Carbonaceous material, method for producing same, electrode active material for electrochemical device, electrode for electrochemical device, and electrochemical device

Abstract

The invention relates to a carbonaceous material, a method for producing the same, an electrode active material for an electrochemical device, an electrode for an electrochemical device, and an electrochemical device. The present invention relates to a carbonaceous material having a BET specific surface area of 1550-2500 m2 / g and a value of oxygen content / hydrogen content per unit specific surface area of 1.00-2.04 mg / m2.

Description

[0001] This application is a divisional application of the PCT patent application PCT / JP2019 / 043727 with the invention title of "Carbonaceous Material, Method for Producing the Same, Electrode Active Material for Electrochemical Device, Electrode for Electrochemical Device, and Electrochemical Device", and the application number of the parent case entering China is 201980073265.5. Technical Field

[0002] The present invention relates to a carbonaceous material, a method for producing the same, an electrode active material for an electrochemical device, an electrode for an electrochemical device, and an electrochemical device. Background Art

[0003] An electric double layer capacitor, which is one of electrochemical devices, utilizes the capacitance (electric double layer capacitance) obtained only by physical adsorption and desorption of ions without accompanying chemical reactions, and thus has excellent output power characteristics and life characteristics compared to batteries. In addition, a lithium ion capacitor, which is one of electrochemical devices, has attracted attention as a hybrid capacitor capable of increasing the energy density of an electric double layer capacitor. In recent years, from the viewpoints of the excellent characteristics of these electrochemical devices and a prompt countermeasure against environmental problems, they have also attracted attention in terms of being mounted on electric vehicles (EVs) and hybrid vehicles (HVs) for use as auxiliary power sources and for storing regenerated energy. For such in-vehicle electrochemical devices, not only higher energy density is required, but also high durability under more severe usage conditions (for example, in a severe temperature environment) compared to consumer applications and further improvement of electrostatic capacitance are required.

[0004] In response to such requirements, various methods for improving the durability and electrostatic capacitance of electrochemical devices have been studied. For example, Patent Documents 1 and 2 disclose that activated carbon before or after pulverization is heat-treated at a high temperature in order to increase the electrostatic capacitance and suppress gas generation after durability. In addition, Patent Document 3 describes an increase in the electrostatic capacitance and durability of highly specific surface area and highly crystallized activated carbon obtained by alkali activation.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Pamphlet of International Publication No. 2008 / 053919

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2011 - 11935

[0009] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2017 - 147338. Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] However, heat treatment at high temperatures as described in the above Patent Documents 1 and 2 easily causes a decrease in the specific surface area and pore volume of activated carbon. Therefore, if the activated carbon as described in these documents is used in an electrochemical device, the initial electrostatic capacitance per unit weight and per unit volume may decrease. In addition, the activated carbon obtained by alkali activation as described in the above Patent Document 3 usually adds a chemical reagent equal to or more than the amount of carbon during activation, and a process for removing the residual chemical reagent after alkali activation is required, so the manufacturing method becomes complicated. In addition, compared with the activated carbon obtained by steam activation, there is a possibility that the amount of functional groups during activation increases and the durability decreases.

[0012] The present invention has been made in view of the above actual situation, and an object thereof is to provide a carbonaceous material and a method for manufacturing the same, an electrode active material for an electrochemical device containing the carbonaceous material, an electrode for an electrochemical device using the same, and an electrochemical device, which can obtain an electrochemical device having a high initial electrostatic capacitance, a gas generation suppression effect during charge and discharge, and excellent durability.

[0013] Means for Solving the Problems

[0014] In order to solve the above problems, the present inventors have repeatedly studied in detail the carbonaceous material and its manufacturing method, and as a result, the present invention has been achieved.

[0015] That is, the present invention includes the following preferred embodiments.

[0016] 〔1〕A carbonaceous material having a BET specific surface area of 1550 to 2500 m 2 / g, and a value of oxygen content / hydrogen content per unit specific surface area of 1.00 to 2.04 mg / m 2 .

[0017] 〔2〕The carbonaceous material according to the above 〔1〕, wherein the conductivity measured by powder resistance at a load of 12 kN is 9 S / cm or less.

[0018] 〔3〕The carbonaceous material according to the above 〔1〕 or 〔2〕, having a hydrogen content of 0.44 to 1.00% by mass.

[0019] 〔4〕The carbonaceous material according to any one of the above 〔1〕 to 〔3〕, having a value of oxygen content / hydrogen content of 2.0 to 4.3.

[0020] 〔5〕The carbonaceous material according to any one of the above [1] to [4], wherein the carbonaceous material is based on a carbon precursor derived from plants.

[0021] 〔6〕The carbonaceous material according to any one of the above 〔1〕 to 〔5〕, wherein the carbon precursor is derived from coconut shells.

[0022] 〔7〕Method for manufacturing carbonaceous material, comprising: a heating step of heating a raw carbonaceous material in an oxidizing gas atmosphere to 330 °C or higher; and a cooling step of cooling the raw carbonaceous material heated to 330 °C or higher in an oxidizing gas atmosphere in a non-oxidizing gas atmosphere,

[0023] When including one heating step performed in an oxidizing gas atmosphere as described above, the cooling step is performed subsequently after the heating step.

[0024] When including multiple heating steps performed in an oxidizing gas atmosphere as described above, the cooling step is performed at least subsequently after the final heating step performed in an oxidizing gas atmosphere.

[0025] 〔8〕The method for manufacturing carbonaceous material according to the above-mentioned 〔7〕, wherein, in the cooling step, the temperature of the raw carbonaceous material is cooled to 200 °C or lower.

[0026] 〔9〕Electrode active material for an electrochemical device, which is formed of the carbonaceous material according to any one of the above-mentioned 〔1〕 to 〔6〕.

[0027] 〔10〕Electrode for an electrochemical device, which contains the electrode active material for an electrochemical device according to the above-mentioned 〔9〕.

[0028] 〔11〕Electrochemical device, which includes the electrode for an electrochemical device according to the above-mentioned 〔10〕.

[0029] Effects of the Invention

[0030] According to the present invention, there can be provided a carbonaceous material and a method for manufacturing the same, an electrode active material for an electrochemical device containing the above-mentioned carbonaceous material, an electrode for an electrochemical device using the same, and an electrochemical device, which can obtain an electrochemical device having a high initial electrostatic capacitance, a gas generation suppression effect during charge and discharge, and excellent durability. Description of the Drawings

[0031] Figure 1 It is a diagram showing a sheet-like electrode composition.

[0032] Figure 2 It is a diagram showing a current collector (etched aluminum foil) coated with a conductive adhesive.

[0033] Figure 3 It is a diagram showing a polarized electrode in which a sheet-like electrode composition is bonded to a current collector and an aluminum pole tab is ultrasonically welded.

[0034] Figure 4 It is a diagram showing a bag-shaped outer packaging sheet.

[0035] Figure 5 It is a diagram showing an electrochemical device. Detailed implementation manners

[0036] Hereinafter, the implementation manners of the present invention will be described in detail. It should be noted that the scope of the present invention is not limited to the implementation manners described herein, and various changes can be made without departing from the gist of the present invention.

[0037] It should be noted that in the present invention, the carbonaceous material before the cooling treatment in the aforementioned cooling process is referred to as "raw material carbonaceous material", and the carbonaceous material obtained by subjecting the raw material carbonaceous material to the aforementioned final heating treatment and implementing the aforementioned cooling treatment is referred to as "carbonaceous material".

[0038] [Carbonaceous material]

[0039] In the carbonaceous material of the present invention, the BET specific surface area is 1550 - 2500 m 2 / g, and the value of hydrogen content / oxygen content per unit specific surface area is 1.00 - 2.04 mg / m 2 .

[0040] The BET specific surface area of the carbonaceous material of the present invention is 1550 m 2 / g or more, preferably 1600 m 2 / g or more, more preferably 1650 m 2 / g or more, and is 2500 m 2 / g or less, preferably 2450 m 2 / g or less, more preferably 2400 m 2 / g or less. Generally, the electrostatic capacitance per unit area is constant. Therefore, if the BET specific surface area is less than 1550 m 2 / g, it is difficult to sufficiently increase the electrostatic capacitance per unit mass. In addition, since the average pore diameter is relatively small, it can be considered that there is a tendency for the resistance caused by the diffusion resistance of non-aqueous electrolyte ions in the pores to increase during charge and discharge at high currents. On the other hand, if the BET specific surface area exceeds 2500 m 2 / g, there is a tendency for the bulk density of the electrode manufactured using the carbonaceous material for the electrode to be low and the electrostatic capacitance per unit volume to be low.

