WO2020071428A1 - Carbon precursor and production method for carbon precursor - Google Patents

Carbon precursor and production method for carbon precursor

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Publication number
WO2020071428A1
WO2020071428A1 PCT/JP2019/038932 JP2019038932W WO2020071428A1 WO 2020071428 A1 WO2020071428 A1 WO 2020071428A1 JP 2019038932 W JP2019038932 W JP 2019038932W WO 2020071428 A1 WO2020071428 A1 WO 2020071428A1
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WIPO (PCT)
Prior art keywords
carbon precursor
temperature
raw material
carbon
oxygen
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PCT/JP2019/038932
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French (fr)
Japanese (ja)
Inventor
隆文 伊澤
祥平 小林
啓一 西村
岩崎　秀治
Original Assignee
株式会社クラレ
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Application filed by 株式会社クラレ filed Critical 株式会社クラレ
Priority to JP2020550505A priority Critical patent/JPWO2020071428A1/en
Publication of WO2020071428A1 publication Critical patent/WO2020071428A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • 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 carbon precursor useful for producing a carbonaceous material suitable for a negative electrode active material of a nonaqueous electrolyte secondary battery, and a method for producing the carbon precursor.
  • Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are widely used in small portable devices such as mobile phones and notebook computers because of their high energy density and excellent output characteristics.
  • application to in-vehicle applications such as hybrid vehicles and electric vehicles has been promoted.
  • As a negative electrode material of a lithium ion secondary battery non-graphitizable carbon capable of doping (charging) and undoping (discharging) lithium in an amount exceeding a theoretical capacity of 372 mAh / g of graphite has been developed and used. .
  • a resin composition such as petroleum pitch or coal pitch, a phenolic resin, or a plant-derived raw material such as coconut shell is used. From the viewpoint of raw material costs, plant-derived raw materials are suitable. However, many plant-derived raw materials contain impurity metals, so that a purification process is required to stabilize the quality as an industrial raw material.
  • Non-Patent Document 1 a method of modifying saccharides, a method of lowering the viscosity by roasting starch at a high temperature is also known (Patent Document 1).
  • a carbon material as described in Non-Patent Document 1 has a graphite-like structure and does not have a sufficient charge / discharge capacity. Further, in order to obtain a non-graphitizable carbon having a high discharge capacity using a saccharide, it is conceivable to modify the saccharide to adjust the structure. For example, the method described in Patent Document 1 is mainly used. However, this method is not suitable as a method for obtaining a non-graphitizable carbon precursor having a high discharge capacity.
  • the present invention is suitable for a negative electrode active material of a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery, a sodium ion secondary battery, a lithium sulfur battery, and a lithium air battery) having high charge / discharge capacity and low resistance. It is an object of the present invention to provide a carbon precursor useful for producing a carbonaceous material.
  • a non-aqueous electrolyte secondary battery for example, a lithium ion secondary battery, a sodium ion secondary battery, a lithium sulfur battery, and a lithium air battery
  • the present inventor has conducted intensive studies in order to solve the above problems, and as a result, the ratio of the oxygen atom content to the carbon atom content (O / C) by elemental analysis is 0.10 to 0.85, and the carbon precursor ratio of the peak intensity at 1720 cm -1 vicinity of the intensity of peak (I a) and 3330cm around -1 of the IR spectrum (I B) (I a / I B) is 0.50 or more, the The inventors have found that the problem is solved, and have completed the present invention.
  • the present invention includes the following preferred embodiments.
  • the ratio (O / C) of the oxygen atom content to the carbon atom content by elemental analysis is 0.10 to 0.85, and the peak intensity (I A ) around 1720 cm ⁇ 1 in the IR spectrum And a ratio (I A / I B ) of peak intensities (I B ) around 3330 cm ⁇ 1 and 0.50 or more.
  • the carbon precursor according to [1] which has no endothermic peak in the range of 100 to 500 ° C. in a DTA curve measured by TG-DTA.
  • the carbon precursor according to [1] or [2] which has a peak in a range of 0 to 50 ppm in a 13 C-NMR spectrum.
  • a carbon precursor useful for producing a carbonaceous material suitable for a negative electrode active material of a nonaqueous electrolyte secondary battery having a high charge / discharge capacity and a low resistance can be provided.
  • FIG. 2 is a view showing an SEM image of a carbon precursor obtained in Example 1.
  • FIG. 4 is a view showing an SEM image of a carbon precursor obtained in Comparative Example 1.
  • the carbon precursor is a raw material used for producing a carbonaceous material, and is obtained by, for example, performing a heat treatment on a raw material of a carbon precursor such as a carbohydrate, a plant raw material, or a substance having a saccharide skeleton.
  • the carbon precursor of the present invention is a substance that can be converted into a carbonaceous material by further heat treatment at a high temperature, for example.
  • the carbon precursor of the present invention is produced by, for example, subjecting a raw material of the carbon precursor to a heat treatment.
  • a heat treatment step it is considered that the physically adsorbed water contained in the substance serving as the raw material of the carbon precursor is dried and a dehydration reaction occurs at a molecular level. If the drying and dehydration of water in the above steps are insufficient, a large amount of water vapor is generated from the carbon precursor when the carbon precursor is further heat-treated at a high temperature in order to obtain a carbonaceous material. It became clear that the precursor melted and a carbonaceous material having a structure suitable for increasing the charge / discharge capacity could not be obtained.
  • the ratio of the oxygen atom content to the carbon atom content (O / C) by elemental analysis is 0.10 to 0.85.
  • the ratio of the oxygen atom content to the carbon atom content is preferably from the viewpoint of easily preventing the melting of the carbon precursor, forming a structure for absorbing and desorbing lithium ions and easily increasing the charge and discharge capacity. Is 0.2 or more and 0.80 or less, more preferably 0.3 or more and 0.79 or less, and still more preferably 0.4 or more and 0.78 or less.
  • the oxygen atom content by elemental analysis is preferably 35% by mass or more, more preferably 38% by mass or more, and even more preferably 40% by mass or more.
  • the oxygen atom content is preferably 45% by mass or less, more preferably 43% by mass or less, and even more preferably 42% by mass or less.
  • the carbon atom content by elemental analysis is preferably 45% by mass or more, more preferably 48% by mass or more, still more preferably 50% by mass or more, and particularly preferably 51% by mass or more.
  • the carbon atom content is preferably 60% by mass or less, more preferably 57% by mass or less, still more preferably 55% by mass or less, and particularly preferably 54% by mass or less.
  • the ratio of the oxygen atom content to the carbon atom content can be calculated by dividing the oxygen atom content by the carbon atom content.
  • the method of adjusting the ratio to the above range is not limited at all. For example, a method of heat-treating the raw material of the carbon precursor for 1 to 12 hours at a temperature of 215 to 240 ° C. under the supply of an oxygen-containing gas may be used. it can.
  • the amount of the raw material of the carbon precursor is increased and the supply amount of the oxygen-containing gas is reduced, it is difficult to remove water vapor when the dehydration reaction occurs, and the raw material hydrothermally reacts with the water vapor, and as a result, contains oxygen atoms.
  • the amount tends to increase. Therefore, by adjusting the amount of the raw material and the supply amount of the oxygen-containing gas, the ratio of the oxygen atom content to the carbon atom content can be adjusted to the above range.
  • the ratio of the peak intensity at 1720cm around -1 of the IR spectrum (I A) and 3330Cm -1 near the peak intensity (I B) is 0.50 That is all.
  • the peak (I A ) around 1720 cm ⁇ 1 in the IR spectrum is a peak derived from a carbonyl group and is usually observed at 1695 to 1750 cm ⁇ 1 .
  • the peak (I B ) around 3330 cm ⁇ 1 is a peak derived from a hydroxyl group and is usually observed at 3200 to 3600 cm ⁇ 1 .
  • I A increases the crosslinking reaction crosslinked structure having a carbonyl group is formed proceeds, at the same time, the I B decreases as dehydration reaction proceeds. By these reactions proceed, it is considered to be I A / I B increases.
  • I and A / I B is 0.50 less than, or crosslinking reaction is insufficient, because dehydration reaction is insufficient, when performing heat treatment at a high temperature to obtain a carbonaceous material from a carbon precursor As a result, the carbon precursor melts.
  • I A / I B is preferably 0.55 or more, more preferably, 0.60 or more , More preferably 0.65 or more. While I limit A / I B is not particularly limited, from the viewpoint of not too allowed to proceed dehydration reaction, preferably 2.0 or less, more preferably 1.6 or less.
  • the peak intensity (I A ) around 1720 cm ⁇ 1 of the IR spectrum is preferably 0.005 to 0.05, more preferably 0.008 to 0.045, and still more preferably 0.1 to 0.045. 010 to 0.040.
  • the peak intensity (I A ) around 1720 cm ⁇ 1 is within the above range, the melting of the carbon precursor is easily prevented, and a structure for absorbing and desorbing lithium ions is easily formed.
  • the peak intensity (I B ) around 3330 cm ⁇ 1 of the IR spectrum is preferably 0.015 to 0.060, more preferably 0.020 to 0.055, and still more preferably 0.1 to 0.055. 025 to 0.050.
  • the peak intensity (I B ) near 3330 cm ⁇ 1 is within the above range, the melting of the carbon precursor is easily prevented, and a structure for absorbing and desorbing lithium ions is easily formed.
  • I A / how the I B is adjusted to the above range is not limited in any way, for example, the raw material of the carbon precursor, the supply of an oxygen-containing gas, a method of heat treatment 1 ⁇ 12hr at a temperature range of 215 ⁇ 240 ° C. Can be used.
  • the amount of the raw material of the carbon precursor is increased and the supply amount of the oxygen-containing gas is reduced, the crosslinking reaction hardly proceeds, and it becomes difficult to remove water vapor when a dehydration reaction occurs. react.
  • I A is small, and / or, the greater the I B, there is a tendency that the I A / I B is reduced. Therefore, by adjusting the supply amount of the raw material amounts and oxygen-containing gas, it is possible to adjust the I A / I B in the above range.
  • the carbon precursor of the present invention does not have an endothermic peak in a range of 100 to 500 ° C. in a DTA curve measured by TG-DTA. Having an endothermic peak in the above temperature range means having a melting point in the above temperature range.
  • the carbon precursor does not have an endothermic peak between 100 and 500 ° C., the carbon structure in the carbon precursor is fixed, and the heat treatment is performed at a high temperature to obtain a carbonaceous material from the carbon precursor. It is considered that the carbon precursor is less likely to be melted, the charge / discharge capacity of the obtained nonaqueous electrolyte secondary battery is easily increased, and the resistance is easily lowered. Details of the TG-DTA measurement are as described in Examples.
  • the raw material of the carbon precursor may be supplied in the temperature range of 215 to 240 ° C. under the supply of an oxygen-containing gas. For 1 to 12 hours.
  • the amount of the raw material of the carbon precursor is increased and the supply amount of the oxygen-containing gas is reduced, the structure tends to have an endothermic peak between 100 and 500 ° C. Therefore, by adjusting the amount of the raw material and the supply amount of the oxygen-containing gas, it can be adjusted so as not to have an endothermic peak in the range of 100 to 500 ° C.
  • the carbon precursor of the present invention preferably has a peak between 0 and 50 ppm in the 13 C-NMR spectrum.
  • the peak observed between 0 and 50 ppm in the 13 C-NMR spectrum is a peak derived from carbon of a methyl group, a methylene group, or a methine group. Having a peak in the above range means that the structure of the saturated hydrocarbon is included in the structure of the carbon precursor. Since the saturated hydrocarbon has an effect of cross-linking the structural skeletons of the carbon precursor, by including the structure of the saturated hydrocarbon in the carbon precursor, the structure of the carbon precursor is fixed and hardly melted. Become.
  • the structure of the saturated hydrocarbon As a mechanism for forming the structure of the saturated hydrocarbon, it is conceivable that a part of the alicyclic structure contained in the raw material is opened and re-reacted by a dehydration reaction or the like.
  • the details of the 13 C-NMR measurement are as described in Examples, and are measured by the solid-state NMR method described later.
  • the method for giving a peak at 0 to 50 ppm in 13 C-NMR is not particularly limited.
  • a raw material of a carbon precursor is heat-treated for 1 to 12 hours in a temperature range of 215 to 240 ° C. under supply of an oxygen-containing gas. Can be used.
  • the alicyclic structure is less likely to open the ring and the crosslinked structure is less likely to be formed, so that no peak is observed between 0 and 50 ppm. Therefore, a peak can be obtained in the above range by adjusting the heat treatment temperature.
  • the circularity measured by shape particle size distribution measurement is preferably 0.95 or more, more preferably 0.97 or more, still more preferably 0.980 or more, and even more preferably 0.1 or more. It is 981 or more, particularly preferably 0.983 or more.
  • the circularity is equal to or more than the above lower limit, it is considered that the fixation of the structure has sufficiently proceeded, and the melting of the carbon precursor particles and the fusion of the carbon precursor particles have not occurred.
  • it is easy to fix the structure of the carbon precursor to form a structure for absorbing and desorbing lithium ions, and to easily increase the charge / discharge capacity.
  • the electrode density can be easily increased.
  • the details of the method of measuring the circularity are as described in Examples, and are measured by a shape particle size distribution measuring method described later.
  • the method for adjusting the circularity to the above range is not limited at all.
  • a method of heat-treating the raw material of the carbon precursor for 1 to 12 hours at a temperature of 215 to 240 ° C. under the supply of an oxygen-containing gas may be used. it can.
  • the circularity can be adjusted to the above range by adjusting the amount of the raw material and the supply amount of the oxygen-containing gas to prevent the carbon precursor from melting.
  • the average particle diameter (D 50 ) of the carbon precursor of the present invention is preferably 30 ⁇ m or less, more preferably 25 ⁇ m or less, still more preferably 20 ⁇ m or less, even more preferably 18 ⁇ m or less, particularly preferably 16 ⁇ m or less, and most preferably. It is 15 ⁇ m or less.
  • the average particle diameter is equal to or less than the above upper limit, in addition to the good coatability at the time of electrode production, the free path of diffusion of lithium ions in the particles of the carbonaceous material obtained from the carbon precursor is small. Therefore, rapid charge and discharge can be easily obtained. Furthermore, in a lithium ion secondary battery, it is important to increase the electrode area in order to improve the input / output characteristics.
  • the average particle diameter D 50 of the carbon precursor of the present invention is preferably 2 ⁇ m or more, more preferably 3 ⁇ m or more, even more preferably 4 ⁇ m or more, still more preferably 5 ⁇ m or more, even more preferably 6 ⁇ m or more, even more It is preferably at least 7 ⁇ m, still more preferably at least 8 ⁇ m, particularly preferably at least 9 ⁇ m.
  • the average particle diameter D 50 is a particle diameter at which the cumulative volume becomes 50%.
  • the particle diameter distribution is measured by a laser scattering method using a particle diameter and particle size distribution measuring device (“Microtrack MT3300EXII” manufactured by Microtrac Bell Co., Ltd.). Can be determined by measuring
  • the method for producing the carbon precursor of the present invention is not particularly limited as long as a carbon precursor having the above properties can be obtained.
  • the carbon precursor can be produced using a production method described below.
  • the present invention is suitable for a negative electrode active material or a conductive material of a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery, a sodium ion battery, a lithium sulfur battery, and a lithium air battery) having a high charge / discharge capacity and a low resistance.
  • a method for producing a carbon precursor useful for producing a carbonaceous material is also provided.
  • the method for producing a carbon precursor of the present invention comprises: (1) A production method in which a carbon precursor raw material is heat-treated at a temperature of 215 to 240 ° C. for 1 to 12 hours under a supply of an oxygen-containing gas to obtain a carbon precursor.
  • the method for producing a carbonaceous material of the present invention comprises: (2) A mixture obtained by mixing a raw material of a carbon precursor with 80 to 500 parts by mass of at least one heat-resistant oil with respect to 50 parts by mass of the raw material is mixed at a temperature of 150 to 300 ° C. to obtain a mixture.
  • This is a production method in which a carbon precursor is obtained by heat treatment for 5 to 12 hours.
  • the raw material of the carbon precursor described in the above-mentioned production methods (1) and (2) gives the carbon precursor of the present invention through a subsequent step such as heat treatment, and finally undergoes a subsequent step such as heat treatment to finally obtain a carbonaceous material.
  • the substance is not particularly limited as long as it gives the compound, and may be, for example, a carbohydrate.
  • a substance having a saccharide skeleton is preferable. By using a substance having a saccharide skeleton as a raw material, a carbon precursor derived from a substance having a saccharide skeleton can be obtained.
  • saccharide skeleton examples include monosaccharides such as glucose, galactose, mannose, fructose, ribose, and glucosamine; disaccharides such as sucrose, trehalose, maltose, cellobiose, maltitol, lactobionic acid, and lactosamine; and starch. , Glycogen, agarose, pectin, cellulose, chitin, chitosan and the like. These saccharides can be used alone or in combination of two or more. Among these saccharides, starch is preferred because it is easily available in large quantities.
  • the above-mentioned production method (1) of the present invention is a production method in which a carbon precursor raw material is heat-treated at a temperature of 215 to 240 ° C. for 1 to 12 hours under a supply of an oxygen-containing gas to obtain a carbon precursor.
  • the oxygen-containing gas is not particularly limited as long as it is a gas containing oxygen, but may be air, oxygen, or a mixed gas of air and oxygen and another gas such as an inert gas.
  • the oxygen concentration in the oxygen-containing gas is not particularly limited. It is preferable that the oxygen-containing gas is air from the viewpoint of easily performing the process and reducing the manufacturing cost.
  • Performing the heat treatment while supplying the oxygen-containing gas means performing the heat treatment while supplying the oxygen-containing gas.
  • heat treatment of an oxygen-containing gas such as air in a mere atmosphere
  • heat treatment in a mere atmosphere does not mean that active supply of an oxygen-containing gas is performed. It cannot be said that heat treatment is performed under supply. Therefore, such a manufacturing method does not correspond to the manufacturing method (1) of the present invention.
  • the supply amount of the oxygen-containing gas is not particularly limited as long as the supply is performed. For example, it is preferably 0.007 to 3.0 L / (min ⁇ m 2 ), more preferably 0 per unit surface area of the raw material of the carbon precursor.
  • the supply amount per unit surface area is calculated, for example, by dividing the supply amount per minute of the oxygen-containing gas by the product of the weight of the object to be processed (raw material of the carbon precursor) and the specific surface area.
  • the heat treatment causes the physically adsorbed water contained in the raw material of the carbon precursor to be dried, and also causes a dehydration reaction at the molecular level in the raw material of the carbon precursor, whereby the carbon precursor becomes It is thought that it can be obtained. Further, it is considered that a cross-linking reaction for forming a cross-linked structure having a carbonyl group is also progressing in the above step.
  • the mechanism described below does not limit the present invention at all, but is supplied when water is removed from the raw material of the carbon precursor by drying and dehydration.
  • Oxygen interacts with the raw material of the carbon precursor to form a crosslinked structure having a carbonyl group, and at the same time, water to be removed is removed from the system together with gas. As a result, it is considered that a carbon precursor which maintains a fine structure without melting the raw material of the carbon precursor by the heat treatment is considered to be obtained.
  • the temperature of the raw material is increased, and the heat treatment is performed in the temperature range of 215 to 240 ° C. for 1 to 12 hours as described above.
  • the heat treatment temperature in the production method (1) of the present invention is preferably from 217 to 235 ° C, more preferably from 219 to 230 ° C.
  • the heat treatment time is preferably 2 to 8 hours, more preferably 2.5 to 6 hours, and even more preferably 3 to 5 hours. If the heat treatment temperature and time are within the above ranges, it is easy to efficiently and sufficiently remove water from the raw material of the carbon precursor by drying and dehydration, and it is easy to finally obtain a carbonaceous material having the above characteristics. Conceivable.
  • the heat treatment temperature may be a constant temperature, but is not particularly limited as long as it is within the above range.
  • the mixture obtained by mixing the raw material of the carbon precursor with 80 to 500 parts by mass of at least one heat-resistant oil is mixed with 50 parts by mass of the raw material.
  • This is a production method in which a carbon precursor is obtained by performing a heat treatment at a temperature in the range of up to 300 ° C. for 0.5 to 12 hours.
  • the heat-resistant oil is not particularly limited, but may be any substance that does not cause volatilization or deterioration at least in the heat treatment temperature range.
  • examples include silicon oil, fluorine oil, creosote oil, diethylene glycol, triethylene glycol, and polyethylene glycol. No.
