JP2008177385A - High-conductive ionic liquid composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor cathode material that will not deteriorate the impedance characteristics, even if a capacitor is used over a long time and at high temperatures, and that has a high-dielectric strength. <P>SOLUTION: The high-conductive compositions, in which inorganic particulates (D) is dispersed in an ionic liquid (A), are used as a cathode material for the capacitor, wherein it is preferable that the inorganic particulate (D) be a composite particle (B), in which a clay-organic cation-intercalation compound having an aspect ratio of 10 to 1,000 is coated with a conductive polymer (C); and the composite particle (B), obtained by polymerizing a precursor monomer (E) of the conductive polymer (C) on a surface of the inorganic particulate (D). It is also preferable that the conductive polymer (C) be at least one selected from among a group comprising polypyrrole, polythiophene, polyfuran, and polyaniline. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a highly conductive composition in which composite fine particles in which inorganic fine particles are coated with a conductive polymer are dispersed in an ionic liquid. More specifically, the present invention relates to a highly conductive composition that is useful for capacitor cathode materials and has excellent impedance characteristics, heat resistance, and withstand voltage.

In recent years, with the digitization of electronic devices and the like, a capacitor having a small size, a large capacity, and a low impedance in a high frequency region is required. Conventionally, there are a plastic film capacitor and a multilayer ceramic capacitor as a capacitor for a high frequency region, but these capacitors are large in shape and difficult to increase in capacity. On the other hand, as a large capacity capacitor, there is an aluminum dry electrolytic capacitor or an aluminum or tantalum solid electrolytic capacitor. These electrolytic capacitors require an anode serving as a valve action metal, an anodic oxide film (dielectric) formed on the anode surface, and an electrolyte serving as a true cathode. For example, in an aluminum dry electrolytic capacitor, an etched anode and cathode aluminum foil are wound up via a separator, and a driving electrolyte is impregnated in the separator.

However, the aluminum dry electrolytic capacitor has a serious problem of characteristic deterioration due to electrolyte leakage, evaporation and the like. Since the liquid electrolyte has ionic conductivity and a large specific resistance, there is a problem that the loss is large and the frequency characteristics of the impedance are extremely inferior. In order to improve these problems, the solidified electrolyte is an aluminum or tantalum solid electrolytic capacitor. Examples of the electrolyte of the solid electrolytic capacitor include manganese oxide, 7,7,8,8-tetracyanoquinodimethane (TCNQ) salt, and conductive polymers such as polypyrrole, polythiophene, and polyaniline.

However, solid electrolytic capacitors using manganese oxide as an electrolyte can improve the temperature characteristics, capacity, loss, and other issues over time, but manganese oxide has a high specific resistance and sufficient frequency characteristics of impedance. It can not be said. Further, when forming an electrolyte made of manganese oxide, the dielectric oxide film is damaged by a plurality of thermal decomposition treatments. In addition, a solid electrolytic capacitor using a TCNQ salt as an electrolyte has a problem that a specific resistance increases when TCNQ is applied, and adhesion to an anode foil is weak.

On the other hand, in the method of forming a conductive polymer on the surface by chemical oxidative polymerization from monomers such as pyrrole, thiophene, or aniline, the influence of deterioration of the dielectric oxide film by the oxidizing agent or the chemical property of the conductive polymer (dielectric) It is difficult to construct an electrolytic capacitor with a rated voltage exceeding 35V because there is almost no defect in the body oxide film), and even when these capacitors are constructed, they will leak during the aging process and high temperature test. In some cases, an increase in current or a short circuit between the anode and the cathode occurred.

In order to solve this problem, for example, a method using an electrolyte made of a conductive polymer and an organic acid onium salt has been proposed (Patent Document 1). However, the mixing ratio of the organic acid onium salt is high and the withstand voltage is increased, but the conductivity is deteriorated, which is not preferable because it deteriorates the impedance characteristics of the capacitor.

