JP2011192963A - Electrolyte for electric double layer capacitor and electric double layer capacitor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce an electrolyte having small variation in capacitance and resistance even at a high operating voltage, generating minimal gas and achieving high durability. <P>SOLUTION: An electrolyte for an electric double layer capacitor contains an organic electrolyte (A) and 4,5-dialkyl-1,3-dioxolan-2-one (B). A mixture of cis-4,5-dialkyl-1,3-dioxolan-2-one (B1) and trans-4,5-dialkyl-1,3-dioxolan-2-one (B2) is preferable as (B). An example of (B) includes 4,5-dimethyl-1,3-dioxolan-2-one, 4-ethyl-5-methyl-1,3-dioxolan-2-one and the like. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrolytic solution for an electric double layer capacitor and an electric double layer capacitor using the same.

Conventionally, an electrolyte of an electric double layer capacitor includes tetraethylammonium = tetrafluoroborate (hereinafter referred to as TEA · BF ₄ ) salt, triethylmethylammonium = tetrafluoroborate (hereinafter referred to as TEMA · BF ₄ ) salt, or 1-ethyl-3-methylimidazolium = tetrafluoroborate (hereinafter referred to as EMI · BF ₄ ) salt or the like is used as an electrolyte. In recent years, new applications such as hybrid electric vehicles that are used for a long period of time and with a large current are spreading. In such a field, there is a demand for an electric double layer capacitor with extremely small change in characteristics and excellent long-term durability. Has been. For this reason, there is an urgent need to develop an electrolytic solution having a high withstand voltage that is chemically stable and can be used for a long period of time even in the electrolytic solution that constitutes the member.

Under such circumstances, an electrolytic solution having a high withstand voltage has been developed by a mixed composition of ethylene carbonate and propylene carbonate solvents conventionally used (for example, Patent Document 1).

JP 2000-208372 A

However, when an ethylene carbonate or propylene carbonate solvent is used, by increasing the operating voltage of the electric double layer capacitor, the ethylene carbonate or propylene carbonate is hydrolyzed, gas is generated, the electrode is deteriorated, and long-term durability is improved. There is a problem that it decreases.
The problem to be solved by the present invention is to produce a highly durable electrolyte with little change in capacity and resistance even at a high operating voltage and with little gas generation.

（Ｒ_１、Ｒ_２は炭素数１〜３のアルキル基であり、互いに同じでも異なっていてもよい。） As a result of intensive studies to solve the above-mentioned problems, the present inventor uses specific 4,5-dialkyl-1,3-dioxolan-2-one as an electrolyte solvent to change the capacity and resistance even at a high operating voltage. Thus, the present invention has been completed.
That is, the invention relates to an electrolyte for an electric double layer capacitor containing an organic electrolyte (A) and 4,5-dialkyl-1,3-dioxolan-2-one (B) represented by the general formula (1), and It is an electric double layer capacitor using

(R ₁ and R ₂ are alkyl groups having 1 to 3 carbon atoms and may be the same as or different from each other.)

The electric double layer capacitor using the electrolytic solution for the electric double layer capacitor of the present invention has a small change in capacity and resistance even at a high operating voltage, and generates little gas and has high durability.

The present invention is described in detail below.
The electrolytic solution for an electric double layer capacitor in the present invention contains an organic electrolyte (A) and 4,5-dialkyl-1,3-dioxolan-2-one (B) represented by the above general formula (1).
In general, it is known that ethylene carbonate and propylene carbonate, which are cyclic carbonates, are ring-opened by an electrochemical reaction or a reaction with an OH ^- ion which is a strong alkali component.
4,5-dialkyl-1,3-dioxolan-2-one (B) represented by the general formula (1) has an alkyl group at the 4-position and 5-position of the cyclic carbonate, and therefore has no alkyl group. Compared with propylene carbonate having an alkyl group only at the 4-position, it is sterically protected with an alkyl group, so that the ring-opening reaction is unlikely to occur and is chemically stable, and the withstand voltage is increased as an electrolyte. It is done.

The 4,5-dialkyl-1,3-dioxolan-2-one (B) represented by the general formula (1) has alkyl groups at the 4-position and 5-position of 1,3-dioxolan-2-one. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, and an i-propyl group, which may be the same or different at the 4-position and 5-position.

Specific examples of 4,5-dialkyl-1,3-dioxolan-2-one (B) represented by the general formula (1) include
4,5-dimethyl-1,3-dioxolan-2-one,
4-ethyl-5-methyl-1,3-dioxolan-2-one,
4,5-diethyl-1,3-dioxolan-2-one,
4-methyl-5-n-propyl-1,3-dioxolan-2-one,
4-methyl-5-i-propyl-1,3-dioxolan-2-one,
4-ethyl-5-n-propyl-1,3-dioxolan-2-one,
4-ethyl-5-i-propyl-1,3-dioxolan-2-one,
4,5-di-n-propyl-1,3-dioxolan-2-one,
4,5-di-i-propyl-1,3-dioxolan-2-one,
4-n-propyl-5-i-propyl-1,3-dioxolan-2-one,
Is mentioned.
Of these, from the viewpoint of the viscosity and molecular weight of the solvent,
4,5-dimethyl-1,3-dioxolan-2-one,
4-ethyl-5-methyl-1,3-dioxolan-2-one,
4,5-diethyl-1,3-dioxolan-2-one,
4-methyl-5-n-propyl-1,3-dioxolan-2-one,
4-methyl-5-i-propyl-1,3-dioxolan-2-one,
And more preferably 4,5-dimethyl-1,3-dioxolan-2-one,
4-ethyl-5-methyl-1,3-dioxolan-2-one.

The 4,5-dialkyl-1,3-dioxolan-2-one (B) represented by the general formula (1) has a cis isomer and a trans isomer as stereoisomers.
When used as an electrolytic solution for an electric double layer capacitor, a mixture of a cis body and a trans body is preferable in order to lower the melting point.
The mixing ratio (molar ratio) of the cis isomer to the trans isomer is preferably (cis isomer) :( trans isomer) = 90: 10 to 10:90, more preferably (cis isomer) :( trans isomer) = 60:40 to 10:90, and more preferably (cis isomer) :( trans isomer) = 30: 70 to 10:90.
The electrolyte solution of the present invention preferably further contains sulfolane (SL) as a solvent from the viewpoint of capacity retention. The content of (SL) is preferably 0 to 50% by weight based on the weight of 4,5-dialkyl-1,3-dioxolan-2-one (B), and preferably 10 from the viewpoint of the internal resistance of the mixed solvent. It is preferable to use -30% by weight.

The organic electrolyte (A) in the present invention comprises an organic cation (C) and an anion (D).
Organic cations (C) include tetraalkylammonium compounds, tetraalkylphosphonium compounds, ethylene diammonium compounds, pyrrolidinium compounds, piperidinium compounds, hexamethylene iminium compounds, morpholinium compounds, piperazinium compounds, tetrahydro Pyrimidinium compounds, pyridinium compounds, picolinium compounds, imidazolinium compounds, imidazolium compounds, quinolinium compounds, bipyridinium compounds, other alicyclic ammonium compounds, and mixtures of two or more of the above. The following compounds are mentioned as main examples.

