WO2009107716A1

WO2009107716A1 - Method for producing electrochemical device electrode

Info

Publication number: WO2009107716A1
Application number: PCT/JP2009/053553
Authority: WO
Inventors: 敬太戸倉
Original assignee: 日本ゼオン株式会社
Priority date: 2008-02-27
Filing date: 2009-02-26
Publication date: 2009-09-03
Also published as: JPWO2009107716A1

Abstract

Disclosed is a method for efficiently mass-producing an electrochemical device electrode which provides an electrochemical device having low resistance. The method for mass-producing an electrochemical device electrode comprises a step of supplying an electrode material to at least one surface of a porous collector, and a step of forming an electrode layer on the porous collector by pressing the porous collector and the electrode material against each other with a pair of rolls. The molding rate in the electrode layer-forming step is set at not less than 10 m/min. The porous collector preferably has an aperture ratio of 10-90% by area and an aperture diameter of 0.1-10 μm.

Description

Method for producing electrochemical element electrode

The present invention relates to an electrochemical element such as an electric double layer capacitor and a lithium ion secondary battery, and particularly an electrochemical element electrode (herein referred to simply as “electrode”) that is preferably used for an electric double layer capacitor. ) Manufacturing method.

Electrochemical elements such as lithium ion secondary batteries and electric double layer capacitors that are small and light, have high energy density, and can be repeatedly charged and discharged are rapidly expanding their demands by taking advantage of their characteristics. Lithium ion secondary batteries are used in mobile phones, notebook personal computers, and other fields because of their relatively high energy density, and electric double layer capacitors can be rapidly charged and discharged. It is used as a power source. Furthermore, the electric double layer capacitor is expected to be applied as a large power source for electric vehicles. Also, with the aim of achieving both high energy density and charge / discharge speed, a hybrid capacitor that uses a Faraday reaction electrode for one of the positive electrode and the negative electrode and a non-Faraday reaction electrode for the other has been developed. In addition, redox capacitors that utilize the oxidation-reduction reaction (pseudo electric double layer capacitance) on the surface of metal oxides or conductive polymers are also attracting attention due to their large capacity. With the expansion and development of applications, these electrochemical elements are required to further improve characteristics such as low resistance, high capacity, and improved mechanical characteristics. Under such circumstances, in order to improve the performance of the electrochemical device, various improvements have been made on the method of forming the electrochemical device electrode.

Electrochemical element electrodes can be obtained, for example, by supplying an electrode material containing an electrode active material or the like onto a current collector and pressing it with a forming roll. Japanese Unexamined Patent Publication No. 2007-005747 introduces a method of manufacturing an electrochemical element electrode using a pair of press rolls or belts arranged substantially horizontally by supplying an electrode material with a quantitative feeder onto a current collector. Has been. In the example of this document, an expanded metal having a thickness of 50 μm and a porosity of 37 area% is used as a current collector, and an electrode having an electrode thickness of 480 μm is obtained by molding at a molding speed of 6 m / min. However, there has been a demand for an electrode that provides an electrochemical element having a lower resistance.

An object of the present invention is to provide a method for efficiently producing a large amount of electrochemical device electrodes that provide a low-resistance electrochemical device.

As a result of diligent investigations in view of the above problems, the present inventor has obtained a low-resistance electrochemical element by thinning an electrode layer made of an electrode material by molding at a specific molding speed using a porous current collector. It has been found that a device electrode can be obtained. Further, (roll gap of press roll) / (current collector thickness + electrode material layer thickness) is 0.01 to 1, the opening area of the porous collector is 10 to 90 area%, and the opening diameter is 0.1 to It has been found that the resistance can be further reduced by setting the thickness to 10 μm. The present inventor has completed the present invention based on these findings.

According to the present invention, a step of supplying an electrode material onto the porous current collector, and an electrode layer is formed on the porous current collector by pressing the porous current collector and the electrode material with a pair of rolls. The manufacturing method of the electrochemical element electrode which consists of the process to form and the shaping | molding speed | rate in the process of forming the electrode layer which consists of said electrode material is 10 m / min or more is provided. Moreover, according to this invention, an electrochemical element provided with the electrochemical element electrode obtained by the said manufacturing method is provided.

According to the present invention, the electrode layer can be easily thinned, and a low-resistance electrochemical device electrode can be efficiently produced in large quantities. The high-power electrochemical element electrode obtained by the production method of the present invention is suitably used for various applications such as electric double layer capacitors and secondary batteries.

The electrode material used in the present invention is used to obtain an electrochemical element electrode. Specifically, an electrode active material, a conductive material, and a binder are essential components, and if necessary, a dispersion material or Other additives and the like can be contained.

Electrode active material is a material that transfers electrons in the electrode. The electrode active material mainly includes an active material for a lithium ion secondary battery and an active material for an electric double layer capacitor.

