JPH09156914A - Solid activated carbon, its production and electric double layer capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solid activated carbon suitable as an electrode of an electric double layer capacitor by impregnating activated carbon powder and/or activated carbon fiber with a liquid forming a pore-protection agent, mixing the powder or fiber with a thermosetting resin and/or coal tar and a thermoplastic resin and forming and heat-treating the obtained mixture. SOLUTION: Activated carbon powder and/or activated carbon fiber are impregnated with a liquid capable of forming a pore-protection agent, mixed with a thermosetting resin and/or coal tar and the obtained mixture is formed and heat-treated in a non-oxidizing atmosphere. The liquid forming a pore- protection agent is selected from pure water, a higher alcohol, a fatty acid, oil and fat and a plasticizer. An electric double layer capacitor having an electrode made of the solid activated carbon has increased electrostatic capacity and lowered internal resistance.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing solid activated carbon that can be widely used as general activated carbon, and further relates to an electric double layer capacitor using the same.

[0002]

2. Description of the Related Art As shown in FIG. 1, an electric double layer capacitor is a capacitor in which an electrolyte 2 is disposed between two electrodes 1 and 1 made of solid activated carbon and an electric double layer formed at the interface between the two electrodes. As the electrode 1, solid activated carbon is used. In addition, solid activated carbon is also used for battery electrode members and various applications, and the method for producing these solid activated carbons is as follows.

A kneaded product of activated carbon, carbon black, pulverized carbon or conductive carbon and PTFE, tetrafluoroethylene resin or fluoropolymer resin is roll-formed, compressed, extruded, rolled, stretched or a combination thereof. To obtain a solid activated carbon (JP-A-62-200715, 63-17311).
No. 63-107011, JP-A-5-121269
No. 5-283287).

[0004] Activated carbon and conductive carbon coated with an acrylic resin, a polyamide resin, a polycarbonate resin, and the like, ethylene tetrafluoride resin and a solvent as a binder are mixed and kneaded with three rolls, and then formed into a sheet and solidified. Shaped activated carbon has been obtained (see JP-A-2-82507).

[0005] Solid carbon is obtained by sintering under pressure and mixing only activated carbon fine particles or carbon fine particles and carbon fiber or activated carbon powder and mesocarbon.
-132009, 3-201516).

A mixture of activated carbon powder and a powdery phenol resin is injection-molded and heat-treated to obtain a solid activated carbon-carbon composite (see JP-A-6-45189).

Papermaking is carried out by adding pulp, dispersant, aromatic polyimide resin fiber or polyflon to activated carbon fiber and pulp fiber, or carbon fiber, fibrous activated carbon and fine powdered activated carbon, to two types (Japanese Patent Application Laid-Open No. Sho 64-64). No. 9611, JP-A-6-61093 and 5-129157).

A prepreg sheet containing activated carbon powder, cellulose fiber and phenol resin as main components is prepared, pressed, cured and fired (see Japanese Patent Application Laid-Open No. 5-121271).

A mixture of activated carbon powder and a particulate or powdery phenol resin dissolved in an organic solvent is formed on a substrate, heat-cured, and then heat-treated in a non-oxidizing atmosphere to obtain solid activated carbon. (JP-A-4-288361)
Reference).

[0010] A spherical carbide obtained by carbonizing a curable spherical phenolic resin and a heat-reactive spherical phenolic resin are mixed, filled in a mold, heat-cured under pressure, heat-treated in an inert atmosphere, and activated. (Japanese Unexamined Patent Publication No.
69075, 6-69076 and 6-69077).

As described above, as the conventional solid activated carbon, those formed by kneading with resin such as ethylene tetrafluoride (), those obtained by sintering powder under pressure (), and those kneaded with resin are used. Injection molding and heat treatment (), prepreg method using paper making, compression bonding, thermosetting (
), Heat treatment after film formation on the substrate (), and hot press ().

[0012]

However, when the conventional solid activated carbon is used for the polarizable electrode of the electric double layer capacitor, there is a problem that the capacitance per unit weight is low and the internal resistance is high.

