplastic resin layer (b) 12 having rigidity superior to that of a urethane adhesive or the like, it is possible to suppress absorption and relaxation of stress applied during molding between the thermoplastic resin layer (a) 11 and the thermoplastic resin layer (c) 13. The film (a) is not a film obtained by laminating two biaxially stretched films, but a film obtained by biaxially stretching a multilayer coextruded film having the thermoplastic resin layers (a) to (c). Therefore, the respective stretching conditions of the thermoplastic resin layers (a) to (c) are uniform, and the stress characteristics are uniform. Therefore, the stress applied during molding is efficiently transmitted to the thermoplastic resin layer (b) 12, and the thermoplastic resin layer (a) 11 and the thermoplastic resin layer (c) 13 can be sufficiently drawn in the plastically deformed region. This can provide excellent formability and excellent shape retention performance, and can suppress the tendency of outer package 1 to return to its original shape after forming or suppress the occurrence of warpage in the portion of outer package 1 other than the recessed portion.

The film (a) is not limited to a three-layer structure in which the thermoplastic resin layer (a)/the thermoplastic resin layer (b)/the thermoplastic resin layer (c) are formed from the outside. For example, the film (a) may be formed of four layers of the thermoplastic resin layer (a)/the thermoplastic resin layer (b)/the thermoplastic resin layer (c)/the thermoplastic resin layer (b) formed from the outside. The film (a) may be formed of five layers from the outside, in which the thermoplastic resin layer (a)/the thermoplastic resin layer (b)/the thermoplastic resin layer (c)/the thermoplastic resin layer (b)/the thermoplastic resin layer (a) are formed.

In the case of the four-layer structure, the base material layer and the metal foil layer can be bonded by the adhesiveness of the thermoplastic resin layer (b) provided on the inner side without providing the outer adhesive layer.

In addition, when the film (a) is a film having three layers of the thermoplastic resin layer (a)/the thermoplastic resin layer (b)/the thermoplastic resin layer (c), a resin layer other than the thermoplastic resin layer (a), the thermoplastic resin layer (b) and the thermoplastic resin layer (c) may be provided on the metal foil layer side of the thermoplastic resin layer (c).

In the base material layer 10, the thermoplastic resin layer (a) 11 is preferably an outermost layer, as shown in this example, from the viewpoint of easily obtaining excellent electrolyte resistance and scratch resistance.

The method for producing the film (a) is not particularly limited, and examples thereof include a melt extrusion method using a T die, an inflation die (inflation die), and the like.

For example, when a T-die is used, the components for forming the thermoplastic resin layers (a) to (c) are melted, and a coextrusion operation is performed using an extruder having a T-die to form a film, and the molten resin thus formed into a film is rapidly cooled on a rotating cooling drum by a known casting method such as an air-knife casting method or an electrostatic casting method. Then, the obtained unstretched film is preheated by a longitudinal roll stretcher comprising a heating roll group having a different peripheral speed, and then longitudinally stretched between a stretching roll for heating the unstretched film to a temperature not lower than the glass transition point thereof and a cooling roll for cooling the film. The longitudinally stretched film is introduced into a tenter, preheated at 50 to 70 ℃, and then transversely stretched at 60 to 110 ℃. If necessary, the ratio of the longitudinal stretching magnification to the transverse stretching magnification is controlled, and further heat treatment and relaxation treatment are performed in a tenter at 210 to 220 ℃.

The biaxial stretching in the film (a) is not limited to the sequential biaxial stretching described above, and may be simultaneous biaxial stretching. The stretch ratio and the heat setting temperature in the film (a) can be appropriately selected.

[ outer adhesive layer 14]

The outer adhesive layer 14 is a layer for bonding the base material layer 10 and the metal foil layer 15.

As the adhesive component constituting the outer adhesive layer 14, a dry laminating adhesive is preferably used, and more preferably: a two-component curable polyurethane adhesive obtained by reacting a bifunctional or higher isocyanate compound as a curing agent with a base material such as polyester polyol, polyether polyol, acrylic polyol, carbonate polyol or polyolefin polyol.

Examples of the polyester polyol include polyols obtained by reacting one or more dibasic acids with one or more diols.

Examples of the dibasic acid include: aliphatic dibasic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and brassylic acid; aromatic dibasic acids such as isophthalic acid, terephthalic acid and naphthalenedicarboxylic acid.

As the hydroxyl groups at both ends of the polyester polyol, there can be used: a monomer of an isocyanate compound, an adduct of at least one isocyanate compound, a biuret compound, or a polyester polyurethane polyol chain-extended with an isocyanurates (isocyanurates) compound, and the like. Examples of the isocyanate compound include: 2, 4-or 2, 6-tolylene diisocyanate, xylylene diisocyanate, 4,4 ' -diphenylmethane diisocyanate, methylene diisocyanate, isopropene diisocyanate, lysine diisocyanate, 2, 4-or 2,4, 4-trimethylhexamethylene diisocyanate, 1, 6-hexamethylene diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, 4,4 ' -dicyclohexylmethane diisocyanate, isopropylidene dicyclohexyl-4, 4 ' -diisocyanate, and the like.

Examples of polyether polyols include: ether polyols such as polyethylene glycol and polypropylene glycol, and polyether polyurethane polyols which act as chain extenders to react the above isocyanate compounds.

Examples of the acrylic polyol include copolymers mainly composed of poly (meth) acrylic acid. Examples of the monomers used for the copolymer include: hydroxyl group-containing monomers such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; alkyl (meth) acrylate monomers (examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a 2-ethylhexyl group, and a cyclohexyl group); amide group-containing monomers such as (meth) acrylamide, N-alkyl (meth) acrylamide, N-dialkyl (meth) acrylamide (examples of alkyl groups include methyl, ethyl, N-propyl, isopropyl, N-butyl, isobutyl, tert-butyl, 2-ethylhexyl, cyclohexyl, and the like), N-alkoxy (meth) acrylamide, N-dialkoxy (meth) acrylamide, (examples of alkoxy groups include methoxy, ethoxy, butoxy, isobutoxy, and the like), N-methylol (meth) acrylamide, and N-phenyl (meth) acrylamide; glycidyl group-containing monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; silane-containing monomers such as (meth) acryloyloxypropyltrimethoxysilane and (meth) acryloyloxypropyltriethoxysilane; isocyanate group-containing monomers such as (meth) acryloyloxypropylisocyanate and the like.

Examples of the carbonate polyol include polyols obtained by reacting a carbonate compound with a diol. Examples of the carbonate compound include dimethyl carbonate, diphenyl carbonate, and ethylene carbonate. Examples of the diol include the diols exemplified in the description of the polyether polyol. In addition, a polycarbonate type polyurethane polyol chain-extended by the above isocyanate compound may also be used.

Examples of the polyolefin polyol include: a polyol obtained by modifying a polyolefin skeleton by copolymerizing an olefin with a hydroxyl group-containing monomer such as 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate, or a polybutadiene diol or a hydrogenated product thereof.

The various polyols described above may be used alone or in combination of two or more types depending on the functions and performances required.

Examples of the isocyanate compound as the curing agent include the isocyanate compounds exemplified in the description of the chain extender.

After the polyurethane adhesive is applied, the polyurethane adhesive is cured at 40 ℃ for 4 days or more, for example, whereby the hydroxyl group of the main agent and the isocyanate group of the curing agent are reacted to achieve strong adhesion. The molar ratio (NCO/OH) of the isocyanate group in the curing agent to the hydroxyl group in the main agent is preferably 1 to 10, more preferably 2 to 5.

The outer adhesive layer 14 may contain a carbodiimide compound, an oxazoline compound, an epoxy compound, a phosphorus compound, a silane coupling agent, or the like to promote adhesion.

Examples of the carbodiimide compound include: n, N ' -di-o-toluyl carbodiimide (N, N ' - ジ -o- トルイルカルボジイミド), N ' -diphenyl carbodiimide, N ' -di-2, 6-dimethylphenyl carbodiimide, N ' -bis (2, 6-diisopropylphenyl) carbodiimide, N ' -dioctyldecyl carbodiimide, N-toluyl-N ' -cyclohexyl carbodiimide (N- トリイル -N ' - シクロヘキシルカルボジイミド), N ' -di-2, 2-di-tert-butylphenyl carbodiimide, N-toluyl-N ' -phenyl carbodiimide (N- トリイル -N ' - フェニルカルボジイミド), N ' -di-p-nitrophenylcarbodiimide, N ' -di-p-aminophenyl carbodiimide, N ' -di-p-nitrophenylcarbodiimide, N ' -di-p-aminophenyl carbodiimide, N, N '-di-p-hydroxyphenyl carbodiimide, N' -dicyclohexylcarbodiimide, N '-di-p-toluoyl carbodiimide (N, N' - ジ -p- トルイルカルボジイミド), and the like.

