WO2015162848A1 - Negative electrode material for lithium ion secondary battery, process for producing same, negative electrode for lithium ion secondary battery, and lithium ion secondary battery - Google Patents

Negative electrode material for lithium ion secondary battery, process for producing same, negative electrode for lithium ion secondary battery, and lithium ion secondary battery Download PDF

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WO2015162848A1
WO2015162848A1 PCT/JP2015/001478 JP2015001478W WO2015162848A1 WO 2015162848 A1 WO2015162848 A1 WO 2015162848A1 JP 2015001478 W JP2015001478 W JP 2015001478W WO 2015162848 A1 WO2015162848 A1 WO 2015162848A1
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graphite
mass
negative electrode
parts
ion secondary
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French (fr)
Japanese (ja)
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田原　知之
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Ｊｆｅケミカル株式会社
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    • 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
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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 negative electrode material for a lithium ion secondary battery having scale-like graphite, a metal that can be alloyed with lithium, fine particle graphite, and / or carbon, and having a specific structure, and a method for producing the same.
  • Lithium ion secondary batteries are widely used as power sources for electronic devices because of their excellent characteristics of high voltage and high energy density. In recent years, miniaturization and higher performance of electronic devices have progressed, and there has been an increasing demand for higher energy density of lithium ion secondary batteries.
  • the alloy negative electrode has a discharge capacity far surpassing that of graphite, but the active material (active material) is pulverized and the electrode film is peeled off due to the large volume expansion accompanying the alloying, so that practical cycle characteristics are obtained. Absent.
  • Patent Document 1 metal particles that can be alloyed with lithium having an average particle size of 1/2 or less of the graphite are adhered to mesophase spherules by mechanochemical treatment, and then a resin binder is blended. It describes a method of granulating, further impregnating the granulated material with a carbon precursor, and heat-treating at 600 ° C. or higher. However, in the method of Patent Document 1, it is difficult to dispose a metal in the voids in particles having a graphite skeleton.
  • Patent Document 2 describes a method in which scaly graphite is laminated in a spherical shape, and amorphous carbon derived from metal particles and an amorphous carbon precursor is dispersed between scaly graphites.
  • it is difficult to form sufficient voids around the metal particles, and the strength of the granulated body is weak and the voids are crushed when the electrode is pressed. Cannot be absorbed sufficiently, and the cycle characteristics at a practical level are not obtained.
  • Patent Document 3 in claim 1, "a spherical composite composed of scaly graphite particles, calcined carbon and metal particles that can be alloyed with lithium, the composite having voids therein, and The scaly graphite particles are present non-parallel inside the composite, exist in a concentric orientation on the surface of the composite, and the metal particles are dispersed inside and / or on the surface of the composite particle.
  • a negative electrode material for a lithium ion secondary battery characterized in that it exists. Although this negative electrode material has metal particles that can be alloyed with lithium and is excellent in discharge capacity and cycle characteristics, a material that is further excellent in both discharge capacity and cycle characteristics is required.
  • Patent Document 4 describes a method in which scaly graphite is laminated in a spherical shape, and amorphous carbon derived from metal particles and an amorphous carbon precursor is dispersed between scaly graphites.
  • JP 2006-294476 A JP 2009-266795 A JP 2014-29833 A JP 2009-535776 A
  • the present invention has been made in view of the above situation, and can be used as a lithium ion secondary battery negative electrode material, which can sufficiently relax the expansion of the metal during charging, and has a high discharge capacity exceeding the theoretical capacity of graphite,
  • An object is to provide a material exhibiting excellent initial charge / discharge efficiency and cycle characteristics.
  • high discharge capacity and cycle characteristics can be obtained if graphite or carbon having an average particle size of 1/2 or less of the scale-like graphite inside is adhered to the surface of the granulated body and present inside. I found out. Furthermore, it has also been found that the cycle characteristics can be further improved by incorporating a conductive material into the granulated material.
  • the inside of the granulated body having flaky graphite has a void structure formed by overlapping non-parallel flaky graphite combined with a metal that can be alloyed with lithium, and the average particle size of the flaky graphite is 1/2 or less of graphite and / or carbon adheres to the surface of the granulated body and exists inside, Furthermore, a negative electrode material for a lithium ion secondary battery in which pyrolytic carbon is coated on the surface and inside of the granulated body,
  • the flake graphite is 50 parts by mass or more and less than 95 parts by mass
  • the metal is 1 part by mass or more and 30 parts by mass or less
  • Graphite and carbon whose average particle diameter is 1/2 or less of the scale-like graphite is more than 5 parts by mass, 50 parts by mass
  • a fibrous conductive material is present inside and on the surface of the granule,
  • the said conductive material is 0.1 mass part or more and 5 mass parts or less,
  • a negative electrode for a lithium ion secondary battery comprising the negative electrode material according to any one of (1) to (3) above.
  • a lithium ion secondary battery comprising the negative electrode for a lithium ion secondary battery according to (6) above.
  • the composite that is the negative electrode material of the present invention can sufficiently relax the expansion of metal particles that can be alloyed with lithium during charging, and exceeds the theoretical charge capacity of graphite. High discharge capacity, excellent initial charge / discharge efficiency and cycle characteristics.
  • the granule that is the negative electrode material of the present invention has a void structure formed by overlapping non-parallel flake graphite combined with a metal that can be alloyed with lithium, on the surface and inside of the granule. It is a spherical granule in which graphite and / or carbon having an average particle size of 1 ⁇ 2 or less of the scale-like graphite is present, and the surface and the inside of the granule are coated with pyrolytic carbon.
  • a fibrous conductive material is further contained.
  • FIG. 2 shows the appearance of the granulated body of the present invention
  • FIG. 4 shows the appearance of the conventional granulated body.
  • the granulated material of the present invention is a granulated material made of flaky graphite and earthy graphite having an average particle size of 1/2 or less of flaky graphite. Graphite is attached.
  • FIG. 4 shows a granulated body made only from flaky graphite. When both are compared, it can be seen that the granulated body of the present invention (FIG. 2) has fewer voids than that of the conventional example (FIG. 4).
  • FIG. 3 shows a cross section of the granulated body of the present invention
  • FIG. 5 shows a cross section of a conventional example.
  • lithium-alloyable metal and scaly graphite can be combined with, for example, lithium-alloyable metal and scaly graphite mixed with a binder that is a precursor of pyrolytic carbon, and then 100 to 600. It can be obtained by heat treatment in the temperature range of ° C. If a metal and scale-like graphite are compounded, it will not be limited to this method.
  • the binder that is a precursor of pyrolytic carbon include, but are not limited to, coal tar pitch, petroleum pitch, phenol resin, acenaphthylene, and the like. The binder may be diluted with a solvent during mixing.
  • composite means that scaly graphite and the metal are integrated and do not behave separately in the production process of the granulated body.
  • voids are effectively formed by non-parallel overlapping of a composite composed of scaly graphite and a metal that can be alloyed with lithium, so that the volume expansion of metal particles accompanying alloying Can be prevented, and the electrode film can be prevented from collapsing and peeling.
  • graphite or carbon having an average particle size of 1/2 or less of the scale-like graphite to the surface of the granulated body and existing inside the granulated body, the particle strength of the granulated body is greatly increased. For this reason, since the collapse of the granulated body due to the volume expansion of the metal particles during pressing and charging of the electrode film can be suppressed, it is considered that the discharge capacity and the cycle characteristics are unlikely to decrease.
  • the particle strength of the granulate is measured with a micro compression tester.
  • the particle strength of the granulated body is preferably 2 to 20 MPa, more preferably 3 to 10 MPa. When the particle strength is within this range, the internal voids are not crushed when the electrode film is pressed, and on the other hand, the particles are too hard and the filling property of the negative electrode is not deteriorated.
  • the average particle diameter D 50 of the granulated body is preferably in the range of 3 to 20 ⁇ m, and more preferably in the range of 5 to 15 ⁇ m.
  • the average particle diameter D 50 is a particle size of which cumulative frequency of a laser diffraction particle size distribution analyzer is 50% in the volume distribution ratio. If the average particle size is within this range, the granule particles are not too small, so it is not difficult to form a spherical granule due to the size limitation of the flake graphite, and the electrode film is too large. It can prevent the filling property of the granule inside.
  • the granulated body of the present invention is composed of 50 parts by mass of the scaly graphite with respect to 100 parts by mass of the total amount of the scaly graphite, the graphite having an average particle size of 1/2 or less of the scaly graphite, and carbon. Or more, less than 95 parts by weight, the metal is 1 part by weight or more and 30 parts by weight or less, the average particle size is less than or equal to 1 ⁇ 2 of the scaly graphite and carbon is more than 5 parts by weight, 50 parts by weight or less,
  • the pyrolytic carbon is 0.25 parts by mass or more and 20 parts by mass or less.
  • the fibrous conductive material is 0.1 parts by mass or more and 5 parts by mass or less.
  • the average particle diameter D 50 of the scaly graphite is preferably 6 ⁇ m or less, and more preferably in the range of 1 ⁇ m to 5 ⁇ m. If it is less than 1 ⁇ m, the influence of the exposure of the edge surface of graphite is large, and the charge / discharge efficiency is lowered. When it exceeds 6 ⁇ m, the void formed by overlapping the flake graphite non-parallelly becomes too large.
  • the average flatness (Ly / t) is preferably 2 or more, more preferably 5 to 40.
  • the average flatness means the ratio (Ly / t) of the thickness t of one particle of scaly graphite to the minor axis length Ly, and 100 scaly graphite particles are observed with a scanning electron microscope. Calculated as a simple average value of the measured flatness of each particle. When the average flatness is within this range, the formation of voids when graphite overlaps non-parallel is appropriate, and is not too small, and the voids when overlapping non-parallel do not become too large.
  • the average aspect ratio is preferably 3 or less, and more preferably 2 or less.
  • the aspect ratio means the ratio (Lx / Ly) of the long axis length Lx of one particle to the short axis length Ly, and the aspect ratio of each particle measured by observing arbitrary 100 particles with a scanning electron microscope.
  • the arithmetic average value of is the average aspect ratio.
  • the scaly graphite may be subjected to various chemical treatments in the liquid phase, gas phase, and solid phase, heat treatment, oxidation treatment, physical treatment, and the like.
  • the ratio of flaky graphite in the granulated body is that the flaky graphite and the average particle diameter are not more than 1 ⁇ 2 of the flaky graphite and the total amount of graphite and carbon: 100 parts by mass with respect to the flaky graphite.
  • Graphite is 50 parts by mass or more and less than 95 parts by mass, and more preferably 70 parts by mass or more and 90 parts by mass or less. This is because, when the amount is less than 50 parts by mass, the internal voids formed by non-parallel overlap of the complex made of the metal that can be alloyed with flaky graphite and lithium are reduced.
  • metals that can be alloyed with lithium As metals that can be alloyed with lithium combined with flaky graphite, Al, Pb, Zn, Sn, Bi, In, Mg, Ga, Cd, Ag, Si, B, Au, Pt, Pd, Sb, Ge, Examples thereof include metals such as Ni, preferably Si and Sn, and more preferably Si.
  • the alloyable metal may be an alloy of two or more of the above metals, and the above metal may form an oxide, a nitride, or a carbide.
  • the surface of the metal may be coated with oxide, nitride, carbide, carbon, or graphite.
  • the shape is not limited to a spherical shape, a flat shape or a crushed shape.
  • the ratio of the metal or metal compound in the granulated body is 1 mass with respect to the total amount of the scaly graphite and graphite and carbon whose average particle diameter is 1/2 or less of the scaly graphite: 100 parts by mass. Part to 30 parts by weight, particularly preferably 2 to 20 parts by weight. When the metal or metal compound is less than 1 part by mass, the effect of improving the discharge capacity is small, and when it exceeds 30 parts by mass, the expansion during charging may not be sufficiently absorbed, and the effect of improving the cycle characteristics may be small. is there.
  • the average particle diameter D 50 of the metal or metal compound is preferably 1 ⁇ m or less, more preferably 0.01 to 0.5 ⁇ m.
  • the metal or metal compound can be prepared by mechanical pulverization of a lump, precipitation by vapor phase or liquid phase reaction, and the shape can be crushed, spherical, fibrous, scale-like, or the like.
  • the crystal structure of the precipitated particles may be either crystalline or amorphous.
