JP2004228148A - Paint for forming electrode and electrode using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paint for forming an electrode, wherein an electro-chemical capacitor having excellent strength and higher capacitance value is obtained at the lower price. <P>SOLUTION: The paint for forming electrode of electro-chemical capacitor comprises: fine particles of carbon; fine particles of metal oxide having the particle size which is smaller than that of the fine particles of carbon; a binder; and water, and/or organic solvent, and the average particle size of fine particle of metal oxide is ranged from 5 to 100 nm. The fine particles of metal oxide are formed of an oxide/composite oxide of at least an element selected from a group including In, Sn, Cu, Mo, Ta, Ni, W, Mn, Sb, Ti, Zr, Co, and Fe or of a mixture of these elements. Particularly, such fine particles of metal oxide are formed of an oxide indium to which Sn or F is doped. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【図面の簡単な説明】
【図１】１００ｍＶ／ｓの一定電位走査速度における各種金属酸化物を含有した電極の電気容量を示す。
【図２】電極中に各金属酸化物粒子を添加した場合の容量走査速度依存性を表す。
【図３】電極中の金属酸化物微粒子含有量を変化させたときの容量変化を示す。
【図４】電極中のＩＴＯ微粒子含有量が０、５、１０重量％の場合の１００ｍＶ／Ｓの走査速度における電位（ポテンシャル）と電流との関係を示すＣＶ曲線を示す。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a novel paint for forming an electrode for an electrochemical capacitor, an electrode for an electrochemical capacitor formed using the paint, and an electrochemical capacitor using the electrode.
More specifically, the present invention relates to a paint for forming an electrode for an electric capacitor capable of producing an electrochemical capacitor having a high strength and a high capacitance, and a use thereof.
[0002]
TECHNICAL BACKGROUND OF THE INVENTION
In recent years, there has been a demand for a power storage device that is small, lightweight, large-capacity, and capable of rapidly charging and discharging. In particular, for an electric vehicle or the like, a conventional capacitor or secondary battery cannot be used, and the development of an electrochemical capacitor as a high-performance energy storage device is urgently required.
[0003]
Conventionally, as an electrochemical capacitor, while a development centered on an electric double layer electrochemical capacitor (EDLC) using a carbon material having a high specific surface area as an electrode material has been developed, a metal capable of obtaining a high output density and an energy density has been developed. There is also interest in electrochemical capacitors based on oxides, metal nitrides, and metal carbides.
High specific surface area (about 1000m²In EDLC using a carbon material of / g) as an electrode material, activated carbon, activated carbon fiber, carbon black and the like have been proposed as electrode materials. In particular, activated carbon and activated carbon fiber have attracted attention as electrode materials for EDLC because they exhibit a relatively large electric capacity.
[0004]
On the other hand, as a metal oxide-based electrode material, oxides of Ru and Ir, which are oxides of noble metals, are being studied. It is known that these noble metal oxides exhibit excellent charge / discharge cycle characteristics because of their high electrochemical reversibility.
However, since noble metal oxides are expensive, there is a problem in practical use. For this reason, noble metal oxides are supported on carbon materials, or composites of inexpensive high-performance oxide materials and carbon materials are used instead. ing.
[0005]
Electrochem. and Solid-state Lett. Vol4, No. 9, 2001, p. Nos. 145-147 show that the carbon material is RuO₂, MoO₃Have been reported.
It has also been reported that an electrochemical capacitor can be manufactured using oxides such as Ni, V, Mo, Mn, or ultrafine particles of a nitride or carbide such as V, Nb, Mo, W, etc. as an electrode material for the electrochemical capacitor. ing. For example, J. Electrochem. Soc. , 143, 124 (1996) report the use of porous NiO / Ni as an electrode material for electrochemical capacitors. In addition, The Electrochemical Society PV95-29, p. 86 (1996) has V₂O₅The use of gels has been reported.
[0006]
In the above, for example, it has been reported that the electric capacity of a carbon composite electrode carrying 3.2% by weight of ruthenium oxide is increased by about 25%. In addition, it has been reported that the capacitance of a carbon composite electrode supporting 1.4% by weight of molybdenum oxide increases by about 35%.
In addition, the use of indium oxide or a mixture of indium oxide and tin oxide, which has conductivity and also serves as an inorganic binder, in the production of a polarizable electrode used for an electric double layer capacitor is disclosed (Patent Document 1). And JP-A-5-304048). Specifically, activated carbon fine particles are dispersed in an alcohol solution of indium alkoxide, a catalyst is added thereto, and the mixture is hydrolyzed, heated at 40 to 60 ° C. to promote gelation, and heated at 150 to 200 ° C. A polarizable electrode obtained by drying and then heating at 400 to 450 ° C. to remove organic substances is described.
[0007]
In addition to the above, an electric energy storage element in which vanadium pentoxide is supported on carbon powder (Patent Document 2, JP-A-2000-36303), and a metal hydroxide hydrate such as ruthenium hydroxide is supported on carbon powder. A disclosed electric energy storage element (Patent Document 3, JP-A-2000-36441) is also disclosed. Further, an electrode material in which a molybdenum compound is supported on a porous carbon material is also known (Patent Document 4, JP-A-2002-289468).
