JP2000077278A - Polarized electrode and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify production process while reducing environmental load by employing a carbon material obtained by integrating a carbon containing substance thermally shrinking more than a basic material with the basic material and then thermally processing the integrated substance in nonoxidative atmosphere. SOLUTION: When a coating layer 2 of a carbon containing substance is formed on a basic material 1 and heated in nonoxidative atmosphere, it is cracked through thermal shrinkage and carbonization proceeds to generate fine pores 3 in the coating layer thus a porous carbon 4. The basic material 1 is any one of synthetic resin, carbon, metal or ceramic. The carbon containing substance being integrated with the basic material 1 is a polymer material thermally shrinking more than the basic material 1 including thermosetting resin, e.g. phenol resin. Carbonization is performed by thermally processing in nonoxidative atmosphere at 500 deg.C-1000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizable electrode for an electric double layer capacitor and a method for manufacturing the same, and more particularly to an electric double capacitor using a porous carbon material as a polarizable electrode.

[0002]

2. Description of the Related Art An electric double layer capacitor is a capacitor that stores electric charges in an electric double layer formed at an interface between porous carbon electrodes in an electrolytic solution, and is known as a large-capacity capacitor. In particular, the electric double layer capacitor has a feature that the environmental load is small because no harmful substance such as heavy metal is used for the constituent material. In addition, since it does not involve a chemical reaction like a secondary battery, the capacitor can be charged in a short time,
Excellent charge and discharge cycle life. For this reason, it is widely used as a backup power supply for a microcomputer, a memory, or the like as a substitute device for a secondary battery. In recent years, power storage devices for hybrid vehicles using both an internal combustion engine and a motor, power storage devices for regenerative energy such as electric vehicles,
It is expected to be used in various applications of power storage such as mitigation of power generation fluctuation such as solar power generation and wind power generation, backup power supply for instantaneous power failure and the like, and supply of rush current during motor operation.

FIG. 3 is a sectional view for explaining an electric double layer capacitor. The electric double-layer capacitor is configured by tightening a unit cell 7, a terminal plate 8 soldered to aluminum on both sides of the unit cell 7, and an insulating bush 9 with a bolt and nut. In this unit cell 7, the positive and negative polarizable electrodes 10 are opposed to each other with a separator 11 interposed therebetween, and the polarizable electrodes are electrically connected to an external circuit and electrically conductively connected to a current collector 12 which does not pass an electrolytic solution. And a gasket 13 that insulates the current collectors 12 of both electrodes and seals the electrolytic solution.

The current collector 12 uses a conductive rubber, a conductive elastomer, a conductive polymer or the like in an aqueous electrolyte, and a metal such as aluminum in a non-aqueous electrolyte. As the separator 11, a nonwoven fabric of glass fiber, a porous film made of plastic, a nonwoven fabric, or the like is used. The operating voltage of the electric double layer capacitor is limited to a voltage range in which the polarizable electrode and the current collector do not cause an electrochemical reaction and the electrolytic solution is not decomposed. The voltage is about 2.5 V for an aqueous electrolyte. Usually, a large number of the basic cells 8 are connected in series according to the voltage to be used, so as to cope with the voltage to be used.

Generally, the polarizable electrode of an electric double layer capacitor is a paste in which powdered activated carbon or activated carbon fiber is mixed with an electrolytic solution, a cloth made of resin fiber carrying activated carbon powder or activated carbon fiber alone, Organic binders such as organic binders such as fluororesins and Japanese Patent Publication No. 7-7044
Japanese Patent Publication No. 7-91449 proposes using powdered activated carbon as shown in FIG. 8 bonded with carbon, or using a complex of activated carbon and polyacene.

[0006] These polarizable electrodes or activated carbon as a raw material of the polarizable electrode are generally produced by a gas activation method or a chemical activation method. In the case of the gas activation method, after the raw material is carbonized, the carbide is crushed and sized, and an activation treatment is performed using steam or carbon dioxide gas to increase the surface area. This is washed with hydrochloric acid or the like to remove impurities, and then further pulverized and classified to obtain a desired particle size to produce activated carbon. In the case of fibrous activated carbon, tar and pitch are spun into a fibrous form and then subjected to infusibilization treatment, which is activated using a gas or a chemical. In chemical activation, carbonization and activation are performed by impregnating with a concentrated solution such as zinc chloride and performing heat treatment.

It is also known that the use of a carbon-containing substance that decomposes without producing tar, such as polyvinylidene chloride, can produce carbon having a microstructure without adding an activator. The use of the carbonaceous material obtained in this way for an electric double layer capacitor is proposed in Japanese Patent Application Laid-Open No. 7-249551.

In order for an electric double layer capacitor to be widely used as a power storage means, not only is it excellent in power storage performance as compared with various energy storage means such as a secondary battery, but also it is easy to manufacture. It is an important requirement that the cost is low and the production cost is low, and the polarizable electrode, which is the main material, or porous carbon, which is the raw material of the polarizable electrode, must be easy to produce and have a low production cost. Have been.

[0009]

Conventionally, to increase the surface area of a carbon material, a gas activation method of chemically reacting with steam or carbon dioxide gas at a high temperature or a chemical activation method of reacting with zinc chloride or sodium hydroxide at a high temperature. Method was used. These gas activation methods and chemical activation methods have problems in that the production process is complicated, large-scale equipment is required, the yield due to the activation treatment is low, and as a result, the production price is high. Also, only the surface that comes into contact with the gas or the chemical is activated, and the inside is not necessarily made porous. For this reason, there is a problem that many parts do not contribute to the function of the electric double layer capacitor. In order to solve these problems, a method of carbonizing polyvinylidene chloride to obtain a carbonaceous material has been proposed as a method of simultaneously activating carbonization only by carbonizing a carbon-containing material. During the process, harmful dioxins and the like may be generated, and there is a problem of causing environmental pollution.

An object of the present invention is to produce a polarizable electrode having excellent characteristics for an electric double layer capacitor. A polarizable electrode made of porous carbon is produced using a carbon-containing organic compound as a raw material. An object of the present invention is to produce a carbonaceous material having a suitable pore diameter and surface area as a polarizable electrode of an electric double layer capacitor without performing post-treatment such as activation only by carbonization. Another object of the present invention is to manufacture a polarizable electrode made of porous carbon that does not emit harmful chemical substances that cause environmental pollution in the carbonization process. It is an object to manufacture a polarizable electrode made of porous carbon for a multilayer capacitor.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a polarizable electrode for an electric double layer capacitor, which comprises a carbon-containing material which, when mixed with a base material or coated on a base material and heated, has a greater thermal shrinkage than the base material. This is a polarizable electrode for an electric double layer capacitor using a carbon material obtained by subjecting a substance to a substrate and heat-treating in a non-oxidizing atmosphere. The substrate is the above-mentioned polarizable electrode for an electric double layer capacitor, which is one kind selected from a synthetic resin, carbon, metal or ceramics. The substrate is the above-mentioned polarizable electrode for an electric double layer capacitor, which is a porous substance or a foam. The polarizable electrode for an electric double layer capacitor, wherein the carbon-containing substance is a thermosetting resin. The polarizable electrode for an electric double layer capacitor, wherein the carbon-containing substance is a phenol resin.

In the method for manufacturing a polarizable electrode for an electric double layer capacitor, after a carbon-containing substance having a larger heat shrinkage than a substrate when heated together with the substrate is integrated with the substrate,
This is a method for producing a polarizable electrode for an electric double layer capacitor, which is carbonized by heating in a non-oxidizing atmosphere. The method for producing a polarizable electrode for an electric double layer capacitor, wherein the surface of the base material is coated with a carbon-containing material or a mixture of the base material and the carbon-containing material is integrated by heating and forming the base material and the carbon-containing material. 500 ° C to 1000 ° C for carbonization
The method for producing a polarizable electrode for an electric double-layer capacitor, which is performed by a heat treatment in a non-oxidizing atmosphere at the temperature described above. An electric double layer capacitor using the polarizable electrode.

[0013] The polarizable electrode for an electric double layer capacitor of the present invention can be obtained by applying a carbon-containing substance to a base material from a thermosetting resin such as a phenol resin which has a large heat shrinkage when heated than the base material, or By using a carbon material obtained by heating and carbonizing in a non-oxidizing atmosphere after being integrated with the base material by a method such as mixing and performing melt molding. Since the heat shrinkage of the carbon-containing material is greater than the heat shrinkage of the base material, a large number of fine cracks are generated during the heat shrinkage, and porous carbon is formed. Therefore, it is suitable as a polarizable electrode without activation treatment. A porous carbon having a large surface area can be obtained.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a polarizable electrode for an electric double layer capacitor according to the present invention is characterized in that it has a low environmental load and activates carbon only by carbonization. The substrate and the carbon-containing material such as a polymer material whose heat shrinkage when heated in a non-oxidizing atmosphere are larger than the substrate are integrated, and the carbon-containing material is carbonized by heating in a non-oxidizing atmosphere. However, since the shrinkage is greater than that of the base material, a large number of fine cracks are formed to form porous carbon.

