JP2016046226A - Composite particle for electrochemical element electrode, electrochemical element electrode, electrochemical element, and method for manufacturing composite particle for electrochemical element electrode and electrochemical element electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide composite particles for an electrochemical element electrode capable of producing an electrode having low weight per unit area and high thickness accuracy, at low costs.SOLUTION: The composite particles for the electrochemical element electrode is obtained by performing a step for obtaining coagulated particles by adding a non-miscible solvent, a surface active agent and coagulated liquid to a slurry containing an electrode active material and binding resin while the slurry is being agitated, and a step for filtering the coagulated particles, then drying them.SELECTED DRAWING: None

Description

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

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

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

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

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

By the way, in recent years, high-power electrochemical elements (batteries) have been required to have a low basis weight electrode in which the basis weight of composite particles is low when forming an electrode active material layer. In this case, it is required to stably and quantitatively supply a small amount of composite particles to the pressure molding apparatus. However, the composite particles obtained by spray drying are used in the hopper of a quantitative feeder for quantitatively supplying the composite particles to a pressure forming part such as a molding roll, or in the quantitative feeder hopper of the composite particle packing process in the composite particle manufacturing process. Since various hopper troubles such as a bridge and a rat hole may occur in the inside, it is difficult to produce an electrode with a low basis weight and a high thickness accuracy.
In the above spray drying, the sprayed droplets may adhere to the wall surface of the spray dryer before drying, and it may be difficult to recover the composite particles with a high yield.

  In Patent Document 2, it is described that granulation is performed by using alginic acid as a dispersant and forming droplets and solidifying them with a two-fluid nozzle.

  However, the particles granulated in Patent Document 2 contain a lot of coarse powder. Even if the composite particles for electrochemical element electrodes are granulated by the method of Patent Document 2, an electrode having a low basis weight and high thickness accuracy can be obtained. It was difficult to produce. In addition, the process is complicated and the manufacturing cost is high.

Japanese Patent No. 4929792 Japanese Patent No. 5185534

  An object of the present invention is to provide a composite particle for an electrochemical element electrode capable of producing an electrode having a low basis weight and a high thickness accuracy at a low production cost, an electrochemical element electrode using the composite particle for an electrochemical element electrode, and an electric It is to provide a chemical element, and to provide a method for producing the composite particle for an electrochemical element electrode and a method for producing the electrochemical element electrode.

  As a result of intensive studies to solve the above problems, the present inventor achieved the above object by adding a solvent immiscible with the slurry while stirring the slurry containing the electrode active material and the like. The present inventors have found that this can be done and have completed the present invention.

That is, according to the present invention,
(1) A step of obtaining coagulated particles by adding a solvent, a surfactant and a coagulating liquid that are immiscible with the slurry while stirring a slurry comprising an electrode active material and a binder resin; and Composite particles for electrochemical element electrodes obtained by filtering the solidified particles and then drying,
(2) The binder resin is in the form of particles, and the slurry further includes a water-soluble polymer, the composite particles for an electrochemical element electrode according to (1),
(3) The water-soluble polymer is a water-soluble alginic acid derivative, a cellulose polymer such as carboxymethyl cellulose, carrageenan, agar, gelatin, glucomannan, pectin, curdlan, gellan gum, polyacrylamide, polysulfonic acid and polyacrylic acid derivative. The composite particle for an electrochemical element electrode according to (2), comprising at least one of the following:
(4) 200-2000 ppm of polyvalent metal salt, wherein the polyvalent metal salt is at least one polyvalent metal selected from calcium salt, magnesium salt, aluminum salt, barium salt, copper salt, ammonium alum, iron salt The composite particle for an electrochemical element electrode according to any one of (1) to (3), comprising a salt,
(5) An electrochemical element electrode comprising an electrode active material layer comprising the composite particles for an electrochemical element electrode according to any one of (1) to (4) laminated on a current collector ,
(6) An electrochemical element comprising the electrochemical element electrode according to (5),
(7) A method for producing a composite particle for an electrochemical element electrode according to any one of (1) to (4), wherein the electrode active material and the binder resin are used. A method for producing composite particles for an electrochemical element electrode, comprising the step of adding the slurry and the immiscible solvent, the surfactant, and the coagulation liquid while stirring the slurry comprising
(8) Electrochemistry including a step of obtaining an electrode active material layer by press-molding an electrode material comprising the composite particles for electrochemical element electrodes according to any one of (1) to (4) on a current collector Device electrode manufacturing method,
Is provided.