Examples of the active material for a lithium ion secondary battery include a positive electrode and a negative electrode. As an electrode active material for a positive electrode of a lithium ion secondary battery, lithium-containing composite metal oxides such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiFeVO ₄ ; TiS ₂ , TiS ₃ , non Transition metal sulfides such as crystalline MoS ₃ ; transition metal oxides such as Cu ₂ V ₂ O ₃ , amorphous V ₂ O · P ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ ; Illustrated. Further examples include conductive polymers such as polyacetylene and poly-p-phenylene. Examples of the electrode active material for the negative electrode of the lithium ion secondary battery include carbonaceous materials such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads (MCMB), and pitch-based carbon fibers; high conductivity such as polyacene Examples include molecules.

The electrode active material used for the electrode of the lithium ion secondary battery is preferably sized into spherical particles. When the shape of the particles is spherical, a higher density electrode can be formed during electrode molding. The volume average particle size distribution is preferably a mixture of fine particles of about 1 μm and relatively large particles of 3 to 8 μm, or particles having a broad particle size distribution of 0.5 to 8 μm. Particles having a particle size of 50 μm or more are preferably used after being removed by sieving. The tap density defined by ASTM D4164 of the electrode active material is not particularly limited, and those having a positive electrode of 2 g / cm ³ or more and those of a negative electrode of 0.6 g / cm ³ or more are preferably used.

An allotrope of carbon is usually used as the electrode active material for the electric double layer capacitor. Specific examples of the allotrope of carbon include activated carbon, polyacene, carbon whisker, and graphite, and these powders or fibers can be used. A preferable electrode active material for the electric double layer capacitor is activated carbon, and specific examples include phenol-based, rayon-based, acrylic-based, pitch-based, and coconut shell-based activated carbon.

The specific surface area of the electrode active material for an electric double layer capacitor is usually 30 m ² / g or more, preferably 500 to 5,000 m ² / g, more preferably 1,000 to 3,000 m ² / g.

The volume average particle diameter of the electrode active material for the electric double layer capacitor is usually 0.1 to 100 μm, preferably 1 to 50 μm, more preferably 5 to 20 μm. When an active material having a volume average particle diameter in this range is used, the electric double layer capacitor electrode can be easily thinned and the capacitance can be increased.

These electrode active materials can be used alone or in combination of two or more depending on the type of electrochemical element.

The conductive material is made of a particulate carbon allotrope having conductivity and no pores capable of forming an electric double layer, and can improve the conductivity of the electrochemical element electrode. Specific examples of the conductive material include conductive carbon black such as furnace black, acetylene black, and ketjen black (registered trademark of Akzo Nobel Chemicals Bethloten Fennot Shap); graphite such as natural graphite and artificial graphite; Can be mentioned. Among these, conductive carbon black is preferable, and acetylene black and furnace black are more preferable.

The volume average particle diameter of the conductive material is preferably smaller than the volume average particle diameter of the electrode active material, and is usually in the range of 0.001 to 10 μm, preferably 0.05 to 5 μm, more preferably 0.01 to 1 μm. is there. When the particle size of the conductive material is within this range, high conductivity can be obtained with a smaller amount of use.

These conductive materials can be used alone or in combination of two or more. The amount of the conductive material is usually in the range of 0.1 to 50 parts by weight, preferably 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. When an electrode having an amount of the conductive material within this range is used, the capacity of the electrochemical element can be increased and the internal resistance can be decreased.

The binder is a compound that can bind an electrode active material, a conductive material, or the like. For example, polymer compounds such as fluorine-based polymers, diene-based polymers, acrylate-based polymers, polyimides, polyamides, and polyurethanes are preferable, and fluorine-based polymers, diene-based polymers, and acrylate-based polymers are preferable. It is done.

A fluoropolymer is a polymer containing a monomer unit containing a fluorine atom. The ratio of the monomer unit containing fluorine in the fluoropolymer is usually 50% by weight or more. Specific examples of the fluorine-based polymer include fluorine resins such as polytetrafluoroethylene and polyvinylidene fluoride, and polytetrafluoroethylene is preferable.

The diene polymer is a homopolymer of a conjugated diene or a copolymer obtained by polymerizing a monomer mixture containing a conjugated diene, or a hydrogenated product thereof. The proportion of the conjugated diene in the monomer mixture is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more. Specific examples of the diene polymer include conjugated diene homopolymers such as polybutadiene and polyisoprene; aromatic vinyl / conjugated diene copolymers such as carboxy-modified styrene / butadiene copolymer (SBR); Examples include vinyl cyanide / conjugated diene copolymers such as acrylonitrile / butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, and the like.

The acrylate polymer is a copolymer obtained by polymerizing a homopolymer of acrylic ester and / or methacrylic ester or a monomer mixture containing these. The ratio of acrylic acid ester and / or methacrylic acid ester in the monomer mixture is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more.

