JP2000353644A - Manufacture of carbon material for electric double- layer capacitor electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a carbon material for an electric double-layer capacitor electrode which can suitably have a high electrostatic capacity and which can be manufactured with a low manufacturing cost. SOLUTION: This method includes the steps of dehydrochlorination and carbonization using a mixture solution of the aqueous solution of alkaline metal hydroxide, an organic solvent which is partly or wholly swelled or dissolved with polyvinylidene chloride or polyvinylindene chloride copolymer, alcohol and/or ether prior to a step of carbonizing under heating at a temperature of 600-1,000 deg.C using polyvinylidene chloride, vinylidene chloride copolymer or a mixture thereof as carbon raw material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbon material for an electrode of an electric double layer capacitor which is suitable for obtaining high capacitance and inexpensive in production cost.

[0002]

2. Description of the Related Art In recent years, as electronic devices have been actively reduced in size, a small, highly reliable, high-capacitance capacitor used for a backup power supply has been adopted. In particular, recently, for the practical use of electric vehicles, an electric double-layer capacitor (ADP) has been developed as a new capacitor having a higher capacitance for the purpose of smoothing the load of an auxiliary power supply or a secondary battery for a power supply. (EDLC) is attracting attention.

An EDLC is a capacitor using an electric double layer generated at an interface between a solid and a liquid. The structure comprises a pair of polarizable electrodes sandwiching a separator, a case for accommodating them, an electrolytic solution and a current collector. Activated carbon having a large specific surface area (solidified powder, non-woven fabric, sheet) is used as the polarizable electrode material. Normally, plant materials such as coconut shell and cellulose, petroleum such as petroleum pitch, phenolic resin, and resin such as PAN are used as raw materials for activated carbon. On the other hand, as an electrolytic solution, for example, an aqueous solution of a sulfuric acid aqueous solution and an aqueous solution of potassium hydroxide are used for an aqueous system, and an organic solvent-based electrolytic solution such as propylene carbonate in which a quaternary ammonium salt is dissolved is used for a non-aqueous system. An aqueous EDLC using an aqueous electrolyte is suitable for low equivalent series resistance (ESR) because of high conductivity of the electrolyte, and is excellent in environmental characteristics without being affected by humidity. Further, an organic EDLC using an organic electrolytic solution has a high withstand voltage, a high energy density, and a feature that it can be miniaturized.

In recent years, EDLCs have been able to store large capacitances and supply large currents due to the development of high-density electrodes employing activated carbon as an electrode material. The capacitance of an EDLC is greatly affected by the structure and physical properties of a carbon material typified by activated carbon as an electrode material, and the required characteristics of activated carbon as a polarizable electrode include:
It has a large specific surface area, is conductive, has low internal resistance, and has a high bulk density.
It is considered that the required properties of these activated carbons are greatly affected by the pore structure such as the pore volume and the pore size distribution of the activated carbon.

[0005] Actually, as a prior art example of controlling the pore structure of a carbon material represented by activated carbon for the purpose of improving the capacitance of EDLC, Japanese Patent Application Laid-Open No.
20985, the technique of JP-A-7-249551 focusing on the carbon material of activated carbon, and the technique of JP-A-9-213, in which activated carbon produced by firing is subjected to an alkali activation treatment.
The technology of Japanese Patent Application Laid-Open No. 590 and Japanese Patent Application Laid-Open No. 9-275042 has already been reported. According to the technique disclosed in Japanese Patent Application Laid-Open No. 7-220985, the shape and size of the pores of activated carbon are specified by using a transmission electron microscope photograph (TEM photograph) and an image analysis method thereof. According to this, the pores are slit-shaped or elliptical, and in an aqueous electrolyte solution, an electrode material having pores with a slit width and a slit length in the range of 1.5 to 3 times the water molecule diameter is effective. It is shown that in the electrolyte, an electrode material having pores having an ion diameter of solvated ions of the electrolyte plus 0.2 nm or more is most suitable for EDLC having a large capacitance. And
As a method for producing such activated carbon, JP-A-3-78
No. 221 discloses a porous production method of sintering activated carbon fine particles by a pulse impact current. However, a special sintering method must be used, and the production cost and versatility are reduced. Is not preferred.

