JP6347165B2 - Method for producing composite particle for electrochemical element electrode, method for producing electrochemical element electrode, and method for producing electrochemical element - Google Patents

Description

  The present invention relates to a method for producing a composite particle for an electrochemical element electrode, a composite particle for an electrochemical element electrode, an electrochemical element electrode, and an electrochemical element.

  Electrochemical elements such as lithium ion secondary batteries and electric double layer capacitors that are small, lightweight, have high energy density, and can be repeatedly charged and discharged are rapidly expanding in demand by utilizing their characteristics. Lithium ion secondary batteries are widely used in fields such as mobile phones and notebook personal computers because of their high energy density. On the other hand, the electric double layer capacitor can be rapidly charged and discharged, and thus is used as a memory backup compact power source for a personal computer or the like. Furthermore, the electric double layer capacitor is also used as a power source for instantaneously recovering regenerative energy by the brake of the automobile. In addition, with the aim of achieving both high energy density and charge / discharge speed, development of hybrid capacitors and lithium ion capacitors that use a polarizable electrode for one of the positive and negative electrodes and a nonpolarizable electrode for the other is progressing. It has been. With the expansion and development of applications, these electrochemical elements are required to further improve characteristics such as low resistance, high capacity, and improved mechanical characteristics. In such a situation, in order to improve the performance of the electrochemical element, various improvements have been made on the material forming the electrochemical element electrode.

  For example, in Patent Document 1, an active material, a conductive material, a dispersion-type binder, and a soluble resin are dispersed or dissolved in a solvent, and the active material, the conductive material, and the dispersion-type binder are dispersed, and a soluble type An electrochemical element electrode having a mixture layer obtained by preparing a slurry in which a resin is dissolved and spray-drying with a pressure nozzle to form composite particles is described. In Patent Document 2, an active material, a conductive material, a dispersion-type binder, and a soluble resin are dispersed or dissolved in a solvent, and the active material, the conductive material, and the dispersion-type binder are dispersed, and a soluble resin. There is described an electrochemical element electrode having a mixture layer obtained by obtaining a slurry obtained by dissolving a slurry and spray-drying a composite particle obtained by a pin-type disk atomizer. Moreover, in patent document 3, compared with the mixture layer film thickness currently used for the electrochemical element electrode of 700, 800 micrometers using the composite particle obtained by spray-drying with a pin type disk atomizer, it is very much. A technique for manufacturing a thick film electrochemical device electrode by roll press molding with high film thickness accuracy is described.

  In Patent Document 4, a pre-molded roll with a reduced roll diameter in a roll pressure forming apparatus is used, and the amount of composite particles biting into the pressure roll is reduced by bringing the P point closer to the nip point, thereby pressing the roll. A technique for producing a practical electrochemical element electrode by a molding method is described.

  In Patent Document 5, there is a technique for making the amount of powder in the hopper on the forming roll constant by using a quantitative feeder equipped with a hopper in a roll pressure forming apparatus and increasing the film thickness accuracy of the electrochemical element electrode in the flow direction. Have been described.

  Patent Document 6 and Patent Document 7 focus on the hopper shape provided on the forming roll in the roll pressure forming apparatus, and control the thickness of the mixture layer in the width direction by controlling the flow of the composite particles in the hopper. Techniques to improve are described.

Japanese Patent No. 5311706 JP 2010-171111 A Japanese Patent No. 4929792 JP 2013-062022 A JP 2013-062427 A JP2013-062268A JP 2013-060611 A

  However, since the composite particles obtained by the manufacturing methods described in Patent Document 1, Patent Document 2, and Patent Document 3 have a substantially spherical shape, the roll pressure molding method is used in comparison with composite particles whose shape is not substantially spherical. While the fluidity of the composite particles in the powder layer on the roll is relatively rich and relatively uniform and suitable for the production of thick film electrodes, the practical use of 200 μm or less using the apparatus described in Patent Document 4 When an electrochemical element electrode having a mixture layer having a thickness formed on a current collector is to be manufactured, it has been difficult to obtain an electrochemical element electrode having a uniform film thickness. In addition, even when the techniques described in Patent Document 5, Patent Document 6, and Patent Document 7 are used, the thickness accuracy can be improved when an electrochemical element electrode having the above thickness is manufactured. There wasn't.

  An object of the present invention is to produce an electrochemical element electrode composed of composite particles by using a roll pressure molding method, and an electrochemical element having a mixture layer thickness of 200 μm or less and excellent in film thickness accuracy. Method for producing composite particle for electrochemical device electrode capable of producing composite particle for electrochemical device electrode for producing electrode with high productivity, composite particle produced by the production method, electrochemical device electrode, and electrochemical device The purpose is to provide.

  As a result of diligent study on this problem, the inventor formed the composite element obtained in Patent Literature 1, Patent Literature 2, and Patent Literature 3 when the electrochemical element electrode was manufactured by the roll pressure molding method. In the hopper provided on the roll, and in the hopper of the quantitative feeder for supplying the composite particles to the molding hopper on the roll provided arbitrarily, the composite particles are in various states such as rat hole, bridge, blocking, etc. As a result of being present in an agglomerated manner, the present inventors have found that a high film thickness accuracy cannot be ensured because the amount of composite particles supplied to the forming roll is not always microscopically constant.

  The inventor has further investigated, the fact that the composite particles having a particle size of 40 μm or less have strong adhesion, and this contribution increases the cohesiveness of the composite particle group including many composite particles having a particle size of 40 μm or less. As a result, it was found that high film thickness accuracy cannot be ensured.

  In order to solve the above problems, it is effective to relatively increase the median diameter of the composite particles to be manufactured and to relatively reduce the composite particles having the particle diameter of 40 μm or less. On the other hand, as a result of taking the above measures, the inventor increased the size of the droplets to be sprayed, so that the droplets adhered to the inner wall of the drying apparatus before solidifying by drying, and the yield of the granulation process was reduced. It was clarified that another problem of significant decline arises. This phenomenon is a particularly significant problem when the rotating disk atomizer found in Patent Document 2 is used.

  Moreover, since the composite particles obtained by using the slurry spraying method described in Patent Document 1, Patent Document 2, and Patent Document 3 have a wide particle size distribution, the median diameter of the composite particles described above is relatively Electrochemical element electrode composite particles obtained by increasing the size of the composite element inevitably increase the frequency of the presence of composite particles having a large particle diameter, and using this composite particle, the electrochemical element has a practical thickness of 200 μm or less. When an electrode mixture layer is produced, the presence of composite particles having a large particle diameter adversely affects the film thickness accuracy of the mixture layer.

  Therefore, spray drying granulation is performed under the condition that the droplets do not adhere to the inner wall of the drying apparatus, and then the composite particles having a particle diameter of 40 μm or less by the classification process, and the electrochemical device electrode mixture layer having a target film thickness By removing the composite particles having a particle diameter which becomes an obstacle in the production of the composite material, it is possible to solve problems such as aggregation of the composite particles in the hopper and low film thickness accuracy of the electrochemical device electrode mixture layer. On the other hand, when the classification operation is applied to the composite particles obtained by spray-drying granulation found in Patent Document 1 and Patent Document 2, the process yield is about 50%. In Patent Document 1 and Patent Document 2, The method for producing composite particles for electrochemical device electrodes in which a classification step is added to the spray-drying granulation step that is seen has low productivity and is not practical.

Therefore, it is no longer possible to produce the composite particles for electrochemical element electrodes that solve all the above-mentioned various problems by the spray-drying granulation method found in Patent Document 1 and Patent Document 2 and also ensure the productivity. is there.
As a result of intensive investigations to solve all of these problems, the inventor produced droplets by electrostatic atomization and dried them to produce composite particles, thereby producing an electrochemical device having a narrow particle size distribution. It has been found that composite particles for electrodes can be produced with high productivity, and the present invention has been completed.

That is, according to the present invention,
(1) A method for producing composite particles for producing an electrochemical device electrode by applying a pressure operation in a dry state to composite particles comprising at least an active material and a binder, wherein A slurrying step (I) for obtaining a slurry comprising an active material and the binder in a solvent, a droplet generating step (II) for converting the slurry into droplets by electrostatic atomization, and the droplets And a droplet drying step (III) for solidifying by drying to obtain composite particles, and the volume of the composite particle group composed of a plurality of the composite particles obtained from the droplet drying step (III) was determined on a volume basis. The method for producing composite particles for electrochemical device electrodes, wherein the median diameter in the particle size distribution is 50 μm or more and 160 μm or less,
(2) The method for producing composite particles for electrochemical element electrodes according to (1), wherein the solvent is water, and the slurry further contains a soluble resin,
(3) The cumulative frequency of 40 μm or less in the particle size distribution of the composite particle group consisting of a plurality of the composite particles obtained from the droplet drying step (III) is 50% or less. (1) or the method for producing a composite particle for an electrochemical element electrode according to (2),
(4) The frequency of the mode diameter in the particle size distribution obtained on a volume basis of the composite particle group composed of a plurality of the composite particles obtained from the droplet drying step (III) is 12% or more. (1) A method for producing the composite particle for an electrochemical element electrode according to any one of (1) to (3)
(5) Composite particles for producing an electrochemical element electrode by applying a pressure operation in a dry state to composite particles having at least an active material and a binder, wherein at least the active material, And a slurry forming step (I) for obtaining a slurry containing the binder in a solvent, a droplet generating step (II) for converting the slurry into droplets by electrostatic atomization, and drying the droplets A droplet drying step (III) for solidifying to obtain composite particles, and obtained on a volume basis of a composite particle group composed of a plurality of the composite particles obtained from the droplet drying step (III). A composite particle for an electrochemical device electrode, wherein the median diameter in the particle size distribution is 50 μm or more and 160 μm or less,
(6) An electrochemical element electrode comprising an electrode mixture layer comprising the composite particle for an electrochemical element electrode according to (5) laminated on a current collector,
(7) An electrochemical element comprising the electrochemical element electrode according to (6),
Is provided.

  According to the method for producing a composite particle for an electrochemical element electrode of the present invention, the composite particle for an electrochemical element electrode for producing an electrochemical element electrode excellent in film thickness accuracy can be produced with high productivity. Moreover, the composite particle for electrochemical element electrodes manufactured by this manufacturing method can be provided. Moreover, the electrochemical element electrode using this composite particle for electrochemical element electrodes can be provided. Moreover, the electrochemical element using this electrochemical element electrode can be provided.

  In addition, the composite particle group composed of composite particles obtained by the production method of the present invention having high productivity, even if the median diameter is a size that can provide a thin electrochemical element electrode, the composite particle group is The content of the composite particles having a specific size or less having strong adhesion due to the narrow particle size distribution is not more than a specific amount. Therefore, an electrochemical element electrode that is thin and excellent in film thickness accuracy can be obtained by manufacturing an electrochemical element electrode using the composite particles obtained by the manufacturing method of the present invention.

