JP2009212469A - Novel energy storage device utilizing electrolyte for storing electricity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To substantially improve charge and discharge capacity in an electric double-layer capacitor, a redox capacitor, a lithium ion electrolytic capacitor, a lithium ion secondary battery and application devices thereof, for example, without spoiling output characteristics, charge and discharge efficiency and a cycle lifetime thereof, while providing them as large capacity energy storage devices. <P>SOLUTION: In the energy storage device including a positive electrode, a negative electrode and an electrolyte, 0.5-50 wt.% of at least one charged by doping/dedoping reaction selected from an aniline tetramer, an aniline tetramer derivative having a molecular weight of not less than 366 and less than 500, an aniline pentamer, and an aniline pentamer derivative having a molecular weight of not less than 457 and less than 500 is contained in the electrolyte. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an energy storage device having a novel energy storage means. The invention relates to an energy storage device having a mechanism for storing energy by doping / de-doping reaction of a compound capable of performing doping / de-doping reaction contained in an electrolyte, an electric double layer capacitor, a redox capacitor, The present invention can be applied to lithium ion electrolyte capacitors, lithium ion secondary batteries, and application devices thereof.

  In recent years, consumer electronic devices are becoming more portable and cordless, 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, large capacity capacitors and batteries are also required for applications such as e-hybrid vehicles (HEV) and fuel cell vehicles (FCEV).

  As one of energy storage devices, an electric double layer capacitor is known. An electric double layer capacitor is an electrochemical device 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 electricity storage by this electric double layer capacity is characterized by being capable of faster charge / discharge and excellent charge / discharge cycle life characteristics as compared to a secondary battery with an electrochemical reaction. .

  In addition, a battery using a pseudo capacitance by a conductive polymer has been proposed. Unlike the electric double layer capacity, the pseudo capacity is stored with an oxidation-reduction reaction of the electrode material. Such a pseudo capacity is manifested by a redox reaction of the conductive polymer, that is, a doping / dedoping reaction when the conductive polymer is used. As such conductive polymer materials, pi-conjugated polymers such as polypyrrole, polyaniline, and polythiophene are known. (For example, refer to Patent Documents 1 and 2).

  In addition, a lithium ion electrolyte type capacitor has been proposed in which the positive electrode side stores the electric double layer capacity on the activated carbon surface, and the negative electrode side stores the lithium ion intercalation capacity to the layered carbon material (for example, Patent Documents). 3).

  Furthermore, 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 is a battery having a large capacity and is used in a wide range of applications. Research on lithium ion secondary batteries has been actively conducted, and improvement research has been conducted not only on positive electrodes and negative electrodes but also on electrolytic solutions (for example, see Patent Document 4).

However, both of the above capacitors and batteries use an oxidation-reduction reaction of the electrode itself or an electric double layer near the electrode as an energy storage means. In other words, electrical energy is stored and released using only the part related to the electrode itself or very close to the electrode, such as redox of the electrode material itself and adsorption / desorption of ions on the electrode surface. For this reason, there is a limit to the capacity of the obtained electricity storage, and it is required to produce a large-capacity energy storage device by using an energy storage means different from the conventional one.
JP-A-6-104141 JP 2002-203742 A Japanese Patent Laid-Open No. 8-1007048 JP 2003-338318 A

  The problem to be solved by the present invention is to provide a high-capacity energy storage device. For example, in electric double layer capacitors, redox capacitors, lithium ion electrolyte capacitors, lithium ion secondary batteries, and their application devices, charging / discharging can be performed without impairing their output characteristics, charging / discharging efficiency, cycle life, etc. The capacity is greatly improved.

  As a result of intensive studies, the present inventors have conducted an aniline tetramer, an aniline tetramer derivative having a molecular weight of 366 or more and less than 500, and an aniline 5 amount capable of performing a doping / dedoping reaction present in an electrolytic solution. It has been found that at least one compound of an aniline pentamer derivative having a body and a molecular weight of 457 or more and less than 500 stores energy by performing a stable doping / de-doping reaction, and has led to the present invention. .

  That is, the first of the present invention is an energy storage device including a positive electrode, a negative electrode, and an electrolytic solution, and a compound represented by the following general formula 1 having a molecular weight of 366 or more and less than 500 charged and discharged by doping / dedoping reaction to the electrolytic solution. Is an energy storage device containing 0.5 wt% or more and 50 wt% or less.

（ここでＲ₁、Ｒ_２、Ｒ_７、Ｒ_１２、Ｒ_１７は同一または異なる置換基であってアミノ基、アシル基、シアノ基、エステル基、アミド基、アルコキシカルボニル基、炭素数が１〜５の範囲内であるアルキル基、炭素数が１〜２の範囲内であるアルコキシ基、炭素数が１〜２の範囲内であるフルオロアルキル基、フッ素原子、水素原子のいずれか、またはメチル基、メトキシ基、フッ素原子、水素原子のいずれかである。Ｒ_３〜Ｒ_６、Ｒ_８〜Ｒ_１１、Ｒ_１３〜Ｒ_１６、Ｒ_１８〜Ｒ_２２は同一または異なる置換基であって、ニトロ基、アミノ基、アシル基、シアノ基、エステル基、アミド基、スルホニルエステル基、炭素数が１〜５の範囲内であるアルキル基、炭素数が１〜２の範囲内であるアルコキシ基、炭素数が１〜２の範囲内であるフルオロアルキル基、フッ素原子、水素原子のいずれか、またはニトロ基、アミノ基、アシル基、シアノ基、エステル基、アミド基、スルホニルエステル基、メチル基、メトキシ基、フッ素原子、水素原子のいずれかである。）
また、本発明の第２は、正極、負極及び電解液を含むエネルギー貯蔵デバイスであって、前記電解液にドープ/脱ドープ反応によって充放電する、分子量が４５７以上、５００未満の下記一般式２に示す化合物を、０．５重量％以上５０重量％以下含有するエネルギー貯蔵デバイス、である。

(Wherein R ₁ , R ₂ , R ₇ , R ₁₂ , R ₁₇ are the same or different substituents, and an amino group, an acyl group, a cyano group, an ester group, an amide group, an alkoxycarbonyl group, and a carbon number of 1 to An alkyl group in the range of 5, an alkoxy group in the range of 1 to 2 carbon atoms, a fluoroalkyl group in the range of 1 to 2 carbon atoms, a fluorine atom, a hydrogen atom, or a methyl group And R _{3 to} R ₆ , R _{8 to} R ₁₁ , R _{13 to} R ₁₆ , and R _{18 to} R ₂₂ are the same or different substituents, and are a nitro group , Amino group, acyl group, cyano group, ester group, amide group, sulfonyl ester group, alkyl group having 1 to 5 carbon atoms, alkoxy group having 1 to 2 carbon atoms, carbon number Is in the range of 1-2 Fluoroalkyl group, fluorine atom, hydrogen atom, or nitro group, amino group, acyl group, cyano group, ester group, amide group, sulfonyl ester group, methyl group, methoxy group, fluorine atom, hydrogen atom Either)
A second aspect of the present invention is an energy storage device including a positive electrode, a negative electrode, and an electrolyte solution, and the electrolyte solution is charged / discharged by a doping / dedoping reaction and has a molecular weight of 457 or more and less than 500. An energy storage device containing 0.5 wt% or more and 50 wt% or less of the compound shown in FIG.