[0008]
However, the method of simply supporting the metal oxide in the pores of the carbon powder as described above has problems such as insufficient improvement of electric capacity and poor economic efficiency.
The inventors of the present application have conducted intensive studies in view of the above problems, and as a result of mixing the carbon metal powder with highly conductive crystalline metal oxide fine particles having a smaller particle size than the carbon powder, instead of supporting the carbon powder on the carbon powder. The obtained electrode was excellent in strength, and it was found that a capacitor using this electrode could greatly improve the electric capacity, and completed the present invention.
[0009]
[Patent Document 1]
JP-A-5-304048
[Patent Document 2]
JP-A-2000-36303
[Patent Document 3]
JP-A-2000-36441
[Patent Document 4]
JP-A-2002-289468
[0010]
[Object of the invention]
The present invention has been made in order to solve the problems associated with the above-described conventional technology, and a paint that is preferably used for forming an electrode for an electrochemical capacitor, and an electrode for an electrochemical capacitor formed using the paint. And an electrochemical capacitor using the electrode.
[0011]
Summary of the Invention
The electrode forming paint for an electrochemical capacitor according to the present invention,
Carbon fine particles, metal oxide fine particles having a smaller particle diameter than the carbon fine particles, a binder and water and / or an organic solvent,
The average particle size of the metal oxide fine particles is in the range of 5 to 100 nm.
[0012]
The metal oxide fine particles are oxides / composite oxides of at least one element selected from the group consisting of In, Sn, Cu, Mo, Ta, Ni, W, Mn, Sb, Ti, Zr, Co, and Fe; Mixtures of these are preferred, and in particular, indium oxide doped with Sn or F is preferred.
The electrode for an electrochemical capacitor according to the present invention is formed using the paint.
[0013]
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, first, the paint for forming an electrode for an electrochemical capacitor according to the present invention will be described.
Paint for forming electrodes for electrochemical capacitors
The electrode forming coating for an electrochemical capacitor according to the present invention comprises carbon fine particles, metal oxide fine particles, a binder, water and / or an organic solvent, and has an average particle diameter of 5 to 100 nm. It is characterized by being in the range.
[0015]
Carbon fine particles
As the carbon fine particles, conventionally known activated carbon, activated carbon fiber, carbon aerogel, carbon black and the like can be used. Among them, activated carbon and activated carbon fiber having a high specific surface area are preferable because they exhibit a relatively large electric capacity.
Raw materials of activated carbon and activated carbon fiber that can be used in the present invention include plant-based wood, sawdust, coconut shell, pulp waste liquor, fossil fuel-based coal, petroleum heavy oil, or coal obtained by thermally decomposing them. Petroleum pitch, petroleum coke, carbon aerogel, fiber spun from tar pitch, synthetic polymer, phenolic resin, furan resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyimide resin, polyamide resin, liquid crystal polymer, plastic waste It is used for a wide variety of items, waste tires, etc. Activated carbon and activated carbon fiber are obtained by carbonizing these raw materials and then performing an activation treatment. This activation method is roughly classified into a gas activation method and a chemical activation method. The gas activation method is also called physical activation, while the chemical activation method is a chemical activation, and the carbonized raw material is converted to steam, carbon dioxide, oxygen, and other oxidizing gases at high temperatures. Activated carbon is obtained by contact reaction. The chemical activation method is a method in which a raw material is uniformly impregnated with an activation chemical, heated in an inert gas atmosphere, and activated carbon is obtained by a dehydration and oxidation reaction of the chemical. Chemicals used in the chemical activation method include zinc chloride, phosphoric acid, sodium phosphate, calcium chloride, potassium sulfide, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium sulfate, potassium sulfate, calcium carbonate, etc. There is. However, the method for producing activated carbon and activated carbon fiber is not particularly limited, and is not limited to the above method.
[0016]
The activated carbon or activated carbon fiber may be in any of various shapes such as crushed, granulated, granulated, fiber, felt, woven, and sheet shapes, and any of them can be used in the present invention. Among these activated carbons or activated carbon fibers, activated carbon or activated carbon fibers obtained from carbonized coconut shell, coal, or phenol resin in the gas activation method have a relatively high capacitance, It is suitable for the present invention because it can be mass-produced and inexpensive.
[0017]
When granular carbon fine particles are used, the average particle diameter is preferably in the range of 0.005 to 50 μm, more preferably 0.01 to 10 μm. Here, the carbon fine particles may be primary particles or secondary particles.
It is difficult to obtain carbon fine particles having an average particle diameter of less than 0.005 μm. If the average particle diameter of the carbon fine particles exceeds 50 μm, the strength of the obtained electrode is reduced or the carbon fine particles are detached from the electrode. There is.
[0018]
The content of the carbon fine particles in the coating for forming an electrode for an electrochemical capacitor is preferably such that the content of the carbon fine particles in the obtained electrode is in the range of 60 to 95% by weight, more preferably 70 to 90% by weight.
When the content of the carbon fine particles in the electrode is less than 60% by weight, the electric capacity of the electrochemical capacitor may be insufficient.
