JPH10149958A - Activated carbon for electrode of organic solvent-based electrical double layered capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide activated carbon for polarizable electrode of an organic solvent-based electrical double layered capacitor having excellent capacitance density per unit volume. SOLUTION: Activated carbon is obtained by subjecting a carbide obtained by baking an easily graphitizable organic matter to alkali reactivation. In the carbon thus obtained, the mode of pore diameter distribution found by the TEM picture analyzing method falls within the range of 10-20Å and the percentage of continuous holes in a TEM picture expressed by the ratio of the total area of pores of 500sq.Å in area to the total area of all pores is >=20%. The mode of the pore distribution falls within the range of 11-15Å, and the number of the pores having the mode which falls within the range is >=40% of the number of all pores. The difference between the mode of the carbide and that of the activated carbon falls within the range of 0.2-3Å. The easily graphitizable organic matter is composed of a vinyl chloride-based resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an activated carbon used for a polarizable electrode of an electric double layer capacitor using an organic solvent-based electrolyte.

[0002]

2. Description of the Related Art An electric double layer capacitor has a farad-class large capacity and excellent charge / discharge cycle characteristics, and is therefore used for applications such as backup power supplies for electronic equipment and in-vehicle batteries.

[0003] This electric double layer capacitor is, for example, shown in FIG.
As shown in the figure, a pair of polarizable electrodes 1 and 1 made of activated carbon are used.
Are provided opposite each other with a separator 2 interposed therebetween, and the polarizable electrode 1 is configured to be impregnated with an organic solvent solution such as a tetraalkylammonium salt as an electrolytic solution so as to function as an anode and a cathode, respectively. In the electric double layer capacitor shown in FIG. 4, the polarizable electrodes 1 and 1 facing each other via the separator 2 are housed in an aluminum container 3 and
The lid is closed by an aluminum lid 5 attached to the aluminum container 3 via the packing 4. In the above configuration, the container 3 and the lid 5 are in contact with the polarizable electrodes 1 and 1 respectively, and the container 3 is a cathode-side current collector for the polarizable electrode 1 and the lid 5 is an anode-side current collector for the polarizable electrode 1. It has become.

Activated carbon having fine pores is used for the polarizable electrode of such an electric double layer capacitor. However, in order to make the electric double layer capacitor smaller, lighter and larger in capacity, Activated carbon capable of increasing the capacitance density of the polarizable electrode is required.

Therefore, in order to obtain activated carbon capable of increasing the capacitance density of the polarizable electrode, various characteristics of the activated carbon have been studied. For example, "Capacitance density per weight of activated carbon in the electrode" has been studied. And the specific surface area of the activated carbon are almost linearly proportional, and the capacitance of the electric double layer on the activated carbon electrode is almost constant without being affected by the type of carbon and pore characteristics. (Electrochemistry, 5
9 , no. 7, p. 607-613, 1991).

[0006] Based on the above assumption, for example,
Japanese Patent No. 02735 describes activated carbon in which the capacitance density per weight is increased by activating the carbonaceous material to increase the specific surface area. The activated carbon described in the above publication forms pores that can adsorb the electrolyte ions by activating a carbonaceous material.

However, in the activated carbon described in the above publication,
If the activation is performed until the capacitance appears, there is a disadvantage that the capacitance density per volume is reduced.

[0008] In order to solve the above inconvenience, the present inventors first tried to examine the above hypothesis. According to the study of the present inventors, the value observed by a mercury electrode or the like as the capacitance of the electric double layer of activated carbon, and the specific surface area of the activated carbon,
When the theoretical value of the capacitance of the electric double layer capacitor of the polarizable electrode using the activated carbon is obtained, the theoretical value may not coincide with the actually measured value of the capacitance of the electric double layer capacitor.

