JP6398461B2 - Method for producing composite particle for electrochemical device electrode - Google Patents

Description

  The present invention relates to a method for producing composite particles for electrochemical device electrodes.

  The demand for electrochemical devices such as lithium-ion secondary batteries, electric double-layer capacitors, and lithium-ion capacitors is rapidly expanding by taking advantage of the small size, light weight, high energy density, and the ability to repeatedly charge and discharge. doing. Lithium ion secondary batteries have a relatively high energy density and are used in mobile fields such as mobile phones and notebook personal computers. On the other hand, since the electric double layer capacitor can be rapidly charged and discharged, the electric double layer capacitor is expected to be used as an auxiliary power source for an electric vehicle or the like in addition to being used as a memory backup small power source for a personal computer or the like. Furthermore, the lithium ion capacitor that takes advantage of the lithium ion secondary battery and the electric double layer capacitor has higher energy density and output density than the electric double layer capacitor. Application to applications that could not meet the specifications for capacitor performance is being considered. Among these, in particular, lithium ion secondary batteries have been studied for application not only to in-vehicle applications such as hybrid electric vehicles and electric vehicles, but also to power storage applications.

  While expectations for these electrochemical devices have increased, these electrochemical devices have further improvements such as lower resistance, higher capacity, and improved mechanical properties and productivity as applications expand and develop. It has been demanded. Under such circumstances, there is a demand for a more productive manufacturing method for electrochemical element electrodes.

  An electrode for an electrochemical element is usually formed by laminating an electrode active material layer formed by binding an electrode active material and a conductive material used as necessary with a binder on a current collector. is there. The electrode for an electrochemical element includes a coated electrode manufactured by a method in which a slurry for a coated electrode containing an electrode active material, a binder, a conductive material, etc. is coated on a current collector, and the solvent is removed by heat, etc. Due to migration of a binder or the like, it was difficult to produce a uniform electrochemical device. In addition, this method has a high cost and a poor working environment, and the manufacturing apparatus tends to be large.

  On the other hand, it has been proposed to obtain an electrochemical element having a uniform electrode active material layer by obtaining composite particles and powder molding. As a method for forming such an electrode active material layer, for example, Patent Document 1 discloses that composite particles are obtained by spraying and drying a slurry containing an electrode active material, a binder, and a dispersion medium, and using the composite particles. A method of forming an electrode active material layer by performing dry molding such as press molding is disclosed.

  Patent Document 2 discloses a method of forming an active material layer having a large thickness by externally adding fine particles to composite particles and controlling fluidity.

  By the way, in recent years, electrochemical elements for high output are required to have a low basis weight electrode in which the basis weight of composite particles is low when forming an electrode active material layer. In this case, it is required to stably and quantitatively supply a small amount of composite particles to the pressure molding apparatus. However, the composite particles obtained according to Patent Documents 1 and 2 are quantified in the hopper of a quantitative feeder for quantitatively supplying composite particles to a pressure forming part such as a molding roll, or in the composite particle packing process in the composite particle manufacturing process. Since there is a possibility that various hopper troubles such as a bridge and a rat hole are occasionally caused in the hopper of the feeder, it is difficult to produce an electrode having a low basis weight and a high thickness accuracy.

Japanese Patent No. 4929792 Japanese Patent No. 514002

  The objective of this invention is providing the manufacturing method of the composite particle for electrochemical element electrodes which can produce an electrode with a low basis weight and high thickness precision.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by producing composite particles with few coarse particles and / or fine particles, and have completed the present invention. .

That is, according to the present invention,
(1) A slurry preparation step of preparing a slurry containing an electrode active material and a binder, a granulation step of granulating the slurry to obtain composite particles, and a coarse from the composite particles using an in-plane kinetic sieving device A method of producing composite particles for an electrochemical element electrode, including a removal step of removing particles and / or fine particles,
(2) The method for producing composite particles for electrochemical element electrodes according to (1), wherein the total amplitude in the in-plane kinetic sieving device is 30 to 150 mm and the rotational speed is 100 to 400 r / min. The

  According to the method for producing composite particles for an electrochemical element electrode of the present invention, an electrode having a low basis weight and a high thickness accuracy can be produced.

It is the schematic of the roll press molding apparatus used for this invention.

  Hereinafter, the manufacturing method of the composite particle for electrochemical element electrodes of this invention is demonstrated. The method for producing composite particles for electrochemical device electrodes of the present invention (hereinafter sometimes referred to as “composite particles”) includes a slurry preparation step of preparing a slurry containing an electrode active material and a binder, and granulating the slurry. And a removal step of removing coarse particles and / or fine particles from the composite particles using an in-plane kinetic sieving device.

  In the following, “positive electrode active material” means an electrode active material for positive electrode, and “negative electrode active material” means an electrode active material for negative electrode. The “positive electrode active material layer” means an electrode active material layer provided on the positive electrode, and the “negative electrode active material layer” means an electrode active material layer provided on the negative electrode.

(Slurry production process)
The slurry produced in the slurry production process of the present invention includes an electrode active material and a binder.

(Electrode active material)
When the electrochemical device is a lithium ion secondary battery, the positive electrode active material is an active material that can be doped and dedoped with lithium ions, and is broadly classified into an inorganic compound and an organic compound. The

  Examples of the positive electrode active material made of an inorganic compound include transition metal oxides, transition metal sulfides, lithium-containing composite metal oxides of lithium and transition metals, and the like. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.

Transition metal oxides include MnO, MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , Cu ₂ V ₂ O ₃ , amorphous V ₂ O—P ₂ O ₅ , MoO ₃ , V ₂ O. ₅ , V ₆ O _{13 and the} like. Among them, MnO, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ are preferable from the viewpoint of cycle stability and capacity. The transition metal sulfide, TiS _2, TiS _3, amorphous MoS _2, FeS, and the like. Examples of the lithium-containing composite metal oxide include a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel structure, and a lithium-containing composite metal oxide having an olivine structure.

The lithium-containing composite metal oxide having a layered structure includes lithium-containing cobalt oxide (LiCoO ₂ ), lithium-containing nickel oxide (LiNiO ₂ ), Co—Ni—Mn lithium composite oxide, and Ni—Mn—Al lithium. Examples thereof include composite oxides and lithium composite oxides of Ni—Co—Al. Examples of the lithium-containing composite metal oxide having a spinel structure include lithium manganate (LiMn ₂ O ₄ ) and Li [Mn _3/2 M _1/2 ] O _{4 in} which a part of Mn is substituted with another transition metal (here, M may be Cr, Fe, Co, Ni, Cu or the like. Li _x MPO ₄ (wherein, M is Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, and the like) is a lithium-containing composite metal oxide having an olivine structure. An olivine type lithium phosphate compound represented by at least one selected from Si, B, and Mo, 0 ≦ X ≦ 2) may be mentioned.

  As the organic compound, for example, a conductive polymer such as polyacetylene or poly-p-phenylene can be used. An iron-based oxide having poor electrical conductivity may be used as a positive electrode active material covered with a carbon material by allowing a carbon source material to be present during reduction firing. These compounds may be partially element-substituted. The positive electrode active material may be a mixture of the above inorganic compound and organic compound.

