JP2006151699A - Carbonized material for producing activated carbon used for electrode of electric double layer capacitor and method of producing activated carbon used for electrode of electric double layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbonized material suitable for producing activated carbon used for an electrode that can give, when used as the electrode of a capacitor, an electric double layer capacitor having low internal resistance and large electrostatic capacity. <P>SOLUTION: The carbonized material for producing activated carbon used for an electrode of an electric double layer capacitor has an anisotropic fine texture and is obtained by heat-treating a mixture comprising of 30-80 mass% of pitch and 20-70 mass% of a phenol resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a carbonized product for producing activated carbon for electric double layer capacitor electrodes and a method for producing activated carbon for electric double layer capacitor electrodes.

Conventionally, non-graphitizable carbon materials and graphitizable carbon materials are known as carbonized materials used in the production of activated carbon for electric double layer capacitor electrodes.
Non-graphitizable carbon materials such as phenol resin charcoal, furan resin charcoal, polyvinylidene chloride resin charcoal, and plant tissue derived charcoal such as coconut shells have an optically isotropic and amorphous structure. It is classified as hard carbon that is difficult to graphitize.

Since non-graphitizable carbon materials are rich in reactivity with water vapor, activated carbon having a large specific surface area and pore volume can be easily obtained. A double layer capacitor is obtained.
However, even if the conditions are more severe with certain activation conditions as a boundary, the specific surface area is increased, but the capacitor electrode density is decreased, and as a result, the capacitance density (F / cm ³ ) is decreased. There is.

On the other hand, needle-like raw coke, bulk mesophase, and mesophase pitch spun fibers, which are easily graphitizable carbon materials, are optically anisotropic graphite-like microcrystals with a dense structure in which carbon hexagonal meshes (basic surfaces) are laminated. And is classified as a soft carbon that is easy to graphitize.
This graphitizable carbon material has a property that it has poor reactivity with an activation gas such as water vapor because of its strong anti-oxidation property on the base surface.
Therefore, alkaline activation methods such as potassium activation and sodium activation are mainly used for activation of the graphitizable carbon material, and an electric double layer capacitor having a high capacitance density can be obtained (Patent Document 1: Special). JP 2002-25867, Patent Document 2: JP 2003-51430 A, etc.).

However, activated carbon obtained by activating an easily graphitizable carbon material by the alkali activation method has a high initial capacitance density, but it is inferior in durability when it is made into an electric double layer capacitor, and a large amount of gas is produced when charging and discharging are continued. There is a problem that the electrostatic capacity is reduced due to the generation of.
Moreover, it is known that when an easily graphitizable carbon material such as mesophase pitch is used as a raw material, it is difficult to stably obtain activated carbon having a high capacitance density.

JP 2002-25867 A JP 2003-51430 A JP-A-9-180969 JP. Randin, E .; Yeager, “J. Electronal. Chem.”, 1972, 36, p. 257-276 JP. Randin, E .; Yeager, “J. Electronal. Chem.”, 1975, 58, p. 313-322

As described above, the difference in characteristics when using a non-graphitizable carbon material and an easily graphitizable carbon material as a carbonized product for the production of activated carbon for an electric double layer capacitor electrode is as follows. Conceivable. First, regarding the capacitance density, the knowledge that the capacitance value to be expressed is larger when the edge surface is exposed than the base surface of the graphite-like microcrystal (Non-Patent Document 1: J. Electroanaly. Chem., 1972, Non-Patent Document 2: J. Electroanaly. Chem., 1975), a graphitizable carbon material in which graphite-like microcrystals exist and the edge surface is exposed by an alkali activation treatment. It is considered that the case of using the material has a higher capacity density (Patent Document 3: Japanese Patent Laid-Open No. 9-180969).
In addition, regarding the durability when making an electric double layer capacitor, in order to consider the reactivity at the time of alkali activation of the next stage, it is gasification, This is thought to be the cause of the decrease in capacitance.

