JP2005223089A - Composite electrode material for redox capacitor and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive new electrode material for a redox capacitor with a high specific capacity, high output density, high energy density, and high stability, and to provide a manufacturing method of the material. <P>SOLUTION: The electrode material for the redox capacitor includes a nano structure which is composed of an oxide of a metal selected from among manganese, tungsten, vanadium and tin, and whose size is 50nm or less, and a porous object of a conductive polymer. The electrode material is manufactured by a method including a process for setting a water solution which contains a monomer of a conductive polymer to be an electrolyte, and electro-depositing the porous object of the conductive polymer by a potential scanning electrodeposition method with 70 mV/s or more of potential scanning speed; and a process for setting the water solution of a compound containing the metal to be an electrolyte, and electro-depositing the nano structure composed of an oxide of the metal by the potential scanning electrodeposition method with 70 mV/s or more of potential scanning speed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel composite electrode material for a redox capacitor having a high specific capacity, a high output density, a high energy density, a high stability, and a low cost, and a manufacturing method thereof.

  In recent years, a power storage device called an electrochemical supercapacitor, which has a power density about 100 to 1000 times higher than that of a normal capacitor and has excellent reversibility, has attracted attention. Due to its characteristics, this supercapacitor has already been used and is expected to be used for load leveling of hybrid vehicle batteries and for memory backup. For example, in a hybrid vehicle, the secondary battery is used for supplying energy during normal driving, while the supercapacitor is used for supplying rapid energy during acceleration and climbing.

Supercapacitors are usually classified into two types based on their mechanism. That is, (1) an electric double layer capacitor (ELDC) using electrostatic capacitance (capacitance) generated by a polarization phenomenon at the electrode / electrolyte interface, and (2) charge transfer simulation generated by a reversible Faraday reaction generated on the electrode surface. This is a redox capacitor using a capacitance. Since the specific capacity of ELDC is in principle proportional to the specific surface area of the electrode that can contact the electrolyte, a carbon material having a high specific surface area (about 2000 m ² / g or more) is usually used as the electrode material. However, since the specific surface area of the electrode material is limited, the specific capacity is about 200 F / g at most.

On the other hand, the specific capacity of the redox capacitor is considered to be due to a reversible redox change of the electrode material. As the electrode material, metal oxides and conductive polymers having various oxidation states are used, and the use is being studied. . For example, RuO ₂ is highly reversible, exhibits excellent charge / discharge characteristics, and has a high specific capacity of 720 F / g in an acidic aqueous electrolyte such as sulfuric acid. However, although RuO ₂ has a high specific capacity, it has a disadvantage that the material is expensive and has toxicity.

In recent years, various metal oxides such as manganese oxide, nickel oxide, tin oxide, molybdenum oxide, indium oxide, titanium oxide, and vanadium oxide have been used as low-cost electrode materials to replace RuO _2. As discussed in Patent Documents 1 and 2, and Patent Documents 1 and 2. Of these, manganese oxide is reported to exhibit a relatively high specific capacity, and in particular, manganese oxide obtained by electrochemical deposition is 230 F / g (0.1 M, 25 mV / s in aqueous sodium sulfate solution). (Capacitance) of the potential scanning speed). (Non-Patent Document 2)
These metal oxide electrode materials have lower material costs than RuO ₂ electrode materials and have the advantage that the electrolyte can be used in a neutral solution, but are still insufficient in terms of capacity. . Therefore, higher specific capacity is required, and at the same time, high output density, high energy density, and high stability are also required.

  Conductive polymers are also known as electrode materials for redox capacitors, and polyaniline obtained by electrochemical deposition may have a specific capacity of 70 F / g (in 1M perchloric acid + 3M sodium perchlorate solution). It has been reported. (Non-patent Document 3) However, this specific capacity is a value of a redox capacitor having an acidic electrolytic solution, and a neutral electrolytic solution advantageous in use shows a lower specific capacity due to the low electrochemical activity of polyaniline. Absent.

