WO2007032374A1

WO2007032374A1 - Composite particle for electrochemical device electrode, method for producing same, electrochemical device electrode material, and electrochemical device electrode

Info

Publication number: WO2007032374A1
Application number: PCT/JP2006/318132
Authority: WO
Inventors: Yoshio Fukumine
Original assignee: Zeon Corporation
Priority date: 2005-09-16
Filing date: 2006-09-13
Publication date: 2007-03-22
Also published as: JPWO2007032374A1; JP4985404B2

Abstract

Composite particles for electrochemical device electrodes containing an electrode active material, a conductive material and a binder, while having a volume average particle diameter of 1-500 μm. The composite particles have a tensile bond strength of not less than 8,000 N/m2 when compressed for 5 seconds at 4.0 MPa at 70˚C, a tensile bond strength of not more than 200 N/m2 when compressed for 60 seconds at 0.1 MPa at 25˚C, and a tensile bond strength of not more than 3,000 N/m2 when compressed for 60 seconds at 0.5 MPa at 25˚C.

Description

Specification

COMPOSITE PARTICLE FOR ELECTROCHEMICAL ELEMENT ELECTRODE, METHOD FOR PRODUCING THE SAME, ELECTROCHEMICAL ELEMENT ELECTRODE MATERIAL, AND ELECTROCHEMICAL ELEMENT ELECTRODE

Technical field

[0001] The present invention relates to an electrochemical element electrode composite particle (this book) for constituting an electrode material suitably used for an electrochemical element such as a lithium ion secondary battery and an electric double layer capacitor, particularly an electric double layer capacitor. In the specification, it may be simply referred to as “composite particles.”) And a method for producing the same. The present invention also relates to an electrochemical element electrode material containing the composite particles, and an electrochemical element electrode using the electrode material.

Background art

[0002] Electrochemical elements such as lithium ion secondary batteries and electric double layer capacitors are rapidly growing in demand due to their small size, light weight, high energy density, and the ability to repeatedly charge and discharge. . Lithium ion secondary batteries are used in fields such as mobile phones and notebook personal computers because of their relatively high energy density. Since electric double layer capacitors can be charged and discharged rapidly, they are used as a memory backup compact power source for personal computers and the like. Furthermore, the electric double layer capacitor is expected to be used as a large power source for electric vehicles. Redox capacitors that utilize the oxidation-reduction reaction (pseudo electric double layer capacitance) on the surface of metal oxides and 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, improving mechanical properties and productivity. Under such circumstances, there is a demand for a more productive manufacturing method for electrochemical element electrodes, and there are various manufacturing methods capable of high-speed molding and various electrochemical element electrode materials suitable for the manufacturing method. Improvements are being made.

[0003] Electrochemical element electrodes are generally formed by laminating an active material layer formed by binding an electrode active material such as activated carbon or lithium metal oxide and a conductive material on a current collector. It is. In order to form this active material layer, Japanese Patent Application Publication No. 2005-78943 discloses a composite particle in which a particulate electrode active material and a particulate conductive additive are adhered to each other with a binder. A method is described in which the child is obtained by pressure molding. The composite particles used in Japanese Patent Application Publication No. 2005-78943 have a structure in which the particulate electrode active material and the particulate conductive auxiliary are uniformly dispersed in the composite particles. However, when this composite particle is used, it is difficult to stably and continuously form an active material layer when the molding speed is increased in the press molding.

Disclosure of the invention

[0004] An object of the present invention is to provide an electrochemical element electrode that has good fluidity at room temperature, excellent transportability and quantitative supply, and has a uniform active material layer especially for mouth pressure molding. High! Provided are composite particles for an electrochemical element electrode that can be obtained at a molding speed, a method for producing the same, an electrochemical element electrode material comprising the composite particle, and an electrochemical element electrode formed from the electrode material It is to be.

[0005] The present inventor pays attention to the powder characteristics of the electrode material, and as a result, the tensile bond strength when the electrode material is compressed greatly affects the moldability, fluidity and storage characteristics of the electrode material. I found. In contrast, conventional electrode materials have low tensile bond strength at high temperatures and lack of binding strength, so the moldability was low. At 70 ° C, 4. Tensile bond when compressed at OMPa for 5 seconds. It has been found that when an electrode material having a certain strength or more is used, the moldability is excellent. Furthermore, it has been found that an electrode material having a tensile bond strength of less than a certain value when compressed at O. lMPa and 0.5 MPa for 60 seconds at 25 ° C is excellent in fluidity and storage characteristics. It came to complete.

[0006] According to a first aspect of the present invention, the composite element for an electrochemical element electrode comprising an electrode active material, a conductive material, and a binder and having a volume average particle diameter of 1 to 500 m. Thus, a composite particle for an electrochemical device electrode having a tensile bond strength of 8, OOONZm ² or more when compressed at OMPa for 5 seconds at 70 ° C is provided.

[0007] The composite particle for an electrochemical element electrode preferably has a tensile adhesion strength of 00 NZm ² or less when compressed with O.lMPa at 25 ° C for 60 seconds. The composite particle for an electrochemical element electrode preferably has a bow tension strength of 3, OOONZm ² or less when compressed at 0.5 MPa for 60 seconds at 25 ° C.

[0008] According to a second aspect of the present invention, an electrode active material, a conductive material, and a binder are dispersed in a solvent. Thus, there is provided a method for producing the composite particle for an electrochemical element electrode, comprising a step of obtaining a slurry and a step of spray-drying the slurry and granulating the slurry.

[0009] According to a third aspect of the present invention, there is provided an electrochemical element electrode material comprising the 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 formed on the electrochemical element electrode material is laminated on a current collector.

[0011] The pressure forming, in which the method of laminating the active material layer on the current collector is preferably pressure forming, is more preferably roll pressure forming.