  According to the composite particle for electrochemical element electrode and the method for producing the composite particle for electrochemical element electrode of the present invention, an electrode with low basis weight and high thickness accuracy can be produced. In addition, it is possible to provide an electrochemical element electrode having a low basis weight and a high thickness accuracy and a method for producing the electrochemical element electrode. Moreover, the electrochemical element using this electrochemical element electrode can be provided.

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

  Hereinafter, the composite particle for an electrochemical element electrode of the present invention will be described. The composite particle for an electrochemical device electrode of the present invention (hereinafter sometimes referred to as “composite particle”) is immiscible with the slurry while stirring the slurry containing the electrode active material and the binder resin. It is obtained by a step of obtaining coagulated particles by adding a neutral solvent, a surfactant and a coagulating liquid, and a step of filtering the coagulated particles and then drying.

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

(Step of obtaining solidified particles)
In the step of obtaining the coagulated particles, the slurry comprising the electrode active material and the binder resin is stirred, and the coagulated particles are added by adding a solvent immiscible with the slurry, a surfactant and a coagulating liquid. Get.

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

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

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

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

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

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

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

Examples of negative electrode active materials preferably used for lithium ion secondary batteries include: carbonaceous materials such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads, pitch-based carbon fibers; conductive polymers such as polyacene; silicon, Metals such as tin, zinc, manganese, iron, nickel 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 nitride; silicon and the like. Further, as the negative electrode active material, a material obtained by attaching a conductive material to the surface of the negative electrode active material particles by, for example, a mechanical modification method may be used. Moreover, a negative electrode active material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
Moreover, as a negative electrode active material preferably used when an electrochemical element is a lithium ion capacitor, the negative electrode active material formed with the said carbon is mentioned.

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

  The volume average particle size of the electrode active material can reduce the blending amount of the binder resin when preparing the slurry, can suppress the decrease in the capacity of the battery, and prepare the slurry to an appropriate viscosity. From the viewpoint of facilitating the process and obtaining a uniform electrode, the thickness is preferably 1 to 50 μm, more preferably 2 to 30 μm.

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

  Examples of the dispersion-type binder resin 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 resin.

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

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

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

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

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

The acrylate polymer has the general formula (I): 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. A polymer comprising, specifically, a homopolymer of a compound represented by the general formula (I), or a copolymer obtained by polymerizing a monomer mixture containing the compound represented by the general formula (I) It is a coalescence. Specific examples of the compound represented by the general formula (I) 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.

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

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

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

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

  Examples of the α, β-unsaturated nitrile compound used in the polymer constituting the dispersion-type binder resin include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-bromoacrylonitrile, and the like. 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 resin is preferably 0.1 to 40% by weight, more preferably 0.5 to 30% by weight, still more preferably 1 to 20% by weight. is there. When an α, β-unsaturated nitrile compound unit is contained in the dispersion-type binder resin, it is difficult to be deformed when the electrode is manufactured, and the strength can be increased. Further, when an α, β-unsaturated nitrile compound unit is contained in the dispersion-type binder resin, the adhesion between the electrode active material layer containing composite particles and the current collector can be made sufficient.

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

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

  The proportion of the vinyl compound unit having an acid component in the dispersion-type binder resin is preferably 0.5 to 10% by weight, more preferably 1 to 8% by weight, from the viewpoint of improving the stability when the slurry is made. More preferably, it is 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 a slurry to become high and for handling to become difficult. Moreover, when there is too little ratio of the vinyl compound unit which has an acid component, there exists a tendency for stability of a slurry to fall.

  The shape of the dispersion-type binder resin 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 resin include those in which the binder resin 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 resin is preferably 0.001 to 10 μm, more preferably from the viewpoint that the strength and flexibility of the obtained electrode are good while making the stability when slurry is good. Is 10 to 5000 nm, more preferably 50 to 1000 nm.

  The method for producing the binder resin used in the present invention is not particularly limited, and a known polymerization method such as an emulsion polymerization method, a suspension polymerization method, a dispersion polymerization method, or a solution polymerization method can be employed. Among these, it is preferable to produce by an emulsion polymerization method because the particle diameter of the binder resin can be easily controlled. Further, the binder resin 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 blending amount of the binder resin in the composite particles of the present invention is a viewpoint that the adhesion between the obtained electrode active material layer and the current collector can be sufficiently secured and the internal resistance of the electrochemical element can be lowered. Therefore, the amount is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, still more preferably 1 to 5 parts by weight based on 100 parts by weight of the electrode active material.