Furthermore, Patent Document 3 discloses a composite electrode material for a redox capacitor in which the surface of a metal oxide electrode material such as manganese is coated with a conductive polymer by chemical or electrochemical means. The manufacturing method of the metal oxide used here is not clear, and the specific capacity of the electrode material achieved is as high as 685 F / g. However, the evaluation method, particularly the potential scanning speed, is unknown, Cannot be compared.
J. Electrochem. Soc. , 142, 142, L6 (1996) J. Electrochem. Soc. , 150, A1079 (2003) J. Electrochem. Soc. , 147, 2923 (2000) JP 2001-93512 A JP 2002-289468 A JP 2003-45750 A

  An object of the present invention is to provide a novel electrode material for a redox capacitor made of a metal oxide having a high specific capacity, a high output density, a high energy density, a high stability, and a low cost, and the production thereof. It is to provide a method.

  The present inventor conducted extensive research to achieve the above-mentioned problems. As a result, a nanostructure having a size of 50 nm or less made of an oxide of a specific metal selected from manganese, tungsten, vanadium, and tin can be used alone. Although it has excellent characteristics as an electrode material for a redox capacitor, it has been found that when it is a composite electrode material containing a porous material of a conductive polymer, it has extremely excellent electrode characteristics for a redox capacitor. It was.

  The nanostructure of a specific metal oxide constituting the composite electrode material of the present invention can be manufactured by a potential scanning electrodeposition method at a potential scanning speed of 70 mV / s or higher, and is provided for the first time by the present inventors. It is. That is, the metal oxide nanostructure is not limited to a chemical synthesis method such as a coprecipitation method or a sol-gel method, but an electrolytic deposition method described in Non-Patent Document 2 above. Even the electrolytic method, and even the same potential scanning electrodeposition method, are not produced when the potential scanning speed is small, and the potential scanning speed is 70 mV / s or more, preferably 100 mV / s or more, particularly preferably 150 mV / s or more. It is a unique one that can be manufactured by an electrolytic method at a scanning speed.

  Such a specific metal oxide nanostructure, when used as an electrode material for a redox capacitor, alone, for example, 482F in the case of manganese oxide, as shown in the examples described later. / G (0.1 M, potential scanning speed of 10 mV / s in sodium sulfate aqueous solution), which is twice or more that of conventional manganese oxide of the same type. However, the composite electrode material in which this nanostructure is combined with a porous material of a conductive polymer has a very high specific capacity of 715 F / g, a high energy density of 200 Wh / kg, when the conductive polymer is polyaniline, In addition, it has high stability, and can provide performance that is remarkably superior to conventional electrode materials for redox capacitors.

Thus, the gist of the present invention is as follows.
(1) A redox capacitor composite comprising a nanostructure having a size of 50 nm or less, and a conductive polymer porous material, the oxide comprising a metal oxide selected from manganese, tungsten, vanadium, and tin. Electrode material.
(2) The electrode material according to (1) above, wherein a nanostructure composed of the metal oxide is present on the surface of the conductive polymer porous material.
(3) The electrode material according to (1) or (2), wherein the nanostructure made of the metal oxide is a nanoparticle having a diameter of 14 nm or less.
(4) The electrode material according to any one of (1) to (4), wherein the conductive polymer is selected from polyanilines, polypyrroles, and polythiophenes.
(5) The electrode material according to any one of (1) to (4), wherein the redox capacitor is a capacitor using an electrolytic solution containing a neutral salt aqueous solution.
(6) A method for producing a composite electrode material for a redox capacitor, comprising: a nanostructure made of an oxide of a metal selected from manganese, tungsten, vanadium, and tin; and a porous material of a conductive polymer. A step of electrodepositing a porous material of a conductive polymer by an electric potential scanning electrodeposition method with an electric potential scanning speed of 70 mV / s or more using an aqueous solution containing a monomer of the conductive polymer, and an aqueous solution of the compound containing the metal Electrodepositing a nanostructure made of the metal oxide by a potential scanning electrodeposition method at a potential scanning speed of 70 mV / s or higher, and a composite electrode material for a redox capacitor, comprising: Manufacturing method.
(7) performing the step of electrodepositing the porous material of the conductive polymer, and then performing the step of electrodepositing the nanostructure made of the metal oxide, and the surface of the porous material of the conductive polymer The manufacturing method according to (6) above, wherein a nanostructure made of the metal oxide is formed thereon.
(8) The production method according to the above (6) or (7), wherein the concentration of the aqueous solution containing the metal-containing compound and the aqueous solution containing the conductive polymer is an aqueous solution having a concentration of 0.1 to 10 mol / liter.
(9) The electrode on which the nanostructure made of the metal oxide is electrodeposited or the electrode on which the conductive polymer porous material is electrodeposited is stainless steel, titanium or nickel, and the electrode is a collection of redox capacitors. The manufacturing method in any one of said (6)-(8) used as an electric body.

