JP2018170328A - Capacitor electrode material, capacitor electrode sheet, and capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor electrode material capable of increasing the electrostatic capacitance of a capacitor and simplifying electrode design.SOLUTION: A capacitor electrode material includes a carbon material and a resin at least a part of which is fixed to the carbon material and substantially does not contain a binder resin different from the resin.SELECTED DRAWING: None

Description

  The present invention relates to a capacitor electrode material, a capacitor electrode sheet using the capacitor electrode material, and a capacitor.

  Conventionally, carbon materials such as graphite, activated carbon, carbon nanofibers, or carbon nanotubes have been widely used as capacitor electrode materials from the environmental aspect.

  Patent Document 1 listed below discloses a capacitor electrode material including a resin residual partially exfoliated exfoliated graphite and a binder resin. Patent Document 1 describes that the resin-retained partially exfoliated graphite has a structure in which graphite is partially exfoliated and a part of the thermally decomposed resin remains. Has been. Patent Document 1 describes that the content of the binder resin is preferably 0.3 to 40 parts by weight with respect to 100 parts by weight of the resin residual partially exfoliated exfoliated graphite.

International Publication No. 2015/098758

  However, even when a capacitor electrode material including a resin-residual partially exfoliated exfoliated graphite and a binder resin is used as in Patent Document 1, the capacitance of the capacitor may not be sufficiently increased. . Moreover, when producing an electrode using the capacitor electrode material of Patent Document 1, the electrode design may be complicated.

  An object of the present invention is to provide a capacitor electrode material, a capacitor electrode sheet using the capacitor electrode material, and a capacitor capable of increasing the capacitance of the capacitor and simplifying the electrode design. There is to do.

  The electrode material for a capacitor according to the present invention includes a carbon material and a resin that is at least partially fixed to the carbon material, and is substantially free of a binder resin different from the resin. .

  On the specific situation with the capacitor electrode material which concerns on this invention, content of the said resin is 3 to 50 weight% in the said capacitor electrode material.

  In another specific aspect of the electrode material for a capacitor according to the present invention, the content of the resin fixed to the carbon material in the resin is 80 wt% or more and 100 wt% or less.

  In still another specific aspect of the electrode material for a capacitor according to the present invention, the carbon material has a graphene laminated structure.

  In still another specific aspect of the electrode material for capacitors according to the present invention, the carbon material is partially exfoliated graphite having a structure in which graphite is partially exfoliated.

  In still another specific aspect of the capacitor electrode material according to the present invention, the capacitor electrode material further includes fine particles.

  In still another specific aspect of the capacitor electrode material according to the present invention, the content of the fine particles in the capacitor electrode material is 1 wt% or more and 90 wt% or less.

  The capacitor electrode sheet according to the present invention includes a capacitor electrode material configured according to the present invention.

  The capacitor according to the present invention includes a capacitor electrode sheet configured according to the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the electrode material for capacitors which can raise the electrostatic capacitance of a capacitor and can simplify electrode design can be provided.

It is a figure which shows the differential thermal analysis result of the electrode material for capacitors in Example 1. FIG.

  Details of the present invention will be described below.

[Capacitor electrode material]
The capacitor electrode material of the present invention includes a carbon material and a resin. The resin is at least partially fixed to the carbon material. Further, the capacitor electrode material of the present invention does not substantially contain a binder resin different from the above resin.

  In the present invention, since at least a part of the resin only needs to be fixed to the carbon material, a resin not fixed to the carbon material may be included. In this case, the resin that is not fixed to the carbon material is also a resin different from the binder resin that is not substantially contained as described above.

  In the present invention, “substantially free” means that the content of the binder resin with respect to 100 parts by weight of the capacitor electrode material is 0.2 parts by weight or less. In the present invention, it is desirable that at least a part of the resin does not contain a binder resin different from the resin fixed to the carbon material, but as described above, 0.2 parts by weight with respect to 100 parts by weight of the capacitor electrode material. The binder resin may be included as long as it is below.

  The capacitor electrode material of the present invention includes a carbon material and a resin that is at least partially fixed to the carbon material, and does not substantially include a binder resin different from the resin. The electrostatic capacity of can be increased. In addition, the electrode design of the capacitor can be simplified. This can be explained as follows.

  Conventionally, when an electrode sheet is produced using a capacitor electrode material, the carbon material is molded by including a binder resin and a solvent. At this time, as a method for shaping the capacitor electrode material, for example, a slurry containing a solvent in a binder resin to which a carbon material is added is formed into a sheet with a rolled sheet, or is applied onto a current collector. There is a way. However, for example, if the compatibility between the binder resin and the carbon material is poor, the carbon material is aggregated, that is, the dispersibility of the carbon material in the slurry is lowered, and an electrode sheet having a uniform structure may not be produced. Therefore, when an electrode sheet produced by a conventional method is used, the capacitance of the capacitor may not be sufficiently increased. Further, in order to obtain an electrode sheet having a uniform structure, it is necessary to consider the dispersibility of the carbon material in the slurry, but in this case, there is a problem that the electrode design becomes complicated.