As the base material, synthetic resin, carbon, metal, or ceramic material can be used. When the base material is a synthetic resin, it is necessary to use a resin that does not melt by heating.Specifically, a heat-insoluble phenol resin, such as Bell Pearl made by Kanebo, a furan resin, an amino resin, Examples include polyester resin, diallyl phthalate resin, allyl diglycol carbonate, and epoxy resin. When a carbon material is used as the base material, any carbon material obtained by carbonizing a carbon-containing substance can be used, and tar, pitch,
What was obtained by carbonizing arbitrary things, such as a coconut shell and synthetic resin waste material, can be used.

When the base material is a metal material, any material can be used as long as it does not melt during the firing process and retains its shape and does not react with the electrolytic solution of the electric double layer capacitor to be used. When an alkaline aqueous solution is used as the electrolytic solution, a metal such as nickel can be used.

Examples of the ceramic material that can be used for the substrate include a conductive material such as titanium nitride and titanium carbide, and alumina. Since these substances have high corrosion resistance to acids, they can be used even when sulfuric acid is used as the electrolyte.

The substrate may be in the form of powder or fiber, and may have a size of 1 μm to 100 μm. Further, it is preferable to use a substrate having a large number of pores on the surface, such as a porous body or a foamed body, because a large surface area can be obtained.

As the carbon-containing substance integrated with the substrate,
Heat shrinkage is a carbon-containing substance such as a polymer material larger than the base material, and specifically, a thermosetting resin such as a phenol resin can be cited, but the possibility of generating harmful substances such as dioxin can be raised. It is preferable to use a material that does not contain a substance such as halogen such as chlorine or fluorine.

The method of integrating the substrate and the carbon-containing substance is as follows:
A method of coating a carbon-containing substance on the surface of a base material may be used.
The coating can be performed by applying the carbon-containing substance as it is or by dissolving it in a solvent, coating, dipping, spraying the substrate under flow, or the like. When the carbon-containing substance is in a solid state and is melted by heat, it can be coated by a method such as application, immersion, or spraying while the base material is flowing as a liquid by heat melting.

Further, the base material and the carbon-containing material are mixed,
After being heated or softened by adding a solvent, it may be integrated by molding into a block or the like. After being integrated with the base material as described above, porous carbon can be obtained by performing carbonization treatment in a non-oxidizing atmosphere at a temperature of 500 ° C to 1000 ° C. Further, the porous carbon obtained as described above may be mixed with a carbon-containing substance which forms carbonized or polyacene by firing and fired in a non-oxidizing atmosphere.

Hereinafter, a process for producing porous carbon obtained by integrating the powder of the present invention with a carbon-containing substance and firing the same will be described with reference to the drawings. FIG. 1 shows on a substrate
It is a figure explaining the manufacturing process of porous carbon which carries out carbonization processing by non-oxidizing atmosphere after forming a coat of a carbon content substance. As shown in FIG. 1 (A), after a coating layer 2 is formed by coating a carbon-containing substance on a base material 1, heating is performed in a non-oxidizing atmosphere, as shown in FIG. 1 (B). The coating layer 2 of the contained material cracks due to heat shrinkage, and carbonization proceeds, so that micropores 3 are generated in the coating layer and porous carbon 4 is obtained.