According to the technique disclosed in Japanese Patent Application Laid-Open No. 7-249551, polyvinylidene chloride (PV
DC) under a non-oxidizing atmosphere (under nitrogen gas N2).
It is shown that carbonization and firing at 00 to 1000 ° C. by an electric current sintering method can provide a carbon material for an EDLC electrode having a large number of pores. As a carbon raw material, a PV which easily provides a suitable field for adsorption of a large number of electrolyte ions by a side chain elimination reaction (dehydrochlorination reaction) by heat treatment during carbonization.
Although the use of DC is a very good finding, the fact that it must be fired at 800 to 1000 ° C. and that a special sintering method such as electric sintering must be used is a problem in terms of manufacturing cost and versatility. (It is not preferable to use a carbon material obtained by dehydrochlorination using PVDC as a raw material. However, the carbon material is not activated carbon in a strict sense. Since it has a diffraction pattern, it may be treated in the same manner as activated carbon below.)

Further, according to the technique disclosed in Japanese Patent Application Laid-Open No. 9-213590, a carbon material is fired in two stages at 320 to 380 ° C. and 450 to 700 ° C. in the presence of an alkali metal hydroxide to convert the alkali metal hydroxide. A method for producing activated carbon for an EDLC electrode, which is characterized by further performing a heat treatment after removal, is shown. Further, according to the technique disclosed in Japanese Patent Application Laid-Open No. 9-275042, after calcination of a vinyl chloride resin at a temperature of 2,000 ° C. at which the first stage of weight loss occurs in thermal analysis, alkali activation is performed using potassium hydroxide or the like. Activation temperature 500 ~
EDL performed at 1000 ° C. for 1 to 20 hours
A method for producing activated carbon for a C electrode is shown. The alkali treatments used in these techniques are all related to the activation treatment of activated carbon after carbonization, and are different from the carbonization treatment. Also, the processing temperature is high, which is completely different from our technology described below.

[0008] By using these conventional techniques, according to the activated carbon having a suitable pore size with respect to the electrolyte ion diameter, an EDLC having a higher capacitance can be obtained as compared with an EDLC obtained using ordinary activated carbon. However, in order to reduce the weight as an auxiliary power supply for an electric vehicle, an EDL having a higher capacitance is required.
C is required.

[0009]

SUMMARY OF THE INVENTION The present invention provides a method for producing a carbon material for an electrode of an electric double layer capacitor, which is suitable for obtaining a high capacitance and inexpensive in production cost.

[0010]

As a result of intensive studies, the present inventor has found that in order to solve the above-mentioned problems, a carbon material obtained by sequentially performing the following primary carbonizing treatment and secondary carbonizing treatment is used. The inventors have found out that it can be used as a carbon electrode of EDLC, and have reached the present invention. PVDC as the primary carbonization treatment
Alternatively, a carbon raw material (hereinafter, referred to as a PVDC resin) using a part or all of a PVDC copolymer is swelled or dissolved in an aqueous solution of an alkali metal hydroxide (hereinafter, referred to as an alkali) and a part or all of the PVDC resin. An organic solvent
The mixed solution with alcohol is subjected to a dehydrochlorination treatment (primary carbonization treatment) at 100 ° C. or lower using a treatment liquid (referred to as an alkali treatment liquid) to obtain a carbon material (primary activated carbon). Then, 2
As the primary carbonization treatment, primary activated carbon is subjected to a non-oxidizing atmosphere (nitrogen gas N ₂ , inert gas, etc.) or an acidic atmosphere (steam H ₂ O,
Carbon dioxide gas (CO ₂ etc.) and heat carbonization treatment (secondary carbonization treatment) at 600 to 1000 ° C. to obtain a carbon material (secondary activated carbon). The capacitance of the EDLC using the carbon material obtained in this way is 600 to 10% for the PVDC resin according to the conventional method.
E using carbon material obtained by heating and carbonizing at 00 ° C
The inventors have found that the capacitance is higher than that of DLC, and have reached the present invention.