Tetraalkylammonium compounds tetramethylammonium, ethyltrimethylammonium, triethylmethylammonium, tetraethylammonium, diethyldimethylammonium, methyltri-n-propylammonium, tri-n-butylmethylammonium, ethyltri-n-butylammonium, tri-n -Octylmethylammonium, ethyltri-n-octylammonium, diethylmethyl-i-propylammonium and the like.
・ Tetraalkylphosphonium compounds Tetramethylphosphonium, tetraethylphosphonium, tetrabutylphosphonium, dimethyldiethylphosphonium, methyltriethylphosphonium, etc. ・ Ethylenediammonium compounds N, N, N, N ′, N ′, N′-hexamethylethylenedi Ammonium, N, N′-diethyl-N, N, N ′, N′-tetramethylethylenediammonium and the like.

Pyrrolidinium compounds N, N-dimethylpyrrolidinium, N-ethyl-N-methylpyrrolidinium, N, N-diethylpyrrolidinium, spiro- (1,1 ′)-bipyrrolidinium, piperidine-1-spiro- 1'-pyrrolidinium and the like.
Piperidinium compounds N, N-dimethylpiperidinium, N-ethyl-N-methylpiperidinium, N, N-diethylpiperidinium, Nn-butyl-N-methylpiperidinium, N-ethyl- Nn-butyl piperidinium, spiro- (1,1 ′)-bipiperidinium and the like.

-Hexamethyleneiminium compounds N, N-dimethylhexamethyleneiminium, N-ethyl-N-methylhexamethyliminium, N, N-diethylhexamethyleneiminium, etc.
-Morpholinium compounds N, N-dimethylmorpholinium, N-ethyl-N-methylmorpholinium, N-butyl-N-methylmorpholinium, N-ethyl-N-butylmorpholinium, and the like.
Piperazinium compounds N, N, N ′, N′-tetramethylpiperazinium, N-ethyl-N, N ′, N′-trimethylpiperazinium, N, N′-diethyl-N, N′-dimethyl Piperazinium, N, N, N′-triethyl-N′-methylpiperazinium, N, N, N ′, N′-tetraethylpiperazinium and the like.

Tetrahydropyrimidinium compounds 1,3-dimethyl-1,4,5,6-tetrahydropyrimidinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidinium, 1,2 , 3,4-tetramethyl-1,4,5,6-tetrahydropyrimidinium, 1,2,3,5-tetramethyl-1,4,5,6-tetrahydropyrimidinium, 8-methyl-1 , 8-diazabicyclo [5.4.0] -7-undecenium, 5-methyl-1,5-diazabicyclo [4.3.0] -5-nonenium, 8-ethyl-1,8-diazabicyclo [5.4. .0] -7-undecenium, 5-ethyl-1,5-diazabicyclo [4.3.0] -5-nonenium, and the like.
-Pyridinium compounds N-methylpyridinium, N-ethylpyridinium, N-methyl-4-dimethylaminopyridinium, N-ethyl-4-dimethylaminopyridinium, and the like.
-Picolinium compounds N-methylpicolinium, N-ethylpicolinium, etc.

・ Imidazolinium compounds 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3- Dimethyl-2,4-diethylimidazolinium, 1,2-dimethyl-3,4-diethylimidazolinium, 1-methyl-2,3,4-triethylimidazolinium, 1,2,3,4-tetraethyl Imidazolinium, 1,3-dimethyl-2-ethylimidazolinium, 1-ethyl-2,3-dimethylimidazolinium, 1,2,3-triethylimidazolinium, 1,1-dimethyl-2-heptyl Imidazolinium, 1,1-dimethyl-2- (2′-heptyl) imidazolinium, 1,1-dimethyl-2- (3′-heptyl) imidazolinium, 1,1 Dimethyl-2- (4′-heptyl) imidazolinium, 1,1-dimethyl-2-dodecylimidazolinium, 1,1-dimethylimidazolinium, 1,1,2-trimethylimidazolinium, 1,1 1,2,4-tetramethylimidazolinium, 1,1,2,5-tetramethylimidazolinium, 1,1,2,4,5-pentamethylimidazolinium and the like.

・ Imidazolium compounds 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,3-diethylimidazolium, 1,2,3-trimethylimidazolium, 1,2,3,4-tetra Methylimidazolium, 1,3,4-trimethyl-2-ethylimidazolium, 1,3-dimethyl-2,4-diethylimidazolium, 1,2-dimethyl-3,4-diethylimidazolium, 1-methyl- 2,3,4-triethylimidazolium, 1,2,3,4-tetraethylimidazolium, 1,3-dimethyl-2-ethylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1,2, 3-triethylimidazolium, 1,1-dimethyl-2-heptylimidazolium, 1,1-dimethyl-2- (2′-heptyl) imi Dazolium, 1,1-dimethyl-2- (3′-heptyl) imidazolium, 1,1-dimethyl-2- (4′-heptyl) imidazolium, 1,1-dimethyl-2-dodecylimidazolium, 1, 1-dimethylimidazolium, 1,1,2-trimethylimidazolium, 1,1,2,4-tetramethylimidazolium, 1,1,2,5-tetramethylimidazolium, 1,1,2,4 5-pentamethylimidazolium and the like.

-Quinolinium compounds N-methylquinolinium, N-ethylquinolinium, etc.
-Bipyridinium compounds N-methyl-2,2'-bipyridinium, N-ethyl-2,2'-bipyridinium and the like.
Other alicyclic ammoniums 1-methyl-1-azabicyclo [2,2,1] heptane-1-ium, 1-methyl-1-azabicyclo [2,2,2] octane-1-ium, 1- Ethyl-1-azabicyclo [2,2,1] heptane-1-ium, 1-ethyl-1-azabicyclo [2,2,2] octane-1-ium and the like.

Among the above cations, preferred are the following.
Tetraalkylammonium compounds, imidazolium compounds, pyrrolidinium compounds, piperidinium compounds, and other alicyclic ammoniums.
Of these, compounds having a 5-membered ring containing a nitrogen atom and / or a 6-membered ring containing a nitrogen atom are more preferred, and are represented by the following general formulas (2) to (4).

（Ｒ_３、Ｒ_４は炭素数１〜２のアルキル基であり、互いに同じでも異なっていてもよい。また、互いに環を形成しても良い。）

(R ₃ and R ₄ are alkyl groups having 1 to 2 carbon atoms and may be the same or different from each other. They may also form a ring with each other.)

（Ｒ_５、Ｒ_６は炭素数１〜３のアルキル基であり、互いに同じでも異なっていてもよい。また、互いに環を形成しても良い。）

(R ₅ and R ₆ are alkyl groups having 1 to 3 carbon atoms and may be the same or different from each other. They may also form a ring with each other.)

［Ｒ_７はハロゲン原子、ニトロ基、シアノ基及びエーテル結合を有する基からなる群より選ばれる少なくとも１種の基を有していてもよい炭素数１〜３の１価炭化水素基である。Ｒ_８〜Ｒ_１９は、炭素数１〜２のアルキル基、炭素数１〜５のフルオロアルキル基、水素原子、又はハロゲン原子である。Ｒ_８〜Ｒ_１９は同じでも異なっていてもよい。ｈ、ｉ、ｊ、ｘ、ｙ及びｚは０〜２の整数であり、同じでも異なっていてもよい。ｈ＋ｘは０〜４の整数、ｉ＋ｙ及びｊ＋ｚは１〜４の整数である。Ｒ_２０はハロゲン原子、ニトロ基、シアノ基及びエーテル結合を有する基からなる群より選ばれる少なくとも１種の基を有していてもよい炭素数１〜３の１価炭化水素基、水素原子、又はハロゲン原子である。］

