Carbonaceous material, negative electrode for power storage devices, power storage device, and method for producing carbonaceous material

Abstract

The present invention relates to a carbonaceous material which has an elemental nitrogen content of 1.0% by mass or more as determined by elemental analysis, while having a true density of 1.50 to 1.65 g / cc as determined by a butanol immersion method, a tap bulk density of 0.7 to 1.0 g / cc, and a carbon interplanar spacing (d002) of 3.65 Å or more as determined by X-ray diffractometry.

Description

Carbonaceous material, negative electrode for power storage device, power storage device, and method for producing carbonaceous material

[0001] The present invention relates to a carbonaceous material, a negative electrode for an electricity storage device, an electricity storage device, and a method for producing a carbonaceous material.

[0002] Electricity storage devices, such as secondary batteries and capacitors, utilize electrochemical phenomena and are widely used. For example, lithium-ion secondary batteries, which are one type of electricity storage device, are widely used in small portable devices such as mobile phones and laptops. As a negative electrode material for lithium-ion secondary batteries, non-graphitizable carbons that can be doped (charged) and dedoped (discharged) with lithium in amounts exceeding the theoretical capacity of graphite, 372 mAh / g, have been developed and used (see, for example, Patent Document 1).

[0003] Non-graphitizable carbon can be obtained using, for example, petroleum pitch, coal pitch, phenolic resin, or plants as a carbon source. Among these carbon sources, plant-derived raw materials, such as sugar compounds, are attracting attention because they can be sustainably supplied through cultivation and are inexpensively available. Furthermore, carbonaceous materials obtained by calcining plant-derived carbon raw materials have many pores, and are therefore expected to have good charge / discharge capacities (see, for example, Patent Documents 1 and 2).

[0004] Further, known carbonaceous materials that can be used as the negative electrode of an electricity storage device such as a nonaqueous electrolyte secondary battery include a carbonaceous material in which the true density, the atomic ratio of hydrogen atoms to carbon atoms determined by elemental analysis, the average particle size, Dv90 / Dv10, and the circularity are adjusted to fall within predetermined ranges (Patent Document 2), a carbonaceous material in which the nitrogen element content, the oxygen content, and the hydrogen element content are adjusted to predetermined amounts and ratios (Patent Documents 3 and 4), and a carbonaceous material in which the tap density and the angle of repose are adjusted to fall within predetermined ranges (Patent Document 5).

[0005] Patent Document 1: JP 2006-083012 A, International Publication No. 2013 / 118757, International Publication No. 2019 / 009332, International Publication No. 2019 / 009333, Patent Document 2012-533864 A

[0006] In various applications of power storage devices that use carbonaceous materials as anode materials, there is a demand for higher energy densities of the anodes in the devices. One possible means for achieving higher energy densities is to increase both the discharge capacity per weight and the discharge capacity per volume, but it has been difficult to provide carbonaceous materials that achieve such properties.

[0007] Therefore, an object of the present invention is to provide a carbonaceous material that, when used as a negative electrode layer, can provide an electricity storage device that has both a high discharge capacity per weight and a high discharge capacity per volume. Another object of the present invention is to provide an electricity storage device negative electrode containing such a carbonaceous material, and an electricity storage device containing such an electricity storage device negative electrode.

[0008] As a result of intensive research by the present inventors, it has been found that the nitrogen element content, true density, tapped bulk density, and carbon interplanar spacing (d ００２ It has been found that by setting the carbonaceous material content within a predetermined range, it is possible to obtain a carbonaceous material suitable for an electricity storage device that has both a high discharge capacity per weight and a high discharge capacity per volume.

[0009] That is, the present invention includes the following preferred embodiments: [1] A carbon nanotube having a nitrogen element content of 1.0 mass% or more as determined by elemental analysis, a true density of 1.50 to 1.65 g / cc as determined by a butanol immersion method, a tapped bulk density of 0.7 to 1.0 g / cc, and a carbon interplanar spacing (d ００２ [2] A carbonaceous material having a D in a volume-based particle size distribution measured by a laser diffraction / scattering particle size distribution measurement method of 3.65 Å or more. ２０ D against ８０ Proportion D ８０ / D ２０ [3] The carbonaceous material according to [1] or [2], wherein the circularity is 0.70 or more as measured on particles having a diameter of a circle corresponding to the projected area of ​​5 μm or more using a flow particle image analyzer. [4] The carbonaceous material according to [1] or [2], wherein the circularity is 0.70 or more as measured on particles having a diameter of a circle corresponding to the projected area of ​​5 μm or more using a flow particle image analyzer. [5] The carbonaceous material according to [1] or [2], wherein the circularity is 0.70 or more as measured on particles having a diameter of 5 μm or more －１ The half-width value of the peak in the vicinity is 240 cm －１[5] The carbonaceous material according to any one of [1] to [3], wherein the carbonaceous material has a Raman spectrum observed by laser Raman spectroscopy of 1650 cm －１ The half-width value of the peak in the vicinity is 98 cm －１ The carbonaceous material according to any one of [1] to [4], wherein the carbonaceous material is a carbonaceous material for a negative electrode of an electricity storage device. [6] The carbonaceous material according to any one of [1] to [5], wherein the carbonaceous material is a carbonaceous material for a negative electrode of an electricity storage device. [7] An negative electrode for an electricity storage device, comprising the carbonaceous material according to any one of [1] to [6]. [8] An electricity storage device, comprising the negative electrode for an electricity storage device according to [7]. [9] A method for producing a carbonaceous material according to any one of [1] to [6], comprising at least the following steps: (1) mixing a compound having a saccharide skeleton, a nitrogen-containing compound, and a crosslinking agent to obtain a mixture, (2) heat-treating the mixture at 500 to 900°C in an inert gas atmosphere to obtain a charcoal, (3) pulverizing and / or classifying the char, and (4) heat-treating the pulverized and / or classified charcoal in an inert gas atmosphere at 800 to 1600°C to obtain a carbonaceous material.

[10] The compound having a saccharide skeleton has a cross-sectional area of ​​3 μm in an image obtained by observing the cross section of a particle of the compound with a secondary electron microscope. ２ 100 μm or more ２ When 20 particles below are randomly selected, ２

[11] The method for producing a carbonaceous material according to [9], further comprising a step (A) of gelatinizing the compound having a saccharide skeleton before, simultaneously with, or after step (1) of mixing the compound having a saccharide skeleton, the nitrogen-containing compound, and the crosslinking agent to obtain a mixture.

[12] The method for producing a carbonaceous material according to

[11] , wherein step (A) is: step (a1) of mixing 5 to 50% by mass of water, relative to the mass of the compound, with a compound having a saccharide skeleton, and heating the mixture at a temperature of 50 to 200°C for 1 minute to 5 hours, before step (1); step (b1) of subjecting the compound having a saccharide skeleton to a mechanical treatment involving impact, crushing, friction, and / or shear, before step (1); step (a2) of mixing 5 to 50% by mass of water, relative to the mass of the compound having a saccharide skeleton, with a mixture containing the compound having a saccharide skeleton, and heating the mixture at a temperature of 50 to 200°C for 1 minute to 5 hours, simultaneously with step (1) or after step (1); and / or step (b2) of subjecting the mixture containing the compound having a saccharide skeleton to a mechanical treatment involving impact, crushing, friction, and / or shear, simultaneously with step (1) or after step (1).

[0010] According to the present invention, it is possible to provide a carbonaceous material that is suitable for an electricity storage device and has both a high discharge capacity per weight and a high discharge capacity per volume.

[0011] Hereinafter, embodiments of the present invention will be described in detail, but it is not intended that the present invention be limited to the following embodiments.

[0012] In this specification, the term "electricity storage device" refers to a general device that includes a negative electrode containing a carbonaceous material and utilizes an electrochemical phenomenon. Specifically, the electricity storage device includes, for example, secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride secondary batteries, and nickel-cadmium secondary batteries, which can be repeatedly used by charging, and capacitors such as electric double layer capacitors. Among these, the electricity storage device may be a secondary battery, particularly a nonaqueous electrolyte secondary battery (e.g., a lithium-ion secondary battery, a sodium-ion battery, a lithium-sulfur battery, a lithium-air battery, an all-solid-state battery, an organic radical battery, etc.), and particularly may be a lithium-ion secondary battery.

