WO2006098213A1

WO2006098213A1 - Electrochemical device

Info

Publication number: WO2006098213A1
Application number: PCT/JP2006/304586
Authority: WO
Inventors: Masamitsu Tachibana; Hideo Yamagishi; Mutsuaki Murakami; Hiroyuki Furutani
Original assignee: Kaneka Corporation
Priority date: 2005-03-17
Filing date: 2006-03-09
Publication date: 2006-09-21
Also published as: JPWO2006098213A1

Abstract

Disclosed is an electrochemical device comprising a conductive bipolar polymer and an electrolyte containing an ionic liquid. The electrolyte is preferably obtained by mixing at least one substance selected from acetonitrile, propylene carbonate, ethylene carbonate and Ϝ-butyl lactone with an ionic liquid in a volume ratio of from 1:3 to 10:1. By having such a constitution, this novel electrochemical device is improved in repeat stability of doping/dedoping reactions.

Description

Specification

Electrochemical element

Technical field

TECHNICAL FIELD [0001] The present invention relates to an electrochemical device, and more particularly to a redox capacitor using a bipolar conductive polymer doping / de-doping reaction.

Background art

An electrochemical element is an element using an electrochemical reaction, and includes elements used for energy storage such as a battery, a capacitor, and a fuel cell. In such devices, it has long been considered to use a conductive polymer doping and dedoping reaction. However, doping and dedoping reactions of conductive polymers have a problem of lack of repeated stability and do not occur during repeated reactions. Electrochemical devices based on these principles are a major problem in practical use. There is.

[0003] An electric double layer capacitor is an electrochemical element for electrical storage that utilizes an electric double layer capacitance generated at the interface between an electrode and an electrolyte when a voltage is applied. The mechanism of storage by this electric double layer capacity is characterized by being able to charge / discharge faster than secondary batteries with electrochemical reaction and having excellent repeated life characteristics. However, the electric double layer capacitor has the disadvantage that its energy density is much lower than that of the secondary battery. Since the electric double layer capacity is proportional to the surface area of the electrode, activated carbon having a large surface area is generally used as the electrode. However, even when using an activated carbon electrode with such a large surface area, the energy density of an electric double layer capacitor remains at around 5 WhZkg, and its capacity density is less than that of a secondary battery.

In view of such a current situation, in order to dramatically improve the capacitance density of the electric double layer capacitor, a capacitor using a pseudo capacitance by a conductive polymer has been proposed. Unlike the electric double layer capacitance, the pseudocapacitance is stored with an electron transfer process (Faraday process) at the electrode interface. In addition, since the electric double layer is formed at the interface even in the process in which the pseudo capacity is developed, the electric double layer capacity and the pseudo capacity are developed in parallel, resulting in a large capacity. Such pseudocapacitance is reduced when the conductive polymer is used. It is manifested by a dox reaction, that is, a dope de-dope reaction. Pseudo capacitance thus expressed in this redox reaction is theoretically estimated to be 10 ⁶ times the electric double layer capacitor, and Therefore, capacitors using pseudo capacitance (referred redox capacitor), the electric double layer capacity Compared to a conventional electric double layer capacitor that uses only the capacitor, the capacitor has a significantly higher capacity. As an example, for example, Japanese Patent Laid-Open No. 6-104141 (Patent Document 1) discloses a capacitor composed of a conductive polymer film.

[0005] As described above, a capacitor using a pseudo-capacitance (redox capacitor) is an element that can exhibit breakthrough characteristics, but has not been put into practical use due to two major technical problems. .

[0006] Firstly, there is a problem that the conductive polymer does not operate as an electrode because it is an insulator in an undoped state. With regard to this problem, there is a proposal related to an electrode for a power storage element made of a carbon Z conductive polymer composite having a structure in which the surface of a carbon material having a high specific surface area is coated with a conductive polymer (for example, Japanese Patent Application Laid-Open No. 2003-2003). No. 109875 (see Patent Document 2).

[0007] Secondly, there is a problem that the repeated stability of conducting polymer doping and dedoping reactions is poor. The fact is that the second problem has not been fundamentally solved.

[0008] In addition to the techniques related to electrochemical devices as described above, molten salts that are liquid at room temperature have recently been developed and attracting attention. These are referred to as ionic liquids and include quaternary salt cations such as imidazolium pyridinium and appropriate key ions (Br-, A1C1-, BF-, PF-, etc.)

It is composed of 4 4 6 combinations. Ionic liquids have features such as non-volatility, nonflammability, chemical stability, and high ionic conductivity, and are attracting attention as reusable green solvents used in chemical reactions such as various syntheses and catalytic reactions. Ionic liquids have a large potential window, excellent voltage resistance, and high ion concentration. In addition, since it is flame retardant and does not volatilize, it has excellent safety without worrying about evaporation. For this reason, application of ionic liquids as electrolytes for electric double layer capacitors is being studied.

Patent Document 1: Japanese Patent Laid-Open No. 6-104141

Patent Document 2: Japanese Patent Laid-Open No. 2003-109875 Non-Patent Document 1: Andy Rudge et al., Journal of Power Sources 47, 1994, 89-107 Disclosure of Invention

Problems to be solved by the invention

[0009] The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a novel electrochemical device having improved repeated stability of doping and dedoping reactions. It is.