[R ₇ is a monovalent hydrocarbon group having 1 to 3 carbon atoms which may have at least one group selected from the group consisting of a halogen atom, a nitro group, a cyano group and a group having an ether bond. R _{8 to} R ₁₉ are an alkyl group having 1 to 2 carbon atoms, a fluoroalkyl group having 1 to 5 carbon atoms, a hydrogen atom, or a halogen atom. R _{8 to} R ₁₉ may be the same or different. h, i, j, x, y, and z are integers of 0 to 2, and may be the same or different. h + x is an integer of 0-4, i + y and j + z are integers of 1-4. R ₂₀ is a monovalent hydrocarbon group having 1 to 3 carbon atoms which may have at least one group selected from the group consisting of a halogen atom, a nitro group, a cyano group and an ether bond group, a hydrogen atom, Or it is a halogen atom. ]

In general, it is known that a quaternary ammonium salt having β-hydrogen is decomposed over time by a Hofmann decomposition reaction when used as an electrolytic solution for an electric double layer capacitor. For example, an ethyl group bonded to a nitrogen atom of a chain ammonium salt such as a tetramethylammonium cation is desorbed as ethylene gas by a Hofmann decomposition reaction, and desorbed as propylene gas in an n-butyl group. On the other hand, in the case of a cyclic ammonium salt such as a spiro- (1,1 ′)-bipyrrolidinium cation containing a nitrogen atom as a ring constituent atom, the decomposition product in the Hofmann decomposition reaction is difficult to desorb as a gas. It preferably has a ring structure. Further, in the ring structure, 1-methyl-1-azabicyclo [2,2,1] is compared with a monocyclic structure such as N, N-dimethylpyrrolidinium and spiro- (1,1 ′)-bipyrrolidinium. A structure in which a plurality of rings such as heptane-1-ium can be sterically intersected is preferable because the Hofmann decomposition reaction is further suppressed.

Of these, preferred are
N, N-dimethylpyrrolidinium, N-ethyl-N-methylpyrrolidinium, spiro- (1,1 ′)-bipyrrolidinium,
N, N-dimethylpiperidinium, N-ethyl-N-methylpiperidinium,
1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,2,3 trimethylimidazolium,
1,3-dimethyl-1,4,5,6-tetrahydropyrimidinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidinium,
1-methyl-1-azabicyclo [2,2,1] heptane-1-ium, 1-methyl-1-azabicyclo [2,2,2] octane-1-ium, 1-ethyl-1-azabicyclo [2, 2,1] heptane-1-ium, 1-ethyl-1-azabicyclo [2,2,2] octane-1-ium, particularly preferred are
1-methyl-1-azabicyclo [2,2,1] heptane-1-ium and 1-methyl-1-azabicyclo [2,2,2] octane-1-ium.

As a specific example of the anion (D),
I ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , F ⁻ , Cl ⁻ , 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 ^- (in the formula, n represents a number from 1 to _{4), 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. Moreover, a carboxylate anion, More preferably, an aromatic carboxylate anion, More preferably, a phthalate anion etc. are mentioned.
Of the above anions, from the viewpoint of electrochemical stability, preferably, a counter anion represented by I ⁻ , BF ₄ ⁻ , PF ₆ ⁻ or N (RfSO ₃ ) ₂ ^— , more preferably I ⁻ , PF ₆ ^- or BF ₄ ^- represented by counter anion in, particularly preferably BF ₄ ^- is a counter anion represented by.

As a specific example of the organic electrolyte (A) composed of the organic cation (C) and the anion (D),
BF ₄ salt and PF ₆ salt of an alkyl ammonium, a BF ₄ salt and PF ₆ salts of imidazolium.
Among these, TEA · BF ₄ salt, TEMA · BF ₄ salt, ethyltrimethylammonium = tetrafluoroborate (hereinafter referred to as ETMA · BF ₄ ) salt, dimethylpyrrolidinium = tetrafluoroborate (hereinafter referred to as DMP · BF ₄ ) salt, N, N-dimethylpiperidinium = tetrafluoroborate salt, N-ethyl-N-methylpiperidinium = tetrafluoroborate (hereinafter referred to as EMPP · BF ₄ ) salt, EMI BF ₄ salt, 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate (hereinafter referred to as EDMI · BF ₄ ) salt, 1,2,3,4-tetramethylimidazolium tetrafluoroborate salt,
1-methyl-1-azabicyclo [2,2,1] heptane-1-ium tetrafluoroborate (hereinafter referred to as MAHI · BF ₄ ) salt, 1-methyl-1-azabicyclo [2,2,2] Examples include octane-1-ium = tetrafluoroborate (hereinafter referred to as MAOI · BF ₄ ) salt.
Of these, MAHI · BF ₄ salt and MAOI · BF ₄ salt are preferred.

4,5-dialkyl-1,3-dioxolan-2-one (B) is preferably contained in an amount of 95 to 50% by weight, more preferably 85, based on the weight of the electrolytic solution for electric double layer capacitor of the present invention. It is contained in 75% by weight. Further, the organic electrolyte (A) is preferably contained in an amount of 5 to 50% by weight, more preferably 15 to 25% by weight.

The electrolytic solution of the present invention may be used in combination with a solvent (G) other than 4,5-dialkyl-1,3-dioxolan-2-one (B) as necessary.
The solvent (G) may be used in an amount of preferably 0 to 50% by weight, more preferably 0 to 30% by weight, based on the weight of (B).

Specific examples of the solvent (G) include the following. Two or more of these can be used in combination.
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.
Carboxylic acid esters: methyl acetate, methyl propionate, etc.
Lactones: γ-butyrolactone, α-acetyl-γ-butyrolactone, β-butyrolactone, γ-valerolactone, δ-valerolactone, and the like.
Nitriles: acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, acrylonitrile, benzonitrile and the like.
Carbonates: dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, etc.
Sulfoxides: dimethyl sulfoxide, sulfolane, 3-methyl sulfolane, 2,4-dimethyl sulfolane, etc.
・ Nitro compounds: Nitromethane, nitroethane, etc.
Benzenes: toluene, xylene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene and the like.
-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, cyclohexane, etc.
-Phosphate esters: trimethyl phosphoric acid, triethyl phosphoric acid, tripropyl phosphoric acid and the like.

Of these, nitriles, lactones, carbonates, sulfoxides and benzenes are preferable, and sulfolane, methylsulfolane, acetonitrile, γ-butyrolactone, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, xylene, Chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene and 1,4-dichlorobenzene.

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 (A) 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.

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.

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

The electrolytic solution of the present invention can be prepared by a known method, and the concentration of the electrolyte (A) in the electrolytic solution is preferably 0.5 to 2.0 mol / L, and preferably 0.7 to 1.7 mol / L. Is more preferable, and 0.8 to 1.5 mol / L is most preferable. When the concentration of (A) is 0.5 mol / L or more, the conductivity of the electrolytic solution is sufficient, and when it is 2.0 mol / L or less, the low temperature characteristics are good and the economy is excellent.

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, ¹ H-NMR, ¹⁹ F-NMR, and ¹³ C-NMR were measured by the following methods.
Measurement conditions for ¹ H-NMR Instrument: AVANCE 300 (manufactured by Nippon Bruker Co., Ltd.), solvent: deuterated dimethyl sulfoxide, frequency: 300 MHz.
¹⁹ F-NMR measurement conditions Instrument: AL-300 (manufactured by JEOL Ltd.), solvent: deuterated dimethyl sulfoxide, frequency: 300 MHz
Measurement conditions for ¹³ C-NMR Instrument: AL-300 (manufactured by JEOL Ltd.), solvent: deuterated dimethyl sulfoxide, frequency: 300 MHz
Moreover, the silver ion content was quantified by the turbidimetric method with an atomic absorption spectrophotometer (Shimadzu Corporation AA-6200).

