阅读说明：本技术 碳材料及其制造方法、蓄电设备用电极材料以及蓄电设备 (Carbon material, method for producing same, electrode material for electricity storage device, and electricity storage device ) 是由 和田拓也 笹川直树 于 2019-07-30 设计创作，主要内容包括：本发明涉及一种比表面积较大,并且即使在实际上不含粘合剂的情况下也能够容易地形成电极膜的碳材料。本发明涉及一种碳材料,其是BET比表面积为100m~2/g以上的碳材料,其中,在将所述碳材料0.2g填充至直径2cm的圆筒形注射器中的状态下,以16kN的压力进行压缩,将进行了压缩的全部所述碳材料从所述注射器取出并投入孔径4.75mm的筛子,将所述筛子震荡1分钟时,震荡后残存在筛子上的所述碳材料的重量相对于投入筛子的所述碳材料的重量100重量％为90重量％以上。(The present invention relates to a carbon material having a large specific surface area and capable of easily forming an electrode film even when a binder is not substantially contained. The invention relates to a carbon material having a BET specific surface area of 100m 2 A carbon material having a particle size of 90 wt% or more per 100 wt% of the weight of the carbon material charged into a sieve, wherein the carbon material is compressed at a pressure of 16kN in a state where 0.2g of the carbon material is charged into a cylindrical syringe having a diameter of 2cm, all of the compressed carbon material is taken out of the syringe and charged into the sieve having a pore diameter of 4.75mm, and when the sieve is shaken for 1 minute, the weight of the carbon material remaining on the sieve after shaking is 90 wt% or more per 100 wt% of the weight of the carbon material charged into the sieve.)

1. A carbon material having a BET specific surface area of 100m²A carbon material per gram or more, wherein,

the carbon material is compressed under a pressure of 16kN in a state where 0.2g of the carbon material is packed in a cylindrical syringe having a diameter of 2cm, all of the compressed carbon material is taken out of the syringe and is put into a sieve having a pore diameter of 4.75mm, and when the sieve is shaken for 1 minute, the weight of the carbon material remaining on the sieve after shaking is 90 wt% or more relative to 100 wt% of the weight of the carbon material put into the sieve.

2. The carbon material according to claim 1,

the carbon material has a plurality of concave portions and a plurality of convex portions.

3. The carbon material according to claim 2,

the plurality of projections are projections that fit into the plurality of recesses.

4. The carbon material according to any one of claims 1 to 3,

the carbon material comprises a carbide of a resin.

5. The carbon material as claimed in any one of claims 1 to 4,

the carbon material comprises a carbon material having a graphene stacked structure.

6. The carbon material according to claim 5,

the carbon material having a graphene stacked structure is graphite or flaked graphite.

7. The carbon material according to claim 6,

the graphite or exfoliated graphite is a partially exfoliated graphite having a graphite structure and in which graphite is partially exfoliated.

8. A method for producing a carbon material, comprising:

mixing graphite or primary exfoliated graphite with a resin to obtain a 1 st mixture;

adding particles other than a carbon material to the 1 st mixture, and disposing the particles in a matrix of the carbon material constituting the 1 st mixture to form a 2 nd mixture;

a heating step of heating the 2 nd mixture at a temperature of 200 ℃ to 1000 ℃; and

and removing the particles from the heated mixture No. 2.

9. A method for producing a carbon material, comprising:

adding particles different from a carbon material to a resin, and disposing the particles in a matrix of the resin to form a mixture;

a heating step of heating the mixture at a temperature of 200 ℃ to 1000 ℃; and

and removing the particles from the heated mixture.

10. A method for producing a carbon material, comprising:

mixing graphite or primary exfoliated graphite with a resin to obtain a 1 st mixture;

a step of adding particles different from a carbon material to the 1 st mixture, and coating the particles with the carbon material constituting the 1 st mixture to form a 2 nd mixture;

a heating step of heating the 2 nd mixture at a temperature of 200 ℃ to 1000 ℃; and

and removing the particles from the heated mixture No. 2.

11. A method for producing a carbon material, comprising:

a step of adding particles different from a carbon material to a resin, and coating the particles with the resin to form a mixture;

a heating step of heating the mixture at a temperature of 200 ℃ to 1000 ℃; and

and removing the particles from the heated mixture.

12. The method for producing a carbon material as claimed in any one of claims 8 to 11,

the heating step is a step of carbonizing at least a part of the resin.

13. The method for producing a carbon material as claimed in any one of claims 8 to 12,

the step of removing the particles is a step of removing the particles with a solvent.

14. The method for producing a carbon material as claimed in any one of claims 8 to 13,

the average particle diameter of the particles is 0.1 to 1000 [ mu ] m.

15. A carbon material obtained by the method for producing a carbon material according to any one of claims 8 to 14.

16. An electrode material for an electric storage device, comprising the carbon material as claimed in any one of claims 1 to 7 and 15.

17. An electrical storage device is provided with:

an electrode comprising the electrode material for an electricity storage device according to claim 16.

Technical Field

The present invention relates to a carbon material, a method for producing the carbon material, and an electrode material for an electric storage device and an electric storage device using the carbon material.

Background

In recent years, research and development of power storage devices have been widely conducted for portable devices, hybrid vehicles, electric vehicles, household power storage applications, and the like. As an electrode material for an electric storage device, carbon materials such as graphite, activated carbon, carbon nanofibers, and carbon nanotubes are widely used from the environmental viewpoint.

Patent document 1 below discloses an electric double layer capacitor having a polarizable electrode layer containing activated carbon, a conductive assistant, and a binder. The binder serves to bind the current collector and the active material in the electrode. In addition, it also serves to bind the active substances to each other.