[0041] It should be noted that in the present invention, the BET specific surface area can be calculated by the nitrogen adsorption method. For example, it can be calculated by the method described in the following examples.

[0042] In the carbonaceous material of the present invention, the value of oxygen content (mass%) / hydrogen content (mass%) per unit specific surface area (hereinafter sometimes abbreviated as "O / H per unit specific surface area") is 1.00 mg / m 2 or more, preferably 1.10 mg / m 2More preferably 1.20 mg / m 2 Above, and 2.04 mg / m 2 Below, preferably 2.02 mg / m 2 Less than, more preferably 2.00 mg / m 2 Below. In the present invention, "oxygen content, O" represents the amount of oxygen in the carbonaceous material obtained from the measurement results of the elemental analysis described later, and represents the sum of the amount of surface oxygen present on the surface of the carbonaceous material and the amount of oxygen present by entering the skeleton. In addition, "hydrogen content, H" represents the amount of hydrogen present in the periphery of the carbon crystals of the carbonaceous material. Here, the amount of surface oxygen present on the surface of the carbonaceous material represents the degree of functional groups that become a cause of durability deterioration and gas production, and the amount of oxygen present by entering the skeleton of the carbonaceous material and the amount of hydrogen present in the periphery of the crystal represent the degree of development of the carbon crystal structure. Therefore, O / H per unit specific surface area becomes an indicator for indicating the appropriate amount of oxygen for inhibiting the growth of carbon crystals of the carbonaceous material, as well as durability and gas production. Therefore, if O / H per unit specific surface area is above the above lower limit, it can be inferred that a state of moderate oxygen presence on the surface of the carbonaceous material is presented, and the affinity with the binder is improved, and the electrode formability is excellent. In addition, it can be inferred that: since the carbon structure of the carbonaceous material is fully developed and the crystallinity is high, the electrical conductivity of the carbonaceous material itself is improved. On the other hand, if the O / H per unit specific surface area is below the above-mentioned upper limit value, it can be inferred that the amount of surface oxygen present on the surface of the carbonaceous material is moderately reduced, and gas generation during charging and discharging is suppressed. It can also be inferred that: the excessive development of the carbon crystal structure of the carbonaceous material can be suppressed, and the pore shrinkage of the carbonaceous material accompanying this is suppressed, and the reduction of the initial electrostatic capacitance per unit mass is easily suppressed. In the manufacturing method of the present invention described later, the value of O / H per unit specific surface area of the carbonaceous material can be adjusted in particular by a process of cooling the raw carbonaceous material heated to above 330°C in an oxidizing gas atmosphere in a non-oxidizing gas atmosphere. It should be noted that the value of O / H per unit specific surface area in the present invention is a value calculated according to the method described in the embodiments described later.

[0043] The average pore diameter of the carbonaceous material of the present invention is preferably 1.82 nm or more, more preferably 1.83 nm or more, and further preferably 1.84 nm or more. If the average pore diameter is above the above lower limit value, it can be considered that the resistance caused by the diffusion resistance of non-aqueous electrolyte ions in the pores tends to decrease during charge and discharge at high current. In addition, the average pore diameter of the carbonaceous material of the present invention is preferably 2.60 nm or less, more preferably 2.55 nm or less, and further preferably 2.50 nm or less. If the average pore diameter is below the above upper limit value, the bulk density of the electrode manufactured using the carbonaceous material for the electrode tends to be high, and the electrostatic capacitance per unit volume tends to be high. By controlling the BET specific surface area and the average pore diameter of the carbonaceous material within the above upper and lower limits respectively, a carbonaceous material more suitable for an electrochemical device capable of ensuring a high electrostatic capacitance per unit mass and per unit volume and having a small resistance can be obtained. It should be noted that the average pore diameter can be measured by the method described in the following examples.

[0044] In addition, the total pore volume of the carbonaceous material of the present invention is preferably 0.75 cm 3 / g or more, more preferably 0.76 cm 3 / g or more, and further preferably 0.77 cm 3 / g or more. If the total pore volume is above the above lower limit value, it can be considered that the resistance caused by the diffusion resistance of non-aqueous electrolyte ions in the pores tends to decrease during charge and discharge at high current. In addition, the total pore volume of the carbonaceous material of the present invention is preferably 1.30 cm 3 / g or less, more preferably 1.29 cm 3 / g or less, and further preferably 1.28 cm 3 / g or less. If the total pore volume is below the above upper limit value, the bulk density of the electrode manufactured using the carbonaceous material for the electrode tends to be high, and the electrostatic capacitance per unit volume tends to be high. It should be noted that the total pore volume can be measured by the method described in the following examples.

[0045] In the carbonaceous material of the present invention, the conductivity obtained by measuring the powder resistance at a load of 12 kN is preferably 9 S / cm or less, more preferably 8.5 S / cm or less. If the conductivity is below the above upper limit value, the excessive development of the carbon crystal structure of the carbonaceous material can be suppressed, and the pore shrinkage of the carbonaceous material associated therewith can be suppressed. Therefore, there is a tendency to suppress the decrease in the initial electrostatic capacitance per unit weight. In addition, the lower limit value of the conductivity is not particularly limited. If the conductivity is too high, the resistance becomes large. Therefore, it is preferably 5 S / cm or more, more preferably 6 S / cm or more.

[0046] The hydrogen content (hereinafter sometimes abbreviated as "H") of the carbonaceous material of the present invention is preferably 0.44% by mass or more, more preferably 0.45% by mass or more, still more preferably 0.46% by mass or more, and preferably 1.00% by mass or less, more preferably 0.9% by mass or less, still more preferably 0.8% by mass or less. If H is at least the above lower limit value, it can be considered that a state in which a certain amount of hydrogen is present in the outer periphery of the crystal is presented, the excessive development of the carbon crystal structure of the carbonaceous material is suppressed, and the pore shrinkage of the carbonaceous material associated therewith is also suppressed. Therefore, there is a tendency that the decrease in the initial electrostatic capacitance per unit weight is suppressed. On the other hand, if H is at most the above upper limit value, the crystallinity is high. Therefore, it can be considered that the conductivity of the carbonaceous material itself is increased, and there is a tendency that the resistance becomes smaller.

[0047] In the carbonaceous material of the present invention, the value of oxygen content (% by mass) / hydrogen content (% by mass) is preferably 2.0 or more, more preferably 2.25 or more, still more preferably 2.5 or more, particularly preferably 2.6 or more, more particularly preferably 2.7 or more, and preferably 4.3 or less, more preferably 4.2 or less, still more preferably 4.1 or less. If within the above range, the effects of suppressing gas generation and suppressing the decrease in electrostatic capacitance can be further improved.

[0048] The average particle diameter of the carbonaceous material of the present invention is preferably 30 μm or less, more preferably 20 μm or less, and preferably 2 μm or more, more preferably 4 μm or more. If within the above range, the electrode manufactured using the carbonaceous material for the electrode can be made thinner, and there is a tendency that the bulk density increases and the electrostatic capacitance per unit volume becomes higher. It should be noted that the value of the average particle diameter in the present invention is a value calculated by the method described in the examples below.

[0049] [Manufacturing method of carbonaceous material]

[0050] The carbonaceous material of the present invention can be manufactured by a method including the following steps: for example, a heating step of heating the raw material carbonaceous material to 330 °C or higher; and a cooling step of cooling the raw material carbonaceous material heated to 330 °C or higher in an oxidizing gas atmosphere in a non-oxidizing gas atmosphere. When including a heating step carried out once in the above-mentioned oxidizing gas atmosphere, the above-mentioned cooling step is carried out subsequently after the above-mentioned heating step. When including multiple heating steps carried out in the above-mentioned oxidizing gas atmosphere, the above-mentioned cooling step is carried out at least subsequently after the final heating step carried out in the oxidizing gas atmosphere.

