JP2014157661A - Process of manufacturing composite particle for positive electrode of electrochemical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process of manufacturing a composite particle for a positive electrode of an electrochemical element, excellent in dispersion of a conductive agent even when a water type slurry is used, and having low resistivity when it is made to be a battery.SOLUTION: The process of manufacturing a composite particle for a positive electrode of an electrochemical element includes the steps of: obtaining a slurry by dispersing a positive electrode active material, a conductive agent, and a binder into water; and obtaining a granulation particle by spray drying and granulating the slurry, wherein a ratio of degree of hydrophobicity (a positive electrode active material/a conductive agent) of the positive electrode active material and the conductive agent obtained by a methanol method is 0.5 or more and 1.5 or less.

Description

  The present invention relates to a method for producing composite particles for an electrochemical device positive electrode that can be used for producing a positive electrode of an electrochemical device such as a lithium ion secondary battery or a lithium ion capacitor.

  Electrochemical elements such as lithium ion secondary batteries that are small and lightweight, have high energy density, and can be repeatedly charged and discharged are rapidly expanding their demands by taking advantage of their characteristics. Lithium ion secondary batteries are used in fields such as mobile phones, notebook personal computers, and electric vehicles because of their relatively high energy density. However, with the expansion and development of electrochemical device applications, low resistance There is a need for further improvements, such as higher capacity, higher capacity, and improved mechanical properties and productivity. Under such circumstances, there is a demand for a more productive manufacturing method for electrochemical element electrodes, and various improvements have been made regarding a manufacturing method capable of high-speed molding and a material for electrochemical element electrodes suitable for this manufacturing method. It has been broken.

Electrochemical element electrodes are usually formed by laminating an electrode active material layer formed by binding an electrode active material and a conductive agent used as necessary with a binder on a current collector. It is. For example, in Patent Document 1, a particulate electrode material is obtained by spray drying a slurry containing an electrode active material, rubber particles, and a dispersion medium, and an electrode active material layer is formed using the obtained electrode material. Yes.
However, in Patent Document 1, the conductive agent is unevenly distributed on the surface in the particulate electrode material, and as a result, the resistance of the battery using the electrode obtained by using the particulate electrode material is lowered. Has occurred.

  On the other hand, Patent Document 2 proposes a technique for treating a positive electrode active material with a coupling agent for the purpose of preventing deterioration of the performance of the active material due to moisture, particularly in an electrochemical element electrode. However, an aqueous binder may be used as a binder when forming a component such as an electrode of a lithium ion secondary battery for the purpose of improving cycle characteristics, but a slurry containing an aqueous binder is used. It was not considered that the positive electrode active material layer was used to form the positive electrode active material layer.

Japanese Patent No. 4219705 JP 2007-18874 A

  An object of the present invention is to provide a method for producing composite particles for an electrochemical device positive electrode that is excellent in dispersion of a conductive agent even when an aqueous slurry is used and has a low resistance when used as a battery.

  As a result of intensive studies, the inventor found that the poor dispersion of the conductive material in the particulate electrode material obtained by using the aqueous slurry is most attributable to the large difference in the degree of flooding between the electrode active material and the conductive agent. As a result, the inventors have found that the above object can be achieved by setting the ratio of the degree of water repellency between the electrode active material and the conductive agent within a specific range, and have completed the present invention.

That is, according to the present invention,
(1) including a step of dispersing a positive electrode active material, a conductive agent and a binder in water to obtain a slurry; and a step of obtaining granulated particles by spray-drying the slurry to obtain granulated particles. Electrochemical element positive electrode composite, characterized in that the ratio of the degree of hydrophobicity obtained by the methanol method (positive electrode active material / conductive agent) between the substance and the conductive agent is 0.5 or more and less than 1.5 Particle manufacturing method,
(2) The method for producing composite particles for electrochemical element positive electrodes according to (1), wherein the positive electrode active material is a positive electrode active material that has been subjected to water repellent treatment.
(3) The method for producing composite particles for electrochemical element positive electrodes according to (2), wherein the water repellent treatment is a coupling agent treatment,
(4) The coupling agent treatment is a silane coupling agent treatment, and the introduction amount of the silane coupling agent is 0.1% or more and less than 3.0% with respect to the weight of the positive electrode active material. (3) The manufacturing method of the composite particle for electrochemical element positive electrodes as described in this invention is provided.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where an aqueous slurry is used, the manufacturing method of the composite particle for electrochemical element positive electrodes which is excellent in dispersion | distribution of a electrically conductive agent and has low resistance when it is set as a battery can be provided.

Hereinafter, the manufacturing method of the composite particle for electrochemical element positive electrodes which concerns on embodiment of this invention is demonstrated. The composite particle for an electrochemical device positive electrode of the present invention comprises a step of obtaining a slurry by dispersing a positive electrode active material, a conductive agent and a binder in water, and spray-drying the slurry to granulate the granulated particles. The ratio of the degree of hydrophobicity obtained by the methanol method (positive electrode active material / conductive agent) between the positive electrode active material and the conductive agent is 0.5 or more and less than 1.5. Features.
Moreover, in order to make the ratio of the degree of hydrophobicity between the positive electrode active material and the conductive agent within the above range, the positive electrode active material is preferably a positive electrode active material that has been subjected to water repellent treatment.

(Positive electrode active material)
As the positive electrode active material used for the composite particle for the electrochemical device positive electrode of the present invention, an active material capable of occluding and releasing lithium ions is used, and the electrode active material for positive electrode for lithium ion secondary battery (positive electrode active material) is inorganic. They are roughly classified into those composed of compounds and those composed of organic compounds.