That is, the present invention provides a method for producing a carbon material for an electric double layer capacitor electrode which is suitable for obtaining high capacitance and inexpensive in production cost. The present invention is characterized by including (1) a step of carbonizing a carbon raw material using a part or all of polyvinylidene chloride or a polyvinylidene chloride copolymer using a solution containing an alkali metal hydroxide. Method for producing carbon material for electrode of electric double layer capacitor (2) As a solution containing an alkali metal hydroxide, an aqueous solution of an alkali metal hydroxide and a part or all of a polyvinylidene chloride or a polyvinylidene chloride copolymer are swollen. Or (1) the method for producing a carbon material for an electrode of an electric double layer capacitor according to (1), wherein a mixed solution of an organic solvent and an alcohol and / or ether is used; (3) a solution containing an alkali metal hydroxide 8 to 16 mol% of potassium hydroxide and part or all of polyvinylidene chloride or a polyvinylidene chloride copolymer Alternatively, a mixed solution containing 1 to 12 mol% of tetrahydrofuran or methyl ether ketone or tetramethylene sulfoxide as an organic solvent to be dissolved, 15 to 60 mol% of methyl alcohol, isopropyl alcohol or ethyl alcohol as an alcohol, and water in the other cases (2) The method for producing a carbon material for an electrode of an electric double layer capacitor according to (2).

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A method for producing activated carbon (carbon material) provided by the present invention will be described below. 1. A method for producing a carbon material provided by the present invention, a method for producing activated carbon that solves the above-mentioned problem, includes a step of carbonizing the PVDC resin by subjecting the PVDC resin to a dehydrochlorination treatment using an alkali treatment liquid as a carbon raw material. A method for producing a carbon material for an electrode of an electric double layer capacitor.

Hereinafter, the manufacturing method will be described in detail. [PVDC resin] There are two important things in the present invention. One is to obtain a carbon material having a large number of pores by dehydrochlorination with an alkaline treatment solution.
That is, a part or all of the VDC resin is used. Therefore, the higher the proportion of the PVDC resin in the carbon raw material, the higher the capacitance of the EDLC finally obtained due to the generation of a large number of pores.

As the carbon raw material to be mixed with the PVDC resin,
There is no particular limitation as long as it does not dissolve in the alkali treatment liquid and does not inhibit the alkali treatment liquid from reacting with the PVDC resin. For example, activated carbon or polytetrafluoroethylene (PTFE) may be used. The most preferred PVDC resin is homovinylidene chloride (homoPVDC). Alternatively, a PVDC copolymer can be used.
However, as the PVDC copolymer, VD in the copolymer
Although the molar composition ratio of the component C is not particularly limited, the higher the VDC molar content in the copolymer is, the larger the number of pores generated by the dehydrochlorination reaction is. Therefore, the capacitance of the finally obtained EDLC is high. Likely to be. Therefore, the content is desirably 60 mol% or more, preferably 80 mol% or more.

