JP2002289468A - Electrode material for electrochemical capacitor and electrode therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost and high-capacity electrode material for an electrochemical capacitor. SOLUTION: An electrode material is used for the electrochemical capacitor containing a porous carbon-like material as its main component and containing a molybdenum component. An electrode for the electrochemical capacitor is formed using the electrode material for the electrochemical capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode material for an electrochemical capacitor and an electrode for an electrochemical capacitor.
More specifically, the present invention relates to an electrode material for an electrochemical capacitor which is inexpensive and has a large capacitance, and an electrode for an electrochemical capacitor using this electrode material.

[0002]

2. Description of the Related Art In recent years, under the situation where various electronic devices have been miniaturized, there has been a demand for a power storage device that is small, lightweight, large in capacity and capable of rapid charge and discharge. In particular, conventional capacitors and secondary batteries cannot cope with general-purpose hybrid vehicles and electric vehicles, and the development of high-performance electrochemical capacitors is urgent.

Conventionally, as an electrochemical capacitor, while development has been developed mainly on an electric double layer type electrochemical capacitor (EDLC) using a carbon material having a high specific surface area as an electrode material, a high output density and an energy density are required. The resulting metal oxide, metal nitride and metal carbide electrochemical capacitors are also of interest.

[0004] E using a carbon material having a high specific surface area as an electrode material
In DLC, activated carbon, activated carbon fiber, carbon aerogel, 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 EDLCs because they exhibit a relatively large capacitance, are excellent in mass productivity, are easy to mold, and the like.
As activated carbon for EDLC, after coconut shell is carbonized,
Steam, activated carbon powder obtained by activation in an oxidizing gas atmosphere such as carbon dioxide, or carbonized phenolic resin fiber,
Similarly, an activated carbon fiber cloth obtained by activating with an oxidizing gas is used. In addition, as activated carbon for a polarizable electrode exhibiting a high capacity, phenol resin, furan resin, polyacrylonitrile, polyvinyl chloride resin, petroleum coke, coal pitch and the like, activated by steam, potassium hydroxide, etc. Many have been proposed. These activated carbons have many nanometer-sized pores in the carbon, and their specific surface areas are all high specific surface areas of 1000 m ² / g or more.

On the other hand, metal oxide-based electrode materials include:
Ru and Ir oxides, which are noble metal oxides, have been studied. RuO ₂ is oxidized and reduced along with hydrogenation and dehydrogenation in the vicinity of the surface in a sulfuric acid aqueous solution, the valence changes, and energy is absorbed and released. This process involves a phase change, but exhibits excellent charge / discharge cycle characteristics due to high electrochemical reversibility. In particular, hydrated RuO ₂ has a high capacity of 720 F / g in an aqueous sulfuric acid solution, and therefore has the feature that the energy density per unit volume and the power density of the system can be increased in addition to the high conductivity. .

[0006] However, noble metal oxides are expensive and therefore have a practical problem. For this reason, noble metal oxides have to be applied to appropriate carbon materials, and composites with inexpensive high-performance oxide materials have been made. An example in which RuO ₂ is carried on a carbon material is described in Journal of Electrochemical Society, Vol.
o.12, 1997, p.309-311 reports that Ru nanoparticles are dispersed in carbon aerogel which is a porous carbon material. Also, Electrochem. Solidstate Let
t. Vol.3, No.3, 2000, p.113-116
By supporting 6.6% by weight of the Ru oxide on 53 m ² / g of activated carbon, the capacitance was improved to 214 F / g after the loading, compared to the specific capacitance of 177 F / g before the loading. It has been reported.

Further, such expensive RuO ₂ , IrO
₂ without using N as an electrode material for electrochemical capacitors
It has also been reported that an electrochemical capacitor can be manufactured using ultrafine particles of an oxide such as i, V, Mo or the like, or a nitride or carbide such as V, Nb, Mo, W or the like.