Means for solving the problem

[0010] The electrochemical element of the present invention is characterized by having a bipolar conductive polymer and an electrolyte containing an ionic liquid. In the prior art, the reason why the doping reaction does not occur gradually during repeated doping and dedoping reactions in the electrolyte is that the dedoped dopant diffuses into the electrolyte, and the conductive polymer during doping This is because there is no effective dopant in the vicinity of. Therefore, we first examined the combination of conductive polymer and ion liquid. If the ion component and Z or cation component of the ionic liquid are selected as components that can also be conductive polymer dopants, the dopant should always be present in the vicinity of the conductive polymer. The In such an ionic liquid, the ion component and the Z or cation component constituting the ionic liquid are incorporated as a dopant of the conductive polymer while repeating the doping and dedoping reactions, and the ionic liquid The ionic liquid and the Z or force thione component constituting the ionic liquid and a part of the dopant of the conductive polymer are considered to form an ionic liquid 'conductive polymer composite. 'Conductive polymer composites are considered to contribute to the development of excellent doping stability of repeated undoping reactions. The present inventors have found that a particularly high performance electrochemical device can be realized by using a bipolar polymer among the conductive polymers, and have completed the present invention. That is, the present invention is as follows.

[0011] The electrochemical device of the present invention is characterized by having a bipolar conductive polymer and an electrolyte containing an ionic liquid.

[0012] Here, the electrolyte is preferably a mixture of an ionic liquid and an organic solvent.

Acetonitorinole, propylene carbonate, ethylene carbonate, y-butinorelatatatone It is more preferable to mix at least one force selected as the intermediate force and an ionic liquid at a volume ratio of 1: 3 to L0: 1.

In the electrochemical device of the present invention, it is preferable that the bipolar conductive polymer further contains an ionic liquid.

[0014] The ionic liquid used in the present invention is BF-on, PF-on or sulfonic acid.

4 6

It is preferable to use ionic liquids containing Yuon 1-Ethyl 3-methyl imidazolium tetrafluoroborate, 1-Butyl 3-methyl imidazole tetrafluoroborate, 1-Ethyl 3-methyl imidazolium At least one selected from xafluorophosphate, 1-butyl-3-methylimidazole hexafluorophosphate, 1-ethyl-3-methylimidazolium mutosylate, 1-butyl 3-methylimidazolium tosylate More preferred.

[0015] The bipolar conductive polymer used in the present invention has an electric conductivity of 1000 times or more in the doped state and the undoped state, and the conductivity in the doped state is not less than 0. OlSZcm. Is preferred.

[0016] In addition, the bipolar conductive polymer used in the present invention is preferably a polythiophene derivative, such as poly 3- (4 fluorophenyl) thiophene, poly 3- (4-tert-butylphenol) thiophene, Poly 3— (4 trifluoromethyl phenol) thiophene, Poly 3 mono (2, 4 difluorophenol) thiophene, Poly 3— (2, 3, 4, 5, 6 Pentafluoro oral phenol) thiophene More preferably, it is at least one selected.

[0017] The electrochemical device of the present invention includes two electrodes facing each other and an electrolyte containing an ionic liquid sandwiched between the electrodes, and at least the surface of the electrode has a conductive high polarity. Preferably, the molecule is present so as to contact the electrolyte.

[0018] The electrochemical element of the present invention is preferably a redox capacitor used as a polar device.

The invention's effect

[0019] According to the present invention, high-performance electrochemical having improved repeated stability of doping and dedoping reactions by having a bipolar conductive polymer and an electrolyte containing an ionic liquid. An element can be provided. Brief Description of Drawings

FIG. 1 is a diagram schematically showing a configuration of a redox capacitor 1 which is a preferred example of an electrochemical element of the present invention.

FIG. 2 is a diagram schematically showing changes in voltage and current during charging / discharging of a system using a bipolar conductive polymer used in the present invention.

FIG. 3 is a diagram schematically showing cells used in Examples and Comparative Examples of the present invention.

FIG. 4 is a graph showing cyclic voltammetry measured in Comparative Example 1.

Explanation of symbols

[0021] 1 redox capacitor, 2, 3 electrodes, 4 separators, 5, 6 electrode elements, 7 gaskets BEST MODE FOR CARRYING OUT THE INVENTION

[0022] The bipolar conductive polymer in the present invention is a conductive polymer capable of both P-doping and N-doping (a-on-cation both-doping type conductive polymer). Fig. 2 schematically shows the state of charge and discharge in a system in which a bipolar conductive polymer is used for two electrodes, with current on the vertical axis and voltage on the horizontal axis. The arrows in Fig. 2 indicate the direction of change in voltage and current during discharge. As shown in Fig. 2, in a system using a bipolar conductive polymer as the active material of each electrode, one of the conductive polymers is P-doped (a- The other conductive polymer is N-doped (force thione doped). As a result, the voltage of the system after charging (the voltage between the two electrodes) is V. Discharge

1

In some cases, contrary to charging, one conductive polymer is de-doped with ions, the other conductive polymer is de-doped with cations, and a doping charge Q is released. And

1

Thus, after the discharge is completed, both conductive polymers return to the state where they are not doped with cation and cation. In the present invention, by using such a bipolar polymer among conductive polymers, it is possible to realize a particularly high-performance electrochemical element in characteristics such as discharge voltage, stored charge, and energy density. it can.