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

Examples of transition metal oxides include MnO, MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , Cu ₂ V ₂ O ₃ , amorphous V ₂ O—P ₂ O ₅ , MoO _{3 and the} like. Among these, MnO, V ₂ O ₅ , V ₆ O ₁₃ , and TiO ₂ are preferable from the viewpoint of cycle stability and capacity of the obtained secondary battery.

The transition metal sulfide, TiS _2, TiS _3, amorphous MoS _2, FeS, and the like. Examples of the lithium-containing composite metal oxide include a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel structure, and a lithium-containing composite metal oxide having an olivine structure.

Examples of the lithium-containing composite metal oxide having a layered structure include lithium-containing cobalt oxide (LiCoO ₂ ), lithium-containing nickel oxide (LiNiO ₂ ), Co—Ni—Mn lithium composite oxide, and Ni—Mn—Al. Lithium composite oxide, lithium composite oxide of Ni—Co—Al, solid solution of LiMaO ₂ and Li ₂ MbO ₃ , xLiMaO _2. (1-x) Li ₂ MbO ₃ (0 <x <1, Ma is average And one or more transition metals having an oxidation state of 3+, and Mb is one or more transition metals having an average oxidation state of 4+). From the viewpoint of improving the cycle characteristics of the secondary battery, LiCoO ₂ is preferably used, and from the viewpoint of improving the energy density of the secondary battery, a solid solution of LiMaO ₂ and Li ₂ MbO ₃ is preferable. Further, as a solid solution of LiMaO ₂ and Li ₂ MbO ₃ , in particular, xLiMaO ₂ · (1-x) Li ₂ MbO ₃ (0 <x <1, Ma = Ni, Co, Mn, Fe, Ti, etc., Mb = Mn, Zr, Ti, etc.) are preferable, and xLiMaO _2. (1-x) Li ₂ MnO ₃ (0 <x <1, Ma = Ni, Co, Mn, Fe, Ti, etc.) is particularly preferable. From the viewpoint of high capacity and easy availability, it is preferable to use a lithium composite oxide of Co—Ni—Mn.

As the lithium-containing composite metal oxide having a spinel structure, Li _a [Mn _2−x Md _x ] O _{4 in} which a part of Mn of lithium manganate (LiMn ₂ O ₄ ) is substituted with another transition metal Md includes one or more transition metals having an average oxidation state of 4+, Md = Ni, Co, Fe, Cu, Cr, etc., 0 <x <1, 0 ≦ a ≦ 1), and the like. Among the lithium-containing metal oxide having a spinel structure, Li _a was replaced with Mn in _{Fe Fe x Mn 2-x O} 4-z (0 ≦ a ≦ 1,0 <x <1,0 ≦ z ≦ 0.1 ) Is preferable because of its low cost. In addition, LiNi _0.5 Mn _1.5 O _{4 and the} like in which Mn is replaced with Ni can replace all Mn ³⁺ which is considered to be a structural deterioration factor, and an electrochemical reaction from Ni ²⁺ to Ni ⁴⁺ is performed. Therefore, it is preferable because it has a high operating voltage and a high capacity.

Examples of lithium-containing composite metal oxides having an olivine structure include Li _y McPO ₄ (wherein Mc is one or more transition metals having an average oxidation state of 3+, Mc = Mn, Co, Fe, etc., 0 ≦ y An olivine type lithium phosphate compound represented by ≦ 2) may be mentioned. Mn, Co or Fe may be partially substituted with other metals, and examples of metals that can be substituted include Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, Si, B, and Mo. Can be mentioned.

Other examples include a positive electrode active material having a polyanion structure such as Li ₂ MeSiO ₄ (where Me is Fe, Mn), LiFeF ₃ having a perovskite structure, Li ₂ Cu ₂ O ₄ having an orthorhombic structure, and the like. .

  The positive electrode active material for a lithium ion secondary battery may be a mixture of the above inorganic compound and organic compound. The particle diameter of the positive electrode active material is appropriately selected in consideration of other constituent elements of the battery, but the load characteristics, cycle characteristics, and the viewpoint of improving battery characteristics such as obtaining a secondary battery having a large charge / discharge capacity and From the viewpoint of easy handling when producing an electrode slurry and an electrode, the 50% volume cumulative particle diameter is preferably 0.1 to 50 μm, more preferably 1 to 20 μm. The 50% volume cumulative particle size can be determined by measuring the particle size distribution by laser diffraction.

  Examples of the positive electrode active material for a lithium ion capacitor include activated carbon, polyacene organic semiconductor (PAS), carbon nanotube, carbon whisker, and graphite that can be reversibly doped and dedoped with anions and / or cations. Preferred positive electrode active materials are activated carbon and carbon nanotubes. The volume average particle diameter of the positive electrode active material used for the lithium ion capacitor is preferably 0.1 to 100 μm, more preferably 0.5 to 50 μm, and still more preferably 0.8 to 20 μm.

(Water repellent treatment)
The positive electrode active material used for the composite particles for electrochemical device positive electrodes of the present invention is preferably a positive electrode active material that has been subjected to water repellent treatment. The method for the water repellent treatment is not particularly limited, but it is preferable to perform the water repellent treatment using a coupling agent. As the coupling agent, a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, or the like can be used.

  Examples of the silane coupling agent include alkyl silane, alkoxy silane, and disilazane.

