JP2014200710A - Silicon simple substance-containing emulsion, microcapsule and active material particle, as well as production method of them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide spherical active material particles which include a carbon-coated silicon-based material and of which the dispersion in the particle size is restrained to a low level.SOLUTION: Mono-dispersed spherical active material particles are obtained by producing a W/O/W or S/O/W type emulsion including a silicon-based material inside thereof via a step to make the suspension pass through predetermined holes, subsequently producing microcapsules by polymerizing a monomer in the oil phase of the emulsion, and then carbonizing organic substances in the microcapsules.

Description

  The present invention relates to an emulsion containing silicon alone, microcapsules and active material particles, and a method for producing them.

Lithium ion secondary batteries are small and have a large capacity, and are therefore used as batteries for various devices such as mobile phones and notebook computers. A lithium ion secondary battery includes a pair of electrodes of a positive electrode and a negative electrode as an essential component. The electrode includes an active material layer and a current collector on which the active material layer is bound. The active material layer included in the negative electrode includes a negative electrode active material that is a material capable of inserting and extracting lithium ions. In recent years, it has been found that silicon-based materials such as silicon alone and SiO _x (0.3 ≦ x ≦ 1.6) disproportionated to silicon simple substance and silicon dioxide are useful as negative electrode active materials. There is a lot of research on system materials.

  In order to use a silicon-based material as a suitable negative electrode active material, a technique is known in which a silicon-based material is coated with carbon to give good conductivity. Examples of a method for carbon coating a silicon-based material include a mechanical alloying method in which the silicon-based material and the carbon material are adhered to each other with a mechanical shear force, and a CVD method in which a carbon-containing gas is chemically vapor-deposited on the silicon-based material. Patent Document 1 discloses a technique in which a material containing silicon alone is carbon-coated by a CVD method to form a negative electrode active material.

JP 2011-192453 A

  However, when the active material particles obtained by the conventional carbon coating method of silicon-based material are observed, unevenness is observed in the degree of carbon coating, and it is actually very difficult to control this unevenness. Moreover, a large dispersion was observed in the particle size of the active material obtained by the conventional carbon coating method, not only between lots but also within lots. If the dispersion of the particle size of the active material is large, the surface area of the entire active material may vary from electrode to electrode, and the filling rate of the active material from electrode to electrode may vary. As a result, the battery capacity varies from electrode to electrode. The dispersion of the particle size of the active material obtained by the conventional carbon coating method mainly depends on the dispersion of the particle size of the silicon-based material before the carbon coating. In general, since the silicon-based material is prepared by pulverization with a ball mill or the like, it is difficult to avoid a large dispersion in the particle size of the silicon-based material. Moreover, it has been practically difficult to make the shape of an active material containing a silicon-based material into an ideal sphere for acting as an active material.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide spherical active material particles that contain a carbon-coated silicon-based material and have low dispersion in particle size.

  The present inventor has intensively studied a carbon coating method for silicon-based materials. The present inventors unexpectedly recalled the application of emulsion and microcapsule manufacturing techniques as a carbon coating method for silicon-based materials. Furthermore, as a result of extensive studies, an emulsion using a silicon-based material and a polymerizable monomer, a microcapsule using the emulsion as a raw material, and active material particles using the microcapsule as a raw material were obtained. The inventors have found that the dispersion of the particle size of the particles can be kept low, and have completed the present invention.

  The W / O / W type emulsion or S / O / W type emulsion of the present invention comprises an inner aqueous phase containing silicon alone or a solid phase containing silicon alone, an oil phase containing a polymerizable monomer, and an outer aqueous phase. Features.

  One aspect of the method for producing a W / O / W type or S / O / W type emulsion of the present invention is a W / O type emulsion forming step of adding a polar liquid containing silicon alone to an organic solvent containing a polymerizable monomer, or The first emulsion forming step selected from any of the S / O suspension forming steps in which silicon alone is dispersed in an organic solvent containing a polymerizable monomer, and the liquid obtained in the first emulsion forming step have pores. It has the 1st hole passage process which passes the said hole of a film | membrane or a partition, and the 2nd emulsion formation process which disperse | distributes the liquid which passed the said 1st hole passage process in a polar continuous phase solution, It is characterized by the above-mentioned.

  In another aspect of the method for producing a W / O / W type or S / O / W type emulsion of the present invention, a W / O type emulsion is formed by adding a polar liquid containing silicon alone to an organic solvent containing a polymerizable monomer. The first emulsion forming step selected from either the step or the S / O type suspension forming step in which silicon alone is dispersed in an organic solvent containing a polymerizable monomer, and the liquid obtained in the first emulsion forming step is polar A third emulsion forming step for dispersing in the continuous phase solution, and a second hole passing step for allowing the emulsion-containing solution formed in the third emulsion forming step to pass through the pores of the membrane or partition wall having pores. It is characterized by that.

  Since the shape of the W / O / W type emulsion or S / O / W type emulsion of the present invention is an emulsion, it is naturally spherical. Further, since the W / O / W type emulsion or S / O / W type emulsion of the present invention is produced by passing through a film or partition having a pore diameter in a specific range, dispersion of the emulsion particle size can be kept low. ing.

  The microcapsule of the present invention is characterized in that it contains silicon alone and the main component of the oil phase is a polymer. The method for producing a microcapsule according to the present invention is characterized by having a polymerization step of polymerizing a polymerizable monomer contained in the W / O / W type or S / O / W type emulsion.

  Since the microcapsule of the present invention is produced through a polymerization step in which the polymerizable monomer contained in the spherical and low-dispersion W / O / W type or S / O / W type emulsion is polymerized, The microcapsule is spherical and its particle size dispersion is kept low.

  The active material particles of the present invention are characterized in that they contain silicon alone and are spherical. Further, the active material particles of the present invention are low-dispersion, preferably mono-dispersed in particle size. The method for producing active material particles of the present invention includes a firing step of firing the microcapsules.

  Since the active material particles of the present invention are manufactured through a firing step of firing the spherical and low-dispersion microcapsules, the active material particles of the present invention are spherical, and the dispersion of the particle size can be kept low. ing.

  The active material particles of the present invention contain a carbon-coated silicon-based material, have a low particle size, and are spherical. Since dispersion of the particle size of the active material particles of the present invention is suppressed, when the active material particles of the present invention are used as an anode active material, for example, in an electrode, it is possible to reduce variation in the surface area of the entire anode active material for each electrode. And the dispersion | variation in the filling rate of the negative electrode active material for every electrode can be reduced. As a result, variation in battery capacity for each electrode can be suppressed.

