WO2018051925A1 - Composite body, negative electrode for lithium ion secondary batteries, and method for producing composite body - Google Patents

Composite body, negative electrode for lithium ion secondary batteries, and method for producing composite body Download PDF

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Publication number
WO2018051925A1
WO2018051925A1 PCT/JP2017/032550 JP2017032550W WO2018051925A1 WO 2018051925 A1 WO2018051925 A1 WO 2018051925A1 JP 2017032550 W JP2017032550 W JP 2017032550W WO 2018051925 A1 WO2018051925 A1 WO 2018051925A1
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Prior art keywords
composite
negative electrode
lithium ion
ion secondary
fibrous carbon
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PCT/JP2017/032550
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French (fr)
Japanese (ja)
Inventor
新井　進
雅裕 清水
恭平 桐畑
有信 堅田
秀悦 藤原
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日本ゼオン株式会社
国立大学法人信州大学
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Priority to JP2018539691A priority Critical patent/JP6975715B2/en
Publication of WO2018051925A1 publication Critical patent/WO2018051925A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/152—Fullerenes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/54—Electroplating of non-metallic surfaces
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/30—Electroplating: Baths therefor from solutions of tin
    • C25D3/32—Electroplating: Baths therefor from solutions of tin characterised by the organic bath constituents used
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a composite, a negative electrode for a lithium ion secondary battery, and a method for manufacturing the composite. Specifically, the present invention relates to a composite containing fibrous carbon nanostructures and tin fine particles. Moreover, this invention relates to the negative electrode for lithium ion secondary batteries provided with the said composite_body
  • Lithium ion secondary batteries are small and light, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications. Therefore, in recent years, improvement of battery members such as electrodes has been studied for the purpose of further improving the performance of lithium ion secondary batteries.
  • a negative electrode including a negative electrode active material layer including a negative electrode active material containing tin having a high theoretical capacity on a current collector has been studied (see, for example, Patent Documents 1 and 2). According to the negative electrodes described in Patent Documents 1 and 2, while increasing the capacity of the lithium ion secondary battery, the generation of cracks in the negative electrode active material during charge / discharge and the detachment from the current collector are suppressed. It has been reported that good cycle characteristics can be secured.
  • JP 2015-43309 A Japanese Patent No. 5275702
  • an object of the present invention is to provide means for advantageously solving the above-described improvements.
  • the present inventor has intensively studied to achieve the above object. Then, the present inventor uses a composite containing fibrous carbon nanostructures and fine particles having an average particle diameter of a predetermined value or less and made of tin as a negative electrode active material layer, so that a lithium ion secondary battery is obtained. The present inventors have found that the capacity can be increased and the lithium ion secondary battery can exhibit sufficiently excellent cycle characteristics, and the present invention has been completed.
  • the present invention aims to advantageously solve the above-mentioned problems, and the composite of the present invention contains fibrous carbon nanostructures and tin fine particles having an average particle diameter of 10 ⁇ m or less. It is characterized by. If a fibrous carbon nanostructure and a composite containing tin fine particles having an average particle size of the above value or less are used as the negative electrode active material layer, the capacity of the lithium ion secondary battery can be increased and the cycle characteristics can be sufficiently improved. it can.
  • tin fine particles refers to particles composed of tin and having a particle diameter of 100 ⁇ m or less.
  • the particle diameter of the tin fine particles is determined by observing the tin fine particles with, for example, a field emission scanning electron microscope (FE-SEM), and measuring the length of a line segment connecting two points on the outer edge of the tin fine particles. It is obtained by measuring the maximum length.
  • the “average particle diameter” of the tin fine particles can be calculated as an average value of the particle diameters of 100 randomly selected tin fine particles.
  • the composite of the present invention preferably has a structure in which the tin fine particles are present inside a carbon matrix containing the fibrous carbon nanostructure. If tin fine particles exist inside the carbon matrix composed of fibrous carbon nanostructures, the desorption of tin fine particles from the fibrous carbon nanostructures can be suppressed, and the cycle characteristics of the lithium ion secondary battery can be reduced. Further improvement can be achieved.
  • the “inside of the carbon matrix” means an inner portion other than the outermost surface of the carbon matrix, and “fine particles exist inside the carbon matrix including the fibrous carbon nanostructure”. This can be confirmed from the presence of tin fine particles embedded in a carbon matrix composed of fibrous carbon nanostructures when the cross section of the composite is observed with, for example, FE-SEM.
  • the fibrous carbon nanostructure includes a carbon nanotube. If the fibrous carbon nanostructure containing carbon nanotubes is used, the cycle characteristics of the lithium ion secondary battery can be further improved.
  • the fibrous carbon nanostructure has a shape in which a t-plot obtained from an adsorption isotherm is convex upward.
  • complex of this invention can be used as an object for lithium ion secondary battery negative electrodes.
  • the negative electrode for lithium ion secondary batteries of this invention is equipped with the negative electrode active material layer, and the said negative electrode active material layer is the composite_body
  • the composite described above is used as the negative electrode active material layer, the capacity of the lithium ion secondary battery can be increased and the cycle characteristics can be sufficiently improved.
  • the present invention aims to advantageously solve the above-described problems, and a method for producing a composite according to the present invention is a method for producing any of the above-described composites, wherein the fibrous
  • the carbon film including the carbon nanostructure includes a step of performing a plating process using a plating solution including a tin-containing compound. If the carbon film is plated using a plating solution containing a tin-containing compound, any of the above-described composites containing tin fine particles can be efficiently produced.
  • the plating solution further includes a polyether-based surfactant and water. If such a plating solution is used, any of the above-described composites containing tin fine particles can be produced more efficiently. Moreover, according to the negative electrode for lithium ion secondary batteries using the obtained composite, the lithium ion secondary battery can exhibit more excellent cycle characteristics.
  • the density of the carbon film is 0.01 g / cm 3 or more 1.80 g / cm 3 or less. If a carbon film having a density within the above-described range is used, the strength of the obtained composite is ensured, and the lithium ion secondary battery negative electrode using the composite further improves the lithium ion secondary battery. Cycle characteristics can be exhibited.
  • a negative electrode for a lithium ion secondary battery capable of increasing the capacity of the lithium ion secondary battery and causing the lithium ion secondary battery to exhibit sufficiently excellent cycle characteristics. be able to.
  • the negative electrode for lithium ion secondary batteries of this invention while being able to increase capacity of a lithium ion secondary battery, the said lithium ion secondary battery can fully exhibit the cycling characteristics which were excellent.
  • the method for producing a composite of the present invention a composite capable of increasing the capacity of a lithium ion secondary battery and exhibiting sufficiently excellent cycle characteristics in the lithium ion secondary battery is efficiently produced. Can be manufactured well.
  • FIG. 6 is a graph showing an example of a t-plot of a sample having pores on the surface.
  • 3 is an FE-SEM photograph of a cross section of composite A obtained in an example.
  • the composite of the present invention is a material in which fibrous carbon nanostructures and tin fine particles are combined.
  • complex of this invention can be used for preparation of the negative electrode for lithium ion secondary batteries of this invention.
  • complex of this invention can be manufactured using the manufacturing method of the composite_body
  • the composite of the present invention includes at least a fibrous carbon nanostructure and tin fine particles having an average particle diameter of 10 ⁇ m or less, and includes components (other components) other than the fibrous carbon nanostructure and the tin fine particles. May be included.
  • the composite of the present invention contains tin fine particles, if the composite of the present invention is used as a negative electrode active material layer of a negative electrode for a lithium ion secondary battery, the tin fine particles function as a negative electrode active material and are lithium ion secondary.
  • the capacity of the battery can be increased.
  • the tin fine particles in the composite of the present invention have an average particle diameter of 10 ⁇ m or less, even if the tin fine particles are repeatedly expanded and contracted by charging / discharging of the lithium ion secondary battery, the tin fine particles The stress applied to is sufficiently small. Therefore, generation of cracks and desorption from the current collector of tin fine particles, which are the negative electrode active material, are suppressed, and excellent cycle characteristics can be exhibited in the lithium ion secondary battery.
  • the fibrous carbon nanostructure is not particularly limited.
  • carbon nanotubes CNT
  • vapor-grown carbon fibers C fibers obtained by carbonizing organic fibers, and cut products thereof are used. Can do. These may be used individually by 1 type and may use 2 or more types together.
  • the fibrous carbon nanostructure it is more preferable to use a fibrous carbon nanostructure including carbon nanotubes. If a fibrous carbon nanostructure containing carbon nanotubes is used, physical properties such as conductivity of the composite can be improved, and more excellent cycle characteristics can be exhibited in the lithium ion secondary battery.
  • a fibrous carbon nanostructure containing CNT it may not be specifically limited but what consists only of CNT may be used, and the mixture of CNT and fibrous carbon nanostructures other than CNT is used. May be.
  • the CNT in the fibrous carbon nanostructure is not particularly limited, and single-walled carbon nanotubes and / or multi-walled carbon nanotubes can be used.
  • the CNT is preferably a single-walled to carbon-walled carbon nanotube, more preferably a single-walled carbon nanotube. If single-walled carbon nanotubes are used, the cycle characteristics of the lithium ion secondary battery can be further improved as compared with the case where multi-walled carbon nanotubes are used.
  • the fibrous carbon nanostructure from the viewpoint of further improving the cycle characteristics of the lithium ion secondary battery, it is preferable that the t-plot obtained from the adsorption isotherm shows a convex shape.
  • adsorption is a phenomenon in which gas molecules are removed from the gas phase to the solid surface, and is classified into physical adsorption and chemical adsorption based on the cause.
  • physical adsorption is used in the nitrogen gas adsorption method used for obtaining the t-plot. Normally, if the adsorption temperature is constant, the number of nitrogen gas molecules adsorbed on the fibrous carbon nanostructure increases as the pressure increases.
  • the plot of the relative pressure (ratio of adsorption equilibrium pressure P and saturated vapor pressure P0) on the horizontal axis and the amount of nitrogen gas adsorption on the vertical axis is called the “isothermal line”. Nitrogen gas adsorption while increasing the pressure The case where the amount is measured is referred to as an “adsorption isotherm”, and the case where the amount of nitrogen gas adsorption is measured while reducing the pressure is referred to as a “desorption isotherm”.
  • the t-plot is obtained by converting the relative pressure to the average thickness t (nm) of the nitrogen gas adsorption layer in the adsorption isotherm measured by the nitrogen gas adsorption method.
  • the average thickness t of the nitrogen gas adsorption layer is plotted against the relative pressure P / P0, and the average thickness t of the nitrogen gas adsorption layer corresponding to the relative pressure is obtained from the known standard isotherm and the above conversion is performed.
  • t-plot method by de Boer et al.
  • FIG. 1 a typical t-plot of a sample having pores on the surface is shown in FIG.
  • the growth of the nitrogen gas adsorption layer is classified into the following processes (1) to (3).
  • the following steps (1) to (3) change the slope of the t-plot as shown in FIG. (1)
  • Monomolecular adsorption layer formation process of nitrogen molecules on the entire surface
  • Multimolecular adsorption layer formation and capillary condensation filling process in the pores accompanying it (3) Apparent filling of the pores with nitrogen Formation process of multimolecular adsorption layer on non-porous surface
  • the t-plot of the preferred fibrous carbon nanostructure used in the present invention is located on a straight line passing through the origin in the region where the average thickness t of the nitrogen gas adsorption layer is small as shown in FIG.
  • the plot is shifted downward from the straight line and shows an upwardly convex shape.
  • the shape of the t-plot is such that the ratio of the internal specific surface area to the total specific surface area of the fibrous carbon nanostructure is large, and a large number of openings are formed in the carbon nanostructure constituting the fibrous carbon nanostructure. As a result, it is assumed that the fibrous carbon nanostructure exhibits excellent characteristics.
  • the bending point of the t-plot of the fibrous carbon nanostructure is preferably in a range satisfying 0.2 ⁇ t (nm) ⁇ 1.5, and 0.45 ⁇ t (nm) ⁇ 1.5. More preferably, it is in a range satisfying 0.55 ⁇ t (nm) ⁇ 1.0.
  • the “position of the bending point” is an intersection of the approximate line A in the process (1) described above and the approximate line B in the process (3) described above.
  • the fibrous carbon nanostructure preferably has a ratio (S2 / S1) of the internal specific surface area S2 to the total specific surface area S1 obtained from the t-plot of 0.05 or more and 0.30 or less. If S2 / S1 is 0.05 or more and 0.30 or less, it is possible to further improve the characteristics of the fibrous carbon nanostructure while sufficiently suppressing the formation of the bundle, so the cycle of the lithium ion secondary battery The characteristics can be further improved.
  • the total specific surface area S1 and the internal specific surface area S2 of the fibrous carbon nanostructure are not particularly limited, but individually, S1 is preferably 600 m 2 / g or more and 1400 m 2 / g or less, and 800 m 2.
  • the total specific surface area S1 and the internal specific surface area S2 of the fibrous carbon nanostructure can be obtained from the t-plot. Specifically, referring to the t-plot shown in FIG. 1, first, the total specific surface area S1 is determined from the slope of the approximate line in the process (1), and the external specific surface area S3 is determined from the slope of the approximate line in the process (3). Can be obtained respectively. Then, the internal specific surface area S2 can be calculated by subtracting the external specific surface area S3 from the total specific surface area S1.
  • the measurement of the adsorption isotherm of the fibrous carbon nanostructure, the creation of the t-plot, and the calculation of the total specific surface area S1 and the internal specific surface area S2 based on the analysis of the t-plot are, for example, commercially available measuring devices.
  • "BELSORP (registered trademark) -mini” manufactured by Nippon Bell Co., Ltd.).
  • the fibrous carbon nanostructure containing CNT is not subjected to CNT opening treatment, and the t-plot has a convex shape. More preferred.
  • the average diameter of the fibrous carbon nanostructure is preferably 0.5 nm or more, more preferably 1 nm or more, preferably 15 nm or less, and more preferably 10 nm or less.
  • the average diameter of the fibrous carbon nanostructure is 0.5 nm or more, a sufficient space is secured between the plurality of fibrous carbon nanostructures when the composite is prepared. Therefore, it can be set as the composite_body
  • the average diameter of fibrous carbon nanostructure is 15 nm or less, physical properties, such as electroconductivity of a composite, can be improved.
  • the lithium ion secondary battery can exhibit more excellent cycle characteristics.
  • the “average diameter of fibrous carbon nanostructures” can be determined by measuring the diameter (outer diameter) of 100 fibrous carbon nanostructures selected at random using a transmission electron microscope. And the average diameter of the fibrous carbon nanostructure containing CNT may be adjusted by changing the manufacturing method and manufacturing conditions of the fibrous carbon nanostructure containing CNT, or CNT obtained by a different manufacturing method. You may adjust by combining multiple types of fibrous carbon nanostructure containing this.
  • the aspect ratio (length / diameter) of the fibrous carbon nanostructure is preferably more than 10.
  • the aspect ratio of the fibrous carbon nanostructure was determined by measuring the diameter and length of 100 fibrous carbon nanostructures selected at random using a transmission electron microscope, and the ratio of the diameter to the length (long It can be obtained by calculating an average value of (thickness / diameter).
  • the BET specific surface area of the fibrous carbon nanostructure is preferably 600 m 2 / g or more, more preferably 800 m 2 / g or more, and preferably 2500 m 2 / g or less. More preferably, it is 2 / g or less. If the BET specific surface area of the fibrous carbon nanostructure containing CNT is 600 m 2 / g or more, physical properties such as conductivity of the composite can be improved. Moreover, if the BET specific surface area of the fibrous carbon nanostructure containing CNT is 2500 m 2 / g or less, excessive crowding of the fibrous carbon nanostructure is suppressed, and the fibrous carbon nanostructure and fine particles are good. Can be obtained.
  • the lithium ion secondary battery can exhibit more excellent cycle characteristics.
  • the “BET specific surface area” refers to a nitrogen adsorption specific surface area measured using the BET method.
  • the fibrous carbon nanostructure (especially the fibrous carbon nanostructure containing CNT) which has the property mentioned above, for example on the base material which has the catalyst layer for carbon nanotube manufacture on the surface, and a raw material compound and
  • a carrier gas is supplied to synthesize CNTs by chemical vapor deposition (CVD)
  • the catalytic activity of the catalyst layer is dramatically increased by the presence of a small amount of oxidant (catalyst activation material) in the system.
  • oxidant catalyst activation material
  • the carbon nanotube obtained by the super growth method may be referred to as “SGCNT”.
  • the fibrous carbon nanostructure containing CNT manufactured by the super growth method may be comprised only from SGCNT, and may be comprised from SGCNT and a non-cylindrical carbon nanostructure.
  • the fibrous carbon nanostructure containing CNT includes a single-layer or multi-layer flat cylindrical carbon nanostructure having a tape-like portion whose inner walls are close to or bonded to each other over the entire length. May be.
  • the fibrous carbon nanostructure is an aggregate (aligned assembly) oriented in a direction substantially perpendicular to the base material on the base material having a catalyst layer for carbon nanotube growth on the surface.
  • the mass density of the fibrous carbon nanostructure as the aggregate is preferably 0.002 g / cm 3 or more and 0.2 g / cm 3 or less. If the mass density is 0.2 g / cm 3 or less, the bonding between the fibrous carbon nanostructures becomes weak, so that the fibrous carbon nanostructures can be uniformly dispersed.
  • the mass density is 0.002 g / cm 3 or more, the integrity of the fibrous carbon nanostructure can be improved, and the handling can be easily performed since it can be prevented from being broken.
  • the composite of the present invention includes tin fine particles having an average particle diameter of 10 ⁇ m or less in addition to the above-described fibrous carbon nanostructure.
  • Tin fine particles serve as a negative electrode active material that absorbs and releases lithium ions when the composite of the present invention is used as a negative electrode active material layer of a negative electrode for a lithium ion secondary battery. Then, by combining tin fine particles as the negative electrode active material and the above-described fibrous carbon nanostructure in a conductive state, the composite functions well as a negative electrode active material layer, and the capacity of the lithium ion secondary battery And it can contribute to improvement of cycle characteristics.
  • the shape of the tin fine particles is not particularly limited, and examples thereof include a spherical shape, a cubic shape, a rectangular shape, a plate shape (such as a hexagonal plate shape), a column shape, and a rod shape (such as a hexagonal rod shape).
  • the average particle size of the tin fine particles is required to be 10 ⁇ m or less, preferably 5 ⁇ m or less, more preferably 100 nm or less, and further preferably 50 nm or less. If the average particle diameter of the tin fine particles exceeds 10 ⁇ m, the cycle characteristics excellent in the secondary battery cannot be exhibited.
  • the average particle diameter of the tin fine particles can be adjusted by changing the preparation method and preparation conditions of the tin fine particles. For example, if the method for producing a composite of the present invention using a plating treatment described later is used for preparing tin fine particles, tin fine particles having a small particle diameter can be easily precipitated.
  • the average particle diameter of the tin fine particles is preferably as small as possible, and the lower limit is not particularly limited, but the average particle diameter of the tin fine particles is, for example, 10 nm. This can be done.
  • the tin particles are present inside the carbon matrix composed of the fibrous carbon nanostructure, and most of the tin particles, for example, 90% or more are carbon. More preferably, it is present inside the matrix (that is, the proportion of tin fine particles present inside the carbon matrix is 90% or more).
  • the ratio of tin fine particles present inside the carbon matrix is more preferably 100%. Even if the tin fine particles existing inside the carbon matrix are repeatedly charged and discharged by the lithium ion secondary battery as compared with the tin fine particles present on the composite surface, the negative electrode active material layer on the current collector It is hard to detach from.
  • the lithium ion secondary battery can exhibit more excellent cycle characteristics.
  • the “ratio of tin fine particles present in the carbon matrix” refers to the number of tin fine particles present in the total tin fine particles and the carbon matrix by observing the cross section of the composite with, for example, FE-SEM. Can be calculated as the ratio (%) of tin fine particles present in the carbon matrix in the total tin fine particles.
  • the composite may contain components other than the above-described fibrous carbon nanostructure and tin fine particles.
  • Other components are not particularly limited.
  • known additives dispenser, binder for negative electrode
  • the ratio of other components in the composite is preferably 5% by mass or less, preferably 3% by mass or less, based on 100% by mass of the solid content (excluding residual solvent) in the composite. More preferred is 1% by mass or less.
  • the method for producing the composite of the present invention described above is not particularly limited, but the composite of the present invention is subjected to a plating treatment using a plating solution containing a tin-containing compound on a carbon film containing a fibrous carbon nanostructure. It is preferred to use a manufacturing method. According to the method for producing a composite of the present invention, it is possible to efficiently obtain a composite in which tin fine particles are present in the carbon matrix by easily depositing tin fine particles in the carbon film.