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

  Examples of such an anionic water-soluble polymer include alginic acid; alkali metal salts of alginic acid (sodium alginate, potassium alginate, etc.) and water-soluble alginic acid derivatives such as ammonium alginate; hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, etc. Cellulosic polymers: polyacrylic acid, polyacrylic acid derivatives, polysulfonic acid polymers, polyacrylamide, agar, gelatin, carrageenan, glucomannan, pectin, curdlan, gellan gum and the like. Among these, carboxymethyl cellulose, alginic acid, water-soluble alginic acid derivatives, polyacrylic acid, and polyacrylic acid derivatives are easy to coagulate, from the viewpoint of obtaining spherical composite particles and from the viewpoint that composite particles are difficult to adhere to each other after coagulation. Preferably, carboxymethylcellulose, polyacrylic acid, alginic acid, and a water-soluble alginic acid derivative are more preferable, and carboxymethylcellulose, polyacrylic acid, alginic acid, or an alkali metal salt of alginic acid (sodium alginate, potassium alginate, etc.) is more preferable.

  These anionic water-soluble polymers can be used singly or in combination of two or more, and moreover, different structures among the same kind (category) of anionic water-soluble polymers. Two or more of these polymers can be used in combination.

  The addition amount of the water-soluble polymer in the slurry is preferably 0.4 to 10 parts by weight in terms of solid content with respect to 100 parts by weight of the electrode active material from the viewpoint of solidifying solidly and having a good particle shape. More preferably, it is 0.7-5 weight part, More preferably, it is 1-2 weight part. If the amount of the water-soluble polymer added is too large, the resulting composite particles will have a large amount of insoluble matter, which will increase the resistance of the battery. If the amount of the water-soluble polymer added is too small, it may be difficult to obtain coagulated particles or the resulting composite particles may be fragile.

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

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

  The amount of the conductive material in the case of adding the conductive material is preferably 1 to 10 parts by weight, more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the electrode active material.

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

  As a solvent used for obtaining the slurry, water is preferably used, but a mixed solvent of water and an organic solvent may be used. Examples of the organic solvent that can be used in this case include alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol; alkyl ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane, and diglyme; diethylformamide, dimethyl Amides such as acetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone; and the like. When using an organic solvent, alcohols are preferred. Thereby, the viscosity and fluidity | liquidity of a slurry can be adjusted and production efficiency can be improved.

  The viscosity of the slurry for composite particles is preferably 10 to 3,000 mPa · s, more preferably 30 to 1,500 mPa · s, more preferably at room temperature, from the viewpoint of improving the productivity of granulation of the composite particles. Is 50 to 1,000 mPa · s.

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

  From the viewpoint of uniformly dispersing the binder resin in the slurry, the amount of the solvent used when preparing the slurry is preferably 1 to 40% by weight, more preferably 2 to 20% by weight, based on the solid content concentration of the slurry. This is the amount.

  The method or order of dispersing or dissolving the electrode active material, the binder resin, the water-soluble polymer and the conductive material added as necessary in the solvent is not particularly limited, and for example, the electrode active material, the binder in the solvent A method in which a resin, a water-soluble polymer and a conductive material are added and mixed, a binder resin in which a water-soluble polymer is dissolved in a solvent, an electrode active material and a conductive material are added and mixed, and finally dispersed in a solvent (For example, latex) is added and mixed. An electrode active material and a conductive material are added to and mixed with a binder resin dispersed in a solvent, and a water-soluble polymer dissolved in the solvent is added to the mixture. And the like.

  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.

(Slurry and immiscible solvent)
The liquid that is immiscible with the slurry is not particularly limited as long as it is a liquid that is immiscible with the slurry, but the liquid when water is used as the solvent of the slurry includes butane, butene, pentane, pentene, hexane, cyclohexane, normal Examples include hydrocarbons having 4 to 10 carbon atoms such as hexane, hexene, heptane, octane, nonane, decane, benzene, toluene and xylene, ethers such as tetrahydrofuran, diethyl ether and diisopropyl ether, and esters such as ethyl acetate. . In view of the production process, among these, those which are liquid at normal pressure and normal temperature and have a low boiling point (specifically, cyclohexane, normal hexane, etc.) are more preferable. Here, when the solvent immiscible with the slurry is added while the slurry is being stirred, droplets incorporating the electrode active material and the like are formed, and the droplets are dispersed in the slurry.

  The amount of the solvent immiscible with the slurry to be added while stirring the slurry is preferably 1 to 50 parts by weight, more preferably 5 to 30 parts by weight with respect to 100 parts by weight of the slurry solvent.

(Surfactant)
The surfactant is not particularly limited as long as it can stabilize the droplets formed by the liquid immiscible with the slurry in the stirring slurry. Examples of the surfactant include amphoteric surfactants such as anionic, cationic, nonionic, and nonionic anions. Among these, anionic or nonionic surfactants are preferable. The compounding amount of the surfactant is not particularly limited, but in the composite particles, it is preferably 0 to 50 parts by weight, more preferably 0.1 to 10 parts by weight, and still more preferably 0 to 100 parts by weight of the electrode active material. .5 to 5 parts by weight.