[0019]
When the content of the carbon fine particles in the electrode exceeds 95% by weight, the electrode becomes brittle due to a shortage of the binder component, and it is difficult to obtain an electrode that can withstand practical use.
Metal oxide fine particles
As the metal oxide fine particles used in the present invention, those having conductivity are used.
[0020]
Among them, oxides / composite oxides of at least one element selected from the group consisting of In, Sn, Cu, Mo, Ta, Ni, W, Mn, Sb, Ti, Zr, Co and Fe, or a mixture thereof Is preferred. These include doped oxides and solid solutions. For example, a doped oxide such as tin-doped indium oxide, F-doped indium oxide, and antimony-doped tin oxide can be used.
[0021]
As described above, the method of supporting the metal oxide in the fine pores of the carbon powder has been widely known, but the improvement of the electric capacity is insufficient or the economical efficiency is poor, and the method is rapidly increasing. There is a problem that it is difficult to obtain charge / discharge characteristics. On the other hand, if carbon particles and finer metal oxide particles are used as in the present invention, a large-capacity electrode material can be obtained at low cost. Further, the strength and adhesion of the electrode obtained by including such metal oxide fine particles can be increased.
[0022]
When the metal oxide fine particles are used in this manner, the metal oxide fine particles are uniformly dispersed on the surface of the carbon particles, so that the pseudo capacitance due to the metal oxide fine particles is added to the electric double layer capacity of the carbon electrode, thereby increasing the electric power. It is considered that an electrode for a capacitor having a large capacity is obtained.
The metal oxide used in the present invention has conductivity, so that the internal resistance of the electrode can be effectively reduced, and the effect of increasing the capacitance similar to the electrochemical pseudo capacitance is obtained. be able to.
[0023]
The effect of increasing the electric capacity by using the metal oxide according to the present invention is clearly shown in FIG. FIG. 1 is an electrochemical diagram using an electrode formed by mixing carbon fine particles, various conductive metal oxide fine particles, and a binder (described later) in a weight ratio (carbon: oxide: binder) of 85: 5: 10. FIG. 9 compares the capacitances of the capacitors at a constant potential scanning speed of 100 mV / s. As is clear from FIG. 1, an electric capacity equivalent to or higher than that of the carbon fine particles alone can be obtained.
[0024]
In the present invention, among the metal oxides, Sn or F-doped indium oxide fine particles are preferable, and such Sn or F-doped indium oxide has high conductivity and provides an electrochemical capacitor having a large electric capacity. Can be. Such Sn or F-doped indium oxide has a significant effect of significantly increasing the electric capacity as compared to undoped indium oxide or tin oxide, as compared to a case where both are simply mixed. Although the reason is not clear, it is presumed that Sn or F-doped indium oxide has high conductivity and therefore has a high function of contributing to charge accumulation. FIG. 2 shows the capacitance scanning speed dependency when each metal oxide particle is added to the electrode. Each of them contains 10% by weight of a binder and metal oxide in the amount shown in FIG. 2, so that the total amount of the binder, metal oxide fine particles and carbon particles is 100% by weight.
[0025]
In the case where the metal oxide fine particles are added, the capacity of the capacitor is higher than that in the case where only carbon is used. In particular, when Sn or F-doped indium oxide is used, a capacitor having a high capacitance is obtained even at a high capacitance scanning speed, and it can be seen that rapid charge and discharge are possible.
The doping amount of Sn or F in the indium oxide fine particles is preferably in the range of 0.5 to 16% by weight, more preferably 1 to 12% by weight in the fine particles.
[0026]
Such metal oxide fine particles have a smaller particle diameter than the carbon fine particles, and preferably have an average particle diameter of 5 to 100 nm, more preferably 10 to 50 nm.
With metal oxide particles having such a particle size range, the metal oxide particles are uniformly dispersed on the surface of the carbon particles without the metal oxide fine particles entering the pores of the electrode formed from the carbon particles. It can adhere and increase the capacity increasing effect. Even within this range, the smaller the particle size, the greater the capacity increasing effect.
[0027]
The particle size of the metal oxide fine particles is smaller than the carbon particles described above, and the particle size ratio is in the range of (1/10000) to (1/10), preferably (1/5000) to (1/100). Is desirable.
When the average particle diameter of the metal oxide fine particles is less than 5 nm, it is difficult to obtain.
When the average particle diameter of the metal oxide fine particles exceeds 100 nm, it is difficult to uniformly disperse the particles around the carbon fine particles, so that the electrode becomes coarse and the strength is reduced, or the adhesion to the base material may be reduced. . In addition, the increase in electric capacity may be insufficient.
[0028]
The method for producing such metal oxide fine particles is not particularly limited, but a conventionally known method may be employed as long as it has a proper conductivity and an average particle diameter in the above range. Can be. For example, it can be obtained by adding an acid or an alkali to an aqueous solution of a metal salt of the above metal element to form a precipitate, aging, washing and drying as necessary, and then performing a heat treatment.
[0029]
In the case of indium oxide fine particles doped with Sn or F, for example, a tin compound such as tin acetate or a fluorine compound such as (tin fluoride) is added to an aqueous solution of an indium salt such as indium nitrate and hydrolyzed. It can be obtained by aging, washing and drying, followed by heat treatment.