It is an optical microscope photograph of the W / O / W type emulsion of the present invention. The scale at the bottom right of the photo is 200 μm. It is an optical microscope photograph of the microcapsule of this invention. The scale size in the lower right of the photo is 100 μm. It is a scanning electron micrograph of the microcapsule of this invention. It is a scanning electron micrograph of the microcapsule of this invention. It is a scanning electron micrograph of the microcapsule of this invention. It is a scanning electron micrograph of the microcapsule of this invention. It is a scanning electron micrograph of the microcapsule of this invention. It is a scanning electron micrograph of the microcapsule of this invention. It is a scanning electron micrograph of the microcapsule of this invention. It is a scanning electron micrograph of the active material particle of this invention. It is a scanning electron micrograph of the active material particle of this invention. It is a scanning electron micrograph of the active material particle of this invention. It is the measurement result of the particle size distribution of the microcapsule (before baking) of this invention and the active material particle (after baking) of this invention by the laser diffraction scattering type particle size distribution measuring apparatus.

  Below, the form for implementing this invention is demonstrated. Unless otherwise specified, the numerical range “ab” described herein includes the lower limit “a” and the upper limit “b”. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from the numerical value range can be used as upper and lower numerical values. In this specification, for example, the notation of (meth) acrylic acid means each of acrylic acid and methacrylic acid independently.

  The W / O / W type emulsion or S / O / W type emulsion of the present invention comprises an inner aqueous phase containing silicon alone or a solid phase containing silicon alone, an oil phase containing a polymerizable monomer, and an outer aqueous phase. Features.

  One aspect of the method for producing a W / O / W type or S / O / W type emulsion of the present invention is a W / O type emulsion forming step of adding a polar liquid containing silicon alone to an organic solvent containing a polymerizable monomer, or The first emulsion forming step selected from any of the S / O suspension forming steps in which silicon alone is dispersed in an organic solvent containing a polymerizable monomer, and the liquid obtained in the first emulsion forming step have pores. It has the 1st hole passage process which passes the said hole of a film | membrane or a partition, and the 2nd emulsion formation process which disperse | distributes the liquid which passed the said 1st hole passage process in a polar continuous phase solution, It is characterized by the above-mentioned.

  In another aspect of the method for producing a W / O / W type or S / O / W type emulsion of the present invention, a W / O type emulsion is formed by adding a polar liquid containing silicon alone to an organic solvent containing a polymerizable monomer. The first emulsion forming step selected from either the step or the S / O type suspension forming step in which silicon alone is dispersed in an organic solvent containing a polymerizable monomer, and the liquid obtained in the first emulsion forming step is polar A third emulsion forming step for dispersing in the continuous phase solution, and a second hole passing step for allowing the emulsion-containing solution formed in the third emulsion forming step to pass through the pores of the membrane or partition wall having pores. It is characterized by that.

  Hereinafter, the W / O / W type or S / O / W type emulsion of the present invention will be described along the emulsion production method.

  The first emulsion forming step is a W / O type emulsion forming step of adding a polar liquid containing silicon alone to an organic solvent containing a polymerizable monomer, or an S / O type suspension in which silicon simple substance is dispersed in an organic solvent containing a polymerizable monomer. Any of the forming steps.

  The polar liquid containing silicon alone (hereinafter sometimes simply referred to as “polar liquid”) corresponds to W of the W / O emulsion. The polar liquid is a liquid which contains silicon alone and water or alcohols having up to 3 carbon atoms (hereinafter simply referred to as “alcohols”) as essential components and is not miscible with an organic solvent containing a polymerizable monomer. The composition of the polar liquid is not particularly limited as long as it forms an emulsion with an organic solvent containing a polymerizable monomer and contains a material containing silicon alone and water or alcohols.

As a material containing silicon simple substance (hereinafter sometimes referred to as silicon-containing material), silicon simple substance, SiO _x (0.3 ≦ x ≦ 1.6) disproportionate to silicon simple substance and silicon dioxide, and these The material to include is mentioned. When the suitable compounding quantity of the silicon-containing substance essential for the polar liquid is exemplified, the range of 1 to 200 parts by mass of the silicon-containing substance is preferable with respect to 100 parts by mass of water, more preferably the range of 10 to 150 parts by mass. The range of 120 parts by mass is more preferable. The average particle size of the silicon-containing material is not particularly limited as long as it is within a range in which a W / O type emulsion or S / O type suspension can be formed. When the average particle diameter of a suitable silicon-containing material is exemplified, it is preferably in the range of 1 nm to 100 μm, more preferably in the range of 5 nm to 10 μm, and particularly preferably in the range of 10 nm to 5 μm. The average particle size of the silicon-containing material can be calculated using an optical or electron microscope, a laser diffraction particle size distribution measuring device, a zeta potential measurement particle size distribution measuring device, a digital image analysis particle size distribution measuring device, or the like. What is necessary is just to calculate the average particle diameter of the other substance described in this specification using these apparatuses.

Examples of alcohols include methanol, ethanol, n-propanol, i-propanol, ethylene glycol, glycerin, and propanediol.
The polar liquid contains silicon alone and water or alcohol as essential components, but in addition to these, a surfactant and a water-soluble W / O emulsion stabilizer may be included. The compounding quantity of the component in a polar liquid will not be specifically limited if the polar liquid is a range which forms an emulsion with the organic solvent containing a polymerizable monomer.

  The surfactant is contained in at least one of a polar liquid or an organic solvent containing a polymerizable monomer described later. The surfactant is present at each emulsion or suspension, that is, at the interface of each phase of W / O, S / O, W / O / W, and S / O / W. When the suitable compounding quantity in case surfactant is contained in a polar liquid is illustrated, the range of 0.001-10 mass parts of surfactant is preferable with respect to 100 mass parts of water, The range of 0.01-5 mass parts Is more preferable, and the range of 0.02 to 2 parts by mass is even more preferable.

  Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants. These surfactants may be used in combination.

  Nonionic surfactants include polyoxyalkylene alkyl ether, polyoxyalkylene sorbitan ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbit fatty acid ester, polyoxyethylene alkylphenyl Examples include known ones such as ether, polyethylene glycol fatty acid ester, glycerin fatty acid ester, sucrose fatty acid ester, and polyoxyalkylene-modified organopolysiloxane. Preferred nonionic surfactants include sorbitan trioleate known as span 85, tetraglycerin condensed ricinoleate, sorbitan monostearate.

  Cationic surfactants include alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, stearyldimethylbenzylammonium chloride, benzalkonium chloride, capric acid dimethylaminopropylamide, lauric acid dimethylaminopropylamide, myristic acid dimethylaminopropylamide. And known ones such as palmitic acid dimethylaminopropylamide, stearic acid dimethylaminopropylamide, behenic acid dimethylaminopropylamide, and oleic acid dimethylaminopropylamide.