Documents of the prior art

Patent document

Patent document 1 International publication No. 2008-029865

Disclosure of Invention

Technical problem to be solved by the invention

In recent years, in the field of electric storage devices such as capacitors and lithium ion secondary batteries, further improvement in battery characteristics is required. However, as described in patent document 1, when a binder is used for an electrode material of an electricity storage device, there is a problem that the internal resistance increases and the battery performance such as cycle characteristics deteriorates. In addition, there is also a problem that battery performance is deteriorated due to side reaction, decomposition, and the like of the binder. Therefore, in an electrode material for an electric storage device, it is desirable to reduce the amount of addition of a binder.

However, when the activated carbon described in patent document 1 is used as an electrode material for an electricity storage device, if the amount of the binder added is not sufficient, there is a problem that it is difficult to form an electrode film. In particular, this tendency is more remarkable when a carbon material having a large specific surface area is used as an electrode material in order to improve battery characteristics such as the capacity of an electric storage device.

The purpose of the present invention is to provide a carbon material having a large specific surface area and capable of easily forming an electrode film even when a binder is not substantially contained, a method for producing the carbon material, and an electrode material for an electric storage device and an electric storage device using the carbon material.

Means for solving the problems

In a broad aspect, the carbon material of the present invention is a carbon material having a BET specific surface area of 100m²A carbon material having a particle size of 90 wt% or more per 100 wt% of the weight of the carbon material charged into a sieve, wherein the carbon material is compressed at a pressure of 16kN in a state where 0.2g of the carbon material is charged into a cylindrical syringe having a diameter of 2cm, all of the compressed carbon material is taken out of the syringe and charged into the sieve having a pore diameter of 4.75mm, and when the sieve is shaken for 1 minute, the weight of the carbon material remaining on the sieve after shaking is 90 wt% or more per 100 wt% of the weight of the carbon material charged into the sieve.

In one specific aspect of the carbon material of the present invention, the carbon material includes a plurality of concave portions and a plurality of convex portions.

In another specific aspect of the carbon material of the present invention, the plurality of convex portions are convex portions that fit into the plurality of concave portions.

In another specific embodiment of the carbon material of the present invention, the carbon material contains a carbide of a resin.

In another specific embodiment of the carbon material of the present invention, the carbon material comprises a carbon material having a graphene stacked structure. Preferably, the carbon material having a graphene stacked structure is graphite or exfoliated graphite. More preferably, the graphite or exfoliated graphite is a partially exfoliated graphite having a graphite structure and in which graphite is partially exfoliated.

In a broad aspect of the method for producing a carbon material of the present invention, the method comprises: mixing graphite or primary exfoliated graphite with a resin to obtain a 1 st mixture; adding particles other than a carbon material to the 1 st mixture, and disposing the particles in a matrix of the carbon material constituting the 1 st mixture to form a 2 nd mixture; a heating step of heating the 2 nd mixture at a temperature of 200 ℃ to 1000 ℃; and a step of removing the particles from the heated 2 nd mixture.

In another broad aspect of the method for producing a carbon material of the present invention, the method comprises: adding particles different from a carbon material to a resin, and disposing the particles in a matrix of the resin to form a mixture; a heating step of heating the mixture at a temperature of 200 ℃ to 1000 ℃; and removing the particles from the heated mixture.

In another broad aspect of the method for producing a carbon material of the present invention, the method comprises: mixing graphite or primary exfoliated graphite with a resin to obtain a 1 st mixture; a step of adding particles different from a carbon material to the 1 st mixture, and coating the particles with the carbon material constituting the 1 st mixture to form a 2 nd mixture; a heating step of heating the 2 nd mixture at a temperature of 200 ℃ to 1000 ℃; and a step of removing the particles from the heated 2 nd mixture.

In another broad aspect of the method for producing a carbon material of the present invention, the method comprises: a step of adding particles different from a carbon material to a resin, and coating the particles with the resin to form a mixture; a heating step of heating the mixture at a temperature of 200 ℃ to 1000 ℃; and removing the particles from the heated mixture.

In one specific aspect of the method for producing a carbon material according to the present invention, the heating step is a step of carbonizing at least a part of the resin.

In another specific aspect of the method for producing a carbon material according to the present invention, the step of removing particles is a step of removing the particles with a solvent.

In another specific embodiment of the method for producing a carbon material of the present invention, the average particle diameter of the particles is 0.1 μm or more and 1000 μm or less.

In another broad aspect of the carbon material of the present invention, the carbon material is obtained by a method for producing a carbon material constituted according to the present invention.

The electrode material for an electric storage device of the present invention contains the carbon material constituted according to the present invention.

The electric storage device of the present invention includes an electrode made of the electrode material for an electric storage device according to the present invention.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there can be provided: a carbon material having a large specific surface area and capable of easily forming an electrode film even when a binder is not substantially contained, a method for producing the carbon material, and an electrode material for an electric storage device and an electric storage device using the carbon material.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) photograph at a magnification of 5000 times of the carbon material obtained in example 2.

FIG. 2 is a Scanning Electron Microscope (SEM) photograph showing the carbon material of comparative example 3 at a magnification of 5000.

FIG. 3 is a photograph showing a carbon material after pressurization in example 2.

FIG. 4 is a photograph showing a carbon material after pressurization in comparative example 3.

Detailed description of the invention

The present invention will be described in detail below.

