JP2002216712A - Multi-layer sheet for battery case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a case storing a battery such as a polymer battery comprising a laminated body having an excellent barrier property against a water vapor, hydrofluoric acid and other gases, a good anti-sticking property, a good mechanical strength or a stable constitution against an electrolyte, an appropriate high temperature resistant property and a high moisture-proof property. SOLUTION: The battery case sheet comprises a laminated body which has a heat seal layer as the innermost layer forming a battery case storing a constitution material of the battery and in which an outer side of the laminated body including at least a metal foil as compared with the metal foil layer is made to an outer layer and an inner side thereof is made to an inner layer. A fluororesin is included in at least one layer constituting the inner layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer sheet for a battery case, which accommodates constituent materials of a battery, and more particularly to a multi-layer sheet which can be suitably used for a case such as a thin sheet battery.

[0002]

2. Description of the Related Art Heretofore, a metal case has been generally used as a case for storing constituent materials of a battery.
However, with the development and spread of various electronic devices such as notebook computers and mobile phones, their weight and thickness have been reduced, and the batteries used have been made as light as possible. In order to reduce the space for the battery in the equipment, the weight and thickness of the battery itself are required to be reduced. To meet such demands,
For example, various types of sheet-shaped batteries that are made light and thin in a sheet shape by introducing a polymer material into an electrode or an electrolyte of the battery have been researched and developed. On the other hand, the battery case used for these sheet batteries is not only light and thin, but also takes into account strength, water vapor and other gas barrier properties, heat resistance, durability, sealing properties, adhesion to electrode terminals, and the like. For example, a case composed of a laminate in which a first base material, a metal foil layer, a second base material, and a heat seal layer are sequentially stacked from the outside of the battery has been used. An adhesive layer or an adhesive resin layer is formed between the layers of such a laminate. By using a sheet made of such a laminate as a battery case and storing battery constituent materials therein, the battery is protected from tearing and pinholes caused by friction and piercing from the outside, and It is also protected from stabs and the like from the inside of the stored battery constituent material.

FIG. 1 is a schematic sectional view showing an example of the structure of a battery case sheet. The battery using the battery case sheet in the present invention is a thin battery such as a polymer battery, and its appearance is such that a battery constituent material is housed in a battery case, and a part of the electrode terminals is projected outside the battery. In the state of storage of the battery constituent materials, the battery case includes the electromotive unit cell and a part of the electrode terminal extended from the cell, the electrode terminal protruding to the outside of the battery case, and the inside of the battery case. The portion between the electrode terminals is tightly adhered to the heat seal portion when the battery case is formed, and is in a sealed state. Since the electrode terminals protrude to the outside of the case, a part of the electrode terminals is thermally bonded to a heat seal resin in a heat seal portion of the case in order to ensure that the battery case is sealed as a case. Therefore, the resin that forms the heat seal layer of the sheet has electrode adhesives formed of a conductive material such as a copper foil or an aluminum foil, which is a material for forming the electrode terminals, at the same time that the resin itself has thermal adhesion to each other. Also, a resin having thermal adhesiveness is used.

Further, as shown in FIG. 1, the laminate of the battery case sheet includes a metal foil layer 1 for barrier properties, the outer side of the metal foil layer as an outer layer 2, and the metal foil layer When the inside of the layer is the inner layer 3, the outer layer first base material 2a,
A second base material 3a is provided on the inner layer 3, and a heat seal layer 3b is provided on the innermost layer. By adopting such a configuration, the metal layer of the intermediate layer imparts excellent water vapor and other gas barrier properties, and the base material layer is laminated on both sides thereof, so that the metal foil layer is protected, cracks and pinholes. Since the occurrence of the gas barrier is prevented, good gas barrier properties are maintained.

Conventionally, polypropylene, acid-modified polypropylene or biaxially stretched nylon has been used as the second substrate 3a. These films prevent piercing of the projecting portions of the battery constituent material, have excellent adhesiveness with the acid-modified polyolefin resin forming the heat seal layer, and are generally used for heat sealing for forming a battery case. In the electrode terminal portion, the heat seal resin becomes thinner due to heat and pressure, and there is a risk of contact with the metal foil of the battery case sheet laminate. However, the presence of the second base material prevents the risk of the contact. For these reasons, it has been used as a base material for the inner layer.

