JPH09213589A - Activated carbon for electric double-layer capacitor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode with a high-electrostatic capacity per unit volume of an electrode besides having little repeating of charge and discharge as well as ageing deterioration thus securing a stable high-electrostatic capacity ranging over a long term. SOLUTION: Activated carbon to be obtained by carbonization and/or excitation and further by heat treatment as occasion demands of an activated carbon material containing a polymer containing vinylidene chloride as a component or other carbonaceous materials and thereby having at least 10wt.% of a content of vinylidene chloride thereof has a large electrostatic capacity per unit volume of an electrode and a low grade of deterioration due to repeating of storage and charge/discharge as well as exhibiting an excellent performance as the activated carbon for an electrode of an electrode double-layer capacitor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to activated carbon for an electrode of an electric double layer capacitor using an electrolytic solution and a method for producing the same.

[0002]

2. Description of the Related Art An electric double layer capacitor is a capacitor utilizing an electric double layer generated at the interface between a solid and a liquid,
It has a much larger electrostatic capacity than batteries, is excellent in charge / discharge cycle characteristics and quick charging, is maintenance-free, and does not cause environmental pollution. Recently, it has attracted particular attention as a compact backup power supply for microcomputers and IC memories. Has been done. The solid in this electric double layer capacitor is a polarizable electrode, and powdered activated carbon is usually used. Electrolytic solutions used for electric double layer capacitors are roughly classified into organic solvent type and aqueous solution type. The organic solvent system has a high withstand voltage, which is advantageous for miniaturization, and a metal can be used for the exterior. The aqueous solution is suitable for low equivalent series resistance (ESR) due to the high conductivity of the electrolytic solution, and has the advantage of being excellent in environmental characteristics without being affected by humidity. In the electric double layer capacitor having such advantageous characteristics, if the electrostatic capacity per unit volume of the electrode can be further increased and deterioration due to repeated charging / discharging can be suppressed, the application is simply a microcomputer or an IC. It can be advantageously used not only as a backup power source for memories, but also as a power source for initial driving of various motors, electric vehicles, preheaters for exhaust gas purification catalysts, and the like. Therefore, in order to obtain an electric double layer capacitor having a much higher electrostatic capacity per unit volume of the electrode, various improvements have been tried so far. One of them is the improvement of activated carbon used as an electrode. Since the capacity of the capacitor element is determined by the surface area of the activated carbon electrode used and the capacity of the electric double layer in the electrolytic solution, it is theoretically advantageous to use activated carbon having a large specific surface area in order to improve the capacity density. Therefore, for example, a high-capacity electric double layer capacitor using activated carbon made of coconut shell, coal, petroleum coke, phenol resin, etc. as a starting material has been proposed (Japanese Patent Laid-Open No. 63-78514, Japanese Patent Publication No.
82324, JP-A-5-306109 and JP-A-7-135127).

[0003]

However, an electric double layer capacitor of activated carbon, that is, a carbonaceous porous body manufactured by using these known techniques generally does not have sufficient capacitance per volume and immediately after manufacturing. Has a high capacitance, but it significantly decreases with time within a short period of time, and after 6 months or more, the capacitance decreases to 1/10 or less of the initial production, and is not put to practical use. hard. Although activated carbon produced by an activation method that does not depend on chemicals such as steam activation does not show a significant decrease in electrostatic capacity over time, among those that have been studied for practical use so far, those using an organic solvent-based electrolyte have a maximum of 25 F / g, about 14 F / ml,
53F / g, 30F / g even with an aqueous electrolyte
It is about ml, and in order to develop the new application mentioned above,
Furthermore, it is necessary to further increase the capacitance per electrode volume.

[0004]