  Examples of the alkylsilane include methyltrichlorosilane, ethyltrichlorosilane, trimethylchlorosilane, triethylchlorosilane, tripropylchlorosilane, trihexylchlorosilane, vinyltrichlorosilane, and the like.

  Alkoxysilanes include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, and dihexyldimethoxy. Silane, trimethylmethoxysilane, triethylmethoxysilane, tripropylmethoxysilane, nonyltriethoxysilane, decyltriethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, dihexyldiethoxysilane, trimethylethoxysilane, triethylethoxysilane, tripropyl Ethoxysilane, trihexylethoxysilane, tetramethoxysilane, tetraethoxysilane, γ- Taku Lilo trimethoxysilane and the like.

  Examples of the disilazane include hexamethyldisilazane, tetramethyldisilazane, divinyltetramethyldisilazane, hexamethylcyclotrisilazane, and octamethylcyclotetrasilazane.

  Titanate coupling agents include isopropyl trioctanoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyl tristearoyl titanate, isopropyl triisostearoyl titanate, isopropyl diacryl titanate, dicumylphenyloxyacetate titanate, diisostearoyl ethylene titanate. Etc. Commercially available titanate coupling agents include KR TTS, KR36B, KR55, KR41B, KR38S, KR138S, KR238S, 338X, KR 44, KR 9SA (all from Ajinomoto Fine Techno Co., Ltd. Trademark)))) and the like.

  In addition, as an aluminate coupling agent, trimethoxyaluminum, triethoxyaluminum, tripropoxyaluminum, triisopropoxyaluminum, tributoxyaluminum, aceturoxyaluminum diisopropylate (commercially available from Ajinomoto Fine Techno Co., Ltd., And alkoxyaluminum such as “Plenact AL-M”).

  Among these, from the viewpoint of good reactivity, it is preferable to use a silane coupling agent, and it is more preferable to use disilazane.

  Moreover, only one type of these coupling agents may be used, or two or more types may be used in combination. When two or more types are used in combination, tetraethoxysilane is preferably used in combination from the viewpoint of increasing the reaction point.

  There is no particular limitation on the method for water-repellent treatment of the positive electrode active material. For example, a dry method in which a coupling agent is brought into direct contact with the surface of the positive electrode active material, or a solution obtained by dissolving the coupling agent in a solvent is used. The wet method of adding and mixing is mentioned. The dry method is preferred because the process is simple and efficient. The positive electrode active material which performed the water-repellent process by drying at 40-200 degreeC after that can be obtained.

  In this case, the coupling agent is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the positive electrode active material. Add coupling agent to. If the amount of the coupling agent is too large, a side reaction of the battery occurs, which is not preferable. If the amount of the coupling agent is too small, the water repellent effect cannot be sufficiently obtained.

  The degree of hydrophobicity of the positive electrode active material subjected to water repellency treatment as measured by the methanol method is preferably 20 to 90%. Further, the ratio of the hydrophobization degree of the conductive agent, which will be described later, is 0.5 or more and less than 1.5, preferably 0.7 or more and 1. It is less than 3, more preferably 0.8 or more and less than 1.2.

(Conductive agent)
The conductive agent used for the composite particle for an electrochemical device positive electrode of the present invention is composed of an allotrope of particulate carbon that has conductivity and does not have pores that can form an electric double layer. Examples thereof include conductive carbon black such as black, acetylene black, and ketjen black (registered trademark of Akzo Nobel Chemicals Bethloten Fennaut Shap). Among these, acetylene black and furnace black are preferable.

  The volume average particle diameter of the conductive agent used in the composite particles for electrochemical device positive electrode of the present invention is preferably smaller than the volume average particle diameter of the positive electrode active material, from the viewpoint of obtaining high conductivity with a smaller amount of use, Preferably it is 0.001-10 micrometers, More preferably, it is 0.05-5 micrometers, More preferably, it is 0.01-1 micrometer. These conductive agents can be used alone or in combination of two or more. The amount of the conductive agent is preferably based on 100 parts by weight of the positive electrode active material from the viewpoint of increasing the capacity of the lithium ion secondary battery using the obtained composite particles for electrochemical device positive electrodes and reducing the internal resistance. It is 0.1-50 weight part, More preferably, it is 0.5-15 weight part, More preferably, it is 1-10 weight part.

(Binder)
The binder used in the composite particle for electrochemical device positive electrode of the present invention is not particularly limited as long as it is a compound capable of binding positive electrode active materials to each other. By using the binder, the binding property of the positive electrode active material layer in the positive electrode is improved, the strength against mechanical force applied during the process of winding the electrode is improved, and the positive electrode active material in the positive electrode Since the layer is difficult to be detached, the risk of a short circuit due to the desorbed material is reduced.

Various resin components can be used as the binder. For example, polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, polyacrylonitrile derivatives, and the like can be used. These may be used alone or in combination of two or more.
Furthermore, the soft polymer illustrated below can also be used as a binder.