<Production Example 1><Production of ETMA salt>
Synthesis of iodide salt 110 parts of N, N-dimethylethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) and 339 parts of acetone were charged into a glass beaker and uniformly dissolved. 234 parts of methyl iodide was slowly added dropwise while stirring the solution, and then stirring was continued at 30 ° C. for 3 hours. The precipitated white solid was filtered and dried at 80 ° C. under reduced pressure to obtain 322 parts of ethyltrimethylammonium iodide salt.

Preparation of AgBF ₄ solution A solution obtained by mixing 174 parts of silver oxide and 314 parts of a 42% by weight aqueous solution of borohydrofluoric acid was dehydrated at 100 ° C. under reduced pressure, and 825 parts of methanol was added to dissolve it. AgBF ₄ methanol A solution was obtained.

-Preparation of BF ₄ salt 1117 parts of AgBF ₄ methanol solution was slowly added dropwise to the above mixed solution of 322 parts of ethyltrimethylammonium iodide salt and 353 parts of methanol, and then filtered to collect the filtrate. . The AgBF ₄ solution or mixed solution was added little by little to the collected filtrate to finely adjust the silver ion content in the solution to 10 ppm or less and the iodine ion content to 5 ppm or less, and then filtered to collect the filtrate.
The filtrate was desolvated at 80 ° C. under reduced pressure to obtain 262 parts of white crystals. Silver ions in the crystal were 10 ppm or less, and iodide ion content was 5 ppm or less. After adding 3000 parts of methanol to the crystal and dissolving at 60 ° C., the solution was cooled to −10 ° C. and allowed to stand for 12 hours for recrystallization. The precipitated crystals were filtered and dried under reduced pressure at 80 ° C. to obtain 124 parts of white crystals. As a result of analysis by ¹ H-NMR, ¹⁹ F-NMR and ¹³ C-NMR, this white crystal (A-1 ′) was ethyltrimethylammonium tetrafluoroborate (ETMA · BF ₄ salt). ^From the integral value of ¹ H-NMR, the purity was 99 mol%.

<Production Example 2><< Production of EDMI Salt >>
A mixture of 31 parts of ethylamine (70% aqueous solution) and 32 parts of ammonia (28% aqueous solution) was charged into a reaction flask equipped with a stirrer, thermometer, dropping funnel, reflux condenser and nitrogen gas inlet tube, and stirred uniformly. Into solution. A liquid mixture composed of 69 parts of glyoxal (40% aqueous solution) and 71 parts of acetaldehyde (30% aqueous solution) was dropped from the dropping funnel while maintaining the temperature at 45 ° C. or lower. The dropwise addition of the mixed solution of glioxal and acetaldehyde was performed over 5 hours, and after completion of the dropwise addition, the mixture was reacted at 40 ° C. for 1 hour. Next, dehydration was carried out by gradually reducing the pressure from 80 ° C. and normal pressure (atmospheric pressure) to 5.0 kPa, followed by simple distillation at a temperature of 105 ° C. and a pressure of 1.0 kPa. -Methylimidazole was obtained.

Next, 100 parts of the obtained 1-ethyl-2-methylimidazole, 135 parts of dimethyl carbonate and 192 parts of methanol were charged into a stainless steel autoclave with a reflux condenser and uniformly dissolved. Subsequently, it heated up to 130 degreeC, the pressure was adjusted to 0.8 Mpa or less, and reaction was performed for 80 hours, and the reaction mixture was obtained. ¹ H-NMR analysis of the reaction mixture revealed that 1-ethyl-2,3-dimethylimidazolium monomethyl carbonate was produced.

427 parts of the resulting reaction mixture was transferred to a flask, and 207 parts of a 42% aqueous solution of borohydrofluoric acid was gradually added dropwise to the flask over about 30 minutes at room temperature (about 25 ° C.). Carbon dioxide gas was generated along with the dripping. After generation | occurrence | production of foam | bubble (carbon dioxide gas) was stopped, the reaction liquid was moved to the rotary evaporator, the solvent (methanol and water) was removed altogether, and 82 parts of a tan transparent solid substance was obtained. As a result of ¹ H-NMR analysis of this solid substance (A-2 ′), the main component was 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate (EDMI · BF ₄ salt). ^From the integral value of ¹ H-NMR, the purity was 99 mol%.

<Production Example 3><Production of DMP salt>
Synthesis of iodide salt 85 parts of N-methylpyrrolidine (manufactured by Tokyo Chemical Industry Co., Ltd.) and 300 parts of acetone were charged into a glass beaker and uniformly dissolved. While stirring the solution, 156 parts of methyl iodide was slowly added dropwise, and stirring was continued at 30 ° C. for 3 hours. The precipitated white solid was filtered and dried at 80 ° C. under reduced pressure to obtain 227 parts of an iodide salt of N, N-dimethylpyrrolidinium.

-Preparation of AgBF ₄ solution A solution obtained by mixing 116 parts of silver oxide and 209 parts of 42 wt% aqueous borofluoric acid solution at 100 ° C under reduced pressure was dissolved in 550 parts of methanol, and dissolved in AgBF ₄ methanol. A solution was obtained.

-Preparation of BF ₄ salt 745 parts of the above AgBF ₄ solution was slowly added dropwise to a mixed solution of 227 parts of N, N-dimethylpyrrolidinium iodide salt and 232 parts of methanol, and then filtered and filtrated. Was recovered. An AgBF ₄ solution or an iodide salt solution was added little by little to the filtrate to finely adjust the silver ion content in the solution to 10 ppm or less and the iodine ion content to 5 ppm or less, and then filtered to collect the filtrate. The filtrate was desolvated at 80 ° C. under reduced pressure to obtain 185 parts of white crystals. 400 parts of methanol was added to the crystals and dissolved at 40 ° C., then cooled to −10 ° C. and allowed to stand for 12 hours for recrystallization. The precipitated crystals were filtered and dried under reduced pressure at 80 ° C. to obtain 146 parts of white crystals. As a result of analysis by ¹ H-NMR, ¹⁹ F-NMR and ¹³ C-NMR, this white crystal (A-3 ′) was dimethylpyrrolidinium = tetrafluoroborate (DMP · BF ₄ salt). ^From the integral value of ¹ H-NMR, the purity was 99%.

<Production Example 4><< Production of MAHI salt >>
-Synthesis of 1-azabicyclo [2,2,1] heptane 110 parts of 4-pyridinemethanol (manufactured by Sigma-Aldrich Japan) and 1000 parts of ethanol were mixed, 250 parts of sodium was gradually added, and the mixture was refluxed for 6 hours. The solution was cooled and 250 parts of water was added. Ethanol was evaporated under reduced pressure, and 200 parts of diethyl ether was added to the residue for extraction. Desolvation under reduced pressure was performed at 30 ° C. to obtain a colorless viscous solution. To 114 parts of this solution, 250 parts of concentrated hydroiodic acid was gradually added dropwise and refluxed for another 3 hours. After adding 350 parts of 50% sodium hydroxide to this solution, it was heated at 50 ° C. for 3 hours. Thereafter, the mixture was cooled to 30 ° C., and 800 parts of diethyl ether was added to this solution for extraction. Sodium carbonate was added for dehydration, and diethyl ether was removed under reduced pressure at 10 ° C., followed by distillation. As a result of analyzing the fraction by ¹ H-NMR, it was found that the raw material disappeared and 1-azabicyclo [2,2,1] heptane was generated. The yield was 40%.