  • the carbon film is composed of an aggregate of fibrous carbon nanostructures obtained by assembling a plurality of fibrous carbon nanostructures into a film shape.
  • a method for obtaining a carbon film by assembling a plurality of fibrous carbon nanostructures into a film shape is not particularly limited, but for example, the following method: (I) A method of forming a film by removing a solvent from a dispersion containing a plurality of fibrous carbon nanostructures and a solvent. (Ii) Fibrous carbon obtained by growing in a substantially vertical direction on a substrate. A step of forming a film by allowing the aggregate of nanostructures to fall on a substrate and then compressing as necessary is mentioned. Among these, the method (i) is preferable. The carbon film obtained through the step (i) tends to have a low density, and the plating solution is likely to penetrate in the plating process.
  • the dispersion used for the preparation of the carbon film is not particularly limited, and a dispersion obtained by dispersing an aggregate of fibrous carbon nanostructures in a solvent using a known dispersion treatment method can be used.
  • a dispersion containing a fibrous carbon nanostructure and a solvent and optionally further containing an additive for dispersion such as a dispersant can be used.
  • the fibrous carbon nanostructure described above in the section “Composite” can be used.
  • the solvent for the dispersion is not particularly limited.
  • Amides polar organic solvents such as ethers, N, N-dimethylformamide and N-methylpyrrolidone, aromatic hydrocarbons such as toluene, xylene, chlorobenzene, orthodichlorobenzene and paradichlorobenzene Kind and the like. These may be used alone or in combination of two or more.
  • the additive for dispersion that is arbitrarily blended in the dispersion is not particularly limited, and examples thereof include additives generally used for preparing dispersions such as dispersants.
  • examples thereof include additives generally used for preparing dispersions such as dispersants.
  • the amount of the additive for dispersion such as is small.
  • the dispersant used for preparing the dispersion is not particularly limited as long as it can disperse the fibrous carbon nanostructure and can be dissolved in the solvent described above. Natural polymers can be used.
  • examples of the surfactant include sodium dodecylsulfonate, sodium deoxycholate, sodium cholate, sodium dodecylbenzenesulfonate, and the like.
  • examples of the synthetic polymer include polyether diol, polyester diol, polycarbonate diol, polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, acetal group-modified polyvinyl alcohol, butyral group-modified polyvinyl alcohol, and silanol group-modified.
  • Polyvinyl alcohol ethylene-vinyl alcohol copolymer, ethylene-vinyl alcohol-vinyl acetate copolymer resin, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, acrylic resin, epoxy resin, modified epoxy resin, phenoxy resin, modified phenoxy system Resin, phenoxy ether resin, phenoxy ester resin, fluorine resin, melamine resin, alkyd resin, phenol resin, Polyacrylamide, polyacrylic acid, polystyrene sulfonic acid, polyethylene glycol, and polyvinylpyrrolidone.
  • examples of natural polymers include polysaccharides such as starch, pullulan, dextran, dextrin, guar gum, xanthan gum, amylose, amylopectin, alginic acid, gum arabic, carrageenan, chondroitin sulfate, hyaluronic acid, curdlan, chitin, chitosan, Examples thereof include cellulose and salts or derivatives thereof. And these dispersing agents can be used 1 type or in mixture of 2 or more types.
  • the aggregate of 1 mm or more is not visually confirmed in the dispersion liquid.
  • the fibrous carbon nanostructures in the dispersion are dispersed at a level at which the median diameter (average particle diameter) measured by a particle size distribution meter is 150 ⁇ m or less. If the fibrous carbon nanostructure is well dispersed in the dispersion, the density unevenness of the carbon film obtained by removing the solvent is suppressed. In addition, the plating solution easily penetrates uniformly into the carbon film with less density unevenness, and a complex in which tin fine particles are present inside the carbon matrix can be efficiently obtained. And if the said composite_body
  • the solid content concentration of the dispersion is preferably 0.001% by mass or more and 20% by mass or less, although it depends on the type of the fibrous carbon nanostructure.
  • the solid content concentration is less than 0.001% by mass, the amount of the carbon film obtained by removing the solvent decreases, and the production efficiency may not be sufficiently increased.
  • solid content concentration exceeds 20 mass%, while there exists a possibility that the dispersibility of the fibrous carbon nanostructure in a dispersion liquid may fall, the viscosity of a dispersion liquid will increase and fluidity
  • dispersion a commercially available dispersion obtained by dispersing an aggregate of fibrous carbon nanostructures in a solvent may be used, but the dispersion was prepared by carrying out a dispersion preparation step prior to the preparation of the carbon film. It is preferable to use a dispersion.
  • the dispersion is It is more preferable to use a dispersion obtained by subjecting a coarse dispersion obtained by adding fibrous carbon nanostructures to a solvent to a dispersion treatment in which a cavitation effect or a crushing effect is obtained.
  • a coarse dispersion obtained by adding the above-described fibrous carbon nanostructure and any additive for dispersion to the solvent described above is a dispersion capable of obtaining a cavitation effect described in detail below. It is preferable to use a dispersion obtained by subjecting to a dispersion treatment capable of obtaining a treatment or crushing effect.
  • the dispersion treatment that provides a cavitation effect is a dispersion method that uses a shock wave generated by bursting of vacuum bubbles generated in water when high energy is applied to the liquid.
  • the fibrous carbon nanostructure can be favorably dispersed.
  • dispersion treatment that provides a cavitation effect
  • dispersion treatment using ultrasonic waves dispersion treatment using a jet mill
  • dispersion treatment using high shear stirring Only one of these distributed processes may be performed, or a plurality of distributed processes may be combined. More specifically, for example, an ultrasonic homogenizer, a jet mill, and a high shear stirring device are preferably used. These devices may be conventionally known devices.
  • the coarse dispersion may be irradiated with ultrasonic waves using the ultrasonic homogenizer.
  • the irradiation time may be appropriately set depending on the amount of the fibrous carbon nanostructure and the like, for example, preferably 3 minutes or more, more preferably 30 minutes or more, and preferably 5 hours or less, more preferably 2 hours or less.
  • the output is preferably 20 W or more and 500 W or less, more preferably 100 W or more and 500 W or less, and the temperature is preferably 15 ° C. or more and 50 ° C. or less.
  • the number of treatments may be appropriately set depending on the amount of the fibrous carbon nanostructure and the like, for example, preferably 2 times or more, preferably 100 times or less, more preferably 50 times or less.
  • the pressure is preferably 20 MPa or more and 250 MPa or less
  • the temperature is preferably 15 ° C. or more and 50 ° C. or less.
  • stirring and shearing may be applied to the coarse dispersion with a high shear stirring device.
  • the operation time time during which the machine is rotating
  • the peripheral speed is preferably 5 m / second or more and 50 m / second or less
  • the temperature is preferably 15 ° C. or more and 50 ° C. or less.
  • the dispersion treatment for obtaining the above-described cavitation effect it is more preferable to perform the dispersion treatment for obtaining the above-described cavitation effect at a temperature of 50 ° C. or lower. This is because a change in concentration due to the volatilization of the solvent is suppressed.
  • the dispersion treatment that provides the crushing effect can uniformly disperse the fibrous carbon nanostructures in the solvent, as well as the fibrous carbon due to the shock wave when the bubbles disappear, compared to the dispersion treatment that provides the cavitation effect described above. This is advantageous in that damage to the nanostructure can be suppressed.
  • the fibrous carbon nanostructure can be uniformly dispersed in the solvent while suppressing the generation of bubbles.
  • the back pressure applied to the coarse dispersion may be reduced to atmospheric pressure all at once, but is preferably reduced in multiple stages.
  • a dispersion system having a disperser having the following structure may be used.
  • the disperser has a disperser orifice having an inner diameter d1, a dispersion space having an inner diameter d2, and a terminal portion having an inner diameter d3 from the inflow side to the outflow side of the coarse dispersion liquid (where d2>d3> d1)).
  • the inflowing high-pressure for example, 10 to 400 MPa, preferably 50 to 250 MPa
  • coarse dispersion passes through the disperser orifice, and becomes a high flow rate fluid with decreasing pressure.
  • the high-velocity coarse dispersion liquid flowing into the dispersion space flows at high speed in the dispersion space and receives a shearing force at that time.
  • the flow rate of the coarse dispersion decreases, and the fibrous carbon nanostructure is well dispersed.
  • a fluid having a pressure (back pressure) lower than the pressure of the inflowing coarse dispersion liquid flows out from the terminal portion as the dispersion liquid of the fibrous carbon nanostructure.
  • the back pressure of the coarse dispersion can be applied to the coarse dispersion by applying a load to the flow of the coarse dispersion.
  • a rough pressure can be obtained by disposing a multistage step-down device downstream of the disperser.
  • a desired back pressure can be applied to the dispersion. Then, by reducing the back pressure of the coarse dispersion in multiple stages using a multistage pressure reducer, bubbles are generated in the dispersion when the dispersion of the fibrous carbon nanostructure is finally released to atmospheric pressure. Can be suppressed.
  • the disperser may include a heat exchanger for cooling the coarse dispersion and a cooling liquid supply mechanism. This is because the generation of bubbles in the coarse dispersion can be further suppressed by cooling the coarse dispersion that has been heated to a high temperature by applying a shearing force with the disperser. In addition, it can suppress that a bubble generate
  • the occurrence of cavitation can be suppressed, so damage to the fibrous carbon nanostructure caused by cavitation that is sometimes a concern, especially when the bubbles disappear. Damage to the fibrous carbon nanostructure due to the shock wave can be suppressed.
  • distribution process from which a crushing effect is acquired can be implemented by controlling a dispersion
  • the method for removing the solvent from the dispersion is not particularly limited, and a known solvent removing method such as drying or filtration can be used. Among these, from the viewpoint of efficiently removing the solvent, it is preferable to use reduced-pressure drying, vacuum drying or filtration as the solvent removal method. Furthermore, from the viewpoint of removing the solvent easily and quickly, the solvent removal method is preferably filtration, and more preferably vacuum filtration. If the solvent is removed quickly and efficiently, the once-dispersed fibrous carbon nanostructures can be prevented from aggregating again, and density unevenness of the resulting carbon film can be suppressed. Here, it is not necessary to completely remove the solvent in the dispersion liquid. If the fibrous carbon nanostructure remaining after the removal of the solvent can be handled as an aggregate (carbon film), some solvent remains. There is no problem even if you do.
  • the thickness of the carbon film to be obtained is preferably 2 ⁇ m or more, more preferably 5 ⁇ m or more, further preferably 10 ⁇ m or more, preferably 200 ⁇ m or less, more preferably 100 ⁇ m or less. More preferably, it is 60 ⁇ m or less.
  • the thickness of the carbon film is 2 ⁇ m or more, the strength of the resulting composite can be ensured.
  • the thickness of the carbon film is 200 ⁇ m or less, the plating solution easily penetrates to the center of the carbon film in the thickness direction during the plating process, and efficiently obtains a composite in which fine particles are present inside the carbon matrix. be able to.
  • complex is used as a negative electrode active material layer, the cycling characteristics which were further excellent in the lithium ion secondary battery can be exhibited.
  • the density of the carbon film is preferably 0.01 g / cm 3 or more, more preferably 0.10 g / cm 3 or more, still more preferably 0.50 g / cm 3 or more, , is preferably 1.80 g / cm 3 or less, more preferably 1.50 g / cm 3 or less, further preferably 1.20 g / cm 3 or less. If the density of the carbon film is 0.01 g / cm 3 or more, the strength of the resulting composite can be ensured. On the other hand, if the density of the carbon film is 1.80 g / cm 3 or less, a composite in which the plating solution easily penetrates to the central portion in the thickness direction of the carbon film and the fine particles are present inside the carbon matrix when plating is performed.
  • the “density of the carbon film” can be determined by measuring the mass, area and thickness of the carbon film and dividing the mass of the carbon film by the volume (area ⁇ thickness).
  • Electrolytic plating treatment By subjecting the above-described carbon film to electrolytic plating treatment or electroless plating treatment, preferably electrolytic plating treatment, using a plating solution, fine particles are precipitated on the carbon film surface and / or inside the carbon film, thereby forming a composite. Can be obtained.
  • the plating solution used for the plating treatment contains a tin-containing compound in the solvent, and optionally contains additives for the plating solution (dissolution aids and nonionic surfactants, and other additives generally added to the plating solution). In addition.
  • the tin-containing compound is not particularly limited as long as it is possible to deposit tin fine particles (tin plating) on the surface of the carbon film and / or the inside of the carbon film through the plating process.
  • the tin-containing compound is not particularly limited, but tin pyrophosphate, tin phosphate, tin (II) sulfate, tin (IV) sulfate, tin (II) chloride, tin (IV) chloride, tin acetate ( II), tin (IV) acetate, and hydrates thereof. These may be used alone or in combination of two or more.
  • the concentration of the tin-containing compound in the plating solution is not particularly limited as long as tin fine particles can be precipitated, and can be adjusted as appropriate.
  • concentration of the tin-containing compound in the plating solution is not particularly limited as long as tin fine particles can be precipitated, and can be adjusted as appropriate.
  • 0.01 mol / L or more and 3.0 mol / L The following is preferable.
  • solubility aid The solubilizer is added for the purpose of ensuring the solubility of the above-described tin-containing compound in a solvent (for example, water).
  • a solubilizing agent is an ionic compound other than the above tin-containing compounds, and examples thereof include metal pyrophosphate, metal phosphate, metal sulfate, metal chloride, and metal acetate.
  • the anionic component contained in a solubilizing agent is the same as the anionic component contained in a tin containing compound.
  • the concentration of the dissolution aid in the plating solution is preferably at least twice the concentration of the tin-containing compound.
  • concentration of the solubilizing agent in a plating solution is not specifically limited, Usually, it is 100 times or less of the density
  • concentration of the dissolution aid in a plating solution is 0.04 mol / L or more and 12.0 mol / L or less, for example.
  • the plating solution preferably contains a nonionic surfactant.
  • the plating solution containing the nonionic surfactant is presumed to be because the nonionic surfactant has excellent affinity with the fibrous carbon nanostructure, but can easily penetrate into the carbon film. Therefore, if a plating solution containing a nonionic surfactant is used, a composite in which tin fine particles are present inside the carbon matrix can be obtained efficiently. And if the said composite_body
  • nonionic surfactants examples include polyether surfactants, alkylphenol surfactants, polyester surfactants, sorbitan ester ether surfactants, alkylamine surfactants, and the like.
  • polyether surfactants are preferable from the viewpoint of improving the physical properties of the composite and further improving the cycle characteristics of the lithium ion secondary battery.
  • Polyether-based surfactants include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene dodecyl ether, polyoxyethylene nonylphenyl ether , Polyoxyethylene octyl phenyl ether, and polyoxyethylene / polyoxypropylene block copolymer.
  • polyethylene glycol is particularly preferable.
  • a nonionic surfactant may be used individually by 1 type and may use 2 or more types together.
  • the weight average molecular weight of the nonionic surfactant is not particularly limited, but is preferably 500 or more, preferably 20000 or less, more preferably 10,000 or less, and still more preferably 5000 or less. It is especially preferable that it is 4000 or less. If the weight average molecular weight of the nonionic surfactant is within the above-mentioned range, the metal and the fibrous carbon nanostructure can be combined more satisfactorily, and the physical properties of the composite can be further improved. In addition, the weight average molecular weight (Mw) of a nonionic surfactant can be calculated
  • the plating solution may contain known additives for plating solutions such as brighteners in addition to the above-described tin-containing compound, solubilizing agent, and nonionic surfactant as long as the effects of the present invention are not impaired. Good.
  • the plating solution can be prepared by dissolving or dispersing the above-described components in a known solvent such as water.
  • the method for plating the carbon film is not particularly limited as long as it is a method capable of precipitating tin fine particles.
  • a carbon film may be used as the cathode, or a laminate formed by adhering a carbon film to the substrate surface via a carbon tape or the like may be used.
  • a cathode it is possible to use a cathode composed only of a carbon film from the viewpoint of facilitating the penetration of the plating solution into the carbon film and efficiently producing a composite having fine particles inside the carbon matrix. preferable.
  • the plating treatment is not limited to electrolytic plating, and electroless plating can also be employed.
  • electrolytic plating there is no limitation to direct current plating, and current reversal plating and pulse plating can also be employed.
  • the plating solution may be stirred with a stirrer, for example.
  • a waiting time from when the carbon film is immersed in the plating solution to when the plating treatment is started (for example, in the case of electrolytic plating treatment, energization is started) (wait time before plating treatment) )
  • the waiting time before the plating treatment is preferably 5 minutes or more, more preferably 10 minutes or more. If the waiting time before the plating process is 5 minutes or more, the carbon film surface is sufficiently wetted with the plating solution (the carbon film surface and the plating solution are familiar), and the plating solution penetrates into the carbon film. Can be encouraged. Further, the waiting time before the plating treatment is preferably 60 minutes or less, more preferably 30 minutes or less, considering the efficiency of the treatment.
  • the amount of energization can be adjusted as appropriate according to the size (area and thickness) of the carbon film, and by appropriately adjusting the amount of energization, tin fine particles can be suitably used inside the carbon film. It can be carried in a state.
  • the plating time is not particularly limited, but is usually 10 minutes or longer.
  • the composite of the present invention described above can be used for producing the negative electrode for a lithium ion secondary battery of the present invention.
  • the negative electrode for a lithium ion secondary battery of the present invention includes a negative electrode active material layer, and the negative electrode active material layer is the composite of the present invention. Since the negative electrode for a lithium ion secondary battery of the present invention uses the composite of the present invention as the negative electrode active material layer, the lithium ion secondary battery has a high capacity and is sufficiently superior to the lithium ion secondary battery. Cycle characteristics can be exhibited.
  • the negative electrode for a lithium ion secondary battery of the present invention is not particularly limited as long as the composite of the present invention can function as a negative electrode active material layer, and is composed only of the composite as a negative electrode active material layer.
  • a negative electrode may be sufficient and the negative electrode by which the composite_body
  • the negative electrode for a lithium ion secondary battery of the present invention is a negative electrode in which a composite as a negative electrode active material layer is disposed on a current collector, the negative electrode active material layer is disposed in contact with the current collector.
  • the negative electrode active material layer may be disposed on the current collector through another layer such as an adhesive layer.
  • an electrically conductive and electrochemically durable material is used.
  • a current collector for example, a current collector made of a metal material such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, or platinum can be used.
  • a collector of a negative electrode the thin film which consists of copper is preferable.
  • the adhesive layer arbitrarily disposed between the current collector and the negative electrode active material layer is not particularly limited as long as electrical conductivity is ensured and the current collector and the negative electrode active material layer can be bonded.
  • the adhesive layer is preferably a layer including a conductive material such as conductive carbon and a binder, for example.
  • a negative electrode for a lithium ion secondary battery in which an adhesive layer is present between a negative electrode active material layer and a current collector has an adhesive layer containing a conductive material, a binder, and a solvent on one surface of the composite.
  • the adhesive paste is applied to the surface of the composite coated with the adhesive layer paste, and the solvent in the adhesive layer paste is removed by drying or the like. it can.
  • the above-described negative electrode for a lithium ion secondary battery of the present invention is used by being incorporated in a lithium ion secondary battery.
  • the lithium ion secondary battery includes a positive electrode, a negative electrode, an electrolytic solution, and a separator, and the negative electrode is used as a negative electrode for a lithium ion secondary battery of the present invention.
  • Any known positive electrode, electrolytic solution, and separator can be used.
  • a lithium ion secondary battery including the negative electrode for a lithium ion secondary battery of the present invention has a high capacity and exhibits sufficiently excellent cycle characteristics.
  • Capacity maintenance ratio ⁇ C 90% or more
  • Capacity maintenance ratio ⁇ C 85% or more and less than 90%
  • Capacity maintenance ratio ⁇ C 80% or more and less than 85%
  • D Capacity maintenance ratio ⁇ C is 75% or more and less than 80%
  • Example 1 ⁇ Synthesis of fibrous carbon nanostructure containing single-walled CNT> A fibrous carbon nanostructure containing single-walled CNTs used in the examples was prepared by the super-growth method (hereinafter referred to as “fibrous carbon nanostructure A”) as described in International Publication No. 2006/011655.
  • the thickness of the iron catalyst thin film layer of the metal catalyst was 2 nm.
  • the obtained fibrous carbon nanostructure A had a BET specific surface area of 1050 m 2 / g (unopened state) and an average diameter (Av) of 3.3 nm.
  • the fibrous carbon nanostructure A was measured with a Raman spectrophotometer, a spectrum of a radial breathing mode (RBM) in a low wavenumber region of 100 to 300 cm ⁇ 1 characteristic for single-walled CNTs was observed.
