JP7414233B2 - Manufacturing method of carbonaceous material for power storage device and carbonaceous material for power storage device - Google Patents

Description

The present invention relates to a carbonaceous material for power storage devices and a method for manufacturing the same.

In recent years, mobile terminals such as mobile phones, notebook computers, and pad-type information terminal devices have become rapidly popular. Various power storage devices (for example, secondary batteries such as lithium ion secondary batteries; various capacitors such as lithium ion capacitors) are used as power sources for these mobile terminals.

Carbonaceous materials are used as conductive agents (including conductive aids) or active materials in electrodes of power storage devices. For example, carbon black, which is a common carbonaceous material, is used not only as a conductive agent but also as an electrode active material for capacitors.

Carbon black is generally obtained by carbonizing hydrocarbon oil. More specifically, the hydrocarbons contained in the oil are incompletely combusted in a high-temperature combustion gas stream to advance a thermal decomposition reaction, thereby converting the hydrocarbons into carbon black. For production, a reactor is used in which a cylindrical combustion zone lined with refractory bricks, a reaction zone, and a reaction termination zone are coaxially connected. First, fuel is combusted in the combustion zone of the reactor to generate high-temperature combustion gas, which is then supplied to the reaction zone. Oil is then introduced into the reaction zone to convert hydrocarbons to carbon black in the combustion gas stream. The gas stream containing carbon black supplied from the reaction zone is rapidly cooled in a reaction termination zone to terminate the reaction and the resulting carbon black is collected.

Thus, carbon black is a product of incomplete combustion of hydrocarbons and therefore contains a large amount of residual hydrogen. Since residual hydrogen becomes a resistance component, the conductivity of carbon black as a single particle tends to decrease. In addition, during the manufacturing process, it comes into contact with cooling water containing metal salts and metal corroded pieces on manufacturing equipment. As a result, the carbon black contains a metal component as an impurity, and therefore, from this point of view as well, the carbon black has poor conductivity.

From the viewpoint of avoiding the contamination of metal components, a method of carbonization using plasma is known. For example, Patent Document 1 proposes a method of manufacturing carbon nanoparticles by performing discharge between electrodes formed of metal in a solution containing carbon atoms. Arc discharge is used for the discharge.

Methods that do not use metal electrodes have also been proposed. For example, Patent Document 2 proposes a method of forming graphene by generating pulsed plasma by spark discharge or instantaneous arc discharge in a solvent between a pair of carbon electrodes. Patent Document 3 proposes a method of producing onion-like carbon by causing pulse plasma discharge between carbon electrodes in a liquid.

In addition, Patent Document 4 discloses that bubbles are generated in a liquid containing a compound containing hydrogen and carbon, and electromagnetic waves (microwaves, etc.) are irradiated to generate plasma in the liquid, decomposing the compound and producing hydrogen. Hydrogen generation methods have been proposed that generate hydrogen and synthesize carbon compounds.

Japanese Patent Application Publication No. 2009-215147 JP2017-222538A International Publication No. 2010/104200 Pamphlet International Publication No. 2004/094306 pamphlet

The method of Patent Document 1 utilizes arc discharge between metal electrodes. Since the metal electrode is consumed by the high heat associated with arc discharge, it is difficult to avoid mixing metal impurities into the resulting carbonaceous material.

In the methods of Patent Document 2 and Patent Document 3, although high-quality carbide is locally formed, the quality of the carbide (crystal structure, physical properties, etc.) is highly uneven in the entire carbonaceous material obtained. Furthermore, since there is a large amount of hydrogen remaining in the carbonaceous material, it is difficult to increase the conductivity of the carbonaceous material. Furthermore, the yield of carbonaceous material decreases due to the large amount of heat generated by the discharge. In addition, the electrodes are severely worn out, resulting in poor continuous productivity.

The method of Patent Document 4 has the main purpose of recovering hydrogen, and since the by-product carbon compound contains a large amount of residual hydrogen, it is difficult to obtain a carbon compound with high conductivity. . Therefore, such carbon compounds recovered as by-products of hydrogen have only been used as fuel to obtain thermal energy by combustion.

In view of the above, one aspect of the present invention includes (1) a step of generating a microwave plasma in a liquid organic material containing a non-aromatic compound as a main component to obtain a carbide;
(2) separating the carbide;
(3) A method for producing a carbonaceous material for an electricity storage device, comprising a step of heating the carbide separated in the step (2) in an inert gas atmosphere to obtain a carbonaceous material.

Another aspect of the present invention is that the crystallite size (L ₀₀₂ ) in the (002) plane obtained by powder X-ray diffraction is in the range of 2 nm or more and 50 nm or less,
The present invention relates to a carbonaceous material for a power storage device having a BET specific surface area in a range of 30 m ² /g or more and 500 m ² /g or less.

According to the above aspect of the present invention, a carbonaceous material that has high conductivity and can be used as an active material for power storage devices can be provided by a simple method.

Embodiments of the present invention will be described in detail below. Note that the scope of the present invention is not limited to the embodiments described here, and various changes can be made without departing from the spirit of the present invention.

A method for manufacturing a carbonaceous material for an electricity storage device according to one aspect of the present invention includes:
(1) A step of generating a microwave plasma in a liquid organic material containing a non-aromatic compound as a main component to obtain a carbide;
(2) a step of separating carbide;
(3) A step of heating the carbide separated in step (2) in an inert gas atmosphere to obtain a carbonaceous material.

The carbonaceous material for a power storage device according to another aspect of the present invention has a crystallite size (L ₀₀₂ ) in the (002) plane obtained by powder X-ray diffraction in a range of 2 nm or more and 50 nm or less, and a BET specific surface area of 30 m ² /g or more and 500m ² /g or less.

In step (1), as in Patent Document 4, the organic material is decomposed to generate a large amount of hydrogen and to obtain carbide. Therefore, a large amount of hydrogen remains in the carbide. Such carbides are only byproducts of hydrogen, have low conductivity, and vary in quality, so it has been difficult to use them as carbonaceous materials for power storage devices. Therefore, such carbides have conventionally been used only as fuel to obtain thermal energy by combustion.

According to the above aspect of the present invention, an organic material containing a non-aromatic compound as a main component is carbonized by microwave plasma, and step (3) is also performed. As a result, hydrogen can be sufficiently removed from low-quality carbide, which is merely a by-product of hydrogen, by a simple method. Furthermore, since carbonization is performed using microwave plasma and there is no need to use metal electrodes, contact of carbide with metal components is reduced. As a result, mixing of metal impurities into the carbonaceous material is suppressed. From these viewpoints, a high-quality carbonaceous material with a small amount of residual hydrogen and suppressed incorporation of metal impurities can be obtained. In carbonaceous materials, by adjusting the amount of residual hydrogen to a small value, the BET specific surface area can be reduced and L ₀₀₂ can be controlled within a specific range. A small amount of residual hydrogen and a small amount of metal impurities suggest that the carbonaceous material has a fine crystal structure, has high crystallinity, and has improved conductivity. Further, the carbonaceous material can also reversibly absorb and release carrier ions (for example, alkali metal ions (lithium ions, etc.)) of the electricity storage device. That is, the carbonaceous material also has a function as an electrode active material of the electricity storage device. Therefore, carbonaceous materials are suitable for use in power storage devices (particularly as electrode materials).

Note that the present invention also includes a carbonaceous material obtained by the manufacturing method according to the above aspect.

The present invention also includes an electrode for a power storage device containing the above-mentioned carbonaceous material, and a power storage device including this electrode.

Hereinafter, a method for manufacturing a carbonaceous material and a carbonaceous material according to an embodiment of the present invention will be described in more detail.

[Method for producing carbonaceous material]
(Step (1))
In step (1), a carbide is generated from an organic material using microwave plasma.
(organic material)
As the organic material, one whose main component is a non-aromatic compound is used. Although such organic materials have a relatively high hydrogen content, the amount of residual hydrogen can be effectively reduced by steps (1) to (3). Further, contamination of metal components is also suppressed. As a result, high conductivity can be ensured.