(carbon Material)

The carbon material of the present invention has a BET specific surface area of 100m²More than gA carbon material. In addition, the carbon material 0.2g in a 2cm diameter cylindrical syringe state, in 16kN pressure compression, the compression of all carbon material from the syringe and put into the hole diameter of 4.75mm sieve. When the screen is shaken for 1 minute after the charging, the weight of the carbon material remaining on the screen after the shaking is 90 wt% or more relative to 100 wt% of the weight of the carbon material charged into the screen. Therefore, the carbon material of the present invention can form a Free-Standing Membrane (Free-Standing Membrane) by the compression of 16kN even though it does not substantially contain a binder. The phrase "substantially free of a binder" means that the content of the binder is 1% by weight or less based on 100% by weight of the material subjected to film formation.

The carbon material of the present invention has a BET specific surface area of 100m²The battery characteristics such as the capacity of the power storage device can be improved by the amount of the electric power storage device. In addition, since the carbon material of the present invention is evaluated to be within the above range, an electrode film can be easily formed even when the carbon material does not substantially contain a binder. The carbon material of the present invention preferably has a plurality of concave portions and a plurality of convex portions. In particular, the plurality of concave portions and the plurality of convex portions are more preferably fitted to each other by pressing. In this case, the electrode film can be further easily formed.

The carbon material of the present invention can reduce the amount of binder added to the electrode film, and thus can reduce the internal electrode resistance of a battery or a capacitor. In addition, since the amount of the binder to be added can be reduced, side reactions, decomposition, and the like of the binder are less likely to occur. Therefore, the battery characteristics of the power storage device can be improved. Further, since the BET specific surface area is within the above range, battery characteristics such as capacity can be improved.

The BET specific surface area can be calculated based on the BET method and from the nitrogen adsorption isotherm. As the measuring apparatus, for example, a specific surface area measuring apparatus (product No. 'ASAP-2000' manufactured by Shimadzu corporation) can be used.

Since the sample having a large BET specific surface area tends to absorb moisture in the humid air, it is desirable to evaporate and remove the absorbed moisture, fat, and the like by vacuum drying at 300 degrees for 1 hour in advance. The sample used in the measurement is about 100mg as a basic condition, but it is desirable to appropriately adjust and use in the range of 50mg to 200mg in accordance with the BET specific surface area.

Further, the shape and size of the plurality of projections and the plurality of recesses are not particularly limited as long as the self-supporting film can be formed.

When the planar shape of each of the plurality of concave portions is substantially circular, the diameter of the concave portion is preferably 0.1 μm or more and 1000 μm or less. When the planar shape of each of the plurality of concave portions is substantially elliptical, the major axis of the concave portion is preferably 0.1 μm or more and 1000 μm or less. When the planar shape of each of the plurality of concave portions is substantially rectangular, the longer side of the concave portion is preferably 0.1 μm or more and 1000 μm or less. The depth of the plurality of concave portions is preferably 0.1 μm or more and 1000 μm or less. In the case where the shapes and sizes of the plurality of concave portions are within the ranges, the plurality of convex portions and the plurality of concave portions are fitted to each other, and therefore, the self-supporting film can be further easily formed.

When the planar shape of each of the plurality of projections is substantially circular, the diameter of the projection is preferably 0.1 μm or more and 1000 μm or less. When the planar shape of each of the plurality of projections is substantially elliptical, the major axis of the projection is preferably 0.1 μm or more and 1000 μm or less. When each of the plurality of projections has a substantially rectangular planar shape, the long side of the projection is preferably 0.1 μm or more and 1000 μm or less. The height of the protruding portion in the protruding portion is preferably 0.1 μm or more and 1000 μm or less. In the case where the shapes and sizes of the plurality of projections are within the ranges, the plurality of projections and the plurality of recesses are fitted to each other, and therefore, the self-supporting film can be further easily formed.

The carbon material of the present invention is preferably a porous body. In this case, the plurality of recesses correspond to the respective pores of the porous body.

In the carbon material of the present invention, the BET specific surface area is preferably 240m²More preferably 450 m/g or more²A total of 1100m or more, preferably 1100m²(ii) more than g, and preferably 4000m²A ratio of 3500m or less per gram²The ratio of the carbon atoms to the carbon atoms is less than g. When the BET specific surface area is within the above range, the battery characteristics such as the capacity of the power storage device can be further improved.

The carbon material of the present invention may have fine pores such as mesopores. The term "mesopores" refers to micropores having a pore diameter of 2nm to 50 nm. The volume of mesopores means the sum of the volumes of all mesopores in the carbon material (total mesopore volume). The volume of mesopores can be measured, for example, by the BJH (Barret, Joyner, Hallender) method which is a gas adsorption method.

The mesopore volume is preferably 0.04mL/g or more, more preferably 0.05mL/g or more, and still more preferably 0.1mL/g or more. The upper limit of the mesopore volume is not particularly limited, but is preferably 20mL/g or less, more preferably 1mL/g or less. When the volume of the mesopores is equal to or greater than the lower limit, the electrolyte can easily penetrate the surface of the carbon material, and a wider specific surface area can be effectively used, so that the capacity of the power storage device can be further increased.

The carbon material of the present invention may be provided with pores such as micropores in addition to mesopores. The volume of the micropores is preferably 1.0mL/g or less, more preferably 0.8mL/g or less. The lower limit of the volume of the micropores is not particularly limited, but is preferably 0.01mL/g or more. The micropores contribute to increase the specific surface area, but have a small pore diameter, and therefore are difficult to permeate the electrolyte solution, and are surface areas that are difficult to use as batteries. When the volume of the micropores is not more than the upper limit, the electrolyte can be made to further easily penetrate the surface of the carbon material, and a wider specific surface area can be further effectively used, so that the capacity of the power storage device can be further improved.