  • the amount of the heat-resistant oil mixed with the raw material of the carbon precursor is from 80 to 500 parts by mass, preferably from 100 to 500 parts by mass with respect to 50 parts by mass of the raw material of the carbon precursor, from the viewpoint that the raw material is dispersed and the fusion hardly occurs.
  • the amount is 400 parts by mass, more preferably 150 to 300 parts by mass, and still more preferably 180 to 280 parts by mass.
  • the method of mixing the raw material of the carbon precursor with the heat-resistant oil is not particularly limited, and the raw material of the carbon precursor may be directly mixed with the heat-resistant oil, or the carbon precursor and / or the organic acid may be mixed with at least one kind of oil. They may be mixed in a state of being dispersed and / or dissolved in a liquid. When mixing is performed using at least one liquid, the liquid may be removed by evaporation or the like, if necessary, to obtain a mixture.
  • the heat treatment causes the physically adsorbed water contained in the raw material of the carbon precursor to be dried, and also causes a dehydration reaction at the molecular level in the raw material of the carbon precursor, whereby the carbon precursor becomes It is thought that it can be obtained. Further, it is considered that a cross-linking reaction for forming a cross-linked structure having a carbonyl group is also progressing in the above step.
  • the mechanism described below does not limit the present invention at all, but water generated by drying and dehydration from the raw material of the carbon precursor may be present in the presence of the heat-resistant oil. Is considered to be efficiently removed from the surface of the carbon precursor. As a result, it is considered that a carbon precursor which maintains a fine structure without melting the raw material of the carbon precursor by the heat treatment is considered to be obtained.
  • the mixture obtained by mixing the raw material of the carbon precursor with the heat-resistant oil is heat-treated at a temperature of 50 to 300 ° C. for 0.5 to 12 hours to obtain a carbon precursor.
  • the heat treatment temperature in the step (7) is 50 to 300 ° C, preferably 150 to 300 ° C, more preferably 180 to 280 ° C, still more preferably 200 to 260 ° C, and particularly preferably 210 to 250 ° C.
  • the heat treatment time is 0.5 to 12 hours, preferably 1 to 8 hours, more preferably 2 to 6 hours, and still more preferably 3 to 5 hours.
  • the heat treatment temperature and time are within the above ranges, the water is easily and efficiently removed from the raw material of the carbon precursor by drying and dehydration, and the charge / discharge capacity is high and the non-aqueous electrolyte secondary has low resistance. It is considered that a carbonaceous material suitable for manufacturing a battery can be finally obtained.
  • the heat treatment temperature may be a constant temperature, but is not particularly limited as long as it is within the above range.
  • a carbonaceous material can be produced by a method including at least the following steps: (3A) heating the carbon precursor of the present invention to a first temperature in the range of 500 to 900 ° C. at a rate of 100 ° C./hour or more in an inert gas atmosphere; (3B) a step of heat-treating the carbon precursor at a temperature of 500 to 900 ° C. under a supply of an inert gas to obtain a carbide, wherein the supply amount of the inert gas is 0. 01 to 5.0 L / (min ⁇ m 2 ), (4A) a step of heating the carbide to a second temperature in a range of 1000 to 1400 ° C.
  • Step (3A) is a step of heating the carbon precursor obtained by the production method of the present invention to a first temperature in the range of 500 to 900 ° C. at a rate of 100 ° C./hour or more in an inert gas atmosphere.
  • Step (3B) is a step of subsequently heat-treating the carbon precursor at a temperature of 500 to 900 ° C. under a supply of an inert gas to obtain a carbide.
  • the step (3A) is performed under an inert gas atmosphere
  • the step (3B) is performed under an inert gas supply
  • the supply amount of the inert gas in the step (3B) is per unit surface area of the carbon precursor. It is 0.01 to 5.0 L / (min ⁇ m 2 ).
  • the process is performed in an inert gas atmosphere means that the process is performed in an inert gas atmosphere, and even if the inert gas is actively supplied, the process is not performed. You may.
  • the fact that the process is performed under the supply of an inert gas means that the process is performed in an atmosphere in which the inert gas is supplied. It cannot be said that the supply of the active gas is being performed, and that the heat treatment is not being performed under the supply of the inert gas.
  • the step (3A) and / or (3B) is also referred to as low-temperature firing (step).
  • the inert gas include an argon gas, a helium gas, and a nitrogen gas, and a nitrogen gas is preferable.
  • the heating rate in the step (3A) is preferably 100 ° C./hour or more from the viewpoint of easily obtaining a carbonaceous material suitable for manufacturing a nonaqueous electrolyte secondary battery having a high charge / discharge capacity and a low resistance. , More preferably at least 300 ° C / hour, still more preferably at least 400 ° C / hour, particularly preferably at least 500 ° C / hour.
  • the upper limit of the rate of temperature rise is not particularly limited, but is preferably 1000 ° C./hour or less, more preferably 800 ° C./hour or less, from the viewpoint of easily increasing the specific surface area due to rapid thermal decomposition.
  • the first temperature in the step (3A) is 500 to 900 ° C., preferably 550 to 880 ° C., more preferably 600 to 860 ° C., and further preferably 700 to 840 ° C.
  • the carbon precursor is heat-treated at a temperature of 500 to 900 ° C. under a supply of an inert gas to obtain a carbide.
  • the heat treatment temperature in the step (3B) is hereinafter also referred to as a low-temperature firing temperature.
  • the low-temperature firing temperature in the step (3B) is 500 to 900 ° C., preferably 550 to 880 ° C., more preferably 600 to 860 ° C., and further preferably 700 to 840 ° C.
  • the low-temperature sintering temperature is within the above range, a carbonaceous material suitable for manufacturing a non-aqueous electrolyte secondary battery having a high charge / discharge capacity and a low resistance can be finally obtained.
  • the low-temperature firing temperature may be a constant temperature, but is not particularly limited as long as it is within the above range.
  • the heat treatment time in the step (3B) is preferably 0.1 to 5 hours, more preferably 0.3 to 3 hours, and still more preferably 0.5 to 2 hours.
  • the supply amount of the inert gas is 0.01 to 5.0 L / (min ⁇ m 2 ), preferably 0.015 to 4.0 L / (min ⁇ m 2 ), more preferably, per unit surface area of the carbon precursor. 0.020 to 3.0 L / (min ⁇ m 2 ). It is preferable that the step (3A) is also performed while supplying the inert gas at the supply amount of the inert gas. From the viewpoint of easy operation, it is preferable that the first temperature in the step (3A) is equal to the heat treatment temperature in the step (3B).
  • Step (4A) is a step of heating the carbide obtained in step (3B) to a second temperature in the range of 1000 to 1400 ° C. in an inert gas atmosphere at a rate of 100 ° C./hour or more.
  • Step (4B) is a step of subsequently heat-treating the carbide at a temperature of 1000 to 1400 ° C. under the supply of an inert gas to obtain a carbonaceous material.
  • the step (4A) is performed under an inert gas atmosphere
  • the step (4B) is performed under the supply of an inert gas
  • the supply amount of the inert gas in the step (4B) is the amount of the carbon precursor. It is 0.01 to 5.0 L / (minute ⁇ m 2 ) per unit surface area.
  • step (4A) and / or (4B) is also referred to as high-temperature firing (step).
  • the inert gas include those described above for (3A) and (3B), and preferably nitrogen gas.
  • the heating rate in the step (4A) is preferably 100 ° C./hour or more from the viewpoint of easily obtaining a carbonaceous material suitable for manufacturing a nonaqueous electrolyte secondary battery having a high charge / discharge capacity and a low resistance. , More preferably at least 300 ° C / hour, still more preferably at least 400 ° C / hour, particularly preferably at least 500 ° C / hour.
  • the upper limit of the heating rate is not particularly limited, it is preferably 800 ° C./hour or less, more preferably 700 ° C./hour or less, and still more preferably 600 ° C./hour, from the viewpoint of easily increasing the specific surface area due to rapid thermal decomposition. Less than an hour.
  • the second temperature in the step (4A) is 1000 to 1400 ° C., preferably 1050 to 1380 ° C., more preferably 1100 to 1370 ° C., still more preferably 1150 to 1360 ° C., and particularly preferably 1200 to 1350 ° C.
  • step (4A) is usually performed following step (3B). Therefore, the temperature raising step in the step (4A) is a step of raising the temperature from the low-temperature firing temperature in the range of 500 to 900 ° C. to the second temperature in the range of 1000 to 1400 ° C.
  • the carbide is heat-treated at a temperature of 1000 to 1400 ° C. under a supply of an inert gas to obtain a carbonaceous material.
  • the heat treatment temperature in the step (4B) is hereinafter also referred to as a high temperature firing temperature.
  • the high-temperature sintering temperature in the step (4B) is from 1000 to 1400 ° C. from the viewpoint that the operation is easy, the charge / discharge capacity is high, and a carbonaceous material suitable for manufacturing a low-resistance nonaqueous electrolyte secondary battery is easily obtained.
  • the temperature is preferably from 1050 to 1380 ° C, more preferably from 1100 to 1370 ° C, further preferably from 1150 to 1360 ° C, and particularly preferably from 1200 to 1350 ° C.
  • the high temperature firing temperature may be a constant temperature, but is not particularly limited as long as it is within the above range.
  • the heat treatment time in the step (4B) is preferably 0.1 to 5 hours, more preferably 0.3 to 3 hours, and still more preferably 0.5 to 2 hours.
  • the supply amount of the inert gas is 0.01 to 5.0 L / (min ⁇ m 2 ), preferably 0.015 to 4.0 L / (min ⁇ m 2 ), more preferably 0.1 to 5.0 L / (min ⁇ m 2 ) per unit surface area of the carbide. 020 to 3.0 L / (min ⁇ m 2 ). It is preferable that the step (4A) is also performed while supplying the inert gas with the supply amount of the inert gas. From the viewpoint of easy operation, it is preferable that the second temperature in the step (4A) is equal to the heat treatment temperature in the step (4B).
  • the high temperature firing temperature (that is, the firing temperature in the step (4B)) is preferably equal to the second temperature in the step (4A), and the carbonaceous material which gives a high charge / discharge capacity, a high charge / discharge efficiency and a low resistance when used for an electrode. From the viewpoint of easily obtaining the material, the temperature is preferably equal to or higher than the firing temperature in the step (3B) (the first temperature in the step (3A) in a preferred embodiment).
  • the high temperature firing temperature is preferably 50 to 700 ° C., more preferably 100 to 600 ° C., still more preferably 150 to 500 ° C., and particularly preferably 200 to 400 ° C. higher than the low temperature firing temperature.
  • the method may further include a step (10) of adding at least one volatile organic substance to the carbide obtained in the step (3B).
  • a step (10) of adding at least one volatile organic substance to the carbide obtained in the step (3B) By performing the step (10), the organic matter volatilized when the carbide is fired at a high temperature adheres to the carbide surface, and as a result, it becomes easy to produce a carbonaceous material having a lower specific surface area.
  • a carbonaceous material reduces the amount of water present in the carbonaceous material while maintaining a high charge / discharge capacity and a low resistance, and suppresses the hydrolysis of the electrolytic solution by water and the electrolysis of water. Can be.
  • Volatile organic substances hardly carbonize when subjected to a heat treatment in an atmosphere of an inert gas such as nitrogen, for example, at a temperature of 500 ° C. or more (for example, preferably 80% or more, more preferably 90% or more of the substance is carbonized).
  • organic compounds that evaporate (evaporate or thermally decompose into gas) include, but are not limited to, a thermoplastic resin and a low molecular weight organic compound.
  • the thermoplastic resin include polystyrene, polyethylene, polypropylene, poly (meth) acrylic acid, and poly (meth) acrylate.
  • (meth) acryl is a general term for methacryl and acryl.
  • Examples of the low molecular weight organic compound include toluene, xylene, mesitylene, styrene, naphthalene, phenanthrene, anthracene, and pyrene.
  • Polystyrene, polyethylene, and polypropylene are preferable as the thermoplastic resin because those that volatilize at the firing temperature and do not oxidize the surface of the carbon precursor when thermally decomposed are preferable.
  • a compound having low volatility at normal temperature for example, 20 ° C.
  • naphthalene, phenanthrene, anthracene, pyrene and the like are particularly preferable.
  • step (10) at least one volatile organic substance is added to the carbide obtained in step (3B).
  • the addition method is not particularly limited.
  • the addition may be performed by mixing the carbide obtained in the step (3B) and at least one volatile organic substance.
  • the amount of the volatile organic substance to be added is not particularly limited, but is preferably 2 to 30 parts by mass, more preferably 4 to 20 parts by mass, and still more preferably 5 to 15 parts by mass with respect to 100 parts by mass of the carbide.
  • the method for producing a carbonaceous material may further include a step (11) of grinding the carbon precursor, carbide and / or carbonaceous material.
  • the pulverizing step (11) may be performed on the carbon precursor, carbide and / or carbonaceous material by a usual method, for example, a method using a ball mill or a jet mill.
  • the pulverizing step (11) may be performed, for example, after the steps (1), (3B) and / or (4B), and is unlikely to cause shrinkage or shape change due to heat treatment, has a high charge / discharge capacity, and has a low resistance. From the viewpoint of finally obtaining a carbonaceous material suitable for manufacturing a water electrolyte secondary battery, it is preferable to perform the step after the step (3B) or (4B).
  • the carbon precursor of the present invention or the carbon precursor obtained by the production method of the present invention, as a raw material for producing a carbonaceous material that can be suitably used as a negative electrode active material of a nonaqueous electrolyte secondary battery are suitable.
  • a method for producing a negative electrode for a non-aqueous electrolyte secondary battery using the carbon precursor of the present invention as a raw material and a carbonaceous material produced by the above-described production method will be specifically described.
  • a binder is added to a carbonaceous material, an appropriate solvent is added in an appropriate amount, and these are kneaded to prepare an electrode mixture.
  • a negative electrode for a non-aqueous electrolyte secondary battery can be manufactured by applying and drying the obtained electrode mixture on a current collector plate made of a metal plate or the like, followed by drying.
  • an electrode (anode) having high conductivity can be produced without adding a conduction aid.
  • a conductive assistant can be added as needed at the time of preparing the electrode mixture.
  • the conductive additive conductive carbon black, vapor grown carbon fiber (VGCF), nanotube, or the like can be used.
  • the amount of the conductive additive varies depending on the type of the conductive additive used.However, if the amount to be added is too small, the expected conductivity may not be obtained.If the amount is too large, the dispersion in the electrode mixture is poor. May be.
  • the binder is not particularly limited as long as it does not react with the electrolyte such as PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and a mixture of SBR (styrene / butadiene rubber) and CMC (carboxymethylcellulose). Not done.
  • a mixture of SBR and CMC is preferable because SBR and CMC adhered to the surface of the active material hardly hinder lithium ion transfer, and good input / output characteristics can be obtained.
  • a polar solvent such as water is preferably used for dissolving an aqueous emulsion such as SBR or CMC to form a slurry, but a solvent-based emulsion such as PVDF may be used by dissolving in N-methylpyrrolidone or the like. If the added amount of the binder is too large, the resistance of the obtained electrode increases, so that the internal resistance of the battery may increase and the battery characteristics may deteriorate.
  • the preferred amount of the binder varies depending on the type of binder used. For example, in the case of a binder using water as a solvent, a plurality of binders such as a mixture of SBR and CMC are often used as a mixture. The total amount of all binders is preferably 0.5 to 5% by mass, more preferably 1 to 4% by mass. On the other hand, for a PVDF-based binder, the content is preferably 3 to 13% by mass, and more preferably 3 to 10% by mass.
  • the amount of the carbonaceous material in the electrode mixture is preferably 80% by mass or more, and more preferably 90% by mass or more.
  • the amount of the carbonaceous material in the electrode mixture is preferably 100% by mass or less, more preferably 97% by mass or less.
  • the electrode active material layer is basically formed on both sides of the current collector plate, but may be formed on one side as needed.
  • the thicker the electrode active material layer the smaller the number of current collector plates and separators, etc., which is preferable for increasing the capacity.
  • the larger the area of the electrode facing the counter electrode is, the more advantageous the improvement of the input / output characteristics is. Therefore, if the electrode active material layer is too thick, the input / output characteristics may deteriorate.
  • the thickness (per side) of the active material layer is preferably from 10 to 80 ⁇ m, more preferably from 20 to 75 ⁇ m, and still more preferably from 30 to 75 ⁇ m, from the viewpoint of output during battery discharge.
  • the non-aqueous electrolyte secondary battery using the carbonaceous material produced from the carbon precursor of the present invention has high charge / discharge capacity and low resistance.
  • other materials constituting the battery such as a positive electrode material, a separator, and an electrolyte are particularly limited. Without using, it is possible to use various materials conventionally used or proposed as a non-aqueous solvent secondary battery.
  • the cathode material one represented layered oxide (LiMO 2, M is a metal: for example LiCoO 2, LiNiO 2, LiMnO 2 or LiNi x Co y Mo z O 2 (where x,, y , Z represent the composition ratio)), olivine-based (LiMPO 4 , M: metal: for example, LiFePO 4 ), spinel-based (LiM 2 O 4 ), M: metal: for example, LiMn 2 O 4 )) Is preferred, and these chalcogen compounds may be used as a mixture if necessary.
  • the positive electrode is formed by molding these positive electrode materials together with a suitable binder and a carbon material for imparting conductivity to the electrodes, and forming a layer on the conductive current collector.
  • a non-aqueous solvent-type electrolytic solution used in combination with these positive and negative electrodes is generally formed by dissolving an electrolyte in a non-aqueous solvent.
  • the non-aqueous solvent include organic solvents such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, ⁇ -butyl lactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, and 1,3-dioxolane. Can be used alone or in combination of two or more.
  • LiClO 4 LiPF 6 , LiBF 4 , LiCF 3 SO 3 , LiAsF 6 , LiCl, LiBr, LiB (C 6 H 5 ) 4 , LiN (SO 3 CF 3 ) 2, or the like is used.
  • a non-aqueous electrolyte secondary battery is generally formed by opposing the positive electrode and the negative electrode formed as described above via a liquid-permeable separator as necessary, and immersing the same in an electrolytic solution.
  • a permeable or liquid-permeable separator made of a nonwoven fabric or other porous material generally used for a secondary battery can be used.
  • a solid electrolyte made of a polymer gel impregnated with an electrolytic solution can be used instead of or together with the separator.
  • the carbon precursor of the present invention is suitable as a raw material for producing a carbonaceous material for a battery (typically, a non-aqueous electrolyte secondary battery for driving a vehicle) mounted on a vehicle such as an automobile.
  • the vehicle can be a target that is not particularly limited, such as a vehicle generally known as an electric vehicle, a hybrid vehicle with a fuel cell or an internal combustion engine, and a power supply device including at least the battery. And an electric drive mechanism driven by power supply from the power supply device, and a control device for controlling the electric drive mechanism.
  • the vehicle may further include a power generation brake and a regenerative brake, and a mechanism that converts energy by braking into electricity and charges the nonaqueous electrolyte secondary battery.
  • the carbonaceous material produced using the carbon precursor of the present invention has low resistance, it can be used, for example, as an additive for imparting conductivity to the electrode material of a battery.
  • the type of the battery is not particularly limited, but a non-aqueous electrolyte secondary battery and a lead storage battery are preferable.
  • a conductive network can be formed, and irreversible reaction can be suppressed by increasing conductivity, so that the battery can have a longer life.
  • the present invention is also suitable for a negative active material or a conductive material of a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery, a sodium ion battery, a lithium sulfur battery, and a lithium air battery) having a high charge / discharge capacity and a low resistance.
  • a non-aqueous electrolyte secondary battery for example, a lithium ion secondary battery, a sodium ion battery, a lithium sulfur battery, and a lithium air battery
  • the present invention also provides a method for producing a carbon precursor, which is used as a raw material for a carbonaceous material.
  • the production method is a method in which a substance having a saccharide skeleton is used as a raw material and heat-treated at a temperature in the range of 215 to 240 ° C. for 1 to 12 hours.
  • the carbon precursor of the present invention can be obtained by such a method.
  • Elemental analysis was performed based on an inert gas dissolution method using an oxygen / nitrogen / hydrogen analyzer EMGA-930 manufactured by Horiba, Ltd.
