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

Abstract

The present invention relates to a carbonaceous material having: a nitrogen element content according to elemental analysis of at least 1.0 mass%; and a phosphorous element content according to X-ray fluorescence analysis of at least 0.5 mass%.

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] Furthermore, known carbonaceous materials that can be used as negative electrodes of lithium ion secondary batteries and the like include carbonaceous materials prepared to contain specific amounts of various elements other than carbon (Patent Document 3).

[0005] International Publication No. 2019 / 009332 International Publication No. 2019 / 009333 Japanese Patent Application Laid-Open No. 2009-200014

[0006] Although carbonaceous materials are known for use as negative electrode materials, there is still a demand for higher capacity and improved current efficiency of negative electrodes in various applications of electricity storage devices. 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 having a high discharge capacity per weight and high current efficiency. 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.

[0007] As a result of extensive research, the present inventors have found that by adjusting the nitrogen element content and phosphorus element content in a carbonaceous material to fall within a predetermined range, a carbonaceous material suitable for an electricity storage device having a high discharge capacity per weight and excellent current efficiency can be obtained.

[0008] That is, the present invention encompasses the following preferred embodiments: [1] A carbonaceous material having a nitrogen element content of 1.0 mass% or more as determined by elemental analysis and a phosphorus element content of 0.5 mass% or more as determined by X-ray fluorescence analysis. [2] A carbonaceous material having a carbon interplanar spacing (d ００２ [3] The carbonaceous material according to [1] or [2], wherein the oxygen element content determined by elemental analysis is less than 1.5 mass%. [4] In a Raman spectrum observed by laser Raman spectroscopy, －１ The half-width value of the peak in the vicinity is 230 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[6] The carbonaceous material according to any one of [1] to [5], 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 any one of [1] to [6]. [8] A 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 and a nitrogen-containing compound to obtain a mixture; (2) heat-treating the mixture in an inert gas atmosphere at 500 to 900°C to obtain a char; (3) pulverizing and / or classifying the char; and (4) heat-treating the pulverized and / or classified char in an inert gas atmosphere at 800 to 1600°C to obtain a carbonaceous material; and (a) prior to the heat treatment in step (4), mixing the compound having a saccharide skeleton, a mixture containing the compound, or a char of the mixture with a phosphorus-containing compound.

[0009] According to the present invention, it is possible to provide a carbonaceous material suitable for an electricity storage device having a high discharge capacity per weight and excellent current efficiency.

[0010] 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.

[0011] 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.

[0012] The carbonaceous material of the present invention is suitable for providing an electricity storage device having a high discharge capacity per weight and excellent current efficiency, and has a nitrogen element content of 1.0 mass% or more as determined by elemental analysis and a phosphorus element content of 0.5 mass% or more as determined by X-ray fluorescence analysis.

[0013] The phosphorus content of the carbonaceous material of the present invention is 0.5% by mass or more as determined by X-ray fluorescence analysis. The phosphorus content is an analytical value obtained by X-ray fluorescence analysis of the carbonaceous material. If the phosphorus content is less than 0.5% by mass, there are fewer sites for absorbing and desorbing lithium ions during charge and discharge, making it impossible to sufficiently increase the discharge capacity and current efficiency per weight. From the viewpoint of more easily increasing the discharge capacity and current efficiency, the phosphorus content is preferably 0.6% by mass or more, more preferably 0.7% by mass or more, even more preferably 0.9% by mass or more, and even more preferably 1.2% by mass or more. From the viewpoint of more easily increasing the discharge capacity, the phosphorus content may be 1.4% by mass or more, 1.6% by mass or more, 1.7% by mass or more, etc. From the viewpoint of easily suppressing the generation of sites that irreversibly adsorb lithium ions and easily increasing current efficiency, the upper limit of the phosphorus content is preferably 4.0 mass % or less, more preferably 3.0 mass % or less, even more preferably 2.7 mass % or less, still more preferably 2.5 mass % or less, particularly preferably 2.3 mass % or less, and particularly preferably 2.0 mass % or less. The phosphorus content of the carbonaceous material determined by X-ray fluorescence analysis can be adjusted to the above range by adjusting the amount of a phosphorus-containing compound that can be added when producing the carbonaceous material, adjusting the temperature and time of heat treatment, etc.