  Based on these findings, in order to obtain activated carbon for high performance electric double layer capacitors, using a carbonized material that has both the activation activity of the non-graphitizable carbon material and the graphite-like microcrystal of the graphitizable carbon material, Although it is considered ideal to perform an activation process that exposes more edge surfaces, there is no method that can produce such activated carbon at a low cost and in a stable manner in large quantities. is there.

  The present invention has been made in view of such circumstances, and is suitable for the production of activated carbon for an electrode that gives an electric double layer capacitor having high capacitance density and durability when used as a capacitor electrode. It aims at providing the manufacturing method of carbonized material and activated carbon for electric double layer capacitor electrodes.

  As a result of intensive studies to achieve the above object, the present inventors have heat-treated a mixture comprising a pitch of 30 to 80% by mass and a phenol resin of 20 to 70% by mass, and have a fine anisotropic structure. Activated carbon obtained by activating carbonized material has high capacitance density and excellent electrical conductivity. By using this as an electrode material for electric double layer capacitors, low internal resistance, high capacitance, and high durability As a result, the present invention was completed.

That is, the present invention
1. A carbonized product for producing activated carbon for an electric double layer capacitor electrode, characterized in that a mixture comprising a pitch of 30 to 80% by mass and a phenol resin of 20 to 70% by mass is heat-treated and has a fine anisotropic structure;
2. 1. The carbonized product according to 1, wherein the fine anisotropic structure has a size of 1 to 15 μm and an optical anisotropy ratio of 10 to 100%.
3. 1 or 2 carbonized product, wherein the pitch contains less than 40% by mass of a toluene-insoluble component;
4). Activated carbon for an electric double layer capacitor electrode, characterized by activating one of the carbonized compounds 1 to 3,
5. An electrode for an electric double layer capacitor comprising the activated carbon for an electric double layer capacitor electrode of 4,
6). A pair of polarizable electrodes, a separator interposed between the electrodes, and an electrolyte, and at least one of the pair of polarizable electrodes is an electrode for 5 electric double layer capacitors Electric double layer capacitor,
7). A carbonization step for obtaining a carbonized product by heat-treating a mixture of 30 to 80% by mass of pitch and 20 to 70% by mass of a phenol resin in an inert gas atmosphere, and an activation treatment step for activating the carbonized product are provided. A method for producing activated carbon for an electric double layer capacitor electrode,
8). 7. The electric double layer according to 7, wherein the mixture is obtained by uniformly mixing the pitch and phenol resin with a solvent in which both of these components are soluble, and then removing the solvent. A method for producing activated carbon for capacitor electrodes,
9. The method for producing activated carbon for an electric double layer capacitor according to 7 is characterized in that the mixture is obtained by mechanically mixing the pitch and the phenol resin having a particle diameter of 74 μm or less.

The carbonized material having a fine anisotropic structure of the present invention has an activation activity of phenol resin charcoal, a graphite-like microcrystalline structure of tarpitch charcoal, and edge surface characteristics. Therefore, by activating this carbonized material, it is possible to lead to activated carbon having an effective pore volume unique to non-graphitizable carbon and a high density and edge surface unique to graphitizable carbon.
In addition, since the carbonized material has a graphite-like microcrystalline structure as a main skeleton, activated carbon obtained by activating the carbonized material has a high density and excellent electrical conductivity. As a result, by using this activated carbon as an electrode material of an electric double layer capacitor, a capacitor having a low internal resistance and a high capacitance value can be obtained.

Hereinafter, the present invention will be described in more detail.
The carbonized product for producing activated carbon for electric double layer capacitor electrodes according to the present invention is obtained by heat-treating a mixture of pitch 30 to 80% by mass and phenol resin 20 to 70% by mass, and has a fine anisotropic structure. Features.
As the pitch in the present invention, for example, a coal-based isotropic pitch, a petroleum-based isotropic pitch, or a mixture thereof can be used, and there is no limitation on whether it is a granule or a melt. Among them, it is preferable to contain a lot of components soluble in an aromatic hydrocarbon solvent such as benzene, toluene and xylene, and the toluene insoluble component is less than 40% by mass, preferably 30% by mass or less, more preferably 20% by mass or less. Pitch is preferably used. By using such a pitch, the miscibility with the phenol resin is improved, and it becomes easy to form a uniform fine anisotropic structure. In addition, the pitch and the phenol resin can be once dissolved in a solvent. Mixtures can be easily prepared.
As the phenol resin used in the present invention, a resol type phenol resin, a novolac type phenol resin, or a mixture of both can be used.

