JP5275011B2 - Electrolyte and electrochemical device using quaternary ammonium salt electrolyte - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical element which is stably usable even at low temperature and has superior long-period stability. <P>SOLUTION: An electrolytic solution for the electrochemical element contains an electrolyte (B) containing a compound (A) expressed by some specific chemical formula (1) and a water-unmixed solvent (H), the water-unmixed solvent (H) containing at least one sulfolane derivative (S) selected from a group of sulfolane, 3-methyl sulfolane and 2,4-dimethyl sulfolane, and a benzene derivative (G) expressed by some specific chemical formula (2). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to an electrolytic solution for an electrochemical device using a quaternary ammonium salt electrolyte.

An electrochemical element stores electrochemical energy inside the element. Specifically, the electrochemical element stores a battery for taking out chemical energy stored inside the element as electric energy, and a static electricity stored inside the element. A capacitor for taking out electric energy as electric energy to the outside, a dye-sensitized solar cell, and the like.
Conventionally, the electrolyte of the capacitor BF ₄ salt of tetraethyl ammonium, BF ₄ salt of triethyl methyl ammonium or 1-ethyl-3-BF ₄ salt of methyl imidazolium have been used as an electrolyte. Particularly in new application fields such as hybrid electric vehicles that are used under severe conditions and with large currents, there is a demand for electrochemical elements that can be used stably even at low temperatures and have excellent long-term stability. There is an urgent need to develop an electrolytic solution that can be used in a low temperature environment and has a high withstand voltage (wide potential window).
Under such circumstances, an electrolytic solution having a high withstand voltage has been developed by using a solvent having high decomposition resistance such as sulfolane (for example, Patent Documents 1 and 2).
JP 08-306591 A JP 2005-260031 A

However, when the non-aqueous electrolyte described in Patent Documents 1 and 2 is used, the withstand voltage is improved, but it cannot be used because electrolyte deposition or solidification of the electrolyte occurs in a low temperature environment of −30 ° C. or lower. In some cases, fatal defects may occur as electrolytes for electrochemical devices, such as a decrease in electrical conductivity due to a rapid increase in viscosity even without solidification.
That is, an object of the present invention is to provide an electrochemical device excellent in long-term stability that can be used stably even in a low temperature environment while maintaining high voltage resistance.

［式中、ｍ及びｎは３〜７を示し同じでも異なっていてもよい。Ｘ⁻は第一原理分子軌道計算によるＨＯＭＯエネルギーが、−０．６０〜−０．２０ａ.u.であるアニオンである。］

［式中、Ｒ^１は、ハロゲン原子、又は炭素数１〜７である有機基（ｇ）、Ｒ^２及びＲ^３は水素原子、ハロゲン原子、又は炭素数１〜７である有機基（ｇ）である。Ｒ^１、Ｒ^２及びＲ^３は同じでも異なっていてもよく、かつ少なくとも１つは炭素数１〜７であるパーフルオロアルキル基である。］
；及び該電解液を用いる電気化学素子である。 As a result of intensive studies to solve the above problems, the present inventors have reached the present invention. That is, the present invention is an electrolyte solution containing an electrolyte (B) containing the compound (A) represented by the general formula (1) and a non-aqueous mixed solvent (H), which is a non-aqueous mixture. The solvent (H) is at least one sulfolane derivative (S) selected from the group consisting of sulfolane, 3-methylsulfolane and 2,4-dimethylsulfolane, and the molecular weight represented by the general formula (2 ′ ) is 400 or less. An electrolytic solution for an electrochemical element, comprising a benzene derivative (G 1 ) that is

[Wherein, m and n represent 3 to 7 and may be the same or different. X ⁻ is an anion having a HOMO energy of −0.60 to −0.20 a.u. ]

[Wherein, R ¹ is a halogen atom or an organic group (g) having 1 to 7 carbon atoms, and R ² and R ³ are a hydrogen atom, a halogen atom, or an organic group (g) having 1 to 7 carbon atoms. It is. R ^1, R ² and R ³ rather good be the same or different, and at least one is a perfluoroalkyl group from 1 to 7 carbon atoms. ]
And an electrochemical element using the electrolytic solution.

The electrochemical element using the electrolytic solution for an electrochemical element of the present invention can be used in a low temperature environment while maintaining high voltage resistance, and is excellent in long-term stability.

The present invention is described in detail below.
The electrolyte (B) will be described.
The electrolyte (B) contains the compound (A) represented by the general formula (1).
In the general formula (1), m and n are 3 to 7, and may be the same or different. Preferably it is 3-6, More preferably, it is 4-5.
When m and n are 2 or less, the chemical stability of the electrolyte (B) is lowered, and the durability of the electrolytic solution is lowered.
When m and n are 8 or more, the molecular weight of the electrolyte (B) increases, and the conductivity of the electrolytic solution decreases. In addition, the solubility of the electrolytic solution in the solvent is lowered, and the low temperature performance is lowered, for example, it is precipitated at a low temperature.