[0014] The carbonaceous material of the present invention has a nitrogen element content of 1.0 mass% or more by elemental analysis. The nitrogen element content is an analytical value obtained by elemental analysis of the carbonaceous material. It has been found that when the carbonaceous material contains 1.0 mass% or more of nitrogen, the discharge capacity and current efficiency can be further improved compared to carbonaceous materials containing only phosphorus. Carbonaceous materials containing only phosphorus tend to have a high oxygen element content due to the ease of oxidation of phosphorus, and the current efficiency is likely to be low. In contrast, carbonaceous materials containing both nitrogen and phosphorus tend to have a low oxygen element content due to the ease of reduction of phosphorus, although the reason is not clear, and are thought to be able to improve the current efficiency. In addition, when 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, which also makes it difficult to sufficiently increase 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 1.9 mass% or more, still more preferably 2.0 mass% or more, and particularly preferably 2.2 mass% or more, from the viewpoint of making it easier to increase the discharge capacity and current efficiency. 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 still more preferably 4.0 mass% or less, from the viewpoint of suppressing a decrease in discharge capacity during repeated charge and discharge. The nitrogen element content determined by elemental analysis of the carbonaceous material can be adjusted to 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, etc.

[0015] The carbon interplanar spacing (d ００２ The carbon interplanar spacing (d) is preferably 3.65 Å or more, more preferably 3.68 Å or more, even more preferably 3.70 Å or more, still more preferably 3.71 Å or more, and particularly preferably 3.73 Å or more, from the viewpoints of widening the spacing between carbon planes, facilitating efficient migration of lithium ions, sufficiently developing micropores, increasing the number of absorption sites for clustered lithium, and easily increasing the discharge capacity per weight and current efficiency. ００２The upper limit of d ００２ From the viewpoint that the volume of the carbonaceous material can be appropriately reduced by appropriately reducing the effective capacity per volume and the discharge capacity per volume, 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.

[0016] 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 From the viewpoint of making it easier to increase the discharge capacity of an electrode made using a carbonaceous material, the value of the half width of the peak in this range is preferably 230 cm －１ More preferably, 240 cm －１ More preferably, 250 cm －１ More preferably, 260 cm －１ That's all. Here, 1360 cm －１ The peak around 1360 cm is a Raman peak generally called the D band, which is a peak caused by disorder and defects in the graphite structure. －１ The peak around 1345 cm －１ ~1375cm －１ , preferably 1350 cm －１ ~1370cm －１ The Raman spectrum is measured using a Raman spectrometer under the conditions described in the Examples. －１ The value of the half width of the peak in the vicinity can be adjusted to fall within the above range by adjusting the amount of nitrogen-containing compound that can be added when producing the carbonaceous material, adjusting the temperature and time of the heat treatment, etc.

[0017] 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 weight of an electrode made using a carbonaceous material. －１ More preferably, 100 cm －１ More preferably, 101 cm －１ or more, and even more preferably 102 cm －１ That's all. Here, 1650 cm －１ The peak around 1650 cm is a Raman peak generally called the G band, which is a peak caused by disorder and defects in the graphite structure. －１ The peak around 90 cm －１ ~120cm －１ in the range of 100 cm －１ ~110cm －１ The Raman spectrum is measured using a Raman spectrometer under the conditions described in the Examples. －１ The value of the half width of the peak in the vicinity can be adjusted to fall within the above range by adjusting the amount of nitrogen-containing compound that can be added when producing the carbonaceous material, adjusting the temperature and time of the heat treatment, etc.

[0018] From the viewpoint of making it easier to increase the current efficiency, the oxygen element content of the carbonaceous material of the present invention as determined by elemental analysis is preferably less than 1.5 mass%, more preferably 1.3 mass% or less, even more preferably 1.2 mass% or less, and even more preferably 1.1 mass% or less. The lower limit of the oxygen element content is preferably as small as possible, and is 0 mass% or more. The oxygen element content as determined by elemental analysis of the carbonaceous material can be reduced by increasing the amount of a nitrogen-containing compound or a phosphorus-containing compound that can be added when producing the carbonaceous material, and can also be adjusted to fall within the above range by adjusting the temperature and time of heat treatment, for example.

[0019] In the carbonaceous material of the present invention, from the viewpoint of easily increasing the electrode density of a negative electrode obtained using the carbonaceous material, and as a result, easily increasing the discharge capacity per volume in addition to the discharge capacity per weight, the true density of the carbonaceous material, as measured by a butanol immersion method, is preferably 1.50 g / cc or more, more preferably 1.51 g / cc or more, even more preferably 1.52 g / cc or more, still more preferably 1.55 g / cc or more, and is preferably 1.65 g / cc or less, more preferably 1.64 g / cc or less, even more preferably 1.62 g / cc or less, and still more preferably 1.60 g / cc or less.

