JP5882598B2 - Electrochemical capacitor - Google Patents

Description

  The present invention relates to an electrochemical capacitor. Specifically, the present invention relates to a flat electrochemical capacitor that can be used as a power source by repeating photocharging and discharging, and that has excellent flexibility.

  In recent years, in order to respond to social problems such as the depletion of fossil fuels as energy raw materials and the destruction of the global environment caused by carbon dioxide generated by the combustion, there is a need for a power supply means that uses sunlight as natural energy. Increasingly increasing.

  One of the means for directly converting sunlight into electric power is a solar cell, and the energy conversion efficiency of a so-called solid junction solar cell using a silicon crystal, an amorphous silicon thin film, or a multilayer thin film of a non-silicon compound semiconductor is improved. Research to improve it is actively conducted.

  However, solid-junction solar cells require a vacuum process or the like for manufacturing and are expensive, and recently, organic solar cells that are low in manufacturing cost and can realize high efficiency, particularly dye-sensitized solar cells. In particular, photoelectric conversion methods using a porous semiconductor film dye-sensitized for practical use have been proposed (for example, “Non-patent Document 1”, “Patent Document 1”, “Patent Document 2”). "reference.).

  In addition, “photocapacitor” has been devised as a photochargeable element in which a solar cell and a power storage element are integrated into a single element configuration, and its principle is disclosed (for example, “Non-Patent Document 2”, “ (See Non-Patent Document 3).) These photocapacitors use activated carbon as a power storage material and a conductive glass substrate as an electrode substrate, and have a function of electrostatic charging by an electric double layer, which is a feature of activated carbon, built in the element. However, since an element using a glass substrate is fragile and not flexible, the place where the glass substrate is installed is limited to a flat surface and cannot be installed on a curved surface or a surface whose shape changes. Moreover, since activated carbon is a black electricity storage layer, the element is opaque, and light can be used only from one direction where the substrate of the photoelectrode is disposed. In order to expand the application range of the element, it is desired to make the element light and flexible, and to make the element an optically transparent structure so that light incident from both sides of the flat element can be effectively used.

US Pat. No. 4,927,721 (claims, etc.) Japanese Patent No. 2664194 (Claims and others)

Nature, 1991, 353, p737-740. Applied Physics Letters, 2004, 85, 3932. Chemical Communications, 2005, p. 3346

  The present invention is a thin film electrochemical capacitor that can arbitrarily perform power generation, charging and discharging when necessary, is lightweight and flexible, and can use incident light on both sides by an optically transparent structure. An object of the present invention is to provide a (stacked optical capacitor) and an electrochemical capacitor adhesive sheet using the same.

  That is, the present invention provides an optically transparent internal counter electrode that carries an optically transparent dye-sensitized semiconductor layer and has a photovoltaic power generation capability, and an optically transparent internal counter electrode that is electrically joined thereto via a charge transport layer. A flat plate-shaped electrochemical capacitor in which an optically transparent external counter electrode that is electrically bonded to the internal counter electrode via an ionic electrolyte layer is sequentially laminated and integrated. Is in contact with the charge transport layer on one side of the both surfaces, is in contact with the ionic electrolyte layer carrying an optically transparent power storage active material on the other side, and the external counter electrode is optically transparent A material is supported and is in contact with the ionic electrolyte layer, and the electrochemical capacitor has a light transmittance of 16% or more in a visible light wavelength region, is flexible in mechanical characteristics, and includes the photoelectrode and the external counter electrode. Are connected by an external circuit. A positive charge to the power storage active material of the internal electrode by light irradiation the photoelectrode, charge respectively accumulated negative charge in the electricity storage active material of the outer counter electrode is to provide an electrochemical capacitor to be performed.

  Moreover, this invention provides the electrochemical capacitor adhesive sheet which further provided the adhesive layer or the adhesive bond layer in the said electrochemical capacitor.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a lightweight and flexible electrochemical capacitor capable of photovoltaic power generation, charging and discharging using incident light from both sides, and an electrochemical capacitor adhesive sheet using the same. .

It is an approximate solution sectional view of the example of basic composition of the electrochemical capacitor of the present invention.

  Next, the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited thereto.