For example, J. Electrochem. Soc., 143, 124 (1
996) reports that porous NiO / Ni is used as an electrode material for electrochemical capacitors. Also, Th
_{e Electrochemical Society PV95-29, V 2 O} 5 gel have been reported to p.86 (1996). Electrochemistry 67,
In 1187 (1999), by carrying a trace amount of molybdenum oxide on the surface of mirror-polished glassy carbon,
A specific capacitance of about 1000 F / g per mass of molybdenum oxide is obtained, and it is reported that molybdenum oxide can be used as an electrode material for capacitors.

[0009]

However, none of the above conventional electrode materials is industrially satisfactory to any extent.

That is, the Journal of Electrochemical Socie
ty, Vol. 144, No. 12, 1997, p. 309-311, the amount of Ru particles was as large as 35% by weight, based on the specific capacitance of 95 F / g of only carbon aerogel not carrying Ru particles. , And a high capacity of a specific capacitance of 206 F / g is obtained. However, since Ru particles are extremely expensive, it is not practical to use such a large amount of Ru particles.

Further, J. Electrochem. Soc., 14 using porous NiO / Ni as an electrode material for an electrochemical capacitor.
In 3,124 (1996), the potential window is very narrow, about 0.4 V,
The resulting energy density is low and therefore impractical.

Further, the Electroc using V ₂ O ₅ gel
In Chemical Society PV95-29, p.86 (1996), LiCl
Although an electrochemical capacitor is manufactured using lithium intercalation in a propylene carbonate solution of O ₄ , it is not suitable for high-speed charging and discharging.

In Electrochemistry 67, 1187 (1999) in which Mo oxide is applied to glassy carbon (electrode material) and dried, glassy carbon has an effective solid-liquid interface of several m ² / g.
Since it is a nonporous carbonaceous material having only a very small surface area, the amount of Mo oxide carried is small, and as a result, the capacitance of the entire electrode is low.

In the case of an EDLC using activated carbon, which is a carbon material having a high specific surface area, as an electrode material, only the movement of electrolyte ions in the solution and the adsorption / desorption reaction (electric double layer) on the activated carbon electrode surface due to charging and discharging are limited. Occur. Conventionally, studies have been made to increase the specific surface area of the activated carbon and to optimize the pore distribution in order to increase the solid-liquid interface effective for the development of the electric double layer capacity. , The specific capacitance of the aqueous solution is 200 F / g or less.

As described above, conventionally, an inexpensive and high-capacity electrode material for an electrochemical capacitor has been provided in a system using a porous carbon material or a metal oxide alone or a combination of a carbon material and a metal oxide. No, its development was desired.

Accordingly, an object of the present invention is to provide an inexpensive and high-capacity electrode material for an electrochemical capacitor and an electrode for an electrochemical capacitor, which are obtained by combining a carbon material and a metal compound.

[0017]

An electrode material for an electrochemical capacitor according to the present invention is an electrode material for an electrochemical capacitor mainly composed of a carbonaceous substance, wherein the carbonaceous substance is a porous carbonaceous substance and a molybdenum compound. It is characterized by containing.

That is, the present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, by using a porous carbonaceous substance as a carbonaceous substance and carrying a molybdenum compound, a small amount of molybdenum compound is supported. It has been found that the capacity can be greatly increased, and thus an inexpensive and high-capacity electrode material for an electrochemical capacitor can be obtained without using a large amount of an expensive molybdenum compound, thereby completing the present invention.

As described above, conventionally, the carbon material has R
Although those supporting uO ₂ and those supporting Ru particles on a carbon aerogel of a porous carbon material are known,
The effect of compounding the molybdenum compound with the porous carbonaceous material in the present invention is significantly different from the case of these Ru oxides.

That is, the Journal of Electrochemical S
ociety, Vol. 144, No. 12, 1997, p. 309-311, Ru
The carbon gel without particles alone has a specific capacitance of 95 F / g, and a large amount of Ru particles as large as 35% by weight supports a specific capacitance of 206 F / g. Also, Electrochem. Solidstate Lett. Vol. 3, N
o.3, 2000, p.113-116, 6.6 Ru oxide on activated carbon.
By weight, the specific electrostatic capacity before loading was increased to 177 F / g after loading. However,
Since RuO ₂ alone has a specific capacitance of 700 F / g or more, these RuO ₂ / carbon aerogels and Ru
With O ₂ / activated carbon, it can be said that the effect of supporting RuO ₂ is small.

On the other hand, the molybdenum compound of the present invention has a remarkable capacity increase effect as compared with the case of such a Ru oxide. With a very small loading of 0.4% by weight, the specific capacitance is from 129 F / g (only activated carbon) to 182 F / g.
And an increase in capacity of as much as 53 F / g (+ 41%) is achieved.

It is presumed that such a large capacity-improving effect can be obtained not only from the capacitance of the molybdenum compound but also from the mutual effect of combining the molybdenum compound and the porous carbonaceous material. Is done. The details of the mechanism of this reciprocal effect are not clear, but are presumed as follows.

That is, a molybdenum compound such as MoO ₃
Has a lower electrical conductivity than RuO ₂ ,
_The capacitance that can be taken out from the _three- particle assembly is small. However, in the MoO _x / C composite as in the present invention, since the porous carbonaceous material has properties such as conductivity and oxidation-reduction property, the porous carbonaceous material having such properties and the molybdenum compound are mixed. It is conceivable that a higher capacity is achieved by a synergistic effect.

In the present invention, the molybdenum compound is preferably one or more molybdenum compounds selected from the group consisting of molybdenum oxide and molybdenum hydroxide.
The content of the molybdenum compound in the electrode material is a mole fraction of molybdenum with respect to 1 g of the carbonaceous material, and is 1 × 10 ⁻⁶ to 1 × 10 ⁻⁶ .
1 × 10 ⁻³ mol (mol / g), and the content of the molybdenum compound with respect to the carbonaceous substance in the electrode material was 0.0%.
It is preferably from 5 to 30% by weight.

The porous carbonaceous substance is preferably a porous carbonaceous substance having a specific surface area of 30 to 3000 m ² / g, and one or more selected from the group consisting of activated carbon, activated carbon fiber, carbon aerogel and carbon black. It is preferable to use two or more types, particularly those obtained by subjecting a carbonaceous raw material to an alkali activation treatment.

The electrode for an electrochemical capacitor of the present invention is made of such an electrode material for an electrochemical capacitor of the present invention, and is inexpensive and effective for reducing the size, weight, and capacity of various electronic devices. It is.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the electrode material for an electrochemical capacitor and the electrode for an electrochemical capacitor according to the present invention will be described in detail.

The electrode material for an electrochemical capacitor of the present invention is mainly composed of a porous carbonaceous substance and contains a molybdenum compound.

In the present invention, a carbonaceous substance is used as a main component of an electrode material for an electrochemical capacitor because it is electrochemically inert to an electrolytic solution and has an appropriate electric conductivity. In addition, a porous carbonaceous material is used in view of a large electrode interface where charges are accumulated. This porous carbonaceous material preferably has a specific surface area of 30 m ² / g or more determined by a BET method using a nitrogen adsorption method.

The specific surface area of the porous carbonaceous material to be used can be generally determined from the reasons such as the capacitance per unit area (F / m ² ) depending on the carbonaceous species and the decrease in bulk density due to the increase in the specific surface area. However, the specific surface area determined by the BET method using a nitrogen adsorption method is preferably 30 to 3000 m ² / g, and in particular, a porous carbonaceous material having a specific surface area of 300 to 2500 m ² / g has a capacitance per volume. Large and preferred.

Examples of the porous carbonaceous substance that can be suitably used in the present invention include activated carbon, activated carbon fiber, carbon aerogel, and carbon black.

The raw materials of the activated carbon and the activated carbon fiber used in the present invention are plant-based wood, sawdust, coconut shell, pulp waste liquor, fossil fuel-based coal, petroleum heavy oil, or coal obtained by thermally decomposing them. And 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 It is used for various purposes such as waste and waste tires. Activated carbon and activated carbon fibers 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. In the gas activation method, while the chemical activation method is a chemical activation,
Also called physical activation, activated carbon is obtained by contacting a carbonized raw material with steam, carbon dioxide, oxygen, other oxidizing gas, or the like at a high temperature. The chemical activation method is a method in which a raw material is uniformly impregnated with an activating 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,
There are potassium sulfide, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium sulfate, potassium sulfate, calcium carbonate and the like. However, there is no particular limitation on the method for producing activated carbon and activated carbon fiber, and the method is not limited to the above method.