[0023] Examples of the bipolar conductive polymer include, but are not limited to, various polythiophene derivatives.

[0024] Suitable as a polythiophene derivative that is a bipolar conductive polymer used in the present invention. Examples include poly-1- (4-fluorophenyl) thiophene, poly-3- (4-trifluoromethylphenol) thiophene, poly-3- (2,4-difluorophenyl) thiophene, poly-3- ( 2, 3, 4, 5, 6 Pentafluorophenyl) thiophene, at least one selected. Among these, polythiophene derivatives having 1 to 4 fluorine atoms per monomer unit are preferable because the N-doped polymer is moderately stabilized. That is, poly-1- (4-fluorophenyl) thiophene, poly-3- (4-t-butylphenol) thiophene, poly-3- (4 trifluoromethylphenol) thiophene, poly-3- (2 , 4-difluorophenyl) thiophene is preferably used.

The bipolar conductive polymer used in the present invention can be doped and dedoped with a large amount of dopants, which is preferable from the viewpoint of increasing the capacitance of the electrochemical device. For this purpose, it is preferable to use a conductive polymer whose electrical conductivity change due to doping and dedoping is 1000 times or more. For example, the polythiophene derivatives exemplified above can be used without any problem. The change in electrical conductivity due to the above-described doping and dedoping can be known, for example, as follows. That is, SnO glass etc. by electrolytic polymerization

A conductive polymer film is formed on the conductive substrate 2 and the produced conductive substrate with the conductive polymer film is used together with a reference electrode (for example, RE5 reference electrode manufactured by BAS Co., Ltd.) and a counter electrode (for example, a platinum plate) as a dopant. Soaked in an electrolyte solution containing ions (for example, propylene carbonate solution of ImolZL tetrachloroammotetrafluoroborate). In this electrolyte solution, a conductive substrate with a conductive polymer film is formed. Doping of molecules Performs sufficient doping of the conductive polymer film by maintaining the potential at a potential for a certain period of time. Next, the conductive substrate with the conductive polymer film is taken out of the solution, and the conductive polymer film is peeled off from the conductive substrate, washed with methanol, and dried. The electrical conductivity of the obtained conductive polymer film in the doped state is measured by a general electrical conductivity measurement method such as the 4-terminal method. Next, the conductive polymer film is electrolytically polymerized in the same manner as above, and this is kept at a potential at which de-doping occurs in the electrolyte for a certain period of time, thereby producing a de-doped conductive polymer film. The electrical conductivity of the conductive polymer film in the doped state is measured. Changes in the electrical conductivity between the doped state and the undoped state of the conducting polymer by these two electrical conductivity measurements I understand. When the conductive polymer is obtained as a powder sample by chemical polymerization or the like, the conductive polymer powder is pressed and solidified into a pellet, and this pellet-like conductive polymer is used as a dopant in the same manner as described above. Conductive polymer pellets in a doped state and in a dedope state are prepared by maintaining a constant potential for a certain period of time in an electrolyte containing ions. If the electrical conductivity of these pellets is measured by the 4-terminal method, etc., the change in the electrical conductivity of the conductive polymer in the doped state and in the undoped state can be seen. For example, in a propylene carbonate solution containing 0.1 lmol ZL monomer and ImolZL tetraethylammonium tetrafluoroborate, SnO glass is +1.2 relative to the RE5 reference electrode.

2

Poly 3- (4 fluorophenyl) thiophene electropolymerized by holding at V for 120 seconds was added to the RE5 reference electrode in a lmol / L tetraethylammonium tetrafluoroborate propylene carbonate solution. On the other hand, if the potential is kept at + 1.0V for 600 seconds, sufficient P-doping is achieved. In addition, if it is maintained at −1.0V for 600 seconds with respect to the RE5 reference electrode, it will be in a sufficiently undoped state, and if it is maintained at 2.0V for 600 seconds, it will be in a sufficiently N-doped state.

[0026] The conductive polymer used in the present invention has a high electrical conductivity, and the viewpoint power to lower the internal resistance of the capacitor is also preferable. For this purpose, it is preferable to use a conductive polymer exhibiting a conductivity of 0.01 S / cm or more (more preferably 1. OSZ cm or more) in a doped state V, but for example, the polythiophene derivatives exemplified above are problematic. It can be used without. The conductivity in the doped state can be measured using, for example, the method described above.