（ここでＲ_２３、Ｒ_２４、Ｒ_２９、Ｒ_３４、Ｒ_３９、Ｒ_４４は同一または異なる置換基であってアミノ基、アシル基、シアノ基、エステル基、アミド基、アルコキシカルボニル基、炭素数が１〜３の範囲内であるアルキル基、メトキシ基、フッ素原子、水素原子のいずれかである。Ｒ_２５〜Ｒ_２８、Ｒ_３０〜Ｒ_３３、Ｒ_３５〜Ｒ_３８、Ｒ_４０〜Ｒ_４３、Ｒ_４５〜Ｒ_４９は同一または異なる置換基であって、ニトロ基、アミノ基、アシル基、シアノ基、エステル基、アミド基、炭素数が１〜３の範囲内であるアルキル基、メトキシ基、フッ素原子、水素原子のいずれかである。）
また、本発明の第３は、本発明の第１に記載のエネルギー貯蔵デバイスであって、前記電解液に含有されるドープ・脱ドープ反応によって充放電する、下記化学式３〜５からなる群より選ばれる少なくとも１種の化合物を、０．５重量％以上５０重量％以下含有するエネルギー貯蔵デバイス、である。

(Wherein R ₂₃ , R ₂₄ , R ₂₉ , R ₃₄ , R ₃₉ , R ₄₄ are the same or different substituents and are an amino group, acyl group, cyano group, ester group, amide group, alkoxycarbonyl group, carbon number Is an alkyl group, a methoxy group, a fluorine atom or a hydrogen atom within the range of 1 to 3. R _{25 to} R ₂₈ , R _{30 to} R ₃₃ , R _{35 to} R ₃₈ , R _{40 to} R ₄₃ , R _{45 to} R ₄₉ are the same or different substituents, and are a nitro group, an amino group, an acyl group, a cyano group, an ester group, an amide group, an alkyl group having 1 to 3 carbon atoms, a methoxy group, It is either a fluorine atom or a hydrogen atom.)
Moreover, 3rd of this invention is an energy storage device of 1st of this invention, Comprising: From the group which consists of following Chemical formula 3-5 charged / discharged by dope and dedoping reaction contained in the said electrolyte solution An energy storage device containing at least one selected compound of 0.5 wt% or more and 50 wt% or less.

また、本発明の第４は、前記電解液の溶媒が、有機溶媒、イオン液体、または有機溶媒とイオン液体との混合物のいずれかである、本発明の第１〜３のいずれかに記載のエネルギー貯蔵デバイス、である。

Moreover, 4th of this invention is the solvent of the said electrolyte solution in any one of 1-3 of this invention which is either a mixture of an organic solvent, an ionic liquid, or an organic solvent and an ionic liquid. An energy storage device.

  According to a fifth aspect of the present invention, the organic solvent comprises acetonitrile, γ-butyrolactone, propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate. It is an energy storage device according to the fourth aspect of the present invention, which is at least one selected from the group.

  According to a sixth aspect of the present invention, the ionic liquid comprises 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluoroborate. At least one selected from the group consisting of fluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium tosylate, 1-butyl-3-methylimidazolium tosylate It is an energy storage device according to the fourth or fifth aspect of the present invention.

  The present invention makes it possible to obtain a large-capacity energy storage device. For example, it is possible to greatly increase the charge / discharge capacity in electric double layer capacitors, redox capacitors, lithium ion electrolyte capacitors, lithium ion secondary batteries, and these application devices.

  The present invention has found that an electrolyte region existing between electrodes, which has not been used as an energy storage means until now, can be used as an energy storage means. Specifically, the electrolyte contains at least one of an aniline tetramer and an aniline tetramer derivative having a molecular weight of 366 or more and less than 500, an aniline pentamer and an aniline pentamer derivative having a molecular weight of 457 or more and less than 500. By adding a compound, efficient energy storage is possible. The present invention solves the problem of further improving the capacity of an electric double layer capacitor, a redox capacitor, a lithium ion electrolyte capacitor, a lithium ion secondary battery, and these applied devices. The present invention is described in detail below, but the present invention is not limited to the following.

  In the present invention, at least one of an aniline tetramer and an aniline tetramer derivative having a molecular weight of 366 or more and less than 500, an aniline pentamer and an aniline pentamer derivative having a molecular weight of 457 or more and less than 500, which are present in the electrolytic solution. This compound can act as an energy storage means by performing a doping / dedoping reaction, so that energy can be stably stored in an electrolyte region that has not been used for energy storage until now. For this reason, energy storage of a larger capacity is possible as compared with the energy storage device using only the conventional electrode region as the energy storage means. Details of the present invention will be further described below.

<Positive electrode, 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 the 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”.

<Electrolyte>
The electrolytic solution of the present invention is characterized in that it contains a compound that stores energy by doping / dedoping. The compound to be doped / dedoped may be dissolved in the electrolytic solution or dispersed. However, in general, it is often difficult to maintain a dispersed state for a long period of time, and the operation becomes unstable as compared with the case where it is dissolved. Therefore, it is preferable that the compound that performs the doping / dedoping reaction is dissolved. In addition, when using a fibrous electrode, a porous electrode, or the like, the compound that can be doped / dedoped should be dissolved in the electrolyte so that the active material can easily enter the gaps in the microstructure of the electrode. preferable.

  For example, a normal organic solvent can be used as the solvent of the electrolytic solution, but a solvent that can dissolve the electrolyte (ion serving as a dopant) at a high concentration and has a wide potential window is preferable. Further, instead of dissolving the electrolyte in the solvent, it is possible to use an ionic liquid (room temperature molten salt) that is a liquid that does not contain a solvent and is composed only of ions at room temperature. The ionic liquid can be used in an energy device because it can have an ionic concentration higher than that of a normal electrolytic solution, does not evaporate, and has no flammability. Furthermore, a mixture of an ionic liquid and an organic solvent is preferably used from the viewpoint of appropriately balancing a high ion concentration and a high electric conductivity.

<Energy storage device>
The energy storage device in the present invention refers to a device capable of storing energy by electrochemical reaction, chemical adsorption, physical adsorption, etc., and is an electrolytic capacitor, an electric double layer capacitor, an oxide, a pi-conjugated polymer, a pi-conjugated. Examples include molecular redox capacitors, lithium ion electrolyte capacitors, lithium ion secondary batteries, and the like.

<Compound that performs doping / dedoping reaction>
The compound that performs the doping / dedoping reaction used in the present invention is relatively easy to dissolve in the electrolytic solution, has a large amount of stored electricity due to the doping / dedoping reaction, and is charged / discharged when a voltage is applied. The following are preferable, for example, which have the effect of suppressing side reactions such as electrolysis and electrolytic polymerization that may occur.

<Compound of general formula 1>
The compound of the general formula 1 is an aniline tetramer and an aniline tetramer derivative having a molecular weight of 366 or more and less than 500. The aniline tetramer is dissolved in a solvent such as propylene carbonate and γ-butyrolactone, and can store three electrons per molecule, and therefore has a large amount of charge that can be stored per molecular weight. In addition, the aniline tetramer derivative having a substituent introduced therein can further increase the concentration in the electrolytic solution, and can further increase the amount of charge that can be stored. Although the effect varies depending on the substituent, the methyl group is remarkable in terms of improving solubility. Since the molecular weight of the aniline tetramer is 366, the molecular weight of the aniline tetramer derivative is 366 or more, and the molecular weight is preferably less than 500 from the viewpoint of the charge amount that can be stored per molecule. The aniline tetramer not only has high solubility in a solvent, but also hardly causes side reactions such as electrolysis and electrolytic polymerization that can occur when a voltage is applied to cause charge and discharge. Furthermore, although the effect varies depending on the substituent, the aniline tetramer derivative is also effective in suppressing side reactions, and the effect is more remarkable as the bulky substituent is present. In some cases, the improvement in solubility and the suppression of side reactions are both realized by the same substituent. For example, if the substituents R ₇ , R ₁₂ , R ₁₇ and R ₂₂ in the general formula 1 are all methyl groups, the solubility in organic solvents such as ionic liquid, propylene carbonate and γ-butyrolactone can be further increased. It is also possible to suppress the occurrence of side reactions such as electrolysis and electrolytic polymerization when a voltage is applied to cause charge and discharge.