[0012] The electrochemical element electrode is preferably for an electric double layer capacitor.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail by way of embodiments. However, the embodiments are merely examples.

The embodiments described below do not limit the present invention.

[0014] The composite particle for an electrochemical element electrode according to an embodiment of the present invention contains an electrode active material, a conductive material, and a binder, and has a volume average particle diameter of 1 to 500 m. At 70 ° C, the tensile bond strength when compressed at OMPa for 5 seconds

8, OOONZm ² or more.

[0015] The electrode active material constituting the composite particle according to the embodiment of the present invention is appropriately selected depending on the type of the electrochemical element. Electrode active materials for the positive electrode of lithium ion secondary batteries include lithium-containing materials such as LiCoO, LiNiO, LiMnO, LiMn O, LiFePO, and LiFeVO.

2 2 2 2 4 4 4

Complex metal oxides; transition metal sulfides such as TiS, TiS, and amorphous MoS; Cu V O,

2 3 3 2 2 3 Amorphous V O 'PO, transition metal oxides such as ΜοΟ, V Ο, V ；; The

2 2 5 3 2 5 6 13

In addition, conductive polymers such as polyacetylene and poly (rho) -phenylene are listed.

[0016] Examples of the electrode active material for the negative electrode of the lithium ion secondary battery include carbonaceous materials such as amorphous force bonbon, graphite, natural graphite, mesocarbon microbeads (MCMB), and pitch-based carbon fibers; Examples thereof include conductive polymers such as polyacene. These electrode active materials can be used alone or in combination of two or more depending on the type of electrochemical element. When using a combination of electrode active materials, use two or more types of electrode active materials with different average particle sizes or particle size distributions. You can do it.

[0017] The shape of the electrode active material used for the electrode of the lithium ion secondary battery is preferably sized into spherical particles. If the particle shape is spherical, a higher-density electrode can be formed during electrode molding. Also, a mixture of fine particles with an average particle size of about 1 μm and relatively large particles with an average particle size of 3 to 8 μm and particles with a broad particle size distribution of 0.5 to 8 m are preferred! /. Particles having a particle size of 50 μm or more are preferably used after being removed by sieving or separating. Tap density defined by ASTM D4164 of the electrode active material 2GZcm ³ or more in particular limited, such bur cathode, is preferably used as a 0. 6gZcm ³ or more in the negative electrode

[0018] 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 with a larger area even with the same weight. Specifically, the specific surface area of 30 m ² Zg above, preferably <is 500~5, 000m ² Zg, more preferably <1, 000-3, is preferably 000m ² Zg. Specific examples of the allotrope of carbon include activated carbon, polyacene, vigorous whisker, and graphite. 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. These carbonaceous materials can be used alone or in combination of two or more as the electrode active material for electric double layer capacitors. When using a combination of carbonaceous materials, use a combination of two or more carbonaceous materials with different average particle sizes or particle size distributions.

[0019] Further, non-porous carbon having microcrystalline carbon similar to graphite and having an increased interlayer distance of the microcrystalline carbon can be used as an electrode active material. Such non-porous carbon is obtained by dry-distilling graphitized charcoal with multi-layered graphite structure microcrystals at 700-850 ° C and then heat-treating with caustic at 800-900 ° C. Further, it can be obtained by removing residual alkali components with heated steam as required.

[0020] As an electrode active material for an electric double layer capacitor, a powder having a volume average particle size of 0.1 to: LOO / zm, preferably 1 to 50 / ζ πι, more preferably 5 to 20 / ζ πι is used. And the electric double layer This is preferable because the capacitor electrode can be easily thinned and the capacitance can be increased.

[0021] The conductive material constituting the composite particle according to the embodiment of the present invention is an allotrope force of particulate carbon that has conductivity and does not have pores that can form an electric double layer. It improves the conductivity of the element electrode. The volume average particle size of the conductive material is preferably smaller than the volume average particle size of the electrode active material. Usually 0.001 to 10 111, preferably 0.05 to 5 μm, more preferably 0.01. It is in the range of ~ 1 μm. 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 thereof include conductive carbon blacks 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. Of these, acetylene black and furnace black are more preferred, with conductive carbon black being preferred. These conductive materials can be used alone or in combination of two or more.

[0022] 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, and more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. By using an electrode in which the amount of the conductive material is within this range, the capacity of the electrochemical element can be increased and the internal resistance can be decreased.

[0023] The binder according to the embodiment of the present invention is not particularly limited as long as it is a compound having a binding force, but a dispersion-type binder is preferable. The dispersion-type binder is a binder having a property of being dispersed in a solvent. For example, a high-molecular compound such as a fluorine-based polymer, a gen-based polymer, an acrylate polymer, a polyimide, a polyamide, or a polyurethane. More preferred are fluorine-based polymers, gen-based polymers, and acrylate polymers. These binders can be used alone or in combination of two or more.

[0024] The fluorine-based polymer is a polymer containing a monomer unit containing a fluorine atom. The proportion of the fluorine-containing monomer unit 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 preferred.

[0025] The gen-based polymer is a homopolymer of conjugated gen or a copolymer obtained by polymerizing a monomer mixture containing conjugated gen, or a hydrogenated product thereof. Monomer The conjugation ratio in the 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 gen-based polymer include conjugated gen homopolymers such as polybutadiene and polyisoprene; carboxy-modified aromatic styrene such as styrene copolymer and butadiene copolymer (SBR) Examples thereof include cyanide bur 'conjugation copolymers such as acrylo-tolyl. Butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, and the like.