[0051] After a final heating step of heating a carbonaceous material to 330 °C or higher in an oxidizing gas atmosphere, the raw material carbonaceous material heated to 330 °C or higher by this heating step is cooled in a non-oxidizing gas atmosphere, whereby it is possible to both suppress pore shrinkage and reduce the surface oxygen amount present on the surface of the obtained carbonaceous material, and a carbonaceous material capable of producing an electrochemical device with a high initial capacitance, an excellent gas generation suppression effect during charge and discharge, and excellent durability can be obtained. Therefore, the present invention also targets a method for manufacturing a carbonaceous material, the method including: a heating step of heating a raw material carbonaceous material to 330 °C or higher in an oxidizing gas atmosphere; and a temperature-lowering step of lowering the temperature of the raw material carbonaceous material heated to 330 °C or higher in an oxidizing gas atmosphere in a non-oxidizing gas atmosphere,

[0052] when including one time the heating step performed in an oxidizing gas atmosphere, the temperature-lowering step is carried out after the heating step,

[0053] when including multiple times the heating step performed in an oxidizing gas atmosphere, the temperature-lowering step is carried out at least after the final heating step performed in an oxidizing gas atmosphere.

[0054] In the above-mentioned manufacturing method, as the heating process implemented under the oxidizing gas atmosphere, there can be listed, for example, an activation process for activating the carbide of the carbon precursor as the raw material; a deacidification process performed after the acid cleaning process for removing impurities as needed, etc. In order to obtain the target specific surface area, the activation process can be implemented in one stage, or it can be implemented in two or more stages. In addition, the acid cleaning for removing impurities in the substance can be implemented after the activation is completed, or it can be implemented during the multi-stage activation process, and it can be repeatedly implemented multiple times. After the acid cleaning, in order to remove the acid components such as chlorine components remaining in the pores, it is preferably subjected to a heat treatment (deacidification process). In the present invention, in the process of heating the raw carbonaceous material to above 330°C under an oxidizing gas atmosphere, it is important to cool the raw carbonaceous material under a non-oxidizing gas atmosphere during the cooling process after the final heating process. It should be noted that when the aforementioned heating process is performed multiple times under an oxidizing gas atmosphere, the cooling (cooling) other than the cooling process of the raw carbonaceous material heated to 330°C or above by the final heating process can be performed under a non-oxidizing atmosphere or under an oxidizing gas atmosphere. In addition, in the method for manufacturing the carbonaceous material of the present invention, after the cooling of the raw carbonaceous material heated to 330°C or above by the final heating process performed under an oxidizing gas atmosphere under a non-oxidizing gas atmosphere, as long as it does not affect the effect of the present invention, it may include heating under a non-oxidizing gas atmosphere. In order to avoid pore shrinkage caused by heating as much as possible, it is preferred that: among the processes of heating the raw carbonaceous material to 330°C or above included in the manufacturing method of the present invention, the final heating process is performed under an oxidizing gas atmosphere, and the subsequent cooling process is performed under a non-oxidizing gas atmosphere. Below, each process is described in detail.

[0055] In the present invention, the carbon precursor that becomes the raw material of carbonaceous material is not particularly limited as long as it forms carbonaceous material by activation, and can be widely selected from carbon precursors from plants, carbon precursors from minerals, carbon precursors from natural raw materials, and carbon precursors from synthetic raw materials, etc. From the viewpoint of reducing harmful impurities, the viewpoint of environmental protection, and the viewpoint of commerce, the carbonaceous material of the present invention is preferably based on a carbon precursor from a plant, in other words, the carbon precursor that becomes the carbonaceous material of the present invention is preferably from a plant.

[0056] Examples of carbon precursors derived from minerals include petroleum-based and coal-based asphalt and coke. Examples of carbon precursors derived from natural raw materials include natural fibers such as cotton and hemp; regenerated fibers such as rayon and artificial cotton; and semi-synthetic fibers such as acetate and triacetate. Examples of carbon precursors derived from synthetic raw materials include polyamides such as nylon; polyvinyl alcohols such as vinylon; polyacrylonitrile such as acrylic acid; polyolefins such as polyethylene and polypropylene; polyurethane, phenolic resins, and vinyl chloride resins.

[0057] In the present invention, the carbon precursor derived from plants is not particularly limited, and examples thereof include coconut shells, coffee beans, tea leaves, sugarcane, fruits (such as oranges, bananas), straws, rice husks, broad-leaved trees, coniferous trees, and bamboo. This exemplification includes waste after being used for its original purpose (such as used tea leaves), or a part of plant raw materials (such as the peels of bananas and oranges). These plant raw materials can be used alone or in combination of two or more. Among these plant raw materials, coconut shells are preferred from the viewpoints of easy availability and the ability to produce carbonaceous materials with various properties. Therefore, the carbonaceous material of the present invention is preferably based on a carbon precursor derived from plants, and more preferably based on a carbon precursor derived from coconut shells.

[0058] As for the coconut shell, there is no particular limitation, and examples thereof include coconut shells of oil palm (oil coconut), coconut, salak, and sea coconut. These coconut shells can be used alone or in combination of two or more. From the viewpoint of easy availability, it is particularly preferred to use the biomass waste generated in large quantities after using coconuts as food, detergent raw materials, biodiesel raw materials, etc., that is, the coconut shells of coconuts and oil palms.

[0059] [Carbonization process]

[0060] As a method for obtaining a carbide from a carbon precursor, there is no particular limitation, and a method known in the art can be used for manufacturing. For example, it can be manufactured by firing (carbonization treatment) the carbon precursor as a raw material at a temperature of about 400 to 800 °C in an atmosphere of an inert gas such as nitrogen, carbon dioxide, helium, argon, carbon monoxide, or fuel exhaust gas, a mixed gas of these inert gases, or a mixed gas having these inert gases as the main component and mixed with other gases.

[0061] [Activation process]

[0062] In the present invention, the carbonaceous material as a raw material can be obtained, for example, by subjecting the above-mentioned carbide to an activation treatment. The activation treatment refers to a treatment for forming pores on the surface of the carbide to become a porous carbonaceous substance, whereby a carbonaceous substance (raw material carbonaceous material) having a large specific surface area and pore volume can be obtained. When the carbide is directly used without undergoing an activation treatment, the specific surface area and pore volume of the obtained carbonaceous substance are insufficient, and when used as an electrode material, it is difficult to ensure a sufficiently high initial electrostatic capacitance, and it is difficult to obtain the carbonaceous material of the present invention. The activation treatment (activation process) generally requires heating the carbide, and the obtained raw material carbonaceous material is heated to 330 °C or higher with the activation process. Therefore, the activation process can be a mode of the heating process in the present invention. The activation treatment can be carried out by a general method in the art, and mainly two treatment methods, namely gas activation treatment and chemical reagent activation treatment, can be cited.

[0063] As a gas activation treatment, it is known to heat a carbide in the presence of, for example, water vapor, carbon dioxide, air, oxygen, combustion gas, or a mixed gas thereof. Further, as a chemical reagent activation treatment, it is known to mix an activator such as zinc chloride, calcium chloride, phosphoric acid, sulfuric acid, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, etc. with a carbon precursor or a carbide of the carbon precursor, and heat it in an inert gas atmosphere. In the present invention, the chemical reagent activation requires a step of removing the residual chemical reagent, the manufacturing method becomes complicated, and the amount of functional groups during activation also increases. Therefore, it is preferable to use a gas activation treatment.

[0064] When water vapor activation is employed as the gas activation treatment, from the viewpoint of efficiently performing activation, it is preferable to use a mixture of an inert gas and water vapor that is the same as the substance used during the carbonization treatment. At this time, the partial pressure of the water vapor is preferably in the range of 10 to 60%. If the partial pressure of the water vapor is 10% or more, it is easy to sufficiently perform activation. If it is 60% or less, it is easy to suppress a rapid activation reaction and easy to control the reaction.

[0065] The total amount of the activation gas supplied during water vapor activation is preferably 50 to 10000 parts by mass or more, more preferably 100 to 5000 parts by mass or more, and further preferably 200 to 3000 parts by mass or more with respect to 100 parts by mass of the carbide. If the total amount of the activation gas supplied is within the above range, the activation reaction can be carried out more efficiently.