An organic material containing a non-aromatic compound as a main component means an organic material in which the ratio of non-aromatic compounds to the entire organic material is 50% by mass or more (even 90% by mass or more).

A non-aromatic compound is a compound that does not have an aromatic ring. Examples of the non-aromatic compound include at least one selected from the group consisting of chain compounds and non-aromatic cyclic compounds. The non-aromatic compound may be a saturated compound or an unsaturated compound. A non-aromatic cyclic compound has a non-aromatic ring. Note that a non-aromatic ring means a ring that does not satisfy Huckel's rule.

The non-aromatic compound may be a hydrocarbon or may contain a heteroatom. Further, the non-aromatic compound may have a substituent. The heteroatom may be included in a chain skeleton or a non-aromatic ring, or may be included in a substituent. The substituent may be a hydrocarbon group, a heteroatom-containing group, or both.

The number of carbon atoms in the non-aromatic compound is, for example, 4 or more, may be 5 or more, 6 or more, or 10 or more. Depending on the structure of the compound, the number of carbon atoms in the compound may be selected within a range that does not volatilize in step (1). The upper limit of the number of carbon atoms in the compound can be selected within a range that allows the organic material to be in a liquid state when the compound is brought into contact with microwave plasma. For example, the number of carbon atoms is 50 or less.

Examples of the heteroatom include at least one selected from the group consisting of a nitrogen atom, an oxygen atom, a sulfur atom, a silicon atom, and a halogen atom. Note that the halogen atom is included in the non-aromatic compound as a substituent. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

The number of heteroatoms contained in one molecule of a non-aromatic compound is not particularly limited, and is, for example, 1 to 10, may be 1 to 6, or may be 1 to 4. Often there may be 1, 2 or 3 pieces.

Among non-aromatic compounds, examples of chain compounds include chain compounds containing hydrocarbons and heteroatoms.

Examples of chain hydrocarbons include saturated or unsaturated aliphatic hydrocarbons. Examples of saturated aliphatic hydrocarbons include hexane, heptane, octane, nonane, decane, dodecane, undecane, paraffin, and the like. Examples of unsaturated aliphatic hydrocarbons include chain olefins (hexene, octene, decene, etc.), dienes, and the like.

Examples of the chain compound containing a hetero atom include a chain hydrocarbon having a hetero atom-containing group as a substituent. Examples of chain hydrocarbons include the above-mentioned saturated or unsaturated aliphatic hydrocarbons. Examples of the heteroatom-containing group as a substituent include a halogen atom (the above-mentioned halogen atom), an oxygen-containing group (hydroxy group, alkoxy group, carboxy group, alkoxycarbonyl group, acyloxy group, oxo group (=O), etc.) ), nitrogen-containing groups (amino groups, substituted amino groups (alkylamino groups, dialkylamino groups, etc.), nitro groups, cyano groups, etc.), sulfur-containing groups (mercapto groups, etc.), and silicon-containing groups (hydrosilyl groups, alkoxysilyl groups, etc.) group, etc.). When the substituent contains carbon atoms, the number of carbon atoms contained in one substituent is, for example, 1 to 10, may be 1 to 6, may be 1 to 4, and may be 1 to 4. , 2 or 3.

The chain compound containing a hetero atom also includes a compound containing a hetero atom in the main chain. Examples of such compounds include polyalkylene imines (such as poly(C _2-4 alkylene imine) such as triethylenetetramine), polyalkylene sulfides (such as poly(C 2-4 alkylene) sulfide), and polyalkylene oxides (such as poly(C _2-4 alkylene) sulfides). poly(C _2-4 alkylene) oxide, etc.). Such a compound may have a substituent. Examples of the substituent include the above heteroatom-containing groups described as substituents for chain hydrocarbons.

Among non-aromatic compounds, examples of non-aromatic cyclic compounds include non-aromatic cyclic hydrocarbons and non-aromatic cyclic compounds containing a hetero atom.

Examples of non-aromatic cyclic hydrocarbons include saturated or unsaturated alicyclic hydrocarbons. The alicyclic hydrocarbon may be a bridged ring. The non-aromatic cyclic hydrocarbon has, for example, 5 to 20 carbon atoms, and may also have 6 to 20 carbon atoms.

The alicyclic hydrocarbon may have at least one substituent selected from the group consisting of an aliphatic hydrocarbon group and an alicyclic hydrocarbon group. The hydrocarbon group as a substituent may be either saturated or unsaturated.

Examples of aliphatic hydrocarbon groups include alkyl groups (C _1-6 alkyl groups (methyl group, ethyl group, n-propyl group, 2-propyl group, n-butyl group, s-butyl group, t-butyl group, etc.) ), alkenyl groups (C _2-6 alkenyl groups (vinyl group, allyl group, etc.), etc.), alkynyl groups (C _2-6 alkynyl groups, etc.), dienyl groups (C _3-6 dienyl groups, etc.), etc. . Examples of alicyclic hydrocarbon groups include cycloalkyl groups (C _4-8 cycloalkyl groups (cyclopentyl, cyclohexyl, etc.), etc.), cycloalkenyl groups (C _4-8 cycloalkenyl groups (cyclohexenyl, etc.), etc.) Examples include.

Specific examples of non-aromatic cyclic hydrocarbons include cycloalkanes (cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, 1,4-dimethylcyclooctane, 1,5-dimethylcyclooctane, etc.), cycloalkanes, Examples include alkenes (cyclopentene, cyclohexene, cyclooctene, etc.), cycloalkadienes (cyclooctadiene, etc.), bridged cyclic hydrocarbons (norbornane, norbornene, decahydronaphthalene, adamantane, dicyclopentadiene, etc.). In addition to these compounds, hydrogenated aromatic hydrocarbons may also be used.

Examples of the non-aromatic cyclic compound containing a hetero atom include a non-aromatic cyclic hydrocarbon having a hetero atom-containing group as a substituent. Examples of the non-aromatic cyclic hydrocarbons include the above-mentioned saturated or unsaturated alicyclic hydrocarbons. Examples of heteroatom-containing groups as substituents include, in addition to the heteroatom-containing groups described above as substituents for chain hydrocarbons, halogen-containing groups (such as halogenated hydrocarbon groups), hydroxyalkyl groups, and aminoalkyl groups. etc. can also be mentioned. The cyclic hydrocarbon has at least one substituent selected from these substituents. When a substituent contains carbon atoms, the number of carbon atoms contained in one substituent can be selected from the ranges described for chain hydrocarbon substituents.

Examples of the halogenated hydrocarbon group as a substituent include a hydrocarbon group having a halogen atom (at least one selected from the halogen atoms listed above). Examples of the hydrocarbon group include the aforementioned hydrocarbon groups (aliphatic hydrocarbon group and alicyclic hydrocarbon group). A halogenated aliphatic hydrocarbon group (such as a halogenated alkyl group) is preferred.

One type of non-aromatic compound may be used, or two or more types may be used in combination.

The non-aromatic compound is preferably a saturated or unsaturated chain compound or a saturated or unsaturated non-aromatic cyclic compound. Among these, saturated hydrocarbons are preferred. Although such compounds contain a relatively large amount of hydrogen, hydrogen can be sufficiently removed through steps (1) to (3), resulting in high-quality carbonaceous materials with high conductivity. can be obtained.

The proportion of saturated hydrocarbons in the entire non-aromatic compound is, for example, 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass. Even when the proportion of saturated hydrocarbons is high in this way, there are many reaction starting points, the crystals of the carbonaceous material produced can be adjusted to be small, and the carbonaceous material tends to become amorphous, which is advantageous for increasing the capacity. The proportion of saturated hydrocarbons in the total non-aromatic compounds may be 100% by mass or less.

