JP5999439B2 - Emulsion containing polysilane derivative, microcapsule containing polysilane derivative, active material particle containing silicon simple substance, and production method thereof - Google Patents

Description

  The present invention relates to an emulsion containing a polysilane derivative, a microcapsule containing a polysilane derivative, active material particles containing silicon alone, and methods 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 intensive studies, an emulsion using a polysilane derivative and a polymerizable monomer as a silicon-based material, a microcapsule using the emulsion as a raw material, and active material particles using the microcapsule as a raw material have been obtained. The inventors have found that the dispersion of the particle size of the active material 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 a polysilane derivative or a solid phase containing a polysilane derivative, an oil phase containing a polymerizable monomer, and an outer aqueous phase. Features.

  The O / W type emulsion of the present invention comprises an oil phase containing a polysilane derivative and a polymerizable monomer, and an outer aqueous phase.

  One aspect of the method for producing a W / O / W type, S / O / W type or O / W type emulsion of the present invention is a W / O type in which a polar liquid containing a polysilane derivative is added to an organic solvent containing a polymerizable monomer. A first step selected from an emulsion forming step, an S / O suspension forming step in which a polysilane derivative is dispersed in an organic solvent containing a polymerizable monomer, and a dissolving step in which the polysilane derivative is dissolved in an organic solvent containing a polymerizable monomer And the first hole passing step for passing the liquid obtained in the first step through the holes of the membrane or partition wall having holes, and the liquid having passed through the first hole passing step is dispersed in a polar continuous phase solution. And a first emulsion forming step.

  In another aspect of the method for producing a W / O / W type, S / O / W type or O / W type emulsion of the present invention, a polar liquid containing a polysilane derivative is added to an organic solvent containing a polymerizable monomer. / O type emulsion forming step, S / O type suspension forming step of dispersing polysilane derivative in organic solvent containing polymerizable monomer, or dissolving step of dissolving polysilane derivative in organic solvent containing polymerizable monomer A first emulsion, a second emulsion formation step in which the liquid obtained in the first step is dispersed in a polar continuous phase solution, and an emulsion-containing solution formed in the second emulsion formation step. And a second hole passing step for passing through the hole of the partition wall.

  The shape of the particles of the W / O / W type, S / O / W type or O / W type emulsion of the present invention is naturally spherical because it is an emulsion. In addition, since the W / O / W type, S / O / W type or O / W type emulsion of the present invention is produced by passing through a membrane or partition wall having a pore diameter in a specific range, Dispersion is kept low.

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

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

  The active material particles of the present invention are characterized by containing silicon alone and the remaining main component being carbon and 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 size in the lower right of the photo is 100 μm. 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 50 μm. It is an optical microscope photograph of the microcapsule of this invention. It is a scanning electron micrograph of the microcapsule of this invention. The numerical value of the scale at the lower right of the photograph is 200 μm. It is a scanning electron micrograph of the microcapsule of this invention. The numerical value of the scale at the lower right of the photograph is 50 μm. It is a scanning electron micrograph of the microcapsule of this invention. The numerical value of the scale at the lower right of the photograph is 50 μm. 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 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 a polysilane derivative or a solid phase containing a polysilane derivative, an oil phase containing a polymerizable monomer, and an outer aqueous phase. Features. The O / W type emulsion of the present invention comprises an oil phase containing a polysilane derivative and a polymerizable monomer, and an outer aqueous phase.

  One aspect of the method for producing a W / O / W type, S / O / W type or O / W type emulsion of the present invention is a W / O type in which a polar liquid containing a polysilane derivative is added to an organic solvent containing a polymerizable monomer. A first step selected from an emulsion forming step, an S / O suspension forming step in which a polysilane derivative is dispersed in an organic solvent containing a polymerizable monomer, and a dissolving step in which the polysilane derivative is dissolved in an organic solvent containing a polymerizable monomer And the first hole passing step for passing the liquid obtained in the first step through the holes of the membrane or partition wall having holes, and the liquid having passed through the first hole passing step is dispersed in a polar continuous phase solution. And a first emulsion forming step.

  In another aspect of the method for producing a W / O / W type, S / O / W type or O / W type emulsion of the present invention, a polar liquid containing a polysilane derivative is added to an organic solvent containing a polymerizable monomer. / O type emulsion forming step, S / O type suspension forming step of dispersing polysilane derivative in organic solvent containing polymerizable monomer, or dissolving step of dissolving polysilane derivative in organic solvent containing polymerizable monomer A first emulsion, a second emulsion formation step in which the liquid obtained in the first step is dispersed in a polar continuous phase solution, and an emulsion-containing solution formed in the second emulsion formation step. And a second hole passing step for passing through the hole of the partition wall.