Specific examples of the acrylate polymer include 2-ethylhexyl acrylate / methacrylic acid / acrylonitrile / ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate / methacrylic acid / methacrylonitrile / diethylene glycol dimethacrylate copolymer, acrylic Crosslinking of 2-ethylhexyl acid / styrene / methacrylic acid / ethylene glycol dimethacrylate copolymer, butyl acrylate / acrylonitrile / diethylene glycol dimethacrylate copolymer, and butyl acrylate / acrylic acid / trimethylolpropane trimethacrylate copolymer Type acrylate polymer; ethylene / methyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / ethyl acrylate copolymer, A copolymer of ethylene and acrylic acid (or methacrylic acid) such as ethylene / ethyl methacrylate copolymer; a radical polymerizable monomer in the above copolymer of ethylene and acrylic acid (or methacrylic acid) And the like, and the like. In addition, as a radically polymerizable monomer used for the said graft polymer, methyl methacrylate, acrylonitrile, methacrylic acid etc. are mentioned, for example. In addition, a copolymer of ethylene and acrylic acid (or methacrylic acid) such as an ethylene / acrylic acid copolymer and an ethylene / methacrylic acid copolymer can be used as a binder.

The binder is not particularly limited depending on its shape, but has good binding properties, and can be prevented from being deteriorated due to a decrease in the capacitance of the created electrode or repeated charge / discharge, so that it is particulate. Is preferred. Examples of the particulate binder include those in which particles of a dispersion-type binder such as latex are dispersed in water, and powders obtained by drying such a dispersion.

The number average particle diameter of the particulate binder is not particularly limited, but is usually 0.0001 to 100 μm, preferably 0.001 to 10 μm, more preferably 0.01 to 1 μm. When the number average particle diameter of the binder is within this range, an excellent binding force can be imparted to the electrode layer even when a small amount of the binder is used. Here, the number average particle diameter is a number average particle diameter calculated as an arithmetic average value obtained by measuring the diameter of 100 binder particles randomly selected in a transmission electron micrograph. The shape of the particles can be either spherical or irregular.

These binders can be used alone or in combination of two or more. The amount of the binder used is usually in the range of 0.1 to 50 parts by weight, preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. .

It is preferable that the electrode material further contains a dispersing agent. The dispersing material is used by being dissolved in a slurry solvent, and further has an action of uniformly dispersing the electrode active material, the conductive material and the like in the solvent. For example, cellulosic polymers such as carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, and ammonium salts or alkali metal salts thereof; polyacrylic acid (or methacrylic acid) salts such as sodium polyacrylic acid (or methacrylic acid); polyvinyl Examples include alcohol, modified polyvinyl alcohol, polyethylene oxide; polyvinyl pyrrolidone, polycarboxylic acid, oxidized starch, phosphate starch, casein, various modified starches, chitin, and chitosan derivatives. These dispersing agents can be used alone or in combination of two or more. Among these, a cellulose polymer is preferable, and carboxymethyl cellulose or an ammonium salt or an alkali metal salt thereof is particularly preferable.

The amount of the dispersing agent used is not particularly limited, but is usually 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, more preferably 0.8 parts per 100 parts by weight of the electrode active material. It is in the range of up to 2 parts by weight. By using the dispersing material, it is possible to suppress sedimentation and aggregation of the solid content in the slurry. Moreover, since the clogging of the atomizer at the time of spray drying can be prevented, spray drying can be performed stably and continuously. Further, in order to increase the surface average porosity of the composite particle surface described later, specifically, in order to increase the surface average porosity to 15% or more, it is preferable to use a dispersion material having a weight average molecular weight of 300,000 or more. .

Other additives include, for example, surfactants. Examples of the surfactant include amphoteric surfactants such as anionic, cationic, nonionic, and nonionic anions. Among them, anionic or nonionic surfactants that are easily thermally decomposed are preferable.

Surfactants can be used alone or in combination of two or more. The amount of the surfactant is not particularly limited, but is 0 to 50 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the electrode active material. It is a range.

The electrode material used in the present invention comprises the above electrode active material, conductive material, and binder as essential components, and contains a dispersing agent and other additives as necessary. A suitably used electrode material is in the form of particles containing the above components in a composite (hereinafter sometimes referred to as composite particles). It is preferable that the composite particles usually include at least an electrode active material, a conductive material, and a binder, and the electrode active material and the conductive material are bound by a binder.

The production method of the composite particles is not particularly limited, and is a spray drying granulation method, a rolling bed granulation method, a compression granulation method, a stirring granulation method, an extrusion granulation method, a crushing granulation method, a fluidized bed granulation method. It can be produced by a known granulation method such as a granulation method, a fluidized bed multifunctional granulation method, or a melt granulation method. Among these, the spray-drying granulation method is preferable because composite particles in which the binder and the conductive auxiliary agent are unevenly distributed near the surface can be easily obtained. When composite particles obtained by the spray drying granulation method are used, the electrode of the present invention can be obtained with high productivity. Moreover, the internal resistance of the electrochemical element obtained using this electrode can be reduced more.

The composite particles suitably used in the present invention are preferably particles obtained by spray drying a slurry containing an electrode active material, a conductive material and a binder. The composite particles are particles obtained by spray-drying the slurry containing the electrode active material, the conductive material and the binder, so that the electrochemical device electrode of the present invention can be obtained with high productivity, In addition, the internal resistance of the electrode can be further reduced.

The slurry can be obtained by dispersing or dissolving optional components such as a dispersing agent and other additives in addition to the essential components of the electrode active material, the conductive material, and the binder.