  On the other hand, the capacitor electrode material of the present invention uses a carbon material on which a resin is fixed, and does not substantially contain a binder resin different from the resin fixed on the carbon material. Therefore, even if the compatibility between the resin and the carbon material is poor, the carbon material hardly aggregates and the dispersibility of the carbon material in the slurry can be improved. Therefore, when the capacitor electrode material of the present invention is used, a uniform electrode sheet can be produced and the capacitance of the capacitor can be increased.

  In addition, since the capacitor electrode material of the present invention uses a carbon material on which a resin is fixed, a uniform electrode sheet can be obtained even if it does not substantially contain a binder resin different from the resin fixed on the carbon material. Can be produced. Therefore, a uniform electrode sheet can be produced without considering the compatibility between the carbon material and the binder resin and the dispersibility of the carbon material in the slurry. Therefore, when the capacitor electrode material of the present invention is used, the electrode design can be simplified.

  In the capacitor electrode material of the present invention, the content of the resin that is at least partially fixed to the carbon material is preferably 3% by weight or more, more preferably 5% by weight or more, and preferably 50% by weight or less. Preferably it is 20 weight% or less. When the content of the resin is not less than the above lower limit, an electrode sheet having a more uniform structure can be obtained. When the content of the resin is not more than the above upper limit, the specific surface area of the carbon material can be further increased in the capacitor electrode material. In addition, content of the said resin is a ratio of the said resin when the electrode material for capacitors is 100 weight%. The resin content can be quantified by thermal analysis.

  For example, the resin content (resin amount) can be confirmed by thermal analysis, for example, using a differential thermothermal gravimetric simultaneous measurement apparatus (manufactured by Hitachi High-Tech Science Co., Ltd., trade name “STA7300”) in the following manner. .

  2 mg of the electrode material for capacitors is weighed in a platinum pan. For example, the sample is measured from 30 ° C. to 1000 ° C. at a heating rate of 10 ° C./min. From the differential thermal analysis result obtained by the measurement, the combustion temperature of the resin and the carbon material can be separated, and the amount of resin (% by weight) with respect to the entire capacitor electrode material can be calculated from the associated thermogravimetric change.

  By setting the amount of resin contained in the capacitor electrode material within the above range, a capacitor electrode material having a higher binding property and a larger specific surface area can be obtained, and a capacitor with a higher capacity can be produced. be able to. This also applies to the case where fine particles are inserted as will be described later.

  In the resin, the content of the resin fixed to the carbon material is preferably 80% by weight or more, more preferably 90% by weight or more. When the content of the resin fixed to the carbon material is within the above range, an electrode sheet having a more uniform structure can be obtained. The content of the resin fixed to the carbon material is the ratio of the resin fixed to the carbon material when the total amount of the resin at least partially fixed to the carbon material is 100% by weight.

  The resin fixed to the carbon material refers to a component that does not elute into the solvent when the capacitor electrode material is washed with a solvent capable of dissolving the resin. Then, whether or not the resin is fixed to the carbon material can be distinguished from the thermogravimetric change of the differential thermal analysis before and after washing with a solvent capable of dissolving the resin.

  In addition, because the resin temperature of the differential thermal analysis resin differs between the resin fixed to the carbon material and the resin not fixed, it is fixed to the carbon material in the resin from the thermogravimetric change of the differential thermal analysis. The content (% by weight) of the resin used can be calculated.

  In the present invention, the shape of the capacitor electrode material is not particularly limited, and a suitable shape such as a film shape, a sheet shape, or a granular shape can be used.

  Details of each material constituting the capacitor electrode material of the present invention will be described below.

(Carbon materials and resins)
At least a part of the resin is fixed to the carbon material used in the present invention. The method for fixing the resin to the carbon material is not particularly limited. For example, the resin can be fixed by chemically bonding or physically adsorbing the resin to the carbon material. Especially, it is preferable to fix by making the resin chemically bond to the carbon material, and it is more preferable to fix by grafting.

  The resin that is at least partially fixed to the carbon material is not particularly limited, for example, polypropylene glycol, polyglycidyl methacrylate, polyvinyl acetate, polybutyral, polyacrylic acid, polyethylene glycol, styrene butadiene rubber, polyimide resin, Examples thereof include fluorine-based polymers such as polytetrafluoroethylene and polyvinylidene fluoride.