However, when a polypropylene-based resin is used, it has excellent moisture-proofing properties and mechanical strength, but has insufficient barrier properties against a small amount of hydrofluoric acid (HF) generated inside the battery, so that HF forms an inner layer. Permeation and corrosion of the metal foil may cause delamination between layers. On the other hand, a biaxially stretched nylon film is hygroscopic, and in fact, a battery case is actually made using a laminate in which the second base material is made of nylon, and the battery containing the battery constituent materials is subjected to constant temperature and humidity. It has been confirmed that when stored for a long period of time, water enters the case. As a cause, moisture is generated by the second base material 3a.
Further, the nylon film used for the battery case, and from the end face of the battery case, penetrates into the nylon layer in the direction of the arrow through the inside of the layer of the heat seal portion, and penetrates the heat seal layer inside the battery case and It has been confirmed that it enters the case K. Conventionally, as the second base material,
A film made of an aliphatic nylon such as 6, or 66 nylon was used. For use as a battery case sheet, a film having a lower hygroscopicity, for example, a stretched film made of a polyester resin is also conceivable, but a polyolefin-based resin or nylon that can obtain a stable adhesive strength in bonding with a heat seal layer is used. Had been.

[0007]

DISCLOSURE OF THE INVENTION The present invention is excellent in water vapor and other gas barrier properties, is excellent in mechanical strength including piercing resistance, is stable against electrolytes, is resistant to high temperatures, and has a high battery resistance. An object of the present invention is to provide a case for accommodating a battery such as a polymer battery comprising a laminate having a barrier property against hydrofluoric acid generated inside.

[0008]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that a fluororesin is suitable as a material having a necessary condition as a second base material and having a low hygroscopicity and an excellent HF barrier property. Found that it can be used. That is, the battery case multilayer sheet of the present invention has a heat seal layer in the innermost layer forming a battery case for housing the constituent materials of the battery,
An outer layer outside the metal foil layer of the laminate including at least the metal foil layer is an outer layer, and a multilayer sheet for a battery case comprising a laminate having the inner layer as an inner layer, wherein the base material constituting the inner layer contains a fluororesin. Features.

Examples of the fluorine-based resin include polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polytrifluoroethylene, polychlorotrifluoroethylene, vinylidene fluoride-ethylene trifluoride ethylene copolymer, and fluorocarbon. There are vinylidene fluoride / ethylene tetrafluoride copolymer, ethylene tetrafluoride / propylene hexafluoride copolymer and the like. Among these, polyvinylidene fluoride is particularly preferably used.

The PVDF resin used in the present invention includes:
There are vinylidene fluoride homopolymers and homopolymers of vinylidene fluoride. The vinylidene fluoride homopolymer is obtained by polymerizing a vinylidene fluoride monomer by a suspension polymerization method, an emulsion polymerization method, or the like.
° C, melt flow rate (MF under 2.16 kg load)
R) is preferably from 0.005 to 300 g / 10 min, more preferably from 0.01 to 30 g / 10 min.

[0011] The vinylidene fluoride copolymer is
A copolymer of a vinylidene fluoride monomer and another monomer copolymerizable therewith, and the vinylidene fluoride component ratio in the copolymer may be 10 to 99% by weight, and more preferably 50 to 99% by weight. % By weight. Other monomers copolymerizable here include fluorine-based monomers such as ethylene tetrafluoride, propylene hexafluoride, ethylene trifluoride, ethylene trifluoride chloride, vinyl fluoride, and perfluoroalkyl vinyl ether, and ethylene and propylene. And unsaturated olefin-based monomers such as
More than one species can be used. This resin is also obtained by polymerizing the above monomer by a suspension polymerization or an emulsion polymerization method, and has a melt flow rate (MFR) at 230 ° C. under a load of 2.16 kg of 0.005 to 300 g / g.
It is preferably 10 minutes, and more preferably 0.1 minute.
01 to 30 g / 10 min.

However, the above-mentioned fluorine-based resins have poor adhesion to metals and other resins. Therefore, when laminating those films with a metal thin film or a heat seal layer, a) the surface of the fluororesin film is treated in advance with plasma, glow discharge, a reducing agent or an oxidizing agent, and polar functional groups are introduced into the surface. Therefore, it is necessary to improve at least one of the following steps: (1) to improve the adhesiveness, and (b) use an appropriate adhesive layer between the metal thin film / fluororesin layer and / or the fluororesin layer / heat seal layer.

Since the surface treatment and the use of the adhesive layer complicate the production process of the multilayer sheet, in the present invention, it is desirable to use a modified fluororesin having a polar group introduced therein as the fluororesin. Such a chemically modified fluorine-based resin is prepared by copolymerizing a fluorine-based monomer with a monomer having a polar group (for example, see JP-A-6-172).
No. 452), a method of grafting a compound having a polar group to a fluororesin (for example, a method described in Japanese Patent Application No. 08-258644), a method in which a fluororesin is treated with partially dehydrofluorinated There is a method of oxidation.

Among these, the fluorine-based resin used in the method of continuously oxidizing the fluorine-based resin with partially dehydrofluorinated one has the following chemical structural units.