  Known anionic surfactants include alkyl sulfates such as sodium lauryl sulfate, α-olefin sulfonates, monoalkyl phosphate esters, sodium alkylbenzene sulfonate, sodium glycocholate, and sodium deoxycholate. Can be mentioned.

  Examples of amphoteric surfactants include known ones such as alkyldimethylaminoacetic acid betaine, alkylamidodimethylaminoacetic acid betaine, and 2-alkyl-N-carboxy-N-hydroxyimidazolinium betaine.

  The water-soluble W / O emulsion stabilizer is not an essential component in the polar liquid, but a suitable blending amount when the water-soluble W / O emulsion stabilizer is contained in the polar liquid is 100 masses of water. The water-soluble W / O emulsion stabilizer is preferably in the range of 0.001 to 200 parts by weight, more preferably in the range of 0.005 to 150 parts by weight, and still more preferably in the range of 0.01 to 120 parts by weight. .

  Water-soluble W / O emulsion stabilizers include methanol, ethanol, ethylene glycol, propylene glycol, pentanediol, hexanediol, hexylene glycol, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol diethyl ether Water-soluble solvents such as, polyvinylpyrrolidone, polyvinyl alcohol, polysorbate, carboxymethylcellulose, hydroxymethylcellulose, starch, gelatin and other water-soluble polymers, acrylic acid, (meth) acrylic acid, (meth) acrylic acid ester, (meth) acrylamide, Fumaramide, ethacrylamide, N, N′-methylenebisacrylonitrile, 2- (meth) acrylo Ruoxyethanesulfonic acid, 2- (meth) acryloyloxypropanesulfonic acid, 2- (meth) acrylamide-2-alkyl-propanesulfonic acid, vinylsulfonic acid, styrenesulfonic acid, (meth) acryloyloxyalkylphosphoric acid, vinyl Water-soluble polymerizable monomers such as phosphonic acid, persulfates such as ammonium persulfate and potassium persulfate, and water-soluble polymerization initiators such as hydrogen persulfide, inorganic salts such as sodium chloride and sodium sulfate, colloidal silica, barium sulfate, Examples thereof include colloid-forming materials such as calcium sulfate, barium carbonate, calcium carbonate, magnesium carbonate, calcium phosphate, aluminum oxide, titanium oxide, aluminum hydroxide, magnesium hydroxide, and ferric hydroxide. These water-soluble W / O emulsion stabilizers may be used in combination.

  The solid phase containing silicon alone is synonymous with the silicon-containing material and corresponds to S of the S / O suspension.

  The polymerizable monomer of the present invention is not particularly limited as long as it is not miscible with water or alcohols.

  Examples of polymerizable monomers that are immiscible with water or alcohols include styrene, bromostyrene, chlorostyrene, vinylnaphthalene, α-methylstyrene, p-methylstyrene, t-butylstyrene, chlorostyrene, benzyl acrylate, benzyl methacrylate, and vinyl toluene. , Vinyl aromatic compounds such as divinylbenzene, divinyltoluene, divinylxylene, divinylnaphthalene, trivinylbenzene, divinyldiphenyl ether and divinyldiphenylsulfone, vinyl chloride, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3 -Olefin compounds such as butadiene, 1,3-pentadiene, chloroprene, acrylic esters such as methyl (meth) acrylate and ethyl (meth) acrylate, vinyl such as vinyl acetate Ester, and (meth) unsaturated nitriles such as acrylonitrile. A polymerizable monomer may be used independently and 2 or more types may be used together.

  Preferred polymerizable monomers include styrene, vinyl naphthalene, α-methyl styrene, p-methyl styrene, t-butyl styrene, vinyl toluene, divinyl benzene, divinyl toluene, divinyl xylene, divinyl naphthalene, trivinyl benzene, 1,3- Examples thereof include compounds composed only of carbon and hydrogen, such as butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and chloroprene. These polymerizable monomers composed only of carbon and hydrogen are preferable because they do not contain oxygen, nitrogen, halogen, or the like that may become impurities in the active material particles after the firing step.

  The organic solvent containing a polymerizable monomer may contain only a polymerizable monomer, but may contain a surfactant, a crosslinking agent, an oil-soluble polymerization initiator, and a thickener.

  The surfactant is contained in at least one of the organic solvent containing a polymerizable monomer and the polar liquid described above. As the surfactant contained in the organic solvent containing the polymerizable monomer, one or more of the above-mentioned specific surfactants can be employed, but a nonionic surfactant is employed from the viewpoint of solubility in the polymerizable monomer. Is preferred. Specific examples of preferred nonionic surfactants include sorbitan trioleate known as span 85, tetraglycerin condensed ricinoleic acid ester, and sorbitan monostearate. When a suitable compounding amount when the surfactant is contained in an organic solvent containing a polymerizable monomer is exemplified, the range of 0.01 to 15 parts by mass of the surfactant is preferable with respect to 100 parts by mass of the polymerizable monomer. The range of 1-10 mass parts is more preferable, and the range of 1-8 mass parts is further more preferable.

  The cross-linking agent is a compound having two or more olefins in the molecule, and is for stabilizing the oil phase of the emulsion or the polymer layer of the microcapsule. Specific crosslinking agents include divinylbenzene, divinylnaphthalene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,4-butanediol diacrylate, N, N-divinylaniline, divinyl ether, pentaerythritol triallyl ether, trimethylol. Propane triacrylate can be exemplified. A crosslinking agent may be used independently and 2 or more types may be used together. Although the compounding quantity of a crosslinking agent is not specifically limited, The range of 0.01-50 mass parts of crosslinking agents is preferable with respect to 100 mass parts of polymerizable monomers, The range of 0.1-30 mass parts is more preferable, 1-15 The range of parts by mass is more preferable.

  Examples of the oil-soluble polymerization initiator include azobisisobutyronitrile, azobispereronitrile, 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis [2-methyl-N- (2 -Hydroxyethyl) propionamide], 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyro Azo compounds such as nitrile, 2,2'-azobis (2-methylpropionate), benzoyl peroxide, lauroyl peroxide, methyl ethyl ketone peroxide, di-t-butyl peroxide, dicumyl peroxide, t- Butyl peroxy-2-ethylhexanoate, t-butyl peroxypivalate, di-isopropyl peroxydicarbonate And peroxides such as di-t-butylperoxyisophthalate, 1,1 ', 3,3'-tetramethylbutylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate Can do. Although the compounding quantity of an oil-soluble polymerization initiator is not specifically limited, The range of 0.01-10 mass parts of an oil-soluble polymerization initiator is preferable with respect to 100 mass parts of polymerizable monomers, and the range of 0.1-5 mass parts is preferable. More preferably, the range of 1-3 mass parts is further more preferable.

