Method for manufacturing carbon materials and electric double layer capacitor

Abstract

To provide a high-density carbon material, or a carbon material with controlled density, while being a graphene mesosponge. Also, to provide an electric double-layer capacitor with high energy density per unit volume. [Solution] A method for manufacturing a carbon material, comprising: a composite formation step of forming a carbon layer on the surface of a mold material by chemical vapor deposition using a carbon-containing raw material gas to obtain a carbon layer coated mold material; a mold material removal step of removing the mold material and isolating the carbon material by contacting the carbon layer coated mold material with an acid that dissolves the mold material; an impregnation step of impregnating the carbon material with a shrinking liquid; and a drying shrinkage step of drying and shrinking the carbon material impregnated with the shrinking liquid; and an electric double layer capacitor suitable for manufacture using this manufacturing method.

Description

[Technical Field]

[0001] This invention relates to a method for producing carbon materials and an electric double-layer capacitor. [Background technology]

[0002] Carbon materials, including carbon black and graphite, have long been used in a variety of applications. For example, conductive carbon and graphite are widely used in battery materials, carbon black as a reinforcing material for rubber and other materials, and activated carbon as an adsorbent in various fields. Carbon materials are also widely used in lithium-ion batteries, which have seen widespread use in everyday life, such as in smartphones and electric vehicles (EVs), since their inception. Recently, much research has been conducted on carbon materials for secondary batteries, including lithium-ion batteries.

[0003] For example, Patent Document 1 discloses a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, in which flake graphite or carbon black is used as a conductive material, thereby improving high-rate discharge characteristics.

[0004] Furthermore, the development of novel carbon materials is also progressing. For example, Patent Documents 2 and 3 disclose porous carbon materials produced by generating a precursor by supplying a carbon source containing graphene to the surface of a template material made of nanoparticles using CVD or the like, and then dissolving the template material with acid.

[0005] The carbon materials described in Patent Documents 2 and 3 have many characteristics, including an extremely large specific surface area due to their three-dimensional structure, the ability to retain a large amount of active material due to the numerous pores, high oxidation resistance due to the small number of functional groups, excellent conductivity, and rubber-like elasticity. Hereafter, the carbon materials described in Patent Documents 2 and 3, and similar carbon materials, may be referred to as graphene mesosponge (GMS). GMS will be described in detail later. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2004-22177 [Patent Document 2] Japanese Patent Publication No. 2015-164889 [Patent Document 3] Japanese Patent Publication No. 2021-84819 [Overview of the project] [Problems that the invention aims to solve]

[0007] The large specific surface area, high oxidation resistance, and good conductivity of GMS (Gross Microstructured Steel) are advantageous for various electrical materials. However, due to its structural characteristics, it has a low density. For example, when used as an electrode material for electric double-layer capacitors, the specific capacitance per unit volume becomes small, making it difficult to increase the energy density per unit volume. Therefore, increasing the density of GMS is sometimes desirable.

[0008] Furthermore, if we can achieve higher density for GMS, which currently has a low density, it is expected that we can control the density of GMS by appropriately adjusting the conditions. If we can control the density of GMS, we will be able to optimize the structure so that the energy density per unit volume is maximized when used as an electrode material for electric double-layer capacitors.

[0009] Beyond applications as electrode materials for electric double-layer capacitors, it is conceivable that controlling the density of GMS as a carbon material may be desirable for purposes such as increasing its density or controlling its adsorption capacity per unit volume in adsorbent applications.

[0010] Therefore, one of the objectives of the present invention is to provide a high-density carbon material or a carbon material with controlled density, even though it is a GMS (Gross Mass Specimen). Another objective of the present invention is to provide an electric double-layer capacitor with a high energy density per unit volume.

Means for Solving the Problems

[0011] The above object is achieved by the following present invention. That is, one aspect of the present invention is <1> A composite generation step of forming a carbon layer on the surface of a mold material by chemical vapor deposition using a raw material gas containing carbon to obtain a carbon layer-coated mold material, A mold material removal step of removing the mold material by bringing an acid that dissolves the mold material into contact with the carbon layer-coated mold material to isolate a carbon material, An impregnation step of selecting a liquid for shrinkage according to the purpose and impregnating the carbon material with the liquid for shrinkage, A drying and shrinkage step of drying and shrinking the carbon material impregnated with the liquid for shrinkage, A method for producing a carbon material, including

[0012] <2> The method for producing a carbon material according to claim 1, wherein the drying and shrinkage step includes an operation of heating the carbon material at 40 to 800 °C for 30 minutes or more.

[0013] <3> The method for producing a carbon material according to <1>, including a heat treatment step of holding the carbon material at 1000 to 3000 °C for 0.1 to 10 hours, which is carried out subsequent to the drying and shrinkage step.

[0014] <4> The method for producing a carbon material according to <1>, wherein the surface tension of the liquid for shrinkage at 80 °C is 1 to 100 mN / m, and the contact angle of the liquid for shrinkage with the cleavage plane of a graphite sheet at room temperature is 90° or less.

[0015] <5>​​​​​​​​​At least a portion of the electrode material constituting either one or both of the positive electrode and the negative electrode is made of carbon material. The carbon material is graphene meso sponge, The specific surface area s of the carbon material is 500 m². 2 / g or more 2200m 2 It is less than / g The apparent density d of the carbon material is 0.5 g / cm³. 3 More than 0.9g / cm 3 The following is an electric double-layer capacitor.

[0017] <7> The carbon material <2> Includes carbon materials manufactured by the carbon material manufacturing method described above, <6> The electric double-layer capacitor described above. [Effects of the Invention]

[0018] According to one aspect of the present invention, it is possible to provide a high-density carbon material or a carbon material with controlled density, even though it is a GMS (Gross Mass Specimen). Furthermore, according to another aspect of the present invention, by controlling the density of the carbon material, it is possible to provide an electric double-layer capacitor with a high energy density per unit volume. [Brief explanation of the drawing]

[0019] [Figure 1] This graph shows the relationship between the specific surface area s (m² / g) and apparent density d (g / cm³) of the carbon material produced in the test example. [Modes for carrying out the invention]

[0020] The present invention will be described in detail based on embodiments, but the present invention is not limited to these embodiments. The method for producing the carbon material according to this embodiment includes a composite formation step, a mold material removal step, an impregnation step, and a drying shrinkage step, and a heat treatment step is included as needed following the drying shrinkage step. Each step will be described below.