It is preferable that the metal oxide fine particles have a uniform composition and have excellent dispersibility in a coating material. For this purpose, to the aqueous solution in which the quaternary ammonium salt is dissolved in the aqueous ammonium hydroxide solution, the above-mentioned indium salt aqueous solution and the tin compound and the fluorine compound are added, hydrolyzed and decomposed, and if necessary, ripened, washed, After drying, heat treatment may be performed. This method is called an inverse uniform precipitation method, and can be made finer.
[0030]
The temperature at the time of the heat treatment is preferably in the range of about 400 to 1100 ° C, and more preferably in the range of 450 to 650 ° C.
When the heat treatment temperature is lower than 400 ° C., the crystallinity of the indium oxide fine particles doped with Sn or F may be low and the conductivity may be insufficient, and therefore, the effect of improving the electric capacity may be insufficient. is there.
[0031]
When the heat treatment temperature exceeds 1100 ° C., the indium oxide fine particles tend to strongly agglomerate or sinter, and it is difficult to uniformly disperse the particles around the carbon fine particles, so that the electric capacity may decrease.
The metal oxide fine particles thus obtained have high crystallinity by X-ray diffraction.
[0032]
The obtained crystalline metal oxide fine particles can be pulverized, if necessary, and used as the average particle diameter range. As a pulverizing method, a conventionally known method can be employed, and examples thereof include a sand mill method, a ball mill method, and a high-pressure collision pulverizing method. When the pulverization is performed in the presence of an acid or an alkali in a wet process, a dispersion of metal oxide fine particles having excellent dispersibility can be obtained.
[0033]
Further, the dispersion can be used after removing acids, alkalis and the like by an ion exchange resin method, an ultrafiltration membrane method or the like. Further, the dispersion medium can be used after replacing the solvent with an organic solvent.
The average particle diameter of the metal oxide particles referred to in the present invention may be determined as follows: (1) When the metal oxide particles are fired at a high temperature and used without passing through a pulverizing step, for example, in the above-mentioned preparation step, before drying and firing, It is a value measured by a dynamic light scattering type particle size distribution analyzer (LB-500, manufactured by Horiba, Ltd.) using an aqueous dispersion of precipitated product particles when washing the product particles. (2) In the case of using after passing through a pulverizing step after firing at a high temperature, for example, using the water or organic solvent dispersion liquid after drying, firing and pulverizing with a sand mill in the above-mentioned preparation step, This is a value measured by a scattering type particle size distribution analyzer (LB-500, manufactured by Horiba, Ltd.).
[0034]
The content of the metal oxide fine particles in the coating for forming an electrode for an electrochemical capacitor is such that the content of the metal oxide fine particles in the obtained electrode is in the range of 0.5 to 35% by weight, and more preferably 1 to 20% by weight. Preferably, there is. Within such a range, a capacitor having a large capacity can be obtained.
If the content of the metal oxide fine particles in the electrode is less than 0.5% by weight, the increase in the electric capacity of the capacitor may be insufficient.
[0035]
If the content of the metal oxide fine particles in the electrode exceeds 35% by weight, the content of the carbon fine particles becomes too small and the electric capacity of the capacitor becomes insufficient.
The weight ratio between the metal oxide fine particles and the carbon fine particles is preferably in the range of 1/200 to 1/2, and more preferably 1/100 to 1/3, in terms of the ratio of (metal oxide / carbon).
[0036]
Specifically, the change in capacitance when the content of the metal oxide fine particles in the electrode is changed will be described with reference to FIG. 3, taking the case where the metal oxide fine particles are Sn-doped indium oxide fine particles (ITO) as an example. . Each of the samples in FIG. 3 contains 10% by weight of a binder, contains ITO fine particles in the amount shown in FIG. 3, and is configured so that the total amount of the binder, the ITO fine particles and the carbon particles becomes 100% by weight. Is done.
[0037]
As is clear from FIG. 3, as the content of the ITO fine particles increased, the capacity increased, and reached a maximum near 5% by weight, showing a remarkably higher capacity increasing effect than the carbon single electrode.
FIG. 4 shows a CV curve showing a relationship between a potential (potential) and a current at a scanning speed of 100 mV / S when the content of the ITO fine particles in the electrode is 0, 5, and 10% by weight. In each case, the binder is contained in the electrode in an amount of 10% by weight. From FIG. 4, it is clear that the shape of the CV curve spreads up and down, that is, the capacity is increased, as compared with the carbon-only electrode.
[0038]
As described above, it is not clear why the capacity is remarkably increased by including metal oxide fine particles, particularly Sn or F-doped indium oxide fine particles together with carbon particles in the electrode, but it is not clear. It is considered that fine metal oxide particles are uniformly attached to the surface of the carbon particles to increase the electric capacity. In addition, if the amount of these metal oxides is small, the effect is small, and if the amount is too large, the entire carbon particles are covered and the electric double layer capacity is reduced, or particles aggregated in the gaps, not on the carbon particle surface. It is thought that the effect is reduced.