[0027] The bipolar conductive polymer dopant preferably used in the present invention includes the conductivity and thermal stability of the bipolar conductive polymer, the capacity of doping and dedoping, the stability, and the speed. Selected in consideration of the effect on The dopants preferably used in the bipolar conductive polymer of the present invention include p-toluenesulfonate ion, benzenesulfonate, anthraquinone 2-sulphonate, triisopropinorenaphthalene sulphonate, Examples thereof include polyvinyl sulfonate ions, dodecyl benzene sulfonate ions, alkyl sulfonate ions, n-propyl phosphate ions, perchlorate ions, and tetrafluoroborate ions. The smaller the dopant, the smaller the doping There is a tendency to have excellent performance, and p-toluenesulfonic acid, benzenesulfonic acid or tetrafluoroborate ion is particularly preferable.

[0028] The bipolar conductive polymer in the present invention can be easily prepared into a thin and uniform conductive polymer film, and the film thickness can be controlled. Therefore, the electropolymerization in the presence of an organic solvent is possible. It is preferable that it is obtained by. In the electropolymerization, for example, a bipolar conductive polymer can be deposited on the anode by a method in which a monomer is dissolved in a solvent together with a supporting electrolyte and anodized to perform dehydrogenation polymerization. In general, the oxidation-reduction potential of a polymer is lower than that of a monomer, so that the acid of the polymer skeleton further progresses during the polymerization process, and as a result, the support electrolyte, ion, is incorporated into the polymer as a dopant. It is. Electrolytic polymerization has the advantage that a conductive polymer can be obtained by such a mechanism without having to add a dopant later. Further, as will be described later, it is preferable to use a carbon electrode for electrolytic polymerization and to deposit a conductive polymer on the surface thereof, because such an electrode can be used as it is as a polarizing electrode for a redox capacitor or the like.

[0029] Examples of supporting electrolytes in which a cation component and a Z or cation component are incorporated into a polymer as a dopant include sodium alkylsulfonate, sodium p-toluenesulfonate, sodium dodecylbenzenesulfonate, triisopropylnaphthalene. Sodium sulfonate, sodium benzoate, sodium dodecyl sulfate, n-propyl phosphate ester, isopropyl phosphate ester, n-butyl phosphate ester, n xyl phosphate ester, sodium polystyrene sulfonate, sodium polybutyl sulfonate, perchloric acid Examples include tetra n-butyl ammonium, boron tetrafluoride tetraethyl ammonium, and boron tetrafluoride tetra n-butyl ammonium. Among these, readily available ionic liquids and key components are common, such as sodium p-toluenesulfonate, tetraethylammonium tetrafluoride, tetra-n-butylammonium tetrafluoride. Are preferred.

[0030] The bipolar conductive polymer in the present invention may be polymerized in an ionic liquid. As a result, a bipolar conductive polymer (described later) containing an ionic liquid can be produced in advance.

[0031] The electrolyte used in the electrochemical device of the present invention includes an ionic liquid. To do. As used herein, the term “ionic liquid” refers to a liquid that is liquid at room temperature even though only ionic forces are formed, and is composed of a combination of a cation such as imidazolium and an appropriate ion. The Since such an ionic liquid is flame retardant and non-volatile, the electrolyte contains an ionic liquid, so that durability and safety are improved compared to the case of using an electrolyte composed of only an ordinary organic solvent. An excellent electrochemical device can be realized. In addition, since the ionic liquid is a liquid that only has ions and has a high ion concentration, an electrochemical element using an electrolyte containing the ionic liquid has an advantage of high doping and dedoping capacity and responsiveness. Furthermore, since the ionic liquid has a wide potential window (high withstand voltage), there is an advantage that an electrochemical element having a high withstand voltage can be produced by using an electrolyte containing the ionic liquid.

[0032] Examples of the cation constituting the ionic liquid preferably used in the present invention include an imidazolium cation, a pyridinium cation, a pyrrolidinium cation, an ammonium cation, and a triazine derivative cation. Force V, not limited to these. Among them, the imidazolium cation is preferably used from the viewpoint of ease of use.

[0033] The key components that make up the ionic liquid are Br-, A1C1-, PF-, NO-, R NO-

4 6 3 A 3

NH CHR COO—, (CF ² SO 4) N—, SO ² etc.

2 A 3 2 2 4

It is not specified. Where R

A represents a substituent containing an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an ether group, an ester group, an acyl group or the like, and may contain fluorine.

[0034] In addition, R COO—, —OOCR CO, which is a caron containing carboxylate (one COO)

B B

OH, “OOCR CCOO—, NH CHR COO— (where R is an aliphatic hydrocarbon group, alicyclic

B 2 B B

The substituent which contains a formula hydrocarbon group, an aromatic hydrocarbon group, an ether group, an ester group, an acyl group, etc. is shown, and may contain fluorine. ) Is preferably used in the present invention.

[0035] In addition, R SO-, R OSO-

3 C 3 C 3 where R is an aliphatic hydrocarbon group, alicyclic hydrocarbon group, aromatic hydrocarbon group, ether

C

A substituent containing a group, an ester group, an acyl group or the like is shown, and may contain fluorine. ), Benzenesulfonic acid, toluenesulfonic acid and the like are preferably used in the present invention.

[0036] Further, when BF- is used, an ionic liquid having a low viscosity is obtained, which is preferable in the present invention. You can!

[0037] The ionic liquid in the present invention is excellent in the repeated stability of doping and undoping, and therefore, among the above, BF-on, PF-on or sulfonic acid-on is used.