＜電解液中のドープ／脱ドープ反応を行う化合物の含有量＞
電解液中のドープ／脱ドープ反応を行う化合物の含有量は、少なすぎると電解液の領域に十分なエネルギー貯蔵が行えないので、ある程度以上の含有量が必要である。効果的にエネルギー貯蔵量を増やすためには、ドープ／脱ドープ反応を行う化合物の含有量が０．５重量％以上であることが望ましい。また、電解液中のドープ／脱ドープ反応を行う化合物の含有量は多すぎると電解液の粘度が高くなるため電気伝導度が下がり、特に高速充放電においては電気抵抗が大きくなってしまう。ドープ／脱ドープ反応を行う化合物の電解液中の含有量は５０重量％以下であることが好ましい。さらにはエネルギー貯蔵量を増やす事ができ、電気抵抗が大きくなり過ぎない電解液中の最適な化合物含有量は２０重量％以上３５重量％以下が好ましい。更には寒冷地での使用や電気機器の加熱等を考慮すれば−２０℃から６０℃の範囲で２０重量％以上３５重量％以下溶解している事が好ましい。

<Content of Compound for Doping / De-Doping Reaction in Electrolyte>
If the content of the compound that performs the doping / dedoping reaction in the electrolytic solution is too small, sufficient energy storage cannot be performed in the region of the electrolytic solution. In order to effectively increase the energy storage amount, it is desirable that the content of the compound that performs the doping / dedoping reaction is 0.5% by weight or more. On the other hand, if the content of the compound that performs the doping / de-doping reaction in the electrolytic solution is too large, the viscosity of the electrolytic solution becomes high, so that the electrical conductivity is lowered, and the electrical resistance is increased particularly in high-speed charge / discharge. The content of the compound that performs the doping / dedoping reaction in the electrolytic solution is preferably 50% by weight or less. Furthermore, the energy storage amount can be increased, and the optimum compound content in the electrolytic solution in which the electric resistance does not become too large is preferably 20% by weight or more and 35% by weight or less. Furthermore, in consideration of use in cold districts, heating of electrical equipment, etc., it is preferable that the resin is dissolved in the range of −20 ° C. to 60 ° C. in the range of 20 wt% to 35 wt%.

<Compound of general formula 2>
The compound of the general formula 2 is an aniline pentamer and an aniline pentamer derivative having a molecular weight of 457 or more and less than 500. The aniline pentamer is dissolved in a solvent such as propylene carbonate and γ-butyrolactone, but the aniline pentamer derivative further introduced with a substituent can have a higher concentration in the electrolytic solution and can be charged with electricity. The amount can be increased. Further, although the effect varies depending on the substituent, the methyl group has a remarkable effect in terms of solubility. Since the molecular weight of the aniline pentamer is 457, the molecular weight of the aniline tetramer derivative is 457 or more, and the molecular weight is preferably less than 500 from the viewpoint of the charge amount that can be stored per molecule. The aniline pentamer not only has high solubility in a solvent, but also has an effect of suppressing side reactions such as electrolysis and electrolytic polymerization that can occur when a voltage is applied to cause charge and discharge. Further, although the effect varies depending on the substituent, the aniline pentamer derivative is also effective in suppressing side reactions, and the effect is more remarkable as the bulky substituent is present. In some cases, the improvement in solubility and the suppression of side reactions are both realized by the same substituent. For example, if the substituent R ₄₉ in the general formula 2 is a methyl group, the solubility in an organic solvent such as an ionic liquid, propylene carbonate, or γ-butyrolactone can be further increased, and charging / discharging is performed by applying a voltage. It is also possible to suppress the occurrence of side reactions such as electrolysis and electropolymerization when the oxidization occurs.

＜アニリン４量体およびその誘導体＞
化合物３はアニリン４量体でありプロピレンカーボネート、γ−ブチロラクトンなどの溶媒に溶解する。さらに化合物４はアニリン４量体の末端基をメチル基で置換した化合物であり、電解液中での濃度を高くすることが可能であり、蓄電可能な電荷量を大きくする事ができる。化合物５は化合物４の窒素上の水素をメチル基で置換した化合物であり、さらに電解液中での濃度を高くすることが可能であり、蓄電可能な電荷量を大きくする事ができる。また化合物３、４、５は溶媒への高い溶解性を有するだけでなく、電圧が印加されて充放電を起こす際に起こりうる、電気分解や電解重合などの副反応を抑制する効果がある。化合物４および５は副反応を抑制するという点において効果が顕著である。

<Aniline tetramer and its derivative>
Compound 3 is an aniline tetramer and is dissolved in a solvent such as propylene carbonate and γ-butyrolactone. Further, compound 4 is a compound in which the terminal group of aniline tetramer is substituted with a methyl group, and the concentration in the electrolytic solution can be increased, and the amount of charge that can be stored can be increased. Compound 5 is a compound obtained by substituting hydrogen on nitrogen of compound 4 with a methyl group, and the concentration in the electrolytic solution can be increased, and the amount of charge that can be stored can be increased. In addition, the compounds 3, 4, and 5 not only have high solubility in a solvent, but also have an effect of suppressing side reactions such as electrolysis and electrolytic polymerization that can occur when a voltage is applied to cause charge and discharge. Compounds 4 and 5 are remarkable in terms of suppressing side reactions.

＜溶解＞
ここで溶解とは、分子レベルで溶媒と均一な混合物になっていることを意味する。電解液に溶解しないで分散している状態でも、電圧の印加によって脱ドープ状態の化合物をドープ状態に変化させることも可能であり、ドープ状態の化合物を脱ドープ状態に変化させることも可能である。しかし、一般に長期に分散状態を維持することは難しい場合が多く、溶解している場合に比べて動作が不安定になるため、ドープ／脱ドープ反応を行うことが可能な化合物は溶解していることが好ましい。また、繊維状電極や多孔質電極を用いる場合には、活物質であるドープ／脱ドープ反応を行うことが可能な化合物が電極の微細構造の中に入り易いようにするために、やはり電解液に溶解させるのが好ましい。電解液中のドープ／脱ドープ反応を行う化合物は濃度が高いほどエネルギー貯蔵可能量が増大するが、一般的に粘度が高くなるため電解液の導電率が低下し、エネルギー貯蔵デバイスの充放電速度が遅くなってしまうため、適当な濃度が存在する。エネルギー貯蔵デバイスの使用目的にもよるが、１重量％以上５０重量％以下が望ましい。特には２０重量％以上３５重量％以下が好ましい。更には寒冷地での使用や電気機器の加熱等を考慮すれば−２０℃から６０℃の範囲で２０重量％以上３５重量％以下溶解している事が好ましい。

<Dissolution>
Here, dissolution means that the mixture is in a uniform mixture with the solvent at the molecular level. Even in a state where it is dispersed without being dissolved in the electrolytic solution, it is possible to change the undoped compound to the doped state by applying a voltage, and it is also possible to change the doped compound to the undoped state. . However, in general, it is often difficult to maintain a dispersed state for a long period of time, and since the operation becomes unstable compared with the case where it is dissolved, the compound capable of performing the doping / dedoping reaction is dissolved. It is preferable. Also, when using a fibrous electrode or a porous electrode, in order to make it easy for a compound capable of performing a doping / de-doping reaction, which is an active material, to enter the fine structure of the electrode, an electrolyte solution is also used. It is preferable to dissolve in. As the concentration of the compound that performs doping / de-doping reaction in the electrolytic solution increases, the energy storage capacity increases, but generally the viscosity increases, so the conductivity of the electrolytic solution decreases, and the charge / discharge rate of the energy storage device There will be a suitable concentration. Although it depends on the intended use of the energy storage device, it is preferably 1% by weight or more and 50% by weight or less. In particular, 20 wt% or more and 35 wt% or less is preferable. Furthermore, in consideration of use in cold districts, heating of electrical equipment, etc., it is preferable that the resin is dissolved in the range of −20 ° C. to 60 ° C. in the range of 20 wt% to 35 wt%.