[0039]
In particular, Sn-doped and F-doped indium oxide fine particles can be manufactured inexpensively and in a fine particle state easily and in a controlled manner, so that a capacitor electrode having excellent economy and high capacity can be formed.
binder
Next, the binder used in the present invention includes: polyvinylidene fluoride, polytetrafluoroethylene, carboxymethylcellulose, crosslinked polymer of fluoroolefin copolymer, polyvinyl alcohol, polyacrylic acid, polyimide, petroleum pitch, coal pitch, polystyrene, phenol resin And the like, and it is preferable to use one or more of these.
[0040]
The content of the binder in the paint for forming an electrode for an electrochemical capacitor is preferably such that the content of the binder in the obtained electrode is in the range of 5 to 20% by weight, more preferably 8 to 15% by weight.
When the content of the binder in the electrode is less than 5% by weight, the strength of the electrode becomes insufficient, and when the content of the binder in the electrode exceeds 20% by weight, the electric capacity of the capacitor may be reduced.
[0041]
Organic solvent
The electrode forming paint for an electrochemical capacitor of the present invention may contain an organic solvent, if necessary. The organic solvent is not particularly limited as long as it can dissolve or disperse the binder and can be easily removed by drying, heating, or the like, and a conventionally known organic solvent can be used.
[0042]
Such organic solvents include methanol, ethanol, propanol, isopropyl alcohol, butanol, diacetone alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, ethylene glycol, hexylene glycol, isopropyl glycol, acetic acid methyl ester, acetic acid ethyl ester, N-methyl-2-pyrrolidone, cyclohexane, etc. in addition to diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, acetone, methyl ethyl ketone, acetylacetone, acetoacetate, etc. Is mentioned. These may be used alone or as a mixture of two or more.
[0043]
The concentration of the solid content (total of carbon fine particles, metal oxide, and binder) in the paint for forming an electrode for an electrochemical capacitor is preferably in the range of 1 to 50% by weight, more preferably 5 to 20% by weight.
When the solid content concentration in the paint is less than 1% by weight, it may not be possible to form a thick-film electrode by one application or the like. There is a problem of decline.
[0044]
If the solids concentration in the coating exceeds 50% by weight, the viscosity may be too high to make the coating difficult, and even if obtained, the coating method is limited or the strength of the obtained electrode is insufficient. It may be.
Such an electrode coating for electrochemical capacitors is prepared by preparing an organic solvent dispersion of metal oxide fine particles, further stirring the binder with an organic solvent as needed, and then uniformly stirring and dispersing the carbon fine particles. Good.
[0045]
Preparation of electrodes and electrodes
The electrode for an electrochemical capacitor according to the present invention was coated with the coating material on a current collector substrate, for example, by a dipping method, a spinner method, a spray method, a roll coater method, or a flexographic printing method. Thereafter, it can be obtained by drying at a temperature in the range of ordinary temperature to about 150 ° C.
[0046]
As the current collector substrate, copper, nickel, iron, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, glassy carbon, or the like can be used. These can be used usually in the form of a sheet, a film, a rod, and the like.
At this time, the thickness of the electrode is preferably in the range of 1 to 500 μm, more preferably 10 to 300 μm.
[0047]
When the thickness of the electrode is less than 1 μm, the electric capacity of the capacitor is reduced, and the output may be insufficient.
When the thickness of the electrode exceeds 500 μm, the charge / discharge speed is reduced, and for example, it may be difficult to obtain a capacitor having a high electric capacity capable of rapid charge / discharge.
Further, the paint may be simply filled in a container.
[0048]
The electrodes are opposed to each other, if necessary, separated by a separator or the like so that the two electrodes are not in contact with each other, placed in a predetermined container / can, and then filled with an electrolytic solution between the electrodes. Obtainable. It is sufficient that only one of the pair of electrodes is formed of the electrode according to the present invention, and the other can be a known electrode. Further, both may be constituted by the electrode according to the present invention.
[0049]
As the electrolytic solution, either an aqueous solution or an organic solution (a non-aqueous electrolytic solution) can be used.
Examples of the aqueous solution include an alkaline aqueous solution such as KOH, NaOH, and LiOH; a neutral aqueous solution such as KCl, NaCl, and LiCl;₂SO₄, HNO₃And the like. The concentration of the electrolyte cannot be determined unconditionally depending on the type of the electrolyte, the operating temperature, and the like, but is preferably in the range of 0.5 to 3 mol / l because the electric conductivity can be increased. In the case of these aqueous electrolytes, capacitance is developed by the occlusion and desorption of protons (hydrogen ions) in the aqueous solution to and from the electrode material.
[0050]
On the other hand, in the case of a non-aqueous electrolyte, a lithium salt that generates lithium ions as a cation is used as a solute. As the lithium salt, LiBF₄, LiClO₄, LiPF₆, LiSbF₆, LiAsF₆, LiCF₃SO₃, LiC (CF₃SO₂)₃, LiB (C₆H₅)₄, LiC₄F₉SO₃, LiC₈F1₇SO₃, LiB (C₆H₅)₄, LiN (CF₃SO₂)₂Etc. are exemplified. As the electrolyte, R₄N⁺, R₄P⁺(However, R is C_nH_{2n + 1}(Preferably an alkyl group represented by n = 1 to 3), and BF₄ ⁻, PF₆ ⁻, ClO₄ ⁻, SbF₆ ⁻Or CF₃SO₃ ⁻And one or more substances selected from salts in combination with anions such as The concentration of the solute in the non-aqueous electrolyte is 0.5 to 2 so that the characteristics of the electrochemical capacitor can be sufficiently obtained regardless of whether the lithium salt or the quaternary onium salt is used alone or in the case where they are mixed. 0.0 mol / l is preferred. Although it does not specifically limit as a solvent, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, sulfolane, methyl sulfolane, γ-butyrolactone, γ-valerolactone, N-methyloxazolidinone, Dimethyl sulfoxide, trimethyl sulfoxide and the like are exemplified.
