WO2004064092A1

WO2004064092A1 - Production method for electric double-layer capacitor-use electrode

Info

Publication number: WO2004064092A1
Application number: PCT/JP2004/000220
Authority: WO
Inventors: Hidekazu Mori; Masahiro Yamakawa
Original assignee: Zeon Corporation
Priority date: 2003-01-15
Filing date: 2004-01-15
Publication date: 2004-07-29
Also published as: JP4678301B2; JPWO2004064092A1

Abstract

A production method for an electric double-layer capacitor-use electrode comprising the step of screw-extrusion-molding a mixture containing a carbonaceous material and fluorine-not-containing polymer, whereby it is possible to mass-produce an electrode for an electric double-layer capacitor large in capacitance density and small in internal resistance.

Description

Description Manufacturing method of electrode for electric double layer capacitor

The present invention relates to a method for manufacturing an electrode for an electric double layer capacitor. BACKGROUND ART-Electric double layer capacitors utilizing an electric double layer formed at the interface between a polarizable electrode and an electrolyte, particularly coin-shaped capacitors, have been rapidly growing in demand as memory backup power supplies in recent years. On the other hand, the use of electric double-layer capacitors, which feature high power density, is attracting attention for applications requiring large capacity, such as power supplies for electric vehicles.

As an active material of an electric double layer capacitor, a force S mainly using a carbonaceous material such as activated carbon, and a mixture of a carbonaceous material and a binder for holding the carbonaceous material in the current collector are preferably used. Normal. Conventionally, fluorine-containing polymers such as polytetrafluoroethylene (hereinafter referred to as “PTF E”) have been used as binders for electric double layer capacitor electrodes from the viewpoint of excellent heat resistance. In addition, as a method of binding a carbonaceous material containing a binder to the surface of the current collector, a slurry (uniform paint) is prepared by mixing and dispersing the carbonaceous material in a binder solution or a latex. The method of painting has been taken.

However, when PTFE was used as the binder, it was difficult to obtain an electrode of uniform quality by continuous molding, because the fiberized portion and the non-fibrous portion of PTFE were generated unevenly. Further, there is a first problem that the binding property with the current collector is not sufficient, and the amount of the binder used increases, so that the internal resistance of the electrode increases. On the other hand, the method of applying the slurry on the current collector has a problem that the slurry viscosity is highly dependent on the solid concentration. In particular, when a carbonaceous material having a large specific surface area is used, a slight increase in the solid content significantly increases the viscosity of the slurry, resulting in poor coatability and a smooth coated surface. Can not be. Therefore, there was the second problem that continuous operation was difficult and mass production was difficult. It has been found that the adoption of this method makes it possible to manufacture an electrode for an electric double layer capacitor having excellent binding properties and low internal resistance, and also facilitates mass production, which was difficult with conventional methods. The present invention has been completed based on these findings.

That is, in order to solve the above problems, the present invention provides a method for producing an electrode for an electric double layer capacitor, which includes a step of screw-extruding a mixture containing a carbonaceous material and a fluorine-free polymer. . In the present invention, “carbonaceous material” is a concept including “active material” and “conductivity imparting agent” as an electrode material.

In the above production method, the fluorine-free polymer is preferably a polymer containing an elastomer.

Further, the fluorine-free polymer is preferably a polymer further containing a dispersant.

The fluorine-free polymer is preferably contained in an amount of 1 to 20% by mass based on the carbonaceous material.

Preferably, the mixture further contains a molding aid.

The molding aid is 0.1 to 100 mass per carbonaceous material. /. Preferably included.

Further, the elastomer is preferably either a gen-based elastomer or a crosslinked acrylate-based elastomer.

In addition, in the above-described production method, it is preferable that the method further includes a step of performing a press treatment in addition to the step of extruding the mixture by screw.

Further, in the above-described production method, it is preferable that the method further includes a step of bonding the mixture extruded with the screw to a current collector with a conductive adhesive.

Further, the extrusion temperature in the screw extrusion molding is preferably 5 to 100 ° C. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing a flow of manufacturing an electric double layer capacitor electrode.

FIG. 2 is a schematic diagram illustrating an example of a manufacturing apparatus used in the manufacturing method of the present invention.

FIG. 3 is a schematic view showing another example of the manufacturing apparatus used in the manufacturing method of the present invention. With respect to the first problem described above, there has been a proposal to use an elastomer as a binder to give flexibility to the electrode. For example, a method in which a mixture obtained by mixing and dispersing activated carbon and latex is dried, pulverized, granulated, and then pressed to obtain an electrode (Japanese Unexamined Patent Publication No.