Further, when using a saturated hydrocarbon having 6 or more carbon atoms (preferably 8 or more or 10 or more), the proportion of such saturated hydrocarbons in the entire non-aromatic compound is, for example, 50% by mass. The content is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass. In this case, the number of reaction starting points is further increased, crystal growth is further suppressed, and the material is more likely to become amorphous, making it possible to further increase the capacity. The proportion of saturated hydrocarbons in the total non-aromatic compounds may be 100% by mass or less.

The carbon number of the above saturated hydrocarbon is, for example, 6 or more and 50 or less, 6 or more and 40 or less, 6 or more and 30 or less, 8 or more and 50 or less, 8 or more and 40 or less, 8 or more and 30 or less, 10 or more and 50 or less, and 10 or more and 40. It may be less than or equal to 10 or more and less than or equal to 30.

As the non-aromatic compound, chain compounds having 6 or more carbon atoms (preferably 8 or more or 10 or more) (eg, decane, dodecane, undecane, etc.) are also preferable. The number of carbon atoms in such a chain compound is, for example, 6 or more and 50 or less, 6 or more and 40 or less, 6 or more and 30 or less, 8 or more and 50 or less, 8 or more and 40 or less, 8 or more and 30 or less, 10 or more and 50 or less, and 10 or more. It may be 40 or less, or 10 or more and 30 or less. When such a compound is used, the carbonaceous material tends to become more amorphous, making it possible to further increase the capacity.

Liquid paraffin is also preferred as the non-aromatic compound. Liquid paraffin is a mixture of hydrocarbons and contains a large amount of naphthenic hydrocarbons (such as cycloalkanes). Liquid paraffin also includes chain aliphatic hydrocarbons. Since liquid paraffin contains a plurality of compounds, the resulting carbonaceous material is more likely to have an amorphous structure. Therefore, the capacity can be further increased.

As the non-aromatic compound, a compound containing a hetero atom (for example, a hetero atom other than a halogen atom (especially at least a nitrogen atom)) is also preferable. When such a compound is used, structural distortion is likely to be formed in the carbonaceous material. Since it easily absorbs carrier ions in power storage devices, it can be easily used as an electrode active material. In addition, higher capacity is expected.

From the viewpoint of more easily achieving the effect of forming structural distortion in carbonaceous materials, non-aromatic compounds containing heteroatoms other than halogen (particularly at least nitrogen atoms) in the entire non-aromatic compound The proportion of the compound is, for example, 10% by mass or more, and may be 30% by mass or more. The proportion of the non-aromatic compound containing a heteroatom other than a halogen atom (especially at least a nitrogen atom) in the entire non-aromatic compound is, for example, 100% by mass or less, and 80% by mass or less. You can. From the perspective of making it easier to control the crystal structure of carbonaceous materials, the proportion of non-aromatic compounds containing heteroatoms other than halogen atoms (especially at least nitrogen atoms) in the total number of non-aromatic compounds should be , preferably 50% by mass or less.

The proportion of non-aromatic compounds containing heteroatoms other than halogen atoms in the total non-aromatic compounds is 10% by mass (or 30% by mass) or more and 100% by mass or less, 10% by mass (or 30% by mass) %) to 80% by mass, or 10% by mass (or 30% by mass) to 50% by mass.

The organic material only needs to contain a non-aromatic compound as a main component, and may further contain an aromatic organic compound. The proportion of the non-aromatic compound in the organic material may be 50% by mass or more. From the viewpoint of easily obtaining higher capacity, the proportion of non-aromatic compounds in the entire organic material is preferably 70% by mass or more, more preferably 80% by mass or more, and 90% by mass. It is more preferable that it is above. Alternatively, an organic material composed only of non-aromatic compounds may be used. The proportion of non-aromatic compounds in the entire organic material is, for example, 100% by mass or less.

A liquid material is used as the organic material. The organic material only needs to be liquid (that is, have fluidity) at least when brought into contact with the microwave plasma. The organic material may be liquefied by heating. By generating microwave plasma in a liquid organic material, that is, by bringing the microwave plasma into contact with the organic material, local exposure of the organic material to high temperatures is suppressed, and the entire organic material is exposed to the microwave plasma. It will be exposed evenly. The presence of the liquid organic material also maintains the microwave plasma for a sufficient period of time for the reaction to proceed. When using an organic material other than a liquid, even when the reaction activity is increased under microwave plasma, the time is too short for complete dehydrogenation of the organic material, and a large amount of hydrogen remains in the product. However, when using a liquid organic material, by going through steps (1) to (3), the amount of residual hydrogen can be reduced and a carbonaceous material having a more uniform crystal structure can be obtained.

Note that the liquid organic material may have a viscosity of 3 mPa·s or less when brought into contact with microwave plasma. Further, the liquid organic material may have a viscosity of 1 mPa·s or less at 25°C.

(Microwave plasma)
Microwave plasma has high temperature and high energy, and can be effectively used for decomposing and synthesizing substances. As a method of generating microwave plasma, a known technique may be referred to, and for example, J. Plasma Fusion Res Vol. 89 No. 4 (2013) 199-216 can be referred to.

Since a liquid organic material is used, the plasma is preferably generated within the organic material (ie, using submerged plasma technology). By using liquid plasma technology, organic substances taken into the plasma during plasma generation are decomposed, but a closed reaction field is formed by organic substances outside the plasma, so a uniform crystal structure is formed in the plasma. Cheap. Plasma generated in a liquid is macroscopically low-temperature because it exists in the liquid, making it safe and easy to handle. Furthermore, since the plasma is in a liquid with a high material density, the reaction rate is extremely high. Further, if microwaves are continuously supplied, plasma can be continuously generated (or maintained).

To generate microwave plasma, for example, a known plasma generation device that can generate microwave plasma in a liquid can be used. A plasma generator includes, for example, a container capable of containing a liquid organic material, a microwave irradiation unit, and a device for receiving (or capturing) microwaves supplied from the microwave irradiation unit to generate plasma in the liquid. It is equipped with an antenna. A plasma generator usually includes an exterior body that houses a container. The microwave irradiation unit may be attached to the exterior body. As the microwave irradiation unit (and the exterior body), a microwave oven or a device having a principle similar to a microwave oven may be used. Such devices are inexpensive and easily available, and can irradiate high-power microwaves.

The antenna is arranged with at least the tip portion (preferably the entire antenna) that generates plasma immersed in the liquid. By using such an antenna, it is possible to suppress the incorporation of impurities compared to the case where the electrodes of Patent Documents 1 to 3 are immersed in a liquid, and it is possible to further suppress a decrease in the conductivity of the carbonaceous material. As the antenna, any antenna can be used without particular limitation as long as it can receive microwaves from the microwave irradiation unit. If the antenna is a conductor with a length that is half the wavelength of the microwave, a standing wave will be generated in the antenna. Therefore, the length of the antenna is determined depending on the frequency of the microwave. For example, when using a microwave with a frequency of 2.45 GHz, the length of the antenna may be about 5 cm. When microwaves are received by an antenna, the electric field becomes stronger at the tip of the antenna, and plasma is generated at this tip.

A microwave irradiation unit usually includes a circuit for emitting microwaves. Examples of such circuits include circuits using magnetrons, klystrons, traveling wave tubes, gyrotrons, Gunn diodes, and the like. Microwave plasma can be generated by setting the frequency of a power source when generating electromagnetic waves to 1 GHz or more (preferably 2 GHz or more (for example, 2.45 GHz)).

The container is preferably made of a heat-resistant material. Furthermore, if the antenna has a structure in which microwaves are received through a container, the container is preferably made of a material that has high transmittance to microwaves. For example, a container made of heat-resistant glass is suitable. The shape of the container is not particularly limited as long as it can hold the organic material while the liquid organic material is brought into contact with the microwave plasma. The contact between the microwave plasma and the organic material may be performed in a batch, semi-batch, or continuous manner. Therefore, the container includes a tubular container (for example, piping, etc.) through which the liquid organic material passes at a predetermined flow rate.