As the solvent used in the slurry for obtaining composite particles, water is usually used, but an organic solvent may be used. Examples of the organic solvent include alkyl alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol; alkyl ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane and diglyme; diethylformamide, dimethylacetamide, N-methyl- Examples include amides such as 2-pyrrolidone and dimethylimidazolidinone; sulfur solvents such as dimethyl sulfoxide and sulfolane; and alcohols are preferable. When an organic solvent having a lower boiling point than water is used in combination, the drying rate can be increased during granulation by the spray drying method. In addition, since the dispersibility of the dispersion-type binder or the solubility of the soluble resin varies depending on the type of solvent, the viscosity and fluidity of the slurry are adjusted by selecting the amount or type of organic solvent, and spray drying production Efficiency can be improved.

The amount of the solvent used when preparing the slurry is such that the solid content concentration of the slurry is usually in the range of 1 to 50% by weight, preferably 5 to 50% by weight, more preferably 10 to 30% by weight. Amount.

A method or a procedure for dispersing or dissolving the electrode active material, the conductive material, the binder, and the optional component in the solvent is not particularly limited. For example, the electrode active material, the conductive material, the binder, and the other components in the solvent A method of adding and mixing components; a method of adding and mixing a binder (for example, latex) dispersed in a solvent; and a method of adding and mixing an electrode active material, a conductive material and the optional component; an electrode active material; Examples include a method in which a conductive material and the above-mentioned optional component dispersed in a solvent are added to a binder and mixed. Examples of the mixing means include mixing equipment such as a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, and a planetary mixer. Mixing is usually carried out in the range of room temperature to 80 ° C. for 10 minutes to several hours.

The spray drying method is a method in which slurry is sprayed and dried in hot air. A typical example of the apparatus used for the spray drying method is an atomizer. There are two types of atomizers: a rotating disk method and a pressure method. The rotating disk system is a system in which slurry is introduced almost at the center of a disk that rotates at high speed, and the slurry is released from the disk by the centrifugal force of the disk, and in that case, the slurry is dried in the form of a mist.

The rotational speed of the disk depends on the size of the disk, but is usually 5,000 to 30,000 rpm, preferably 15,000 to 30,000 rpm. On the other hand, the pressurization method is a method in which the slurry is pressurized and sprayed from a nozzle to be dried.

The temperature of the slurry to be sprayed is usually room temperature, but it may be heated to room temperature or higher. The hot air temperature at the time of spray drying is usually 80 to 250 ° C., preferably 100 to 200 ° C. In the spray drying method, the method of blowing hot air is not particularly limited. Examples include a contact method, and a method in which sprayed droplets first flow in parallel with hot air and then drop by gravity to make countercurrent contact. Furthermore, heat treatment is performed to cure the surface of the composite particles. The heat treatment temperature is usually 80 to 300 ° C.

The shape of the composite particles suitably used in the present invention is preferably substantially spherical. That is, when the short axis diameter of the composite particles is Ls, the long axis diameter is Ll, La = (Ls + Ll) / 2, and the value of (1− (Ll−Ls) / La) × 100 is sphericity (%). The sphericity is preferably 80% or more, more preferably 90% or more. Here, the minor axis diameter Ls and the major axis diameter Ll are values measured from a transmission electron micrograph image.

The volume average particle diameter of the composite particles suitably used in the present invention is usually in the range of 10 to 100 μm, preferably 20 to 80 μm, more preferably 30 to 60 μm. The volume average particle diameter can be measured using a laser diffraction particle size distribution measuring apparatus.

The composite particles suitably used in the present invention have a surface average porosity of preferably 15% or more, more preferably 20% or more, and further preferably 20% or more and 40% or less. Here, the “surface average porosity” is an apparent appearance of voids of 0.1 μm ² or more on the surface of the composite particle for 5 particles or more (each with different fields of view) and 10 particles or more per composite particle. This is a value obtained as an average value of the ratio (%) of the apparent surface area of the void to the entire visual field area (hereinafter, sometimes referred to as “void ratio”). When the surface average porosity of the composite particles is less than 15%, the diffusion resistance of the electrolyte ions in the composite particles increases, and the resistance of the electrode obtained by using this increases. In order to increase the surface average porosity of the composite particles suitably used in the present invention to 15% or more, it can be achieved by using a dispersion material having a weight average molecular weight of 300,000 or more when producing the composite particles. .

Specifically, the surface average porosity is obtained by taking an electron micrograph of the composite particles suitably used in the present invention, observing 5 fields or more per arbitrarily selected particle, and having an area of 0.1 μm ² or more. The apparent surface area of the continuous voids is measured, the same measurement is performed for 10 particles or more, and the average value of the obtained void ratios is calculated. The apparent surface area of the void is an area corresponding to the surface area of the opening of the void observed on the electron micrograph, and is not an actual area taking into consideration the area in the pores of the void. When individual composite particles are seen, composite particles having a porosity of less than 15% may be included, but since the porosity includes a large number of particles having a porosity of 15% or more, the overall surface average porosity is As high as

The composite particles suitable for the present invention usually have a particle size displacement rate of 5 to 70%, preferably 20 to 50% when compressed to a maximum load of 9.8 mN at a load speed of 0.9 mN / sec using a micro compression tester. is there. The particle size displacement rate is a ratio (= ΔD / D ₀ × 100) of the amount of particle size reduction (ΔD = D ₀ −D ₁ ) due to compression to the particle size D ₀ before compression of the composite particles. Incidentally, D ₁ is a value that varies according to the load amount of the particle diameter when being under a load.