4 6

U, which is preferably an ionic liquid containing.

[0038] Specific examples of ionic liquids preferably used in the present invention include 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluororeborate, 1-ethinoleo. At least selected from 3-methinoreimidoxalium hexaphleoleophosphate, 1-butyl-3-methylimidazole hexafluorophosphate, 1-ethyl-3-ethyl imidazolium tosylate, 1-butyl 3-methylimidazolium tosylate One is mentioned. Among them, 1-ethyl-3-methylimidazole tetrafluoroborate and 1-butyl-3-methylimidazolium are used because of the large accumulated charge due to doping and undoping and excellent repeat stability of doping and undoping. It is preferable to use mutetrafluoroborate as the ionic liquid.

[0039] It is preferable that the ionic liquid is contained in a ratio of 1: 3 to 1: 10000 with respect to the bipolar conductive polymer. The ratio of 1: 5 to 1: 100 is preferable. More preferably, it is contained. If the ionic liquid is less than 1: 10000 with respect to the bipolar conductive polymer, the proportion of the ionic liquid is too small to contribute to the improvement of the doping and dedoping performance. Moreover, if the ionic liquid exceeds 1: 3 with respect to the bipolar conductive polymer, there is a problem that the strength of the conductive polymer film is weakened.

[0040] The ionic liquid preferably used in the present invention can be synthesized by combining the above-mentioned ions and cations using a known method. Specific examples of the synthesis method include a key exchange method, an acid ester method, and a neutralization method.

[0041] The electrolyte used in the present invention may be composed only of an ionic liquid as long as it contains an ionic liquid, and may be a mixture of an ionic liquid and an organic solvent. However, by using a mixture of an ionic liquid and an organic solvent as an electrolyte, a high ion concentration and a low viscosity can be realized with an appropriate balance. Doping capacity and response speed can be increased, which is preferable.

[0042] Examples of the organic solvent used in the mixture include acetonitrile, propylene power, and the like. Organic solvents that have been widely used in the art, such as carbonate, ethylene carbonate, and γ-butyllatatone, can be used without particular limitation. Above all, when it mixes with various ionic liquids at an arbitrary ratio and the viscosity of the liquid mixture decreases! For this reason, it is preferable to use acetonitrile.

[0043] When the electrolyte is a mixture of an ionic liquid and an organic solvent, the mixing ratio is not particularly limited, but as described above, among organic solvents such as acetonitrile, propylene carbonate, ethylene carbonate, and y-butyllatatone. Force When using at least one selected, organic solvent: ionic liquid = 1: 3 to 10: 1 (volume ratio) is preferred 1: 3 to 3: 1 is more preferred . If the volume ratio of the ionic liquid to the organic solvent is less than 1:10, the ion concentration tends to be low, which tends to be unfavorable for doping and dedoping, and the volume ratio of the ionic liquid to the organic solvent. If the ratio exceeds 3: 1, the viscosity of the mixed solution tends to increase and the electrical conductivity tends to decrease.

[0044] The electrochemical device of the present invention preferably further comprises a bipolar conductive polymer force S ionic liquid. Here, the bipolar conductive polymer containing the ionic liquid may be produced by impregnating the conductive polymer with the ionic liquid later, or polymerization of the conductive polymer. It may be produced by coexisting an ionic liquid from the process. As the ionic liquid contained in the bipolar conductive polymer, those described above can be used without particular limitation. The cationic component constituting the ionic liquid may be a component that can be a dopant for a bipolar conductive polymer or a component that cannot be a dopant for a conductive polymer. . Even if it is not a dopant for a conductive polymer, it can be contained in the conductive polymer (coexist with the conductive polymer). As described above, by using a bipolar conductive polymer further containing an ionic liquid, an electrochemical device having further improved charge storage and release capability can be realized.

[0045] The cation component or the anion component constituting the ionic liquid is a component that can serve as a dopant for a bipolar conductive polymer. Even when a dedoping reaction of the bipolar conductive polymer occurs, It is realized that the ion component and the Z or cation component, which can be effective dopants for the conductive polymer, are always present in the vicinity of the conductive polymer. It becomes possible to show. Therefore, it is important to dope 'de-doping reaction in ionic liquid, and to make the ion component that constitutes the ionic liquid as a component that can be a dopant of a bipolar conductive polymer. This will have a significant effect on improving the repeated stability of the dedoping reaction.

[0046] After repeating the doping and dedoping reaction in the electrochemical device of the present invention, the ionic component and the Z or cation component of the ionic liquid constituting the bipolar conductive polymer dopant and Part of the ionic liquid conductive polymer composite, which is a common component, is formed. That is, at the start of the doping and dedoping reaction, the bipolar conductive polymer dopant and the ionic component and the Z or cation component of the ionic liquid are not necessarily the same, but repeatedly. At the time after the doping and de-doping reaction has proceeded, at least a part of the ionic component and the Z or cation component constituting the ionic liquid is incorporated as a dopant of the bipolar conductive polymer, and the ionic liquid At least a part of the ion component, the cation component, and the conductive polymer dopant constituting the body have the same component. Of course, for example, tetrafluoroborate ion (BF

4) It is more preferable to use the same force as the first component and / or the cation component and the dopant.