In step (1), a liquid organic material is brought into contact with microwave plasma to convert the organic material into carbide. More specifically, a liquid organic material is placed in a container with at least the tip of the antenna immersed in the organic material, and by irradiating microwaves, the antenna receives (or captures) the microwaves in the liquid. Generate plasma. The microwave is irradiated from a microwave irradiation unit. By generating microwave plasma in a liquid, it is possible to bring the microwave plasma into contact with the organic material. The organic material is carbonized by the energy of the microwave plasma and a carbide is obtained.

The temperature of the organic material when bringing the organic material into contact with the microwave plasma may be any temperature as long as the organic material as a whole maintains a liquid state. The temperature of the organic material is, for example, in a range of 0°C or higher and 200°C or lower. Considering the vapor pressure, safety (flash point, etc.) of the organic material, the temperature of the organic material is preferably in the range of 0°C or more and 100°C or less, and more preferably in the range of 0°C or more and 60°C or less. Note that the above temperature of the organic material is an average temperature obtained by averaging the temperatures of the organic material measured at ten arbitrary locations in the organic material using a non-contact thermometer from the outside.

The time for irradiating the microwave is not particularly limited. The irradiation time is determined in consideration of, for example, the frequency and output of the microwave, the amount of organic material (in the case of a continuous type, the flow rate of the organic material, etc.), and the like. For example, in the case of a batch type, the irradiation time is, for example, in a range of 0.1 seconds or more and 600 seconds or less, and may be in a range of 1 second or more and 300 seconds or less.
Note that the microwave irradiation may be performed continuously or intermittently.

Step (1) may be performed in the atmosphere or under an inert gas atmosphere. Examples of the inert gas include at least one selected from the group consisting of helium, nitrogen, and argon. Among these, from the viewpoint of availability, economy, and reactivity under plasma, it is preferable to use nitrogen or argon, and it is preferable to use an inert gas containing at least nitrogen. In consideration of safety, it is preferable to perform step (1) (particularly microwave irradiation) under an inert gas atmosphere. When the organic material includes a material that is easily ignited, step (1) may be performed, for example, while supplying an inert gas to the space above the organic material (such as the space above the organic material in a container).

Step (1) may be performed under pressure, but from the viewpoint of easily ensuring safety, it is preferably performed under atmospheric pressure.

(Step (2))
In step (2), the carbide obtained in step (1) is separated from the organic material remaining in liquid form without carbonization. Separation is not particularly limited, and any known separation method (for example, sedimentation, centrifugation, and/or filtration) can be employed. Further, if necessary, the carbide may be rinsed with a liquid organic material (for example, fresh organic material), and the carbide may be separated again.

If the carbide used in step (3) contains a large amount of liquid organic material, the carbonaceous material may stick together during step (3), or hydrogen and dioxide generated by thermal decomposition of the organic material may Crystal destruction and porosity easily progress due to gases such as carbon. By performing step (2), impurities contained in the carbonaceous material can be reduced and high conductivity can be easily ensured. From this point of view, in step (2), it is preferable to reduce the amount of organic material remaining in the carbide to be separated. Further, it is preferable to reduce the amount of organic material remaining in the carbide, also from the viewpoint of making it easier to remove the organic material by volatilization or the like in step (3).

The carbide separated in step (2) may be pulverized or classified as necessary prior to step (3). By performing the pulverization treatment prior to step (3), the specific surface area can be increased, so even if oxidizing gas is generated in step (3), the influence of structural changes in the carbonaceous material can be reduced. Moreover, by performing the classification process, the average particle size of the carbide can be controlled, and the heat treatment in step (3) can be performed more uniformly.

The particle size of the carbide after pulverization is not particularly limited, and may be determined depending on the purpose and usage form of the carbonaceous material finally obtained. For example, carbide is pulverized so that the average particle size of the carbonaceous material falls within the range described below.

Grinding of the carbide is not particularly limited, and can be carried out using a known grinder. Examples of the crusher include at least one selected from the group consisting of jet mills, ball mills, hammer mills, and rod mills.

Classification is not particularly limited, and examples thereof include classification using a sieve, wet classification, and dry classification. Examples of the wet classifier include classifiers that utilize the principles of gravity classification, inertial classification, hydraulic classification, or centrifugal classification. Examples of the dry classifier include classifiers that utilize the principles of sedimentation classification, mechanical classification, or centrifugal classification.

Grinding and classification can be performed using independent grinders and classifiers, respectively. In this case, classification may be performed while pulverizing, continuous classification may be performed after pulverizing, or classification may be performed once pulverizing. Grinding and classification can also be performed using a grinder that has both functions. For example, pulverization and classification can be performed using a jet mill equipped with a dry classification function.

(Step (3))
In step (3), a carbonaceous material is obtained from the carbide separated in step (2). More specifically, a carbonaceous material is obtained by heating carbide in an inert gas atmosphere. By performing step (3), impurity elements (oxygen, hydrogen, etc.) that can become resistance components can be reduced, and the conductivity of the carbonaceous material can be increased. In step (3), the carbide separated in step (2) may be provided as is, or the separated carbide may be subjected to pulverization treatment and/or classification treatment.

As the carbide to be heated in step (3), two or more types of carbide having different compositions may be mixed and used, if necessary. For example, two or more types of carbide obtained under different conditions in step (1) and/or step (2) may be combined, or two or more types of carbide obtained under different conditions for crushing and/or classification may be combined. good.

Further, if necessary, a hydrocarbon such as polyethylene, polypropylene, polystyrene, etc. may be mixed as an additive into the carbide heated in step (3) within a range that does not impair the effects of the present invention. These additions can promote dehydrogenation or reductively remove oxygen on the surface.

The heating temperature in step (3) is, for example, 550°C or higher, may be 600°C or higher or 800°C or higher, preferably 900°C or higher or 1000°C or higher, more preferably 1100°C or higher or 1150°C or higher. . When the heating temperature is within this range, it is easy to reduce the amount of functional groups remaining in the carbonaceous material, and the value of the hydrogen content ratio (= hydrogen content / carbon content) in the carbonaceous material becomes high. things are suppressed. Therefore, it becomes easier to ensure high electrical conductivity, and it becomes easier to grow the crystal structure. Furthermore, when used as an electrode material for an electricity storage device, an increase in irreversible capacity is suppressed. The heating temperature is, for example, 3000°C or lower, preferably 2000°C or lower or 1500°C or lower, and may be 1200°C or lower. When the heating temperature is within this range, the crystals are small and the particles formed are amorphous, making it easier to ensure a high capacity. Heating may be performed in one step, in multiple steps, or while increasing the temperature.

The heating temperature in step (3) is 550°C to 3000°C (or 2000°C), 600°C to 3000°C (or 2000°C), 800°C to 3000°C (or 2000°C), 900°C to 3000°C ( (or 2000℃) or less, 1000℃ or more and 3000℃ (or 2000℃) or less, 1100℃ or more and 3000℃ (or 2000℃) or less, 1150℃ or more and 3000℃ (or 2000℃) or less, 550℃ or more and 1500℃ (or 1200℃) or less ℃) or less, 600℃ or more and 1500℃ (or 1200℃) or less, 800℃ or more and 1500℃ (or 1200℃) or less, 900℃ or more and 1500℃ (or 1200℃) or less, 1000℃ or more and 1500℃ (or 1200℃) or less , 1100°C or more and 1500°C (or 1200°C) or less, or 1150°C or more and 1500°C (or 1200°C) or less.

Heating is performed under an inert gas atmosphere. A non-oxidizing gas is used as the inert gas. Examples of the non-oxidizing gas include at least one selected from the group consisting of helium, nitrogen, and argon.

Heating may be performed under the flow of inert gas. In this case, the flow rate of the inert gas is not particularly limited, but may be 1 mL/min or more, 5 mL/min or more, or 10 mL/min or more per 1 g of carbide. When the amount of inert gas supplied is within such a range, impurities can be efficiently removed and the specific surface area of the carbonaceous material can be easily adjusted.