SUMMARY OF THE INVENTION The inventors of the present invention have developed an electric capacitor which has a high electrostatic capacity per unit volume of an electrode, has a small decrease in electrostatic capacity over time, and is not easily deteriorated by repeated charging and discharging. In order to obtain activated carbon for electrodes of multilayer capacitors, as a result of various studies on the type of activated carbon raw material used, carbonization method, activation method and heat treatment method, a polymer containing vinylidene chloride as a constituent component or other carbonaceous material Activated carbon obtained by carbonizing and / or activating an activated carbon raw material having a vinylidene chloride content of at least 10% by weight, and further heat treating the same as an electrode for a conventional electric double layer capacitor. It was found that the problems of activated carbon can be sufficiently overcome, and further research was conducted to complete the present invention. That is, the present invention comprises 1) a polymer containing vinylidene chloride as a constituent or a carbonaceous material containing the same or a carbonaceous material, and carbonizing and / or carbonizing an activated carbon raw material in which the content of vinylidene chloride is at least 10% by weight. Activated carbon for an electric double layer capacitor electrode obtained by activation, 2) The content of vinylidene chloride in the activated carbon raw material is 30 to 99.
1) The activated carbon for electrodes as described in 1) above, wherein the content of vinylidene chloride in the activated carbon raw material is 50 to 98.
%, The activated carbon for an electrode according to 1) above, 4) the content of vinylidene chloride in the activated carbon raw material is 80 to 97.
%) The activated carbon for electrodes as described in 1) above, 5) The activated carbon for electrodes as described in 1) above, wherein the raw material for activated carbon is a vinylidene chloride homopolymer, and 6) The abovementioned 1) wherein the raw material for activated carbon is a vinylidene chloride copolymer. Activated carbon for electrodes, 7) Activated carbon for electrodes described in the above 1) obtained by carbonizing and / or activating an activated carbon raw material, and 8) A polymer containing vinylidene chloride as a constituent component or another carbonaceous material thereof. 9. A method for producing activated carbon for an electrode of an electric double layer capacitor, characterized by comprising carbonizing and / or activating an activated carbon raw material having a vinylidene chloride content of at least 10% by weight, and 9) The method for producing activated carbon for an electrode according to 8) above, which further comprises heat treatment after carbonization and / or activation.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION As a method for obtaining activated carbon for an electrode of an electric double layer capacitor of the present invention, a polymer containing vinylidene chloride as a constituent, for example, a homopolymer or copolymer of vinylidene chloride, or other materials For carbonizing and / or activating a mixture with a carbonaceous material, carbonizing a polymer containing vinylidene chloride as a constituent and / or
Alternatively, after activation, a method of mixing with another carbonaceous material to further carbonize and / or activate, a polymer containing vinylidene chloride as a constituent component is carbonized and / or activated, and other carbonaceous materials are carbonized and / or activated. A method of mixing with an activated product is included. The proportion of vinylidene chloride contained in the activated carbon raw material used in the present invention is usually 10 to 10.
100% by weight, preferably 30-99% by weight, more preferably 50-98% by weight, most preferably 80-97.
% By weight. Examples of the polymer containing vinylidene chloride as a constituent used in the present invention include, as described above, a homopolymer of vinylidene chloride and a copolymer of vinylidene chloride and another polymerizable monomer.

As the other polymerizable monomer in the vinylidene chloride copolymer, any known one can be used. For example, ethylene, acetylene, propylene, butylene, butyne, butadiene, isoprene, isobutylene, vinyl chloride, odor. Vinyl chloride, 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, acrylic acid, acrylic chloride, acrylic bromide, acryloguanamine, acryloylmorpholine, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, tert acrylate -Butyl, hexyl acrylate,
Cyclohexyl acrylate, methylpropyl acrylate, lauryl acrylate, tridecyl acrylate, benzyl acrylate, n-amyl acrylate, isoamyl acrylate, tetrahydrofurfuryl acrylate, dimethylaminoethyl acrylate, ethylene glycol ethoxylate acrylate, Ethylene glycol methoxylate acrylate, diethylene glycol ethoxylate acrylate, diethylene glycol methoxylate acrylate, ethylhexyl acrylate, epoxy acrylate, acrylic acid esters of pentaerythritol, n-
Stearyl acrylate, acrylic acid esters of dipentaerythritol, acrylic acid esters of trimethylolpropane, caprolactone-modified acrylic acid esters, acrylic acid esters 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 glycol diacrylate, sodium acrylate, potassium acrylate, Aluminum acrylate, zinc acrylate, calcium acrylate, magnesium acrylate, acrylamide, N, N-dimethylacrylamide, N, N-dimethylpropylacrylamide, acrolein, methacrylic acid, methacrylic acid chloride, methacrylic acid bromide, methyl methacrylate, Ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, meta Tert-Butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, methylpropyl methacrylate, lauryl methacrylate, tridecyl methacrylate, benzyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, tetrahydrofurfuryl methacrylate, dimethyl methacrylate Aminoethyl, ethylene glycol ethoxylate methacrylate, ethylene glycol methoxylate methacrylate,
Methacrylic acid diethylene glycol ethoxylate, methacrylic acid diethylene glycol methoxylate, ethyl hexyl methacrylate, epoxy methacrylate, pentaerythritol methacrylic acid ester, n-stearyl methacrylate, dipentaerythritol methacrylic acid ester, trimethylolpropane methacrylic acid ester, Caprolactone-modified methacrylic acid esters, neopentyl glycol methacrylic acid esters, 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, dimethacrylic acid-1,3-
Butylene glycol, sodium methacrylate, potassium methacrylate, aluminum methacrylate, zinc methacrylate, calcium methacrylate, magnesium methacrylate, methacrylamide, N, N-dimethylmethacrylamide, N, N-dimethylaminopropylmethacrylamide, methacrolein , Sodium methallyl sulfonate, potassium methallyl sulfonate, styrene, methyl styrene, vinyl pyridine, hydroxyethyl vinyl acetate, derivatives of hydroxyethyl vinyl acetate ester, ether and urethane, allyl alcohol, allyl chloride, sodium allyl sulfonate ,
Allyl amine, allyl aldehyde, allyl bromide,
Allyl glycidyl ether, allyl caproate, allyl mustard oil, allyl diglycol carbonate, allyl methacrylate, allyl adenine, allyl adenosine, allyl amino purine, allyl amino ribofuranosyl purine, glycerol diaryl ether, dicyclopentadiene, 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, itaconic acid, itaconic acid derivative, crotonaldehyde, chloroethyl vinyl ether, diallyldimethylammonium chloride, diallyldimethylammonium chloride Bromide, diallyldimethylammonium iodide, allylpyridinium chloride, allylpyridinium bromide, allylpyridinium iodide, diisobutylene, diethylene glycol bisallyl carbonate, unsaturated carboxylic acid and its derivatives, unsaturated aldehydes, unsaturated alkyls, N-phenylmaleimide , N-methylphenylmaleimide, N-cyclohexylmaleimide, and other N-substituted maleimides are typical examples. It is below.