  If the pitch and phenol resin content in the mixture is out of the above range, the carbonized product is insufficiently formed with a fine anisotropic structure, which may reduce the density and electrical conductivity of the obtained activated carbon. In order to obtain a carbonized product having a sufficient fine anisotropic structure, the content of pitch and phenol resin is preferably 30 to 80% by mass, particularly preferably 40 to 80% by mass, and more preferably 20 to 70% by mass, particularly phenol resin. 20-60 mass% is preferable.

The carbonized material of the present invention has a fine anisotropic structure, and the size of the structure is not particularly limited, but is preferably 1 to 15 μm, particularly preferably 1 to 10 μm.
If the size of the fine anisotropic structure is less than 1 μm, the edge surface effect of graphite-like microcrystals may not be exhibited, whereas if it exceeds 15 μm, the uniform activation reaction may be adversely affected. There is. In addition, the magnitude | size of a fine anisotropic structure | tissue is a measured value based on the classification | category method by an optical structure | tissue when a sample is observed under crossed Nicols with a polarizing microscope.

  Further, the carbonized product of the present invention preferably has an optical anisotropy ratio of 10 to 100%, particularly 20 to 100%. If the optical anisotropy ratio is less than 10%, there is a concern that the capacitance density when the capacitor is formed becomes small. The optical anisotropy ratio means the area ratio (%) of the optically anisotropic phase in the sample of the photograph taken by taking a photograph of the carbonized product under crossed Nicols with a polarizing microscope.

The method for preparing the mixture of pitch and phenol resin is not particularly limited, and examples thereof include the following methods (1) and (2).
(1) Solvent mixing method (wet)
This is a method in which a predetermined amount of pitch and phenol resin and a solvent in which both of these components are soluble are uniformly mixed, and then the solvent is removed to form a mixture.
Solvents that are soluble in pitch and phenol resin are appropriately selected from aromatic hydrocarbon solvents, amine solvents, amide solvents, sulfoxide solvents, ether solvents, alcohol solvents, halogen-containing chain hydrocarbon solvents, etc. Can be used. Specific examples include benzene, toluene, pyridine, quinoline, aniline, dimethyl sulfoxide, dimethylformamide, chloroform, tetrahydrofuran, ethylene glycol, and the like. These may be used alone or in combination of two or more. Can do.

The blending amount of the solvent is not limited as long as the pitch and the phenolic resin can be dissolved to prepare a uniform solution. For example, 50 parts by mass or more with respect to 100 parts by mass in total of the pitch and the phenolic resin. , 100 parts by mass or more. In addition, the mixing | blending order of a pitch, a phenol resin, and a solvent is arbitrary.
The solvent removal method may be appropriately selected and used from various known methods. In general, a method of removing the solvent by heating under reduced pressure is used.

(2) Mechanical mixing method (dry type)
This is a method of mixing a powdery or granular pitch and a phenol resin, and then mechanically stirring, pulverizing, etc. to obtain a mixture.
As a stirrer and a grinder, it can select suitably from well-known apparatuses, for example, a powder mixer, a ball mill, a pot mill, a planetary ball mill, a jet mill, a stirring rye crusher etc., These are 1 Species can be used alone or in combination of two or more.
The pitch used in this mechanical mixing method and the particle diameter of the phenol resin are not particularly limited, but in order to obtain a uniform mixture, the pitch has a particle diameter of 180 μm or less. It is preferable to use one having a particle size of 74 μm or less (JIS standard sieve 200 mesh permeation product).
The particle diameter is a value measured by a laser diffraction particle size distribution measuring device Microtrac HRA (manufactured by Nikkiso Co., Ltd.).