That is, since activated carbon has a large number of pores and a large specific surface area, when used as an electrode of an electric double layer capacitor, it is possible to increase the electric charge of the electric double layer generated at the interface with the electrolyte. , The capacitance can be increased. However, the activated carbon substrate produced by the conventional method has a problem that the electrostatic capacitance is low because the binder component blocks the pores of the activated carbon and reduces the specific surface area.

[0014]

Therefore, the present invention provides a solid form of activated carbon powder and / or activated carbon fibers impregnated with a liquid forming a pore protecting agent, and a thermosetting resin and / or a charcoal obtained by heat treatment of coal tar. It is composed of activated carbon.

Further, the present invention is obtained by impregnating activated carbon powder and / or activated carbon fiber with a liquid forming a pore protecting agent, and then mixing a thermosetting resin and / or coal tar with a thermoplastic resin. The method for producing solid activated carbon is characterized by comprising the steps of shaping the mixture and heat treating it in a non-oxidizing atmosphere.

That is, by previously impregnating activated carbon powder or activated carbon fibers with a liquid, the liquid is filled in the pores of the activated carbon particles, and when mixed with a binder component such as a thermosetting resin or coal tar, these binders are mixed. It has the effect of preventing the components from blocking the pores of the activated carbon particles. In this way, the liquid acts as a pore protecting agent, and as a result maintains the specific surface area of the activated carbon particles high, improves the capacitance when solid activated carbon is used as an electrode, and lowers the internal resistance. It is possible.

Explaining the production method of the present invention in detail, first, 20 to 120 parts by weight of a liquid as a pore protecting agent is impregnated with 100 parts by weight of activated carbon powder and / or activated carbon fiber, and after vacuum degassing, After mixing the thermosetting resin and / or coal tar and the thermoplastic resin and molding the resulting mixture, the mixture is heat-treated in a non-oxidizing atmosphere to carbonize the thermosetting resin and / or coal tar. To obtain solid activated carbon.

The solid activated carbon of the present invention is formed into various shapes such as a sheet-shaped activated carbon substrate, a block formed by press molding or the like, or a rod or cylinder formed by extrusion. be able to.

As a method of forming a sheet,
A doctor blade method, a rolling roll method, a calendar roll method, or the like can be used.
The binder may be removed at 00 ° C, the thermosetting resin and / or the coal tar may be cured, and heat treatment may be performed at 600 to 1100 ° C, preferably 700 to 900 ° C in a non-oxidizing atmosphere.

Further, according to the present invention, it is also possible to heat-treat in a non-oxidizing atmosphere after laminating a plurality of the above sheet-shaped compacts. That is, in the sheet forming method by the doctor blade method or the calendar roll method, the thickness that can be preferably formed is 1
Although it is up to about mm, even a product having a thickness of more than 1 mm can be easily manufactured by laminating the obtained sheet-like molded bodies and joining them by thermocompression bonding or an adhesive liquid or an adhesive.

Here, as the liquid forming the pore protecting agent,
At least one of pure water such as ion-exchanged water, higher alcohol, fatty acid, oil and fat, and plasticizer is used.

The above-mentioned higher alcohol means an alcohol having a large molecular weight, but generally means a chain alcohol having 6 or more carbon atoms. The main ones are C6 hexter alcohol, C8 octyl alcohol,
Examples include cetyl alcohol having 16 carbon atoms, stearyl alcohol having 18 carbon atoms, ceryl alcohol having 26 carbon atoms, and myricyl alcohol having 30 carbon atoms.

The fatty acid is a general term for a chain compound having one carboxyl group, that is, a chain monocarboxylic acid,
It is so called because the glycerin ester of high-order (high carbon number) fatty acid constitutes fats and oils. Also, esters of higher fatty acids and higher monohydric alcohols exist as wax. The lower ones are free acids,
Widely distributed in the animal and plant kingdoms as salts or esters. Most naturally occurring products are straight-chain and have an even number of carbon atoms. Fatty acids are generally colorless liquids or solids, with lower ones having a pungent odor and sourness and soluble in water, while higher ones are insoluble. Both of them dissolve well in alcohol and ether to form metal salts and esters as monobasic acids.
The sodium salt of higher fatty acid is obtained under the saponification of fats and oils and becomes soap.

