JPH09183604A - Solid activated carbon, its production and electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid activated carbon large in specific surface area and low in specific resistance by mixing a prescribed quantity of an acicular and/or flake electric conductive agent with active carbon and a resin based binder, molding and heat treating the mixture in a non-oxidizing atmosphere. SOLUTION: (A) The active carbon powder and/or an activated carbon fiber, (B) a prescribed quantity of the acicular and/or flake electric conductive agent (e.g. acicular tungsten) and (C) the binder composed of a thermosetting resin or a thermoplastic resin are mixed. Next, the mixture is molded and heat treated in the non-oxidizing atmosphere to produce a solid activated carbon. As a result, the solid activated carbon containing 0.5-20wt.% acicular and/or flake electric conductive agent and having 1×10<-2> -9×10<-5> Ωcm specific resistance is obtained. A high performance electric double layer capacitor high in capacitance and low in internal resistance is produced by using the resultant activated carbon to form electrodes 1, 1 for the electric double layer capacitor and arranging an electrolyte 2 between the electrodes 1, 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid activated carbon which can be widely used as a general activated carbon, a method for producing the same, and 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]

When the above solid activated carbon is used for the polarizable electrode of an electric double layer capacitor, it is required to increase the capacitance per unit weight and reduce the internal resistance. However, both of them cannot be satisfied by the conventional activated carbon substrate.

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 specific resistance tends to increase as the number of pores increases in order to increase the electrostatic capacity, and it has been impossible to decrease the specific resistance while increasing the electrostatic capacity.

When the activated carbon having a high specific resistance is used for the electrode of the electric double layer capacitor, the electrode must be made large in order to reduce the internal resistance, and there is a problem that the electric double layer capacitor cannot be miniaturized. It was

[0015]

Therefore, the present invention is characterized in that solid activated carbon is constituted by containing 0.5 to 20% by weight of a needle-shaped and / or scaly conductive agent.

Further, the present invention is characterized in that the specific resistance of the solid activated carbon is in the range of 1 × 10 ^{−2 to} 9 × 10 ⁻⁵ Ω · cm.

That is, the present invention relates to solid activated carbon having needle-like and / or
Alternatively, the internal resistance is lowered by containing a flaky conductive agent. However, in general, when a conductive agent such as a metal is contained in activated carbon, the characteristic of activated carbon itself that the specific surface area is large is lost, and the electrostatic capacity tends to be low when used as an electric double layer capacitor.
Therefore, the present invention finds that both high capacitance and low resistance value can be satisfied because the resistance value can be lowered with a small content by making the conductive agent to be contained into a needle shape or a flaky shape. It was.

The content of the needle-like and / or scaly conductive agent is set to 0.5 to 20% by weight. When the content is less than 0.5% by weight, the effect of lowering the resistance value is poor, and the content is 20% by weight. This is because if it exceeds, the specific surface area of the activated carbon becomes small and the capacitance when used as an electric double layer capacitor becomes low.

As the conductive agent, a metal such as tungsten, molybdenum, iron, or carbon fiber is used, but activated carbon (specific resistance 6 × 10 ⁻² Ω · c) is used.
Any material may be used as long as it has a resistance value lower than that of m).

In the present invention, the needle shape means an elongated shape such as a needle shape or a fiber shape, and the scaly shape means a thin plate shape. In any case, the aspect ratio of the major axis and the minor axis (= major axis / minor axis) is in the range of 2 to 80, and the major axis is 1.
What is in the range of -40 μm is used. In the case of the scaly shape, the aspect ratio is such that the thickness has a short diameter and the longest diameter has a long diameter.

Since such a needle-shaped or scale-shaped conductive agent has an elongated shape, the conductive effect can be enhanced with a small weight. Therefore, the resistance value can be lowered while reducing the content in the activated carbon and maintaining the characteristic of the activated carbon itself that the specific surface area is large.