[0015]

Embedded image

Here, X and X 'are the same or different and each represents an atom selected from hydrogen, halogen (particularly fluorine or chlorine), and perhaloalkyl (particularly perfluoroalkyl). A functional group having adhesiveness can be introduced into such a fluororesin by the above-described chemical reaction.

The fluororesin used for the chemically modified fluororesin is obtained by polymerizing an unsaturated olefin monomer. In order to obtain a fluorine-based polymer having the structural unit of the formula (1), it is necessary to polymerize a monomer composed of both a hydrogen atom bonded to a carbon atom and a fluorine atom bonded to a carbon atom. For example, as such a fluororesin, there is a homopolymer of a monomer which is a hydrofluorocarbon or a copolymer of a perfluorounsaturated monomer and one or more monomers containing a hydrogen atom.

The unsaturated olefin monomers used in the fluororesin B include ethylene tetrafluoride, propylene hexafluoride, vinylidene fluoride, ethylene trifluoride chloride,
-Chloropentafluoropropene, ethylene trifluoride, perfluoroalkyl vinyl ether, 1-hydropentafluoropropene, 2-hydropentafluoropropene, dichlorodifluoroethylene, 1,1-dichlorofluoroethylene and perfluoro-1, 3-dioxol (see US Pat. No. 4,558,142). Also, ethylene,
Unsaturated olefin monomers containing no fluorine, such as propylene and butylene, can also be used.

The fluororesins A and B are produced by a known method. In particular, vinylidene fluoride homopolymerization,
Suspension polymerization of vinylidene fluoride (US Pat. No. 3,553,18)
5 and EP 0 120 524) or emulsion polymerization methods (US 4,025,709, US 4,569,977).
8, US Pat. No. 4,360,652, US Pat. No. 4,626,396 and EP 0 655 468).

Generally, the unsaturated fluorinated olefin monomer can be polymerized in the form of an aqueous emulsion, and can be copolymerized with an olefin monomer containing no fluorine. In this case, water-soluble initiators such as ammonium or alkali metal persulfates and alkali metal permanganates and emulsifiers such as ammonium or alkali metal perfluorooctanoate are used. On the other hand, in the case of polymerization in an aqueous colloidal suspension, initiators such as dialkyl peroxides, alkyl hydroperoxides, dialkyl peroxydicarbonates, and dialkyl azo peroxides that are soluble in an organic phase are used. As an agent,
Methylcellulose, methylhydroxypropylcellulose, methylpropylcellulose, methylhydroxyethylcellulose and the like are used.

As the fluororesins A and B, many commercially available fluororesins can be used. An example is "Kyner", a product of Elf Atochem SA.

In order to make the fluororesin B into B 'by chemical modification, B is preferably in a dispersed state like an aqueous suspension or emulsion. Such a dispersion is obtained by the above polymerization recipe. Such a fluororesin B is partially dehydrofluorinated by a base,
Subsequently, the obtained resin is reacted with an oxidizing agent to obtain a chemically modified fluororesin B ′.

The dehydrofluorination of the fluororesin is carried out by the action of a base in water or an organic solvent. Examples of usable bases include, for example, hydroxides such as potassium hydroxide, sodium hydroxide and lithium hydroxide, aqueous ammonia, as described in WO 98/08880.
There are carbonates such as potassium carbonate and sodium carbonate, various tertiary amines, quaternary ammonium hydroxides, metal alkoxides and the like. An amine compound having a hydrocarbon structure soluble or partially soluble in water or an organic solvent is also used, and as a typical example, 1,8-diazobicyclo [5.
4.0] undec-7-ene (DBU) and 1,4-diazobicyclo 2.2.2 octane (DABCO).
The process of dehydrofluorination of fluororesins emulsified in aqueous media is described, for example, in WO 98/08879.

The above-mentioned base is optionally used together with a catalyst. Examples of the catalyst used include tetrabutylammonium bromide (TBAB), tetraalkylphosphoric acid, alkylallylphosphoric acid, alkylammonium halide and alkylphosphate.

The oxidation reaction of the dehydrofluorinated fluororesin is carried out in an aqueous medium using an oxidizing agent. As the oxidizing agent, hydrogen peroxide is particularly preferably used. In this case, since the reaction can be performed using water as a medium, there are advantages in environmental measures and costs as compared with the reaction in an organic solvent system. Another advantage is that wastewater treatment after the reaction is easier than other oxidizing agents. As other oxidants,
Palladium halides such as PdCl2, chromium halides such as CrCl2, alkali metal salts of permanganate such as potassium permanganate, alkyl peroxides, various peroxides, and persulfuric acid can also be used. These are combined with hydrogen peroxide. Can also be used.