  As described above, in the present invention, it is preferable that at least a part of the resin does not contain a binder resin different from the resin fixed to the carbon material. If it is 2 parts by weight or less, a binder resin may be included.

  Examples of such a binder resin include polybutyral, polytetrafluoroethylene, styrene butadiene rubber, polyimide resin, fluorine-based polymers such as polyvinylidene fluoride, and water-soluble carboxymethyl cellulose. These may be used alone or in combination.

  The carbon material is not particularly limited, and for example, graphite, exfoliated graphite, graphene, ketjen black, carbon black, porous carbon material, and the like can be used. Among these, a carbon material having a graphene laminated structure such as graphite or exfoliated graphite is desirable. In this case, the conductivity of the capacitor electrode material can be further increased. In addition, also in the carbon material which has a graphene laminated structure, resin can be fix | immobilized by making it graft | graft or adsorb | suck, for example.

  Graphite is a laminate of a plurality of graphene sheets. The number of graphite graphene sheets stacked is usually about 100,000 to 1,000,000 layers. As the graphite, for example, natural graphite, artificial graphite or expanded graphite can be used. Expanded graphite has a larger interlayer between graphene layers than normal graphite. Therefore, it is preferable to use expanded graphite as the graphite.

  Exfoliated graphite is obtained by exfoliating the original graphite, and refers to a graphene sheet laminate that is thinner than the original graphite. The number of graphene sheets laminated in exfoliated graphite should be less than the original graphite. Further, the specific surface area can be further increased by oxidizing the surface of the graphene sheet by a peeling treatment.

  In the exfoliated graphite, the number of graphene sheets stacked is preferably 1000 layers or less, more preferably 500 layers or less. When the number of graphene sheets stacked is not more than the above upper limit, the specific surface area of exfoliated graphite can be further increased.

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

  More specifically, “partially exfoliated graphite” means that in the graphene laminate, the graphene layer is open from the edge to some extent inside, that is, a part of the graphite is exfoliated at the edge. In the central part, the graphite layer is laminated in the same manner as the original graphite or primary exfoliated graphite. Therefore, the part where the graphite is partially peeled off at the edge is continuous with the central part.

  Partially exfoliated graphite has many portions where graphite is exfoliated at the edge portion. The portion where the graphite is exfoliated refers to a portion of the graphite or primary exfoliated graphite where the graphene laminate or graphene is partially peeled off at the edge.

  In the partially exfoliated exfoliated graphite, the abundance ratio between the edge part where the graphite is partially exfoliated and the unexfoliated central part is preferably 1:30 to 1:60. In this case, the edge portion may be a left-right indefinite shape. When the abundance ratio of the edge portion and the central portion is within the above range, it is possible to achieve both a larger specific surface area and a larger conductivity.

  In the edge portion, the number of graphene layers in the portion where the graphite is partially exfoliated and thinned is small. The number of graphene layers in the portion where graphite is partially exfoliated is preferably 100 layers or less, more preferably 50 layers or less, and even more preferably 30 layers or less. When the number of laminated graphenes in the exfoliated portion is not more than the above upper limit, the compatibility with the binder resin described later can be further enhanced.

  Note that the partially exfoliated exfoliated graphite has a structure in which graphene is laminated in the central portion in the same manner as the original graphite or primary exfoliated graphite. However, even in the central portion, there may be a portion where the graphene layer is expanded from the original graphite or primary exfoliated graphite due to thermal decomposition of the resin.

  Thus, the partially exfoliated exfoliated graphite has the feature that the specific surface area is large because the interlayer distance between the graphene layers is widened and the number of graphene layers laminated at the edge is small. ing. Therefore, the conductivity of the capacitor electrode material can be further increased, and the capacitance of the capacitor can be further increased.

  Moreover, when manufacturing partially exfoliated exfoliated graphite, since the resin fixed to the partially exfoliated exfoliated graphite can be obtained simultaneously by grafting or adsorption, the resin immobilization step can be omitted. .

  Partially exfoliated graphite includes graphite or primary exfoliated graphite and a resin, and a composition in which the resin is fixed to the graphite or primary exfoliated graphite by grafting or adsorption is prepared and included in the composition. The resin is thermally decomposed. When the resin is thermally decomposed, the resin is thermally decomposed while a part of the resin remains. More specifically, the partially exfoliated exfoliated graphite can be manufactured, for example, by the same method as the exfoliated graphite / resin composite material described in International Publication No. 2014/034156. As the graphite, it is preferable to use expanded graphite because the graphite can be peeled off more easily.

