JPH07201676A - Electric double layer capacitor - Google Patents

Abstract

PURPOSE:To realize rapid charge/discharge and large capacity of an electric double layer capacitor by constructing at least one of polarizable electrodes by a conductive polymer film which is acquired by an electrolytic polarization method by suspending powder-like or fiber-like carbon in polymerization liquid and by taking in carbon during polymerization. CONSTITUTION:In an electric dipole layer capacitor, a separator 3 and polarizable electrodes 1, 2 impregnated with electrolytic solution are contained in a can 5. As for at least one of both polarizable electrodes 1, 2, a conductive polymer film is used, which is generated on a polymerization electrode through electrolytic polymerization by melting monomer and dopant in water or organic solvent being stable without oxidation even in an electric potential whereat electrolytic oxidation reaction of monomer is caused, suspending powder-like or fiber-like carbon in the solution and electrolytically polymerizing it. In this case, as for the other one, a layer of active carbon can be used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electric double layer capacitor.

[0002]

As is well known, electric double layer capacitors are
It is mainly composed of a pair of polarizable electrodes, a collector electrode of each polarizable electrode, and a porous separator interposed between the polarizable electrodes. Each polarizable electrode is impregnated with an electrolytic solution.

Conventionally, the polarizable electrode is usually made of activated carbon or fibrous activated carbon.
According to this, there is a drawback that the discharge capacity is small, and therefore the discharge cannot be maintained for a long time in actual use. Further, since the internal resistance is large, there is a drawback that a large current cannot be taken out.

In order to solve this, the present inventors have previously proposed a structure in which a conductive polymer film produced by an electrolytic polymerization method is used as a polarizable electrode of an electric double layer capacitor (Japanese Patent Application No. 4-300237). issue). According to this, there is an advantage that the capacity is larger and the internal resistance is smaller than the case where the conventional polarizable electrode is used, but it is not always satisfactory.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to further speed up charge / discharge and increase capacity in an electric double layer capacitor using a conductive polymer film obtained by electrolytic polymerization as a polarizable electrode. And

[0006]

The present invention provides an electric double layer capacitor in which a pair of polarizable electrodes are impregnated with an electrolytic solution and a separator is interposed between at least one of the polarizable electrodes. The powdery or fibrous carbon is suspended in a polymerization solution, and the carbon is taken in during the polymerization to constitute the conductive polymer film itself obtained by an electrolytic polymerization method.

[0007]

[Function] By suspending powdery or fibrous carbon in a polymerization solution, a conductive polymer film incorporating carbon during polymerization improves conductivity and enables high-speed charging / discharging. Capacity increases. The conductive polymer used here is prepared as follows. That is, the monomer and the dopant are dissolved in an organic solvent or water that is stable and does not oxidize even at the potential where the monomer is dissolved and the electrolytic oxidation reaction of the monomer occurs, and carbon is suspended in this solution and electropolymerized. . A conductive polymer film is formed on the polymerization electrode (anode) by this electrolytic polymerization.

As the polymerization electrode used for this electrolytic polymerization, any conductor can be used as long as it is stable at the working potential. For example, metals such as gold, silver, copper, platinum, stainless steel, titanium, nickel, lead, tin, aluminum, and tungsten, alloys thereof, or graphite (polyacrylonitrile-based, pitch-based, phenol-based, etc.) can be used. Further, it may be an arbitrary object to which conductivity is imparted by plating or the like.

The monomer used here is pyrrole,
It is also possible to use aniline, thiophene, furan, selenophene, isothianaphthene, phenylene sulfide, phenylene oxide, azulene, or derivatives thereof, or a combination thereof (copolymer).

As the dopant, generally used sulfonate ion, perchlorate ion, hexafluorophosphate ion, tetrafluorophosphate ion, tetrafluoroborate ion, arsenic hexafluoride ion, Hexafluoroantimonate ion, tetrachloroaluminate ion, halogen ion, phosphate ion, sulfate ion, nitrate ion and the like can be used. In addition to these, polyvalent anions and surfactants having a critical micelle concentration or more can also be used.

The carbon to be suspended may be powdery or fibrous, but carbon which precipitates in the polymerization liquid is not preferred. However, when the solution is settled, the solution may be stirred to prevent the settling.

As described above, the electroconductive polymer film formed on the surface of the polymerizing electrode during the electropolymerization is used as the polarizable electrode as it is, or the electroconductive polymer film separated from the polymerized electrode is used as the polarizable electrode. To do. A conductive polymer film may be used as both polarizable electrodes forming a pair of the electric double layer capacitor, or only one of them may be used. In that case, the other polarizable electrode may be made of a conductive material having a large surface area (for example, powdered or fibrous activated carbon).

As the electrolytic solution with which the polarizable electrode and the separator are impregnated, a solution prepared by dissolving an electrolyte in water or an organic solvent (single or a mixture of carbonates, alcohols, nitriles, amides, ethers, etc.) can be used. .