In addition, the composite particles suitably used in the present invention preferably have a change amount of particle size displacement rate per unit second when compressed to a maximum load of 9.8 mN at a load speed of 0.9 mN / sec by a micro compression tester. It is 25% or less, more preferably 10% or less, and particularly preferably 7% or less. The change amount of the particle size displacement rate per unit second is the change amount per unit second of the particle size change rate when the load is increased at a load speed of 0.9 mN / second. The particle size displacement rate when compressed to a maximum load of 9.8 mN measured by a micro-compression tester is a numerical value necessary to show the shape maintenance force of the composite particles. If the particle size displacement rate is too small, the composite particles are hardly deformed even by pressurization, so that the contact area between the particles is small and the conductivity is not increased. On the other hand, when the particle size displacement rate is too large, the composite particles are crushed, the network formed by the conductive material and the electrode active material formed in the composite particles is broken, and the conductivity is lowered. Further, the change amount of the particle size displacement rate per unit second is an index for determining the presence or absence of crushing. When crushing occurs, the particle size decreases rapidly, so the amount of change in particle size displacement rate per unit second exceeds 25%. By crushing, the network formed by the conductive material and the electrode active material formed in the composite particles is broken, and the conductivity is lowered. Composite particles having a particle size displacement rate of 5 to 70% when compressed to a maximum load of 9.8 mN have moderate softness, so that the contact area between the particles is large. And since it does not crush, the network of an electroconductive material and an electrode active material is maintained. These composite particles can be used alone or in combination of two or more.

The porous current collector used in the present invention is an electrode substrate having a current collecting function having front and back through holes. As the material, for example, metal, carbon, conductive polymer, and the like can be used, and metal is preferably used. As the current collector metal, aluminum, platinum, nickel, tantalum, titanium, stainless steel, copper, other alloys and the like are usually used. Among these, it is preferable to use aluminum or an aluminum alloy in terms of conductivity and voltage resistance. Examples of the shape of the current collector holes include a quadrangle, a rhombus, a turtle shell, a hexagon, a circle, a star, and a cross. Specific examples of the sheet-like current collector having pores include expanded metal obtained by expanding a flat plate into a rhombus or turtle shell-shaped net, punching metal obtained by perforating a flat plate, or a metal wire or a metal band plain weave or Examples thereof include a wire net obtained by twilling or fitting a crimp metal wire.

The aperture ratio of the porous current collector used in the present invention is not particularly specified, but is preferably 10 to 90 area%, more preferably 40 to 60 area%, because the strength and molding speed can be increased. The opening diameter is not particularly specified, but is usually 0.01 to 10 μm, more preferably 1 to 5 μm because the molding speed can be increased. The opening diameter here is a diameter of a circumscribed circle of the opening. The diameter of the circumscribed circle is obtained by observing the surface of the current collector with a laser microscope or a tool microscope, fitting the circumscribed circle to the opening, and averaging the results. The thickness of the porous current collector is appropriately selected according to the purpose of use, but is preferably 10 to 100 μm, more preferably 50 to 100 μm from the viewpoint of achieving both high strength and low resistance.

Further, the current collector may be one obtained by applying a conductive adhesive on the surface thereof. The conductive adhesive is obtained by dispersing a conductive auxiliary powder, a binder, and a dispersant added as necessary in water or an organic solvent. Examples of the conductive assistant for the conductive adhesive include silver, nickel, gold, graphite, acetylene black, and ketjen black, and graphite and acetylene black are preferable. As the binder of the conductive adhesive, any of those exemplified as the binder used in the electrode layer of the electrode of the present invention can be used. Moreover, water glass, an epoxy resin, a polyamideimide resin, a urethane resin, etc. can also be used, and each can be used individually or in combination of 2 or more types. The binder of the conductive adhesive is preferably an acrylate polymer, an ammonium salt or alkali metal salt of carboxymethyl cellulose, water glass, or polyamideimide resin. Moreover, as a dispersing agent of a conductive adhesive, a dispersing agent or a surfactant that may be used for the electrode layer of the electrode of the present invention can be used.

In the present invention, the electrode material is supplied to at least one surface of the porous current collector. The feeder used in the step of supplying the electrode material is not particularly limited, but is preferably a quantitative feeder capable of supplying composite particles quantitatively. Here, being able to supply quantitatively means that the electrode material is continuously supplied using such a feeder, the supply amount is measured a plurality of times at regular intervals, and the average value m of the measured values and the standard deviation σm are obtained. It means that the CV value (= σm / m × 100) is 4 or less. The quantitative feeder used in the present invention preferably has a CV value of 2 or less. Specific examples of the quantitative feeder include a gravity feeder such as a table feeder and a rotary feeder, and a mechanical force feeder such as a screw feeder and a belt feeder. Of these, the rotary feeder is preferred.