[0066] The specific surface area and pore volume of the carbonaceous material can be controlled by changing the activation treatment method and conditions of the carbide, etc. For example, when obtaining a raw material carbonaceous material by water vapor activation treatment, it can be controlled according to the type of gas used, concentration, heating temperature, and reaction time, etc. In the present invention, when obtaining a raw material carbonaceous material by water vapor activation treatment, its heating temperature (activation temperature) also varies depending on the type of gas used, and is usually 700 to 1100 °C, preferably 800 to 1000 °C. In addition, the heating time and heating rate are not particularly limited, and can be appropriately determined according to the heating temperature and the desired specific surface area of the raw material carbonaceous material, etc.

[0067] [Acid cleaning process]

[0068] In the present invention, the method for manufacturing a carbonaceous material may include an acid cleaning step. The acid cleaning step is a step for removing impurities such as metal components contained in the raw material carbonaceous material by cleaning the raw material carbonaceous material with a cleaning liquid containing an acid. The acid cleaning step can be carried out by immersing the raw material carbonaceous material obtained after activation in a cleaning liquid containing an acid. Examples of the cleaning liquid include inorganic acids or organic acids. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, etc. Examples of the organic acid include saturated carboxylic acids such as formic acid, acetic acid, propionic acid, oxalic acid, tartaric acid, and citric acid; aromatic carboxylic acids such as benzoic acid and terephthalic acid, etc. From the viewpoint of cleanability, the acid used in the cleaning liquid is preferably an inorganic acid, more preferably hydrochloric acid. It should be noted that after cleaning with an acid, it is preferably further cleaned with water or the like to remove the excess acid. By this operation, the load on the equipment in the subsequent process can be reduced. When the activation step is divided into a single activation step or a multi-stage activation step, the acid cleaning step can be carried out after the single activation step or after the multi-stage activation step.

[0069] The cleaning liquid can generally be prepared by mixing an acid with an aqueous solution. Examples of the aqueous solution include water, a mixture of water and a water-soluble organic solvent, etc. Examples of the water-soluble organic solvent include alcohols such as methanol, ethanol, propylene glycol, and ethylene glycol.

[0070] The acid concentration in the cleaning liquid is not particularly limited and can be appropriately adjusted according to the type of acid used. The acid concentration of the cleaning liquid is preferably 0.1 to 3.0%, more preferably 0.3 to 1.0% based on the total amount of the cleaning liquid. If the hydrochloric acid concentration is too low, the number of acid washing times needs to be increased to remove impurities. On the contrary, if it is too high, more residual hydrochloric acid remains. By setting the concentration within the above range, the acid cleaning step can be carried out efficiently, which is preferable from the aspect of productivity.

[0071] The pH of the cleaning liquid is not particularly limited and can be appropriately adjusted according to the type of acid used and the object to be removed.

[0072] The liquid temperature during acid washing and water washing is not particularly limited, and it is preferably 0 to 98 °C, more preferably 10 to 95 °C, and further preferably 15 to 90 °C. If the temperature of the cleaning liquid when immersing the raw material carbonaceous material is within the above range, the cleaning can be carried out in a practical time while suppressing the load on the device, so it is ideal.

[0073] When the raw material carbonaceous material is impregnated in the cleaning liquid, the mass ratio of the cleaning liquid to the carbonaceous material can be appropriately adjusted according to the type, concentration, temperature, etc. of the cleaning liquid used. The mass of the raw material carbonaceous material to be impregnated is usually 0.1 to 50% by mass, preferably 1 to 20% by mass, and more preferably 1.5 to 10% by mass, relative to the mass of the cleaning liquid. If within the above range, the impurities dissolved in the cleaning liquid are difficult to precipitate from the cleaning liquid, it is easy to suppress reattachment to the raw material carbonaceous material, and in addition, the volumetric efficiency becomes appropriate. Therefore, it is ideal from the economic point of view.

[0074] The atmosphere for cleaning is not particularly limited and can be appropriately selected according to the method used for cleaning. In the present invention, the cleaning is usually carried out in an atmospheric atmosphere.

[0075] The cleaning can be carried out once or multiple times with one kind of cleaning liquid, or multiple times by combining two or more kinds of cleaning liquids.

[0076] As a method for cleaning the raw material carbonaceous material, as long as the raw material carbonaceous material can be impregnated in the cleaning liquid, there is no particular limitation. It can be a method of continuously adding the cleaning liquid and allowing it to stay for a specified time, and impregnating while extracting, or a method of impregnating the raw material carbonaceous material in the cleaning liquid, allowing it to stay for a specified time and then draining, and then re-adding the cleaning liquid and repeatedly impregnating-draining. In addition, it can be a method of completely renewing the cleaning liquid or a method of partially renewing the cleaning liquid. As the time for impregnating the raw material carbonaceous material in the cleaning liquid, it can be appropriately adjusted according to the acid used, the concentration of the acid, the treatment temperature, etc.

[0077] [Deacidification step]

[0078] In the present invention, the manufacturing method of the carbonaceous material may include a deacidification step for removing the acid (such as hydrochloric acid, etc.) remaining from the acid cleaning liquid after acid cleaning. In the present invention, the deacidification step can be carried out by heating the raw material carbonaceous material in an oxidizing gas atmosphere after acid cleaning. In the deacidification step, usually the raw material carbonaceous material is heated to 330 °C or higher. Therefore, the deacidification step can be a form of the heating step in the present invention. In addition, the contact time and temperature with the oxidizing gas can be adjusted to remove the remaining acid while accompanying a further activation reaction.

[0079] As the oxidizing gas, the gas used in the above gas activation step can be utilized. It should be noted that in the present invention, "in an oxidizing gas atmosphere" means a state where the total amount of the oxidizing gas per unit raw material carbonaceous material in the container is 1.5 L / kg or more.

[0080] As the above treatment temperature, it is preferably 500 to 1000 °C, more preferably 650 to 850 °C. If within the above temperature range, deacidification can be carried out without causing significant changes to the pore structure of the raw carbonaceous material, so it is preferred. The time varies with the temperature and is usually about 30 minutes to 3 hours.

[0081] The average particle size of the carbon precursor or the raw carbonaceous material from coconut shells used in the above activation process or deacidification process can be adjusted according to the activation and deacidification processes.

[0082] The above carbonization, activation, and deacidification methods are not particularly limited, and known methods such as a fixed-bed method, a moving-bed method, a fluidized-bed method, a multi-stage bed method, a rotary kiln, etc. can be adopted.

[0083] [Cooling process after heating]

[0084] The manufacturing method of the carbonaceous material of the present invention includes: a cooling process of cooling the raw carbonaceous material heated to 330 °C or higher in an oxidizing gas atmosphere in a non-oxidizing gas atmosphere. That is, in order to suppress the formation of functional groups due to the reaction between the oxidizing gas (such as oxygen) present in the environment during cooling and the carbon surface, it includes: a process of cooling the raw carbonaceous material heated to 330 °C or higher in an oxidizing gas atmosphere in a non-oxidizing gas atmosphere after the final heating process among the processes. Thus, the carbonaceous material of the present invention can be obtained. After the activation treatment and after the deacidification process, a method of heating the raw carbonaceous material in an inert gas atmosphere to remove the acidic functional groups present on the surface of the raw carbonaceous material is known, but in this method, pore shrinkage sometimes easily occurs due to heating, and it is difficult to ensure a sufficiently high initial electrostatic capacitance when used in an electrochemical device. In addition, there are still problems in terms of productivity, such as the need for a further process for heating or the necessity of strictly controlling the heating conditions. In the present invention, heating of the raw carbonaceous material in an inert gas atmosphere for reducing the acidic functional groups present on the surface of the raw carbonaceous material is not required. Therefore, a carbonaceous material that can be used to fabricate an electrochemical device with a high initial electrostatic capacitance without pore shrinkage can be obtained.

[0085] In the cooling process, it is preferred to cool the temperature of the raw carbonaceous material to 200 °C or lower, more preferably to 150 °C or lower, in a non-oxidizing gas atmosphere. The cooling time until the above temperature also varies depending on the amount of oxidizing gas present in the cooling environment. Considering productivity as well, it is ideal to be within 3 hours, preferably within 1 hour. In addition, from the viewpoints of suppressing oxidation and productivity, it is more ideal to use an indirect cooling device (such as a cooling furnace, etc.) to accelerate the cooling rate and shorten the time in the temperature region where the raw carbonaceous material can be oxidized.

