JPH0974052A - Method for manufacturing polarizable electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrical double-layer capacitor with a high capacity density and a low resistance by depositing and adhering a layer with an active carbon as a main constituent to a conductive substrate by cataphoresis electrolytic deposition. SOLUTION: An active carbon powder 10 wt.pts and acetylene black 2 wt.pts are uniformly mixed and dissipated to methanol 5 wt.pts to obtain a liquid A. On the other hand, polyvinylpyrrolidone 2 wt.pt is dissolved to water 10 wt.pts to obtain a liquid B. The liquids A and B are mixed to obtain an active carbon slurry 2. By dipping Al foil which is subjected to surface polishing as a conductive substrate and Al plate as a counter electrode into an active carbon slurry 2 and setting Al foil 3 and Al plate 4 as positive and negative polarities, respectively, DC is applied between both at a room temperature. Then, the Al foil 3 is pulled up from the active carbon slurry 2 and the Al foil with the obtained active carbon layer is dried and is cut to a specific size, thus obtaining a foil electrode and hence obtaining a carbon electrode whose manufacture control can be simplified and which has a uniform film thickness where the volume filling rate of the active carbon is high and the controllability of the carbon film thickness can easily be controlled by an application voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a polarizable electrode used in an electric double layer capacitor.

[0002]

2. Description of the Related Art An electric double layer capacitor is a large-capacity capacitor which uses activated carbon as a polarizable electrode and utilizes the electric double layer capacitance accumulated in the interface electric double layer between the activated carbon and the electrolytic solution. The electric double layer capacitor is conventionally classified into a coin type and a cylindrical type. FIG. 4 shows a typical structure of a coin type capacitor. A pair of polarizable electrodes in which aluminum sprayed layers 23 and 24 are formed on one surface of sheets 21 and 22 made of woven cloth of activated carbon fiber, a separator 25 interposed between the electrodes, and tetraethylammonium permeate impregnated therein An electrolytic solution composed of a propylene carbonate solution of lorate is housed in metal cases 26, 27 and an insulating gasket ring 28.

The cylindrical capacitor has a structure as shown in FIG. 2 described later. Activated carbon, a conductivity-imparting material, a binder, and a slurry composed of a solvent of a binder is applied to an aluminum foil, and a pair of electrodes on which an activated carbon layer is formed by drying is wound with a separator, which is an aluminum case
It is a housing with a rubber sealing material. This capacitor also uses an organic electrolytic solution as the electrolytic solution as in the coin type. Furthermore, a capacitor using a sulfuric acid aqueous solution as an electrolytic solution has been developed.

[0004]

It is an important point to increase the capacitance density per cell volume of the electric double layer capacitor. For this purpose, it is necessary to pack as much activated carbon per unit cell volume as possible. A conventional cylindrical capacitor electrode has an activated carbon filling rate of 30 to 7
It was 0%. Various methods can be used for supporting a conventional slurry on an aluminum substrate, such as coating, printing, roll coating, doctor blade, and dipping, but the filling rate of each method was limited to 70%. Also,
The electric resistance value of the electrode becomes smaller in proportion to the filling rate because the contact area between the activated carbons increases as the filling rate of the activated carbon increases. As described above, in order to further increase the capacitance density of the capacitor and further reduce the resistance, it is an essential condition to increase the packing density of activated carbon. It is an object of the present invention to provide a method for manufacturing a polarizable electrode that provides an electric double layer capacitor having high capacitance density and low internal resistance.

[0005]

The method of manufacturing a polarizable electrode according to the present invention is to deposit a layer containing activated carbon as a main component on a conductive substrate by electrophoretic deposition. here,
Electrophoretic electrodeposition is performed by applying a DC electric field between the counter electrode and a positive electrode in a slurry containing activated carbon, a binder, and a solvent of the binder. It is preferable that the slurry further contains a conductivity imparting material.

The conductivity-imparting material is preferably selected from the group consisting of carbon black, acetylene black, Ketjen black, graphite powder, carbon fiber, and ruthenium oxide. Further, the binder is preferably selected from polysaccharides. A metal or carbon foil, a net, or a punching plate is used as the conductive substrate. The solvent is preferably selected from water and alcohol.

According to the present invention, the volume filling factor of the activated carbon of the electrode is remarkably increased, and therefore, an electric double layer capacitor having a high capacity density and a low resistance can be obtained. Also,
It is also possible to easily control the thickness of the activated carbon layer during electrode production.

[0008]

Embodiments of the present invention will be described below. FIG. 1 shows a schematic configuration of an apparatus for electrophoretic electrodeposition. The conductive substrate 3 and the counter electrodes 4 and 4 constituting the polarizable electrode are immersed in a container 1 containing a slurry 2 composed of activated carbon, a conductivity-imparting material, a binder, and a solvent of the binder, and the conductive substrate 3 is positively charged. , Negative electrode 4 and DC power supply 5
A DC voltage is applied between both electrodes by. In this way, polarizable electrodes composed of activated carbon, a conductivity-imparting material and a binder can be formed on both surfaces of the conductive substrate. Next, specific examples will be described.

[Example 1] Activated carbon powder (specific surface area: 17
00 m ² / g, average particle size: 2 μm) 10 parts by weight and 2 parts by weight of acetylene black are uniformly mixed and dispersed in 5 parts by weight of methanol to prepare a liquid A. On the other hand, polyvinylpyrrolidone 2
Part by weight is dissolved in 10 parts by weight of water to prepare a liquid B. Liquid A and liquid B
Are mixed to obtain an activated carbon slurry. A surface-polished aluminum foil having a thickness of 30 μm is used as a conductive substrate, and an aluminum plate having a thickness of 1 mm is used as a counter electrode. These are immersed in the above activated carbon slurry 2 as shown in FIG.
The aluminum foil 3 is made positive and the aluminum plates 4, 4 are made negative, and a direct current of 10 V is applied between them for 5 minutes at room temperature. Then, the aluminum foil 3 is pulled up from the activated carbon slurry 2. The obtained aluminum foil having an activated carbon layer is dried at 150 ° C. for 30 minutes and cut into a predetermined size to obtain a foil electrode.