[0013] The carbonaceous material of the present invention is a carbonaceous material suitable for providing an electricity storage device having both a high discharge capacity per weight and a high discharge capacity per volume, and has a nitrogen element content of 1.0 mass% or more as determined by elemental analysis, a true density of 1.50 to 1.65 g / cc as determined by a butanol immersion method, a tapped bulk density of 0.7 to 1.0 g / cc, and a carbon interplanar spacing (d ００２ ) is 3.65 Å or more.

[0014] The nitrogen element content of the carbonaceous material of the present invention is 1.0 mass% or more by elemental analysis. The nitrogen element content is an analytical value obtained by elemental analysis of the carbonaceous material. If the nitrogen element content is less than 1.0 mass%, the carbon surfaces are close to each other, resulting in fewer sites for adsorbing and desorbing lithium ions during charge and discharge, making it impossible to sufficiently increase both the discharge capacity per volume and the discharge capacity per weight. From the viewpoint of more easily increasing the discharge capacity per volume and the discharge capacity per weight, the nitrogen element content is preferably 1.2 mass% or more, more preferably 1.5 mass% or more, even more preferably 2.0 mass% or more, and even more preferably 2.2 mass% or more. From the viewpoint of suppressing a decrease in discharge capacity during repeated charge and discharge, the upper limit of the nitrogen element content is preferably 8.0 mass% or less, more preferably 6.0 mass% or less, even more preferably 5.0 mass% or less, and even more preferably 4.0 mass% or less. The nitrogen element content of the carbonaceous material determined by elemental analysis can be adjusted to fall within the above range by adjusting the amount of a nitrogen-containing compound that can be added when producing the carbonaceous material, adjusting the temperature and time of heat treatment, and the like.

[0015] The true density of the carbonaceous material of the present invention, as measured by the butanol immersion method, is 1.50 to 1.65 g / cc. If the true density is less than 1.50 g / cc, the density will not be sufficiently high even when an electrode is prepared, and therefore the discharge capacity per volume cannot be sufficiently increased. Furthermore, if the true density exceeds 1.65 g / cc, the crystallization of the carbonaceous material is advanced, resulting in fewer sites for adsorption and desorption of lithium ions derived from intercrystalline voids, which are characteristic of non-graphitizable carbon, and therefore the discharge capacity per weight cannot be sufficiently increased. From the viewpoint of easily increasing the discharge capacity per volume, the true density of the carbonaceous material of the present invention is preferably 1.51 g / cc or more, more preferably 1.52 g / cc or more, and even more preferably 1.55 g / cc or more. Furthermore, from the viewpoint of sufficiently increasing the discharge capacity per weight derived from the absorption sites of clustered lithium, the true density is preferably 1.64 g / cc or less, more preferably 1.62 g / cc or less, and even more preferably 1.60 g / cc or less. The true density of the carbonaceous material is the true density by the butanol method, and is measured, for example, by the method described in the Examples. The true density can be adjusted to the above range by selecting the compound having a saccharide skeleton used in producing the carbonaceous material, gelatinizing the compound having a saccharide skeleton, etc.

[0016] The tapped bulk density of the carbonaceous material of the present invention is 0.7 to 1.0 g / cc. If the tapped bulk density is less than 0.7 g / cc, it is difficult to sufficiently increase the discharge capacity per volume. Furthermore, if the tapped bulk density exceeds 1.0 g / cc, battery performance, including the discharge capacity per weight, is reduced. It is believed that the tapped bulk density of the carbonaceous material of the present invention leads to an increase in the electrode density of the negative electrode obtained using the carbonaceous material, and as a result, the discharge capacity per volume can be increased. From the viewpoint of easily sufficiently increasing both the discharge capacity per volume and the discharge capacity per weight, the tapped bulk density is preferably 0.72 g / cc or more, more preferably 0.75 g / cc or more, even more preferably 0.78 g / cc or more, and even more preferably 0.80 g / cc or more. Furthermore, from the viewpoint of the absorption of the electrolyte into the carbonaceous material when preparing an electrode, the tapped bulk density is preferably 0.97 g / cc or less, more preferably 0.95 g / cc or less, even more preferably 0.93 g / cc or less, and even more preferably 0.91 g / cc or less. The tapped bulk density of the carbonaceous material is measured by repeatedly performing 100 cycles of a process in which a cylindrical glass container having a diameter of 1.8 cm filled with the carbonaceous material and passed through a sieve with a mesh size of 300 μm is allowed to freely drop from a height of 5 cm, until the rate of change in density, calculated from the volume and mass of the carbonaceous material, before and after one set of operations is 2% or less. The tapped bulk density can be adjusted to the above range by selecting the nitrogen-containing compound or crosslinking agent used in producing the carbonaceous material, or by adjusting the particle size, shape, particle size distribution, etc. of the carbonaceous material.

[0017] The carbon interplanar spacing (d ００２ The carbon spacing (d ００２ When the carbon interplanar spacing (d) is less than 3.65 Å, the carbon planes are close to each other, preventing efficient movement of lithium ions, and the micropores are not sufficiently developed, reducing the number of storage sites for clustered lithium, making it impossible to sufficiently increase both the discharge capacity per volume and the discharge capacity per weight. ００２From the viewpoint of easily increasing the discharge capacity per volume and the discharge capacity per weight, the carbon interplanar spacing (d ００２ The upper limit of d ００２ By appropriately reducing the carbonaceous material volume, the effective capacity per volume can be increased, and the discharge capacity per volume can be easily increased. From this viewpoint, the carbon interplanar spacing (d ００２ The carbon interplanar spacing (d) is measured by X-ray diffraction measurement using the Bragg equation, specifically by the method described in the Examples. ００２ ) can be adjusted to fall within the above range by adjusting the amount of the nitrogen-containing compound that can be added when producing the carbonaceous material, adjusting the temperature and time of the heat treatment, etc.

[0018] In a preferred embodiment of the present invention, the carbonaceous material of the present invention has a volume-based particle size distribution measured by a laser diffraction / scattering particle size distribution measurement method. ２０ D against ８０ Proportion D ８０ / D ２０ It has been found that by setting the D to be preferably 3.5 to 20, the tap bulk density and the electrode density of the negative electrode obtained using the carbonaceous material can be increased. ８０ / D ２０ When D is within the above range, it indicates that the particle size distribution of the carbonaceous material is wide, and in this case, an appropriate amount of small particles is filled into the gaps between the large particles, reducing the porosity, which is thought to facilitate an increase in the tap bulk density and the electrode density of a negative electrode obtained using the carbonaceous material. ８０ / D ２０is preferably 4.0 or more, more preferably 4.5 or more, even more preferably 5.0 or more, still more preferably 5.5 or more, and particularly preferably 6.0 or more, and from the same viewpoint, is preferably 18 or less, more preferably 16 or less, and even more preferably 15 or less. The volume-based particle size distribution measured by the laser diffraction scattering particle size distribution measurement method can be measured using a particle size / particle size distribution measurement device with a dispersion of a carbonaceous material as a measurement sample, and the particle size at which the cumulative volume is 80% in the particle size distribution is defined as D ８０ The particle diameter at which the cumulative volume becomes 20% is D ２０ Let's say.

[0019] In a preferred embodiment of the present invention, the circularity of the carbonaceous material of the present invention, measured using a flow particle image analyzer for particles having a diameter of 5 μm or more of a circle corresponding to the projected area, is preferably 0.70 or more, more preferably 0.71 or more, even more preferably 0.72 or more, and even more preferably 0.73 or more, from the viewpoint of easily increasing the electrode density of a negative electrode obtained using the carbonaceous material, and from the same viewpoint, is preferably 0.99 or less, more preferably 0.98 or less, and even more preferably 0.96 or less. When the circularity is within the above range, the carbonaceous material is close to a sphere, which makes it easier to increase the fluidity, and it is thought that the tap bulk density and the electrode density of a negative electrode obtained using the carbonaceous material are easier to increase. The circularity is determined by using a dispersion of the carbonaceous material as a measurement sample, obtaining a projected image of the particles using a flow particle image analyzer, and calculating the circularity using the following formula: circularity=(D / M), where D μm is the diameter of an equivalent circle having the same projected area for one particle in the projected image, and M μm is the length at which the distance between two parallel lines sandwiching the particle image is greatest. ２ The circularity per particle is calculated by the above formula, and the circularity per particle is measured for, for example, 5,000 or more particles, preferably 10,000 or more particles having a D of 5 μm or more, and the average circularity is obtained.