And a method in which a binder made of an elastomer is dissolved in an organic solvent, a carbonaceous material is mixed and dispersed in the binder, and the solvent is evaporated, and then molded by a roll or a press (Japanese Unexamined Patent Publication No. — Japanese Patent No. 104316 and Japanese Patent Application Laid-Open No. 8-250380) have been proposed. Also, a method has been proposed in which activated carbon powder, styrene-butadiene rubber, and a water-soluble thickener are mixed to prepare a coating for an electrode, and the resultant is applied to a current collector and dried to produce an electrode (for example, see Japanese Patent Application Laid-Open Publication No. 11-162794, JP-A-2000-208368).

On the other hand, with respect to the second problem, JP-A-11-283887 discloses that a mixture comprising a carbonaceous material, polytetrafluoroethylene and a processing aid is subjected to screw extrusion molding, and the obtained extrusion is obtained. There is disclosed a method of forming an object into a sheet shape with a rolling roll.

However, the methods disclosed in JP-A-62-16506 and JP-A-63-104316 involve complicated production steps and difficulties in continuity. Was. Further, the method disclosed in Japanese Patent Application Laid-Open No. 11-162794 and Japanese Patent Application Laid-Open No. 2000-208368 can solve the problem of coatability due to the above-mentioned fluctuation in slurry viscosity. However, there was a problem that mass production was difficult. Further, the method disclosed in Japanese Patent Application Laid-Open No. 11-283887 has not yet solved the problem that the uniformity and binding properties of the electrode are poor when PTFE is used as the binder. The present invention has been made to solve the above-mentioned conventional problems, and it is possible to industrially mass-produce an electrode for an electric double layer capacitor having a flexible electrode and a small internal resistance. It is an object to provide a manufacturing method. Disclosure of the invention

The present inventors have studied various types of binder materials and methods of binding a carbonaceous material containing a binder to the current collector surface. As a result, the electrode sheet formed by extrusion using a fluorine-free polymer as a binder is adhered to the current collector surface.

Two It is extruded to form an “electrode sheet” III (step S 4). Here, the “fluorine-free polymer” in the raw material group A and the raw material group B have the same concept. Therefore, for example, the same fluorine-free polymer may be used in step S1 and step S3. The materials constituting the raw material groups A and B and their mixing ratios will be described later in detail.

On the other hand, if necessary (see Figure 3 below), they are kneaded using raw material group A (the same composition as in step S1) (step S5), and then diluted with a molding aid ( Step S6), “Conductive adhesive” Ib is prepared. In the kneading step in step S5 as well as in the kneading step in step S1, shearing is applied by a kneader (not shown) to sufficiently sufficiently disperse the conductivity imparting agent. In the production apparatus 200, the conductive adhesive Ib is given sufficient fluidity by dilution with a solvent or the like, and is stored in the adhesive bath 106 in a predetermined amount. The lower part of the lower roll of the roll set 107 is immersed in the adhesive bath 106, and the conductive adhesive Ib that has adhered to the lower roll surface and rolled up by the rotation of the roll is a doctor blade. It is dropped to an appropriate amount by 106a, and is applied to the back side of the aluminum foil 104 as a current collector wound out from the payoff reel 103 (step S7). The above conductive adhesive Ib is applied on the current collector by force, and the “current collector sheet with adhesive” IVb is prepared. In the above description, the step of preparing the conductive adhesive Ib through the steps S5 and S6 using the raw material group A is an optional step, and may be omitted as the case may be, and the payoff reel 3 The unwinding current collector sheet IVa may be used as it is (see Fig. 2).

The current collector sheet IVa or the current collector sheet IVb with adhesive prepared in this manner is pressure-bonded to the electrode sheet III in the next step S8. That is, the electrode sheet III and the current collector sheet IVa, or the current collector sheet with adhesive IVb, which are stacked on top and bottom, are composed of the first cooling roll 11 and the second cooling roll 12 In this way, the sheets are bonded together, cooled, and rolled to a predetermined sheet thickness. The sheet laminated together (hereinafter referred to as “intermediate sheet” V) then passes between the second cooling roll 12 and the third cooling roll 13, and is further cooled to obtain a sheet thickness. Is precisely adjusted.