  • the graphite adhering to the surface of the granulated body and existing inside is natural graphite or artificial graphite, and carbon is hard carbon or soft carbon.
  • the graphite and carbon are important to make it easy to gather on the surface of the droplets by riding on the liquid flow in the droplets at the time of dry granulation, which will be described later. 1/3 or less is preferable.
  • the average particle size is preferably 2 ⁇ m or less, more preferably 1 ⁇ m or less.
  • the shape preferably has an average aspect ratio of 3 or less, more preferably 2 or less. When the average aspect ratio exceeds 3, resistance to the flow of the liquid in the droplet during dry granulation, which will be described later, becomes resistance and may be prevented from collecting on the surface of the droplet.
  • the ratio of graphite and carbon in the granulated body is 5 parts by mass with respect to 100 parts by mass of the total amount of graphite and carbon having the scale-like graphite and the average particle size of 1/2 or less of the scale-like graphite. More than 50 parts by mass, preferably 10 parts by mass or more and 30 parts by mass or less. When the amount of graphite and carbon is 5 parts by mass or less, it does not effectively adhere to the surface and inside of the granulated body, and when it exceeds 50 parts by mass, the granulated body becomes too dense and the granulated body becomes hard and the electrode density does not increase. Sometimes.
  • the granulated body further contains a fibrous conductive material.
  • the conductive material has a role of assisting electrical connection between the graphite or carbon forming the skeleton of the granulated body and the metal particles, and reduces the electrical resistance of the granulated body and improves the cycle characteristics.
  • the fibrous conductive material is preferably fibrous graphite and / or carbon, and any type can be used as long as it plays the role of electrically connecting graphite or carbon and metal particles, but carbon nanotubes and carbon nano-particles are particularly preferable. Such as fiber.
  • the average aspect ratio is preferably 30 or more and 300 or less.
  • the aspect ratio means the ratio (L / D) of the fiber diameter D to the fiber length L.
  • the content ratio of the fibrous conductive material is 0.1 parts by mass or more with respect to 100 parts by mass of the total amount of graphite and carbon having the scale-like graphite and the average particle size of 1/2 or less of the scale-like graphite.
  • the amount is preferably not more than mass parts, more preferably not less than 0.5 parts by mass and not more than 2 parts by mass.
  • the conductive material When the conductive material is less than 0.1 parts by mass, the effect of assisting electrical contact between particles is reduced, and the improvement in cycle characteristics may be reduced. When the conductive material exceeds 5 parts by mass, the bulky conductive material is sterically hindered. Therefore, the electrode density is difficult to increase and the initial efficiency may be lowered.
  • the method for producing a granulated body of the present invention further includes flaky graphite in which a metal that can be alloyed with lithium is combined, and graphite or carbon having an average particle size of 1/2 or less of the flaky graphite.
  • a fibrous conductive material is dispersed in an aqueous solution in which a binder, which is a precursor of pyrolytic carbon, is dissolved, dried and granulated, and then heat-treated in a temperature range of 700 to 1500 ° C.
  • Lithium-alloyable metal and scaly graphite composite is mixed with lithium-alloyable metal and scaly graphite and binder which is a precursor of pyrolytic carbon and heat treated at 100-600 ° C. Can be obtained. However, it is not limited to this method if the metal and the flake graphite are combined.
  • the binder that is a precursor of pyrolytic carbon include coal tar pitch, petroleum pitch, phenol resin, saccharides, and acenaphthylene.
  • the binder may be diluted with a solvent during mixing.
  • the proportion of pyrolytic carbon derived from the binder in the composite is 0.25 parts by mass or more and 20 parts by mass with respect to 100 parts by mass of the total amount of metal and scaly graphite that can be alloyed with lithium. Part or less, more preferably 0.5 part by weight or more and 10 parts by weight or less, and most preferably 1.0 part by weight or more and 10 parts by weight or less. If the amount is less than 0.25 parts by mass, the metal may not bind to the flaky graphite. If the amount exceeds 20 parts by mass, a lump of composite particles may be formed, and a granulated body having a void structure may not be produced.
  • the composite powder has a water-soluble carbon precursor binder together with graphite and / or carbon having an average particle size of 1 ⁇ 2 or less of the scale-like graphite, and, if necessary, a fibrous conductive material. Disperse in dissolved aqueous solution.
  • the proportion of pyrolytic carbon derived from the water-soluble binder is the total amount of the composite powder and the average particle size of graphite and carbon that is 1/2 or less of the flake graphite: 100 parts by mass, 0.25 mass part or more and 20 mass parts or less are preferable, More preferably, they are 1 mass part or more and 10 mass parts or less. If the amount is less than 0.25 parts by mass, the particle strength of the granulated material may be insufficient.
  • the total concentration of the composite powder, graphite, carbon, and fibrous conductive material is preferably adjusted to 10 to 50% by mass. If it is less than 10 parts by mass, the production efficiency is poor, and if it exceeds 50 parts by mass, the viscosity becomes so high that dry granulation described later may not be performed. Since the average particle size of the resulting granulated body is affected by the viscosity and concentration of the dispersion, the concentration may be adjusted according to the desired average particle size.
  • the obtained aqueous dispersion is dried and granulated with a spray dryer.
  • the spray drying method is a method in which an aqueous dispersion is sprayed and dried in high-temperature heated air, so that a granulated body having a uniform shape can be obtained.
  • the particle size of the dried granulated body can be adjusted by selecting a rotating disk type or a nozzle type as the solid content concentration and viscosity of the solution and the spraying method.
  • the inlet temperature (heated air temperature) of the spray dryer is preferably 100 to 250 ° C. If the inlet temperature is 100 to 250 ° C., the ultimate temperature of the dried product to be generated is 80 to 150 ° C., depending on the balance with the amount of liquid to be fed.
  • the firing step is a step of obtaining a negative electrode material for a lithium ion secondary battery by firing a dried granule coated with a carbon precursor of pyrolytic carbon in a non-oxidizing atmosphere.
  • the non-oxidizing atmosphere means, for example, an inert gas atmosphere such as nitrogen or argon having an oxygen concentration of 1000 ppm or less; a reducing gas atmosphere containing a reducing gas such as hydrogen or carbon monoxide; .
  • an inert gas atmosphere such as nitrogen or argon having an oxygen concentration of 1000 ppm or less
  • a reducing gas atmosphere containing a reducing gas such as hydrogen or carbon monoxide
  • the firing temperature in the firing step is preferably 700 to 1500 ° C, more preferably 800 to 1100 ° C.
  • the granulated body of the present invention may be fired at 700 to 1500 ° C. in a non-oxidizing atmosphere by mixing a granulated body after dry granulation with a precursor of pyrolytic carbon. By this step, the surface of the granulated body is covered with pyrolytic carbon.
  • the content of pyrolytic carbon finally obtained is 0.25 with respect to the total amount of graphite and carbon of the scale-like graphite and the average particle diameter of 1/2 or less of the scale-like graphite: 100 parts by mass. It is not less than 20 parts by mass, preferably 1 to 15 parts by mass, more preferably 5 to 10 parts by mass.
  • the negative electrode material of the present invention may be used by mixing with carbon materials such as different types of graphite materials and hard carbon in order to adjust battery characteristics such as capacity, density, and efficiency of the electrode to be produced.
  • the measurement methods used in the examples are as follows. (1) Measurement of average particle diameter The average particle diameter was measured by a particle diameter at which the cumulative frequency measured by a laser diffraction particle size meter was 50% by volume.
  • the metal content was defined by the amount added.
  • ICP emission analysis can be performed.
  • the ratio of flaky graphite, graphite 1/2 or less of flaky graphite, carbon, pyrolytic carbon, and fibrous conductive material The content of flaky graphite, graphite or carbon 1 ⁇ 2 or less of flaky graphite, and fibrous conductive material was defined by the added amount.
  • the content of the pyrolytic carbon amount can be calculated by multiplying the addition amount of the precursor by the residual carbon ratio at the firing temperature.
  • Cycle characteristics (%) (discharge capacity in 20th cycle / discharge capacity in 1st cycle) ⁇ 100 [Production of negative electrode material]
  • Example 1 A flaky graphite having an average particle size of 5 ⁇ m, an average flatness of 10 and an aspect ratio of 1.2 and silicon particles having an average particle size of 0.2 ⁇ m were kneaded at a soft pitch of 100 ° C. with a softening point of 60 ° C. and fired at 400 ° C. Composite particles were obtained.
  • the composite particles and soil graphite having an average particle size of 0.7 ⁇ m, an average flatness of 5 and an aspect ratio of 1.1 are added to an aqueous solution in which a resol-type phenol resin is dissolved, and spray-dried with a spray-drying device to obtain a spherical dry structure. Granules were obtained. Subsequently, the negative electrode material which is the target granulated body was obtained by baking at 1000 ° C. in a non-oxidizing atmosphere of nitrogen. The blending amount of each material was prepared such that the respective abundance ratios in the granulated body as the final product are as shown in Table 1.
  • Example 2 In Example 1, a negative electrode material was obtained in the same manner as in Example 1 except that flaky graphite having an average particle size of flaky graphite of 2.5 ⁇ m, an average flatness of 10 and an aspect ratio of 1.2 was used.
  • Example 3 In Example 1, a negative electrode material was obtained in the same manner as in Example 1 except that hard carbon having an average particle size of 1.5 ⁇ m and an aspect ratio of 1.2 was used instead of earth graphite.
  • Example 4 In Example 1, a negative electrode material was obtained in the same manner as in Example 1 except that multiwall-type carbon nanotubes having an outer diameter of 10 nm and a length of 3 ⁇ m were added as fibrous conductive materials to an aqueous solution in which a resol type phenol resin was dissolved.
  • Example 5 In Example 4, a negative electrode material was obtained in the same manner as in Example 4 except that the amount of fibrous conductive material added was halved.
  • Example 6 In Example 4, a negative electrode material was obtained in the same manner as in Example 4 except that multiwall-type carbon nanotubes having an outer diameter of 150 nm and a length of 5 ⁇ m were used as the fibrous conductive material.
  • Comparative Example 1 A flaky graphite having an average particle size of 5 ⁇ m, an average flatness of 10 and an aspect ratio of 1.2 and silicon particles having an average particle size of 0.2 ⁇ m were kneaded at a soft pitch of 100 ° C. with a softening point of 60 ° C.
  • Example 3 (Comparative Example 3)
  • a negative electrode material was obtained in the same manner as in Example 1 except that scaly graphite having an average flatness of 10 and an average particle size of 3.0 ⁇ m having an aspect ratio of 1.2 was used instead of soil graphite. It was.
  • evaluation battery Using the negative electrode materials produced in Examples 1 to 3 and Comparative Examples 1 to 3, evaluation batteries were produced in the following steps, and battery characteristics were evaluated.
  • the copper foil and the negative electrode mixture layer were punched into a columnar shape having a diameter of 15.5 mm to produce a working electrode (negative electrode) having a negative electrode mixture layer adhered to the copper foil.
  • the density of the negative electrode mixture layer was 1.4 g / cm 3 .
  • the electrolytic solution was prepared by dissolving LiPF 6 at a concentration of 1 mol / L in a mixed solvent of 33% by volume of ethylene carbonate and 67% by volume of methyl ethyl carbonate to prepare a nonaqueous electrolytic solution.
  • the obtained nonaqueous electrolytic solution was impregnated into a 20 ⁇ m-thick polypropylene porous body as a separator to produce a separator impregnated with the electrolytic solution.
  • it can produce according to a well-known method based on the concept of this invention.
  • FIG. 1 shows a button type secondary battery as a configuration of the evaluation battery.
  • the outer cup 1 and the outer can 3 were sealed by interposing an insulating gasket 6 at the peripheral portion thereof and caulking both peripheral portions.
  • a copper current collector 7 a made of nickel net, a cylindrical counter electrode (positive electrode) 4 made of lithium foil, a separator 5 impregnated with an electrolytic solution, and a negative electrode mixture 2 are attached to the inside of the outer can 3 in that order.
  • the separator 5 impregnated with the electrolytic solution was sandwiched between the current collector 7b and the working electrode (negative electrode) made of the negative electrode mixture 2, and the counter electrode 4 in close contact with the current collector 7a.
  • the current collector 7b is accommodated in the exterior cup 1
  • the counter electrode 4 is accommodated in the exterior can 3
  • the exterior cup 1 and the exterior can 3 are combined, and an insulating gasket is provided at the peripheral edge between the exterior cup 1 and the exterior can 3. 6 was interposed, and both peripheral portions were caulked and sealed.