Moreover, the electrolyte containing an ionic liquid is proposed paying attention to that an ionic liquid has a chemical conversion property (patent document 2). However, since the conductive polymer is formed on the dielectric oxide film and then impregnated with the ionic liquid, the amount of the ionic liquid contained in the conductive polymer is very small. As a result, the chemical property of the ionic liquid is reduced. As a result, the withstand voltage is not improved so much.

Furthermore, there is a problem that the conductive polymer is insulated in a high temperature environment, and as a result, it can be used only for applications that do not require heat resistance. In order to solve this problem, for example, a method for increasing the molecular weight of a conductive polymer dopant has been proposed (Patent Document 3). However, it is known that the use of such a dopant decreases the conductivity of the conductive polymer, which is not preferable because it decreases the impedance characteristics of the capacitor.
JP2003-22938 Republished patent 2005-012599 JP 2006-185973 A

From the above, there is no known material having heat resistance and high withstand voltage while maintaining impedance characteristics derived from the conductive polymer at present. An object of the present invention is to solve such problems and to provide a capacitor cathode material having a high withstand voltage without deteriorating impedance characteristics even when the capacitor is used at a high temperature for a long time.

The present inventors diligently studied to solve the above problem and arrived at the present invention.
The present invention is characterized in that a composite fine particle (B) in which an inorganic fine particle (D) is coated with a conductive polymer (C) is dispersed in an ionic liquid (A). And a cathode material for a capacitor comprising the highly conductive composition.

  If the highly conductive composition of the present invention is used as a cathode material for a capacitor, the impedance characteristics are not deteriorated even when the capacitor is used at a high temperature for a long time, and an electrolytic capacitor having a high withstand voltage can be provided.

The ionic liquid (A) used in the present invention is also called a room temperature molten salt, and is composed of an anionic component and a cationic component. An ionic liquid suitable for the purpose of the present invention includes, for example, room temperature molten salts described in WO2005 / 012599. Usually, an ionic liquid is a liquid that is liquid at room temperature, but the ionic liquid (A) used in the present invention does not necessarily need to be liquid near room temperature. For example, in a capacitor, the liquid is generated by Joule heat generated during repair of an oxide film. If it becomes what becomes.

Examples of the cation constituting the ionic liquid (A) include an imidazolium cation, a pyridinium cation, and a phosphonium cation. Examples of the imidazolium cation include 1-ethyl-3-methylimidazolium and 1-ethyl-2,3-dimethylimidazolium.

As anions constituting the ionic liquid (A), for example, chloroaluminate anions such as AlCl ₄ ⁻ and Al ₂ Cl ₇ ^— , fluorine-based inorganic anions such as BF ₄ ⁻ , PF ₆ ⁻ and F (HF) _n ⁻ , ^{_{CF 3 COO -, CF 3 SO}} 3 - (TfO), (CF 3 SO 2) 2 N - (TFSI), (CF 3 SO 2) 3 C - (TFSM) fluorinated organic anions such as, NO ₃ ^-; CH ₃ COO ^-, and the like.

The ionic liquid (A) may be one or a combination of two or more of the above cation species and one or more of the above anion species. Preferably, the cation liquid and the fluorine-based organic compound are used. It is a combination with an anion, more preferably an imidazolium cation or a combination of a pyridinium cation and a fluorine-based inorganic anion, and particularly preferably a combination of an imidazolium cation or a pyridinium cation and BF ₄ ⁻ .

The conductive polymer (C) used in the present invention is present as composite fine particles (B) by coating inorganic fine particles (D) described later.
The present invention is characterized in that the composite fine particles (B) are dispersed in an ionic liquid. As a method for synthesizing the composite fine particles (B), (1) the composite fine particles (B) are synthesized in advance and then the ionic liquid is synthesized. (2) A method of synthesizing the composite fine particles (B) in an ionic liquid.