  • the t plot in the unopened state shows an upwardly convex shape, the inflection point is in the range of 0.55 ⁇ t (nm) ⁇ 1.0, and the ratio between the total specific surface area S1 and the internal specific surface area S2. Satisfies 0.05 ⁇ S2 / S1 ⁇ 0.30.
  • the median diameter (average particle diameter) of the fibrous carbon nanostructure A in the dispersion A was 24.1 ⁇ m.
  • the obtained dispersion A was filtered under reduced pressure using Kiriyama filter paper (No. 5A) to obtain a carbon film A having a thickness of 40 ⁇ m and a density of 0.85 g / cm 3 .
  • Composite A was produced by performing electroplating under the following conditions in a tin plating bath using the carbon film A described above as a cathode and a pure tin plate as an anode.
  • the pure tin plate as an anode was disposed on both the front and back sides of the carbon film A as a cathode, one in total so as not to contact the carbon film A.
  • Electrodeposition mode Current regulation method Current density: 0.05 A / dm 2 Energization amount: 96C Waiting time before plating: 30 minutes
  • a conductive carbon paste (adhesive layer paste) containing conductive carbon as a conductive material was applied to one side of the composite A having a thickness of 40 ⁇ m obtained as described above.
  • a copper foil having a thickness of 20 ⁇ m as a current collector was placed on the coated surface, and a negative electrode A in which the composite A as a negative electrode active material layer and the copper foil as a current collector were adhered by an adhesive layer was obtained.
  • LiCoO 2 volume average particle diameter D50: 12 ⁇ m
  • the positive electrode slurry composition obtained as described above was applied on a current collector 20 ⁇ m thick aluminum foil with a comma coater so that the film thickness after drying was about 150 ⁇ m and dried. It was. This drying was performed by transporting the aluminum foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a positive electrode raw material. The positive electrode raw material before pressing was rolled with a roll press to obtain a positive electrode after pressing with a thickness of 80 ⁇ m.
  • a laminate was obtained by laminating the positive electrode after pressing obtained above, a separator having adhesive layers on both sides, and the negative electrode A obtained above in this order and adhering them together.
  • the obtained laminate was wound with a winding machine to obtain a wound body.
  • the wound body was pressed at 60 ° C. and 0.5 MPa to obtain a flat body.
  • a negative electrode B was obtained in the same manner as the negative electrode A, except that a tin plate was used instead of the composite A.
  • a lithium ion secondary battery was produced in the same manner as in Example 1 except that the negative electrode B was used instead of the negative electrode A. And when the cycle characteristic of the obtained lithium ion secondary battery was evaluated, it was D evaluation.
  • Example 2 A lithium ion secondary battery was produced in the same manner as in Example 1 except that the negative electrode C produced as follows was used instead of the negative electrode A. And when the cycle characteristic of the obtained lithium ion secondary battery was evaluated, it was C evaluation.
  • ⁇ Preparation of negative electrode C> In a 5 MPa pressure vessel with a stirrer, 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 63.5 parts of styrene, 0.4 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water and a polymerization initiator After adding 0.5 parts of potassium persulfate as a mixture and sufficiently stirring, the mixture was heated to 50 ° C.
  • the reaction was stopped by cooling to obtain a mixture containing a particulate binder (SBR) for the negative electrode.
  • SBR particulate binder
  • a 5% aqueous sodium hydroxide solution was added to the mixture containing the particulate binder and the pH was adjusted to 8, and then the unreacted monomer was removed by heating under reduced pressure. Then, it cooled to 30 degrees C or less, and obtained the water dispersion liquid containing a desired particulate-form binder.
  • aqueous dispersion containing the particulate binder described above and ion-exchanged water are added to the obtained mixed liquid so that the final solid content concentration is 52%. Adjust and mix for an additional 10 minutes. This was defoamed under reduced pressure to obtain a negative electrode slurry composition having good fluidity.
  • the negative electrode slurry composition obtained as described above was applied on a copper foil having a thickness of 20 ⁇ m, which was a current collector, using a comma coater and dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Then, the negative electrode C was obtained by heat-processing at 120 degreeC for 2 minute (s).
  • Example 1 using a composite containing fibrous carbon nanostructures and tin fine particles having an average particle diameter of 10 ⁇ m or less as a negative electrode active material layer, as compared with Comparative Examples 1 and 2, It can be seen that excellent cycle characteristics can be exhibited in the lithium ion secondary battery.
  • Example 1 since tin fine particles were used as the negative electrode active material, a high-capacity lithium ion secondary battery could be obtained.
  • a negative electrode for a lithium ion secondary battery capable of increasing the capacity of the lithium ion secondary battery and causing the lithium ion secondary battery to exhibit sufficiently excellent cycle characteristics. be able to.
  • the negative electrode for lithium ion secondary batteries of this invention while being able to increase capacity of a lithium ion secondary battery, the said lithium ion secondary battery can fully exhibit the cycling characteristics which were excellent.
  • the method for producing a composite of the present invention a composite capable of increasing the capacity of a lithium ion secondary battery and exhibiting sufficiently excellent cycle characteristics in the lithium ion secondary battery is efficiently produced. Can be manufactured well.

Abstract

The purpose of the present invention is to provide a novel technique which enables a lithium ion secondary battery to have a higher capacity, while enabling the lithium ion secondary battery to exhibit sufficiently excellent cycle characteristics. A composite body according to the present invention comprises a fibrous carbon nanostructure and fine tin particles having an average particle diameter of 10 μm or less.

Description

複合体およびリチウムイオン二次電池用負極、並びに複合体の製造方法Composite, negative electrode for lithium ion secondary battery, and method for producing composite
　本発明は、複合体およびリチウムイオン二次電池用負極、並びに複合体の製造方法に関するものである。具体的には、本発明は、繊維状炭素ナノ構造体と、スズの微粒子とを含む複合体に関するものである。また、本発明は、当該複合体を備えるリチウムイオン二次電池用負極、および当該複合体の製造方法に関するものである。 The present invention relates to a composite, a negative electrode for a lithium ion secondary battery, and a method for manufacturing the composite. Specifically, the present invention relates to a composite containing fibrous carbon nanostructures and tin fine particles. Moreover, this invention relates to the negative electrode for lithium ion secondary batteries provided with the said composite_body | complex, and the manufacturing method of the said composite_body | complex.
　リチウムイオン二次電池は、小型で軽量、且つエネルギー密度が高く、さらに繰り返し充放電が可能という特性があり、幅広い用途に使用されている。そのため、近年では、リチウムイオン二次電池の更なる高性能化を目的として、電極などの電池部材の改良が検討されている。具体的には、集電体上に、理論容量の高いスズを含有する負極活物質を含む負極活物質層を備えてなる負極が検討されている（例えば、特許文献１および２参照）。そして特許文献１および２に記載された負極によれば、リチウムイオン二次電池を高容量化しつつ、充放電した際の負極活物質のクラックの発生や集電体からの脱離を抑制して、良好なサイクル特性を確保することができると報告されている。 Lithium ion secondary batteries are small and light, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications. Therefore, in recent years, improvement of battery members such as electrodes has been studied for the purpose of further improving the performance of lithium ion secondary batteries. Specifically, a negative electrode including a negative electrode active material layer including a negative electrode active material containing tin having a high theoretical capacity on a current collector has been studied (see, for example, Patent Documents 1 and 2). According to the negative electrodes described in Patent Documents 1 and 2, while increasing the capacity of the lithium ion secondary battery, the generation of cracks in the negative electrode active material during charge / discharge and the detachment from the current collector are suppressed. It has been reported that good cycle characteristics can be secured.
特開２０１５－４３３０９号公報JP 2015-43309 A 特許第５２７５７０２号Japanese Patent No. 5275702
　ここで、上記従来の技術では、理論容量の高いスズを含有する負極活物質を用いることでリチウムイオン二次電池の高容量化が図られている。しかしながら、上記従来の技術を用いても、スズを含有する負極活物質を用いた場合に、負極活物質の膨張および収縮に起因するサイクル特性低下を十分に抑制することはできなかった。すなわち、上記従来の技術には、リチウムイオン二次電池の高容量化を実現しつつ、サイクル特性を更に向上させるという点で改善の余地があった。
　そこで、本発明は、上述した改善点を有利に解決する手段を提供することを目的とする。 Here, in the above-described conventional technique, the capacity of the lithium ion secondary battery is increased by using a negative electrode active material containing tin having a high theoretical capacity. However, even when the above-described conventional technique is used, when a negative electrode active material containing tin is used, it has not been possible to sufficiently suppress a decrease in cycle characteristics due to expansion and contraction of the negative electrode active material. In other words, the conventional technology has room for improvement in terms of further improving the cycle characteristics while realizing a higher capacity of the lithium ion secondary battery.
Therefore, an object of the present invention is to provide means for advantageously solving the above-described improvements.
　本発明者は、上記目的を達成するべく、鋭意検討を行った。そして、本発明者は、繊維状炭素ナノ構造体と、平均粒子径が所定の値以下であり且つスズからなる微粒子とを含む複合体を負極活物質層として用いれば、リチウムイオン二次電池を高容量化すると共に、当該リチウムイオン二次電池に十分に優れたサイクル特性を発揮させうることを見出し、本発明を完成させた。 The present inventor has intensively studied to achieve the above object. Then, the present inventor uses a composite containing fibrous carbon nanostructures and fine particles having an average particle diameter of a predetermined value or less and made of tin as a negative electrode active material layer, so that a lithium ion secondary battery is obtained. The present inventors have found that the capacity can be increased and the lithium ion secondary battery can exhibit sufficiently excellent cycle characteristics, and the present invention has been completed.
　即ち、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の複合体は、繊維状炭素ナノ構造体と、平均粒子径が１０μｍ以下であるスズ微粒子を含むことを特徴とする。繊維状炭素ナノ構造体、および平均粒子径が上記値以下のスズ微粒子を含む複合体を負極活物質層として用いれば、リチウムイオン二次電池の容量を高めると共にサイクル特性を十分に向上させることができる。
　なお、本発明において、「スズ微粒子」とは、スズで構成され、粒子径が１００μｍ以下である粒子を指す。そして、本発明において、スズ微粒子の粒子径は、例えば電界放出形走査電子顕微鏡（ＦＥ－ＳＥＭ）等でスズ微粒子を観察し、当該スズ微粒子の外縁上の２点を結ぶ線分の長さのうち最大の長さを測定することで得られる。また、本発明において、スズ微粒子の「平均粒子径」は、無作為に選択した１００個のスズ微粒子の粒子径の平均値として算出することができる。 That is, the present invention aims to advantageously solve the above-mentioned problems, and the composite of the present invention contains fibrous carbon nanostructures and tin fine particles having an average particle diameter of 10 μm or less. It is characterized by. If a fibrous carbon nanostructure and a composite containing tin fine particles having an average particle size of the above value or less are used as the negative electrode active material layer, the capacity of the lithium ion secondary battery can be increased and the cycle characteristics can be sufficiently improved. it can.
In the present invention, “tin fine particles” refers to particles composed of tin and having a particle diameter of 100 μm or less. In the present invention, the particle diameter of the tin fine particles is determined by observing the tin fine particles with, for example, a field emission scanning electron microscope (FE-SEM), and measuring the length of a line segment connecting two points on the outer edge of the tin fine particles. It is obtained by measuring the maximum length. In the present invention, the “average particle diameter” of the tin fine particles can be calculated as an average value of the particle diameters of 100 randomly selected tin fine particles.
　ここで、本発明の複合体は、前記繊維状炭素ナノ構造体を含む炭素マトリックスの内部に、前記スズ微粒子が存在する構造を有することが好ましい。スズ微粒子が繊維状炭素ナノ構造体で構成される炭素マトリックスの内部に存在すれば、繊維状炭素ナノ構造体からのスズ微粒子の脱離が抑制され、そして、リチウムイオン二次電池のサイクル特性を更に向上させることができる。
　なお、本発明において、「炭素マトリックスの内部」とは、炭素マトリックスの最表面以外の内側の部分をいい、そして、「繊維状炭素ナノ構造体を含む炭素マトリックスの内部に微粒子が存在する」ことは、例えばＦＥ－ＳＥＭ等で複合体の断面を観察した際に、繊維状炭素ナノ構造体で構成される炭素マトリックスに埋没した状態のスズ微粒子が存在していることから確認することができる。 Here, the composite of the present invention preferably has a structure in which the tin fine particles are present inside a carbon matrix containing the fibrous carbon nanostructure. If tin fine particles exist inside the carbon matrix composed of fibrous carbon nanostructures, the desorption of tin fine particles from the fibrous carbon nanostructures can be suppressed, and the cycle characteristics of the lithium ion secondary battery can be reduced. Further improvement can be achieved.
In the present invention, the “inside of the carbon matrix” means an inner portion other than the outermost surface of the carbon matrix, and “fine particles exist inside the carbon matrix including the fibrous carbon nanostructure”. This can be confirmed from the presence of tin fine particles embedded in a carbon matrix composed of fibrous carbon nanostructures when the cross section of the composite is observed with, for example, FE-SEM.
　そして、本発明の複合体において、前記繊維状炭素ナノ構造体は、カーボンナノチューブを含むことが好ましい。カーボンナノチューブを含む繊維状炭素ナノ構造体を用いれば、リチウムイオン二次電池のサイクル特性を更に向上させることができる。 In the composite of the present invention, it is preferable that the fibrous carbon nanostructure includes a carbon nanotube. If the fibrous carbon nanostructure containing carbon nanotubes is used, the cycle characteristics of the lithium ion secondary battery can be further improved.
　更に、本発明の複合体において、前記繊維状炭素ナノ構造体は、吸着等温線から得られるｔ－プロットが上に凸な形状を示すことが好ましい。吸着等温線から得られるｔ－プロットが上に凸な形状を示す繊維状炭素ナノ構造体を用いれば、リチウムイオン二次電池のサイクル特性を更に向上させることができる。 Furthermore, in the composite of the present invention, it is preferable that the fibrous carbon nanostructure has a shape in which a t-plot obtained from an adsorption isotherm is convex upward. By using a fibrous carbon nanostructure in which the t-plot obtained from the adsorption isotherm has an upwardly convex shape, the cycle characteristics of the lithium ion secondary battery can be further improved.
　そして、本発明の複合体は、リチウムイオン二次電池負極用として用いることができる。 And the composite_body | complex of this invention can be used as an object for lithium ion secondary battery negative electrodes.
　また、この発明は、上記課題を有利に解決することを目的とするものであり、本発明のリチウムイオン二次電池用負極は、負極活物質層を備え、前記負極活物質層が上述した複合体であることを特徴とする。上述した複合体を負極活物質層として用いれば、リチウムイオン二次電池の容量を高めると共に、サイクル特性を十分に向上させることができる。 Moreover, this invention aims at solving the said subject advantageously, The negative electrode for lithium ion secondary batteries of this invention is equipped with the negative electrode active material layer, and the said negative electrode active material layer is the composite_body | complex mentioned above. It is a body. When the composite described above is used as the negative electrode active material layer, the capacity of the lithium ion secondary battery can be increased and the cycle characteristics can be sufficiently improved.
　また、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の複合体の製造方法は、上述した何れかの複合体を製造する方法であって、前記繊維状炭素ナノ構造体を含む炭素膜に、スズ含有化合物を含むめっき液を用いてめっき処理を行う工程を含むことを特徴とする。スズ含有化合物を含むめっき液を用いて炭素膜にめっき処理を行えば、スズ微粒子の微粒子を含む上述した何れかの複合体を、効率良く製造することができる。 In addition, the present invention aims to advantageously solve the above-described problems, and a method for producing a composite according to the present invention is a method for producing any of the above-described composites, wherein the fibrous The carbon film including the carbon nanostructure includes a step of performing a plating process using a plating solution including a tin-containing compound. If the carbon film is plated using a plating solution containing a tin-containing compound, any of the above-described composites containing tin fine particles can be efficiently produced.
　ここで、本発明の複合体の製造方法において、前記めっき液は、更に、ポリエーテル系界面活性剤と、水とを含むことが好ましい。このようなめっき液を用いれば、スズ微粒子を含む上述した何れかの複合体を、一層効率良く製造することができる。また、得られる複合体を用いたリチウムイオン二次電池用負極によれば、リチウムイオン二次電池に一層優れたサイクル特性を発揮させることができる。 Here, in the method for producing a composite according to the present invention, it is preferable that the plating solution further includes a polyether-based surfactant and water. If such a plating solution is used, any of the above-described composites containing tin fine particles can be produced more efficiently. Moreover, according to the negative electrode for lithium ion secondary batteries using the obtained composite, the lithium ion secondary battery can exhibit more excellent cycle characteristics.
　そして、本発明の複合体の製造方法において、前記炭素膜の密度が０．０１ｇ／ｃｍ3以上１．８０ｇ／ｃｍ3以下であることが好ましい。密度が上述の範囲内である炭素膜を用いれば、得られる複合体の強度を確保すると共に、当該複合体を用いたリチウムイオン二次電池用負極によれば、リチウムイオン二次電池に一層優れたサイクル特性を発揮させることができる。 The method of manufacturing a composite of the present invention, it is preferable that the density of the carbon film is 0.01 g / cm 3 or more 1.80 g / cm 3 or less. If a carbon film having a density within the above-described range is used, the strength of the obtained composite is ensured, and the lithium ion secondary battery negative electrode using the composite further improves the lithium ion secondary battery. Cycle characteristics can be exhibited.
　本発明の複合体によれば、リチウムイオン二次電池を高容量化すると共に、当該リチウムイオン二次電池に十分に優れたサイクル特性を発揮させることができるリチウムイオン二次電池用負極を提供することができる。
　また、本発明のリチウムイオン二次電池用負極によれば、リチウムイオン二次電池を高容量化すると共に、当該リチウムイオン二次電池に十分に優れたサイクル特性を発揮させることができる。
　そして、本発明の複合体の製造方法によれば、リチウムイオン二次電池を高容量化すると共に、当該リチウムイオン二次電池に十分に優れたサイクル特性を発揮させることができる複合体を、効率良く製造することができる。 According to the composite of the present invention, there is provided a negative electrode for a lithium ion secondary battery capable of increasing the capacity of the lithium ion secondary battery and causing the lithium ion secondary battery to exhibit sufficiently excellent cycle characteristics. be able to.
Moreover, according to the negative electrode for lithium ion secondary batteries of this invention, while being able to increase capacity of a lithium ion secondary battery, the said lithium ion secondary battery can fully exhibit the cycling characteristics which were excellent.
According to the method for producing a composite of the present invention, a composite capable of increasing the capacity of a lithium ion secondary battery and exhibiting sufficiently excellent cycle characteristics in the lithium ion secondary battery is efficiently produced. Can be manufactured well.
表面に細孔を有する試料のｔ－プロットの一例を示すグラフである。6 is a graph showing an example of a t-plot of a sample having pores on the surface. 実施例で得られた複合体Ａ断面のＦＥ－ＳＥＭ写真である。3 is an FE-SEM photograph of a cross section of composite A obtained in an example.
　以下、本発明の実施形態について詳細に説明する。
　本発明の複合体は、繊維状炭素ナノ構造体と、スズ微粒子が複合化された材料である。そして、本発明の複合体は、本発明のリチウムイオン二次電池用負極の作製に用いることができる。また、本発明の複合体は、本発明の複合体の製造方法を用いて製造することができる。 Hereinafter, embodiments of the present invention will be described in detail.
The composite of the present invention is a material in which fibrous carbon nanostructures and tin fine particles are combined. And the composite_body | complex of this invention can be used for preparation of the negative electrode for lithium ion secondary batteries of this invention. Moreover, the composite_body | complex of this invention can be manufactured using the manufacturing method of the composite_body | complex of this invention.
（複合体）
　本発明の複合体は、少なくとも、繊維状炭素ナノ構造体と、平均粒子径が１０μｍ以下であるスズ微粒子を含み、前記繊維状炭素ナノ構造体と前記スズ微粒子以外の成分（その他の成分）を含んでいてもよい。 (Complex)
The composite of the present invention includes at least a fibrous carbon nanostructure and tin fine particles having an average particle diameter of 10 μm or less, and includes components (other components) other than the fibrous carbon nanostructure and the tin fine particles. May be included.