Examples of the oxazoline compound include: a mono-oxazoline compound such as 2-oxazoline, 2-methyl-2-oxazoline, 2-phenyl-2-oxazoline, 2, 5-dimethyl-2-oxazoline, or 2, 4-diphenyl-2-oxazoline, and a bis-oxazoline compound such as 2,2 '- (1, 3-phenylene) -bis (2-oxazoline), 2, 2' - (1, 2-ethylene) -bis (2-oxazoline), 2,2 '- (1, 4-butylene) -bis (2-oxazoline), or 2, 2' - (1, 4-phenylene) -bis (2-oxazoline).

Examples of the epoxy compound include: diglycidyl ethers of aliphatic diols such as 1, 6-hexanediol, neopentyl glycol, and polyalkylene glycols; polyglycidyl ethers of aliphatic polyhydric alcohols such as sorbitol, sorbitan, polyglycerol, pentaerythritol, diglycerol, glycerol, and trimethylolpropane; polyglycidyl ethers of alicyclic polyols such as cyclohexanedimethanol; diglycidyl esters or polyglycidyl esters of aliphatic or aromatic polycarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, trimellitic acid, adipic acid, and sebacic acid; diglycidyl ethers or polyglycidyl ethers of polyhydric phenols such as resorcinol, bis- (p-hydroxyphenyl) methane, 2, 2-bis- (p-hydroxyphenyl) propane, tris- (p-hydroxyphenyl) methane, and 1,1,2, 2-tetrakis (p-hydroxyphenyl) ethane; n-glycidyl derivatives of amines such as N, N '-diglycidylaniline, N-diglycidyltoluidine, and N, N' -tetraglycidyl-bis- (p-aminophenyl) methane; triglycidyl derivatives of aminophenols; triglycidyl tris (2-hydroxyethyl) isocyanurate; triglycidyl isocyanurate; o-cresol type epoxy resins; phenol novolac type epoxy resin.

Examples of the phosphorus-based compound include: tris (2, 4-di-tert-butylphenyl) phosphite, tetrakis (2, 4-di-tert-butylphenyl) 4, 4' -biphenylenephosphonite, bis (2, 4-di-tert-butylphenyl) pentaerythritol-di-phosphite, bis (2, 6-di-tert-butyl-4-methylphenyl) pentaerythritol-di-phosphite, 2-methylenebis (4, 6-di-tert-butylphenyl) octyl phosphite, 4,4 '-butylidene-bis (3-methyl-6-tert-butylphenyl-ditridecyl) phosphite, 1, 3-tris (2-methyl-4-ditridecyl) phosphite-5-tert-butyl-phenyl) butane, tris (mixed mono-and dinonylphenyl) phosphite, tris (nonylphenyl) phosphite, 4' -isopropylidene bis (phenyl-dialkyl phosphite) and the like.

Examples of the silane coupling agent include: vinyltriethoxysilane, vinyltris (β -methoxyethoxy) silane, γ -methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ -glycidoxypropyltrimethoxysilane, γ -glycidoxypropyltriethoxysilane, β - (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, γ -chloropropylmethoxysilane, vinyltrichlorosilane, γ -mercaptopropyltrimethoxysilane, γ -aminopropyltriethoxysilane, N- β (aminoethyl) - γ -aminopropyltrimethoxysilane and the like.

In addition, various additives and stabilizers may be further added to the outer adhesive layer 14 depending on the required performance of the adhesive.

From the viewpoint of adhesive strength, conformability, and workability, the thickness of the outer adhesive layer 14 is preferably 1 to 10 μm, more preferably 3 to 7 μm.

As for the outer adhesive layer 14, an adhesive component used in a heat lamination method can be used, similarly to the inner adhesive layer 17 described later.

In the case where the base layer 10 is a film composed of four layers of the thermoplastic resin layer (a)/the thermoplastic resin layer (b)/the thermoplastic resin layer (c)/the thermoplastic resin layer (b) from the outside, the outer adhesive layer 14 may not be provided.

[ Metal foil layer 15]

As the metal foil layer 15, various metal foils such as aluminum and stainless steel can be used. Aluminum foil is preferable from the viewpoint of processability such as moisture resistance and ductility, and cost. As the aluminum foil, a general soft aluminum foil can be used. Among these, aluminum foil containing iron is more preferable from the viewpoint of being able to impart pinhole resistance and ductility during molding. In this case, the iron content in the aluminum foil (100 mass%) is preferably 0.1 to 9.0 mass%, more preferably 0.5 to 2.0 mass%. If the iron content is not less than the lower limit (0.1 mass%), the pinhole resistance and ductility of the aluminum foil are improved. When the iron content is not more than the upper limit (9.0 mass%), the flexibility of the aluminum foil is improved.

The metal foil is preferably degreased in advance. The degreasing treatment is roughly classified into a wet treatment and a dry treatment.

Examples of the wet degreasing treatment include acid degreasing and alkali degreasing.

Examples of the acid degreasing include a method in which an inorganic acid such as sulfuric acid, nitric acid, hydrochloric acid, or hydrofluoric acid is used alone or two or more kinds of them are used in combination. In addition, from the viewpoint of improving the etching effect of the metal foil, various metal salts as supply sources of Fe ions, Ce ions, and the like may be blended as necessary. As the alkali degreasing, a strong etching type alkali degreasing such as sodium hydroxide can be mentioned. In addition, a weak base system or a surfactant may be added. The degreasing is performed by a dipping method or a spraying method.

The dry degreasing treatment may be performed by an annealing step of aluminum. Further, flame treatment, corona treatment, and the like can be given. Further, there is also exemplified a degreasing treatment in which the pollutants are oxidatively decomposed and removed by active oxygen generated by irradiation with ultraviolet rays of a certain wavelength.

The degreasing treatment may be performed on one side of the aluminum foil or on both sides of the aluminum foil.

From the viewpoint of barrier properties, pinhole resistance, and workability, the thickness of the metal foil layer 15 is preferably 9 to 200 μm, and more preferably 15 to 100 μm.

[ Corrosion prevention treated layer 16]

The corrosion prevention treatment layer 16 functions as follows: corrosion of the metal foil layer 15 by hydrofluoric acid generated by a reaction between the electrolyte and moisture is suppressed, and adhesion to the inner adhesive layer 17 is improved by improving interaction with the metal foil layer 15.

Examples of the corrosion-prevention treated layer 16 include a layer formed by degreasing treatment, hot water modification treatment, anodic oxidation treatment, chemical synthesis treatment, or a combination treatment of these treatments.

Examples of the layer formed by degreasing include layers formed by acid degreasing and alkali degreasing. Examples of the layer formed by acid degreasing include a layer formed by a method using a material obtained by mixing the above-mentioned inorganic acid such as sulfuric acid, nitric acid, hydrochloric acid, or hydrofluoric acid, alone or in combination. As the layer formed by the acid degreasing, a layer which has not only the degreasing effect of the metal foil but also a passive metal fluoride can be formed by using an acid degreasing agent obtained by dissolving a fluorine-containing compound such as sodium ammonium bifluoride (アンモニウム, mono ナトリウム, di フッ) in the inorganic acid can be used. The layer thus formed is effective from the viewpoint of resistance to hydrofluoric acid. Examples of the layer formed by alkali degreasing include a layer formed by a method using sodium hydroxide or the like.

Examples of the layer formed by the hot water modification treatment include a layer formed by boehmite treatment in which a metal foil is immersed in boiling water to which triethanolamine is added.

Examples of the layer formed by the anodic oxidation treatment include a layer formed by an Alumite treatment (aluminum anodic oxidation treatment).

Examples of the layer formed by the chemical synthesis treatment include: chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, or various chemical synthesis treatments composed of a combination of these treatments.

The layer formed by the hot water modification treatment, the anodic oxidation treatment, and the chemical synthesis treatment is preferably a layer formed by previously performing the degreasing treatment. The layer formed by these chemical synthesis treatments is not limited to a layer formed by a wet type, and may be a layer formed by a coating type in which these treatment agents are mixed with a resin component.

Among the above layers, particularly, the layers formed by the hot water modification treatment and the anodic oxidation treatment, a co-continuous structure is formed from the metal foil layer to the corrosion-resistant treated layer by dissolving the surface of the metal foil (aluminum foil) with the treating agent and further forming a compound excellent in corrosion resistance. Therefore, these treatments are sometimes included in the definition of chemical synthesis treatment. On the other hand, the corrosion prevention treated layer 16 may be a layer formed by a pure coating type corrosion prevention treatment, which is not included in the definition of the chemical synthesis treatment described later.

Examples of the layer formed by the coating type corrosion prevention treatment include a layer formed by using a method in which a sol of a rare earth oxide such as cerium oxide having an average particle diameter of 100nm or less is used as a material having an effect of preventing corrosion of a metal foil (an effect of suppressing corrosion) and being suitable for environmental use. By using this method, the corrosion prevention treated layer 16 can be formed which also imparts an effect of preventing corrosion of the metal foil by a usual coating method.