  • the lithium ion secondary battery using the negative electrode material of the present invention has a high discharge capacity exceeding the theoretical capacity of graphite.
  • Comparative Examples 1 to 3 do not have graphite or carbon whose average particle diameter is 1/2 or less of the scale-like graphite, so that the particle strength is low and the cycle characteristics are inferior.
  • the negative electrode material of this invention is a negative electrode material with high particle
  • Table 2 when a fibrous conductive material is added, the electrical contact between silicon and graphite is further improved, and the cycle characteristics are particularly improved.
  • the present invention provides a negative electrode material that can sufficiently relieve the expansion during charging of metal, exhibits a high discharge capacity exceeding the theoretical capacity of graphite, excellent initial charge / discharge efficiency, and cycle characteristics. provide. Therefore, the lithium ion secondary battery using the negative electrode material of the present invention satisfies the recent demand for higher energy density of the battery, and is useful for downsizing and higher performance of equipment to be mounted.
  • the negative electrode material of the present invention can be used for high-performance lithium ion secondary batteries ranging from small to large, taking advantage of the characteristics.

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  • Chemical Kinetics & Catalysis (AREA)
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Abstract

The present invention is a negative electrode material for lithium ion secondary batteries which comprises granules including flake graphite, the inside of each granule having a porous structure configured of the flake graphite that has stacked in a non-parallel manner and that has been composited with a metal capable of being alloyed with lithium, wherein graphite and/or carbon having an average particle diameter not larger than 1/2 that of the flake graphite is adherent to the surface of the granules and is present in the inside thereof, and the surface and inside of each granule has been coated with pyrolytic carbon. The negative electrode material for lithium ion secondary batteries is characterized by comprising 50 parts by mass or more but less than 95 parts by mass of the flake graphite, 1-30 parts by mass of the metal, more than 5 parts by mass but not larger than 50 parts by mass of the graphite and carbon having an average particle diameter not larger than 1/2 that of the flake graphite, and 0.25-20 parts by mass of the pyrolytic carbon, relative to 100 parts by mass of the sum of the flake graphite and the graphite and carbon having an average particle diameter not larger than 1/2 that of the flake graphite.

Description

リチウムイオン二次電池用負極材料およびその製造方法、リチウムイオン二次電池負極ならびにリチウムイオン二次電池Negative electrode material for lithium ion secondary battery and method for producing the same, lithium ion secondary battery negative electrode and lithium ion secondary battery
　本発明は鱗片状黒鉛、リチウムと合金化可能な金属、微粒子黒鉛および／または炭素を有し、これらが特定の構造を有するリチウムイオン二次電池用負極材料及びその製造方法に関する。 The present invention relates to a negative electrode material for a lithium ion secondary battery having scale-like graphite, a metal that can be alloyed with lithium, fine particle graphite, and / or carbon, and having a specific structure, and a method for producing the same.
　リチウムイオン二次電池は、高電圧、高エネルギー密度という優れた特性を有するため電子機器の電源として広く普及している。近年、電子機器の小型化および高性能化が進み、リチウムイオン二次電池のさらなる高エネルギー密度化に対する要望が高まっている。 Lithium ion secondary batteries are widely used as power sources for electronic devices because of their excellent characteristics of high voltage and high energy density. In recent years, miniaturization and higher performance of electronic devices have progressed, and there has been an increasing demand for higher energy density of lithium ion secondary batteries.
　現在のリチウムイオン二次電池は、正極にＬｉＣｏＯ２、負極に黒鉛を用いたものが主流である。負極の黒鉛は充放電（charge and discharge）の可逆性に優れるものの、その放電容量はすでに層間化合物（intercalation compound）ＬｉＣ６に相当する理論値３７２ｍＡｈ／ｇに近い値まで到達している。このため、さらなる高エネルギー密度化を達成するためには、黒鉛より放電容量の大きい負極材料を開発する必要がある。 Current lithium ion secondary batteries are mainly those using LiCoO 2 for the positive electrode and graphite for the negative electrode. Although graphite negative electrode is excellent in reversibility of charging and discharging (charge and discharge), which reached a value close to the theoretical value 372 mAh / g, which corresponds to the discharge capacity already intercalation compound (intercalation compound) LiC 6. For this reason, in order to achieve higher energy density, it is necessary to develop a negative electrode material having a discharge capacity larger than that of graphite.
　そこで、黒鉛に替わる負極材料として、リチウムと合金を形成する金属が注目されている。合金負極は、黒鉛を遥かに凌ぐ放電容量を有するが、合金化に伴う大きな体積膨張による活物質（active material）の粉化や電極膜の剥離が生じるので、実用レベルのサイクル特性が得られていない。 Therefore, a metal forming an alloy with lithium is attracting attention as a negative electrode material replacing graphite. The alloy negative electrode has a discharge capacity far surpassing that of graphite, but the active material (active material) is pulverized and the electrode film is peeled off due to the large volume expansion accompanying the alloying, so that practical cycle characteristics are obtained. Absent.
　特許文献１では、メソフェーズ小球体の黒鉛表面に平均粒径が該黒鉛の１／２以下であるリチウムと合金化可能な金属粒子をメカノケミカル処理して付着させた後、樹脂バインダーを配合して造粒し、さらに該造粒物に炭素前駆物質を含浸させ、６００℃以上で熱処理する方法が記載されている。しかしながら特許文献１の方法では、黒鉛を骨格とする粒子中の空隙に金属を配置することが難しい。 In Patent Document 1, metal particles that can be alloyed with lithium having an average particle size of 1/2 or less of the graphite are adhered to mesophase spherules by mechanochemical treatment, and then a resin binder is blended. It describes a method of granulating, further impregnating the granulated material with a carbon precursor, and heat-treating at 600 ° C. or higher. However, in the method of Patent Document 1, it is difficult to dispose a metal in the voids in particles having a graphite skeleton.
　特許文献２では、鱗片状黒鉛を球形に積層させ、鱗片状黒鉛間に金属粒子および非晶質カーボン前駆体を由来とする非晶質カーボンを分散させる方法が記載されている。しかし、特許文献２の方法では、金属粒子の周囲に十分な空隙を形成することが難しいことに加え、造粒体の強度が弱く電極のプレス時に空隙が潰れてしまうため、金属粒子の充電膨張を十分に吸収することができず、実用レベルのサイクル特性が得られていない。 Patent Document 2 describes a method in which scaly graphite is laminated in a spherical shape, and amorphous carbon derived from metal particles and an amorphous carbon precursor is dispersed between scaly graphites. However, in the method of Patent Document 2, it is difficult to form sufficient voids around the metal particles, and the strength of the granulated body is weak and the voids are crushed when the electrode is pressed. Cannot be absorbed sufficiently, and the cycle characteristics at a practical level are not obtained.
　特許文献３では、請求項１で、「鱗片状黒鉛粒子、焼成炭素およびリチウムと合金化可能な金属粒子からなる球状の複合体であって、前記複合体が内部に空隙を有し、かつ前記鱗片状黒鉛粒子が前記複合体の内部では非平行に存在し、前記複合体の表面では同心円状に配向して存在し、かつ、前記金属粒子が前記複合体粒子内部および／または表面に分散して存在することを特徴とするリチウムイオン二次電池用負極材料。」が記載されている。この負極材料はリチウムと合金化可能な金属粒子を有し、放電容量、サイクル特性に優れているが、放電容量とサイクル特性の両方にさらに優れる材料が求められている。 In Patent Document 3, in claim 1, "a spherical composite composed of scaly graphite particles, calcined carbon and metal particles that can be alloyed with lithium, the composite having voids therein, and The scaly graphite particles are present non-parallel inside the composite, exist in a concentric orientation on the surface of the composite, and the metal particles are dispersed inside and / or on the surface of the composite particle. A negative electrode material for a lithium ion secondary battery, characterized in that it exists. Although this negative electrode material has metal particles that can be alloyed with lithium and is excellent in discharge capacity and cycle characteristics, a material that is further excellent in both discharge capacity and cycle characteristics is required.
　特許文献４では、鱗片状黒鉛を球形に積層させ、鱗片状黒鉛間に金属粒子および非晶質カーボン前駆体を由来とする非晶質カーボンを分散させる方法が記載されている。 Patent Document 4 describes a method in which scaly graphite is laminated in a spherical shape, and amorphous carbon derived from metal particles and an amorphous carbon precursor is dispersed between scaly graphites.
　特許文献４の方法では、金属粒子の周囲に十分な空隙を形成することが難しいことに加え、造粒体の強度が弱く電極のプレス時に空隙が潰れてしまうため、金属粒子の充電膨張を十分に吸収することができず、実用レベルのサイクル特性が得られていない。 In the method of Patent Document 4, it is difficult to form sufficient voids around the metal particles, and the strength of the granulated material is weak and the voids are crushed when the electrode is pressed. The cycle characteristics at a practical level are not obtained.
特開２００６－２９４４７６号公報JP 2006-294476 A 特開２００９－２６６７９５号公報JP 2009-266795 A 特開２０１４－２９８３３号公報JP 2014-29833 A 特開２００９－５３５７７６号公報JP 2009-535776 A
　本発明は、上述の状況を鑑みてなされたものであり、リチウムイオン二次電池負極材料として用いて、充電時の金属の膨張を充分に緩和でき、黒鉛の理論容量を超える高い放電容量と、優れた初期充放電効率およびサイクル特性を示す材料を提供することを目的とする。 The present invention has been made in view of the above situation, and can be used as a lithium ion secondary battery negative electrode material, which can sufficiently relax the expansion of the metal during charging, and has a high discharge capacity exceeding the theoretical capacity of graphite, An object is to provide a material exhibiting excellent initial charge / discharge efficiency and cycle characteristics.
　本発明では、平均粒径が内部の鱗片状黒鉛の１／２以下の黒鉛または炭素を造粒体の表面に付着させ、かつ内部に存在させれば、高い放電容量とサイクル特性が得られることを知見した。さらに導電材を上記の造粒体に含有させることにより、サイクル特性がさらに向上することも知見した。 In the present invention, high discharge capacity and cycle characteristics can be obtained if graphite or carbon having an average particle size of 1/2 or less of the scale-like graphite inside is adhered to the surface of the granulated body and present inside. I found out. Furthermore, it has also been found that the cycle characteristics can be further improved by incorporating a conductive material into the granulated material.
　上記のように高い放電容量とサイクル特性が得られる理由は、平均粒径が内部の鱗片状黒鉛の１／２以下の黒鉛または炭素を造粒体の表面に付着させ、かつ内部に存在させることで造粒体の粒子強度が向上するので、金属粒子を複合（composite）化した鱗片状黒鉛で形成される空隙が維持できるため、金属粒子の充電膨張が吸収されると考えられる。しかし、本発明はこれらの機序に限定されない。 The reason why high discharge capacity and cycle characteristics can be obtained as described above is that graphite or carbon having an average particle size of 1/2 or less of the scale-like graphite inside is adhered to the surface of the granulated body and exists inside. Since the particle strength of the granulated body is improved, the void formed by the scale-like graphite obtained by compositing the metal particles can be maintained, so that it is considered that the charge expansion of the metal particles is absorbed. However, the present invention is not limited to these mechanisms.