The activated carbon or activated carbon fiber may be in any of various shapes such as crushed, granulated, 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 phenolic resin as a raw material in the gas activation method show a relatively high capacitance, and It is suitable for the present invention because it can be mass-produced and inexpensive.

Activated carbon or activated carbon fiber obtained by chemical activation (alkali activation) using an alkali such as potassium hydroxide or sodium hydroxide has a slightly higher production cost than the above-mentioned gas-activated products. It is particularly preferable because the capacity tends to be large. Further, in the case of activated carbon or activated carbon fiber obtained by alkali activation, some exhibit a specific surface area of less than 300 m ² / g depending on the type of raw material before activation and the activation conditions. Since there are some which are shown, these can also be used as the electrode material of the present invention.

Ketjen Black, # 3230B (manufactured by Mitsubishi Chemical Corporation), Vulcan
XC-72 (manufactured by Cabot Corporation) (both trade names) has a high specific surface area of 200 m ² / g or more, and these are also preferably used in the present invention because they have excellent conductivity. I can do it.

Carbon aerogel is obtained by condensation polymerization of a mixture of an aromatic compound having a hydroxyl group such as 1,3-dihydroxybenzene and formalin under specific conditions, followed by drying under freezing or supercritical conditions. Next, it is a porous carbonaceous substance obtained by a carbonization treatment. Although the carbon aerogel varies depending on the preparation conditions, it is usually 300 to 1200.
Since it has a high specific surface area of m ² / g and is excellent in conductivity due to its carbon structure, it can be suitably used as the electrode material of the present invention.

The porous carbonaceous materials such as activated carbon and carbon black used in the present invention include nitrogen, argon, helium,
Under an inert atmosphere such as xenon, at 500 to 2500 ° C.
Preferably, heat treatment may be performed at 700 to 1500 ° C. to remove unnecessary surface functional groups, or to increase electron conductivity by developing carbon crystallinity.

When the porous carbonaceous material used in the present invention is granular, the average particle diameter is preferably 50 μm or less, and particularly preferably 1 to 5 from the viewpoint of improving the bulk density of the electrode and reducing the internal resistance.
30 μm, more preferably 5 to 20 μm
Is preferred.

One of these porous carbonaceous materials may be used alone, or two or more thereof may be used in combination.

In the present invention, as the molybdenum compound used together with such a porous carbonaceous material, there are nine types of compounds including 0, from 0 to +6 oxidation number of molybdenum, and the composition is simple. There are also various compounds and complexes including those containing a cluster or a condensed acid ion, and those whose oxidation number is difficult to specify. For example, among the molybdenum compounds, the oxide MoO ₂ having an oxidation number of 4 has a rutile structure, but has metal conductivity due to the contribution of the Mo—Mo structure. A molybdenum compound having an oxidation number of 6 is the most stable as compared with a molybdenum compound having another oxidation number.
O ₃ there is. Mo between MoO ₂ and MoO _3
9 O _26, Magneli phase such as _{Mo 8 O 23, Mo 4 O} 11 are present. In addition, molybdate ion MoO ₄ ^2-
Gives many stable salts and easily generates condensed acid, and thus generates many heteropoly acids (paramolybdic acid, metamolybdic acid, etc.). In the case of oxidation number 4, MoO ₂
Oxo halides such as Cl, MoO ₂ Cl ₃ and MoOBr ₃ are mentioned. If the oxidation number of 3, other trihalides such as _{MoCl 3, [Mo (H 2} O) 6] 3+ compound is present, many salts ^{O 2-,} or OH ^- in multimers crosslinked with is there.

That is, examples of molybdenum compounds include oxides (MoO _x (X = 2 to 3)) and hydroxides (M
_{o (H 2 O) 6 (} OH) y) (y = 1~6)), oxo halide _{(MoO z X a) (z} = 1~2, X = C
1, halogen such as Br, F, a = 1 to 3), halide (MoX _b (X = halogen such as Cl, Br, F, b =
3 to 5) are used.