Examples of the sol of the rare earth element-based oxide such as cerium oxide include various solvents such as aqueous, alcohol, hydrocarbon, ketone, ester, and ether solvents. For reasons described below, an aqueous sol is preferably used.

In order to stabilize dispersion of such an oxide sol, an inorganic acid such as nitric acid, hydrochloric acid, or phosphoric acid, or an organic acid such as acetic acid, malic acid, ascorbic acid, or lactic acid is used as a dispersion stabilizer. Among these dispersion stabilizers, the following is expected particularly for phosphoric acid: the "dispersion of the sol is stabilized", the "adhesiveness to the metal foil" is improved by chelating ability, the "electrolyte resistance" is provided by trapping metal ions (forming a passive state) eluted under the influence of hydrofluoric acid, and the "cohesive force of the oxide layer" is improved by the characteristic that dehydration condensation is easily caused even at low temperature. Examples of such phosphoric acid or a salt thereof include: orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, or alkali metal salts and ammonium salts thereof. In addition, in order to exhibit the function as an outer covering material, a preferred material is a condensed phosphoric acid such as trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, and hypermetaphosphoric acid, or an alkali metal salt or an ammonium salt thereof. In particular, in consideration of the film forming property (drying ability, heat) by drying when forming a layer made of a rare earth oxide by various coating methods using the rare earth oxide sol, it is preferable to use a treating agent having excellent reactivity at low temperature. Therefore, it is preferable to use a Na ion salt having excellent dehydrating condensation properties at low temperatures. The phosphate is not particularly limited, but is preferably a water-soluble salt.

The mixing ratio of the cerium oxide and the phosphoric acid (or a salt thereof) is preferably 1 part by mass or more of the phosphoric acid (or a salt thereof) per 100 parts by mass of the cerium oxide. If the amount is less than 1 part by mass, the sol may be less stabilized and the function as an outer coating material may be difficult to satisfy. The amount of the phosphoric acid (or a salt thereof) added is more preferably 5 parts by mass or more with respect to 100 parts by mass of the cerium oxide. The upper limit of the mixing ratio of the phosphoric acid (or a salt thereof) may be within a range not accompanied by the function of reducing the cerium oxide sol; the amount is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 20 parts by mass or less, per 100 parts by mass of cerium oxide.

Since the layer formed from the rare earth oxide sol is an aggregate of inorganic particles, the cohesive force of the layer itself is low even after the drying and solidifying step. Therefore, in order to enhance the cohesive force of the layer, it is preferable to perform a composite treatment with an anionic polymer.

Examples of the anionic polymer include a polymer having a carboxyl group, and specifically, a poly (meth) acrylic acid (or a salt thereof), or a copolymer obtained by copolymerizing a monomer mixture containing (meth) acrylic acid as a main component. Examples of the monomer used in the monomer mixture together with (meth) acrylic acid include: alkyl (meth) acrylate monomers (examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a 2-ethylhexyl group, and a cyclohexyl group); amide group-containing monomers such as (meth) acrylamide, N-alkyl (meth) acrylamide, N-dialkyl (meth) acrylamide (examples of alkyl groups include methyl, ethyl, N-propyl, isopropyl, N-butyl, isobutyl, tert-butyl, 2-ethylhexyl, cyclohexyl, and the like), N-alkoxy (meth) acrylamide, N-dialkoxy (meth) acrylamide (examples of alkoxy groups include methoxy, ethoxy, butoxy, isobutoxy, and the like), N-methylol (meth) acrylamide, and N-phenyl (meth) acrylamide; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; glycidyl group-containing monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; silane-containing monomers such as (meth) acryloyloxypropyltrimethoxysilane and (meth) acryloyloxypropyltriethoxysilane; isocyanate group-containing monomers such as (meth) acryloyloxypropylisocyanate and the like.

The anionic polymer is used to improve the stability of the oxide layer obtained by using the rare earth element oxide sol as described above. By using such a material, an effect of protecting a hard and brittle oxide layer by an acrylic resin component and an effect of capturing (a cation capturing agent) an ion contaminant derived from a phosphate (particularly, a sodium ion) contained in the rare earth element oxide sol can be obtained. This is not limited to the application to the lithium ion battery used in the embodiment of the present invention, and for example, if an ionic contaminant, particularly an alkali metal ion such as sodium or an alkaline earth metal ion, is contained in a protective layer (anti-corrosion treatment layer) provided for preventing corrosion of a metal foil by a corrosive compound, a phenomenon in which the protective layer is attacked from the ionic contaminant as a starting point is caused. That is, an anionic polymer such as polyacrylic acid is effective from the viewpoint of immobilizing ionic contaminants such as sodium ions contained in the rare earth element oxide sol and improving the durability of the coating film.

As described above, the anionic polymer is used as an anticorrosive coating layer of the exterior material in combination with the rare earth element oxide sol, whereby the same anticorrosive performance as that of a layer formed by chromate treatment can be imparted. This effect is further enhanced by crosslinking the anionic polymer which is water-soluble in nature as described above.

The anionic polymer can be crosslinked by using a crosslinking agent, and examples of such a crosslinking agent include compounds containing an isocyanate group, a glycidyl group, a carboxyl group, and an oxazoline group.

Examples of the compound having an isocyanate group include: diisocyanates such as toluene diisocyanate, xylylene diisocyanate or its hydride, hexamethylene diisocyanate, 4' -diphenylmethane diisocyanate or its hydride, isophorone diisocyanate, and the like; or polyisocyanates such as adducts obtained by reacting these isocyanates with polyhydric alcohols such as trimethylolpropane, biuret compounds obtained by reacting these isocyanates with water, and isocyanurate (isocyanurate) compounds which are trimers; or blocked polyisocyanates obtained by blocking these polyisocyanates with alcohols, lactams, oximes, and the like.

Examples of the compound having a glycidyl group include: epoxy compounds obtained by reacting epichlorohydrin with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1, 4-butanediol, 1, 6-hexanediol, and neopentyl glycol; epoxy compounds obtained by reacting epichlorohydrin with polyhydric alcohols such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol, and sorbitol; epoxy compounds obtained by reacting epichlorohydrin with dicarboxylic acids such as phthalic acid, terephthalic acid, oxalic acid, and adipic acid.

Examples of the compound having a carboxyl group include various aliphatic or aromatic dicarboxylic acids, and poly (meth) acrylic acid and alkali (alkaline earth) metal salts of poly (meth) acrylic acid can also be used.

When a low-molecular compound having two or more oxazoline units or a polymerizable monomer such as isopropenyloxazoline is used as the oxazoline group-containing compound, a compound obtained by copolymerization with an acrylate monomer, for example, (meth) acrylic acid, an alkyl (meth) acrylate, a hydroxyalkyl (meth) acrylate, or the like can be used.

Further, a silane coupling agent may be used to form a siloxane bond at the crosslinking point. Examples of the silane coupling agent include: gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxypropyltriethoxysilane, beta- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, gamma-chloropropylmethoxysilane, vinyltrichlorosilane, gamma-mercaptopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, N-beta (aminoethyl) -gamma-aminopropyltrimethoxysilane, gamma-isocyanatopropyltriethoxysilane, etc. Among them, epoxy silane, amino silane, and isocyanate silane are preferable in view of reactivity with the anionic polymer.

The amount of the crosslinking agent is preferably 1 to 50 parts by mass, more preferably 10 to 20 parts by mass, based on 100 parts by mass of the anionic polymer. When the blending amount of the crosslinking agent is not less than the lower limit (1 part by mass), a crosslinked structure is sufficiently formed. If the amount of the crosslinking agent is not more than the upper limit (50 parts by mass), the pot life of the coating liquid is prolonged.

The method of crosslinking the anionic polymer is not limited to the above crosslinking agent, and may be a method of performing ionic crosslinking using a titanium or zirconium compound.

When the corrosion prevention treated layer is formed by the coating type corrosion prevention treatment described above, unlike the chemical synthesis treatment typified by chromate treatment, it is not necessary to form an inclined structure between the metal foil layer and the corrosion prevention treated layer. In the chemical synthesis treatment represented by chromate treatment, as described above, in order to form the above-described inclined structure, a chemical synthesis treatment agent containing hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, or a salt thereof is particularly used to treat the metal foil and act on the metal foil with chromium or a non-chromium compound. However, these treatment agents use acids, and therefore, the treatment is accompanied by corrosion of the working environment and the coating apparatus.

On the other hand, the corrosion-prevention treated layer formed by the coating treatment described above does not require the metal foil to have an inclined structure. As a result, the coating agent may be acidic, alkaline, or neutral. Therefore, the working environment is also excellent, and it is effective as an alternative when the environmental hygiene of the chromium compound used for chromate treatment is considered.

The corrosion prevention treated layer 16 may have a multilayer structure as follows: the multilayer structure is obtained by laminating a layer formed from the rare earth element oxide sol or a layer formed by combining a rare earth element oxide sol and an anionic polymer, and a coating layer formed by using a cationic polymer and a crosslinking agent in combination.