Then, the intermediate product sheet V is adjusted further downstream of the third cooling roll 13. BEST MODE FOR CARRYING OUT THE INVENTION

<1> Manufacturing process flow and manufacturing equipment

The present invention provides a method for producing an electrode for an electric double layer capacitor, which includes a step of screw-extruding a mixture containing a carbonaceous material (active material, conductivity imparting agent) and a fluorine-free polymer. In the screw extrusion forming step according to the present invention, the formed product (electrode sheet) is extruded onto a current collector, the two are adhered to each other, dried, and if necessary, pressed with a rolling nozzle or the like. As a result, an electrode sheet for an electric double layer capacitor is manufactured.

Hereinafter, a method for manufacturing an electrode for an electric double layer capacitor according to the present invention will be described with reference to FIG. 1 showing the flow of the manufacturing method and FIG. 2 and FIG. 3 showing the outline of the manufacturing apparatus. The basic configuration of the manufacturing apparatus is the apparatus 100 shown in FIG. 2, and the apparatus 200 of FIG. 3 includes an optional configuration. Therefore, regarding the manufacturing apparatus, the following description basically refers to FIG. 2 and also to FIG. 3 as necessary. In FIG. 3, the same members as those shown in FIG. 2 are denoted by the same reference numerals as those in FIG. 2, and the description thereof is omitted.

In the method for producing an electrode for an electric double layer capacitor according to the present invention, first, a raw material containing a conductivity-imparting agent, which is a kind of carbonaceous material, a fluorine-free polymer, and a shaping aid added as necessary. Hereinafter, the “raw material group A” is kneaded by the kneader 9 (step S1) and extruded by the extruder 10 (step S2) to obtain the “conductive material pellet” la. The kneading step of step S1 is a step in which sufficient shear is applied by the kneader 9 to uniformly disperse the conductivity-imparting agent. However, in the following step S3, the conductive material is added and kneaded together with the active material, the fluorine-free polymer and the molding aid optionally added, and the mixture is kneaded. S 2 can be omitted.

Next, in step S3, the conductive material pellet Ia is a raw material (hereinafter referred to as “raw material group B”) containing an active material, a fluorine-free polymer, and a molding aid added as needed. It is not shown in Figures 2 and 3.) and is fed into the screw extruder 1 and uniformly kneaded to form the “electrode paste” II. The electrode paste I is formed into a sheet by a film die 2 attached to the tip of a screw extruder 1.

Four When passing through the rolls 15a and 15b, the sensor detects the thickness and tension of the sheet. The result is fed back to the extruder 1, the first cooling roll 11, the second cooling roll 12, and the third cooling roll 13, and in order to secure the appropriate sheet thickness, etc., the feed speed and the gap between each roll , Pressure, etc. are adjusted.

The intermediate product sheet V that has passed through the adjusting rolls 15a and 15b passes through a drying furnace 16, during which the molding aid added during kneading is removed. Next, the intermediate product sheet V is pressed by a pair of press rolls 17a and 17b arranged above and below as necessary (step S10), and is further wound up by a wind-up roll 18. In this manner, the “capacitor electrode sheet” VI is formed.

<2> Raw material components

Hereinafter, the compounding amounts of the carbonaceous materials, the fluorine-free polymers, and the molding aids constituting the raw material groups A and B will be described. The “carbonaceous material” is a concept including an “active material” and a “conductivity-imparting agent” made of a carbonaceous material, and each is described separately.

(1) Active material

The active material to which electrolyte ions are adsorbed in the electric double layer capacitor is made of activated carbon, polyacene, etc. and has a specific surface area of 3 As described above, a powder having a weight of 200 to 3500 m ² / g is preferable. Fibers such as carbon fibers, carbon whiskers, and graphite, or powders can also be used as long as the specific surface area is within the above range, as long as the extrudability is not impaired. As the activated carbon, phenol-based, rayon-based, acrylic-based, pitch-based, or coconut husk-based can be used. Further, non-porous carbon having microcrystalline carbon similar to graphite and having an increased inter-phase distance between the microcrystalline carbons described in Japanese Patent Application Laid-Open No. 11-31733 / 2002-25867, etc. Can also be used as an electrode active material. When the particle diameter of the active material is 0.1 to 100 / im, preferably 1 to 20 μπι, it is preferable because the capacitor electrode can be easily formed into a thin film and the capacity density can be increased.

