JP2006193391A - Carbon composition, method for producing the same, and polarizable electrode for electrochemical capacity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon composition capable of providing a polarizable electrode for an electrochemical capacitor having a high capacitance at a high charge / discharge current of 50 mA / square centimeter or more, preferably 100 mA / square centimeter or more, a method for producing the carbon composition, and the like A capacitor for an electrochemical capacitor formed using the carbon composition is provided.
A carbon composition containing 0.1 part by mass to 30 parts by mass of fullerene with respect to 100 parts by mass of activated carbon and a method for producing the same. The fullerene is preferably fullerene C60 having 60 carbon atoms per molecule and spherical, and the means for supporting the fullerene on the activated carbon is to disperse the activated carbon in a solution in which the organic solvent is dissolved, and to reduce the pressure. It is preferred to filter. A polarizable electrode for electrochemical capacity is formed using this carbon composition.
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Description

  The present invention relates to a carbon composition, a method for producing the carbon composition, and a polarizable electrode for electrochemical capacity, and particularly suitable for use in an electrochemical capacitor excellent in high current charge / discharge characteristics and the electrochemical capacitor. The present invention relates to a carbon composition and a method for producing the carbon composition.

  Electrochemical capacitors (hereinafter referred to as “capacitors”) including electric double layer capacitors are energy storage devices that exhibit high power density and excellent cycle characteristics, and can be used for auxiliary power supplies and electrically heated catalyst (EHC) power supplies for hybrid and fuel cell vehicles. Higher capacity is expected for application, and for that purpose, improvement of capacitor characteristics at high charge / discharge current, particularly at high charge / discharge current of 50 mA / square centimeter or more, preferably 100 mA / square centimeter or more is indispensable.

Various researches and developments have been made to increase the capacity of capacitors (for example, Patent Document 1). However, the technical development of high-power capacitor electrodes corresponding to high charge / discharge currents has been mainly focused on the low resistance of the current extraction part. Technology development as a capacitor unit such as reduction of the death volume without electrode or reduction of the electrode (for example, Patent Document 2) is the mainstream, and improvement of high charge / discharge current capacitor characteristics by technical development of the carbon composition as the electrode material is can not see.
Capacitor electrodes for application of capacitors to auxiliary power supplies and energized heating catalyst (EHC) power supplies for hybrid vehicles and fuel cell vehicles, especially at high charge / discharge currents, particularly high charge / discharge currents of 50 mA / square centimeters or more, preferably 100 mA / square centimeters or more An increase in capacitance is necessary.

  Moreover, as a similar technique using fullerene, Patent Document 3 can be cited. The technique is directed to a polarizable electrode mainly composed of fullerene. However, a polarizable electrode mainly composed of fullerene is not preferable because the specific surface area decreases.

JP-A-11-008167 Japanese Patent Application Laid-Open No. 2000-200738 JP-A-10-097956

  Accordingly, an object of the present invention is to provide a carbon composition capable of providing a polarizable electrode for an electrochemical capacitor having a high capacitance at a high charge / discharge current of 50 mA / square centimeter or more, preferably 100 mA / square centimeter or more. It is an object of the present invention to provide a production method and a capacitor for an electrochemical capacitor formed using these carbon compositions.

The manufacturing method of the carbon composition of the present invention for solving the above-mentioned problems is based on 100 parts by mass of activated carbon, 100 parts by mass of activated carbon containing 0.1 to 30 parts by mass of fullerene, and 100 parts by mass of activated carbon. And a fullerene C60 having a carbon number of 60 per molecule and a spherical shape as a fullerene. preferable.
The polar electrode for electrochemical capacity according to the present invention for solving the above-mentioned problems is a polarizable electrode for electrochemical capacity formed by using the carbon composition obtained by the above production method.

According to the carbon composition and the method for producing the carbon composition of the present invention, as a material for a polarizable electrode for an electrochemical capacitor having a high capacitance at a high charge / discharge current of 50 mA / square centimeter or more, preferably 100 mA / square centimeter or more. It is valid.
In addition, according to the polarizable electrode for electrochemical capacity of the present invention, there is provided a polarizable electrode for an electrochemical capacitor having a high capacitance at a high charge / discharge current of 50 mA / square centimeter or more, preferably 100 mA / square centimeter or more. Can do.

