JPH03201516A - Electric double layer capacitor - Google Patents

Abstract

PURPOSE:To increase capacitance, and to reduce internal resistance by mixing powder mainly valuing specific accuracy as activated-carbon fines and mesocarbon of several mum at a specific rate and sintering a mixture to an electrode body. CONSTITUTION:Activated-carbon fines A use a phenol resin or petroleum coke, coal tar or the like as a raw material, and have the peak of the particle size distribution in approximately 20-30mum. As for mesocarbon B, coal tar is purified as a raw material, and the mesocarbon B having the particle size extending over 3mum to 8mum occupies approximately ninety % of the whole. Mesocarbon B uniform in spherical dimensions is employed, the mesocarbon B 3-10% in weight is mixed with activated-carbon fine powder A, and the mesocarbon B is sintered together with the activated-carbon fine powder A by means of a sintering device. An electric double layer capacitor is composed of polarizable electrodes 20 obtained by impregnating a sintered electrode body with dilute sulfuric acid, a gasket 30 using a nonconductive rubber and a separator 40 separating the capacitor into upper and lower sections, and the charges of the polarizable electrodes 20, 20 are collected by the use of current collecting plates 50, 50 employing a conductive rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electric double layer capacitor using an electrode body formed by sintering fine activated carbon powder as a polarizable electrode.

(Prior Art) In recent years, large capacitance capacitors using the electric double layer principle have been developed, and attempts are being made to increase their scale and use them for battery applications.

As an electric double layer capacitor of this type, a proposal has been made in Japanese Patent Application Publication No. 2003-12101 in which the element is constructed by interposing a separator and an electrolytic solution between carbon electrodes made of activated carbon fiber cloth, and t-2 carbon black is mixed in the electrolytic solution. It is disclosed in Japanese Patent No. 64-53523 as an electric double layer capacitor.

(Problems to be Solved by the Invention) Attempts have been made to increase the capacitance of the electrode body of such electric double layer capacitors by increasing the surface area that comes into contact with the electrolyte, and to reduce the internal resistance of the electrode body itself. It will be done, but
Although carbon black is mixed in the electrolyte in the proposal shown in the above-mentioned publication, there is no clear disclosure of the mixing ratio or its range, and if the mixing ratio is increased too much, the capacitance will increase. There is a risk that this will decrease.

Further, since carbon black cannot be sintered, there arises the problem that it is unsuitable for electrode bodies to be sintered.

The present invention was made in view of such problems,
The purpose is to select the particle size and mixing ratio of the activated carbon powder used when sintering the electrode body, and to provide an electric double layer capacitor with high capacitance and low internal resistance.

(Means for Solving the Problems) According to the present invention, in an electric double layer capacitor in which an electrode body obtained by sintering fine activated carbon powder is impregnated with an electrolytic solution, the fine activated carbon powder mainly has a particle size of 20 μ to 30 μ. An electric double layer capacitor is provided in which activated carbon powder and mesocarbon mainly having a particle size of several microns and which is 3% to 10% by weight of the activated carbon powder are mixed and sintered into an electrode body.

(Function) In the present invention, the activated carbon fine powder used for sintering the electrode body is 2
Powder mainly having a particle size of 0 to 30μ and mesocarbon having a particle size of several μ are mixed at a predetermined ratio and fired, so mesocarbon is interposed between the powders and the surface area of the electrode body is increased. At the same time, the number of electrical paths through which charges pass increases, so that an electric double layer capacitor with large capacitance and low internal resistance can be obtained.

(Example) Next, an example of the present invention will be described in detail using the drawings.

FIG. 1 is an enlarged cross-sectional view of a part of a fired electrode body in an embodiment of an electric double layer capacitor according to the present invention;
FIG. 2 is a schematic diagram of the sintering apparatus for the electrode body.

In FIG. 1, A is activated carbon powder, which is made from phenolic resin, petroleum coke, coal tar, etc., and whose particle size distribution has a peak on the side of 20 to 30 microns.

B is a mesocarbon refined from coal tar as a raw material, and has a particle size of 3 to 8μ, accounting for approximately 90% of the total, and has uniform spherical dimensions. 3 to 10% of mesocarbon B was mixed therein and fired together with activated carbon powder A using a sintering apparatus as shown in FIG.