[0047] Further, in the present invention, an electropolymerized film containing an electroconductive polymer having a bipolar polarity electropolymerized in an organic solvent containing an ionic liquid, an electrode composite comprising the electrode, and an electrolyte containing the ionic liquid, It is good also as an electrochemical element which combined. In this case, the doping and dedoping reactions should be carried out, and at that time, the ionic component and the Z or force thione component constituting the ionic liquid should be set as components capable of becoming a bipolar conductive polymer dopant. This significantly improves the repeated stability of the doping and dedoping reactions.

[0048] The term "electrochemical element" in the present specification refers to all elements that repeatedly use conductive polymer doping and dedoping reactions, and includes capacitors such as redox capacitors, batteries, electrochromic elements, Includes sensors and the like. In particular, the electrochemical device of the present invention is preferably realized by a redox capacitor (type III redox capacitor)!

[0049] The electrochemical device of the present invention includes, for example, two opposing electrodes and an electrolyte containing an ionic liquid sandwiched between the electrodes, and at least the surface of the electrode has a bipolar conductive property. It is preferable to realize the structure in which the conductive polymer exists so as to be in contact with the electrolyte.

FIG. 1 is a diagram schematically showing a configuration of a redox capacitor 1 which is a preferred example of the electrochemical device of the present invention. Here, the redox capacitor is a capacitor obtained by expanding the capacitance of the electric double layer capacitor by using a pseudo capacitance. The redox capacitor of the present invention uses all or part of oxidation / reduction of an electrode material, charge / discharge in an electric double layer, and desorption of ions on the electrode surface for storage and release of electric energy. It is a type of electrochemical capacitor including metal oxide electrode systems, reversible redox solution systems, and underpotential chanore systems. In general, an electrochemical capacitor has been developed that has a capacity density of 120 WhZkg at the active material level, an output density of about 20 kwZkg or more, and can be charged and discharged at high speed within a few seconds.

[0051] The redox capacitor 1 of the example shown in FIG. 1 includes, for example, two plate-like electrodes 2 and 3 arranged with a separator 4 interposed therebetween, and each of the electrode elements 2 and 3 is an electrode element. It has a structure where 5 and 6 are in contact. The laminated structure composed of the electrode 2, the separator 4, and the electrode 3 is fixed between the electrode elements 5 and 6 by the gasket 7 so that the electrode elements 5 and 6 do not contact each other.

[0052] The material for forming the electrodes 2 and 3 is not particularly limited as long as it can be used for a redox capacitor. For example, an electrode formed only of a bipolar conductive polymer, a composite electrode of a carbon material and a bipolar conductive polymer, a composite electrode of a metal material and a bipolar conductive polymer, a metal material And a composite material electrode of carbon material and a bipolar conductive polymer can be used. Thus, in the present invention, it is preferable that at least the surface of the electrode be realized so as to be in contact with the above-described bipolar conductive polymer force electrolyte.

[0053] The composite material electrode of the carbon material and the bipolar conductive polymer is formed by using, for example, an organic solvent such as ethanol ethanol and methyl pyrrolidone and the bipolar conductive polymer as the electrode material and the carbon material. Further, a binder can be added to form a dispersion, which can be applied to the surface of the metal current collector and then dried. As the binder, fluorine resin such as polytetrafluoroethylene and polyvinylidene fluoride is preferably used. The amount of binder used with respect to the electrode material is preferably about 5 to 20% by weight. Metal current collector As the body, metals such as aluminum, nickel, stainless steel, titanium, and tantalum are preferably used, and these metals may be gold or platinum plated, or may be a polymer film formed with a metal layer. . The metal current collector is more preferably used in the form of a rolled foil, a punching foil, an etched foil, an expanded metal foil or the like. When the polarizing electrode is not a current collector but in the form of a sheet, the conductive polymer Z-carbon composite material is mixed with the above binder, and a lubricant is added to form a paste, which is then extruded. These can be rolled with a rolling roll to form an electrode sheet.

[0054] Further, carbon may be dispersed by dispersing a carbon material in a polymerization solution of a bipolar conductive polymer, followed by chemical polymerization, and coating the surface of the carbon material with a bipolar conductive polymer. A composite electrode of a material and a bipolar conductive polymer can be produced. An electrode is produced in the same manner as described above using the carbon material coated with the bipolar conductive polymer thus produced.

[0055] The composite material electrode of the carbon material and the ambipolar conductive polymer can also be produced as follows. First, a carbon material and a binder are added to an organic solvent such as ethanol, methanol, or methylpyrrolidone to form a dispersion, which is applied to the surface of a metal current collector and then dried to produce a carbon electrode. Next, electrolytic polymerization is performed using this as an electrode to form a conductive polymer thin film on the surface of the carbon electrode, and the surface of the carbon material is coated with a thin conductive polymer. An electrode produced by this method is a useful method for reducing impedance because the conductive polymer layer can be made extremely thin.

