JP2006339184A - Method of manufacturing composite particle for electrochemical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing composite particles for electrochemical element which is superior in roll formation, and by which the active material layer of an electrochemical element electrode can be manufactured at high formation speed. <P>SOLUTION: The composite particles for electrochemical element electrode is manufactured through the step (I) to disperse a conductive material and a binder in a solvent to obtain a slurry, step (II) to flow an electrode active material in a tank, spray the slurry thereto and obtain flow granulating particles, and step (III) to classify the flow granulating particles and remove those of less than 5 μm in diameter therefrom. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a composite particle (hereinafter simply referred to as “composite particle” in the present specification) for constituting an electrode material suitably used for an electrochemical element such as a lithium ion secondary battery or an electric double layer capacitor, particularly an electric double layer capacitor. It is related to the manufacturing method. The present invention also relates to an electrode material containing composite particles obtained by this production method, and an electrochemical element electrode using the electrode material.

  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 utilizing their characteristics. Lithium ion secondary batteries have a relatively high energy density, so they are used in the fields of mobile phones and notebook personal computers. Electric double layer capacitors can be charged and discharged rapidly, so they can be used as memory backups for personal computers, etc. It is used as a small power source. Furthermore, the electric double layer capacitor is expected to be applied as a large power source for electric vehicles. 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 devices are required to be further improved, such as lowering resistance, increasing capacity, and improving mechanical properties. There is also a need for a more productive manufacturing method.

  As a method for producing an electrochemical element electrode, a paste-like mixed material containing an electrode active material such as activated carbon or lithium metal oxide, a binder, and a solvent is prepared, and this is applied to a current collector to obtain an active material. A method of forming a layer on a current collector, removing the solvent in the active material layer by drying the active material layer laminated on the current collector, and pressing the dried active material layer together with the current collector (Wet molding method) is known. However, in this method, when a thick active material layer is applied and dried, the active material layer is liable to crack and peel off, and the drying time becomes longer, so the length of the drying furnace must be increased or the application speed must be reduced. There was a problem that productivity was lowered. As a result, it is difficult to obtain an electrode having a thick active material layer by the wet molding method, and the amount of the active material per unit volume is reduced, resulting in a problem that the resulting electrochemical device has a low capacity.

  Also known is a method (dry molding method) in which composite particles containing an electrode active material and a binder are produced, and the composite particles are formed by means such as hot pressing or roll pressing to form an active material layer. Yes. For example, Patent Document 1 discloses that a primary kneaded material obtained by mixing and kneading raw materials composed of carbon fine powder, a conductive auxiliary agent and a binder is dried and pressure-molded, and then crushed and classified to obtain an electrode material. A method for obtaining an electrode by roll pressing is disclosed. However, in this method, in order to obtain a homogeneous electrode sheet, it is necessary to use a liquid lubricant to promote the fiber formation of the binder, and it is necessary to recover the solvent in a subsequent process, resulting in a decrease in productivity. There was a problem that the manufacturing process became complicated.

  Further, in Patent Document 2, the electrode active material is caused to flow in a fluidized tank, and a raw material liquid containing a binder, a conductive auxiliary agent and a solvent is sprayed thereon, and the composite particles obtained by granulation are roll pressed. Thus, a method for obtaining an electrode sheet is disclosed. However, in this method, the electrode sheet could not be obtained continuously and stably, and the productivity was low. In addition, there is a problem that the composite particles are easily scattered as dust and the working environment is easily deteriorated.

JP 2001-230158 A JP 2005-26191 A

  The objective of this invention is providing the manufacturing method of the composite particle for electrochemical element electrodes which is excellent in roll moldability and can manufacture the active material layer of an electrochemical element electrode at a high shaping | molding speed.