Of these molybdenum compounds, electrochemically stable oxides (MoO ₂ , MoO ₃ , Mo ₉ O)
₂₆ , Mo ₈ O ₂₃ , Mo ₄ O ₁₁ ) are preferred.
MoO ₃ is particularly preferable because the proton exchange capacity per o atom is large.

In addition to the above molybdenum compounds, molybdenum complexes, molybdates, and molybdenum bronzes can also be used for the electrode material of the present invention.

As the molybdenum compound, Ru,
Rh, Pd, Os, Ir, Co, Cr, Ni, Mn, F
e, Pt, Ag, Au, Al, Zn, W, Ti, V, T
a, Nb, Zr, Si, Sn, La
Molybdenum composite oxide with one or more metals, molybdenum
Den complex oxide salts can also be used in the present invention. These moly
When using butene composite oxide or molybdenum composite oxide salt
If you select a metal to be composited,
Increase, increase electrical conductivity, improve proton exchange efficiency,
An effect such as improvement of the aerochemical stability is expected. In particular, R
uO_x-MoO _xElectrochemistry using composite oxide as electrode material
Capacitors have better capacitance than Mo oxide only
This is preferable because it tends to cause

One of these molybdenum compounds may be used alone, or a plurality of molybdenum compounds may be used in combination.

The method for producing the electrode material for an electrochemical capacitor of the present invention containing a porous carbonaceous substance and a molybdenum compound is not particularly limited. For example, a molybdenum compound such as molybdenum pentachloride may be used as the molybdenum compound. A halide is used as a solute, and it is usually used in a solvent such as methanol, ethanol, and 1-butanol.
0.01 mol / l, especially 0.0002 to 0.00
A method in which a porous carbonaceous material is dispersed in a solution dissolved at a concentration of 8 mol / liter and then dried to support a molybdenum halide on the porous carbonaceous material. Here, the porous carbonaceous material supporting the molybdenum halide is dried and calcined to obtain a molybdenum oxide-supported porous carbonaceous material. In this case, most of the molybdenum halide is converted to an oxide during drying and firing, but a part of the molybdenum halide may remain as a hydroxide or halide to form a mixture.

When a molybdenum compound is supported on a porous carbonaceous material such as activated carbon by the above-described method, a slight amount of oxygen-containing functional groups such as a phenolic hydroxyl group, a carboxyl group and a lactone are introduced onto the surface of the particles of the carbonaceous material. Accordingly, there is a tendency that the molybdenum compound as a supporting substance can be supported in a highly dispersed state. By increasing the dispersion of the molybdenum compound, further improvement in the capacitance as an electrode material can be expected.
The method for introducing the oxygen-containing functional group on the surface of the porous carbonaceous material is not particularly limited. For example, air, an oxidizing gas such as ozone, or an oxidizing agent such as nitric acid or sulfuric acid may be used to introduce the porous carbonaceous material There is a method of contacting. The amount of the oxygen-containing functional group to be introduced cannot be unconditionally determined depending on the specific surface area, pore size distribution and the like of the porous carbonaceous material. However, in the case of activated carbon, the amount of oxygen is preferably 2 to 50 mg / g-activated carbon.

As a method for supporting the molybdenum compound on the porous carbonaceous material, other than the above, a particle diameter of 1 μm obtained by finely pulverizing molybdenum oxide with a pulverizer such as a jet mill.
m or less, uniformly dispersed in water or an organic solvent such as methanol or ethanol, and then impregnated with the dispersion in a porous carbonaceous material and dried. Deposited on porous carbonaceous material (CVD
Method).

In the electrode material of the present invention, the content of the molybdenum compound is 1 × 10 ⁻⁶ to 1 × 10 ⁻³ mol (mol / g) in terms of the molar fraction of molybdenum per 1 g of the porous carbonaceous substance, and in particular, 1 × 10 ⁻⁵ to 8 × 10 ⁻⁴ mol (mol / g), especially 0.00002 to 0.000.
It is preferably 5 mol (mol / g). The content of the molybdenum compound with respect to the porous carbonaceous material in the electrode material is 0.05 to 30% by weight, particularly 0.1 to 20% by weight, particularly 0.2 to 10% by weight, and most preferably 0.1 to 10% by weight. It is preferably 5 to 5% by weight.