Examples of the conductive polymer (C) include polypyrrole, polythiophene, polyaniline, polyfuran, and derivatives thereof. A derivative refers to a derivative in which a functional group such as carboxylic acid is introduced in order to adjust the solvent solubility and other physical properties of the conductive polymer (C). As a method for synthesizing these conductive polymers, a chemical polymerization method, an electrolytic polymerization method, and an organometallic chemical condensation polymerization method are used, and a chemical polymerization method and an electrolytic polymerization method are particularly preferably used. In the present invention, the chemical polymerization method is particularly preferred because it is necessary to synthesize the composite fine particles (B).

Chemical polymerization is a method of polymerizing and synthesizing a precursor monomer (E) of a conductive polymer (C) such as aniline hydrochloride in the presence of a suitable oxidizing agent by oxidative dehydration. As the oxidizing agent, persulfates, hydrogen peroxide, or transition metal salts such as iron, copper, and manganese can be used. Since the conductive polymer synthesized by chemical polymerization is also incorporated into the polymer in the polymerization process as an anion of the oxidizing agent as a dopant, a conductive polymer can be obtained by a one-step reaction.

In the method of polymerizing the precursor monomer (E) of the conductive polymer (C) on the surface of the inorganic fine particles (D), the inorganic fine particles (D) are dispersed in an ionic liquid or an appropriate solvent (for example, in water). Thereafter, the precursor monomer may be mixed and the oxidizing agent may be mixed and polymerized. When the polymerization is not performed in the ionic liquid, the obtained composite fine particles (B) may be dispersed in the ionic liquid. It is important that the inorganic fine particles (D) or the composite fine particles (B) are dispersed in the ionic liquid, and a dispersant or the like may be appropriately used in order to improve dispersibility.

When chemical polymerization is performed in an ionic liquid, it is known that the anionic component of the ionic liquid is taken into the conductive polymer as a dopant, and it is possible to increase the amount of the dopant in the conductive polymer, and the capacitor lengthens. It is more preferable to perform polymerization in an ionic liquid from the viewpoint that impedance characteristics do not deteriorate even when used at a high temperature for a long time.

In addition, the conductive polymer has conductivity due to the presence of the dopant, but it is generally known that the dopant is detached and insulated in a high temperature environment. However, the present inventor has found that the conductive polymer present in the ionic liquid is not insulated even in a high temperature environment. This function provides the heat resistance characteristic of the present invention.

Examples of the inorganic fine particles (D) used in the present invention include nanofillers conventionally used for improving the mechanical strength of polymers. Examples thereof include spherical fine particles of silica (such as colloidal silica), inorganic crystals such as calcium carbonate, fiber shaped bodies such as carbon fibers, and clay that is an inorganic layered compound (D1).

Among the inorganic fine particles (D), the inorganic layered compound (D1) has a large aspect ratio (ratio of long side length to short side length) of 10 to 1000. If it coat | covers, the high electroconductivity which is the characteristics of this invention will express and it is preferable. In order to develop further high conductivity, the aspect ratio is more preferably 100 to 1000, and particularly preferably 500 to 1000.

The inorganic layered compound (D1) may be any of a natural product (D11), a modified natural product (D12), and a synthetic product (D13).

Examples of the natural product (D11) include clay, graphite, metal chalcogenide, metal oxide, metal oxyhalide, metal phosphate, double hydroxide and the like.

Among these, clay is preferable, and examples of the clay include montmorillonite, saponite, hectorite, beidellite, stevensite, nontronite, vermiculite, halloysite, talc, mica and mica, and among these, montmorillonite is preferable.