As a comonomer copolymerized with the VDC component of the PVDC copolymer (hereinafter, referred to as VDC / (comonomer name) copolymer), a comonomer copolymerized with VDC can be used. For example, ethylene, acetylene,
Propylene, butylene, butyne, butadiene, isoprene, isobutylene, vinyl chloride (VC), vinyl bromide,
Vinyl iodide, vinyl acetate, vinyl methyl ether, vinyl ethyl ether, vinyl isopropyl ether, vinyl propyl ether, vinyl isobutyl ether, vinyl normal amyl ether, vinyl isoamyl ether, vinyl-2-ethylhexyl ether, vinyl-n
Octadecyl ether, sodium vinyl sulfonate, divinylbenzene, vinyltoluene, acrylonitrile (AN), acrylic acid, acrylic acid chloride, bromide acrylate, acryloganamin, acryloylmorpholine, methyl acrylate (MA), ethyl acrylate, acrylic Propyl acrylate, isopropyl acrylate, butyl acrylate (BA), isobutyl acrylate, tert-butyl acrylate, hexyl acrylate, cyclohexyl acrylate, methylpropyl acrylate, lauryl acrylate, tridecyl acrylate, benzyl acrylate, acrylic N-amyl acid, isoamyl acrylate, tetrahydrofurfuryl acrylate, dimethylaminoethyl acrylate, ethylene glycol ethoxylate acrylate, Acrylic acid ethylene glycol methoxy rate, acrylic acid diethylene glycol ethoxylate, acrylic acid diethylene glycol methoxy rate, ethylhexyl acrylate, epoxy acrylate, acrylic acid esters of pentaerythritol,
n-stearyl acrylate, acrylates of dipentaerythritol, acrylates of trimethylolpropane, acrylates modified with caprolactone, acrylates of neopentyl glycol, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate , 2-hydroxybutyl acrylate, 1,4-butanediol diacrylate,
1,6-hexanediol diacrylate, glycidyl acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, 1,3-butylene diacrylate, sodium acrylate, acrylic acid Potassium, aluminum acrylate, zinc acrylate, calcium acrylate,
Magnesium acrylate, acrylamide, N, N-dimethylacrylamide, N, N-dimethylpropylacrylamide, acrolein, methacrylic acid, methacrylic chloride, methacrylic bromide, methyl methacrylate (MMA), ethyl methacrylate, propyl methacrylate, methacryl Isopropyl acrylate, Butyl methacrylate, Isobutyl methacrylate, Ter methacrylate
t-butyl, hexyl methacrylate, cyclohexyl methacrylate, methylpropyl methacrylate, lauryl methacrylate, tridecyl methacrylate, benzyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, tetrahydrofurfuryl methacrylate, dimethylaminoethyl methacrylate , Ethylene glycol methacrylate methacrylate, ethylene glycol methacrylate methacrylate, diethylene glycol methacrylate methacrylate, diethylene glycol methacrylate methacrylate, ethylhexyl methacrylate, epoxy methacrylate, methacrylates of pentaerythritol, n-stearyl methacrylate, dipentaerythritol Methacrylates, trimethylolpropane Acrylates, caprolactone-modified methacrylates, methacrylates of neopentyl glycol, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 1,4-butanediol dimethacrylate, 1, 6-hexanediol dimethacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, sodium methacrylate , Potassium methacrylate, aluminum methacrylate, zinc methacrylate, calcium methacrylate, magnesium methacrylate, methacrylate Ruamido,
N, N-dimethylmethacrylamide, N, N-dimethylaminopropylmethacrylamide, methacrolein, sodium methallylsulfonate, potassium methallylsulfonate, styrene, methylstyrene, vinylpyridine, hydroxyethylvinyl acetate, hydroxyethylvinyl acetate Derivatives of esters, ethers and urethanes, allyl alcohol, allyl chloride, sodium allyl sulfonate, allylamine, allyl aldehyde, allyl bromide, allyl glycidyl ether, allyl caproate, allyl poppy oil, allyl diglycol carbonate, allyl methacrylate, Allyl adenine, allyl adenosine, allyl amino purine, allyl amino ribofuranosyl purine, glycerol diaryl ether, dicyclopen Diene, chloroprene, cyclohexene, α-methylstyrene, polymerizable silicon compound, polymerizable fluorine compound, maleic acid, maleic acid derivative, fumaric acid, fumaric acid derivative, crotonic acid, crotonic acid derivative, oleic acid, oleic acid derivative, itacone Acid, itaconic acid derivative, crotonaldehyde, chloroethyl vinyl ether, diallyldimethylammonium chloride, diallyldimethylammonium bromide,
Diallyldimethylammonium iodide, allylpyridinium chloride, allylpyridinium bromide,
Allylpyridinium iodide, diisobutylene, diethylene glycol bisallyl carbonate, unsaturated carboxylic acids and derivatives thereof, unsaturated aldehydes, unsaturated alkyls, N-phenylmaleimide, N-methylphenylmaleimide, N-cyclohexylmaleimide, other N- Representative examples thereof include substituted maleimides.

The PVDC resin may be in the form of a powder,
An aqueous dispersion of PVDC resin (latex state) or a dried fiber or nonwoven fabric of cellulose or PAN impregnated with a solution of the latex or PVDC resin dissolved in an organic solvent may be used. Preferably, in a fine powder state of 75 μ or less (particularly preferably 25 μ or less), or PVDC
The fiber / nonwoven fabric state obtained by impregnating and drying the resin is suitable from the viewpoint of suppression of foaming during heating carbonization, efficiency of carbonization treatment, and the like. Although there is no particular limitation on the molecular weight of the PVDC resin, a PVDC resin having a number average molecular weight of about 5 to 100,000 obtained by ordinary polymerization (emulsion polymerization, suspension polymerization, solution polymerization, etc.) may be used.