[0086] Examples of non-oxidizing gases include nitrogen, dry hydrogen, ammonia, argon, helium, hydrogen, carbon monoxide gas, and hydrocarbon gases. These gases can be used alone, or as a mixed gas containing two or more of them.

[0087] The non-oxidizing gas atmosphere means, for example, an atmosphere in which the amount of oxidizing gas is significantly reduced compared to an atmosphere containing a large amount of oxidizing gas such as air. Specifically, in the present invention, the "non-oxidizing gas atmosphere" means a state in which the total amount of oxidizing gas per unit of raw material carbonaceous material in the container is 0.7 L / kg or less. To further improve the effect of the present invention, the total amount of oxidizing gas present in the environment during cooling is preferably 0.5 L / Kg or less, more preferably 0.1 L / Kg or less, relative to the raw material carbonaceous material. If within the above range, the formation of functional groups due to the reaction between the oxidizing gas and the carbon surface during cooling can be suppressed.

[0088] [Crushing process]

[0089] In the present invention, the manufacturing method of the carbonaceous material may include a crushing process. The crushing process is a process for controlling the shape and particle size of the finally obtained carbonaceous material into a desired shape and particle size. The carbonaceous material of the present invention is particularly suitable as a material for a non-aqueous polarizable electrode used in an electrochemical device or the like. As a particle size suitable for such a use, the carbonaceous material is preferably crushed so that the average particle size preferably reaches 4 to 15 μm, more preferably 5 to 10 μm.

[0090] The crusher used for crushing is not particularly limited, and known crushers such as a cone crusher, a double roll crusher, a disk crusher, a rotary crusher, a ball mill, a centrifugal roll mill, an annular roll mill, a centrifugal ball mill, and a jet mill can be used alone or in combination.

[0091] [Classification process]

[0092] In the present invention, the manufacturing method of the carbonaceous material may include a classification process. For example, by removing particles having a particle size of 1 μm or less, carbonaceous material particles having a narrow particle size distribution range can be obtained. By removing such fine particles, the amount of binder during electrode formation can be reduced. The classification method is not particularly limited, and examples include classification using a sieve, wet classification, and dry classification. As a wet classifier, examples include classifiers using the principles of gravity classification, inertial classification, hydraulic classification, and centrifugal classification. As a dry classifier, examples include classifiers using the principles of sedimentation classification, mechanical classification, and centrifugal classification. From the viewpoint of economy, a dry classifier is preferably used.

[0093] Crushing and classification can also be carried out using one device. For example, a jet mill equipped with a dry classification function can be used to carry out crushing and classification. Furthermore, a device in which a crusher and a classifier are independent can also be used. At this time, crushing and classification can be carried out continuously or discontinuously.

[0094] The carbonaceous material of the present invention can be suitably used as an electrode material for various electrochemical devices, etc. Therefore, in one embodiment of the present invention, the carbonaceous material of the present invention can be used to provide an electrode material for an electrochemical device and a method for manufacturing the same. In addition, an electrode for an electrochemical device and a method for manufacturing the same can be provided using the electrode material or an electrode material obtained by the method for manufacturing the electrode material. Furthermore, an electrochemical device and a method for manufacturing the same can be provided using the electrode or an electrode obtained by the method for manufacturing the electrode.

[0095] The aforementioned electrode material for an electrochemical device can be manufactured by using the carbonaceous material of the present invention. As its manufacturing process, it may include, for example, the following processes: a process of kneading the carbonaceous material of the present invention as a raw material with components such as a conductivity imparting agent, a binder, and a solvent; a process of coating / drying the kneaded product, etc., which are existing general manufacturing processes in the art as manufacturing processes for electrode materials. In addition, the aforementioned electrode for an electrochemical device can be manufactured by using the aforementioned electrode material. As its manufacturing process, it may include, for example, the following processes: a process of preparing a paste by adding a solvent to the aforementioned electrode material as a raw material; a process of drying and removing the solvent after coating the aforementioned paste on a current collector such as an aluminum foil; a process of putting the aforementioned paste into a mold and performing pressure molding.

[0096] As the conductivity imparting agent used in the electrode, for example, acetylene black, Ketjen black, etc. can be used. As the binder, for example, fluorine-based polymer compounds such as polytetrafluoroethylene and polyvinylidene fluoride, carboxymethyl cellulose, styrene-butadiene rubber, petroleum pitch, phenolic resin, etc. can be used. In addition, as the solvent, for example, alcohols such as water, methanol, and ethanol; saturated hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as toluene, xylene, and mesitylene; ketones such as acetone and methyl ethyl ketone; esters such as methyl acetate and ethyl acetate; amides such as N,N-dimethylformamide and N,N-diethylformamide; cyclic amides such as N-methylpyrrolidone and N-ethylpyrrolidone, etc. can be used.

[0097] The electrochemical device of the present invention can be manufactured by using the aforementioned electrodes. Electrochemical devices generally mainly consist of electrodes, electrolytes, and separators, and have a structure in which a separator is disposed between a pair of electrodes. As the electrolyte, for example, an electrolyte in which an amidine salt is dissolved in an organic solvent such as propylene carbonate, ethylene carbonate, or ethyl methyl carbonate; an electrolyte in which a quaternary ammonium salt of perchloric acid is dissolved; an electrolyte in which a tetrafluoroborate salt or a hexafluorophosphate salt of an alkali metal such as quaternary ammonium or lithium is dissolved; an electrolyte in which a phosphonium salt is dissolved, etc. can be cited. In addition, as the separator, for example, a non-woven fabric, a cloth, or a microporous film mainly composed of cellulose, glass fiber, or a polyolefin such as polyethylene or polypropylene can be cited. The electrochemical device can be manufactured by, for example, arranging these main components by a method generally used in the art.

[0098] The electrochemical device manufactured using the carbonaceous material of the present invention is not accompanied by a decrease in specific surface area and pore volume due to cooling in a non-oxidizing atmosphere. Therefore, the initial electrostatic capacitance can be increased, and the formation of surface functional groups present on the surface of the carbonaceous material can be suppressed. As a result, the reactivity with the electrolyte is low, the gas generation suppression effect during charge and discharge is high, the decrease in electrostatic capacitance due to long-term use can be suppressed, the durability is excellent, and furthermore, excellent performance can be maintained even at low temperatures.

[0099] Examples

[0100] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples. The physical property values in the examples and comparative examples were measured by the following methods.

[0101] [Measurement of specific surface area]

[0102] Using BELSORP-mini manufactured by MicrotracBEL Corporation, the carbonaceous material to be the sample was heated at 300 °C for 3 hours in a nitrogen gas stream (nitrogen gas flow rate: 50 mL / minute), and then the nitrogen adsorption isotherm of the carbonaceous material at 77.4 K was measured. Based on the obtained adsorption isotherm, analysis by the BET equation using the multi-point method was performed, and the specific surface area was calculated from the straight line in the region of the relative pressure P / P0 = 0.01 to 0.1 of the obtained curve.

[0103] [Total pore volume · average pore diameter]

[0104] Using BELSORP-mini manufactured by Microtrack Bell Co., Ltd., the carbonaceous material to be the sample was heated at 300 °C for 3 hours under a nitrogen gas flow (nitrogen gas flow rate: 50 mL / minute), and then the nitrogen adsorption isotherm of the carbonaceous material at 77.4 K was measured. Using the total pore volume obtained from the nitrogen adsorption amount at a relative pressure P / P0 = 0.99 in the obtained adsorption isotherm, based on this total pore volume and the specific surface area obtained by the aforementioned BET method, the average pore diameter was calculated based on the following formula.

[0105] [Mathematical formula 1]

[0106] Average pore diameter (nm) = total pore volume (cm 3 / g) / specific surface area (m 2 / g) × 4000.