The cation of compound (A) is a spiro quaternary ammonium cation. A salt having the spiro quaternary ammonium cation as a cation is generally excellent in solubility in a non-aqueous solvent.
Preferred examples of the spiro quaternary ammonium cation of the compound (A) include spiro- (1,1 ′)-biadecidinium ion, azacyclopropane-1-spiro-1′-azacyclobutyl ion, azacyclopropane. -1-spiro-1′-azacyclopentyl ion, azacyclopropane-1-spiro-1′-azacyclohexyl ion, azacyclopropane-1-spiro-1′-azacyclooctyl ion, spiro- (1,1 ′ ) -Bipyrrolidinium ion, piperidine-1-spiro-1′-pyrodinium ion, azacyclobutane-1-spiro-1′-azacyclohexyl ion, azacyclobutane-1-spiro-1′-azacycloheptyl ion, aza Cyclobutyl-1-spiro-1′-azacyclooctyl ion, spiro- (1,1 ′)-bipipe Dinium ion, azacyclopentane-1-spiro-1′-azacyclohexyl ion, azacyclopentane-1-spiro-1′-azacycloheptyl ion, azacyclopentane-1-spiro-1′-azacyclooctyl ion, Spiro- (1,1 ′)-bihexamethylenium ion, azacyclohexane-1-spiro-1′-azacycloheptyl ion, azacyclohexane-1-spiro-1′-azacyclooctyl ion, spiro- (1, 1 ')-biheptamethyleneiminium ion. Of these, from the viewpoint of electrochemical stability, spiro- (1,1 ′)-bipyrrolidinium ion, azacyclobutane-1-spiro-1′-azacyclopentyl ion, spiro- (1,1 ′)-bipipe Ridinium ions are preferred.

The anion component (counter anion X ⁻ ) of the compound (A) represented by the general formula (1) will be described. X ⁻ has a HOMO energy (hereinafter abbreviated as HOMO energy) by the first principle molecular orbital calculation in the range of −0.60 to −0.20 a.u., preferably −0.60 to − Counter anion in the range of 0.25 a.u. Here, the HOMO (highest occupied molecular orbital) energy by first-principles molecular orbital calculation is a semi-empirical molecular orbital method by performing conformational analysis on the calculated anion by force field calculation. This value is calculated by the HartleyFock method with the basis function of 6-31G (d) after structural optimization by AM1. Gaussian 03 (manufactured by Gaussian) is used as a program for calculation (Reference 1: “Exploration of Chemistry by Electronic Structure Theory (Second Edition), James B. Foresman, AElen Frisch, written by Kenzo Tazaki, Gaussian, Inc.)” .

Specific examples of the counter anion X ⁻ whose HOMO energy calculated by the above method is in the range of −0.60 to −0.20 a.u. include BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , PCl ₆ ⁻ , BCl ₄ ⁻ , AsCl ₆ ⁻ , SbCl ₆ ⁻ , TaCl ₆ ⁻ , NbCl ₆ ⁻ , PBr ₆ ⁻ , BBr ₄ ⁻ , AsBr ₆ ⁻ , AlBr ₄ ⁻ , TaBr ₆ ⁻ , NbBr ₆ ⁻ , SbF ₆ ⁻ , AlF ₄ ⁻ , ClO ₄ ⁻ , AlCl ₄ ⁻ , TaF ₆ ⁻ , NbF ₆ ⁻ , CN ⁻ , F (HF) _n ⁻ (wherein n represents a numerical value of 1 or more and 4 or less), N ( ^{_{RfSO 3) 2 -, C (}} RfSO 3) 3 -, RfSO 3 -, RfCO 2 - and the like.
^{_{N (RfSO 3) 2 -,}} C (RfSO 3) 3 -, RfSO 3 - or RfCO ₂ ^- Rf contained in the anions represented by represents a fluoroalkyl group having 1 to 12 carbon atoms, trifluoromethyl, Examples include pentafluoroethyl, heptafluoropropyl, and nonafluorobutyl. Of these, trifluoromethyl, pentafluoroethyl and heptafluoropropyl are preferable, trifluoromethyl and pentafluoroethyl are more preferable, and trifluoromethyl is particularly preferable.

Among the above counter anions, from the viewpoint of electrochemical stability, a counter anion having a small HOMO energy by first-principles molecular orbital calculation is preferable, and is represented by BF ₄ ⁻ , PF ₆ ^— or N (RfSO ₃ ) ₂ ^—. that counter anion, more preferably PF ₆ ^- or BF ₄ ^- represented by counter anion, particularly preferably BF ₄ ^- is a counter anion represented by.
The counter anion preferably has a small HOMO energy, but no compound having a value lower than −0.60 a.u. (hereinafter sometimes abbreviated as a.u.) is not known, and substantially. , PF6 @ - (HOMO energy ^{_{= -0.39), BF 4 - (}} HOMO energy ^{_{= -0.35), CF 3 SO 3}} - (HOMO energy = -0.27) is preferred. Conversely, a counter anion having a HOMO energy greater than −0.20 a.u. (small negative value) such as formic acid, acetic acid, benzoic acid (HOMO energy = −0.18), phthalic acid, succinic acid (HOMO) Carboxylic acid anions such as energy = −0.18), I ⁻ (HOMO energy = −0.16), Cl ⁻ (HOMO energy = −0.12), F ⁻ (HOMO energy = −0.08), etc. Inorganic anions are low in electrochemical stability of the electrolyte, and therefore, when used as an electrolytic solution, the withstand voltage is low, the long-term reliability is poor, and it is not useful as an electrochemical element.