Acrylic acid such as polybutyl acrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, polyacrylamide, polyacrylonitrile, butyl acrylate / styrene copolymer, butyl acrylate / acrylonitrile copolymer, butyl acrylate / acrylonitrile / glycidyl methacrylate copolymer Or an acrylic soft polymer which is a homopolymer of a methacrylic acid derivative or a copolymer with a monomer copolymerizable therewith;
Isobutylene-based soft polymers such as polyisobutylene, isobutylene-isoprene rubber, isobutylene-styrene copolymer;
Polybutadiene, polyisoprene, butadiene / styrene random copolymer, isoprene / styrene random copolymer, acrylonitrile / butadiene copolymer, acrylonitrile / butadiene / styrene copolymer, butadiene / styrene / block copolymer, styrene / butadiene / Diene-based soft polymers such as styrene block copolymer, isoprene / styrene block copolymer, styrene / isoprene / styrene block copolymer;
Silicon-containing soft polymers such as dimethylpolysiloxane, diphenylpolysiloxane, dihydroxypolysiloxane;
Liquid polyethylene, polypropylene, poly-1-butene, ethylene / α-olefin copolymer, propylene / α-olefin copolymer, ethylene / propylene / diene copolymer (EPDM), ethylene / propylene / styrene copolymer, etc. Olefinic soft polymers of
Vinyl-based soft polymers such as polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, vinyl acetate / styrene copolymer;
Epoxy-based soft polymers such as polyethylene oxide, polypropylene oxide, epichlorohydrin rubber;
Fluorine-containing soft polymers such as vinylidene fluoride rubber and tetrafluoroethylene-propylene rubber;
Examples thereof include other soft polymers such as natural rubber, polypeptide, protein, polyester-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, and polyamide-based thermoplastic elastomer. These soft polymers may have a cross-linked structure or may have a functional group introduced by modification.

  The amount of the binder used in the positive electrode active material layer (the binder for the positive electrode active material layer) is 100 wt% of the positive electrode active material from the viewpoint of preventing the positive electrode active material from falling off the electrode without inhibiting the battery reaction. The amount is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 4 parts by weight, and particularly preferably 0.5 to 3 parts by weight with respect to parts.

  The binder for the positive electrode active material layer is prepared as a solution or a dispersion to produce an electrode. The viscosity of this solution or dispersion is preferably 1 to 300,000 mPa · S, more preferably 50 to 10,000 mPa · S. The viscosity is a value measured using a B-type viscometer at 25 ° C. and a rotation speed of 60 rpm.

(Manufacture of composite particles for electrochemical device cathode)
Electrochemical element positive electrode composite particles (hereinafter sometimes simply referred to as “composite particles”) are granulated using a positive electrode active material, a conductive agent, a binder, and other components added as necessary. A positive electrode active material, a conductive agent, and a binder, each of which is not present as an individual particle, but is a constituent component of a positive electrode active material, a conductive agent, and a binder. One particle is formed by three or more components including an agent. Specifically, a plurality of individual particles of three or more components are combined to form secondary particles, and a plurality of (preferably several to several tens) positive electrode active materials are bound. Those that are bound by an agent to form particles are preferred.

The shape of the composite particles is preferably substantially spherical. That is, the short axis diameter of the composite particles is L _s , the long axis diameter is L _l , L _a = (L _s + L _l ) / 2, and a value of (1− (L _l −L _s ) / L _a ) × 100 Is a sphericity (%), the sphericity is preferably 80% or more, and more preferably 90% or more. Here, the minor axis diameter L _s and the major axis diameter L _l are values measured from a scanning electron micrograph image.

  The average particle diameter of the composite particles is preferably 30 to 100 μm, more preferably 35 to 90 μm, and still more preferably, from the viewpoint of a good balance between the uniformity of the basis weight when producing the electrode and the fluidity of the composite particles. 40-80 μm. If the average particle diameter of the composite particles is too large, the variation in weight per unit area when the electrodes are produced using the composite particles will be large. If the average particle diameter of the composite particles is too small, the fluidity of the composite particles will be poor.

  The average particle size of the composite particles is a volume average particle size calculated by measuring with a laser diffraction particle size distribution measuring device (for example, SALD-3100; manufactured by Shimadzu Corporation).

  Composite particles can be obtained by spray drying granulation. Hereinafter, the spray drying granulation method will be described. First, a slurry for composite particles containing a positive electrode active material, a conductive agent, a binder, and other components added as necessary is prepared. The slurry for composite particles can be prepared by dispersing or dissolving a positive electrode active material, a conductive agent, a binder, and other components added as necessary in water as a solvent. In this case, when the binder is dispersed in water as a dispersion medium, it can be added in a state dispersed in water.

  Moreover, the viscosity at room temperature of the slurry for composite particles is preferably 10 to 3,000 mPa · s, more preferably 30 to 1,500 mPa · s, and still more preferably 50, from the viewpoint of increasing the productivity of the spray drying granulation step. ˜1,000 mPa · s.

  Moreover, in this invention, when preparing the slurry for composite particles, you may add a dispersing agent and surfactant as needed. Examples of the surfactant include amphoteric surfactants such as anionic, cationic, nonionic, and nonionic anions, and anionic or nonionic surfactants that are easily thermally decomposed are preferable. The compounding amount of the surfactant is preferably 50 parts by weight or less, more preferably 0.1 to 10 parts by weight, and further preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the positive electrode active material. .

  From the viewpoint of uniformly dispersing the binder in the slurry, the amount of water that is the solvent used when preparing the composite particle slurry is preferably 1 to 50% by weight, more preferably the solid content concentration of the slurry. The amount is 5 to 50% by weight, more preferably 10 to 30% by weight.

  The method or order of dispersing or dissolving the positive electrode active material, the conductive agent and the binder, and other components added as necessary in water as a solvent is not particularly limited. A method of adding and mixing a positive electrode active material, a conductive agent, a binder and a dispersant, dissolving a dispersant in water as a solvent, and then adding a binder (for example, latex) dispersed in the solvent (water) Finally, a method of adding and mixing the positive electrode active material and the conductive agent, and adding and mixing the positive electrode active material and the conductive agent to a binder dispersed in water as a solvent. And a method in which a dispersant dissolved in a solvent (water) is added and mixed.