[0107] [Determination method of oxygen content, hydrogen content, O / H, O / H per unit specific surface area]

[0108] Performed using EMGA-930 manufactured by Horiba, Ltd. Regarding the detection method of this device, oxygen: non-active gas dissolution - non-diffusion type infrared absorption method (NDIR), hydrogen: non-active gas dissolution - non-diffusion type infrared absorption method (NDIR), calibration was carried out using (oxygen) Ni capsule, TiH2 (H standard sample) SS-3 (O standard sample). 5 mg of the sample with a pretreatment of drying treatment at 220 °C for about 10 minutes was placed in the Ni capsule, and after degassing for 30 seconds in the above device, the measurement was carried out. The test was analyzed using 3 specimens, and the average value was used as the analysis value. O / H was obtained from the obtained value, and by dividing this value by the BET specific surface area obtained above, the O / H per unit specific surface area was obtained.

[0109] [Determination method of electrical conductivity]

[0110] Using the powder resistance measurement unit "MCP-PD51" manufactured by Mitsubishi Chemical Analytech Co., Ltd., the electrical conductivity of the carbonaceous material was measured. In the measurement of electrical conductivity, a material with an amount such that the thickness of the carbonaceous material pellets reached 3.5 - 4.5 mm when a load of 12 kN was applied was used, and the electrical conductivity of the carbonaceous material pellets in the state where a load of 12 kN was applied was measured.

[0111] [Average particle size measurement]

[0112] The particle size of the carbonaceous material was measured by laser diffraction. That is, the carbonaceous material to be measured and a surfactant were put into ion-exchanged water together, and ultrasonic vibration was applied using BRANSONIC M2800-J manufactured by EMERSON to prepare a uniformly dispersed liquid. Microtrac MT3000 manufactured by Microtrac Inc. of the United States was used to perform the measurement by the absorption method. In addition, "Triton-X 100" manufactured by Kao Corporation was used as the surfactant for the purpose of uniform dispersion. An appropriate amount of the surfactant was added to enable uniform dispersion without generating bubbles or the like that would affect the measurement.

[0113] <Example 1>

[0114] For the charcoal made from the coconut shell of Philippine coconuts (BET specific surface area: 370 m 2 / g), propane combustion gas and water vapor (water vapor partial pressure: 25%) were used, and it was activated once at 850 °C until the following specific surface area was reached, obtaining a primary activated granular carbonaceous material with a BET specific surface area of 1674 m 2 / g and an average pore diameter of 1.89 nm. Thereafter, hydrochloric acid (concentration: 0.5 equivalent, diluent: ion-exchanged water) was used, and it was pickled at a temperature of 70 °C for 30 minutes, then washed with ion-exchanged water and dried. Thereafter, in order to remove the chlorine component remaining in the pores, treatment was carried out at 700 °C in a propane combustion gas atmosphere (hereinafter referred to as deacidification treatment). After the treatment was completed, in order to actively replace the combustion gas accompanying the discharge, nitrogen with a purity of 99.99% was circulated in the flow-through container. And after replacing with nitrogen of the above purity until the total amount of oxidizing gas per unit mass of the primary activated granular carbonaceous material in the container reached 0.5 L / Kg or less, the aforementioned carbonaceous material was discharged and cooled to 200 °C or less in this atmosphere (cooling time was 1.0 hour), obtaining a carbonaceous material.

[0115] The carbonaceous material was micro-crushed so that the average particle size reached 6 μm, obtaining a carbonaceous material (1) with a BET specific surface area of 1686 m 2 / g and an average pore diameter of 1.89 nm. Various physical properties of the obtained carbonaceous material (1) were measured. The results are shown in Table 1.

[0116] <Example 2>

[0117] For the charcoal made from the coconut shell of Philippine coconuts (BET specific surface area: 370 m 2 / g), propane combustion gas and water vapor (water vapor partial pressure: 25%) were used, and it was activated once at 850 °C until the following specific surface area was reached, obtaining a BET specific surface area of 1185 m 2The once-activated granular carbonaceous material per / g. Thereafter, hydrochloric acid (concentration: 0.5 equivalent, diluent: ion-exchanged water) was used to perform acid washing at a temperature of 70 °C for 30 minutes, and then, in order to remove the residual acid, it was thoroughly washed with ion-exchanged water and desalted. After desalting, it was dried at 120 °C to obtain a secondarily washed granular carbonaceous material. Using propane combustion gas and steam (steam partial pressure of 15%), the granular carbonaceous material was further secondarily activated at 950 °C until the following specific surface area was reached, and a secondarily activated granular carbonaceous material with a BET specific surface area of 1710 m 2 / g and an average pore diameter of 1.99 nm was obtained. Thereafter, hydrochloric acid (concentration: 0.5 equivalent, diluent: ion-exchanged water) was used to perform acid washing at a temperature of 70 °C for 30 minutes, then washed with ion-exchanged water and dried. Thereafter, in order to remove the chlorine component remaining in the pores, a deacidification treatment was carried out at 700 °C in a propane combustion gas atmosphere. After the treatment was completed, in order to actively displace the combustion gas accompanying the discharge, nitrogen with a purity of 99.99% was circulated in the flow-through container. And after replacing with nitrogen of the above purity until the total amount of oxidizing gas per unit mass of the secondarily activated granular carbonaceous material in the container reached a state of 0.5 L / Kg or less, the aforementioned carbonaceous material was discharged and cooled to 200 °C or less (cooling time was 1.0 hour) in this atmosphere to obtain a carbonaceous material.

[0118] The carbonaceous material was micro-crushed so that the average particle size reached 6 μm, and a carbonaceous material (2) with a BET specific surface area of 1721 m 2 / g and an average pore diameter of 1.99 nm was obtained. Various physical properties of the carbonaceous material (2) were measured. The results are shown in Table 1.

[0119] <Example 3>

[0120] The same operations as in Example 2 were performed to obtain a once-activated granular carbonaceous material. Thereafter, acid water washing and drying were carried out in the same manner as the primary washing in Example 1 to obtain a primary washed granular carbonaceous material. Using propane combustion gas and steam (steam partial pressure of 15%), the granular carbonaceous material was further secondarily activated at 970 °C until the following specific surface area was reached, and a carbonaceous material with a specific surface area of 2252 m 2 / g and a secondary-activated granular carbonaceous material with an average pore diameter of 2.25 nm. For the obtained secondary-activated granular carbonaceous material, acid water washing, drying, and deacidification treatment were carried out in the same manner as in the secondary cleaning of Example 1. After the treatment, in order to actively displace the combustion gas accompanying the discharge, nitrogen with a purity of 99.99% was circulated in the circulation container. And, after replacing with nitrogen of the above purity until the total amount of oxidizing gas per unit mass of the secondary-activated granular carbonaceous material in the container reached 0.5 L / Kg or less, the aforementioned carbonaceous material was discharged and cooled to 200 °C or lower (cooling time was 1.0 hour) in this atmosphere to obtain a carbonaceous material.

[0121] The carbonaceous material was micro-crushed so that the average particle diameter reached 6 μm to obtain a carbonaceous material (3) with a BET specific surface area of 2259 m 2 / g and an average pore diameter of 2.25 nm. Various physical properties of the carbonaceous material (3) were measured. The results are shown in Table 1.

[0122] <Comparative Example 1-1>

[0123] The same operation as in Example 1 was carried out to obtain a primary-activated granular carbonaceous material with a BET specific surface area of 1661 m 2 / g and an average pore diameter of 1.89 nm. Subsequently, hydrochloric acid (concentration: 0.5 equivalent, diluent: ion-exchanged water) was used for acid washing at a temperature of 70 °C for 30 minutes, and then thoroughly washed with ion-exchanged water and desalted to remove the remaining acid. Subsequently, in order to remove the chlorine component remaining in the pores, deacidification treatment was carried out at 700 °C in a propane combustion gas atmosphere. After the treatment, the accompanying combustion gas and the aforementioned carbonaceous material were simultaneously discharged into a container filled with air, and cooled to 200 °C or lower (cooling time was about 1.0 hour) in this atmosphere (the total amount of oxidizing gas per unit mass of the primary-activated granular carbonaceous material in the container was 1.5 L / Kg or more) to obtain a carbonaceous material.

[0124] The carbonaceous material was micro-crushed so that the average particle diameter reached 6 μm to obtain a carbonaceous material (1-1) with a BET specific surface area of 1675 m 2 / g and an average pore diameter of 1.89 nm. Various physical properties of the carbonaceous material (1-1) were measured. The results are shown in Table 1.