　すなわち本発明は、以下を提供する。
（１）鱗片状黒鉛を有する造粒体の内部がリチウムと合金化可能な金属と複合した鱗片状黒鉛が非平行に重なり合って形成する空隙構造を有し、平均粒径が前記鱗片状黒鉛の１／２以下の黒鉛および／または炭素が前記造粒体の表面に付着し、かつ内部に存在し、
さらに前記造粒体の表面および内部に熱分解炭素が被覆されたリチウムイオン二次電池用負極材料であって、
　前記鱗片状黒鉛と前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素の合計量：１００質量部に対して、
　前記鱗片状黒鉛が５０質量部以上、９５質量部未満、
　前記金属が１質量部以上、３０質量部以下、
　前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素が５質量部超、５０質量部以下、
前記熱分解炭素が０．２５質量部以上、２０質量部以下であることを特徴とするリチウムイオン二次電池用負極材料。
（２）さらに、繊維状導電材が前記造粒体の内部および表面に存在し、
前記鱗片状黒鉛と前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素の合計量：１００質量部に対して、
前記導電材が０．１質量部以上、５質量部以下であることを特徴とする（１）に記載のリチウムイオン二次電池用負極材料。
（３）前記繊維状導電材が、繊維状の黒鉛および／または繊維状の炭素である（１）または（２）に記載のリチウムイオン二次電池用負極材料。
（４）リチウムと合金化可能な金属粒子を複合した鱗片状黒鉛ならびに平均粒径が前記鱗片状黒鉛の１／２以下の黒鉛および／または炭素を、熱分解炭素の前駆物質である結着剤が溶解した溶液に分散させ、乾燥造粒した後、７００～１５００℃の温度範囲で熱処理して、（１）に記載のリチウムイオン二次電池用負極材料を製造する方法。
（５）熱分解炭素の前駆物質である結着剤が溶解した溶液にさらに繊維状導電材を分散させることを特徴とする（４）に記載のリチウムイオン二次電池用負極材料を製造する方法。
（６）上記（１）ないし（３）のいずれかに記載の負極材料を含有することを特徴とするリチウムイオン二次電池用負極。
（７）上記（６）に記載のリチウムイオン二次電池用負極を有することを特徴とするリチウムイオン二次電池。 That is, the present invention provides the following.
(1) The inside of the granulated body having flaky graphite has a void structure formed by overlapping non-parallel flaky graphite combined with a metal that can be alloyed with lithium, and the average particle size of the flaky graphite is 1/2 or less of graphite and / or carbon adheres to the surface of the granulated body and exists inside,
Furthermore, a negative electrode material for a lithium ion secondary battery in which pyrolytic carbon is coated on the surface and inside of the granulated body,
The total amount of the scaly graphite and the average particle diameter of graphite and carbon ½ or less of the scaly graphite: 100 parts by mass,
The flake graphite is 50 parts by mass or more and less than 95 parts by mass,
The metal is 1 part by mass or more and 30 parts by mass or less,
Graphite and carbon whose average particle diameter is 1/2 or less of the scale-like graphite is more than 5 parts by mass, 50 parts by mass or less,
The said pyrolytic carbon is 0.25 mass part or more and 20 mass parts or less, The negative electrode material for lithium ion secondary batteries characterized by the above-mentioned.
(2) Furthermore, a fibrous conductive material is present inside and on the surface of the granule,
The total amount of the scaly graphite and the average particle diameter of graphite and carbon ½ or less of the scaly graphite: 100 parts by mass,
The said conductive material is 0.1 mass part or more and 5 mass parts or less, The negative electrode material for lithium ion secondary batteries as described in (1) characterized by the above-mentioned.
(3) The negative electrode material for a lithium ion secondary battery according to (1) or (2), wherein the fibrous conductive material is fibrous graphite and / or fibrous carbon.
(4) A scaly graphite compounded with metal particles that can be alloyed with lithium, and a graphite and / or carbon whose average particle diameter is ½ or less of the scaly graphite, and a binder that is a precursor of pyrolytic carbon. A method for producing a negative electrode material for a lithium ion secondary battery according to (1), wherein the negative electrode material for lithium ion secondary battery according to (1) is dispersed by being dispersed in a solution in which is dissolved and dried and granulated, followed by heat treatment in a temperature range of 700 to 1500 ° C.
(5) The method for producing a negative electrode material for a lithium ion secondary battery according to (4), wherein a fibrous conductive material is further dispersed in a solution in which a binder as a precursor of pyrolytic carbon is dissolved. .
(6) A negative electrode for a lithium ion secondary battery, comprising the negative electrode material according to any one of (1) to (3) above.
(7) A lithium ion secondary battery comprising the negative electrode for a lithium ion secondary battery according to (6) above.
　本発明の負極材料である複合体は、リチウムイオン二次電池用負極材料に用いた場合に、充電時にリチウムと合金化可能な金属粒子の膨張を充分に緩和でき、黒鉛の理論充電容量を超える高い放電容量、優れた初期充放電効率およびサイクル特性を示す。 When used as a negative electrode material for a lithium ion secondary battery, the composite that is the negative electrode material of the present invention can sufficiently relax the expansion of metal particles that can be alloyed with lithium during charging, and exceeds the theoretical charge capacity of graphite. High discharge capacity, excellent initial charge / discharge efficiency and cycle characteristics.
単極評価用のボタン型二次電池の断面図である。It is sectional drawing of the button type secondary battery for single pole evaluation. シリコンを複合した鱗片状黒鉛と平均粒径が鱗片状黒鉛の１／２以下の土状黒鉛で作製した造粒体の外観を示す電子顕微鏡写真である。It is an electron micrograph which shows the external appearance of the granulated material produced with the scale-like graphite which compounded silicon, and the earth-like graphite whose average particle diameter is 1/2 or less of the scale-like graphite. シリコンを複合した鱗片状黒鉛と平均粒径が鱗片状黒鉛１／２以下の土状黒鉛で作製した造粒体の断面を示す電子顕微鏡写真である。It is an electron micrograph which shows the cross section of the granulated material produced with the scale-like graphite which compounded silicon, and the earth-like graphite whose average particle diameter is 1/2 or less of scale-like graphite. シリコンを複合した鱗片状黒鉛のみで作製した造粒体の外観を示す電子顕微鏡写真である。It is an electron micrograph which shows the external appearance of the granule produced only with the scale-like graphite which compounded silicon. シリコンを複合した鱗片状黒鉛のみで作製した造粒体の断面を示す電子顕微鏡写真である。It is an electron micrograph which shows the cross section of the granule produced only with the scale-like graphite which compounded silicon.
　〔本発明の造粒体〕
　本発明の負極材料である造粒体は、内部がリチウムと合金化可能な金属と複合した鱗片状黒鉛が非平行に重なり合って形成する空隙構造を有し、前記造粒体の表面および内部に平均粒径が前記鱗片状黒鉛の１／２以下の黒鉛および／または炭素が存在する球状の造粒体であり、さらに前記造粒体の表面および内部に熱分解炭素が被覆される。好ましくはさらに繊維状導電材を含有する。 [Granulated product of the present invention]
The granule that is the negative electrode material of the present invention has a void structure formed by overlapping non-parallel flake graphite combined with a metal that can be alloyed with lithium, on the surface and inside of the granule. It is a spherical granule in which graphite and / or carbon having an average particle size of ½ or less of the scale-like graphite is present, and the surface and the inside of the granule are coated with pyrolytic carbon. Preferably, a fibrous conductive material is further contained.
　図２は本願発明の造粒体の外観を、図４は従来例の造粒体の外観を各々示す。本願発明の造粒体は鱗片状黒鉛と平均粒径が鱗片状黒鉛の１／２以下の土状黒鉛で作製した造粒体であり、この造粒体の表面には鱗片状黒鉛と土状黒鉛が付着している。一方、図４は鱗片状黒鉛のみで作製した造粒体である。両者を比較すると本願発明（図２）の造粒体の方が従来例（図４）のそれよりも空隙が少ないのが良くわかる。
図３は本願発明の造粒体の断面を、図５は従来例の断面を各々示す。図３に示す造粒体の断面は、粒径４μｍ程度の鱗片状黒鉛粒子が非平行に重なり合って形成する空隙が内部に存在している。また図３では明確にはわからないが、平均粒径が鱗片状黒鉛の１／２以下の黒鉛(粒径1μｍ程度)が、造粒体の表面では略同心円状に存在しかつ内部にも存在することが確かめられている。本願発明の図３と従来例の図５を比較すると明らかなように、本願発明の造粒体の方が空隙率が非常に少ないことが良くわかる。 FIG. 2 shows the appearance of the granulated body of the present invention, and FIG. 4 shows the appearance of the conventional granulated body. The granulated material of the present invention is a granulated material made of flaky graphite and earthy graphite having an average particle size of 1/2 or less of flaky graphite. Graphite is attached. On the other hand, FIG. 4 shows a granulated body made only from flaky graphite. When both are compared, it can be seen that the granulated body of the present invention (FIG. 2) has fewer voids than that of the conventional example (FIG. 4).
FIG. 3 shows a cross section of the granulated body of the present invention, and FIG. 5 shows a cross section of a conventional example. In the cross section of the granulated body shown in FIG. 3, voids formed by non-parallel overlapping of scaly graphite particles having a particle size of about 4 μm are present inside. Although not clearly shown in FIG. 3, graphite having an average particle size of 1/2 or less than that of scaly graphite (particle size of about 1 μm) is present on the surface of the granule in a substantially concentric shape and also in the interior. It has been confirmed. As is apparent from a comparison between FIG. 3 of the present invention and FIG. 5 of the conventional example, it is well understood that the granulated body of the present invention has a much lower porosity.
　リチウムと合金化可能な金属と鱗片状黒鉛との複合化は、例えば、リチウムと合金化可能な金属と鱗片状黒鉛を熱分解炭素の前駆物質である結着剤と混合したあと、１００～６００℃の温度範囲で熱処理することで得られる。金属と鱗片状黒鉛が複合されれば本方法に限定されない。熱分解炭素の前駆物質である結着剤は、コールタールピッチ、石油ピッチ、フェノール樹脂、アセナフチレンなどを使用できるが、これらに限定されない。結着剤は混合時に溶媒で希釈してもよい。 For example, lithium-alloyable metal and scaly graphite can be combined with, for example, lithium-alloyable metal and scaly graphite mixed with a binder that is a precursor of pyrolytic carbon, and then 100 to 600. It can be obtained by heat treatment in the temperature range of ° C. If a metal and scale-like graphite are compounded, it will not be limited to this method. Examples of the binder that is a precursor of pyrolytic carbon include, but are not limited to, coal tar pitch, petroleum pitch, phenol resin, acenaphthylene, and the like. The binder may be diluted with a solvent during mixing.
　ここで、複合とは鱗片状黒鉛と前記金属とが一体となっており造粒体の製造工程において別々に分かれて挙動することがないことをいう。 Here, “composite” means that scaly graphite and the metal are integrated and do not behave separately in the production process of the granulated body.
　本発明の造粒体は、鱗片状黒鉛とリチウムと合金化可能な金属からなる複合体が非平行に重なり合うことにより内部に空隙が有効に形成されるので、合金化に伴う金属粒子の体積膨張を吸収し、電極膜の崩壊や剥離を防ぐことができる。さらに、平均粒径が該鱗片状黒鉛の１／２以下の黒鉛または炭素を該造粒体の表面に付着させ、かつ内部に存在させることで、造粒体の粒子強度が大幅に増大する。このため電極膜のプレスおよび充電時の金属粒子の体積膨張による造粒体の崩壊を抑制できるので放電容量やサイクル特性の低下を起こしにくいと考えられる。 In the granulated material of the present invention, voids are effectively formed by non-parallel overlapping of a composite composed of scaly graphite and a metal that can be alloyed with lithium, so that the volume expansion of metal particles accompanying alloying Can be prevented, and the electrode film can be prevented from collapsing and peeling. Further, by attaching graphite or carbon having an average particle size of 1/2 or less of the scale-like graphite to the surface of the granulated body and existing inside the granulated body, the particle strength of the granulated body is greatly increased. For this reason, since the collapse of the granulated body due to the volume expansion of the metal particles during pressing and charging of the electrode film can be suppressed, it is considered that the discharge capacity and the cycle characteristics are unlikely to decrease.
　造粒体の粒子強度は微小圧縮試験機で測定する。造粒体の粒子強度は２～２０ＭＰａが好ましく、３～１０ＭＰａが好ましい。この範囲内の粒子強度であると、電極膜のプレス時に内部空隙が圧壊することがなく、一方で粒子が硬すぎて負極の充填性が悪くなることもない。 The particle strength of the granulate is measured with a micro compression tester. The particle strength of the granulated body is preferably 2 to 20 MPa, more preferably 3 to 10 MPa. When the particle strength is within this range, the internal voids are not crushed when the electrode film is pressed, and on the other hand, the particles are too hard and the filling property of the negative electrode is not deteriorated.
　造粒体の平均粒子径Ｄ５０は３～２０μｍの範囲であることが好ましく、５～１５μｍの範囲であることがさらに好ましい。本発明において、平均粒子径Ｄ５０はレーザー回折式粒度分布計の累積度数が体積分布率で５０％となる粒子径である。平均粒子径がこの範囲であると、造粒体の粒子が小さすぎないので鱗片状黒鉛の大きさの制約により球状の造粒体を形成することが難しくなることがなく、大きすぎて電極膜中における造粒体の充填性が悪くなることを防げる。 The average particle diameter D 50 of the granulated body is preferably in the range of 3 to 20 μm, and more preferably in the range of 5 to 15 μm. In the present invention, the average particle diameter D 50 is a particle size of which cumulative frequency of a laser diffraction particle size distribution analyzer is 50% in the volume distribution ratio. If the average particle size is within this range, the granule particles are not too small, so it is not difficult to form a spherical granule due to the size limitation of the flake graphite, and the electrode film is too large. It can prevent the filling property of the granule inside.