[0020] In a preferred embodiment of the present invention, in the Raman spectrum observed by laser Raman spectroscopy of the carbonaceous material of the present invention, －１ The half width of the peak in the vicinity of 240 cm is preferably 240 cm from the viewpoint of making it easier to increase the discharge capacity per volume and the discharge capacity per weight. －１More preferably, 250 cm －１ More preferably, 260 cm －１ The Raman spectrum is measured using a Raman spectrometer under the conditions described in the Examples, for example.

[0021] In a preferred embodiment of the present invention, in the Raman spectrum observed by laser Raman spectroscopy of the carbonaceous material of the present invention, －１ The half width of the peak in the vicinity of 98 cm is preferably 98 cm from the viewpoint of making it easier to increase the discharge capacity per volume and the discharge capacity per weight. －１ More preferably, 100 cm －１ More preferably, 102 cm －１ The Raman spectrum is measured using a Raman spectrometer under the conditions described in the Examples, for example.

[0022] The method for producing the carbonaceous material of the present invention is not particularly limited as long as it can produce a carbonaceous material having the above-mentioned properties, but examples include a method in which a carbon precursor is mixed with a nitrogen-containing compound and a crosslinking agent, the resulting mixture is heat-treated in an inert gas atmosphere at 500° C. or higher and 900° C. or lower, and then pulverized and / or classified, and the resulting charcoal is further heat-treated at 800 to 1600° C. For example, the carbon precursor is not particularly limited as long as it can produce a carbonaceous material satisfying the above-mentioned properties, but from the viewpoint of making it easy to adjust the above-mentioned properties of the carbonaceous material to within preferred ranges, a compound having a saccharide skeleton is preferred.

[0023] In a preferred embodiment of the present invention, the method for producing a carbonaceous material of the present invention includes at least the following steps: (1) mixing a compound having a saccharide skeleton, a nitrogen-containing compound, and a crosslinking agent to obtain a mixture, (2) heat-treating the mixture at 500 to 900°C in an inert gas atmosphere to obtain a charcoal, (3) pulverizing and / or classifying the char, and (4) heat-treating the pulverized and / or classified charcoal at 800 to 1600°C in an inert gas atmosphere to obtain a carbonaceous material. The present invention also provides a method for producing the above carbonaceous material.

[0024] Step (1) is a step of mixing a compound having a saccharide skeleton, a nitrogen-containing compound, and a crosslinker to obtain a mixture. Examples of compounds having a saccharide skeleton used as raw materials include monosaccharides such as glucose, galactose, mannose, fructose, ribose, and glucosamine; disaccharides such as sucrose, trehalose, maltose, cellobiose, maltitol, lactobionic acid, and lactosamine; and polysaccharides such as starch, glycogen, agarose, pectin, cellulose, chitin, chitosan, oligosaccharides, and xylitol. As the compound having a saccharide skeleton, one of these compounds may be used, or two or more may be used in combination. Among these compounds having a saccharide skeleton, starch is preferred because it is easily available in large quantities. Examples of starches include corn starch, potato starch, wheat starch, rice starch, tapioca starch, sago starch, sweet potato starch, mylostarch, kudzu starch, bracken starch, lotus root starch, mung bean starch, and potato chestnut starch. These starches may be physically, enzymatically, or chemically processed, and may be starches processed into pregelatinized starch, phosphate cross-linked starch, acetate starch, hydroxypropyl starch, oxidized starch, dextrin, etc. Corn starch and wheat starch, as well as pregelatinized starches thereof, are preferred as starches because of their availability and low cost.

[0025] In a preferred embodiment of the production method of the present invention, the compound having a saccharide skeleton has a cross-sectional area of ​​3 μm in an image obtained by observing the cross section of a particle of the compound with a secondary electron microscope. ２ 100 μm or more ２ When 20 particles below are randomly selected, ２ The number of particles having the above voids is preferably 3 or less, more preferably 2 or less, and even more preferably 1 or less. By producing a carbide using such a compound with few voids as a raw material, it is easy to produce a carbonaceous material that satisfies the characteristics of the present invention without performing additional processing such as step (A) described below, and it is easy to produce a carbonaceous material that is suitable for an electricity storage device that combines a high discharge capacity per weight and a high discharge capacity per volume.

[0026] The nitrogen-containing compound that can be used in step (1) is not particularly limited as long as it is a compound having a nitrogen atom in the molecule. Examples include inorganic ammonium salts such as ammonium chloride, ammonium sulfate, ammonium carbonate, and ammonium nitrate; organic ammonium salts such as ammonium formate, ammonium acetate, ammonium oxalate, and diammonium hydrogen citrate; aromatic amine hydrochlorides such as aniline hydrochloride and aminonaphthalene hydrochloride; and nitrogen-containing organic compounds such as melamine, pyrimidine, pyridine, pyrrole, imidazole, indole, urea, cyanuric acid, and benzoguanamine. As the nitrogen-containing compound, one of these nitrogen-containing compounds may be used alone, or two or more may be used in combination. Among these nitrogen-containing compounds, melamine and urea, which have a high intramolecular nitrogen content, are preferred from the viewpoint of facilitating incorporation of a large amount of nitrogen element into the carbonaceous material. As the nitrogen-containing compound, a compound having a volatilization temperature of preferably 100° C. or higher, more preferably 150° C. or higher, is preferred from the viewpoint of reaction with a saccharide compound during the heat treatment process.

[0027] The crosslinking agent that can be used in step (1) is a compound capable of crosslinking the starting compound having a saccharide skeleton, and acts as a catalyst to promote the interchain bond formation reaction of saccharide compounds and / or the reaction of saccharide compounds with nitrogen-containing compounds, which proceed in parallel with the hydrolysis reaction or dehydration reaction of saccharide compounds, or it itself crosslinks saccharide compounds and / or nitrogen-containing compounds. The type of crosslinking agent is not particularly limited, and examples thereof include aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, linoleic acid, and oleic acid; aromatic monocarboxylic acids such as benzoic acid, salicylic acid, and toluic acid; oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, phthalic acid, and terephthalic acid. Examples of suitable crosslinking agents include polycarboxylic acids such as phthalic acid; hydroxycarboxylic acids such as lactic acid, tartaric acid, citric acid, and malic acid; carboxylic acids such as ethylenediaminetetraacetic acid; sulfonic acids such as p-toluenesulfonic acid and methanesulfonic acid; amino acids such as glycine, alanine, valine, leucine, isoleucine, serine, threonine, cysteine, methionine, asparagine, glutamine, proline, phenylalanine, tyrosine, and tryptophan; and hydrochloric acid, sulfuric acid, and phosphoric acid. These crosslinking agents may be used alone or in combination of two or more. Among these crosslinking agents, polycarboxylic acids and hydroxycarboxylic acids are preferred, with succinic acid, adipic acid, and citric acid being more preferred, from the viewpoint of suppressing melting and foaming of the raw materials during the heat treatment process to obtain a carbonized material. When a carbonaceous material is produced by calcining a raw material containing a compound having a saccharide skeleton, the compound is prone to melting, fusion, foaming, and the like during the calcination process, resulting in a flat, rather than spherical, shape of the resulting carbonaceous material. By performing calcination using a crosslinking agent, it is possible to reduce fusion and foaming between the raw materials, and as a result, it is possible to sufficiently increase the tap bulk density of the obtained carbonaceous material, which makes it easier to increase both the discharge capacity per volume and the discharge capacity per weight in an electricity storage device.

[0028] The mixing ratio of the saccharide-based compound, the nitrogen-containing compound, and the crosslinking agent is not particularly limited and may be adjusted appropriately to obtain a carbonaceous material with the desired properties. For example, increasing the amount of the nitrogen-containing compound tends to increase the nitrogen element content in the carbonaceous material, while increasing the amount of the crosslinking agent tends to increase the true density. In a preferred embodiment of the present invention, the amount of the saccharide-based compound contained in the mixture obtained in step (1) is preferably 50 to 99 mass%, more preferably 80 to 95 mass%, based on the total amount of the saccharide-based compound, the nitrogen-containing compound, and the crosslinking agent. The amount of the nitrogen-containing compound contained in the mixture is preferably 1 to 30 mass%, more preferably 3 to 15 mass%, based on the total amount of the saccharide-based compound, the nitrogen-containing compound, and the crosslinking agent. The amount of the crosslinking agent contained in the mixture is preferably 1 to 30 mass%, more preferably 3 to 10 mass%, based on the total amount of the saccharide-based compound, the nitrogen-containing compound, and the crosslinking agent.