[0026] The acrylate polymer is a copolymer obtained by polymerizing a homopolymer of acrylic ester and Z or methacrylic ester or a monomer mixture containing these. The proportion of acrylic acid ester and Z 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, methacrylo-tolyl, diethylene glycol diacrylate. Methyl acrylate copolymer, 2-ethylhexyl acrylate 'styrene' methacrylic acid · ethylene glycol dimethacrylate copolymer, butyl acrylate.acrylonitrile.diethylene glycol dimethacrylate copolymer, and butyl acrylate · acrylic Cross-linked acrylate polymers such as acid 'trimethylolpropane trimetatalylate copolymer; ethylene' methyl acrylate copolymer, ethylene 'methyl methacrylate copolymer, ethylene' ethyl acrylate copolymer, and Ethylene A copolymer of ethylene and acrylic acid (or methacrylic acid) such as an ethyl acrylate copolymer; a radical polymerizable monomer grafted onto the above copolymer of ethylene and acrylic acid (or methacrylate) Polymerized graft polymer; and the like. Examples of the radical polymerizable monomer used for the graft polymer include methyl methacrylate, acrylonitrile, methacrylic acid and the like. In addition, ethylene 'acrylic acid copolymer, ethylene' methacrylic acid copolymer, and the like can be used as a binder.

Among these, from the viewpoint of obtaining an active material layer excellent in binding property and strength to the current collector, a gen-based polymer and an acrylate polymer are preferable.

[0028] The binder preferably has a glass transition temperature (Tg), and the Tg is usually 80 ° C to + 180 ° C, preferably 50 ° C to + 40 ° C, more preferably 30 ° C to + 20 ° C. In the present invention, the glass transition temperature is a value measured according to JIS K7210. Whether Tg is too high or too low, the tensile bond strength tends to decrease when compressed at 4. OMPa for 5 seconds at 70 ° C. On the other hand, the tensile bond strength when compressed at 0. IMPa or 0.5 MPa at 25 ° C for 60 seconds tends to decrease as Tg increases, so these values can be obtained by using binders with different Tg. Can be adjusted.

[0029] The binder used in the embodiment of the present invention is not particularly limited depending on the shape thereof, but has good binding properties. Also, the capacitance of the prepared electrode is reduced due to repeated charge / discharge. Since it can suppress, it is preferable that it is a particulate form. Examples of the particulate binder include those in which binder particles such as latex are dispersed in a solvent, and powders obtained by drying such a dispersion.

[0030] The binder used in the embodiment of the present invention may be a particle having a core-shell structure obtained by stepwise polymerization of a mixture of two or more monomers. The binder having the core shell structure first polymerizes the monomer that gives the first-stage polymer to obtain seed particles, and gives the second-stage polymer in the presence of the seed particles. It is preferable to produce by polymerizing monomers.

[0031] 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: by mass ratio. 1, more preferably 70:30 to 99: 1. The polymer constituting the core part and the shell part can be selected from the above polymers. Since the tensile bond strength tends to increase as the ratio of the core portion decreases, the tensile bond strength can be adjusted by changing the ratio of the core portion.

[0032] The Tg of the core is usually 80 ° C or higher and lower than 0 ° C, preferably 60 ° C or higher and lower than 0 ° C, more preferably -40 ° C or higher and lower than 0 ° C. The higher the Tg of the core, the higher the tensile bond strength when compressed at 4. OM Pa for 5 seconds at 70 ° C. On the other hand, the tensile bond strength when compressed at 0. IMPa or 0.5 MPa for 60 seconds at 25 ° C tends to decrease as the core Tg increases. These values can be adjusted by using. [0033] The Tg of the shell is usually 0 ° C or higher and + 180 ° C or lower, preferably 0 ° C or higher and + 120 ° C or lower, more preferably 0 ° C or higher and + 80 ° C or lower. Further, the difference in Tg between the core portion and the shell portion is usually 20 ° C or higher, preferably 50 ° C or higher.

[0034] The particulate binder used in the embodiment of the present invention has a specific limit depending on the particle diameter. Normal strength Normal temperature 0.001 to 100111, preferably 0.001 to 10 m. More preferably, it has a volume average particle diameter of 0.01 to: m. When the average particle size of the binder is within this range, even if a small amount of the binder is used, an excellent binding force can be imparted to the active material layer.

[0035] The amount of the binder used is usually 0.1 to 50 parts by weight, preferably 0.5 to 20 parts by weight, more preferably 1 to: 100 parts by weight of the electrode active material. The range is LO parts by weight. Since the tensile bond strength tends to increase as the amount of the binder increases, the tensile bond strength can be adjusted by adjusting the amount of the binder.

[0036] In addition to the above, the composite particles of the embodiment of the present invention preferably contain a soluble resin. Dissolved resin is a resin that dissolves in a solvent, and is preferably used by dissolving it in a solvent when preparing slurry A or slurry B, which will be described later, so that an electrode active material, a conductive material, and the like are uniformly used in the solvent. It has an action of dispersing. Dissolved rosins include cellulosic polymers such as carboxymethylcellulose, methylcellulose, ethylcellulose and hydroxypropylcellulose, and their ammonium or alkali metal salts; poly (poly (meth) acrylate) Examples include (meth) acrylates; polybulal alcohol, modified polybulal alcohol, polyethylene oxide; polybulurpyrrolidone, polycarboxylic acid, oxidized starch, phosphate starch, casein, various modified starches, chitin, and chitosan derivatives. These soluble type rosins can be used alone or in combination of two or more. Of these, carboxymethylcellulose, which is preferred as a cellulose polymer, or an ammonium salt or alkali metal salt thereof is particularly preferred. The use amount of the soluble type resin 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 to 100 parts by weight of the electrode active material. The range is 8 to 2 parts by weight. By using dissolved type rosin, it is possible to suppress sedimentation and aggregation of solids in slurry A and slurry B. It also prevents clogging of the atomizer during spray drying. Therefore, spray drying can be performed stably and continuously.

[0037] The composite particles according to the embodiment of 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, a cationic surfactant or a nonionic surfactant is used for heat distribution. What is easy to understand is 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.