　そして、本発明の複合体はスズ微粒子を含んでいるため、本発明の複合体をリチウムイオン二次電池用負極の負極活物質層として用いれば、スズ微粒子が負極活物質として働きリチウムイオン二次電池を高容量化することができる。加えて、本発明の複合体中のスズ微粒子は、平均粒子径が１０μｍ以下であるため、リチウムイオン二次電池の充放電によりスズ微粒子が膨張および収縮を繰り返した場合であっても、スズ微粒子にかかる応力が十分に小さい。そのため、負極活物質であるスズ微粒子の、クラックの発生や、集電体からの脱離が抑制され、リチウムイオン二次電池に優れたサイクル特性を発揮させることができる。 Since the composite of the present invention contains tin fine particles, if the composite of the present invention is used as a negative electrode active material layer of a negative electrode for a lithium ion secondary battery, the tin fine particles function as a negative electrode active material and are lithium ion secondary. The capacity of the battery can be increased. In addition, since the tin fine particles in the composite of the present invention have an average particle diameter of 10 μm or less, even if the tin fine particles are repeatedly expanded and contracted by charging / discharging of the lithium ion secondary battery, the tin fine particles The stress applied to is sufficiently small. Therefore, generation of cracks and desorption from the current collector of tin fine particles, which are the negative electrode active material, are suppressed, and excellent cycle characteristics can be exhibited in the lithium ion secondary battery.
＜繊維状炭素ナノ構造体＞
　繊維状炭素ナノ構造体としては、特に限定されることなく、例えば、カーボンナノチューブ（ＣＮＴ）、気相成長炭素繊維、有機繊維を炭化して得られる炭素繊維、およびそれらの切断物などを用いることができる。これらは、１種単独で使用してもよいし、２種以上を併用してもよい。
　中でも、繊維状炭素ナノ構造体としては、カーボンナノチューブを含む繊維状炭素ナノ構造体を用いることがより好ましい。カーボンナノチューブを含む繊維状炭素ナノ構造体を使用すれば、複合体の導電性などの物性を高めて、リチウムイオン二次電池に一層優れたサイクル特性を発揮させることができる。 <Fibrous carbon nanostructure>
The fibrous carbon nanostructure is not particularly limited. For example, carbon nanotubes (CNT), vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and cut products thereof are used. Can do. These may be used individually by 1 type and may use 2 or more types together.
Among these, as the fibrous carbon nanostructure, it is more preferable to use a fibrous carbon nanostructure including carbon nanotubes. If a fibrous carbon nanostructure containing carbon nanotubes is used, physical properties such as conductivity of the composite can be improved, and more excellent cycle characteristics can be exhibited in the lithium ion secondary battery.
　そして、ＣＮＴを含む繊維状炭素ナノ構造体としては、特に限定されることなく、ＣＮＴのみからなるものを用いてもよいし、ＣＮＴと、ＣＮＴ以外の繊維状炭素ナノ構造体との混合物を用いてもよい。
　また、ＣＮＴを含む繊維状炭素ナノ構造体を使用する場合、繊維状炭素ナノ構造体中のＣＮＴとしては、特に限定されることなく、単層カーボンナノチューブおよび／または多層カーボンナノチューブを用いることができるが、ＣＮＴは、単層から５層までのカーボンナノチューブであることが好ましく、単層カーボンナノチューブであることがより好ましい。単層カーボンナノチューブを使用すれば、多層カーボンナノチューブを使用した場合と比較し、リチウムイオン二次電池のサイクル特性を一層向上させることができる。 And as a fibrous carbon nanostructure containing CNT, it may not be specifically limited but what consists only of CNT may be used, and the mixture of CNT and fibrous carbon nanostructures other than CNT is used. May be.
When a fibrous carbon nanostructure containing CNT is used, the CNT in the fibrous carbon nanostructure is not particularly limited, and single-walled carbon nanotubes and / or multi-walled carbon nanotubes can be used. However, the CNT is preferably a single-walled to carbon-walled carbon nanotube, more preferably a single-walled carbon nanotube. If single-walled carbon nanotubes are used, the cycle characteristics of the lithium ion secondary battery can be further improved as compared with the case where multi-walled carbon nanotubes are used.
　また、繊維状炭素ナノ構造体としては、リチウムイオン二次電池のサイクル特性を一層高める観点から、吸着等温線から得られるｔ－プロットが上に凸な形状を示すものが好ましい。
　ここで、一般に、吸着とは、ガス分子が気相から固体表面に取り去られる現象であり、その原因から、物理吸着と化学吸着に分類される。そして、ｔ－プロットの取得に用いられる窒素ガス吸着法では、物理吸着を利用する。なお、通常、吸着温度が一定であれば、繊維状炭素ナノ構造体に吸着する窒素ガス分子の数は、圧力が大きいほど多くなる。また、横軸に相対圧（吸着平衡状態の圧力Ｐと飽和蒸気圧Ｐ０の比）、縦軸に窒素ガス吸着量をプロットしたものを「等温線」といい、圧力を増加させながら窒素ガス吸着量を測定した場合を「吸着等温線」、圧力を減少させながら窒素ガス吸着量を測定した場合を「脱着等温線」という。
　そして、ｔ－プロットは、窒素ガス吸着法により測定された吸着等温線において、相対圧を窒素ガス吸着層の平均厚みｔ（ｎｍ）に変換することにより得られる。即ち、窒素ガス吸着層の平均厚みｔを相対圧Ｐ／Ｐ０に対してプロットした、既知の標準等温線から、相対圧に対応する窒素ガス吸着層の平均厚みｔを求めて上記変換を行うことにより、繊維状炭素ナノ構造体のｔ－プロットが得られる（de Boerらによるｔ－プロット法）。 Further, as the fibrous carbon nanostructure, from the viewpoint of further improving the cycle characteristics of the lithium ion secondary battery, it is preferable that the t-plot obtained from the adsorption isotherm shows a convex shape.
Here, in general, adsorption is a phenomenon in which gas molecules are removed from the gas phase to the solid surface, and is classified into physical adsorption and chemical adsorption based on the cause. In the nitrogen gas adsorption method used for obtaining the t-plot, physical adsorption is used. Normally, if the adsorption temperature is constant, the number of nitrogen gas molecules adsorbed on the fibrous carbon nanostructure increases as the pressure increases. Also, the plot of the relative pressure (ratio of adsorption equilibrium pressure P and saturated vapor pressure P0) on the horizontal axis and the amount of nitrogen gas adsorption on the vertical axis is called the “isothermal line”. Nitrogen gas adsorption while increasing the pressure The case where the amount is measured is referred to as an “adsorption isotherm”, and the case where the amount of nitrogen gas adsorption is measured while reducing the pressure is referred to as a “desorption isotherm”.
The t-plot is obtained by converting the relative pressure to the average thickness t (nm) of the nitrogen gas adsorption layer in the adsorption isotherm measured by the nitrogen gas adsorption method. That is, the average thickness t of the nitrogen gas adsorption layer is plotted against the relative pressure P / P0, and the average thickness t of the nitrogen gas adsorption layer corresponding to the relative pressure is obtained from the known standard isotherm and the above conversion is performed. Gives a t-plot of the fibrous carbon nanostructure (t-plot method by de Boer et al.).
　ここで、表面に細孔を有する試料の典型的なｔ－プロットを図１に示す。表面に細孔を有する試料では、窒素ガス吸着層の成長は、次の（１）～（３）の過程に分類される。そして、下記の（１）～（３）の過程によって、図１に示すようにｔ－プロットの傾きに変化が生じる。
（１）全表面への窒素分子の単分子吸着層形成過程
（２）多分子吸着層形成とそれに伴う細孔内での毛管凝縮充填過程
（３）細孔が窒素によって満たされた見かけ上の非多孔性表面への多分子吸着層形成過程 Here, a typical t-plot of a sample having pores on the surface is shown in FIG. In the sample having pores on the surface, the growth of the nitrogen gas adsorption layer is classified into the following processes (1) to (3). Then, the following steps (1) to (3) change the slope of the t-plot as shown in FIG.
(1) Monomolecular adsorption layer formation process of nitrogen molecules on the entire surface (2) Multimolecular adsorption layer formation and capillary condensation filling process in the pores accompanying it (3) Apparent filling of the pores with nitrogen Formation process of multimolecular adsorption layer on non-porous surface
　そして、本発明で用いる好適な繊維状炭素ナノ構造体のｔ－プロットは、図１に示すように、窒素ガス吸着層の平均厚みｔが小さい領域では、原点を通る直線上にプロットが位置するのに対し、ｔが大きくなると、プロットが当該直線から下にずれた位置となり、上に凸な形状を示す。かかるｔ－プロットの形状は、繊維状炭素ナノ構造体の全比表面積に対する内部比表面積の割合が大きく、繊維状炭素ナノ構造体を構成する炭素ナノ構造体に多数の開口が形成されていることを示しており、その結果として、繊維状炭素ナノ構造体は、優れた特性を発揮すると推察される。 The t-plot of the preferred fibrous carbon nanostructure used in the present invention is located on a straight line passing through the origin in the region where the average thickness t of the nitrogen gas adsorption layer is small as shown in FIG. On the other hand, when t becomes large, the plot is shifted downward from the straight line and shows an upwardly convex shape. The shape of the t-plot is such that the ratio of the internal specific surface area to the total specific surface area of the fibrous carbon nanostructure is large, and a large number of openings are formed in the carbon nanostructure constituting the fibrous carbon nanostructure. As a result, it is assumed that the fibrous carbon nanostructure exhibits excellent characteristics.
　なお、繊維状炭素ナノ構造体のｔ－プロットの屈曲点は、０．２≦ｔ（ｎｍ）≦１．５を満たす範囲にあることが好ましく、０．４５≦ｔ（ｎｍ）≦１．５を満たす範囲にあることがより好ましく、０．５５≦ｔ（ｎｍ）≦１．０を満たす範囲にあることが更に好ましい。ｔ－プロットの屈曲点の位置が上記範囲であると、繊維状炭素ナノ構造体の特性が更に向上するため、リチウムイオン二次電池のサイクル特性をより一層高めることができる。
　ここで、「屈曲点の位置」とは、前述した（１）の過程の近似直線Ａと、前述した（３）の過程の近似直線Ｂとの交点である。 The bending point of the t-plot of the fibrous carbon nanostructure is preferably in a range satisfying 0.2 ≦ t (nm) ≦ 1.5, and 0.45 ≦ t (nm) ≦ 1.5. More preferably, it is in a range satisfying 0.55 ≦ t (nm) ≦ 1.0. When the position of the inflection point of the t-plot is within the above range, the characteristics of the fibrous carbon nanostructure are further improved, so that the cycle characteristics of the lithium ion secondary battery can be further improved.
Here, the “position of the bending point” is an intersection of the approximate line A in the process (1) described above and the approximate line B in the process (3) described above.
　更に、繊維状炭素ナノ構造体は、ｔ－プロットから得られる全比表面積Ｓ１に対する内部比表面積Ｓ２の比（Ｓ２／Ｓ１）が０．０５以上０．３０以下であるのが好ましい。Ｓ２／Ｓ１が０．０５以上０．３０以下であれば、バンドルの形成を十分に抑制しつつ、繊維状炭素ナノ構造体の特性を更に向上させることができるので、リチウムイオン二次電池のサイクル特性を一層向上させることができる。
　また、繊維状炭素ナノ構造体の全比表面積Ｓ１および内部比表面積Ｓ２は、特に限定されないが、個別には、Ｓ１は、６００ｍ2／ｇ以上１４００ｍ2／ｇ以下であることが好ましく、８００ｍ2／ｇ以上１２００ｍ2／ｇ以下であることが更に好ましい。一方、Ｓ２は、３０ｍ2／ｇ以上５４０ｍ2／ｇ以下であることが好ましい。
　ここで、繊維状炭素ナノ構造体の全比表面積Ｓ１および内部比表面積Ｓ２は、そのｔ－プロットから求めることができる。具体的には、図１に示すｔ－プロットにより説明すると、まず、（１）の過程の近似直線の傾きから全比表面積Ｓ１を、（３）の過程の近似直線の傾きから外部比表面積Ｓ３を、それぞれ求めることができる。そして、全比表面積Ｓ１から外部比表面積Ｓ３を差し引くことにより、内部比表面積Ｓ２を算出することができる。 Further, the fibrous carbon nanostructure preferably has a ratio (S2 / S1) of the internal specific surface area S2 to the total specific surface area S1 obtained from the t-plot of 0.05 or more and 0.30 or less. If S2 / S1 is 0.05 or more and 0.30 or less, it is possible to further improve the characteristics of the fibrous carbon nanostructure while sufficiently suppressing the formation of the bundle, so the cycle of the lithium ion secondary battery The characteristics can be further improved.
The total specific surface area S1 and the internal specific surface area S2 of the fibrous carbon nanostructure are not particularly limited, but individually, S1 is preferably 600 m 2 / g or more and 1400 m 2 / g or less, and 800 m 2. / G or more and 1200 m 2 / g or less is more preferable. On the other hand, S2 is preferably 30 m 2 / g or more and 540 m 2 / g or less.
Here, the total specific surface area S1 and the internal specific surface area S2 of the fibrous carbon nanostructure can be obtained from the t-plot. Specifically, referring to the t-plot shown in FIG. 1, first, the total specific surface area S1 is determined from the slope of the approximate line in the process (1), and the external specific surface area S3 is determined from the slope of the approximate line in the process (3). Can be obtained respectively. Then, the internal specific surface area S2 can be calculated by subtracting the external specific surface area S3 from the total specific surface area S1.
　因みに、繊維状炭素ナノ構造体の吸着等温線の測定、ｔ－プロットの作成、および、ｔ－プロットの解析に基づく全比表面積Ｓ１と内部比表面積Ｓ２との算出は、例えば、市販の測定装置である「ＢＥＬＳＯＲＰ（登録商標）－ｍｉｎｉ」（日本ベル（株）製）を用いて行うことができる。 Incidentally, the measurement of the adsorption isotherm of the fibrous carbon nanostructure, the creation of the t-plot, and the calculation of the total specific surface area S1 and the internal specific surface area S2 based on the analysis of the t-plot are, for example, commercially available measuring devices. "BELSORP (registered trademark) -mini" (manufactured by Nippon Bell Co., Ltd.).
　なお、ＣＮＴを含む繊維状炭素ナノ構造体を用いる場合、ＣＮＴを含む繊維状炭素ナノ構造体は、ＣＮＴの開口処理が施されておらず、ｔ－プロットが上に凸な形状を示すことがより好ましい。 When a fibrous carbon nanostructure containing CNT is used, the fibrous carbon nanostructure containing CNT is not subjected to CNT opening treatment, and the t-plot has a convex shape. More preferred.
　また、繊維状炭素ナノ構造体の平均直径は、０．５ｎｍ以上であることが好ましく、１ｎｍ以上であることがより好ましく、１５ｎｍ以下であることが好ましく、１０ｎｍ以下であることがより好ましい。繊維状炭素ナノ構造体の平均直径が０．５ｎｍ以上であれば、複合体を調製する際、複数の繊維状炭素ナノ構造体間に空間が十分に確保される。そのため、繊維状炭素ナノ構造体とスズ微粒子が良好に複合化した複合体とすることができる。また、繊維状炭素ナノ構造体の平均直径が１５ｎｍ以下であれば、複合体の導電性などの物性を高めることができる。従って、繊維状炭素ナノ構造体の平均直径が上述の範囲内であれば、リチウムイオン二次電池に一層優れたサイクル特性を発揮させることができる。
　なお、「繊維状炭素ナノ構造体の平均直径」は、透過型電子顕微鏡を用いて無作為に選択した繊維状炭素ナノ構造体１００本の直径（外径）を測定して求めることができる。そして、ＣＮＴを含む繊維状炭素ナノ構造体の平均直径は、ＣＮＴを含む繊維状炭素ナノ構造体の製造方法や製造条件を変更することにより調整してもよいし、異なる製法で得られたＣＮＴを含む繊維状炭素ナノ構造体を複数種類組み合わせることにより調整してもよい。 The average diameter of the fibrous carbon nanostructure is preferably 0.5 nm or more, more preferably 1 nm or more, preferably 15 nm or less, and more preferably 10 nm or less. When the average diameter of the fibrous carbon nanostructure is 0.5 nm or more, a sufficient space is secured between the plurality of fibrous carbon nanostructures when the composite is prepared. Therefore, it can be set as the composite_body | complex which fibrous carbon nanostructure and the tin microparticles | fine-particles compounded favorably. Moreover, if the average diameter of fibrous carbon nanostructure is 15 nm or less, physical properties, such as electroconductivity of a composite, can be improved. Therefore, if the average diameter of the fibrous carbon nanostructure is within the above range, the lithium ion secondary battery can exhibit more excellent cycle characteristics.
The “average diameter of fibrous carbon nanostructures” can be determined by measuring the diameter (outer diameter) of 100 fibrous carbon nanostructures selected at random using a transmission electron microscope. And the average diameter of the fibrous carbon nanostructure containing CNT may be adjusted by changing the manufacturing method and manufacturing conditions of the fibrous carbon nanostructure containing CNT, or CNT obtained by a different manufacturing method. You may adjust by combining multiple types of fibrous carbon nanostructure containing this.
　そして、繊維状炭素ナノ構造体のアスペクト比（長さ／直径）は、１０を超えることが好ましい。なお、繊維状炭素ナノ構造体のアスペクト比は、透過型電子顕微鏡を用いて無作為に選択した繊維状炭素ナノ構造体１００本の直径および長さを測定し、直径と長さとの比（長さ／直径）の平均値を算出することにより求めることができる。 The aspect ratio (length / diameter) of the fibrous carbon nanostructure is preferably more than 10. The aspect ratio of the fibrous carbon nanostructure was determined by measuring the diameter and length of 100 fibrous carbon nanostructures selected at random using a transmission electron microscope, and the ratio of the diameter to the length (long It can be obtained by calculating an average value of (thickness / diameter).
　ここで、繊維状炭素ナノ構造体のＢＥＴ比表面積は、６００ｍ2／ｇ以上であることが好ましく、８００ｍ2／ｇ以上であることがより好ましく、２５００ｍ2／ｇ以下であることが好ましく、１２００ｍ2／ｇ以下であることがより好ましい。ＣＮＴを含む繊維状炭素ナノ構造体のＢＥＴ比表面積が６００ｍ2／ｇ以上であれば、複合体の導電性などの物性を高めることができる。また、ＣＮＴを含む繊維状炭素ナノ構造体のＢＥＴ比表面積が２５００ｍ2／ｇ以下であれば、繊維状炭素ナノ構造体の過度な密集を抑制して、繊維状炭素ナノ構造体と微粒子が良好に複合化した複合体を得ることができる。従って、繊維状炭素ナノ構造体のＢＥＴ比表面積が上述の範囲内であれば、リチウムイオン二次電池に一層優れたサイクル特性を発揮させることができる。
　なお、本発明において、「ＢＥＴ比表面積」とは、ＢＥＴ法を用いて測定した窒素吸着比表面積を指す。 Here, the BET specific surface area of the fibrous carbon nanostructure is preferably 600 m 2 / g or more, more preferably 800 m 2 / g or more, and preferably 2500 m 2 / g or less. More preferably, it is 2 / g or less. If the BET specific surface area of the fibrous carbon nanostructure containing CNT is 600 m 2 / g or more, physical properties such as conductivity of the composite can be improved. Moreover, if the BET specific surface area of the fibrous carbon nanostructure containing CNT is 2500 m 2 / g or less, excessive crowding of the fibrous carbon nanostructure is suppressed, and the fibrous carbon nanostructure and fine particles are good. Can be obtained. Therefore, if the BET specific surface area of the fibrous carbon nanostructure is within the above range, the lithium ion secondary battery can exhibit more excellent cycle characteristics.
In the present invention, the “BET specific surface area” refers to a nitrogen adsorption specific surface area measured using the BET method.
　そして、上述した性状を有する繊維状炭素ナノ構造体（特には、ＣＮＴを含む繊維状炭素ナノ構造体）は、例えば、カーボンナノチューブ製造用の触媒層を表面に有する基材上に、原料化合物およびキャリアガスを供給して、化学的気相成長法（ＣＶＤ法）によりＣＮＴを合成する際に、系内に微量の酸化剤（触媒賦活物質）を存在させることで、触媒層の触媒活性を飛躍的に向上させるという方法（スーパーグロース法；国際公開第２００６／０１１６５５号参照）に準じて、効率的に製造することができる。なお、以下では、スーパーグロース法により得られるカーボンナノチューブを「ＳＧＣＮＴ」と称することがある。 And the fibrous carbon nanostructure (especially the fibrous carbon nanostructure containing CNT) which has the property mentioned above, for example on the base material which has the catalyst layer for carbon nanotube manufacture on the surface, and a raw material compound and When a carrier gas is supplied to synthesize CNTs by chemical vapor deposition (CVD), the catalytic activity of the catalyst layer is dramatically increased by the presence of a small amount of oxidant (catalyst activation material) in the system. Can be efficiently produced according to a method of improving the efficiency (super growth method; see International Publication No. 2006/011655). Hereinafter, the carbon nanotube obtained by the super growth method may be referred to as “SGCNT”.