[0020] In the carbonaceous material of the present invention, from the viewpoint of facilitating an increase in electrode density, the tapped bulk density of the carbonaceous material is preferably 0.70 g / cc or more, more preferably 0.72 g / cc or more, even more preferably 0.75 g / cc or more, still more preferably 0.78 g / cc or more, and particularly preferably 0.80 g / cc or more. Furthermore, from the viewpoint of the absorption of an electrolytic solution when preparing an electrode, the tapped bulk density is preferably 1.0 g / cc or less, more preferably 0.97 g / cc or less, even more preferably 0.95 g / cc or less, still more preferably 0.93 g / cc or less, and particularly preferably 0.91 g / cc or less. The tapped bulk density of the carbonaceous material is measured by repeating a process of freely dropping a cylindrical glass container having a diameter of 1.8 cm, filled with the carbonaceous material and passed through a sieve with openings of 300 μm, from a height of 5 cm 100 times, until the rate of change in density, which is calculated from the volume and mass of the carbonaceous material, before and after one set of operations is 2% or less.

[0021] In the carbonaceous material of the present invention, from the viewpoint of easily increasing the electrode density, D in the volume-based particle size distribution of the carbonaceous material by a laser diffraction scattering particle size distribution measurement method is ２０ D against ８０ Proportion D ８０ / D ２０is preferably 3.5 or more, more preferably 4.0 or more, even more preferably 4.5 or more, still more preferably 5.0 or more, particularly preferably 5.5 or more, especially more preferably 6.0 or more, and from the same viewpoint, is preferably 18 or less, more preferably 16 or less, even more preferably 15 or less. ８０ / D ２０ 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.

[0022] In the carbonaceous material of the present invention, from the viewpoint of facilitating an increase in electrode density, the circularity measured on particles of the carbonaceous material with a flow-type particle image analyzer, the diameter of a circle corresponding to the projected area of ​​which is 5 μm or more, 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, 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. The circularity is determined by using a dispersion of the carbonaceous material as a measurement sample, obtaining a projected image of the particles with the flow-type 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 as one particle in the projected image, and M μm is the maximum length between two parallel lines sandwiching the particle image. 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.

[0023] The method for producing a carbonaceous material of the present invention is not particularly limited as long as it can produce a carbonaceous material having the above-described properties. Examples of suitable methods include mixing a carbon source compound with a nitrogen-containing compound, heat-treating the resulting mixture under an inert gas atmosphere at 500°C to 900°C, pulverizing and / or classifying the mixture, and further heat-treating the resulting charcoal at 800 to 1600°C, which method includes a mixing step with a phosphorus-containing compound before the heat treatment at 800 to 1600°C. The carbon source compound used as a raw material is not particularly limited as long as it can produce a carbonaceous material satisfying the above-described properties. However, from the viewpoint of easily adjusting the above-described properties of the carbonaceous material to a preferred range, a compound having a saccharide skeleton is preferred. Therefore, the carbonaceous material of the present invention is preferably a sugar-derived carbonaceous material. Below, a production method using a compound having a saccharide skeleton as a carbon source is described. In this specification, a compound having a saccharide skeleton is also referred to as a saccharide compound.

[0024] In a preferred embodiment of the present invention, the method for producing a carbonaceous material of the present invention comprises at least the following steps: (1) mixing a compound having a saccharide skeleton and a nitrogen-containing compound to obtain a mixture, (2) heat-treating the mixture in an inert gas atmosphere at 500 to 900°C 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, and further comprises: (a) prior to the heat treatment in step (4), mixing the compound having a saccharide skeleton, a mixture containing the compound, or a char of the mixture with a phosphorus-containing compound. The present invention also provides a method for producing the above carbonaceous material.

[0025] Step (1) is a step of mixing a compound having a saccharide skeleton and a nitrogen-containing compound to obtain a mixture. Examples of compounds having a saccharide skeleton that can be used as a raw material 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.

[0026] In a preferred embodiment of the production method of the present invention, from the viewpoint of easily increasing the density of an electrode obtained from a carbonaceous material, the compound having a saccharide skeleton is a compound having 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 It is preferable to use a compound in which 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. When producing a carbide using such a compound with few voids as a raw material, additional treatment such as step (b) described below is usually not required.