Synthesis of iodide salt 100 parts of 1-azabicyclo [2,2,1] heptane obtained and 300 parts of acetone were charged into a glass beaker and uniformly dissolved. While stirring the solution, 156 parts of methyl iodide was slowly added dropwise, and stirring was continued at 30 ° C. for 3 hours. The precipitated white solid was filtered and dried at 80 ° C. under reduced pressure to obtain 242 parts of 1-methyl-1-azabicyclo [2,2,1] heptan-1-ium iodide salt.

-Preparation of AgBF ₄ solution A solution obtained by mixing 116 parts of silver oxide and 209 parts of 42 wt% aqueous borofluoric acid solution at 100 ° C under reduced pressure was dissolved in 550 parts of methanol, and dissolved in AgBF ₄ methanol. A solution was obtained.

-Preparation of BF ₄ salt 745 parts of the above AgBF ₄ solution was mixed with 239 parts of 1-methyl-1-azabicyclo [2,2,1] heptan-1-ium iodide salt and 239 parts of methanol. The solution was slowly dropped and mixed, and then filtered to collect the filtrate. An AgBF ₄ solution or an iodide salt solution was added little by little to the filtrate to finely adjust the silver ion content in the solution to 10 ppm or less and the iodine ion content to 5 ppm or less, and then filtered to collect the filtrate. The filtrate was desolvated at 80 ° C. under reduced pressure to obtain 194 parts of white crystals. After adding 600 parts of methanol to the crystal and dissolving at 30 ° C., it was cooled to −5 ° C. and allowed to stand for 12 hours for recrystallization. The precipitated crystals were filtered and dried under reduced pressure at 80 ° C. to obtain 138 parts of a white solid. As a result of analysis by ¹ H-NMR, ¹⁹ F-NMR and ¹³ C-NMR, this white solid (A-4 ′) was found to be 1-methyl-1-azabicyclo [2,2,1] heptane-1-ium = tetra It was fluoroborate (MAHI · BF ₄ salt). ^From the integral value of ¹ H-NMR, the purity was 99%.

<Production Example 5><< Production of MAOI salt >>
Synthesis of iodide salt 113 parts of 1-azabicyclo [2,2,2] octane (manufactured by Sigma-Aldrich Japan) and 339 parts of acetone were charged into a glass beaker and dissolved uniformly. While stirring the solution, 156 parts of methyl iodide was slowly added dropwise, and stirring was continued at 30 ° C. for 3 hours. The precipitated white solid was filtered and dried at 80 ° C. under reduced pressure to obtain 255 parts of 1-methyl-1-azabicyclo [2,2,2] octane-1-ium iodide salt.

-Preparation of AgBF ₄ solution A solution obtained by mixing 116 parts of silver oxide and 209 parts of 42 wt% aqueous borofluoric acid solution at 100 ° C under reduced pressure was dissolved in 550 parts of methanol, and dissolved in AgBF ₄ methanol. A solution was obtained.

-Preparation of BF ₄ salt 745 parts of AgBF ₄ methanol solution was mixed with 253 parts of the above-mentioned 1-methyl-1-azabicyclo [2,2,2] octane-1-ium iodide salt and 253 parts of methanol. The mixture was mixed while dropping slowly, and the filtrate was collected by filtration. The AgBF ₄ solution or mixed solution was added little by little to the collected filtrate to finely adjust the silver ion content in the solution to 10 ppm or less and the iodine ion content to 5 ppm or less, and then filtered to collect the filtrate.
The filtrate was desolvated at 80 ° C. under reduced pressure to obtain 206 parts of white crystals. Silver ions in the crystal were 10 ppm or less, and iodide ion content was 5 ppm or less. After adding 600 parts of methanol to the crystal and dissolving at 30 ° C., it was cooled to −5 ° C. and allowed to stand for 12 hours for recrystallization. The precipitated crystals were filtered and dried under reduced pressure at 80 ° C. to obtain 147 parts of white crystals. As a result of analysis by ¹ H-NMR, ¹⁹ F-NMR and ¹³ C-NMR, white crystals (A-5 ′) showed 1-methyl-1-azabicyclo [2,2,2] octane-1-ium = tetrafluoro. It was borate (MAOI · BF ₄ salt). ^From the integral value of ¹ H-NMR, the purity was 99 mol%.

<Production Example 6><< Production of TEMA Salt >>
Synthesis of iodide salt 102 parts of triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) and 300 parts of acetone were charged into a glass beaker and dissolved uniformly. While stirring the solution, 156 parts of methyl iodide was slowly added dropwise, and stirring was continued at 30 ° C. for 3 hours. The precipitated white solid was filtered and dried at 80 ° C. under reduced pressure to obtain 243 parts of an iodide salt of triethylmethylammonium.

-Preparation of AgBF ₄ solution A solution obtained by mixing 116 parts of silver oxide and 209 parts of 42 wt% aqueous borofluoric acid solution at 100 ° C under reduced pressure was dissolved in 550 parts of methanol, and dissolved in AgBF ₄ methanol. A solution was obtained.

-Preparation of BF ₄ salt 745 parts of the above AgBF ₄ solution was slowly added dropwise to a mixed solution of 243 parts of triethylmethylammonium iodide salt and 232 parts of methanol, and then filtered to collect the filtrate. An AgBF ₄ solution or an iodide salt solution was added little by little to the filtrate to finely adjust the silver ion content in the solution to 10 ppm or less and the iodine ion content to 5 ppm or less, and then filtered to collect the filtrate. The filtrate was desolvated at 80 ° C. under reduced pressure to obtain 186 parts of white crystals. 300 parts of methanol was added to the crystal and dissolved at 30 ° C., then cooled to −5 ° C. and allowed to stand for 12 hours for recrystallization. The precipitated crystals were filtered and dried under reduced pressure at 80 ° C. to obtain 152 parts of white crystals. As a result of analysis by ¹ H-NMR, ¹⁹ F-NMR and ¹³ C-NMR, this white crystal (A-6 ′) was triethylmethylammonium tetrafluoroborate (TEMA · BF ₄ salt). ^From the integral value of ¹ H-NMR, the purity was 99%.

<Production Example 7><< Production of EMI Salt >>
96 parts of 1-ethylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.), 135 parts of dimethyl carbonate and 192 parts of methanol were charged into a stainless steel autoclave with a cooling capacitor and dissolved uniformly. Subsequently, the temperature was raised to 130 ° C. to initiate the reaction. The pressure was about 4.5 kg / cm ² at first, but gradually increased due to the generation of carbon dioxide gas. Therefore, the pressure was adjusted to 0.8 MPa or less by appropriately venting from the upper part of the cooling condenser. After 60 hours, the reaction solution was cooled to 30 ° C. and analyzed by ¹ H-NMR. As a result, 1-ethylimidazole disappeared and 1-ethyl-3-methylimidazolium monomethyl carbonate was produced almost quantitatively. I understood it. To 415 parts of the obtained 1-ethyl-3-methylimidazolium monomethyl carbonate / methanol / dimethyl carbonate solution, 205 parts of a 42 wt% aqueous solution of borofluoric acid was gradually added dropwise at 25 ° C. over about 30 minutes. did. Along with the dropping, bubbles of carbon dioxide gas were generated. After the completion of the dropping and the generation of bubbles was stopped, the entire solvent was distilled off at 20 Torr and 150 ° C. to obtain 194 parts of a pale yellow liquid. As a result of analysis by ¹ H-NMR, ¹⁹ F-NMR and ¹³ C-NMR, the obtained liquid (A-7 ′) was 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI · BF ₄ salt). )Met. ^From the integral value of ¹ H-NMR, the purity was 99 mol%.