Examples of the cationic polymer include: an ionic polymer complex comprising ethyleneimine, polyethyleneimine and a polymer having a carboxylic acid, a primary amine graft acrylic resin obtained by grafting a primary amine onto an acrylic main skeleton, polyallylamine or a derivative thereof, aminophenol, or the like.

As the crosslinking agent, a material having a functional group which can react with amine/imine, such as a carboxyl group or a glycidyl group, is preferably used. In addition, polymers having carboxylic acids that form ionic polymer complexes with polyethyleneimine may also be used as crosslinking agents. Examples of such crosslinking agents include: polycarboxylic acids (salts) such as polyacrylic acids or salts thereof, copolymers obtained by copolymerizing such polycarboxylic acids with comonomers, and polysaccharides having carboxyl groups such as carboxymethylcellulose or salts thereof.

As the polyallylamine, a single polymer or copolymer of allylamine, allylamine amide sulfate, diallylamine, dimethylallylamine, or the like can be used. These amines, either free amines or amines stabilized on the basis of acetic acid or hydrochloric acid, can be used. Further, maleic acid, sulfur dioxide, or the like may be used as the copolymer component. Further, a type in which a primary amine is locally methoxylated to impart thermal crosslinkability may be used. Aminophenols may also be utilized. Among them, allyl amine or a derivative thereof is particularly preferable.

In the present embodiment, the cationic polymer is also described as one of the components constituting the anticorrosive coating layer. The reason for this is that, in order to impart electrolyte solution resistance and hydrofluoric acid resistance required for exterior materials, various compounds have been studied, and as a result, it has been found that cationic polymers are compounds which themselves impart electrolyte solution resistance and hydrofluoric acid resistance. This is presumably because the metal foil is inhibited from being damaged when fluorine ions (anion scavenger) are trapped by the cation group. For this reason, when a rare earth oxide sol is used as the corrosion prevention treated layer, a cationic polymer may be used as the protective layer instead of the anionic polymer.

As the layer formed by the coating type corrosion prevention treatment, there can be mentioned, but not limited to, the following:

(1) a layer formed only with a rare earth element oxide sol;

(2) a layer formed using only an anionic polymer;

(3) a layer formed only with a cationic polymer;

(4) a layer formed from a rare earth oxide sol and an anionic polymer (laminated composite);

(5) a layer formed of a rare earth oxide sol and a cationic polymer (laminated composite);

(6) a layer in which a layer made of a cationic polymer is laminated on a layer made of a rare earth oxide sol and an anionic polymer (laminated composite);

(7) a layer in which a layer made of an anionic polymer is laminated on a layer made of a rare earth oxide sol and a cationic polymer (laminated composite).

The cationic polymer has good adhesion to the modified polyolefin resin exemplified in the description of the inner adhesive layer 17 to be described later. Therefore, when the inner adhesive layer 17 is formed of a modified polyolefin resin, it is preferable that a layer formed of a cationic polymer is provided in a state where the inner adhesive layer 17 is connected (for example, structures (5) and (6).

The corrosion-resistant treated layer 16 may be formed by blending a treating agent containing phosphoric acid and a chromium compound in a resin binder (such as aminophenol) as in the coating chromate treatment known in the art, and may have both corrosion-resistant function and adhesion. In addition, the corrosion prevention treated layer 16 may be a layer obtained by performing a composite treatment using a cationic polymer or an anionic polymer in order to improve the adhesion of the corrosion prevention treated layer 16 in the chemical synthesis treatment of the above-described degreasing treatment, hot water modification treatment, anodic oxidation treatment, chemical synthesis treatment, or a combination thereof. The corrosion-prevention treated layer 16 may be a layer in which a layer made of a cationic polymer or an anionic polymer is laminated on a layer formed by the chemical synthesis treatment. The corrosion prevention treated layer 16 may be a layer formed by a coating agent obtained by liquefying a rare earth element oxide sol together with a cationic polymer or an anionic polymer in advance.

The thickness of the anticorrosive treatment layer 16 is preferably set to 0.005 to 0.200g/m in mass per unit area²More preferably 0.010 to 0.100g/m²The range of (1). If the thickness of the anticorrosive treated layer 16 is set to the lower limit (0.005 g/m)²) In this way, a sufficient corrosion prevention function is obtained. When the thickness of the corrosion-resistant treated layer 16 exceeds the upper limit (0.200 g/m)²) The corrosion protection function is limited and substantially unchanged. When the rare earth oxide sol is used, the thickness of the anti-corrosion treatment layer 16 is set to an upper limit (0.200 g/m)²) In the following cases, solidification by heat during drying is likely to be sufficient, and the cohesive force is unlikely to decrease.

The thickness of the corrosion-resistant treated layer 16 is expressed as a mass per unit area, but may be converted into a thickness by specific gravity.

The thickness of the corrosion-preventing treated layer 16 is preferably 0.025 to 0.2 μm from the viewpoint of the corrosion-preventing function and the function as an anchor.

In the exterior material according to the embodiment of the present invention, an anticorrosive treatment layer may be provided on the outer side of the metal foil layer.

[ inside adhesive layer 17]

The adhesive components constituting the inner adhesive layer 17 can be roughly classified into two types, i.e., an adhesive component of a hot lamination structure and an adhesive component of a dry lamination structure.

The adhesive component of the heat laminated structure is preferably an acid-modified polyolefin resin. Examples of the acid-modified polyolefin resin include the same resins as those exemplified in the description of the thermoplastic resin layer (b). The maleic anhydride-modified polyolefin resin is preferably graft-modified with maleic anhydride. The acid-modified polyolefin resin is provided with adhesiveness by utilizing reactivity between the grafted unsaturated carboxylic acid derivative component and a polymer containing various metals or various functional groups.

The acid-modified polyolefin resin may be dispersed with a thermoplastic elastomer such as an acid-modified styrene elastomer, depending on the desired properties. This relieves residual stress generated when laminating the acid-modified polyolefin resin, and improves viscoelastic adhesiveness. As the acid-modified styrene-based elastomer, a maleic anhydride-modified styrene-based elastomer graft-modified with maleic anhydride is preferable. As the thermoplastic elastomer (elastomer), preferred are: "タフマー (Tafmer)" manufactured by Mitsui chemical Co., Ltd, "タフセレン (Tafthren)" manufactured by Sumitomo chemical Co., Ltd, "ゼラス (Zealous)" manufactured by Mitsubishi chemical Co., Ltd, "キャタロイ (Cataloy)" manufactured by モンテル (Montell Co.), and "ノティオ (Notio)" manufactured by Mitsui chemical Co., Ltd, and a styrene-based elastomer. Particularly preferred are: hydrogenated styrene elastomers (e.g., "タフテック (Tuftec)" manufactured by AK エラストマー corporation, "セプトン/ハイブラー (Septon/Hybrar)" manufactured by クラレ (Kuraray co., Ltd.), "ダイナロン (Dynalon)" manufactured by JSR corporation, "エスポレックス (Espolex)" manufactured by sumitomo chemical corporation, and "クレイトン g (Kraton g)" manufactured by クレイトンポリマー (Kraton Polymers Inc.).

The inner adhesive layer 17 of the heat laminated structure can be formed by, for example, extruding the adhesive composition by an extrusion device.

Examples of the adhesive component of the dry lamination structure include polyurethane adhesives exemplified in the description of the outer adhesive layer 14. However, since swelling due to the electrolytic solution and hydrolysis due to hydrofluoric acid may occur, it is necessary to design the composition such as "using a main agent having a skeleton that is difficult to hydrolyze" and "improving the crosslinking density.

Examples of a method for increasing the crosslink density include a method using a dimer fatty acid, an ester of a dimer fatty acid, a hydride of a dimer fatty acid, or a reducing diol thereof. The bulky hydrophobic units of dimer fatty acids increase the crosslink density as a binder. The dimer fatty acid is an acid obtained by dimerizing various unsaturated fatty acids, and examples of the structure thereof include acyclic type, monocyclic type, polycyclic type, and aromatic ring type.