The heating time is not particularly limited, but the time during which the carbide is exposed to the temperature in the above range is, for example, 0.05 hours or more and 10 hours or less, and 0.05 hours or more and 3 hours or less. The duration may be 0.05 hours or more and 1 hour or less.

Heating may be performed under atmospheric pressure or under increased pressure. Moreover, heating can also be performed under reduced pressure (for example, under a pressure of 10 kPa or less).

The carbonaceous material obtained in this way may be pulverized or classified as necessary. However, the surface exposed when the carbonaceous material is pulverized is highly active and may cause side reactions in the electricity storage device, so when adjusting the average particle size, it is necessary to pulverize the carbonaceous material before step (3). It is preferable to do this.

[Carbonaceous material]
The carbonaceous material according to the above aspect of the present invention can be obtained by the manufacturing method described above.
The BET specific surface area of the carbonaceous material is 30 m ² /g or more, preferably 40 m ² /g or more, and more preferably 50 m ² /g or more. When the BET specific surface area is less than 30 m ² /g, there are few electrical contacts and it is difficult to ensure high conductivity. Further, when used as an electrode active material, the carrier ion storage capacity is also reduced. Further, the BET specific surface area is 500 m ² /g or less, may be 400 m ² /g or less, and is preferably 300 m ² /g or less or 200 m ² /g or less. When the BET specific surface area exceeds 500 m ² /g, the dispersibility becomes low and the irreversible capacity increases when used as an electrode active material.

The BET specific surface area of the carbonaceous material is 30 m ² /g (or 40 m ² /g) or more and 500 m ² /g or less, 30 m ² /g (or 40 m ² /g) or more and 400 m ² /g or less, 30 m ² /g ( or 40 m ² /g to 200 m ² /g, 50 m ² /g to 500 m ² /g, 50 m ² /g to 400 m ² /g, or 50 m ² /g to 200 m ² /g. good.

The crystallite size (L ₀₀₂ ) in the (002) plane obtained by X-ray diffraction of the carbonaceous material is 2 nm or more, preferably 3 nm or more, and more preferably 5 nm or more. When L ₀₀₂ is within such a range, a carbonaceous material having higher conductivity can be easily obtained. L ₀₀₂ may be 50 nm or less. From the viewpoint that the carbonaceous material tends to become amorphous and is advantageous for increasing capacity, L ₀₀₂ is preferably 15 nm or less, more preferably 10 nm or less.

L ₀₀₂ is 2 nm (or 3 nm) or more and 50 nm or less, 2 nm (or 3 nm) or more and 15 nm or less, 2 nm (or 3 nm) or more and 10 nm or less, 5 nm or more and 50 nm or less, 5 nm or more and 15 nm or less, or 5 nm or more and 10 nm or less. good.

The interplanar spacing (d ₀₀₂ ) of (002) obtained in X-ray diffraction of the carbonaceous material is, for example, 0.34 nm or more, preferably 0.341 nm or more. When d ₀₀₂ is in such a range, it tends to become amorphous, which is advantageous from the viewpoint of increasing capacity. d ₀₀₂ is, for example, 0.36 nm or less, preferably 0.359 nm or less, and may be 0.347 nm or less. When d ₀₀₂ is within such a range, the crystal structure can be easily controlled and the conductivity can be further improved.

d ₀₀₂ is 0.34 nm (or 0.341 nm) or more and 0.36 nm or less, 0.34 nm (or 0.341 nm) or more and 0.359 nm or less, or 0.34 nm (or 0.341 nm) or more and 0.347 nm or less There may be.

In the argon laser Raman spectrum of a carbonaceous material at a wavelength of 532 nm, the intensity ratio of the intensity (ID) of a peak (second peak) in the range of 1300 cm ^-1 to 1400 cm ^-1 to the first peak intensity (IG): ID /IG is, for example, 0.6 or more, preferably 0.8 or more, and may be 0.87 or more or 0.89 or more. When the ID/IG ratio is within such a range, it is easier to ensure higher conductivity and to exhibit high capacity while suppressing the growth of a graphite-type layered crystal structure. The ID/IG ratio is, for example, 1 or less, and may be 0.95 or less. When the ID/IG ratio is in such a range, defects are likely to be formed in the carbonaceous material that can function as reversible adsorption (or occlusion) and desorption sites for carrier ions. Therefore, the function as an electrode active material is enhanced, which is advantageous from the viewpoint of increasing capacity. Note that the ID/IG ratio is a parameter related to the crystallinity of the carbonaceous material.

ID/IG ratio is 0.6 or more and 1 (or 0.95) or less, 0.8 or more and 1 (or 0.95) or less, 0.87 or more and 1 (or 0.95) or less, or 0.89 or more It may be 1 (or 0.95) or less.

The average particle diameter of the carbonaceous material is, for example, 200 μm or less. When the average particle size is within this range, there are fewer free paths for diffusion of metal ions and hydrogen ions within the particles, making it easier to ensure high ionic conductivity, and the contact rate between particles increases, making it even more effective. Easy to ensure high conductivity. The average particle diameter of the carbonaceous material is preferably 0.02 μm or more from the viewpoint of easy recovery using a filter or the like while suppressing particle aggregation.

In the carbonaceous material, contamination with impurities is reduced, and the content of metal elements contained in the carbonaceous material is kept low. Carbonaceous materials are of high quality while ensuring higher conductivity. The content of metal elements contained in the carbonaceous material is, for example, 500 ppm or less, and can also be reduced to 200 ppm or less. Therefore, it is particularly suitable as a carbonaceous material for power storage devices.

Despite the small average diameter of the primary particles contained in carbonaceous materials, carbonaceous materials have high sensitivity and high quality when used as electrode materials for power storage devices, and have excellent functionality as electrode active materials. has. In the carbonaceous material, the average diameter of the primary particles is, for example, 1 nm or more and 500 nm or less, preferably 5 nm or more and 300 nm or less.

《Analysis of carbonaceous materials or carbides》
Note that the analysis of carbonaceous materials or carbides is performed according to the following procedure.

(1) X-ray diffraction Powder X-ray diffraction of carbonaceous materials was performed using an X-ray diffraction device "MiniFlex II" manufactured by Rigaku Co., Ltd., using CuKα rays made monochromatic by a Ni filter as a radiation source, and using a carbonaceous material filled in a sample holder. This is done on powdered materials. More specifically, in powder X-ray diffraction, for example, a sample holder filled with carbonaceous material powder is set on the observation stand of an X-ray diffraction device, the scanning axis is 2θ/θ, and the sampling width is 0.01°. ~0.02° and a scan speed of 20°/min. In the obtained diffraction pattern, the peak position is determined by the centroid method (a method of determining the centroid position of the diffraction line and determining the peak position using the corresponding 2θ value), and the diffraction pattern of the (111) plane of the high-purity silicon powder for standard material Correct using the peak.

The average interplanar spacing d ₀₀₂ of the (002) planes of the carbonaceous material is determined from the following formula, which is a modification of the Bragg formula.
d ₀₀₂ =λ/(2×sinθ)
λ: Wavelength of CuKα ray (=0.15418 nm)
θ: 1/2 angle of 2θ of the peak position determined by the center of gravity method

The crystallite size L ₀₀₂ of the carbonaceous material is determined by the following Scherrer formula L ₀₀₂ = Κλ/(β×cosθ)
β = ((half width (measured value)) x 2 - (half width (reference value)) x 2)/2
Note that the half-width (measured value) is the 2θ of the peak position determined by the centroid method (peak top in the range of 25.9 to 26.6), and the half-width (reference value) is the height of the standard material. This is the 2θ (28.443) of the diffraction peak of the (111) plane of pure silicon powder.