　本発明の造粒体は、前記鱗片状黒鉛と前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素の合計量：１００質量部に対して、前記鱗片状黒鉛が５０質量部以上、９５質量部未満、前記金属が１質量部以上、３０質量部以下、前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素が５質量部超、５０質量部以下、前記熱分解炭素が０．２５質量部以上、２０質量部以下である。好ましくは、さらに前記繊維状導電材が０．１質量部以上、５質量部以下である。
〔造粒体の原料〕
＜鱗片状黒鉛＞
　本発明で用いられる鱗片状黒鉛は、リチウムイオンを吸蔵・放出ができ、後述の特定の形状であることが好ましい。 The granulated body of the present invention is composed of 50 parts by mass of the scaly graphite with respect to 100 parts by mass of the total amount of the scaly graphite, the graphite having an average particle size of 1/2 or less of the scaly graphite, and carbon. Or more, less than 95 parts by weight, the metal is 1 part by weight or more and 30 parts by weight or less, the average particle size is less than or equal to ½ of the scaly graphite and carbon is more than 5 parts by weight, 50 parts by weight or less, The pyrolytic carbon is 0.25 parts by mass or more and 20 parts by mass or less. Preferably, the fibrous conductive material is 0.1 parts by mass or more and 5 parts by mass or less.
[Raw material of granulated body]
<Scaly graphite>
The scaly graphite used in the present invention can occlude and release lithium ions, and preferably has a specific shape described later.
　鱗片状黒鉛の平均粒子径Ｄ５０は６μｍ以下であることが好ましく、１μｍ～５μｍの範囲であることがさらに好ましい。１μｍ未満であると黒鉛のエッジ面の露出の影響が大きく充放電効率が低下する。６μｍを超えると鱗片状黒鉛が非平行に重なり合って形成する空隙が大きくなり過ぎる。形状については、平均扁平度（Ｌｙ／ｔ）が２以上であるのが好ましく、５～４０であるのがより好ましい。ここで平均扁平度とは、鱗片状黒鉛の１粒子の厚さｔの短軸長Ｌｙに対する比（Ｌｙ／ｔ）を意味し、走査型電子顕微鏡によって１００個の鱗片状黒鉛粒子を観察して測定した各粒子の扁平度の単純平均値として算出する。平均扁平度がこの範囲であると黒鉛が非平行に重なり合ったときの空隙の形成が適切で、小さすぎることがなく、また非平行に重なり合ったときの空隙が大きくなり過ぎることもない。 The average particle diameter D 50 of the scaly graphite is preferably 6 μm or less, and more preferably in the range of 1 μm to 5 μm. If it is less than 1 μm, the influence of the exposure of the edge surface of graphite is large, and the charge / discharge efficiency is lowered. When it exceeds 6 μm, the void formed by overlapping the flake graphite non-parallelly becomes too large. As for the shape, the average flatness (Ly / t) is preferably 2 or more, more preferably 5 to 40. Here, the average flatness means the ratio (Ly / t) of the thickness t of one particle of scaly graphite to the minor axis length Ly, and 100 scaly graphite particles are observed with a scanning electron microscope. Calculated as a simple average value of the measured flatness of each particle. When the average flatness is within this range, the formation of voids when graphite overlaps non-parallel is appropriate, and is not too small, and the voids when overlapping non-parallel do not become too large.
　さらに形状については、平均アスペクト比が３以下であることが好ましく、２以下であることがより好ましい。平均アスペクト比が３を超える場合には、鱗片状黒鉛が非平行に重なり合って形成する空隙が大きくなり過ぎること、造粒体が球形状になりにくいことがある。なおアスペクト比は、１粒子の長軸長Ｌｘの短軸長Ｌｙに対する比（Ｌｘ／Ｌｙ）を意味し、走査型電子顕微鏡によって任意の１００個の粒子を観察して測定した各粒子のアスペクト比の算術平均値を平均アスペクト比とする。 Further, regarding the shape, the average aspect ratio is preferably 3 or less, and more preferably 2 or less. When the average aspect ratio exceeds 3, the voids formed by the non-parallel overlap of the scaly graphite may become too large, and the granulated body may be difficult to have a spherical shape. The aspect ratio means the ratio (Lx / Ly) of the long axis length Lx of one particle to the short axis length Ly, and the aspect ratio of each particle measured by observing arbitrary 100 particles with a scanning electron microscope. The arithmetic average value of is the average aspect ratio.
　前記鱗片状黒鉛は、液相、気相、固相における各種化学的処理、熱処理、酸化処理、物理的処理などを施したものであってもよい。 The scaly graphite may be subjected to various chemical treatments in the liquid phase, gas phase, and solid phase, heat treatment, oxidation treatment, physical treatment, and the like.
　前記造粒体中の鱗片状黒鉛の割合は、前記鱗片状黒鉛と前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素の合計量：１００質量部に対して、前記鱗片状黒鉛が５０質量部以上、９５質量部未満であり、７０質量部以上、９０質量部以下であることがより好ましい。５０質量部未満だと鱗片状黒鉛とリチウムと合金化可能な金属からなる複合体が非平行に重なり合うことにより形成される内部空隙が減少するためである。９５質量部以上だと鱗片状黒鉛の１／２以下の黒鉛および炭素が造粒体の表面および内部に十分に存在できないことがあり造粒体の強度が向上しにくい。
＜リチウムと合金可能な金属＞
　鱗片状黒鉛と複合させるリチウムと合金化可能な金属としては、Ａｌ、Ｐｂ、Ｚｎ、Ｓｎ、Ｂｉ、Ｉｎ、Ｍｇ、Ｇａ、Ｃｄ、Ａｇ、Ｓｉ、Ｂ、Ａｕ、Ｐｔ、Ｐｄ、Ｓｂ、Ｇｅ、Ｎｉ等の金属が挙げられ、好ましくはＳｉ、Ｓｎであり、より好ましくはＳｉである。また合金化可能な金属は上記金属の二種以上の合金であってもよく、上述金属が酸化物、窒化物、炭化物を形成していてもよい。また上述金属の表面に、酸化物、窒化物、炭化物、炭素または黒鉛が被覆されていてもよい。形状は、球状、扁平状、破砕状など限定されない。前記造粒体中の金属または金属化合物の割合は、前記鱗片状黒鉛と前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素の合計量：１００質量部に対して、１質量部以上、３０質量部以下であり、２～２０質量部であるのが特に好ましい。金属または金属化合物が１質量部未満の場合は放電容量向上の効果が小さく、３０質量部超の場合は充電時の膨張を十分に吸収できない場合があり、サイクル特性の改良効果が小さくなることがある。 The ratio of flaky graphite in the granulated body is that the flaky graphite and the average particle diameter are not more than ½ of the flaky graphite and the total amount of graphite and carbon: 100 parts by mass with respect to the flaky graphite. Graphite is 50 parts by mass or more and less than 95 parts by mass, and more preferably 70 parts by mass or more and 90 parts by mass or less. This is because, when the amount is less than 50 parts by mass, the internal voids formed by non-parallel overlap of the complex made of the metal that can be alloyed with flaky graphite and lithium are reduced. If it is 95 parts by mass or more, graphite and carbon less than ½ of the scale-like graphite may not be sufficiently present on the surface and inside of the granulated body, and it is difficult to improve the strength of the granulated body.
<Metal that can be alloyed with lithium>
As metals that can be alloyed with lithium combined with flaky graphite, Al, Pb, Zn, Sn, Bi, In, Mg, Ga, Cd, Ag, Si, B, Au, Pt, Pd, Sb, Ge, Examples thereof include metals such as Ni, preferably Si and Sn, and more preferably Si. The alloyable metal may be an alloy of two or more of the above metals, and the above metal may form an oxide, a nitride, or a carbide. The surface of the metal may be coated with oxide, nitride, carbide, carbon, or graphite. The shape is not limited to a spherical shape, a flat shape or a crushed shape. The ratio of the metal or metal compound in the granulated body is 1 mass with respect to the total amount of the scaly graphite and graphite and carbon whose average particle diameter is 1/2 or less of the scaly graphite: 100 parts by mass. Part to 30 parts by weight, particularly preferably 2 to 20 parts by weight. When the metal or metal compound is less than 1 part by mass, the effect of improving the discharge capacity is small, and when it exceeds 30 parts by mass, the expansion during charging may not be sufficiently absorbed, and the effect of improving the cycle characteristics may be small. is there.
　金属または金属化合物の平均粒子径Ｄ５０は１μｍ以下であるのが好ましく、０．０１～０．５μｍであるのがより好ましい。金属または金属化合物の平均粒子径Ｄ５０が１μｍを超える場合は充電膨張時の粉化が起こりやすくなり、０．０１μｍ未満では凝集および酸化による劣化を抑制するのが難しくなり、放電容量が低下する場合がある。金属または金属化合物の調製は、塊状物の機械粉砕、気相または液相反応による析出により行うことができ、形状は破砕状、球状、繊維状、鱗片状などを使用することができる。該析出粒子の結晶構造は結晶質、非晶質の何れでもよい。
＜平均粒径が鱗片状黒鉛の１／２以下の黒鉛および／または炭素＞
　造粒体の表面に付着および内部に存在する黒鉛は天然黒鉛または人造黒鉛、炭素はハードカーボンまたはソフトカーボンであることが好ましい。該黒鉛および炭素は、後述の乾燥造粒時に液滴中の液の流れに乗って液滴表面に集まりやすくすることが肝要のため、平均粒子径は鱗片状黒鉛の１／２以下であり、１／３以下が好ましい。平均粒径は、好ましくは２μｍ以下、より好ましくは１μｍ以下である。さらに形状は、平均アスペクト比が３以下であることが好ましく、２以下であることがより好ましい。平均アスペクト比が３を超える場合には、後述の乾燥造粒時の液滴中の液の流れに対して抵抗となり液滴表面に集まることが阻害されることがある。 The average particle diameter D 50 of the metal or metal compound is preferably 1 μm or less, more preferably 0.01 to 0.5 μm. When the average particle diameter D 50 of the metal or metal compound is more than 1μm are likely to occur pulverization during charging inflated, is to suppress difficult degradation due to aggregation and oxidation is less than 0.01 [mu] m, the discharge capacity is reduced There is a case. The metal or metal compound can be prepared by mechanical pulverization of a lump, precipitation by vapor phase or liquid phase reaction, and the shape can be crushed, spherical, fibrous, scale-like, or the like. The crystal structure of the precipitated particles may be either crystalline or amorphous.
<Graphite and / or carbon whose average particle size is 1/2 or less of flaky graphite>
It is preferable that the graphite adhering to the surface of the granulated body and existing inside is natural graphite or artificial graphite, and carbon is hard carbon or soft carbon. The graphite and carbon are important to make it easy to gather on the surface of the droplets by riding on the liquid flow in the droplets at the time of dry granulation, which will be described later. 1/3 or less is preferable. The average particle size is preferably 2 μm or less, more preferably 1 μm or less. Further, the shape preferably has an average aspect ratio of 3 or less, more preferably 2 or less. When the average aspect ratio exceeds 3, resistance to the flow of the liquid in the droplet during dry granulation, which will be described later, becomes resistance and may be prevented from collecting on the surface of the droplet.
　前記造粒体中の黒鉛および炭素の割合は、前記鱗片状黒鉛と前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素の合計量：１００質量部に対して、５質量部超、５０質量部以下であり、１０質量部以上、３０質量部以下であるのが好ましい。黒鉛および炭素が５質量部以下の場合は、造粒体の表面および内部に有効に付着せず、５０質量部超の場合は表面に密集し過ぎて造粒体が硬くなり電極密度が上がらないことがある。 The ratio of graphite and carbon in the granulated body is 5 parts by mass with respect to 100 parts by mass of the total amount of graphite and carbon having the scale-like graphite and the average particle size of 1/2 or less of the scale-like graphite. More than 50 parts by mass, preferably 10 parts by mass or more and 30 parts by mass or less. When the amount of graphite and carbon is 5 parts by mass or less, it does not effectively adhere to the surface and inside of the granulated body, and when it exceeds 50 parts by mass, the granulated body becomes too dense and the granulated body becomes hard and the electrode density does not increase. Sometimes.