FIG. 2 is a view for explaining a process of producing a porous carbon by molding and integrating a base material and a carbon-containing substance, followed by firing. As shown in FIG. 2 (A), the base 1 and the carbon-containing substance 5 are pressed and molded under heating to produce a molded body 6. Next, as shown in FIG.
In a non-oxidizing atmosphere, heating is performed to carbonize the carbon-containing substance, and the fine pores 3 are formed in a state where the shape of the molded body is maintained to obtain porous carbon 4.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below by showing embodiments of the present invention. Example 1 A waste material of a phenol resin plate for a print substrate was roughly pulverized into a chop shape, and this was heat-treated at 900 ° C. in a nitrogen atmosphere and carbonized. This carbide is further reduced to an average particle size of 10 μm.
Into a substrate. Next, a phenol resin diluted with ethanol (Kanebo Bellpearl S890) was sprayed onto the stirred base material by an air current, and the surface of the base material was coated with the phenol resin. Phenolic resin thickness is 10μm
Met. This was heat-treated at 900 ° C. for 2 hours in a nitrogen atmosphere. The carbon slightly expanded thermally, and the phenol resin shrank, and the porous carbon of Sample 1 was obtained. The adsorption isotherm of the obtained porous carbon was measured by a constant volume method by nitrogen adsorption, and the specific surface area was obtained by a BET method.
Shown in

The center of a rubber sheet having a thickness of 0.5 mm and a diameter of 30 mm is punched into a circular shape having a diameter of 0.8 mm and a diameter of 3 mm.
It was arranged on a platinum plate having a thickness of 0 mm and a thickness of 0.1 mm. Two electrode plates were prepared in which 3 mg of the porous carbon of Sample 1 obtained in the punched portion of the rubber sheet and 4 ml of sulfuric acid having a concentration of 30% by weight were mixed and kneaded to apply a paste. The obtained pair of electrode plates was disposed via a porous film made of polypropylene to assemble an electric double layer capacitor. The capacitance of the obtained electric double layer capacitor was measured, and the measurement results are shown in Table 1.

Further, a porous carbon of Sample 2 was produced in the same manner as in Sample 1 using a heat-insoluble phenol resin having an average particle diameter of 20 μm (Bellpearl R800 manufactured by Kanebo) as a substrate. Samples 3 and 4 were prepared in the same manner as Sample 1 by using nickel powder having an average particle diameter of 10 μm, conductive ceramic powder composed of titanium nitride having an average particle diameter of 5 μm, and alumina particles having an average particle diameter of 15 μm. , And sample 5
Was produced.

As for Samples 2 to 5, similarly to Sample 1, the specific surface area was measured, and an electric double layer capacitor was manufactured to determine the capacitance. Table 1 shows the measurement results. The capacitance was measured by a constant current discharge method. That is, 1.0 V is applied to the capacitor to discharge for 30 minutes, and then immediately discharged at a constant current of 100 μA.
The time Δt at which the charge voltage changes from 60% to 50%, that is, from 0.6 V to 0.5 V, is measured. Capacitance C
Is determined by C = 1 × Δt / ΔV. Since the true density of the base material was large, it was standardized per paste volume.
For comparison, coconut shell activated carbon was similarly measured, and the measurement results are shown in Table 1. Although the capacitance is lower than that of coconut shell activated carbon, it can be seen that it can be used as a polarizable electrode.

[0028]

[Table 1] Substrate Specific surface area (m ² / g) Capacitance (F / cm ³ ) Sample 1 Carbon 550 15 Sample 2 Heat-insoluble phenol resin 620 13 Sample 3 Nickel 658 Sample 4 Titanium nitride 80 12 Sample 5 Alumina 72 12 Coconut shell activated carbon 1500 23

Example 2 A carbon powder having an average particle size of 10 μm was used as a base material, and a phenol resin (Bellpearl S890 manufactured by Kanebo) in a weight ratio of 50: 5.
0 and mixed. Next, a compact of 70 × 50 × 1 mm was obtained by hot pressing at 150 ° C. Samples 6 to 14 were prepared by firing the obtained molded body in a nitrogen atmosphere at a heating rate of 100 ° C./hour and changing the firing temperature from 400 ° C. to 1200 ° C.

The gasket and the current collector were bonded to each other with an epoxy adhesive through the obtained porous carbon through a glass fiber separator having a thickness of 500 μm. Thereafter, sulfuric acid having a concentration of 30% by weight was injected from an injection hole provided on the side surface of the gasket, and the injection hole was sealed by ultrasonic fusion to form a unit cell. An electric double layer capacitor as shown in FIG. 3 is manufactured by laminating terminal plates solder-plated on aluminum from both sides of the unit cell and fixing them with bolts and nuts via insulating bushes.
V electric double layer capacitor was obtained.