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

  The first step is a W / O type emulsion forming step of adding a polar liquid containing a polysilane derivative to an organic solvent containing a polymerizable monomer, an S / O type suspension forming step of dispersing the polysilane derivative in an organic solvent containing a polymerizable monomer, It is any step of a dissolution step of dissolving a polysilane derivative in an organic solvent containing a polymerizable monomer.

  A polar liquid containing a polysilane derivative (hereinafter sometimes simply referred to as “polar liquid”) corresponds to W in a W / O emulsion. The polar liquid is a liquid which contains a polysilane derivative and water or an alcohol 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 a polysilane derivative, water, and a water-soluble solvent.

  The polysilane derivative means a linear or branched polysilane represented by the following general formula (1) or a cyclic polysilane represented by the general formula (2).

R ¹ SinR ² nR ³ nR ⁴ (1)
R ¹ , R ² , R ³ and R ⁴ are hydrogen, an alkyl group which may be substituted with a substituent, an alkenyl group which may be substituted with a substituent, an alkynyl group which may be substituted with a substituent, Each independently selected from an aromatic group optionally substituted with a substituent, a halogen, a hydroxyl group, an alkoxy group optionally substituted with a substituent, and —OC (O) R ⁵ , wherein R ⁵ is substituted with a substituent And n is an integer of 2 or more.

(SiR ⁶ R ⁷ ) m (2)
R ⁶ and R ⁷ are hydrogen, an alkyl group which may be substituted with a substituent, an alkenyl group which may be substituted with a substituent, an alkynyl group which may be substituted with a substituent, or a substituent. Each independently selected from an aromatic group, a halogen, a hydroxyl group, an alkoxy group optionally substituted with a substituent, and —OC (O) R ⁸ , wherein R ⁸ is an alkyl optionally substituted with a substituent And m is an integer of 3 or more.

  The alkyl group may be linear, branched or cyclic. Although there is no restriction | limiting in particular in carbon number of an alkyl group, C1-C30 alkyl is preferable from the ease of acquisition or manufacture, C1-C18 alkyl is more preferable, C1-C6 alkyl is especially preferable. The same applies to the alkyl group of the alkoxy group.

  The shape of the alkenyl group or alkynyl group may be linear, branched or cyclic. Although there is no restriction | limiting in particular in carbon number of an alkenyl group or an alkynyl group, C2-C30 alkenyl or alkynyl is preferable from the ease of acquisition or manufacture, C2-C18 alkenyl or alkynyl is more preferable, Carbon number 2-6 alkenyl or alkynyl are particularly preferred.

  Aromatic groups include phenyl, indenyl, fluorenyl, naphthyl, anthryl, phenanthryl, biphenyl and other aryl groups, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, thiophenyl, furanyl Groups, heteroaryl groups such as an oxazolyl group, a thiazolyl group, an imidazolyl group and a pyrazolyl group, and a phenyl group is particularly preferred.

  As the substituent, in addition to the above-mentioned alkyl group, alkenyl group, alkynyl group, aromatic group, halogen, hydroxyl group, alkoxy group, amino group, alkylamino group, dialkylamino group, aryloxy group, acyl group, alkoxycarbonyl Group, acyloxy group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, sulfinyl group, ureido Group, phosphoric acid amide group, mercapto group, cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, silyl group and the like. These substituents may be further substituted. When there are two or more substituents, the substituents may be the same or different.

Depending on the type of R ^{1 to} R ⁸ or the type of substituent, the properties of the polysilane derivative can be changed to water-soluble, oil-soluble, and hardly soluble. Therefore, if the first step is the W / O emulsion forming step, a water-soluble polysilane derivative into which a hydrophilic group has been introduced may be employed. If the first step is to be an S / O emulsion forming step, a water-soluble polysilane derivative having a hydrophilic group introduced therein is adopted, or a poorly soluble group having a poorly soluble group introduced into an organic solvent containing a polymerizable monomer. The polysilane derivative may be used. If the first step is the dissolution step, a polysilane derivative that dissolves in an organic solvent containing a polymerizable monomer into which a lipophilic group has been introduced may be employed.