  • the detection method of this apparatus is as follows: oxygen: inert gas melting-non-dispersive infrared absorption method (NDIR), nitrogen: inert gas melting-thermal conduction method (TCD), hydrogen: inert gas melting-non-dispersive infrared absorption
  • NDIR inert gas melting-non-dispersive infrared absorption
  • TCD inert gas melting-thermal conduction method
  • Calibration is performed using (oxygen / nitrogen) Ni capsule, TiH 2 (H standard sample) and SS-3 (N, O standard sample). Twenty mg of the sample whose amount was measured was taken in a Ni capsule and measured after degassing in an elemental analyzer for 30 seconds.
  • the average value was used as the analysis value.
  • the oxygen atom content, the nitrogen atom content, and the hydrogen atom content in the carbon precursor were obtained.
  • the carbon atom content was calculated by subtracting the oxygen, nitrogen and hydrogen atom contents from 100% by mass.
  • IR measurement was performed based on the total reflection measurement method using a Fourier transform infrared spectrophotometer Nicolet is10 + Nicolet Continum manufactured by Thermo Fisher Scientific Co., Ltd. The measurement sample was placed on a diamond cell, irradiated with infrared light, and the obtained spectrum data was collected.
  • TG-DTA measurement TG analysis was performed using a TG-DTA analyzer TG / DTA6300 (trade name) manufactured by Hitachi High-Tech Science Corporation. 10 mg of the sample was placed in a sample pan made of alumina, and heated to 500 ° C. at a rate of 10 ° C./min under a nitrogen stream of 100 mL / min. In the differential heat (DTA) curve obtained at this time, the presence or absence of an endothermic peak was confirmed in the range of 100 to 500 ° C. When the endothermic peak was present in the above range, it was evaluated as “ ⁇ ”, and when it was not present, as “x”.
  • DTA differential heat
  • the circularity of the carbon precursor was measured by the following method.
  • the sample was put into an aqueous solution containing 5% by mass of a surfactant (“Toriton X100” manufactured by Wako Pure Chemical Industries, Ltd.) and dispersed in the aqueous solution.
  • a surfactant (“Toriton X100” manufactured by Wako Pure Chemical Industries, Ltd.)
  • shape particle size distribution was measured using a shape particle size distribution analyzer FPIA-3000 manufactured by Sysmex Corporation, and the circularity was calculated.
  • the average particle size (particle size distribution) of the carbon precursor was measured by the following method.
  • the sample was put into an aqueous solution containing 5% by mass of a surfactant (“Toriton X100” manufactured by Wako Pure Chemical Industries, Ltd.) and dispersed in the aqueous solution.
  • the particle size distribution was measured using this dispersion.
  • the particle size distribution was measured using a particle size / particle size distribution analyzer (“Microtrack MT3300EII” manufactured by Microtrac Bell Inc.).
  • D 50 is the cumulative volume is a particle diameter at 50%, using this value as the average particle size.
  • Electrode density The electrode density was calculated by measuring the weight of the electrode manufactured by the method of Reference Example 1 described below and dividing the weight by the electrode volume calculated from the product of the electrode area and the electrode thickness.
  • Example 1 10 g of starch was heated to 215 ° C. in an air atmosphere. At this time, the heating rate up to 215 ° C. was 600 ° C./hour (10 ° C./minute). Next, a heat treatment was performed at 215 ° C. for 8 hours in an air stream to obtain a carbon precursor. At this time, the supply amount of air was 35 L / min per 100 g of starch, and 0.49 L / (min ⁇ m 2 ) per unit surface area of the starch.
  • Example 2 The same treatment as in Example 1 was carried out except that the heat treatment temperature was 220 ° C. and the air supply amount was 10 L / min per 100 g of starch (0.14 L / (min ⁇ m 2 ) per unit surface area of starch). A precursor was obtained.
  • Example 3 A process was performed in the same manner as in Example 2 except that the amount of starch was 20 g, and the supply amount of air was 50 L / min per 100 g of starch (0.35 L / (min ⁇ m 2 ) per unit surface area of starch). A precursor was obtained.
  • Example 2 The same procedure as in Example 1 was carried out except that the amount of starch was 20 g and no gas was introduced, to obtain a carbon precursor.
  • Example 3 (Comparative Example 3) Except that the treatment temperature was 250 ° C. and the treatment time was 6 hours, the same treatment as in Example 1 was performed to obtain a carbon precursor.
  • Table 1 shows the firing conditions in each example and each comparative example, and Table 2 shows the evaluation results of the physical properties of the obtained carbon precursor.
  • TG-DTA when the endothermic peak is observed in the range of 100 to 500 ° C. according to the above TG-DTA measurement, it is described as ⁇ , and when it is not observed, it is described as ⁇ .
  • 13 C-NMR when a peak is observed in the range of 0 to 50 ppm according to the above 13 C-NMR measurement, it is described as ⁇ , and when it is not observed, it is described as x.
  • FIG. 1 shows an SEM image of the carbon precursor obtained in Example 1
  • FIG. 2 shows an SEM image of the carbon precursor obtained in Comparative Example 1.
  • the heating rate up to 1200 ° C. was 600 ° C./hour (10 ° C./minute).
  • the above temperature rise and heat treatment were performed under a nitrogen gas stream.
  • the supply amount of nitrogen gas was 3 L / min per 5 g of the pulverized carbide.
  • a negative electrode was manufactured according to the following procedure.
  • a slurry was obtained by mixing 95 parts by mass of the carbonaceous material, 2 parts by mass of conductive carbon black (“Super-P (registered trademark)” manufactured by TIMCAL), 1 part by mass of CMC, 2 parts by mass of SBR, and 90 parts by mass of water.
  • the obtained slurry was applied to a copper foil having a thickness of 18 ⁇ m, dried and pressed to obtain an electrode having a thickness of 45 ⁇ m.
  • the density of the obtained electrode was as shown in Table 3.
  • an electrochemical measurement apparatus (“1255WB-type high-performance electrochemical measurement system” manufactured by Solartron) was used to give an amplitude of 10 mV centered on 0 V at 25 ° C. and a frequency of 10 mHz to 1 MHz.
  • the constant voltage AC impedance was measured at the frequency, and the real part resistance at the frequency of 1 kHz was measured as the impedance resistance.
  • the obtained results are shown in Table 3 as the impedance at the time of the first charge / discharge.
  • the electrode prepared above was used as a working electrode, and metallic lithium was used as a counter electrode and a reference electrode.
  • ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate were mixed and used at a volume ratio of 1: 1: 1. 1 mol / L of LiPF 6 was dissolved in this solvent and used as an electrolyte.
  • a polypropylene film was used for the separator.
  • a coin cell was prepared in a glove box under an argon atmosphere.
  • a charge / discharge test was performed after a DC resistance value was measured before initial charging using a charge / discharge test device (“TOSCAT” manufactured by Toyo System Co., Ltd.). Lithium was doped at a rate of 70 mA / g with respect to the mass of the active material, and was doped until the potential of lithium became 1 mV. Further, a constant voltage of 1 mV with respect to the lithium potential was applied for 8 hours to complete doping. The capacity (mAh / g) at this time was defined as the charging capacity.
  • Table 3 shows the results of the evaluation of the battery as described above.
  • Example 1 When the carbon precursor of Example 1 was fired at a high temperature, melting and fusion did not occur, and a carbonaceous material was obtained while keeping the particle shape of the raw material, showing a carbon structure suitable for a battery material.
  • the battery manufactured using the carbonaceous material shown in Reference Example 1 had a low resistance value and a high discharge capacity.
  • do not show a predetermined range O / C ratio show no I A / I B, using carbon precursors, Comparative Examples, in the same manner as in Reference Example 1, carbide, when the high temperature firing Did not show a carbon structure suitable for battery materials.

Abstract

The present invention provides a carbon precursor wherein the ratio (O/C) of the oxygen atom content to the carbon atom content, as determined by elemental analysis, is 0.10-0.85, and the ratio (IA/IB) of the intensity (IA) of a peak near 1720 cm-1 to the intensity (IB) of a peak near 3330 cm-1 in an IR spectrum is 0.50 or higher.

Description

炭素前駆体および炭素前駆体の製造方法Carbon precursor and method for producing carbon precursor
　本発明は、非水電解質二次電池の負極活物質に適した炭素質材料を製造するに有用な炭素前駆体ならびに該炭素前駆体の製造方法に関する。 The present invention relates to a carbon precursor useful for producing a carbonaceous material suitable for a negative electrode active material of a nonaqueous electrolyte secondary battery, and a method for producing the carbon precursor.
　リチウムイオン二次電池等の非水電解質二次電池は、エネルギー密度が高く、出力特性に優れるため、携帯電話やノートパソコンのような小型携帯機器に広く用いられている。近年では、ハイブリッド自動車や電気自動車などの車載用途への適用も進められている。リチウムイオン二次電池の負極材としては、黒鉛の理論容量３７２ｍＡｈ／ｇを超える量のリチウムのドープ（充電）および脱ドープ（放電）が可能な難黒鉛化性炭素が開発され、使用されてきた。 非 Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are widely used in small portable devices such as mobile phones and notebook computers because of their high energy density and excellent output characteristics. In recent years, application to in-vehicle applications such as hybrid vehicles and electric vehicles has been promoted. As a negative electrode material of a lithium ion secondary battery, non-graphitizable carbon capable of doping (charging) and undoping (discharging) lithium in an amount exceeding a theoretical capacity of 372 mAh / g of graphite has been developed and used. .
　難黒鉛化性炭素の原料としては、石油ピッチや石炭ピッチ、フェノール樹脂などの樹脂組成物、椰子殻等の植物由来原料が用いられる。原料コストの観点からは、植物由来原料が好適であるが、多くの植物由来原料は不純物金属を含んでいるため、工業原料として品質を安定させるためには、精製工程が必要となる。 原料 As a raw material of non-graphitizable carbon, a resin composition such as petroleum pitch or coal pitch, a phenolic resin, or a plant-derived raw material such as coconut shell is used. From the viewpoint of raw material costs, plant-derived raw materials are suitable. However, many plant-derived raw materials contain impurity metals, so that a purification process is required to stabilize the quality as an industrial raw material.
　植物由来原料の中でも、予め精製工程を経たものとしては、例えば、でんぷん等の糖類が挙げられ、これらを用いて炭素材料を得る試みがなされている（例えば、非特許文献１）。また、糖類を変性させる方法として、でんぷんを高温焙煎することにより粘度を低下させる方法も知られている（特許文献１）。 Among the plant-derived raw materials, saccharides such as starch are listed as those that have been subjected to a purification step in advance, and attempts have been made to obtain a carbon material using these (eg, Non-Patent Document 1). Further, as a method of modifying saccharides, a method of lowering the viscosity by roasting starch at a high temperature is also known (Patent Document 1).
特開２０１２－１００６５０号公報JP 2012-100650 A
　近年、リチウムイオン二次電池の車載用途などへの適用が検討され、リチウムイオン二次電池のさらなる高容量化が求められている。また、非水電解質二次電池の入出力特性をさらに高めるために、低い内部抵抗を有する電池を与える炭素質材料も必要とされている。 In recent years, the application of lithium ion secondary batteries to in-vehicle applications has been studied, and there is a demand for higher capacity lithium ion secondary batteries. Further, in order to further enhance the input / output characteristics of the non-aqueous electrolyte secondary battery, a carbonaceous material that provides a battery having low internal resistance is also required.
　例えば非特許文献１に記載されるような炭素材料は、黒鉛様の構造を有しており、十分な充放電容量を有するものではない。また、糖類を用いて高い放電容量を有する難黒鉛化性炭素を得るために、糖類を変性させて構造調整を行うことが考えられるが、例えば特許文献１に記載されるような方法は、主に食品用途を指向した方法であり、高い放電容量を有する難黒鉛化性炭素の前駆体を得る方法として適するものではない。 For example, a carbon material as described in Non-Patent Document 1 has a graphite-like structure and does not have a sufficient charge / discharge capacity. Further, in order to obtain a non-graphitizable carbon having a high discharge capacity using a saccharide, it is conceivable to modify the saccharide to adjust the structure. For example, the method described in Patent Document 1 is mainly used. However, this method is not suitable as a method for obtaining a non-graphitizable carbon precursor having a high discharge capacity.
　したがって、本発明は、高い充放電容量と、低い抵抗を有する非水電解質二次電池（例えばリチウムイオン二次電池、ナトリウムイオン二次電池、リチウム硫黄電池、リチウム空気電池）の負極活物質に適した炭素質材料を製造するに有用な炭素前駆体を提供することを目的とする。 Therefore, the present invention is suitable for a negative electrode active material of a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery, a sodium ion secondary battery, a lithium sulfur battery, and a lithium air battery) having high charge / discharge capacity and low resistance. It is an object of the present invention to provide a carbon precursor useful for producing a carbonaceous material.
　本発明者は、上記課題を解決すべく鋭意検討を行った結果、元素分析による酸素原子含有量と炭素原子含有量の比（Ｏ／Ｃ）が０．１０～０．８５であり、かつ、ＩＲスペクトルの１７２０ｃｍ－１付近のピークの強度（ＩＡ）と３３３０ｃｍ－１付近のピークの強度（ＩＢ）の比（ＩＡ／ＩＢ）が０．５０以上である炭素前駆体によって、上記課題が解決されることを見出し、本発明を完成するに至った。 The present inventor has conducted intensive studies in order to solve the above problems, and as a result, the ratio of the oxygen atom content to the carbon atom content (O / C) by elemental analysis is 0.10 to 0.85, and the carbon precursor ratio of the peak intensity at 1720 cm -1 vicinity of the intensity of peak (I a) and 3330cm around -1 of the IR spectrum (I B) (I a / I B) is 0.50 or more, the The inventors have found that the problem is solved, and have completed the present invention.
　すなわち、本発明は以下の好適な態様を含む。
〔１〕元素分析による酸素原子含有量と炭素原子含有量の比（Ｏ／Ｃ）が０．１０～０．８５であり、かつ、ＩＲスペクトルの１７２０ｃｍ－１付近のピークの強度（ＩＡ）と３３３０ｃｍ－１付近のピークの強度（ＩＢ）の比（ＩＡ／ＩＢ）が０．５０以上である、炭素前駆体。
〔２〕ＴＧ－ＤＴＡ測定によるＤＴＡ曲線において、１００～５００℃の範囲に吸熱ピークを有さない、前記〔１〕に記載の炭素前駆体。
〔３〕１３Ｃ－ＮＭＲスペクトルにおいて、０～５０ｐｐｍの範囲にピークを有する、前記〔１〕または〔２〕に記載の炭素前駆体。
〔４〕糖類骨格を有する物質に由来する、前記〔１〕～〔３〕のいずれかに記載の炭素前駆体。
〔５〕炭素前駆体の原料を、酸素含有気体の供給下、２１５～２４０℃の温度範囲で１～１２時間熱処理して炭素前駆体を得る、前記〔１〕～〔４〕のいずれかに記載の炭素前駆体の製造方法。
〔６〕酸素含有気体の供給量は、炭素前駆体の原料の単位表面積あたり０．００５～５．０Ｌ／（分・ｍ２）である、前記〔５〕に記載の製造方法。 That is, the present invention includes the following preferred embodiments.
[1] The ratio (O / C) of the oxygen atom content to the carbon atom content by elemental analysis is 0.10 to 0.85, and the peak intensity (I A ) around 1720 cm −1 in the IR spectrum And a ratio (I A / I B ) of peak intensities (I B ) around 3330 cm −1 and 0.50 or more.
[2] The carbon precursor according to [1], which has no endothermic peak in the range of 100 to 500 ° C. in a DTA curve measured by TG-DTA.
[3] The carbon precursor according to [1] or [2], which has a peak in a range of 0 to 50 ppm in a 13 C-NMR spectrum.
[4] The carbon precursor according to any one of [1] to [3], which is derived from a substance having a saccharide skeleton.
[5] The method according to any of [1] to [4], wherein the raw material of the carbon precursor is heat-treated at a temperature of 215 to 240 ° C. for 1 to 12 hours under a supply of an oxygen-containing gas to obtain a carbon precursor. The production method of the carbon precursor described in the above.
[6] The production method according to [5], wherein the supply amount of the oxygen-containing gas is 0.005 to 5.0 L / (min · m 2 ) per unit surface area of the raw material of the carbon precursor.
　本発明によれば、高い充放電容量および低い抵抗を有する非水電解質二次電池の負極活物質に適した炭素質材料を製造するに有用な炭素前駆体を提供することができる。 According to the present invention, a carbon precursor useful for producing a carbonaceous material suitable for a negative electrode active material of a nonaqueous electrolyte secondary battery having a high charge / discharge capacity and a low resistance can be provided.
実施例１で得た炭素前駆体のＳＥＭ画像を示す図である。FIG. 2 is a view showing an SEM image of a carbon precursor obtained in Example 1. 比較例１で得た炭素前駆体のＳＥＭ画像を示す図である。FIG. 4 is a view showing an SEM image of a carbon precursor obtained in Comparative Example 1.
　以下、本発明の実施の形態について、詳細に説明する。なお、本発明の範囲はここで説明する実施の形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲で種々の変更を加えることができる。 Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiment described here, and various changes can be made without departing from the spirit of the present invention.
　本発明において、炭素前駆体は、炭素質材料の製造に用いる原料であって、炭水化物、植物原料、糖類骨格を有する物質等の炭素前駆体の原料に、例えば熱処理を施して得られるものをいう。本発明の炭素前駆体は、例えば高温でさらに熱処理することにより、炭素質材料へと導くことができる物質である。 In the present invention, the carbon precursor is a raw material used for producing a carbonaceous material, and is obtained by, for example, performing a heat treatment on a raw material of a carbon precursor such as a carbohydrate, a plant raw material, or a substance having a saccharide skeleton. . The carbon precursor of the present invention is a substance that can be converted into a carbonaceous material by further heat treatment at a high temperature, for example.
　本発明の炭素前駆体は、炭素前駆体の原料に、例えば熱処理を施して製造される。かかる熱処理工程においては、炭素前駆体の原料となる物質に含まれる物理吸着水が乾燥されると共に、分子レベルでの脱水反応が起こると考えられる。上記工程における水分の乾燥および脱水が不十分である場合、炭素質材料を得るために、炭素前駆体を高温でさらに熱処理する際に、炭素前駆体から多量の水蒸気が発生し、該水蒸気により炭素前駆体が溶融し、充放電容量を高めるに適した構造を有する炭素質材料が得られないことが明らかになった。また、上記工程における脱水反応が進行しすぎている場合、構造が固定化され過ぎてしまい、後の熱処理での構造形成が生じ難いために、炭素質材料を得るために炭素前駆体を高温でさらに熱処理する際に、リチウムイオンを吸脱着するサイトが形成されにくいことがわかった。 炭素 The carbon precursor of the present invention is produced by, for example, subjecting a raw material of the carbon precursor to a heat treatment. In such a heat treatment step, it is considered that the physically adsorbed water contained in the substance serving as the raw material of the carbon precursor is dried and a dehydration reaction occurs at a molecular level. If the drying and dehydration of water in the above steps are insufficient, a large amount of water vapor is generated from the carbon precursor when the carbon precursor is further heat-treated at a high temperature in order to obtain a carbonaceous material. It became clear that the precursor melted and a carbonaceous material having a structure suitable for increasing the charge / discharge capacity could not be obtained. In addition, if the dehydration reaction in the above step is excessively progressing, the structure is excessively fixed, and it is difficult to form a structure in a subsequent heat treatment. Further, it was found that during the heat treatment, sites for absorbing and desorbing lithium ions were hardly formed.
　さらに、炭素前駆体の原料に、例えば熱処理を施して、本発明の炭素前駆体を製造する際、上記に述べた脱水反応に加えて、カルボニル基を有する架橋構造が形成される架橋反応が進行していると考えられる。上記架橋構造が形成されるメカニズムは明らかではないが、かかる構造が形成されることにより、炭素質材料を得るために炭素前駆体を高温でさらに熱処理する際に、リチウムイオンを吸脱着するサイトが形成されやすく、その結果、非水電解質二次電池の充放電容量を高めやすく、かつ、抵抗を低下させやすいことがわかった。 Further, when the raw material of the carbon precursor is subjected to, for example, heat treatment to produce the carbon precursor of the present invention, in addition to the dehydration reaction described above, a crosslinking reaction in which a crosslinked structure having a carbonyl group is formed proceeds. it seems to do. The mechanism by which the crosslinked structure is formed is not clear, but by forming such a structure, when the carbon precursor is further heat-treated at a high temperature in order to obtain a carbonaceous material, sites for adsorbing and desorbing lithium ions are formed. It was found that they were easily formed, and as a result, the charge / discharge capacity of the nonaqueous electrolyte secondary battery was easily increased and the resistance was easily lowered.
