JPH05258993A - Electrochemical capacitor - Google Patents

Abstract

PURPOSE:To provide a low-cost electrochemical capacitor of high capacitance, which has higher specific capacitance than a conventional electric double-layer capacitor using active carbon and has larger specific surface area than a capacitor of pseudo-capacity where ruthenium oxide particles are used. CONSTITUTION:Hydrogen peroxide is made to drip down into the mixed solution of porous activated carbon and ruthenium chloride to obtain ruthenium oxide- loaded porous activated carbon. Activated carbon is bonded by pressure to support plates 1 which function as a current collecting plate together with binder to form polarizable electrodes 2. The polarizable electrodes 2 are arranged at a certain interval confronting each other, interposing a separating film 3 between them, the end faces of a capacitor of this design are sealed up with gaskets 4, and electrolytic solution 5 is filled into a space produced inside the capacitor to form an electrochemical capacitor of high capacitance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a principle of electrochemistry, and more particularly to a large capacity capacitor utilizing an electrochemical double layer.

[0002]

2. Description of the Related Art When an electrode is immersed in an electrolyte solution, the electrode generally exhibits a certain electric potential. Ions having a sign opposite to the sign of this potential are attracted from the solution to the vicinity of the electrode to form an electric double layer at the interface between the electrode and the solution. It Conventionally, as a capacitor applying this principle, activated carbon powder and binder PTFE were used.
There was an electric double layer capacitor in which two electrodes each composed of a polarizable electrode formed by molding powder and a collector electrode were used, and an electrolytic solution was housed between the electrodes.

When a DC voltage is applied to the two collecting electrodes of the electric double layer capacitor having such a property, in the electric double layer on the positive electrode side, a positive charge is generated on the activated carbon side, which is a polarizable electrode, on the electrolyte side. In the electric double layer on the negative electrode side, on the other hand, the negative charge increases on the activated carbon side, which is the polarizable electrode, and the positive charge increases on the electrolyte side, respectively.
A large amount of charge is accumulated in the two electric double layers. In this electric double layer capacitor, the capacitance increases in proportion to the specific surface area of the polarizable electrode.

This electric double layer capacitor has a large surface area because it uses a porous carbon thin film molded body as an electrode, but on the other hand, the capacitance value formed between the activated carbon surface and the electrolyte is 20. Was about 50 μF / cm ² . On the other hand, conventionally, there has been a capacitor having pseudo capacitance using ruthenium oxide fine particles. Examples of such technology include, for example, 607 of the 33rd International Power Source Symposium Proceedings.
Pp. 617 (June 1988) entitled "Filter Performance of Ultracapacitors", it is disclosed that this ultracapacitor is based on porous carbon electrodes and is classified as pseudocapacitance. Also, the journal
Of Power Source, 29 (1990) 355-364
Discloses that a ruthenium oxide-ionomer composition structure resulted in a high energy density electrochemical capacitor completely free of liquid electrolyte. Also,
The Proceeding Of The Electrical
Society, 582-593 (1987), prepared an electrochemical capacitor based on a high surface area ruthenium dioxide thin film electrode, reported on the electrochemical response of the capacitor, and showed a specific capacitance value of 170 μF. It was disclosed that the capacity was as high as / cm ² .

[0005]

By the way, as described above, the conventional general electric double layer capacitor has a specific capacitance value lower than that of the pseudo capacitance capacitor using fine particles of ruthenium oxide. On the other hand, it is difficult to make the polarizable electrode porous in a capacitor using a pseudo capacity using ruthenium oxide fine particles, and therefore the specific surface area is currently 1
It is a 20m ² / g, of activated carbon 300~2000m ²
The specific surface area was very small compared to / g.

Therefore, in order to further increase the capacity of the capacitor by the pseudo capacity using fine particles of ruthenium oxide, it was necessary to increase the specific surface area. In addition, since ruthenium oxide fine particles are mainly used to form the polarizable electrode, the ruthenium oxide fine particles themselves are expensive, so that the cost is high.
Therefore, the present invention is a large-capacity electrochemical capacitor that has a higher specific capacitance value than the conventional electric double layer capacitor, can have a larger specific surface area than a capacitor using a pseudo capacitance using ruthenium oxide fine particles, and can keep the cost low. The purpose is to provide.

[0007]

In order to solve the above-mentioned problems, the present invention provides an electrochemical capacitor using an electric double layer formed at a polarizable electrode and an electrolyte interface,
The electrochemical capacitor is characterized by using porous activated carbon or activated carbon fiber supporting fine particles of ruthenium oxide as a decomposition electrode.

In the present invention, the method for supporting fine particles of ruthenium oxide on the porous activated carbon was carried out as follows.
Put a mixed solution of fine powder of porous activated carbon and ruthenium chloride in a container, and stir the solution while keeping the temperature of the solution at 3
The reaction represented by the following formula 1 is carried out by dropping a drop of hydrogen peroxide from above while keeping the temperature at 0 to 40 ° C.