The specific resistance of the solid activated carbon of the present invention is 1
The limit to the range of × 10 ^{-2 to} 9 × 10 ^-5 Ω · cm is
If the resistance value is larger than 1 × 10 ⁻² Ω · cm, the internal resistance becomes too large when used as the electrode of the electric double layer capacitor, while if it is made smaller than 9 × 10 ⁻⁵ Ω · cm, This is because the electrostatic capacity becomes low.

Further, in the present invention, a mixture obtained by mixing activated carbon powder and / or activated carbon fibers, a needle-shaped and / or scaly conductive agent, and a binder such as a thermosetting resin or a thermoplastic resin is obtained. It is characterized in that solid activated carbon is produced from the step of molding and heat treating in a non-oxidizing atmosphere.

The production method of the present invention will be described in detail. First, 0.5 to 0.5 is added to the activated carbon powder and / or the activated carbon fiber.
A needle-shaped and / or flake-shaped conductive agent is added to a content of 20% by weight, and a thermosetting resin and / or coal tar and a thermoplastic resin are mixed as a binder to obtain a product. After molding the mixture, it 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 a cylinder formed by extrusion. be able to.

As a method for 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.

Further, the mixing ratio of the solid component composed of the above-mentioned activated carbon powder and / or the activated carbon fiber, the acicular metal and / or the scaly metal, and the binder composed of the thermosetting resin and / or coal tar is the solid component. 50 to 95% by weight,
The binder is in the range of 5 to 50% by weight. Here, since the thermosetting resin and / or coal tar is carbonized by heat treatment, the final solid activated carbon is 50
It will be composed of a composite of activated carbon particles and metal powder in an amount of at least wt% and carbon that binds these particles in an amount of at most 50 wt%. At this time, since the ratio of activated carbon can be increased, the electrostatic capacity can be increased when used as an electrode of an electric double layer capacitor, for example.

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.

Furthermore, 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-based polymer, acrylic resin, butyral resin, polyacetal resin, polyethylene phthalate (PB) is used.
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.

[0033]

Example 1 Phenol-based activated carbon powder (specific surface area by BET method 17
00 m ² / g), a phenol formaldehyde resin (Bellpearl S890 made by Kanebo) as a thermosetting resin, and a needle-shaped (fibrous) metal composed of tungsten (W), molybdenum (Mo) and iron (Fe). It was mixed at the ratio shown in. The acicular metal used had a major axis of 3 to 12 μm, a minor axis of 0.05 to 0.15 μm and an aspect ratio of 60 to 80. To 100 parts by weight of these, 30 parts by weight of powdered butyral resin as a thermoplastic resin and D. B. P25 parts by weight was added, and the mixture was mixed using a high-speed mixer at a rotation speed of 2000 rpm and a temperature of 130 ° C. for 20 minutes to perform granulation. The obtained granular raw material was molded by a calender roll molding machine to obtain a sheet-shaped molded product having a thickness of 1 mm.

The obtained sheet-shaped molded body is 50 × 70 mm
After cutting into the size of 400 ℃, curing the denol resin and debinding the thermoplastic resin at 400 ℃ × 2 hours, heat treatment at 800 ℃ in a vacuum furnace to carbonize the phenol resin, activated carbon and acicular metal. An activated carbon substrate, which is a composite of carbon and carbon, was prepared.

Tables 1 and 2 show the results of measuring the electrostatic capacity and the internal resistance when the obtained activated carbon substrate was used as the electrode 1 of the simple double layer capacitor shown in FIG.

From the results, it is seen that the one containing no needle-shaped metal (No. 1 and 12) has a high internal resistance, and the one containing 25 wt% of the needle-shaped metal (No. 11 and 22) has a capacitance. Was as low as less than 18 F / g.

On the other hand, the examples of the present invention (Nos. 2 to 1) containing the needle-shaped metal in the range of 0.5 to 20% by weight.
0, 12 to 20), the specific resistance is 1 × 10 ^{−2 to} 9 × 10.
Within the range of ^-6 Ω · cm, while maintaining the electrostatic capacity of 18 F / g or more required for electric double layer capacitors,
It turns out that the internal resistance can be lowered.