Examples of the modified natural product (D12) include clay modified with an organic compound (organized clay). Examples of the organized clay include a clay-organic cation insertion compound modified by an organic cation (organic cation) (a cation of the clay ion-exchanged with an organic cation) and the like.
There are no particular limitations on the organic method, and any known method can be used. For example, clay having a cationic group between layers is dispersed in hot water at 80 ° C., and an organic cation is added to the clay and stirred vigorously. The resulting precipitate is filtered, washed with water and freeze-dried to obtain a clay-organic cation insertion compound. ("The world of nanocomposites", written by Susumu Nakajo, published by the Industrial Research Council, p. 178)

The organic cation is not particularly limited, but is preferably an alkyl ammonium ion having an alkyl group having 2 to 70 carbon atoms (hexyl ammonium ion, octyl ammonium ion, 2-ethylhexyl ammonium ion, dodecyl ammonium ion, lauryl ammonium ion, Octadecylammonium ion, stearylammonium ion, dioctyldimethylammonium ion, trioctylammonium ion, distearyldimethylammonium ion, stearylbenzyldimethylammonium ion, ammonium dodecanoate ion, laurylammonium ion, etc.) and mixtures thereof.
Among these, from the viewpoint of ion exchange properties, an organic cation having an alkyl group with 12 or more carbon atoms is preferable. More preferred are distearyl dimethyl ammonium ion and stearyl benzyl dimethyl ammonium ion, and particularly preferred is stearyl benzyl dimethyl ammonium ion. In addition, examples of the anion to be paired include halide anions (such as chloride anions and bromide anions).

The highly conductive composition of the present invention comprises composite fine particles (B) dispersed in an ionic liquid (A). The weight of the composite fine particles (B) is preferably 5% by weight to 95% by weight and more preferably 10% by weight to 80% by weight with respect to the weight of the highly conductive composition.
The composite fine particles (B) are formed by coating the inorganic fine particles (D) with the conductive polymer (C). The weight of the conductive polymer (C) is preferably 10% by weight to 100% by weight and more preferably 50% by weight to 100% by weight with respect to the weight of the composite fine particles (B).

The solvent (F) used in the present invention is added from the viewpoint of workability. The highly conductive composition of the present invention is in a liquid state, a gel state or a solid state depending on the composition of the ionic liquid and the amount of the composite fine particles (B) added. For example, when it is used as a cathode material for an aluminum electrolytic capacitor, it is desired to use it by impregnating an oxide film as will be described later. Therefore, a liquid state is preferable from the viewpoint of workability and the like. When the highly conductive composition of the present invention is not liquid, it is not problematic in performance to add the solvent (F) for liquefaction. For example, after being liquefied with the solvent (F) when used in the capacitor, The solvent (F) may be volatilized after the dielectric is coated and impregnated. The solvent (F) used in the present invention is preferably a low-boiling solvent considering that it is compatible with the ionic liquid (A) and volatilized later, and a solvent having a boiling point of 50 ° C. to 149 ° C. can be used. Specific examples of (F) include alcohols such as methanol and ethanol, and aromatic solvents such as toluene and xylene. The amount of the solvent (F) added is preferably 3 to 80% by weight, more preferably 5 to 50% by weight, based on the weight of the highly conductive composition.
When the highly conductive composition of the present invention is in the gel state, it is not always necessary to add the solvent (F), and the high conductivity composition in the gel state is directly applied to the oxide film and then impregnated under vacuum. Thus, a capacitor cathode material can also be produced.

The highly conductive composition of the present invention can contain a solvent (G) that is compatible with the ionic liquid (A). The boiling point of the solvent (G) is 150 ° C to 300 ° C. The content of the solvent (G) is preferably 3 to 50% by weight, more preferably 5 to 20% by weight, based on the weight of the highly conductive composition.
Examples of the solvent (G) include the following.