  According to the present invention, a high specific capacity, a high output density, a high energy density, a high structure including a nanostructure having a size of 50 nm or less and a conductive polymer porous material made of a low-cost metal oxide. A novel composite electrode material for a redox capacitor having stability and a method for manufacturing the same are provided. The characteristics of the redox capacitor obtained by the present invention as an electrode material are synergistic characteristics of a nanostructure made of a metal oxide composing a composite and a porous material of a conductive polymer. Compared to the above, it has excellent features such as remarkably high high specific capacity, high output density, high energy density, and high stability, which are not achieved in the past.

  The reason why the composite electrode material of the present invention has such excellent characteristics is not necessarily clear. However, the characteristics of the redox capacitor as an electrode cannot be achieved with an electrode material made of a conductive polymer alone and a nanostructure made of a metal oxide alone. In particular, as shown in the examples to be described later, the specific capacity and energy density of the electrode are dramatically increased even when the amount of nanostructures made of metal oxide in the composite electrode material is extremely small (FIGS. 3 and 3). 4 and FIG. 5), and the specific capacity of the electrode increases as the thickness of the porous porous polymer material increases (see FIG. 3).

  As described above, the nanostructure made of the oxide of the specific metal constituting the high-performance composite electrode material of the present invention is the first by the present inventor by the potential scanning electrodeposition method at a high potential scanning speed. Although provided, the same potential scanning electrodeposition method cannot be obtained when the potential scanning speed is low. The reason for this is that in the case of the potential scanning electrodeposition method, electrodeposition is performed discontinuously according to the potential scanning cycle. A thing becomes a lump. However, the discontinuity of electrodeposition increases as the potential scanning speed increases, and when a certain potential scanning speed is exceeded, the resulting electrodeposits vary from lump to granular, rod-like, depending on the type of metal. Furthermore, electrodeposition is performed so as to form a porous structure on the electrode surface in the form of whiskers, and as a result, it is considered that the electrode material has an extremely large specific capacity.

  One material constituting the composite electrode for the redox capacitor of the present invention is a nanostructure having a size of 50 nm or less made of an oxide of a metal selected from manganese, tungsten, vanadium and tin. It is reported that nanostructures are generally structures having a size expressed at a level of 100 nm, and metal oxide nanostructures are conventionally manufactured by a vapor phase growth method, a solution phase growth method, a sol-gel method, or the like. However, a nanostructure having a size of 50 nm or less is first produced by a potential scanning electrodeposition method. In addition, the present inventors provide for the first time nanostructures such as granular materials, rod shapes, and whisker shapes that exhibit a high specific capacity as electrode materials for redox capacitors.

  The nanostructure of the specific metal oxide used in the present invention has a size of 50 nm or less, more preferably 30 nm or less. In the present invention, “size” means the average diameter when the nanostructure is spherical, the thickness when it is a rod or whisker, and the short diameter when it is a flat object. To do. The form of the nanostructure also varies depending on the type of metal, the type of substrate to be electrodeposited, the surface condition, etc., but the thickness is 50 nm or less, preferably 30 nm or less in granular or rod form, and the thickness is 13 nm or less. A whisker-like material having a length of preferably 10 nm or less and a length of 100 nm or less, preferably 50 nm or less. When the size of the nanostructure is larger than 50 nm, it is not preferable because a large specific capacity cannot be obtained.

  In the present invention, the metal forming the oxide nanostructure is selected from manganese, tungsten, vanadium and tin. These metals provide nanostructures that are preferable as electrode materials for redox capacitors because they form metal oxides having various oxidation numbers. Among these, manganese, tin, and vanadium are particularly preferable metal oxides in the present invention. The metal oxide is amorphous (amorphous). In some cases, the metal oxide is preferably a hydrate, and the preferred hydration number varies depending on the type of metal.