  In the case where the electrochemical element is a lithium ion capacitor, the positive electrode active material may be any material that can reversibly carry lithium ions and anions such as tetrafluoroborate. Specifically, carbon allotropes can be preferably used, and electrode active materials used in electric double layer capacitors can be widely used. Specific examples of the allotrope of carbon include activated carbon, polyacene (PAS), carbon whisker, carbon nanotube, and graphite.

  In addition, examples of the negative electrode active material in the case where the electrochemical element is a lithium ion secondary battery include a substance that can transfer electrons in the negative electrode of the electrochemical element. As the negative electrode active material in the case where the electrochemical device is a lithium ion secondary battery, a material that can occlude and release lithium can be usually used.

  Examples of negative electrode active materials preferably used for lithium ion secondary batteries include carbonaceous materials such as amorphous carbon, graphite (natural graphite, artificial graphite), mesocarbon microbeads, pitch-based carbon fibers; Molecules; metals such as silicon, tin, zinc, manganese, iron, nickel or alloys thereof; oxides or sulfates of the metals or alloys; lithium metal; Li-Al, Li-Bi-Cd, Li-Sn-Cd And lithium alloys; lithium transition metal nitrides; silicon and the like. Further, as the negative electrode active material, a material obtained by attaching a conductive material to the surface of the negative electrode active material particles by, for example, a mechanical modification method may be used. Moreover, a negative electrode active material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Moreover, as a negative electrode active material preferably used when an electrochemical element is a lithium ion capacitor, the negative electrode active material formed with the said carbon is mentioned.

  The content of the electrode active material in the electrode active material layer can increase the capacity of the lithium ion secondary battery, and improve the flexibility of the electrode and the binding property between the current collector and the electrode active material layer. From the viewpoint of being able to achieve, it is preferably 90 to 99.9% by weight, more preferably 95 to 99% by weight.

  The volume average particle diameter of the electrode active material can be adjusted to a viscosity suitable for spraying the slurry from the viewpoint of being able to reduce the blending amount of the binder when preparing the slurry, and suppressing the decrease in battery capacity. From the viewpoint of facilitating the process and obtaining a uniform electrode, the thickness is preferably 1 to 50 μm, more preferably 2 to 30 μm.

(binder)
The binder used in the present invention is not particularly limited as long as the above-described electrode active materials can be bound to each other. As the binder, a dispersion-type binder having a property of being dispersed in a solvent can be preferably used.

  Examples of the dispersion type binder include high molecular compounds such as silicon-based polymers, fluorine-containing polymers, conjugated diene-based polymers, acrylate-based polymers, polyimides, polyamides, and polyurethanes, preferably fluorine-containing polymers, Conjugated diene polymers and acrylate polymers, more preferably conjugated diene polymers and acrylate polymers. These polymers can be used alone or in combination of two or more as a dispersion type binder.

  The fluorine-containing polymer is a polymer containing a monomer unit containing a fluorine atom. Specific examples of the fluorine-containing polymer include polytetrafluoroethylene, polyvinylidene fluoride (PVDF), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, ethylene / tetrafluoroethylene copolymer, and ethylene / chlorotrifluoroethylene copolymer. Examples thereof include a polymer and a perfluoroethylene / propene copolymer. Among these, it is preferable to include PVDF.

  The conjugated diene polymer is a homopolymer of a conjugated diene monomer or a copolymer obtained by polymerizing a monomer mixture containing a conjugated diene monomer, or a hydrogenated product thereof. As conjugated diene monomers, 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadiene It is preferable to use alkenyl, substituted and side chain conjugated hexadienes, etc., and 1,3-butadiene is used in that it can improve flexibility when used as an electrode and can have high resistance to cracking. It is more preferable. Further, the monomer mixture may contain two or more of these conjugated diene monomers.

  When the conjugated diene polymer is a copolymer of the above conjugated diene monomer and a monomer copolymerizable therewith, examples of the copolymerizable monomer include α, Examples thereof include β-unsaturated nitrile compounds and vinyl compounds having an acid component.

  Specific examples of conjugated diene polymers include conjugated diene monomer homopolymers such as polybutadiene and polyisoprene; aromatic vinyl monomers such as carboxy-modified styrene-butadiene copolymer (SBR). Monomer / conjugated diene monomer copolymer; vinyl cyanide monomer / conjugated diene monomer copolymer such as acrylonitrile / butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, etc. Is mentioned.

  The ratio of the conjugated diene monomer unit in the conjugated diene polymer is preferably 20 to 60% by weight, and more preferably 30 to 55% by weight. When the ratio of the conjugated diene monomer unit is too large, when an electrode is produced using composite particles containing a binder, the electrolytic solution resistance tends to decrease. When the ratio of the conjugated diene monomer unit is too small, there is a tendency that sufficient adhesion between the composite particles and the current collector cannot be obtained.

The acrylate polymer has the general formula (1): CH ₂ ═CR ¹ —COOR ² (wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkyl group or a cycloalkyl group. R ² further represents A monomer unit derived from a compound represented by an ether group, a hydroxyl group, a phosphate group, an amino group, a carboxyl group, a fluorine atom, or an epoxy group. Copolymer obtained by polymerizing a polymer containing, specifically, a homopolymer of a compound represented by the general formula (1) or a monomer mixture containing the compound represented by the general formula (1) It is a coalescence. Specific examples of the compound represented by the general formula (1) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylate n. -Butyl, isobutyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isopentyl (meth) acrylate, isooctyl (meth) acrylate, isobornyl (meth) acrylate, (meth) (Meth) acrylic acid alkyl esters such as isodecyl acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and tridecyl (meth) acrylate; butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate , (Meth) acrylic acid methoxydipropylene Recall, (meth) acrylic acid methoxypolyethylene glycol, (meth) acrylic acid phenoxyethyl, (meth) acrylic acid tetrahydrofurfuryl ether group-containing (meth) acrylic acid ester; (meth) acrylic acid-2-hydroxyethyl, Hydroxyl-containing (meth) acrylic such as (meth) acrylic acid-2-hydroxypropyl, (meth) acrylic acid-2-hydroxy-3-phenoxypropyl, 2- (meth) acryloyloxyethyl-2-hydroxyethylphthalic acid Acid ester; 2- (meth) acryloyloxyethylphthalic acid, carboxylic acid-containing (meth) acrylic acid ester such as 2- (meth) acryloyloxyethylphthalic acid; Fluorine such as perfluorooctylethyl (meth) acrylate Group-containing (meth) acrylic acid ester; Phosphoric acid group-containing (meth) acrylic acid esters such as ethyl phosphate; Epoxy group-containing (meth) acrylic acid esters such as glycidyl (meth) acrylate; Amino group content such as dimethylaminoethyl (meth) acrylate ( (Meth) acrylic acid ester; and the like.

  In the present specification, “(meth) acryl” means “acryl” and “methacryl”. “(Meth) acryloyl” means “acryloyl” and “methacryloyl”.

  These (meth) acrylic acid esters can be used alone or in combination of two or more. Among these, (meth) acrylic acid alkyl ester is preferable, and (meth) acrylic acid methyl, (meth) acrylic acid ethyl, and (meth) acrylic acid n-butyl and the alkyl group have 6 to 12 carbon atoms. (Meth) acrylic acid alkyl ester is more preferred. By selecting these, it becomes possible to reduce the swellability with respect to the electrolytic solution, and to improve the cycle characteristics.