[0125] <Comparative Example 1-2>

[0126] The same operations as in Comparative Example 1-1 were performed to obtain a carbonaceous material. Subsequently, the obtained carbonaceous material was gradually heated to 600 °C at a heating rate of 24 °C / min, to 900 °C at a heating rate of 12 °C / min, and to 1000 °C at a heating rate of 1.67 °C / min in a nitrogen atmosphere (gas flow rate: 1 L / min), and then held at 1000 °C for 60 minutes for heat treatment. Thereafter, it was naturally cooled in the atmosphere of the gas used (nitrogen) until the furnace temperature reached below 70 °C (cooling time was about 3.0 hours) to obtain a heat-treated carbonaceous material. The carbonaceous material was finely pulverized so that the average particle size reached 6 μm to obtain a carbonaceous material (1-2) with a BET specific surface area of 1593 m 2 / g and an average pore diameter of 1.87 nm. Various physical properties of the carbonaceous material (1-2) were measured. The results are shown in Table 1.

[0127] <Comparative Example 1-3>

[0128] The same operations as in Comparative Example 1-1 were performed to obtain a carbonaceous material. Subsequently, the obtained carbonaceous material was gradually heated to 600 °C at a heating rate of 24 °C / min, to 900 °C at a heating rate of 12 °C / min, and to 1100 °C at a heating rate of 1.67 °C / min in a nitrogen atmosphere, and then held at 1100 °C for 60 minutes for heat treatment. Thereafter, it was naturally cooled in the atmosphere of the gas used (nitrogen) until the furnace temperature reached below 70 °C (cooling time was about 3.0 hours) to obtain a heat-treated carbonaceous material. The carbonaceous material was finely pulverized so that the average particle size reached 6 μm to obtain a carbonaceous material (1-3) with a BET specific surface area of 1515 m 2 / g and an average pore diameter of 1.87 nm. Various physical properties of the carbonaceous material (1-3) were measured. The results are shown in Table 1.

[0129] <Comparative Example 1-4>

[0130] The same operations as in Comparative Example 1-1 were performed to obtain a carbonaceous material. Subsequently, the obtained carbonaceous material was gradually heated to 600 °C at a heating rate of 24 °C / min, to 900 °C at a heating rate of 12 °C / min, and to 1200 °C at a heating rate of 1.67 °C / min in a nitrogen atmosphere, and then held at 1200 °C for 60 minutes for heat treatment. Thereafter, it was naturally cooled in the atmosphere of the gas used (nitrogen) until the furnace temperature reached below 70 °C (cooling time was about 3.0 hours) to obtain a heat-treated carbonaceous material. The carbonaceous material was finely pulverized so that the average particle size reached 6 μm to obtain a carbonaceous material with a BET specific surface area of 1476 m 2 / g, a carbonaceous material (1-4) with an average pore diameter of 1.88 nm. Various physical properties of the carbonaceous material (1-4) were measured. The results are shown in Table 1.

[0131] <Comparative Example 2-1>

[0132] In the same manner as in Example 2, a secondary activated granular carbonaceous material with a BET specific surface area of 1695 m 2 / g and an average pore diameter of 2.07 nm was obtained. Thereafter, acid cleaning and deacidification treatment were carried out in the same manner as in Comparative Example 1-1. After the treatment, the accompanying combustion gas and the aforementioned carbonaceous material were discharged together into a container filled with air, and cooled to 200 °C or lower (cooling time was about 1.0 hour) in this atmosphere (the total amount of oxidizing gas per unit mass of the secondary activated granular carbonaceous material in the container was 1.5 L / Kg or more), to obtain a carbonaceous material. The carbonaceous material was micro-crushed so that the average particle size reached 6 μm, to obtain a carbonaceous material with a BET specific surface area of 1709 m 2 / g and an average pore diameter of 2.07 nm (2-1). Various physical properties of the carbonaceous material (2-1) were measured. The results are shown in Table 1.

[0133] <Comparative Example 2-2>

[0134] In the same manner as in Comparative Example 2-1, a carbonaceous material was obtained. Thereafter, heat treatment was carried out in the same manner as in Comparative Example 1-2, and natural cooling was carried out in a nitrogen atmosphere, thereby obtaining a carbonaceous material. The carbonaceous material was micro-crushed so that the average particle size reached 6 μm, to obtain a carbonaceous material with a BET specific surface area of 1648 m 2 / g and an average pore diameter of 2.10 nm (2-2). Various physical properties of the carbonaceous material (2-2) were measured. The results are shown in Table 1.

[0135] <Comparative Example 2-3>

[0136] In the same manner as in Comparative Example 2-1, a carbonaceous material was obtained. Thereafter, heat treatment was carried out in the same manner as in Comparative Example 1-3, and natural cooling was carried out in a nitrogen atmosphere, thereby obtaining a carbonaceous material. The carbonaceous material was micro-crushed so that the average particle size reached 6 μm, to obtain a carbonaceous material with a BET specific surface area of 1581 m 2 / g and an average pore diameter of 2.04 nm (2-3). Various physical properties of the carbonaceous material (2-3) were measured. The results are shown in Table 1.

[0137] <Comparative Example 2-4>

[0138] The same operation as in Comparative Example 2-1 was carried out to obtain a carbonaceous material. Thereafter, the same operation as in Comparative Example 1-4 was carried out for heat treatment, and natural cooling was carried out in a nitrogen atmosphere, whereby a carbonaceous material was obtained. The carbonaceous material was finely pulverized so that the average particle size reached 6 μm, and a carbonaceous material (2-4) having a BET specific surface area of 1526 m 2 / g and an average pore diameter of 2.11 nm was obtained. Various physical properties of the carbonaceous material (2-4) were measured. The results are shown in Table 1.

[0139] The same operation as in Example 1 was carried out to prepare an electrode composition (2-4), a polarizable electrode (2-4), and an electrochemical device (2-4). Various measurements were carried out in the same manner as in Example 1. The results of each measurement are shown in Table 2.

[0140] <Comparative Example 3-1>

[0141] The same operation as in Example 3 was carried out to obtain a secondary activated granular carbonaceous material having a BET specific surface area of 2232 m 2 / g and an average pore diameter of 2.23 nm. Thereafter, acid cleaning and deacidification treatment were carried out in the same manner as in Comparative Example 1-1. After the treatment was completed, the accompanying combustion gas was discharged into a container filled with air, and it was cooled to 200 °C or lower (the cooling time was about 1.0 hour) in this atmosphere (the total amount of oxidizing gas per unit mass of the secondary activated granular carbonaceous material in the container was 1.5 L / Kg or more), and a carbonaceous material was obtained. The carbonaceous material was finely pulverized so that the average particle size reached 6 μm, and a carbonaceous material (3-1) having a BET specific surface area of 2243 m 2 / g and an average pore diameter of 2.23 nm was obtained. Various physical properties of the carbonaceous material (3-1) were measured.

[0142] The results are shown in Table 1.

[0143]

[0144] [Fabrication of the measurement electrode element]

[0145] Using the carbonaceous materials prepared in Examples 1 to 3 and Comparative Examples 1-1 to 3-1, an electrode composition was obtained according to the following method for fabricating an electrode, and a polarizable electrode was fabricated using the same. Further, a measurement electrode element (electrochemical device) was fabricated using the polarizable electrode. Using the obtained measurement electrode element, capacitance measurement, durability test, resistance measurement, and gas generation amount measurement were carried out according to the following methods. The results of each measurement are shown in Table 2.

[0146] As electrode constituent components, the carbonaceous materials, conductive aids, and binders prepared in Examples 1 to 3 and Comparative Examples 1-1 to 3-1 were previously dried under reduced pressure (0.1 KPa or less) in an atmosphere at 120°C for 16 hours or more before use.

[0147] The above-mentioned carbonaceous material, conductive aid, and binder were weighed so that the ratio of (mass of carbonaceous material):(mass of conductive aid):(mass of binder) reached 81:9:10, and kneaded. As the above-mentioned conductive aid, conductive carbon black "DENKA BLACK Granular" manufactured by Denki Kagaku Kogyo Co., Ltd. was used, and as the above-mentioned binder, polytetrafluoroethylene "6J" manufactured by Mitsui DuPont Co., Ltd. was used. After kneading, it was cut into thin sheets with a side length of 1 mm or less for further homogenization, and a pressure of 400 Kg / cm 2 was applied using a coin forming machine to obtain a coin-shaped secondary formed product. Using a roll press, the obtained secondary formed product was formed into a sheet with a thickness of 160 μm ± 5%, and then cut into a specified size (30 mm × 30 mm) to produce Figure 1 the electrode composition 1 as shown. After drying the obtained electrode composition 1 in a reduced pressure atmosphere at 120°C for 16 hours or more, the mass, sheet thickness, and dimensions were measured and used for the following measurements.