It is the schematic of the composite particle manufacturing apparatus used for the manufacturing method of the composite particle for electrochemical element electrodes which concerns on embodiment of this invention.

  Hereinafter, a method for producing an electrochemical element electrode composite particle (hereinafter, simply referred to as “composite particle”) according to an embodiment of the present invention will be described with reference to the drawings.

<Method for producing composite particle for electrochemical element electrode>
The method for producing composite particles for an electrochemical device electrode according to the present invention comprises a slurrying step (I) in which at least an active material and a binder are dispersed in a solvent to obtain a slurry, and the slurry is dropped into a droplet by electrostatic atomization. And a droplet drying step (III) for solidifying the generated droplets by drying. Hereinafter, each step will be described.

(Slurry process (I))
In the slurrying step (I), the active material and the binder are dispersed or dissolved in the solvent, and the active material and the binder are dissolved or dissolved in the solvent as necessary. A slurry is obtained in which a dissolving resin, a conductive material and other additives are dispersed or dissolved as required. Hereinafter, each component used for the slurry will be described.

<Active material>
The active material constituting the composite particle of the present invention is appropriately selected depending on the type of electrochemical element. For example, by using an active material for a positive electrode of a lithium ion secondary battery as an active material used for the composite particle, the composite particle can function as a composite particle for a lithium ion secondary battery positive electrode. Similarly, by using an active material for a negative electrode of a lithium ion secondary battery as an active material used for the composite particles, the composite particles can function as composite particles for a lithium ion secondary battery negative electrode.

The active material for the positive electrode of the lithium ion secondary battery is not limited to those exemplified here. For example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiFeVO ₄ , and Lithium-containing composite metal oxide partially substituted with these elements; transition metal sulfides such as TiS ₂ , TiS ₃ , and amorphous MoS ₃ ; Cu ₂ V ₂ O ₃ , amorphous V ₂ O · P ₂ O ₅ , transition metal oxides such as MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ ; Furthermore, conductive polymers such as polyacetylene and poly-p-phenylene are listed.

Furthermore, you may use the active material for positive electrodes which consists of a composite material which combined the inorganic compound and the organic compound.
Further, for example, a composite material covered with a carbon material may be produced by reducing and firing an iron-based oxide in the presence of a carbon source material, and the composite material may be used as an active material for a positive electrode. Iron-based oxides tend to be poor in electrical conductivity, but can be used as a high-performance positive electrode active material by using a composite material as described above. Furthermore, you may use as a positive electrode active material what substituted the said compound partially elementally. These positive electrode active materials may be used alone or in combination of two or more at any ratio. Moreover, you may use the mixture of the above-mentioned inorganic compound and organic compound as a positive electrode active material.

  The particle diameter of the positive electrode active material is appropriately selected in view of other constituent elements of the battery. From the viewpoint of improving battery characteristics such as load characteristics and cycle characteristics, the median diameter of the positive electrode active material is usually 0.1 μm or more, preferably 1 μm or more, and usually 50 μm or less, preferably 20 μm or less. When the median diameter of the positive electrode active material is within this range, a secondary battery having a large charge / discharge capacity can be obtained, and handling at the time of producing a mixture slurry is easy.

The active material for the negative electrode of the lithium ion secondary battery is not limited to those exemplified here. For example, amorphous carbon, graphite, natural graphite, artificial graphite, mesocarbon microbeads, pitch-based carbon fiber And carbonaceous materials; conductive polymers such as polyacene; and the like. Further, metals such as silicon, tin, zinc, manganese, iron and nickel, and alloys thereof; oxides of the metals or alloys; sulfates of the metals or alloys; Alternatively, metallic lithium; lithium alloys such as Li—Al, Li—Bi—Cd, and Li—Sn—Cd; lithium transition metal nitride; silicon; lithium titanate, titanium oxide, and the like may be used. Further, the active material may be a material obtained by attaching a conductive material to the surface by a mechanical modification method.
These negative electrode active materials may be used alone or in combination of two or more at any ratio.

  The particle diameter of the negative electrode active material is appropriately selected in view of other constituent elements of the battery. From the viewpoint of improving battery characteristics such as initial efficiency, load characteristics, and high-temperature cycle characteristics, the median diameter of the negative electrode active material is usually 1 to 50 μm, preferably 5 to 30 μm.

Moreover, an electrochemical element can be functioned as a sodium ion secondary battery by using a sodium ion secondary battery active material for the active material used for composite particles.
The active material for the positive electrode of the sodium ion secondary battery is not limited to those exemplified here, but is an oxidation represented by NaM1 _a1 O ₂ such as NaFeO ₂ , NaMnO ₂ , NaNiO ₂ and NaCoO _2. Na _0.44 Mn _1-a2 M1 _a2 O ₂ oxide, Na _0.7 Mn _1-a2 M1 _a2 O _2.05 oxide (M1 is one or more transition metal elements, 0 <a1 < 1, 0 ≦ a2 <1); oxides represented by Na _b M2 _c Si ₁₂ O ₃₀ such as Na ₆ Fe ₂ Si ₁₂ O ₃₀ and Na ₂ Fe ₅ Si ₁₂ O ₃₀ (M2 is one or more transitions) Metal elements, 2 ≦ b ≦ 6, 2 ≦ c ≦ 5); oxides represented by Na _d M3 _e Si ₆ O ₁₈ such as Na ₂ Fe ₂ Si ₆ O ₁₈ and Na ₂ MnFeSi ₆ O ₁₈ (M3 is One or more transition metal elements, 2 ≦ d ≦ 6, 1 ≦ e ≦ 2); N such as Na ₂ FeSiO ₆ oxide represented by a _f M4 _g Si ₂ O ₆ (M4 is one or more elements selected from the group consisting of transition metal elements, Mg and Al, 1 ≦ f ≦ 2, 1 ≦ g ≦ 2) NaFePO ₄ Phosphates such as NaMnPO ₄ and Na ₃ Fe ₂ (PO ₄ ) ₃ ; Na ₂ FePO ₄ F, Na ₂ VPO ₄ F, Na ₂ MnPO ₄ F, Na ₂ CoPO ₄ F, Na ₂ NiPO ₄ F, etc. Fluorophosphates; fluorinated sulfates such as NaFeSO ₄ F, NaMnSO ₄ F, NaCoSO ₄ F, NaFeSO ₄ F; borate salts such as NaFeBO ₄ , Na ₃ Fe ₂ (BO ₄ ) ₃ ; and Na ₃ FeF _6, Na ₂ MnF ₆ fluorides represented by NahM5F ₆ such (M5 is one or more transition metal elements, 2 ≦ h ≦ 3).

  As an active material for a negative electrode of a sodium ion secondary battery, a material capable of doping and dedoping sodium ions can be used as an active material for a negative electrode of a sodium ion secondary battery. Although not limited to what is illustrated here, a carbon material is mentioned, for example.

  Moreover, an electrochemical element can be functioned as an electrochemical capacitor by using the active material for electrochemical capacitors for the active material used for composite particles. By selecting activated carbon as the active material and using an electrochemical element electrode composed of composite particles using this active material for the positive electrode and the negative electrode, the electrochemical capacitor can function as an electric double layer capacitor.

  In addition, an electrochemical element electrode composed of composite particles using the activated carbon as an active material is used as a positive electrode, and an electrochemical element electrode composed of composite particles using the active material for a negative electrode of the lithium ion secondary battery as an active material is used as a negative electrode. Thus, the electrochemical element can function as a lithium ion capacitor.

  As described above, the electrochemical device to which the composite particle of the present invention can be applied is merely an example, and is not limited to the disclosed electrochemical device. A person skilled in the art can easily conceive that various electrochemical elements function by using an electrochemically active material as an active material in the composite particles of the present invention.

<Binder>
The binder used in the present invention is not particularly limited as long as it is a substance that can bind the above active materials to each other. As the binder, a water-soluble binder and a dispersion-type binder having a property of being dispersed in a solvent can be preferably used, and a dispersion-type binder is more preferably used.

  Examples of the dispersion-type binder include high molecular compounds such as silicon polymers, fluorine-containing polymers, conjugated diene polymers, acrylate polymers, polyimides, polyamides, polyurethanes, and 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-based polymer is a polymer containing a monomer unit containing a fluorine atom. Specific examples of the fluoropolymer 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, PVDF is preferably included.

  The conjugated 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. 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 homopolymers such as polybutadiene and polyisoprene; aromatic vinyl / conjugated diene copolymers such as carboxy-modified styrene / butadiene copolymers (SBR) A vinyl cyanide / conjugated diene copolymer such as acrylonitrile / butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, and the like.

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-mentioned copolymerizable monomers, it is difficult to be deformed when an electrode is produced, and it can be strong, and sufficient adhesion between the mixture 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.

  In addition, when there is too much ratio of an aromatic vinyl-type monomer, there exists a tendency for sufficient adhesiveness of a mixture layer and a collector to be not acquired. 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.

  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. is there. 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. In addition, when the α, β-unsaturated nitrile compound unit is contained in the dispersion-type binder, the adhesion between the mixture layer containing the composite particles and the current collector can be made sufficient.

  If the proportion of the α, β-unsaturated nitrile compound unit is too large, there is a tendency that sufficient adhesion between the mixture layer and the current collector cannot 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 vinyl compound units having an acid component in the dispersion-type binder is preferably 0.5 to 10% by weight, more preferably 1 to 8% from the viewpoint of improving the stability when the composite particle slurry is prepared. % By weight, more preferably 2 to 7% by 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 the slurry for composite particles to become high, and for handling to become difficult. Moreover, when the ratio of the vinyl compound unit which has an acid component is too small, there exists a tendency for stability of the slurry for composite particles 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 from the viewpoint that the strength and flexibility of the obtained electrode are good while making the stability when making a composite particle slurry good. More preferably, it is 10-5000 nm, More preferably, it is 50-1000 nm.

  Among these, as the binder, it is preferable to use a conjugated diene polymer and an acrylate polymer from the viewpoint that a mixture layer excellent in binding property and strength to the current collector can be obtained.

  The binder used in the present invention preferably has a glass transition temperature, and the glass transition temperature is usually −40 ° C. to + 80 ° C., preferably −40 ° C. to + 50 ° C., more preferably −40 ° C. to + 30 ° C.

  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, a suspension polymerization method, a dispersion polymerization method, or a solution polymerization method, are employable. Among them, it is preferable to produce by an emulsion polymerization method because the particle diameter of the binder is easy to control. Further, the binder used in the present invention may be particles having a core-shell structure obtained by stepwise polymerization of a mixture of two or more monomers.