[Alkali Treatment Solution] The second important and most characteristic feature of the present invention is to carry out a primary carbonization treatment using the following alkali treatment solution. The alkaline treatment liquid includes an aqueous solution (alkali aqueous solution) of an alkali metal hydroxide (hereinafter referred to as alkali) such as potassium hydroxide (KOH), sodium hydroxide (NaOH), and lithium hydroxide;
Tetrahydrofuran (THF), 1,4-dioxane,
Cyclohexane, cyclopentanone, chlorobenzene,
Dichlorobenzene, dimethylformamide (DMF),
Solvent of PVDC copolymer such as methyl ether ketone (MEK), ethyl acetate (homo-PVDC swelling reagent)
And hexamethylphosphoramide, tetramethylene sulfoxide, N-acetylpiperidene, N-methylpyrrolidone, N-formylhexamethyleneimine, trimethylene sulfide, Nn-butylpyrrolidone, isopropylsulfoxide, N- Formyl piperidine, N
An organic solvent which swells or dissolves a part or all of a PVDC resin such as a homo PVDC solvent such as acetylpyrrolidine, N, N-dimethylacetamide, cyclooctanone, cycloheptanone, n-butylsulfoxide, etc. Solvent)), methanol (MeOH),
It is a mixed solution thereof with an alcohol such as ethyl alcohol, isopropyl alcohol and 1-dodecanol and / or an ether such as diethyl ether (referred to as a diluent).

The alkali metal hydroxide is for dehydrochlorinating and carbonizing the PVDC resin. Among them, KOH can be increased in concentration, cost is low, and potassium chloride (KCl) generated by dehydrochlorination is 2%. It is most preferable because it acts as an activator during the next carbonization treatment. The alkali concentration in the alkali treatment liquid is preferably from 8 to 16 mol%, and more preferably from 10 to 15 mol%. A low concentration means that dehydrochlorination takes time or is insufficient. On the other hand, if the concentration exceeds 16 mol%, it is difficult to obtain a uniform alkaline treatment liquid due to phase separation of the organic solvent, precipitation of solids (including decomposed products) and turbidity.

The addition of a swelling organic solvent requires only an aqueous alkali solution, particularly in the case of a PVDC resin having a high VDC composition or a highly crystalline PVDC resin, since the alkali does not penetrate into the resin, so that the dehydrochlorination is slow and the time for carbonization is short. This is because it may take too much time or sufficient carbonization may not proceed to the inside of the PVDC resin particles. Further, by adjusting the concentration of the swelling organic solvent in accordance with the composition and crystallinity of the PVDC resin, the pore diameter and pore distribution generated during carbonization can be determined by EDLC.
This is also for controlling the pore structure, that is, optimizing the ionic diameter of the electrolytic solution used for the above. As the swelling organic solvent, TH
F or MEK or tetramethylene sulfoxide at a low temperature (from room temperature to the boiling point of the swelling organic solvent or lower, ie, 100
C. or lower) because the PVDC resin easily swells, and THF is particularly preferable because the cost is low. The concentration of the organic swelling agent in the alkali treatment liquid is 1 to 12
Mol% is preferred, and more preferably 4 to 11 mol%. When the concentration is low, the PVDC resin cannot be swollen, and the dehydrochlorination by alkali tends to be insufficient. On the other hand, when the concentration exceeds 12 mol%, the organic swelling agent undergoes phase separation or completely dissolves the PVDC resin, making it difficult to obtain a carbon material having pores.