(2) Conductivity imparting agent

Acetylene black, Ketjen black, carbon black And conductive carbon such as carbon black. It is preferable that these conductive additives are uniformly dispersed in advance, and then mixed with the above-mentioned active material before use. By using the conductivity-imparting agent in this way, the electrical contact between the active materials is further improved, the internal resistance of the electric double layer capacitor is reduced, and the capacitance density can be increased. The compounding ratio of the active material and the conductivity-imparting agent is 0.1 to 20 parts by mass, and preferably 2 to 10 parts by mass, per 100 parts by mass of the active material.

(3) Fluorine-free polymer

The fluorine-free polymer used in the present invention is not particularly limited, and examples thereof include a conjugated diene, an ethylenically unsaturated carboxylic acid ester, an ethylenically unsaturated carboxylic acid, an aromatic vinyl compound, a thiolefin, and a Examples include a homopolymer or a copolymer of a monomer such as a saturated nitrile conjugate, etc. Further, even when these are copolymerized polyfunctional ethylenically unsaturated monomers to form a crosslinked polymer. Among them, elastomers having a glass transition temperature of 50 ° C. or lower, preferably 150 ° C. to 0 ° C. are preferable, and monomer units derived from conjugated gens such as butadiene and isoprene are used as main components. A cross-linked acrylate-based elastomer having a cross-linked structure and containing as a main component a monomer unit derived from an acrylate ester and Z or a methacrylate ester Ma one; is needed use particularly preferred.

Examples of the gen-based elastomer include polybutadiene, carboxy-modified styrene-butadiene-based copolymer, and acrylonitrile Z-butadiene-based copolymer having a crosslinked structure. Examples of the cross-linked acrylate-based elastomer include 2-ethylhexyl acrylate / methacrylic acid / acrylonitrile / ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate methacrylic acid / methacrylonitrile. Examples include Z-diethylene glycol dimethacrylate copolymer, butyl acrylonitrile acrylate / diethylene glycol dimethacrylate copolymer, and butyl acrylate / acrylic acid / trimethylol pantolimethacrylate copolymer.

In the production method of the present invention, the fluorine-free polymer is used in an amount of 1 to 20% by mass, more preferably 1 to 10% by mass on a dry mass basis relative to the carbonaceous material (total amount of the active material and the conductivity-imparting agent). It is preferable to be blended so as to be contained by mass%. Fluorine-free polymer is charcoal The base material is bound to the current collector and is included in the electrode as a binder for maintaining the shape of the electrode sheet. By setting the fluorine-free polymer to 1% by mass or more, the strength of the electrode can be increased. When the content is 20% by mass or less, the internal resistance of the electrode can be reduced.

Among the fluorine-free polymers, a polymer soluble in water or an organic solvent or a polymer melted by heat can be used alone, but is preferably used in combination with the elastomer because it also has an effect as a dispersant. The use of a fluorine-free polymer that exhibits an effect as a dispersant (hereinafter, simply referred to as “dispersant”) can impart fluidity and viscosity to the electrode paste II.

Examples of the fluorine-free polymer as a water-soluble dispersing agent include, for example, carboxymethyl cenorellose (CMC), methinoresenolose, ethnoresenolose and other senoreloses, polyvinyl alcohol, polybutyl methyl ether, or polyacrylic acid ( Salt, oxidized starch, phosphoric acid starch, casein, and various modified starches. On the other hand, fluorine-free polymers as dispersants soluble in organic solvents include:

1. Soluble in solvent,

2. Insoluble in the electrolyte used in the capacitor;

3. It is required to be electrochemically stable with respect to the electrolysis solution used for the capacitor.

Acrylonitrile-based polymers such as polyacrylonitrile, acrylonitrile / acrylic acid ester copolymer, Atari-mouth nitrile / methacrylic acid ester copolymer, acrylonitrile / butadiene copolymer (NBR) and hydrogenated products thereof; ethylene Zacril And olefin polymers such as acid ester copolymers, ethylene / methacrylic acid ester copolymers, and graft polymers obtained by grafting a radical polymerizable monomer onto an ethylene acrylate ester copolymer.

Examples of the fluorine-free polymer as a dispersant which is melted by heat include polyolefins such as polyethylene and polypropylene; styrene copolymers such as acrylate / styrene copolymer and methacrylate Z-styrene copolymer; And the like.