  Note that primary exfoliated graphite widely includes exfoliated graphite obtained by exfoliating graphite by various methods. The primary exfoliated graphite may be partially exfoliated graphite. In addition, since primary exfoliated graphite is obtained by exfoliating graphite, the specific surface area should just be larger than graphite.

  The resin remaining in the partially exfoliated exfoliated graphite is not particularly limited, but is preferably a polymer of a radical polymerizable monomer. The resin may be a copolymer of a plurality of types of radical polymerizable monomers or a homopolymer of one type of radical polymerizable monomer.

  Examples of resins used include polypropylene polymers such as polypropylene glycol, polyglycidyl methacrylate, polyvinyl acetate, polybutyral, polyacrylic acid, polyethylene glycol, styrene butadiene rubber, polyimide resins, or polytetrafluoroethylene polyvinylidene fluoride. Is mentioned. Preferably, polyethylene glycol or polyvinyl acetate is used. When polyethylene glycol or polyvinyl acetate is used, the binding property between these resins and between the resin and the current collector can be further improved, and the specific surface area of the partially exfoliated graphite is further increased. be able to.

  As will be described later, when forming the electrode material for a capacitor, an organic solvent or water is used as a solvent (dispersion medium). At this time, from the viewpoint of dispersibility of the carbon material in each dispersion medium, as the resin, when using an organic solvent, polypropylene glycol or polyvinyl acetate is preferable, and when water is used, Polyethylene glycol and styrene butadiene rubber are preferred.

  The amount of the resin remaining in the partially exfoliated graphite is preferably 3 parts by weight to 350 parts by weight, more preferably 3 parts by weight to 250 parts by weight with respect to 100 parts by weight of the partially peeled exfoliated graphite. Part, more preferably 3 parts by weight to 80 parts by weight. By setting the amount of the residual resin within the above range, the binding property between the resins or between the resin and the current collector and the specific surface area of the partially exfoliated exfoliated graphite can be achieved at an even higher level.

  It should be noted that the resin amount can be adjusted to an appropriate amount by removing a part of the resin remaining in the partially exfoliated exfoliated graphite. At this time, a removal method by heating, chemical treatment, or the like is possible, and a partial structure can be modified.

  As described above, in this production method, since the composition in which the resin is fixed to the graphite or primary exfoliated graphite by grafting or adsorption is used as the raw material composition, it remains in the obtained partially exfoliated exfoliated graphite. The fixed resin is fixed to the partially exfoliated exfoliated graphite by grafting or adsorption. Therefore, the immobilizing step can be omitted.

  However, in the present invention, the residual resin in the partially exfoliated exfoliated graphite may be completely removed by thermal decomposition. In that case, a step of separately fixing the resin to the obtained partially exfoliated exfoliated graphite is required.

In the present invention, the specific surface area of the carbon material measured by the methylene blue adsorption method is preferably 500 m ² / g or more, and preferably 3000 m ² / g or less.

  If the specific surface area of the carbon material measured by the methylene blue adsorption method is too small, the capacitance of the capacitor may not be sufficiently increased. In addition, if the specific surface area of the carbon material measured by the methylene blue adsorption method is too large, restacking or scrolling may occur, so that an optimal structure may not be maintained when a capacitor electrode sheet is formed.

  In addition, the specific surface area by a methylene blue adsorption method can be measured with the following method.

  First, the methylene blue adsorption amount of the measurement sample is obtained. The amount of methylene blue adsorbed is based on the difference between the absorbance of a methylene blue methanol solution having a concentration of 10 mg / L and the absorbance of the supernatant obtained by centrifugation after the measurement sample is put into the methylene blue methanol solution and stirred. Measured.

  More specifically, the methylene blue adsorption amount is determined by the following method. A measurement sample is put into a methanol solution of methylene blue having a concentration of 10 mg / L and stirred. Next, the mixture is centrifuged, and the change in absorbance at the maximum absorption wavelength of the obtained supernatant is observed. Methylene blue is adsorbed to the measurement sample by π conjugation. On the other hand, methylene blue emits fluorescence when irradiated with light. When methylene blue is adsorbed on the measurement sample, it does not emit fluorescence. That is, the fluorescence intensity is reduced. Therefore, the amount of methylene blue adsorbed can be determined from the amount of decrease in the fluorescence intensity obtained from the supernatant with respect to the fluorescence intensity of the original methylene blue.

  In the present invention, the median diameter of the carbon material is preferably 1 μm or more and 100 μm or less. If the median diameter of the carbon material is too small, the pore diameter is also small, ion diffusion is slow, and the output characteristics may not be sufficiently improved. Further, if the median diameter of the carbon material is too large, the specific surface area may not be sufficiently increased.