The addition of alcohol and / or ether serves as a diluent and further prevents phase separation between a highly concentrated aqueous alkali solution and an organic swelling agent. As the alcohol and / or ether to be added, methyl alcohol, ethyl alcohol, and isopropyl alcohol are preferable. Among them, methyl alcohol has a wide range of preventing phase separation (the alkali concentration can be increased),
It is preferable because the cost is low. The concentration of the alcohol in the alkali treatment liquid varies depending on the types and concentrations of the aqueous alkali solution and the organic swelling agent to be mixed, but the concentration required for obtaining a uniform solution varies, but may be 15 to 60 mol%. If the concentration is lower than 15 mol%, the aqueous alkaline solution and the organic swelling agent are likely to undergo phase separation, or become a heterogeneous mixed solution in which solids (decomposed products) are precipitated or turbid. On the other hand, when the concentration exceeds 60 mol%, the alkali concentration becomes low, and the dehydrochlorination of the PVDC resin tends to be insufficient.

The alkaline treatment liquid of the present invention includes an aqueous solution of an alkali metal hydroxide, an organic solvent for swelling or dissolving a part or all of polyvinylidene chloride or a polyvinylidene chloride copolymer, an alcohol and / or an ether. The effect of the present invention cannot be sufficiently achieved with a non-uniform mixed solution in which phase separation, precipitation of a solid (decomposed product) or turbidity has occurred. In order to perform the dehydrochlorination of the present invention in a short time or with a low-concentration alkaline aqueous solution, a quaternary ammonium salt such as tetra-n-butylammonium hydroxide (TBAH) and a quaternary ammonium salt such as tetrabutylphosphonium bromide are used. Phosphonium salt, dibenzo-
A catalyst such as crown ether such as 18-crown-6, cryptand, glyme may be added. Particularly preferably, TBAH is used as a catalyst concentration in the alkali treatment solution at 0.1.
Add 0.5-0.2 mol%.

[Production Process of Carbon Material] The production process of activated carbon of the present invention comprises two processes. In the first step, the above PVDC resin is immersed in the above alkali treatment liquid at a temperature equal to or lower than the boiling point of the alkali treatment liquid for 10 minutes to 1 week while stirring, dehydrochlorinated, and subjected to PVDC resin. Is a carbonization treatment (primary carbonization treatment) to obtain a primary carbon material. Not only the reaction temperature and reaction time in this step but also the pore diameter and pore distribution in the obtained carbon material are EDL.
The type and concentration of the alkali or organic swelling agent in the alkali treatment liquid can be appropriately adjusted according to the ion diameter of the electrolytic solution used for C. However, when the reaction time is less than 10 minutes, carbonization of the PVDC resin by the alkali is insufficient, and when the reaction time is 1 week or more, the productivity is lowered, which is not preferable.

In the second step, the primary activated carbon is prepared in a non-oxidizing atmosphere (N ₂ , inert gas) in the range of 600 to 600 in accordance with a normal activated carbon production method (a carbon material production method in the case of a PVDC resin).
1000 ° C (preferably 700 to 850 ° C), 10 minutes to
Heat carbonization treatment (secondary carbonization treatment) for 2 hours, and finally E
This is a step of obtaining a carbon material for a DLC electrode. In the second step, if necessary, an acid atmosphere (H ₂ O, C
O ₂ or the like) may be used for activation (if activated, the activated carbon becomes activated carbon in a normal sense. This case is also included in the present invention). The activation treatment includes (a) H ₂ O,
Activating gases such as CO ₂ , hydrogen chloride, carbon monoxide, oxygen and the like, and a gas activating method in which the activating gas is used as a main component and firing is performed using a mixed gas, and (b) alkali hydroxides and alkaline earth hydroxides And activation treatment using alkaline carbonate, alkaline earth carbonate, alkali salt, alkaline earth salt, boric acid, phosphoric acid, sulfuric acid, hydrochloric acid, zinc chloride and the like.
The present invention is a method for producing a carbon material for an EDLC electrode, comprising subjecting a PVDC resin to a primary carbonization treatment using an alkaline treatment liquid. 2. Method for Confirming Effect of Primary Carbonization Treatment of PVDC Resin by Alkaline Treatment Solution Next, a method for confirming whether or not a primary carbon material has been produced from the PVDC resin by the primary carbonization treatment described in the present invention will be described.
In order to confirm that the primary carbon material has been formed, it may be confirmed by using an X-ray diffraction method commonly used in crystal structure analysis. That is,
Since the X-ray diffraction pattern of the primary carbon material is the same as that of ordinary activated carbon, it can be confirmed that the PVDC resin has been carbonized.