[0029] Next, in step (2), the mixture obtained in step (1) is heat-treated at 500 to 900°C under an inert gas atmosphere to obtain a carbide. This carbide is also referred to as a carbon precursor. The heat treatment temperature in step (2) is preferably 550 to 850°C, more preferably 600 to 800°C. The heating rate until the heat treatment temperature (the ultimate temperature) is reached is 50°C / hour or more, preferably 50°C / hour to 200°C / hour. The heat treatment time is typically a holding time at the ultimate temperature of 5 minutes or more, preferably 5 minutes to 2 hours, more preferably 10 minutes to 1 hour, and even more preferably 30 minutes to 1 hour. When the heat treatment temperature and time are within the above ranges, it is easy to control the carbonization of the compound having a saccharide skeleton, and it is easy to adjust the above-mentioned characteristic values ​​of the carbonaceous material to the desired ranges. The heat treatment temperature may be a constant temperature, but is not particularly limited as long as it is within the above range.

[0030] Step (2) is carried out in an inert gas atmosphere. As long as the step is carried out in an inert gas atmosphere, the inert gas may or may not be actively supplied. Examples of the inert gas include argon gas, helium gas, and nitrogen gas, and nitrogen gas is preferred. This heat treatment step produces a carbide, which is a precursor for producing a carbonaceous material.

[0031] In step (3), the obtained carbide is pulverized and / or classified. The pulverization and classification methods are not particularly limited, and may be performed by a conventional method, such as a method using a ball mill or a jet mill. By pulverizing and / or classifying the carbide, it is possible to break down or remove agglomerates formed by the heat treatment in step (2).

[0032] In step (4), the pulverized and / or classified carbide is heat-treated at 800 to 1600°C under an inert gas atmosphere to obtain the carbonaceous material of the present invention. The heat treatment temperature in step (4) is preferably 900 to 1400°C, more preferably 1000 to 1400°C, and even more preferably 1100 to 1200°C. The heating rate until the heat treatment temperature (ultimate temperature) is reached is 50°C / hour or more, preferably 50°C / hour to 200°C / hour. The heat treatment time is typically 1 minute or more, preferably 5 minutes to 2 hours, more preferably 10 minutes to 1 hour, and even more preferably 10 minutes to 30 minutes. If the heat treatment temperature and time are within the above ranges, the above-mentioned characteristic values ​​of the final carbonaceous material can be easily adjusted to the desired ranges. The heat treatment temperature may be a constant temperature, but is not particularly limited as long as it is within the above range.

[0033] In this case, a volatile organic compound may be added to the pulverized and / or classified carbonized material obtained in step (3) and then subjected to step (4). Volatile organic compounds refer to organic compounds that are hardly carbonized (e.g., 80% or more, preferably 90% or more) and volatilize (vaporize or pyrolyze into gas) when heat-treated with an inert gas such as nitrogen (e.g., at 500°C or higher). Examples of volatile organic compounds include, but are not limited to, thermoplastic resins and low-molecular-weight organic compounds. Specific examples of thermoplastic resins include polystyrene, polyethylene, polypropylene, poly(meth)acrylic acid, and poly(meth)acrylic acid esters. In this specification, (meth)acrylic is a general term for methacrylic and acrylic. Examples of low-molecular-weight organic compounds include hexane, toluene, xylene, mesitylene, styrene, naphthalene, phenanthrene, anthracene, and pyrene. Since thermoplastic resins that volatilize at firing temperatures and do not oxidize and activate the surface of the carbon precursor when pyrolyzed are preferred, polystyrene, polyethylene, and polypropylene are preferred. Further, from the viewpoint of safety, it is preferable that the low molecular weight organic compound has low volatility at room temperature (for example, 20° C.), and preferred examples are naphthalene, phenanthrene, anthracene, pyrene, etc. Addition of such a volatile organic compound is preferable in that it can further reduce the specific surface area while maintaining the characteristic structure of the present invention.

[0034] When a carbonaceous material is produced by the above-described production method, the production method may further include, in addition to steps (1) to (4), step (A) of gelatinizing the compound having a saccharide skeleton before, simultaneously with, or after step (1) of mixing a compound having a saccharide skeleton, a nitrogen-containing compound, and a crosslinking agent to obtain a mixture. By performing gelatinization in step (A), cavities contained in the compound having a saccharide skeleton used as a raw material are closed, and as a result, the true density, tapped bulk density, and carbon interplanar spacing of the finally obtained carbonaceous material can be easily adjusted to desired ranges, and a carbonaceous material suitable for an electricity storage device having both a high discharge capacity per weight and a high discharge capacity per volume can be easily produced.

[0035] The gelatinization method in step (A) is not particularly limited, and examples thereof include a method of heating a compound having a saccharide skeleton alone or in any mixture with a nitrogen-containing compound or the like in the presence of water, and a method of subjecting a compound having a saccharide skeleton alone or in any mixture with a nitrogen-containing compound or the like to mechanical treatment involving impact, crushing, friction, and / or shear. By applying such heat or external force, cavities contained in the compound having a saccharide skeleton are closed. The gelatinization in the above step (A) can be carried out, for example, by observing the cross-section of a particle of the compound having a saccharide skeleton after gelatinization under a secondary electron microscope, and then forming a particle having a cross-sectional area of ​​3 μm or less. ２ 100 μm or more ２ When 20 particles below are randomly selected, ２ It is preferable to continue the process until the number of particles having the above voids is reduced to a predetermined amount or less, preferably 3 or less, more preferably 2 or less, and even more preferably 1 or less. The above-mentioned microscopic observation may be carried out after removing aggregates contained in the gelatinized compound by pulverization or classification. The mixture obtained through the above-mentioned step (1) and optional step (A) is heat-treated in step (2). Therefore, when step (A) is carried out, step (A) is a step carried out before step (2).

[0036] In a preferred embodiment of the present invention, the production method of the present invention may comprise the following step as step (A): step (a1) of mixing a compound having a saccharide skeleton with 5 to 50% by mass of water relative to the mass of the compound, and heating the mixture at a temperature of 50 to 200°C for 1 minute to 5 hours, prior to step (1); step (b1) of subjecting the compound having a saccharide skeleton to a mechanical treatment involving impact, crushing, friction, and / or shear, prior to step (1); step (a2) of mixing a mixture containing the compound having a saccharide skeleton with 5 to 50% by mass of water relative to the mass of the compound, and heating the mixture at a temperature of 50 to 200°C for 1 minute to 5 hours, simultaneously with step (1) or after step (1); and / or step (b2) of subjecting the mixture containing the compound having a saccharide skeleton to a mechanical treatment involving impact, crushing, friction, and / or shear, simultaneously with step (1) or after step (1).

[0037] Step (a1) is a step in which, prior to step (1), 5 to 50% by mass of water is mixed with a compound having a saccharide skeleton, relative to the mass of the compound, and the mixture is heated at a temperature of 50 to 200°C for 1 minute to 5 hours. When mixing water with a compound having a saccharide skeleton, a certain amount of water is required. However, in order to reduce the energy required to distill off the mixed water during the process of producing a carbonaceous material, a smaller amount of water is preferable. The amount of water is 5 to 50% by mass, preferably 10 to 50% by mass, more preferably 10 to 30% by mass, relative to the mass of the compound. The heating temperature is 50 to 200°C, preferably 60 to 180°C, more preferably 80 to 180°C. The heating time is 1 minute to 5 hours, preferably 3 minutes to 1 hour, more preferably 10 to 30 minutes.

[0038] Step (b1) is a step of subjecting the compound having a saccharide skeleton to a mechanical treatment involving impact, crushing, friction, and / or shearing, prior to step (1). Examples of equipment used in the mechanical treatment involving impact, crushing, friction, and / or shearing include a pulverizer, extruder, flour mill, grinder, and kneader. Treatment conditions such as treatment time are not particularly limited, but examples of treatment conditions that can be used include 20 Hz and 10 minutes when a ball vibration mill is used.