[0021] <Composite Generation Process> In this embodiment, the composite generation process is a process of forming a carbon layer on the surface of a mold material by chemical vapor deposition (CVD) using a raw material gas containing carbon to obtain a carbon layer-coated mold material.

[0022] The mold material used in this embodiment is preferably one that can realize a high-order structure in which the carbon material to be manufactured is complex and extends long, and the internal spaces are also connected. For example, those having an aggregate structure in which primary particles have a plurality of branched structures and are connected in a bead shape can be used.

[0023] The primary structure size constituting the mold material used in this embodiment is preferably in the range of 1 to 150 nm, more preferably 2 to 100 nm, still more preferably 3 to 75 nm, even more preferably 4 to 50 nm, and particularly preferably 5 to 20 nm. When the primary structure size constituting the mold material is within this range, for example, a continuous structure with a large mesopore volume is likely to be formed, and the specific surface area of the carbon material to be manufactured can be increased, which is preferable. Also, if the primary structure size constituting the mold material is within this range, it is easy to handle, and the permeability of the raw material gas serving as the carbon source for the carbon layer is also good, so uniform carbon coating becomes easy.

[0024] The BET specific surface area of the mold material used in this embodiment is not particularly limited, but for example, it may be 1 to 1000 m 2 / g, preferably 10 to 500 m 2 / g, more preferably 20 to 300 m 2 / g, still more preferably 40 to 200 m 2 / g, and particularly preferably in the range of 50 to 160 m 2 / g. When the BET specific surface area of the mold material is within this range, the mesopore volume of the carbon material to be manufactured can be significantly increased, which is preferable.

[0025] The specific surface area of ​​the intermediate carbon material produced in the stage prior to the impregnation process depends on the specific surface area of ​​the mold. The smaller the skeletal structure constituting the mold, the larger the surface area per unit mass. Therefore, using a mold material with a small primary structure makes it easier to obtain carbon material with a high specific surface area.

[0026] The mold material used in this embodiment may have an aggregate structure in which particles are linked together in a bead-like manner with multiple branching structures. Such a complex aggregate structure is similar to that of carbon black.

[0027] The average primary structure size of the template material (aggregate) in this embodiment is not particularly limited, but may be, for example, 1 to 100 nm, or in the range of 2 to 50 nm, 4 to 50 nm, or 3 to 30 nm. The size of the aggregate structure is not particularly limited, but may be, for example, in the range of 0.01 to 100 μm, preferably 0.05 to 10 μm, and preferably 0.1 to 5 μm. The average particle size of the aggregate structure is not particularly limited, but may be, for example, in the range of 0.05 to 10 μm, and preferably 0.1 to 5 μm.

[0028] The mold material used in this embodiment is preferably basic or acidic. Suitable basic compounds include, for example, magnesium oxide and calcium carbonate. Suitable acidic compounds include, for example, aluminum oxide and silica compounds containing silanol. The acidic pH is usually 7 or less, preferably 6.5 or less, more preferably 6 or less, even more preferably 5.5 or less, and particularly preferably 5 or less, based on a 4% water content. The lower limit is usually 1 or more, preferably 2 or more, more preferably 3 or more, even more preferably 3.5 or more, and particularly preferably 4 or more.

[0029] The template material used in this embodiment is not particularly limited as long as it has an aggregate structure in which primary particles have multiple branched structures linked together in a bead-like manner, but preferably it is a compound that has catalytic activity in the carbon deposition reaction. Examples of template materials include metal compounds, metalloid (semimetallic) compounds, and nonmetallic compounds, and preferably ceramic particles and / or carbonate particles.

[0030] There are no particular restrictions on the ceramic particles that can be used as mold materials, but examples include particles of glass, cement, and fine ceramics, and more specifically, particles of silica (silicon dioxide), alumina, magnesia (magnesium oxide), etc.

[0031] Furthermore, alumina has acidic sites on its surface and acts as a solid acid. When the acidic sites of the solid acid come into contact with hydrocarbons, the acidic sites act as catalysts for the hydrocarbon reforming reaction. Also, when the acidic sites come into contact with hydrocarbons, a carbon material deposition reaction occurs, and carbon material can precipitate on the surface of the solid acid. This function is called solid acid catalytic function, and by utilizing it, it becomes possible to decompose the raw material gas, polymerize the carbon radicals that are the decomposition products, and precipitate the carbon layer even at temperatures below the decomposition temperature of the raw material gas that serves as the carbon layer source.

[0032] Examples of carbonate particles that can be used as a mold material include, but are not limited to, particles of calcium carbonate, magnesium carbonate, dolomite, barium carbonate, lithium carbonate, sodium carbonate, and potassium carbonate. Among these, calcium carbonate and / or magnesium carbonate particles are particularly preferred.

[0033] Examples of metal compounds other than carbonate particles that can be used as mold materials include monovalent metal compounds and polyvalent metal compounds, but polyvalent metal compounds are preferred. Examples of monovalent metal compounds include chlorides, sulfates, nitrates, and phosphates of alkali metals such as sodium and potassium. Examples of polyvalent metal compounds include alkaline earth metal compounds such as calcium and magnesium, and trivalent metal compounds such as aluminum, but calcium compounds, magnesium compounds, and aluminum compounds are preferred. Examples of calcium, magnesium, and aluminum compounds include chlorides, sulfates, nitrates, phosphates, and oxides, but oxides are preferred.

[0034] There are no particular restrictions on the metalloid (semimetallic) compounds that can be used as mold materials, but examples include compounds of boron, silicon, germanium, and antimony, with silicon compounds being preferred. Examples of silicon compounds include silicon monoxide, silicon dioxide, silicon nitride, silicon carbide, and silicone, with silicon dioxide being preferred, and these are classified as ceramic particles.

[0035] Furthermore, aerosol compounds (particulate compounds in aerosol state) form aggregate structures in which primary particles are linked together in a chain-like manner with multiple branching structures, making them suitable for use as mold materials. Examples of aerosol compounds include compounds obtained by flame hydrolysis, which is one of the dry manufacturing methods for inorganic materials.

[0036] A typical example of an atomized compound is fumed silicon dioxide. Fumed silicon dioxide (commonly called fumed silica) produced by flame hydrolysis does not go through a liquid phase process during its production, resulting in slow aggregation. For this reason, fumed silicon dioxide has excellent dispersibility in liquids and compounds (solid phases). Fumed silicon dioxide is produced by the medium-to-high temperature gas-phase hydrolysis of silicon tetrachloride in an oxyhydrogen flame, accompanied by hydrochloric acid as a byproduct. By changing production conditions such as flame temperature, oxygen and hydrogen supply ratio, raw material supply amount, and residence time, for example, an average particle size of 7-40 nm and a specific surface area of ​​50-380 m² can be produced. 2 Particles of silicon dioxide are obtained at a density of / g.