  As a result of intensive studies, the inventors have made the electrode active material flow in the tank, and then sprayed the slurry in which the conductive material and the binder are dispersed in a solvent to perform flow granulation, and classify the obtained particles. Then, it was found that the above problems can be solved by using composite particles obtained by removing particles having a particle diameter of less than 5 μm, and the present invention has been completed based on this finding.

Thus, according to the first aspect of the present invention, step (I) of obtaining a slurry by dispersing a conductive material and a binder in a solvent, flowing an electrode active material in a tank, spraying the slurry thereon, There is provided a method for producing composite particles for an electrochemical element electrode, comprising the step (II) of obtaining granulated particles, and the step (III) of classifying the fluidized granulated particles to remove particles having a particle diameter of less than 5 μm. .
The slurry preferably further contains a resin soluble in the solvent.
The electrode active material is preferably activated carbon, and its weight average particle diameter is more preferably 1 to 15 μm.

According to the second aspect of the present invention, there are provided composite particles for an electrochemical element electrode obtained by the above production method.
The weight average particle diameter of the composite particle for an electrochemical element electrode is preferably 30 to 100 μm.

  According to a third aspect of the present invention, there is provided an electrochemical element electrode material comprising the above composite particle for an electrochemical element electrode.

According to a fourth aspect of the present invention, there is provided an electrochemical element electrode in which an active material layer made of the above electrochemical element electrode material is laminated on a current collector.
The active material layer is preferably formed by pressure molding, and more preferably formed by roll pressure molding.
The electrochemical element electrode is preferably for an electric double layer capacitor.

  Since the composite particles obtained by the production method of the present invention are excellent in roll moldability, it is possible to produce an active material layer of an electrochemical element electrode stably at a high molding speed and productivity. Excellent. Moreover, since the generation | occurrence | production of the dust at the time of shaping | molding can also be suppressed, it is excellent also in environmental safety.

  In the method for producing composite particles for an electrochemical element electrode of the present invention, the step (I) of obtaining a slurry by dispersing a conductive material and a binder in a solvent, the electrode active material is caused to flow in a tank, and the slurry is added thereto. Spraying to obtain fluidized granulated particles (II) and step (III) of classifying the fluidized granulated particles to remove particles having a particle diameter of less than 5 μm.

  The conductive material used in the production method of the present invention is composed of an allotrope of particulate carbon that has conductivity and does not have pores that can form an electric double layer, and improves the conductivity of the electrochemical element electrode. Is. The weight average particle diameter of the conductive material is preferably smaller than the weight 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. Specific examples include conductive carbon blacks such as furnace black, acetylene black, and ketjen black (registered trademark of Akzo Nobel Chemicals Bethloten Fennaut Shap); graphite such as natural graphite and artificial graphite. Among these, conductive carbon black is preferable, and acetylene black and furnace black are more preferable. These conductive materials can be used alone or in combination of two or more.

  The amount of the conductive material is usually 0.1 to 50 parts by weight, preferably 0.5 to 15 parts by weight, and more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the electrode active material described later. When the amount of the conductive material is within this range, the capacity of the electrochemical device using the obtained electrode can be increased and the internal resistance can be decreased.

  The binder used in the present invention is not particularly limited as long as it is a compound capable of binding the electrode active material and the conductive material. A suitable binder is a dispersion type binder having a property of being dispersed in a solvent. Examples of the dispersion-type binder include polymer compounds such as fluorine-based polymers, diene-based polymers, acrylate-based polymers, polyimides, polyamides, polyurethane-based polymers, and more preferably fluorine-based polymers and diene. And acrylate polymers. These binders can be used alone or in combination of two or more.

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

  The acrylate polymer is a polymer containing a monomer unit obtained by polymerizing an acrylic ester and / or a methacrylic ester. The proportion of monomer units obtained by polymerizing acrylic acid ester and / or methacrylic acid ester in the acrylate polymer 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, and Copolymer of ethylene and (meth) acrylic acid ester such as ethylene / ethyl methacrylate copolymer; Graft obtained by grafting a radical polymerizable monomer to the above copolymer of ethylene and (meth) acrylic acid ester Polymer; 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 (meth) acrylic acid such as an ethylene / acrylic acid copolymer or an ethylene / methacrylic acid copolymer can be used as a binder.