　＜繊維状導電材＞
　前記造粒体はさらに繊維状導電材を含有することがより望ましい。導電材は造粒体の骨格を形成する黒鉛または炭素と金属粒子とを電気的接続を補助する役割を持ち、造粒体の電気抵抗を低減しサイクル特性を向上させる。
繊維状導電材は繊維状の黒鉛および／または炭素であることが好ましく、黒鉛または炭素と金属粒子を電気的に接続する役割を果たせば、種類は問わないが、特に好ましくはカーボンナノチューブ、カーボンナノファイバーなどである。平均アスペクト比は３０以上、３００以下であることが好ましい。平均アスペクト比が３０未満であると黒鉛または炭素と金属粒子とを有効に電気的接続ができない場合が有り、３００超えだと導電材の均一分散が難しくなる場合があるからである。なおアスペクト比は、繊維長Ｌに対する繊維径Ｄの比（Ｌ／Ｄ）を意味する。
繊維状導電材の含有割合は、前記鱗片状黒鉛と前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素の合計量１００質量部に対して、０．１質量部以上、５質量部以下であるのが好ましく、０．５質量部以上、２質量部以下がより好ましい。導電材が０．１質量部未満の場合は粒子間の電気的接触を補助する効果が小さくなりサイクル特性の向上が小さくなることがあり、５質量部超の場合は嵩高い導電材が立体障害となり電極密度が上がりにくく初期効率が低下することがある。 <Fibrous conductive material>
More preferably, the granulated body further contains a fibrous conductive material. The conductive material has a role of assisting electrical connection between the graphite or carbon forming the skeleton of the granulated body and the metal particles, and reduces the electrical resistance of the granulated body and improves the cycle characteristics.
The fibrous conductive material is preferably fibrous graphite and / or carbon, and any type can be used as long as it plays the role of electrically connecting graphite or carbon and metal particles, but carbon nanotubes and carbon nano-particles are particularly preferable. Such as fiber. The average aspect ratio is preferably 30 or more and 300 or less. This is because if the average aspect ratio is less than 30, graphite or carbon and metal particles may not be effectively electrically connected, and if it exceeds 300, uniform dispersion of the conductive material may be difficult. The aspect ratio means the ratio (L / D) of the fiber diameter D to the fiber length L.
The content ratio of the fibrous conductive material is 0.1 parts by mass or more with respect to 100 parts by mass of the total amount of graphite and carbon having the scale-like graphite and the average particle size of 1/2 or less of the scale-like graphite. The amount is preferably not more than mass parts, more preferably not less than 0.5 parts by mass and not more than 2 parts by mass. When the conductive material is less than 0.1 parts by mass, the effect of assisting electrical contact between particles is reduced, and the improvement in cycle characteristics may be reduced. When the conductive material exceeds 5 parts by mass, the bulky conductive material is sterically hindered. Therefore, the electrode density is difficult to increase and the initial efficiency may be lowered.
　〔造粒体の製造方法〕
　本発明の造粒体の製造方法は、リチウムと合金化可能な金属を複合した鱗片状黒鉛、および平均粒径が該鱗片状黒鉛の１／２以下の黒鉛または炭素を、さらには必要な場合は繊維状導電材を、熱分解炭素の前駆物質である結着剤を溶解した水溶液に分散させ、乾燥造粒した後、７００～１５００℃の温度範囲で熱処理を行う。 [Production method of granulated body]
The method for producing a granulated body of the present invention further includes flaky graphite in which a metal that can be alloyed with lithium is combined, and graphite or carbon having an average particle size of 1/2 or less of the flaky graphite. In the method, a fibrous conductive material is dispersed in an aqueous solution in which a binder, which is a precursor of pyrolytic carbon, is dissolved, dried and granulated, and then heat-treated in a temperature range of 700 to 1500 ° C.
　リチウムと合金化可能な金属と鱗片状黒鉛の複合物は、リチウムと合金化可能な金属および鱗片状黒鉛と熱分解炭素の前駆物質である結着剤と混合して、１００～６００℃で熱処理をして得ることができる。しかし金属と鱗片状黒鉛が複合されれば本方法に限定されない。熱分解炭素の前駆物質である結着剤としては、コールタールピッチ、石油ピッチ、フェノール樹脂、糖類、アセナフチレンなどが挙げられる。結着剤は混合時に溶剤で希釈してもよい。前記複合体中の該結着剤に由来する熱分解炭素の割合は、前記リチウムと合金可能な金属および鱗片状黒鉛の合計量：１００質量部に対して、０．２５質量部以上、２０質量部以下が好ましく、さらに好ましくは０．５質量部以上、１０質量部以下、最も好ましくは１．０質量部以上、１０質量部以下である。０．２５質量部未満では金属が鱗片状黒鉛と結着しない場合が有り、２０質量部を超えると複合粒子の塊が形成されるため空隙構造のある造粒体が作製できない場合がある。 Lithium-alloyable metal and scaly graphite composite is mixed with lithium-alloyable metal and scaly graphite and binder which is a precursor of pyrolytic carbon and heat treated at 100-600 ° C. Can be obtained. However, it is not limited to this method if the metal and the flake graphite are combined. Examples of the binder that is a precursor of pyrolytic carbon include coal tar pitch, petroleum pitch, phenol resin, saccharides, and acenaphthylene. The binder may be diluted with a solvent during mixing. The proportion of pyrolytic carbon derived from the binder in the composite is 0.25 parts by mass or more and 20 parts by mass with respect to 100 parts by mass of the total amount of metal and scaly graphite that can be alloyed with lithium. Part or less, more preferably 0.5 part by weight or more and 10 parts by weight or less, and most preferably 1.0 part by weight or more and 10 parts by weight or less. If the amount is less than 0.25 parts by mass, the metal may not bind to the flaky graphite. If the amount exceeds 20 parts by mass, a lump of composite particles may be formed, and a granulated body having a void structure may not be produced.
　次に、前記複合粉を平均粒径が前記鱗片状黒鉛の１／２以下の黒鉛および／または炭素、さらには必要な場合は繊維状導電材とともに、水溶性の炭素前駆物質の結着剤が溶解した水溶液に分散させる。前記水溶性の結着剤に由来する熱分解炭素の割合は、前記複合粉と前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素の合計量：１００質量部に対して、０．２５質量部以上、２０質量部以下が好ましく、さらに好ましくは１質量部以上、１０質量部以下である。０．２５質量部未満では造粒体の粒子強度が不足する場合が有り、２０質量部を超えると粒子が硬すぎて負極の充填性が悪くなる。複合粉と黒鉛および炭素、および繊維状導電材を合わせた総量の濃度は、１０～５０質量％で調製するのが好ましい。１０質量部未満では生産効率が悪く、５０質量部超えでは粘度が高くなりすぎて後述の乾燥造粒ができない場合がある。得られる造粒体の平均粒径は分散液の粘度、濃度に影響されるため、所望の平均粒径に合わせて濃度を調製すればよい。 Next, the composite powder has a water-soluble carbon precursor binder together with graphite and / or carbon having an average particle size of ½ or less of the scale-like graphite, and, if necessary, a fibrous conductive material. Disperse in dissolved aqueous solution. The proportion of pyrolytic carbon derived from the water-soluble binder is the total amount of the composite powder and the average particle size of graphite and carbon that is 1/2 or less of the flake graphite: 100 parts by mass, 0.25 mass part or more and 20 mass parts or less are preferable, More preferably, they are 1 mass part or more and 10 mass parts or less. If the amount is less than 0.25 parts by mass, the particle strength of the granulated material may be insufficient. If the amount exceeds 20 parts by mass, the particles are too hard and the filling property of the negative electrode is deteriorated. The total concentration of the composite powder, graphite, carbon, and fibrous conductive material is preferably adjusted to 10 to 50% by mass. If it is less than 10 parts by mass, the production efficiency is poor, and if it exceeds 50 parts by mass, the viscosity becomes so high that dry granulation described later may not be performed. Since the average particle size of the resulting granulated body is affected by the viscosity and concentration of the dispersion, the concentration may be adjusted according to the desired average particle size.
　得られた水分散液は、スプレードライヤ装置で乾燥造粒する。スプレードライ法は、高温加熱空気中に水分散液を噴霧して乾燥する方法であるため、形状の揃った造粒体を得ることができる。乾燥造粒体の粒径は、溶液の固形分濃度や粘度、噴霧方法として回転ディスク式やノズル式の選択により調整することができる。スプレードライ装置の入口温度（加熱空気温度）は１００～２５０℃とすることが好ましい。入口温度を１００～２５０℃にすれば、生成する乾燥物の到達温度は、送液量とのバランスにも依存するが、８０～１５０℃となる。 The obtained aqueous dispersion is dried and granulated with a spray dryer. The spray drying method is a method in which an aqueous dispersion is sprayed and dried in high-temperature heated air, so that a granulated body having a uniform shape can be obtained. The particle size of the dried granulated body can be adjusted by selecting a rotating disk type or a nozzle type as the solid content concentration and viscosity of the solution and the spraying method. The inlet temperature (heated air temperature) of the spray dryer is preferably 100 to 250 ° C. If the inlet temperature is 100 to 250 ° C., the ultimate temperature of the dried product to be generated is 80 to 150 ° C., depending on the balance with the amount of liquid to be fed.
　焼成工程は、熱分解炭素の炭素前駆物質を被覆した乾燥造粒体を非酸化性雰囲気下で焼成してリチウムイオン二次電池用負極材を得る工程である。 The firing step is a step of obtaining a negative electrode material for a lithium ion secondary battery by firing a dried granule coated with a carbon precursor of pyrolytic carbon in a non-oxidizing atmosphere.
　非酸化性雰囲気下とは、例えば、酸素濃度が１０００ｐｐｍ以下の窒素、アルゴンなどの不活性ガス雰囲気下；水素、一酸化炭素などの還元性ガスを含む還元性ガス雰囲気下；等のことをいう。焼成を非酸化性雰囲気下で行うのは、酸化を防止するためである。 The non-oxidizing atmosphere means, for example, an inert gas atmosphere such as nitrogen or argon having an oxygen concentration of 1000 ppm or less; a reducing gas atmosphere containing a reducing gas such as hydrogen or carbon monoxide; . The reason why baking is performed in a non-oxidizing atmosphere is to prevent oxidation.
　焼成工程における焼成温度は、７００～１５００℃が好ましく、８００～１１００℃がさらに好ましい。 The firing temperature in the firing step is preferably 700 to 1500 ° C, more preferably 800 to 1100 ° C.
　焼成温度が７００℃未満の場合には、揮発成分であるＨ2Ｏ，ＣＯ2，Ｈ2および炭化水素の熱分解除去が不十分となる。一方、焼成温度が１５００℃を超えると、金属と黒鉛または炭素との反応（例えばＳｉ＋Ｃ→ＳｉＣ）が進行し、得られるリチウムイオン二次電池用負極材の放電容量が低下する。 When the calcination temperature is less than 700 ° C., the thermal decomposition removal of H 2 O, CO 2 , H 2 and hydrocarbons, which are volatile components, is insufficient. On the other hand, when the firing temperature exceeds 1500 ° C., the reaction between the metal and graphite or carbon (for example, Si + C → SiC) proceeds, and the discharge capacity of the obtained negative electrode material for a lithium ion secondary battery decreases.
　本発明の造粒体は、乾燥造粒後の造粒体に熱分解炭素の前駆物質を混合し７００～１５００℃で非酸化性雰囲気下で焼成してもよい。この工程により、造粒体の表面が熱分解炭素で被覆される。 The granulated body of the present invention may be fired at 700 to 1500 ° C. in a non-oxidizing atmosphere by mixing a granulated body after dry granulation with a precursor of pyrolytic carbon. By this step, the surface of the granulated body is covered with pyrolytic carbon.