The unsaturated fatty acid as a starting material of the dimer fatty acid is not particularly limited, and examples thereof include: monounsaturated fatty acids, dibasic unsaturated fatty acids, tribasic unsaturated fatty acids, tetrabasic unsaturated fatty acids, pentabasic unsaturated fatty acids, hexabasic unsaturated fatty acids, and the like. Examples of monounsaturated fatty acids include: crotonic acid, Myristoleic acid (Myristoleic acid), palmitoleic acid, oleic acid, elaidic acid, vaccenic acid (vaccenic acid), gadoleic acid (gadolenic acid), eicosenoic acid, erucic acid, nervonic acid, and the like. Examples of the dibasic unsaturated fatty acid include: linoleic acid, eicosadienoic acid, docosadienoic acid, and the like. Examples of the tri-unsaturated fatty acid include: linolenic acid, pinolenic acid (ビノレン acid), eleostearic acid (Meadacid), dihomo-gamma-linolenic acid, eicosatrienoic acid, and the like. Examples of the quaternary unsaturated fatty acid include: stearidonic acid, arachidonic acid, eicosatetraenoic acid, docosatetraenoic acid (Adrenic acid), and the like. Examples of the pentanary unsaturated fatty acid include: octadecatrienoic acid (bosseepentaenoic acid), eicosapentaenoic acid, docosapentaenoic acid (Osbond acid), clupanodonic acid (clupanodonic acid), tetracosapentaenoic acid and the like. Examples of the six-membered unsaturated fatty acid include: docosahexaenoic acid, nicotinic acid, and the like. The combination of unsaturated fatty acids in the dimerization of unsaturated fatty acids may be any combination.

Further, the dibasic acids exemplified in the description of the polyester polyol may be introduced as the essential component of the dimer fatty acid.

In addition, from the viewpoint of electrolyte resistance (particularly solubility/swelling properties with respect to an electrolyte), it is effective to use, as the curing agent, at least one polyisocyanate selected from the group consisting of crude toluene diisocyanate (クルードトリレンジイソシアネート), crude diphenylmethane diisocyanate (クルードジフェニルメタンジイソシアネート), and polymeric diphenylmethane diisocyanate (ポリメリックジフェニルメタンジイソシアネート), or an adduct thereof. The curing agent is expected to improve the adhesion between the corrosion-resistant treated layer 16 and the sealant layer 18 from the viewpoint of increasing the urethane group concentration while improving the solubility and the swelling properties by increasing the crosslinking density of the adhesive coating film. In addition, at least one polyisocyanate selected from the group consisting of crude toluene diisocyanate, crude diphenylmethane diisocyanate, and polymeric diphenylmethane diisocyanate, or an adduct thereof is preferably used as the chain extender.

The ratio of the main agent to the curing agent in the inner adhesive layer 17 as a dry lamination structure is preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass, based on 100 parts by mass of the main agent. When the ratio of the curing agent is not less than the lower limit (1 part by mass), the adhesiveness and the electrolyte resistance are excellent. When the ratio of the curing agent is not more than the upper limit (100 parts by mass), it is easy to suppress the residual unreacted curing agent from adversely affecting the adhesiveness and the hardness.

In the inner adhesive layer 17 of the dry laminate structure, a carbodiimide compound, an oxazoline compound, an epoxy compound, a phosphorus compound, a silane coupling agent, and the like, which are exemplified in the description of the outer adhesive layer 14, can be blended.

The inner adhesive layer 17 may contain various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier.

[ sealant layer 18]

The sealant layer 18 is a layer of the outer package 1 that imparts sealability under heat-seal conditions.

The sealant layer 18 may be a film made of a polyolefin resin, an ethylene-vinyl acetate copolymer, an ethylene- (meth) acrylic acid copolymer, or an esterified or ion-crosslinked product thereof.

Examples of the polyolefin-based resin include: low, medium or high density polyethylene; vinyl-alpha olefin copolymers, homo-, block-or random polypropylene, propylene-alpha olefin copolymers, and the like. These polyolefin-based resins may be used alone or in combination of two or more.

The sealant layer 18 may be a film formed of one kind of resin, or may be a film formed of two or more kinds of resins. Further, the film may be a single layer film or a multilayer film, and may be selected according to the required function. For example, a multilayer film in which a resin such as an ethylene-cyclic olefin copolymer or polymethylpentene is incorporated may be used from the viewpoint of imparting moisture resistance. Further, a multilayer film in which a resin having gas barrier properties such as a partially or completely saponified ethylene-vinyl acetate copolymer or a partially or completely saponified polyvinyl acetate copolymer is included can be used.

Various additives such as flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, and tackifiers may be blended in the sealant layer 18.

The thickness of the sealant layer 18 is preferably 10 to 100 μm, more preferably 20 to 60 μm.

As the structure of outer package 1, from the viewpoint of improving adhesiveness, it is preferable to adopt the following structure: an acid-modified polyolefin resin is used as an adhesive component for forming the inner adhesive layer 17, and the sealant layer 18 is laminated on the corrosion-resistant treated layer 16 of the metal foil layer 15 by sandwich lamination.

[ production method ]

Next, a method for manufacturing outer package 1 will be described. However, the method for manufacturing outer package 1 is not limited to the following method. Examples of the method for producing outer package 1 include a method including the following steps (X1) to (X3).

(X1) forming the corrosion prevention treated layer 16 on the metal foil layer 15.

(X2) a step of bonding the base material layer 10 to the side surface of the metal foil layer 15 opposite to the side surface on which the corrosion-prevention treated layer 16 is formed, with the outside adhesive layer 14 interposed therebetween.

(X3) a step of bonding the sealant layer 18 to the corrosion prevention treated layer 16 of the metal foil layer 15 via the inner adhesive layer 17.

(step (X1))

An anticorrosive treatment layer 16 is formed on one surface of the metal foil layer 15.

Examples of the corrosion prevention treatment include degreasing treatment, hot water modification treatment, anodic oxidation treatment, chemical synthesis treatment, and application of a coating agent having corrosion prevention performance. For the degreasing treatment, an annealing method, a spraying method, or a dipping method can be selected. The hot water modification treatment and the anodic oxidation treatment may be carried out by an immersion method. The chemical synthesis treatment can be suitably selected from a dipping method, a spraying method, a coating method, and the like, depending on the type of the chemical synthesis treatment. Various methods such as gravure coating, reverse coating, roll coating, and bar coating can be used as a coating method of the coating agent.

When drying and solidification are required, the drying and solidification can be carried out at a substrate temperature in the range of 60 to 300 ℃ depending on the type of the anticorrosive treatment layer 16.

(step (X2))

The resin components forming the respective thermoplastic resin layers (a) to (c) are charged into an extrusion apparatus, and a multilayer coextruded film is obtained by a coextrusion method, and then the multilayer coextruded film is biaxially stretched to form the film (a). The thickness of the film (a) can be adjusted depending on stretching conditions such as the stretching magnification and temperature.

The base layer 10 is laminated by bonding the film (a) to the metal foil layer 15 on the side opposite to the side on which the corrosion prevention treated layer 16 is formed, by a method such as dry lamination, non-solvent lamination, or wet lamination, using an adhesive component for forming the outer adhesive layer 14. The film (a) is laminated to the metal foil layer 15 on the side of the thermoplastic resin layer (c) so that the thermoplastic resin layer (a) becomes the outer side.

Preferably, the dry coating weight of the adhesive is 1 to 10g/m²More preferably 3 to 5g/m²。

In the step (X2), curing (maintenance) treatment may be performed at room temperature to 100 ℃ to promote adhesion.

When the base layer 10 is formed from the film composed of the four layers of the thermoplastic resin layer (a)/the thermoplastic resin layer (b)/the thermoplastic resin layer (c)/the thermoplastic resin layer (b) from the outside, the four layers may be laminated by using the thermoplastic resin layer (b) provided on the inside and using various methods such as an extrusion sandwich lamination method and a hot lamination method. As described above, various methods can be used as a method of laminating the base material layer 10 and the metal foil layer 15.

(step (X3))

The sealant layer 18 is laminated to the corrosion prevention treated layer 16 of a laminate in which the base material layer 10, the outer adhesive layer 14, the metal foil layer 15, and the corrosion prevention treated layer 16 are laminated in this order with the inner adhesive layer 17 interposed therebetween.

As a method for laminating the sealant layer 18, in the case of a dry lamination structure, dry lamination, non-solvent lamination, wet lamination, and the like can be given. Preferably, the dry coating weight of the adhesive is 1 to 10g/m²More preferably 3 to 5g/m². In addition, the curing (maintenance) treatment may be performed in a range of room temperature to 100 ℃ in order to promote the adhesiveness.

In the case of the thermal lamination structure, the sandwich lamination method is preferable from the viewpoint of facilitating thickening of the inner adhesive layer 17 as compared with coating and improving the sealant property.

The inner adhesive layer 17 and the sealant layer 18 may be formed into a film by coextrusion. In this case, the heat treatment is preferably performed from the viewpoint of further improving the adhesion between the metal foil layer 15 and the sealant layer 18 and providing excellent electrolyte resistance and hydrofluoric acid resistance. The heat treatment temperature in this case is preferably within a range from room temperature to a temperature 20 ℃ higher than the melting point of the sealant layer 18, and more preferably within a range from the melting point of the inner adhesive layer 17 to the melting point of the sealant layer 18, as the maximum reaching temperature of the laminate. The heat treatment time depends on the heat treatment temperature, and it is preferable that the lower the heat treatment temperature is, the longer the heat treatment time is.