  Among these, from the viewpoint that an active material layer excellent in binding property to the current collector and surface smoothness can be obtained, and an electrode for an electrochemical element having a high capacity and a low internal resistance can be produced. Of these, cross-linked acrylate polymers and cross-linked acrylate polymers are preferred, and cross-linked acrylate polymers are particularly preferred.

  The binder used in the present invention is not particularly limited depending on its shape, but it has good binding properties, and can be prevented from being deteriorated due to reduction in the capacity of the prepared electrode or repeated charge / discharge, so that it is in the form of particles. Preferably there is. Examples of the particulate binder include those in which binder particles such as latex are dispersed in water, and powders obtained by drying such a dispersion.

  Further, the binder used in the present invention may be particles having a core-shell structure obtained by stepwise polymerization of a mixture of two or more monomers. A binder having a core-shell structure is obtained by first polymerizing a monomer that gives the first-stage polymer to obtain seed particles, and in the presence of the seed particles, a single quantity that gives the second-stage polymer. It is preferable to manufacture by polymerizing the body.

  The ratio between the core and the shell of the binder having the core-shell structure is not particularly limited, but the core part: shell part is usually 50:50 to 99: 1, preferably 60:40 to 99: 1 by mass ratio. Preferably it is 70: 30-99: 1. The polymer which comprises a core part and a shell part can be selected from said polymer. It is preferable that one of the core part and the shell part has a glass transition temperature of less than 0 ° C and the other has a glass transition temperature of 0 ° C or higher. Moreover, the difference of the glass transition temperature of a core part and a shell part is 20 degreeC or more normally, Preferably it is 50 degreeC or more.

  The particulate binder used in the present invention is not particularly limited depending on the number average particle diameter, but is usually 0.0001 to 100 μm, preferably 0.001 to 10 μm, more preferably 0.01 to 1 μm. It has a number average particle size. When the number average particle diameter of the binder is within this range, an excellent binding force can be imparted to the active material 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.

  The amount of the binder used in the present invention is usually 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 a range.

  The slurry used in the present invention preferably further contains a resin soluble in a solvent described below (hereinafter sometimes referred to as “dissolvable resin”). The soluble resin preferably further has an action of uniformly dispersing the electrode active material, the conductive material and the like in a solvent. The dissolving resin may or may not have a binding force. Examples of the soluble resin include cellulosic polymers such as carboxymethylcellulose, methylcellulose, ethylcellulose and hydroxypropylcellulose, and ammonium salts or alkali metal salts thereof; poly (meth) acrylates such as sodium poly (meth) acrylate; 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 soluble resins 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 use amount of the soluble resin is not particularly limited, but is usually 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, and more preferably 0.8 to 100 parts by weight of the electrode active material. It is in the range of 8 to 2 parts by weight. By using the dissolution type resin, the conductive material can be uniformly dispersed in the slurry, and the sedimentation and aggregation of the solid content can be suppressed.

  The slurry used in the present invention may further contain other additives as necessary. Examples of other additives include a surfactant. 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. 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.

  In step (I) in the production method of the present invention, the above-mentioned conductive material and binder are dispersed in a solvent, and if necessary, the above-mentioned soluble resin and other additives are further dispersed or dissolved to obtain a slurry. As the solvent used for obtaining the slurry, water is usually used, but an organic solvent can also 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 and N-methyl- Examples include 2-pyrrolidone (hereinafter sometimes referred to as NMP) and amides such as 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 fluid granulation. Further, since the dispersibility of the binder or the solubility of the soluble resin changes, the viscosity and fluidity of the slurry can be adjusted by the amount or type of the organic solvent, so that the 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. It is a quantity. When the amount of the solvent is within this range, the binder is preferably dispersed uniformly.