  In the general formula (1), n is not particularly limited as long as it is an integer of 2 or more, preferably in the range of 2 to 30000, more preferably in the range of 10 to 10000, and particularly preferably in the range of 15 to 1000. In the general formula (2), m is not particularly limited as long as m is an integer of 3 or more, but is preferably in the range of 3-18, more preferably in the range of 4-12, and particularly preferably in the range of 5-8.

  The weight average molecular weight of the polysilane derivative is not particularly limited, but the weight average molecular weight is preferably in the range of 200 to 100,000, more preferably in the range of 700 to 50000, and particularly preferably in the range of 1000 to 25000.

As a particularly preferred polysilane derivative, R ² in the general formula (1) is a methyl group and R ³ is a phenyl group and is dissolved in an organic solvent. In the general formula (1), R ² is a methyl group, R ³ Is represented by an ethyl group and is dissolved in an organic solvent, R ² and R ³ in the general formula (1) are both represented by a methyl group, and is poorly soluble polymethylsilane, R ² in the general formula (2) and Examples of the water-soluble polyphenylhydroxysilane in which R ³ is both represented by a phenyl group and hardly soluble and is decaphenylcyclopentasilane, R ² in the general formula (1) is a phenyl group, and R ³ is a hydroxyl group. .

A commercially available polysilane derivative may be used, may be produced according to a known method, or may be produced by appropriately substituting a group of polysilane obtained by a commercially available or known method. For example, a polysilane derivative can be synthesized by polymerizing R ² trihalosilane in the presence of metallic magnesium, and can also be synthesized by polymerizing R ² R ³ dihalosilane in the presence of metallic sodium. In these syntheses, polysilane derivatives having various groups can be synthesized by using silane derivatives having different chemical structures in combination. Introduction of various substituents may be appropriately performed according to a known substituent introduction method.

  When the suitable compounding quantity of the polysilane derivative essential for a polar liquid is illustrated, the range of 1-200 mass parts of polysilane derivatives is preferable with respect to 100 mass parts of water, the range of 10-150 mass parts is more preferable, 50-120 masses A range of parts is more preferred.

  Moreover, when the suitable compounding quantity of the polysilane derivative with respect to the organic solvent containing a polymerizable monomer is illustrated, the range of 0.1-200 mass parts of polysilane derivatives is preferable with respect to 100 mass parts of organic solvents containing a polymerizable monomer, The range of 150 parts by mass is more preferable, and the range of 5 to 120 parts by mass is more preferable.

  The average particle size of the polysilane derivative used in the S / O type suspension forming step is not particularly limited as long as it is within a range in which the S / O type suspension can be formed. When the average particle diameter of a suitable polysilane derivative is illustrated, 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 polysilane derivative can be calculated using an optical or electron microscope, a laser diffraction particle size distribution measurement device, a zeta potential measurement particle size distribution measurement device, a digital image analysis particle size distribution measurement device, and the like. What is necessary is just to calculate the average particle diameter of the other substance described in this specification using these apparatuses.

  The polar liquid contains polysilane derivatives and water as essential components, but may contain a surfactant and a water-soluble W / O emulsion stabilizer in addition to these. 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, S / O / W, and 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 polymerizable monomer of the present invention is not particularly limited as long as it is immiscible with water.

  Examples of polymerizable monomers that are not miscible with water include styrene, bromostyrene, chlorostyrene, vinylnaphthalene, α-methylstyrene, p-methylstyrene, t-butylstyrene, chlorostyrene, benzyl acrylate, benzyl methacrylate, vinyl toluene, and divinylbenzene. Vinyl aromatic compounds such as divinyltoluene, divinylxylene, divinylnaphthalene, trivinylbenzene, divinyldiphenyl ether and divinyldiphenylsulfone, vinyl chloride, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, Olefin compounds such as 1,3-pentadiene and chloroprene, acrylic esters such as methyl (meth) acrylate and ethyl (meth) acrylate, vinyl esters such as vinyl acetate, (meth It can be mentioned unsaturated nitrile 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.

  In the first step, a W / O type emulsion forming step in which a polar liquid containing a polysilane derivative is added to an organic solvent containing a polymerizable monomer, or an S / O type suspension formation in which the polysilane derivative is dispersed in an organic solvent containing a polymerizable monomer The process is performed in the presence of a shearing force generated by a stirring device or an ultrasonic device. 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. 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 type suspension forming step of dispersing the polysilane derivative in the organic solvent containing the polymerizable monomer may be performed by adding the polysilane derivative to the organic solvent containing the polymerizable monomer, or by adding the polymerizable monomer to the silicon-containing material. You may carry out by adding the organic solvent containing.