The mixture of pitch and phenol resin prepared by the above method may be subjected to pitch oxygen crosslinking treatment and phenol resin curing treatment as necessary before carbonization.
The method for oxygen crosslinking treatment of the pitch in the mixture is not particularly limited, and for example, a method of heat treatment at 100 to 180 ° C. for 1 to 30 hours in the presence of oxygen such as in the air can be employed. . In addition, it is preferable to perform oxygen bridge | crosslinking treatment into a powder or a gas stream so that a mixture may be an environment which is easy to contact oxygen. However, if the oxygen crosslinking treatment is excessively advanced, it may be difficult to obtain the fine anisotropic structure of the present invention because the development of the optically anisotropic phase is inhibited.

  It does not specifically limit as a method to harden the phenol resin in a mixture, According to the used phenol resin and the curing catalyst, it selects suitably. For example, a method of heat treatment at 100 to 200 ° C. for 1 to 10 hours under an inert gas atmosphere such as nitrogen gas can be employed.

  The method for carbonizing the mixture of pitch and phenol resin prepared by the above method is not particularly limited. For example, heat treatment is performed at 550 to 1000 ° C. for 1 to 3 hours in an inert gas atmosphere such as nitrogen gas. The method to do can be adopted. If the heat treatment is less than 550 ° C., sufficient carbonization treatment cannot be performed, which may cause gasification when the capacitor is formed. Further, heat treatment at a temperature higher than 1000 ° C. may reduce the activation activity after the carbonization treatment. Note that the heat treatment may be performed under normal pressure or under a pressure of about 500 to 1000 kPa.

The activated carbon for an electric double layer capacitor electrode according to the present invention is obtained by activating the carbonized material having the fine anisotropic structure described above.
As an activation method, any of a gas activation method, an alkali activation method, or a combination of these methods can be used.
The gas activation treatment method is not particularly limited, and a known method according to the gas to be used can be appropriately employed. As an example of the steam activation treatment method, for example, under a nitrogen gas flow of 2 to 3 L / min, 700 to 900 ° C., preferably up to 800 to 900 ° C., 1.5 to 5 hours, preferably 2 to 4 hours. After raising the temperature, there is a method in which the final temperature is maintained for 1 to 5 hours, preferably 3 to 4 hours, and steam treatment is performed in the presence of nitrogen gas.
As an alkali activation treatment method, for example, there is a method of using KOH as an activator and holding it at a holding temperature of 500 to 900 ° C. under a nitrogen gas stream for 1 to 10 hours.

The activated carbon of the present invention changes the activation activity by appropriately changing the compounding ratio of pitch and phenol resin, the size of the fine anisotropic structure, and the optical anisotropy ratio for the carbonized product in the pre-activation stage. It is possible to control the physical properties of the activated carbon such as the specific surface area, pore volume and peak pore diameter after the activation treatment.
Preferred physical properties of the activated carbon are listed below: BET specific surface area 500-2500 m ² / g, total pore volume 0.3-1.5 mL / g, peak pore diameter of micropores by MP method is 0.8-1 .8 nm.

Here, if the BET specific surface area is less than 500 m ² / g, there is a concern that sufficient capacitance may not be obtained when used as a capacitor electrode material. If the BET specific surface area exceeds 2500 m ² / g, the obtained capacitor electrode There is a possibility that the density is lowered. Considering these facts, a more preferable range of the BET specific surface area is 700 to 2100 m ² / g, particularly 900 to 2000 m ² / g.
If the total pore volume is less than 0.3 mL / g, sufficient capacitance may not be obtained. On the other hand, if it exceeds 1.5 mL / g, mesopores and macropores increase. As a result of the electrode density of the capacitor being reduced, the capacitance per volume may be reduced.
If the peak pore diameter of the micropores by the MP method is less than 0.8 nm, the large current charge / discharge characteristics and low temperature characteristics of the capacitor may be deteriorated, and if it exceeds 1.8 nm, mesopores and macropores increase. As a result of the electrode density of the obtained capacitor being lowered, the capacitance per volume may be reduced. In addition, for the purpose of placing importance on the energy density of electric double layer capacitors, graphite-like microcrystals have developed, and even when producing microporous activated carbon with a small specific surface area and small pore volume, the conventional activated carbon does not expand due to charging. However, since the activated carbon of the present invention partially has a non-graphitizable carbon structure, it can suppress expansion.