[0039] Step (a2) is a step, which is carried out simultaneously with or after step (1), of mixing a mixture containing a compound having a saccharide skeleton with 5 to 50% by mass of water relative to the mass of the compound having a saccharide skeleton, and heating the mixture at a temperature of 50 to 200°C for 1 minute to 5 hours, and the descriptions of the preferred embodiments and the like described with respect to step (a1) similarly apply to step (a2).

[0040] Step (b2) is a step of subjecting a mixture containing a compound having a saccharide skeleton to a mechanical treatment involving impact, crushing, friction, and / or shearing, either simultaneously with step (1) or after step (1), and the descriptions of the preferred embodiments and the like described with respect to step (b1) also apply to step (b2).

[0041] The carbonaceous material of the present invention or the carbonaceous material obtained by the production method of the present invention can be suitably used as an active material for a negative electrode of an electricity storage device.

[0042] A method for producing a negative electrode for an electricity storage device using the carbonaceous material of the present invention will be specifically described below. The negative electrode can be prepared, for example, by adding a binder to the carbonaceous material, adding an appropriate amount of a suitable solvent, and then kneading these to prepare an electrode mixture. The obtained electrode mixture can be applied to a current collector plate made of a metal plate or the like, dried, and then pressure-molded to produce a negative electrode for an electricity storage device, such as a negative electrode for a nonaqueous electrolyte secondary battery such as a lithium-ion secondary battery, a sodium-ion battery, a lithium-sulfur battery, or a lithium-air battery.

[0043] By using the carbonaceous material of the present invention, an electrode (negative electrode) having a high discharge capacity per weight and a high discharge capacity per volume can be produced. If it is desired to impart higher conductivity to the electrode, a conductive additive can be added as needed during the preparation of the electrode mixture. Examples of conductive additives that can be used include conductive carbon black, vapor-grown carbon fiber (VGCF), and nanotubes. The amount of conductive additive added varies depending on the type of conductive additive used. Adding too little may result in the desired conductivity not being achieved, while adding too much may result in poor dispersion in the electrode mixture. From this perspective, when a conductive additive is added, the amount is preferably 0.5 to 10% by mass, more preferably 0.5 to 7% by mass, and even more preferably 0.5 to 5% by mass, where the amount of active material (carbonaceous material) + the amount of binder + the amount of conductive additive = 100% by mass. The binder is not particularly limited as long as it does not react with the electrolyte, but examples include PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and a mixture of SBR (styrene butadiene rubber) and CMC (carboxymethyl cellulose). A mixture of SBR and CMC is particularly preferred because the SBR and CMC attached to the active material surface do not significantly inhibit lithium ion migration, resulting in good input / output characteristics. A polar solvent such as water is preferably used to dissolve an aqueous emulsion of SBR or CMC to form a slurry, but a solvent-based emulsion of PVDF or the like can also be dissolved in N-methylpyrrolidone or the like. Adding too much binder can increase the resistance of the resulting electrode, thereby increasing the internal resistance of the battery and degrading battery performance. Adding too little binder can result in insufficient bonding between the particles of the negative electrode material and with the current collector. The preferred amount of binder to be added varies depending on the type of binder used, but for example, in binders that use water as a solvent, a mixture of multiple binders, such as a mixture of SBR and CMC, is often used, and the total amount of all binders used is preferably 0.5 to 5 mass %, more preferably 1 to 4 mass %. On the other hand, in the case of PVDF-based binders, the amount is preferably 3 to 13 mass %, more preferably 3 to 10 mass %.The amount of the carbonaceous material in the electrode mixture is preferably 80% by mass or more, more preferably 90% by mass or more, and is preferably 100% by mass or less, more preferably 97% by mass or less.

[0044] The electrode active material layer is generally formed on both sides of the current collector plate, but may be formed on one side if necessary. A thicker electrode active material layer is preferable for achieving higher capacity because fewer current collector plates, separators, etc. are required. However, since a larger electrode area facing the counter electrode is advantageous for improving input / output characteristics, if the electrode active material layer is too thick, the input / output characteristics may deteriorate. From the viewpoint of output during battery discharge, the thickness of the active material layer (per side) is preferably 10 to 80 μm, more preferably 20 to 75 μm, and even more preferably 30 to 75 μm.

[0045] An electricity storage device using the carbonaceous material of the present invention has a high discharge capacity per weight and a high discharge capacity per volume. When the carbonaceous material of the present invention is used to form a negative electrode for an electricity storage device, other materials constituting the battery, such as a positive electrode material, a separator, and an electrolyte, are not particularly limited, and various materials that have conventionally been used or proposed for electricity storage devices can be used.

[0046] For example, the positive electrode material is a layered oxide (LiMO ２ where M is a metal, for example, LiCoO ２ , LiNiO ２ , LiMnO ２ , or LiNi ｘ Co ｙ Mo ｚ O ２ (where x, y, and z represent the composition ratio), olivine-based (LiMPO ４ where M is a metal, for example LiFePO ４ etc.), spinel type (LiM ２ O ４ where M is a metal, for example LiMn ２ O ４These positive electrode materials are preferably composite metal chalcogen compounds such as those described above, and these chalcogen compounds may be mixed and used as needed. 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 electrode, and forming a layer on a conductive current collector.

[0047] For example, when the electricity storage device is a non-aqueous electrolyte secondary battery, the non-aqueous solvent-type electrolyte solution is generally formed by dissolving an electrolyte in a non-aqueous solvent. As the non-aqueous solvent, for example, organic solvents such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, γ-butyl lactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, or 1,3-dioxolane can be used singly or in combination. In addition, as the electrolyte, LiClO ４ , LiPF ６ , LiBF ４ , LiCF ３ SO ３ , LiAsF ６ , LiCl, LiBr, LiB(C ６ H ５ ) ４ , or LiN(SO ３ CF ３ ) ２ etc. are used.

[0048] Furthermore, when the power storage device is a nonaqueous electrolyte secondary battery, the nonaqueous electrolyte secondary battery is generally formed by arranging the positive electrode and negative electrode formed as described above facing each other, with a liquid-permeable separator interposed between them as necessary, and immersing them in an electrolyte solution. Such separators can be nonwoven fabrics commonly used in secondary batteries or other permeable or liquid-permeable separators made of porous materials. Alternatively, a solid electrolyte made of a polymer gel impregnated with an electrolyte solution can be used instead of or together with the separator.

[0049] The carbonaceous material of the present invention is suitable as a carbonaceous material for an electricity storage device (typically, a nonaqueous electrolyte secondary battery for driving a vehicle) mounted on a vehicle such as an automobile. The vehicle in the present invention is not particularly limited to those generally known as electric vehicles, hybrid vehicles with fuel cells or internal combustion engines, etc., and is equipped with at least a power supply unit including the above-mentioned battery, an electric drive mechanism driven by power supply from the power supply unit, and a control device for controlling the same. The vehicle may further be equipped with a dynamic brake or a regenerative brake, and may be equipped with a mechanism for converting braking energy into electricity and charging the nonaqueous electrolyte secondary battery.

[0050] The present invention will be described in detail below with reference to examples, but these examples are not intended to limit the scope of the present invention. While methods for measuring the physical properties of carbonaceous materials and negative electrodes using the same are described below, the physical properties and measurements (or physical property values ​​and measured values) described in this specification, including the examples, are based on values ​​determined by the following methods.

[0051] (Nitrogen element content) Elemental analysis was carried out based on the inert gas dissolution method using an oxygen, nitrogen and hydrogen analyzer EMGA-930 manufactured by Horiba, Ltd. The detection methods of this device were oxygen: inert gas fusion - non-dispersive infrared absorption (NDIR), nitrogen: inert gas fusion - thermal conductivity (TCD), and hydrogen: inert gas fusion - non-dispersive infrared absorption (NDIR), and calibration was performed using a Ni capsule (oxygen / nitrogen), TiH ２ (H standard sample), SS-3 (O standard sample), and SiN (N standard sample). As a pretreatment, 20 mg of the sample was measured for moisture content at 250°C for approximately 10 minutes, placed in a Ni capsule, and measured after degassing for 30 seconds in an elemental analyzer. Three samples were analyzed in the test, and the average value was used as the analytical value. The nitrogen element content in the sample was obtained as described above.