The term "micropores" means pores having a pore diameter of less than 2 nm. The volume of the micropores can be measured, for example, by an mp (micropore analysis) method which is a gas adsorption method. The volume of the micropores refers to the sum of the volumes of all micropores in the carbon material.

The carbon material of the present invention may contain a carbide of a resin. The carbide of the resin may be amorphous carbon. When amorphous carbon is measured by X-ray diffraction alone, it is preferable that no peak is detected in the vicinity of 26 ° 2 θ. A part of the resin may remain without being carbonized. The resin is used for forming carbide, and therefore is different from a binder used in an electrode material of an electric storage device.

Further, examples of the resin used for the carbide of the resin include: and fluorine-based polymers such as polypropylene glycol, polyethylene glycol, styrene polymers (polystyrene), vinyl acetate polymers (polyvinyl acetate), polyglycidyl methacrylate, polyvinyl butyral, polyacrylic acid, styrene butadiene rubber, polyimide resins, polytetrafluoroethylene, and polyvinylidene fluoride. The resins may be used alone or in combination of two or more. Preferred examples include polyethylene glycol and polyvinyl acetate.

In the present invention, the content of the resin and/or the carbide of the resin contained in 100 wt% of the carbon material is preferably 1 wt% or more, more preferably 3 wt% or more, further preferably 10 wt% or more, particularly preferably 15 wt% or more, and preferably 99 wt% or less, more preferably 95 wt% or less. By setting the content of the resin and/or the carbide of the resin to be not less than the lower limit and not more than the upper limit, the battery characteristics of the power storage device can be further improved.

The carbon material of the present invention preferably comprises a carbon material having a graphene stacked structure. In this case, the conductivity can be further improved. Therefore, when used as an electrode material for an electric storage device, battery characteristics such as rate characteristics can be further improved.

The carbon material of the present invention may contain only a carbon material having a graphene stacked structure, or may contain only a carbide of a resin. Further, a mixture of a carbon material having a graphene stacked structure and a carbide of a resin may be used. The carbon material of the present invention may further contain a resin remaining without carbonization.

Whether or not the graphene has a laminated structure can be determined by using CuK α rays (wavelength)) When the X-ray diffraction spectrum of the carbon material was measured, it was confirmed whether or not a peak (peak derived from the graphene stacked structure) was observed in the vicinity of 2 θ ═ 26 °. The X-ray diffraction spectrum can be measured by a wide-angle X-ray diffraction method. For example, SmartLab (manufactured by RIG AKU) is used as an X-ray diffraction apparatus.

The carbon material of the present invention may be a composite of a carbon material having a graphene layered structure and a carbide of a resin. In this case, when the composite is measured by an X-ray diffraction method, the intensity of a peak having a 2 θ of around 26 ° changes depending on the mixing ratio of amorphous carbon and crystalline graphite which are carbides of the resin. In this case, a part of the resin may remain without being carbonized.

In the present invention, examples of the carbon material having a graphene stacked structure include graphite, exfoliated graphite, and the like.

Graphite is a laminate of a plurality of graphene sheets. The number of graphene sheets of graphite stacked is usually about 10 to 100 ten thousand. As the graphite, for example, natural graphite, artificial graphite, expanded graphite, or the like can be used. In expanded graphite, the ratio of the distance between graphene layers is higher than that of ordinary graphite. Therefore, as the graphite, expanded graphite is preferably used.

The exfoliated graphite is obtained by subjecting raw graphite to a exfoliation treatment, and refers to a graphene sheet laminate that is thinner than the raw graphite. The number of graphene sheets in the exfoliated graphite may be smaller than that of the original graphite. The flaked graphite may be oxidized flaked graphite.

In the exfoliated graphite, the number of graphene sheets stacked is not particularly limited, but is preferably 2 or more layers, more preferably 5 or more layers, preferably 1000 or less layers, and more preferably 500 or less layers. When the number of graphene sheets stacked is equal to or greater than the lower limit, the occurrence of rolling of the exfoliated graphite in the liquid or stacking of the exfoliated graphite with each other is suppressed, and therefore, the electrical conductivity of the exfoliated graphite can be further improved. When the number of graphene sheets stacked is not more than the upper limit, the specific surface area of the exfoliated graphite can be further increased.

The exfoliated graphite is preferably a partially exfoliated graphite having a structure in which graphite is partially exfoliated.

More specifically, "the graphite is partially exfoliated" means that the graphene layers in the graphene laminate are expanded to some extent from the edges to the inner side, that is, a part of the graphite is exfoliated at the edges (edge portions). The graphite layers in the central portion are laminated in the same manner as in the case of the raw graphite or the primary exfoliated graphite. Therefore, a portion where a part of graphite is peeled off at the end edge is connected to the central portion. The partially exfoliated graphite may include graphite in which graphite at the edges is exfoliated and exfoliated.

In this way, in the partially exfoliated graphite, graphite layers are laminated in the central portion in the same manner as in the original graphite or the primary exfoliated graphite. Therefore, compared to conventional graphene oxide and carbon black, the degree of graphitization is high and the conductivity is excellent. Therefore, in the case of an electrode used for an electricity storage device, the electron conductivity in the electrode can be further improved, so that charge and discharge at a larger current are possible.

Whether or not the graphite is partially exfoliated can be confirmed by observation with a Scanning Electron Microscope (SEM) or X-ray diffraction spectroscopy, for example, in the same manner as in the flaked graphite/resin composite material described in international publication No. 2014/034156.