[0009]

[Chemical 1]

In this way, the fine powder of ruthenium oxide RuO ₂ can be carried on the surface of the fine powder of porous activated carbon. Next, fine powder of porous activated carbon carrying fine powder of ruthenium oxide RuO ₂ is collected from the solution and dried. Polytetrafluoroethylene (hereinafter referred to as PTFE) particles as a binder are mixed with the dried material. 50 kg /
A polarizable electrode bonded to a support plate is obtained by molding at a pressure of about cm ² .

As the support plate, stainless steel (SUS316) which has a role of a current collector plate and a role of a stopper which does not leak sulfuric acid as an electrolytic solution to an adjacent cell can be used. In addition to the SUS316, titanium, aluminum, tungsten, tantalum, or the like having a low specific gravity can be used as the material of the support plate. Next, two polarizable electrodes joined to the support plate are prepared, the polarizable electrodes are opposed to each other with a certain distance, a separation membrane is placed in the middle, and both ends are sealed with a gasket to create a space. Fill the inside with electrolyte.

In the present invention, as the porous activated carbon, for example, one having a particle diameter of 400 Å or less and a specific surface area of 200 m ² / g or more is used. The amount of PTFE added to the porous activated carbon is about 10-12% by weight. The electrolytic solution used in combination with the polarizable electrode in the present invention is not particularly limited,
A non-aqueous solution or an aqueous solution can be used. Nafion 117 (trade name: manufactured by DuPont) is used as the non-aqueous solution, and H ₂ SO _{4 of} about 1 to ₄ M is used as the aqueous solution.

From the transmission electron micrograph, it is observed that ruthenium oxide is attached to the surface of activated carbon.

[0014]

Example 1 Porous activated carbon having a particle size of 300 liters and a specific surface area of 280 m ² / g was put into a 10 wt% ruthenium chloride aqueous solution and stirred with a stirrer to disperse the porous activated carbon. While maintaining the temperature of the dispersion solution at 30 ° C., hydrogen peroxide was added dropwise while stirring the dispersion solution using the apparatus for preparing an electrode material for electrochemical capacitors shown in FIG.

Filtration was carried out to obtain porous activated carbon on which moist fine particles of ruthenium oxide RuO ₂ were adsorbed. This porous activated carbon was dried at 120 ° C. under reduced pressure of about 1 Torr.
Then, polyflon TFE disversion (trade name: manufactured by Daikin Industries, Ltd.) as PTFE particles was added and mixed so as to be 10% by weight, and the mixture was placed on a stainless steel plate (SUS316) having a thickness of 0.2 mm as a supporting plate and 50
A polarizable electrode bonded to the support plate was obtained by press molding under a pressure of kg / cm ² .

The two polarizable electrodes are made to face each other with a certain distance therebetween, and in the middle of them, there is used a separation resin having a hole diameter of 40 μm and a thickness of 0.17 mm of polyvinyl-based resin Umicron (trade name: Yuasa Battery). 2) is placed, both ends are sealed with gaskets, and 2
He was charged with H ₂ SO ₄ of M. The electrochemical capacitor thus obtained is shown in FIG. Reference numeral 1 is a support plate, 2 is a polarizable electrode, 3 is a separation membrane, 4 is a gasket, and 5 is an electrolytic solution.

The capacitance value of the electrochemical capacitor obtained in Example 1 was about 2 F / cm ² . On the other hand, as a comparative example, the specific capacity value of the capacitor similarly manufactured from porous activated carbon not supporting ruthenium oxide was 0.2F.
Was / cm ² .

[0018]

The electrochemical capacitor of the present invention has a higher capacity than conventional electric double layer capacitors and uses ruthenium oxide fine particles because it uses porous activated carbon carrying fine particles of ruthenium oxide as a polarizable electrode. The specific surface area can be made larger than the capacitor with the pseudo capacitance,
Moreover, a large-capacity electrochemical capacitor whose cost can be kept low can be obtained.

[Brief description of drawings]

FIG. 1 shows an electrochemical capacitor of the present invention.

FIG. 2 shows an apparatus for preparing an electrode material for electrochemical capacitors.

[Explanation of symbols]

 1 Support plate 2 Polarizable electrode 3 Separation membrane 4 Gasket 5 Electrolyte

Front Page Continuation (72) Inventor Masashi Nakamura 10 Takane, Fujii-cho, Anjo-shi, Aichi Aisin AW Co., Ltd.

Claims (1)

[Claims] 1. An electrochemical capacitor using an electric double layer formed at an interface between a polarizable electrode and an electrolyte, wherein porous activated carbon or activated carbon fiber carrying fine particles of ruthenium oxide is used as a polarizable electrode. Characteristic electrochemical capacitor.