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

  Subsequently, the obtained slurry for composite particles is granulated by spray drying. Spray drying is a method of spraying and drying a slurry in hot air. An atomizer is used as an apparatus used for spraying slurry. There are two types of atomizers: a rotating disk system and a pressurizing system. In the rotating disk system, slurry is introduced almost at the center of a disk that rotates at high speed, and the slurry is removed from the disk by the centrifugal force of the disk. In this case, the slurry is atomized. In the rotating disk system, the rotational speed of the disk depends on the size of the disk, but is preferably 5,000 to 30,000 rpm, more preferably 15,000 to 30,000 rpm. The lower the rotational speed of the disk, the larger the spray droplets and the larger the average particle size of the resulting composite particles. Examples of the rotating disk type atomizer include a pin type and a vane type, and a pin type atomizer is preferable. A pin-type atomizer is a type of centrifugal spraying device that uses a spraying plate, and the spraying plate has a plurality of spraying rollers removably mounted on a concentric circle along its periphery between upper and lower mounting disks. It consists of The slurry for composite particles is introduced from the center of the spray disk, adheres to the spray roller by centrifugal force, moves outward on the roller surface, and finally sprays away from the roller surface. On the other hand, the pressurization method is a method in which the slurry for composite particles is pressurized and sprayed from a nozzle to be dried.

  The temperature of the slurry for composite particles to be sprayed is preferably room temperature, but may be heated to a temperature higher than room temperature. Moreover, the hot air temperature at the time of spray drying becomes like this. Preferably it is 25-200 degreeC, More preferably, it is 50-150 degreeC, More preferably, it is 80-120 degreeC. In the spray drying method, the method of blowing hot air is not particularly limited. For example, the method in which the hot air and the spraying direction flow side by side, the method in which the hot air is sprayed at the top of the drying tower and descends with the hot air, and the sprayed droplets and hot air flow countercurrently Examples include a contact method, and a method in which sprayed droplets first flow in parallel with hot air, then drop by gravity and contact countercurrent.

  In addition to the method of spraying the slurry for composite particles having the positive electrode active material, the conductive agent and the binder in a batch, the spraying method includes a conductive agent, a binder and other additives as required. A method of spraying the contained slurry onto the flowing positive electrode active material can also be used. From the viewpoint of ease of particle size control, productivity, and reduction in particle size distribution, an optimal method may be appropriately selected according to the components of the composite particles.

(Electrochemical element positive electrode)
The electrochemical element positive electrode used in the present invention is formed by laminating a positive electrode active material layer composed of the above-described composite particle for an electrochemical element positive electrode on a current collector. As the current collector material, for example, metal, carbon, conductive polymer and the like can be used, and metal is preferably used. As the metal, copper, aluminum, platinum, nickel, tantalum, titanium, stainless steel, other alloys and the like are usually used. Among these, it is preferable to use copper, aluminum, or an aluminum alloy in terms of conductivity and voltage resistance. In addition, when high voltage resistance is required, high-purity aluminum disclosed in JP 2001-176757 A can be suitably used. The current collector is in the form of a film or a sheet, and the thickness thereof is appropriately selected according to the purpose of use, but is preferably 1 to 200 μm, more preferably 5 to 100 μm, and still more preferably 10 to 50 μm.

  When laminating the positive electrode active material layer on the current collector, the composite particles may be formed into a sheet shape and then laminated on the current collector, but the composite particles are directly pressure-molded on the current collector. Is preferred. As a method for pressure molding, for example, a roll type pressure molding apparatus provided with a pair of rolls is used, and a roll type pressure molding apparatus is used to feed composite particles with a feeder such as a screw feeder while feeding a current collector with the roll. By supplying to the roll pressure forming method for forming the positive electrode active material layer on the current collector, and dispersing the composite particles on the current collector, adjusting the thickness by smoothing the composite particles with a blade, Next, a method of forming with a pressurizing apparatus, a method of filling composite particles into a mold, and pressurizing the mold to form are included. Among these, the roll pressure molding method is preferable. In particular, since the composite particle for electrochemical device positive electrode of the present invention has high fluidity, it can be molded by roll press molding due to its high fluidity, thereby improving productivity. It becomes.

  The temperature at the time of roll press molding is preferably 25 to 200 ° C., more preferably 50 to 150 ° C., and still more preferably, from the viewpoint of sufficient adhesion between the positive electrode active material layer and the current collector. Is 80-120 ° C. Moreover, the press linear pressure between rolls at the time of roll press molding is preferably 10 to 1000 kN / m, more preferably 200 to 900 kN / m, from the viewpoint of improving the uniformity of the thickness of the positive electrode active material layer. More preferably, it is 300-600 kN / m. Moreover, the molding speed at the time of roll pressure molding is preferably 0.1 to 20 m / min, more preferably 4 to 10 m / min.

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

(Electrochemical element)
The electrochemical element includes an electrochemical element positive electrode, a negative electrode, a separator, and an electrolytic solution obtained as described above. Examples of the electrochemical element include a lithium ion secondary battery and a lithium ion capacitor. Hereinafter, a case where the electrochemical element is a lithium ion secondary battery will be described.

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

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

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

  Moreover, the electrolyte solution may contain an additive. 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.