[0038] The composite particles of the embodiment of the present invention have a volume average particle diameter of 1 to 500 µm, preferably 5 to 300 111, more preferably 10 to 100 / ζ πι. Since the tensile adhesion strength tends to increase as the particle size decreases, the tensile adhesion strength can be adjusted by adjusting the particle size. If necessary, the particle size may be adjusted by sieving. Here, the volume average particle diameter is a median diameter of a volume distribution measured by an optical diffraction method.

[0039] When the active material layer is molded at a high speed, the pressing time is shortened, so that the composite particles must be bound in a short time. Therefore, the higher the tensile bond strength when compressed for a short time at a relatively high pressure, the faster the molding becomes possible. The composite particles according to the embodiment of the present invention have a tensile bond strength of 8,000 N / m ² or more, preferably 10,000 to 30, OOONZm ² when compressed at 4. OMPa for 5 seconds at 70 ° C. . Higher values enable faster molding. In the embodiment of the present invention, the tensile adhesion strength is defined as: an aluminum upper and lower divided cylindrical cell (inner diameter: 25 mm) is filled with composite particles, and the cell is placed in a thermostatic chamber adjusted to a predetermined temperature. It is the maximum tensile stress when the composite particle layer breaks when the upper cell is lifted at 0.4 mmZ seconds after compressing to a predetermined pressure in ImmZ seconds and holding in that state for a predetermined time. The tensile adhesion strength can be measured using, for example, “Agg Robot” manufactured by Hosokawa Mikulon.

[0040] If the composite particles have low fluidity or agglomerate at room temperature, the composite particles are not uniformly supplied to the molding apparatus at the time of molding, which makes it difficult to form a uniform active material layer. . Therefore, the tensile bond strength when compressed at a relatively low temperature 'pressure should be small. Is preferred. The composite particles of the embodiment of the present invention preferably have a tensile bond strength of 400 NZm ² or less, more preferably 120 to 380 NZm ² when compressed at 0. IMPa for 60 seconds at 25 ° C. The smaller this value, the better the fluidity at room temperature. Further, the tensile bond strength when compressed at 0.5 MPa for 60 seconds at 25 ° C. is preferably 3,000 NZm ² or less, more preferably 600 to 2,700 NZm ² . The smaller this value, the better the storage stability at which the composite particles hardly aggregate at room temperature. Therefore, as the two values are smaller, the particles can be quantitatively supplied without being agglomerated, so that an active material layer having a uniform thickness can be obtained.

[0041] The composite particles having tensile strength characteristics as described above can be obtained by appropriately selecting the amount and type of the binder used, the method for producing the composite particles, and the like. The composite particles according to the embodiment of the present invention can be preferably obtained by a production method in which a binder can be unevenly distributed on the surface of the composite particles. In the conventional technology, since the binder is uniformly distributed in the composite particles, there are few binders on the surface of the particles that are involved in the binding properties between the particles, and the tensile bond strength during short-time compression is insufficient. Met. By making the binder unevenly distributed on the surface of the composite particles, the binding property between the particles can be improved, and the tensile bond strength when compressed at 4. OMPa for 5 seconds at 70 ° C can be increased.

[0042] Further, the binder suitably used for the composite particles according to the embodiment of the present invention is a binder having a low viscosity near room temperature and a high binding property at the molding temperature. Using such a binder, the tensile bond strength is high when compressed at 4. OMPa for 5 seconds at 70 ° C. At 25 ° C, the tensile strength when compressed at 0. IMPa or 0.5 MPa for 60 seconds. Composite particles having low adhesion strength can be obtained. The strong binder is preferably a gen-based polymer, an acrylate polymer or a core-shell structure having a glass transition temperature in the above range, and a core-shell structure having a glass transition temperature in the above range. Particularly preferred is a binder having

[0043] The electrochemical device electrode composite particles according to the embodiment of the present invention are not particularly limited by the manufacturing method thereof, but according to the two manufacturing methods described below, the surface of the composite particles is formed. Since it is easy to make the binder unevenly distributed, the composite particles according to the embodiment of the present invention can be easily obtained, which is preferable. [0044] The first production method includes a step of obtaining a slurry A containing an electrode active material, a conductive material, and a binder, and a spray-drying granulation method including a step of spray-drying and granulating the slurry A It is.

In the spray drying granulation method, first, the electrode active material, the conductive material, the binder, and, if necessary, a soluble resin and other additives are dispersed or dissolved in a solvent to obtain an electrode active material, a conductive material. A slurry A is obtained in which an electric material, a binder, and, if necessary, a dissolving type resin and other additives are dispersed or dissolved.

[0046] The solvent used for obtaining the slurry A is not particularly limited, but when the above-mentioned soluble resin is used, a solvent capable of dissolving the soluble resin is preferably used. Specifically, a force organic solvent in which water is usually used 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; Preference is given to alcohols such as dimethylacetoamide, N—methyl-1-pyrrolidone, dimethylimidazolidinone and other amides; dimethyl sulfoxide, sulfolane and other amide solvents; When water and an organic solvent having a lower boiling point than water are used in combination, the drying rate can be increased during spray drying. In addition, since the dispersibility of the binder or the solubility of the soluble resin is changed, the viscosity and fluidity of the slurry A can be adjusted depending on the amount or type of the organic solvent. Therefore, production efficiency can be improved. The amount of solvent used when preparing slurry A is typically in the range of 1 to 50% by weight, preferably 5 to 50% by weight, more preferably 10 to 30% by weight. Is such an amount. When the solid content concentration is within this range, the binder is preferably dispersed uniformly. Further, since the particle diameter of the composite particles increases as the solid content concentration of the slurry A increases, the tensile adhesion strength of the composite particles obtained by adjusting the solid content concentration of the slurry A can be adjusted.