　最終的に得られる熱分解炭素の含有量は、前記鱗片状黒鉛と前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素の合計量：１００質量部に対して、０．２５質量部以上、２０質量部以下、好ましくは１～１５質量部、さらに好ましくは５～１０質量部である。
本発明の負極材料は、作製する電極の容量、密度、効率などの電池特性を調整するために、異種の黒鉛材料、ハードカーボンなどの炭素材料と混合して使用してもよい。 The content of pyrolytic carbon finally obtained is 0.25 with respect to the total amount of graphite and carbon of the scale-like graphite and the average particle diameter of 1/2 or less of the scale-like graphite: 100 parts by mass. It is not less than 20 parts by mass, preferably 1 to 15 parts by mass, more preferably 5 to 10 parts by mass.
The negative electrode material of the present invention may be used by mixing with carbon materials such as different types of graphite materials and hard carbon in order to adjust battery characteristics such as capacity, density, and efficiency of the electrode to be produced.
　実施例で用いた測定法は以下である。
（１）平均粒径の測定
　平均粒子径は、レーザー回折式粒度計で測定される累積度数が体積百分率で５０％となる粒子径で測定した。 The measurement methods used in the examples are as follows.
(1) Measurement of average particle diameter The average particle diameter was measured by a particle diameter at which the cumulative frequency measured by a laser diffraction particle size meter was 50% by volume.
　（リチウムと合金化可能な金属の含有割合）
　金属の含有量は添加量で規定した。定量測定を行う場合はＩＣＰ発光分析で行うことができる。 (Content of metal that can be alloyed with lithium)
The metal content was defined by the amount added. When quantitative measurement is performed, ICP emission analysis can be performed.
　（鱗片状黒鉛、鱗片状黒鉛の１／２以下の黒鉛または炭素、熱分解炭素、繊維状導電材の割合）
　鱗片状黒鉛、鱗片状黒鉛の１／２以下の黒鉛または炭素、繊維状導電材の含有量は添加量で規定した。熱分解炭素量の含有量は、前駆物質の添加量に焼成温度での残炭率を乗じて算出できる。
（２）粒子強度の測定
　微小圧縮試験機（島津製作所社製、ＭＣＴ－Ｗ５００）で１０個の粒子を測定し、その平均値を得た。
（３）粉体特性
　表面、断面の観察は、走査型電子顕微鏡（ＳＥＭ）写真で行った。断面観察は、造粒体を樹脂に埋め込んで研磨したものを用いた。
（４）電池特性
　下記の構成で作製された評価電池について、２５℃の温度下で以下に示す充放電試験を行い、初期充放電特性、およびサイクル特性を計算した。 (The ratio of flaky graphite, graphite 1/2 or less of flaky graphite, carbon, pyrolytic carbon, and fibrous conductive material)
The content of flaky graphite, graphite or carbon ½ or less of flaky graphite, and fibrous conductive material was defined by the added amount. The content of the pyrolytic carbon amount can be calculated by multiplying the addition amount of the precursor by the residual carbon ratio at the firing temperature.
(2) Measurement of particle strength Ten particles were measured with a micro compression tester (manufactured by Shimadzu Corporation, MCT-W500), and the average value was obtained.
(3) Powder characteristics The surface and cross-section were observed with a scanning electron microscope (SEM) photograph. For cross-sectional observation, a granulated body embedded in a resin and polished was used.
(4) Battery characteristics About the evaluation battery produced with the following structure, the following charge / discharge test was done at the temperature of 25 degreeC, and the initial stage charge / discharge characteristic and cycling characteristics were calculated.
　［初期充放電特性］
　回路電圧が０ｍＶに達するまで０．９ｍＡの定電流充電を行った後、回路電圧が０ｍＶに達した時点で定電圧充電に切替え、さらに電流値が２０μＡになるまで充電を続けた。その間の通電量から質量当たりの充電容量（単位：ｍＡｈ／ｇ）を求めた。その後、１２０分間保持した。次に０．９ｍＡの電流値で回路電圧が１．５Ｖに達するまで定電流放電を行い、この間の通電量から質量当たりの放電容量（単位：ｍＡｈ／ｇ）を求めた。初期充放電効率は下記式により計算した。 [Initial charge / discharge characteristics]
After constant current charging of 0.9 mA until the circuit voltage reached 0 mV, switching to constant voltage charging was performed when the circuit voltage reached 0 mV, and charging was continued until the current value reached 20 μA. The charging capacity per unit mass (unit: mAh / g) was determined from the amount of electricity applied during that time. Thereafter, it was held for 120 minutes. Next, constant current discharge was performed until the circuit voltage reached 1.5 V at a current value of 0.9 mA, and the discharge capacity per unit mass (unit: mAh / g) was determined from the amount of electricity supplied during this period. The initial charge / discharge efficiency was calculated by the following formula.
　初期充放電効率（％）＝（放電容量／充電容量）×１００
　なおこの試験では、リチウムイオンを負極材料に吸蔵する過程を充電、負極材料から離脱する過程を放電とした。結果を表２に示した。 Initial charge / discharge efficiency (%) = (discharge capacity / charge capacity) × 100
In this test, the process of occluding lithium ions in the negative electrode material was charged, and the process of detaching from the negative electrode material was discharged. The results are shown in Table 2.
　［サイクル特性］
　質量当たりの放電容量、急速充電率、急速放電率を評価した評価電池とは別の評価用電池を作製し、以下のような評価を行なった。 [Cycle characteristics]
An evaluation battery different from the evaluation battery that evaluated the discharge capacity per mass, the rapid charge rate, and the rapid discharge rate was produced, and the following evaluation was performed.
　回路電圧が０ｍＶに達するまで４.０ｍＡの定電流充電を行った後、定電圧充電に切替え、電流値が２０μＡになるまで充電を続けた後、１２０分間休止した。次に４.０ｍＡの電流値で、回路電圧が１.５Ｖに達するまで定電流放電を行った。２０回充放電を繰返し、得られた質量当たりの放電容量から、次式を用いてサイクル特性を計算した。結果を表２に示した。 After constant current charging of 4.0 mA until the circuit voltage reached 0 mV, switching to constant voltage charging was continued until the current value reached 20 μA, and then rested for 120 minutes. Next, constant current discharge was performed at a current value of 4.0 mA until the circuit voltage reached 1.5V. The charge / discharge was repeated 20 times, and the cycle characteristics were calculated from the obtained discharge capacity per mass using the following formula. The results are shown in Table 2.
　サイクル特性（％）＝（第２０サイクルにおける放電容量／第１サイクルにおける放電容量）×１００
　［負極材料の作製］
（実施例１）
　平均粒径５μｍ、平均扁平度１０かつアスペクト比１．２の鱗片状黒鉛と、平均粒径０．２μｍのシリコン粒子を軟化点６０℃の軟ピッチと１００℃で混練したあと４００℃で焼成し複合体粒子を得た。この複合粒子および平均粒径０．７μｍ、平均扁平度５かつアスペクト比１．１の土状黒鉛をレゾール型フェノール樹脂が溶解した水溶液に加え、スプレードライ装置で噴霧乾燥処理し、球状の乾燥造粒体を得た。次いで窒素の非酸化性雰囲気下において１０００℃で焼成することにより目的の造粒体である負極材料を得た。各素材の配合量は、最終製品である造粒体におけるそれぞれの存在比率が表１に示す通りになるように調製した。
（実施例２）
　実施例１において、鱗片状黒鉛の平均粒径が２．５μｍ、平均扁平度１０かつアスペクト比１．２の鱗片状黒鉛を用いた以外は実施例１と同様の方法で負極材料を得た。
（実施例３）
　実施例１において、土状黒鉛の替わりに平均粒径が１．５μｍ、アスペクト比１．２のハードカーボンを用いた以外は実施例１と同様の方法で負極材料を得た。
（実施例４）
実施例１において、繊維状導電材として外径１０ｎｍ、長さ３μｍのマルチウォール型カーボンナノチューブをレゾール型フェノール樹脂が溶解した水溶液に加えた以外は実施例１と同様の方法で負極材料を得た。
（実施例５）
実施例４において、繊維状導電材の添加量を半量にした以外は実施例４と同様の方法で負極材料を得た。
（実施例６）
実施例４において、繊維状導電材として外径φ１５０ｎｍ、長さ５μｍのマルチウォール型カーボンナノチューブを用いた以外は実施例４と同様の方法で負極材料を得た。
（比較例１）
　平均粒径５μｍ、平均扁平度１０かつアスペクト比１．２の鱗片状黒鉛と、平均粒径０．２μｍのシリコン粒子を軟化点６０℃の軟ピッチと１００℃で混練したあと４００℃で焼成し複合体粒子を得た。この複合体粒子をレゾール型フェノール樹脂が溶解した水溶液に加え、スプレードライ装置で噴霧乾燥処理し、球状の乾燥造粒体を得た。次いで窒素の非酸化性雰囲気下において１０００℃で焼成することにより目的の造粒体である負極材料を得た。
（比較例２）
　比較例１において、レゾール型フェノール樹脂の熱分解炭素量の合計量を表１に示す量に替えた以外は比較例１と同様の方法で負極材料を得た。
（比較例３）
　実施例１において、土状黒鉛の替わりに平均扁平度１０かつアスペクト比１．２の平均粒径３．０μｍの鱗片状黒鉛を用いた以外は、実施例１と同様の方法で負極材料を得た。 Cycle characteristics (%) = (discharge capacity in 20th cycle / discharge capacity in 1st cycle) × 100
[Production of negative electrode material]
Example 1
A flaky graphite having an average particle size of 5 μm, an average flatness of 10 and an aspect ratio of 1.2 and silicon particles having an average particle size of 0.2 μm were kneaded at a soft pitch of 100 ° C. with a softening point of 60 ° C. and fired at 400 ° C. Composite particles were obtained. The composite particles and soil graphite having an average particle size of 0.7 μm, an average flatness of 5 and an aspect ratio of 1.1 are added to an aqueous solution in which a resol-type phenol resin is dissolved, and spray-dried with a spray-drying device to obtain a spherical dry structure. Granules were obtained. Subsequently, the negative electrode material which is the target granulated body was obtained by baking at 1000 ° C. in a non-oxidizing atmosphere of nitrogen. The blending amount of each material was prepared such that the respective abundance ratios in the granulated body as the final product are as shown in Table 1.
(Example 2)
In Example 1, a negative electrode material was obtained in the same manner as in Example 1 except that flaky graphite having an average particle size of flaky graphite of 2.5 μm, an average flatness of 10 and an aspect ratio of 1.2 was used.
Example 3
In Example 1, a negative electrode material was obtained in the same manner as in Example 1 except that hard carbon having an average particle size of 1.5 μm and an aspect ratio of 1.2 was used instead of earth graphite.
Example 4
In Example 1, a negative electrode material was obtained in the same manner as in Example 1 except that multiwall-type carbon nanotubes having an outer diameter of 10 nm and a length of 3 μm were added as fibrous conductive materials to an aqueous solution in which a resol type phenol resin was dissolved. .
(Example 5)
In Example 4, a negative electrode material was obtained in the same manner as in Example 4 except that the amount of fibrous conductive material added was halved.
(Example 6)
In Example 4, a negative electrode material was obtained in the same manner as in Example 4 except that multiwall-type carbon nanotubes having an outer diameter of 150 nm and a length of 5 μm were used as the fibrous conductive material.
(Comparative Example 1)
A flaky graphite having an average particle size of 5 μm, an average flatness of 10 and an aspect ratio of 1.2 and silicon particles having an average particle size of 0.2 μm were kneaded at a soft pitch of 100 ° C. with a softening point of 60 ° C. and fired at 400 ° C. Composite particles were obtained. The composite particles were added to an aqueous solution in which a resol-type phenol resin was dissolved, and spray-dried with a spray drying apparatus to obtain spherical dry granules. Subsequently, the negative electrode material which is the target granulated body was obtained by baking at 1000 ° C. in a non-oxidizing atmosphere of nitrogen.
(Comparative Example 2)
In Comparative Example 1, a negative electrode material was obtained in the same manner as in Comparative Example 1 except that the total amount of pyrolytic carbon of the resol type phenol resin was changed to the amount shown in Table 1.
(Comparative Example 3)
In Example 1, a negative electrode material was obtained in the same manner as in Example 1 except that scaly graphite having an average flatness of 10 and an average particle size of 3.0 μm having an aspect ratio of 1.2 was used instead of soil graphite. It was.
　［評価用電池の作製］
　実施例１～３、比較例１～３で作製した負極材料を用いて以下の工程で評価用電池を作製し電池特性を評価して表２に記載した。 [Production of evaluation battery]
Using the negative electrode materials produced in Examples 1 to 3 and Comparative Examples 1 to 3, evaluation batteries were produced in the following steps, and battery characteristics were evaluated.