(Coagulation liquid)
As the coagulation liquid, it is possible to use a low pH acidic liquid in which the water-soluble polymer contained in the slurry coagulates, a polyvalent metal salt aqueous solution, or a cationic polymer aqueous solution. Alternatively, an aqueous cationic polymer solution is preferably used.

  As an aqueous solution of a polyvalent metal salt, a calcium salt, a magnesium salt, an aluminum salt, a barium salt are used from the viewpoint of easily coagulating the slurry and obtaining spherical composite particles, and from the viewpoint of difficult binding of the composite particles to each other after solidification An aqueous solution containing copper salt, ammonium alum, iron salt, etc. is preferable, calcium chloride, magnesium sulfate, zinc sulfate, copper sulfate, aluminum nitrate, barium chloride, magnesium chloride, ferric chloride, ferric sulfate, aluminum sulfate, More preferred are aqueous solutions of inorganic salts such as iron alum, and more preferred are aqueous solutions of calcium chloride, magnesium sulfate, zinc sulfate, copper sulfate, aluminum nitrate, barium chloride, ferric chloride, and ferric sulfate, calcium chloride, magnesium sulfate. The aqueous solution is particularly preferable. Moreover, it is possible to suppress the co-adhesion of the solidified particles by using, as the coagulation liquid, a solvent in which a specific water-soluble polymer is easily coagulated. In addition, when water-soluble polymers that are highly heat-responsive, solidify by heat, and are irreversible even when cooled, hot water at 80 ° C. or higher may be used, and washing after water is omitted. Is possible. When an anionic water-soluble polymer is used as the water-soluble polymer, an acidic coagulating liquid may be used. In that case, the pH value is preferably 5 or less, and when coagulated with a volatile acidic liquid, the coagulating liquid component can be easily removed.

  The composite particles obtained when an aqueous polyvalent metal salt solution is used as the coagulating liquid are at least one polyvalent metal salt selected from calcium salt, magnesium salt, aluminum salt, barium salt, copper salt, ammonium alum, and iron salt It is preferable to contain. Further, the content of the polyvalent metal salt is preferably 200 to 2000 ppm, more preferably 300 to 2000 ppm, and still more preferably 300 to 1500 ppm, from the viewpoint of improving the adhesion between the electrode active material layer and the current collector. Especially preferably, it is 300-1000 ppm. If the content of the polyvalent metal salt is too much or too little, the adhesion between the electrode active material layer and the current collector becomes insufficient. In addition, content of the polyvalent metal salt described here points out the thing remove | excluding the quantity of the polyvalent metal salt derived from an electrode active material. In addition, when a water-soluble polymer such as alginic acid is coagulated with a metal salt, a gel-like film is formed with the metal salt, and the thickness is 1 to 500 nm between the surface of the composite particle and the electrode active material inside the particle. Exists. The presence of this gel film provides a reinforcing effect on the particles.

  Examples of cationic polymer aqueous solutions include polyethyleneimine, polyvinylamine, polyvinylpyridine, polyaminesulfone, polyallylamine, polyacrylamide, polydiallylmethylamine, polyamidoamine, polyacrylic acid ester, polyaminoalkylacrylamide, and polyepoxyamine. , Polyamide polyamine, polyester polyamine, chitosan, diallylammonium chloride sulfur dioxide copolymer, diallylmethylethylammonium ethyl sulfate / sulfur dioxide copolymer, diallyldimethylammonium chloride / acrylamide copolymer, dicyandiamide / formalin condensate, polyalkylene Polymers of polyamine / dicyandiamide condensates and salts thereof, and polydiallyldimethyla It is preferable to use aqueous solutions of quaternary ammonium salts such as quaternary ammonium salts such as monium chloride, polyvinylpyridinium chloride, polymethacrylate methyl chloride, polyethyleneimine, polyvinylamine, polyaminesulfone, polyallylamine, polyacrylamide, polydiallyl. Methylamine, polyamidoamine, polyacrylic (methacrylic acid) ester, polyaminoalkylacrylamide, polyamide polyamine, polyester polyamine, diallylammonium chloride sulfur dioxide copolymer, diallylmethylethylammonium ethyl sulfate / sulfur dioxide copolymer, diallyldimethylammonium Chloride / acrylamide copolymer, dicyandiamide / formalin condensate, polyalkylene poly More preferably, an aqueous solution of a quaternary ammonium salt such as a quaternary ammonium salt such as poly (diallyldimethylammonium chloride) or polyacrylic (methacrylic acid) methyl chloride is used. , Quaternary ammonium salts such as quaternary ammonium salts such as polyethylenimine, polyacrylamide, polyacrylic (methacrylic) ester, polyacrylic (methacrylic) methyl chloride, diallylammonium chloride sulfur dioxide copolymer, diallylmethylethylammonium More preferably, an aqueous solution of ethyl sulfate / sulfur dioxide copolymer or diallyldimethylammonium chloride / acrylamide copolymer is used.