  When the fine particles described later are combined with the carbon material, the median diameter of the carbon material is more preferably 2 μm or more, further preferably 5 μm, from the viewpoint of further increasing the specific surface area and further increasing the capacitance of the capacitor. Above, more preferably 60 μm or less, and still more preferably 40 μm or less.

  The median diameter is a diameter corresponding to the median value of the particle size distribution of the powder. For example, the particle size distribution is obtained by measuring a sample in which powder is dispersed in ethanol using a particle size distribution measuring apparatus (manufactured by Horiba, product number “LA-950”) using the laser diffraction / scattering method as a principle. Can be calculated.

(Fine particles)
The capacitor electrode material of the present invention may further contain fine particles.

  The fine particles are not particularly limited, but are preferably fine particles capable of physical adsorption / desorption of ions and / or fine particles having conductivity, that is, conductive fine particles. Specifically, activated carbon, carbon black, graphene oxide, metal oxide such as graphite, graphite oxide, and titanium oxide, zeolite oxide, polyacid such as tungstophosphoric acid, and the like can be used. These fine particles may be used alone or in combination.

  The fine particles are preferably present on the surface of the carbon material. In the case where the carbon material is a carbon material having a graphene stacked structure, the fine particles are preferably present between layers of the carbon material having a graphene stacked structure. That is, the fine particles are preferably inserted between layers of a carbon material having a graphene stacked structure. When the fine particles are present between the layers of the carbon material having a graphene laminated structure, the output characteristics can be further improved by further expanding the pore diameter in the electrolytic solution. In addition, when the fine particles have electrical conductivity, the electrical conductivity of the carbon material can be further enhanced by allowing the fine particles to be present between the layers of the carbon material.

  In addition, when the carbon material is partially exfoliated graphite, it is preferable that fine particles exist between layers of exfoliated graphenes or graphene laminates. However, when the carbon material is partially exfoliated exfoliated graphite, it is preferable that the fine particles are present both in the interlayer between the exfoliated graphenes or between the graphene laminates and on the surface of the carbon material. In addition, when the fine particles are present between the exfoliated graphenes of the partially exfoliated graphite or between the graphene laminates, the pore diameter in the electrolyte can be further expanded, and the specific surface area can be further increased. It can be made even larger.

  Thus, the capacitor electrode material of the present invention can further increase the capacitance of the capacitor while maintaining a higher specific surface area by stably adsorbing or enclosing fine particles.

  The median diameter of the fine particles is preferably 0.01 μm or more, and preferably 20 μm or less.

  If the median diameter of the fine particles is too small, when using partially exfoliated exfoliated graphite as the carbon material, the pore diameter cannot be expanded sufficiently when inserted into the exfoliated part, or the aggregation of fine particles is accelerated May be. If the median diameter of the fine particles is too large, the fine particles may not be inserted into the thinned portion.

  From the viewpoint of further improving the output characteristics of the capacitor, the median diameter of the fine particles is more preferably 0.02 μm or more, further preferably 0.03 μm or more, more preferably 10 μm or less, and even more preferably 5 μm or less.

  The upper limit of the particle size distribution of the fine particles is desirably 50 μm or less.

  The shape of the fine particles is not limited to a spherical shape, and may be various shapes such as a crushed shape, an elliptical shape, and a scale shape.

  The weight ratio of the fine particles to the carbon material is preferably 1/20 or more and 4 or less. If the weight of the carbon material is too small, the required amount to be inserted between the layers of the carbon material may not be satisfied. On the other hand, if the weight of the fine particles is too large, the proportion of fine particles that do not contribute as a complex with the carbon material increases, and the effect as a complex may not be exhibited.

  In the electrode material for a capacitor, the content of fine particles is preferably 1% by weight or more, more preferably 5% by weight or more, preferably 90% by weight or less, more preferably 60% by weight or less. When the content of the fine particles is not less than the above lower limit, the conductivity of the capacitor electrode material can be further enhanced. Further, when the content of the fine particles is not more than the above upper limit, the dispersibility of the carbon material containing the fine particles in the slurry can be further stabilized.

[Capacitor electrode sheet]
The capacitor electrode sheet of the present invention includes a capacitor electrode material configured according to the present invention.

  The capacitor electrode sheet of the present invention is applied with a composition containing a solvent, if necessary, on a capacitor electrode material containing, for example, a carbon material and a resin at least partially fixed to the carbon material. It can be manufactured by molding.

  The shaping of the composition can be performed, for example, by forming into a sheet with a rolling roller and then drying. It can also be carried out by applying a slurry comprising a capacitor electrode material and a solvent to a current collector and then drying. As the solvent, an organic solvent or water can be used. Examples of the organic solvent include ethanol and N-methylpyrrolidone (NMP). Moreover, you may obtain the electrode sheet for capacitors of this invention by pressing with a roll press machine after shaping | molding of the said composition.