  A method or procedure for dispersing or dissolving the conductive material, the binder, and, if necessary, the soluble resin in a solvent is not particularly limited. For example, the conductive material, the binder, and the soluble resin are added to the solvent and mixed. After dissolving the soluble resin in the solvent, add the binder (for example, latex) dispersed in the solvent and mix, and finally add and mix the conductive material. Dissolve the conductive material in the solvent. For example, there may be mentioned a method of adding to and mixing with the dissolved resin, and adding and mixing a dispersion type binder dispersed in a solvent. 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 performed in the range of room temperature to 80 ° C. for 10 minutes to several hours.

Step (II) in the production method of the present invention is a step in which the electrode active material is flowed in a tank, the slurry is sprayed thereon, and fluidized granulation is performed.
The electrode active material used in the present invention is appropriately selected depending on the type of electrochemical element. 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. Furthermore, conductive polymers such as polyacetylene and poly-p-phenylene are listed.

  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. These electrode active materials can be used individually or in combination of 2 or more types according to the kind of electrochemical element. When the electrode active materials are used in combination, two or more types of electrode active materials having different particle diameters or particle size distributions may be used in combination.

  The shape of the electrode active material used for the electrode of the lithium ion secondary battery is preferably adjusted to spherical particles. When the shape of the particles is spherical, a higher density electrode can be formed during electrode molding. The weight average particle diameter of the electrode active material for a lithium ion secondary battery is usually 0.1 to 100 μm, preferably 1 to 50 μm, and more preferably 1 to 15 μm. When the particle diameter is within this range, a more uniform and high-density electrode can be obtained.

Further, a mixture of fine particles having a particle size of about 1 μm and relatively large particles having a particle size of 3 to 8 μm, or particles having a broad particle size distribution of 0.5 to 8 μm is preferable. It is preferable to use particles having a particle diameter of 50 μm or more by removing them by sieving. The tap density defined by ASTM D4164 of the electrode active material is not particularly limited, but 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.

As an electrode active material for an electric double layer capacitor, an allotrope of carbon is usually used. The electrode active material for an electric double layer capacitor is preferably one having a large specific surface area that can form an interface having a larger area even with the same weight. Specifically, the specific surface area of ^{30 m} 2 / g or more, preferably preferably 500~5,000m ² / g, more preferably 1,000~3,000m ² / g. 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 production method of the present invention is particularly suitable when an electrode active material having a small bulk specific gravity, such as activated carbon, in which it is difficult to increase the particle diameter during fluid granulation. These allotropes of carbon can be used singly or in combination of two or more as an electrode active material for electric double layer capacitors. When carbon allotropes are used in combination, two or more types of carbon allotropes having different particle diameters or particle size distributions may be used in combination.

In addition, nonporous carbon having microcrystalline carbon similar to graphite and having an increased interlayer distance of the microcrystalline carbon can be used as the electrode active material. Such non-porous carbon is obtained by dry-distilling graphitized charcoal with microcrystals of a multilayer graphite structure at 700 to 850 ° C., then heat-treating with caustic at 800 to 900 ° C., and if necessary with heated steam. It is obtained by removing the residual alkali component.
When a powder having a weight average particle diameter of 0.1 to 100 μm, preferably 1 to 50 μm, more preferably 1 to 15 μm is used as an electrode active material for an electric double layer capacitor, the electric double layer capacitor electrode can be made thin. It is preferable because it is easy and the capacitance can be increased.