  On the other hand, another material constituting the composite electrode for the redox capacitor of the present invention is a porous material of a conductive polymer. The porous material may be in the form of particles, but preferably has a thickness of 10 to 200 μm, particularly preferably 30 to 100 μm. The conductive polymer is preferably selected from polyanilines, polypyrroles, and polythiophenes such as polythiophene, polytrimethylthiophene, and polyethylenedioxythiophene. Of these, polyanilines are preferred for reasons such as ease of synthesis, high stability, low toxicity, and high conductivity.

  The composite electrode material for a redox capacitor of the present invention comprising the specific metal oxide nanostructure and the conductive polymer porous material is a metal oxide nanostructure formed on the surface of the conductive polymer porous material. A mode in which a porous material of a conductive polymer exists on the surface of a metal oxide nanostructure, a mode in which a metal oxide nanostructure and a porous material of a conductive polymer are uniformly included, Various modes such as a laminated structure of a metal oxide nanostructure and a conductive polymer porous material can be employed.

In the present invention, in particular, the conductive polymer formed on the electrode exhibits particularly excellent conductivity. When a specific metal oxide is further formed on the surface by electrodeposition, the conductive polymer itself is used. In addition, since it functions as an electrode (current collector), electrodeposition of metal oxide is facilitated. For this reason, an embodiment in which a metal oxide nanostructure is present on the surface of the porous material of the conductive polymer is preferable. In this case, the porous material of the conductive polymer is preferably formed as a porous film, and a mode in which a metal oxide nanostructure having a size of 50 nm or less is attached on the surface of the porous film is preferable. The thickness of the conductive polymer porous film is preferably 0.5 to 10 mg / cm ² and particularly preferably ² to 5 mg / cm ² . On the other hand, nanostructures deposited the metal oxide is preferably 0.01 to 1 mg / cm ^2, and particularly preferably 0.05 to 0.5 / cm ^2.

  The metal oxide nanostructure constituting the composite electrode material of the present invention is obtained by using an aqueous solution of a compound containing these metals as an electrolytic solution, and by using a potential scanning electrodeposition method at a potential scanning speed of 70 mV / s or more. It is preferably produced by electrodepositing oxide nanostructures on the electrode surface. Here, it is important to use the potential scanning electrodeposition method and to set the potential scanning speed in the potential scanning electrodeposition method to 70 mV / s or more. In the potential scanning electrodeposition method as well as in the constant potential electrodeposition method and the constant current electrodeposition method, when the potential difference speed is smaller than 70 mV / s, the deposited material is sized as shown in the examples described later. Thus, a nanostructure electrodeposit cannot be obtained. Among them, the potential difference speed of the potential scanning electrodeposition method is preferably 100 mV / s or more, particularly preferably 150 mV / s or more. However, if it is excessively large, an electrodeposit having excellent characteristics cannot be obtained, so 350 mV / s or less, preferably 300 mV / s or less is suitable.

  As the potential scanning electrodeposition method, known methods and cells can be used. As the electrolytic solution, a water-soluble metal compound that forms an oxide is preferably used. For example, inorganic acids such as sulfuric acid, hydrochloric acid, carbonic acid, phosphoric acid, and nitric acid, or organic acid salts such as acetic acid, citric acid, formic acid, and malic acid are used. These metal water-soluble compounds are used as an aqueous solution having a concentration of preferably 0.01 to 10 mol / liter, particularly preferably 0.1 to 5 mol / liter.

  As an electrode in the potential scanning electrodeposition method in the present invention, a material that is not easily oxidized, for example, a noble metal material such as platinum or carbon can be used, but in the present invention, an inexpensive material such as stainless steel, titanium, nickel or the like is used. it can. In particular, stainless steel can be advantageously used in the present invention in terms of characteristics and cost.

  On the other hand, the porous material of the conductive polymer can be produced by various methods such as a chemical method and an electrochemical method. Among them, in the present invention, an electrochemical method by an electrodeposition method such as a constant potential electrodeposition method or a constant current electrodeposition method is preferable because the thickness of the porous material of the obtained conductive polymer can be easily controlled. . Among them, the same potential scanning electrodeposition method used for the production of the metal oxide nanostructure is particularly preferable because a more porous material can be obtained. In the present invention, a conductive polymer porous material having excellent characteristics can be produced by a potential scanning electrodeposition method at a high potential shift speed of preferably 70 mV / s or more, particularly preferably 150 mV / s or more.

  When producing a porous material of a conductive polymer by the potential scanning electrodeposition method, an aqueous solution of a monomer that forms a conductive polymer by electrolytic polymerization is preferably used as the electrolytic solution. The aqueous monomer solution is preferably used as an aqueous solution having a concentration of 0.1 to 5 mol / liter, particularly preferably 0.2 to 2 mol / liter. The electrolytic solution is preferably an acidic aqueous solution, and as the acid, an inorganic acid such as sulfuric acid, hydrochloric acid or nitric acid, or an organic acid such as acetic acid, citric acid, formic acid or malic acid is used. The concentration of the acid is preferably 0.1 to 5 mol / liter, particularly preferably 0.2 to 2 mol / liter. The potential scanning electrodeposition method for producing a porous material of a conductive polymer can be carried out in the same manner as the potential scanning electrodeposition method for producing the metal oxide nanostructure.

  In the present invention, when a composite electrode material is produced from the metal oxide nanostructure produced as described above and a conductive polymer porous material, for example, these are made into a metal oxide nanostructure. The conductive polymer porous material can be made into a slurry using an appropriate medium and binder, respectively, and the slurry can be applied simultaneously or sequentially to the current collector of the redox capacitor to produce a redox capacitor electrode.

  However, in the present invention, the composite electrode material of the present invention can be easily manufactured by manufacturing both the nanostructure of the specific metal oxide and the porous material of the conductive polymer by the potential scanning electrodeposition method. it can. That is, a step of electrodepositing a porous material of a conductive polymer by a potential scanning electrodeposition method using an aqueous solution containing the monomer of the conductive polymer as an electrolytic solution and a potential scanning speed of 70 mV / s or more, and containing the metal And a step of depositing the nanostructure made of the metal oxide by a potential scanning electrodeposition method at a potential scanning speed of 70 mV / s or more. .

  In particular, in the present invention, the step of electrodepositing the porous material of the conductive polymer is performed, and then the step of electrodepositing the nanostructure made of the metal oxide is performed. A method of forming a nanostructure made of the metal oxide on the surface of the material is preferable because the obtained electrode material has excellent characteristics. Further, in this case, it is preferable to use a current collector used for a redox capacitor as an electrode in the potential scanning electrodeposition method. In this case, an electrodeposit obtained by electrodeposition is particularly preferable because it can be used as it is as a composite electrode of a redox capacitor. In the present invention, an inexpensive material such as stainless steel, titanium or nickel can be used as the material in this case, which is particularly advantageous.

The composite electrode material of the present invention thus obtained is, for example, a porous electrodeposit of polyaniline (thickness 3 mg / cm ² ) as demonstrated from the scanning electron micrograph of FIG. It has a structure in which manganese oxide nano-particles are electrodeposited on the surface. Manganese oxide nanostructures are in the form of particles having a diameter of 10 to 20 nm, and are adhered to form a very porous structure on the surface of the porous polyaniline (0.2 mg / cm ² ). . This composite electrode material exhibits a specific capacity as high as 715 F / g and 200 Wh / kg (calculated from the charge / discharge cycle at a current density of 5 mA / cm ² ), as demonstrated from FIG. It can be seen that the electrode material is extremely superior to the polyaniline single electrode.

  Furthermore, the composite electrode material of the present invention has a large cycle durability. As demonstrated from FIG. 7 to be described later, for example, in the case of a polyaniline / manganese oxide composite electrode, the specific capacity decreases only by 3.5% even after 5000 cycles of charge / discharge. This is very small compared to the specific capacity reduction of about 35% reported for conventional polyaniline electrodeposits.

  The composite electrode material of the present invention also has an advantage that can be applied to a redox capacitor using a neutral aqueous solution as an electrolytic solution. Capacitors that use neutral aqueous electrolytes are superior in terms of handling, safety, and cost as compared to alkaline aqueous solutions, acidic aqueous solutions, and non-aqueous solutions as electrolytic solutions. As the neutral aqueous solution, preferably, chloride, sulfate, hydrochloride, acetate and the like such as potassium, sodium and lithium can be used. Of course, in the present invention, it is of course possible to use an alkaline aqueous solution, an acidic aqueous solution, or even a non-aqueous aqueous solution as the case requires. The concentration of these electrolytic solutions is preferably 0.1 to 5 mol / liter, particularly preferably 0.3 to 1 mol / liter.

  The redox capacitor using the composite electrode material of the present invention can adopt a known structure other than the electrode material. Further, the composite electrode material of the present invention can be used for one or both of the positive electrode and the negative electrode of a redox capacitor, and when used for one of the electrodes, an electrode such as a conductive polymer material is used as the other electrode. The In addition, the composite electrode material of the present invention may be used alone, but if necessary, in order to improve the conductivity of the electrode, an appropriate conductive material such as a conductive carbon such as activated carbon or a conductive polymer is used. It can be used by mixing with a functional material. In this case, a binder such as a fluoropolymer such as tetrafluoroethylene for bonding the electrode material of the present invention and the conductive material can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention should not be construed as being limited to such examples.

Example 1
The H ₂ SO ₄ , MnSO ₄ .5H ₂ O, and Na ₂ SO ₄ used in the examples were from Aldric (USA) and all aqueous solutions were prepared using double distilled water. The electrolysis cell was a four-electrode cell provided with a working electrode, a reference electrode, and two counter electrodes, and the working electrode was set between two counter electrodes made of Pt. A saturated calomel electrode (SCE) was used as the reference electrode. As the working electrode, a commercially available 0.2 mm thick stainless steel (304 grade) foil (area: 1 cm ² ) was previously ground with a sandpaper, the abrasive particles were washed away, and air dried.

An aqueous solution of 0.5 mol / liter H ₂ SO ₄ and 0.5 mol / liter aniline monomer was used as the electrolyte, and electrodeposition was performed at a potential scan rate of 200 mV / s with a S.E. By carrying out at a potential width of 2 to 1.2 V, an electrodeposit of polyaniline was obtained on the surface of the stainless steel foil. The electrodeposit on the stainless steel was washed with distilled water as it was and then dried at room temperature for about 12 hours, and the weight of the polyaniline electrodeposit was measured.

Next, in the same electrolytic cell, an aqueous solution of H ₂ SO ₄ having a concentration of 0.5 mol / liter and MnSO ₄ .5H ₂ O having a concentration of 0.5 mol / liter was used as an electrolyte solution. Manganese oxide was electrodeposited on the polyaniline deposit on the stainless steel surface at a potential width of 1.35 V and a potential scanning speed of 200 mV / s. The polyaniline / manganese oxide was dried as it was at room temperature for about 12 hours, and the weight of all electrodeposits was measured. The weight of the manganese oxide electrodeposit was determined from the difference between the weight of the total electrodeposit and the weight of the polyaniline electrodeposit. The manganese oxide electrodeposit was confirmed to be in an amorphous state by X-ray diffraction analysis.

About the polyaniline electrodeposit obtained above and the polyaniline / manganese oxide electrodeposit, an aqueous solution of Na ₂ SO ₄ having a concentration of 0.1 mol / liter was used as the electrolyte, and the polypropylene thickness was 0.1 mm. Evaluation as an electrode material of a redox capacitor using a porous sheet as a separator was performed at various current densities by a charge / discharge cycle.

  The X-ray diffraction analysis of the electrodeposits was performed using CuKα rays with the Rigaku X-ray diffractometer: RINT2100, and the surface state of the electrodeposits was observed with a scanning electron microscope apparatus of JEOL: This was carried out using JSM-6340F.

Observation of surface state of electrodeposits FIG. 1 shows scanning electron micrographs of polyaniline electrodeposits and polyaniline / manganese oxide electrodeposits obtained on the stainless steel surface in Example 1. In FIG. 1, a is an electrodeposit of polyaniline, and it can be seen that the surface form is a porous material composed of granular materials. In FIG. 1, b is an electrodeposit of polyaniline / manganese oxide, and it can be seen that innumerable manganese oxide nano-particles adhere to the surface to form a porous structure.

Evaluation of Electrodeposit as Electrode Material of Redox Capacitor FIG. 2 shows six types (0.9 mg / cm ² ) of polyaniline electrodeposits having different thicknesses by changing the number of cycles (time) during polyaniline electrodeposition. 1.5 mg / cm ² , 2.0 mg / cm ² , 2.8 mg / cm ² , 3.5 mg / cm ² , 4.0 mg / cm ² ) polyaniline / manganese oxide electrode (adhesion of manganese oxide) Shows the same charge / discharge curve. The evaluation of the six polyaniline / manganese oxide electrodeposits in the redox capacitor electrode is the same as described above, except that an aqueous solution of Na ₂ SO ₄ having a concentration of 0.1 mol / liter is used as the electrolyte, and the current density is 10 mA / cm. ² performed. As a result, the charge / discharge cycle efficiency was found to be extremely high in the range of 0.98 to 0.99.

FIG. 3 shows the change in the specific capacity of the redox capacitor electrode of the six types of polyaniline / manganese oxide deposits having the same polyaniline deposit thickness as used in FIG. The specific capacity was evaluated in the same manner as described above by a charge / discharge cycle at a current density of 10 mA / cm ^{2 using} a Na ₂ SO ₄ aqueous solution having a concentration of 0.1 mol / liter as an electrolyte. For comparison, the specific capacities of polyaniline electrodeposits having no manganese oxide electrodeposits on the surface were evaluated together.

  It can be seen that the specific capacity of the polyaniline / manganese oxide electrode of the present invention is much larger than that of the polyaniline electrode. On the other hand, the specific capacity of the polyaniline electrode increases linearly as the thickness of the polyaniline electrodeposit increases. It can be seen that when this is reached, it saturates there. This fact means that the manganese oxide electrodeposition is effective only on the surface layer of the polyaniline electrodeposit.

FIG. 4 shows the charge / discharge current density for the polyaniline / manganese oxide electrode of the present invention (polyaniline electrodeposit thickness: 4 mg / cm ² , manganese oxide thickness: 0.2 mg / cm ² ). The change of the specific capacity when changing is shown. For comparison, the specific capacity of a polyaniline electrode having no manganese oxide electrode on the surface is also shown.

  The polyaniline / manganese oxide electrode has a high specific capacity of 690 F / g. This specific capacity is the specific capacity of the polyaniline electrodeposited electrode shown in FIG. 4 and the manganese oxide reported in Patent Document 2 above. It can be seen that it is dramatically higher than the specific capacity of the electrode.

  FIG. 5 shows the energy density at a power density of 2.5 kW / kg for the redox capacitor electrodes of the six kinds of polyaniline / manganese oxide deposits having different thicknesses. For comparison, the energy density of a polyaniline electrode having no manganese oxide electrodeposit on the surface is also shown.

  As a result, in the polyaniline / manganese oxide electrodeposit, an extremely high energy density of 180 Wh / kg was obtained, whereas the energy density of the polyaniline single electrode was 118 Wh / kg.

FIG. 6 shows the specific capacity of the polyaniline / manganese oxide electrode when the deposition amount of the manganese oxide electrodeposited on the surface of the polyaniline electrodeposit of a predetermined thickness (4 mg / cm ² ) is changed. It shows how (a) and energy density (b) change. These relationships were calculated from charge / discharge cycles at current densities of 5 mA / cm ² , 8 mA / cm ² , and 10 mA / cm ² . Initially, the specific capacity and energy density increase linearly as the amount of deposited manganese oxide deposit increases, but seems to be saturated with a certain amount of manganese oxide deposit. It is worthy of special mention that an energy density as high as 200 Wh / kg can be obtained when the deposited amount of the manganese oxide electrodeposit is 0.24 mg / cm ² .

FIG. 7 shows that a polyaniline / manganese oxide electrode comprising a polyaniline electrodeposit having a thickness of 4 mg / cm ² and an adhesion amount of 0.24 mg / cm ² was charged / discharged up to 5000 cycles at a current density of 10 mA / cm ² . The cycle life is shown. Even after 5000 cycles of charge / discharge, the rate of decrease in capacity is 3.5%, which is very small compared to the decrease in capacity of about 35% reported for polyaniline electrodeposits. This fact represents that the polyaniline / manganese oxide electrode of the present invention is stable over time.

Examples 2-5
In Example 1 above, the conductive polymer electrodeposits shown in Table 1 (thickness: 4 mg / cm ² ) were used instead of the polyaniline electrodeposits obtained on the surface of the stainless steel electrode, and The same electrolytic cell as in Example 1 was used, except that the metal oxide shown in Table 1 (adhesion amount: 0.2 mg / cm ² ) was electrodeposited on the surface of the conductive polymer electrodeposit. Similarly, a composite electrode material was manufactured.

  When the obtained composite electrode material was evaluated as an electrode material for a redox capacitor in the same manner as in Example 1, the results shown in Table 1 were obtained.

  Since the novel composite electrode material for redox capacitors provided by the present invention has high specific capacity, high output density, high energy density, high stability, and low cost, redox capacitors using this are various types of redox capacitors. As electric devices are becoming smaller, they are widely used in various electric devices, portable devices, hybrid vehicles, electric vehicles, etc. as electric storage devices that are compact, lightweight, high specific capacity, high energy density, and capable of rapid charge and discharge. It is possible.

The scanning electron micrograph about the deposit of polyaniline and the deposit of polyaniline / manganese oxide obtained on the stainless steel surface is shown. Six types of polyaniline electrodeposits having different thicknesses (0.9 mg / cm ² , 1.5 mg / cm ² , 2.0 mg / cm ² , 2.8 mg / cm ² , 3.5 mg / cm ² , 4.0 mg / Cm ² ) of the polyaniline / manganese oxide electrode (the amount of manganese oxide deposited is the same). The change of the specific capacity of the redox capacitor electrode of six types of polyaniline / manganese oxide electrodeposits having different thicknesses of the polyaniline electrodeposits is shown. When the charge / discharge current density is changed for the polyaniline / manganese oxide electrode of the present invention (polyaniline electrodeposit thickness: 4 mg / cm ² , manganese oxide thickness: 0.2 mg / cm ² ) The change in specific capacity is shown. The energy density at the power density: 2.5 kW / kg of the redox capacitor electrode of the six types of polyaniline / manganese oxide electrodeposits having different thicknesses of the polyaniline electrodeposits is shown. The specific capacity (a) of the polyaniline / manganese oxide electrode when the deposition amount of the manganese oxide electrodeposited on the surface of the polyaniline electrodeposit having a predetermined thickness (4 mg / cm ² ) is changed. It shows how the energy density (b) changes. The cycle life up to 5000 cycles of charge / discharge at a current density of 10 mA / cm ² of a polyaniline / manganese oxide electrode comprising a polyaniline electrodeposit having a thickness of 4 mg / cm ² and an adhesion amount of 0.24 mg / cm ² is shown.

Claims (9)

  A composite electrode material for a redox capacitor, comprising a nanostructure having a size of 50 nm or less made of an oxide of a metal selected from manganese, tungsten, vanadium and tin, and a porous material of a conductive polymer.   The electrode material according to claim 1, wherein a nanostructure composed of the metal oxide is present on a surface of the porous material of the conductive polymer.   The electrode material according to claim 1, wherein the nanostructure made of the metal oxide is a nanoparticle having a diameter of 14 nm or less.   The electrode material according to claim 1, wherein the conductive polymer is selected from polyanilines, polypyrroles, and polythiophenes.   The electrode material according to claim 1, wherein the redox capacitor is a capacitor using an electrolytic solution containing a neutral salt aqueous solution.   A method for producing a composite electrode material for a redox capacitor, comprising a nanostructure made of an oxide of a metal selected from manganese, tungsten, vanadium and tin, and a porous material of a conductive polymer, An aqueous solution containing a monomer is used as an electrolytic solution, and a step of electrodepositing a porous material of a conductive polymer by a potential scanning electrodeposition method at a potential scanning speed of 70 mV / s or more, and an aqueous solution of the compound containing the metal are used as the electrolytic solution And depositing the nanostructure made of the metal oxide by a potential scanning electrodeposition method at a potential scanning speed of 70 mV / s or more, and a method for producing a composite electrode material for a redox capacitor, .   Performing a step of electrodepositing a porous material of the conductive polymer, then performing a step of electrodepositing a nanostructure made of the metal oxide, and forming the surface on the surface of the porous material of the conductive polymer. The manufacturing method according to claim 6, wherein a nanostructure made of a metal oxide is formed.   The method according to claim 6 or 7, wherein the concentration of the aqueous solution containing the metal-containing compound and the aqueous solution containing the conductive polymer monomer is an aqueous solution having a concentration of 0.1 to 10 mol / liter.   The electrode on which the nanostructure made of the metal oxide is electrodeposited or the electrode on which the porous porous polymer is electrodeposited is stainless steel, titanium or nickel, and the electrode is a redox capacitor current collector. The manufacturing method in any one of Claims 6-8.

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