[0037] Other examples of atomized compounds produced by flame hydrolysis include atomized alumina, atomized titania, and atomized zirconia. Other examples of atomized metal compounds include chlorides of Na, Ba, or Sr, sulfates of K, Na, Sr, or Mg, nitrates of Na or K, phosphates of Na or K, carbonates of Na, K, Ca, or Mg, and metal oxides of Na, K, Ca, or Ba. The shape of the mold material is preferably in an atomized form.

[0038] Precipitating silica can also be used as a mold material. Precipitating silica is obtained by reacting a sodium silicate solution with an acid in the liquid phase, followed by precipitation, filtration, washing, drying, and grinding. By adjusting the reaction conditions, an average particle size of approximately 7-140 nm and a specific surface area of ​​approximately 20-400 m² can be obtained. 2 Particles of silicon dioxide are obtained at a density of / g.

[0039] The moisture content of the mold material used in this embodiment is not particularly limited, but is, for example, in the range of 5% or less, preferably 3% or less, more preferably 1.5% or less, even more preferably 1% or less, and most preferably 0.5% or less.

[0040] Furthermore, there are no particular restrictions on the carbon content of the mold material used in this embodiment, but it may be, for example, 0.0001% by mass or more, preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, with an upper limit of, for example, 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass or less, even more preferably 2.5% by mass or less, particularly preferably 2% by mass or less. When the carbon content of the mold material is within this range, it is preferable because it facilitates the formation of a carbon layer on the mold surface.

[0041] In this embodiment, a chemical vapor deposition (CVD) method, as described later, can be used as a means to form a carbon layer on the mold surface. In this case, the amount of carbon deposited on the mold material surface is greatly influenced by the CVD reaction conditions such as the type of raw material gas, raw material gas concentration, flow rate, reaction temperature, and reaction time, as well as the mold material surface itself.

[0042] Suitable compounds for carbon deposition by CVD include, for example, compounds containing oxygen atoms. In the CVD reaction, carbon in the raw material gas is replaced by oxygen atoms, and this becomes the starting point for the deposition of carbon material. Examples of oxygen-containing compounds include the metal oxides and metal carbonates mentioned above. Among these compounds, acidic or basic compounds are particularly suitable. Examples of basic oxygen-containing compounds include magnesium oxide and calcium carbonate.

[0043] Furthermore, suitable surfaces for carbon layer formation by the CVD method include those having hydrocarbons that serve as a carbon source. Hydrocarbons include compounds that become the raw material gases described later, such as compounds having methyl groups or carbon-carbon unsaturated bonds. Suitable template materials are inorganic compounds having hydrocarbons on their surface.

[0044] There are no particular restrictions on the inorganic compound having hydrocarbons on its surface, but for example, inorganic materials surface-treated with a silane coupling agent, particularly silica compounds, are preferred. As the silane coupling agent, those commonly used as surface treatment agents can be used without particular restrictions, such as methoxy-type silane coupling agents, ethoxy-type silane coupling agents, vinyl-type silane coupling agents, dialkoxy-type silane coupling agents, and trialkoxy-type silane coupling agents. Among these, trialkoxy-type silane coupling agents with a large number of methyl groups per molecule are preferred, and trimethoxysilane compounds are particularly preferred.

[0045] The amount of silane coupling agent is appropriately selected depending on the intended use, but is expressed as the amount of hydrocarbons in the inorganic material, and is usually in the range of 0.01 to 10% by mass, preferably 0.02 to 8% by mass, more preferably 0.05 to 5% by mass, even more preferably 0.1 to 3% by mass, and particularly preferably 0.5 to 1.5% by mass. When the amount of silane coupling agent (amount of hydrocarbons) in the inorganic compound is within this range, it is preferable because the carbon mass on the mold surface can be easily adjusted.

[0046] The mold materials described above can be used individually or in combination of two or more types.

[0047] Generally, the carbon layer on the surface of the mold material can be formed, for example, by contacting the mold material with an organic substance that serves as a carbon source and performing a carbonization heat treatment. Contact with the carbon source and the carbonization heat treatment can be performed simultaneously or separately. Contact between the mold material and the carbon source is carried out, for example, in a temperature range of room temperature to about 1000°C.

[0048] Methods for bringing a carbon source into contact with a mold material can be broadly classified into liquid-phase contact methods and gas-phase contact methods. Liquid-phase contact methods include, for example, immersing the mold material in a liquid of organic matter. Gas-phase contact methods include, for example, introducing an organic gas at medium to high temperatures and bringing it into contact with the mold material. In this embodiment, the gas-phase contact method, or in other words, chemical vapor deposition (CVD), is used. In the CVD method, it is preferable to carry out the process in a temperature range in which a dehydrogenation reaction can proceed in order to bring an organic compound as a carbon source into contact with the mold material and to strongly bond the carbon source and the mold material.

[0049] Organic compounds used as carbon sources in the gas-phase contact process can be appropriately selected according to the intended use, but hydrocarbons such as saturated hydrocarbons, unsaturated hydrocarbons having double and / or triple bonds, alicyclic hydrocarbons, and aromatic hydrocarbons are preferably used. Saturated hydrocarbons may be either straight-chain or branched-chain, and examples include methane, ethane, and propane. Unsaturated hydrocarbons may be either straight-chain or branched-chain, and examples include ethylene, propylene, isoprene, and acetylene. Examples of alicyclic hydrocarbons include cyclopropane and cyclohexane. Examples of aromatic hydrocarbons include benzene and toluene.

[0050] Among these hydrocarbons, it is desirable to use methane, ethane, acetylene, ethylene, propylene, benzene, etc., and from the viewpoint of precipitating highly crystalline carbon, methane, propylene, and benzene are preferred. In particular, methane is preferably used from the viewpoint of obtaining highly crystalline carbon due to its high thermal decomposition temperature.

[0051] Organic compounds that can be used in the gas-phase contact process include alcohols such as methanol, ethanol, propanol, and butanol, as well as nitrogen-containing compounds such as acetonitrile and acrylonitrile.

[0052] The reaction temperature during CVD is appropriately selected according to the decomposition temperature of the organic compound used as the carbon source, but may be in the range of 400 to 1000°C, preferably 600 to 950°C, and preferably 800 to 900°C.