[0027] 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.

[0028] The mixing ratio of the compound having a saccharide skeleton and the nitrogen-containing compound is not particularly limited and may be adjusted appropriately so as to obtain a carbonaceous material having desired properties. For example, increasing the amount of the nitrogen-containing compound tends to increase the nitrogen element content in the carbonaceous material.

[0029] In a preferred embodiment of the present invention, the amount of the compound having a saccharide skeleton contained in the mixture obtained in step (1) is preferably 50 to 99% by mass, more preferably 80 to 95% by mass, based on the total amount of the compound having a saccharide skeleton and the nitrogen-containing compound. The amount of the nitrogen-containing compound contained in the mixture is preferably 1 to 30% by mass, more preferably 3 to 15% by mass, based on the total amount of the compound having a saccharide skeleton and the nitrogen-containing compound. The amount of the nitrogen-containing compound mixed in step (1) is preferably 0.03 to 0.30 mol, more preferably 0.05 to 0.20 mol, and even more preferably 0.07 to 0.15 mol, based on 1 mol of starch monosaccharide units in the compound having a saccharide skeleton used as a raw material.

[0030] In step (1), when the carbon precursor and the nitrogen-containing compound are mixed to obtain a mixture, at least one crosslinking agent may be further mixed. The crosslinking agent is a compound capable of crosslinking the compound having a saccharide skeleton used as a raw material. The crosslinking agent acts as a catalyst to promote the interchain bond formation reaction of the saccharide compound and / or the reaction between the saccharide compound and the nitrogen-containing compound, which proceeds in parallel with the hydrolysis reaction or dehydration reaction of the saccharide compound, or it itself crosslinks the saccharide compound and / or the nitrogen-containing compound. Compounds having a saccharide skeleton often melt, fuse, foam, etc. during the firing process, and as a result, the resulting carbonaceous material often has a flat shape rather than a spherical shape. When firing is performed using a crosslinking agent, it is easy to suppress fusion and foaming between the raw materials, and as a result, it is easy to improve the density of the electrode obtained using the resulting carbonaceous material.

[0031] When a crosslinking agent is used, the type thereof 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, and phenylalanine. Examples of suitable crosslinking agents include polycarboxylic acids such as taric acid and terephthalic 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 and sulfuric acid. When a crosslinking agent is used, one of these crosslinking agents may be used alone, or two or more may be used in combination. Among these crosslinking agents, polycarboxylic acids and hydroxycarboxylic acids are preferred from the viewpoint of suppressing melting and foaming of the raw materials during the heat treatment process to obtain a carbonized product, and succinic acid, adipic acid, and citric acid are more preferred.

[0032] Furthermore, when a crosslinking agent is used, the amount thereof is preferably 1 to 30 mass %, more preferably 3 to 10 mass %, based on the total amount of the compound having a saccharide skeleton, the nitrogen-containing compound, and the crosslinking agent contained in the mixture. When a crosslinking agent is added, increasing the amount of the crosslinking agent tends to increase the true density of the carbonaceous material.

[0033] 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 carbonized product. 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 (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. If 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. Here, the heat treatment temperature may be a constant temperature, but is not particularly limited as long as it is within the above range.

[0034] 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.

[0035] 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).

[0036] 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.

[0037] Here, the production method of the present invention includes step (a) of mixing a compound having a saccharide skeleton, a mixture containing the compound, or a carbonized product of the mixture with a phosphorus-containing compound before performing heat treatment at 800 to 1600°C in step (4). By producing a carbonaceous material by a production method including step (a), elemental phosphorus can be contained in the carbonaceous material. The presence of predetermined amounts of elemental nitrogen and elemental phosphorus in the carbonaceous material makes it possible to provide a carbonaceous material suitable for an electricity storage device having a high discharge capacity per weight and excellent current efficiency, although the reason is not clear.

[0038] Step (a) may be carried out by mixing the compound having a saccharide skeleton used in step (1) with a phosphorus-containing compound, or by mixing the phosphorus-containing compound together when mixing the compound having a saccharide skeleton and the nitrogen-containing compound to obtain a mixture in step (1), or by mixing the mixture obtained in step (1) with a phosphorus-containing compound, or by mixing the carbonized material obtained in step (2) with a phosphorus-containing compound, or by mixing the pulverized and / or classified carbonized material obtained in step (3) with a phosphorus-containing compound.