The oxidation reaction of the fluororesin with the aqueous hydrogen peroxide is desirably performed at a pH of 6.5 to 8.0, and more desirably 6.7 to 7.6. The reason for this is that if the pH is lower than 6.5, the oxidation reaction will be significantly slower, while if the pH is higher than 8, decomposition of hydrogen peroxide will occur and may be out of control.
The reaction is preferably carried out at a temperature of 20 ° C to 100 ° C, more preferably 50 ° C to 90 ° C.

The amount of hydrogen peroxide used in the oxidation reaction is 1% by weight based on the total amount of the fluororesin to be charged.
~ 50%, more preferably 2
% To 12%.

The chemically modified fluororesin B 'obtained as described above exhibits remarkably high adhesiveness to various organic and inorganic materials as compared with a fluororesin which has not been chemically modified.

In the present invention, the chemically modified fluororesin B 'may be mixed with the fluororesin A which has not been chemically modified. As for this ratio, A / B 'is 30/70 to 99/1 by weight, preferably 50/5.
0 to 98/2. By mixing both in such a ratio, the adhesion to the fluororesin can be achieved without impairing the inherent chemical resistance, solvent resistance, electrochemical stability, mechanical properties, weather resistance, etc. of the fluororesin. Can be granted.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the constitution of the multilayer sheet of the present invention include the following. a) metal foil layer / second substrate layer / heat seal layer b) metal foil layer / adhesive layer 2 / second substrate layer / heat seal layer c) metal foil layer / second substrate layer / adhesive layer 3 / Heat seal layer d) metal foil layer / adhesive layer 2 / second base layer / adhesive layer 3 / heat seal layer e) first base layer / metal foil layer / second base layer / heat seal layer f) 1 base layer / metal foil layer / adhesive layer 2 / second base layer / heat seal layer g) 1st base layer / metal foil layer / second base layer / adhesive layer 3 / heat seal layer h) 1 base layer / metal foil layer / adhesive layer 2 / second base layer / adhesive layer 3 / heat seal layer i) first base layer / adhesive layer 1 / metal foil layer / second base layer / heat seal Layer j) 1st base material layer / adhesive layer 1 / metal foil layer / adhesive layer 2 / second
Base layer / Heat seal layer k) First base layer / Adhesive layer 1 / Metal foil layer / Second base layer / Adhesive layer 3 / Heat seal layer l) First base layer / Adhesive layer 1 / Metal foil Layer / adhesive layer 2 / second
Base layer / adhesive layer 3 / heat seal layer

In the present invention, of the above, the second base material layer is mainly a layer containing the above-mentioned fluororesin,
It is sufficient that at least one of the second base material layer, the adhesive layer 3 and the heat seal layer contains the fluororesin in an amount of 30% by weight or more, preferably 50% by weight or more of the layer.

Further, the case is formed by heat bonding (bag making), and the innermost layer of the laminate is a heat seal layer.
The heat seal layer is mainly composed of an acid-modified polyolefin resin which can be thermally bonded to the metal of the electrode terminal T.

The battery is used in a high temperature state,
It may also be left unattended. If the battery case does not have heat resistance, the heat seal portion may peel off in a high temperature state, and the electrolyte or the like may leak out. For example, it is required that an electronic device in which a battery is set be able to withstand even when left in a car. As a specific test standard for the heat resistance, it is required that the liquid does not leak after a lapse of 5 hours in an environment of 100 ° C. (called a dashboard test). In order to solve the above problem, as a result of studying various laminate structures and respective materials, as a laminate structure that satisfies the conditions to be provided as a case for a lithium battery, by adopting the following material structure, The inventors have found that the above problems can be solved, and have completed the present invention.

The first base material layer is desirably used as a base material for forming a laminate, such as one having strength and good workability during production of a laminate such as printing and lamination.
In addition, various characteristics such as friction resistance are required for the surface layer of the battery. In addition, not only the polymer battery but also the battery case needs various gas barrier properties including water vapor. In the present invention, a metal foil is used as the layer imparting the barrier property. In order to protect the barrier layer made of the metal foil and to reinforce the strength of the battery case, a second base material layer is provided inside the metal foil, and a heat seal layer is provided as the innermost layer. That is, the material composition of the present invention includes at least a base layer including a barrier layer made of a metal foil and a heat seal layer. Using an acid-modified polyolefin resin as the heat seal layer,
In addition, in order to comply with the dashboard test, the acid-modified polyolefin resin having a heat resistance of 100 ° C. or more is used. Examples of the method of laminating each layer include a dry lamination method, a sandwich lamination method in which an adhesive resin is extruded and bonded between layers to be bonded, and a thermal lamination method in which a film made of a thermoadhesive resin is interposed and pressed. Is available. Among these laminations, a sandwich lamination method by extruding an adhesive resin, a thermal lamination method with a film made of a thermoadhesive resin interposed, and the like are preferable among the above-mentioned laminations from the viewpoint of the resistance to an electrolytic solution. Also,
The method can also be used by coating with a solvent.

