JP4985404B2 - Electrochemical element electrode manufacturing method, electrochemical element electrode material, and electrochemical element electrode - Google Patents

Description

The present invention relates to an electrochemical element electrode composite particle for use in an electrochemical element such as a lithium ion secondary battery or an electric double layer capacitor, particularly an electrode material suitably used for an electric double layer capacitor (in this specification, simply It is related with the manufacturing method of the electrochemical element electrode using the electrochemical element electrode material containing a "composite particle." Moreover, this invention relates to the electrochemical element electrode material containing this composite particle, and the electrochemical element electrode using this electrode material.

  Electrochemical elements such as lithium ion secondary batteries and electric double layer capacitors are rapidly expanding in demand by taking advantage of their small size, light weight, high energy density, and the ability to repeatedly charge and discharge. Lithium ion secondary batteries have a relatively high energy density and are used in the fields of mobile phones and notebook personal computers. Since the electric double layer capacitor can be rapidly charged and discharged, it is used as a memory backup compact power source for a personal computer or the like. Furthermore, the electric double layer capacitor is expected to be used 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 elements are required to be further improved, such as lowering resistance, increasing capacity, improving mechanical properties and productivity. In such circumstances, there is a demand for a more productive manufacturing method for electrochemical element electrodes, and various improvements have been made to manufacturing methods capable of high-speed molding and materials for electrochemical element electrodes suitable for the manufacturing method. ing.

  An electrochemical element electrode is 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 with a binder on a current collector. is there. In order to form this active material layer, Japanese Patent Application Publication No. 2005-78943 discloses a method in which composite particles obtained by adhering a particulate electrode active material and a particulate conductive auxiliary agent with a binder are pressure-molded. Are described. 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 additive 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 pressure molding.

An object of the present invention is to provide an electrochemical element electrode having a uniform active material layer at a high molding speed, particularly in roll press molding, with excellent fluidity at room temperature, excellent transportability and quantitative supply. Method for producing electrochemical element electrode formed by electrochemical element electrode material including composite particle for electrochemical element electrode, electrochemical element electrode material including the composite particle, and electricity formed by this electrode material It is to provide a chemical element electrode .

The present inventor paid attention to the powder characteristics of the electrode material, and as a result, found that the tensile adhesion strength when the electrode material was compressed greatly affected the moldability, fluidity and storage characteristics of the electrode material. . And while conventional electrode materials have low tensile bond strength at high temperature and lack of binding force, the moldability was low, whereas tensile bond strength when compressed at 70 MPa at 4.0 MPa for 5 seconds. It has been found that if an electrode material having a certain range is used, the moldability is excellent. Furthermore, it has been found that an electrode material having a tensile bond strength of not more than a certain value when compressed at 0.1 MPa and 0.5 MPa for 60 seconds at 25 ° C. is excellent in fluidity and storage characteristics. It came to be completed.

Thus, according to the first aspect of the present invention, there are composite particles for an electrochemical element electrode containing an electrode active material, a conductive material, a soluble resin, and a dispersion-type binder and having a volume average particle diameter of 1 to 500 μm. Te, tensile strength when compressed 5 seconds at 4.0MPa at 70 ° C. is 8000 N / ^{m 2} or more 14020N / ^{m 2} or less, an electrochemical device electrode material comprising an electrochemical element composite particles for an electrode, supplied Electrochemical device electrode comprising a step of forming an electrode active material layer by supplying to a roll-type pressure forming apparatus using the apparatus and performing roll-pressure forming at a press linear pressure between rolls of 0.2 to 30 kN / cm A manufacturing method is provided.

The composite particle for an electrochemical element electrode preferably has a tensile adhesion strength of 400 N / m ² or less when compressed at 0.1 MPa for 60 seconds at 25 ° C. The composite particle for an electrochemical element electrode preferably has a tensile adhesion strength of 3,000 N / m ² or less when compressed at 0.5 MPa for 60 seconds at 25 ° C.

According to a second aspect of the present invention, the electrochemical method comprising: a step of obtaining a slurry by dispersing an electrode active material, a conductive material and a binder in a solvent; and a step of spray-drying the slurry and granulating the slurry. A method for producing composite particles for device electrodes is provided.

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 the 4th viewpoint of this invention, the electrochemical element electrode formed by laminating | stacking the said electrode active material layer formed from the said electrochemical element electrode material on a collector is provided.