  Since the capacitor electrode sheet of the present invention includes the capacitor electrode material configured according to the present invention, the capacitance of the capacitor can be increased, and the electrode design of the capacitor can be simplified.

[Capacitor]
The capacitor of the present invention includes a capacitor electrode sheet configured according to the present invention. Therefore, the capacitor of the present invention has an increased capacitance, and the electrode design is simplified. The capacitor electrode material of the present invention can be shaped into the capacitor electrode sheet and used for a capacitor. The capacitor of the present invention is, for example, an electric double layer capacitor.

  As the electrolytic solution of the capacitor, an aqueous system may be used, or a non-aqueous system (organic system) may be used.

  Examples of the aqueous electrolyte include an electrolyte using water as a solvent and sulfuric acid or potassium hydroxide as an electrolyte.

On the other hand, as the nonaqueous electrolytic solution, for example, an electrolytic solution using the following solvent, electrolyte, or ionic liquid can be used. Specifically, examples of the solvent include acetonitrile, propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). As electrolytes, lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), tetraethylammonium tetrafluoroborate (TEABF ₄ ), or triethylmethylammonium tetrafluoroborate (TEMAF) ₄ ). Furthermore, as the ionic liquid, for example, an ionic liquid having the following cation and anion can be used. Examples of the cation include imidazolium ion, pyridinium ion, ammonium ion, phosphonium ion, 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 ⁻ ), and tris (trifluoro). Romethanesulfonyl) methane ion (C (CF ₃ SO ₂ ) ₃ ⁻ ) and the like. When the ionic liquid is used, the withstand voltage is further improved, and therefore the driving voltage can be further improved in the capacitor of the present invention which does not substantially contain a binder. That is, in the capacitor of the present invention, the energy density can be further improved.

  In the present invention, the capacitance is preferably 10 F / g or more, and more preferably 12 F / g or more when the charge / discharge measurement of the capacitor is performed. From the viewpoint of the specific surface area obtained from the methylene blue adsorption amount measurement, the upper limit of the capacitance can be set to, for example, about 40 F / g.

  Next, the present invention will be clarified by giving specific examples and comparative examples of the present invention. In addition, this invention is not limited to a following example.

Example 1
Preparation of partially exfoliated exfoliated graphite;
1 g of expanded graphite (trade name “PF powder 8”, manufactured by Toyo Tanso Co., Ltd., BET surface area = 22 m ² / g), 20 g of polyethylene glycol (PEG, manufactured by Wako Pure Chemical Industries, Ltd.), and 30 g of water as a solvent The raw material composition was prepared by mixing. The prepared raw material composition was irradiated with ultrasonic waves at 100 W and an oscillation frequency of 28 kHz for 2 hours using an ultrasonic treatment apparatus (manufactured by Honda Electronics Co., Ltd.). Polyethylene glycol was adsorbed on the expanded graphite by ultrasonic irradiation. In this way, a composition in which polyethylene glycol was adsorbed on expanded graphite was prepared.

  After the ultrasonic irradiation, the temperature was maintained at 150 ° C. for 6 hours. Thereby, water was dried in the composition in which the polyethylene glycol was adsorbed on the expanded graphite. Next, the heating process which maintains the dried composition at the temperature of 400 degreeC for 3 hours was implemented. Thereby, the polyethylene glycol was thermally decomposed to obtain partially exfoliated exfoliated graphite (EEXG) to which polyethylene glycol (resin) was fixed by adsorption. In addition, partially exfoliated exfoliated graphite (EEXG) in which polyethylene glycol (resin) was fixed by adsorption was used as a capacitor electrode material as it was.

  The resin content (resin amount) in the capacitor electrode material was confirmed using a differential thermothermal gravimetric simultaneous measurement apparatus (manufactured by Hitachi High-Tech Science Co., Ltd., trade name “STA7300”) as follows.

  2 mg of the capacitor electrode material was weighed in a platinum pan. The sample was measured from 30 ° C. to 1000 ° C. at a heating rate of 10 ° C./min in the atmosphere. From the results of differential thermal analysis obtained by measurement, the combustion temperature of the resin (polyethylene glycol) and the carbon material (partially exfoliated exfoliated graphite) is separated, and from the associated thermogravimetric change, as shown in FIG. The amount of resin (% by weight) relative to the entire material was calculated.

  Further, the content of the resin fixed to the carbon material in the resin was also calculated from the measurement using a differential thermothermal gravimetric simultaneous measurement apparatus (manufactured by Hitachi High-Tech Science Co., Ltd., trade name “STA7300”). As measurement conditions, the temperature was raised in the range from 30 ° C. to 1000 ° C. at a temperature rising rate of 10 ° C./min in the atmosphere. Whether or not the resin was fixed was confirmed by the fact that the chart did not change before and after washing with THF.