<Organic solvent>
There is no particular limitation on the solvent used as the solvent of the electrolytic solution of the present invention, but acetonitrile, γ-butyrolactone, propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl Carbonate has a wide potential window and low viscosity, and is preferable as a solvent used in the electrolytic solution of the present invention. In particular, γ-butyrolactone and propylene carbonate are preferred from the viewpoint of high solubility of the compounds of general formulas 1 and 2. In addition, these organic solvents can form a uniform mixed solution with an ionic liquid at a very wide mixing ratio, and can produce an electrolytic solution with high withstand voltage and high electrical conductivity. Is also preferable.

<Ionic liquid>
An ionic liquid is a salt that maintains a liquid state at room temperature, and various compounds exist. As a typical example, the cation component is an imidazolium derivative, an ammonium derivative, a pyridinium derivative, a phosphonium derivative, or the like, and the anion component is an atomic group containing fluorine, such as BF ₄ ⁻ or PF ₆ ^—, or a sulfonate anion. An atomic group containing (—SO ₃ ^— ), an atomic group containing an anion component containing carboxylate (—COO ⁻ ), and the like are known. Since these ionic liquids are all composed of ionic atomic groups, they exhibit high ionic conductivity, can be made higher in ionic concentration than ordinary electrolytes, do not evaporate, and are not flammable . For this reason, it can be suitably used as a safe electrolytic solution. Examples of ionic liquids include 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-butyl- Examples thereof include 3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium tosylate, 1-butyl-3-methylimidazolium tosylate, and the like.

  Furthermore, instead of the ionic liquid alone, other supporting electrolytes such as tetraethylammonium tetrafluoroborate can be dissolved and used, or other solvents such as acetonitrile can be mixed and used. However, when a mixture of an ionic liquid and an organic solvent is used for the electrolytic solution, the solubility of the pi-conjugated polymer is lowered, so that 15% or more (volume ratio) of the electrolytic solution component is preferably an ionic liquid. .

<Mixture of ionic liquid and organic solvent>
An organic solvent is added to the ionic liquid and stirred to prepare a mixed liquid of the ionic liquid and the organic solvent. Conversely, an ionic liquid may be added to an organic solvent and stirred to produce a mixed solution. Depending on the combination and mixing ratio of the ionic liquid and the organic solvent, it may take about 3 hours at 30 ° C. to 50 ° C. to mix uniformly. Can be obtained. Depending on the application of the electrolyte, such as a capacitor electrolyte that charges and discharges at a high voltage, it is necessary to prevent moisture from entering the electrolyte. Mixing of the ionic liquid and organic solvent is performed in an atmosphere such as nitrogen gas or argon gas. It may be necessary to do this. If an organic solvent and an ionic liquid are mixed, the viscosity can generally be lowered. However, since it is necessary to keep the ionic concentration of the mixed solution high from the viewpoint of conductivity, it is not preferable to mix the organic solvent excessively. In general, it is most desirable to mix the ionic liquid and the organic solvent at a mixing ratio that maximizes the electric conductivity of the mixed liquid, but the content of the ionic liquid is within ± 50% from the mixing ratio that maximizes the electric conductivity. If the ratio is within the range (volume ratio), a mixed liquid having sufficient electric conductivity can be produced even if mixed at an arbitrary ratio, and can be used favorably for the purpose of the present invention. A mixed liquid of an ionic liquid and an organic solvent mixed at a ratio within this range can be widely used as an electrolytic solution for an electrochemical element, and there is almost no fear of impairing the response speed of the electrochemical element. Outside this range, for example, even if the ion concentration of the electrolytic solution can be made extremely high, the viscosity of the electrolytic solution increases, the electrical resistance of the energy storage device increases, and the loss of energy increases as the electrical speed increases. End up. For example, when a mixed solution prepared at a mixing ratio within the above range is used as an electrolytic solution for an electric double layer capacitor or a redox capacitor, both the charge / discharge capacity and the charge / discharge rate are higher than when a conventional electrolytic solution is used. It is possible to improve. A more desirable mixing ratio is a ratio (volume ratio) in which the content of the ionic liquid is within ± 20% from the mixing ratio at which the electric conductivity is maximized, and more desirably, the electric conductivity is at the maximum. From the mixing ratio, the content of the ionic liquid is a ratio (volume ratio) within a range of ± 10%. A preferable mixing ratio as described above is generally in the range of ionic liquid: organic solvent = 1: 5 to 5: 1 (volume ratio).

<Inhibition of free diffusion of electrolyte>
The energy storage device of the present invention has two or more electrodes and stores energy by providing a potential difference between the two electrodes. However, the storage energy due to the doping / dedoping of the compound that can be doped / dedoped in the electrolytic solution cannot be taken out as energy when the compound to be doped / dedoped is separated from the vicinity of the electrode by free diffusion after charging. An electrolyte free diffusion suppressing means for preventing the charge in the liquid from being uniform is required. For example, by using a porous material such as activated carbon or a fibrous material such as carbon fiber as the electrode, it is possible to suppress the free diffusion of the electrolyte solution in the vicinity of the electrode to some extent.

<Separator>
The energy storage device of the present invention has one or more pairs of electrodes, and stores energy by providing a potential difference between the electrodes. When there is electronic conduction between both electrodes in the energy storage device, a short circuit occurs and power storage efficiency decreases. Therefore, in order to prevent contact between the electrodes, a separator is generally interposed between the two electrodes. Since the separator that exists so as to be in contact with the electrode has the effect of suppressing free diffusion of the electrolyte near the electrode as it is, it is preferably used for the energy storage device of the present invention.

<Dope state>
The doped state of a compound is that the compound itself is positively or negatively charged by oxidation or reduction, and an anion or cation exists in the vicinity of the pi-conjugated compound so as to cancel the charge, and becomes neutral as a whole. Is stable.

The anion and cation are supplied from the anion and cation contained in the electrolytic solution in the doping / dedoping reaction in the electrolytic solution. Examples of anions contained in the electrolytic solution include BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , organic sulfonate ions, sulfate ions, (CF ₃ SO ₂ ) ₂ N ^{− and the} like. As the cation, various quaternary ammonium cations, pyridinium cations, imidazolium cations, Li ⁺ , Na ^{+ and the} like can be used, but are not limited thereto.

Examples of the dopant of the compound in the doped state include BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , iodine, organic sulfonate ion, sulfate ion, (CF ₃ SO ₂ ) ₂ N ⁻ , various quaternary ammonium cations, and various pyridinium cations. Various imidazolium cations, Li ⁺ , Na ^{+ and the} like can be used, and are not particularly limited, but those that can be more doped with respect to the compound to be used are preferable from the viewpoint of increasing the capacity of the energy storage device. It is desirable that the ions (dopants) contained in the liquid are also common.