[0051]
【The invention's effect】
According to the present invention, since the coating for forming an electrode for an electric capacitor has excellent conductivity and fine metal oxide fine particles, the obtained electrode has excellent strength (adhesion to a substrate and the like), In addition, an electrochemical capacitor having a high electric capacity can be obtained.
Further, an electrochemical capacitor can be obtained at low cost without using a conventional noble metal oxide.
[0052]
In particular, when the metal oxide fine particles are Sn-doped or F-doped indium oxide, the electric capacity can be extremely increased, the cost is low, and the particle size can be easily controlled. The use of the electrochemical capacitor obtained in this way makes it possible to reduce the size, weight, and capacity of various electronic devices, and their public utility is extremely large.
[0053]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
[0054]
Embodiment 1
Metal oxide fine particles (1) Preparation of
Indium nitrate (Kishida Chemical Co., Ltd.) was added to a strong alkaline aqueous solution obtained by adding 1.5 g of tetrapropylammonium bromide (Tokyo Chemical Co., Ltd.) to 60 ml of a 2% by weight aqueous solution of tetramethylammonium hydroxide (Kishida Chemical Co., Ltd.). 100 ml of an aqueous solution in which 6.3 g of (manufactured by K.K.) and 0.2 g of tin acetate (manufactured by Kishida Chemical Co., Ltd.) were added dropwise at a rate of 1 ml / min until the pH of the mixed aqueous solution became 11. Thereafter, after stirring for 1 hour, centrifugation was repeated to wash the precipitated product particles. At this time, the average particle diameter of the precipitated product particles was 44 nm. The tin doping amount was 5% by weight in terms of oxide.
[0055]
Then, after drying at 120 ° C., it was baked at 600 ° C. for 3 hours to prepare tin-doped indium oxide (ITO) metal oxide fine particles (1).
Paint for forming electrodes for electric capacitors (1) Preparation of
After mixing 50 g of ethanol with 0.65 g of the metal oxide fine particles (1) and performing ultrasonic dispersion, 50 g of N-methyl-2-pyrrolidone (manufactured by Kishida Chemical Co., Ltd.) was mixed and stirred (dispersion liquid 1). . Separately, a solution obtained by mixing 1.3 g of N-methyl-2-pyrrolidone and 1.3 g of polyvinylidene fluoride (KF-Polymer L, manufactured by Kureha Chemical Co., Ltd.) is blended in the dispersion liquid 1. Then, 11.1 g of carbon fine particles (manufactured by Kansai Thermochemical Co., Ltd .: MSP-20, average particle size: 4 μm) were blended and sufficiently stirred to prepare an electrode forming coating for an electric capacitor (1).
[0056]
Electrode for electric capacitor (1) Preparation of
After a paint (1) for forming an electrode for an electric capacitor is applied on a nickel sheet (Nirako Co., Ltd .: 310428, 20 × 30 × 0.3 tmm) as a current collector substrate in a 15 mm square by a roll coating method, 120 It dried at 12 degreeC for 12 hours, and prepared the electrode (1) for electric capacitors. The thickness of the electrode was 30 μm.
[0057]
The hardness and adhesion of the electrode (1) for an electric capacitor were evaluated, and the results are shown in Table 1.
Pencil hardness measurement
It measured with the pencil hardness tester according to JIS-K-5400. The results are shown in Table 1.
[0058]
Evaluation of adhesion
Eleven parallel scratches were made on the surface of the electrode for an electric capacitor (1) at intervals of 1 mm vertically and horizontally to make 100 squares, and a cellophane tape was adhered to this, and then the cellophane tape was peeled off. The adhesion was evaluated by classifying the number of squares in which the electrode did not peel off and remained in the following four stages. The results are shown in the table.
[0059]
98 or more remaining squares: ◎
Number of remaining squares 95 to 97: ○
Number of remaining squares 90-94: △
Number of remaining squares 89 or less: ×
Measurement cell (1) Assembly and electric capacity measurement
The electrode (1) for an electric capacitor is used as a working electrode (1), a platinum plate (15 × 20 × 0.1 tmm) is used as a counter electrode, and an Ag / AgCl electrode (HX-R2 manufactured by Hokuto Denko KK) is used as a reference electrode. ) Was used to assemble the measurement cell (1) using a 1M-KOH aqueous solution as an electrolyte solution. Using this, an electrochemical measurement (10 mV / s, 100 mV / s) was performed at 25 ± 1 ° C. by a cyclic voltammetry method (manufactured by Hokuto Denko Corporation: standard voltammetry tool, HSV-100). The electric capacity (F / g) was calculated from the CV curve, and the results are shown in Table 1.