　［作用電極（負極）の作製］
　前記造粒体からなる負極材料を９６質量部、結合剤としてのカルボキシメチルセルロース２質量部、およびスチレン－ブタジエンゴム２質量部を水に入れ、攪拌して負極合剤ペーストを調製した。前記負極合剤ペーストを厚さ１５μｍの銅箔上に均一な厚さで塗布し、さらに真空中１００℃で分散媒の水を蒸発させて乾燥した。次いで、この銅箔上に塗布された負極合剤層をハンドプレスによって加圧した。さらに、銅箔と負極合剤層を直径１５．５ｍｍの円柱状に打抜いて、銅箔に密着した負極合剤層を有する作用電極（負極）を作製した。負極合剤層の密度は１.４ｇ／ｃｍ３であった。 [Production of working electrode (negative electrode)]
96 parts by mass of the negative electrode material composed of the granulated body, 2 parts by mass of carboxymethyl cellulose as a binder, and 2 parts by mass of styrene-butadiene rubber were placed in water and stirred to prepare a negative electrode mixture paste. The negative electrode mixture paste was applied on a copper foil having a thickness of 15 μm to a uniform thickness, and further, water in a dispersion medium was evaporated at 100 ° C. in a vacuum to dry the paste. Next, the negative electrode mixture layer applied on the copper foil was pressed by a hand press. Further, the copper foil and the negative electrode mixture layer were punched into a columnar shape having a diameter of 15.5 mm to produce a working electrode (negative electrode) having a negative electrode mixture layer adhered to the copper foil. The density of the negative electrode mixture layer was 1.4 g / cm 3 .
　［電解液、セパレータ］
　電解液は、エチレンカーボネート３３体積％とメチルエチルカーボネート６７体積％の混合溶剤に、ＬｉＰＦ６を１ｍｏｌ／Ｌとなる濃度で溶解させ、非水電解液を調製した。得られた非水電解液をセパレータとして厚さ２０μｍのポリプロピレン多孔質体に含浸させ、電解液が含浸したセパレータを作製した。なお、実電池については、本発明の概念に基づき、公知の方法に準じて作製することができる。 [Electrolyte, separator]
The electrolytic solution was prepared by dissolving LiPF 6 at a concentration of 1 mol / L in a mixed solvent of 33% by volume of ethylene carbonate and 67% by volume of methyl ethyl carbonate to prepare a nonaqueous electrolytic solution. The obtained nonaqueous electrolytic solution was impregnated into a 20 μm-thick polypropylene porous body as a separator to produce a separator impregnated with the electrolytic solution. In addition, about a real battery, it can produce according to a well-known method based on the concept of this invention.
　［評価電池の構成］
　図１に評価電池の構成としてボタン型二次電池を示す。 [Configuration of evaluation battery]
FIG. 1 shows a button type secondary battery as a configuration of the evaluation battery.
　外装カップ１と外装缶３は、その周縁部において絶縁ガスケット６を介在させ、両周縁部をかしめて密閉した。その内部に外装缶３の内面から順に、ニッケルネットからなる集電体７ａ、リチウム箔よりなる円筒状の対極（正極）４、電解液が含浸されたセパレータ５、負極合剤２が付着した銅箔からなる集電体７ｂが積層された電池系である。 The outer cup 1 and the outer can 3 were sealed by interposing an insulating gasket 6 at the peripheral portion thereof and caulking both peripheral portions. A copper current collector 7 a made of nickel net, a cylindrical counter electrode (positive electrode) 4 made of lithium foil, a separator 5 impregnated with an electrolytic solution, and a negative electrode mixture 2 are attached to the inside of the outer can 3 in that order. A battery system in which current collectors 7b made of foil are laminated.
　前記評価電池は電解液を含浸させたセパレータ５を集電体７ｂと負極合剤２からなる作用電極（負極）と、集電体７ａに密着した対極４との間に挟んで積層した後、集電体７ｂを外装カップ１内に、対極４を外装缶３内に収容して、外装カップ１と外装缶３とを合わせ、さらに、外装カップ１と外装缶３との周縁部に絶縁ガスケット６を介在させ、両周縁部をかしめて密閉して作製した。 In the evaluation battery, the separator 5 impregnated with the electrolytic solution was sandwiched between the current collector 7b and the working electrode (negative electrode) made of the negative electrode mixture 2, and the counter electrode 4 in close contact with the current collector 7a. The current collector 7b is accommodated in the exterior cup 1, the counter electrode 4 is accommodated in the exterior can 3, the exterior cup 1 and the exterior can 3 are combined, and an insulating gasket is provided at the peripheral edge between the exterior cup 1 and the exterior can 3. 6 was interposed, and both peripheral portions were caulked and sealed.
　以上の評価結果を表１～２に示した。実施例１～３から、本発明の負極材料を用いたリチウムイオン二次電池は、黒鉛の理論容量を超える高い放電容量を有していることが分かる。比較例１～３は、平均粒径が該鱗片状黒鉛の１／２以下の黒鉛または炭素を有しないので粒子強度が低くサイクル特性に劣る。また、実施例と比較例の比較から、本発明の負極材料は粒子強度が高く、初期充放電効率、充電膨張率およびサイクル特性がより優れた負極材料であることが分かる。また表２に示されるように繊維状導電材を加えるとシリコンと黒鉛の電気的接触がさらに向上し、特にサイクル特性がよくなる。 The above evaluation results are shown in Tables 1-2. From Examples 1 to 3, it can be seen that the lithium ion secondary battery using the negative electrode material of the present invention has a high discharge capacity exceeding the theoretical capacity of graphite. Comparative Examples 1 to 3 do not have graphite or carbon whose average particle diameter is 1/2 or less of the scale-like graphite, so that the particle strength is low and the cycle characteristics are inferior. Moreover, it turns out that the negative electrode material of this invention is a negative electrode material with high particle | grain intensity | strength and the more excellent initial stage charge / discharge efficiency, charge expansion coefficient, and cycling characteristics from the comparison of an Example and a comparative example. Further, as shown in Table 2, when a fibrous conductive material is added, the electrical contact between silicon and graphite is further improved, and the cycle characteristics are particularly improved.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
  
Figure JPOXMLDOC01-appb-T000002
  
　本発明は、リチウムイオン二次電池用負極材料として、金属の充電時の膨張を充分に緩和でき、黒鉛の理論容量を超える高い放電容量、優れた初期充放電効率およびサイクル特性を示す負極材料を提供する。そのため、本発明の負極材料を用いるリチウムイオン二次電池は、近年の電池の高エネルギー密度化に対する要望を満たし、搭載する機器の小型化および高性能化に有用である。本発明の負極材料は、その特性を活かして、小型から大型までの高性能リチウムイオン二次電池に使用することができる。 As a negative electrode material for lithium ion secondary batteries, the present invention provides a negative electrode material that can sufficiently relieve the expansion during charging of metal, exhibits a high discharge capacity exceeding the theoretical capacity of graphite, excellent initial charge / discharge efficiency, and cycle characteristics. provide. Therefore, the lithium ion secondary battery using the negative electrode material of the present invention satisfies the recent demand for higher energy density of the battery, and is useful for downsizing and higher performance of equipment to be mounted. The negative electrode material of the present invention can be used for high-performance lithium ion secondary batteries ranging from small to large, taking advantage of the characteristics.
　　１　外装カップ
　　２　負極合剤
　　３　外装缶
　　４　対極
　　５　セパレータ
　　６　絶縁ガスケット
　　７ａ、７ｂ　集電体 DESCRIPTION OF SYMBOLS 1 Exterior cup 2 Negative electrode mixture 3 Exterior can 4 Counter electrode 5 Separator 6 Insulation gasket 7a, 7b Current collector

Claims (7)

  1. 　鱗片状黒鉛を有する造粒体の内部がリチウムと合金化可能な金属と複合した鱗片状黒鉛が非平行に重なり合って形成する空隙構造を有し、平均粒径が前記鱗片状黒鉛の１／２以下の黒鉛および／または炭素が前記造粒体の表面に付着し、かつ内部に存在し、
    さらに前記造粒体の表面および内部に熱分解炭素が被覆されたリチウムイオン二次電池用負極材料であって、
    　前記鱗片状黒鉛と前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素の合計量：１００質量部に対して、
    　前記鱗片状黒鉛が５０質量部以上、９５質量部未満、
    　前記金属が１質量部以上、３０質量部以下、
    　前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素が５質量部超、５０質量部以下、
    前記熱分解炭素が０．２５質量部以上、２０質量部以下であることを特徴とするリチウムイオン二次電池用負極材料。     The inside of the granulated body having flaky graphite has a void structure formed by overlapping flaky graphite combined with a metal that can be alloyed with lithium in a non-parallel manner, and the average particle size is 1/2 that of the flaky graphite. The following graphite and / or carbon adheres to the surface of the granulated body and exists inside,
    Furthermore, a negative electrode material for a lithium ion secondary battery in which pyrolytic carbon is coated on the surface and inside of the granulated body,
    The total amount of the scaly graphite and the average particle diameter of graphite and carbon ½ or less of the scaly graphite: 100 parts by mass,
    The flake graphite is 50 parts by mass or more and less than 95 parts by mass,
    The metal is 1 part by mass or more and 30 parts by mass or less,
    Graphite and carbon whose average particle diameter is 1/2 or less of the scale-like graphite is more than 5 parts by mass, 50 parts by mass or less,
    The said pyrolytic carbon is 0.25 mass part or more and 20 mass parts or less, The negative electrode material for lithium ion secondary batteries characterized by the above-mentioned.
  2. 　さらに、繊維状導電材が前記造粒体の内部および表面に存在し、
    前記鱗片状黒鉛と前記平均粒径が該鱗片状黒鉛の１／２以下の黒鉛および炭素の合計量：１００質量部に対して、
    前記導電材が０．１質量部以上、５質量部以下であることを特徴とする請求項１に記載のリチウムイオン二次電池用負極材料。     Furthermore, a fibrous conductive material is present inside and on the surface of the granulated body,
    The total amount of the scaly graphite and the average particle diameter of graphite and carbon ½ or less of the scaly graphite: 100 parts by mass,
    2. The negative electrode material for a lithium ion secondary battery according to claim 1, wherein the conductive material is 0.1 parts by mass or more and 5 parts by mass or less.
  3. 　前記繊維状導電材が、繊維状の黒鉛および／または繊維状の炭素である請求項１または２に記載のリチウムイオン二次電池用負極材料。 3. The negative electrode material for a lithium ion secondary battery according to claim 1, wherein the fibrous conductive material is fibrous graphite and / or fibrous carbon.
  4. 　リチウムと合金化可能な金属粒子を複合した鱗片状黒鉛ならびに平均粒径が前記鱗片状黒鉛の１／２以下の黒鉛および／または炭素を、熱分解炭素の前駆物質である結着剤が溶解した溶液に分散させ、乾燥造粒した後、７００～１５００℃の温度範囲で熱処理して、請求項１に記載のリチウムイオン二次電池用負極材料を製造する方法。 The scaly graphite compounded with metal particles that can be alloyed with lithium, and graphite and / or carbon having an average particle size of 1/2 or less than that of the scaly graphite were dissolved into a binder that is a precursor of pyrolytic carbon. The method for producing a negative electrode material for a lithium ion secondary battery according to claim 1, wherein the negative electrode material for a lithium ion secondary battery according to claim 1 is dispersed in a solution, dried and granulated, and then heat-treated in a temperature range of 700 to 1500 ° C.
  5. 　熱分解炭素の前駆物質である結着剤が溶解した溶液にさらに繊維状導電材を分散させることを特徴とする請求項４に記載のリチウムイオン二次電池用負極材料を製造する方法。 The method for producing a negative electrode material for a lithium ion secondary battery according to claim 4, wherein the fibrous conductive material is further dispersed in a solution in which the binder, which is a precursor of pyrolytic carbon, is dissolved.
  6. 　請求項１ないし３のいずれか１項に記載の負極材料を含有することを特徴とす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 the negative electrode material according to any one of claims 1 to 3.
  7. 　請求項６に記載のリチウムイオン二次電池用負極を有することを特徴とするリチウムイオン二次電池。 A lithium ion secondary battery comprising the negative electrode for a lithium ion secondary battery according to claim 6.
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