The copolymerizable monomer used in the present invention is not limited to this, and any known copolymerizable component known so far may be used. The bodies may be used in any combination. The polymerization and copolymerization of vinylidene chloride can be carried out by a method known per se. As stabilizers and antioxidants for preventing deterioration of the obtained polymer by heat and light, UV absorbers, auxiliaries for improving moldability at the time of molding, plasticizers, antistatic agents, release agents, etc. It may be a mixture of conventionally known materials as necessary. The properties of the polymer or copolymer may be any of solid, solid, liquid, and liquid forms, and part of the above-mentioned vinylidene chloride or other copolymerization component remains in a monomer state without being polymerized. It is also possible to add them as necessary. The other carbonaceous material used in the present invention is not particularly limited as long as it is a carbon source normally used as a raw material for activated carbon, and examples thereof include wood, wood flour, sawdust, sawdust carbonized distillate, charcoal and coconut coconut shell. , Palm husks, walnut husks, fruit seeds, by-products from pulp production, bacas, molasses, peat, grass charcoal, lignite, brown coal, bituminous coal, anthracite, peat charcoal, petroleum distillation residue components, petroleum pitch, coal pitch, coke, coal Wood-based raw materials such as tar, fossil-based raw materials, mineral-based raw materials and their carbonized and activated products, phenolic resins,
Polyvinyl chloride, melamine resin, urea resin, resorcinol resin, celluloid, epoxy resin, xylene resin,
Polysulfone, allyl resin, alkyd resin, fluororesin, silicone resin, polystyrene, polyamide, polyimide, polyamideimide, polyarylate, vinyl acetate resin, coumarone resin, ketone resin, phenoxy resin, butadiene resin, polycarbonate, polyvinyl alcohol and their derivatives. , Polyphenylene oxide, polyphenylene sulfide, polymethylpentene, polysulfone, various ion exchange resins, various cellulose derivatives, polyglutamic acid, polyterpenes, cellophane, poly-α-methylstyrene, cyclopentadiene resin, polybutylene, polybutadiene, polychloroprene, maleic acid Resin, phthalic acid resin, fumaric acid resin, poly-p-hydroxybenzoic acid, synthetic wood, synthetic pulp, carboxyvinyl polymer, polya Styrene, polyvinyl butyral, polyvinyl formal, methacrylic resins, acrylic resins, polyurethane, polyester, polyethylene, polypropylene, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, synthetic resins and their carbides such as polyhexamethylene ethylene glycol.