[0047] The method or procedure for dispersing or dissolving the electrode active material, the conductive material, the binder, the soluble resin and other additives in a solvent is not particularly limited. Method of adding and mixing electrical material, binder and soluble type resin, dissolving soluble type resin in solvent, adding binder (for example, latex) dispersed in solvent, mixing, and finally To electrode A method of adding and mixing an active material and a conductive material, and adding and mixing an electrode active material and a conductive material in a binder dispersed in a solvent, and then adding a dissolved resin dissolved in the solvent to the mixture. The method of combining is mentioned. 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.

Next, the slurry A is granulated by spray drying. The spray drying method is a method of spraying and drying slurry in hot air. An atomizer is one of the devices used for the spray drying method. There are two types of atomizers, a rotating disk method and a pressure method. In the rotating disk method, slurry is introduced almost at the center of a high-speed rotating disk, and the slurry is released outside 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 disc is a force depending on the size of the disc. Usually, it is 5,000-30, OOOrpm, preferably 15,000-30, OOOrpm. The lower the rotational speed of the disk, the larger the spray droplets and the larger the particle size of the composite particles. As a rotating disk type atomizer, a force capable of raising a pin type and a vane type, preferably a pin type atomizer is used. A pin-type atomizer is a type of centrifugal spraying device that uses a spray plate. The spray plate is detachably mounted between upper and lower mounting disks on a substantially concentric circle along its periphery. Consists of things that are attached. Slurry A is introduced from the center of the spray plate, adheres to the spraying roller by centrifugal force, moves to the outside of the roller surface, and finally sprays away from the roller surface. On the other hand, the pressurization method is a method in which the slurry A is pressurized and sprayed from the nozzle and dried.

[0049] The temperature of the slurry A to be sprayed may be a room temperature or higher by heating with a force usually at room temperature. The hot air temperature during 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. For example, the method in which the hot air and the spraying direction flow in parallel to each other, the method in which the hot air is sprayed at the top of the drying tower and descends with the hot air, Examples are the contact method, and the sprayed droplets co-flow with the hot air first and then drop by gravity and contact countercurrent.

[0050] In the second production method, a step of obtaining a slurry B containing a conductive material, a binder, and a soluble resin added as necessary and other additives, and flowing an electrode active material in a tank. , The slurry B is sprayed there for fluid granulation, and the particles obtained in the fluid granulation step are tumbled and granulated.

[0051] First, a slurry B containing a conductive material, a binder, and, if necessary, a soluble resin and other additives is obtained. Examples of the solvent used for obtaining the slurry B include the same solvents as those mentioned in the spray drying granulation method. The amount of solvent used when preparing slurry B 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 an amount. When the solid content concentration is within this range, it is preferable because the binder is uniformly dispersed.

There is no particular limitation on the method or procedure for dispersing or dissolving the conductive material and the binder, and if necessary, the soluble type resin in the solvent. For example, the conductive material, the binder and the soluble type resin are added to the solvent. A method of mixing and dissolving, dissolving a soluble resin in a solvent, adding and mixing a binder (for example, latex) dispersed in a solvent, and finally adding and mixing a conductive material, conductive material There is a method of adding and mixing a dispersible binder dissolved in a solvent and mixing it with a dispersible 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.

[0052] Next, the electrode active material is caused to flow in a tank, and the slurry B is sprayed thereon for fluid granulation. Examples of the method of fluid granulation in the tank include a fluidized bed, a deformed fluidized bed, and a spouted bed. In the fluidized bed, the electrode active material is fluidized with hot air, and the slurry B is also sprayed with the slurry B to perform agglomeration and granulation. The modified fluidized bed is the same as the fluidized bed described above, but is a method of giving a circulating flow to the powder 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 slurry B of spray isotropic force is adhered to coarse particles using the characteristics of the spouted bed and granulated while drying at the same time. As a manufacturing method according to the embodiment of the present invention, a method using a fluidized bed or a deformed fluidized bed among these three methods is preferable. The temperature of the slurry B to be sprayed may be a room temperature or higher by heating with a force normally at room temperature. The temperature of the hot air used for fluidization is usually 80 to 300 ° C, preferably 100. ~ 200 ° C.

[0053] Particles obtained by fluid granulation (hereinafter sometimes referred to as "Particle B" t) may be completely dried with hot air, but may be granulated in the next rolling granulation step. In order to increase the grain efficiency, it is preferable to be in a wet state.

[0054] Next, the particles B obtained in the fluidized granulation step are subjected to rolling granulation in the presence of slurry B containing a conductive material and a binder. The slurry B used for rolling granulation is the same as or different from the slurry B used for fluid granulation as long as it contains a conductive material and a binder. Also good. 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 sand method, the slurry B is sprayed on the particles B supplied in the inclined rotating sand to produce an agglomerated granulated product, and the granulated powder that has grown relatively large by utilizing the classification effect of the rotating sand. This is a method of discharging objects from the rim. The rotating cylinder system is a system in which wet particles B are supplied to an inclined rotating cylinder, and this is rolled in a cylinder, and the slurry B is sprayed to obtain an agglomerated granulated product. The rotating truncated cone method is the same as the operating method of the rotating cylinder, but is a method of discharging the granulated material that has grown relatively large while utilizing the classification effect of the aggregated granulated material by the truncated cone shape. In this rolling granulation step, coating granulation is mainly performed, and agglomeration granulation is partially performed.

[0055] The temperature during 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 B. Furthermore, in order to remove the residual solvent from the composite particles, it can be dried as necessary after rolling granulation.

[0056] By the above method, composite particles containing an electrode active material, a conductive material, and a binder can be obtained. In this composite particle, the electrode active material and the conductive material are bound by a binder and / or a soluble type resin, and the outer layer portion of the composite particle has a relatively small average particle diameter. The material is formed by binding, and the inner part of the composite particle has a relatively large average particle diameter, and is formed by binding of an electrode active material and Z or a conductive material.