[0052] (True density by butanol method) True density ρ Ｂｔ was measured by the butanol method in accordance with the method specified in JIS R 7212. The mass (m １Next, the sample was placed flat on the bottom of the container to a thickness of about 10 mm, and its mass (m ２ ) was accurately measured. 1-butanol was gently added to this to a depth of about 20 mm from the bottom. Next, the pycnometer was gently shaken, and after confirming that no large bubbles were being generated, it was placed in a vacuum desiccator and gradually evacuated to 2.0-2.7 kPa. This pressure was maintained for 20 minutes or more, and after the generation of bubbles had stopped, the pycnometer was removed, further filled with 1-butanol, stoppered, and immersed in a thermostatic water bath (adjusted to 30±0.03°C) for 15 minutes or more, until the liquid level of the 1-butanol was aligned with the marked line. Next, it was removed, the outside was wiped clean, and it was cooled to room temperature, after which the mass (m ４ Next, the same pycnometer was filled with 1-butanol only, and immersed in a thermostatic water bath in the same manner as above. After aligning the gauge line, the mass (m ３ ) was measured. Also, immediately before use, distilled water was boiled to remove dissolved gases, and placed in a pycnometer. This was immersed in a thermostatic water bath in the same manner as above, and after aligning the gauge line, the mass (m ５ ) was measured. Ｂｔ was calculated using the following formula: where d is the specific gravity of water at 30°C (0.9946).

[0053] (Tap Bulk Density) A carbonaceous material was dried in a vacuum dryer at 100°C for 3 hours, and then dropped through a sieve with 300 µm openings into a cylindrical glass container with a diameter of 1.8 cm to fill it. The glass container filled with the carbonaceous material was allowed to freely fall from a height of 5 cm, counting one tap, and 100 taps were performed, with the process of repeating these 100 taps counting as one set. The density measured repeatedly until the rate of change in density, calculated from the volume and mass of the carbonaceous material, before and after one set of operations was 2% or less was taken as the tapped bulk density.

[0054] (Average interplanar spacing d using the Bragg equation obtained by X-ray diffraction measurement) ００２Measurement) Using a "MiniFlex II manufactured by Rigaku Corporation," powders of the carbonaceous materials prepared in the examples and comparative examples described below were filled into a sample holder, and CuKα rays monochromated by a Ni filter were used as the radiation source to obtain an X-ray diffraction pattern. The peak positions of the diffraction pattern were determined by the centroid method (a method in which the centroid position of the diffraction lines is determined and the peak position is determined using the corresponding 2θ value), and correction was made using the diffraction peak of the (111) plane of high-purity silicon powder for standard material. The wavelength λ of CuKα rays was set to 0.15418 nm, and d was calculated using the Bragg formula shown below. ００２ was calculated.

[0055]

[0056] (Particle size distribution by laser scattering method) The average particle size (particle size distribution) of the carbonaceous material was measured by the following method. 5 mg of a sample was added to 2 mL of an aqueous solution containing 5 mass % of a surfactant ("Toriton X100" manufactured by Wako Pure Chemical Industries, Ltd.), and the sample was treated in an ultrasonic cleaner for 10 minutes or more to be dispersed in the aqueous solution. The particle size distribution was measured using this dispersion. The particle size distribution measurement was performed using a particle size / particle size distribution measuring device ("Microtrac MT3300EXII" manufactured by Microtrac Bell Co., Ltd.). D ５０ is the particle diameter at which the cumulative volume becomes 50%, and this value was used as the average particle diameter. ８０ The particle diameter at which the cumulative volume becomes 20% is D ２０ and the particle size distribution index D ８０ / D ２０ The particle size distribution index D ８０ / D ２０ = D ８０ / D ２０

[0057] (Circularity) The circularity of the carbonaceous material was measured by the following method. 5 mg of a sample was placed in 2 mL of an aqueous solution containing 5% by mass of a surfactant ("Toriton X100" manufactured by Wako Pure Chemical Industries, Ltd.), treated in an ultrasonic cleaner for 10 minutes or more, and dispersed in the aqueous solution. This dispersion was used to obtain a particle image projected onto a two-dimensional plane using a flow-type particle image analyzer ("PartAn SI" manufactured by Microtrac Bell Corporation). One particle image projected onto the two-dimensional plane was selected, and the diameter of an equivalent circle having the same projected area as the particle was defined as D μm, and the length at which the distance between two parallel lines sandwiching the particle image was maximized was defined as M μm. The circularity of the particle was calculated using the following formula: circularity = (D / M) ２ The circularity is calculated for each of 10,000 or more particle images having a D in the range of 5 to 40 μm projected onto the two-dimensional plane, and the average value of the obtained results is taken as the circularity of the carbonaceous material.

[0058] (Raman Spectrum) Using a Raman spectrometer ("Laser Raman Microscope Ramanforce" manufactured by Nanophoton Inc.), the particles to be measured, which were carbonaceous materials, were placed on the observation stage, the magnification of the objective lens was set to 20 times, the particles were focused, and measurements were performed while irradiating argon ion laser light. The detailed measurement conditions were as follows: Wavelength of argon ion laser light: 532 nm Laser power on sample: 100-300 W / cm ２ Resolution: 5-7cm －１ Measurement range: 150-4000 cm －１ Measurement mode: XY Averaging Exposure time: 20 seconds Number of integrations: 2 Peak intensity measurement: Baseline correction Polynom-3rd order automatic correction Peak search & fitting processing GaussLoren

[0059] Example 1: 10 g of starch (corn starch), 1.16 g of melamine (0.15 mol per mol of starch monosaccharide units), 0.76 g of adipic acid (0.084 mol per mol of starch monosaccharide units), and 5 g of water were placed in a plastic bag and mixed by kneading for 5 minutes. The resulting raw material mixture was immersed in a 90°C hot bath, held for 2 hours, and then dried at 90°C in a vacuum dryer to obtain a gelatinized product (Steps 1 and A). The resulting gelatinized product was heated to 600°C in a nitrogen gas atmosphere at a heating rate of 600°C / hour (10°C / min). The mixture was then carbonized by heat treatment at 600°C for 30 minutes under a nitrogen gas stream to obtain a carbonized product (Step 2). The nitrogen gas supply rate was 1 L / min per 10 g of starch. The resulting carbides were then pulverized in a ball mill to obtain D ５０ is 10 μm and D ５０ A crushed carbide having a particle size of 2.2 μm was obtained (Step 3). ５０ is 10 μm and D ５０ The crushed carbide particles having a particle size of 2.2 μm were placed in a 100 ml container at a mass ratio of 1:2 and mixed by shaking at 2 Hz for 5 minutes. The resulting crushed and mixed carbide was heated to 1100°C and subjected to a high-temperature firing treatment at 1100°C for 60 minutes to obtain a carbonaceous material (Step 4). The heating rate to 1100°C was 600°C / hour (10°C / min). The heating and heat treatment were carried out under a nitrogen gas flow. The nitrogen gas supply rate was 3 L / min per 5 g of crushed carbide.

[0060] Example 2: 10 g of starch (wheat starch), 1.16 g of melamine (0.15 mol per mol of starch monosaccharide units), and 0.76 g of adipic acid (0.084 mol per mol of starch monosaccharide units) were placed in a 100 ml container and mixed by shaking at 2 Hz for 5 minutes (Step 1). The resulting mixture was heated to 600°C in a nitrogen gas atmosphere. The heating rate to 600°C was 600°C / hour (10°C / min). Next, a carbonization treatment was performed by heat treatment at 600°C for 30 minutes under a nitrogen gas flow, thereby obtaining a carbonized product (Step 2). The nitrogen gas supply rate was 1 L / min per 10 g of starch. The resulting carbonized product was then pulverized in a ball mill to obtain D ５０ A pulverized carbide having a particle size of 6 μm was obtained (Step 3). Next, Step 4 was carried out in the same manner as in Example 1 to obtain a carbonaceous material.