From the viewpoint of productivity and handling, the heat treatment method is preferably a method of passing through a drying furnace or a baking treatment furnace, a thermal lamination (thermocompression bonding) method, or a Yankee dryer (held in a hot drum).

The outer cover 1 can be obtained by the steps (X1) to (X3) described above.

The method for manufacturing outer package 1 is not limited to the method in which steps (X1) to (X3) are performed in this order. For example, the step (X1) may be performed after the step (X2) is performed. Further, an anticorrosive treatment layer may be provided on both surfaces of the metal foil layer.

In order to further improve moldability, a coating agent in which a lubricant is dissolved in a solvent may be applied to at least one of the base layer 10 and the sealant layer 18 to reduce the static friction coefficient. Examples of the lubricant include silicone, polymer wax, and fatty acid amide (e.g., erucamide). The lubricant may be blended in advance with the film forming the base layer 10 and the sealant layer 18 and may be precipitated by a bleeding out phenomenon.

The outer packaging material for a lithium ion battery according to the embodiment of the present invention described above has excellent moldability by using the film (a) as a base material layer, excellent performance of retaining a shape after molding processing such as cold molding, and excellent electrolyte solution resistance and scratch resistance.

The lithium ion battery outer package according to the embodiment of the present invention is not limited to the outer package 1. For example, an anticorrosive treatment layer may be formed on both surfaces of the metal foil layer.

< lithium ion Battery >

Next, a lithium ion battery 100, which is an example of a lithium ion battery according to an embodiment of the present invention, will be described with reference to fig. 2.

As shown in fig. 2, the lithium ion battery 100 includes: the container 110 formed of the outer package 1 includes a battery component 112 housed in the container 110 so that a part of the sheet member 114 is exposed to the outside, and an electrolyte (not shown) housed in the container 110 together with the battery component 112.

The container body 110 has a first container portion 110a and a second container portion 110b which are formed by folding a rectangular outer packaging material 1 in two such that the sealant layer 18 is disposed inside the container body 110. The first container portion 110a is formed in a container shape by deep-drawing the first container portion 110a so as to protrude from the sealant layer 18 to the base material layer 10, thereby providing a concave portion 116 for housing the battery component 112.

The top edge portion 118 is located on the opposite side of the fold 110c between the first container portion 110a and the second container portion 110 b. The distal edge portion 118 is a band-like edge portion where the sealant layers 18 are in contact with each other, and is heat-sealed in a state where a part of the sheet body 114 is sandwiched therebetween. In addition, the first side edge portion 120 and the second side edge portion 122 of the band-shaped edge portions located on both sides of the recess 116 are also heat-sealed.

As such, in the container body 110, three belt-like edge portions of the top edge portion 118, the first side edge portion 120, and the second side edge portion 122, which form three sides of the rectangular lithium ion battery 100, respectively, are in a state of being enclosed inside the container body 110 because the three belt-like edge portions are heat-sealed. The container body 110 is sealed in a state where the electrolyte is housed in the concave portion 116 together with the battery member 112.

The battery part 112 includes: a battery member body 124 having a positive electrode, a separator, and a negative electrode, and sheets 114, 114 connected to the positive electrode and the negative electrode of the battery member body 124, respectively.

The structure of the battery component body portion 124 is not particularly limited as long as it is a structure generally used for a lithium ion battery, and examples thereof include a laminate in which a positive electrode, a separator, a negative electrode, and a separator are sequentially laminated. As the positive electrode, the negative electrode, and the separator, those generally used in lithium ion batteries can be used without particular limitation.

The sheets 114, 114 include: lead wires 126 and 126 connected to the positive electrode and the negative electrode, respectively, and sheet sealants 128 and 128 that wrap the lead wires 126 and are welded to the sealant 18 of the distal edge portion 118. In the sheet members 114, the proximal end side (proximal end portion) of the lead 126 is connected to the positive electrode and the negative electrode, respectively, and the distal end side (distal end portion) is provided so as to be exposed to the outside of the container body 110.

Examples of the material of the lead 126 include aluminum, nickel, and nickel-plated copper.

The sheet sealing agent 128 may be made of any material that can be welded to the sealant layer 18 of the outer package 1, and examples thereof include acid-modified polyolefin resins exemplified in the description of the inner adhesive layer 17 of the outer package 1. The sheet sealing agent 128 may have a multilayer structure for providing insulation. For example, the sheet sealing agent 128 may have a structure (a layer made of an acid-modified polyolefin resin, a heat-resistant base material layer, a layer made of an acid-modified polyolefin resin, or the like) with a heat-resistant base material (a polyester base material or the like) interposed as an intermediate layer.

The lithium ion battery 100 can be applied to, for example, a mobile terminal device such as a personal computer or a mobile phone, a video camera, a satellite, an electric vehicle, an electric motorcycle, an electric bicycle, and the like. As the lithium ion battery 100, lithium ion batteries applied to these applications are particularly preferable.

(method for producing lithium ion Battery)

The lithium ion battery according to the embodiment of the present invention can be manufactured by a known method, except for using the outer package for a lithium ion battery according to the embodiment of the present invention. Next, an example of a method for manufacturing the lithium ion battery 100 will be described with reference to fig. 3A to 3C. Examples of the method for manufacturing the lithium ion battery 100 include a method including the following steps (Y1) to (Y3).

(Y1) a recess forming step of preparing outer package 1 and forming recess 116 by cold forming the portion of outer package 1 that becomes first container portion 110 a.

(Y2) a heat-sealing step of storing the battery component 112 in the concave portion 116 so that part of the sheet body 114 is exposed to the outside of the concave portion 116, folding back a portion to be the second container portion 110b of the exterior material 1 to form the exterior material 1 into a container shape, and heat-sealing the top edge portion 118 and the first side edge portion 120.

(Y3) a sealing step of injecting the electrolyte solution into the recess 116 from an opening provided in the second skirt portion 122, and heat-sealing the second skirt portion 122 so as to close the opening.

(step (Y1))

First, as shown in fig. 3A, a rectangular outer package 1 is prepared. Then, the rectangular outer package 1 is deep-drawn from the sealant layer 18 toward the base material layer 10 using a die to a desired molding depth, and the concave portion 116 is formed in a portion to be the first container portion 110 a.

As the mold, a mold generally used for deep drawing can be used. In the deep drawing, for example, the friction coefficient of the surface of outer package 1 is reduced in advance by a lubricant or the like, thereby reducing the friction between the die and outer package 1. This makes it easier for the outer package 1 to flow from the film pressing portion of the die into the molding portion. This enables formation of deeper concave portion 116 without generation of cracks or pinholes.

(step (Y2))

Next, as shown in fig. 3B, battery components 112 are disposed in concave portions 116 formed in step (Y1), and a portion to be second container portion 110B of outer package 1 is folded back. The tip edge portion 118 is heat-sealed so that the sheet body 114 is sandwiched between the tip edge portions 118 on the opposite side of the flap portion 110c and a part of the sheet body 114 is exposed to the outside of the recess 116. At this time, the sheet sealing agent 128 of the sheet 114 welds both the sealant layer 18 provided in the first container portion 110a and the sealant layer 18 provided in the second container portion 110b in the outer package 1. The first side edge portion 120 is also heat-sealed, and the outer package material 1 is formed into a container shape having an opening provided in the second side edge portion 122.

In the heat-sealing method, the state of the outer packaging material 1 having the container shape can be controlled by adjusting three conditions of the temperature of the heat-sealing bar, the surface pressure at the time of sealing, and the sealing time.

(step (Y3))

The electrolytic solution is injected into the concave portion 116 from the opening provided to the second side edge portion 122, and then the gas inside the concave portion 116 is evacuated to form a vacuum state. Then, the second side edge portion 122 provided with the opening that is not heat-sealed is heat-sealed under vacuum, whereby the second side edge portion 122 is encapsulated, obtaining the lithium ion battery 100 (refer to fig. 3C).

The lithium ion battery 100 is obtained through the above-described steps (Y1) to (Y3).

The method for manufacturing the lithium ion battery 100 is not limited to the above method. For example, the following method may be adopted: the second side edge portion 122 is heat-sealed, and after the electrolyte is injected into the recess 116 through the opening provided on the first side edge portion 120 side, the first side edge portion 120 is heat-sealed to close the opening.

The lithium ion battery according to the embodiment of the present invention described above can form a deeper concave portion by using the exterior material for a lithium ion battery according to the embodiment of the present invention, and has excellent electrolyte solution resistance and scratch resistance.

The lithium ion battery according to the embodiment of the present invention is not limited to the lithium ion battery 100 described above. For example, the present invention can be applied to a tetragonal sealed lithium ion battery 100 manufactured by the following manufacturing method. In this case, a concave portion is formed by cold forming in a part of the exterior material for a lithium ion battery of the present invention. Then, a battery component having a positive electrode, a separator, a negative electrode, and a sheet body is disposed inside the recess. Then, another lithium ion battery outer package of the present invention is laminated on the lithium ion battery outer package having the recessed portion formed therein such that the sealant layers face each other. Further, the lithium ion battery outer package is heat-sealed at the side edge portions of the three sides. Then, the electrolytic solution is injected from the side provided with the opening in a vacuum state. After the end of the injection of the electrolyte, the side edge portion of the side provided with the opening is heat-sealed to perform encapsulation.