Hereinafter, the case for a polymer battery of the present invention will be described in detail. In the present invention, in the configuration of the laminate, in the lamination between the barrier layer and the inner layer, the adhesion between the layers is laminated by a sandwich lamination method using an adhesive resin, or
A previously formed thermal adhesive sheet may be interposed between the metal layer and the inner layer and laminated by a thermal lamination method. As the heat laminate, a high-frequency welding method or a thermocompression bonding method can be used. The innermost layer is formed by extrusion-coating a thermo-adhesive resin. However,
In the lamination outside the metal foil layer, the lamination may be performed by the dry lamination method. Further, a plasma treatment may be applied to the inner layer or the surface of the heat-adhesive sheet laminated with the metal foil layer. Plasma treatment is performed by placing a rare gas into a solution containing a functional group as a raw material gas in a vacuum chamber, or a gas obtained by premixing a gas containing a functional group with a rare gas in the chamber. May be used to perform a plasma treatment on the treated surface of the film. In addition to the plasma processing in the vacuum chamber, a method of continuously performing atmospheric pressure glow discharge plasma processing on a film may be used.

Next, the individual layers forming the laminate of the sheet for a polymer battery case according to the present invention will be further described. As described above, the sheet for a battery case of the present invention uses a metal foil layer excellent in water vapor and other gas barrier properties in the middle, and has first and second bases excellent in various strengths and durability outside or inside thereof. Material layers are appropriately laminated, and a heat seal layer is further laminated on the innermost layer.

In the above configuration, an aluminum foil, a copper foil, or the like can be suitably used for the intermediate metal foil layer for imparting gas barrier properties. Among them, aluminum foil is most preferably used because it is relatively inexpensive and has excellent workability such as bonding. An appropriate thickness of such a metal foil layer is 5 to 25 μm.

As the first substrate, for example, a biaxially stretched polyethylene terephthalate film (hereinafter, referred to as a biaxially oriented polyethylene terephthalate film)
PET film or PET), biaxially stretched nylon film (hereinafter, ON film or ON), polyethylene naphthalate film, polyimide film, polycarbonate film, etc. can be used, but processed with various performances including durability etc. Sex and economics,
PET film, ON film, etc. are particularly suitable. here
Comparing the properties of PET and ON, PET film is not a big difference, but PET film has low moisture absorption, excellent rigidity, scratch resistance, heat resistance, etc., ON has slightly higher moisture absorption, but flexibility, piercing strength Excellent in bending strength, cold resistance, etc.
The thickness of the film used as such a substrate layer,
It is preferably from 5 to 100 μm, more preferably from 12 to 30 μm.

As described above, the innermost heat seal layer has good thermal adhesiveness to the metal of the electrode terminal in addition to thermal adhesiveness between itself, In order to minimize the infiltration of water, it is preferable that the material itself has low hygroscopicity or water absorption, and more preferably, it is stable without being swollen or eroded by the electrolytic solution.

As a resin used for such a heat seal layer, a polyolefin resin having a polar group is preferably used. Examples of the polyolefin-based resin having such a polar group include, for example, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, and polyethylene or polypropylene copolymer. Polyolefin resins such as a blend of one or two or more can also be used, especially, acid-modified polyolefin resins,
For example, ethylene-acrylic acid copolymer, polyolefin resin modified by copolymerizing an acid component such as ethylene-methacrylic acid copolymer, or polyethylene, polypropylene, or a copolymer of ethylene and propylene Other copolymers with α-olefin, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-methacrylate copolymer,
Alternatively, polyolefin resins such as these terpolymers, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic anhydride, itaconic acid, unsaturated carboxylic acids such as itaconic anhydride, or A polyolefin resin modified by graft copolymerization of an anhydride is preferably used. By using a resin having a melting point of 100 ° C. or more from these resins, the battery case has excellent heat resistance. The melting point of the acid-modified polyolefin resin used for the heat seal layer is 100 ° C
If it is less than 7, when the battery is placed in a high temperature state, a peeling phenomenon may occur at the sealing portion of the case, and the electrolyte may leak.

The acid content of the acid-modified polyolefin resin is preferably in the range of 0.01 to 10% by weight. When the amount of the acid component is less than 0.01%, the heat adhesion to the metal is insufficient, and when the amount of the acid component exceeds 10% by weight, the film-forming properties are poor, which is not preferable. The thickness of such a heat seal layer is suitably in the range of 10 to 100 μm.