FIG. 2 shows the structure of a cylindrical capacitor using the polarizable electrode obtained as described above. 12 and 1
Reference numeral 5 denotes a polarizable electrode, and conductive substrates 10 and 13 and activated carbon layers 11 and 14 formed on both surfaces thereof, respectively.
It is composed of The size of the polarizable electrode is 10m wide
m and length 50 mm. These electrodes are wound via the separator 16 and inserted into the aluminum case 17, and after the electrolytic solution is injected, the electrodes are sealed with the rubber packing 18. 19, 2
0 represents an electrode lead. As the electrolytic solution, propylene carbonate in which 1 mol / l tetraethylammonium perchlorate was dissolved was used.

FIG. 3 schematically shows a cross section of the polarizable electrode obtained in this example. 3 is an aluminum foil, 6 is activated carbon powder, 7 is acetylene black as a conductivity-imparting material, and 8 is a binder. It represents. The filling factor of the activated carbon powder of the polarizable electrode obtained in this example was about 90%.
The high filling factor of activated carbon is due to the fact that activated carbon is strongly attracted to the surface of the aluminum foil by the force of the DC electric field, and the activated carbons are also strongly attracted to each other by the electric energy in the electric field. Conceivable.

Example 2 A polarizable electrode was manufactured in the same manner as in Example 1 except that ammonium salt of carboxymethyl cellulose was used instead of polyvinylpyrrolidone, and a cylindrical capacitor was assembled.

[Example 3] A polarizable electrode was manufactured in the same manner as in Example 1 except that a flexible conductive substrate made of a mixture of graphite and styrene-butadiene rubber (SBR) was used in place of the aluminum foil, and a cylindrical electrode was prepared. Shaped capacitors were assembled.

[Comparative Example] Activated carbon powder (specific surface area: 170
0 m ² / g, average particle size: 2 μm) 10 parts by weight, acetylene black 2 parts by weight, polyvinylpyrrolidone 2 parts by weight,
A slurry composed of 5 parts by weight of methanol and 10 parts by weight of water was applied to a surface-polished aluminum foil having a thickness of 30 μm and dried to manufacture a polarizable electrode, thereby forming a cylindrical capacitor as shown in FIG. Table 1 shows the characteristics of the capacitors obtained in the above Examples and Comparative Examples.

[0015]

[Table 1]

In the above embodiments, activated carbon powder was used as the activated carbon material, but chopped activated carbon fibers can also be used. Further, although the aluminum foil and the carbon / SBR mixture are used as the conductive base material, a structure such as carbon fiber or a woven fabric made of the carbon fiber may be used.
Graphite powder, ruthenium oxide, and carbon fiber can also be used as the conductivity imparting agent. The conductivity imparting agent may not be used.
As a binder, all polysaccharides can be used. Also,
It is also possible to develop a concept of obtaining a carbon layer having a high packing density by electrophoretic electrodeposition to obtain a high density negative electrode carbon electrode for a lithium battery.

[0017]

As described above, according to the present invention, it is possible to obtain a carbon electrode having a very high filling factor of activated carbon, and a capacitor using this as a polarizable electrode has a very high energy density per volume. Become. The internal resistance of the cell is also very low. The controllability of the carbon film thickness during the production of the electrode foil can be easily controlled by the applied voltage, and a carbon electrode with a very uniform film thickness can be obtained by simple production control, and the value of the present invention is industrially very high. Is the first one.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an apparatus for manufacturing an electrode used in an example of the present invention.

FIG. 2 is a perspective view in which a part of an electric double layer capacitor according to an exemplary embodiment of the present invention is cut away.

FIG. 3 is a schematic view showing a cross section of a polarizable electrode according to an example of the present invention.

FIG. 4 is a vertical cross-sectional view showing a configuration example of a conventional capacitor.

[Explanation of symbols]

 1 Container 2 Slurry 3 Conductive Substrate 4 Counter Electrode 5 DC Power Supply 6 Activated Carbon Powder 7 Conductivity-Giving Material 8 Binder 10, 13 Conductive Substrate 11, 14 Activated Carbon Layer 12, 15 Polarity Electrode 16 Separator 17 Container 18 Rubber Packing 19, 20 Electrode lead

Front page continued (72) Inventor Susumu Nomoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Inventor Masaki Ikeda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A method for producing a polarizable electrode, which comprises depositing a layer containing activated carbon as a main component on a conductive substrate by electrophoretic deposition. 2. The electrophoretic electrodeposition is performed by applying a DC electric field between the counter electrode and a positive electrode of the conductive substrate in a slurry containing activated carbon, a binder, and a solvent of the binder. Manufacturing method of polarizable electrode. 3. The method of manufacturing a polarizable electrode according to claim 2, wherein the slurry further contains a conductivity imparting material. 4. The production of a polarizable electrode according to claim 3, wherein the conductivity-imparting material is selected from the group consisting of carbon black, acetylene black, Ketjen black, graphite powder, carbon fiber, and ruthenium oxide. Method. 5. The method for producing a polarizable electrode according to claim 2, wherein the binder is selected from polysaccharides. 6. The method for producing a polarizable electrode according to claim 1, wherein the conductive substrate is one of a metal or carbon foil, a net, and a punching plate. 7. The method for producing a polarizable electrode according to claim 2, wherein the solvent is selected from the group consisting of water and alcohol.