<Production Example 8><< Production of EMPP Salt >>
Synthesis of iodide salt 113 parts of N-ethylpiperidine (manufactured by Tokyo Chemical Industry Co., Ltd.) and 300 parts of acetone were charged into a glass beaker and uniformly dissolved. While stirring the solution, 156 parts of methyl iodide was slowly added dropwise, and stirring was continued at 30 ° C. for 3 hours. The precipitated white solid was filtered and dried at 80 ° C. under reduced pressure to obtain 255 parts of an iodide salt of N-ethyl-N-methylpiperidinium.
-Preparation of AgBF ₄ solution A solution obtained by mixing 116 parts of silver oxide and 209 parts of 42 wt% aqueous borofluoric acid solution at 100 ° C under reduced pressure was dissolved in 550 parts of methanol, and dissolved in AgBF ₄ methanol. A solution was obtained.
-Preparation of BF ₄ salt 745 parts of the above AgBF ₄ solution was slowly added dropwise to a mixed solution of 255 parts of N-ethyl-N-methylpiperidinium iodide salt and 268 parts of methanol, followed by filtration. The filtrate was collected. An AgBF ₄ solution or an iodide salt solution was added little by little to the filtrate to finely adjust the silver ion content in the solution to 10 ppm or less and the iodine ion content to 5 ppm or less, and then filtered to collect the filtrate. The filtrate was desolvated at 80 ° C. under reduced pressure to obtain 215 parts of white crystals. 400 parts of methanol was added to the crystal and dissolved at 40 ° C., then cooled to −5 ° C. and allowed to stand for 12 hours for recrystallization. The precipitated crystals were filtered and dried under reduced pressure at 80 ° C. to obtain 193 parts of white crystals. As a result of analysis by ¹ H-NMR, ¹⁹ F-NMR and ¹³ C-NMR, this white crystal (A-8 ′) was an EMPP · BF ₄ salt. ^From the integral value of ¹ H-NMR, the purity was 99%.

<< Production Example 9 >><< Production of SBP Salt >>
100 parts of pyrrolidine and 97 parts of potassium carbonate were charged into an autoclave coated with Teflon (registered trademark), 198 parts of 1,5-dichloropentane was added, and the reaction was performed 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. This solid was crystallized twice using ethanol and 2-propanol to obtain 155 parts of white crystals. As a result of analysis by ¹ H-NMR, ¹⁹ F-NMR and ¹³ C-NMR, the white crystal (A-9 ′) was spirobipyrrolidinium = tetrafluoroborate. ^From the integral value of ¹ H-NMR, the purity was 99 mol%.

<Production Example 10><< Solvent: Production of 23BC >>
A vessel equipped with a stirrer is charged with 90 parts of 2,3-butanediol, 660 parts of di-t-butyl dicarbonate, 122 parts of 4-dimethylaminopyridine, and 800 parts of acetonitrile (all manufactured by Tokyo Chemical Industry Co., Ltd.). The mixture was stirred at room temperature for 1 hour to carry out the reaction. After the solvent was distilled off from the solution after the reaction, 100 parts of 4,5-dimethyl-1,3-dioxolan-2-one was obtained by precision distillation. As a result of analysis by ¹ H-NMR, the mixture ratio was (cis isomer) :( trans isomer) = 25: 75.
(Reference "The Journal of Organic Chemistry, 2000, 65 (20), pp 6368-6380")
Electrolyte solvent dehydration Add 3 parts of molecular sieve (Nacalai Tesque, 3A1 / 16; hereinafter the same) to 100 parts of 4,5-dimethyl-1,3-dioxolan-2-one obtained. After drying for 60 hours at 25 ° C., the molecular sieve was filtered off to obtain dehydrated 4,5-dimethyl-1,3-dioxolan-2-one (hereinafter referred to as 23BC). It was.

<Production Example 11><< Solvent: Production of 23PeC >>
By changing 2,3-butanediol, which is the raw material of Production Example 10, to 104 parts of 2,3-pentanediol, 102 parts of 4-ethyl-5-methyl-1,3-dioxolan-2-one was similarly obtained. Got. As a result of analysis by ¹ H-NMR, the mixture ratio was (cis isomer) :( trans isomer) = 20: 80.
Electrolyte solvent dehydration To 100 parts of the obtained 4-ethyl-5-methyl-1,3-dioxolan-2-one, 3 parts of molecular sieve (Nacalai Tesque, 3A1 / 16) were added at 40 ° C. After drying for 60 hours, the molecular sieve was separated by filtration to obtain dehydrated 4-ethyl-5-methyl-1,3-dioxolan-2-one (hereinafter referred to as 23PeC).

<Production Example 12><< Solvent: Production of 23HC >>
In the same manner, 4-ethyl-5-n-propyl-1,3-dioxolan-2-one was obtained by changing 2,3-butanediol, which is a raw material of Production Example 10, to 118 parts of 2,3-hexanediol. 105 parts were obtained. As a result of analysis by ¹ H-NMR, the mixture ratio was (cis isomer) :( trans isomer) = 20: 80.
Electrolyte solvent dehydration 40 parts by adding 3 parts of molecular sieve (Nacalai Tesque, 3A1 / 16) to 100 parts of the obtained 4-ethyl-5-n-propyl-1,3-dioxolan-2-one After drying at 60 ° C. for 60 hours, the molecular sieve was filtered off and dehydrated 4-ethyl-5-n-propyl-1,3-dioxolan-2-one (hereinafter referred to as 23HC). Got.

<Production Example 13>
20 parts of sulfolane is dissolved in 80 parts of 4,5-dimethyl-1,3-dioxolan-2-one (23BC) obtained in Production Example 10, 3 parts of molecular sieves are added, and the mixture is allowed to stand at 25 ° C. for 60 hours. After drying, the molecular sieve was filtered off to obtain a dehydrated 4,5-dimethyl-1,3-dioxolan-2-one / sulfolane mixed solvent (hereinafter referred to as 23BC / SL).

Electrolyte solvent dehydration <Production Example 14>
After adding 3 parts of molecular sieve to 100 parts of propylene carbonate and leaving it to stand at 25 ° C. for 60 hours for drying, the molecular sieve was separated by filtration to obtain dehydrated propylene carbonate.

<Production Example 15>
Dissolve 20 parts of ethylene carbonate in 80 parts of propylene carbonate, add 3 parts of molecular sieve, leave it at 25 ° C. for 60 hours to dry, then filter off the molecular sieve, and add dehydrated propylene carbonate / ethylene carbonate mixed solvent. Obtained.

Production Example 16 << Solvent: Production of trans-23BC >>
In a vessel equipped with a stirrer, 90 parts of (2R, 3R)-(−)-2,3-butanediol (manufactured by Sigma Aldrich), 660 parts of di-t-butyl dicarbonate, 122 parts of 4-dimethylaminopyridine, 800 parts of acetonitrile Parts (both manufactured by Tokyo Chemical Industry Co., Ltd.) were stirred at room temperature for 1 hour to carry out the reaction. After the solvent was distilled off from the solution after the reaction, 100 parts of trans-4,5-dimethyl-1,3-dioxolan-2-one was obtained by precision distillation. As a result of analysis by ¹ H-NMR, the mixing ratio was (cis isomer) :( trans isomer) = 0: 100.
Electrolyte solvent dehydration 3 parts of molecular sieve (Nacalai Tesque, 3A1 / 16; hereinafter the same) to 100 parts of trans-4,5-dimethyl-1,3-dioxolan-2-one obtained The mixture was allowed to stand at 25 ° C. for 60 hours to dry, and the molecular sieve was filtered off and dehydrated trans-4,5-dimethyl-1,3-dioxolan-2-one (hereinafter referred to as trans-23BC). Described.).

