JP7297383B2 - electrochemical capacitor - Google Patents

Description

The present invention relates to electrochemical capacitors. More particularly, it relates to an electrochemical capacitor suitably used as a hybrid capacitor and a positive electrode used to obtain the electrochemical capacitor.

Electrochemical capacitors (for example, electric double layer capacitors, hybrid capacitors represented by lithium ion capacitors, etc.) generally have a smaller capacity than secondary batteries, but have excellent output performance and high durability. It is attracting a great deal of attention as it is used as an auxiliary power source for hybrid vehicles, a regenerative power storage device, an alternative device for secondary batteries, and an energy buffer for photovoltaic power generation. In particular, research and development of hybrid capacitors, which have a relatively large capacity and generate an electromotive force between electrodes, are progressing rapidly.

For example, as a hybrid capacitor, an electrochemical capacitor is disclosed which has an activated carbon cloth electrode as a positive electrode, a zinc electrode as a negative electrode, and an alkaline hydroxide aqueous solution containing zinc oxide as an electrolyte (see, for example, Patent Document 1).
Zinc electrodes are excellent in safety because water can be used as the electrolyte, and the voltage that can be output and the amount of electric power per unit weight are high, and they are inexpensive.

JP-A-2008-66681

However, in the electrochemical capacitor described in Patent Document 1, hydrogen gas was generated from the zinc electrode during use, and the electrochemical capacitor could not be sealed. Prevention of human injury (chemical injury, etc.) and property damage (alkali contamination) due to electrolyte leakage, aging deterioration of electrochemical capacitors due to electrolyte evaporation, suppression of electrolyte concentration decrease due to atmospheric carbon dioxide contamination, etc. Therefore, there is room for improvement in order to make the electrochemical capacitor hermetically sealed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for sealing an electrochemical capacitor having a zinc electrode as a negative electrode.

As described above, the present inventors have studied various methods for sealing an electrochemical capacitor having a zinc electrode as a negative electrode, and found that the electrochemical capacitor includes a positive electrode, a zinc negative electrode, and a gas-permeable separator. and the positive electrode contains a hydrogen decomposition catalyst, hydrogen gas generated from the zinc negative electrode can be decomposed very favorably on the positive electrode side. The inventors of the present invention have found that the electrochemical capacitor can be hermetically sealed, conceived that the above problems can be solved admirably, and arrived at the present invention.

That is, the present invention is an electrochemical capacitor comprising a positive electrode, a zinc negative electrode, and a gas-permeable separator, wherein the positive electrode is an electrochemical capacitor containing a hydrogen decomposition catalyst.

According to the present invention, an electrochemical capacitor having the structure described above and including a zinc negative electrode can be hermetically sealed.

The present invention will be described in detail below.
A combination of two or more of the individual preferred embodiments of the invention described below is also a preferred embodiment of the invention.

<Electrochemical capacitor of the present invention>
The electrochemical capacitor of the present invention is an electrochemical capacitor comprising a positive electrode, a zinc negative electrode, and a gas-permeable separator, the positive electrode containing a hydrogen decomposition catalyst.

First, the mechanism by which hydrogen generated from the zinc negative electrode can be decomposed in the electrochemical capacitor of the present invention will be described.
The reaction near the zinc negative electrode in an electrochemical capacitor including a zinc negative electrode is represented by the following reaction formula.
Charge/discharge reaction: (charge) Zn+4OH ⁻ ⇔ Zn(OH) ₄ ²⁻ +2e ⁻ (discharge)
A zinc negative electrode tends to form an internal battery structure between zinc and impurities contained in the electrode. At that time, the following hydrogen generation reaction occurs in the vicinity of the impurities, and the discharge reaction of the above formula occurs on the zinc side.
Hydrogen evolution reaction: 2H ₂ O + 2e ^- → H ₂ + 2OH ^-