  The compounding amount of the binder in the composite particles is active from the viewpoint of ensuring sufficient adhesion between the obtained mixture layer and the current collector and reducing the internal resistance of the electrochemical element. The amount is usually 0.5 to 20 parts by mass, preferably 0.5 to 10 parts by mass, and more preferably 0.5 to 8 parts by mass with respect to 100 parts by mass of the substance.

<Dissolving resin>
In addition to the above, the composite particles of the present invention may contain a soluble resin. The soluble resin is a resin that dissolves in a solvent, and is preferably used by being dissolved in a solvent at the time of preparing a slurry to be described later, and has an action of uniformly dispersing an active material, a conductive material, and the like in the solvent. . Examples of the soluble resin include cellulose polymers such as carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose, and ammonium salts or alkali metal salts thereof; ammonium salts or alkalis of polyacrylic acid or polymethacrylic acid Metal salts; polyvinyl alcohol, modified polyvinyl alcohol, polyethylene oxide, polyacrylamide; polyvinyl pyrrolidone, polycarboxylic acid, oxidized starch, phosphate starch, casein, various modified starches, chitin, chitosan derivatives and the like. These soluble resins can be used alone or in combination of two or more. Among these, as the soluble resin, a cellulose polymer is preferable, and carboxymethyl cellulose or its ammonium salt or alkali metal salt is particularly preferable.

  Although the usage-amount of melt | dissolving resin is not specifically limited, Usually, 0.3-10 mass parts with respect to 100 mass parts of active materials in a composite particle, Preferably it is 0.3-7 mass parts, More preferably It is the range of 0.5-5 mass parts. By using the dissolution type resin, sedimentation and aggregation of solid content in the slurry can be suppressed. These soluble resins may be used alone, or different types of soluble resins may be used in combination. Moreover, even if it is the same soluble resin, you may use it combining the soluble resin from which molecular weight and other physical properties differ. When used in combination, the dispersion stability of the slurry and the stability over time of the viscosity can be controlled.

(Water-insoluble polysaccharide polymer fiber)
If necessary, a water-insoluble polysaccharide polymer fiber may be further added to the water-soluble polymer. In the technique described in the present invention, it is possible to improve the strength of the composite particles obtained by adding a water-insoluble polysaccharide polymer fiber. The water-insoluble polysaccharide polymer fiber belongs to a so-called polymer compound among polysaccharides, and there is no other limitation as long as it is a water-insoluble fiber-like fiber. It is the fiber (short fiber) fibrillated by. In addition, the water-insoluble polysaccharide polymer fiber used in the present invention is a high-polysaccharide fiber having an undissolved content of 90% by weight or more when 0.5 g of polysaccharide polymer fiber is dissolved in 100 g of pure water at 25 ° C. Refers to molecular fiber.

  Polysaccharide polymer nanofibers are preferably used as water-insoluble polysaccharide polymer fibers, and among the polysaccharide polymer nanofibers, they are flexible and have high tensile strength. Independently selected from bio-derived bio-nanofibers such as cellulose nanofibers, chitin nanofibers, chitosan nanofibers, etc., from the viewpoints of high effects and the ability to improve particle strength and the good dispersibility of conductive materials Or any mixture is more preferred. 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.

  These water-insoluble polysaccharide polymer fibers can be fibrillated (short fiber) by applying mechanical shearing force. After water-insoluble polysaccharide polymer fibers are dispersed in water, they are beaten. The method of making it pass is mentioned. As the water-insoluble polysaccharide polymer fiber, short fibers having various fiber diameters are commercially available, and these may be used by dispersing in water.

  The average fiber diameter of the water-insoluble polysaccharide polymer fibers used in the present invention is such that more water-insoluble polysaccharide polymer fibers are present in the composite particles, and the strength of the composite particles and the electrodes is increased by increasing the adhesion between the active materials. Is preferably 5 to 3000 nm, more preferably 5 to 2000 nm, still more preferably 5 to 1000 nm, and particularly preferably 5 to 100 nm. It is. If the average fiber diameter of the water-insoluble polysaccharide polymer fiber is too large, the water-insoluble polysaccharide polymer fiber cannot be sufficiently present in the composite particle, so that the strength of the composite particle cannot be made sufficient. Further, the fluidity of the composite particles is deteriorated, and it is difficult to form a uniform mixture layer.

<Conductive material>
A conductive material may be added to the composite particles of the present invention as necessary. The conductive material is a particulate or fibrous substance having conductivity, and improves the conductivity of the electrochemical element electrode. For example, conductive carbon black such as furnace black, acetylene black, and ketjen black (registered trademark of Akzo Nobel Chemicals Besloten Fennaut Shap); graphite such as natural graphite and artificial graphite; polyacrylonitrile carbon fiber, pitch carbon Examples thereof include fiber, VGCF (vapor grown carbon fiber), carbon nanotube, and graphene. These conductive materials can be used alone or in combination of two or more.

  The compounding amount of the conductive material in the composite particles is usually 0.1 to 50 parts by mass, preferably 0.5 to 15 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the active material. is there. By forming the electrode using composite particles containing an amount of the conductive material in this range, the capacity of the electrochemical element can be increased and the internal resistance can be decreased.

<Other additives>
The composite particles 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 that are easily thermally decomposed are preferable. The amount of the surfactant is not particularly limited, but in the composite particles, 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 active material. Part range. The surface tension of the slurry can be adjusted by adding a surfactant. In the electrostatic atomization method of the present invention, the surface tension is a factor affecting the atomization characteristics. By controlling the surface tension, the particle size distribution of the composite particle group in the electrostatic atomization granulation method of the present invention can be adjusted.

<Solvent>
Although it does not specifically limit as a solvent used in order to obtain a slurry, 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 may be used, or a mixed solvent of water and an organic solvent may be used.

  Examples of the organic solvent include alkyl alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol; alkyl ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane and diglyme; diethylformamide, dimethylacetamide and N-methyl- Amides such as 2-pyrrolidone and dimethylimidazolidinone; Sulfur solvents such as dimethyl sulfoxide and sulfolane; and the like. Among these, alcohols and N-methyl-2-pyrrolidone are preferable as the organic solvent. For example, when water and an organic solvent having a lower boiling point than water are used in combination, the drying speed can be increased when the droplets are dried. Further, the dispersibility of the binder or the solubility of the soluble resin and the surface tension of the slurry vary depending on the amount or type of the organic solvent used in combination with water. Thereby, the viscosity and fluidity of the slurry can be adjusted, and the production efficiency can be improved and the particle size distribution of the resulting composite particle group can be controlled.

  In the method for producing composite particles for an electrochemical element electrode using the electrostatic atomization method of the present invention, the solid content concentration of the slurry is related to the size of the droplet generated in the droplet generation step (II). That is, the smaller the solid content concentration of the slurry, the smaller the size of the generated droplets, and the smaller the median diameter of the composite particle group composed of composite particles obtained by the subsequent droplet drying step (III).

<Median diameter>
The median diameter is the particle diameter at a cumulative 50% point in the particle diameter distribution obtained on the volume basis from the small particle diameter side (oversize). Sometimes referred to as 50% average particle size.

Although it is not this limitation disclosed by this specification, the viscosity of a slurry is 10-3,000 mPa * s normally at room temperature, Preferably it is 15-1,500 mPa * s, More preferably, it is 20-1,000 mPa * s. It is a range. In the method for producing composite particles for an electrochemical element electrode using the electrostatic atomization method of the present invention, the viscosity of the slurry is related to the size of the droplet generated in the droplet generation step (II) described later. That is, the smaller the viscosity of the slurry, the smaller the size of the generated droplets, and the smaller the median diameter of the composite particle group composed of composite particles obtained by the subsequent droplet drying step (III).
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.

  The method or procedure for dispersing or dissolving the active material, conductive material, binder, soluble resin and other additives in the solvent is not particularly limited. For example, the active material, conductive material, binder, and soluble type are used in the solvent. Method of adding and mixing the resin, dissolving the soluble resin in the solvent, then adding and mixing the binder (for example, latex) dispersed in the solvent, and finally adding and mixing the active material and conductive material And a method in which an active material and a conductive material are added to a binder dispersed in a solvent and mixed, and a soluble resin dissolved in a solvent is added to the mixture and mixed. Examples of the mixing means include mixing equipment such as a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a homomixer, and a planetary mixer. Mixing is usually performed in the range of room temperature to 80 ° C. for 10 minutes to several hours.

  Here, in the particle size distribution of the obtained slurry, the cumulative frequency of particles having a size of 100 μm or more is preferably less than 1% in the particle size distribution obtained on the volume basis from the small particle size side (oversize). Within the above range, the slurry can be stably sprayed from an atomizer nozzle described later, and a composite particle group having a narrow particle size distribution can be obtained. On the other hand, when the cumulative frequency of particles having a size of 100 μm or more is 1% or more, the median diameter and particle size distribution of the composite particles obtained by depositing the particles inside the atomizer nozzle gradually change, or the atomizer nozzle If the inside is blocked, spraying cannot be performed, causing problems in quality and operation.

The particle size distribution of the slurry can be measured using a laser diffraction / scattering particle size distribution measuring device (for example, Nikkiso Co., Ltd .: Microtrac MT-3200II).
Here, there are cases where there is no channel of exactly 100 μm due to the convenience of the apparatus specification of the particle size distribution measuring apparatus. In this case, the cumulative frequency of particles having a size of 100 μm or more may be replaced with the cumulative frequency from the measurement channel closest to 100 μm.

(Droplet generation process (II))
Next, the droplet generation step (II) will be described. In the droplet generation step (II) of the present invention, droplets are generated from the slurry obtained in the slurrying step (I) by an electrostatic atomization method, and the droplets are sprayed toward a drying apparatus.
Here, the electrostatic atomization method, which is a droplet generation method according to the present invention, applies a high voltage of several kV or more to the atomizer nozzle, and concentrates the electric charge at the tip of the atomizer nozzle, thereby the slurry supplied to the atomizer nozzle. This is a method for promoting the division and generating droplets composed of the slurry.

By changing the voltage applied to the atomizer nozzle, uniform droplets of several hundred μm to several μm can be generated and sprayed.
In addition, by sharpening the shape of the tip of the nozzle in a needle shape, it is possible to concentrate charges on the tip of the atomizer nozzle, and it is possible to promote the generation of droplets in the electrostatic atomization method. By devising the shape of the tip of the nozzle, it is possible to set the applied voltage required for the production of a composite particle group having a particle size distribution in the desired range low, and the equipment cost, running cost, and safety in operation Works in favor.