For example, as shown in FIG. 4, the electric double layer capacitor having a pair of polarizable electrodes 1 and 1 with a separator 2 interposed therebetween has a capacitance C ₀ , Assuming that the capacitance of ₁ is C ₁ and C ₂ , it can be expressed as 1 / C ₀ = 1 / C ₁ + 1 / C ₂ (1). Here, the capacitance of the electric double layer of activated carbon observed by the mercury electrode is about 20 μF / cm ² , and thus the capacitance of the electric double layer of activated carbon having a specific surface area of 1500 m ² / cc is 20 (ΜF / cm ² ) × 1500 (m ² / cc) = 30
0 (F / cc). Therefore, in equation (1), C ₁ and C ₂ are each set to 30.
0 If (F / cc) by substituting seek C _0, C ₀ = 15
0 (F / cc). C ₀ is a polarizable electrode 1 for 2 volumes
, The theoretical capacitance of the electric double layer capacitor is 75 F by dividing the value of C ₀ by 2.
/ Cc.

However, the capacitance of the electric double layer capacitor is actually only about 13 F / cc. Even between activated carbons having the same specific surface area, the electric double layer capacitor using the same may have completely different capacitances.

Next, the inventors of the present invention focused on the fact that the above-mentioned hypothesis was made based on the specific surface area measured by the BET method by nitrogen gas adsorption, and used the BET method with an image of a transmission electron microscope. A special image analysis that can analyze fine pores smaller than the limit was performed, and the relationship between the capacitance density and the specific surface area of activated carbon for electrodes having different specific surface areas was examined. As a result, it was concluded that there was no linear proportional relationship between the two, and that there were other factors affecting the capacitance.

As a result of further studies based on the above conclusions, the present inventors have found that in the electrolyte, the organic solvent is solvated with the electrolyte ions such as the tetraalkylammonium salt to form electrolyte ions. The present inventors have found that by forming a large number of pores having a pore diameter suitable for adsorbing the electrolyte ions on the activated carbon, an activated carbon having an excellent capacitance density per volume can be obtained.

On the basis of this finding, Japanese Patent Application Laid-Open No. 7-30
In the activated carbon described in Japanese Patent No. 2735, when considering the reason why the capacitance density per volume is reduced when activation is performed until the capacitance is developed, the activated carbon is activated on a carbonaceous material and has a specific surface area. The pore size that can adsorb the electrolyte ions is formed by enlarging the pore size. However, it is considered that the distribution of the pore diameter to be formed is widened from a small pore to a large pore. In the activated carbon, as a result, the number of pores having pore diameters suitable for the adsorption of the electrolyte ions is relatively reduced, in other words, the number of pores that do not contribute to the capacitance is increased. It is considered that the capacitance density per unit cannot be sufficiently obtained.

Further, based on the above findings, the present inventors have found an activated carbon for an electric double layer capacitor electrode in which the pore diameter suitable for the adsorption of the electrolyte ions has a mode in the pore diameter distribution. A patent application has already been filed for such activated carbon (see Japanese Patent Application No. 8-46912). The activated carbon described in the specification is one in which a carbide obtained by calcining a vinyl chloride resin is alkali-activated at a temperature in the range of 400 to 1000 ° C., and the mode of the pore size distribution is the electrolyte ion Is in the range of 10 to 20 angstroms, which is suitable for the adsorption of water. According to the activated carbon, since the mode of the pore size distribution is in the above range, the electrode density is high, and the capacitance density per volume can be increased.
When performed for up to 20 hours, the capacitance density per volume reaches a maximum value.

In the above specification, the mode is defined as
Based on the transmission electron microscope image of activated carbon, in the frequency distribution of the pore diameters of the pores obtained from the power spectrum obtained by Fourier transform of the image obtained by binarizing the activated carbon, the largest relative Points to a value.

According to the activated carbon, a polarizable electrode having a high capacitance density per volume can be formed.
An electric double layer capacitor having a high energy density can be constituted by the polarizable electrode, but further improvement is desired.

[0017]

Therefore, the present invention provides a polarizable electrode for an organic solvent-based electric double layer capacitor,
An object of the present invention is to provide an activated carbon which has an excellent capacitance density per volume and is further improved.