Preferred examples of the compound (A) (cation component + anion component) are spiro - (1,1 ') - BF ₄ salt of bi pyrrolidinium ion, BF ₄ salt of piperidine-1-spiro-1'-pyrrolidinium, spiro - (1,1 ') - BF ₄ salt Bipiperijiniumu, spiro - (1,1') - PF ₆ salt of bi pyrrolidinium ion, piperidine-1-PF ₆ salt of the spiro-1'-pyrrolidinium, spiro - (1,1 ′)-bipiperidinium PF ₆ salt.
Of these, particularly preferred, from the viewpoint of electrochemical stability, spiro - (1,1 ') - BF ₄ salt of bi pyrrolidinium ion, piperidin-1-spiro-1'-pyrrolidinium of BF ₄ Salt, spiro- (1,1 ′)-bipiperidinium BF ₄ salt.

The electrolyte (B) preferably contains 50 to 100% by weight, more preferably 70 to 100% by weight of the compound (A).
The electrolyte (B) may contain, in addition to the compound (A), another organic salt compound (D) different from the compound (A). Other organic salt compounds (D) include alkyl ammonium salts, amidinium salts (such as imidazolium salts), and the like. Specifically, for example, BF ₄ salt and PF ₆ salt of an alkyl ammonium, a BF ₄ salt and PF ₆ salts of imidazolium. For example, tetraethylammonium BF ₄ salt, triethylmethylammonium BF ₄ salt, 1,2,3-trimethylimidazolium BF ₄ salt and 1-ethyl-2,3-dimethylimidazolium BF ₄ salt, 1,2,3,4 Examples include tetramethylimidazolium BF ₄ salt. The amount of the other organic salt compound (D) is preferably 0 to 50% by weight, more preferably 5 to 25% by weight, based on the weight of the compound (A).

The electrolyte (B) may contain various additives (E). As the additive (E), LiBF ₄ , LiPF ₆ , phosphoric acids and derivatives thereof (phosphoric acid, phosphorous acid, phosphoric esters, phosphonic acids, etc.), boric acids and derivatives thereof (boric acid, boric acid oxide, Borate esters, complexes of boron with compounds having hydroxyl and / or carboxyl groups, etc., nitrates (lithium nitrate, etc.) and nitro compounds (nitrobenzoic acid, nitrophenol, nitrophenetole, nitroacetophenone, aromatic nitro compounds) Etc.). From the viewpoint of electrochemical stability and conductivity, the amount of the additive (E) is preferably 50% by weight or less, more preferably 20% by weight or less, based on the weight of the compound (A).

The non-aqueous mixed solvent (H) of the present invention is represented by at least one sulfolane derivative (S) selected from the group consisting of sulfolane, 3-methylsulfolane and 2,4-dimethylsulfolane, and the general formula (2). Containing the benzene derivative (G).
The sulfolane derivative (S) is preferably sulfolane alone, a mixed solvent of sulfolane and 3-methylsulfolane, or a mixed solvent of sulfolane and 2,4-dimethylsulfolane.
The sulfolane derivative (S) is a solvent for the electrolyte solution, which has a high viscosity and thus has a low electrical conductivity. When an electrochemical device is produced, there is a problem that the internal resistance is high. By using it, the viscosity of the electrolytic solution can be lowered, and as a result, the conductivity of the electrolytic solution can be improved and the internal resistance of the electrochemical device can be lowered. Conventional quaternary ammonium electrolytes have problems such as insolubility in non-aqueous mixed solvent (H) or precipitation at low temperature, but compound (A) is soluble in non-aqueous mixed solvent (H). Therefore, the electrolyte is hardly deposited even at a low temperature, and the performance can be stably exhibited in a wide temperature range. Since benzene derivatives generally have a low viscosity, it is possible to increase the conductivity of the electrolyte, and since the affinity with the activated carbon electrode is high, the permeability to the inner diameter of the activated carbon is also high. Electrochemical capacitors using benzene derivatives as solvents tend to have lower internal resistance than expected from the conductivity of the electrolyte.

The benzene derivative (G) used in the present invention is represented by the above general formula (2) and has a molecular weight of 400 or less. The molecular weight of (G) is preferably 300 or less, more preferably 92 to 200. When the molecular weight of (G) exceeds 400, the viscosity of (G) rises and is not suitable as a solvent, and (G) less than 92 does not exist.
R ¹ is a halogen atom (fluorine atom, chlorine atom, bromine atom) or an organic group (g) having 1 to 7 carbon atoms.
If the organic group (g) has 8 or more carbon atoms, the benzene derivative (G) becomes a solid at room temperature, which is not suitable for an electrolyte solvent.
R ² and R ³ are a hydrogen atom, a halogen atom, or an organic group (g) having 1 to 7 carbon atoms. R ¹ , R ² and R ³ may be the same or different. If the organic group (g) has 8 or more carbon atoms, the benzene derivative (G) becomes a solid at room temperature, which is not suitable for an electrolyte solvent.