In the production method of the present invention, the fluorine-free polymer as a dispersant is a carbonaceous material. It is preferable that it is contained so as to be contained in an amount of 1 to 5% by mass, more preferably 1 to 3% by mass on a dry mass basis with respect to (the total amount of the active material and the conductivity imparting agent). As described above, the addition of a fluorine-free polymer as a dispersant can be used for imparting fluidity and viscosity to the electrode paste II. When the content of the polymer is 1% by mass or more, sufficient viscosity can be imparted to the electrode paste, and the moldability of the electrode sheet ΙΠ extruded from the extruder can be improved. Further, when the content is 5% by mass or less, the internal resistance of the electrode can be reduced.

(4) Molding aid

The molding aid in the present invention is added for the purpose of improving the moldability in forming the electrode sheet III by extruding the electrode paste II from an extruder. Specifically, water; ketones such as acetone, ethyl methyl ketone, and methyl isobutyl ketone; hydrocarbons such as kerosene and naphtha; amides such as N-methylpyrrolidone; stearic acid, palmitic acid, and myristin Fatty acids such as acid, oleic acid and lauric acid; fatty acid amides such as stearic acid amide and palmitic acid amide; or methanol, ethanol, propanol, butanol, ethylene glycolone, propylene glycolone, dipropylene glycol, Other examples include alcohols such as glycerin; and nonionic surfactants such as polyoxyethylene alkyl phenyl ether and polyoxyethylene higher alcohol ether. These molding aids may be used alone or in combination of two or more. These molding aids can be used as needed depending on the type and combination of the fluorine-free polymer to be used, and may be used as a solvent for the dispersion medium and the dispersant of the elastomer.

In particular, the above-mentioned elastomer is preferably used by dispersing it in water or a solvent other than water, and it is particularly preferable to use a water-dispersed elastomer in consideration of the environment. When the elastomer is used as particles dispersed in water or a solvent other than water, the amount of the elastomer can be reduced because it can be uniformly attached to the surface of the carbon material.

In the production method of the present invention, the molding aid is contained in an amount of 0.1 to 100% by mass, and more preferably 5 to 50% by mass, based on the carbonaceous material (total amount of the active material and the conductivity-imparting agent). It is preferable to mix them as follows. By setting the amount of the molding aid to 0.1% by mass or more, the effect of improving the molding can be sufficiently obtained. Also, by setting the content to 100% by mass or less, The extrusion pressure can be increased, and it is possible to effectively prevent the electrode paste II from flowing backward and flowing out of the extruder hopper.

<3> Screw extruder

In the production method of the present invention, the screw extruder 1 is used to perform screw extrusion. By using the screw extruder 1, each of the above-mentioned raw material components is uniformly kneaded, and a uniform electrode sheet can be continuously formed. The screw extruder 1 has a screw having an annular groove that rotates in the barrel of the extruder, and a mixture containing an active material, a conductivity-imparting agent, a fluorine-free polymer, and, if necessary, a molding aid. The kneading is performed while rotating barrel によって by rotating the screw to form electrode paste II, which is extruded to form electrode sheet III. The thickness of the electrode sheet III is usually from 10 to 500 μπι, preferably from 20 to 100 μπι. When the thickness of the extruded electrode sheet III is large, it can be rolled to a thickness suitable for an electrode for an electric double layer capacitor by a pressing process described later. In the production method of the present invention, any of screw extruders for resin, rubber, and building materials can be used. Further, either a single screw extruder or a multi-screw extruder can be used. The ratio L / D between the length (L) and the inner diameter (D) of the extruder barrel is usually 10-50. As the screw shape, various shapes such as a full-flight screw, a noble pitch screw, and a screw with a mixing pitch can be adopted, but it is particularly preferable to use a full-flight screw whose extrusion pressure can be easily adjusted.

As the die, a film die such as a straight manifold die, a fish-tail die, and a coat hanger die is used.

The extrusion temperature in the screw extrusion molding is preferably from 5 to 100 ° C, particularly preferably from 30 to 80 ° C. By setting the extrusion temperature to 5 ° C or more, the extruded material can be effectively prevented from becoming brittle, and the shape can be easily maintained. In addition, by setting the extrusion temperature to 10 ° C. or less, it is possible to prevent the processing aid from evaporating and to effectively prevent a situation in which extrusion becomes difficult.

The extrusion pressure in screw extrusion molding is preferably from 0.2 to 1 OMPa, more preferably from 0.3 to 5 MPa.