[0018]

In order to achieve the above object, an activated carbon for an organic solvent-based electric double layer capacitor electrode of the present invention is obtained by alkali-activating a carbide obtained by firing a graphitizable organic substance. The mode of the pore size distribution by TEM image analysis is in the range of 10 to 20 Å, and the area in the TEM image is 50
The continuous porosity represented by the ratio of the total area of pores of 0 square angstroms or more to the total pore area is 20% or more.

Here, the TEM image analysis method means that a negative image of a photograph of an object obtained by a transmission electron microscope (TEM) is read into a computer by a high-resolution film scanner and converted into a digital image. The processing is performed by performing the corresponding processing. The TEM
According to the image analysis method, it is possible to analyze even fine pores smaller than the measurement limit of the BET method, and it is possible to specify even the shape of the pores.

In order to determine the frequency distribution of the pore diameter by the TEM image analysis method, first, a TEM photograph at a magnification of 200,000 times is taken at a resolution of 1200 dpi (pixels / inch) and 256 times.
It is assumed that the digital image has a gradation and an image size of 512 pixels × 512 pixels. Next, the digital image is subjected to a two-dimensional Fourier transform while keeping the 256 gradations to obtain a two-dimensional power spectrum. Then, when the two-dimensional power spectrum is integrated with respect to all azimuth angles, a one-dimensional power spectrum is obtained.

The one-dimensional power spectrum gives the appearance probability of the spatial frequency as a function of the spatial frequency, and can be regarded as a frequency distribution of the pore diameter. Here, assuming that the spatial frequency of the distribution peak when the one-dimensional power spectrum is regressed with a Gaussian curve is x (Å ⁻¹ ), the mode value of the pore diameter is given by 1 / x (Å).

In order to determine the continuous porosity by the TEM image analysis method, first, the digital image is subjected to a two-dimensional Fourier transform, and fundamental, second and third harmonic components are cut, and then inverse Fourier transform is performed. By converting, the TEM
Eliminates shading in photos. Next, the obtained image is divided into a bright part (1) and a dark part (0) using the gradation 128 as a threshold.
And binarized.

Next, the binarized image is converted to Ul
The image is analyzed by image analysis software such as image (trade name). In the analysis, each pixel of the digital image is defined as a square, and if the square is a bright portion, this is determined as a pore. At this time, the bright portion in contact with the sides of the square is determined as one continuous pore, but the bright portion in contact with the apex of the square is determined as a different pore. Also, if the area is 3
Pores smaller than 0 square angstroms are excluded because they are below the TEM resolution, and pores in contact with the edge of the TEM image are also excluded.

Thus, one image usually contains 400 to 800 pores. Therefore, first, the total area of the pores (total pore area; S) is determined. Next, the pores are divided into those having an area of 500 angstrom or more and those having an area of less than 500 angstrom, and the total area ( _S500 ) of the pores having an area of 500 angstrom or more is determined. The ratio of S ₅₀₀ / S expressed as a percentage is defined as the continuous porosity (%).

According to the present invention, by baking the graphitizable organic material, a carbide having a large number of pores having a pore size in a range suitable for the adsorption of the electrolyte ions is obtained. Therefore, by activating the carbide with alkali, an activated carbon having a mode of the pore size distribution in the range of 10 to 20 Å is obtained.

In the activated carbon of the present invention, the mode of the pore size distribution is in the range of 10 to 20 angstroms, so that the solvated ions of the organic solvent used for the electrolyte of the electric double layer capacitor can be rapidly formed. Can be adsorbed,
The capacitance density per volume of activated carbon can be increased. If the mode of the pore diameter distribution is less than 10 angstroms, the number of extremely fine pores that do not contribute to the adsorption of the solvated ions increases, and the capacitance itself decreases.
Further, when the mode of the pore diameter distribution exceeds 20 angstroms, the number of pores having a pore diameter larger than the diameter suitable for the adsorption of the solvated ions increases, and the activated carbon becomes smaller than the rate at which the capacitance increases. The rate at which the volume of
The capacitance density per volume of activated carbon is reduced.