The organic group (g) of the benzene derivative (G) is, for example, a nitrile group, an organosilyl group, a perfluoroalkyl group, or an ester bond, an ether bond, a carbonate bond, a sulfonyl bond, a fluorine atom, a chlorine atom, a bromine atom, A nitrile group, an alkyl group which may have an organosilyl group, etc., and having 1 to 7 carbon atoms. Among these, preferred are a nitrile group, an organosilyl group, a perfluoroalkyl group, or an alkyl group which may have an ester bond, an ether bond, a carbonic acid ester bond, a sulfonyl bond, or a nitrile group.
Examples of the alkyl group having an ester bond include —C (═O) OCH ₃ ,
_{-C (= O) OC 2 H} 5, -CH 2 OC (= O) CH 3, -CH 2 C (= O) OCH 3
Etc.
Examples of the alkyl group having an ether bond include a methoxy group, an ethoxy group, and a methoxymethyl group.
Examples of the alkyl group having a carbonate ester bond include —OC (═O) OCH ₃ ,
_{-OC (= O) OCH 2 CH} 3, etc. -CH 2 -OC (= O) OCH 3 and the like.
Examples of alkyl groups having a sulfonyl bond include
_{-S (= O) 2 -CH 3} , -S (= O) such as 2 _-CH 2 CH ₃ and the like.
Examples of the alkyl group having a nitrile group include —CH ₂ —CN.
Examples of the organosilyl group include —CH ₂ —Si (CH ₃ ) ₃ , —Si (CH ₃ ) _{3 and the} like.
Specific examples of the benzene derivative (G) include the following.
Toluene, xylene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5 -Trichlorobenzene, 2-chlorotoluene, 3-chlorotoluene, 4-chlorotoluene, 2,3-dichlorotoluene, 2,4-dichlorotoluene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1-chloro-2-fluorobenzene, 1-chloro-2-fluorobenzene, bromobenzene, benzotrifluoride, 2-methylbenzotrifluoride, 4-chlorobenzotrifluoride, benzonitrile, phthalo Nitrile, 2-fluorobenzonitrile, 4-cyanobenzene Zotrifluoride, phenylacetonitrile, benzyl chloride, benzyl bromide, α-chloro-o-xylene, dialkyl phthalate (eg, dimethyl phthalate, ethyl methyl phthalate, diethyl phthalate, etc.), methyl o-toluate, Examples include methyl m-toluate, methyl p-toluate, dimethyl isophthalate, dimethyl terephthalate, methoxybenzene, methoxymethylbenzene, methylphenyl carbonate, methylphenylsulfone, and trimethylphenylsilane.
The benzene derivative (G) is preferably a liquid at 25 ° C. or higher.
The viscosity of the benzene derivative (G) at 20 ° C. (viscosity measured with a Brookfield viscometer. For example, it can be measured with a TV-22 type viscometer manufactured by Toki Sangyo Co., Ltd.) is preferably 0. 0.1 mPa · s to 6 mPa · s, more preferably 0.2 mPa · s to 2 mPa · s.
Of the above, toluene, chlorobenzene, benzotrifluoride, and benzonitrile are preferable.

The non-aqueous mixed solvent (H) may contain a solvent (J) other than the sulfolane derivative (S) and the benzene derivative (G). The content of the solvent (J) is preferably 0 to 50% by weight, more preferably 10 to 20% by weight, based on the total weight of the sulfolane derivative (S) and the benzene derivative (G).
Specific examples of the solvent (J) include the following.
Ethers: chain ether [carbon number 2-6 (diethyl ether, methyl isopropyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc.); carbon number 7-12 (diethylene glycol diethyl ether, triethylene glycol dimethyl ether, etc.)], cyclic ether [C2-C4 (tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, etc.); C5-C18 (4-butyldioxolane, crown ether, etc.)].
Amides: N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylpropionamide, hexamethylphosphorylamide, N-methylpyrrolidone and the like.
Carbonic acid esters: ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, methyl ethyl carbonate, diethyl carbonate and the like.
-Sulfoxides: dimethyl sulfoxide, dimethyl sulfone, diethyl sulfone, etc.
・ Nitro compounds: Nitromethane, nitroethane, etc.
-Heterocyclic solvent: N-methyl-2-oxazolidinone, 3,5-dimethyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidinone and the like.
Ketones: acetone, 2,5-hexanedione, cyclohexanone, etc.
-Phosphate esters: trimethyl phosphoric acid, triethyl phosphoric acid, tripropyl phosphoric acid and the like.
Is mentioned.

In the non-aqueous mixed solvent (H), the content (% by weight) of the sulfolane derivative (S) is preferably 20 to 80% by weight with respect to the total weight of the sulfolane derivative (S) and the benzene derivative (G). 30 to 70% by weight is more preferable, and 40 to 60% by weight is most preferable. When the content of the sulfolane derivative (S) is within these ranges, the performance at a low temperature is particularly excellent, and the electrolyte solution can have a high capacity and conductivity. The benzene derivative (G) may be a mixture of two or more solvents.