[0057] The electrochemical element electrode material according to the embodiment of the present invention includes the composite particles according to the embodiment of the present invention, and additionally includes other binders and other additives as necessary. Is. 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. [0058] Examples of the other binder contained in the electrode material as necessary include the same binders as those used for obtaining the composite particles. Since the composite particles already contain the binder, it is not necessary to add them separately when preparing the electrode material. Force To increase the binding force between the composite particles, the binder and the electrode material are used. It may be added during preparation. The amount of the other binder added when preparing the electrode material is generally 0.001 to 50 parts by weight with respect to 100 parts by weight of the electrode active material in total with the binder in the composite particles. Preferably it is 0.01-20 weight part, More preferably, it is the range of 0.1-10 weight part. Other additives include, in addition to the above-mentioned dissolved type rosy surfactant, molding aids such as water and alcohol, and the like, which can be added by appropriately selecting an amount that does not impair the effects of the present invention.

[0059] An electrochemical element electrode according to an embodiment of the present invention (hereinafter sometimes simply referred to as "electrode";) has an active material layer formed of the above-described electrochemical element electrode material on a current collector. It is made by laminating. 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. 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 depending on the purpose of use, but is usually 1 to 200 μm, preferably 5 to: LOO μm, more preferably 10 to 50 μm. m.

[0060] 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 active material layer is formed directly on the current collector by forming the electrochemical element electrode material directly. May be formed. As a method for forming the active material layer, there are a dry molding method such as a pressure molding method, and a wet molding method such as a coating method. However, there is a dry molding method that does not require a drying process and can reduce manufacturing costs. preferable. Examples of dry molding methods include pressure molding and extrusion (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. In the extrusion method, the electrochemical element electrode material is extruded with an extruder. This is a method of forming into a film or sheet.

[0061] Of these, it is preferable to use pressure molding because it can be performed with simple equipment. Examples of the pressure forming include a roll pressure forming method in which an electrode material containing composite particles is supplied to a roll type pressure forming device with a supply device such as a screw feeder, and an active material layer is formed. Disperse the material on the current collector, adjust the thickness by leveling the electrode material with a blade, etc., then mold with a pressure device, fill the mold with the electrode material, and press the mold to mold There are ways to do it.

[0062] Of these pressure moldings, roll pressure molding is preferred. In this method, the active material layer may be directly laminated on the current collector by feeding the current collector to the roll simultaneously with the supply of the electrode material. The molding temperature is usually from 0 to 200 ° C., preferably higher than the melting point or glass transition temperature of the binder, more preferably 20 ° C. or more higher than the melting point or glass transition temperature. In roll pressing, the forming speed is usually 0.1 to 20 mZ, preferably 1 to 10 mZ. The pressing linear pressure between rolls is usually 0.2 to 30 kN / cm, preferably 0.5 to LOkNZcm.

[0063] In order to eliminate variations in the thickness of the molded electrode and increase the density of the active material layer to achieve high capacity, further post-pressurization may be performed as necessary. The post-pressing method is generally a pressing process using a roll. In the roll press process, two cylindrical rolls are arranged vertically in parallel at a predetermined interval, and each is rotated in the opposite direction. The temperature of the roll may be adjusted by heating or cooling.

[0064] Since the composite particles for electrochemical element electrodes according to the embodiment of the present invention can firmly bind the composite particles to each other by pressing, an active material layer can be obtained at a high forming speed in roll press forming. Can do. Furthermore, since the fluidity at room temperature is good, the supply accuracy is increased and a uniform active material layer can be obtained. In addition, since it does not easily aggregate at room temperature, its storage characteristics are good.

Example

[0065] Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited to these examples. In the examples and comparative examples, “parts” and “%” are based on weight unless otherwise specified. [0066] Example 1

100 parts of activated carbon “Kuraray Coal RP-20” (manufactured by Kuraray Chemical Co., Ltd.) with a volume average particle size of 5 μm as the electrode active material, and the composition ratio of the monomer unit as the binder is 2-ethylhexyl acrylate : Acrylonitrile: Methacrylic acid: Ethylene glycol dimethacrylate = 68: 28: 2: 2 (weight ratio) Latex formed by dispersing a crosslinked acrylate polymer in water (volume average particle size 0.11 m) 15 parts of glass transition temperature, concentration 40%) 15 parts of acetylene black “Denka black powder” (manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, carboxymethylcellulose ammonia as a soluble resin -A TK homomixer (specialized machine) containing 93.3 parts of 1.5% aqueous solution of DN-800H (produced by Daicel Chemical Industries, Ltd.) and 348.7 parts of ion-exchanged water. (Mixed by Kogyo Co., Ltd.) -Obtained (I). Using this slurry (I), spray dryer “OC-16” (Okawara Kako Co., Ltd.), rotating disk type pin-type atomizer (diameter 65mm), rotation speed 20,000 rpm, hot air temperature 150 ° C, spray drying at a particle recovery outlet temperature of 90 ° C. to obtain composite particles. The volume average particle diameter of the obtained composite particles was measured with a laser diffraction particle size distribution analyzer (SALD-2000: manufactured by Shimadzu Corporation), and found to be 44 μm.

[0067] The tensile bond strength of the obtained composite particles was measured using "Aggrobot" (manufactured by Hosokawa Micron Corporation). That is, when the composite particles are packed in an aluminum upper and lower split cell (inner diameter 25mm), compression is performed under the following conditions at a compression head speed of 0. ImmZ seconds, and then the upper cell is pulled vertically at a speed of 0.4 mmZ seconds. The maximum stress was measured three times, and the average value was taken as the tensile adhesion strength. The measurement was performed in a room at a temperature of 25 ± 3 ° C and a humidity of 60 ± 5%.

[0068] Conditions 1. Pressure: 4.0 MPa, Compression holding time: 5 seconds, Temperature: 70 ° C

Condition 2. Pressure: 0.5 MPa, Compression retention time: 60 seconds, Temperature: 25 ° C

Condition 3. Pressure: 0. IMPa, Compression retention time: 60 seconds, Temperature: 25 ° C

The measurement at 70 ° C. was carried out after holding the cell filled with the composite particles in a constant temperature bath at 70 ° C. for 20 minutes. The results are shown in Table 1.