Activated carbon obtained by activating the carbonized material having the fine anisotropic structure as described above has an effective pore volume unique to non-graphitizable carbon, and has a high density and edge surface unique to graphitizable carbon. Is. For this reason, a capacitor excellent in electrostatic capacity and electrode density can be obtained by using the activated carbon as an electrode material of an electric double layer capacitor.
In the case of an electric double layer capacitor electrode material, an electrode composition comprising the above-mentioned activated carbon of the present invention as a main component and further blended with this activated carbon with a binder polymer and, if necessary, a conductive material, is applied onto a current collector. Can be used.
In this case, the binder polymer, the conductive material, and the current collector are not particularly limited, and may be appropriately selected from known ones.

Examples of the binder polymer include fluorine resins such as polytetrafluoroethylene, polyvinylidene fluoride, and fluoroolefin copolymer cross-linked polymers, polysaccharides such as carboxymethyl cellulose, latex such as styrene butadiene copolymer, polyimide, and phenol resin. A thermosetting resin or the like can be used.
The addition amount of a binder polymer can be 0.5-20 mass parts with respect to 100 mass parts of activated carbon, for example, Preferably it is 1-10 mass parts.

Examples of the conductive material added as necessary include carbon black, ketjen black, acetylene black, carbon whisker, carbon fiber, natural graphite, artificial graphite, (oxide) titanium, ruthenium oxide, aluminum, nickel, and other metals. A fiber etc. are mentioned, These 1 type can be used individually or in combination of 2 or more types.
The amount of the conductive material added can be, for example, 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the activated carbon.

In addition, there is no limitation in particular in the preparation method of an electrode composition, For example, activated carbon, a binder polymer, and the electrically conductive material added as needed can also be prepared in a solution form, Moreover, as needed to this solution It can also be prepared by adding a solvent.
An electrode can be obtained by applying the electrode composition thus obtained onto a current collector. The application method is not particularly limited, and a known application method such as a doctor blade or an air knife may be appropriately employed.
As the positive electrode current collector, an aluminum foil or an aluminum oxide foil is preferably used. On the other hand, as the negative electrode current collector, an aluminum foil, an aluminum oxide foil, a copper foil, a nickel foil, or a surface thereof is a copper plating film or a nickel plating film. It is preferable to use a metal foil or the like formed by

As the shape of the foil constituting each of the current collectors, a thin foil shape, a sheet shape spread on a plane, a stampable sheet shape with holes formed, or the like can be adopted. The thickness of the foil is usually about 1 to 200 μm, but considering the density of the activated carbon in the entire electrode, the strength of the electrode, etc., 8 to 100 μm is preferable, and 8 to 30 μm is particularly preferable.
The electrode can also be formed by melt-kneading the electrode composition and then extruding and film-forming.

The electric double layer capacitor according to the present invention comprises a pair of polarizable electrodes, a separator interposed between the electrodes, and an electrolyte, and at least one of the pair of polarizable electrodes is configured as described above. The obtained electrode is used. In this case, other capacitor components other than the electrodes may be appropriately selected from known members.
As an example of the manufacturing method, an electric double layer capacitor structure having a separator interposed between the pair of electrodes obtained as described above is laminated, folded, or wound as necessary. After being housed in a battery container such as a battery can or a laminate pack, there is a method of assembling by filling the electrolyte, sealing the battery can, and heat sealing the laminate pack. However, the present invention is not limited to this, and an appropriate method may be used depending on the type of capacitor constituent member.