  Examples of the method for fluid granulation in the tank include a method using a fluidized bed, a method using a deformed fluidized bed, and a method using a spouted bed. In the fluidized bed, the electrode active material is fluidized with hot air, and the slurry is sprayed from the spray or the like to perform agglomeration and granulation. The modified fluidized bed is the same as the fluidized bed, but it is a method of giving a circulating flow in the bed and discharging the granulated material that has grown relatively large by using the classification effect. In addition, the method using the spouted bed is a method in which the sprayed slurry is attached to the rough electrode active material by utilizing the characteristics of the spouted bed and granulated while being simultaneously dried. As the production method of the present invention, a fluidized bed or a deformed fluidized bed is preferred among these three methods. The temperature of the slurry to be sprayed is usually room temperature, but may be heated to room temperature or higher. The temperature of the hot air used for fluidization is usually 80 to 300 ° C, preferably 100 to 200 ° C.

  Rolling granulation may be further performed following fluid granulation. There are various types of rolling granulation, such as a rotating coarse method, a rotating cylindrical method, and a rotating truncated cone method. In the rotating texture method, the flow granulated particles supplied into the inclined rotating texture are sprayed with a binder or the slurry as necessary to produce an aggregated granulated product, and utilizing the classification effect of the rotating texture. This is a method of discharging a granulated material that has grown relatively large from the rim. A rotating cylinder system is a system in which wet granulated particles are supplied to an inclined rotating cylinder, and this is rolled in the cylinder, and if necessary, a binder or the slurry is sprayed to obtain an agglomerated granulated material. It is. The rotating truncated cone method is the same as the operating method of the rotating cylinder, but is a method in which the granulated material that has grown relatively large is discharged by utilizing the classification effect of the aggregated granulated material by the truncated cone shape. The temperature at the time of rolling granulation is not particularly limited, but is usually 80 to 300 ° C., preferably 100 to 200 ° C., in order to remove the solvent constituting the slurry. Furthermore, you may heat-process in order to harden the surface of a fluid granulated particle. The heat treatment temperature is usually 80 to 300 ° C.

  In step (III) in the production method of the present invention, the particles obtained by the fluidized granulation are classified to remove particles having a particle diameter of less than 5 μm to obtain composite particles. The classification method is not particularly limited, but dry classification methods such as gravity classification, inertia classification, and centrifugal classification; wet classification methods such as sedimentation classification, mechanical classification, and hydraulic classification; vibration sieves, in-plane motion sieves, etc. Classification methods such as a sieving classification method using a sieving net can be adopted. Among them, the dry classification method is preferable because drying after classification is unnecessary.

  By classification, particles having a particle diameter of less than 5 μm are removed, and the composite particles of the present invention are obtained. The ratio of particles having a particle diameter of less than 5 μm in the composite particles of the present invention is usually 10% by weight or less, preferably 2% by weight or less.

  The composite particles of the present invention have a weight average particle diameter in the range of usually 10 to 500 μm, more preferably 30 to 100 μm. When the weight average particle diameter is within this range, an active material layer having a uniform thickness can be easily obtained.

  The electrochemical element electrode material of the present invention comprises the composite particle for an electrochemical element electrode of the present invention. The composite particles of the present invention are used alone or in addition to other binders and other additives as required, and used as electrochemical element electrode materials. The amount of the composite particles contained in the electrochemical element electrode material is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more.

Examples of the other binder contained as needed include the same binders as those used for preparing the slurry. Since the composite particles already contain a binder, it is not necessary to add them separately when preparing the electrode material, but other binders may be added to the electrode material in order to increase the binding force between the composite particles. You may add when preparing. The amount of the other binder added when preparing the electrode material is a total of the binder in the composite particles, and is usually 0.1 to 50 parts by weight with respect to 100 parts by weight of the electrode active material. Preferably it is 0.5-20 weight part, More preferably, it is the range of 1-10 weight part.
Other additives include molding aids such as water and alcohol, and can be appropriately selected in an amount that does not impair the effects of the present invention.