[X-ray Diffraction Measurement] A diffractometer system equipped with a curved monochromator of Rigaku Rotaflex RU-200 was used as an X-ray diffractometer. The measurement conditions were as follows: X-ray output, 4 using Cu-Kα ray.
0KV, 120mA, divergence slit 1/2 degree, solar slit 1/2 degree, light receiving slit 0.3 degree, measurement range 2
The measurement was performed under the condition of θ = 5 to 60 degrees. 2θ for ordinary activated carbon
= Produces a broad peak at 10 to 50 degrees. Thereby, it can be confirmed (actually, it is confirmed in combination with elemental analysis such as an X-ray microanalyzer). 3. Production of Electrode and Measurement of Capacitance An EDLC for evaluation using the carbon material of the present invention is produced by the following method, and its capacitance is measured.

(I) Manufacturing method of EDLC The carbon material obtained by the manufacturing method of the present invention is pulverized to 75 μm or less using a pulverizing mill. Next, 2% by weight of polytetrafluoroethylene (PTFE) latex as a binder was added to about 40 mg of the fine powder, and the mixture was kneaded in an agate mortar, and then water was removed (120 ° C. with a hot air drier,
After drying for 2 hours), the kneaded material of 40 to 50 mg (per single pole) was press-formed using a tablet press at a pressure of about 200 MPa (per one side of the electrode) (the specific gravity of the electrode was 0.9 to 0. 0).
6, particularly preferably adjusting the molding pressure to 0.8 to 0.7) to obtain a tablet-like EDLC electrode having a diameter of 10 mm and a thickness of about 1 mm.

Subsequently, in the case of an aqueous EDLC, the above E
The DLC electrode was placed in a 30% sulfuric acid aqueous solution having the same concentration as the electrolytic solution, subjected to boiling impregnation for 1 hour, and then vacuum impregnated using an aspirator for 24 hours. In boiling and vacuum impregnation, the weight of the activated carbon after the electrolyte impregnation is about 1.
It continued until it became 6 times or more. After vacuum impregnation, excess electrolyte was removed by filtration to obtain an electrode impregnated with the electrolyte. Furthermore,
The two electrodes impregnated with the electrolyte were separated by a 100 μm-thick polyethylene microporous membrane separator (H-1100 manufactured by Asahi Kasei Corporation).
Aqueous EDLC was assembled by facing each other through A) and sandwiching it between platinum plates (current collectors) with both electrodes insulated at a pressure of 10 kPa.

On the other hand, in the case of an organic system, work was performed in an Ar box to prevent the adsorption of moisture, and a PC solution containing 1 M (C ₂ H ₅ ) ₄ NBF ₄ as a solute was used as an electrolyte. Organic EDLC is the same as water-based except that it is used
Was assembled.

(Ii) Method of Measuring Capacitance The capacitance was measured by a constant-current discharging method in which the battery was discharged at a constant current and obtained from a change in voltage with respect to the amount of charge. That is,
Water-based EDLC is a constant current charge of 20 mA at 0.8 V (about 5
After charging for 1 hour and holding the voltage for 1 hour, a constant current discharge at 20 mA was performed, and the terminal voltage at the time of discharging was 0.25 V
The capacitance was calculated by measuring the time required to reach. On the other hand, in the case of an organic EDLC, constant voltage charging was performed at 2.5 V for 15 minutes, and then constant current discharging at 3 mA was performed.
The capacitance was calculated by measuring the time required to reach.