(BET specific surface area)
The specific surface area of a carbonaceous material determined by the BET method (sometimes simply referred to as the BET specific surface area) can be calculated from the following formula (A1) using an approximate formula derived from the BET formula using a gas adsorption method using nitrogen gas. This is the required specific surface area.
BET specific surface area = (v _m Na/22400) x 10 ^-18 (A1)
(Here, v _m is the adsorption amount (cm ³ /g) required to form a monomolecular layer on the sample surface, N is Avogadro's number 6.022×10 ²³ , and a (nm ² ) is This is the area occupied by adsorbate molecules on the sample surface (molecular occupied cross-sectional area).

v _m in formula (A1) is determined by a three-point method using nitrogen adsorption at liquid nitrogen temperature using the following approximate formula (A2) derived from the BET formula.
p/[v(p ₀ -p)]=(1/v _m c)+[(c-1)/v _m c](p/p ₀ ) (A2)
(Here, v is the actually measured adsorption amount (cm ³ /g), p ₀ is the saturated vapor pressure, p is the absolute pressure, and c is a constant reflecting the heat of adsorption.)

The adsorption amount v is measured as the amount of nitrogen adsorbed onto the carbonaceous material at the liquid nitrogen temperature using "BELL Sorb Mini" manufactured by BELL Japan in the following manner. A carbonaceous material pulverized to a particle size of about 5 μm to 50 μm is used as a sample. A sample is filled into a sample tube, and while the sample tube is cooled to -196° C., the pressure is once reduced, and then nitrogen (purity 99.999%) is adsorbed onto the sample at a desired relative pressure. The amount of nitrogen adsorbed on the sample when equilibrium pressure is reached at each relative pressure is defined as adsorption amount v.

(Raman spectrum)
The Raman spectrum of the carbonaceous material is measured using a Raman spectrometer (Raman spectrometer "LabRAM ARAMIS (VIS)" manufactured by Horiba, Ltd.). More specifically, it is measured by the following procedure.
A particle to be measured, arbitrarily selected from a carbonaceous material, is set on the stage of the observation stand of a Raman spectrometer, the magnification of the objective lens is set to 100x, and the particle is focused. Raman spectra are measured while irradiating particles with argon ion laser light under the following analysis conditions.
<Analysis conditions>
Raman spectrometer: LabRAM ARAMIS (VIS) manufactured by Horiba, Ltd.
Measurement wavelength range: 50cm ^-1 ~ 4000cm ^-1
Integration number: 100 times Exposure time: 1 second Laser wavelength: 532 nm

In the measured Raman spectrum, a peak (first peak) in the range of 1580 cm ^-1 to 1620 cm ^-1 is defined as the G band. Further, a peak (second peak) in the range of 1300 cm ^-1 to 1400 cm ^-1 is defined as the D band. The peak top intensity of each peak (IG: peak top intensity of the first peak, ID: peak top intensity of the second peak) is measured. From these peak top intensities, the ratio of ID to IG (=ID/IG) is determined.

(Average particle size)
The average particle diameter of each carbonaceous material is a particle diameter (median diameter (D50)) at which the cumulative volume is 50% in a volume-based particle size distribution determined by a laser scattering method. More specifically, the average particle diameter is determined by the following procedure. First, a predetermined amount of carbonaceous material is poured into an aqueous solution containing 0.3% by mass of a surfactant, and treated with an ultrasonic cleaner for 10 minutes or more to be dispersed in the aqueous solution. As the surfactant, "Toriton X-100" manufactured by Nacalai Tesque Co., Ltd. is used. The particle size distribution of the obtained dispersion liquid is measured using a laser scattering type particle size/particle size distribution measuring device ("Microtrack MT3000" manufactured by Nikkiso Co., Ltd.). D50 is determined from this particle size distribution.
Regarding the average particle diameter of the carbide, the average particle diameter (D50) is determined in the same manner as above except that the carbide is used instead of the carbonaceous material.

(Average diameter of primary particles)
The average diameter of the primary particles of the carbonaceous material is determined by the following procedure.
First, ten primary particles whose shapes are clear in a scanning electron microscope (SEM) photograph of a carbonaceous material are selected. The diameter of a circle having the same area as the area surrounded by the outline of each primary particle is determined and taken as the particle diameter of each primary particle. The average diameter is determined by averaging this particle diameter for 10 primary particles.

(Analysis of metal element content (ash content))
The content of metal elements may be measured as the ash content. Since the ash content may also contain oxygen atoms, it can be determined that the amount of metal elements is less than the ash content.
The mass of an alumina crucible that was air-baked at 900°C and left to cool in a desiccator containing silica gel was measured. After vacuum drying for 8 to 10 hours in a constant temperature dryer adjusted to 120°C, 20g of the carbonaceous material, which had been left to cool in a desiccator containing silica gel as a desiccant, was placed in a 50ml alumina crucible, and the crucible and carbonaceous material were separated. Weigh the total mass (crucible + carbonaceous material mass) accurately to 0.1 mg. The alumina crucible containing the carbonaceous material was placed in an electric furnace, and while dry air was introduced into the electric furnace at a rate of 20 L/min, the temperature was raised to 200°C in 1 hour, and then to 700°C over 2 hours. and held at 700° C. for 14 hours to incinerate the carbonaceous material. After ashing, the mixture is left to cool in a desiccator containing silica gel, the total mass of the crucible and ash (crucible + ash mass) is accurately weighed to 0.1 mg, and the ash content is calculated from the following formula.
Ash content (ppm) = 10000000×
{(Mass of crucible + ash) - (Mass of crucible) / (Mass of crucible + carbonaceous material) - (Mass of crucible)}

[Electrode for power storage device and power storage device]
Carbonaceous materials have high conductivity as described above, and therefore can be used as conductive agents. Further, since carbonaceous materials can reversibly occlude and release carrier ions in power storage devices, they can also be used as electrode active materials in power storage devices (capacitors, secondary batteries, etc.). By using a carbonaceous material as an electrode material, high sensitivity and high charge/discharge efficiency can be ensured. Carbonaceous materials are particularly suitable for electrode materials for negative electrodes of non-aqueous electrolyte secondary batteries, lithium ion capacitors, etc. because they can reversibly absorb and release alkali metal ions such as lithium ions.

(Negative electrode)
The negative electrode includes, for example, a negative electrode mixture containing the above carbonaceous material (hereinafter sometimes referred to as a first carbonaceous material) and a binder. Since the first carbonaceous material has high conductivity, the negative electrode mixture does not necessarily need to contain a conductive additive, but may further contain a conductive additive if necessary.

The negative electrode usually includes a negative electrode mixture and a negative electrode current collector that supports the negative electrode mixture. The negative electrode can be formed, for example, by mixing the components of the negative electrode mixture with a dispersion medium to prepare a paste, supporting the paste on a current collector, and press-molding the paste. The dispersion medium is removed by drying at an appropriate stage. The dispersion medium can be selected depending on the type of binder, and for example, an organic dispersion medium and/or water are used. Examples of the organic dispersion medium include alcohols, esters, ketones, amides, nitriles, and/or hydrocarbons.

As the negative electrode current collector, a metal foil or a porous metal body may be used. By coating or filling such a negative electrode current collector with the above paste, the negative electrode mixture is supported. As the metal constituting the current collector, a metal is selected that is stable at the potential to which the negative electrode is exposed during charging and discharging. Examples of the metal constituting the current collector include copper or a copper alloy.

The binder is not particularly limited as long as it does not react with the electrolyte. As the binder, fluororesin (polyvinylidene fluoride (PVDF), polytetrafluoroethylene, etc.), rubbery polymer (styrene-butadiene rubber (SBR), etc.), cellulose ether (for example, carboxymethyl cellulose (CMC) or its salt, etc.). Examples of CMC salts include alkali metal salts (such as sodium salts) and ammonium salts. One type of binder may be used alone, or two or more types may be used in combination. For example, a rubbery polymer such as SBR and CMC or a salt thereof may be combined.

The content of the binder in the negative electrode mixture (solid content) is, for example, 0.1% by mass or more and 15% by mass or less, and may be 0.5% by mass or more and 13% by mass or less, and 1% by mass or more. % or more and 10% by mass or less. The content of the binder is determined in consideration of the specific surface area of the carbonaceous material, the resistance of the electrode, the binding effect, etc.