  The electric double layer capacitor of the present invention is a memory backup power source for mobile phones, notebook computers and portable terminals, power sources for mobile phones and portable audio equipment, power supplies for instantaneous power failures such as personal computers, solar power generation, It can be suitably used for various low current power storage devices such as a load leveling power source by combining with wind power generation. An electric double layer capacitor that can be charged and discharged with a large current can be suitably used as a large current storage device that requires a large current, such as an electric vehicle or a power tool.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example.
In the following, the particle diameter is a value measured by a laser diffraction particle size distribution measuring device Microtrac HRA (manufactured by Nikkiso Co., Ltd.).

<Manufacture of activated carbon for electric double layer capacitor electrode>
[Example 1]
[1] Preparation of mixture Coal-based isotropic tar pitch (AD-PC, formerly Adchemco, softening point 110 ° C., fixed carbon content 60% by mass, toluene insoluble content 20% by mass, quinoline insoluble content 3% by mass, ash content 0 .1 mass%) powder (particle size 180 μm or less) 80 g and resol type phenolic resin powder (Resitop Marilyn HF-020, Gunei Chemical Industry Co., Ltd., particle size 10-30 μm) 20 g 500 ml three-neck flask Then, 150 g of pyridine as a solvent was added thereto and stirred at room temperature for 30 minutes. Next, the flask was heated to 50 ° C. in an oil bath, and stirred and mixed for 2 hours to obtain a uniformly dissolved mixed composition. From this homogeneously dissolved mixed composition, pyridine was removed under reduced pressure at 60 ° C. for 32 hours to obtain a uniform mixed composition.

[2] Carbonization step The obtained uniform mixed composition is spread on a metal tray thinly, and is dried in an air atmosphere at 120 ° C. for 5 hours in a dryer (constant temperature oven DN610H, manufactured by Yamato Scientific Co., Ltd.). Then, thermosetting treatment was performed at 200 ° C. for 5 hours in a nitrogen atmosphere.
The heat-cured product is placed in a graphite boat, and the graphite boat is installed in the soaking part of a small glass tube tubular furnace (TK-30N, manufactured by Seiwa Riko Co., Ltd.) under nitrogen gas flow (2 L / min) ), Heated up to 600 ° C. over 6 hours and held at this temperature for 2 hours. After cooling, the carbonized product was recovered from the graphite boat and the carbonization yield was determined.
A part of the obtained carbonized product was collected, and the structure was observed with a polarizing microscope (DMLM type, manufactured by Leica). For the optical anisotropy rate, the micrograph was subjected to image processing, and the area ratio of the optically anisotropic phase in the screen was calculated. The micrograph is shown in FIG. 1, and the size of the fine anisotropic structure and the optical anisotropy ratio are shown in Table 1.
The remaining carbonized product was pulverized to 74 μm or less with a desktop ball mill (V-1M, manufactured by Irie Shokai Co., Ltd.), and further pulverized with a planetary ball mill (07.301 type, manufactured by Fritsch) for 3 minutes. The sample for activation processing was obtained by processing.

[3] Activation treatment step 40 g of the carbonized product pulverized product is put into a glass tube type small tubular furnace (TK-30N, manufactured by Hoshiwa Riko Co., Ltd.), under a nitrogen gas flow (2 L / min), 900 ° C. After raising the temperature in 4 hours, the nitrogen introduction tube was connected to a steam generator, and steam treatment was performed at the above temperature for 3.5 hours in the presence of nitrogen. The amount of steam introduced was 4.2 g / g · hr. After the steam treatment, it was connected again to a nitrogen introduction tube, cooled to room temperature, and dried to obtain activated carbon.
Table 1 shows the results obtained by measuring the BET specific surface area, the total pore volume, and the micropore peak pore diameter for the obtained activated carbon by nitrogen adsorption.

