JP3032226B2 - Polarizing electrode and its manufacturing method - Google Patents

Abstract

PURPOSE:To reduce a manufacture time of a polarizable electrode by using pitch activated carbon whose raw material is petroleum pitch as activated carbon powder and putting the carbon in a sintering mold, by sintering it while holding it at a high temperature by applying electric power while applying a presence and by incorporating dilute sulfuric acid of a specified concentration in the sintered body. CONSTITUTION:Activated carbon powder of a specified grating size whose raw material is petroleum pitch is weighed, scattered by an amount to form one electrode body from above a hole of a sintering mold 10, laid on an upper surface of an inserted lower punch 13 to an average thickness and an upper punch 12 is inserted from above a hole. After the upper punch 12 is inserted, a pressing force is applied to the upper punch 12 and the lower punch 13 by hydraulic mechanism and a specified pressure is applied to activated carbon powder 1' between both punches. Electric energy from a variable power supply 16 stored in a capacitor C is supplied for a specified time repeatedly as a pulse-like current through electrodes 14, 15 and both ends punches 12, 13 by controlling switching timing of switches SW1, SW2 by a control device 17 to burn the inside activated carbon powder 1' to a sintered body. In the process, dilute sulfuric acid of 35 to 40wt.% is dropped and impregnated into the sintered body.

Description

Description: TECHNICAL FIELD The present invention relates to a polarizable electrode used for an electric double layer capacitor and a method for producing the same.

(Prior Art) In recent years, an electric double layer capacitor having a large capacitance has been used as a backup power supply for a memory of an electronic device, and is widely used by being incorporated in a microcomputer or an IC memory.

Japanese Patent Application Laid-Open No. 63-213915 discloses a method of manufacturing this type of electric double layer capacitor element. After filling a carbon paste, equilibration is performed in an atmosphere at a temperature of 25 ° C. and a relative humidity of 50%. The proposal has a process of forming a carbon paste electrode by removing excess moisture until the filled portion is filled with carbon paste to form a carbon paste electrode, in order to obtain a predetermined equivalent series resistance value under a small mechanical pressure. The proposal has been disclosed.

(Problem to be Solved by the Invention) In the proposal disclosed in the above-mentioned publication, the dent of the filling portion of the carbon paste in which the activated carbon powder and the diluted sulfuric acid are mixed is eliminated by filling it with a new carbon paste. However, the raw material of the activated carbon powder used for the carbon paste is not specified, and in the above-described production method, it is necessary to leave until equilibrium with the atmosphere. ,
There is a problem that the manufacturing process takes a long time due to the repeated leaving and filling.

On the other hand, as the raw material of the activated carbon powder used for the polarizable electrode, there are pitch-based activated carbon and phenol-based, etc., but how the relationship between the concentration of the diluted sulfuric acid contained in the polarizable electrode and the raw material of the activated carbon affects the capacitor capacity. It was not understood.

The present invention has been made in view of such a problem, and an object thereof is to determine a raw material of an activated carbon powder capable of obtaining a large electrostatic capacity, a concentration of diluted sulfuric acid to be contained, and further, a production time of a polarizable electrode. And to provide a method of manufacturing the same.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, (1)
The method for producing a polarizable electrode of an electric double layer capacitor used as a polarizable electrode by sintering activated carbon powder accommodated in a sintering mold, adding an electrolytic solution of diluted sulfuric acid to the sintered body, and using the activated carbon powder as A step of accommodating a sintered body using a pitch-based activated carbon made of petroleum pitch as a raw material and holding it at a high temperature by applying power while applying pressure; A method of producing a polarizable electrode.

(2) In a polarizable electrode of an electric double layer capacitor in which an electrolyte solution composed of diluted sulfuric acid is contained in a sintered body of pitch-based activated carbon powder made from petroleum pitch, the pitch-based activated carbon powder made from petroleum pitch is used. Wherein the concentration of dilute sulfuric acid contained in the sintered body is set in the range of 35 wt% to 40 wt%. Is provided.

(Action) In the present invention, a petroleum pitch-based activated carbon is used as the activated carbon powder sintered by the sintering mold, and a pulse-like voltage is applied while applying pressure in the sintering mold to cause discharge between the activated carbon powders. This causes the porous sintered body to be fired while maintaining the high temperature, and the diluted sulfuric acid concentration of the sintered body is reduced.
A polarizable electrode is manufactured to contain 35 to 40% by weight of an electrolytic solution.

Example Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a sintering apparatus used in an embodiment of the method for producing a polarizable electrode according to the present invention,
FIG. 2 is a sectional view of an electric double layer capacitor using an electrode body sintered by the sintering device as a polarizable electrode.

In FIG. 1, 10 contains activated carbon powder and is sintered,
It is a sintered type that is fired on a porous sintered electrode body, is formed in a thick cylindrical shape, the hole at the center is the part that stores the activated carbon powder, and the inner diameter is the diameter of the electrode body to be sintered Is formed in a size corresponding to. Reference numeral 11 denotes an insulating layer on the inner peripheral wall, which is coated with, for example, a ceramic material. The main body of the sintering die 10 is made of a high-strength material such as tungsten steel.

12 is an upper punch, 13 is a lower punch, which is inserted into the hole of the sintering die 10 using a heat-resistant and strong steel material, between which the activated carbon powder 1 'described later is sealed. It is processed.

Reference numerals 14 and 15 denote electrodes, respectively, which are configured such that pressure is applied in the direction of the arrow by a hydraulic mechanism (not shown), and the material enclosed through the upper punch 12 and the lower punch 13 is pressed.

A series circuit of switches SW1 and SW2 and a capacitor C is connected to the electrodes 14 and 15, and a series circuit of a variable power supply 16 and a variable resistor R is connected to the circuit of the capacitor C and the switch SW2. Then, the high-voltage power from the variable power supply 16 is charged to the capacitor C via the variable resistor R and the switch SW2 of the closed circuit, and when the switch SW1 is closed in this state, the electric charge stored in the capacitor C becomes an electrode. 1
The powder is applied to the sealed and pressurized activated carbon powder through the punches 4 and 15 and the upper and lower punches 12 and 13 to generate a discharge between the powders and heat the powder. The interior of the sintering mold 10 is maintained at a high temperature by repeating such discharge. Reference numeral 17 denotes a control device which controls the opening / closing timing of the switches SW1 and SW2 to charge the power of the variable power supply 16 to the capacitor C and to transfer the electric charge stored in the capacitor C to the electrodes 14 and 1.
It operates to apply a pulse to 5.

Next, a method of manufacturing a porous sintered body to be an electrode body using the sintering apparatus configured as described above will be described. First, a lower punch 13 is inserted into a sintering mold 10 shown in FIG. I do.

Then, as a first sample, an activated carbon powder of petroleum pitch as a raw material having a predetermined particle size is weighed, and an amount equivalent to one electrode body is scattered from above the hole of the sintering mold 10, and the lower punch inserted is inserted. 13 is laid so as to have an average thickness, and the upper punch 12 is inserted from above the hole.

After the insertion of the upper punch 12, pressure is applied to the upper punch 12 and the lower punch 13 by a hydraulic mechanism, and a predetermined pressure is applied to the activated carbon powder 1 'between both punches. As described above, the control unit 17 controls the opening and closing timing of the switches Sw1 and Sw2 to control the variable power supply stored in the capacitor C.
The electric energy from 16 is applied to electrodes 14, 15 and both punches 12,
Power is repeatedly supplied as a pulsed current for a predetermined period of time through 13 to sinter the activated carbon powder 1 'inside into a sintered body.

FIG. 2 is a cross-sectional view of an electric double layer capacitor using a sintered body of activated carbon powder thus sintered for a polarizable electrode.
Reference numeral 1 denotes a polarizable electrode, which is obtained by dropping and impregnating 30 wt% of dilute sulfuric acid into the above-mentioned sintered body and adhering a current collector 2 to one surface thereof. A conductive thin plate obtained by kneading powder and butyl rubber is used to collect polarizable charges.

Reference numeral 3 denotes a separator which is interposed between a pair of polarizable electrodes and separates the two. For example, a separator in which a microporous film made of polypropylene is impregnated with an electrolytic solution is used. It is buried in the central part.

The gasket 4 is made of a non-conductive synthetic resin material, is formed in a cylindrical shape, and serves as a container for accommodating the pair of polarizable electrodes 1, 1 therein. The gasket 4 is bonded to the upper and lower end surfaces, respectively.

FIG. 3 is a curve diagram showing the relationship between the concentration of dilute sulfuric acid contained in the polarizable electrode and the capacitance per activated carbon surface area for each type of activated carbon raw material.

The circles shown in the figure are data in the case of activated carbon powder using petroleum pitch used as the raw material for the first sample described above.
Indicates the capacitance when impregnated with 30 wt% dilute sulfuric acid as described above in a sintered body of petroleum pitch-based activated carbon,
B, C and D were diluted sulfuric acid concentrations of 40, 50 and 60 wt, respectively.
% Is, for example, data of an electric double-layer capacitor using a polarizable electrode whose moisture has been removed by placing it in an oven.

Also, the points indicated by triangles in FIG.
Activated carbon powder made from coconut shell was used as a sintered body by using the above-mentioned sintering mold, and there was data when diluted sulfuric acid was added to each of the sintered bodies to give concentrations shown on the horizontal axis. It is clear that a large capacitance can be obtained in the case of the petroleum pitch type 1 sample, and even in the case of the petroleum pitch type activated carbon, the dilute sulfuric acid contained is required to obtain a large capacitance. A good result can be obtained by setting the concentration of Rn to around 40% by weight.

In the present embodiment, the first sample petroleum pitch-based activated carbon is, for example, Osaka Gas M-30, and the second sample is coconut shell-based, activated carbon such as Kuraray YP-17. This is the data obtained.

FIG. 4 is a curve diagram showing the freezing points of sulfuric acid and fuming sulfuric acid. The horizontal axis represents the sulfuric acid concentration, and the vertical axis represents the temperature.

As is clear from the figure, those having a sulfuric acid concentration of about 37 wt% have an extremely low freezing point, and the melting point of dilute sulfuric acid having a concentration of 35 to 40 wt% is about -60 ° C. When used, when used at a low temperature, the electric double layer capacitor can withstand sufficiently without reducing its capacitance.

As described above, the present invention has been described with reference to the above-described embodiment. However, various modifications may be made within the scope of the present invention, for example, by sintering using a different sintering mold from the above-described embodiment. It is possible and does not exclude them from the scope of the present invention.

(Effects of the Invention) As described above, according to the present invention, activated carbon powder made from petroleum pitch is accommodated in a sintering mold, and a pulsed voltage is applied while applying pressure to generate a discharge between the powders to cause high temperature. The sintered body is fired, and diluted sulfuric acid is contained in the sintered body, and the diluted sulfuric acid concentration is used as a polarizable electrode having a concentration of 35 to 40% by weight in an electric double layer capacitor. Without repeatedly standing until equilibrium with the atmosphere, the time required for the manufacturing process of the sintered body is reduced, and a sintered body of pitch-based activated carbon powder using petroleum pitch as a raw material as described above is used, By incorporating dilute sulfuric acid with a concentration in the range of 35 wt% to 40 wt% in this sintered body, it has a large capacitance and is simpler to manufacture than an electrode using conventional activated carbon particles. To get an electric double layer capacitor with There is an effect that kill.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of a sintering apparatus used in one embodiment of the method for producing a polarizable electrode according to the present invention, and FIG. 2 shows the use of an electrode body by the sintering apparatus as a polarizable electrode. FIG. 3 is a cross-sectional view of the electric double layer capacitor, FIG. 3 is a curve diagram showing the relationship between the concentration of dilute sulfuric acid and the capacitance with respect to the type of activated carbon powder, and FIG. 4 is a curve diagram showing the freezing points of sulfuric acid and fuming sulfuric acid. 1 ... Polarizable electrode, 1 '... Activated carbon powder, 10 ... Sintered mold, 12 ... Upper punch, 13 ... Lower punch, 16 ... Variable power supply, 17 ... Control device.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshinobu Tsuchiya 8 Tsuchiya, Fujisawa City, Kanagawa Prefecture Inside the Fujisawa Plant of Isawa Motor Co., Ltd. (72) Inventor Hiroyoshi Morohoshi 8 Tsuchiya, Fujisawa City, Kanagawa Prefecture Isuzu Motors Stock (72) Inventor Masanori Nakanishi 5-36-11 Shimbashi, Minato-ku, Tokyo Fuji Electric Chemical Co., Ltd. (72) Inventor Mitsuhiro Nakamura 5-36-11 Shimbashi, Minato-ku, Tokyo Fuji Electric (56) References JP-A-63-186414 (JP, A) JP-A-63-43310 (JP, A) JP-A-49-8753 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) H01G 9/058

Claims (2)

(57) [Claims] 1. A method of manufacturing a polarizable electrode of an electric double layer capacitor, comprising sintering activated carbon powder contained in a sintering mold, adding an electrolytic solution comprising dilute sulfuric acid to the sintered body, and using the same as a polarizable electrode. , Containing the activated carbon powder in a sintered mold using pitch-based activated carbon made from petroleum pitch,
Manufacturing a polarizable electrode, comprising: sintering while maintaining the temperature at a high temperature by applying power while applying pressure; and causing the sintered body to contain 35 wt% to 40 wt% of diluted sulfuric acid. Method. 2. A pitch-type activated carbon powder made from petroleum pitch in a polarizable electrode of an electric double-layer capacitor in which a sintered body of pitch-based activated carbon powder made from petroleum pitch contains an electrolyte solution made of diluted sulfuric acid. Wherein the concentration of dilute sulfuric acid contained in the sintered body is set in the range of 35 wt% to 40 wt%.