[0056] The carbon material used for the composite material electrode of the carbon material and the bipolar conductive polymer is not particularly limited as long as it is a carbon material used for electrode formation in this field. It is preferable to contain activated carbon powder and / or graphite powder. This is because the addition of activated carbon powder or graphite powder can reduce electrode resistance and increase surface area. Accordingly, carbon blacks such as acetylene black and furnace black having a large surface area, activated carbon particles having a relatively large pore size, carbon fibers having a relatively small particle size, graphite fibers, and carbon nanotubes are particularly preferred as the carbon material. It is mentioned as a thing. Carbon materials have a specific surface area (analysis of nitrogen adsorption isotherm data at liquid nitrogen temperature). It is preferable to use a material having a BET specific surface area value of 20 m ² Zg or more.

[0057] The laminated structure of the electrode 2, the separator 4, and the electrode 3 shown in FIG. 1 is impregnated with an electrolyte containing the ionic liquid described above (preferably a mixture of the ionic liquid and the organic solvent). . As the separator 4, those conventionally used for capacitors can be used without any particular limitation, and a porous one is preferably used. Further, the electrode elements 5 and 6 and the gasket 7 can be used without any particular limitation as long as they are conventionally used for capacitors. As the gasket 7, an electrically insulating material is used.

[0058] The method of charging / discharging the electrochemical device of the present invention is the same as that of a normal electric double layer capacitor, and can be performed by applying a voltage between a pair of electrodes or passing a current. There is no particular limitation. However, if the electrode on one side is used only as a positive electrode and the other electrode is used only as a negative electrode, the lifetime of the electrochemical device of the present invention can be greatly prolonged. For this reason, the electrochemical device of the present invention is preferably realized as a redox capacitor used as a polar device that distinguishes between a positive electrode and a negative electrode, since the cycle life can be extended. In general, this is the direction of repeating only union or deionization of either a cation or a cation in a bipolar conductive polymer. This is because there is little deterioration of the dedoping property.

[0059] The electrochemical device of the present invention is preferably used in an appropriate voltage range so as not to be overcharged from the viewpoint of extending the cycle life. This is because when the dopant is excessively doped, the bipolar conductive polymer is strongly oxidized or reduced, so that the bipolar conductive polymer itself deteriorates and functions as an electrode that repeats doping and dedoping. This is because the performance decreases.

[0060] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[0061] <Comparative Example 1>

Using the cell schematically shown in Fig. 3, both polarities are formed on SnO glass by electrolytic polymerization.

2

A film of poly-3- (4 fluorophenyl) thiophene, which is a conductive polymer, was formed. Note that the operation using the cell shown in Fig. 3 eliminates the influence of moisture and oxygen in the atmosphere. All were performed in a glove box replaced with high purity argon gas.

[0062] The electropolymerization solution was 4-fluorophenylthiophene 0.1M as a monomer and boron tetrafluoride tetraethylammonium (Tetraethylammonium tetrafluoroborate HTEA'BF) as a supporting salt. ) A propylene carbonate (PC) solution containing 1M was used. here

Four

The TEA 'BF 1M propylene carbonate solution used was purchased from Sanwa Oil.

Four

It is.

[0063] As the working electrode, 3 3 ^ 11 3110 glass plate was used. As a counter electrode, 3 X 4cm

2

A platinum plate was used. The SnO glass plate, which is the working electrode, has a SnO coating on one side

twenty two

In order for the SnO coated side to face the counter electrode

2

Arranged. In addition, as a reference electrode, BAS RE-5 reference electrode (AgZAg + reference electrode, the solution in the reference electrode is 0.1 M of tetrachloramine perchlorate (Bu N'CIO), silver nitrate.

4 4

(Acetonitrile solution containing 0.01M of (AgNO 3)) was used. The potential of this reference electrode is standard

Three

Compared to hydrogen electrode (NHE), it is + 490mV (+ 0.49V).

[0064] As shown in FIG. 3, the electrolytic polymerization solution is accommodated in a container, and these are electrolyzed in a state in which the working electrode is arranged with an interval of lcm between the reference electrode and the counter electrode. It was immersed in the polymerization solution. The working electrode was soaked only in the region of lcm from the end side in the electrolytic polymerization solution (that is, the area of the working electrode immersed in the electrolytic polymerization solution was 3 X lcm). In this state, the potential of the working electrode is maintained at +1.2 V for 120 seconds with respect to the reference electrode for 120 seconds.

2

A film of 3- (4 fluorophenyl) thiophene was formed. At this point, the poly-3- (4-fluorophenol) thiophene film is P-doped (in this case, BF-ion doped)

Four

It is in. Next, the potential of the S ηθ glass (working electrode) partially formed with a poly-3- (4 fluorophenyl) thiophene film was maintained at 0.0 V with respect to the RE-5 reference electrode for 240 seconds.

2

De-doping of one (4 monofluorophenyl) thiophene film was performed.

[0065] After the dedope film of poly 3- (4 fluorophenyl) thiophene formed as described above was formed on SnO glass (working electrode), it was rinsed lightly with propylene carbonate.

2

Prepare a container containing a PC solution (manufactured by Sanwa Yuka) containing 1M TEA'BF as the supporting salt.