　上記の観点から、本発明の炭素前駆体において、元素分析による酸素原子含有量と炭素原子含有量の比（Ｏ／Ｃ）は、０．１０～０．８５である。上記の酸素原子含有量と炭素原子含有量の比が０．８５よりも大きい場合、上記工程における水分の乾燥および脱水が不十分であり、かかる比が０．１０よりも小さいと、脱水反応が進行しすぎているといえる。炭素前駆体の溶融を防止しやすく、リチウムイオンを吸脱着する構造を形成しやすく、これらの結果、充放電容量を高めやすい観点からは、酸素原子含有量と炭素原子含有量の比は、好ましくは０．２以上０．８０以下、より好ましくは、０．３以上０．７９以下、さらに好ましくは、０．４以上０．７８以下である。 From the above viewpoint, in the carbon precursor of the present invention, the ratio of the oxygen atom content to the carbon atom content (O / C) by elemental analysis is 0.10 to 0.85. When the ratio between the oxygen atom content and the carbon atom content is larger than 0.85, the drying and dehydration of water in the above step are insufficient, and when the ratio is smaller than 0.10. It can be said that it is progressing too much. The ratio of the oxygen atom content to the carbon atom content is preferably from the viewpoint of easily preventing the melting of the carbon precursor, forming a structure for absorbing and desorbing lithium ions and easily increasing the charge and discharge capacity. Is 0.2 or more and 0.80 or less, more preferably 0.3 or more and 0.79 or less, and still more preferably 0.4 or more and 0.78 or less.
　本発明の炭素前駆体において、元素分析による酸素原子含有量は、好ましくは３５質量％以上、より好ましくは３８質量％以上、さらにより好ましくは４０質量％以上である。また、酸素原子含有量は、好ましくは４５質量％以下、より好ましくは４３質量％以下、さらにより好ましくは４２質量％以下である。酸素原子含有量が上記の範囲内であれば、炭素前駆体の溶融を防止しやすく、リチウムイオンを吸脱着する構造を形成させやすい。 に お い て In the carbon precursor of the present invention, the oxygen atom content by elemental analysis is preferably 35% by mass or more, more preferably 38% by mass or more, and even more preferably 40% by mass or more. The oxygen atom content is preferably 45% by mass or less, more preferably 43% by mass or less, and even more preferably 42% by mass or less. When the oxygen atom content is within the above range, melting of the carbon precursor is easily prevented, and a structure for absorbing and desorbing lithium ions is easily formed.
　本発明の炭素前駆体において、元素分析による炭素原子含有量は、好ましくは４５質量％以上、より好ましくは４８質量％以上、さらにより好ましくは５０質量％以上、特に好ましくは５１質量％以上である。また、炭素原子含有量は、好ましくは６０質量％以下、より好ましくは５７質量％以下、さらにより好ましくは５５質量％以下、特に好ましくは５４質量％以下である。炭素原子含有量が上記の範囲内であれば、炭素前駆体の溶融を防止しやすく、リチウムイオンを吸脱着する構造を形成させやすい。 In the carbon precursor of the present invention, the carbon atom content by elemental analysis is preferably 45% by mass or more, more preferably 48% by mass or more, still more preferably 50% by mass or more, and particularly preferably 51% by mass or more. . Further, the carbon atom content is preferably 60% by mass or less, more preferably 57% by mass or less, still more preferably 55% by mass or less, and particularly preferably 54% by mass or less. When the carbon atom content is within the above range, melting of the carbon precursor is easily prevented, and a structure for absorbing and desorbing lithium ions is easily formed.
　酸素原子含有量および炭素原子含有量の測定の詳細は後述の通りであり、元素分析法（不活性ガス溶解法）により測定される。また、酸素原子含有量を炭素原子含有量で除して、酸素原子含有量と炭素原子含有量の比（Ｏ／Ｃ）を算出することができる。該比を上記の範囲に調整する方法は何ら限定されないが、例えば、炭素前駆体の原料を、酸素含有気体の供給下、２１５～２４０℃の温度範囲で１～１２ｈｒ熱処理する方法を用いることができる。特に、炭素前駆体の原料の量を増やす、酸素含有気体の供給量を小さくすると、脱水反応が生じる際に水蒸気を除去しにくくなり、原料が水蒸気と水熱反応し、その結果、酸素原子含有量が増加する傾向にある。そのため、原料の量や酸素含有気体の供給量を調整することにより、酸素原子含有量と炭素原子含有量の比を上記の範囲に調整することができる。 (4) The details of the measurement of the oxygen atom content and the carbon atom content are described below, and are measured by elemental analysis (inert gas dissolution method). Further, the ratio of the oxygen atom content to the carbon atom content (O / C) can be calculated by dividing the oxygen atom content by the carbon atom content. The method of adjusting the ratio to the above range is not limited at all. For example, a method of heat-treating the raw material of the carbon precursor for 1 to 12 hours at a temperature of 215 to 240 ° C. under the supply of an oxygen-containing gas may be used. it can. In particular, when the amount of the raw material of the carbon precursor is increased and the supply amount of the oxygen-containing gas is reduced, it is difficult to remove water vapor when the dehydration reaction occurs, and the raw material hydrothermally reacts with the water vapor, and as a result, contains oxygen atoms. The amount tends to increase. Therefore, by adjusting the amount of the raw material and the supply amount of the oxygen-containing gas, the ratio of the oxygen atom content to the carbon atom content can be adjusted to the above range.
　本発明の炭素前駆体において、ＩＲスペクトルの１７２０ｃｍ－１付近のピークの強度（ＩＡ）と３３３０ｃｍ－１付近のピークの強度（ＩＢ）の比（ＩＡ／ＩＢ）は、０．５０以上である。ＩＲスペクトルの１７２０ｃｍ－１付近のピーク（ＩＡ）は、カルボニル基由来のピークであり、通常１６９５～１７５０ｃｍ－１に観察される。また、３３３０ｃｍ－１付近のピーク（ＩＢ）は、水酸基由来のピークであり、通常３２００～３６００ｃｍ－１に観察される。炭素前駆体を製造する際の熱処理において、カルボニル基を有する架橋構造が形成される架橋反応が進行するとＩＡが大きくなり、それと同時に、脱水反応が進行するとＩＢが小さくなる。これらの反応が進行することで、ＩＡ／ＩＢが大きくなると考えられる。ＩＡ／ＩＢが０．５０より小さいと、架橋反応が不十分であるか、脱水反応が不十分であるために、炭素前駆体から炭素質材料を得るために高温で熱処理を行う際に、炭素前駆体が溶融してしまう。炭素前駆体の溶融を防ぎ、リチウムイオンを吸脱着する構造を形成し、放電容量を高めやすい観点から、ＩＡ／ＩＢは、好ましくは、０．５５以上、より好ましくは、０．６０以上、さらに好ましくは０．６５以上である。ＩＡ／ＩＢの上限は特に限定されないが、脱水反応を進行させ過ぎない観点からは、好ましくは２．０以下、より好ましくは１．６以下である。 In the carbon precursor of the present invention, the ratio of the peak intensity at 1720cm around -1 of the IR spectrum (I A) and 3330Cm -1 near the peak intensity (I B) (I A / I B) is 0.50 That is all. The peak (I A ) around 1720 cm −1 in the IR spectrum is a peak derived from a carbonyl group and is usually observed at 1695 to 1750 cm −1 . The peak (I B ) around 3330 cm −1 is a peak derived from a hydroxyl group and is usually observed at 3200 to 3600 cm −1 . In the heat treatment in the preparation of the carbon precursor, I A increases the crosslinking reaction crosslinked structure having a carbonyl group is formed proceeds, at the same time, the I B decreases as dehydration reaction proceeds. By these reactions proceed, it is considered to be I A / I B increases. I and A / I B is 0.50 less than, or crosslinking reaction is insufficient, because dehydration reaction is insufficient, when performing heat treatment at a high temperature to obtain a carbonaceous material from a carbon precursor As a result, the carbon precursor melts. Prevent melting of the carbon precursor, the lithium ions to form a structure for adsorption and desorption, the discharge capacity from the enhanced easily standpoint, I A / I B is preferably 0.55 or more, more preferably, 0.60 or more , More preferably 0.65 or more. While I limit A / I B is not particularly limited, from the viewpoint of not too allowed to proceed dehydration reaction, preferably 2.0 or less, more preferably 1.6 or less.
　本発明の炭素前駆体において、ＩＲスペクトルの１７２０ｃｍ－１付近のピーク強度（ＩＡ）は、好ましくは０．００５～０．０５、より好ましくは０．００８～０．０４５、さらに好ましくは０．０１０～０．０４０である。１７２０ｃｍ－１付近のピーク強度（ＩＡ）が上記の範囲内であれば、炭素前駆体の溶融を防止しやすく、リチウムイオンを吸脱着する構造を形成させやすい。 In the carbon precursor of the present invention, the peak intensity (I A ) around 1720 cm −1 of the IR spectrum is preferably 0.005 to 0.05, more preferably 0.008 to 0.045, and still more preferably 0.1 to 0.045. 010 to 0.040. When the peak intensity (I A ) around 1720 cm −1 is within the above range, the melting of the carbon precursor is easily prevented, and a structure for absorbing and desorbing lithium ions is easily formed.
　本発明の炭素前駆体において、ＩＲスペクトルの３３３０ｃｍ－１付近のピーク強度（ＩＢ）は、好ましくは０．０１５～０．０６０、より好ましくは０．０２０～０．０５５、さらに好ましくは０．０２５～０．０５０である。３３３０ｃｍ－１付近のピーク強度（ＩＢ）が上記の範囲内であれば、炭素前駆体の溶融を防止しやすく、リチウムイオンを吸脱着する構造を形成させやすい。 In the carbon precursor of the present invention, the peak intensity (I B ) around 3330 cm −1 of the IR spectrum is preferably 0.015 to 0.060, more preferably 0.020 to 0.055, and still more preferably 0.1 to 0.055. 025 to 0.050. When the peak intensity (I B ) near 3330 cm −1 is within the above range, the melting of the carbon precursor is easily prevented, and a structure for absorbing and desorbing lithium ions is easily formed.
　ＩＲの測定方法の詳細は実施例に記載する通りであり、後述するＡＴＲ法（全反射測定法）により測定される。ＩＡ／ＩＢを上記の範囲に調整する方法は何ら限定されないが、例えば、炭素前駆体の原料を、酸素含有気体の供給下、２１５～２４０℃の温度範囲で１～１２ｈｒ熱処理する方法を用いることができる。特に、炭素前駆体の原料の量を増やす、酸素含有気体の供給量を小さくすると、架橋反応が進行しにくくなると共に、脱水反応が生じる際に水蒸気を除去しにくくなり、原料が水蒸気と水熱反応する。その結果、ＩＡが小さくなる、および／または、ＩＢが大きくなり、ＩＡ／ＩＢが小さくなる傾向がある。そのため、原料の量や酸素含有気体の供給量を調整することにより、ＩＡ／ＩＢを上記の範囲に調整することができる。 The details of the IR measurement method are as described in Examples, and are measured by the ATR method (total reflection measurement method) described later. I A / how the I B is adjusted to the above range is not limited in any way, for example, the raw material of the carbon precursor, the supply of an oxygen-containing gas, a method of heat treatment 1 ~ 12hr at a temperature range of 215 ~ 240 ° C. Can be used. In particular, when the amount of the raw material of the carbon precursor is increased and the supply amount of the oxygen-containing gas is reduced, the crosslinking reaction hardly proceeds, and it becomes difficult to remove water vapor when a dehydration reaction occurs. react. As a result, I A is small, and / or, the greater the I B, there is a tendency that the I A / I B is reduced. Therefore, by adjusting the supply amount of the raw material amounts and oxygen-containing gas, it is possible to adjust the I A / I B in the above range.
　本発明の炭素前駆体は、ＴＧ－ＤＴＡ測定によるＤＴＡ曲線において、１００～５００℃の範囲に吸熱ピークを有さないことが好ましい。上記温度範囲に吸熱ピークを有することは、上記温度範囲に融点を有することを表す。炭素前駆体が１００～５００℃の間に吸熱ピークを有さない場合、炭素前駆体中の炭素構造が固定化されており、炭素前駆体から炭素質材料を得るために高温で熱処理を行う際に炭素前駆体が溶融しにくく、得られる非水電解質二次電池の充放電容量を高めやすく、抵抗を低下させやすいと考えられる。ＴＧ－ＤＴＡ測定の詳細は実施例に記載する通りである。ＤＴＡ曲線において、１００～５００℃の間に吸熱ピークを有さないようにする方法は何ら限定されないが、例えば、炭素前駆体の原料を、酸素含有気体の供給下、２１５～２４０℃の温度範囲で１～１２ｈｒ熱処理する方法を用いることができる。特に、炭素前駆体の原料の量を増やす、酸素含有気体の供給量を小さくすると、１００～５００℃の間に吸熱ピークを有する構造となり易い傾向がある。そのため、原料の量や酸素含有気体の供給量を調整することにより、１００～５００℃の範囲に吸熱ピークを有さないように調整することができる。 炭素 It is preferable that the carbon precursor of the present invention does not have an endothermic peak in a range of 100 to 500 ° C. in a DTA curve measured by TG-DTA. Having an endothermic peak in the above temperature range means having a melting point in the above temperature range. When the carbon precursor does not have an endothermic peak between 100 and 500 ° C., the carbon structure in the carbon precursor is fixed, and the heat treatment is performed at a high temperature to obtain a carbonaceous material from the carbon precursor. It is considered that the carbon precursor is less likely to be melted, the charge / discharge capacity of the obtained nonaqueous electrolyte secondary battery is easily increased, and the resistance is easily lowered. Details of the TG-DTA measurement are as described in Examples. There is no particular limitation on a method for preventing an endothermic peak from 100 to 500 ° C. in the DTA curve. For example, the raw material of the carbon precursor may be supplied in the temperature range of 215 to 240 ° C. under the supply of an oxygen-containing gas. For 1 to 12 hours. In particular, when the amount of the raw material of the carbon precursor is increased and the supply amount of the oxygen-containing gas is reduced, the structure tends to have an endothermic peak between 100 and 500 ° C. Therefore, by adjusting the amount of the raw material and the supply amount of the oxygen-containing gas, it can be adjusted so as not to have an endothermic peak in the range of 100 to 500 ° C.
　本発明の炭素前駆体は、１３Ｃ－ＮＭＲスペクトルにおいて、０～５０ｐｐｍの間にピークを有することが好ましい。１３Ｃ－ＮＭＲスペクトルにおける０～５０ｐｐｍの間に観測されるピークは、メチル基やメチレン基、メチン基の炭素に由来するピークである。上記範囲にピークを有することは、炭素前駆体の構造中に飽和炭化水素の構造が含まれることを意味する。飽和炭化水素は、炭素前駆体の構造骨格同士を架橋するような作用があるため、飽和炭化水素の構造が炭素前駆体に含まれることにより、炭素前駆体の構造が固定化され、溶融しにくくなる。飽和炭化水素の構造が形成される機構としては、原料に含まれる脂環式構造の一部が開環し、脱水反応などにより再反応することなどが考えられる。１３Ｃ－ＮＭＲ測定の詳細は実施例に記載する通りであり、後述の固体ＮＭＲ法により測定される。１３Ｃ－ＮＭＲで０～５０ｐｐｍにピークを有するようにする方法は何ら限定されないが、例えば、炭素前駆体の原料を、酸素含有気体の供給下、２１５～２４０℃の温度範囲で１～１２ｈｒ熱処理する方法を用いることができる。特に熱処理温度が高くなると、脂環式構造が開環しにくく、架橋構造を形成しにくくなるため、０～５０ｐｐｍの間にピークが観察されなくなる傾向がある。そのため、熱処理温度を調整することで、上記範囲にピークを有するようにすることができる。 The carbon precursor of the present invention preferably has a peak between 0 and 50 ppm in the 13 C-NMR spectrum. The peak observed between 0 and 50 ppm in the 13 C-NMR spectrum is a peak derived from carbon of a methyl group, a methylene group, or a methine group. Having a peak in the above range means that the structure of the saturated hydrocarbon is included in the structure of the carbon precursor. Since the saturated hydrocarbon has an effect of cross-linking the structural skeletons of the carbon precursor, by including the structure of the saturated hydrocarbon in the carbon precursor, the structure of the carbon precursor is fixed and hardly melted. Become. As a mechanism for forming the structure of the saturated hydrocarbon, it is conceivable that a part of the alicyclic structure contained in the raw material is opened and re-reacted by a dehydration reaction or the like. The details of the 13 C-NMR measurement are as described in Examples, and are measured by the solid-state NMR method described later. The method for giving a peak at 0 to 50 ppm in 13 C-NMR is not particularly limited. For example, a raw material of a carbon precursor is heat-treated for 1 to 12 hours in a temperature range of 215 to 240 ° C. under supply of an oxygen-containing gas. Can be used. In particular, when the heat treatment temperature is increased, the alicyclic structure is less likely to open the ring and the crosslinked structure is less likely to be formed, so that no peak is observed between 0 and 50 ppm. Therefore, a peak can be obtained in the above range by adjusting the heat treatment temperature.
　本発明の炭素前駆体において、形状粒度分布測定により測定される円形度は、好ましくは０．９５以上、より好ましくは０．９７以上、さらにより好ましくは０．９８０以上、さらにより好ましくは０．９８１以上、特に好ましくは０．９８３以上である。円形度が上記の下限以上である場合、構造の固定化が十分に進行しており、炭素前駆体粒子の溶融や、炭素前駆体粒子同士の融着が生じていないと考えられる。その結果、炭素前駆体の構造固定化を進めやすく、リチウムイオンを吸脱着する構造を形成し、充放電容量を高めやすい。また、炭素前駆体から得られる炭素質材料において、電極密度を高めやすい。円形度の測定方法の詳細は実施例に記載する通りであり、後述する形状粒度分布測定法により測定される。円形度を上記の範囲に調整する方法は何ら限定されないが、例えば、炭素前駆体の原料を、酸素含有気体の供給下、２１５～２４０℃の温度範囲で１～１２ｈｒ熱処理する方法を用いることができる。特に、炭素前駆体の原料の量を増やす、酸素含有気体の供給量を小さくすると、炭素前駆体から炭素質材料を製造する際に、炭素前駆体が溶融しやすくなる。そのため、原料の量や酸素含有気体の供給量を調整し、炭素前駆体の溶融を防ぐことにより、円形度を上記範囲に調整することができる。 In the carbon precursor of the present invention, the circularity measured by shape particle size distribution measurement is preferably 0.95 or more, more preferably 0.97 or more, still more preferably 0.980 or more, and even more preferably 0.1 or more. It is 981 or more, particularly preferably 0.983 or more. When the circularity is equal to or more than the above lower limit, it is considered that the fixation of the structure has sufficiently proceeded, and the melting of the carbon precursor particles and the fusion of the carbon precursor particles have not occurred. As a result, it is easy to fix the structure of the carbon precursor, to form a structure for absorbing and desorbing lithium ions, and to easily increase the charge / discharge capacity. In the carbonaceous material obtained from the carbon precursor, the electrode density can be easily increased. The details of the method of measuring the circularity are as described in Examples, and are measured by a shape particle size distribution measuring method described later. The method for adjusting the circularity to the above range is not limited at all. For example, a method of heat-treating the raw material of the carbon precursor for 1 to 12 hours at a temperature of 215 to 240 ° C. under the supply of an oxygen-containing gas may be used. it can. In particular, when the amount of the raw material of the carbon precursor is increased and the supply amount of the oxygen-containing gas is reduced, the carbon precursor is easily melted when producing the carbonaceous material from the carbon precursor. Therefore, the circularity can be adjusted to the above range by adjusting the amount of the raw material and the supply amount of the oxygen-containing gas to prevent the carbon precursor from melting.