0 <4> Current collector and conductive adhesive

(1) Current collector

The electrode paste II is formed into an electrode sheet III by the screw extruder 1, extruded onto a current collector, dried, and optionally pressed to form an electrode VI for an electric double layer capacitor. The current collector is preferably a metal foil, particularly an aluminum foil. The aluminum foil can be continuously drawn from the rolled foil coil and used.

(2) Conductive adhesive

By applying the conductive adhesive Ib to the current collector in advance, it becomes easy to reduce the internal resistance between the electrode sheet III and the current collector. The conductive adhesive Ib can be obtained by kneading a conductivity-imparting agent using the above-mentioned fluorine-free polymer. Specifically, the elastomer is 5 to 20 parts by mass on a dry mass basis with respect to 100 parts by mass of a conductivity-imparting agent such as acetylene black, Ketjen black, and carbon black, and fluorine as a dispersant is used. The non-containing polymer can be prepared by adding 1 to 5 parts by mass on a dry mass basis and using a kneader capable of applying shearing.

When the amount of the elastomer used is 5 parts by mass or more, the electrode sheet 電極 and the current collector can be sufficiently bonded. When the amount of the above-mentioned elastomer is not more than 20 parts by mass, the conductivity-imparting agent can be sufficiently dispersed, and the internal resistance can be reduced by / J. When the amount of the fluorine-free polymer used as the dispersant is 1 part by mass or more, the conductive material can be sufficiently dispersed and the internal resistance can be reduced. In addition, when the amount of the fluorine-free polymer used as the dispersant is set to 5 parts by mass or less, the internal resistance increases due to the fact that the conductivity-imparting agent is coated with the fluorine-free polymer as the dispersant. Can be prevented.

As a kneader used for producing the conductive adhesive Ib, a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, or the like can be used.

The method of applying the conductive adhesive Ib to the current collector is not particularly limited. For example, it is applied by a doctor blade method, a dip method, a rippers roll method, a direct roll method, a gravure method, an eta-strusion method, a brush coating, or the like. The amount to be applied is not particularly limited.

One However, the thickness of the conductive layer formed after drying is adjusted to be usually 0.5 to 10 μιη, preferably 2 to 7 μπι.

<5> Drying and pressing

The type of the drying oven 16 is not particularly limited, and includes, for example, drying by warm air, hot air, low-humidity air, and drying by irradiation with (far) infrared rays or electron beams. The drying conditions are adjusted so that the molding aid can be removed as soon as possible within a speed range where stress collection does not occur and the electrode layer does not crack or the electrode layer does not peel from the current collector.

Further, the electrode may be stabilized by pressing the dried current collector. The press treatment method is not particularly limited, but a method such as a die press or a roll press can be used. Among these methods, a roll press suitable for mass production is preferably employed.

(Example)

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited thereto. In the examples, parts and% are based on mass unless otherwise specified. Measuring method>

(1) Electrode density

An electrode sheet for a capacitor cut into 5 cm X 5 cm to measure its mass and thickness, determined the current collector weight and thickness as the density of the electrode layer is calculated by subtracting respectively (g / cm ³⁾ Was.

(2) Peel strength of electrode

Cut a capacitor electrode sheet into a rectangle of 100 mm in length and 25 mm in width to form a test piece, and fix it with the electrode layer side up. After a cellophane tape was attached to the surface of the electrode layer of the test piece, the stress was measured when one end of the cellophane tape was peeled off by pulling it vertically at a speed of 5 O mmZ. The measurement was performed three times, the average value was determined, and this was used as the peel strength. The higher the peel strength, the higher the binding force of the electrode layer to the current collector.

(3) Capacitance and internal resistance of electric double layer capacitor

Two The electric double layer capacitor was charged at a constant current of 10 mA to 2.7 V for 10 minutes at 25 ° C, and then discharged at a constant current of 1 mA to 0 V. The capacitance per unit mass of the electrode layer was obtained by calculating the capacitance from the obtained charge / discharge curve, dividing the mass of the electrode by the mass of the electrode layer obtained by subtracting the mass of the current collector from the mass of the electrode. . The internal resistance was calculated from the charge / discharge curve according to the calculation method of the standard RC-2377 specified by the Japan Electronics and Information Technology Industries Association. Preparation of conductive adhesive Ib>