[0053] The reaction time during CVD (CVD treatment time at a predetermined heating temperature) is appropriately selected depending on the type of template material, the type of organic compound used as the carbon source, or the number of carbon layers deposited. For example, it may be in the range of 0.1 to 10 hours, preferably 0.5 to 5 hours, and more preferably 1 to 3 hours. Furthermore, the product can be analyzed, and the time required for sufficient carbon deposition can be appropriately set based on the results.

[0054] CVD reactions can be carried out under an inert gas atmosphere if necessary. Examples of inert gases include nitrogen, helium, neon, and argon, with argon being preferred. In the CVD method, carbon can usually be easily adsorbed or deposited on the mold material in the gas phase by heating while passing a gaseous organic compound in contact with the mold material together with a carrier gas. The type of carrier gas, flow rate, flow rate, and heating temperature can be appropriately adjusted depending on the type of organic compound used. Examples of carrier gases include the inert gases mentioned above, but a mixture with oxygen gas or hydrogen gas may also be used. Argon is preferably used as the carrier gas.

[0055] The number of carbon layers introduced onto the mold material can be appropriately selected by the CVD reaction time, but for the formation of a thin graphene layer, it is preferable to adjust the carrier gas flow rate to preferably 0.05 to 5 m / min, more preferably 0.1 to 1 m / min, even more preferably 0.2 to 0.8 m / min, and particularly preferably 0.32 to 0.64 m / min. Furthermore, for the formation of the optimal number of graphene layers, it is preferable to adjust the amount of organic compound introduced to preferably 1 to 70 volume%, more preferably 5 to 50 volume%, even more preferably 10 to 40 volume%, and particularly preferably 15 to 35 volume%, relative to the total amount of carrier gas and organic compound.

[0056] In the method for manufacturing the carbon material of this embodiment, the number of carbon layers is appropriately selected according to the intended use, but for example, it is 1 or more, preferably 1.1 or more layers, and the upper limit is, for example, 15 layers or less, preferably 10 layers or less, more preferably 4 layers or less, even more preferably 2 layers or less, and particularly preferably 1.5 layers or less. A high surface area per unit mass can be obtained while maintaining the hollow structure of carbon. Here, the number of carbon layers of the carbon material is calculated, for example, by laminating carbon layers on mold particles, then calculating the mass of the carbon layers using thermogravimetric analysis (TG), and calculating the mass of the carbon layers per mold area from the mass of the carbon layers and the surface area of ​​the mold particles, and this is used as the mass of the carbon layers per unit area of ​​single-layer graphene (7.61 × 10⁻⁶). -4 g / m 2 It can be calculated by dividing by ).

[0057] Since carbonization can also occur during the CVD reaction, a separate carbonization treatment is not necessary, but carbonization can be performed if desired.

[0058] <Mold material removal process> In this embodiment, the mold material removal step is a step in which the mold material is removed by contacting the carbon layer coated mold material produced in the composite formation step with an acid that dissolves the mold material, thereby isolating the carbon material as a carbon material precursor. In this step, any method that removes the mold material and leaves the formed carbon layer is acceptable, for example, dissolution by acid or alkali, but in this embodiment, dissolution by acid is preferred.

[0059] The acid used in the mold material removal process in this embodiment is appropriately selected depending on the type of mold material, but examples include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, and hydrofluoric acid, with hydrochloric acid and hydrofluoric acid being preferred. The concentration of the acid used is appropriately adjusted within a range that allows for the dissolution and removal of the mold material. The amount of acid used is not particularly limited as long as it allows for the dissolution and removal of the mold material, but for example, it may be 30 times or more the stoichiometric ratio of the mold material, or 50 times or more the stoichiometric ratio.

[0060] The temperature in the mold material removal process is not particularly limited, but is, for example, in the range of 5 to 100°C, preferably 10 to 50°C, and more preferably 20 to 30°C. The mold material removal process may be carried out with stirring, vibration, and other operations. The time required for the removal process is appropriately selected within a range in which the mold material can be dissolved and removed. The carbon material after mold removal can be recovered by, for example, immersion in water to wash it off and then filtration. The washing-filtration process may be repeated multiple times.

[0061] <Impregnation process> In this embodiment, the impregnation step is a step in which a shrinking liquid is selected according to the purpose, and the carbon material obtained as a carbon material precursor in the above mold material removal step is impregnated with the shrinking liquid. The carbon material formed after the above mold material removal step is in a low-density state in which the spaces where the mold material was present remain as pores, and in this step, the shrinking liquid fills these pores. When water is used as the shrinking liquid, the water that is rinsed out at the end of the mold material removal step can be used as is without suction filtration. Therefore, in that case, the operation of supplying water for rinsing corresponds to the operation of this impregnation step.

[0062] Then, during the subsequent drying and shrinking process, the graphene layers of the carbon material are pulled together between the pores due to the interaction of the wettability of the shrinking liquid with respect to the carbon material and the surface tension of the shrinking liquid, causing the entire material to shrink. Therefore, it is desirable for the shrinking liquid to have a relatively high surface tension and to be relatively wettable with respect to the carbon material.

[0063] The surface tension of the shrinking liquid is preferably in the range of 1 to 100 mN / m at 80°C, more preferably in the range of 10 to 95 mN / m, even more preferably in the range of 30 to 90 mN / m, and particularly preferably in the range of 50 to 80 mN / m. If the surface tension of the shrinking liquid at 80°C (hereinafter, when simply referred to as "surface tension," it refers to the surface tension at 80°C unless otherwise specified) is too low, the effect of shrinking the carbon material may be insufficient, and if the surface tension of the shrinking liquid is too high, it may not be able to penetrate sufficiently between the pores, and in either case, it will affect the function of shrinking the carbon material.

[0064] The shrinking liquid preferably has a contact angle of 90° or less with the cleavage surface of the graphite sheet at room temperature, more preferably 50° or less, even more preferably 20° or less, and particularly preferably 5° or less. Here, "room temperature" refers to a range of 5°C to 35°C, and if the temperature can be adjusted, it is preferable to set it to, for example, 25±2°C.

[0065] Since the carbon material consists of layers of graphene and is similar to a graphite sheet, its wettability can be estimated by determining the contact angle with the cleavage surface of the graphite sheet at room temperature (hereinafter, when simply referred to as "contact angle," it refers to the contact angle with the cleavage surface of the graphite sheet at room temperature unless otherwise specified). If the contact angle is too large, the wettability will be poor, and the effect of shrinking the carbon material may be insufficient. Note that the more easily the shrinking liquid wets the carbon material, the better, so there is no lower limit to the contact angle, but in practice a contact angle of 0° is impossible, and both the measurement limit and the practical lower limit are around 0.1°.

[0066] Specific examples of shrinking liquids include water (surface tension: 63.5 mN / m, contact angle: 64°), sulfuric acid (surface tension: 34 mN / m, contact angle: 23° at a concentration of 100% by volume), acetone (surface tension: 17 mN / m, contact angle: 2-3°), ethanol (surface tension: 17 mN / m, contact angle: 5°), toluene (surface tension: 27 mN / m, contact angle: 2°), isopropyl alcohol (surface tension: 19 mN / m, contact angle: 4°), and tert-butyl alcohol (surface tension: 20 mN / m, contact angle: 4°) (all contact angles of the shrinking liquids are measured values). When using sulfuric acid as the shrinking liquid, an aqueous solution (for example, 5% by volume or more and less than 100% by volume) is also acceptable. Furthermore, since contact angles are difficult to measure and less accurate when the numerical value is small, it is presumed that there is little correlation between magnitudes for data of 5° or less.

[0067] When selecting a shrinking liquid, the objective should be to determine how much the carbon material should shrink in the subsequent drying shrinkage process. In other words, generally, a higher surface tension and a smaller contact angle tend to result in a greater shrinkage effect on the carbon material, so the shrinking liquid should be selected based on a comprehensive assessment of these factors.

[0068] The shrinking liquid may be selected according to the type of mold material. For example, when alumina is used as the mold material, water or sulfuric acid (0.01 to 100% by volume) can be used. When magnesium oxide is used as the mold material, water, sulfuric acid (0.01 to 20% by volume), or acetone can be used.

[0069] As a method for impregnating the carbon material with shrinkage liquid, the shrinkage liquid may be poured or sprayed onto the carbon material, but in order to ensure that it is sufficiently distributed into the pores in the carbon material, it is preferable to immerse the carbon material in the shrinkage liquid, and it is preferable to leave it immersed for a certain period of time.

[0070] The immersion time for the carbon material in the shrinking liquid varies depending on the type of shrinking liquid and the characteristics of the carbon material, such as the pore volume, and therefore cannot be stated definitively. However, it is preferable to immerse it for approximately 5 minutes or more, and more preferably 60 minutes or more. There is no particular upper limit on the immersion time, but since some types of shrinking liquid may affect the structure of the carbon material, it is preferable not to immerse it for an unnecessarily long time. It is preferable to immerse it for approximately 100,000 minutes or less, and more preferably 5,000 minutes or less.

[0071] The carbon material after the predetermined immersion time can be recovered by filtration. However, it is preferable not to wash with pure water or the like, as this would affect the surface tension and contact angle of the liquid that replaces the pores with a liquid other than the shrinking liquid.

[0072] <Drying shrinkage process> In this embodiment, the drying shrinkage step is a process of shrinking a carbon material impregnated with a shrinking liquid by drying it to remove the shrinking liquid. Note that "removal" here does not mean complete removal; some residue of the shrinking liquid may remain in the pores of the carbon material. In this step, the material is thoroughly dried by heating and drying under atmospheric pressure or vacuum, but at least to the point where the carbon material shrinks.

[0073] Drying methods in this process include suction filtration, centrifugal deliquidation, standing at room temperature (e.g., around 5°C to 35°C), hot air drying, and heating drying under atmospheric pressure or vacuum. These methods can be used individually or in combination. The carbon material obtained by drying the carbon material in the drying shrinkage process is in powder form.

[0074] In this embodiment, the drying method preferably includes heating the carbon material at 40 to 800°C for 30 minutes or more (hereinafter, this heating operation will be referred to as the "medium-high temperature heating operation"). Applying the medium-high temperature heating operation ensures that the carbon material shrinks properly. In particular, when sulfuric acid is used as the shrinking liquid, it is desirable to apply the medium-high temperature heating operation.

[0075] The heating temperature in the medium-to-high temperature heating operation can be appropriately selected within the range of 40 to 800°C, depending on the type and concentration of the shrinking liquid. For example, when sulfuric acid is used as the shrinking liquid, the heating temperature in the medium-to-high temperature heating operation is preferably set to 300 to 800°C, more preferably to 400 to 700°C, and even more preferably to 500 to 650°C. When the heating temperature is within this range, the effect of the shrinking liquid is fully exerted, and high density can be achieved. If the heating temperature is too low, it may not be possible to obtain sufficient shrinkage, which is undesirable. On the other hand, if the heating temperature is too high, it may corrode the carbon structure and reduce the durability of the carbon, which is also undesirable. When water or acetone is used as the shrinking liquid, the heating temperature in the medium-to-high temperature heating operation is preferably set to 40 to 400°C, more preferably to 60 to 250°C, and even more preferably to 80 to 150°C.

[0076] The heating time (holding time at the predetermined heating temperature) in the medium-to-high temperature heating operation can be 30 minutes or more, preferably 60 minutes or more, and more preferably 90 minutes or more. If the heating time is too short, the effect of shrinking the carbon skeleton may be insufficient, which is undesirable.

[0077] On the other hand, although there is no upper limit to the heating time, if it is too long, there is a concern that the carbon structure will corrode and the durability of the carbon will decrease, so it is preferable to keep it to 600 minutes or less, more preferably 180 minutes or less, even more preferably 150 minutes or less, and particularly preferably 120 minutes or less. There are no particular restrictions on the atmospheric pressure in the drying shrinkage process, but it is preferable to carry it out under atmospheric pressure or reduced pressure. Furthermore, the heating environment can be an inert atmosphere, such as a nitrogen atmosphere, or an air atmosphere depending on the temperature range and the state of the sample.

[0078] A typical drying method in this embodiment involves, for example, performing a dewatering-level drying by suction filtration after the impregnation process, followed by preliminary drying by vacuum heating drying, and then applying a medium-to-high temperature heating operation. The conditions for the preliminary vacuum heating drying are not particularly limited, but for example, they can be set to a temperature of 100-200°C for 1-10 hours. This typical drying method is merely illustrative and is not limited to this method.

[0079] <Heat treatment process> Through the process described above, a precursor for the carbon layer constituting GMS can be produced. The obtained carbon material can be further subjected to heat treatment (heat treatment process) to enhance the crystallinity of the carbon, and for example, a graphene crystal structure is formed and stabilized. Therefore, by subjecting it to the heat treatment process, a carbon material with high levels of conductivity, corrosion resistance, and / or high specific surface area can be produced.