  In addition, when the acrylate polymer is a copolymer of the compound represented by the general formula (1) and a monomer copolymerizable therewith, as the copolymerizable monomer, For example, carboxylic acid esters having two or more carbon-carbon double bonds, aromatic vinyl monomers, amide monomers, olefins, diene monomers, vinyl ketones, and heterocyclic rings In addition to vinyl compounds, α, β-unsaturated nitrile compounds and vinyl compounds having an acid component are mentioned.

  Among the above copolymerizable monomers, it is difficult to be deformed when an electrode is produced, and it can be strong, and sufficient adhesion between the electrode active material layer and the current collector can be obtained. It is preferable to use an aromatic vinyl monomer. Examples of the aromatic vinyl monomer include styrene.

  If the ratio of the aromatic vinyl monomer is too large, sufficient adhesion between the electrode active material layer and the current collector tends not to be obtained. Moreover, when the ratio of an aromatic vinyl-type monomer is too small, there exists a tendency for electrolyte solution resistance to fall, when manufacturing an electrode.

  The proportion of the (meth) acrylic acid ester unit in the acrylate polymer is preferably 50 to 95% by weight from the viewpoint of improving the flexibility when used as an electrode and increasing the resistance to cracking. Yes, more preferably 60 to 90% by weight.

  Examples of the α, β-unsaturated nitrile compound used in the polymer constituting the dispersion type binder include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and α-bromoacrylonitrile. These may be used alone or in combination of two or more. Among these, acrylonitrile and methacrylonitrile are preferable, and acrylonitrile is more preferable.

  The proportion of the α, β-unsaturated nitrile compound unit in the dispersion type binder is preferably 0.1 to 40% by weight, more preferably 0.5 to 30% by weight, and further preferably 1 to 20% by weight. . When an α, β-unsaturated nitrile compound unit is contained in the dispersion type binder, it is difficult to be deformed when the electrode is manufactured, and the strength can be increased. Further, when an α, β-unsaturated nitrile compound unit is contained in the dispersion-type binder, the adhesion between the electrode active material layer containing composite particles and the current collector can be made sufficient.

  If the proportion of α, β-unsaturated nitrile compound units is too large, sufficient adhesion between the electrode active material layer and the current collector tends not to be obtained. On the other hand, if the proportion of the α, β-unsaturated nitrile compound unit is too small, the resistance to the electrolytic solution tends to decrease when the electrode is produced.

  Examples of the vinyl compound having an acid component include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid. These may be used alone or in combination of two or more. Among these, acrylic acid, methacrylic acid, and itaconic acid are preferable, and methacrylic acid is more preferable in terms of improving adhesive strength.

  The proportion of the vinyl compound unit having an acid component in the dispersion type binder is preferably 0.5 to 10% by weight, more preferably 1 to 8% by weight, and more preferably 1 to 8% by weight, from the viewpoint of improving the stability in the slurry. Preferably it is 2-7 weight%.

  In addition, when there are too many ratios of the vinyl compound unit which has an acid component, there exists a tendency for the viscosity of a slurry to become high and for handling to become difficult. Moreover, when there is too little ratio of the vinyl compound unit which has an acid component, there exists a tendency for stability of a slurry to fall.

  The shape of the dispersion-type binder is not particularly limited, but is preferably particulate. By being particulate, the binding property is good, and it is possible to suppress deterioration of the capacity of the manufactured electrode and deterioration due to repeated charge and discharge. Examples of the particulate binder include those in which binder particles such as latex are dispersed in water, and powders obtained by drying such a dispersion.

  The average particle size of the dispersion-type binder is preferably 0.001 to 10 μm, more preferably from the viewpoint that the strength and flexibility of the obtained electrode are good while making the stability when slurry is good. It is 10-5000 nm, More preferably, it is 50-1000 nm.

  Moreover, the manufacturing method of the binder used for this invention is not specifically limited, Well-known polymerization methods, such as an emulsion polymerization method, suspension polymerization method, dispersion polymerization method, or solution polymerization method, are employable. Among these, it is preferable to produce by an emulsion polymerization method because it is easy to control the particle diameter of the binder. In addition, the binder used in the present invention may be particles having a core-shell structure obtained by stepwise polymerization of a mixture of two or more monomers.

  From the viewpoint that the compounding amount of the binder in the composite particles of the present invention can sufficiently ensure the adhesion between the obtained electrode active material layer and the current collector, and can reduce the internal resistance of the electrochemical element, Preferably it is 0.1-20 weight part with respect to 100 weight part of electrode active materials on a dry weight basis, More preferably, it is 0.5-10 weight part, More preferably, it is 1-5 weight part.

(Water-soluble polymer)
The slurry used in the present invention preferably contains a water-soluble polymer. The water-soluble polymer used in the present invention refers to a polymer having an undissolved content of less than 10.0% by weight when 25 g of polymer is dissolved in 100 g of pure water at 25 ° C.

  Specific examples of the water-soluble polymer include cellulosic polymers such as carboxymethylcellulose, methylcellulose, ethylcellulose and hydroxypropylcellulose, and ammonium salts or alkali metal salts thereof, alginates such as propylene glycol alginate, and sodium alginate. Alginate, polyacrylic acid, and polyacrylic acid (or methacrylic acid) salts such as sodium polyacrylic acid (or methacrylic acid), polyvinyl alcohol, modified polyvinyl alcohol, poly-N-vinylacetamide, polyethylene oxide, polyvinylpyrrolidone, poly Carboxylic acid, oxidized starch, phosphate starch, casein, various modified starches, chitin, chitosan derivatives, etc.Moreover, you may use in combination with a water-insoluble polysaccharide polymer, and the reinforcement effect of a composite particle is acquired by doing so.

  Here, as the water-insoluble polysaccharide polymer fiber, it is preferable to use polysaccharide polymer nanofibers, which are flexible among the polysaccharide polymer nanofibers and have a high tensile strength. From the viewpoint of high particle reinforcing effect, improved particle strength, and good dispersibility of conductive material, from bio-derived bio-nanofibers such as cellulose nanofiber, chitin nanofiber, chitosan nanofiber, etc. It is more preferred to use a single selected or arbitrary mixture. Among these, it is more preferable to use cellulose nanofibers, and it is particularly preferable to use cellulose nanofibers made from bamboo, conifers, hardwoods, and cotton.

(Conductive material)
The slurry used for this invention may contain the electrically conductive material as needed. Conductive materials used as necessary include furnace black, acetylene black (hereinafter sometimes abbreviated as “AB”), and ketjen black (registered trademark of Akzo Nobel Chemicals Bethloten Fennaut Shap), carbon Conductive carbon such as nanotubes, carbon nanohorns, and graphene is preferably used. Among these, acetylene black is more preferable. The average particle diameter of the conductive material is not particularly limited, but is preferably smaller than the average particle diameter of the electrode active material, preferably 0.001 to 10 μm, from the viewpoint of expressing sufficient conductivity with a smaller amount of use. More preferably, it is 0.005-5 micrometers, More preferably, it is 0.01-1 micrometer.
The amount of the conductive material in the case of adding the conductive material is preferably 1 to 10 parts by weight, more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the electrode active material.