Acetylene black 100 parts, 10% carboxymethylcellulose aqueous solution (Cellogen 7H; manufactured by Daiichi Kogyo Pharmaceutical) 30 parts, 40% carboxy-modified styrene-butadiene copolymer latex (BM-400B; Nippon Zeon) 30 parts, soft water 10. Two parts were kneaded using a kneader, and then diluted using soft water. Thus, a conductive adhesive Ib having an average particle size of acetylene black of 0.5 m and a solid concentration of 30% as measured by a light scattering method was obtained. Preparation of Ku conductive material Peretsuto I _a>

Acetylene black 100 parts, 10% carboxymethylcellulose aqueous solution (Cellogen 7H; Daiichi Kogyo Pharmaceutical) 30 parts, 40% carboxy-modified styrene-butadiene copolymer latex (BM-400B; Nippon Zeon) 30 parts, soft water 10. Two parts were kneaded using a kneader and extruded using an extruder to obtain a conductive material pellet Ia having a solid content of 72% with a diameter of 1 mm and a length of 2 mm. Example 1

83 parts of high-purity activated carbon powder with a specific surface area of 1,500 m ² / g and an average particle size of 10 μm, 13.9 parts of conductive material pellets Ia, solid matter with a glass transition temperature of 15 ° C as a gen-based elastomer 12.5 parts of a 40% carboxy-modified styrene-butadiene copolymer latex (BM-400B), 20 parts of a 10% carboxymethylcellulose aqueous solution (cellogen 7H; manufactured by Daiichi Kogyo Seiyaku) as a dispersant, and a molding aid Of ethylene glycol and 37.9 parts of soft water were kneaded using a kneader. This kneaded material is screwed with a screw diameter of 40

Three Feeding at a rate of 20 g / min to a twin screw extruder with a barrel length (L) and inner diameter (D) ratio of 22 mm in LZD and drying from a 4 Omm wide, 150 μιη thick die The sheet was extruded on a current collector to which a conductive adhesive Ib had been previously applied so that the thickness became 5 μm. The extrusion temperature was 40 ° C, the extrusion pressure was IMPa, the compression ratio was 2, and the screw rotation speed was 20 rpm. After drying the above-mentioned sheet at 150 ° C for 1 hour, a press treatment was performed using a roll press machine to obtain a capacitor electrode sheet having an electrode density of 0.65 g / cc and an electrode thickness of 130 / im.

In addition, it was confirmed that the extrusion molding was continuously performed for 20 minutes, and that a long-sized capacitor electrode sheet could be formed stably.

The above capacitor electrode sheet is cut out of 4 (: 111 髙 6 ₍ ; 111), leaving two lead electrodes, and the electrode surfaces of the two capacitor electrode sheets are opposed to each other. This was sandwiched between two polypropylene plates 2 mm thick, 5 cm wide, and 7 cm high to form a device.

As the electrolytic solution, a solution in which 1.5 mol 1 ZL of triethyl monomethylammonium tetrafluoroporate was dissolved in propylene carbonate was used. The above element was vacuum-heated at 200 ° C for 3 hours to remove impurities such as water contained in the element.Then, the electrolytic solution was impregnated in vacuum and housed in a polypropylene container to form an electric double layer capacitor. Made. The DC resistance and capacitance were measured at a current density of 2 OmAZ cm ² , and the capacitance per unit mass (capacity density) and volume resistance of the electrode layer were calculated, confirming good performance as a capacitor. Table 1 shows the results of evaluating various characteristics of the obtained electrode sheet and electric double layer capacitor. Example 2

40% carboxy-modified styrene-butadiene copolymer latex (BM-400B) added as a fluorine-free polymer in Example 1 (BM-400 contained in conductive adhesive lb and conductive material pellet Ia) B).) Instead of 15 parts of acrylonitrile, 80 parts of 2-ethylhexyl acrylate, 2 parts of methacrylic acid and 3 parts of ethylene glycol dimethacrylate by emulsion polymerization. Acrylate-based elastomer (glass transition temperature-40 ° C) aqueous dispersion (solids concentration)

Four In this manner, an electrode sheet for a capacitor and an electric double layer capacitor were prepared in the same manner as in Example 1 except that the temperature was 40%. It was confirmed that a long electrode sheet for a capacitor could be formed stably and good performance as a capacitor could be confirmed. Table 1 shows the results. Example 3