[0080] In this embodiment, the heat treatment step is a step of holding the carbon material dried in the drying shrinkage step at a predetermined temperature for a predetermined time. In the heat treatment step, the heating temperature is set to a range of 1000 to 3000°C, preferably 1200 to 2500°C, more preferably 1400 to 2000°C, even more preferably 1500 to 1900°C, and particularly preferably 1600 to 1850°C. If the heating temperature is within this range, it is preferable to obtain a carbon material that has higher levels of conductivity, corrosion resistance, and / or high specific surface area. If the heating temperature is too low, it may not be possible to sufficiently increase the crystallinity of the carbon, which is undesirable. On the other hand, if the heating temperature is too high, there is a concern that the carbon structure will corrode and the durability of the carbon will decrease, which is also undesirable.

[0081] Furthermore, during the heat treatment process, functional groups that bond to carbon (mainly oxygen-containing functional groups) and carbon chains that do not form six-membered rings detach when the temperature exceeds 1000°C, potentially forming unbonded bonds. When these unbonded bonds bond to other nearby carbon atoms, the surface of the carbon material becomes less receptive to the bonding of functional groups. Therefore, by heat treatment at, for example, 1500°C or higher, preferably 1600°C or higher, it is possible to make the carbon material more electrically conductive and more likely to maintain its internal space.

[0082] In the heat treatment process, the heating time (holding time at a predetermined heating temperature) can be in the range of 0.001 to 10 hours, preferably 0.01 to 5 hours, and more preferably 0.05 to 5 hours. If the heating time is too short, it may not be possible to sufficiently increase the crystallinity of the carbon, which is undesirable. On the other hand, if the heating time is too long, there is a concern that the carbon structure will corrode and the durability of the carbon will decrease, which is also undesirable. There are no particular restrictions on the atmospheric pressure in the heat treatment process, but it is preferable to carry it out at atmospheric pressure or under reduced pressure. Furthermore, the heat treatment environment can also be an inert atmosphere, such as a nitrogen atmosphere or an argon atmosphere.

[0083] During the heat treatment process, structural defects in the graphene and non-graphene components of the carbon material may be adjusted. These structural defects include spaces created within the aggregate structure due to the dissolution of the mold material and penetration pores created in the outer shell formed from the carbon material. By changing reaction conditions such as heat treatment temperature and heat treatment time, the degree of these structural defects can be adjusted; that is, the size of the spaces within the carbon material and the size of the penetration pores that allow oil or electrolyte to penetrate into the particles can be adjusted.

[0084] The manufacturing method according to this embodiment, as described above, allows for the easy production of carbon materials. The carbon material obtained in this embodiment may be graphene mesosponge (GMS). Graphene mesosponge is a porous carbon material having a graphene crystal structure, or a porous carbon material. GMS has a large specific surface area. The average number of graphene layers N is, for example, 0.9 to 5.0, and preferably 1.0 to 2.0. The fewer layers of the graphene crystal structure there are, the larger the specific surface area of ​​the porous carbon material. GMS also has a particularly large elastic deformation work rate and tends to recover without plastic deformation under weak stress.

[0085] In this embodiment, the graphene layers of the carbon material are attracted between pores due to the surface tension and wettability (contact angle) of the shrinking liquid, causing the entire structure to shrink and change, thereby reducing the pore volume. In other words, according to this embodiment, it is possible to produce a carbon material with improved density while still being a GMS (Gross Mass Specimen). Furthermore, the density of the resulting carbon material can be controlled by selecting and adjusting the type and concentration of the shrinking liquid.

[0086] The density of carbon materials can be calculated using the following formula (2). The density calculated using formula (2) (the density of the particles themselves) will be referred to as "apparent density" below to distinguish it from the measured density (density affected by the voids between particles = bulk density).

[0087]

number

[0088] <Applications of carbon materials> The carbon material obtained by the manufacturing method of this embodiment is a GMS with a high specific surface area and high density, making it suitable for use as an electrode material for electric double-layer capacitors. In addition to the excellent characteristics of GMS, it can be suitably used as a material for electronic devices where improved density is desired, or where density control is desired. Specifically, examples include dielectric sensors, optoelectronic devices, gas sensors, catalyst supports, and current collectors. Furthermore, the carbon material obtained by the manufacturing method of this embodiment can also be used for applications other than electronic devices.

[0089] An electric double-layer capacitor is an electronic component comprising a positive electrode, a negative electrode, and an electrolyte. The carbon material obtained by the manufacturing method of this embodiment can be used as at least a part of the electrode material constituting either one or both of the positive and negative electrodes.

[0090] In the manufacturing method of this embodiment, high density is achieved by reducing the pore volume in the carbon material. However, since pore volume is roughly proportional to the specific surface area, high density leads to a decrease in the specific surface area. In other words, there is a trade-off relationship between the density and specific surface area of ​​the carbon material.

[0091] When used as an electrode material for electric double-layer capacitors, our research has confirmed that carbon materials exhibiting the following conditions (1) and (2) can be manufactured under controlled conditions (see the examples described later).

[0092] (Condition 1) The specific surface area s of the carbon material is 500 m² 2 / g or more 2200m 2 / g or less (Condition 2) Apparent density d (g / cm³) of carbon material 3 ) and specific surface area s(m 2 / g) satisfies the following equation (1) -4×10 -4 ×s + 0.89 ≤ d ≤ -4 × 10 -4 ×s+1.1 …Formula (1)

[0093] The graph in Figure 1 shows the specific surface area s(m²) of the carbon material produced by the manufacturing method of this embodiment in the examples described later. 2 ( / g) and apparent density d (g / cm³) 3 This graph shows the relationship between the apparent density and the specific surface area. From the plot of the graph in Figure 1, an approximate straight line with a slope of -4 can be drawn, and it can be seen that the apparent density d can be controlled by selecting and adjusting the type, characteristics, and concentration of the shrinking liquid, as shown in the test conditions of the examples described later. Also, as can be seen from the graph in Figure 1, controlling the apparent density d to increase it reduces the specific surface area s.

[0094] When used as an electrode material for an electric double-layer capacitor, a higher specific surface area s of the carbon material is preferable. On the other hand, when used as an electrode material for an electric double-layer capacitor, the apparent density d (g / cm³) is preferable. 3 As such, the higher the value, the better.