　なお、スーパーグロース法により製造したＣＮＴを含む繊維状炭素ナノ構造体は、ＳＧＣＮＴのみから構成されていてもよいし、ＳＧＣＮＴと、非円筒形状の炭素ナノ構造体とから構成されていてもよい。具体的には、ＣＮＴを含む繊維状炭素ナノ構造体には、内壁同士が近接または接着したテープ状部分を全長に亘って有する単層または多層の扁平筒状の炭素ナノ構造体が含まれていてもよい。 In addition, the fibrous carbon nanostructure containing CNT manufactured by the super growth method may be comprised only from SGCNT, and may be comprised from SGCNT and a non-cylindrical carbon nanostructure. Specifically, the fibrous carbon nanostructure containing CNT includes a single-layer or multi-layer flat cylindrical carbon nanostructure having a tape-like portion whose inner walls are close to or bonded to each other over the entire length. May be.
　また、繊維状炭素ナノ構造体は、上述したスーパーグロース法によれば、カーボンナノチューブ成長用の触媒層を表面に有する基材上に、基材に略垂直な方向に配向した集合体（配向集合体）として得られるが、当該集合体としての、繊維状炭素ナノ構造体の質量密度は、０．００２ｇ／ｃｍ3以上０．２ｇ／ｃｍ3以下であることが好ましい。質量密度が０．２ｇ／ｃｍ3以下であれば、繊維状炭素ナノ構造体同士の結びつきが弱くなるので、繊維状炭素ナノ構造体を均質に分散させることができる。また、質量密度が０．００２ｇ／ｃｍ3以上であれば、繊維状炭素ナノ構造体の一体性を向上させ、バラけることを抑制できるため取り扱いが容易になる。 Further, according to the super-growth method described above, the fibrous carbon nanostructure is an aggregate (aligned assembly) oriented in a direction substantially perpendicular to the base material on the base material having a catalyst layer for carbon nanotube growth on the surface. The mass density of the fibrous carbon nanostructure as the aggregate is preferably 0.002 g / cm 3 or more and 0.2 g / cm 3 or less. If the mass density is 0.2 g / cm 3 or less, the bonding between the fibrous carbon nanostructures becomes weak, so that the fibrous carbon nanostructures can be uniformly dispersed. In addition, when the mass density is 0.002 g / cm 3 or more, the integrity of the fibrous carbon nanostructure can be improved, and the handling can be easily performed since it can be prevented from being broken.
＜スズ微粒子＞
　本発明の複合体は、上述した繊維状炭素ナノ構造体に加え、平均粒子径が１０μｍ以下であるスズ微粒子を含む。スズ微粒子は、本発明の複合体をリチウムイオン二次電池用負極の負極活物質層として用いた場合、リチウムイオンを吸蔵および放出する負極活物質としての役割を果たす。そして、負極活物質としてのスズ微粒子と、上述した繊維状炭素ナノ構造体が導通可能な状態で結合することで、複合体は負極活物質層として良好に機能し、リチウムイオン二次電池の容量およびサイクル特性の向上に資することができる。
　また、スズ微粒子の形状は特に限定されず、例えば、球状、立方体、長方形、板状（六角板状など）、柱状、棒状（六角棒状など）が挙げられる。 <Tin fine particles>
The composite of the present invention includes tin fine particles having an average particle diameter of 10 μm or less in addition to the above-described fibrous carbon nanostructure. Tin fine particles serve as a negative electrode active material that absorbs and releases lithium ions when the composite of the present invention is used as a negative electrode active material layer of a negative electrode for a lithium ion secondary battery. Then, by combining tin fine particles as the negative electrode active material and the above-described fibrous carbon nanostructure in a conductive state, the composite functions well as a negative electrode active material layer, and the capacity of the lithium ion secondary battery And it can contribute to improvement of cycle characteristics.
The shape of the tin fine particles is not particularly limited, and examples thereof include a spherical shape, a cubic shape, a rectangular shape, a plate shape (such as a hexagonal plate shape), a column shape, and a rod shape (such as a hexagonal rod shape).
　スズ微粒子の平均粒子径は、１０μｍ以下であることが必要であり、５μｍ以下であることが好ましく、１００ｎｍ以下であることがより好ましく、５０ｎｍ以下であることが更に好ましい。スズ微粒子の平均粒子径が１０μｍを超えると、二次電池に優れたサイクル特性を発揮させることができない。ここで、スズ微粒子の平均粒子径は、スズ微粒子の調製方法や調製条件を変更することにより調整することができる。例えば、スズ微粒子の調製に、後述するめっき処理を用いる本発明の複合体の製造方法を使用すれば、粒子径の小さいスズ微粒子を容易に析出させることができる。
　なお、リチウムイオン二次電池におけるサイクル特性などの特性向上という観点からは、スズ微粒子の平均粒子径はできるだけ小さいことが好ましく、その下限は特に限定されないが、スズ微粒子の平均粒子径は、例えば１０ｎｍ以上とすることができる。 The average particle size of the tin fine particles is required to be 10 μm or less, preferably 5 μm or less, more preferably 100 nm or less, and further preferably 50 nm or less. If the average particle diameter of the tin fine particles exceeds 10 μm, the cycle characteristics excellent in the secondary battery cannot be exhibited. Here, the average particle diameter of the tin fine particles can be adjusted by changing the preparation method and preparation conditions of the tin fine particles. For example, if the method for producing a composite of the present invention using a plating treatment described later is used for preparing tin fine particles, tin fine particles having a small particle diameter can be easily precipitated.
From the viewpoint of improving characteristics such as cycle characteristics in the lithium ion secondary battery, the average particle diameter of the tin fine particles is preferably as small as possible, and the lower limit is not particularly limited, but the average particle diameter of the tin fine particles is, for example, 10 nm. This can be done.
　そして、本発明の複合体において、少なくとも一部のスズ微粒子は、繊維状炭素ナノ構造体で構成される炭素マトリックスの内部に存在することが好ましく、スズ微粒子の大部分、例えば９０％以上が炭素マトリックスの内部に存在すること（すなわち、炭素マトリックスの内部に存在するスズ微粒子の割合が９０％以上であること）がより好ましい。そして、炭素マトリックスの内部に存在するスズ微粒子の割合は、１００％であることが更に好ましい。炭素マトリックスの内部に存在するスズ微粒子は、複合体表面に存在するスズ微粒子に比して、リチウムイオン二次電池の充放電を繰り返した場合であっても、集電体上の負極活物質層から脱離し難い。従って、炭素マトリックスの内部にスズ微粒子が存在する複合体を負極活物質層として用いれば、リチウムイオン二次電池に一層優れたサイクル特性を発揮させることができる。
　なお、本発明において、「炭素マトリックスの内部に存在するスズ微粒子の割合」は、例えばＦＥ－ＳＥＭ等で複合体の断面を観察して全スズ微粒子と炭素マトリックスの内部に存在するスズ微粒子の数を数え、全スズ微粒子に占める炭素マトリックスの内部に存在するスズ微粒子の割合（％）として算出することができる。 In the composite of the present invention, it is preferable that at least some of the tin particles are present inside the carbon matrix composed of the fibrous carbon nanostructure, and most of the tin particles, for example, 90% or more are carbon. More preferably, it is present inside the matrix (that is, the proportion of tin fine particles present inside the carbon matrix is 90% or more). The ratio of tin fine particles present inside the carbon matrix is more preferably 100%. Even if the tin fine particles existing inside the carbon matrix are repeatedly charged and discharged by the lithium ion secondary battery as compared with the tin fine particles present on the composite surface, the negative electrode active material layer on the current collector It is hard to detach from. Therefore, if a composite in which tin fine particles are present inside the carbon matrix is used as the negative electrode active material layer, the lithium ion secondary battery can exhibit more excellent cycle characteristics.
In the present invention, the “ratio of tin fine particles present in the carbon matrix” refers to the number of tin fine particles present in the total tin fine particles and the carbon matrix by observing the cross section of the composite with, for example, FE-SEM. Can be calculated as the ratio (%) of tin fine particles present in the carbon matrix in the total tin fine particles.
＜その他の成分＞
　複合体は、上述した繊維状炭素ナノ構造体およびスズ微粒子以外の成分を含んでいてもよい。その他の成分としては特に限定されず、例えば、複合体形成に用いる炭素膜の調製や、一般的な負極活物質層の調製の際に使用しうる既知の添加剤（分散剤、負極用結着材など）が挙げられる。なお、複合体中に占めるその他の成分の割合は、複合体中の固形分（残留溶媒を除く）の質量を１００質量％として、５質量％以下であることが好ましく、３質量％以下であることがより好ましく、１質量％以下であることが更に好ましい。 <Other ingredients>
The composite may contain components other than the above-described fibrous carbon nanostructure and tin fine particles. Other components are not particularly limited. For example, known additives (dispersant, binder for negative electrode) that can be used for preparing a carbon film used for forming a composite or for preparing a general negative electrode active material layer. Materials). The ratio of other components in the composite is preferably 5% by mass or less, preferably 3% by mass or less, based on 100% by mass of the solid content (excluding residual solvent) in the composite. More preferred is 1% by mass or less.
（複合体の製造方法）
　上述した本発明の複合体を製造する方法は、特に限定されないが、繊維状炭素ナノ構造体を含む炭素膜に、スズ含有化合物を含むめっき液を用いてめっき処理を行う本発明の複合体の製造方法を使用することが好ましい。本発明の複合体の製造方法によれば、炭素膜中にスズ微粒子を容易に析出させて、炭素マトリックスの内部にスズ微粒子が存在する複合体を効率良く得ることができる。 (Production method of composite)
The method for producing the composite of the present invention described above is not particularly limited, but the composite of the present invention is subjected to a plating treatment using a plating solution containing a tin-containing compound on a carbon film containing a fibrous carbon nanostructure. It is preferred to use a manufacturing method. According to the method for producing a composite of the present invention, it is possible to efficiently obtain a composite in which tin fine particles are present in the carbon matrix by easily depositing tin fine particles in the carbon film.
＜炭素膜＞
　炭素膜は、複数本の繊維状炭素ナノ構造体を膜状に集合させてなる繊維状炭素ナノ構造体の集合体よりなる。 <Carbon film>
The carbon film is composed of an aggregate of fibrous carbon nanostructures obtained by assembling a plurality of fibrous carbon nanostructures into a film shape.
＜＜炭素膜の調製＞＞
　複数本の繊維状炭素ナノ構造体を膜状に集合させて炭素膜を得る方法は、特に限定されないが、例えば以下の方法：
（ｉ）複数本の繊維状炭素ナノ構造体と溶媒とを含む分散液から溶媒を除去することにより製膜する方法
（ｉｉ）基材上に略垂直方向に成長させて得られた繊維状炭素ナノ構造体の集合体を基材に倒伏させ、その後必要に応じて圧縮することにより製膜する工程
　が挙げられる。中でも、（ｉ）の方法が好ましい。（ｉ）の工程を経て得られた炭素膜は、密度が疎となり易く、めっき処理においてめっき液が浸透し易い。そのため、炭素マトリックスの内部にスズ微粒子が存在する複合体を効率良く得ることができる。そして、当該複合体を負極活物質層として用いれば、リチウムイオン二次電池に一層優れたサイクル特性を発揮させることができる。以下、（ｉ）の方法を例に挙げて炭素膜の調製方法について詳述する。 << Preparation of carbon film >>
A method for obtaining a carbon film by assembling a plurality of fibrous carbon nanostructures into a film shape is not particularly limited, but for example, the following method:
(I) A method of forming a film by removing a solvent from a dispersion containing a plurality of fibrous carbon nanostructures and a solvent. (Ii) Fibrous carbon obtained by growing in a substantially vertical direction on a substrate. A step of forming a film by allowing the aggregate of nanostructures to fall on a substrate and then compressing as necessary is mentioned. Among these, the method (i) is preferable. The carbon film obtained through the step (i) tends to have a low density, and the plating solution is likely to penetrate in the plating process. Therefore, a composite in which tin fine particles are present inside the carbon matrix can be obtained efficiently. And if the said composite_body | complex is used as a negative electrode active material layer, the cycling characteristics which were further excellent in the lithium ion secondary battery can be exhibited. Hereinafter, the carbon film preparation method will be described in detail by taking the method (i) as an example.
［分散液］
　炭素膜の調製に用いる分散液としては、特に限定されることなく、既知の分散処理方法を用いて繊維状炭素ナノ構造体の集合体を溶媒に分散させてなる分散液を用いることができる。具体的には、分散液としては、繊維状炭素ナノ構造体と、溶媒とを含み、任意に分散剤などの分散液用添加剤を更に含有する分散液を用いることができる。 [Dispersion]
The dispersion used for the preparation of the carbon film is not particularly limited, and a dispersion obtained by dispersing an aggregate of fibrous carbon nanostructures in a solvent using a known dispersion treatment method can be used. Specifically, as the dispersion, a dispersion containing a fibrous carbon nanostructure and a solvent and optionally further containing an additive for dispersion such as a dispersant can be used.
―分散液中の成分―
　繊維状炭素ナノ構造体としては、「複合体」の項で上述した繊維状炭素ナノ構造体を用いることができる。 -Components in the dispersion-
As the fibrous carbon nanostructure, the fibrous carbon nanostructure described above in the section “Composite” can be used.
　また、分散液の溶媒（繊維状炭素ナノ構造体の分散媒）としては、特に限定されることなく、例えば、水、メタノール、エタノール、ｎ－プロパノール、イソプロパノール、ｎ－ブタノール、イソブタノール、ｔ－ブタノール、ペンタノール、ヘキサノール、ヘプタノール、オクタノール、ノナノール、デカノール、アミルアルコールなどのアルコール類、アセトン、メチルエチルケトン、シクロヘキサノンなどのケトン類、酢酸エチル、酢酸ブチルなどのエステル類、ジエチルエーテル、ジオキサン、テトラヒドロフランなどのエーテル類、Ｎ，Ｎ－ジメチルホルムアミド、Ｎ－メチルピロリドンなどのアミド系極性有機溶媒、トルエン、キシレン、クロロベンゼン、オルトジクロロベンゼン、パラジクロロベンゼンなどの芳香族炭化水素類などが挙げられる。これらは１種類のみを単独で用いてもよいし、２種類以上を混合して用いてもよい。 The solvent for the dispersion (dispersion medium for the fibrous carbon nanostructure) is not particularly limited. For example, water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t- Alcohols such as butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, amyl alcohol, ketones such as acetone, methyl ethyl ketone, cyclohexanone, esters such as ethyl acetate and butyl acetate, diethyl ether, dioxane, tetrahydrofuran, etc. Amides polar organic solvents such as ethers, N, N-dimethylformamide and N-methylpyrrolidone, aromatic hydrocarbons such as toluene, xylene, chlorobenzene, orthodichlorobenzene and paradichlorobenzene Kind and the like. These may be used alone or in combination of two or more.
　更に、分散液に任意に配合される分散液用添加剤としては、特に限定されることなく、分散剤などの分散液の調製に一般に使用される添加剤が挙げられる。
　なお、例えばろ過により分散液から溶媒を除去する際にろ紙が目詰まりするのを防止する観点、および、得られる複合体の物性（例えば、導電性）の低下を抑制する観点からは、分散剤などの分散液用添加剤の添加量は少量であることが好ましい。 Furthermore, the additive for dispersion that is arbitrarily blended in the dispersion is not particularly limited, and examples thereof include additives generally used for preparing dispersions such as dispersants.
In addition, for example, from the viewpoint of preventing the filter paper from being clogged when removing the solvent from the dispersion by filtration, and from the viewpoint of suppressing a decrease in physical properties (for example, conductivity) of the obtained composite, It is preferable that the amount of the additive for dispersion such as is small.
　そして、分散液の調製に用いる分散剤としては、繊維状炭素ナノ構造体を分散可能であり、前述した溶媒に溶解可能であれば、特に限定されることなく、界面活性剤、合成高分子または天然高分子を用いることができる。 The dispersant used for preparing the dispersion is not particularly limited as long as it can disperse the fibrous carbon nanostructure and can be dissolved in the solvent described above. Natural polymers can be used.
　ここで、界面活性剤としては、ドデシルスルホン酸ナトリウム、デオキシコール酸ナトリウム、コール酸ナトリウム、ドデシルベンゼンスルホン酸ナトリウムなどが挙げられる。
　また、合成高分子としては、例えば、ポリエーテルジオール、ポリエステルジオール、ポリカーボネートジオール、ポリビニルアルコール、部分けん化ポリビニルアルコール、アセトアセチル基変性ポリビニルアルコール、アセタール基変性ポリビニルアルコール、ブチラール基変性ポリビニルアルコール、シラノール基変性ポリビニルアルコール、エチレン－ビニルアルコール共重合体、エチレン－ビニルアルコール－酢酸ビニル共重合樹脂、ジメチルアミノエチルアクリレート、ジメチルアミノエチルメタクリレート、アクリル系樹脂、エポキシ樹脂、変性エポキシ系樹脂、フェノキシ樹脂、変性フェノキシ系樹脂、フェノキシエーテル樹脂、フェノキシエステル樹脂、フッ素系樹脂、メラミン樹脂、アルキッド樹脂、フェノール樹脂、ポリアクリルアミド、ポリアクリル酸、ポリスチレンスルホン酸、ポリエチレングリコール、ポリビニルピロリドンなどが挙げられる。
　更に、天然高分子としては、例えば、多糖類であるデンプン、プルラン、デキストラン、デキストリン、グアーガム、キサンタンガム、アミロース、アミロペクチン、アルギン酸、アラビアガム、カラギーナン、コンドロイチン硫酸、ヒアルロン酸、カードラン、キチン、キトサン、セルロース、並びに、その塩または誘導体が挙げられる。
　そして、これらの分散剤は、１種または２種以上を混合して用いることができる。 Here, examples of the surfactant include sodium dodecylsulfonate, sodium deoxycholate, sodium cholate, sodium dodecylbenzenesulfonate, and the like.
Examples of the synthetic polymer include polyether diol, polyester diol, polycarbonate diol, polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, acetal group-modified polyvinyl alcohol, butyral group-modified polyvinyl alcohol, and silanol group-modified. Polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene-vinyl alcohol-vinyl acetate copolymer resin, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, acrylic resin, epoxy resin, modified epoxy resin, phenoxy resin, modified phenoxy system Resin, phenoxy ether resin, phenoxy ester resin, fluorine resin, melamine resin, alkyd resin, phenol resin, Polyacrylamide, polyacrylic acid, polystyrene sulfonic acid, polyethylene glycol, and polyvinylpyrrolidone.
Furthermore, examples of natural polymers include polysaccharides such as starch, pullulan, dextran, dextrin, guar gum, xanthan gum, amylose, amylopectin, alginic acid, gum arabic, carrageenan, chondroitin sulfate, hyaluronic acid, curdlan, chitin, chitosan, Examples thereof include cellulose and salts or derivatives thereof.
And these dispersing agents can be used 1 type or in mixture of 2 or more types.
―分散液の性状―
　そして、分散液は、１ｍｍ以上の凝集体が目視で確認されないことが好ましい。また、分散液中の繊維状炭素ナノ構造体は、粒度分布計で測定した際のメジアン径（平均粒子径）の値が１５０μｍ以下となるレベルで分散していることが好ましい。分散液中で繊維状炭素ナノ構造体を良好に分散させれば、溶媒を除去して得られる炭素膜の密度むらが抑制される。そして密度むらの少ない炭素膜には、めっき液が満遍なく浸透し易く、炭素マトリックスの内部にスズ微粒子が存在する複合体を効率良く得ることができる。そして、当該複合体を負極活物質層として用いれば、リチウムイオン二次電池に一層優れたサイクル特性を発揮させることができる。 -Dispersion properties-
And it is preferable that the aggregate of 1 mm or more is not visually confirmed in the dispersion liquid. Moreover, it is preferable that the fibrous carbon nanostructures in the dispersion are dispersed at a level at which the median diameter (average particle diameter) measured by a particle size distribution meter is 150 μm or less. If the fibrous carbon nanostructure is well dispersed in the dispersion, the density unevenness of the carbon film obtained by removing the solvent is suppressed. In addition, the plating solution easily penetrates uniformly into the carbon film with less density unevenness, and a complex in which tin fine particles are present inside the carbon matrix can be efficiently obtained. And if the said composite_body | complex is used as a negative electrode active material layer, the cycling characteristics which were further excellent in the lithium ion secondary battery can be exhibited.
　また、分散液の固形分濃度は、繊維状炭素ナノ構造体の種類にもよるが、０．００１質量％以上２０質量％以下が好ましい。固形分濃度が０．００１質量％未満の場合、溶媒を除去して得られる炭素膜の量が少なくなり、製造効率を十分に高めることができない虞がある。また、固形分濃度が２０質量％超の場合、分散液中での繊維状炭素ナノ構造体の分散性が低下する虞があると共に、分散液の粘度が増加し、流動性が低下する。 Further, the solid content concentration of the dispersion is preferably 0.001% by mass or more and 20% by mass or less, although it depends on the type of the fibrous carbon nanostructure. When the solid content concentration is less than 0.001% by mass, the amount of the carbon film obtained by removing the solvent decreases, and the production efficiency may not be sufficiently increased. Moreover, when solid content concentration exceeds 20 mass%, while there exists a possibility that the dispersibility of the fibrous carbon nanostructure in a dispersion liquid may fall, the viscosity of a dispersion liquid will increase and fluidity | liquidity will fall.
