JPH0744133B2 - Electric double layer capacitor and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electric double layer capacitor using a porous sintered body obtained by sintering activated carbon fine particles as a polarizable electrode, and a method for manufacturing the same.

(Prior Art) In recent years, a capacitor having a large electrostatic capacitance using the electric double layer principle has been used as a power source for backing up a memory of an electronic device, and has been widely used by being incorporated in a microcomputer or an IC memory. There is.

On the other hand, it has been proposed to use the electric charge of this type of electric double layer capacitor for the purpose of simulating an in-vehicle battery.
In such a large-capacity electric double layer capacitor, as the polarizable electrode, for example, as shown in Japanese Patent Application No. 215277 in 1991, a porous layer of only activated carbon in which activated carbon fine particles are sinter-bonded to each other. A quality sintered body is used.

The activated carbon used for sintering is made of fine particles having a large specific surface area to form an electrode body to obtain a capacitor having a large capacitance.

(Problems to be Solved by the Invention) As described above, in an electric double layer capacitor having an electrode body obtained by sintering activated carbon fine particles without a binder as a polarizable electrode, sintering is performed in order to prevent a decrease in surface area after sintering. The applied pressure at this time, the sintering temperature, and the sintering time are reduced to reduce the degree of sintering. However, when the degree of sintering is lowered too much, there is a problem that the bond as a sintered body is broken when the electrolytic solution is impregnated after sintering.

The present invention has been made in view of such problems,
The purpose of this method is to provide an electric double layer capacitor and a method for manufacturing the same in order to specify the degree of sintering of an electrode body that can obtain a large capacitance without breaking even when the sintered body is immersed in an electrolytic solution when sintering the activated carbon fine particles. To provide.

(Means for Solving the Problems) In order to achieve the above-mentioned object, according to the present invention, an electric double layer capacitor using as a polarizable electrode a porous electrode body made of only activated carbon obtained by sintering activated carbon particles to each other. In the method of manufacturing, the sintering of the activated carbon fine particles is performed by controlling the sintering temperature, the applied pressure at the time of sintering, and the sintering time after the specific surface area (A) of the activated carbon fine particles before sintering and after sintering to the electrode body. Area reduction rate (B / A), which is the ratio with the specific surface area (B) of
Provided is a method for manufacturing an electric double layer capacitor having a thickness of 0.85 or less, and an electric double layer capacitor using an electrode body according to the manufacturing method.

(Operation) In the present invention, when the activated carbon fine powder is sintered, the sintering temperature,
By appropriately controlling the applied pressure and the sintering time, the reduction rate of the specific surface area before / after sintering is set to 0.85 or less, so when the electrolytic solution is impregnated and it acts as a polarizable electrode, Since there is no liberation and a large amount of charge is stored, a large capacitance is obtained.

(Example) Next, the Example of this invention is described in detail using drawing.

FIG. 1 is a cross-sectional view showing the configuration of an embodiment of the electric double layer capacitor according to the present invention, FIG. 2 is a data tabulation diagram of the relation between the specific surface area reduction rate of the electrode body and the capacitance, and FIG. FIG. 4 is a curve diagram showing the relation, FIG. 4 is an explanatory view showing a first sintering method for producing the electrode body in the present embodiment, and FIG. 5 is a second sintering method for producing the electrode body. It is a configuration block diagram showing.

In FIG. 1, reference numeral 1 denotes an electrode body, which is made into a polarizable electrode by impregnating a predetermined electrolytic solution, and has a specific particle size of activated carbon powder having a large specific surface area. It is formed into a plate-shaped porous sintered body by a method or the like.

Reference numeral 2 denotes a current collector which is in close contact with one surface of the electrode body 1 and collects electric charges of the polarizable electrode to serve as a capacitor terminal. For example, a conductive thin film obtained by kneading powder of a conductive material and butyl rubber is used. Has been done.