  The electrochemical device electrode of the present invention (hereinafter sometimes simply referred to as “electrode”) is formed by laminating an active material layer made of the electrochemical device electrode material of the present invention on a current collector. As the current collector material used for the electrode, 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, and other alloys are usually used. Among these, it is preferable to use aluminum or an aluminum alloy in terms of conductivity and voltage resistance. In addition, when high voltage resistance is required, high-purity aluminum disclosed in JP 2001-176757 A can be suitably used. The current collector is in the form of a film or a sheet, and the thickness thereof is appropriately selected according to the purpose of use, but is usually 1 to 200 μm, preferably 5 to 100 μm, more preferably 10 to 50 μm.

  The active material layer may be formed by forming the electrochemical element electrode material into a sheet and then laminating it on the current collector. However, the electrochemical element electrode material is directly molded on the current collector to form the active material layer. It is preferable. There are dry forming methods such as pressure forming methods and wet forming methods such as coating methods as a method for forming an active material layer made of an electrochemical element electrode material. Possible dry molding methods are preferred. Examples of the dry molding method include a pressure molding method and an extrusion molding method (also referred to as paste extrusion). The pressure forming method is a method of forming an active material layer by applying pressure to the electrochemical element electrode material to perform densification by rearrangement and deformation of the electrode material. The extrusion molding method is a method in which an electrochemical element electrode material is formed into an extruded film, a sheet, or the like with an extruder, and an active material layer can be continuously formed as a long product. Among these, it is preferable to use pressure molding because it can be performed with simple equipment. As pressure molding, for example, as shown in FIG. 1, roll pressure is applied to form an active material layer by supplying an electrode material containing composite particles to a roll-type pressure molding device with a feeder such as a screw feeder. Forming method, spraying electrode material on current collector, adjusting electrode material thickness with blade etc., then forming with pressure device, filling electrode material with mold, mold There is a method of molding by pressing.

  Of these dry moldings, roll pressure molding is preferred. In this method, the active material layer may be laminated directly on the current collector by feeding the current collector to the roll simultaneously with the supply of the electrode material. In the electrode material of the present invention, particles having a particle diameter of less than 5 μm are removed, so that particles having a small particle diameter are scattered as dust during roll press molding, or particles are scattered between a pair of rolls. Deterioration of work environment and formability due to falling are suppressed. In addition, since the supply amount of the electrode material is stabilized, a variation in thickness is small, and a uniform active material layer can be obtained at a high molding speed.

  The temperature at the time of roll pressing 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. In roll press molding, the molding speed is usually 0.1 to 20 m / min, preferably 1 to 10 m / min. The pressing linear pressure between rolls is usually 0.2 to 30 kN / cm, preferably 0.5 to 10 kN / cm.

  In order to eliminate the variation in the thickness of the molded electrode and increase the density of the active material layer to increase the capacity, post-pressurization may be further performed as necessary. 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.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to these Examples. In the examples and comparative examples, “part” and “%” are based on weight unless otherwise specified. The thickness of the active material layer was measured using a contact web thickness meter RC-101 manufactured by Meisho Co., Ltd., and the electrode thickness at 20 points was measured at intervals of 0.5 mm to obtain an average value and variation.

Example 1
2 parts of conductive material (acetylene black “denka black powder” having an average particle diameter of 0.7 μm: manufactured by Denki Kagaku Kogyo Co., Ltd.), 40% of modified styrene-butadiene copolymer having a glass transition temperature of −5 ° C. as a binder 7.5 parts of an aqueous dispersion ("BM-400B": manufactured by Nippon Zeon Co., Ltd.) and 3.33 of a 4% aqueous dispersion of carboxymethyl cellulose ("DN-10L": manufactured by Daicel Chemical Industries) as a soluble resin 17.76 parts of a 1.5% aqueous dispersion of carboxymethyl cellulose (“DN-800H” manufactured by Daicel Chemical Industries, Ltd.) and 36.9 parts of ion-exchanged water and a slurry having a solid content concentration of 8% Was prepared.