As the adhesive layer 2, the above-mentioned acid-modified polyolefin resin is preferably used. As the adhesive layer 3, in addition to the same acid-modified polyolefin resin, ethylene-
A vinyl acetate copolymer, an ethylene-acrylate copolymer, an ethylene-methacrylate copolymer and the like are preferably used.

As a method of laminating each layer as described above,
In the present invention, as a laminating method inside the metal foil layer 1, an adhesive resin is bonded by a sandwich lamination method in which the resin is melt-extruded and pressure-bonded between two layers to be bonded. As the adhesive resin, the above-mentioned acid-modified polyolefin resin is used. In addition, the innermost heat seal layer is formed by directly melt-extrusion coating an acid-modified polyolefin-based resin on the second base material layer.
In forming the laminate of the battery case sheet according to the present invention, the acid-modified polyolefin-based resin is bonded to the inner layer of the metal foil layer 1 without using a dry lamination method using an organic adhesive. However, in the lamination outside the metal foil layer, a dry lamination method may be adopted.

[0044]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples. In the lithium ion type polymer batteries used in the present Examples and Comparative Examples, as a battery constituent material, a battery case sheet, a laminate including an aluminum foil layer described in the Examples or Comparative Examples, and a polymer electrolyte solution were used. , LiP
1 mol / kg of F ₆ was added to EC / MEC / DMC (1/1 /
1) Kynar 280 which is a copolymer of vinylidene fluoride and hexafluoropropylene in an electrolytic solution (EC: ethylene carbonate; MEC: methyl ethyl carbonate; DMC: dimethyl carbonate) dissolved in a mixed solvent
1 (melting point: 142 ° C .; melt viscosity at 230 ° C., 100 sec ⁻¹ : 2400 Pa · s; manufactured by Atofina Co., Ltd.), a polymer gel obtained by adding 20%, and a lithium cobaltate and acetylene black as a positive electrode material 97: 3, as a negative electrode material, artificial graphite (MCMB manufactured by Osaka Gas Chemicals) and acetylene black mixed at a ratio of 99: 1, as a separator,
Kiner RC-10, a vinylidene fluoride-6-propylene copolymer (melting point: 151 ° C; 230 ° C, 10 ° C)
The melt viscosity at ⁰ sec ^-1 is 3500 Pa · s; manufactured by Atofina) and silica (TS-53 manufactured by Cabot).
0) and 2: 1 and a polymer gel swollen with the electrolytic solution, an aluminum foil was used as a current collector for the positive electrode, and a copper foil was used as a current collector for the negative electrode.

As a method of a battery storage test, 10 batteries each of the obtained batteries were used at 40 ° C. and 90 ° C. in each of Examples and Comparative Examples.
The battery was put in a constant temperature and humidity chamber of% RH and the performance of the battery was confirmed 4 months later.

[0046]

Synthesis Example 1 Polyvinylidene fluoride (PV) was prepared by an emulsion polymerization method described in US Pat. No. 4,025,709.
DF) Latex (Latex 1) was synthesized. The latex contained 42% by weight of PVDF, and the resin obtained by drying the latex had a melt index (MI) under a load of 10 kg at 230 ° C. of 0.6 to 1 g / 10 min.

7.2 kg of an aqueous solution containing 15% by weight of sodium hydroxide was placed in a 20-liter container and heated to 70 ° C. To this, 7.2 kg of the latex 1 was added.
The mixture was added at a rate of 0.72 kg / min while stirring at 80 rpm. Immediately, a dehydrofluorination reaction occurs, and brown PV
An aggregate of DF was obtained. When this was left under stirring at the same temperature, the color of the PVDF aggregate became darker with time.

After performing the above-described dehydrofluorination reaction with sodium hydroxide for 30 minutes, the suspension is continuously kept for 7 minutes.
Keep at 0 ° C, add about 2.5 kg of 36% hydrochloric acid, pH
Was set to 5. Thereafter, 1.68 k of 35% hydrogen peroxide was added.
g was added at a rate of 0.4 kg / min. Subsequently, a 15% aqueous sodium hydroxide solution was added to adjust the pH to a range of 6.6 to 7.6. While adding the required amount of the same aqueous sodium hydroxide solution, the pH is adjusted to this pH range.
The DF suspension was kept for a predetermined time to perform an oxidation reaction. PV
The DF aggregate gradually decolorized with time and eventually turned pale yellow. After this oxidation treatment was performed for 150 minutes, the aggregate dispersion was separated by filtration, sufficiently washed with distilled water, and dried at 105 ° C. to obtain a powder (resin B1 ′).

The absorbance at 300 nm of a solution having a resin concentration of 0.1% by weight prepared by dissolving the obtained powder in NMP was measured and found to be 0.19.