―分散液の調製―
　なお、分散液として、繊維状炭素ナノ構造体の集合体を溶媒に分散させてなる市販の分散液を用いてもよいが、炭素膜の調製に先んじて分散液調製工程を実施して調製した分散液を用いることが好ましい。中でも、溶媒中で繊維状炭素ナノ構造体が良好に分散した分散液を使用し、炭素膜の密度むらを抑制して導電性などの物性に優れる複合体を得る観点からは、分散液としては、溶媒中に繊維状炭素ナノ構造体を添加してなる粗分散液をキャビテーション効果または解砕効果が得られる分散処理に供して得た分散液を用いることがより好ましい。 -Preparation of dispersion-
As the dispersion, a commercially available dispersion obtained by dispersing an aggregate of fibrous carbon nanostructures in a solvent may be used, but the dispersion was prepared by carrying out a dispersion preparation step prior to the preparation of the carbon film. It is preferable to use a dispersion. Above all, from the viewpoint of using a dispersion in which fibrous carbon nanostructures are well dispersed in a solvent, and obtaining a composite having excellent physical properties such as conductivity by suppressing uneven density of the carbon film, the dispersion is It is more preferable to use a dispersion obtained by subjecting a coarse dispersion obtained by adding fibrous carbon nanostructures to a solvent to a dispersion treatment in which a cavitation effect or a crushing effect is obtained.
　具体的には、上述した溶媒に対して上述した繊維状炭素ナノ構造体と任意の分散液用添加剤とを添加してなる粗分散液を、以下に詳細に説明するキャビテーション効果が得られる分散処理または解砕効果が得られる分散処理に供して得た分散液を用いることが好ましい。 Specifically, a coarse dispersion obtained by adding the above-described fibrous carbon nanostructure and any additive for dispersion to the solvent described above is a dispersion capable of obtaining a cavitation effect described in detail below. It is preferable to use a dispersion obtained by subjecting to a dispersion treatment capable of obtaining a treatment or crushing effect.
　キャビテーション効果が得られる分散処理は、液体に高エネルギーを付与した際、水に生じた真空の気泡が破裂することにより生じる衝撃波を利用した分散方法である。この分散方法を用いることにより、繊維状炭素ナノ構造体を良好に分散させることができる。 The dispersion treatment that provides a cavitation effect is a dispersion method that uses a shock wave generated by bursting of vacuum bubbles generated in water when high energy is applied to the liquid. By using this dispersion method, the fibrous carbon nanostructure can be favorably dispersed.
　ここで、キャビテーション効果が得られる分散処理の具体例としては、超音波による分散処理、ジェットミルによる分散処理および高剪断撹拌による分散処理が挙げられる。これらの分散処理は一つのみを行なってもよく、複数の分散処理を組み合わせて行なってもよい。より具体的には、例えば超音波ホモジナイザー、ジェットミルおよび高剪断撹拌装置が好適に用いられる。これらの装置は従来公知のものを使用すればよい。 Here, specific examples of the dispersion treatment that provides a cavitation effect include dispersion treatment using ultrasonic waves, dispersion treatment using a jet mill, and dispersion treatment using high shear stirring. Only one of these distributed processes may be performed, or a plurality of distributed processes may be combined. More specifically, for example, an ultrasonic homogenizer, a jet mill, and a high shear stirring device are preferably used. These devices may be conventionally known devices.
　繊維状炭素ナノ構造体の分散に超音波ホモジナイザーを用いる場合には、粗分散液に対し、超音波ホモジナイザーにより超音波を照射すればよい。照射する時間は、繊維状炭素ナノ構造体の量等により適宜設定すればよく、例えば、３分以上が好ましく、３０分以上がより好ましく、また、５時間以下が好ましく、２時間以下がより好ましい。また、例えば、出力は２０Ｗ以上５００Ｗ以下が好ましく、１００Ｗ以上５００Ｗ以下がより好ましく、温度は１５℃以上５０℃以下が好ましい。 When an ultrasonic homogenizer is used to disperse the fibrous carbon nanostructure, the coarse dispersion may be irradiated with ultrasonic waves using the ultrasonic homogenizer. The irradiation time may be appropriately set depending on the amount of the fibrous carbon nanostructure and the like, for example, preferably 3 minutes or more, more preferably 30 minutes or more, and preferably 5 hours or less, more preferably 2 hours or less. . For example, the output is preferably 20 W or more and 500 W or less, more preferably 100 W or more and 500 W or less, and the temperature is preferably 15 ° C. or more and 50 ° C. or less.
　また、ジェットミルを用いる場合、処理回数は、繊維状炭素ナノ構造体の量等により適宜設定すればよく、例えば、２回以上が好ましく、１００回以下が好ましく、５０回以下がより好ましい。また、例えば、圧力は２０ＭＰａ以上２５０ＭＰａ以下が好ましく、温度は１５℃以上５０℃以下が好ましい。 In the case of using a jet mill, the number of treatments may be appropriately set depending on the amount of the fibrous carbon nanostructure and the like, for example, preferably 2 times or more, preferably 100 times or less, more preferably 50 times or less. For example, the pressure is preferably 20 MPa or more and 250 MPa or less, and the temperature is preferably 15 ° C. or more and 50 ° C. or less.
　さらに、高剪断撹拌を用いる場合には、粗分散液に対し、高剪断撹拌装置により撹拌および剪断を加えればよい。旋回速度は速ければ速いほどよい。例えば、運転時間（機械が回転動作をしている時間）は３分以上４時間以下が好ましく、周速は５ｍ／秒以上５０ｍ／秒以下が好ましく、温度は１５℃以上５０℃以下が好ましい。 Furthermore, when high shear stirring is used, stirring and shearing may be applied to the coarse dispersion with a high shear stirring device. The faster the turning speed, the better. For example, the operation time (time during which the machine is rotating) is preferably 3 minutes or more and 4 hours or less, the peripheral speed is preferably 5 m / second or more and 50 m / second or less, and the temperature is preferably 15 ° C. or more and 50 ° C. or less.
　なお、上記したキャビテーション効果が得られる分散処理は、５０℃以下の温度で行なうことがより好ましい。溶媒の揮発による濃度変化が抑制されるからである。 In addition, it is more preferable to perform the dispersion treatment for obtaining the above-described cavitation effect at a temperature of 50 ° C. or lower. This is because a change in concentration due to the volatilization of the solvent is suppressed.
　解砕効果が得られる分散処理は、繊維状炭素ナノ構造体を溶媒中に均一に分散できることは勿論、上記したキャビテーション効果が得られる分散処理に比べ、気泡が消滅する際の衝撃波による繊維状炭素ナノ構造体の損傷を抑制することができる点で有利である。 The dispersion treatment that provides the crushing effect can uniformly disperse the fibrous carbon nanostructures in the solvent, as well as the fibrous carbon due to the shock wave when the bubbles disappear, compared to the dispersion treatment that provides the cavitation effect described above. This is advantageous in that damage to the nanostructure can be suppressed.
　この解砕効果が得られる分散処理では、粗分散液にせん断力を与えて繊維状炭素ナノ構造体の凝集体を解砕・分散させ、さらに粗分散液に背圧を負荷し、また必要に応じ、粗分散液を冷却することで、気泡の発生を抑制しつつ、繊維状炭素ナノ構造体を溶媒中に均一に分散させることができる。
　なお、粗分散液に背圧を負荷する場合、粗分散液に負荷した背圧は、大気圧まで一気に降圧させてもよいが、多段階で降圧することが好ましい。 In the dispersion treatment that provides this crushing effect, a shear force is applied to the coarse dispersion to break up and disperse the aggregates of the fibrous carbon nanostructures, and the back pressure is applied to the coarse dispersion. Accordingly, by cooling the coarse dispersion, the fibrous carbon nanostructure can be uniformly dispersed in the solvent while suppressing the generation of bubbles.
When a back pressure is applied to the coarse dispersion, the back pressure applied to the coarse dispersion may be reduced to atmospheric pressure all at once, but is preferably reduced in multiple stages.
　ここに、粗分散液にせん断力を与えて繊維状炭素ナノ構造体をさらに分散させるには、例えば、以下のような構造の分散器を有する分散システムを用いればよい。
　すなわち、分散器は、粗分散液の流入側から流出側に向かって、内径がｄ１の分散器オリフィスと、内径がｄ２の分散空間と、内径がｄ３の終端部と（但し、ｄ２＞ｄ３＞ｄ１である。）、を順次備える。
　そして、この分散器では、流入する高圧（例えば１０～４００ＭＰａ、好ましくは５０～２５０ＭＰａ）の粗分散液が、分散器オリフィスを通過することで、圧力の低下を伴いつつ、高流速の流体となって分散空間に流入する。その後、分散空間に流入した高流速の粗分散液は、分散空間内を高速で流動し、その際にせん断力を受ける。その結果、粗分散液の流速が低下すると共に、繊維状炭素ナノ構造体が良好に分散する。そして、終端部から、流入した粗分散液の圧力よりも低い圧力（背圧）の流体が、繊維状炭素ナノ構造体の分散液として流出することになる。 Here, in order to further disperse the fibrous carbon nanostructure by applying a shearing force to the coarse dispersion, for example, a dispersion system having a disperser having the following structure may be used.
In other words, the disperser has a disperser orifice having an inner diameter d1, a dispersion space having an inner diameter d2, and a terminal portion having an inner diameter d3 from the inflow side to the outflow side of the coarse dispersion liquid (where d2>d3> d1)).
In this disperser, the inflowing high-pressure (for example, 10 to 400 MPa, preferably 50 to 250 MPa) coarse dispersion passes through the disperser orifice, and becomes a high flow rate fluid with decreasing pressure. Into the dispersed space. Thereafter, the high-velocity coarse dispersion liquid flowing into the dispersion space flows at high speed in the dispersion space and receives a shearing force at that time. As a result, the flow rate of the coarse dispersion decreases, and the fibrous carbon nanostructure is well dispersed. Then, a fluid having a pressure (back pressure) lower than the pressure of the inflowing coarse dispersion liquid flows out from the terminal portion as the dispersion liquid of the fibrous carbon nanostructure.
　なお、粗分散液の背圧は、粗分散液の流れに負荷をかけることで粗分散液に負荷することができ、例えば、多段降圧器を分散器の下流側に配設することにより、粗分散液に所望の背圧を負荷することができる。
　そして、粗分散液の背圧を多段降圧器により多段階で降圧することで、最終的に繊維状炭素ナノ構造体の分散液を大気圧に開放した際に、分散液中に気泡が発生するのを抑制できる。 Note that the back pressure of the coarse dispersion can be applied to the coarse dispersion by applying a load to the flow of the coarse dispersion. For example, a rough pressure can be obtained by disposing a multistage step-down device downstream of the disperser. A desired back pressure can be applied to the dispersion.
Then, by reducing the back pressure of the coarse dispersion in multiple stages using a multistage pressure reducer, bubbles are generated in the dispersion when the dispersion of the fibrous carbon nanostructure is finally released to atmospheric pressure. Can be suppressed.
　また、この分散器は、粗分散液を冷却するための熱交換器や冷却液供給機構を備えていてもよい。というのは、分散器でせん断力を与えられて高温になった粗分散液を冷却することにより、粗分散液中で気泡が発生するのをさらに抑制できるからである。
　なお、熱交換器等の配設に替えて、粗分散液を予め冷却しておくことでも、繊維状炭素ナノ構造体を含む溶媒中で気泡が発生することを抑制できる。 Further, the disperser may include a heat exchanger for cooling the coarse dispersion and a cooling liquid supply mechanism. This is because the generation of bubbles in the coarse dispersion can be further suppressed by cooling the coarse dispersion that has been heated to a high temperature by applying a shearing force with the disperser.
In addition, it can suppress that a bubble generate | occur | produces in the solvent containing a fibrous carbon nanostructure also by cooling a rough dispersion liquid beforehand instead of arrangement | positioning of a heat exchanger etc.
　上記したように、この解砕効果が得られる分散処理では、キャビテーションの発生を抑制できるので、時として懸念されるキャビテーションに起因した繊維状炭素ナノ構造体の損傷、特に、気泡が消滅する際の衝撃波に起因した繊維状炭素ナノ構造体の損傷を抑制することができる。加えて、繊維状炭素ナノ構造体への気泡の付着や、気泡の発生によるエネルギーロスを抑制して、繊維状炭素ナノ構造体を均一かつ効率的に分散させることができる。 As described above, in the dispersion treatment that can obtain this crushing effect, the occurrence of cavitation can be suppressed, so damage to the fibrous carbon nanostructure caused by cavitation that is sometimes a concern, especially when the bubbles disappear. Damage to the fibrous carbon nanostructure due to the shock wave can be suppressed. In addition, it is possible to uniformly and efficiently disperse the fibrous carbon nanostructure by suppressing the attachment of bubbles to the fibrous carbon nanostructure and energy loss due to the generation of bubbles.
　以上のような構成を有する分散システムとしては、例えば、製品名「ＢＥＲＹＵ　ＳＹＳＴＥＭ　ＰＲＯ」（株式会社美粒製）などがある。そして、解砕効果が得られる分散処理は、このような分散システムを用い、分散条件を適切に制御することで、実施することができる。 As a distributed system having the above-described configuration, for example, there is a product name “BERYU SYSTEM PRO” (manufactured by Mie Co., Ltd.). And the dispersion | distribution process from which a crushing effect is acquired can be implemented by controlling a dispersion | distribution condition appropriately using such a dispersion | distribution system.
［溶媒の除去］
　分散液から溶媒を除去する方法としては、特に限定されることなく、乾燥やろ過などの既知の溶媒除去方法を用いることができる。中でも、効率的に溶媒を除去する観点からは、溶媒除去方法としては、減圧乾燥、真空乾燥またはろ過を用いることが好ましい。更に、容易かつ迅速に溶媒を除去する観点からは、溶媒除去方法としては、ろ過を用いることが好ましく、減圧ろ過を用いることが更に好ましい。迅速かつ効率的に溶媒を除去すれば、一度分散させた繊維状炭素ナノ構造体が再び凝集するのを抑制し、得られる炭素膜の密度むらを抑制することができる。
　ここで、分散液中の溶媒は完全に除去する必要はなく、溶媒の除去後に残った繊維状炭素ナノ構造体が集合体（炭素膜）としてハンドリング可能な状態であれば、多少の溶媒が残留していても問題はない。 [Removal of solvent]
The method for removing the solvent from the dispersion is not particularly limited, and a known solvent removing method such as drying or filtration can be used. Among these, from the viewpoint of efficiently removing the solvent, it is preferable to use reduced-pressure drying, vacuum drying or filtration as the solvent removal method. Furthermore, from the viewpoint of removing the solvent easily and quickly, the solvent removal method is preferably filtration, and more preferably vacuum filtration. If the solvent is removed quickly and efficiently, the once-dispersed fibrous carbon nanostructures can be prevented from aggregating again, and density unevenness of the resulting carbon film can be suppressed.
Here, it is not necessary to completely remove the solvent in the dispersion liquid. If the fibrous carbon nanostructure remaining after the removal of the solvent can be handled as an aggregate (carbon film), some solvent remains. There is no problem even if you do.
＜＜炭素膜の性状＞＞
　得られる炭素膜の厚みは、２μｍ以上であることが好ましく、５μｍ以上であることがより好ましく、１０μｍ以上であることが更に好ましく、２００μｍ以下であることが好ましく、１００μｍ以下であることがより好ましく、６０μｍ以下であることが更に好ましい。炭素膜の厚みが２μｍ以上であれば、得られる複合体の強度を確保することができる。一方、炭素膜の厚みが２００μｍ以下であれば、めっき処理の際に、めっき液が炭素膜の厚み方向中心部まで容易に浸透し、炭素マトリックスの内部に微粒子が存在する複合体を効率良く得ることができる。そして、当該複合体を負極活物質層として用いれば、リチウムイオン二次電池に一層優れたサイクル特性を発揮させることができる。 << Characteristics of carbon film >>
The thickness of the carbon film to be obtained is preferably 2 μm or more, more preferably 5 μm or more, further preferably 10 μm or more, preferably 200 μm or less, more preferably 100 μm or less. More preferably, it is 60 μm or less. When the thickness of the carbon film is 2 μm or more, the strength of the resulting composite can be ensured. On the other hand, if the thickness of the carbon film is 200 μm or less, the plating solution easily penetrates to the center of the carbon film in the thickness direction during the plating process, and efficiently obtains a composite in which fine particles are present inside the carbon matrix. be able to. And if the said composite_body | complex is used as a negative electrode active material layer, the cycling characteristics which were further excellent in the lithium ion secondary battery can be exhibited.
　また、炭素膜の密度は、０．０１ｇ／ｃｍ3以上であることが好ましく、０．１０ｇ／ｃｍ3以上であることがより好ましく、０．５０ｇ／ｃｍ3以上であることが更に好ましく、また、１．８０ｇ／ｃｍ3以下であることが好ましく、１．５０ｇ／ｃｍ3以下であることがより好ましく、１．２０ｇ／ｃｍ3以下であることが更に好ましい。炭素膜の密度が０．０１ｇ／ｃｍ3以上であれば、得られる複合体の強度を確保することができる。一方、炭素膜の密度が１．８０ｇ／ｃｍ3以下であれば、めっき処理の際にめっき液が炭素膜の厚み方向中心部まで容易に浸透し、炭素マトリックスの内部に微粒子が存在する複合体を効率良く得ることができる。そして、当該複合体を負極活物質層として用いれば、リチウムイオン二次電池に一層優れたサイクル特性を発揮させることができる。
　なお、本発明において、「炭素膜の密度」は、炭素膜の質量、面積および厚みを測定し、炭素膜の質量を体積（面積×厚み）で除して求めることができる。 The density of the carbon film is preferably 0.01 g / cm 3 or more, more preferably 0.10 g / cm 3 or more, still more preferably 0.50 g / cm 3 or more, , is preferably 1.80 g / cm 3 or less, more preferably 1.50 g / cm 3 or less, further preferably 1.20 g / cm 3 or less. If the density of the carbon film is 0.01 g / cm 3 or more, the strength of the resulting composite can be ensured. On the other hand, if the density of the carbon film is 1.80 g / cm 3 or less, a composite in which the plating solution easily penetrates to the central portion in the thickness direction of the carbon film and the fine particles are present inside the carbon matrix when plating is performed. Can be obtained efficiently. And if the said composite_body | complex is used as a negative electrode active material layer, the cycling characteristics which were further excellent in the lithium ion secondary battery can be exhibited.
In the present invention, the “density of the carbon film” can be determined by measuring the mass, area and thickness of the carbon film and dividing the mass of the carbon film by the volume (area × thickness).
＜めっき処理＞
　上述した炭素膜に対して、めっき液を用いて電解めっき処理または無電解めっき処理、好ましくは電解めっき処理を施すことにより、炭素膜表面および／または炭素膜内部に微粒子を析出させて、複合体を得ることができる。 <Plating treatment>
By subjecting the above-described carbon film to electrolytic plating treatment or electroless plating treatment, preferably electrolytic plating treatment, using a plating solution, fine particles are precipitated on the carbon film surface and / or inside the carbon film, thereby forming a composite. Can be obtained.
＜＜めっき液＞＞
　めっき処理に用いるめっき液は、溶媒中に、スズ含有化合物を含み、任意に、めっき液用添加剤（溶解補助剤およびノニオン系界面活性剤、並びにその他めっき液に一般に添加される添加剤）を更に含む。 << Plating solution >>
The plating solution used for the plating treatment contains a tin-containing compound in the solvent, and optionally contains additives for the plating solution (dissolution aids and nonionic surfactants, and other additives generally added to the plating solution). In addition.