Further, instead of the electrolyte solution, for example, a polymer electrolyte such as polyethylene oxide or polyacrylonitrile; a gel polymer electrolyte obtained by impregnating the polymer electrolyte with an electrolyte solution; an inorganic solid electrolyte such as LiI or Li ₃ N; May be used.

(Negative electrode)
As the negative electrode, one having a current collector and a negative electrode active material layer formed on the surface of the current collector is usually used. As the negative electrode current collector, for example, the same as the positive electrode current collector may be used. Among these, copper is preferable as the current collector for the negative electrode. Moreover, you may use metals, such as lithium and silicon, and those alloys, for example, without using a collector as a negative electrode.

  The negative electrode active material layer is a layer containing a negative electrode active material and, if necessary, a binder. The binder may be omitted if not necessary. Examples of the negative electrode active material include carbonaceous materials such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads, and pitch-based carbon fibers; conductive polymers such as polyacene; silicon, tin, zinc, manganese, iron, nickel Metals or alloys thereof; oxides or sulfates of the metals or alloys; metal lithium; lithium alloys such as Li—Al, Li—Bi—Cd, Li—Sn—Cd; lithium transition metal nitrides; silicon, etc. Is mentioned. Further, as the negative electrode active material, a material obtained by attaching a conductive additive to the surface of the negative electrode active material particles by, for example, a mechanical modification method may be used. Moreover, a negative electrode active material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The particle diameter of the negative electrode active material particles is appropriately selected in view of other components of the lithium ion secondary battery. Among these, from the viewpoint of improving battery characteristics such as initial efficiency, load characteristics, and cycle characteristics, the 50% volume cumulative particle diameter of the negative electrode active material is preferably 1 to 50 μm, more preferably 15 to 30 μm.

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

  As a binder used for a negative electrode active material layer as needed, you may use the thing similar to the particulate-form binder used in the positive electrode active material layer, for example. In addition, for example, polymers such as polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, polyacrylonitrile derivatives; acrylics A soft polymer such as a soft polymer, a diene-based soft polymer, an olefin-based soft polymer, or a vinyl-based soft polymer may be used. Moreover, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  In addition, the negative electrode active material layer may contain components other than the negative electrode active material and the binder as necessary. As components other than the negative electrode active material and the binder, for example, carboxymethyl cellulose, methyl cellulose, (modified) poly (meth) acrylic acid, (modified) polyvinyl alcohol, acrylic acid or a copolymer of acrylate and vinyl alcohol, polyethylene glycol , Polyethylene oxide, polyvinyl pyrrolidone, modified polyacrylic acid, oxidized starch, phosphate starch, casein, various modified starches, acrylonitrile-butadiene copolymer hydride, maleic anhydride or maleic acid or copolymer of fumaric acid and vinyl alcohol And water-soluble polymers such as polyvinyl alcohols. “(Modified) poly” means “unmodified poly” or “modified poly”.

  The thickness of the negative electrode is preferably 5 to 300 μm, more preferably 10 to 250 μm, from the viewpoint that the load collector and the energy density can be improved satisfactorily with the total of the current collector and the negative electrode active material layer.

  For example, the negative electrode may be manufactured by preparing a negative electrode slurry containing a negative electrode active material, a binder, and a solvent, forming a layer of the negative electrode slurry on a current collector, and drying the layer. Examples of the solvent include water and N-methyl-2-pyrrolidone (NMP).

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

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

(Method for producing lithium ion secondary battery)
As a specific method for producing a lithium ion secondary battery, for example, a positive electrode and a negative electrode are overlapped via a separator, and this is wound into a battery container according to the shape of the battery. A method of injecting and sealing the liquid can be mentioned. 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.

  ADVANTAGE OF THE INVENTION According to this invention, the dispersion | distribution of a conductive agent is good in an aqueous system, and the manufacturing method of the composite particle for electrochemical element positive electrodes with low resistance when it is set as a battery can be provided. In addition, since the positive electrode active material that has been subjected to water repellent treatment is used, composite particles in which the uneven distribution of the binder and the conductive agent near the surface of the composite particles can be obtained. Moreover, resistance when it is set as a battery by suppressing uneven distribution becomes low. Moreover, since the uneven distribution of the binder can be prevented, the fluidity of the composite particles is improved. Furthermore, since uneven distribution of the conductive material can be prevented, migration of the conductive material in the composite particles can be suppressed.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and may be arbitrarily changed without departing from the gist and equivalent scope of the present invention. Can be implemented. In the following description, “%” and “parts” representing amounts are based on weight unless otherwise specified.
In the examples and comparative examples, the conductive agent dispersibility, the electrolyte solution pouring property, the battery resistance, and the capacity retention rate were evaluated as follows.

(Conductive agent dispersibility)
The cross section of the lithium ion secondary battery positive electrode manufactured by the Example and the comparative example was processed using the Hitachi High-Tech ion milling device (E-3500). While observing the cross section of the processed positive electrode with SEM (S-3400N manufactured by Hitachi High-Tech), the content of carbon atoms was detected using EDX (INCA Energy 350 manufactured by Oxford Instruments).