[0095] The region enclosed by lines A, B, C, and D in the graph of Figure 1 is the region that satisfies conditions 1) and 2). Therefore, when using the carbon material obtained by the manufacturing method of this embodiment in an electric double-layer capacitor, the carbon material can be controlled and used within the region enclosed by lines A, B, C, and D in the graph of Figure 1.

[0096] For electrode materials in electric double-layer capacitors, high density is desirable to achieve high capacitance, but if the specific surface area decreases too much, it will also lead to a decrease in capacitance. Therefore, the energy density per unit volume (F / cm²) is determined when the rate of increase in density exceeds the rate of decrease in capacitance (F / g) due to the decrease in specific surface area. 3 This can improve the relationship between apparent density and specific surface area. Therefore, when the carbon material obtained by the manufacturing method of this embodiment is used as an electrode material for an electric double-layer capacitor, an optimal region may exist in the relationship between apparent density and specific surface area. [Examples]

[0097] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples except as specified above. In the following, "%", "ppm", and "parts" used to express quantities refer to mass unless otherwise specified.

[0098] <Manufacturing Example 1> In Manufacturing Example 1, each of the carbon materials (GMS) from Test Examples 1 to 12 was manufactured. The specific manufacturing process is as follows:

[0099] (1) Complex generation process Magnesium oxide (MF-150; central particle diameter 710 nm, BET specific surface area 119 m²) was used as the mold. 2 Approximately 8g of (99.5% CaO content, manufactured by Kyowa Chemical Industry Co., Ltd.) was spread on a quartz boat and placed in the center of a quartz reaction tube in a horizontal CVD apparatus (transparent electric furnace manufactured by Ishikawa Sangyo Co., Ltd.). Argon gas was flowed into the reaction tube at a flow rate of 400 mL / min while the temperature was raised to 900°C at a heating rate of 10°C / min. Then, argon gas was flowed at a flow rate of 320 mL / min and methane gas at a flow rate of 80 mL / min (raw material gas concentration 20%), and the temperature was maintained at 540°C for the time shown in the "Carbon Coating Time" column in Table 1 below for each test example. After that, the material was cooled to room temperature while argon gas was flowed at a flow rate of 400 mL / min, and the carbon layer coated mold material A was removed.

[0100] (2) Mold material removal process Next, the mold was removed from the obtained carbon layer coated mold material A by the following operations a) to g) to obtain the carbon material. a) Approximately 5 g of carbon layer coated mold material A was placed in a 500 ml glass beaker, and approximately 40 ml of ultrapure water was added and stirred with a stirrer. b) After adding approximately 40 mL of 8% (2.3 M) hydrochloric acid, the mixture was stirred with a stirrer for 2 hours. c) The stirred liquid was filtered by suction using a PTFE membrane filter (90 mm diameter, pore size 1 μm). d) A sufficient amount of ultrapure water was added to the sample remaining in the beaker, stirred, washed, and then filtered by suction. e) The sample (carbon material) on the filter was collected back into the original glass beaker, and steps b) to d) were repeated five times.

[0101] (3) Impregnation process For Test Examples 6-12, for 1 g of the sample (carbon material) after the final suction filtration in step e) of the mold material removal process, a shrinking liquid was prepared with the formulation shown in the "Shrinking Liquid Formulation (Volume %)" column of Table 1 below, the sample (carbon material) was dispersed in it, and stirred overnight at room temperature.

[0102] In the case of Test Examples 1 to 5, where the shrinking liquid consists solely of water, the final suction filtration in step e) of the above "(2) Mold Material Removal Process" was omitted, and the water contained in the carbon material was used directly as the shrinking liquid. In this case, the operation of supplying water for the final rinse corresponds to the operation of this impregnation process.

[0103] The properties of the shrinking liquid used in each test example (measurement results of surface tension [mN / m] and contact angle [°]) are summarized in Table 1 below. However, the contact angle [°] is precisely the contact angle [°] between the shrinking liquid and the cleavage surface of the graphite sheet at room temperature (adjusted to 25±2℃) (the same applies to Table 2 described later).

[0104] (4) Drying shrinkage process For test examples 7-11, where the shrinking liquid contained sulfuric acid, the sample (carbon material) after the completion of the impregnation process (3) was placed directly onto a quartz boat, the atmosphere was changed by flowing 1 L / min of nitrogen for 10 min, then the flow was switched to 0.4 L / min, the temperature was raised to 600°C at a heating rate of 10°C / min, and heat treatment was performed for 3 hours to remove the shrinking liquid.

[0105] For test examples 1-6 and 12, in which the shrinking liquid did not contain sulfuric acid, the shrinking liquid was removed by vacuum-drying the sample (carbon material) overnight at 60°C or 150°C after the completion of the impregnation process (3), as shown in Table 1 below.

[0106] (5) Heat treatment process (4) After the drying shrinkage process was completed, the sample (carbon material) was degassed under vacuum in an electric furnace, then the electric furnace was filled with argon (Ar), and the temperature was raised to 1800°C at a heating rate of 10°C / min, followed by a heat treatment for 1 hour to produce carbon materials (GMS) for Test Examples 1 to 12.

[0107] <Characterization of carbon material (GMS) manufactured in Manufacturing Example 1> For the carbon materials (GMS) of Test Examples 1 to 12, manufactured as described above, the specific surface area, pore volume, and apparent density were determined as follows. The results are summarized in Table 1 below.

[0108] (specific surface area) Samples that had been vacuum-dried at 150°C for 6 hours were subjected to nitrogen adsorption / desorption measurements at -196°C using a nitrogen adsorption / desorption analyzer (Bel-mini X, manufactured by Microtrac Bell Co., Ltd.). The specific surface area was determined by applying the BET method to the obtained adsorption isotherms.

[0109] (pore volume) Based on the adsorption capacity at a relative pressure of 0.96 in the nitrogen adsorption isotherm described above, the volume of adsorbed nitrogen assuming it exists in liquid form was calculated, and the pore volume was determined.

[0110] (Apparent density) The apparent density was calculated using the measured values ​​and specified values, according to the formula (2) described above.

[0111] <Results from Manufacturing Example 1> Table 1 below summarizes the measurement results for each carbon material (GMS) produced in Manufacturing Example 1 and Test Examples 1 to 12, including (1) carbon coating time during the composite formation process, (4) drying temperature, composition and properties of the shrinkage liquid during the drying shrinkage process, and the properties of the carbon material (GMS).