[Example 2]
Activated carbon was obtained in the same manner as in Example 1 except that the mixture was prepared by the following method. FIG. 2 shows a micrograph of the obtained carbonized product, and Table 1 shows the results of measuring the size and optical anisotropy ratio of the fine anisotropic structure and the same physical properties as in Example 1 for activated carbon.
[1] Preparation of mixture 70 g of coal-based isotropic tar pitch powder and 30 g of resol type phenol resin powder were put in a pot of a desktop ball mill and subjected to a rotation treatment at 150 rpm for 3 hours. afterwards,
The mixture was obtained by performing a treatment for 3 minutes in a planetary ball mill.

[Example 3]
Activated carbon was obtained in the same manner as in Example 1 except that 60 g of coal-based isotropic tar pitch powder and 40 g of resol type phenol resin powder were used. A microphotograph of the obtained carbonized product is shown in FIG. 3, and the size and optical anisotropy ratio of the fine anisotropically manufactured structure, and the results of measuring the same physical properties as in Example 1 for activated carbon are shown in Table 1.

[Example 4]
Activated carbon was obtained in the same manner as in Example 2 except that 60 g of coal-based isotropic tar pitch powder and 40 g of resol type phenol resin powder were used. FIG. 4 shows a micrograph of the obtained carbonized product, and Table 1 shows the results of measuring the size of the fine anisotropic structure, the optical anisotropy rate, and the same physical properties as in Example 1 for the activated carbon.

[Example 5]
40 g of coal-based isotropic tar pitch powder, 60 g of novolak-type phenol resin powder (Shonol BRP-510F, Showa Polymer Co., Ltd., particle size 10 to 40 μm) were used, and the steam activation treatment time was 4 hours. Except that, activated carbon was obtained in the same manner as in Example 1. FIG. 5 shows a micrograph of the obtained carbonized product, and Table 1 shows the results of measuring the size of the fine anisotropic structure and the optical anisotropy rate, and the same physical properties as in Example 1 for the activated carbon.

[Comparative Example 1]
100 g of coal-based isotropic tar pitch powder is put into a graphite boat, and the graphite boat is installed in the soaking part of a small glass tube tubular furnace. Under nitrogen gas flow (2 L / min), it takes 6 hours to 600 ° C. The temperature was raised and maintained at this temperature for 2 hours. After cooling, the carbonized product was recovered from the graphite boat and the carbonization yield was determined.
The obtained carbonized product was pulverized in the same manner as in Example 1, then charged into a glass tube type small tubular furnace and heated to 900 ° C. in 2 hours under a nitrogen gas flow (2 L / min), The nitrogen inlet tube was connected to a steam generator, and steam treatment was performed at the above temperature for 3 hours in the presence of nitrogen. The amount of steam introduced was 4.2 g / g · hr. After the steam treatment, it was connected again to a nitrogen introduction tube, cooled to room temperature, and dried to obtain activated carbon. FIG. 6 shows a micrograph of the obtained carbonized product, and Table 1 shows the results of measuring the size and optical anisotropy ratio of the fine anisotropic structure and the physical properties similar to those of Example 1 for activated carbon.

<Production of electric double layer capacitor>
[Examples 6 to 10, Comparative Example 2]
Each activated carbon, conductive material (Denka Black HS100, manufactured by Denki Kagaku Kogyo Co., Ltd.), and binder (poly (vinylidene fluoride), manufactured by Aldrich) were used as activated carbon: conductive material: binder = 90: 5: 5 and a N-methyl-2-pyrrolidone (hereinafter referred to as NMP, manufactured by Gordo Solvent Industry Co., Ltd.), and the packing material: NMP = 100: 212. An electrode slurry mixed at a ratio of 5 (mass ratio) was prepared.
This electrode slurry was applied on one side of an Al / AlO _X sheet (30CB, manufactured by Nippon Electric Power Industry Co., Ltd.) so that the coating thickness after drying was 0.070 mm, then dried (80 ° C.), rolled ( An electrode sheet was obtained with a packing density of about 0.6 g / cm ³ . Thereafter, the electrode sheet was punched to φ12 mm with a punching machine and dried under reduced pressure at 120 ° C. for 2 hours to obtain a test electrode.
Subsequently, using a bipolar coin cell, the two test electrodes were assembled into a coin cell via a cellulose separator (TF40-35, manufactured by Nippon Kogyo Paper Industries Co., Ltd.), and N, N-diethyl-N was used as an electrolyte. Each Example and Comparative Example capacitor cell was prepared using a 1 mol / L propylene carbonate (Kanto Chemical Co., Ltd.) solution of -methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate (Kanto Chemical Co., Ltd.). Produced.