Preferable examples of the non-aqueous mixed solvent (H) include the following examples.
(1) A mixed solvent of sulfolane and toluene.
The weight ratio of sulfolane: toluene is 20:80 to 80:20, preferably 30:70 to 70:30.
(2) A mixed solvent of sulfolane and chlorobenzene.
The weight ratio of sulfolane: chlorobenzene is 20:80 to 80:20, preferably 30:70 to 70:30.
(3) A mixed solvent of sulfolane and benzotrifluoride.
The weight ratio of sulfolane: benzotrifluoride is 20:80 to 80:20, preferably 30:70 to 70:30. (4) The mixed solvent weight ratio of sulfolane and benzonitrile is such that sulfolane: benzonitrile is 20:80 to 80:20, preferably 30:70 to 70:30.

The water content in the electrolytic solution of the present invention is preferably 300 ppm or less, more preferably 100 ppm or less, particularly preferably 50 ppm or less based on the weight of the electrolytic solution from the viewpoint of electrochemical stability. Within this range, it is possible to suppress the deterioration in performance of the electrochemical capacitor over time.
The water content in the electrolytic solution can be measured by the Karl Fischer method (JIS K0113-1997, coulometric titration method).
Examples of the method for setting the water content in the electrolytic solution in the above range include a method using a sufficiently dried electrolyte (B) and a non-aqueous solvent sufficiently dehydrated in advance.
Examples of the drying method include heating and drying under reduced pressure (for example, heating at 150 ° C. under reduced pressure of 20 Torr), evaporating and removing a trace amount of water contained therein, recrystallization, and the like.
As the dehydration method, heat dehydration under reduced pressure (for example, heating at 100 Torr) to evaporate and remove a trace amount of water, molecular sieve (manufactured by Nacalai Tesque, 3A 1/16, etc.), activated alumina powder And a method using a dehydrating agent such as
In addition to these, the electrolytic solution is heated and dehydrated under reduced pressure (for example, heated at 100 ° C. under reduced pressure of 100 Torr) to evaporate and remove a trace amount of water, molecular sieve, activated alumina powder, etc. And a method of using a dehydrating agent. These methods may be performed alone or in combination. Among these, the method of highly purifying the electrolyte (B) by recrystallization and further heating and drying (B) under reduced pressure, and the method of adding molecular sieve to the non-aqueous mixed solvent (H) or the electrolytic solution are preferable.

The electrolytic solution of the present invention can be used for electrochemical devices. An electrochemical element shows an electrochemical capacitor, a secondary battery, a dye-sensitized solar cell, etc. An electrochemical capacitor includes an electrode, a current collector, and a separator as basic components, and optionally includes a case, a gasket, and the like that are generally used for capacitors. The electrolytic solution is impregnated into the electrode and the separator, for example, in a glove box in an argon gas atmosphere (dew point −50 ° C.). The electrolytic solution of the present invention is suitable for an electric double layer capacitor (one using a polarizable electrode such as activated carbon) as an electrochemical capacitor among electrochemical capacitors.

As a basic structure of the electric double layer capacitor, a separator is sandwiched between two polarizable electrodes and impregnated with an electrolytic solution. The main component of the polarizable electrode is preferably a carbonaceous material such as activated carbon, graphite, or polyacene organic semiconductor because it is electrochemically inert to the electrolyte and has an appropriate electrical conductivity. Thus, at least one of the positive electrode and the negative electrode is a carbonaceous material. A porous carbon material (for example, activated carbon) having a specific surface area of 10 m ² / g or more determined by the BET method by the nitrogen adsorption method is more preferable because of the large electrode interface where charges are accumulated. The specific surface area of the porous carbon material is selected in consideration of the target capacitance per unit area (F / m ² ) and the decrease in bulk density associated with the increase in the specific surface area. preferably it has a specific surface area determined is 30~2,500m ² / g by the BET method, since the electrostatic capacity per volume is large, the specific surface area is particularly preferably activated carbon 300~2,300m ² / g.

The electrolytic solution for electrochemical capacitors of the present invention can also be used for aluminum electrolytic capacitors. The basic structure of an aluminum electrolytic capacitor is that an oxide film is formed by electrochemical treatment on the surface of the aluminum foil that becomes the electrode, and this is used as a dielectric, and the electrolytic solution is impregnated between the aluminum foil that becomes the other electrode. Electrolytic paper is sandwiched between them.

Examples of the electrochemical capacitor of the present invention include a coin type, a wound type, and a rectangular type. The electrolytic solution for electrochemical capacitors of the present invention can be applied to any electric double layer capacitor or any aluminum electrolytic capacitor.