  The cationic polymer contained in the cationic polymer aqueous solution may be used alone or in combination of two or more at any ratio.

  Moreover, when a water-soluble polymer such as alginic acid is coagulated with a metal salt or a cationic polymer, a gel-like film is formed with the metal salt or the cationic polymer, and the surface of the composite particle has a thickness of 1 nm to 500 nm. And exist between the active materials inside the particles. The presence of this gel film provides a reinforcing effect on the particles.

  The concentration of the cationic polymer in the case of using the cationic polymer aqueous solution as the coagulation liquid is preferably 0.4 from the viewpoint that the droplets of the slurry can be solidified firmly and the shape of the resulting composite particles is good. It is -20 wt%, More preferably, it is 0.5-15 wt%, More preferably, it is 1.0-10 wt%. If the concentration of the cationic polymer is too high, the adhesion between the electrode active material layer and the current collector is deteriorated. On the other hand, if the concentration of the cationic polymer is too low, the slurry as droplets may not solidify or the resulting composite particles may be brittle.

(Method of adding each component to the slurry)
While the slurry is being stirred, the method and order of adding the solvent immiscible with the slurry, the surfactant and the coagulating liquid are not particularly limited as long as the object of the present invention is not impaired, but the slurry is being stirred. It is preferable to add a solvent immiscible with the slurry and a surfactant, and then add a coagulating liquid. The solvent and surfactant immiscible with the slurry may be added all at once while the slurry is being stirred, or may be added in portions or continuously. In the case of divided addition or continuous addition, the addition amount can be uniform or constant, and can be changed according to the degree of droplet formation.

  Moreover, the stirring conditions of the slurry are not particularly limited as long as the composite particle droplets are formed by a non-miscible solvent with the slurry.

  In addition, if the solvent, surfactant, and coagulating liquid that are immiscible with the slurry are added without stirring the slurry, the proportion of particles of 40 μm or less increases in the particle size distribution in terms of number. This deteriorates, and hopper troubles easily occur in the composite particle supply apparatus when the electrode active material layer is formed. Moreover, the thickness accuracy of the obtained electrode deteriorates.

  As described above, while stirring the slurry comprising the electrode active material and the binder resin, the solidified particles are added to the slurry by adding a solvent immiscible with the slurry, a surfactant, and a coagulating liquid. Produces. That is, droplets can be obtained by utilizing the miscibility of the solvent used for the slurry and the solvent immiscible with the slurry, and solidified particles can be obtained from the droplets.

(Separation from coagulation liquid and drying)
As described above, the coagulated particles are separated from the coagulated liquid by filtration or the like. Moreover, the composite particles of the present invention can be obtained by drying the coagulated particles separated from the coagulation liquid.

  Examples of a method for separating the solidified particles obtained in the slurry from the slurry include filtration.

  There is no particular limitation on the filtration method, and natural filtration, pressure filtration, and vacuum filtration can be employed. Further, filtration using a filtration filter, scraping filtration, sieving filtration, or the like may be employed. Moreover, when performing sieving filtration, you may filter using the sieve of a predetermined opening in the slurry containing a coagulated particle.

  The method for drying the coagulated particles separated from the coagulation liquid is not particularly limited. For example, drying with hot air, hot air, low-humidity air, vacuum drying, or drying by irradiation with (far) infrared rays or electron beams. Etc. The drying time is preferably 5 to 30 minutes, and the drying temperature is, for example, 30 to 180 ° C., although depending on the heat resistance of the material used. If the drying temperature is too high, the composite particles may adhere to each other and become coarse particles.

  In addition, a water washing step of adding water to the coagulated particles separated from the coagulation liquid, re-stirring, and performing filtration or the like may be performed a predetermined number of times. In this case, the solidified particles that have undergone the water washing step are dried by vacuum drying or the like.

(Physical properties of composite particles)
The shape of the composite particles of the present invention is good in fluidity, can prevent hopper troubles in the composite particle supply device when forming the electrode active material layer, the composite particles are supplied from the hopper, and the thickness accuracy From the viewpoint of obtaining a good electrode, it is preferably substantially 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 basis weight accuracy of the electrode deteriorates, and it becomes difficult to obtain an electrode with good thickness accuracy.