The applied voltage suitable for generating droplets is the shape of the tip of the atomizer nozzle, the surface tension of the slurry, the viscosity, the solid content concentration, the supply speed, the electric conductivity, the capacitance that can accumulate the active material, and the atomizer nozzle described later. Although it is not particularly limited because it varies depending on the shape and installation position of the ground electrode that can be installed in the vicinity, it is usually 2 kV or more. A person skilled in the art can generate a droplet having a desired size by considering voltage conditions suitable for generating a droplet as appropriate while considering these factors.
Here, the temperature of the slurry supplied to the atomizer nozzle is usually room temperature, but it may be heated to room temperature or higher according to the situation or purpose.

  A plurality of atomizer nozzles for generating droplets are provided in the drying device, and the droplets generated and sprayed from each atomizer nozzle by applying a voltage from a single power source dry the droplets described later. And supplied to a drying device for solidification.

  As disclosed in the present invention, if a voltage is applied to the nozzles of the atomizer by one power source, and droplets are generated and sprayed from the nozzles of the plurality of atomizers by this single power source, the power source is changed for each atomizer. Reliability is improved as compared with the case of providing. The reason is that when there are multiple power supplies, each power supply may fail independently, and as a result, the particle size distribution of the generated and sprayed droplets may change. This is because this problem can be avoided. In view of this point of view, it is most preferable that the reliability increases as the number of nozzle holes of the atomizer on which one power supply acts increases, and that one set of a predetermined particle size distribution described later is obtained by a single power supply. However, the present invention is not limited to the case where one set of a predetermined particle size distribution is obtained by a single power source.

  The number of atomizer nozzles to be applied by the one power source is not particularly limited, but from the viewpoint of suppressing disturbance applied to the atomizer nozzle, it is desirable that the distribution of the opening area is not extremely biased. Further, the distance between the nozzles needs to be set so that the sprayed droplets do not contact each other. This condition varies depending on the generation of droplets by the electrostatic atomization method, the charged state of droplets in spraying, the droplet diameter, the density of the droplets, the airflow state in the drying apparatus, and the like.

  However, the closest distance between the atomizer nozzles is the most ideal condition, i.e., there is no voltage fluctuation and no airflow in the direction different from the droplet flight direction is generated in the drying device. Is preferably greater than the sum of the radii of the droplets sprayed from adjacent nozzles. Moreover, it is preferable that the closest distance between the atomizer nozzles for producing the droplets having the same particle diameter and the composite particles is more than the diameter of the formed droplet diameter.

  As explained in detail above, by providing a large number of atomizer nozzles in the droplet generation unit, the number of particles due to droplets generated from the discharge holes of the atomizer nozzle is extremely high, from tens of thousands to several millions per second. It can be increased and is excellent from the viewpoint of productivity.

Although not shown (see FIG. 1 below), a ground electrode is provided directly below the nozzle tip so as to face the atomizer nozzle. There is no restriction | limiting in particular as a shape of a ground electrode, Although it can select suitably, For example, forming in a ring shape is preferable.
By providing a ground electrode directly under the atomizer nozzle, it is possible to further promote the generation of droplets by electrostatic atomization.

(Droplet drying process (III))
In the droplet drying step (III) of the present invention, the droplets generated in the droplet generation step (II) are solidified by drying to obtain composite particles, and the composite particles are discharged after the charges charged in the composite particles are removed. Recover.

  A heat exchange medium heated to room temperature or higher is introduced into the drying apparatus. The heat exchange medium introduced into the drying apparatus may be dry air or heated steam. When the solvent contains an organic solvent, it is desirable that the heat exchange medium be inert heated nitrogen or the like in order to prevent accidents such as electrostatic ignition. Moreover, it is preferable that the said drying apparatus is an exposure protection specification.

  The temperature of the heat exchange medium for drying and solidifying the droplets is usually 60 to 500 ° C, preferably 100 to 400 ° C. In this droplet drying step (III), the method of blowing hot air is not particularly limited, for example, a method in which the hot air and the spraying direction flow side by side, 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 a method in which the hot air is in countercurrent contact, and a method in which the sprayed droplets first flow in parallel with the hot air and then drop by gravity and contact in countercurrent.

  In addition, it is preferable to provide an electric field curtain charged with the same polarity as the electric charge of the liquid droplets on the inner wall surface of the drying apparatus in order to suppress a decrease in yield caused by the droplets adhering to the wall surface of the drying apparatus. . By forming a transport path whose periphery is covered with an electric field curtain and allowing the droplets to pass through the transport path without adhering the droplets to the drying device wall surface, solidification of the droplets is sufficiently performed, which will be described later. The composite particles can be sent to a static elimination unit and a recovery unit (for example, a cyclone 38 and a composite particle recovery tank 18 in FIG. 1 below). Thus, a composite particle group having a high yield and a sharp particle size distribution can be produced.

  The static elimination unit is a part that neutralizes the electric charge charged to the composite particles by the static eliminator and safely sends the composite particles to the composite particle recovery unit. There is no particular limitation on the method of static elimination by the static eliminator, and a generally known method can be appropriately selected and used. However, since neutralization can be efficiently performed, for example, soft X-ray irradiation, It is preferably performed by plasma irradiation or the like.

  The recovery unit for the composite particles is provided at the bottom of the drying device from the viewpoint of efficiently collecting and transporting the composite particles. The structure of the composite particle recovery unit is not particularly limited as long as the particles can be collected, but a cyclone structure is preferable from the viewpoint of reliably transferring the composite particles to the recovery container.

(Composite particles for electrochemical device electrodes)
As described above, the composite particles according to the present invention are obtained by a production method having at least a slurrying step (I), a droplet generation step (II) and a droplet drying step (III).

  The composite particle of the present invention comprises at least an active material and a binder, but each of the active material and the binder does not exist as independent particles, but is an active material that is a constituent component, One particle is formed by two or more components including a binder. Specifically, a plurality of particles (preferably dozens to thousands) are formed by combining a plurality of the above-described individual particles having two or more components while maintaining a substantial shape. The active material is preferably bound with a binder to form particles.

In addition, the shape of the composite particles of the present invention is substantially 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 excellent thickness accuracy. It is preferably spherical. 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 film thickness accuracy of the electrode to be manufactured deteriorates.
Although the composite particle manufacturing apparatus used for manufacture of a composite particle is not specifically limited, For example, the composite particle manufacturing apparatus shown in FIG. 1 can be used.

  As shown in FIG. 1, the composite particle manufacturing apparatus 2 manufactures composite particles 12 from a slurry tank 10 that produces a slurry 8 and a slurry 8 by stirring the raw material that has been input through the raw material input pipe 4 with a stirring blade 6. A granulating device 14, a composite particle pipe 16 for transferring the composite particles 12 produced by the granulating device 14, and a composite particle recovery tank 18 for recovering the composite particles 12 transferred through the composite particle pipe 16 are provided. Yes.

  Here, the granulating apparatus 14 includes a drying tower 22 and a high-voltage power supply 24, and a plurality of atomizer nozzles 26 for spraying the slurry 8 are provided in the upper part of the drying tower 22. The atomizer nozzle 26 is provided with a slurry pipe 28 for introducing the slurry 8 produced in the slurry tank 10, and a pump for supplying the slurry 8 to the atomizer nozzle 26 in the middle of the slurry pipe 28. 30 is provided. Further, at the upper part of the drying tower 22, a heat exchanger 32 and a blower 34 for introducing a heat exchange medium into the heat exchanger 32 are provided. In addition, a cool air fan 36 for introducing cooling air is provided above the atomizer nozzle 26.

  The positive pole of the high voltage power supply 24 is connected to the atomizer nozzle 26, the negative pole is grounded, and is connected to the lower part of the drying tower 22.

  A cyclone 38 is provided above the composite particle recovery tank 18 to separate the composite particles 12 and the air and allow a part of the air to flow out. The cyclone 38 is provided with an air outlet 40, and air is sucked from the air outlet 40 by a blower 42.

  The slurrying step (I) is performed, for example, in the slurry tank 10 of the composite particle manufacturing apparatus 2 shown in FIG. 1, and the slurry 8 is charged with raw materials including an active material, a binder, and a solvent in the slurry tank 10, It can be obtained by stirring with the stirring blade 6.

  The droplet generation step (II) can be performed using, for example, the granulating device 14 of the composite particle manufacturing device 2 shown in FIG. That is, the slurry 8 obtained in the slurrying step (I) is supplied to the atomizer nozzle 26 by applying a high voltage of several kV or more to the atomizer nozzle 26 and concentrating charges on the tip of the atomizer nozzle 26. 8 is promoted to generate droplets of the slurry 8 and sprayed toward the drying tower 22 as a drying device.

  The droplet drying step (III) can be carried out, for example, using a drying tower 22 provided in the granulating device 14 of the composite particle manufacturing device 2 shown in FIG. That is, the droplet sprayed in the drying tower 22 as a drying device in the droplet generation step (II) is solidified by drying to obtain the composite particle 12, and the charge charged on the composite particle 12 is neutralized, The composite particles 12 are transferred through the composite particle pipe 16, and the composite particles 12 separated from the air by the cyclone 38 are recovered in the composite particle recovery tank 18.

<Median diameter>
Further, the median diameter in the particle size distribution obtained on a volume basis of the composite particle group composed of a plurality of composite particles obtained by the production method of the present invention is 50 μm or more and 160 μm or less, preferably 50 μm or more and 130 μm or less, more preferably The range is 50 μm or more and 110 μm or less.

  Here, as described above, the median diameter is a particle diameter at a cumulative 50% point in the particle diameter distribution determined on the volume basis from the small particle diameter side (oversize). Sometimes referred to as 50% average particle size.

  When the median diameter is in the above range, an electrochemical element electrode having a practical film thickness and excellent film thickness accuracy in the production of an electrochemical element electrode by roll pressure molding can be obtained in roll pressure molding.

  When the median diameter of the composite particle group becomes smaller than the above range, the composite particle contains many particles having a strong adhesion of 40 μm or less, so that the composite particles tend to cause aggregation such as blocking in the hopper portion, and the roll The accuracy of the film thickness obtained in the production of the electrochemical element electrode by the pressure molding method is lowered. On the other hand, when the median diameter of the composite particle group is increased from the above range, it is difficult to obtain an electrochemical element electrode having a practical film thickness of 200 μm or less in the production of an electrochemical element electrode by a roll pressure molding method. A large unevenness occurs in the electrode obtained due to the size of the composite particle being too large in the chemical element electrode, and the film thickness accuracy is lowered.