EXAMPLES Next, specific examples of the present invention will be described, but the present invention is not limited thereto. Hereinafter, “parts” means “parts by weight” unless otherwise specified.
In the following examples, 1H-NMR, 19F-NMR and 13C-NMR were measured by the following methods.
Measurement conditions for 1H-NMR Instrument: AVANCE 300 (manufactured by Nippon Bruker Co., Ltd.), solvent: deuterated dimethyl sulfoxide, frequency: 300 MHz.
Measurement conditions for 19F-NMR Instrument: AL-300 (manufactured by JEOL Ltd.), solvent: deuterated dimethyl sulfoxide, frequency: 300 MHz
Measurement conditions for 13C-NMR Instrument: AL-300 (manufactured by JEOL Ltd.), solvent: deuterated dimethyl sulfoxide, frequency: 300 MHz

The content of compound (A) was quantified by high performance liquid chromatography (HPLC). The calibration curve can be prepared using the compound (A) crystallized to increase the purity as a standard.
The electrolyte solution of the present invention was diluted 500 times with a mobile phase used for HPLC, and this solution was filtered with a 0.20 μm hydrophilic filter (ADVANTEC: DISMIC-13JP, PTFE non-sterile). did.

<Production Example 1>
Production of Electrolyte (B-1) 100 parts of pyrrolidine and 97 parts of potassium carbonate were charged into an autoclave coated with Teflon (registered trademark), 179 parts of 1,4-dichlorobutane were added, and the reaction was carried out at 90 ° C. for 8 hours. To this reaction solution, 294 parts of a 42% by weight aqueous borohydrofluoric acid solution was gradually added dropwise at 25 ° C. over about 30 minutes. After the completion of the dropping and the generation of bubbles was stopped, the whole solvent was distilled off at 20 Torr and 100 ° C. to obtain 195 parts of a solid. Ethanol (50 parts) and 2-propanol (1950 parts) were added to this solid, the temperature was raised to 80 ° C., the mixture was stirred for 1 hour, and cooled to room temperature three times. Tetrafluoroborate spiro- (1,1 ') -46 parts of bipyrrolidinium compound (A-1) (white solid) was obtained. As a result of ¹ H-NMR, ¹⁹ F-NMR, ¹³ C-NMR and HPLC analysis of the compound (A-1), it was 99.99 mol%. The measurement conditions for HPLC analysis are as described above.
The compound (A-1) was used as the electrolyte (B-1).
The same applies to the following synthesis examples.

<Production Example 2>
245 parts of a solid were obtained in the same manner except that the borohydrofluoric acid aqueous solution of Production Example 1 was replaced with 342 parts of a 60 wt% aqueous hexafluorophosphoric acid solution. This solid was subjected to the same crystallization operation as in Production Example 1 three times to obtain 48 parts of a compound (A-2) (white solid) of spiro- (1,1 ′)-bipyrrolidinium hexafluorophosphate. . As a result of ¹ H-NMR, ¹⁹ F-NMR, ¹³ C-NMR and HPLC analysis of the compound (A-2), it was 99.99 mol%. The measurement conditions for HPLC analysis are as described above. The compound (A-2) was used as the electrolyte (B-2).

<Production Example 3>
An autoclave coated with 100 parts of pyrrolidine and 97 parts of potassium carbonate in Teflon was added, 198 parts of 1,5-dichloropentane was added, and the reaction was carried out at 90 ° C. for 8 hours. To this reaction solution, 294 parts of a 42% by weight aqueous borohydrofluoric acid solution was gradually added dropwise at 25 ° C. over about 30 minutes. After the dropping was completed and the generation of bubbles was stopped, the whole solvent was distilled off at 20 Torr and 100 ° C. to obtain 200 parts of a solid. Crystallization operation similar to manufacture example 1 was performed 3 times with respect to this solid, and 155 parts of compounds (A-3) (white solid) of piperidine-1-spiro-1'-pyrodinium tetrafluoroborate were obtained. As a result of ¹ H-NMR, ¹⁹ F-NMR, ¹³ C-NMR and HPLC analysis of the compound (A-3), it was 99.99 mol%. The measurement conditions for HPLC analysis are as described above. Compound (A-3) was used as electrolyte (B-3).

<Production Example 4>
260 parts of solid were obtained in the same manner except that the borohydrofluoric acid aqueous solution of Production Example 3 was replaced with 342 parts of a 60% by weight hexafluorophosphoric acid aqueous solution. The solid was subjected to the same crystallization operation as in Production Example 1 three times to obtain 185 parts of a compound (A-4) (white solid) of piperidine-1-spiro-1′-pyrodinium hexafluorophosphate. It was 99.99 mol% as a result of analyzing a compound (A-4) by < ¹ > H-NMR, < ¹⁹ > F-NMR, < ¹³ > C-NMR, and HPLC. The measurement conditions for HPLC analysis are as described above. Compound (A-4) was used as electrolyte (B-4).

Electrolyte solvent dehydration All the electrolyte solvents used below were used after the following dehydration treatment.
After adding 3 parts of molecular sieve to 100 parts of the solvent to be used and drying it by leaving it at 25 ° C. for 60 hours, the molecular sieve was separated by filtration to obtain a dehydrated solvent.

<Reference Example 1>
50 parts of dehydrated sulfolane, 50 parts of dehydrated chlorobenzene, and 18 parts of electrolyte (B-1) were uniformly mixed and dissolved at 25 ° C. to obtain an electrolytic solution. The water content of the electrolytic solution was 32 ppm.

<Reference Example 2>
50 parts of dehydrated sulfolane, 50 parts of dehydrated chlorobenzene, and 23 parts of electrolyte (B-2) were uniformly mixed and dissolved at 25 ° C. to obtain an electrolytic solution. The water content of the electrolytic solution was 32 ppm.