Specifically, a square observation region having a length of 50 μm was selected in the observation region, and further divided into 25 square regions having a length of 10 μm. Thereafter, the ratio (minimum value / maximum value) between the maximum value and the minimum value of the carbon atom content in the 25 region was calculated. The results were evaluated according to the following criteria and are shown in Table 1.
A: 0.9 or more and less than 1.0 B: 0.7 or more and less than 0.9 C: 0.4 or more and less than 0.7 D: 0.1 or more and less than 0.4 E: Less than 0.1

(Electrolytic solution injection)
2 μL of electrolytic solution (solvent: EC / DEC = 1/2, electrolyte: LiPF _{6 with a} concentration of 1 mol / L) was dropped onto the positive electrode of the lithium ion secondary battery produced in the examples and comparative examples, and the liquid was completely liquid after the dropping. The time until the drop disappeared was measured. It shows that electrolyte solution pouring property is so high that this value is small. The results were evaluated according to the following criteria and are shown in Table 1.
A: Less than 1 minute B: 1 minute or more and less than 2 minutes C: 2 minutes or more and less than 3 minutes D: 3 minutes or more

(Battery resistance)
The lithium ion secondary batteries produced in the examples and comparative examples were allowed to stand for 24 hours, and then charged and discharged at a charge / discharge rate of 4.2 V and 0.5 C. Thereafter, charging and discharging operations were performed in an environment of −35 ° C., and the voltage 10 seconds after the start of discharge was measured. The smaller this value, the smaller the internal resistance, indicating that high-speed charge / discharge is possible. The measurement results were evaluated according to the following criteria and are shown in Table 1.
A: Less than 0.15 V B: 0.15 V or more and less than 0.25 V C: 0.25 V or more and less than 0.45 V D: 0.45 V or more and less than 0.65 V E: 0.65 V or more

(Capacity maintenance rate)
The lithium ion secondary batteries produced in the examples and comparative examples were allowed to stand for 24 hours, and then charged and discharged at a charge / discharge rate of 4.2 V and 0.1 C, and the initial capacity C ₀ was measured. Furthermore, after charging to 4.2 V and storing at 60 ° C. for 28 days, charge / discharge operation was performed at a charge / discharge rate of 4.2 V and 0.1 C, and the capacity C ₁ after storage at high temperature was measured. Next, the capacity change rate represented by ΔC = C ₁ / C ₀ × 100 (%) was calculated. The higher the capacity change rate, the better the high temperature storage characteristics. The calculated capacity change rate was evaluated according to the following criteria and shown in Table 1.
A: 85% or more B: 70% or more and less than 85% C: 60% or more and less than 70% D: 50% or more and less than 60% E: Less than 50%

(Hydrophobicity)
Moreover, the hydrophobicity of the active material and the conductive material was measured as follows. Put 50 ml of ion-exchanged water and 0.2 g of sample (active material or conductive agent) in a beaker, add methanol dropwise from the burette while stirring with a magnetic stirrer, and the mass of methanol in the methanol / water mixed solution at the end of the sample The fraction was defined as the degree of hydrophobicity.

Example 1
(Manufacture of binder)
In an autoclave equipped with a stirrer, 300 parts of ion exchange water, 93.8 parts of n-butyl acrylate, 2 parts of acrylonitrile, 1.0 part of allyl glycine ether, 2.0 parts of methacrylic acid, 1.2 parts of N-methylol acrylamide and molecular weight adjustment After adding 0.05 part of t-dodecyl mercaptan as an agent and 0.3 part of potassium persulfate as a polymerization initiator and stirring sufficiently, the mixture was heated to 70 ° C. for polymerization, and a solid content concentration of 40% as a binder. An aqueous dispersion of the binder was obtained. The polymerization conversion rate determined from the solid content concentration was approximately 99%.

(Water repellent treatment)
In a glass container, 100 parts of LNM (composition: Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ (particle diameter: 15 μm)) as a positive electrode active material and hexamethyldisilazane (abbreviation: HMDS, Shin-Etsu Silicone) as a coupling agent 1 part (1% based on the positive electrode active material) was added. Subsequently, it stirred for 15 minutes using the stirrer, flowing nitrogen into the glass container. Then, it was put into an inert oven and dried for 1 hour while flowing nitrogen at 100 ° C. to obtain a positive electrode active material subjected to water repellent treatment.

(Manufacture of composite particles)
93 parts of a positive electrode active material subjected to water repellent treatment, 2.0 parts of the above binder in terms of solid content, acetylene black (AB35, Denka Black powder manufactured by Denki Kagaku Kogyo Co., Ltd .: particle diameter: 35 nm) Further, 5.0 parts by specific surface area of 68 m ^{2 /} g) and ion-exchanged water were added so that the solid content concentration would be 40%, and mixed and dispersed to obtain a positive electrode slurry. This positive electrode slurry was sprayed using a spray dryer (Okawara Kako Co., Ltd.), a rotary disk type atomizer (diameter 65 nm), a rotational speed of 25,000 rpm, a hot air temperature of 120 ° C., and a particle recovery outlet temperature of 90 ° C. As a result, spray drying granulation was performed to obtain composite particles. The average volume particle diameter of the composite particles was 50 μm.

(Manufacture of lithium ion secondary battery positive electrode)
Next, the obtained composite particles are supplied to a roll (roll temperature 100 ° C., press linear pressure 4 kN / cm) of a roll press machine (pressed rough surface heat roll, manufactured by Hirano Giken Kogyo Co., Ltd.) at a molding speed of 20 m / min. The positive electrode active material layer was formed into a sheet on an aluminum foil having a thickness of 15 μm to obtain a lithium ion secondary battery positive electrode having a thickness of 60 μm.