For the capacitor cells obtained in Examples 6 to 10 and Comparative Example 2, the capacitance, internal resistance, and electrode density were measured by the following methods. The results are shown in Table 2.
[1] Capacitance Each capacitor cell was evaluated by charging / discharging with a charge / discharge system (1005SM8, manufactured by Hokuto Denko Co., Ltd.).
As an initial capacity confirmation test, a current density of 0.88 mA / cm ² in a room temperature environment, a setting voltage of 2.50 V, a constant voltage time of 15 minutes (end condition), and a current density of 0.88 mA / cm ² The battery was discharged at a final voltage of 0.0V.
[2] Electrode density About each said capacitor cell, mass and thickness were measured and the electrode density was computed from the obtained value. The calculation was performed by dividing the total mass of both electrodes (not including the mass of the Al / AlO _x sheet) by the volume of the electrode punched to φ12 mm (not including the thickness of the Al / AlO _x sheet).
[3] Internal resistance It was calculated by dividing the voltage difference between the y-intercept of the approximate curve at 25% of the total discharge time from the start of charging and the rated specification voltage by the reference current.

  As shown in Table 2, in the capacitor cells of Examples 6 to 10 using the activated carbons of Examples 1 to 5, the activated carbon of Comparative Example 1 was used in any of capacitance, internal resistance, and electrode density. It turns out that it is superior to a capacitor.

2 is a diagram showing a micrograph of the carbonized product obtained in Example 1. FIG. 3 is a diagram showing a micrograph of the carbonized product obtained in Example 2. FIG. 6 is a view showing a micrograph of a carbonized product obtained in Example 3. FIG. It is a figure which shows the microscope picture of the carbonized material obtained in Example 4. It is a figure which shows the microscope picture of the carbonized material obtained in Example 5. It is a figure which shows the microscope picture of the carbonized material obtained by the comparative example 1.

Claims (9)

  A carbonized product for producing activated carbon for an electric double layer capacitor electrode, comprising a heat treatment of a mixture comprising a pitch of 30 to 80% by mass and a phenol resin of 20 to 70% by mass and having a fine anisotropic structure.   The carbonized material according to claim 1, wherein the fine anisotropic structure has a size of 1 to 15 µm and an optical anisotropy ratio of 10 to 100%.   The carbonized product according to claim 1 or 2, wherein the pitch contains less than 40% by mass of a toluene-insoluble component.   An activated carbon for an electric double layer capacitor electrode, wherein the carbonized product according to claim 1 is activated.   An electrode for an electric double layer capacitor comprising the activated carbon for an electric double layer capacitor electrode according to claim 4.   The electric double layer capacitor electrode according to claim 5, comprising a pair of polarizable electrodes, a separator interposed between the electrodes, and an electrolyte, wherein at least one of the pair of polarizable electrodes is an electrode for an electric double layer capacitor according to claim 5. An electric double layer capacitor characterized by that.   A carbonization step for obtaining a carbonized product by heat-treating a mixture of 30 to 80% by mass of pitch and 20 to 70% by mass of a phenol resin in an inert gas atmosphere, and an activation treatment step for activating the carbonized product are provided. A method for producing activated carbon for an electric double layer capacitor electrode.   8. The mixture according to claim 7, wherein the mixture is obtained by uniformly mixing the pitch and phenol resin and a solvent in which both of these components are soluble, and then removing the solvent. A method for producing activated carbon for an electric double layer capacitor electrode. The method for producing activated carbon for an electric double layer capacitor according to claim 7, wherein the mixture is obtained by mechanically mixing the pitch and the phenol resin having a particle diameter of 74 µm or less.

Images