<Reference Example 3>
50 parts of dehydrated sulfolane, 50 parts of dehydrated chlorobenzene, and 19 parts of electrolyte (B-3) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 20 ppm.

<Reference Example 4>
50 parts of dehydrated sulfolane, 50 parts of dehydrated chlorobenzene and 24 parts of electrolyte (B-4) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 29 ppm.

<Example 5>
60 parts of dehydrated sulfolane, 40 parts of benzotrifluoride, and 18 parts of electrolyte (B-1) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 21 ppm.

<Example 6>
40 parts of dehydrated sulfolane, 60 parts of benzotrifluoride, and 23 parts of electrolyte (B-2) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 21 ppm.

<Example 7>
60 parts of dehydrated sulfolane, 40 parts of 4-chlorobenzotrifluoride, and 18 parts of electrolyte (B-1) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 20 ppm.

<Reference Example 8>
80 parts of dehydrated sulfolane, 20 parts of toluene, and 23 parts of electrolyte (B-2) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 19 ppm.

<Reference Example 9>
20 parts of dehydrated sulfolane, 80 parts of methyl benzoate and 20 parts of electrolyte (B-1) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 43 ppm.

<Reference Example 10>
50 parts of dehydrated sulfolane, 50 parts of benzonitrile and 20 parts of electrolyte (B-1) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 43 ppm.

<Reference Example 11>
50 parts of dehydrated sulfolane, 50 parts of benzyl methyl ether and 20 parts of electrolyte (B-1) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 28 ppm.

<Reference Example 12>
40 parts of dehydrated sulfolane, 20 parts of 2,4-dimethylsulfolane, 40 parts of benzotrifluoride, and 23 parts of electrolyte (B-2) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 19 ppm.

<Example 13>
40 parts of dehydrated sulfolane, 20 parts of 2,4-dimethylsulfolane, 40 parts of benzotrifluoride, and 23 parts of electrolyte (B-2) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 19 ppm.

<Comparative Example 1>
50 parts of dehydrated sulfolane and 50 parts of chlorobenzene and 20 parts of tetraethylammonium BF ₄ (manufactured by Tokyo Chemical Industry Co., Ltd.) (B-5 ′) as an electrolyte were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 21 ppm.

<Comparative example 2>
50 parts of dehydrated sulfolane and 50 parts of chlorobenzene and 17 parts of triethylmethylammonium BF ₄ (manufactured by Tokyo Chemical Industry Co., Ltd.) (B-6 ′) as an electrolyte were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 21 ppm.

<Comparative Example 3>
100 parts of dehydrated propylene carbonate and 18 parts of electrolyte (B-1) were uniformly mixed and dissolved at 25 ° C. to obtain an electrolytic solution. The water content of the electrolytic solution was 22 ppm.

<Comparative example 4>
100 parts of dehydrated propylene carbonate and 23 parts of electrolyte (B-2) were uniformly mixed and dissolved at 25 ° C. to obtain an electrolytic solution. The water content of the electrolytic solution was 22 ppm.

<Comparative Example 5>
40 parts of dehydrated sulfolane, 60 parts of propylene carbonate, and 18 parts of electrolyte (B-1) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 24 ppm.

<Comparative Example 6>
100 parts of dehydrated sulfolane and 18 parts of electrolyte (B-1) were uniformly mixed to obtain an electrolytic solution. The water content of the electrolytic solution was 21 ppm.

In order to evaluate the characteristics of the electrolytic solution, the electrolytic solution was cooled from room temperature to −30 ° C. and allowed to stand for 3 hours, and the presence or absence of solidification of the electrolytic solution and precipitation of the electrolyte was visually confirmed.

Moreover, polarization measurement was performed using a glassy carbon electrode (manufactured by BAS, outer diameter 6 mm, inner diameter 1 mm) at a scanning potential speed of 5 mV / sec. The potential for Ag / Ag ⁺ reference electrode when a current of 10 μA / cm ² flows is an oxidation potential, and the potential for Ag / Ag ⁺ reference electrode when a current of −10 μA / cm ² flows is a reduction potential. The potential window was calculated from the difference in potential values. The potential window of the electrolytic solution indicates an electrochemically stable range of the electrolytic solution. An electrochemical element using an electrolytic solution having a wide potential window can be used in a wide voltage range. That is, it can be said that the withstand voltage is high.

The results are shown in Table 1. When the electrolyte was solidified by visual confirmation at −30 ° C., “solidified” or “precipitation” was observed when precipitation was observed, and “no change” when solidification or precipitation was not observed.

As is clear from Table 1, the electrolytes of Examples 5 to 7, Example 13, Reference Examples 1 to 4 and 8 to 12 are free from solidification or precipitation at a low temperature of −30 ° C., and have a potential window. Is as large as 6.3 V or more, it was shown that it can be used at a low temperature of −30 ° C. and has a high withstand voltage. Comparative Examples 1 and 2 cannot be used at low temperatures because electrolyte deposition occurs at low temperatures. Moreover, since the comparative example 6 is solidified at -30 degreeC, it cannot be used at low temperature.