[table 1] Tensile strength (NZm ² ) S large molding

Particle size 70. C 25 ° C 25 ° C Speed Thickness Density

m) 4. O Pa 0.5 MPa 0.1 MPa (m Nominal) Variation Variation Example 1 44 10820 647 216 9 3.1 2.5

Example 2 51 9040 964 288 3 3.5 2.8

Example 3 46 9020 1852 288 9 4.5 2.6

Example 4 47 8520 674 316 3 3.6 2.1

Example 5 45 8480 3380 316 9 5.8 4.5

Example 6 51 14020 1593 459 9 6.4 5.6

Example 7 48 8 200 500 216 3 3.0 2.5

Example 8 45 8 100 1 100 216 4 3.9 2.6

Example 9 45 12000 1000 288 9 3.9 2.5

Example 1 0 48 8500 3560 567 5 7.8 6.9

Example 1 1 32 13 890 1235 388 θ 4.8 3.7

Example 1 2 60 8 200 500 188 5 2.5 2.8

Example 1 3 34 8500 1600 459 3 4.5 4.4

Comparative Example 1 41 7040 1 135 388 1 3.9 3.5

Comparative Example 2 46 6320 974 33S 1 4.1 3 8

Comparative Example 3 48 6000 500 188 1 4.0. 4.1

[0069] Next, the obtained composite particles were subjected to a roll press machine (pressed rough surface heat roll, Hirano Giken Kogyo Co., Ltd.).

The sheet-like active material layer was formed by roll pressure molding using a fixed feeder. The roll was supplied to a roll (manufactured by Kogyo Co., Ltd.) (roll temperature 120 ° C, press linear pressure 4 kNZm). Forming is performed by increasing the roll speed in the range of l to 9mZ by lmZ, and the upper limit roll speed obtained continuously without breaking more than the sheet-like active material layer force Sim is the maximum forming speed. did. In addition, the active material layer obtained at a molding speed of 3 mZ was randomly punched into 20 shapes with a diameter of 12 mm, thickness and density were measured, and each variation was calculated by the following formula. The results are shown in Table 1.

[0070] Variation = standard deviation Z average value X 100

Example 2

As a binder, the composition ratio of monomer units is 2-ethylhexyl acrylate: atari mouth-tolyl: methacrylic acid: ethylene glycol dimetatalylate = 86: 10: 2: 2 (weight ratio), cross-linking Except that a latex (volume average particle size of 0.11 m, glass transition temperature—40 ° C., concentration 40%) obtained by dispersing a type acrylate polymer in water was used, the same as in Example 1. Combined particles were obtained.

[0071] Example 3 As the binder, the monomer unit that forms the core part is 2-ethylhexyl acrylate, the monomer unit that forms the shell part is ethyl acetate, methacrylic acid, and methacrylic acid. A latex (volume average particle size 0) in which a core-shell type polymer is dispersed in water with a composition ratio of 2-ethylhexyl acrylate: ethyl methacrylate: metatalic acid = 81: 16: 3 (weight ratio). A composite particle was obtained in the same manner as in Example 1 except that 23 μm, the glass transition temperature of the core portion—60 ° C., the glass transition temperature of the shell portion + 70 ° C., and a concentration of 40% were used.

[0072] Example 4

As a binder, the composition ratio of monomer units is 2-ethylhexyl acrylate: styrene: methacrylic acid: ethylene glycol dimethacrylate = 70: 26: 2: 2 (weight ratio), cross-linked attalylate type Composite particles were obtained in the same manner as in Example 1 except that latex (volume average particle size 0.12 / ζ πι, glass transition temperature—10 ° C, concentration 40%) obtained by dispersing the polymer in water was used. I got a child.

[0073] Example 5

As a binder, instead of water-dispersed latex of a cross-linked acrylate polymer, polytetrafluoroethylene “POLYFLON D2CE” (manufactured by Daikin Chemical Co., Ltd.), which is a fluoropolymer, is used in water. Composite particles were obtained in the same manner as in Example 1 except that 9.3 parts of a dispersed latex (glass transition temperature + 120 ° C., concentration 64.5%) was used.

[0074] Example 6

Composite particles were obtained in the same manner as in Example 2 except that the amount of the latex obtained by dispersing a crosslinked acrylate polymer as a binder in water was 37.5 parts.

[0075] Example 7

As a binder, the composition ratio of monomer units is 2-ethylhexyl acrylate: atari mouth-tolyl: methacrylic acid: ethylene glycol dimethacrylate = 58: 38: 2: 2 (weight ratio), cross-linked type Composite particles were obtained in the same manner as in Example 1 except that latex (volume average particle size: 0.11 μm, glass transition temperature: 24 ° C, concentration: 40%) obtained by dispersing an acrylate polymer in water was used. Got.

[0076] Example 8 As the binder, the monomer unit that forms the core part is 2-ethylhexyl acrylate, the monomer unit that forms the shell part is ethyl acetate, methacrylic acid, and methacrylic acid. A latex (volume average particle size 0) having a composition ratio of 2-ethylhexyl acrylate: ethyl ethyl methacrylate: methacrylic acid = 89: 8: 3 (weight ratio) dispersed in water. 24 ^ m, glass transition temperature of the core part—60 ° C, glass transition temperature of the shell part + 70 ° C, concentration 40%) were used in the same manner as in Example 1 to obtain composite particles.