Production of electrode sheets;
The partially exfoliated exfoliated graphite, to which polyethylene glycol (resin) is fixed by adsorption, obtained as described above, was subjected to N-methyl using an ultrasonic crusher (trade name “XL2020” manufactured by MISONIX). Dispersed in pyrrolidone. The obtained coating liquid was applied onto an aluminum foil as a current collector and dried to obtain an electrode sheet.

(Example 2)
In the process of thermally decomposing polyethylene glycol in Example 1 (heating process), partially exfoliated exfoliated graphite (EEXG) was obtained by the same method as in Example 1 except that the heating time was 4 hours. The ratio of the resin fixed to the partially exfoliated exfoliated graphite was adjusted by increasing the heating time. In addition, partially exfoliated exfoliated graphite (EEXG) in which polyethylene glycol (resin) was fixed by adsorption was used as a capacitor electrode material as it was. About the obtained capacitor electrode material, the amount of resin and the amount of resin fixed to the carbon material were calculated in the same manner as in Example 1. Further, an electrode sheet was obtained in the same manner as in Example 1 using partially exfoliated exfoliated graphite to which polyethylene glycol (resin) was fixed by adsorption.

(Example 3)
1 g of expanded graphite (trade name “PF powder 8” manufactured by Toyo Tanso Co., Ltd., BET surface area = 22 m ² / g), 10 g of vinyl acetate polymer (trade name “SN-04T” manufactured by Denka Co., Ltd.), Tetrahydrofuran (20 g) was mixed to prepare a raw material composition. The raw material composition was irradiated with ultrasonic waves for 2 hours at 100 W and an oscillation frequency of 28 kHz using an ultrasonic treatment apparatus (manufactured by Honda Electronics Co., Ltd.). The vinyl acetate polymer was adsorbed on the expanded graphite by ultrasonic treatment. In this way, a composition in which the vinyl acetate polymer was adsorbed on the expanded graphite was prepared.

  After the ultrasonic irradiation, the temperature was maintained at 80 ° C. for 2 hours, and then maintained at a temperature of 110 ° C. for 1 hour. Thereby, the THF was completely dried in the composition in which the vinyl acetate polymer was adsorbed on the expanded graphite.

  Next, the heating process which maintains the dried composition at the temperature of 500 degreeC for 6 hours was implemented. Thereby, the vinyl acetate polymer was thermally decomposed to obtain partially exfoliated exfoliated graphite (EEXG) to which the vinyl acetate polymer (resin) was fixed. Note that partially exfoliated graphite (EEXG) to which a vinyl acetate polymer (resin) was fixed was used as an electrode material for a capacitor as it was. About the obtained capacitor electrode material, the amount of resin and the amount of resin fixed to the carbon material were calculated in the same manner as in Example 1. In addition, an electrode sheet was obtained in the same manner as in Example 1 using partially exfoliated exfoliated graphite to which a vinyl acetate polymer (resin) was fixed.

Example 4
Ketjen black (product number “EC300J” manufactured by Lion Corporation) as fine particles was obtained by partially exfoliating graphite (EEXG) obtained by the same method as in Example 1 to which polyethylene glycol (resin) was fixed by adsorption. Was mixed with 10% of the total weight to obtain a composite. The obtained composite was used as a capacitor electrode material as it was. About the obtained capacitor electrode material, the amount of resin and the amount of resin fixed to the carbon material were calculated in the same manner as in Example 1. Moreover, the electrode sheet was obtained like Example 1 using the obtained composite_body | complex.

(Example 5)
In the step of thermally decomposing polyethylene glycol in Example 1, partially exfoliated graphite exfoliated graphite to which polyethylene glycol (resin) was fixed by adsorption in the same manner as in Example 1 except that the heating time was 2 hours. Obtained. The ratio of the resin fixed to the partially exfoliated exfoliated graphite was adjusted by further shortening the heating time. A composite was obtained in the same manner as in Example 4 except that the partially exfoliated exfoliated graphite thus obtained was used and the amount of ketjen black added was 60% of the total weight. . The obtained composite was used as a capacitor electrode material as it was. About the obtained capacitor electrode material, the amount of resin and the amount of resin fixed to the carbon material were calculated in the same manner as in Example 1. Moreover, the electrode sheet was obtained like Example 1 using the obtained composite_body | complex.