  Of the first step, the dissolving step of dissolving the polysilane derivative in the organic solvent containing the polymerizable monomer may be performed using the stirring device or the ultrasonic device.

  The organic solvent and / or polar liquid containing the polymerizable monomer used in the first step may be heated.

  The first hole passing step is a step of allowing the liquid obtained in the first 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. The 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, S / O / W type or O / W type emulsion of the present invention depends on the pore size of the membrane or partition wall having pores. For example, the size of the particle size of the emulsion formed in the first 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, S / O / W type, or 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 1st 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 first emulsion forming step are preferably carried out continuously. In the first 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 when surfactant is contained in a continuous phase solution is illustrated, the range of 0.005-1 mass part of surfactant is preferable with respect to 100 mass parts of water, 0.01-0.5 mass The range of parts is more preferable, and the range of 0.05 to 0.5 parts by mass is more 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, S / O / W type or 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.

  In the second emulsion forming step, the liquid obtained in the first step is dispersed in a polar continuous phase solution before the hole passing step, and a W / O / W type, S / O / W type or O / W type emulsion is obtained. It is a process of forming. What is necessary is just to use the same component for the continuous phase solution of a 2nd emulsion formation process as the continuous phase solution demonstrated by the above-mentioned 1st emulsion formation process in the same quantity. The second emulsion forming step is performed in the presence of a shearing force by the same stirring device or ultrasonic device as described in the first step.

  In the second hole passing step, the W / O / W type, S / O / W type, or O / W type emulsion-containing solution formed in the second emulsion forming step is passed through the hole of the membrane or partition wall having holes. It is a process to make. 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, S / O / W type or O / W type emulsion of the present invention formed through the second hole passing step is the membrane used in the second hole passing step or It is approximately equal to the pore diameter of the partition wall.

  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, S / O / W type or O / W type emulsion of the present invention to a lower level, a film or a partition wall having excellent pore size uniformity in the hole passing step is used. It may be used or the hole passing step may be repeated until the desired dispersion is obtained. Then, a monodispersed W / O / W type, S / O / W type or 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 contains a polysilane derivative, and the main component of the oil phase is a polymer. In the case of the microcapsules of the present invention in which the oil phase contains a polysilane derivative, the main component other than the oil phase polysilane derivative is a polymer. The method for producing a microcapsule of the present invention polymerizes a polymerizable monomer contained in an oil phase of a W / O / W type, S / O / W type or O / W type emulsion obtained by the production method of the present invention. It has the superposition | polymerization process, It is characterized by the above-mentioned. 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, S / O / W type or 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, S / O / W type or O / W type emulsion of the present invention. However, the W / O / W type, S / O / W type or 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, S / O / W-type or O / W-type emulsion of the present invention becomes a microcapsule containing a polysilane derivative and having 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, S / O / W type or O / W type emulsion. The particle size of the microcapsule is smaller than the particle size of the W / O / W type, S / O / W type or 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 that of the W / O / W type, S / O / W type or O / W type emulsion used as the raw material. It is about 2/5 to 4/5. However, it is known that the particle size of the emulsion may vary over time. If the measurement time of the particle size of the emulsion is different from the start time of the polymerization process, the relationship between the particle size of the obtained microcapsule and the measured particle size of the emulsion may greatly differ from the above-described relationship. 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, S / O / W type, or O / W type emulsion.

  The active material particles of the present invention are characterized by containing silicon alone and the remaining main component being carbon and 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 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 alone to carbon in the active material particles of the present invention, the amounts of the polysilane derivative and the polymerizable monomer used in the first 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, a freeze-dried W / O / W type, S / O / W type or O / W type emulsion obtained by the production method of the present invention is charged in an electric furnace, and the heating temperature is gradually increased. If it goes, a polymerization process 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 the variation coefficient of the particle size of the W / O / W type, S / O / W type or O / W type emulsion of the present invention, and the particle size of the microcapsule of the present invention. It is almost equal to the coefficient of variation.

  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 described above, the embodiments of the W / O / W type, S / O / W type or O / W type emulsion, microcapsule and active material particles of the present invention, and the production method thereof have been described. It is not limited to the embodiment. 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.

  A commercially available polysilane derivative (2.0 g), potassium persulfate (0.01 g), and water (2.0 g) were mixed to obtain a polar liquid containing the polysilane derivative. As the polysilane derivative, polymethylphenylsilane, cyclopentasilane, or polyphenylsilane was used.