With respect to the obtained electric double layer capacitor, the specific surface area and the capacitance of the polarizable electrode were measured in the same manner as in Example 1, and the equivalent series resistance (hereinafter referred to as ESR) at 1 kHz was measured.
And the capacitance was measured. ESR is 1kHz,
An AC of 10 mV was applied to the electric double layer capacitor, and the magnitude of the current and the phase difference with respect to the voltage were measured without applying a DC bias.

[0032]

[Table 2] Firing temperature Specific surface area Specific resistance Capacitance (° C) (m ² / g) (Ωcm) (F / cm ³ ) ───────────────────試 料 Sample 6 400 180 12.50-Sample 7 500 220 1.50 7.1 Sample 8 600 340 0.20 10.8 Sample 9 700 450 0. 065 12.3 Sample 10 800 540 0.050 15.5 Sample 11 900 520 0.030 15.4 Sample 12 1000 350 0.022 11.1 Sample 13 1100 200 0.021 6.5 Sample 14 1200 150 0. 022 4.2

Example 3 The porous carbon of Sample 1 was mixed with a phenolic resin (Kanebo Bellpearl S890) and heated at 150 ° C. under a pressure of 100 kg / cm ² for 10 minutes at 70 × 50.
A molded body of × 1 mm was obtained. The obtained molded body was fired at 900 ° C. for 2 hours in a nitrogen atmosphere to produce a porous carbon composite material. The obtained porous carbon composite material was subjected to elemental analysis, and the molar ratio of carbon atoms to hydrogen atoms was measured, whereby polyacene was formed. Next, an electric double layer capacitor having an operating voltage of 1.0 V using the porous carbon composite material obtained in the same manner as in Example 2 as a polarizable electrode was manufactured, and the capacitance was measured in the same manner as in Example 2. It was 19.5 F / cm ³ , confirming that it functions as a polarizable electrode.

[0034]

As described above, the present invention does not include an activation step in the manufacturing process of the polarizable electrode, so that the manufacturing process is simple and the environmental load can be reduced. In addition, by using the polarizable electrode of the present invention for an electric double layer capacitor, an inexpensive one can be obtained.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram illustrating a process for producing porous carbon by forming a coating of a carbon-containing substance on a base material and then performing carbonization treatment in a non-oxidizing atmosphere.

FIG. 2 is a diagram illustrating a process of forming a porous carbon by molding and integrating a base material and a carbon-containing substance, and then firing the resultant.

FIG. 3 is a diagram illustrating an electric double-layer capacitor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base material, 2 ... Coating layer, 3 ... Micropore, 4 ... Porous carbon,
5 ... Carbon-containing substance, 6 ... Molded body, 7 ... Unit cell, 8 ... Terminal plate, 9 ... Insulating bush, 10 ... Polarizable electrode, 11 ... Separator, 12 ... Current collector, 13 ... Gasket

Claims (9)

[Claims] In a polarizable electrode for an electric double layer capacitor, a carbon-containing substance having a larger thermal shrinkage than a base material when mixed with a base material or coated on a base material and heated is integrated with the base material. A polarizable electrode for an electric double layer capacitor, wherein a carbon material obtained by heat treatment in a non-oxidizing atmosphere is used. 2. The polarizable electrode for an electric double layer capacitor according to claim 1, wherein the base material is any one of synthetic resin, carbon, metal and ceramics. 3. The polarizable electrode for an electric double layer capacitor according to claim 1, wherein the substrate is a porous substance or a foam. 4. The polarizable electrode for an electric double layer capacitor according to claim 1, wherein the carbon-containing substance is a thermosetting resin. 5. The polarizable electrode for an electric double layer capacitor according to claim 4, wherein the carbon-containing substance is a phenol resin. 6. A method for manufacturing a polarizable electrode for an electric double layer capacitor, comprising: integrating a carbon-containing substance having a larger thermal shrinkage than a substrate when heated together with the substrate; A method for producing a polarizable electrode for an electric double-layer capacitor, comprising carbonizing by heating. 7. The base material and the carbon-containing material are integrated by coating the surface of the base material with the carbon-containing material, or heat molding a mixture of the base material and the carbon-containing material.
A method for producing a polarizable electrode for an electric double layer capacitor according to the above. 8. The carbonization treatment is performed at 500 ° C. to 1000 ° C.
7. The method for producing a polarizable electrode for an electric double layer capacitor according to claim 6, wherein the heat treatment is carried out at a temperature in a non-oxidizing atmosphere. 9. An electric double-layer capacitor using the polarizable electrode according to claim 1.