Next, the porous current collector and the supplied electrode material are pressurized with a pair of rolls to form an electrode layer on the porous current collector. In this step, the electrode material heated as necessary is formed into a sheet-like electrode layer by a pair of rolls. The temperature of the electrode material supplied is preferably 40 to 160 ° C., more preferably 70 to 140 ° C. When an electrode material in this temperature range is used, there is no slip of the electrode material on the surface of the press roll, and the electrode material is continuously and uniformly supplied to the press roll. An electrochemical element electrode sheet with small variations can be obtained.

The molding temperature is usually 0 to 200 ° C., preferably higher than the melting point or glass transition temperature of the binder, and more preferably 20 ° C. higher than the melting point or glass transition temperature. When a roll is used, the forming speed is usually 10 m / min or more, and it is preferably 20 to 200 m / min, and more preferably 30 to 80 m / min, because the moldability is high and thinning is easy. The forming speed here means the rotational speed of the roll. The press linear pressure between the press rolls is not particularly specified, but is preferably 0.2 to 30 kN / cm, more preferably 0.5 to 10 kN / cm because the electrode strength can be increased.

In the production method of the present invention, the arrangement of the pair of rolls is not particularly limited, but is preferably arranged substantially horizontally or substantially vertically. When arranged substantially horizontally, the porous current collector is continuously supplied between a pair of rolls, and an electrode material is supplied to at least one of the rolls, so that the gap between the porous current collector and the rolls is increased. An electrode material is supplied to the electrode layer, and an electrode layer can be formed by pressurization. In the case of disposing substantially vertically, the porous current collector is conveyed in the horizontal direction, an electrode material is supplied onto the current collector, and an electrode material layer is formed. After the supplied electrode material layer is made uniform with a blade or the like as necessary, the current collector is supplied between a pair of rolls, and the electrode layer can be formed by pressurization. In this case, the thickness of the electrode material layer supplied between the pair of rolls is a value represented by (roll gap between the pair of rolls) / (current collector thickness + electrode material layer thickness). From the viewpoint of excellent properties, it is preferably 0.01 to 1, more preferably 0.05 to 0.75, and particularly preferably 0.1 to 0.5.

¡Post-pressurization may be further performed as necessary in order to eliminate variations in the thickness of the molded body and increase the density and increase the capacity. The post-pressing method is generally a press process using a roll. In the roll press process, two cylindrical rolls are arranged in parallel at a narrow interval in the vertical direction, and each is rotated in the opposite direction. The temperature of the roll may be adjusted by heating or cooling.

The electrochemical element of the present invention has an electrode for an electrochemical element obtained by the production method of the present invention. An electrochemical element can be manufactured according to a conventional method using components such as an electrode obtained by the manufacturing method of the present invention, an electrolytic solution, and a separator. Specifically, for example, the electrode is cut into an appropriate size, and then the electrodes are overlapped through a separator, and then wound, folded, laminated, etc., and then put into a container, and an electrolyte is injected into the container. Can be manufactured by sealing.

The electrolytic solution is usually composed of an electrolyte and a solvent. The electrolyte may be cationic or anionic. As the cationic electrolyte, (1) imidazolium, (2) quaternary ammonium, (3) quaternary phosphonium, (4) lithium and the like as shown below can be used.
(1) Imidazolium 1,3-Dimethylimidazolium, 1-Ethyl-3-methylimidazolium, 1,3-Diethylimidazolium, 1,2,3-Trimethylimidazolium, 1,2,3,4-Tetra Methylimidazolium, 1,3,4-trimethyl-ethylimidazolium, 1,3-dimethyl-2,4-diethylimidazolium, 1,2-dimethyl-3,4-diethylimidazolium, 1-methyl-2, 3,4-triethylmethylimidazolium, 1,2,3,4-tetraethylimidazolium, 1,3-dimethyl-2-ethylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1,2,3 -Triethylimidazolium, etc. (2) Quaternary ammonium tetramethylammonium, ethyltrimethylammonium, diethyl (3) Quaternary phosphonium Tetramethylphosphonium, tetraethylphosphonium, tetrabutylphosphonium, methyltriethylphosphonium, methyltributylphosphonium, dimethyldiethylphosphonium, etc. ( 4) Lithium

As the anionic _{_{_{_{electrolyte, PF 6 -, BF 4 -}}}} , AsF 6 -, SbF 6 -, N (RfSO 3) 2 -, C (RfSO 3) 3 -, RfSO 3 - (Rf respectively 1 -C To 12 fluoroalkyl groups), F—, ClO ₄ —, AlCl ₄ —, AlF ₄ — and the like. These electrolytes can be used alone or in combination of two or more.

The solvent of the electrolytic solution is not particularly limited as long as it is generally used as a solvent for the electrolytic solution. Specific examples include carbonates such as propylene carboat, ethylene carbonate, and butylene carbonate; lactones such as γ-butyrolactone; sulfolanes; nitriles such as acetonitrile. These can be used alone or as a mixed solvent of two or more. Of these, carbonates are preferred.