Also, even if the pores of the carbide have a pore diameter in a range suitable for the adsorption of the electrolyte ions, a narrow portion (bottleneck portion) is often formed inside the pores. Therefore, the bottleneck portion is eliminated by the alkali activation, and pores having a pore diameter in a range suitable for the adsorption of the electrolyte ions are made to more effectively act on the adsorption of the electrolyte ions. Here, the pores in which the bottleneck portion has been eliminated are expressed as a series of pixels having an area of 500 square angstroms or more in the TEM image.

Therefore, the activated carbon of the present invention has a ratio (S ₅₀₀ / S × 100) of the total area (S ₅₀₀ ) of pores having an area of 500 square angstroms or more to the total pore area (S) in the TEM image. When the continuous porosity is defined as 20% or more, the number of pores in which the bottleneck portion is eliminated increases, and the capacitance density per volume of activated carbon can be increased. When the continuous porosity is less than 20%, even if the mode is activated carbon in the range suitable for the adsorption of electrolyte ions, many of the pores have a bottleneck portion inside. Since the pores having the portion do not effectively act on the adsorption of the electrolyte ions, a sufficient capacitance density per volume of the activated carbon cannot be obtained.

The mode of the pore size distribution is preferably in the range of 11 to 15 angstroms, and most preferably about 13 angstroms, in order for the electrolyte ions to be quickly adsorbed.

The activated carbon of the present invention is characterized in that the number of pores having the mode in the above range is 40% or more of the total number of pores. Even in the case of activated carbon whose mode is in a range suitable for the adsorption of electrolyte ions, if the number of pores having a mode in the range is less than 40% of the total number of pores, the solvation will occur. As the number of pores that do not contribute to the adsorption of ionic ions increases, the number of pores that exceeds the rate at which the volume of activated carbon decreases is greater than the rate at which the capacitance density increases, and the capacitance per volume The density cannot be obtained sufficiently.

Further, the activated carbon of the present invention eliminates a bottleneck portion by alkali-activating a carbide having a large number of pores in a range suitable for adsorbing the electrolyte ions as described above. Therefore, the alkali activation may be performed to such an extent that the bottleneck portion can be eliminated. Accordingly, the present invention provides a method wherein the difference between the mode of the pore size distribution by the TEM image analysis of the carbide and the mode of the pore size distribution by the TEM image analysis of the activated carbon obtained by alkali-activating the carbide is 0%. 0.2 to 3 angstroms. When the mode difference between the activated carbon and the carbide is larger than 3 Å, the number of pores having a pore size larger than the range suitable for the adsorption of the electrolyte ions is not limited to the alkali activation not only for eliminating the bottleneck, but also for the alkali activation. Will increase. Further, since the activated carbon of the present invention activates the carbides with alkali, it is practically difficult to make the difference between the modes less than 0.2 Å. The mode difference is further increased by 0.1 in order to suppress the increase in the number of pores having a pore diameter larger than a range suitable for the adsorption of the electrolyte ions, because the alkali activation only eliminates the bottleneck and suppresses the increase in the number of pores having a pore diameter larger than a range suitable for the adsorption of the electrolyte ions. Preferably, it is in the range of 2 to 1.5 angstroms.

In the activated carbon of the present invention, the alkali activation is carried out at a temperature in the range of 500 to 1000 ° C. to a set temperature of 10 to 200 ° C./° C. in order to make the mode difference between the activated carbon and the carbide within 3 Å. The method is characterized in that the temperature is raised over time and the holding time after reaching the set temperature is set to 0 to 20 hours.

Setting the holding time to 0 hours means that the heating is stopped as soon as the set temperature is reached.

If the alkali activation is less than 500 ° C., it is difficult to eliminate the bottleneck portion. If the temperature exceeds 1000 ° C. and the time exceeds 20 hours, the difference in the mode between the activated carbon and the carbide is 3 Å. Be larger.

As described above, according to the activated carbon of the present invention,
The above-mentioned alkali activation is described in Japanese Patent Application No. Hei.
It can be carried out under a milder condition in a shorter time than the activated carbon described in -46912, and the capacitance density per volume can be equivalent to that of the activated carbon described in the above specification.