The specific resistance of tungsten forming the acicular metal is 5.65 × 10 ⁻⁶ Ω · cm, the specific resistance of molybdenum is 5.2 × 10 ⁻⁶ Ω · cm, and the specific resistance of iron is 9. 71 x
Since it was 10 ⁻⁶ Ω · cm, and the result when molybdenum was contained was almost the same as the example of tungsten (Table 1), it was omitted.

[0039]

[Table 1]

[0040]

[Table 2]

Example 2 The granular raw material obtained in Example 1 was subjected to dry press molding at a molding pressure of 1.0 ton / cm ² using a 40 ton press molding machine to obtain a 50 × 70 × 1 mm molded body. Obtained.

The obtained sheet-shaped compact was heat-cured and debindered with a phenol resin at 400 ° C. for 2 hours, and then heat-treated at 800 ° C. in a vacuum furnace to carbonize the phenol resin to form activated carbon and needles. An activated carbon substrate, which is a composite of metal and carbon, was produced.

When the obtained activated carbon substrate was used as the electrode 1 of the simple double layer capacitor shown in FIG. 1, the electrostatic capacity and the internal resistance were measured. The results are as shown in Tables 3 and 4.

From these results, those having no acicular metal (Nos. 23 and 34) have a high internal resistance, and the acicular metal content exceeds 20% by weight (Nos. 33 and 44).
Then, the electrostatic capacity was as low as less than 18 F / g.

On the other hand, the examples of the present invention (Nos. 24 to 3) in which the acicular metal is contained in the range of 0.5 to 20% by weight.
2, 35-43), the specific resistance is 1 × 10 ^{-2 to} 9 × 10.
Within the range of ^-6 Ω · cm, while maintaining the electrostatic capacity of 18 F / g or more required for electric double layer capacitors,
It turns out that the internal resistance can be lowered.

The results of the case of containing molybdenum as in Example 1 were omitted because they were almost the same as those of the example of tungsten (Table 3).

[0047]

[Table 3]

[0048]

[Table 4]

In the above examples, an example in which a needle-shaped metal is contained is shown, but the same is true when a scale-like metal is contained.

The solid activated carbon of the present invention is not limited to a substrate and can have various shapes and can be used for various purposes.

[0051]

As described above, according to the present invention, since the solid activated carbon is constituted by containing 0.5 to 20% by weight of the needle-shaped and / or scaly conductive agent, the specific surface area is large. The specific resistance can be reduced while maintaining the characteristic of activated carbon.

Therefore, if the electrode of the electric double layer capacitor is formed by using this activated carbon, a high performance electric double layer capacitor having a high capacitance and a low internal resistance can be obtained. Further, since the internal resistance is low, the electrodes can be made small, and the electric double layer capacitor can be made compact.

According to the present invention, activated carbon powder and / or
Or activated carbon fiber, and needle-shaped and / or flaky conductive agent,
After mixing with a binder and molding the resulting mixture,
By producing solid activated carbon from the step of heat treatment in a non-oxidizing atmosphere, activated carbon having a high specific surface area can be easily produced.

[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 needle-shaped and / or flake-shaped conductive agent is added in an amount of 0.5 to 5.
Solid activated carbon characterized by containing 20% by weight. 2. The specific resistance is 1 × 10 ^{−2 to} 9 × 10 ⁻⁵ Ω · cm.
2. The solid activated carbon according to claim 1, which is in the range. 3. An activated carbon powder and / or activated carbon fiber, a needle-shaped and / or scaly conductive agent, and a binder such as a thermosetting resin or a thermoplastic resin are mixed, and the resulting mixture is molded. A method for producing solid activated carbon, comprising a step of heat treatment in a non-oxidizing atmosphere. 4. An electric double layer capacitor, wherein the solid activated carbon according to claim 1 is used as an electrode.