Not only the above-mentioned examples of carbonaceous materials, but also various wastes such as various kinds of waste resins, various kinds of waste plastics, waste tires, other waste rubbers, molding burrs during the production of resins and plastics, and other wastes. Products, squeezed lees such as sake lees produced in the brewing process, refined sugar wastes, industrial wastes such as various distillation residue components, etc. can also be used. Furthermore, compounds mainly containing carbon are mainly used in an inert gas atmosphere. It is also possible to use those obtained by heating below and carbonization and activation products thereof. Further, activated carbon used as an adsorbent in exhaust gas treatment, solvent recovery, and other applications and activated carbon obtained by regenerating them can also be used. Examples of the method for carbonizing and activating the activated carbon raw material of the present invention include known methods for producing activated carbon such as a fixed bed system, a moving bed system, a fluidized bed system, a slurry system and a rotary kiln system. As a carbonization method,
Examples thereof include a method of firing using an inert gas such as nitrogen gas, carbon dioxide, helium, argon, xenon, neon, carbon monoxide, and combustion exhaust gas, and a mixed gas containing these inert gases as main components.

Examples of the activation method include a gas activation method in which an activation gas such as steam, carbon dioxide gas, hydrogen chloride, carbon monoxide, and oxygen and a mixed gas containing these activation gases as main components are used for firing, and sodium hydroxide. Examples of the so-called chemical activation method include activating the above-mentioned activated carbon raw material in the presence of potassium hydroxide, calcium hydroxide, boric acid, phosphoric acid, sulfuric acid, hydrochloric acid, zinc chloride and the like. The conditions for the temperature and time of carbonization are usually 200 to 1200 ° C., 10 minutes to 30 hours,
The temperature is preferably 250 to 1000 ° C. for about 15 minutes to 25 hours, more preferably 300 to 850 ° C. for about 20 minutes to 20 hours. The conditions of activation temperature and time are usually 200 to 1200 ° C., 10 minutes to 30 hours, preferably 400 to 1100 ° C., 15 minutes to 25 hours, more preferably 600 to 1000 ° C., 20 minutes to 20 hours. It is a degree. It is also possible to omit the activation step and use activated carbon obtained by the carbonization only step or activated carbon obtained by the carbonization step only by the activation step. Activated carbon with high performance as an electrode can be obtained by applying it. 500 if only carbonization step is performed
It is desirable to carry out at a rather low temperature of 850 ° C. for about 20 minutes to 20 hours. Further, activated carbon produced by adding a so-called heat treatment step of further heating and firing in an inert gas atmosphere after the step of carbonizing and / or activating for the purpose of modifying the surface of activated carbon can also be suitably used for electrodes. . The heat treatment temperature and time conditions are usually 200 to 1
200 ° C., 5 minutes to 20 hours, preferably 500 to 110
0 ° C., 10 minutes to 10 hours, more preferably 600 to 10
00 ° C., 20 minutes to 5 hours. If necessary, the activated carbon obtained is washed with various acidic aqueous solutions such as hydrochloric acid, sulfuric acid, boric acid and other water or alkaline aqueous solutions, mainly for the purpose of removing components other than carbon, before carbonization,
It may be performed in any step after carbonization, before activation, and after activation.

The surface area of the activated carbon obtained by the present invention is
It is usually about 400 to 4000 m ² / g, preferably 500 to 3500 m ² / g, more preferably 700 as measured by the BET method by nitrogen adsorption under liquid nitrogen temperature conditions.
~ 3000 m ² / g, particularly preferably 900-2500
m ² / g. If necessary, the activated carbon of the present invention is crushed to a desired particle size, and if necessary, the particle size is adjusted by classification. The particle size of activated carbon which meets the object of the present invention is such that the median diameter measured by a Coulter counter is 1 to 100.
μm, preferably 2 to 80 μm. To manufacture an electrode of an electric double layer capacitor using the activated carbon of the present invention,
A method known per se can be adopted. For example, a mixture of activated carbon, binder and water is well kneaded in a mixer. The obtained paste-like mixture is rolled using a roll and stretched under heating at about 100 to 400 ° C. to obtain a sheet-like electrode material having an appropriate thickness, for example, about 0.3 to 1.2 mm. The electrode material can be punched out to form a polarizable electrode. To prepare an electric double layer capacitor unit cell by stacking two to several disc-shaped materials obtained in this way with a separator interposed between them, storing them in an outer container, and injecting an electrolytic solution into the outer container. You can
As the electrolytic solution, there are an organic solvent type and an aqueous solution type. Propylene carbonate is generally used as the solvent for the organic solvent-based electrolytic solution, and various known quaternary phosphonium salts and quaternary ammonium salts can be used as the electrolyte. Dilute sulfuric acid is generally used as the aqueous electrolyte, but other inorganic substances such as tetrafluoroboric acid and nitric acid can also be used. Further, an aqueous solution containing an inorganic salt such as potassium hydroxide, sodium hydroxide or ammonium hydroxide as a solute can be conveniently used. The concentration of each electrolyte can be appropriately selected in the range of 5 to 95% by weight.