In the alkali activation, the mode difference between the activated carbon and the carbide can be easily controlled.
It is characterized in that it was carried out using a monovalent base of an alkali metal hydroxide. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, and the like. Of these, potassium hydroxide is preferable because of its low cost.

The alkali metal hydroxide is used in an amount of 1 to 4 parts by weight with respect to 1 part by weight of the carbide in order to keep the mode difference between the activated carbon and the carbide within 3 angstroms. It is characterized by having. If the amount of the alkali metal hydroxide is less than 1 part by weight with respect to 1 part by weight of the carbide, the bottleneck cannot be sufficiently eliminated. If the amount exceeds 4 parts by weight, the difference in the mode between the carbide and the activated carbon is reduced. It is larger than 3 Å. The alkali metal hydroxide may be used in an amount of 1.5 to 3.0 parts by weight with respect to 1 part by weight of the carbide in order to easily control the difference in the mode between the activated carbon and the carbide. Preferably 1.8
It is more preferred to use ~ 2.2 parts by weight.

The alkali activation can be performed, for example, by mixing a carbide and an activator and then heating the mixture in an inert gas stream such as nitrogen gas or argon gas. The method can be carried out by a usual method such as a method in which the activator is supported and then carbonization and activation are simultaneously performed by heating, or a method in which the carbide is activated by a gas activation method such as steam and then the surface is treated with the activator. .

Further, the carbide is pulverized into particles having a particle size in the range of 0.1 to 300 μm before the alkali activation. The carbide can be uniformly activated by crushing the carbide into particles having a particle size in the range of 0.1 to 300 μm before the alkali activation. When the particle size of the carbide is less than 0.1 μm, the self-discharge characteristic may be reduced when the polarizable electrode of the electric double layer capacitor is formed from the obtained activated carbon.
On the other hand, when the particle size exceeds 300 μm, there is a possibility that activation within the particles does not easily progress uniformly. The carbide is preferably pulverized into particles in a range of 1 to 100 μm in order to more uniformly activate the particles.

The graphitizable organic substance used in the present invention refers to an organic compound which easily forms a graphite structure by a firing treatment at a relatively low temperature, for example, at about 800 ° C. or lower. Aromatic polymer compounds such as tar, mesophase pitch, and polyimide can be used in addition to aliphatic polymer compounds such as resin and polyacrylonitrile, and vinyl chloride resin is preferable from the viewpoint of production cost. The formation of the graphite structure can be confirmed by, for example, having a clear peak at 25 around 25 ° in the X-ray diffraction pattern.

The activated carbon of the present invention is formed by mixing with a conductive material such as furnace black and a binder such as tetrafluoroethylene, and is used as the polarizable electrode 1 of the organic solvent-based electric double layer capacitor shown in FIG. Can be

The electrolyte impregnated in the polarizable electrode 1 is perchloric acid, hexafluorophosphoric acid, tetrafluoroboric acid, trifluoroalkylsulfonic acid, tetraalkylammonium salt of tetrafluoromethanesulfonic acid or perchloric acid. Examples include acids, hexafluorophosphoric acid, tetrafluoroboric acid, trifluoroalkylsulfonic acid, and dialkylamine salts of tetrafluoromethanesulfonic acid. Further, as the organic solvent for dissolving the electrolyte, propylene carbonate, butylene carbonate, γ-butyrolactone, acetonitrile, dimethylformamide, 1,2-
Examples include dimethoxyethane, sulfolane, nitroethane, and the like. The electrolyte is added to the organic solvent in an amount of 0.1%.
３3 mol / l, preferably 0.5-1.5 mol / l
Dissolved at a concentration of 1 liter and used as electrolyte.

As the separator 2, a sheet of polyolefin such as polyethylene or polypropylene, polyester, PVDF, cellulose or the like, or a glass filter is used.