　本発明の炭素前駆体の平均粒子径（Ｄ５０）は、好ましくは３０μｍ以下、より好ましくは２５μｍ以下、さらにより好ましくは２０μｍ以下、さらにより好ましくは１８μｍ以下、特に好ましくは１６μｍ以下、最も好ましくは１５μｍ以下である。平均粒子径が上記の上限以下である場合、電極作製時の塗工性が良好となることに加えて、炭素前駆体から得た炭素質材料の粒子内でのリチウムイオンの拡散自由行程が少なくなるため、急速な充放電が得やすくなる。さらに、リチウムイオン二次電池では、入出力特性を向上させるために電極面積を大きくすることが重要であり、そのためには、電極調製時に集電板への活物質の塗工厚みを薄くする必要がある。炭素前駆体の平均粒子径が上記の上限以下である場合、活物質となる炭素質材料の平均粒子径も低下させやすく、その結果、電極調製時に塗工厚みを薄くしやすい。また、本発明の炭素前駆体の平均粒子径Ｄ５０は、好ましくは２μｍ以上、より好ましくは３μｍ以上、さらにより好ましくは４μｍ以上、さらにより好ましくは５μｍ以上、さらにより好ましくは６μｍ以上、さらにより好ましくは７μｍ以上、さらにより好ましくは８μｍ以上、特に好ましくは９μｍ以上である。平均粒子径Ｄ５０が上記の下限以上である場合、炭素前駆体中の微粉に由来する炭素質材料の微粉による比表面積の増加および電解液との反応性の増加を抑制し、不可逆容量の増加を抑制しやすい。また、炭素前駆体から得た炭素質材料を用いて負極を製造する場合に、炭素質材料の間に形成される空隙を確保しやすく、電解液中でのリチウムイオンの移動が抑制されにくく、非水電解質二次電池の抵抗を低下させやすい。平均粒子径Ｄ５０は、累積体積が５０％となる粒子径であり、例えば粒子径・粒度分布測定装置（マイクロトラック・ベル株式会社製「マイクロトラックＭＴ３３００ＥＸII」）を用いたレーザー散乱法により粒度分布を測定することにより求めることができる。 The average particle diameter (D 50 ) of the carbon precursor of the present invention is preferably 30 μm or less, more preferably 25 μm or less, still more preferably 20 μm or less, even more preferably 18 μm or less, particularly preferably 16 μm or less, and most preferably. It is 15 μm or less. When the average particle diameter is equal to or less than the above upper limit, in addition to the good coatability at the time of electrode production, the free path of diffusion of lithium ions in the particles of the carbonaceous material obtained from the carbon precursor is small. Therefore, rapid charge and discharge can be easily obtained. Furthermore, in a lithium ion secondary battery, it is important to increase the electrode area in order to improve the input / output characteristics. For that purpose, it is necessary to reduce the thickness of the active material applied to the current collector during electrode preparation. There is. When the average particle diameter of the carbon precursor is equal to or less than the above upper limit, the average particle diameter of the carbonaceous material serving as the active material is also easily reduced, and as a result, the coating thickness is easily reduced during electrode preparation. The average particle diameter D 50 of the carbon precursor of the present invention is preferably 2μm or more, more preferably 3μm or more, even more preferably 4μm or more, still more preferably 5μm or more, even more preferably 6μm or more, even more It is preferably at least 7 μm, still more preferably at least 8 μm, particularly preferably at least 9 μm. If the average particle diameter D 50 is the above lower limit or more, suppressing an increase in reactivity with the carbonaceous particulates by increasing the specific surface area and electrolyte material from the fine carbon precursor, an increase in irreversible capacity Is easy to control. In addition, when manufacturing a negative electrode using a carbonaceous material obtained from a carbon precursor, it is easy to secure voids formed between the carbonaceous materials, and it is difficult to suppress the movement of lithium ions in the electrolyte, The resistance of the non-aqueous electrolyte secondary battery is easily reduced. The average particle diameter D 50 is a particle diameter at which the cumulative volume becomes 50%. For example, the particle diameter distribution is measured by a laser scattering method using a particle diameter and particle size distribution measuring device (“Microtrack MT3300EXII” manufactured by Microtrac Bell Co., Ltd.). Can be determined by measuring
　本発明の炭素前駆体を製造するための方法は、上記特性を有する炭素前駆体が得られる限り特に限定されないが、例えば後述する製造方法を用いて製造することができる。 方法 The method for producing the carbon precursor of the present invention is not particularly limited as long as a carbon precursor having the above properties can be obtained. For example, the carbon precursor can be produced using a production method described below.
　本発明は、高い充放電容量および低い抵抗を有する、非水電解質二次電池（例えばリチウムイオン二次電池、ナトリウムイオン電池、リチウム硫黄電池、リチウム空気電池）の負極活物質または導電材に適した炭素質材料を製造するに有用な、炭素前駆体の製造方法も提供する。 The present invention is suitable for a negative electrode active material or a conductive material of a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery, a sodium ion battery, a lithium sulfur battery, and a lithium air battery) having a high charge / discharge capacity and a low resistance. A method for producing a carbon precursor useful for producing a carbonaceous material is also provided.
　本発明の一態様において、本発明の炭素前駆体の製造方法は、
（１）炭素前駆体の原料を、酸素含有気体の供給下、２１５～２４０℃の温度範囲で１～１２時間熱処理して炭素前駆体を得る、製造方法である。 In one embodiment of the present invention, the method for producing a carbon precursor of the present invention comprises:
(1) A production method in which a carbon precursor raw material is heat-treated at a temperature of 215 to 240 ° C. for 1 to 12 hours under a supply of an oxygen-containing gas to obtain a carbon precursor.
　本発明の別の一態様において、本発明の炭素質材料の製造方法は、
（２）炭素前駆体の原料を、該原料５０質量部に対して８０～５００質量部の少なくとも１種の耐熱性オイルと混合して得た混合物を、１５０～３００℃の温度範囲で０．５～１２時間熱処理して炭素前駆体を得る、製造方法である。 In another aspect of the present invention, the method for producing a carbonaceous material of the present invention comprises:
(2) A mixture obtained by mixing a raw material of a carbon precursor with 80 to 500 parts by mass of at least one heat-resistant oil with respect to 50 parts by mass of the raw material is mixed at a temperature of 150 to 300 ° C. to obtain a mixture. This is a production method in which a carbon precursor is obtained by heat treatment for 5 to 12 hours.
　上記製造方法（１）および（２）に記載する炭素前駆体の原料は、続く熱処理等の工程を経て本発明の炭素前駆体を与え、さらに続く熱処理等の工程を経て最終的に炭素質材料を与える物質であれば特に限定されず、例えば炭水化物等であってよいが、上記特徴を有する本発明の炭素前駆体を得やすい観点から、好ましくは糖類骨格を有する物質である。糖類骨格を有する物質を原料として用いることにより、糖類骨格を有する物質に由来する炭素前駆体を得ることができる。糖類骨格を有する物質（糖類）としては、例えばグルコース、ガラクトース、マンノース、フルクトース、リボース、グルコサミンなどの単糖類や、スクロース、トレハロース、マルトース、セロビオース、マルチトール、ラクトビオン酸、ラクトサミンなどの二糖、でんぷん、グリコーゲン、アガロース、ペクチン、セルロース、キチン、キトサンなどの多糖類が挙げられる。これらの糖類を、単独でまたは２種以上を組み合わせて使用することができる。これらの糖類の中で、大量入手が容易であるためでんぷんが好ましい。 The raw material of the carbon precursor described in the above-mentioned production methods (1) and (2) gives the carbon precursor of the present invention through a subsequent step such as heat treatment, and finally undergoes a subsequent step such as heat treatment to finally obtain a carbonaceous material. The substance is not particularly limited as long as it gives the compound, and may be, for example, a carbohydrate. However, from the viewpoint of easily obtaining the carbon precursor of the present invention having the above characteristics, a substance having a saccharide skeleton is preferable. By using a substance having a saccharide skeleton as a raw material, a carbon precursor derived from a substance having a saccharide skeleton can be obtained. Examples of substances having a saccharide skeleton (saccharides) include monosaccharides such as glucose, galactose, mannose, fructose, ribose, and glucosamine; disaccharides such as sucrose, trehalose, maltose, cellobiose, maltitol, lactobionic acid, and lactosamine; and starch. , Glycogen, agarose, pectin, cellulose, chitin, chitosan and the like. These saccharides can be used alone or in combination of two or more. Among these saccharides, starch is preferred because it is easily available in large quantities.
　上記の本発明の製造方法（１）は、炭素前駆体の原料を、酸素含有気体の供給下、２１５～２４０℃の温度範囲で１～１２時間熱処理して炭素前駆体を得る製造方法である。酸素含有気体としては、酸素を含有する気体であれば特に限定されないが、空気、酸素、空気または酸素と例えば不活性ガス等のその他の気体との混合気体であってもよい。酸素含有気体中の酸素濃度も特に限定されない。当該工程を実施しやすく、製造コストを下げやすい観点からは、酸素含有気体が空気であることが好ましい。 The above-mentioned production method (1) of the present invention is a production method in which a carbon precursor raw material is heat-treated at a temperature of 215 to 240 ° C. for 1 to 12 hours under a supply of an oxygen-containing gas to obtain a carbon precursor. . The oxygen-containing gas is not particularly limited as long as it is a gas containing oxygen, but may be air, oxygen, or a mixed gas of air and oxygen and another gas such as an inert gas. The oxygen concentration in the oxygen-containing gas is not particularly limited. It is preferable that the oxygen-containing gas is air from the viewpoint of easily performing the process and reducing the manufacturing cost.
　酸素含有気体の供給下で熱処理を行うとは、酸素含有気体を供給しながら熱処理を行うことを意味する。ここで、例えば空気等の酸素含有気体の単なる雰囲気下での熱処理、例えば単なる大気雰囲気下での熱処理は、積極的な酸素含有気体の供給が行われているとはいえず、酸素含有気体の供給下で熱処理が行われているとはいえない。よって、このような製造方法は、本発明の製造方法（１）には該当しない。酸素含有気体の供給量は、供給が行われる限り特に限定されないが、例えば炭素前駆体の原料の単位表面積あたり、好ましくは０．００７～３．０Ｌ／（分・ｍ２）、より好ましくは０．００９～２．０Ｌ／（分・ｍ２）、さらに好ましくは０．０１～０．５０Ｌ／（分・ｍ２）である。なお、単位表面積あたりの供給量は、例えば酸素含有気体の１分あたりの供給量を、被処理物（炭素前駆体の原料）の重量と比表面積の積で除して算出される。 Performing the heat treatment while supplying the oxygen-containing gas means performing the heat treatment while supplying the oxygen-containing gas. Here, for example, heat treatment of an oxygen-containing gas such as air in a mere atmosphere, for example, heat treatment in a mere atmosphere, does not mean that active supply of an oxygen-containing gas is performed. It cannot be said that heat treatment is performed under supply. Therefore, such a manufacturing method does not correspond to the manufacturing method (1) of the present invention. The supply amount of the oxygen-containing gas is not particularly limited as long as the supply is performed. For example, it is preferably 0.007 to 3.0 L / (min · m 2 ), more preferably 0 per unit surface area of the raw material of the carbon precursor. 0.009 to 2.0 L / (min · m 2 ), more preferably 0.01 to 0.50 L / (min · m 2 ). The supply amount per unit surface area is calculated, for example, by dividing the supply amount per minute of the oxygen-containing gas by the product of the weight of the object to be processed (raw material of the carbon precursor) and the specific surface area.
　ここで、上記の熱処理工程においては、熱処理により、炭素前駆体の原料に含まれる物理吸着水が乾燥されると共に、炭素前駆体の原料中の分子レベルでの脱水反応が起こり、炭素前駆体が得られると考えられる。さらに、上記工程において、カルボニル基を有する架橋構造が形成される架橋反応も進行していると考えられる。この工程を酸素含有気体の供給下で行うことにより、後述するメカニズムは本発明を何ら限定するものではないが、炭素前駆体の原料から水が乾燥、脱水により除去される際に、供給される酸素が炭素前駆体の原料と相互作用し、カルボニル基を有する架橋構造が形成されると同時に、除去される水が気体と共に系中から除去される。その結果、炭素前駆体の原料が熱処理により融化することなく、微細な構造を維持する炭素前駆体が得られると考えられる。 Here, in the heat treatment step, the heat treatment causes the physically adsorbed water contained in the raw material of the carbon precursor to be dried, and also causes a dehydration reaction at the molecular level in the raw material of the carbon precursor, whereby the carbon precursor becomes It is thought that it can be obtained. Further, it is considered that a cross-linking reaction for forming a cross-linked structure having a carbonyl group is also progressing in the above step. By performing this step under the supply of an oxygen-containing gas, the mechanism described below does not limit the present invention at all, but is supplied when water is removed from the raw material of the carbon precursor by drying and dehydration. Oxygen interacts with the raw material of the carbon precursor to form a crosslinked structure having a carbonyl group, and at the same time, water to be removed is removed from the system together with gas. As a result, it is considered that a carbon precursor which maintains a fine structure without melting the raw material of the carbon precursor by the heat treatment is considered to be obtained.
　本発明の製造方法（１）では、原料を昇温し、上記のように２１５～２４０℃の温度範囲で１～１２時間熱処理を行う。本発明の製造方法（１）における熱処理温度は、好ましくは２１７～２３５℃、より好ましくは２１９～２３０℃である。熱処理時間は、好ましくは２～８時間、より好ましくは２．５～６時間、さらにより好ましくは３～５時間である。熱処理温度および時間が上記範囲内であれば、炭素前駆体の原料から、乾燥および脱水により水を効率的かつ十分に除去しやすく、また、上記特徴を有する炭素質材料を最終的に得やすいと考えられる。ここで、熱処理温度は、一定の温度であってよいが、上記範囲内であれば特に限定されない。 製造 In the production method (1) of the present invention, the temperature of the raw material is increased, and the heat treatment is performed in the temperature range of 215 to 240 ° C. for 1 to 12 hours as described above. The heat treatment temperature in the production method (1) of the present invention is preferably from 217 to 235 ° C, more preferably from 219 to 230 ° C. The heat treatment time is preferably 2 to 8 hours, more preferably 2.5 to 6 hours, and even more preferably 3 to 5 hours. If the heat treatment temperature and time are within the above ranges, it is easy to efficiently and sufficiently remove water from the raw material of the carbon precursor by drying and dehydration, and it is easy to finally obtain a carbonaceous material having the above characteristics. Conceivable. Here, the heat treatment temperature may be a constant temperature, but is not particularly limited as long as it is within the above range.
　上記の本発明の製造方法（２）は、炭素前駆体の原料を、該原料５０質量部に対して８０～５００質量部の少なくとも１種の耐熱性オイルと混合して得た混合物を、１５０～３００℃の温度範囲で０．５～１２時間熱処理して炭素前駆体を得る製造方法である。耐熱性オイルとしては、特に限定されないが、少なくとも熱処理温度範囲で揮発や変質が起こらない物質であれば良く、例えば、シリコンオイル、フッ素オイル、クレオソート油、ジエチレングリコール、トリエチレングリコール、ポリエチレングリコール等が挙げられる。 In the production method (2) of the present invention, the mixture obtained by mixing the raw material of the carbon precursor with 80 to 500 parts by mass of at least one heat-resistant oil is mixed with 50 parts by mass of the raw material. This is a production method in which a carbon precursor is obtained by performing a heat treatment at a temperature in the range of up to 300 ° C. for 0.5 to 12 hours. The heat-resistant oil is not particularly limited, but may be any substance that does not cause volatilization or deterioration at least in the heat treatment temperature range.Examples include silicon oil, fluorine oil, creosote oil, diethylene glycol, triethylene glycol, and polyethylene glycol. No.
　炭素前駆体の原料と混合する耐熱性オイルの量は、原料を分散させ、融着を生じさせ難い観点から、炭素前駆体の原料５０質量部に対して８０～５００質量部、好ましくは１００～４００質量部、より好ましくは１５０～３００質量部、さらにより好ましくは１８０～２８０質量部である。炭素前駆体の原料を耐熱性オイルと混合する方法は特に限定されず、炭素前駆体の原料を耐熱性オイルと直接混合してもよいし、炭素前駆体および／または有機酸を少なくとも１種の液体に分散および／または溶解させた状態で混合してもよい。また、少なくとも１種の液体を用いて混合を行う場合、必要に応じて該液体を蒸発等により除去して混合物を得てもよい。 The amount of the heat-resistant oil mixed with the raw material of the carbon precursor is from 80 to 500 parts by mass, preferably from 100 to 500 parts by mass with respect to 50 parts by mass of the raw material of the carbon precursor, from the viewpoint that the raw material is dispersed and the fusion hardly occurs. The amount is 400 parts by mass, more preferably 150 to 300 parts by mass, and still more preferably 180 to 280 parts by mass. The method of mixing the raw material of the carbon precursor with the heat-resistant oil is not particularly limited, and the raw material of the carbon precursor may be directly mixed with the heat-resistant oil, or the carbon precursor and / or the organic acid may be mixed with at least one kind of oil. They may be mixed in a state of being dispersed and / or dissolved in a liquid. When mixing is performed using at least one liquid, the liquid may be removed by evaporation or the like, if necessary, to obtain a mixture.
　ここで、上記の熱処理工程においては、熱処理により、炭素前駆体の原料に含まれる物理吸着水が乾燥されると共に、炭素前駆体の原料中の分子レベルでの脱水反応が起こり、炭素前駆体が得られると考えられる。さらに、上記工程において、カルボニル基を有する架橋構造が形成される架橋反応も進行していると考えられる。この工程を耐熱性オイルと混合した状態で行うことにより、後述するメカニズムは本発明を何ら限定するものではないが、炭素前駆体の原料から乾燥、脱水により生じた水が、耐熱性オイルの存在により炭素前駆体表面から効率的に除去されると考えられる。その結果、炭素前駆体の原料が熱処理により融化することなく、微細な構造を維持する炭素前駆体が得られると考えられる。 Here, in the heat treatment step, the heat treatment causes the physically adsorbed water contained in the raw material of the carbon precursor to be dried, and also causes a dehydration reaction at the molecular level in the raw material of the carbon precursor, whereby the carbon precursor becomes It is thought that it can be obtained. Further, it is considered that a cross-linking reaction for forming a cross-linked structure having a carbonyl group is also progressing in the above step. By performing this step in the state of being mixed with the heat-resistant oil, the mechanism described below does not limit the present invention at all, but water generated by drying and dehydration from the raw material of the carbon precursor may be present in the presence of the heat-resistant oil. Is considered to be efficiently removed from the surface of the carbon precursor. As a result, it is considered that a carbon precursor which maintains a fine structure without melting the raw material of the carbon precursor by the heat treatment is considered to be obtained.
　本発明の製造方法（２）では、炭素前駆体の原料を耐熱性オイルと混合して得た混合物を５０～３００℃の温度範囲で０．５～１２時間熱処理して炭素前駆体を得る。工程（７）における熱処理温度は、５０～３００℃、好ましくは１５０～３００℃、より好ましくは１８０～２８０℃、さらにより好ましくは２００～２６０℃、特に好ましくは２１０～２５０℃である。熱処理時間は、０．５～１２時間、好ましくは１～８時間、より好ましくは２～６時間、さらにより好ましくは３～５時間である。熱処理温度および時間が上記範囲内であれば、炭素前駆体の原料から、乾燥および脱水により水を効率的かつ十分に除去しやすく、また、充放電容量が高く、抵抗が低い非水電解質二次電池を製造するに適した炭素質材料を最終的に得やすいと考えられる。ここで、熱処理温度は、一定の温度であってよいが、上記範囲内であれば特に限定されない。 In the production method (2) of the present invention, the mixture obtained by mixing the raw material of the carbon precursor with the heat-resistant oil is heat-treated at a temperature of 50 to 300 ° C. for 0.5 to 12 hours to obtain a carbon precursor. The heat treatment temperature in the step (7) is 50 to 300 ° C, preferably 150 to 300 ° C, more preferably 180 to 280 ° C, still more preferably 200 to 260 ° C, and particularly preferably 210 to 250 ° C. The heat treatment time is 0.5 to 12 hours, preferably 1 to 8 hours, more preferably 2 to 6 hours, and still more preferably 3 to 5 hours. When the heat treatment temperature and time are within the above ranges, the water is easily and efficiently removed from the raw material of the carbon precursor by drying and dehydration, and the charge / discharge capacity is high and the non-aqueous electrolyte secondary has low resistance. It is considered that a carbonaceous material suitable for manufacturing a battery can be finally obtained. Here, the heat treatment temperature may be a constant temperature, but is not particularly limited as long as it is within the above range.