(1) Alcohols monohydric alcohols (such as diacetone alcohol, benzyl alcohol, amino alcohol, furfuryl alcohol), dihydric alcohols (such as ethylene glycol, propylene glycol, diethylene glycol, hexylene glycol), trivalent alcohols (such as glycerin) Tetravalent or higher alcohols (eg hexitol);

(2) Ether monoethers (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monophenyl ether, etc.);

(3) Amides formamides (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, etc.), acetamides (N-methylacetamide, N, N-dimethylacetamide, N -Ethylacetamide, N, N-diethylacetamide, etc.), propionamides (N, N-dimethylpropionamide, etc.), pyrrolidones (N-methylpyrrolidone, N-ethylpyrrolidone, etc.), hexamethylphosphorylamide, etc .;

(4) Oxazolidinones N-methyl-2-oxazolidinone, 3,5-dimethyl-2-oxazolidinone, etc .;

(5) Lactones γ-butyrolactone (hereinafter referred to as GBL), α-acetyl-γ-butyrolactone, β-butyrolactone, γ-valerolactone, δ-valerolactone, and the like;

(6) Nitriles Acetonitrile, propionitrile, butyronitrile, acrylonitrile, methacrylonitrile, benzonitrile, etc .;

(7) carbonates such as ethylene carbonate, propion carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate;

(8) Other organic solvents 1,3-dimethyl-2-imidazolidinone, aromatic solvents (toluene, xylene, etc.) paraffinic solvents (normal paraffin, isoparaffin, etc.), etc .;

The organic solvents may be used alone or in combination of two or more.
Of these, γ-butyrolactone, sulfolane, and ethylene glycol are particularly preferable.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to this.

Example 1
(material)
1-Ethyl-3methylimidazolium tetrafluoroborate (manufactured by Aldrich) was used as the ionic liquid. As the clay, montmorillonite (aspect ratio 600, Kunimine Kogyo Kunipia F) was used. Aniline hydrochloride (manufactured by Wako Pure Chemical Industries) was used as a precursor monomer for the conductive polymer. Ammonium persulfate (manufactured by Wako Pure Chemical Industries) was used as a polymerization oxidant.
(Synthesis)
16.30 g of clay was mixed with 309.73 g of water. Thereafter, 16.30 g of the precursor monomer previously dissolved in 38.04 g of water was mixed. Then, what dissolved 34.57 g of oxidizing agents beforehand in 51.86 g of water was mixed, and it mixed under stirring for 24 hours at room temperature, and obtained the aqueous dispersion of the inorganic fine particle coat | covered with the conductive polymer. The aqueous dispersion was filtered under reduced pressure to extract inorganic fine particles, and then lyophilized. After mixing this with 309.73 g of ionic liquid, using a TK homomixer (manufactured by Tokushu Kika), mixing and dispersing at 25 ° C. for 1 minute at a rotational speed of 12000 rpm, a highly conductive composition (P-1) (The property at 25 ° C. is liquid).

Example 2
(material)
The same as in Example 1 was used.
(Synthesis)
25.44 g of water was mixed with 25.05 g of clay. Then, what melt | dissolved the precursor monomer 25.05g in water 58.45g previously was mixed. Thereafter, a solution in which 53.13 g of an oxidizing agent was previously dissolved in 79.69 g of water was mixed, and mixed at room temperature with stirring for 24 hours to obtain an aqueous dispersion of inorganic fine particles coated with a conductive polymer. The aqueous dispersion was filtered under reduced pressure to extract inorganic fine particles, and then lyophilized. After mixing this with 225.44 g of ionic liquid, using a TK homomixer (manufactured by Tokushu Kika), mixing and dispersing at 25 ° C. for 1 minute at a rotational speed of 12000 rpm, a highly conductive composition (P-2) (The property at 25 ° C. was a gel).