[0050]

Reference Example 1 Each of the chemically modified vinylidene fluoride resin compositions obtained in Synthesis Example 1 was dissolved in N-methylpyrrolidone (NMP) to prepare a solution having a resin concentration of 10% by weight. Each solution was applied to an aluminum plate having a thickness of 1 mm, left at 120 ° C. for 1 hour, and dried under reduced pressure. The coated surface was cut at 1 mm intervals and subjected to a grid test (according to JIS K5400 6.15). As a result, the adhesion residual ratio of the polymer coated layer was 100%. Further, when a tape peeling test was performed, the residual adhesion ratio was 100%. Thus, it was confirmed that the adhesiveness between the obtained chemically-modified vinylidene fluoride resin composition and aluminum was good.

[0051]

Example 1 Each of the chemically modified vinylidene fluoride resin (MPVDF) obtained in Synthesis Example 1 was dissolved in N-methylpyrrolidone (NMP) to prepare a solution having a resin concentration of 10% by weight. Each solution was applied to one surface of a 20 μm-thick aluminum foil (AL), left at 120 ° C. for 1 hour, and dried under reduced pressure. The thickness of the MPVDF layer is
It was 15 μm.

A biaxially stretched polyester film (PET) having a thickness of 50 μm, a polyurethane resin (PU) having a thickness of 15 μm as an adhesive layer, the above-mentioned aluminum foil coated with MPVDF, and an acid-modified polyethylene resin (MPE) were thermally laminated. Lamination, PET / PU / AL / MPVDF / MP
A multilayer sheet having the structure of E was produced. As a result of a storage test performed using this sheet, it was confirmed that there was no abnormality in the performance of the battery.

[0053]

Example 2 In Example 1, an acid-modified polyethylene resin layer was formed as a two-layer film comprising an acid-modified polyethylene layer (MPE) and an acid-modified polypropylene layer (MPP) produced by co-extrusion. A multi-layer sheet having a structure of PET / PU / AL / MPVDF / MPE / MPP was produced by heat lamination in the same manner as described above. As a result of the storage test, it was confirmed that there was no abnormality in the battery performance.

[0054]

Example 3 An acid-modified polyethylene (M
PE) layer, chemically modified vinylidene fluoride resin (MPVDF) layer described in Synthesis Example 1, acid-modified polyethylene (MPE)
4 consisting of a layer and an acid-modified polypropylene (MPP) layer
A layer film was prepared. 50 μm thick biaxially oriented polyester film (PET), 15 μm thick as adhesive layer
A multilayer sheet having a structure of PET / PU / AL / MPE / MPVDF / MPE / MPP was produced by a heat laminating method using the polyurethane resin (PU), aluminum foil having a thickness of 20 μm, and the above four-layer film. As a result of the battery storage test,
It was confirmed that there were no abnormalities in the battery performance.

[0055]

Comparative Example 1 A multilayer sheet having a PET / PU / AL / MPE / MPP structure was prepared by heat laminating a PET / PU two-layer film, an aluminum foil and an MPE / MPP two-layer film produced by co-extrusion. Battery storage test results, 1
In 8 out of 0, peeling of the aluminum foil layer from the inner layer and deterioration of battery performance were observed.

[0056]

Comparative Example 2 PET / PU two-layer film produced by co-extrusion, MPE / PA (nylon 6) / MPP three-layer film, and aluminum foil were thermally laminated, and PET / PU / AL.
A multilayer sheet having a structure of / MPE / PA / MPP was prepared.
As a result of the battery storage test, a decrease in performance was observed in 5 out of 10 batteries.

[0057]

Example 4 In Comparative Example 1, the MPE layer forming the inner layer was mixed with the chemically modified vinylidene fluoride resin described in Synthesis Example 1 by a twin screw extruder so that the weight ratio of the MPE and the chemically modified vinylidene fluoride resin described in Synthesis Example 1 was 50:50. A multilayer sheet was prepared in the same manner as in Comparative Example 1, except that the composition obtained by mixing was used. As a result of a battery storage test performed using this sheet, it was confirmed that there were no abnormalities in the performance of the battery. Moreover, the peeling of the aluminum foil layer and the inner layer observed in Comparative Example 1 was not observed.

[0058]

As described above in detail, the sheet for a battery case of the present invention is a laminate laminated in the order of outer layer / metal foil layer / inner layer, and at least one layer constituting the inner layer is made of a fluororesin. By incorporating, it is lightweight, thin, flexible, and has various mechanical strengths and heat resistance. No moisture ingress,
Furthermore, a sheet for a battery case having stable gas barrier properties of water vapor and other gases could be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a multilayer sheet showing an example of a configuration of a multilayer sheet for a battery case.

[Explanation of symbols]

 1: Metal foil layer 2: Outer layer 2a: First substrate 2t: Adhesive layer 3: Inner layer 3a: Second substrate 3b: Heat seal layer 3t: Adhesive layer

 ──────────────────────────────────────────────────の Continuing on the front page F term (reference) 4F100 AB01A AB10 AB33A AK03B AK03G AK04 AK17C AK17K AK18C AK19C AK19K AK41 AK51G AL07C AR00B BA03 BA07 BA10A BA10B CB00 EJ12C GB41 JB01 J02A01J02 JD12 JJ03 J02A DD14 KK02

Claims (19)

[Claims] 1. A laminate comprising at least a metal foil layer used for a battery case accommodating a constituent material of a battery, an outer layer outside the metal foil layer, an inner layer inside the metal foil layer, and a heat seal layer as an innermost layer. A multilayer sheet for a battery case comprising a body, wherein at least one layer constituting an inner layer contains a fluorine resin. 2. The fluororesin is selected from ethylene tetrafluoride, ethylene trifluoride, ethylene trifluoride chloride, vinylidene fluoride, vinyl fluoride, propylene hexafluoride, and perfluoroalkyl vinyl ethers. 2. The multilayer sheet for a battery case according to claim 1, wherein the multilayer sheet for a battery case is selected from thermoplastic fluororesins which contain at least one kind of monomer as a constituent unit, and a sum of ratios of these monomers to the whole resin is 30% by weight or more. 3. The multilayer sheet for a battery case according to claim 1, wherein the fluororesin is a modified fluororesin into which a polar group is introduced. 4. The multilayer sheet for a battery case according to claim 1, wherein the inner layer comprises a heat seal layer and a fluorine-based resin layer. 5. The multilayer sheet for a battery case according to claim 1, wherein the inner layer comprises a heat seal layer and a fluorine-based resin layer, and the adhesive layer 3 is disposed between the two layers. 6. The multilayer sheet for a battery case according to claim 1, wherein an adhesive layer 2 for bonding the two is provided between the metal foil layer and the fluorine-based resin layer. 7. The method according to claim 1, wherein the inner layer comprises an adhesive layer 2, a fluorine resin layer, an adhesive layer 3, and a heat seal layer.
7. The multilayer sheet for a battery case according to any one of items 6 to 6. 8. The multilayer sheet for a battery case according to claim 1, wherein the heat seal layer is a polyolefin resin. 9. The multilayer sheet for a battery case according to claim 1, wherein the adhesive layer 2 is an acid-modified polyolefin. 10. The multilayer sheet for a battery case according to claim 2, wherein the heat seal layer is a polyolefin resin having a polar group, and the fluororesin is a modified fluororesin having a polar group introduced therein. 11. The method according to claim 1, wherein the fluororesin is a modified polyvinylidene fluoride resin into which a polar group has been introduced.
11. The multilayer sheet for a battery case according to 10. 12. The multilayer sheet for a battery case according to claim 1, wherein the fluororesin is a chemically modified fluororesin obtained by partially dehydrofluorinating and oxidizing. 13. The fluororesin comprises at least a fluororesin A and a partially dehydrofluorinated and chemically modified fluororesin B 'by an oxidation reaction, wherein A / B' is a weight ratio of 3%.
The multilayer sheet for a battery case according to claim 12, which is a fluorine-based adhesive resin composition having a ratio of 0/70 to 99/1. 14. The multilayer sheet for a battery case according to claim 13, wherein the fluororesin A is a vinylidene fluoride homopolymer. 15. The fluororesin A is ethylene tetrafluoride,
A copolymer of vinylidene fluoride and at least one monomer selected from propylene hexafluoride, ethylene trifluoride, and ethylene trifluoride chloride, wherein the ratio of the vinylidene fluoride component in the copolymer is 50. The multilayer sheet for a battery case according to claim 13, wherein the content is from about 98% by weight. 16. The fluororesin A is a mixture of 1 to 99% by weight of a vinylidene fluoride homopolymer and 99 to 1% by weight of a vinylidene fluoride copolymer resin according to claim 11. The multilayer sheet for a battery case according to the above. 17. The multilayer sheet for a battery case according to claim 13, wherein the chemically modified fluororesin B 'is a resin obtained by partially dehydrofluorinating and oxidizing vinylidene fluoride homopolymer. 18. The copolymer of vinylidene fluoride and at least one monomer selected from the group consisting of ethylene tetrafluoride, propylene hexafluoride, ethylene trifluoride, and ethylene trifluoride chloride. A polymer,
When the ratio of the vinylidene fluoride component in the copolymer is 50 to 9
17. The multilayer sheet for a battery case according to claim 13, which is a resin obtained by partially dehydrofluorinating and oxidizing a resin at 8% by weight. 19. The multilayer sheet for a battery case according to claim 1, wherein the battery is a non-aqueous battery.