[0044]

Next, preferred embodiments of the activated carbon of the present invention will be described in more detail with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

FIG. 1 is a chart of a thermogravimetric measurement of a vinyl chloride resin, FIG. 2 is a graph showing a one-dimensional power spectrum of a carbide by TEM image analysis (which can be regarded as a frequency distribution of pore diameters), and FIG. FIG. 4 is a graph showing the relationship between the continuous porosity of activated carbon and the capacitance density per volume of a polarizable electrode using the activated carbon. FIG. FIG.

As shown in FIG. 1, vinyl chloride (PVC)
When the temperature of the system resin gradually rises from room temperature,
And the second stage of weight reduction starting at approximately 420 ° C. and ending at approximately 500 ° C. From the thermogravimetry chart of FIG. 1, when firing the vinyl chloride resin,
From about 250 ° C. where the first-stage weight loss starts to about 420 ° C. where the second-stage weight loss starts, a side chain is eliminated to form a carbon skeleton, and the second-stage weight loss starts about 420 ° C. to about 700 ° C. It is considered that chlorine is desorbed and the pores are formed before the temperature reaches ℃. And from about 700 ° C to about 100
At 0 ° C., hydrogen is desorbed and micropores are formed.
When the temperature is between 000 ° C. and about 2000 ° C., the pores are blocked by sintering of carbon.

As shown in FIG.
It is considered that by firing in the range of 000 ° C., a carbide having pores is obtained. Therefore, in this embodiment, the vinyl chloride resin is heated from room temperature to 6 ° C under a nitrogen atmosphere.
The temperature was raised to 00 ° C., and calcined while maintaining the temperature at 600 ° C. for 30 minutes to obtain a carbide.

Using a transmission electron microscope (manufactured by Philips, CM120), the carbide was accelerated at an accelerating voltage of 120 kV.
And an image (photograph) with a magnification of 200,000 was obtained. The negative image of this photograph was read into a computer using a high-resolution film scanner (LS-4500AF, manufactured by Nikon Corporation) to obtain a digital image having a resolution of 1200 dpi (pixels / inch), 256 gradations, and an image size of 512 pixels × 512 pixels. FIG. 2 shows a one-dimensional power spectrum obtained from the digital image according to the TEM image analysis method described above.
Shown in

The one-dimensional power spectrum shown in FIG. 2 gives the appearance probability of the spatial frequency as a function of the spatial frequency as described above, and can be regarded as the frequency distribution of the pore diameter of the carbide. From FIG. 2, the carbide is
The mode value is 12 angstroms, and it is clear that it has the most pores with a pore size of 12 angstroms.

Next, the carbide obtained as described above is pulverized to a particle size of 1 to 100 μm, 2 parts by weight of potassium hydroxide is mixed with 1 part by weight of the carbide, and the mixture is mixed under a nitrogen stream.
Activated carbon was obtained by heating at 800 ° C. for 3 hours to activate the alkali (Example 1). The activated carbon is analyzed by the same means as the carbide to obtain a digital image, and the digital image is analyzed by the TEM image analysis method described above. The frequency (approximately indicated by the ratio of the number of pores having a pore size of the mode of ± 2 angstroms to the total number of pores) and the continuous porosity were measured.
Table 1 shows the results.

The obtained activated carbon is used as a polarizable electrode of an electric double layer capacitor to form an electric double layer capacitor shown in FIG. 4, and the polarizable electrode when the electric double layer capacitor is charged to 4V. The capacitance density per volume was measured. The results are shown in Table 1.

Next, the activated carbon (Example 2) obtained in the same manner as in Example 1 except that the alkali activation was carried out by heating at 860 ° C. for 4 hours was carried out in the same manner as in Example 1 and the pore size was changed. Mode, relative frequency of mode, continuous porosity, and capacitance density per volume of the polarizable electrode when the activated carbon was charged up to 4 V of the electric double layer capacitor used for the polarizable electrode did. Table 1 shows the results.

The activated carbon (Example 3) obtained in the same manner as in Example 1 except that the alkali activation was carried out by heating at 900 ° C. for 5 hours was performed. The mode, the relative frequency of the mode, the continuous porosity, and the capacitance density per volume of the polarizable electrode when the activated carbon was charged to 4 V of the electric double layer capacitor used for the polarizable electrode were measured. . Table 1 shows the results.