  A thickener is an oil-soluble polymer that increases the viscosity of the oil phase of the emulsion or suspension and stabilizes the emulsion or suspension. Specific thickeners include polystyrene, polyethylene, polypropylene, styrene-butadiene copolymer, polymethyl methacrylate, polyvinyl acetate, poly (meth) acrylate, polymethyl (meth) acrylate, polyester, polyvinyl chloride, polyacrylonitrile. And acrylonitrile-α-methylstyrene copolymer, styrene-divinylbenzene copolymer, and polyethylene carbonate. Although the weight average molecular weight of a thickener is not specifically limited, The range of 10,000-4 million is preferable and the range of 25,000-2 million is more preferable. Although the compounding quantity of a thickener is not specifically limited, The range of 0.001-10 mass parts of thickeners is preferable with respect to 100 mass parts of polymerizable monomers, The range of 0.01-5 mass parts is more preferable, 0 More preferably, the range is 1-2 parts by mass.

  S / O type suspension in which silicon simple substance is dispersed in organic solvent containing polymerizable monomer or W / O type emulsion forming process in which polar liquid containing silicon simple substance is added to organic solvent containing polymerizable monomer in first emulsion forming process The forming step is performed in the presence of a shearing force generated by a stirring device or an ultrasonic device. The organic solvent and / or polar liquid containing the polymerizable monomer used in the first emulsion forming step may be heated.

  The stirring device or the ultrasonic device is not particularly limited as long as it can generate a shearing force sufficient to form a W / O emulsion or an S / O suspension. Specific examples of the stirring device or the ultrasonic device include a homomixer, a homogenizer, a vortex mixer, a nanomizer, a colloid mill, a high-pressure emulsifier, and an ultrasonic emulsifier.

  The compounding quantity of the organic solvent containing a polymerizable monomer and a polar liquid can be suitably selected within the range in which a W / O type emulsion can be formed. The blending amount of the organic solvent containing a suitable polymerizable monomer and the polar liquid is preferably in the range of 1 to 100 parts by weight of the polar liquid with respect to 100 parts by weight of the organic solvent containing the polymerizable monomer, and 5 to 70 parts by weight of the polar liquid. The range of 10 to 50 parts by mass of the polar liquid is particularly preferable. If the polar liquid exceeds 100 parts by mass, the W / O type emulsion may invert to the O / W type emulsion.

  The S / O suspension forming step of dispersing silicon alone in an organic solvent containing a polymerizable monomer may be performed by adding a silicon-containing material to an organic solvent containing a polymerizable monomer, or the polymerizable monomer may be added to the silicon-containing material. You may carry out by adding the organic solvent containing.

  The blending amount of the organic solvent containing the polymerizable monomer and the silicon-containing material can be appropriately selected within a range where an S / O type suspension can be formed. The blending amount of the organic solvent containing a suitable polymerizable monomer and the silicon-containing material is preferably in the range of 0.1 to 100 parts by mass of the silicon-containing material with respect to 100 parts by mass of the organic solvent containing the polymerizable monomer. The range of 1-50 mass parts is more preferable, and the range of 5-20 mass parts of silicon-containing materials is particularly preferable.

  The first hole passing step is a step of allowing the liquid obtained in the first emulsion forming step to pass through the hole of the film or partition having holes.

  As a membrane or partition having pores, a porous membrane made of Shirasu porous glass known as an SPG membrane, a membrane used for ultrafiltration treatment, a silica alumina porous membrane, a zeolite porous membrane, Teflon (registered trademark) Examples thereof include a resin film such as, a metal column, or a partition wall thereof, a through-hole type microchannel array, a microreactor, or the like. Since the uniformity of the pore size of the membrane or partition affects the dispersion of the particle size of the W / O / W type or S / O / W type emulsion, microcapsule and active material particles of the present invention, the pore size of the membrane or partition is It is preferably uniform. An SPG film is particularly preferable from the viewpoint of uniformity of pore diameter, operability, and the like.

  The particle size of the W / O / W type emulsion or S / O / W type emulsion of the present invention depends on the pore size of the membrane or partition wall having pores. For example, the particle size of the emulsion formed in the second emulsion forming step, which will be described later through the first hole passing step, is about three times the pore size of the membrane or partition used in the first hole passing step. Therefore, the pore diameter of the membrane or partition having pores may be appropriately selected according to the desired size of the W / O / W type or S / O / W type emulsion. When the pore diameter of a suitable membrane or partition is exemplified, the range of 0.05 μm to 250 μm is preferable, the range of 0.5 μm to 50 μm is more preferable, and the range of 1 μm to 40 μm is particularly preferable.

  The first hole passing step is preferably performed under a gas pressurizing condition with air or nitrogen gas or under a pressurizing condition with a syringe. The pressurizing condition may be appropriately determined according to the liquid used and the pore size of the membrane or partition. If the suitable pressure at the time of using an SPG membrane is illustrated, the inside of the range of 1 kPa-5 MPa will be preferable, the inside of the range of 2 kPa-1 MPa will be more preferable, and the inside of the range of 3 kPa-100 kPa will be especially preferable.

  A 2nd emulsion formation process is a process of disperse | distributing the liquid which passed through the 1st hole passage process to a polar continuous phase solution. The first hole passing step and the second emulsion forming step are preferably carried out continuously. In the second emulsion formation step, it is preferable that the continuous phase solution is under flow conditions or stirring conditions.

  The continuous phase solution contains water as an essential component, but may further contain a water-soluble emulsion stabilizer, a surfactant, and a water-soluble polymerization inhibitor.

  Examples of the water-soluble emulsion stabilizer are the same as the above-mentioned water-soluble W / O emulsion stabilizer. When the suitable compounding quantity in case a water-soluble emulsion stabilizer is contained in a continuous phase solution is illustrated, the range of 0.001-200 mass parts of water-soluble emulsion stabilizers is preferable with respect to 100 mass parts of water. The range of 005 to 150 parts by mass is more preferable, and the range of 0.01 to 120 parts by mass is more preferable. A water-soluble emulsion stabilizer may be used in combination. In particular, it is preferable to use a water-soluble polymer such as polyvinyl pyrrolidone, polyvinyl alcohol, polysorbate, carboxymethyl cellulose, hydroxymethyl cellulose, starch and gelatin together with an inorganic salt such as sodium chloride and sodium sulfate.