Examples of the conductive aid include conductive carbonaceous materials other than the first carbonaceous material (hereinafter sometimes referred to as second carbonaceous materials). Examples of the conductive aid include carbon black, carbon nanotubes, carbon fibers, vapor grown carbon fibers (VGCF), and the like. One type of conductive aid may be used, or two or more types may be used in combination.

The content of the conductive support agent in the negative electrode mixture (solid content) is, for example, 0.1% by mass or more and 10% by mass or less, and may be 0.5% by mass or more and 7% by mass or less, and 0.1% by mass or more and 10% by mass or less, and may be 0.5% by mass or more and 7% by mass or less. It may be 5% by mass or more and 5% by mass or less. The content of the conductive additive may be determined by taking into consideration, for example, the conductivity of the first carbonaceous material, the type of the conductive additive, the dispersibility of the conductive additive in the negative electrode mixture, and the like.

The thickness of the negative electrode mixture layer formed on the surface of the negative electrode current collector is, for example, 10 μm or more and 80 μm or less, may be 20 μm or more and 75 μm or less, or may be 20 μm or more and 60 μm or less. When forming a negative electrode mixture layer on the surface of a sheet-like current collector such as metal foil, the negative electrode mixture layer may be formed on one surface (principal surface) of the current collector, or may be formed on both surfaces ( It may be formed on the main surface). When forming negative electrode mixture layers on both surfaces of the current collector, the thickness of the negative electrode mixture layer formed on each surface may be within the above range.

(Electricity storage device)
In addition to the above-mentioned negative electrode, the power storage device can include a positive electrode and an electrolyte (such as a non-aqueous electrolyte). A separator may be interposed between the negative electrode and the positive electrode. For components other than the negative electrode, known configurations can be adopted. Below, the configuration of a power storage device will be described using a non-aqueous electrolyte secondary battery as an example.

The positive electrode includes, for example, a positive electrode mixture containing a material (active material) capable of reversibly occluding and releasing carrier ions, a binder, and a conductive agent. A positive electrode typically includes a positive electrode mixture and a positive electrode current collector that supports the positive electrode mixture. The positive electrode can be formed in the same manner as the negative electrode. As the material constituting the positive electrode, known materials for positive electrodes of non-aqueous electrolyte secondary batteries can be used. As the metal constituting the positive electrode current collector, a metal is selected that is stable at the potential to which the positive electrode is exposed during charging and discharging. Examples of the metal constituting the positive electrode current collector include aluminum or an aluminum alloy.

Examples of the positive electrode material (active material) include composite metal chalcogen compounds that can reversibly occlude and release carrier ions. Examples of such compounds include layered oxides (LiM ¹ O ₂ ), olibic acids (LiM ² PO ₄ ), spinel compounds (LiM ³ ₂ O ₄ , etc.). ^{M 1} to M ³ are metal elements; As ^M1 , for example, at least one selected from the group consisting of Co, Ni, and Mn may be mentioned, and a combination of these metal elements and other metal atoms may be used.As ^M2 , , Fe is preferable, and it may be a combination of Fe and other metal elements.Mn is preferable as ^M3 , and it may be a combination of Mn and other metal elements.As the layered oxide, Examples include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , and _LiNix Co _y Mo _z O ₂ (where x+y+z=1). Examples of olibic acids include LiFePO _4. Spinel type Examples of the compound include LiMn ₂ O ₄ and the like.
These positive electrode materials may be used alone or in combination of two or more.

Examples of the binder include the binders exemplified for the negative electrode. The content of the binder in the positive electrode mixture (solid content) can be selected from the range described for the content of the binder in the negative electrode mixture.

Examples of the conductive agent include at least one selected from the group consisting of the second carbonaceous material, the first carbonaceous material, and graphite (artificial graphite, natural graphite, etc.) exemplified as conductive aids for the negative electrode. The content of the conductive agent in the positive electrode mixture (solid content) can be selected from the range described for the content of the conductive aid in the negative electrode mixture.

The thickness of the positive electrode mixture layer can be selected from the range described for the thickness of the negative electrode mixture layer.

As the separator, any known separator used in non-aqueous electrolyte secondary batteries can be used without particular limitation. Examples of the separator include nonwoven fabrics, porous films, and laminates of nonwoven fabrics and porous films. The separator may contain a resin, or may contain a resin and a filler (such as an inorganic filler). When using a gel electrolyte (or solid electrolyte) containing a non-aqueous electrolyte and a swelling polymer, this electrolyte may be interposed between the positive electrode and the negative electrode instead of the separator. A gel electrolyte (or solid electrolyte) may be used in combination with a separator.

The non-aqueous electrolyte includes a salt (solute) containing carrier ions and a non-aqueous solvent that dissolves the salt. In addition to these components, the nonaqueous electrolyte may be a gel electrolyte that further contains a swelling polymer. For the non-aqueous electrolyte, known materials used for non-aqueous electrolytes of non-aqueous electrolyte secondary batteries can be used.

The salt can be selected depending on the type of nonaqueous electrolyte secondary battery. Lithium salts are used in nonaqueous electrolyte secondary batteries that use lithium ions as carriers. Examples of lithium salts include LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , lithium halide (LiCl, LiBr, etc.), LiB(C ₆ H ₅ ) ₄ , and LiN(SO ₃ CF ₃ ). ₂ etc. The non-aqueous electrolyte may contain one type of lithium salt, or may contain two or more types of lithium salts.

Examples of nonaqueous solvents include cyclic carbonates (propylene carbonate, ethylene carbonate, etc.), chain carbonates (dimethyl carbonate, diethyl carbonate, etc.), chain ethers (dimethoxyethane, diethoxyethane, etc.), and cyclic ethers (tetrahydrofuran, 2 -methyltetrahydrofuran, 1,3-dioxolane, etc.), lactones (γ-butyl lactone, etc.), sulfolane, etc., but are not limited to these. The non-aqueous electrolyte may contain one type of non-aqueous solvent, or may contain two or more types of non-aqueous solvents.

A non-aqueous electrolyte secondary battery can be manufactured by immersing a positive electrode and a negative electrode in a non-aqueous electrolyte while electrically isolated. The positive electrode and the negative electrode can be electrically isolated, for example, by interposing a separator or a gel electrolyte between them. Usually, a battery is produced by accommodating a positive electrode, a negative electrode, a separator if necessary, and a nonaqueous electrolyte in a battery case.

The shape of the battery is not particularly limited, and may be coin-shaped, button-shaped, circular, square, or laminated. The positive electrode and the negative electrode may be wound or laminated with a separator interposed therebetween to form a wound type electrode group or a laminated type electrode group.

[Example]
EXAMPLES Hereinafter, the present invention will be specifically explained based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

《Preparation of plasma generator》
Using a commercially available general-purpose microwave oven capable of irradiating microwaves at 2.45 GHz, a plasma generator was prepared according to the following procedure. First, a hole was formed in the top of the microwave oven to allow the gas generated inside the microwave to escape to the outside, and piping was arranged. In order to reduce the leakage of microwaves from the hole to the outside of the microwave oven, copper tape was wrapped around the piping at the top of the microwave oven, and it was surrounded by stainless steel mesh. Then I covered the entire top of the microwave with aluminum foil.

《Example 1》
(1) Manufacture of carbonaceous material Using the prepared plasma generator and special grade liquid paraffin manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. as a non-aromatic compound, carbonaceous material was produced using the following procedure. manufactured the material.

300 mL of liquid paraffin was measured and placed in a 1 L beaker, and the antenna was immersed in the liquid paraffin. In this state, the beaker was placed in a plasma generator. The device was operated to irradiate the antenna in the beaker with microwaves at a rated high frequency output of 700W. At this time, it was confirmed that plasma was generated in the liquid paraffin due to the generation of bubbles accompanied by light emission from the tip of the antenna. The microwave irradiation was repeated except that the microwave irradiation was temporarily interrupted every time 1000 mL of gas was generated from inside the plasma generator. The time from the start of microwave irradiation to the end of irradiation was 3 minutes and 21 seconds. The liquid paraffin in the beaker was carbonized by the action of plasma generated from the tip of the antenna, and the formation of black particulate solids was confirmed.