Activated carbon obtained in the same manner as in Example 1 except that 1 part by weight of the carbide was mixed with 1 part by weight of potassium hydroxide and the alkali activation was carried out by heating at 750 ° C. for 4 hours. Example 1 (Comparative Example 1)
The same as above, the mode of the pore diameter, the relative frequency of the mode, the continuous porosity, and the volume per volume of the polarizable electrode when the activated carbon was charged to 4 V of the electric double layer capacitor used for the polarizable electrode. The capacitance density was measured. Table 1 shows the results.

The activated carbon (Comparative Example 2) obtained in the same manner as in Comparative Example 1 except that the alkali activation was carried out by heating at 600 ° C. for 4 hours was carried out in the same manner as in Example 1 to obtain the finest pore size. Frequency, relative frequency of mode, continuous porosity, 4 of electric double layer capacitor using the activated carbon as polarizable electrode
The capacitance density per volume of the polarizable electrode when charged to V was measured. Table 1 shows the results.

FIG. 3 shows the relationship between the continuous porosity shown in Table 1 and the capacitance density per volume of the polarizable electrode.

[0057]

[Table 1]

As shown in Table 1 and FIG. 3, in each embodiment of the present invention, the difference between the mode of the raw material carbide and the mode of the activated carbon obtained by alkali-activating the carbide is 0.6 to 0. 0.8 Å, which is in the range of 0.2 to 3 Å. As a result, the mode of the pore diameter of the activated carbon was 12.6 to 12.8 angstroms, and the relative frequency of the mode was 43 to 60.4%. It is clear that a large number of pores having a pore diameter of are formed.

The activated carbon of each embodiment of the present invention has a continuous porosity of 20% or more and a continuous porosity of 20% or more.
It is apparent that each of the comparative examples less than the above has an excellent capacitance density per volume of the polarizable electrode.

Further, it is apparent from FIG. 3 that the capacitance density per volume of the polarizable electrode is different in magnitude from the boundary of continuous porosity of 20%.

[Brief description of the drawings]

FIG. 1 is a chart of a thermogravimetric measurement of a vinyl chloride resin.

FIG. 2: One-dimensional power spectrum of carbide by TEM image analysis (can be regarded as frequency distribution of pore diameter)
A graph showing.

FIG. 3 is a graph showing a relationship between continuous porosity of activated carbon and capacitance density per volume of a polarizable electrode using the activated carbon.

FIG. 4 is an explanatory cross-sectional view showing a part of a configuration example of an electric double-layer capacitor in a cutaway manner.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Polarizable electrode, 2 ... Separator, 3,5 ... Current collecting member.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Shigeki Koyama 1-4-1 Chuo, Wako-shi, Saitama

Claims (5)

[Claims] An activated carbon obtained by calcining a carbide obtained by calcining an easily graphitizable organic substance, wherein the mode of pore size distribution by TEM image analysis is in the range of 10 to 20 angstroms. , The area in the TEM image is 5
Activated carbon for an organic solvent-based electric double layer capacitor electrode, wherein a continuous porosity represented by a ratio of a total area of pores of 00 square angstroms or more to a total pore area is 20% or more. 2. The activated carbon for an organic solvent-based electric double layer capacitor electrode according to claim 1, wherein the mode of the pore diameter distribution is in the range of 11 to 15 Å. 3. The organic solvent-based electric double layer capacitor electrode according to claim 1, wherein the number of pores having a mode value in the range is 40% or more of the total number of pores. For activated carbon. 4. The difference between the mode of the pore size distribution of the carbide by TEM image analysis and the mode of the pore size distribution of the activated carbon obtained by alkali-activating the carbide by TEM image analysis is 0. The activated carbon for an organic solvent-based electric double layer capacitor electrode according to any one of claims 1 to 3, wherein the activated carbon is in the range of 2 to 3 angstroms. 5. The activated carbon for an organic solvent-based electric double layer capacitor electrode according to claim 1, wherein the graphitizable organic substance is a vinyl chloride resin.