［スズ含有化合物］
　スズ含有化合物としては、めっき処理を経て、炭素膜表面および／または炭素膜内部に、これら化合物に由来してスズ微粒子（スズめっき）を析出させることが可能であれば特に限定されない。スズ含有化合物としては、特に限定されるものではないが、ピロリン酸スズ、リン酸スズ、硫酸スズ（II）、硫酸スズ（IV）、塩化スズ（II）、塩化スズ（IV）、酢酸スズ（II）、および酢酸スズ（IV）、並びにこれらの水和物などが挙げられる。これらは、１種類のみを単独で用いてもよいし、２種類以上を併用してもよい。また、めっき液中におけるスズ含有化合物の濃度は、スズ微粒子を析出させることが可能であれば特に限定されず、適宜調整することができるが、例えば、０．０１ｍｏｌ／Ｌ以上３．０ｍｏｌ／Ｌ以下であることが好ましい。 [Tin-containing compounds]
The tin-containing compound is not particularly limited as long as it is possible to deposit tin fine particles (tin plating) on the surface of the carbon film and / or the inside of the carbon film through the plating process. The tin-containing compound is not particularly limited, but tin pyrophosphate, tin phosphate, tin (II) sulfate, tin (IV) sulfate, tin (II) chloride, tin (IV) chloride, tin acetate ( II), tin (IV) acetate, and hydrates thereof. These may be used alone or in combination of two or more. In addition, the concentration of the tin-containing compound in the plating solution is not particularly limited as long as tin fine particles can be precipitated, and can be adjusted as appropriate. For example, 0.01 mol / L or more and 3.0 mol / L The following is preferable.
［溶解補助剤］
　溶解補助剤は、上述したスズ含有化合物の、溶媒（例えば水）への溶解性を確保する目的で添加される。このような溶解補助剤は、上述したスズ含有化合物以外のイオン性化合物であり、例えば、ピロリン酸金属塩、リン酸金属塩、硫酸金属塩、金属塩化物、酢酸金属塩などが挙げられる。そして、溶解補助剤としてのイオン性化合物を用いる場合、溶解補助剤中に含まれる陰イオン成分は、スズ含有化合物中に含まれる陰イオン成分と同一であることが好ましい。例えば、スズ含有化合物としてピロリン酸スズを用いる場合は、溶解補助剤としてピロリン酸金属塩（ピロリン酸カリウムなど）を用いることが好ましい。
　なお、スズ含有化合物の溶解性を十分に向上させる観点から、めっき液中における溶解補助剤の濃度は、スズ含有化合物の濃度の２倍以上であることが好ましい。また、めっき液中における溶解補助剤の濃度の上限は特に限定されないが、通常スズ含有化合物の濃度の１００倍以下である。そして、めっき液中における溶解補助剤の濃度は、例えば、０．０４ｍｏｌ／Ｌ以上１２．０ｍｏｌ／Ｌ以下であることが好ましい。 [Solubility aid]
The solubilizer is added for the purpose of ensuring the solubility of the above-described tin-containing compound in a solvent (for example, water). Such a solubilizing agent is an ionic compound other than the above tin-containing compounds, and examples thereof include metal pyrophosphate, metal phosphate, metal sulfate, metal chloride, and metal acetate. And when using the ionic compound as a solubilizing agent, it is preferable that the anionic component contained in a solubilizing agent is the same as the anionic component contained in a tin containing compound. For example, when tin pyrophosphate is used as the tin-containing compound, it is preferable to use a metal pyrophosphate salt (such as potassium pyrophosphate) as a solubilizing agent.
In addition, from the viewpoint of sufficiently improving the solubility of the tin-containing compound, the concentration of the dissolution aid in the plating solution is preferably at least twice the concentration of the tin-containing compound. Moreover, although the upper limit of the density | concentration of the solubilizing agent in a plating solution is not specifically limited, Usually, it is 100 times or less of the density | concentration of a tin containing compound. And it is preferable that the density | concentration of the dissolution aid in a plating solution is 0.04 mol / L or more and 12.0 mol / L or less, for example.
［ノニオン系界面活性剤］
　めっき液は、ノニオン系界面活性剤を含むことが好ましい。ノニオン系界面活性剤を含むめっき液は、ノニオン系界面活性剤が繊維状炭素ナノ構造体との親和性に優れるためと推察されるが、炭素膜内部に容易に浸透することができる。そのため、ノニオン系界面活性剤を含むめっき液を用いれば、炭素マトリックスの内部にスズ微粒子が存在する複合体を効率良く得ることができる。そして、当該複合体を負極活物質層として用いれば、リチウムイオン二次電池に一層優れたサイクル特性を発揮させることができる。 [Nonionic surfactant]
The plating solution preferably contains a nonionic surfactant. The plating solution containing the nonionic surfactant is presumed to be because the nonionic surfactant has excellent affinity with the fibrous carbon nanostructure, but can easily penetrate into the carbon film. Therefore, if a plating solution containing a nonionic surfactant is used, a composite in which tin fine particles are present inside the carbon matrix can be obtained efficiently. And if the said composite_body | complex is used as a negative electrode active material layer, the cycling characteristics which were further excellent in the lithium ion secondary battery can be exhibited.
　そして、ノニオン系界面活性剤としては、ポリエーテル系界面活性剤、アルキルフェノール系界面活性剤、ポリエステル系界面活性剤、ソルビタンエステルエーテル系界面活性剤、アルキルアミン系界面活性剤等が挙げられる。これらの中でも、複合体の物性を高めてリチウムイオン二次電池のサイクル特性をより一層向上させる観点からは、ポリエーテル系界面活性剤が好ましい。ポリエーテル系界面活性剤としては、ポリエチレングリコール、ポリプロピレングリコール、ポリテトラメチレングリコール、ポリオキシエチレンオレイルエーテル、ポリオキシエチレンステアリルエーテル、ポリオキシエチレンラウリルエーテル、ポリオキシエチレンドデシルエーテル、ポリオキシエチレンノニルフェニルエーテル、ポリオキシエチレンオクチルフェニルエーテル、ポリオキシエチレン・ポリオキシプロピレンブロック共重合体が挙げられる。これらの中でもポリエチレングリコールが特に好ましい。なお、ノニオン系界面活性剤は１種単独で使用してもよいし、２種以上を併用してもよい。 Examples of nonionic surfactants include polyether surfactants, alkylphenol surfactants, polyester surfactants, sorbitan ester ether surfactants, alkylamine surfactants, and the like. Among these, polyether surfactants are preferable from the viewpoint of improving the physical properties of the composite and further improving the cycle characteristics of the lithium ion secondary battery. Polyether-based surfactants include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene dodecyl ether, polyoxyethylene nonylphenyl ether , Polyoxyethylene octyl phenyl ether, and polyoxyethylene / polyoxypropylene block copolymer. Among these, polyethylene glycol is particularly preferable. In addition, a nonionic surfactant may be used individually by 1 type and may use 2 or more types together.
　ノニオン系界面活性剤の重量平均分子量は、特に限定されないが、５００以上であることが好ましく、また２００００以下であることが好ましく、１００００以下であることがより好ましく、５０００以下であることが更に好ましく、４０００以下であることが特に好ましい。ノニオン系界面活性剤の重量平均分子量が上述の範囲内であれば、金属と繊維状炭素ナノ構造体を一層良好に複合化することができ、複合体の物性を更に高めることができる。
　なお、ノニオン系界面活性剤の重量平均分子量（Ｍｗ）は、テトラヒドロフランを溶離液とするゲルパーミエーションクロマトグラフィーにより、標準ポリスチレン換算で求めることができる。 The weight average molecular weight of the nonionic surfactant is not particularly limited, but is preferably 500 or more, preferably 20000 or less, more preferably 10,000 or less, and still more preferably 5000 or less. It is especially preferable that it is 4000 or less. If the weight average molecular weight of the nonionic surfactant is within the above-mentioned range, the metal and the fibrous carbon nanostructure can be combined more satisfactorily, and the physical properties of the composite can be further improved.
In addition, the weight average molecular weight (Mw) of a nonionic surfactant can be calculated | required in standard polystyrene conversion by the gel permeation chromatography which uses tetrahydrofuran as an eluent.
［その他のめっき液用添加剤］
　めっき液は、本発明の効果を損なわない範囲で、上述したスズ含有化合物、溶解補助剤、およびノニオン性界面活性剤以外に、光沢剤などの既知のめっき液用添加剤を含有していてもよい。 [Other additives for plating solution]
The plating solution may contain known additives for plating solutions such as brighteners in addition to the above-described tin-containing compound, solubilizing agent, and nonionic surfactant as long as the effects of the present invention are not impaired. Good.
［めっき液の製造方法］
　めっき液は、上述した成分を水などの既知の溶媒中に溶解または分散させることにより調製することができる。 [Plating solution manufacturing method]
The plating solution can be prepared by dissolving or dispersing the above-described components in a known solvent such as water.
＜＜めっき処理の方法＞＞
　炭素膜にめっき処理を施す方法は、スズ微粒子を析出させうる方法であれば特に限定されない。例えば、電解めっき処理を行う場合、陰極として、炭素膜のみを使用してもよいし、基板表面にカーボンテープ等を介して炭素膜を接着してなる積層体を使用してもよい。中でも、陰極としては、炭素膜内部へのめっき液の浸透を容易として、炭素マトリックスの内部に微粒子が存在する複合体を効率良く製造する観点からは、炭素膜のみからなる陰極を使用することが好ましい。また、炭素膜の両側に、この炭素膜と接しないように二枚の陽極を配置した状態で電解めっき処理を行うことで、炭素膜の両面から炭素膜の内部にかけて、微粒子を満遍なく析出させることもできる。
　まためっき処理としては、電解めっきに限らず、無電解めっきを採用することもできる。電解めっきの場合、直流めっきに限定されることはなく、電流反転めっき法やパルスめっき法も採用することができる。
　なお、めっき処理中、例えばスターラー等でめっき液を撹拌してもよい。
　そして炭素膜にめっき処理を行うに際し、めっき液中に炭素膜を浸漬させてからめっき処理を開始（例えば、電解めっき処理の場合においては通電を開始）するまでの待ち時間（めっき処理前待ち時間）を設けるのが好ましい。めっき処理前待ち時間は、好ましくは５分以上、より好ましくは１０分以上である。めっき処理前待ち時間が５分以上であれば、炭素膜表面がめっき液に十分に濡れた状態（炭素膜表面とめっき液とが馴染んだ状態）となり、炭素膜内部にまで、めっき液の浸透を促すことができる。また、めっき処理前待ち時間は、処理の効率等を考慮すれば、好ましくは６０分以下、より好ましくは３０分以下とすることができる。
　さらに、電解めっき処理の場合、通電量は、炭素膜のサイズ（面積および厚み）に応じて適宜調整することができ、通電量を適切に調整することで、炭素膜内部にスズ微粒子を好適な状態で担持させることができる。
　なお、めっき処理時間は、特に限定されないが、通常１０分以上である。 << Method of plating treatment >>
The method for plating the carbon film is not particularly limited as long as it is a method capable of precipitating tin fine particles. For example, when performing an electroplating process, only a carbon film may be used as the cathode, or a laminate formed by adhering a carbon film to the substrate surface via a carbon tape or the like may be used. Among them, as a cathode, it is possible to use a cathode composed only of a carbon film from the viewpoint of facilitating the penetration of the plating solution into the carbon film and efficiently producing a composite having fine particles inside the carbon matrix. preferable. In addition, by performing electroplating treatment with two anodes arranged on both sides of the carbon film so as not to contact the carbon film, fine particles can be uniformly deposited from both sides of the carbon film to the inside of the carbon film. You can also.
The plating treatment is not limited to electrolytic plating, and electroless plating can also be employed. In the case of electrolytic plating, there is no limitation to direct current plating, and current reversal plating and pulse plating can also be employed.
During the plating process, the plating solution may be stirred with a stirrer, for example.
When performing plating treatment on the carbon film, a waiting time from when the carbon film is immersed in the plating solution to when the plating treatment is started (for example, in the case of electrolytic plating treatment, energization is started) (wait time before plating treatment) ) Is preferably provided. The waiting time before the plating treatment is preferably 5 minutes or more, more preferably 10 minutes or more. If the waiting time before the plating process is 5 minutes or more, the carbon film surface is sufficiently wetted with the plating solution (the carbon film surface and the plating solution are familiar), and the plating solution penetrates into the carbon film. Can be encouraged. Further, the waiting time before the plating treatment is preferably 60 minutes or less, more preferably 30 minutes or less, considering the efficiency of the treatment.
Furthermore, in the case of electrolytic plating treatment, the amount of energization can be adjusted as appropriate according to the size (area and thickness) of the carbon film, and by appropriately adjusting the amount of energization, tin fine particles can be suitably used inside the carbon film. It can be carried in a state.
The plating time is not particularly limited, but is usually 10 minutes or longer.
（リチウムイオン二次電池用負極）
　上述した本発明の複合体は、本発明のリチウムイオン二次電池用負極の作製に用いることができる。具体的には、本発明のリチウムイオン二次電池用負極は、負極活物質層を備え、前記負極活物質層が本発明の複合体である。本発明のリチウムイオン二次電池用負極は、負極活物質層として本発明の複合体を用いているので、リチウムイオン二次電池を高容量化すると共に、当該リチウムイオン二次電池に十分に優れたサイクル特性を発揮させることができる。 (Anode for lithium ion secondary battery)
The composite of the present invention described above can be used for producing the negative electrode for a lithium ion secondary battery of the present invention. Specifically, the negative electrode for a lithium ion secondary battery of the present invention includes a negative electrode active material layer, and the negative electrode active material layer is the composite of the present invention. Since the negative electrode for a lithium ion secondary battery of the present invention uses the composite of the present invention as the negative electrode active material layer, the lithium ion secondary battery has a high capacity and is sufficiently superior to the lithium ion secondary battery. Cycle characteristics can be exhibited.
　ここで、本発明のリチウムイオン二次電池用負極は、本発明の複合体が負極活物質層として機能し得れば特に限定されず、負極活物質層としての複合体のみで構成されている負極であってもよいし、集電体上に負極活物質層としての複合体が配置された負極であってもよい。
　なお、本発明のリチウムイオン二次電池用負極が、集電体上に負極活物質層としての複合体が配置された負極である場合、負極活物質層は、集電体に接して配置されていてもよいが、負極活物質層は、接着層などの他の層を介して集電体上に配置されていてもよい。
　集電体としては、電気導電性を有し、かつ、電気化学的に耐久性のある材料が用いられる。具体的には、集電体としては、例えば、鉄、銅、アルミニウム、ニッケル、ステンレス鋼、チタン、タンタル、金、白金などの金属材料からなる集電体を用い得る。中でも、負極の集電体としては、銅からなる薄膜が好ましい。
　また、集電体と負極活物質層の間に任意に配置される接着層は、電気伝導性が確保され、且つ集電体と負極活物質層を接着可能であれば特に限定されない。接着層は、例えば、導電性カーボン等の導電材と、結着材とを含む層であることが好ましい。 Here, the negative electrode for a lithium ion secondary battery of the present invention is not particularly limited as long as the composite of the present invention can function as a negative electrode active material layer, and is composed only of the composite as a negative electrode active material layer. A negative electrode may be sufficient and the negative electrode by which the composite_body | complex as a negative electrode active material layer is arrange | positioned on the electrical power collector may be sufficient.
When the negative electrode for a lithium ion secondary battery of the present invention is a negative electrode in which a composite as a negative electrode active material layer is disposed on a current collector, the negative electrode active material layer is disposed in contact with the current collector. However, the negative electrode active material layer may be disposed on the current collector through another layer such as an adhesive layer.
As the current collector, an electrically conductive and electrochemically durable material is used. Specifically, as the current collector, for example, a current collector made of a metal material such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, or platinum can be used. Especially, as a collector of a negative electrode, the thin film which consists of copper is preferable.
The adhesive layer arbitrarily disposed between the current collector and the negative electrode active material layer is not particularly limited as long as electrical conductivity is ensured and the current collector and the negative electrode active material layer can be bonded. The adhesive layer is preferably a layer including a conductive material such as conductive carbon and a binder, for example.
　そして、リチウムイオン二次電池用負極の製造方法は特に限定されない。例えば、負極活物質層と集電体の間に接着層が存在するリチウムイオン二次電池用負極は、複合体の一方の表面に、導電材と、結着材と、溶剤とを含む接着層用ペーストを塗布する工程、接着層用ペーストが塗布された複合体の表面に集電体を積層する工程、および、接着層用ペースト中の溶剤を乾燥などにより除去する工程を経て製造することができる。 And the manufacturing method of the negative electrode for lithium ion secondary batteries is not specifically limited. For example, a negative electrode for a lithium ion secondary battery in which an adhesive layer is present between a negative electrode active material layer and a current collector has an adhesive layer containing a conductive material, a binder, and a solvent on one surface of the composite. The adhesive paste is applied to the surface of the composite coated with the adhesive layer paste, and the solvent in the adhesive layer paste is removed by drying or the like. it can.
（リチウムイオン二次電池）
　上述した本発明のリチウムイオン二次電池用負極は、リチウムイオン二次電池に組み込んで使用される。具体的には、リチウムイオン二次電池は、正極と、負極と、電解液と、セパレータを備え、前記負極を本発明のリチウムイオン二次電池用負極とする。なお、正極、電解液、およびセパレータは、いずれも既知のものを使用することができる。
　本発明のリチウムイオン二次電池用負極を備えるリチウムイオン二次電池は、高容量であると共に、十分に優れたサイクル特性を発揮する。 (Lithium ion secondary battery)
The above-described negative electrode for a lithium ion secondary battery of the present invention is used by being incorporated in a lithium ion secondary battery. Specifically, the lithium ion secondary battery includes a positive electrode, a negative electrode, an electrolytic solution, and a separator, and the negative electrode is used as a negative electrode for a lithium ion secondary battery of the present invention. Any known positive electrode, electrolytic solution, and separator can be used.
A lithium ion secondary battery including the negative electrode for a lithium ion secondary battery of the present invention has a high capacity and exhibits sufficiently excellent cycle characteristics.
　以下、本発明について実施例に基づき具体的に説明するが、本発明はこれら実施例に限定されるものではない。
　なお、リチウムイオン二次電池のサイクル特性評価は、以下の方法を使用して行った。
＜サイクル特性＞
　製造したリチウムイオン二次電池を、２５℃の環境下で２４時間静置した。次に、２５℃の環境下で、４．４Ｖ、０．１Ｃの充電、２．７５Ｖ、０．１Ｃの放電にて充放電の操作を行い、初期容量Ｃ０を測定した。その後、さらに、２５℃の環境下で、同様の充放電の操作を繰り返し、１０００サイクル後の容量Ｃ１を測定した。そして、サイクル前後での容量維持率ΔＣ（％）＝Ｃ１／Ｃ０×１００を算出し、下記の基準で評価した。容量維持率ΔＣの値が大きいほど、サイクル特性に優れていることを示す。
　Ａ：容量維持率ΔＣが９０％以上
　Ｂ：容量維持率ΔＣが８５％以上９０％未満
　Ｃ：容量維持率ΔＣが８０％以上８５％未満
　Ｄ：容量維持率ΔＣが７５％以上８０％未満 EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
The cycle characteristic evaluation of the lithium ion secondary battery was performed using the following method.
<Cycle characteristics>
The manufactured lithium ion secondary battery was left to stand in an environment of 25 ° C. for 24 hours. Next, in an environment of 25 ° C., charging and discharging operations were performed by charging at 4.4 V, 0.1 C, and discharging at 2.75 V, 0.1 C, and the initial capacity C0 was measured. Thereafter, the same charge / discharge operation was repeated under an environment of 25 ° C., and the capacity C1 after 1000 cycles was measured. Then, the capacity retention ratio ΔC (%) before and after the cycle = C1 / C0 × 100 was calculated and evaluated according to the following criteria. It shows that it is excellent in cycling characteristics, so that the value of capacity | capacitance maintenance factor (DELTA) C is large.
A: Capacity maintenance ratio ΔC is 90% or more B: Capacity maintenance ratio ΔC is 85% or more and less than 90% C: Capacity maintenance ratio ΔC is 80% or more and less than 85% D: Capacity maintenance ratio ΔC is 75% or more and less than 80%
（実施例１）
＜単層ＣＮＴを含む繊維状炭素ナノ構造体の合成＞
　実施例において用いる単層ＣＮＴを含む繊維状炭素ナノ構造体を、国際公開第２００６／０１１６５５号の記載に従って、スーパーグロース法により調製した（以下、「繊維状炭素ナノ構造体Ａ」という）。なお、金属触媒の鉄薄膜層の厚みは２ｎｍとした。
　得られた繊維状炭素ナノ構造体Ａは、ＢＥＴ比表面積が１０５０ｍ2／ｇ（未開口状態）、平均直径（Ａｖ）が３．３ｎｍであった。また、繊維状炭素ナノ構造体Ａを、ラマン分光光度計での測定において、単層ＣＮＴに特長的な１００～３００ｃｍ-1の低波数領域におけるラジアルブリージングモード（ＲＢＭ）のスペクトルが観察された。また、未開口状態におけるｔプロットは上に凸な形状を示し、その屈曲点は０．５５≦ｔ（ｎｍ）≦１．０の範囲にあり、全比表面積Ｓ１と内部比表面積Ｓ２との比は０．０５≦Ｓ２／Ｓ１≦０．３０を満たしていた。 (Example 1)
<Synthesis of fibrous carbon nanostructure containing single-walled CNT>
A fibrous carbon nanostructure containing single-walled CNTs used in the examples was prepared by the super-growth method (hereinafter referred to as “fibrous carbon nanostructure A”) as described in International Publication No. 2006/011655. The thickness of the iron catalyst thin film layer of the metal catalyst was 2 nm.