  In general, a compound can be referred to as a doped state (doped state) as long as it is in a state where a dopant is doped even a little. However, the term “doped” in the present invention refers to the maximum within the range in which electrochemically stable doping / undoping can be repeated from the viewpoint of effectively increasing the charge / discharge charge amount of the energy storage device. It is preferable to be in a state in which near doping is performed, and here, a state where 100 to 50% of dopant is introduced as compared with the amount of dopant that can be introduced to the maximum within a range where stable doping / undoping can be repeated. Is called the “doped” state.

<Dedoped state>
The undoped state of a compound refers to a compound that is not oxidized or reduced and is electrically neutral.

<Charge / discharge charge>
The amount of charge that can be repeatedly charged / discharged by an individual electrode or energy storage device is referred to as chargeable / dischargeable charge amount. In the conventional energy storage device in which the charge is not accumulated by the redox of the compound in the electrolyte as in the present invention, the chargeable / dischargeable charge amount of the energy storage device is the chargeable / dischargeable charge of the two electrodes. It is defined by the chargeable / dischargeable charge amount of the electrode with the smaller amount.

<Supplementary charge amount on the negative electrode side is supplemented by a compound that performs a doping / de-doping reaction in the electrolytic solution>
For example, when the chargeable / dischargeable charge amounts of the positive electrode and the negative electrode are 100 and 50, respectively, the chargeable / dischargeable charge amount of the entire energy storage device is 50. Various methods are conceivable for improving the energy density of the energy storage device. For example, it is extremely effective to increase the chargeable / dischargeable charge amount as in the present invention. In order to effectively improve the chargeable / dischargeable charge amount of the energy storage device, the capacity on the electrode side where the chargeable / dischargeable charge quantity is small is preferentially increased so that the capacity of both electrodes is the same. Increase it. For example, in the above example, if the capacity on the negative electrode side is increased by 50 to 100, the chargeable / dischargeable charge amount of the entire energy storage device can be set to 100. In the above example, if the capacity on the negative electrode side is increased to 130 and the capacity on the positive electrode side is increased to 30 to 130, the chargeable / dischargeable charge amount of the entire energy storage device can be set to 130. These have most effectively increased the chargeable / dischargeable charge amount of the entire energy storage device.

  The increase in the chargeable / dischargeable charge amount of such an efficient energy storage device can be achieved by changing the ratio of the compound added to the electrolytic solution, the ratio of the dedope state, and the compound type (p-type, n-type, pn-type). It can be realized by selecting well. For example, in the above case, it is possible to effectively increase the chargeable / dischargeable charge amount of the energy storage device by supplementing the chargeable / dischargeable charge amount of the negative electrode. It is. For that purpose, a compound capable of doping / de-doping that compensates for the amount of electricity stored on the negative electrode side and does not increase the amount of electricity stored on the positive electrode side, that is, n-doped n-type compound, de-doped p-type compound, It is desirable that many doped pn-type compounds and n-doped pn-type compounds are contained in the electrolyte solution (50 mol% or more with respect to the compounds capable of performing all doping / dedoping reactions). .

<Supplementary charge amount on the positive electrode side is supplemented by a compound that performs a doping / de-doping reaction in the electrolyte>
For example, conversely to the above, when the chargeable / dischargeable charge amount of the energy storage device can be effectively increased by supplementing the chargeable / dischargeable charge amount of the positive electrode, the charged amount on the positive electrode side may be preferentially increased. is important. To that end, a compound capable of doping / dedoping reaction that compensates for the amount of electricity stored on the positive electrode side and does not increase the amount of electricity stored on the negative electrode side, that is, a p-doped p-type compound, a dedoped n-type compound, Many undoped pn-type compounds and p-doped pn-type compounds are contained in the electrolyte solution (50 mol% or more with respect to the compounds capable of performing all-doping / de-doping reactions). Is desirable.

<Supplementary charge amount on both the positive electrode side and the negative electrode side is compensated by a compound that performs doping / de-doping reaction in the electrolyte solution>
In order to increase the chargeable / dischargeable charge amount of the energy storage device by the compound that performs the doping / dedoping reaction in the electrolyte, it is necessary to increase both the chargeable / dischargeable charge amount on the positive electrode side and the negative electrode side in a balanced manner. It can be effective. In such a case, a compound capable of performing a doping / dedoping reaction in a state in which the charged amount on the negative electrode side is supplemented and the charged amount on the positive electrode side is not increased (that is, an n-doped n-type compound, a dedoped p-type compound). Compound, dedoped pn-type compound and n-doped pn-type compound) or a compound capable of doping / de-doping reaction that compensates for the amount of charge on the positive electrode side and does not increase the amount of charge on the negative electrode side (ie It is important that the p-doped p-type compound, the dedope n-type compound, the dedope pn-type compound, and the p-doped pn-type compound) are biased and not contained in the electrolyte. is there.

<P-dope>
This is a doping (p-dope) in which the compound itself is oxidized and positively charged, and the anion comes close to the compound and neutralizes and stabilizes as a whole so as to cancel the charge. A compound that causes this type of doping / undoping is called a p-type compound. Examples of the p-type compound include polyaniline and derivatives thereof, polypyrrole, polythiophene, N, N′-diphenylbenzidine and the like.

<N-dope>
This is a doping (n-dope) in which the compound itself is negatively charged upon reduction, and the cation comes close to the compound so as to cancel the charge and becomes neutral as a whole and stabilized. A compound that causes this type of doping / undoping is called an n-type compound.

<Pn both dope>
Both the p-doped and the n-doped are collectively referred to as pn-doped. A compound capable of both pn doping is called a pn-type compound. Examples of pn-type compounds include poly-3- (4-fluorophenyl) thiophene, poly-3- (4-trifluoromethylphenyl) thiophene, poly-3- (2,4-difluorophenyl) thiophene. Can do.

<The process of mixing the compound which performs dope / dedope reaction in electrolyte solution>
As a method of adding a compound that performs a doping / de-doping reaction in the electrolytic solution, a method of synthesizing (polymerizing) the compound in the electrolytic solution may be considered, but by simply mixing the compound into the electrolytic solution. Fully realized. Many compounds that dope / dedope reactions (pi-conjugated polymers, pi-conjugated molecules) are commercially available products that are relatively inexpensive, and the step of mixing them with the electrolyte is a compound that performs the dope / dedope reaction. Is very convenient as a method for producing an electrolyte solution containing benzene, which is convenient from the viewpoint of production cost. Here, the compound to be mixed with the electrolytic solution may be more preferably dissolved in the electrolytic solution.

<Method of adding compound to electrolyte solution for doping / de-doping reaction>
When the compound that performs the doping / de-doping reaction is mixed with the electrolyte, the doping / doping state of the compound that performs the total doping / de-doping reaction according to the ratio of the charge / discharge charge amount of the positive electrode and the negative electrode By selecting the ratio of the compound that performs the dedoping reaction and the type of p-type / n-type / pn-type, it is possible to effectively improve the charge / discharge charge amount of the entire energy storage device.

  The inventors of the present invention do not need to perform doping after mixing the compound with the electrolytic solution when the compound of the doped state is desired to be present in the electrolytic solution. I found that it was only necessary to mix. In addition, the inventors of the present invention can mix a compound containing a dopant different from the dopant contained in the electrolytic solution into the electrolytic solution as long as the compound is in a doped state. It has been found that there is no problem as long as the dopant contained in advance does not adversely affect the subsequent doping / dedoping reaction in the electrolytic solution. In addition, when it is desired to have a dedope compound in the electrolyte solution, it is not necessary to perform the dedope treatment again after mixing the compound with the electrolyte solution, and the dedope compound is mixed with the electrolyte solution in advance. I just found out that it was good. Therefore, as explained above, if the type of compound (p-type, n-type, pn-type) desired to be present in the electrolyte and the doped / undoped state are known, these compounds can be used in the desired doped / undoped state. Since the energy storage amount of the energy storage device can be easily increased simply by mixing with the electrolyte, the method for improving the capacity of the energy storage device according to the present invention is extremely useful as a method for producing a high-performance energy storage device. Here, the compound to be mixed with the electrolytic solution may be more preferably dissolved in the electrolytic solution.