<Production Example 17><< Solvent: Production of cis-23BC >>
In a vessel equipped with a stirrer, 90 parts of meso-2,3-butanediol (manufactured by Sigma Aldrich), 660 parts of di-t-butyl dicarbonate, 122 parts of 4-dimethylaminopyridine, and 800 parts of acetonitrile (all of which are Tokyo Chemical Industry) Made by Co., Ltd.) and stirred at room temperature for 1 hour to carry out the reaction. After the solvent was distilled off from the solution after the reaction, 100 parts of cis-4,5-dimethyl-1,3-dioxolan-2-one was obtained by precision distillation. As a result of analysis by ¹ H-NMR, the mixture ratio was (cis isomer) :( trans isomer) = 100: 0.
Electrolyte solvent dehydration 3 parts of molecular sieve (Nacalai Tesque, 3A1 / 16; hereinafter the same) to 100 parts of the obtained cis-4,5-dimethyl-1,3-dioxolan-2-one The mixture was allowed to stand at 25 ° C. for 60 hours to dry, and the molecular sieve was filtered off and dehydrated cis-4,5-dimethyl-1,3-dioxolan-2-one (hereinafter referred to as cis-23BC). Was obtained.).

Example 1
35 parts of ETMA · BF ₄ salt (A-1 ′) of Production Example 1 was uniformly dissolved in 23BC obtained in Production Example 10 and the whole was adjusted to 200 ml (electrolyte concentration: 1.0 mol / L). The electrolytic solution (A-1) of the invention was obtained.

Example 2
The electrolytic solution (A-2) of the present invention was obtained in the same manner except that (A-1 ′) in Example 1 was changed to 43 parts of EDMI · BF ₄ salt (A-2 ′) in Production Example 2. .

Example 3
The electrolytic solution (A-3) of the present invention was obtained in the same manner except that (A-1 ′) in Example 1 was changed to 38 parts of the DMP · BF ₄ salt (A-3 ′) in Production Example 3. .

Example 4
Except for changing in Example 1 'The MAHI · BF ₄ salt of Preparation Example 4 (A-4 (A- 1)') in 40 parts were obtained in the same manner electrolytic solution of the present invention (A-4) .

Example 5
Except for changing in Example 1 'The MAOIs · BF ₄ salt of Preparation Example 5 (A-5 (A- 1)') in 43 parts were obtained in the same manner electrolytic solution of the present invention (A-5) .

Example 6
41 parts of TEMA · BF ₄ salt (A-6 ′) of Production Example 6 was uniformly dissolved in 23PeC obtained in Production Example 11 to adjust the whole to 200 ml (electrolyte concentration 1.0 mol / L). The electrolytic solution (A-6) of the invention was obtained.

Example 7
The electrolytic solution (A-7) of the present invention was obtained in the same manner except that (A-6 ′) in Example 6 was changed to 40 parts of the EMI • BF ₄ salt (A-7 ′) in Production Example 7. .

Example 8
The electrolytic solution (A-8) of the present invention was obtained in the same manner except that (A-6 ′) in Example 6 was changed to 40 parts of MAHI · BF ₄ salt (A-4 ′) in Production Example 4. .

Example 9
43 parts of EMPP · BF ₄ salt (A-8 ′) of Production Example 8 was uniformly dissolved in 23HC obtained in Production Example 12, and the whole was adjusted to 200 ml (electrolyte concentration: 1.0 mol / L). An electrolytic solution (A-9) of the invention was obtained.

Example 10
35 parts of ETMA · BF ₄ salt (A-1 ′) of Production Example 1 were uniformly dissolved in 23BC / SL obtained in Production Example 13 to adjust the whole to 200 ml (electrolyte concentration 1.0 mol / L). The electrolytic solution (A-10) of the present invention was obtained.

Example 11
Except for changing in Example 10 'The EDMI · BF ₄ salt of Preparation 2 (A-2 (A- 1)') in 43 parts were obtained in the same manner electrolytic solution of the present invention (A-11) .

Example 12
An electrolytic solution (A-12) of the present invention was obtained in the same manner except that (A-1 ′) in Example 10 was changed to 43 parts of MAOI · BF ₄ salt (A-5 ′) in Production Example 5. .

Example 13
Except for changing in Example 10 'The SBP · BF ₄ salt of Preparation 9 (A-9 (A- 1)') in 43 parts were obtained in the same manner electrolytic solution of the present invention (A-13) .

Example 14
35 parts of (A-1 ′) of Production Example 1 was uniformly dissolved in trans-23BC obtained in Production Example 16, and the whole was adjusted to 200 ml (electrolyte concentration: 1.0 mol / L). A liquid (A-14) was obtained.

Example 15
35 parts of (A-1 ′) of Production Example 1 were uniformly dissolved in cis-23BC obtained in Production Example 17, and the whole was adjusted to 200 ml (electrolyte concentration: 1.0 mol / L). A liquid (A-15) was obtained.

Comparative Example 1
A comparative electrolyte solution (ratio A-1) of the present invention was obtained in the same manner except that the solvent of Example 1 was changed to dehydrated propylene carbonate (PC) of Production Example 14.

Comparative Example 2
A comparative electrolyte solution (ratio A-2) of the present invention was obtained in the same manner except that the solvent of Example 2 was changed to the dehydrated propylene carbonate of Production Example 14.

Comparative Example 3
A comparative electrolytic solution (ratio A-3) of the present invention was obtained in the same manner except that the solvent of Example 3 was changed to dehydrated propylene carbonate of Production Example 14.

Comparative Example 4
A comparative electrolyte solution (ratio A-4) of the present invention was obtained in the same manner except that the solvent of Example 4 was changed to dehydrated propylene carbonate of Production Example 14.

Comparative Example 5
A comparative electrolytic solution (ratio A-5) of the present invention was obtained in the same manner except that the solvent of Example 5 was changed to dehydrated propylene carbonate of Production Example 14.

Comparative Example 6
A comparative electrolyte solution (ratio A-6) of the present invention was obtained in the same manner except that the solvent of Example 6 was changed to dehydrated propylene carbonate of Production Example 14.

Comparative Example 7
A comparative electrolytic solution (ratio A-7) of the present invention was obtained in the same manner except that the solvent of Example 7 was changed to dehydrated propylene carbonate of Production Example 14.

Comparative Example 8
A comparative electrolyte solution (ratio A-8) of the present invention was obtained in the same manner except that the solvent of Example 4 was changed to the dehydrated propylene carbonate / ethylene carbonate (PC / EC) mixed solvent of Production Example 15.

Comparative Example 9
A comparative electrolyte solution (ratio A-9) of the present invention was obtained in the same manner except that the solvent of Example 5 was changed to the dehydrated propylene carbonate / ethylene carbonate mixed solvent of Production Example 15.

The electrolytic solutions for Examples 1 to 15 and Comparative Examples 1 to 9 were evaluated for electrolytic solutions for electric double layer capacitors by the following method, and the evaluation results are shown in Table 1.