  The surfactant is contained in at least one of the continuous phase solution and the organic solvent containing the polymerizable monomer described above. As the surfactant contained in the continuous phase solution, one or more of the above-mentioned specific surfactants can be adopted, but from the viewpoint of solubility in the continuous phase solution, a cationic surfactant, an anionic surfactant, It is preferable to employ an amphoteric surfactant, and it is particularly preferable to employ an anionic surfactant such as sodium lauryl sulfate. When the suitable compounding quantity in case a surfactant is contained in a continuous phase solution is illustrated, the range of 0.001-10 mass parts of surfactant is preferable with respect to 100 mass parts of water, 0.005-1 mass part of The range is more preferable, and the range of 0.01 to 0.5 parts by mass is further preferable.

  The water-soluble polymerization inhibitor can be appropriately selected from known nitrites, sulfites, hydroquinones, ascorbic acids, and amine compounds. Specific water-soluble polymerization inhibitors include sodium nitrite, ammonium nitrite, hydroquinone, sulfonated naphthohydroquinone ammonium salt, p-phenylenediamine, and N-phenyl-N′-isopropyl-p-phenylenediamine. If the suitable compounding quantity in case a water-soluble polymerization inhibitor is contained in a continuous phase solution is illustrated, the range of 0.001-5 mass parts of water-soluble polymerization inhibitors is preferable with respect to 100 mass parts of water, 0.01- The range of 1 part by mass is more preferable, and the range of 0.02 to 0.5 part by mass is more preferable.

  The amount of the continuous phase solution is not particularly limited as long as the W / O / W type or S / O / W type emulsion of the present invention is obtained. When the quantity of a suitable continuous phase solution is illustrated, 10 mass parts or more of continuous phase solutions are preferable with respect to 100 mass parts of organic solvents containing a polymerizable monomer, 50 mass parts or more of continuous phase solutions are more preferable, 100-10000 mass parts The range of is particularly preferable.

  The third emulsion forming step is a step of forming a W / O / W type or S / O / W type emulsion by dispersing the liquid obtained in the first emulsion forming step in a polar continuous phase solution before the hole passing step. It is. What is necessary is just to use the same component for the continuous phase solution of a 3rd emulsion formation process as the continuous phase solution demonstrated by the above-mentioned 2nd emulsion formation process in the same quantity. The third emulsion forming step is performed in the presence of a shearing force by the same stirring device or ultrasonic device as in the first emulsion forming step.

  The second hole passing step is a step of allowing the W / O / W type or S / O / W type emulsion-containing solution formed in the third emulsion forming step to pass through the holes of the film or partition wall having holes. The film or partition having the holes used in the second hole passage step and the conditions of the second hole passage step are basically the same as those in the first hole passage step. However, the size of the diameter of the W / O / W type emulsion or S / O / W type emulsion of the present invention formed through the second hole passing step is roughly the same as the hole diameter of the membrane or partition used in the second hole passing step. equal.

  Since the second hole passing step is a step of passing the emulsion dispersed in the polar continuous phase solution, the polar continuous phase solution is in direct contact with the hydrophilic film or partition. Then, the component of the inner water phase of the W / O / W type emulsion or the solid phase component of the S / O / W type emulsion comes into contact with the hydrophilic film or partition, and these components contact the hydrophilic film or partition. Any adhesion is suppressed. Therefore, there is almost no risk of clogging of the holes of the film or partition used in the second hole passing step.

  In order to suppress the dispersion of the particle size of the W / O / W type emulsion or S / O / W type emulsion of the present invention to a lower level, a film or a partition wall having excellent pore size uniformity is used in the hole passing step, or a desired The hole passing step may be repeated until dispersion is obtained. Then, a monodispersed W / O / W type or S / O / W type emulsion can be obtained.

In the present invention, monodispersion means a coefficient of variation (CV) calculated by the following formula of 15% or less.
Coefficient of variation (CV (%)) = (standard deviation of average particle diameter / average particle diameter) × 100

  The microcapsule of the present invention is characterized in that it contains silicon alone and the main component of the oil phase is a polymer. In the case of the microcapsule of the present invention in which the oil phase contains simple silicon, the main component other than the simple silicon in the oil phase is a polymer. The microcapsule production method of the present invention has a polymerization step of polymerizing a polymerizable monomer contained in the oil phase of the W / O / W type or S / O / W type emulsion obtained by the production method of the present invention. It is characterized by. That is, the composition of the microcapsules of the present invention depends on the composition of the emulsion subjected to the polymerization process.

  The polymerization process is started by heating the W / O / W type or S / O / W type emulsion of the present invention. The polymerization step is preferably performed under stirring conditions, and is preferably performed in an inert gas atmosphere such as nitrogen or argon. The polymerization step is preferably carried out continuously from the method for producing a W / O / W type or S / O / W type emulsion of the present invention. However, the W / O / W type or S / O / W type emulsion obtained by the production method of the present invention may be freeze-dried and the water from the outer phase removed to be subjected to the polymerization step.

  The heating temperature is not particularly limited as long as the polymerization of the polymerizable monomer is started. If an oil-soluble polymerization initiator is contained in the oil phase, it is preferable to heat to a temperature at which the oil-soluble polymerization initiator starts to decompose. The range of 60-80 degreeC can be illustrated as preferable heating temperature.

  The W / O / W type emulsion or S / O / W type emulsion of the present invention becomes a microcapsule containing a silicon simple substance and a main component of an oil phase through a polymerization process. The shape of the microcapsules of the present invention is similar to the particle shape of a W / O / W type or S / O / W type emulsion. The particle size of the microcapsule is smaller than the particle size of the W / O / W type or S / O / W type emulsion used as a raw material. The degree of particle size reduction depends on the amount of oil phase, but the microcapsule particle size is 2 / 5-4 of the particle size of the W / O / W type or S / O / W type emulsion used as the raw material. / 5 or so. The variation coefficient of the particle size of the microcapsule is equivalent to the variation coefficient of the particle size of the W / O / W type or S / O / W type emulsion.

  The active material particles of the present invention are characterized in that they contain silicon alone and are spherical. In the active material particles of the present invention, the main component other than silicon alone is carbon. Furthermore, the active material particles of the present invention are low-dispersion, preferably monodisperse in particle size. The method for producing active material particles of the present invention includes a firing step of firing the microcapsules of the present invention. That is, the composition of the active material particles of the present invention depends on the composition of the microcapsules subjected to the firing step, and by extension, the composition of the emulsion that is the raw material of the microcapsules. The mass ratio of silicon simple substance to carbon in the active material particles of the present invention (silicon simple substance / carbon) is not particularly limited, but is preferably in the range of 1/100 to 100, more preferably in the range of 1/50 to 10, and 1/10. A range of ˜1 is particularly preferred. In order to obtain a desired mass ratio of silicon simple substance to carbon in the active material particles of the present invention, the amount of silicon simple substance and polymerizable monomer used in the first emulsion forming step may be appropriately adjusted.