　本発明の炭素前駆体を原料とし、以下の工程を少なくとも含む方法により、炭素質材料を製造することができる：
（３Ａ）本発明の炭素前駆体を、不活性ガス雰囲気下、１００℃／時間以上の昇温速度で、５００～９００℃の範囲の第１温度まで加熱する工程、
（３Ｂ）前記炭素前駆体を、不活性ガスの供給下、５００～９００℃の温度で熱処理して炭化物を得る工程、ここで、不活性ガスの供給量は炭素前駆体の単位表面積あたり０．０１～５．０Ｌ／（分・ｍ２）である、
（４Ａ）前記炭化物を、不活性ガス雰囲気下、１００℃／時間以上の昇温速度で、１０００～１４００℃の範囲の第２温度まで加熱する工程、および
（４Ｂ）前記炭化物を、不活性ガスの供給下、１０００～１４００℃の温度で熱処理して炭素質材料を得る工程、ここで、不活性ガスの供給量は炭化物の単位表面積あたり０．０１～５．０Ｌ／（分・ｍ２）である。 Using the carbon precursor of the present invention as a raw material, a carbonaceous material can be produced by a method including at least the following steps:
(3A) heating the carbon precursor of the present invention to a first temperature in the range of 500 to 900 ° C. at a rate of 100 ° C./hour or more in an inert gas atmosphere;
(3B) a step of heat-treating the carbon precursor at a temperature of 500 to 900 ° C. under a supply of an inert gas to obtain a carbide, wherein the supply amount of the inert gas is 0. 01 to 5.0 L / (min · m 2 ),
(4A) a step of heating the carbide to a second temperature in a range of 1000 to 1400 ° C. at a rate of 100 ° C./hour or more in an inert gas atmosphere; and (4B) a step of heating the carbide to an inert gas. Heat treatment at a temperature of 1000 to 1400 ° C. under the supply of carbon to obtain a carbonaceous material, wherein the supply amount of the inert gas is 0.01 to 5.0 L / (min · m 2 ) per unit surface area of the carbide. It is.
　工程（３Ａ）は、本発明の製造方法で得た炭素前駆体を、不活性ガス雰囲気下、１００℃／時間以上の昇温速度で、５００～９００℃の範囲の第１温度まで加熱する工程であり、工程（３Ｂ）は、次いで、該炭素前駆体を、不活性ガスの供給下、５００～９００℃の温度で熱処理して炭化物を得る工程である。工程（３Ａ）は、不活性ガス雰囲気下で行われ、工程（３Ｂ）は、不活性ガスの供給下で行われ、工程（３Ｂ）における不活性ガスの供給量は炭素前駆体の単位表面積あたり０．０１～５．０Ｌ／（分・ｍ２）である。ここで、工程が不活性ガス雰囲気下で行われるとは、該工程が不活性ガス雰囲気中で行われることを表し、不活性ガスの積極的な供給が行われていても、行われていなくてもよい。これに対し、工程が不活性ガス供給下で行われるとは、不活性ガスが供給される雰囲気下であることを意味し、例えば不活性ガスの単なる雰囲気下での熱処理は、積極的な不活性ガスの供給が行われているとはいえず、不活性ガスの供給下で熱処理が行われているとはいえない。なお、本明細書において、当該工程（３Ａ）および／または（３Ｂ）を低温焼成（工程）とも称する。不活性ガスとしては、例えば、アルゴンガス、ヘリウムガス、窒素ガスが挙げられ、好ましくは窒素ガスである。 Step (3A) is a step of heating the carbon precursor obtained by the production method of the present invention to a first temperature in the range of 500 to 900 ° C. at a rate of 100 ° C./hour or more in an inert gas atmosphere. Step (3B) is a step of subsequently heat-treating the carbon precursor at a temperature of 500 to 900 ° C. under a supply of an inert gas to obtain a carbide. The step (3A) is performed under an inert gas atmosphere, the step (3B) is performed under an inert gas supply, and the supply amount of the inert gas in the step (3B) is per unit surface area of the carbon precursor. It is 0.01 to 5.0 L / (min · m 2 ). Here, that the process is performed in an inert gas atmosphere means that the process is performed in an inert gas atmosphere, and even if the inert gas is actively supplied, the process is not performed. You may. On the other hand, the fact that the process is performed under the supply of an inert gas means that the process is performed in an atmosphere in which the inert gas is supplied. It cannot be said that the supply of the active gas is being performed, and that the heat treatment is not being performed under the supply of the inert gas. In the present specification, the step (3A) and / or (3B) is also referred to as low-temperature firing (step). Examples of the inert gas include an argon gas, a helium gas, and a nitrogen gas, and a nitrogen gas is preferable.
　工程（３Ａ）における昇温速度は、充放電容量が高く、抵抗が低い非水電解質二次電池を製造するに適した炭素質材料を最終的に得やすい観点から、好ましくは１００℃／時間以上、より好ましくは３００℃／時間以上、さらに好ましくは４００℃／時間以上、特に好ましくは５００℃／時間以上である。昇温速度の上限は特に限定されないが、急激な熱分解による比表面積増大を抑制しやすい観点から、好ましくは１０００℃／時間以下、より好ましくは８００℃／時間以下である。工程（３Ａ）における第１温度は、５００～９００℃、好ましくは５５０～８８０℃、より好ましくは６００～８６０℃、さらに好ましくは７００～８４０℃である。 The heating rate in the step (3A) is preferably 100 ° C./hour or more from the viewpoint of easily obtaining a carbonaceous material suitable for manufacturing a nonaqueous electrolyte secondary battery having a high charge / discharge capacity and a low resistance. , More preferably at least 300 ° C / hour, still more preferably at least 400 ° C / hour, particularly preferably at least 500 ° C / hour. The upper limit of the rate of temperature rise is not particularly limited, but is preferably 1000 ° C./hour or less, more preferably 800 ° C./hour or less, from the viewpoint of easily increasing the specific surface area due to rapid thermal decomposition. The first temperature in the step (3A) is 500 to 900 ° C., preferably 550 to 880 ° C., more preferably 600 to 860 ° C., and further preferably 700 to 840 ° C.
　次いで、工程（３Ｂ）では、炭素前駆体を、不活性ガスの供給下、５００～９００℃の温度で熱処理して炭化物を得る。工程（３Ｂ）における熱処理温度を以下において低温焼成温度とも称する。工程（３Ｂ）における低温焼成温度は、５００～９００℃、好ましくは５５０～８８０℃、より好ましくは６００～８６０℃、さらに好ましくは７００～８４０℃である。低温焼成温度が上記の範囲内であれば、充放電容量が高く、抵抗が低い非水電解質二次電池を製造するに適した炭素質材料を最終的に得やすい。低温焼成温度は、一定の温度であってよいが、上記範囲内であれば特に限定されない。工程（３Ｂ）における熱処理時間は、好ましくは０．１～５時間、より好ましくは０．３～３時間、さらにより好ましくは０．５～２時間である。不活性ガスの供給量は、炭素前駆体の単位表面積あたり０．０１～５．０Ｌ／（分・ｍ２）、好ましくは０．０１５～４．０Ｌ／（分・ｍ２）、より好ましくは０．０２０～３．０Ｌ／（分・ｍ２）である。工程（３Ａ）も上記不活性ガスの供給量で不活性ガスを供給しながら行われることが好ましい。また、操作を簡便にし易い観点から、工程（３Ａ）における第１温度と工程（３Ｂ）における熱処理温度とが等しいことが好ましい。 Next, in the step (3B), the carbon precursor is heat-treated at a temperature of 500 to 900 ° C. under a supply of an inert gas to obtain a carbide. The heat treatment temperature in the step (3B) is hereinafter also referred to as a low-temperature firing temperature. The low-temperature firing temperature in the step (3B) is 500 to 900 ° C., preferably 550 to 880 ° C., more preferably 600 to 860 ° C., and further preferably 700 to 840 ° C. When the low-temperature sintering temperature is within the above range, a carbonaceous material suitable for manufacturing a non-aqueous electrolyte secondary battery having a high charge / discharge capacity and a low resistance can be finally obtained. The low-temperature firing temperature may be a constant temperature, but is not particularly limited as long as it is within the above range. The heat treatment time in the step (3B) is preferably 0.1 to 5 hours, more preferably 0.3 to 3 hours, and still more preferably 0.5 to 2 hours. The supply amount of the inert gas is 0.01 to 5.0 L / (min · m 2 ), preferably 0.015 to 4.0 L / (min · m 2 ), more preferably, per unit surface area of the carbon precursor. 0.020 to 3.0 L / (min · m 2 ). It is preferable that the step (3A) is also performed while supplying the inert gas at the supply amount of the inert gas. From the viewpoint of easy operation, it is preferable that the first temperature in the step (3A) is equal to the heat treatment temperature in the step (3B).
　工程（４Ａ）は、前記工程（３Ｂ）で得た炭化物を、不活性ガス雰囲気下、１００℃／時間以上の昇温速度で、１０００～１４００℃の範囲の第２温度まで加熱する工程であり、工程（４Ｂ）は、次いで、該炭化物を、不活性ガスの供給下、１０００～１４００℃の温度で熱処理して炭素質材料を得る工程である。ここで、工程（４Ａ）は、不活性ガス雰囲気下で行われ、工程（４Ｂ）は、不活性ガスの供給下で行われ、工程（４Ｂ）における不活性ガスの供給量は炭素前駆体の単位表面積あたり０．０１～５．０Ｌ／（分・ｍ２）である。ここで、不活性ガス雰囲気下、不活性ガス供給下という条件については、上記で（３Ａ）および（３Ｂ）について記載したとおりである。また、本明細書において、当該工程（４Ａ）および／または（４Ｂ）を高温焼成（工程）とも称する。不活性ガスとしては、上記で（３Ａ）および（３Ｂ）について上記に記載したものが挙げられ、好ましくは窒素ガスである。 Step (4A) is a step of heating the carbide obtained in step (3B) to a second temperature in the range of 1000 to 1400 ° C. in an inert gas atmosphere at a rate of 100 ° C./hour or more. Step (4B) is a step of subsequently heat-treating the carbide at a temperature of 1000 to 1400 ° C. under the supply of an inert gas to obtain a carbonaceous material. Here, the step (4A) is performed under an inert gas atmosphere, the step (4B) is performed under the supply of an inert gas, and the supply amount of the inert gas in the step (4B) is the amount of the carbon precursor. It is 0.01 to 5.0 L / (minute · m 2 ) per unit surface area. Here, the conditions of the inert gas atmosphere and the inert gas supply are as described in (3A) and (3B) above. In this specification, the step (4A) and / or (4B) is also referred to as high-temperature firing (step). Examples of the inert gas include those described above for (3A) and (3B), and preferably nitrogen gas.
　工程（４Ａ）における昇温速度は、充放電容量が高く、抵抗が低い非水電解質二次電池を製造するに適した炭素質材料を最終的に得やすい観点から、好ましくは１００℃／時間以上、より好ましくは３００℃／時間以上、さらに好ましくは４００℃／時間以上、特に好ましくは５００℃／時間以上である。昇温速度の上限は特に限定されないが、急激な熱分解による比表面積増大を抑制しやすい観点から、好ましくは８００℃／時間以下、より好ましくは７００℃／時間以下、さらにより好ましくは６００℃／時間以下である。工程（４Ａ）における第２温度は、１０００～１４００℃、好ましくは１０５０～１３８０℃、より好ましくは１１００～１３７０℃、さらに好ましくは１１５０～１３６０℃、特に好ましくは１２００～１３５０℃である。 The heating rate in the step (4A) is preferably 100 ° C./hour or more from the viewpoint of easily obtaining a carbonaceous material suitable for manufacturing a nonaqueous electrolyte secondary battery having a high charge / discharge capacity and a low resistance. , More preferably at least 300 ° C / hour, still more preferably at least 400 ° C / hour, particularly preferably at least 500 ° C / hour. Although the upper limit of the heating rate is not particularly limited, it is preferably 800 ° C./hour or less, more preferably 700 ° C./hour or less, and still more preferably 600 ° C./hour, from the viewpoint of easily increasing the specific surface area due to rapid thermal decomposition. Less than an hour. The second temperature in the step (4A) is 1000 to 1400 ° C., preferably 1050 to 1380 ° C., more preferably 1100 to 1370 ° C., still more preferably 1150 to 1360 ° C., and particularly preferably 1200 to 1350 ° C.
　リチウムイオンを吸蔵しやすい構造を作り、放電容量を高めやすい観点から、通常、工程（３Ｂ）に続いて工程（４Ａ）が行われる。したがって、工程（４Ａ）における昇温工程は、５００～９００℃の範囲の低温焼成温度から、上記１０００～１４００℃の範囲の第２温度まで昇温する工程である。例えば、上記の昇温速度で、低温焼成温度（５００～９００℃）から第２温度（１０００～１４００℃）まで、好ましくは低温焼成温度（５５０～８８０℃）から第２温度（１０５０～１３８０℃）まで、より好ましくは低温焼成温度（６００～８６０℃）から第２温度（１１００～１３７０℃）まで、さらにより好ましくは低温焼成温度（６００～８６０℃）から第２温度（１１５０～１３６０℃）まで、特に好ましくは低温焼成温度（７００～８４０℃）から第２温度（１２００～１３５０℃）まで、昇温される。 工程 From the viewpoint of creating a structure that easily absorbs lithium ions and easily increasing the discharge capacity, step (4A) is usually performed following step (3B). Therefore, the temperature raising step in the step (4A) is a step of raising the temperature from the low-temperature firing temperature in the range of 500 to 900 ° C. to the second temperature in the range of 1000 to 1400 ° C. For example, at the above-mentioned heating rate, from the low-temperature firing temperature (500 to 900 ° C.) to the second temperature (1000 to 1400 ° C.), preferably from the low-temperature firing temperature (550 to 880 ° C.) to the second temperature (1050 to 1380 ° C.) ), More preferably from the low-temperature firing temperature (600 to 860 ° C) to the second temperature (1100 to 1370 ° C), and still more preferably from the low-temperature firing temperature (600 to 860 ° C) to the second temperature (1150 to 1360 ° C). , Particularly preferably from a low-temperature firing temperature (700 to 840 ° C) to a second temperature (1200 to 1350 ° C).
　次いで、工程（４Ｂ）では、炭化物を、不活性ガスの供給下、１０００～１４００℃の温度で熱処理して炭素質材料を得る。工程（４Ｂ）における熱処理温度を以下において高温焼成温度とも称する。工程（４Ｂ）における高温焼成温度は、操作を簡便にしやすく、充放電容量が高く、抵抗が低い非水電解質二次電池を製造するに適した炭素質材料を得やすい観点から、１０００～１４００℃、好ましくは１０５０～１３８０℃、より好ましくは１１００～１３７０℃、さらに好ましくは１１５０～１３６０℃、特に好ましくは１２００～１３５０℃である。高温焼成温度は、一定の温度であってよいが、上記範囲内であれば特に限定されない。工程（４Ｂ）における熱処理時間は、好ましくは０．１～５時間、より好ましくは０．３～３時間、さらにより好ましくは０．５～２時間である。不活性ガスの供給量は、炭化物の単位表面積あたり０．０１～５．０Ｌ／（分・ｍ２）、好ましくは０．０１５～４．０Ｌ／（分・ｍ２）、より好ましくは０．０２０～３．０Ｌ／（分・ｍ２）である。工程（４Ａ）も上記不活性ガスの供給量で不活性ガスを供給しながら行われることが好ましい。また、操作を簡便にしやすい観点から、工程（４Ａ）における第２温度と工程（４Ｂ）における熱処理温度とが等しいことが好ましい。 Next, in the step (4B), the carbide is heat-treated at a temperature of 1000 to 1400 ° C. under a supply of an inert gas to obtain a carbonaceous material. The heat treatment temperature in the step (4B) is hereinafter also referred to as a high temperature firing temperature. The high-temperature sintering temperature in the step (4B) is from 1000 to 1400 ° C. from the viewpoint that the operation is easy, the charge / discharge capacity is high, and a carbonaceous material suitable for manufacturing a low-resistance nonaqueous electrolyte secondary battery is easily obtained. The temperature is preferably from 1050 to 1380 ° C, more preferably from 1100 to 1370 ° C, further preferably from 1150 to 1360 ° C, and particularly preferably from 1200 to 1350 ° C. The high temperature firing temperature may be a constant temperature, but is not particularly limited as long as it is within the above range. The heat treatment time in the step (4B) is preferably 0.1 to 5 hours, more preferably 0.3 to 3 hours, and still more preferably 0.5 to 2 hours. The supply amount of the inert gas is 0.01 to 5.0 L / (min · m 2 ), preferably 0.015 to 4.0 L / (min · m 2 ), more preferably 0.1 to 5.0 L / (min · m 2 ) per unit surface area of the carbide. 020 to 3.0 L / (min · m 2 ). It is preferable that the step (4A) is also performed while supplying the inert gas with the supply amount of the inert gas. From the viewpoint of easy operation, it is preferable that the second temperature in the step (4A) is equal to the heat treatment temperature in the step (4B).
　高温焼成温度（すなわち工程（４Ｂ）における焼成温度）は、好ましくは上記工程（４Ａ）における第２温度と等しく、電極に用いた際に高い充放電容量および充放電効率と低い抵抗を与える炭素質材料を得やすい観点で、工程（３Ｂ）における焼成温度（好ましい態様において工程（３Ａ）における第１温度）以上の温度であることが好ましい。高温焼成温度は、低温焼成温度よりも、好ましくは５０～７００℃、より好ましくは１００～６００℃、さらにより好ましくは１５０～５００℃、特に好ましくは２００～４００℃高い温度である。 The high temperature firing temperature (that is, the firing temperature in the step (4B)) is preferably equal to the second temperature in the step (4A), and the carbonaceous material which gives a high charge / discharge capacity, a high charge / discharge efficiency and a low resistance when used for an electrode. From the viewpoint of easily obtaining the material, the temperature is preferably equal to or higher than the firing temperature in the step (3B) (the first temperature in the step (3A) in a preferred embodiment). The high temperature firing temperature is preferably 50 to 700 ° C., more preferably 100 to 600 ° C., still more preferably 150 to 500 ° C., and particularly preferably 200 to 400 ° C. higher than the low temperature firing temperature.
　炭化物を高温で焼成する工程（４Ａ）および（４Ｂ）に供する前に、工程（３Ｂ）で得た炭化物に少なくとも１種の揮発性有機物を添加する工程（１０）をさらに含んでいてもよい。工程（１０）を行うことにより、炭化物を高温で焼成する際に揮発した有機物が炭化物表面に付着し、その結果、より低い比表面積を有する炭素質材料を製造しやすくなる。このような炭素質材料は、高い充放電容量および低い抵抗を維持しつつ、炭素質材料中に存在する水分の量を低下させ、水分による電解液の加水分解および水の電気分解を抑制することができる。 前 Before subjecting the carbide to the steps (4A) and (4B) of firing at a high temperature, the method may further include a step (10) of adding at least one volatile organic substance to the carbide obtained in the step (3B). By performing the step (10), the organic matter volatilized when the carbide is fired at a high temperature adheres to the carbide surface, and as a result, it becomes easy to produce a carbonaceous material having a lower specific surface area. Such a carbonaceous material reduces the amount of water present in the carbonaceous material while maintaining a high charge / discharge capacity and a low resistance, and suppresses the hydrolysis of the electrolytic solution by water and the electrolysis of water. Can be.
　揮発性有機物は、窒素等の不活性ガス雰囲気下、例えば５００℃以上の温度で熱処理をする際に、ほぼ炭化せず（例えば物質の好ましくは８０％以上、より好ましくは９０％以上が炭化せず）、揮発する（気化もしくは熱分解し、ガスになる）有機化合物である。揮発性有機物としては、以下に限定されるものではないが、例えば熱可塑性樹脂、低分子有機化合物が挙げられる。熱可塑性樹脂としては、ポリスチレン、ポリエチレン、ポリプロピレン、ポリ（メタ）アクリル酸、ポリ（メタ）アクリル酸エステル等が挙げられる。なお、本明細書において、（メタ）アクリルとは、メタクリルとアクリルの総称である。低分子有機化合物としては、トルエン、キシレン、メシチレン、スチレン、ナフタレン、フェナントレン、アントラセン、ピレン等が挙げられる。焼成温度下で揮発し、熱分解した場合に炭素前駆体の表面を酸化賦活しないものが好ましいことから、熱可塑性樹脂としてはポリスチレン、ポリエチレン、ポリプロピレンが好ましい。低分子有機化合物としては、安全上の観点から常温下（たとえば２０℃）において揮発性が小さい化合物がさらに好ましく、ナフタレン、フェナントレン、アントラセン、ピレン等が特に好ましい。 Volatile organic substances hardly carbonize when subjected to a heat treatment in an atmosphere of an inert gas such as nitrogen, for example, at a temperature of 500 ° C. or more (for example, preferably 80% or more, more preferably 90% or more of the substance is carbonized). And organic compounds that evaporate (evaporate or thermally decompose into gas). Examples of the volatile organic substance include, but are not limited to, a thermoplastic resin and a low molecular weight organic compound. Examples of the thermoplastic resin include polystyrene, polyethylene, polypropylene, poly (meth) acrylic acid, and poly (meth) acrylate. In this specification, (meth) acryl is a general term for methacryl and acryl. Examples of the low molecular weight organic compound include toluene, xylene, mesitylene, styrene, naphthalene, phenanthrene, anthracene, and pyrene. Polystyrene, polyethylene, and polypropylene are preferable as the thermoplastic resin because those that volatilize at the firing temperature and do not oxidize the surface of the carbon precursor when thermally decomposed are preferable. As the low molecular weight organic compound, a compound having low volatility at normal temperature (for example, 20 ° C.) is more preferable from the viewpoint of safety, and naphthalene, phenanthrene, anthracene, pyrene and the like are particularly preferable.