In Figure 2, 10 is activated carbon powder A and mesocarbon B.
This is a sintered mold that accommodates a mixture of powder and powder, and a hole is formed in the center to be filled with the mixed powder.The inner circumferential wall of the hole is made of an insulating layer 11 made of ceramics, and the outer circumference is made of a high-strength material such as tungsten steel. ing.

12 is an upper bottle, 13 is a lower pin, which are inserted into the hole in the center of the sintering mold 10, and both pins 1
Activated carbon powder 16 is sealed between 2 and 13 and processed into a sintered body.

Reference numerals 14 and 15 designate electrodes, which are arranged above the upper pin 12 and below the lower bottle 13, and a pressure P is applied in the direction of the arrow by a hydraulic device (not shown).
13, the mixed activated carbon powder 16 is pressurized from both the upper and lower directions.

A series circuit of switches SWI, SW2 and capacitor C is connected in parallel to the electrodes 14.15, and a variable power supply 1 is connected to the series connection part of switch SW2 and capacitor C.
7 and variable resistor R are connected to supply power. 1
A control circuit 8 controls the opening and closing of the normally open switch SWI and the normally closed switch SW2.

Figure 3 shows the capacitance and internal resistance of an electric double layer capacitor using an electrode body that was sintered using the sintering equipment described above and the mixing ratio of activated carbon powder A and mesocarbon B was changed. FIG. 4 is a diagram showing the relationship between the mixing ratio, capacitance, and internal resistance.

As is clear from these drawings and diagrams, when the mixing ratio of mesocarbon B to activated carbon powder A ranges from 3% to 10%, characteristics of large capacitance and low internal resistance are obtained. There is.

FIG. 5 is a sectional view of an example of an electric double layer capacitor to which this embodiment is applied. In the same figure, 20 is a polarizable electrode obtained by mixing the materials based on this example at the predetermined mixing ratio described above and filling a sintering mold, and impregnating the sintered electrode body with dilute sulfuric acid, and 30 is a non-conductive electrode. A gasket 40 made of conductive rubber is a separator that separates the polarizable electrodes 20.20 into upper and lower parts. This is what I did.

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

(Effects of the Invention) According to the present invention, as activated carbon fine powder used for a sintered electrode body of an electric double layer capacitor, powder mainly having a particle size of 20 to 30 μm and mesocarbon of several μm are used as described above. Since the mixture is mixed at a predetermined ratio and sintered into an electrode body, fine mesocarbons are interposed between the activated carbon powders of large particle size, which increases the surface area of the electrode body in contact with the electrolyte. Since the number of electric paths through which electric charge passes also increases, there is an effect that an efficient electric double layer capacitor with a large capacitance and a low internal resistance can be obtained.

Further, according to the present invention, since carbon black is not used as a material for activated carbon, there is an advantage that the electrode body can be easily sintered.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional view of a part of a fired electrode body in an embodiment of the electric double layer capacitor according to the present invention, FIG. 2 is a schematic diagram of the firing apparatus for the electrode body, and FIG. A curve diagram showing the capacitance and internal resistance of an electric double layer capacitor having an electrode body in which the mixing ratio of two different types of powders is varied. FIG. 4 shows the relationship between the mixing ratio, capacitance, and internal resistance. The diagram shown in FIG. 5 is a sectional view of an example of an electric double layer capacitor to which this embodiment is applied. A...Activated carbon powder, B...Mesocarbon, 10...
・Sintered mold, 20... Polarizable electrode (electrode body), 50...
・Current collector plate.

Claims (2)

[Claims] (1) In an electric double layer capacitor in which an electrode body made of sintered activated carbon fine powder is impregnated with an electrolyte, the activated carbon fine powder mainly has a particle size of 20μ to 30μ and 3% to 10% of the activated carbon powder. An electric double layer capacitor characterized in that an electrode body is formed by mixing mesocarbon with a particle size of several micrometers per % of the weight and sintering the mixture. (2) The activated carbon powder is made from phenolic resin, petroleum coke, and coal tar and has a peak particle size distribution of 20μ to 30μ, and the mesocarbon contains 90% of the particle size of 3μ to 8μ produced from coal tar.
Claim (1) characterized in that a powder having a certain degree is used.
The electric double layer capacitor described.