[0060]
Embodiment 2
Metal oxide fine particles (2) Preparation of
In a strong alkaline aqueous solution obtained by adding 1.5 g of tetrapropylammonium bromide to 60 ml of a 2% by weight aqueous solution of tetramethylammonium hydroxide, 100 ml of an aqueous solution of indium nitrate having a concentration of 0.2 mol / L was mixed at a rate of 1 ml / min. It was added dropwise until the pH reached 11. Thereafter, after stirring for 1 hour, centrifugation was repeated to wash the precipitated product particles. At this time, the average particle diameter of the precipitated product particles was 58 nm.
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Then, after drying at 120 ° C., it was baked at 600 ° C. for 3 hours to prepare metal oxide fine particles (2) of indium oxide.
Measurement cell (2) Assembly and electric capacity measurement
In Example 1, a coating (2) for forming an electrode for an electric capacitor and an electrode (2) for an electric capacitor were prepared in the same manner except that the metal oxide fine particles (2) were used. The results were evaluated and the results are shown in Table 1.
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Then, the measurement cell (2) was assembled and electrochemical measurement was performed. The obtained electric capacity is shown in Table 1.
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Embodiment 3
Paint for forming electrodes for electric capacitors (3) Preparation of
After mixing 50 g of ethanol with 0.39 g of the metal oxide fine particles (1) and performing ultrasonic dispersion, 50 g of N-methyl-2-pyrrolidone is mixed and stirred (dispersion liquid (2)). Separately, a solution obtained by mixing 1.3 g of N-methyl-2-pyrrolidone and 1.3 g of polyfukkavinylidene is blended into the dispersion liquid (2). Then, 11.3 g of carbon fine particles (manufactured by Kansai Thermochemical Co., Ltd .: MSP-20, average particle size: 4 μm) were blended and sufficiently stirred to prepare a coating (3) for forming an electrode for an electric capacitor.
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Measurement cell (3) Assembly and electric capacity measurement
In Example 1, an electrode (3) for an electric capacitor was prepared in the same manner except that the paint (3) for forming an electrode for an electric capacitor was used. Then, a measurement cell (3) was assembled, and an electrochemical measurement was performed. Table 1 shows the obtained electric capacities.
[0065]
Embodiment 4
Paint for forming electrodes for electric capacitors (4) Preparation of
After mixing 50 g of ethanol with 1.3 g of the metal oxide fine particles (1) and performing ultrasonic dispersion, 50 g of N-methyl-2-pyrrolidone was mixed and stirred (dispersion liquid (3)). Separately, a solution obtained by mixing 1.3 g of N-methyl-2-pyrrolidone and 1.3 g of polyvinylidene fluoride was blended in the dispersion liquid 3. Then, 10.5 g of carbon fine particles (manufactured by Kansai Thermochemical Co., Ltd .: MSP-20, average particle size: 4 μm) were blended and sufficiently stirred to prepare an electrode-forming paint (4) for an electric capacitor.
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Measurement cell (4) Assembly and electric capacity measurement
In Example 1, an electrode (4) for an electric capacitor was prepared in the same manner except that the paint (4) for forming an electrode for an electric capacitor was used. Then, a measurement cell (4) was assembled, and an electrochemical measurement was performed. The obtained electric capacity is shown in the table.
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Embodiment 5
Metal oxide fine particles (3) Preparation of
A solution obtained by dissolving 79.7 g of indium nitrate trihydrate in 686 g of water and a solution obtained by dissolving 5.4 g of potassium stannate trihydrate in 414 g of a 10% by weight potassium hydroxide solution. Solutions were prepared, and these solutions were added to 1000 g of pure water maintained at 50 ° C. over 2 hours. During this time, the pH in the system was maintained at 11. The tin-doped indium oxide hydrate dispersion was filtered and washed from the tin-doped indium oxide hydrate dispersion, dried, then calcined at 350 ° C. for 3 hours in air, and further heated at 600 ° C. in air. By firing at a temperature for 2 hours, tin-doped indium oxide fine particles were obtained. The tin doping amount was 8% by weight in terms of oxide.
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This was dispersed in pure water so as to have a concentration of 30% by weight, and the pH was adjusted to 3.5 with an aqueous nitric acid solution. Was prepared. Next, this sol is treated with an ion exchange resin to remove nitrate ions, pure water is added, and a dispersion of metal oxide fine particles (3) of indium oxide (ITO) doped with tin at a concentration of 20% by weight. Was prepared. Subsequently, the solvent was replaced with an ultrafiltration membrane to prepare an ethanol dispersion of metal oxide fine particles (3) having a concentration of 20% by weight. At this time, the average particle size of the metal oxide fine particles (3) was 40 nm.
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Paint for forming electrodes for electric capacitors (5) Preparation of
After mixing 47.4 g of ethanol with 3.25 g of an ethanol dispersion of the metal oxide fine particles (3) and performing ultrasonic dispersion, 50 g of N-methyl-2-pyrrolidone is mixed and stirred (dispersion (4)). . Separately, a solution obtained by mixing 1.3 g of N-methyl-2-pyrrolidone and 1.3 g of polyvinylidene fluoride was blended in the dispersion liquid (4). Then, 11.1 g of carbon fine particles (manufactured by Kansai Thermochemical Co., Ltd .: MSP-20, average particle size: 4 μm) were blended and sufficiently stirred to prepare an electrode-forming paint (5) for an electric capacitor.