ＥＴＭＡ：エチルトリメチルアンモニウム＝テトラフルオロボラート
ＥＤＭＩ：１−エチル−２，３−ジメチルイミダゾリウム＝テトラフルオロボラート
ＤＭＰ：ジメチルピロリジニウム＝テトラフルオロボラート
ＭＡＨＩ：１−メチル−１−アザビシクロ［２，２，１］ヘプタン−１−イウム＝テトラフルオロボラート
ＭＡＯＩ：１−メチル−１−アザビシクロ［２，２，２］オクタン−１−イウム＝テトラフルオロボラート
ＴＥＭＡ：トリエチルメチルアンモニウム＝テトラフルオロボラート
ＥＭＩ：１−エチル−３−メチルイミダゾリウム＝テトラフルオロボラート
ＥＭＰＰ：Ｎ−エチル−Ｎ’−メチルピペリジニウム＝テトラフルオロボラート
ＳＢＰ：スピロビピロリジニウム＝テトラフルオロボラート
２３ＢＣ：４，５−ジメチル−１，３−ジオキソラン−２−オン
２３ＰｅＣ：４−エチル−５−メチル−１，３−ジオキソラン−２−オン
２３ＨＣ：４−メチル−５−ｎ−プロピル−１，３−ジオキソラン−２−オン
ＳＬ：スルホラン
ＰＣ：プロピレンカーボネート
ＥＣ：エチレンカーボネート

ETMA: ethyltrimethylammonium = tetrafluoroborate EDMI: 1-ethyl-2,3-dimethylimidazolium = tetrafluoroborate DMP: dimethylpyrrolidinium = tetrafluoroborate MAHI: 1-methyl-1-azabicyclo [2 , 2,1] heptane-1-ium = tetrafluoroborate MAOI: 1-methyl-1-azabicyclo [2,2,2] octane-1-ium = tetrafluoroborate TEMA: triethylmethylammonium = tetrafluoroborate Lat EMI: 1-ethyl-3-methylimidazolium = tetrafluoroborate EMPP: N-ethyl-N′-methylpiperidinium = tetrafluoroborate SBP: spirobipyrrolidinium = tetrafluoroborate 23BC: 4 , 5-dimethyl- 1,3-dioxolan-2-one 23PeC: 4-ethyl-5-methyl-1,3-dioxolan-2-one 23HC: 4-methyl-5-n-propyl-1,3-dioxolan-2-one SL : Sulfolane PC: Propylene carbonate EC: Ethylene carbonate

-Preparation of electric double layer capacitor 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 electrolytes of <Examples 1 to 15> and <Comparative Examples 1 to 9> were injected into the cell, followed by vacuum impregnation to produce an electric double layer capacitor.

・ Charge / discharge test equipment (“CDT-5R2-4” manufactured by Power System Co., Ltd.) is connected to the electric double layer capacitor created in the durability test and the capacity retention rate after the test, and constant current charging is performed at 25 mA up to the set voltage. After 3600 seconds from the start of charging, constant current discharge was performed at 25 mA. This was carried out for 150 cycles at a set voltage of 3.0 V and 60 ° C., and the capacity retention rate (%) and resistance change rate (%) were obtained from the initial capacity and resistance, and the capacity and resistance after 150 cycles by the following equations. It was used as an index of withstand voltage.
Capacity retention (%) = ((X ₁₅₀ ) × 100 / (X ₀ ))
Resistance change rate (%) = ((Y ₁₅₀ ) × 100 / (Y ₀ ))
However, X ₀ : Initial capacity value before durability test, X ₁₅₀ : Capacity value after 150 cycles,
Y ₀ : initial resistance value before endurance test, Y ₁₅₀ : resistance value after 150 cycles.
The larger the capacity retention rate and the smaller the resistance change rate, the smaller the change in the electrolyte solution, indicating that the electrolyte solution is electrochemically stable and has a high withstand voltage.

-Gas generation amount measurement The gas generated from the three-electrode electric double layer capacitor after the cycle test was collected and its volume was measured.

As is clear from Table 1, the electric double layer capacitors using the electrolytic solutions of Examples 1 to 15 of the present invention were after the cycle test as compared with the electric double layer capacitors using the electrolytic solutions of Comparative Examples 1 to 9. Since the capacity retention rate is large and the resistance increase rate is small, the withstand voltage is high. Therefore, it is clear that the electrolytic solution of the present invention can drastically improve the deterioration of performance over time of the electric double layer capacitor and can constitute a highly reliable electric double layer capacitor.

The electrolytic solution for an electric double layer capacitor of the present invention has a high withstand voltage, so that the storage capacity can be increased, and since the durability is high, it can be applied to power storage applications such as industrial machine applications, automobile assist power supplies, and wind power generation.

Claims (10)

An electrolytic solution for an electric double layer capacitor containing the organic electrolyte (A) and 4,5-dialkyl-1,3-dioxolan-2-one (B) represented by the general formula (1).

(R ₁ and R ₂ are alkyl groups having 1 to 3 carbon atoms and may be the same as or different from each other.) 4,5-dialkyl-1,3-dioxolan-2-one (B) is converted to cis-4,5-dialkyl-1,3-dioxolan-2-one (B1) and trans-4,5-dialkyl-1 The electrolytic solution according to claim 1, which is a mixture of 1,3-dioxolan-2-one (B2). 4,5-dialkyl-1,3-dioxolan-2-one (B) represented by the general formula (1) is 4,5-dimethyl-1,3-dioxolan-2-one and / or 4-ethyl The electrolytic solution according to claim 1 or 2, which is -5-methyl-1,3-dioxolan-2-one. Furthermore, the electrolyte solution of any one of Claims 1-3 containing a sulfolane (SL). The electrolyte solution according to any one of claims 1 to 4, wherein the organic electrolyte (A) is an amidine salt (A1). The electrolyte solution according to claim 5, wherein the cation of the amidine salt (A1) has a 5-membered ring or a 6-membered ring. The electrolyte solution according to claim 5 or 6, wherein the amidine salt (A1) is 1-ethyl-2,3-dimethylimidazolium = tetrafluoroborate. The electrolyte according to any one of claims 1 to 4, wherein the organic electrolyte (A) is a tetraalkylammonium salt (A2). The electrolytic solution according to claim 8, wherein the cation of the tetraalkylammonium salt (A2) is at least one selected from the group consisting of cations represented by the general formulas (2) to (4).

(R ₃ and R ₄ are alkyl groups having 1 to 2 carbon atoms and may be the same or different from each other. They may also form a ring with each other.)

(R ₅ and R ₆ are alkyl groups having 1 to 3 carbon atoms and may be the same or different from each other. They may also form a ring with each other.)

(R ₇ is a halogen atom, a nitro group, monovalent hydrocarbon group of a cyano group and at least one carbon atoms which may have a group 1 to 3 selected from the group consisting of groups having an ether bond. R _{8 to} R ₁₉ are an alkyl group having 1 to 2 carbon atoms, a fluoroalkyl group having 1 to 5 carbon atoms, a hydrogen atom, or a halogen atom, and R _{8 to} R ₁₉ may be the same or different. , I, j, x, y and z are integers of 0 to 2, and may be the same or different, h + x is an integer of 0 to 4, i + y and j + z are integers of 1 to 4. R ₂₀ is C1-C3 monovalent hydrocarbon group, hydrogen atom, or halogen atom which may have at least one group selected from the group consisting of a halogen atom, a nitro group, a cyano group and a group having an ether bond .) The cation of the tetraalkylammonium salt (A2) is 1-ethyl-1-azabicyclo [2,2,1] heptane-1-ium and / or 1-ethyl-1-azabicyclo [2,2,2] octane-1 The electrolytic solution according to claim 8 or 9, which is -ium.