When the content of the molybdenum compound is less than the above range, the effect of improving the capacitance is hardly recognized. When the content exceeds the above range, the capacitance tends to decrease due to an increase in internal resistance and the like.

In the present invention, for the purpose of imparting conductivity to the obtained electrode material, metal fine particles such as Pt, Au, Ni, etc., graphite powder having an average particle diameter of 10 μm or less, or conductive carbon black are porous with a molybdenum compound. It is also possible to support on a carbonaceous material. The method is not particularly limited, but the loading amount is 1 g of the porous carbonaceous material.
It is preferably 0.5 g or less, more preferably 0.01 to 0.5 g per volume, and particularly preferably about 0.05 to 0.4 g in order not to lower the capacitance per volume.

In order to further improve the capacitance,
A ruthenium oxide or iridium oxide having a large capacitance per unit weight may be supported on a porous carbonaceous material together with a molybdenum compound. In this case, the amount of the carried is determined so that the capacitance is efficiently expressed. The amount is preferably 0.05 g to 0.3 g per 1 g of the porous carbonaceous material.

The electrode material of the present invention is usually a conductive material,
The mixture is mixed with a binder component or the like and molded according to a conventional method to form an electrode body. For example, a method in which a binder such as polytetrafluoroethylene is added to a mixture of a molybdenum compound-supporting porous carbonaceous material, which is an electrode material of the present invention, and a conductive agent such as acetylene black, mixed, and then press-formed. Further, there is a method in which the electrode material of the present invention is mixed with a binder substance such as pitch, tar, and phenol resin, molded, and then heat-treated in an inert atmosphere to form a sintered body. Furthermore, it is also possible to form a polarizable electrode by molding and sintering only the electrode material of the present invention without using a conductive agent and a binder. Alternatively, the electrode material of the present invention and a binder can be mixed, molded, and sintered to form a polarizable electrode without using a conductive agent.

Examples of the form of the electrode for an electrochemical capacitor of the present invention produced using the electrode material of the present invention include a thin coating film, a sheet-like or plate-like molded body, and a plate-like molded body composed of a composite. Any of these may be used. Further, a paste obtained by mixing an electrolyte solution and the electrode material of the present invention without using a binder may be applied to a current collector, or may be filled in a container.

Examples of the conductive agent used in the production of the electrode body include carbon black such as acetylene black and Ketjen black, natural graphite, thermally expanded graphite, carbon fiber, metal fiber such as ruthenium oxide, titanium oxide, aluminum and nickel. At least one conductive agent selected from the group consisting of Acetylene black and Ketjen black are particularly preferred in that the conductivity is effectively improved with a small amount.For example, when the porous carbonaceous material is activated carbon, the blending ratio with respect to the activated carbon varies depending on the bulk density of the activated carbon. If the amount is too high, a sufficient effect cannot be obtained. If the amount is too high, the ratio of the activated carbon is relatively reduced and the capacity is reduced. Therefore, the amount is preferably 5 to 50% by weight, more preferably about 10 to 30% by weight of the activated carbon. .

Examples of the binder include polytetrafluoroethylene, polyvinylidene fluoride, carboxymethylcellulose, crosslinked fluoroolefin copolymer, polyvinyl alcohol, polyacrylic acid, polyimide, petroleum pitch, coal pitch, phenol resin and the like. It is preferable to use one or more of these.

As the electrolytic solution used when the electrode for an electrochemical capacitor of the present invention is used for an electrochemical capacitor, any of an aqueous solution and an organic solution (non-aqueous solution) can be used.

In an aqueous solution, KOH, NaOH, LiOH
And the like, a neutral aqueous solution such as KCl, NaCl, and LiCl, and an acidic aqueous solution such as H ₂ SO ₄ and HNO ₃ can be used. Among these, an aqueous NaOH solution and an aqueous H ₂ SO ₄ solution are preferable in terms of electric conductivity and a potential window region.
The concentration of the electrolyte cannot be unconditionally determined depending on the type of the electrolyte, the operating temperature, and the like, but is preferably 0.5 to 3 mol / liter because the electric conductivity is large. 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.

On the other hand, in the case of a non-aqueous electrolyte,
Solutes lithium salts that generate lithium ions when turned on
Used as As the lithium salt, LiBF₄, Li
ClO₄, LiPF₆, LiSbF₆, LiAsF₆,
LiCF₃SO₃, LiC (CF₃SO₂)₃, LiB
(C₆H₅)₄, LiC₄F₉SO₃, LiC₈F1 ₇
SO₃, LiB (C₆H₅)₄, LiN (CF₃S
O₂)₂And the like, in particular, in terms of electrical conductivity and stability.
From LiBF₄, LiClO₄, LiPF₆And Li
SbF₆Is preferred as the lithium salt.

The following non-aqueous electrolytes exhibit a large electric double layer capacity with respect to a porous carbonaceous material such as activated carbon. Therefore, these are used alone or in combination with the above lithium salt. be able to.

As the electrolyte, R ₄ N ⁺ , R ₄ P ⁺
(However, R is C _n H _{2n + 1} (preferably n = 1 to
R ₄ N ⁺ is particularly preferably (C ₂ H ₅ ) ₄ N ⁺ with n = 2. ), Quaternary onium cations such as triethylmethylammonium ion, and BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , SbF ₆ ⁻
Or CF ₃ SO ₃ ^- 1 or more kinds of substances selected anion and a salt which combines the like, such as.
In particular, the cation is preferably R ₄ N ⁺ (where R is C _n H _{2n + 1) in} terms of electrical conductivity, stability, and low cost.
(Preferably an alkyl group represented by n = 1 to 3) and / or triethylmethylammonium ion, wherein the anions are BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , and SbF
₆ ^- is a kind of salt a combination thereof are preferred.

The solute concentration in these non-aqueous electrolytes is adjusted so that the characteristics of the electrochemical capacitor can be sufficiently obtained regardless of whether a lithium salt or a quaternary onium salt is used alone or in a case where they are mixed. , 0.5-2.0
Mole / liter is preferred. That is, when charging and discharging at a low temperature of −20 ° C. or less, if the concentration exceeds 2.0 mol / liter, the electric conductivity of the electrolytic solution is undesirably reduced. vice versa,
If the concentration is less than 0.5 mol / liter, the electric conductivity is unfavorably low at both room temperature and low temperature. In particular, 0.7-
When the concentration is 1.9 mol / liter, high electric conductivity is obtained, which is preferable.

The solvent for the non-aqueous electrolyte is not particularly limited, but includes propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, sulfolane, methyl sulfolane, γ-butyrolactone, γ -An organic solvent comprising at least one selected from valerolactone, N-methyloxazolidinone, dimethylsulfoxide, and trimethylsulfoxide is preferable. Among them, electrochemical and chemical stability, from the viewpoint of excellent electrical conductivity, selected from propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, sulfolane, methyl sulfolane, γ-butyrolactone One or more organic solvents are particularly preferred. However, a high melting point solvent such as ethylene carbonate alone cannot be used because it becomes a solid at a low temperature, and must be a mixed solvent of propylene carbonate and a low melting point solvent.

The water content in the non-aqueous electrolyte is 200 ppm or less, and more preferably 50 ppm, so as to obtain a high withstand voltage.
It is preferable to set the following.

[0065]

The present invention will be specifically described below with reference to examples and comparative examples.

Example 1 A specific surface area of 1990 m ² / obtained by KOH-activating a carbonized phenol resin in a methanol solution of molybdenum pentachloride.
g of activated carbon powder (average particle size 9 μm), ultrasonic dispersion and stirring, then drying at 60 ° C.
Molybdenum oxide /
An activated carbon composite (hereinafter, referred to as MoO ₃ / C) was obtained.
MoO ₃ activated carbon (C) per 1g of _MoO 3 / C
Was 0.0001 mol, and the amount of MoO ₃ impregnated was 1.4% by weight based on 1 g of activated carbon.