Four

Then, the reference electrode, working electrode and counter electrode were immersed in this solution in the same manner as described above (the working electrode was immersed only in the region where the edge force was 1 cm), and cyclic voltammetry (CV) measurement was performed. CV In the measurement, a potential sweep was started from the natural potential of the dedope film of poly 3- (4 fluorophenyl) thiophene toward the positive side. Figure 4 shows the obtained CV. As shown in Fig. 4, the width of the potential sweep was 2. lV to + 0.8V relative to the RE-5 reference electrode, and the potential sweep (sweep) speed was 25 mVZs.

[0066] Here, in the CV shown in Fig. 4, the horizontal axis represents the potential of the working electrode with the reference electrode potential as the standard of OV, and the horizontal axis OV in the graph represents + 490mV (+ 0. 4 9V). Also, the upward peak on the right side of Fig. 4 (the peak of the current in the direction where the absolute value of the current increases in the + direction in the region above the horizontal axis OV) is P-doped (BF- dopin

4) and the downward peak on the right side (the peak of the current in the direction where the absolute value of the current increases in one direction in the region of OV or more on the horizontal axis) corresponds to P dedoping (BF− dedoping). To do. Also

Four

In Fig. 4, the downward peak on the left (the peak of the current in the direction where the absolute value of the current increases in one direction in the region below the horizontal axis of 1.5 V) is N-doped (doping of tetraethylamine-mucation) And the left upward peak (current peak in the direction where the absolute value of the current increases in the + direction in the region of 0 V or more on the horizontal axis) is N-dedoped (dedoped with tetraethylammonium cation) Equivalent to.

[0067] The capacities of P-doped, dedope and N-doped 'undope' calculated by time integration of the current values in the graph shown in Fig. 4 were 0.025C and 0.021C, respectively.

Poly 3- (4 fluorophenyl) thiophene film formed on part of SnO as above

2

did. After that, change to a PC solution containing 1M TEA'BF.

Four

CV measurement was performed in the same manner as in Comparative Example 1 except that a mixed solution in which 3-methylimidazole tetrafluoroborate and acetonitrile were mixed at a volume ratio of 1: 1 was used. The capacities of P-doped / dedoped and N-doped / dedope were 0.029C and 0.024C, respectively. In Example 1, repeated stability (cycle characteristics) was improved as compared with Comparative Example 1 described above.

Poly 3- (4 fluorophenyl) thiophene film formed on part of SnO as above

2

did. After that, change to a PC solution containing 1M TEA'BF. CV measurement was performed in the same manner as in Comparative Example 1 except that rho-3-methylimidazole tetrafluoroborate was used. Similarly, the capacitances of P-doped and N-doped and N-doped and dedoped were measured. Was found to be 0.003C and 0.002C, respectively. In Example 2 as well, repeatability (cycle characteristics) was improved as compared to Comparative Example 1 described above.

It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims

The scope of the claims

[1] An electrochemical element comprising a bipolar conductive polymer and an electrolyte containing an ionic liquid.

[2] The electrochemical element according to claim 1, wherein the electrolyte is a mixture of an ionic liquid and an organic solvent.

[3] The electrolyte is a mixture of at least one selected from among acetonitrile, propylene carbonate, ethylene carbonate, and γ-butyl lactone and an ionic liquid in a volume ratio of 1: 3 to 10: 1. The electrochemical element according to the second item of the range.

[4] The electrochemical element according to claim 1, wherein the ambipolar conductive polymer further contains an ionic liquid.

[5] The ionic liquid contains BF—on, PF—on or sulfonic acid on.

4 6

2. The electrochemical device according to claim 1, which is an ionic liquid.

[6] The ionic liquid is 1-ethyl 3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazole tetrafluoroborate, 1-ethyl 3-methylimidazolium hexafluorophosphate 1-butyl-3-methylimidazole hexaphosphate, 1-ethyl-3-methylimidazolium tosylate, 1-butyl-3-methylimidazolium tosylate The electrochemical element as described in.

[7] The electric conductivity of the ambipolar conductive polymer changes 1000 times or more in a doped state and an undoped state, and the conductivity in the doped state is not less than 0. OlSZcm. The electrochemical element as described in.

8. The electrochemical element according to claim 1, wherein the bipolar conductive polymer is a polythiophene derivative.

[9] Bipolar conductive polymer forces Poly-3 (4-fluorophenyl) thiophene, Poly-3 1 (4 tert-butylphenol) thiophene, Poly 3— (4 trifluoromethylphenol) -Le) thiophene, poly 3- (2,4 difluorophenol) thiophene, poly 3- (2, 3, 4, 5, 6 pentafluorophenol) thiophene, at least one of which force is also selected The electrochemical element according to claim 8, wherein

[10] It includes two electrodes facing each other and an electrolyte containing an ionic liquid sandwiched between the electrodes, and at least a surface of the electrode has a bipolar conductive polymer in contact with the electrolyte The electrochemical device according to claim 1, wherein the electrochemical device is a device.

[11] The electrochemical element according to claim 10, which is a redox capacitor used as a polar device.