The electrochemical element of the present invention is obtained by impregnating the above element with an electrolytic solution. Specifically, the capacitor element can be manufactured by winding, stacking, or folding into a container as necessary, and pouring the electrolyte into the container and sealing it. Further, a device in which an element is previously impregnated with an electrolytic solution may be stored in a container. Any known container such as a coin shape, a cylindrical shape, or a square shape can be used as the container.

As the separator, for example, a microporous film made of polyolefin such as polyethylene or polypropylene, or a nonwoven fabric, a porous film mainly made of pulp called electrolytic capacitor paper can be used. Moreover, it can replace with a separator and a solid electrolyte can also be used.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In the examples and comparative examples, “part” and “%” are based on weight unless otherwise specified.

Each characteristic in an Example and a comparative example was measured in accordance with the following method.
(Measurement of electrode layer thickness)
The electrode layer thickness was measured using an eddy current displacement sensor (sensor head part EX-110V, amplifier unit part EX-V02: manufactured by Keyence Corporation) after forming electrode layers on both sides of the current collector. The thickness of each electrode layer was measured at intervals of 10 cm in the longitudinal direction and at intervals of 2 cm in the width direction, and the average value thereof was taken as the thickness of the electrode layer.

(Measurement of internal resistance)
The electrochemical capacitor was charged at a constant current of 15 mA. When a predetermined charging voltage was reached, the voltage was maintained to be constant voltage charging, and charging was completed when constant voltage charging was performed for 5 minutes. Next, immediately after the end of charging, discharging was performed at a constant current of 15 mA until reaching 0V. This charge / discharge operation was performed for 3 cycles, and the voltage was calculated from the relationship of R = ΔV / I from the voltage 0.1 seconds after the third cycle discharge.

(Surface average porosity of composite particles)
The surface average porosity of the composite particles produced in the following examples and comparative examples was determined by the following method. First, an electron micrograph of the composite particles was measured at a magnification of 2000 times, and arbitrary particles were read into image analysis software (analySIS: Soft Imaging System) as black and white 256-gradation image data within a field of view of 20 μm ² . The contrast is optimized so that the brightest part of the image is 255 and the darkest part is 0. Next, the threshold value is set to 77, binarization processing is performed, and the ratio of voids having an area of 0.1 μm ² or more on the composite particle surface is obtained from the obtained binarized image. For the same particle, the same measurement is performed 5 times in any different field of view, and the same measurement is performed for 10 particles, and the average is the surface average porosity of the composite particles.

Example 1
100 parts of an electrode active material (activated carbon with a specific surface area of 2000 m ² / g and a volume average particle size of 5 μm), 5 parts of a conductive material (acetylene black “Denka Black Powder” manufactured by Denki Kagaku Kogyo Co., Ltd.), a dispersion-type binder (40% aqueous dispersion of a cross-linked acrylate polymer having a number average particle size of 0.15 μm and a glass transition temperature of −40 ° C .: “AD211”; manufactured by Nippon Zeon Co., Ltd.) 7.5 parts, carboxymethylcellulose as a dispersing agent Of 1.5% aqueous solution (“DN-800H”: manufactured by Daicel Chemical Industries, Ltd., weight average molecular weight of less than 300,000) and 231.8 parts of ion-exchanged water K. The mixture was stirred and mixed with a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to obtain a slurry having a solid content concentration of 25%. Next, the slurry was spray-dried with hot air at 150 ° C. using a spray dryer (with a pin-type atomizer manufactured by Okawahara Kako Co., Ltd.), and spherical composite particles having a surface average porosity of 11% and a volume average particle size of 60 μm were obtained. Obtained.

Using a fixed feeder (Nikka Co., Ltd., Nikka Spray KV) at a feed rate of 70 g / min, a roll for a press (roll) in a roll press machine (cut-off rough surface heat roll; manufactured by Hirano Giken Co., Ltd.) Temperature 120 ° C., press linear pressure 4 kN / cm, (roll gap) / (electrode layer thickness + electrode material layer thickness) = 1). Between the rolls for pressing, an expanded metal having a thickness of 50 μm, an opening area of 37 area%, and an opening diameter of 1,000 μm is inserted as a porous current collector, and the composite particles supplied from the quantitative feeder are adhered to both sides of the expanded metal. Then, an electrochemical device electrode having an electrode layer with an average single-side thickness of 300 μm and an average single-side density of 0.50 g / cm ³ was obtained.

The electrode produced above was cut out so that the current collector sheet portion on which the electrode layer was not formed remained 2 cm long × 2 cm wide, and the portion where the electrode layer was formed was 5 cm long × 5 cm wide. (The collector sheet portion where the electrode layer is not formed is formed so as to extend one side of the 5 cm × 5 cm square where the electrode layer is formed.) 10 sets of positive electrodes and 11 sets of negative electrodes thus cut out were prepared, and the uncoated portions were ultrasonically welded. Furthermore, the current collector sheet portion in which the electrode layer is formed by laminating and welding the tab material having a length of 7 cm, a width of 1 cm and a thickness of 0.01 cm made of aluminum for the positive electrode and nickel for the negative electrode is measured by ultrasonic welding. An electrode was prepared. The measurement electrode is vacuum-dried at 200 ° C. for 24 hours. Using a cellulose / rayon mixed non-woven fabric with a thickness of 35 μm as a separator, the terminal welds of the positive electrode current collector and the negative electrode current collector are arranged on opposite sides, and the positive electrode and the negative electrode are alternated and laminated. All of the outermost electrodes were laminated so that all of them were negative electrodes. Separators were placed on the top and bottom, and four sides were taped.