  As described above, the median diameter range needs to be 50 μm or more and 160 μm or less, preferably 50 μm or more and 130 μm or less, more preferably 50 μm or more and 110 μm or less. This is because, when the median diameter is 50 μm or more and 130 μm or less, more preferably 50 μm or more and 110 μm or less, higher film thickness accuracy can be obtained in manufacturing a thin electrochemical element electrode.

  The median diameter of the composite particle group can be measured by pressurizing and spraying the composite particles with compressed air using a dry laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd .: Microtrac MT-3200II). .

<Cumulative frequency>
Further, the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number of composite particles composed of a plurality of composite particles obtained by the present invention is 50% of the cumulative frequency of 40 μm or less in the oversized cumulative particle size distribution curve. Below, it is preferably 30% or less, more preferably 15% or less, and most preferably 0%.

  Although it exists also in the above, since the composite particle of the size of 40 micrometers or less has strong adhesiveness, in the manufacturing process of the electrochemical element electrode by roll press molding, the amount of composite particles of 40 micrometers or less increases in the composite particle group. In the hopper portion upstream from the forming roll, the composite particles tend to cause aggregation such as blocking, and the film thickness accuracy of the obtained electrochemical element electrode is lowered. Therefore, the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number of composite particle groups is preferably as small as possible.

  The number frequency of the particle size distribution of the composite particle group is the same as the median diameter, and the composite particle group is pressurized with compressed air using a dry laser diffraction / scattering type particle size distribution measuring device (manufactured by Nikkiso Co., Ltd .: Microtrac MT-3200II). Can be measured by spraying.

  Note that there may be no channel of 40 μm just due to the equipment specifications of the particle size distribution measuring apparatus. In this case, the measurement channel closest to 40 μm may be replaced with 40 μm defined in the present invention. The number-based particle size distribution is determined by measuring the composite particles by pressure spraying with compressed air using a laser diffraction particle size distribution measuring device, and converting the resulting volume-based particle size distribution into the number-based distribution. Can do.

<Mode diameter>
Further, the frequency of the mode diameter of the composite particle group composed of a plurality of composite particles obtained by the present invention is 12% or more, preferably 13% or more, more preferably 15% or more.

  Here, the mode diameter means a particle diameter having the highest particle existence probability, and shows a maximum value in a particle diameter distribution curve in which the frequency of the existence of individual particle diameters is plotted against the logarithm of the particle diameter. It is the particle diameter, and the frequency of the mode diameter in the present invention is the maximum value in the particle diameter distribution curve. As the frequency of the mode diameter increases, the particle size distribution curve of the composite particle group shows a sharp particle size distribution curve.

  When the frequency of the mode diameter is 12% or more, even if the median diameter of the composite particle group approaches 50 μm which is the lower limit value of the range defined in the present invention, it has a strong adhesiveness contained in the composite particle group of 40 μm or less. Therefore, an electrochemical element electrode having a practical film thickness and excellent film thickness accuracy can be obtained in the production of an electrochemical element electrode by a roll pressure molding method.

  Similar to the median diameter, the mode diameter of the composite particle group is measured by spraying the composite particle group with compressed air using a dry laser diffraction / scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd .: Microtrac MT-3200II). can do.

(Electrochemical element electrode)
The electrochemical element electrode of the present invention (hereinafter sometimes simply referred to as “electrode”) is formed by laminating a mixture layer formed from the above-described composite particle for an electrochemical element electrode on a current collector. is there.

(Current collector)
As the current collector, a material having electrical conductivity and electrochemical durability can be used. Among these, metal materials such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum are preferable from the viewpoint of heat resistance. Among them, in order to make the electrochemical element function as a lithium ion secondary battery or a lithium ion capacitor among electrochemical capacitors, aluminum is particularly preferable for the positive electrode and copper is particularly preferable for the negative electrode. Moreover, in order to make an electrochemical element function as an electric double layer capacitor among sodium ion secondary batteries or electrochemical capacitors, it is particularly preferable that both positive electrode and negative electrode are aluminum.

  The shape is a film or a sheet, and the thickness is appropriately selected depending on the purpose of use, but is usually 1 to 200 μm, preferably 5 to 100 μm, more preferably 8 to 50 μm. Further, the sheet-like current collector may have a shape having holes such as expanded metal, punching metal, and net-like shape.

  The current collector may be subjected to a surface chemical treatment or a surface roughening treatment in advance to reduce contact resistance with the mixture layer or improve adhesion to the mixture layer as necessary. . Examples of the surface chemical treatment include acid treatment and chromate treatment. Examples of the surface roughening treatment include electrochemical etching treatment and etching treatment with acid or alkali.

  Further, for the purpose of improving the adhesion between the current collector and the mixture layer, a current collector having an adhesive coating applied to the surface thereof may be used. In addition, since the binder contained in the adhesive paint is usually insulative, if the current collector coated with the adhesive paint is used for an electrochemical element electrode, the resistance as an electrochemical element is significantly increased. More preferably, the adhesive paint contains a conductive material. An adhesive paint using a conductive material is usually referred to as a conductive adhesive, undercoat slurry, carbon coat slurry or the like.

  The conductive adhesive is obtained by dispersing a conductive material, a binder, and a soluble resin added as necessary in water or an organic solvent. Examples of the conductive material of the conductive adhesive include silver, nickel, gold, graphite, acetylene black, and ketjen black, and graphite and acetylene black are preferable.

  As the binder for the adhesive paint, any of those exemplified as the binder used in the composite particles of the present invention can be used. Moreover, water glass, an epoxy resin, a polyamideimide resin, a urethane resin, etc. can also be used, and each can be used individually or in combination of 2 or more types. Preferred binders for adhesive paints are acrylate polymers, ammonium salts or alkali metal salts of carboxymethyl cellulose, water glass, and polyamideimide resins. Further, as the dispersant for the conductive adhesive, a soluble resin or a surfactant that may be used for the composite particles can be used.

(Mixture layer)
As a method for forming the mixture 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 a mixture layer by applying pressure to the composite particles to perform densification by rearrangement and deformation of the electrode material. The extrusion molding method is a method of molding composite particles into an extruded film, sheet or the like with an extruder.

  Of these, the pressure molding method is preferably employed because it can be performed with simple equipment. As the pressure molding method, for example, the composite particles are supplied to the roll pressure molding device with a supply device such as a screw feeder, and the composite particles are nipped between the two molding rolls to be supplied together with the roll. The composite particles are spread on the current collector provided with the adhesive layer as in the method of forming the mixture layer on the electric body or the support, or the technique disclosed in Japanese Patent No. 4687458, and the composite particles are bladed For example, there is a method of adjusting the thickness by adjusting the thickness and then forming with a roll pressure forming apparatus, a method of filling the mold with an electrode material, and pressurizing the mold to form.

  Among these pressure forming methods, a method of forming a mixture layer on a current collector or a support as seen in Japanese Patent No. 5293383 using a roll pressure forming apparatus is suitable. The molding temperature is usually room temperature to 150 ° C., preferably higher than the melting point or glass transition temperature of the binder of the composite particles, and more preferably 20 ° C. higher than the melting point or glass transition temperature. In roll press molding, the molding speed is usually in the range of 0.1 to 30 m / min, preferably 4 to 30 m / min. The press linear pressure between the forming rolls is usually 0.2 to 30 kN / cm, preferably 1.5 to 15 kN / cm.

  In the roll pressure forming apparatus, a pre-forming roll may be provided before the forming roll. When the composite particles are compressed by the pre-molding roll, the amount of biting of the composite particles into the roll can be reduced as the roll diameter of the pair of rolls constituting the pre-molding roll becomes smaller. And the thickness of the composite material layer in the electrochemical element electrode finally obtained can be made small. On the other hand, if the roll diameter of the pair of rolls constituting the pre-molded roll is too small, the roll may be distorted when the composite particles are compressed, thereby causing variations in the thickness of the sheet-shaped pre-molded body.

  Here, the point at which the peripheral speed of the roll in the vicinity of the roll nip point (the point at which the gap between the pair of rolls becomes narrowest) and the moving speed of the composite particles are the same is referred to as P point. When the sheet-shaped pre-molded body is molded, if it is not filled with the composite particles, the area from the outlet to the composite particle outlet (lower part of the roll of the pre-molding roll) is defective as an electrochemical element electrode. May occur.

  The above defects are likely to occur when a large number of composite particles of 40 μm or less are contained in the particle size distribution of the composite particle group. Further, when the roll rotation speed is constant, the point P decreases as the roll diameter decreases. Therefore, by reducing the roll diameter, the capacity between the point P and the exit of the composite particles can be reduced, and the finally obtained electrochemical device electrode mixture layer can be made into a thin film.

  Therefore, considering such points, the roll diameter of the pair of rolls constituting the pre-molded roll is preferably 10 to 500 mm, more preferably 10 to 250 mm, and still more preferably 10 to 150 mm.

  Moreover, the roll diameter of a pair of roll which comprises a forming roll is a pair of roll which comprises a pre-forming roll so that the pressure at the time of compressing a sheet-like pre-molding body may become larger than the pressure by a pre-forming roll. The roll diameter may be larger than the roll diameter, but the roll diameter is preferably 50 to 1000 mm, more preferably 100 to 500 mm.

  In order to eliminate variations in the thickness of the molded electrode and increase the density of the mixture layer to increase the capacity and strength, post-pressurization may be further performed as necessary. The post-pressing method is generally a roll press process. In the roll press step, two cylindrical rolls are arranged vertically in parallel at a narrow interval, and each is rotated in the opposite direction, and the electrode is bitten and pressed between them. The temperature of the roll may be adjusted by heating or cooling. The roll temperature when heating the roll is 25 to 200 ° C, more preferably 50 to 150 ° C, and still more preferably 80 to 120 ° C. Within this range, not only the strength of the mixture layer can be increased, but also the adhesion between the mixture layer and the current collector can be further enhanced.

(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 secondary battery and an electrochemical capacitor. Examples of the secondary battery include a lithium ion secondary battery and a sodium ion secondary battery. Examples of the electrochemical capacitor include an electric double layer capacitor and a lithium ion capacitor.

(separator)
As the separator, for example, a polyolefin resin such as polyethylene or polypropylene, or a microporous membrane or nonwoven fabric containing an aromatic polyamide resin; a porous resin coat containing inorganic ceramic powder; a nonwoven fabric made of cellulose; it can. 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 dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), butylene carbonate (BC), methyl ethyl carbonate ( Carbonates such as MEC); 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; ions used also as a supporting electrolyte Examples include liquids. 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, an electric double layer capacitor, or a lithium ion capacitor, for example, a positive electrode and a negative electrode are overlapped via a separator, and this is wound according to the battery shape. For example, the battery may be folded and put into a battery container, and an electrolyte solution may be injected into the battery container and sealed. 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 a composite particle for an electrochemical element electrode of the present invention, the composite particle for an electrochemical element electrode for producing an electrochemical element electrode excellent in film thickness accuracy can be produced with high productivity. Moreover, the electrochemical element electrode and electrochemical element which are thin and are excellent in film thickness precision can be obtained by manufacturing an electrochemical element electrode using the composite particle for electrochemical element electrodes which concerns on this invention.