(method for producing carbon Material)

The following describes methods 1 and 2 as examples of the method for producing a carbon material of the present invention.

The method 1;

in the method 1, first, graphite or primary exfoliated graphite is mixed with a resin to obtain a mixture 1 (mixing step). The mixing method is not particularly limited, and for example, the following methods can be used: ultrasonic wave-based mixing, mixer-based mixing, stirrer-based mixing, charging graphite or primary exfoliated graphite and resin in a sealable container and shaking the container, and the like.

The mixing ratio of graphite or primary exfoliated graphite to resin (graphite or primary exfoliated graphite/resin) is preferably 1/1000 or more, more preferably 1/300 or more, preferably 1/3 or less, and more preferably 1/5 or less in terms of mass ratio.

In the mixing step, a solvent or the like may be further added. Examples of the solvent include water, ethanol, methanol, THF (tetrahydrofuran), NMP (N-methyl-2-pyrrolidone), and the like. The 1 st mixture obtained in the mixing step is preferably a mixed solution. Next, the mixture is dried. The drying method is not particularly limited, and for example, air drying, hot plate drying, vacuum drying, or freeze drying may be used. The dried product of the mixed solution is also preferably a liquid. In the mixing step, a dispersant such as carboxymethyl cellulose (CMC) or Sodium Dodecyl Sulfate (SDS) may be further mixed.

The mixing ratio of the resin and the solvent (resin: solvent) may be, for example, 20:80 to 100:0 in terms of mass ratio. The mixing ratio of the resin and the dispersant (resin: dispersant) may be, for example, 80:20 to 100:0 in terms of a mass ratio.

As the graphite, expanded graphite is preferably used from the viewpoint that graphite can be more easily exfoliated in a heating step described later. Further, the primary exfoliated graphite widely includes exfoliated graphite obtained by exfoliating graphite by various methods. The primary exfoliated graphite may be partially exfoliated. The primary exfoliated graphite is obtained by exfoliating graphite, and therefore has a larger specific surface area than graphite.

The resin is not particularly limited, and examples thereof include: and fluorine-based polymers such as polypropylene glycol, polyethylene glycol, polyglycidyl methacrylate, vinyl acetate polymers (polyvinyl acetate), polyvinyl butyral, polyacrylic acid, styrene polymers (polystyrene), styrene butadiene rubber, polyimide resins, polytetrafluoroethylene, and polyvinylidene fluoride. The resin used here is a resin for producing a carbon material, and is distinguished from a binder used as a binder. The resin used here is mostly carbonized by heating described later.

Next, particles other than the carbon material are further added and mixed to the dried product of the obtained 1 st mixture. Thus, particles different from the carbon material are arranged in the matrix of the carbon material constituting the 1 st mixture to form a 2 nd mixture. Further, the 2 nd mixture may also be formed by coating particles other than the carbon material with the carbon material constituting the 2 nd mixture. The mixing method is not particularly limited, and examples thereof include: ultrasonic wave-based mixing, mixer-based mixing, stirrer-based mixing, a method of charging the dried product and particles of the mixture 1 into a sealable container and shaking the container, and the like.

The mixing ratio of graphite or primary exfoliated graphite to particles other than the carbon material (graphite or primary exfoliated graphite/particles other than the carbon material) is preferably 0/100 or more, more preferably 1/99 or more, preferably 50/50 or less, and more preferably 30/70 or less in terms of mass ratio.

The particles other than carbon material may be an activator. The particles other than the carbon material are not particularly limited, and for example, the following particles can be used: zinc hydroxide, zinc chloride, zinc sulfide, calcium hydroxide, calcium chloride, calcium sulfide, calcium carbonate, sodium hydroxide, sodium chloride, sodium sulfide, sodium carbonate, potassium hydroxide, potassium chloride, potassium sulfide, potassium carbonate, phosphoric acid, zinc phosphate, calcium phosphate, sodium phosphate, potassium phosphate. These may be used alone or in combination of plural kinds.

The particle diameter of the particles other than the carbon material is preferably 0.1 μm or more and 1000 μm or less. The particle diameter of the particles other than the carbon material is more preferably 1 μm or more, still more preferably 10 μm or more, still more preferably 500 μm or less, and still more preferably 300 μm or less. By setting the particle diameter of the particles other than the carbon material within the above range, the obtained carbon material can be further easily formed into a self-supporting film. The particle size refers to an average particle size calculated by a dry laser diffraction method using a volume-based distribution. The average particle diameter can be measured, for example, using MT3000II manufactured by MICROTRAC BELL.

Next, the 2 nd mixture is heated (heating step). The heating temperature in the heating step may be, for example, 200 to 1000 ℃. The heating may be performed in air or in an inert gas atmosphere such as nitrogen. By this heating process, it is desirable that at least a part of the resin is carbonized. The resin may also be fully carbonized. In the heating step, the partially exfoliated graphite may be obtained by partially exfoliating a part of graphite or primary exfoliated graphite. After the heating step, the activation treatment may be further performed by a chemical activation method or a gas activation method.

Next, the particles are removed from the heated 2 nd mixture. In this case, the portions obtained by removing the particles disposed in the matrix of the 2 nd mixture become the plurality of concave portions and the plurality of convex portions. The method for removing the particles is not particularly limited, and examples thereof include a method of washing with a solvent such as water and drying.

The carbon material obtained by such a production method includes the plurality of concave portions and the plurality of convex portions. The weight of the carbon material remaining on the screen after the shaking may be 90% by weight or more relative to 100% by weight of the carbon material charged into the screen. Therefore, even when the amount of the binder added is small, the electrode film can be easily formed.