  The firing step is a step of thermally decomposing and carbonizing organic substances contained in the microcapsules. Since the elements and water other than carbon and silicon contained in the microcapsules are generally removed as a gas by the firing step, active material particles in which silicon alone is carbon-coated or active material particles in which silicon alone is dispersed in a carbon matrix Can be obtained. The heating temperature is preferably in the range of 500 to 1500 ° C. The firing step is preferably performed in an inert gas atmosphere such as nitrogen or argon. The firing process may also serve as a polymerization process. For example, if the W / O / W type emulsion or S / O / W type emulsion obtained by the production method of the present invention is freeze-dried and charged in an electric furnace and the heating temperature is gradually increased, the polymerization step And a baking process can be performed continuously.

  The shape of the active material particles of the present invention is generally similar to the shape of the microcapsule used as a raw material. In the case of active material particles obtained by firing microcapsules having an aqueous phase therein, a concave depression may be observed on the particle surface.

  The variation coefficient of the particle size of the active material particles is almost equal to the variation coefficient of the particle size of the W / O / W type emulsion or the S / O / W emulsion of the present invention and the variation coefficient of the particle size of the microcapsule of the present invention. .

  Since the active material particles of the present invention have a spherical shape and a low particle size, they are suitable secondary battery active materials. When the active material particles of the present invention are used as a negative electrode active material of a lithium ion secondary battery, the silicon simple substance in the active material particles acts as a material capable of occluding and releasing lithium ions. When the active material particles of the present invention are used as a negative electrode active material, the active material particles of the present invention are preferably used alone, but may be used in combination with a known negative electrode active material.

  The negative electrode of the secondary battery has a current collector and a negative electrode active material layer bound to the surface of the current collector.

  The current collector refers to a chemically inert electronic high conductor that keeps a current flowing through an electrode during discharge or charging of a lithium ion secondary battery. As the current collector, at least one selected from silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel Examples of such a metal material can be given. The current collector may be covered with a known protective layer. The current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. Therefore, metal foils, such as copper foil, nickel foil, aluminum foil, stainless steel foil, can be used suitably as a collector. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 10 μm to 100 μm.

  The negative electrode active material layer includes a negative electrode active material and, if necessary, a binder.

  The binder plays a role of binding the active material to the surface of the current collector. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, and alkoxysilyl group-containing resins. be able to. The blending ratio of the binder in the negative electrode active material layer is preferably a mass ratio of negative electrode active material: binder = 1: 0.05 to 1: 0.5. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

  A positive electrode used for a lithium ion secondary battery has a positive electrode active material capable of inserting and extracting lithium ions. The positive electrode has a current collector and a positive electrode active material layer bound to the surface of the current collector. The positive electrode active material layer includes a positive electrode active material and, if necessary, a binder and / or a conductive aid. The current collector and binder for the positive electrode may be the same as those described for the negative electrode. What is necessary is just to use a well-known thing as a conductive support agent suitably.

Examples of positive electrode active materials include LiCoO ₂ , LiNi _p Co _q Mn _r O ₂ (0 ≦ p ≦ 1, 0 ≦ q ≦ 1, 0 ≦ r ≦ 1, p + q + r = 1), Li ₂ MnO ₂ , Li ₂ MnO _3. , LiFePO ₄ , Li ₂ FeSO ₄ as a basic composition or a lithium-containing metal oxide or a solid solution material containing one or more of them.

  In order to form an active material layer on the surface of the current collector, the surface of the current collector can be formed using a conventionally known method such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method. What is necessary is just to apply | coat an active material to. Specifically, an active material layer-forming composition containing an active material and, if necessary, a binder and a conductive aid is prepared, and an appropriate solvent is added to the composition to make a paste, and then the collection is performed. After applying to the surface of the electric body, it is dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, and methyl isobutyl ketone. In order to increase the electrode density, the dried product may be compressed.

  A separator is used in the lithium ion secondary battery as necessary. The separator separates the positive electrode and the negative electrode and allows lithium ions to pass while preventing a short circuit of current due to contact between the two electrodes. Examples of the separator include a porous film using one or more synthetic resins such as polytetrafluoroethylene, polypropylene, and polyethylene, or a ceramic porous film.

  A separator is sandwiched between the positive electrode and the negative electrode as necessary to form an electrode body. After connecting the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal leading to the outside with a current collecting lead or the like, an electrolyte is added to the electrode body to form a lithium ion secondary battery. Good. The shape of the lithium ion secondary battery is not particularly limited, and various shapes such as a cylindrical shape, a laminated shape, a coin shape, and a laminated shape can be employed.

  The lithium ion secondary battery may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from a lithium ion secondary battery for all or a part of its power source, and may be, for example, an electric vehicle or a hybrid vehicle. When a lithium ion secondary battery is mounted on a vehicle, a plurality of lithium ion secondary batteries may be connected in series to form an assembled battery. Examples of the lithium ion secondary battery include various home electric appliances, office equipment, industrial equipment, and the like driven by batteries, such as personal computers and portable communication devices, in addition to vehicles.

  As mentioned above, although embodiment of the W / O / W type | mold or S / O / W type | mold emulsion, microcapsule, active material particle, and these manufacturing method of this invention was described, this invention is limited to the said embodiment. It is not something. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.

Example 1
The W / O / W emulsion of the present invention was produced as follows.

Commercially available SiO _x (0.3 ≦ x ≦ 1.6) 2.0 g having a particle size of 2 μm or less, 0.01 g of potassium persulfate and 2.0 g of water were mixed to obtain a polar liquid containing silicon alone.

  12.6 g of styrene, 1.26 g of ethylene glycol dimethacrylate, 0.3 g of 2,2′-azobis (2,4-dimethylvaleronitrile), 0.8 g of sorbitan trioleate, 0.075 g of polystyrene having a weight average molecular weight of 2 million It mixed and melt | dissolved and it was set as the organic solvent containing a polymerizable monomer.

  225 g of water, 4.0 g of polyvinylpyrrolidone, 0.075 g of sodium lauryl sulfate, 0.2 g of sodium sulfate and 0.1 g of p-phenylenediamine were mixed and dissolved to obtain a polar continuous phase solution.

  After mixing an organic solvent containing a polymerizable monomer and a polar liquid containing silicon alone, ultrasonic waves were generated using an ultrasonic emulsifier under conditions of 150 W and 40 kHz to form a W / O type emulsion.