  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
(Manufacture of particulate binder resin for positive electrode)
In a reactor equipped with a mechanical stirrer and a condenser, under a nitrogen atmosphere, 210 parts of ion exchange water, 30% concentration of alkyldiphenyl oxide disulfonate (Dowfax (registered trademark) 2A1, manufactured by Dow Chemical Co.) 1.67 parts, Was 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 ( 1.67 parts of Dowfax (registered trademark) 2A1, manufactured by Dow Chemical Co., Ltd.) and 22.7 parts of ion-exchanged water were added, and this was stirred and emulsified to prepare a monomer mixture. Then, in a state of stirring and emulsifying the monomer mixture, it was added to a reactor charged with 210 parts of ion exchange water and an aqueous potassium persulfate solution at a constant rate over 2.5 hours, and the polymerization conversion rate To 95%, an aqueous dispersion of particulate binder resin A (acrylate polymer) was obtained.

(Preparation of mixture slurry for lithium ion secondary battery positive electrode)
100 parts of lithium cobaltate (hereinafter sometimes referred to as “LCO”) having a 50% volume average particle size of 5 μm as the positive electrode active material, acetylene black (HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) 2 as the conductive material 1.0 parts of a sodium salt of carboxymethyl cellulose as a solid content amount was mixed as a soluble resin, and an appropriate amount of ion-exchanged water was added, and the mixture was sufficiently kneaded in a high viscosity state using a planetary mixer. Thereafter, it is diluted with ion-exchanged water, and 1.5 parts of an aqueous dispersion of the particulate binder resin A as a binder is added in terms of solid content, so as to be used for a lithium ion secondary battery positive electrode having a solid content concentration of 40%. A mixture slurry was prepared.

(Manufacture of composite particles)
The lithium ion secondary battery is installed in an electrostatic atomization granulator provided with a large number of atomizers for electrostatic atomization, each comprising a metal nozzle having an outer diameter of 200 μm and an inner diameter of 120 μm in the upper part of a drying tower having a predetermined tower diameter. The positive electrode mixture slurry was supplied, and a voltage was applied to the atomizer, whereby the lithium ion secondary battery positive electrode mixture slurry supplied to the atomizer was dropletized and sprayed into the tower. The voltage applied at this time was 7.0 kV.

  Next, the sprayed droplets are heat-exchanged by heated air introduced into an electrostatic atomization granulator to dry and solidify the droplets, and neutralize, collect, and remove coarse powder. Thus, composite particles for a lithium ion secondary battery positive electrode of Example 1 having a spherical shape with a moisture content of less than 1% were obtained. The lithium ion secondary battery positive electrode mixture slurry is combined with the ratio of the yield of the lithium ion secondary battery positive electrode composite particles of Example 1 and the sprayed lithium ion secondary battery positive electrode mixture slurry solid weight. When the process yield until it was granulated and the coarse powder was removed was determined, the yield was 96.0%. In addition, the median diameter of the composite particles for the positive electrode of the lithium ion secondary battery of Example 1 is 78 μm, the cumulative frequency of 40 μm or less in the particle size distribution determined on the basis of the number is 0%, and the frequency of the mode diameter is 16 8%. The particle recovery outlet temperature at this time was 85 ° C. In addition, cooling air was introduced into the periphery of the atomizer so that the hot air would spread to the atomizer and the atomizer would not be blocked by drying.

(Preparation of lithium ion secondary battery positive electrode)
First, a conductive adhesive was applied on an aluminum current collector with a die coater and dried in advance on a pair of pre-molded rolls having a roll diameter of 50 mmφ heated to 50 ° C. in a roll pressure molding apparatus. An aluminum current collector foil with a conductive adhesive layer was installed. Next, the lithium ion secondary battery positive electrode composite particles obtained above were supplied to a hopper provided on the top of the pre-molding roll via a quantitative feeder. When the accumulated amount of the composite particles in the hopper provided on the upper part of the pre-molding roll reaches a certain height, a roll press molding apparatus is operated at a speed of 10 m / min. Was molded, and a pre-molded body of a mixture layer for a lithium ion secondary battery positive electrode was formed on the aluminum current-collecting foil with the conductive adhesive layer. Thereafter, the electrode on which the positive electrode mixture layer is pre-formed is pressed with two pairs of 300 mmφ forming rolls provided downstream of the pre-forming roll of the roll pressure forming apparatus and heated to 100 ° C., and the surface of the electrode And the electrode density was increased. In this state, the roll pressure molding apparatus was continuously operated for 10 minutes to produce about 100 m of the lithium ion secondary battery positive electrode of Example 1.

(Example 2)
(Manufacture of particulate binder resin for positive electrode)
Except that the composition ratios of butyl acrylate and ethyl methacrylate were 81.3 parts and 16.3 parts, respectively, a particulate binder resin for a positive electrode was produced in the same manner as in Example 1 to form particulate particles. An aqueous dispersion of landing resin B (acrylate polymer) was obtained.

Further, a spherical shape was obtained in the same manner as in Example 1 except that the particulate binder resin B was used as the binder and the solid content concentration of the lithium ion secondary battery positive electrode mixture slurry was 50%. The composite particle for lithium ion secondary battery positive electrodes of Example 2 was obtained. When the yield was determined in the same manner as in Example 1, the yield was 95.5%. In addition, the median diameter of the obtained composite particle group for a lithium ion secondary battery positive electrode of Example 2 is 153 μm, the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 0%, and the mode diameter The frequency of was 14.7%.
About 100 m of the lithium ion secondary battery positive electrode of Example 2 was produced in the same manner as the production method of the lithium ion secondary battery positive electrode of Example 1 using the composite particles obtained above.

(Example 3)
Spherical composite particles for a lithium ion secondary battery positive electrode of Example 3 were obtained in the same manner as Example 2 except that the solid content concentration was 36%. When the yield was determined in the same manner as in Example 1, the yield was 96.2%.
Further, the median diameter of the obtained composite particle group for the lithium ion secondary battery positive electrode of Example 3 is 54 μm, and the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 31.0%. The frequency of mode diameter was 13.9%.
About 100 m of the lithium ion secondary battery positive electrode of Example 3 was produced in the same manner as the production method of the lithium ion secondary battery positive electrode of Example 1 using the composite particles obtained above.

Example 4
Spherical composite particles for a lithium ion secondary battery positive electrode of Example 4 were obtained in the same manner as Example 3 except that the applied voltage was 10.0 kV. When the yield was determined in the same manner as in Example 1, the yield was 96.3%.
Further, the median diameter of the obtained composite particle group for the lithium ion secondary battery positive electrode of Example 4 is 61 μm, and the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 21.2%, The frequency of mode diameter was 12.8%.
About 100 m of the lithium ion secondary battery positive electrode of Example 4 was produced using the composite particles obtained as described above in the same manner as the production method of the lithium ion secondary battery positive electrode of Example 1.

(Example 5)
(Manufacture of particulate binder resin for positive electrode)
A particulate binder resin C was produced in the same manner as in Example 1 except that the composition ratios of butyl acrylate and ethyl methacrylate were 97.6 parts and 0 parts, respectively. An aqueous dispersion of (acrylate polymer) was obtained.

The spherical composite particle for a lithium ion secondary battery positive electrode of Example 5 was used in the same manner as in Example 1 except that the particulate binder resin C was used as the binder and the solid content concentration was 38%. Obtained. When the yield was determined in the same manner as in Example 1, the yield was 96.2%.
In addition, the median diameter of the obtained composite particle group for the lithium ion secondary battery positive electrode of Example 5 is 70 μm, and the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 11.8%. The frequency of mode diameter was 15.8%.
About 100 m of the lithium ion secondary battery positive electrode of Example 5 was produced in the same manner as the production method of the lithium ion secondary battery positive electrode of Example 1 using the composite particles obtained above.

(Example 6)
A spherical composite particle for a lithium ion secondary battery positive electrode of Example 6 is obtained in the same manner as in Example 5 except that the aqueous dispersion of the particulate binder resin C is 3.0 parts in terms of solid content. It was. When the yield was determined in the same manner as in Example 1, the yield was 96.1%.
Further, the median diameter of the obtained composite particle group for a lithium ion secondary battery positive electrode of Example 6 is 72 μm, and the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 9.8%, The frequency of mode diameter was 16.7%.
About 100 m of the lithium ion secondary battery positive electrode of Example 5 was produced in the same manner as the production method of the lithium ion secondary battery positive electrode of Example 1 using the composite particles obtained above.

(Example 7)
(Preparation of mixture slurry for lithium ion secondary battery positive electrode)
100 parts of lithium cobaltate having a 50% volume average particle diameter of 5 μm as the positive electrode active material, 2 parts of acetylene black (HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as the conductive material, and polyvinylidene fluoride (hereinafter referred to as “binder”) (It may be referred to as “PVDF”.) Mix 5.0 parts, add an appropriate amount of N-methyl-2-pyrrolidone (hereinafter sometimes referred to as “NMP”), and use a planetary mixer to maintain a high viscosity state. Then, the mixture slurry was diluted with N-methyl-2-pyrrolidone to prepare a mixture slurry for a positive electrode of a lithium ion secondary battery having a solid content concentration of 30%.

The same as in Example 1 except that the mixture slurry obtained above was used, that heated nitrogen was used as the heat exchange medium used when producing the composite particles, and that the applied voltage was 10.0 kV. Thus, spherical composite particles for a positive electrode for a lithium ion secondary battery of Example 7 were obtained. When the yield was determined in the same manner as in Example 1, the yield was 96.1%.
Further, the median diameter of the obtained composite particle group for the lithium ion secondary battery positive electrode of Example 7 is 82 μm, the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 0%, and the mode diameter The frequency of was 16.5%.
About 100 m of the lithium ion secondary battery positive electrode of Example 7 was produced in the same manner as the production method of the lithium ion secondary battery positive electrode of Example 1 using the composite particles obtained above.