The weight of the carbon material remaining on the screen after the shaking may be increased, for example, by: bringing the amount of the resin and the amount of the particles other than the carbon material mixed close to the same amount in terms of volume ratio; reducing the particle size of particles other than carbon material; cleaning the second mixture to remove particles other than the carbon material from the first mixture in such a manner that the particles other than the carbon material do not remain; or, the time for grinding after washing is prolonged.

In the method 1, a carbon material which is a composite material of a carbon material having a graphene laminated structure, such as raw graphite, primary exfoliated graphite, or partially exfoliated graphite, and a resin and/or a carbide of the resin can be obtained.

The 2 nd method;

in the 2 nd method, first, particles other than the carbon material are added to and mixed with the resin that becomes the matrix. Thereby, particles different from the carbon material are arranged in the matrix of the resin to form a mixture. Further, a mixture may also be formed by coating particles other than the carbon material with a resin. The mixing method is not particularly limited, and examples thereof include: ultrasonic wave-based mixing, mixer-based mixing, stirrer-based mixing, pouring of resin and particles in a sealable container and shaking of the container, and the like.

The mixing ratio of the resin to the particles other than the carbon material (resin/particles other than the carbon material) is preferably 1/100 or more, more preferably 10/90 or more, preferably 1000/1 or less, more preferably 500/1 or less in terms of a mass ratio.

As the resin, a liquid resin is preferably used. The resin is not particularly limited, and examples thereof include: and fluorine-based polymers such as polypropylene glycol, polyethylene glycol, polyglycidyl methacrylate, vinyl acetate polymers (polyvinyl acetate), polyvinyl butyral, polyacrylic acid, styrene polymers (polystyrene), styrene butadiene rubber, polyimide resins, polytetrafluoroethylene, and polyvinylidene fluoride. The resin used here is a resin for producing a carbon material, and is distinguished from a binder used as a binder. The resin used here is mostly carbonized by heating described later.

The particles other than carbon material may be an activator. The particles other than the carbon material are not particularly limited, and for example, the following particles can be used: zinc hydroxide, zinc chloride, zinc sulfide, calcium hydroxide, calcium chloride, calcium sulfide, calcium carbonate, sodium hydroxide, sodium chloride, sodium sulfide, sodium carbonate, potassium hydroxide, potassium chloride, potassium sulfide, potassium carbonate, phosphoric acid, zinc phosphate, calcium phosphate, sodium phosphate, potassium phosphate. These may be used alone or in combination of plural kinds.

The particle diameter of the particles other than the carbon material is preferably 0.1 μm or more and 1000 μm or less. The particle diameter of the particles other than the carbon material is more preferably 1 μm or more, still more preferably 10 μm or more, still more preferably 500 μm or less, and still more preferably 300 μm or less. By setting the particle diameter of the particles other than the carbon material within the above range, the obtained carbon material can be further easily formed into a self-supporting film. The average particle size is an average particle size calculated by a dry laser diffraction method using a volume-based distribution. The average particle diameter can be measured, for example, using MT3000II manufactured by MICROTRAC BELL.

Next, the mixture is heated (heating process). The heating temperature in the heating step may be, for example, 200 to 1000 ℃. The heating may be performed in air or in an inert gas atmosphere such as nitrogen. It is desirable that at least a part of the resin is carbonized by the heating process. After the heating step, the activation treatment may be further performed by a chemical activation method or a gas activation method.

Next, the particles are removed from the heated mixture. In this case, the portions obtained by removing the particles disposed in the matrix become the plurality of concave portions and the plurality of convex portions. The method for removing the particles is not particularly limited, and examples thereof include a method of washing with a solvent such as water and drying.

The carbon material obtained by the method 2 also has the plurality of concave portions and the plurality of convex portions. The weight of the carbon material remaining on the screen after the shaking may be 90 wt% or more with respect to 100 wt% of the weight of the carbon material charged into the screen. Therefore, even when the amount of the binder added is small, the electrode film can be easily formed.

The weight of the carbon material remaining on the screen after the shaking can be increased by: bringing the amount of the resin and the amount of the particles other than the carbon material mixed close to the same amount in terms of volume ratio; reducing the particle size of particles other than carbon material; cleaning the second mixture to remove particles other than the carbon material from the first mixture in such a manner that the particles other than the carbon material do not remain; or, the time for grinding after washing is prolonged.

Therefore, as the starting material, a mixture of graphite or primary exfoliated graphite and a resin may be used as in the method 1, or only a resin may be used without using graphite or primary exfoliated graphite as in the method 2.

In the method 2, a carbon material containing only a carbide of a resin can be obtained. However, the resin may further contain a resin that is not carbonized.

The carbon material of the present invention can easily form an electrode film even when the amount of the binder to be added is reduced, and can improve battery characteristics such as the capacity of an electric storage device. Therefore, the carbon material of the present invention can be suitably used as an electrode material for an electricity storage device.

(electrode Material for electric storage device and electric storage device)

The power storage device of the present invention is not particularly limited, and examples thereof include: a nonaqueous electrolyte primary battery, an aqueous electrolyte primary battery, a nonaqueous electrolyte secondary battery, an aqueous electrolyte secondary battery, a capacitor, an electric double layer capacitor, a lithium ion capacitor, or the like. The electrode material for an electric storage device of the present invention is an electrode material used for an electrode of an electric storage device as described above.