(Other additives)
The composite particles of the present invention may further contain other additives as necessary. Examples of other additives include surfactants. Examples of the surfactant include amphoteric surfactants such as anionic, cationic, nonionic, and nonionic anions. Among these, anionic or nonionic surfactants are preferable. The compounding amount of the surfactant is not particularly limited, but in the composite particles, it is preferably 0 to 50 parts by weight, more preferably 0.1 to 10 parts by weight, and still more preferably 0 to 100 parts by weight of the electrode active material. .5 to 5 parts by weight. By adding the surfactant, the surface tension of the droplets obtained from the slurry can be adjusted.

(Slurry production method)
The slurry used in the present invention contains an electrode active material, a binder, a water-soluble polymer added as necessary, and a conductive material. The slurry can be prepared by dispersing or dissolving an electrode active material, a binder, a water-soluble polymer added as necessary, and a conductive material in a solvent. In this case, when the binder is dispersed in a solvent, it can be added in a state dispersed in a solvent.

  As a solvent used for obtaining the slurry, water is preferably used, but a mixed solvent of water and an organic solvent may be used, or only an organic solvent may be used alone or in combination of several kinds. Examples of the organic solvent that can be used in this case include 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, dimethyl Amides such as acetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone; and the like. When using an organic solvent, alcohols are preferred. Thereby, the viscosity and fluidity | liquidity of a slurry can be adjusted and production efficiency can be improved.

  In addition, the viscosity of the slurry is preferably 10 to 3,000 mPa · s, more preferably 30 to 1,500 mPa · s, more preferably at room temperature, from the viewpoint of improving the productivity of the composite particles by spray drying granulation. 50 to 1,000 mPa · s.

In addition, the viscosity described in this specification is a viscosity at 25 ° C. and a shear rate of 10 s ⁻¹ . Measurement is possible using a Brookfield digital viscometer DV-II + Pro.

  From the viewpoint of uniformly dispersing the binder in the slurry, the amount of the solvent used when preparing the slurry is preferably 1 to 50% by weight, more preferably 5 to 50% by weight, and more preferably 5% to 50% by weight. The amount is preferably 10 to 40% by weight.

  The method or order of dispersing or dissolving the electrode active material, binder, water-soluble polymer and conductive material added as necessary in the solvent is not particularly limited. For example, the electrode active material, binder, water-soluble in the solvent A method of adding and mixing a polymer and a conductive material. After dissolving a water-soluble polymer in a solvent, an electrode active material and a conductive material are added and mixed, and finally a binder (for example, latex) dispersed in a solvent is added. Examples thereof include a method of adding and mixing, a method of adding and mixing an electrode active material and a conductive material to a binder dispersed in a solvent, and adding and mixing a water-soluble polymer dissolved in a solvent to the mixture. .

  Moreover, as a mixing apparatus, a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a homomixer, a planetary mixer, etc. can be used, for example. The mixing is preferably performed at room temperature to 80 ° C. for 10 minutes to several hours.

(Granulation process)
In the granulation step of the present invention, the slurry obtained in the slurry preparation step is granulated to obtain composite particles. “Granulation” of the slurry consists of removing a solvent from the slurry and drying, and an electrode active material that is a component of the slurry, a binder, and a plurality of conductive material particles added as necessary, It is a manufacturing process of composite particles including both forming composite particles containing a water-soluble polymer added as necessary.

  The granulation method of the slurry in the granulation step is not particularly limited, but is spray drying granulation method, spray coagulation granulation method, fluidized bed granulation method, rolling bed granulation method, compression type granulation method, stirring type granulation Manufacturing methods such as a method, an extrusion granulation method, a crushing granulation method, a fluidized bed multifunctional granulation method, and a melt granulation method can be employed.

The production method of the composite particles may be appropriately selected from the viewpoints of ease of particle size control, productivity, ease of control of particle size distribution, etc. according to the components of the composite particles, etc. The spray-drying granulation method described in 1 is preferable because the composite particles can be produced relatively easily.
Hereinafter, the spray drying granulation method will be described.

  The spray-drying granulation method is a method of spraying and drying a slurry in hot air. An atomizer is used as an apparatus used for spraying slurry. Atomizers include devices such as a rotating disk method, cup method, two-fluid nozzle method, and pressure method. The rotating disk method and cup method introduce slurry into the center of the disk that rotates at high speed, and centrifuge the disk. This is a system in which the slurry is released out of the disk by force and the slurry is atomized at that time. In the rotating disk system, the rotational speed of the disk depends on the size of the disk, but is preferably 5,000 to 30,000 rpm, more preferably 15,000 to 30,000 rpm. The lower the rotational speed of the disk, the larger the spray droplets and the larger the average particle size of the resulting 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 The slurry is introduced from the center of the spray platen, adheres to the spraying roller by centrifugal force, moves outside the roller surface, and finally sprays away from the roller surface.

  The cup-type atomizer used in the cup system introduces slurry into the cup at the tip of the atomizer that rotates at a predetermined number of revolutions and discharges it from the end of the cup while applying rotational force to the slurry, thereby spraying the slurry with centrifugal force. It is configured to obtain mist-like droplets. Moreover, although the direction of a cup has an upward direction and a downward direction, it is not restricted to any one of them, and favorable atomization is possible for both.

  The rotational speed of the disk or cup in the rotating disk system or the cup system is not particularly limited, but is preferably 5,000 to 40,000 rpm, more preferably 15,000 to 30,000 rpm. The lower the rotational speed of the disk or cup, the larger the spray droplets and the larger the average particle size of the resulting composite particles.

  Moreover, a pressurization system is a system which pressurizes a slurry and makes a slurry mist form from a nozzle.

  Alternatively, droplets may be generated from the slurry by using an electrostatic atomization method. That is, the slurry may be sprayed by electrostatic spraying.

  The temperature of the slurry to be sprayed is preferably room temperature, but may be heated to a temperature higher than room temperature. Moreover, the hot air temperature at the time of spray-drying becomes like this. Preferably it is 25-250 degreeC, More preferably, it is 50-200 degreeC, More preferably, it is 80-150 degreeC. 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 side by side, the 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 hot air flow countercurrently. Examples include a contact method, and a method in which sprayed droplets first flow in parallel with hot air, then drop by gravity and contact countercurrent.

  The spray coagulation granulation method is a method of obtaining spherical or granular composite particles by bringing droplets obtained by spraying a slurry into contact with a coagulation liquid. In addition, as a spraying method of the slurry in the spray coagulation granulation method, a spraying method similar to the spraying method that can be used in the spray drying granulation method can be used.

(Removal process)
In the present invention, coarse particles and / or fine particles are removed from the composite particles obtained in the granulation step using an in-plane motion sieving device. As the in-plane motion type sieving, sieving using a sieving screen, such as those that vibrate only in the horizontal direction, there is no vertical vibration component at the time of sieving, or a sieving method that is so small that it can be ignored, Examples include a method of sieving the composite particles softly by three-dimensional movement combining axial eccentric radial inclination and tangential inclination.