[0039] The phosphorus-containing compound that can be used in step (a) is not particularly limited as long as it is a compound having a phosphorus atom in the molecule, and examples thereof include inorganic phosphoric acid, organic phosphoric acid, and salts thereof, organic phosphorus, phosphonium salts, etc. As the phosphorus-containing compound, one type of phosphorus-containing compound may be used, or two or more types may be used in combination.

[0040] Examples of inorganic phosphoric acids include phosphoric acid, dihydrogen phosphate, ammonium dihydrogen phosphate, primary phosphate, secondary phosphate, tertiary phosphate, pyrophosphoric acid, pyrophosphate, tripolyphosphoric acid, tripolyphosphate, phosphorous acid, phosphite, hypophosphorous acid, hypophosphite, diphosphorous acid, and diphosphorus pentoxide. Examples of organic phosphoric acids include phosphonic acid (phosphonic acid compounds), and examples of phosphonic acids include nitrilotrismethylenephosphonic acid, phosphonobutanetricarboxylic acid, methyldiphosphonic acid, methylenephosphonic acid, ethylidenediphosphonic acid, and triphenyl phosphate. When these phosphoric acids are in the form of a salt, the salt may be, for example, an alkali metal salt and / or an alkaline earth metal salt, or an ammonium salt. Examples of organic phosphoric acids include triphenylphosphine, triphenylphosphine oxide, tricyclohexylphosphine, tricyclohexylphosphine oxide, trialkylphosphine, and trialkylphosphine oxide. Examples of phosphonium salts include tetraalkylphosphonium salts and tetraphenylphosphonium salts. These salts may be, for example, halides, sulfates, phosphates, or acetates. Among these phosphorus-containing compounds, phosphoric acid and ammonium dihydrogen phosphate, which have a high intramolecular phosphorus content, are preferred from the viewpoint of facilitating the incorporation of a large amount of phosphorus element into the carbonaceous material. As the phosphorus-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.

[0041] The method for mixing the phosphorus-containing compound in step (a) is not particularly limited, and when the phosphorus-containing compound is solid, the solid phosphorus-containing compound may be mixed with the compound having a saccharide skeleton, etc. Furthermore, when the phosphorus-containing compound is, for example, water-soluble, an aqueous solution of the phosphorus-containing compound may be mixed with the compound having a saccharide skeleton, etc.

[0042] The amount of the phosphorus-containing compound mixed in step (a) is not particularly limited as long as a carbonaceous material having a phosphorus element content within the above range is finally obtained, but is, for example, preferably 0.5 to 10 mass %, more preferably 0.6 to 8 mass %, based on the total amount of the compound having a saccharide skeleton and the nitrogen-containing compound, or based on the amount of the carbonized product obtained in step (2). The amount of the phosphorus-containing compound mixed in step (a) is preferably 0.001 to 0.20 mol, more preferably 0.005 to 0.15 mol, and even more preferably 0.01 to 0.10 mol, relative to 1 mol of starch monosaccharide units in the compound having a saccharide skeleton used as a raw material.

[0043] Alternatively, in step (4), 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 ethylene, propane, hexane, toluene, xylene, mesitylene, styrene, naphthalene, phenanthrene, anthracene, and pyrene. The thermoplastic resin is preferably one that volatilizes at the firing temperature and does not oxidize and activate the surface of the carbon precursor when thermally decomposed, and therefore polystyrene, polyethylene, and polypropylene are preferred. Furthermore, from a safety perspective, the low-molecular-weight organic compound is preferably one that is less volatile at room temperature (e.g., 20°C), and naphthalene, phenanthrene, anthracene, pyrene, and the like are preferred. Adding such a volatile organic compound is preferred because it can further reduce the oxygen element content and specific surface area while maintaining the characteristic structure of the present invention.

[0044] Alternatively, the volatile organic compound may be gasified and mixed with an inert gas such as nitrogen, followed by subjecting to step (4). The volatile organic compound is not particularly limited, but examples thereof include low-molecular-weight organic compounds. Examples of low-molecular-weight organic compounds include ethylene, propane, hexane, toluene, xylene, mesitylene, styrene, naphthalene, phenanthrene, anthracene, and pyrene. From the viewpoint of mixability with an inert gas such as nitrogen, the low-molecular-weight organic compound is preferably one with high volatility, and ethylene, propane, hexane, and toluene are preferred. Adding such a volatile organic compound is preferred because it can further reduce the oxygen element content and specific surface area while maintaining the characteristic structure of the present invention.

[0045] 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), a step (b) of gelatinizing the compound having a saccharide skeleton before, simultaneously with, or after step (1) of mixing the compound having a saccharide skeleton and the nitrogen-containing compound to obtain a mixture. When step (b) is further performed, cavities contained in the compound having a saccharide skeleton used as a raw material are closed, which makes it easier to increase the density of the electrode formed from the finally obtained carbonaceous material and to increase the discharge capacity per volume.

[0046] When step (b) is carried out, the gelatinization method 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 (b) 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 measurement 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 performed after removing aggregates contained in the gelatinized compound by pulverization or classification. When step (b) is performed, the mixture obtained through step (1) and optional step (b) as described above is heat-treated in step (2). Therefore, when step (b) is performed, step (b) is a step performed before step (2).

[0047] In a preferred embodiment of the present invention, the production method of the present invention may include the following step as step (b): step (b1) 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, prior to step (1); step (c1) of subjecting the compound having a saccharide skeleton to a mechanical treatment involving impact, crushing, friction, and / or shear, prior to step (1); step (b2) 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 (c2) 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).

[0048] Step (b1) 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, and 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, and more preferably 80 to 180°C. The heating time is 1 minute to 5 hours, preferably 3 minutes to 1 hour, and more preferably 10 to 30 minutes.

[0049] Step (c1) 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.

[0050] Step (b2) 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 for step (b1) similarly apply.

[0051] Step (c2) 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 (c1) also apply to step (c2).

[0052] 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.

[0053] 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.

[0054] By using the carbonaceous material of the present invention, an electrode (negative electrode) having a high discharge capacity per weight and excellent current efficiency 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.

[0055] 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.

[0056] An electricity storage device using the carbonaceous material of the present invention has a high discharge capacity per weight and excellent current efficiency. 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.

[0057] 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.

[0058] 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-butyrolactone, 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] (Oxygen and 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), hydrogen: inert gas fusion - non-dispersive infrared absorption (NDIR), and calibration was performed using a Ni capsule (oxygen and 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 oxygen and nitrogen element contents in the samples were obtained as described above.

[0063] (Phosphorus Content) Manufactured by Rigaku Corporation. Analysis was performed based on X-ray fluorescence analysis using a ZSX Primus-μ. A top-illumination holder was used, and the sample measurement area was within a 30 mm diameter circle. 2.0 g of the sample to be measured and 2.0 g of polymer binder (Spectro Blend 44μ Powder manufactured by Chemplex) were mixed in a mortar and placed in a molding machine. A load of 15 ton was applied to the molding machine for 1 minute to produce pellets with a diameter of 40 mm. The pellets were wrapped in polypropylene film and placed in a sample holder for measurement. The X-ray source was set to 30 kV and 100 mA. To determine the phosphorus content from the intensity of the phosphorus Kα ray, a Ge(111) crystal and a gas-flow proportionality tube were used as the detector, and measurements were taken over a 2θ range of 137 to 144° at a scanning rate of 4° / min.

[0064] (Average interplanar spacing d using the Bragg equation obtained by X-ray diffraction measurement) ００２ Measurement) 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.

[0065]

[0066] (Particle size distribution by laser scattering method) The average particle size (particle size distribution) of the carbide 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.), and treated with an ultrasonic cleaner for 10 minutes or more to disperse the sample 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 ５０is the particle size at which the cumulative volume becomes 50%, and this value was used as the average particle size.

[0067] (Raman Spectrum) Using a Raman spectrometer ("Laser Raman Microscope Ramanforce" manufactured by Nanophoton Inc.), the measurement target particles, 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 them with 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

[0068] Example 1 10 g of starch (corn starch), 0.54 g of melamine (0.07 mol per mol of starch monosaccharide units), 0.38 g of adipic acid (0.04 mol per mol of starch monosaccharide units), and 0.2 g of ammonium dihydrogen phosphate (0.03 mol per mol of starch monosaccharide units) were placed in a sample bottle and shaken to obtain a mixture (steps 1 and a). The obtained 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 in a nitrogen gas stream at 600°C for 30 minutes to obtain a carbonized product (step 2). The nitrogen gas supply rate was 0.5 L / min per 10 g of starch. The obtained carbonized product was then pulverized in a ball mill to obtain D ５０ A pulverized carbide having a particle size of 5.5 μm was obtained (Step 3). The obtained pulverized 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 (Step 4). 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 pulverized carbide.