  The particle diameter of the composite particles of the present invention is a particle using a laser light diffraction method from the viewpoint that the fluidity of the composite particles is good, hopper troubles are less likely to occur, and a uniform electrode with high thickness accuracy can be obtained. In the particle size distribution in terms of the number obtained by diameter measurement, it is preferable that particles of 40 μm or less are 50% or less of the whole. The particle size distribution can be obtained by measuring with a laser diffraction particle size distribution measuring device (for example, SALD-3100; manufactured by Shimadzu Corporation or Microtrac MT-3200II; manufactured by Nikkiso Co., Ltd.).

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

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

  In addition, since the compressibility of the composite particles of the present invention is such that the fluidity of the composite particles is good, it is possible to prevent hopper troubles in the composite particle supply device when forming the electrode active material layer, and supply of composite particles from the hopper Is preferably 15% or less from the viewpoint of obtaining an electrode with good thickness accuracy. If the compression degree of the composite particles is too large, the fluidity of the composite particles is deteriorated, so that a hopper trouble is likely to occur, and the thickness accuracy of the obtained electrode is deteriorated.

  The degree of compression can be measured using a powder physical property measuring apparatus such as a powder tester-PT-S type manufactured by Hosokawa Micron Corporation.

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

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

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

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

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

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

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

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

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

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

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

Moreover, you may contain an additive in electrolyte solution. Examples of the additive include carbonates such as vinylene carbonate (VC); sulfur-containing compounds such as ethylene sulfite (ES); and fluorine-containing compounds such as fluoroethylene carbonate (FEC).
An additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  In addition, as an electrolyte solution for lithium ion capacitors, the same electrolyte solution that can be used for the above-described lithium ion secondary battery can be used.

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

  According to the present invention, a composite particle for an electrochemical element electrode capable of producing an electrode having a low basis weight and a high thickness accuracy, an electrochemical element electrode and an electrochemical element using the composite particle for an electrochemical element electrode, and the above The manufacturing method of the composite particle for electrochemical element electrodes and the manufacturing method of the said electrochemical element electrode can be provided.

  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 Examples and Comparative Examples, measurement of particle size distribution and measurement of the amount of polyvalent metal salt contained in the composite particles, and evaluation of electrode thickness accuracy, basis weight unevenness, yield, and peel strength were performed as follows. .

<Measurement of particle size distribution>
The particle size distribution of the composite particles was measured using a dry laser diffraction / scattering type particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd .: Microtrac MT-3200II).

<Measurement of content of polyvalent metal salt in composite particles>
About 0.01 g of the composite particles obtained in the examples and comparative examples are weighed in a platinum crucible, and the crucible and the empty crucible are heated with a heater. It was ashed for 2 hours in the furnace. Subsequently, 0.2 mL of nitric acid and about 7 mL of ultrapure water were added and then heated with a heater to dissolve ash. After the constant volume of 10 mL, the total amount of polyvalent metal salts (divalent and trivalent metal salts) contained in the composite particles was measured using ICP-AES (manufactured by SII Nanotechnology, Inc .: SPS-5100). The amount of metal derived from the electrode active material was excluded.

<Electrode thickness accuracy>
Electrodes (lithium ion secondary battery negative electrodes) produced in the examples and comparative examples were equally spaced at 3 points from the center in the width direction (TD direction) to both ends, and evenly spaced by 10 cm in the length direction (MD direction). The film thickness was measured at 5 points, and the average value A of the film thickness and the value B farthest from the average value were obtained. Then, from the average value A and the farthest value B, thickness unevenness was calculated according to the following formula (1), and formability was evaluated according to the following criteria. The results are shown in Table 1. It can be judged that the smaller the thickness unevenness, the better the thickness uniformity and the better the thickness accuracy of the electrode.
Unevenness of thickness (%) = (| A−B |) × 100 / A (1)
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

<Unevenness of basis weight>
The electrodes (lithium ion secondary battery negative electrodes) produced in the examples and comparative examples were cut in the width direction (TD direction) 10 cm and the length direction (MD direction) 1 m, and the cut electrodes were equally 3 in the TD direction. A total of 15 points (= 3 points x 5 points) in the MD direction and 5 points are measured in a circular shape by measuring the weight of 2 cm ² and subtracting the weight of the current collector foil from the punched electrode. And an average value A and a value B farthest from the average value were obtained. Then, the basis weight unevenness was calculated from the average value A and the farthest value B according to the following formula (2), and the moldability was evaluated according to the following criteria. The results are shown in Table 1. It can be determined that the uniformity of the electrode is better as the basis weight unevenness is smaller.
Unevenness per unit area (%) = (| A−B |) × 100 / A (2)
A: Unevenness per unit area is less than 5% B: Unevenness per unit area is 5% or more and less than 10% C: Unevenness per unit area is 10% or more and less than 15% D: Unevenness per unit area is 15% or more E: There is a hole in the electrode layer