100 parts of an electrode active material (activated carbon with a specific surface area of 2000 m ² / g and a weight average particle size of 5 μm) is supplied to Agromaster (manufactured by Hosokawa Micron) and fluidized with hot air at 80 ° C. It sprayed in and fluidized granulation was performed. Subsequently, the obtained particles were classified by an airflow classifier (Classeal: manufactured by Seishin Enterprise Co., Ltd.) to remove particles having a particle size of less than 5 μm, thereby obtaining composite particles having a weight average particle size of 60 μm. The obtained composite particles are supplied to a roll (roll temperature 100 ° C., press linear pressure 3.9 kN / cm) of a roll press machine (pressed rough surface heat roll: manufactured by Hirano Giken Co., Ltd.) as shown in FIG. Then, it was molded into a sheet at a molding speed of 2.5 m / min to obtain an active material layer having a thickness of 220 μm, a width of 10 cm, and a density of 0.585 g / cm ³ . The generation of dust on the rolls was slight, and the composite particles were not dropped from between the rolls. The thickness variation of the obtained active material layer was ± 5 μm.

Comparative Example 1
Molding was attempted in the same manner as in Example 1 except that the particles obtained by fluid granulation were supplied to the roll without classification, but could not be molded. Therefore, when the forming speed was lowered to 1.0 m / min, a sheet-like active material layer could be formed, but generation of dust on the roll was severe. The obtained active material layer had a thickness of 250 μm, a width of 10 cm, a density of 0.58 g / cm ³ , and a thickness variation of ± 30 μm.

Comparative Example 2
100 parts of an electrode active material, 10 parts of a conductive material, 10 parts of polytetrafluoroethylene resin as a binder, and 77 parts of ethanol were mixed using a mixer. The electrode active material and the conductive material were the same as those in Example 1. The obtained mixture was dried and then kneaded while applying a shearing force using a kneader. The kneading was performed at a pressure of 0.1 MPa and a temperature of 100 ° C. for 15 minutes.
The obtained kneaded material was pulverized with a mixer so that the particle size was 2 mm or less, and further sieved and classified. At this time, meshes of # 200 (particles having a particle size of less than 47 μm are dropped) and # 20 (particles having a particle size of less than 840 μm are dropped) are used as sieve meshes, and the particle size is 47 μm or more and less than 840 μm. A range of composite particles was obtained. Molding was attempted using the composite particles in the same manner as in Example 1, but continuous molding was difficult because the composite particles stayed on the roll without biting into the roll.

It is a figure which shows an example of the method of manufacturing an electrode.

Explanation of symbols

1: current collector 2: active material layer 3: composite particles 4: feeder 5: roll

Claims (11)

Step (I) for obtaining a slurry by dispersing a conductive material and a binder in a solvent, Step (II) for obtaining fluidized granulated particles by causing the electrode active material to flow in a tank and spraying the slurry thereon. A method for producing composite particles for an electrochemical element electrode, comprising the step (III) of classifying the fluidized granulated particles to remove particles having a particle diameter of less than 5 μm. The manufacturing method according to claim 1, wherein the slurry further contains a resin soluble in the solvent. The production method according to claim 1 or 2, wherein the electrode active material is activated carbon. The manufacturing method according to claim 1, wherein the electrode active material has a weight average particle diameter of 1 to 15 μm. Electrochemical element electrode composite particles obtained by the production method according to claim 1. The composite particle for an electrochemical element electrode according to claim 5, wherein the weight average particle diameter is 30 to 100 μm. An electrochemical element electrode material comprising the composite particle for an electrochemical element electrode according to claim 5 or 6. The electrochemical element electrode formed by laminating | stacking the active material layer which consists of an electrochemical element electrode material of Claim 7 on a collector. The electrochemical element electrode according to claim 8, wherein the active material layer is formed by pressure molding. The electrochemical element electrode according to claim 9, wherein the pressure molding is roll pressure molding. The electrochemical device electrode according to claim 9 or 10, which is used for an electric double layer capacitor.

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