  FIG. 1 is a schematic cross-sectional view showing a typical configuration example of the electrochemical capacitor of the present invention. In FIG. 1, two plate electrodes, that is, a photoelectrode I and an internal counter electrode II are laminated with the charge transport layer 1 interposed therebetween. The photoelectrode I, the charge transport layer 1, and the internal counter electrode II constitute a photovoltaic unit. Here, an ion electrolyte solution containing a redox agent or a solid hole transport material is used for the charge transport layer. The photoelectrode I is a photoelectrode constituted by a semiconductor layer 4 carried on an optically transparent transparent conductive substrate 3. The internal counter electrode II is composed of a chargeable storage active material layer 6 supported on an optically transparent transparent conductive substrate 5, and the storage active material layer 6 is on the opposite side of the charge transport layer 1. It is the structure supported by. An external counter electrode III made of an optically transparent substrate is opposed to and bonded to the internal counter electrode II with the ionic electrolyte layer 2 as an intermediate layer. The external counter electrode III carries a chargeable storage active material layer 8 on the surface of an optically transparent transparent conductive substrate 7 like the internal counter electrode. Here, the electricity storage active material layers 6 and 8 are formed of a thin film of optically transparent nanoparticles.

  Contact between the charge transport layer 1 and the ionic electrolyte layer 2 is physically completely blocked by the insertion of the internal electrode II. The charge transport layer 1 and the ionic electrolyte layer 2 include a separator (such as a porous film) for preventing an electrical short circuit between the opposing electrodes. In addition, an external circuit is coupled to each of the three conductive electrodes I, II, and III, and switches A, B, and C for opening and closing the circuits A, B, and C are provided.

  The thickness of the entire electrochemical capacitor of the present invention is not particularly limited, and can be, for example, about 1 mm to about 10 mm, about 1 mm to about 5 mm, or about 1.5 mm to about 3 mm. Of these, the thickness is preferably about 2 mm.

  In the electrochemical capacitor of the present invention, an adhesive layer or an adhesive layer may be provided on at least one outer surface of the transparent conductive substrate 3 or the transparent conductive substrate 7. These pressure-sensitive adhesive layers or adhesive layers are layers composed of conventionally known pressure-sensitive adhesives or adhesives. By providing the pressure-sensitive adhesive layer or the adhesive layer, the electrochemical photocapacitor can be easily installed on the surface of a window, a panel, a partition or the like.

  When an adhesive layer or an adhesive layer is provided, a release liner made of a known material may be provided on the outside thereof. The release liner protects the surface of the pressure-sensitive adhesive layer or the adhesive layer during the manufacturing process or transportation process of the electrochemical photocapacitor.

  Next, the operation principle of the electrochemical capacitor of the present invention will be described. In the capacitor according to the present invention, charge separation of electrons and holes is performed under light excitation in a light-sensitive electrode (hereinafter sometimes referred to as “photoelectrode”) that is excited to a base potential electrochemically by light absorption. Happens. The generated holes move to the internal counter electrode by the charge transport layer and are stored in the electricity storage active material layer 6 supported on the surface of the internal counter electrode. The charge transport layer is composed of an ionic electrolyte containing a redox agent or a hole transport material. The power storage active material layer 6 is a solid active material that accumulates charges by oxidation-reduction reaction, specifically, a metal oxide that stores power by changing the charge of the metal, or a redox state changes by ion doping. It is made of a polymer material that stores electricity.

  Electrons generated at the photoelectrode move to the external counter electrode through an external circuit, and are stored in the power storage active material layer 8 supported on the external counter electrode. The electricity storage active material layer 8 of the external counter electrode is composed of an active material similar to that of the electricity storage active material layer 6. In this way, a positive amount of electricity is charged on the inner counter electrode side and a negative amount of electricity is charged on the outer counter electrode side under light irradiation of the photoelectrode.

  Charging / discharging of the electrochemical capacitor of the present invention (hereinafter sometimes referred to as “photocapacitor”) is performed as follows. In charging, the circuits A and B in FIG. 1 are closed, the circuit C is opened, the circuits A to B connecting the photoelectrode I and the external counter electrode III are short-circuited, and the photoelectrode I is irradiated with light. By this light irradiation, a positive charge is accumulated in the internal counter electrode II and a negative charge is accumulated in the external counter electrode III, and charging proceeds (hereinafter, this process may be referred to as “photo charge”). Completion of photocharging can be known by the phenomenon that the charging current approaches zero as much as possible, and the open circuit voltage between the photoelectrode and the external counter electrode is saturated. In discharging, the element is placed in the dark, the circuit A is opened, the circuits B and C are closed, and discharging is performed with the internal counter electrode II and the external counter electrode III connected. At this time, a current passes through a load (resistor in FIG. 1) placed in the circuit C, and electrical work is performed here. The load means a target electric device or the like intended to be driven using the power of the charged optical capacitor. In the measurement of the discharge characteristics, the load resistance value is electrically controlled to measure a change in voltage under a condition where the discharge current is controlled to a constant discharge current, a so-called galvanostatic condition.

  When using an optical capacitor outdoors, where the amount of light changes significantly, various devices such as rectifiers, diodes, and switches are used in the circuit to prevent reverse current flow due to sudden changes in photocurrent during charging. Can be worn.