  The total amplitude in the in-plane kinetic sieving is preferably 30 to 150 mm, more preferably 40 to 120 mm, and still more preferably 50 to 90 mm. If the total amplitude in the in-plane kinetic sieving is too large, the composite particles are destroyed by collision between the particles or the apparatus wall surface, and the particle size distribution becomes broad. In addition, if the total amplitude in the in-plane kinetic sieving is too small, in the coarse particle removal process, the ability of the composite particles obtained in the granulation process to pass through the sieve is reduced, and composite particles other than the coarse particles are also removed. Therefore, loss increases. In the fine particle removal step, the ability of the composite particles obtained in the granulation step to pass through the sieve is reduced, and the fine particles remain in the composite particles as product particles, so the particle size distribution becomes broad. As a result, the basis weight accuracy and thickness accuracy deteriorate.

  Moreover, the rotation speed in the in-plane kinetic sieving is preferably 100 to 400 r / min, more preferably 150 to 350 r / min, and still more preferably 200 to 300 r / min. If the number of rotations in the in-plane kinetic sieving is too large, the composite particles are destroyed by collision between the particles or the apparatus wall surface, and the particle size distribution becomes broad. As a result, the basis weight accuracy and thickness accuracy deteriorate. In addition, if the rotational speed in the in-plane kinetic sieving is too small, in the coarse particle removal step, the ability of the composite particles obtained in the granulation step to pass through the sieve is reduced, and composite particles other than the coarse particles are also removed. Therefore, loss increases. In the fine particle removal step, the ability of the composite particles obtained in the granulation step to pass through the sieve is reduced, and the fine particles remain in the composite particles as product particles, so the particle size distribution becomes broad. As a result, the basis weight accuracy and thickness accuracy deteriorate.

  In addition, as a method for removing coarse particles and / or fine particles, a method other than in-plane kinetic sieving such as vibration sieving, wind sieving, dry classification (centrifugal force classification, gravity classification, inertial classification), When sieving is performed, the load on the composite particles is large and the composite particles are destroyed. On the other hand, when sieving by the in-plane motion method is performed, since the load on the composite particles is small, coarse particles and / or fine particles can be efficiently removed without destroying the composite particles.

  In the removing step, coarse particles and / or fine particles can be removed by using a desired mesh screen.

(Physical properties of composite particles)
The shape of the composite particles of the present invention is substantially spherical from the viewpoint of good fluidity and prevention of hopper troubles, good supply of composite particles from the hopper, and the ability to obtain an electrode with good thickness accuracy. Preferably there is. That is, when the minor axis diameter of the composite particle is ls, the major axis diameter is ll, and la = (ls + ll) / 2, the sphericity (%) represented by (ll−ls) × 100 / la is preferably 15 % Or less, more preferably 13% or less, still more preferably 12% or less, and most preferably 10% or less. Here, the minor axis diameter ls and the major axis diameter ll can be measured from a photographic image of a transmission electron microscope or a scanning electron microscope. When the sphericity is too large, the fluidity of the composite particles is deteriorated, and hopper trouble is likely to occur. In addition, the basis weight accuracy of the electrode deteriorates, and it becomes difficult to obtain an electrode with good thickness accuracy.

  The particle size of the composite particles of the present invention is such that the fluidity of the composite particles is good, hopper troubles are unlikely to occur, and further, from the viewpoint of obtaining a uniform electrode with high thickness accuracy, the particle size using laser light diffraction / scattering method In the particle size distribution in terms of the number obtained by measurement, particles having a size of 40 μm or less are preferably 50% or less of the whole, more preferably 40% or less, still more preferably 10% or less, and particularly preferably 5% or less. The particle size distribution can be obtained by measuring with a laser diffraction / scattering particle size distribution measuring apparatus (for example, SALD-3100; manufactured by Shimadzu Corporation, Microtrac MT-3200II; manufactured by Nikkiso Co., Ltd.).

  If the proportion of particles of 40 μm or less is too large in the particle size distribution in terms of number, the fluidity of the composite particles is deteriorated, and hopper troubles are likely to occur. Moreover, the thickness accuracy of the obtained electrode deteriorates.

  Further, the particle diameter of the composite particles of the present invention is good in fluidity and can prevent hopper troubles. In addition, the composite particles are supplied from the hopper, and from the viewpoint of obtaining an electrode with good thickness accuracy, laser light diffraction is performed. -In a volume conversion particle size distribution obtained by particle size measurement using a scattering method, the cumulative 95% size (D95 size) is preferably 300 µm or less, more preferably 40 to 250 µm, still more preferably 50 to 225 µm, particularly preferably. Is 60-200 μm.

  If the cumulative 95% diameter (D95 diameter) is too large in the volume-converted particle size distribution, there are many coarse particles in the composite particles, resulting in uneven thickness when the electrode active material layer is formed. Further, if the cumulative 95% diameter (D95 diameter) is too small in the volume-converted particle size distribution, the fluidity of the composite particles is deteriorated, and hopper troubles are likely to occur. In addition, thickness unevenness occurs when the electrode active material layer is formed.

  The particle diameter of the composite particles of the present invention is preferably 50 to 160 μm in cumulative 50% diameter (D50 diameter) in a volume-converted particle diameter distribution obtained by particle diameter measurement using a laser light diffraction / scattering method. More preferably, it is 50-130 micrometers, More preferably, it is 50-110 micrometers.

  The compressibility of the composite particles of the present invention is such that the fluidity of the composite particles is good and hopper troubles can be prevented, and the composite particles are supplied from the hopper and an electrode with good thickness accuracy can be obtained. Therefore, it is preferably 15% or less. If the compression degree of the composite particles is too large, the fluidity of the composite particles is deteriorated, so that a hopper trouble is likely to occur, and the thickness accuracy of the obtained electrode is deteriorated. The degree of compression can be measured using a powder physical property measuring apparatus such as a powder tester-PT-S type manufactured by Hosokawa Micron Corporation.

(Electrochemical element electrode)
An electrochemical element electrode can be obtained by laminating an electrode active material layer containing the composite particle for an electrochemical element electrode of the present invention on a current collector. As a material for the current collector, for example, metal, carbon, conductive polymer, and the like can be used, and metal is preferably used. As the metal, copper, aluminum, platinum, nickel, tantalum, titanium, stainless steel, other alloys and the like are usually used. Among these, it is preferable to use copper, 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 preferably 1 to 200 μm, more preferably 5 to 100 μm, and still more preferably 10 to 50 μm.

  When laminating the electrode active material layer on the current collector, the composite particles may be formed into a sheet shape and then laminated on the current collector. However, the composite particles may be directly pressed on the current collector. Is preferred. As a method of pressure molding, for example, a roll type pressure molding apparatus having a pair of rolls is used, and the composite particles are rolled by a feeding device such as a vibration feeder or a screw feeder while feeding the current collector by the roll. By supplying to the pressure forming device, roll press molding method for forming the electrode active material layer on the current collector, or by dispersing the composite particles on the current collector and smoothing the composite particles with a blade etc. Examples include a method of adjusting and then molding with a pressurizing apparatus, a method of filling composite particles into a mold, and pressurizing and molding the mold. Among these, the roll pressure molding method is preferable. In particular, since the composite particles of the present invention have high fluidity, they can be molded by roll press molding due to the high fluidity, thereby improving productivity.