　工程（１０）において、工程（３Ｂ）で得た炭化物に少なくとも１種の揮発性有機物を添加する。添加方法は特に限定されないが、例えば工程（３Ｂ）で得た炭化物と少なくとも１種の揮発性有機物とを混合して添加を行ってよい。揮発性有機物の添加量は、特に限定されないが、炭化物１００質量部に対して、好ましくは２～３０質量部、より好ましくは４～２０質量部、さらに好ましくは５～１５質量部である。 In step (10), at least one volatile organic substance is added to the carbide obtained in step (3B). The addition method is not particularly limited. For example, the addition may be performed by mixing the carbide obtained in the step (3B) and at least one volatile organic substance. The amount of the volatile organic substance to be added is not particularly limited, but is preferably 2 to 30 parts by mass, more preferably 4 to 20 parts by mass, and still more preferably 5 to 15 parts by mass with respect to 100 parts by mass of the carbide.
　上記炭素質材料の製造方法は、炭素前駆体、炭化物および／または炭素質材料を粉砕する工程（１１）をさらに含んでいてもよい。粉砕工程（１１）は、炭素前駆体、炭化物および／または炭素質材料を、通常の方法、例えばボールミルやジェットミルを用いる方法等により行ってよい。粉砕工程（１１）は、例えば工程（１）、（３Ｂ）および／または（４Ｂ）の後で行ってよく、熱処理による収縮や、形状変化が生じにくく、充放電容量が高く、抵抗が低い非水電解質二次電池を製造するに適した炭素質材料を最終的に得やすい観点からは、工程（３Ｂ）または（４Ｂ）の後に行うことが好ましい。 The method for producing a carbonaceous material may further include a step (11) of grinding the carbon precursor, carbide and / or carbonaceous material. The pulverizing step (11) may be performed on the carbon precursor, carbide and / or carbonaceous material by a usual method, for example, a method using a ball mill or a jet mill. The pulverizing step (11) may be performed, for example, after the steps (1), (3B) and / or (4B), and is unlikely to cause shrinkage or shape change due to heat treatment, has a high charge / discharge capacity, and has a low resistance. From the viewpoint of finally obtaining a carbonaceous material suitable for manufacturing a water electrolyte secondary battery, it is preferable to perform the step after the step (3B) or (4B).
　本発明の炭素前駆体、又は、本発明の製造方法により得られる炭素前駆体は、非水電解質二次電池の負極活物質として好適に使用することができる炭素質材料を製造するための原料として適している。 The carbon precursor of the present invention, or the carbon precursor obtained by the production method of the present invention, as a raw material for producing a carbonaceous material that can be suitably used as a negative electrode active material of a nonaqueous electrolyte secondary battery Are suitable.
　以下において、本発明の炭素前駆体を原料として、上記のような製造方法で製造した炭素質材料を用いて、非水電解質二次電池用の負極を製造する方法を具体的に述べる。負極は、例えば、炭素質材料に結合剤（バインダー）を添加し、適当な溶媒を適量添加した後、これらを混練し電極合剤を調製する。得られた電極合剤を、金属板等からなる集電板に塗布および乾燥後、加圧成形することにより、非水電解質二次電池用の負極を製造することができる。 Hereinafter, a method for producing a negative electrode for a non-aqueous electrolyte secondary battery using the carbon precursor of the present invention as a raw material and a carbonaceous material produced by the above-described production method will be specifically described. In the negative electrode, for example, a binder is added to a carbonaceous material, an appropriate solvent is added in an appropriate amount, and these are kneaded to prepare an electrode mixture. A negative electrode for a non-aqueous electrolyte secondary battery can be manufactured by applying and drying the obtained electrode mixture on a current collector plate made of a metal plate or the like, followed by drying.
　本発明の炭素前駆体から製造した炭素質材料を用いることにより、導電助剤を添加しなくとも高い導電性を有する電極（負極）を製造することができる。さらに高い導電性を賦与することを目的として、必要に応じて電極合剤の調製時に、導電助剤を添加することができる。導電助剤としては、導電性のカーボンブラック、気相成長炭素繊維（ＶＧＣＦ）、ナノチューブ等を用いることができる。導電助剤の添加量は、使用する導電助剤の種類によっても異なるが、添加する量が少なすぎると期待する導電性が得られないことがあり、多すぎると電極合剤中の分散が悪くなることがある。このような観点から、添加する導電助剤の好ましい割合は０．５～１０質量％（ここで、活物質（炭素質材料）量＋バインダー量＋導電助剤量＝１００質量％とする）であり、さらにより好ましくは０．５～７質量％、特に好ましくは０．５～５質量％である。結合剤としては、ＰＶＤＦ（ポリフッ化ビニリデン）、ポリテトラフルオロエチレン、およびＳＢＲ（スチレン・ブタジエン・ラバー）とＣＭＣ（カルボキシメチルセルロース）との混合物等のように電解液と反応しないものであれば特に限定されない。中でもＳＢＲとＣＭＣとの混合物は、活物質表面に付着したＳＢＲとＣＭＣがリチウムイオン移動を阻害することが少なく、良好な入出力特性が得られるため好ましい。ＳＢＲ等の水性エマルジョンやＣＭＣを溶解し、スラリーを形成するために、水等の極性溶媒が好ましく用いられるが、ＰＶＤＦ等の溶剤性エマルジョンをＮ－メチルピロリドン等に溶解して用いることもできる。結合剤の添加量が多すぎると、得られる電極の抵抗が大きくなるため、電池の内部抵抗が大きくなり電池特性を低下させることがある。また、結合剤の添加量が少なすぎると、負極材料の粒子相互間および集電材との結合が不十分になることがある。結合剤の好ましい添加量は、使用するバインダーの種類によっても異なるが、例えば溶媒に水を使用するバインダーでは、ＳＢＲとＣＭＣとの混合物など、複数のバインダーを混合して使用することが多く、使用する全バインダーの総量として０．５～５質量％が好ましく、１～４質量％がより好ましい。一方、ＰＶＤＦ系のバインダーでは好ましくは３～１３質量％であり、より好ましくは３～１０質量％である。また、電極合剤中の炭素質材料の量は、８０質量％以上が好ましく、９０質量％以上がより好ましい。また、電極合剤中の炭素質材料の量は１００質量％以下が好ましく、９７質量％以下がより好ましい。 電極 By using the carbonaceous material produced from the carbon precursor of the present invention, an electrode (anode) having high conductivity can be produced without adding a conduction aid. For the purpose of imparting higher conductivity, a conductive assistant can be added as needed at the time of preparing the electrode mixture. As the conductive additive, conductive carbon black, vapor grown carbon fiber (VGCF), nanotube, or the like can be used. The amount of the conductive additive varies depending on the type of the conductive additive used.However, if the amount to be added is too small, the expected conductivity may not be obtained.If the amount is too large, the dispersion in the electrode mixture is poor. May be. From such a viewpoint, the preferable ratio of the conductive additive to be added is 0.5 to 10% by mass (here, the amount of the active material (carbonaceous material) + the amount of the binder + the amount of the conductive additive = 100% by mass). And still more preferably 0.5 to 7% by mass, particularly preferably 0.5 to 5% by mass. The binder is not particularly limited as long as it does not react with the electrolyte such as PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and a mixture of SBR (styrene / butadiene rubber) and CMC (carboxymethylcellulose). Not done. Above all, a mixture of SBR and CMC is preferable because SBR and CMC adhered to the surface of the active material hardly hinder lithium ion transfer, and good input / output characteristics can be obtained. A polar solvent such as water is preferably used for dissolving an aqueous emulsion such as SBR or CMC to form a slurry, but a solvent-based emulsion such as PVDF may be used by dissolving in N-methylpyrrolidone or the like. If the added amount of the binder is too large, the resistance of the obtained electrode increases, so that the internal resistance of the battery may increase and the battery characteristics may deteriorate. If the amount of the binder is too small, the bonding between the particles of the negative electrode material and the current collector may be insufficient. The preferred amount of the binder varies depending on the type of binder used. For example, in the case of a binder using water as a solvent, a plurality of binders such as a mixture of SBR and CMC are often used as a mixture. The total amount of all binders is preferably 0.5 to 5% by mass, more preferably 1 to 4% by mass. On the other hand, for a PVDF-based binder, the content is preferably 3 to 13% by mass, and more preferably 3 to 10% by mass. Further, the amount of the carbonaceous material in the electrode mixture is preferably 80% by mass or more, and more preferably 90% by mass or more. The amount of the carbonaceous material in the electrode mixture is preferably 100% by mass or less, more preferably 97% by mass or less.
　電極活物質層は、基本的には集電板の両面に形成されるが、必要に応じて片面に形成されていてもよい。電極活物質層が厚いほど、集電板やセパレータ等が少なくて済むため、高容量化には好ましい。しかし、対極と対向する電極面積が広いほど入出力特性の向上に有利なため、電極活物質層が厚すぎると入出力特性が低下することがある。活物質層の厚み（片面当たり）は、電池放電時の出力の観点から、好ましくは１０～８０μｍ、より好ましくは２０～７５μｍ、さらにより好ましくは３０～７５μｍである。 The electrode active material layer is basically formed on both sides of the current collector plate, but may be formed on one side as needed. The thicker the electrode active material layer, the smaller the number of current collector plates and separators, etc., which is preferable for increasing the capacity. However, the larger the area of the electrode facing the counter electrode is, the more advantageous the improvement of the input / output characteristics is. Therefore, if the electrode active material layer is too thick, the input / output characteristics may deteriorate. The thickness (per side) of the active material layer is preferably from 10 to 80 μm, more preferably from 20 to 75 μm, and still more preferably from 30 to 75 μm, from the viewpoint of output during battery discharge.
　本発明の炭素前駆体から製造した炭素質材料を用いた非水電解質二次電池は、高い充放電容量および低い抵抗を有する。本発明の炭素前駆体から製造した炭素質材料を用いて非水電解質二次電池用の負極を形成する場合、正極材料、セパレータ、および電解液などの電池を構成する他の材料は特に限定されることなく、非水溶媒二次電池として従来使用され、あるいは提案されている種々の材料を使用することが可能である。 非 The non-aqueous electrolyte secondary battery using the carbonaceous material produced from the carbon precursor of the present invention has high charge / discharge capacity and low resistance. When forming a negative electrode for a non-aqueous electrolyte secondary battery using a carbonaceous material produced from the carbon precursor of the present invention, other materials constituting the battery such as a positive electrode material, a separator, and an electrolyte are particularly limited. Without using, it is possible to use various materials conventionally used or proposed as a non-aqueous solvent secondary battery.
　例えば、正極材料としては、層状酸化物系（ＬｉＭＯ２と表されるもので、Ｍは金属：例えばＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＭｎＯ２、またはＬｉＮｉｘＣｏｙＭｏｚＯ２（ここでｘ、ｙ、ｚは組成比を表わす））、オリビン系（ＬｉＭＰＯ４で表され、Ｍは金属：例えばＬｉＦｅＰＯ４など）、スピネル系（ＬｉＭ２Ｏ４で表され、Ｍは金属：例えばＬｉＭｎ２Ｏ４など）の複合金属カルコゲン化合物が好ましく、これらのカルコゲン化合物を必要に応じて混合して使用してもよい。これらの正極材料を適当なバインダーと電極に導電性を付与するための炭素材料とともに成形して、導電性の集電材上に層形成することにより正極が形成される。 For example, as the cathode material, one represented layered oxide (LiMO 2, M is a metal: for example LiCoO 2, LiNiO 2, LiMnO 2 or LiNi x Co y Mo z O 2 ( where x,, y , Z represent the composition ratio)), olivine-based (LiMPO 4 , M: metal: for example, LiFePO 4 ), spinel-based (LiM 2 O 4 ), M: metal: for example, LiMn 2 O 4 )) Is preferred, and these chalcogen compounds may be used as a mixture if necessary. The positive electrode is formed by molding these positive electrode materials together with a suitable binder and a carbon material for imparting conductivity to the electrodes, and forming a layer on the conductive current collector.
　これらの正極および負極と組み合わせて用いられる非水溶媒型電解液は、一般に非水溶媒に電解質を溶解することにより形成される。非水溶媒としては、例えばプロピレンカーボネート、エチレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、ジメトキシエタン、ジエトキシエタン、γ－ブチルラクトン、テトラヒドロフラン、２－メチルテトラヒドロフラン、スルホラン、または１，３－ジオキソラン等の有機溶媒を、一種または二種以上を組み合わせて用いることができる。また、電解質としては、ＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣＦ３ＳＯ３、ＬｉＡｓＦ６、ＬｉＣｌ、ＬｉＢｒ、ＬｉＢ（Ｃ６Ｈ５）４、またはＬｉＮ（ＳＯ３ＣＦ３）２等が用いられる。 A non-aqueous solvent-type electrolytic solution used in combination with these positive and negative electrodes is generally formed by dissolving an electrolyte in a non-aqueous solvent. Examples of the non-aqueous solvent include organic solvents such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, γ-butyl lactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, and 1,3-dioxolane. Can be used alone or in combination of two or more. As the electrolyte, LiClO 4 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 , LiAsF 6 , LiCl, LiBr, LiB (C 6 H 5 ) 4 , LiN (SO 3 CF 3 ) 2, or the like is used.
　非水電解質二次電池は、一般に上記のようにして形成した正極と負極とを必要に応じて透液性セパレータを介して対向させ、電解液中に浸漬させることにより形成される。このようなセパレータとしては、二次電池に通常用いられる不織布、その他の多孔質材料からなる透過性または透液性のセパレータを用いることができる。あるいはセパレータの代わりに、もしくはセパレータと一緒に、電解液を含浸させたポリマーゲルからなる固体電解質を用いることもできる。 A non-aqueous electrolyte secondary battery is generally formed by opposing the positive electrode and the negative electrode formed as described above via a liquid-permeable separator as necessary, and immersing the same in an electrolytic solution. As such a separator, a permeable or liquid-permeable separator made of a nonwoven fabric or other porous material generally used for a secondary battery can be used. Alternatively, a solid electrolyte made of a polymer gel impregnated with an electrolytic solution can be used instead of or together with the separator.
　本発明の炭素前駆体は、例えば自動車などの車両に搭載される電池（典型的には車両駆動用非水電解質二次電池）用の炭素質材料を製造する原料として好適である。本発明において車両とは、通常、電動車両として知られるものや、燃料電池や内燃機関とのハイブリッド車など、特に限定されることなく対象とすることができるが、少なくとも上記電池を備えた電源装置と、該電源装置からの電源供給により駆動する電動駆動機構と、これを制御する制御装置とを備えるものである。車両は、さらに、発電ブレーキや回生ブレーキを備え、制動によるエネルギーを電気に変換して、前記非水電解質二次電池に充電する機構を備えていてもよい。 The carbon precursor of the present invention is suitable as a raw material for producing a carbonaceous material for a battery (typically, a non-aqueous electrolyte secondary battery for driving a vehicle) mounted on a vehicle such as an automobile. In the present invention, the vehicle can be a target that is not particularly limited, such as a vehicle generally known as an electric vehicle, a hybrid vehicle with a fuel cell or an internal combustion engine, and a power supply device including at least the battery. And an electric drive mechanism driven by power supply from the power supply device, and a control device for controlling the electric drive mechanism. The vehicle may further include a power generation brake and a regenerative brake, and a mechanism that converts energy by braking into electricity and charges the nonaqueous electrolyte secondary battery.
　本発明の炭素前駆体を用いて製造した炭素質材料は、低抵抗性を有することから、例えば、電池の電極材に導電性を付与する添加剤として使用することもできる。電池の種類は特に限定されないが、非水電解質二次電池、鉛蓄電池が好適である。このような電池の電極材に添加することにより、導電ネットワークを形成することができ、導電性が高まることで、不可逆反応を抑制することができるため、電池を長寿命化することもできる。 炭素 Since the carbonaceous material produced using the carbon precursor of the present invention has low resistance, it can be used, for example, as an additive for imparting conductivity to the electrode material of a battery. The type of the battery is not particularly limited, but a non-aqueous electrolyte secondary battery and a lead storage battery are preferable. By adding to the electrode material of such a battery, a conductive network can be formed, and irreversible reaction can be suppressed by increasing conductivity, so that the battery can have a longer life.
　本発明はまた、高い充放電容量と、低い抵抗を有する非水電解質二次電池（例えばリチウムイオン二次電池、ナトリウムイオン電池、リチウム硫黄電池、リチウム空気電池）の負極活物質または導電材に適した炭素質材料の原料となる、炭素前駆体の製造方法も提供する。該製造方法は、糖類骨格を有する物質を原料とし、２１５～２４０℃の温度範囲で１～１２ｈｒ熱処理する方法であって、かかる方法により本発明の炭素前駆体を得ることができる。 The present invention is also suitable for a negative active material or a conductive material of a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery, a sodium ion battery, a lithium sulfur battery, and a lithium air battery) having a high charge / discharge capacity and a low resistance. The present invention also provides a method for producing a carbon precursor, which is used as a raw material for a carbonaceous material. The production method is a method in which a substance having a saccharide skeleton is used as a raw material and heat-treated at a temperature in the range of 215 to 240 ° C. for 1 to 12 hours. The carbon precursor of the present invention can be obtained by such a method.
　以下、実施例によって本発明を具体的に説明するが、これらは本発明の範囲を限定するものではない。なお、以下に炭素質材料の物性値の測定法を記載するが、実施例を含めて、本明細書中に記載する物性値は、以下の方法により求めた値に基づくものである。 Hereinafter, the present invention will be described specifically with reference to Examples, but these do not limit the scope of the present invention. The method for measuring the physical properties of the carbonaceous material is described below. The physical properties described in this specification, including the examples, are based on the values obtained by the following methods.
（元素分析）
　株式会社堀場製作所製、酸素・窒素・水素分析装置ＥＭＧＡ－９３０を用いて、不活性ガス溶解法に基づいて元素分析を行った。
　当該装置の検出方法は、酸素：不活性ガス融解－非分散型赤外線吸収法（ＮＤＩＲ）、窒素：不活性ガス融解－熱伝導法（ＴＣＤ）、水素：不活性ガス融解－非分散型赤外線吸収法（ＮＤＩＲ）であり、校正は、（酸素・窒素）Ｎｉカプセル、ＴｉＨ２（Ｈ標準試料）、ＳＳ－３（Ｎ、Ｏ標準試料）で行い、前処理として２５０℃、約１０分で水分量を測定した試料２０ｍｇをＮｉカプセルに取り、元素分析装置内で３０秒脱ガスした後に測定した。試験は３検体で分析し、平均値を分析値とした。上記のようにして、炭素前駆体における酸素原子含有量、窒素原子含有量および水素原子含有量を得た。次いで、炭素原子含有量は、１００質量％から酸素、窒素および水素原子含有量を減算することにより算出した。 (Elemental analysis)
Elemental analysis was performed based on an inert gas dissolution method using an oxygen / nitrogen / hydrogen analyzer EMGA-930 manufactured by Horiba, Ltd.