  In the following, “when the compound that performs the doping / de-doping reaction is mixed with the electrolyte, the state of the doped state with respect to the compound that performs the total doping / de-doping reaction depends on the charge / discharge charge amount ratio of the positive electrode and the negative electrode. Three examples are shown in which the charge / discharge charge amount of the entire energy storage device is improved by selecting the ratio of the compound that performs the doping / de-doping reaction and the type of p-type / n-type / pn-type.

<Example 1 Improvement of chargeable / dischargeable charge amount of electric double layer capacitor>
An electric double layer capacitor is an energy storage device that stores electric charges in an electric double layer generated at an electrode interface with an electrolyte. Since the capacitance of the electric double layer capacitor is proportional to the electrode area, activated carbon having a high specific surface area is used for the electrode. There is no distinction between a positive electrode and a negative electrode, and it can be seen that the capacities of the two electrodes are substantially the same. During charging, an oxidation reaction occurs on one electrode side. If a p-doped or n-dedoping reaction of a compound in the electrolytic solution occurs in a region near the electrode of the electrolytic solution at this time, the oxidizing reaction occurs. It is possible to increase the amount of electricity stored by charging. On the other hand, since the reduction reaction occurs during charging on the other electrode side, if an n-doped or p-dedoping reaction of the compound in the electrolytic solution occurs in the region near the electrode of the electrolytic solution at this time, It is possible to increase the charged amount of charge due to the reduction reaction.

  Therefore, for example, by equimolarly mixing p-doped and dedope-type p-type compounds in the electrolyte, the capacity of both electrodes can be increased to the same extent, and the electric double layer capacitor as a whole can be effectively charged and discharged. The amount can be increased, that is, the effective energy density can be increased.

  Similarly, the same applies to the case where an n-type compound in an n-doped state and an undoped state are mixed in the electrolyte solution in an equimolar amount. The p-type or n-type compound to be mixed here is not necessarily one kind, and two or more kinds may be mixed together in the charge liquid. In these two cases, the charge / discharge voltage due to the redox of the electrolyte is generally not so high. The potential at which one of p-doped / p-dedope or n-doped / n-dedope occurs is generally not so different even if the type of compound is changed, and it is p-type or n-type even if two or more types of compounds are used. When only one of these is used, the charge / discharge voltage is up to about 1.5V.

  Even when an equimolar mixture of a p-type compound in a dedope state and an n-type compound in a dedope state is mixed in the electrolytic solution, the electric double layer capacitor as a whole can effectively increase the chargeable / dischargeable amount, that is, effectively Energy density can be increased. However, in this case, the charge / discharge voltage can be increased to about 3 V, which is more preferable from the viewpoint of improving the energy density. The potential at which p-doping / p-de-doping occurs is generally different from the potential at which n-doping / n-de-doping occurs. When both p-type and n-type are used for charging and discharging, p-type, n-type In many cases, a higher charge / discharge voltage can be obtained than when only one of the molds is used. Here, the p-type or n-type compound to be mixed is not necessarily one kind, and two or more kinds may be mixed together in the charge liquid. In this case, only one of the p-type and n-type compounds can contribute to charging / discharging in the vicinity of one electrode, and the other compound basically does not participate in charging / discharging.

  Furthermore, the energy density of the electric double layer capacitor can be effectively improved even if a pn-type compound in the undoped state is mixed with the electrolytic solution. Also in this case, the charge / discharge voltage can be increased to about 3 V, which is preferable from the viewpoint of improving the energy density. Furthermore, since all the compounds present in the vicinity of the electrodes can contribute to charging / discharging on each electrode side, even if the compounds are mixed in an equimolar amount, more charges can be charged / discharged than in the above case, which is more preferable. Here, the pn-type compound to be mixed is not necessarily one kind, and two or more kinds may be mixed together in the charge liquid.

<Example 2 Improvement of chargeable / dischargeable charge amount of redox capacitor>
It is an energy storage device that stores electric charges by utilizing a redox reaction of an active material of an electrode. For example, a conductive polymer redox capacitor using poly-3- (4-fluorophenyl) thiophene, which is a pn-type pi-conjugated polymer, for both electrodes. Such a conductive polymer redox capacitor can also be considered to have basically the same capacity of the two electrodes. During charging, an oxidation reaction occurs on one electrode side. If a p-doped or n-dedoping reaction of a compound in the electrolytic solution occurs in a region near the electrode of the electrolytic solution at this time, the oxidizing reaction occurs. It is possible to increase the amount of electricity stored by charging. On the other hand, since the reduction reaction occurs during charging on the other electrode side, if an n-doped or p-dedoping reaction of the compound in the electrolytic solution occurs in the region near the electrode of the electrolytic solution at this time, It is possible to increase the charged amount of charge due to the reduction reaction. Since the basic idea is the same, the energy density can be improved by the same method as the above electric double layer capacitor. When there is a difference in the chargeable / dischargeable charge amount of each electrode, the doped state of the compound mixed in the electrolyte solution so that the redox capacity of the electrolyte solution is greatly expressed on the electrode side with the smaller chargeable / dischargeable charge amount If the ratio of the dedope state and the type (p-type, n-type, pn-type) of the conjugated compound are selected, the effective energy density of the capacitor can be improved.

<Example 3 Improvement of chargeable / dischargeable charge amount of lithium ion electrolyte capacitor>
Lithium ion electrolyte type capacitors use an electrolyte containing lithium ions, the positive electrode uses an electric double layer at the interface between the activated carbon electrode and the electrolyte to accumulate charge, and the negative electrode intercalates lithium ions into graphite. Uses to accumulate charges. Since the potential difference between the positive electrode and the negative electrode is large, charging / discharging at a high voltage is possible. However, since the capacity of the positive electrode is smaller than that of the negative electrode, it is desirable to improve the energy density by increasing the charge amount that can be charged and discharged on the positive electrode side. Accordingly, at least one of the undoped p-type compound, the doped n-type compound, and the undoped pn-type compound is mixed with the electrolytic solution, and conversely, the doped p-type compound and the undoped n-type compound are mixed. It is possible to improve the energy density of the lithium ion electrolyte type capacitor if the pn type compound in the p-doped state is not mixed in the electrolytic solution or if a small amount is mixed with the above three. From the viewpoint of increasing the discharge voltage, it is preferable to mix a dedoped p-type compound and / or a dedoped pn-type compound into the electrolyte rather than a doped n-type compound.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples, In the range which does not change the summary, it can change suitably.