Next, in order to measure the capacitance of the obtained MoO ₃ / C, MoO ₃ / C was uniformly dispersed in distilled water so as to be 2 g / liter. As a current collector, a glassy carbon rod whose surface was polished smoothly was used, and MoO ₃ / C was dropped to a predetermined amount of MoO ₃ / C,
After drying at 60 ° C., an ionomer (Nafion117) was added dropwise, followed by drying to prepare a sample electrode. For this sample electrode, a 1 mol / liter NaOH aqueous solution was used as an electrolytic solution, and the specific capacitance at 25 ° C. was measured by cyclic voltametry (reference electrode: Ag / AgCl, scan speed 50 mV / s, scan range 0. 2V to 1.2V vs. R
As a result, the specific capacitance of MoO ₃ / C was 182 F / g.

FIG. 1 shows the obtained cyclic voltammogram.

[0069] In Example 1, 0.00002 mol MoO ₃ supported amount of activated carbon (C) per 1g of _MoO 3 / C, is prepared sample was produced in the same manner except that a 0.3 wt% When the specific capacitance was measured in the same manner, the specific capacitance was 138.
F / g.

Comparative Example 1 In order to measure the capacitance of activated carbon powder (average particle size 9 μm) having a specific surface area of 1990 m ² / g obtained by activating KOH of the carbonized phenol resin used in Example 1, In the same manner as in 1, the activated carbon powder was uniformly dispersed in distilled water, then the activated carbon powder dispersion was dropped on a smooth polished glassy carbon rod, dried at 60 ° C., and ionomer (Nafion117) was dropped. The sample electrode was produced by drying. When the specific capacitance of this sample electrode was measured in the same manner as in Example 1, the specific capacitance of the activated carbon powder was 129 F / g.

FIG. 2 shows the obtained cyclic voltammogram.

From these results, it can be seen that the specific capacitance can be significantly increased by supporting the molybdenum compound on the porous carbonaceous material.

[0073]

As described in detail above, according to the present invention, an inexpensive and high-capacity electrode material for an electrochemical capacitor is provided.

Therefore, according to the electrode for an electrochemical capacitor of the present invention using such an electrode material for an electrochemical capacitor, it is possible to reduce the size, weight and capacity of various electronic devices while keeping the price down. The industrial utility is extremely large.

[Brief description of the drawings]

FIG. 1 is a cyclic voltammogram of an activated carbon electrode supporting 1.4% by weight of MoO ₃ in Example 1.

FIG. 2 is a cyclic voltammogram of an electrode using only activated carbon in Comparative Example 1.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takeshi Onuma 3-1-1, Tsuneta, Ueda-shi, Nagano Pref.

Claims (8)

[Claims] 1. An electrode material for an electrochemical capacitor mainly comprising a carbonaceous material, wherein the carbonaceous material is a porous carbonaceous material and contains a molybdenum compound. 2. The electrode material for an electrochemical capacitor according to claim 1, wherein the molybdenum compound is one or more molybdenum compounds selected from the group consisting of molybdenum oxide and molybdenum hydroxide. 3. The electrode material according to claim 1, wherein the content of the molybdenum compound in the electrode material is 1 × 10 ⁻⁶ to 1 × 10 ^{−3 in} terms of a molar fraction of molybdenum per 1 g of the carbonaceous substance.
An electrode material for an electrochemical capacitor, which is a mole. 4. The electrochemical capacitor according to claim 1, wherein the content of the molybdenum compound with respect to the carbonaceous substance in the electrode material is 0.05 to 30% by weight. Electrode material. 5. The porous carbonaceous material according to claim 1, wherein the specific surface area is 30 to 3000 m ² /
g, a porous carbonaceous material. 6. The porous carbonaceous material according to claim 1, wherein the porous carbonaceous substance is at least one selected from the group consisting of activated carbon, activated carbon fiber, carbon aerogel, and carbon black. An electrode material for an electrochemical capacitor, comprising: 7. The electrode material for an electrochemical capacitor according to claim 1, wherein the porous carbonaceous material is obtained by subjecting a carbonaceous raw material to an alkali activation treatment. 8. An electrode for an electrochemical capacitor using the electrode material for an electrochemical capacitor according to any one of claims 1 to 7.