The detection method of this apparatus is as follows: oxygen: inert gas melting-non-dispersive infrared absorption method (NDIR), nitrogen: inert gas melting-thermal conduction method (TCD), hydrogen: inert gas melting-non-dispersive infrared absorption Calibration is performed using (oxygen / nitrogen) Ni capsule, TiH 2 (H standard sample) and SS-3 (N, O standard sample). Twenty mg of the sample whose amount was measured was taken in a Ni capsule and measured after degassing in an elemental analyzer for 30 seconds. In the test, three samples were analyzed, and the average value was used as the analysis value. As described above, the oxygen atom content, the nitrogen atom content, and the hydrogen atom content in the carbon precursor were obtained. Next, the carbon atom content was calculated by subtracting the oxygen, nitrogen and hydrogen atom contents from 100% by mass.
（ＩＲ測定）
  サーモフィッシャーサイエンティフィック株式会社製、フーリエ変換赤外分光光度計Ｎｉｃｏｌｅｔ ｉｓ１０＋Ｎｉｃｏｌｅｔ Ｃｏｎｔｉｎｕｕｍを用いて、全反射測定法に基づいてＩＲ測定を行った。測定試料をダイヤモンド製のセルに載せ、赤外光を照射し、得られるスペクトルデータを採取した。 (IR measurement)
IR measurement was performed based on the total reflection measurement method using a Fourier transform infrared spectrophotometer Nicolet is10 + Nicolet Continum manufactured by Thermo Fisher Scientific Co., Ltd. The measurement sample was placed on a diamond cell, irradiated with infrared light, and the obtained spectrum data was collected.
（ＴＧ－ＤＴＡ測定）
　株式会社日立ハイテクサイエンス社製のＴＧ－ＤＴＡ分析装置ＴＧ／ＤＴＡ６３００（商品名）を用いて、ＴＧ分析をした。試料１０ｍｇをアルミナ製の試料パンの中に入れ、１００ｍＬ／ｍｉｎの窒素気流下、昇温速度１０℃／ｍｉｎで５００℃まで昇温した。この時に得られる示差熱（ＤＴＡ）曲線において、１００～５００℃の範囲で吸熱ピークの有無を確認した。上記範囲に吸熱ピークが存在する場合は「○」、存在しない場合は「×」と評価した。 (TG-DTA measurement)
TG analysis was performed using a TG-DTA analyzer TG / DTA6300 (trade name) manufactured by Hitachi High-Tech Science Corporation. 10 mg of the sample was placed in a sample pan made of alumina, and heated to 500 ° C. at a rate of 10 ° C./min under a nitrogen stream of 100 mL / min. In the differential heat (DTA) curve obtained at this time, the presence or absence of an endothermic peak was confirmed in the range of 100 to 500 ° C. When the endothermic peak was present in the above range, it was evaluated as “○”, and when it was not present, as “x”.
（１３Ｃ－ＮＭＲ測定）
　ＢＲＵＫＥＲ製、核磁気共鳴装置ＡＶＡＮＣＥ３００によりＣＰ／ＭＡＳ－１３Ｃ－ＮＭＲの測定を行った。測定に際して、アダマンタンを基準物質として、これのメチン由来のピークを２９．４７ｐｐｍに設定した。得られた結果において、０～５０ｐｐｍの範囲でピークの有無を確認した。上記範囲にピークが存在する場合は「○」、存在しない場合は「×」と評価した。 ( 13 C-NMR measurement)
CP / MAS- 13 C-NMR was measured by a nuclear magnetic resonance apparatus AVANCE300 manufactured by Bruker. In the measurement, a peak derived from methine was set at 29.47 ppm using adamantane as a reference substance. In the obtained results, the presence or absence of a peak was confirmed in the range of 0 to 50 ppm. When a peak was present in the above range, it was evaluated as “○”, and when no peak was present, as “×”.
（円形度）
  炭素前駆体の円形度は、以下の方法により測定した。試料を界面活性剤（和光純薬工業株式会社製「ＴｏｒｉｔｏｎＸ１００」）が５質量％含まれた水溶液に投入し、水溶液中に分散させた。この分散液を用いて、シスメックス株式会社製、形状粒度分布測定装置ＦＰＩＡ－３０００を用いて、形状粒度分布測定を行い、円形度の算出を行った。 (Roundness)
The circularity of the carbon precursor was measured by the following method. The sample was put into an aqueous solution containing 5% by mass of a surfactant (“Toriton X100” manufactured by Wako Pure Chemical Industries, Ltd.) and dispersed in the aqueous solution. Using this dispersion, shape particle size distribution was measured using a shape particle size distribution analyzer FPIA-3000 manufactured by Sysmex Corporation, and the circularity was calculated.
（レーザー散乱法による平均粒子径）
　炭素前駆体の平均粒子径（粒度分布）は、以下の方法により測定した。試料を界面活性剤（和光純薬工業株式会社製「ＴｏｒｉｔｏｎＸ１００」）が５質量％含まれた水溶液に投入し、水溶液中に分散させた。この分散液を用いて粒度分布を測定した。粒度分布測定は、粒子径・粒度分布測定装置（マイクロトラック・ベル株式会社製「マイクロトラックＭＴ３３００ＥII」）を用いて行った。Ｄ５０は、累積体積が５０％となる粒子径であり、この値を平均粒子径として用いた。 (Average particle size by laser scattering method)
The average particle size (particle size distribution) of the carbon precursor was measured by the following method. The sample was put into an aqueous solution containing 5% by mass of a surfactant (“Toriton X100” manufactured by Wako Pure Chemical Industries, Ltd.) and dispersed in the aqueous solution. The particle size distribution was measured using this dispersion. The particle size distribution was measured using a particle size / particle size distribution analyzer (“Microtrack MT3300EII” manufactured by Microtrac Bell Inc.). D 50 is the cumulative volume is a particle diameter at 50%, using this value as the average particle size.
（電極密度）
  後述の参考例１の方法で作製した電極の重量を計測し、該重量を、電極面積と電極の厚さの積から算出した電極体積で除することで、電極密度を算出した。 (Electrode density)
The electrode density was calculated by measuring the weight of the electrode manufactured by the method of Reference Example 1 described below and dividing the weight by the electrode volume calculated from the product of the electrode area and the electrode thickness.
（実施例１）
　でんぷん１０ｇを、空気雰囲気中、２１５℃まで昇温した。この際、２１５℃までの昇温速度は６００℃／時間（１０℃／分）とした。次いで、空気気流下、２１５℃で８時間熱処理することにより炭素前駆体を得た。この際、空気の供給量は、でんぷん１００ｇあたり３５Ｌ／分であり、でんぷんの単位表面積あたり０．４９Ｌ／（分・ｍ２）であった。 (Example 1)
10 g of starch was heated to 215 ° C. in an air atmosphere. At this time, the heating rate up to 215 ° C. was 600 ° C./hour (10 ° C./minute). Next, a heat treatment was performed at 215 ° C. for 8 hours in an air stream to obtain a carbon precursor. At this time, the supply amount of air was 35 L / min per 100 g of starch, and 0.49 L / (min · m 2 ) per unit surface area of the starch.
（実施例２）
　熱処理温度を２２０℃、空気の供給量をでんぷん１００ｇあたり１０Ｌ／分（でんぷんの単位表面積あたり０．１４Ｌ／（分・ｍ２））とした以外は、実施例１と同様に処理を行い、炭素前駆体を得た。 (Example 2)
The same treatment as in Example 1 was carried out except that the heat treatment temperature was 220 ° C. and the air supply amount was 10 L / min per 100 g of starch (0.14 L / (min · m 2 ) per unit surface area of starch). A precursor was obtained.
（実施例３）
　でんぷんの量を２０ｇ、空気の供給量をでんぷん１００ｇあたり５０Ｌ／分（でんぷんの単位表面積あたり０．３５Ｌ／（分・ｍ２））とした以外は、実施例２と同様に処理を行い、炭素前駆体を得た。 (Example 3)
A process was performed in the same manner as in Example 2 except that the amount of starch was 20 g, and the supply amount of air was 50 L / min per 100 g of starch (0.35 L / (min · m 2 ) per unit surface area of starch). A precursor was obtained.
（比較例１）
　流入するガスを窒素とした以外は、実施例１と同様にして、炭素前駆体を得た。 (Comparative Example 1)
A carbon precursor was obtained in the same manner as in Example 1 except that the flowing gas was nitrogen.
（比較例２）
　でんぷんの量を２０ｇとし、ガスを流入しなかった以外は、実施例１と同様に処理を行い、炭素前駆体を得た。 (Comparative Example 2)
The same procedure as in Example 1 was carried out except that the amount of starch was 20 g and no gas was introduced, to obtain a carbon precursor.
（比較例３）
　処理温度を２５０℃とし、処理時間を６時間とした以外は、実施例１と同様に処理を行い、炭素前駆体を得た。 (Comparative Example 3)
Except that the treatment temperature was 250 ° C. and the treatment time was 6 hours, the same treatment as in Example 1 was performed to obtain a carbon precursor.
　各実施例および各比較例における焼成条件を表１に、得られた炭素前駆体の物性の評価結果を表２に示す。なお、表２中のＴＧ－ＤＴＡに関し、上記ＴＧ－ＤＴＡ測定に従い１００～５００℃の範囲に吸熱ピークが見られた場合○とし、見られなかった場合×と記載する。また、表２中の１３Ｃ－ＮＭＲに関し、上記１３Ｃ－ＮＭＲ測定に従い０～５０ｐｐｍの範囲にピークが見られた場合○とし、見られなかった場合×と記載する。また、実施例１で得た炭素前駆体のＳＥＭ画像を図１に、比較例１で得た炭素前駆体のＳＥＭ画像を図２に示す。 Table 1 shows the firing conditions in each example and each comparative example, and Table 2 shows the evaluation results of the physical properties of the obtained carbon precursor. Regarding TG-DTA in Table 2, when the endothermic peak is observed in the range of 100 to 500 ° C. according to the above TG-DTA measurement, it is described as ○, and when it is not observed, it is described as ×. Regarding the 13 C-NMR in Table 2, when a peak is observed in the range of 0 to 50 ppm according to the above 13 C-NMR measurement, it is described as ○, and when it is not observed, it is described as x. FIG. 1 shows an SEM image of the carbon precursor obtained in Example 1, and FIG. 2 shows an SEM image of the carbon precursor obtained in Comparative Example 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
（参考例１）
  実施例１で得られた炭素前駆体を用いて、窒素ガス雰囲気中、６００℃まで昇温した。この際、６００℃までの昇温速度は６００℃／時間（１０℃／分）とした。次いで、窒素ガス気流下、６００℃で６０分間熱処理することにより炭化処理を行なうことにより炭化物を得た。この際、窒素ガスの供給量は、炭素前駆体１０ｇあたり１Ｌ／分であった。その後、得られた炭化物をボールミルで粉砕することにより、粉砕炭化物を得た。次に、粉砕炭化物を、１２００℃まで昇温し、１２００℃で６０分間熱処理することにより高温焼成処理を行い、炭素質材料を得た。この際、１２００℃までの昇温速度は６００℃／時間（１０℃／分）とした。上記の昇温および熱処理は窒素ガス気流下で行った。窒素ガスの供給量は、粉砕炭化物５ｇあたり３Ｌ／分であった。 (Reference Example 1)
Using the carbon precursor obtained in Example 1, the temperature was raised to 600 ° C. in a nitrogen gas atmosphere. At this time, the heating rate up to 600 ° C. was 600 ° C./hour (10 ° C./minute). Next, a carbide was obtained by performing a carbonization treatment by performing a heat treatment at 600 ° C. for 60 minutes in a nitrogen gas stream. At this time, the supply amount of the nitrogen gas was 1 L / min per 10 g of the carbon precursor. Thereafter, the obtained carbide was pulverized with a ball mill to obtain a pulverized carbide. Next, the temperature of the pulverized carbide was increased to 1200 ° C., and heat treatment was performed at 1200 ° C. for 60 minutes to perform a high-temperature baking treatment to obtain a carbonaceous material. At this time, the heating rate up to 1200 ° C. was 600 ° C./hour (10 ° C./minute). The above temperature rise and heat treatment were performed under a nitrogen gas stream. The supply amount of nitrogen gas was 3 L / min per 5 g of the pulverized carbide.
（電極の作製）
　参考例１で得た炭素質材料を用いて、以下の手順に従って負極の作製を行った。
　炭素質材料９５質量部、導電性カーボンブラック（TIMCAL製「Ｓｕｐｅｒ－Ｐ（登録商標）」）２質量部、ＣＭＣ１質量部、ＳＢＲ２質量部および水９０質量部を混合し、スラリーを得た。厚さ１８μｍの銅箔に、得られたスラリーを塗布し、乾燥後プレスして、厚さ４５μｍの電極を得た。得られた電極の密度は、表３に示す通りであった。 (Preparation of electrode)
Using the carbonaceous material obtained in Reference Example 1, a negative electrode was manufactured according to the following procedure.
A slurry was obtained by mixing 95 parts by mass of the carbonaceous material, 2 parts by mass of conductive carbon black (“Super-P (registered trademark)” manufactured by TIMCAL), 1 part by mass of CMC, 2 parts by mass of SBR, and 90 parts by mass of water. The obtained slurry was applied to a copper foil having a thickness of 18 μm, dried and pressed to obtain an electrode having a thickness of 45 μm. The density of the obtained electrode was as shown in Table 3.
（インピーダンス）
　上記で作製した電極を用いて、電気化学測定装置（ソーラトロン社製「１２５５ＷＢ型高性能電気化学測定システム」）を用い、２５℃で、０Ｖを中心に１０ｍＶの振幅を与え、周波数１０ｍＨｚ～１ＭＨｚの周波数で定電圧交流インピーダンスを測定し、周波数１ｋＨｚにおける実部抵抗をインピーダンス抵抗として測定した。得られた結果を、表３中、初回充放電時インピーダンスとして示す。 (Impedance)
Using the electrodes prepared above, an electrochemical measurement apparatus (“1255WB-type high-performance electrochemical measurement system” manufactured by Solartron) was used to give an amplitude of 10 mV centered on 0 V at 25 ° C. and a frequency of 10 mHz to 1 MHz. The constant voltage AC impedance was measured at the frequency, and the real part resistance at the frequency of 1 kHz was measured as the impedance resistance. The obtained results are shown in Table 3 as the impedance at the time of the first charge / discharge.
（直流抵抗値、電池初期容量および充放電効率）
　上記で作製した電極を作用極とし、金属リチウムを対極および参照極として使用した。溶媒として、エチレンカーボネートとジメチルカーボネートとエチルメチルカーボネートを、体積比で１：１：１となるように混合して用いた。この溶媒に、ＬｉＰＦ６を１ｍｏｌ／Ｌ溶解し、電解質として用いた。セパレータにはポリプロピレン膜を使用した。アルゴン雰囲気下のグローブボックス内でコインセルを作製した。
　上記構成のリチウム二次電池について、充放電試験装置（東洋システム株式会社製、「ＴＯＳＣＡＴ」）を用いて、初期充電前に直流抵抗値を測定後、充放電試験を行った。リチウムのドーピングは、活物質質量に対し７０ｍＡ／ｇの速度で行い、リチウム電位に対して１ｍＶになるまでドーピングした。さらにリチウム電位に対して１ｍＶの定電圧を８時間印加して、ドーピングを終了した。このときの容量（ｍＡｈ／ｇ）を充電容量とした。次いで、活物質質量に対し７０ｍＡ／ｇの速度で、リチウム電位に対して２．５Ｖになるまで脱ドーピングを行い、このとき放電した容量を放電容量とした。放電容量／充電容量の百分率を充放電効率（初期の充放電効率）とし、電池内におけるリチウムイオンの利用効率の指標とした。 (DC resistance, initial battery capacity and charge / discharge efficiency)
The electrode prepared above was used as a working electrode, and metallic lithium was used as a counter electrode and a reference electrode. As a solvent, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate were mixed and used at a volume ratio of 1: 1: 1. 1 mol / L of LiPF 6 was dissolved in this solvent and used as an electrolyte. A polypropylene film was used for the separator. A coin cell was prepared in a glove box under an argon atmosphere.
With respect to the lithium secondary battery having the above configuration, a charge / discharge test was performed after a DC resistance value was measured before initial charging using a charge / discharge test device (“TOSCAT” manufactured by Toyo System Co., Ltd.). Lithium was doped at a rate of 70 mA / g with respect to the mass of the active material, and was doped until the potential of lithium became 1 mV. Further, a constant voltage of 1 mV with respect to the lithium potential was applied for 8 hours to complete doping. The capacity (mAh / g) at this time was defined as the charging capacity. Next, undoping was performed at a rate of 70 mA / g with respect to the mass of the active material until the potential of the lithium became 2.5 V with respect to the lithium potential. The percentage of discharge capacity / charge capacity was defined as charge / discharge efficiency (initial charge / discharge efficiency), and was used as an index of lithium ion use efficiency in the battery.
　上記のようにして電池の評価を行った結果を表３に示す。
Figure JPOXMLDOC01-appb-T000003
 Table 3 shows the results of the evaluation of the battery as described above.
Figure JPOXMLDOC01-appb-T000003
　実施例１の炭素前駆体を用いて、高温焼成した場合、溶融や融着が生じず、原料の粒子形状を保ったまま炭素質材料が得られ、電池材料として適した炭素構造を示した。特に、参考例１に示した炭素質材料を用いて作製した電池は、低い抵抗値を有すると共に、高い放電容量を示した。一方で、所定の範囲Ｏ／Ｃ比を示さないか、ＩＡ／ＩＢを示さない、各比較例の炭素前駆体を用いて、参考例１と同様の方法で、炭化、高温焼成した場合では、得られた炭素質材料は電池材料に適した炭素構造を示さなかった。 When the carbon precursor of Example 1 was fired at a high temperature, melting and fusion did not occur, and a carbonaceous material was obtained while keeping the particle shape of the raw material, showing a carbon structure suitable for a battery material. In particular, the battery manufactured using the carbonaceous material shown in Reference Example 1 had a low resistance value and a high discharge capacity. On the other hand, do not show a predetermined range O / C ratio, show no I A / I B, using carbon precursors, Comparative Examples, in the same manner as in Reference Example 1, carbide, when the high temperature firing Did not show a carbon structure suitable for battery materials.

Claims (6)

  1. 　元素分析による酸素原子含有量と炭素原子含有量の比（Ｏ／Ｃ）が０．１０～０．８５であり、かつ、ＩＲスペクトルの１７２０ｃｍ－１付近のピークの強度（ＩＡ）と３３３０ｃｍ－１付近のピークの強度（ＩＢ）の比（ＩＡ／ＩＢ）が０．５０以上である、炭素前駆体。 The ratio (O / C) of the oxygen atom content to the carbon atom content by elemental analysis is 0.10 to 0.85, and the peak intensity (I A ) near 1720 cm −1 in the IR spectrum and 3330 cm − the ratio of 1 near the peak intensity (I B) (I a / I B) is 0.50 or more, carbon precursor.
  2. 　ＴＧ－ＤＴＡ測定によるＤＴＡ曲線において、１００～５００℃の範囲に吸熱ピークを有さない、請求項１に記載の炭素前駆体。 2. The carbon precursor according to claim 1, wherein the carbon precursor has no endothermic peak in a range of 100 to 500 ° C. in a DTA curve measured by TG-DTA.
  3. 　１３Ｃ－ＮＭＲスペクトルにおいて、０～５０ｐｐｍの範囲にピークを有する、請求項１または２に記載の炭素前駆体。 3. The carbon precursor according to claim 1, which has a peak in a range of 0 to 50 ppm in a 13 C-NMR spectrum.
  4. 　糖類骨格を有する物質に由来する、請求項１～３のいずれかに記載の炭素前駆体。 4. The carbon precursor according to claim 1, which is derived from a substance having a saccharide skeleton.
  5. 　炭素前駆体の原料を、酸素含有気体の供給下、２１５～２４０℃の温度範囲で１～１２時間熱処理して炭素前駆体を得る、請求項１～４のいずれかに記載の炭素前駆体の製造方法。 The carbon precursor according to any one of claims 1 to 4, wherein the raw material of the carbon precursor is heat-treated at a temperature of 215 to 240 ° C for 1 to 12 hours under supply of an oxygen-containing gas to obtain a carbon precursor. Production method.
  6. 　酸素含有気体の供給量は、炭素前駆体の原料の単位表面積あたり０．００５～５．０Ｌ／（分・ｍ２）である、請求項５に記載の製造方法。 The production method according to claim 5, wherein the supply amount of the oxygen-containing gas is 0.005 to 5.0 L / (min · m 2 ) per unit surface area of the raw material of the carbon precursor.
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