  The obtained W / O type emulsion-containing liquid is filled into a dispersed phase tank of a nitrogen gas pressure type SPG membrane emulsification apparatus (manufactured by SPG Techno Co., Ltd.) equipped with an SPG membrane having a pore diameter of 10 to 30 μm. The phase solution was filled into the continuous phase container of the SPG membrane emulsifier. The W / O emulsion-containing liquid in the dispersed phase tank was pressurized at a pressure of 6 kPa and passed through the SPG membrane. And the SPG membrane passage liquid was disperse | distributed to the continuous phase solution under stirring at the speed of 500 rpm, and the W / O / W type | mold emulsion was obtained. When observed with an optical microscope, many W / O / W emulsions having a particle size of about 25 μm were confirmed. An optical micrograph of the obtained W / O / W emulsion is shown in FIG.

The microcapsules of the present invention were produced as follows.
The obtained W / O / W emulsion containing liquid was heated to 70 ° C. in a nitrogen gas atmosphere and stirred at a speed of 500 rpm for 20 hours. As a result, microcapsules in which styrene contained in the oil phase of the W / O / W emulsion was polymerized to form polystyrene were obtained. When observed with an optical microscope and a scanning electron microscope, many microcapsules having a particle size of about 19 μm were confirmed.

An optical micrograph of the microcapsule is shown in FIG. 2, and scanning electron micrographs are shown in FIGS. When the surface composition of the microcapsule was analyzed by an energy dispersive X-ray analyzer, carbon was 74%, oxygen was 14%, and silicon was 12%. 5-9, the dark part of the microcapsule particle surface corresponds to SiO _x (0.3 ≦ x ≦ 1.6), and the thin part corresponds to polystyrene.

The active material particles of the present invention were produced as follows.
The microcapsules of the present invention were heated and fired at 600 ° C. for 20 minutes in an Ar atmosphere using a 2 kW high-frequency heating furnace. The microcapsules of the present invention were housed in a carbon crucible so that the heat generated by induction heating was uniform, and further fired in a state where the crucible was wrapped with copper foil.

Observation of the obtained active material particles with a scanning electron microscope revealed that carbonized composite SiO _x (0.3 ≦ x ≦ 1. 2) having a particle size of about 2 μm, carbonized with polystyrene and ethylene glycol dimethacrylate as a crosslinking agent. 6) Many active material spherical particles were confirmed. Scanning electron micrographs of the active material particles of the present invention after firing are shown in FIGS.

  The particle size distribution of the W / O / W emulsion, microcapsule and active material particle of the present invention was measured with a laser diffraction / scattering particle size distribution measuring device, and the standard deviation, average diameter and coefficient of variation (CV) were calculated. The results are shown in Table 1.

  The W / O / W emulsion, microcapsule and active material particles of the present invention were all monodispersed. The measurement results of the particle size distribution of the microcapsules of the present invention (before firing) and the active material particles of the present invention (after firing) are shown in FIG.

In addition, the microcapsule of the present invention is heated at 200 ° C. to 500 ° C. for about 1 hour in an Ar or N ₂ atmosphere to remove impurities and extra substituents of organic substances contained in the microcapsule, thereby obtaining active material particles. Good. In this case, not all organic substances contained in the active material particles are carbonized, but the active material particles exhibit the same effects as the carbonized active material particles of Example 1 described above. When only an organic solvent containing carbon and hydrogen is used as the organic solvent containing a polymerizable monomer, the particle diameter of the obtained active material particles can be maintained as that of the microcapsules before firing.

(Example 2)
A W / O / W emulsion, microcapsule and active material particles of the present invention were produced in the same manner as in Example 1 except that ethylene glycol dimethacrylate was replaced with divinylbenzene.

(Example 3)
A W / O emulsion-containing liquid was obtained in the same manner as in Example 1.
After mixing the continuous phase solution described in Example 1 and the W / O emulsion-containing liquid, ultrasonic waves were generated using an ultrasonic emulsifier under the conditions of 150 W and 40 kHz, and the W / O / W emulsion was obtained. Formed.
The obtained W / O / W type emulsion-containing liquid was filled in a dispersed phase tank of a nitrogen gas pressure type SPG membrane emulsifying apparatus (manufactured by SPG Techno Co., Ltd.) equipped with an SPG membrane having a pore diameter of 10 to 30 μm. The W / O / W type emulsion-containing liquid in the dispersed phase tank is pressurized at a pressure of 6 kPa and passed through the SPG membrane (corresponding to the second hole passing step) to obtain the W / O / W type emulsion of the present invention. It was.
Thereafter, microcapsules and active material particles were produced in the same manner as in Example 1.

Example 4
A W / O / W emulsion of the present invention was produced in the same manner as in Example 1.
The W / O / W emulsion-containing liquid was frozen at −30 ° C. and then vacuum-dried to remove ice (external phase water). The obtained particles were charged into an electric furnace, heated to 100 ° C. in an Ar atmosphere, and held for 2 hours to polymerize styrene in the oil phase to form microcapsules. After the polymerization, the electric furnace was further heated to 600 ° C. and held for 20 minutes, whereby the microcapsules were fired to obtain active material particles.

  In addition, it is good also as active material particle which removed the impurity and the extra substituent by making temperature rise after superposition | polymerization into 200 to 500 degreeC and hold | maintaining for 1 hour.

(Example 5)
The S / O / W type emulsion of the present invention was produced as follows.
After mixing 2.0 g of commercially available SiO _x (0.3 ≦ x ≦ 1.6) having a particle size of 2 μm or less into an organic solvent containing the polymerizable monomer of Example 1 or Example 2, an ultrasonic emulsifier was used. Then, ultrasonic waves were generated under conditions of 150 W and 40 kHz to form an S / O type emulsion.
The obtained S / O type emulsion-containing liquid is filled in a dispersed phase tank of a nitrogen gas pressure type SPG membrane emulsification apparatus (manufactured by SPG Techno Co., Ltd.) equipped with an SPG membrane having a pore diameter of 10 to 30 μm. A continuous phase solution equivalent to that used in Example 1 was filled into the continuous phase container of the SPG membrane emulsifier. The S / O type emulsion-containing liquid in the dispersed phase tank was pressurized at a pressure of 6 kPa and passed through the SPG membrane. And the SPG membrane passage liquid was disperse | distributed to the continuous phase solution under stirring at the speed of 500 rpm, and the S / O / W type | mold emulsion was obtained. When observed with an optical microscope, a large number of S / O / W emulsions having a particle size of about 26 μm were confirmed.