  The inventors of the present invention have arrived at the present invention as a result of intensive studies to achieve the above object. That is, the present invention is a carbon composition containing 0.1 to 30 parts by mass of fullerenes with respect to 100 parts by mass of activated carbon. It is preferable to disperse activated carbon in a solution in which an organic solvent is dissolved and filter under reduced pressure. In addition, it is also preferable to disperse activated carbon in a solution in which fullerene is dissolved in an organic solvent and to perform ultrasonic treatment.

In the present invention, fullerenes include spherical fullerene C60 and fullerene C70 having 60 and 70 carbon atoms per molecule, cylindrical carbon nanotubes, etc., and these are particularly excellent in oxidation stability. ing.
Among these fullerenes, fullerene C60 having 60 carbon atoms per molecule and preferably spherical. Fullerene C60 is a molecule in which carbon atoms are bonded in the shape of a soccer ball, and π electrons are delocalized on the surface of the molecule. Due to this unique molecular shape, fullerene C60 exhibits semiconducting properties as an electron acceptor, and has properties similar to π-conjugated conductive polymers. Although the π-conjugated conductive polymer electrode has a larger capacity per unit area than the activated carbon electrode, it has a smaller specific surface area than the activated carbon electrode.

  Electrochemical having high capacitance at a high charge / discharge current of 50 mA / square centimeter or more, preferably 100 mA / square centimeter or more, by a carbon composition in which fullerene, preferably fullerene C60 is supported in a highly dispersed form in activated carbon powder having a large specific surface area. A polarizable electrode for a capacitor can be provided.

  The amount of fullerene dispersed and supported with respect to the activated carbon powder is 0.1 to 30 parts by mass, and particularly preferably 1 to 10 parts by mass with respect to 100 parts by mass of the activated carbon. When the fullerene exceeds 30% by mass with respect to the activated carbon, the capacity of the polarizable electrode of the electrode formed using the carbon composition decreases, and when the fullerene is less than 0.1% by mass with respect to the activated carbon, The amount of fullerene supported is too small, and the effects of the present invention cannot be obtained sufficiently, which is not preferable.

  As for the method of supporting fullerene on activated carbon powder, in particular, a) a method in which fullerene is dissolved in an organic solvent, the solution is subjected to suction filtration and dried under reduced pressure, and b) the activated carbon powder and fullerene are dried. A method of drying after mixing, adding an organic solvent, ultrasonicating, and the like is desirable.

  a) In a method in which fullerene is dissolved in an organic solvent, the solution is filtered under reduced pressure and the residue is dried, and the organic solvent capable of dissolving fullerene is toluene, xylene, benzene, cyclohexane, carbon tetrachloride , Dichloroethane, trichloroethane, trichloroethylene, and the like. Of these organic solvents, toluene, xylene, benzene, and the like are preferably used from the viewpoint of solubility with respect to fullerene dissolution. As conditions for vacuum filtration, 20-100 kPa is preferable, More preferably, it is 40-80 kPa. The drying temperature is 20 to 120 ° C, more preferably 40 to 80 ° C.

  b) After mixing the activated carbon powder and fullerene, in the method of adding an organic solvent, sonicating and drying, ethanol, methanol, acetone, acetonitrile, etc. can be used as the organic solvent. Ethanol, acetone, and the like are preferably used because they have good wettability to fullerene and good drying properties. As ultrasonic treatment conditions, an ultrasonic output of 20 to 120 W is preferable with an ultrasonic cleaner (SHARP, trade name UT-105HS), and the treatment time is 5 to 120 minutes, preferably 10 to 60 minutes.

  By using fullerene C60 as a fullerene and dissolving it in a toluene solvent, applying a suction pressure and performing vacuum filtration, a higher capacitor capacitance can be obtained as compared with ultrasonic treatment dispersion support.

A polarizable electrode for an electrochemical capacitor is obtained from the carbon composition obtained as described above, a conductive material, and a binder. The polarizable electrode is formed, for example, by kneading the carbon composition, a conductive material, and a binder such as polytetrafluoroethylene in the presence of alcohol to form a sheet, drying it, and then passing through a conductive adhesive or the like. And obtained by bonding with a current collector. Further, the carbon composition, the conductive material, the binder and the solvent are mixed to form a slurry, which is coated on the current collector metal foil and dried to obtain an electrode integrated with the current collector.

  As the conductive material, powder of carbon black, natural graphite, artificial graphite, titanium oxide, ruthenium oxide or the like is used. Of these, ketjen black or acetylene black, which is a kind of carbon black, is preferably used since the effect of improving conductivity is large even in a small amount.

  The blending amount of the conductive material such as carbon black in the polarizable electrode is preferably 5% by mass or more, particularly 10% by mass or more in the total amount with the carbon composition so as to improve the conductivity. . Moreover, since the capacity | capacitance of a polarizable electrode will reduce if the mixture ratio of this carbon composition reduces, it is preferable that the compounding quantity of the electrically conductive material in a polarizable electrode shall be 5-40 mass%, especially 10-30 mass%.

  For example, polytetrafluoroethylene, polyvinylidene fluoride, fluoroolefin / vinyl ether copolymer cross-linked polymer, carboxymethyl cellulose, polyvinyl pyrrolidone, polyvinyl alcohol, or polyacrylic acid can be used as the binder to be mixed with the slurry. The content of the binder in the polarizable electrode is preferably 0.5 to 20% by mass in the total amount of the carbon material and the binder. This is because if the amount of the binder is less than 0.5% by mass, the strength of the electrode is insufficient, and if it exceeds 20% by mass, the electrical resistance increases and the capacity decreases. From the balance of electrode capacity and strength, the blending amount of the binder is more preferably 0.5 to 10% by mass.

  In the present invention, an electric double layer capacitor can be formed by using the above polarizable electrode as both a positive electrode and a negative electrode. However, only the negative electrode is a polarizable electrode and the positive electrode is used mainly as a battery active material such as a metal oxide. A non-polarizable electrode that uses only a positive electrode as a non-polarizable electrode and a negative electrode that contains lithium metal, a lithium alloy, or a carbon material capable of reversibly occluding and releasing lithium ions as a negative electrode. You can also.

Among these electric double layer capacitors, electric double layer capacitors using a carbon material capable of reversibly occluding and releasing lithium ions for the negative electrode and the polarizable electrode described above for the positive electrode are charge / discharge cycle durability and safety. It is particularly preferable because of its excellent characteristics, high operating voltage and large capacity.

  Carbon materials that can occlude and release lithium ions, which are the main materials of non-polarizable electrodes, include natural graphite, artificial graphite, graphitized mesocarbon spherules, graphitized whiskers, vapor-grown graphitized carbon fibers, A fired product of furfuryl alcohol resin and a fired product of novolak resin can be preferably used.

  The current collector of the electrode may be a conductor that is electrochemically and chemically corrosion resistant. Stainless steel, aluminum, titanium, tantalum, nickel, or the like is used as the current collector of the electrode mainly composed of fullerene. Of these, stainless steel and aluminum are preferred current collectors in terms of both performance and cost. Stainless steel, copper or nickel can be preferably used as the current collector of the nonpolarizable electrode mainly composed of a carbon material occluded with lithium ions.

  The shape of the current collector may be a foil, a nickel or aluminum foam metal having a three-dimensional structure, a stainless steel net, or wool.

The electrolytic solution of the electrochemical capacitor of the present invention is not particularly limited, and a conventionally known or well-known non-aqueous electrolytic solution can be used. Solvents include electrochemically stable propylene carbonate, ethylene carbonate, γ-butyrolactone, sulfolane, 3-methylsulfolane, 1,2-dimethoxyethane, acetonitrile, dimethylformamide, diethyl carbonate, ethyl methyl carbonate, or dimethyl carbonate. The solvent which consists of 1 or more types chosen is preferable.

  As a separator refurbished between the positive electrode and the negative electrode in the present invention, for example, a polypropylene fiber nonwoven fabric and a glass fiber nonwoven fabric can be suitably used.

The electrochemical capacitor of the present invention includes a coin type housed in a metal case together with an electrolyte solution via a separator between a pair of sheet-like electrodes, and a winding type obtained by winding a pair of positive and negative electrodes via a separator. Any configuration such as a stacked type in which a large number of electrodes are stacked via a separator can be used.

  In the present invention, the capacitance was measured by the following method. A constant current charge is performed at 100 mA / square centimeter or 150 mA / square centimeter per electrode surface area until an ultimate voltage of 1.0 V, and a supplementary charge is performed at a constant voltage of 1.0 V for 30 minutes. After supplementary charging is completed, constant current discharge is performed at the same current value as the charging current. At that time, the capacitance was determined from the discharge slope from 0.6V to 0.5V.

[Example 1]
Fullerene C60 (MTR, trade name Fullerene C60) is dissolved using 10 ml of toluene solution as a solvent to prepare a fullerene C60 / toluene solution, and then activated carbon powder (Kansai Thermochemical, trade name MSP-20) is dispersed in the solution and sucked. The filtration was performed under reduced pressure at a pressure of 300 mmHg (40 kPa) for 20 minutes. The obtained residue was dried at 50 degrees to obtain a carbon composition. The filtrate was colorimetrically analyzed at a wavelength of 329 nm, and the amount of fullerene C60 remaining in the filtrate was confirmed. The fullerene C60 / toluene solution concentration was prepared so that the mass ratio of fullerene C60 to activated carbon was 1 mass%.

  The carbon composition obtained in the above procedure and carbon black (Electrochemical Industry, trade name AB-3), polytetrafluoroethylene powder (Daikin, trade name F-104) are taken at a mass ratio of 8: 1: 1, and ethanol is added. Kneading while adding 0.3 ml. 0.1 g of the kneaded product was taken, compression-molded at 10 MPa using a pellet former having a diameter of 16 mm, and vacuum-fired at 330 degrees for 5 hours to produce a molded electrode.

  The molded electrode and the separator were deaerated in the electrolytic solution for 40 minutes, and then a constant current charge / discharge test measurement was performed using a coin-type two-terminal cell. Glass fiber filter paper (ADVANTEC, trade name GA-55) was used as the separator, and a 0.5 M sulfuric acid aqueous solution was used as the electrolyte. The results at 100 mA / square centimeter are shown in FIG. 1, and the increase ratio from the untreated activated carbon electrode (Comparative Example 3) capacitance at 150 mA / square centimeter is shown in Table 1.

[Example 2]
The same operation as in Example 1 was performed except that vacuum filtration was performed with a suction pressure of 600 mmHg (80 kPa) in Example 1. The results are shown in FIG.

[Example 3]
The same activated carbon powder and fullerene C60 as in Example 1 were mixed so that the mass ratio of fullerene C60 to activated carbon was 1% by mass. 1.2 ml of ethanol was added and subjected to ultrasonic treatment for 30 minutes with an ultrasonic cleaner (SHARP, trade name: UT-105HS), followed by drying to obtain a carbon compound. Fabrication and measurement of the molded electrode were performed in the same manner as in Example 1.

[Comparative Example 1]
It carried out like Example 1 except having used only activated carbon powder as a carbon composition. The results are shown in FIG.

  1 and Table 1, according to the polarizable electrodes of Examples 1, 2, and 3 of the present invention, compared with the polarizable electrode of Comparative Example 1 formed using only activated carbon, the capacitance and its increase rate are In particular, a polarizable electrode produced by dissolving a fullerene in an organic solvent, forming the carbon composition obtained by filtering the solution under reduced pressure and applying a suction pressure, and drying the residue (Example 1, In 2), the capacitance and the rate of increase thereof are greatly improved.

It is a graph which shows the increase rate of the electrostatic capacitance with respect to the comparative example of the Example of this invention.

Claims (9)

  A carbon composition comprising 0.1 to 30 parts by mass of fullerene with respect to 100 parts by mass of activated carbon. The carbon composition according to claim 1, wherein the fullerene is fullerene C60 having 60 carbon atoms per molecule and is spherical.   The carbon composition according to claim 1 or 2, wherein the carbon composition is used for a polarizable electrode for electrochemical capacity.   A method for producing a carbon composition, comprising supporting 0.1 part by mass to 30 parts by mass of fullerene with respect to 100 parts by mass of activated carbon.   5. The method for producing a carbon composition according to claim 4, wherein the fullerene is fullerene C60 having 60 carbon atoms per molecule and is spherical.   The method for producing a carbon composition according to claim 4 or 5, wherein the activated carbon is dispersed in a solution in which fullerene is dissolved in an organic solvent, followed by filtration under reduced pressure.   6. The method for producing a carbon composition according to claim 4 or 5, wherein the activated carbon is dispersed in a solution in which an organic solvent is dissolved in fullerene and subjected to ultrasonic treatment.   The method for producing a carbon composition according to any one of claims 4 to 7, wherein the carbon composition is used for a polarizable electrode for electrochemical capacity.   A carbon composition produced by the carbon composition according to any one of claims 1 to 3 or the carbon composition production method according to any one of claims 4 to 8 was molded. Electropolar capacity polarizable electrode.

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