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

  Hereinafter, the present invention will be described in detail by way of embodiments. However, the embodiments are merely examples, and the embodiments described below do not limit the present invention.

The composite particle for an electrochemical element electrode according to an embodiment of the present invention is an electrochemical element electrode composite particle containing an electrode active material, a conductive material, and a binder, and having a volume average particle diameter of 1 to 500 μm. The tensile bond strength when compressed at 4.0 MPa at 70 ° C. for 5 seconds is 8,000 N / m ² or more.

The electrode active material constituting the composite particle according to the embodiment of 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 average 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. A mixture of fine particles having an average particle size of about 1 μm and relatively large particles having an average 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. These carbonaceous materials can be used alone or in combination of two or more as an electrode active material for an electric double layer capacitor. When the carbonaceous materials are used in combination, two or more types of carbonaceous materials having different average 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 an electrode active material for an electric double layer capacitor is a powder having a volume average particle diameter of 0.1 to 100 μm, preferably 1 to 50 μm, more preferably 5 to 20 μm, the electric double layer capacitor electrode can be made thin. It is preferable because it is easy and the capacitance can be increased.

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

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

  The acrylate polymer is a copolymer obtained by polymerizing a homopolymer of acrylic acid ester and / or methacrylic acid ester or a monomer mixture containing them. The ratio of acrylic acid ester and / or methacrylic acid ester in the monomer mixture is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more. Specific examples of the acrylate polymer include 2-ethylhexyl acrylate / methacrylic acid / acrylonitrile / ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate / methacrylic acid / methacrylonitrile / diethylene glycol dimethacrylate copolymer, acrylic Crosslinking of 2-ethylhexyl acid / styrene / methacrylic acid / ethylene glycol dimethacrylate copolymer, butyl acrylate / acrylonitrile / diethylene glycol dimethacrylate copolymer, and butyl acrylate / acrylic acid / trimethylolpropane trimethacrylate copolymer Type acrylate polymer; ethylene / methyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / ethyl acrylate copolymer, and A copolymer of ethylene and acrylic acid (or methacrylic acid) such as an ethylene / ethyl methacrylate copolymer; a radical polymerizable monomer in the copolymer of ethylene and acrylic acid (or methacrylic acid) A graft polymer obtained by graft polymerization; 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, ethylene / acrylic acid copolymers, ethylene / methacrylic acid copolymers, and the like can be used as binders.

  Among these, a diene polymer and an acrylate polymer are preferable from the viewpoint that an active material layer excellent in binding property and strength to the current collector can be obtained.

  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. is there. In the present invention, the glass transition temperature is a value measured according to JIS K7210. If Tg is too high or too low, the tensile bond strength tends to decrease when compressed at 70 ° C. at 4.0 MPa for 5 seconds. On the other hand, tensile adhesion strength when compressed at 0.1 MPa or 0.5 MPa at 25 ° C. for 60 seconds tends to decrease as Tg increases, so these values are adjusted by using binders having different Tg. can do.

  The binder used in the embodiment of the present invention is not particularly limited depending on its shape, but has good binding properties, and can suppress deterioration of the created electrode due to a decrease in capacitance or repeated charge / discharge. Since it can do, it is preferable that it is particulate. 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.

  Further, the binder used in the embodiment of 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. 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.

  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 part, the higher the tensile bond strength when compressed at 4.0 MPa at 4.0 MPa for 5 seconds. On the other hand, since the tensile bond strength when compressed at 0.1 MPa or 0.5 MPa for 60 seconds at 25 ° C. tends to decrease as the Tg of the core part increases, binders having different Tg of the core part should be used. To adjust these values.

  The Tg of the shell part 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. The difference in Tg between the core part and the shell part is usually 20 ° C. or higher, preferably 50 ° C. or higher.

  The particulate binder used in the embodiment of the present invention is not particularly limited depending on the particle diameter, but is usually 0.0001 to 100 μm, preferably 0.001 to 10 μm, more preferably 0.01 to It has a volume average particle diameter of 1 μm. When the average particle size 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.

  The amount of the binder used is usually in the range of 0.1 to 50 parts by weight, preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. It is. 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.

  In addition to the above, the composite particles of the embodiment of the present invention preferably contain a soluble resin. The soluble resin is a resin that dissolves in a solvent, and is preferably used by dissolving in a solvent when preparing slurry A or slurry B, which will be described later, to uniformly disperse the electrode active material, conductive material, etc. in the solvent. It has an action. 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, sedimentation and aggregation of solids in the slurry A and the slurry B can be suppressed. Moreover, since the clogging of the atomizer at the time of spray drying can be prevented, spray drying can be performed stably and continuously.