Reference numeral 3 denotes a separator that is interposed between a pair of polarizable electrodes to separate the two from each other. For example, a non-woven fabric made of polypropylene is impregnated with an electrolytic solution.
The outer peripheral portion of is embedded in the central portion of the inner wall of the gasket 4. The gasket 4 is made of a non-conductive synthetic resin and is formed into a tubular shape to serve as a container for accommodating a pair of polarizable electrodes therein. It is adhered to the upper and lower end faces respectively.

In an explanatory view of the first manufacturing method of the electrode body shown in FIG. 4, 6 is a sinter type in which activated carbon powder is contained and sintered and fired into a porous electrode body, and a steel material having high strength is used. The hole 61 used corresponds to the outer shape of the electrode body to be manufactured in the center.
Are pierced and formed into a thick cylindrical shape.

Reference numeral 7 is a pressure plate made of compressed carbon material, the outer diameter of which is formed to fit into the hole 61, and 8 is a compression pin which is used to press the activated carbon powder contained in the hole 61 from above and below. 7 is used for compression.

When manufacturing the electrode body 1, first, the lower compression pin 8 is inserted into the hole 61, and the pressure plate 7 is placed on the hole 61,
The activated carbon powder of a predetermined particle size is sprinkled from above a predetermined amount of holes 61 and spread on the upper surface of the compression pin 8 in layers.

Next, the pressure plate 7 is placed above the layered activated carbon powder, and then the compression pin 8 is inserted from above to apply a predetermined pressure to the upper and lower compression pins 8 and 8 to pressurize the stored activated carbon powder.

Then, the sintering die 6 is heated from the outside to raise the temperature of the activated carbon powder housed in the hole 61 to a predetermined temperature, continue pressurization and heating for a predetermined time, and cool it after a lapse of time. , The upper and lower compression pins 8 and 8 are removed, and the sintered electrode body is taken out from the sintering die 6.

In addition, when heating the above-mentioned activated carbon powder during sintering, electric power may be applied to the upper and lower compression pins 8 to generate heat due to the passing current of the activated carbon powder to form a sintered body. Needless to say, the inner wall of the hole 61 must be coated with a heat-resistant / non-conductive material such as ceramics.

Fig. 2 shows the specific surface area reduction rate and capacitance of an electric double layer capacitor in which the electrode body made of such a sintered body of activated carbon powder was used as a polarizable electrode, under various sintering conditions. The data of the characteristics are as follows. As the sintering conditions, for example, the sintering temperature is in the range of 750 ° C to 850, the sintering time is in the range of 1 minute to 3 minutes, and the applied pressure is in the range of 100 to 400 kg / cm ^2. It is a part of the data that has changed. And
It is known from experience so far that there is a large correlation between the specific surface area of the electrode body and the electrostatic capacity. Therefore, the degree of sintering, that is, the reduction rate of the specific surface area, can be expressed as "specific surface area after sintering / specific surface area when powdered". And the capacitance is the unit of specific surface area, that is, the capacitance value F / m ² obtained as “capacitance / specific surface area as polarizable electrode” is shown in FIG. It shows the relationship between the specific surface area reduction rate and the capacitance per specific surface area in such electric double layer capacitors.

From the data summary table and related curve diagrams, it can be seen that in order to obtain an electric double layer capacitor with a large capacitance, when the above-mentioned specific surface area reduction rate (sintering degree) is around 1.0, Is unstable, so it is better to set this value to 0.85 or less.

Therefore, as the electrode body 1 of the electric double layer capacitor shown in FIG. 1, the one having a specific surface area reduction rate of 0.85 or less as described above is used, and this is impregnated with an electrolytic solution to form a polarizable electrode. A capacitor having a large electric capacity can be obtained.

FIG. 5 is a schematic view of a sintering apparatus by a pulsed electric current, 10 is a sintering machine containing activated carbon powder, and a hole for filling activated carbon powder is formed in the center, and an inner peripheral wall of the hole is formed. The insulating layer 11 is provided, and the main body of the sintering machine 10 is made of high-strength material such as tungsten steel.

Reference numeral 12 is an upper pin, and 13 is a lower pin, which are respectively inserted into the holes at the center of the sintering machine 10, and the activated carbon powder to be the electrode body is sealed between these two pins.