[0011]

【Example】

Example 1 Vinylidene chloride-vinyl chloride copolymer containing about 80% by weight of vinylidene chloride as a constituent (molecular weight of about 60,000)
Place in a rotary kiln, and from room temperature to 7 under nitrogen atmosphere.
Heat to 00 ° C over 3 hours and then at 700 ° C for 3 hours
It was carbonized by heating for 0 minutes. Then, under the temperature condition of 900 ° C in the rotary kiln, 200 g of this carbonized product
On the other hand, steam activation was performed by adding steam at a rate of 200 g / hour. 30 minutes each activation at this time,
What was performed for 60 minutes, 120 minutes, 180 minutes, 240 minutes, and 300 minutes was pulverized to obtain powdered activated carbon (activated carbons 1 to 6) having a median diameter of 4.5 μm as measured by a Coulter counter.
Vinylidene chloride-vinyl chloride copolymer containing 90% by weight of vinylidene chloride as a raw material for activated carbon (molecular weight: about 50,000)
750 under nitrogen atmosphere instead of steam activation
What was calcined at 30 ° C for 30 minutes, what was calcined at 800 ° C for 30 minutes, what was calcined at 850 ° C for 30 minutes, and those which had been carbonized by further heating at 700 ° C for 30 minutes were crushed in the same manner and powdered activated carbon ( Activated carbon 7-10) was obtained. Next, carbonization and steam activation are performed under the same conditions as in the case of producing activated carbons 1 to 6 using coconut shell as a starting material, washed with dilute hydrochloric acid, dried, and pulverized to have the same medium diameter as above. Granular powder activated carbon (activated carbon 11-16)
I got The above-mentioned electrodes prepared by using the respective powdered activated carbons obtained, and (C ₂ H ₅ ) ₄ PBF ₃ 0.5 mol
/ Capacitance of an organic solvent-based electrolyte capacitor unit cell made using a propylene carbonate electrolyte solution and an aqueous solution-based electrolyte capacitor unit cell made using the above electrode and a 40% sulfuric acid electrolyte solution were measured, respectively, and the results were obtained. Are shown in [Table 1].

[0012]

[Table 1]

[0013]

The electric double layer capacitor using activated carbon as a polarizable electrode, which has been proposed so far, has a remarkable deterioration in electrostatic capacity over time or an insufficient electrostatic capacity per unit volume of the electrode. It was an obstacle to application development. The activated carbon for an electrode of the electrode double-layer capacitor of the present invention provides an electrode with a high electrostatic capacity per unit volume of the electrode, and is capable of ensuring a stable high electrostatic capacity for a long period of time with little deterioration due to repeated charging / discharging or aging. Is.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hide Ueda 4-8 A2-210 Takemidai, Osaka City, Osaka Prefecture (72) 5-12 No. 12 Kamigaki-cho, Nishinomiya-shi, Hyogo Prefecture

Claims (9)

[Claims] 1. An activated carbon raw material comprising a polymer containing vinylidene chloride as a constituent or a carbonaceous material thereof and another carbonaceous material, wherein the content of vinylidene chloride is at least 10% by weight is carbonized and / or activated. Activated carbon for electrodes of the obtained electric double layer capacitor. 2. The content of vinylidene chloride in the activated carbon raw material is 3
The activated carbon for an electrode according to claim 1, which is 0 to 99% by weight. 3. The content of vinylidene chloride in the activated carbon raw material is 5.
The activated carbon for an electrode according to claim 1, which is 0 to 98%. 4. The content of vinylidene chloride in the activated carbon raw material is 8.
The activated carbon for an electrode according to claim 1, which is 0 to 97%. 5. The activated carbon for an electrode according to claim 1, wherein the raw material for the activated carbon is a vinylidene chloride homopolymer. 6. The activated carbon for an electrode according to claim 1, wherein the raw material for the activated carbon is a vinylidene chloride copolymer. 7. The activated carbon for an electrode according to claim 1, which is obtained by carbonizing and / or activating the activated carbon raw material and then further heat-treating it. 8. Carbonizing and / or activating an activated carbon raw material comprising a polymer containing vinylidene chloride as a constituent component or a carbonaceous material containing the same and having a vinylidene chloride content of at least 10% by weight therein. A method for producing activated carbon for an electrode of an electric double layer capacitor characterized by the above. 9. The method for producing an activated carbon for an electrode according to claim 8, wherein the activated carbon raw material is carbonized and / or activated and then further heat-treated.