Examples

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

< materials used >

The materials used in this example are as follows.

[ base Material layer ]

Table 1 shows the layer structure of the films A-1 to A-11 used as the base layer. The films a-1 to a-11 are produced by biaxially stretching a multilayer coextruded film formed by coextruding the resins forming the thermoplastic resin layers (a) to (c).

In addition, the abbreviations in table 1 have the following meanings.

PET: polyethylene terephthalate.

b-1: a polypropylene resin graft-modified with maleic anhydride.

b-2: styrene-based elastomers graft-modified with maleic anhydride.

b-3: a polyester elastomer graft-modified with maleic anhydride.

Ny-6: nylon 6.

TABLE 1

Further, films B-1 to B-5 to be compared are shown below.

Film B-1: a film obtained by biaxially stretching a multilayer coextruded film of a two-layer structure of PET (thickness: 5 μm) and Ny-6 (thickness: 25 μm) (the same as film A-1 except that the thermoplastic resin layer (b) was not present).

Film B-2: a laminated film was formed by laminating a biaxially stretched PET film having a thickness of 5 μm and a biaxially stretched Ny film having a thickness of 25 μm with a polyurethane adhesive (trade name "TM-K55/CAT-10L", manufactured by DONGYOU インキ, DONGYOU Ink K.Co., Ltd.)) (thickness: 1 μm).

Film B-3: a laminated film was formed in the same manner as the film B-2 except that the thickness of the adhesive layer formed with the urethane adhesive was set to 5 μm.

Film B-4: a biaxially stretched PET film having a thickness of 12 μm and a biaxially stretched Ny film having a thickness of 15 μm were laminated together with a polyurethane adhesive (trade name "TM-K55/CAT-10L", manufactured by Toyo ink Co., Ltd.) (thickness: 1 μm).

Film B-5: a laminated film was formed in the same manner as in film B-4, except that the thickness of the adhesive layer formed with the urethane adhesive was set to 3 μm.

[ outer adhesive layer 14]

Adhesive C-1: a polyurethane adhesive (trade name "TM-K55/CAT-10L", manufactured by Toyo Ink Co., Ltd.) prepared by blending an adduct-based curing agent of toluene diisocyanate with a polyester polyol-based main agent.

[ Metal foil layer 15]

Metal foil D-1: a soft aluminum foil 8079 (made by Toyo aluminum K.K, Inc.) manufactured by DONGYANG アルミニウム, Bao, 40 μm thick).

[ Corrosion prevention treated layer 16]

Treatment agent E-1: "Sodium polyphosphate-stabilized ceria sol" adjusted to a solid content concentration of 10 mass% using distilled water as a solvent. The phosphate was 10 parts by mass with respect to 100 parts by mass of cerium oxide.

Treatment agent E-2: the treatment agent was composed of 90 mass% of "ammonium polyacrylate salt (manufactured by east asian synthesis corporation)" and 10 mass% of "propylene-isopropenyl oxazoline copolymer (manufactured by Nippon Shokubai co., Ltd.) by using distilled water as a solvent to adjust the solid content concentration to 5 mass%.

Treatment agent E-3: a treatment agent comprising "polyallylamine (manufactured by Nitto Boseki co., Ltd.)" 90 mass% and "polyglycerol polyglycidyl ether (manufactured by Nagase Chemtex Corp.)" 10 mass% using distilled water as a solvent to adjust the solid content concentration to 5 mass%.

Treatment agent E-4: chromium fluoride (CrF) was adjusted in a water-soluble phenol resin (manufactured by Sumitomo electric Wood Co., Ltd.) using a phosphoric acid aqueous solution having a concentration of 1 mass% as a solvent to adjust the solid content concentration to 1 mass%₃) To a concentration of 10mg/m as Cr content present in the final dried film²And the treatment agent is prepared.

[ inside adhesive layer 17]

Adhesive F-1: the main agent is a polyester polyol (trade name "Takelac (タケラック)", manufactured by mitsui chemical co., ltd.) composed of a hydrogenated dimer fatty acid and a diol, and the curing agent is a mixture of crude toluene diisocyanate, crude (or polymerized) diphenylmethane diisocyanate, or an adduct thereof (trade name "Takenate (タケネート)", manufactured by mitsui chemical co., ltd.).

Adhesive F-2: a modified polyolefin resin (trade name "アドマー (Admer)", manufactured by mitsui chemical corporation) obtained by blending an elastomer composed of an ethylene- α olefin copolymer with a modified PP obtained by graft-modifying random polypropylene (tm (ar)) with maleic anhydride.

[ sealant layer 18]

Film G-1: two three-layer multilayer films (thickness: 60 μm, manufactured by オカモト corporation, Okamoto co., Ltd.) each composed of random propylene/block propylene/random propylene.

Film G-2: two three-layer multilayer films (thickness 80 μm, manufactured by オカモト corporation, Okamoto co., Ltd.) each composed of random propylene/block propylene/random propylene.

[ production of outer packaging Material for lithium ion Battery ]

The anticorrosive treatment layer 16 was formed by applying the treatment agents E-1 to E-4 having the compositions shown in table 2 to one surface of the metal foil D-1 serving as the metal foil layer 15 by a micro gravure coating method and drying the applied treatment agents. The amount of the treating agent applied is such that the final dry amount of the treating agent applied is 70 to 100mg/m²The mode of (2) is set. When the corrosion-resistant treated layer 16 has a multilayer structure, the final dry coating amount is 70 to 100mg/m²The mode of (2) is set. Then, in the drying unit, a baking process (け sintering process) is performed at 150-250 ℃ according to the type of the coating agent.

Then, the adhesive C-1 is applied by reverse gravure coating method in a dry coating amount of 4 to 5g/m²The coating is applied to the surface of the metal foil layer 15 opposite to the anticorrosive treated layer 16, and the resultant is bonded to the base by a dry lamination methodFilm of the layer 10. The thermoplastic resin layer (c) of the films A-1 to A-11 and B-1 was oriented toward the metal foil layer 15. The films B-2 to B-5 were set such that the biaxially stretched Ny film faced the metal foil layer 15 side. Then, aging was carried out at 60 ℃ for 6 days.

Next, the sealant layer 18 is laminated on the corrosion prevention treated layer 16 of the obtained laminate through the inner adhesive layer 17.

In the heat lamination structure, the film G-1 was laminated on the anticorrosion-treated layer 16 of the laminate obtained by extrusion of the adhesive F-2 at 260 to 300 ℃ through an extrusion laminator so as to have a thickness of 20 μm by a sandwich lamination method. Then, at 160 ℃ under 4kg/cm²And heat pressing was performed at 2 m/min, thereby preparing an outer packaging material.

In the dry lamination structure, the adhesive F-1 is applied onto the anticorrosion treated layer 16 of the obtained laminate by reverse gravure coating method so that the dry coating amount is 4-5 g/m²The film G-2 was applied by a dry lamination method. Then, aging was carried out at 60 ℃ for 6 days.

Moldability, rebound resilience, curling properties, electrolyte solution resistance and scratch resistance were evaluated as follows.

As an evaluation of formability, a drawing depth was measured to determine whether or not a deep concave portion can be formed by cold forming. It is important that the molded recess has no pin hole and no local thin portion and no fracture at the corner of the recess. Specifically, the thickness of the metal foil layer in the portion thinned by cold forming is preferably 60% or more of the original thickness of the metal foil layer. Particularly in an electric vehicle, the thickness of the corner of the recess has a large influence on the battery reliability.

As the evaluation of the rebound, an actual drawing depth from a predetermined drawing depth is measured, and whether or not a criterion is satisfied is determined. When each thermoplastic resin layer of the base material layer in the outer package is cold-formed in the plastic deformation region, the actual drawing depth approaches a predetermined drawing depth.

As evaluation of curling properties, an angle (described later) in the installation surface was measured, and it was determined whether or not the amount of warpage of the portion other than the concave portion when the concave portion was formed by cold forming satisfies a criterion. When each thermoplastic resin layer of the base material layer in the outer package is cold-formed in the plastic deformation region, stress at the time of forming is less likely to remain in each thermoplastic resin layer of the base material layer, and the amount of warpage is reduced. If the warpage of the outer package is small, the problem of poor sealing is unlikely to occur when the package is sealed at the heat-sealed edge portion, and the workability is excellent.