The electric storage device of the present invention includes an electrode made of the electrode material for electric storage devices containing the carbon material of the present invention, and therefore, battery characteristics such as the capacity of the electric storage device can be improved.

In particular, the carbon material contained in the electrode material for an electricity storage device can effectively improve the capacity of a capacitor or a lithium ion secondary battery. The capacitor is, for example, an electric double layer capacitor.

The electrode material for an electricity storage device can be used as an electrode for an electricity storage device by incorporating a binder and a solvent necessary for the carbon material of the present invention and shaping the carbon material. However, the amount of the binder may be reduced or the binder may not be contained. The amount of the binder added is preferably 5% by weight or less, more preferably 3% by weight or less, and still more preferably 1% by weight or less, based on 100% by weight of the electrode material for an electricity storage device.

The electrode material for an electric storage device may be formed into a sheet by, for example, a calender roll and then dried. The coating solution containing the carbon material of the present invention, a solvent and, if necessary, a binder may be applied to a current collector and then dried.

As the binder, for example, there can be used: polyvinyl butyral, polytetrafluoroethylene, styrene butadiene rubber, polyimide resin, acrylic resin, fluorine-based polymers such as polyvinylidene fluoride, and resins such as water-soluble carboxymethyl cellulose. Polytetrafluoroethylene may preferably be used. When polytetrafluoroethylene is used, dispersibility and heat resistance can be further improved.

As the solvent, ethanol, N-methylpyrrolidone (NMP), water, or the like can be used.

When the power storage device is used as a capacitor, an aqueous or nonaqueous (organic) electrolyte may be used as the electrolyte of the capacitor.

Examples of the aqueous electrolyte solution include: an electrolytic solution using water as a solvent and sulfuric acid, potassium hydroxide, or the like as an electrolyte.

As the nonaqueous electrolytic solution, for example, there can be used: the following solvents, electrolytes, and ionic liquids were used. Specifically, examples of the solvent include: acetonitrile, Propylene Carbonate (PC), Ethylene Carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), Acrylonitrile (AN), or the like.

Further, as the electrolyte, there may be mentionedAnd (3) discharging: lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) Tetraethylammonium Tetrafluoroborate (TEABF)₄) Or triethylmethyl ammonium Tetrafluoroborate (TEMABF)₄) And the like.

Further, as the ionic liquid, for example, an ionic liquid having the following cation and anion can be used. Examples of the cation include: imidazolium ions, pyridinium ions, ammonium ions, phosphonium ions, and the like. Examples of the anion include: boron tetrafluoride ion (BF)₄ ^-) Boron hexafluoride ion (BF)₆ ^-) Aluminum tetrachloride ion (AlCl)₄ ^-) Tantalum hexafluoride ion (TaF)₆ ^-) Tris (trifluoromethanesulfonyl) methane ion (C (CF))₃SO₂)₃ ^-) And the like. When an ionic liquid is used, the driving voltage can be further increased in the power storage device. That is, the energy density can be further improved.

The present invention will be described below by referring to specific examples and comparative examples thereof. The present invention is not limited to the following examples.

(example 1)

To 1g of polyethylene glycol (PEG, molecular weight 600, manufactured by Sanyo chemical industries Co., Ltd.), potassium carbonate (K) was added as an activator₂CO₃And Wako pure chemical industries, average particle size: 600 μm)2g, and mixed uniformly using a mill. The obtained mixture was kept at a temperature of 370 ℃ (carbonization temperature) under nitrogen atmosphere for 1 hour, and then heated to 800 ℃, and kept at 800 ℃ for 1 hour, thereby performing activation treatment. Finally, the carbon material is obtained by washing in hot water to neutrality.

(example 2)

Expanded graphite (trade name "PF POWDER 8" manufactured by TOYOTANSO, Inc., BET specific surface area of 22m²1g of a graphite dispersion, 3g of a 1% aqueous solution of carboxymethyl cellulose (CMC, molecular weight 25 ten thousand, manufactured by ALD RICH Co., Ltd.) as a dispersant, and 30g of water as a solvent were mixed together. The prepared graphite dispersion was subjected to ultrasonic treatment using an ultrasonic treatment apparatus(this system of many electronic meters), 100W, frequency of oscillation: ultrasonic irradiation was carried out at 28kHz for 6 hours. Then, 234g of polyethylene glycol (PEG, molecular weight 600, manufactured by Sanyo chemical industry Co., Ltd.) was mixed with the mixture at 8000rpm for 30 minutes by a mixer, and then dried in a dryer at 150 ℃ to remove water, thereby preparing a composition in which polyethylene glycol was adsorbed to expanded graphite.

Next, potassium carbonate (K) was added as an activator to the dried composition₂CO₃And Wako pure chemical industries, average particle size: 600 μm)470g, mixed homogeneously using a mill. The obtained mixture was kept at 370 ℃ for 1 hour under nitrogen atmosphere, then heated to 850 ℃ and kept at 850 ℃ for 1 hour, thereby performing activation treatment. Finally, the carbon material was washed to neutrality in hot water to obtain a carbon material. The polyethylene glycol used is modified into a resin carbide by the heating treatment, and the resulting carbon material is a composite of exfoliated graphite and the resin carbide.

The content of the resin carbide in the obtained carbon material was confirmed based on the following points using a differential thermal weight simultaneous measurement apparatus (manufactured by HIT ACHI HIGH-TECH SCIENCE, trade name "STA 7300").