  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 a polar liquid containing a polysilane derivative in an organic solvent containing a polymerizable monomer, ultrasonic waves were generated under conditions of 150 W and 40 kHz using an ultrasonic emulsifier 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 38 μm were confirmed. 1 and 2 show optical micrographs of the obtained W / O / W emulsion.

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 diameter of about 54 μm were confirmed.

  An optical micrograph of this microcapsule is shown in FIG. 3, 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 71.5%, oxygen was 14.6%, and silicon was 13.8%.

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.
When the obtained active material particles were observed with a scanning electron microscope, a large number of carbonized composite Si active material spherical particles having a particle size of about 3 μm, in which polystyrene and ethylene glycol dimethacrylate as a crosslinking agent were carbonized, 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.

  From the result of the above particle size distribution measurement, it can be seen that the particle size of the microcapsule is larger than the particle size of the emulsion. This is because the W / O / W emulsion at the time of particle size distribution measurement did not reach a stable state in which the osmotic pressure of the inner aqueous phase and the osmotic pressure of the outer aqueous phase were in equilibrium, Since the water moved from the phase to the inner aqueous phase and the inner aqueous phase droplets expanded, and the oil phase emulsified particles covering the inner aqueous phase droplets expanded accordingly, an emulsion having an average diameter of 38.4 μm was formed before polymerization. This can be explained by growing into an emulsion of about 60 μm. 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 O / W emulsion of the present invention was produced as follows.
2.0 g of a commercially available polysilane derivative was dissolved in an organic solvent containing the polymerizable monomer of Example 1 or Example 2.
The obtained polysilane derivative solution was 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. A continuous phase solution equivalent to that in the SPG membrane emulsifier was filled into a continuous phase container. The polysilane derivative solution 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 O / W type | mold emulsion was obtained. When observed with an optical microscope, many O / W emulsions having a particle size of about 30 μm were confirmed.

The microcapsules of the present invention were produced as follows.
The obtained 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 obtained by polymerizing styrene contained in the oil phase of the O / W emulsion into polystyrene were obtained. When observed with an optical microscope and a scanning electron microscope, many microcapsules having a particle diameter of about 54 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)
A lithium ion secondary battery was obtained in the same manner as in Application Example 1 except that the active material particles in Example 1 used in Application Example 1 were changed to commercially available polysilane derivatives.

<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 performed in which a cycle of discharging to 10 minutes and resting for 10 minutes was 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 particle shape of the W / O / W type, S / O / W type or O / W type emulsion of the present invention is naturally spherical because it is an emulsion. In addition, since the W / O / W type, S / O / W type or O / W type emulsion of the present invention is produced by passing through a membrane or partition wall having a pore diameter in a specific range, Dispersion is kept low. The microcapsules of the present invention are produced through a polymerization step of polymerizing a polymerizable monomer contained in the spherical, low-dispersion W / O / W type, S / O / W type or O / W type emulsion. Therefore, the microcapsules of the present invention are spherical and the dispersion of the particle size is also 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 (4)

A W / O emulsion forming step of adding a polar liquid containing a polysilane derivative to an organic solvent containing a polymerizable monomer, an S / O type suspension forming step of dispersing the polysilane derivative in an organic solvent containing a polymerizable monomer, and a polymerizable monomer A first step selected from any one of the dissolving steps for dissolving the polysilane derivative in an organic solvent;
A first hole passing step for allowing the liquid obtained in the first step to pass through the holes of the membrane or partition wall having holes;
A first 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, S / O / W type, or O / W type emulsion characterized by comprising: A W / O emulsion forming step of adding a polar liquid containing a polysilane derivative to an organic solvent containing a polymerizable monomer, an S / O type suspension forming step of dispersing the polysilane derivative in an organic solvent containing a polymerizable monomer, and a polymerizable monomer A first step selected from any one of the dissolving steps for dissolving the polysilane derivative in an organic solvent;
A second emulsion forming step of dispersing the liquid obtained in the first step in a polar continuous phase solution;
A second hole passing step of passing the emulsion-containing solution formed in the second emulsion forming step through the pores of the membrane or partition having pores;
A method for producing a W / O / W type, S / O / W type, or O / W type emulsion characterized by comprising:   A microcapsule having a polymerization step of polymerizing a polymerizable monomer contained in a W / O / W type, S / O / W type, or O / W type emulsion obtained by the production method according to claim 1. Production method.   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.