[0061] Example 3: 10 g of starch (corn starch), 1.16 g of melamine (0.15 mol per mol of starch monosaccharide units), and 0.76 g of adipic acid (0.084 mol per mol of starch monosaccharide units) were placed in a 100 ml container and mixed by shaking at 2 Hz for 5 minutes (Step 1). The resulting mixture was shaken in a ball mill at 30 Hz for 1 hour to obtain a mechanically gelatinized product (Step A). ​​The resulting mechanically gelatinized product was heated to 600°C in a nitrogen gas atmosphere at a heating rate of 600°C / hour (10°C / min). Next, the mixture was carbonized by heat treatment at 600°C for 30 minutes under a nitrogen gas flow to obtain a carbonized product (Step 2). The nitrogen gas supply rate was 1 L / min per 10 g of starch. Steps 3 and 4 were then performed in the same manner as in Example 1 to obtain a carbonaceous material.

[0062] Example 4: 10 kg of starch (corn starch), 1.16 kg of melamine (0.15 mol per mol of starch monosaccharide units), and 4.3 kg of adipic acid (0.48 mol per mol of starch monosaccharide units) were placed in a 90 L container and mixed by kneading for 5 minutes (Step 1). The mixed raw materials were extruded at 150°C and 300 rpm using a twin-screw extruder (OMEGA30H, manufactured by STEEL) to obtain a mechanically gelatinized product (Step A). ​​The obtained mechanically gelatinized product was then subjected to Steps 2, 3, and 4 in the same manner as in Example 2 to obtain a carbonaceous material.

[0063] Example 5: 10 g of starch (corn starch), 1.16 g of melamine (0.15 mol per mol of starch monosaccharide units), and 0.76 g of adipic acid (0.084 mol per mol of starch monosaccharide units) were placed in a 100 ml container and mixed by shaking at 2 Hz for 5 minutes (Step 1). The resulting mixture was heated to 800°C in a nitrogen gas atmosphere. The heating rate to 800°C was 600°C / hour (10°C / min). Next, a carbonization treatment was performed by heat treatment at 800°C for 30 minutes under a nitrogen gas flow, thereby obtaining a carbonized product (Step 2). The nitrogen gas supply rate was 1 L / min per 10 g of starch. The resulting carbonized product was then pulverized in a ball mill to obtain D ５０ is 10 μm and D ５０ A crushed carbide having a particle size of 2.2 μm was obtained (Step 3). ５０ is 10 μm and D ５０ Pulverized carbide with a particle size of 2.2 μm and polystyrene (manufactured by Sekisui Plastics Co., Ltd., average particle size 400 μm, residual carbon content 1.2 mass%) were placed in a 100 ml container at a mass ratio of 1:2:0.3 and mixed by shaking at 2 Hz for 5 minutes. The resulting pulverized and mixed carbide was heated to 1100°C and subjected to a high-temperature firing treatment at 1100°C for 60 minutes to obtain a carbonaceous material (step 4). The heating rate to 1100°C was 600°C / hour (10°C / min). The heating and heat treatment were carried out under a nitrogen gas flow. The nitrogen gas supply rate was 3 L / min per 5 g of pulverized carbide.

[0064] Example 6: 21.0 kg of starch (corn starch), 2.43 kg of melamine (0.15 mol per mol of starch monosaccharide units), and 1.39 kg of adipic acid (0.07 mol per mol of starch monosaccharide units) were mixed in a 50 L conical ribbon-type reactor (Okawahara Manufacturing Co., Ltd., RM-50VD) for 5 minutes (Step 1). The resulting mixture was heated to 225°C under an operating pressure of 12 kPaA while introducing nitrogen at a rate of 1 L / min, and then maintained at this temperature for 10 minutes. After cooling to 80°C or below, a treated product was obtained. Steps 2 and 3 of the treated product were carried out in the same manner as in Example 2, and a pulverized and mixed carbonized product was obtained. The pulverized and mixed carbonized product was then heated to 1000°C and subjected to a high-temperature calcination treatment at 1000°C for 60 minutes, yielding a carbonaceous material (Step 4). The temperature was increased to 1000°C at a rate of 600°C / hour (10°C / min). The temperature increase and heat treatment were carried out under a nitrogen gas flow. The nitrogen gas supply rate was 3 L / min per 5 g of pulverized carbide.

[0065] Example 7 10 g of starch (corn starch), 1.16 g of melamine (0.15 mol per mol of starch monosaccharide units), and 0.76 g of adipic acid (0.084 mol per mol of starch monosaccharide units) were placed in a 100 ml container and mixed by shaking at 2 Hz for 5 minutes (Step 1). The resulting mixture was heated to 400°C in a nitrogen gas atmosphere. The heating rate to 400°C was 600°C / hour (10°C / min). Next, a treated product was obtained by heat treatment at 400°C for 30 minutes under a nitrogen gas flow. Thereafter, Steps 2, 3, and 4 of the treated product obtained here were performed in the same manner as in Example 5, except that polystyrene was not added before Step 4, to obtain a carbonaceous material.

[0066] Comparative Example 1: 10 g of starch (corn starch) and 36 g of ammonium chloride (1.1 moles per mole of starch monosaccharide unit) were placed in a 100 ml container and mixed by shaking at 2 Hz for 5 minutes. The resulting mixture was heated to 600°C in a nitrogen gas atmosphere. The heating rate to 600°C was 600°C / hour (10°C / min). Next, a carbonization treatment was performed by heat treatment at 600°C for 60 minutes under a nitrogen gas flow, thereby obtaining a carbonized product. The nitrogen gas supply rate was 1 L / min per 10 g of starch. The resulting carbonized product was then pulverized in a ball mill to obtain D ５０ A pulverized carbide having a particle size of 6 μm was obtained. Next, the pulverized carbide and polystyrene were placed in a 100 ml container at a mass ratio of 1:0.1 and mixed by shaking at 2 Hz for 5 minutes. The pulverized and mixed carbide was heated to 1200°C and subjected to a high-temperature firing treatment at 1200°C for 60 minutes to obtain a carbonaceous material. In this case, the heating rate to 1200°C was 600°C / hour (10°C / min). The above heating and heat treatment were carried out under a nitrogen gas flow. The nitrogen gas supply rate was 3 L / min per 5 g of pulverized carbide.

[0067] Comparative Example 2: 10 g of glucose and 3.3 g of ammonium chloride (1.1 moles per mole of glucose) were placed in a 100 ml container and mixed by shaking at 2 Hz for 5 minutes. The resulting mixture was heated to 1000°C in a nitrogen gas atmosphere. The heating rate to 1000°C was 240°C / hour (4°C / min). Next, a carbonization treatment was performed by heat treatment at 1000°C for 60 minutes under a nitrogen gas flow, thereby obtaining a charcoal. The nitrogen gas supply rate was 1 L / min per 5 g of glucose. The mixture was then pulverized in a ball mill to obtain a carbonaceous material.

[0068] (Comparative Example 3) The carbide obtained in Comparative Example 1 was pulverized in a ball mill to obtain D ５０ is 10 μm and D ５０ The pulverized carbide having a size of 2.2 μm was obtained. ５０ is 10 μm and D ５０Crushed carbide with a particle size of 2.2 μm and polystyrene were placed in a 100 ml container in a mass ratio of 1:2:0.3 and mixed by shaking at 2 Hz for 5 minutes. The resulting crushed and mixed carbide was heated to 1200°C and subjected to a high-temperature firing treatment at 1200°C for 60 minutes to obtain a carbonaceous material. The heating rate to 1200°C was 600°C / hour (10°C / min). The heating and heat treatment were carried out under a nitrogen gas flow. The nitrogen gas supply rate was 3 L / min per 5 g of crushed carbide.