Example 1
<Synthesis of aniline tetramer>
Diphenylamine (Wako Pure Chemical Industries, Ltd.) (1.69 g, 0.01 mol) and 4,4-diaminodiphenylamine sulfate (Wako Pure Chemical Industries, Ltd.) were placed in a 300 ml round bottom flask in a nitrogen atmosphere. (3.50 g, 0.01 mol) was added, and the system was purged with nitrogen. Then, 100 ml of dimethylformamide, 20 ml of distilled water, and 15 ml of concentrated hydrochloric acid were added and stirred well. Subsequently, the reaction solution was cooled to 0 ° C., and an ammonium persulfate solution (2.28 g / 1M hydrochloric acid 50 ml) was added dropwise little by little. After completion of the dropwise addition, the reaction solution was added to 700 ml of distilled water after stirring for 1 hour at 0 ° C. The reaction solution was filtered, washed with 1M hydrochloric acid (50 ml × 3), and the resulting filtrate was vacuum dried at 40 ° C. for 3 hours to obtain 2.56 g of black crystals. Subsequently, the obtained black powder was stirred in a 25% aqueous ammonia solution (5.0 ml) for 12 hours, filtered and vacuum dried at 40 ° C. for 3 hours to recover 2.42 g of black powder. Further, the obtained black powder was stirred in hydrazine hydride (10 ml) for 12 hours, filtered, and then vacuum dried at 40 ° C. for 3 hours to obtain 2.35 g of black powder. Subsequently, the black powder was dissolved in ethanol at 50 ° C., and the insoluble matter was separated by filtration. Subsequently, ethanol was distilled off under reduced pressure, and the obtained solid was dissolved in chloroform to recover an insoluble matter, followed by vacuum drying for 5 hours to obtain 0.35 g of a black powder. (Yield 10%)

^１Ｈ ＮＭＲ（ＤＭＳＯ、３００ＭＨｚ、Ｖａｒｉａｎ ＵＮＩＴＹ−３００）δ４．６２（ｓ、２Ｈ）、６．５２（ｄ、２Ｈ）、６．７５（ｔ、１Ｈ）、６．７８−７．３１（ｍ、１５Ｈ）、７．４１（ｓ、１Ｈ）、７．６８（ｓ、１Ｈ）

＜溶解度の検討＞
有機溶媒に対するアニリン４量体（式４）溶解度を検討した。有機溶媒としては、電池に使用されるプロピレンカーボネート、γ―ブチロラクトン、ジエチルカーボネートを用いた。各有機溶媒をビーカーに入れ、アニリン４量体を室温で添加し、スターラーで３０分間攪拌した。アニリン４量体はγ-ブチロラクトンに対して最も良く溶解し０．２Ｍ以上溶解した。

¹ H NMR (DMSO, 300 MHz, Varian UNITY-300) δ 4.62 (s, 2H), 6.52 (d, 2H), 6.75 (t, 1H), 6.78-7.31 (m, 15H), 7.41 (s, 1H), 7.68 (s, 1H)

<Examination of solubility>
The solubility of aniline tetramer (formula 4) in organic solvents was examined. As the organic solvent, propylene carbonate, γ-butyrolactone, and diethyl carbonate used for batteries were used. Each organic solvent was put into a beaker, aniline tetramer was added at room temperature, and the mixture was stirred with a stirrer for 30 minutes. The aniline tetramer dissolved best in γ-butyrolactone and dissolved more than 0.2M.

<Adjustment of electrolyte>
0.110 g (0.1 M) of aniline tetramer (formula 4) is added to 3.0 cc of a solution of tetraethylammonium tetrafluoroborate in γ-butyrolactone (concentration 1 M), and the mixture is stirred at room temperature with a stirrer for 30 minutes. The solution was used for cyclic voltammetry measurement (CV measurement), charge / discharge measurement, and residual rate measurement. All aniline tetramers were dissolved.

<Cyclic voltammetry measurement (CV measurement)>
The electrolytic solution in which the aniline tetramer was dissolved was subjected to CV measurement by Solartron (trade name Solartron 1400). A platinum disk having a diameter of 1.6 mm was used as the working electrode, and a platinum wire having a diameter of 0.5 mm was immersed in an electrolyte of about 1 cm as the counter electrode. The reference electrode used was a product of BAS Co., Ltd. (trade name: RE-5 reference electrode (Ag / Ag ⁺ , +490 mV with respect to the standard hydrogen electrode)). The potential sweep of the CV measurement was started from a natural potential, and was initially performed for 3 cycles in the range of +1.0 to −1.0 V with respect to the reference electrode in the + direction. The above CV measurements were performed in a glove box that was completely replaced with high-purity argon in order to eliminate the influence of moisture in the atmosphere. The obtained cyclic voltammogram has three pairs of upper and lower peaks (the positions of the upper peaks are +0.05 V, +0.45 V, +1.50 V with respect to the reference electrode, respectively), and the aniline tetramer has 3 It was found to repeat the reversible redox of the stage. That is, the aniline tetramer molecule can store three electrons. Also, the cyclic voltammogram has almost the same shape in all three cycles, and it can be seen that the three-stage redox reaction is relatively stable.

<Charge / discharge measurement>
Charge / discharge measurement was performed using the above electrolytic solution in which the tetramer for aniline was dissolved. The working electrode and the counter electrode were platinum plates having a width of 1 cm and a length of 4 cm, and both were immersed in the electrolytic solution prepared above for 1 cm. The reference electrode used was a product of BAS Co., Ltd. (trade name: RE-5 reference electrode (Ag / Ag ⁺ , +490 mV with respect to the standard hydrogen electrode)). The charge / discharge measurement was performed at a constant current of 1.6 mA. Measurement was started from the natural potential of the working electrode, and charging and discharging were repeated for 5 cycles when the potential of the working electrode was in the range of +1.0 to -1.0 V with respect to the reference electrode. The above charge and discharge measurements were performed in a glove box that was completely replaced with high-purity argon in order to eliminate the influence of moisture in the atmosphere. When the discharge charge (C) at the fifth cycle was calculated from the obtained data, it was 0.13 C.

<Analysis of electrolytic solution after voltage application (measurement of residual rate of aniline tetramer)>
It was examined how stable the aniline tetramer was when voltage was continuously applied. The working electrode and the counter electrode were platinum plates having a width of 1 cm and a length of 4 cm, and both were immersed in 3 cc of the electrolytic solution prepared above. The reference electrode used was a product of BAS Co., Ltd. (trade name: RE-5 reference electrode (Ag / Ag ⁺ , +490 mV with respect to the standard hydrogen electrode)). While the electrolyte was stirred with a stirrer, the potential of the working electrode was maintained at the three upper peak potentials in the cyclic voltammogram (+0.05 V, +0.45 V, +1.50 V with respect to the reference electrode), and 174 C. It was left at room temperature until a charge (corresponding to a charge of 6 electrons per molecule of aniline tetramer) flows. If the aniline tetramer is completely stable against voltage application, the charge of 174C only flows to the counter electrode due to the shuttle effect of the aniline tetramer, and the decomposition and polymerization of the aniline tetramer do not occur. The residual rate of the aniline tetramer is 100%. If side reactions such as decomposition and polymerization occur preferentially, the aniline tetramer is considered to disappear almost completely due to the charge of 174C. After flowing a 174 C charge with the working electrode kept at each of the above peak potentials, each electrolyte was analyzed to determine the residual rate of the aniline tetramer. In the case of 0.05 V (potential at which electricity storage for one electron occurs), the residual rate of aniline tetramer was 32%, and at 0.45 V (potential at which electricity storage for two electrons occurs), the residual rate was 17%. . The fact that the substance before the voltage application remains after the voltage application is important in terms of stable operability of the energy storage device.

(Comparative Example 1)
<Examination of solubility>
The solubility of N, N′-diphenylbenzidine (manufactured by Aldrich) in an organic solvent was examined. As the organic solvent, propylene carbonate, γ-butyrolactone, and diethyl carbonate used for batteries were used. Each organic solvent was put into a beaker, N, N′-diphenylbenzidine was added at room temperature, and the mixture was stirred with a stirrer for 30 minutes. N, N′-diphenylbenzidine was best dissolved in γ-butyrolactone and was found to be 0.03M or more, but it was impossible to dissolve 0.05M.