[0148] As Figure 2 shown, the conductive adhesive 2 "HITASOL GA-703" manufactured by Hitachi Chemical Co., Ltd. was coated on the etched aluminum foil 3 manufactured by Hozen Co., Ltd. to a coating thickness of 100 μm. Then, as Figure 3 shown, the etched aluminum foil 3 coated with the conductive adhesive 2 was bonded to the pre-cut sheet-like electrode composition 1. Further, using an ultrasonic welding machine, the ear 4 made of aluminum with a sealing material 5 manufactured by Hozen Co., Ltd. was welded to the etched aluminum foil 3. After welding, the obtained laminate was vacuum dried at 120°C to obtain a polarized electrode 6 having an aluminum current collector.

[0149] As Figure 4 shown, the aluminum laminated resin sheet manufactured by Hozen Co., Ltd. was cut into a rectangle (200 mm in length × 60 mm in width) and folded in half, and one side ( Figure 4 in (1)) was thermocompression bonded to prepare a bag-shaped outer packaging sheet 7 with the remaining two sides open. With the help of a cellulose separator "TF-40" (not shown) manufactured by Nippon Kodo Paper Co., Ltd., a laminate formed by overlapping two of the above-mentioned polarized electrodes 6 was produced. This laminate was inserted into the outer packaging sheet 7, and one side ([[]]END]] Figure 5Perform thermocompression bonding on (2) in it to fix the polarizable electrode 6. Then, after vacuum drying it at 120°C in a reduced-pressure atmosphere for 16 hours or more, inject an electrolyte solution into a drying oven with an argon atmosphere (dew point of -90°C or lower). As the electrolyte solution, use an acetonitrile solution of 1.0 mol / L tetraethylammonium tetrafluoroborate manufactured by Kishida Chemical Co., Ltd. After the electrolyte solution has infiltrated the laminate within the outer packaging sheet 7, thermocompression bond the remaining side (( Figure 5 in (3)) to fabricate Figure 5 the electrochemical device 8 shown.

[0150] [Capacitance measurement]

[0151] For the obtained electrochemical device 8, use "CAPACITOR TESTER PFX2411" manufactured by Kikusui Electronics Industry Co., Ltd. At 25°C and -30°C, perform constant-current charging at a current of 200 mA relative to the electrode surface area until the voltage reaches 3.0 V. Furthermore, perform supplementary charging at a constant voltage of 3.0 V for 30 minutes, and after the supplementary charging is completed, perform discharging at 25 mA. Calculate the obtained discharge curve data by the energy conversion method as the capacitance (F). Specifically, after charging, discharge until the voltage reaches zero, and calculate the capacitance (F) from the discharge energy of the discharge at this time. Obtain the capacitance (F / g) obtained by dividing the calculated capacitance (F) by the mass of the carbonaceous material of the electrode and the capacitance (F / cc) obtained by dividing it by the volume per unit electrode.

[0152] [Durability test]

[0153] The durability test is carried out according to the following method. After the aforementioned capacitance measurement, while applying a voltage of 3.0 V to the electrochemical device in a constant-temperature bath at 60°C and maintaining it for 400 hours, perform capacitance measurement at 25°C and -30°C in the same manner as above. According to the following formula, calculate the capacity retention rate for each temperature from the capacitance before and after the durability test. Consider before starting to apply a voltage of 3.0 V in the constant-temperature bath at 60°C as before the durability test, and after maintaining it for 400 hours as after the durability test.

[0154] Capacity retention rate (%)

[0155] = Capacitance per unit mass of the carbonaceous material after the durability test / Capacitance per unit mass of the carbonaceous material before the durability test × 100.

[0156] [Measurement of gas generation amount]

[0157] Measure the dry mass and the mass in water of the measurement electrode element. Calculate the volume of the element from the buoyancy force generated and the density of water. Correct the gas volume calculated from the change in the volume of the element before and after the durability test with the temperature difference during the measurement to obtain the gas generation amount. That is, the gas generation amount is obtained according to the following formula. Note that in the formula, the element mass A represents the mass of the element in air (g), and the element mass W represents the mass of the element in water (g).

[0158] Gas generation amount (cc) =

[0159] {(Element mass A after durability test - Element mass W after durability test) - (Element mass A before durability test - Element mass W before durability test)} / (273 + Measurement temperature after durability test (°C) / (273 + Measurement temperature before durability test (°C)).

[0160] The value obtained by dividing the above gas generation amount by the mass of the carbonaceous material further constituting the electrode composition is taken as the gas generation amount per unit mass (cc / g) of the carbonaceous material.

[0161]

[0162] As shown in Table 2, it can be confirmed that in Examples 1 to 3, the electrochemical devices (1) to (3) respectively fabricated using the polarizable electrodes (1) to (3) incorporating the carbonaceous material of the present invention have a higher initial capacitance, an excellent capacitance retention rate, and can suppress the gas generation amount, as compared with the electrochemical devices (1-1) to (3-1) fabricated using the carbonaceous materials (1-1) to (3-1) of Comparative Examples 1-1 to 3-1.

[0163] The electrochemical device of the present invention can suppress the decrease in the initial capacitance associated with the reduction in specific surface area and pore volume, can maintain a sufficient capacitance even after the durability test, and shows a high gas generation suppression effect. That is, if the carbonaceous material of the present invention is used for the electrode, an electrochemical device with a high initial capacitance, a high gas generation suppression effect, and excellent durability can be obtained.

[0164] Description of the reference numerals

[0165] 1 Electrode composition

[0166] 2 Conductive adhesive

[0167] 3 Etched aluminum foil

[0168] 4 Tab

[0169] 5 Sealing material

[0170] 6 Polarizable electrode

[0171] 7 Bag-shaped outer packaging sheet

[0172] 8 Electrochemical device

[0173] (1) One side joined by thermal compression

[0174] (2) One side contacted by the tab

[0175] (3) The remaining side of the bag-shaped outer packaging sheet

Claims

1. A carbonaceous material having a BET specific surface area of 1550 to 2500 m 2 / g, and the value of oxygen content / hydrogen content per unit specific surface area is 1.00 to 2.04 mg / m 2 , and the value of oxygen content / hydrogen content is 2.0 to 4.

3.

2. The carbonaceous material according to claim 1, wherein The conductivity obtained by measuring the powder resistance at a load of 12 kN is 9 S / cm or less.

3. The carbonaceous material according to claim 1 or 2, having a hydrogen content of 0.44 to 1.00% by mass.

4. The carbonaceous material according to any one of claims 1 to 3, wherein, The carbonaceous material is based on a carbon precursor derived from plants.

5. The carbonaceous material according to claim 4, wherein the carbon precursor is derived from coconut shells.

6. A method for manufacturing a carbonaceous material, comprising: A heating step of heating the raw material carbonaceous material to 330 °C or higher in an oxidizing gas atmosphere; and a cooling step of cooling the raw material carbonaceous material heated to 330 °C or higher in an oxidizing gas atmosphere in a non-oxidizing gas atmosphere. Including multiple heating steps carried out at 330 °C or higher in an oxidizing gas atmosphere, and the heating step includes an activation step and a deacidification step. After the acid cleaning is carried out after the cooling step following any one of the multiple heating steps carried out in an oxidizing gas atmosphere, and then the deacidification step is carried out. At least after the final heating step carried out in an oxidizing gas atmosphere, the cooling step is carried out in a non-oxidizing gas atmosphere.

7. The manufacturing method of the carbonaceous material according to claim 6, wherein, In the cooling step, the temperature of the raw material carbonaceous material is cooled to 200 °C or lower.

8. An electrode active material for an electrochemical device, which is formed of the carbonaceous material according to any one of claims 1 to 5.

9. An electrode for an electrochemical device, which contains the electrode active material for an electrochemical device according to claim 8.

10. An electrochemical device, which includes the electrode for an electrochemical device according to claim 9.

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