[0069] Example 2 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 (0.08 mol per mol of starch monosaccharide units), and 0.4 g of ammonium dihydrogen phosphate (0.06 mol per mol of starch monosaccharide units) were placed in a sample bottle and shaken to obtain a mixture (steps 1 and a). Thereafter, the same treatments as in steps 2, 3, and 4 of Example 1 were carried out to obtain a carbonaceous material.

[0070] (Example 3) A pulverized carbide was obtained by carrying out the same processes as steps 1, a, 2, and 3 of Example 2. The obtained pulverized carbide was heated to 1100°C and subjected to a high-temperature firing treatment in which the pulverized carbide was heat-treated at 1100°C for 60 minutes, thereby obtaining a carbonaceous material (step 4). In this case, the heating rate up to 1100°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.

[0071] Example 4 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 (0.08 mol per mol of starch monosaccharide units), and 0.2 g of ammonium dihydrogen phosphate (0.03 mol per mol of starch monosaccharide units) were placed in a sample bottle and shaken to obtain a mixture (steps 1 and a). Thereafter, the same treatments as in steps 2, 3, and 4 of Example 3 were carried out to obtain a carbonaceous material.

[0072] Example 5 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 (0.08 mol per mol of starch monosaccharide units), and 0.1 g of ammonium dihydrogen phosphate (0.01 mol per mol of starch monosaccharide units) were placed in a sample bottle and shaken to obtain a mixture (steps 1 and a). Thereafter, the same treatments as in steps 2, 3, and 4 of Example 3 were carried out to obtain a carbonaceous material.

[0073] Example 6 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 (0.08 mol per mol of starch monosaccharide units), and 0.6 g of ammonium dihydrogen phosphate (0.08 mol per mol of starch monosaccharide units) were placed in a sample bottle and shaken to obtain a mixture (steps 1 and a). Thereafter, the same treatments as in steps 2, 3, and 4 of Example 3 were carried out to obtain a carbonaceous material.

[0074] (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 (0.08 mol per mol of starch monosaccharide units) were placed in a sample bottle and shaken to obtain a mixture (Step 1). The obtained mixture was heated to 600°C in a nitrogen gas atmosphere. At this time, the heating rate up 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 to obtain a carbonized product (Step 2). At this time, the nitrogen gas supply rate was 0.5 L / min per 10 g of starch. The obtained carbonized product was then pulverized in a ball mill to obtain D ５０ A pulverized carbide having a particle size of 5.5 μm was obtained (step 3). 0.5 g of an 85% by mass aqueous solution of phosphoric acid was added to 5 g of the obtained pulverized carbide, and the mixture was mixed in a mortar to obtain a mixed carbide of phosphorus-containing compounds (step a). The obtained 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.

[0075] Comparative Example 1: 10 g of starch (corn starch) was heated to 600°C in a nitrogen gas atmosphere. The heating rate to 600°C was 600°C / hour (10°C / min). Subsequently, 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 obtained carbonized product was then pulverized in a ball mill to obtain D ５０ A pulverized carbide having a particle size of 5.5 μm was obtained. 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. 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 pulverized carbide.

[0076] (Comparative Example 2) 10 g of starch (corn starch) and 0.2 g of an 85% by mass aqueous solution of phosphoric acid were mixed in a mortar to obtain a mixture. The obtained mixture was heated to 600°C in a nitrogen gas atmosphere. At this time, 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 to obtain a charcoal. At this time, the nitrogen gas supply rate was 0.5 L / min per 10 g of starch. Thereafter, the obtained charcoal was pulverized in a ball mill to obtain D ５０ A pulverized carbide having a particle size of 5.5 μm was obtained. The pulverized 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 pulverized carbide.

[0077] (Comparative Example 3) 10 g of starch (corn starch), 0.58 g of melamine (0.08 mol per mol of starch monosaccharide units), and 0.38 g of adipic acid (0.04 mol per mol of starch monosaccharide units) were placed in a sample bottle and shaken to obtain a mixture. The obtained mixture was heated to 600°C in a nitrogen gas atmosphere. At this time, the heating rate up 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 to obtain a carbonized product. At this time, the nitrogen gas supply rate was 0.5 L / min per 10 g of starch. The obtained carbonized product was then pulverized in a ball mill to obtain D ５０ A pulverized carbide having a particle size of 5.5 μm was obtained. The pulverized 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 pulverized carbide.