After covering the laminated electrode with an exterior laminate film and fusing three sides, a solution of propylene carbonate dissolved in tetraethylammonium borofluoride at a concentration of 1.4 mol / L was vacuum impregnated as an electrolyte, and then the remaining side was melted. A film type capacitor (electrochemical capacitor) was produced. The internal resistance of the obtained film type capacitor was measured. The results are shown in Table 1.

Example 2
In Example 1, a punching metal having an opening area of 37 area% and an opening diameter of 0.1 μm was used as the current collector, and an electrochemical element electrode was obtained in the same manner as in Example 1 except that the molding speed was 40 m / min. It was. The results are shown in Table 1.

Example 3
In Example 2, an electrochemical element electrode was obtained in the same manner as in Example 2 except that a punching metal having an opening area of 60 area% and an opening diameter of 0.1 μm was used as the current collector. The results are shown in Table 1.

Example 4
An electrochemical element electrode was obtained in the same manner as in Example 3 except that the molding speed in Example 3 was changed to 60 m / min. The results are shown in Table 1.

Example 5
In Example 4, an electrochemical device electrode was obtained in the same manner as in Example 4 except that a punching metal having an opening area of 60 area% and an opening diameter of 3 μm was used as the current collector. The results are shown in Table 1.

Example 6
An electrochemical device electrode was obtained in the same manner as in Example 5 except that (roll gap) / (electrode layer thickness + electrode material layer thickness) = 0.3 in Example 5. The results are shown in Table 1.

Example 7
In Example 1, 1% of carboxymethylcellulose was used instead of 1.5% aqueous solution of carboxymethylcellulose (“DN-800H”: manufactured by Daicel Chemical Industries, Ltd.) as a dispersant used in preparing composite particles. Spherical composite particles were obtained in the same manner as in Example 1, except that an aqueous solution (“BSH-12” (Daiichi Kogyo Seiyaku Co., Ltd., weight average molecular weight: 330,000 to 380,000)) was used. The particles had a volume average particle size of 60 μm and a surface porosity of 25%, and in Example 6, an electrochemical device electrode was prepared in the same manner as in Example 6 except that the composite particles were used as the electrode material. The results are shown in Table 1.

Comparative Example 1
An electrochemical element electrode was obtained in the same manner as in Example 1 except that the molding speed was 6 m / min in Example 1. The results are shown in Table 1.

Comparative Example 2
An electrochemical element electrode was obtained in the same manner as in Example 4 except that the molding speed was 6 m / min in Example 7. The results are shown in Table 1.

From the above examples, according to the production method of the present invention, it is possible to produce an electrochemical element electrode having a thin electrode layer thickness with high productivity, and when the obtained electrochemical element electrode is used, the internal resistance is reduced. It can be seen that a low electrochemical element can be obtained.

The embodiments and examples described above are described for facilitating understanding of the present invention, and are not described for limiting the present invention. Accordingly, each element disclosed in the above embodiment or example is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

The present invention relates to the subject matter contained in Japanese Patent Application No. 2008-46495 filed on Feb. 27, 2008, the entire disclosure of which is expressly incorporated herein by reference.

Claims

A step of supplying an electrode material to at least one surface of the porous current collector, and the porous current collector and the electrode material are pressurized with a pair of rolls and made of the electrode material on the porous current collector Comprising the step of forming an electrode layer,
The manufacturing method of the electrochemical element electrode whose shaping | molding speed in the process of forming the said electrode layer is 10 m / min or more.
The method for producing an electrochemical element electrode according to claim 1, wherein (the roll gap between the pair of rolls) / (thickness of the porous collector + thickness of the electrode material) is 0.01 to 1.
The electricity according to claim 1 or 2, wherein the electrode material contains at least an electrode active material, a conductive material, and a binder, and the electrode active material and the conductive material are composite particles formed by binding with a binder. A method for producing a chemical element electrode.
4. The method for producing an electrochemical element electrode according to claim 3, wherein the composite particles are particles obtained by spray drying a slurry containing an electrode active material, a conductive material and a binder.
The method for producing an electrochemical element electrode according to claim 3, wherein the composite particles have a surface average porosity of 15% or more.
The method for producing an electrochemical element electrode according to claim 1 or 2, wherein an opening area of the porous current collector is 10 to 90 area%.
The method for producing an electrochemical element electrode according to any one of claims 1 to 3, wherein an opening diameter of the porous current collector is 0.1 to 10 µm.
An electrochemical element comprising an electrochemical element electrode obtained by the production method according to any one of claims 1 to 7.