[0077] Example 9

As a binder, the monomer unit forming the core part is ethyl acrylate, the monomer unit forming the shell part is ethyl acrylate and methacrylic acid, and the composition ratio of all monomer units is Is a latex in which a core-shell polymer is dispersed in water with a volume average particle size of 0.22 m and a core portion of ethyl acrylate: ethyl methacrylate: methacrylic acid = 81: 16: 3 (weight ratio) Composite particles were obtained in the same manner as in Example 1 except that the glass transition temperature—13 ° C., the glass transition temperature of the shell portion + 70 ° C., and the concentration 40% were used.

[0078] Example 10

5 parts of acetylene black as a conductive material, 37.5 parts of latex in which a cross-linked acrylate polymer is dispersed in water as a binder, and carboxymethylcellulose ammonium salt “DN-10L” (Daicel®) as a soluble resin. 8.25 parts of 4% aqueous dispersion from Gaku Kogyo Co., Ltd. and 1.5% aqueous dispersion of DN-800H carboxymethylcellulose ammonium salt (Daicel Chemical Industries, Ltd.) 44.67 parts and 77.1 parts of ion-exchanged water were added to a slurry (II) having a solid content concentration of 8% by stirring and mixing with a hobart mixer (Aiesha Seisakusho Co., Ltd.). Supply 100 parts of activated carbon as an electrode active material to “Agromaster” (manufactured by Hosokawa Micron Co., Ltd.), flow it with hot air at 80 ° C, spray the slurry (soot) here, and perform fluidized bed granulation. Composite particles were obtained. The acetylene black, the water-dispersed latex and activated carbon of the cross-linked acrylate polymer were the same as those in Example 1.

[0079] Example 11

Composite particles were obtained in the same manner as in Example 1 except that the rotational speed of the rotating disk type pin type atomizer was 25, OOOrpm. [0080] Example 12

Composite particles were obtained in the same manner as in Example 1 except that the rotational speed of the rotating disk type pin type atomizer was set to 15, OOOrpm.

[0081] Example 13

Fluidized bed granulation was carried out in the same manner as in Example 10 except that 15 parts of a latex obtained by dispersing a crosslinked acrylate polymer in water as a binder was used, and a sieve having a mesh size of 155 microns. !, And sieved to obtain composite particles.

[0082] The volume average particle diameter and tensile adhesion strength of the composite particles obtained in Examples 2 to 13 were measured in the same manner as in Example 1. In addition, the active material layer was molded using these composite particles in the same manner as in Example 1, and the maximum molding speed, variation in thickness and density were measured. The results are shown in Table 1.

[0083] Comparative Example 1

Composite particles were obtained in the same manner as in Example 10 except that the amount of the latex obtained by dispersing the crosslinked acrylate polymer as a binder in water was 15 parts.

[0084] Comparative Example 2

The slurry (I) obtained in Example 1 was poured into a vat, and the solid material dried at 110 ° C. for 24 hours under reduced pressure in a vacuum dryer was pulverized to obtain composite particles.

[0085] Comparative Example 3

Composite particles were obtained in the same manner as in Example 2 except that the amount of the latex obtained by dispersing the crosslinked acrylate polymer as a binder in water was 7.5 parts.

[0086] The volume average particle diameter and tensile adhesion strength of the composite particles obtained in Comparative Examples 1 and 3 were measured in the same manner as in Example 1. Also, the active material layer was molded using these composite particles in the same manner as in Example 1, and the maximum molding speed was measured. As a result, all were lmZ minutes, and the active material layer obtained at this molding speed was used. The thickness and density variations were measured in the same manner as in Example 1. The results are shown in Table 1.

As is clear from the above examples and comparative examples, when the composite particles for electrochemical devices according to the examples of the present invention were used, high-speed molding was possible as compared with the composite particles of the comparative examples. In addition, the obtained electrochemical device electrode has small variations in electrode thickness and electrode density. I

[0088] It should be noted that as long as the national laws of the designated country selected in this international application or the selected selected country permit, the description of this specification is incorporated with the disclosure of JP 2001-176757 cited in the embodiment. As part of

[0089] This disclosure also relates to the subject matter contained in Japanese Patent Application No. 2005-270713 filed on September 16, 2005, the entire disclosure of which is expressly incorporated herein by reference. Expected.

Industrial applicability

[0090] As described above, the composite particle for an electrochemical element electrode, the method for producing the composite particle for an electrochemical element electrode, the electrochemical element electrode material, and the electrochemical element electrode of the present invention have high performance lithium ion secondary. Suitable for use in double layer capacitors for batteries and electricity.

Claims

The scope of the claims

[1] Electrochemical device electrode composite particles containing an electrode active material, a conductive material, and a binder and having a volume average particle diameter of 1 to 500 μm, compressed at 70 ° C 4. OMPa for 5 seconds Electrochemical element electrode composite particles having a tensile bond strength of 8,000 N / m ² or more.

[2] The composite particle for electrochemical device electrodes according to claim 1, wherein the tensile adhesion strength when compressed with O.lMPa at 25 ° C for 60 seconds is 400 NZm ^{2 or} less.

[3] The composite particle for an electrochemical device electrode according to claim 1 or 2, wherein the tensile adhesion strength when compressed at 0.5 MPa for 60 seconds at 25 ° C is 3,000 N / m ² or less.

[4] A method for producing composite particles for an electrochemical device electrode according to claim 1,

A method for producing composite particles for an electrochemical element electrode, comprising: a step of dispersing an electrode active material, a conductive material and a binder in a solvent to obtain a slurry; and a step of spray-drying the slurry to granulate.

[5] An electrochemical element electrode material comprising the electrochemical element electrode composite particle according to claim 1.

[6] An electrochemical element electrode obtained by stacking an active material layer formed of the electrochemical element electrode material according to claim 5 on a current collector.

7. The electrochemical element electrode according to claim 6, wherein the method of laminating the active material layer on the current collector is pressure molding.

8. The electrochemical element electrode according to claim 7, wherein the pressure molding is roll pressure molding.

[9] The electrochemical device electrode according to [6], which is used for an electric double layer capacitor.