The above-mentioned fats and oils are glycerin esters of fatty acids, which are widely distributed in the animal and plant kingdoms, and are a group of substances most necessary for organisms. Pure is a colorless, tasteless, and odorless neutral substance that is lighter than water, insoluble in water, slightly soluble in alcohol, and well soluble in ether, petroleum ether, benzene, and the like. Its properties depend on the type of acid that makes it. Fatty acids forming naturally occurring fats and oils account for the majority of saturated fatty acids ranging from butyric acid having 4 carbon atoms to 30 melicinic acid, especially palmitic acid and stearic acid. As unsaturated acids, oleic acid, linoleic acid, linolenic acid, Sardine acid and the like are known, but each is composed of an even number of carbon atoms. It should be noted that fatty acids having an odd number of carbon atoms are also found in fats and oils of various animals and plants, though in trace amounts.

The above-mentioned plasticizer is a substance which is added to a rigid polymer to impart plasticity and improve workability. Typical examples include tricresyl phosphate, dibutyl phthalate, and dioctyl phthalate.

The liquid forming these pore protecting agents is
It is preferable to add 20 to 120 parts by weight to 100 parts by weight of activated carbon powder and / or activated carbon fiber, but when a component other than dibutyl phthalate is used as a pore protecting agent, 20 to 100 parts by weight of Ranges are preferred.

The mixing ratio of the activated carbon powder and / or activated carbon fiber to the thermosetting resin and / or coal tar is 50 to 95% by weight of the activated carbon powder and / or activated carbon fiber, and the thermosetting resin and / or coal tar. Or 5 to 50 coal tar
% By weight. Here, the thermosetting resin and /
Alternatively, since coal tar is carbonized by heat treatment, the final solid activated carbon is composed of a composite of 50% by weight or more of activated carbon particles and 50% by weight or less of carbon binding them. . At this time, since the ratio of activated carbon can be increased to 50% by weight or more, when used as an electrode of an electric double layer capacitor, for example, the electrostatic capacity can be increased and the internal resistance can be decreased.

As the thermosetting resin, resole type phenol resin, phenol, formaldehyde resin, polyimide resin, unsaturated polyester, bismaleide polyimide resin, cyanate resin, thermosetting polyphenylene ether (PPE), polyphenylene oxide ( PPO) or the like is used.

Further, the present invention is characterized in that a thermoplastic resin is added and mixed in addition to the above components. That is, by adding the thermoplastic resin, the shape retention property at the time of molding was improved even if the ratio of activated carbon was increased to 50% by weight or more, and good molding could be performed.

As the thermoplastic resin, a polyolefin polymer, acrylic resin, butyral resin, polyacetal resin, polyethylene phthalate (PB
O), polypropylene (PP), polycarbonate (P
C), polyethylene (PE), polystyrene or the like is used. These thermoplastic resins are based on 100 parts by weight of the total amount of activated carbon, thermosetting resin and / or coal tar,
It is added in the range of 0 to 60 parts by weight, preferably 5 to 30 parts by weight.

Further, the present invention is characterized in that the above solid activated carbon is used for an electrode to constitute an electric double layer capacitor.

[0032]

Example 1 Yashigara activated carbon powder (specific surface area of 160 according to BET method)
0 m ² / g) to 100 parts by weight of impregnated water with 0 to 120 parts by weight of ion-exchanged water as a pore protecting agent, and after vacuum defoaming, 20 parts by weight of coal tar, 25 parts by weight of butyral resin as a thermoplastic resin, As a plasticizer, 25 parts by weight of dibutyl phthalate and a solvent were added. After mixing with a high-speed stirrer at a rotation speed of 1500 rpm to prepare a paste-like mixture, a calender roll forming machine was used to obtain a sheet-like formed body having a thickness of 1 mm. In addition, it turned out that the sheet thickness in this case is preferably in the range of 0.2 to 2.0 mm.