(Example 6)
In the preparation of the electrode sheet, PVDF as a binder resin was further added to the partially exfoliated graphite to which vinyl acetate polymer (resin) was fixed in an amount of 0.02% based on the total weight. An electrode sheet was obtained in the same manner as in Example 3 except that the dispersion was performed. In Example 6, an electrode material for a capacitor was obtained by adding a binder resin to partially exfoliated exfoliated graphite to which a vinyl acetate polymer (resin) was fixed.

(Example 7)
1 g of ketjen black (product name “EC300J”, product name “EC300J”, BET surface area = 800 m ² / g), 20 g of polyethylene glycol (PEG, manufactured by Wako Pure Chemical Industries, Ltd.) and 30 g of water as a solvent are mixed, A raw material composition was prepared. The prepared raw material composition was irradiated with ultrasonic waves at 100 W and an oscillation frequency of 28 kHz for 2 hours using an ultrasonic treatment apparatus (manufactured by Honda Electronics Co., Ltd.). Polyethylene glycol was adsorbed onto ketjen black by ultrasonic irradiation. In this way, a composition in which polyethylene glycol was adsorbed on ketjen black was prepared.

  After the ultrasonic irradiation, the temperature was maintained at 150 ° C. for 6 hours. Thereby, water was dried in the composition in which the polyethylene glycol was adsorbed on the ketjen black. Next, the heating process which maintains the dried composition at the temperature of 400 degreeC for 3 hours was implemented. Thereby, the polyethylene glycol was thermally decomposed to obtain ketjen black on which polyethylene glycol (resin) was fixed. Note that ketjen black to which polyethylene glycol (resin) was fixed was used as a capacitor electrode material. About the obtained capacitor electrode material, the amount of resin and the amount of resin fixed to the carbon material were calculated in the same manner as in Example 1. In addition, an electrode sheet was obtained in the same manner as in Example 1 using ketjen black to which polyethylene glycol (resin) was fixed.

(Comparative Example 1)
In place of partially exfoliated graphite, activated carbon (made by Wako Pure Chemical Industries, Ltd.) with no resin fixed was used, and when producing an electrode sheet, PVDF was added to the activated carbon as a binder resin with respect to the total weight. An electrode sheet was obtained in the same manner as in Example 1 except that 0.02% was added and dispersed in N-methylpyrrolidone.

(Comparative Example 2)
Instead of partially exfoliated graphite, graphene (XG Science Co., product number: C-750) with no resin fixed was used, and when making an electrode sheet, PVDF was added to the graphene as a binder resin as a whole. An electrode sheet was obtained in the same manner as in Example 1 except that 0.02% of the total weight was added and dispersed in N-methylpyrrolidone.

(Comparative Example 3)
In the production of the electrode sheet, the same as in Example 1 except that PVDF as a binder resin was further added to the partially exfoliated exfoliated graphite in an amount of 10% based on the total weight and dispersed in N-methylpyrrolidone. Thus, an electrode sheet was obtained.

(Evaluation)
Evaluation of coatability;
In Examples 1 to 7 and Comparative Examples 1 to 3, the coatability when producing electrode sheets was determined according to the following criteria.

◎… Coating possible (no cracks)
○… Coating possible (with some cracks)
× ... Coating not possible

Capacitor evaluation by charge / discharge measurement (capacitance evaluation);
The capacitance was measured as follows.

  A cell was prepared using an electrode punched from the electrode sheet, an electrolytic solution, and a separator, and charge / discharge measurement was performed. The capacitance per weight was calculated by dividing the obtained capacitance by the weight of the electrode sheet.

  The output characteristics (capacitance C) were determined according to the following criteria.

[Criteria for capacitance per weight]
A: 12 F / g ≦ C
○: 8F / g ≦ C <12F / g
X: 0F / g <C <8F / g
XX: Cannot be measured due to poor film formation

  The results are shown in Table 1 below.

Claims (9)

Carbon materials,
A resin that is at least partially fixed to the carbon material,
An electrode material for capacitors that does not substantially contain a binder resin different from the resin.   2. The capacitor electrode material according to claim 1, wherein the content of the resin in the capacitor electrode material is 3 wt% or more and 50 wt% or less.   The electrode material for capacitors according to claim 1 or 2 whose content of resin fixed to said carbon material in said resin is 80 to 100 weight%.   The capacitor electrode material according to claim 1, wherein the carbon material has a graphene laminated structure.   5. The capacitor electrode material according to claim 1, wherein the carbon material is partially exfoliated exfoliated graphite having a structure in which graphite is partially exfoliated.   The capacitor electrode material according to claim 1, further comprising fine particles.   The capacitor electrode material according to claim 6, wherein the content of the fine particles in the capacitor electrode material is 1 wt% or more and 90 wt% or less.   A capacitor electrode sheet comprising the capacitor electrode material according to claim 1.   A capacitor comprising the capacitor electrode sheet according to claim 8.

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