[0029]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. [PVDC resin] As the carbon raw material of the present invention, a powdered PVDC resin obtained by performing emulsion polymerization with the monomer composition described below, salting out the resulting latex using a calcium chloride solution, and drying was used. . The composition of the obtained PVDC resin is VDC / VC copolymer (VDC / VC = 85/1).
5), VDC / MA / BA / MMA copolymer (VDC /
MA / BA / MMA = 45/30/13/12), VD
C / AN copolymer (VDC / AN = 85/15) and homo-PVDC. [Alkali treatment liquid] KOH 12 as the alkaline treatment liquid 1
Mol%, THF 9 mol%, MeOH 42 mol%, water 37
A mixture of 9 mol% of KOH, 3 mol% of THF, 61 mol% of MeOH and 27 mol% of water as an alkali treatment liquid 2 and 15 mol% of KOH as an alkali treatment liquid 3
Was used. [Secondary carbonization (heating carbonization)] Primary activated carbon or P
The VDC resin was heated to 700 ° C. at a rate of 10 ° C./min in a N ₂ atmosphere using a tubular electric furnace, and was heated at 700 ° C. for 30 minutes.
The mixture was kept warm for a minute and carbonized, and then allowed to cool naturally to obtain a target carbon material.

[0030]

Example 1 and Comparative Example 1 As PVDC resin, VDC /
Example 1 was obtained by treating the VC copolymer powder with the alkaline treatment liquid 1 at room temperature under primary carbonization conditions for 5 days.
A sample treated for 0.5 hour (Hr) and a sample not treated were designated as Comparative Example 1. After each primary carbonization condition, secondary carbonization was performed to assemble the EDLC. P in primary carbonization
Although the VDC resin was carbonized, the capacitance of the water-based EDLC was 0.5 Hr, which did not carbonize, and the capacitance increased as compared with the case where the primary carbonization treatment was not performed.

[0031]

Examples 2 and 3 and Comparative Examples 2 and 3
VDC / MA / BA / MMA copolymer powder and VDC / AN copolymer powder as VDC resin are subjected to primary carbonization treatment at room temperature as primary carbonization conditions using each alkali treatment solution.
The VDC resin was primary carbonized. Although the PVDC resin was carbonized in the primary carbonization treatment, the capacitance of the water-based EDLC was increased as compared to those not carbonized and those not subjected to the primary carbonization treatment. According to Examples 1 and 2, the higher the ratio of the VDC component in the PVDC resin, the higher the capacitance of the EDLC can be obtained. Furthermore, from Examples 2 and 3, as the carbonization by the primary carbonization treatment progresses, the E of higher capacitance becomes higher.
It can be seen that DLC is obtained.

[0032]

Example 4 and Comparative Example 4 In the same manner as in Example 1, a homo-PVDC powder as a PVDC resin was subjected to primary carbonization using an alkaline treatment liquid 1 at room temperature under primary carbonization conditions.
After performing the secondary carbonization treatment, an organic EDLC was assembled (Example 4). At this time, the capacitance increased as compared with the case where the primary carbonization treatment was not performed (Comparative Example 4). Therefore, it can be seen that the carbonization treatment according to the present invention is also effective for improving the capacitance of the organic EDLC. Table 1 summarizes the results of all Examples and Comparative Examples.

[0033]

[Table 1]

[0034]

According to the present invention, it is possible to provide a method for producing a carbon material for an electric double layer capacitor electrode which is suitable for obtaining a high capacitance and is inexpensive in production cost. The present invention is particularly useful for organic EDLCs.

Claims (3)

[Claims] 1. An electric double layer comprising a step of carbonizing a carbon raw material using part or all of polyvinylidene chloride or a polyvinylidene chloride copolymer using a solution containing an alkali metal hydroxide. Method for producing carbon material for capacitor electrode 2. A solution containing an alkali metal hydroxide, an aqueous solution of an alkali metal hydroxide, an organic solvent for swelling or dissolving a part or all of polyvinylidene chloride or a polyvinylidene chloride copolymer, an alcohol, 2. A method for producing a carbon material for an electrode of an electric double layer capacitor according to claim 1, wherein a mixed solution with ether is used. 3. A solution containing an alkali metal hydroxide, 8-16 mol% of potassium hydroxide and tetrahydrofuran or an organic solvent for swelling or dissolving a part or all of polyvinylidene chloride or a polyvinylidene chloride copolymer. A mixed solution comprising 1 to 12 mol% of methyl ether ketone or tetramethylene sulfoxide, 15 to 60 mol% of methyl alcohol, isopropyl alcohol or ethyl alcohol as an alcohol, and water in addition to the above. Item 2. The method for producing a carbon material for an electrode of an electric double layer capacitor according to Item 2.