The black dispersion in the beaker was subjected to centrifugal separation, and the solid content, charcoal, was recovered. The recovered charred material was washed with acetone, filtered under suction, and dried at 80° C. for 6 hours using a drier. In this way, the char was separated (yield: 0.9 g).

The separated carbide was placed in a crucible and heat-treated. Specifically, the carbide was placed in a horizontal annular furnace made by Koyo Thermo in its crucible, and heated to 1000°C at a heating rate of 7°C/min under a nitrogen stream (flow rate: 1 L/min), and then heated at 1000°C for 30 minutes. Maintained. Then, it was cooled to room temperature under a nitrogen atmosphere. In this way, a carbonaceous material (yield: 0.6 g) was obtained.

(2) Preparation of coin-shaped lithium secondary battery (counter electrode Li half cell) (preparation of electrode)
Using the carbonaceous materials obtained in each Example and each Comparative Example, electrodes were produced according to the following procedure.
96 parts by mass of a carbonaceous material, 4 parts by mass of PVDF (polyvinylidene fluoride), and 90 parts by mass of NMP (N-methylpyrrolidone) were mixed to obtain a slurry. The obtained slurry was applied to a copper foil with a thickness of 14 μm, and after drying, it was pressed to obtain an electrode with a thickness of 75 μm. The density of the obtained electrode was 0.8 to 1.0 g/cm ³ .

(Preparation of half cell)
The electrode produced above was used as a working electrode, and metallic lithium was used as a counter electrode and a reference electrode. As a solvent, propylene carbonate and ethylene glycol dimethyl ether were mixed at a volume ratio of 1:1. LiClO ₄ was dissolved in this solvent at a concentration of 1 mol/L and used as a nonaqueous electrolyte. A porous membrane made of polypropylene was used as the separator. Coin half cells were prepared in a glove box under an argon atmosphere.

《Example 2》
0.7 g of the carbide separated in the same manner as in Example 1 was placed in a crucible in a horizontal annular furnace manufactured by Koyo Thermo, and heated at a temperature increase rate of 7° C./min under a nitrogen stream (flow rate: 1 L/min). The temperature was raised to 1200°C and maintained at 1200°C for 30 minutes. Except for the above, a carbonaceous material (yield: 0.5 g) was obtained in the same manner as in Example 1.
A lithium secondary battery was produced in the same manner as in Example 1 except that the obtained carbonaceous material was used.

《Example 3》
0.9 g of the carbide separated in the same manner as in Example 1 was placed in a crucible in a horizontal annular furnace manufactured by Koyo Thermo, and heated at a temperature increase rate of 7° C./min under a nitrogen stream (flow rate: 1 L/min). The temperature was raised to 600°C and maintained at 600°C for 30 minutes. Except for the above, a carbonaceous material (yield: 0.7 g) was obtained in the same manner as in Example 1.
A lithium secondary battery was produced in the same manner as in Example 1 except that the obtained carbonaceous material was used.

《Comparative example 1》
A lithium secondary battery was produced in the same manner as in Example 1, except that the dried carbide obtained in Example 1 was used as the carbonaceous material.

"evaluation"
(1) Physical properties of carbonaceous material The BET specific surface area, d ₀₀₂ , L ₀₀₂ , ID/IG ratio, D50, and average diameter of primary particles of the carbonaceous material were determined by the previously described procedure. In addition, the content of metal components contained in the carbonaceous material was determined by the procedure described above.

(2) DC resistance and charging/discharging characteristics A charging/discharging test was conducted using a charging/discharging test device (manufactured by Toyo System Co., Ltd., "TOSCAT"). The initial DC resistance was the resistance value generated when 0.5 mA was applied for 3 seconds. Lithium doping was performed at a rate of 70 mA/g relative to the mass of the active material (carbonaceous material), and doping was performed until the lithium potential became 1 mV. Further, a constant voltage of 1 mV was applied to the lithium potential for 8 hours to complete the doping. The capacity (mAh/g) at this time was defined as the charging capacity. Next, dedoping was performed at a rate of 70 mA/g relative to the mass of the active material until the lithium potential reached 2.5 V, and the discharged capacity at this time was defined as the discharge capacity. The percentage of discharge capacity/charge capacity was defined as charge/discharge efficiency.

Table 1 shows the results of Examples and Comparative Examples. In Table 1, T1 to T3 are Examples 1 to 3, and R1 is Comparative Example 1.

As shown in Table 1, in the example, the DC resistance is significantly lower than that in the comparative example, and high initial charge/discharge efficiency is shown. This shows that the carbonaceous material of the example has high conductivity and functions as an active material that reversibly stores and releases lithium ions, which are carrier ions of a lithium secondary battery. In the example, since the initial charge/discharge efficiency is high, the irreversible capacity is also low.

According to the above aspect of the present invention, a carbonaceous material having high electrical conductivity can be obtained. This carbonaceous material can reversibly occlude and release carrier ions of the electricity storage device, and also has a function as an electrode active material. Therefore, carbonaceous materials are useful as carbonaceous materials (especially electrode materials, etc.) for power storage devices. In addition, the obtained electricity storage device can be used for various purposes, for example, it may be used for mobile terminals that are required to be smaller, thinner, lighter, and/or higher performance, and flexibility is required. May be used for equipment.

Claims (9)

(1) A step of generating a microwave plasma in a liquid organic material containing a non-aromatic compound as a main component to obtain a carbide;
(2) separating the carbide;
(3) a step of heating the carbide separated in the step (2) in an inert gas atmosphere to obtain a carbonaceous material ;
The non-aromatic compound includes at least one selected from the group consisting of a saturated or unsaturated chain compound and a saturated or unsaturated non-aromatic cyclic compound,
The number of carbon atoms in the chain compound is 10 or more,
The non-aromatic compound does not contain a non-aromatic compound containing at least a nitrogen atom, or contains a non-aromatic compound containing at least a nitrogen atom,
A method for producing a carbonaceous material for an electricity storage device , wherein the proportion of the non-aromatic compound containing at least a nitrogen atom to the total non-aromatic compound is 50% by mass or less . The method for manufacturing a carbonaceous material for an electricity storage device according to claim 1, wherein the non-aromatic compound includes a saturated or unsaturated chain compound. The method for producing a carbonaceous material for an electricity storage device according to claim 1, wherein the non-aromatic compound includes a saturated or unsaturated non-aromatic cyclic compound. The method for producing a carbonaceous material for a power storage device according to any one of claims 1 to 3, wherein the non-aromatic compound includes the non-aromatic compound containing at least a nitrogen atom . The method for producing a carbonaceous material for a power storage device according to any one of claims 1 to 4 , wherein the heating temperature in the step (3) is 550°C or more and 3000°C or less. The crystallite size (L ₀₀₂ ) in the (002) plane obtained by powder X-ray diffraction is in the range of 2 nm or more and 10 nm or less,
BET specific surface area is in the range of 30 m ² /g or more and 500 m ² /g or less ,
In the argon laser Raman spectrum with a wavelength of 532 nm, the intensity (ID) of the second peak in the range of 1300 cm -1 to 1400 cm -1 with respect to the intensity (IG) ^of the ^first peak in the range of 1580 cm ^{-1 to} 1620 cm -1 ratio: ID/IG is 0.6 or more and 1 or less , a carbonaceous material for an electricity storage device. The carbonaceous material for an electricity storage device according to claim 6 , wherein the interplanar spacing (d ₀₀₂ ) of the (002) plane is in a range of 0.34 nm or more and 0.36 nm or less. The carbonaceous material for an electricity storage device according to claim 6 or 7 , wherein the content of metal elements is 500 ppm or less. The carbonaceous material for a power storage device according to any one of claims 6 to 8 , which is an electrode active material of a power storage device.