[ evaluation of moldability ]

The outer wrapper obtained in each of the above examples was cut into a blank shape of 150mm × 190mm, and a concave portion was formed in the central portion thereof by cold forming. As the punch, a punch having a shape of 100mm × 150mm, a punch bend angle (punch corner) R (RCP) of 1.5mm, a punch shoulder (punch shoulder) R (RP) of 0.75mm, and a die shoulder (die shoulder) R (RD) of 0.75mm was used. The mold clamping pressure (air cylinder) is 0.5-0.8 MPa, and the stroke speed is 5 mm/s.

Evaluation: the deep drawing depth was increased to a range of 4mm to 1mm, and cold forming was performed 10 times at the same deep drawing depth to confirm the presence or absence of pinholes and cracks in each sample, thereby performing evaluation. The evaluation criteria are as follows. The value "Δ" or more was regarded as passed.

". o": the cold forming is possible without generating pin holes and breakage and with a drawing depth of 8mm or more.

". DELTA": cold forming with a drawing depth of 7mm or less is possible without generating pinholes and breakage.

"×": no pin hole and no breakage are generated, and cold forming with a drawing depth of more than 5mm cannot be performed.

[ evaluation of rebound resilience ]

The distance from the bottom to the top of the concave portion (substantial forming depth) was measured with a vernier caliper with respect to a sample having a drawing depth of 5mm obtained by the evaluation of the formability, and the difference from 5mm, which is the set forming depth, was used as the rebound amount. Evaluation was carried out according to the following criteria. The value "Δ" or more was regarded as passed.

". o": the rebound volume is less than 0.3 mm.

". DELTA": the rebound volume is more than 0.3mm and less than 0.8 mm.

"×": the rebound volume is more than 0.8 mm.

[ evaluation of crimpability ]

In a single-side region (region of 100mm × 120 mm) of a sample 200 (fig. 4) obtained by cutting the outer jacket material obtained in each example into blank shapes of 200mm × 120mm, a concave portion 210 (fig. 4) is formed by cold forming. As the punch, a punch having a shape of 70mm X80 mm, a punch bend angle (punch corner) R (RCP) of 1mm, a punch shoulder (punch outer) R (RP) of 1mm, and a die shoulder (dieshoulder) R (RD) of 1mm was used. The mold clamping pressure (air cylinder) is 0.5-0.8 MPa, and the stroke speed is 5 mm/s.

As shown in fig. 4, the sample 200 was placed so that the bottom of the recess 210 was directed upward, and the angle θ was measured. The angle θ is an angle formed between a straight line connecting the end 220 where the recess 210 is not formed and the portion 210a of the installation surface where the edge of the recess 210 is continuous, and the installation surface. The crimpability was evaluated according to the following criteria, and a value of "Δ" or more was regarded as acceptable.

". o": the angle theta is lower than 13 deg..

". DELTA": the angle theta is 13 DEG or more and less than 30 deg.

"×": the angle theta is greater than 30 deg..

[ evaluation of electrolyte solution resistance and scratch resistance ]

The surface of the base layer of the outer package obtained in each of the above examples was rubbed 50 times with steel wool (# 0000) to which a load of 250g was applied. Then, the user can use the device to perform the operation,an electrolyte (the electrolyte was prepared by mixing 1/1/1 (mass ratio) with ethylene carbonate/dimethyl carbonate/diethyl carbonate so that LiPF was present₆Lithium hexafluorophosphate (lithium hexafluorophosphate) was adjusted to 1.5M and dissolved, and then water was added in an amount of 1500 mass ppm to generate hydrofluoric acid) was dropped onto the surface of the base material layer in a few drops, and the base material was left to stand at 25 ℃ under 95% RH for 24 hours. Then, the electrolyte solution was wiped off, and the deterioration of the surface of the base layer was visually confirmed. Evaluation was carried out according to the following criteria.

". o": the surface of the substrate layer was rubbed with steel wool, and no trace of the electrolyte adhesion and deterioration were observed.

". DELTA": the surface of the substrate layer was rubbed with steel wool, and traces of the electrolyte were observed, but no change in quality was observed.

"×": deterioration was observed in the portion rubbed with steel wool on the surface of the base layer.

Examples 1 to 13 and comparative examples 1 to 5

The exterior materials having the structures shown in table 2 were prepared by the foregoing preparation methods. The results of evaluation of moldability, rebound resilience, curling properties, electrolyte solution resistance and scratch resistance are shown in table 2.

TABLE 2

As shown in Table 2, examples 1 to 13 were excellent in moldability, rebound resilience, curling properties, and electrolyte resistance and scratch resistance; the substrate layers of examples 1 to 13 used the film (a) obtained by biaxially stretching a multilayer coextruded film having a thermoplastic resin layer (a), a thermoplastic resin layer (b) and a thermoplastic resin layer (c) from the outside. In addition, examples 1 to 12 obtained excellent electrolyte resistance without applying chromate treatment, which is also effective in the case of strengthening the restriction of chromium compounds in the future.

On the other hand, in comparative example 1 in which a film obtained by biaxially stretching a multilayer coextruded film without the thermoplastic resin layer (b) was used, cold forming could not be performed, and moldability was significantly reduced. In comparative examples 2 to 5 in which the biaxially stretched PET film and the biaxially stretched Ny film were laminated by a dry lamination method, the reverse elasticity and the curling property were deteriorated.

Industrial applicability

The lithium ion battery outer casing of the present invention can be formed by cold forming to a deep drawing depth without causing cracks or pinholes. The lithium ion battery outer packaging material of the present invention is excellent in the ability to retain the shape after molding and also excellent in the electrolyte solution resistance and scratch resistance, and therefore can be used for applications requiring long-term reliability and safety. The outer package material for a lithium ion battery of the present invention is effective particularly for applications requiring a large current to be obtained, such as an electric vehicle.

Description of reference numerals

1 external packaging material for lithium ion battery

10 base material layer

11 thermoplastic resin layer (a)

12 thermoplastic resin layer (b)

13 thermoplastic resin layer (c)

14 outer adhesive layer

15 Metal foil layer

16 anticorrosive treatment layer

17 inner side adhesive layer

18 sealant layer

100 lithium ion battery

110 container body

112 cell component

114 sheet body

116 recess

118 tip edge portion

120 first side edge portion

122 second side edge portion

Claims

1. An exterior material for a lithium ion battery, characterized in that,

it includes:

a substrate layer formed by biaxially stretching a multilayer coextruded film including a first thermoplastic resin layer having rigidity and chemical resistance and disposed on the outer side, a second thermoplastic resin layer having stress propagation properties and adhesiveness, and a third thermoplastic resin layer having toughness;

a metal foil layer laminated on one surface of the base material layer;

an anticorrosion treated layer laminated on the metal foil layer;

an inner adhesive layer laminated on the corrosion-resistant treated layer; and

and a sealant layer laminated on the inner adhesive layer.

2. The outer packaging material for lithium ion batteries according to claim 1,

the thickness of the first thermoplastic resin layer is 1 [ mu ] m or more and 10 [ mu ] m or less;

the thickness of the second thermoplastic resin layer is 0.1 [ mu ] m or more and 5 [ mu ] m or less;

the thickness of the third thermoplastic resin layer is 10 [ mu ] m or more and 50 [ mu ] m or less.

3. The outer packaging material for lithium ion batteries according to claim 1 or 2,

the first thermoplastic resin layer is a layer containing an aromatic polyester resin;

the second thermoplastic resin layer is a layer containing a modified thermoplastic resin obtained by graft modification of at least one unsaturated carboxylic acid derivative component selected from the group consisting of an unsaturated carboxylic acid, an anhydride of an unsaturated carboxylic acid, and an ester of an unsaturated carboxylic acid;

the third thermoplastic resin layer is a layer containing a polyamide resin.

4. The exterior packaging material for lithium ion batteries according to any one of claims 1 to 3,

the first thermoplastic resin layer is on the surface layer side of the base material layer.

5. A lithium ion battery is characterized in that,

it includes:

a container body formed by the exterior material for a lithium ion battery according to any one of claims 1 to 4;

a battery member housed in the container body so that a part of the sheet body is exposed to the outside; and

an electrolyte solution housed in the container body together with the battery component,

and the number of the first and second electrodes,

the container body has a concave portion formed on the lithium ion battery outer packaging material by cold forming,

the container body is formed in a container shape in which the sealant layer is disposed inside the container body,

and heat-sealing an edge portion where the sealant layers are in contact with each other in a state where the battery member and the electrolyte are accommodated in the concave portion, thereby sealing the battery member and the electrolyte.

6. A method for manufacturing a lithium ion battery is characterized in that,

preparing the exterior material for a lithium ion battery according to any one of claims 1 to 4;

forming a concave portion on the exterior material for a lithium ion battery by cold forming;

the battery component is accommodated in the concave part in a mode that the part of the sheet body is exposed outside the concave part,

forming the lithium ion battery outer packaging material into a container shape, and heat-sealing the edge portions so that openings are formed at the edge portions where the sealant layers are in contact with each other;

injecting an electrolyte into the recess through the opening;

the edge portion is heat-sealed in such a manner as to close the opening to perform the sealing.