(Comparative Example 1)
Spherical composite particles for a positive electrode for a lithium ion secondary battery of Comparative Example 1 were obtained in the same manner as in Example 5 except that the solid content concentration was 33%. When the yield was determined in the same manner as in Example 1, the yield was 95.7%.
Moreover, the median diameter of the obtained composite particle group for a lithium ion secondary battery positive electrode of Comparative Example 1 is 43 μm, and the cumulative frequency of 40 μm or less in the particle size distribution determined on the basis of the number is 53.7%. The frequency of mode diameter was 13.0%.
About 100 m of the lithium ion secondary battery positive electrode of Comparative Example 1 was produced in the same manner as the production method of the lithium ion secondary battery positive electrode of Example 1 using the composite particles obtained above.

(Comparative Example 2)
Except that the binder was changed from the aqueous dispersion of the particulate binder resin B to the aqueous dispersion of the particulate binder resin C, and the applied voltage was changed to 2.5 kV, the same as in Example 2. A composite particle for a positive electrode for a lithium ion secondary battery of Comparative Example 2 having a spherical shape was obtained. When the yield was determined in the same manner as in Example 1, the yield was 95.1%.
Further, the median diameter of the obtained composite particle group for the lithium ion secondary battery positive electrode of Comparative Example 2 is 185 μm, the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 0%, and the mode diameter The frequency of was 15.7%.
About 100 m of the lithium ion secondary battery positive electrode of Comparative Example 2 was produced in the same manner as the method of producing the lithium ion secondary battery positive electrode of Example 1 using the composite particles obtained above.

(Comparative Example 3)
Comparative Example as in Example 1 except that the solid content concentration was 65% and the binder was changed from the aqueous dispersion of the particulate binder resin A to the aqueous dispersion of the particulate binder resin B. No. 3 lithium ion secondary battery positive electrode mixture slurry was prepared.

(Manufacture of composite particles)
Using a spray dryer (ODB-8, manufactured by Okawahara Chemical Co., Ltd.), the above mixture slurry was put into a pin type disk atomizer (diameter 84 mm) rotating at 17,000 rpm incorporated in the spray dryer. Supplied and produced droplets by centrifugation. And heated air was introduce | transduced as a heat exchange medium, and the composite particle by the centrifugal granulation method was obtained by drying on the conditions from which the temperature of a particle | grain collection exit becomes 90 degreeC. Next, the composite particles for a lithium ion secondary battery positive electrode of Comparative Example 3 having a spherical shape were obtained by removing the coarse powder of the obtained composite particles. When the yield was determined in the same manner as in Example 1, the yield was 82.0%.
Further, the median diameter of the obtained composite particle group for the lithium ion secondary battery positive electrode of Comparative Example 3 is 57 μm, and the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 63.4%, The frequency of mode diameter was 10.8%.
About 100 m of the lithium ion secondary battery positive electrode of Comparative Example 3 was produced in the same manner as the production method of the lithium ion secondary battery positive electrode of Example 1 using the composite particles obtained above.

(Example 8)
(Manufacture of particulate binder resin for negative electrode)
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 a particulate binder resin S (styrene / butadiene copolymer; hereinafter abbreviated as “SBR”).

(Preparation of mixture slurry for lithium ion secondary battery negative electrode)
100 parts of bulk natural graphite coated with amorphous carbon having a 50% volume average particle diameter of 10 μm as the negative electrode active material, and 1.0 part of sodium salt of carboxymethyl cellulose as a soluble resin in terms of solid content, Further, an appropriate amount of ion-exchanged water was added, and the mixture was sufficiently kneaded in a high viscosity state using a planetary mixer. Thereafter, it is diluted with ion-exchanged water, and 1.5 parts of an aqueous dispersion of the particulate binder resin S as a binder is added in terms of solid content, so as to be used for a lithium ion secondary battery negative electrode having a solid content concentration of 32%. A mixture slurry was prepared.

(Manufacture of composite particles)
The lithium ion secondary battery is installed in an electrostatic atomization granulator provided with a large number of atomizers for electrostatic atomization, each comprising a metal nozzle having an outer diameter of 200 μm and an inner diameter of 120 μm in the upper part of a drying tower having a predetermined tower diameter. The negative electrode mixture slurry was supplied and a voltage was applied to the atomizer, whereby the lithium ion secondary battery negative electrode mixture slurry supplied to the atomizer was made into droplets and sprayed into the tower. The voltage applied at this time was 11.0 kV.

Next, the sprayed droplets are heat-exchanged by heated air introduced into an electrostatic atomization granulator to dry and solidify the droplets, and neutralize, collect, and remove coarse powder. Thus, composite particles for a lithium ion secondary battery negative electrode of Example 8 having a spherical shape were obtained. The particle recovery outlet temperature at this time was 80 ° C. When the yield was determined in the same manner as in Example 1, the yield was 96.7%.
Further, the median diameter of the obtained composite particle group for lithium ion secondary battery negative electrode of Example 8 is 85 μm, the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 0%, and the mode diameter The frequency of was 15.1%.
In addition, cooling air was introduced into the periphery of the atomizer so that the hot air would spread to the atomizer and the atomizer would not be blocked by drying.

(Preparation of negative electrode for lithium ion secondary battery)
First, on a pair of pre-molded rolls having a roll diameter of 50 mmφ heated to 30 ° C. in a roll press molding apparatus, a different type of conductive adhesive from that for the positive electrode was previously applied on a copper current collector with a die coater. Then, a copper current collector foil with a conductive adhesive layer obtained by drying was installed. Next, the composite particles for a lithium ion secondary battery negative electrode obtained above were supplied to a hopper provided on the upper part of the pre-molding roll via a quantitative feeder. When the accumulated amount of the composite particles in the hopper provided on the upper part of the pre-molding roll reaches a certain height, a roll press molding apparatus is operated at a speed of 10 m / min. Was molded, and a pre-molded body of a negative electrode mixture layer for a negative electrode of a lithium ion secondary battery was formed on the copper current collector foil with the conductive adhesive layer. Thereafter, the electrode on which the negative electrode mixture layer is pre-formed is pressed with two pairs of 300 mmφ forming rolls provided downstream of the pre-forming roll of the roll pressure forming apparatus and heated to 100 ° C., and the surface of the electrode And the electrode density was increased. In this state, the roll pressure molding apparatus was continuously operated for 10 minutes to produce about 100 m of the lithium ion secondary battery negative electrode of Example 8.

Example 9
The same as Example 8 except that the amount of the particulate binder resin S used was 3.0 parts in terms of solid content, and the solid content concentration of the lithium ion secondary battery negative electrode mixture slurry was 29%. Thus, spherical composite particles for a lithium ion secondary battery negative electrode of Example 9 were obtained. When the yield was determined in the same manner as in Example 1, the yield was 96.2%.
Further, the median diameter of the obtained composite particle group for lithium ion secondary battery negative electrode of Example 9 is 58 μm, and the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 39.0%, The frequency of mode diameter was 14.2%.
About 100 m of the lithium ion secondary battery negative electrode of Example 9 was produced in the same manner as the production method of the lithium ion secondary battery negative electrode of Example 8 using the composite particles obtained above.

(Comparative Example 4)
The lithium ion secondary battery negative electrode mixture slurry of Comparative Example 4 was prepared by setting the solid content concentration of the lithium ion secondary battery negative electrode mixture slurry of Example 8 to 35%.

(Manufacture of composite particles)
Using a spray dryer (ODB-8, manufactured by Okawara Chemical Co., Ltd.), the above mixture slurry was put into a pin type disk atomizer (diameter: 84 mm) rotating at a rotational speed of 25,000 rpm incorporated in the spray dryer. Supplied and produced droplets by centrifugation. And heated air was introduce | transduced as a heat exchange medium, and the composite particle by the centrifugal granulation method was obtained by drying on the conditions from which the temperature of a particle | grain collection exit becomes 90 degreeC. Next, the composite particles for a lithium ion secondary battery negative electrode of Comparative Example 4 having a spherical shape were obtained by removing the coarse powder of the obtained composite particles. When the yield was determined in the same manner as in Example 1, the yield was 87.0%.
Further, the median diameter of the obtained composite particle group for lithium ion secondary battery negative electrode of Comparative Example 4 is 55 μm, and the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 87.5%, The frequency of mode diameter was 6.8%.

  About 100 m of the lithium ion secondary battery negative electrode of Comparative Example 4 was produced in the same manner as the production method of the lithium ion secondary battery negative electrode of Example 8 using the composite particles obtained above.

(Comparative Example 5)
A spherical lithium ion secondary battery negative electrode of Comparative Example 5 was obtained in the same manner as in Comparative Example 4 except that the rotation speed of the pin type disk atomizer was changed to 17,000 rpm. When the yield was determined in the same manner as in Example 1, the yield was 79.0%.
In addition, the median diameter of the obtained composite particle group for lithium ion secondary battery negative electrode of Comparative Example 5 is 84 μm, and the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 59.5%. The frequency of the mode diameter was 10.0%.
About 100 m of the lithium ion secondary battery negative electrode of Comparative Example 5 was produced using the composite particles obtained as described above in the same manner as the production method of the lithium ion secondary battery negative electrode of Example 8.

(Comparative Example 6)
The composite particles for the negative electrode of the lithium ion secondary battery of Comparative Example 4 were classified with a sieve having an opening of 45 μm. The recovery rate on the sieve having an opening of 45 μm after the classification operation, that is, the classification yield was 56%. A spherical lithium ion secondary battery negative electrode of Comparative Example 6 was obtained in the same manner as in Example 8 except that the composite particles on the sieve having an opening of 45 μm were used.
Further, the median diameter of the obtained composite particle group for lithium ion secondary battery negative electrode of Comparative Example 6 is 90 μm, the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 0%, and the mode diameter The frequency of was 14.1%.
About 100 m of the lithium ion secondary battery negative electrode of Comparative Example 6 was produced in the same manner as the production method of the lithium ion secondary battery negative electrode of Example 8 using the composite particles obtained above.

(Example 10)
(Preparation of mixture slurry for electric double layer capacitor)
100 parts of activated carbon having a 50% volume average particle diameter of 6 μm and a specific surface area of 1650 m ² / g as an active material, 5 parts of acetylene black (HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, and carboxymethylcellulose as a soluble resin The sodium salt was mixed with 3.5 parts in terms of solid content, and an appropriate amount of ion-exchanged water was added, and the mixture was sufficiently kneaded in a high viscosity state using a planetary mixer. Thereafter, it is diluted with ion-exchanged water, and 8.0 parts of the aqueous dispersion of the particulate binder resin B as a binder is added in terms of solid content, thereby being used for an electric double layer capacitor having a solid content concentration of 20%. A mixture slurry was prepared.

(Manufacture of composite particles)
For the electric double layer capacitor in an electrostatic atomization granulator provided with a large number of atomizers for electrostatic atomization comprising metal nozzles having an outer diameter of 200 μm and an inner diameter of 120 μm in the upper part of a drying tower having a predetermined tower diameter The mixture slurry was supplied, and by applying voltage to the atomizer, the mixture slurry for electric double layer capacitor supplied to the atomizer was made into droplets and sprayed into the tower. The voltage applied at this time was 6.0 kV.

