WO2013146792A1

WO2013146792A1 - Hybrid capacitor

Info

Publication number: WO2013146792A1
Application number: PCT/JP2013/058817
Authority: WO
Inventors: 渉杉本; 航清水; 翔牧野
Original assignee: 国立大学法人信州大学
Priority date: 2012-03-28
Filing date: 2013-03-26
Publication date: 2013-10-03
Also published as: JPWO2013146792A1; JP6109153B2

Abstract

[Problem] To provide a hybrid capacitor with which there is safety and robustness, and it is possible to obtain high energy density with high cell voltage. [Solution] A hybrid capacitor comprises at least: a positive electrode (11) having a carbon material and/or a metallic oxide; a negative electrode which is configured of a lithium composite electrode; and a neutral aqueous electrolyte (13) which is filled between the positive electrode (11) and the negative electrode (12). The lithium composite electrode (12) is configured to be a layered electrode of a lithium ion conductive solid-state electrolyte (21), a polymer electrolyte (22), and an active material layer (23) including lithium, thus solving the problem. It is desirable for the neutral aqueous electrolyte (13) to have a ph of 5-8.5, and for the metallic oxide to be chosen from manganese oxide, ruthenium oxide, or lead oxide.

Description

Hybrid capacitor

The present invention relates to a hybrid capacitor, and more particularly to a hybrid capacitor capable of obtaining a high energy density at a high cell voltage.

An electrochemical capacitor is a device that uses a physical electric double layer or a pseudo double layer (a fast redox reaction on the electrode surface) with a Faraday reaction for charge accumulation. The former is a charge accumulation mechanism when an activated carbon electrode is used as an active material, and the latter is a charge accumulation mechanism when a metal oxide electrode such as RuO ₂ or MnO ₂ is used as an active material. Electrolytic solutions used in such electrochemical capacitors can be broadly divided into two types: aqueous electrolytic solutions and nonaqueous electrolytic solutions.

Non-aqueous electrolytes represented by organic electrolytes are inferior in ionic conductivity compared to aqueous electrolytes. However, the electrochemical capacitor using the non-aqueous electrolyte is advantageous in that a high cell voltage and a high energy density can be obtained because the electrolytic voltage of the electrolyte can be 3 V or higher. In such an electrochemical capacitor, when the specific capacitance of the single electrode itself is approximately the same as that of the aqueous electrolyte, the energy density is improved by the amount of the cell voltage being higher. Since the energy density is proportional to the square of the cell voltage, the energy density can be dramatically improved by increasing the cell voltage by 1V. In particular, when an ionic liquid having a wide potential window is used as the electrolyte, a cell voltage exceeding 3 V and a high energy density can be obtained.

On the other hand, the aqueous electrolyte has better ion conductivity than the non-aqueous electrolyte, and an electrochemical capacitor using the aqueous electrolyte is advantageous in terms of output density. However, it is difficult for an aqueous electrolyte to obtain a cell voltage exceeding the electrolysis voltage of water, and it is difficult to increase the energy density.

To deal with such problems, Non-Patent Document 1 proposes an asymmetric hybrid capacitor in which different types of electrodes are used for the positive electrode and the negative electrode, respectively, and the cell voltage and energy density are increased in the aqueous electrolyte. In this technique, it is said that a cell voltage on the positive electrode side exceeding the theoretical oxygen generation voltage can be obtained by using MnO ₂ having a relatively high oxygen generation overvoltage for the positive electrode. Specifically, according to this technique, a maximum cell voltage of 2.2 V is obtained, and an energy density (19 Wh / kg) comparable to that of an electrochemical capacitor using an organic electrolyte is obtained.

Further, Patent Document 1 proposes a technology that can charge and discharge at a working voltage exceeding the theoretical voltage of water electrolysis in a pseudo-capacitor capacitor using both an aqueous electrolyte and a non-aqueous electrolyte. Specifically, the pseudo-capacitor has a resin case disposed between a positive current collector and a negative current collector, and a capacitor structure is provided in the center hole of the case. The capacitor structure includes a positive electrode disposed at the upper part of the central hole, a negative electrode disposed at the lower part of the central hole, a solid electrolyte plate disposed at the step of the central hole, and an aqueous electrolyte containing Li ions. A first liquid chamber filled and a second liquid chamber filled with a non-aqueous electrolyte containing Li ions are provided. The positive electrode is an electrode containing a metal oxide capable of redox change, the negative electrode is an electrode capable of inserting and extracting Li ions, the solid electrolyte plate has Li ion conductivity, and the contact between the aqueous electrolyte and the negative electrode Plays a role in hindering.

JP 2011-198925 A

However, the technique of Patent Document 1 can obtain a relatively high cell voltage because the second liquid chamber is filled with the nonaqueous electrolytic solution, but there is a problem in safety. Further, since the first liquid chamber is filled with an alkaline aqueous electrolyte, the durability of the solid electrolyte and the positive electrode may be reduced.

Electrochemical capacitors using aqueous electrolytes and non-aqueous electrolytes aim to improve cell voltage and energy density using various technologies, but the energy density will be further improved in the future compared to lithium ion batteries. is necessary.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a hybrid capacitor that is safe and durable and that can obtain a high energy density at a high cell voltage. .

In order to solve the above problems, a hybrid capacitor according to the present invention includes a positive electrode having one or both of a carbon material and a metal oxide, a negative electrode composed of a lithium composite electrode, and a gap between the positive electrode and the negative electrode. The lithium composite electrode is a laminated electrode of a lithium ion conductive solid electrolyte, a polymer electrolyte, and an active material layer containing lithium.

According to the present invention, since a neutral aqueous electrolyte is used and a water-stable lithium composite electrode is used as the negative electrode, a safe and durable new aqueous hybrid capacitor can be obtained. In addition to capacitor charge accumulation of a positive electrode having one or both of a carbon material and a metal oxide, a high cell voltage can be obtained by utilizing a standard electrode potential of M / M ⁺ (M is a metal). I was able to.

In the hybrid capacitor according to the present invention, the neutral aqueous electrolyte is pH 5 or more and pH 8.5 or less, and the metal oxide is any one selected from manganese oxide, ruthenium oxide and lead oxide.

In the hybrid capacitor according to the present invention, the positive electrode includes a sheet containing one or both of a carbon material and a metal oxide, and a metal oxide film provided on at least the surface of the sheet.

In the hybrid capacitor according to the present invention, the sheet is a paper-like body having carbon fibers.

In the hybrid capacitor according to the present invention, the active material layer containing lithium includes lithium, a lithium alloy, or a carbon material doped with lithium.

The hybrid capacitor according to the present invention has safety and durability, and can obtain a high energy density at a high cell voltage.

It is a schematic diagram which shows the structure of the hybrid capacitor which concerns on this invention. It is an example of the cyclic voltammogram obtained by cyclic voltammetry. It is an example of the charging / discharging curve obtained by the charging / discharging measurement. It is an example of the charging / discharging cycle curve obtained by charging / discharging cycle measurement.

Hereinafter, although the hybrid capacitor according to the present invention will be described in detail, the present invention is not limited to the following description within the scope of the technical scope, and can be implemented in various modes.

As shown in FIG. 1, the hybrid capacitor 1 according to the present invention includes a positive electrode 11 having one or both of a carbon material and a metal oxide, a negative electrode 12 composed of a lithium composite electrode, and a positive electrode 11 and a negative electrode 12. And at least a neutral aqueous electrolyte 13 filled therebetween. And the lithium composite electrode which is the negative electrode 12 is a laminated electrode of the lithium ion conductive solid electrolyte 23, the polymer electrolyte 22, and the active material layer 21 containing lithium. Further, the neutral aqueous electrolyte solution 13 has a pH of 5 or more and a pH of 8.5 or less, and preferably has a pH of 5 or more and pH 8. In addition, the code | symbol 18 is a container in FIG.

(Neutral aqueous electrolyte)
The neutral aqueous electrolyte 13 is an electrolyte filled between the positive electrode 11 and the negative electrode 12. In the present invention, an aqueous neutral electrolyte is used. Examples of the neutral aqueous electrolyte include an aqueous electrolyte in which an alkali metal salt is dissolved. The alkali metal salts include LiCl, LiNO ₃ , Li ₂ SO ₄ , Li ₂ CO ₃ , Li ₂ HPO ₄ , LiH ₂ PO ₄ , LiCOOCH ₃ , LiCOO (OH) CHCH ₃ , Li ₂ C ₂ O ₂ , NaCl. , Na ₂ SO ₄ , KCl, K ₂ SO ₄ , and other inorganic acid salts and organic acid salts. In addition, a water-based electrolytic solution in which a plurality of alkali metal salts are mixed and adjusted to neutrality may be used, or a water-based electrolytic solution in which an alkali metal salt and an acid or base are mixed to provide a buffering action. Also good. The aqueous electrolyte having a buffering action has a stable pH during the charge / discharge process, and can improve the safety and durability of the hybrid capacitor 1.

Examples of the neutral aqueous electrolyte solution 13 having a buffering action include lithium dihydrogen phosphate-lithium hydroxide (LiH ₂ PO ₄ -LiOH) solution (pH 6.87), lithium acetate-acetic acid (CH ₃ COOLi-CH ₃ COOH). Liquid (pH 5.41).

In the present invention, since the aqueous electrolytic solution 13 is neutral, the electrolytic solution does not damage the negative electrode 12 and the positive electrode 11, and a stable hybrid capacitor can be configured. In addition, since the hybrid capacitor 1 does not use a non-aqueous electrolyte using a solvent other than water as described in Patent Document 1, it is easy to handle, safe, and low cost.

The neutrality of the neutral aqueous electrolyte solution 13 means a range of pH 5 or more and pH 8.5 or less, preferably a pH of 5 or more and pH 8 or less. Moreover, it is preferable that the salt concentration in the neutral aqueous electrolyte solution 13 is 0.01 mol / L or more and 5 mol / L or less.

(Positive electrode)
The positive electrode 11 has one or both of a carbon material and a metal oxide, and causes a reversible redox reaction in contact with the neutral aqueous electrolyte solution 13 described above. Specifically, as long as the positive electrode 11 has one or both of a carbon material and a metal oxide capable of causing a reversible redox reaction, the positive electrode 11 may be composed of a single metal oxide or a metal. It may be composed of an oxide and a binder material, or may be composed of a metal oxide, a binder material, and a conductive material. Moreover, the positive electrode 11 may be comprised with the carbon material single-piece | unit, may be comprised with the carbon material and the binder material, and may be comprised with the carbon material, the binder material, and the electrically-conductive material. Furthermore, the positive electrode 11 may be composed of both a metal oxide and a carbon material.

As the carbon material, various carbon materials can be exemplified, and preferably, activated carbon, acetylene black, carbon nanotube, graphite, conductive diamond, graphene and the like can be exemplified. These carbon materials may be used alone or in combination of two or more. Various metal oxides can be used as long as they can cause a reversible redox reaction, such as manganese oxide, ruthenium oxide, lead oxide, tungsten oxide, cobalt oxide, tin oxide, and oxide. Examples thereof include nickel, molybdenum oxide, titanium oxide, iridium oxide, vanadium oxide, indium oxide, and the like, and hydrates thereof. These metal oxides may be used alone or in combination of two or more. Preferable examples include manganese oxide, ruthenium oxide, lead oxide and the like.

Note that conventionally known binder materials and conductive materials can be applied. As the binder material, for example, a fluorine-based resin, a thermoplastic resin, ethylene-propylene-dienemer, natural butyl rubber and the like can be arbitrarily used. As the conductive material, for example, natural graphite, artificial graphite, acetylene black, carbon black, ketjen black, carbon whisker, needle coke, carbon fiber, metal powder or fiber can be used. These binder materials and conductive materials may be used alone or in combination of two or more.

The positive electrode 11 may have a sheet containing one or both of a carbon material and a metal oxide, and a metal oxide film provided on at least the surface of the sheet. Specifically, the sheet may be composed of a single metal oxide, may be composed of a metal oxide and an additive such as a binder material, or may be composed of a single carbon material. Alternatively, it may be composed of a carbon material and an additive such as a binder material. The sheet may contain both a metal oxide and a carbon material.

As a sheet | seat containing a carbon material, the sheet | seat formed with carbon fiber, for example, the cloth-like body formed with carbon fiber, etc. can be mentioned, for example.
Examples of the sheet containing both the metal oxide and the carbon material include a sheet obtained by molding a material obtained by kneading the metal oxide and the carbon material into a sheet shape.

Examples of the binder contained in the sheet include fluororesin materials such as Fluon (manufactured by Asahi Glass Co., Ltd., registered trademark) and Lubron (manufactured by Daikin Industries, Ltd., registered trademark), and styrene butadiene rubbers such as TRD2001 (manufactured by JSR Corporation) Examples thereof include system materials.

The metal oxide film may be provided on at least the surface of the sheet. For example, the metal oxide film may be provided only on the surface of the sheet, or may be provided on the surface of the sheet and enter the inside of the sheet. For example, when the sheet is formed of carbon fibers, the metal oxide film may be provided so as to cover the surface of each carbon fiber. The hybrid capacitor 1 using the positive electrode 11 in which the metal oxide film is provided on the surface of each carbon fiber can obtain characteristics that greatly reflect the characteristics of the metal oxide of the positive electrode 11.

Examples of the method for forming the metal oxide film include thin film formation methods such as electrodeposition, electrophoresis, CVD (chemical vapor deposition), sputtering, and vacuum deposition. Among these, the electrodeposition method is advantageous in increasing the production efficiency of the hybrid capacitor because the metal oxide film can be formed in a relatively short time.

The shape of the positive electrode 11 is not particularly limited, but is usually preferably a sheet shape or a plate shape. The thickness of the positive electrode 11 is not particularly limited, but is, for example, in the range of 1 nm or more and 10 mm or less. The positive electrode 11 is usually provided on the positive electrode current collector 16. A conventionally known positive electrode current collector 16 can be arbitrarily applied.

(Negative electrode)
The negative electrode 12 is composed of a lithium composite electrode (represented by reference numeral 12). Such a negative electrode 12 is in contact with the aqueous electrolyte solution 13 described above, and acts to occlude and release metal ions that cause a redox reaction. As shown in FIG. 1, the lithium composite electrode 12 is a laminated electrode having a lithium ion conductive solid electrolyte 23, a polymer electrolyte 22, and an active material layer 21 containing lithium.

As the active material layer 21 containing lithium, metallic lithium, a lithium alloy, or a carbon material doped with lithium is used.

The lithium alloy may be any lithium alloy or lithium compound mainly composed of lithium, and examples thereof include a lithium-aluminum alloy, a lithium-zinc alloy, a lithium-tin alloy, and a lithium-silicon alloy.

Examples of the carbon material doped with lithium include graphitizable carbon, non-graphitizable carbon, and graphite. Examples of the graphitizable carbon include pyrolytic carbons, and cokes such as pitch coke, needle coke, and petroleum coke. Examples of the non-graphitizable carbon include glassy carbon fibers, organic polymer compound fired bodies, activated carbon, and carbon blacks. Here, the organic polymer compound fired body is obtained by firing and carbonizing a phenol resin, a furan resin, or the like at an appropriate temperature. The amount of lithium doped into the carbon material is suitably 1 μg / cm ² or more and 1 g / cm ² or less.

As shown in the following formula, a lithium-doped carbon material releases lithium ions from the carbon material when a discharge voltage is applied to the hybrid capacitor, and stores lithium ions in the carbon material when a charge voltage is applied. It functions as a negative electrode active material.

The active material layer 21 made of such a carbon material is unlikely to deposit lithium dendritic crystals (dendrites) upon charging, and the polymer electrolyte 22 and the like provided on the active material layer 21 are caused by the lithium dendritic crystals. It is possible to avoid damage or short circuit. As a result, the durability and safety of the hybrid capacitor can be further increased. Moreover, since the amount of lithium used can be reduced by using a carbon material as the material of the active material layer 21 compared to the case of using metallic lithium or the like, it is possible to improve the safety of the hybrid capacitor and reduce the cost. Can be planned.

Examples of the shape of the active material layer 21 containing lithium include a sheet shape or a film shape. Although the thickness of the active material layer 21 is not specifically limited, For example, it exists in the range of 0.1 mm or more and 3 mm or less.

The lithium ion conductive solid electrolyte 23 has lithium ion conductivity and water impermeability, and acts to isolate the aqueous electrolyte solution 13 and the negative electrode 12. The polymer electrolyte 22 contains a solid polymer and a lithium salt.

As the solid polymer constituting the polymer electrolyte 22, polyethylene oxide (PEO), polypropylene oxide (PPO) or the like can be used. These have polyalkylene oxide chains that are molecular chains in which alkylene groups and ether oxygens are alternately arranged, and have a large number of ether oxygens that solvate lithium ions, so that lithium salts can be dissolved.

Examples of the lithium salt constituting the polymer electrolyte 22 include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiTFSI (Li (SO ₂ CF ₃ ) ₂ N), Li (SO ₂ C ₂ F ₅ ) ₂ N, LiBOB ( Lithium bisoxalatoborate) and the like. These lithium salts may be used alone or in combination of two or more.

The polymer electrolyte 22 may be blended with a ceramic material such as barium titanate in consideration of mechanical characteristics and electrical characteristics, or other materials that do not hinder the function of the polymer electrolyte 22. You may mix | blend.

The amount of these materials constituting the polymer electrolyte 22 is set in consideration of the desired function of the polymer electrolyte 22. The polymer electrolyte 22 can be produced by a conventionally known method. For example, a solution in which various constituent materials are dispersed in an organic solvent can be dried to be molded into a predetermined shape. The thickness of the polymer electrolyte 22 is not particularly limited, but is usually in the range of 0.05 mm or more and 0.5 mm or less. The polymer electrolyte 22 produced in this way is disposed between the lithium 21 and the lithium ion conductive solid electrolyte 23, and can prevent both from coming into direct contact and reacting. As a result, the lifetime of the hybrid capacitor 1 can be increased.

The lithium ion conductive solid electrolyte 23 is preferably a NASICON (sodium superionic conductor) type lithium ion conductor having water resistance and lithium ion conductivity. Specifically, the lithium ion conductive solid electrolyte _{_{23, Li 1 + X Ti 2}} Si X P 3-X O 12 · AlPO 4 (LICGC, Ohara _{_{_{glass), Li 1.5 Al 0.5 Ge 1.5}}} (PO 4) 3 (LAGP), Li 1 + x + u Al x Ti 2-x P 3-y Si y O 12 (LATP), mention may be made of a garnet-type oxide _{_{_{_{Li 7 La 3 Zr 2 O 12}}}} , LiPON like. The lithium ion conductive solid electrolyte 23 is preferably in the form of a sheet or a plate, and the thickness is usually in the range of 0.05 mm or more and 0.5 mm or less.

The negative electrode 12 is usually provided on the negative electrode current collector 17. A conventionally known negative electrode current collector 17 can be arbitrarily applied.

(Hybrid capacitor)
The hybrid capacitor 1 composed of at least the positive electrode 11, the negative electrode 12, and the aqueous electrolyte solution 13 may be provided with other constituent materials and constituent members as necessary. The size of the hybrid capacitor 1 is not particularly limited, and the shape thereof is not particularly limited. Examples of the shape include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, and a square type.

As described above, according to the hybrid capacitor 1 according to the present invention, the neutral aqueous electrolyte 13 is used, and the water-stable lithium composite electrode 12 is used as the negative electrode. A hybrid capacitor could be obtained. Further, in addition to the capacitor charge accumulation of the metal oxide electrode as the positive electrode, a high cell voltage could be obtained by utilizing the standard electrode potential of Li / Li ⁺ .

Hereinafter, the present invention will be specifically described by experimental examples.

[Preparation of positive electrode]
(Production of activated carbon electrode)
The positive electrode 11 using activated carbon was produced as follows. First, 20 mg of activated carbon powder (manufactured by Kansai Thermal Chemical Co., Ltd., trade name: MSP-20, BET specific surface area 2200 m ² / g, average particle size 8 μm) was added to 10 mL of ultrapure water, and the activated carbon powder was sonicated. An activated carbon dispersion was obtained by uniformly dispersing in ultrapure water. Next, 20 μL of this activated carbon dispersion was dropped onto the end surface of the tip of cylindrical glassy carbon (trade name: GC-20S, manufactured by Tokai Carbon Co., Ltd.) having a diameter of 5 mm, and dried at 60 ° C. for 30 minutes. Next, 20 μL of 1% by mass of Nafion (Nafion: a registered trademark of DuPont, Sigma-Aldrich) alcohol water mixed solution is dropped onto the same end face of the glassy carbon, and kept at 60 ° C. for 30 minutes to dry. 11 was produced. The active material supported on the end face of the activated carbon electrode is 40 μg. Before use, the glassy carbon was polished to a mirror surface with a polishing paper as a pretreatment, and then ultrasonicated in distilled water and alcohol and dried.

(Preparation of manganese oxide electrode A)
Manganese oxide (MnO ₂ ) powder was synthesized according to Non-Patent Document 1. Specifically, the positive electrode 11 using manganese oxide was produced as follows. First, 0.773 g of fumaric acid [C ₂ H ₂ (COOH) ₂ ] is added to an aqueous potassium permanganate solution in which 3.16 g of potassium permanganate (KMnO ₄ ) is dissolved in 100 mL of ultrapure water. After stirring under reduced pressure for minutes, the mixture was allowed to stand at room temperature for 1 day to obtain a slurry. Next, this slurry was washed with 0.1 M sulfuric acid (H ₂ SO ₄ ), ultrapure water and acetone in this order, dried, pulverized, and average pore diameter was 5 nm, BET specific surface area was A 235 m ² / g manganese oxide (MnO ₂ ) powder was obtained. The obtained manganese oxide powder was mixed with acetylene black, which is a conductive material, in a mass ratio of 7: 3, and used in place of the activated carbon powder in the above-described activated carbon electrode production method, to produce a manganese oxide electrode A.

(Preparation of manganese oxide electrode B)
Manganese oxide electrode B was produced by electrodepositing manganese oxide on the surface of carbon fiber of carbon paper. Specifically, an aqueous solution of manganese sulfate hydrate (MnSO ₄ .5H ₂ O) and an aqueous sulfuric acid solution were mixed to prepare a sulfuric acid solution (electrolytic solution for electrodeposition) containing 0.1M MnSO ₄ . Next, carbon paper (manufactured by SGL, trade name: SIGRACET GDL10) is immersed in the electrolytic solution for electrodeposition, the carbon paper is used as an anode electrode, a platinum electrode is used as a cathode electrode, and a current density is 0. Electrodeposition was performed under the conditions of 0.5 mA / cm ² , temperature: 25 ° C., and electrodeposition time: 1800 seconds, and a manganese oxide electrode B was produced. The manganese oxide deposition amount of this manganese oxide electrode B was 0.4 mg / cm ² .

(Production of ruthenium oxide hydrate electrode)
Hydrated ruthenium oxide (RuO ₂ .nH ₂ O) powder was synthesized according to Non-Patent Document 2 described above. Specifically, the positive electrode 11 using ruthenium oxide hydrate was produced as follows. First, an aqueous solution obtained by dissolving 0.638 g of ruthenium chloride (RuCl ₃ ) in 50 mL of ultrapure water and dropwise adding an aqueous solution of 0.6 g of sodium hydroxide in 50 mL of ultrapure water with stirring until pH 7 is reached. Thereafter, the slurry was allowed to stand at 25 ° C. for 15 hours to obtain a slurry. Next, this slurry was washed with ultrapure water and filtered, and this washing and filtration was repeated 5 times until the slurry became neutral. The slurry was dried and then pulverized to obtain ruthenium oxide hydrate having an average particle diameter of 2 nm, a specific capacitance of 600 F / g in an H ₂ SO ₄ electrolyte solution at 25 ° C. and 0.5 mol / L. A powder (RuO ₂ · nH ₂ O) was obtained. The obtained ruthenium oxide hydrate powder was used in place of the activated carbon powder in the above-described method for producing an activated carbon electrode to produce a ruthenium oxide hydrate electrode.

(Preparation of ruthenium oxide nanosheet A)
Ruthenium oxide nanosheet A (Ru ⁴⁺ O _2.1 ) was synthesized according to Non-Patent Document 3 described above. Specifically, the positive electrode 11 using the ruthenium oxide nanosheet A was produced as follows. First, 0.60 g of ruthenium oxide (RuO ₂ ) and 0.39 g of potassium carbonate (K ₂ CO ₃ ) were mixed in acetone to form pellets. Next, the pellet was fired at 800 ° C. in an argon gas atmosphere for 12 hours and then washed with ultrapure water to obtain layered potassium ruthenate. This layered potassium ruthenate was added to 100 mL of 1M HCl aqueous solution, stirred at 60 ° C. for 72 hours, and then washed with ultrapure water to obtain layered ruthenate. This layered ruthenic acid was added to 100 mL of an aqueous solution containing 6.88 mL of 10% by weight TBAOH (tetrabutylammonium hydroxide) and the remainder being ultrapure water, stirred at 25 ° C. for 10 days, and then centrifuged (2000 rpm, 30 minutes) to obtain a colloidal solution of ruthenium oxide nanosheet A. 20 μL of the obtained colloidal solution containing 0.2 g / L of ruthenium oxide nanosheet A was dropped onto the end face of the tip of cylindrical glassy carbon (trade name: GC-20S, manufactured by Tokai Carbon Co., Ltd.) having a diameter of 5 mm, and 60 ° C. Held for 30 minutes to dry. Then, 20 μL of 0.033 mass% Nafion (registered trademark of DuPont, manufactured by Sigma-Aldrich) alcohol water mixed solution is dropped onto the same end face of the glassy carbon, and kept at 60 ° C. for 30 minutes to dry. Then, a ruthenium oxide nanosheet electrode A as the positive electrode 11 was produced. The active material carried on the end face of this electrode is 4 μg.

(Preparation of ruthenium oxide nanosheet B)
Ruthenium oxide nanosheet B (Ru ^3.8+ O ₂ ) was synthesized according to Non-Patent Document 4 described above. Specifically, the positive electrode 11 using the ruthenium oxide nanosheet B was produced as follows. First, 0.298 g of ruthenium, 0.560 g of ruthenium oxide (RuO ₂ ), and 0.142 g of sodium carbonate (Na ₂ CO ₃ ) were mixed in acetone to form pellets. Next, the pellet was fired at 700 ° C. for 1 hour and 900 ° C. for 12 hours in order in an argon gas atmosphere to obtain layered sodium ruthenate. This layered sodium ruthenate is added to a solution obtained by dissolving 1.257 g of Na ₂ S ₂ O _{8 in} 420 g of ultrapure water, then washed with ultrapure water, and further added to 200 mL of 1 M HCl aqueous solution at 60 ° C. After stirring for 72 hours, laminar ruthenic acid was obtained by washing with ultrapure water. This layered ruthenic acid was added to 183 mL of an aqueous solution containing 2.8 mL of 10% by mass TBAOH (tetrabutylammonium hydroxide) and the remainder being ultrapure water, stirred at 25 ° C. for 10 days, and then centrifuged (2000 rpm, 30 minutes) to obtain a colloidal solution of ruthenium oxide nanosheet B. 20 μL of the resulting colloidal solution containing 0.2 g / L of ruthenium oxide nanosheet B was dropped onto the end face of the tip of cylindrical glassy carbon (trade name: GC-20S, manufactured by Tokai Carbon Co., Ltd.) having a diameter of 5 mm, and 60 ° C. Held for 30 minutes to dry. Then, 20 μL of 0.033 mass% Nafion (registered trademark of DuPont, manufactured by Sigma-Aldrich) alcohol water mixed solution is dropped onto the same end face of the glassy carbon, and kept at 60 ° C. for 30 minutes to dry. Then, an activated carbon electrode as the positive electrode 11 was produced. The active material supported on the end face of the activated carbon electrode is 4 μg.

[Preparation of negative electrode]
(Lithium composite electrode A)
The negative electrode 12 using the lithium composite electrode A was synthesized according to Non-Patent Document 5 described above. Specifically, the negative electrode 12 using the lithium composite electrode A was produced as follows. First, metallic lithium (manufactured by Honjo Metal Industry Co., Ltd., 0.2 × 5 × 5 mm, active material) at one end of a metallic nickel foil (manufactured by Niraco Co., Ltd., 0.1 × 5 × 150 mm, negative electrode current collector 17) Layer 21) was loaded. PEO (manufactured by Sigma-Aldrich Co., Ltd.)-LiTFSI (lithium bistrifluoromethanesulfonylimide, Li (CF ₃ SO ₂ ) ₂ N, manufactured by Wako Pure Chemical Industries, Ltd.) composite sheet cut into 6 mm square on this metallic lithium ( A polymer electrolyte 22) was laminated. Furthermore, LTAP (LICGC, lithium ion conductive glass ceramics, OHARA, Inc., thickness 0.15 mm, lithium ion conductive solid electrolyte 23) cut into a 10 mm square was laminated thereon. This laminate was sandwiched between two laminate films (produced by Nihon Co., Ltd., trade name: Rami Zip AL-15, made of aluminum) cut into 100 mm squares, and laminator (vacuum packaging machine made by Bonmac Co., Ltd.). (Trade name: BMV-281). A 5 mm square hole was made in the laminate film in contact with LTAP, and a measurement window in which LTAP was in contact with the aqueous electrolyte was used. A nickel foil drawn from one side of the four sides of the lithium composite electrode was used for collecting the lithium composite negative electrode. The cell resistance of the produced lithium composite electrode A was 185 Wcm ² .

(Lithium composite electrode B)
The negative electrode 12 using the lithium composite electrode B was produced as follows. First, a laminate (hereinafter, also referred to as “lithium pre-doped graphite electrode”) of a copper foil (current collector 17 for negative electrode) and a graphite layer (active material layer 21) doped with lithium was prepared.

Specifically, 0.5 g of graphite powder (average particle size less than 20 μm, manufactured by Sigma-Aldrich), 0.05 g of polyvinylidene fluoride (manufactured by Sigma-Aldrich), and N-methyl-pyrrolidinone (manufactured by Kanto Chemical Co., Ltd.) ) 1.25 mL was mixed for 5 minutes to prepare a paint. This paint was applied to a copper foil (thickness: 100 μm) with a thickness of 100 μm to form a coating film. This coating film was dried at 60 ° C. for 1 hour and then naturally dried. Next, the copper foil on which the coating film was formed was punched into a 1 cm ² circle and pressed at a pressure of 700 kg / cm ² for 1 minute. Thereafter, the coating film was vacuum-dried at 150 ° C. for 16 hours to obtain a graphite electrode having a graphite layer formed on the surface of the copper foil.

Next, lithium was doped into the graphite layer using a galvano / potentiostat (trade name: HZ3000 manufactured by Hokuto Denko Co., Ltd.) to obtain a lithium pre-doped graphite electrode. Specifically, Li foil (manufactured by Honjo Metal Co., Ltd.) is used as the counter electrode, and 1M LiPF ₆ is a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (1: 1 by volume) as the electrolyte. Using a non-aqueous electrolyte solution (manufactured by Kishida Chemical Co., Ltd.) dissolved in 1 and using the graphite electrode produced as described above as a working electrode, the Li foil and the graphite electrode were short-circuited for 72 hours to dope the graphite layer with lithium . Here, the natural potential of the graphite electrode was 3.0 V (vs. Li ^/ Li ⁺ ) at the start of the short circuit and 0 V (vs. Li ^/ Li ⁺ ) at the end of the short circuit. The obtained lithium pre-doped graphite electrode was used in place of the metal nickel foil and metal lithium in the above-described method for producing the lithium composite electrode A to produce a lithium composite electrode B.

[Preparation of aqueous electrolyte]
(Lithium chloride aqueous solution / lithium sulfate aqueous solution)
As an aqueous electrolyte, an aqueous lithium chloride solution and an aqueous lithium sulfate solution were prepared. As the lithium chloride aqueous solution, lithium chloride was dissolved in ultrapure water to prepare a 1M aqueous solution. Similar to the lithium sulfate aqueous solution, lithium sulfate was dissolved in ultrapure water to prepare a 1M aqueous solution.

(Lithium acetate aqueous solution)
As an aqueous electrolyte, 33 g of lithium acetate (CH ₃ COOLi) was dissolved in 250 mL of ultrapure water to prepare a 2M aqueous solution (pH 8.30).

(Lithium dihydrogen phosphate-lithium hydroxide solution)
A lithium dihydrogen phosphate-lithium hydroxide solution was prepared as an aqueous electrolyte. First, 4.7786 g of lithium dihydrogen phosphate (LiH ₂ PO ₄ ) was dissolved in 500 mL of ultrapure water to prepare a 0.1 M lithium dihydrogen phosphate aqueous solution. Further, 2.098 g of lithium hydroxide (LiOH) was dissolved in 500 mL of ultrapure water to prepare a 0.1 M lithium hydroxide aqueous solution. The prepared 0.1 M lithium hydroxide aqueous solution (29.1 mL) and 0.1 M lithium dihydrogen phosphate aqueous solution (50 mL) were mixed to prepare a lithium dihydrogen phosphate-lithium hydroxide solution (pH 6.87).

(Lithium acetate-acetic acid solution)
A lithium acetate-acetic acid solution was prepared as an aqueous electrolyte. First, 33 g of lithium acetate (CH ₃ COOLi) was dissolved in 250 mL of ultrapure water to prepare a 2M lithium acetate aqueous solution. Further, 30 g of acetic acid (CH ₃ COOH) was dissolved in 250 mL of ultrapure water to prepare a 2M acetic acid aqueous solution. The prepared 2M lithium acetate aqueous solution 87.5 mL and 2M acetic acid aqueous solution 12.5 mL were mixed, and ultrapure water was added to make the total volume 200 mL, thereby preparing a lithium acetate-acetic acid solution (pH 5.41).

Note that any aqueous electrolyte was subjected to nitrogen gas bubbling to remove dissolved oxygen. The pH of the aqueous electrolyte was measured at 60 ° C. using a pH meter (manufactured by Toa DKK Corporation, HM-60E).

[Example 1]
Using the above-mentioned activated carbon electrode as the positive electrode 11, using the above-mentioned lithium composite electrode A as the cathode 12, and using the above-described lithium chloride aqueous solution (pH 7.64) and lithium sulfate aqueous solution (pH 5.15) as the aqueous electrolyte solution 13, Two types of hybrid capacitors 1 were constructed as shown in FIG.

[Example 2]
The above-described manganese oxide electrode is used as the positive electrode 11, the above-described lithium composite electrode A is used as the cathode 12, and the above-described lithium chloride aqueous solution (pH 6.52) and lithium sulfate aqueous solution (pH 5.50) are used as the aqueous electrolyte solution 13. Two types of hybrid capacitors 1 were constructed as shown in FIG.

[Example 3]
The above-described ruthenium oxide hydrate electrode is used as the positive electrode 11, the above-described lithium composite electrode A is used as the cathode 12, and the above-described lithium chloride aqueous solution (pH 6.52) and lithium sulfate aqueous solution (pH 5.50) are used as the aqueous electrolyte solution 13. Two types of hybrid capacitors 1 were constructed as shown in FIG.

[Example 4]
The above-described ruthenium oxide sheet electrode A is used as the positive electrode 11, the above-described lithium composite electrode A is used as the cathode 12, and the above-described lithium chloride aqueous solution (pH 6.54) and lithium sulfate aqueous solution (pH 5.36) are used as the aqueous electrolyte solution 13. In use, two types of hybrid capacitors 1 were constructed as shown in FIG.

[Example 5]
The above-described ruthenium oxide sheet electrode B is used as the positive electrode 11, the above-described lithium composite electrode A is used as the cathode 12, and the above-described lithium chloride aqueous solution (pH 6.6) and lithium sulfate aqueous solution (pH 5.7) are used as the aqueous electrolyte solution 13. In use, two types of hybrid capacitors 1 were constructed as shown in FIG.

[Example 6]
The above-described manganese oxide electrode B is used as the positive electrode 11, the above-described lithium composite electrode A is used as the cathode 12, and the above-described lithium sulfate aqueous solution (pH 5.7) is used as the aqueous electrolyte solution 13. Configured as shown.

[Example 7]
The above-described activated carbon electrode was used as the positive electrode 11, the above-described lithium composite electrode B was used as the cathode 12, and the above-described lithium chloride aqueous solution was used as the aqueous electrolyte solution 13, so that the hybrid capacitor 1 was configured as shown in FIG.

[Example 8]
The hybrid capacitor 1 is illustrated using the above-described ruthenium oxide hydrate electrode as the positive electrode 11, the above-described lithium composite electrode A as the cathode 12, and the above-described aqueous lithium acetate solution (pH 8.30) as the aqueous electrolyte solution 13. As shown in FIG.

[Example 9]
The above-described manganese oxide electrode B is used as the positive electrode 11, the above-described lithium composite electrode A is used as the cathode 12, and the above-described lithium dihydrogen phosphate-lithium hydroxide buffer (pH 6.87) is used as the aqueous electrolyte solution 13. The hybrid capacitor 1 was configured as shown in FIG.

[Example 10]
The above-described ruthenium oxide hydrate electrode is used as the positive electrode 11, the above-described lithium composite electrode A is used as the cathode 12, and the above-described lithium dihydrogen phosphate-lithium hydroxide buffer (pH 6.87) is used as the aqueous electrolyte solution 13. The hybrid capacitor 1 was configured as shown in FIG.

[Example 11]
Using the above-described ruthenium oxide hydrate electrode as the positive electrode 11, using the above-described lithium composite electrode A as the cathode 12, and using the above-described lithium acetate-acetic acid buffer solution (pH 5.41) as the aqueous electrolyte solution 13, a hybrid capacitor 1 was constructed as shown in FIG.

[Measurement]
Using the hybrid capacitor 1 of Examples 1 to 11, capacitor characteristics and charge / discharge characteristics were evaluated. Capacitor characteristics were evaluated by cyclic voltammetry using a tripolar electrochemical measurement cell. The charge / discharge characteristics were evaluated from the charge / discharge measurement results using a bipolar electrochemical measurement cell.

(Cyclic voltammetry (CV))
Cyclic voltammetry measurement was performed using a potentiostat (HZ3000, manufactured by Hokuto Denko Co., Ltd.) and a cell (semi-micro separable cover, semi-micro separable flask, manufactured by Nihon Rikenki Co., Ltd.). The same aqueous electrolytic solution as used in each example was used as the electrolytic solution, glassy carbon (φ5, 19.625 mm ² ) carrying a positive electrode material was used as the working electrode, and a silver / silver chloride electrode (HS -205C, manufactured by Toa DKK Co., Ltd.) and a Pt mesh (100 mesh, 20 × 30 mm, Niraco Co., Ltd.) was used as the counter electrode. However, in Examples 6 and 9, carbon paper on which a manganese oxide film was electrodeposited was used as a working electrode. This cyclic voltammetry measurement was performed under the temperature condition of 60 ° C. and in the range of potential scanning speed of 2 mV / s to 500 mV / s.

(Charge / discharge measurement)
For the charge / discharge measurement, the same aqueous electrolyte as that used in each example was used as the electrolyte, glassy carbon (φ5, 19.625 mm ² ) carrying a positive electrode material as the working electrode, and each example as the counter electrode. The same lithium composite electrode as used in Example 1 was used, and a silver / silver chloride electrode (HS-205C, manufactured by Toa DKK Corporation) was used as a reference electrode. However, in Examples 6 and 9, carbon paper on which a manganese oxide film was electrodeposited was used as a working electrode. Charging and discharging measurements, at a temperature of 60 ° C., as a constant current density ^was carried out in the range of 0.08mA / cm 2 ~ 1.53mA / cm 2.

(Charge / discharge cycle measurement)
The same aqueous electrolyte as that used in each example was used as an electrolyte, glassy carbon (φ5, 19.625 mm ² ) carrying a cathode material was used as a working electrode, and a lithium composite electrode A (Li | PEO-) was used as a counter electrode. LiTFSI | LTAP) was used as a constant current density under a temperature condition of 60 ° C.

[result]
(Capacitor characteristics)
FIG. 2 is a cyclic voltammogram using the activated carbon electrode obtained in Example 1 and an aqueous lithium chloride solution. The shape of the cyclic voltammogram was rectangular, and it showed an ideal electric double layer behavior even when the scanning speed was changed. The obtained specific capacitance Cp was 102 F / g (2 mV / sec). Table 1 shows the specific capacitance Cp at each scanning speed. If this activated carbon electrode is used for the positive electrode of a hybrid capacitor, it is considered that the charge / discharge behavior like a capacitor is exhibited. In addition, since a peak due to an irreversible capacity is not seen up to 1.2 V (vs. RHE), in a cell combined with a lithium composite electrode, about 4.2 V is considered in consideration of the standard electrode potential of Li / Li ⁺ . A cell voltage is considered to be obtained.

Cyclic voltammograms using each positive electrode obtained in Examples 2 to 11 and an aqueous electrolyte were also obtained (not shown). The specific capacitance Cp at each scanning speed of Examples 1 to 5 is shown in Table 1, and the specific capacitance Cp at each scanning speed of Examples 6 and 8 to 11 is shown in Table 2.

Thus, any cyclic voltammogram showed an electric double layer behavior. From this, it is thought that the hybrid capacitor of each Example exhibits a capacitor-like charge / discharge behavior.

In the case of an electrochemical capacitor that uses a non-Faraday (ie, physical) electric double layer for charge storage in an aqueous electrolyte, the operating voltage on the positive electrode side is greatly limited by the oxygen generation reaction (OER). . If the OER overvoltage is high, expansion of the operating voltage on the positive electrode side can be expected. Even in the hybrid capacitor of the present invention, a manganese oxide electrode having a high OER overvoltage (stable up to 1.6 V vs. RHE), a lead oxide electrode (stable up to 2.0 V vs. RHE), a conductive diamond electrode (stable up to 2.5 V vs. RHE) Etc. can be expected to further increase the operating voltage.

(Charge / discharge characteristics)
FIG. 3 is a charge / discharge curve obtained in a charge / discharge test of the hybrid capacitor 1 using the activated carbon electrode obtained in Example 1 and an aqueous lithium chloride solution. The cut-off potential was 3.9 V for charging and 2.9 V for discharging. Each charge / discharge characteristic was obtained by converting the specific capacitance obtained from the discharge curve into the battery capacity. The results are shown in Table 3. This hybrid capacitor uses a two-phase electrolyte. That is, Li ⁺ moves between the aqueous electrolyte (1M LiCl aqueous solution) between the positive electrode and the negative electrode and the polymer electrolyte (PEO-LiTFSI | LTAP). With this cell configuration, it is considered that a voltage of about 3 V can be obtained on the negative electrode side by the reaction of Li / Li ⁺ and a voltage of about 1 V can be obtained on the positive electrode side by the electric double layer. The voltage between the positive and negative electrodes obtained can be expected to be about 4 V, and a cell voltage exceeding that of a conventional lithium ion capacitor can be obtained. Along with this, a great improvement in energy density can be expected. As shown in FIG. 3, the charge / discharge curve changes with a constant slope, and a triangular shape is obtained, which indicates that the capacitor-like behavior is exhibited. That is, it can be seen that the capacity of the activated carbon electrode is not due to the battery reaction but to the electric double layer. Moreover, a high cell voltage of 3.9 V was obtained, and a high cell voltage could be obtained even when compared with the current lithium ion capacitor.

The charge / discharge test of the hybrid capacitor 1 using the manganese oxide electrode obtained in Example 2 and each aqueous electrolyte was performed. The cut-off potential was 4.3V for charging and 3.3V for discharging. Each charge / discharge characteristic was obtained by converting the specific capacitance obtained from the discharge curve into the battery capacity. The results are shown in Table 4. The charge / discharge curve changed with a constant slope, and the triangular shape was obtained. Moreover, a high cell voltage of 4.3 V was obtained, and a high cell voltage could be obtained even when compared with the current lithium ion capacitor.

The charge / discharge test of the hybrid capacitor 1 using the ruthenium oxide hydrate electrode obtained in Example 3 and each aqueous electrolyte was performed. The cut-off potential was 3.8 V for charging and 2.8 V for discharging. Each charge / discharge characteristic was obtained by converting the specific capacitance obtained from the discharge curve into the battery capacity. The results are shown in Table 5. The charge / discharge curve changed with a constant slope, and the triangular shape was obtained. Further, a high cell voltage of 3.8 V was obtained, and a high cell voltage could be obtained even when compared with the current lithium ion capacitor.

The charge / discharge test of the hybrid capacitor 1 using the ruthenium oxide nanosheet electrode obtained in Example 4 and each aqueous electrolyte was performed. The cut-off potential was 3.9 V for charging and 2.9 V for discharging. Each charge / discharge characteristic was obtained by converting the specific capacitance obtained from the discharge curve into the battery capacity. The results are shown in Table 6. The charge / discharge curve changed with a constant slope, and the triangular shape was obtained. Moreover, a high cell voltage of 3.9 V was obtained, and a high cell voltage could be obtained even when compared with the current lithium ion capacitor.

The charge / discharge test of the hybrid capacitor 1 using the ruthenium oxide nanosheet electrode obtained in Example 5 and each aqueous electrolyte was performed. The cut-off potential was 3.9 V for charging and 2.9 V for discharging. Each charge / discharge characteristic was obtained by converting the specific capacitance obtained from the discharge curve into the battery capacity. The results are shown in Table 7. The charge / discharge curve changed with a constant slope, and the triangular shape was obtained. Moreover, a high cell voltage of 3.9 V was obtained, and a high cell voltage could be obtained even when compared with the current lithium ion capacitor.

The charge / discharge test of the hybrid capacitor 1 using the manganese oxide electrode B obtained in Example 6 and the aqueous electrolyte was performed. The cut-off potential was set to 4.2V for charging and 3.2V for discharging. Each charge / discharge characteristic was obtained by converting the specific capacitance obtained from the discharge curve into the battery capacity. The results are shown in Table 8. The charge / discharge curve changed with a constant slope, and the triangular shape was obtained. Moreover, a high cell voltage of 4.2 V was obtained, and a high cell voltage could be obtained even when compared with the current lithium ion capacitor.

The charge / discharge test of the hybrid capacitor 1 using the activated carbon electrode obtained in Example 7, the aqueous electrolyte, and the lithium composite electrode B was performed. The cut-off potential was 3.6 V for charging and 2.6 V for discharging. Each charge / discharge characteristic was obtained by converting the specific capacitance obtained from the discharge curve into the battery capacity. The results are shown in Table 9. The charge / discharge curve changed with a constant slope, and the triangular shape was obtained. Moreover, a high cell voltage of 3.6 V was obtained, and a cell voltage close to that of a hybrid capacitor using the lithium composite electrode A could be obtained.

The charge / discharge test of the hybrid capacitor 1 using the ruthenium oxide hydrate electrode obtained in Example 8 and the aqueous electrolyte was performed. The cut-off potential was set to 3.7V for charging and 2.7V for discharging. Each charge / discharge characteristic was obtained by converting the specific capacitance obtained from the discharge curve into the battery capacity. The results are shown in Table 10. The charge / discharge curve changed with a constant slope, and the triangular shape was obtained. Moreover, a high cell voltage of 3.7 V was obtained, and a high cell voltage could be obtained even when compared with the current lithium ion capacitor.

The charge / discharge test of the hybrid capacitor 1 using the manganese oxide electrode A obtained in Example 9 and the aqueous electrolyte was performed. The cut-off potential was set to 4.3V for charging and 3.3V for discharging. Each charge / discharge characteristic was obtained by converting the specific capacitance obtained from the discharge curve into the battery capacity. The results are shown in Table 11. The charge / discharge curve changed with a constant slope, and the triangular shape was obtained. Moreover, a high cell voltage of 4.3 V was obtained, and a high cell voltage could be obtained even when compared with the current lithium ion capacitor.

The charge / discharge test of the hybrid capacitor 1 using the ruthenium oxide hydrate electrode obtained in Example 10 and the aqueous electrolyte was performed. The cut-off potential was 3.9 V for charging and 2.9 V for discharging. Each charge / discharge characteristic was obtained by converting the specific capacitance obtained from the discharge curve into the battery capacity. The results are shown in Table 12. The charge / discharge curve changed with a constant slope, and the triangular shape was obtained. Moreover, a high cell voltage of 3.9 V was obtained, and a high cell voltage could be obtained even when compared with the current lithium ion capacitor.

The charge / discharge test of the hybrid capacitor 1 using the ruthenium oxide hydrate electrode obtained in Example 11 and the aqueous electrolyte was performed. The cut-off potential was 3.9 V for charging and 2.9 V for discharging. Each charge / discharge characteristic was obtained by converting the specific capacitance obtained from the discharge curve into the battery capacity. The results are shown in Table 13. The charge / discharge curve changed with a constant slope, and the triangular shape was obtained. Moreover, a high cell voltage of 3.9 V was obtained, and a high cell voltage could be obtained even when compared with the current lithium ion capacitor.

(Charge / discharge cycle characteristics)
The charge / discharge cycle curve obtained by the charge / discharge cycle test of the hybrid capacitor 1 using the activated carbon electrode obtained in Example 1 and the lithium chloride aqueous solution is shown in FIG. The charge / discharge cycle test was performed for 200 cycles at a constant current density of 255 μA / cm ² with a cut-off potential of 3.9 V for charge and 2.9 V for discharge. Table 14 shows the result of converting the specific capacitance obtained from the cycle discharge curve into the battery capacity. Even after 200 cycles of charge / discharge, 95% or more of the initial capacity was maintained.

The charge / discharge cycle test of the hybrid capacitor 1 using the ruthenium oxide hydrate electrode obtained in Example 3 and the lithium sulfate aqueous solution was performed. The charge / discharge cycle test was performed for 200 cycles at a constant current density of 255 μA / cm ² with a cut-off potential of 3.8 V for charge and 2.8 V for discharge. Table 15 shows the result of converting the specific capacitance obtained from the cycle discharge curve into the battery capacity. Even after 200 cycles of charge / discharge, 95% or more of the initial capacity was maintained.

The charge / discharge cycle test of the hybrid capacitor 1 using the manganese oxide electrode B obtained in Example 6 and the lithium sulfate aqueous solution was performed. The charge / discharge cycle test was performed 2000 cycles at a constant current density of 0.6 mA / cm ² with a cut-off potential of 4.2 V for charge and 3.2 V for discharge. Table 16 shows the results of the energy density and the capacity retention rate obtained by converting the specific capacitance obtained from the charge / discharge cycle curve into the battery capacity. Even after 2000 cycles of charge and discharge, 80% or more of the initial capacity was maintained.

As shown in the above experimental results, the hybrid capacitor 1 of the present invention showed capacitor characteristics having a high cell voltage and a high energy density. As described above, the hybrid capacitor 1 using the aqueous electrolyte 13 was able to achieve a dramatic improvement in energy density because of the positive electrode active material having a cell voltage of 5 V class and a very high single electrode capacity. Two were the factors. Further, the hybrid capacitor 1 of the present invention uses a neutral aqueous electrolyte, and thus has an advantage of being safe and easy to handle, and improves durability without damaging the positive electrode 11 and the lithium composite electrode 12. be able to.

1 Hybrid capacitor 11 Positive electrode (metal oxide electrode)
12 Negative electrode (lithium composite electrode)
13 Neutral Aqueous Electrolyte 16 Current Collector for Positive Electrode 17 Current Collector for Negative Electrode 18 Container 21 Active Material Layer Containing Lithium 22 Polymer Electrolyte 23 Lithium Ion Conductive Solid Electrolyte

Claims

At least a positive electrode having one or both of a carbon material and a metal oxide, a negative electrode composed of a lithium composite electrode, and a neutral aqueous electrolyte filled between the positive electrode and the negative electrode, the lithium composite A hybrid capacitor, wherein the electrode is a laminated electrode of a lithium ion conductive solid electrolyte, a polymer electrolyte, and an active material layer containing lithium.
The hybrid capacitor according to claim 1, wherein the neutral aqueous electrolyte solution has a pH of 5 or more and a pH of 8.5 or less, and the metal oxide is selected from manganese oxide, ruthenium oxide, and lead oxide.
The hybrid capacitor according to claim 1 or 2, wherein the positive electrode includes a sheet containing one or both of a carbon material and a metal oxide, and a metal oxide film provided on at least a surface of the sheet.
The hybrid capacitor according to claim 3, wherein the sheet is a cloth-like body having carbon fibers.
The hybrid capacitor according to any one of claims 1 to 4, wherein the lithium-containing active material layer includes lithium, a lithium alloy, or a carbon material doped with lithium.