The microcapsules of the present invention were produced as follows.
The obtained S / O / W type emulsion-containing liquid was heated to 70 ° C. in a nitrogen gas atmosphere and stirred at a speed of 500 rpm for 20 hours. As a result, microcapsules in which styrene contained in the oil phase of the S / O / W emulsion was polymerized to become polystyrene were obtained. When observed with an optical microscope and a scanning electron microscope, many microcapsules having a particle diameter of about 19 μm were confirmed.
The active material particles of the present invention were produced in the same manner as in Example 1.

(Application Example 1)
A battery was fabricated as follows using the active material particles of Example 1.
A slurry was prepared by mixing 45 parts by mass of the active material particles of Example 1, 40 parts by mass of natural graphite powder, 5 parts by mass of acetylene black, and 33 parts by mass of the binder solution. As the binder solution, a solution in which polyamideimide (PAI) resin was dissolved in N-methyl-2-pyrrolidone at a concentration of 30% by mass was used. This slurry was applied to the surface of an electrolytic copper foil (current collector) having a thickness of about 20 μm by using a doctor blade to form a negative electrode active material layer on the copper foil. Thereafter, the current collector and the negative electrode active material layer were firmly and closely joined by a roll press. This was vacuum dried at 100 ° C. for 2 hours to form a negative electrode having a negative electrode active material layer thickness of 16 μm.

A lithium ion secondary battery (half cell) was produced using the negative electrode produced by the above procedure as an evaluation electrode. The counter electrode was a metal lithium foil (thickness 500 μm).
The counter electrode was cut to φ13 mm, the evaluation electrode was cut to φ11 mm, and a separator (Hoechst Celanese glass filter and Celgard “Celgard2400”) was sandwiched between the two electrodes to form an electrode body battery. This electrode body battery was accommodated in a battery case (CR2032 type coin battery member, manufactured by Hosen Co., Ltd.). A non-aqueous electrolyte solution in which LiPF ₆ is dissolved at a concentration of 1 M in a mixed solvent of ethylene carbonate and diethyl carbonate mixed at 1: 1 (volume ratio) is injected into the battery case, the battery case is sealed, and lithium ions are sealed. A secondary battery was obtained.

(Comparative Example 1)
Except that the active material particles of Example 1 used in Application Example 1 were changed to commercially available SiOx (0.3 ≦ x ≦ 1.6) powder having a particle size of 2 μm or less, the same as Application Example 1 was performed. A lithium ion secondary battery was obtained.

<Battery characteristics test>
For the lithium ion secondary batteries of Application Example 1 and Comparative Example 1, the initial charge capacity when charged under the conditions of a temperature of 25 ° C. and a current of 0.2 mA was measured, and subsequently discharged under the conditions of a current of 0.2 mA. The discharge capacity was measured. The initial efficiency (discharge capacity / charge capacity × 100 (%)) was calculated, and the results are shown in Table 2.

  Using the lithium ion secondary batteries of Application Example 1 and Comparative Example 1, the battery was charged to 1 V under the conditions of a temperature of 25 ° C. and a current of 0.2 mA, paused for 10 minutes, and then 0.01 V under the conditions of a current of 0.2 mA. A cycle test was repeated in which 50 cycles of a 10 minute discharge and a 10 minute pause were repeated. Then, a capacity retention ratio that is a ratio of the discharge capacity at the Nth cycle to the discharge capacity at the first cycle was calculated. Table 2 shows the capacity retention ratio at the 50th cycle.

  From Table 2, it can be seen that by using the active material particles of the present invention for a battery, the initial efficiency was improved and the cycle characteristics were greatly improved.

  As described above, the shape of the particles of the W / O / W type emulsion or S / O / W type emulsion of the present invention is naturally spherical because it is an emulsion. In addition, since the W / O / W type emulsion or S / O / W type emulsion of the present invention is produced by passing through a membrane or partition having a specific range of pore sizes, dispersion of the emulsion particle size can be kept low. ing. Since the microcapsule of the present invention is produced through a polymerization step in which the polymerizable monomer contained in the spherical and low-dispersion W / O / W type or S / O / W type emulsion is polymerized, The microcapsule is spherical and its particle size dispersion is kept low. Since the active material particles of the present invention are manufactured through a firing step of firing the spherical and low-dispersion microcapsules, the active material particles of the present invention are spherical, and the dispersion of the particle size can be kept low. And monodisperse. Since the active material particles of the present invention have a suppressed particle size dispersion, when the active material particles of the present invention are used for an electrode as a negative electrode active material, variation in the surface area of the entire negative electrode active material for each electrode can be reduced. The variation in the filling rate of the negative electrode active material for each electrode can be reduced. As a result, variation in battery capacity for each electrode can be suppressed. Further, when the active material particles of the present invention are used in a battery, the negative electrode active material can be effectively filled, so that the filling rate of the active material layer can be improved, and thus the capacity of the battery can be increased. Furthermore, when the active material particles of the present invention are used in a battery, the initial efficiency and the capacity retention rate are greatly improved, so that the battery life can be greatly extended.

Claims (7)

Select from either W / O type emulsion forming step of adding polar liquid containing silicon simple substance to organic solvent containing polymerizable monomer, or S / O type suspension forming step of dispersing silicon simple substance in organic solvent containing polymerizable monomer A first emulsion forming step,
A first hole passing step for allowing the liquid obtained in the first emulsion forming step to pass through the pores of the membrane or partition having pores;
A second emulsion forming step of dispersing the liquid that has passed through the first hole passing step in a polar continuous phase solution;
A method for producing a W / O / W-type or S / O / W-type emulsion, characterized by comprising: Select from either W / O type emulsion forming step of adding polar liquid containing silicon simple substance to organic solvent containing polymerizable monomer, or S / O type suspension forming step of dispersing silicon simple substance in organic solvent containing polymerizable monomer A first emulsion forming step,
A third emulsion forming step for dispersing the liquid obtained in the first emulsion forming step in a polar continuous phase solution;
A second hole passage step of passing the emulsion-containing solution formed in the third emulsion formation step through the pores of the membrane or partition having pores;
A method for producing a W / O / W-type or S / O / W-type emulsion, characterized by comprising:   The manufacturing method of the microcapsule which has the superposition | polymerization process which polymerizes the polymerizable monomer contained in the W / O / W type | mold or S / O / W type | mold emulsion obtained by the manufacturing method of Claim 1 or 2.   The manufacturing method of the active material particle which has a baking process which bakes the microcapsule obtained by the manufacturing method of Claim 3.   A W / O / W type emulsion or S / O / W type emulsion comprising an inner aqueous phase containing silicon alone or a solid phase containing silicon alone, an oil phase containing a polymerizable monomer, and an outer aqueous phase.   A microcapsule containing simple silicon and the main component of the oil phase is a polymer.   Spherical active material particles containing simple silicon.