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Measurement cell (5) Assembly and electric capacity measurement
In Example 1, an electrode (5) for an electric capacitor was prepared in the same manner except that the paint (5) for forming an electrode for an electric capacitor was used. Then, a measurement cell (5) was assembled, and an electrochemical measurement was performed. Table 1 shows the obtained electric capacities.
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Embodiment 6
Metal oxide fine particles (4) Preparation of
A solution was prepared by dissolving 57.7 g of tin chloride and 7.0 g of antimony chloride in 100 g of methanol. The obtained solution was added to 1000 g of pure water with stirring at 90 ° C. for 4 hours to perform hydrolysis, and the formed precipitate was separated by filtration and washed, and calcined at 500 ° C. for 2 hours in dry air. Antimony-doped tin oxide fine powder was obtained. 30 g of this powder was added to 70 g of an aqueous potassium hydroxide solution (3.0 g as KOH), and the mixture was pulverized with a sand mill for 3 hours while maintaining the mixture at 30 ° C. to prepare a sol. Next, the sol was treated with an ion-exchange resin, dealkalized, and pure water was added to prepare a dispersion of metal oxide fine particles (4) of tin oxide (ATO) doped with antimony at a concentration of 20% by weight.
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Subsequently, the solvent was replaced with an ultrafiltration membrane to prepare an ethanol dispersion of metal oxide fine particles (4) having a concentration of 20% by weight. At this time, the average particle diameter of the metal oxide fine particles (4) was 10 nm.
Paint for forming electrodes for electric capacitors (6)
After mixing 47.4 g of ethanol with 3.25 g of an ethanol dispersion of the metal oxide fine particles (4) and performing ultrasonic dispersion, 50 g of N-methyl-2-pyrrolidone is mixed and stirred (dispersion (5)). . Separately, a solution obtained by mixing 1.3 g of N-methyl-2-pyrrolidone and 1.3 g of polyfukkavinylidene is blended in the dispersion liquid (5). Then, 11.1 g of carbon fine particles (manufactured by Kansai Thermochemical Co., Ltd .: MSP-20, average particle diameter: 4 μm) were blended and sufficiently stirred to prepare an electrode-forming paint (6) for an electric capacitor.
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Measurement cell (6) Assembly and electric capacity measurement
In Example 1, an electrode (6) for an electric capacitor was prepared in the same manner except that the paint (6) for forming an electrode for an electric capacitor was used. Then, a measurement cell (6) was assembled, and an electrochemical measurement was performed. Table 1 shows the obtained electric capacities.
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[Comparative Example 1]
Paint for forming electrodes for electric capacitors (R1) Preparation of
A solution obtained by mixing 1.3 g of N-methyl-2-pyrrolidone and 1.3 g of polyvinylidene fluoride is mixed with 50 g of ethanol and 50 g of N-methyl-2-pyrrolidone. Next, 11.8 g of carbon fine particles (manufactured by Kansai Thermochemical Co., Ltd .: MSP-20, average particle size: 4 μm) were blended and sufficiently stirred to prepare an electrode forming coating for an electric capacitor (R1).
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Measurement cell (R1) Assembly and electric capacity measurement
In Example 1, an electrode (R1) for an electric capacitor was prepared in the same manner except that the paint (R1) for forming an electrode for an electric capacitor was used. Then, a measurement cell (R1) was assembled, and an electrochemical measurement was performed. Table 1 shows the obtained electric capacities.
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[Table 1]

[Brief description of the drawings]
FIG. 1 shows the electric capacity of an electrode containing various metal oxides at a constant potential scanning speed of 100 mV / s.
FIG. 2 shows the capacity scanning speed dependency when each metal oxide particle is added to an electrode.
FIG. 3 shows a change in capacitance when the content of metal oxide fine particles in an electrode is changed.
FIG. 4 is a CV curve showing a relationship between a potential (potential) and a current at a scanning speed of 100 mV / S when the content of ITO fine particles in an electrode is 0, 5, and 10% by weight.

Claims (4)

It comprises carbon fine particles, metal oxide fine particles having a smaller particle diameter than the carbon fine particles, a binder and water and / or an organic solvent, and the average particle diameter of the metal oxide fine particles is in the range of 5 to 100 nm. Paint for forming electrodes for electrochemical capacitors. The metal oxide fine particles are oxides / composite oxides of at least one element selected from the group consisting of In, Sn, Cu, Mo, Ta, Ni, W, Mn, Sb, Ti, Zr, Co, and Fe; The paint for forming an electrode for an electrochemical capacitor according to claim 1, which is a mixture of these. The paint for forming an electrode for an electrochemical capacitor according to claim 1 or 2, wherein the metal oxide fine particles are indium oxide doped with Sn or F. An electrode for an electrochemical capacitor formed using the paint for forming an electrode for an electrochemical capacitor according to claim 1.

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