<Yield>
In Examples and Comparative Examples, when the solid content (weight) of the slurry is A and the weight obtained by subtracting the residual solvent amount from the composite particles recovered after the drying step is B, the yield R is R = B / A × 100. (%), And the yield was evaluated according to the following criteria. The results are shown in Table 1.
A: Yield is 95% or more B: Yield is 85% or more and less than 95% C: Yield is 75% or more and less than 85% D: Yield is less than 75%

<Peel strength>
The electrode (lithium ion secondary battery negative electrode) produced in the examples and comparative examples was cut into a rectangular shape having a width of 1 cm and a length of 10 cm. The cut electrode is fixed with the electrode active material layer side up, and a cellophane tape is applied to the surface of the electrode active material layer, and then the cellophane tape is pulled from one end of the test piece in a 180 ° direction at a speed of 50 mm / min. The stress when peeled was measured. This stress was measured 10 times, and the average value was defined as the peel strength. The peel strength was evaluated according to the following criteria, and the results are shown in Table 1. In addition, it shows that the adhesiveness in an electrode active material layer and the adhesiveness between an electrode active material layer and a collector are so favorable that peel strength is large.
A: Peel strength is 15 N / m or more B: Peel strength is 7 N / m or more and less than 15 N / m C: Peel strength is 3 N / m or more and less than 7 N / m D: Peel strength is less than 3 N / m E: Unevaluable

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

(Preparation of slurry for composite particles)
Graphite (average particle diameter: 24.5 μm, graphite interlayer distance (interval of (002) plane by X-ray diffraction (d value)): 0.354 nm as a negative electrode active material in a container having an internal volume of 500 ml having a stirring blade ), 97.7 parts of the above-mentioned particulate binder resin S in terms of solid content, and a 1.0% aqueous solution of sodium alginate as a water-soluble polymer (Argitex LL; manufactured by Kimika Co., Ltd.) Was mixed in an amount of 0.7% in terms of solid content, and ion-exchanged water was added so that the total solid content concentration was 3.5%, and the mixture was uniformly mixed and dispersed to obtain a slurry.

(Preparation of solidified particles)
Next, in the container, the alkyl diphenyl oxide disulfonate (Dowfax (registered trademark) 2A1, manufactured by Dow Chemical Co., Ltd.) as a surfactant is converted into solid content while stirring the slurry with the rotation speed of the stirrer set at 800 rpm. 1.6 parts by weight, 264 parts of cyclohexane as a solvent immiscible with the slurry were added, and cyclohexane droplets incorporating graphite as an electrode active material were dispersed. Thereafter, 304 parts of a 2% calcium chloride aqueous solution was dropped to solidify the cyclohexane droplet surface to obtain solidified particles. Subsequently, the slurry liquid containing the coagulated particles was filtered through a 400 mesh SUS metal mesh to separate the composite particles.

  Next, ion-exchanged water was added to the collected solidified particles to reslurry, and after stirring for 10 minutes, a water washing step of filtering again was performed. After repeating this water washing step twice, the coagulated particles were separated by filtration to obtain wet coagulated particles. The wet coagulated particles were vacuum-dried at a temperature of 40 ° C., and soft aggregation was loosened with a sieve having an opening of 500 μm to obtain composite particles. In the particle size distribution in terms of the number of the composite particles, the number of particles of 40 μm or less was 49% of the total. The content of the polyvalent metal salt was 610 ppm.

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

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

(Example 2)
The composite particles and the negative electrode of the lithium ion secondary battery were prepared in the same manner as in Example 1 except that the stirring condition of the slurry for preparing the solidified particles was that the rotational speed of the stirrer was 1200 rpm. In the particle size distribution in terms of the number of the composite particles obtained, the number of particles of 40 μm or less was 50% of the total. The content of the polyvalent metal salt was 840 ppm.

(Example 3)
A composite particle and a lithium ion secondary battery negative electrode were prepared in the same manner as in Example 1 except that the type of the solvent immiscible with the slurry added when preparing the solidified particles was changed to normal hexane. The number of particles of 40 μm or less in the particle size distribution in terms of the number of composite particles obtained was 48% of the total. The content of the polyvalent metal salt was 630 ppm.

Example 4
A composite particle and a lithium ion secondary battery negative electrode were prepared in the same manner as in Example 1 except that the type of surfactant added when preparing the solidified particles was changed to sodium linear alkylbenzene sulfonate. The number of particles of 40 μm or less in the particle size distribution in terms of the number of composite particles obtained was 48% of the total. The content of the polyvalent metal salt was 720 ppm.

(Example 5)
A composite particle and a lithium ion secondary battery negative electrode were prepared in the same manner as in Example 1 except that the type of coagulation liquid used for preparing the coagulated particles was changed to a 2% aqueous solution of aluminum sulfate. In the particle size distribution in terms of the number of the composite particles obtained, the number of particles of 40 μm or less was 49% of the total. The content of the polyvalent metal salt was 590 ppm.

(Comparative Example 1)
A composite particle and a lithium ion secondary battery negative electrode were prepared in the same manner as in Example 1 except that stirring was not performed when cyclohexane, a surfactant, and a coagulating liquid were added to the slurry. In the particle size distribution in terms of the number of the composite particles obtained, the particle size of 40 μm or less was 98% of the total. The content of the polyvalent metal salt was 820 ppm.

(Comparative Example 2)
A composite particle and a lithium ion secondary battery negative electrode were prepared in the same manner as in Example 1 except that a solvent immiscible with the slurry was not used when preparing the solidified particles. In the particle size distribution in terms of the number of the composite particles obtained, the particle size of 40 μm or less was 98% of the total. The content of the polyvalent metal salt was 910 ppm.

(Comparative Example 3)
A composite particle and a lithium ion secondary battery negative electrode were produced in the same manner as in Example 1 except that the surfactant was not used when producing the solidified particles. In the particle size distribution in terms of the number of the composite particles obtained, the particle size of 40 μm or less was 98% of the total. The content of the polyvalent metal salt was 730 ppm.

(Comparative Example 4)
The solid content concentration of the slurry used in Example 1 was changed to 35%. Using a rotary disk type atomizer (84 mm in diameter) in a spray dryer (Okawara Kako Co., Ltd.), the hot air temperature is 150 ° C., the temperature of the particle recovery outlet is 90 ° C., and this slurry is supplied at 255 mL / min. Spray drying granulation was performed at 17,000 rpm to obtain composite particles.

  In the particle size distribution in terms of the number of the composite particles obtained, the particle size of 40 μm or less was 74% of the total. The content of the polyvalent metal salt was 19 ppm. A lithium ion secondary battery negative electrode was produced in the same manner as in Example 1 except that the composite particles obtained above were used.

  As shown in Table 1, while stirring the slurry comprising the electrode active material and the binder resin, the coagulated particles were formed by adding a solvent, a surfactant and a coagulating liquid that were immiscible with the slurry. The yield of the composite particle for electrochemical device electrodes obtained by the step of obtaining and filtering the solidified particles and then drying is good, and the thickness accuracy, basis weight unevenness and peel strength of the electrode using the composite particles are good Met.

Claims (8)

While stirring the slurry comprising the electrode active material and the binder resin, a step of obtaining solidified particles by adding a solvent immiscible with the slurry, a surfactant and a coagulating liquid; and Electrochemical element electrode composite particles obtained by filtration and then drying.   The composite particle for an electrochemical element electrode according to claim 1, wherein the binder resin is in the form of particles, and the slurry further contains a water-soluble polymer.   The water-soluble polymer is at least one of water-soluble alginic acid derivatives, cellulosic polymers such as carboxymethylcellulose, carrageenan, agar, gelatin, glucomannan, pectin, curdlan, gellan gum, polyacrylamide, polysulfonic acid and polyacrylic acid derivatives. The composite particle for an electrochemical element electrode according to claim 2, comprising a seed.   The polyvalent metal salt contains 200 to 2000 ppm of polyvalent metal salt, and the polyvalent metal salt contains at least one polyvalent metal salt selected from calcium salt, magnesium salt, aluminum salt, barium salt, copper salt, ammonium alum, and iron salt. The composite particle for electrochemical element electrodes according to any one of claims 1 to 3.   An electrochemical element electrode comprising an electrode active material layer comprising the composite particles for an electrochemical element electrode according to any one of claims 1 to 4 laminated on a current collector.   An electrochemical device comprising the electrochemical device electrode according to claim 5. A method for producing a composite particle for an electrochemical element electrode for obtaining the composite particle for an electrochemical element electrode according to any one of claims 1 to 4,
An electrochemical device comprising a step of adding the slurry, the immiscible solvent, the surfactant, and the coagulating liquid while stirring the slurry comprising the electrode active material and the binder resin. A method for producing composite particles for an electrode.   The manufacturing method of an electrochemical element electrode including the process of obtaining an electrode active material layer by press-molding the electrode material containing the composite particle for electrochemical element electrodes in any one of Claims 1-4 on a collector .

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