Next, the sprayed droplets are heat-exchanged by heated air introduced into an electrostatic atomization granulator to dry and solidify the droplets, and neutralize, collect, and remove coarse powder. Thus, spherical composite particles for an electric double layer capacitor of Example 10 were obtained. The particle recovery outlet temperature at this time was 75 ° C. When the yield was determined in the same manner as in Example 1, the yield was 98.0%.
In addition, the median diameter of the composite particle group for the electric double layer capacitor of Example 10 obtained as described above is 118 μm, the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 0%, and the mode diameter The frequency of was 15.3%.
In addition, cooling air was introduced into the periphery of the atomizer so that the hot air would spread to the atomizer and the atomizer would not be blocked by drying.

(Production of electrode for electric double layer capacitor)
First, a conductive adhesive was applied on an aluminum current collector with a die coater and dried in advance on a pair of pre-molded rolls having a roll diameter of 50 mmφ heated to 50 ° C. in a roll pressure molding apparatus. An aluminum current collector foil with a conductive adhesive layer was installed. Next, the composite particles for an electric double layer capacitor obtained above were supplied to a hopper provided on the top of the pre-molding roll via a quantitative feeder. When the accumulated amount of the composite particles in the hopper provided on the upper part of the pre-molding roll reaches a certain height, a roll press molding apparatus is operated at a speed of 10 m / min. Was molded, and a pre-molded body of a mixture layer for an electric double layer capacitor was formed on the aluminum current collector foil with the conductive adhesive layer. Thereafter, the electrode on which the mixture layer for the electric double layer capacitor is pre-formed is pressed with two pairs of 300 mmφ forming rolls that are provided downstream of the pre-forming roll of the roll pressure forming apparatus and heated to 100 ° C., The surface of the electrode was leveled and the electrode density was increased. The roll pressure molding apparatus was continuously operated for 10 minutes as it was, and about 100 m of an electric double layer capacitor electrode of Example 10 was produced.

  After producing the electrochemical device electrodes of each Example and Comparative Example, the appearance of each electrode was inspected to confirm whether there was any defect such as chipping or scraping. Further, in the appearance inspection, a portion where the above-mentioned chipping, blurring or the like was not observed was cut into 2 m in the longitudinal direction, and the uniformity of the thickness of the electrode produced as described below was evaluated. The results are shown in Table 1.

<Thickness uniformity>
Electrochemical element electrodes cut out as described above are formed at three points evenly at intervals of 5 cm from the center in the width direction (TD direction) to both ends, and at equal intervals of 10 cm in the length direction (MD direction). Measurement was performed to determine an average value A and a value B farthest from the average value. 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.
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

  According to the present invention, as shown in Examples 1 to 10 in Table 1, a slurry containing at least an active material and a binder in a solvent is formed into droplets by an electrostatic atomization method, and the droplets are dried. The composite particles having a median diameter in the particle size distribution obtained on a volume basis of 50 μm or more and 160 μm or less are obtained when a thin electrochemical device electrode is manufactured using a roll press molding method. An electrochemical device electrode with excellent thickness accuracy could be manufactured.

  On the other hand, the composite particles of Comparative Example 1 and Comparative Example 2 produced the composite particles by the electrostatic atomization method described in the present invention as in Examples, but the median in the particle size distribution obtained on a volume basis. Since the diameter is out of the range of 50 μm or more and 160 μm or less, when a thin electrochemical element electrode is manufactured using the roll press molding method, the median diameter is in the range of 50 μm or more and 160 μm or less. It can be confirmed that the film thickness accuracy is inferior to that of the example.

  The composite particle group of Comparative Example 1 has a high cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number as high as 53.7%, and has strong cohesiveness. Therefore, the positive electrode of the lithium ion secondary battery using the roll pressure molding method Even if the composite particle group is supplied to the pre-molding roll part in a locally non-uniform state in this manufacturing process, and this is subjected to compression / thickening operation in the subsequent post-pressing process (roll press process) It is estimated that it has not been resolved.

  Contrary to the composite particles of Comparative Example 1, the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 0%, and the lithium ion secondary battery of Comparative Example 2 should be good with respect to the cohesiveness of the composite particles In order to investigate the reason why the film thickness accuracy of the positive electrode is inferior to that of the lithium ion secondary battery positive electrode described in the examples, the thickness difference in the lithium ion secondary battery positive electrode of Comparative Example 2 in which the film thickness accuracy was evaluated was large, As a result of observing the cross section of the part where the film thickness shows the median value, the composite having a large deviation is estimated to exceed 200 μm before the composite particle group is subjected to the pressure / compression operation in the roll press molding process. The presence of particles was confirmed.

In Comparative Example 3 and Comparative Example 4, the production of an electrochemical element electrode using a roll press molding method, although the median diameter in the particle size distribution determined on a volume basis is in the range of 50 μm to 160 μm. The film thickness accuracy obtained in Example 3 is inferior to that of Example 3 and Example 9 because the composite particle groups of Comparative Example 3 and Comparative Example 4 have a low mode diameter frequency and a wide distribution of composite particle groups. In addition, it is considered that the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number as in Comparative Example 1 is high, and the composite particles are highly cohesive.
In addition, it is surmised that the lithium ion secondary battery positive electrode of Example 4 has better film thickness accuracy than Example 3 because of the same reason as described above.

  This is because the negative electrode of the lithium ion secondary battery of Comparative Example 6 is a comparative example in which the composite particle group of Comparative Example 4 is classified and the cumulative frequency of 40 μm or less in the particle size distribution obtained on the basis of the number is 0%. This is also clear from the fact that the film thickness accuracy is improved as compared with the lithium ion secondary battery negative electrode No. 4.

However, the composite particle of Comparative Example 6 is a particle obtained by subjecting the composite particle of Comparative Example 4 having a yield of 87% to the classification operation, and as described above, the yield in the classification operation is 56%. Therefore, the yield for obtaining composite particles having a desired particle size distribution is 49%.
Therefore, as a method for producing composite particles in order to produce an electrochemical device electrode having a thin thickness and excellent film thickness accuracy by a roll pressure forming method, a conventional production method using a droplet generation method by a centrifugal method is devised. Even if it is added, it is not realistic in terms of productivity.

  From these facts, a particle size distribution obtained on a volume basis is obtained by forming a slurry containing at least an active material and a binder in a solvent into droplets by an electrostatic atomization method and drying the droplets. The composite particles having a median diameter in the range of 50 μm or more and 160 μm or less are less agglomerated in the composite particle group when the thin electrochemical element electrode is produced using the roll press molding method, and the fluidity is high. It is considered that the film thickness accuracy is excellent because there are few composite particles having a size that hinders the construction of a thin electrode.

  In relation to the above, from Table 1, it can be confirmed that the lithium ion secondary battery positive electrode of Example 4 has higher film thickness accuracy than the lithium ion secondary battery positive electrode of Example 2. When the median diameters of Example 4 and Example 2 are compared, the median diameter of the composite particle group of Example 4 is smaller. In the composite particle group of Example 4, in producing a thin lithium ion secondary battery positive electrode, there are no particles that interfere with the film thickness accuracy. It is considered that the thickness accuracy is excellent.

Next, attention is focused on a method for obtaining composite particles.
Compared to the composite particles of Comparative Example 3, Comparative Example 4, and Comparative Example 5 manufactured using the conventional droplet generation method by the centrifugal method, the manufacturing was performed using the electrostatic atomization method. It can be confirmed that all the composite particles of Examples 1 to 9 have a high yield. In the conventional method of producing droplets by centrifugation and solidifying the droplets by drying, the droplets sprayed from the substantially central portion of the drying tower toward the outer periphery must be liquid before solidifying by drying. Part of the droplets, that is, large droplets having a size equal to or larger than a certain value in the sprayed droplet distribution, adhere as droplets to the drying tower wall due to insufficient drying, and composite particles cannot be produced with high yield. In contrast, the droplet generation method of the present invention does not spray from the center of the drying tower to the outer periphery substantially horizontally, but sprays in a substantially vertical direction, so the drying time of the droplets on the equipment is easy. It is possible to prevent the droplets from adhering to the tower wall of the drying tower, and it is possible to efficiently solidify the droplets and recover the solidified composite particle group. is there. As a result, it is possible to produce composite particles with high yield.

  Note that the yield of the composite particles of Comparative Example 5 is lower than that of Comparative Example 4 when the average droplet size is increased by decreasing the rotational speed of the pin type disk atomizer. This is because the adhesion of droplets is becoming more serious.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In other words, those specific examples that have been appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention.

DESCRIPTION OF SYMBOLS 2 ... Composite particle manufacturing apparatus, 6 ... Agitation blade, 8 ... Slurry, 10 ... Slurry tank, 12 ... Composite particle, 14 ... Granulation apparatus, 18 ... Composite particle recovery tank, 22 ... Drying tower, 24 ... High pressure power supply, 26 ... Atomizer nozzle

Claims (6)

A method for producing composite particles for producing an electrochemical device electrode by applying a pressure operation in a dry state to composite particles comprising at least an active material and a binder,
A slurrying step (I) for obtaining a slurry comprising at least the active material and the binder in a solvent;
A droplet generation step (II) in which the slurry is converted into droplets by electrostatic atomization; and
A droplet drying step (III) for solidifying the droplets by drying to obtain composite particles,
An electrochemical element characterized in that a median diameter in a particle size distribution determined on a volume basis of a composite particle group composed of a plurality of composite particles obtained from the droplet drying step (III) is 50 μm or more and 160 μm or less A method for producing composite particles for an electrode.   The method for producing composite particles for an electrochemical element electrode according to claim 1, wherein the solvent is water, and the slurry further contains a soluble resin.   The cumulative frequency of 40 μm or less in the particle size distribution of the composite particle group composed of a plurality of the composite particles obtained from the droplet drying step (III) is 50% or less. Item 3. A method for producing composite particles for an electrochemical element electrode according to Item 1 or 2.   The frequency of the mode diameter in the particle size distribution determined on a volume basis of the composite particle group composed of a plurality of the composite particles obtained from the droplet drying step (III) is 12% or more. The manufacturing method of the composite particle for electrochemical element electrodes in any one of 1-3. An electrode mixture layer containing the composite particles for electrochemical element electrodes obtained by the production method according to any one of claims 1 to 4 is laminated on a current collector. A method for producing an electrochemical element electrode. Method for producing an electrochemical element which comprises a method for producing an electrochemical device electrode according to claim 5.

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