Example 3
(material)
1-Ethyl-3methylimidazolium tetrafluoroborate (manufactured by Aldrich) was used as the ionic liquid. As the clay, a clay-organic cation insertion compound (aspect ratio 700, Nanofil 9 manufactured by Tomen Plastic, cation species: dimethylbenzylammonium cation) was used. Aniline hydrochloride (manufactured by Wako Pure Chemical Industries) was used as a precursor monomer for the conductive polymer. Ammonium persulfate (manufactured by Wako Pure Chemical Industries) was used as a polymerization oxidant.
(Synthesis)
After mixing 25.44 g of clay with 225.44 g of ionic liquid, TK homomixer (manufactured by Tokushu Kika) was used and mixed at 25 ° C. for 1 minute at a rotation speed of 12000 rpm. Then, what melt | dissolved precursor monomer 25.05g in methanol 58.45g previously was mixed. Then, what dissolved 53.13g of oxidizing agents beforehand in 79.69g of water was mixed, and it mixed under room temperature under stirring for 24 hours. An ionic liquid (P-1) in which a conductive polymer containing methanol and water was dispersed was obtained. Water and methanol contained in the ionic liquid were removed by evaporation by heating to obtain a highly conductive composition (P-3) (characteristic at 25 ° C.).

Example 4
(material)
The raw materials used are the same as in Example 1 except that 2-thiophenecarboxylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) is used as the precursor monomer.
(Synthesis)
Synthesis was carried out in the same manner as in Example 2 to obtain a highly conductive composition (P-4) (the property at 25 ° C. was a gel).

Example 5
(material)
The raw materials used are the same as in Example 3 except that 2-thiophenecarboxylic acid (manufactured by Wako Pure Chemical Industries) is used as the precursor monomer.
(Synthesis)
Synthesis was carried out in the same manner as in Example 3 to obtain a highly conductive composition (P-5) (characteristic at 25 ° C.).

Example 6
(material)
The raw materials used are the same as in Example 1 except that pyrrole (manufactured by Wako Pure Chemical Industries, Ltd.) is used as the precursor monomer.
(Synthesis)
Synthesis was performed in the same manner as in Example 2 except that the precursor monomer was previously dissolved in methanol to obtain a highly conductive composition (P-6) (characteristic at 25 ° C.).

Example 7
(material)
The raw materials used are the same as in Example 3 except that pyrrole (manufactured by Wako Pure Chemical Industries) is used as the precursor monomer.
(Synthesis)
Synthesis was performed in the same manner as in Example 3 except that the precursor monomer was previously dissolved in methanol to obtain a highly conductive composition (P-7) (characteristic at 25 ° C.).

Examples 8-13
(material)
1-butyl-4-methylpyridinium tetrafluoroborate (manufactured by Aldrich) was used as the ionic liquid. Others were the same as in Examples 2 to 7, respectively.
(Synthesis)
Synthesis was carried out in the same manner as in Examples 2 to 7 to obtain highly conductive compositions (P-8 to 13). The properties of P-8 to 13 at 25 ° C. were gel-like.

(Manufacture of capacitors)
A capacitor element was obtained by winding with a separator interposed between the anode aluminum foil and the cathode aluminum foil. Thereafter, methanol is added to the capacitor element in advance and impregnated with a highly conductive composition (P-2-13) adjusted to 50% by weight, and then heated at 60 ° C. for 1 hour to volatilize the methanol. Thus, an aluminum electrolytic capacitor element having a rated voltage of 50 V and an electrostatic capacity of 220 μF was obtained. As for the highly conductive composition (P-1), an aluminum electrolytic capacitor element having a rated voltage of 50 V and a capacitance of 220 μF was obtained by impregnating the capacitor element without adding methanol. After enclosing this capacitor element together with a sealing member in an aluminum metal case, the opening was sealed by curling treatment to constitute an aluminum electrolytic capacitor (size: φ13 mm × L10.2 mm).