[0069] (Comparative Example 4) Coconut shell char (containing 98% by mass of particles with a particle size of 0.850 to 2.360 mm) obtained by crushing coconut shells and dry distilling them at 500°C was treated at 950°C for 80 minutes with nitrogen gas containing 1% by volume of hydrogen chloride gas supplied at a flow rate of 10 L / min. After that, the supply of hydrogen chloride gas was stopped and the coconut shell char was further heat-treated at 950°C for 30 minutes. ５０ The powder was coarsely crushed to 10 μm, and then crushed using a compact jet mill ("Cojet System α-mkIII" manufactured by Seishin Enterprise Co., Ltd.). The powder was further classified using Labocruseal N-01 (manufactured by Seishin Enterprise Co., Ltd.) to obtain a D ５０ Carbon precursor A having a diameter of 5.1 μm and D ５０ Carbon precursor B having a particle size of 9.7 μm was obtained. ５０ Carbon precursor A having a particle size of 5.1 μm was further pulverized in a fine mill SF5 (manufactured by Nippon Coke Co., Ltd.) and D ５０ Carbon precursor C with a particle size of 2.1 μm was obtained. ５０ 9.1 g of carbon precursor C having a particle size of 2.1 μm was mixed with 0.9 g of polystyrene. 10 g of this mixture was placed in a graphite sheath so that the sample layer thickness was approximately 3 mm, and placed in a high-speed heating furnace manufactured by Motoyama Corporation. Under a nitrogen flow rate of 5 L per minute, the heating rate from 600°C to 900°C was 20°C per minute (heating time: 15 minutes), and 60°C per minute in other temperature ranges. After heating to 1050°C, the temperature was maintained at that temperature for 20 minutes and then allowed to cool naturally. After confirming that the temperature inside the furnace had dropped to 200°C or below, the carbonaceous material was removed from the furnace, and carbonaceous material C was obtained. D ５０ Carbon precursor B and D ５０The carbon precursor C was treated in the same manner as the carbon precursor C having a particle size of 2.1 μm to obtain a carbonaceous material B. The carbonaceous material C and the carbonaceous material B were mixed in a mass ratio of 1:1 to obtain a final carbonaceous material.

[0070] (Electrode Fabrication) Using the carbonaceous materials obtained in each Example and Comparative Example, negative electrodes were fabricated according to the following procedure. 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 carboxymethyl cellulose (CMC), 2 parts by mass of styrene-butadiene rubber (SBR), and 90 parts by mass of water were mixed to obtain a slurry. The obtained slurry was applied to a copper foil with a thickness of 15 μm, dried, and pressed, and a 14 mm diameter punch was used to obtain a 45 μm thick electrode.

[0071] (Electrode density) The thickness of the negative electrode layer was determined by measuring the thickness of the fabricated electrode with a micrometer and then subtracting the thickness of the copper foil. The volume of the negative electrode layer was determined by multiplying the thickness of the negative electrode layer determined above by the electrode area calculated from a diameter of 14 mm. The mass of the carbonaceous material in the negative electrode layer was determined by multiplying the mass of the fabricated electrode minus the mass of the copper foil by the ratio of the carbonaceous material in the materials constituting the negative electrode layer. The electrode density (g / cc) was determined by dividing the mass (g) of the carbonaceous material in the negative electrode layer by the volume (cc) of the negative electrode layer (g / cc).

[0072] (Discharge capacity per weight and discharge capacity per volume) The electrode prepared above was used as the working electrode, and metallic lithium was used as the counter electrode and reference electrode. As the solvent, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate were mixed in a volume ratio of 1:1:1. LiPF ６A 1 mol / L solution of 1 mol / L of ethylenediaminetetraacetic acid (ETA) was used as the electrolyte. A polypropylene membrane was used as the separator. Coin cells were fabricated in a glove box under an argon atmosphere. A charge / discharge test was performed on the lithium secondary battery configured as described above using a charge / discharge tester ("TOSCAT" manufactured by Toyo Systems Co., Ltd.). Lithium doping was performed at a rate of 70 mA / g relative to the active material mass until the doping reached 1 mV relative to the lithium potential. A constant voltage of 1 mV relative to the lithium potential was applied for 8 hours to terminate the doping. The capacity at this time was recorded as the charge capacity. Next, undoping was performed at a rate of 70 mA / g relative to the active material mass until the doping reached 1.5 V relative to the lithium potential. The discharge capacity at this time was recorded as the discharge capacity (mAh). The obtained discharge capacity was divided by the weight of the negative electrode to obtain the discharge capacity per weight (mAh / g). Furthermore, the discharge capacity per weight was multiplied by the electrode density to obtain the discharge capacity per volume (mAh / cc).

[0073] The carbonaceous materials obtained in the examples and comparative examples were measured for nitrogen element content, true density, tap bulk density, and carbon interplanar spacing (d ００２ ), D ８０ / D ２０ , circularity, 1360 cm －１ The half-width of the peak near 1650 cm －１ The results of measuring the half-width of the peak near 0.01 were shown in Table 1. Table 2 also shows the electrode density, discharge capacity per weight, and discharge capacity per volume measured for the obtained batteries. The batteries fabricated using the carbonaceous materials of each Example exhibited a high discharge capacity per weight as well as a high discharge capacity per volume. On the other hand, the batteries fabricated using the carbonaceous materials of each Comparative Example, which did not have the specified nitrogen element content, true density, and tapped bulk density, did not have sufficiently high discharge capacities per weight and volume.

[0074]

[0075]

Claims

1. The nitrogen element content by elemental analysis is 1.0 mass% or more, the true density by butanol immersion method is 1.50 to 1.65 g / cc, the tapped bulk density is 0.7 to 1.0 g / cc, and the carbon interplanar spacing (d ００２ ) is 3.65 Å or more.

2. D in volumetric particle size distribution by laser diffraction scattering particle size distribution measurement method ２０ D against ８０ Proportion D ８０ / D ２０ The carbonaceous material according to claim 1, wherein the Mn content is 3.5 to 20.

3. 3. The carbonaceous material according to claim 1, wherein the circularity of particles having a diameter of a circle corresponding to the projected area of ​​5 μm or more measured by a flow-type particle image analyzer is 0.70 or more.

4. In the Raman spectrum observed by laser Raman spectroscopy, －１ The half-width value of the peak in the vicinity is 240 cm －１ The carbonaceous material according to claim 1 or 2.

5. In the Raman spectrum observed by laser Raman spectroscopy, －１ The half-width of the peak in the vicinity is 98 cm －１ The carbonaceous material according to claim 1 or 2.

6. The carbonaceous material according to claim 1 or 2, which is a carbonaceous material for a negative electrode of an electricity storage device.

7. A negative electrode for an electricity storage device, comprising the carbonaceous material according to claim 1 or 2.

8. An electricity storage device comprising the electricity storage device negative electrode according to claim 7 .

9. The following steps: (1) mixing a compound having a saccharide skeleton, a nitrogen-containing compound, and a crosslinker to obtain a mixture; (2) heat-treating the mixture at 500 to 900° C. in an inert gas atmosphere to obtain a carbide; (3) crushing and / or classifying the carbide; and (4) A step of heat-treating the pulverized and / or classified carbide at 800 to 1600° C. in an inert gas atmosphere to obtain a carbonaceous material. The method for producing a carbonaceous material according to claim 1 or 2, comprising at least

10. The compound having a saccharide skeleton has a cross-sectional area of ​​3 μm in an image obtained by observing the cross section of a particle of the compound with a secondary electron microscope. ２ 100 μm or more ２ When 20 particles are randomly selected, ２ The method for producing a carbonaceous material according to claim 9 , wherein the compound has three or less particles having the above voids.

11. 10. The method for producing a carbonaceous material according to claim 9, further comprising a step (A) of gelatinizing the compound having a saccharide skeleton before, simultaneously with, or after step (1) of mixing the compound having a saccharide skeleton, the nitrogen-containing compound, and the crosslinking agent to obtain a mixture.

12. Step (A) is a step (a1) prior to the step (1), in which a compound having a saccharide skeleton is mixed with water in an amount of 5 to 50% by mass based on the mass of the compound, and the mixture is heated at a temperature of 50 to 200° C. for 1 minute to 5 hours; A step (b1) of subjecting the compound having a saccharide skeleton to a mechanical treatment having an action of impact, crushing, friction, and / or shearing, prior to the step (1); and / or a step (a2) of mixing a mixture containing a compound having a saccharide skeleton with 5 to 50% by mass of water based on the mass of the compound having a saccharide skeleton, simultaneously with the step (1) or after the step (1), and heating the mixture at a temperature of 50 to 200° C. for 1 minute to 5 hours; and / or A step (b2) of subjecting the mixture containing the compound having a saccharide skeleton to a mechanical treatment having an action of impact, crushing, friction, and / or shearing, simultaneously with the step (1) or after the step (1); A method for producing the carbonaceous material according to claim 11.