The carbon material was weighed in a platinum pan to about 2 mg. The sample was subjected to measurement at a temperature rising rate of 10 ℃/min under a nitrogen atmosphere from 30 ℃ to 1000 ℃. From the results of the differential thermal analysis obtained by the measurement, the combustion temperatures of the resin (polyethylene glycol) carbide and the partially exfoliated graphite were separated, and the amount (% by weight) of the resin carbide relative to the entire carbon material was calculated from the thermogravimetric change associated therewith. In example 2, the amount of the resin char was 90% by weight.

(example 3)

A carbon material was obtained in the same manner as in example 2, except that the activation temperature was changed to 950 ℃.

(example 4)

A carbon material was obtained in the same manner as in example 2, except that the amount of potassium carbonate added was changed to 94 g.

(example 5)

Expanded graphite (trade name "PF POWDER 8" manufactured by TOYOTANSO, Inc., BET specific surface area of 22m²1g, 468g of polyethylene glycol (PEG, molecular weight 400, manufactured by Sanyo chemical Co., Ltd.), zinc chloride (manufactured by NACALAITESQUE Co., Ltd., average particle diameter: 100 μm)23g of the powder was mixed by a mixer at 8000rpm for 30 minutes, and then dried in a dryer at 150 ℃ to remove water, thereby preparing a composition in which zinc chloride is adsorbed with a mixture of expanded graphite and polyethylene glycol.

Next, the obtained composition was subjected to a heat treatment at a temperature of 420 ℃ for 1 hour. Thereafter, zinc chloride was removed by hot water washing to obtain a carbon material.

Comparative example 1

As the carbon material, expanded graphite powder (product name "PERMA-FOILPF 8" manufactured by TOYOTANSO) was used as it is.

Comparative example 2

As the carbon material, carbon nanotubes (CNT, product name "VGCF-H" manufactured by SHOWA AND ELECTRIC WORKS Co., Ltd.) were used as they were.

Comparative example 3

As a carbonaceous material, activated carbon (product name "KURAAYOAL YP 50F" manufactured by KURARARAY) was used as it is.

Comparative example 4

Ketjen black (trade name "Ketjen black EC600 JD", manufactured by LION-SPECIATY-CHEM) was used as a carbon material.

[ evaluation ]

The carbon materials of examples 1 to 5 and comparative examples 1 to 4 were evaluated as follows. The results are shown in Table 1 below.

(confirmation of appearance of carbon Material)

Fig. 1 is a Scanning Electron Microscope (SEM) photograph showing the carbon material obtained in example 2 at a magnification of 5000. Incidentally, the SEM photograph was observed using HITACHI HIGH-TECHNOLOGIES, trade name "SU 8220". As is clear from fig. 1, the carbon material obtained in example 2 had a plurality of concave portions and a plurality of convex portions. Similarly, in examples 1, 3, 4 and 5, it was confirmed that the resin composition had a plurality of concave portions and a plurality of convex portions.

Fig. 2 is a Scanning Electron Microscope (SEM) photograph showing the carbon material of comparative example 3 at a magnification of 5000. As is clear from fig. 2, in the carbon material of comparative example 3, a plurality of concave portions and a plurality of convex portions as in example 2 were not observed.

(BET specific surface area)

The BET specific surface area of the carbon material was measured using a specific surface area measuring apparatus (product number "ASAP-2000", nitrogen gas, manufactured by shimadzu corporation), and the BET specific surface area was evaluated according to the following evaluation criteria.

[ evaluation standards ]

O … BET specific surface area of 100m²More than g

X … BET specific surface area less than 100m²/g

(confirmation of formation or non-formation of self-supporting film)

In the following manner, whether or not a self-supporting film was formed was confirmed.

In a state where a cylindrical syringe having a diameter of 2cm was filled with 0.2g of the carbon material, the syringe was gradually pressurized and compressed at a pressure of 16kN for 10 seconds. Next, the whole of the compressed carbon material was taken out of the syringe and put into a sieve (inner diameter: 150mm, depth: 45mm) made of stainless steel having a pore diameter of 4.75mm according to JIS Z8801-1. Next, the sieve was shaken at a speed of 60rpm for 1 minute in a recipcomator mode using a shaker (product number "SHAKERSSR-2" manufactured by ASONE corporation), and then the weight of the carbon material remaining on the sieve was measured, and whether or not the film was formed was evaluated according to the following evaluation criteria.

[ evaluation standards ]

The weight of the carbon material remaining on the screen was 90 wt% or more based on 100 wt% of the carbon material charged into the screen

The weight of the carbon material remaining on the sieve at X … was less than 90% by weight based on 100% by weight of the carbon material charged into the sieve

Fig. 3 is a photograph showing the carbon material after pressurization in example 2. Fig. 4 is a photograph showing the carbon material after pressurization in comparative example 3. As is clear from fig. 3, in the case of the carbon material of example 2, a self-supporting film was formed. On the other hand, as is clear from fig. 4, in the case of the carbon material of comparative example 3, a self-supporting film could not be formed.

In addition, the carbon materials obtained in examples 1 to 5 and comparative example 1 after pressurization were visually observed to confirm the formation state of a circular film having a diameter of 2 cm. On the other hand, the carbon materials obtained in comparative examples 2 to 4 after pressurization were not able to form a self-supporting film by visual observation. The results are shown in Table 1 below.

As is clear from table 1, in the carbon materials of examples 1 to 5, the self-supporting film can be formed, the BET specific surface area is large, and the capacity of the power storage device can be improved. On the other hand, in comparative examples 1 and 2, the BET specific surface area was small, and the capacity of the electric storage device could not be increased. In comparative examples 3 and 4, since the self-supporting film could not be formed, the electrode film could not be formed without increasing the amount of the binder to be added.