Using the electrolytic solution of the present invention and the electrolytic solution of the comparative example, a three-electrode electric double layer capacitor (manufactured by Power System Co., Ltd., FIG. 1) was prepared. A charge / discharge cycle test was performed using this capacitor, and the capacitance and resistance were evaluated.

  Powdered activated carbon (“MSP-20” manufactured by Kansai Thermal Chemical Co., Ltd.) was mixed with carbon black and polytetrafluoroethylene powder (PTFE). The weight ratio was 10: 1: 1.

  The obtained mixture was kneaded for about 5 minutes in a mortar and rolled with a roll press to obtain an activated carbon sheet. The thickness of the activated carbon sheet was 400 μm. This activated carbon sheet was punched into a 20 mmφ disk shape to obtain an activated carbon electrode.

A three-electrode electric double layer capacitor (manufactured by Power System Co., Ltd.) was assembled using the obtained activated carbon electrodes (positive electrode, negative electrode and reference electrode). These cells were dried in vacuum at 170 ° C. for 7 hours and cooled to 30 ° C. In a dry atmosphere, the electrolytic solutions of <Examples 5 to 7, Example 13, Reference Examples 1 to 4, 8 to 12>, and <Comparative Examples 1 to 6> were injected into the cell, and then vacuum impregnation was performed to form an electric double layer. A capacitor was produced.

  Connect the charge / discharge test device (“CDT-5R2-4” manufactured by Power System Co., Ltd.) to the created electric double layer capacitor, perform constant current charging at 25 mA to the set voltage, and 25 mA 7200 seconds after the start of charging. A constant current discharge was performed at. This was carried out for 50 cycles at a set voltage of 3.3 V and 45 ° C., and the capacitance value and capacitance retention ratio (%) after the initial and 50 cycles of the cell, and the internal resistance and internal resistance after the initial and 50 cycles. Was measured as an index of long-term reliability. The test results are shown in Table 2.

As is apparent from Table 2, the electric double layer capacitors using the electrolytic solutions of Examples 5 to 7, Example 13, Reference Examples 1 to 4 and 8 to 12 of the present invention are the electrolytic solutions of Comparative Examples 3 to 5. It can be seen that the capacity retention after the cycle test is high and the internal resistance increase rate is low as compared with the electric double layer capacitor using. In Comparative Examples 1, 2, and 6, the capacity retention after the cycle test is high and the internal resistance increase rate is low as in Examples 5 to 7, Example 13, Reference Examples 1 to 4, and 8 to 12, but the internal resistance increase rate is low. Since the electrolyte is deposited at ℃, it cannot be used at low temperatures.
Therefore, it is clear that the electrochemical capacitor using the electrolytic solution of the present invention can constitute a highly reliable electrochemical element having high durability, and can constitute an electrochemical element that can be used stably even at low temperatures.

The electrochemical element using the electrolytic solution for an electrochemical element of the present invention can be applied to an electrochemical capacitor, a secondary battery, a dye-sensitized solar cell and the like.

3 electrode type electric double layer capacitor

Claims (7)

An electrolyte solution (B) containing the compound (A) represented by the general formula (1) and an electrolyte solution containing a non-aqueous mixed solvent (H), wherein the non-aqueous mixed solvent (H) is And at least one sulfolane derivative (S) selected from the group consisting of sulfolane, 3-methylsulfolane and 2,4-dimethylsulfolane, and a benzene derivative having a molecular weight of 400 or less represented by the general formula (2 ′ ) ( An electrolytic solution for an electrochemical element, comprising G 1 ).

[Wherein, m and n represent 3 to 7 and may be the same or different. X ⁻ is an anion having a HOMO energy of −0.60 to −0.20 a.u. ]

[Wherein, R ¹ is a halogen atom or an organic group (g) having 1 to 7 carbon atoms, and R ² and R ³ are a hydrogen atom, a halogen atom, or an organic group (g) having 1 to 7 carbon atoms. It is. R ^1, R ² and R ³ rather good be the same or different, and at least one is a perfluoroalkyl group from 1 to 7 carbon atoms. ] The electrolytic solution according to claim 1, wherein the organic group (g) of the benzene derivative (G 1 ) is a perfluoroalkyl group. Relative to the total weight of the sulfolane derivative (S) and benzene derivative (G 1), weight 20 to 80 wt% of sulfolane derivative (S), wherein the weight of a benzene derivative (G 1) is 80 to 20 wt% Item 3. The electrolyte according to Item 1 or 2. In the general formula (1), the counter ion X ⁻ is BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , N (RfSO ₃ ) ₂ ⁻ , C (RfSO ₃ ) ₃ ⁻ and RfSO ₃ ⁻ (Rf). The electrolytic solution according to any one of claims 1 to 3, which is at least one selected from the group consisting of a fluoroalkyl group having 1 to 12 carbon atoms. An electrochemical element using the electrolytic solution according to any one of claims 1 to 4. An electrochemical capacitor using the electrolytic solution according to any one of claims 1 to 4. An electric double layer capacitor using the electrolytic solution according to any one of claims 1 to 4.

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