<Adjustment of electrolyte>
0.025 g (0.25 M) of N, N′-diphenylbenzidine was added to 3.0 cc of a γ-butyrolactone solution (concentration 1 M) of tetraethylammonium tetrafluoroborate and stirred with a stirrer at room temperature for 30 minutes. The solution was used for click voltammetry measurement (CV measurement), charge / discharge measurement, and residual rate measurement. All N, N′-diphenylbenzidine was dissolved.
<Cyclic voltammetry measurement (CV measurement)
CV measurement was performed on the electrolyte solution in which N, N′-diphenylbenzidine was dissolved. A platinum disk having a diameter of 1.6 mm was used as the working electrode, and a platinum wire having a diameter of 0.5 mm was immersed in an electrolyte of about 1 cm as the counter electrode. As a reference electrode, a RE-5 reference electrode (Ag / Ag ⁺ , +490 mV with respect to a standard hydrogen electrode) manufactured by BAS was used. The potential sweep of the CV measurement was started from a natural potential, and was initially performed for 3 cycles in the range of +0.6 to -1.0 V with respect to the reference electrode in the + direction. The above CV measurements were performed in a glove box that was completely replaced with high-purity argon in order to eliminate the influence of moisture in the atmosphere.
The obtained cyclic voltammogram has two pairs of upper and lower peaks (the positions of the upper peaks are +0.37 V and +0.65 V with respect to the reference electrode, respectively), and N, N′-diphenylbenzidine has two stages. It was found that the reversible redox of was repeated. That is, the N, N′-diphenylbenzidine molecule can store two electrons. In addition, the cyclic voltammogram has almost the same shape in all three cycles, and it can be seen that the two-stage redox reaction is relatively stable.

<Charge / discharge measurement>
Charge / discharge measurement was performed using the above electrolytic solution in which N, N′-diphenylbenzidine was dissolved. The working electrode and the counter electrode were platinum plates having a width of 1 cm and a length of 4 cm, and both were immersed in the electrolytic solution prepared above for 1 cm. As a reference electrode, a RE-5 reference electrode (Ag / Ag ⁺ , +490 mV with respect to a standard hydrogen electrode) manufactured by BAS was used. The charge / discharge measurement was performed at a constant current of 1.6 mA. Measurement was started from the natural potential of the working electrode, and charging and discharging were repeated for 5 cycles in the range where the potential of the working electrode was +0.6 to −1.0 V with respect to the reference electrode. The above charge and discharge measurements were performed in a glove box that was completely replaced with high-purity argon in order to eliminate the influence of moisture in the atmosphere. When the discharge charge (C) at the fifth cycle was calculated from the obtained data, it was 5.1 × 10 ⁻³ C.

<Analysis of electrolyte solution after voltage application (N, N′-diphenylbenzidine residual ratio measurement)>
It was examined how stable N, N′-diphenylbenzidine was when voltage was continuously applied. The working electrode and the counter electrode were platinum plates having a width of 1 cm and a length of 4 cm, and both were immersed in 3 cc of the electrolytic solution prepared above. As a reference electrode, a RE-5 reference electrode (Ag / Ag ⁺ , +490 mV with respect to a standard hydrogen electrode) manufactured by BAS was used. While stirring the electrolyte solution with a stirrer, the electric potential of the working electrode was maintained at the two upper peak potentials in the cyclic voltammogram (+0.37 V, +0.65 V with respect to the reference electrode), and a charge of 29.0 C ( N, N′-diphenylbenzidine was allowed to stand at room temperature until it flowed (corresponding to a charge of 4 electrons). If N, N'-diphenylbenzidine is completely stable against voltage application, the charge of 29.0C only flows to the counter electrode due to the shuttle effect of N, N'-diphenylbenzidine, and N, N'- Diphenylbenzidine is not decomposed or polymerized, and the residual rate of N, N′-diphenylbenzidine is 100%. If side reactions such as decomposition and polymerization occur preferentially, it is considered that N, N′-diphenylbenzidine is almost completely extinguished by the charge of 29.0C. After flowing a charge of 29.0 C with the working electrode kept at each peak potential, each electrolyte was analyzed to determine the residual ratio of N, N′-diphenylbenzidine. In both cases of 0.37 V (potential at which electricity storage for one electron occurs) and 0.45 V (potential at which electricity storage for two electrons occur), the residual rate was 0%. The substance before the voltage application does not remain at all after the voltage application, and there remains a problem in terms of stable operability of the energy storage device.

  As is clear from the results of Example 1 and Comparative Example 1, the energy storage device using aniline tetramer has a larger stored charge per molecule than the energy storage device using N, N′-diphenylbenzidine, It is stable against voltage application.

Claims (6)

An energy storage device including a positive electrode, a negative electrode, and an electrolytic solution, the compound represented by the following general formula 1 having a molecular weight of 366 or more and less than 500 charged and discharged by doping / dedoping reaction in the electrolytic solution is 0.5% by weight. Energy storage device containing 50% by weight or less.

(Wherein R ₁ , R ₂ , R ₇ , R ₁₂ , R ₁₇ are the same or different substituents, and an amino group, an acyl group, a cyano group, an ester group, an amide group, an alkoxycarbonyl group, and a carbon number of 1 to An alkyl group in the range of 5, an alkoxy group in the range of 1 to 2 carbon atoms, a fluoroalkyl group in the range of 1 to 2 carbon atoms, a fluorine atom, a hydrogen atom, or a methyl group And R _{3 to} R ₆ , R _{8 to} R ₁₁ , R _{13 to} R ₁₆ , and R _{18 to} R ₂₂ are the same or different substituents, and are a nitro group , Amino group, acyl group, cyano group, ester group, amide group, sulfonyl ester group, alkyl group having 1 to 5 carbon atoms, alkoxy group having 1 to 2 carbon atoms, carbon number Is in the range of 1-2 Fluoroalkyl group, fluorine atom, hydrogen atom, or nitro group, amino group, acyl group, cyano group, ester group, amide group, sulfonyl ester group, methyl group, methoxy group, fluorine atom, hydrogen atom Either) An energy storage device including a positive electrode, a negative electrode, and an electrolytic solution, and 0.5 weight by weight of a compound represented by the following general formula 2 having a molecular weight of 457 or more and less than 500, which is charged / discharged by doping / dedoping reaction in the electrolytic solution. An energy storage device containing at least 50% by weight.

(Wherein R ₂₃ , R ₂₄ , R ₂₉ , R ₃₄ , R ₃₉ , R ₄₄ are the same or different substituents and are an amino group, acyl group, cyano group, ester group, amide group, alkoxycarbonyl group, carbon number Is an alkyl group, a methoxy group, a fluorine atom or a hydrogen atom within the range of 1 to 3. R _{25 to} R ₂₈ , R _{30 to} R ₃₃ , R _{35 to} R ₃₈ , R _{40 to} R ₄₃ , R _{45 to} R ₄₉ are the same or different substituents, and are a nitro group, an amino group, an acyl group, a cyano group, an ester group, an amide group, an alkyl group having 1 to 3 carbon atoms, a methoxy group, It is either a fluorine atom or a hydrogen atom.) 2. The energy storage device according to claim 1, wherein at least one compound selected from the group consisting of the following chemical formulas 3 to 5 charged / discharged by a doping / dedoping reaction contained in the electrolyte solution is given as follows: An energy storage device containing 5% by weight or more and 50% by weight or less.

  The energy storage device according to any one of claims 1 to 3, wherein a solvent of the electrolytic solution is any one of an organic solvent, an ionic liquid, or a mixture of an organic solvent and an ionic liquid.   The organic solvent is at least one selected from the group consisting of acetonitrile, γ-butyrolactone, propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate. The energy storage device according to claim 4.   The ionic liquid is 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3- The at least one selected from the group consisting of methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium tosylate, and 1-butyl-3-methylimidazolium tosylate. Energy storage devices.