Electrodes 14 and 15 are pressed in the direction of the arrow by a hydraulic device (not shown), and the activated carbon powder is compressed via the upper pin 12 and the lower pin 13.

The switches SW1 and SW2 and the capacitor C are connected to the electrodes 14 and 15.
When the series circuit is connected, the high voltage power from the variable power source 17 is charged in the capacitor C via the resistor R and the closed circuit switch SW2, and the switch SW1 is closed in this state, the electrode 14 , 15 and the upper and lower pins 12, 13 are used as electric paths to apply a high voltage pulse to the activated carbon powder that has been pressed to generate a discharge, and a high temperature is maintained by repeating this,
It is configured to be processed into a porous sintered body. Note that this is a control device that controls the opening / closing timing of the illustrated 18 switches SW1 and SW2.

When sintering activated carbon powder using such a sintering device,
As a sintering condition, for example, a sintering temperature by applying a pulsed high voltage is in a range of 750 ° C to 850 ° C, a sintering time is in a range of 1 minute to 3 minutes, and a pressure applied by a hydraulic device is 100 to 400 kg / cm ^2. By changing the range to a range such as 1), a porous electrode body having characteristics similar to those of the electrode body obtained by the first sintering method shown in FIG. 4 can be obtained.

Therefore, by appropriately controlling the above-mentioned sintering temperature, sintering time and applied pressure, an electrolyte having a specific surface reduction rate of 0.85 or more is produced, and by constructing an electric double layer capacitor with the electrode body, a large electrostatic capacity is obtained. It is possible to obtain a capacitor having a capacity.

Although the present invention has been described with reference to the above-described embodiments, various modifications are possible within the scope of the gist of the present invention, and these modifications are not excluded from the scope of the present invention.

(Effect of the invention) As described above, according to the present invention, when the activated carbon powder is sintered to manufacture the porous electrode body, the sintering temperature, the sintering time and the applied pressure are appropriately controlled, Since the reduction rate of the specific surface area of the activated carbon powder before and after sintering is set to 0.85 or less, when the electrolytic carbon is impregnated and used for the polarizable electrode of the electric double layer capacitor, the activated carbon powder does not liberate properly. The effect is that they can be combined and store a sufficient charge, and thus an electric double layer capacitor having a large capacitance is obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of an embodiment of the electric double layer capacitor of the present invention, FIG. 2 is a data tabulation diagram of the relationship between the specific surface area reduction rate of the electrode body and the capacitance, and FIG. FIG. 4 is a curve diagram showing the relation, FIG. 4 is an explanatory view showing a first sintering method of the electrode body, and FIG. 5 is a block diagram showing a second sintering method of the electrode body. 1 ... Electrode body, 2 ... Current collector, 3 ... Separator, 4 ...
… Gasket, 6 …… Sintering type, 7 …… Pressure plate, 8 …… Compression pin, 10 …… Sintering machine, 12 …… Upper pin, 13 …… Lower pin, 14,15 …… Electrodes.

Claims (2)

[Claims] 1. A method for manufacturing an electric double-layer capacitor, wherein a porous electrode body made of only activated carbon is used as a polarizable electrode by sintering activated carbon particles to each other. The area reduction rate (B / A), which is the ratio of the specific surface area (A) of the activated carbon fine particles before sintering and the specific surface area (B) of the electrode body after sintering, can be controlled by controlling the applied pressure during sintering and the sintering time. ) Is 0.85 or less, a method for producing an electric double layer capacitor. 2. In an electric double layer capacitor using a porous electrode body made of only activated carbon as a polarizable electrode by sintering the activated carbon fine particles to each other, a sintering temperature, an applied pressure and By controlling the sintering time, the area reduction rate (B / B), which is the ratio of the specific surface area (A) of the activated carbon fine particles before sintering to the specific surface area (B) of the electrode body after sintering.
An electric double layer capacitor characterized in that an electrode body obtained by sintering A) to 0.85 or less is used as a polarizable electrode.