[0078] (Comparative Example 4) 10 g of starch (corn starch), 0.2 g of melamine (0.026 mol per mol of starch monosaccharide units), 0.76 g of adipic acid (0.08 mol per mol of starch monosaccharide units), and 0.4 g of ammonium dihydrogen phosphate (0.06 mol per mol of starch monosaccharide units) were placed in a sample bottle and shaken to obtain a mixture (steps 1 and a). The obtained mixture was heated to 600°C in a nitrogen gas atmosphere. At this time, 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 to obtain a carbonized product (step 2). At this time, the nitrogen gas supply rate was 0.5 L / min per 10 g of starch. The obtained carbonized product was then pulverized in a ball mill to obtain D ５０A pulverized carbide having a particle size of 5.5 μm was obtained (Step 3). The obtained pulverized 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 (Step 4). 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 pulverized carbide.

[0079] (Comparative 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 (0.08 mol per mol of starch monosaccharide units) were placed in a sample bottle and shaken to obtain a mixture. The obtained mixture was heated to 600°C in a nitrogen gas atmosphere. At this time, the heating rate up 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 to obtain a carbonized product. At this time, the nitrogen gas supply rate was 0.5 L / min per 10 g of starch. The obtained carbonized product was then pulverized in a ball mill to obtain D ５０ A pulverized carbide having a particle size of 5.5 μm was obtained. The pulverized carbide obtained was heated to 1100°C and subjected to a high-temperature firing treatment at 1100°C for 60 minutes to obtain a carbonaceous material. 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.

[0080] (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.

[0081] (Discharge capacity per weight) 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 ６ A 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 (Toyo Systems Co., Ltd., "TOSCAT"). 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, and doping was terminated when the doping rate reached 2 mA / g relative to the active material mass. 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 charge capacity (mAh) and discharge capacity (mAh) were recorded as the charge capacity and discharge capacity (mAh). The obtained charge capacity and discharge capacity were divided by the weight of the negative electrode, respectively, to obtain the charge capacity (mAh / g) and discharge capacity (mAh / g) per weight. The discharge capacity was divided by the charge capacity, and the percentage of the obtained value was taken as the current efficiency (%).

[0082] The carbonaceous materials obtained in the examples and comparative examples were measured for the nitrogen element content, phosphorus element content, and carbon interplanar spacing (d ００２ ), oxygen element content, 1360 cm －１ The half-width of the peak near 1650 cm －１ The half-width of the peak in the vicinity was measured, and the results are shown in Table 1. Table 1 also shows the discharge capacity and current efficiency per weight measured for the obtained battery.

[0083] The batteries fabricated using the carbonaceous materials of each Example had a high discharge capacity per weight and showed excellent current efficiency, whereas the batteries fabricated using the carbonaceous materials of each Comparative Example, which did not have the specified nitrogen element content and phosphorus element content, did not have a sufficiently high discharge capacity per weight or a sufficiently high current efficiency.

[0084]

Claims

1. A carbonaceous material having a nitrogen element content of 1.0% by mass or more as determined by elemental analysis and a phosphorus element content of 0.5% by mass or more as determined by X-ray fluorescence analysis.

2. Carbon interplanar spacing (d ００２ 2. The carbonaceous material according to claim 1, wherein the surface roughness (f) is 3.65 Å or greater.

3. 2. The carbonaceous material according to claim 1, wherein the oxygen element content determined by elemental analysis is less than 1.5 mass%.

4. In the Raman spectrum observed by laser Raman spectroscopy, －１ The half-width value of the peak in the vicinity is 230 cm －１ The carbonaceous material according to claim 1 .

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

6. A negative electrode for an electricity storage device, comprising the carbonaceous material according to any one of claims 1 to 5.

7. An electricity storage device comprising the electricity storage device negative electrode according to claim 6 .

8. The following steps: (1) a step of mixing a compound having a saccharide skeleton and a nitrogen-containing compound 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. At least (a) a step of mixing a compound having a saccharide skeleton, a mixture containing the compound, or a carbonized product of the mixture with a phosphorus-containing compound prior to the heat treatment in the step (4) above. The method for producing the carbonaceous material according to any one of claims 1 to 5, comprising: