JP2009290116A - Energy storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a small, large-capacity energy storage device with small self-discharge. <P>SOLUTION: The energy storage device includes one sealed cabinet in which at least a positive pole, a negative pole, electrolyte, an active material which can be oxidized or reduced, and a plurality of separators 4 or one separator 4 are provided. In the energy storage device, at least a part of the active material is dissolved in the electrolyte at a concentration of 0.2 mol/l or more, and the separator 4 contains anion exchange resin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an energy storage device, and more particularly to a novel energy storage device having a mechanism for storing energy by an oxidation / reduction reaction of an active material dissolved in an electrolytic solution.

  In recent years, consumer electronic devices have become portable, cordless, and the like, and there is an increasing demand for small, lightweight, large-capacity capacitors and batteries that serve as power sources for driving these electronic devices. In addition, a large-capacity energy storage device is also required for applications such as hybrid vehicles (HEV) and fuel cell vehicles (FCEV).

  Lithium ion secondary batteries form the largest market for small devices for energy storage. A lithium ion secondary battery using a lithium-containing transition metal oxide for the positive electrode and a layered carbon material for the negative electrode has a large capacity and has already been used in a wide range of applications. Research on lithium ion secondary batteries has been actively conducted, and improvement research not only on positive electrodes and negative electrodes but also on electrolytes has been conducted (Patent Document 1). However, in recent years, there has been a strong demand for further reduction in size and weight of portable electronic devices for consumer use, and further improvements in the capacity of current lithium ion secondary batteries are required.

  On the other hand, electric double layer capacitors have been put to practical use as energy storage devices that can be charged and discharged at high speed. An electric double layer capacitor is an energy storage device that utilizes an electric double layer capacity generated at an interface between an electrode and an electrolyte when a voltage is applied. Compared to the lithium ion secondary battery with electrochemical reaction, the energy storage by electric double layer capacity is characterized by being able to charge / discharge faster and having excellent repeated life characteristics of charge / discharge. ing. However, the electric double layer capacitor has a disadvantage that it has a small capacity, and there is a strong demand for a large capacity.

  As another proposal, a redox capacitor using a pseudocapacitor made of a metal oxide or a conductive polymer has been proposed (Patent Documents 2 and 3). The pseudo capacitance is expressed by, for example, a redox reaction of a conductive polymer, that is, a doping / dedoping reaction. As such a conductive polymer material, pi-conjugated polymers such as polypyrrole, polyaniline, polythiophene and derivatives thereof are known, but the improvement in capacity is still a problem.

  An energy storage device called a lithium ion capacitor has been proposed (Patent Document 4). This is to store energy by using the electric double layer capacity on the surface of activated carbon on the positive electrode side and the intercalation capacity of lithium ions to the layered carbon material on the negative electrode side, with a good balance between large capacity and high-speed charge / discharge performance. It is an energy storage device to be realized. However, since the electric double layer capacity used on the positive electrode side is small, there is a limit to increasing the capacity of the entire device.

  Each of the above capacitors and batteries is an energy storage device that uses an oxidation / reduction reaction of the solid electrode itself or / and an electric double layer capacity in the vicinity of the solid electrode as energy storage means. In other words, electrical energy can be stored and released because only the part related to the electrode itself or very close to the electrode is used, such as oxidation / reduction of the electrode material itself and adsorption / desorption of ions on the surface of the solid electrode. Capacity is limited.

On the other hand, an energy storage device by another method for storing energy in the active material itself dissolved in the electrolytic solution has been proposed. This is known as a redox flow battery, and practical application studies are in progress. For example, ^Fe 3+ / ^{Fe 2+} salt solution as the electrolyte on the positive electrode side, the system (Patent Document 5) with ^Cr 2+ / ^{Cr 3+} salt solution as a liquid on the negative electrode side and, in the liquid of the positive electrode side _^VO 2+ / ^{VO 2 +} A system using a V ²⁺ / V ³⁺ aqueous solution as an aqueous solution or negative electrode solution (Patent Document 6) has been proposed. This battery circulates the active material in the electrolyte solution oxidized and reduced on the electrode surface and stores it in separate large tanks for large-scale energy storage. The pump uses a pump to flow the active material. It is characterized by charging and discharging. This method requires a pump and a tank, and requires a large installation space. Thus, the redox flow battery requires large-scale equipment, and an electrode having a large capacity per weight like a lithium ion battery cannot be effectively used for energy storage. Only the active material in the electrolytic solution can substantially contribute to energy storage. However, since the active material concentration in the electrolytic solution is lower than that of the solid electrode, there is a limit to the capacity per weight that can be exhibited. For this reason, the redox flow battery has a drawback that the total weight and / or capacity per whole volume of the device is reduced, and it is not suitable as a small-sized energy storage device for portable use or in-vehicle use.

Further, there is a proposal of a Li / TiS ₂ battery in which ferrocenes are dissolved in an electrolytic solution for the purpose of preventing overcharge. This uses a redox shuttle by oxidation / reduction reactions of ferrocenes to prevent the battery from exceeding a predetermined voltage. Here, ferrocenes are added in a special role of preventing overcharge, are not used as active materials, and do not improve the capacity of the energy storage device itself (Patent Document 7).

  It has also been proposed to add a small amount of additives (ferrocenes and the like) to the electrolytic solution to promote the oxidation / reduction reaction of the conductive organic electrode. However, the additive (ferrocenes, etc.) in the electrolyte here has a very low concentration (about 1 millimol / liter to 10 millimol / liter), and only assists the oxidation / reduction reaction of the solid electrode itself. Does not work, and does not improve the capacity of the energy storage device itself (Patent Documents 8 and 9).

  On the other hand, a new type of large-capacity energy storage device that actively dissolves an active material in an electrolytic solution and uses oxidation / reduction reactions of the dissolved active material has been proposed (Patent Document 10). In this case, in order to store a large amount of energy, it is necessary to increase the concentration of the active material dissolved in the electrolytic solution. However, there is a problem that it is difficult to obtain sufficient solubility when a high molecular weight compound is used as the active material. On the other hand, when the molecular weight is lowered in order to enhance the solubility, there is a problem that the diffusion rate of the active material oxidized or reduced near the positive electrode or the negative electrode is large and reaches the counter electrode and loses charge and self-discharges.

We pay attention to the above points and prevent charge loss associated with the movement of the active material to the counter electrode, that is, self-discharge, in an energy device that uses an oxidation / reduction reaction of the active material dissolved in the electrolyte. To achieve a large-capacity energy storage device.
JP 2003-338318 A Japanese Patent Laying-Open No. 2005-223089 Special table 2007-529586 JP 2006-286919 A Japanese Patent Laid-Open No. 1-60967 JP-A-8-138716 JP-A-1-206571 JP 59-60967 A Japanese Patent Laid-Open No. 11-214009 International Publication WO2007 / 052762 Pamphlet

  An object of the present invention is to provide a small-sized and large-capacity energy storage means with less self-discharge.

  As a result of intensive studies, the present inventors have discovered that a large amount of energy can be stored in an electrolytic solution in which a specific active material capable of repeated oxidation / reduction reactions is dissolved. Furthermore, in order to store and take out energy effectively, it has been found that it is effective to use an ion exchange resin for at least a part of the separator, and the present invention has been achieved. The method of the present invention is completely different from the conventional redox flow battery, because it does not flow the active material dissolved in the electrolyte, and therefore does not require a separate tank or the like for storing the active material. It is extremely effective as a means for improving the capacity of a small energy storage device.

  That is, a first aspect of the present invention is an energy storage device in which at least a positive electrode, a negative electrode, an electrolytic solution, an oxidizable / reducible active material, and a separator are contained in a single sealed casing. The energy storage device is characterized in that the part is dissolved in the electrolyte and the separator contains an anion exchange resin. The anion exchange resin or the anion exchange membrane used in the present invention selectively permeates the anion in the electrolytic solution and restricts the movement of the cation and the active material in a neutral state. The device suppresses self-discharge by restricting the movement of cations and neutral compounds. Anion migration is necessary for the device to perform charge and discharge functions.

  A second aspect of the present invention is the first energy storage device according to the present invention, wherein at least a part of the active material is dissolved in the electrolytic solution at a concentration of 0.2 mol / liter or more. The active material concentration of the electrolytic solution is an average value of the concentration of the active material with respect to the solvent of the total electrolytic solution contained in the device, and there is partially an electrolytic solution having a concentration of 0.2 mol / liter or less. Also good. The concentration of the active material is preferably higher from the viewpoint of increasing the energy density, and if it is less than 0.2 mol / liter, a large energy density improvement effect cannot be obtained.

  A third aspect of the present invention is the first or second energy storage device according to the present invention, wherein the electrolytic solution is an organic electrolytic solution having a water content of 1 weight percent or less. In general, ion exchange resins are often used in aqueous electrolytes. However, in order to obtain a high energy density in the energy storage device, a high driving voltage is required, and it is preferable to use an organic electrolyte. The present invention is characterized in that it can also be applied to an organic electrolyte.

  A fourth aspect of the present invention is the energy storage device according to any one of the first, second, and third aspects of the present invention, wherein the active material dissolved in the electrolytic solution is positively charged when charged at the positive electrode. . Using an anion exchange resin or an anion exchange membrane, permeation of positively charged cations during charging at the positive electrode is prevented and self-discharge is suppressed.

  A fifth aspect of the present invention is the energy storage device according to any one of the first, second, and third aspects of the present invention, wherein the active material dissolved in the electrolytic solution is positively charged during discharge at the negative electrode. is there. As described above, the anion exchange resin or the anion exchange membrane selectively permeates the anion in the electrolytic solution and restricts the movement of the cation and the active material in a neutral state. It is possible to prevent the self-discharge by restricting the movement of the active material in a charged state that is neutral.

  A sixth aspect of the present invention is the energy storage device according to any one of the first to fifth aspects of the present invention, wherein at least two kinds of active materials are dissolved in an electrolytic solution. The active material may be one type or a plurality of types. For example, it is also possible to select two types of active materials that operate on the positive electrode and increase the total dissolved amount of the active materials to increase the energy density. It is also possible to increase the capacity of both the positive electrode and the negative electrode by dissolving the active material that operates in each of the positive electrode and the negative electrode.

  A seventh aspect of the present invention is characterized in that at least one of the active materials dissolved in the electrolytic solution is positively charged during charging at the positive electrode, and at least one is positively charged during discharging at the negative electrode. It is an energy storage device according to 6 of the present invention. This is an energy storage device using both 4 of the present invention at the positive electrode and 5 of the present invention at the negative electrode, and an anion exchange membrane can be suitably used.

  An eighth aspect of the present invention is the energy storage device according to any one of claims 1 to 7, wherein at least a part of the separator is an anion exchange membrane.

    A ninth aspect of the present invention is the energy storage device according to any one of the first to fourth and sixth to eighth aspects of the present invention, wherein the active material that is positively charged during charging on the positive electrode side is a transition metal complex. Transition metal complexes such as ferrocene are effective for the positive electrode.

  In the tenth aspect of the present invention, the positively charged active material when charged on the positive electrode side contains 2 or more and 10 or less benzene rings, and 2 or more and 10 or less nitrogen atoms, It is the 1st-4th and 6-8th energy storage device of the present invention characterized by being an organic molecule whose molecular weight is 184 or more. These active materials are also effective as the positive electrode active material.

  The eleventh aspect of the present invention is an active material that is positively charged during charging on the positive electrode side. These active materials are also effective for the positive electrode. The first to fourth and sixth to eighth energy storage devices of the present invention, wherein the quality is a neutral radical compound. These active materials are also effective for the positive electrode.

  A twelfth aspect of the present invention is the energy storage device according to any one of the first to fourth and sixth to eighth aspects of the present invention, wherein the active material positively charged upon charging on the positive electrode side is a π-conjugated polymer. .

  A thirteenth aspect of the present invention is the energy storage device according to any one of the first to third aspects and the fifth to eighth aspects of the present invention, wherein the active material positively charged at the time of discharging at the negative electrode is a viologen derivative. These active materials are also effective for the negative electrode.

  According to a fourteenth aspect of the present invention, the concentration of the active material dissolved in at least one of the positive electrode side and the negative electrode side divided by the separator is 0.2 mol / liter or less, and the concentration of the entire active material is 0. The energy storage device according to any one of the first to thirteenth aspects of the present invention, wherein the energy storage device is 1 mol / liter or more. As described above, in the present invention, the average concentration of the active material dissolved in the electrolytic solution in the entire device needs to be 0.2 mol / liter or more, but this concentration is not necessary in all regions. Absent. In a region other than the vicinity of the electrode where the redox of the active material occurs, the concentration of the active material does not affect the energy density. The use of active materials in these areas also increases costs and weight.

  According to the fifteenth aspect of the present invention, 90% by weight or more of the composition of the anion exchange resin or anion exchange membrane is composed of a polymer copolymer having a three-dimensional cross-linked structure having a fixed ion exchange group. The energy storage device according to any one of the present inventions 1 to 14, wherein a quaternary ammonium group is used. As an anion exchange membrane used for a separator of an energy storage device, one having high conductivity and small weight and volume is preferable. For this reason, a polymerization type homogeneous ion exchange membrane is preferable to a heterogeneous membrane obtained by molding an ion exchange resin using an appropriate binder resin. When strength is required, it may be applied to a part of a general separator such as a porous membrane or a non-woven fabric that allows easy passage of the electrolytic solution.

  A sixteenth aspect of the present invention is the energy storage device according to the first to fifteenth aspects of the present invention, wherein a component of the anion exchange resin or anion exchange membrane is a fluorocarbon anion exchange resin. As a material for the separator of the energy storage device, a fluorocarbon-based anion exchange resin that exhibits high anion conductivity with little deterioration during charging is preferable. In particular, it is superior to hydrocarbon anion exchange resins in that it has a high affinity for organic electrolytes.

  A seventeenth aspect of the present invention is the energy according to the first to sixteenth aspects of the present invention, wherein the separator includes a membrane in which an anion exchange resin is applied to at least one surface of a membrane having no fixed ion exchange group. Storage device. By adopting such a film for the separator, high mechanical strength can be obtained while maintaining electrical conductivity.

  An eighteenth aspect of the present invention is the energy storage device according to the first to seventeenth aspects of the present invention, wherein the positive electrode and / or the negative electrode are activated carbon electrodes. The present invention can be applied to an energy storage device including many secondary batteries, but can be applied to an electric double layer capacitor having an activated carbon electrode that has a high power density and is capable of high-speed charge / discharge, but is difficult to obtain an energy density. If you do it, it will have a great effect. That is, the energy density can be dramatically improved as compared with the conventional device while maintaining the high-speed charge / discharge function.

  According to the present invention, it is possible to obtain a small-sized and large-capacity energy storage device with little self-discharge. For example, by using the energy storage means of the present invention on the positive electrode side, and using a negative electrode for an electric double layer capacitor, a negative electrode for a redox capacitor, a negative electrode for a lithium ion capacitor, a negative electrode for a lithium ion battery, etc. as the negative electrode Various new configurations of energy storage devices can be constructed. With these new energy storage devices that can store energy in these electrolytes, the capacity is not only greatly improved without substantially losing the output characteristics, charge / discharge efficiency, cycle life characteristics, etc. of conventional devices, but also in the electrolyte. Self-discharge generated by storing energy can be almost completely prevented.

  For example, by using the energy storage means of the present invention on the positive electrode side and using a graphite electrode of a lithium ion capacitor on the negative electrode, a new energy storage device with improved self-discharge and less capacity than a normal lithium ion capacitor is constructed. Can do.

  The present invention uses an electrolyte region, which has not been generally used as an energy storage means of a small energy storage device, as an energy storage means. It was made by discovering that self-discharge due to diffusion of substances can be prevented by appropriately arranging ion exchange resins.

  The device of the present invention is composed of an electrolyte solution in which an active material capable of storing energy is dissolved and a positive electrode, a negative electrode, and a separator for separating the positive electrode and the negative electrode. In order to store energy, it is very effective to use an anion exchange resin for at least a part of the separator. The present invention is described in detail below, but the present invention is not limited to the following.

<Positive electrode and negative electrode>
The electrode on the side where positive charge is accumulated in or near the electrode during charging is called a positive electrode, and the electrode on the side where negative charge is accumulated in or near the electrode during charging is called a negative electrode. Like an electric double layer capacitor, one electrode can function as both a positive electrode and a negative electrode depending on a device, and therefore, one electrode may not always be a positive electrode or a negative electrode. However, even in such a case, if one electrode works as a positive electrode at a certain moment, the other electrode works as a negative electrode. Therefore, here, such a case is also referred to as “positive electrode, negative electrode”. “Electrode” refers to a positive electrode and a negative electrode.

  For the positive electrode and the negative electrode of the present invention, a normal lithium ion battery, a lithium ion capacitor, an electric double layer capacitor and other batteries, and a positive electrode and a negative electrode used for the capacitor can be used. For example, an activated carbon electrode used for an electric double layer capacitor can be used for the positive electrode, and a carbon negative electrode used for a lithium ion capacitor can be used for the negative electrode.

<Electrolyte>
The electrolyte of the present invention is used in a stationary state in an energy storage device. The reason for using the electrolyte in a stationary state is that when the energy storage device is in a charged state, the electrolyte flows and the active material in the electrolyte separates from the electrode, so that energy cannot be extracted effectively during discharge, This is to prevent the active material in the liquid from moving to the opposite electrode and causing a short circuit.

  In addition to the solvent and the supporting salt dissolved in the solvent, the electrolytic solution is characterized by dissolving at least a part of the active material capable of storing energy by causing repeated oxidation / reduction reactions as described above. . In principle, the active material of the present invention may be dissolved or dispersed in the electrolytic solution, but it is sufficient to maintain the dispersed state stably for a long period of time or to be dissolved in the dispersed state. Since it is difficult to take out a large capacity, the active material of the present invention is preferably dissolved in the electrolytic solution.

<Supporting salt of electrolyte>
Examples of the supporting salt dissolved in the electrolytic solution other than water include lithium salts such as LiPF ₆ and LiBF ₄ that are solid at room temperature, quaternary ammonium salts, and quaternary phosphonium salts. In addition to the purpose of increasing the conductivity of the electrolytic solution and carrying ions, these supporting salts may act as a dopant and play a role of stably maintaining the active material dissolved in the electrolytic solution in an oxidized state. In this case, the supporting salt concentration is preferably higher than the active material concentration, but this does not limit the scope of the present invention. The cation component of these supporting salts includes lithium, ethyltrimethylammonium, diethyldimethylammonium, triethylmethylammonium, tetraethylammonium, tetrabutylammonium, 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazole. An example is lithium. As the anionic component BF ₆ ^- anion, ClO ₄ ^- anion, PF ₆ ^- anion, AsF ₆ ^- anion, _CF 3 SO ₃ ^- can be exemplified anion ^- _{anion, (CF 3 SO 2) 2} N.

<Solvent of electrolyte>
As a solvent for the electrolytic solution, for example, a normal organic solvent can be used in addition to water, but a solvent capable of dissolving the supporting salt at a high concentration and having a wide potential window is preferable. Specifically, acetonitrile (AN), γ-butyrolactone (GBL), propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC), diethyl carbonate (DEC), dimethyl carbonate (DMC) ), Ethyl methyl carbonate (EMC), sulfolane (SL) and the like.

<Electrolyte using ionic liquid>
Instead of the supporting salt or the solvent in which the supporting salt is dissolved, it is also possible to use an ionic liquid (room temperature molten salt) that is a liquid composed only of ions at room temperature. It is also possible to use a mixed liquid of an ionic liquid and a normal solvent. The ionic liquid is a salt in a liquid state at room temperature, and examples of the cation component include imidazolium derivatives, quaternary ammonium derivatives, pyridinium derivatives, and quaternary phosphonium derivatives. Further, as an anion component, an atomic group containing fluorine such as BF ₄ ⁻ , PF ₆ ^— , an atomic group containing a sulfonate anion (—SO ₃ ⁻ ), an atomic group containing a carboxylate anion (—COO ⁻ ), etc. are known. It has been. These ionic liquids exhibit high ionic conductivity and can have an ionic concentration higher than that of a normal electrolytic solution.

<Concentration of electrolyte>
The combination of the solvent, the supporting salt (and / or ionic liquid), and the active material is determined by the solubility of the supporting salt (and / or ionic liquid) and the active material. The higher the solubility of the active material in the solvent, the higher the energy. This is preferable because the capacity of the storage device is increased. The solubility of the active material is preferably 0.2 mol / l or more, and more preferably 0.5 mol / l or 1.1 mol / l or more. In general, the higher the concentration, the higher the energy density can be expected. However, when the concentration is too high, the viscosity of the electrolyte increases and the electrical resistance increases. Exists. In addition to the purpose of increasing the conductivity of the electrolyte and transporting ions, the supporting salt acts as a dopant and may also keep the active material dissolved in the electrolyte in a stable oxidized state. It is preferably higher than the substance concentration.

<Example of electrolyte>
The present invention can be applied to a wide range of electrolyte solutions as long as certain conditions are satisfied. Specifically, the minimum requirement is that the active material capable of redox can be dissolved at a high concentration and does not decompose at the operating voltage of the energy storage device, but it is applied to water-based electrolytes that have been widely studied. It is also possible. Generally, an organic solvent having a wider decomposition voltage range than water is often used except for problems such as cost.

  In the present invention, an anion exchange resin or an anion exchange membrane is used. These anion exchange resins and membranes, along with the cation exchange resins and membranes, have been used in salt production and manufacturing industries such as chlorine and caustic soda to conduct various research and development. These membranes are collectively referred to as ion exchange membranes, and all are premised on handling aqueous electrolyte solutions. As described above, the present invention can be applied to an aqueous electrolyte solution, but is very unique in that these ion exchange membranes are applied to a non-aqueous electrolyte solution. By applying it to an electricity storage device using an electrolyte other than an aqueous electrolyte, the invention has a wide application range and high value.

Taking a ferrocene derivative which is an active material having high solubility as an example, as an organic electrolyte, for example, a preferable combination includes solvent: diethyl carbonate (DEC), active material: t-butylferrocene, supporting salt: LiBF _4. In this combination, a t-butylferrocene concentration of 1.2 mol / l and a LiBF ₄ concentration of 1.6 mol / l can be realized. In the combination of the solvent: γ-butyrolactone (GBL), the active material: acetylferrocene, and the supporting salt: LiPF ₆ , an acetyl ferrocene concentration of 1.5 mol / l and a LiPF ₆ concentration of 2.0 mol / l can be realized. In the combination of solvent: ethylene carbonate (EC) / GBL (volume ratio 1: 1), active material: acetyl ferrocene, supporting salt: LiPF ₆ , acetyl ferrocene concentration 1.5 mol / l, LiPF ₆ concentration 2. 0 mol / l can be realized. Furthermore, a combination of solvent: GBL, active material: ferrocene acetonitrile, and supporting salt: LiPF ₆ can realize a ferrocene acetonitrile concentration of 1.5 mol / l and a LiPF ₆ concentration of 2.0 mol / l. Of course, these combinations show a preferable example of the present invention, and the scope of the present invention is not limited to these examples.

  For example, when an electrolytic solution in which 1.5 mol / l acetylferrocene is dissolved in GBL and the supporting salt concentration is 2.0 mol / l is used for energy storage on the positive electrode side, the utilization factor of the active material in the electrolytic solution is 90. In theory, the capacity density (per weight of the electrolytic solution) on the positive electrode side by the electrolytic solution is theoretically 27 Ah / Kg.

<Active material>
The active material here is one that stores and releases energy directly in the energy storage device by causing a stable oxidation / reduction reaction itself, and plays a central role in the energy storage device. It refers to the substance that plays. In the present invention, an active material that is positively charged in an oxidized or reduced state is used as an active material after being dissolved in an electrolytic solution. In particular, it is effective when an active material that is positively charged in an oxidized state is dissolved in an electrolytic solution. Here, dissolution means that the mixture is in a uniform mixture with the solvent at the molecular level.

  Examples of the active material capable of storing energy include π-conjugated polymers such as polyaniline, polythiophene, and polypyrrole and derivatives thereof, and π-conjugated low-molecular compounds such as pyrene, paracenylphenyl, pentacene, and coronene, and derivatives thereof. , Low-polymerization compounds of π-conjugated polymers such as aniline tetramer, N, N′-diphenyl-1,4-phenylenediamine, N, N `-diphenylbenzidine and their derivatives, 2,2,6,6 -Organic radical compounds typified by tetramethylpiperidinyloxy radical (TEMPO) and derivatives thereof, pyridinium derivative salts typified by viologen salts, organometallic complexes typified by ferrocene and derivatives thereof, etc. As long as it is a compound that dissolves in a simple electrolyte and is positively or negatively charged during oxidation or reduction, it is used as the active material of the present invention Could be possible.

  Among these, those having a large molecular weight such as π-conjugated polymers and derivatives thereof are relatively difficult to cause self-diffusion, but are difficult to dissolve in an electrolyte at a high concentration. In contrast, many low molecular weight compounds can be dissolved in an electrolyte at a relatively high concentration, but self-diffusion tends to increase. Some of these compounds decompose or polymerize depending on the voltage applied at the time of charging, and in this case, the lifetime is reduced.

The energy storage system of the present invention is used in principle on both the positive electrode side and the negative electrode side, but for example, when a ferrocene derivative is used, it is preferably used on the positive electrode side. This is because the ferrocene derivative is oxidized on the positive electrode side and iron becomes trivalent and becomes charged. During discharge, the ferrocene derivative is reduced and becomes neutral and iron becomes divalent, but this reaction occurs at a relatively high potential. Therefore, it is generally convenient to use for energy storage on the positive electrode side. As described above, most of the active materials have a redox potential on the positive side with respect to the Ag / Ag ⁺ potential. However, like many pyridinium derivative salts, a redox potential also exists on the negative side. Some can be used as an active material in the electrolyte.

FIG. 1 shows the redox characteristics of the aniline type low molecular weight compound. This property was measured using γ-butyrolactone (GBL) as a solvent and N, N′-diphenyl-1,4-phenylenediamine, 0.33 mol / l, triethylammonium BF ₄ 1.0 mol / l as a supporting salt. It is the result of having done. The assumed voltage measurement range is -1.0 V to +1.0 V, the electrode used is a Pt disk electrode, 20 mV / sCV. Since this compound is a relatively low-molecular aniline type compound, it has higher solvent solubility than polyaniline and has a redox peak. For this reason, it can be used as an active material of an electrolytic solution storage device that is an object of the present invention. However, as described later, this device has a problem that self-discharge is larger than a device using polyaniline.

FIG. 2 shows the redox characteristics of the TEMPO-based active materials (4-acetamido TEMPO and 4-oxo TEMPO). A 0.1 mol / l TEMPO active material was dissolved in the same solvent and supporting salt as in FIG. 1, the voltage measurement expected range was 0.0 V to +1.0 V, the electrode used was a Pt disk electrode, 20 mV / s. . Many of the TEMPO-based active materials are highly soluble and exhibit a redox potential that is nobler than the Ag / Ag ⁺ potential, and are positively charged by oxidation. Therefore, it becomes a material suitable as the active material of the present invention.

FIG. 3 shows the redox characteristics of ferrocene-based active materials (t-butyl ferrocene and acetyl ferrocene). Measurement was performed using GBL as a solvent, ferrocene-based active material, 1.0 mol / l, and triethylammonium BF ₄ 1.0 mol / l as the supporting salt. The assumed voltage measurement range was -1.0 V to +1.0 V, the electrode used was a Pt disk electrode, and measurement was performed at 20 mV / s. Like TEMPO, it is highly soluble and exhibits a redox potential that is nobler than the Ag / Ag ⁺ potential and is positively charged by oxidation. Similar to TEMPO, it is a material suitable as the active material of the present invention.

A viologen derivative is mentioned as a material which shows a redox potential lower than Ag / Ag ⁺ potential and is positively charged by oxidation. 1,1′-dimethyl-4,4′-bipyridinium · BF ₄ salt (abbreviated as methylviologen · BF ₄ salt) and 1,1′-di-n-heptyl-4,4′-bipyridinium · BF ₄ salt ( FIG. 4 shows the reduction / oxidation characteristics of heptylviologen / BF ₄ salt. This is a result of measurement using GBL as a solvent, 0.1 mol / l viologen derivative, and 1.0 mol / l triethylammonium BF ₄ as a supporting salt. The assumed voltage measurement range is -1.0 V to 0 V, the electrode used is a Pt disk electrode, 20 mV / sCV. When used in the negative electrode, this active material is positively charged during discharge.

  Further, since the oxidation / reduction reaction between the pentavalent and tetravalent vanadium oxides occurs at a relatively high potential, the oxidation / reduction reaction is used for energy storage on the positive electrode side. In contrast, the potential of the oxidation / reduction reaction between trivalent and divalent vanadium ions is relatively low, and this reaction is used for energy storage on the negative electrode side.

  The oxidation / reduction of the active material, which is the energy storage source of the present invention, is performed by providing a potential difference between the positive electrode and the negative electrode. Here, when the transition metal complex oxidized on the electrode surface and becomes a charged state diffuses in the electrolyte, moves away from the vicinity of the positive electrode, moves to the negative electrode and is reduced, the stored charge can be taken out as discharge energy. Disappear. Therefore, the electrode of the present invention requires means for suppressing the diffusion of the dissolved active material and / or means for taking out the discharge energy even if it is diffused.

  Only one type of active material capable of oxidation / reduction may be dissolved in the electrolytic solution, or a plurality of types may be dissolved. In principle, the energy storage system of the present invention can be used on both the positive electrode side and the negative electrode side, but depending on the type of active material, it is determined whether it is used on the positive electrode side or on the negative electrode side.

<Separator>
In a normal energy storage device, a separator is generally interposed for the purpose of preventing a short circuit between the positive electrode and the negative electrode. However, the separator is an important component with a more positive meaning in the energy storage device of the configuration of the present invention. That is, in the present invention, since the active material is dissolved in the electrolytic solution, for example, the active material in a charged state (oxidized state) at the positive electrode moves by diffusion in the electrolytic solution, reaches the negative electrode, and is discharged as it is. The phenomenon of returning to the reduced state is likely to occur. This phenomenon is known as the redox shuttle effect and causes self-discharge of the battery or capacitor. In the method of the present invention, how to prevent this self-discharge is important. As a method for preventing self-discharge, a plurality of methods such as the use of a solid electrolyte or a gel electrolyte, an increase in the affinity between the active material and the electrode surface, and the difficulty in separating the active material from the electrode can be considered. There is a need to develop effective methods.

  In order to solve such problems, we have intensively studied. As a result, when a glass fiber filter, a polypropylene (PP) porous filter, a cellulose separator, or the like that is usually used as a separator is used, it is difficult to completely prevent self-discharge. It has been found that self-discharge can be effectively prevented by using as a part. Although the movement of the active material is effectively blocked by the anion exchange resin, the supporting salt can move in the ion exchange resin.

The anion exchange resin used for the energy storage device of the present invention is required to have a resistance value as small as possible. For this reason, it is desirable to have a large ion exchange capacity and to form a thin film. In the present invention, among an ion exchange resin and an ion exchange membrane, an anion exchange resin and an anion exchange membrane are used. The most common ion exchange membrane is one in which a fixed ion exchange group is introduced into a polymer copolymer having a three-dimensional crosslinked structure. For example, when a sulfonic acid group (—SO ₃ ⁻ ) is introduced as a fixed ion exchange group into a copolymer of styrene and divinylbenzene, a cation exchange membrane (cation exchange membrane) is formed, and a quaternary ammonium salt (—N ^{When +} (CH ₃ ) ₃ ) is introduced, an anion exchange membrane (anion exchange membrane) is formed. In terms of production, a cation exchange membrane can be obtained by sulfonation of styrene with concentrated sulfuric acid, and an anion exchange membrane can be obtained by amination of chloromethylstyrene with trimethylamine. However, this production method limits the ion exchange membrane used in the present invention. It is not a thing.

  Typical examples of the ion exchange resin used for the purpose of the present invention include fluorocarbon ion exchange membranes and hydrocarbon ion exchange membranes. Historically, the former has been developed mainly in the chlorine / caustic manufacturing industry and the latter in the salt manufacturing industry.

  The fluorocarbon-based ion exchange membrane is a fluorine-based membrane having perfluoroalkyl as a main skeleton and having an ion exchange group such as a sulfonic acid group, a carboxylic acid group, or an amino group at the end of a part of the perfluoroether side chain. Examples of the hydrocarbon ion exchange membrane include a styrene divinylbenzene copolymer and an aromatic polymer material. The latter is obtained by directly introducing a sulfonic acid group, a carboxylic acid group, an amino group or the like into an aromatic polymer material such as polybenzimidazole, polyethersulfone, or polyetheretherketone. Of these fluorocarbon ion exchange membranes and hydrocarbon ion exchange membranes, anion exchange membranes can be preferably used for the purpose of the present invention.

  As a separator of a general energy device, a glass fiber filter, a polypropylene (PP) porous filter, a cellulose separator, or the like is used. A membrane not containing these fixed ion exchange groups may be used as a part of the separator of the present invention. The present invention can be carried out by applying an ion exchange membrane to these separators.

  The present invention prevents self-discharge due to diffusion of an active material by utilizing selective permeability of ions in an electrolyte solution by an anion exchange membrane. Anion exchange resins and membranes are used as sites that selectively permeate anions by suppressing permeation of cations and neutral compounds.

Three types of separators are used in examples and comparative examples of the present invention described later. The first is an anion exchange membrane. Here, TOSFLEX (SF-34) manufactured by Tosoh Corporation, which is a fluorine-based anion exchange membrane, was immersed overnight in an electrolytic solution containing a supporting salt to perform anion exchange. This membrane is effective for practicing the present invention. The second was a cation exchange membrane, and Nafion ^R 212 (film thickness 50 μm) manufactured by DuPont was used after the same treatment. Since this membrane is not an anion exchange membrane which is a component of the present invention, the self-discharge suppressing effect is insufficient. However, since it shows some selectivity in the cation permeability depending on the ionic radius or the like, it exhibits a self-discharge suppression effect to some extent as compared with the third film described below. As the third membrane, a polypropylene nonwoven fabric separator widely used as a general ordinary separator was used for both a glass fiber separator and a cellulose fiber separator. In many cases, the self-discharge is large and the energy storage device does not function.

<Energy storage device>
The energy storage device of the present invention is a conventional solid electrode oxidation / reduction reaction and / or solid electrode surface by effectively adding the capacity of the solid electrode itself and the capacity of the active material contained in the electrolyte. This is a small energy storage device that realizes a large capacity as a whole device rather than a small energy storage device that uses only the electric double layer for charging and discharging. The small energy storage device here refers to portable electronic devices such as mobile phones and notebook computers, and power sources for driving hybrid vehicles (HEV), taking advantage of the large capacity per weight and / or volume. It can be used satisfactorily.

<Configuration 1 of energy storage device>
In FIG. 5, the conceptual diagram of the energy storage device of this invention is shown. Reference numeral 2 denotes a positive electrode, which is formed so as to be in electrical contact with the positive electrode current collector 1 using, for example, activated carbon or lithium cobaltate. A porous shape or the like can be selected so that the electrolytic solution is easily impregnated. The inside of the positive electrode is impregnated with the electrolytic solution 3 as in the case of the separator and the negative electrode. In a normal energy storage device, the area of the electrolyte solution in the gap of the positive electrode is not directly involved in energy storage, and is a useless space. In the energy storage device of this configuration, an active material that becomes positively charged by oxidation upon charging, such as acetylferrocene, is dissolved in the electrolytic solution 3, and energy storage is performed using the oxidation / reduction reaction of this active material. I do. For this reason, energy can be effectively stored using the gap of the positive electrode. Thereby, the capacity | capacitance of the positive electrode side can be enlarged compared with a normal energy storage device, and it is possible to increase a capacity | capacitance as the whole energy storage device. In the case of this device configuration, the “electrode that positively charges the active material during charging or discharging” in the present invention refers to the positive electrode.

  If the active material in the electrolyte is separated from the electrode to some extent (about 10 μm), it cannot be efficiently used for energy storage. It is preferable that the positive electrode has a porous or fibrous structure so that the electrolyte contained in the positive electrode is not always separated from the positive electrode by 10 μm or more.

  Reference numeral 4 denotes a separator, which is used only in order to prevent a short circuit due to contact between the positive electrode and the negative electrode in a normal energy storage device. However, when the active material is dissolved in the electrolytic solution as in the present invention, the active material in the oxidized state (charged state) in the electrolytic solution is diffused to move from the positive electrode side through the separator to the negative electrode side to be charged. If the energy is lost, the efficiency of energy storage will deteriorate. In addition, long-term energy storage becomes difficult. Therefore, in the present invention, it is important that the separator has a function of preventing the active material from moving from the positive electrode side to the negative electrode side. Specifically, an anion exchange resin is used as a separator. Thereby, it is possible to prevent the active material in the electrolytic solution from moving from the positive electrode side to the negative electrode side, and the active material in the electrolytic solution can be efficiently used for charging and discharging. The separator may be an anion exchange membrane itself, or may be one in which an anion exchange resin is coated on a separator having no fixed ion exchange group.

  Reference numeral 6 denotes a negative electrode, and an activated carbon electrode for an electric double layer capacitor or a graphite electrode into which lithium ions can be inserted / removed can be used if necessary. Can be increased.

  In addition, in order for this device to function, the separator 4 and the negative electrode 6 vicinity need to contain the electrolyte solution 5 and the electrolyte solution 7, respectively. This device is for driving through the anion of the supporting salt in the electrolyte solution that can pass through the anion permeable membrane. However, in order to perform a minimum charge / discharge operation, the electrolytic solution 5 and the electrolytic solution 7 do not necessarily contain the active material. When using these devices for a long period of time, a part of the active material having no charge in the reduced state may permeate the anion exchange membrane and the active material concentration near the positive electrode may decrease. The active material can be dissolved in the electrolytic solution 5 and the electrolytic solution 7. The selection is made in consideration of disadvantages such as an increase in weight and cost as compared with the case where the active material is not dissolved.

  FIG. 5 is a simplified schematic diagram, and the device shape of the present invention is not limited to this. For example, various shapes such as a thin shape, a cylindrical shape, a coin shape, a button shape, a sheet shape, and a laminated shape are available. The present invention can also be applied to a shape or a vehicle-mounted type used for an electric vehicle or the like. Further, the capacity on the negative electrode side can be improved depending on the kind of the active material to be added. In this case, the negative electrode is preferably porous or fibrous.

<Configuration 2 of energy storage device>
This configuration is obtained when the active material dissolved in the electrolytic solution is changed with almost the same device configuration. That is, an active material that is oxidized near the negative electrode during discharge and is positively charged is used. As an example, a case where activated carbon is used for both the positive electrode and the negative electrode will be described. When used in an electrolytic solution in which a viologen derivative such as methyl viologen radical cation is dissolved as an active material to be dissolved, oxidation-reduction occurs at a potential on the negative side with respect to the Ag / Ag ⁺ potential. Here, for the sake of convenience, description will be given using Ag / Ag ⁺ potential, but which is a positive electrode and which is a negative electrode is relative and whether the potential is higher or lower than Ag / Ag ⁺ potential. Needless to say, is not an absolute one, but only a guide. Hereinafter, various device configurations will be described, but it is the same that the discussion of the level of the potential with respect to the Ag / Ag ⁺ potential is only a guideline until it gets tired.

  In the case of this device configuration, the active material is dissolved in at least the electrolytic solution 7 immersed in the negative electrode of FIG. The electrolytes 3 and 5 may or may not dissolve this active material. When this device is discharged, the neutral active material in the vicinity of the negative electrode is oxidized and becomes a cation to have a positive charge. As a result, in addition to the 20-layer capacity at the negative electrode, the redox capacity of the active material in the electrolytic solution is exhibited, and the energy density can be increased. Moreover, the active material which became a cation and the active material in a neutral state are blocked by the anion exchange membrane and do not reach the positive electrode, and self-discharge is suppressed.

<Configuration 3 of energy storage device>
This configuration is obtained when device configurations 1 and 2 are combined. That is, the essential requirement of this configuration is that an active material that is positively charged by being oxidized at a noble potential with respect to the standard Ag / Ag ⁺ potential is dissolved in at least the electrolyte solution in the vicinity of the positive electrode, and the Ag / Ag ⁺ potential is obtained. On the other hand, an active material that is oxidized at a base potential and positively charged is dissolved in at least an electrolyte near the negative electrode, and an anion exchange resin is used for the separator. In this case, the active material positively charged at the time of charging and the active material positively charged at the time of discharging together with the active material in the neutral state are suppressed without being transmitted due to the charge selectivity of the separator. The charge / discharge function of the device is realized by movement of anions generated from the supporting salt contained in the electrolytic solution.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples.

(Example 1)
<Preparation of electrolyte>
In γ-butyrolactone, 1.5 mol / l of t-butylferrocene as an active material and 2.0 mol / l of TEA · BF ₄ as a supporting salt were dissolved to obtain a solution used as an electrolytic solution.

<Preparation of electrode and separator>
An activated carbon sheet electrode having a diameter of 13 mm and a thickness of 0.5 mm was used for the positive electrode, and an activated carbon sheet electrode having a diameter of 15 mm and a thickness of 0.5 mm was used for the negative electrode. The activated carbon sheet electrode is obtained by adding acetylene black as a conductive additive to activated carbon powder (average particle size 5 to 20 μm) subjected to activation treatment, and forming it into a sheet shape using PTFE as a binder. The density of this sheet electrode is 0.45-0.55 g / cm ³ and the specific surface area is 1700-2200 m ² / g. The separator was used by immersing TOSFLEX (SF-34) manufactured by Tosoh Corporation in the above electrolytic solution overnight to perform ion exchange, and punching it into a circle having a diameter of 19 mm. These positive electrode, negative electrode and separator were kept at 120 ° C. under vacuum for 3 hours and dried. Next, the dried positive electrode, negative electrode, and separator were immersed in an electrolytic solution, vacuumed for 10 minutes, impregnated with the electrolytic solution, and returned to normal pressure. This vacuum impregnation was further performed twice, and the electrolytic solution was impregnated three times in total.

<Assembly of cell>
The produced negative electrode, separator, and positive electrode were placed in an HS cell manufactured by Hosen Co., Ltd. so as to overlap concentrically in order from the bottom, and covered to obtain an electric double layer capacitor type model cell for measurement. In order to prevent mixing of moisture in the atmosphere, the preparation of the electrolyte solution, the impregnation of the electrolyte solution into the electrode and separator, and the assembly of the cell were all carried out in a glove box with a dew point of −70 ° C. or less substituted with high-purity argon. .

<Charge / discharge measurement>
The produced electric double layer capacitor model cell was charged and discharged for 3 cycles at a constant current of 1 mA. The charging / discharging voltage range was 0 to 1.23 V, and charging was started from a natural potential at the beginning of the measurement. A Solartron 1470E multistat was used for charge / discharge measurements.
The charge, discharge charge, and Coulomb efficiency of charge / discharge at the third cycle were 6.07C, 6.04C, and 99.6%, respectively.

  Table 1 shows the experimental levels and measurement results of Examples 1 to 7 and Comparative Examples 1 to 11. From the comparison with Comparative Example 1 below, it can be seen that the capacity of the electric double layer capacitor type energy storage device can be increased by adding t-butylferrocene to the electrolytic solution. In this example, although the area of the negative electrode is slightly larger than that of the positive electrode, the increase in device capacity is not proportional to the increase in the positive electrode capacity. Also, from the comparison with Comparative Example 9, when a polypropylene nonwoven fabric separator that is normally used as a separator is used, self-discharge is large and does not function as an energy storage device, but self-discharge is effective by using an anion exchange membrane as a separator. It can be seen that an increase in capacity can be realized. Compared with Comparative Example 11, it can be seen that the anion exchange membrane sufficiently exhibits the effect of suppressing self-discharge which is insufficient in the cation exchange membrane (Nafion (registered trademark) 212) because of its high discharge capacity and coulomb efficiency. .

(Example 2)
An experiment similar to that of Example 1 was performed except that acetylferrocene was used instead of t-butylferrocene as an active material to be dissolved in the electrolytic solution. As a result, the charge charge / discharge charge and coulombic efficiency of charge / discharge at the third cycle of the electric double layer capacitor type model cell were 6.45C, 6.38C and 98.9%, respectively. From the comparison with Comparative Example 1, it can be seen that by adding acetylferrocene to the electrolyte, the capacity of the electric double layer capacitor type energy storage device can be increased as in Example 1. Compared with Comparative Example 12, the discharge capacity and Coulomb efficiency are high, and the anion exchange membrane has a sufficient self-discharge suppression effect that is insufficient with the cation exchange membrane (Nafion (registered trademark) 212) as in Example 1. You can see that it is demonstrating. Moreover, combining the results of Example 3 and Example 4, it can be seen that the capacity increases as the concentration of acetylferrocene increases.

<Self-discharge measurement>
Next, the produced electric double layer capacitor type model cell was charged to 1.23 V at a constant current, and then the change in voltage was measured in an open state.

  The results are shown in FIG. 6 and FIG. 6 shows the results of Comparative Examples 2, 3, 4, 5, and 6, and FIG. 7 shows the results of Example 2 and Comparative Examples 10 and 11.

  It can be seen that when the active material is dissolved, the voltage decreases in a relatively short time. It shows that the smaller the molecular weight, the easier it is to diffuse. It can also be seen that the use of a cation exchange membrane instead of a normal separator suppresses self-diffusion to some extent, but it is not sufficient, and the use of an anion exchange membrane almost completely suppresses self-diffusion.

(Example 3)
An electric double layer capacitor model cell was produced in the same manner as in Example 2 except that the concentration of acetylferrocene dissolved in the electrolyte was 0.5 mol / l, and charge / discharge measurement was performed. As a result, the charge, discharge, and coulombic efficiency of charge / discharge at the third cycle of the electric double layer capacitor type model cell were 5.71C, 5.62C, and 98.4%, respectively.

Example 4
An electric double layer capacitor type model cell was manufactured in the same manner as in Example 2 except that the concentration of acetylferrocene dissolved in the electrolytic solution was 1.0 mol / l, and charge / discharge measurement was performed. As a result, the charge charge, discharge charge, and coulombic efficiency in the third cycle of the electric double layer capacitor type model cell were 6.11C, 6.02C, and 98.5%, respectively.

(Example 5)
The electric double layer capacitor was prepared in the same manner as in Example 1 except that the active material dissolved in the electrolyte was N, N'-diphenyl-1,4-phenylenediamine (NNDP) and the concentration was 1.0 mol / l. A model cell was fabricated and charge / discharge measurement was performed. As a result, the charge charge, discharge charge, and Coulomb efficiency of charge and discharge in the third cycle of the electric double layer capacitor model cell were 5.39C, 5.20C, and 96.5%, respectively. By comparing with Comparative Example 1, it was found that the aniline derivative is also effective as an active material like ferrocenes.

(Example 6)
An electric double layer capacitor type model cell was manufactured in the same manner as in Example 1 except that 2,2,6,6-tetramethylpiperidinyloxy radical (TEMPO) was used as the active material to be dissolved in the electrolytic solution. Charge / discharge measurement was performed. As a result, the charge charge, discharge charge, and Coulomb efficiency of charge and discharge in the third cycle of the electric double layer capacitor type model cell were 6.73C, 6.45C, and 95.8%, respectively. Comparing with Comparative Example 1, it was found that neutral radicals are also effective as active materials like ferrocenes.

(Example 7)
An electric double layer capacitor model cell was manufactured in the same manner as in Example 1 except that the active material dissolved in the electrolyte was acetylferrocene and methyl viologen · BF ₄ and the concentration was 0.5 mol / l. Charge / discharge measurement was performed. As a result, the charge / discharge charge and discharge charge of the third cycle of the electric double layer capacitor model cell and the Coulomb efficiency were 6.48 C, 6.12 C, and 94.4%, respectively. By comparing with Comparative Example 1, it was found that the viologen derivative is also effective as an active material like ferrocenes, and that an increase in capacity can be seen by using an anion exchange membrane. Furthermore, the effect of adding viologen appeared even when compared with Example 3, and it was considered that the device was operated with the negative electrode. This viologen is considered to be positively charged during discharge.

(Example 8)
The electric double layer capacitor model cell was prepared in the same manner as in Example 1 except that the electrolyte immersed in the separator and the negative electrode did not dissolve the active material, but used an electrolytic solution in which t-butylferrocene was dissolved only in the positive electrode. Manufactured and measured for charge and discharge. As a result, the charge charge / discharge charge and coulombic efficiency of charge / discharge at the third cycle of the electric double layer capacitor type model cell were 6.09C, 6.05C and 99.3%, respectively. Since the characteristics equivalent to or higher than those of Example 1 were obtained, it was found that the capacity can be effectively increased even when the active material is dissolved only in the electrolyte solution in the portion where the positive electrode is involved.

(Comparative Example 1)
An electric double layer capacitor type model cell was produced in the same manner as in Example 1 except that a polypropylene nonwoven fabric was used for the separator, the active material was not dissolved in the electrolyte, and the supporting salt concentration was 1.0 mol / l. Charge / discharge measurement was performed. As a result, the charge charge, discharge charge, and coulombic efficiency in the third cycle of the electric double layer capacitor type model cell were 3.21C, 3.11C, and 96.9%, respectively.

(Comparative Example 2)
Example 1 except that a polypropylene non-woven fabric is used as the separator, the active material dissolved in the electrolyte is an aniline tetramer, the concentration is 0.1 mol / l, and the concentration of the supporting salt is 1.0 mol / l. An electric double layer capacitor model cell was manufactured in the same manner as described above, and charge / discharge measurement and self-discharge measurement were performed. As a result, the charge, discharge, and coulombic efficiency of charge and discharge in the third cycle of the electric double layer capacitor type model cell were 5.11C, 1.20C, and 23.5%, respectively. The result of the self-discharge measurement is shown in FIG.

(Comparative Example 3)
A polypropylene non-woven fabric is used as the separator, the active material dissolved in the electrolytic solution is NNDP, the concentration is 0.1 mol / l, and the concentration of the supporting salt is 1.0 mol / l. An electric double layer capacitor type model cell was manufactured by this method, and charge / discharge measurement and self-discharge measurement were performed. As a result, the charge charge, discharge charge, and Coulomb efficiency of charge and discharge in the third cycle of the electric double layer capacitor type model cell were 14.63 C, 0.66 C, and 4.5%, respectively. The result of the self-discharge measurement is shown in FIG.

(Comparative Example 4)
The same method as in Example 1 except that a polypropylene nonwoven fabric is used as the separator, the concentration of t-butylferrocene dissolved in the electrolyte is 0.1 mol / l, and the concentration of the supporting salt is 1.0 mol / l. An electric double layer capacitor type model cell was manufactured by charging and discharging measurement and self-discharging measurement. As a result, the charge charge, discharge charge, and Coulomb efficiency of charge and discharge in the third cycle of the electric double layer capacitor type model cell were 18.45C, 0.55C, and 3.0%, respectively. The result of the self-discharge measurement is shown in FIG.

(Comparative Example 5)
Example 1 except that a polypropylene nonwoven fabric is used for the separator, the active material dissolved in the electrolyte is n-butylferrocene, the concentration is 0.1 mol / l, and the concentration of the supporting salt is 1.0 mol / l. An electric double layer capacitor model cell was manufactured in the same manner as described above, and charge / discharge measurement and self-discharge measurement were performed. As a result, the charge, discharge, and coulombic efficiency of charge / discharge at the third cycle of the electric double layer capacitor type model cell were 35.62C, 0.16C, and 0.4%, respectively. The result of the self-discharge measurement is shown in FIG.

(Comparative Example 6)
A polypropylene nonwoven fabric is used as the separator, the active material dissolved in the electrolytic solution is ferrocene, the concentration is 0.1 mol / l, and the concentration of the supporting salt is 1.0 mol / l. An electric double layer capacitor type model cell was manufactured by this method, and charge / discharge measurement and self-discharge measurement were performed. As a result, the charge charge, discharge charge, and Coulomb efficiency of charge / discharge in the third cycle of the electric double layer capacitor type model cell were 25.45C, 0.02C, and 0.1%, respectively. The result of the self-discharge measurement is shown in FIG. The self-discharge was intense and the initial voltage of the self-discharge test did not reach 1.23V.

(Comparative Example 7)
An electric double layer capacitor model cell was manufactured in the same manner as in Example 1 except that a polypropylene nonwoven fabric was used as the separator and the concentration of t-butylferrocene as an active material was changed to 0.5 mol / l, and charge / discharge measurement was performed. However, the self-discharge was large and the charging voltage did not reach 1.23V.

(Comparative Example 8)
An electric double layer capacitor type model cell was manufactured in the same manner as in Example 1 except that a polypropylene nonwoven fabric was used as a separator and the concentration of t-butylferrocene as an active material was 1.0 mol / l, and a charge / discharge test was performed. However, as in Comparative Example 7, the self-discharge was large and the charging voltage did not reach 1.23V.

(Comparative Example 9)
An electric double layer capacitor model cell was manufactured in the same manner as in Example 1 except that a polypropylene nonwoven fabric was used as the separator and the concentration of t-butylferrocene as an active material was 1.5 mol / l, and a charge / discharge test was performed. However, as in Comparative Examples 7 and 8, self-discharge was large and the charging voltage did not reach 1.23V.

(Comparative Example 10)
An electric double layer capacitor model cell was manufactured in the same manner as in Example 1 except that Nafion ^R 212 was used as the separator and the active material was not dissolved in the electrolyte, and charge / discharge measurement and self-discharge test were performed. . As a result, the charge charge / discharge charge and coulombic efficiency in the third cycle of the electric double layer capacitor model cell were 3.03C, 2.96C, and 97.7%, respectively. The result of the self-discharge test is shown in FIG.

(Comparative Example 11)
An electric double layer capacitor model cell was manufactured in the same manner as in Example 1 except that Nafion ^R 212 was used as the separator, and charge / discharge measurement and self-discharge test were performed. As a result, the charge / discharge charge and discharge charge of the third cycle of the electric double layer capacitor model cell and the Coulomb efficiency were 5.95 C, 5.03 C, and 84.5%, respectively. The result of the self-discharge test is shown in FIG.

(Comparative Example 12)
An electric double layer capacitor model cell was manufactured in the same manner as in Example 1 except that Nafion ^R 212 was used as the separator and acetylferrocene was used as the active material to be dissolved in the electrolyte solution. Charge / discharge measurement and self-discharge test Was done. As a result, the charge, discharge, and coulombic efficiency of charge / discharge at the third cycle of the electric double layer capacitor type model cell were 6.24C, 6.06C, and 97.1%, respectively. The result of the self-discharge test is shown in FIG.

Cyclic voltammogram of aniline type low molecular weight compound (N, N'-diphenyl-1,4-phenylenediamine). Cyclic voltammogram of TEMPO derivatives (acetamide TEMPO and 4 oxo TEMPO). Cyclic voltammogram of ferrocene derivatives (t-butyl ferrocene and acetyl ferrocene). Cyclic voltammograms of viologen derivatives (methyl viologen · BF ₄ and heptyl viologen · BF ₄ ). The energy storage device conceptual diagram of this invention. The self-discharge curve of the capacitor which contains an aniline tetramer, NNDP, t-butyl ferrocene, n-butyl ferrocene, and ferrocene in an active material. Self-discharge curve of a capacitor using an electrolyte containing no active material, an anion exchange membrane, and a cation exchange membrane as a separator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode collector 2 Positive electrode 3 Positive electrode side electrolyte solution 4 Separator (anion exchange membrane)
5 Electrolyte in separator 6 Negative electrode 7 Negative electrode side electrolyte 8 Negative electrode current collector

Claims (18)

  An energy storage device in which at least a positive electrode, a negative electrode, an electrolytic solution, an oxidizable / reducible active material, and a separator are in a single sealed casing, and a part of the active material is dissolved in the electrolytic solution The energy storage device, wherein the separator contains an anion exchange resin.   2. The energy storage device according to claim 1, wherein at least a part of the active material is dissolved in the electrolytic solution at a concentration of 0.2 mol / liter or more.   The energy storage device according to claim 1, wherein the electrolytic solution is an organic electrolytic solution having a water content of 1 weight percent or less.   The energy storage device according to claim 1, wherein the active material dissolved in the electrolytic solution is positively charged during charging at the positive electrode.   The energy storage device according to claim 1, wherein the active material dissolved in the electrolytic solution is positively charged during discharge at the negative electrode.   The energy storage device according to claim 1, wherein at least two kinds of active materials are dissolved in the electrolytic solution.   7. The energy according to claim 6, wherein at least one of the active materials dissolved in the electrolytic solution is positively charged during charging at the positive electrode, and at least one is positively charged during discharging at the negative electrode. Storage device.   The energy storage device according to claim 1, wherein at least a part of the separator is an anion exchange membrane.   The energy storage device according to any one of claims 1 to 4 and 6 to 8, wherein the active material positively charged during charging on the positive electrode side is a transition metal complex.   An active material that is positively charged when charged on the positive electrode side contains 2 or more and 10 or less benzene rings, 2 or more and 10 or less nitrogen atoms, and an organic molecular weight of 184 or more The energy storage device according to claim 1, wherein the energy storage device is a molecule.   9. The energy storage device according to claim 1, wherein the active material that is positively charged during charging on the positive electrode side is a neutral radical compound.   The energy storage device according to any one of claims 1 to 4 and 6 to 8, wherein the active material that is positively charged during charging on the positive electrode side is a π-conjugated polymer.   The energy storage device according to any one of claims 1 to 3 and 5 to 8, wherein the active material positively charged at the time of discharging at the negative electrode is a viologen derivative.   The concentration of the active material dissolved in at least one of the positive electrode side and the negative electrode side divided by the separator is 0.2 mol / liter or less, and the concentration of the entire active material is 0.2 mol / liter or more. The energy storage device according to claim 1, wherein there is an energy storage device.   90% by weight or more of the composition of the anion exchange resin or the anion exchange membrane is composed of a polymer copolymer having a three-dimensional crosslinked structure having a fixed ion exchange group, and a quaternary ammonium group is used as a main fixed ion exchange group. The energy storage device according to claim 1, wherein:   The energy storage device according to claim 1, wherein a component of the anion exchange resin or anion exchange membrane is a fluorocarbon anion exchange resin.   The energy storage device according to claim 1, wherein the separator includes a membrane in which an anion exchange resin is applied to at least one surface of a membrane having no fixed ion exchange group. The energy storage device according to claim 1, wherein the positive electrode and / or the negative electrode is an activated carbon electrode.