The obtained sheet-shaped molded body is 50 × 70 mm
After punching with a die of No. 3, debinding in vacuum at 300 ° C. for 2 hours, heat treatment at 800 ° C. was carried out to carbonize coal tar, and an activated carbon substrate which was a composite of activated carbon and carbon was produced.

Table 1 shows the results of measurement of electrostatic capacity and internal resistance when the obtained 50 × 70 × 1 mm activated carbon substrate was used as the electrode 1 of the simple double layer capacitor shown in FIG.

From this result, the pore protective agent was added in the range of 20-100.
Those impregnated in the range of parts by weight (No. 2 to 6) have higher electrostatic capacity per unit weight and higher internal resistance than those impregnated with no pore protecting agent (No. 1). I was able to lower it.

[0036]

[Table 1]

Example 2 Yashigara-based activated carbon powder (specific surface area 160 according to BET method)
0 m ² / g) 100 parts by weight, and impregnated with 0 to 120 parts by weight of oleic acid as a pore protecting agent, after vacuum defoaming, 20 parts by weight of coal tar, 25 parts by weight of butyral resin as a thermoplastic resin, As a plasticizer, 25 parts by weight of dibutyl phthalate and a solvent were added. After mixing with a high-speed stirrer at a rotation speed of 1500 rpm to prepare a paste-like mixture, a calender roll forming machine was used to obtain a sheet-like formed body having a thickness of 1 mm. In addition, it turned out that the sheet thickness in this case is preferably in the range of 0.2 to 2.0 mm.

The obtained sheet-shaped molded body is 50 × 70 mm
After punching with a die of No. 1 and debinding in vacuum at 300 ° C. for 2 hours, heat treatment was performed at 800 ° C. to carbonize coal tar to produce an activated carbon substrate which is a composite of activated carbon and carbon.

When the obtained 50 × 70 × 1 mm activated carbon substrate was used as the electrode 1 of the simple double-layer capacitor shown in FIG. 1, the electrostatic capacity and internal resistance were measured. The results are as shown in Table 2.

From this result, the pore protective agent was added in the range of 20-100.
Those impregnated in the range of parts by weight (No. 2 to 6) have higher electrostatic capacity per unit weight and higher internal resistance than those impregnated with no pore protecting agent (No. 1). I was able to lower it.

[0041]

[Table 2]

Example 3 Yashigara type activated carbon powder (specific surface area of 160 by BET method)
0 m ² / g) 100 parts by weight, and impregnated with 0 to 140 parts by weight of dibutyl phthalate as a pore protecting agent and vacuum defoaming, 20 parts by weight of coal tar, 25 parts by weight of butyral resin as a thermoplastic resin. Then, 25 parts by weight of dibutyl phthalate as a plasticizer and further a solvent were added. After mixing at a rotation speed of 1500 rpm with a high-speed stirrer to prepare a paste-like mixture, a calender roll molding machine was used to obtain a thickness of 1 m.
m was obtained. In addition, it turned out that the sheet thickness in this case is preferably in the range of 0.2 to 2.0 mm.

The obtained sheet-shaped molded body is 50 × 70 mm
After punching with a die of No. 1 and debinding in vacuum at 300 ° C. for 2 hours, heat treatment was performed at 800 ° C. to carbonize coal tar to produce an activated carbon substrate which is a composite of activated carbon and carbon.

When the obtained 50 × 70 × 1 mm activated carbon substrate was used as the electrode 1 of the simple double layer capacitor shown in FIG. 1, the electrostatic capacity and internal resistance were measured. The results are as shown in Table 3.

From this result, the pore protecting agent was added in the range of 20 to 120.
Those impregnated in the range of parts by weight (No. 2 to 7) have higher electrostatic capacity per unit weight and higher internal resistance than those impregnated with no pore protecting agent (No. 1). I was able to lower it.

[0046]

[Table 3]

Example 4 Yashigara activated carbon powder (specific surface area 160 according to BET method)
0 m ² / g) 100 parts by weight, and impregnated with 0 to 120 parts by weight of oleic acid as a pore protecting agent, and after vacuum defoaming, 20 parts by weight of coal tar, 50 parts by weight of a thermoplastic resin and an acrylic binder, Further solvent was added.

After rotating with a mill for 5 hours, the clay was adjusted to 50 to 60 poise, the slurry was discharged and defoamed, and then tape molding was performed by a doctor blade method, and a sheet having a thickness of 1 mm at a drying temperature of 50 to 90 ° C. A molded body was obtained. It has been found that the sheet thickness in this case is preferably in the range of 0.1 to 1.5 mm.

The obtained sheet-shaped molded product is 50 × 70 mm
After punching with a die of No. 1 and debinding in vacuum at 300 ° C. for 2 hours, heat treatment was performed at 800 ° C. to carbonize coal tar to produce an activated carbon substrate which is a composite of activated carbon and carbon.

When the obtained 50 × 70 × 1 mm activated carbon substrate was used as the electrode 1 of the simple double-layer capacitor shown in FIG. 1, the electrostatic capacity and internal resistance were measured. The results are as shown in Table 4.

From this result, the pore protective agent was added in an amount of 20 to 100.
Those impregnated in the range of parts by weight (No. 2 to 6) have higher electrostatic capacity per unit weight and higher internal resistance than those impregnated with no pore protecting agent (No. 1). I was able to lower it.

[0052]

[Table 4]

In the above examples, only the activated carbon substrate molded into a sheet and heat-treated was shown, but it goes without saying that the solid activated carbon of the present invention is not limited to the substrate and can have various shapes.

[0054]

As described above, according to the present invention, solids are formed from activated carbon powder and / or activated carbon fibers impregnated with a liquid forming a pore protecting agent, and a thermosetting resin and / or a carbide obtained by heat treatment of coal tar. By forming the shape-activated carbon, it is possible to prevent the pores of the activated carbon particles from being blocked by the binder component and maintain a high specific surface area, so when used as an electrode for an electric double layer capacitor, the electrostatic capacity is high. , The internal resistance can be reduced.

Further, according to the present invention, activated carbon powder and / or
Alternatively, after impregnating the activated carbon fiber with a liquid, a thermosetting resin and / or coal tar is mixed with a thermoplastic resin, the obtained mixture is formed into a sheet, and then heat-treated in a non-oxidizing atmosphere. By producing solid activated carbon from the process, it is possible to prevent the pores of the activated carbon particles from being blocked by the binder component and maintain a high specific surface area. The capacitance is high and the internal resistance can be reduced.

Further, according to the present invention, since the thermoplastic resin is added, the shape-retaining property at the time of molding can be enhanced and the production can be preferably performed even if the ratio of activated carbon is increased. Furthermore, by forming the sheet, it is possible to increase the mass productivity and manufacture it easily, and it is easy to process such as cutting, punching, and laminating in the state of the green sheet. Since it can be dissolved, efficient use of raw materials enables efficient use of resources at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a general electric double layer capacitor.

[Explanation of symbols]

 1: Electrode 2: Electrolyte

Claims (4)

[Claims] 1. A solid activated carbon comprising activated carbon powder and / or activated carbon fibers impregnated with a liquid which constitutes a pore protecting agent, and a thermosetting resin and / or a carbide obtained by heat treatment of coal tar. 2. An activated carbon powder and / or activated carbon fibers are impregnated with a liquid forming a pore-protecting agent, and then a thermosetting resin and / or coal tar and a thermoplastic resin are mixed to obtain a mixture. Then, a method for producing solid activated carbon, comprising a step of heat treatment in a non-oxidizing atmosphere. 3. The solid activated carbon according to claim 1, wherein the liquid forming the pore protecting agent is at least one of pure water, higher alcohols, fatty acids, oils and fats, and plasticizers. Production method. 4. An electric double layer capacitor, wherein the solid activated carbon according to claim 1 is used as an electrode.