  As a semiconductor material of the semiconductor layer 4 carried on the photoelectrode, various materials such as an organic semiconductor and an inorganic semiconductor can be used. The semiconductor material may be crystalline or amorphous. Preferred is a crystalline inorganic semiconductor, and as the inorganic semiconductor material, a so-called compound semiconductor represented by a single semiconductor such as silicon or germanium, a metal oxide, and a metal chalcogenide (for example, sulfide, selenide, etc.) or A compound having a perovskite structure can be used. Among these, preferred are metal oxide and metal chalcogenide semiconductors.

The semiconductor material of the semiconductor layer 4 is preferably one in which fine particles are aggregated or porous. Such a porous membrane preferably has a surface roughness coefficient of 500 or more. Here, the surface roughness coefficient R (roughness factor) means the ratio of the actual surface area of the material to the apparent projected area. This ratio is represented by R = SM using the specific surface area S (m ² / g) of the material and the amount M (g / m ² ) of the material supported on the electrode substrate.

  Preferred examples of metal oxide and metal chalcogenide semiconductors include titanium, tin, zinc, iron, tungsten, zirconium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxides such as cadmium , Zinc, lead, silver, antimony, bismuth sulfide, cadmium, lead selenide, cadmium telluride, phosphide such as zinc, gallium, indium, cadmium, gallium arsenide, copper-indium-selenide, copper- Examples include indium sulfide.

Among the above semiconductors, a semiconductor preferably used in the present invention is an n-type metal oxide semiconductor, and for example, TiO ₂ , TiSrO ₃ , ZnO, Nb ₂ O ₃ , SnO ₂ , or WO ₃ is used. . Two or more of these oxide semiconductors may be combined and used as a semiconductor layer.

  When a semiconductor is used alone for the photoelectrode of the electrochemical capacitor of the present invention, the semiconductor is preferably an n-type semiconductor having at least light absorption in a visible light wavelength region of 400 nm or more. Specifically, it is an n-type semiconductor having an absorption rise corresponding to the band gap of the semiconductor in the visible light wavelength region of 400 nm or more, or a semiconductor sensitized to have photosensitivity at a wavelength of 400 nm or more. Is preferred. Visible light means light corresponding to a wavelength of 400 nm or more and 850 nm or less, and the photoelectrode of the capacitor of the present invention must absorb at least part of light in such a wavelength range. Examples of the semiconductor material that absorbs visible light alone include chalcogenide-based compound semiconductors such as cadmium sulfide, cadmium selenide, zinc sulfide, and zinc selenide.

  As the semiconductor layer 4 of the photoelectrode of the present invention, a porous semiconductor whose surface is coated with dye molecules and optically spectrally sensitized with the dye molecules is preferably used. Here, a mesoporous semiconductor thin film formed by bonding primary particles having a nano-sized average particle diameter is particularly effective for the porous semiconductor. The semiconductor particles constituting such a nanoporous semiconductor layer can have an average particle size of about 5 to about 100 nm, or about 10 to about 80 nm. The semiconductor layer 4 constituting the photoelectrode can have a thickness of about 5 μm to about 30 μm, or about 7 μm to about 20 μm. The porosity of the semiconductor layer 4 can be about 40% or more, or about 60% or more.

  When the semiconductor layer 4 is sensitized with a dye, various sensitizing dyes such as an organic dye molecule and a metal complex dye molecule are used as the sensitizing dye molecule coated on the porous semiconductor. Examples of such dyes include organic dyes such as cyanine, merocyanine, oxonol, rhodamine, indolenine, xanthene, squarylium, polymethine, coumarin, riboflavin and perylene, Ru complexes and metals. There are complex dyes such as phthalocyanine derivatives, metal porphyrin derivatives, and chlorophyll derivatives. In addition, synthetic dyes and natural dyes described in “Functional Materials”, June 2003, P5-18, “J. Chem. Phys.”, 2003, B No. Organic dyes centered on coumarin described in Vol. 107, P597 can also be used.

  In addition to the inorganic semiconductor material and dye-sensitized semiconductor material described above, an organic semiconductor material that absorbs visible light and an organic conductive material can be used for the semiconductor layer 4. Examples of organic semiconductors include merocyanine dyes, cyanine dyes and their J aggregates, coumarin dyes, polyene dyes, metal phthalocyanine and its derivatives, porphyrin and its derivatives, perylene and its derivatives, etc. It is done. Examples of the organic conductive material include polymers such as polyaniline, polypyrrole, polyacene, polythiophene and derivatives thereof, poly (p-phenylene) and derivatives thereof, poly (p-phenylene vinylene) and derivatives thereof, and polytoluidine and derivatives thereof. Conductive polymers such as fullerene and derivatives thereof can be used. These organic conductive materials can be used with a function as a hole transport material in addition to photosensitivity.

  The material constituting the storage active material layer used for the internal counter electrode and the external counter electrode of the electrochemical capacitor of the present invention (hereinafter sometimes referred to as “storage material”) is a common type of material for the internal counter electrode and the external counter electrode. It may be a different material.

  Here, a power storage active material that has redox activity and can store electric energy by a redox reaction, that is, a Faraday reaction, is used as the power storage material for the internal counter electrode and the external counter electrode.

  As an electricity storage material for storing electric charge in the electricity storage active material layer by an oxidation-reduction reaction, that is, a Faraday reaction, various electrode active materials of inorganic materials and organic materials can be used. Examples of the inorganic electrode active material include carbon materials such as graphite, mesophase pitch, fibrous carbon, and carbon nanotube, and these give activity by insertion of a cation or anion and an oxidation-reduction reaction. In addition, polyvalent metal oxides such as ruthenium, iridium, nickel, tin, cobalt, vanadium, zirconium, titanium, manganese, and tungsten, transition metal oxides, metal sulfides, and the like can also be used as the electrode active material. As the organic electrode active material, for example, conductive polymers such as polyaniline, polypyrrole, polyacene, polythiophene, and polyindole and derivatives thereof, polyquinoxaline and derivatives thereof, organic charge transfer complexes and oligomers thereof, and the like can be used. . These electrode active materials can be carried on one or both of the internal counter electrode and the external counter electrode. Moreover, these electrode active materials can also be used by mixing with a carbon material for the electric double layer electricity storage layer.

  In the case of using a metal oxide for the power storage material, it is preferable to use an oxide selected from ruthenium, nickel, and manganese and a mixture thereof from the viewpoint of providing a high charge capacity. In terms of charge capacity, a material that can achieve a high charge accumulation amount within a voltage range of 1 V that is close to the upper limit of the generated voltage at which the dye-sensitized porous semiconductor can be produced is preferable. Moreover, the material which can give the thin film with a high light transmittance at the point of optical transparency is preferable. From these points, the ruthenium oxide is particularly preferable because it is light-transmitted and has a high charge capacity per unit weight.

  Various binders can be added to the electricity storage active material layer constituting the internal electrode and the external counter electrode for the purpose of fixing the layer. As the binder, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, polytrifluoroethylene chloride, isoprene rubber, butadiene rubber, ethylene-propylene rubber, nitrile rubber, butadiene rubber, Examples include chloroprene rubber, acrylonitrile-butadiene-styrene copolymer, polyester, polyamide, and polycarbonate.

  In the electrochemical capacitor of the present invention, an ionic electrolyte containing a redox compound can be used for the charge transport layer 1 in contact with the semiconductor layer 4. These include, for example, liquid electrolytes using volatile organic solvents, liquid electrolytes using non-volatile ionic liquids (room temperature molten salts), high viscosity quasi-solid electrolytes using polymer electrolytes and polymer gels, inorganic and organic Quasi-solid electrolyte containing a fine particle or nanoparticle dispersion as a matrix. Also. Various organic and inorganic solid conductive materials capable of moving holes (positive charges) can also be used for the charge transport layer.

As a redox agent to be contained in these liquid and quasi-solid electrolytes, a combination of I ₂ and iodide (as iodide, metal iodide such as LiI, NaI, KI, tetraalkylammonium iodide, pyridinium iodide, etc.) Electrolyte solution containing quaternary ammonium compounds such as imidazolium iodide, combinations of Br ₂ and bromides (metal bromides such as LiBr, NaBr and KBr as bromides, or tetraalkylammonium bromides and pyridinium bromides) In addition to electrolyte solutions containing quaternary ammonium compound bromine salts, etc., metal complexes such as ferrocyanate-ferricyanate and ferrocene-ferricinium ions, sulfur compounds such as sodium polysulfide, etc. may be used. it can. Among these, an electrolyte in which an iodine salt of a quaternary ammonium compound such as I ₂ and LiI, pyridinium iodide, imidazolium iodide or the like is combined is preferable in terms of obtaining high performance.

  Examples of the organic solvent used in the ionic liquid electrolyte containing the redox compound include carbonate compounds such as ethylene carbonate and propylene carbonate, alcohols including ethylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, ethylene glycol, Polyhydric alcohols such as polyethylene glycol, polypropylene glycol, glycerin, ethers such as dioxane, ethylene glycol dialkyl ether, polyethylene glycol dialkyl ether, γ-butyrolactone, α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, Lactones such as γ-valerolactone, 3-methyl-γ-valerolactone, acetonitrile, methoxyacetonitrile, propionite Le, nitrile compounds such as benzonitrile and aprotic polar substances such as dimethylsulfoxide are used. These may be used alone or in combination of two or more.

  The non-volatile ionic liquid (room temperature molten salt) includes various alkyl imidazolium salts such as dimethyl imidazolium, methyl propyl imidazolium, methyl butyl imidazolium, methyl hexyl imidazolium and its boron tetrafluoride salt, trifluoride. Methanesulfonylimide salt, iodide and the like. In addition, pyridinium salts, imidazolium salts, triazolium salts, and the like can also be used. These molten salts are the functional materials November 2004 issue (CMC Publishing), supervised by Hiroyuki Ohno, ionic liquids-the forefront and future of development (CMC Publishing, 2003), JP 2002-190323 A Also, known molten salts described in JP 2001-199961 A, JP 2001-196105 A, and the like can be used.

  When a hole transport material is used for the charge transport layer 1, organic, inorganic, or a solid hole transport material that combines both can be used. Organic hole transport materials include aromatic amines, oligothiophene compounds, and other polymer compounds such as polyvinyl carbazole, polypyrrole, polyacetylene and derivatives thereof, poly (p-phenylene) and derivatives thereof, and poly (p-phenylene). Vinylene) and derivatives thereof, polythienylene vinylene and derivatives thereof, polythiophene and derivatives thereof, polyaniline and derivatives thereof, polytoluidine and derivatives thereof, polysilane and derivatives thereof, and the like can also be used. Moreover, the various hole transport materials used for the hole transport layer of an organic EL element including said compound can be used.

As the inorganic hole transport material, a p-type inorganic compound semiconductor can be used. A preferable p-type inorganic compound semiconductor is a compound semiconductor containing monovalent copper, and examples of the compound semiconductor containing monovalent copper include CuI, CuSCN, CuInSe ₂ , Cu (In, Ga) Se ₂ , CuGaSe ₂ , Cu. _{2 O,} CuS, and the like _{CuGaS 2, CuInS 2, CuAlSe 2} . Among these, CuI and CuSCN are preferable, and CuI is most preferable. As other p-type inorganic compound semiconductors, GaP, NiO, CoO, FeO, Bi ₂ O ₃ , MoO ₂ , Cr ₂ O _{3 and the} like can be used.

  The electrolytic solution used for the ionic electrolyte layer used between the internal counter electrode and the external counter electrode in the electrochemical capacitor of the present invention is not particularly limited, and is an organic electrolyte, an aqueous electrolyte, a molten salt electrolyte, or a polymer electrolyte. Various electrolyte solutions that can be used for electrochemical capacitors are used. As the aqueous electrolyte solution, various acid solutions, aqueous salt solutions, and alkaline aqueous solutions containing ammonium salts can be used.

  When an organic electrolytic solution is used for the ionic electrolyte layer, the organic solvent is not particularly limited. For example, carbonates such as dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, acetonitrile, propionitrile Nitriles such as γ-butyrolactone, α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone, lactones such as 3-methyl-γ-valerolactone, dimethyl sulfoxide, diethyl sulfoxide, etc. Examples thereof include sulfoxides, amides such as dimethylformamide and diethylformamide, ethers such as tetrahydrofuran and dimethoxyethane, dimethylsulfolane and sulfolane. These organic solvents can also be used as a 1 type, or 2 or more types of mixed solvent.

  In the case of using an aqueous electrolyte, for example, an acid such as sulfuric acid or hydrochloric acid, a base such as potassium hydroxide, or a salt thereof can be used. In this case, it is preferable to use an aqueous solution of at least one lanthanoid element salt having excellent charge / discharge characteristics under a high current density as an electrolyte in the presence of an acid.

  It is preferable that the ionic electrolyte layer sandwiched between the internal counter electrode and the external counter electrode of the electrochemical capacitor of the present invention does not contain an oxidation-reduction active compound except for the substance constituting the solvent. That is, the ionic electrolyte layer is preferably composed only of an electrochemically stable supporting salt and a polar solvent that dissolves the supporting salt. However, the supporting salt and the polar solvent serve to assist the redox reaction of charge / discharge by a part of the ion species given as a result of the ionization involved in the redox equilibrium reaction of the power storage active material that performs power storage. Take on. For example, when water is used as a polar solvent, hydrogen ions may be involved in a redox equilibrium reaction of metal ions in the metal oxide by addition and desorption from the metal oxide as the active material. .

  An optically transparent material is used as a conductive material used for the transparent conductive substrate of the photoelectrode, internal counter electrode, and external counter electrode of the electrochemical capacitor of the present invention. As such a conductive material, an opaque material such as a metal (aluminum, stainless steel, titanium, copper, or the like) or a carbon material can be used as a mesh pattern. A uniform thin film of a transparent conductive film material including tin oxide, indium tin oxide (ITO), zinc oxide, and the like can also be used. In addition, a thin film of a polymer material having high conductivity can be used. Examples of such a polymer include polyacetylene-based, polypyrrole-based, polythiophene-based, and polyphenylene vinylene-based polymers. Etc. are used. The surface resistance of these transparent conductive films is preferably 15Ω / □ or less, more preferably 5Ω / □ or less, and most preferably 1Ω / □ or less.

  As the transparent conductive substrates 3, 5, and 7 for the photoelectrode, the internal counter electrode, and the external counter electrode, optically transparent flat plate materials are used. The light transmittance of the transparent conductive substrate needs to exceed at least 80%, and a colorless and transparent substrate exceeding 90% is particularly preferable.

  The transparent conductive substrates 3, 5, and 7 are mechanically flexible. By doing so, the electrochemical capacitor of the present invention can be made flexible so that it can be mechanically bent and turned.

  As such a transparent conductive substrate, for example, a plastic film or a glass film can be used. A plastic film is particularly preferable. The transparent conductive substrate has a uniform thickness, and the thickness is preferably about 500 μm or less, or about 200 μm or less.

  For the plastic film, a material that is not colored and highly transparent, is excellent in heat resistance, chemical resistance and gas barrier properties, and is low cost is preferably selected. From this point of view, as plastic materials, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polystyrene (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PAr), polysulfone (PSF) Polyestersulfone (PES), polyetherimide (PEI), transparent polyimide (PI), and the like can be used. Particularly preferably used in the present invention is polyethylene terephthalate (PET) or polyethylene naphthalate (PEN).

  In the electrochemical capacitor of the present invention, a layered separator can be provided on the charge transport layer 1 and the ionic electrolyte layer 2 for the purpose of preventing a short circuit between the electrodes. This separator is inserted by being impregnated with an electrolytic solution. When the separator is provided, the charge transport layer 1 and the ionic electrolyte layer 2 are each integrated with the separator, and therefore the thicknesses of these layers are substantially equal to the thickness of the separator.

  The material forming the separator is an electrically insulating material, and the shape thereof may be either a film shape or a particle shape, but it is preferable to use a film-like separator. Examples of the film-like material include a porous resin film used for a filter and a film made of a fibrous polymer material. As the fibrous polymer material, a resin nonwoven fabric such as a polypropylene nonwoven fabric can be used. In addition, well-known materials such as a microporous membrane made of polyolefin such as polyethylene and polypropylene, and a porous membrane mainly made of pulp called electrolytic capacitor paper can be used. These separators can be subjected to hydrophilic treatment and hydrophobic treatment on the surface according to the purpose.

  When a film separator is used, the thickness is about 80 μm or less, preferably about 5 to about 50 μm, more preferably about 5 to about 25 μm. In this case, it is preferable to use a film having a porosity of about 40 to about 85%.

  The electrochemical capacitor of the present invention has a light transmittance of 16% or more in the visible light wavelength region. The wavelength region of visible light refers to a wavelength region of 400 nm or more and 850 nm or less. By including a dye that absorbs light in such a wavelength region in the photoelectrode, the above light transmittance can be obtained.

  The electrochemical capacitor of the present invention can also be referred to as a photovoltaic cell, and can be charged in the dark and discharged in the dark without the use of external power. And can be repeatedly charged and discharged.

  Since the electrochemical capacitor of the present invention is a lightweight and flexible sheet or film, it can be installed on various surfaces including curved surfaces. Furthermore, since it is optically transparent and has a design property by a pigment, it can be mounted on a window, a panel, or the like that requires transparency or design property.

  Furthermore, by providing a pressure-sensitive adhesive layer or an adhesive layer on at least one outermost layer of the electrochemical capacitor of the present invention, it can be used as an electrochemical capacitor pressure-sensitive adhesive sheet that can be easily mounted on a window, a panel, or the like.

Example 1
1. Production of photocapacitor using plastic substrate (1) Production of photoelectrode Titanium dioxide nanoparticles (catalyst conversion, average particle size of 15 nm) were mixed with tert-butyl alcohol (purity 99.5% or more) and acetonitrile (purity 99.5% or more). ) 30 g in 100 ml of a mixed solvent (mass ratio 95: 5) is stirred and dispersed. In this dispersion, titanium dioxide particles having a particle diameter of 5 nm are dispersed in a mixed solvent of water and ethyl alcohol (mass ratio 50:50). A sol liquid (concentration: 8% by mass) was added by 10% by mass, and the obtained mixed dispersion was uniformly mixed using a rotating / revolving mixing conditioner to prepare a viscous paste. This titania paste is screen-printed on the IZO surface of a transparent conductive polyethylene naphthalate (IZO-PEN) film (thickness 200 μm, surface resistance 10Ω / □) coated with an indium-zinc oxide (IZO) conductive film on one side. It was applied by the method and dried at 150 ° C. for 10 minutes to form a porous titanium dioxide particle layer having an average thickness of 5 μm on the IZO-PEN substrate. This porous titanium dioxide-coated IZO-PEN film was immersed at 40 ° C. for 30 minutes in an acetonitrile-tert-butanol (1: 1) mixed solution in which an indolenine dye (trade name: D149, manufactured by Chemicrea) was dissolved as a dye. The titanium dioxide film was dye-sensitized to obtain a flexible photoelectrode on the film. For comparison experiments, a photoelectrode was also prepared which was made up of only a titanium dioxide layer and was not subjected to dye sensitization.
(2) Production of internal counter electrode A conductive PEN film substrate (thickness: 200 μm) in which a stainless steel mesh with a thickness of 10 μm, a line width of 25 μm, and a spacing of 75 μm is embedded on both sides of the film by mechanical press Prepared as an electrode support. One side of the internal electrode was coated by vacuum deposition using a platinum ultrathin film having a thickness of 3 nm as a catalyst. The other surface was coated with a thin film containing a ruthenium oxide (RuO ₂ ) nanosheet as a nanosize active material. This RuO ₂ nanosheet was produced by the synthesis method disclosed in Japanese Patent Application Laid-Open No. 2004-315347. In thin film production, the liquid in which the nanosheets are dispersed is mixed with an N-methylpyrrolidone solution in which polyvinylidene fluoride (PVDF) is dispersed as a resin binder, and spherical alumina particles for forming a porous structure. Prepared. This coating solution was applied onto the above film substrate and dried at 150 ° C. for 10 minutes to coat a porous film containing a RuO ₂ nanosheet as a storage active material. The thickness of the porous film was about 10 μm, and the degree of coloration and light transmittance depended on the concentration of RuO ₂ , but it became translucent when the concentration was low. As described above, a translucent flexible intermediate electrode having both surfaces coated with the catalyst and the electricity storage active material was produced.
(3) Production of external counter electrode Porous film containing RuO ₂ nanosheet as an active material for electricity storage on the same surface as the intermediate electrode by using the same IZO-PEN film as the substrate used in the internal counter electrode Was coated to prepare an external counter electrode. The thickness of the porous film was about 10 μm. The amount of the active material carried by the external counter electrode was made equal to the amount of the active material carried by the internal counter electrode.
(4) Photocapacitor assembly An organic electrolyte (iodine 0.05M, lithium iodide 0.1M, 4-tert-butylpyridine 0) using iodine and iodine ions as a redox agent and propyl carbonate as a solvent as a charge transport layer. .5M) was used. Moreover, 1M sulfuric acid aqueous solution was used as an ionic electrolyte used between an intermediate electrode and an external electrode. A hydrophilic cellulose filter (thickness 20 μm, porosity 70%) was used as a separator film for short circuit prevention used between the intermediate electrode and the external electrode. The element on the flat plate which piled up the three film-form electrode substrates according to the laminated structure of FIG. 1 was assembled, and the circumference | surroundings of the electrode were sealed using the thermocompression-bonding sealing material.

Each of the above electrolytes was injected into a gap (20 μm) between the electrodes through small holes provided in advance in the photoelectrode and the external electrode. An organic electrolyte containing iodine and iodine ions was injected between the photoelectrode and the internal counter electrode, and an aqueous sulfuric acid solution was injected between the internal counter electrode and the external counter electrode. Finally, a small hole was sealed, and a thin plate-like optical capacitor a having a thickness of about 840 μm and an effective light receiving area of light irradiation of 4 cm ² was produced. This capacitor is a flexible element that can be bent mechanically, and when the light transmittance was measured, the light transmittance was 14% at a wavelength of 600 nm and 24% at 700 nm. The element body became a translucent element with a reddish brown color. As a comparative experiment, a capacitor produced using titanium dioxide not subjected to dye sensitization was designated as b, a capacitor not carrying an active material on the internal counter electrode was designated as c, and a capacitor not carrying an active material on the external counter electrode was designated as d.
Example 2
2. Production of Optical Capacitor Using Various Metal Oxides for Storage Active Material In Example 1, except that RuO ₂ was used for the storage active material, a mixture of MnO ₂ , Ni oxide and Co oxide was used. In the same manner as in Example 1, PVDF was used as a binder to produce an intermediate electrode and an external electrode, and photo capacitors e to f were produced.
Example 3
As a charge transport layer in contact with the photoelectrode, an iodine-doped polyvinyl carbazole thin film (thickness 0.6 μm) was used as a solid polymer hole transport agent instead of the iodine-based redox electrolyte used in Examples 1 and 2. An optical capacitor g was produced according to Example 1 except that it was used. The method of coating iodine-doped polyvinylcarbazole on a dye-sensitized porous titanium oxide film was in accordance with the literature (N. Ikeda and T. Miyasaka, Chem. Comm., 1886-1888 (2005)).
3. Measurement of Photocharge Performance Charge / discharge experiments of the photocapacitors assembled in Examples 1 to 3 were carried out as follows to evaluate the ability of photocharge. The photoelectrode and the external counter electrode were connected and short-circuited by an external circuit, and the interelectrode voltage was set to zero. Next, using an artificial solar light source (solar simulator) using a 500 W xenon lamp and an Air Mass 1.5 (AM1.5) filter, white light of 100 mW / cm ² is applied to the capacitor. Irradiated to the photoelectrode side. During this irradiation, an anode photocurrent was generated in the shunted external circuit indicating electron injection into the photoelectrode and electron flow from the photoelectrode to the external counter electrode. When the photocurrent 5 seconds after the start of irradiation was measured as the initial charge current and the light irradiation was continued in the state of the shunt circuit, the photocurrent tended to decrease with the irradiation time. Moreover, when the open-circuit electromotive force was measured during the irradiation process, a phenomenon in which the voltage of the external counter electrode changed more negatively with respect to the photoelectrode with the irradiation time was observed. That is, charging progressed due to the accumulation of negative charges on the external counter electrode due to light irradiation. After light irradiation was continued and photocharging was performed for 30 minutes, the circuit was opened under light irradiation, and the charging voltage was measured.

In discharging, the capacitor was placed in the dark, the external circuit was closed, and discharging was performed at a constant current density of 0.03 mA / cm ² using a charge / discharge control device (Toho Giken Multipotentiostat PS-08) (constant current). Current discharge conditions). A characteristic of voltage drop with discharge time was observed. The discharge end voltage was set to 0 V, and after constant current discharge was reached and reached 0 V, the discharge current was decreased to maintain 0 V (constant voltage discharge condition). The amount of electricity (mC / cm ² ) per unit electrode area released by this discharge was measured and used as the discharge capacity. The results are shown in Table 1.
Example 4
Instead of the case where the light irradiation was performed on one side of the plate-shaped optical capacitor as in the above method, the light irradiation using the artificial solar light source was performed on both sides of the plate-shaped optical capacitor. The photocharging by this double-sided light irradiation (capacitor h) was performed using the photocapacitor having the configuration of Example 1, and the photocharged amounts were compared. The results are shown in Table 1.

  As an integrated solar cell capable of storing electricity, it can be widely used for electric energy supply.

DESCRIPTION OF SYMBOLS 1 Charge transport layer 2 Ionic electrolyte layer 3 Transparent conductive substrate 4 Semiconductor layer 5 Transparent conductive substrate 6 Power storage active material layer 7 Transparent conductive substrate 8 Power storage active material layer

Claims (3)

A photoelectrode carrying an optically transparent dye-sensitized semiconductor layer and having a photovoltaic capacity, an optically transparent internal counter electrode electrically connected to the photoelectrode via a charge transport layer, and the internal counter electrode A plate-like electrochemical capacitor in which optically transparent external counter electrodes that are electrically joined to each other through an ionic electrolyte layer are sequentially laminated and integrated.
The internal counter electrode is in contact with the charge transport layer on one side of the both surfaces, and on the other side, carries an optically transparent power storage active material composed of metal oxide nanoparticles selected from ruthenium oxide and manganese oxide. In contact with the ionic electrolyte layer,
The external counter electrode carries an optically transparent power storage active material and is in contact with the ionic electrolyte layer;
The electrochemical capacitor has a light transmittance of 16% or more in a visible light wavelength region;
Flexible in mechanical properties,
The photoelectrode, the internal counter electrode, and the external counter electrode each include a transparent conductive substrate as a component,
By connecting the photoelectrode and the external counter electrode with an external circuit and irradiating the photoelectrode with light, a positive charge is accumulated in the storage active material of the internal counter electrode, and a negative charge is accumulated in the storage active material of the external counter electrode, respectively. Electrochemical capacitors that are charged by The electrochemical capacitor according to claim 1, wherein the electricity storage active material is a nanosheet-like electricity storage active material made of ruthenium oxide nanoparticles . The electrochemical capacitor according to claim 1, wherein each of the transparent conductive substrates is an optically transparent conductive plastic film.