  The roll temperature at the time of roll pressing is preferably 10 to 100 ° C, more preferably 20 to 60 ° C, and still more preferably 20 to 50 ° C in order to produce a uniform electrode. Moreover, from a viewpoint which can make adhesiveness of an electrode active material layer and an electrical power collector sufficient, Preferably it is 25-200 degreeC, More preferably, it is 50-150 degreeC, More preferably, it is 80-120 degreeC. . When a preferable temperature region for producing a uniform electrode and a preferable temperature region for improving adhesion do not overlap, it is possible to make them compatible by roll pressing in multiple stages. Moreover, the press linear pressure between rolls at the time of roll press molding is preferably 10 to 1000 kN / m, more preferably 200 to 900 kN / m, and still more preferably 300 to 600 kN / m, from the viewpoint of preventing destruction of the electrode active material. m. Moreover, the molding speed at the time of roll pressure molding is preferably 0.1 to 20 m / min, more preferably 4 to 10 m / min.

  Further, post-pressurization may be further performed as necessary in order to eliminate variations in the thickness of the formed electrochemical element electrode and increase the density of the electrode active material layer to increase the capacity. The post-pressing method is preferably a pressing process using a roll. In the roll pressing step, two cylindrical rolls are arranged vertically in parallel with a narrow interval, each is rotated in the opposite direction, and pressure is applied by interposing an electrode therebetween. In this case, the temperature of the roll may be adjusted as necessary, such as heating or cooling.

  Moreover, in order to improve the adhesive strength and electroconductivity of an electrode active material layer, you may form an intermediate | middle layer in the collector surface, and it is preferable to form a conductive adhesive layer especially.

The density of the electrode active material layer is not particularly limited, but is usually 0.30 to 10 g / cm ³ , preferably 0.35 to 8.0 g / cm ³ , more preferably 0.40 to 6.0 g / cm ^3. It is. The thickness of the electrode active material layer is not particularly limited, but is usually 5 to 1000 μm, preferably 20 to 500 μm, more preferably 30 to 300 μm.

(Electrochemical element)
The electrochemical element of the present invention includes the positive electrode, the negative electrode, the separator and the electrolytic solution obtained as described above, and uses the electrochemical element electrode of the present invention for at least one of the positive electrode and the negative electrode. Examples of the electrochemical element include a lithium ion secondary battery and a lithium ion capacitor.

(separator)
As the separator, for example, a polyolefin resin such as polyethylene or polypropylene, or a microporous film or nonwoven fabric containing an aromatic polyamide resin; a porous resin coat containing an inorganic ceramic powder; Specific examples include microporous membranes made of polyolefin resins (polyethylene, polypropylene, polybutene, polyvinyl chloride), and resins such as mixtures or copolymers thereof; polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, Examples thereof include a microporous film made of a resin such as polyimide, polyimide amide, polyaramid, polycycloolefin, nylon, and polytetrafluoroethylene; a polyolefin fiber woven or non-woven fabric thereof; an aggregate of insulating substance particles, and the like. Among these, since the film thickness of the entire separator can be reduced and the active material ratio in the lithium ion secondary battery can be increased to increase the capacity per volume, a microporous film made of polyolefin resin is used. preferable.

  The thickness of the separator is preferably 0.5 to 40 μm from the viewpoint of reducing the internal resistance due to the separator in the lithium ion secondary battery and excellent workability when manufacturing the lithium ion secondary battery. More preferably, it is 1-30 micrometers, More preferably, it is 1-25 micrometers.

(Electrolyte)
As an electrolytic solution for a lithium ion secondary battery, for example, a nonaqueous electrolytic solution in which a supporting electrolyte is dissolved in a nonaqueous solvent is used. As the supporting electrolyte, a lithium salt is preferably used. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi , (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and the like. Among these, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferable. One of these may be used alone, or two or more of these may be used in combination at any ratio. Since the lithium ion conductivity increases as the supporting electrolyte having a higher degree of dissociation is used, the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.

  The concentration of the supporting electrolyte in the electrolytic solution is preferably used at a concentration of 0.5 to 2.5 mol / L depending on the type of the supporting electrolyte. If the concentration of the supporting electrolyte is too low or too high, the ionic conductivity may decrease.

  The non-aqueous solvent is not particularly limited as long as it can dissolve the supporting electrolyte. Examples of non-aqueous solvents include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), methyl ethyl carbonate (MEC); Examples include esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; and ionic liquids used also as supporting electrolytes. Among these, carbonates are preferable because they have a high dielectric constant and a wide stable potential region. A non-aqueous solvent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. In general, the lower the viscosity of the non-aqueous solvent, the higher the lithium ion conductivity, and the higher the dielectric constant, the higher the solubility of the supporting electrolyte, but since both are in a trade-off relationship, the lithium ion conductivity depends on the type of solvent and the mixing ratio. It is recommended to adjust the conductivity. In addition, the nonaqueous solvent may be used in combination or in whole or in a form in which all or part of hydrogen is replaced with fluorine.

Moreover, you may contain an additive in electrolyte solution. Examples of the additive include carbonates such as vinylene carbonate (VC); sulfur-containing compounds such as ethylene sulfite (ES); and fluorine-containing compounds such as fluoroethylene carbonate (FEC).
An additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.
In addition, as an electrolyte solution for lithium ion capacitors, the same electrolyte solution that can be used for the above-described lithium ion secondary battery can be used.

(Method for producing electrochemical element)
As a specific method for producing an electrochemical element such as a lithium ion secondary battery or a lithium ion capacitor, for example, a positive electrode and a negative electrode are overlapped via a separator, and this is wound or folded according to the shape of the battery. Examples of the method include putting the battery in a battery container, injecting an electrolyte into the battery container, and sealing. Further, if necessary, an expanded metal; an overcurrent prevention element such as a fuse or a PTC element; a lead plate or the like may be inserted to prevent an increase in pressure inside the battery or overcharge / discharge. The shape of the lithium ion secondary battery may be any of a coin type, a button type, a sheet type, a cylindrical type, a square type, a flat type, and the like. The material of the battery container is not particularly limited as long as it inhibits the penetration of moisture into the battery, and is not particularly limited, such as a metal or a laminate such as aluminum.

  According to the method for producing composite particles for an electrochemical element electrode of the present invention, an electrode having a low basis weight and a high thickness accuracy can be produced.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and may be arbitrarily changed without departing from the gist and equivalent scope of the present invention. Can be implemented. In the following description, “%” and “parts” representing amounts are based on weight unless otherwise specified.

  In the examples and comparative examples, the basis weight accuracy, the appearance of the electrode, and the thickness accuracy were evaluated as follows.

<Weight accuracy>
About electrodes cut in the width direction (TD direction) 10 cm and the length direction (MD direction) 1 m after cutting the electrodes (lithium ion secondary battery negative electrode or lithium ion secondary battery positive electrode) prepared in Examples and Comparative Examples , 3 points equally in the TD direction and 5 points equally in the MD direction, a total of 15 points (= 3 points x 5 points) was measured in a 2 cm ² punch weight, and the weight of the current collector foil was measured from the punched electrodes. The average value A and the value B farthest from the average value were obtained by subtracting the thickness. The basis weight unevenness was calculated from the average value A and the farthest value B according to the following formula (1), and the moldability was evaluated according to the following criteria. It can be determined that the smaller the unevenness of basis weight, the better the uniformity of the electrode and the better the basis weight accuracy.
Unevenness per unit area (%) = (| A−B |) × 100 / A (1)
A: Unevenness per unit area is less than 5% B: Unevenness per unit area is 5% or more and less than 10% C: Unevenness per unit area is 10% or more and less than 15% D: Unevenness per unit area is 15% or more E: There is a hole in the electrode layer

<Appearance of electrode>
The appearance of the electrodes (lithium ion secondary battery negative electrode or lithium ion secondary battery positive electrode) produced in the examples and comparative examples was inspected, and it was confirmed that there was no defect such as chipping or scraping. In addition, it was determined that there was a chipping when a streak pattern was seen on the surface, and a chip was found when a crater, a crack, or a portion where the current collector was exposed.

<Thickness accuracy>
In the above-described appearance inspection of the electrodes (lithium ion secondary battery negative electrode or lithium ion secondary battery positive electrode) produced in the examples and comparative examples, a portion where no chipping or blurring is observed is cut to 2 m in the longitudinal direction, and the width direction The film thickness is measured at 3 points evenly from the center of the (TD direction) at 5 cm intervals and at 10 cm intervals uniformly in the length direction (MD direction), and is the most distant from the average value A and the average value. B was determined. Then, from the average value A and the farthest value B, thickness unevenness was calculated according to the following formula (2), and formability was evaluated according to the following criteria. It can be determined that the smaller the thickness unevenness, the better the thickness uniformity, that is, the thickness accuracy.
Unevenness of thickness (%) = (| A−B |) × 100 / A (2)
A: Thickness variation is less than 2.5% B: Thickness variation is 2.5% or more and less than 5.0% C: Thickness variation is 5.0% or more and less than 7.5% D: Thickness variation is 7.5 % Or more and less than 10% E: thickness unevenness is 10% or more

Example 1
(Manufacture of binder)
In a 5 MPa pressure vessel with a stirrer, 62 parts of styrene, 34 parts of 1,3-butadiene, 3 parts of methacrylic acid, 4 parts of sodium dodecylbenzenesulfonate, 150 parts of ion-exchanged water, 0.4 part of t-dodecyl mercaptan as a chain transfer agent Then, 0.5 part of potassium persulfate was added as a polymerization initiator, and after sufficiently stirring, the mixture was heated to 50 ° C. to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain particulate binder S (styrene / butadiene copolymer; hereinafter abbreviated as “SBR”).

(Preparation of slurry)
Artificial graphite (average particle diameter: 24.5 μm, graphite interlayer distance (interval of (002) plane by X-ray diffraction (d value)): 0.354 nm as negative electrode active material, 100 parts of the above particulate binder 1 part in terms of solid content and 1 part in terms of solid content of carboxymethyl cellulose (BSH-12; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (hereinafter sometimes referred to as “CMC”) as a water-soluble polymer. Further, ion-exchanged water was added so as to have a solid content concentration of 35 wt%, and mixed and dispersed to obtain a slurry.

(Manufacture of composite particles)
The slurry was supplied at 255 mL / min to a spray dryer (Okawara Chemical Co., Ltd.) using a pin type atomizer (diameter 84 mm) of a rotating disk system, rotating at 17,000 rpm, hot air temperature 150 ° C., and particle recovery outlet Spray drying granulation was performed at a temperature of 90 ° C. The obtained composite particles had a volume average particle diameter of 85 μm.

(Composite particle removal process)
The composite particles obtained above are sieved using an in-plane motion type sieving device with an effective mesh area of 0.3 m ² under conditions of a total amplitude of 70 mm, a rotational speed of 250 r / min, and a sieve mesh opening of 135 μm. Coarse particles were removed. Subsequently, sieving was carried out under the conditions of a total amplitude of 70 mm, a rotational speed of 250 r / min, and a sieve mesh opening of 75 μm, and fine particles were removed to obtain composite particles for a negative electrode.

(Preparation of negative electrode for lithium ion secondary battery)
The negative electrode of the lithium ion secondary battery was manufactured using the roll press molding apparatus shown in FIG. Here, as shown in FIG. 1, the roll press-molding apparatus 2 compresses the hopper 4 and the composite particles 6 supplied to the hopper 4 through the quantitative feeder 16 into the current collector foil 8 with the conductive adhesive layer. A pre-molding roll 10 comprising a pair of rolls (10A, 10B), a molding roll 12 comprising a pair of rolls (12A, 12B) for further pressing a pre-molded body formed by the pre-molding roll 10, and a pair of rolls (14A) , 14B).

First, the collector foil 8 with a conductive adhesive layer was installed on a pair of pre-molded rolls 10 (rolls 10A and 10B) having a roll diameter of 50 mmφ heated to 50 ° C. in the roll pressure molding apparatus 2. Here, the collector foil 8 with a conductive adhesive layer is a copper collector foil with a conductive adhesive layer obtained by applying a conductive adhesive on a copper collector with a die coater and drying. Next, the composite particles obtained above were supplied as composite particles 6 to the hopper 4 provided on the upper part of the pre-molding roll 10 via the quantitative feeder 16. When the accumulated amount of the composite particles 6 in the hopper 4 provided on the upper part of the pre-molding roll 10 reaches a certain height, the roll press molding apparatus 2 is operated at a speed of 10 m / min, and the pre-molding is performed. The composite particles 6 were pressure-formed with a roll 10 to form a pre-formed body of a negative electrode active material layer on the copper current collector foil with the conductive adhesive layer. Thereafter, the electrode on which the negative electrode active material layer is pre-formed is pressed with two pairs of 300 mmφ forming rolls 12 and 14 provided downstream of the pre-forming roll 10 of the roll pressure forming apparatus 2 and heated to 100 ° C. The surface of the electrode was leveled and the electrode density was increased. In this state, the roll pressure forming apparatus 2 was continuously operated for 10 minutes to produce about 100 m of a lithium ion secondary battery negative electrode.
(Example 2)
(Manufacture of binder)
In a reactor equipped with a mechanical stirrer and a condenser, 210 parts of deionized water and 30% alkyl diphenyl oxide disulfonate (Dowfax (registered trademark) 2A1, manufactured by Dow Chemical Co.) in a nitrogen atmosphere Then, 1.67 parts were charged and heated to 70 ° C. with stirring, and 25.5 parts of a 1.96% aqueous potassium persulfate solution was added to the reactor. Next, in a container different from the above equipped with a mechanical stirrer, in a nitrogen atmosphere, 35 parts of butyl acrylate, 62.5 parts of ethyl methacrylate, 2.4 parts of methacrylic acid, 30% alkyl diphenyl oxide disulfonate ( Dowfax (registered trademark) 2A1, manufactured by Dow Chemical Co., Ltd.), 1.67 parts in terms of solid content, and 22.7 parts of deionized water are added, and this is stirred and emulsified to obtain a monomer mixture. Was prepared. Then, this monomer mixture is stirred and emulsified, and added to a reactor charged with 210 parts of deionized water and an aqueous potassium persulfate solution at a constant rate over 2.5 hours, and polymerized. The reaction was carried out until the conversion rate reached 95% to obtain an aqueous dispersion of particulate binder A (acrylate polymer).

(Preparation of slurry)
LiCoO ₂ as a positive electrode active material (hereinafter sometimes referred to as “LCO”) 100 parts, acetylene black as a conductive material (HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) (hereinafter sometimes referred to as “AB”). ) 4 parts, 1 part of an aqueous dispersion of a particulate binder A (acrylate polymer) as a binder, in terms of solid content, solid carboxymethyl cellulose (BSH-12; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a water-soluble polymer One part was mixed in terms of a fraction, and an appropriate amount of ion-exchanged water was added, followed by mixing and dispersing with a planetary mixer to prepare a positive electrode slurry having a solid content concentration of 50%.

(Manufacture of composite particles)
The slurry was supplied at 255 mL / min to a spray dryer (Okawara Chemical Co., Ltd.) using a pin type atomizer (diameter 84 mm) of a rotating disk system, rotating at 17,000 rpm, hot air temperature 150 ° C., and particle recovery outlet Spray drying granulation was performed at a temperature of 90 ° C. The obtained composite particles had a volume average particle diameter of 55 μm.

(Composite particle removal process)
The composite particles obtained above are sieved using an in-plane kinetic sieving device with an effective mesh area of 0.3 m ² under the conditions of a total amplitude of 70 mm, a rotational speed of 250 r / min, and a sieve mesh opening of 150 μm. Coarse particles were removed. Subsequently, sieving was carried out under the conditions of a total amplitude of 70 mm, a rotational speed of 250 r / min, and a sieve mesh opening of 45 μm, and fine particles were removed to obtain composite particles for a positive electrode.

(Preparation of lithium ion secondary battery positive electrode)
First, the collector foil 8 with a conductive adhesive layer was placed on a pair of pre-molded rolls 10 (rolls 10A and 10B) having a roll diameter of 50 mmφ heated to 50 ° C. in the roll pressure molding apparatus 2 shown in FIG. . Here, the current collector foil 8 with a conductive adhesive layer is an aluminum current collector foil with a conductive adhesive layer obtained by applying a conductive adhesive onto an aluminum current collector with a die coater and drying. Next, the composite particles obtained above were supplied as composite particles 6 to the hopper 4 provided on the upper part of the pre-molding roll 10 via the quantitative feeder 16. When the accumulated amount of the composite particles 6 in the hopper 4 provided on the upper part of the pre-molding roll 10 reaches a certain height, the roll press molding apparatus 2 is operated at a speed of 10 m / min, and the pre-molding is performed. The composite particles 6 were pressure-formed with a roll 10 to form a positive molded body of a positive electrode active material layer on the aluminum current-collecting foil with the conductive adhesive layer. Thereafter, the electrode on which the positive electrode active material layer is pre-formed is pressed with two pairs of 300 mmφ forming rolls 12 and 14 provided downstream of the pre-forming roll 10 of the roll pressure forming apparatus 2 and heated to 100 ° C. The surface of the electrode was leveled and the electrode density was increased. In this state, the roll pressure forming apparatus 2 was continuously operated for 10 minutes to produce about 100 m of a lithium ion secondary battery positive electrode.

(Example 3)
In the composite particle removal step, negative electrode composite particles were obtained in the same manner as in Example 1 except that fine particles were not removed. Further, a lithium ion secondary battery negative electrode was produced in the same manner as in Example 1 except that this negative electrode composite particle was used.

Example 4
Negative electrode composite particles were obtained in the same manner as in Example 1 except that coarse particles were not removed in the composite particle removal step. Further, a lithium ion secondary battery negative electrode was produced in the same manner as in Example 1 except that this negative electrode composite particle was used.

(Example 5)
In the composite particle removal step, negative electrode composite particles were obtained in the same manner as in Example 1 except that the total amplitude of the in-plane kinetic sieving device for removing coarse particles and fine particles was 120 mm. Further, a lithium ion secondary battery negative electrode was produced in the same manner as in Example 1 except that this negative electrode composite particle was used.

(Example 6)
In the composite particle removal step, negative electrode composite particles were obtained in the same manner as in Example 1, except that the total amplitude of the in-plane kinetic sieving device for removing coarse particles and fine particles was 50 mm. Further, a lithium ion secondary battery negative electrode was produced in the same manner as in Example 1 except that this negative electrode composite particle was used.

(Example 7)
In the composite particle removal step, negative electrode composite particles were obtained in the same manner as in Example 1 except that the rotational speed of the in-plane motion sieving device for removing coarse particles and fine particles was 350 r / min. It was. Further, a lithium ion secondary battery negative electrode was produced in the same manner as in Example 1 except that this negative electrode composite particle was used.

(Example 8)
In the composite particle removal step, composite particles for negative electrode were obtained in the same manner as in Example 1 except that the rotational speed of the in-plane kinetic sieving device for removing coarse particles and fine particles was 150 r / min. It was. Further, a lithium ion secondary battery negative electrode was produced in the same manner as in Example 1 except that this negative electrode composite particle was used.

(Comparative Example 1)
In the composite particle removal step, composite particles for negative electrode were obtained in the same manner as in Example 1 except that the sieving device used for removing coarse particles and fine particles was a vibration sieving device. Further, a lithium ion secondary battery negative electrode was produced in the same manner as in Example 1 except that this negative electrode composite particle was used.

(Comparative Example 2)
In the composite particle removal step, composite particles for negative electrode were obtained in the same manner as in Example 1 except that the sieving device used when removing coarse particles and fine particles was replaced with an air sieving device. Further, a lithium ion secondary battery negative electrode was produced in the same manner as in Example 1 except that this negative electrode composite particle was used.

  As shown in Table 1, using a slurry preparation step of preparing a slurry containing an electrode active material and a binder, a granulation step of granulating the slurry to obtain composite particles, and an in-plane kinetic sieving device The basis weight accuracy of the composite particle for an electrochemical element electrode obtained by a process including a removal step of removing coarse particles and / or fine particles from the composite particle, the appearance of an electrode produced using the composite particle for electrochemical element, and Thickness accuracy was good.

DESCRIPTION OF SYMBOLS 2 ... Roll press molding apparatus, 6 ... Composite particle, 8 ... Current collecting foil with a conductive adhesive layer, 10 ... Pre-molding roll, 12, 14 ... Molding roll, 16 ... Fixed quantity feeder

Claims (2)

A slurry preparation step of preparing a slurry containing an electrode active material and a binder;
A granulation step of granulating the slurry to obtain composite particles;
Removing the coarse particles and / or fine particles from the composite particles using an in-plane motion sieving device ,
The degree of compression of the composite particles after the removing step is 15% or less,
The electrode active material has a volume average particle diameter of 1 to 50 μm,
The compounding quantity of the said binder in the said composite particle is a manufacturing method of the composite particle for electrochemical element electrodes which is 0.5-10 weight part on a dry weight basis with respect to 100 weight part of said electrode active materials . The method for producing composite particles for electrochemical element electrodes according to claim 1, wherein the in-plane kinetic sieving device has a total amplitude of 30 to 150 mm and a rotation speed of 100 to 400 r / min.

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