Table 1 shows the withstand voltage, initial impedance at 100 kHz, impedance after the heat test, and impedance change rate ΔI of the obtained capacitor. The heat resistance test was left for 100 hours in an environment of 125 ° C.
The impedance was measured using an LCR meter (manufactured by ZN2353 NF circuit design block company). The withstand voltage was measured at a voltage at which leakage current began to increase when the voltage was increased at a constant rate. The rate of change (ΔI) of impedance (I) is expressed by the following equation.
ΔI = 100 × (| initial impedance−impedance after heat test |) / initial impedance

Comparative Example 1
An electrolytic capacitor was fabricated by forming a conductive polymer on an aluminum oxide film by electrolytic polymerization, and the ionic liquid was added to the obtained electrolytic capacitor to measure the capacitor characteristics.
That is, an aluminum foil (aluminum etched foil) in which pores were formed on the surface by an etching process of 7 mm in length and 10 mm in width with an anode lead immersed in a 3% aqueous solution of ammonium adipate and an applied voltage of 70 V at 70 ° C. Anodization was performed under the conditions, and a dielectric film as an oxide film was formed on the surface of the aluminum foil. Next, this was immersed in a 30% aqueous solution of manganese nitrate and allowed to dry naturally, and then subjected to a thermal decomposition treatment at 300 ° C. for 30 minutes to form a conductive layer comprising a manganese oxide layer on the dielectric film.
Next, an electrolytic polymerization polypyrrole layer was formed on the foil. The electrolytic solution used for the polymerization was an electrolytic solution composed of pyrrole (0.5M), a 30% alcohol solution of sodium triisopropylnaphthalenesulfonate (0.1M), and water. An aluminum foil is placed in the electrolytic polymerization solution, the polymerization initiating electrode is brought close to the manganese dioxide conductive layer, and a constant voltage of 1.5 V is applied between the polymerization initiating electrode and the cathode for 50 minutes to conduct the electropolymerization reaction. An electropolymerized polypyrrole layer was formed on the conductive layer.
Electrolyze the ionic liquid by washing it with water, drying it, then immersing it in a methanol solution of 1-ethyl-3methylimidazolium tetrafluoroborate (Aldrich), which is an ionic liquid, and then drying to remove the methanol. The electrolyte of Comparative Example 1 was obtained by adding to the polymerized polypyrrole layer. The addition amount was 0.5 to 5% by weight of the conductive polymer. Next, a carbon layer and a silver paste layer were provided on the electrolyte to produce a capacitor. The withstand voltage, the impedance at 100 kHz, and the impedance after the heat test of the capacitor thus obtained were measured.
Table 1 shows the characteristics of the obtained capacitor.

Comparative Example 2
A capacitor was produced in the same manner as in Comparative Example 1 except that 1-butyl-4-methylpyridinium tetrafluoroborate (manufactured by Aldrich) was used as the ionic liquid of Comparative Example 1, and the capacitor characteristics were evaluated.

From Table 1, it can be seen that the highly conductive ionic liquid composition obtained in the present invention is useful as a capacitor cathode material having excellent withstand voltage without deterioration in impedance characteristics even after the heat resistance test.

The highly conductive composition of the present invention is useful as a capacitor cathode material and the like.

Claims (9)

A highly conductive composition, wherein composite fine particles (B) in which inorganic fine particles (D) are coated with a conductive polymer (C) are dispersed in an ionic liquid (A). The highly conductive composition according to claim 1, wherein the composite fine particles (B) are obtained by polymerizing the precursor monomer (E) of the conductive polymer (C) on the surface of the inorganic fine particles (D). The highly conductive composition according to claim 1 or 2, wherein the inorganic fine particles (D) have an aspect ratio of 10 to 1,000. The highly conductive composition according to any one of claims 1 to 3, wherein the inorganic fine particles (D) are clay. The highly conductive composition according to claim 4, wherein the inorganic fine particles (D) are a clay-organic cation insertion compound. The highly conductive composition according to any one of claims 1 to 5, wherein the conductive polymer (C) is at least one selected from the group consisting of polypyrrole, polythiophene, polyfuran, and polyaniline. The highly electroconductive composition of any one of Claims 1-6 containing the solvent (G) compatible with an ionic liquid (A). The highly conductive composition according to claim 1, wherein the ionic liquid (A) is an imidazolium salt. The cathode material of the capacitor | condenser which consists of a highly conductive composition of any one of Claims 1-8.