  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, anionic or nonionic surfactants which 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.

  The composite particles according to the embodiment of the present invention have a volume average particle diameter in the range of 1 to 500 μm, preferably 5 to 300 μm, more preferably 10 to 100 μm. Since the tensile adhesion strength tends to increase as the particle diameter decreases, the tensile adhesion strength can be adjusted by adjusting the particle diameter. If necessary, the particle size may be adjusted by sieving. In addition, the volume average particle diameter here is a median diameter of a volume distribution measured by a light diffraction method.

When the active material layer is molded at a high speed, the pressurization time is shortened, so that the composite particles must be bound together 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. Composite particles according to the embodiment of the present invention, 70 tensile adhesion strength when compressed 5 seconds at 4.0MPa at ℃ is 8,000N / ^{m 2} or more, preferably 10,000~30,000N / ^{m 2} is there. Higher values enable higher speed molding. In the embodiment of the present invention, the tensile adhesion strength refers to the aluminum upper and lower divided cylindrical cells (inner diameter: 25 mm) filled with composite particles, placed in a thermostatic chamber adjusted to a predetermined temperature, and the compression speed: 0. The maximum tensile stress when the composite particle layer breaks when the upper cell is lifted at a pulling speed of 0.4 mm / second after being compressed to a predetermined pressure at 1 mm / second and held in that state for a predetermined time. The tensile adhesion strength can be measured using, for example, “Agrobot” manufactured by Hosokawa Micron.

Further, if the composite particles have low fluidity or agglomerate at room temperature, the composite particles are not uniformly supplied to the molding apparatus during molding, and it becomes difficult to mold a uniform active material layer. Therefore, it is preferable that the tensile adhesion strength when compressed at a relatively low temperature and pressure is small. Composite particles of embodiments of the present invention, the tensile adhesion strength are preferred when compressed for 60 seconds at 0.1MPa at 25 ℃ 400N / ^{m 2} or less, more preferably 120~380N / ^{m 2.} The smaller this value, the better the fluidity at room temperature. Furthermore, the tensile bond strength when compressed at 0.5 MPa for 60 seconds at 25 ° C. is preferably 3,000 N / m ² or less, more preferably 600 to 2,700 N / m ² . The smaller this value is, the less likely the aggregation of the composite particles is at room temperature and the better the storage stability. Therefore, as the two values are smaller, the particles can be supplied quantitatively without becoming a lump, and an active material layer having a uniform thickness can be obtained.

  The composite particles having the 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 property between the particles, and the tensile adhesion 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 adhesion strength when compressed at 4.0 MPa at 70 MPa for 5 seconds can be increased.

  Moreover, 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. By using such a binder, the tensile bond strength when compressed at 4.0 MPa for 5 seconds at 70 ° C. is high, and the tensile bond strength when compressed at 0.1 MPa or 0.5 MPa for 60 seconds at 25 ° C. Composite particles having a low particle size can be obtained. As such a binder, a diene polymer, an acrylate polymer or a binder having a core-shell structure having a glass transition temperature in the above range is preferable, and a binder having a glass transition temperature in the above range and having a core-shell structure is preferable. A dressing is particularly preferred.

  The electrochemical device electrode composite particles according to the embodiment of the present invention are not particularly limited by the manufacturing method, but according to the following two manufacturing methods, the binder is unevenly distributed on the surface of the composite particles. Therefore, the composite particles according to the embodiment of the present invention can be easily obtained, which is preferable.

  The first production method is a spray-drying granulation method including a step of obtaining a slurry A containing an electrode active material, a conductive material and a binder, and a step of spray-drying and granulating the slurry A.

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

  Although it does not specifically limit as a solvent used in order to obtain the slurry A, When using said soluble resin, the solvent which can melt | dissolve soluble resin is used suitably. Specifically, 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 amides such as 2-pyrrolidone and dimethylimidazolidinone; sulfur solvents such as dimethyl sulfoxide and sulfolane; and alcohols are preferable. 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. Further, 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 the solvent used when preparing the slurry A is such that the solid content concentration of the slurry A 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 like this. When the solid content concentration is in this range, the binder is preferably dispersed uniformly. Moreover, 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.

  The method or procedure for dispersing or dissolving the electrode active material, conductive material, binder, soluble resin and other additives in a solvent is not particularly limited. For example, the electrode active material, conductive material, binder in the solvent. And a method of adding and mixing the soluble resin, after dissolving the soluble resin in the solvent, adding and mixing a binder (for example, latex) dispersed in the solvent, and finally adding the electrode active material and the conductive material. Examples thereof include a method of adding and mixing, a method of adding and mixing an electrode active material and a conductive material in a binder dispersed in a solvent, and adding and mixing a soluble resin dissolved in the 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.

  Next, the slurry A is spray-dried and granulated. The spray drying method is a method of spraying and drying a slurry in hot air. An atomizer is mentioned as an apparatus used for the spray drying method. There are two types of atomizers: a rotating disk method and a pressure method. The rotating disk system is a system in which slurry is introduced almost at the center of a disk rotating at high speed, and the slurry is released from the disk by the centrifugal force of the disk, and in that case, the slurry is dried in a mist form. The rotational speed of the disc depends on the size of the disc, but is usually 5,000 to 30,000 rpm, preferably 15,000 to 30,000 rpm. The lower the rotational speed of the disk, the larger the spray droplets and the larger the particle size of the composite particles. Examples of the rotating disk type atomizer include a pin type and a vane type, and a pin type atomizer is preferable. A pin-type atomizer is a type of centrifugal spraying device that uses a spraying plate, and the spraying plate has a plurality of spraying rollers removably mounted on a concentric circle along its periphery between upper and lower mounting disks. It consists of Slurry A is introduced from the center of the spray disc, adheres to the spraying roller by centrifugal force, moves outward on 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 a nozzle to be dried.

  The temperature of the slurry A to be sprayed is usually room temperature, but it may be heated to room temperature or higher. Moreover, the hot air temperature at the time of spray-drying is 80-250 degreeC normally, Preferably it is 100-200 degreeC. In the spray drying method, the hot air blowing method is not particularly limited, for example, a method in which the hot air and the spraying direction flow in parallel, a method in which the hot air is sprayed at the top of the drying tower and descends with the hot air, and the sprayed droplets and the hot air are countercurrently flowed. Examples include a contact method, and a method in which sprayed droplets first flow in parallel with hot air and then drop by gravity to make countercurrent contact.

  The second production method is a step of obtaining a slurry B containing a conductive material, a binder, and a soluble resin to be added as necessary and other additives, an electrode active material is flowed in a tank, The slurry B is sprayed and fluidized and granulated, and the particles obtained in the fluidized granulation are tumbled and granulated.

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 the solvent used when preparing the slurry B is such that the solid content concentration of the 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 like this. When the solid content concentration is within this range, the binder is suitable for uniform dispersion. The conductive material and the binder, and if necessary, the method or procedure for dispersing or dissolving the soluble resin in a solvent are particularly suitable. Without limitation, for example, a method of adding a conductive material, a binder, and a soluble resin to a solvent and mixing, after dissolving a soluble resin in a solvent, and then adding a binder (for example, latex) dispersed in the solvent Finally, a conductive material is added and mixed, and the conductive material is added to a dissolved resin dissolved in a solvent, mixed, and a dispersion-type binder dispersed in the solvent is added thereto. The method of mixing etc. 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 performed in the range of room temperature to 80 ° C. for 10 minutes to several hours.

  Next, the electrode active material is caused to flow in the tank, and the slurry B is sprayed thereon for fluid granulation. Examples of the method for fluid granulation in the tank include a method using a fluidized bed, a method using a modified 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 B 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 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 from a spray or the like is adhered to coarse particles using the characteristics of the spouted bed, and granulated while simultaneously drying. As a manufacturing method according to the embodiment of the present invention, a fluidized bed or a deformed fluidized bed is preferable among these three methods. The temperature of the slurry B 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.

  Particles obtained by fluid granulation (hereinafter sometimes referred to as “particle B”) may be completely dried with hot air, but in order to increase the granulation efficiency in the next rolling granulation step In addition, it is preferable that it is in a wet state.

  Next, the particles B obtained in the fluidized granulation step are tumbled and granulated in the presence of the slurry B containing a conductive material and a binder. In addition, the slurry B used for rolling granulation should just contain a electrically conductive material and a binder, and even if it is the same as the slurry B used by fluid granulation, it is different. 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 rotary coarse method, the slurry B is sprayed on the particles B supplied into the inclined rotary finer to produce an agglomerated granulated product, and a granulated product that has grown relatively large by using the classification effect of the rotary coarser. It is a method of discharging from the rim. The rotating cylinder system is a system in which wet particles B are supplied to an inclined rotating cylinder, and the particles B roll in the 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 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. In this rolling granulation step, coating granulation is mainly performed, and agglomeration granulation is partially performed.

  Although the temperature at the time of rolling granulation is not specifically limited, in order to remove the solvent which comprises the slurry B, it is normally performed at 80-300 degreeC, Preferably it is 100-200 degreeC. Furthermore, in order to remove the residual solvent from the composite particles, it can be dried as necessary after rolling granulation.

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

  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 contains other binders and other additives as necessary. 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 in the electrode material as necessary include the same binders as those used for obtaining the composite particles. Since the composite particles already contain a binder, it is not necessary to add them separately when preparing the electrode material, but the binder is prepared to increase the binding force between the composite particles, and the electrode material is prepared. You may add when you do. 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 molding aids such as water and alcohol in addition to the above-mentioned soluble resin and surfactant, and can be added by appropriately selecting an amount that does not impair the effects of the present invention.

  An electrochemical element electrode (hereinafter, simply referred to as “electrode”) according to an embodiment of the present invention is obtained by laminating an active material layer formed of the above-described electrochemical element electrode material on a current collector. It will be. 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, but forming the active material layer by directly forming the electrochemical element electrode material on the current collector. May be. 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, but a dry molding method that does not require a drying step and can reduce manufacturing costs is preferable. . 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 molded into an extruded film, sheet, or the like with an extruder.

  Among these, it is preferable to use pressure molding because it can be performed with simple equipment. As pressure molding, for example, an electrode material containing composite particles is supplied to a roll-type pressure molding apparatus with a feeder such as a screw feeder, and a roll pressure molding method for molding an active material layer, or an electrode material is used. A method of spraying on a current collector, adjusting the thickness of the electrode material with a blade, etc., and then forming with a pressurizing device, a method of filling the electrode material with a mold and pressurizing the mold, etc. There is.

  Of these pressure 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. The temperature at the time of molding 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.

  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. Furthermore, since the fluidity at room temperature is good, the supply accuracy is increased and a uniform active material layer can be obtained. Moreover, since it is hard to aggregate at room temperature, its storage characteristics are good.

  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.

Example 1
100 parts of activated carbon “Kuraray Coal RP-20” (manufactured by Kuraray Chemical Co., Ltd.) having a volume average particle diameter of 5 μm as an electrode active material, and the composition ratio of monomer units as a binder is 2-ethylhexyl acrylate: acrylonitrile: methacryl Latex (volume average particle diameter of 0.11 μm, glass transition temperature of −5 ° C.) obtained by dispersing a cross-linked acrylate polymer in water, acid: ethylene glycol dimethacrylate = 68: 28: 2: 2 (weight ratio) , Concentration 40%) 15 parts, 5 parts of acetylene black “Denka black powder” (manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, ammonium salt “DN-800H” of carboxymethyl cellulose as a soluble resin (Daicel Chemical Industries ( "TK homomixer" by adding 93.3 parts of 1.5% aqueous solution and 348.7 parts of ion-exchanged water. The slurry (I) having a solid content concentration of 20% was obtained by stirring and mixing with (Special Machine Industries Co., Ltd.). Using this slurry (I), a spray dryer “OC-16” (manufactured by Okawahara Chemical Co., Ltd.), a rotating disk type pin-type atomizer (diameter 65 mm) with a rotational speed of 20,000 rpm and a hot air temperature of 150 ° C. The particle recovery outlet was spray dried at 90 ° C. to obtain composite particles. It was 44 micrometers when the volume average particle diameter of the obtained composite particle was measured with the laser diffraction type particle size distribution measuring apparatus (SALD-2000: Shimadzu Corporation Corp. make).

  The tensile adhesion strength of the obtained composite particles was measured using “Ag Robot” (manufactured by Hosokawa Micron Corporation). That is, composite particles are filled in an aluminum upper and lower divided cell (inner diameter 25 mm) and compressed under the following conditions at a compression head speed of 0.1 mm / sec. The maximum stress during pulling was measured three times, and the average value was taken as the tensile bond strength. The measurement was performed in a room at a temperature of 25 ± 3 ° C. and a humidity of 60 ± 5%.

Condition 1. Pressure: 4.0 MPa, compression holding time: 5 seconds, temperature: 70 ° C.
Condition 2. Pressure: 0.5 MPa, compression holding time: 60 seconds, temperature: 25 ° C.
Condition 3. Pressure: 0.1 MPa, compression holding time: 60 seconds, temperature: 25 ° C.
The measurement at 70 ° C. was performed 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.

  Next, the obtained composite particles are supplied to a roll (roll temperature 120 ° C., press linear pressure 4 kN / m) of a roll press machine (pressed rough surface heat roll, manufactured by Hirano Giken Kogyo Co., Ltd.) using a quantitative feeder. Then, a sheet-like active material layer was formed by roll pressing. Molding is performed by increasing the roll speed by 1 m / min within the range of 1 to 9 m / min, and the upper limit roll speed at which the sheet-like active material layer is continuously obtained without breaking 1 m or more is maximized. It was speed. Further, 20 active material layers obtained at a molding speed of 3 m / min were randomly punched into a shape having a diameter of 12 mm, thickness and density were measured, and each variation was calculated by the following equations. The results are shown in Table 1.

Variation = standard deviation / average value × 100
Example 2
As a binder, a crosslinkable acrylate polymer having a composition ratio of monomer units of 2-ethylhexyl acrylate: acrylonitrile: methacrylic acid: ethylene glycol dimethacrylate = 86: 10: 2: 2 (weight ratio) is water. 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 −40 ° C., concentration 40%) was used.

Example 3
As the binder, the monomer unit forming the core part is 2-ethylhexyl acrylate, the monomer unit forming the shell part is ethyl methacrylate and methacrylic acid, and the composition of all monomer units Latex (volume average particle diameter 0.23 μm, core part) in which the ratio of 2-ethylhexyl acrylate: ethyl methacrylate: methacrylic acid = 81: 16: 3 (weight ratio) and a core-shell polymer dispersed in water Composite particles were obtained in the same manner as in Example 1 except that the glass transition temperature of −60 ° C., the glass transition temperature of the shell portion + 70 ° C., and the concentration of 40% were used.

Example 4
As a binder, a crosslinked acrylate polymer having a composition ratio of monomer units of 2-ethylhexyl acrylate: styrene: methacrylic acid: ethylene glycol dimethacrylate = 70: 26: 2: 2 (weight ratio) is water. Composite particles were obtained in the same manner as in Example 1 except that latex (volume average particle diameter 0.12 μm, glass transition temperature −10 ° C., concentration 40%) dispersed in was used.

Example 5
As a binder, polytetrafluoroethylene “POLYFLON D2CE” (manufactured by Daikin Chemical Industries, Ltd.), which is a fluorine-based polymer, is dispersed in water instead of a water-dispersed latex of a cross-linked acrylate polymer. Composite particles were obtained in the same manner as in Example 1 except that 9.3 parts of latex (glass transition temperature + 120 ° C., concentration 64.5%) was used.

Example 6
Composite particles were obtained in the same manner as in Example 2 except that the amount of latex obtained by dispersing a cross-linked acrylate polymer in water as a binder was 37.5 parts.

Example 7
As a binder, a crosslinkable acrylate polymer having a monomer unit composition ratio of 2-ethylhexyl acrylate: acrylonitrile: methacrylic acid: ethylene glycol dimethacrylate = 58: 38: 2: 2 (weight ratio) is water. Composite particles were obtained in the same manner as in Example 1 except that latex (volume average particle diameter of 0.11 μm, glass transition temperature of 24 ° C., concentration of 40%) was used.

Example 8
As the binder, the monomer unit forming the core part is 2-ethylhexyl acrylate, the monomer unit forming the shell part is ethyl methacrylate and methacrylic acid, and the composition of all monomer units Latex (volume average particle diameter 0.24 μm, core part) in which the ratio of 2-ethylhexyl acrylate: ethyl methacrylate: methacrylic acid = 89: 8: 3 (weight ratio) and a core-shell polymer dispersed in water Composite particles were obtained in the same manner as in Example 1 except that the glass transition temperature of −60 ° C., the glass transition temperature of the shell portion + 70 ° C., and the concentration of 40% were used.

Example 9
As the binder, the monomer unit forming the core part is ethyl acrylate, the monomer unit forming the shell part is ethyl methacrylate and methacrylic acid, and the composition ratio of all monomer units is Latex (volume average particle diameter 0.22 μm, glass transition temperature of the core part) in which a core-shell type polymer is dispersed in water with 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 -13 ° C, glass transition temperature of shell part + 70 ° C, concentration 40%) was used.

Example 10
5 parts of acetylene black as a conductive material, 37.5 parts of latex obtained by dispersing a cross-linked acrylate polymer in water as a binder, and ammonium salt “DN-10L” of carboxymethyl cellulose as a soluble resin (Daicel Chemical Industries ( 8.25 parts of a 4% aqueous dispersion of the product) and 44.67 parts of a 1.5% aqueous dispersion of the ammonium salt “DN-800H” (manufactured by Daicel Chemical Industries, Ltd.) of carboxymethyl cellulose, and 77.1 parts of ion-exchanged water was added and stirred and mixed with a Hobart mixer (Aikosha Seisakusho Co., Ltd.) to prepare slurry (II) having a solid content concentration of 8%. “Agromaster” (manufactured by Hosokawa Micron Co., Ltd.) is supplied with 100 parts of activated carbon as the electrode active material, fluidized with hot air at 80 ° C., sprayed with the slurry (II), fluidized bed granulated, and composite particles Got. The same kind of acetylene black, cross-linked acrylate polymer water-dispersed latex and activated carbon as in Example 1 were used.

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 changed to 25,000 rpm.

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 changed to 15,000 rpm.

Example 13
Fluidized bed granulation was performed 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 an opening of 155 microns was used. And sieving to obtain composite particles.

  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. Further, using these composite particles, the active material layer was molded in the same manner as in Example 1, and the maximum molding speed and the variations in thickness and density were measured. The results are shown in Table 1.

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.

Comparative Example 2
The slurry (I) obtained in Example 1 was poured into a vat, and the solids dried for 24 hours at 110 ° C. under reduced pressure in a vacuum dryer were pulverized to obtain composite particles.

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.

  The volume average particle diameter and tensile bond strength of the composite particles obtained in Comparative Examples 1 and 3 were measured in the same manner as in Example 1. Moreover, when 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, all were 1 m / min. Therefore, the active material obtained at this molding speed was used. The thickness and density variations were measured using the layers 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. Further, the obtained electrochemical device electrode had small variations in electrode thickness and electrode density.

  In addition, as long as the national laws of the designated country designated in the present international application or the selected selected country permit, a part of the description of the present specification is incorporated with the disclosure of JP 2001-176757 cited in the embodiment. And

  The present disclosure also relates to the subject matter included in Japanese Patent Application No. 2005-270713 filed on September 16, 2005, the entire disclosure of which is expressly incorporated herein by reference.

As described above, the electrochemical element electrode manufacturing method, electrochemical element electrode material, and electrochemical element electrode of the present invention are suitable for use in high-performance lithium ion secondary batteries and electric double layer capacitors.

Claims (7)

Electrochemical element electrode composite particles containing an electrode active material, a conductive material, a soluble resin, and a dispersion type binder and having a volume average particle diameter of 1 to 500 μm, and compressed at 4.0 MPa at 70 ° C. for 5 seconds tensile strength is 8000 N / m ² or more 14020N / m ² or less when the feed electrochemical device electrode material comprising an electrochemical element composite particles for an electrode, the roll pressing device using a feed device And the manufacturing method of the electrochemical element electrode including the process of carrying out roll press molding by the press linear pressure of 0.2-30 kN / cm between rolls, and forming an electrode active material layer. ^{2. The} method for producing an electrochemical element electrode according to claim 1, wherein the composite particle for an electrochemical element electrode has a tensile adhesion strength of 400 N / m ² or less when compressed at 0.1 MPa at 25 ° C. for 60 seconds. The method for producing an electrochemical element electrode according to claim 1 or 2, wherein the composite particle for an electrochemical element electrode has a tensile adhesion strength of 3,000 N / m ² or less when compressed at 0.5 MPa for 60 seconds at 25 ° C. . A method for producing composite particles for an electrochemical element 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. The electrochemical element electrode material containing the composite particle for electrochemical element electrodes as described in any one of Claims 1-3. The electrochemical element electrode formed by laminating | stacking the said electrode active material layer formed from the electrochemical element electrode material of Claim 5 on a collector. The electrochemical device electrode according to claim 6 , which is used for an electric double layer capacitor .