[0112] [Table 1]

[0113] <Manufacturing Example 2> In Manufacturing Example 2, each of the carbon materials (GMS) from Test Examples 13 to 16 was manufactured. The specific manufacturing process is as follows:

[0114] (1) Complex generation process Alumina nanoparticles, SASOL SBa200, crystalline phase: γ-alumina, average particle size: 8 nm, specific surface area: 220 m². 2 Approximately 8 g of ( / g) was spread in a quartz boat and placed in the center of a quartz reaction tube in a horizontal CVD apparatus (a transparent electric furnace manufactured by Ishikawa Sangyo Co., Ltd.). Argon gas was flowed into the reaction tube at a flow rate of 400 mL / min while the mixture was heated to 900°C at a heating rate of 10°C / min. Then, argon gas was flowed at a flow rate of 320 mL / min and methane gas at a flow rate of 80 mL / min (raw material gas concentration 20%), and the temperature was maintained at 540°C for the time shown in the "Carbon Coating Time" column in Table 2 below for each test example. After that, the mixture was cooled to room temperature while argon gas was flowed at a flow rate of 400 mL / min, and the carbon layer coated mold material B was removed.

[0115] (2) Mold material removal process Except for the fact that in the (2) mold material removal step in <Production Example 1> above, carbon layer coated mold material A was replaced with carbon layer coated mold material B obtained in the (1) composite formation step in this production example, and 8% (2.3M) hydrochloric acid was replaced with 47% (27M) hydrofluoric acid, the operation of this step was carried out in the same manner as in the (2) mold material removal step in <Production Example 1> above.

[0116] (3) Impregnation process For Test Examples 13-15, for 1 g of the sample (carbon material) after the final suction filtration in step e) of the mold material removal process, a shrinking liquid was prepared with the formulation shown in the "Shrinking Liquid Formulation (Volume %)" column of Table 2 below, the sample (carbon material) was dispersed in it, and stirred overnight at room temperature.

[0117] In the case of Test Example 16, where the shrinking liquid consists solely of water, the final suction filtration in step e) of "(2) Mold Material Removal Process" above was omitted, and the water contained in the carbon material was used directly as the shrinking liquid. In this case, the operation of supplying water for the final rinse corresponds to the operation of this impregnation process. The characteristics of the shrinking liquid used in each test example (measurement results of surface tension [mN / m] and contact angle [°]) are summarized in Table 1 below.

[0118] (4) Drying shrinkage process For Test Examples 13-15, where the shrinking liquid contained sulfuric acid, the sample (carbon material) after the completion of the impregnation process (3) was placed directly onto a quartz boat, the atmosphere was changed by flowing 1 L / min of nitrogen for 10 min, then the flow was switched to 0.4 L / min, and the temperature was increased at a heating rate of 10°C / min to 600°C for Test Examples 13 and 14, and to 400°C for Test Example 15, and heat treatment was performed for 3 hours to remove the shrinking liquid.

[0119] For Test Example 16, in which the shrinking liquid did not contain sulfuric acid, the shrinking liquid was removed by vacuum-drying the sample (carbon material) at 100°C overnight after the completion of the impregnation process (3).

[0120] (5) Heat treatment process The carbon materials (GMS) for Test Examples 13-16 were manufactured in the same manner as in step (5) of the heat treatment process in <Manufacturing Example 1> above.

[0121] <Characterization of carbon material (GMS) manufactured in manufacturing example 2> For the carbon materials (GMS) of Test Examples 13-16 manufactured as described above, the specific surface area, pore volume, and apparent density were determined as follows, in the same manner as in <Measurement of properties of carbon material (GMS)> in <Manufacturing Example 1>. The results are summarized in Table 2 below.

[0122] <Results from Manufacturing Example 2> Table 2 below summarizes the measurement results for each carbon material (GMS) produced in Manufacturing Example 2, specifically (1) the carbon coating time during the composite formation process, (4) the drying temperature, the composition and properties of the shrinkage liquid during the drying shrinkage process, and the properties of the carbon material (GMS).

[0123] [Table 2]

[0124] The specific surface area s(m²) of the carbon material (GMS) from Test Examples 1-16 produced in Manufacturing Example 1 and Manufacturing Example 2. 2 ( / g) and apparent density d (g / cm³) 3 The relationship between ( ) and ( ) is shown in a graph in Figure 1.

[0125] As can be seen from Tables 1 and 2 above, and the graph in Figure 1, the apparent density d can be controlled by selecting and adjusting the type, properties, and concentration of the shrinking liquid. By controlling the apparent density d, the effect of voids between particles can be suppressed by standardizing the particle packing state, and as a result, the true density of the carbon material can be controlled.

Claims

1. A composite material formation process to obtain a carbon layer coated mold material by forming a carbon layer on the surface of a mold material using a carbon-containing raw material gas by chemical vapor deposition, A mold material removal step involves removing the mold material and isolating the carbon material by bringing an acid that dissolves the mold material into contact with the carbon layer coated mold material, An impregnation step is taken to select a shrinking liquid appropriate to the purpose and to impregnate the carbon material with the shrinking liquid, A method for producing a carbon material, comprising a drying shrinkage step of drying and shrinking the carbon material impregnated with the shrinkage liquid.

2. The method for producing a carbon material according to claim 1, wherein the drying shrinkage step includes heating the carbon material at 40 to 800°C for 30 minutes or more.

3. A method for producing a carbon material according to claim 1, comprising a heat treatment step of holding the carbon material at 1000 to 3000°C for 0.1 to 10 hours, which is performed following the drying shrinkage step.

4. The method for producing a carbon material according to claim 1, wherein the surface tension of the shrinking liquid at 80°C is 1 to 100 mN / m, and the contact angle of the shrinking liquid with the cleavage surface of the graphite sheet at room temperature is 90° or less.

5. The method for producing the carbon material according to claim 1, wherein the carbon material is used as an electrode material for an electric double-layer capacitor.

6. An electric double-layer capacitor comprising a positive electrode, a negative electrode, and an electrolyte, At least a portion of the electrode material constituting either one or both of the positive electrode and the negative electrode is made of carbon material. The carbon material is graphene meso sponge, The specific surface area s of the carbon material is 500 m². ２ / g or more 2200m ２ / g or less, The apparent density d of the carbon material is 0.5 g / cm³. ３ 0.9g / cm or more ３ The following is an electric double-layer capacitor.

7. The electric double-layer capacitor according to claim 6, wherein the carbon material comprises a carbon material manufactured by the method for manufacturing a carbon material described in claim 2.

Images