(Manufacture of negative electrode slurry and lithium ion secondary battery negative electrode)
Artificial graphite as the negative electrode active material (average particle size: 24.5 μm, graphite interlayer distance ((002) plane spacing (d value): 0.354 nm by X-ray diffraction method) 96 parts, styrene-butadiene copolymer latex ( BM-400B) is 3.0 parts in terms of solid content, and 1.5 parts of a carboxymethylcellulose 1.5% aqueous solution (DN-800H: manufactured by Daicel Chemical Industries) as a dispersant is mixed in 1.0 part in terms of solid content. Further, ion exchange water was added so as to have a solid content concentration of 50%, and mixed and dispersed to obtain a negative electrode slurry, which was applied to a copper foil having a thickness of 18 μm and dried at 120 ° C. for 30 minutes. Thereafter, roll pressing was performed to obtain a negative electrode having a thickness of 50 μm.

(Manufacture of lithium ion secondary batteries)
The lithium ion secondary battery positive electrode was cut into a circle having a diameter of 13 mm, and the lithium ion secondary battery negative electrode was cut into a circle having a diameter of 14 mm. Moreover, the separator provided with the porous film was cut into a circle having a diameter of 18 mm. A separator and a negative electrode were sequentially laminated on the surface of the positive electrode on the electrode active material layer side, and stored in a stainless steel coin-type outer container provided with a polypropylene packing. An electrolytic solution (solvent: EC / DEC = 1/2, electrolyte: LiPF6 with a concentration of 1 mol / L) was poured into this container so that no air remained, and the thickness of the outer container was reduced to 0 through a polypropylene-made packing. A lithium-ion secondary battery (coin cell CR2032) having a diameter of 20 mm and a thickness of 3.2 mm was manufactured by covering with a 2 mm stainless steel cap and fixing the battery can.

(Example 2)
Production of lithium ion secondary battery positive electrode and lithium ion secondary battery in the same manner as in Example 1 except that the type of conductive agent used in the production of the composite particles was Ketjen Black (product name “EC300J” manufactured by Lion Corporation). Was manufactured.

(Example 3)
The production of the lithium ion secondary battery positive electrode and the lithium ion secondary battery in the same manner as in Example 1 except that the type of coupling agent used for the water repellent treatment was hexamethylcyclotrisilazane (manufactured by Tokyo Chemical Industry Co., Ltd.). Manufactured.

Example 4
Except that the type of coupling agent used for the water repellent treatment was hexyltriethoxysilane (trade name “KBE-3063” manufactured by Shin-Etsu Silicone Co., Ltd.), A lithium ion secondary battery was manufactured.

(Example 5)
The production of the positive electrode for the lithium ion secondary battery and the same as in Example 1 except that the type of coupling agent used for the water repellent treatment was decyltrimethoxysilane (manufactured by Shin-Etsu Silicone Co., Ltd., trade name “KBE-3103”) A lithium ion secondary battery was manufactured.

(Example 6)
A lithium ion secondary battery positive electrode and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the amount of HMDS used for the water repellent treatment was 0.1 parts.

(Example 7)
A lithium ion secondary battery positive electrode and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the amount of HMDS used for the water repellent treatment was 3 parts.

(Example 8)
Production of lithium ion secondary battery positive electrode and lithium in the same manner as in Example 1 except that the type of coupling agent used in the water repellent treatment was titanate coupling agent (trade name “KR TTS” manufactured by Ajinomoto Fine Techno Co., Ltd.) An ion secondary battery was manufactured.

Example 9
Lithium was the same as in Example 1 except that the type of coupling agent used for the water repellent treatment was an aluminate coupling agent (acetoalkoxyaluminum diisopropylate, Ajinomoto Fine Techno Co., Ltd., trade name “AL-M”). An ion secondary battery positive electrode and a lithium ion secondary battery were manufactured.

(Comparative Example 1)
A lithium ion secondary battery positive electrode and a lithium ion secondary battery were produced in the same manner as in Example 1 except that composite particles were produced using a positive electrode active material that was not subjected to water repellent treatment.

(Comparative Example 2)
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the positive electrode slurry was applied onto a current collector and dried to obtain a lithium ion secondary battery positive electrode.

  As shown in Table 1, the method includes a step of dispersing a positive electrode active material, a conductive agent and a binder in water to obtain a slurry, and a step of obtaining granulated particles by spray-drying the slurry and granulating the slurry. Lithium ions prepared using composite particles having a ratio of the degree of hydrophobicity obtained from the methanol method (positive electrode active material / conductive agent) of 0.5 or more and less than 1.5 between the positive electrode active material and the conductive agent The positive electrode for the secondary battery has good conductive agent dispersibility and electrolyte solution pouring property, and the battery resistance and capacity retention rate of the lithium ion secondary battery produced using this positive electrode for the lithium ion secondary battery are It was good.

Claims (4)

A step of dispersing a positive electrode active material, a conductive agent and a binder in water to obtain a slurry;
A step of obtaining granulated particles by spray-drying and granulating the slurry,
An electrochemical device characterized in that the ratio of the degree of hydrophobicity obtained by the methanol method (positive electrode active material / conductive agent) between the positive electrode active material and the conductive agent is 0.5 or more and less than 1.5 A method for producing composite particles for a positive electrode.   The method for producing composite particles for an electrochemical device positive electrode according to claim 1, wherein the positive electrode active material is a positive electrode active material subjected to a water repellent treatment.   The method for producing composite particles for an electrochemical device positive electrode according to claim 2, wherein the water repellent treatment is a coupling agent treatment. The coupling agent treatment is a silane coupling agent treatment,
The method for producing composite particles for an electrochemical device positive electrode according to claim 3, wherein the amount of the silane coupling agent introduced is 0.1% or more and less than 3.0% based on the weight of the positive electrode active material. .