40% carboxy-modified styrene-butadiene copolymer latex (BM-400B) added in Example 1 as a fluorine-free polymer (included in conductive adhesive Ib and conductive material pellet Ia) BM-400 B)), but emulsify a monomer mixture consisting of 75 parts of butyl acrylate and 25 parts of methyl methacrylate in the presence of 5 parts of polyvinyl alcohol. An electrode for a capacitor was prepared in the same manner as in Example 1 except that a polymer aqueous dispersion (solid content: 30%) obtained by polymerization was used, and an aqueous solution of 10% carboxymethylcellulose (cellogen 7H) was not used. A sheet and an electric double layer capacitor were prepared, and the same measurement was performed. It was confirmed that a long capacitor electrode sheet could be formed stably, and good performance as a capacitor was confirmed. Table 1 shows the results. Comparative Example 1

83 parts of the same high-purity activated carbon powder as used in Example 1, 40% carboxy-modified styrene-butadiene copolymer latex (BM-400B) 12.5 parts, 10% carboxymethylcellulose An aqueous solution (cellogen 7H) (20 parts), conductive adhesive Ib (33.3 parts) and water were mixed using a planetary mixer to obtain an electrode slurry having a solid concentration of 40%. The slurry was applied on a current collector made of aluminum foil and dried at 150 ° C., and then an electric double layer capacitor was produced in the same operation as in Example 1 and the same measurement was performed. When the prepared slurry was transferred to a glass beaker and stirred for 1 hour, the slurry lost its fluidity. The solid content at that time was 41%. Thus, it was confirmed that continuous operation was difficult because the slurry of carbon material with a large specific surface area lost its fluidity due to a slight concentration change. Table 1 shows the results.

Five Comparative Example 2

80 parts of high-purity activated carbon powder with a specific surface area of 1,500 m ² / g and an average particle size of 10 m, 10 parts of acetylene black, 10 parts of PTFE, 1 part of ethylene glycol as a molding aid, 58.5 parts of soft water Was kneaded using a kneader. This kneaded material was extruded into a sheet using a twin-screw extruder in the same manner as in Example 1, but the sheet was intermittently torn off, and a continuous sheet was not obtained.

After drying the part where the sheet was obtained at 150 ° C for 1 hour, it was pressed using a roll press machine to produce a capacitor with an electrode density of 0.66 g / cc and an electrode thickness of 13 μμπι. An electrode sheet was obtained. Table 1 shows the results. table 1 Industrial availability

As described above, according to the present invention, it is easy to provide a manufacturing method capable of giving flexibility to an electrode and capable of mass-producing an electrode for an electric double layer capacitor having a large capacitance density and a small internal resistance. It will be. In addition, when PTFE was used as the binder, 100 parts by mass or more of the carbonaceous material required 10 parts by mass or more of the binder, but a fluorine-free polymer was used as the binder. In this case, a higher binding force can be obtained by using a relatively small amount of a binder of about 8 parts by mass. As a result, the ratio of the carbonaceous material can be increased as a whole, and as a result, the capacitance density of the electrode for the electric double layer capacitor can be further increased. Further, since the fluorine-free polymer-based material as the binder bonds between the carbonaceous materials in a fine shape, the flexibility of the electrode is not lacking as in the case of using PTFE as the binder.

6

Claims

The scope of the claims

1. A method for producing an electrode for an electric double layer capacitor, comprising a step of extruding a mixture containing a carbonaceous material and a fluorine-free polymer by screw extrusion. '

2. The production method according to claim 1, wherein the fluorine-free polymer contains an elastomer.

3. The method according to claim 2, wherein the fluorine-free polymer further contains a dispersant.

4. The production method according to any one of claims 1 to 3, wherein the fluorine-free polymer is contained in an amount of 1 to 20% by mass based on the carbonaceous material.

5. The method according to claim 1, wherein the mixture further contains a molding aid.

6. The method according to claim 5, wherein the molding aid is contained in an amount of 0.1 to 100% by mass based on the carbonaceous material.

7. The method according to any one of claims 2 to 6, wherein the elastomer is one of a gen-based elastomer and a cross-linked acrylate-based elastomer.

8. The production method according to any one of claims 1 to 7, further comprising a step of performing a press treatment in addition to the step of extruding the mixture with a screw.

9. The method according to any one of claims 1 to 8, further comprising a step of bonding the mixture extruded with the screw to a current collector with a conductive adhesive.

10. The production method according to any one of claims 1 to 9, wherein the extrusion temperature in the screw extrusion molding is 5 to 100 ° C.

(Raw material group B) (Raw material group A)

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Z60t90 contract OAV

ZZ000 / l700Zdf / X3d