As the electrolyte, a single or plural cations such as a proton, an alkali metal ion, a quaternary ammonium ion and a quaternary phosphonium ion, and a sulfonate ion, a perchlorate ion, an arsenic hexafluoride ion, a halogen ion and a phosphorus ion. A single or a combination of plural anions such as an acid ion, a sulfate ion and a nitrate ion is preferable.

The separator may be an insulating porous body which prevents an electrical short circuit between both polarizable electrodes, is electrochemically stable, has a large ion permeability, and has a certain mechanical strength. Specifically, a non-woven fabric, a porous polypropylene film, a polyethylene film, or the like can be used.

[0016]

1 shows the structure of an electric double layer capacitor according to an embodiment of the present invention. Reference numerals 1 and 2 denote polarizable electrodes paired as positive and negative electrodes, 3 is a separator interposed between the polarizable electrodes 1 and 2, 4 is a cap, 5 is a can, and 6 is a packing. Polarizable electrode 1, in which the electrolytic solution is impregnated in the can 5,
2 and the separator 3 are stored. The can 5 and the cap 4 are insulated by the packing 6. The packing 6 also serves to prevent leakage of the electrolytic solution.

At least one of the polarizable electrodes 1 and 2 is formed of the conductive polymer film according to the present invention. When one is a conductive polymer film, the other may utilize a layer of activated carbon.

FIG. 2 shows an electric double layer capacitor 8 in which a plurality of electric double layer capacitors 7 each having the structure shown in FIG. 1 are used as a unit. In the figure, 9 is a lead electrode of each polarizable electrode, 10 is an exterior case, and 11 is an insulating case. If a plurality of unit units are stacked in this manner, the withstand voltage will be increased, which is convenient.

Next, specific experimental examples of the present invention will be described. The first experimental example relates to the diffusion coefficient of a conductive polymer film. The possibility of high-speed charging and discharging of this type of capacitor can be evaluated by measuring the diffusion coefficient.

First Experimental Example 0.1 (mol / liter)
0.1 (mol / liter) of 1,3 containing
From a solution obtained by adding 0.03 g of carbon powder per 1 ml of this solution to an aqueous solution of 6-naphthalene trisulfonate, a potentiostatic electropolymerization method (800 mV vs.
A polypyrrole film was formed on the gold electrode by SSCE) (polymerization charge amount 2 coulomb / square centimeter). The membrane was transferred to an aqueous sodium chloride solution, and the diffusion coefficient was determined by the AC impedance method. As a result, 10 ⁻² to 10
A diffusion coefficient of ⁻³ (cm ² s ⁻¹ ) was obtained.

As a first comparative example for comparison, a conductive polymer film was prepared in exactly the same manner as in the first experimental example except that carbon powder was not added, and the diffusion coefficient was determined by the same method. As a result, a diffusion coefficient of 10 ⁻³ to 10 ⁻⁵ (cm ² s ⁻¹ ) was obtained. From this, it is clear that the case of the first experimental example can obtain a larger diffusion coefficient than that of the first comparative example.

Next, a second experimental example will be described. This experimental example is for evaluation as a capacitor.

Second Experimental Example A polypyrrole film prepared according to the first experimental example was punched into a circle having a diameter of 13 mm, which was used as a positive electrode, and 1000 m2 / g of fibrous activated carbon (13 mm in diameter) was used as a negative electrode. A polypropylene porous film was used as the separator. Then, an electric double layer capacitor as shown in FIG. 1 was constructed by using a 0.1 (mol / liter) sodium chloride aqueous solution as the electrolytic solution. It was charged at 1.0 volt and then discharged with a constant current of 0.1 milliamps to 0.4 volt. The capacitance of the obtained capacitor is 8F,
The internal resistance was 0.6 ohm.

As a second comparative example for comparison, an electric double layer capacitor was constructed in exactly the same manner as in the second experimental example except that carbon powder was not added, and an experiment was conducted in the same manner as in the second experimental example. did. The obtained capacitor had a capacity of 7 F and an internal resistance of 1.3 ohm. Even from this, the case of the second experimental example is better than that of the second comparative example.
It is found that a capacitor having a large capacity and a small internal resistance can be obtained.

[0025]

As described above, according to the present invention, a conductive polymer film prepared by electrolytic polymerization from a solution in which carbon is suspended is used as a polarizable electrode.
It has an effect that it has a larger capacity than the already proposed electric double layer capacitor and can be charged and discharged at high speed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 1-polarity electrode 2 2-polarity electrode 3 Separator

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takehiko Iinuma 47 Umezutakaunecho, Ukyo-ku, Kyoto City Nissin Electric Co., Ltd.

Claims (1)

[Claims] 1. In an electric double layer capacitor configured by impregnating a pair of polarizable electrodes with an electrolytic solution and interposing a separator, at least one of the polarizable electrodes comprises powdery or fibrous carbon. An electric double layer capacitor obtained by suspending the above in a polymerization liquid and incorporating the above-mentioned carbon at the time of polymerization to form a conductive polymer film itself obtained by an electrolytic polymerization method.