The obtained fibrous carbon nanostructure A had a BET specific surface area of 1050 m 2 / g (unopened state) and an average diameter (Av) of 3.3 nm. Further, when the fibrous carbon nanostructure A was measured with a Raman spectrophotometer, a spectrum of a radial breathing mode (RBM) in a low wavenumber region of 100 to 300 cm −1 characteristic for single-walled CNTs was observed. In addition, the t plot in the unopened state shows an upwardly convex shape, the inflection point is in the range of 0.55 ≦ t (nm) ≦ 1.0, and the ratio between the total specific surface area S1 and the internal specific surface area S2. Satisfies 0.05 ≦ S2 / S1 ≦ 0.30.
＜炭素膜の調製＞
　繊維状炭素ナノ構造体Ａを４００ｍｇ量り取り、溶媒としてのメチルエチルケトン２Ｌ中に混ぜ、ホモジナイザーにより２分間撹拌し、粗分散液を得た。湿式ジェットミル（株式会社常光製、ＪＮ－２０）を使用し、得られた粗分散液を湿式ジェットミルの０．５ｍｍの流路に１００ＭＰａの圧力で２サイクル通過させて、繊維状炭素ナノ構造体Ａをメチルエチルケトンに分散させた。そして、固形分濃度０．２０質量％の分散液Ａを得た。なお、得られた分散液Ａの性状を評価したところ、分散液Ａ中の繊維状炭素ナノ構造体Ａのメジアン径（平均粒子径）は２４．１μｍであった。得られた分散液Ａをキリヤマろ紙（Ｎｏ．５Ａ）を用いて減圧ろ過し、厚みが４０μｍ、密度が０．８５ｇ／ｃｍ3である炭素膜Ａを得た。 <Preparation of carbon film>
400 mg of fibrous carbon nanostructure A was weighed, mixed in 2 L of methyl ethyl ketone as a solvent, and stirred with a homogenizer for 2 minutes to obtain a crude dispersion. Using a wet jet mill (manufactured by Joko Co., Ltd., JN-20), the obtained coarse dispersion was passed through a 0.5 mm flow path of the wet jet mill for two cycles at a pressure of 100 MPa to obtain a fibrous carbon nanostructure. Form A was dispersed in methyl ethyl ketone. Then, a dispersion A having a solid content concentration of 0.20% by mass was obtained. In addition, when the property of the obtained dispersion A was evaluated, the median diameter (average particle diameter) of the fibrous carbon nanostructure A in the dispersion A was 24.1 μm. The obtained dispersion A was filtered under reduced pressure using Kiriyama filter paper (No. 5A) to obtain a carbon film A having a thickness of 40 μm and a density of 0.85 g / cm 3 .
＜複合体Ａの作製＞
　上述した炭素膜Ａを陰極、純スズ板を陽極として、スズめっき浴中で以下の条件で電解めっきを行うことで複合体Ａを作製した。なお、陽極としての純スズ板は、陰極としての炭素膜Ａの表裏両側に、それぞれ１枚ずつ合計２枚を、炭素膜Ａとは接しないように配置した。
［スズめっきのめっき液組成（溶媒：水）］
　スズ含有化合物：ピロリン酸スズ（Ｓｎ2Ｐ2Ｏ7）、濃度０．２５ｍｏｌ／Ｌ
　溶解補助剤：ピロリン酸カリウム（Ｋ4Ｐ2Ｏ7）、濃度１．０ｍｏｌ／Ｌ
　ノニオン系界面活性剤：ポリエチレングリコール（重量平均分子量６００）、濃度０．００２ｍｏｌ／Ｌ
　光沢剤：ホルムアルデヒド、濃度０．００５ｍｏｌ／Ｌ
［電析条件］
　電析モード：電流規制法
　電流密度：０．０５Ａ／ｄｍ2
　通電量：９６Ｃ
　めっき処理前待ち時間：３０分 <Preparation of composite A>
Composite A was produced by performing electroplating under the following conditions in a tin plating bath using the carbon film A described above as a cathode and a pure tin plate as an anode. In addition, the pure tin plate as an anode was disposed on both the front and back sides of the carbon film A as a cathode, one in total so as not to contact the carbon film A.
[Plating composition of tin plating (solvent: water)]
Tin-containing compound: tin pyrophosphate (Sn 2 P 2 O 7 ), concentration 0.25 mol / L
Solubilizer: potassium pyrophosphate (K 4 P 2 O 7 ), concentration 1.0 mol / L
Nonionic surfactant: Polyethylene glycol (weight average molecular weight 600), concentration 0.002 mol / L
Brightener: formaldehyde, concentration 0.005 mol / L
[Electrodeposition conditions]
Electrodeposition mode: Current regulation method Current density: 0.05 A / dm 2
Energization amount: 96C
Waiting time before plating: 30 minutes
　得られた複合体Ａの断面をＦＥ－ＳＥＭにて観察したところ、炭素マトリックスの内部にスズ微粒子が均一に析出している様子が観察された（図２参照）。なお、スズ微粒子の平均粒子径は５０ｎｍであった。また、スズ微粒子の９０％以上が炭素マトリックスの内部に存在することを確認した。 When the cross section of the obtained composite A was observed with an FE-SEM, it was observed that tin fine particles were uniformly deposited inside the carbon matrix (see FIG. 2). The average particle size of the tin fine particles was 50 nm. Further, it was confirmed that 90% or more of the tin fine particles were present inside the carbon matrix.
＜負極の作製＞
　上述のようにして得られた厚み４０μｍの複合体Ａの片面に、導電材としての導電性カーボンを含む導電性カーボンペースト（接着層用ペースト）を塗布した。次いで、この塗布面に集電体としての厚み２０μｍの銅箔を載せ、負極活物質層としての複合体Ａと集電体としての銅箔が接着層により接着してなる負極Ａを得た。 <Production of negative electrode>
A conductive carbon paste (adhesive layer paste) containing conductive carbon as a conductive material was applied to one side of the composite A having a thickness of 40 μm obtained as described above. Next, a copper foil having a thickness of 20 μm as a current collector was placed on the coated surface, and a negative electrode A in which the composite A as a negative electrode active material layer and the copper foil as a current collector were adhered by an adhesive layer was obtained.
＜正極の作製＞
　正極活物質としてのＬｉＣｏＯ2（体積平均粒子径Ｄ５０：１２μｍ）を１００質量部、導電材としてのアセチレンブラック（電気化学工業社製、「ＨＳ－１００」）を２質量部、正極用結着材としてのポリフッ化ビニリデン（クレハ社製、「＃７２０８」）を固形分相当で２質量部、およびＮ－メチルピロリドンを混合し、全固形分濃度を７０％とした。これらをプラネタリーミキサーにより混合し、正極用スラリー組成物を調製した。
　上述のようにして得られた正極用スラリー組成物を、コンマコーターで、集電体である厚み２０μｍのアルミ箔の上に、乾燥後の膜厚が１５０μｍ程度になるように塗布し、乾燥させた。この乾燥は、アルミ箔を０．５ｍ／分の速度で６０℃のオーブン内を２分間かけて搬送することにより行った。その後、１２０℃にて２分間加熱処理して、正極原反を得た。このプレス前の正極原反をロールプレスで圧延して、厚みが８０μｍのプレス後の正極を得た。 <Preparation of positive electrode>
100 parts by mass of LiCoO 2 (volume average particle diameter D50: 12 μm) as a positive electrode active material, 2 parts by mass of acetylene black (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, binder for positive electrode Polyvinylidene fluoride (“# 7208” manufactured by Kureha Co., Ltd.) as a solid content was mixed with 2 parts by mass and N-methylpyrrolidone to give a total solid content concentration of 70%. These were mixed by a planetary mixer to prepare a positive electrode slurry composition.
The positive electrode slurry composition obtained as described above was applied on a current collector 20 μm thick aluminum foil with a comma coater so that the film thickness after drying was about 150 μm and dried. It was. This drying was performed by transporting the aluminum foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a positive electrode raw material. The positive electrode raw material before pressing was rolled with a roll press to obtain a positive electrode after pressing with a thickness of 80 μm.
＜リチウムイオン二次電池の製造＞
　上記で得られたプレス後の正極と、両面に接着層を有するセパレータと、上記で得られた負極Ａとを、この順に積層すると共にこれらを接着することで、積層体を得た。得られた積層体を捲回機により捲回して、捲回体を得た。この捲回体を、６０℃、０．５ＭＰａでプレスし、扁平体とした。次いで、得られた扁平体を、電池の外装としてのアルミ包材外装で包み、アルミ包材外装に、電解液（溶媒：エチレンカーボネート／ジエチルカーボネート／ビニレンカーボネート（体積混合比）＝６８．５／３０／１．５、電解質：濃度１ＭのＬｉＰＦ6）を空気が残らないように注入した。さらに、アルミ包材外装の開口を密封するために、１５０℃のヒートシールをしてアルミ包材外装を閉口し、捲回型リチウムイオン二次電池を製造した。
　得られたリチウムイオン二次電池のサイクル特性を評価したところ、Ａ評価であった。 <Manufacture of lithium ion secondary batteries>
A laminate was obtained by laminating the positive electrode after pressing obtained above, a separator having adhesive layers on both sides, and the negative electrode A obtained above in this order and adhering them together. The obtained laminate was wound with a winding machine to obtain a wound body. The wound body was pressed at 60 ° C. and 0.5 MPa to obtain a flat body. Next, the obtained flat body is wrapped with an aluminum packaging material exterior as a battery exterior, and the electrolytic solution (solvent: ethylene carbonate / diethyl carbonate / vinylene carbonate (volume mixing ratio)) = 68.5 / 30 / 1.5, electrolyte: LiPF 6 ) with a concentration of 1M was injected so that no air remained. Further, in order to seal the opening of the aluminum packaging material exterior, heat sealing at 150 ° C. was performed to close the aluminum packaging material exterior, and a wound type lithium ion secondary battery was manufactured.
When the cycle characteristics of the obtained lithium ion secondary battery were evaluated, it was A evaluation.
（比較例１）
　複合体Ａに替えてスズ板を用いた以外は、負極Ａと同様にして負極Ｂを得た。
　そして、負極Ａに替えて負極Ｂを使用した以外は、実施例１と同様にして、リチウムイオン二次電池を作製した。そして、得られたリチウムイオン二次電池のサイクル特性を評価したところ、Ｄ評価であった。 (Comparative Example 1)
A negative electrode B was obtained in the same manner as the negative electrode A, except that a tin plate was used instead of the composite A.
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the negative electrode B was used instead of the negative electrode A. And when the cycle characteristic of the obtained lithium ion secondary battery was evaluated, it was D evaluation.
（比較例２）
　負極Ａに替えて、以下のようにして作製した負極Ｃを使用した以外は、実施例１と同様にして、リチウムイオン二次電池を作製した。そして、得られたリチウムイオン二次電池のサイクル特性を評価したところ、Ｃ評価であった。
＜負極Ｃの作製＞
　攪拌機付き５ＭＰａ耐圧容器に、１，３－ブタジエン３３部、イタコン酸３．５部、スチレン６３．５部、乳化剤としてのドデシルベンゼンスルホン酸ナトリウム０．４部、イオン交換水１５０部および重合開始剤としての過硫酸カリウム０．５部を入れ、十分に攪拌した後、５０℃に加温して重合を開始した。重合転化率が９６％になった時点で冷却して反応を停止して、負極用の粒子状結着材（ＳＢＲ）を含む混合物を得た。上記粒子状結着材を含む混合物に、５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整後、加熱減圧蒸留によって未反応単量体の除去を行った。その後、３０℃以下まで冷却し、所望の粒子状結着材を含む水分散液を得た。
　負極活物質としての人造黒鉛（体積平均粒子径Ｄ５０：１５．６μｍ）１００質量部、増粘剤としてのカルボキシメチルセルロースナトリウム塩（日本製紙社製、「ＭＡＣ３５０ＨＣ」）の２％水溶液を固形分相当で１質量部、および、固形分濃度が６８質量％となる量の水を混合した後、更に２５℃で６０分間混合した。次いで、固形分濃度が６２％となるようにイオン交換水を加え、２５℃で１５分間混合した。その後、得られた混合液に、上述した粒子状結着材を含む水分散液を固形分相当で１．５質量部、およびイオン交換水を加え、最終固形分濃度が５２％となるように調整し、さらに１０分間混合した。これを減圧下で脱泡処理し、流動性の良い負極用スラリー組成物を得た。
　上述のようにして得られた負極用スラリー組成物を、コンマコーターで、集電体である厚み２０μｍの銅箔の上に塗布し、乾燥させた。この乾燥は、銅箔を０．５ｍ／分の速度で６０℃のオーブン内を２分間かけて搬送することにより行った。その後、１２０℃にて２分間加熱処理して負極Ｃを得た。 (Comparative Example 2)
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the negative electrode C produced as follows was used instead of the negative electrode A. And when the cycle characteristic of the obtained lithium ion secondary battery was evaluated, it was C evaluation.
<Preparation of negative electrode C>
In a 5 MPa pressure vessel with a stirrer, 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 63.5 parts of styrene, 0.4 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water and a polymerization initiator After adding 0.5 parts of potassium persulfate as a mixture and sufficiently stirring, the mixture was heated to 50 ° C. to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing a particulate binder (SBR) for the negative electrode. A 5% aqueous sodium hydroxide solution was added to the mixture containing the particulate binder and the pH was adjusted to 8, and then the unreacted monomer was removed by heating under reduced pressure. Then, it cooled to 30 degrees C or less, and obtained the water dispersion liquid containing a desired particulate-form binder.
100% by mass of artificial graphite (volume average particle diameter D50: 15.6 μm) as a negative electrode active material, 2% aqueous solution of carboxymethyl cellulose sodium salt (“MAC350HC” manufactured by Nippon Paper Industries Co., Ltd.) as a thickener After mixing 1 part by mass and water in an amount such that the solid content concentration was 68% by mass, the mixture was further mixed at 25 ° C. for 60 minutes. Subsequently, ion-exchange water was added so that solid content concentration might be 62%, and it mixed at 25 degreeC for 15 minutes. Thereafter, 1.5 parts by mass of the aqueous dispersion containing the particulate binder described above and ion-exchanged water are added to the obtained mixed liquid so that the final solid content concentration is 52%. Adjust and mix for an additional 10 minutes. This was defoamed under reduced pressure to obtain a negative electrode slurry composition having good fluidity.
The negative electrode slurry composition obtained as described above was applied on a copper foil having a thickness of 20 μm, which was a current collector, using a comma coater and dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Then, the negative electrode C was obtained by heat-processing at 120 degreeC for 2 minute (s).
　上述した結果から、繊維状炭素ナノ構造体と、平均粒子径が１０μｍ以下であるスズ微粒子を含む複合体を負極活物質層として用いた実施例１では、比較例１および２に比して、リチウムイオン二次電池に優れたサイクル特性を発揮させ得ることが分かる。また、実施例１では、負極活物質としてスズ微粒子を用いているので、高容量のリチウムイオン二次電池を得ることができた。 From the results described above, in Example 1 using a composite containing fibrous carbon nanostructures and tin fine particles having an average particle diameter of 10 μm or less as a negative electrode active material layer, as compared with Comparative Examples 1 and 2, It can be seen that excellent cycle characteristics can be exhibited in the lithium ion secondary battery. In Example 1, since tin fine particles were used as the negative electrode active material, a high-capacity lithium ion secondary battery could be obtained.
　本発明の複合体によれば、リチウムイオン二次電池を高容量化すると共に、当該リチウムイオン二次電池に十分に優れたサイクル特性を発揮させることができるリチウムイオン二次電池用負極を提供することができる。
　また、本発明のリチウムイオン二次電池用負極によれば、リチウムイオン二次電池を高容量化すると共に、当該リチウムイオン二次電池に十分に優れたサイクル特性を発揮させることができる。
　そして、本発明の複合体の製造方法によれば、リチウムイオン二次電池を高容量化すると共に、当該リチウムイオン二次電池に十分に優れたサイクル特性を発揮させることができる複合体を、効率良く製造することができる。 According to the composite of the present invention, there is provided a negative electrode for a lithium ion secondary battery capable of increasing the capacity of the lithium ion secondary battery and causing the lithium ion secondary battery to exhibit sufficiently excellent cycle characteristics. be able to.
Moreover, according to the negative electrode for lithium ion secondary batteries of this invention, while being able to increase capacity of a lithium ion secondary battery, the said lithium ion secondary battery can fully exhibit the cycling characteristics which were excellent.
According to the method for producing a composite of the present invention, a composite capable of increasing the capacity of a lithium ion secondary battery and exhibiting sufficiently excellent cycle characteristics in the lithium ion secondary battery is efficiently produced. Can be manufactured well.

Claims (9)

  1. 　繊維状炭素ナノ構造体と、
    　平均粒子径が１０μｍ以下であるスズ微粒子を含む、複合体。     A fibrous carbon nanostructure;
    A composite comprising tin fine particles having an average particle diameter of 10 μm or less.
  2. 　前記繊維状炭素ナノ構造体を含む炭素マトリックスの内部に、前記スズ微粒子が存在する構造を有する、請求項１に記載の複合体。 The composite according to claim 1, wherein the composite has a structure in which the tin fine particles are present inside a carbon matrix containing the fibrous carbon nanostructure.
  3. 　前記繊維状炭素ナノ構造体は、カーボンナノチューブを含む、請求項１または２に記載の複合体。 The composite according to claim 1 or 2, wherein the fibrous carbon nanostructure includes carbon nanotubes.
  4. 　前記繊維状炭素ナノ構造体は、吸着等温線から得られるｔ－プロットが上に凸な形状を示す、請求項１～３の何れかに記載の複合体。 4. The composite according to claim 1, wherein the fibrous carbon nanostructure has a shape in which a t-plot obtained from an adsorption isotherm is convex upward.
  5. 　リチウムイオン二次電池負極用である、請求項１～４の何れかに記載の複合体。 The composite according to any one of claims 1 to 4, which is used for a negative electrode of a lithium ion secondary battery.
  6. 　負極活物質層を備え、前記負極活物質層が請求項５に記載の複合体である、リチウムイオン二次電池用負極。 A negative electrode for a lithium ion secondary battery, comprising a negative electrode active material layer, wherein the negative electrode active material layer is the composite according to claim 5.
  7. 　請求項１～５の何れかに記載の複合体を製造する方法であって、前記繊維状炭素ナノ構造体を含む炭素膜に、スズ含有化合物を含むめっき液を用いてめっき処理を行う工程を含む、製造方法。 A method for producing the composite according to any one of claims 1 to 5, wherein a plating treatment is performed on a carbon film containing the fibrous carbon nanostructure using a plating solution containing a tin-containing compound. A manufacturing method.
  8. 　前記めっき液は、更に、ポリエーテル系界面活性剤と、水とを含む、請求項７に記載の複合体の製造方法。 The method for producing a composite according to claim 7, wherein the plating solution further includes a polyether-based surfactant and water.
  9. 　前記炭素膜の密度が０．０１ｇ／ｃｍ3以上１．８０ｇ／ｃｍ3以下である、請求項７または８に記載の複合体の製造方法。 The density of the carbon film is less than 0.01 g / cm 3 or more 1.80 g / cm 3, method for manufacturing a composite body according to claim 7 or 8.
PCT/JP2017/032550 2016-09-16 2017-09-08 Composite body, negative electrode for lithium ion secondary batteries, and method for producing composite body WO2018051925A1 (en)

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JP2013243117A (en) * 2012-04-25 2013-12-05 Kyocera Corp Negative electrode for secondary battery, and secondary battery using the same
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WO2015064772A1 (en) * 2013-10-31 2015-05-07 日本ゼオン株式会社 Carbon nanotubes
JP2016088815A (en) * 2014-11-06 2016-05-23 日本ゼオン株式会社 Carbon nano structure aggregate and method for producing the same

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JP2013243117A (en) * 2012-04-25 2013-12-05 Kyocera Corp Negative electrode for secondary battery, and secondary battery using the same
JP2014038798A (en) * 2012-08-20 2014-02-27 Ulvac Japan Ltd Negative electrode structure of lithium ion secondary battery, and method of manufacturing the same
WO2015064772A1 (en) * 2013-10-31 2015-05-07 日本ゼオン株式会社 Carbon nanotubes
JP2016088815A (en) * 2014-11-06 2016-05-23 日本ゼオン株式会社 Carbon nano structure aggregate and method for producing the same

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