The electrochemical capacitor of the present invention includes a positive electrode, a zinc negative electrode, and a gas-permeable separator, and the positive electrode includes a hydrogen decomposition catalyst, so that hydrogen gas generated from the zinc negative electrode permeates the separator and decomposes the hydrogen decomposition catalyst. As it moves to the positive electrode side containing hydrogen, the positive electrode side causes the following hydrogen decomposition reaction as self-discharge. Gases can be decomposed very well.
Hydrogen decomposition reaction: H ₂ +2OH ⁻ →2H ₂ O+2e ⁻
Hydroxide ions (OH ⁻ ) generated by the hydrogen generation reaction are also naturally diffused in order to maintain an equilibrium state in an electrolyte such as an electrolytic solution, permeate the separator, and are supplied to the positive electrode side.
The positive electrode, separator, zinc negative electrode, and electrolyte that constitute the electrochemical capacitor of the present invention will be described below in order.

(positive electrode)
The positive electrode in the electrochemical capacitor of the present invention contains a hydrogen decomposition catalyst.
The hydrogen cracking catalyst is a catalyst for carrying out a hydrogen cracking reaction, and contains at least one element selected from the group consisting of Pt, Ru, Ir, Co, P, Ni, Fe, and Mn, for example. polycyclic compound having Fe or Co as a central metal; tungsten carbide with tantalum added; oxides, oxynitrides, and nitrides of group 4 and group 5 transition metals (e.g., zirconium) of the periodic table; hydrogen Alloys known as storage alloys (hydrogen storage alloys) and the like can be mentioned, and one or more of these can be used.

For example, the hydrogen cracking catalyst preferably contains at least one element selected from the group consisting of Pt, Ru, Ir, Co, P, Ni, Fe, and Mn. Among them, it is more preferable to contain Pt. Examples of those containing Pt include Pt alone, and alloys such as Pt--Cr, Pt--Co, Pt--Ni, and Pt--Fe, and one or more of these can be used. preferable.

The hydrogen cracking catalyst preferably contains a hydrogen storage alloy. As the hydrogen storage alloy _, conventionally known ones can _be used, and there is no particular limitation. AB ₅ types such as MmNi ₅ , which are mainly made of metal (Mm), A ₂ B ₇ types such as Ce ₂ Ni ₇ and Gd ₂ Ni ₇ , AB ₃ types such as CeNi ₃ , AB such as ZrMn ₂ and MgCu ₂ Type ₂ , AB type such as TiFe, and A ₂ B type such as Mg ₂ Ni are preferred. Among them, AB ₅ type, AB ₂ type, AB type and A ₂ B type are more preferable.

Among them, it is particularly preferable that the hydrogen decomposition catalyst is Pt alone and/or a hydrogen storage alloy.

The positive electrode active material is not particularly limited, and any material used as a positive electrode active material for an electrochemical capacitor can be used. Preference is given to using coalescence, among which activated carbon is preferred. In other words, the positive electrode is preferably a carbon electrode.
The positive electrode can be obtained by adding a binder, a conductive aid, a solvent, etc. to form a slurry, applying the slurry to a substrate, and drying the slurry. It can also be press-molded into pellets. The binder and conductive aid will be described later.

The content of the hydrogen decomposition catalyst is preferably 0.1% by mass or more with respect to 100% by mass of the positive electrode active material. The content is more preferably 0.5% by mass or more, still more preferably 1% by mass or more, and particularly preferably 2% by mass or more. The content is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 7% by mass or less.

(separator)
The separator according to the present invention is a member that separates the positive electrode and the zinc negative electrode, ensures ion conductivity between the positive electrode and the zinc negative electrode, and has gas permeability (hydrogen gas permeability).
The gas permeability means that the air permeability is 10000 seconds or less in terms of Gurley value, and hydrogen gas generated from the zinc negative electrode can sufficiently permeate. The Gurley value is preferably 9500 seconds or less.
The Gurley value is preferably 500 seconds or more, more preferably 1000 seconds or more.
The Gurley value is measured by the Gurley method described in Examples. The Gurley value is an index that expresses the ease with which gas can pass through.
In addition, when the separator is a laminate in which a plurality of layers are laminated, the Gurley value is the Gurley value measured for the laminate.

The separator may permeate the ions involved in the reaction of the electrochemical capacitor in the electrochemical capacitor and permeate hydrogen gas, for example, nonwoven fabric made of polyolefin; microporous membrane made of polyolefin; filter paper; Examples include anion-conducting membranes containing mixtures with inorganic compounds.

Among them, the separator is more preferably an anion conductive membrane from the viewpoint of extending the life of the electrochemical capacitor of the present invention.

The anion conductive membrane will be described below.
In the present specification, the anion conductive membrane is a membrane that allows the passage of anions such as hydroxide ions involved in the reaction of the electrochemical capacitor, and contains a polymer and an inorganic compound. The anion conductive membrane has selectivity for permeating anions due to the action of an inorganic compound or the like, which will be described later. The selectivity of the anions is such that anions such as hydroxide ions are easily permeable, and metal-containing ions (for example, Zn(OH) ₄ ²⁻ ) derived from the active material and having a large ionic radius even for anions Such permeation is sufficiently prevented. In the present specification, anion conductivity means sufficient permeation of anions having a small ionic radius such as hydroxide ions, or permeation performance of the anions. Anions having a large ionic radius, such as metal-containing ions, are more difficult to permeate, and may not be permeated at all.

〔polymer〕
Various polymers can be used as the polymer, and may be either thermoplastic or thermosetting. At least one selected from the group consisting of conjugated diene-based polymers, (meth)acrylic-based polymers, fluorine-containing ethylene-based polymers, polyolefin-based polymers, and polysulfone-based polymers. is preferred. The polymer preferably functions as a binder polymer.

The above polymer can be produced by copolymerizing monomer components that form the structural units contained in the polymer in the presence of a radical generator, and if necessary, by graft modification or the like.
The polymerization method of the monomer component is not particularly limited, and examples thereof include aqueous solution polymerization method, emulsion polymerization method, reverse phase suspension polymerization method, suspension polymerization method, solution polymerization method, bulk polymerization method and the like.

[Inorganic compound]
Although the inorganic compound is not particularly limited, for example, it is preferably at least one selected from the group consisting of oxides, hydroxides, layered double hydroxides, and phosphoric acid compounds. and/or layered double hydroxides are more preferred. In this specification, the hydroxide refers to a compound having a hydroxy group, other than the layered double hydroxide.

Examples of the hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, scandium hydroxide, yttrium hydroxide, lanthanide hydroxide, titanium hydroxide, water Zirconium oxide, niobium hydroxide, ruthenium hydroxide, nickel hydroxide, palladium hydroxide, copper hydroxide, cadmium hydroxide, boric acid, aluminum hydroxide, gallium hydroxide, indium hydroxide, thallium hydroxide, silicic acid, water Germanium oxide, tin hydroxide, lead hydroxide, phosphoric acid, bismuth hydroxide and the like can be mentioned, and one or more of these can be used. Among them, those having low solubility under alkaline conditions are preferable, and for example, magnesium hydroxide, calcium hydroxide, titanium hydroxide, and zirconium hydroxide are preferable, and magnesium hydroxide is more preferable.

The above layered double hydroxide has the following general formula:
[M ¹ _1-x M ² _x (OH) ₂ ](A ⁿ⁻ ) _x/n ·mH ₂ O
( ^M1 represents a divalent metal ion that is any of Mg, Fe, Zn, Ca, Li, Ni, Co, Cu, Mn; ^M2 represents Al, Fe, Mn, Co, Cr, In Represents a trivalent metal ion that is any ^{A n-} represents an anion having a valence of 1 or more and 3 or less, such as Cl ⁻ , NO ₃ ⁻ , CO ₃ ²⁻ , COO ^{− ,} etc. Among them, A ⁿ⁻ is , preferably represents a divalent or less anion, m is a number of 0 or more, n is a number of 1 or more and 3 or less, and x is a number of 0.20 or more and 0.40 or less.) Examples of such layered double hydroxides include hydrotalcite, manassite, motucoleite, stichtite, shoglenite, barbertite, pyroaurite, iomite, chloromagarminite, hydro Calmite, Green Rust 1, Bercherin, Takovite, Liebesite, Honesite, Yeardrite, Meikisenerite and the like can be mentioned, and one or more of these can be used. Among them, hydrotalcite in which ^M1 is Mg and ^M2 is Al in the above general formula is preferable because it is easy to use industrially.
These layered hydroxides are, for example, compounds dehydrated by firing at 150 ° C. or higher and 900 ° C. or lower, compounds in which anions in the layers are decomposed, anions in the layers to hydroxide ions, etc. It may be an exchanged compound.
A compound having a functional group such as a hydroxyl group, an amino group, a carboxy group, or a silanol group may be coordinated to the layered double hydroxide. Moreover, the layered double hydroxide may have an organic substance such as a polymer between the layers.

The inorganic compound is more preferably a hydroxide from the viewpoint of improving the strength of the separator, and a layered double hydroxide from the viewpoint of improving the ionic conductivity of the separator. is more preferable.

The above inorganic compound is in the form of particles, and examples thereof include fine powder, powder, granules, granules, flakes, polyhedrons, rods, curved surfaces, and the like.
The inorganic compound preferably has a volume average particle size of 2 μm or less. The volume average particle diameter is preferably 0.001 μm or more, more preferably 0.01 μm or more, and even more preferably 0.1 μm or more.
The volume average particle size is the average particle size in the volume-based particle size distribution, and the inorganic compound particles are diluted with a dispersion medium (ion-exchanged water containing 0.2% sodium hexametaphosphate) to obtain a diluted solution of about 10 mL is sampled in a glass cell, and this is measured using a particle size distribution analyzer (manufactured by Particle Sizing Systems, trade name: NICOMP Model 380) using the dynamic light scattering method.

Particles having a volume-average particle size in the above range can be obtained, for example, by pulverizing the particles with a ball mill or the like, dispersing the obtained coarse particles in a dispersant to obtain a desired particle size, and then drying and solidifying. In addition to the method of sieving the coarse particles to select the particle size, it is possible to obtain (nano)particles with the desired particle size by optimizing the preparation conditions at the stage of producing particles. .

The volume ratio of the polymer to the inorganic compound can be, for example, 1:99 to 99:1. The volume ratio is preferably 5:95 to 95:5, more preferably 10:90 to 90:10.

[Porous support]
When the separator is an anion conductive membrane, the separator further has a porous support (porous substrate) made of a polyolefin polymer or the like, and the porous support is a mixture of a polymer and an inorganic compound (resin composition) may be impregnated with a resin-impregnated layer. The separator can usually be obtained by coating a release substrate with a resin composition, contacting and impregnating a porous support with the resin composition, drying the film, and then peeling it off from the release substrate.

The mass ratio of the porous support is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more in 100% by mass of the separator. Moreover, the mass ratio is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[Other ingredients]
The separator may further contain other components such as conventionally known dispersants, thickeners, conductive carbon, and conductive ceramics.
From the viewpoint of strength of the separator, the content of other components in the separator is preferably 10% by mass or less in 100% by mass of the separator. It is more preferably 5% by mass or less, still more preferably 1% by mass or less, and particularly preferably 0.1% by mass or less.

The separator preferably has an average thickness of 10 μm to 1 mm. When the thickness is 10 μm or more, it is possible to sufficiently prevent the occurrence of breakage during film formation. In addition, if the thickness is 1 mm or less, it is advantageous in terms of cost, and the ability to transmit ions is sufficiently excellent. More preferably, the average film thickness is 20 μm or more. Moreover, the average film thickness is more preferably 500 μm or less.
The average film thickness is an average value obtained by measuring arbitrary 10 points using a Digimatic micrometer (manufactured by Mitutoyo Corporation).

(zinc anode)
The electrochemical capacitor of the present invention comprises a zinc negative electrode.
The above zinc negative electrode means one containing zinc alone or a zinc compound as a negative electrode active material. Any zinc compound can be used as long as it can be used as an active material. Hydroxy zinc alkali metal salt, tetrahydroxy zinc alkaline earth metal salt, zinc halogen compound, zinc carboxylate compound, zinc alloy, zinc solid solution, zinc borate, zinc phosphate, zinc hydrogen phosphate, zinc silicate, zinc aluminate - A zinc (alloy) compound having at least one element selected from the group consisting of elements belonging to groups 1 to 17 of the periodic table represented by carbonate compounds, hydrogen carbonate compounds, nitrate compounds, sulfate compounds, etc. Examples include organic zinc compounds and zinc compound salts. Among these, simple zinc and/or zinc oxide are preferred.

The positive electrode and the zinc negative electrode may contain, if necessary, a binder, a conductive aid, other components, etc. together with the active material in the active material layer.

Various known polymers can be used as the binder, and they may be either thermoplastic or thermosetting. Aromatic group-containing polymers such as hydrocarbon moiety-containing polymers and polystyrene; ether group-containing polymers such as alkylene glycol; hydroxyl group-containing polymers such as polyvinyl alcohol; amide bond-containing polymers such as polyamide and polyacrylamide; Polymer; carboxyl group-containing polymer such as poly(meth)acrylic acid; carboxylic acid group-containing polymer such as poly(meth)acrylate; sulfonate moiety-containing polymer; quaternary ammonium salt or quaternary phosphonium salt-containing polymer artificial rubbers such as styrene-butadiene rubber (SBR); sugars such as hydroxyalkylcellulose (e.g., hydroxyethylcellulose) and carboxymethylcellulose; amino group-containing polymers such as polyethyleneimine; . In addition, the said binder can be used by 1 type or 2 or more types.

The conductive aid is not particularly limited, but for example, one or more of conductive carbon, conductive ceramics, metals such as zinc, copper, brass, nickel, silver, bismuth, indium, lead, and tin. can be used.

The average thickness of the active material layer according to the present invention is preferably 100 μm or more, more preferably 200 μm or more, and even more preferably 500 μm or more. When used as , it is particularly preferably 1 mm or more from the viewpoint of suppressing dropout of the active material and constructing an electrochemical capacitor with a high energy density loaded with a large amount of active material. The average thickness of the active material layer is, for example, preferably 10 mm or less, more preferably 5 mm or less.
The average thickness of the active material layer can be calculated by arbitrarily measuring five points with a micrometer.

The electrode of the present invention preferably further contains a current collector.
Examples of the current collector include (electrolytic) copper foil, copper mesh (expanded metal), foamed copper, punched copper, copper alloys such as brass, brass foil, brass mesh (expanded metal), foamed brass, punched brass, and nickel foil. , corrosion-resistant nickel, nickel mesh (expanded metal), punching nickel, metallic zinc, corrosion-resistant metallic zinc, zinc foil, zinc mesh (expanded metal), (punched) steel plate, nonwoven fabric with conductivity; Ni Zn Sn Pb・Hg, Bi, In, Tl, brass, etc. added (electrolytic) copper foil ・Copper mesh (expanded metal) ・Foamed copper ・Punched copper ・Copper alloys such as brass ・Brass foil ・Brass mesh (expanded metal) ・Foam Brass, punched brass, nickel foil, corrosion-resistant nickel, nickel mesh (expanded metal), punched nickel, metallic zinc, corrosion-resistant metallic zinc, zinc foil, zinc mesh (expanded metal), (punched) steel plate, nonwoven fabric; Ni, Zn, Sn・(Electrolytic) copper foil plated with Pb, Hg, Bi, In, Tl, brass, etc. ・Copper mesh (expanded metal) ・Foamed copper ・Punched copper ・Copper alloys such as brass ・Brass foil ・Brass mesh (expanded metal) ), foamed brass, perforated brass, nickel foil, corrosion-resistant nickel, nickel mesh (expanded metal), punched nickel, metallic zinc, corrosion-resistant metallic zinc, zinc foil, zinc mesh (expanded metal), (punched) steel plate, non-woven fabric; silver; Examples include materials used as current collectors and containers for electrochemical capacitors.

(Electrolytes)
As the electrolyte used in the electrochemical capacitor of the present invention, a solid electrolyte may be used, but an electrolytic solution normally used as an electrolytic solution for an electrochemical capacitor (more preferably, a water-based electrolytic solution) can be preferably used. can. Examples of aqueous electrolytes include potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, zinc sulfate aqueous solution, zinc nitrate aqueous solution, zinc phosphate aqueous solution, zinc acetate aqueous solution and the like. Among these, alkaline electrolytes such as an aqueous potassium hydroxide solution, an aqueous sodium hydroxide solution, and an aqueous lithium hydroxide solution are preferred. One type or two or more types of electrolytes can be used in the aqueous electrolytic solution. The aqueous electrolytic solution may contain an organic solvent.

The electrochemical capacitor of the present invention includes a zinc negative electrode that causes an electrochemical reaction, and is also called a hybrid capacitor. Among others, the electrochemical capacitor of the present invention is preferably a hybrid capacitor including a carbon positive electrode.

The electrochemical capacitor of the present invention is preferably hermetically sealed. Since the electrochemical capacitor of the present invention is hermetically sealed, it is possible to suppress the evaporation of the electrolytic solution and the contamination of carbon dioxide in the atmosphere. For example, the reaction between carbon dioxide in the atmosphere and hydroxide ions in the electrolyte can be suppressed.

The electrochemical capacitor of the present invention can be manufactured by appropriately using known methods. For example, an electrochemical capacitor can be produced by disposing a zinc negative electrode in a cell, introducing an electrolyte solution into the cell, and further disposing a positive electrode, a reference electrode, a separator, etc. as necessary.

Since the electrochemical capacitor of the present invention can decompose hydrogen gas generated from the zinc negative electrode, it can be sealed, and is used as an auxiliary power source for hybrid vehicles, a regenerative power storage device, an alternative device for secondary batteries, and a photovoltaic power generation device. can be suitably used in many applications such as energy buffers for

<Positive electrode of the present invention>
The present invention also provides a positive electrode used to obtain an electrochemical capacitor comprising a positive electrode, a zinc negative electrode and a gas permeable separator, the positive electrode comprising a hydrogen decomposition catalyst, good too.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited only to these examples. Unless otherwise specified, "part" means "part by weight" and "%" means "% by mass".

Various measurements were performed by the following methods.
<Measurement of film thickness>
The average film thickness (μm) was calculated as the average value of arbitrarily measured five points using Digimatic Indicator 543-394 manufactured by Mitutoyo Corporation.

<Air Permeability>
According to JIS P 8117, the time required for 100 cc of air to permeate was measured using a Gurley measuring instrument.
<Average particle size>
Measured according to the method described above.

[Comparative Example 1]
An electrochemical capacitor (hybrid capacitor) is constructed by placing the following two electrodes in a positive electrode tank and a negative electrode tank holding the following electrolytic solution so as to be isolated from each other by the following separator, and sealing them with vacuum lamination. It was driven according to the driving conditions.

(separator)
Magnesium hydroxide (average particle diameter: 250 nm) is used as hydrophilic particles, and PTFE (average particle diameter: 300 nm) is used as hydrophobic particles. The dispersion is mixed in a volume ratio of 1:1 to form a slurry. bottom. The Gurley value was about 5000 seconds.

(positive electrode)
Activated carbon (specific surface area 1098 m ² /g), PTFE (polytetrafluoroethylene) emulsion (Nv [solid content] 60%) and water were mixed at a mass ratio of 20: 2: 50, and the slurry was applied on a nickel foil. It was created by applying to

(zinc anode)
Zinc and zinc oxide are mixed at a mass ratio of 1:1, and the mixed powder, PTFE emulsion (Nv 60%) and water are kneaded at a mass ratio of 40:2:10, made into a paste, and Sn-plated punching It was made by rolling a steel plate.

(Electrolyte)
KOH aqueous solution adjusted to 7 mol / L (ZnO saturated amount added)

(driving conditions, etc.)
Electrode size: 3 cm x 3 cm
Drive current: 1000mA (equivalent to 100C)
Stop condition: charge 1.5V, discharge 0.5V

When the above configuration was driven for 10,000 cycles, the cell expanded due to gas generation from the electrodes.

[Example 1]
When 5 wt % of Pt/C powder (manufactured by Wako Pure Chemical Industries, Ltd.) was added to the positive electrode with respect to the activated carbon, and other conditions were the same as in Comparative Example 1, the positive electrode did not expand even after 10,000 cycles.

[Example 2]
When 5 wt % of hydrogen storage alloy (AB ₅ type LaNi ₅ manufactured by Sigma-Aldrich Co.) was added to the positive electrode with respect to the activated carbon, and other conditions were the same as in Comparative Example 1, the positive electrode did not expand even after 10,000 cycles.

[Example 3]
5 wt % hydrogen storage alloy (AB ₂ type ZrMn ₂ , Sigma-Aldrich Co.) was added to the positive electrode with respect to the activated carbon.

[Example 4]
5 wt % hydrogen storage alloy (AB type TiFe, manufactured by Sigma-Aldrich Co.) was added to the positive electrode with respect to the activated carbon, and other conditions were the same as in Comparative Example 1, but the positive electrode did not expand even after 10,000 cycles.

[Example 5]
5% by weight of hydrogen storage alloy (A ₂ B type Mg ₂ Ni, manufactured by Sigma-Aldrich Co.) was added to the positive electrode with respect to the activated carbon. rice field.

From the results of the above examples, in an electrochemical capacitor comprising a positive electrode, a zinc negative electrode, and a gas-permeable separator, it is possible to seal the electrochemical capacitor by including a hydrogen decomposition catalyst in the positive electrode. It turned out to be

Claims (3)

An electrochemical capacitor comprising a positive electrode, a zinc negative electrode, a separator having an air permeability of 10000 seconds or less in terms of Gurley value, and an aqueous electrolytic solution containing a liquid alkaline electrolyte ,
The positive electrode comprises a positive electrode active material and a hydrogen decomposition catalyst comprising a hydrogen storage alloy,
The hydrocracking catalyst contains at least one element selected from the group consisting of Pt, Ru, Ir, Co, P, Ni, Fe, and Mn,
The content of the hydrogen storage alloy is 2% by mass or more and 20% by mass or less with respect to 100% by mass of the positive electrode active material.
An electrochemical capacitor characterized by: 2. The electrochemical capacitor of claim 1, wherein said electrochemical capacitor is hermetically sealed. A positive electrode used for obtaining an electrochemical capacitor comprising a positive electrode, a zinc negative electrode, a separator having an air permeability of 10,000 seconds or less in terms of Gurley value , and an aqueous electrolytic solution containing a liquid alkaline electrolyte. hand,
The positive electrode comprises a positive electrode active material and a hydrogen decomposition catalyst comprising a hydrogen storage alloy,
The hydrocracking catalyst contains at least one element selected from the group consisting of Pt, Ru, Ir, Co, P, Ni, Fe, and Mn,
The content of the hydrogen storage alloy is 2% by mass or more and 20% by mass or less with respect to 100% by mass of the positive electrode active material.
A positive electrode characterized by: